Light-adjusting sheets and how to manage them

Abstract

To provide a light control sheet capable of reducing opacity variations in the light control sheet; a light control device; and a method of controlling the light control sheet.SOLUTION: There is provided a light control sheet including: a light control layer 11 configured to be switched in a state, between a transparent state and an opaque state; and a pair of transparent electrode layers 12 sandwiching the light control layer 11. The light control layer 11 includes a polymer network 11A containing a plurality of domains 11D, and a liquid crystal composition 11B filling each of the domains 11D. The liquid crystal composition 11B in the light control layer 11 has concentration of 37% or more and 55% or less, and the domains 11D have an average size of 1.0 μm or more and 1.55 μm or less. A minimum value of clarity is present within the range of 1.0 μm or more to 1.55 μm or less for the average size of the domains 11D.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-adjusting sheet, a light-adjusting device, and a method for managing the light-adjusting sheet. [Background technology]

[0002] A light-controlling sheet contains a liquid crystal composition in a polymer layer. The light-controlling sheet changes between transparent and opaque depending on the voltage applied to the polymer layer (see, for example, Patent Document 1). Light-controlling sheets are classified into normal and reverse types. Normal-type light-controlling sheets are opaque when no current is applied and transparent when current is applied. Reverse-type light-controlling sheets are transparent when no current is applied and opaque when current is applied (see, for example, Patent Document 2).

[0003] Haze (JIS K 7136:2000), transmitted image clarity (JIS K 7374:2007), and clarity are known as physical properties that indicate the opacity of a light-controlling film (see, for example, Patent Documents 3 and 4). In particular, among the opacity characteristics, transmitted image clarity or clarity is required to determine whether or not the outline of an object can be discerned through the light-controlling film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-091986 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-321562 [Patent Document 3] Japanese Patent Application Publication No. 2018-031870 [Patent Document 4] Patent No. 6493598 Summary of the Invention [Problem to be solved by the invention]

[0005] The clarity and sharpness of transmitted light images are significantly affected by the degree of narrow-angle scattering generated by the light-controlling film, but it is unclear how these depend on the components of the polymer layer. In a light-controlling device incorporating a light-controlling film, a predetermined value for clarity and sharpness is required, and the voltage applied to the light-controlling film is adjusted to achieve a predetermined opacity. For example, to protect the privacy of people present in a space, one light-controlling film that divides a space is set to operate at a predetermined voltage, while the other light-controlling film that divides the same space is set to operate at a higher voltage. However, adjusting the opacity by changing the applied voltage complicates the drive device and initial setup, and also causes significant variations in the power consumption of the light-controlling device.

[0006] The present invention aims to provide a light-adjusting sheet, a light-adjusting device, and a method for managing a light-adjusting sheet that can suppress variations in opacity of the light-adjusting sheet. [Means for solving the problem]

[0007] A light-controlling sheet for solving the above problem comprises a light-controlling layer configured to be changeable between a transparent state and an opaque state, and a pair of transparent electrode layers sandwiching the light-controlling layer, wherein the light-controlling layer comprises a transparent polymer layer having a plurality of domains and a liquid crystal composition filling each domain, wherein the concentration of the liquid crystal composition in the light-controlling layer is 37% or more and 55% or less, the average size of the domains is 1.0 μm or more and 1.55 μm or less, and the minimum value of clarity exists within the range of the average size of the domains being 1.0 μm or more and 1.55 μm or less.

[0008] The present inventors have found that when the concentration of the liquid crystal composition is 37% or more and 55% or less, a decrease in the average domain size results in minimum values ​​for the clarity and sharpness of a transmitted image. That is, the present inventors have found that the minimum values ​​for the clarity and sharpness of a transmitted image are near the center of the range in which the average domain size is 1.0 μm or more and 1.55 μm or less.

[0009] The liquid crystal composition of each domain in the light-controlling layer is a factor that contributes to the opacity of the light-controlling sheet. A light-controlling sheet with a liquid crystal composition concentration of 37% to 55% and an average domain size of 1.0 μm to 1.55 μm approximately specifies the size of the elements that contribute to opacity and the number of elements present per unit volume. The transmitted image clarity and clarity values ​​are minimized near the center of the average domain size range of 1.0 μm to 1.55 μm. This makes it easy to distribute a large number of domains within the conditions required to achieve a predetermined opacity, even if the domain sizes vary. The predetermined opacity is an opacity that renders the contours of the observed object visually unrecognizable. As a result, it is possible to achieve an opacity that renders the contours of the observed object visually unrecognizable and to suppress variation in that opacity.

[0010] In the above-mentioned light-adjusting sheet, when the light-adjusting layer is in the opaque state, the clarity of the light-adjusting sheet is 71% or less, and the clarity is calculated by 100×(LC-LR) / (LC+LR), where LC is the amount of light that, among the light that passes through the light-adjusting sheet, travels straight along the optical axis of the parallel light that entered the light-adjusting sheet, and LR is the amount of light that is narrow-angle scattered light whose angle with respect to the optical axis of the parallel light is within ±2.5°.

[0011] In the above-mentioned light-adjusting sheet, the transmitted image clarity in accordance with JIS K 7374:2007 when the optical comb width is set to 0.125 mm is the transmitted image clarity of the light-adjusting sheet, and when the light-adjusting layer is in the opaque state, the transmitted image clarity of the light-adjusting sheet is 47% or less.

[0012] In the light-modulating sheet, the light-modulating layer may be sandwiched so that the entire surface of the light-modulating layer facing the transparent electrode layer is in contact with the transparent electrode layer.

[0013] In the light controlling sheet, the transparent polymer layer may be a polymer of an ultraviolet-polymerizable compound.

[0014] A method for managing a light-controlling sheet to solve the above problem is a method for managing a light-controlling sheet, the light-controlling sheet comprising a light-controlling layer that changes between a transparent state and an opaque state, and a pair of transparent electrode layers sandwiching the light-controlling layer, the light-controlling layer comprising a transparent polymer layer having a plurality of domains and a liquid crystal composition that fills the domains, and including determining whether the light-controlling layer is normal, wherein the conditions for determining that the light-controlling layer is normal include a concentration of the liquid crystal composition in the light-controlling layer being 37% or more and 55% or less, an average size of the domains being 1.0 μm or more and 1.55 μm or less, and a minimum clarity value being within the range of the average size of the domains being 1.0 μm or more and 1.55 μm or less. [Effects of the Invention]

[0015] According to the light controlling sheet, light controlling device, and light controlling sheet management method of the present invention, it is possible to suppress variations in opacity of the light controlling sheet. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 10 is a cross-sectional view showing a normal-type light controlling sheet when no voltage is applied. [Figure 2] FIG. 10 is a cross-sectional view showing a normal-type light-control sheet when a voltage is applied. [Figure 3]FIG. 10 is a cross-sectional view showing a reverse-type light-controlling sheet when no voltage is applied. [Figure 4] FIG. 10 is a cross-sectional view showing a reverse-type light-control sheet when a voltage is applied. [Figure 5] FIG. 1 is a diagram showing the configuration of a device for measuring transmitted image clarity. [Figure 6] 10 is a graph showing the relationship between the amount of transmitted light and the light receiving position in a measurement device for measuring transmitted image clarity. [Figure 7] FIG. 1 is a schematic diagram showing the configuration of a clarity measurement device. [Figure 8] 1 is a graph showing the relationship between haze, transmitted image clarity, and clarity and visual ranking. [Figure 9] (a) (b) (c) (d) (e) Illustrates an example of a transmitted image of a light-controlling sheet. [Figure 10] A graph showing the relationship between average domain size and clarity. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1 to 10, an embodiment of a light-adjusting sheet, a light-adjusting device, and a method for managing the light-adjusting sheet will be described. In this embodiment, an object on the opposite side of the light-adjusting sheet from the observation point is referred to as an observation target. The observation target includes, for example, moving objects such as people, and static objects such as devices and ornaments.

[0018] [Light-adjusting sheet] Light-controlling sheets are attached to windows of moving objects such as vehicles and aircraft, for example. Light-controlling sheets are also attached to windows of various buildings such as houses, train stations, and airports, partitions installed in offices, and show windows installed in stores, for example. Light-controlling sheets are also used for screens for projecting images.

[0019] The shape of the light controlling sheet may be flat or curved. The shape of the light controlling sheet may be a shape that follows the shape of the object to which the light controlling sheet is attached, or may be a shape different from the object to which the light controlling sheet is attached. The type of the light controlling sheet may be a normal type or a reverse type.

[0020] A normal-type light controlling sheet and a light controlling device equipped with the normal-type light controlling sheet will be described with reference to Figures 1 and 2. Figure 1 shows the cross-sectional structure of the normal-type light controlling sheet when it is in an opaque state, and Figure 2 shows the cross-sectional structure of the normal-type light controlling sheet when it is in a transparent state.

[0021] 1, a normal-type light-control sheet 10 includes a light-control layer 11 and a pair of transparent electrode layers 12. The light-control layer 11 includes a transparent polymer layer having multiple domains and a liquid crystal composition filling each domain.

[0022] The type of liquid crystal composition that is held is any one selected from the group consisting of a polymer network type, a polymer dispersion type, and a capsule type. The polymer network type has a polymer network with a three-dimensional mesh structure. The polymer network holds the liquid crystal composition in interconnected mesh-like voids. The polymer dispersion type has a polymer layer that partitions a large number of isolated voids, and holds the liquid crystal composition in the voids dispersed in the polymer layer. The capsule type holds a capsule-shaped liquid crystal composition in the polymer layer.

[0023] The domains are voids formed by the polymer network, isolated voids dispersed in the polymer layer, or capsules dispersed in the polymer layer. The domains may be voids surrounded by transparent polymers, or voids connected to adjacent domains. The light-control sheets shown in Figures 1 to 4 are examples of polymer network-type retention structures.

[0024] As shown in FIG. 1, the light-controlling layer 11 includes a polymer network 11A, which is an example of a transparent polymer layer, and a liquid crystal composition 11B. The polymer network 11A defines a plurality of domains 11D. Each domain 11D is a gap connecting adjacent domains 11D. The light-controlling layer 11 is formed, for example, by irradiating a coating film with ultraviolet light. The coating film is a mixture of a UV-polymerizable compound for forming the polymer network 11A and the liquid crystal composition 11B.

[0025] The polymer network 11A is a polymer of an ultraviolet-polymerizable compound. The polymer network 11A may include spacers for maintaining the thickness of the photochromic layer 11. The spacers are, for example, glass particles or resin particles, and preferably have the same color as the photochromic layer 11.

[0026] The liquid crystal composition 11B includes a plurality of liquid crystal molecules 11BL. The liquid crystal composition 11B fills the domain 11D. The liquid crystal molecules 11BL are, for example, one selected from the group consisting of Schiff bases, azos, azoxys, biphenyls, terphenyls, benzoates, tolanes, pyrimidines, cyclohexanecarboxylic acid esters, phenylcyclohexanes, and dioxanes. The main component of the liquid crystal composition 11B is the liquid crystal molecules 11BL.

[0027] The weight concentration of the main component in liquid crystal composition 11B is 80% or more relative to liquid crystal composition 11B. Liquid crystal composition 11B may contain, in addition to the main component, a dichroic dye, a weatherproofing agent, and unavoidable components that are mixed in during the formation of light-control layer 11. The weatherproofing agent is an ultraviolet absorber or a light stabilizer that suppresses deterioration of liquid crystal composition 11B. The unavoidable components are, for example, unreacted components of the ultraviolet-polymerizable compound used to form polymer network 11A.

[0028] In the cross-sectional structure of the light-controlling sheet 10, if the domain 11D is circular, the domain size is the diameter of the domain 11D. In the cross-sectional structure of the light-controlling sheet 10, if the domain 11D is elliptical, the domain size is the major axis of the domain 11D. In the cross-sectional structure of the light-controlling sheet 10, if the domain 11D is irregular, the domain size is the diameter of a circle circumscribing the domain 11D. The average domain size is the average value of the domain sizes.

[0029] The pair of transparent electrode layers 12 sandwich the switchable layer 11 in the thickness direction of the switchable layer 11. Each transparent electrode layer 12 transmits light in the visible light region. The material constituting each transparent electrode layer 12 is, for example, any one selected from the group consisting of indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, and poly(3,4-ethylenedioxythiophene).

[0030] The light-controlling sheet 10 includes a pair of transparent substrates 13. The pair of transparent substrates 13 sandwich a pair of transparent electrode layers 12 in the thickness direction of the light-controlling layer 11. Each transparent substrate 13 transmits light in the visible light range. The material constituting each transparent substrate 13 is, for example, transparent glass or transparent synthetic resin.

[0031] The light-controlling layer 11 has a transparent state and an opaque state. The light-controlling layer 11 changes the orientation of the liquid crystal molecules 11BL in response to the application of a voltage that changes the orientation of the liquid crystal molecules 11BL. The light-controlling layer 11 switches between a transparent state and an opaque state based on the change in the orientation of the liquid crystal molecules 11BL. The transparent state of the light-controlling layer 11 is a state in which the outline of an object to be observed can be visually recognized through the light-controlling sheet 10. The opaque state of the light-controlling layer 11 is a state in which the outline of an object to be observed cannot be visually recognized through the light-controlling sheet 10.

[0032] The light-controlling sheet 10 in FIG. 1 shows a state in which no voltage is applied to change the orientation. When no voltage is applied to the light-controlling layer 11 to change the orientation, the orientation direction of the liquid crystal molecules 11BL located in each domain 11D is random. Light incident on the light-controlling sheet 10 from either of the pair of transparent substrates 13 is scattered in various directions in the light-controlling layer 11. As a result, the normal-type light-controlling layer 11 is in an opaque state, which is a cloudy state, when no voltage is applied. The light-controlling layer 11 in the opaque state may be cloudy white, or the light-controlling layer 11 may contain a pigment and be cloudy colored.

[0033] When the light-controlling layer 11 is in an opaque state, the transmitted image clarity of the light-controlling sheet 10 in accordance with JIS K 7374:2007 is 47% or less. The transmitted image clarity is the transmitted image clarity when the optical comb width is set to 0.125 mm. If the transmitted image clarity of the light-controlling sheet 10 is 47% or less, the contour of the observed object can be made sufficiently visually unrecognizable through the light-controlling sheet 10.

[0034] When the light-controlling layer 11 is in an opaque state, the clarity value of the light-controlling sheet 10 is 71% or less. This makes it possible to obtain the same effect as when the transmitted image clarity of the light-controlling sheet 10 is 47% or less.

[0035] When the light-control layer 11 is in an opaque state, the haze of the light-control sheet conforming to JIS K 7136:2000 is preferably 95% or more. This makes it possible to make the contour of the object to be observed unrecognizable, as well as the presence or absence of the object unrecognizable.

[0036] As shown in Figure 2, when a voltage that changes the orientation of the liquid crystal molecules 11BL is applied from the drive circuit 10D to the light-controlling layer 11, the orientation of the multiple liquid crystal molecules 11BL changes from a random orientation to a direction that transmits light. For example, each liquid crystal molecule 11BL changes its orientation so that the long axis of the liquid crystal molecule 11BL is approximately perpendicular to the plane in which the light-controlling layer 11 extends. Light that enters the light-controlling sheet 10 from either of the pair of transparent substrates 13 is transmitted through the light-controlling layer 11 with almost no scattering in the light-controlling layer 11. As a result, the normal-type light-controlling layer 11 becomes transparent when a voltage is applied.

[0037] A reverse-type light-control sheet and a light-control device including the same will be described with reference to Figures 3 and 4. Figure 3 shows the cross-sectional structure of the reverse-type light-control layer 11 when it is in a transparent state, and Figure 4 shows the cross-sectional structure of the reverse-type light-control layer 11 when it is in an opaque state.

[0038] 3, the reverse-type light-controlling sheet 20 includes a pair of alignment layers 21 in addition to a light-controlling layer 11, a pair of transparent electrode layers 12, and a pair of transparent substrates 13. The pair of alignment layers 21 sandwich the light-controlling layer 11 in the thickness direction of the light-controlling layer 11 and are located closer to the center of the light-controlling layer 11 in the thickness direction than the pair of transparent electrode layers 12.

[0039] One alignment layer 21 is located between the light control layer 11 and one transparent electrode layer 12, and applies an alignment regulating force to the liquid crystal molecules 11BL. The other alignment layer 21 is located between the light control layer 11 and the other transparent electrode layer 12, and applies an alignment regulating force to the liquid crystal molecules 11BL. The alignment layer 21 is made of a material such as an organic compound, such as polyimide, polyamide, polyvinyl alcohol, or a cyanide compound; an inorganic compound, such as silicone, silicon oxide, or zirconium oxide; or a mixture of these.

[0040] When each alignment layer 21 is a vertical alignment layer, the alignment direction of the liquid crystal molecules 11BL located in each domain 11D is vertical when no voltage that changes the alignment of the liquid crystal molecules 11BL is applied to the light control layer 11. Light that enters the light control sheet 20 from either of the pair of transparent substrates 13 passes through the light control layer 11 with almost no scattering in the light control layer 11. As a result, the reverse-type light control layer 11 is in a transparent state when no voltage that changes the alignment of the liquid crystal molecules 11BL is applied.

[0041] As shown in Figure 4, when a voltage that changes the orientation of the liquid crystal molecules 11BL is applied from the drive circuit 10D to the light-controlling layer 11, the orientation of the multiple liquid crystal molecules 11BL changes, for example, from vertical to horizontal. At this time, each liquid crystal molecule 11BL is located in the domain 11D so that the long axis of the liquid crystal molecule 11BL extends along the plane in which the light-controlling layer 11 extends. Light that enters the light-controlling sheet 20 from either of the pair of transparent substrates 13 is scattered by the light-controlling layer 11. As a result, the reverse-type light-controlling layer 11 becomes opaque when a voltage that changes the orientation of the liquid crystal molecules 11BL is applied.

[0042] The transmitted image clarity value and clarity value of the reverse-type light-adjusting sheet 20 are also the same as those of the normal-type light-adjusting sheet 10. That is, when the light-adjusting layer 11 is in an opaque state, the transmitted image clarity of the light-adjusting sheet 20, which complies with JIS K 7374:2007 and when the optical comb width is set to 0.125 mm, is 47% or less. Furthermore, when the light-adjusting layer 11 is in an opaque state, the clarity value of the light-adjusting sheet 20 is 71% or less. Furthermore, when the light-adjusting layer 11 is in an opaque state, the transmitted image clarity value of the light-adjusting sheet 20, which complies with JIS K 7374:2007 and when the optical comb width is set to 0.125 mm, is 47% or less. It is preferable that the haze of the light controlling sheet 20 conforming to 7136:2000 is 95% or more.

[0043] Here, the transmitted image clarity value and clarity value are greatly affected by the degree of narrow-angle scattering that occurs in the dimming sheets 10 and 20, but as mentioned above, it is not clear how they depend on the components of the dimming layer 11.

[0044] On the other hand, in a normal-type light-controlling layer 11, the transmitted image clarity and clarity values ​​tend to decrease as the applied voltage decreases. In a reverse-type light-controlling layer 11, the transmitted image clarity and clarity values ​​tend to decrease as the applied voltage increases. A light-controlling device incorporating the light-controlling sheets 10 and 20 requires predetermined values ​​for transmitted image clarity and clarity, so the voltage applied to the light-controlling sheets 10 and 20 is adjusted to achieve a predetermined opacity. However, adjusting the opacity by changing the applied voltage complicates the drive circuit 10D and the initial setup of the drive circuit 10D, and also causes significant variations in the power consumption of the light-controlling device.

[0045] In this regard, the inventors have found that when the concentration of the liquid crystal composition is within a predetermined range, a decrease in the average domain size results in minimum values ​​for the clarity and sharpness of the transmitted image. That is, the inventors have found that when the following condition 1 is satisfied, the minimum values ​​for the clarity and sharpness of the transmitted image are near the center of the range of the average size indicated by the following condition 2. The light controlling sheets 10 and 20 of the present embodiment satisfy the following conditions 1 and 2. (Condition 1) The concentration of the liquid crystal composition is 37% or more and 55% or less. (Condition 2) The average size of the domains is 1.0 μm or more and 1.55 μm or less.

[0046] The concentration of the liquid crystal composition is the ratio of the weight of the liquid crystal composition 11B to the weight of the light control layer 11. The concentration of the liquid crystal composition is a parameter that roughly corresponds to the blending ratio of the liquid crystal molecules 11BL to the light control layer 11. The concentration of the liquid crystal composition is a parameter related to the density of the element that contributes to the opacity of the light control sheets 10, 20. The element that contributes to the opacity of the light control sheets 10, 20 is the liquid crystal composition 11B that fills one domain 11D.

[0047] Regarding the elements that contribute to the opacity of the light controlling sheet 10, 20 that satisfies conditions 1 and 2, the number of elements present per unit volume and the size of the elements can be approximately specified. Note that if the concentration of the liquid crystal composition is 37% or higher, sufficient contrast between the transparent state and the opaque state can be obtained. Furthermore, if the concentration of the liquid crystal composition is 55% or lower, the liquid crystal composition can be sufficiently dissolved in the monomer for forming the polymer network 11A. In addition, near the center of the average size range defined by condition 2, the transmitted image sharpness and clarity have minimum values. Therefore, even if the size of the domains 11D varies, it is easy to distribute a large number of domains 11D within the above-mentioned conditions for achieving opacity. The conditions for achieving opacity are the number of domains 11D per unit volume and the average size of the domains 11D. This makes it possible to achieve the opacity of the light controlling sheet 10, 20 such that the outline of an object is visually indiscernible, while suppressing the variation in opacity. This makes it possible to adjust the voltage to achieve an opacity that makes the outline of the object to be observed unrecognizable, thereby reducing the complexity of the drive circuit 10D and the initial setup of the drive circuit 10D. Furthermore, it also makes it possible to uniformize the voltage applied to the light controlling sheets 10 and 20, thereby reducing variations in the power consumption of the light controlling device.

[0048] [Transmission image clarity] Next, a method for measuring the clarity of a transmitted image in the opaque state will be described with reference to Figures 5 and 6. As described above, the clarity of a transmitted image is a value measured by a method conforming to JIS K 7374:2000. In the normal-type light-control sheet 10, the opaque state is defined as a state in which no voltage is applied to the light-control layer 11. In the reverse-type light-control sheet 20, the opaque state is defined as a state in which a predetermined reference voltage is applied to the light-control layer 11.

[0049] As shown in FIG. 5, the transmitted image clarity measuring device 30 includes a light source 31, an optical comb 32, and a light receiving unit 33. In the measuring device 30, the light controlling sheet 10 or 20 to be measured is placed between the light source 31 and the optical comb 32. When measuring the transmitted image clarity, the optical comb 32 moves at a constant speed along a plane perpendicular to the direction in which the light source 31, the light controlling sheet, and the optical comb 32 are arranged. In the optical comb 32, the width of the shielding portions 32a that block light along the direction in which the optical comb 32 moves is the optical comb width. In the optical comb 32, the width of the shielding portions 32a and the width of the slits are equal to each other in the direction in which the optical comb 32 moves. In this embodiment, the optical comb width is 0.125 mm.

[0050] As shown in Figure 6, the amount of light transmitted through the optical comb 32, in other words, the amount of light received by the light receiving unit 33, changes periodically. The maximum amount of light received by the light receiving unit 33 is the maximum light amount M, and the minimum amount of light is the minimum light amount MB. The maximum light amount M is the amount of light obtained when light transmitted through the light controlling sheets 10, 20 is not blocked by the optical comb 32. The minimum light amount MB is the amount of light obtained when light transmitted through the light controlling sheets 10, 20 is blocked by the optical comb 32. The transmitted image clarity C(n) (%) when the optical comb width is n can be calculated by the following formula (1) using the maximum light intensity M and the minimum light intensity MB. C(n) =100×(M-MB) / (M+MB) … Equation (1)

[0051] [Clarity] Next, a method for measuring clarity in the opaque state will be described with reference to FIG. 7. FIG. 7 schematically shows an example of a measuring device used to measure clarity. In the normal-type light-controlling sheet 10, the opaque state is defined as a state in which no voltage is applied to the light-controlling layer 11. In the reverse-type light-controlling sheet 20, the opaque state is defined as a state in which a predetermined reference voltage is applied to the light-controlling layer 11.

[0052] As shown in FIG. 7, clarity measurement device 40 includes an irradiation unit 41, a light receiving unit 42, and an integrating sphere 43. Irradiation unit 41 includes a light source 41A and a lens 41B. Light source 41A is a white LED, and lens 41B converts the light emitted by light source 41A into parallel light. Light receiving unit 42 includes a central sensor 42C and an outer peripheral sensor 42R. Central sensor 42C and outer peripheral sensor 42R have annular shapes with the same central axis. Outer peripheral sensor 42R is located outside central sensor 42C. Note that measurement device 40 can be used not only to measure the clarity of the object to be measured, but also to measure haze. Integrating sphere 43 of measurement device 40 is used only when measuring haze.

[0053] In the measuring device 40, the light controlling sheets 10, 20 to be measured are placed between the irradiation unit 41 and the integrating sphere 43. In this embodiment, the diameter of the beam of collimated light LP emitted from the lens 41B is 14 mm. The light transmitted through the light controlling sheets 10, 20 includes straight light LS that travels straight along the optical axis of the collimated light LP that entered the light controlling layer 11, and narrow-angle scattered light LNS that does not include the straight light LS and has an angle with respect to the optical axis of the collimated light LP within ±2.5°. The range of the angle that the straight light LS forms with the optical axis of the collimated light LP is determined by the specifications of the measuring device 40, for example, so that it is substantially 0° within the range in which the collimated light LP travels in the absence of the light controlling sheets 10, 20.

[0054] In the light receiving unit 42, the central sensor 42C receives the straight light LS, and the peripheral sensor 42R receives the narrow-angle scattered light LNS. Of the light that has passed through the light-admitting layer 11, the amount of straight light LS received by the central sensor 42C is the central light amount LC, and the amount of narrow-angle scattered light LNS received by the peripheral sensor 42R is the peripheral light amount LR. The clarity value is calculated using the following equation (2): 100×(LC-LR) / (LC+LR) … Formula (2)

[0055] As described above, the haze of the light-controlling sheet can be measured using the measuring device 40. The haze is measured by a method conforming to JIS K 7136:2000. When measuring the haze using the measuring device 40, the light-receiving unit arranged in the integrating sphere 43 receives light that has passed through the light-controlling sheet.

[0056] Haze is the percentage of transmitted light that deviates by 2.5° or more from the incident light due to forward scattering among the transmitted light that passes through the object to be measured. In measuring haze, light whose angle with respect to the optical axis of the above-mentioned parallel light LP is less than ±2.5° is parallel light, and light whose angle with respect to the optical axis is ±2.5° or more is wide-angle scattered light. The transmittance of wide-angle scattered light is defined as diffuse transmittance Td, the transmittance of parallel light is defined as parallel transmittance Tp, and the sum of parallel transmittance Tp and diffuse transmittance Td is defined as total light transmittance Tt. In this case, haze is the proportion of diffuse transmittance Td in total light transmittance Tt.

[0057] As described above, it is possible to measure clarity and haze using the measuring device 40. However, clarity and haze represent different properties in the light controlling sheets 10 and 20. Transmission image clarity and haze also represent different properties in the light controlling sheets 10 and 20. Note that transmission image clarity and clarity represent equivalent properties in the light controlling sheets 10 and 20, and are interchangeable parameters.

[0058] Haze indicates the properties of the light controlling sheets 10, 20 based on wide-angle scattered light. Haze indicates the overall degree of cloudiness of the light controlling sheets 10, 20 perceived by an observer when visually observing the light controlling sheets 10, 20, for example, the overall degree of whitish discoloration of the light controlling sheets 10, 20. For example, the greater the haze in the light controlling sheets 10, 20, the hazier the observed object appears to the observer.

[0059] Clarity indicates the properties of the light-adjusting sheets 10 and 20 based on narrow-angle scattered light. Clarity indicates how clear the boundary between the object being observed and other objects, or how clear a small part of the object being observed, is. For example, the smaller the clarity value of the light-adjusting sheets 10 and 20, the blurrier the outline of the object being observed through the light-adjusting sheets 10 and 20 becomes; in other words, the sharpness of the object being observed decreases.

[0060] When the opacity of the light-controlling sheets 10 and 20 is determined by haze, the contour of the object being observed may be clear in some cases, and unclear in other cases, even if the degree of opacity of the light-controlling sheets 10 and 20 is sufficient. When the light-controlling sheets 10 and 20 are visually inspected by an observer, this difference in the degree of contour blurring is perceived by the observer as a difference in the degree of opacity. As a result, a discrepancy occurs between the opacity due to haze and the opacity perceived visually.

[0061] On the other hand, when the opacity of the light-controlling sheets 10, 20 is determined by the clarity range, the smaller the clarity value, the greater the blurriness of the contours of the observed object. As a result, the discrepancy between the opacity determined by the clarity and the opacity perceived by the eye is reduced. Furthermore, by keeping the clarity value within the above-mentioned range (≦71%), the blurriness of the contours of the observed object is ensured. Such light-controlling sheets 10, 20 are particularly useful for use in situations where the distance from the light-controlling sheets 10, 20 to the observed object is short, the illumination range of the light source illuminating the observed object is narrow, or the amount of light irradiating the observed object is large.

[0062] Note that when the clarity of transmitted image is used to evaluate the opacity of the light controlling sheets 10 and 20, the same effect as when the clarity of transmitted image is used to evaluate the opacity can be obtained. In other words, the clarity of transmitted image can prevent a discrepancy from occurring between the opacity determined by the clarity of transmitted image and the opacity perceived visually.

[0063] [Average Domain Size] Next, we will explain how to measure the average domain size. The average domain size is determined by observing a cross section of the polymer network 11A using an electron beam scanning microscope. The polymer network 11A is sandwiched between a pair of transparent electrode layers 12 and is obtained by removing the liquid crystal composition 11B from the light-controlling layer 11 sandwiched between the pair of transparent electrode layers 12.

[0064] For example, a rectangular sheet piece having a side length of 10 cm is cut out from the light control sheet 10, 20. Next, the sheet piece is immersed in an organic solvent such as isopropyl alcohol that dissolves the liquid crystal composition 11B but does not dissolve the polymer network 11A, thereby removing the liquid crystal composition 11B from the sheet piece.

[0065] Next, the cross section of the sheet piece from which liquid crystal composition 11B has been removed is imaged using an electron scanning microscope. At this time, images are obtained using the electron scanning microscope at a magnification of 1000 times for 30 rectangular regions arbitrarily selected from the cross section of the sheet piece. Note that each rectangular region is selected so that the distance between two adjacent rectangular regions is at least 1 mm.

[0066] Next, the domain sizes of 10 domains 11D randomly selected from one image are measured, and the average value of the remaining 8 domain sizes, excluding the maximum and minimum values, is calculated, and the calculated average value is used as the representative value of the domain size for one image.Then, the average value of the representative values ​​of the domain sizes for 30 images is calculated, and the calculated value is used as the average domain size.At this time, for domains 11D having a circular shape in the image, the diameter of the domain 11D is measured as the domain size.For domains 11D having an elliptical shape in the image, the major axis of the domain 11D is measured as the domain size.For domains 11D having an irregular shape in the image, the diameter of a circle circumscribing the domain 11D is measured as the domain size.

[0067] [How to manage dimming devices] The method for managing a light controlling sheet is used in a method for manufacturing a light controlling sheet. The method for managing a light controlling sheet determines whether the light controlling sheet is normal. The conditions for determining whether the light controlling sheet is normal include the above conditions 1 and 2.

[0068] The method for manufacturing a light-adjusting sheet includes manufacturing a roll of light-adjusting sheet that satisfies condition 1 or a large-sized light-adjusting sheet that satisfies condition 1, and cutting out sheet pieces from the manufactured light-adjusting sheet. The method for manufacturing a light-adjusting sheet also includes measuring the average size of domains in the cut-out sheet pieces. The method for manufacturing a light-adjusting sheet also includes determining that a light-adjusting sheet whose average domain size satisfies condition 2 is normal, and determining that a light-adjusting sheet whose average domain size does not satisfy condition 2 is abnormal.

[0069] According to this manufacturing method, the opacity of the light-controlling sheet can be adjusted so that the contour of the object being observed is not visually recognizable, and variation in opacity between light-controlling sheets can be reduced.

[0070] [Visual evaluation] Next, we will explain the relationship between haze, transmitted image clarity, and clarity and the visually perceived opacity of the opaque light-adjusting sheet. Note that the normal-type light-adjusting sheet 10 and the reverse-type light-adjusting sheet 20 have similar relationships between each parameter and the visually perceived opacity, so the following will explain the evaluation using the normal-type light-adjusting sheet 10.

[0071] The visually perceived opacity was evaluated by placing a fluorescent lamp LT with a light output of approximately 3,500 lm 80 cm behind the opaque light-control sheet, and visually observing the sheet from a position 20 cm in front of the sheet. The observer's viewpoint, the light-control sheet, and the fluorescent lamp LT were all positioned on the same straight line. The visual ranking was given as 1st, 2nd, 3rd, 4th, and 5th, in order of the level where the fluorescent lamp LT was closest to the observer.

[0072] The transmitted image clarity was measured using an image clarity measuring instrument (ICM-1T, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7374:2007. The haze was measured using a haze meter (NDH7000SD, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136:2000. The clarity was measured using a haze / transparency measuring instrument (Haze Guard i, manufactured by BYK-Gardner).

[0073] The measured values ​​of haze, transmitted image clarity, and clarity at each visual ranking are shown in Figure 8. The results of imaging the light controlling sheet 10 from the observation side at each visual ranking are shown in Figures 9(a)(b)(c)(d)(e).

[0074] As shown in Figure 8, the transmitted image clarity values ​​for the light controlling sheets 10, in order from highest visual ranking to lowest, are 30.4%, 36.5%, 42.6%, 51.5%, and 56.2%. The clarity values ​​for the light controlling sheets 10, in order from highest visual ranking to lowest, are 49.0%, 64.6%, 66.8%, 75.8%, and 81.7%. As such, the transmitted image clarity values ​​and clarity values ​​decrease as the visual ranking increases.

[0075] As shown in Figure 9(a), the first-place light-controlling sheet has a cloudy white color over almost the entire surface, making it impossible to visually recognize the outline of the fluorescent light LT. As shown in Figures 9(b) and 9(c), the second- and third-place light-controlling sheets also have a faded white color in parts, making it impossible to visually recognize the outline of the fluorescent light LT. In contrast, as shown in Figures 9(d) and 9(e), the fourth- and fifth-place light-controlling sheets make it possible to visually recognize part of the outline of the fluorescent light LT. In particular, as shown in Figure 9(e), the fifth-place light-controlling sheet 10 makes it possible to visually recognize the bottom edge of the outline of the fluorescent light LT.

[0076] Thus, clarity and transmitted image clarity correspond to the opacity perceived by the eye in the range of higher opacity. If the transmitted image clarity value is 47% or less, sufficient opacity is obtained so that the outline of the fluorescent lamp LT is not visible. If the clarity value is 71% or less, sufficient opacity is obtained so that the outline of the fluorescent lamp LT is not visible.

[0077] Returning to Figure 8, the haze values ​​for the light-control films, in descending order of visual ranking, are 98.5%, 98.2%, 98.5%, 97.9%, and 98.1%. As such, the haze has a very low correlation with the visual ranking in the range of higher opacity. In the range of higher opacity, the haze does not match the opacity perceived by the eye.

[0078] [Relationship between average domain size and clarity] Next, we will explain the relationship between the average size of the domains in the light-adjusting sheet and clarity. Note that the normal-type light-adjusting sheet 10 and the reverse-type light-adjusting sheet 20 have similar relationships between the average size of the domains and clarity, so we will explain an example using the normal-type light-adjusting sheet 10 below.

[0079] First, formulations 1 to 3 with different concentrations of the liquid crystal composition were prepared as the light controlling sheet 10. The concentration of the liquid crystal composition in formulation 1 was 41.5%. The concentration of the liquid crystal composition in formulation 2 was 42.5%. The concentration of the liquid crystal composition in formulation 3 was 50.0%.

[0080] Next, for seven examples having a liquid crystal composition concentration of Blend 1 (=41.5%), the exposure conditions for forming the switchable layer 11 were changed, thereby obtaining seven test examples with different average domain sizes within Blend 1. Furthermore, for five examples having a liquid crystal ratio of Blend 2 (=42.5%), the exposure conditions for forming the switchable layer 11 were changed, thereby obtaining five test examples with different average domain sizes within Blend 2. Furthermore, for five examples having a liquid crystal composition concentration of Blend 3 (=50.0%), the exposure conditions for forming the switchable layer 11 were changed, thereby obtaining five test examples with different average domain sizes within Blend 3.

[0081] Then, following the clarity measurement method described above, a haze / transparency measuring device (Hazegard i, manufactured by BYK-Gardner) was used to measure the clarity value for each test example. Additionally, following the method for measuring the average domain size described above, the average domain size for each test example was measured. The relationship between the average domain size measurements and the clarity measurements is shown in Figure 10.

[0082] As shown in Figure 10, in the light-control sheet 10 of Formula 1, when the average domain size is 1.54 μm, the clarity is 85.1%. When the average domain size is in the range of 1.40 μm or more and 1.54 μm or less, the clarity decreases from 85.1% to 47% as the average domain size decreases. On the other hand, when the average domain size is in the range of 0.83 μm or more and 1.40 μm or less, the clarity increases from 47% to 79.4% as the average domain size decreases.

[0083] That is, in the light control sheet 10 of Blend 1, the clarity has a minimum value when the average domain size is 1.40 μm. The clarity value is located on a U-shaped curve with the average domain size (= 1.40 μm) that gives the minimum value as its base.

[0084] In the light-controlling sheet 10 of Blend 2, when the average domain size is 1.65 μm, the clarity is 73.0%. When the average domain size is in the range of 1.28 μm or more and 1.65 μm or less, the clarity decreases from 73.0% to 56.5% as the average domain size decreases. On the other hand, when the average domain size is in the range of 0.90 μm or more and 1.28 μm or less, the clarity increases from 56.5% to 86.2% as the average domain size decreases.

[0085] That is, in the light control sheet 10 of Blend 2, the clarity has a minimum value when the average domain size is 1.28 μm. The clarity value is located on a U-shaped curve with the average domain size (= 1.28 μm) that gives the minimum value as its base.

[0086] In the light-controlling film 10 of Blend 3, when the average domain size is 1.58 μm, the clarity is 78.5%. When the average domain size is in the range of 1.28 μm to 1.58 μm, the clarity decreases from 78.5% to 44.4% as the average domain size decreases. On the other hand, when the average domain size is in the range of 0.90 μm to 1.28 μm, the clarity increases from 44.4% to 80.7% as the average domain size decreases.

[0087] That is, in the light control sheet 10 of Blend 3, the clarity has a minimum value when the average domain size is 1.28 μm. The clarity value is located on a U-shaped curve with the average domain size (= 1.28 μm) that gives the minimum value as its base.

[0088] As shown in the visual evaluation above, the opacity at which the outline of the observed object is not discernible by the naked eye is in the range where the clarity value is 71% or less. Furthermore, if the average domain size is 1.0 μm or more and 1.55 μm or less, the clarity value is 71% or less, and opacity at which the outline of the observed object is not discernible by the naked eye is obtained. Additionally, if the average domain size is 1.0 μm or more and 1.55 μm or less, the clarity value has a minimum value near the center of this range. Therefore, even if the size of the domains 11D varies, a large number of domains 11D are likely to be distributed within the size range that achieves opacity at which the outline of the observed object is not discernible by the naked eye. As a result, variation in the opacity of the light-control sheet can be suppressed.

[0089] As described above, according to the above embodiment, the following effects can be obtained. (1) If the light-controlling sheets 10 and 20 satisfy conditions 1 and 2, it is possible to distribute a large number of domains 11D within a range that achieves opacity that makes the contours of the object being observed visually unrecognizable. As a result, it is possible to suppress variations in the opacity of the light-controlling sheets 10 and 20.

[0090] (2) Since the clarity of the light-controlling sheets 10, 20 is 71% or less, the light-controlling sheets 10, 20 that make the contours of the object of observation sufficiently invisible to the eye can be obtained with reduced variation in opacity.

[0091] (3) Since the transmitted image clarity of the light controlling sheets 10, 20 is 47% or less, the light controlling sheets 10, 20 that make the contour of the object to be observed sufficiently unrecognizable can be obtained with reduced variation in opacity.

[0092] (4) In particular, in the case of the reverse-type light-controlling sheet 20, the variation in opacity of the light-controlling sheet 20 is suppressed, which in turn makes it possible to suppress the adjustment of opacity by changing the applied voltage, thereby suppressing the complexity of the driving device, the complication of initial setting, and the variation in power consumption of the light-controlling device.

[0093] The above embodiment can be modified as follows. The light-controlling sheets 10 and 20 may further include a barrier layer that covers the end faces of the light-controlling layer 11 and the surface of the transparent electrode layer 12. The barrier layer may have at least one of a gas barrier function and an ultraviolet barrier function.

[0094] The light-controlling sheets 10 and 20 may further include a light-transmitting substrate that increases the mechanical strength of the light-controlling sheet. Examples of materials that can be used to form the light-transmitting substrate include transparent inorganic materials such as glass and silicon, and transparent organic materials such as polymethacrylate resin, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl alcohol, polycarbonate, polyvinyl chloride, polyimide, and polysulfone. In the normal-type light-control sheet 10, the opaque state of the light-control layer 11 may be achieved by applying a voltage lower than that required for the transparent state.

[0095] The light-adjusting device can further include a control unit that changes the opacity of the light-adjusting sheets 10, 20 between opacity with a clarity of 71% or less and opacity with a clarity of more than 71%. The control unit that controls the driving of the light-adjusting sheets 10, 20 has information such as a table for converting different clarities into voltages, and applies a voltage corresponding to the clarity specified by an external operating device to the drive circuit 10D. A light-adjusting device equipped with such a control unit can change the opacity of the light-adjusting sheets 10, 20 between visually imperceptible opacity and visually perceptible opacity, making it possible for the light-adjusting device to achieve the opacity desired by the user of the light-adjusting device.

[0096] The drive circuit 10D provided in the light control device may apply an equal voltage between the transparent electrode layers of two different light control sheets. Since variations in opacity among the light control sheets 20 are suppressed among multiple light control sheets 20, applying an equal voltage to each sheet makes it possible to achieve equal opacity for the two light control sheets. This also makes it possible to omit the function of changing the voltage for each light control sheet, thereby simplifying the drive circuit 10D.

[0097] [Note] The technical ideas that can be derived from the above embodiments and examples are described below. [Appendix 1] A method for managing a light-control sheet, comprising: The light-control sheet is a photochromic layer that changes between a transparent state and an opaque state; a pair of transparent electrode layers sandwiching the light control layer, The light-controlling layer is a transparent polymer layer having a plurality of domains; a liquid crystal composition filling the domains, determining whether the photochromic layer is normal; The conditions for determining that the light-modulating layer is normal include that the concentration of the liquid crystal composition in the light-modulating layer is 37% or more and 55% or less, and the average size of the domains is 1.0 μm or more and 1.55 μm or less. How to manage light-adjusting sheets. [Explanation of symbols]

[0098] LP...parallel light, LS...direct light, LNS...narrow-angle scattered light, M...maximum light intensity, MB...minimum light intensity, Td...diffuse transmittance, Tt...total light transmittance, Tp...parallel transmittance, LC...central light intensity, LR...peripheral light intensity, 10, 20...light-controlling sheet, 10D...driving circuit, 11...light-controlling layer, 11A...polymer network, 11B...liquid crystal composition, 11BL...liquid crystal molecules, 12...transparent electrode layer, 13...transparent substrate, 21...alignment layer, 30, 40...measuring device, 31...light source, 32...optical comb, 32a...shielding portion, 33...light-receiving portion, 41...irradiation portion, 41A...light source, 41B...lens, 42...light-receiving portion, 42C...central sensor, 42R...peripheral sensor, 43...integrating sphere.

Claims

1. a light-control layer configured to be changeable between a transparent state and an opaque state; A light-controlling sheet comprising a pair of transparent electrode layers sandwiching the light-controlling layer, The light-controlling layer is a transparent polymer layer having a plurality of domains; a liquid crystal composition filling each domain; the concentration of the liquid crystal composition in the light-modulating layer is 37% or more and 55% or less; the average size of the domains is in the range of 1.0 μm or more and 1.55 μm or less; When the clarity value of each of the light-adjusting sheets is measured for a plurality of light-adjusting sheets having different average domain sizes, a minimum value of the clarity exists within the range of the average domain size, The clarity is calculated by the following formula, where, among the light transmitted through the light controlling sheet, the light amount of the straight light that travels straight along the optical axis of the parallel light that entered the light controlling sheet is defined as the light amount LC, and the light amount of the narrow-angle scattered light whose angle with respect to the optical axis of the parallel light is within ±2.5° is defined as the light amount LR. 100×(LC-LR) / (LC+LR) Dimming sheet.

2. When the light-control layer is in the opaque state, the clarity of the light-control sheet is 71% or less. The light-controlling sheet according to claim 1 .

3. The transmitted image clarity of the light-modulating sheet is determined in accordance with JIS K 7374:2007 when the optical comb width is set to 0.125 mm, When the light-controlling layer is in the opaque state, the transmitted image clarity of the light-controlling sheet is 47% or less. The light-controlling sheet according to claim 1 or 2.

4. The light-controlling layer is sandwiched so that the entire surface thereof facing the transparent electrode layer is in contact with the transparent electrode layer. The light-controlling sheet according to claim 1 .

5. The transparent polymer layer is a polymer of an ultraviolet-polymerizable compound. The light-controlling sheet according to claim 1 .

6. the transparent polymer layer includes a spacer for maintaining the thickness of the light-controlling layer; The spacer has the same color as the color of the light-controlling layer. The light-controlling sheet according to claim 1 .

7. The light-controlling layer comprises a light-transmitting substrate. The light-controlling sheet according to claim 1 .

8. When in the opaque state, the haze of the light-controlling sheet in accordance with JIS K 7136:2000 is 95% or more. The light-controlling sheet according to claim 1 .

9. A method for managing a light-control sheet, comprising: The light-control sheet is a photochromic layer that changes between a transparent state and an opaque state; a pair of transparent electrode layers sandwiching the light control layer, The light-controlling layer is a transparent polymer layer having a plurality of domains; a liquid crystal composition filling the domains, determining whether the photochromic layer is normal; The conditions for determining that the light-modulating layer is normal include that the concentration of the liquid crystal composition in the light-modulating layer is 37% or more and 55% or less, and the average size of the domains is within the range of 1.0 μm or more and 1.55 μm or less, When the clarity value of each of the light-controlling sheets is measured for a plurality of light-controlling sheets having different average domain sizes, the minimum clarity value is found within the range of the average domain size, The clarity is calculated by the following formula, where, among the light transmitted through the light controlling sheet, the light amount of the straight light that travels straight along the optical axis of the parallel light that entered the light controlling sheet is defined as the light amount LC, and the light amount of the narrow-angle scattered light whose angle with respect to the optical axis of the parallel light is within ±2.5° is defined as the light amount LR. 100×(LC-LR) / (LC+LR) How to manage light-adjusting sheets.

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