JP2014026135A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of reducing power consumption by a line inversion drive system and improving display qualities by suppressing generation of crosstalk.SOLUTION: In a liquid crystal display device 1, a first thin film transistor TFT1 is connected to a first source wiring line 224a between a first pixel P1 and a second pixel P2; a second thin film transistor TFT2 is connected to a second source wiring line 224b between the second pixel P2 and a third pixel P3; and a third thin film transistor TFT3 is connected to the first source wiring line 224a at an opposite side of the third pixel P3 to the second pixel P2.

Description

  The present invention relates to a liquid crystal display device used for various applications such as a mobile phone, a digital camera, a portable game machine, or a portable information terminal.

  The liquid crystal display device includes a pair of substrates facing each other and a liquid crystal layer interposed between the pair of substrates. On one substrate side of the pair of substrates, a plurality of gate wirings arranged in the Y direction, a plurality of source wirings arranged in the X direction orthogonal to the Y direction, and a plurality of source wirings A plurality of thin film transistors provided for each pixel surrounded by a gate wiring and a plurality of source wirings and a signal electrode located in the pixel are provided, and a common electrode located in the pixel is provided on the other substrate side. Is provided.

  Each pixel has a rectangular shape with the Y direction as the long side direction, and the thin film transistors of the pixels adjacent in the Y direction are connected to the same source wiring. A signal voltage is applied to the signal electrode located in the pixel via the source wiring and the thin film transistor, and an electric field is generated between the signal electrode and the common electrode to control the direction of the liquid crystal molecules in the liquid crystal layer.

  In such a liquid crystal display device, a line inversion driving method is adopted. In the line inversion driving method, as shown in FIG. 9A, a signal voltage applied to each source wiring is positive or negative on a screen (called one frame) displayed when all pixels are scanned once. The signal voltage applied to each source wiring when shifting to the next one frame is inverted to a different polarity. Further, in the line inversion driving method, the polarity of the signal voltage applied by the adjacent source wiring in one frame period is inverted. As a result, the polarity of the applied signal voltage is inverted in pixels adjacent in the X direction.

  However, the line inversion driving method has a problem that a voltage distribution having the same polarity occurs between pixels adjacent in the Y direction, crosstalk occurs, and display quality deteriorates.

  In order to solve this problem, there is a liquid crystal display device adopting a dot inversion driving method (for example, see Patent Document 1). In the dot inversion driving method, as shown in FIG. 9B, the polarity of the signal voltage applied to each source wiring in one frame period is alternately inverted between positive and negative, and the X direction and the Y direction in one frame period. The polarity of the signal voltage applied to the adjacent pixels is inverted, the occurrence of voltage distribution of the same polarity in the adjacent pixels is suppressed, and the occurrence of crosstalk is reduced.

JP 2003-255905 A

  However, in such a liquid crystal display device, as shown in FIG. 9B, since the polarity of the signal voltage in each source line is repeatedly inverted in one frame period, charging and discharging are repeated in each source line. Is repeated, and there is a problem that the power consumption of the liquid crystal display device increases. Further, this problem becomes more prominent as the number of source wirings is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce power consumption by a line inversion driving method and to improve display quality by suppressing the occurrence of crosstalk. It is to provide a display device.

  The liquid crystal display device according to the present invention includes a first substrate and a second substrate disposed so that main surfaces thereof are opposed to each other, a liquid crystal layer disposed between the first substrate and the second substrate, and the second substrate. A first gate wiring, a second gate wiring, a third gate wiring, and a fourth gate wiring that are sequentially arranged on the main surface of the second substrate in the Y direction; and a Y gate on the main surface of the second substrate. The first source wiring and the second source wiring, which are arranged in order in the orthogonal X direction and intersect each of the first gate wiring to the fourth gate wiring, and are located on the second gate wiring. A first thin film transistor; a second thin film transistor positioned on the third gate wiring; a third thin film transistor positioned on the fourth gate wiring; the first gate wiring to the fourth gate wiring; and the first source wiring. The second saw An insulating film provided on the main surface of the second substrate so as to cover the wiring and the first thin film transistor to the third thin film transistor, and the first thin film transistor to the third thin film transistor provided on the insulating film A plurality of first display electrodes electrically connected to each of the first display electrodes and a second display electrode for forming an electric field between the first display electrodes, the first gate wiring, and the second gate A rectangular first pixel having a long side in the X direction surrounded by a wiring, the first source wiring, and the second source wiring; the second gate wiring; the third gate wiring; and the first source. A rectangular second pixel having a long side in the X direction surrounded by the wiring and the second source wiring; the third gate wiring; the fourth gate wiring; the first source wiring; A third pixel having a rectangular shape with a long side in the X direction surrounded by a source wiring; and the first thin film transistor is connected to the first source wiring between the first pixel and the second pixel. The second thin film transistor is connected to the second source line between the second pixel and the third pixel, and the third thin film transistor is opposite to the second pixel of the third pixel. And connected to the first source wiring.

  According to the liquid crystal display device of the present invention, the power consumption can be reduced by the line inversion driving method, and the display quality can be improved by suppressing the occurrence of crosstalk.

It is a top view which shows the liquid crystal display device in the 1st Embodiment of this invention. It is sectional drawing along the II line | wire of FIG. FIG. 2 is an enlarged plan view of a portion K in FIG. 1. It is a top view which shows the wiring on the 2nd board | substrate of each pixel, an electrode, and a thin-film transistor. It is sectional drawing along the II-II line of FIG. FIG. 2 is a schematic diagram illustrating the polarity of each pixel during driving in the liquid crystal display device of FIG. 1. It is a top view which shows the principal part of the liquid crystal display device in the 2nd Embodiment of this invention. It is sectional drawing along the III-III line of FIG. (A) is a figure which shows the drive waveform of the signal voltage applied to the source wiring in a line inversion drive system. (B) is a diagram showing a drive waveform of the signal voltage applied to the source wiring in the dot inversion drive method.

[First Embodiment]
A liquid crystal display device 1 according to a first embodiment of the present invention will be described with reference to FIGS.

  The liquid crystal display device 1 includes a liquid crystal panel 2, a light source device 3 that emits light toward the liquid crystal panel 2, a first polarizing plate 4 disposed on the liquid crystal panel 2, and the liquid crystal panel 2 and the light source device 3. And a second polarizing plate 5 disposed therebetween.

  In the liquid crystal panel 2, the first substrate 21 and the second substrate 22 are disposed to face each other, and a liquid crystal layer 23 is provided between the first substrate 21 and the second substrate 22, so as to surround the liquid crystal layer 23. In addition, a sealing material 24 for joining the first substrate 21 and the second substrate 22 is provided.

  The first substrate 21 has a first main surface 21a used as a display surface when displaying an image, and a second main surface 21b located on the opposite side of the first main surface 21a. The first substrate 21 is made of, for example, glass or plastic.

On the second main surface 21b of the first substrate 21, a light shielding film 211, a color filter 212, and a first planarization film 213 are formed.
A common electrode 214 is provided.

The light shielding film 211 has a function of shielding light. The light shielding film 211 is provided in a lattice shape along the outer periphery of each pixel P on the second main surface 21 b of the first substrate 21. Examples of the material of the light shielding film 211 include a resin to which a dye or pigment having a high light shielding property (for example, black) is added, or a metal such as chromium. Although the light shielding film 211 in the present embodiment is formed in a lattice shape on the second main surface 21b, the present invention is not limited to this.

The color filter 212 has a function of transmitting only a specific wavelength of visible light. The plurality of color filters 212 are located on the second main surface 21 b of the first substrate 21 and are provided for each pixel P. Each color filter 212 has one of red (R), green (G), and blue (B). In addition, the color filter 212 is not limited to the above color, for example, yellow,
A color filter 212 such as white may be arranged. Examples of the material of the color filter 212 include a resin to which a dye or a pigment is added.

As shown in FIG. 3, the pixel P has a rectangular shape with the X direction as the long side direction. The color filter 212 is arranged in the Y direction in the order of red (R), green (G), and blue (B), but is not limited to this, and blue (B), green (G), and red You may arrange in the Y direction in the order of (R).

The first planarizing film 213 is provided so as to cover the light shielding film 211 and the color filter 212. The first planarization film 213 is formed of an organic material, and examples thereof include an acrylic resin, an epoxy resin, and a polyimide resin. The film thickness of the first planarizing film 213 is, for example, 1 μm to 5
It is set in the range of μm.

The common electrode 214 has a function of generating an electric field with the signal electrode 226 by a voltage applied from a driving IC (not shown). The common electrode 214 is provided on the first planarization film 213. The common electrode 214 is formed of a conductive transparent material, for example, ITO, IZO, A
It is formed of TO, AZO, tin oxide, zinc oxide or a conductive polymer.

  The second substrate 22 has a first main surface 22a facing the second main surface 21b of the first substrate 21, and a second main surface 22b located on the opposite side of the first main surface 22a. The second substrate 22 can be formed of the same material as the first substrate 21.

A plurality of gate wirings 221 are provided on the first main surface 22 a of the second substrate 22, and a gate insulating film 222 is provided so as to cover the plurality of gate wirings 221. A source wiring 224 is provided on the gate insulating film 222, and a first interlayer insulating film 223 is provided so as to cover the plurality of source wirings 224. A second planarizing film 225 is provided on the first interlayer insulating film 223. A signal electrode 226 is provided on the second planarization film 225.

The gate wiring 221 has a function of applying a voltage supplied from a driving IC (not shown) to the thin film transistor TFT. As shown in FIG. 4, the gate wiring 221 includes the first main surface 22 of the second substrate 22.
It extends in the X direction on a. The plurality of gate wirings 221 are arranged along the Y direction.
The gate wiring 221 is formed of a conductive material, for example, aluminum, molybdenum, titanium, neodymium, chromium, copper, or an alloy containing these.

FIG. 4 shows a plurality of gate wirings 221. For convenience of explanation, these are referred to as a first gate wiring 221a, a second gate wiring 221b, a third gate wiring 221c, a fourth gate wiring 221d, and a fifth gate wiring 221e.

  The gate wiring 221 is formed by the following method, for example.

  First, a material is formed as a film on the first main surface 22a of the second substrate 22 by sputtering, vapor deposition, or chemical vapor deposition. A photosensitive resin is applied to the surface of the film, and a pattern having a desired shape is formed on the photosensitive resin by performing an exposure process and a development process on the applied photosensitive resin. Next, this film is etched with a chemical solution to make the film into a desired shape, and then the applied photosensitive resin is peeled off. Thus, the gate wiring 221 can be formed by forming and patterning the material.

The gate insulating film 222 is provided on the first main surface 22a so as to cover the gate wiring 221. The gate insulating film 222 is formed using an insulating material such as silicon nitride or silicon oxide. The gate insulating film 222 can be formed on the first main surface 22a of the second substrate 22 by the above-described sputtering method, vapor deposition method, chemical vapor deposition method, or the like.

The source wiring 224 has a function of applying a signal voltage supplied from the driving IC to the signal electrode 226 through the thin film transistor TFT. As shown in FIG. 4, the plurality of source lines 224 extend in the Y direction. The plurality of source lines 224 are arranged on the gate insulating film 222 along the X direction. Further, the signal voltage supplied to the source wiring 224 has a driving waveform as shown in FIG. 9A, and the signal voltage applied to each source wiring 224 in one frame period is either positive or negative. The polarity is reversed, and the signal voltage applied to each source line 224 is inverted to negative or positive when shifting to the next one frame period. Further, the polarities of the signal voltages supplied from the adjacent source wirings 224 in one frame period are different. Note that the polarity of the signal voltage applied to the source wiring 224 is positive with respect to the voltage applied to the common electrode 214, for example, if it is higher than this voltage, and negative if it is lower. it can.

The source wiring 224 may be formed using the same material as the gate wiring 221. The source wiring 224 can be formed by a method similar to that for the gate wiring 221.

FIG. 4 shows a plurality of source wirings 224. For convenience of explanation, these are referred to as a first source line 224a, a second source line 224b, and a third source line 224c.

Further, FIG. 4 shows a plurality of pixels P. For convenience of explanation, the first gate wiring 221
a, a region surrounded by the second gate wiring 221b, the first source wiring 224a, and the second source wiring 224b is the first pixel P1, and the second gate wiring 221b, the third gate wiring 221c, the first source wiring 224a, and the first source wiring 224a The region surrounded by the two source wirings 224b is the second pixel P2, and the third gate wiring 221c, the fourth gate wiring 221d, the first source wiring 224a and the second source wiring 224 are used.
A region surrounded by b is a third pixel P3, and a region surrounded by the fourth gate wiring 221d, the fifth gate wiring 221e, the first source wiring 224a and the second source wiring 224b is a fourth pixel P4.

A red (R) color filter 212 is provided on the second main surface 21b of the first substrate 21 in the first pixel P1, and a green (G) color filter 212 is provided on the second pixel P2. The third pixel P3 is provided with a blue (B) color filter 212, and the fourth pixel P4 is provided with a red (R) color filter 212.

The first interlayer insulating film 223 is provided on the gate insulating film 222 so as to cover the source wiring 224. The first interlayer insulating film 223 is formed of an insulating material, and examples thereof include inorganic materials such as silicon nitride and silicon oxide.

The thin film transistor TFT includes a semiconductor layer such as amorphous silicon, polysilicon, or an oxide semiconductor, a source electrode provided on the semiconductor layer, connected to the source wiring 224, and a drain electrode. The thin film transistor TFT is located on the gate wiring 221. The drain electrode of the thin film transistor TFT is connected to the signal electrode 226 through a contact hole.

In the thin film transistor TFT, the resistance of the semiconductor layer between the source electrode and the drain electrode changes in accordance with the voltage applied to the semiconductor layer through the gate wiring 221, thereby writing or non-writing the image signal to the signal electrode 226. Be controlled.

FIG. 4 shows a plurality of thin film transistors TFT. For convenience of explanation, the first
A thin film transistor TFT connected to the first source line 224a between the pixel P1 and the second pixel P2 is a first thin film transistor TFT1, and is connected to the second source line 224b between the second pixel P2 and the third pixel P3. The thin film transistor TFT is a second thin film transistor TFT2, the thin film transistor TFT connected to the first source line 224a between the third pixel P3 and the fourth pixel P4 is a third thin film transistor TFT3, and the third pixel P3 of the fourth pixel P4. A thin film transistor TFT connected to the second source line 224b on the opposite side is referred to as a fourth thin film transistor TFT4.

The second planarization film 225 is formed of an organic material, and examples thereof include an acrylic resin, an epoxy resin, and a polyimide resin. The film thickness of the second planarization film 225 is, for example, 1 μm to
It is set in the range of 5 μm. From the viewpoint of reducing the parasitic capacitance, it is preferable to increase the thickness of the second planarization film 225.

  The signal electrode 226 has a function of generating an electric field with the common electrode 214 by a voltage applied from the driving IC. The plurality of signal electrodes 226 are provided on the second planarization film 225 and are located for each pixel P. Note that the signal electrode 226 may be formed using the same material as the common electrode 214.

In the liquid crystal display device 1, the first thin film transistor TFT1 is connected to the first source line 224a between the first pixel P1 and the second pixel P2, and the second thin film transistor TFT2 is connected between the second pixel P2 and the third pixel P3. To the second source line 224b, the third thin film transistor TFT3 is connected to the first source line 224a between the third pixel P3 and the fourth pixel P4, and the fourth thin film transistor TFT4 is the third pixel of the fourth pixel P4. The other side of P3 is connected to the second source line 224b.
As a result, even when the polarity is inverted between adjacent pixels P, the signal voltage applied to each source line 224 in one frame period is either positive or negative, as in the line inversion driving method. If the polarities of the signal voltages applied to the first source wiring 224a and the second source wiring 224b adjacent in the X direction are different from each other in the X direction, the first pixel P1 and the second pixel P2 adjacent in the Y direction, The polarities of the signal voltages applied to the second pixel P2, the third pixel P3, the third pixel P3, and the fourth pixel P4 can be reversed. Therefore, there is no need to repeatedly invert the polarity of the signal voltage within one frame period in each of the first source line 224a and the second source line 224b, so that charging and discharging in the source line 224 are reduced, and the liquid crystal display The power consumption of the device 1 can be reduced, and the polarity is inverted between the pixels P adjacent in the X direction and the Y direction, so that the occurrence of crosstalk can be suppressed and the display quality can be improved.

  FIG. 6 is a schematic diagram illustrating the polarity of each pixel when the liquid crystal display device 1 is driven. 6A is a schematic diagram showing the polarity of each pixel P in a specific one frame period, and FIG. 6B is the polarity of each pixel P in the next one frame period in FIG. 6A. It is the schematic which showed. In FIGS. 6A and 6B, the + symbol represents positive polarity and the − symbol represents negative polarity.

As shown in FIGS. 6A and 6B, the source wiring 224 to which the thin film transistor TFT is connected differs between the pixels P adjacent in the Y direction. Further, the signal voltage applied to each source wiring 224 is either positive or negative voltage in one frame period as shown in FIG. 9A, and is applied to the source wiring 224 adjacent in the X direction. The polarity of the signal voltage is reversed. Accordingly, in the liquid crystal display device 1, a line inversion driving method is used for inverting the polarity of the signal voltage applied to the adjacent source line 224 in one frame period as shown in FIG. Even in the case of adopting, it is possible to reverse the polarity in the pixel P adjacent in the Y direction in addition to the X direction. Then, as shown in FIG. 6B, when shifting to the next frame, the polarity of the signal voltage applied to each source line 224 is simply reversed, and the pixel P adjacent in the X direction and the Y direction is used. Its polarity can be reversed.

  Further, in the liquid crystal display device 1, the pixel P has a rectangular shape with the X direction as the long side direction. Here, in the case of a rectangular pixel whose long side is the Y direction, it is necessary to form the source wiring 224 in each of the three RGB pixels. On the other hand, in the liquid crystal display device 1, since the pixel P has a rectangular shape with the X direction as the long side direction, for example, the first pixel line P1 ( R), the second pixel P2 (G), and the third pixel P3 (B) can be driven. That is, since the number of source wirings 224 that tend to increase power consumption can be reduced, the power consumption of the liquid crystal display device 1 can be reduced.

  The liquid crystal layer 23 is provided between the first substrate 21 and the second substrate 22. The liquid crystal layer 23 includes liquid crystal molecules such as nematic liquid crystal.

  The sealing material 24 has a function of bonding the first substrate 21 and the second substrate 22 together. The sealing material 24 is provided between the first substrate 21 and the second substrate 22. This sealing material 24 is formed of an epoxy resin or the like.

  The light source device 3 has a function of emitting light toward the liquid crystal panel 2. The light source device 3 includes a light source 31 and a light guide plate 32. In the light source device 3 in the present embodiment, a point light source such as an LED is used as the light source 31, but a linear light source such as a cold cathode tube may be used.

  The first polarizing plate 4 has a function of selectively transmitting light in a predetermined vibration direction. The first polarizing plate 4 is disposed so as to face the first main surface 21 a of the first substrate 21 of the liquid crystal panel 2.

  The second polarizing plate 5 has a function of selectively transmitting light in a predetermined vibration direction. The second polarizing plate 5 is disposed so as to face the second main surface 22 b of the second substrate 22.

[Second Embodiment]
7 and 8 are diagrams showing the main part of the liquid crystal display device 1A according to the second embodiment.

Compared to the liquid crystal display device 1 in the first embodiment, the liquid crystal display device 1A has a signal electrode 226.
The difference is that a common electrode 214 is formed thereon via a second interlayer insulating film 227.

  The second interlayer insulating film 227 is provided on the second planarization film 225 so as to cover the signal electrode 226. The second interlayer insulating film 227 is formed of an insulating material, and examples thereof include inorganic materials such as silicon nitride and silicon oxide.

The common electrode 214 is provided on the signal electrode 226 via the second interlayer insulating film 227. In addition, a slit S is formed in the common electrode 214. When a voltage is applied to the signal electrode 226 and the common electrode 214, a horizontal electric field is generated between the signal electrode 226 and the common electrode 214 through the slit S, and the alignment of liquid crystal molecules in the liquid crystal layer 23 is controlled by the horizontal electric field. By doing so, a wide viewing angle can be realized.

  In the liquid crystal display device 1A, the common electrode 214 is formed on the signal electrode 226 via the second interlayer insulating film 227, but the present invention is not limited to this. The common electrode 214 may be formed below the signal electrode 226 via the second interlayer insulating film 227. In this case, a slit S is formed in the signal electrode 226.

Further, both the signal electrode 226 and the common electrode 214 may be formed on the second planarizing film 225 without providing the second interlayer insulating film 227.

  The present invention is not particularly limited to the first and second embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

1, 1A liquid crystal display device 2 liquid crystal panel
21 First board
21a 1st main surface
21b Second main surface (main surface)
211 Shading film
212 Color filter
213 First planarization film
214 Common electrode
22 Second board
22a First main surface (main surface)
22b 2nd main surface
221 Gate wiring
221a First gate wiring
221b Second gate wiring
221c Third gate wiring
221d 4th gate wiring
221e 5th gate wiring
222 Gate insulation film
223 First interlayer insulating film
224 source wiring
224a First source wiring
224b Second source wiring
224c Third source wiring
225 Second planarization film
226 Signal electrode
227 Second interlayer insulating film
TFT thin film transistor
TFT1 first thin film transistor
TFT2 Second thin film transistor
TFT3 Third thin film transistor
TFT4 Fourth thin film transistor
23 Liquid crystal layer
24 Sealing material 4 First polarizing plate 5 Second polarizing plate 3 Light source device
31 Light source
32 Light guide plate S Slit

Claims (2)

A first substrate and a second substrate arranged with their main surfaces facing each other, a liquid crystal layer arranged between the first substrate and the second substrate, and a Y direction on the main surface of the second substrate First gate wiring, second gate wiring, third gate wiring, and fourth gate wiring, which are sequentially arranged, and sequentially arranged in the X direction orthogonal to the Y direction on the main surface of the second substrate. A first source line and a second source line that intersect with each of the first gate line to the fourth gate line, a first thin film transistor positioned on the second gate line, and the third gate line. A second thin film transistor positioned on a gate wiring; a third thin film transistor positioned on the fourth gate wiring; the first gate wiring to the fourth gate wiring; the first source wiring; the second source wiring; First thin film An insulating film provided on the main surface of the second substrate so as to cover the transistor to the third thin film transistor, and each of the first thin film transistor to the third thin film transistor provided on the insulating film is electrically connected A plurality of first display electrodes connected to each other and a second display electrode for forming an electric field between the first display electrodes,
A rectangular first pixel having a long side direction in the X direction surrounded by the first gate wiring, the second gate wiring, the first source wiring, and the second source wiring, and the second gate wiring, A rectangular second pixel having a long side direction in the X direction surrounded by the third gate line, the first source line, and the second source line; the third gate line; the fourth gate line; A rectangular third pixel surrounded by the first source line and the second source line and having a long side direction in the X direction;
The first thin film transistor is connected to the first source line between the first pixel and the second pixel, and the second thin film transistor is connected to the second pixel between the second pixel and the third pixel. A liquid crystal display device, wherein the liquid crystal display device is connected to a source line, and the third thin film transistor is connected to the first source line on the opposite side of the third pixel to the second pixel. Only a positive voltage is applied to the first source line in one frame period,
The liquid crystal display device according to claim 1, wherein only a negative voltage is applied to the second source line in the one frame period.

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