Light control unit

A light control unit including a light control sheet including a first transparent electrode layer, a second transparent electrode layer, and a light control layer formed between the first and second transparent electrode layers and including a liquid crystal composition, and at least one first connection member that connects the first transparent electrode layer and a power supply. The light control sheet includes a light control region where the light control layer is located and at least one first region contiguous to the light control region in a plan view of the light control sheet. The first connection member includes a first wiring member connected to a first conductive adhesive layer formed on the light control sheet in the first region. The first wiring member includes a wiring layer that has a conductive patterned end portion where the wiring layer makes contact with the first conductive adhesive layer.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a light control unit that includes a light control sheet and a connection member for connecting the light control sheet to a power supply.

Discussion of the Background

A light control sheet includes a light control layer containing a liquid crystal composition and a pair of transparent electrode layers sandwiching the light control layer. Applying a driving voltage across the pair of transparent electrode layers changes alignment of the liquid crystal molecules in the light control layer, thereby changing the light transmittance of the light control sheet (see, for example, JP 2006-162823 A). Such a light control sheet and a connection member for connecting the transparent electrode layers to a power supply constitute a light control unit.

An example configuration of a light control unit will be described below with reference to drawings. As shown inFIG.11, a light control unit100is attached to a transparent plate200such as a window pane. The light control sheet110includes a pair of electrode sheets130A and130B. A connection member160A is connected to the electrode sheet130A, while a connection member160B is connected to the electrode sheet130B. In more detail, the electrode sheet130A is a laminate consisting of a transparent electrode layer140A and a transparent support layer150A, as shown inFIG.12. The transparent electrode layer140A is in contact with one side of the light control layer120. The transparent support layer150A is attached to the transparent plate200via an adhesive layer210. The connection member160A is connected to a region of the transparent electrode layer140A not covered by the light control layer120and the electrode sheet130B. As shown inFIG.13, the electrode sheet130B is a laminate formed of a transparent electrode layer140B and a transparent support layer150B. The transparent electrode layer140B is in contact with the other side of the light control layer120. The connection member160B is connected to a region of the transparent electrode layer140B not covered by the light control layer120and the electrode sheet130A, and faces the transparent plate200.

The connection members160A and160B each include a conductive adhesive layer161joined to the respective transparent electrode layers140A and140B, and a conductive tape162joined to the conductive adhesive layer161. The conductive adhesive layer161is formed of a conductive paste such as a silver paste. The conductive tape162is, for example, a copper tape. The connection members160A and160B further include a solder ball163, which is disposed on a surface of the conductive tape162, and a lead wire164connected to the conductive tape162with the solder ball163. The lead wire164is connected to a driver circuit that converts a voltage supplied from the power supply into a driving voltage. The driving voltage is applied across the transparent electrode layers140A and140B through the connection members160A and160B.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a light control unit includes a light control sheet including a first transparent electrode layer, a second transparent electrode layer, and a light control layer formed between the first and second transparent electrode layers and comprising a liquid crystal composition, and at least one first connection member that connects the first transparent electrode layer and a power supply. The light control sheet includes a light control region where the light control layer is located and at least one first region contiguous to the light control region in a plan view of the light control sheet. The first connection member includes a first wiring member connected to a first conductive adhesive layer formed on the light control sheet in the first region. The first wiring member includes a wiring layer and an insulating resin layer supporting the wiring layer. The wiring layer has a conductive patterned end portion where the wiring layer makes contact with the first conductive adhesive layer.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of a light control unit will be described with reference toFIGS.1to7.

(Configuration of a Light Control Unit)

As shown inFIG.1, a light control unit10includes a light control sheet20, and a first connection member30A and a second connection member30B. The light control unit10is attached to a transparent plate50for use. The transparent plate50is a transparent plate member made of glass, resin, or the like. The transparent plate50may be, for example, a building material such as a window pane, a partition, and a glass wall, or a vehicle member such as a window pane of an automobile.

In plan view of the light control sheet20, the light control sheet20is substantially rectangular and includes a light control region Si, and a first wiring region SA and a second wiring region SB. A first connection member30A is connected to the first wiring region SA, while a second connection region30B is connected to the second wiring region SB. These two wiring regions SA and SB are each located at an end of the light control sheet20and aligned along one side of the sheet20. The wiring regions SA and SB may be disposed on any side according to how the transparent plate50, the driver circuit, etc. are arranged.

The first wiring region SA and the second wiring region SB are disposed, for example, in part of the light control sheet20including a corner thereof. In other words, the first wiring region SA extends from a corner of the light control sheet20including one end of the above-mentioned side, while the second wiring region SB extends from a corner of the light control sheet20including the other end of the above-mentioned side.

An inter-terminal region Se, which is a part of the light control region Si, is located between the first wiring region SA and the second wiring region SB. In other words, in plan view of the light control sheet20, the first wiring region SA, the inter-terminal region Se, and the second wiring region SB are disposed in this order along the above-mentioned side of the light control sheet20, with the inter-terminal region Se located between the first connection member30A and the second connection member30B.

In the light control region Si, the region other than the inter-terminal region Se is a main region Sm. The inter-terminal region Se and the main region Sm have an identical layer structure, the former protruding from the main region Sm to a space between the first connection member30A and the second connection member30B.

In plan view of the light control sheet20, the first connection member30A extends from the first wiring region SA toward the outside of the light control sheet20, while the second connection member30B extends from the second wiring region SB toward the outside of the light control sheet20. The first connection member30A and the second connection member30B are separate from each other outside the light control sheet20and are separately connected to the driver circuit.

FIG.2is a cross-sectional view taken along the line II-II inFIG.1.FIG.3is a cross-sectional view taken along the line III-III inFIG.1. As shown inFIGS.2and3, the light control sheet20has a light control layer21, a first electrode sheet22A, and a second electrode sheet22B. The first electrode sheet22A consists of a first transparent electrode layer23A and a first transparent support layer24A, which supports the first transparent electrode layer23A. A surface of the first transparent support layer24A facing away from a surface in contact with the first transparent electrode layer23A is attached to a transparent plate50via an adhesive layer60. The second electrode sheet22B consists of a second transparent electrode layer23B and a second transparent support layer24B, which supports the second transparent electrode layer23B.

In the light control region Si, the light control layer21is sandwiched between the first electrode sheet22A and the second electrode sheet22B. In more detail, the light control layer21is located between the first transparent electrode layer23A and the second transparent electrode layer23B facing each other. The light control region Si is thus a region where the light control layer21is located.

The light control layer21contains a liquid crystal composition. The light control layer21is composed of, for example, a polymer network liquid crystal (PNLC), 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 layer21have, for example, positive dielectric anisotropy, and have a higher dielectric constant in a major axis direction 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 di oxane molecules.

Each of the first transparent conductive layer23A and the second transparent conductive layer23B is a conductive transparent layer. The transparent electrode layer23A and23B may be composed of, for example, indium tin oxide (ITO), fluorine doped tin oxide (FTO), tin oxide, zinc oxide, carbon nanotubes (CNT), or a polymer such as poly(3,4-ethylenedioxythiophene) (PEDOT).

Each of the first transparent support layer24A and the second transparent support layer24B is a transparent substrate. The transparent support layers24A and24B 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, cyclo-olefin polymer, triacetyl cellulose, or the like.

The adhesive layer60is transparent, and may be composed of an adhesive that does or does not need solidification when joined to an object. The adhesive layer60is composed of, for example, an adhesive made of an acrylic resin, an epoxy resin, or the like.

When no driving voltage is applied across the transparent electrode layers23A and23B, the major axes of the liquid crystal molecules are irregularly oriented. Accordingly, light incident on the light control layer21is scattered and the light control region Si appears whitish. Thus, when no driving voltage is applied to the light control layer21, the light control region Si is opaque. On the other hand, when a driving voltage is applied across the first transparent electrode layer23A and the second transparent electrode layer23B through the connection members30A and30B, the liquid crystal molecules are aligned, and the major axes of the liquid crystal molecules are oriented in the direction of an electric field between the transparent electrode layers23A and23B. As a result, light is more likely to be transmitted through the light control layer21and the light control region Si becomes transparent.

As shown inFIG.2, in the first wiring region SA, the first electrode sheet22A is present, while the light control layer21and the second electrode sheet22B are not present. In the first wiring region SA, the first transparent electrode layer23A has a surface exposed from another layer of the light control sheet20. The first connection member30A is connected to this surface of the first transparent electrode layer23A.

In more detail, the first electrode sheet22A continuously extends from the main region Sm of the light control region Si to the first wiring region SA. In other words, the first electrode sheet22A includes a region corresponding to the light control region Si and a region contiguous to this region and corresponding to the first wiring region SA.

The light control layer21and the second electrode sheet22B are located only in the main region Sm. At an edge of the main region Sm contiguous to the first wiring region SA, end faces of the light control layer21, the second transparent electrode layer23B, and the second transparent support layer24B are aligned along a thickness direction of the light control sheet20.

In other words, the first wiring region SA is a region of the light control sheet20from which the light control layer21and the second electrode sheet22B are removed. The first connection member30A is connected to the region of the first transparent electrode layer23A which corresponds to the first wiring region SA.

The first connection member30A includes a first conductive adhesive layer31A; a first wiring member32A which has a conductive patterned end; and a first sealing member36A. The first conductive adhesive layer31A is joined to a surface of the first transparent electrode layer23A. The first wiring member32A is joined to a surface of the first conductive adhesive layer31A facing away from the surface in contact with the first transparent electrode layer23A. In other words, the first wiring member32A is fixed to the first transparent electrode layer23A via the first conductive adhesive layer31A. The first wiring member32A is joined to the first conductive adhesive layer31A at an end of the first wiring member32A, and extends toward an outside of the light control20from this joint part.

The first conductive adhesive layer31A may be, for example, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), an isotropic conductive film (ICF), or an isotropic conductive paste (ICP). Using the anisotropic material among these allows a conductive path along a conductive pattern to be formed within the first conductive adhesive layer31A, which helps to obtain electrical characteristics as designed. In addition, using the isotropic material among them allows a resistance value to be kept low all over the first conductive adhesive layer31A. It is therefore appropriate to use an isotropic material especially if a large amount of current needs to be applied to the light control sheet20through the connection members30A and30B. In addition to these advantages, the anisotropic conductive film is preferable as the first conductive adhesive layer31A from the viewpoint of ease of handling in manufacturing processes or the like.

The first wiring member32A includes an insulating resin layer33A, which is a flexible substrate composed of an insulating resin such as polyimide, a wiring layer34A composed of a metal thin film of copper or the like, and a protective layer35A composed of an insulating resin. More specifically, a flexible printed circuit (FPC) is used as the first wiring member32A.

The wiring layer34A is supported by the insulating resin layer33A, and more specifically is attached to one of the two major surfaces of the insulating resin layer33A via an adhesive layer (not shown). A protective layer35A covers part of the wiring layer34A on an opposite side of the wiring layer34A from the insulating resin layer33A. The wiring layer34A has an end exposed from the protective layer35A.

The first wiring member32A is arranged so that the surface of the insulating resin layer33A on which the wiring layer34A is located faces the conductive adhesive layer31A, and the part of the surface of the wiring layer34A exposed from the protective layer35A is joined to the first conductive adhesive layer31A. The part of the wiring layer34A covered by the protective layer35A may also be partially joined to the first conductive adhesive layer31A.

The first sealing member36A is made of an insulating resin. The first sealing member36A covers a periphery of a joint part between the first conductive adhesive layer31A and the first wiring member32A, and a periphery of a joint part between the first connection member30A and the first transparent electrode layer23A. More specifically, the first sealing member36A includes a part that fills a gap between the first connection member30A and the light control layer21in the light control region Si. The first sealing member36A also includes a part that fills a gap between the first transparent electrode layer23A and a part of the first wiring member32A extending from the joint part with the first conductive adhesive layer31A toward the outside of the light control sheet20.

The first sealing member36A protects a joint part between the first conductive adhesive layer31A and the first wiring member32A and a joint part between the first connection member30A and the first transparent electrode layer23A from dirt, etc., thereby preventing deterioration of joining the respective members to each other. In addition, the first sealing member36A fills the gap between the first connection member30A and the light control layer21in the light control region Si, thereby preventing the light control sheet20from being crushed at an edge of the light control region Si and causing a short circuit between the first transparent electrode layer23A and the second transparent electrode layer23B.

A total thickness Te1of the first wiring member32A and the first conductive adhesive layer31A at the joint part between the first wiring member32A and the first conductive adhesive layer31A is less than a total thickness Ts2of the light control layer21and the second electrode sheet22B. In other words, a maximum thickness of a part of the first connection member30A joined to the first wiring region SA is less than the thickness Ts2.

This prevents the first connection member30A from protruding from the surface of the light control sheet20, which in turn prevents the first connection member30A from coming into contact with an object around the light control unit10. This in turn prevents an external force from acting on the joint part between the first connection member30A and the first transparent electrode layer23A or the joint part between the first conductive adhesive layer31A and the first wiring member32A and weakening the joint.

As shown inFIG.3, in the second wiring region SB, a second electrode sheet22B is present, while the light control layer21and the first electrode sheet22A are not present. In the second wiring region SB, the second transparent electrode layer23B has a surface exposed from another layer of the light control sheet20. This surface faces a surface of the transparent plate50. The second connection member30B is connected to the above-mentioned surface of the second transparent electrode layer23B.

In more detail, the second electrode sheet22B continuously extends from the main region Sm of the light control region Si to the second wiring region SB. In other words, the second electrode sheet22B includes a region corresponding to the light control region Si and a region contiguous to this region and corresponding to the second wiring region SB.

The light control layer21and the second electrode sheet22B are located only in the main region Sm. At an edge of the main region Sm contiguous to the second wiring region SB, end faces of the light control layer21, the first transparent electrode layer23A, and the first transparent support layer24A are aligned along the thickness direction of the light control sheet20.

In other words, the second wiring region SB is the region of the light control sheet20from which the light control layer21and the first electrode sheet22A are removed. The second connection member30B is connected to the region of the second transparent electrode layer23B which corresponds to the second wiring region SB. The adhesive layer60may not be disposed in a part facing the second wiring region SB.

The second connection member30B includes a second conductive adhesive layer31B; a second wiring member32B which has a conductive patterned end; and a second sealing member36B. As the second conductive adhesive layer31B for example, any of an anisotropic conductive film, an anisotropic conductive paste, an isotropic conductive film, or an isotropic conductive paste is used, as with the first conductive adhesive layer31A. As with the first wiring member32A, the second wiring member32B is also composed of a flexible printed circuit board. The second wiring member32B includes an insulating resin layer33B, a wiring layer34B composed of a metal thin film attached to one side of the insulating resin layer33B, and a protective layer35B partially covering the wiring layer34B.

The second conductive adhesive layer31B is joined to a surface of the second transparent electrode layer23B. The second wiring member32B is arranged such that the wiring layer34B faces the second conductive adhesive layer31B, and an end of the surface of the wiring layer34B exposed from the protective layer35B is joined to the second conductive adhesive layer31B. The surface of the second wiring member32B on a side opposite to that joined to the second conductive adhesive layer31B faces the transparent plate50. The second wiring member32B is joined to the second conductive adhesive layer31B at an end thereof, and extends toward the outside of the light control sheet20from this joint part.

The second sealing member36B is made of an insulating resin. The second sealing member36B includes a part that fills a gap between the second connection member30B and the light control layer21in the light control region Si. The second sealing member36B also includes a part that fills a gap between the second transparent electrode layer23B and a part of the second wiring member32B extending from the joint part with the second conductive adhesive layer31B toward the outside of the light control sheet20. This protects the joint part between the second conductive adhesive layer31B and the second wiring member32B or the joint part between the second connection member30B and the second transparent electrode layer23B, and additionally prevents the first transparent electrode layer23A and the second transparent electrode layer23B from coming into contact with each other at an edge of the light control region Si and causing a short circuit.

A total thickness Te2of the second wiring member32B and the second conductive adhesive layer31B at the joint part between the second wiring member32B and the second conductive adhesive layer31B is less than a total thickness Ts1of the light control layer21and the first electrode sheet22A. In other words, the maximum thickness of the part of the second connection member30B connected to the second wiring region SB is less than the thickness Ts1, and even less than a total thickness T3of the light control layer21, first electrode sheet22A, and adhesive layer60.

This prevents the second connection member30B from coming into contact with the transparent plate50, thereby preventing an external force from acting on the joint part between the second connection member30B and the second transparent electrode layer23B or the joint part between the second conductive adhesive layer31B and the second wiring member32B and weakening the joint. This also prevents the second wiring region SB from projecting from the surface of the light control sheet20, which in turn prevents distortion such as folding in the second electrode sheet22B.

FIG.4is a cross-sectional view taken along the line IV-IV ofFIG.1. As shown inFIG.4, the light control sheet20includes the light control layer21, the first electrode sheet22A, and the second electrode sheet22B in the inter-terminal region Se located between the first wiring region SA and the second wiring region SB. As described above, the light control sheet20in the inter-terminal region Se and the light control sheet20in the main region Sm have the same layer structure. Each of the light control layer21, the first electrode sheet22A, and the second electrode sheet22B extends continuously from the main region Sm to the inter-terminal region Se. The first electrode sheet22A extends continuously from the inter-terminal region Se to the first wiring region SA. The second electrode sheet22B extends continuously from the inter-terminal region Se to the second wiring region SB.

At an edge of the inter-terminal region Se contiguous to the first wiring region SA, end faces of the light control layer21, the second transparent electrode layer23B, and the second transparent support layer24B are aligned along the thickness direction of the light control sheet20. At an edge of the inter-terminal region Se contiguous to the second wiring region SB, end faces of the light control layer21, the first transparent electrode layer23A, and the first transparent support layer24A are aligned along the thickness direction of the light control sheet20.

(Configuration of Pattern of Conductor)

The wiring layer34A of the first wiring member32A has a conductive patterned end, and is joined to the first conductive adhesive layer31A at the end. Similarly, the wiring layer34B of the second wiring member32B has a conductive patterned end, and is joined to the second conductive adhesive layer31B at the end. Such a conductive pattern is formed, for example, by etching a thin metal film.

With reference toFIGS.5to7, a specific example of this conductive pattern will be described taking the first wiring member32A as an example. InFIGS.5to7, dotted regions are used to indicate the position of the pattern of the conductor of the wiring layer34A.

AsFIG.5shows, the pattern of the conductor may be striped. In this conductive pattern, conductive parts40, where a conductor is located, each have a strip shape extending along the direction of extension of the first wiring member32A, and the conductive parts40are aligned at a fixed interval along a width direction of the first wiring member32A. The conductive pattern has openings41A, each being a part between two conductive parts40adjacent to each other. Each of the openings41also has a strip shape extending along the direction of extension of the first wiring member32A.

AsFIG.6shows, the pattern of the conductor may have a mesh form. In this conductive pattern, a conductive part40includes a plurality of strips extending along the direction of extension of the first wiring member32A and a plurality of strips extending along the width direction thereof, with these strips crossing each other to form a mesh pattern. Parts of the conductive pattern surrounded by the conductive part40are openings41. The openings41form dots in the conductive pattern.

AsFIG.7shows, the mesh pattern may be inclined relative to the direction of extension of the first wiring member32A. In other words, in this conductive pattern, the conductive part40includes a plurality of first strips extending obliquely to the direction of extension of the first wiring member32A and a plurality of second strips extending along a direction crossing the first strips to form a mesh form.

The conductive pattern is not limited to the example described above, but may be a pattern in which openings are defined between the conductors. The openings41may each be sandwiched by the conductive parts40along at least one direction. More specifically, the entire periphery of the openings41may be surrounded by the conductive parts40, or be sandwiched by the conductive parts40in one direction and not in another direction.

In the opening41, an adhesive layer underneath the wiring layer34A or the insulating resin layer33A is exposed from the wiring layer34A. These exposed parts are joined to the first conductive adhesive layer31A. In other words, the first conductive adhesive layer31A is in contact with metal at the conductive part40and with a resin at the opening41. The first conductive adhesive layer31A is thus in partial contact with the resin at the joint part between the first wiring member32A and the first conductive adhesive layer31A, thereby strengthening the joint between the first wiring member32A and the first conductive adhesive layer31A, compared with the case where the first conductive adhesive layer31A is in contact only with the metal, that is, the conductive part40spreads without any openings41.

There is no limitation on the ratio of the openings41, but preferably the openings41are evenly arranged. In other words, the area ratio of the openings41to the conductive part40is preferably constant per unit area in plan view of a region where the pattern of the conductor is located. Such a configuration prevents unevenness in joint strength in a joint part between the first wiring member32A and the first conductive adhesive layer31A.

In addition, if the first wiring member32A and the first conductive adhesive layer31A are joined by thermocompression bonding, evenly arranging the openings41prevents unevenness in the strength of a force applied to the first conductive adhesive layer31A during thermocompression bonding. This in turn prevents unevenness in joint strength and in formation of a conductive path in the first conductive adhesive layer31A. In particular, if the first conductive adhesive layer31A is composed of an anisotropic conductive adhesive material, a preferable conductive path is formed along the conductive pattern in the first conductive adhesive layer31A.

Generally, during connection of the first wiring member32A and the first conductive adhesive layer31A, pressure is applied to the part where the first wiring member32A and the first conductive adhesive layer31A are in contact with each other such that the position where the pressure is applied progresses along the direction of extension of the first wiring member32A. Such a manufacturing method appropriately prevents unevenness in joint strength and in formation of a conductive path in the first conductive adhesive layer31A if the conductive parts40are arranged at an equal interval in the width direction of the first wiring member32A and have the same area ratio as the openings41in the direction of extension of the first wiring member32A.

In the first wiring member32A, it is preferred that a portion of the wiring layer34A covered by the protective layer35A is not patterned, that is, has no openings. In other words, the wiring layer34A preferably has a patterned part42that constitutes the conductive pattern described above and an unpatterned part43that spreads without any openings41. The patterned part42and the unpatterned part43are connected to each other and form a contiguous layer. In other words, the patterned part42and the unpatterned part43are electrically connected to each other. The unpatterned part43is located in a portion of the wiring layer34A extending from an end thereof where the patterned part42is located, that is, in a portion of the first wiring member32A not connected to the first conductive adhesive layer31A.

An end of the first wiring member32A on a side opposite to that joined to the first conductive adhesive layer31A is connected to a driver circuit, whereby the first transparent electrode layer23A and a power supply are electrically connected to each other. The driver circuit converts a voltage supplied from the power supply into a driving voltage and applies it to the first transparent electrode layer23A through the first connection member30A. It is sufficient that the wiring layer34A serves as a single wire as a whole. Thus the load required for patterning can be alleviated and a resistance value in the wiring layer34A can be inhibited from increasing if a part of the wiring layer34A not connected to the first conductive adhesive layer31A is unpatterned.

A portion of the unpatterned part43may be located in the part of the first wiring member32A joined to the first conductive adhesive layer31A. A portion of the patterned part42may be located in the part of the first wiring member32A not connected to the first conductive adhesive layer31A.

Although the conductive pattern has been described taking the first wiring member32A of the first connection member30A as an example, the configurations thereof described above can be applied to the second wiring member32B of the second connection member30B, and achieve a similar effect. The wiring layer34A of the first wiring member32A and the wiring layer34B of the second wiring member32B may have the same or different conductive pattern.

(Method of Manufacturing a Light Control Unit)

The light control unit10is manufactured, for example, by the following manufacturing method.

First, a multilayer sheet having the light control layer21and the electrode sheets22A and22B is formed. The multilayer sheet is then cut or stamped out into a shape corresponding to that of the transparent plate50to form a multilayer having the light control layer21and the electrode sheets22A and22B. After or before the multilayer is attached to the transparent plate50via an adhesive layer60, wiring regions SA and SB are formed and the connection members30A and30B are connected thereto.

The first wiring region SA is formed by removing the second electrode sheet22B and the light control layer21from a part of the multilayer described above. The second wiring region SB is formed by removing the first electrode sheet22A and the light control layer21from a part of the multilayer described above. The removal of the parts in the electrode sheets22A and22B are performed by, for example, cutting off them from the remaining part. The removal of the part in the light control layer21is performed by, for example, wiping off it. The light control20is thus formed. With this manufacturing method, arranging the wiring regions SA and SB to include a corner of the light control sheet20allows the wiring regions SA and SB to be easily formed.

The connection members30A and30B are then arranged and joined on the exposed surface of the transparent electrode layers23A and23B, whereby the light control unit10is formed. A sealant may be formed as necessary on an outer circumference of the light control sheet20on the transparent plate50. This manufacturing method aligns end faces of the light control layer21and the electrode sheets22A and22B in the thickness direction of the light control sheet20at an edge of the light control region Si in the light control sheet20, that is, at an edge that constitutes an outer edge of the light control sheet20and at an edge contiguous to the wiring regions SA and SB.

The above manufacturing method improves the efficiency of manufacturing the light control sheet20as compared with a manufacturing method in which for each light control sheet20, a sealing structure is formed between the electrode sheets22A and22B, followed by injecting liquid crystals between the electrode sheets22A and22B to form the light control layer21. Furthermore, since the outer shape of the light control sheet20is formed by cutting out or stamping out a multilayer sheet, the manufacturing method facilitates formation of the light control sheet20having a shape corresponding to the shape of the transparent plate50.

Since the wiring regions SA and SB are formed by partially removing the light control layer21and the electrode sheets22A and22B, the light control layer21and the electrode sheets22A and22B are easily formed as compared with a manufacturing method in which the light control layer21and the electrode sheets22A and22B are formed that have parts of the wiring regions SA and SB removed. It is also easy to adjust a size and arrangement of the wiring regions SA and SB.

An operation of the light control unit10will now be described. In the light control unit10, the connection members30A and30B are structured such that the wiring layers34A and34B of the wiring members32A and32B are joined to surfaces of the conductive adhesive layers31A and31B, respectively. In such a structure, the part where the conductive adhesive layers31A and31B are joined to the wiring members32A and32B extends in a planar shape. A joint part between each member constituting the connection members30A and30B does not include a dot-like joint structure, such as a lead wire and solder joint. The reliability of connection at the connection members30A and30B thus increases. This consequently prevents poor joints at the connection members30A and30B even if an external force acts on the connection members30A and30B when, for example, the light control unit10is mounted on the transparent plate50or when the light control unit10is moved along with the transparent plate50, such as when the light control unit10is used on a window or the like.

In particular, the wiring layers34A and34B have a conductive pattern in a part joined to the adhesive layers31A and31B, which enables a more reliable joint at the connection members30A and30B, as described above.

In the present embodiment, the transparent electrode layers23A and23B, to which a signal from the driver circuit is supplied, are unpatterned, that is, have no openings, in a joint part with the connection members30A and30B. Thus, the conductive pattern of the wiring layers34A and34B does not serve as mutually insulated wiring for supplying separate signals to a plurality of elements. In the light control unit10, the wiring layers34A and34B do not need to be patterned in terms of wiring for supplying signals to the transparent electrode layers23A and23B. In the present embodiment, forming a conductive pattern on the wiring layers34A and34B in the light control unit10increases the joint strength between the wiring members32A and32B and the conductive adhesive layers31A and31B due to the presence of openings between conductors.

In addition, affixing copper tape on a silver paste in a conventional light control unit tends to result in poor joints due to the joint strength of the copper tape decreasing in a cool, hot, or humid environment. By contrast, if any of an anisotropic conductive film, an anisotropic conductive paste, an isotropic conductive film, and an isotropic conductive paste is used as the conductive adhesive layers31A and31B, and the wiring layers34A and34B are joined to the conductive adhesive layers31A and31B as in the present embodiment, the connection members30A and30B have sufficient joint reliability in a cool, hot, or humid environment.

The connection members30A and30B of the present embodiment are thinner at a part connected to the wiring regions SA and SB than conventional connection members including lead wire and solder. This readily makes it possible to make the first connection member30A thinner than the total thickness of the light control layer21and the second electrode sheet22B, and also to make the second connection member30B thinner than the total thickness of the light control layer21and the first electrode sheet22A, as described above. This in turn makes it possible to prevent the connection members30A and30B from protruding and suffering an impact upon coming into contact with other members, and also the second electrode sheet22B from distorting due to a bump of the second wiring region SB in the light control sheet20.

As described above, the light control unit10of the present embodiment achieves the following effects.

(1) The connection members30A and30B consist of the conductive adhesive layers31A and31B and the wiring members32A and32B, respectively. A joint part between the conductive adhesive layers31A and31B and the wiring members32A and32B extends in a planar shape. This improves joint reliability at the connection members30A and30B, compared with the case where the connection members30A and30B include a dot-like joint structure with solder and lead wire.

(2) The wiring layers34A and34B of the wiring members32A and32B have a conductive patterned end, and are joined to the conductive adhesive layers31A and31B at their respective ends. Accordingly, the conductive adhesive layers31A and31B are joined to the wiring members32A and32B so as to be in partial contact with a resin part between metal parts. This improves joint strength between the conductive adhesive layers31A and31B and the wiring members32A and32B, which in turn improves joint reliability at the connection members30A and30B, compared with the case where the conductive adhesive layers31A and31B are joined to a uniform metal surface.

(3) If an area ratio of the conductive part40to the opening41is constant in unit area in plan view of the region of the wiring members32A and32B where the conductive pattern is formed, uneven joint strength is prevented in a joint part between the conductive adhesive layers31A and31B and the wiring members32A and32B. For example, in the case of the conductive pattern having a striped or mesh form, a desired area ratio between the conductive part40and the opening41is easily provided in unit area described above.

(4) The first connection member30A has a thickness less than the total thickness of the light control layer21and the second electrode sheet22B. The second connection member30B has a thickness less than the total thickness of the light control layer21and the first electrode sheet22A. Such a configuration makes the light control unit10thinner in the wiring regions SA and SB than the light control sheet20in the light control region Si. This prevents the connection members30A and30B from protruding and suffering an impact upon coming into contact with other components, and also the second electrode sheet22B from undergoing distortion due to the second wiring region22B in the light control sheet20being raised.

(5) The wiring layers34A and34B in the wiring members32A and32B include an unpatterned part43, which has no opening41and extends from the end where the conductive pattern is located. Unlike the entire wiring layers34A and34B being patterned, such a configuration described above reduces the load required for patterning and inhibits a resistance value from increasing in the wiring layers34A and34B.

(6) In plan view of the light control sheet20, the first wiring region SA and the second wiring region SB are aligned along a side of the light control sheet20, and the inter-terminal region Se, which is a part of the light control region Si, is located between the first wiring region SA and the second wiring region SB. In such a configuration, the connection members30A and30B are disposed together along one side of the light control sheet20, allowing a large main region Sm to be easily available. In addition, the configuration prevents expansion of a path from the connection members30A and30B to the driver circuit or of a region required to arrange each connection member outside the light control sheet20. Further, according to the configuration described above, after forming, from a multilayer sheet, a multilayer laminate serving as the light control sheet20, the wiring regions SA and SB are formed by removing the light control layer21and the electrode sheets22A and22B, thereby allowing the light control sheet20to be easily produced.

(7) The first connection member30A and the second connection member30B can be separately attached to the wiring regions SA and SB, respectively, because the first connection member30A and the second connection member30B are separate from each other outside the light control sheet20. It is therefore easy to assemble the light control unit10, as compared with the case where the first connection member30A and the second connection member30B are connected to each other.

(8) The wiring members32A and32B are flexible printed circuit boards. The conductive adhesive layers31A and31B are any of an anisotropic conductive film, an anisotropic conductive paste, an isotropic conductive film, and an isotropic conductive paste. This configuration provides wiring members32A and32B suitable for the connection members30A and30B. The configuration also achieves a sufficiently reliable joint at the connection members30A and30B in a cold, hot, or humid environment.

The above embodiment can be implemented with modifications as described below. Note that each of the following modifications can be implemented in combination.

As shown inFIG.8, the first wiring member32A and the second wiring member32B may be connected to each other outside the light control sheet20. In more detail, an insulating resin layer33A of the first wiring member32A and an insulating resin layer33B of the second wiring member32B constitute a single substrate33, which bifurcates near the light control sheet20. The wiring layer34A is located on one side of the substrate33. The substrate33and the wiring layer34A constitute the first wiring member32A. In addition, the wiring layer34B is located on the other side of the substrate33. The substrate33and the wiring layer34B constitute the second wiring member32B. That is, the above embodiment uses a flexible printed circuit board having a metal thin film disposed on both sides of the substrate33, with the metal film serving as a wiring layer.

The first modification reduces an area occupied by the connection members30A and30B outside the light control sheet20.

In plan view of the light control sheet20, the first wiring region SA and the second wiring region SB may be disposed along different sides of the light control sheet20. In other words, the first connection member30A and the second connection member30B may not be aligned along one side of the light control sheet20.

The configuration of the second modification allows a higher degree of freedom in arranging the first connection member30A and the second connection member30B, and also enables adjustment of the positions of the first connection member30A and the second connection member30B depending on the size, location of installation, etc. of the light control sheet20.

The light control sheet20may have a plurality of first wiring regions SA, to each of which a first connection member30A may be connected. In other words, the light control unit10may have a plurality of first connection members30A. The plurality of first connection members30A may be controlled at the same potential, and also be separately connected to the driver circuit. Alternatively, the plurality of first connection members30A may be connected to each other outside the light control sheet20. In other words, the plurality of first connection members30A may constitute a connection member having a single terminal to which a signal is applied from the driver circuit and a plurality of terminals for outputting the signal to the light control sheet20.

The configuration described above reduces the load on the driver circuit when controlling the first transparent electrode layer23A at a predetermined potential.

Similarly, the light control sheet20may have a plurality of second wiring regions SB, and the light control unit10may have a plurality of second connection members30B, each of which may be connected to a respective one of the second wiring regions SB. The plurality of second connection members30B may be separately connected to the driver circuit and be connected to each other outside the light control sheet20.

The configuration described above reduces the load on the driver circuit when controlling the second transparent electrode layer23B at a predetermined potential. The configuration of the third modification is particularly effective when the light control region Si is large.

As shown inFIG.9, the wiring layer34A may not be patterned in a part of the first wiring member32A joined to the first conductive adhesive layer31A. In other words, the wiring layer34A may extend without any openings41, in a part joined to the first conductive adhesive layer31A. Similarly, the wiring layer34B may not be patterned in a part of the second wiring member32B joined to the second conductive adhesive layer31B.

The configuration of the fourth modification also has a planar joint part between the conductive adhesive layers31A and31B and the wiring members32A and32B. This improves joint reliability at the connection members30A and30B, compared with the case where the connection members30A and30B include a dot-like joint structure with solder and lead wire. That is, the effect (1) described above can be obtained.

The first connection member30A may not include the first sealing member36A. Similarly, the second connection member30B may not include the second sealing member36B. In a configuration without the sealing members36A and36B, an edge21aof the light control layer21may protrude from an edge of the second electrode sheet22B at the edge of the light control region Si contiguous to the first wiring region SA, as shown inFIG.10. Similarly, an edge of the light control layer21may protrude from an edge of the first electrode sheet22A at the edge of the light control region Si contiguous to the second wiring region SB. According to such a configuration, the protrusion of the light control layer21makes it hard for the first transparent electrode layer23A and the second transparent electrode layer23B to come into contact with each other even if the light control sheet20is crushed at the end of the light control region Si, thereby preventing a short circuit.

Each end face of the electrode sheets22A and22B may not be aligned with a corresponding end face of the light control layer21at the edges of the light control region Si, regardless of whether the sealing members36A and36B are present.

Flexible flat cables (FFC) may be used as the wiring members32A and32B. A flexible flat cable is structured such that a plurality of conductor strips arranged in parallel are sandwiched by two insulating resin films. At an end of the flexible flat cable, the conductor strips are exposed from the insulating resin films, and these exposed parts are joined to the conductive adhesive layers31A and31B. The plurality of conductor strips correspond to wiring layers, the array pattern of the plurality of conductor strips corresponds to a pattern of a conductor, and the insulating resin film corresponds to an insulating resin layer.

If a flexible printed circuit board is used as the wiring members32A and32B, a conductive pattern is formed by etching a metal thin film, which allows a higher degree of freedom in pattern shape and makes it possible to form a fine pattern. If a flexible flat cable is used as the wiring members32A and32B, the wiring members32A and32B can be provided at a low cost. Flexible flat cables only allow a limited degree of freedom in pattern shape but still allow adjustment of the ratio of a conductor to an opening through adjustment of the width and array interval of conductor strips, thereby improving the joint strength.

In the embodiment described above, the wiring members32A and32B include at least the wiring layers34A and34B and the insulating resin layers33A and33B. The wiring members32A and32B may be, for example, a flexible printed circuit board having a metal thin film on a surface of the insulating resin layers33A and33B facing away from the surface joined to the conductive adhesive layers31A and31B, respectively. In addition, the wiring layers34A and34B are metal layers and may be composed of a plurality of layers including a plating layer, etc. The insulating resin layers33A and33B are resin layers and may be composed of a plurality of layers. Furthermore, the conductive adhesive layers31A and31B are layers that are conductive and adhesive, and may be composed of a plurality of layers.

The light control sheet20may include an additional layer as well as the light control layer21and the electrode sheets22A and22B. Examples of the additional layers include a layer for protecting the light control layer21and the transparent electrode layers23A and23B, such as a layer having a UV barrier function; a layer contributing to control optical transparency of the light control sheet20; and a layer improving characteristics such as strength or heat resistance of the light control sheet20.

Furthermore, the light control sheet20may include a pair of orientation layers that are located between the light control layer21and the electrode sheets22A and22B and that sandwich the light control layer21. The orientation layer is a layer that controls orientation of the liquid crystal molecules contained in the light control layer21. When no driving voltage is applied, the orientation layer orients the liquid crystal molecules in a normal direction thereof. In the configuration including the orientation layer, when no driving voltage is applied across the transparent electrode layers23A and23B, the light control region Si is transparent, and when a driving voltage is applied across the transparent electrode layers23A and23B, the light control region Si is opaque.

If the light control sheet20further includes a layer other than the light control layer21and electrode sheets22A and22B, in the first wiring region SA, a surface of the first transparent electrode layer23A may be exposed from the other layers and the first connection member30A may be connected to this surface, while in the second wiring region SB, a surface of the second transparent electrode layer23B may be exposed from the other layers and the second connection member30B may be connected to this surface.

The light control layer21may 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 layer21. Such a configuration provides a light control sheet20having a predetermined color.

The wiring regions SA and SB may be disposed at a location that does not include a corner of the light control sheet20. If the light control unit is formed by the manufacturing method of the embodiment described above, the entire region other than the wiring regions SA and SB in the light control sheet20serves as the light control region Si. The light control sheet20may not be rectangular.

A surface of the transparent plate50to which the light control sheet20is attached may be flat or curved. Using a flexible printed circuit board or a flexible flat cable as the wiring members32A and32B keeps the wiring members32A and32B highly flexible while improving joint reliability at the connection members30A and30B. The light control unit10thus readily fits with a curved surface, and is therefore suitable for being mounted on a curved surface.

Either of the first electrode sheet22A or the second electrode sheet22B may be attached to the transparent plate50. The light control sheet20may be sandwiched between two transparent plates50.

The present application addresses the following. During, for example, transportation of the light control unit100or attachment of the light control unit100to the transparent sheet200, the lead wire164moves against the light control sheet110or a shock caused by collision of the solder ball163with the transparent sheet200is applied to the connection member160B. In the connection members160A and160B, the conductive tape162and the lead wire164are connected to each other with the solder ball163to form a dot-like joint structure, so that the joint can hardly be said to be highly durable against the movement or shock described above.

An aspect of the present invention is to provide a light control unit that enables a more reliable joint at a connection member connected to a transparent electrode layer.

A light control unit includes a light control sheet including a light control layer containing a liquid crystal composition, a first transparent electrode layer, and a second transparent electrode layer; and a first connection member configured to connect the first transparent electrode layer and a power supply. The light control layer is sandwiched by the first transparent electrode layer and the second transparent electrode layer. In plan view of the light control sheet, the first transparent electrode layer includes a first region contiguous to a light control region where the light control layer is located. The first connection member includes a first conductive adhesive layer joined to the first region and a first wiring member joined to the first conductive adhesive layer. The first wiring member includes a wiring layer and an insulating resin layer supporting the wiring layer. The wiring layer has a conductive patterned end, and is in contact with the first conductive adhesive layer at the end.

The configuration described above has a planar joint part between between the first conductive adhesive layer and the first wiring member. This achieves a more reliable joint at the first connection member, compared with the case where the first connection member includes a dot-like joint structure formed with solder and lead wire. In addition, the first wiring member has a conductive patterned end, and is joined to the first conductive adhesive layer at the end. Accordingly, the first conductive adhesive layer is joined to the first wiring member so as to be in contact with a resin part between metal parts. This improves joint strength between the first conductive adhesive layer and the first wiring member, compared with the case where the first conductive adhesive layer is joined to a uniform metal surface, thus further increasing the reliability of joint at the first connection member.

In the light control unit, in plan view of a region where the conductive patterned end is located, an area ratio per unit area between the conductive patterned end and an opening defined by the conductive patterned end may be constant.

The configuration described above prevents unevenness in joint strength in a part where the first conductive adhesive layer is joined to the first wiring member.

In the light control unit described above, the conductive patterned end may have a striped or mesh form.

The configuration described above makes it easy for the area ratio per unit area between the conductive patterned end and the opening to be a desired value.

In the light control unit described above, the light control sheet may include a second transparent support layer supporting the second transparent electrode layer, and the first connection member may have a thickness less than the total thickness of the light control layer, the second transparent electrode layer, and the second transparent support layer.

With the configuration described above, the thickness of the light control unit in a part where the first connection member is located is less than the thickness of the light control sheet in the light control region. This prevents the first connection member from protruding from a surface of the light control sheet or the first region from being raised relative to the light control region.

In the light control unit described above, the wiring layer may be composed of a metal thin film and include an unpatterned part having no opening and extending from the end.

Unlike the entire wiring layer being patterned, the configuration described above reduces the amount of load required to form a pattern and prevents a resistance value from increasing in the wiring layer.

The light control unit described above includes a second connection member configured to connect the second transparent electrode layer and the power supply. The second transparent electrode layer includes a second region contiguous to the light control region in plan view of the light control sheet. The second connection member includes a second conductive adhesive layer joined to the second region and a second wiring member joined to the second conductive adhesive layer. With this light control unit, in plan view of the light control sheet, the first region and the second region may be aligned along one side of the light control sheet and part of the light control region may be located therebetween.

The configuration described above readily provides a large light control area, and prevents expansion of a path from each connection member to a driver circuit or of a region required to arrange each connection member outside the light control sheet. In addition, the first region is formed by removing, for example, the light control layer and the transparent electrode layer from a multilayered laminate including the light control layer and each transparent electrode layer, thus facilitating manufacture of the light control sheet.

With the light control unit described above, in plan view of the light control sheet, the first connection member and the second connection member may extend toward the outside of the light control sheet, and the first wiring member and the second wiring member may be separate from each other outside the light control sheet.

The configuration described above allows the first connection member and the second connection member to be attached to the light control sheet as separate members. This facilitates assembly of the light control unit, as compared with the case where the first connection member and the second connection member are connected to each other.

With the light control unit described above, in plan view of the light control sheet, the first connection member and the second connection member may extend toward the outside of the light control sheet and be connected to each other outside the light control sheet.

This configuration reduces an area occupied by the first connection member and the second connection member outside the light control sheet.

The light control unit described above includes a second connection member configured to connect the second transparent electrode layer to the power supply. The second transparent electrode layer includes a second region contiguous to the light control region in plan view of the light control sheet. The second connection member includes a second conductive adhesive layer joined to the second region and a second wiring member joined to the second conductive adhesive layer. With this light control unit, in plan view of the light control sheet, the first region and the second region may be disposed along different sides of the light control sheet.

The configuration described above allows a higher degree of freedom in arranging the first connection member and the second connection member, and also facilitates adjustment of positions of the first connection member and the second connection member according to the size, location of installation, etc. of the light control sheet.

In the light control unit described above, the first transparent electrode layer may include a plurality of the first regions, and the light control unit may include a plurality of the first connection members, each of which may be connected to any one of the plurality of first regions for each of the first connection members.

The configuration described above reduces the amount of load required for a driver circuit to control the first transparent electrode layer at a predetermined potential.

In the light control unit described above, the first wiring member may be a flexible printed circuit board, and the first conductive adhesive layer may be composed of any of an anisotropic conductive film, an anisotropic conductive paste, an isotropic conductive film, and an isotropic conductive paste.

The configuration described above provides a first wiring member suitable for the first connection member. The configuration also offers a sufficiently reliable joint at the first connection member in a cold, hot, or humid environment.

The present invention in an aspect offers a more reliable joint at a connection member of a light control unit.

REFERENCE SIGNS LIST