Electrowetting device

Abstract

An electrowetting device according to the present invention includes an array substrate, a plurality of control electrodes, a counter electrode, and a counter substrate. The plurality of control electrodes are located on the array substrate and disposed in a matrix having first to m-th rows and first to n-th columns. The counter electrode is located above the plurality of control electrodes and overlaps the plurality of control electrodes. The counter substrate is located above the counter electrode and has a first opening and a second opening. The first opening is disposed so as to partially overlap each of the control electrodes located in the first row. The second opening is disposed so as to partially overlap each of the control electrodes located in the m-th row. m and n are each selected from integers of 4 or greater.

Description

Electrowetting Device

[0001] One embodiment of the present invention relates to an electrowetting device suitable for transporting microdroplets.

[0002] In recent years, development of electrowetting devices utilizing the electrowetting effect has been progressing. The electrowetting effect is a phenomenon in which, when a voltage is applied between a liquid and an electrode, the energy at the solid-liquid interface between the electrode surface and the liquid changes, resulting in a change in the surface shape of the liquid. By utilizing this phenomenon, it is possible to construct a liquid delivery device capable of transporting microdroplets (see Patent Documents 1 to 6).

[0003] Japanese Patent Application Publication No. 2018-51685 Japanese Patent Application Publication No. 2012-163956 U.S. Patent No. 6,565,727 U.S. Patent No. 6,911,132 U.S. Patent Application Publication No. 2023 / 0110598 Japanese Patent Application Publication No. 2006-125900

[0004] An object of one embodiment of the present invention is to provide an electrowetting device having a novel structure. Alternatively, an object of one embodiment of the present invention is to provide an electrowetting device capable of transporting microdroplets. Alternatively, an object of one embodiment of the present invention is to provide a highly reliable electrowetting device at low cost that can easily inject, collect, and discharge microdroplets.

[0005] One embodiment of the present invention is an electrowetting device. The electrowetting device includes an array substrate, a plurality of control electrodes, a counter electrode, and a counter substrate. The plurality of control electrodes are located on the array substrate and arranged in a matrix having a first row to an mth row and a first column to an nth column. The counter electrode is located on the plurality of control electrodes and overlaps the plurality of control electrodes. The counter substrate is located on the counter electrode and has a first opening and a second opening. The first opening is located so as to partially overlap each of the control electrodes located in the first row. The second opening is located so as to partially overlap each of the control electrodes located in the mth row. m and n are each selected from integers equal to or greater than 4.

[0006] One embodiment of the present invention is an electrowetting device. The electrowetting device includes an array substrate, a plurality of control electrodes, a counter electrode, and a counter substrate. The plurality of control electrodes are located on the array substrate and arranged in a matrix having a first row to an mth row and a first column to an nth column. The counter electrode is located on the plurality of control electrodes and overlaps the plurality of control electrodes. The counter substrate is located on the counter electrode and has a first opening, a second opening, and a third opening. The first opening is located so as to partially overlap with each of the control electrodes located in the first row. The second opening is located so as to partially overlap with each of the control electrodes located in the mth row. The third opening is located so as to partially overlap with each of the control electrodes located in the second row to the (m-1)th row and in the first column. m and n are each selected from integers equal to or greater than 4.

[0007] 1 is a schematic development view of an electrowetting device according to one embodiment of the present invention; 2 is a schematic top view of an electrowetting device according to one embodiment of the present invention; 3 is a schematic top view of an electrowetting device according to one embodiment of the present invention; 4 is a schematic top view of an electrowetting device according to one embodiment of the present invention; 5 is a schematic top view of an electrowetting device according to one embodiment of the present invention; 6 is a schematic top view of an electrowetting device according to one embodiment of the present invention; 7 is a schematic end view of a part of an electrowetting device according to one embodiment of the present invention; 8 is a schematic end view of a part of an electrowetting device according to one embodiment of the present invention; 9 is a schematic top view of a part of an electrowetting device according to one embodiment of the present invention; 10 is a schematic end view of a part of an electrowetting device according to one embodiment of the present invention; 11 is a schematic top view of a part of an electrowetting device according to one embodiment of the present invention; 12 is a schematic top view of a part of an electrowetting device according to one embodiment of the present invention; 13 is a schematic top view of a part of an electrowetting device according to one embodiment of the present invention; 1 is a block diagram of a drive circuit of an electrowetting device according to an embodiment of the present invention; 2 is a block diagram of a drive circuit of an electrowetting device according to an embodiment of the present invention; 3 is a schematic top view of an electrowetting device according to an embodiment of the present invention; 4 is a schematic top view of an electrowetting device according to an embodiment of the present invention;

[0008] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0009] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same function as those described in the previous drawings may be assigned the same reference numerals, and duplicated explanations may be omitted. This reference numeral is used to collectively represent multiple identical or similar structures, and when representing these individually, a hyphen and a natural number may be added after the reference numeral. When indicating an element within a single structure, a lowercase alphabet may be used after the reference numeral.

[0010] In this specification and claims, when expressing an aspect of placing another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case in which another structure is placed directly on top of a certain structure so as to be in contact with the certain structure, and a case in which another structure is placed above a certain structure via yet another structure.

[0011] In the present invention, when a single film is processed to form multiple films, these multiple films may have different functions and roles. However, these multiple films originate from films formed as the same layer in the same process, and have substantially the same layer structure, the same material, and the same morphology. Therefore, these multiple films are defined as existing in the same layer.

[0012] In this specification and claims, the expression "a structure exposed from another structure" means a state in which a part of a structure is not covered by another structure, and includes a state in which the part not covered by another structure is covered by yet another structure. The state expressed by this expression also includes a state in which a structure is not in contact with another structure.

[0013] 1. Overall Configuration of the Electrowetting Device FIG. 1 shows a schematic development view of an electrowetting device 100 according to one embodiment of the present invention. The electrowetting device 100 is a device that has the function of transporting minute droplets by utilizing the electrowetting effect. Such devices are also called microchannel chips or lab-on-chips. The electrowetting device 100 can be used to perform analysis, chemical reactions, and the like of minute amounts of liquid samples.

[0014] As shown in Figure 1, the electrowetting device 100 includes an array substrate 102 and a counter substrate 104, which are fixed together using a sealing material (not shown). Various patterned conductive films, insulating films, and semiconductor films are formed between the array substrate 102 and the counter substrate. By appropriately combining these conductive films, insulating films, and semiconductor films, a plurality of control electrodes 120, as well as counter electrodes (not shown in Figure 1), drive circuits (gate line drive circuit 106, signal line drive circuit 108), signal terminals 110, power supply terminals 112, auxiliary wiring (not shown in Figure 1), and other components are formed. These components will be described below.

[0015] (1) Array Substrate and Counter Substrate The array substrate 102 and counter substrate 104 provide physical strength to the electrowetting device 100 and also provide a surface on which the various components described above are arranged to configure and control the droplet flow path. There are no restrictions on the materials used for the array substrate 102 and counter substrate 104. Metal substrates containing metals or alloys such as aluminum or stainless steel, as well as glass substrates, quartz substrates, and plastic substrates containing polymers such as polyimide and polycarbonate, can be used for the array substrate 102 and counter substrate 104. The array substrate 102 and / or counter substrate 104 may be configured to transmit at least a portion of visible light. This allows droplets injected into and transported by the electrowetting device 100 to be easily observed and tracked visually, using an optical microscope, or various spectrometers. The array substrate 102 and / or counter substrate 104 may be flexible.

[0016] The sizes of the array substrate 102 and the counter substrate 104 can also be determined arbitrarily, and for example, a rectangular glass substrate or plastic substrate with one side measuring 1 cm to 20 cm can be used as the array substrate 102 and the counter substrate 104. A part of the array substrate 102 is exposed from the counter substrate 104, and signal terminals 110, power supply terminals 112, etc. are provided on the exposed part.

[0017] The counter substrate 104 has at least two openings (or cutouts; the same applies below). FIG. 1 shows the counter substrate 104 having two openings (a first opening 104a and a second opening 104b). One opening can be used as an inlet for introducing droplets, and the other opening can be used as an outlet for discharging droplets. Specifically, droplets can be injected into the electrowetting device 100 by dropping droplets from one of the first opening 104a and the second opening 104b using a dropper, pipette, micropipette, syringe, or the like, and the droplets can be collected and discharged from the other opening. The opening is a through-hole formed in the counter substrate 104, and has a closed outline. The cutout is a portion formed by removing a portion of the counter substrate 104 from the outer periphery, and its outline forms part of the outer periphery of the counter substrate 104.

[0018] (2) Drive Circuits and Signal Terminals The gate line drive circuit 106 and the signal line drive circuit 108 are provided on the array substrate 102 and are electrically connected to the signal terminals 110 by wiring (not shown). Although not shown, the signal terminals 110 are electrically connected to an external control circuit board via a flexible printed circuit (FPC). Various signals and power supplies input from the external control circuit board are input to the signal terminals 110, and these signals and power supplies are further input to the gate line drive circuit 106 and the signal line drive circuit 108. The gate line drive circuit 106 and the signal line drive circuit 108 generate control signals for controlling the control electrodes 120 based on the input signals and supply them to control circuits (described below) for controlling each control electrode 120. This controls the potential of the control electrodes 120.

[0019] 1, two gate line driving circuits 106 are provided on either side of an area including a plurality of control electrodes 120, but a single gate line driving circuit 106 may be provided on one side of this area. Also, the signal line driving circuit 108 may be formed by appropriately combining conductive films, semiconductor films, and insulating films formed on the array substrate 102, or the signal line driving circuit 108 may be partially or entirely constituted by an integrated circuit formed on a semiconductor substrate.

[0020] (3) Control Electrode and Counter Electrode Figures 2 to 4 show schematic top views of the electrowetting device 100. Figure 3 shows the structure of Figure 2 with the counter substrate 104 removed, and Figure 4 shows the structure of Figure 3 with the counter electrode 122 removed. As can be seen from these figures, the multiple control electrodes 120 are arranged in a matrix having multiple rows and multiple columns. Hereinafter, the number of rows and the number of columns are defined as m and n, respectively. m and n are each selected from integers equal to or greater than 4.

[0021] As shown in FIG. 2, the multiple control electrodes 120 are arranged to overlap with the counter substrate 104. However, each of the control electrodes 120-1 in the row (first row) located farthest from the signal terminal 110 partially overlaps with the counter substrate 104, with a portion of the electrode exposed from the counter substrate 104 through the first opening 104a. That is, each of the control electrodes 120-1 in the first row partially overlaps with the first opening 104a. The portion of each of the control electrodes 120-1 in the first row that overlaps with the first opening 104a is located on the opposite side to the second row adjacent to the first row. Similarly, each of the control electrodes 120-m in the row (mth row) located on the signal terminal 110 side also partially overlaps with the counter substrate 104, with a portion of the electrode exposed from the counter substrate 104 through the second opening 104b. That is, each of the control electrodes 120-m in the mth row partially overlaps with the second opening 104b. The portion of each of the control electrodes 120-m in the m-th row that overlaps with the second opening 104b is located on the opposite side of the (m-1)-th row adjacent to the m-th row. On the other hand, each of the control electrodes 120 arranged in the second to (m-1)-th rows overlaps with the opposing substrate 104 entirely.

[0022] The counter electrode 122 is provided below the counter substrate 104 and is disposed between the first opening 104a and the second opening 104b, as shown in FIG. 3 . The counter electrode 122 overlaps with the plurality of control electrodes 120. In other words, the counter electrode 122 is shared by all of the control electrodes 120. However, each of the control electrodes 120-1 in the first row partially overlaps with the counter electrode 122, with a portion thereof exposed from the counter electrode 122. The portion of each of the control electrodes 120-1 in the first row that is exposed from the counter electrode 122 is located on the opposite side to the second row. Similarly, each of the control electrodes 120 in the mth row partially overlaps with the counter electrode 122, with a portion thereof exposed from the counter electrode 122. The portion of each of the control electrodes 120-m in the mth row that is exposed from the counter electrode 122 is located on the opposite side to the (m−1)th row. On the other hand, each of the control electrodes 120 arranged in the second to (m−1)th rows entirely overlaps the counter electrode 122 .

[0023] 4, the size (area) of the control electrodes 120-1, 120-m located in the first and m-th rows is larger than the size (area) of the control electrodes 120 located in the second to (m-1)-th rows. Therefore, even if each of the control electrodes 120-1, 120-m located in the first and m-th rows is partially exposed from the counter electrode 122, a relatively large area overlapping with the counter electrode 122 can be ensured. This arrangement not only makes it possible to easily place droplets on the control electrodes 120 located in the first or m-th row using the opening (first opening 104a or second opening 104b), but also makes it possible to reliably introduce the dropped droplets between the control electrode 120 and the counter electrode 122 by utilizing capillary action, thereby applying a voltage. Conversely, when collecting or discharging droplets, at least a portion of the droplets on the control electrodes 120-1, 120-m located in the first or mth row are exposed from the opening (first opening 104a or second opening 104b), so the droplets can be easily collected or discharged by sucking them out using a pipette or syringe.

[0024] (4) Control Circuit The configuration of the control circuit connected to each control electrode 120 will be described using the equivalent circuit diagram shown in FIG. 5 . A plurality of gate lines 124 extend in the row direction from the gate line driving circuit 106. Meanwhile, a plurality of signal lines 126 extend in the column direction from the signal line driving circuit 108. Each gate line 124 is electrically connected to n control circuits 130 located in the corresponding row, and each signal line 126 is electrically connected to m control circuits 130 located in the corresponding column. Therefore, each control circuit 130 is electrically connected to one gate line 124 and one signal line. Each control circuit 130 includes at least one transistor 132. Each control circuit 130 may consist of a single transistor 132, or may include one or more transistors as well as one or more capacitors for maintaining the potential of the control electrode 120. In the example shown in FIG. 5 , the control circuit 130 includes one transistor 132 and one capacitor 150.

[0025] The gate of the transistor 132 is electrically connected to the gate line 124. One terminal of the transistor 132 is connected to the signal line 126, and the other terminal is electrically connected to one electrode of the capacitance element 150 and the control electrode 120. A constant potential (e.g., ground potential) is supplied to the other electrode of the capacitance element 150. As will be described later, the counter electrode 122 is electrically connected to an auxiliary wiring 166, thereby supplying a constant potential to the counter electrode 122. The voltage applied to the liquid sandwiched between the control electrode 120 and the counter electrode 122 can be adjusted by controlling the potential of the control electrode 120 while maintaining the potential of the counter electrode 122 constant.

[0026] (5) End Surface Structure The positional and connection relationships of the above-described configuration will be explained in more detail using end surface views. Figures 6 and 7 show schematic end surface views of a portion of the electrowetting device 100. Figure 6 is a schematic end surface view centered on one of the control electrodes 120 located in the second to (m-1)th rows, and Figure 7 is a schematic end surface view centered on one of the control electrodes 120 located in the first row.

[0027] As shown in FIGS. 6 and 7 , the transistor 132 of the control circuit 130 is provided on the array substrate 102 directly or via an undercoat 114 of any desired configuration. The configuration of the transistor 132 is not limited, and various transistor configurations can be used, such as a top-gate transistor, a bottom-gate transistor, or a transistor with a pair of gate electrodes sandwiching a channel from above and below. In the example shown in FIG. 6 , the transistor 132 is a top-gate transistor and includes a semiconductor film 134, a gate insulating film 136 on the semiconductor film 134, a gate electrode 138 overlapping the semiconductor film 134 via the gate insulating film 136, an interlayer insulating film 140 having a single-layer structure or a multilayer structure covering the gate electrode 138, and a pair of terminals 142 and 144 electrically connected to the semiconductor film 134 via openings provided in the gate insulating film 136 and the interlayer insulating film 140. A planarization film 152 is provided on the control circuit 130 including the transistor 132, which absorbs unevenness caused by the control circuit 130 and provides a flat surface. The control electrode 120 is provided on the planarization film 152, and is electrically connected to the terminal 144 through an opening formed in the planarization film 152. On the control electrode 120, an insulating film (first insulating film) 118-1 is provided.

[0028] A potential difference can be generated between the control electrode 120 and the counter electrode 122 by supplying a gate potential to the gate line 124 to open the transistor 132, and during this time supplying a predetermined potential from the signal line driving circuit 108 to the control circuit via the signal line 126. The contact angle of a droplet present between the control electrode 120 and the counter electrode 122 changes due to the electric field between the control electrode 120 and the counter electrode 122. By utilizing this phenomenon, i.e., the electrowetting effect, it is possible to transport the droplet onto the adjacent control electrode 120.

[0029] A counter electrode 122 is provided on the counter substrate 104 (below the counter substrate 104 in Figures 6 and 7) either directly or via an overcoat 116 of any configuration. Furthermore, an insulating film (second insulating film) 118-2 is provided to cover the counter electrode 122. Spacers 154 are provided between the array substrate 102 and the counter substrate 104 to maintain a constant distance therebetween, i.e., the distance between the control electrode 120 and the counter electrode 122. Droplets injected into the electrowetting device 100 are transported along a path between adjacent control electrodes 120. For this reason, as shown in Figure 8, the spacers 154 are preferably provided so as not to overlap with the control electrodes 120, i.e., so as not to interfere with droplet transport, such that the control electrodes 120 are exposed from the spacers 154. Furthermore, the spacers 154 are preferably not provided in regions sandwiched between adjacent control electrodes 120 in the row or column direction, but are preferably provided between adjacent control electrodes 120 in directions diagonal to both of these directions. In general, where j is an integer variable selected from 1 to (m-1) and k is an integer variable selected from 1 to (n-1), it is preferable to place a spacer 154 between the control electrode 120 in the jth row and kth column and the control electrode 120 in the (j+1)th row and (k+1)th column. The height of the spacer 154 is adjusted appropriately so that the distance between the control electrode 120 and the counter electrode 122 is in the range of 10 μm to 30 μm. The shape of the end face of the spacer 154 (the end face in a plane parallel to the main surface of the array substrate 102) can also be set arbitrarily, and may be a circle, a polygon, an ellipse, or a shape having an outline composed of straight lines and curves.

[0030] The method for forming each of the above-described components can also be selected appropriately. For example, the undercoat 114, gate insulating film 136, interlayer insulating film 140, and overcoat 116 may be composed of one or more films containing an inorganic compound, such as a silicon-containing inorganic compound, such as silicon oxide or silicon nitride. The first insulating film 118-1 and the second insulating film 118-2 preferably contain a material with low affinity for the droplets to be dropped. Therefore, when water is used as the main component of the droplets, it is preferable to configure the first insulating film 118-1 so as to contain a water-repellent material such as silicon nitride. These films may be formed by sputtering or chemical vapor deposition (CVD).

[0031] The semiconductor film 134 may be configured to include a group 14 element such as silicon, or a compound semiconductor such as indium-gallium oxide or indium-gallium-zinc oxide. The semiconductor film 134 is also formed by using a sputtering method, a CVD method, or the like. There are no restrictions on the crystallinity of the semiconductor film 134, and it may be polycrystalline or amorphous.

[0032] The gate electrode 138, terminals 142 and 144, auxiliary wiring 166, and the like may be composed of one or more films containing molybdenum, titanium, tantalum, tungsten, aluminum, or an alloy containing a metal selected from these. These structures are also formed using a sputtering method, a CVD method, or the like. The planarizing film 152 and spacers 154 are formed to contain polymers such as polyimide, polyamide, silicone resin, acrylic resin, and epoxy resin. These may be formed using an inkjet method, a spin coating method, a slot coating method, a dip coating method, or the like.

[0033] The control electrode 120 and the counter electrode 122 may be configured to contain molybdenum, titanium, tantalum, tungsten, aluminum, or an alloy selected from these, or may be configured to contain a conductive oxide that transmits visible light, such as indium-tin oxide (ITO) or indium-zinc oxide (IZO). By configuring the control electrode 120 and the counter electrode 122 to transmit visible light, it becomes possible to directly observe the droplets visually or using an optical microscope, etc. The control electrode 120 and the counter electrode 122 may also be formed using a sputtering method, a CVD method, etc.

[0034] As described above, each of the control electrodes 120-1 located in the first row partially overlaps with the first opening 104a. Therefore, as shown in FIG. 7, by dropping a droplet 190 onto the electrowetting device 100 using the first opening 104a, the droplet 190 can be reliably deposited onto the control electrode 120 via the first insulating film 118-1. Furthermore, because capillary action occurs in the droplet 190 due to the minute space between the first insulating film 118-1 and the second insulating film 118-2, the droplet 190 can be reliably permeated between the control electrode 120 and the counter electrode 122. As a result, an electric field of any desired strength can be applied to the droplet 190 via the first insulating film 118-1 and the second insulating film 118-2. Furthermore, as described above, the control electrode 120-1 overlapping with the first opening 104a is formed with a larger area than the control electrodes 120 located in the second to (m-1)th rows. This increases the capacitance formed by the control electrode 120 and the counter electrode 122, resulting in a large change in contact angle. This feature enables the droplet 190 dropped through the first opening 104a to be quickly transported to the second row side.

[0035] Although not shown, the same is true for the second opening 104b and the control electrode 120 overlapping therewith. Therefore, even when the second opening 104b is used as a droplet inlet, the droplets can be easily injected and the injected droplets can be quickly transported. Conversely, when the second opening 104b is used as a droplet outlet, the droplets can be dropped from the second opening 104b by utilizing gravity, or a dropper, pipette, syringe, or the like can be inserted into the second opening 104b to suck out the droplets, so that the droplets can be easily collected and discharged.

[0036] To further facilitate the injection and ejection of droplets, the thickness of a portion of the planarization film 152 may be reduced in the rows where the control electrodes 120-1 and / or 120-m overlapping the first opening 104a and / or the second opening 104b, respectively, are arranged, i.e., the first row and / or the mth row. Specifically, in the second to (m-1)th rows, the planarization film 152 is formed so that its upper surface (excluding the upper surface of the opening portion used for electrical connection between the control electrode 120 and the transistor 132; the same applies below) is flat (see FIG. 6). In contrast, as shown in FIG. 9, in the first row, the planarization film 152 may be configured so that the height of the upper surface of the planarization film 152 overlapping the first opening 104a is lower than that of the second to (m-1)th rows. As a result, a step is created on the upper surface of the planarization film 152 in the first row, and the control electrode 120 is formed to cover this step. Although not shown, the same applies to the m-th row, and the height of the upper surface of the planarization film 152 overlapping the control electrode 120 and the second opening 104b may be set lower than the height of the upper surface of the planarization film 152 in the second to (m-1)-th rows. As a result, a step occurs on the upper surface of the planarization film 152 in the m-th row as well, and the control electrode 120 is formed to cover this step.

[0037] The planarization film 152, whose upper surface has different heights, can be formed by exposure using a gray-tone mask or half-tone mask. For example, a positive resist for providing the planarization film 152 is applied to the array substrate 102, on which the control circuit has been formed, and then exposed to light through the gray-tone mask or half-tone mask. The gray-tone mask or half-tone mask is positioned so that a slit in the gray-tone mask that is smaller than the resolution of the exposure device or a semi-transparent portion of the half-tone mask overlaps with the portion to be reduced in height. On the other hand, the gray-tone mask or half-tone mask is positioned so that light is not irradiated onto the portion to be reduced in height. This results in the portion to be reduced in height becoming an intermediately exposed portion, and the portion not to be reduced in height becoming an unexposed portion. Subsequent development can form the planarization film 152 with different upper surface heights. If a negative resist is used, the unexposed and exposed portions can be swapped.

[0038] (6) Connection between Counter Electrode and Auxiliary Wiring: Auxiliary wiring 166 electrically connected to the power terminal 112 is also provided on the array substrate 102 (see FIG. 4 ). The auxiliary wiring 166 receives a constant potential from an external control circuit board (not shown) via the power terminal 112. Because the auxiliary wiring 166 is electrically connected to the counter electrode 122, it can also supply a constant potential to the counter electrode 122. In the example shown in FIG. 4 , the auxiliary wiring 166 is arranged along three sides of a rectangular region encompassing the control electrodes 120, excluding the side closest to the signal terminal 110, and is connected to the power terminal 112 at both ends. However, the configuration of the auxiliary wiring 166 is not limited to this. For example, one power terminal 112 may be connected to only one end. Alternatively, although not shown, two auxiliary wirings 166 may be arranged to extend in the column direction, with the power terminal 112 connected to each end. By providing the auxiliary wiring 166, voltage drop across the counter electrode 122 can be prevented, and a uniform potential can be maintained across the entire counter electrode 122.

[0039] The positions and number of electrical connections between the counter electrode 122 and the auxiliary wiring 166 can be set arbitrarily. As shown in the enlarged view of FIG. 4 and the schematic view of the end surface along the chain line A-A' (FIG. 10), the electrical connection between the counter electrode 122 and the auxiliary wiring 166 is made through contact holes (dotted circle in the enlarged view of FIG. 4) on the auxiliary wiring 166. Note that a protective electrode and a connector, which will be described later, are not shown in FIG. 4.

[0040] Specifically, auxiliary wiring 166 is provided on the array substrate 102 in the same layer as the gate electrode 138 of the transistor 132 or the terminals 142, 144. Preferably, the auxiliary wiring 166 is provided on the interlayer insulating film 140 so as to be in the same layer as the terminals 142, 144, which can use a metal with lower resistance (see FIG. 12). A contact hole exposing the auxiliary wiring 166 is formed in the planarization film 152 formed on the auxiliary wiring 166, and a protective electrode 168 is formed to cover this contact hole. The protective electrode 168 is preferably formed in the same layer as the control electrode 120. This allows the protective electrode 168 to be formed of, for example, ITO or IZO, so that corrosion of the auxiliary wiring 166, even if it is exposed in the contact hole, can be prevented.

[0041] An opening is formed in the first insulating film 118-1 provided on the protective electrode 168 to expose the protective electrode 168, and a conductive connector 170 is provided on the protective electrode 168 so as to overlap this opening. This allows the connector 170 to contact the protective electrode 168 and the counter electrode 122, electrically connecting the auxiliary wiring 166 and the counter electrode 122. The connector 170 may be made of a metal such as titanium, molybdenum, tungsten, tantalum, aluminum, or copper, or an alloy containing a metal selected from these. Alternatively, the connector 170 may contain a polymer such as polyimide, polyamide, acrylic resin, or epoxy resin. In this case, the surface is covered with the metal described above. Therefore, the connector 170 containing the polymer may be formed in the same layer as the spacer 154, and then the surface of the connector 170 may be coated with a metal. Alternatively, a metal paste or an anisotropic conductive film may be used as the connector 170.

[0042] Furthermore, a partition 156 for protecting the connector 170 may be provided on the array substrate 102 to prevent contact with the droplets (see FIGS. 4 and 10 ). The partition 156 can be provided so as to contact the planarizing film 152 and the counter electrode 122. Therefore, its height may be the same as or substantially the same as that of the spacer 154. Therefore, it is also possible to form the partition 156 and the spacer 154 simultaneously. By providing the partition 156, even if a droplet is unintentionally transported toward the connector 170, corrosion of the connector 170 by the droplet is prevented, and electrical connection between the counter electrode 122 and the auxiliary wiring 166 is ensured. This feature contributes to improving the reliability of the electrowetting device 100.

[0043] The planar shape of the partition wall 156 is not limited, and for example, as shown in FIG. 11 , the partition wall 156 may be provided so as to partially surround the connector 170. Alternatively, as shown in FIG. 12 , the partition wall 156 may be provided so as to completely surround the connector 170. Alternatively, when a region including all of the control electrodes 120 exists on one side of the connector 170, the partition wall 156 may be provided between the connector 170 and the region so as to be composed of one linear portion extending in the row or column direction ( FIG. 13 ). Alternatively, the partition wall 156 may be provided so as to have an L-shape composed of two linear portions extending in the row and column directions, respectively ( FIG. 14 ).

[0044] As described above, by connecting the counter electrode 122 and the auxiliary wiring 166, the power supply terminal 112, which is a terminal for supplying a potential to the counter electrode 122, can be formed on the substrate on which the signal terminal 110 is formed, i.e., the array substrate 102. Therefore, the electrowetting device 100 can be driven by connecting an FPC only to the array substrate 102. It can be said that such a feature contributes to simplifying the structure of the electrowetting device 100 and reducing manufacturing costs.

[0045] A droplet is dropped onto the control electrode 120-1 arranged in the first row using an opening (e.g., the first opening 104a). Then, by using a drive circuit to appropriately control the potentials applied to the multiple control electrodes 120 while supplying a constant potential to the counter electrode 122, the contact angle of the droplet on the first insulating film 118-1 changes, resulting in the droplet being able to move in any direction (see the arrows in Figure 15). Furthermore, multiple droplets can be mixed and reacted within the electrowetting device 100, making the electrowetting device 100 useful for synthetic reactions, testing various specimens, and the like. The counter substrate 104 has openings, and the control electrodes 120 that overlap the openings are larger than the control electrodes 120 that do not overlap the openings, allowing for easy injection, recovery, and discharge of droplets. Furthermore, the height of the top surface of the planarization film 152 in the portion overlapping the openings can be set lower, which also contributes to facilitating the injection, recovery, and discharge of droplets.

[0046] 2. Modifications (1) Modification 1 As described above, the areas of the control electrodes 120-1 and 120-m arranged in the first and m-th rows are larger than those of the control electrodes 120 arranged in the second to (m-1)-th rows. For this reason, it is preferable to make the contact angle of the droplets on the control electrodes 120-1 and 120-m arranged in the first and m-th rows change more significantly, and to more efficiently transport the droplets toward the control electrodes 120 in the second or (m-1)-th row. For example, the drive circuit may be configured so that the voltage applied to the control electrodes 120-1 and 120-m arranged in the first and m-th rows is larger than the voltage applied to the control electrodes 120 arranged in the second to (m-1)-th rows. Specifically, as shown in FIG. 16 , a shift register 180 to which a start pulse Vstart is input may be provided in the gate line driving circuit 106 so as to correspond to all gate lines 124-1 to 124-m, and an output buffer 182 may be provided between the shift register 180 and the gate lines 124-1 and 124-m in the first and m-th rows. Alternatively, as shown in FIG. 17 , an output buffer 182 may be provided between each gate line 124 and its corresponding shift register 180, and a level shifter 184 may be provided between the shift register 180 and the output buffer 182 in the first and m-th rows. In this case, the shift register 180 and the output buffer 182 may be directly connected in the second to (m−1)-th rows, or a delay buffer 186 may be provided between the shift register 180 and the output buffer 182 as shown in FIG.

[0047] (2) Modification 2 In the above example, two openings are provided in the counter substrate 104, but there is no restriction on the number of openings or cutouts. For example, as shown in FIG. 18 , in addition to the first opening 104a and the second opening 104b, whose longitudinal directions are parallel to the row direction, a third opening 104c, whose longitudinal direction is parallel to the column direction, may be provided in the counter substrate 104. Since the first opening 104a is provided so as to overlap with the control electrodes 120 arranged in the first and m-th rows, the third opening 104c is provided so as to overlap with a portion of each of the control electrodes 120 located in the first column and arranged in the second to (m−1)-th rows. In other words, a portion of each of the control electrodes 120 located in the first column and arranged in the second to (m−1)-th rows overlaps with the counter substrate 104, and another portion is exposed from the counter substrate 104 through the third opening 104c. The portion of each control electrode 120 located in the first column that overlaps with the third opening 104c is located on the opposite side of the second column. Therefore, although not shown, similar to the control electrodes 120 located in the first and m-th rows, each of the control electrodes 120 located in the first column and arranged in the second to (m-1)th rows has a portion overlapping with the counter electrode 122 and another portion exposed from the counter electrode 122. The portion of each control electrode 120 located in the first column that is exposed from the counter electrode 122 is located on the opposite side of the second column. Note that when the first opening 104a and the second opening 104b do not overlap with the control electrodes 120 in the first and n-th columns, respectively, the third openings 104c are formed so that all of the control electrodes 120 located in the first column partially overlap with the third opening 104c and the counter electrode 122.

[0048] Although a description using drawings will be omitted to avoid repetition, the area of ​​the control electrodes 120 arranged in the first column may also be larger than the areas of the control electrodes 120 arranged in the other columns. That is, in the second to (m-1)th rows, the area of ​​the control electrodes 120 arranged in the first column may be larger than the areas of the control electrodes 120 arranged in the second to nth columns. Furthermore, the height of the upper surface of the planarization film 152 overlapping with the third opening 104c may be lower than the height of the upper surface of the planarization film 152 not overlapping with the first opening 104a, the second opening 104b, or the third opening 104c.

[0049] Furthermore, the counter substrate 104 may have a fourth opening 104d instead of or in addition to the third opening 104c (FIG. 19). The fourth opening 104d overlaps a portion of each of the control electrodes 120 located in the nth column. That is, each of the control electrodes 120 located in the nth column and arranged in the second to (m-1)th rows partially overlaps with the counter substrate 104, and another portion is exposed from the counter substrate 104 through the fourth opening 104d. The portion of each of the control electrodes 120 located in the nth column that overlaps with the fourth opening 104d is located on the opposite side of the (n-1)th column. Therefore, although not shown, similar to the control electrodes 120 arranged in the first and mth rows, each of the control electrodes 120 located in the nth column and arranged in the second to (m-1)th rows partially overlaps with the counter electrode 122, and another portion is exposed from the counter electrode 122. The portions of the control electrodes 120 located in the n-th column that are exposed from the opposing electrodes 122 are located on the opposite side of the (n-1)-th column. When the first openings 104a and the second openings 104b do not overlap with the control electrodes 120 in the first and n-th columns, respectively, all of the control electrodes 120 located in the n-th column are arranged so as to partially overlap with the fourth openings 104d and the opposing electrodes 122.

[0050] Similarly, the area of ​​the control electrode 120 arranged in the nth column may be larger than the area of ​​the control electrodes 120 arranged in the other columns. That is, in the second to (m-1)th rows, the area of ​​the control electrode 120 arranged in the nth column may be larger than the area of ​​the control electrodes 120 arranged in the first to (n-1)th columns. When the third opening 104c is also provided, the area of ​​the control electrode 120 arranged in the nth column may be larger than the area of ​​the control electrode 120 arranged in the second to (n-1)th columns. Furthermore, the height of the upper surface of the planarization film 152 overlapping with the fourth opening 104d may be lower than the height of the upper surface of the planarization film 152 not overlapping with the first opening 104a, the second opening 104b, the third opening 104c, or the fourth opening 104d.

[0051] In the above-described modified example, the opposing substrate 104 is provided with the third opening 104c and / or the fourth opening 104d in addition to the first opening 104a and the second opening 104b, so that the droplets can be easily injected, collected, and discharged. Furthermore, the control electrode 120 is arranged so as to overlap the third opening 104c or the fourth opening 104d, so that the injected droplets can be easily transported, collected, and discharged. Setting the height of the planarization film 152 overlapping the third opening 104c or the fourth opening 104d low makes it even easier to inject, collect, and discharge the droplets.

[0052] The above-described embodiments of the present invention can be combined as appropriate as long as they are not mutually inconsistent. Furthermore, even if a person skilled in the art appropriately adds or deletes components or modifies designs, or adds or omits processes or modifies conditions based on the embodiments, such combinations are included within the scope of the present invention as long as they include the gist of the present invention.

[0053] Even if there are other effects and advantages different from those brought about by the aspects of each of the above-mentioned embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0054] 100: electrowetting device, 102: array substrate, 104: opposing substrate, 104a: first opening, 104b: second opening, 104c: third opening, 104d: fourth opening, 106: gate line driving circuit, 108: signal line driving circuit, 110: signal terminal, 112: power supply terminal, 114: undercoat, 116: overcoat, 118-1: first insulating film, 118-2: second insulating film, 120: control electrode, 122: opposing electrode, 124: Gate line, 126: signal line, 130: control circuit, 132: transistor, 134: semiconductor film, 136: gate insulating film, 138: gate electrode, 140: interlayer insulating film, 142: terminal, 144: terminal, 150: capacitance element, 152: planarization film, 154: spacer, 156: partition wall, 166: auxiliary wiring, 168: protective electrode, 170: connector, 180: shift register, 182: output buffer, 184: level shifter, 186: delay buffer, 190: droplet

Claims

1. An electrowetting device comprising: an array substrate; a plurality of control electrodes located on the array substrate and arranged in a matrix having a first row to an mth row and a first column to an nth column; a counter electrode located on the plurality of control electrodes and overlapping the plurality of control electrodes; and a counter substrate located on the counter electrode and having a first opening and a second opening, wherein the first opening is arranged so as to partially overlap each of the control electrodes located in the first row, and the second opening is arranged so as to partially overlap each of the control electrodes located in the mth row, and m and n are each selected from integers greater than or equal to 4.

2. An electrowetting device as described in claim 1, wherein in each of the first column to the nth column, the portion of the control electrode in the first row exposed from the first opening is located on the opposite side to the second row, and the portion of the control electrode in the mth row exposed from the second opening is located on the opposite side to the (m-1)th row.

3. The electrowetting device according to claim 1, wherein each of the control electrodes located in the first row and the mth row partially overlaps the counter electrode.

4. An electrowetting device as described in claim 1, wherein the size of the control electrodes located in the first row and the mth row is larger than the size of the control electrodes located in the second row to the (m-1)th row.

5. An electrowetting device as described in claim 1, further comprising a plurality of transistors electrically connected to the plurality of control electrodes, respectively, and a planarization film located between the plurality of transistors and the plurality of control electrodes, wherein at least one of the height of the upper surface of the planarization film overlapping the first opening and the height of the upper surface of the planarization film overlapping the second opening is lower than the height of the upper surface of the planarization film not overlapping the first opening or the second opening.

6. An electrowetting device as described in claim 1, further comprising auxiliary wiring located on the array substrate and electrically connected to the opposing electrode via a conductive connector, and a partition wall on the array substrate, the partition wall being arranged to at least partially surround the conductive connector in a planar view.

7. The electrowetting device according to claim 1, further comprising a plurality of spacers disposed between the array substrate and the opposing substrate, and wherein all of the plurality of control electrodes are exposed from the plurality of spacers.

8. An electrowetting device as described in claim 1, further comprising a plurality of transistors electrically connected to the plurality of control electrodes respectively, and a gate line driving circuit configured to supply gate signals to the plurality of transistors, wherein the potential of the gate signals supplied to the transistors connected to the control electrodes located in the first row and the mth row is greater than the gate signals supplied to the transistors connected to the control electrodes located in the second row to the (m-1)th row.

9. An electrowetting device comprising: an array substrate; a plurality of control electrodes located on the array substrate and arranged in a matrix having first to m-th rows and first to n-th columns; a counter electrode located on the plurality of control electrodes and overlapping the plurality of control electrodes; and a counter substrate located on the counter electrode and having a first opening, a second opening, and a third opening, wherein the first opening is arranged to partially overlap with each of the control electrodes located in the first row, the second opening is arranged to partially overlap with each of the control electrodes located in the m-th row, and the third opening is arranged to partially overlap with each of the control electrodes located in the second row to the (m-1)th row and in the first column, and m and n are each selected from integers greater than or equal to 4.

10. An electrowetting device as described in claim 9, wherein in each of the first column to the nth column, the portion of the control electrode in the first row exposed from the first opening is located on the opposite side to the second row, and the portion of the control electrode in the mth row exposed from the second opening is located on the opposite side to the (m-1)th row.

11. An electrowetting device as described in claim 9, wherein in each of the second row to the (m-1)th row, the portion of the control electrode located in the first column that is exposed from the third opening is located on the opposite side to the second column.

12. The electrowetting device according to claim 9, wherein each of the control electrodes located in the first row and the mth row partially overlaps the counter electrode.

13. The electrowetting device according to claim 9, wherein in each of the second row to the (m-1)th row, each of the control electrodes located in the first column partially overlaps the counter electrode.

14. An electrowetting device as described in claim 9, wherein the size of the control electrodes located in the first row and the mth row is larger than the size of the control electrodes located in the second row to the (m-1)th row.

15. An electrowetting device as described in claim 9, wherein the size of the control electrodes located in the second row to the (m-1)th row and in the first column is greater than the size of the control electrodes located in the second row to the (m-1)th row and in the second column to the nth column.

16. An electrowetting device as described in claim 9, further comprising a plurality of transistors electrically connected to the plurality of control electrodes, respectively, and a planarization film located between the plurality of transistors and the plurality of control electrodes, wherein at least one of the height of the upper surface of the planarization film overlapping the first opening and the height of the upper surface of the planarization film overlapping the second opening is lower than the height of the upper surface of the planarization film not overlapping the first opening or the second opening.

17. An electrowetting device as described in claim 9, further comprising a plurality of transistors electrically connected to the plurality of control electrodes, respectively, and a planarization film located between the plurality of transistors and the plurality of control electrodes, wherein the height of an upper surface of the planarization film overlapping the third opening is lower than the height of the upper surface of the planarization film that does not overlap the first opening, the second opening, or the third opening.

18. An electrowetting device as described in claim 9, further comprising auxiliary wiring located on the array substrate and electrically connected to the opposing electrode via a conductive connector, and a partition wall on the array substrate, the partition wall being arranged to at least partially surround the conductive connector in a planar view.

19. The electrowetting device according to claim 9, further comprising a plurality of spacers disposed between the array substrate and the opposing substrate, and wherein all of the plurality of control electrodes are exposed from the plurality of spacers.

20. An electrowetting device as described in claim 9, further comprising a plurality of transistors electrically connected to the plurality of control electrodes, respectively, and a gate line driving circuit configured to supply gate signals to the plurality of transistors, wherein the potential of the gate signals supplied to the transistors connected to the control electrodes located in the first row and the mth row is greater than the potential of the gate signals supplied to the transistors connected to the control electrodes located in the second row to the (m-1)th row.

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