JP3847419B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device used for a TV, a monitor, a notebook personal computer, a portable terminal, and the like.
[0002]
[Prior art]
In recent years, a thin film transistor (hereinafter referred to as a TFT) made of amorphous Si (hereinafter referred to as a-Si) or polycrystalline Si (hereinafter referred to as Poly-Si) for each pixel in view of obtaining high image quality as a direct-view type liquid crystal display device. The active matrix type liquid crystal display device which drives the liquid crystal by applying a voltage to the pixel electrode by this switching operation has come to be used in many cases.
As an active matrix liquid crystal display device, a TN (Twisted Nematic) display method in which the direction of the electric field applied to the liquid crystal is perpendicular to the substrate surface is mainly employed. In recent years, an IPS (In-Plane Switching) type liquid crystal display device in which the direction of the electric field applied to the liquid crystal is substantially parallel to the substrate surface has been developed as a technique for realizing a wide viewing angle.
[0003]
FIG. 4 is a plan view of a TFT array of the IPS liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 7-36058. In the figure, 1 is a gate wiring made of a conductor such as Al, Cr, Ta, Mo, W, Ti, Zr, Cu and alloys thereof, 2 is a counter electrode formed simultaneously with the gate wiring 1, and 3 is a counter electrode 2. Connected common wiring, 4 is a TFT portion made of a-Si, poly-Si or the like for forming a switching element, 5 is a conductor such as Al, Cr, Ta, Mo, W, Ti, Zr, Cu and alloys thereof 6 is a pixel electrode formed at the same time as the source wiring 5, 7 is a storage capacitor portion for holding a liquid crystal driving voltage formed by sandwiching an insulating layer between the common wiring 3 and the pixel electrode 6, and 8 is Each liquid crystal molecule is shown.
[0004]
In the IPS system, the pixel electrode 6 and the counter electrode 2 are formed on the same substrate, the electric field applied to the liquid crystal 8 is in a direction substantially parallel to the substrate surface, and the liquid crystal molecules rotate in the plane. On the pixel electrode 6 and the counter electrode 2, the liquid crystal molecules do not rotate because no electric field is applied in the horizontal direction to the liquid crystal molecules. That is, in the IPS method, the pixel electrode 6 and the counter electrode 2 do not need to be transparent in principle. Therefore, in this conventional example, in order to simplify the manufacturing process, the counter electrode 2 is formed simultaneously with the gate wiring 1, the common wiring 3, and the pixel electrode 6 with the source wiring 5 by the same member. In the conventional TN method, apart from the gate wiring and the source wiring, it is necessary to form a pixel electrode made of a transparent conductive oxide film such as ITO (In and Sn oxide) and a counter electrode of the color filter substrate. The IPS method has the advantage that the two steps of forming the transparent pixel electrode and the counter electrode can be omitted, and the manufacturing process can be greatly reduced.
[0005]
[Problems to be solved by the invention]
In the IPS liquid crystal display device, the pixel electrode 6 and the counter electrode 2 do not need to be transparent, so that a transparent conductive oxide film such as ITO used in the conventional TN method is not required. Therefore, the connection terminals provided around the liquid crystal panel for connecting the liquid crystal display panel and the drive circuit are composed of the constituent members of the gate wiring 1, the source wiring 5 and the common wiring 3. However, in general, a thermo-compression anisotropic conductive film is used for connection between a liquid crystal display panel and a TCP (Tape Carrier Package) on which a drive circuit IC is mounted. The connection reliability with a transparent conductive oxide film such as ITO used in the TN connection terminals is most established. Since the connection terminal composed of a conductive oxide film such as ITO is originally an oxide film, unlike metal film terminals such as Al, Cr, Cu, etc., corrosion due to surface oxidation, decrease in conductivity, decrease in adhesion, etc. There is an advantage that there is less worry. Therefore, when the connection terminal is made of a member such as the gate wiring 1, the source wiring 5, and the common wiring 3, and other than the conductive oxide film such as ITO, a new connection condition must be established and reliability must be established. There was a problem.
[0006]
Further, when the connection terminal is formed of a conductive oxide film such as ITO separately from the constituent members of the gate wiring 1, the source wiring 5, and the common wiring 3, the conductive oxide film is formed only for the formation of the connection terminal. There has been a problem that manufacturing processes such as formation, photoengraving and etching increase.
Further, when any one of the gate wiring 1, the source wiring 5 and the common wiring 3 is formed of a transparent conductive oxide film such as ITO, there is a problem in reliability if the connection terminal is formed of the same conductive oxide film. Although there is no increase in the number of manufacturing steps, conductive oxide films such as ITO generally have high electrical resistance, which increases wiring resistance and causes problems such as signal delay. There was a problem that I could not.
[0007]
The present invention has been made to solve the above-described problems. The connection reliability between the liquid crystal display panel and the drive circuit is as high as that of the conventional TN panel, and the number of manufacturing steps is small. An object of the present invention is to provide an IPS liquid crystal display device that can handle large panels.
[0008]
[Means for Solving the Problems]
The liquid crystal display device according to the present invention includes a pixel electrode connected to a thin film transistor provided at each intersection of a plurality of gate lines and source lines arranged on a substrate, and an insulating film sandwiched between the pixel electrodes. A common wiring that forms a storage capacitor, a counter electrode that is arranged in parallel with the pixel electrode and connected to the common wiring, and is arranged on the periphery of the substrate, and connects the gate wiring, the source wiring, and the common wiring to each drive circuit. A liquid crystal device is provided with a connection terminal and a liquid crystal sandwiched between the substrate on which these are formed and an opposing substrate via an alignment film. A voltage is applied between the pixel electrode and the opposing electrode, and an electric field is applied substantially parallel to the substrate surface. A liquid crystal display device in which liquid crystal is generated and makes a liquid crystal respond in-plane, wherein the pixel electrode and the counter electrode are formed in a layer different from the gate wiring, the source wiring, and the common wiring, and at least the pixel electrode and the counter electrode Re or is constituted by laminated films including a conductive oxide film, and the connecting terminals are made form the above stacked film, a connection terminal surface intended to be conductive oxide film.
[0009]
The pixel electrode and the counter electrode are formed in an upper layer than the gate wiring and the common wiring.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Reference Example 1
Reference Example 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a TFT array of a liquid crystal display device which is Reference Example 1 of the present invention. In the figure, 1 is a gate wiring made of a conductor such as Al, Cr, Ta, Mo, W, Ti, Zr, Cu and alloys thereof, and 2 is formed simultaneously with the gate wiring 1 and arranged in parallel with a pixel electrode 61 described later. The common electrode 3, which is connected to the counter electrode 2 and forms a storage capacitor with an insulating film sandwiched between the pixel electrode 61 (described later), and 4, each of the gate wiring 1 and the source wiring 51 (described later). TFT section made of a-Si, poly-Si or the like provided at the intersection and forming a switching element, 51 is an alloy made of Cr, Ta, Mo, W, Ti, Zr, Cu, Pt, or a combination thereof, or Al A source wiring 61 having a structure in which a conductive oxide film such as ITO is laminated on a metal film such as an Al alloy to which these are added, and a pixel electrode 61 connected to the TFT portion 4 and formed simultaneously with the source wiring 51 A.
[0011]
Further, reference numerals 100, 300, and 500 are connection terminals that are disposed at the periphery of the substrate and are formed simultaneously with the source wiring 51 and the pixel electrode 61. The gate wiring 1, the common wiring 3, the source wiring 51, and the respective driving circuits are respectively connected. Connecting. Reference numerals 101 and 301 denote contact holes for connecting the connection terminals 100 and 300 to the gate wiring 1 and the common wiring 3, respectively. The surfaces of the connection terminals 100, 300, 500 are all conductive oxide films.
The liquid crystal display device according to this reference example has a liquid crystal sandwiched between the TFT array substrate and the counter substrate shown in FIG. 1 via an alignment film, and a voltage is applied between the pixel electrode 61 and the counter electrode 2. An electric field is generated substantially parallel to the surface to cause the liquid crystal to respond in-plane, and the source wiring 51, the pixel electrode 61, and the connection terminals 100, 300, and 500 are formed of the same material in order to reduce the manufacturing process. It is characterized by.
[0012]
A manufacturing method of the TFT array according to this reference example will be described below.
In this reference example, in the formation of the laminated film that becomes the source wiring 51, the pixel electrode 61, and the connection terminals 100, 300, and 500, a conductive oxide film is continuously formed on a metal film having a low electrical resistance. For example, ITO, which is a representative conductive oxide film, may be continuously sputtered on Mo4000? Although the photoengraving process is the same as before, it should be noted that when the photoresist is exposed to alkali, the potential of the metal film in the alkali developer is, for example, in the case of a film configuration in which ITO and a metal film are laminated. If the potential is lower than that, electrical corrosion may occur in the ITO. For example, in the case of a configuration in which ITO is laminated on pure Al, the potential of ITO in the alkaline developer is -1.3 to -1.4V, and pure Al is -1.9V. Electrically corrodes and melts. Therefore, when the conductive oxide film is ITO, it is necessary to select a metal film having a higher potential than that of ITO in the alkaline developer. For example, Cr is -0.3V, Cu is -0.2V, Mo is -0.6V, Ta is -0.85V, and W is -0.7V, and can be used. Further, instead of pure Al, an Al alloy in which the above-described metal having a high potential is added to Al, such as Al—W, Al—Mo, Al—Pt, or the like, can also be used.
[0013]
Next, using the photoresist mask formed in the photoengraving process, the laminated film may be successively wet etched and dry etched in the order of the conductive oxide film and the metal film.
In this reference example , a process of continuously forming a thin conductive oxide film and a process of etching need only be added to the process of forming the source wiring 51 and the pixel electrode 61 in the conventional manufacturing process. The photoengraving mask pattern may be designed in a pattern shape including the connection terminals 100, 300, and 500 in addition to the source wiring 51 and the pixel electrode 61. Thus, according to this reference example , there is an effect that the reliability of the connection terminal of the liquid crystal display device can be ensured to be equal to that of the conventional panel with a slight increase in manufacturing steps. Further, since the source wiring 51 is composed of a laminated film including a conductive oxide film, the wiring resistance can be lowered by laminating with a low resistance metal, and it can be applied to a large panel.
[0014]
Reference Example 2
FIG. 2 is a plan view of a TFT array of a liquid crystal display device which is Reference Example 2 of the present invention. In the figure, 5 is a source wiring made of a conductor such as Al, Cr, Ta, Mo, W, Ti, Zr, Cu and alloys thereof, 6 is a pixel electrode formed simultaneously with the source wiring 5, 11 is Cr, Ta, A gate wiring comprising a structure in which a conductive oxide film such as ITO is laminated on a metal film such as an alloy made of Mo, W, Ti, Zr, Cu, Pt, or a combination thereof, or an Al alloy obtained by adding these to Al; Reference numerals 21 and 31 are a counter electrode and a common wiring formed simultaneously with the gate wiring 11. Reference numerals 102, 302, and 502 are connection terminals formed simultaneously with the gate wiring 11, the counter electrode 21, and the common wiring 31. Reference numeral 501 denotes a contact hole for connecting the connection terminal 502 and the source wiring 5. Reference numerals 103, 303, and 503 denote connection terminal holes for removing the insulating film on the connection terminals and exposing the surface of the conductive oxide film. By the connection terminal holes 103, 303, and 503, the surfaces of the connection terminals 102, 302, and 502 are conductive oxide films. In this reference example , the gate wiring 11, the counter electrode 21, the common wiring 31, and the connection terminals 102, 302, and 502 are simultaneously formed of the same material in order to reduce the manufacturing process. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof is omitted.
[0015]
In this reference example , a process of continuously forming a thin conductive oxide film and a process of etching need only be added to the process of forming the gate wiring 11, the counter electrode 21 and the common wiring 31 in the conventional manufacturing process. The photoengraving mask pattern may be designed to have a pattern shape including the connection terminals 102, 302, and 502 in addition to the gate wiring 11, the counter electrode 21, and the common wiring 31, and the same effect as in the first reference example can be obtained.
[0016]
Embodiment 1 FIG .
FIG. 3 is a plan view of the TFT array of the liquid crystal display device according to the first embodiment of the present invention. In the figure, reference numerals 22 and 62 denote a conductive oxide film such as ITO, an alloy composed of Cr, Ta, Mo, W, Ti, Zr, Cu, Pt, or a combination thereof, or an Al alloy obtained by adding these to Al. It is a counter electrode and a pixel electrode having a configuration in which a conductive oxide film such as ITO is laminated on a metal film. The counter electrode 22 and the pixel electrode 62 are simultaneously formed of the same material. Reference numerals 104, 304, and 504 denote connection terminals formed simultaneously with the pixel electrode 62 and the counter electrode 22. Reference numeral 23 is a contact hole for connecting the counter electrode 22 and the common wiring 3, and 105, 305 and 505 are contact holes for connecting the connection terminals 104, 304 and 504 to the gate wiring 1, the common wiring 3 and the source wiring 5. The surfaces of the connection terminals 104, 304, and 504 are all conductive oxide films. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof is omitted.
In the present embodiment, when the pixel electrode 62 and the counter electrode 22 are conductive oxide films such as ITO, the connection terminals 104, 304, and 504 are connected to the pixel electrode 62 and the counter electrode 22 in addition to the pixel electrode 62 and the counter electrode 22 with a photolithography mask pattern. It is only necessary to change the design to include the pattern shape. In the case where the pixel electrode 62 and the counter electrode 22 are laminated films including a conductive oxide film such as ITO, a thin conductive oxide film is continuously formed in the formation process of the pixel electrode 62 and the counter electrode 22 in the conventional manufacturing process. It is only necessary to add a process and an etching process. The mask pattern for photolithography may be designed in a pattern shape including the connection terminals 104, 304, and 504 in addition to the pixel electrode 62 and the counter electrode 22.
[0017]
In the present embodiment, the pixel electrode 62 and the counter electrode 22 are formed of a film different from the gate wiring 1, the source wiring 5, and the common wiring 3. The gate wiring 1, the source wiring 5 and the common wiring 3 are preferably thicker in order to reduce electrical resistance, while the pixel electrode 62 and the counter electrode 22 are for improving the liquid crystal alignment characteristics by the alignment film rubbing. In addition, it is desirable that the film thickness is small so that the level difference due to the electrode is reduced. Since the length of the pixel electrode 62 and the counter electrode 22 is short in one pixel, the electrical resistance is not a problem. Therefore, for example, the film thickness of the pixel electrode 62 and the counter electrode 22 is set to a thin film thickness of 1000 mm or less so that the step difference between the electrodes is reduced with respect to the film thickness of 2000 to 4000 mm of the gate wiring 1 and the source wiring 5. Is possible.
[0018]
As described above, according to the present embodiment, there is an effect that the reliability of the connection terminal of the liquid crystal display device can be ensured to be equal to that of the conventional panel with a slight increase in manufacturing steps. In addition, since the gate wiring 1, the source wiring 5, and the common wiring 3 are made of a metal film, the wiring resistance can be lowered, and it can be applied to a large panel. Further, since the pixel electrode 62 and the counter electrode 22 can be formed of thin films with few steps, the liquid crystal alignment characteristics can be improved.
[0019]
In the first embodiment, the case where a TFT is used as the switching element has been described. However, the present invention is also effective in the case of a MOS transistor made of single crystal Si using a Si substrate.
[0020]
【The invention's effect】
As described above, according to the present invention, the pixel electrode and the counter electrode are formed in a layer different from the gate wiring, the source wiring, and the common wiring, and at least one of the pixel electrode and the counter electrode includes the conductive oxide film. forming a film, and the connection terminals form the shape in the laminated film, since it is configured to connect terminal surface with a conductive oxide film, an increase of less manufacturing steps, the reliability of high connection terminals can be obtained, furthermore, There is an effect that a liquid crystal display device having low wiring resistance and compatible with a large panel can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view showing a TFT array of a liquid crystal display device which is Reference Example 1 of the present invention.
FIG. 2 is a plan view showing a TFT array of a liquid crystal display device which is Reference Example 2 of the present invention.
FIG. 3 is a plan view showing a TFT array of the liquid crystal display device according to the first embodiment of the present invention.
FIG. 4 is a plan view showing a TFT array of a conventional liquid crystal display device.
[Explanation of symbols]
1, 11 Gate wiring, 2, 21, 22 Counter electrode, 3, 31 Common wiring, 4 TFT section, 5, 51 Source wiring, 6, 61, 62 Pixel electrode, 7 Storage capacitance portion, 8 Liquid crystal molecule, 100, 102 104, 300, 302, 304, 500, 502, 504 Connecting terminal, 23, 101, 105, 301, 305, 501, 505 Contact hole,
103, 303, 503 Connection terminal holes.

Claims (2)

A pixel electrode connected to a thin film transistor provided at each intersection of a plurality of gate wirings and source wirings disposed on the substrate;
A common wiring that forms a storage capacitor with an insulating film interposed between the pixel electrode and the pixel electrode;
A counter electrode disposed in parallel with the pixel electrode and connected to the common wiring;
A connection terminal that is disposed in the periphery of the substrate and connects the gate wiring, the source wiring, and the common wiring to each drive circuit;
A liquid crystal sandwiched between the substrate and the counter substrate with an alignment film interposed between them; a voltage is applied between the pixel electrode and the counter electrode to generate an electric field substantially parallel to the substrate surface; A liquid crystal display device that responds in-plane,
The pixel electrode and the counter electrode, the gate wire, and the source wiring and the common wiring are formed in different layers, a laminated film comprising any conductive oxide film of at least the pixel electrode and the counter electrode it is configured, and the connection terminals are made form the above stacked film, a liquid crystal display device, wherein said connection terminal surface is electrically conductive oxide layer.  2. The liquid crystal display device according to claim 1, wherein the pixel electrode and the counter electrode are formed in an upper layer than the gate line and the common line.

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