JP2012003088A - Electroluminescence display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroluminescence display device capable of reducing unevenness of luminance in a display screen due to voltage drop of metal wiring which supplies a power-supply voltage to a pixel electrode through a switching element.SOLUTION: An electroluminescence display device includes a substrate 101, multiple pixel electrodes 122 on the substrate 101, each of which is formed in each pixel 120, an electroluminescence layer 123 formed on the pixel electrodes 122, a common electrode 124 formed on the electroluminescence layer 123 over the multiple pixels 120, multiple switching elements 110 each of which is connected to the respective pixel electrodes 122, a power source line 130 inside a display region, which is connected to the multiple switching elements 110 in the display region in which the pixel 120 is arranged, a power source line outside the display region, which is connected to the power source line 130 inside the display region out of the display region, and an auxiliary power source line which is electrically connected to the power source line outside the display region and covers at least a part of the power source line outside the display region.

Description

  The present invention relates to an electroluminescent display device.

  In a so-called top emission type electroluminescent display device in which light is extracted to the side where the light emitting layer is formed with respect to the substrate, indium tin oxide or indium over the entire surface of the display region is formed on the upper surface of the electroluminescent layer as a common electrode. A transparent conductive film such as zinc oxide is provided. A transparent conductive film such as indium tin oxide or indium zinc oxide is similarly used as the pixel electrode on the lower surface of the electroluminescent layer, and these pixel electrodes are connected to switching elements such as TFTs (Thin Film Transistors) for each pixel. The Each switching element is supplied with a power supply voltage by a metal wiring arranged in the display area.

  In such an electroluminescent display device, since the electrical resistance of the transparent conductive film such as indium tin oxide or indium zinc oxide is relatively large, a voltage drop occurs in the common electrode in the display region, and the luminance in the display screen is increased. It is difficult to keep it constant.

  Patent Document 1 discloses an electroluminescence display device in which an auxiliary electrode is provided on a wall-like insulating wall and a common electrode is provided on the auxiliary insulating wall in order to reduce such a problem.

  Patent Document 2 discloses an electroluminescence display device in which an auxiliary electrode is provided below the electroluminescence layer and is connected to a common electrode through a contact hole.

JP 2006-59796 A JP 2007-108469 A

  The applicant has found that a voltage drop also occurs in the metal wiring that supplies the power supply voltage to the pixel electrode via the switching element, which can cause the luminance in the display screen to be not constant. This is particularly noticeable when the electroluminescence display device is small and / or high definition or both because the dimensions such as the width of the metal wiring become small.

  The present invention has been made in view of such a viewpoint, and an object thereof is to reduce unevenness in luminance in a display screen due to a voltage drop in a metal wiring that supplies a power supply voltage to a pixel electrode through a switching element. It is to provide an electroluminescent display device that can be used.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  (1) A substrate, a plurality of pixel electrodes formed for each pixel on the substrate, an electroluminescence layer formed on the pixel electrode, and a plurality of pixels on the electroluminescence layer The formed common electrode, a plurality of switching elements connected to each of the pixel electrodes, a display area power line connected to the plurality of switching elements in the display area in which the pixels are arranged, and the display area A power line outside the display area connected to the power line inside the display area outside, and an auxiliary power line electrically connected to the power line outside the display area and covering at least a part of the power line outside the display area, An electroluminescence display device.

  (2) In (1), at least one insulating layer is formed between the power supply line outside the display area and the auxiliary power supply line, and the power supply line outside the display area and the auxiliary power supply line are electrically connected by a contact hole. Electroluminescent display device connected to

  (3) The electroluminescent display device according to (1) or (2), wherein the auxiliary electrode is formed in the same layer as the common electrode.

  (4) In any one of (1) to (3), a connection terminal group for connecting to an external device is further provided on the substrate, and the auxiliary power line is connected to the connection terminal group. 2. The electroluminescent display device according to 1.

  According to the invention disclosed in the present application as described above, the electroluminescence that can reduce the unevenness of luminance in the display screen due to the voltage drop in the metal wiring that supplies the power supply voltage to the pixel electrode via the switching element. A display device can be provided.

1 is a schematic cross-sectional view showing the structure of an electroluminescent display device according to a first embodiment of the present invention. It is a top view which shows typically the wiring on a board | substrate of the electroluminescent display apparatus of 1st Embodiment. It is a top view which shows arrangement | positioning of the auxiliary power supply line of 1st Embodiment. It is sectional drawing of the electroluminescent display apparatus in the position containing the auxiliary power line containing a contact hole. It is a top view which shows arrangement | positioning of the auxiliary power line of 2nd Embodiment. It is a top view which shows arrangement | positioning of the power line in a display area and the power line outside a display area of 3rd Embodiment.

  A first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic cross-sectional view showing the structure of the electroluminescent display device 100 according to the first embodiment. The electroluminescent display device 100 according to the present embodiment is formed on the substrate 101 by switching elements 110 such as TFTs (Thin Film Transistors) formed on a substrate 101 made of glass or the like, as in a general similar device. The amount of light emitted from the pixel 120 is controlled. In the present embodiment, since the electroluminescent display device 100 is a so-called top emission type that extracts light to the electroluminescent layer 123 formed on the substrate 101, the substrate 101 is not necessarily transparent. The material is not particularly limited.

In the figure, reference numeral 102 denotes a gate insulating layer, reference numeral 103 denotes an interlayer insulating layer, reference numeral 104 denotes a protective layer, reference numeral 105 denotes a pixel separation layer, and reference numeral 106 denotes an insulating flattening layer. In this embodiment, the gate insulating layer 102 and the interlayer insulating layer 103 are silicon dioxide (SiO ₂ ) films, the protective layer 104 is a so-called inorganic passivation film, the pixel isolation layer 105 is acrylic resin or polyimide resin, and the planarization layer 106 is This is a so-called organic passivation film. However, the material of these films is not particularly limited as long as it has insulating properties and sufficient performance for forming the pixel 120, and may be any material.

  Reference numeral 111 denotes a channel made of polysilicon or the like, reference numeral 112 denotes a gate electrode, and reference numerals 113 and 114 denote a source electrode and a drain electrode, respectively. The source electrode 113, the drain electrode 114, the channel 111 connecting them, the gate electrode 112 for generating an electric field in the channel 111 through the gate insulating layer 102, the interlayer insulating layer 103 for insulating each electrode, and the protective layer 104, the TFT That is, the switching element 110 is formed. If necessary, a base film for preventing contamination of the channel 111 due to impurities from the substrate 101 may be provided further below the channel 111. For example, a silicon nitride (SiN) film or a silicon dioxide film may be used as the base film.

  Further, reference numeral 121 denotes a reflective layer, and reference numeral 122 denotes a pixel electrode connected to the source electrode 113, which functions as an anode for supplying holes to the electroluminescent layer 123. In the present embodiment, the pixel electrode 122 is a metal oxide thin film such as indium tin oxide or indium zinc oxide, but the material is not particularly limited as long as the function as an anode is satisfied. The reflective layer 121 is a layer for reflecting the downward light from the electroluminescent layer 123 and extracting it upward, and a metal film such as silver or aluminum may be suitably used. In the case where the pixel electrode 122 itself is a metal film and has a function of reflecting light, the reflective layer 121 may be omitted.

  The common electrode 124 is provided over the plurality of pixels on the upper surface of the electroluminescent layer 123 and functions as a cathode for supplying electrons to the electroluminescent layer 123. The common electrode 124 preferably has a high light transmittance and an electrical resistance as low as possible. In this embodiment, a metal thin film made of silver is used as the common electrode 124, but a transparent conductive film made of a metal oxide such as indium tin oxide, indium zinc oxide, zinc oxide, or tin oxide may be used. As a material for the thin film, copper, gold, aluminum, or an alloy thereof may be used in addition to silver. Further, the common electrode 124 may be formed by stacking a metal thin film and a metal oxide film.

  The drain electrode 114 of the switching element 110 is connected to the power line 130 in the display area, and a power supply voltage is applied. On the other hand, the common electrode 124 is grounded. Therefore, when a signal voltage from a video signal line (not shown) is applied to the gate electrode 112, a current corresponding to the signal voltage flows from the drain electrode 114 to the source electrode 113, and holes are transferred from the pixel electrode 122 to the electroluminescent layer 123. Is supplied from the common electrode 124. As a result, the electroluminescent layer 123 is injected with holes and electrons in the light emitting region 150, which is a region in contact with the pixel electrode 122, and emits light with a light emission amount corresponding to the signal voltage. That is, the light emitting region 150 is a region in the electroluminescent layer 123 where light can be extracted. The ratio of the light emitting region 150 to the area of the display region, which is a region where the pixels 120 are formed on the substrate 101, is generally called an aperture ratio.

  In the electroluminescent display device 100, the potential applied to the pixel electrode 122 and the common electrode 124 may be reversed, and the pixel electrode 122 may be used as a cathode and the common electrode 124 may be used as an anode. In this embodiment, a positive voltage power supply is used, the common electrode 124 is on the ground side, and the pixel electrode 122 (that is, the drain electrode 114) is on the power supply side, but this distinction is relative, and the distinction between power supply and ground is For convenience. That is, even if a voltage is applied to the common electrode 124 from the negative voltage power source with the pixel electrode 122 side as the ground potential, there is no problem. Therefore, in this specification, the side connected to the pixel electrode 122 via the switching element 110 is the power source and the side connected to the common electrode 124 is grounded, regardless of whether the voltage is positive or negative or connected to an external device. Call.

  The sealing substrate 140 is a transparent substrate such as glass or plastic, and an inert gas such as nitrogen gas and a desiccant (not shown) are sealed in a space 141 between the sealing substrate 140 and the substrate 101, and moisture or oxygen Prevents the electroluminescent layer 123 from deteriorating. The outer periphery of the sealing substrate 140 is bonded to the substrate 101 with a sealing material, and the space 141 is sealed. The electroluminescent layer 123 may be protected by a method using the sealing substrate 140 as in this embodiment, or a so-called resin in which a transparent resin is applied on the substrate 101 to seal the electroluminescent layer. A sealing method may be used.

  In this embodiment, the electroluminescent layer 123 is also formed on the pixel separation layer 105 outside the light emitting region 150. However, this structure is not essential, and the electroluminescent layer 123 is formed in the light emitting region 150. Only the top may be covered.

  FIG. 2 is a plan view schematically showing wiring on the substrate 101 of the electroluminescent display device 100 of the present embodiment. A terminal group 160 for connection to an external device is provided on one side of the lower side of the substrate 101, and a power supply voltage, an installation voltage, and various control signals are input to each terminal from the external device. Various control signals include a clock signal and a video signal. In addition, the number and shape of the terminals shown in the figure are schematically illustrated and are not limited thereto.

  A display area 161 in which a large number of pixels 120 are formed is disposed in the center of the substrate 101. A video signal control circuit 162 is disposed below the display area 161. The video signal input from the terminal group 160 is distributed by the video signal control circuit 162 to video signal lines formed for each pixel column. In the figure, only two video signal lines 163a and 163b are shown, and the others are omitted. Further, scanning circuits 164 are arranged on the left and right sides of the display area 161. Scanning signals are sequentially output from the scanning circuit 164 to the scanning signal lines formed for each row of pixels. In the figure, only the scanning signal lines 165a and 165b are shown, and the others are omitted.

  A region surrounded by the adjacent video signal lines 163a and 163b and the scanning signal lines 165a and 165b is the pixel 120. The illustrated pixel 120 is connected to the video signal line 163a and the scanning signal line 165a.

  Note that wiring between the video signal control circuit 162 and the scanning circuit 164 and the terminal group 160 is omitted for simplification of illustration. In the present embodiment, the video signal control circuit 162 and the scanning circuit 164 are directly formed on the substrate 101 by a so-called SOG (System On Glass) method. However, the present invention is not limited to this, and an IC (Integrated Circuit) chip is used. Etc. may be mounted on the substrate 101. In the present embodiment, the scanning circuit 164 is divided into the left and right sides of the display area 161 and the scanning signal lines are alternately extended from the left and right scanning circuits 164. However, the present invention is not limited to this, and the scanning circuit 164 is displayed. It may be arranged on either the left or right side of the region 161.

  Reference numeral 166 denotes a ground line, and a ground potential is input from the terminal group 160. The ground lines 166 are arranged on the left and right sides of the display area 161, and the ground connection areas 167 are provided on the upper and lower sides of the display area 161 by connecting the left and right ground lines 166. The common electrode 124 (see FIG. 1) is formed in a rectangular region surrounded by the upper and lower ground connection regions 167, and is electrically connected to the ground line 166 through a contact hole 168 appropriately provided in the ground connection region 167. .

  Reference numeral 131 denotes a power line outside the display area, and a power supply potential is inputted from the terminal group 160. In the present embodiment, the power line 131 outside the display area is provided on the lower side and the left and right sides of the display area 161 as illustrated. A contact hole 168 is appropriately provided on the power line 131 outside the display area, and is electrically connected to an auxiliary power line described later.

  Note that the video signal lines 163a and 163b, the scanning signal lines 165a and 165b, the ground line 166 and the ground connection area 167, the power supply line 131 outside the display area and the power supply line 130 within the display area, which are described above, sandwich an insulating layer as appropriate. Are insulated from each other.

  In the present embodiment, the auxiliary power supply line is provided on the power supply line 131 outside the display area so as to cover at least a part thereof. FIG. 3 is a plan view showing the arrangement of the auxiliary power lines 133 according to the present embodiment. This figure corresponds to FIG. 2 and shows the position and shape of the auxiliary power line 133 on the substrate 101. As can be understood with reference to FIG. 2, the auxiliary power line 133 has the same position and the same shape as the power line 131 outside the display area, and has a shape that completely covers the power line 131 outside the display area. However, the auxiliary power supply line 133 does not necessarily have the same position and the same shape as the power supply line 131 outside the display area, and may have a shape covering at least a part thereof. Further, the end 134 of the auxiliary power line 133 is preferably connected to the terminal group 160 (see FIG. 2).

  The broken line in the figure is the common electrode 124. As shown in the figure, the auxiliary power line 133 and the common electrode 124 partially overlap in plan view, but an appropriate insulating layer is formed between the auxiliary power line 133 and the common electrode 124 in order to prevent a short circuit therebetween. .

  FIG. 4 is a cross-sectional view of the electroluminescent display device 100 at a position including the auxiliary power supply line 133 including the contact hole 132. In the figure, members shown in common with FIG. 1 are given the same reference numerals, and the detailed description thereof is referred to the above description regarding FIG. As shown in the figure, the power line 131 outside the display area is formed in the same layer as the power line 130 in the display area (see FIG. 1), and the auxiliary power line 133 is formed on the upper surface of the pixel isolation layer 105. Then, in the contact hole 132, the power supply line 131 outside the display area and the auxiliary power supply line 133 are electrically connected through the intermediate electrode 135. The intermediate electrode 135 is provided to ensure electrical connection between the power supply line 131 outside the display area and the auxiliary power supply line 133, and may be omitted if unnecessary. The material of the auxiliary power line 133 is not particularly limited as long as it has excellent conductivity, and various metal films and metal oxide films may be used. In the present embodiment, the same material as the common electrode 124 (see FIG. 1), that is, a metal thin film made of silver is used. By making the material of the auxiliary power supply line 133 the same material as the common electrode 124 or other electrodes, the auxiliary electrode line 133 is formed without increasing the types of materials and processes used in the manufacture of the electroluminescent display device 100. . A pixel isolation layer 105, a planarization layer 106, and a protective layer 104, which are insulating layers, are arranged between the auxiliary electrode line 133 and the power supply line 131 outside the display area. The position of the auxiliary electrode line 133 is the same as that of this embodiment. Thus, the present invention is not limited to the upper part of the pixel isolation layer 105, and may be a position where at least one insulating layer is sandwiched between the power supply line 131 outside the display area. Further, the auxiliary electrode line 133 may be formed over a plurality of layers, for example, further between the pixel separation layer 105 and the planarization layer 106.

  A plurality of contact holes 132 are provided at appropriate intervals (see FIG. 2), and electrically connect the auxiliary electrode line 133 and the power supply line 131 outside the display area. Thus, by providing the auxiliary electrode line 133 electrically connected by the contact hole 132 in parallel with the power line 131 outside the display area, the cross-sectional area of the power line 131 outside the display area is substantially increased. Its electrical resistance decreases. Thereby, a decrease in the power supply potential due to the electric resistance of the power line 131 outside the display area is suppressed, and unevenness in luminance of the electroluminescent display device 100 is reduced. Further, when the end portion 134 (see FIG. 2) of the auxiliary electrode line 133 is connected to the terminal group 160 (see FIG. 1), the contact area between the power line 131 outside the display area and the terminal group 160 is substantially increased. As a result, the electrical resistance also decreases.

  Then, the manufacturing method of the electroluminescent display apparatus 100 of this embodiment is demonstrated.

  Referring to FIG. 1 again, first, an amorphous silicon film is formed on the substrate 101 by CVD (Chemical Vapor Deposition), converted to a polysilicon film by laser irradiation, and a channel 111 is formed. Next, the gate insulating layer 102 and the gate electrode 112 are formed. Further, using the gate electrode 112 as a mask, an impurity such as phosphorus or boron is applied to the channel 2 by ion implantation to form a source portion and a drain portion. Further, an interlayer insulating layer 103 is formed so as to cover the gate electrode 112, and the source electrode 113 and the drain electrode 114 are formed so as to be connected to the channel 111 through a through hole. At the same time, the video signal lines 163a and 163b, the scanning signal lines 165a and 165b, the display area power line 130, the display area power line 131, the ground line 166, and the ground connection area 167 are formed (see FIG. 2). Thereafter, in order to protect the completed switching element 110, a protective layer 104 is formed, and a planarization layer 106 is further formed thereon. The video signal control circuit 162, the scanning circuit 164, and the terminal group 160 (see FIG. 2) are formed on the substrate 101 at the same time, before or after these processes.

  A reflective layer 121 is formed of aluminum or an alloy thereof on the planarizing layer 106, and a pixel electrode 122 is formed of indium tin oxide. Indium tin oxide is heated to about 200 degrees Celsius and annealed to reduce electrical resistance. The pixel electrode 122 is connected to the source electrode 113 through a through hole.

  Next, after forming the pixel separation layer 105 that separates the light emitting region 150 of each pixel, the electroluminescence layer 123 is formed. The electroluminescent layer 123 is composed of five layers including a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer from the lower layer. Each layer constituting the electroluminescent layer 123 is formed by mask vapor deposition. At this time, when the electroluminescent layer 123 includes a plurality of types of electroluminescent layers that emit light in different colors, mask vapor deposition is performed for each luminescent color.

  Then, the common electrode 124 is formed on the electroluminescent layer 123 by a vacuum process such as vapor deposition, sputtering, or ion plating. In the present embodiment, the material amount of the common electrode 124 is silver, but may be copper, gold, aluminum, or an alloy thereof.

  Thereafter, an appropriate insulating layer is formed on a position where the common electrode 124 and the auxiliary power line 133 overlap in a plane or on the entire surface, and then the auxiliary power line 133 is again connected by a vacuum process such as vapor deposition, sputtering, or ion plating. Form. Note that the order of forming the common electrode 124 and the auxiliary power line 133 may be reversed. The common electrode 124 is electrically connected to the power supply line 131 outside the display area through a contact hole 132 (see FIG. 4).

  As described above, when the pixel 120 including the switching element 110, the electroluminescent layer 123, and the like is formed on the substrate 101, the sealing substrate 140 is attached to the substrate 101 with the space 141 interposed therebetween. An inert gas such as a gas and a drying material such as silica gel are enclosed to complete the process.

  In addition, the manufacturing method of the electroluminescent display apparatus 100 demonstrated here was demonstrated as an example, and may be followed by another order or method.

  Subsequently, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 5 is a plan view showing the arrangement of the auxiliary power supply lines 233 according to the second embodiment. In the figure, the same reference numerals are assigned to members common to the first embodiment, and detailed description thereof is omitted.

  As shown in the figure, the present embodiment is different from the first embodiment only in the planar shape of the auxiliary power supply line 233, and the other points are all the same. The auxiliary power line 233 has a shape that covers a part of the power line 131 outside the display area (see FIG. 2), but does not cover all of the power line 131. The important point here is that the auxiliary power supply line 233 and the common electrode 124 do not overlap in a planar manner. In this way, the common electrode 124 and the auxiliary power supply line 233 are formed at the same time by using an appropriate mask shape when forming the common electrode 124. Therefore, almost no additional process is required, and the auxiliary power supply line 233 is formed, so that an increase in manufacturing cost can be suppressed.

  Subsequently, a third embodiment of the present invention will be described with reference to FIG.

  FIG. 6 is a plan view showing the arrangement of the display area power lines 330 and the display area power lines 331 according to the third embodiment. This embodiment is different from the first embodiment only in the planar shape of the power line 330 in the display area and the power line 331 outside the display area, and the other points are all the same.

  As shown in the figure, the power line 331 outside the display area has a shape that surrounds the four sides of the display area (not shown), and the power line 330 within the display area is displayed in a grid pattern in the vertical and horizontal directions. Placed inside. With such a shape, a decrease in power supply potential supplied to the display region can be suppressed to a small level. Further, the shape of the auxiliary power line (not shown) provided corresponding to the power line 331 outside the display area may be the same as the power line outside the display use area, or an arbitrary shape covering at least a part thereof. Good.

  The arrangement and shape of the display area power supply line 330 and the display area power supply line 331 are arbitrary. As in the present embodiment, the power line 331 outside the display area may have a shape that surrounds the display area from all sides, or may be disposed on the left and right and lower portions of the display area as in the first and second embodiments, or You may make it arrange | position to either the right and left or left and right of a display area, or the upper and lower sides or the lower part of a display area. In addition, the display area power supply line 330 may be arranged in a grid pattern in the vertical direction and the horizontal direction as in the present embodiment, or may be arranged in any one direction within the display area. It can be changed arbitrarily.

  100 Electroluminescent Display Device, 101 Substrate, 102 Gate Insulating Layer, 103 Interlayer Insulating Layer, 104 Protective Layer, 105 Pixel Isolation Layer, 106 Planarizing Layer, 110 Switching Element, 111 Channel, 112 Gate Electrode, 113 Source Electrode, 114 Drain electrode, 120 pixels, 121 reflective layer, 122 pixel electrode, 123 electroluminescence layer, 124 common electrode, 130 power line in display area, 131 power line outside display area, 132 contact hole, 133 auxiliary electrode line, 134 end , 135 intermediate electrode, 140 sealing substrate, 141 space, 150 light emitting area, 160 terminal group, 161 display area, 162 video signal control circuit, 163a, 163b video signal line, 164 scanning circuit, 165a, 165b scanning signal line, 166 Contact Line, 167 ground connection region 168 a contact hole, 233 auxiliary electrode lines, 330 the display area in the power supply line, 331 outside the display area the power line.

Claims (4)

A substrate,
A plurality of pixel electrodes formed for each pixel on the substrate;
An electroluminescent layer formed on the pixel electrode;
A common electrode formed on the electroluminescent layer across a plurality of pixels;
A plurality of switching elements connected to each of the pixel electrodes;
A power line in the display area connected to the plurality of switching elements in the display area in which the pixels are arranged;
A power line outside the display area connected to the power line inside the display area outside the display area;
An auxiliary power line electrically connected to the power line outside the display area and covering at least a part of the power line outside the display area;
An electroluminescent display device. At least one insulating layer is formed between the power line outside the display area and the auxiliary power line,
The electroluminescence display device according to claim 1, wherein the power supply line outside the display area and the auxiliary power supply line are electrically connected through a contact hole.   The electroluminescent display device according to claim 1, wherein the auxiliary electrode does not overlap the common electrode in plan view. On the substrate, further comprising a connection terminal group for connecting to an external device,
The electroluminescent display device according to claim 1, wherein the auxiliary power line is connected to the connection terminal group.

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