An active-matrix display device and a method for the production of the same

Abstract: An active-matrix display device having low-resistance added capacitance electrode wires (91) in which single or plural secondary wires (121) connected electrically to the added capacitance electrode wires reduce the apparent electrical resistance of the added capacitance electrode wires, which makes the time constant of the added capacitance electrode wires smaller, so that the charging characteristics of the added capacitance are improved and contrast and other display characteristics of the liquid crystal display device are improved.

Description: BACKGROUND OF THE INVENTION 1. Field of the invention: This invention relates to an active-matrix display device and a method for its production. 2. Description of the prior art: A display pattern is formed on the screen of liquid crystal display devices, EL display devices, plasma display devices, etc., by selectively driving picture element electrodes arranged in a matrix. A voltage is applied between the selected picture element electrode and the opposing electrode positioned opposite the selected picture element electrode so as to optically modulate a display medium disposed therebetween. This optical modulation is observed as the display pattern. One drive method used to drive picture element electrodes is the active-matrix drive method wherein the independent picture element electrodes are arranged in rows and driven by switching elements that are connected with the corresponding picture element electrodes. The switching elements which selectively drive the picture element electrodes are generally thin-film transistor (TFT) elements, metal-insulator-metal (MIM) elements, MOS transistors, diodes, or varistors. Active-matrix drive systems make high-contrast displays possible and are used in liquid crystal television, word processors and computer terminal display devices. Figure 9A is a perspective view of an active-matrix liquid crystal display device which employs a conventional active-matrix substrate. Figure 9B is a cross sectional view of the device of Figure 9A taken along the line B-B. Figure 9C is a diagram of the active-matrix substrate used in the device of Figure 9A. The active-matrix liquid crystal display device has a liquid crystal layer 68 that is sandwiched between the active-matrix substrate 51 on which thin-film transistors (TFT) functioning as switching elements are formed and the opposing substrate 52 positioned opposite the substrate 51 . The liquid crystal layer 68 is sealed by a sealant resin 70 . This active-matrix substrate 51 has an insulation substrate 50 , numerous parallel gate electrode wires 61 disposed on the insulation substrate 50 , and numerous source electrode wires 62 which run perpendicular to the wires 61 . The gate electrode wires 61 are connected to the corresponding gate electrode terminals 53 running along one edge of the substrate 50 . In a similar manner, the source electrode wires 62 are connected to the corresponding source electrode terminals 54 running along another edge of the substrate 50 . As shown in Figure 9B, the opposing electrodes 65 on the opposing substrate 56 are connected electrically via the connecting electrodes 67 to the opposing electrode terminals 55 on the substrate 50 . The orientation films 69 and 69 are formed on the top of the picture element electrodes 64 on the substrate 50 and on top of the opposing electrodes 65 on the opposing substrate 56 . As shown in Figure 9C, each of the TFTs 63 is positioned near the intersection between the gate electrode wire 61 and the source electrode wire 62 . A scanning signal is supplied from the gate electrode wire 61 to the gate electrode of the TFT 63 , and a video signal is supplied from the source electrode wire 62 to the source electrode of the TFT 63 . The drain electrode of the TFT 63 is connected to the corresponding picture element electrode 64 . This kind of liquid crystal display device performs the display operation as described below. First, a gate ON voltage is applied to the gate electrode wires 61 , and all of the TFTs 63 connected to the gate electrode wires 61 become ON. At the same time, a voltage corresponding to the video signal in synchronism with the gate ON signal is applied to the picture element electrodes 64 via the source electrode wires 62 . Next, a gate OFF voltage is applied to the above-mentioned gate electrode wires 61 , and all of the TFTs 63 connected to these electrode wires 61 become OFF. When the TFTs 63 become OFF, the charge stored in the picture element electrodes 64 is retained. The period of time for which the charge is stored is dependent on the time constant determined by the electrical capacitance of the liquid crystal cell composed of the picture element electrodes 64 , the opposing electrodes 65 , the liquid crystal layer 68 , etc., and the OFF resistance of the TFTs 63 . This display operation is repeatedly performed on the gate electrode wires 61 to display the video image on the display device. However, it is known that the charge retained by the picture element electrodes 64 drops due to the action of the TFTs 63 . This drop in voltage is explained using Figure 10 showing a portion of the TFT 63 . Figure 11 is an equivalent circuit of the TFT 63 of Figure 10. An amorphous silicon intrinsic semiconductor layer (hereinafter, referred to as a-Si(i) layer) 9 which functions as an electron transit layer is formed as part of the gate electrode wires 61 on the gate electrodes 71 in a manner to sandwich an insulation film therebetween, and then on top of the semiconductor layer 9 , the source electrodes 72 connected to the source electrode wires 62 and the drain electrodes 73 connected to the picture element electrodes 64 are formed. A liquid crystal cell 76 is formed between the picture element electrodes 64 and the opposing electrodes 65 (not shown). The above-mentioned voltage drop is due to the parasitic capacitance Cgd which forms in the area of the part S1 where the drain electrodes 73 and the gate electrodes 71 overlap each other. As shown in Figure 11, the parasitic capacitance Cgd is formed parallel to the TFT 63 . The drop V shift in the potential of the drain electrodes 73 due to the parasitic capacitance Cgd is given by the following equation. V shift = Cgd Cgd + Clc x V gate wherein Clc is the electrical capacitance due to the liquid crystal cell 76 and the V gate is the potential difference between the ON signal and the OFF signal applied to the gate electrodes 71 . Due to the presence of this parasitic capacitance Cgd in the TFT 63 , when the signal applied to the gate electrodes 71 changes from an ON signal to an OFF signal, the potential difference between the ON signal and the OFF signal is divided by the ratio of the parasitic capacitance Cgd to the capacitance Clc of the liquid crystal cell. Therefore, the potential of the drain electrodes 73 i.e., the potential of the picture element electrodes 64 , drops by the amount indicated by V shift in the above equation. In order to make the V shift value small, electrodes 91 for added capacitance made from a transparent conductive film are often disposed below the picture element electrodes 64 as shown in Figure 12. Figures 13 and 14 are cross sectional views taken along the lines P-P and Q-Q of Figure 12. As shown in Figure 12, the added capacitance electrode wires 91 are parallel to the gate electrode wires 61 , and the added capacitance electrode wires 91 positioned below the picture element electrodes 64 are wider than connecting portions for connecting one added capacitance electrode wire to the adjacent added capacitance electrode wire. As shown in Figures 13 and 14, the added capacitance electrode wires 91 are formed below a gate insulation film 101 that has been formed under the picture element electrodes 64 . The added capacitance C S forms between parts of the added capacitance electrode wires 91 and the picture element electrodes 64 . Figure 15 is an equivalent circuit on the substrate in Figure 12. As shown in Figure 15, since the added capacitance C S is disposed parallel to the liquid crystal cell capacitance Clc, the above-mentioned voltage drop V shift is given by the following equation. V shift = Cgd Cgd + Clc + C S x V gate By including an added capacitance C S in this manner, the voltage drop V shift can be made small. However, the added capacitance electrode wires 91 are made from ITO, SnO₂, and other types of transparent conductive films, so they have a larger resistance than do the metal films used for the gate electrode wires 61 , etc. When the electrical resistance of the added capacitance electrode wires 91 is large, the time constant of the added capacitance C S becomes large, which prevents the storage of a sufficiently large charge while the ON signal is being applied to the gate electrodes 71 of the TFT 63 . This tendency becomes more pronounced when the display device is made larger because the total length of the added capacitance electrode wires 91 becomes greater. Moreover, as the resolution of the display screen is increased, the number of gate electrode wires 61 increases, so it becomes necessary to shorten the length of time the ON signal is applied to the gate electrodes 71. Furthermore, Japanese Patent application JP-A-59 7344 discloses an active-matrix display device of the type defined in the first part of claim 1. In the case of this prior art device , no secondary wire electrically connected to the added capacitance electrode for reducing the effective electrical resistance is formed. SUMMARY OF THE INVENTION In one aspect, this invention provides an active-matrix display device comprising a pair of insulating substrates that face each other, a number of scanning lines that are disposed in a parallel manner on the inner surface of one of said substrates, a number of source lines that intersect said scanning lines and are disposed in a parallel manner on the inner surface of said one of the substrates, an optically-modulatable display medium disposed between said insulating substrates, picture element electrodes that are arranged in a matrix on the inner surface of said one of the substrates, a respective switch means on said one of the substrates for each picture element electrode, and a number of added capacitance electrode wires each of which is arranged in a parallel manner between the adjacent scanning lines, said added capacitance electrode wires being made of a transparent conductive film on said one of the substrates so as to sandwich at least one insulating film between said picture element electrode and said added capacitance electrode wire, characterised by a secondary wire that is disposed above or beneath said added capacitance electrode wire, said secondary wire being electrically connected to said added capacitance electrode wire so as to reduce the effective electrical resistance of the added capacitance electrode wire. In another aspect, this invention provides a method for the production of the above-defined active-matrix display device, in which device said switch means comprises a thin film transistor, the method being characterised by: patterning a conductive layer on the inner surface of said one substrate to form simultaneously gate electrodes of the thin film transistors, gate electrode wires as said scanning wires, and said secondary wire. The invention disclosed herein makes possible the objectives of:(1) providing an active-matrix display device with low-resistance added capacitance electrode wires in which single or plural secondary wires connected electrically to the added capacitance electrode wires reduce the apparent electrical resistance of the added capacitance electrode wires, which makes the time constant of the added capacitance electrode wires smaller, so that the charging characteristics of the added capacitance are improved and contrast and other display characteristics of the active-matrix display device are improved; (2) providing an active-matrix display device with added capacitance electrode wires, in which single or plural secondary wires are formed on the added capacitance electrode wires made of transparent conductive films so as to sandwich an insulation film therebetween and the added capacitance electrode wires and secondary wires are connected electrically through connection grooves or through-holes which are openings formed in the insulation film, and moreover an anodic oxide film is formed on the secondary wires, so that the picture element electrodes and secondary wires can be fully insulated; (3) providing an active-matrix display device with added capacitance electrode wires, in which single or plural secondary wires connected electrically to the added capacitance electrode wires are arranged in a zigzag manner, and accordingly it is not necessary to add another process for electrically connecting the secondary wires on the substrate; (4) providing an active-matrix display device with added capacitance electrode wires, in which the occurrence of insulation failure in the added capacitance electrode wires can be reduced, thus improving the yield of an active matrix substrate; (5) providing a method for the production of active-matrix display devices with low-resistance added capacitance electrode wires in which single or plural secondary wires to be connected electrically to the added capacitance electrode wires are formed at the same time the gate electrode wires of thin film transistors are formed on a glass substrate, and accordingly a new production process for forming the secondary wires need not be added and an active-matrix display device with secondary wires can be produced using conventional production processes; and (6) providing a method for the production of active-matrix display devices with low resistance added capacitance electrode wires, which produces active-matrix substrates with secondary wires for the added capacitance electrode wires without increase in production processes, which makes it possible to reduce the cost of the active-matrix display devices. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a plan view showing an active-matrix substrate used in this invention. Figure 1B is a sectional view taken along line B-B of Figure 1A. Figures 2A-2D are schematic diagrams showing a production process of the substrate of Figure 1A. Figures 3A-3D are schematic diagrams showing a production process of the substrate of Figure 1B. Figure 4A is a plan view showing another active-matrix substrate used in this invention. Figures 4B and 4C, respectively, are sectional views taken along lines B-B and C-C of Figure 4A. Figures 5A-5D are schematic diagrams showing a production process of the substrate of Figure 4B. Figures 6A-6D are schematic diagrams showing a production process of the substrate of Figure 4C. Figure 7 is a plan view showing still another active-matrix substrate used in this invention. Figures 8A-8C, respectively, are plan views showing other active-matrix substrates used in this invention. Figure 9A is a perspective view showing a conventional active-matrix display device. Figure 9B is a sectional view taken along line B-B of Figure 9A. Figure 9C is a schematic diagram showing the substrate of Figure 9A. Figure 10 is a plan view showing a region of the TFT in the substrate shown in Figure 9A. Figure 11 is an equivalent circuit diagram of the TFT of Figure 10. Figure 12 is a plan view showing a conventional active-matrix substrate with added capacitance. Figures 13 and 14, respectively, are sectional views taken along lines P-P and Q-Q of Figure 12. Figure 15 is an equivalent circuit diagram of the substrate of Figure 12. DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Figure 1A is a plan view of the active-matrix substrate used in an active-matrix display device of this invention. Figure 1B is a cross sectional view of the substrate taken along line B-B of Figure 1A. Figures 2A through 2D and Figures 3A through 3D show a production process of the active-matrix substrate of Figure 1A. Figures 2A-2D are plan views showing the entire substrate of Figure 1A and Figures 3A-3D are sectional views taken along line B-B of Figure 1A. First, as shown in Figures 2A and 3A, gate electrode wires 61 , gate electrode terminals 53 , secondary wires 121 , and a peripheral wire 130 are formed by a metal film on a glass substrate 50 . The gate electrode terminals 53 are positioned on the ends of the gate electrode wires 61 . The gate electrode terminals 53 are connected to the peripheral wire 130 . The peripheral wire 130 is positioned around the area where the gate electrode wires 61 and the secondary wires 121 are formed. Next, an anodic oxide film 122 is formed on the gate electrode wires 61 by anodic oxidation (Figure 3B). Anodic oxidation of the gate electrode wires 61 is performed by current flow via the peripheral wire 130 . Therefore, all of the gate electrode wires 61 undergo anodic oxidation at the same time. The added capacitance electrode wires 91 made of a transparent conductive film of ITO, SnO₂, etc., are then formed so they cover the secondary wires 121 as shown in Figures 2B and 3C. Part of each of the added capacitance electrode wires 91 functions as an added capacitance electrode. The shape of the added capacitance electrode wire 91 in Figure 1A is shown in a rectangular shape in Figure 2B to simplify the diagram. The thickness of the added capacitance electrode wires 91 is 500-2000 Å. A gate insulation film 101 of SiO₂, SiNx, etc., is then laid over the entire surface of the substrate 50 (Figure 3D). The areas of gate insulation film 101 above the ends of the added capacitance electrode wires 91 are removed to make connection holes 131 (Figure 2C). Next, as shown in Figure 2D, a connection wire 132 which electrically connects the added capacitance electrode wires 91 through each of the connection holes 131 , opposing electrode terminals 55 , source electrode wires 62 , and source electrode terminals 54 are formed at the same time. One end of the connection wire 132 is electrically connected to the opposing electrode terminal 55 , and when assembled as a display device, it is electrically connected to the opposing electrode. The source electrode terminals 54 are electrically connected to one end of each of the source electrode wires 62 . As shown in Figure 1B, the picture element electrodes 64 are formed over the added capacitance electrode wires 91 in a manner so as to sandwich a gate insulation film 101 therebetween, and the peripheral wire 130 is separated from the gate electrode terminals 53 and the source electrode terminals 54 to yield the active-matrix substrate in Figure 1A. However, as shown in Figure 1B, the added capacitance electrode wires 91 and gate insulation film 101 are formed on the stepped part of the secondary wires 121 , so there is a greater tendency that the covering of the added capacitance electrode wires 91 by the gate insulation film 101 becomes less complete than when there are no secondary wires 121 . Moreover, it is also possible for the insulation to become defective due to pin holes which form in the gate insulation film 101 , which causes more serious defects such as line defects. Example 2 Figure 4A is a plan view of an example designed to solve the above-mentioned problem. TFTs 17 are formed as switching elements on the gate electrodes 19 connected to the gate electrode wires 5 , the source electrodes 14 of the TFTs 17 are connected to the source electrode wires 13 , and the drain electrodes 15 thereof are connected to picture element electrodes 16 . The gate electrode wires 5 and the source electrode wires 13 intersect to sandwich a gate insulation film 8 therebetween, which will be described below. The added capacitance electrode wires 2 are positioned below the picture element electrodes 16 . Figure 4B and Figure 4C, respectively, are cross sectional views taken along lines B-B and C-C of Figure 4A. Figures 5A to 5D show a production process for the substrate in Figure 4B. A film, 500-2000 Å thick, was formed on a glass substrate 1 from ITO, SnO₂ or other transparent conductive material, and the added capacitance electrode wires 2 were formed by patterning this film in the prescribed shape (Figure 5A). A base insulation film 3 made of SiO₂, Ta₂O₅ or Al₂O₃ was then laid over the entire surface of this substrate. When a material other than an oxide such as SiNx is used as the base insulation film 3 , the added capacitance electrode wire 2 formed below the base insulation film 3 from a transparent conductive material is reduced during the production process and it loses its transparency, which is undesirable. The thickness of the base insulation film 3 is set at about 1000 Å when a material with a small specific dielectric constant such as SiO₂ (the specific dielectric constant thereof being 4 ) is used, but the thickness can be greater when a material with a large specific dielectric constant such as Ta₂O₅ (the specific dielectric constant thereof being 23-25) is used. The base insulation film 3 can have a multilayer structure in which a nitride film or an oxide film of a different material is formed on the above-mentioned oxide film. When a multilayer structure is used for the base insulation film 3 , the first layer that is in contact with the added capacitance electrode wire 2 below it must be formed using the oxide materials mentioned above for the same reason as mentioned above. Next, the through-holes 4 were formed in the base insulation film 3 (Figure 5B). The through-holes 4 are provided to electrically connect the added capacitance electrode wires 2 and the secondary wires 6 to be formed later. In this example, as shown in Figure 4A, the through-holes 4 were made in two places, but they may also be a continuous groove shape. A metal film of Ta or the like, which is subject to anodic oxidation, was formed over the entire surface of the base insulation film 3 including holes 4 , and this was then patterned into the prescribed shape by an etching technique to form the secondary wires 6 , the gate electrode wires 5 and the gate electrodes 19 (Figure 5C). At this time, the width of the secondary wires 6 must be greater than the through-holes 4 to prevent exposure of the added capacitance electrode wires 2 . Patterns are selectively formed in this Ta metal film by a dry etching technique when the base insulation film 3 is a SiO₂ film and by a wet etching technique using a mixture of HF and HNO₃ when the base insulation film 3 is a Ta₂O₅ film. Next, the anodic oxide film 7 is formed by anodic oxidation of the surface of the secondary wires 6 , the gate electrode wires 5 (Figure 5D) and the gate electrodes 19 . The Ta metal undergoes anodic oxidation in an ammonium borate solution, a citric acid solution or an ammonium tartrate solution, so a Ta₂O₅ is formed on the surface of the Ta metal. Moreover, a gate insulation film 8 of SiNx was laid over the entire surface of this substrate to form the picture element electrodes 16 and yield the configuration shown in Figure 4B. Figures 6A through 6D show a production process of the TFT 17 in Figure 4C. An anodic oxide film 7 was formed on the top of the gate electrodes 19 as described above, and then a SiNx gate insulation film 8 was formed over the entire surface of the base insulation film 3 including the anodic oxide film 7 . The entire surface of the substrate was then covered with an a-Si(i) layer 22 which serves as a semiconductor layer and a SiNx layer 10 which serves as an etching stop layer (Figure 6A). The SiNx layer 10 was then patterned in the prescribed shape, except for a part positioned above the gate electrodes 19 , so as to form the etching stop layer 11 (Figure 6B). An a-Si(n⁺) layer with a thickness of 1000 Å (not shown) covering the etching stop layer 11 was formed by the plasma CVD method over the entire surface of the a-Si(i) layer 22 , the a-Si(n⁺) layer later becoming a contact layer. Next, the a-Si(i) layer 22 and the a-Si(n⁺) layer were patterned in the prescribed shape to form the semiconductor layer 9 and the contact layer 12 (Figure 6C). Ti, Mo or other metal was then laid over the entire surface of this substrate by spattering, and this metal film was patterned by an etching technique to form the source electrode wires 13 , the source electrodes 14 , and the drain electrodes 15 . At this time, a portion of the contact layer 12 on the etching stop layer 11 was also removed by etching so the contact layer 12 was divided into the part below the source electrode 14 and the part below the drain electrode 15 (Figure 6D). An ITO film with a thickness of 1000 Å was then laid over the entire surface of the substrate by spattering. This ITO film was patterned in the prescribed shape to form the picture element electrodes 16 . The ITO film that is positioned above the source electrode wires 13 , the source electrodes 14 and the drain electrodes 15 was not removed in order to strengthen them (Figure 4C). In this example, an added capacitance is formed between each picture element electrodes 16 and part of the corresponding added capacitance electrode wire 2 . The secondary wires 6 are connected electrically to the added capacitance electrode wires 2 . Since an anodic oxide film 7 is formed on the top surface of the secondary wires 6 toward the picture element electrodes 16 , the occurrence of insulation defects between the secondary wires 6 and the picture element electrodes 16 can be reduced. Moreover, since there are two insulation films, the base insulation film 3 and the gate insulation film 8 , between the picture element electrodes 16 and the added capacitance electrode wires 2 , the occurrence of insulation defects between the added capacitance electrode wires 2 and the picture element electrodes 16 can also be reduced. Example 3 This example is intended to solve the problem arising in Example 1, in which the active-matrix substrate provided with added capacitance electrode wires 91 with secondary wires 121 , as explained in Figure 2C and Figure 2D, requires that the secondary wires 121 be connected to each other electrically, thus requiring an extra production process. Figure 7 is a plan view showing the active-matrix substrate of this example in the course of the production. Gate electrode wires 43 that function as scanning lines, gate electrode terminals 44 , a secondary wire 6 , and a peripheral wire 41 are formed from a metal film on a glass substrate. Gate electrode wires 43 with gate electrode terminals at one end and gate electrode wires 43 with gate electrode terminals at the opposite ends were alternately disposed, and each of the gate electrode terminals 44 were connected to the peripheral wire 41 . The peripheral wire 41 was positioned around the area where the gate electrode wires 43 and the secondary wire 6 were formed. An anodic oxide film formed by means of an anodic oxidation current passing through the peripheral wire 41 was positioned over each of the gate electrode wires 43 . The secondary wire 6 was positioned in a zigzag manner between the gate electrode wires 43 . Opposing electrode terminals 45 for connecting to the opposing electrodes were formed on both ends of the secondary wire 6 . Added capacitance electrode wires 2 were formed from a transparent conductive material above those parts of the secondary wires 6 that were parallel to the gate electrode wires 43 . For simplicity sake, the shape of the added capacitance electrode wire 2 is shown rectangular in Figure 7. The configuration of the part where the added capacitance was formed in this example is the same as in the example shown in Figure 1B. A gate insulation film, picture element electrodes, TFTs, etc., were then formed to yield an active-matrix substrate. In this example, a single continuous secondary wire 6 with no breaks was formed, so no process was required to electrically connect separate secondary wires as in the above-mentioned previous conventional example. In addition, when attempting to make the picture elements smaller and increase the density of the gate electrode wires 43 in the configuration of the above-mentioned conventional example, the wiring density was determined by the width of the gate electrode terminals since all of the gate electrode terminals were on one end of the gate electrode wires and the gate electrode terminals 44 were wider than the gate electrode wires 43 . In this example, however, high density wiring could be achieved because the gate electrode terminals 44 were alternately disposed. Example 4 Figure 8A is a plan view of the active-matrix substrate of this example in the course of production. This example differs from that of Figure 7 in that the secondary wire 6 was connected to the peripheral wire 41 . Moreover, the configuration of the part where the added capacitance was formed in this example was the same as the example shown in Figure 4B, and an anodic oxide film was formed on the top of the secondary wire 6 . By connecting the secondary wire 6 to the peripheral wire 41 in at least one place, anodic oxidation could be performed on the secondary wire 6 at the same time as the gate electrode wires 43 . Anodic oxidation was performed by forming a resist on the areas indicated by A1 and A2 using a printing technique or the like and then immersing the substrate in an anodic oxidation solution and applying a voltage thereto via the peripheral wire 41 . A single, continuous secondary wire 6 with no breaks was also formed in this example, so no process was required to electrically connect the secondary wires as in Example 1. Also, few connections with the peripheral wire 41 are required to perform anodic oxidation, so high-density wiring is possible. Moreover, high-density wiring can also be achieved by alternately disposing the gate electrode terminals 44 . Examples 5 and 6 As shown in Figure 8B, a configuration is also possible in which the secondary wire 6 is connected to the opposing electrode terminals 45 in four places. As shown in Figure 8C, a configuration is also possible in which the secondary wire is divided up into multiple wires, each of the secondary wires 6 has an opposing electrode terminal 45 , and the opposing electrode terminals 45 are connected to the peripheral wire 41 .

Claims: An active-matrix display device comprising a pair of insulating substrates that face each other, a number of scanning lines (61,5) that are disposed in a parallel manner on the inner surface of one of said substrates, a number of source lines (62,13) that intersect said scanning lines and are disposed in a parallel manner on the inner surface of said one of the substrates (50,1), an optically-modulatable display medium disposed between said insulating substrates, picture element electrodes (64,16) that are arranged in a matrix on the inner surface of said one of the substrates (50,1), a respective switch means on said one of the substrates for each picture element electrode, and a number of added capacitance electrode wires (91,2) each of which is arranged in a parallel manner between the adjacent scanning lines, said added capacitance electrode wires (91,2) being made of a transparent conductive film on said one of the substrates (50,1) so as to sandwich at least one insulating film (101,8) between said picture element electrode and said added capacitance electrode wire, characterised by a secondary wire (121,6) that is disposed above or beneath each said added capacitance electrode wire, said secondary wire (121,6) being electrically connected to said added capacitance electrode wire (91,2) so as to reduce the effective electrical resistance of the added capacitance electrode wire. An active-matrix display device according to claim 1, wherein said secondary wire (6) is disposed above said added capacitance electrode wire (2) so as to sandwich an insulation film (3) therebetween, said insulation film having a connection groove or through-holes (4) by which said added capacitance electrode wire and said secondary wire are electrically connected to each other, and wherein an anode oxidation film (7) is disposed on said secondary wire. An active-matrix display device according to claim 1, wherein a respective connection terminal is formed at one end of each scanning line, adjacent ones of said scanning lines having their connection terminals at opposite ends, and said secondary wire is composed of first parts that are electrically connected to corresponding ones of said added capacitance electrode wires so as to be parallel to said scanning lines and second parts that electrically connect with said first parts of said secondary wire at the non-terminal ends of the intervening scanning lines, so that said secondary wire is arranged in a zigzag manner. An active-matrix display device according to claim 3, wherein said secondary wire is arranged to be divided into plural portions. A method for the production of the active-matrix display device defined by claim 1, in which device said switch means comprises a thin film transistor, the method being characterised by: patterning a conductive layer on the inner surface of said one substrate (50) to form simultaneously gate electrodes of the thin film transistors, gate electrode wires (61) as said scanning wires, and said secondary wire (121). A method according to claim 5, comprising: forming said added capacitance electrode wire on the inner surface of said one substrate, forming a first insulation film on said added capacitance electrode wire, forming a connection groove or through-holes in said insulation film, forming said conductive layer on the entire surface of said first insulation film including said connection groove or through-holes, performing said patterning of the conductive layer, forming a second insulation film on the entire surface of said first insulation film on which said secondary wire has been formed, and forming said picture element electrodes on said second insulation film. A method according to claim 5, comprising: forming said conductive layer on the inner surface of said one substrate, performing said patterning of the conductive layer, forming said added capacitance electrode wire to cover said secondary wire therewith, forming said insulation film on said added capacitance electrode wire, and forming said picture element electrodes on said insulation film.

Inventors: SAITO HISASHI, SHIMADA YASUNORI, TANAKA HIROHISA, UJIMASA HITOSHI, SAITO, HISASHI, SHIMADA, YASUNORI, TANAKA, HIROHISA, UJIMASA, HITOSHI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1990
Main classification: G02F1
IPC codes: H01L27, H01L21, G02F1