JP4874599B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device.

Conventionally, a technique for driving a liquid crystal display device based on a capacitive coupling driving method in an IPS (in-plane switching) mode has been proposed. In this case, in order to compensate for the luminance loss for each of the R, B, and G colors provided in the liquid crystal display device, the charge storage capacity provided for each pixel decreases in the order of Cg, Cr, and Cb. A technique for making the setting is disclosed (see, for example, Patent Document 1).
JP 2003-241213 A

  However, in the liquid crystal display device having the above configuration, a specific configuration for changing the charge storage capacity for each color is not disclosed. In addition, when performing color display by R, G, and B, the wavelength differs depending on each color. Therefore, even if the same voltage is applied, the transmittance is different. As described above, the charges are in the order of G, R, and B colors. When the storage capacity is changed, there is a problem that unevenness is observed in the maximum luminance.

  In view of the above problems, the present invention eliminates the difference in transmittance for each color of the color filter even if the image signal supplied to the signal line is supplied with the same gradation voltage, and in this case, the drive circuit Thus, there is provided a liquid crystal display device capable of correcting the gradation difference for each color on the array substrate without performing the adjustment.

The present invention includes an array substrate, a counter substrate disposed opposite to the array substrate, a liquid crystal layer disposed between the substrates, a plurality of gate lines and a plurality of gate lines wired in a grid pattern on the array substrate. A signal line, an auxiliary capacitance line wired in parallel to the gate line on the array substrate, a switching semiconductor layer connected to the gate line and the signal line, and the switching semiconductor layer overlapping the auxiliary capacitance line The auxiliary capacitance semiconductor layer formed extending to the position, the pixel electrode connected to the switching semiconductor layer, the counter electrode disposed on the counter substrate side, and a color for each pixel provided on the array substrate Different color filter layers, and the color filter layers are formed of R (red), G (green), and B (blue), and in the order of B (blue), G (green), and R (red) , before A liquid crystal display device, characterized in that to reduce the area S of the overlap portion between the auxiliary capacitor line auxiliary capacity semiconductor layer.

  The present invention will be described. When the color filter layer is composed of, for example, R (red), G (green), and B (blue) colors, the wavelength differs depending on each color. The transmittance decreases in the order of B color, G color, and R color. This order is different from the order of Patent Document 1. Therefore, the lower the transmittance, the smaller the area of the overlapping portion between the auxiliary capacitance line and the auxiliary capacitance semiconductor layer, and the gradation voltage is adjusted. As a result, even if the colors are different, if the same gradation voltage is applied, the same transmittance can be obtained to achieve a good display.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

(1) Structure of Array Substrate 12 The pixel portion on the array substrate 12 will be described with reference to FIG. As necessary, reference is made to FIG. 2 which is a cross-sectional view of the AA ′ portion of FIG. 1 and FIG. 3 which is a cross-sectional view of the BB ′ portion of FIG.

On the array substrate 12, semiconductor layers 36 and 38 made of polysilicon are stacked for each pixel (in FIG. 1, hatched portions). The semiconductor layer 36 is L-shaped in plan and has a role as a switching element. Further, the semiconductor layer 38 is a semiconductor layer for forming a rectangular plane shape, and the area thereof varies depending on each pixel. The region of the semiconductor layer 38 constitutes the auxiliary capacitance unit Cs. That is, the auxiliary capacitance portion Cs is configured by the semiconductor layer 38, the gate insulating film 40, and the auxiliary capacitance line 42 from FIGS.

The semiconductor layer 36 and the semiconductor layer 38 are connected by a first connection line 46 formed of the same semiconductor layer.

  The gate insulating film 40 shown in FIGS. 2 and 3 is stacked on the semiconductor layers 36 and 38, and the auxiliary capacitance line (Cs line) 42 and the gate line 20 shown in FIG. 1 are formed on the gate insulating film 40. Layers (hereinafter collectively referred to as gate line layers) are stacked. On the gate line layer, the signal line 18 is laminated via the interlayer insulating film 44 shown in FIG. When the signal line 18 of FIG. 1 is laminated, the second connection line 19 is formed together with the signal line 18 above the semiconductor layer 38 and the first connection line 46 of FIG. The second connection line 19 and the first connection line 46 are connected by a contact hole 48. Further, a contact hole 52 is provided to connect the signal line 18 of FIG. 1 and the L-shaped semiconductor layer 36.

  An organic insulating film 56 is laminated on the signal line 18 via the protective film 54 shown in FIG. Then, a contact hole 50 is provided in the organic insulating film 56 at the position of the connection line 46 corresponding to the semiconductor layer 38, and after this contact hole 50 is provided, a transparent pixel electrode 60 is formed of ITO. Finally, the alignment film 62 shown in FIGS. 2 and 3 is laminated on the pixel electrode 60.

  In the counter substrate 14 shown in FIG. 2, a black matrix 64 is provided on the lower surface of the glass substrate 70 so as to partition each pixel, and a color filter layer 66 is provided between the black matrices 64. The color filter layer 66 is formed with R color (red), G color (green), and B color (blue) corresponding to each pixel. Finally, an alignment film 68 is formed on the lower surface of the color filter layer 66.

(2) Regarding Configuration of Auxiliary Capacitor Cs Next, the configuration of the auxiliary capacitor Cs will be described with reference to FIG.

  A storage capacitor Cs is provided for each pixel. The auxiliary capacity Cs is determined by the area where the auxiliary capacity line 42 and the semiconductor layer 38 shown in FIG. 1 overlap. Therefore, this area S is changed for each color. Specifically, the hatched location in FIG. 1 is that portion, and the area Sb corresponding to the B color, the area Sg corresponding to the G color, and the area Sr corresponding to the R color are set such that Sb> Sg> Sr.

  In order to form the area S so as to decrease in order, the area of the semiconductor layer 38 is decreased in the order of B, G, and R as described above.

  For example, the lateral direction of the semiconductor layer 36 in B color is 42 μm and the longitudinal direction is 22 μm, and the auxiliary capacitance CsB of the auxiliary capacitance unit 26 is 0.6 pF.

  In G color, the horizontal direction of the semiconductor layer 36 is 40 μm and the vertical direction is 20 μm, and the auxiliary capacitance CsG of the auxiliary capacitance unit 26 is 0.5 pF.

  In the R color, the horizontal direction of the semiconductor layer 36 is 38 μm and the vertical direction is 18 μm, and the auxiliary capacitance CsR of the auxiliary capacitance unit 26 is 0.4 pF.

  Thus, the reason why the auxiliary capacitance of the auxiliary capacitance unit Cs is reduced in the order of B, G, and R is that the transmittance decreases in the order of B, G, and R as shown in FIG. . When the transmittance is low, the luminance decreases, so that the same luminance is obtained even when the same gradation voltage is applied. Therefore, the liquid crystal can be applied so that the luminance is the same even when the same gradation voltage is applied for each color. This is because the voltage is increased as the color has lower transmittance. That is, even when the same gradation voltage is applied, in order to increase the liquid crystal applied voltage as the color has lower transmittance, the auxiliary capacity is reduced as the transmittance is lower.

  Here, the reason why the auxiliary capacitance Cs is determined by the area of the semiconductor layer 38 will be described with reference to FIG.

  As shown in FIG. 3, the semiconductor layer 38 and the auxiliary capacitance line 22 are provided via a gate insulating film 40, and an auxiliary capacitance Cs is generated between them. The semiconductor layer 38 is connected to the pixel electrode 60 by the first connection line 46 and the second connection line 19 through the contact hole 48. That is, since the semiconductor layer 38 is the same as the pixel electrode 60 in terms of potential, the auxiliary capacitor Cs becomes the auxiliary capacitor Cs in the pixel electrode 60.

(3) Circuit Configuration of Liquid Crystal Display Device FIG. 4 is a circuit configuration diagram of the liquid crystal display device in the present embodiment.

  The liquid crystal display device 10 includes a liquid crystal capacitor portion 16 such as a twisted nematic (TN) mode and an auxiliary capacitor portion 26 connected to a drain electrode of a thin film transistor 24 (hereinafter referred to as a TFT) serving as a switching element. An equivalent circuit is configured. The gate electrode of the TFT 24 is connected to the gate line 20, and the source electrode of the TFT 24 is connected to the signal line 18.

In addition, an auxiliary capacitance line 22 connected to the auxiliary capacitance portion 22 is wired in parallel with the gate line 20.

  The signal line 18 is connected to a signal line driver circuit 30, and the signal line driver circuit 30 outputs an image signal to each signal line 18 based on a video signal input from the outside.

  The gate line 20 is connected to a gate driver circuit 32. The gate driver circuit 32 outputs a trigger-like gate signal based on a clock signal output from a control circuit (not shown). Further, the auxiliary capacitance line 22 is connected to the gate driver circuit 32, and an auxiliary capacitance signal whose potential is inverted is supplied.

  The liquid crystal capacitor 16 is also connected to the signal line driver circuit 30 via the signal line 18 and supplied with a counter voltage having a constant potential.

(4) Driving Method of Liquid Crystal Display Device 10 The liquid crystal display device 10 in FIG. 4 is driven by a so-called capacitive coupling driving method. That is, the liquid crystal capacitor unit 16 has an auxiliary capacitor unit 26 formed between the pixel electrode and the auxiliary capacitor line, and redistributes charges when the potential of the auxiliary capacitor line 22 connected to the auxiliary capacitor unit 26 is changed. The voltage applied to is determined. In the conventional liquid crystal display device, the potential difference between the potential written in the pixel electrode and the potential between the counter electrodes is the liquid crystal applied voltage. On the other hand, in the capacitive coupling driving method, the potential of the pixel electrode 60 shown in FIG. 1 is changed by changing the potential of the auxiliary capacitance line 22 connected to the auxiliary capacitance Cs of the auxiliary capacitance section 26, thereby determining the liquid crystal applied voltage. Therefore, the gradation voltage can be adjusted by making the auxiliary capacitance Cs of each pixel different. By adjusting the output amplitude and capacitance size / potential amplitude of the digital / analog converter (DAC) of the gate driver circuit 32, different γ curves can be realized using the same gradation resistance (see FIG. 7).

  Specifically, a description will be given based on FIG.

  FIG. 5 shows the relationship between the gate voltage Vg, the pixel electrode Vpix, the counter electrode potential Vcom, the image signal Vs, and the auxiliary capacitance potential Vcs that is driven to be inverted.

  As shown in FIG. 5, the pixel electrode Vpix is determined by swinging the auxiliary capacitance potential Vcs of the auxiliary capacitance line 22. At this time, since the counter electrode potential Vcom is constant, the fluctuation amount ΔVpix of the pixel potential Vpix is expressed by the equation (1).

ΔVpix = ΔVcs · Cs / (Cs + C _lc ) (1)

For this reason, when the auxiliary capacitance Cs is increased, the voltage / transmittance characteristics become steep, and when the auxiliary capacitance Cs is small, it becomes gentle.

  Therefore, in the conventional case, the gradation-transmittance characteristics of each pixel of RGB are the darkest in R and the brightest in B when the same voltage is applied. For this reason, when a halftone raster is displayed, it appears slightly bluish. In order to prevent this, when the auxiliary capacitance of the auxiliary capacitance unit 26 is sequentially reduced in the order of B, G, and R as described above, and the liquid crystal applied voltage is reduced, substantially the same voltage as shown in FIG. -It becomes a transmission characteristic.

  In addition, since the TFT 24 is formed of polysilicon, the size of the TFT 24 can be reduced, and higher cycle efficiency can be obtained.

(5) Modification 1
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

  In the above embodiment, the color filter layer 66 is provided on the counter substrate 14 side, but may be provided on the array substrate 12 side instead. That is, the organic insulating film 56 may be formed in RGB.

  Moreover, in the said embodiment, although the change of the auxiliary capacitance was 0.4 pF, 0.5 pF, and 0.6 pF, you may change in order in the range of 0.1 pF to 1.0 pF.

  In the above embodiment, the three colors of RGB have been described. In addition, the present invention can be applied even when the color filter layer has four or more colors. The auxiliary capacity of the low auxiliary capacity unit 26 may be reduced.

  In the above-described embodiment, the TN mode liquid crystal layer 16 has been described. However, the present invention is not limited to this, and a VA (vertical alignment) mode liquid crystal may be used.

  In the above embodiment, the area of the semiconductor layer 36 is changed for each pixel to change the auxiliary capacity Cs of the auxiliary capacity unit 26. Instead, the area of the auxiliary capacity line 22 is changed for each pixel. May be.

  Further, the portion where the storage capacitor line 22 and the semiconductor layer 36 overlap may be shifted for each pixel, and the area formed by the overlapping portion may be changed for each color.

  In the above embodiment, the polysilicon TFT 24 is used, but a single crystal silicon thin film transistor or an amorphous silicon thin film transistor may be used instead.

It is a top view of the array substrate of the liquid crystal display device which shows one Embodiment of this invention. It is a longitudinal cross-sectional view of the A-A 'line | wire in FIG. It is a longitudinal cross-sectional view of the B-B 'line in FIG. It is a figure which shows the circuit structure of a liquid crystal display device. It is a figure which shows the application state of a voltage. It is a graph which shows the conventional voltage-transmittance characteristic. It is a graph which shows the characteristic of the voltage-transmittance of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 12 Array substrate 14 Counter substrate 16 Liquid crystal layer 18 Signal line 20 Gate line 22 Auxiliary capacity line 24 TFT
26 Auxiliary Capacitor 38 Counter Electrode 30 Signal Line Driver Circuit 32 Gate Line Driver Circuit 36 Semiconductor Layer 38 Semiconductor Layer 66 Color Filter Layer

Claims (6)

An array substrate;
A counter substrate disposed opposite to the array substrate;
A liquid crystal layer disposed between the substrates;
A plurality of gate lines and a plurality of signal lines wired in a grid pattern on the array substrate;
An auxiliary capacitance line wired in parallel with the gate line on the array substrate;
A switching semiconductor layer connected to the gate line and the signal line;
A storage capacitor semiconductor layer formed by extending the switching semiconductor layer to a position overlapping the storage capacitor line;
A pixel electrode connected to the switching semiconductor layer;
A counter electrode disposed on the counter substrate side;
A color filter layer having a different color for each pixel provided on the array substrate;
Comprising
The color filter layer is formed of R (red), G (green), and B (blue);
An area S of a portion where the auxiliary capacitance line and the auxiliary capacitance semiconductor layer overlap is reduced in the order of B (blue), G (green), and R (red) . 2. The liquid crystal display device according to claim 1, wherein the area of the auxiliary capacitor semiconductor layer is reduced in the order of B (blue), G (green), and R (red) . 2. The liquid crystal display device according to claim 1, wherein the area of each storage capacitor line for each pixel is reduced in the order of B (blue), G (green), and R (red) . The liquid crystal display device according to claim 1, wherein the color filter layer is provided on the counter substrate side. 2. The liquid crystal display device according to claim 1, wherein a capacitive coupling driving method is performed by setting a counter voltage supplied to the counter electrode constant and inverting an auxiliary capacitance signal supplied to the auxiliary capacitance line. By reducing the area S, the auxiliary capacitance Cs of the auxiliary capacitance portion formed by the auxiliary capacitance line and the auxiliary capacitance semiconductor layer is set to a value in the range of 0.1 pF to 1.0 pF. The liquid crystal display device according to claim 1.

Images