JP2006202709A - Organic electroluminescent display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent display device capable of realizing high definition and increase in the size without unduly complicating a structure or processes. <P>SOLUTION: For the organic electroluminescent display device 40 of a structure of aligning thin-film organic transistors 4 each having an organic semiconductor layer 12 and first transparent electrodes 14 each connected to the thin-film transistor on one face of a transparent substrate 2, and laminating organic electroluminescent layers 16 and second electrodes 18 on the first electrodes, color conversion layers 42, 42R, 42G, 42B converting colors of light emitted from the organic electroluminescent layers into other colors are fitted at a side of organic electroluminescent layers opposite to the first electrodes. With this, a higher definition and a scaling up can be realized without unduly making a structure or processes complicated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence display device, and more particularly to an active matrix color organic electroluminescence display device using an organic semiconductor.

  In general, an organic electroluminescence display device (hereinafter, also simply referred to as “organic EL display device”) has high-speed response unlike a liquid crystal display device, and emits light having no viewing angle dependency with low power consumption. Therefore, application is considered as a next generation display or the like (for example, Patent Document 1). In particular, this organic EL display device has been studied to be applied to a display of a portable terminal device or a personal computer, and is practically used as an area color display device in which a mono color is partially combined with an in-vehicle audio display panel. It has become.

In this type of organic EL display device, full color display is possible by combining display elements corresponding to red (R), green (G), and blue (B). Various studies have been made on high-performance organic EL display devices. Also, active matrix organic EL display devices, which are superior to the simple matrix method, are being studied for high-definition display.
FIG. 2 is a plan view of the pixel configuration of the active matrix organic EL display device as viewed from above, and FIG. 3 is a cross-sectional view taken along line AA in FIG. It is a schematic sectional drawing which shows. FIG. 4 is a simplified view of the organic electroluminescent layer shown in FIG.

First, as shown in FIG. 2, the organic EL display device is formed by arranging a large number of pixels Px vertically and horizontally in a matrix. FIG. 3 shows a cross section of the one pixel Px. This organic EL display device has a transparent substrate 2 common to all pixels Px made of, for example, a glass substrate, and a thin film organic transistor 4 having a switching function is formed thereon. The thin film organic transistor 4 is composed of a source 6, a drain 8, a gate 10, and the like. Specifically, a gate insulating film 10A made of, for example, a SiO ₂ film is formed on the upper surface of the gate 10.

  An organic semiconductor layer 12 is formed on the gate 10 covered with the gate insulating film 10A so as to cover the whole. The source 6 and the drain 8 are connected to each other on the organic semiconductor layer 12. They are separated from each other. The organic semiconductor 12 is provided in common over all the pixels Px. For example, pentacene can be used as the organic semiconductor layer 12. With this configuration, the thin film organic transistor 4 can be switched by controlling the voltage applied to the gate 10. The source 6 is connected to a signal line (not shown) for supplying an image signal, and the gate 10 is connected to a selection line (not shown) for selecting the pixel.

Above the thin film organic transistor 4, an anode 14, which is a lower electrode, is disposed for each pixel Px via an insulating layer 13, and the drain 8 is connected to the anode 14, and actually an image is formed. A voltage corresponding to the signal is applied.
On the anode 14, an organic electroluminescence layer (hereinafter simply referred to as “organic EL layer”) 16 that emits light L 1 and a cathode 18 that is an upper electrode are sequentially laminated. The cathode 18 is common to all the pixels Px. The anode 14 is generally a transparent electrode made of a transparent material having a work function around 5 eV (electron volts), for example, indium-tin oxide (hereinafter also simply referred to as “ITO”).

  The configuration of the organic EL layer 16 is shown in FIG. 4, and this organic EL layer 16 is composed of, for example, three layers of a hole transport layer 20, a light emitting layer 22, and an electron transport layer 24 in the illustrated example. However, there are various configurations such as a single layer type formed of a single layer and a stacked type formed of layers corresponding to the functions of charge injection, charge transport, and light emission. As the hole transport layer 20, for example, an aryldiamine compound (hereinafter also simply referred to as “TPD”) is used.

  The light emitting layer 22 is widely used from a high molecular material having fluorescence to a low molecular material and a metal complex. As a method for forming the light emitting layer 22, a wet method such as coating from a solution or a dry method such as vacuum deposition is used. Is selected. Here, as an example of the light emitting layer 22, there is a tris (8-quinolinol) aluminum organometallic complex (hereinafter also simply referred to as “Alq 3”). The Alq3 can also be used as the electron transport layer 24 because of its electron transport property. As the cathode 18, for example, a silver-magnesium alloy film having a small work function is used.

  As shown in FIG. 4, when a voltage is applied between the anode 14 and the cathode 18 from a power source 26 (actually the voltage of the image signal), holes injected from the anode 14 pass through the hole transport layer 20. On the other hand, the electrons injected from the cathode 18 of the silver-magnesium alloy film move in the light emitting layer 22 through the electron transport layer 24, and these electrons and holes are transferred in the light emitting layer 22. To emit light and emit light L1 to the outside. The light L1 emitted from the light emitting layer 22 is extracted to the outside through the transparent anode 14 and the transparent substrate 2. The emission color at this time is monochromatic emission depending on the emission color of the light emitting layer 22, and in the case of Alq3, it is green emission.

Japanese Patent Laid-Open No. 2001-230086

  By the way, in the case of performing color image elements, it is necessary to output R, G, and B colors for each of the pixels Px. Therefore, the organic EL layers 16 having different emission colors for the respective pixels Px. Need to form. FIG. 5 is a process diagram showing an example when the organic EL layer is formed. For example, the central pixel Px in FIG. 5 uses the organic EL layer 16G that emits green light, the right adjacent pixel Px uses the organic EL layer 16R that emits red light, and the left adjacent pixel Px uses blue light. An organic EL layer 16B that emits light is used. At this time, each organic EL material is dissolved in an organic solvent or water and deteriorates, so that general photolithography cannot be performed, and the pattern of the organic EL layer is generally different for each color. It is formed using the metal mask 28 (FIG. 5 shows a state in which the green organic EL layer 16G is formed).

  That is, as shown in FIG. 5, when the organic EL layer 16G is formed, the organic EL material is deposited and formed through the metal mask 28 opened only at a portion corresponding to the green organic EL layer 16G. Similarly, a panel capable of color display can be created by forming each organic EL material of red and blue.

  However, in the case of using three kinds of organic EL materials different for each pixel in this way, not only the manufacturing process becomes complicated, but when the size is increased, the metal mask 28 is bent so that it is not suitable for enlargement. Moreover, there is a problem that high definition is difficult. Therefore, recently, it is possible to adopt a color filter method using a color filter for white light emission or a color conversion film method using a color conversion film for blue light emission in a simple matrix organic EL display device. It is being considered.

  Here, FIG. 6 shows an example of a configuration in which a color filter or a color conversion film is applied to an active matrix organic EL display device. In the panel manufacturing process of the organic EL display device in the active matrix system, the thin film organic transistor 4 made of amorphous silicon or polysilicon TFT is formed. In the manufacturing process, heat of at least 400 degrees or more is generated. As shown in FIG. 6, a color filter or color conversion films 30R, 30G, and 30B made of a resin material having low heat resistance are formed on a transparent thin plate 32, and this thin plate 32 is formed on the lower substrate. It is conceivable to arrange them so as to face each other.

For this reason, light emission from the organic EL layer 16 must be extracted on the side of the upward arrow L2. However, as described above, the cathode 18 which is the upper electrode of the organic EL layer 16 is formed of a metal film such as silver-magnesium in order to inject electrons, and the light emission L2 cannot be taken out as it is. The problem arises. Therefore, it is conceivable to make the cathode 18 thin enough to obtain a certain light transmittance. In this case, however, the resistance value of the film of the cathode 18 becomes high, and the element deteriorates due to heat generation during current driving. In addition, since the light transmittance is lower than that of the transparent electrode, there is a problem that the power efficiency is extremely deteriorated, and it cannot be adopted.
The present invention has been developed to pay attention to the above-mentioned problems and to solve them effectively, and its purpose is to realize high definition and large size without complicating the structure and process so much. An organic electroluminescence display device is provided.

  In the invention according to claim 1, a thin film organic transistor having an organic semiconductor layer and a transparent first electrode connected to the thin film organic transistor are arranged side by side on one surface side of the transparent substrate, In the organic electroluminescence display device having the configuration in which the organic electroluminescence layer and the second electrode are stacked on each other, the organic electroluminescence layer emits light on the opposite side of the organic electroluminescence layer with respect to the first electrode. An organic electroluminescent display device comprising a color conversion layer for converting the color of the emitted light into another color.

According to the organic electroluminescence display device of the present invention, the following excellent operational effects can be exhibited.
Light emitted from the organic electroluminescent layer below the lower electrode, which is the first electrode connected to the thin-film organic transistor, instead of the conventional inorganic semiconductor as a switching element for operating as an active matrix Since a color conversion layer that converts colors into other colors is provided, and color light is converted and output by this color conversion layer, the overall structure of the device can be simplified and the number of manufacturing steps can be omitted. In addition, manufacturing at a low temperature is possible, and high miniaturization and large size can be realized. Furthermore, since light can be extracted from the transparent substrate side as in the conventional apparatus, good electron injection can be performed and light extraction efficiency can be improved.

Below, one example of an organic electroluminescence display device concerning the present invention is explained in full detail based on an accompanying drawing.
FIG. 1 is an enlarged sectional view showing one pixel portion of an organic electroluminescence display device according to the present invention. The same parts as those shown in FIG. 3 will be described with the same reference numerals.
As shown in FIG. 1, this organic electroluminescence display device 40 has a transparent substrate 2 common to all the pixels Px made of, for example, a glass substrate. The color conversion layer 42 is provided. The color conversion layer 42 is a layer for converting a color emitted from an organic electroluminescence layer, which will be described later, into another color. Here, the color conversion layer 42R for red (R) is matched to the three primary colors of light. In addition, the color conversion layer 42 includes three types of a color conversion layer 42G for green (G) and a color conversion layer 42B for blue (B).

  Each of the R color conversion layer 42R, the G color conversion layer 42G, and the B color conversion layer 42B is assembled to form one color element. The thin film organic transistor 4 having a switching function and the transparent anode 14 serving as the lower electrode as the first electrode are formed side by side on the color conversion layers 42R, 42G, and 42B. The thin film organic transistor 4 is composed of a source 6, a drain 8, a gate 10, and the like.

Specifically, a gate insulating film 10A made of, for example, a SiO ₂ film is formed on the upper surface of the gate 10. An organic semiconductor layer 12 is formed on the gate 10 covered with the gate insulating film 10A so as to cover the whole. Unlike the case shown in FIG. 3, the organic semiconductor layer 12 is formed individually for each pixel Px. The source 6 and the drain 8 are provided on the organic semiconductor layer 12 so as to be separated from each other. For example, pentacene can be used as the organic semiconductor layer 12. With this configuration, the thin film organic transistor 4 can be switched by controlling the voltage applied to the gate 10. The source 6 is connected to a signal line (not shown) for supplying an image signal, and the gate 10 is connected to a selection line (not shown) for selecting the pixel.

  Then, the anode 14 is connected to the drain 8, and a voltage corresponding to the pixel signal is actually applied. On the anode 14, an organic electroluminescence layer (hereinafter also simply referred to as “organic EL layer”) 16 that emits light L 1 and a cathode 18 that is an upper electrode as a second electrode are sequentially laminated. Unlike the case shown in FIG. 3, the cathode 18 is formed individually for each pixel Px. The anode 14 is generally a transparent electrode made of a transparent material having a work function around 5 eV (electron volts), for example, indium-tin oxide (hereinafter also simply referred to as “ITO”).

Here, as each of the color conversion layers 42R, 42G, and 42B, a color conversion filter such as a color filter, a color conversion phosphor film, or the like can be used. As the color conversion filter, a photosensitive colored resist corresponding to each color can be used, and the color conversion phosphor film is formed by dispersing a fluorescent material emitting a fluorescent color corresponding to each color in the photosensitive resist. can do. Thereby, the light L1 corresponding to each color can be output downward through the transparent substrate 2.
A protective film made of, for example, silicon nitride is preferably formed on the entire surface including the thin film organic transistor 4 and the cathode 18 formed as described above.

The manufacturing method of the organic EL display device 40 is, for example, as follows.
First, for example, a color conversion filter for color is formed by repeating the operation of applying, exposing, and developing, for example, a photosensitive colored resist on the upper surface side of the transparent substrate 2 corresponding to the red, green, and blue pigments. Color conversion layers 42R, 42G, and 42B are formed. In this case, a color conversion phosphor film may be formed in place of the color conversion filter by dispersing a fluorescent material emitting each color instead of a pigment in the photosensitive resist. Next, ITO is deposited on the entire surface with a thickness of 150 nm by RF sputtering, for example, as an anode material. Then, the ITO film is wet-etched with photolithography and an etching solution for ITO to form a transparent anode 14 as a lower electrode.

Next, metal tungsten is formed on the entire surface by sputtering to a thickness of 200 nm, and the gate 10 is formed by performing photolithography, dry etching with SF ₆ gas, or the like. Next, SiO ₂ is formed on the entire surface with a thickness of 100 nm by low-temperature plasma CVD, and then gate oxide film 10A is obtained by performing photolithography, dry etching with CHF ₃ gas, or the like. Next, a pentacene thin film is formed as the organic semiconductor layer 12 by vacuum vapor deposition through a metal mask. Next, αNPD (4,4′-bis [N- (1-naptyl) -N-pheny] -amino) bipheny) is 50 nm as the hole transporting layer 20 by vacuum vapor deposition through a metal mask, electron transport. The organic EL layer 16 is formed by depositing DPVBi (distyrylbiphenyl derivative) with a thickness of 50 nm as the layer / light emitting layers 22 and 24.

  Next, a source 6 and a drain 8 are formed by depositing a gold film through a metal mask, and then aluminum is formed on the uppermost surface of the organic EL layer 16 to form a cathode 18 as an upper electrode. Thus, the active matrix organic EL display device 40 can be manufactured.

As described above, in the organic EL display device 40 of the present invention, the color conversion layer 42 including the color conversion filter and the color conversion phosphor film is provided on the transparent substrate 2 for each pixel Px, and the organic semiconductor layer 12 is provided above the color conversion layer 42. Since the thin-film organic transistor 4 and the lower electrode (anode) 14 are provided side by side, and the organic EL layer 16 and the upper electrode (cathode) 18 are further provided on the lower electrode 14, color display can be performed. Not only can all processes be formed at low temperatures, but the structure can be simplified.
In addition, since light from the organic EL layer 16 can be output from the lower transparent substrate 2 side in the illustrated example, not only the light extraction efficiency can be increased, but also high miniaturization and large size can be achieved. be able to.
Moreover, in the said Example, although the color conversion layer was formed as one continuous layer between the thin film organic transistor 4 and the anode 14, and the transparent substrate 2, this color conversion layer was emitted from the organic EL layer at least. It suffices if it is partially formed in the range through which light passes.

It is an expanded sectional view which shows one pixel part of the organic electroluminescent display apparatus which concerns on this invention. It is a top view which shows the state which looked at the pixel structure of the active matrix type organic electroluminescence display from the upper surface. It is AA arrow sectional drawing in FIG. It is a figure which simplifies and shows the organic electroluminescent layer shown in FIG. It is a figure which shows the structure of an organic electroluminescent layer. It is sectional drawing which shows a structure at the time of applying a color filter and a color conversion film to an active-matrix type organic electroluminescent display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Transparent substrate, 4 ... Thin film organic transistor, 6 ... Source, 8 ... Drain, 10 ... Gate, 12 ... Organic-semiconductor layer, 14 ... Anode (lower electrode: 1st electrode), 16 ... Organic EL layer, 18 ... Cathode (upper electrode: second electrode), 40 ... organic EL (electroluminescence) display device, 42, 42R, 42G, 42B ... color conversion layer.

Claims (1)

A thin film organic transistor having an organic semiconductor layer and a transparent first electrode connected to the thin film organic transistor are arranged side by side on one side of the transparent substrate, and the organic electroluminescence layer and the first electrode are arranged on the first electrode. In the organic electroluminescence display device having a configuration in which two electrodes are laminated,
An organic electro, wherein a color conversion layer for converting the color of light emitted from the organic electroluminescent layer to another color is provided on the opposite side of the organic electroluminescent layer with respect to the first electrode. Luminescence display device.

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