JP2010251156A - Color organic electroluminescent display device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color organic EL display device which can be manufactured by less man-hours and has superior display performance. <P>SOLUTION: The color organic EL display device 1, organic EL elements 2R, 2G, 2B which are to emit lights of respective red, green, and blue are arranged on the lower part substrate 10. For respective organic EL elements 2R, 2G, 2B, at least a reflecting electrode 13, the lower part transparent electrode 14, a light-emitting layer 18 containing an organic material capable of carrying out electric field light emission, and the upper part transparent electrode 21 are laminated on the lower part substrate 10, in this order. An optical distance between the light-emitting layer 18 and the reflecting electrode 13 is the same in the red organic EL element 2R and the green organic EL element 2G. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a color organic electroluminescence (EL) display device and a manufacturing method thereof.

  An organic EL display device is a light-emitting display device that utilizes an electroluminescence phenomenon of an organic compound, and has been put into practical use as a small-sized display device used for a mobile phone or the like.

  An organic EL display device is configured by arranging on a substrate a plurality of organic EL elements that can be independently controlled for each pixel. A color organic EL display device can be configured by periodically arranging a plurality of organic EL elements that emit light of different colors (different wavelengths) on a substrate.

  As one typical example, an upper light emitting organic EL display device is manufactured by laminating at least a drive circuit, a reflective electrode, a lower transparent electrode, a light emitting functional layer, and an upper transparent electrode in this order on a substrate. . In the light emitting functional layer, one or more of a plurality of functional layers such as an electron injection layer, an electron transport layer, a hole transport layer, and a hole injection layer are stacked together with a light emitting layer made of an organic compound.

  In such a configuration, electric charges are injected from the anode and the cathode into the light emitting layer through a hole transport layer and the like, and light emission occurs when the injected electric charges are recombined in the light emitting layer. Part of the generated light is emitted as direct light through the upper transparent electrode, and the other part is reflected by the reflective electrode as reflected light and then emitted through the upper transparent electrode.

  By adjusting the optical distance between the light emitting layer and the reflective electrode of each organic EL element, the emitted light that combines direct light and reflected light has the desired intensity and chromaticity based on the cavity effect. Can be optimized.

  In the organic EL elements having different emission colors, the optical distance between the light emitting layer and the reflective electrode from which the emitted light having a desired intensity and chromaticity is obtained differs due to the difference in wavelength. Therefore, the color organic EL display device is generally manufactured by changing the optical distance between the light emitting layer of the organic EL element and the reflective electrode for each emission color (see, for example, Patent Document 1). .

JP 2003-142277 A

  However, in the conventional color organic EL display device, in order to change the optical distance between the light emitting layer of the organic EL element and the reflective electrode for each emission color, the emission color is independent for each emission color (for example, the emission color is red). , At least three times for three colors of green and blue), it is necessary to perform processing including film formation and patterning.

  When the number of processing increases, not only the number of manufacturing steps of the organic EL display device increases, but also the display of the organic EL display device as the necessary processing margin (for example, the overlap margin for patterning by photolithography) increases. The aperture ratio which is one of the performances deteriorates.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color organic EL display device that can be manufactured with a smaller number of processings than before and that can obtain desired display performance, and a method for manufacturing the same. And

  In order to solve the above problems, an organic EL display device of the present invention is a color organic EL display device in which a plurality of organic EL elements that should emit light in different colors are arranged on a substrate, and each of the organic EL display devices described above. The element is formed by laminating at least a reflective electrode, a lower transparent electrode, a light emitting layer containing an organic material capable of electroluminescence, and an upper transparent electrode in this order on the substrate, and between the light emitting layer and the reflective electrode. Is the same in at least two of the organic EL elements.

  According to such a configuration, the optical distance between the light emitting layer and the reflective electrode only needs to be controlled by the number of types smaller than the number of light emission colors, so the optical distance for all light emission colors. The manufacturing process of the organic EL display device is simplified as compared with the case where the control is independently performed.

  Here, the plurality of organic EL elements are a blue organic EL element, a green organic EL element, and a red organic EL element, and an optical distance between the light emitting layer and the reflective electrode is the green organic EL element. The same may be applied to the red organic EL element.

  According to such a configuration, it is easy to obtain red light and green light whose intensities and chromaticities are within practical ranges by designing the optical distances to be the same for red and green whose wavelengths are close. For blue having a different wavelength, the optical distance for obtaining the optimum blue light may be designed independently.

  For example, the optical distance can be controlled by the thickness of the lower transparent electrode. For example, with the configuration in which the thickness of the lower transparent electrode is the same for red and green, it is possible to reduce the number of processing steps required for each type of thickness of the lower transparent electrode. Such processing steps include, for example, film formation and patterning.

  The lower transparent electrode may be formed by laminating two or more layers in at least the two organic EL elements.

  According to such a configuration, after the lower transparent electrode is once formed on the entire surface, it is completely removed in the organic EL element excluding at least the two organic EL elements, and then the lower transparent electrode is again added to the entire surface. It is efficiently manufactured by the method of forming.

  The present invention can be realized not only as such an organic EL display device but also as a method for manufacturing an organic EL display device.

  An organic EL display device according to the present invention is a color organic EL display device in which a plurality of organic EL elements that should emit light in different colors are arranged on a substrate, and in at least two of the organic EL elements, a light emitting layer and The optical distance between the reflective electrode is the same.

  This feature allows the optical distance between the light emitting layer and the reflective electrode to be controlled by a number of types smaller than the number of light emission colors, so that the optical distance is independently controlled for all light emission colors. Compared with the case where it does, the manufacturing process of the said organic EL display apparatus is simplified.

The top view which shows an example of a structure of the organic electroluminescent display apparatus in embodiment Sectional drawing which shows an example of a structure of the organic electroluminescent display apparatus in embodiment Graph showing simulation results of current luminous efficiency versus thickness of lower transparent electrode Graph showing the simulation result of chromaticity against the thickness of the lower transparent electrode The figure explaining the manufacturing process of the principal part of the organic electroluminescence display in embodiment The figure which shows the example of the resist pattern used for manufacture of the organic electroluminescence display in embodiment

  An organic EL display device according to an embodiment of the present invention is a color organic EL display device in which a plurality of organic EL elements that should emit light in different colors are arranged on a substrate, and is between a light emitting layer and a reflective electrode. These optical distances are the same in the organic EL elements of at least two colors. As an example, the optical distance between the light emitting layer and the reflective electrode is controlled by the thickness of the transparent electrode provided between the light emitting layer and the reflective electrode.

  The inventors have determined the optical distance (specifically, the light emitting layer and the light emitting layer) between the light emitting layer and the reflective electrode for three light emission colors commonly used in color organic EL display devices, namely red, green, and blue. The relationship between the thickness of the transparent electrode provided between the reflecting electrode and the intensity and chromaticity of the emitted light was determined by simulation. As a result, it was found that the same thickness of transparent electrode exists that can be applied to red and green.

  Based on the result of this simulation, in the color organic EL display device of red, green, and blue, a specific configuration is proposed in which transparent electrodes having the same thickness are provided on the red and green organic EL elements.

  Hereinafter, a configuration of an organic EL display device according to an embodiment of the present invention, a result of the above-described simulation, and a manufacturing method will be described with reference to the drawings.

(Constitution)
FIG. 1 is a top view showing an example of the configuration of an organic EL display device 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the organic EL display device 1 is configured by disposing organic EL elements 2R, 2G, and 2B that emit light in red, green, and blue, respectively, on a substrate. The organic EL elements 2R, 2G, and 2B are separated by a partition wall 17.

  FIG. 2 is a cross-sectional view of the organic EL display device 1 taken along the line AA ′.

  Here, FIG. 1 and FIG. 2 are schematic diagrams for explanation, and the ratios of the sizes of the respective parts are drawn unequally.

  As shown in FIG. 2, for example, the organic EL display device 1 includes a driving circuit layer 11 including a driving thin film transistor on a lower substrate 10 made of transparent glass, and a planarization layer made of an insulating organic material. 12, reflective electrode 13 made of APC (Ag, Pd, Cu alloy), lower transparent electrode 14 made of ITO (Indium, Tin, Oxide), hole injection layer 15 made of tungsten oxide, hole transport layer 16, photosensitive A partition wall 17 made of resin, a light emitting layer 18 containing an organic material capable of electroluminescence, an electron transport layer 19, an electron injection layer 20, an upper transparent electrode 21 made of ITO, and an upper substrate 22 made of transparent glass are laminated in this order. Configured.

  The hole transport layer 16 may be a polymer material or a low molecular material, but it is preferable that the hole transport layer 16 can be formed by a wet printing method, and when forming the organic light emitting layer as an upper layer, the hole transport layer 16 is not easily eluted. It is preferable to include a crosslinking agent. As an example of the hole transporting material, a copolymer containing a fluorene moiety and a triarylamine moiety or a low molecular weight triarylamine derivative can be used. As an example of the crosslinking agent, dipentaerythritol hexaacrylate or the like can be used.

  The materials of the electron transport layer 19 and the electron injection layer 20 are not limited in the present invention, and a well-known organic material or inorganic material is used.

  The optical distance from the light emitting layer 18 to the reflective electrode 13 is the same first distance in the organic EL elements 2R and 2G, and is a second distance shorter than the first distance in the organic EL element 2B.

As an example for realizing such two different optical distances, the lower transparent electrode 14 of the organic EL elements 2R and 2G includes a first portion 14A having a thickness t1 and a second portion having a thickness t2. 14B is laminated | stacked, and the lower transparent electrode 14 of the organic EL element 2B is comprised only by the 2nd part 14B whose thickness is t2.
(Examination of the thickness of the lower transparent electrode)
In the simulation described above, the refractive index n, the absorption coefficient k, and the thickness t of the reflective electrode 13, the lower transparent electrode 14, the hole injection layer 15, and the hole transport layer 16 are set to the values shown in Table 1, The thickness of the transparent electrode 14 was shaken from 10 nm to 200 nm. The values of n and k were defined as a function of light wavelength. Table 1 shows the range of n and k values for typical wavelengths.

  Under such conditions, when red, green, and blue lights having center wavelengths of 630 nm, 550 nm, and 450 nm are generated in the light emitting layer 18 of the organic EL elements 2R, 2G, and 2B, electrons are emitted from the light emitting layer 18. The light intensity and chromaticity of each color emitted to the transport layer 19 were determined. The light intensity and chromaticity were specifically expressed by current luminous efficiency and CIE color coordinates, respectively.

  FIG. 3 and FIG. 4 are graphs showing the results of simulation regarding the relationship between the thickness of the lower transparent electrode 14 and the intensity and chromaticity of the emitted light of each color.

  From the results shown in FIGS. 3 and 4, the inventors have noted that the lower transparent electrode 14 having a thickness of 110 nm can be commonly applied to red and green.

  As shown in FIG. 3, by setting the thickness of the lower transparent electrode 14 to 110 nm, the green current luminous efficiency becomes a maximum of 4.2 [cd / A]. When this thickness of 110 nm is applied to red, the current luminous efficiency of red is 2.8 [cd / A]. Although this value has an attenuation of about 10% compared to 3.1 [cd / A] which is the maximum of red current luminous efficiency, it is considered that there is no problem in practical use. Further, as shown in FIG. 4, in the vicinity of the thickness of 110 nm, the variation of the red CIE color coordinate with respect to the variation of the thickness is slight.

  Therefore, even if the thickness of the lower transparent electrode 14 applied to red is set to 110 nm as in the case of green, it is considered that practical red light can be obtained in terms of intensity and chromaticity.

  Note that the thickness of the lower transparent electrode 14 applied to blue may be 90 nm when emphasizing light emission efficiency and 50 nm when emphasizing desirable chromaticity of blue.

  Table 2 shows the current luminous efficiency and CIE color coordinates of each color when the thickness of the lower transparent electrode 14 is the same 110 nm in the red and green organic EL elements 2R and 2G and 50 nm in the blue organic EL element 2B. Shown in

(Production method)
Next, an example of a method for manufacturing the organic EL display device 1 having the above-described configuration will be described.

  In the manufacturing method of the present invention, the optical distance from the light emitting layer 18 to the reflective electrode 13 is set to the same first distance in the organic EL elements 2R and 2G, and the second distance shorter than the first distance in the organic EL element 2B. It is characterized by including a step of making a distance (specifically, a step of forming the lower transparent electrode 14 in two kinds of thicknesses). As other processes for manufacturing the organic EL display device 1, well-known processes used for general organic EL display devices are used.

  Hereinafter, description of general matters will be omitted as appropriate, and a process of mainly forming the lower transparent electrode 14 will be described in detail.

  FIG. 5A to FIG. 5F are diagrams illustrating a process for forming the reflective electrode 13 to the light emitting layer 18 at a desired optical distance in the manufacture of the organic EL display device 1. 5A to FIG. 5F correspond to the AA ′ cross section of the organic EL display device 1.

  FIGS. 6A and 6B are diagrams showing two types of resist patterns used in this step. Hereinafter, the patterns in FIGS. 6A and 6B are referred to as a pattern A and a pattern B, respectively.

  First, according to a general method for manufacturing an organic EL display device, a drive circuit layer 11 is formed by depositing a semiconductor in a thin film on the surface of the lower substrate 10. A drive circuit including an element such as a TFT (Thin Film Transistor) for each pixel is formed in the formed drive circuit layer 11. A planarization layer 12 made of an insulating organic material is formed on the drive circuit layer 11.

  Next, APC is deposited on the planarizing layer 12 to a thickness of 150 nm by sputtering. A photosensitive resist is applied to a thickness of about 1.5 μm, exposed with pattern B, and developed with 2.38% TMAH (tetramethylammonium hydroxide aqueous solution) (not shown). The reflective electrode 13 is formed by etching APC with a mixed solution of phosphoric acid, acetic acid and nitric acid (FIG. 5A).

  ITO is deposited to a thickness of 60 nm. A photosensitive resist 23 is applied to a thickness of about 1.5 μm, exposed with pattern A, and developed with 2.38% TMAH (FIG. 5B).

  The first portion 14A of the lower transparent electrode 14 is formed by etching ITO with 0.5% HF (hydrogen fluoride) (FIG. 5C).

  The second portion 14B of the lower transparent electrode 14 is formed by depositing ITO to a thickness of 50 nm (FIG. 5D).

  A photosensitive resist 24 is applied to a thickness of about 1.5 μm, exposed with pattern B, and developed with 2.38% TMAH (FIG. 5E).

  The lower transparent electrode 14 is separated for each pixel by etching ITO with 0.5% HF (FIG. 5F).

  Thereafter, the barrier ribs 17, the light emitting layer 18, the electron transport layer 19, the electron injection layer 20, and the upper transparent electrode 21 are formed and sealed with the upper substrate 22 in accordance with a general method for manufacturing an organic EL display device.

(Summary)
In the organic EL display device 1, the thickness of the lower transparent electrode 14 is the same 110 nm for the red and green organic EL elements 2R and 2G, and 90 nm is used for efficiency in the blue organic EL element 2B, and chromaticity is used. Is 50 nm, and the thickness of the lower transparent electrode 14 is covered by two types, so that the number of times of processing of the lower transparent electrode 14 is smaller than the case of using the lower transparent electrode 14 having three different thicknesses for each color. Reduced.

  In addition, as studied based on the simulation results, even when the lower transparent electrode 14 having the same 110 nm thickness is used in the red and green organic EL elements 2R and 2G, there is a problem in practical use in terms of strength and chromaticity. No red and green light is obtained.

  As a result, the increase in the number of manufacturing steps and the deterioration of display performance (particularly the aperture ratio) that accompanies an increase in the processing margin, which are caused by an increase in the number of times of processing, which are the aforementioned problems, can be suppressed. In addition, an organic EL display device having high display performance can be realized.

  Although the organic EL display device of the present invention has been described based on the embodiment, the present invention is not limited to this embodiment. Unless it deviates from the meaning of the present invention, those in which various modifications conceived by those skilled in the art have been made in the present embodiment are also included in the scope of the present invention.

  The organic EL display device of the present invention can be used for all display devices such as a mobile phone, a television, and a personal computer.

DESCRIPTION OF SYMBOLS 1 Organic EL display device 2R, 2G, 2B Organic EL element 10 Substrate 11 Drive circuit 12 Flattening layer 13 Reflective electrode 14 Lower transparent electrode 14A First part of lower transparent electrode 14B Second part of lower transparent electrode 15 Hole injection layer 16 hole transport layer 17 partition 18 light emitting layer 19 electron transport layer 20 electron injection layer 21 upper transparent electrode 22 upper substrate 23, 24 photosensitive resist

Claims (5)

A color organic electroluminescence display device in which a plurality of organic electroluminescence elements to emit light in different colors are arranged on a substrate,
Each of the organic electroluminescence elements is formed by laminating at least a reflective electrode, a lower transparent electrode, a light emitting layer containing an organic material capable of electroluminescence, and an upper transparent electrode in this order on the substrate.
The color organic electroluminescence display device, wherein an optical distance between the light emitting layer and the reflective electrode is the same in at least two of the organic electroluminescence elements. The plurality of organic electroluminescence elements are a blue organic electroluminescence element, a green organic electroluminescence element, and a red organic electroluminescence element,
2. The color organic electroluminescence display device according to claim 1, wherein an optical distance between the light emitting layer and the reflective electrode is the same in the green organic electroluminescence element and the red organic electroluminescence element. . The color organic electroluminescence display device according to claim 1, wherein the thickness of the lower transparent electrode is the same in at least two of the organic electroluminescence elements. The color organic electroluminescence display device according to claim 1, wherein the lower transparent electrode is formed by laminating two or more layers in at least the two organic electroluminescence elements. A method for producing a color organic electroluminescence display device, wherein a plurality of organic electroluminescence elements to emit light in different colors are arranged in a predetermined region on a substrate,
Forming a reflective electrode and a lower transparent electrode in this order on each of the regions on the substrate;
Removing the lower transparent electrode in a region excluding at least two of the plurality of regions;
Additionally forming the lower transparent electrode on the lower transparent electrode remaining without being removed and on the reflective electrode from which the lower transparent electrode has been removed;
Forming a light emitting layer containing an organic material capable of electroluminescence on the additionally formed lower transparent electrode;
Forming a top electrode on the light emitting layer. A method for manufacturing a color organic electroluminescence display device.

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