JP4492491B2 - Display device - Google Patents

Description

  The present invention relates to an active matrix display device in which display elements (electro-optical elements) of pixels are arranged in a matrix in a display area.

  A display device, for example, a liquid crystal display device using a liquid crystal cell as a pixel display element (electro-optical element), is characterized by being thin and low power consumption, for example, a personal digital assistant (PDA), portable It is applied to a wide range of electronic devices such as telephones, digital cameras, video cameras, and display devices for personal computers.

FIG. 1 is a block diagram illustrating a configuration example of a liquid crystal display device (see, for example, Patent Documents 1 and 2).
As shown in FIG. 1, the liquid crystal display device 1 includes an effective pixel unit 2, a vertical drive circuit (VDRV) 3, and a horizontal drive circuit (HDRV) 4.

In the effective pixel portion 2, a plurality of pixel circuits 21 are arranged in a matrix.
Each pixel circuit 21 includes a thin film transistor (TFT) 21 as a switching element, a liquid crystal cell LC 21 having a pixel electrode connected to the drain electrode (or source electrode) of the TFT 21, and one electrode connected to the drain electrode of the TFT 21. The storage capacitor Cs21 is connected.
For each of these pixel circuits 21, scanning lines (gate lines) 5-1 to 5-m are wired along the pixel arrangement direction for each row, and signal lines 6-1 to 6-n are provided for each column. Wiring is performed along the pixel array direction.
The gate electrodes of the TFTs 21 of the pixel circuits 21 are connected to the same scanning lines 5-1 to 5-m in units of rows. The source electrode (or drain electrode) of each pixel circuit 21 is connected to the same signal line 6-1 to 6-n in each column unit.

Further, in a general liquid crystal display device, the storage capacitor line Cs is independently wired, and the storage capacitor line Cs21 is formed between the storage capacitor line Cs and the first electrode of the liquid crystal cell LC21. Cs receives a common voltage VCOM and an in-phase pulse, and is used as a storage capacitor. In a general liquid crystal display device, the storage capacitors Cs21 of all the pixel circuits 21 in the effective pixel unit 2 are commonly connected to one storage capacitor line Cs.
The second electrode of the liquid crystal cell LC21 of each pixel circuit 21 is commonly connected to the supply line 7 of the common voltage Vcom whose polarity is inverted every horizontal scanning period (1H), for example.

  The scanning lines 5-1 to 5-m are driven by the vertical driving circuit 3, and the signal lines 6-1 to 6-n are driven by the horizontal driving circuit 4.

The vertical driving circuit 3 performs a process of sequentially selecting each pixel circuit 21 connected to the scanning lines 5-1 to 5-m in units of rows by scanning in the vertical direction (row direction) every field period.
That is, when the scanning pulse GP1 is applied to the scanning line 5-1 from the vertical drive circuit 3, the pixels in each column of the first row are selected, and the scanning pulse GP2 is applied to the scanning line 5-2. In this case, the pixels in each column of the second row are selected. Similarly, scanning pulses GP3,..., GPm are sequentially applied to the scanning lines 5-3,.

  2A to 2E are timing charts in the so-called 1HVcom inversion driving method of the general liquid crystal display device shown in FIG.

As another driving method, a capacitive coupling driving method is known in which the voltage applied to the liquid crystal is modulated using coupling from the storage capacitor wiring Cs (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-119746 JP 2000-298459 A Japanese Patent Laid-Open No. 2-157815

  Compared with the 1HVcom inversion driving method, the capacitive coupling driving method described above can improve the response speed of the liquid crystal due to so-called overdrive, reduce audio noise generated in the Vcom frequency band, and compensate for contrast in the ultra-high definition panel. There are features such as being able to do it.

However, this capacitive coupling driving service described in Patent Document 3 is applied to a liquid crystal display device using a liquid crystal material (for example, normally white) having a characteristic of a liquid crystal dielectric constant ε with respect to an applied voltage as shown in FIG. If this is used, there is a disadvantage that the luminance change is large when the liquid crystal gap fluctuation / gate oxide film thickness fluctuation at the time of manufacturing or the relative permittivity fluctuation of the liquid crystal at the time of temperature environment change occurs when the effective pixel potential is considered. There is.
Further, when trying to optimize the black luminance, there is a disadvantage that the white luminance becomes black (sinks).

(Equation 1)
ΔVpix1 = Vsig + (Ccs / Ccs + Clc) * ΔVcs−Vcom (1)

In Expression (1), ΔVpix represents the effective pixel potential, Vsig represents the video signal voltage, Ccs represents the storage capacitor, Clc represents the liquid crystal capacitance, ΔVcs represents the potential of the signal CS, and Vcom represents the common voltage.
As described above, when the black luminance is optimized, the white luminance is sunk in the term (Ccs / Ccs + Clc) * ΔVcs in the above equation (1), and the nonlinearity of the liquid crystal dielectric constant is effective. This is because the pixel potential is affected.

  An object of the present invention is to provide a liquid crystal device capable of optimizing (correcting) luminance.

The display device according to the first aspect of the present invention corresponds to a pixel portion in which a plurality of pixel circuits for writing video pixel data propagated through a signal line through a switching element are arranged in a matrix, and a row arrangement of the pixel circuits. A plurality of scan lines for controlling conduction of the switching elements, a plurality of capacitance lines arranged to correspond to the row arrangement of the pixel circuits, the plurality of scan lines, and the plurality of scan lines. A drive circuit that selectively drives the capacitor wiring, a generation circuit that generates a common voltage signal, and a correction unit that corrects a signal that drives the capacitor wiring of the drive circuit, and is arranged in the pixel portion. and each pixel circuit includes a display element having a first pixel electrode and second pixel electrode, a storage capacitor having a first electrode and a second electrode, the first stroke of the display elementary DOO An electrode, a first electrode of the storage capacitor, and one terminal of the switching element are connected, a second electrode of the storage capacitor is connected to the capacitor wiring arranged in a corresponding row, and a second pixel electrode of the display element The common voltage signal is applied to the driving circuit , and the driving circuit selects a first level or a second level lower than the first level as a signal for driving the capacitive wiring to the corresponding capacitive wiring. By applying and driving the drive circuit, the amplitude value of the common voltage signal and the value of the potential difference between the first level and the second level are the same as the increase in effective pixel potential due to the common voltage signal and the potential difference. is selected variation of the increment of time of white display with respect to the increment of time the black display to compensate by the common voltage signal, the correction unit may mimic the pixel circuit A monitor pixel circuit for monitoring the pixel potential is formed above the pixel portion Te, the level of the signal for driving the capacitance line which is selected by the driving circuit, further corrected based on the monitoring result of the monitor pixel circuits correction circuit And having.

で規定され、上記補正回路は、上記式中のCcs／（Ccs＋Cｌｃ）で表される液晶容量Cｌｃと保持容量Ccsの容量配分係数のプロセス変動を軽減するΔVｃｓを与えるように、上記容量配線の電位Vcsを補正する。 Preferably, the correction circuit sets the level of a signal for driving the capacitor wiring so as to reduce the pixel potential obtained by the monitor pixel circuit from being deviated from the ideal pixel potential by the influence of the capacitor wiring driving. Correct .
Preferably, the pixel potential monitored by the monitor pixel circuit is expressed by the following equation:

And the correction circuit provides the potential of the capacitor wiring so as to provide ΔVcs that reduces the process variation of the capacitance distribution coefficient of the liquid crystal capacitor Clc and the holding capacitor Ccs represented by Ccs / (Ccs + Clc) in the above equation. Correct Vcs.

Preferably, the correction unit may monitor the pixel potential of the monitor pixel circuit outputs above SL correction circuit when on and has a load separation switch disconnecting from the monitor pixel circuits loads the correction circuit side turned off at the time of the monitor .

Preferably, the input section of the monitor pixel circuit and the correction circuit that is disposed close to each other in substrate on which the pixel portion is formed.

Preferably, the monitor pixel circuit is formed on the same substrate as the pixel portion, on the same substrate as the monitor pixel circuit, a monitor pixel potential of the monitor pixel circuit outputs to the substrate outside of the correction circuit when turned on, the monitor Sometimes it has a load separation switch that is turned off to separate the load on the correction circuit side from the monitor pixel circuit .
Preferably, the monitor pixel circuit includes a plurality of the monitor pixel circuits imitating the pixel circuit , and the first electrodes of the plurality of monitor pixel circuits corresponding to the first pixel electrode are commonly connected via a common connection line. are connected, the common connection line is connected to a connection line between the correction circuit.

  The drive circuit drives the scanning line in the selected row to write pixel data in a desired pixel circuit, and then drives the capacitor wiring in the same row.

Preferably, the drive circuit applies to the capacitor wiring corresponding by selecting one of the first level and the lower than the first level a second level signal for driving the capacitance line.

  Preferably, the display element of the pixel circuit is a liquid crystal cell.

A display device according to a second aspect of the present invention corresponds to a pixel portion in which a plurality of pixel circuits for writing video pixel data propagated through a signal line through a switching element are arranged in a matrix, and a row arrangement of the pixel circuits. A plurality of scan lines for controlling conduction of the switching elements, a plurality of capacitance lines arranged to correspond to the row arrangement of the pixel circuits, the plurality of scan lines, and the plurality of scan lines. A drive circuit for selectively driving the capacitor wiring, a generation circuit for generating a common voltage signal, and a reference driver for generating video pixel data to be propagated to the signal line, and arranged in the pixel portion Each pixel circuit includes a display element having a first pixel electrode and a second pixel electrode, and a storage capacitor having a first electrode and a second electrode. One terminal of the first electrode and the switching element of the first pixel electrode and the storage capacitor ment is connected, it is connected to the capacitor wiring and the second electrode are arranged in a corresponding row of the storage capacitor, the display The common voltage signal is applied to the second pixel electrode of the element, and the driving circuit selects either the first level or the second level lower than the first level as the signal for driving the capacitive wiring. The amplitude value of the common voltage signal and the value of the potential difference between the first level and the second level are applied to the corresponding capacitance wiring and the effective pixel based on the common voltage signal and the potential difference is driven. the increase in potential, the selected variation of the increment of time of white display with respect to the increment of time the black display to compensate by the common voltage signal, the correction unit Has a monitor pixel circuit is formed to imitate the serial pixel circuits for monitoring the pixel potential of the pixel portion, a correction circuit for correcting a signal voltage in the upper cut file Reference driver, a.

  According to the present invention, there is an advantage that the luminance can be optimized (corrected).

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

  FIG. 4 is a diagram illustrating a configuration example of an active matrix display device according to an embodiment of the present invention using, for example, a liquid crystal cell as a pixel display element (electro-optical element).

  As shown in FIG. 4, the display device 100 includes an effective pixel unit 101, a vertical drive circuit (V / CSDRV) 102, a horizontal drive circuit (HDRV) 103, a common voltage generation circuit (VcomGen) 104, a gate line (scanning). Lines) 105-1 to 105-m, storage capacitor lines (hereinafter referred to as storage lines) 106-1 to 106-m, signal lines 107-1 to 107-n, for example, detection areas comprising dummy pixel portions (monitor portions) 108 and a correction circuit 109 as main components.

As shown in FIG. 5, the effective pixel unit 101 includes a plurality of pixel circuits PXLC arranged in an m × n matrix. Specifically, for example, 320 × RGB × 320 pixel circuits are arranged so that normal display is possible as a whole.
In FIG. 5, a 4 × 4 matrix arrangement is shown for simplification of the drawing.

As shown in FIG. 5, each pixel circuit PXLC includes a TFT (thin film transistor) 201 as a switching element, a liquid crystal cell LC201 having a first pixel electrode connected to the drain electrode (or source electrode) of the TFT 201, The storage capacitor Cs201 includes a first electrode connected to the drain electrode of the TFT201.
Note that a node ND201 is formed by a connection point between the drain of the TFT 201, the first pixel electrode of the liquid crystal cell LC201, and the first electrode of the storage capacitor CS201.

  For each of these pixel circuits PXLC, gate lines (scanning lines) 105-1 to 105-m and storage lines 106-1 to 106-m are wired along the pixel arrangement direction for each row, and the signal line 107 -1 to 107-n are wired along the pixel arrangement direction for each column.

The gate electrode of the TFT 201 of each pixel circuit PXLC is connected to the same gate line 105-1 to 105-m for each row.
The second electrode of the storage capacitor Cs of each pixel circuit PXLC is connected to the same storage line 106-1 to 106-m for each row.
Further, the source electrode (or drain electrode) of each pixel circuit PXLC is connected to the same signal line 107-1 to 107-n for each column.
The second pixel electrode of the liquid crystal cell LC201 of each pixel circuit PXLC is connected in common to a supply line (not shown) of a small amplitude common voltage VCOM whose polarity is inverted during one horizontal scanning period (1H).

  Each of the gate lines 105-1 to 105-m is driven by a gate driver of the vertical drive circuit 102, and each of the storage lines 106-1 to 106-m is driven by a capacity driver (CS driver) of the vertical drive circuit 102. The signal lines 107-1 to 107-n are driven by the horizontal drive circuit 103.

In the effective pixel portion 101, a dummy pixel portion 108 is formed as a monitor circuit including one row or one pixel. The dummy pixel unit 108 has a pixel configuration similar to that of a normal effective pixel. For example, the dummy pixel unit 108 is formed in the effective pixel unit 101 by one extra line, or the m-th row positioned at the lowest position of the effective pixel unit 101 is assigned. Are possible.
The dummy pixel unit 108 detects the potential of the connection node ND201 of the pixel circuit PXLC and outputs it to the detection circuit 109.
The dummy pixel portion 108 is provided for the following reason.
The liquid crystal applied voltage fluctuates due to fluctuations in the dielectric constant of the liquid crystal due to changes in driving temperature, fluctuations in the thickness of the insulating film forming the storage capacitor CS201 due to variations during mass production, and fluctuations in the liquid crystal cell gap. In order to electrically detect this variation, a dummy pixel portion 108 is provided.
As will be described later, the storage signal CS output from the CS driver is corrected so that the pixel potential detected from the dummy pixel unit 108 becomes an arbitrary potential.

The vertical drive circuit 102 basically scans in the vertical direction (row direction) for each field period and sequentially selects each pixel circuit PXLC connected to the gate lines 105-1 to 105-m in units of one row. Perform the process.
That is, the vertical driving circuit 102 applies the gate pulse GP1 to the gate line 105-1 to select the pixels in each column of the first row, and applies the gate pulse GP2 to the gate line 105-2. A pixel in each column in the second row is selected. Similarly, gate pulses GP3,..., GPm are sequentially applied to the gate lines 105-3,.

  Further, the vertical drive circuit 102 has a first level (CSH, for example, 3V-4V) or a second level (CSL) for each storage line 106-1 to 106-m independently wired corresponding to each gate line. , For example, 0V), the capacitance signals (hereinafter referred to as storage signals) CS1 to CSm selected in order are given.

  FIGS. 6A to 6L are timing charts showing examples of driving the gate lines and the storage lines of the vertical drive circuit of this embodiment.

The vertical drive circuit 102 drives the gate lines 105-1 to 105-m and the storage lines 106-1 to 106-m in order from the first row, for example, but drives one gate line with a gate pulse. After (after signal writing), the levels of the storage signals CS1 to CSm applied to the storage lines 106-1 to 106-m at the timing of the rise of the gate pulse of the next gate line are changed to the first level CSH as follows. And the second level CSL are alternately selected and applied.
For example, when the vertical drive circuit 102 selects the first level CSH and applies the storage signal CS1 to the storage line 106-1 in the first row, the second level in the storage line 106-2 in the second row. The CSL is selected and the storage signal CS2 is applied, the first level CSH is selected and the storage signal CS3 is applied to the third row storage line 106-3, and the fourth row storage line 106-4 is applied. Selects the second level CSL, applies the storage signal CS4, and similarly selects the first level CSH and the second level CSL alternately to transfer the storage signals CS5 to CSm to the storage lines 106-5 to 106-m. Apply to.
Further, when the storage signal CS1 is applied by selecting the second level CS1 to the first-line storage line 106-1, the first-level CSH is selected and stored in the second-line storage line 106-2. The signal CS2 is applied, the second level CSL is selected for the third row storage line 106-3 and the storage signal CS3 is applied, and the first level CSH is applied to the fourth row storage line 106-4. The storage signal CS4 is selected and applied, the second level CSL and the first level CSH are alternately selected in the same manner, and the storage signals CS5 to CSm are applied to the storage lines 106-5 to 106-m.

In the present embodiment, after the fall of the gate pulse GP (after writing from the signal line), the storage lines 106-1 to 106-m are driven and coupled via the storage capacitor CS201, thereby causing the pixel potential (node). The voltage applied to the liquid crystal is modulated by changing the potential of the ND 201.
As will be described later, the storage signal CS by the CS driver 1020 is corrected by the detection circuit 109 so that the pixel potential detected from the dummy pixel unit 108 becomes an arbitrary potential.

FIG. 5 schematically illustrates an example of the level selection output unit of the CS driver 1020 of the vertical drive circuit 102.
The CS driver 1020 includes a variable power supply unit 1021, a first level supply line 1022 connected to the positive electrode side of the power supply unit 1021, a second level supply line 1023 connected to the negative electrode side of the power supply unit 1021, and a first level. It includes switches SW1 to SWm that selectively connect the storage lines 106-1 to 106-m in which the supply line 1022 or the second level supply line 1023 is wired for each row of the pixel array.

In FIG. 5, ΔVcs indicates a level difference (potential difference) between the first level CSH and the second level CSL.
As will be described in detail later, ΔVcs and the amplitude ΔVcom of the AC common voltage Vcom having a small amplitude are selected to values that can optimize both the black luminance and the white luminance.
For example, as will be described later, the effective pixel potential ΔVpix applied to the liquid crystal during white display. The values of ΔVcs and ΔVcom are determined so that W becomes a value of 0.5V or less.

The vertical drive circuit 102 includes a vertical shift register group, and includes a plurality of shift registers VSR provided corresponding to gate buffers to which gate lines arranged for each row are connected corresponding to the pixel arrangement. Each shift register VSR is supplied with a vertical start pulse VST for instructing the start of vertical scanning generated by a clock generator (not shown) and a vertical clock VCK (or vertical clocks VCK and VCKX having opposite phases to each other) as a reference for vertical scanning. The
For example, the shift register shifts the vertical start pulse VST in synchronization with the vertical clock VCK and supplies it to the corresponding gate buffer.
Further, the vertical start pulse VST is propagated from the upper side or the lower side of the effective pixel portion 101 and is sequentially shifted into each shift register.
Therefore, basically, the gate lines are sequentially driven through the gate buffers by the vertical clock supplied from the shift register VSR.

  The horizontal drive circuit 103 receives an input video signal Vsig based on a horizontal start pulse HST for instructing the start of horizontal scanning and a horizontal clock HCK (or vertical clocks HCK and HCKX having opposite phases to each other) as a reference for horizontal scanning. Sampling is sequentially performed every 1H (H is a horizontal scanning period), and writing processing is performed on each pixel circuit PXLC selected in units of rows by the vertical driving circuit 102 via the signal lines 107-1 to 107-n.

The common voltage generation circuit 104 generates a small-amplitude common voltage VCOM whose polarity is inverted every horizontal scanning period (1H), and supplies the liquid crystal cells LC201 of all the pixel circuits PXLC of the effective pixel unit 101 through a supply line (not shown). Commonly supplied to the two pixel electrodes.
The value of the amplitude ΔVcom of the amplitude of the common voltage Vcom is selected such that the black luminance and the white luminance can be optimized together with the difference ΔVcs between the first level of the storage signal CS and the CSH and the second level CSL.
For example, as will be described later, the effective pixel potential ΔVpix applied to the liquid crystal during white display. The values of ΔVcs and ΔVcom are determined so that W becomes a value of 0.5V or less.

  In FIG. 4, a configuration in which the common voltage generation circuit 104 is provided in the liquid crystal panel is shown as an example. However, the common voltage generation circuit 104 may be arranged outside the panel and supplied with the common voltage Vcom from the outside of the panel. .

FIG. 7 is a circuit diagram illustrating a configuration example of the common voltage generation circuit according to the present embodiment.
The example of FIG. 7 shows a case where a small amplitude common voltage Vcom is generated by an external part of the panel.

The common voltage generation circuit of FIG. 7 includes flicker adjustment resistance elements R1 and R2, a smoothing capacitor C1, a capacitor C2 for making an amplitude by a small amplitude ΔVcom, a wiring resistance Rcom of the Vcom supply line 110, and a parasitic capacitance of the Vcom supply line 108. Ccom is included.

Resistance elements R1 and R2 are connected in series between the supply line of the power supply voltage VCC and the ground line GND, and a voltage divided by the resistance elements R1 and R2 is generated at the connection node ND1 of the resistance elements. The resistance element R2 is a variable resistance, and the generated voltage can be adjusted.
A connection node ND1 is connected to the panel terminal T. The first electrode of the capacitor C1 is connected to the connection line between the connection node ND1 and the terminal T, and the second electrode is grounded.
The first electrode of the capacitor C2 is connected to the connection line between the connection node ND1 and the terminal T, and the second electrode is connected to the supply line of the signal FRP.

  In the common voltage generation circuit of FIG. 7, the small amplitude ΔVcom is determined according to the following equation.

(Equation 2)
ΔVcom = {C2 / (C1 + C2 + Ccom)} × FRP (2)

Small amplitudes can be used using capacitive coupling (digital coupling) or digitally generated.
The value of the small amplitude ΔVcom is preferably as small as possible, for example, about 10 mV to 1.0 V. The reason is that otherwise, effects such as improvement of response speed by overdrive and reduction of acoustic noise are reduced.

As described above, in the liquid crystal display device 100, when performing capacitive coupling drive using capacitive coupling, the value of the amplitude ΔVcom of the amplitude of the common voltage Vcom, the first level, the CSH, and the second level of the storage signal CS. The value of the difference ΔVcs from the CSL is selected to be a value that can optimize both the black luminance and the white luminance.
For example, the effective pixel potential ΔVpix applied to the liquid crystal during white display The values of ΔVcs and ΔVcom are determined so that W becomes a value lower than 0.5V.
Hereinafter, capacitive coupling driving according to the present embodiment will be described in more detail.

8A to 8E are timing charts showing driving waveforms of main liquid crystal cells of the present embodiment.
FIG. 8A shows the gate pulse GP. FIG. 8B shows the common voltage Vcom, and FIG. 8C shows the storage signal CS. N, FIG. 8D shows the video signal Vsig, and FIG. 8E shows the signal Pix applied to the liquid crystal cell. N is shown respectively.

In the capacitive coupling driving according to the present embodiment, the common voltage Vcom is not a constant DC voltage but is generated as a small amplitude AC signal whose polarity is inverted every horizontal scanning period (1H), and the liquid crystal of each pixel circuit PXLC. The voltage is applied to the second pixel electrode of the cell LC201.
The storage signal CS N is the first level (CSH, for example, 3V to 4V) or the second level (CSL, for example, 0V) for each storage line 106-1 to 106-m independently wired corresponding to each gate line. Choose to give one.
The effective pixel potential ΔVpix applied to the liquid crystal when driven in this way is given by the following equation.

As shown in FIG. 9, in Equation (3), Vsig is the video signal voltage, Ccs is the storage capacitor, Clc is the liquid crystal capacitance, Cg is the capacitance between the node ND201 and the gate line, and Csp is between the node ND201 and the signal line. ΔVcs represents the potential of the signal CS, and Vcom represents a common voltage.
In Equation (3), the second term {(Ccs / Ccs + Clc) * ΔVcs} of the approximate expression is a term that causes the white luminance side to become black (sink) due to the nonlinearity of the liquid crystal dielectric constant, and the third term of the approximate expression. {(Ccl / Ccs + Clc) * ΔVcom / 2} is a term for making the white luminance side white (floating) due to the nonlinearity of the liquid crystal dielectric constant.
That is, the second potential of the approximate expression is compensated for by the function of making the low potential side white (floating) according to the third term.
The optimum contrast can be obtained by selecting values that can optimize both the black luminance and the white luminance.

10A and 10B show the effective pixel potential ΔVpix applied to the liquid crystal during white display when the liquid crystal material (normally white liquid crystal) used in the liquid crystal display device is used. It is a figure for demonstrating the selection criteria of W. FIG. 10A is a diagram showing the characteristic of the relative dielectric constant ε with respect to the applied voltage, and FIG. 10B is an enlarged view of a region where the characteristic of FIG. 10A greatly changes.

As shown in the figure, in the liquid crystal characteristics used in the liquid crystal display device, when a voltage of about 0.5 V or more is applied, white luminance is reduced.
Therefore, in order to optimize the white luminance, the effective pixel potential ΔVpix applied to the liquid crystal at the time of white display. W needs to be 0.5V or less. Therefore, the effective pixel potential ΔVpix The values of ΔVcs and ΔVcom are determined so that W is 0.5V or less.

  As a result of actual evaluation, an optimum contrast was obtained when ΔVcs = 3.8V and ΔVcom = 0.5V.

FIG. 11 is a diagram illustrating a relationship between the video signal voltage and the effective pixel potential in the driving method, the related capacitive coupling driving method, and the normal 1HVcom driving method according to the embodiment of the present invention.
In FIG. 11, the horizontal axis indicates the video signal voltage Vsig, and the vertical axis indicates the effective pixel potential ΔVpix. In FIG. 11, the line indicated by A indicates the characteristics of the driving method according to the embodiment of the present invention, the characteristic indicated by C indicates the characteristics of the capacitive coupling driving method, and the line indicated by B indicates the normal 1HVcom driving method. The characteristics are shown.

  As can be seen from FIG. 11, according to the driving method according to the present embodiment, a sufficient characteristic improvement is obtained as compared with the related capacitive coupling driving method.

FIG. 12 is a diagram showing the relationship between the video signal voltage and the luminance in the driving method according to the embodiment of the present invention and the related capacitively coupled driving method.
In FIG. 12, the horizontal axis indicates the video signal voltage Vsig, and the vertical axis indicates the luminance. In FIG. 12, the line indicated by A indicates the characteristic of the driving method according to the embodiment of the present invention, and the characteristic indicated by the line B indicates the characteristic of the capacitive coupling driving method.

  As can be seen from FIG. 12, in the related capacitively coupled drive method, when the black luminance (2) was optimized, the white luminance (1) was sunk. On the other hand, according to the driving method according to the present embodiment, both black luminance (2) and white luminance (1) can be optimized by setting Vcom to a small amplitude.

In the following number (4), the effective pixel potential ΔVpix at the time of black display and black display when a specific numerical value is set to the number (3) of the driving method according to the present embodiment. Effective pixel potential ΔVpix when displaying B and white The value of W is shown.
Further, the effective pixel potential ΔVpix at the time of black display and black display when a specific numerical value is set to the above-described number (1) of the capacitive coupling driving method related to the number (5). B and effective pixel potential ΔVpix The value of W is shown.

As shown in the equations (4) and (5), when displaying black, the effective pixel potential ΔVpix is used for both the driving method according to the present embodiment and the driving method related to this embodiment. B is 3.3 V, and the black luminance is optimized.
At the time of white display, as shown in the equation (5), the effective pixel potential ΔVpix of the related driving method. W becomes 0.8V of 0.5V or more, and the white luminance is reduced as described in relation to FIG.
On the other hand, the effective pixel potential ΔVpix of the driving method according to the present embodiment. W becomes 0.4V, which is 0.5V or less, and the white luminance is optimized as described with reference to FIG.

  Next, the storage signal CS, which is one of the features of this embodiment, is optically applied to the correction circuit 109 so that the pixel potential detected from the detection area 108 including the dummy pixel portion (monitor portion) becomes an arbitrary potential. A specific configuration example for correcting the characteristics to be optimized will be described.

  In this embodiment, the applied voltage of the liquid crystal is changed due to a change in the dielectric constant of the liquid crystal due to a change in driving temperature, a change in the thickness of the insulating film forming the storage capacitor CS201 due to a variation during mass production, and a change in the liquid crystal cell gap. It will fluctuate. This variation is electrically detected, and the variation due to variations in display temperature and mass production is suppressed by suppressing variations in the liquid crystal applied voltage.

  The reason why the correction circuit system that optimizes the optical characteristics is employed will be described in relation to the model formula of the effective pixel voltage.

Equation (6) is a model expression of an effective pixel voltage of a general 1 HVcom inversion drive. It can be seen that the liquid crystal applied voltage (ΔVpix) does not change because the denominator numerator is the same even if Ccs (CS capacity) and Clc (liquid crystal capacity) change, as indicated by the underlined items in equation (6). . In other words, it means that the applied voltage of the liquid crystal does not change even if the film thickness variation of the gate insulating film, which is an element that changes Ccs, the liquid crystal layer gap variation, which is the element that changes Clc, and the dielectric constant change due to temperature change.

The number (7) shown below is the number of models when capacitive coupling driving is performed. It can be seen that the denominator numerator is different as in the term shown by the underline in the number (7), so that it is affected by the variation variation described above.
In order to solve this problem, in order to correct the change in the capacitance C of the underlined term in the above formula (7), in this embodiment, the value of ΔVcs is changed (corrected) to correct the underline. Keep the value of the term constant.

This disadvantage in the liquid crystal driving method using the coupling from the capacitive line means that the luminance change can be freely changed using the potential difference of the capacitive line.
In this embodiment, dummy pixels (sensor pixels) that monitor variation changes during mass production and temperature changes are arranged in the liquid crystal panel, and the change is detected to correct the potential of the capacitance line or the reference driver. The liquid crystal display device capable of optimizing (correcting) the luminance is realized.

  That is, according to the present embodiment, the dummy pixel (sensor pixel) that monitors the variation change at the time of mass production or temperature change is arranged in the liquid crystal panel, and the potential of the capacitance line or the reference is detected by detecting the change. There is an advantage that the driver can be corrected and the luminance can be optimized (corrected).

  Note that the reference driver not shown in FIG. 4 functions as a gradation voltage generation circuit that generates video pixel data to be propagated to the signal line.

  Basically, during actual driving, the potential of a pixel arranged on a glass substrate or a dummy pixel for monitoring is detected, and the CS potential ΔVcs (FIG. 5) is fed back to a reference driver (not shown). To optimize the optical properties. In addition, regarding manufacturing variations, the same effect can be obtained by manual adjustment during the inspection process.

  In the present embodiment, the CS potential ΔVcs is not a constant value, but is varied depending on, for example, a correction circuit system formed on a glass substrate or a circuit system formed on single crystal Si to improve optical characteristics. The same effect can be obtained even if adjustment is performed in the inspection process.

  FIG. 4 shows an example of the system configuration, but an example of a system configuration suitable for practical use will be described below with reference to FIGS.

FIG. 13 is a diagram illustrating an example in which the display device according to the present embodiment has the detection area 108 and the correction circuit 109 formed on the system-on-glass panel.
In this case, the correction circuit 109 detects a liquid crystal gap, a gate oxide film, a liquid crystal relative dielectric constant change, etc. generated in the detection area 108 disposed in the effective pixel portion 101 or an adjacent region so that the optical characteristics are optimized. Feedback is applied to the CS potential ΔVcs to correct ΔVcs.

FIG. 14 is a diagram illustrating an example in which the display device according to the present embodiment has the detection area 108 and the correction circuit 109 formed on the COG mounting panel.
Also in this case, the correction circuit 109 detects a liquid crystal gap, a gate oxide film, a liquid crystal relative dielectric constant change, and the like generated in the detection area 108 disposed in the effective pixel portion 101 or in an adjacent region so that the optical characteristics are optimized. Then, feedback is applied to the CS potential ΔVcs to correct ΔVcs.

FIG. 15 is a diagram showing an example in which the detection area 108 is formed on the panel and the correction circuit 109 is formed in the single crystal LSI in the display device according to the present embodiment.
Also in this case, the correction circuit 109 detects a liquid crystal gap, a gate oxide film, a liquid crystal relative dielectric constant change, and the like generated in the detection area 108 disposed in the effective pixel portion 101 or in an adjacent region so that the optical characteristics are optimized. Then, feedback is applied to the CS potential ΔVcs to correct ΔVcs.

FIG. 16 is a diagram showing a second example in which the display device according to the present embodiment has the detection area 108 and the correction circuit 109 formed on the system-on-glass panel.
In this case, the correction circuit 109 detects a liquid crystal gap, a gate oxide film, a change in the liquid crystal relative dielectric constant, and the like generated in the detection area 108 arranged in the effective pixel portion 101 or in an adjacent region, and the reference is set so that the optical characteristics are optimized. The driver 111 is configured to provide feedback.
In this case, the correction circuit 109 corrects the signal voltage of the reference driver 111 that generates video pixel data.

FIG. 17 is a diagram showing a second example in which the display device according to the present embodiment has the detection area 108 and the correction circuit 109 formed on the COG mounting panel.
Also in this case, the correction circuit 109 detects a liquid crystal gap, a gate oxide film, a liquid crystal relative dielectric constant change, and the like generated in the detection area 108 disposed in the effective pixel portion 101 or in an adjacent region so that the optical characteristics are optimized. The reference driver 111 is configured to provide feedback.

FIG. 18 is a diagram showing a second example in which the detection area 108 is formed on the panel and the correction circuit 109 is formed in the single crystal LSI in the display device according to the present embodiment.
Also in this case, the correction circuit system 109 detects the liquid crystal gap, the gate oxide film, the change in the liquid crystal relative dielectric constant, and the like generated in the detection area 108 arranged in the effective pixel portion 101 or in the adjacent region so that the optical characteristics are optimized. The reference driver 111 is fed back.

  Next, the configuration and functions of the monitor dummy pixel unit included in the detection area 108 and the correction circuit system will be described in more detail.

FIG. 19 is a diagram illustrating a first configuration example of the correction circuit system according to the present embodiment. In FIG. 19, only the correction circuit system and the effective pixel portion are shown for easy understanding.
FIG. 20 is a block diagram showing the basic configuration of the correction circuit of FIG.

In the correction circuit system 300 of FIG. 19, one dummy pixel 301 and the correction circuit 302 (indicated by reference numeral 109 in FIG. 4) are formed in the same device (panel). In this case, the correction circuit 302 can be incorporated in the device by using, for example, a low-temperature polysilicon process.
The dummy (monitor) pixel 301 has a circuit configuration similar to the effective pixel circuit PXLC of the effective pixel unit 101.
The correction circuit 302 compares the monitor pixel voltage Pin with the comparison reference voltage Pref, and a signal Vcsh that controls the CS potential ΔVcs to be changed for optimization according to the comparison result of the comparator 3021. And an output voltage control circuit 3022 that outputs to the power supply unit of the CS driver of the vertical drive circuit 102.
In the circuit system 300 of FIG. 19, the dummy pixel 301 and the comparator 3021 of the correction circuit 300 are arranged close to each other.

  In this case, for example, the holding capacitor Cs of the dummy pixel 301 is 0.5 pF, the liquid crystal capacitor Clc is 0.5 pF (that is, the storage capacity of the dummy pixel is 1.0 pF), and the connection node ND301 between the dummy pixel 301 and the comparator 3021 is used. When the parasitic capacitance C1 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, the video signal voltage Vsig is 3.3 V, and Vcom is 1.65 V, the effective pixel potential Vp is 3.21 V as shown in the following equation. Thus, a good monitor pixel potential can be obtained only by being affected by a voltage drop of about 90 mV.

  FIG. 21 is a diagram illustrating a second configuration example of the correction circuit system according to the present embodiment. In FIG. 21, only the correction circuit system and the effective pixel portion are shown for easy understanding.

The correction circuit system 300A of the second configuration example is different from the correction circuit system 300 of FIG. 19 in that the pixel potential is connected to the connection line (for example, the pixel potential of the dummy pixel) to the connection line between the dummy pixel 301 and the comparator 3021. Is provided with a switch 303 capable of selectively outputting.
The monitor pixel potential Vpin in this case is given by the following equation (Equation 10).

  As described above, the dummy capacitor 301 has a storage capacitor Cs of 0.5 pF, a liquid crystal capacitor Ccl of 0.5 pF (that is, a dummy pixel storage capacitor of 1.0 pF), and the connection between the dummy pixel 301 and the comparator 3021. Assuming that the parasitic capacitance C1 of the node ND301 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, and the video signal voltage Vsig is 3.3 V, the effective pixel potential Vp is 3.28 V as shown in the following equation (11). Thus, a good monitor pixel potential can be obtained only by being affected by a voltage drop of about 20 mV.

  Thus, by providing the switch 303 so as to minimize the influence of the parasitic capacitance C1, a better monitor pixel potential can be obtained.

  For example, a precharge circuit or a reset circuit is provided on the connection line between the dummy pixel 301 and the comparator 3021 to discharge the parasitic capacitance to some extent, and then the switch 303 is turned on to turn on the monitor pixel potential Vpin, the reference potential, and the comparator 3021. It is also possible to make a comparison with

  The above is a case where the correction circuit 302 is formed in the same device as the dummy pixel 301 and arranged close to the dummy pixel 301. Hereinafter, a case where the correction circuit 302 is mounted on an external substrate will be considered.

  FIG. 22 is a diagram illustrating a third configuration example of the correction circuit system according to the present embodiment. In FIG. 22, only the correction circuit system and the effective pixel portion are shown for easy understanding.

  The correction circuit system 300B of the third configuration example has a circuit configuration equivalent to that in which the correction circuit is moved to the external substrate 304 from the configuration of FIG.

In this case, for example, the storage capacitor Cs of the dummy pixel 301 is 0.5 pF, the liquid crystal capacitor Ccl is 0.5 pF (that is, the storage capacity of the dummy pixel is 1.0 pF), and the connection node ND301 between the dummy pixel 301 and the comparator 3021 is used. When the parasitic capacitance C1 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, the video signal voltage Vsig is 3.3 V, and Vcom is 1.65 V, the effective pixel potential Vp is expressed by the following equation (Equation 12). To 1.925V.
That is, while the potential of Vp is ideally 3.3 V, the configuration of FIG. 22 has voltage drops of about 1.925 V and 1300 mV, so that a good monitor pixel potential can be obtained. It ’s not good.

  FIG. 23 is a diagram illustrating a fourth configuration example of the correction circuit system according to the present embodiment. In FIG. 23, only the correction circuit system and the effective pixel portion are shown for easy understanding.

  The correction circuit system 300C of the fourth configuration example has a circuit configuration equivalent to that in which the correction circuit is transferred to the external substrate 304 from the configuration of FIG. That is, the switch 303 is provided.

  As described above, the dummy capacitor 301 has a storage capacitor Cs of 0.5 pF, a liquid crystal capacitor Ccl of 0.5 pF (that is, a dummy pixel storage capacitor of 1.0 pF), and the connection between the dummy pixel 301 and the comparator 3021. When the parasitic capacitance C1 of the node ND301 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, and the video signal voltage Vsig is 3.3 V, the effective pixel potential Vp is 3.05 V as shown in the following equation (Equation 13). Thus, a voltage effect of about 1300 mV can be suppressed to a voltage drop of about 250 mV, and a good monitor pixel potential that can withstand practical use can be obtained.

  In this way, by providing the switch 303 so as to minimize the influence of the parasitic capacitance C1, a good monitor pixel potential can be obtained.

  For example, a precharge circuit or a reset circuit is provided on the connection line between the dummy pixel 301 and the comparator 3021 to discharge the parasitic capacitance to some extent, and then the switch 303 is turned on to turn on the monitor pixel potential Vpin, the reference potential, and the comparator 3021. It is also possible to make a comparison with

  FIG. 24 is a diagram illustrating a fifth configuration example of the correction circuit system according to the present embodiment. In FIG. 24, only the correction circuit system and the effective pixel portion are shown for easy understanding.

The correction circuit system 300D of the fifth configuration example is different from the correction circuit system 300B of FIG. 22 in that, instead of providing one dummy pixel 301 as a monitor pixel, one horizontal line as shown in FIG. By connecting all the dummy pixel electrodes, the total storage capacity of the monitor pixel 305 is increased.
If there are 320 horizontal lines, 1 pF × 320 × 3 (RGB) = 960 pF.
This value is sufficiently larger than the parasitic capacitance 1 pF of the connection line.

  In this case, for example, the storage capacitor Cs of the dummy pixel 301 is 0.5 pF, the liquid crystal capacitor Ccl is 0.5 pF (that is, the storage capacity of the dummy pixel is 1.0 pF), and the connection node ND301 between the dummy pixel 301 and the comparator 3021 is used. Assuming that the parasitic capacitance C1 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, the video signal voltage Vsig is 3.3 V, and Vcom is 1.65 V, the effective pixel potential Vp is expressed by the following equation (Formula 14). Therefore, a good monitor pixel potential can be obtained only by being affected by a voltage drop of about 10 mV from the voltage effect of 1300 mV.

25 and 26 are diagrams illustrating a seventh configuration example of the correction circuit system according to the present embodiment. In FIG. 26, only the correction circuit system and the effective pixel portion are shown for easy understanding.

  The correction circuit system 300E of the sixth configuration example is different from the correction circuit system 300D of FIG. 24 in that a switch 303 is provided at the output portion of the monitor pixel 305.

  As described above, the dummy capacitor 301 has a storage capacitor Cs of 0.5 pF, a liquid crystal capacitor Ccl of 0.5 pF (that is, a dummy pixel storage capacitor of 1.0 pF), and the connection between the dummy pixel 301 and the comparator 3021. When the parasitic capacitance C1 of the node ND301 is 0.06 pF, the storage line charge voltage Vcs is 3.3 V, and the video signal voltage Vsig is 3.3 V, the effective pixel potential Vp is 3.298 V as shown in the following equation (15). Thus, the voltage effect of about 200 mV can be suppressed to a voltage drop of about 2 mV, and a good monitor pixel potential can be obtained.

  Next, a specific circuit configuration of the correction circuit system 302 described above will be described.

FIG. 27 is a circuit diagram showing a specific configuration example of the correction circuit according to the present embodiment.
FIG. 28 is a timing chart of the correction circuit of FIG.

  The correction circuit 302 includes a comparator 3021, an output voltage control block 3022, and an output buffer 3023.

First, the comparator 3021 is composed of two inputs of voltage Pin and Pref, and the input voltage Pin is connected to the monitor pixel potential.
Here, as described above, the monitor pixel uses a part of the dummy pixel 301 or the monitor pixel 305 arranged on the outer periphery of the effective pixel.
This makes it possible to detect temperature changes and manufacturing variations.
Further, as described above, the dummy pixel has the same circuit configuration / structure as the effective pixel, so that the state of the effective pixel can be detected with higher accuracy.
The input voltage Pref is an arbitrary reference voltage.
The voltage applied to the monitor pixel is a voltage of an arbitrary gradation, and Pref is set to a voltage to be applied to the monitor pixel.
Then, by sequentially comparing Pref and Pin (monitor pixel potential), the state of whether the monitor pixel potential is lower or higher than Pref is detected and reflected in the output of the comparator.
The output of the comparator 3021 is a digital output and outputs HorL.

By the way, the voltage polarity of both the effective pixel potential and the pixel potential Vpix to be compared is inverted every other field.
However, since the comparison reference voltage Pref is a direct current voltage, a malfunction occurs if each field is compared.
Therefore, the operation of the comparator 3021 repeats the valid / invalid period every other field.

The output voltage control block 3022 includes a step-up circuit 30221 and a step-down circuit 30222, and controls the voltage applied to the gate of M1 by enabling one circuit based on the output of the comparator 3021.
When the output of the comparator is L (low level), the step-up circuit 30221 operates effectively, and the step-down circuit 30222 becomes high impedance (Hi-Z).
When the output of the comparator 3021 is H (high level), the booster circuit 30221 operates at high impedance (Hi-Z), the step-down circuit 30222 operates effectively, and controls the voltage VcsA.

  The output buffer 3023 includes an M constant current source / Nch source follower 30231. The voltage VcsA output from the output voltage control block 3022 is applied to the gate electrode of the Nch transistor M1, so that the output impedance of the Nch transistor M1 is As a result, the output voltage Vcsh is also controlled.

  By sequentially adjusting Vcsh in the above system, Vcsh is controlled so that the detection dummy pixel potential becomes the same potential as the reference potential Pref applied from the outside, and is reflected in the effective pixel.

  The effect when the above correction circuit is employed will be described.

  As an outline, in a display device that drives the liquid crystal layer alternating current, after writing from the signal line (after the fall of the Gate), the pixel potential is changed by applying coupling from the storage line (CS line) through the capacitor. This is a driving method for modulating the liquid crystal applied voltage. The counter electrode has a feature of optimizing the white luminance / black luminance by making the AC small amplitude.

  When displaying an image by such driving, the voltage gain Avcs applied from the Cs line is expressed by the following equation:

(Equation 16)
Avcs = Vcs * Ccs / (Ccs + Clc)
(Ccs: retention capacity per pixel, Clc: capacitance formed by the pixel electrode with the counter electrode, Vcs: amplitude potential of the Cs line = Vcsh-Vss)

Is obtained. Clc in the above formula is represented by the following formula.

(Equation 17)
Clc = ε _lc * S _pix / d _pix
(Ε _lc : liquid crystal dielectric constant, S _pix : pixel electrode area per pixel, d _pix : gap between counter electrode and pixel electrode)

Here, since the liquid crystal permittivity ε _lc has temperature characteristics, Clc varies depending on the operating environment.
Also, due to manufacturing variations, the gap d _pix between the electrodes 1 and 2 shown in FIG. 29 does not have a constant value depending on the panel, which causes fluctuations in Clc.
Further, Ccs is formed by sandwiching an interlayer film between the metal layer 1 and the metal layer 2 shown in FIG.
This is expressed as follows.

(Equation 18)
Ccs = ε _IL * S _cs / d _IL
(Ε _IL : dielectric constant of interlayer film, S _cs : Ccs area per pixel, d _IL : film pressure of interlayer film)

As for this interlayer film, the film pressure d _IL varies from panel to panel due to manufacturing variations, and Ccs varies as well as Clc.
Due to the change in the operating environment and manufacturing variations, Clc / Ccs does not become a constant value, and the voltage gain Avcs applied from the Cs line varies greatly.
When this is expressed by the γ characteristic of the liquid crystal display device, it can be seen that there is a great influence as shown in FIG.
As described above, in the general driving method, the γ characteristic of the liquid crystal is greatly affected by the operating environment and manufacturing variations.

On the other hand, the correction circuit system of this embodiment is characterized in that the influence is suppressed.
For this purpose, Vcs (= Vcsh Vss) is dynamically corrected to suppress voltage variation of the voltage gain Avcs applied from the Cs line.
In addition, a part of the dummy pixels arranged around the effective pixel is used to detect the variation of the operating environment and the manufacturing variation.
It can be seen that the variation of the final γ characteristic is improved by the correction circuit 302 as shown in FIG. 31B by mounting the correction circuit of the present embodiment.
That is, according to the present embodiment, the influence on the γ characteristic of the liquid crystal display device due to the operating environment and manufacturing variations is suppressed more than in the past.

  Next, the operation according to the above configuration will be described.

The shift register of the vertical drive circuit 102 is supplied with a vertical start pulse VST for instructing the start of vertical scanning generated by a clock generator (not shown) and vertical clocks VCK and VCKX having opposite phases as a reference for vertical scanning.
In the shift register, the level shift operation of the vertical clock is performed, and each is delayed by a different delay time. For example, in the shift register, the vertical start pulse VST is shifted in synchronization with the vertical clock VCK and supplied to the corresponding gate buffer.
Further, the vertical start pulse VST is propagated from the upper side or the lower side of the effective pixel portion 101 and is sequentially shifted into each shift register.
Therefore, basically, the gate lines 105-1 to 105-m are sequentially driven through the gate buffers by the vertical clock supplied from the shift register VSR.

As described above, the gate lines 105-1 to 105-m are sequentially driven from the first row by the vertical drive circuit 102, for example, and the storage lines 106-1 to 106-m are driven accordingly. To go. At this time, after driving one gate line with the gate pulse, the levels of the storage signals CS1 to CSm applied to the storage lines 106-1 to 106-m at the rising timing of the gate pulse of the next gate line are The first level CSH and the second level CSL are alternately selected and applied.
For example, when the first level CSH is selected for the storage line 106-1 in the first row and the storage signal CS1 is applied, the second level CSL is selected for the storage line 106-2 in the second row. The storage signal CS2 is applied, the first level CSH is selected and applied to the storage line 106-3 in the third row, the storage signal CS3 is applied, and the second level CSL is applied to the storage line 106-4 in the fourth row. The storage signal CS4 is selected and the first level CSH and the second level CSL are alternately selected in the same manner, and the storage signals CS5 to CSm are applied to the storage lines 106-5 to 106-m.
The storage signal is corrected so that the pixel potential of the dummy pixel portion 108 is detected by the detection circuit 109 and becomes an arbitrary potential based on the detection potential.

  Further, an alternating common voltage Vcom having a small amplitude ΔVcom is commonly applied to the second pixel electrodes of the liquid crystal cells LC201 of all the pixel circuits PXLC of the effective pixel unit 101.

The horizontal drive circuit 103 generates a sampling pulse in response to a horizontal start pulse HST for instructing the start of horizontal scanning generated by a clock generator (not shown) and horizontal clocks HCK and HCKX which are opposite in phase to be a reference for horizontal scanning. Then, the input video signal is sequentially sampled in response to the generated sampling pulse, and is supplied to each signal line 107-1 to 107-n as a data signal SDT to be written to each pixel circuit PXLC.
For example, first, the R corresponding selector switch is driven and controlled to be conductive, R data is output to each signal line, and R data is written. When the writing of R data is completed, only the selector switch corresponding to G is driven and controlled so that the G data is output and written to each signal line. When the writing of the G data is completed, only the selector switch corresponding to B is driven and controlled so that the B data is output to each signal line and written.

In the present embodiment, after writing from this signal line (after the fall of the gate pulse GP), coupling is performed from the storage lines 106-1 to 106-m via the storage capacitor CS201, thereby causing the pixel potential (of the node ND201). The voltage applied to the liquid crystal is modulated by changing the potential.
At this time, the common voltage Vcom is supplied as an alternating signal with a small amplitude ΔVcom (10 mV to 1.0 V) instead of a constant value.
Thereby, not only the black luminance but also the white luminance is optimized.

  As described above, according to the present embodiment, the plurality of pixel circuits PXLC for writing the pixel data for video through the TFT 201 are arranged so as to correspond to the effective pixel portion 101 arranged in a matrix and the row arrangement of the pixel circuits. Gate lines 105-1 to 105-m, a plurality of capacitor wirings 106-1 to 106-m arranged to correspond to the row arrangement of the pixel circuits, and arranged to correspond to the column arrangement of the pixel circuits. Vertical drive circuit 102 that selectively drives the signal lines 107-1 to 107-m, gate lines, and capacitor lines, and a generation circuit 104 that generates a common voltage signal with a small amplitude whose level is switched at a predetermined cycle. Each pixel circuit includes a liquid crystal cell LC201 having a first pixel electrode and a second pixel electrode, and a storage capacitor CS having a first electrode and a second electrode. 01, the first pixel electrode of the liquid crystal cell, the first electrode of the storage capacitor, and one terminal of the TFT are connected, and the second electrode of the storage capacitor is connected to the capacitor wiring arranged in the corresponding row, and the liquid crystal Since the common voltage signal is applied to the second pixel electrode of the cell, both black luminance and white luminance can be optimized. As a result, there is an advantage that the contrast can be optimized.

  Further, in this embodiment, liquid crystal application is caused by fluctuations in the dielectric constant of the liquid crystal due to changes in the driving temperature, fluctuations in the thickness of the insulating film forming the storage capacitor CS201 due to variations during mass production, and fluctuations in the liquid crystal cell gap. The voltage will fluctuate. This variation is electrically detected, and the variation due to variations in display temperature and mass production is suppressed by suppressing variations in the liquid crystal applied voltage.

Further, the CS driver in the vertical drive circuit 102 of this embodiment determines the polarity of the CS signal only by the polarity at the time of pixel writing (indicated by POL) without depending on the polarity of the previous or next stage of the driver stage or the previous frame. Yes.
That is, it is possible to control only with the signal of its own stage without depending on the signals of the preceding and following stages of this embodiment.
In addition, the CS block and the like of the vertical drive circuit of this embodiment can be formed with a small number of elements, which contributes to a reduction in circuit scale. For example, it can be constituted by 20 or less transistors.

  In the above embodiment, an analog video signal is input to the liquid crystal display device, and after latching the analog video signal, it is applied to a liquid crystal display device equipped with an analog interface driving circuit that writes the analog video signal to each pixel in a dot sequence. As described above, the present invention can be similarly applied to a liquid crystal display device equipped with a drive circuit that inputs a digital video signal and writes the video signal to pixels in a line-sequential manner using a selector method.

In the above embodiment, the case where the present invention is applied to an active matrix liquid crystal display device using a liquid crystal cell as a display element (electro-optical element) of each pixel has been described as an example. The present invention is not limited, and the present invention can be applied to all active matrix display devices such as an active matrix EL display device using an electroluminescence (EL) element as a display element of each pixel.
The display device according to the embodiment described above is used as a display panel of a direct-view type video display device (liquid crystal monitor, liquid crystal viewfinder) and a projection type liquid crystal display device (liquid crystal projector), that is, an LCD (liquid crystal display) panel. Is possible.

It is a block diagram which shows the structural example of a general liquid crystal display device. 2 is a timing chart in the so-called 1HVcom inversion driving method of the general liquid crystal display device shown in FIG. It is a figure which shows the relationship between the applied voltage of a normally white liquid crystal, and a dielectric constant. It is a figure which shows the structural example of the active matrix type display apparatus which concerns on one Embodiment of this invention. FIG. 2 is a circuit diagram illustrating a specific configuration example of a pixel portion of the circuit of FIG. 1. 4 is a timing chart showing an example of driving a gate line and a storage line of the vertical drive circuit according to the embodiment. It is a circuit diagram which shows the structural example of the common voltage generation circuit which concerns on this embodiment. It is a timing chart which shows the drive waveform of the main liquid crystal cells of this embodiment. FIG. 4 is a diagram illustrating each capacity of a liquid crystal cell in Formula 3. Effective pixel potential ΔVpix applied to the liquid crystal during white display when the liquid crystal material (normally white liquid crystal) used in the liquid crystal display device is used. It is a figure for demonstrating the selection criteria of W. It is a figure which shows the relationship between the video signal voltage and effective pixel electric potential of the drive system which concerns on embodiment of this invention, the related capacitive coupling drive system, and the normal 1HVcom drive system. It is a figure which shows the relationship between the video signal voltage of a drive system which concerns on embodiment of this invention, and a related capacitive coupling drive system, and a brightness | luminance. It is a figure which shows the example which formed the detection area and the correction circuit system in the display apparatus which concerns on this embodiment in the system on glass panel. It is a figure which shows the example which formed the detection area and the correction circuit system in the display apparatus which concerns on this embodiment in the COG mounting panel. It is a figure which shows the example which formed the detection circuit on the panel in the display apparatus which concerns on this embodiment, and formed the correction circuit system in single crystal LSI. It is a figure which shows the 2nd example in which the display apparatus which concerns on this embodiment formed the detection area and the correction circuit system in the system on glass panel. It is a figure which shows the 2nd example in which the display apparatus which concerns on this embodiment formed the detection area and the correction circuit system in the COG mounting panel. It is a figure which shows the 2nd example which formed the detection area on the panel in the display apparatus which concerns on this embodiment, and formed the correction circuit system in single crystal LSI. It is a figure which shows the 1st structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows the 2nd structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows the 3rd structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows the 4th structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows the 5th structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows the 6th structural example of the correction circuit system which concerns on this embodiment. It is a figure which shows an example of the monitor pixel comprised by connecting all the dummy pixel electrodes of 1 line of horizontal directions. It is a figure which shows the 7th structural example of the correction circuit system which concerns on this embodiment. It is a circuit diagram which shows the specific structural example of the correction circuit which concerns on this embodiment. It is a timing chart of the correction circuit of FIG. It is a figure for demonstrating the effect of a correction circuit in relation to a pixel structure. It is a figure for demonstrating the effect of a correction circuit in relation to a pixel structure. It is a figure which shows the mode of the dispersion | variation in the (gamma) characteristic before and after mounting of the correction circuit which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Liquid crystal display device, 101 ... Effective pixel part, 102 ... Vertical drive circuit (VDRV), 103 ... Horizontal drive circuit (HDRV), 104 ... Common voltage generation circuit, 105-1 ˜105-m... Gate line, 106-1 to 106-m... Capacitance wiring (storage line), 107-1 to 107-n... Signal line, 108. 109, correction circuit, PXLC, pixel circuit, 201, TFT (switching element), LC201, liquid crystal cell, CS201, storage capacitor, 300, 300A to 300E, correction circuit system, 301, dummy Pixel, 302 ... correction circuit, 303 ... switch, 304 ... external substrate, 305 ... monitor pixel, 3021 ... comparator, 3022 ... output Pressure control circuit (block), 3023 ... the output buffer.

Claims (13)

A pixel unit in which a plurality of pixel circuits for writing image pixel data propagated through a signal line through a switching element are arranged in a matrix;
A plurality of scan lines arranged to correspond to the row arrangement of the pixel circuits, and for controlling conduction of the switching elements;
A plurality of capacitor wirings arranged to correspond to the row arrangement of the pixel circuits;
A drive circuit for selectively driving the plurality of scan lines and the plurality of capacitance lines;
A generation circuit for generating a common voltage signal;
A correction unit for correcting a signal for driving the capacitive wiring of the drive circuit;
Have
Each pixel circuit arranged in the pixel portion is
A display element having a first pixel electrode and a second pixel electrode;
A storage capacitor having a first electrode and a second electrode;
Including
One terminal of the first electrode and the switching element of the first pixel electrode and the storage capacitor of the display elementary: it is connected,
The second electrode of the storage capacitor is connected to the capacitor wiring arranged in a corresponding row, the common voltage signal is applied to the second pixel electrode of the display element,
The drive circuit selects a first level or a second level lower than the first level and applies a signal for driving the capacitance line to a corresponding capacitance line,
Due to the driving of the driving circuit, the amplitude value of the common voltage signal and the value of the potential difference between the first level and the second level are displayed in black for the increase in effective pixel potential due to the common voltage signal and the potential difference. Selected to compensate for the variation of the increase in white display relative to the increase in time by the common voltage signal,
The correction unit is
A monitor pixel circuit formed by imitating the pixel circuit and monitoring the pixel potential of the pixel portion;
A correction circuit for further correcting the level of a signal for driving the capacitive wiring selected by the drive circuit based on the monitoring result of the monitor pixel circuit ;
A display device. The correction circuit corrects the level of a signal for driving the capacitor wiring so as to reduce the deviation of the pixel potential obtained by the monitor pixel circuit from the ideal pixel potential due to the influence of the capacitor wiring drive.
  The display device according to claim 1. The pixel potential monitored by the monitor pixel circuit is expressed by the following equation:

Stipulated in
The correction circuit corrects the potential Vcs of the capacitance wiring so as to provide ΔVcs that reduces the process variation of the capacitance distribution coefficient of the liquid crystal capacitance Clc and the holding capacitance Ccs represented by Ccs / (Ccs + Clc) in the above formula. The display device according to claim 2. The correction unit, a monitor pixel potential of the monitor pixel circuit outputs above SL correction circuit when on and claims has a load separation switch for disconnecting the load of the correction circuit side turned off at the time of the monitor from the monitor pixel circuits 1 3. The display device according to 3 . The monitor pixel circuit and the input of the correction circuit display device according to claim 1 to 4, characterized in that disposed close to each other in substrate on which the pixel portion is formed. The monitor pixel circuit is formed on the same substrate as the pixel portion ,
The same substrate as the monitor pixel circuits, a load separation switch disconnecting the monitor pixel potential of the monitor pixel circuit outputs to the substrate outside of the correction circuit when turned on, the load of the correction circuit side turned off at the time of the monitor from the monitor pixel circuit the display device according to claim 1 having a. The monitor pixel circuit includes a plurality of the monitor pixel circuits imitating the pixel circuit ,
First electrodes of the monitor pixel circuits corresponding to the first pixel electrode is connected in common via a common connection line, the common connection line is the correction circuit and according to claim 6, wherein connected to the connection line Display device. The drive circuit, after writing the pixel data into the desired pixel circuits by driving the scanning lines of the selected row, the display device according to claim 1 to 7, wherein for driving the capacity lines of the same row. The drive circuit, a display device according to claim 8, wherein applying the capacitor wiring corresponding by selecting one of the first level and the first lower level a second level signal for driving the capacitance line . The display device according to claim 1-9, wherein the display elements of the pixel circuit is a liquid crystal cell. The amplitude value of the common voltage signal and the value of the potential difference are selected so that the effective pixel potential during white display is not more than a predetermined threshold value.
The display device according to claim 10 . The predetermined threshold is a voltage value at which the dielectric constant starts to change when the applied voltage is increased in the characteristics of the dielectric constant with respect to the applied voltage of the liquid crystal in the liquid crystal cell.
The display device according to claim 11 . A pixel unit in which a plurality of pixel circuits for writing image pixel data propagated through a signal line through a switching element are arranged in a matrix;
A plurality of scan lines arranged to correspond to the row arrangement of the pixel circuits, and for controlling conduction of the switching elements;
A plurality of capacitor wirings arranged to correspond to the row arrangement of the pixel circuits;
A drive circuit for selectively driving the plurality of scan lines and the plurality of capacitance lines;
A generation circuit for generating a common voltage signal;
A reference driver for generating video pixel data to be propagated to the signal line;
Have
Each pixel circuit arranged in the pixel portion is
A display element having a first pixel electrode and a second pixel electrode;
A storage capacitor having a first electrode and a second electrode;
Including
One terminal of the first electrode and the switching element of the first pixel electrode and the storage capacitor of the display elementary: it is connected,
A second electrode of the storage capacitor is connected to the capacitor wiring arranged in a corresponding row;
The common voltage signal is applied to the second pixel electrode of the display element,
The drive circuit selects a first level or a second level lower than the first level and applies a signal for driving the capacitance line to a corresponding capacitance line,
Due to the driving of the driving circuit, the amplitude value of the common voltage signal and the value of the potential difference between the first level and the second level are displayed in black for the increase in effective pixel potential due to the common voltage signal and the potential difference. Selected to compensate for the variation of the increase in white display relative to the increase in time by the common voltage signal,
The correction unit is
A monitor pixel circuit formed by imitating the pixel circuit and monitoring the pixel potential of the pixel portion;
A correction circuit for correcting a signal voltage in the upper cut file Reference driver,
A display device.

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