JP2008310312A - Organic electroluminescent display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display device whose electric field-effect mobility is high and which has a TFT of high ON/OFF ratio. <P>SOLUTION: An organic electroluminescent display device comprises at least a driving TFT, and pixels comprising organic EL elements, formed by patterning on the same substrate of the driving TFT. The driving TFT has at least a substrate, a gate electrode, a gate insulating film, a semiconductor layer, a source electrode, and a drain electrode, and is so constituted such that the semiconductor layer has at least a resistive layer and an active layer whose electrical conductivity is higher than that of the resistive layer; the active layer contacts the gate insulating film; the resistive layer is arranged between the active layer and at least either of the source electrode and the drain electrode and is electrically connected to each other; and at least a light-emitting layer of the pixels is formed by patterning by an ink-jet method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent display device including an organic electroluminescent element and a TFT (Thin Film Transistor). In particular, the present invention relates to an organic light emitting display device including a TFT using an improved amorphous oxide semiconductor. In the present invention, a TFT means a field effect TFT unless otherwise specified.

2. Description of the Related Art In recent years, flat and thin image display devices (Flat Panel Displays: FPD) have been put into practical use due to advances in liquid crystal and electroluminescence (EL) technologies. In particular, an organic electroluminescent device using a thin film material that emits light when excited by passing an electric current (hereinafter sometimes referred to as “organic EL device”) can emit light with high luminance at a low voltage. Device thinning, lightening, miniaturization, and power saving are expected in a wide range of fields including mobile phone displays, personal digital assistants (PDAs), computer displays, automobile information displays, TV monitors, or general lighting. ing.
These FPDs are driven by an active matrix circuit of a TFT using an amorphous silicon thin film or a polycrystalline silicon thin film provided on a glass substrate as an active layer.

On the other hand, in order to further reduce the thickness, weight, and breakage resistance of these FPDs, an attempt has been made to use a lightweight and flexible resin substrate instead of a glass substrate.
However, the manufacture of the transistor using the above-described silicon thin film requires a relatively high temperature thermal process and is generally difficult to form directly on a resin substrate having low heat resistance.
Therefore, active development of TFTs using semiconductor thin films of amorphous oxides that can be formed at low temperatures, for example, In—Ga—Zn—O amorphous oxides, has been actively carried out (see, for example, Patent Document 1). .
A TFT using an amorphous oxide semiconductor can be formed at room temperature and can be formed on a film, and thus has recently attracted attention as a material for an active layer of a film (flexible) TFT. In particular, Tokyo Institute of Technology, Hosono et al. Reported that a TFT using a-IGZO has a field effect mobility of about 10 cm ² / Vs even on a PEN substrate, which is higher than that of an a-Si TFT on glass. In particular, it has attracted attention as a film TFT (see, for example, Patent Document 2).

On the other hand, higher definition of FPD has been demanded. In order to achieve high definition, the pixel of the organic EL element is required to be fine, and the TFT is required to be miniaturized.
As a means for forming high-definition pixels, an ink jet method is disclosed (for example, see Patent Document 3). However, a current-driven organic EL element needs to control a constant current even if the pixel becomes small. However, since the current value decreases with downsizing of a conventional TFT, it can cope with high definition of the pixel. It was difficult.

When using the TFT using the a-IGZO as a drive circuit of a display device, for ^example, the mobility of 1cm ² / Vs~10cm 2 / Vs, is insufficient to supply enough current, also the OFF current There is a problem that it is high and the ON / OFF ratio is low. In particular, in order to use it for driving an organic EL element, further improvement in mobility and ON / OFF ratio have been required.
JP 2006-165529 A JP 2006-186319 A Japanese Patent Laid-Open No. 10-12377

  An object of the present invention is to provide an organic electroluminescent display device (hereinafter referred to as “organic EL display device”) having a TFT using an amorphous oxide semiconductor having a high field effect mobility and a high ON / OFF ratio. Is to provide). In particular, it is an object to provide a high-definition organic EL display device that can be manufactured on a flexible resin substrate.

The above-described problems of the present invention have been solved by the following means.
<1> An organic electroluminescent display device in which at least a driving TFT and a pixel made of an organic electroluminescent element are patterned on the same substrate as the driving TFT. The driving TFT includes at least a substrate, a gate electrode, and a gate insulating film A semiconductor layer, a source electrode, and a drain electrode, wherein the semiconductor layer has at least a resistance layer and an active layer having higher electrical conductivity than the resistance layer, the active layer is in contact with the gate insulating film, A driving TFT in which the resistance layer is electrically connected between at least one of the active layer and the source electrode and the drain electrode, and at least the light emitting layer of the pixel is patterned by an inkjet method. An organic light emitting display device characterized by that.
<2> The driving TFT has at least the resistance layer and the active layer in layers on the substrate, the active layer is in contact with the gate insulating film, and the resistance layer includes at least the source electrode and the drain electrode. The organic electroluminescence display device according to <1>, which is in contact with one side.
<3> The organic electroluminescence display device according to <2>, wherein the thickness of the resistance layer of the driving TFT is larger than the thickness of the active layer.
<4> The organic electroluminescence display device according to <1>, wherein electrical conductivity between the resistance layer and the active layer continuously changes in the semiconductor layer of the driving TFT.
<5> The organic electroluminescence display device according to any one of <1> to <4>, wherein the semiconductor layer of the driving TFT contains an oxide semiconductor.
<6> The organic electroluminescence display device according to <5>, wherein the oxide semiconductor is an amorphous oxide semiconductor.
<7> The organic electroluminescence display device according to <5> or <6>, wherein an oxygen concentration of the active layer of the driving TFT is lower than an oxygen concentration of the resistance layer.
<8> The organic electric field according to any one of <5> to <7>, wherein the oxide semiconductor includes at least one selected from the group consisting of In, Ga, and Zn, or a composite oxide thereof. Luminescent display device.
<9> The oxide semiconductor contains the In and Zn, and the composition ratio of Zn and In (represented by the ratio of Zn to In, Zn / In) of the resistance layer is larger than the composition ratio Zn / In of the active layer <8> The organic electroluminescence display device according to <8>.
<10> The organic electroluminescence display device according to any one of <1> to <9>, wherein the electric conductivity of the active layer is 10 ⁻⁴ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ .
<11> The organic electroluminescence display device according to <10>, wherein the electric conductivity of the active layer is 10 ⁻¹ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ .
<12> The ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is from 10 ^{1 to} 10 ^10. <1>-<11> Organic electroluminescent display apparatus in any one of.
<13> The ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is 10 ² or more and 10 ⁸ or less. <12> The organic electroluminescent display device according to <12>.
<14> The organic electroluminescent display device according to any one of <1> to <13>, wherein the substrate is a flexible resin substrate.
<15> The organic electroluminescence display device according to any one of <1> to <14>, wherein the pixel is a high-definition pixel of 150 ppi or more.

A TFT using an amorphous oxide semiconductor can be formed at room temperature and can be manufactured using a flexible plastic film as a substrate, and thus has attracted attention as a material for an active layer of a film (flexible) TFT. In particular, as disclosed in JP-A-2006-165529, by using an In—Ga—Zn—O-based oxide for a semiconductor layer (active layer), a field effect mobility of 10 cm ² / Vs, ON / OFF TFTs formed on PET having a performance of more than 10 ³ have been reported. However, when this is used as a driving TFT of an organic EL display device, for example, the performance is still insufficient in terms of mobility and ON / OFF ratio. Conventionally, if a means for reducing the electron carrier concentration in the active layer is taken to reduce the OFF current, the electron mobility is steadily reduced, so that a TFT having both good OFF characteristics and high mobility is formed. Because it was difficult.
In addition, organic EL display devices are required to have high definition, which requires finer pixels and at the same time miniaturization of TFTs, and allows for better ON / OFF characteristics and application of high current with high mobility. Requested to do.
The inventors diligently searched for means for increasing the field effect mobility of the TFT and improving the ON / OFF ratio. As a result, it has at least a substrate, a gate electrode, a gate insulating film, a semiconductor layer, and a source / drain electrode, and the semiconductor layer has at least a resistance layer and an active layer having higher electrical conductivity than the resistance layer, The active layer is in contact with the gate insulating film, and the resistive layer is electrically connected between the active layer and at least one of the source electrode and the drain electrode, thereby solving the problem. I found it. In particular, the semiconductor layer includes at least an active layer in contact with the gate insulating film and a resistance layer in contact with the source electrode and the drain electrode, and the electrical conductivity of the active layer is higher than the electrical conductivity of the resistance layer. It has been found as an effective means.
As a means for achieving high definition of pixels, it has been found that patterning an organic EL material by an ink jet method is most preferable in combination with the above TFT, and the present invention has been achieved. Therefore, the organic EL display device of the present invention and a patterning method using an inkjet method in the organic EL display device are provided.

  According to the present invention, an organic electroluminescence display device (hereinafter, referred to as “organic EL display device”) including a TFT using an amorphous oxide semiconductor having high field effect mobility and a high ON / OFF ratio. ) Is provided. In particular, a high-definition organic EL display device that can be manufactured on a flexible resin substrate is provided.

1. TFT
The thin film field effect transistor of the present invention has at least a gate electrode, a gate insulating film, a semiconductor layer, a source electrode, and a drain electrode in sequence, applies a voltage to the gate electrode, and controls a current flowing through the semiconductor layer, This is an active element having a function of switching a current between a source electrode and a drain electrode. As the TFT structure, either a staggered structure or an inverted staggered structure can be formed.

The semiconductor layer in the present invention includes at least a resistance layer and an active layer having higher electrical conductivity than the resistance layer, the active layer is in contact with the gate insulating film, the active layer, the source electrode, and the drain electrode The resistance layer is electrically connected to at least one of the two.
Preferably, the substrate includes at least the resistance layer and the active layer in layers, the active layer is in contact with the gate insulating film, and the resistance layer is in contact with at least one of the source electrode and the drain electrode.
From the viewpoint of operational stability, it is preferable that the thickness of the resistance layer is larger than the thickness of the active layer.
Further, as another aspect, an aspect in which the electrical conductivity between the resistance layer and the active layer in the semiconductor layer continuously changes is also preferable.
Preferably, the semiconductor layer preferably contains an oxide semiconductor from the viewpoint that low temperature film formation is possible. In particular, the oxide semiconductor is more preferably in an amorphous state.
Preferably, the oxygen concentration of the active layer is lower than the oxygen concentration of the resistance layer.
Preferably, the oxide semiconductor includes at least one selected from the group consisting of In, Ga, and Zn, or a composite oxide thereof. More preferably, the oxide semiconductor contains In and Zn, and the composition ratio of Zn and In (represented by the ratio of Zn to In, Zn / In) of the resistance layer is greater than the composition ratio Zn / In of the active layer. large. Preferably, the Zn / In ratio of the resistance layer is 3% or more larger than the Zn / In ratio of the active layer, and more preferably 10% or more.
Preferably, the electric conductivity of the active layer is 10 ⁻⁴ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ , more preferably 10 ⁻¹ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ .
The electric conductivity of the resistance layer is preferably 10 ⁻² Scm ⁻¹ or less, more preferably 10 ⁻⁹ Scm ⁻¹ or more and less than 10 ⁻⁴ Scm ^−1, which is smaller than the electric conductivity of the active layer.
Preferably, the ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is from 10 ^{1 to} 10 ¹⁰ , more preferably Is 10 ² or more and 10 ⁸ or less.
From the viewpoint of operational stability, it is preferable that the thickness of the resistance layer is larger than the thickness of the active layer. Preferably, the ratio of the thickness of the resistance layer to the thickness of the active layer is more than 1 and 100 or less, more preferably more than 1 and 10 or less.
As another aspect, an aspect in which the electrical conductivity between the resistance layer and the active layer continuously changes is also preferable.
Preferably, the substrate is a flexible resin substrate.

When the electric conductivity of the active layer is less than 10 ⁻⁴ Scm ⁻¹ , high field effect mobility cannot be obtained, and when it is 10 ² Scm ⁻¹ or more, the OFF current increases and good ON / OFF is achieved. Since the ratio cannot be obtained, it is not preferable.

1) Structure Next, the structure of the TFT used in the present invention will be described.
FIG. 3 is a schematic diagram showing an example of an inverted stagger structure of the TFT of the present invention. When the substrate 51 is a flexible substrate such as a plastic film, an insulating layer 56 is disposed on one surface of the substrate 51, and a gate electrode 52, a gate insulating film 53, an active layer 54-1, and a resistance layer 54- are formed thereon. 2 and a source electrode 55-1 and a drain electrode 55-2 are provided on the surface thereof. The active layer 54-1 is in contact with the gate insulating film 53, and the resistance layer 54-2 is in contact with the source electrode 55-1 and the drain electrode 55-2. The composition of the active layer and the resistance layer is determined so that the electrical conductivity of the active layer when no voltage is applied to the gate electrode is higher than the electrical conductivity of the resistance layer. Here, for the active layer and the resistance layer, an oxide semiconductor disclosed in JP-A-2006-165529, for example, an In—Ga—Zn—O-based oxide semiconductor is used. These oxide semiconductors are known to have higher electron mobility as the electron carrier concentration is higher. That is, the higher the electric conductivity, the higher the electron mobility.
According to the structure of the present invention, when a voltage is applied to the gate electrode of the TFT and a channel is formed and turned on, the active layer serving as the channel has high electrical conductivity, so that the electric field of the transistor The effective mobility becomes high and a high ON current can be obtained. In the OFF state in which no voltage is applied to the gate electrode and the channel is not formed, an OFF current is kept low by interposing a resistance layer having a large electric resistance therebetween, and therefore the ON / OFF ratio The properties are greatly improved.

  The purpose of the structure of the TFT in the present invention is to provide a semiconductor layer so that the electrical conductivity in the vicinity of the gate insulating film of the semiconductor layer is higher than the electrical conductivity in the vicinity of the source electrode and the drain electrode of the semiconductor layer. As long as the state can be obtained, the means for achieving this is not limited to providing two semiconductor layers as shown in FIG. A multilayer structure of three or more layers may be used, or the electric conductivity may be changed continuously.

  FIG. 4 is a schematic diagram showing an example of a top gate structure, which is a TFT of the present invention. When the substrate 61 is a flexible substrate such as a plastic film, an insulating layer 66 is disposed on one surface of the substrate 61, a source electrode 65-1 and a drain electrode 65-2 are disposed on the insulating layer, and the resistance layer 64. -2, after laminating the active layer 64-1, the gate insulating film 63 and the gate electrode 62 are disposed. As in the inverted staggered configuration, the active layer (high electrical conductivity layer) is in contact with the gate insulating film 63, and the resistance layer (low electrical conductivity layer) is in contact with the source electrode 65-1 and the drain electrode 65-2. The active layer 64-1 and the resistance layer 64-2 have an electrical conductivity higher than that of the resistance layer 64-2, when the voltage is not applied to the gate electrode 62. The composition is determined.

2) Electric conductivity The electric conductivity of the semiconductor layer in the present invention will be described.
The electrical conductivity is a physical property value indicating the ease of electrical conduction of a substance. When the carrier concentration n and the carrier mobility μ of the substance are used, the electrical conductivity σ of the substance is expressed by the following formula. e is the elementary charge.
σ = neμ
When the semiconductor layer is an n-type semiconductor, the carriers are electrons, the carrier concentration indicates the electron carrier concentration, and the carrier mobility indicates the electron mobility. Similarly, when the semiconductor layer is a p-type semiconductor, the carriers are holes, the carrier concentration indicates the hole carrier concentration, and the carrier mobility indicates the hole mobility. The carrier concentration and carrier mobility of the substance can be obtained by Hall measurement.
<How to find electrical conductivity>
By measuring the sheet resistance of a film whose thickness is known, the electrical conductivity of the film can be determined. Although the electrical conductivity of a semiconductor varies with temperature, the electrical conductivity described in the text indicates the electrical conductivity at room temperature (20 ° C.).

3) Gate insulating film As the gate insulating film, at least two insulators such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , Y _s O ₃ , Ta ₂ O ₅ , or HfO ₂ , or a compound thereof are used. The mixed crystal compound containing the above is used. A polymer insulator such as polyimide can also be used as the gate insulating film.

The thickness of the gate insulating film is preferably 10 nm to 10 μm. The gate insulating film needs to be thickened to some extent in order to reduce leakage current and increase voltage resistance. However, increasing the thickness of the gate insulating film results in an increase in the driving voltage of the TFT. Therefore, it is more preferable that the film thickness of the gate insulating film is 50 nm to 1000 nm for an inorganic insulator and 0.5 μm to 5 μm for a polymer insulator. In particular, it is particularly preferable to use a high dielectric constant insulator such as HfO ₂ for the gate insulating film because TFT driving at a low voltage is possible even if the film thickness is increased.

4) Semiconductor layer It is preferable to use an oxide semiconductor for the semiconductor layer used in the present invention. In particular, an amorphous oxide semiconductor is more preferable. An oxide semiconductor, particularly an amorphous oxide semiconductor, can be formed at a low temperature, and thus can be formed over a flexible resin substrate such as a plastic. Good amorphous oxide semiconductors that can be manufactured at low temperatures include oxides containing In, oxides containing In and Zn, In, Ga, and Zn as disclosed in JP-A-2006-165529. It is known that InGaO ₃ (ZnO) _m (m is a natural number of less than 6) is preferable as the composition structure. These are n-type semiconductors whose carriers are electrons. Of course, a p-type oxide semiconductor such as ZnO.Rh ₂ O ₃ , CuGaO ₂ , or SrCu ₂ O ₂ may be used for the active layer.

Specifically, the amorphous oxide semiconductor according to the present invention includes In—Ga—Zn—O, and the composition in the crystalline state is represented by InGaO ₃ (ZnO) _m (m is a natural number of less than 6). A physical semiconductor is preferred. In particular, InGaZnO ₄ is more preferable. As an amorphous oxide semiconductor having this composition, the electron mobility tends to increase as the electrical conductivity increases. Japanese Patent Laid-Open No. 2006-165529 discloses that the electric conductivity can be controlled by the oxygen partial pressure during film formation.
Of course, the semiconductor layer can be applied not only to oxide semiconductors but also to inorganic semiconductors such as Si and Ge, compound semiconductors such as GaAs, and organic semiconductor materials such as pentacene and polythiophene.

<Electrical conductivity of semiconductor layer>
The electrical conductivity of the semiconductor layer in the present invention is higher in the vicinity of the gate insulating film than in the vicinity of the source electrode and the drain electrode of the semiconductor layer.
More preferably, the ratio of the electrical conductivity in the vicinity of the gate insulating film to the electrical conductivity in the vicinity of the source electrode and the drain electrode (the electrical conductivity in the vicinity of the gate insulating film / the electrical conductivity in the vicinity of the source electrode and the drain electrode) is: Preferably, it is 10 ¹ or more and 10 ¹⁰ or less, more preferably 10 ² or more and 10 ⁸ or less. Preferably, the electric conductivity in the vicinity of the gate insulating film interface of the semiconductor layer is 10 ⁻⁴ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ . More preferably, it is 10 ⁻¹ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ .
Preferably, the semiconductor layer is composed of at least two layers, and the electric conductivity of the active layer in contact with the gate insulating film is larger than the electric conductivity of the resistance layer in contact with the source electrode and the drain electrode, more preferably, The ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is preferably from 10 ^{1 to} 10 ¹⁰ , more preferably 10 ² or more and 10 ⁸ or less. Preferably, the electric conductivity of the active layer is 10 ⁻⁴ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ . More preferably, it is 10 ⁻¹ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ . The electric conductivity of the resistance layer is preferably 10 ⁻¹ Scm ⁻¹ or less, more preferably 10 ⁻⁹ Scm ⁻¹ or more and 10 ⁻³ Scm ⁻¹ or less.

<Thickness of active layer and resistance layer>
The resistance layer is preferably thicker than the active layer. More preferably, the ratio of the thickness of the resistance layer to the thickness of the active layer is more than 1 and 100 or less, more preferably more than 1 and 10 or less.
The thickness of the active layer is preferably 1 nm to 100 nm, more preferably 2.5 nm to 30 nm. The thickness of the resistance layer is preferably 5 nm or more and 500 nm or less, and more preferably 10 nm or more and 100 nm or less.

By using the semiconductor layer having the above structure, a transistor characteristic with a high mobility of 10 cm ² / (V · sec) or more and an ON / OFF ratio of 10 ⁶ or more can be realized.

<Measuring means for electrical conductivity>
As described above, the electrical conductivity of the semiconductor layer in the present invention is adjusted to be larger in the vicinity of the gate insulating film than in the vicinity of the source electrode and the drain electrode of the semiconductor layer.
As a means for adjusting the electrical conductivity, the following means can be exemplified when the semiconductor layer is an oxide semiconductor.
(1) Adjustment by oxygen defect It is known that when an oxygen defect is formed in an oxide semiconductor, carrier electrons are generated and electric conductivity is increased. Therefore, the electric conductivity of the oxide semiconductor can be controlled by adjusting the amount of oxygen defects. Specific methods for controlling the amount of oxygen defects include oxygen partial pressure during film formation, oxygen concentration and treatment time during post-treatment after film formation, and the like. Specific examples of post-treatment include heat treatment at 100 ° C. or higher, oxygen plasma, and UV ozone treatment. Among these methods, a method of controlling the oxygen partial pressure during film formation is preferable from the viewpoint of productivity. JP-A 2006-165529 discloses that the electric conductivity of an oxide semiconductor can be controlled by adjusting the oxygen partial pressure during film formation, and this technique can be used.
(2) Adjustment by composition ratio It is known that the electrical conductivity changes by changing the metal composition ratio of an oxide semiconductor. For example, Japanese Patent Laid-Open No. 2006-165529 discloses that in InGaZn _1-X Mg _X O ₄ , the electrical conductivity decreases as the Mg ratio increases. In addition, in the oxide system of (In ₂ O ₃ ) _1-X (ZnO) _X , it has been reported that when the Zn / In ratio is 10% or more, the electrical conductivity decreases as the Zn ratio increases. ("New Development of Transparent Conductive Film II", CMC Publishing, pages 34-35). As specific methods for changing these composition ratios, for example, in a film formation method by sputtering, targets having different composition ratios are used.
Alternatively, it is possible to change the composition ratio of the film by co-sputtering with a multi-target and adjusting the sputtering rate individually.
(3) Adjustment by impurities By adding an element such as Li, Na, Mn, Ni, Pd, Cu, Cd, C, N, or P to an oxide semiconductor as an impurity, the electron carrier concentration is reduced. It is disclosed in Japanese Patent Application Laid-Open No. 2006-165529 that electric conductivity can be reduced.
As a method for adding an impurity, an oxide semiconductor and an impurity element are co-evaporated, an ion of the impurity element is added to the formed oxide semiconductor film by an ion doping method, or the like.
(4) Adjustment by oxide semiconductor material In the above (1) to (3), the method for adjusting the electric conductivity in the same oxide semiconductor system has been described. Of course, the electric conductivity can be changed by changing the oxide semiconductor material. You can change the degree. For example, it is generally known that a SnO ₂ oxide semiconductor has a lower electrical conductivity than an In ₂ O ₃ oxide semiconductor. By changing the oxide semiconductor material in this manner, the electric conductivity can be adjusted. In particular, as an oxide material having low electrical conductivity, oxide insulator materials such as Al ₂ O ₃ , Ga ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Ta ₂ O ₃ , MgO, or HfO ₃ are known. These can also be used.
As means for adjusting the electrical conductivity, the above methods (1) to (4) may be used alone or in combination.

<Method for forming semiconductor layer>
As a method for forming the semiconductor layer, it is preferable to use a vapor phase film formation method using a polycrystalline sintered body of an oxide semiconductor as a target. Among vapor deposition methods, sputtering and pulsed laser deposition (PLD) are suitable. Furthermore, the sputtering method is preferable from the viewpoint of mass productivity.

  For example, the film is formed by controlling the degree of vacuum and the oxygen flow rate by RF magnetron sputtering deposition. The greater the oxygen flow rate, the smaller the electrical conductivity.

The formed film can be confirmed to be an amorphous film by a known X-ray diffraction method.
The film thickness can be determined by stylus surface shape measurement. The composition ratio can be determined by an RBS (Rutherford backscattering) analysis method.

5) Gate electrode Examples of the gate electrode in the present invention include metals such as Al, Mo, Cr, Ta, Ti, Au, and Ag, alloys such as Al-Nd and APC, tin oxide, zinc oxide, indium oxide, Preferable examples include metal oxide conductive films such as indium tin oxide (ITO) and zinc indium oxide (IZO), organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, or mixtures thereof.
The thickness of the gate electrode is preferably 10 nm or more and 1000 nm or less.

  The electrode film formation method is not particularly limited, and may be a printing method, a wet method such as a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, a CVD method, a plasma CVD method, or the like. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material from among chemical methods. For example, when ITO is selected, it can be performed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like. When an organic conductive compound is selected as the material for the gate electrode, it can be performed according to a wet film forming method.

6) Source electrode and drain electrode As the source electrode and drain electrode material in the present invention, for example, metals such as Al, Mo, Cr, Ta, Ti, Au, or Ag, alloys such as Al—Nd, APC, tin oxide, Preferred examples include metal oxide conductive films such as zinc oxide, indium oxide, indium tin oxide (ITO), and zinc indium oxide (IZO), organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, or mixtures thereof. .
The thickness of the source electrode and the drain electrode is preferably 10 nm or more and 1000 nm or less.

  The electrode film formation method is not particularly limited, and may be a printing method, a wet method such as a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, a CVD method, a plasma CVD method, or the like. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material from among chemical methods. For example, when ITO is selected, it can be performed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like. Further, when an organic conductive compound is selected as a material for the source electrode and the drain electrode, it can be performed according to a wet film forming method.

7) Substrate The substrate used in the present invention is not particularly limited. For example, YSZ (zirconia stabilized yttrium), inorganic materials such as glass, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate Synthetic resins such as polyester such as polyester, polystyrene, polycarbonate, polyethersulfone, polyarylate, allyl diglycol carbonate, polyimide, polycycloolefin, norbornene resin, poly (chlorotrifluoroethylene), etc. Organic materials, and the like. In the case of the organic material, it is preferable that the organic material is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, workability, low air permeability, low moisture absorption, and the like.

  In the present invention, a flexible substrate is particularly preferably used. The material used for the flexible substrate is preferably an organic plastic film having a high transmittance. For example, polyesters such as polyethylene terephthalate, polybutylene phthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycyclo Plastic films such as olefin, norbornene resin, and poly (chlorotrifluoroethylene) can be used. In addition, if the insulating property is insufficient for the film-like plastic substrate, the insulating layer, the gas barrier layer for preventing the transmission of moisture and oxygen, the flatness of the film-like plastic substrate and the adhesion with the electrode and active layer It is also preferable to provide an undercoat layer or the like for improvement.

  Here, the thickness of the flexible substrate is preferably 50 μm or more and 500 μm or less. This is because it is difficult for the substrate itself to maintain sufficient flatness when the thickness of the flexible substrate is less than 50 μm. Further, when the thickness of the flexible substrate is more than 500 μm, it is difficult to bend the substrate itself freely, that is, the flexibility of the substrate itself is poor.

8) Protective insulating film If necessary, a protective insulating film may be provided on the TFT. The protective insulating film has the purpose of protecting the semiconductor layer (the active layer and the resistance layer) from deterioration due to the atmosphere and the purpose of insulating the electronic device manufactured on the TFT.

Specific examples of the protective insulating film material include metal oxides such as MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ , or TiO ₂ , SiN metal nitrides such as _x and SiN _x O _y , metal fluorides such as MgF ₂ , LiF, AlF ₃ , and CaF ₂ , polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoro Copolymer obtained by copolymerizing ethylene, polydichlorodifluoroethylene, a copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, a monomer mixture containing tetrafluoroethylene and at least one comonomer, and a copolymer main chain Fluorine-containing copolymer having a cyclic structure, water absorption of 1% or less The above water-absorbing substances, moisture-proof substances having a water absorption rate of 0.1% or less, and the like can be mentioned.

  The method for forming the protective insulating film is not particularly limited. For example, the vacuum evaporation method, the sputtering method, the reactive sputtering method, the MBE (molecular beam epitaxy) method, the cluster ion beam method, the ion plating method, the plasma polymerization method ( High-frequency excitation ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, printing method, or transfer method can be applied.

9) Post-treatment If necessary, heat treatment may be performed as a post-treatment of the TFT. The heat treatment is performed at a temperature of 100 ° C. or higher in the air or in a nitrogen atmosphere. The heat treatment may be performed after the semiconductor layer is formed or at the end of the TFT manufacturing process. By performing the heat treatment, there are effects such as suppression of in-plane variation in TFT characteristics and improvement in driving stability.

2. Organic EL Element The organic EL element of the present invention has a cathode and an anode on a substrate, and has an organic compound layer including an organic light emitting layer (hereinafter sometimes simply referred to as “light emitting layer”) between both electrodes. . In view of the properties of the light emitting element, at least one of the anode and the cathode is preferably transparent.

  As an aspect of lamination of the organic compound layer in the present invention, an aspect in which a hole transport layer, a light emitting layer, and an electron transport layer are laminated in this order from the anode side is preferable. Further, a charge blocking layer or the like may be provided between the hole transport layer and the light-emitting layer, or between the light-emitting layer and the electron transport layer. A hole injection layer may be provided between the anode and the hole transport layer, and an electron injection layer may be provided between the cathode and the electron transport layer. Each layer may be divided into a plurality of secondary layers.

  Next, the elements constituting the light emitting material of the present invention will be described in detail.

<Board>
The substrate used in the present invention is preferably a substrate that does not scatter or attenuate light emitted from the organic compound layer. Specific examples thereof include zirconia stabilized yttrium (YSZ), inorganic materials such as glass, polyesters such as polyethylene terephthalate, polybutylene phthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, and polycycloolefin. , Organic materials such as norbornene resin and poly (chlorotrifluoroethylene).
For example, when glass is used as the substrate, it is preferable to use non-alkali glass as the material in order to reduce ions eluted from the glass. Moreover, when using soda-lime glass, it is preferable to use what gave barrier coatings, such as a silica. In the case of an organic material, it is preferable that it is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, and workability.

  There is no restriction | limiting in particular about the shape of a board | substrate, a structure, a magnitude | size, It can select suitably according to the use, purpose, etc. of a light emitting element. In general, the shape of the substrate is preferably a plate shape. The structure of the substrate may be a single layer structure, a laminated structure, may be formed of a single member, or may be formed of two or more members.

  The substrate may be colorless and transparent or colored and transparent, but is preferably colorless and transparent in that it does not scatter or attenuate light emitted from the organic light emitting layer.

The substrate can be provided with a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface.
As a material for the moisture permeation preventive layer (gas barrier layer), inorganic materials such as silicon nitride and silicon oxide are preferably used. The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sputtering method.
When a thermoplastic substrate is used, a hard coat layer, an undercoat layer, or the like may be further provided as necessary.

<Anode>
The anode usually has a function as an electrode for supplying holes to the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element. , Can be appropriately selected from known electrode materials. As described above, the anode is usually provided as a transparent anode.

  Suitable examples of the material for the anode include metals, alloys, metal oxides, conductive compounds, and mixtures thereof. Specific examples of the anode material include conductive metals such as tin oxide (ATO, FTO) doped with antimony or fluorine, tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. Metals such as oxides, gold, silver, chromium, nickel, and mixtures or laminates of these metals and conductive metal oxides, inorganic conductive materials such as copper iodide and copper sulfide, polyaniline, polythiophene, polypyrrole, etc. Organic conductive materials, and a laminate of these and ITO. Among these, conductive metal oxides are preferable, and ITO is particularly preferable from the viewpoints of productivity, high conductivity, transparency, and the like.

  The anode is composed of, for example, a wet method such as a printing method and a coating method, a physical method such as a vacuum deposition method, a sputtering method, and an ion plating method, and a chemical method such as a CVD and a plasma CVD method. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material to be processed. For example, when ITO is selected as the anode material, the anode can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like.

  In the organic electroluminescent element of the present invention, the formation position of the anode is not particularly limited and can be appropriately selected according to the use and purpose of the light emitting element. Is preferably formed on the substrate. In this case, the anode may be formed on the entire one surface of the substrate, or may be formed on a part thereof.

  The patterning for forming the anode may be performed by chemical etching such as photolithography, or may be performed by physical etching such as laser, or vacuum deposition or sputtering with a mask overlapped. It may be performed by a lift-off method or a printing method.

  The thickness of the anode can be appropriately selected depending on the material constituting the anode and cannot be generally defined, but is usually about 10 nm to 50 μm, and preferably 50 nm to 20 μm.

The resistance value of the anode is preferably 10 ³ Ω / □ or less, and more preferably 10 ² Ω / □ or less. When the anode is transparent, it may be colorless and transparent or colored and transparent. In order to take out light emission from the transparent anode side, the transmittance is preferably 60% or more, and more preferably 70% or more.

  The transparent anode is described in detail in the book “New Development of Transparent Electrode Films” published by CMC (1999), supervised by Yutaka Sawada, and the matters described here can be applied to the present invention. In the case of using a plastic substrate having low heat resistance, a transparent anode formed using ITO or IZO at a low temperature of 150 ° C. or lower is preferable.

<Cathode>
The cathode usually has a function as an electrode for injecting electrons into the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element, It can select suitably from well-known electrode materials.

  Examples of the material constituting the cathode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof. Specific examples include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloys, lithium-aluminum alloys, magnesium. -Rare earth metals such as silver alloys, indium, ytterbium, and the like. These may be used alone, but two or more can be suitably used in combination from the viewpoint of achieving both stability and electron injection.

Among these, as a material constituting the cathode, an alkali metal or an alkaline earth metal is preferable from the viewpoint of electron injecting property, and a material mainly composed of aluminum is preferable from the viewpoint of excellent storage stability.
The material mainly composed of aluminum is aluminum alone, an alloy of aluminum and 0.01% by mass to 10% by mass of alkali metal or alkaline earth metal, or a mixture thereof (for example, lithium-aluminum alloy, magnesium-aluminum alloy). Etc.).

  The materials for the cathode are described in detail in JP-A-2-15595 and JP-A-5-121172, and the materials described in these public relations can also be applied in the present invention.

  There is no restriction | limiting in particular about the formation method of a cathode, According to a well-known method, it can carry out. For example, the cathode described above is configured from a wet method such as a printing method or a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a chemical method such as CVD or plasma CVD method. It can be formed according to a method appropriately selected in consideration of suitability with the material. For example, when a metal or the like is selected as the cathode material, one or more of them can be simultaneously or sequentially performed according to a sputtering method or the like.

  Patterning when forming the cathode may be performed by chemical etching such as photolithography, physical etching by laser, or the like, or by vacuum deposition or sputtering with the mask overlaid. It may be performed by a lift-off method or a printing method.

In the present invention, the cathode formation position is not particularly limited, and may be formed on the entire organic compound layer or a part thereof.
Further, a dielectric layer made of an alkali metal or alkaline earth metal fluoride or oxide may be inserted between the cathode and the organic compound layer with a thickness of 0.1 to 5 nm. This dielectric layer can also be regarded as a kind of electron injection layer. The dielectric layer can be formed by, for example, a vacuum deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the cathode can be appropriately selected depending on the material constituting the cathode and cannot be generally defined, but is usually about 10 nm to 5 μm, and preferably 50 nm to 1 μm.
Further, the cathode may be transparent or opaque. The transparent cathode can be formed by depositing a thin cathode material to a thickness of 1 to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

<Organic compound layer>
The organic compound layer in the present invention will be described.
The organic electroluminescent element of the present invention has at least one organic compound layer including a light emitting layer, and the organic compound layer other than the organic light emitting layer includes a hole transport layer, an electron transport layer as described above. , Charge blocking layer, hole injection layer, electron injection layer and the like.

-Organic light emitting layer-
The organic light emitting layer receives holes from the anode, the hole injection layer, or the hole transport layer when an electric field is applied, receives electrons from the cathode, the electron injection layer, or the electron transport layer, and recombines holes and electrons. It is a layer having a function of providing a field to emit light.
The light emitting layer in the present invention may be composed of only a light emitting material, or may be a mixed layer of a host material and a light emitting material. The light emitting material may be a fluorescent light emitting material or a phosphorescent light emitting material, and the dopant may be one type or two or more types. The host material is preferably a charge transport material. The host material may be one type or two or more types, and examples thereof include a configuration in which an electron transporting host material and a hole transporting host material are mixed. Further, the light emitting layer may include a material that does not have charge transporting properties and does not emit light.
Further, the light emitting layer may be a single layer or two or more layers, and each layer may emit light in different emission colors.

  Examples of fluorescent materials that can be used in the present invention include, for example, benzoxazole derivatives, benzimidazole derivatives, benzothiazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives. , Condensed aromatic compounds, perinone derivatives, oxadiazole derivatives, oxazine derivatives, aldazine derivatives, pyralidine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, cyclopentadiene derivatives, styryl Of amine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidin compounds, metal complexes of 8-quinolinol derivatives and pyromethene derivatives And various metal complexes typified by metal complex, polythiophene, polyphenylene, polyphenylene vinylene polymer compounds include compounds such as organic silane derivatives.

Examples of the phosphorescent material that can be used in the present invention include complexes containing transition metal atoms or lanthanoid atoms.
Although it does not specifically limit as a transition metal atom, Preferably, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, and platinum are mentioned, More preferably, they are rhenium, iridium, and platinum.
Examples of lanthanoid atoms include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these lanthanoid atoms, neodymium, europium, and gadolinium are preferable.

Examples of the ligand of the complex include G.I. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H.C. Examples include ligands described in Yersin's "Photochemistry and Photophysics of Coordination Compounds" published by Springer-Verlag 1987, Akio Yamamoto "Organic Metal Chemistry-Fundamentals and Applications-" .
Specific ligands are preferably halogen ligands (preferably chlorine ligands), nitrogen-containing heterocyclic ligands (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, phenanthroline, etc.), diketones Ligand (for example, acetylacetone), carboxylic acid ligand (for example, acetic acid ligand), carbon monoxide ligand, isonitrile ligand, cyano ligand, more preferably nitrogen-containing Heterocyclic ligand. The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more. Different metal atoms may be contained at the same time.

  The phosphorescent material is preferably contained in the light emitting layer in an amount of 0.1% by mass to 40% by mass, and more preferably 0.5% by mass to 20% by mass.

  Examples of the host material contained in the light emitting layer in the present invention include those having a carbazole skeleton, those having a diarylamine skeleton, those having a pyridine skeleton, those having a pyrazine skeleton, those having a triazine skeleton, and aryl. Examples thereof include materials having a silane skeleton and materials exemplified in the sections of a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer described later.

  Although the thickness of a light emitting layer is not specifically limited, Usually, it is preferable that they are 1 nm-500 nm, it is more preferable that they are 5 nm-200 nm, and it is still more preferable that they are 10 nm-100 nm.

-Hole injection layer, hole transport layer-
The hole injection layer and the hole transport layer are layers having a function of receiving holes from the anode or the anode side and transporting them to the cathode side. Specifically, the hole injection layer and the hole transport layer are carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamines. Derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds, porphyrin compounds, organosilane derivatives, carbon In addition, a layer containing various metal complexes represented by an Ir complex having phenylazole or phenylazine as a ligand is preferable.
The thicknesses of the hole injection layer and the hole transport layer are each preferably 500 nm or less from the viewpoint of lowering the driving voltage.
The thickness of the hole transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 200 nm. The thickness of the hole injection layer is preferably 0.1 nm to 200 nm, more preferably 0.5 nm to 200 nm, and still more preferably 1 nm to 200 nm.
The hole injection layer and the hole transport layer may have a single-layer structure composed of one or more of the materials described above, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. .

-Electron injection layer, electron transport layer-
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side. Specifically, the electron injection layer and the electron transport layer are triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, Carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, aromatic tetracarboxylic anhydrides such as naphthalene and perylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazoles and benzothiazoles as ligands It is preferably a layer containing various metal complexes typified by metal complexes, organosilane derivatives, and the like.

The thicknesses of the electron injection layer and the electron transport layer are each preferably 500 nm or less from the viewpoint of lowering the driving voltage.
The thickness of the electron transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 100 nm. In addition, the thickness of the electron injection layer is preferably 0.1 nm to 200 nm, more preferably 0.2 nm to 100 nm, and still more preferably 0.5 nm to 50 nm.
The electron injection layer and the electron transport layer may have a single layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

-Hole blocking layer-
The hole blocking layer is a layer having a function of preventing holes transported from the anode side to the light emitting layer from passing through to the cathode side. In the present invention, a hole blocking layer can be provided as an organic compound layer adjacent to the light emitting layer on the cathode side.
Examples of the organic compound constituting the hole blocking layer include aluminum complexes such as BAlq, triazole derivatives, phenanthroline derivatives such as BCP, and the like.
The thickness of the hole blocking layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 100 nm.
The hole blocking layer may have a single layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

-Formation of organic compound layer-
In the organic electroluminescent element of the present invention, each layer constituting the organic compound layer can be suitably formed by any of a dry film forming method such as a vapor deposition method and a sputtering method, a transfer method, and a printing method.
In the organic electroluminescent element of the present invention, conventionally known means can be used as a patterning method, but at least one layer constituting the organic compound layer is patterned by an ink jet method.

  The ink jet method is a method of forming pixels by ejecting a liquid of an organic material forming the pixels from a nozzle and fixing the liquid onto a substrate. Depending on the jetting control method, there are a piezo electronic method, a heated ink jet method (sometimes called a bubble jet (registered trademark)), an electrohydrodynamic method, and the like.

  In the ink jet method, the substrate is hardly heated, and particularly in an organic EL display device including a driving TFT and an organic EL element on a flexible substrate, the substrate does not cause a dimensional change, and there is a problem such as pixel misalignment. This is advantageous in that it does not cause

  In the pattern formation technology using the ink jet method, it is important to prepare an organic material ink for forming a pixel. In order to fix a necessary amount of an organic material on a substrate, a liquid in which an organic material is dissolved at an appropriate concentration, Alternatively, it is necessary to prepare an ink composed of a dispersion dispersed in fine particles. In order to form a high-definition pixel, it is required to discharge particularly fine ink droplets from a nozzle.

  The composition for the organic EL element in the ink prevents the solid component in the organic EL composition from adhering or clogging at the inkjet nozzle port, and maintains a high ink contact angle at the nozzle port. In order to contribute to this and thereby prevent the ink from bending, it is preferably dissolved or dispersed in a solvent.

  Examples of the solvent include alcohols such as water, methanol, ethanol, 1-methoxy-2-propanol, methoxyethanol, and phenoxyethanol; ketones such as acetone, methyl ethyl ketone, diethyl ketone, n-propyl methyl ketone, and cyclohexanone; Ethers such as butyl ether, tetrahydrofuran and dioxane, ethyl acetate, butyl acetate, ethyl 2-ethylhexanoate, methyl propionate, ethyl propionate, γ-butyrolactone, and esters such as diethyl carbonate, formamide, N, N-dimethylformamide (DMF), amides such as N, N-dimethylacetamide, aliphatic hydrocarbons such as hexane, heptane, octane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene Halogenated hydrocarbons such as chloroform, carbon tetrachloride, dichloromethane, 1,2-dichloroethane, organic solvents such as N-methylpyrrolidone (NMP), dimethylimidazoline (DMI), dimethyl sulfoxide (DMSO), and inorganic solvents. Two or more of these solvents may be appropriately mixed. It is also possible to use a mixture of these solvents.

  Furthermore, it is preferable that a wetting agent is contained in the composition. Thereby, it can prevent effectively that a composition dries and solidifies at an inkjet nozzle opening. Examples of the wetting agent include polyhydric alcohols such as glycerin and diethylene glycol, and a mixture of two or more of these may be used. The addition amount of the wetting agent is preferably about 5% by mass to 20% by mass with respect to the total amount of the composition.

  In addition, the composition for organic EL elements may further contain other additives and film stabilizing materials, for example, stabilizers, viscosity modifiers, anti-aging agents, pH adjusters, preservatives, resin emulsions. Alternatively, a leveling agent or the like can be used.

  The viscosity of the composition for an organic EL device is preferably 1 mPa · s to 20 mPa · s, and more preferably 2 mPa · s to 4 mPa · s. When the viscosity of the composition for organic EL devices is less than 1 mPa · s, the formed coloring layer may not be able to exhibit sufficient coloring ability. On the other hand, if it exceeds 20 mPa · s, the composition cannot be smoothly ejected from the nozzle holes, and patterning may be difficult unless the specifications of the apparatus such as increasing the nozzle hole diameter are changed. Furthermore, when the viscosity is large, the solid component in the composition is likely to precipitate, and the frequency of occurrence of clogging of the nozzle holes increases.

Moreover, the surface tension of the composition for organic EL elements is 20 mN / m to 70 mN / m, and preferably 25 mN / m to 40 × 10 ⁻³ N / m. By setting the surface tension within this range, as in the case of the contact angle described above, it is possible to suppress the flight bending and to reduce the flight bending frequency. When the surface tension is less than 20 mN / m, the wettability of the composition to the constituent material of the nozzle surface increases, so that flight bending occurs as in the case of the contact angle, and the flight bending frequency may increase. On the other hand, if it exceeds 70 mN / m, the meniscus shape at the tip of the nozzle is not stable, and it may be difficult to control the discharge amount and discharge timing of the composition.

  Further, the composition for organic EL elements preferably satisfies the numerical range for at least one of the above-described viscosity and surface tension, but satisfies the conditions for the characteristics of any combination of two or more, You may be satisfied about all the characteristics. Thereby, it can be set as the composition more suitable for the inkjet system.

  Moreover, the composition for organic EL elements may be prepared as a polymer dispersion containing a polymer for dispersing the organic material. In the case of a polymer dispersion, each component of the organic compound layer is preferably dispersed in the polymer. By dispersing the constituent components of the organic compound layer in the polymer, the stability of the constituent components of the organic compound layer in the dispersion is improved, and an organic electroluminescent device that is further excellent in luminous efficiency and durability can be obtained.

Polymers used for dispersion include polyvinyl carbazole, polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, Vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester, alkyd resin, epoxy resin, silicon resin, polyvinyl butyral, polyvinyl acetal, or the like can be used.
These may be used alone or in combination of two or more. The light emitting layer containing a polymer binder can be easily applied and formed in a large area by a wet film forming method.
Among these, for example, polymers described in JP-A Nos. 2001-11568, 2002-25779, 2004-152746, and the like are preferably used.

  The apparatus and materials used in the ink jet method, the ink preparation conditions, the ink ejection means, and the like are not limited and can be applied to the present invention by applying means commonly known in the ink jet method.

<Protective layer>
In the present invention, the entire organic EL element may be protected by a protective layer.
As a material contained in the protective layer, any material may be used as long as it has a function of preventing materials that promote device deterioration such as moisture and oxygen from entering the device.
Specific examples thereof include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni, MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, and Fe ₂ O. ₃ , metal oxides such as Y ₂ O ₃ , TiO ₂ , metal nitrides such as SiN _x , SiN _x O _y , metal fluorides such as MgF ₂ , LiF, AlF ₃ , CaF ₂ , polyethylene, polypropylene, polymethyl Monomer mixture containing methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, tetrafluoroethylene and at least one comonomer Copolymer obtained by copolymerization, cyclic in the copolymer main chain Examples thereof include a fluorine-containing copolymer having a structure, a water-absorbing substance having a water absorption of 1% or more, and a moisture-proof substance having a water absorption of 0.1% or less.

  The method for forming the protective layer is not particularly limited, and for example, vacuum deposition, sputtering, reactive sputtering, MBE (molecular beam epitaxy), cluster ion beam, ion plating, plasma polymerization (high frequency) Excited ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, printing method, transfer method can be applied.

<Sealing>
Furthermore, the organic electroluminescent element of this invention may seal the whole element using a sealing container.
Further, a moisture absorbent or an inert liquid may be sealed in a space between the sealing container and the light emitting element. Although it does not specifically limit as a moisture absorber, For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride Cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like. The inert liquid is not particularly limited, and examples thereof include fluorinated solvents such as paraffins, liquid paraffins, perfluoroalkanes, perfluoroamines, perfluoroethers, chlorinated solvents, and silicone oils. It is done.

The organic electroluminescence device of the present invention emits light by applying a direct current (which may include an alternating current component as necessary) voltage (usually 2 to 15 volts) or a direct current between the anode and the cathode. Obtainable.
The driving method of the organic electroluminescence device of the present invention is described in JP-A-2-148687, JP-A-6-301355, JP-A-5-29080, JP-A-7-134558, JP-A-8-234658, and JP-A-8-2441047. The driving methods described in each publication, Japanese Patent No. 2784615, US Pat. Nos. 5,828,429, 6023308, and the like can be applied.

3. Configuration of Organic EL Display Device The organic EL display device of the present invention is an organic EL display device including at least an organic electroluminescent element and a driving TFT for supplying a current to the organic electroluminescent element.
Preferably, the substrate of the organic electroluminescent element and the substrate of the driving TFT in the present invention are both flexible resin substrates, and more preferably are arranged on a common substrate.
Preferably, the drain electrode of the driving TFT and the electrode of the organic EL element, for example, the anode are made of the same material and formed in the same process. Preferably, the drain electrode and the organic EL element anode are indium tin oxide.
Preferably, an insulating film is formed on the periphery of the pixel electrode of the organic EL element. More preferably, the insulating film and the insulating film of the driving TFT are made of the same material and formed in the same process.
Therefore, it is preferable that the organic electroluminescent element and the driving TFT in the present invention are partly formed of the same material and the same process, thereby simplifying and simplifying the manufacturing process. Therefore, failures such as short circuit due to poor connection can be reduced, and the insulating film can be uniformly formed with sufficient insulating performance.

The structure of the organic EL display device of the present invention and the manufacturing process thereof will be described below with reference to the drawings.
FIG. 1 is a conceptual diagram showing the configuration of the driving TFT 100 and the organic EL element 10 of the organic EL display device of the present invention. The substrate 1 is a flexible support, and is a plastic film such as PEN, and has a substrate insulating layer 2 on the surface in order to be insulating. In addition, the driving TFT unit 100 and the switching TFT unit 200 have a gate electrode 101, and a gate insulating film 102 is provided over the entire TFT and the organic EL element. A part of the gate insulating film 102 is electrically connected. A connection hole has been opened for this purpose. The semiconductor layer 103 in the present application is provided in the driving TFT and switching TFT portions, and the source electrode 104 and the drain electrode 105 are provided thereon. The drain electrode 105 and the pixel electrode (anode) 3 of the organic EL element 10 are continuous and integrated, and are formed of the same material and in the same process. The drain electrode of the switching TFT 200 and the driving TFT 101 are electrically connected through a connection hole by the connection electrode 201. Further, the whole is covered with the insulating film 4 except for the portion where the organic EL element of the pixel electrode portion is formed. An organic layer 5 including a light emitting layer and a cathode 6 are provided on the pixel electrode portion to form an organic EL element 10. In the present invention, at least one layer of the organic layer 5 is patterned by an ink jet method, and preferably an organic layer including at least a light emitting layer is patterned by an ink jet method. In the configuration illustrated in FIG. 1, only the light emitting layer is patterned by the ink jet method, and the other layers are formed by the resistance heating vapor deposition method, and are not particularly patterned.

  Although not shown, it is also a preferable aspect of the present invention to use a top gate type TFT as the driving TFT in FIG.

  FIG. 2 is a schematic circuit diagram of main parts of the switching TFT, the driving TFT, and the organic EL element in the organic EL display device of the present invention. The circuit of the organic EL display device in the present invention is not particularly limited to that shown in FIG. 2, and a conventionally known circuit can be applied as it is.

(application)
The organic EL display device of the present invention is applied in a wide range of fields including a mobile phone display, a personal digital assistant (PDA), a computer display, an automobile information display, a TV monitor, or general lighting.

  Hereinafter, the organic EL display device of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1
1. Production of Organic EL Display Device An organic EL display device 1 having the configuration shown in FIG. 1 was produced.
1) Formation of Substrate Insulating Film On a polyethylene naphthalate (abbreviated as PEN) film, SiON was deposited by sputtering to 500 nm to form a substrate insulating film.

Sputtering conditions: An RF magnetron sputtering apparatus was used and Si ₃ N ₄ was used as a target at an RF power of 400 W and a sputtering gas flow rate Ar / O 2 = 12.0 / 3.0 sccm.

2) Formation of gate electrode (and scanning electric wire) After cleaning the substrate, Mo was deposited to 100 nm by sputtering. Next, a photoresist was applied, a photomask was overlaid thereon, exposed through the photoresist, an unexposed portion was cured by heating, and the uncured resist was removed by a subsequent treatment with an alkaline developer. Next, an etching solution was applied to dissolve and remove the portion of the electrode not covered with the cured photoresist. Finally, the photoresist was removed to complete the patterning process. Patterned gate electrodes and scanning wires were formed.

The processing conditions for each step are as follows.
Mo sputtering conditions: DC power 380 W and sputtering gas flow rate Ar = 12 sccm by a DC magnetron sputtering apparatus.

Photoresist application condition: Photoresist OFPR-800 (manufactured by Tokyo Ohka Co., Ltd.) was applied by spin coating 4000 rpm 50 sec. Pre-bake conditions: 80 ° C., 20 min.
Exposure condition: 5 sec. (Ultra-high pressure mercury lamp of g-line, 100 mJ / cm ² equivalent)
Developing condition Developer NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.): 30 sec. (Immersion) + 30 sec. (Stirring)
Rinse: pure water ultrasonic cleaning, 1 min. 2 times Post-bake: 120 ° C., 30 min.
Etching conditions: Etching solution, mixed acid (nitric acid / phosphoric acid / acetic acid)
Resist stripping conditions: stripping solution-104 (manufactured by Tokyo Ohka Co., Ltd.), 5 min. (Immersion) 2 times Cleaning: IPA ultrasonic wave for 5 min. 2 times, pure water ultrasonic cleaning for 5 min.
Drying: N ₂ blow and baking at 120 ° C. for 1 h.

3) Formation of gate insulating film Subsequently, SiO ₂ was deposited to 200 nm by sputtering to form a gate insulating film.

Sputtering conditions: RF magnetron sputtering apparatus, RF power 400 W, sputtering gas flow rate Ar / O ₂ = 12.0 / 2.0 sccm.

4) Formation of semiconductor layer On the gate insulating film, an IZGO film (active layer) having a high electric conductivity of 10 nm and an IZGO film (resistance layer) of 40 nm having a low electric conductivity were sequentially formed by sputtering. Subsequently, an active layer was formed by performing a patterning process by a photoresist method.

  The sputtering conditions for the high electrical conductivity IZGO film (active layer) and the low electrical conductivity IZGO film (resistance layer) are as follows.

Sputtering conditions for IZGO film with high electrical conductivity: DC power 200 W, sputtering gas flow rate Ar / O ₂ = 12.0 /, with a polycrystalline sintered body having a composition of InGaZnO ₄ using an RF magnetron sputtering apparatus. Performed at 0.6 sccm.
Low electrical conductivity IZGO film sputtering conditions: Using a RF magnetron sputtering apparatus and targeting a polycrystalline sintered body having a composition of InGaZnO ₄ , DC power 200 W, sputtering gas flow rate Ar / O ₂ = 12.0 / 1 .6 sccm.

  The patterning process by the photoresist method is the same as that in the patterning of the gate electrode except that hydrochloric acid is used as an etching solution.

5) Source / Drain Electrode and Pixel Electrode Formation Following the formation of the semiconductor layer, indium tin oxide (abbreviated as ITO) was deposited to 40 nm by sputtering. Subsequently, a source / drain electrode and a pixel electrode were formed by performing a patterning process by a photoresist method similar to the patterning of the gate electrode.

    ITO sputtering conditions: Using an RF magnetron sputtering apparatus, the DC power was 40 W and the sputtering gas flow rate was Ar = 12.0 sccm.

  The patterning process by the photoresist method is the same as that in the patterning of the gate electrode except that oxalic acid is used as the etching solution.

6) Contact hole formation Subsequently, a patterning process using a photoresist method is performed in the same manner as in the patterning of the gate electrode, and the portions other than the contact hole formation portion are protected with photoresist, and then gate insulation is performed using buffered hydrofluoric acid as an etching solution. A hole was made in the film to expose the gate electrode. Subsequently, the photoresist was removed as in the patterning of the gate electrode to form a contact hole.

7) Formation of connection electrode (and common electric wire / signal electric wire) Subsequently, Mo was deposited to 200 nm by sputtering.
Mo sputtering conditions: Same as sputtering conditions in the gate electrode forming step.
Subsequently, a patterning process was performed by a photoresist method similar to the patterning of the gate electrode, thereby forming a connection electrode and a common wire / signal wire.

8) Insulating film formation Subsequently, 2 μm of a photosensitive polyimide film was applied and patterned by a photoresist method to form an insulating film.
Application and patterning process conditions are as follows.
Application conditions: Spin coating 1000 rpm 30 sec.
Exposure condition: 20 sec. (Energy equivalent to 400 mJ / cm ² using g line of ultra high pressure mercury lamp)
Development conditions Developer: NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), 1 min. (Immersion) +1 min. (Stirring)
Rinse: pure water ultrasonic cleaning, 1 min. 2 times +5 min. 1 time + N ₂ blow post bake: 1 h at 120 ° C.

  The TFT substrate of the organic EL display device was produced through the above steps.

9) Preparation of organic EL element A hole injection layer and a hole transport layer were sequentially provided on a TFT substrate subjected to oxygen plasma treatment by resistance heating vacuum deposition.

The oxygen plasma conditions and the structure of each layer are as follows.
Oxygen plasma conditions: O ₂ flow rate = 10 sccm, RF power 200 W, treatment time 1 min.

Hole injection layer: 4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenylamine (abbreviated as 2-TNATA), thickness 140 nm.
Hole transport layer: N, N′-dinaphthyl-N, N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (abbreviated as α-NPD), thickness 10 nm.

Subsequently, the following red, green, and blue light emitting material precursor liquids were patterned and ejected by an inkjet method so as to form 160 ppi pixels.
Red light-emitting material: cyanopolyphenylene vinylene Green light-emitting material: polyphenylene vinylene Blue light-emitting material: polyphenylene vinylene and polyalkylphenylene Thereafter, the polymer was polymerized by additional heating.

Subsequently, a hole blocking layer, an electron transport layer, and an electron injection layer were provided on the light emitting layer, and the cathode was provided by patterning with a shadow mask. Each layer was provided by resistance heating vacuum deposition.
Hole blocking layer: bis- (2-methyl-8-quinolinylphenolate) aluminum (abbreviated as BAlq), thickness 10 nm.
Electron transport layer: Tris (8-hydroxyquinolinate) aluminum (abbreviated as Alq3), thickness 20 nm.
Electron injection layer: LiF, thickness 1 nm
Cathode: Al, thickness 200 nm

10) Sealing process On the TFT substrate provided with the organic EL element, a 2 μm SiN _X film was formed as a sealing film by plasma CVD (PECVD). Further, on the sealing film, a protective film (PEN film SiON deposited by 50 nm) was adhered (90 ° C., 3 h.) With a thermosetting epoxy resin adhesive.

2. The performance of the organic EL display device The organic EL display device manufactured by the above steps was high definition (160 ppi) when emitting light under the condition of an applied voltage of 7 V, and there was no unevenness in emission, and green light emission with high luminance was obtained. .

Example 2
An organic EL display device 2 was produced in the same manner as in Example 1 except that the TFT was changed to the top gate TFT shown in FIG.
As a result of evaluation in the same manner as in Example 1, green light emission with high definition (160 ppi), no light emission unevenness, and high luminance was obtained as in Example 1.

FIG. 2 is a conceptual diagram showing a configuration of a driving TFT 100 and an organic EL element 10 in the organic EL display device of the present invention. It is a schematic circuit diagram of the principal part of the switching TFT, drive TFT, and organic EL element in the organic EL display device of the present invention. It is a conceptual diagram which shows the structure of TFT in this invention. It is a conceptual diagram which shows the structure of the top gate type TFT in this invention.

Explanation of symbols

Display element 10: Organic EL element 100: Drive TFT
200: Switching TFT
1: Substrate 2: Substrate insulating film 3: Pixel electrode (anode)
4: Insulating film 5: Organic layer 6: Cathode 7: Hole injection layer 8: Organic layer including light emitting layer 101: Gate electrode 102: Gate insulating film 103: Semiconductor layer 104: Source electrode 105: Drain electrode 201: Connection electrode 81: Organic EL element 82: Cathode 83: Driving TFT
84: Switching TFT
85: Capacitor 86: Common wire 87: Signal wire 88: Scanning wire TFT
51, 61: Substrate 52, 62: Gate electrode 53, 63: Gate insulating film 54-1, 64-1: Active layer 54-2, 64-2: Resistance layer 55-1, 65-1: Source electrode 55- 2, 65-2: Drain electrode 56, 66: Insulating layer

Claims (15)

  An organic electroluminescence display device in which at least a driving TFT and a pixel made of an organic electroluminescence element are patterned on the same substrate as the driving TFT. The driving TFT includes at least a substrate, a gate electrode, a gate insulating film, and a semiconductor layer The semiconductor layer has at least a resistance layer and an active layer having higher electrical conductivity than the resistance layer, the active layer is in contact with the gate insulating film, and the active layer A driving TFT in which the resistance layer is electrically connected between at least one of the source electrode and the drain electrode, and at least a light emitting layer of the pixel is formed by patterning by an inkjet method; An organic electroluminescent display device characterized by the above.   The driving TFT has at least the resistance layer and the active layer in layers on the substrate, the active layer is in contact with the gate insulating film, and the resistance layer is in contact with at least one of the source electrode and the drain electrode. The organic electroluminescent display device according to claim 1.   The organic electroluminescent display device according to claim 2, wherein the thickness of the resistance layer of the driving TFT is larger than the thickness of the active layer.   2. The organic light emitting display device according to claim 1, wherein electrical conductivity between the resistance layer and the active layer continuously changes in the semiconductor layer of the driving TFT.   The organic electroluminescence display device according to claim 1, wherein the semiconductor layer of the driving TFT contains an oxide semiconductor.   The organic electroluminescent display device according to claim 5, wherein the oxide semiconductor is an amorphous oxide semiconductor.   The organic electroluminescent display device according to claim 5, wherein an oxygen concentration of the active layer is lower than an oxygen concentration of the resistance layer.   The organic electroluminescence according to any one of claims 5 to 7, wherein the oxide semiconductor includes at least one selected from the group consisting of In, Ga, and Zn, or a composite oxide thereof. Display device.   The oxide semiconductor contains In and Zn, and the composition ratio of Zn and In of the resistance layer (the ratio of Zn to In, Zn / In) is larger than the composition ratio of the active layer Zn / In. The organic electroluminescent display device according to claim 8. The organic electroluminescence display device according to claim 1, wherein the active layer has an electric conductivity of 10 ⁻⁴ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ . The organic electroluminescent display device according to claim 10, wherein the electrical conductivity of the active layer is 10 ⁻¹ Scm ⁻¹ or more and less than 10 ² Scm ⁻¹ . The ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is 10 ¹ or more and 10 ¹⁰ or less. The organic electroluminescent display device according to claim 11. The ratio of the electrical conductivity of the active layer to the electrical conductivity of the resistive layer (the electrical conductivity of the active layer / the electrical conductivity of the resistive layer) is 10 ² or more and 10 ⁸ or less. The organic electroluminescent display device described in 1.   The organic electroluminescent display device according to claim 1, wherein the substrate is a flexible resin substrate.   The organic electroluminescent display device according to claim 1, wherein the pixel is a high-definition pixel of 150 ppi or more.

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