JP2007042443A - Indicating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an indicating device which hardly causes the deterioration with time of white balance and is excellent in indication quality. <P>SOLUTION: The indicating device is equipped with a plurality of pixels each provided with a first subpixel including a first light emission element; a second subpixel including a second light emission element which has an emission color different from that of the first light emission element, and deteriorates faster than the first light emission element, when the light emission element is continued to be energized at the same current density; and a third subpixel including a third light emission element with the third and second light emission elements interposing the first one and deteriorating slower than the first light emission element, when the third light emission element is continued to be energized at the same current density. The distance X<SB>12</SB>between the centers of a light emission area EA1 of the first subpixel, and the light emission area EA2 of the second subpixel, and the distance X<SB>13</SB>between the centers of the light emission area EA1 of the first subpixel and the light emission area EA3 of the third subpixel satisfy the inequality: 0<(X<SB>12</SB>-X<SB>13</SB>)/(X<SB>12</SB>+X<SB>13</SB>)<0.17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device including a plurality of light emitting elements in which each pixel emits light of different colors.

  In a display device capable of displaying a color image, each pixel usually includes three sub-pixels whose display colors are blue, green, and red. For example, in an organic electroluminescence (EL) display device capable of displaying a color image, each pixel typically includes a sub-pixel including a light-emitting element whose emission color is blue and a light-emitting element whose emission color is green. The sub-pixel and the sub-pixel including a light-emitting element whose emission color is red are configured.

  By the way, when the blue, green, and red organic EL elements are continuously energized with the same current density, in general, the blue organic EL elements are deteriorated more quickly than the green and red organic EL elements. Therefore, for example, when a design is adopted in which a white image is displayed with the current densities of blue, green, and red organic EL elements equal to each other, the white image changes from pure white to yellowish white over time. And change.

  With respect to this problem, Patent Document 1 describes that the emission area of a blue organic EL element is made larger than the emission areas of green and red organic EL elements. By adopting such a structure, the current density of the blue organic EL element can be made smaller than that of the green and red organic EL elements when displaying a white image. Therefore, for example, the deterioration rates of blue, green, and red organic EL elements can be made substantially equal to each other, and therefore white balance can be hardly deteriorated over time.

However, the inventors of the present invention have found that when the above structure is adopted in the organic EL display device, the display quality may be deteriorated in making the present invention.
JP 2003-168561 A

  An object of the present invention is to provide a display device which is less likely to cause white balance deterioration with time and has excellent display quality.

According to an aspect of the present invention, the first sub-pixel including the first light emitting element and the first light emitting element have different emission colors and are compared with the first light emitting element when the current continues to be supplied with the same current density. And the second sub-pixel including the second light-emitting element that deteriorates more rapidly, and the second light-emitting element is adjacent to the second light-emitting element with the first light-emitting element interposed therebetween, and the first and second light-emitting elements have different emission colors. A plurality of pixels each including a third sub-pixel including a third light-emitting element that is slower in deterioration than the first light-emitting element when the current continues to be supplied at an equal current density. center distance between the center-to-center distance X ₁₂ between the light emitting region and the light emitting region of the second sub-pixels in one sub-pixel, a light emitting region of the third sub-pixel and the light emitting region of the first subpixel X ₁₃ is an inequality: 0 <(X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) <0. A display device characterized by satisfying the relationship shown in FIG. 17 is provided.

  According to the present invention, it is possible to provide a display device that hardly deteriorates over time in white balance and has excellent display quality.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a plan view schematically showing a display device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a structure that can be employed in the display device of FIG. In FIG. 2, the display device is drawn such that its display surface, that is, the front surface or the light emitting surface faces downward, and the back surface faces upward.

  The display device of FIG. 1 is a bottom emission organic EL display device that employs an active matrix driving method. This display device can display a color image, and each pixel PX includes three sub-pixels PX1 to PX3.

  This organic EL display device includes an array substrate AS, a video signal line driver XDR, and a scanning signal line driver YDR.

The array substrate AS includes, for example, an insulating substrate SUB such as a glass substrate.
On the substrate SUB, as shown in FIG. 2, for example, a SiN _x layer and a SiO _x layer are sequentially stacked as the undercoat layer UC.

  On the undercoat layer UC, for example, a gate insulating film GI that can be formed using a semiconductor layer SC that is a polysilicon layer in which a channel and a source / drain are formed, for example, TEOS (TetraEthyl OrthoSilicate), etc., and MoW, for example, The gates G are sequentially stacked, and they constitute a top gate type thin film transistor which is a field effect transistor. In this example, these thin film transistors are p-channel thin film transistors and are used as the drive control element DR and the switches SWa to SWc in FIG.

  On the gate insulating film GI, scanning signal lines SL1 and SL2 shown in FIG. 1 and a lower electrode (not shown) are further arranged. The scanning signal lines SL1 and SL2 and the lower electrode can be formed in the same process as the gate G.

  As shown in FIG. 1, the scanning signal lines SL1 and SL2 each extend in the row direction (X direction) of the pixels PX, and are alternately arranged in the column direction (Y direction) of the pixels PX. These scanning signal lines SL1 and SL2 are connected to the scanning signal line driver YDR.

  The lower electrode is connected to the gate of the drive control element DR. The lower electrode is used as one electrode of a capacitor C described later.

The gate insulating film GI, the gate G, the scanning signal lines SL1 and SL2, and the lower electrode are covered with an interlayer insulating film II shown in FIG. The interlayer insulating film II is made of, for example, SiO _x formed by a plasma CVD method or the like. A portion of the interlayer insulating film II on the lower electrode is used as a dielectric layer of the capacitor C.

  On the interlayer insulating film II, the source electrode SE and the drain electrode DE shown in FIG. 2, the video signal line DL and the power supply line PSL shown in FIG. 1, and an upper electrode (not shown) are arranged. These can be formed in the same process and have, for example, a three-layer structure of Mo / Al / Mo.

  The source electrode SE and drain electrode DE are electrically connected to the source and drain of the thin film transistor through contact holes provided in the interlayer insulating film II.

  As shown in FIG. 1, each video signal line DL extends in the Y direction and is arranged in the X direction. One end of each of the video signal lines DL is connected to the video signal line driver XDR.

  In this example, the power supply lines PSL extend in the Y direction and are arranged in the X direction. In this example, the power supply line PSL is connected to the video signal line driver XDR.

  The upper electrode is connected to the power supply line PSL. The upper electrode is used as the other electrode of the capacitor C.

The source electrode SE, the drain electrode DE, the video signal line DL, the power supply line PSL, and the upper electrode are covered with the passivation film PS shown in FIG. The passivation film PS is made of, for example, SiN _x .

  On the passivation film PS, light-transmitting first electrodes PE are juxtaposed apart from each other as front electrodes. Each first electrode PE is a pixel electrode, and is connected to the drain electrode DE of the switch SWa through a through hole provided in the passivation film PS.

  The first electrode PE is an anode in this example. As a material of the first electrode PE, for example, a transparent conductive oxide such as ITO (Indium Tin Oxide) can be used.

  A partition insulating layer PI shown in FIG. 2 is further disposed on the passivation film PS. In the partition insulating layer PI, a through hole is provided at a position corresponding to the first electrode PE, or a slit is provided at a position corresponding to a column or row formed by the first electrode PE. Here, as an example, the partition insulating layer PI is provided with a through hole at a position corresponding to the first electrode PE.

  The partition insulating layer PI is, for example, an organic insulating layer. The partition insulating layer PI can be formed using, for example, a photolithography technique.

  On the first electrode PE, an organic layer ORG including a light emitting layer is disposed as an active layer. The light emitting layer is, for example, a thin film containing a luminescent organic compound whose emission color is red, green, or blue. The organic layer ORG can further include a hole injection layer, a hole transport layer, a hole blocking layer, an electron transport layer, an electron injection layer, and the like in addition to the light emitting layer.

  The partition insulating layer PI and the organic layer ORG are covered with a second electrode CE that is a back electrode. The second electrode CE is a counter electrode connected to each other between the sub-pixels PX1 to PX3, that is, a common electrode, and is a light-reflective cathode in this example. For example, the second electrode CE is electrically connected to an electrode wiring (not shown) formed on the same layer as the video signal line DL through a contact hole provided in the passivation film PS and the partition insulating layer PI. It is connected to the. Each organic EL element OLED includes a first electrode PE, an organic layer ORG, and a second electrode CE.

  In each pixel PX, the sub-pixel PX1 is located between the sub-pixels PX2 and PX3. Each of the subpixels PX1 to PX3 includes a pixel circuit and an organic EL element OLED.

  The organic EL elements OLED included in the sub-pixels PX1 to PX3 have different emission colors. The organic EL element OLED included in the sub-pixel PX2 is deteriorated more rapidly when energized at the same current density as compared with the organic EL element OLED included in the sub-pixel PX1. In addition, the organic EL element OLED included in the subpixel PX3 is deteriorated more slowly when the current continues to be supplied with the same current density as compared with the organic EL element OLED included in the subpixel PX1. In this example, the emission color of the organic EL element OLED included in the sub-pixel PX1 is green, the emission color of the organic EL element OLED included in the sub-pixel PX2 is blue, and the emission color of the organic EL element OLED included in the sub-pixel PX3. Is red.

  In this example, the pixel circuit included in each of the subpixels PX1 to PX3 includes a drive control element (drive transistor) DR, an output control switch SWa, a video signal supply control switch SWb, a diode connection switch SWc, and a capacitor C. Is included. As described above, in this example, the drive control element DR and the switches SWa to SWc are p-channel thin film transistors. In this example, the video signal supply control switch SWb and the diode connection switch SWc are connected to each other in the connection state between the drain of the drive control element DR, the video signal line DL, and the gate of the drive control element DR. The switch group which switches between a 1st state and the 2nd state from which they were interrupted | blocked from each other is comprised.

  The drive control element DR, the output control switch SWa, and the organic EL element OLED are connected in series in this order between the first power supply terminal ND1 and the second power supply terminal ND2. In this example, the first power supply terminal ND1 is a high potential power supply terminal, and the second power supply terminal ND2 is a low potential power supply terminal.

  The gate of the output control switch SWa is connected to the scanning signal line SL1. The video signal supply control switch SWb is connected between the video signal line DL and the drain of the drive control element DR, and its gate is connected to the scanning signal line SL2. The diode connection switch SWc is connected between the gate and the drain of the drive control element DR, and the gate is connected to the scanning signal line SL2.

  The capacitor C is connected between the gate of the drive control element DR and the constant potential terminal ND1 '. The constant potential terminal ND1 'is connected to the first power supply terminal ND1, for example.

  In this organic EL display device, the structure from the insulating substrate SUB to the partition insulating layer PI corresponds to the array substrate AS.

  In this example, the video signal line driver XDR and the scanning signal line driver YDR are arranged on the array substrate AS. That is, in this example, the video signal line driver XDR and the scanning signal line driver YDR are mounted on a COG (chip on glass). The video signal line driver XDR and the scanning signal line driver YDR may be mounted by TCP (tape carrier package) instead of COG mounting.

  When an image is displayed on this organic EL display device, for example, each of the scanning signal lines SL1 and SL2 is line-sequentially driven. In the writing period in which video signals are written to the subpixels PX1 to PX3 in a certain row, first, the switch SWa is opened from the scanning signal line driver YDR to the scanning signal line SL1 to which the previous subpixels PX1 to PX3 are connected. The (OFF) scanning signal is output as a voltage signal, and then the switches SWb and SWc are closed (ON) as a voltage signal to the scanning signal line SL2 to which the previous subpixels PX1 to PX3 are connected. In this state, the video signal line driver XDR outputs the video signal as a current signal to the video signal line DL to which the previous sub-pixels PX1 to PX3 are connected, and the gate-source voltage of the drive control element DR is Set to a size corresponding to the video signal. Thereafter, the scanning signal line driver YDR outputs a scanning signal as a voltage signal for opening (SW) the switches SWb and SWc to the scanning signal line SL2 to which the previous subpixels PX1 to PX3 are connected, and then the previous subpixel. A scanning signal that closes the switch SWa (ON) is output as a voltage signal to the scanning signal line SL1 to which PX1 to PX3 are connected.

  In the effective display period in which the switch SWa is closed (ON), a drive current having a magnitude corresponding to the gate-source voltage of the drive control element DR flows through the organic EL element OLED. The organic EL element OLED emits light with a luminance corresponding to the magnitude of the drive current.

FIG. 3 is a plan view of the display device of FIG. 1 as viewed from the display surface side. In FIG. 3, reference numerals EA1 to EA3 indicate the light emission areas of the sub-pixels PX1 to PX3, that is, areas where light emission is visible when the display surface is viewed from the front. Reference numeral X ₁₂ represents the distance between the center of the light emitting area EA1 and the center of the light emitting area EA2, reference numeral X ₁₃ is indicated the distance between the center of the light emitting area EA1 and the center of the light emitting area EA3 Yes. Reference numerals X _{1 to} X ₃ indicate the dimensions of the light emitting areas EA1 to EA3 along the X direction, respectively.

In this display device, the dimension X ₂ is larger than the dimension X ₁ and the dimension X ₃ is smaller than the dimension X ₁ . The dimensions of the light emitting areas EA1 to EA3 along the Y direction are equal to each other. That is, the light emitting area EA2 has a larger area compared to the light emitting area EA1, and the light emitting area EA3 has a smaller area compared to the light emitting area EA1. These areas are determined such that the luminance half-life when the white image is continuously displayed on the display device is substantially equal between the sub-pixels PX1 to PX3.

By the way, in the display device adopting a structure in which the dimensions X _{1 to} X ₃ are equal to each other and the dimensions along the Y direction of the light emitting areas EA1 to EA3 are equal to each other, it is most excellent when the distance X ₁₂ and the distance X ₁₃ are equal to each other. Display quality can be realized. The present inventors have found that when the dimensions X _{1 to} X ₃ are made different from each other, the display quality is deteriorated as compared with the case where the dimensions X _{1 to} X ₃ are equal to each other. That is, in a display device in which the dimensions X _{1 to} X ₃ are different from each other, excellent display quality cannot be realized when the distance X ₁₂ and the distance X ₁₃ are equal to each other.

In this display device, the distance X ₁₂ and the distance X ₁₃ satisfy the relationship represented by the inequality: 0 <(X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) <0.17. Typically, the distance X ₁₂ and the distance X ₁₃ satisfy the relationship shown by the inequality: 0.08 <(X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) <0.12. When the distance X ₁₂ and the distance X ₁₃ satisfy the relationship shown in the above inequality, it is possible to prevent white balance deterioration over time and to achieve excellent display quality. This will be described in detail below.

  4 to 6 are plan views schematically showing examples of images that can be displayed by the display device of FIG. 4 to 6, among the display areas EA1 to EA3, the white areas indicate areas that do not emit light, and the hatched areas indicate areas that emit light.

Here, the dimension X ₁ to X ₃ are equal to each other and the ratio _{(X 12 -X 13) / (} X 12 + X 13) and an organic EL display device is zero is different from each other dimensions X ₁ to X ₃ and the ratio ( The images of FIGS. 4 to 6 were displayed with an organic EL display device in which X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) was greater than zero. These images were observed indoors by 30 subjects, and it was examined whether or not differences could be identified. Here, QCIF (quarter common intermediate format) is adopted for all organic EL display devices, and the size of the pixel PX is 198 μm × 198 μm. Here, the image was observed from a position 15 cm away from the screen. The results are shown in the table below.

In the above table, the result obtained when the image of FIG. 4 is displayed in the line indicated by “straight line”, and the result obtained when the image of FIG. 5 is displayed in the line indicated by “dotted line”. In the row indicated by “hatched lines”, the results obtained when the image of FIG. 6 is displayed are shown. In the row indicated by “ratio X ₁ : X ₂ : X ₃ ”, the ratio of the dimension X ₁ , the dimension X _2, and the dimension X ₃ is shown. Also, the evaluation “A” indicates that all subjects could not identify the difference, the evaluation “B” indicates that 1 to 5 subjects have identified the difference, and the evaluation “C” indicates that It shows that many subjects have identified differences.

As is clear from the above table, when the distance X ₁₂ and the distance X ₁₃ satisfy the relationship shown in the previous inequality, an excellent display quality can be realized. Further, when the dimension X ₂ is larger than the dimension X ₁ and the dimension X ₃ is smaller than the dimension X ₁ , the deterioration rates of the organic EL elements OLED can be made substantially equal between the sub-pixels PX1 to PX3. . Therefore, according to this aspect, it is possible to make it difficult for white balance to deteriorate over time, and to realize excellent display quality.

  In this embodiment, the present invention is applied to a bottom emission type organic EL display device, but the present invention is also applicable to a top emission type organic EL display device. Further, in this aspect, the configuration in which the current signal is written as the video signal in the pixel circuit is adopted, but the configuration in which the voltage signal is written in the pixel circuit as the video signal may be employed.

1 is a plan view schematically showing a display device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically illustrating an example of a structure that can be employed in the display device of FIG. 1. The top view which looked at the display apparatus of FIG. 1 from the display surface side. FIG. 2 is a plan view schematically showing an example of an image that can be displayed by the display device of FIG. 1. FIG. 2 is a plan view schematically showing an example of an image that can be displayed by the display device of FIG. 1. FIG. 2 is a plan view schematically showing an example of an image that can be displayed by the display device of FIG. 1.

Explanation of symbols

  AS ... array substrate, C ... capacitor, CE ... counter electrode, DE ... drain electrode, DL ... video signal line, DR ... drive control element, EA1 ... light emitting region, EA2 ... light emitting region, EA3 ... light emitting region, G ... gate, GI ... Gate insulating film, II ... Interlayer insulating film, ND1 ... Power supply terminal, ND1 '... Constant potential terminal, ND2 ... Power supply terminal, OLED ... Organic EL element, ORG ... Organic material layer, PE ... Pixel electrode, PI ... Partition insulating layer , PS ... passivation film, PSL ... power supply line, PX ... pixel, PX1 ... sub-pixel, PX2 ... sub-pixel, PX3 ... sub-pixel, SC ... semiconductor layer, SE ... source electrode, SL1 ... scanning signal line, SL2 ... scanning signal Wire, SUB ... insulating substrate, SWa ... output control switch, SWb ... video signal supply control switch, SWc ... diode connection switch, UC ... undercoat layer, XD ... the video signal line driver, YDR ... scanning signal line driver.

Claims (5)

The first sub-pixel including the first light-emitting element and the first light-emitting element are different in light emission color and have a faster deterioration than the first light-emitting element when the current continues to be supplied with the same current density. A second sub-pixel including a light-emitting element is adjacent to the second light-emitting element with the first light-emitting element interposed therebetween, and the first and second light-emitting elements have different emission colors and continue to be energized with an equal current density. A plurality of pixels each including a third sub-pixel including a third light-emitting element whose deterioration is slower than that of the first light-emitting element.
Center between the between-center distance X ₁₂ between the light emitting region and the light emitting region of the second sub-pixel of the first sub-pixel, the light emitting region of the third sub-pixel and the light emitting region of the first subpixel The display device is characterized in that the distance X ₁₃ satisfies the relationship represented by the inequality: 0 <(X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) <0.17. The center distances X ₁₂ and X ₁₃ satisfy a relationship represented by an inequality: 0.08 <(X ₁₂ −X ₁₃ ) / (X ₁₂ + X ₁₃ ) <0.12. The display device according to 1.   In each of the plurality of pixels, the light emitting area of the second sub-pixel has a larger dimension along the arrangement direction than the light emitting area of the first sub pixel, and the light emitting area of the third sub pixel is 2. The display device according to claim 1, wherein a dimension along an arrangement direction of the first sub-pixels is smaller than that of the light-emitting region of the first sub-pixel.   The display according to claim 1, wherein the emission color of the first light emitting element is green, the emission color of the second light emitting element is blue, and the emission color of the first light emitting element is red. apparatus.   The display device according to claim 1, wherein the first to third light emitting elements are organic EL elements.

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