JP2007012387A - Manufacturing method of organic electroluminescent display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an organic electroluminescent display device excelling in luminance uniformity in an entire pixel formation area. <P>SOLUTION: In this manufacturing method of an organic electroluminescent display device composed by forming the pixel formation area by arranging a plurality of pixels in a matrix-like shape on a substrate, when an organic material layer for each pixel is formed by applying a solution to the pixel formation area by an ink jet method, the solution is sequentially applied from a generally central part to a peripheral part of the image formation area. For instance, the application is carried out such that a line formed by connecting the respective pixels in an order of the application draws a nearly spiral shape or nearly concentric circles starting from a generally central part of the pixel formation area. Alternatively, when the organic material layer for each pixel is formed by applying the solution to the pixel formation area by an ink jet method, temperature control for the substrate is executed such that the generally central part of the pixel formation area is set at a temperature higher than that of the peripheral part. The temperature control for the substrate is executed by heating the generally central part of the pixel formation area 1 of the substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an organic electroluminescence display device in which a plurality of pixels are arranged in a matrix on a substrate to form a pixel formation region.

  An organic electroluminescence (hereinafter referred to as EL) element is a self-luminous element, has a wide viewing angle, does not require a backlight, is easy to reduce thickness and power consumption, and has a high response speed. Because of its advantages, it has attracted attention as a next-generation display device that replaces liquid crystal display devices. Organic EL elements can be broadly classified into high molecular types and low molecular types depending on the material of the light emitting layer. Among these, the polymer type organic EL element is suitable for a high-definition, large-screen display device because the area can be easily increased. A light emitting layer of a polymer type organic EL element is formed by applying a solution containing a polymer organic material and a solvent to a substrate, and is often formed by, for example, an ink jet method.

When an organic material layer including a light emitting layer is formed by an inkjet method, a predetermined liquid material (solution) is discharged to the pixel formation region on a substrate including a pixel formation region in which a plurality of pixels are continuously formed at a predetermined interval. The discharged liquid material is dried (for example, refer to Patent Document 1). Normally, when applying the solution in the pixel formation region, as indicated by an arrow B in FIG. 3, by scanning the pixel formation region 11 in parallel from one edge of the pixel formation region 11 to the other edge, Application of the pixel formation region 11 is performed. Thereafter, the applied solution is dried to remove the solvent, whereby an organic material layer or the like is formed.
JP 2001-291484 A

  By the way, the drying of the solution applied by the ink jet method does not proceed uniformly throughout the pixel formation region 11. For example, the solution applied to the pixels in the vicinity of the peripheral edge portion 12 of the pixel formation region 11 is dried quickly, but the solution is positioned away from the outer peripheral edge of the pixel formation region 11 toward the inner peripheral side, that is, at the center of the pixel formation region 11. The solution applied to the pixel tends to be slower to dry. Such a difference in drying speed at each part in the pixel formation region 11 causes uneven coating, which causes uneven luminance in the obtained display device.

  Accordingly, the present invention has been proposed in view of such a conventional situation, and an object thereof is to provide a method of manufacturing an organic electroluminescence display device having excellent luminance uniformity in the entire pixel formation region.

  In order to solve the above-described problems, a method for manufacturing an organic electroluminescence display device according to the present invention is a method for manufacturing an organic electroluminescence display device in which a plurality of pixels are arranged in a matrix on a substrate to form a pixel formation region. In the method, when the organic material layer of each pixel is formed by applying a solution in the pixel formation region by an inkjet method, the solution is sequentially applied from a substantially central portion to a peripheral portion of the pixel formation region. It is characterized by.

  When the solution is applied by the inkjet method, the solvent in the solution gradually evaporates immediately after the application and diffuses into the surrounding atmosphere. At this time, in the atmosphere around the substantially central portion of the pixel formation region, it is affected by the solvent evaporated from the surrounding (peripheral edge) pixels, so that the vapor density tends to be higher than that of the peripheral portion. As a result, in the conventional method, drying of the solution applied to the substantially central portion is hindered to cause uneven coating, resulting in a difference in the drying speed.

  Accordingly, in the present invention, the vapor density of the solvent that evaporates from the applied solution is controlled according to the location of the pixel formation region by devising the application order of the pixel formation region. That is, by applying the substantially central portion where the vapor density tends to be high and then sequentially applying the periphery (peripheral portion), the vapor density of the atmosphere around the central portion due to the vapor of the pixels in the peripheral portion is remarkable. The rise is suppressed. As a result, the difference in vapor density is reduced between the substantially central portion and the peripheral portion of the pixel formation region, and drying proceeds uniformly in each portion of the pixel formation region.

  The method for manufacturing an organic electroluminescence display device according to the present invention is a method for manufacturing an organic electroluminescence display device in which a plurality of pixels are arranged in a matrix on a substrate to form a pixel formation region, and the pixel When the organic material layer of each pixel is formed by applying a solution by an inkjet method in the formation region, the temperature of the substrate is controlled so that the substantially central portion of the pixel formation region is hotter than the peripheral portion. To do.

  In the method of manufacturing an organic electroluminescence display device as described above, the substrate temperature at the substantially central portion that is slow to dry is made high, and the substrate temperature at the peripheral portion that is fast to dry is made relatively low, so The drying speed is controlled at the substantially central portion and the peripheral portion, respectively. As a result, the difference in vapor density is reduced between the substantially central portion and the peripheral portion of the pixel formation region, and drying proceeds uniformly in each portion of the pixel formation region.

  According to the present invention, there is provided an organic electroluminescence display device capable of eliminating unevenness of brightness in a pixel formation region and suppressing occurrence of unevenness of brightness and realizing uniform display over the entire region of the pixel formation region. Can be manufactured.

  Hereinafter, a method for producing an organic electroluminescence display device to which the present invention is applied will be described in detail with reference to the drawings.

(First embodiment)
First, an organic electroluminescence (EL) display device to be manufactured will be described. The organic EL display device includes, for example, a plurality of thin film transistors (TFTs) on a substrate made of glass or the like, and a protective film made of SiN _x or the like formed on substantially the entire surface of the substrate so as to cover the TFTs. For example, a plurality of pixels arranged in a matrix, for example, corresponding to each TFT are provided. Here, a region where a plurality of pixels on the substrate are arranged is referred to as a pixel formation region. Adjacent pixels are partitioned by, for example, a grid-like pixel separation bank formed on the protective film.

  In each pixel, a stacked body of a pixel electrode (anode), an organic material layer including a light emitting layer, and a cathode is formed. Note that the stacked body may have a structure in which a cathode, an organic material layer, and an anode are stacked in this order.

  As the anode, for example, a transparent electrode such as indium tin oxide (ITO) can be used. As the cathode, for example, a metal such as aluminum or an alloy can be used.

  The organic material layer is a layer containing an organic material such as an organic EL material. The structure of the organic material layer may be a single layer structure of a light emitting layer that contributes to light emission or a multilayer structure. When the organic material layer has a multilayer structure, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and the like can be included in addition to the light emitting layer.

  In the organic EL display device having the above-described configuration, when the organic material layer of each pixel is formed by applying a paint by an ink jet method, uneven coating is a problem in the above-described conventional method. Therefore, in this embodiment, the coating unevenness is eliminated by devising the application order. That is, in the manufacturing method of the organic EL display device of this embodiment, first, a drive circuit, a TFT, and the like are formed on a substrate such as glass, and these are covered with a protective film. Next, a pixel electrode is formed on the protective film. When forming an anode made of ITO as a pixel electrode, an ITO film is formed on substantially the entire surface of a protective film or the like and then patterned into a desired shape by, for example, a photolithography method.

  Next, for example, a lattice-like pixel separation bank is formed on the protective film to partition each pixel. At this time, the pixel separation bank is disposed so as to surround each pixel electrode, and the surface of the pixel electrode is exposed on the bottom surface of the opening of the pixel separation bank.

  Next, an organic material layer is formed on the pixel electrode arranged in each pixel. In order to form an organic material layer, a solution containing an organic material for forming an organic material layer and a solvent is applied by a so-called inkjet method in which a solution discharge nozzle is discharged onto a pixel electrode.

  In the first embodiment, when the organic material layer of each pixel is formed by applying a solution in the pixel formation region by an inkjet method, the solution is sequentially applied from the substantially central portion to the peripheral portion of the pixel formation region. Examples of the application pattern include a pattern in which a line connecting the pixels in the order in which the pixels are applied draws an approximate spiral starting from the approximate center of the pixel formation region. Specifically, as shown in FIG. 1, each pixel is drawn so as to draw a substantially spiral trajectory A starting from a pixel located substantially in the center of the pixel formation region 1 and extending outward from the pixel. Apply the solution. Although FIG. 1 illustrates a state in which one region obtained by dividing the pixel formation region 1 with a solid line is regarded as one pixel and a solution is applied pixel by pixel, a plurality of pixels may be applied simultaneously. Further, the solution application pattern may be a pattern in which a line connecting the pixels in the order in which the pixels are applied draws a substantially concentric circle starting from the substantially central portion of the pixel forming region 1 and having the center.

  After the application of the pixel formation region 1 is completed, the applied solution is dried to remove the solvent, thereby obtaining an organic material layer. An organic EL display device is obtained by forming a cathode on the formed organic material layer and performing sealing or the like as necessary.

  As described above, in the first embodiment, the substantially central portion of the pixel formation region 1 that tends to have a high vapor density is applied first, and then, for example, the line connected in the order in which the pixels are applied is the approximate center of the pixel formation region. The coating sequence is such that the coating is sequentially applied in the outer circumferential direction so as to draw a substantially spiral or a substantially concentric circle starting from the portion, thereby suppressing a significant increase in vapor density at the substantially central portion of the pixel formation region 1. ing. As a result, the difference in vapor density between the surrounding atmosphere is reduced between the substantially central portion and the peripheral portion to be applied later. As a result, the difference in drying speed between the substantially central portion and the peripheral portion of the pixel formation region 1 is reduced. Therefore, in the obtained organic EL display device, the occurrence of uneven brightness due to the difference in drying speed is suppressed, and a uniform screen display can be performed over the entire pixel formation region 1.

  The first embodiment described above can also be applied to an organic EL display device capable of full color display. As an organic EL display device capable of full-color display, an organic EL display in which light emitting elements of three colors, a red light emitting element, a blue light emitting element, and a green light emitting element, are arranged in, for example, a stripe shape or a delta shape as an organic EL element in a pixel formation region When the manufacturing method according to the first embodiment is applied to an apparatus, a pixel of a corresponding color is selectively applied for each color of a light-emitting element by discharging a solution from a solution discharge nozzle of an inkjet head. What is necessary is just to apply | coat a solution one by one from the approximate center part of a formation area to a peripheral part.

(Second Embodiment)
In the manufacturing method of the organic EL display device of the present embodiment, the uneven coating is eliminated by giving the substrate a temperature distribution. The organic EL display device to be manufactured is the same as that in the first embodiment.

  A second embodiment of the method for manufacturing an organic EL display device will be described with reference to FIG. 2. First, a drive circuit, a TFT, and the like are formed on a substrate such as glass, and these are covered with a protective film. Next, a pixel electrode and a pixel separation bank arranged so as to surround each pixel electrode are formed on the protective film, thereby partitioning each pixel. Up to this point, the process is the same as in the first embodiment.

  Next, an organic material layer is formed on the pixel electrode arranged in each pixel. In order to form an organic material layer, a solution containing an organic material for forming an organic material layer and a solvent is applied by a so-called inkjet method in which a solution discharge nozzle is discharged onto a pixel electrode.

  In the second embodiment, when the organic material layer of each pixel is formed by applying a solution by an inkjet method in the pixel formation region, the temperature of the substrate is set so that the substantially central portion of the pixel formation region is higher than the peripheral portion. There is a feature in the point to control. For example, as shown in FIG. 2, by heating the substantially central portion of the pixel formation region 1 of the substrate, the substrate temperature is such that the substantially central portion of the pixel formation region 1 becomes the highest temperature and gradually decreases toward the peripheral portion. To control. When the solution is applied to the pixel formation region 1 of the substrate having such a temperature distribution, evaporation of the solvent from the applied solution is promoted in a region showing a relatively high temperature, that is, in a substantially central portion of the pixel formation region 1, Drying is accelerated.

  In the second embodiment, the order of applying the solution to the pixel formation region 1 and the application pattern are not particularly limited. As described in the first embodiment, for example, a substantially central portion of the pixel formation region 1 is applied first, and then, for example, a line connected in the order in which the pixels are applied is an abbreviation starting from the substantially central portion of the pixel formation region. The application sequence may be such that the application is sequentially performed in the outer circumferential direction so as to draw a spiral or a substantially concentric circle, or the pixel formation region is sequentially scanned from one edge of the pixel formation region to the other edge. It is good also as an order.

  As described above, in the second embodiment, the peripheral portion is obtained by, for example, heating the substantially central portion of the pixel forming region 1 to increase the evaporation rate (drying) of the solvent from the solution applied to the substantially central portion. The difference between the drying rate of the solution applied to the substrate is reduced. Therefore, in the obtained organic EL display device, the occurrence of uneven brightness due to the difference in drying speed is suppressed, and a uniform screen display can be performed over the entire pixel formation region 1.

  In the second embodiment described above, full-color display is possible in which light emitting elements of three colors, a red light emitting element, a blue light emitting element, and a green light emitting element, are arranged in a stripe shape or a delta shape as organic EL elements in the pixel formation region. Needless to say, the present invention can be applied to other organic EL display devices.

It is a schematic plan view which shows the manufacturing method of the organic electroluminescence display of 1st Embodiment. It is a schematic plan view which shows the manufacturing method of the organic electroluminescence display of 2nd Embodiment. It is a schematic plan view which shows the manufacturing method of the conventional organic EL display apparatus.

Explanation of symbols

  1 Pixel formation area

Claims (4)

A method of manufacturing an organic electroluminescence display device comprising a plurality of pixels arranged in a matrix on a substrate to form a pixel formation region,
When the organic material layer of each pixel is formed by applying a solution in the pixel formation region by an ink jet method, the solution is sequentially applied from a substantially central portion to a peripheral portion of the pixel formation region. A method for manufacturing an electroluminescence display device.   2. The organic electroluminescence display device according to claim 1, wherein the application is performed such that a line connecting the pixels in the order of application draws a substantially spiral or a substantially concentric circle starting from a substantially central portion of the pixel formation region. Manufacturing method. A method of manufacturing an organic electroluminescence display device comprising a plurality of pixels arranged in a matrix on a substrate to form a pixel formation region,
When the organic material layer of each pixel is formed by applying a solution in the pixel formation region by an ink jet method, the temperature of the substrate is controlled so that the substantially central portion of the pixel formation region is hotter than the peripheral portion. A method for manufacturing an organic electroluminescence display device.   4. The method of manufacturing an organic electroluminescence display device according to claim 3, wherein the temperature of the substrate is controlled by heating a substantially central portion of the pixel formation region of the substrate.

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