WO1997034190A1 - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device having active elements of a novel structure that can be fabricated as a finished article without losing pixel regions even in case active elements develop leakage or patterns are cut. Split electrodes (16, 17) are superposed on an oxide film (13a) that is formed on the surface of a coupling layer (13), and they are coupled capacitively through the coupling layer (13) and the oxide film (13a) thereby to constitute a pixel electrode (18) of a unitary structure. MIM elements are connected to the split electrodes (16) and (17). Even in case leakage occurs in the junction portion of either MIM element, the other split electrode properly operates. The same state as when the pattern is cut is established if a defective MIM element is cut off. Even in case the pattern is cut, the split electrodes (16) and (17) are coupled capacitively. Therefore, the potential of the defective split electrode can be indirectly controlled upon controlling the potential of the normal split electrode.

Description

 Description Liquid crystal display device Technical field

 The present invention relates to a liquid crystal display device, and particularly to a technique for compensating for a defect of an active element formed on a liquid crystal panel. Background art

 Conventionally, a liquid crystal panel with a liquid crystal layer interposed between two substrates is provided with a plurality of pixel areas, and each pixel area has an active (active) element such as a TFT (thin film transistor) or MIM (metal-insulator-metal) element. A liquid crystal display device of a type in which elements (for example, non-linear elements) are provided and driven by a method of setting the display state of each pixel region via these active elements is manufactured. For example, by turning on / off the active element based on its non-linearity, the potential applied to the pixel electrode in each pixel area connected to the active element is controlled, and the voltage applied to the liquid crystal layer is controlled. Is adjusted to select the liquid crystal state in the pixel area.

FIG. 5 is a perspective view showing a pattern shape on one substrate of a liquid crystal display device provided with a MIM (metal-insulator-metal) element as an example of an active element. A wiring layer 2 formed by applying tantalum (Ta) on a substrate is provided, and a first electrode portion 2a is formed in the wiring layer 2 for each pixel region G. Anodizing is performed on the surface of the first electrode portion 2a to form an anodized film, and a second electrode 3 formed by depositing chromium (Cr) thereon is formed. The transparent electrode 4 corresponding to the pixel region G is formed of IT 0 (indium oxide) so as to overlap the tip of the second electrode 3. In addition, reflective liquid crystal display When configuring the device, the transparent electrode 4 may be formed as a chrome electrode integrated with the second electrode 3 in some cases.

 An empty cell is formed on the substrate thus formed by forming a transparent electrode on the other transparent substrate and joining the transparent electrode through a sealing material and a spacer. A liquid crystal panel is formed by injecting liquid crystal into these empty cells. For each pixel region, the driving potential of the transparent electrode 4 is controlled from the wiring layer 2 through the MIM element including the first electrode portion 2 a, the anodic oxide film, and the second electrode 3.

 In the above-described liquid crystal display device, if a defect occurs in the MIM element formed for each pixel region G, the pixel region G cannot be driven, and a display defect occurs. . Since the MIM element has an unstable metal-insulator junction, it is easy for defects to occur at this junction, and due to its microstructure, not only at the junction but also at any places such as the wiring section In this case, there is a possibility that leakage (short circuit) at the junction and breakage of the pattern may occur.

 If a junction leak occurs in the MIM element, the non-linearity of the current-voltage characteristic is broken (dotted line in the figure) compared to the normal operating characteristics (solid line in the figure), as shown in Fig. 4. Effective shut-off operation between the part 2 and the pixel electrode 4 cannot be performed. Further, when the pattern is out, it becomes impossible to supply a driving potential to the pixel electrode 4 in the first place.

 In particular, in a normally white liquid crystal display device, which has been increasing in recent years, the charge supplied to the pixel electrode cannot be held not only when the pattern is cut, but also when a leak occurs. The pixel area becomes a white point. Since such white spots are conspicuous, even if such a defect occurs in any part, it becomes a fatal defect for a liquid crystal display device.

To prevent display defects due to the defects of the active elements as described above. For example, there is a method of connecting a plurality of active elements in series to a pixel electrode, as described in Japanese Patent Application Laid-Open No. 2-27133. In this case, there is an advantage that a display defect does not occur even if a leak occurs in any of the active elements. However, in this case, since the active element is connected in series, the pattern configuration becomes complicated and manufacturing becomes difficult, and in the case where the active element and its series circuit portion are cut off, any measures are taken. However, there is a problem that the risk of a break in the pattern is increased by connecting a plurality of active elements.

 Accordingly, the present invention is to solve the above-mentioned problem, and to provide a liquid crystal display device having an active element without losing the pixel area even if a leak or pattern cut of the active element occurs. The goal is to achieve a new structure that can be implemented. Disclosure of the invention

 Means taken by the present invention to solve the above-mentioned problem is that at least one of the pair of substrates has a liquid crystal layer interposed between a pair of light-transmitting substrates, and is formed on at least one of the pair of substrates. What is claimed is: 1. A liquid crystal display device comprising a plurality of pixel areas corresponding to pixel electrodes, wherein a plurality of active elements conductively connected to a wiring layer are formed for each of the pixel areas, and the pixel electrodes are capacitively connected to each other. A liquid crystal display device comprising: a plurality of divided and / or resistance-coupled divided electrode portions; and each of the active elements is conductively connected to a different one of the divided electrode portions.

According to this device, when a leak occurs in an active element, the controllability of the display state by the divided electrode portion corresponding to the active element is reduced, so that a defective active element is found by a display test. Then, by disconnecting the connection, the divided electrode section is capacitively coupled and / or resistively coupled. It is indirectly driven by the divided electrode portion, thereby preventing the occurrence of display defects. Further, when a pattern break occurs in the active element or in the vicinity thereof, the split electrode portion in which the pattern is cut is indirectly driven by the capacitively or resistively coupled split electrode portion, thereby preventing display defects from occurring. Note that the coupling between the split electrode portions may be any of a capacitive coupling portion and a resistive coupling portion, as long as the movement of charges is restricted. Also, a coupled state having both capacitance and resistance may be used.

 Here, the active element may be a non-linear element having a conductor-insulator-conductor junction. In this case, the present invention is particularly effective because a leak at the conductor-insulator-conductor junction easily occurs.

 In this case, the coupling part for capacitively coupling and / or resistance-coupling the divided electrode part is further provided with a capacitive coupling structure using at least one metal and / or insulator constituting the two-terminal nonlinear element. It is preferable to configure. In this case, by using the same metal and / or insulator as the structural pattern of the active element, the element can be easily formed without increasing the number of manufacturing steps.

 Further, it is preferable that a coupling portion for capacitively coupling and / or resistance coupling the divided electrode portion is formed of an insulating layer in contact with the two divided electrode portions for capacitive coupling, and a metal layer opposed to the contact portion. . In this case, a capacitor can be separately formed between the two divided electrode portions via the metal layer, so that the occurrence of insulation failure of the insulating layer can be suppressed and the insulation can be suppressed. Capacitance coupling between the divided electrode portions can be easily performed in the production by the laminated structure of the layer and the metal layer.

Further, it is preferable that a coupling portion that capacitively couples and / or resistance-couples the divided electrode portions is formed so as to shield a gap between the divided electrode portions from light. In this case, the gap formed between the divided electrode portions is Since light is shielded, light leakage in the pixel region can be prevented. In addition, it is desirable that the active element be electrically connected at a plurality of locations of the split electrode portion. In this case, the reliability of the conductive connection between the active element and the divided electrode can be improved.

 In this case, by arranging the plurality of locations on both sides of the corner of the split electrode portion, a sufficient contact area can be secured without taking up a large space. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a perspective view showing a pattern configuration on one substrate in an embodiment of a liquid crystal display device according to the present invention.

 FIG. 2 is an explanatory sectional view schematically showing a sectional structure in the embodiment.

 FIG. 3 is a perspective view showing a pattern configuration on one substrate in a different embodiment.

 FIG. 4 is a graph showing drive characteristics of the MIM element.

 FIG. 5 is a perspective view showing a pattern configuration on one substrate of a liquid crystal display device provided with a conventional MIM element. BEST MODE FOR CARRYING OUT THE INVENTION

 Next, an embodiment of a liquid crystal display device according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory plan view (perspective view) showing a state of one transparent substrate surface of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional structure of the embodiment. FIG. 4 is an explanatory view of a cross-sectional structure shown in FIG.

Hereinafter, a liquid crystal display device including a MIM element will be described in detail as an example of the active element. On a transparent substrate 10 made of glass, tantalum (Ta) is applied to a thickness of about 500 to 100 A by a sputtering method, and is subjected to thermal oxidation to form an oxide film. To form The oxidized film 11 is for improving the adhesion between the transparent substrate 10 made of non-alkali glass and a wiring layer described later.

 Next, tantalum is deposited on the surface of the tantalum oxide film 11 to a thickness of about 1200 to 180 A by a sputtering method, and patterned in a predetermined pattern. Wiring layer (Desert line) 12 is formed. In the wiring layer 12, two extended first electrode portions 12a and 12b are formed for each pixel region G arranged along the extension direction. At this time, the bonding layer 13 made of tantalum is formed simultaneously with the above-mentioned sputtering and patterning.

 Next, the first electrode portions 12a and 12b are anodized, and an anodic oxide film 12c is formed on the surface. Further, since anodizing treatment cannot be applied to the bonding layer 13 formed in an island shape as it is, an oxide film 13a is formed on the surface of the bonding layer 13 by thermal oxidation.

 Thereafter, the transparent substrate 10 was heat-treated (annealed) in an inert gas such as nitrogen at 300 to 450 ° C. for about 2 hours, and then rapidly cooled in air. Chromium (Cr) is deposited on the surface of the liquid crystal substrate 10 treated in this manner to a thickness of about 1000 A by sputtering, and a part thereof is formed on the anodic oxide film 12 c. The second electrode layers 14 and 15 are formed by performing patterning as they are formed.

Finally, ITO (indium tin oxide) was applied to a thickness of about 50 OA by sputtering and patterned to form the second electrode layers 14 and 15. Pixel electrodes formed for each pixel area G so as to overlap the surface of the two conductive connections 14a, 14b, 15a, and 15b Two divided electrode portions 16 and 17 are provided.

 Here, the split electrode portions 16 and 17 are formed so as to overlap the oxide film 13a formed on the surface of the bonding layer 13 respectively. Therefore, the two divided electrode portions 16 and 17 are capacitively coupled via the coupling layer 13 and the oxide film 13a to form an integral pixel electrode 18.

 The other transparent substrate 20 is bonded to the transparent substrate 10 thus formed via a sealing material and a spacer (not shown). On the inner surface of the transparent substrate 20, a transparent electrode 21 is formed. By injecting a predetermined liquid crystal between the transparent substrates 10 and 20, a liquid crystal layer between the transparent electrode 21 and the opposing pixel electrode 18 forms a pixel region G.

 In the present embodiment, two divided electrode portions 16 and 17 are formed for each pixel region G, and MIM elements are formed on the divided electrode portions 16 and 17 respectively. Further, the divided electrode portions 16 and 17 are capacitively coupled to each other via the coupling layer 13. Therefore, even if one of the MIM elements has a defect such as a poor junction and a leak occurs at the junction, no charge moves between the split electrodes, so the other split electrode is normal. Works.

 On the other hand, in the divided electrode section to which the defective MIM element is connected, the potential changes according to the potential of the wiring layer 12 with time due to leakage of the MIM element. And the coupling layer 13 via the oxide film 13a.

If a pattern break occurs between the wiring layer 12 and one of the divided electrode sections 16 and 17, it becomes impossible to supply a drive potential to the divided electrode section where the pattern break has occurred. However, since the two divided electrode portions 16 and 17 are capacitively coupled via the coupling layer 13 and the oxide film 13a, the defect division can be performed by controlling the potential of the normal divided electrode portion. The potential of the electrode can also be controlled indirectly, making it possible to operate almost normally. is there.

 In this case, it is preferable that the capacitance of the capacitive coupling portion be relatively large in order to suppress display defects at the time of leakage and to ensure normal operation at the time of pattern breakage. It should be set to an appropriate capacity value in relation. In the present embodiment, since the capacitive coupling portion is formed over the entire length of the opposing sides of the two divided electrode portions 16 and 17, the capacitance can be increased, while the capacitance coupling portion is formed via the coupling layer 13. Therefore, the two capacitors are connected in series, so that the capacitance value is smaller than that in the case where they are connected via one insulating layer.

 Also, since the coupling layer 13 made of tantalum exists over the entire length of the opposing side between the divided electrode portions 16 and 17, the gap between the divided electrode portions is optically blocked. Therefore, it is possible to prevent leakage in the pixel and to form the wiring layer 12 at the same time when the wiring layer 12 is manufactured, so that the manufacturing can be performed with almost no change in the manufacturing process.

 In addition, since the oxide film 13a is interposed twice between the split electrode portions 16 and 17 via the coupling layer 13, leakage of the capacitance coupling portion due to a pinhole or the like is prevented. The incidence can be reduced.

If a leak occurs in one of the MIM elements, the completed liquid crystal panel is held in the fully lit state or in the half-tone state, and the test is performed to reduce the contrast (normally white). (In the case of a type display, the transmittance is large and it looks white.) By specifying the pixel area, defects caused by leakage can be found. In the pixel region where a defect has occurred, the MIM element having a poor connection is identified, and the conductive connection between the wiring layer corresponding to the MIM element and the split electrode portion is cut by laser light or the like, thereby forming the above-described pattern. The same state as the cut can be obtained, and the display defect can be eliminated. This embodiment was applied to a normally white transmission type liquid crystal display device, and the transmittance of each pixel in a lighting state was measured. As a result, the leakage rate of the MIM element was about 5%, and the occurrence rate of pattern break was less than 1%. The 0 N transmittance of a pixel in which a leak has occurred in one of the MIM elements of the split electrode is about 1.2, where the ON transmittance of a normal pixel is 1, and the ON transmittance after a defective element is cut by laser. The transmittance was about 1.05. Further, the 0 N transmittance of a pixel in which a pattern was cut on one of the divided electrode portions was about 1.05. As a result, the incidence of white spot defects was reduced by about 10% after laser correction, and a significant improvement in yield was obtained.

 In the above embodiment, the divided electrode portions 16 and 17 are connected to each other by the capacitive coupling portion. However, without providing an insulating layer such as the oxide film 13a, the divided electrode portions 16 and 17 have an appropriate resistance value. By forming a resistance layer in place of the bonding layer 13 and the oxide film 13a using a conductive material, it is also possible to obtain substantially the same effect as described above.

This resistive layer suppresses the transfer of electric charge between the split electrodes, guarantees the potential control of the split electrode section to which a normal MIM element is connected in the event of a leak, and ensures the potential control from the normal split electrode section when a pattern break occurs. This is because electric potential can be transmitted. If the resistance of the resistive layer is too large and close to the insulator, the pattern will be cut.A display defect will occur in the corrected state after the leak has occurred.If the resistance of the resistive layer is too low, the split electrode on the leak side will be damaged. The appearance makes it difficult to identify. If the resistance value is too small, the allowable width for the element characteristics of the MIM element is reduced, and the pixel having the divided electrode section connected to the MIM element having a small leakage level has a normal divided electrode section. The effect is that the effect on the image becomes large and the number of pixels to be corrected increases. Therefore, the resistance value of the resistance layer is adjusted to the most preferable resistance value according to the material such as the layer thickness, the layer width, and the alloy composition. The number of the divided electrode portions may be plural, and may be three or more. FIG. 3 shows a case where a pixel electrode 40 in which three divided electrode portions 41, 42, and 43 are capacitively coupled to each other via two coupling layers 33 and 34 is formed in one pixel region G. 3 shows a plane pattern. In this case, three MIM elements are formed from the wiring layer 32 to the first electrode portions 32a, 32b, and 32c, an anodic oxide film (not shown), and the second electrode layers 35, 36, and 37. They are connected to the electrode portions 41, 42, 43.

 In this case, as in the above-described embodiment, even if any one or any two of the MIM elements leak or the pattern is cut, the display failure is eliminated by cutting the pattern of the leak portion. It can be operated with little trouble even if there is a break in the power.

 Here, of the three divided electrode portions, the intermediate divided electrode portion 42 capacitively coupled to the two divided electrode portions 41 and 43 does not need to be connected to the MIM element from the beginning. In this case, this is equivalent to the case where any part of the MIM element including the first electrode portion 32c and the second electrode layer 36 has a cut pattern.

 In the present embodiment, the conductive connection portion between the second electrode layer and the split electrode portion of the MIM element is provided in two places (14a, 14b, 15a, 15b, 3b in FIGS. 1 and 2). Since it is provided at 35a, 35b, 36a, 36b, 37a, 37b) in the figure, it is possible to reduce the possibility of the pattern being cut off at that portion. In this case, the conductive connection portions are formed on both sides of the junction of the MIM element, and are provided on both sides near the corners of the split electrode portion. It can be suppressed, and the pixel area is hardly reduced.

In the above embodiment, the second electrode layers 14 and 15 are formed of chromium and have the MIM structure. However, the second electrode layers are the same as the divided electrode sections 16 and 17. It may be formed soon by IT◦. In this case, the second electrode and the pixel electrode can be formed simultaneously in the same step, and the number of steps can be reduced. Further, in the above-described embodiment, the description has been given by taking the transmission type liquid crystal display device as an example. The pixel electrode can be formed so as to also serve as a reflective layer. In this case, the metal may be a chromium electrode that can be formed integrally with the second electrode layers 14 and 15.

 In addition, the material of each conductor described above can be variously used without being limited to the above example. Further, titanium, molybdenum, aluminum, or the like may be used instead of the chromium.

 In the above embodiment, one active element is connected to each divided electrode part of the pixel electrode. However, the number of active elements connected to the divided electrode part is not limited to one. The active elements described above may be connected in series or in parallel to the divided electrode section. The areas of the divided electrode portions may not be the same as each other, and divided electrode portions having different areas may be provided.

 Further, in the above-described embodiment, only an example in which a plurality of simplest divided electrode portions are arranged in parallel has been described. It is also possible to provide a plurality of divided electrode portions in a shape or concentric angle shape. In this case, it is possible to reduce the apparent difference between the pixel in which the pattern is cut or the laser-cut pixel and the normal pixel.

Industrial applicability As described above, the present invention provides a liquid crystal display device having an active element, which can be commercialized without losing the pixel area even when the active element leaks or the pattern is cut. Has been realized.

Claims

The scope of the claims 1. A liquid crystal having a plurality of pixel regions corresponding to pixel electrodes formed on at least one of the pair of substrates, with a liquid crystal layer interposed between a pair of substrates having at least one of which has a light-transmitting property. In a display device, a plurality of active elements conductively connected to a wiring layer are formed for each of the pixel regions, and the pixel electrodes are divided into a plurality of divided electrode portions that are capacitively and / or resistively coupled to each other. A liquid crystal display device, wherein the liquid crystal display device is formed by dividing and electrically connecting each of the active elements to the different one of the divided electrode portions. 2. The liquid crystal display device according to claim 1, wherein the active element is a two-terminal non-linear element having a conductor-insulator-conductor junction.  3. The method according to claim 2, wherein at least one metal and / or insulator constituting the two-terminal nonlinear element is used as the coupling part for capacitively coupling and / or resistance coupling the divided electrode part. A liquid crystal display device having a capacitive coupling structure.  4. In Claim 1, the coupling part that capacitively and / or resistanceally couples the divided electrode part is an insulating layer that is in contact with the two divided electrode parts that is capacitively coupled, and a metal that faces the contact part. A liquid crystal display device characterized by comprising a layer.  5. The liquid crystal according to claim 1, wherein the coupling portion for capacitively coupling and / or resistance coupling the divided electrode portion is formed so as to shield a gap between the divided electrode portions from light. Display device. 6. The liquid crystal display device according to any one of claims 1 to 3, wherein the active element is conductively connected at a plurality of portions of the split electrode portion. 7. The liquid crystal display device according to claim 6, wherein the plurality of portions are arranged on both sides of a corner of the divided electrode portion.