JP2005166687A - Color el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color EL display device capable of keeping a high color purity even by high integration by preventing the deterioration of color purity caused by mixing of colors between adjacent pixels in a color EL display device having light emitting layers emitting different colors for every pixel. <P>SOLUTION: A part of a capacitor 5 is arranged in the horizontal direction of a light emitting area 7 to ensure the horizontal space of the light emitting area. Even if a fitting slippage of a metal mask is caused at the time of evaporation of the light emitting layers, different colors are hardly mixed because the horizontal distance is ensured. Part of the capacitor 5 or TFT 4 and 6 are arranged also in the vertical direction of the light emitting area. Accordingly, high color purity can be ensured also for pixels adjacent in the line direction in a delta array. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an active color EL display device that drives an electroluminescence (EL) element using a thin film transistor (TFT).

  Since organic EL elements emit light themselves, they do not require a backlight necessary for liquid crystal display devices and are optimal for thinning, and there are no restrictions on viewing angles. ing.

  In a display device using such an organic EL element, three methods are currently proposed as methods for realizing color display.

  The first method uses a different light emitting material for the light emitting layer for each of the three primary colors of RGB to independently form each pixel that directly emits RGB light, and the second method uses white light emitted from the light emitting layer. A method of realizing light emission and dividing it into three primary colors with a color filter, and a third method are methods for converting light from a blue light emitting layer into three primary colors with a color conversion layer (CCM). Among these three methods, the second and third methods use a color filter and a color conversion layer, and thus there is a loss of light. However, the first method has the highest efficiency because it directly emits necessary light.

  By the way, there are two types of driving methods for the organic EL display device: a passive type using a simple matrix and an active type using a TFT, and the circuit configuration shown in FIG. 8 is generally used in the active type.

  FIG. 8 shows a circuit configuration per pixel, and includes an organic EL element 20, a first TFT 21 for switching that is turned on / off by a display signal Data applied to the drain and a selection signal Scan applied to the gate. The TFT is charged by the display signal Data supplied when the TFT 21 is turned on. When the TFT 21 is turned off, the capacitor 22 holding the charging voltage Vh and the drain are connected to the drive power supply voltage COM, and the source is connected to the anode of the organic EL element 20. And a second TFT 23 that drives the organic EL element 20 by supplying the holding voltage Vh from the capacitor 22 to the gate.

  The selection signal Scan becomes H level during the selected one horizontal scanning period (1H). When the TFT 21 is turned on by this, the display signal Data is supplied to one end of the capacitor 22, and the voltage Vh corresponding to the display signal Data is supplied to the capacitor. 22 is charged. This voltage Vh continues to be held in the capacitor 22 for one vertical scan (1 V) period even when the TFT becomes L level and the TFT 21 is turned off. Since the voltage Vh is supplied to the gate of the TFT 23, the EL element is controlled to emit light with a luminance corresponding to the voltage Vh.

  A conventional configuration for realizing color display by the above-described first method in such an active EL display device will be described below.

  FIG. 5 is a plan view showing a conventional configuration, and FIG. 6 is a cross-sectional view taken along the line CC in FIG. 5, showing three pixels of RGB.

In the figure, 50 is a drain line for supplying a display signal DATA, 51 is a power supply line for supplying a power supply voltage COM, 52 is a gate line for supplying a selection signal Scan, 53 is a first TFT 21, 54 in FIG. The capacitors 22 and 55 in FIG. 8 represent the anodes of the EL elements 20 constituting the pixel electrodes and the second TFTs 23 and 56 in FIG. The anode 56 is formed separately for each pixel on the planarization insulating film 60, and a hole transport layer 61, a light emitting layer 62, an electron transport layer 63, and a cathode 64 are sequentially stacked thereon, so that the EL An element is formed. Then, the holes injected from the anode 56 and the electrons injected from the cathode 64 are recombined inside the light emitting layer 62 to emit light, and this light is transparent on the anode side as shown by the arrows in FIG. Is emitted from the outside. The light emitting layer 62 is formed in the same shape as the anode 56 separately for each pixel, and further, by using a different light emitting material for each RGB, each light of RGB is emitted from each EL element. Incidentally, 65 is a transparent glass substrate, 66 is a gate insulating film, and 67 is an interlayer insulating film.

  The arrangement of the conventional first TFT 53, capacitor 54, second TFT 55, and anode 56 does not fully consider the degree of integration, and higher integration is desired.

  In general, the color display device adopts the stripe arrangement shown in FIG. 7A or the delta arrangement shown in FIG. 7C as the arrangement of the three primary colors RGB. On the other hand, as described above, in order to directly emit light of each color of RGB from independent EL elements, it is necessary to change the light emitting material used for each RGB. Therefore, for example, when the stripe arrangement shown in FIG. 7A is adopted, a metal mask 70 as shown in FIG. 7B is used, and a light emitting material of only R is first deposited on the hole transport layer. Then, the R light emitting layer is formed, and then the metal mask 70 is shifted by one pixel in the horizontal direction to deposit a G light emitting material on the hole transport layer to form the G light emitting layer. The B light emitting layer may be formed by further shifting the mask 70 in the horizontal direction by one pixel and evaporating only the B light emitting material on the hole transport layer. In the case of the delta arrangement shown in FIG. 7C, it can be formed by the same method using the metal mask shown in FIG.

  In such a method, if the dimensional accuracy of the metal mask and the alignment accuracy when shifting the metal mask are not good, there is a problem that colors are mixed between adjacent pixels and the color purity is deteriorated. If further higher integration is performed in the future, the alignment accuracy of the metal mask may become a problem.

  Accordingly, an object of the present invention is to provide a pixel arrangement that realizes further higher integration and to provide a color EL display device in which the alignment accuracy of a metal mask is less likely to be a problem even when higher integration is performed.

  The present invention includes an EL element having a light emitting layer between an anode and a cathode, a gate line, a drain line, a power line for supplying a current corresponding to a signal of the drain line to the light emitting layer, the gate line, In a color EL display device including a first thin film transistor connected to a drain line, a second thin film transistor for driving the EL element, and a capacitor for holding a voltage supplied to the second thin film transistor, a gate is formed in a first direction. Drain lines are arranged in a second direction intersecting the first direction, the light emitting areas adjacent to each other in the direction in which the gate line extends are different from each other, and the light emitting areas are formed for the same color, The ratio of the length in the first direction / the length in the second direction of the light emitting region of each pixel is the first direction of the pixel pitch. Wherein the smaller than the ratio of length / length of the second direction.

  According to the present invention, in an active type color EL display device, it is possible to prevent color purity between adjacent colors from being mixed and to deteriorate color purity, and to maintain good color purity even in high-definition display. become able to.

  In other words, since the horizontal / vertical ratio of the light emitting area of each pixel is made smaller than the horizontal / vertical ratio of the pixel pitch, there is room in the horizontal direction within the pixel, and high definition is achieved even if the alignment accuracy for shifting the metal mask is low Can be.

  In addition, since at least a part of the capacitor or thin film transistor is arranged in the horizontal direction of the light emitting area of each pixel, similarly, there is a margin in the horizontal direction within the pixel, and high definition even if the alignment accuracy for shifting the metal mask is low. can do.

  The present invention is naturally applicable to a delta arrangement, but the above effect is particularly effective in a stripe arrangement.

  Embodiments of the EL display device of the present invention will be described below.

  FIG. 1 is a plan view showing an embodiment of a color EL display device according to the present invention, showing three pixels of RGB. 2 is a cross-sectional view taken along the line AA in FIG. The present embodiment is an example of the stripe arrangement of FIG.

  The drive circuit of each pixel is exactly the same as the circuit shown in FIG. 8, and the difference from the conventional example of FIGS. 5 and 6 is the pattern arrangement.

  1 and 2, 1 is a drain line made of aluminum for supplying a display signal DATA, 2 is a power line made of aluminum for supplying a power supply voltage COM, 3 is a gate line made of chrome for supplying a selection signal Scan, Reference numeral 4 denotes the first TFT 21 in FIG. 8, 5 denotes the capacitor 22 in FIG. 8, 6 denotes the second TFT 23 in FIG. 8, and 7 denotes the anode of the EL element 20 made of ITO and constituting the pixel electrode. In FIG. 1, the dotted line represents chromium, the alternate long and short dash line represents ITO, and the solid line other than the drain line 1 and the power supply line 2 represents a polysilicon thin film.

  First, the second TFT 6 is formed as follows. That is, a chromium gate electrode 9 is formed on a transparent glass substrate 8, and a gate insulating film 10 is formed thereon. Next, a polysilicon thin film 11 is formed on the gate insulating film 10, and the drain line 1 and the power supply line 2 are formed on the polysilicon thin film 11 covered with the interlayer insulating film 12. Further, a planarization insulating film 13 is laminated, and an anode 7 made of ITO is formed thereon. Then, the drain region of the polysilicon thin film 11 is contacted to the power supply line 2, and the source region is contacted to the anode 7.

  The structure of the first TFT 4 is the same as that of the second TFT 6, and the capacitor 5 connected to the first TFT 4 is composed of a chromium electrode and a polysilicon thin film with a gate insulating film interposed therebetween.

Further, as in the conventional example of FIG. 6, the anode 7 is formed separately for each pixel on the planarization insulating film 13, on which the hole transport layer 14, the light emitting layer 15, the electron transport layer 16, and the cathode are formed. The EL elements are formed by sequentially stacking 17. Then, the holes injected from the anode 7 and the electrons injected from the cathode 17 are recombined inside the light emitting layer 15 to emit light, and this light is emitted from the transparent anode side to the outside as indicated by arrows. Radiated. Further, the light emitting layer 15 is formed in the same shape as the anode 7 separately for each pixel, and further, by using a different light emitting material for each RGB, each light of RGB is emitted from each EL element.

  Here, as materials for the hole transport layer 14, the electron transport layer 16, and the cathode 17, for example, MTDATA, Alq3, and MgIn alloy are used, and for each of the R, G, and B light emitting layers 15, a DCM system is used. Alq containing a dopant, Alq containing quinacridone as a dopant, and DPVBi containing a distyrylarylene system as a dopant are used.

  In the present embodiment, as shown in the figure, the second TFT 6 and a part of the capacitor are arranged in the horizontal direction of the anode 7 which is the pixel electrode. Can be vertically long. As described above, since the pixel electrode 7 and the light emitting layer 15 are formed in substantially the same shape, the light emitting region of the pixel has substantially the same shape as the pixel electrode. Therefore, in this case, assuming that the horizontal dimension and the vertical dimension of the light emitting region are EH and EV, respectively, and the horizontal dimension and the vertical dimension of the pixel pitch are PH and PV, respectively, EH / EV <PH / PV.

  Therefore, when depositing the RGB light emitting layers while shifting the metal mask, the horizontal margin for shifting the metal mask will increase compared to the conventional case, and there is a possibility that colors will be mixed even if deposited with the same accuracy. Will be less. Note that the first TFT 4 may be disposed in the horizontal direction of the anode 7 instead of the second TFT 6.

  By the way, in the step of depositing the light emitting layer, a phenomenon of so-called wrapping occurs in which the light emitting layer is deposited not only directly below the openings of the metal masks 70 and 71 but also in other regions. When the wraparound occurs or the error in the dimensional accuracy of the metal mask itself occurs, there is a problem that colors are mixed between adjacent pixels and the color purity is deteriorated. In particular, in the delta arrangement, pixels adjacent to each other in the row direction and the column direction are pixels of different colors, and thus the above-described problem becomes more significant.

  In the present embodiment, a part of the capacitor 5 is arranged in the horizontal direction of the light emitting region and continuously extends to the vertical direction of the light emitting region. As a result, since at least a part of the capacitor or the thin film transistor is arranged in the vertical direction of the light emitting region of each pixel, similarly, there is a margin in the vertical direction between the pixels, and high definition even if the alignment accuracy of the metal mask is low. As a result, good color purity can be maintained even in high-definition display.

  Next, another embodiment will be described with reference to FIGS.

  FIG. 3 is a plan view showing another embodiment, and FIG. 4 is a sectional view taken along line BB in FIG. The same configurations as those in FIGS. 1 and 2 are denoted by the same reference numerals, and this embodiment differs from the above-described embodiment only in the pattern arrangement.

  That is, in FIGS. 3 and 4, 4 is the first TFT 21 of FIG. 8, 5 is the capacitor 22 of FIG. 8, 6 is the second TFT 23 of FIG. 20 anodes are represented. In particular, FIG. 4 clearly shows that the capacitor 5 is composed of a chromium electrode 500 and a polysilicon thin film 501 with the gate insulating film 10 interposed therebetween.

  In this embodiment, as shown in the figure, the capacitor 5 is arranged in the horizontal direction of the anode 7 which is the pixel electrode. Therefore, the shape of the pixel electrode can be made longer than the conventional example of FIGS. Therefore, in this case as well, the horizontal dimension and the vertical dimension of the light emitting region are respectively EH and EV, and the horizontal dimension and the vertical dimension of the pixel pitch are PH and PV, respectively, as in the above-described embodiment. EH / EV <PH / PV.

  Therefore, when forming each RGB light emitting layer while shifting the metal mask, the horizontal margin for shifting the metal mask is increased compared to the conventional case, and there is less possibility of color mixing even when forming with the same accuracy. Become.

  In the present embodiment, the capacitor 5 is arranged in the horizontal direction of the light emitting region, and both the first TFT 4 and the second TFT 6 are arranged in the vertical direction of the light emitting region. The capacitor 5 secures the horizontal spacing between the pixels in the light emitting area, and the two TFTs 4 and 6 secure the vertical direction between the pixels in the light emitting area, thereby preventing color blur due to wraparound as in the first embodiment. .

  Of course, the arrangement of the light emitting regions to ensure the interval between the light emitting regions may not be a capacitor. However, the capacity of the capacitor is proportional to the area, and if the capacity of the capacitor is large, the voltage Vh corresponding to the display signal Data can be held reliably. Therefore, the area of the capacitor is increased and the necessary interval is secured. be able to. Therefore, it is most efficient to adjust the interval by arranging the capacitor 5.

It is a top view which shows the 1st Embodiment of this invention. It is sectional drawing which shows the 1st Embodiment of this invention. It is a top view which shows the 2nd Embodiment of this invention. It is sectional drawing which shows the 2nd Embodiment of this invention. It is a top view which shows the structure of the conventional color EL display apparatus. It is sectional drawing which shows the structure of the conventional color EL display apparatus. It is a figure for demonstrating the color arrangement | sequence in a color EL display apparatus. It is a figure which shows the circuit structure of an active type color EL display apparatus.

Explanation of symbols

1,50 Drain line 2,51 Power line 3,52 Gate line 4,21,53 First TFT
5, 22, 54 Capacitor 6, 23, 55 Second TFT
7,56 Anode 20 EL element 14 Hole transport layer 15 Light emitting layer 16 Electron transport layer 17 Cathode

Claims (8)

An EL element having a light emitting layer between an anode and a cathode, a gate line, a drain line, a power line for supplying a current corresponding to a signal of the drain line to the light emitting layer, and a connection to the gate line and the drain line A color EL display device comprising: a first thin film transistor that performs a second thin film transistor that drives the EL element; and a capacitor that holds a voltage supplied to the second thin film transistor.
A gate line in a first direction and a drain line in a second direction intersecting the first direction, respectively,
The colors of the light emitting areas adjacent in the first direction are different from each other,
The light emitting area is formed for each same color,
The ratio of the length in the first direction / the length in the second direction of the light emitting region of each pixel is the ratio of the length in the first direction / the length in the second direction of the pixel pitch. A color EL display device characterized by being small. The color EL display device according to claim 1, wherein the capacitor is disposed in a region adjacent to the light emitting region in the first direction. The color EL display device according to claim 2, wherein the capacitor is disposed in a region adjacent to the light emitting region in the second direction. 2. The capacitor according to claim 1, wherein the capacitor is continuously extended from a region adjacent to the light emitting region in the first direction to a region adjacent to each light emitting region in the second direction. 4. A color EL display device according to item 3. 5. The color EL display device according to claim 1, wherein the second thin film transistor is disposed in a region adjacent to the light emitting region in the first direction. The color EL display device according to claim 5, wherein the first thin film transistor is disposed in a region adjacent to the light emitting region in the second direction. 7. The color EL display device according to claim 1, wherein the light emitting regions are arranged in a matrix, and the light emitting regions of the same color are arranged in a stripe arrangement adjacent to each other in the column direction. The color EL display device according to claim 1, wherein the light emitting layer is deposited using a mask.

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