JP4062766B2 - Electronic device and display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic device and a display device provided to the pixel by switching the signal output from the driver circuit.
[0002]
[Prior art]
In a liquid crystal display device, a driving side substrate on which a plurality of thin film transistors (TFTs) is formed and a counter side substrate on which a color filter, a counter electrode, and the like are formed are overlapped, and liquid crystal is sealed between them. The liquid crystal orientation is controlled by switching by the TFT and voltage application based on the image signal, and the image is displayed by changing the light transmittance.
[0003]
In such a liquid crystal display device, the image quality can be improved by inverting the polarity (+, −) of the voltage applied to adjacent pixels. In other words, the polarity of the voltage applied to adjacent pixels is reversed, so that the jump voltage from the cross capacitance between the signal line and the gate line of the TFT is cancelled. Thereby, the pixel potential is stably input, and flicker at the time of liquid crystal display is reduced.
[0004]
Further, when the polarity of the voltage is not reversed, in a state where the ground level of the gate line fluctuates, it becomes impossible to determine the OFF state of the gate switch of the TFT, and the held pixel potential is discharged. For this reason, the transmittance of the pixel is lowered and the contrast of the pixel cannot be obtained. Further, since the jump voltage from the signal has the same polarity, the contrast of the pixels for each line becomes conspicuous, and even if the same gradation is displayed, the display is different for each line.
[0005]
From this point of view, driving that inverts the polarity of the voltage applied to adjacent pixels is necessary to improve the image quality of the liquid crystal display device. In the following description, driving that inverts the polarity of the voltage applied to adjacent pixels is referred to as “dot inversion driving”.
[0006]
FIG. 10 is a diagram for explaining dot inversion driving in a conventional liquid crystal display device. In this liquid crystal display device, a signal line output from a driver circuit (IC) that supplies a signal to a pixel is branched into two input lines and switched by a switch TFT.
[0007]
The signal sent from each input line is supplied to each pixel line by line. In the example shown in the figure, pixels corresponding to one line correspond to R (red), G (green), and B (blue) in this order (R1, G1, B1, R2, G2, B2,...).
[0008]
When dot inversion driving is performed in this liquid crystal display device, the polarity of the signal is inverted for every odd number (ODD) and even number (EVEN) of the output lines of the driver circuit, and the switch TFTs are switched alternately.
[0009]
FIG. 11 is a diagram for explaining a signal state by dot inversion driving. In this figure, the horizontal direction indicates pixels corresponding to one line, and the vertical direction indicates the operation order of the switch TFTs 1 and 2.
[0010]
That is, in this liquid crystal display device, when the switch TFT1 is in the closed state and the switch TFT2 is in the open state, the high level (H) and low level (L) signals are alternately applied to every other pixel. When the switch TFT2 is closed and the switch TFT1 is open, Low level (L) and High level (H) signals are alternately applied to every other pixel.
[0011]
Next, when the switch TFT1 is closed and the switch TFT2 is open, a low level (L) signal and a high level (H) signal are alternately applied to every other pixel in the opposite direction. When the switch TFT2 is in the closed state and the switch TFT1 is in the open state, high level (H) and low level (L) signals are alternately applied to every other pixel in the opposite direction.
[0012]
By repeating this, dot inversion driving is performed in the entire display unit.
[0013]
[Problems to be solved by the invention]
However, when dot inversion driving is performed with this liquid crystal display device, the polarity of the voltage applied to adjacent pixels in one line may be the same as the case where the polarity is inverted, and every adjacent pixel is completely Polarity inversion cannot be performed. That is, a state occurs in which dot inversion driving is performed in a certain adjacent pixel, but dot inversion driving is not performed in another adjacent pixel. For this reason, a decrease in contrast and a decrease in the transmittance of the pixel due to the discharge of the pixel potential are caused, and there is a problem that sufficient image quality cannot be improved.
[0014]
[Means for Solving the Problems]
The present invention is a liquid crystal display device made to solve such a problem. That is, the present invention includes a switch circuit that switches a signal output from the output line of the driver circuit to any one of a plurality of input lines provided correspondingly in the same row of pixels. Is an electronic device in which signals having different polarities are given to two input lines adjacent to each other in adjacent units in a plurality of input line units corresponding to the output lines of the driver circuit at the same switching timing.
In addition, the present invention provides a display portion in which a plurality of pixels are arranged, and a signal output from an output line of the driver circuit, which is any one of a plurality of input lines provided corresponding to the same row of pixels in the display portion. Switch circuit for switching to the two input lines adjacent to each other in adjacent units of the plurality of input line units corresponding to the output lines of the driver circuit by switching signals in the switch circuit. Is a display device that is given the same opening / closing timing.
[0015]
In the present invention, when the signal output from the driver circuit is switched by the switch circuit, the two input lines adjacent to each other in the unit of the plurality of input lines corresponding to the output line of the driver circuit are connected to each other. Since signals having different polarities are given at the same opening / closing timing, the polarities of signals finally given to adjacent pixels in one column can be completely inverted.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the liquid crystal display device of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a liquid crystal display device according to the present embodiment. That is, the liquid crystal display device includes a display unit 10 including pixels at positions where a plurality of source lines SL and a plurality of gate lines GL intersect, and a driver IC 20 that supplies a predetermined image signal to the source lines SL. In order to switch the signal output from each output line of the driver IC 20 to the two source lines SL in a time-sharing manner, a switch that performs switching operation by signals S1 and S2 sent from a switch control circuit (for example, a timing generator (not shown)) A circuit 30 and a vertical shift register circuit 40 that sequentially outputs signals to a plurality of gate lines GL are provided.
[0017]
As shown in FIG. 2, the display unit 10 is provided with a TFT for driving the liquid crystal LC and a signal holding capacitor C at the intersections of the source line SL and the gate line GL. By arranging a backlight on the back side of the display unit 10 having such matrix-like pixels and changing the transmittance of each liquid crystal LC according to a signal applied to the TFT, an image based on the intensity of the backlight can be displayed. become.
[0018]
As shown in FIG. 3, the driver IC 20 includes a horizontal shift register circuit 21, a sampling switch 22, a level shifter circuit 23, a memory latch circuit 24, and a digital / analog conversion circuit 25.
[0019]
The horizontal shift register circuit 21 sequentially scans the sampling switch 22 in the horizontal direction. The level shifter circuit 23 is a circuit that boosts digital image data (for example, 5 V) to a necessary liquid crystal drive voltage. The memory latch circuit 24 is a memory that accumulates digital image data for one horizontal period. The digital / analog conversion circuit 25 converts the digital image data output from the memory latch circuit 24 into an analog signal.
[0020]
This analog signal has an inverted polarity at each output line on the ODD side and the EVEN side. This analog signal is input to the switch circuit 30 (see FIG. 1), branched into two input lines, and liquid crystal driving is performed in a time division manner.
[0021]
The driver IC 20 receives, for example, digital image data that enables display of 8 gradations or more and 512 colors or more, and is provided to each pixel in a time division manner by the switch circuit 30 (see FIG. 1).
[0022]
In addition, the driver IC 20 rotates a signal to be output in order to realize dot inversion driving described later. With signal rotation, R (red), G (green), and B (blue) signals are not output synchronously, but a certain output line starts with R and outputs G and B signals in order. The other output line starts from G and outputs B and R signals in order, and the other output line starts from B and outputs R and G signals in order.
[0023]
To do this, a buffer memory for rearranging the signals before sending the color signal data to the driver IC 20 is provided.
[0024]
From the output line of the driver IC 20, an analog signal in which the polarity of the signal is inverted every odd number (ODD) and even number (EVEN) is output. In this way, dot inversion drive is performed to improve image quality such as contrast.
[0025]
4A and 4B are cross-sectional views showing an example of the structure of a TFT applied in the liquid crystal display device of this embodiment. FIG. 4A shows an example of a bottom gate type, and FIG. 4B shows an example of a top gate type.
[0026]
That is, in the bottom gate type in (a), the gate electrode 101 is formed on the substrate 100 such as glass, and the polysilicon P-Si is formed thereon with the gate insulating film 102 interposed therebetween. Note that amorphous silicon may be formed instead of polysilicon P-Si.
[0027]
Further, a source region and a drain region made of an N ⁺ region are formed on both sides of the portion corresponding to the gate electrode 101 of this polysilicon P-Si. A source electrode SD is connected to the source region, and a drain electrode DD is connected to the drain region.
[0028]
In the top gate type shown in (b), polysilicon P-Si is formed on a substrate 100 such as glass, and a gate electrode 101 is formed thereon via a gate insulating film 102. Further, a source region and a drain region composed of an N ⁺ region are formed on both sides of a portion corresponding to the gate electrode 101 of the polysilicon P-Si, and a source electrode SD is connected to the source region, and a drain region is connected to the source region. Is connected to the drain electrode DD.
[0029]
In any TFT structure, in the case of a driving TFT provided in each pixel, the gate electrode 101 is connected to the gate line GL shown in FIG. 1, and a voltage is applied to the gate line GL. The TFT is turned on. The source electrode SD is connected to the source line SL shown in FIG. 1, and the drain electrode DD is connected to the counter electrode potential.
[0030]
That is, when a signal is applied to the source line SL while a voltage is applied to the gate line GL, a current flows from the source electrode SD of the TFT to the drain electrode DD, and the light transmittance of the liquid crystal of the pixel can be changed. It becomes like this.
[0031]
Note that the switch circuit 30 has the same configuration as the TFT shown in FIG. 4, and the switching operation is performed by applying the signals S <b> 1 and S <b> 2 shown in FIG. 1 to the gate electrode 101.
[0032]
FIG. 5 is a diagram illustrating the configuration of the switch circuit of the liquid crystal display device according to this embodiment. The switch circuit 30 includes a plurality of switch TFTs 1 and 2. In this example, one output line of the driver IC 20 is branched into two, and switches TFT 1 and 2 are provided for each to serve as an input line to the pixel. This input line corresponds to the order of R (red), G (green), and B (blue) of pixels corresponding to one line (R1, G1, B1, R2, G2, B2,...).
[0033]
Here, the switch TFTs having the same reference numerals are opened and closed at the same timing. In this example, each switch TFT1 and each switch TFT2 are opened and closed in order.
[0034]
In particular, in the liquid crystal display device of this embodiment, when the polarity of the signal is inverted between the ODD side output line and the EVEN side output line of the driver IC 20, every two input lines due to the branching of each output line of the driver IC 20. 3 is characterized in that the switching order of the switch TFTs 1 and 2 is reversed.
[0035]
That is, when each of the switch TFT1 and each of the switch TFT2 operates at the same timing (when the same reference sign operates at the same timing), the switch TFTs 1, 2, 2 are arranged along the arrangement of the input lines corresponding to one line. The order of arrangement is changed as 2, 1,.
[0036]
FIG. 6 is a diagram for explaining a signal state in such an array of switch TFTs. In this figure, the horizontal direction indicates pixels corresponding to one line, and the vertical direction indicates the operation order of the switch TFTs 1 and 2. H indicates a writing state at a high voltage (High level), and L indicates a writing state at a low voltage (Low level).
[0037]
That is, when the ODD side of the driver IC 20 is at the high level (H), the EVEN side is at the low level (L), the switch TFT1 is in the closed state, and the switch TFT2 is in the open state, the first pixel in the pixel array is at the high level (H). 2 pixels are opened, the 4th pixel is the Low level (L), the 5th pixel is the High level (H), the 2nd pixel is opened, the 8th pixel is the Low level (L), and the 9th pixel is called the High level (H). A signal is applied by rule.
[0038]
When the switch TFT2 is closed and the switch TFT1 is open, the second pixel has a low level (L), the third pixel has a high level (H), the second pixel is opened, and the sixth pixel has a low level (L). A signal is applied in accordance with a rule of a high level (H) at the seventh pixel, a low level (L) at the tenth pixel when two pixels are opened, and a high level (H) at the eleventh pixel.
[0039]
Next, when the switch TFT1 is closed and the switch TFT2 is open, the ODD side of the driver IC 20 is at a low level (L) and the EVEN side is at a high level (H), which is opposite to the previous operation state. Are applied to the same pixel. Similarly, when the switch TFT2 is next closed and the switch TFT1 is open, a signal having a polarity opposite to that of the previous state is applied to the same pixel.
[0040]
By repeating this, when the switch TFTs 1 and 2 are closed and a signal is applied to each pixel in one line, the polarity of each signal can be inverted in any adjacent pixel in that one line. It becomes.
[0041]
For example, the potential of the counter electrode is set with a DC voltage of 6 V, and the AC voltage (dot inversion driving) is realized by changing the signal voltage with a high level (H) and low level (L) in one field cycle. it can. This AC driving can reduce the polarization action of the liquid crystal molecules and can prevent the liquid crystal molecules from being charged and the insulating film existing on the electrode surface from being charged.
[0042]
In the above embodiment, an example in which one output line of the driver IC 20 is branched into two input lines and switching is performed by the two switches TFT 1 and 2 has been described. However, the present invention provides an even number of output lines 1 of the driver IC 20. The signal polarity of the adjacent pixel can be inverted by the same idea as long as the signal is switched by branching to the input line.
[0043]
FIG. 7 is a diagram illustrating an example in which one output line of the driver IC 20 is branched into four input lines and signal switching is performed by the switch TFTs 1, 2, 3, and 4. In this case, the switch circuit 30 is configured to include a plurality of sets of switch TFTs 1, 2, 3, and 4 provided on the four branched input lines. This input line corresponds to the order of R (red), G (green), and B (blue) of pixels corresponding to one line (R1, G1, B1, R2, G2, B2,...).
[0044]
Also in this example, the switch TFTs having the same reference numerals are opened / closed at the same timing as before. That is, each switch TFT1, each switch TFT2, each switch TFT3, and each switch TFT4 is opened and closed in order.
[0045]
Further, in this configuration in which one output line of the driver IC 20 is branched into four input lines and the switches TFT1, 2, 3, and 4 are provided, the polarity of the signal in one line of adjacent pixels is inverted. The switch TFTs are rearranged in the order of 1, 2, 3, 4, 4, 3, 2, 1, 1, 2, 3, 4,... Along the input line corresponding to one line.
[0046]
FIG. 8 is a diagram for explaining the state of signals in such an array of switch TFTs. In this figure, the horizontal direction indicates pixels corresponding to one line, and the vertical direction indicates the operation order of the switch TFTs 1, 2, 3, and 4.
[0047]
That is, when the ODD side of the driver IC 20 is at a high level (H), the EVEN side is at a low level (L), the switch TFT1 is in a closed state, and the switch TFTs 2, 3, and 4 are in an open state, the first pixel in the pixel array is high. Level (H), 6 pixels are opened, a signal is applied in accordance with a rule of Low level (L) at the 8th pixel, High level (H) at the 9th pixel, and 6 pixels open at the 16th pixel. The
[0048]
When the switch TFT2 is closed and the switches TFT1, 3, 4 are open, the Low level (L) is opened for the second pixel, the High level (H) is opened for the fourth pixel, the second pixel is opened, and the ten pixels are opened for the second pixel. A signal is applied in accordance with a rule of a low level (L) in the eyes and a high level (H) in the 15th pixel after opening four pixels.
[0049]
When the switch TFT3 is closed and the switches TFT1, 2, and 4 are open, the third pixel is at the high level (H), the second pixel is opened, the sixth pixel is the low level (L), the fourth pixel is opened, and the eleven pixels are opened. A signal is applied in accordance with a rule of High level (H) in the eyes and Low level (L) in the 14th pixel after opening two pixels.
[0050]
Further, when the switch TFT 4 is in the closed state and the switch TFTs 1, 2, and 3 are in the open state, the fourth pixel is at the low level (L), the fifth pixel is at the high level (H), and the six pixels are opened to the low level at the twelfth pixel. (L) A signal is applied to the thirteenth pixel in accordance with a rule of High level (H).
[0051]
After each of the switch TFTs 1, 2, 3, 4 is closed once in this way, the ODD side of the driver IC 20 is at the low level (L), the EVEN side is at the high level (H), and the switch TFT1, It becomes a closed state once in the order of 2, 3, and 4.
[0052]
In this cycle, a signal having a polarity opposite to that in the case where each of the switch TFTs 1, 2, 3, 4 is in the same operation state as before is applied to the corresponding same pixel.
[0053]
FIG. 9 is a timing chart of various signals when one output line of the driver IC is divided into four input lines. That is, ODD and EVEN in the driver IC alternately output a high level and a low level so that the polarities are different from each other.
[0054]
Further, the signals S1 to S4 for opening and closing the four switch TFTs are sequentially set to the High level from S1 to S4 in synchronization with the ODD and EVEN signals of the driver IC, and the switches TFT1 to 4 are sequentially closed.
[0055]
In synchronization with the switches TFT1 to TFT4 being sequentially closed, the input line R1 is at a high level, the input line G1 is at a low level, the input line B1 is at a high level, and the input line R2 is at a low level. Similarly, in synchronization with the closed state of the switches TFT1 to 4, the input line G3 is at the low level, the input line R3 is at the high level, the input line B2 is at the low level, and the input line G2 is at the high level.
[0056]
By repeating such an operation, when each of the switches TFT1, 2, 3, 4 is closed and a signal is applied to each pixel in one line, the signal of each signal is applied to any adjacent pixel in that one line. The polarity can be reversed.
[0057]
【The invention's effect】
As described above, the liquid crystal display device of the present invention has the following effects. That is, when High level and Low level signals are alternately output from the driver circuit, High level and Low level signals can be alternately applied to adjacent pixels in one line, and the signals are switched in a time division manner. Even in this case, complete dot inversion driving can be performed. As a result, the flicker of the liquid crystal display device can be reduced, and the difference in contrast for each line can be eliminated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating a liquid crystal display device according to an embodiment.
FIG. 2 is a schematic configuration diagram illustrating a display unit.
FIG. 3 is a schematic configuration diagram illustrating a driver IC.
FIG. 4 is a cross-sectional view illustrating a structure example of a TFT.
FIG. 5 is a diagram illustrating a configuration of a switch circuit of the liquid crystal display device of the present embodiment.
FIG. 6 is a diagram for explaining a signal state by a switch TFT;
FIG. 7 is a diagram illustrating a configuration of a switch circuit having four branches.
FIG. 8 is a diagram for explaining a signal state by a four-branch switch TFT;
FIG. 9 is a timing chart of various signals in the case of four branches.
FIG. 10 is a diagram illustrating dot inversion driving in a conventional liquid crystal display device.
FIG. 11 is a diagram illustrating a state of a signal for dot inversion driving in a conventional liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Display part, 20 ... Driver IC, 21 ... Horizontal shift register circuit, 22 ... Sampling switch, 23 ... Level shifter circuit, 24 ... Memory latch circuit, 25 ... Digital-analog conversion circuit, 30 ... Switch circuit, 40 ... Vertical shift register circuit

Claims (2)

A switch circuit that switches a signal output from the output line of the driver circuit to one of a plurality of input lines provided correspondingly in the same row of pixels;
By switching the signal in the switch circuit, signals having different polarities on the two input lines adjacent to each other in the unit of the plurality of input lines corresponding to the output line of the driver circuit have the same switching timing. Given
An electronic device characterized by that. A display unit in which a plurality of pixels are arranged ;
A switch circuit that switches a signal output from an output line of the driver circuit to any one of a plurality of input lines provided correspondingly in the same row of pixels of the display unit,
By switching the signal in the switch circuit, signals having different polarities on the two input lines adjacent to each other in the unit of the plurality of input lines corresponding to the output line of the driver circuit have the same switching timing. Given
A display device characterized by that.

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