Patent Publication Number: US-11036092-B2

Title: Light control unit and window light control plate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of International Application No. PCT/JP2018/042880, filed Nov. 20, 2018, which is based upon and claims the benefits of priority to Japanese Application No. 2017-226921, filed Nov. 27, 2017. The entire contents of all of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a light control unit and a window light control plate including the light control unit. 
     Discussion of the Background 
     A light control device includes a light control sheet and a driving circuit. The light control sheet has a light transmittance that varies between when a driving voltage is applied and when no driving voltage is applied. The driving circuit generates a driving voltage applied to the light control sheet.  FIG. 9  shows an example of a cross-sectional structure of the light control sheet. A light control sheet  100  includes a light control layer  110 , a transparent conductive layer  120 A and a transparent conductive layer  120 B which are a pair of conductive layers, and a transparent substrate  130 A and a transparent substrate  130 B which are a pair of substrates. The light control layer  110  is sandwiched between the transparent conductive layer  120 A and the transparent conductive layer  120 B, and the light control layer  110  and the transparent conductive layers  120 A and  120 B are sandwiched between the transparent substrate  130 A and the transparent substrate  130 B. The light control layer  110  is composed of, for example, a liquid crystal such as a polymer network liquid crystal (PNLC) (see, for example, JP 2006-162823 A). Furthermore, the light control sheet  100  includes a sealing section  140  that is located between the transparent conductive layer  120 A and the transparent conductive layer  120 B at an edge of the light control sheet  100 . The sealing section  140  has a function of preventing a liquid crystal composition contained in the light control layer  110  from leaking and preventing water or the like from seeping into the light control layer  110 . 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a light control unit includes a light control sheet which includes a light control layer and is to be bonded to a surface of a transparent plate having an edge portion to be held in a window frame, and a buffer member including a portion that has a higher indentation hardness and a larger thickness than the light control sheet. The buffer member is to be positioned outside an edge of the light control sheet in the edge portion of the transparent plate on the surface such that the buffer member makes contact with the window frame when the edge portion of the transparent plate is held in the window frame. 
     According to another aspect of the present invention, a window light control plate includes a transparent plate having an edge portion to be held in a window frame, a light control sheet bonded to a surface of the transparent plate and including a light control layer, and a buffer member which has a portion having a higher indentation hardness and a larger thickness than the light control sheet. The buffer member is positioned outside an edge of the light control sheet in the edge portion of the transparent plate on the surface such that the buffer member makes contact with the window frame when the edge portion of the transparent plate is held in the window frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  shows a planar structure of a window light control plate including a light control unit of an embodiment. 
         FIG. 2  shows a state in which a window including the window light control plate of the embodiment is approximately half opened. 
         FIG. 3  shows a state in which the window including the window light control plate of the embodiment is completely closed. 
         FIG. 4  shows a cross-sectional structure at an edge of the window light control plate of the embodiment. 
         FIG. 5  shows a state in which the edge of the window light control plate of the embodiment is held in a window frame. 
         FIG. 6  shows an example of a cross-sectional structure at an upper edge of the window light control plate of the embodiment. 
         FIG. 7  shows an example of a cross-sectional structure at a side edge of the window light control plate of the embodiment. 
         FIG. 8  shows a cross-sectional structure at an edge of a window light control plate of a modification. 
         FIG. 9  shows a cross-sectional structure of a conventional light control sheet. 
         FIG. 10  shows a state in which an edge of a conventional window light control plate is held in a window frame. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. 
     An embodiment of a light control unit and a window light control plate will be described with reference to  FIGS. 1 to 7 . 
     &lt;Basic Structure&gt; 
     A basic structure of the light control unit and the window light control plate will be described with reference to  FIGS. 1 to 4 . 
     As shown in  FIG. 1 , a window light control plate  10  includes a transparent plate  20  that functions as a window plate, and a light control unit  30  that is attached to the transparent plate  20 . The light control unit  30  includes a light control sheet  40  and a buffer member  50 . 
     The window light control plate  10  of the present embodiment is used as a component of a movable window device mounted to automobiles. Specifically, the window light control plate  10  is assembled to a door member of the vehicle. In the following description, an up direction is defined as a direction in which the window light control plate  10  is moved when a window including the window light control plate  10  is closed, and a down direction is defined as a direction in which the window light control plate  10  is moved when the window including the window light control plate  10  is opened. 
     The transparent plate  20  is a plate-shaped member, and has a support surface  21 S which is a surface to which the light control unit  30  is attached. The support surface  21 S is, for example, a surface facing inside a vehicle cabin, and supports the light control unit  30 . An edge of the transparent plate  20 , i.e., an outer peripheral portion of the transparent plate  20  includes a lower edge  22   a , an upper edge  22   b , and a side edge  22   c . Each of the lower edge  22   a , the upper edge  22   b , and the side edge  22   c  is a portion including an edge of the support surface  21 S, specifically, a portion including the entire thickness direction of the transparent plate  20  in a region in which the edge of the support surface  21 S is located. The lower edge  22   a  is located inside the door member, and even when the window light control plate  10  is moved upward/downward due to opening/closing of the window, the lower edge  22   a  is not exposed to the outside of the door member. 
     The light control sheet  40  and the buffer member  50  are bonded to the support surface  21 S. As viewed from a direction facing to the support surface  21 S, an outer edge of the light control sheet  40  is located inside an outer edge of the transparent plate  20 , and extends along an outer edge of the support surface  21 S. An edge of the light control sheet  40 , i.e., an outer peripheral portion of the light control sheet  40  includes a lower edge  41   a , an upper edge  41   b , and side edges  41   c . The lower edge  41   a  is overlapped with the lower edge  22   a  of the transparent plate  20 , the upper edge  41   b  is overlapped with the upper edge  22   b  of the transparent plate  20 , and the side edges  41   c  are overlapped with the side edges  22   c  of the transparent plate  20 . At the lower edge  41   a , the light control sheet  40  includes a first electrode  42 A and a second electrode  42 B which are electrodes for applying a driving voltage to the light control sheet  40 . The lower edge  41   a  of the light control sheet  40  may extend outward from the lower edge  22   a  of the transparent plate  20 , i.e., downward from the lower edge  22   a.    
     Each of the first electrode  42 A and the second electrode  42 B is connected to a driving circuit that generates a driving voltage applied to the light control sheet  40 . The driving circuit and the window light control plate  10  constitute a light control device. 
     On the support surface  21 S, the buffer member  50  is located outside the light control sheet  40 . In other words, as viewed from a direction facing to the support surface  21 S, the buffer member  50  is located between the outer edge of the light control sheet  40  and the outer edge of the transparent plate  20 . Specifically, the buffer member  50  is located at the upper edge  22   b  and the side edges  22   c  of the transparent plate  20 , and extends along the outer edge of the light control sheet  40  outside the upper edge  41   b  and the side edges  41   c  of the light control sheet  40 . The buffer member  50  has an upper edge buffer portion  51  and side edge buffer portions  52 . the upper edge buffer portion  51  is located at the upper edge  22   b  of the transparent plate  20  and extends along the upper edge  41   b  of the light control sheet  40 . The side edge buffer portion  52  is located at the side edges  22   c  of the transparent plate  20  and extends along the side edges  41   c  of the light control sheet  40 . The buffer member  50  may also be arranged outside the lower edge  41   a  of the light control sheet  40 . 
       FIG. 2  shows a state in which the window including the window light control plate  10  is approximately half opened, and  FIG. 3  shows a state in which the window including the window light control plate  10  is completely closed. 
     As shown in  FIGS. 2 and 3 , the window light control plate  10  is assembled to a door member  60 . Due to upward/downward movement of the window light control plate  10 , an opening  61 P defined by a window frame portion of the door member  60  is opened/closed. When the window is opened, the window light control plate  10  is moved downward, and when the window is closed, the window light control plate  10  is moved upward. In a state in which the window is completely opened, the window light control plate  10  is housed inside a door body  62  that constitutes a lower portion of the door member  60 , and the opening  61 P is completely opened. In a state in which the window is completely closed, the opening  61 P is completely closed by the window light control plate  10 . 
     The portion of the door member  60  that functions as a window frame is composed of an upper edge portion of the door body  62 , a door frame  63 , and a holding section  64 . The door frame  63  extends from the upper edge portion of the door body  62  and surrounds the upper side and the lateral sides of the opening  61 P. The holding section  64  is provided at an inner circumferential portion of the door frame  63 . The holding section  64  is, for example, a glass run, and has a structure in which an edge of the window light control plate  10  can be held. 
     An upper edge of the window light control plate  10  composed of the upper edge  22   b  of the transparent plate  20 , the upper edge buffer portion  51  of the buffer member  50 , and the upper edge  41   b  of the light control sheet  40  is exposed from the holding section  64  during at least part of the process of opening the window. While the window is completely closed, the upper edge of the window light control plate  10  is held in the holding section  64 . Thus, at an initial stage of the process of opening the window, the upper edge of the window light control plate  10  is moved out of the holding section  64  and exposed from the holding section  64 . At an edge stage of the process of closing the window, the upper edge of the window light control plate  10  enters the holding section  64  and held in the holding section  64 . 
     In a region inside the door frame  63 , side edges of the window light control plate  10  composed of the side edges  22   c  of the transparent plate  20 , the side edge buffer portions  52  of the buffer member  50 , and the side edges  41   c  of the light control sheet  40  are held in the holding section  64  both during the process of opening/closing the window and in a state in which the window is completely closed. Thus, the side edges of the window light control plate  10  are not exposed from the holding section  64 , and during the process of opening/closing the window, the side edges of the window light control plate  10  slide along the holding section  64  in a state of being held in the holding section  64 . 
     For ease of understanding,  FIGS. 1 to 3  show an example in which as viewed from a direction facing to the support surface  21 S, the window light control plate  10  has a substantially rectangular shape. The shape of the window light control plate  10  is not limited to this, and the window light control plate  10  may have a shape different from a rectangular shape. For example, the upper edge of the window light control plate  10  may extend obliquely with respect to a direction orthogonal to the vertical direction, or may have a curved shape. Furthermore, for example, the side edge of the window light control plate  10  may extend obliquely with respect to the vertical direction, or may have a curved shape. 
     Of the edge of the window light control plate  10 , the upper edge of the window light control plate  10  is a portion that is exposed from the holding section  64  during at least part of the process of opening the window, that is, a portion that is moved into/out of the holding section  64  when the window is opened/closed. Of the edge of the window light control plate  10 , the side edge of the window light control plate  10  is a portion that is not exposed from the holding section  64  in the opening  61 P, that is, a portion that slides within the holding section  64  when the window is opened/closed. 
     A structure of the edge of the window light control plate  10  will be described with reference to  FIG. 4 . 
     The transparent plate  20  is a transparent plate-shaped member composed of a single layer or a plurality of layers. The material of the transparent plate  20  is not particularly limited as long as the transparent plate  20  can be used as a window plate. The transparent plate  20  may be, for example, a glass plate made of single-plate glass, double glass, laminated glass, or the like, or an acrylic plate. 
     The light control sheet  40  includes a light control layer  43 , a transparent conductive layer  44 A and a transparent conductive layer  44 B which are a pair of conductive layers, and a transparent substrate  45 A and a transparent substrate  45 B which are a pair of substrates. The light control layer  43  is sandwiched between the transparent conductive layer  44 A and the transparent conductive layer  44 B, and the light control layer  43  and the transparent conductive layers  44 A and  44 B are sandwiched between the transparent substrate  45 A and the transparent substrate  45 B. The transparent conductive layer  44 A is electrically connected to the first electrode  42 A, and the transparent conductive layer  44 B is electrically connected to the second electrode  42 B. The light control layer  43 , the transparent conductive layers  44 A and  44 B, and the transparent substrates  45 A and  45 B constitute a light control multilayer  46 . 
     The light control layer  43  contains a liquid crystal composition. The light control layer  43  is composed of, for example, a polymer network liquid crystal, a polymer dispersed liquid crystal (PDLC), a nematic curvilinear aligned phase (NCAP) liquid crustal, or the like. For example, a polymer network liquid crystal has a three-dimensional mesh polymer network, and holds liquid crystal molecules in voids in the polymer network. The liquid crystal molecules contained in the light control layer  43  have, for example, positive dielectric anisotropy, and have a higher dielectric constant in a major axis direction of the liquid crystal molecules than in a minor axis direction of the liquid crystal molecules. The liquid crystal molecules are, for example, liquid crystal molecules based on a Schiff base, azo, azoxy, biphenyl, terphenyl, benzoic acid ester, tolan, pyrimidine, cyclohexanecarboxylic acid ester, phenylcyclohexane, or dioxane molecules. 
     Each of the transparent conductive layer  44 A and the transparent conductive layer  44 B is a conductive transparent layer. Examples of a material of the transparent conductive layers  44 A and  44 B include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide, and zinc oxide. 
     Each of the transparent substrate  45 A and the transparent substrate  45 B is a transparent substrate. The transparent substrates  45 A and  45 B may be, for example, a glass substrate, a silicon substrate, or a polymer film made of polyethylene, polystyrene, polyethylene terephthalate, polyvinyl alcohol, polycarbonate, polyvinyl chloride, polyimide, polysulfone, or the like. 
     A surface of the transparent substrate  45 B on a side opposite to the light control layer  43  is bonded to the support surface  21 S of the transparent plate  20  via an adhesive layer  48 . The adhesive layer  48  is transparent and is composed of, for example, an adhesive made of an acrylic resin, an epoxy resin, or the like. The adhesive layer  48  is one of the components of the light control sheet  40 . 
     The light control sheet  40  further includes a sealing section  47 . The sealing section  47  is located outside the light control multilayer  46 , and covers an edge surface of the light control multilayer  46  and an edge surface of the adhesive layer  48 . The sealing section  47  has a function of preventing seeping of liquid and gas into the light control layer  43  from the outside, and preventing leakage of the liquid crystal composition and the like from the light control layer  43 . The sealing section  47  is composed of, for example, an epoxy resin, an acrylic resin, or the like. The sealing section  47  only needs to cover at least the edge surface of the light control multilayer  46 . Thus, the edge surface of the adhesive layer  48  may be exposed from the sealing section  47 , or the adhesive layer  48  may extend to a position between the sealing section  47  and the transparent plate  20 . Furthermore, the sealing section  47  and the adhesive layer  48  may be composed of the same material to be a single continuous member. 
     When no driving voltage is applied to the light control layer  43 , the major axes of the liquid crystal molecules are irregularly oriented. Accordingly, light incident on the light control layer  43  is scattered and the light control sheet  40  appears whitish. Thus, when no driving voltage is applied to the light control layer  43 , the light control sheet  40  is opaque. On the other hand, when a driving voltage is applied between the transparent conductive layer  44 A and the transparent conductive layer  44 B through the first electrode  42 A and the second electrode  42 B, the liquid crystal molecules are aligned, and the major axes of the liquid crystal molecules are oriented in a direction of an electric field between the transparent conductive layers  44 A and  44 B. As a result, light is more likely to be transmitted through the light control layer  43  and the light control sheet  40  becomes transparent. 
     The buffer member  50  is composed of a synthetic rubber, a thermoplastic elastomer, or the like. In terms of preventing a reduction in visibility and designability of the window, in the buffer member  50 , at least the upper edge buffer portion  51  is preferably transparent. The buffer member  50  is bonded to the support surface  21 S of the transparent plate  20 , for example, via an adhesive layer (not shown). 
     In a thickness direction of the light control sheet  40 , the buffer member  50  has a higher hardness than the light control sheet  40 . Specifically, the buffer member  50  has a higher hardness than the light control multilayer  46  and the sealing section  47 . Furthermore, the buffer member  50  preferably has a higher hardness than the holding section  64 . The hardness mentioned in the present embodiment is indentation hardness exemplified by Shore hardness and durometer hardness. 
     The buffer member  50  has higher rigidity than the light control sheet  40 . Specifically, the buffer member  50  has higher rigidity than the light control multilayer  46  and the sealing section  47 . 
     A thickness Tk of the buffer member  50  is a maximum length from the support surface  21 S to a top of the buffer member  50  in the thickness direction of the light control sheet  40 . The top of the buffer member  50  is a portion of the buffer member  50  on a side opposite to a portion of the buffer member  50  attached to the support surface  21 S.  FIG. 4  shows an example in which the top of the buffer member  50  is flat and the entire buffer member  50  has a constant thickness. 
     A thickness Tc of the light control sheet  40  is a maximum thickness from the support surface  21 S to an outermost surface of the light control sheet  40  in the thickness direction of the light control sheet  40 .  FIG. 4  shows an example in which the sealing section  47  has a thickness of not more than a thickness of a multilayer including the light control multilayer  46  and the adhesive layer  48 . In this case, the thickness Tc of the light control sheet  40  is the thickness of the multilayer including the light control multilayer  46  and the adhesive layer  48 . The sealing section  47  may be raised from the light control multilayer  46 , and in this case, the thickness Tc of the light control sheet  40  is a maximum thickness of the sealing section  47 . 
     The thickness Tk of the buffer member  50  is larger than the thickness Tc of the light control sheet  40 . The buffer member  50  and the light control sheet  40  may be in contact with each other, but are preferably separated from each other. Thus, a gap G is preferably formed between the buffer member  50  and the sealing section  47 . 
     The holding section  64  is composed of, for example, a synthetic rubber, a thermoplastic elastomer, a synthetic resin, or the like. 
     The window light control plate  10  is manufactured, for example, by the following manufacturing method. First, a multilayer sheet including the light control layer  43 , the transparent conductive layers  44 A and  44 B, and the transparent substrates  45 A and  45 B is formed. Then, from the multilayer sheet, the control multilayer  46  having a shape corresponding to a shape of the transparent plate  20  is cut out or punched. Next, the light control multilayer  46  is bonded to the support surface  21 S of the transparent plate  20  via the adhesive layer  48 . Then, the sealing section  47  is formed to cover the edge surface of the light control multilayer  46  and the edge surface of the adhesive layer  48 . In this manner, the light control sheet  40  is formed. Subsequently, the buffer member  50  is arranged outside the light control sheet  40  to form the window light control plate  10 . The sealing section  47  may be formed after the buffer member  50  is arranged, or the buffer member  50  may be fixed to the support surface  21 S before the light control multilayer  46 . 
     The above manufacturing method improves efficiency in the manufacturing of the light control sheet  40  as compared with a manufacturing method in which for each light control multilayer  46 , a sealing structure is formed between two transparent substrates, i.e., the transparent substrates  45 A and  45 B, followed by injecting a liquid crystal between the transparent substrates  45 A and  45 B to form the light control layer  43 . Furthermore, since the light control multilayer  46  is formed by cutting out or punching from a multilayer sheet, the light control multilayer  46  having a shape corresponding to the shape of the transparent plate  20  can be easily formed. 
     &lt;Action&gt; 
     Action of the light control unit  30  and the window light control plate  10  will be described.  FIG. 5  shows a state in which the edge of the window light control plate  10  is held in the holding section  64 . 
     As shown in  FIG. 5 , since the buffer member  50  having a larger thickness than the light control sheet  40  is provided outside the light control sheet  40 , the top of the buffer member  50  is in contact with the holding section  64  at an outermost portion of the light control unit  30  in the thickness direction. Furthermore, since the buffer member  50  has a higher hardness, when a compression force is applied from the holding section  64 , the buffer member  50  is less likely to be compressed compared to the light control sheet  40 . Thus, the compression force applied from the holding section  64  is concentrated on the buffer member  50  at the outermost portion of the light control unit  30  in the thickness direction. Accordingly, the compression force in the thickness direction applied from the holding section  64  to the edge of the light control sheet  40  is smaller than in the case where the buffer member  50  is not arranged. Thus, compression of the edge of the light control sheet  40  is prevented, and as a result, a short circuit caused by contact between the transparent conductive layer  44 A and the transparent conductive layer  44 B is also prevented. 
     In the case where the buffer member  50  is not provided, when the upper edge of the window light control plate  10  is moved into the holding section  64 , the upper edge  41   b  of the light control sheet  40  also receives compression force from the holding section  64  in an edge surface direction which is a direction facing to an edge surface of the light control sheet  40 . As a result, the upper edge  41   b  of the light control sheet  40  may peel off from the transparent plate  20 . On the other hand, in the configuration of the light control unit  30  of the present embodiment, since the buffer member  50  is arranged outside the light control sheet  40 , the compression force applied in the edge surface direction from the holding section  64  to the upper edge  41   b  of the light control sheet  40  is small. Thus, the upper edge  41   b  of the light control sheet  40  is prevented from being peeled from the transparent plate  20 . 
     Furthermore, since the gap G is formed between the buffer member  50  and the sealing section  47 , even when the buffer member  50  is pressed by the holding section  64  and deformed to extend in the edge surface direction of the light control sheet  40 , the deformed buffer member  50  is prevented from pressing the edge surface of the light control sheet  40 . This also makes it possible to prevent the light control sheet  40  from being deformed or peeled off from the transparent plate  20 . 
     &lt;Configuration Example of Buffer Member&gt; 
     A preferred embodiment of a shape of the buffer member  50  will be described. 
     An example of the shape of the buffer member  50  at the upper edge of the window light control plate  10  will be described with reference to  FIG. 6 . Thus,  FIG. 6  shows an example of a cross-sectional shape of the upper edge buffer portion  51 . 
     As shown in  FIG. 6 , a surface of the upper edge buffer portion  51  includes a curved surface. Of both edges in the upper edge buffer portion  51  in the edge surface direction of the light control sheet  40 , i.e., in a width direction of the buffer member  50 , an edge closer to the light control sheet  40  is a first edge  53 , and an edge farther from the light control sheet  40  is a second edge  54 . In the cross section in the width direction, the first edge  53  has a first curved portion  55  that is curved with a curvature from a top of the upper edge buffer portion  51  toward the support surface  21 S. 
     As described above, when the window is opened, the upper edge of the window light control plate  10  moves out of the holding section  64 . At this time, starting with the first edge  53 , the upper edge buffer portion  51  moves from the inside of the holding section  64  to the outside of the holding section  64 . In the configuration in which the first edge  53  has the first curved portion  55 , when the upper edge buffer portion  51  moves to the outside of the holding section  64 , the first edge  53  is less likely to be caught in the holding section  64  as compared with a configuration in which the first edge  53  has a corner portion that is bent at a right angle from the top of the upper edge buffer portion  51 . Thus, the operation of opening the window of the window device is smoothly performed. 
     In the cross section in the width direction, the second edge  54  has a second curved portion  56  that is curved with a curvature from the top of the upper edge buffer portion  51  toward the support surface  21 S. 
     When the window is closed, the upper edge of the window light control plate  10  enters the holding section  64 . At this time, starting with the second edge  54 , the upper edge buffer portion  51  moves into the inside of the holding section  64  from the outside of the holding section  64 . In the configuration in which the second edge  54  has the second curved portion  56 , when the upper edge buffer portion  51  moves into the inside of the holding section  64 , the second edge  54  is less likely to be caught in the holding section  64  as compared with a configuration in which the second edge  54  has a corner portion that is bent at a right angle from the top of the upper edge buffer portion  51 . Thus, the operation of closing the window of the window device is smoothly performed. 
     The second curved portion  56  preferably has a smaller curvature than the first curved portion  55 . That is, the second curved portion  56  is preferably more gently curved than the first curved portion  55 . 
     As compared with the case in which the upper edge buffer portion  51  is moved out of the holding section  64 , when the upper edge buffer portion  51  is moved into the holding section  64 , a larger impact is applied from the holding section  64  to the upper edge buffer portion  51 , and a large force is instantaneously applied to the upper edge buffer portion  51 . The more the second curved portion  56  has a smaller curvature, when the upper edge buffer portion  51  is moved into the holding section  64 , the more the upper edge buffer portion  51  is gradually pressed by the holding section  64 , starting with an edge of the second edge  54 . Thus, the pressure applied from the holding section  64  is prevented from being concentrated on a specific portion of the upper edge buffer portion  51 . Therefore, durability of the buffer member  50  is improved and the operation of closing the window is more smoothly performed. 
     In the configuration in which the second curved portion  56  has a smaller curvature than the first curved portion  55 , the upper edge buffer portion  51  has a shape that reflects a difference in the force applied to the upper edge buffer portion  51  between when the upper edge buffer portion  51  is moved out of the holding section  64  and when the upper edge buffer portion  51  is moved into the holding section  64 . Therefore, the upper edge buffer portion  51  suitable for the upper edge of the window light control plate  10  is obtained. 
     An example of the shape of the buffer member  50  at the side edge of the window light control plate  10  will be described with reference to  FIG. 7 . Thus,  FIG. 7  shows an example of a cross-sectional shape of the side edge buffer portion  52 . 
     As shown in  FIG. 7 , the side edge buffer portion  52  has an extending portion  58  that is overlapped with the light control sheet  40  in the thickness direction of the light control sheet  40 . The extending portion  58  extends from a top of a main body  57  toward the side edges  41   c  of the light control sheet  40  and is in contact with the outermost surface of the light control sheet  40  on the side edges  41   c . The main body  57  is a portion of the side edge buffer portions  52  located outside the light control sheet  40  on the support surface  21 S. The main body  57  and the light control sheet  40  may be in contact with each other, or may be separated from each other. 
     In the above configuration, the side edge buffer portion  52  surrounds a space in the vicinity of the edge of the light control sheet  40 . This makes it possible to prevent water or water vapor due to rainwater or the like from seeping into the vicinity of the edge surface of the light control multilayer  46 . 
     As compared with the upper edge buffer portion  51  shown in  FIG. 6 , the side edge buffer portion  52  shown in  FIG. 7  has a large size in the width direction, and thus tends to be conspicuous. As described above, the side edge of the window light control plate  10  is not exposed from the holding section  64 . Thus, the side edge buffer portion  52  is located inside the holding section  64  and does not enter the opening  61 P, and is accordingly less likely to be visually recognized. Therefore, even when the side edge buffer portion  52  shown in  FIG. 7  is arranged at the side edge  22   c  of the transparent plate  20 , the side edge buffer portion  52  is rarely visually recognized. This makes it possible to prevent a reduction in visibility and designability of the window due to the conspicuous buffer member  50 . 
     When the buffer member  50  has a configuration in which the upper edge buffer portion  51  shown in  FIG. 6  is arranged at the upper edge  22   b  of the transparent plate  20  and the side edge buffer portion  52  shown in  FIG. 7  is arranged at the side edge  22   c  of the transparent plate  20 , the buffer member  50  can have a configuration in which at the upper edge at which the buffer member  50  is more likely to be visually recognized, visibility and designability of the window are prioritized, and at the side edge at which the buffer member  50  is less likely to be visually recognized, protection of the light control multilayer  46  is prioritized. Thus, it is possible to achieve the buffer member  50  in which the upper edge buffer portion  51  and the side edge buffer portion  52  have functions corresponding to their respective positions. 
     According to the configuration in which the buffer member  50  having a harder and thicker portion than the light control sheet  40  is arranged outside the light control sheet  40 , the effect of preventing compression of the edge of the light control sheet  40  is obtained regardless of the shape of the buffer member  50 . For example, the upper edge buffer portion  51  may only have one of the first curved portion  55  and the second curved portion  56 . Furthermore, for example, the upper edge buffer portion  51  and the side edge buffer portion  52  may have the same shape, the upper edge buffer portion  51  may have the shape of the side edge buffer portion  52  shown in  FIG. 7 , or the side edge buffer portion  52  may have the shape of the upper edge buffer portion  51  shown in  FIG. 6 . Furthermore, the buffer member  50  may have three or more portions having different cross-sectional shapes in the width direction. 
     As shown in  FIGS. 6 and 7 , in the cross section in the width direction, the thickness of the buffer member  50  in the thickness direction may not necessarily be constant, and the buffer member  50  may have a thinner portion than the light control sheet  40 . In short, the thickness Tk of the buffer member  50  which is the maximum length from the support surface  21 S to the top of the buffer member  50  only needs to be larger than the thickness Tc of the light control sheet  40 . In other words, the buffer member  50  only needs to have a thicker portion than the light control sheet  40 , and a hardness of the portion only needs to be higher than the hardness of the light control sheet  40 . 
     As the buffer member  50  has a larger width and thickness, the buffer member  50  has higher resistance against the pressure from the holding section  64 , and this improves the effect of preventing compression of the edge of the light control sheet  40 . However, the larger the width and thickness the buffer member  50  has, the more conspicuous the buffer member  50  tends to be. Thus, it is preferable to use at least one of a configuration in which the side edge buffer portion  52  has a larger width than the upper edge buffer portion  51 , and a configuration in which the side edge buffer portion  52  has a larger thickness than the upper edge buffer portion  51 . According to such a configuration, the buffer member  50  can have a configuration in which at the upper edge at which the buffer member  50  is more likely to be visually recognized, visibility and designability of the window are prioritized, and at the side edge at which the buffer member  50  is less likely to be visually recognized, enhancement of the effect of preventing compression of the edge of the light control sheet  40  is prioritized. 
     The buffer member  50  may be composed of a plurality of portions separated from each other. For example, a gap may be formed between the upper edge buffer portion  51  and the side edge buffer portion  52 , or the upper edge buffer portion  51  and the side edge buffer portion  52  may be composed of a plurality of portions arranged with a gap therebetween along the edge of the light control sheet  40 . 
     Furthermore, the buffer member  50  only needs to be arranged at a part of the edge of the transparent plate  20  held in the window frame, and for example, the buffer member  50  may only have one of the upper edge buffer portion  51  and the side edge buffer portion  52 . As compared with a configuration in which no buffer member  50  is arranged, in the configuration in which the buffer member  50  is arranged in at least part of the region outside the upper edge  41   b  and the side edges  41   c  of the light control sheet  40 , the effect of preventing compression of the edge of the light control sheet  40  is obtained at the portion at which the buffer member  50  is arranged. 
     In comparison between the upper edge and the side edge of the window light control plate  10 , since the upper edge is moved into/out of the holding section  64 , a large compression force is more likely to be applied from the holding section  64  to the upper edge. In particular, as described above, as compared with when the upper edge is moved out of the holding section  64 , when the upper edge is moved into the holding section  64 , a large force is more likely to be instantaneously applied to the upper edge, and thus compression of the edge of the light control sheet  40  is more likely to occur. Therefore, in the configuration in which the upper edge of the window light control plate  10  includes the buffer member  50 , the effect of preventing compression of the edge of the light control sheet  40  is high. 
     At the portion at which the buffer member  50  is not arranged, the edge of the light control sheet  40  may be located inside the edge of the transparent plate  20 . Thus, the edge of the light control sheet  40  may not enter the holding section  64  and be exposed in the opening  61 P. 
     As described above, according to the light control unit and the window light control plate of the present embodiment, the following effects are obtained. 
     (1) The buffer member  50  having a harder and thicker portion than the light control sheet  40  is located outside the edge of the light control sheet  40  at the edge of the support surface  21 S of the transparent plate  20 . According to this configuration, a compression force generated when the edge of the window light control plate  10  is held in the window frame acts more on the buffer member  50  than on the light control sheet  40 , and the buffer member  50  is less likely to be compressed than the light control sheet  40 . This makes it possible to prevent compression of the edge of the light control sheet  40  when the edge of the window light control plate  10  is held in the window frame. 
     (2) The light control sheet  40  includes the sealing section  47  that is located outside the light control multilayer  46  and seals the edge surface of the light control multilayer  46 . Such a configuration can prevent gas and liquid from seeping into/out of the light control multilayer  46 . Since the sealing section  47  which is a member for sealing the edge surface of the light control multilayer  46  is a separate member from the buffer member  50  which is a member to which a compression force from the window frame is to be applied, the members can be formed as members specialized in their respective functions, and thus the functions of the members can be improved. Furthermore, the light control sheet  40  can be formed by the method in which the light control multilayer  46  which is processed into a desired shape is bonded to the transparent plate  20 , followed by forming the sealing section  47 . Accordingly, efficiency in the manufacturing of the light control sheet  40  is improved as compared with a configuration in which a sealing structure is formed inside the light control multilayer  46 . 
     (3) According to the configuration in which the gap G is formed between the sealing section  47  and the buffer member  50 , even when the buffer member  50  is pressed by the window frame and deformed to extend in the width direction, the deformed buffer member  50  can be prevented from pressing the light control sheet  40 . 
     (4) According to the configuration in which the buffer member  50  has the upper edge buffer portion  51  and the side edge buffer portion  52 , in the configuration in which the upper edge and the side edge of the window light control plate  10  are held in the window frame, compression of the edge of the light control sheet  40  can be prevented at both the upper edge and the side edge. 
     (5) According to the configuration in which the cross-sectional shape of the upper edge buffer portion  51  in the width direction differs from the cross-sectional shape of the side edge buffer portion  52  in the width direction, the buffer member  50  can be configured to have a shape suitable for the upper edge and the side edge of the window light control plate  10 , considering, for example, the presence or absence of exposure from the window frame at the upper edge and the side edge of the window light control plate  10  and differences in position to which a compression force is applied and in magnitude of the compression force between the upper edge and the side edges of the window light control plate  10 . 
     (6) According to the configuration in which the buffer member  50  has the curved portions  55  and  56  that are curved with a curvature from the top of the buffer member  50  toward the support surface  21 S, the buffer member  50  is prevented from being caught in the window frame when the edge of the window light control plate  10  is moved into/out of the window frame. Thus, the window can be smoothly opened/closed. 
     (7) The buffer member  50  has the main body  57  that is located outside the edge of the light control sheet  40  on the support surface  21 S and the extending portion  58  that extends from the top of the main body  57  toward the edge of the light control sheet  40  and is in contact with the outermost surface of the light control sheet  40 . According to such a configuration, since the buffer member  50  surrounds the vicinity of the edges of the light control sheet  40 , it is possible to prevent seeping of gas and liquid, for example, seeping of water vapor or water due to rainwater or the like into the light control layer  43  or the light control sheet  40 . 
     &lt;Modifications&gt; 
     The above embodiment can be implemented with modifications as described below. 
     The light control sheet  40  may not necessarily include the sealing section  47 , and the buffer member  50  may also serve as the sealing section  47 . In this case, as shown in  FIG. 8 , the buffer member  50  is arranged to be in contact with the edge surface of the light control multilayer  46  and seals the edge surface of the light control multilayer  46 . The buffer member  50  is composed of a material that can impart, to the buffer member  50 , a higher hardness than the light control sheet  40  and the function of preventing gas and liquid from seeping into/out of the light control multilayer  46 . According to the above configuration, the region in which the light control multilayer  46  is arranged can be extended to a position closer to the edge of the transparent plate  20  as compared with the configuration which is provided with the sealing section  47  and the buffer member  50 . 
     A surface of the buffer member  50  may be subjected to processing for reducing friction generated between the buffer member  50  and the holding section  64  and improving lubricating properties of the buffer member  50  in the holding section  64 . Such processing is embodied, for example, as application of a lubricant to the buffer member  50 , or adjustment of surface roughness of the buffer member  50 . If the lubricating properties of the buffer member  50  in the holding section  64  are improved, the window light control plate  10  is smoothly moved into/out of the holding section  64  and the window light control plate  10  smoothly slides along the holding section  64 . This also reduces the compression force applied from the holding section  64  to the buffer member  50 . 
     In addition to the light control layer  43 , the transparent conductive layers  44 A and  44 B, and the transparent substrates  45 A and  45 B, the light control multilayer  46  may include one or more additional layers. Regardless of the layer configuration of the light control multilayer  46 , the buffer member  50  has a hardness higher than the light control multilayer  46 . Examples of the additional layers include a layer having a UV barrier function or the like, a layer for protecting the light control layer  43  and the transparent conductive layers  44 A and  44 B, a layer contributing to control optical transparency of the light control multilayer  46 , and a layer improving strength or a characteristic such as heat resistance of the light control multilayer  46 . 
     Furthermore, the light control multilayer  46  may include a pair of orientation layers that are located between the light control layer  43  and the transparent conductive layers  44 A and  44 B and that sandwich the light control layer  43 . The orientation layer is a layer that controls orientation of the liquid crystal molecules contained in the light control layer  43 . When no driving voltage is applied to the light control layer, the orientation layer causes the liquid crystal molecules to be oriented in a predetermined direction. In the configuration including the orientation layer, when no driving voltage is applied to the light control layer  43 , the light control sheet  40  is transparent, and when a driving voltage is applied to the light control layer  43 , the light control sheet  40  is opaque. 
     The light control layer  43  may include a dye that has a predetermined color and does not hinder movement of the liquid crystal molecules according to a magnitude of the voltage applied to the light control layer  43 . Such a configuration achieves the light control sheet  40  having a predetermined color. 
     The window including the window light control plate  10  is not limited to the window of the door member of automobiles. A window only has to be one in which while the window is closed, an edge of a window plate is held in a window frame, and when the window is opened/closed, the window plate is moved while at least part of the edge of the window plate is exposed. If such a window is used in the window light control plate  10  of the above embodiment, the effect of preventing compression of the edge of the light control sheet  40  is obtained. The window provided with the window light control plate  10  is not limited to the window provided between indoors and outdoors, and may be a window that divides an indoor space into two spaces or a window that divides an outdoor space into two spaces. Furthermore, the window light control plate  10  may be moved by driving a mechanism such as a motor, or may be manually moved. 
     The window including the window light control plate  10  is not limited to the window of the door member of automobiles. A window only has to be one in which while the window is closed, an edge of a window plate is held in a window frame, and when the window is opened/closed, the window plate is moved while at least part of the edge of the window plate is exposed. If such a window is used in the window light control plate  10  of the above embodiment, the effect of preventing compression of the edge of the light control sheet  40  is obtained. The window provided with the window light control plate  10  is not limited to the window provided between indoors and outdoors, and may be a window that divides an indoor space into two spaces or a window that divides an outdoor space into two spaces. Furthermore, the above window may also be a window that has a structure in which a window plate is not moved relative to a window frame and that has an edge of the window plate held in the window frame. A compression force from the window frame is applied to the edge of the window plate. Accordingly, also in the case where the window light control plate  10  including the light control sheet  40  and the buffer member  50  is used in the window in which the window plate is not moved relative to the window frame, the compression force acts more on the buffer member  50  than on the light control sheet  40 , and thus the effect of preventing compression of the edge of the light control sheet  40  is reasonably and sufficiently obtained. Furthermore, the movable window light control plate  10  may be moved by driving a mechanism such as a motor, or may be manually moved. 
     The present application addresses the following. As an example of application of the light control device, it has been proposed to apply the light control device to a movable window device mounted to automobiles. According to this proposal, the light control sheet is bonded to a window glass assembled to a door member of the automobile, and by operating the light control device, the window is switched between a light transmitting mode and a light blocking mode. In such a window, the light control sheet preferably extends to an edge of the window glass in order to prevent leakage of light from the outside of the light control sheet. 
     On the other hand, a window frame of the door member includes a holding section such as a glass run, and while the window is closed, the edge of the window glass is held in the holding section. When the window is opened/closed, due to upward/downward movement of the window glass, an upper edge of the window glass is moved into/out of the holding section, and a side edge of the window glass slides in the holding section. In the case where an edge of the light control sheet is located at the edge of the window glass, when the window is opened/closed, the edge of the light control sheet is moved into/out of the holding section or slides in the holding section together with the edge of the window glass. As a result, the edge of the light control sheet receives, from the holding section, a force that compresses the light control sheet in a thickness direction of the light control sheet, and a force that presses to peel off the light control sheet from an edge surface of the light control sheet. 
       FIG. 10  shows an example of a state in which an edge of a window glass  150  and an edge of the light control sheet  100  are held in a holding section  160 . The light control sheet  100  is bonded to the window glass  150  via an adhesive layer (not shown). As shown in  FIG. 10 , when in particular a force compressing the light control sheet in the thickness direction acts on the edge of the light control sheet  100 , the edge of the light control sheet  100  is deformed as if it is crushed. The compression of the edge of the light control sheet  100  may cause a short circuit due to contact between the transparent conductive layer  120 A and the transparent conductive layer  120 B. 
     An aspect of the present invention is to provide a light control unit and a window light control plate capable of preventing compression of an edge of a light control sheet. 
     A light control unit in an aspect of the present invention includes a light control sheet including a light control layer, and a buffer member. The light control sheet is bonded to a surface of a transparent plate having an edge that is held in a window frame. The buffer member has a portion having a higher indentation hardness and a larger thickness than the light control sheet. Also, the buffer member is located outside an edge of the light control sheet at the edge of the transparent plate on the surface. The light control unit is configured such that while the transparent plate is held in the window frame, the buffer member is in contact with the window frame. 
     A window light control plate in an aspect of the present invention includes a transparent plate having edges that are held in a window frame, a light control sheet, and a buffer member. The light control sheet includes a light control layer and is bonded to a surface of the transparent plate. The buffer member has a portion having a higher indentation hardness and a larger thickness than the light control sheet. Also, the buffer member is located outside an edge of the light control sheet at the edge of the transparent plate on the surface. The window light control plate is configured such that while the transparent plate is held in the window frame, the buffer member is in contact with the window frame. 
     According to the above configuration, a compression force generated when the edge of the light control sheet and the edge of the transparent plate are held in the window frame acts more on the buffer member than on the light control sheet, and the buffer member is less likely to be compressed than the light control sheet. This makes it possible to prevent compression of the edge of the light control sheet when the edge of the light control sheet and the edge of the transparent plate are held in the window frame. 
     The embodiments of the present invention can prevent compression of an edge of a light control sheet. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.