JP2007073608A - Display apparatus and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus which controls generation of a light emitting failure due to a short-circuit in display element arranged for each pixel, and also to provide the manufacturing method of the same apparatus. <P>SOLUTION: The display apparatus comprises display elements 40 on the substrate 120. Each display element 40 is formed of: a first electrode 60 arranged for each pixel; a separation wall 70 arranged along the edge 60E of the first electrode 60 for separating each pixel; an optical active layer 64 arranged on the first electrode 60; and a second electrode 66 arranged to cover the optical active layer 64 of each pixel. In the display element 40, a value of D2/D1 is equal to 1.2 or larger, when film thickness in the center area PXC of the pixel is defined as D1, and film thickness at the peripheral area PXP of the pixel as D2, in regard to the film thickness of the optical active layer 64 overlapped on the first electrode 60. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device including a self-luminous display element and a method for manufacturing the display device, and more particularly to a shape of a photoactive layer constituting the display element and a method for forming the photoactive layer.

  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. In such an organic EL display device, organic EL elements each holding an organic active layer containing an organic compound having a light emitting function are arranged in a matrix between a first electrode (anode) and a second electrode (cathode). The array substrate is provided. In such a configuration, for example, the first electrode (anode) and the organic active layer are arranged for each pixel. Further, the second electrode is arranged in common for a plurality of pixels.

In the manufacturing process of such an organic EL element, in the step of forming an organic active layer made of a low molecular organic compound, a vapor deposition method of vapor-depositing a material source scattered from a vapor deposition source can be applied. When the organic active layer is formed by such a vapor deposition method, foreign matter may be mixed. In the vicinity of the mixed foreign matter, the thickness of the organic active layer is thin, and there is a possibility that the first electrode and the second electrode are short-circuited. For this reason, a technique is known in which, after forming the organic active layer, a step of heating is added to melt the organic active layer and ensure the thickness of the organic active layer so as to suppress a short circuit around the foreign matter. (For example, refer to Patent Document 1).
US Pat. No. 6,506,088

  When the organic active layer is formed by the vapor deposition method as described above, the thickness of the organic active layer that overlaps the first electrode tends to be thin in the vicinity of the partition separating each pixel. Further, the steeper slope of the side wall of the partition wall tends to reduce the thickness of the organic active layer formed in the vicinity of the partition wall. For this reason, there is a possibility that the first electrode and the second electrode are short-circuited in the vicinity of the partition wall. Such a short causes a light emission failure of the display element.

  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 and a display device capable of suppressing the occurrence of a light emission failure due to a short circuit in a display element arranged for each pixel. It is to provide a manufacturing method.

The display device according to the first aspect of the present invention includes:
A first electrode arranged for each pixel;
A partition wall disposed along an edge of the first electrode and separating adjacent pixels;
A photoactive layer disposed on the first electrode;
A display device provided on a substrate, the display device including a second electrode disposed in common with a plurality of pixels and disposed to cover the photoactive layer,
Regarding the film thickness of the photoactive layer, D2 / D1 is 1.2 or more, where D1 is the film thickness at the center of the pixel and D2 is the film thickness at the periphery of the pixel. And

A display device according to a second aspect of the present invention provides:
A first electrode arranged for each pixel;
A partition wall disposed along an edge of the first electrode and separating adjacent pixels;
A photoactive layer formed on the first electrode by vapor deposition;
A display device provided on a substrate, the display device including a second electrode disposed in common with a plurality of pixels and disposed to cover the photoactive layer,
The photoactive layer is formed so that a film thickness in a peripheral part of the pixel is larger than a film thickness in a central part of the pixel.

A manufacturing method of the display device according to the third aspect of the present invention is as follows.
Forming a first electrode for each pixel;
Forming a partition separating each pixel along an edge of the first electrode;
Forming a photoactive layer on the first electrode by vapor deposition;
Forming a second electrode so as to cover the photoactive layer of each pixel,
The step of forming the photoactive layer is D2 / D1 when the film thickness of the photoactive layer is D1 at the center of the pixel and D2 at the periphery of the pixel. The step of heating the photoactive layer at a temperature equal to or higher than its melting point so as to be 1.2 or more.

  According to the present invention, it is possible to provide a display device and a method for manufacturing the display device capable of suppressing the occurrence of light emission failure due to a short circuit in a display element arranged for each pixel.

  Hereinafter, a display device and a manufacturing method thereof according to an embodiment of the present invention will be described 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 FIG. 1, 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.

  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 power supply for supplying power to the first electrode 60 side of the organic EL element 40 Line P.

  Furthermore, the array substrate 100 has a scanning line driving circuit 107 that supplies a scanning signal to each of the scanning lines Ym and a signal that supplies a video signal to each of the signal lines Xn in the peripheral area 104 along the outer periphery of the display area 102. A line driving circuit 108. 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 electrically separates an on pixel and an off pixel and has a function of holding a video signal to the on pixel, and a display element based on a video signal supplied via the pixel switch 10. The driving transistor 20 supplies a desired driving current, 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 driving transistor 20 are constituted by, for example, thin film transistors, and here, polysilicon is used for a semiconductor layer.

  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 configurations of the various organic EL elements 40 (R, G, B) are basically the same. That is, as shown in FIG. 2, the array substrate 100 includes a plurality of organic EL elements 40 arranged on the main surface side of the wiring substrate 120. Note that the wiring substrate 120 is formed on an insulating support substrate such as a glass substrate or a plastic sheet, 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, and various wirings (scanning). Line, signal line, power supply line, etc.).

  The organic EL element 40 is arranged in a matrix and is arranged in an independent island shape for each pixel PX, and a second electrode that is opposed to the first electrode 60 and is commonly arranged in the plurality of pixels PX. The electrode 66 and the photoactive layer 64 held between the first electrode 60 and the second electrode 66 are configured.

  The first electrode 60 constituting the organic EL element 40 is disposed on the insulating film on the surface of the wiring substrate 120 and functions as an anode.

  The photoactive layer 64 includes a light emitting layer. The photoactive layer 64 may include a functional layer other than the light emitting layer, and may include, for example, a hole injection layer, a hole transport layer, a blocking layer, an electron transport layer, an electron injection layer, a buffer layer, and the like. The photoactive layer 64 may have a layer structure in which a plurality of functional layers are combined. In the photoactive layer 64, the light emitting layer may be an organic material, and layers other than the light emitting layer may be an inorganic material or an organic material. The light-emitting layer is formed of an organic compound having a light-emitting function that emits red, green, or blue light.

  The second electrode 66 is disposed in common on the photoactive layer 64 of each pixel. The second electrode 66 is formed of a metal material having an electron injection function and functions as a cathode.

  In addition, the array substrate 100 includes a partition wall 70 that separates the pixels PX (R, G, B) for each adjacent color in the display area 102. The partition wall 70 is preferably formed so as to separate each pixel. The partition wall 70 is arranged in a lattice shape or a stripe shape along the edge 60E of each first electrode 60, and the opening shape of the partition wall exposing the first electrode 60 is rectangular. It is formed to become. The partition wall 70 is made of a resin material.

  In the organic EL element 40 configured as described above, holes and electrons are injected into the photoactive layer 64 sandwiched between the first electrode 60 and the second electrode 66, and these are recombined in the light emitting layer. Excitons are generated, and light is emitted by light emission of a predetermined wavelength that occurs when the excitons are deactivated. Here, the EL light emission is emitted from the lower surface side of the array substrate 100, that is, the first electrode 60 side, and constitutes a display screen.

  In the organic EL display device as described above, regarding the film thickness of the photoactive layer 64 that overlaps the first electrode 60, the film thickness at the central portion PXC of the pixel PX is D1, and the film at the peripheral portion PXP of the pixel PX. When the thickness is D2, D2 is set to be thicker than D1, and preferably D2 / D1 is set to 1.2 or more. Here, the film thickness of the photoactive layer 64 corresponds to the height of the photoactive layer 64 that overlaps from the surface 60S of the first electrode 60 in the normal direction of the surface 60S. This corresponds to the gap between the electrode 60 and the second electrode 66.

  The central portion PXC of the pixel PX corresponds to the central portion of the first electrode 60 and may be the center of the effective portion (portion overlapping the photoactive layer 64) of the first electrode 60 exposed from the partition wall 70, for example. . That is, the film thickness D1 corresponds to the film thickness of the photoactive layer 64 that overlaps the central portion of the first electrode 60. In the central part PXC, the photoactive layer 64 is formed substantially flat. That is, the surface 64S of the deposited photoactive layer 64 is substantially parallel to the surface 60S of the first electrode 60.

  The peripheral portion PXP of the pixel PX corresponds to a portion inside the partition 70 and adjacent to the partition 70 in the effective portion of the first electrode 60. That is, the film thickness D2 corresponds to the film thickness of the photoactive layer 64 that overlaps the first electrode 60 in the vicinity of the intersection between the side surface 70L of the partition wall 70 and the surface 60S of the first electrode 60. In the peripheral portion PXP, the photoactive layer 64 is formed while being influenced by the side surface 70L of the partition wall 70. That is, the surface 64S of the deposited photoactive layer 64 is not parallel to the surface 60S of the first electrode 60, and extends along the side surface 70L of the partition wall 70.

  The fact that the film thickness ratio is set as described above is that the photoactive layer 64 is formed with a film thickness necessary for light emission with sufficient luminance in the central portion PXC of the pixel PX, while the peripheral portion PXP of the pixel PX. It means that it is formed thicker than the central part PXC. That is, the photoactive layer 64 is formed in a thick film in the vicinity of the partition wall 70 where the film thickness tends to be thin, and it is possible to suppress a short circuit between the first electrode 60 and the second electrode 66. In the peripheral portion PXP of the pixel PX, it is possible to sufficiently prevent a short circuit between the first electrode 60 and the second electrode 66 by forming the photoactive layer 64 having a film thickness D2 of 1000 angstroms or more. It is.

  FIG. 3 is a diagram showing the relationship of the defect rate (%) due to occurrence of a short to the film thickness ratio (D2 / D1) of the photoactive layer 64. The defect rate corresponds to the proportion of organic EL display devices that have caused a light emission defect with respect to 100 organic EL display devices. As shown in FIG. 3, when the film thickness ratio was set to 1.2 or more, the defect rate could be reduced to 40% or less. Moreover, when the film thickness ratio was set to 1.5 or more, the defect rate could be reduced to 20% or less.

  Based on such a result, the ratio (D2 / D1) of the film thickness D1 at the central portion PXC of the pixel PX to the film thickness D2 at the peripheral portion PXP of the pixel PX is 1.2 or more for the photoactive layer 64. More preferably, by setting it to 1.5 or more, a short circuit between the first electrode 60 and the second electrode 66 can be effectively suppressed.

  Thus, the larger the film thickness ratio is set, that is, the thicker the film thickness of the peripheral part PXP with respect to the central part PXC of the pixel PX, the lower the defect rate due to the short circuit can be suppressed to 20% or less. . On the other hand, if the film thickness D2 at the peripheral portion PXP is made too thick with respect to the film thickness D1 at the central portion PXC of the pixel PX, a difference in luminous efficiency occurs between the central portion PXC and the peripheral portion PXP. Display unevenness may occur in the pixel PX. For this reason, the film thickness ratio (D2 / D1) of the photoactive layer 64 is set to 3 or less, preferably 2.5 or less.

  That is, the film thickness ratio (D2 / D1) of the photoactive layer 64 is set to 1.2 to 3, preferably 1.5 to 2.5. As a result, it is possible to simultaneously suppress a defect caused by a short circuit and a defect caused by display unevenness.

  The short circuit in the vicinity of the partition as described above is likely to occur particularly when the photoactive layer 64 made of a low molecular material is formed by vapor deposition. That is, the film thickness D2 of the photoactive layer 64 in the vicinity of the partition wall 70 tends to decrease as the inclination of the side surface 70L of the partition wall 70 already formed before forming the photoactive layer 64 becomes steeper. When the angle θ formed by the side surface 70L of the partition wall 70 and the surface 60S of the first electrode 60 exceeds 90 °, the film is formed not only on the photoactive layer 64 but also on the photoactive layer 64 by a dry process such as vapor deposition. Since the second electrode 66 is interrupted in the vicinity of the partition wall 70 and there is a possibility of causing a display defect, θ is set to 90 ° or less. If θ is less than 15 °, the partition wall 70 cannot be formed stably, and the pixels cannot be reliably separated, and the interval between adjacent pixels PX increases, There is a risk of hindering refinement. For this reason, θ is set to 15 ° or more.

  That is, the angle θ formed between the side surface 70L of the partition wall 70 and the surface 60S of the first electrode 60 is set to 15 ° to 90 °, and more preferably 30 ° to 60 °. Accordingly, the photoactive layer 64 and the second electrode 66 are not interrupted in the vicinity of the partition wall 70, and the pixels can be separated without increasing the interval between the pixels.

  Next, a method for manufacturing the display device having the above-described configuration will be described.

  First, as shown in FIG. 4A, in the display area 102 on the wiring substrate 120, the independent island-shaped first electrode 60 is formed for each pixel PX. That is, the first electrode 60 is formed by patterning a light-transmitting conductive film functioning as an anode on one main surface side of the wiring substrate 120. The first electrode 60 can be generally formed by a photolithography process.

  Subsequently, as shown in FIG. 4B, a partition wall 70 for separating each pixel is formed. That is, a photosensitive resin material such as an acrylic type positive tone resist is formed on the entire main surface of the wiring substrate 120 including the first electrode 60, and then patterned by a photolithography process, and then at 220 ° C. for 60 minutes. Is fired. Thereby, a grid-like partition wall 70 is formed along the edge 60E of the first electrode 60 so as to surround each pixel PX. In this embodiment, the partition wall 70 is formed such that the angle θ formed between the side surface 70L and the surface 60S of the first electrode 60 is 45 °. This angle θ can be controlled by the formation conditions of the partition wall 70, for example, the patterning conditions in the photolithography process, the baking conditions, and the like.

  Subsequently, the photoactive layer 64 is formed on the first electrode 60 in each pixel PX. That is, a low molecular material is selected as the photoactive layer 64, and a low molecular material source is deposited through the mask M having the opening pattern AP corresponding to the pixel PX. The step of forming the photoactive layer 64 includes a step of heating the material source at a temperature equal to or higher than its melting point after forming the material source by vapor deposition.

  In this embodiment, the step of forming the photoactive layer 64 includes a first film formation step of forming the bottom portion 64B of the photoactive layer 64 on the first electrode 60, and a bottom portion formed by the first film formation step. A step of heating 64B and a second film forming step of forming the upper portion 64T on the bottom portion 64B.

  In the first film forming step, as shown in FIG. 4C, first, a material source for forming the hole injection layer by the vapor deposition method is formed, and then the material for forming the hole transport layer by the vapor deposition method. Film the source. Thereby, the bottom 64B of the photoactive layer 64 is formed. In this embodiment, the hole injection layer was formed with a thickness of 30 Å, and the hole transport layer was formed with a thickness of 900 Å.

  In the heating step subsequent to the first film formation step, as shown in FIG. 4D, the substrate on which the bottom portion 64B is formed is heated at a temperature equal to or higher than the melting point of the material forming the bottom portion 64B, here the hole transport layer. In this embodiment, heating was performed at 160 ° C. for 40 minutes in a nitrogen atmosphere. As a result, the hole transport layer melts and has fluidity. Therefore, a part of the photoactive layer 64 formed along the side surface 70L of the partition wall 70 flows to the first electrode 60 side along the side surface 70L, and reaches the surface 60S of the first electrode 60 near the partition wall 70. accumulate. For this reason, the film thickness of the bottom portion 64B of the photoactive layer 64 that overlaps the first electrode 60 is thicker at the peripheral portion PXP of the pixel PX that is closer to the partition wall 70 than the central portion PXC of the pixel PX.

  In the second film formation process following the heating process, as shown in FIG. 4E, first, after forming a material source for forming the hole transport layer by vapor deposition, a light emitting layer is formed by mask vapor deposition. A material source for film formation is formed. Further, after forming a material source for forming the blocking layer by the vapor deposition method, a material source for forming the electron transport layer is formed by the vapor deposition method. Thereby, the upper part 64T of the photoactive layer 64 is formed. In the step of forming the upper portion 64T in this embodiment, the hole transport layer is formed with a thickness of 600 Å, the light emitting layer is formed with a thickness of 300 Å, and the blocking layer is formed with a thickness of 100 Å. The electron transport layer was formed to a thickness of 200 Å.

  As a result, a photoactive layer 64 is formed in which the film thickness D2 at the peripheral portion PXP of the pixel PX closer to the partition wall 70 is thicker than the film thickness D1 at the central portion PXC of the pixel PX. In this embodiment, the film thickness ratio D2 / D1 of the photoactive layer 64 is set to 2.

  As described above, the total film thickness of the bottom 64B formed in the first film formation process prior to the heating process is the total film of the upper part 64T formed in the second film formation process after the heating process. Thick enough than the thickness. For this reason, the film thickness of the bottom 64B is dominant in the film thickness of the photoactive layer 64. That is, by heating the bottom portion 64B and optimizing the film thickness ratio between the pixel central portion PXC and the pixel peripheral portion PXP (in other words, heating so that the film thickness ratio becomes 1.2 or more), When the upper portion 64T is formed, the photoactive layer 64 having an optimum film thickness ratio (D2 / D1) is obtained.

  Further, the film thickness ratio (D2 / D1) of the photoactive layer 64 can be controlled by the film forming conditions in the first film forming process and the second film forming process and the heating conditions in the heating process.

  Subsequently, as shown in FIG. 4F, a second electrode 66 common to the plurality of pixels PX is formed on the photoactive layer 64. That is, the second electrode 66 can be formed by a dry process, for example, a vapor deposition method, with a metal material source functioning as a cathode on one main surface side of the wiring substrate 120 on which the photoactive layer 64 is disposed.

  By such a process, the organic EL element 40 is formed. According to the organic EL element 40 thus formed, it was confirmed that a short circuit between the first electrode 60 and the second electrode 66 could be suppressed.

  As described above, according to this embodiment, with respect to the photoactive layer interposed between the first electrode and the second electrode, the film thickness at the peripheral part of the pixel is changed to the film thickness at the central part of the pixel. Increasing the thickness and optimizing the film thickness ratio can suppress the occurrence of light emission failure due to a short between the first electrode and the second electrode. In addition, the photoactive layer having such an optimal film thickness ratio can be formed by adding a step of heating the photoactive layer at a temperature equal to or higher than its melting point to the forming step.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. In addition, 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 the structure of one pixel of the organic EL display device shown in FIG. FIG. 3 is a diagram showing the relationship of the defect rate to the film thickness ratio of the photoactive layer constituting the organic EL element. FIG. 4A is a diagram for explaining a manufacturing process for forming the organic EL display device, and shows a process of forming the first electrode. FIG. 4B is a diagram for explaining a manufacturing process for forming the organic EL display device, and shows a process of forming a partition. FIG. 4C is a diagram for explaining a manufacturing process for forming the organic EL display device, and shows a process for forming the bottom of the photoactive layer. FIG. 4D is a diagram for explaining a manufacturing process for forming the organic EL display device, and is a diagram illustrating a process of heating the photoactive layer. FIG. 4E is a diagram for explaining a manufacturing process for forming the organic EL display device, and shows a process for forming the upper portion of the photoactive layer. FIG. 4F is a diagram for explaining a manufacturing process for forming the organic EL display device, and is a diagram illustrating a process of forming the second electrode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL display apparatus, 10 ... Pixel switch, 20 ... Drive transistor, 30 ... Storage capacitor element, 40 ... Organic EL element, 60 ... 1st electrode, 60E ... Edge part, 64 ... Photoactive layer, 64B ... Bottom part, 64T ... Upper part, 66 ... Second electrode, 70 ... Partition, 70L ... Side face, 100 ... Array substrate, 120 ... Wiring substrate, PX ... Pixel, PXC ... Center part of pixel, PXP ... Peripheral part of pixel, D1 ... Film thickness at the center, D2 ... Film thickness at the periphery of the pixel,

Claims (7)

A first electrode arranged for each pixel;
A partition wall disposed along an edge of the first electrode and separating adjacent pixels;
A photoactive layer disposed on the first electrode;
A display device provided on a substrate, the display device including a second electrode disposed in common with a plurality of pixels and disposed to cover the photoactive layer,
Regarding the film thickness of the photoactive layer, D2 / D1 is 1.2 or more, where D1 is the film thickness at the center of the pixel and D2 is the film thickness at the periphery of the pixel. Display device.   The display device according to claim 1, wherein D2 / D1 is 1.5 or more.   The display device according to claim 1, wherein D2 / D1 is 3 or less.   The display device according to claim 1, wherein an angle formed between a side surface of the partition wall and a surface of the first electrode is 30 ° or more and 60 ° or less. A first electrode arranged for each pixel;
A partition wall disposed along an edge of the first electrode and separating adjacent pixels;
A photoactive layer formed on the first electrode by vapor deposition;
A display device provided on a substrate, the display device including a second electrode disposed in common with a plurality of pixels and disposed to cover the photoactive layer,
The display device, wherein the photoactive layer is formed so that a film thickness in a peripheral part of the pixel is larger than a film thickness in a central part of the pixel. Forming a first electrode for each pixel;
Forming a partition separating each pixel along an edge of the first electrode;
Forming a photoactive layer on the first electrode by vapor deposition;
Forming a second electrode so as to cover the photoactive layer of each pixel,
The step of forming the photoactive layer is D2 / D1 when the film thickness of the photoactive layer is D1 at the center of the pixel and D2 at the periphery of the pixel. The manufacturing method of the display apparatus characterized by including the process of heating the said photoactive layer at the temperature more than the melting | fusing point so that it may become 1.2 or more. The step of forming the photoactive layer includes a first film forming step of forming a bottom portion on the first electrode, and a second film forming step of forming an upper portion on the bottom portion,
The method for manufacturing a display device according to claim 6, wherein the heating step is performed between the first film formation step and the second film formation step.

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