JP2005227475A - Electrooptical apparatus, method for driving electrooptical apparatus, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrooptical apparatus constituted in such a manner that the luminance unevenness in a vertical direction is suppressed by a simple configuration, a driving method for the electrooptical apparatus, and electronic equipment. <P>SOLUTION: In a liquid crystal display device 20, a potential is applied to a counter electrode 30 facing the pixel electrode of each pixel across a liquid crystal in such a manner that a potential gradient is made in a scanning direction. The potential gradient is created by utilizing silver points 51 to 54 existing on an element substrate 22 in order to apply a voltage to the counter electrode 30 on the side of the counter substrate 50 side from the element substrate 22 side. The voltage applied to the silver points 51 and 52 existing on the upper side in the scanning direction among the silver points 51 to 54 and the voltage applied to the silver points 53 and 54 existing on the lower side are varied, and thereby the potential gradient varied in the potential differences to be applied between the top and bottom in the scanning direction is made on the counter electrode 30. In case of the occurrence of, for example, the luminance unevenness in the vertical direction that lower pixels in an active matrix section are brighter, such a potential difference that makes the upper pixels brighter than the lower pixels within the active matrix section 21 is applied between the top and bottom of the counter electrode 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electro-optical device such as a liquid crystal display device, a driving method of the electro-optical device, and an electronic apparatus.

  As a conventional electro-optical device, an active matrix liquid crystal display device in which a plurality of pixels arranged in a matrix are provided with thin film transistors, and the potential of the counter electrode facing each pixel electrode and the liquid crystal is set for each field. What is reversed is known (for example, refer to FIG. 4 of Patent Document 1). In this liquid crystal display device, the potential of the counter electrode is inverted for each field, and a positive video signal and a negative video signal are alternately written to each pixel for each field, and the liquid crystal is AC driven. As a result, the amplitude of a data signal such as a video signal can be reduced, and advantages such as low power consumption can be obtained.

Also, in the driving method in which a positive video signal and a negative video signal are alternately written to each pixel for each field, luminance unevenness occurs in the vertical direction of the screen, and a technique for suppressing this luminance unevenness is known. (For example, refer to Patent Document 2). In this prior art, the signal readout line of the frame memory is made random, and the scanning order of the scanning electrodes (scanning lines) by the scanning electrode driving circuit is set in correspondence with the readout line. In other words, the uneven brightness in the vertical direction of the screen is suppressed by making the scanning order random.
Japanese Patent Laid-Open No. 8-334741 JP-A-6-266310

  By the way, in the prior art of the above-mentioned patent document 2, the scanning line driving circuit is driven and controlled so that a plurality of scanning lines are selected at random, and data is stored in pixels for one row connected to the randomly selected scanning lines. It is necessary to drive and control the signal line driver circuit so as to write a signal. Therefore, there is a problem that the drive control of the scanning line driving circuit and the signal line driving circuit becomes complicated.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an electro-optical device, a driving method for an electro-optical device, and an electronic device that can suppress luminance unevenness in a vertical direction with a simple configuration. To provide equipment.

  An electro-optical device according to the present invention includes an electro-optical element provided between two substrates, and a plurality of pixels arranged in a matrix corresponding to intersections of a plurality of scanning lines and a plurality of signal lines, In the electro-optical device configured to alternately write a positive data signal and a negative data signal to each pixel every frame period via a switching element provided in the pixel, the pixel electrode of each pixel The gist is that a potential is applied to a counter electrode opposed via the electro-optic element so that a potential gradient is generated in a scanning direction in which the plurality of scanning lines are sequentially selected.

According to this, a potential gradient can be generated in the scanning direction in which a plurality of scanning lines are sequentially selected on the counter electrode facing the pixel electrode of each pixel through the electro-optic element. For example, when “brightness unevenness in the vertical direction” is generated such that the lower pixel in the vertical direction (scanning direction) of the display region including a plurality of pixels becomes brighter, the upper pixel in the display region is A potential difference that is brighter than the lower pixel is applied between the upper side and the lower side of the counter electrode. Accordingly, it is possible to suppress “brightness unevenness in the vertical direction” such that the lower pixels in the vertical direction of the display area become brighter. Therefore, uneven brightness in the vertical direction can be suppressed with a simple configuration in which a potential is applied so that a potential gradient is generated in the scanning direction.

  In this electro-optical device, the potential gradient is generated when a display area including the plurality of pixels is displayed in a halftone of a half-brightness transmittance of an all-black transmittance and an all-white transmittance. The potential difference is set so as to generate a potential gradient in the scanning direction. Therefore, in any case of display with any brightness, brightness unevenness in the vertical direction can be suppressed, and high-quality display can be obtained.

Here, the “potential difference” refers to a difference between the potential of the counter electrode on one end side in the scanning direction and the potential of the counter electrode on the other end side in the scanning direction.
In the electro-optical device, the two substrates are an element substrate on which a display region including the plurality of pixels is formed and an opposite substrate on which the counter electrode is formed, and the potential gradient is generated from the element substrate side. Of the four silver spots provided at the four corners on the element substrate to apply a voltage to the counter electrode, a pair of silver spots on one end side in the scanning direction and the other end side in the scanning direction The gist is that the voltage applied to each pair of silver dots is made different.

  According to this, the potential gradient is created in the counter electrode by utilizing the four silver points originally provided on the element substrate in order to apply a voltage from the element substrate side to the counter electrode on the counter substrate side. ing. Therefore, it is not necessary to add new parts to the element substrate or the counter substrate of the liquid crystal display device, and the luminance unevenness in the vertical direction is suppressed without increasing the cost in the conventional liquid crystal display device. High quality display can be realized.

  In this electro-optical device, the counter substrate side is provided with a metal wire that electrically connects a potential application point provided by a pair of silver points on the one end side, and a pair of silver points on the other end side. The gist of the present invention is to provide a metal wire that electrically connects the application point of the potential to be generated.

  According to this, a uniform potential can be applied to one end side in the scanning direction of the counter electrode via the pair of silver dots and the metal wire, and a pair of silver is applied to the other end side in the scanning direction of the counter electrode. A uniform potential different from the one end side in the scanning direction can be applied via the point and the metal line. Therefore, a more uniform potential gradient can be created in the counter electrode, and luminance unevenness in the vertical direction can be reduced.

  In this electro-optical device, a frame memory that holds display data for one frame and an average value of gradations of the whole display data for one frame held in the frame memory are calculated, and a potential difference of the potential gradient is calculated. The gist of the present invention is to provide a potential difference adjusting means that changes every frame period in accordance with the average value.

  According to this, the potential difference adjusting means calculates the average value of the gradation of the entire display data for one frame held in the frame memory, and the potential difference of the potential gradient is calculated for each frame period according to the average value. I try to change it. For this reason, in the case of a display with little luminance unevenness in the vertical direction, no extra current flows in the display area. Thereby, power consumption can be reduced. Such an effect is particularly effective for a liquid crystal display device that is a direct-view type and that alternately writes a positive data signal and a negative data signal to each pixel every frame period.

An electro-optical device driving method according to the present invention includes an electro-optical element provided between two substrates, and a plurality of pixels arranged in a matrix corresponding to intersections of a plurality of scanning lines and a plurality of signal lines. In the method of driving an electro-optical device configured to alternately write a positive polarity data signal and a negative polarity data signal to each pixel every frame period via a switching element provided in each pixel, The gist is to apply a potential to a counter electrode facing the pixel electrode of each pixel through the electro-optic element so that a potential gradient is generated in a scanning direction in which the plurality of scanning lines are sequentially selected.

  According to this, a potential gradient can be generated in the scanning direction in which a plurality of scanning lines are sequentially selected on the counter electrode facing the pixel electrode of each pixel through the electro-optic element. For example, when “brightness unevenness in the vertical direction” occurs such that the lower pixel in the vertical direction of the display area becomes brighter, the upper pixel in the display area is brighter than the lower pixel. A significant potential difference is provided between the top and bottom of the counter electrode. Thereby, it is possible to suppress “brightness unevenness in the vertical direction” such that the pixels below the display area become brighter. Accordingly, uneven brightness in the vertical direction can be suppressed with a simple configuration in which a potential is applied so that a potential gradient is generated in the scanning direction.

The gist of an electronic apparatus according to the present invention is that it includes the electro-optical device according to the invention.
According to this, it is possible to realize a high-quality display in which luminance unevenness in the vertical direction is suppressed.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.
[First embodiment]
A liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 schematically shows an electrical configuration of the liquid crystal display device 20 according to the first embodiment, and FIG. 2 shows a part of an electrical equivalent circuit of an active matrix portion 21 as a display region. FIG. 7 is a conceptual diagram for explaining a potential applied to the counter electrode 30 (see FIG. 2) in the liquid crystal display device 20.

The liquid crystal display device 20 is an active matrix liquid crystal display device (peripheral circuit built-in type TFT liquid crystal display device) of a p-Si type TFT drive system incorporating a peripheral drive circuit.
As shown in FIG. 1, the liquid crystal display device 20 includes a plurality of scanning lines Y1 to Ym, a plurality of signal lines X1 to Xn formed so as to intersect the scanning lines Y1 to Ym, and scanning lines Y1 to Ym. An active matrix portion 21 is provided as a display region including a plurality of pixels 25 arranged in a matrix corresponding to each intersection of the signal lines X1 to Xn. Each pixel 25 is formed with a polysilicon thin film transistor (p-Si TFT) 26 as a switching element (see FIG. 2). A data signal is written to each pixel 25 via a polysilicon thin film transistor 26 (hereinafter referred to as “TFT 26”).

Further, the liquid crystal display device 20 includes an element substrate 22 and a counter substrate 50 (see FIG. 7) as a pair of substrates, and a TN (Twisted Nematic) type liquid crystal as an electro-optical element is sealed between the two substrates. Has been.

  On the element substrate 22, as shown in FIG. 1, an active matrix unit 21, a scanning line drive circuit 33 for driving the plurality of scanning lines Y1 to Ym, and a plurality of signal lines X1 to Xn are driven. The signal line drive circuit 34 is formed.

  The liquid crystal display device 20 includes a control circuit 35 for controlling the scanning line driving circuit 33 and the signal line driving circuit 34. Display data, a synchronization signal, a clock signal, and the like are input to the control circuit 35 from an external circuit. In the present embodiment, the display data is digital gradation data such as a video signal. The synchronization signal is a vertical synchronization signal and a horizontal synchronization signal. The clock signals are the clock signal CY and the inverted clock signal / CY shown in FIG.

Various signals for performing frame inversion driving and the like are supplied from the control circuit 35 to the scanning line driving circuit 33 and the signal line driving circuit 34 through signal lines 37a and 37b, respectively.
The liquid crystal display device 20 transmits a positive data signal (voltage signal) and a negative data signal to each pixel 25 via each TFT 26 of a plurality of pixels 25 arranged in a matrix for each frame (one frame period). Frame inversion driving is performed alternately. Further, as shown in FIG. 3, the liquid crystal display device 20 performs common swing driving in which the counter electrode potential is inverted for each frame between the low voltage Vss and the high voltage Vdd.

  The “counter electrode potential” shown in FIGS. 3 and 4 is a potential applied to the counter electrode facing the pixel electrode 29 of each pixel 25 formed on the element substrate 22 via the liquid crystal 24. Further, “one frame” refers to a period during which one screen is displayed by sequentially selecting the scanning lines Y1 to Ym and writing data signals to the capacitors (liquid crystal capacitors 31 and storage capacitors 32) of all the pixels 25. .

  As shown in FIG. 2, the gate of the TFT 26 of each pixel 25 is one of the scanning lines Y1 to Ym, its source is one of the signal lines X1 to Xn, and its drain is the corresponding one of the pixels 25. Each is connected to the pixel electrode 29. The pixel electrode 29 of each pixel 25 is opposed to one counter electrode 30 provided on the counter substrate 50 side via the liquid crystal 24. The potential of the counter electrode 30 is inverted between the low voltage Vss and the high voltage Vdd for each frame to perform the frame inversion driving and common swing driving. Each pixel 25 is connected in parallel with the liquid crystal capacitor 31 composed of the liquid crystal 24 between the rectangular pixel electrode 29 and the counter electrode 30, and charge leakage from the liquid crystal capacitor 31. And a storage capacitor 32 which is a capacitor element for reducing the voltage drop due to. The negative terminal of each storage capacitor 32 is connected to the capacitor wiring 41.

  In the pixel circuit of each pixel 25, when the TFT 26 is turned on (conductive state), a data signal (voltage signal) obtained by D / A converting digital gradation data such as a video signal is connected to the liquid crystal capacitor 31 via the TFT 26. When data is written in the storage capacitor 32 and the TFT 26 is turned off (non-conducting state), electric charges are held in these capacitors.

  As shown in FIG. 3, the scanning line driving circuit 33 is supplied with a vertical synchronization signal (not shown), a clock signal CY and an inverted clock signal / CY supplied at the beginning of a vertical scanning period for sequentially selecting the scanning lines Y1 to Ym. The scanning lines G1 to Ym are sequentially selected by sequentially generating and outputting the scanning signals G1 to Gm. In each horizontal scanning period (see FIG. 4) in which the scanning lines Y1 to Ym are sequentially selected and the scanning signals G1 to Gm are supplied to the scanning lines, the scanning line Y1 to Ym is selected. All the connected TFTs 26 are configured to be turned on. In the present embodiment, vertical scanning for sequentially selecting the scanning lines Y1 to Ym is sequentially performed from the scanning line Y1 side by the transfer start signal DY shown in FIG.

  As shown in FIG. 3, after the counter electrode potential is inverted from Vdd to Vss at time t1, when the transfer start signal DY is supplied to the scanning line driving circuit 33 at time t2, the scanning line driving circuit 33 starts from time t3. By generating and outputting the scanning signals G1 to Gm in order until the time point t5, the scanning lines Y1 to Ym are selected in order. After the selection period by the scanning signal Gm ends at time t5, the counter electrode potential is inverted from Vss to Vdd at time t6. Such an operation is repeated.

The signal line driving circuit 34 includes a sampling circuit for writing a data signal (voltage signal) to each pixel 25 via a plurality of signal lines X1 to Xn, a shift register for controlling the operation timing of the sampling circuit, and a video signal line (illustrated). A latch circuit that holds one row of digital grayscale data of each pixel input to (Omitted), an analog / digital conversion circuit, and the like.

  FIG. 5 is a conceptual diagram showing luminance unevenness in the vertical direction generated in the active matrix portion 21 by performing the frame inversion driving and common swing driving in the liquid crystal display device 20 shown in FIG. FIG. 5 shows that when all the pixels are displayed with the same luminance, the pixels in the vertical direction of the active matrix portion 21, that is, the lower pixels in the scanning direction in which the plurality of scanning lines Y1 to Ym are sequentially selected from the top are brighter. It shows that “brightness unevenness in the vertical direction” occurs.

Such “uneven luminance in the vertical direction” occurs for the following reason.
In the active matrix unit 21, a plurality of scanning lines Y1 to Ym are selected in order from the top, and positive data signals are sequentially written in the pixels 25 to form one frame (positive field). In the next frame (negative field), the plurality of scanning lines Y1 to Ym are similarly selected, and negative-polarity data signals are sequentially written to the respective pixels.

  Since such an operation is repeated for each frame, among the scanning lines Y1 to Ym, the pixel 25 connected to the scanning line whose order is selected later in one frame is connected to the scanning line whose order is earlier. Compared with the pixel 25, the time from the writing of the data signal to the transition to the next frame becomes shorter. That is, each pixel 25 connected to a scanning line that is selected later has a longer time to be affected by the potential applied to the signal line in the next frame. Thereby, the potential (pixel electrode potential) of the pixel electrode 29 of each pixel 25 corresponding to the data signal written and held in each pixel connected to each of the scanning lines Y1 to Ym leaks through the off-resistance of the TFT 26. . The amount of leakage (potential that decreases at each pixel electrode) increases as the pixel 25 is located below the active matrix portion 21. As a result, the luminance in the vertical direction of the active matrix portion 21 becomes brighter because the lower pixel 25 has a lower voltage value at each pixel electrode 29 as shown in FIG. Mode).

  As shown in FIG. 6, the uneven luminance in the vertical direction generated due to the above reason is a halftone (half luminance of all black transmittance and all white transmittance) due to the characteristics of the liquid crystal. This is the middle tone of the transmittance of the light. In other words, on the characteristic of the liquid crystal indicating the relationship between the voltage applied to the liquid crystal and the change in transmittance, the largest change in transmittance (change in luminance) with respect to the same voltage change is the 1/2 intermediate luminance. This is the case when it is displayed.

  In order to suppress the occurrence of such uneven brightness in the vertical direction, the liquid crystal display device 20 according to the present embodiment includes a plurality of counter electrodes 30 that are opposed to the pixel electrodes 29 of the respective pixels 25 via the liquid crystal 24. The scanning lines Y1 to Ym are selected in order to provide a potential difference that creates a potential gradient in the scanning direction.

  In the present embodiment, the potential gradient is generated by using a silver point originally provided on the element substrate 22 in order to apply a voltage from the element substrate 22 side to the counter electrode 30 on the counter substrate 50 side. .

In the conventional liquid crystal display device, as shown in FIG. 7, in order to apply a voltage from the element substrate 22 side to the counter electrode 30 on the counter substrate 50 side, four corners of the outer region of the active matrix portion 21 on the element substrate 22 are provided. In addition, four silver dots 51 to 54 are provided. The counter electrode 30 is a single rectangular electrode formed on the entire surface of the counter substrate 50 on the element substrate 22 side, and is a transparent electrode such as an indium tin oxide (hereinafter referred to as “ITO”) film. It consists of a membrane.

  In the conventional liquid crystal display device, the same voltage is applied to the counter electrode 30 from the element substrate 22 side through four silver dots 51 to 54, respectively. This counter electrode potential corresponds to the counter electrode potential (normal) indicated by the potential waveform 82 in FIG.

  On the other hand, in this embodiment, among the four silver dots 51 to 54, a pair of silver dots 51 and 52 on the upper side (one end side) in the scanning direction shown in FIG. By making the voltages applied to the pair of silver points 53 and 54 on the end side different from each other, the counter electrode 30 has a potential gradient with a potential difference between the upper and lower sides in the scanning direction.

  For example, as shown in FIG. 5, when “brightness unevenness in the vertical direction” is generated in the active matrix unit 21 so that the pixels in the vertical direction (scanning direction) of the active matrix unit 21 become brighter. 7, a potential difference is applied between the upper and lower counter electrodes 30 such that the upper pixel in the active matrix portion 21 is brighter than the lower pixel. In this case, the potential applied to the pair of silver spots 51 and 52 on the upper side is set lower than the potential applied to the pair of silver spots 53 and 54 on the lower side. Since the potential gradient having such a potential difference can be formed in the counter electrode 30, the luminance unevenness in the vertical direction in which the luminance of each pixel changes from black to white in the scanning direction as shown in FIG. 5 is suppressed or eliminated. Thus, the state where the luminance unevenness in the vertical direction is suppressed or eliminated is indicated by the active matrix portion 21 in FIG.

  The potential gradient created in the counter electrode 30 in this way is uneven luminance in the vertical direction when display is performed in a halftone of approximately 1/2 luminance where the uneven luminance in the vertical direction of the active matrix portion 21 is the largest. Is set to have a potential difference that disappears.

FIG. 8 shows potential waveforms and the like applied to the top and bottom of the counter electrode 30 when performing the frame inversion driving in the liquid crystal display device 20 according to the present embodiment.
In FIG. 8, reference numeral 80 denotes a video potential which is a reference potential of a data signal written to the pixel electrode 29 of each pixel 25, and a potential waveform 81 denotes a waveform indicating the potential of the data signal of 1/2 intermediate luminance (see FIG. 6). It is. The potential waveform 82 is a waveform indicating a normal counter electrode potential (normal) potential for performing frame inversion driving and common swing driving in the conventional liquid crystal display device as described above. This counter electrode potential (usually) is the same potential in the scanning direction of the counter electrode 30. The potential waveform 83 is a waveform showing the potential of the counter electrode potential (upper) applied to the upper side of the counter electrode 30 via the pair of silver spots 51 and 52 on the upper side in the liquid crystal display device 20 according to the present embodiment. is there. The potential waveform 84 is a waveform indicating the potential of the counter electrode potential (lower) applied to the lower side of the counter electrode 30 through the pair of silver dots 53 and 54 on the lower side in the liquid crystal display device 20. is there.

  As is clear from FIG. 8, the potential of the counter electrode potential (upper) indicated by the potential waveform 83 is lower than the counter electrode potential (normal) indicated by the potential waveform 82. That is, the counter electrode potential indicated by the potential waveform 83 in each of one frame (positive field) for writing a positive video signal to each pixel 25 and one frame (negative field) for writing a negative video signal to each pixel 25. The (upper) potential is an absolute value smaller than the counter electrode potential (normal) indicated by the potential waveform 82.

  On the other hand, the counter electrode potential (lower) potential indicated by the potential waveform 84 is higher than the counter electrode potential (normal) indicated by the potential waveform 82. That is, in each of the positive field and the negative field, the counter electrode potential (lower) potential indicated by the potential waveform 84 is larger in absolute value than the counter electrode potential (normal) indicated by the potential waveform 82.

According to 1st Embodiment comprised as mentioned above, there exist the following effects.
A potential gradient with a potential difference between the upper side and the lower side in the scanning direction in which the scanning electrodes Y1 to Ym are sequentially selected is formed on the counter electrode 30 facing the pixel electrode 29 of each pixel 25 via the liquid crystal 24. ing. The potential gradient is created using the four silver points 51 to 54 originally provided on the element substrate 22 in order to apply a voltage from the element substrate 22 side to the counter electrode 30 on the counter substrate 50 side. ing.

  Specifically, in the case where “brightness unevenness in the vertical direction” occurs such that the lower pixel in the vertical direction of the active matrix portion 21 becomes brighter (see FIG. 5), as shown in FIG. A potential difference is applied between the upper and lower electrodes of the counter electrode 30 such that the upper pixel in 21 is brighter than the lower pixel. Therefore, the potential applied to the pair of silver spots 51 and 52 on the upper side is set lower than the potential applied to the pair of silver spots 53 and 54 on the lower side. Since a potential gradient having such a potential difference can be formed in the counter electrode 30, uneven luminance in the vertical direction in which the luminance of each pixel changes from black to white in the scanning direction as shown in FIG. 5 can be suppressed (FIG. 7). reference). Therefore, the luminance unevenness in the vertical direction can be suppressed with a simple configuration in which the potential applied to the pair of silver points 51 and 52 is different from the potential applied to the pair of silver points 53 and 54.

  The potential gradient created in the counter electrode 30 is a halftone between the transmittance of all black where the luminance unevenness in the vertical direction of the active matrix portion 21 is the largest and the transmittance of about half the luminance of the transmittance of all white. When the display is performed, the potential difference is set so that the luminance unevenness in the vertical direction disappears. Therefore, in any case of display with any brightness, brightness unevenness in the vertical direction can be suppressed, and high-quality display can be obtained.

  The counter electrode 30 is obtained by utilizing the four silver points 51 to 54 originally provided on the element substrate 22 in order to apply a voltage to the counter electrode 30 on the counter substrate 50 side from the element substrate 22 side. I try to make it. Therefore, it is not necessary to add new components to the element substrate 22 and the counter substrate 50 of the liquid crystal display device 20, and the luminance unevenness in the vertical direction is suppressed without increasing the cost in the conventional liquid crystal display device. High quality display can be realized.

[Second Embodiment]
A liquid crystal display device 20A according to the second embodiment will be described with reference to FIG.
In the liquid crystal display device 20A, in the first embodiment, the metal wire 56 that electrically connects the application point of the potential given by the pair of silver points 51 and 52 on the upper side to the counter substrate 50 side, and the lower side And a metal wire 57 for electrically connecting a potential application point provided by a pair of silver points 53, 54. The metal wires 56 and 57 are each preferably a metal with low resistance such as aluminum or silver paste. Other configurations are the same as those in the first embodiment.

  In the liquid crystal display device 20A, a uniform potential is applied to the upper side of the counter electrode 30 in the scanning direction via the pair of silver dots 51 and 52 and the metal line 56, and the lower side of the counter electrode 30 in the scanning direction. Applies a potential different from the upper side in the scanning direction through a pair of silver points 53 and 54 and a metal line 57. Thereby, the potential gradient can be generated in the counter electrode 30.

The metal wire 56 and the metal wire 57 may have the same resistance value (same material) or may have different resistance values.
According to 2nd Embodiment comprised as mentioned above, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  A uniform potential can be applied to the upper side of the counter electrode 30 in the scanning direction via the pair of silver points 51 and 52 and the metal line 56, and a pair of silver on the lower side of the counter electrode 30 in the scanning direction. A uniform potential different from the upper side in the scanning direction can be applied via the points 53 and 54 and the metal line 57. Therefore, a more uniform potential gradient can be created in the counter electrode 30 than in the first embodiment, and luminance unevenness in the vertical direction can be reduced.

  In the first embodiment, a simple structure in which the metal lines 56 and 57 are simply added to the counter substrate 50 side can realize a higher quality display in which luminance unevenness in the vertical direction is further suppressed.

[Third embodiment]
A liquid crystal display device 20B according to a third embodiment will be described with reference to FIG.
In the liquid crystal display device 20B, in the second embodiment shown in FIG. 9, the average value of the gradation of the entire display data for one frame is calculated, and the potential difference of the potential gradient is calculated for one frame period according to the average value. The feature is that it is changed every time.

  For this purpose, the liquid crystal display device 20B calculates a frame memory 61 that holds display data for one frame, an average value of the gradation of the entire display data for one frame held in the frame memory 61, and the potential. A control circuit 62 is provided that changes the potential difference of the gradient every frame period in accordance with the average value. This control circuit 62 corresponds to “potential difference adjusting means”.

  In the liquid crystal display device 20 </ b> B shown in FIG. 10, the signal line drive circuit 34 is provided below the active matrix portion 21. However, the signal line drive circuit 34 is the same as the signal line drive circuit 34 provided above the active matrix portion 21 in the liquid crystal display device 20A shown in FIG.

The control circuit 62 includes a counter electrode potential adjustment circuit unit 63, a drive waveform generation circuit unit 64, and a video potential generation circuit unit 65.
The drive waveform generation circuit unit 64 transmits drive waveforms such as a vertical synchronization signal, a horizontal synchronization signal, a clock signal CY, and an inverted clock signal / CY necessary for the scanning line drive circuit 33 to perform the vertical scanning via the signal line 71. Are output to the scanning line driving circuit 33.

  The video potential generation circuit unit 65 displays display data corresponding to the luminance of each video signal to be written to pixels for one row connected to the scanning lines Y1 to Ym sequentially selected by the vertical scanning among the scanning lines Y1 to Ym. (Digital data) is output to the signal line drive circuit 34 via the signal line 72.

  The counter electrode potential adjustment circuit unit 63 calculates the average value of the gradation of the entire display data for one frame held in the frame memory 61, and the counter electrode potential (upper electrode) having a potential difference corresponding to the calculated average value. ) (Potential waveform 83 in FIG. 8) and counter electrode potential (lower) (potential waveform 84 in FIG. 8). The counter electrode potential adjustment circuit unit 63 applies the counter electrode potential (upper) to the silver spots 51 and 52 via the signal lines 73 and 74 and applies the counter electrode potential (lower) via the signal lines 75 and 76. Applied to the silver dots 53 and 54.

  For example, in the case where the luminance unevenness in the vertical direction shown in FIG. 6 is displayed at half the maximum half luminance (when the luminance is 1/4 or 3/4), the counter electrode potential (upper ) And the counter electrode potential (lower) is halved compared to the case of displaying at 1/2 intermediate luminance. Further, in the case of displaying in white or black, since there is almost no luminance unevenness in the vertical direction, the potential difference between the counter electrode potential (upper) and the counter electrode potential (lower) is set to approximately “0”.

  In this way, the counter electrode potential adjustment circuit unit 63 calculates the average value of the gradation of the entire display data for one frame held in the frame memory 61, and sets the potential difference of the potential gradient in one frame period according to the average value. It is designed to change every time.

According to 3rd Embodiment comprised as mentioned above, in addition to the effect which the said 1st Embodiment and 2nd Embodiment show | play, there exist the following effects.
In the first embodiment and the second embodiment, as shown in FIG. 7, a constant potential difference is set above and below the counter electrode 30 so that the upper pixel is brighter than the lower pixel in the active matrix portion 21. Therefore, current always flows through the active matrix portion 21. Such excess current is not desired to flow through the active matrix portion 21 when there is little luminance unevenness in the vertical direction.

  In the liquid crystal display device 20B according to the third embodiment, the counter electrode potential adjustment circuit unit 63 calculates the average value of the gradation of the entire display data for one frame held in the frame memory 61, and the potential difference of the potential gradient is calculated. Is changed for each frame period in accordance with the average value. For this reason, in the case of a display with less luminance unevenness in the vertical direction, an excess current does not flow through the active matrix portion 21. Thereby, power consumption can be reduced. Such an effect is particularly effective for a liquid crystal display device that is a direct-view type and performs the frame inversion driving.

[Electronics]
Next, an electronic apparatus using the liquid crystal display device 20, 20A, or 20B described in the above embodiments will be described. The liquid crystal display device 20, 20A or 20B can be applied to a projection display device 110 such as a liquid crystal projector as shown in FIG. The projection display device 110 is a three-plate projection color display device that includes transmissive liquid crystal light valves 112, 113, and 114 for different colors of R (red), G (green), and B (blue). . These transmissive liquid crystal light valves 112, 113, and 114 are respectively configured by the liquid crystal display devices 20, 20A, and 20B described in the above embodiments.

  As shown in FIG. 11, the projection display device 110 includes a projector main body 111, an illumination device 120, a color separation / synthesis system 130, and a projection optical system 140 as a projection device having a plurality of projection lenses. . The projector main body 111 includes a lighting device 120, a color separation / synthesis system 130, a power supply device 150, and the like.

  The illumination device 120 includes a light source 115, two fly-eye lenses 116 and 117, and a polarization conversion device 118. The color separation / combination system 130 includes two dichroic mirrors 121 and 122, three reflection mirrors 123 to 125, three relay lenses 126 to 128, three liquid crystal light valves 112 to 114, and a cross dichroic prism 129. Have.

  The light source 115 includes a lamp 120a such as a high-pressure mercury lamp or a metal halide lamp, and a reflector 120b that reflects light L from the lamp 120a (hereinafter referred to as “light source light L”). Further, in order to make the illuminance distribution of the light source light L uniform in the liquid crystal light valves 112 to 114, two fly-eye lenses 116 and 117 are provided. Each fly-eye lens 116, 117 is composed of a plurality of (for example, 6 × 8) lenses 116a, 117a arranged two-dimensionally. Thus, the liquid crystal light valves 112 to 114 are illuminated with uniform illumination by the fly-eye lenses 116 and 117 with the light source light L.

  The polarization conversion device 118 includes a polarization beam splitter array (PBS array) provided on the fly-eye lens 117 side, and a half-wave plate that converts the polarization direction of polarized light reflected by the PBS array, and is a light source light The polarization direction of light is aligned in one direction without impairing the light intensity of L.

  The dichroic mirrors 121 and 122 are formed, for example, by laminating a dielectric multilayer film having a predetermined wavelength selectivity on a glass substrate. The dichroic mirror 121 transmits the red light LR of the light source light L and reflects the green light LG and the blue light LB. The dichroic mirror 122 reflects the green light LG among the green light LG and the blue light LB reflected by the dichroic mirror 121 and transmits the blue light LB.

  As a result, in the color separation / combination system 130, the red light LR out of the light source light L incident from the illumination device 120 passes through the dichroic mirror 121, is reflected by the reflection mirror 123, and is then the liquid crystal light valve 112 for red light. Is incident on. The green light LG is reflected by the dichroic mirror 121, then reflected by the dichroic mirror 122, and enters the liquid crystal light valve 112 for green light. The blue light LB is reflected by the dichroic mirror 121, then passes through the dichroic mirror 122, passes through a relay system including three relay lenses 126 to 128 and two reflection mirrors 124 and 125, and is a liquid crystal light valve for blue light. 114.

The liquid crystal light valves 112 to 114 as light modulation devices are respectively driven by drive circuits (not shown) based on the display data such as video signals.
The cross dichroic prism 129 has a structure in which a right angle prism is bonded, and a dielectric multilayer film that reflects the red light LR and transmits the green light LG is formed on one of the two mirror surfaces orthogonal to the cross shape. On the other side, dielectric multilayer films that reflect the blue light LB and transmit the green light LG are formed. The three color lights of the red light LR, the green light LG, and the blue light LB are combined by the cross dichroic prism 129 to form light representing a color image, and this light is enlarged and projected onto the screen 141 by the projection optical system 140. It has come to be.

According to the projection display device 110, it is possible to realize a high-quality display in which uneven brightness in the vertical direction of each liquid crystal light valve 112, 113, 114 is suppressed.
[Modification]
In addition, this invention can also be changed and embodied as follows.

In each of the above embodiments, the vertical scanning is started from the first scanning line Y1 side as an example, but the present invention is also applied to the case where the vertical scanning is started from the mth scanning line Ym side. Is done.
In each of the above-described embodiments, the case where “brightness unevenness in the vertical direction” such that the lower pixel in the vertical direction of the active matrix portion 21 becomes brighter has been described as an example. However, the present invention can also be applied to the case where “brightness unevenness in the vertical direction” occurs such that the upper pixel in the vertical direction of the active matrix portion 21 becomes brighter. In this case, the counter electrode indicated by the potential waveform 84 has a slope opposite to the potential gradient applied to the counter electrode 30 in each of the above embodiments, that is, the potential of the counter electrode potential (upper) shown by the potential waveform 83 of FIG. The potential should be higher than the potential (below).

  As an example, the liquid crystal display device 20 of the first embodiment is configured as a p-Si TFT driving type active matrix liquid crystal display device incorporating a peripheral driving circuit. However, the present invention can also be applied to an active matrix liquid crystal display device other than a peripheral circuit built-in type.

  The liquid crystal display device 20 of the first embodiment is a liquid crystal display device with a built-in peripheral circuit in which an active matrix unit 21, a scanning line driving circuit 33, and a signal line driving circuit 34 are formed on an element substrate 22. However, the present invention can also be applied to a liquid crystal display device provided on the element substrate 22 for a part of the control circuit 35.

  In the first embodiment, the signal line driving circuit 34 includes, as an example, a sampling circuit, a shift register, a latch circuit that holds one row of digital gradation data of each pixel, an analog / digital conversion circuit, and the like. However, the present invention is not limited to such a configuration.

In each of the above embodiments, the liquid crystal is inverted and the counter electrode potential is inverted every frame. However, the present invention can also be applied to the case where the counter electrode is driven by another method.
In each of the above embodiments, the TN (Twisted Nematic) type liquid crystal 24 is used, but the present invention is not limited to this. Any liquid crystal may be used as long as it can perform frame inversion by alternately writing a positive data signal and a negative data signal to each pixel through a switching element at predetermined intervals, for example, every frame. For example, a wide variety of well-known liquid crystals including STN (Super Twisted Nematic) type, BTN (Bi-stable Twisted Nematic) type, polymer dispersion type, guest host type, etc. having a twisted orientation of 180 ° or more are used as the liquid crystal. Can do.

  The liquid crystal display device 20, 20A or 20B according to each of the above embodiments is not limited to the projection display device 110 such as a liquid crystal projector as shown in FIG. 11, but various electronic devices such as a personal computer, a mobile phone, and a digital camera. Applicable to.

  In each of the above embodiments, the electro-optical device has been described as a liquid crystal display device, but the present invention is not limited to this, and an electro-optical device using an electro-optical element that is AC driven like a liquid crystal and the electro-optical device The present invention can also be applied to an electronic device provided with a device.

FIG. 3 is a block diagram showing an electrical configuration of the drive circuit according to the first embodiment. The circuit diagram which shows a part of electrical equivalent circuit of an active matrix part. 3 is a timing chart showing the operation of a scanning line driving circuit. 4 is a timing chart showing the operation of the signal line driver circuit. The conceptual diagram which shows the brightness irregularity in the up-down direction in 1st Embodiment. The graph which shows the characteristic of a liquid crystal. The conceptual diagram for demonstrating the electric potential given to a counter electrode in 1st Embodiment. 6 is a timing chart showing potential waveforms when performing frame inversion driving and common swing driving. The conceptual diagram similar to FIG. 7 which shows 2nd Embodiment. The block diagram which shows the electric constitution of 3rd Embodiment. FIG. 11 is a plan view illustrating an electronic device using a liquid crystal display device.

Explanation of symbols

  X1 to Xn ... signal lines, Y1 to Ym ... scanning lines, Vdd, Vss ... voltage, 20, 20A, 20B ... liquid crystal display device as an electro-optical device, 21 ... active matrix part as a display region, 22 ... element substrate, 25 ... Pixel, 29 ... Pixel electrode, 30 ... Counter electrode, 50 ... Counter substrate, 51-54 ... Silver point, 56, 57 ... Metal wire, 61 ... Frame memory, 62 ... Control circuit as potential difference adjusting means, 110 ... A projection display device as an electronic device.

Claims (7)

An electro-optical element provided between two substrates, and a plurality of pixels arranged in a matrix corresponding to the intersections of the plurality of scanning lines and the plurality of signal lines, and through a switching element provided in each pixel In the electro-optical device configured to alternately write a positive polarity data signal and a negative polarity data signal to each pixel every frame period,
An electro-optical device, wherein a potential is applied to a counter electrode facing the pixel electrode of each pixel through the electro-optical element so that a potential gradient is generated in a scanning direction in which the plurality of scanning lines are sequentially selected. . The electro-optical device according to claim 1.
The potential gradient is a potential in the scanning direction when a display area including the plurality of pixels is displayed with a halftone of approximately 1/2 luminance transmittance of all black transmittance and all white transmittance. An electro-optical device, which is set so as to give a potential difference capable of forming a gradient. The electro-optical device according to claim 1 or 2,
The two substrates are an element substrate on which a display region including the plurality of pixels is formed and a counter substrate on which the counter electrode is formed;
The potential gradient is a pair of silver dots on one end side in the scanning direction among four silver spots provided at four corners on the element substrate for applying a voltage from the element substrate side to the counter electrode. And an electro-optical device produced by making different voltages to be applied to a pair of silver dots on the other end side in the scanning direction. The electro-optical device according to claim 3.
A metal wire that electrically connects a potential application point provided by a pair of silver points on the one end side to the counter substrate side, and a potential application point provided by a pair of silver points on the other end side. An electro-optical device comprising a metal wire for electrical connection. The electro-optical device according to any one of claims 1 to 4,
A frame memory for holding display data for one frame;
A potential difference adjusting unit that calculates an average value of gradations of the entire display data for one frame held in the frame memory and changes a potential difference of the potential gradient for each frame period according to the average value; An electro-optical device. An electro-optical element provided between two substrates, and a plurality of pixels arranged in a matrix corresponding to the intersections of the plurality of scanning lines and the plurality of signal lines, and through a switching element provided in each pixel In the driving method of the electro-optical device configured to alternately write the positive data signal and the negative data signal to each pixel every frame period,
An electro-optical device characterized in that a potential is applied to a counter electrode facing the pixel electrode of each pixel through the electro-optical element so that a potential gradient is generated in a scanning direction in which the plurality of scanning lines are sequentially selected. Driving method. An electronic apparatus comprising the electro-optical device according to claim 1.

Images