JP2006126470A - Organic electroluminescence display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescence display apparatus capable of reducing a luminance slope caused by a resister portion which exists in a common electrode wiring line. <P>SOLUTION: A printed wiring board 21, on which a common driver 11 is mounted and wiring is applied from each output terminal of the common driver 11, extending to both right and left ends or their neighborhood, is provided and a flexible cable 22 connects the common electrode wiring line to the wiring line of the left end of the printed wiring board 21 or its neighborhood. A flexible cable 23 connects the common electrode wiring line to the wiring line of the right end of the printed circuit board or to a wiring in the vicinity of the board. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic EL display device using an organic electroluminescence light emitting element (hereinafter referred to as an organic EL element).

  An organic EL display device using an organic EL panel having a structure in which an organic EL element is arranged in each pixel portion of a matrix electrode is realized. In an organic EL panel, for example, on a substrate such as a glass substrate, a plurality of anode wirings using a transparent conductive film such as ITO that is connected to an anode or forms the anode itself is arranged in a vertical direction, for example, and orthogonal thereto. In this direction, a plurality of cathode wirings using a metal that is connected to the cathode or forms the cathode itself is arranged, for example, in the lateral direction. The intersection of the anode wiring and the cathode wiring becomes a pixel, and an organic thin film (organic EL element) is sandwiched between the wirings. As described above, the pixels formed of the organic EL elements are arranged on the substrate in a matrix form (see, for example, Patent Document 1).

  Organic EL elements have characteristics similar to semiconductor light emitting diodes. That is, when the anode side is set to the high voltage side and a predetermined voltage is applied between both electrodes to supply a current to the organic EL element, light is emitted. Specifically, when the difference between the potential on the anode side and the potential on the cathode side becomes equal to or higher than the emission start voltage, current starts to flow through the organic EL element. Conversely, when the cathode side is set to a high potential, no current flows and no light is emitted.

  A passive organic EL panel can be driven by a simple matrix driving method. When driving, the anode wiring and cathode wiring of the organic EL panel can be set to either scanning electrode wiring (common electrode wiring) or data electrode wiring (segment electrode wiring). That is, the anode wiring can be a common electrode wiring and the cathode wiring can be a segment electrode wiring, or the anode wiring can be a segment electrode wiring and the cathode wiring can be used as a common electrode wiring. Hereinafter, a case where the cathode wiring is a common electrode wiring and the anode wiring is a segment electrode wiring is taken as an example.

  In an organic EL display device using a passive organic EL panel, a common driver is mounted in order to apply a drive voltage (generally a ground potential) as a selection voltage to each common electrode wiring line by line. In addition, a segment driver that includes a constant current circuit connected to each segment electrode wiring and drives the constant current circuit according to display data is mounted. The common driver and the segment driver are each realized by a one-chip LSI. In general, as shown in the explanatory diagram of FIG. 9, the common driver 11 is disposed on the right outer side or the left outer side of the organic EL panel 10 (left outer side in FIG. 9), and the segment driver 12 is the upper outer side or the lower side of the organic EL panel 10. It is arranged outside (upper outside in FIG. 9). The common driver 11 and segment driver 12 are mounted by COG (chip on glass) mounting or COF (chip on film) mounting. When the number of segment electrode wires is large, a plurality of segment drivers may be installed.

Japanese Patent Application Laid-Open No. 9-232074

  Since the organic EL element is a current driving element that emits light when a current flows, the luminance depends on the amount of current. In the passive organic EL panel, when line-sequential driving is performed, a current flows through the organic EL element of each pixel only in one selection period in one frame. Therefore, in order to ensure high luminance as the entire organic EL panel, it is necessary to pass a large amount of current through each organic EL element.

  The current supplied from the constant current circuit at the time of lighting flows through the common electrode wiring and into the common driver 11 having the ground potential as the selection voltage. Since the common electrode wiring extending in the horizontal direction in the organic EL panel is formed of a metal wiring such as Al or Cr, it has a sheet resistance of about 0.1Ω / □. Therefore, as shown in the explanatory diagram of FIG. 10, in the common electrode wiring, the potential (COM potential) ΔV increases as the distance from the common driver 11 increases. Specifically, being far from the common driver 11 means being far from the connection portion with the common driver 11 in the common electrode wiring.

  As described above, since the organic EL element is a current driving element, the luminance of each pixel does not vary as long as a constant current is supplied even if a potential difference occurs in the common electrode wiring. However, when particularly high luminance is required for the organic EL panel, or when the screen size is large and the common electrode wiring length is long, the luminance of the pixel is lowered at a portion away from the common driver 11 as described below. However, a phenomenon in which the luminance changes in the display screen (luminance gradient) may occur.

FIG. 11 is a schematic diagram showing one common electrode wiring 81, a switching unit 11a in the common driver 11, and constant current circuits 12a, 12b, 12c, and 12n in the segment driver 12 together with diodes that schematically represent pixels. The voltage applied to the pixel is V _pi (i = 1 to n), the power supply voltage of the constant current circuits 12a to 12n is V _in , the potential of the pixel on the wiring 81 side is V _i (i = 1 to n), and the pixel is When the flowing current is I _i (i = 1 to n),
V _in −V _pi −V _i ≧ V _th (Formula 1)
As long as the above conditions are satisfied, the constant current circuits 12a to 12n can pass a constant current regardless of the value of the applied voltage, and the luminance does not change. Here, _Vth is a lower limit voltage at which the constant current circuits 12a to 12n can flow a constant current (a lower limit value of an applied voltage of the constant current circuits 12a to 12n that can flow a constant current). In FIG. 11, SEG _i (i = 1 to n) indicates the i-th segment electrode, and COM _x indicates the x-th common electrode.

However, V _i increases on the side far from the common driver 11 in the common electrode wiring 81. If V _i rises so that Equation 1 cannot be satisfied, as shown in FIG. 12, the constant current circuit cannot supply a constant current sufficient to generate the original luminance, and is connected to the constant current circuit. The brightness of the pixel is reduced. As a result, a luminance gradient occurs as shown in FIG. In FIG. 13, the rectangle indicates the display area of the organic EL panel. As described above, the conventional organic EL display device has a problem that there is a possibility that a luminance gradient may occur.

  Therefore, an object of the present invention is to provide an organic EL display device capable of reducing a luminance gradient due to a resistance component existing in a common electrode wiring.

  The organic EL display device according to the present invention is arranged in the vertical direction in the display area so as to intersect with the plurality of common electrode wirings, the organic EL layer, and the common electrode wiring arranged in the horizontal direction in the display area according to display data. An organic EL display device comprising an organic EL panel in which a plurality of segment electrode wirings to be driven are formed on a substrate and a single common driver that drives the plurality of common electrode wirings in a line-sequential manner. Equipotential equalizing means for aligning the potentials at both ends of the common electrode wiring is provided.

  According to a first preferred embodiment of the organic EL display device of the present invention, the equipotential means has a common driver and is printed with wiring extending from each output terminal of the common driver to the left and right ends or the vicinity thereof. A wiring board, a first flexible cable for connecting the wiring at the left end of the printed wiring board or in the vicinity thereof and the common electrode wiring, and a second flexible cable for connecting the wiring at the right end of the printed wiring board or in the vicinity thereof and the common electrode wiring And a flexible cable.

  In a second preferred embodiment of the organic EL display device according to the present invention, the equipotential means is equipped with a common driver, and wiring extending from each output terminal of the common driver to the end portion or the vicinity thereof is applied. A flexible substrate having a first connection portion for connecting the wiring to one end portion of the common electrode wiring and a second connection portion for connecting each wiring to the other end portion of the common electrode wiring; It is characterized by that.

  In a third preferred embodiment of the organic EL display device according to the present invention, the common driver is mounted on a substrate on which the common electrode wiring, the organic EL layer, and the segment electrode wiring are formed, and the equipotential means includes at least the common electrode wiring. The same number of wires are provided, the first flexible cable having a connecting portion for connecting each wire to one end portion of the common electrode wire, and at least the same number of wires as the common electrode wire are provided, and each wire is connected to the common electrode. A second flexible cable having a connection portion for connecting to the other end portion of the wiring, wherein the first flexible cable and the second flexible cable are each wiring in the own cable and each wiring in the other cable, It has the connection part for connecting 1 to 1 to 1 characterized by the above-mentioned.

  According to the present invention, there is provided an organic EL display device that can make the left end and the right end of the common electrode wiring have the same potential without increasing the cost, and can reduce the possibility of occurrence of a luminance gradient. be able to.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a front view showing a first embodiment of an organic EL display device according to the present invention, and FIG. The organic EL panel 10 has a structure in which an organic EL element (not shown) in which a plurality of common electrode wirings, a plurality of segment electrode wirings, and a plurality of organic EL layers are formed on a glass substrate 13 is provided. . Furthermore, in order to protect the organic EL panel 10 from moisture or the like, a counter substrate (sealing substrate) 14 made of a glass substrate is installed. The area where the intersection of the common electrode line and the segment electrode line exists becomes the display area 100. In FIG. 1, the common electrode wiring is shown as COM, and the segment electrode wiring is shown as SEG.

  In the front view of FIG. 1A, wirings connected to the respective common electrode wirings are provided on the left and right sides of the organic EL panel 10. Alternatively, the common electrode wiring is formed so that both ends of the common electrode wiring extend to the vicinity of both the left and right ends of the organic EL panel 10. That is, the organic EL panel 10 is formed such that portions that can be electrically connected to the respective common electrode wirings exist in the vicinity of the left and right ends of the organic EL panel 10.

  A common driver 11 of a single one-chip LSI that applies a driving voltage to the common electrode wiring is mounted on a rigid (hard) printed wiring board 21. FIG. 2 is a plan view of the printed wiring board 21 as viewed from the side where the common driver 11 in FIG. 1B is installed. As shown in FIG. 2, wirings 27 and 29 extending from the output terminal of the common driver 11 to the vicinity of both left and right ends of the printed wiring board 21 are formed on the printed wiring board 21 with copper or gold. The wiring is formed so as to extend to the vicinity of the left and right ends of the printed wiring board 21 for each output terminal of the common driver 11, that is, each terminal that applies a driving voltage to one common electrode. In FIG. 2, only the wiring from one output terminal of the common driver 11 is representatively attached.

  In the example shown in FIG. 2, the through hole 25 is provided in the middle of the wiring 27 extending to the right side from the output terminal of the common driver 11, and the wiring 28 is electrically connected to the through hole 25 on the back surface of the printed wiring board 21. The wiring 28 is electrically connected to the through hole 26 provided on the left side of the common driver 11. A wiring 29 that is electrically connected to the through hole 26 is provided on the surface of the printed wiring board 21. Accordingly, wirings 27 and 29 extending from one output terminal of the common driver 11 to the vicinity of both left and right ends of the printed wiring board 21 are formed.

  Such a wiring pattern is an example, and other wiring patterns can be adopted as long as wiring extending from the respective output terminals of the common driver 11 to the vicinity of both left and right ends of the printed wiring board 21 can be formed.

  As shown in FIGS. 1 and 2, one end of the flexible cable 22 is connected to one end of a portion that can be electrically connected to the common electrode wiring in the organic EL panel 10, and the other end of the flexible cable 22 is printed. The wiring board 21 is connected to a wiring 29 extending to the left end (or the vicinity of the left end). The flexible cable 22 is formed with wirings for electrically connecting the respective wirings 29 and the respective common electrode wirings in the organic EL panel 10 in a one-to-one relationship.

  One end of the flexible cable 23 is connected to the other end of the portion that can be electrically connected to the common electrode wiring in the organic EL panel 10, and the other end of the flexible cable 23 is connected to the right end (or right end of the printed wiring board 21). Connected to the wiring 27 extending to the vicinity. In the flexible cable 23, wirings for electrically connecting the respective wirings 27 and the respective common electrode wirings in the organic EL panel 10 in a one-to-one manner are formed.

  Wiring is exposed at the portion connected to the organic EL panel 10 and the portion connected to the printed wiring board 21 in the flexible cable 22. Further, the wiring is exposed at the portion connected to the organic EL panel 10 and the portion connected to the printed wiring board 21 in the flexible cable 23.

Therefore, in a state where the organic EL panel 10 and the printed wiring board 21 are connected by the flexible cables 22 and 23, each common electrode wiring is in a ring shape, and the left end and the right end of the common electrode wiring are substantially equipotential. Become. As a result, as shown in the explanatory diagram of FIG. 3, in the organic EL panel 10, the COM potential increases as the distance from the end (left end or right end) of the common electrode wiring increases, but the potential difference from the end of the common electrode wiring increases. The potential difference ΔV / 2 at the largest portion is halved compared to the conventional case (see FIG. 10). Therefore, the possibility that the potential difference ΔV / 2 exceeds V _th (see FIG. 12) is lower than in the conventional case. As a result, the possibility of luminance gradients is reduced.

  Note that the sum of the resistance of the wiring 29 in the printed wiring board 21 and the resistance of the wiring in the flexible cable 22 is exactly the same as the sum of the resistance of the wiring 27 in the printed wiring board 21 and the resistance of the wiring in the flexible cable 23. Since it is rare that the value becomes a value, it is rare that the left end and the right end of the common electrode wiring have exactly the same potential. However, the resistance of the wirings 27 and 29 in the printed wiring board 21 and the resistance of the wirings in the flexible cables 22 and 23 are much smaller than the resistance of the common electrode wiring. And the right end are equipotential.

(Embodiment 2)
In the first embodiment, the common driver 11 is mounted on a hard printed wiring board 21 separated from the organic EL panel 10, and the printed wiring board 21 and the organic EL panel 10 are connected by two flexible cables 22 and 23. Although the left and right ends of each common electrode wiring are made equipotential by connecting, even when the common driver 11 is mounted on a flexible substrate, that is, when COF mounting is performed, the left and right ends of the common electrode wiring are equal. Can be a potential.

  4A is a front view showing a second embodiment in which the common driver 11 is mounted on the flexible substrate 31, and FIG. 4B is a cross-sectional view taken along the line BB. 5 is a plan view of the flexible substrate 31 on which the common driver 11 is mounted as viewed from the side where the common driver 11 is installed in FIG. 4B (the side opposite to the side where the organic EL panel 10 is present). FIG.

  As in the case of the first embodiment, wirings connected to the respective common electrode wirings are provided on the left and right sides of the organic EL panel 10. Alternatively, the common electrode wiring is formed so that both ends of the common electrode wiring extend to the vicinity of both the left and right ends of the organic EL panel 10. That is, the organic EL panel 10 is formed so that the connection portions 33 and 34 that can be electrically connected to the respective common electrode wirings exist in the vicinity of the left and right ends of the organic EL panel 10 (FIG. 4 ( A)).

  As shown in FIG. 5, a single common driver 11 is mounted on the flexible substrate 31, and each output terminal of the common driver 11, that is, each terminal that applies a drive voltage to one common electrode, has a flexible substrate 31. The wiring 32 is formed of copper or gold so as to extend to the right end or the vicinity thereof. In FIG. 5, only the wiring from one output terminal of the common driver 11 is represented by a representative symbol.

  As shown in FIGS. 4 and 5, the flexible substrate 31 is connected to the organic EL panel 10 at connection portions 33 and 34.

  In the example shown in FIG. 5, each wiring 32 extending from the common driver 11 is exposed at least at the connection portions 33 and 34. Further, the respective wirings 32 are formed so as to be electrically connected to the respective common electrode wirings on a one-to-one basis at least at the connection portions 33 and 34. That is, when the organic EL panel 10 and the flexible substrate 31 are connected in the connection portions 33 and 34, each wiring 32 is formed to be connected to the corresponding common electrode wiring.

Therefore, in a state where the organic EL panel 10 and the flexible substrate 31 are connected at the connection portions 33 and 34, each common electrode wiring is in a ring shape, and the left and right ends of the common electrode wiring in the organic EL panel 10 are Are substantially equipotential. As a result, even in this embodiment, as shown in the explanatory diagram of FIG. 3, in the organic EL panel 10, the COM potential increases as the distance from the end (left end or right end) of the common electrode wiring increases. The potential difference ΔV / 2 at the portion where the potential difference from the end is the largest is half that of the conventional case (see FIG. 10). Therefore, the possibility that the potential difference ΔV / 2 exceeds V _th (see FIG. 12) is lower than in the conventional case. As a result, the possibility of luminance gradients is reduced.

(Embodiment 3)
The common driver and the segment driver may be integrated on a single one-chip LSI. Such a driver using a one-chip LSI is used particularly in a portable terminal such as a cellular phone that requires a reduction in the size of the device. Such a driver generally has a plurality of output terminals for applying a drive voltage to the common electrode wiring on each of the left and right sides. For example, each output terminal on the left side is an output terminal for applying a drive voltage to odd-numbered common electrode lines, and each output terminal on the right side is an output for applying a drive voltage to even-numbered common electrode lines. Terminal.

  6A is a front view showing a third embodiment using a one-chip driver 111 in which a common driver and a segment driver are integrated, FIG. 6B is a cross-sectional view taken along the line BB, and FIG. It is sectional drawing (C) in C cross section. In the example illustrated in FIG. 6, the one-chip driver 111 is COG-mounted on the back side of the glass substrate 13 (on the counter substrate 14 side) at the lower part of the organic EL panel 10.

  Similar to the first and second embodiments, wirings connected to the respective common electrode wirings are provided on the left and right sides of the organic EL panel 10. Alternatively, the common electrode wiring is formed so that both ends of the common electrode wiring extend to the vicinity of both the left and right ends of the organic EL panel 10. That is, the organic EL panel 10 is formed so that the connection portions 33 and 34 that can be electrically connected to the respective common electrode wirings exist in the vicinity of the left and right sides of the organic EL panel 10 (FIG. 6A). reference).

  Then, one end of the flexible cable 41 is connected to the connection portion 33. One end of the flexible cable 42 is connected to the connection portion 34. Furthermore, as shown in FIG. 6, the other end of the flexible cable 41 and the other end of the flexible cable 42 are connected at a connection portion 43. FIG. 6 shows a state before the flexible cables 41 and 42 are connected.

  FIG. 7 is a plan view of the organic EL panel 10 as viewed from the side on which the one-chip driver 111 is mounted. As shown in FIG. 7, wiring 44 is formed on the flexible cable 41, and wiring 45 is formed on the flexible cable 42. In FIG. 7, only one wiring is represented by a reference symbol, but the number of wirings 44 and wirings 45 is at least equal to the number of common electrode wirings. Each wiring in the flexible cable 41 is formed in the connection portion 33 so as to be electrically connected to each common electrode wiring on a one-to-one basis. That is, when the organic EL panel 10 and the flexible cable 41 are connected in the connection portion 33, each wiring 44 is formed to be connected to the corresponding common electrode wiring. In addition, each wiring in the flexible cable 42 is formed so as to be electrically connected to each common electrode wiring in the connection portion 34 on a one-to-one basis. That is, when the organic EL panel 10 and the flexible cable 42 are connected at the connection portion 34, each wiring 45 is formed to be connected to the corresponding common electrode wiring.

  Furthermore, the wirings 44 and 45 are formed in the flexible cables 41 and 42 so that the respective wirings 44 and the respective wirings 45 are electrically connected one-to-one at the connection portion 43.

  Further, the wiring 44 is exposed at a portion of the flexible cable 41 connected to the organic EL panel 10 and the connection portion 43. Further, the wiring 45 is exposed at the portion of the flexible cable 42 connected to the organic EL panel 10 and the connecting portion 43.

Therefore, in a state where the organic EL panel 10 and the flexible cables 41 and 42 are connected at the connection portions 33 and 34 and the flexible cable 41 and the flexible cable 42 are connected at the connection portion 43, each common electrode wiring is a ring. In the organic EL panel 10, the left end and the right end of the common electrode wiring are substantially equipotential. As a result, also in this embodiment, as shown in the explanatory diagram of FIG. 3, in the organic EL panel 10, the COM potential increases as the distance from the end (left end or right end) of the common electrode wiring increases. The potential difference ΔV / 2 at the portion where the potential difference from the end is the largest is half that of the conventional case (see FIG. 10). Therefore, the possibility that the potential difference ΔV / 2 exceeds V _th (see FIG. 12) is lower than in the conventional case. As a result, the possibility of luminance gradients is reduced.

(Comparative example)
When the driving capability of the common driver (current drawing capability from the constant current circuit) is insufficient, a configuration is adopted in which common drivers 11A and 11B are installed on both the left and right sides of the organic EL panel 10 as shown in FIG. Sometimes. All common electrode wirings in the organic EL panel 10 are connected to the common drivers 11A and 11B, respectively. Also in the configuration shown in FIG. 8, the left end and the right end of the common electrode wiring can be made equipotential in the organic EL panel 10. However, since the configuration of the comparative example shown in FIG. 8 requires two common drivers 11A and 11B, the cost of the organic EL display device is increased. On the other hand, the organic EL display devices according to the first to third embodiments described above can make the left end and the right end of the common electrode wiring have the same potential in the organic EL panel 10 without increasing the cost. Therefore, the possibility of the occurrence of a luminance gradient can be reduced.

  The present invention can be used in a passive organic EL display device in order to suppress the occurrence of a luminance gradient in the common electrode wiring direction.

BRIEF DESCRIPTION OF THE DRAWINGS The front view and sectional drawing which show 1st Embodiment of the organic electroluminescence display by this invention. The top view which looked at the printed wiring board from the side in which the common driver is installed about the organic EL panel. Explanatory drawing which shows the electric potential in common electrode wiring. The front view and sectional drawing which show 2nd Embodiment of the organic electroluminescence display by this invention. The top view which looked at the flexible substrate from the side in which the common driver is installed about the organic EL panel. The front view and sectional drawing which show 3rd Embodiment of the organic electroluminescent display apparatus by this invention. The top view which looked at the organic electroluminescent panel from the side in which the 1-chip driver is mounted. Explanatory drawing which shows a comparative example. Explanatory drawing for demonstrating the mounting method of a common common driver and a segment driver. Explanatory drawing which shows the electric potential in common electrode wiring. The schematic diagram which shows a common driver, a segment driver, a pixel, etc. typically. Explanatory drawing for demonstrating generation | occurrence | production of a brightness | luminance inclination. Explanatory drawing which shows an example of the element of a brightness | luminance inclination.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Organic EL panel 11 Common driver 12 Segment driver 13 Glass substrate 14 Opposite substrate 21 Printed wiring board 22 and 23 Flexible cable 31 Flexible substrate 33 and 34 Connection part 41 and 42 Flexible cable 43 Connection part 100 Display area 111 1 chip driver

Claims (4)

A plurality of segment electrode wirings arranged in the vertical direction in the display area so as to intersect with the plurality of common electrode wirings, organic EL layers, and common electrode wirings arranged in the horizontal direction in the display area are driven according to display data. In an organic EL display device comprising an organic EL panel formed on a substrate and a single common driver that drives the plurality of common electrode lines in a line sequential manner,
An organic EL display device comprising equipotential means for aligning potentials at both ends of each common electrode wiring. The equipotential means is
A printed wiring board equipped with a common driver and provided with wiring extending from each output terminal of the common driver to the left and right ends or the vicinity thereof,
A first flexible cable for connecting the wiring at the left end of the printed wiring board or the vicinity thereof and the common electrode wiring;
The organic EL display device according to claim 1, comprising: a second flexible cable that connects wiring at a right end of the printed wiring board or in the vicinity thereof and common electrode wiring. The equipotential means is
A common driver is mounted, and wiring extending from each output terminal of the common driver to the end portion or the vicinity thereof is applied, and a first connection portion for connecting each wiring to one end portion of the common electrode wiring; The organic EL display device according to claim 1, comprising a flexible substrate having a second connection portion for connecting each wire to the other end portion of the common electrode wire. The common driver is mounted on the substrate on which the common electrode wiring, the organic EL layer, and the segment electrode wiring are formed,
The equipotential means is
A first flexible cable having at least the same number of wires as the common electrode wires, and having a connection portion for connecting each wire to a portion of one end of the common electrode wire;
At least the same number of wires as the common electrode wires are provided, and the second flexible cable having a connection portion for connecting each wire to the other end portion of the common electrode wire,
The organic EL display according to claim 1, wherein each of the first flexible cable and the second flexible cable includes a connection portion for connecting each wiring in the own cable and each wiring in the other cable in a one-to-one relationship. apparatus.