Patent ID: 12253770

DETAILED DESCRIPTION

Embodiments of the present application will be described below in detail with reference to the drawings.

Before describing embodiments according to the invention, electrostatic discharge resistance has been considered on the basis of various evaluations. This will be described with reference toFIG.6andFIG.7illustrating the cross-sectional views around peripheral portions of a liquid crystal display device.

As shown inFIG.6andFIG.7, in an existing FFS mode liquid crystal display device10Z, a first substrate100Z and a second substrate200Z are adhered to each other by a seal304Z, and liquid crystal302Z is held between these substrates100Z,200Z. A circuit wiring group104Z is arranged on a support substrate102Z of the first substrate100Z, and an insulating film114Z is arranged so as to cover the circuit wiring group104Z. Note that the circuit wiring group104Z is schematically shown in the drawing. A translucent conductive film208Z is arranged on an outer surface of a support substrate202Z of the second substrate200Z, and this translucent conductive film208Z extends over the entire surface of the above outer surface, that is, to the outer periphery of the support substrate202Z, that is, to the outer periphery of the second substrate200z. Note that, for example, by forming the translucent conductive film208Z over the entire surface of a substrate, which includes multiple number of unit substrates, and then separating the substrate into the unit substrates, the translucent conductive film208Z is formed so as to extend to the outer periphery of the second substrate200Z.

When aerial discharge has been performed on the translucent conductive film208Z, aerial discharge that is generated at the outer peripheral portion of the translucent conductive film208Z, as shown inFIG.6, was observed, and breakage was found in the circuit wiring group104Z and circuit elements connected thereto. According to the above, it is conceivable that static electricity is transmitted from the outer peripheral portion of the translucent conductive film208Z through the side of the outer peripheral portion of the second substrate200Z to the circuit wiring group104Z. In this case, of the circuit wiring group104Z, static electricity tends to be transmitted to a circuit wiring closer to the outer periphery of the substrate.

In addition, breakage also found in a circuit wiring remote from the outer periphery of the substrate and circuit elements connected thereto. It is conceivable that this breakage occurs because the electric potential of the translucent conductive film208Z rises due to static electricity that has entered the translucent conductive film208Z, and then the electric potential of the circuit wiring group104Z rises due to coupling with the electric potential rise of the translucent conductive film208Z. That is, it is conceivable that the breakage occurs due to the transmission of static electricity on the basis of coupling (seeFIG.7). Note thatFIG.7is a schematic view illustrating a state of coupling using the graphic symbols of capacitors. The coupling with the translucent conductive film208Z tends to occur as the area of wiring pattern is increased, that is, the width and/or length, or the like, of wiring is increased. It is conceivable that, for example, the coupling tends to occur with a power supply wiring that has a wide line width for reducing a resistance.

In addition, it has been found that breakage tends to occur more likely in the circuit wiring that extends along the outer periphery of the substrate than in the circuit wiring that extends in a direction which intersects with the outer periphery of the substrate.

An embodiment according to the invention will now be described with reference to the accompanying drawings.FIG.1is a schematic view of a liquid crystal display device10according to the embodiment. Note that, for easily understanding the drawings, components that are shown inFIG.1and in the following drawings, when they are shown in the other drawings as well, are partially omitted.

As shown inFIG.1, the liquid crystal display device10is configured to include a liquid crystal panel12, a case14for the liquid crystal panel12, an FPC16, and an external circuit18. The liquid crystal panel12is connected to the external circuit18through the FPC16. In place of the FPC16, various wiring bodies may be used. The following will exemplify a case where the liquid crystal panel12uses an FFS mode. Note that the liquid crystal panel12may be any one of a transmissive type liquid crystal panel, a reflective type liquid crystal panel and a transflective type liquid crystal panel.

FIG.2is a cross-sectional view around an outer periphery of the liquid crystal panel12. The liquid crystal panel12is configured to include a first substrate100, a second substrate200, liquid crystal302and a seal304. The substrates100,200are opposed to each other with a predetermined gap formed therebetween, and are adhered to each other at the peripheral portions by the seal304. The liquid crystal302is held in a casing that is formed of the substrates100,200and the seal304.

The first substrate100includes a support substrate102that is, for example, formed of a translucent substrate, such as glass, and is configured to include, on the inner surface side of the support substrate102, that is, on the side adjacent to the liquid crystal302, insulating films110,112, at least one common electrode116, pixel electrodes118, a peripheral circuit150, and an alignment layer (not shown).

The common electrode116and the pixel electrodes118are paired electrodes that control the alignment of the liquid crystal302, that is, that drive the liquid crystal302. The common electrode116is commonly provided for a plurality of pixels, and each of the pixel electrodes118is provided for each of the pixels. An electric potential corresponding to a display of each pixel is supplied to the pixel electrode118. Note that it may also be configured that the common electrode116is provided for each of the pixels and then a common electric potential is supplied to the common electrode116. That is, the plurality of pixels are formed of the plurality of pixel electrodes118and the at least one common electrode116. Note that the outermost pixels, arranged all around, or more number of pixels, may possibly be used as dummy pixels that do not directly contribute to image display.

In the FFS mode liquid crystal panel12, the electrodes116,118both are provided in the first substrate100, and the electrodes116,118are laminated through the insulating film112. The following will exemplify a case where the pixel electrodes118are arranged in an upper side layer, that is, on the side adjacent to the liquid crystal302; however, the common electrodes116may be arranged in the upper side layer. Slits (not shown) are formed in each of the upper layer pixel electrodes118, and the alignment of the liquid crystal302is controlled by an electric field generated between the electrodes116,118through the slits. The electrodes116,118are, for example, formed of a translucent conductive film, such as ITO (Indium Tin Oxide).

The peripheral circuit150is a circuit that is arranged outside the electrodes116,118and the pixel area13. Here, the pixel area13is an area in which a plurality of the pixels are arranged. In other words, the plurality of pixels are arranged in the pixel area13. Note that an area for the dummy pixels also included in the pixel area13. The peripheral circuit150will be exemplified later.

The insulating films110,112are, for example, formed of silicon oxide, silicon nitride, or the like, and are laminated on the support substrate102. Note that, for easy description, it exemplifies a case where the insulating film110is located in a layer lower than the common electrode116, that is, the layer adjacent to the support substrate102, and the insulating film112is laminated on the insulating film110; however, these insulating films110,112are collectively called as an insulating film114. The insulating films110,112each may be a monolayer film or may be a multilayer film. The alignment layer (not shown) is arranged to cover the pixel electrodes118, and the alignment layer is treated with a rubbing process.

Note thatFIG.2exemplifies a case where the peripheral circuit150is in contact with the support substrate102and is covered with the insulating film110; however, it may be configured so that the peripheral circuit150is embedded in the insulating film114formed of a multilayer film and is not in contact with the support substrate102.

The second substrate200includes a support substrate202that is, for example, formed of a translucent substrate, such as glass, and is configured to include, on the inner surface side of the support substrate202, that is, on the side adjacent to the liquid crystal302, a light shielding film204, a color filter206and an alignment layer (not shown) and to include, on the outer surface side of the support substrate202, that is, on the side opposite to the liquid crystal302, a translucent conductive film208.

The support substrate202is opposed to the first substrate100, and has a size to be opposed to be opposed to the electrodes116,118and the peripheral circuit150. The light shielding film204is arranged on the support substrate202. The light shielding film204extends over the entire surface on the support substrate202and has an opening at a position opposite each of the pixel electrodes118. Note that no opening is provided at a position opposite each of the dummy pixels. The light shielding film204is, for example, formed a resin, or the like, containing black pigment. The color filter206is arranged on the support substrate202and is provided in each opening portion of the light shielding film204so as to be opposed to the electrodes116,118. The alignment layer (not shown) is arranged to cover the light shielding film204and the color filter206, and the alignment layer is treated with a rubbing process.

The translucent conductive film208is arranged on the outer surface of the support substrate202and is opposed to the liquid crystal302and the electrodes116,118, and the like, through the substrate202. That is, the translucent conductive film208is provided in the second substrate200and is located on an opposite side to a surface that is in contact with the liquid crystal302. The translucent conductive film208is maintained at an arbitrarily predetermined electric potential, for example, a ground electric potential, and releases static electricity, which enters from the outside of the panel toward the second substrate200, thus preventing electrostatic charge of the second substrate200. That is, the translucent conductive film208serves as a shielding film. Thus, it is possible to suppress a trouble due to electrostatic charge of the second substrate200, that is, for example, a decrease in contrast and chrominance non-uniformity. The translucent conductive film208may be provided without patterning (without any gaps), or, as long as the body portion208aachieves a shielding effect against static electricity, it may be patterned to form a mesh.

The translucent conductive film208is, for example, formed of ITO, or the like, and may be formed of any one of an inorganic material or an organic material. The translucent conductive film208may be formed by a process, such as a sputtering process, a plasma CVD (Chemical Vapor Deposition) process, a spin coating process, and a printing process. The translucent conductive film208has a resistivity (sheet resistance) of, for example, 105Ω/□, which is preferably as low as possible. Note that it exemplifies a case where the outer periphery of the translucent conductive film208extends to the outer periphery of the support substrate202, that is, to the outer periphery of the second substrate200; however, an area, in which the translucent conductive film208is arranged, is not limited to this.

The liquid crystal panel12will now be exemplified.FIG.3toFIG.5are plan views that illustrate liquid crystal panels12A to12C according to first example to third example. Note that, for avoiding complicated drawing, an area outside the pixel area13is shown wide, and a connection state, or the like, of a wiring is partially omitted from the drawing.

In the liquid crystal panel12A that is exemplified inFIG.3, the peripheral circuit150is configured to include an H scanner152, a V scanner154, a V system circuit156, a circuit158, a COM wiring162, wirings164,166, and the like.

The H scanner152and the V scanner154are circuits for scanning pixels horizontally and vertically on a display screen. The V system circuit156is, for example, a level shifter, and is connected to the V scanner154. The circuit158is, for example, a control circuit, a signal processing circuit, a detection circuit, and the like. Here, the circuit158is connected to the scanners152,154. The COM wiring162is a wiring that supplies an electric potential (common electric potential) to be applied to the common electrode116(seeFIG.2). The COM wiring162extends from the end, which is connected to the FPC16, toward the pixel area13. Here, the COM wiring162extends from a portion near the pixel area13along three sides of the area13. The wiring164is a control signal wiring for the V scanner154and extends from the end, which is connected to the FPC16, toward the V scanner154. The wiring166is, for example, an input signal wiring to the V system circuit156and extends from the end, which is connected to the FPC16, toward the V system circuit156. Note thatFIG.3exemplifies a case where the two wirings166are provided.

The liquid crystal panel12A includes a dummy wiring168outside the pixel area13. The dummy wiring168is arranged on the outer peripheral side of the substrate than the peripheral circuit150that is configured to include the scanners152,154, and the like. The dummy wiring168is a wiring that is located on the outermost periphery among various wirings of the liquid crystal panel12A. In addition, the dummy wiring168is not connected to the peripheral circuit150, that is, the dummy wiring168is provided independently of the peripheral circuit150in terms of circuit. According to the above arrangement and connection state, the dummy wiring168does not intersect with the peripheral circuit150. The dummy wiring168surrounds the peripheral circuit150. The dummy wiring168preferably avoids an intersection with the peripheral circuit150also at a portion connected to the FPC16. In this case, the dummy wiring168does not constitute a closed path (closed loop) within the liquid crystal panel12A, and both ends of the dummy wiring168are pulled out to the portion connected to the FPC16. Both end portions of the dummy wiring168are connected through the FPC16to the ground electric potential of the external circuit18. Both end portions of the dummy wiring168may be connected to the ground electric potential through a resistance of 10 kΩ to 1 mΩ.

According to the above configuration, even when static electricity enters from the outer peripheral portion of the translucent conductive film208over the side face of the support substrate202to the first substrate100, it is possible to flow the static electricity through the dummy wiring168to the ground electric potential of the external circuit18. Thus, it is possible to suppress transmission of static electricity to the peripheral circuit150, and electrostatic discharge resistance is improved.

The dummy wiring168does not intersect with the peripheral circuit150. For this reason, static electricity entering the dummy wiring168is suppressed from being transmitted to the peripheral circuit150due to coupling. Thus, electrostatic discharge resistance is improved.

Because the dummy wiring168is connected to the ground electric potential of the external circuit18, the ground electric potential may possibly rise when static electricity enters the dummy wiring168. However, in terms of a signal, a power supply electric potential, or the like, to which a voltage value is set relatively to the ground electric potential as a reference, an influence of a rise in ground electric potential is suppressed. Therefore, electrostatic discharge resistance is improved in comparison with a case where the dummy wiring168is, for example, connected to the ground electric potential of the liquid crystal panel12A.

In the liquid crystal panel12B as exemplified inFIG.4, the peripheral circuit150is configured to include the H scanner152, the V scanner154, the V system circuit156, the circuit158, the COM wiring162, the wirings164,166, a power supply wiring169, and the like. In addition, the liquid crystal panel12B includes a dummy wiring170and protective resistances180. Note that the same reference numerals are assigned to the same or similar components described above, and a description there of is omitted.

The power supply wiring169is, for example, a wiring that supplies a power supply electric potential Vss, and extends from the end, which is connected to the FPC16, to be connected to the V system circuit156and the H scanner152. Note that the electric potential Vss is, for example, supplied through the V system circuit156to the V scanner154and supplied through the H scanner152to the circuit158.

The dummy wiring170is connected through the resistance180to the power supply wiring169, and extends around the panel and then is connected through the other resistance180to the power supply wiring169again. Here, the dummy wiring170is located on the outermost periphery than various wirings of the peripheral circuit150. The dummy wiring170surrounds the scanners152,154, the V system circuit156, the circuit158, and the like. The dummy wiring170extends along the outer periphery of the substrate to form a closed loop in the liquid crystal panel12B.

The protective resistances180have a resistance value of, for example, 10 kΩ to 10 MΩ. The protective resistances180may be, for example, formed by using a silicon film.

According to the above configuration, even when static electricity enters from the outer peripheral portion of the translucent conductive film208over the side face of the support substrate202to the dummy wiring170, which is the outermost wiring of the first substrate100, the static electricity is consumed in the protective resistances180. In addition, even when static electricity entering the translucent conductive film208causes fluctuation in electric potential of the dummy wiring170due to coupling, the fluctuation in electric potential is consumed by the protective resistances180. For this reason, the entered static electricity is suppressed from being transmitted to a circuit element, such as the scanner152. Thus, electrostatic discharge resistance is improved.

In the liquid crystal panel12C as exemplified inFIG.5, the peripheral circuit150includes, in addition to the above configuration exemplified inFIG.4, a power supply wiring172and a protective resistance182. The power supply wiring172and the protective resistance182are arranged inside the above closed loop portion of the dummy wiring17in the liquid crystal panel12C. Note that the same reference numerals are assigned to the same or similar components described above, and a description thereof is omitted.

The power supply wiring172is a wiring that supplies a power supply electric potential used in the V scanner154and in the circuit158. Note that the power supply electric potential may be an electric potential that is generated in the liquid crystal panel12C, or may be an electric potential that is supplied from the external circuit18(seeFIG.1), or the like. The power supply wiring172passes through the V scanner154and extends along the outer periphery of the substrate, and then is connected through the protective resistance182to the circuit158. The protective resistance182has a resistance value of, for example, 10 kΩ to 10 MΩ. The protective resistance182may be, for example, formed by using a silicon film.

The circuit158in the liquid crystal panel12C uses the above power supply electric potential that is supplied by the power supply wiring172as a control signal. For example, the circuit158may be a signal processing circuit, a detection circuit, or the like, that is shared by the H scanner152and the V scanner154. When the power supply electric potential is supplied through the power supply wiring172, the circuit158is switched to a circuit for the V scanner154. When no power supply electric potential is supplied, the circuit158is switched to a circuit for the H scanner152. The thus switching may be, for example, achieved by using a switching element, such as a MOS (Metal Oxide Semiconductor) transistor, and the power supply wiring172is connected to a control terminal of the switching element, that is, for example, the gate of the MOS transistor.

Particularly, the protective resistance182is connected in the power supply wiring172in a midway of the path from the V scanner154to the control terminal, and the protective resistance182is provided upstream of the control terminal.

According to the above configuration, even when static electricity entering the translucent conductive film208causes fluctuation in electric potential of the power supply wiring172due to coupling, the fluctuation in electric potential is consumed by the protective resistance182. In addition, even when static electricity enters from the outer peripheral portion of the translucent conductive film208over the side face of the support substrate202to the power supply wiring172of the first substrate100, the static electricity is consumed in the protective resistance182. For this reason, the entered static electricity is suppressed from being transmitted to the control circuit of the switching element. Thus, electrostatic discharge resistance is improved.

Here, in light of the evaluation that static electricity tends to be transmitted to a wiring that extends along the outer periphery of the substrate, electrostatic discharge resistance is reliably improved by connecting the protective resistances180,182to the wirings170,172, respectively.

In addition, the wirings170,172to which the protective resistances180,182are connected and the dummy wiring168may be variously combined, and, thereby, it is possible to further improve electrostatic discharge resistance. Furthermore, the dummy wiring168and the wirings170,172, to which the protective resistances180,182are connected, are effective against static electricity that enters the first substrate100without passing through the translucent conductive film208.

Moreover, the above description exemplifies the FFS mode in which the electrodes116,118that drive the liquid crystal302are laminated through the insulating film112. However, it may be configured as an IPS mode in which both electrodes116,118are arranged in the same layer (for example, on the insulating film112). When in the IPS mode, for example, the electrodes116,118having a comb-shaped pattern are arranged so that the comb-shaped portions are alternately meshed with each other. In addition, the above configured liquid crystal display device10may be applied to a liquid crystal display device, such as a TN (Twisted Nematic) mode, in which the common electrode116is opposed to the pixel electrodes118through the liquid crystal302.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.