JP4374950B2 - Electro-optical device and electronic apparatus - Google Patents

Description

  The present invention relates to an electro-optical device and an electronic apparatus.

  In an electro-optical device such as an active matrix liquid crystal device, a plurality of independent display pixels are arranged in a matrix on one of a pair of substrates constituting a liquid crystal panel. This display pixel is formed of a switching element and a pixel electrode for displaying an image.

  As a switching element of a liquid crystal device, a TFT (Thin Film Transistor) element has been put into practical use in many fields, and a driving voltage is applied to the pixel electrode via the TFT element. The pixel electrode to which the drive voltage is applied orients the liquid crystal interposed between the pixel electrode and the counter electrode due to a potential difference with the counter electrode disposed opposite to the pixel electrode. Depending on the alignment state of the liquid crystal, transmission / blocking of light incident on the liquid crystal is controlled to enable image display.

  The display pixel will be described with reference to FIG. 9, FIG. 10, and FIG. As shown in FIGS. 9 and 11, one display element 5 is provided with one TFT element 8, and a scanning line 6 is provided on the gate electrode 10, and a source electrode 11 is provided on the TFT element 8. Are connected to data lines 7 respectively. Further, one terminal of the storage capacitor 19 is connected to the drain electrode 12 of the TFT element 8, and the pixel electrode 9 is connected through a contact hole.

  The other terminal of the storage capacitor 19 is connected to the additional capacitor wiring 13. The additional capacity wiring 13 is connected to a counter electrode (not shown). The scanning lines 6 and the data lines 7 pass through the periphery of the pixel electrode 9 so as to be orthogonal to each other, and are connected to the scanning line driving circuit 3 and the data line driving circuit 4, respectively. When the scanning line driving circuit 3 inputs a gate signal to the scanning line 6, the TFT element 8 is driven and controlled. When the data line driving circuit 4 drives the TFT element 8, the TFT element 8 is driven. The data signal is input to the pixel electrode 9 through the pixel electrode 9. Further, the holding capacitor 19 is used to hold a voltage applied to the liquid crystal. Although not shown, a protective circuit and a protective resistor for preventing intrusion of static electricity may be provided at a connection portion between the display pixel 5 and the scanning line driving circuit 3 or the data line driving circuit 4 in some cases.

  FIG. 10 is a schematic configuration diagram of the TFT 8, and is a cross-sectional view when cut at a position corresponding to the A-A 'line in FIG. A semiconductor layer 22 is formed on the substrate 20, and a gate insulating film 21 is formed thereon. A gate electrode 10 extending from the gate signal line is formed on the gate insulating film 21. Further, an insulating film 23 is formed on the gate electrode 10, and a source electrode 11 and a drain electrode 12 are formed extending from the source signal line through a contact hole formed in the insulating film 23. The

  Incidentally, the switching element such as the TFT element 8 generally has a property of being weak against a strong electric field. Therefore, in the manufacturing process of the liquid crystal device, particularly when the static electricity generated in the rubbing process enters from the signal line and the TFT element 8 is turned on regardless of the gate voltage exceeding the breakdown voltage between the source and drain, There is a problem in that the junction point that should become a thermal breakdown causes a leak (SD leak) between the source electrode 11 and the drain electrode 12 due to the loss of the OFF breakdown voltage, and the TFT element 8 is destroyed. Thus, since the TFT element 8 in which the SD leak occurs does not function as a switching element, it appears as a point defect, which deteriorates the manufacturing yield in manufacturing the liquid crystal device.

  Conventionally, as a countermeasure against such electrostatic breakdown, in addition to a method of providing a protective circuit and a protective resistor between a pixel and a pixel driving circuit, as shown in FIG. 12, a plurality of the displays serving as an effective display area 1 of a liquid crystal device are provided. In the periphery of the pixel 5, a dummy pixel region 2 called a dummy pixel 14 that forms a plurality of pixels that do not directly contribute to image display is performed. A method of preventing destruction of the display pixel 5 by absorbing external static electricity with the dummy pixel 14 is known (see, for example, Patent Document 1).

  According to this technique, even if static electricity is applied, the dummy pixel region 2 is preferentially destroyed, so that the switching elements connected to the display pixels 5 in the effective display region 1 can be protected.

JP-A-10-213816

  However, the conventional countermeasures against electrostatic breakdown described above have the following problems. In other words, in the prior art, static electricity is absorbed by the surrounding dummy pixel region 2, so that the switching elements of the pixels in the effective display region 1 can be protected. However, the electrostatic breakdown of the dummy pixel region 2 may cause problems such as deterioration or destruction of the TFT element 8 and occurrence of a short circuit due to dielectric breakdown of wiring intersections such as electrodes and signal lines.

  The present invention has been made in view of the above-mentioned problems. By forming the dummy pixel region 2 in the active matrix display device of the prior art, a sudden large voltage is applied to the dummy pixel 14 due to the influence of static electricity, and the visual It is an object of the present invention to provide an electro-optical device and an electronic apparatus using the electro-optical device that avoids the occurrence of a defective product and improves the production efficiency.

  The electro-optical device according to the present invention includes a plurality of scanning lines, a plurality of data lines, a plurality of switching elements arranged in a matrix corresponding to intersections of the scanning lines and the data lines, and the switching elements. A pixel region having a pixel electrode connected to the pixel region, wherein the pixel region includes an effective pixel region in which a plurality of effective pixels for displaying an image are formed, and an outer peripheral portion of the effective pixel. Including a dummy region in which a plurality of dummy pixels that are covered with a light shielding member and do not directly contribute to image display are formed, and limits a voltage at a connection point between the dummy pixel and a peripheral circuit portion formed around the pixel region Input voltage limiting means.

  According to the present invention, by providing the input voltage limiting means at the connection point between the dummy pixel and the peripheral circuit unit, it is possible to prevent a sudden large voltage from being applied to the switching element when static electricity occurs. In addition, it is possible to avoid the occurrence of a defect that is not visible to the electro-optical device due to electrostatic breakdown of the dummy pixel region.

  The above-described electro-optical device includes a data line driving circuit that drives the plurality of data lines as the peripheral circuit unit, and the input voltage limiting unit is connected only to the dummy pixels among the plurality of data lines. It is preferable to be provided at a connection point between the dummy data line and the data line driving circuit. Further, it is preferable that the input voltage limiting means is not provided on the data line to which the effective pixel and the dummy pixel are connected.

  In this case, the input voltage limiting means is arranged on the dummy data line, while the other data lines are not provided with the input voltage limiting means, so that the effective pixel region can be prevented while preventing the electrostatic breakdown of the dummy pixel region. It is possible to improve the quality of the display image.

  In the electro-optical device described above, the peripheral circuit unit includes a scanning line driving circuit that drives the plurality of scanning lines, and the input voltage limiting unit is connected to only the dummy pixels among the plurality of scanning lines. It is preferable to be provided at a connection point between the dummy scanning line and the scanning line driving circuit. Further, it is preferable that the input voltage limiting means is not provided on the scanning line to which the effective pixel and the dummy pixel are connected.

  In this case, the input voltage limiting means is arranged on the dummy scanning line, while the other scanning lines are not provided with the input voltage limiting means, so that the effective pixel region is prevented while preventing the electrostatic breakdown of the dummy pixel region. It is possible to improve the quality of the display image.

  In the electro-optical device described above, it is preferable that an arbitrary potential having an input voltage amplitude or less is supplied to the dummy data line or the dummy scanning line. According to the present invention, the dummy data line or the dummy scanning line can be prevented from being in a floating state, and the effect of preventing electrostatic breakdown of the dummy pixel region can be improved. The input voltage amplitude means a voltage amplitude corresponding to the withstand voltage of the switching element, and may be a direct current fixed potential or an alternating current.

  The input voltage limiting means is preferably formed of a resistor. According to the present invention, when static electricity is generated, a voltage drop occurs by providing a resistor as an input voltage limiting means at a connection point between the dummy pixel and the pixel driving circuit, and a voltage applied to the circuit is reduced. Therefore, the ability to prevent electrostatic breakdown of the dummy pixel region can be improved.

  Further, the input voltage limiting means is preferably formed of a resistor and a capacitor. According to the present invention, when static electricity occurs, the propagation delay of static electricity can be increased by providing a resistor and a capacitor as input voltage limiting means at the connection point between the dummy pixel and the pixel driving circuit. Since it becomes possible to prevent sudden application of a large voltage and noise such as static electricity that is a high frequency component can be reduced by forming a low-pass filter, the effect of preventing electrostatic breakdown in the dummy pixel region can be further improved. Can be improved.

  In addition, an electronic apparatus according to the present invention includes the above-described electro-optical device. According to the present invention, even when static electricity is generated, the effect of preventing electrostatic breakdown of the electro-optical device can be improved. Can be realized. Examples of the electronic device include a liquid crystal projector, a personal computer, a mobile phone, an electronic camera, and a PDA.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. First Embodiment>
FIG. 1 is a block diagram showing the configuration of a TFT substrate used in the electro-optical device of the present invention. The TFT substrate includes an effective display area 1, a dummy pixel area 2, a scanning line driving circuit 3, and a data line driving circuit 4. In the effective display area 1, pixels (hereinafter referred to as display pixels) 5 for displaying an image are formed. In the peripheral region, a dummy pixel region 2 that does not contribute to actual display in which the dummy pixel 14 for one pixel is formed so as to surround the periphery is formed. In addition, a scanning line driving circuit 3 to which the scanning line 6 is connected and a data line driving circuit 4 to which the data line 7 are connected are formed outside the dummy pixel region 2 to perform pixel driving control. Although not shown here, a protective circuit and a protective resistor may be provided at a connection portion between the scanning line driving circuit 3 or the data line driving circuit 4 and the pixel portion. Further, input voltage limiting means 100 is provided for limiting the voltage at the connection point between the dummy pixel 14 and the data line driving circuit 4.

  In the following description, if necessary, a plurality of data lines 7 connected only to the dummy pixels 14 are referred to as dummy data lines 7a, and the other data lines 7 are referred to as effective data lines 7b. Called. Of the plurality of scanning lines 6, those connected only to the dummy pixels 14 are referred to as dummy scanning lines 6 a, and the other scanning lines 6 are referred to as effective scanning lines 6.

  FIG. 2 is an enlarged equivalent circuit diagram of FIG. As shown in this figure, a plurality of TFT elements 8 are provided in a matrix corresponding to the intersections of the scanning lines 6 and the data lines 7. The display pixel 5 includes a TFT element 8, a pixel electrode 9, and a storage capacitor 19, and the dummy pixel 14 includes a TFT element 8, a pixel electrode 9, and a storage capacitor 19, similar to the display pixel 5. The pixel electrode 9 of the dummy pixel 14 is made of the same material as the display pixel 5 and is made of a light-transmitting conductive material such as ITO. However, since the dummy pixel region 2 is covered with the light shielding member, it does not contribute to image display. The scanning lines 6 and the data lines 7 from the scanning line driving circuit 3 and the data line driving circuit 4 are connected to the pixel region and intersect in a matrix in the pixel region. The scanning line 6 is connected to the gate electrode 10 of the TFT element, and the data line 7 is connected to the source electrode 11 of the TFT element. In FIG. 2, a resistor 110 is provided as an input voltage limiting means at the connection point between the dummy pixel 14 and the data line driving circuit 4 on the dummy data line 7a to which only the dummy pixel 14 is connected, while the display pixel 5 The point that the resistor 110 is not provided on the effective data line 7b to which the dummy pixel 14 is connected is important from the viewpoint of protection against electrostatic breakdown.

  That is, in the liquid crystal device having such a configuration, for example, when static electricity generated during the rubbing process enters from the outside, a voltage drop occurs while passing through the resistor 110, and the voltage applied to the circuit becomes small. In addition, it is possible to suppress the occurrence of defects such as wiring short-circuit caused by the deterioration or destruction of the TFT element 8 in the dummy pixel region 2 due to static electricity or the insulation film destruction at the wiring intersection. On the other hand, the resistor 110 forms a low-pass filter together with the parasitic capacitance associated with the data line 7. Therefore, when the resistor 110 is connected to the effective data line 7b disposed in the effective display area 1, the image signal can be sufficiently written in the parasitic capacitance of the effective data line 7b during the period in which the effective data line 7b is selected. In other words, the display quality may be deteriorated. Therefore, the resistor 110 is connected to the dummy data line 7a corresponding only to the dummy pixel region 2, while the resistor 110 is not provided to the effective data line 7b corresponding to the effective display region 1. Needless to say, the effective data line 7b may be provided with the resistor 110 having such a small resistance value that does not affect the display quality.

  The data line driving circuit 4 supplies the dummy data line 7 a with an arbitrary potential having a voltage voltage amplitude or less corresponding to the withstand voltage of the TFT element 8. Thereby, it is possible to prevent the dummy data line 7a from being in a floating state, and it is possible to improve the effect of preventing electrostatic breakdown of the dummy pixel region 2. Note that the potential supplied to the dummy data line 7a may be a fixed DC potential or an alternating current.

  FIG. 3 is a plan view showing a configuration of an example in which a polysilicon semiconductor layer doped with impurities such as B (boron) and P (phosphorus) is used as the resistor 110. FIG. 4 is a cross-sectional view when cut at a position corresponding to the line A-A ′ of FIG. 3. In this example, a polysilicon semiconductor layer 24 is formed on the substrate 20. Polysilicon semiconductor layer 24 is connected to dummy data line 7a through a contact hole. In the embodiment described above, the resistor 110 is not limited to polysilicon but may be formed of a metal film (Al, Cr, Ta, etc.). Further, if the data line 7 is formed of the same material as the data line 7, it can be formed without increasing the number of steps.

  Further, the resistance value is determined by the shape of the resistor 110 in addition to the material. FIG. 5 shows an example of the shape of the signal line at the connection point between the dummy pixel 14 and the data line driving circuit 4. R = RS · L / W (RS: sheet resistance [W / um2], L: wiring length, W: wiring width), and the resistance is obtained by extending the data line 7 into a shape like a winding. Establish a body. When static electricity enters from the outside, a voltage drop of ΔV = I · R = I · Rs · L / W is caused through this wiring resistance, and the voltage applied to the circuit is reduced.

  Here, the resistor 110 is provided at the connection point between the dummy pixel 14 and the data line driving circuit 4, but may be provided at the connection point between the dummy pixel 14 and the scanning line driving circuit 3. Also in this case, it is preferable that the resistor 110 is disposed on the dummy scanning line 6a, but not disposed on the effective scanning line 6b. Further, the scanning line driving circuit 3 supplies the dummy scanning line 6 a with an arbitrary potential having a voltage voltage amplitude or less corresponding to the withstand voltage of the TFT element 8. Thereby, it is possible to prevent the dummy scanning line 6a from being in a floating state, and it is possible to improve the effect of preventing electrostatic breakdown of the dummy pixel region 2. Note that the potential supplied to the dummy scanning line 6a may be a fixed direct potential or an alternating current.

  Further, when a protective circuit and a protective resistor are provided at the connection portion between the scanning line driving circuit 3 or the data line driving circuit 4 and the pixel portion, the same effect can be expected by further providing the resistor 110 in the dummy region. .

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described below with reference to FIG. FIG. 6 is an enlarged equivalent circuit diagram of the TFT substrate according to the second embodiment. The present embodiment is the same as the first embodiment described above except that a capacitor 120 is provided in addition to the resistor 110 as an input voltage limiting means at the connection point between the dummy pixel 14 and the data line driving circuit 4. .

  In the liquid crystal device having such a configuration, when static electricity generated in the rubbing process enters from the outside, the propagation delay of static electricity can be increased, so that it is possible to mitigate sudden application of a large voltage. Since the resistor 110 and the capacitor 120 form a low-pass filter, noise such as static electricity that is a high-frequency component can be reduced. Accordingly, it is possible to suppress the occurrence of defects such as wiring short-circuiting caused by the deterioration or destruction of the TFT element 8 in the dummy pixel region due to static electricity or the insulation film destruction at the wiring intersection. In the second embodiment described above, the resistor 110 may be formed of the polysilicon semiconductor layer 24 and a metal film as in the first embodiment. Further, the low-pass filter may be of any type, for example, a pie type in which a capacitor 120 is connected to both ends of the resistor 110. In this case, even if static electricity enters from the outside, the high frequency noise is grounded by the capacitors located at both ends of the resistor, so that electrostatic breakdown can be effectively prevented.

  FIG. 7 is a plan view showing a configuration of an example in which polysilicon is used as the resistor 110 and the polysilicon semiconductor layer 24 is intersected with the dummy data line 7a as the capacitor 120. FIG. 8 is a cross-sectional view when cut at a position corresponding to the line B-B ′ of FIG. 7. The polysilicon semiconductor layer 24 of the resistor 110 is connected to the dummy data line 7a through a contact hole. The capacitor 120 is formed at the intersection of the polysilicon semiconductor layer 24 and the dummy data line 7a. In the above-described embodiment, the material for forming the capacitor 120 is not limited to the polysilicon semiconductor layer but may be a metal film (Al, Cr, Ta, etc.). Further, if the metal film is formed of the same material as that of the data line, it can be formed without increasing the number of processes.

  Here, the resistor 110 and the capacitor 120 are provided at the connection point between the dummy pixel 14 and the data line driving circuit 4, but may be provided at the connection point between the dummy pixel 14 and the scanning line driving circuit 3. Also in this case, it is preferable that the resistor 110 and the capacitor 120 are disposed on the dummy scanning line 6a, but not disposed on the effective scanning line 6b. Further, when a protective circuit and a protective resistor are provided at the connection portion between the scanning line driving circuit 3 or the data line driving circuit 4 and the pixel portion, the resistor 110 is further added to the dummy region, and the capacitor 120 is provided. Combine effects.

<3. Application example>
The active matrix liquid crystal device configured as described above can be used as a display portion of various electronic devices, and an example thereof will be described with reference to FIGS.

  FIG. 13 shows a mobile personal computer which is an embodiment of an electronic apparatus according to the present invention. The personal computer 80 shown here has a main body 82 provided with a keyboard 81 and a liquid crystal display unit 83. The liquid crystal display unit 83 includes the liquid crystal device described above. FIG. 14 shows a mobile phone which is another embodiment of the electronic apparatus according to the invention. A cellular phone 90 shown here includes a plurality of operation buttons 91 and a display unit including the liquid crystal device described above.

  In addition to the electronic devices described with reference to FIGS. 13 and 14, a liquid crystal television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation , A video phone, a POS terminal, a device equipped with a touch panel, and the like. Needless to say, the present invention can be applied to these various electronic devices.

1 is a block diagram of a liquid crystal device according to an embodiment of the present invention. 1 is an equivalent circuit diagram of a liquid crystal device according to Embodiment 1 of the present invention. FIG. 3 is a plan view showing a configuration of each pixel formed on a TFT array substrate in the liquid crystal device shown in the equivalent circuit diagram of FIG. 2. FIG. 4 is a cross-sectional view when the plan view shown in FIG. 3 is cut at a position corresponding to the line A-A ′. It is an example of the shape of the resistor used as an input voltage limiting means which concerns on Embodiment 1 of this invention. FIG. 6 is an equivalent circuit diagram of a liquid crystal device according to Embodiment 2 of the present invention. FIG. 7 is a plan view showing the configuration of each pixel formed on the TFT array substrate in the liquid crystal device shown in the equivalent circuit diagram of FIG. 6. It is sectional drawing when the top view shown in FIG. 7 is cut | disconnected in the position corresponded to a B-B 'line | wire. It is a top view which shows the structure of each pixel formed in the TFT array substrate of the conventional liquid crystal device. It is sectional drawing when the top view shown in FIG. 9 is cut | disconnected in the position corresponded to the A-A 'line. FIG. 10 is an equivalent circuit diagram of the liquid crystal device shown in FIG. 9. It is a block diagram of the conventional liquid crystal device. 1 is a perspective view of a mobile personal computer that is an embodiment of an electronic apparatus according to the present invention. It is a perspective view of the mobile telephone which is other embodiment of the electronic device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Effective display area 2 Dummy pixel area 3 Scan line line drive circuit 4 Data line drive circuit 5 Display pixel 6 Scan line 7 Data line 8 TFT element 14 Dummy pixel 100 Input voltage limiting means 110 Resistor 120 Capacity

Claims (9)

A plurality of scanning lines; a plurality of data lines; a plurality of switching elements arranged in a matrix corresponding to intersections of the scanning lines and the data lines; and a pixel electrode connected to the switching elements. An electro-optical device having a pixel region,
The pixel area includes an effective pixel area in which a plurality of effective pixels for displaying an image is formed, and a plurality of dummy pixels that are covered with a light shielding member on the outer periphery of the effective pixel and do not directly contribute to image display. Including a dummy area
An electro-optical device comprising: input voltage limiting means for limiting a voltage at a connection point between the dummy pixel and a peripheral circuit portion formed around the pixel region. A data line driving circuit for driving the plurality of data lines as the peripheral circuit section;
2. The input voltage limiting means is provided at a connection point between a dummy data line to which only the dummy pixel is connected and the data line driving circuit among the plurality of data lines. Electro-optic device.   The electro-optical device according to claim 2, wherein the input voltage limiting unit is not provided on the data line to which the effective pixel and the dummy pixel are connected. A scanning line driving circuit for driving the plurality of scanning lines as the peripheral circuit section;
2. The input voltage limiting means is provided at a connection point between a dummy scanning line to which only the dummy pixels are connected and the scanning line driving circuit among the plurality of scanning lines. Electro-optic device.   The electro-optical device according to claim 4, wherein the input voltage limiting unit is not provided in the scanning line to which the effective pixel and the dummy pixel are connected.   6. The electro-optical device according to claim 2, wherein the dummy data line or the dummy scanning line is supplied with an arbitrary potential that is equal to or less than an input voltage amplitude.   The electro-optical device according to claim 1, wherein the input voltage limiting unit is formed of a resistor.   The electro-optical device according to claim 1, wherein the input voltage limiting unit is formed of a resistor and a capacitor.   An electronic apparatus comprising the electro-optical device according to claim 1.

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