JP2008234932A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with excellent display quality and extended life without giving rise to cost hike. <P>SOLUTION: There are provided on a substrate: a first electrode 60 arranged at each pixel; an organic active layer 62 arranged on the first electrode 60; a second electrode 64 arranged on the organic active layer 62 common to a plurality of pixels; and barrier ribs 70 arranged so as to cover a peripheral edge of the first electrode 60 for separating each pixel. A base layer 80 including the first electrode to be a ground of the organic active layer is provided with recessed parts 81 at a peripheral part 90P of an effective part 90 exposed from the barrier ribs. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device including a self-luminous element.

  In recent years, organic electroluminescence (EL) display devices have attracted attention as flat display devices. Since this organic EL display device is a self-luminous element, it has a wide viewing angle, can be thinned without requiring a backlight, has low power consumption, and has a high response speed. ing.

  Because of these characteristics, organic EL display devices are attracting attention as potential candidates for next-generation flat display devices that can replace liquid crystal display devices. Such an organic EL display device includes an organic EL element in which an organic active layer containing an organic compound having a light emitting function is sandwiched between an anode and a cathode. The organic EL element has an element configuration using a low molecular material for an organic active layer and an element configuration using a high molecular material.

  In many cases, low-molecular elements are formed by a dry process such as a vacuum evaporation method, and a laminated structure is easily formed. On the other hand, polymer elements are often formed by a selective coating method such as an ink jet method, and this selective coating method has an advantage that the use efficiency of a material for forming an organic active layer is remarkably good.

  When an organic active layer is formed using a polymer material by a selective coating method, it is required to apply a liquid material to each pixel with high accuracy. In response to such a demand, for example, a difference in wettability between a material for forming a partition and an anode (pixel electrode) for separating (insulating) adjacent pixels and a liquid material for forming an organic active layer is described. A technique for improving the pattern accuracy is used. In this case, the partition wall material is designed to have low wettability with respect to the organic active layer material, and conversely, the anode material is designed to have high wettability with respect to the liquid material.

  In this case, the liquid material applied and climbed on the partition wall flows down toward the effective part exposed from the partition wall (that is, the surface of the anode exposed from the partition wall) due to the liquid repellent action on the partition wall surface. However, since the liquid material is not compatible with the partition wall, the liquid material may be extremely thin in the periphery of the effective portion (that is, in the vicinity of the portion where the partition wall and the anode are in contact). In such a case, the thickness of the organic active layer formed by drying the liquid material may be extremely thin at the periphery.

  In the thinned portion of the organic active layer, a short circuit is likely to occur between the electrode (cathode) and the anode disposed on the organic active layer, and there is a possibility that non-lighting pixels (point defects) are generated. Further, in the thinned portion of the organic active layer, there is a possibility that the lifetime is reduced due to the concentration of current.

In order to solve such a problem, a configuration has been proposed in which a partition is provided with a lyophilic insulating film having lyophilicity so that the applied liquid material is evenly applied to the pixels (for example, Patent Document 1). reference).
JP 2002-202735 A

  In forming such a lyophilic insulating film, after depositing an inorganic insulating material by CVD or the like, a photoresist is applied, the photoresist is patterned by a photoetching process, and the inorganic insulating material exposed from the photoresist is exposed. It is conceivable to form by removing the material and further removing the photoresist. For this reason, the number of manufacturing steps is large, resulting in an increase in manufacturing cost.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a display device that has good display quality and can have a long life without causing an increase in manufacturing cost. There is.

A display device according to an aspect of the present invention includes:
A first electrode disposed in each pixel;
An organic active layer disposed on the first electrode;
A second electrode disposed on the organic active layer and common to a plurality of pixels;
A partition wall disposed on the periphery of the first electrode and separating each pixel, the substrate comprising:
The underlayer including the first electrode serving as the underlayer of the organic active layer has a recess in the periphery of the effective portion exposed from the partition.

  According to the present invention, it is possible to provide a display device that has good display quality and can have a long life without causing an increase in manufacturing cost.

  A display device according to an embodiment of the present invention will be described below with reference to the drawings. In this embodiment, a self-luminous display device such as an organic EL (electroluminescence) display device will be described as an example of the display device.

  As shown in FIGS. 1 and 2, the organic EL display device 1 includes an array substrate 100 having a display area 102 for displaying an image. The display area 102 includes a plurality of pixels PX (R, G, B) arranged in a matrix. At least the display area 102 of the array substrate 100 is sealed with a sealing body 200.

  In addition, the array substrate 100 includes a plurality of scanning lines Ym (m = 1, 2,...) Arranged along the row direction of the pixels PX (that is, the Y direction in FIG. 1) and columns substantially orthogonal to the scanning lines Ym. A plurality of signal lines Xn (n = 1, 2,...) Arranged along the direction (that is, the X direction in FIG. 1), and a power supply line P for supplying power to the organic EL element 40. ing.

  Furthermore, the array substrate 100 has at least a portion functioning as a scanning line driving circuit 107 that supplies a scanning signal to each of the scanning lines Ym in the peripheral area 104 along the outer periphery of the display area 102, and each of the signal lines Xn. And at least a part functioning as a signal line driver circuit 108 for supplying a video signal. All the scanning lines Ym are connected to the scanning line driving circuit 107. All signal lines Xn are connected to the signal line driving circuit 108.

  Each pixel PX (R, G, B) includes a pixel circuit and a display element that is driven and controlled by the pixel circuit. The pixel circuit shown in FIG. 1 is an example, and it goes without saying that a pixel circuit having another configuration may be applied. In the example shown in FIG. 1, the pixel circuit is supplied via the pixel switch 10 and a pixel switch 10 having a function of electrically separating an on pixel and an off pixel and holding a video signal to the on pixel. The driving transistor 20 supplies a desired driving current to the display element based on the video signal, and the storage capacitor element 30 holds the gate-source potential of the driving transistor 20 for a predetermined period. The pixel switch 10 and the drive transistor 20 are constituted by, for example, thin film transistors, and here, a thin film transistor including a semiconductor layer made of polysilicon is applied.

  The gate 20G of the drive transistor 20 is connected to the drain of the pixel switch 10 and one end of the storage capacitor element 30. A source 20 </ b> S of the driving transistor 20 is connected to the power supply line P and the other end of the storage capacitor element 30.

  The display element is composed of organic EL elements 40 (R, G, B) which are self-luminous elements. That is, the red pixel PXR includes an organic EL element 40R that mainly emits light corresponding to the red wavelength. The green pixel PXG includes an organic EL element 40G that mainly emits light corresponding to the green wavelength. The blue pixel PXB includes an organic EL element 40B that mainly emits light corresponding to the blue wavelength.

  The various organic EL elements 40 (R, G, B) have basically the same configuration, and are disposed on the wiring substrate 120 as shown in FIG. The wiring substrate 120 is formed on a first insulating layer (undercoat layer) 111, a second insulating layer (gate insulating film) 112, and a third insulating layer (on the insulating support substrate 101 such as a glass substrate or a plastic sheet). In addition to providing an insulating layer such as an interlayer insulating film 113 and a fourth insulating layer 114, the pixel switch 10, the driving transistor 20, the storage capacitor element 30, the scanning line driving circuit 107, the signal line driving circuit 108, various wirings (scanning lines) , Signal lines, power supply lines, etc.).

  The organic EL element 40 includes a first electrode 60 arranged in an independent island shape for each pixel PX, a second electrode 64 arranged opposite to the first electrode 60 and common to the plurality of pixels PX, The organic active layer 62 is held between the first electrode 60 and the second electrode 64.

  The first electrode 60 is disposed on the fourth insulating layer 114 on the surface of the wiring substrate 120 and functions as an anode. The first electrode 60 is connected to the drain 20D of the driving transistor 20 through a contact hole formed in the fourth insulating layer 114.

  The organic active layer 62 is disposed on the first electrode 60 and includes at least a light emitting layer. The organic active layer 62 may include, for example, a hole transport layer, a hole injection layer, a blocking layer, an electron transport layer, an electron injection layer, a buffer layer, and the like as a layer other than the light emitting layer, and these functions. In some cases, a composite layer may be included. The light-emitting layer is formed of an organic compound having a light-emitting function that emits red, green, or blue light. Such an organic active layer 62 is formed of at least a part of a polymer material, and can be formed by applying a liquid material by a selective coating method such as an inkjet method and then drying.

  The second electrode 64 is disposed on the organic active layer 62 and functions as a cathode. The second electrode 64 is disposed around the display area 102 and is connected to a second electrode power line (not shown) that supplies a common potential, here, a ground potential.

  Further, the array substrate 100 includes a partition wall 70 that separates the pixels PX (R, G, B) in the display area 102. The partition walls 70 are arranged in a lattice shape so as to cover the entire periphery of the first electrode 60. The partition wall 70 is formed of a material having liquid repellency with respect to the polymer material for forming the organic active layer 62, or is treated so that at least the surface has liquid repellency.

  By the way, in this embodiment, the base layer serving as the base of the organic active layer 62 has a recess in the periphery of the effective part exposed from the partition wall 70. In the configuration example illustrated in FIG. 2, the base layer 80 includes the first electrode 60 and further includes layers from the first insulating layer 111 to the fourth insulating layer 114 on the support substrate 101. The effective portion 90 corresponds to a portion of the base layer 80 exposed from the partition wall 70 (that is, a surface portion of the first electrode 60 exposed from the partition wall 70 and contributing to light emission). The peripheral portion 90P of the effective portion 90 corresponds to the vicinity of the portion where the first electrode 60 and the partition wall 70 are in contact, and the central portion 90C of the effective portion 90 substantially corresponds to the central portion PXC of the pixel PX. The underlayer 80 has a shape in which the central portion 90C of the effective portion 90 protrudes toward the organic active layer 62, and has a step between the central portion 90C and the peripheral portion 90P. That is, the foundation layer 80 has a concave portion 81 that is recessed from the central portion 90C in the peripheral portion 90P.

  With such a configuration, when the liquid material for forming the organic active layer 62 is applied toward the effective portion 90, the liquid material that has run on the partition wall 70 and the liquid material that has reached the central portion 90C of the effective portion 90 are: It becomes easy to flow down toward the concave portion 81 of the peripheral portion 90P. That is, the liquid material is not easily adapted to the partition wall 70, but collects in the recess 81 formed in the vicinity of the partition wall 70. For this reason, in the organic active layer 62 formed after the liquid material is dried, it is possible to suppress the thinning of the peripheral portion (near the partition wall).

  As a result, it is possible to prevent a short circuit between the first electrode 60 and the second electrode 64, and it is possible to suppress a decrease in lifetime due to current concentration in the thinned portion of the organic active layer 62. It becomes. In addition, since the partition 70 does not require an insulating film having high lyophilicity with respect to the liquid material for forming the organic active layer 62, an increase in manufacturing cost can be suppressed. Therefore, it is possible to provide a display device that has good display quality and can have a long life without causing an increase in manufacturing cost.

  Next, a specific configuration example of the base layer 80 will be described.

  In the first configuration example shown in FIGS. 2 and 3, the base layer 80 includes a convex pattern CP disposed in the central portion PXC of the pixel. By disposing such a convex pattern CP, in the effective portion 90 surrounded by the partition wall 70, the central portion 90C protrudes from the peripheral portion 90P, and the concave portion 81 is formed in the peripheral portion 90P.

  In other words, the base layer 80 has a cross-sectional shape in which the central portion 90C of the effective portion 90 protrudes from the peripheral portion 90P. At this time, in the example shown in FIG. 2, on the support substrate 101 having a substantially uniform thickness, the central portion 90C includes the first insulating layer 111, the second insulating layer 112, the third insulating layer 113, and the convex pattern CP. The peripheral portion 90P is thinner than the central portion 90C by the thickness of the convex pattern CP, while having a thickness corresponding to the total thickness of the fourth insulating layer 114 and the first electrode 60. . Thereby, the recessed part 81 is formed in the peripheral part 90P between the partition 70 and the center part 90C.

  In particular, in the example shown in FIG. 3, the convex patterns CP are arranged in an island shape. Therefore, the foundation layer 80 has the concave portion 81 in the peripheral portion 90P around the entire effective portion. For this reason, it is possible to suppress the thinning of the formed organic active layer 62 in the entire peripheral portion 90P.

  Such a convex pattern CP can be formed of the same material as the wiring of the same layer. In the example shown in FIG. 2, the convex pattern CP is an island-shaped metal layer formed by patterning the same material as the signal line X and the source 20S and drain 20D of the driving transistor 20 in the same process. This eliminates the need for a separate process for forming the convex pattern CP, that is, for forming the concave portion 81 in the underlying layer 80, and does not increase the manufacturing cost.

  Also in the second configuration example shown in FIGS. 2 and 4, the underlayer 80 includes the convex pattern CP arranged in the central portion PXC of the pixel. In particular, in the example shown in FIG. 4, the convex pattern CP is arranged along the longitudinal direction of the substantially rectangular effective portion 90. Therefore, the foundation layer 80 has the recessed part 81 in the peripheral part 90P along the longitudinal direction of the effective part. For this reason, at least in the peripheral portion 90P corresponding to the long side of the effective portion 90, it is possible to suppress the thinning of the formed organic active layer 62. Further, since the short side of the effective portion 90 is sufficiently short with respect to the long side, the influence of thinning is extremely small, and the same effect as in the first configuration example can be obtained.

  Such a convex pattern CP can be formed by wiring of the same layer. In the example illustrated in FIG. 4, the convex pattern CP is one wiring, for example, the signal line Xn. This eliminates the need for a separate process for forming the convex pattern CP, that is, for forming the concave portion 81 in the underlying layer 80, and does not increase the manufacturing cost. Note that the convex pattern CP may be two or more wires as shown in FIG. 5, and even in this case, the same effect can be obtained.

  Next, a method for manufacturing an organic EL display device will be described. Here, it is assumed that the organic active layer 62 is formed by a selective coating method using inkjet using a polymer material.

  First, as shown in FIG. 6A, a convex pattern CP is formed on the third insulating layer 113. That is, processing such as film formation and patterning of a metal film and an insulating film is repeated, and the pixel switch 10, the drive transistor 20, the storage capacitor element 30, the scanning line drive circuit 107, and the signal line drive circuit 108 are formed on the support substrate 101. , Signal lines Xn, scanning lines Ym, power supply lines P, and the like are formed. Among these steps, in the step of forming the source and drain of each of the pixel switch 10 and the driving transistor 20 and the signal line Xn, a conductive film, for example, an aluminum film is formed on the third insulating layer 113. Then, patterning is performed by a photolithography process or the like. In the same process, patterning is performed so that an aluminum film remains in a predetermined shape in the central portion PXC of the pixel, thereby forming a convex pattern CP having a thickness of 700 nm.

  Subsequently, as shown in FIG. 6B, a fourth insulating layer 114 is formed. That is, by depositing an organic material such as an acrylic resin material, the fourth insulating layer 114 having a thickness of 2.5 μm is formed. After this step, a step of 200 nm was observed between the region having the convex pattern CP and the other region. Thereafter, the first electrode 60 in contact with the drain 20 </ b> D of the driving transistor 20 is formed on the fourth insulating layer 114. That is, a conductive film such as indium tin oxide (ITO) is formed on the fourth insulating layer 114 and then patterned. Thereby, the first electrode 60 having a thickness of 50 nm is formed. Even after this step, the step between the region having the convex pattern CP and the other region remained at 200 nm. That is, a step is formed in the foundation layer 80 including the first electrode 60. The first electrode 60 may be generally formed by a photolithography process or may be formed by a mask sputtering method. Thereafter, the partition wall 70 is formed. That is, an organic material, for example, an acrylic resin material is formed and patterned in accordance with the pixel opening shape. Then, plasma treatment is performed for the purpose of fluorinating the surface of the acrylic resin material. Thereby, the partition wall 70 having liquid repellency is formed on the surface.

  In this manner, a concave portion 81 that is recessed by 200 nm from the central portion 90C is formed in the peripheral portion 90P of the effective portion 90 of the foundation layer 80 exposed from the partition wall 70.

  Subsequently, as shown in FIG. 6C, the organic active layer 62 is formed on the first electrode 60. That is, a liquid material containing an organic material having a hole injection function and a hole transport function is sequentially applied to each pixel by a selective coating method, and heat-dried at 200 ° C. for 5 minutes to form a film. Then, a liquid material containing an organic material having a light emitting function and an electron injection function and an electron transport function is applied by a selective coating method, and is heated and dried at 150 ° C. for 60 minutes. Thereby, the organic active layer 62 is formed.

Subsequently, as illustrated in FIG. 6D, the second electrode 64 is formed on the organic active layer 62. That is, a conductive layer to be the second electrode is formed by a vacuum evaporation method. Thereafter, the sealing body 200 is sealed in an inert gas, for example, nitrogen (N ₂ ) atmosphere.

  According to the organic EL display device thus manufactured, it was confirmed that light was emitted uniformly in the region corresponding to the effective portion of each pixel. Therefore, the current does not concentrate on a part of the organic active layer, and by adopting such a structure, it is possible to extend the lifetime of the organic EL element and improve the display quality. Become.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the gist of the invention in the stage of implementation. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 is a diagram schematically showing a configuration of an organic EL display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a structure when the organic EL display device shown in FIG. 1 is cut. FIG. 3 is a plan view schematically showing the structure of the effective portion in the first configuration example of the underlayer. FIG. 4 is a plan view schematically showing the structure of the effective portion in the second configuration example of the underlayer. FIG. 5 is a plan view schematically showing the structure of the effective portion in a modification of the second configuration example of the underlayer. FIG. 6A is a diagram for explaining a manufacturing process for forming an organic EL element, and is a diagram for explaining a process of forming a convex pattern. FIG. 6B is a diagram for explaining a manufacturing process for forming the organic EL element, and is a diagram for explaining a process of forming the fourth insulating layer, the first electrode, and the partition. FIG. 6C is a diagram for explaining a manufacturing process for forming an organic EL element, and is a diagram for explaining a process of forming an organic active layer. FIG. 6D is a diagram for explaining a manufacturing process for forming the organic EL element, and is a diagram for explaining a process of forming the second electrode.

Explanation of symbols

PX ... pixel Ym ... scanning line Xn ... signal line P ... power supply line 1 ... organic EL display device 10 ... pixel switch 20 ... drive transistor 30 ... storage capacitor element 40 ... organic EL element 60 ... first electrode 62 ... organic active layer 64 ... Second electrode 70 ... Partition wall 80 ... Underlayer 81 ... Recess 90 ... Effective part 100 ... Array substrate 101 ... Support substrate 111 ... First insulating layer 112 ... Second insulating layer 113 ... Third insulating layer 114 ... Fourth insulating Layer CP ... Convex pattern 120 ... Wiring substrate 200 ... Encapsulant

Claims (8)

A first electrode disposed in each pixel;
An organic active layer disposed on the first electrode;
A second electrode disposed on the organic active layer and common to a plurality of pixels;
A partition wall disposed on the periphery of the first electrode and separating each pixel, the substrate comprising:
The display device according to claim 1, wherein the base layer including the first electrode serving as a base of the organic active layer has a recess in a peripheral portion of the effective portion exposed from the partition.   The display device according to claim 1, wherein the base layer includes a convex pattern disposed in a central portion of the pixel.   The display device according to claim 2, wherein the convex pattern is an island-shaped metal layer formed of the same material as the wiring of the same layer.   The display device according to claim 2, wherein the base layer has a recess in a peripheral portion of the entire circumference of the effective portion.   The display device according to claim 2, wherein the convex pattern is at least one wiring along a longitudinal direction of the effective portion.   The display device according to claim 5, wherein the base layer has a concave portion in a peripheral portion along a longitudinal direction of the effective portion.   The display device according to claim 1, wherein the organic active layer is formed of a polymer material.   The display device according to claim 1, wherein at least a surface of the partition wall has liquid repellency.

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