JP2007140276A - Active matrix type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active matrix type display device whose display quality is improved. <P>SOLUTION: The active matrix type display device has a plurality of pixel parts PX arranged on a substrate in a matrix and a plurality of linear video signal lines X provided by columns of pixel parts. Each pixel part has sub-pixels R, G and B in a delta array including a self-light-emitting element and a pixel circuit supplying a driving current to the self-light-emitting element, and the sub-pixels of the three colors are provided alternately by rows so that sub-pixels in odd-numbered rows and sub-pixels in even-numbered rows shift in the row directions. Sub-pixels of the same colors are provided in the same rows in every plurality of columns. Each video signal line is connected to sub-pixels of the same color in the same column among sub-pixels arrayed in one of an odd-numbered row and an even-numbered row, and sub-pixels of the same color in the same column among sub-pixels arrayed in other rows are connected to video signal lines to which sub-pixels of the same color are connected through branch wiring lines respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an active matrix display device in which a display screen is configured by arranging display pixels including self-luminous elements such as organic electroluminescence (hereinafter referred to as EL) elements in a matrix.

  In recent years, the demand for flat display devices typified by liquid crystal display devices has been rapidly increased by taking advantage of the features of thinness, light weight, and low power consumption. In particular, an active matrix display device in which a pixel switch having a function of electrically separating an on pixel and an off pixel and holding a video signal to the on pixel is provided in each pixel has crosstalk between adjacent pixels. Since a good display quality without any problem can be obtained, it has come to be used for various displays including portable information devices.

  As such a flat-type active matrix display device, an organic electroluminescence (EL) display device using a self-luminous element has attracted attention, and research and development has been actively conducted. This organic EL display device does not require a backlight that obstructs the reduction in thickness and weight, is suitable for moving image reproduction because of its high-speed response, and further has a feature that it can be used even in cold regions because the luminance does not decrease at low temperatures. .

  The organic EL display device includes an organic EL element as a display element for each pixel and a pixel circuit that supplies a drive current to the display element, and performs a display operation by controlling the light emission luminance of the display element. The pixel circuit includes, for example, a drive transistor and an output switch connected in series to the organic EL element, a diode connection switch connected between the gate and drain of the drive transistor, and holding a gate potential corresponding to a video signal. These drive transistors, output switches, and diode connection switches are composed of thin film transistors, for example. As such an organic EL display device, a method of supplying image information to a pixel circuit by a current signal is known.

  In the active matrix display device as described above, when performing color display, each pixel has three sub-pixels for red, green, and blue, respectively. These three color sub-pixels are arranged in, for example, a delta shape (hereinafter referred to as a delta arrangement). In such a display device in which one pixel is constituted by three subpixels, when performing color display, each signal line is connected to the same color subpixel and is configured to drive only the same color subpixel. It is desirable that When the subpixels are arranged in a delta arrangement, if only the subpixels of the same color are driven by the signal lines extending in a straight line, the number of signal lines increases. In addition, when the number of signal lines is reduced and two color sub-pixels arranged along each signal line are connected alternately, the video signal supplied to each signal line is matched to the color of each sub-pixel every horizontal period. You must switch to the correct signal. For this reason, the signal line driving circuit requires a signal output capability for two colors for each signal line, which complicates the driving circuit.

For example, according to the liquid crystal display device disclosed in Patent Document 1, each pixel has three color pixel electrodes arranged in a delta arrangement. In adjacent row arrangements, pixel electrodes of the same color are located shifted in the row direction. Each signal line is formed in a zigzag manner, and is connected to a plurality of pixels of the same color arranged in a state shifted in the row direction. With such a configuration, the number of signal lines can be reduced and the configuration of the drive circuit can be simplified.
Japanese Patent No. 2641778

However, when the zigzag signal lines as described above are used, the signal lines become longer than the linear signal lines, and the wiring capacity also increases. In the case of a display device that supplies a signal using a current signal like the organic EL display device described above, there is a risk that sufficient signal supply may not be possible due to the wiring capacity of the signal supply wiring. In particular, when the current value to be written is small, a display defect due to insufficient writing occurs. In addition, when performing multi-gradation display, writing becomes difficult on the low gradation side where the set current amount is small, resulting in luminance variations between display pixels. As a result, display quality is degraded.
In addition, when zigzag signal lines are used, the signal lines are arranged on both sides of each pixel in both the row direction and the column direction, so that the area occupied by the wiring increases and the aperture ratio decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide an active matrix display device capable of color display and improved in display quality.

In order to achieve the above object, an active matrix display device according to an aspect of the present invention includes a plurality of pixel portions arranged in a matrix on a substrate and a plurality of pixel portions arranged side by side in each column of the pixel portions. A linear video signal line,
Each pixel unit includes a self-light-emitting element and a pixel circuit that supplies a driving current to the self-light-emitting element, and includes three-color subpixels arranged in a delta arrangement. The three color subpixels are alternately arranged in each row. The odd-numbered row subpixels and the even-numbered row subpixels are arranged so as to be shifted in the row direction, and the subpixels of the same color are provided in the same column for each of the plurality of columns.
Each of the video signal lines is connected to sub-pixels arranged in the same column in sub-pixels arranged in either one of the odd-numbered rows or even-numbered rows, and out of sub-pixels arranged in the other row. The sub-pixels of the same color arranged in the same column are connected to the video signal lines to which the sub-pixels of the same color are connected through branch wirings.

  According to the present invention, it is possible to provide an active matrix display device capable of performing a good display operation without being affected by the wiring capacity and having improved display quality.

Hereinafter, an organic EL display device will be described in detail as an embodiment of the present invention with reference to the drawings.
FIG. 1 is a plan view schematically showing an organic EL display device. FIG. 2 shows an arrangement structure of video signal lines, voltage power supply lines, and subpixels of the organic EL display device. As shown in FIG. 1, the organic EL display device is configured as, for example, a large active matrix display device of 10 type or more, and includes an organic EL panel 10 and a controller 12 that controls the organic EL panel 10.

  The organic EL panel 10 includes a light-transmitting substrate 8 such as a glass plate, m × n display pixels PX arranged in a matrix of a plurality of rows and a plurality of columns on the substrate 8, and a display region 11. The first scanning line Sga (1 to m) and the second scanning line Sgb (1 to m), which are connected for each row of pixels and provided independently by m, are respectively provided for each column of the display pixels PX. A scanning line driving circuit for sequentially driving the n video signal lines X (1 to n), the first and second scanning lines Sga (1 to m), and Sgb (1 to m) connected to each row of display pixels. (YDR) 14 and a signal line driving circuit (XDR) 15 for driving a plurality of video signal lines X (1 to n). The scanning line driving circuit 14 and the signal line driving circuit 15 are integrally formed on the substrate 8 outside the display area 11.

  As shown in FIG. 1 and FIG. 2, each display pixel PX that functions as a pixel unit has three color sub-pixels PXR, PXG, and PXB (indicated as R, G, and B in FIG. 2). . These sub-pixels PXR, PXG, and PXB are respectively configured by three types of organic EL elements (OLEDs) that self-emit with different emission colors such as red (R), green (G), and blue (B). ing. In each display pixel PX, the sub-pixels PXR, PXG, and PXB are delta-arranged, and in this case, the vertices of the triangles are vertically directed downward. In each row, subpixels PXR, PXG, and PXB of three colors are provided alternately, and the odd-numbered subpixels and the even-numbered subpixels are arranged so as to be shifted in the row direction by one column. Furthermore, the sub-pixels of the same color are provided side by side in the same column every plural columns, here, every three columns.

  The plurality of video signal lines X (1 to n) are each formed in a straight line and extend alongside the subpixels in each column. Each of the video signal lines X (1 to n) has the same color arranged in the same column among the subpixels PXR, PXG, and PXB arranged in either the odd row or the even row, here, the odd row. Connected to a subpixel. Of the sub-pixels PXR, PXG, and PXB arranged in the other row, here even-numbered rows, the sub-pixels of the same color arranged in the same column are respectively connected to the same color via the branch wiring H (1 to n). The video signal lines X (1 to n) to which the subpixels are connected are connected. In the present embodiment, each branch line H (1 to n) extends from the subpixel to one side, for example, the left side in FIG. 2, and extends between the even-numbered subpixels and the odd-numbered subpixels. For example, the branch wiring H extending from the red subpixel PXR extends beyond the green subpixel PXG column and the blue subpixel PXB column arranged on the left side, and is connected to the red subpixel PXR column. Connected to X.

  On the substrate 8, a plurality of linear voltage power supply lines Vdd are provided. These voltage power supply lines Vdd are connected to a common voltage power supply. The voltage power supply line Vdd is provided side by side with the subpixels PXR, PXG, and PXB in each column. The plurality of voltage power supply lines Vdd are alternately arranged with the video signal lines X (1 to n). For each column of subpixels, the video signal lines X (1 to n) are provided side by side, for example, on the left side, and the voltage power supply line Vdd is provided on the right side. Each voltage power supply line Vdd is connected to subpixels in columns located on both sides of the voltage power supply line.

  As shown in FIGS. 1 and 3, each of the subpixels PXR, PXG, and PXB includes a display element having a photoactive layer between opposing electrodes, and a pixel circuit 18 that supplies a driving current to the display element. It is out. The display element is a self-luminous element, and in this embodiment, an organic EL element 16 having at least an organic light-emitting layer as a photoactive layer is used.

  FIG. 3 shows a green sub-pixel PXG as a representative. The pixel circuit 18 is a current-driven pixel circuit that controls light emission of the organic EL element 16 in accordance with a video signal including a current signal. The pixel circuit 18 includes a pixel switch 20, a drive transistor 22, a first switch 24, an output switch 26, and a holding circuit. The capacitor Cs is provided. Here, the pixel switch 20, the drive transistor 22, the first switch 24, and the output switch 26 are configured by the same conductivity type, for example, a P-channel type thin film transistor. In this embodiment, all the thin film transistors constituting the pixel circuit 18 are formed in the same process and the same layer structure, and are top gate thin film transistors using polysilicon as a semiconductor layer.

  The drive transistor 22, the output switch 26, and the organic EL element 16 are connected in series in this order between the voltage power supply line Vdd and the reference voltage power supply line Vss. The reference voltage power supply line Vss and the voltage power supply line Vdd are set to potentials of −9 V and +6 V, for example. The drive transistor 22 has its first terminal, here the source, connected to the voltage power supply line Vdd. The organic EL element 16 has one electrode, here the cathode, connected to the reference voltage power supply line Vss. The drive transistor 22 outputs a light emission current having a current amount corresponding to the video signal to the organic EL element 16.

  The source of the output switch 26 is connected to the second terminal of the driving transistor 22, here the drain. The output switch 26 has a drain connected to the anode of the organic EL element 16 and a gate connected to the second scanning line Sgb. The output switch 26 is controlled to be on (conductive state) and off (non-conductive state) by a control signal Sb (1 to m) from the second scanning line Sgb, and the connection between the driving transistor 22 and the organic EL element 16 is not connected. Control the connection.

  The holding capacitor Cs is connected between the first terminal and the control terminal of the driving transistor 22, here, between the source and the gate, and holds the gate control potential of the driving transistor 22 determined by the video signal. The pixel switch 20 is connected between the corresponding video signal line X (1 to n) and the drain of the driving transistor 22, and its gate is connected to the first scanning line Sga. The pixel switch 20 captures the video signal current Idata as the gradation current from the corresponding video signal line X (1 to n) in response to the control signal Sa (1 to m) supplied from the first scanning line Sga.

  The first switch 24 is connected between the drain and gate of the drive transistor 22, and the gate thereof is connected to the first scanning line Sga. The first switch 24 is on / off controlled in accordance with a control signal Sa (1 to m) from the first scanning line Sga, controls connection / disconnection between the gate and drain of the drive transistor 22, and holds capacitance. Regulates current leakage from Cs.

  The red and blue subpixels PXR and PXB are formed in the same manner as the green subpixel PXG. However, in the subpixels PXR, PXG, and PXB arranged in the even rows, the pixel circuit 18 is formed on the left and right sides with the pixel circuits 18 of the subpixels PXR, PXG, and PXB arranged in the odd rows. As shown in FIGS. 1 and 2, in the subpixels PXR, PXG, and PXB arranged in even rows, the pixel switch 20 of the pixel circuit 18 is separated by two columns through the branch wiring H (1 to n). It is connected to video signal lines (1 to n) to which sub-pixels of the same color are connected.

Next, the configuration of the drive transistor 22 and the organic EL element 16 will be described in detail with reference to FIG. FIG. 4 shows a cross section of a subpixel including the organic EL element 16.
The P-channel type thin film transistor that constitutes the driving transistor 22 includes a semiconductor layer 50 made of polysilicon formed on the substrate 8, and this semiconductor layer is located between the source region 50a, the drain region 50b, and between the source and drain regions. Channel region 50c. A gate insulating film 52 is formed over the semiconductor layer 50, and a gate electrode G is provided on the gate insulating film so as to face the channel region 50c. An interlayer insulating film 54 is formed over the gate electrode G, and a source electrode (source) S and a drain electrode (drain) D are provided on the interlayer insulating film. The source electrode S and the drain electrode D are respectively connected to the source region 50a and the drain region 50b of the semiconductor layer 50 through contacts formed through the interlayer insulating film 54 and the gate insulating film 52, respectively. The drain electrode D of the drive transistor 22 is connected to the output switch 26 via a wiring formed on the interlayer insulating film 54 and the first switch 24a.
The thin film transistors constituting the pixel switch 20, the first switch 24a, and the output switch 26 are also formed in the same structure as described above.

  A plurality of wirings including the video signal lines X (1 to n) are provided on the interlayer insulating film 54. A protective film 56 is formed on the interlayer insulating film 54 so as to cover the source electrode S, the drain electrode D, and the wiring. On the protective film 56, a hydrophilic film 58 and a partition film 60 are laminated in this order.

  The organic EL element 16 has a structure in which an organic light emitting layer 64 containing a luminescent organic compound is sandwiched between an anode (anode) 62 and a cathode (cathode) 66. The anode 62 is made of a transparent electrode material such as ITO (indium tin oxide) and is provided on the protective film 56. Of the hydrophilic film 58 and the partition wall film 60, the part facing the anode 62 is removed by etching. An anode buffer layer 63 and an organic light emitting layer 64 are formed on the anode 62, and a cathode 66 made of silver / aluminum alloy is laminated on the organic light emitting layer 64 and the partition wall film 60.

  In the organic EL element 16 having such a structure, when the holes injected from the anode 62 and the electrons injected from the cathode 66 recombine inside the organic light emitting layer 64, organic molecules constituting the organic light emitting layer are formed. Is excited to generate excitons. The excitons emit light in the process of radiation deactivation, and the light is emitted from the organic light emitting layer 64 to the outside through the transparent anode 62 and the substrate 8.

  Here, the cathode 66 may be made light transmissive, and light may be taken out from the surface facing the substrate 8. Further, a reverse lamination type in which the anode 62 is disposed on the substrate 8 side with respect to the cathode 66 may be employed. In either case, it is necessary to form the light emitting surface side with a transparent conductive material. For example, when the anode 62 is disposed on the light emitting surface side, the alkaline earth metal and the rare earth metal are thin enough to have optical transparency. This can be achieved by forming.

  Wiring electrodes including the video signal lines X (1 to n) and the first and second scanning lines Sga and Sgb formed on the substrate 8 are Al, Ti or titanium nitride (TiN), Ta, Mo, Cr, W , Cu, Nd, Zr, or any other kind of metal is formed in a single layer or a laminated structure of two or more layers. The present invention is not limited to this material.

  On the other hand, the controller 12 shown in FIG. 1 is formed on a printed circuit board disposed outside the organic EL panel 10 and controls the scanning line driving circuit 14 and the signal line driving circuit 15. The controller 12 receives a digital video signal and a synchronization signal supplied from the outside, and generates a vertical scanning control signal for controlling the vertical scanning timing and a horizontal scanning control signal for controlling the horizontal scanning timing based on the synchronizing signal. The controller 12 supplies the vertical scanning control signal and the horizontal scanning control signal to the scanning line driving circuit 14 and the signal line driving circuit 15, respectively, and drives the digital video signal in synchronization with the horizontal and vertical scanning timings. Supply to the circuit 15. The signal line driving circuit 15 converts the video signals sequentially obtained in each horizontal scanning period into the analog format under the control of the horizontal scanning control signal to generate the video signal current Idata, and is parallel to the plurality of video signal lines X (1 to n). To supply.

  The operation of the pixel circuit 18 is divided into a video signal writing operation and a light emission operation. As shown in FIG. 3, in the video signal writing operation, the control signals Sa1 and Sb1, in which the pixel switch 20 and the first switch 24 are turned on (conductive state) and the output switch 26 is turned off (non-conductive state), here , The control signal Sa is low level and the control signal Sb is high level. Thereby, the pixel switch 20 and the first switch 24 are turned on (conductive state), the output switch 26 is turned off (non-conductive state), and the video signal writing operation is started.

  In the video signal writing period, the video signal current Idata supplied from the signal line driving circuit 15 to the corresponding video signal line X (1 to n) is supplied to the selected subpixels PXR, PXG, and PXB via the pixel switch 20. Supplied. In the sub-pixels PXR, PXG, and PXB, the pixel switch 20 and the first switch 24 are in an on state, and the captured video signal current Idata is supplied to the drive transistor 22 so that the drive transistor 22 is in a write state. As a result, a write current flows from the voltage power supply line Vdd to the video signal line X through the drive transistor 22, and the gate-source potential of the drive transistor 22 corresponding to the current amount of the video signal current Idata is written to the storage capacitor Cs.

  Next, the control signal Sa1 becomes a high level (off potential), and the pixel switch 20 and the first switch 24 are turned off. Thereby, the video signal writing operation is completed. Subsequently, the control signal Sb1 becomes low level, and the output switch 26 is turned on. Thereby, the light emission operation starts. In the light emission period, the drive transistor 22 is maintained in a conductive state by the gate control voltage written in the storage capacitor Cs, and supplies a light emission current having a current amount corresponding to the video signal current Idata from the voltage power supply line Vdd to the output switch 26 side. To do. This light emission current is supplied to the organic EL element 16 after passing through the output switch 26. Thereby, the organic EL element 16 emits light, and the light emission operation is started. The organic EL element 16 maintains the light emission state until the control signal Sb1 becomes the off potential again after one frame period.

  According to the organic EL display device configured as described above, the sub-pixels of the three colors constituting each display pixel are arranged in a delta arrangement, and each video signal line is formed in a straight line and arranged in odd rows. Among the sub-pixels, they are connected to the same-color sub-pixels arranged in the same column. Of the sub-pixels arranged in even rows, the sub-pixels of the same color arranged in the same column are connected to the video signal lines to which the sub-pixels of the same color are connected via branch wirings. Thus, even when the subpixels of the three colors are arranged in a delta arrangement, each video signal line can be formed in a straight line, and the wiring capacity of the video signal line can be compared with the case where a zigzag video signal line is used. Can be reduced. Therefore, even when writing a low-gradation video signal current, the video signal current can be written sufficiently and in a short time without being affected by the wiring capacity, resulting in poor display at low brightness, unevenness, and roughness. Visual recognition can be eliminated and high-quality image display can be realized.

  The sub-pixels in the even rows are connected to the video signal lines to which the sub-pixels of the same color are connected through the branch wirings, respectively, and the branch wirings are unevenly distributed closer to the sub-pixels in the even rows. . Therefore, branch wiring exists only on one side in the column direction of each subpixel, and the occupied area of the wiring in the entire effective region can be reduced. Thereby, it is possible to prevent the aperture ratio from being lowered and to improve the display quality.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  In the embodiment described above, each video signal line is connected to subpixels of the same color arranged in the same column among the subpixels arranged in an odd row. Of the sub-pixels arranged in even rows, the sub-pixels of the same color arranged in the same column are connected to the video signal lines to which the sub-pixels of the same color are connected via branch wirings. Not limited to this, each video signal line is connected to sub-pixels of the same color arranged in the same column among sub-pixels arranged in even rows, and arranged in the same column among sub-pixels arranged in odd rows. The sub-pixels of the same color may be connected to the video signal line to which the sub-pixels of the same color are connected through branch wirings. In this case, the branch wiring is provided unevenly near the odd-numbered subpixels.

  In the above-described embodiments, the semiconductor layer of the thin film transistor is not limited to polysilicon, but can be composed of amorphous silicon. The self-luminous elements constituting the display pixels are not limited to organic EL elements, and various display elements capable of self-luminance are applicable.

FIG. 1 is a plan view schematically showing an organic EL display device according to an embodiment of the present invention. FIG. 2 is a plan view showing an arrangement of a plurality of subpixels, video signal lines, and voltage power supply lines in the organic EL display device. FIG. 3 is a plan view showing an equivalent circuit of the display pixel. FIG. 4 is a cross-sectional view of the organic EL display device including the driving transistor and the organic EL element.

Explanation of symbols

8 ... Insulating substrate, 10 ... Organic EL panel, 12 ... Controller,
14 ... scanning line driving circuit, 15 ... signal line driving circuit, 16 ... organic EL element,
18 ... Pixel circuit, 20 ... Pixel switch, 22 ... Drive transistor,
24 ... 1st switch, 26 ... Output switch, X (1-n) ... Video signal line,
H (1 to n): Branch wiring, Vdd: Voltage power supply line

Claims (6)

A plurality of pixel portions arranged in a matrix on the substrate;
A plurality of linear video signal lines provided side by side for each column of the pixel portion,
Each pixel unit includes a self-light-emitting element and a pixel circuit that supplies a driving current to the self-light-emitting element, and includes three-color subpixels arranged in a delta arrangement. The three color subpixels are alternately arranged in each row. The odd-numbered row subpixels and the even-numbered row subpixels are arranged so as to be shifted in the row direction, and the subpixels of the same color are provided in the same column for each of the plurality of columns.
Each of the video signal lines is connected to sub-pixels arranged in the same column in sub-pixels arranged in either one of the odd-numbered rows or even-numbered rows, and out of sub-pixels arranged in the other row. An active matrix display device in which sub-pixels of the same color arranged in the same column are connected to video signal lines to which the sub-pixels of the same color are connected through branch wirings. A plurality of linear voltage power supply lines provided side by side in each column of the pixel portion,
2. The active matrix display device according to claim 1, wherein the voltage power supply line is provided alternately with the video signal line and is connected to a sub-pixel of each column.   3. The video signal line and the voltage power supply line are provided side by side on each side of each column of subpixels, and the branch wiring is unevenly distributed closer to the subpixels in odd rows or even rows. Active matrix display device.   The drive circuit of the sub-pixel includes a drive transistor that supplies a drive current corresponding to a video signal current to the self-light-emitting element, and the self-light-emitting element and the drive transistor between the voltage power line and another voltage power source. An output switch connected in series, a first switch for holding a video signal current written to the driving transistor, a holding capacitor for holding a potential difference between the gate and source of the driving transistor constant, and selection and non-selection of subpixels The active matrix display device according to claim 1, further comprising: a pixel switch that controls selection.   5. The active matrix display device according to claim 4, wherein the drive transistor, the first switch, the pixel switch, and the output switch are configured by thin film transistors using polysilicon as a semiconductor layer.   6. The active matrix display device according to claim 1, wherein each of the self-light-emitting elements includes an opposing electrode and an organic light-emitting layer sandwiched between the electrodes.

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