JP2009058809A - Liquid crystal display device and method for driving the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce vibration and abnormal sound caused by COM signals supplied to a common electrode provided in a liquid crystal display device. <P>SOLUTION: The liquid crystal display device 10 is equipped with a liquid crystal display panel 11 having a liquid crystal layer disposed between an active matrix substrate and a counter substrate. A common electrode is disposed on the counter substrate for forming a potential with respect to a pixel electrode disposed on the active matrix substrate; and the common electrode is divided into a first common electrode 33a and a second common electrode 33b in the liquid crystal display panel 11. The liquid crystal device 10 is equipped with a display panel drive circuit 21 (driving unit) to respectively supply drive signals in inverted phases from each other to the divided common electrodes 33a, 33b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to improvement of abnormal noise and vibration generated in a liquid crystal display device.

  Conventionally, a liquid crystal display (LCD) has been widely used as a display of a portable information terminal device such as a mobile phone or a PDA (Personal Digital Assistant). There is a strong demand for lighter, smaller and thinner LCDs used in such portable information terminal devices.

  LCD adjusts the voltage applied to the liquid crystal molecules sandwiched between two transparent substrates, thereby changing the alignment of the liquid crystal molecules and changing the state of light passing through the liquid crystal (change, intensity, scattering, etc.). The display device uses the changed light for display. The LCD is formed by laminating two polarizing plates, transparent electrodes, etc. in addition to two transparent substrates. Among these members, the thickness of the two transparent substrates occupies a large proportion. In order to reduce the thickness of the LCD for portable information terminals, it is necessary to reduce the thickness of the two transparent substrates.

  However, when a thin glass substrate is used to reduce the thickness of the LCD, an abnormal fine vibration or abnormal noise may occur in the LCD triggered by an LCD drive signal. In particular, in the case of an LCD module for a mobile phone terminal, the phenomenon is uncomfortable for the user because the terminal is used close to the ear.

  Therefore, Patent Document 1 discloses a technique for preventing abnormal fine vibrations and abnormal noises from occurring in an LCD module for a portable telephone terminal. In this document, it is assumed that the cause of abnormal micro vibrations and abnormal noise is due to the piezo effect due to the residual charge in the device casing, and there is a static elimination means for reducing the charging voltage between the glass substrate for liquid crystal and the device casing A liquid crystal display device has been proposed.

Patent Document 2 discloses a technique for reducing noise, vibration, and noise in a touch panel integrated display device in which an input device and a display device such as a liquid crystal display device are combined.
JP 2003-295162 A (released on October 15, 2003) JP-A-2005-164709 (released on June 23, 2005)

  By the way, in order to generate a common voltage applied to the common electrode (counter electrode) provided on the entire surface of the color filter substrate (opposite substrate) disposed opposite to the TFT substrate, the liquid crystal display panel vibrates. Some are caused by signals. In addition, when the frequency of the COM signal is in the audible range, a sound is generated. The above-described Patent Document 1 does not specifically examine countermeasures against vibration and sound generated due to such a COM signal. Moreover, since the above-mentioned Patent Document 2 is for improving the sounding of a touch panel integrated display device, it does not improve the vibration and abnormal noise of a liquid crystal display device that is not a touch panel integrated type. In other words, the invention described in each of the above patent documents is not sufficient as a countermeasure against vibration and abnormal noise of the liquid crystal display device caused by the COM signal.

  Therefore, an object of the present invention is to reduce vibrations and abnormal noise caused by a COM signal for generating a common voltage applied to a common electrode provided in a liquid crystal display device.

  In order to solve the above problems, a liquid crystal display device according to the present invention is a liquid crystal display device including a liquid crystal display panel in which a liquid crystal layer is provided between an active matrix substrate and a counter substrate. The substrate is provided with a common electrode for forming a potential with the pixel electrode provided on the active matrix substrate, and the common electrode is divided in the liquid crystal display panel, A drive unit that supplies drive signals having opposite phases to each of the divided common electrodes is provided.

  The drive signal supplied to the common electrode is a signal for generating a common voltage applied to the common electrode. In the conventional liquid crystal display device, the liquid crystal display panel vibrates in synchronization with the frequency of the drive signal, and when the frequency is in an audible range, this sound is heard as an audible noise (abnormal sound). This is caused by the Coulomb force generated by the charge accumulated on the surface of the liquid crystal display panel being affected and changed by the drive signal.

  In the liquid crystal display device of the present invention, the common electrode is divided in the liquid crystal display panel, and a drive unit that supplies drive signals having opposite phases to each of the divided common electrodes is provided. According to this, the above-mentioned Coulomb force generated by one drive signal can be canceled by the other opposite-phase drive signal. Thereby, vibration and abnormal noise generated in the liquid crystal display device can be reduced.

  Further, according to the present invention, vibrations and abnormal noises generated in the liquid crystal display device with a simpler configuration can be obtained without modifying the LSI provided in the liquid crystal display device, adding a process in the manufacturing process, or adding parts. Can be reduced.

  In the liquid crystal display device of the present invention, it is preferable that the common electrode is divided into at least a part of the non-display area and the other area.

  Here, the non-display area of the liquid crystal display panel is an area where a light blocking layer such as a black matrix existing in the frame portion (peripheral portion) of the panel is provided and no image is displayed.

  If the common electrode is divided within the display area, and signals that are out of phase with each other are supplied to each divided common electrode, there will be a slight difference in the gradation of the display image for each area where the common electrode is divided. However, this may cause display unevenness.

  According to the above configuration, since the common electrode is divided into at least a part of the non-display area and the other area, it is possible to avoid separation of the common electrode in the display area. Therefore, display unevenness caused by the separation of the common electrode within the display area can be prevented.

  In the liquid crystal display device of the present invention, the drive unit includes a drive circuit that generates the drive signal and a signal inversion unit that inverts the signal, and the signal inversion unit is divided from the drive circuit as described above. It is preferable that the wiring is provided between a wiring for supplying a driving signal to at least one common electrode of the common electrodes and a wiring for supplying a driving signal to the other common electrode.

  According to the above configuration, since the signal inversion unit is provided between the wirings, the common voltage (COM signal) can be applied to each divided common electrode using the same wiring. it can. Therefore, vibration and sound generation can be reduced with a simple circuit configuration using an existing LSI.

  The liquid crystal display device of the present invention includes a wiring for supplying a driving signal to the divided common electrode, and the wiring is formed on the active matrix substrate and connected to the liquid crystal layer. It is preferable to be connected to the common electrode through a portion.

  According to the above configuration, the driving circuit for the common electrode provided on the counter substrate can be collectively arranged on the same substrate as the driving circuit such as the scanning wiring and the signal wiring provided on the active matrix substrate.

  In order to solve the above problems, a driving method of a liquid crystal display device according to the present invention includes a liquid crystal display panel in which a liquid crystal layer is provided between an active matrix substrate and a counter substrate. A common electrode for forming a potential between the pixel electrodes provided on the active matrix substrate is provided, and the common electrode is a method for driving a liquid crystal display device divided in the liquid crystal display panel. The drive signals having opposite phases to each other are supplied to the divided common electrodes.

  In the driving method of the liquid crystal display device of the present invention, driving signals having opposite phases are supplied to the common electrodes divided in the liquid crystal display panel. According to this, the above-mentioned Coulomb force generated by one drive signal can be canceled by the other opposite-phase drive signal. Thereby, vibration and abnormal noise generated in the liquid crystal display device can be reduced.

  Further, according to the driving method described above, the vibration generated in the liquid crystal display device with a simpler configuration without modifying the LSI provided in the liquid crystal display device, adding a process in the manufacturing process, or adding parts, etc. Abnormal noise can be reduced.

  As described above, the liquid crystal display device of the present invention is a liquid crystal display device including a liquid crystal display panel in which a liquid crystal layer is provided between an active matrix substrate and a counter substrate. A common electrode for forming a potential between the pixel electrodes provided on the active matrix substrate is provided, and the common electrode is divided in the liquid crystal display panel and each divided common electrode is provided. A drive unit that supplies drive signals having opposite phases to each other is provided.

  The liquid crystal display device driving method of the present invention includes a liquid crystal display panel in which a liquid crystal layer is provided between an active matrix substrate and a counter substrate, as described above, and the counter substrate includes the active matrix substrate. A common electrode for forming a potential between the pixel electrode and the pixel electrode provided in the liquid crystal display device is provided in the liquid crystal display panel. In addition, drive signals having opposite phases to each other are supplied to the common electrodes.

  Therefore, according to the present invention, it is possible to reduce vibrations and noise generated due to the COM signal applied to the common electrode provided in the liquid crystal display device with a simple configuration.

  One embodiment of the present invention is described below with reference to FIGS. Note that the present invention is not limited to this.

  The liquid crystal display device of this embodiment is an active matrix type liquid crystal display device using TFT (Thin Film Transistor) elements. However, the present invention is not limited to this, and a liquid crystal display device to which a switching element such as MIM (Metal Insulator Metal) is attached may be used.

  FIG. 1 shows a configuration of a liquid crystal display device 10 of the present embodiment. FIG. 2 shows a cross-sectional configuration of the liquid crystal display panel 11 provided in the liquid crystal display device 10 shown in FIG.

  As shown in FIG. 1, a liquid crystal display device 10 generates and supplies a liquid crystal display panel 11 and signals to be applied to various wirings such as scanning wirings and signal wirings arranged on the liquid crystal display panel 11. A drive circuit 21 (a drive unit or a drive circuit) is provided. The display panel drive circuit 21 includes, for example, a source driver, a gate driver, a common electrode drive circuit, and the like.

  As shown in FIG. 2, the liquid crystal display panel 11 has a structure in which a liquid crystal layer 14 is disposed between two substrates (an active matrix substrate 12 and a counter substrate 13) disposed to face each other. The panel surface of the liquid crystal display panel 11 is provided on the display area R1 (the hatched area in FIG. 1) for displaying an image visually recognized by the observer and on the outer side (outer peripheral part) of the display area R1. It is divided into a non-display area (also called a frame area) R2 where an image is not visually recognized. As shown in FIG. 2, a black matrix BM is provided in the non-display area R2 to shield light from a light source such as a backlight.

  Although not shown, the display region R1 of the liquid crystal display panel 11 is provided with a plurality of picture elements arranged in a matrix. In accordance with each of these picture elements, a scanning wiring (not shown) to which a scanning signal is applied and a signal wiring (not shown) to which a data signal (video signal) is applied are formed on the active matrix substrate 12. It is formed to intersect.

  Specifically, on the active matrix substrate 12, a scanning wiring (not shown) to which scanning signals given from a gate driver are sequentially applied, and a signal wiring (not shown) to which data signals given from a source driver are sequentially applied. Are arranged so as to be orthogonal to each other. A TFT (not shown) as a switching element electrically connected to the scanning wiring and the signal wiring is provided in the vicinity of each intersection of the scanning wiring and the signal wiring, and a transparent pixel electrode is provided in each TFT. (Not shown) is connected. Thereby, a picture element is formed.

  Further, on the active matrix substrate 12 further outside the non-display region R2, a display panel drive circuit 21 that supplies signals to various wirings such as scanning wirings and signal wirings provided on the liquid crystal display panel 11 is provided. It has been.

  In addition, a counter substrate 13 (also referred to as a color filter substrate) disposed to face the active matrix substrate 12 with the liquid crystal layer 14 interposed therebetween is common to a color filter layer 32 and a transparent conductive film on a glass substrate 31. The electrode 33 has a laminated structure. Connected to the common electrode 33 is a common wiring 34 (wiring) for transmitting a COM signal (also referred to as a drive signal or a common electrode drive signal) for generating a common voltage applied to the electrode. In the present embodiment, the common wiring 34 is formed on the active matrix substrate 12.

  The pixel electrode on the active matrix substrate 12 and the common electrode 33 on the counter substrate constitute a capacitor for securing a capacitance in the liquid crystal layer 14.

  In this configuration, when a scanning signal is sequentially input to the scanning wiring by the gate driver in the display panel driving circuit 21, the gates of the TFTs for one row are simultaneously turned on by the scanning signal input, and the display panel driving circuit 21 The display data signal is input for each picture element from the signal wiring by the source driver.

  As a result, these data signals are applied to the picture element electrodes, the transmissivity of the liquid crystal changes due to the potential difference between the picture element electrodes and the common electrode, and characters, images, etc. are displayed on the liquid crystal display panel surface.

  In the color filter layer 32, a colored layer 32a composed of three primary colors of R (Red: Red), G (Green: Green), and B (Blue: Blue) corresponds to each pixel electrode on the active matrix substrate 12. Are arranged. A black matrix BM is formed in a lattice shape between the colored layers 32a. The black matrix BM is also arranged in the non-display area R2. As described above, the color filter layer 32 is provided on the counter substrate 13, so that the liquid crystal display panel 11 can display a color image.

  The common electrode 33 is formed by disposing a transparent conductive film on substantially the entire surface of the counter substrate 13. However, in the liquid crystal display device 10 of the present embodiment, the common electrode 33 is separated into a region A indicated by a broken line in FIG. Here, the region A (33a) is a region including the entire display region R1 and a part of the non-display region R2, and the region B (33b) is a region including the remaining part of the non-display region R2. . The common electrode formed in the region A is referred to as a first common electrode 33a, and the common electrode formed in the region B is referred to as a second common electrode 33b.

  The above-described method of separating the common electrode is an example, and the present invention is not limited to this. In the present invention, the common electrode may be divided into at least two regions, and any common electrode driving signal having an opposite phase may be applied to each divided common electrode.

  However, when the common electrode is divided in the display area, a slight difference occurs in the gradation of the display image for each area where the common electrode is divided, which may cause display unevenness. . Therefore, as in the present embodiment, a common electrode is formed in a part of the non-display region R2 and the other region (that is, a region including the remaining part of the non-display region R2 and the entire region of the display region R1). Are preferably divided. According to this, it is possible to prevent display unevenness that occurs due to the separation of the common electrode in the display region. The same effect can be obtained even if the common electrode is divided between the display region R1 and the non-display region R2.

  The formation of the common electrode divided into regions as described above can be performed by a thin film patterning method using a photolithography technique or the like that is generally performed conventionally. That is, after a metal thin film (for example, ITO) for a common electrode is formed on the color filter layer 32 of the counter substrate 13 by sputtering or the like, a photoresist is applied and an exposure process is performed. Then, the divided common electrode can be formed by etching a predetermined portion.

  Further, a polarizing plate (not shown) is provided outside the active matrix substrate 12 and the counter substrate 13.

  Further, inside the liquid crystal layer 14, a connection portion 41 for connecting the common wiring 34 formed on the active matrix substrate 12 and the common electrode 33 formed on the counter substrate 13 is formed. The material of the connection part 41 will not be specifically limited if it has electroconductivity. In addition, a spacer for maintaining a distance between the active matrix substrate 12 and the counter substrate 13 can be used as the connection portion 41.

  Next, a method of supplying a COM signal (common electrode drive signal) to the common electrode 33 (33a / 33b) in the liquid crystal display device 10 of the present embodiment will be described. In the present invention, COM signals having opposite phases are supplied to the divided common electrodes.

  FIG. 3 shows the waveform of the COM signal supplied to the common electrode 33. 3A shows a waveform of a COM signal (this is referred to as COM1) supplied to the first common electrode 33a in the region A (mainly the display region R1), and FIG. The waveform of the COM signal (this is referred to as COM2) supplied to the common electrode 33b in the almost entire display area R2 is shown.

  As shown in FIG. 3, COM signals (COM1, COM2) having opposite phases are supplied to the regions A and B corresponding to the divided common electrodes 33a and 33b, respectively.

  1 and 2 show the configuration of the common wiring 34 and the connection portion 41 that supply two types of COM signals (COM1, COM2) to the common electrodes 33a and 33b. As shown in FIGS. 1 and 2, in the liquid crystal display panel 11 of the present embodiment, a common wiring 34 for supplying a COM signal to be applied to the common electrode 33 (33 a and 33 b) is provided on the active matrix substrate 12. Is formed. As shown in FIG. 1, a common wiring 34a that supplies a driving signal to one common electrode 33a of the divided common electrodes 33 and a common wiring 34b that supplies a driving signal to the other common electrode 33b. An inverter (driving unit, signal inverting unit) 35 for inverting the signal is disposed between them.

  Thus, by using the inverter 35, a common voltage (COM signal) can be applied to each of the divided common electrodes 33a and 33b using the same common wiring 34. Further, two types of COM signals (that is, COM1 and COM2) having opposite phases are generated from one type of COM signal (drive signal) generated by the display panel drive circuit 21 and supplied to each common electrode. Can do. Therefore, vibration and noise can be reduced by using an LSI provided in a conventional liquid crystal display device and making a simple circuit configuration change thereto.

  In the liquid crystal display device 10 according to the present embodiment, as shown in FIG. 1, two common wires 34 and 34 are connected to the display panel drive circuit 21. The two common wirings 34 and 34 are supplied with drive signals having the same phase. Thus, by applying a drive signal from the display panel drive circuit to the common electrode 33 through a plurality of common wires, the wires can be shortened and the drive signals can be supplied efficiently. However, the present invention is not necessarily limited to such a configuration, and it is sufficient that at least one common wiring is provided.

  However, the present invention is not necessarily limited to a configuration in which a common voltage is applied using an inverter as described above, and a drive signal is separately supplied to each divided common electrode using a separate wiring. Such a configuration may be adopted.

  Further, the arrangement of the common wiring 34 and the inverter 35 shown in FIG. 1 is an example, and the present invention is not limited to this configuration.

  Specifically, in the configuration shown in FIG. 1, four inverters 35 are provided for one liquid crystal display panel 11, and a total of eight connection portions 41 (on the first common electrode 33 a side: 2 and the second common electrode 33b side: 6). However, in the present invention, it is sufficient that at least one inverter is provided for one liquid crystal display panel, and at least one connection portion is provided for each common electrode. According to this, it is possible to obtain the effect of the present invention that the vibration and abnormal noise caused by the COM signal are reduced.

  However, considering the wiring efficiency, it is preferable to provide a plurality of inverters. Further, regarding the connection portions, it is possible to suppress variation in potential in the plane by providing a plurality of connection portions for each electrode.

  In the conventional liquid crystal display device, the liquid crystal display panel vibrates in synchronization with the frequency of the COM signal supplied to the common electrode, and when the frequency is in an audible range, this is heard as a sound (abnormal sound). It was. This is caused by the Coulomb force generated by the charge accumulated on the surface of the liquid crystal display panel being affected and changed by the drive signal.

  In the liquid crystal display device of the present embodiment, the common electrode is divided in the liquid crystal display panel, and a display panel drive circuit 21 (drive unit) that supplies drive signals having opposite phases to the divided common electrodes. Is provided. According to this, the Coulomb force generated by one drive signal (COM1) can be canceled by the other drive signal (COM2) having the opposite phase. Thereby, vibration and abnormal noise generated in the liquid crystal display device can be reduced.

  Further, according to the present invention, vibrations and abnormal noises generated in the liquid crystal display device with a simpler configuration can be obtained without modifying the LSI provided in the liquid crystal display device, adding a process in the manufacturing process, or adding parts. Can be reduced.

  In the above-described embodiment, the configuration in which the common electrode is divided into two and the drive signals having the opposite phases to each other is applied to each of the divided common electrodes has been described as an example. However, the present invention is not limited to one in which the common electrode is divided into two.

  When the common electrode is divided into three or more, it is only necessary to apply common electrode drive signals having opposite phases to at least two common electrodes among the divided common electrodes.

  In the present invention, the number of divided counter electrodes is not particularly limited, but is preferably an even number. According to this, a COM signal is supplied to half of the divided counter electrodes, and a COM inversion signal (eg, COM2) having a phase opposite to that of the COM signal (eg, COM1) is supplied to the other half of the counter electrodes. can do.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope shown in the claims, and the present invention also relates to an embodiment obtained by appropriately combining the technical means disclosed herein. Is included in the technical scope.

  According to the present invention, vibration and abnormal noise can be reduced by applying a simple structural change to a conventional liquid crystal display device. Therefore, the liquid crystal display device of the present invention can be suitably used particularly as a display device for a mobile phone or the like in which the sound is harsh.

It is a top view which shows the structure of the liquid crystal display device concerning one embodiment of this invention. It is the sectional view on the AA line of the liquid crystal display panel with which the liquid crystal display device shown in FIG. 1 was equipped. It is a figure which shows the waveform of the COM signal supplied to the common electrode of the liquid crystal display device shown in FIG. (A) shows the waveform of the COM signal (COM1) supplied to the common electrode in the region A, and (b) shows the waveform of the COM signal (COM2) supplied to the common electrode in the region B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 Liquid crystal display panel 12 Active matrix substrate 13 Opposite substrate 14 Liquid crystal layer 21 Display panel drive circuit (drive part, drive circuit)
32 Color filter layer 33 Common electrode 33a First common electrode (common electrode)
33b Second common electrode (common electrode)
34 Common wiring (wiring)
34a Common wiring (wiring)
34b Common wiring (wiring)
35 Inverter (drive unit, signal inversion unit)
41 connection part BM black matrix R1 display area R2 non-display area COM1 COM signal (drive signal, common electrode drive signal)
COM2 COM signal (drive signal, common electrode drive signal)

Claims (5)

A liquid crystal display device comprising a liquid crystal display panel in which a liquid crystal layer is provided between an active matrix substrate and a counter substrate,
The counter substrate is provided with a common electrode for forming a potential with the pixel electrode provided on the active matrix substrate,
The common electrode is divided in the liquid crystal display panel,
A liquid crystal display device comprising: a drive unit that supplies drive signals having opposite phases to each of the divided common electrodes.   The liquid crystal display device according to claim 1, wherein the common electrode is divided into at least a part of the non-display area and the other area. The drive unit includes a drive circuit that generates the drive signal, and a signal inversion unit that inverts the signal,
The signal inversion unit includes a wiring for supplying a driving signal from the driving circuit to at least one common electrode among the divided common electrodes, and a wiring for supplying a driving signal to the other common electrode. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided between the two. Provided with wiring for supplying a drive signal to the divided common electrode,
4. The wiring according to claim 1, wherein the wiring is formed on the active matrix substrate and connected to the common electrode through a connection provided in the liquid crystal layer. Liquid crystal display device. A liquid crystal display panel having a liquid crystal layer provided between an active matrix substrate and a counter substrate is provided, and the counter substrate is commonly used to form a potential with a pixel electrode provided on the active matrix substrate. An electrode is provided, and the common electrode is a driving method of a liquid crystal display device divided in the liquid crystal display panel,
A driving method of a liquid crystal display device, characterized in that driving signals having mutually opposite phases are supplied to each of the divided common electrodes.

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