JP2008234929A - Organic electroluminescent display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to restrain a pinhole from being generated at an organic matter layer. <P>SOLUTION: The organic EL display device is provided with an insulation board, a first electrode coating a part of one of the main faces of the insulation board, a barrier-rib insulation layer PI coating the main face and with a through-hole TH with its contour waving as seen from a direction vertical to the main face at a position corresponding to the first electrode, a second electrode facing the first electrode, and an active layer intercalated between the first electrode and the second electrode and containing a light-emitting layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence (EL) display technique.

  As described in Patent Document 1, in an organic EL display device manufacturing process, an organic material layer included in an active layer of an organic EL element may be formed by a solution coating method such as an inkjet method. In this method, for example, a partition insulating layer provided with a through hole is formed, and this through hole is used as a liquid reservoir. That is, an organic material layer such as a light emitting layer or a buffer layer is obtained by filling the previous through-hole with a solution containing a polymer organic material and drying the coating film.

According to this method, it is easy to dispose light emitting layers having different emission colors at predetermined positions. However, this method tends to cause pinholes in the organic layer.
JP 2004-47215 A

  An object of the present invention is to make it possible to suppress the occurrence of pinholes in an organic layer.

  According to one aspect of the present invention, an insulating substrate, a first electrode that covers a part of one main surface of the insulating substrate, a contour that covers the main surface and is perpendicular to the main surface. A partition insulating layer provided with a corrugated through-hole at a position corresponding to the first electrode, a second electrode facing the first electrode, and a light emitting layer interposed between the first and second electrodes There is provided an organic EL display device characterized by comprising an active layer containing.

  According to the present invention, it is possible to suppress the occurrence of pinholes in the organic material layer.

  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 an organic EL display device according to an aspect of the present invention. FIG. 2 is a cross-sectional view schematically showing the display panel of the organic EL display device shown in FIG.

  The display device shown in FIG. 1 is a top emission organic EL display device adopting an active matrix driving method. This display device includes a display panel DP, a video signal line driver XDR, and a scanning signal line driver YDR.

  As shown in FIGS. 1 and 2, the display panel DP includes an array substrate AS and a sealing substrate CS. The array substrate AS and the sealing substrate CS face each other and form a hollow body. Specifically, the central portion of the sealing substrate CS is separated from the array substrate AS. The peripheral edge of the sealing substrate CS is attached to one main surface of the array substrate AS via a frame-shaped seal layer SS shown in FIG.

  The array substrate AS includes the insulating substrate SUB shown in FIGS. The insulating substrate SUB is, for example, a glass substrate.

  An undercoat layer UC shown in FIG. 2 is formed on the substrate SUB. For example, the undercoat layer UC is formed by laminating a silicon nitride layer and a silicon oxide layer in this order on the substrate SUB.

  A semiconductor pattern is formed on the undercoat layer UC. The semiconductor pattern is made of polysilicon containing impurities, for example. Part of this semiconductor pattern is used as a semiconductor layer SC of the thin film transistor. In each semiconductor layer SC, impurity diffusion regions used as a source and a drain are formed. Further, another part of the semiconductor pattern is used as a lower electrode of a capacitor C described later. The lower electrodes are arranged corresponding to the pixels PX described later.

  The semiconductor pattern is covered with a gate insulating film GI. The gate insulating film GI can be formed using, for example, TEOS (tetraethyl orthosilicate).

  Scan signal lines SL1 and SL2 shown in FIG. 1 are formed on the gate insulating film GI. The scanning signal lines SL1 and SL2 extend in the X direction along the row of the pixels PX, and are alternately arranged in the Y direction along the column of the pixels PX. The scanning signal lines SL1 and SL2 are made of, for example, MoW. The Z direction is a direction perpendicular to the X direction and the Y direction.

  An upper electrode of the capacitor C is further disposed on the gate insulating film GI. These upper electrodes are arranged corresponding to the pixels PX and face the lower electrode of the capacitor C. The upper electrode is made of, for example, MoW, and can be formed in the same process as the scanning signal lines SL1 and SL2.

  The scanning signal lines SL1 and SL2 intersect the semiconductor layer SC. The intersection between the scanning signal line SL1 and the semiconductor layer SC constitutes the switching transistor SWa shown in FIG. The intersection between the scanning signal line SL2 and the semiconductor layer SC constitutes switching transistors SWb and SWc. Further, the lower electrode and the upper electrode described above and the insulating film GI interposed therebetween constitute a capacitor C. The upper electrode includes a protrusion protruding from the capacitor C in a direction perpendicular to the Z direction, and the protrusion intersects the semiconductor layer SC. This intersection constitutes the drive transistor DR. In this example, the drive transistor DR and the switching transistors SWa to SWc are top-gate p-channel thin film transistors.

  The gate insulating film GI, the scanning signal lines SL1 and SL2, and the upper electrode are covered with an interlayer insulating film II shown in FIG. The interlayer insulating film II is made of, for example, silicon oxide deposited by a plasma CVD method.

  On the interlayer insulating film II, the video signal line DL and the power supply line PSL shown in FIG. 1 are formed. The video signal lines DL extend in the Y direction and are arranged in the X direction. For example, the power supply line PSL extends in the Y direction and is arranged in the X direction.

  A source electrode SE and a drain electrode DE are further formed on the interlayer insulating film II. The source electrode SE and the drain electrode DE connect the elements in each pixel PX.

  The video signal line DL, the power supply line PSL, the source electrode SE, and the drain electrode DE have, for example, a three-layer structure of Mo / Al / Mo. These can be formed in the same process.

  The video signal line DL, the power supply line PSL, the source electrode SE, and the drain electrode DE are covered with a passivation film PS shown in FIG. A through hole is formed in the passivation film PS at a position corresponding to the drain electrode DE connected to the drain of the switching transistor SWa. The passivation film is made of, for example, silicon nitride.

  The passivation film PS is covered with a relief layer RL having a concavo-convex structure on the surface. The relief layer RL may be a continuous film, and may be patterned in a plurality of portions. Here, as an example, the relief layer RL is assumed to be a continuous film.

  The relief layer RL can be formed using a dispersion containing a resin and particles. Alternatively, the relief layer RL may be formed using a plate provided with an uneven structure. The relief layer RL is typically made of an insulator. The relief layer RL may be omitted.

  The relief layer RL is covered with a reflective layer REF. The reflective layer REF is made of, for example, a metal or alloy such as aluminum and silver.

  The surface of the reflective layer REF includes an uneven structure similar to that provided in the relief layer RL, and serves as a light scattering surface. That is, the reflective layer REF serves as a light scattering layer. The reflective layer REF may constitute a diffraction grating.

The reflective layer REF may be a continuous film, and may be patterned in a plurality of portions. Here, as an example, it is assumed that the reflective layer REF is a light-scattering continuous film. Here, as an example, it is assumed that a substantially hemispherical convex portion is provided on the surface of the reflective layer REF. The average diameter of these convex portions is, for example, in the range of 0.2 μm to 1.0 μm, and typically in the range of 0.5 μm to 0.8 μm. The density of these convex portions is, for example, in the range of 5,000,000 pieces / mm ^{2 to} 1,000,000 pieces / mm ² , and typically 2,000,000 pieces / mm ^{2 to} 1 , 250,000 pieces / mm ² .

  The reflective layer REF is covered with a planarizing layer FL whose surface is substantially flat. The planarization layer FL is made of, for example, a hard resin such as an acrylic resin. The flattening layer FL may be omitted when the surface of the reflective layer REF does not include an uneven structure.

  On the planarization layer FL, pixel electrodes PE which are first electrodes are arranged. The pixel electrode PE has optical transparency and is made of a transparent conductive material such as indium tin oxide (ITO), for example.

  On the planarizing layer FL, a partition insulating layer PI is further provided. In the partition insulating layer PI, a through hole TH is provided at a position corresponding to the pixel electrode PE. Typically, the partition insulating layer PI covers the peripheral edge of the pixel electrode PE.

  The partition insulating layer PI is an organic insulating layer such as an acrylic resin layer, for example. The partition insulating layer PI can be formed using, for example, a photolithography technique. As a material for the partition insulating layer PI, a positive photoresist is typically used, but a negative photoresist may be used. The partition insulating layer PI will be described in detail later.

  An active layer ACT including a light emitting layer is formed on each pixel electrode PE. The light emitting layer is made of a luminescent organic material. The active layer ACT may further include at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer.

  Each layer included in the active layer ACT is typically made of an organic material such as a polymer organic material. At least one of these organic layers is formed by a solution coating method such as an inkjet method. Note that a part of the layer included in the active layer ACT such as the electron injection layer may be an inorganic layer.

  The partition insulating layer PI and the active layer ACT are covered with a light transmissive counter electrode CE. In this aspect, the counter electrode CE is a common electrode shared between the pixels PX. In this embodiment, the counter electrode CE is a cathode. The counter electrode CE is formed on the same layer as the video signal line DL, for example, through contact holes provided in the partition insulating layer PI, the planarizing layer FL, the reflective layer REF, the relief layer RF, and the passivation film PS. The electrode wiring (not shown) is electrically connected.

  The counter electrode CE may have a single layer structure or a multilayer structure. The counter electrode CE having a single layer structure is a layer made of an alloy such as an alloy of magnesium and silver or a metal. The counter electrode CE having a multilayer structure is, for example, a laminate of a layer made of the above alloy or metal and a layer made of a transparent conductive material such as ITO.

  The pixel electrode PE, the active layer ACT, and the counter electrode CE constitute a plurality of organic EL elements OLED. These organic EL elements OLED are arranged in a matrix.

  Each of the pixels PX includes a drive transistor DR, switching transistors SWa to SWc, an organic EL element OLED, and a capacitor C as shown in FIG. As described above, in this example, the drive transistor DR and the switching transistors SWa to SWc are p-channel thin film transistors.

  The drive transistor DR, the switching transistor 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 power supply terminal ND1 is a high potential power supply terminal, and the power supply terminal ND2 is a low potential power supply terminal.

  The gate of the switching transistor SWa is connected to the scanning signal line SL1. The switching transistor SWb is connected between the video signal line DL and the drain of the drive transistor DR, and its gate is connected to the scanning signal line SL2. The switching transistor SWc is connected between the drain and gate of the driving transistor DR, and the gate is connected to the scanning signal line SL2.

  The capacitor C is connected between the gate of the driving transistor DR and the constant potential terminal ND1 '. In this example, the constant potential terminal ND1 'is connected to the power supply terminal ND1.

  As shown in FIG. 2, the sealing substrate CS faces the substrate SUB with the organic EL element OLED interposed therebetween. The sealing substrate CS is, for example, a glass substrate.

  As described above, the seal layer SS has a frame shape, and is interposed between the array substrate AS and the peripheral portion of the sealing substrate CS. The seal layer SS surrounds a pixel group constituted by all the pixels PX. As a material of the sealing layer SS, for example, frit glass and an adhesive can be used.

  The video signal line driver XDR and the scanning signal line driver YDR are mounted on the array substrate AS as shown in FIG. A video signal line DL is connected to the video signal line driver XDR. In this example, a power supply line PSL is further connected to the video signal line driver XDR. The video signal line driver XDR outputs the video signal as a current signal to the video signal line DL and supplies a power supply voltage to the power supply line PSL. Scanning signal lines SL1 and SL2 are connected to the scanning signal line driver YDR. The scanning signal line driver YDR outputs the first and second scanning signals as voltage signals to the scanning signal lines SL1 and SL2, respectively.

  When displaying an image on this organic EL display device, for example, the pixels PX are sequentially selected for each row. In a selection period in which a certain pixel PX is selected, a writing operation is performed on the pixel PX. In a non-selection period in which a certain pixel PX is not selected, a display operation is performed on the non-selected pixel PX.

Specifically, in the selection period in which the pixels PX in a certain row are selected, first, the switching transistor SWa is opened from the scanning signal line driver YDR to the scanning signal line SL1 to which the previous pixel PX is connected (non-conducting state). The scanning signal is output as a voltage signal. Subsequently, the scanning signal line driver YDR outputs, as a voltage signal, a scanning signal that closes the switching transistors SWb and SWc (sets the conductive state) to the scanning signal line SL2 to which the previous pixel PX is connected. In this state, the video signal line driver YDR outputs the video signal to the video signal line DL as a current signal (write current) I _sig , and the gate-source voltage V _gs of the drive transistor DR is changed to the previous video signal. Set to a size corresponding to I _sig . Thereafter, a scanning signal for opening the switching transistors SWb and SWc is output as a voltage signal from the scanning signal line driver YDR to the scanning signal line SL2 to which the previous pixel PX is connected. Subsequently, a scanning signal for closing the switching transistor SWa is output as a voltage signal from the scanning signal line driver YDR to the scanning signal line SL1 to which the previous pixel PX is connected. This ends the selection period.

In the non-selection period following the selection period, a scanning signal for closing the switching transistor SWa is output as a voltage signal from the scanning signal line driver YDR to the scanning signal line SL1 to which the previous pixel PX is connected. The switching transistor SWa remains closed, and the switching transistors SWb and SWc remain open. In the non-selection period, a drive current I _drv having a magnitude corresponding to the gate-source voltage V _gs of the drive transistor 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 I _drv .

  In this organic EL display device, the through hole TH of the partition insulating layer PI has a wavy outline when viewed from a direction perpendicular to the main surface of the insulating substrate SUB.

  FIG. 3 is a plan view schematically showing an example of a partition insulating layer that can be used in the display panel shown in FIG. 4 is an enlarged plan view showing a part of the partition insulating layer shown in FIG.

  In the partition insulating layer PI shown in FIGS. 3 and 4, when viewed from a direction perpendicular to the main surface of the insulating substrate SUB, the outline of the through hole TH is irregularly undulated. On each side of the outline of the through hole TH, the wave peaks are distributed at a density of, for example, 20 pieces / mm to 50 pieces / mm, and typically at a density of 30 pieces / mm to 46 pieces / mm. The average of the heights H of these peaks is, for example, in the range of 0.5 μm to 4 μm, and typically in the range of 1 μm to 3 μm.

  When this configuration is adopted, it is difficult to generate a gap between the organic material layer formed by the solution coating method and the partition insulating layer PI. That is, when this configuration is adopted, it is possible to suppress the occurrence of pinholes in the organic layer formed by the solution coating method.

  The partition insulating layer PI can be formed using, for example, a photomask having a wavy contour of the light shielding layer. Alternatively, the partition insulating layer PI may be formed using a photomask that does not have a wavy contour of the light shielding layer. For example, the light-scattering by the reflective layer REF can be used to make the outline of the through-hole TH undulate. That is, by appropriately setting the diameter and / or density of the convex portions provided on the surface of the reflective layer REF, even if a photomask having a wavy contour is not used, the through hole The contour of TH can be made into a waved shape.

  Various modifications can be made to the organic EL display device described above. For example, the organic EL display device may be a bottom emission type instead of a top emission type. Further, the organic EL display device may adopt a configuration in which a voltage signal is written as a video signal instead of a configuration in which a current signal is written as a video signal. Further, in the organic EL display device, other driving methods such as a passive matrix driving method and a segment driving method may be used instead of the active matrix driving method.

Examples of the present invention will be described below.
(Example)
In this example, the organic EL display device described with reference to FIGS. 1 to 4 was manufactured by the following method.

  First, a structure was prepared in which the relief layer RF, the reflective layer REF, the partition insulating layer PI, and the organic EL element OLED were omitted from the array substrate AS of FIG.

  Next, a dispersion containing a resin and glass particles was applied on the passivation film PS. The relief layer RF was obtained by drying this coating film.

Next, a reflective layer RF made of silver and having a thickness of 200 nm was formed on the relief layer RF by sputtering. When this reflective layer RF was observed with a scanning electron microscope, convex portions having an average particle diameter of about 0.5 μm were distributed on the surface thereof at a density of about 2,000,000 pieces / mm ² .
Thereafter, a planarizing layer FL made of an acrylic resin was formed on the reflective layer RF.
Next, a pixel electrode PE made of ITO was formed on the planarizing layer FL. The pixel electrode PE was obtained by forming an ITO layer on the planarizing layer FL by sputtering and patterning it.

  Next, a partition insulating layer PI made of an acrylic resin was formed on the planarization layer FL and the pixel electrode PE. The partition insulating layer PI was formed by photolithography using a positive photoresist. The dimension of the through hole TH in the X direction was about 78 μm, and the dimension in the Y direction was about 314 μm.

  When the partition insulating layer PI was observed with a scanning electron microscope, the outline of the through hole TH was irregularly waved. On each side of the outline of the through hole TH, the density of the wave peaks was about 46 / mm. The average height H of these peaks was about 3 μm.

  Next, the surface of the partition insulating layer PI was subjected to a liquid repellent treatment, and the first solution was supplied to each through hole TH of the partition insulating layer PI by an ink jet method. Here, the first solution was prepared by dissolving polyethylene dioxythiophene (PEDOT) in pure water. Subsequently, the coating film was heated at 130 ° C. for 5 minutes to remove the organic solvent from the coating film. In this way, a hole transport layer was formed on the pixel electrode PE.

  Subsequently, the second solution was supplied to each through hole TH of the partition insulating layer PI by an ink jet method. The second solution was prepared by dissolving polyphenylene vinylene (PPV) in toluene. Thereafter, the coating film was subjected to preliminary baking in which the coating film was heated at 120 ° C. for 5 minutes, and subsequently subjected to main baking in which the coating film was heated at 200 ° C. for 10 minutes. In this way, a light emitting layer was formed on the hole transport layer.

  Thereafter, the counter electrode CE was formed on the light emitting layer by vacuum deposition. Barium and silver were used as the material of the counter electrode CE. The array substrate AS was completed as described above.

  Next, the display panel DP was formed by bonding the array substrate AS and the sealing substrate CS through the seal layer SS in an inert atmosphere. As a material for the seal layer SS, an ultraviolet curable resin was used. Further, the organic EL display device was completed by mounting the video signal line driver XDR and the scanning signal line driver YDR on the display panel DP.

  Five organic EL display devices were manufactured by the above method, and the presence or absence of dark spots was examined for each of these organic EL display devices. As a result, no dark spot was confirmed in all organic EL display devices.

(Comparative example)
FIG. 5 is a plan view schematically showing a partition insulating layer of an organic EL display device according to a comparative example. In this partition insulating layer PI, the outline of the through hole TH is an octagon in which each side is not wavy.

  In this example, five organic EL display devices are formed by the same method as described in the example except that the relief layer RF is omitted and the through hole TH of the partition insulating layer PI is formed in the shape shown in FIG. Manufactured.

  Each of these organic EL display devices was examined for the presence of dark spots. As a result, a dark spot was confirmed in five organic EL display devices. In the organic EL element OLED visually recognized as a dark spot, pinholes were generated in the hole transport layer and / or the light emitting layer.

1 is a plan view schematically showing an organic EL display device according to one embodiment of the present invention. Sectional drawing which shows schematically the display panel of the organic electroluminescence display shown in FIG. FIG. 3 is a plan view schematically showing an example of a partition insulating layer that can be used in the display panel shown in FIG. 2. The top view which expands and shows a part of partition insulating layer shown in FIG. The top view which shows roughly the partition insulating layer of the organic electroluminescence display which concerns on a comparative example.

Explanation of symbols

  ACT ... Active layer, AS ... Array substrate, C ... Capacitor, CE ... Counter electrode, CS ... Sealing substrate, DE ... Drain electrode, DL ... Video signal line, DP ... Display panel, DR ... Drive transistor, FL ... Flattening Layer, 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, PE ... Pixel electrode, PI ... Partition insulation Layer, PS ... passivation film, PSL ... power supply line, PX ... pixel, REF ... reflection layer, RL ... relief layer, SC ... semiconductor layer, SE ... source electrode, SL1 ... scan signal line, SL2 ... scan signal line, SS ... Seal layer, SUB ... insulating substrate, SWa ... switching transistor, SWb ... switching transistor, SWc ... switching transistor, SWF ... sidewall formation layer, TH Holes, UC ... undercoat layer, XDR ... video signal line driver, YDR ... scanning signal line driver.

Claims (3)

An insulating substrate;
A first electrode covering a part of one main surface of the insulating substrate;
A partition insulating layer that covers the main surface and has a through hole having a wavy outline when viewed from a direction perpendicular to the main surface, corresponding to the first electrode;
A second electrode facing the first electrode;
An organic EL display device comprising an active layer interposed between the first and second electrodes and including a light emitting layer.   The organic EL display device according to claim 1, further comprising a light scattering layer interposed between the insulating substrate and the first electrode.   The organic EL display device according to claim 2, wherein the light scattering layer includes a light reflection layer.

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