JP4713010B2 - Light emitting device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device using a thin film made of a light emitting material. The present invention also relates to an electric appliance using the light emitting device as a display portion. An organic EL display and an organic light emitting diode (OLED) are included in the light emitting device of the present invention.
[0002]
The luminescent material that can be used in the present invention includes all luminescent materials that emit light (phosphorescence and / or fluorescence) via singlet excitation, triplet excitation, or both excitation.
[0003]
[Prior art]
In recent years, development of a light emitting element (hereinafter referred to as an EL element) using a thin film (hereinafter referred to as an EL film) made of a light emitting material capable of obtaining EL (Electro Luminescence) has been advanced. A light emitting device having an EL element (hereinafter referred to as an EL light emitting device) has an EL element having a structure in which an EL film is sandwiched between an anode and a cathode, and emits light by applying a voltage between the anode and the cathode. Get. In particular, a film using an organic film as the EL film is called an organic EL film.
[0004]
A metal having a low work function (typically a metal belonging to Group 1 or 2 of the periodic table) is often used as the cathode, and a conductive film transparent to visible light (hereinafter referred to as a transparent conductive film) is used as the anode. ) Is often used. Due to such a structure, the obtained light emission is visible through the anode.
[0005]
Recently, an active matrix EL light emitting device that controls light emission of an EL element provided in each pixel by using a TFT (Thin Film Transistor) has been developed, and a prototype has been announced. Here, the structure of the active matrix EL light-emitting device is shown in FIGS.
[0006]
In FIG. 9A, a TFT 902 is formed over a substrate 901, and an anode 903 is connected to the TFT 902. An organic EL film 904 and a cathode 905 are formed on the anode 903, and an EL element 906 including the anode 903, the organic EL film 904, and the cathode 905 is formed.
[0007]
At this time, the light generated by the organic EL film 904 passes through the anode 903 and is emitted in the direction of the arrow in the figure. Accordingly, the TFT 902 becomes a shielding object that blocks light emission from the viewpoint of the observer, and is a factor for narrowing the effective light emission area (area where the observer can observe light emission). Further, when the effective light emitting area is narrow, it is necessary to increase the light emission luminance in order to obtain a bright image. However, increasing the light emission luminance results in the deterioration of the organic EL film.
[0008]
Thus, an active matrix EL light emitting device having a structure as shown in FIG. 9B has been proposed. In FIG. 9B, a TFT 902 is formed over a substrate 901, and a cathode 907 is connected to the TFT 902. An organic EL film 908 and an anode 909 are formed on the cathode 907, and an EL element 910 including the cathode 907, the organic EL film 908, and the anode 909 is formed. In other words, an EL element having a structure opposite to that of the EL element 906 illustrated in FIG.
[0009]
At this time, in principle, light generated by the EL film 908 is transmitted through the anode 909 and emitted in the direction of the arrow in the figure. Therefore, the TFT 901 is provided at a position that cannot be seen by an observer, and the entire region where the cathode 903 is provided can be an effective light emitting region.
[0010]
However, the structure shown in FIG. 9B potentially has a problem that a uniform voltage cannot be applied to the anode 909. A transparent conductive film generally used as an anode has a higher resistance value than a metal film, but it is known that the resistance value can be lowered by heat treatment. However, since the organic EL film has low heat resistance, heat treatment exceeding 150 ° C. cannot be performed after the organic EL film is formed.
[0011]
Therefore, heat treatment cannot be performed when an anode (transparent conductive film) is laminated on the organic EL film, and it is difficult to form an anode having a low resistance value. That is, there is a possibility that the voltage applied between the end portion and the central portion of the anode is different, and there is a concern that this problem may cause image quality defects.
[0012]
As described above, a light emitting device including a structure using a transparent conductive film after forming an organic EL film has a problem that it is difficult to reduce the resistance of the transparent conductive film.
[0013]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a light-emitting device that is bright and has good image quality. It is another object of the present invention to provide an electric appliance with good image quality using such a light emitting device as a display portion.
[0014]
[Means for Solving the Problems]
The present invention is characterized in that the resistance of the transparent electrode is substantially reduced by connecting an auxiliary electrode in parallel to the transparent electrode provided after the organic EL film is formed. Here, the present invention will be described with reference to FIG.
[0015]
In FIG. 1, 101 is an insulator, 102 is an electrode including a reflective surface, 103 is an organic EL layer, and 104 is an electrode that is transparent or translucent to visible light (hereinafter referred to as a transparent electrode). The EL element 105 including the electrode 102 including the reflective surface, the organic EL layer 103 and the transparent electrode 104 is formed.
[0016]
Transparent to visible light refers to transmitting visible light with a transmittance of 80 to 100%, and translucent to visible light refers to transmitting visible light with a transmittance of 50 to 80%. Say. Of course, the transmittance varies depending on the film thickness, but the film thickness may be appropriately designed so as to be within the above range.
[0017]
Here, the insulator 101 is an insulating substrate or a substrate provided with an insulating film on the surface, and may be any substrate that can support an EL element.
[0018]
The electrode 102 including a reflective surface refers to an electrode in which a metal electrode or a metal electrode and a transparent electrode are stacked. That is, the electrode includes a surface (reflecting surface) that can reflect visible light on the front surface, back surface, or interface inside the electrode.
[0019]
The organic EL layer 103 can be an organic EL film or a stacked film of an organic EL film and an organic material. That is, the organic EL film may be provided as a single layer as the light emitting layer, or the organic EL film may be provided as a light emitting layer and an organic material may be stacked as a charge injection layer or a charge transport layer. Some inorganic materials can be used as a charge injection layer or a charge transport layer, and such an inorganic material can be used as a charge injection layer or a charge transport layer.
[0020]
As the transparent electrode 104, an electrode made of a transparent conductive film or an electrode made of a metal film (hereinafter referred to as a semi-transparent metal film) having a film thickness of 5 to 70 nm (typically 10 to 50 nm) is used. it can. As the transparent conductive film, an oxide conductive film (typically an indium oxide film, a tin oxide film, a zinc oxide film, a compound film of indium oxide and tin oxide, or a compound film of indium oxide and zinc oxide) or an oxide A conductive film to which gallium oxide is added can be used. When a transparent conductive film is used as the transparent electrode 104, 80 to 95% of visible light can be transmitted by setting the thickness to 10 to 200 nm (preferably 50 to 100 nm).
[0021]
On the EL element 105 having the above structure, the sealing body 106 and the auxiliary electrode 107 provided on the surface of the sealing body 106 are provided. The auxiliary electrode 107 is electrically connected to the transparent electrode 104 through the conductor 108. Connected. Note that the conductor 108 is provided on the transparent electrode 104 in a scattered manner, but it is preferable to disperse the conductor 108 over the entire surface of the transparent electrode as much as possible.
[0022]
Here, the sealing body 106 is a substrate or film that is transparent to visible light, and a glass substrate, a quartz substrate, a crystallized glass substrate, a plastic substrate, or a plastic film can be used. However, when a plastic substrate or a plastic film is used, it is desirable to provide a protective film (preferably a carbon film, specifically a diamond-like carbon film) for preventing permeation of oxygen and water on the front surface or the back surface.
[0023]
The auxiliary electrode 107 is an auxiliary electrode provided for the purpose of lowering the resistance value of the transparent electrode 104. Similar to the transparent electrode 104, an electrode made of a transparent conductive film or an electrode made of a semi-transparent metal film. Can be used. Further, 80 to 95% of visible light can be transmitted by setting the film thickness of the auxiliary electrode 107 to 10 to 200 nm (preferably 50 to 100 nm) similarly to the transparent electrode 104.
[0024]
The conductor 108 can be formed using a conductive film called an anisotropic conductive film or the like. Therefore, it can also be called an anisotropic conductive film. An anisotropic conductive film is a resin film in which conductive particles (typically metal particles or carbon particles) are uniformly dispersed. In the present invention, it is preferable to selectively provide the anisotropic conductive film 108 by patterning by photolithography, or selectively by an inkjet method or a printing method. This is because the anisotropic conductive film has a low transmittance for visible light, and if it is provided on the entire surface of the transparent electrode 104, light emitted from the organic EL layer 103 is absorbed.
[0025]
In the light emitting device of the present invention including the above structure, the auxiliary electrode 107 functions as an electrode connected in parallel to the transparent electrode 104 made of a transparent conductive film. At this time, since the auxiliary electrode 107 is formed on the sealing body 106 side, the resistance value can be reduced without being restricted by the heat resistance of the organic EL film as described in the conventional example. Therefore, by implementing the present invention, it is possible to apply a uniform voltage to the transparent electrode 104, and an image with good image quality can be obtained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. In FIG. 2, reference numeral 201 denotes a substrate on which an element is formed. In the present invention, any material may be used for the substrate 201, and glass (including quartz glass), crystallized glass, single crystal silicon, ceramics, metal, or plastic can be used.
[0027]
A pixel 202 is formed on the substrate 201, and the pixel 202 has a structure including a switching TFT 203 and a current control TFT 204. FIG. 2 shows three pixels, each of which emits red, green, or blue light. The switching TFT 203 functions as a switch for taking a video signal into the pixel, and the current control TFT 204 functions as a switch for controlling a current flowing through the EL element. At this time, the drain of the switching TFT 203 is electrically connected to the gate of the current control TFT 204.
[0028]
The structures of the switching TFT 203 and the current control TFT 204 are not limited, and a top gate type (typically a planar type) or a bottom gate type (typically an inverted stagger type) may be used. Both TFTs may be n-channel TFTs or p-channel TFTs.
[0029]
Further, the switching TFT 203 and the current control TFT 204 are covered with an interlayer insulating film 205, and a pixel electrode 207 made of a metal film and a drain of the current control TFT 204 are electrically connected to each other via a conductor plug 206. . A first transparent electrode 208 is stacked on the pixel electrode 207 with a thickness of 10 to 200 nm (preferably 50 to 100 nm). Here, the pixel electrode 207 and the first transparent electrode 208 form an anode 230.
[0030]
In this embodiment mode, a contact hole where the drain of the current control TFT 204 and the pixel electrode 207 are connected is filled with a conductor. A conductor provided to fill the contact hole is called a conductor plug. The conductor plug 206 may be formed by etching an anisotropic conductive film. Of course, the pixel electrode 207 may be directly connected to the drain of the current control TFT 204.
[0031]
By the way, in the recessed part resulting from the said contact hole, since the coverage of an organic electroluminescent layer is bad and there exists a possibility of causing the short circuit (short circuit) of a cathode and an anode, it is not preferable. In this embodiment mode, the use of the conductor plug 206 can prevent the pixel electrode 207 from being formed with a recess due to the contact hole, so that a short circuit between the cathode and the anode can be prevented.
[0032]
The pixel electrode 207 is preferably formed using a metal film with high reflectivity, and an aluminum film (including an aluminum alloy film or an aluminum film containing an additive) or a silver thin film is preferably used. A film in which a metal film is plated with aluminum or silver may be used.
[0033]
Next, reference numeral 209 denotes an insulating film (hereinafter referred to as a bank) provided between the anodes 230 so as to cover the step formed at the end of the anode 230. In this embodiment, by providing the bank 209, the organic EL layer is moved away from the end of the anode 230 where electric field concentration is likely to occur, and the organic EL layer is prevented from being deteriorated due to electric field concentration. Note that the bank 209 may be a resin film or an insulating film containing silicon (typically a silicon oxide film).
[0034]
Next, 210 is an organic EL layer that emits red light, 211 is an organic EL layer that emits green light, and 212 is an organic EL layer that emits blue light. The layer structure of the organic EL layers 210 to 212 may be referred to a known technique.
[0035]
The second transparent electrode 213 provided so as to cover the organic EL layers 210 to 212 is an electrode for injecting electrons into the organic EL layer. The work function of the second transparent electrode 213 is preferably 2.5 to 3.5 eV, and a metal film containing an element belonging to Group 1 or 2 of the periodic table may be used. Here, an alloy film in which aluminum and lithium are co-evaporated (hereinafter referred to as an Al-Li film) is used. Further, since the Al—Li film is a metal film, a transparent electrode can be obtained by setting the film thickness to 10 to 70 nm (typically 20 to 50 nm).
[0036]
Further, a third transparent electrode 214 made of a transparent conductive film having a thickness of 100 to 300 nm (preferably 150 to 200 nm) is provided thereon. The third transparent electrode 214 is an electrode that plays a role for applying a voltage to the second transparent electrode 213. Here, the second transparent electrode 213 and the third transparent electrode 214 form a cathode 231.
[0037]
In addition, the sealing body 215 provided to face the substrate 201 (herein, the substrate including the thin film provided on the substrate 201) has a thickness of 10 to 200 nm (preferably 50 to 100 nm). An auxiliary electrode (fourth transparent electrode) 216 made of a transparent conductive film is formed, and the third transparent electrode 214 and the auxiliary electrode 216 are anisotropic conductive films (resin films in which metal particles or carbon particles are dispersed). It is electrically connected through a conductor 217 made of
[0038]
It is preferable that the conductor 217 is partially provided on the third transparent electrode 214. That is, since the anisotropic conductive film is black or gray, it is desirable to provide it so as not to overlap at least the light emitting region of the pixel. Of course, it is also possible to positively use it as a black matrix by providing it between pixels, and to increase the directivity of light for each pixel.
[0039]
Note that the substrate 201 and the sealing body 215 are bonded to each other with a sealant (not shown) provided on the outer edge of the substrate 201. In addition, when the substrate 201 and the sealing body 215 are bonded together, a spacer (preferably 1 to 3 μm) for determining the distance between the substrate 201 and the sealing body 215 may be provided. In particular, it is effective to use this spacer also as the conductor 217.
[0040]
In addition, it is preferable that nitrogen gas or a rare gas is sealed in a space 218 formed between the substrate 201 and the sealing body (counter substrate) 215. In addition, it is desirable to provide a material having a hygroscopic property or a material having a deoxidizing property in the space 218.
[0041]
Here, a detailed structure of the region 219 is illustrated in FIG. In FIG. 2B, the anode 230, the organic EL layer 212, and the cathode 231 form the EL element 220. The most characteristic point in the light-emitting device shown in FIG. 2A is that light emission is observed through the cathode 231.
[0042]
Of the light generated by the EL element 220, the light directed toward the anode 230 is reflected by the pixel electrode 207 having a highly reflective surface and travels toward the cathode 231. In other words, the pixel electrode 207 is an electrode that supplies current to the anode 230 (extracts electrons) and also has a function as a reflective electrode.
[0043]
Note that the second transparent electrode 213 has a very high resistance value because it is very thin. Therefore, the third transparent electrode 214 is stacked to reduce the resistance. However, since the transparent conductive film used as the third transparent electrode 214 is formed after the organic EL layer 212 is formed, it is difficult to reduce the resistance value. Therefore, in the present embodiment, the auxiliary electrode 216 made of a transparent conductive film is connected in parallel to the third transparent electrode 214 made of a transparent conductive film, thereby substantially reducing the resistance of the third transparent electrode 214. Yes.
[0044]
The light emitting device having the above structure can obtain a very bright image because the entire pixel 202 is an effective light emitting region. In addition, since a uniform voltage can be applied to the entire cathode 231 by implementing the present invention, an image with good image quality can be obtained.
[0045]
【Example】
[Example 1]
In this embodiment, a manufacturing process of the light-emitting device illustrated in FIG. 2 will be described with reference to FIGS. 3 and 4 are cross-sectional views showing a manufacturing process in the pixel portion. FIG. 5A shows a top view of a pixel manufactured according to this embodiment (however, a top view when an anode is formed), and FIG. 5B shows a circuit diagram of a final pixel. The reference numerals used in FIG. 5 correspond to the reference numerals used in FIGS.
[0046]
First, as shown in FIG. 3A, a glass substrate 301 is prepared as a substrate, and a base film 302 made of a silicon oxide film is formed thereon with a thickness of 200 nm. The base film 302 may be formed by a low pressure thermal CVD method, a plasma CVD method, a sputtering method, or an evaporation method.
[0047]
Next, a crystalline silicon film 303 is formed on the base film 302 to a thickness of 50 nm. As a method for forming the crystalline silicon film 303, known means can be used. The amorphous silicon film may be crystallized by laser using a solid laser or excimer laser, or the amorphous silicon film may be crystallized by heat treatment (furnace annealing). In this embodiment, crystallization is performed by irradiation with an excimer laser using XeCl gas.
[0048]
Next, as shown in FIG. 3B, the crystalline silicon film 303 is patterned to form island-shaped crystalline silicon films 304 and 305. Then, a gate insulating film 306 made of a silicon oxide film is formed to a thickness of 80 nm so as to cover the island-like crystalline silicon films 304 and 305. Further, gate electrodes 307 and 308 are formed on the gate insulating film 306. Note that although the gate electrode 307 appears to be two in the drawing, it is actually the same electrode divided into two.
[0049]
In this embodiment, a tungsten film or a tungsten alloy film having a thickness of 350 nm is used as a material for the gate electrodes 307 and 308. Of course, other known materials can be used as the material of the gate electrode. Furthermore, in this embodiment, the connection wiring 309 is also formed at this time. The connection wiring 309 is a wiring for electrically connecting the source of the current control TFT and the current supply line later.
[0050]
Next, as shown in FIG. 3C, an element (typically boron) belonging to Group 13 of the periodic table is added using the gate electrodes 307 and 308 as masks. The addition method may be a known means. Thus, impurity regions (hereinafter referred to as p-type impurity regions) 310 to 314 having p-type conductivity are formed. In addition, channel formation regions 315a, 315b, and 316 are defined immediately below the gate electrode. Note that the p-type impurity regions 310 to 314 serve as a source region or a drain region of the TFT.
[0051]
Next, the element which belongs to the 13th group of the periodic table added by heat processing is activated. A pattern made of an island-shaped crystalline silicon film that has been subjected to this activation step is referred to as an active layer. This activation may be performed by furnace annealing, laser annealing or lamp annealing, or a combination thereof. In this embodiment, the heat treatment at 500 ° C. for 4 hours is performed in a nitrogen atmosphere.
[0052]
However, in this activation step, it is desirable that the oxygen concentration in the processing atmosphere is 1 ppm or less (preferably 0.1 ppm or less). This is because if the oxygen concentration is high, the surfaces of the gate electrodes 307 and 308 and the connection wiring 309 are oxidized, making it difficult to make electrical contact with the gate wiring and current supply line to be formed later.
[0053]
When activation is completed, it is effective to perform hydrogenation treatment. For the hydrogenation treatment, a known hydrogen annealing technique or plasma hydrogenation technique may be used.
[0054]
Next, as shown in FIG. 3D, a current supply line 317 is formed so as to be in contact with the connection wiring 309. With such a structure (a top view is shown in a region indicated by 501 in FIG. 5A), the connection wiring 309 and the current supply line 317 are electrically connected. Although not shown, a gate wiring (wiring indicated by 502 in FIG. 5A) is also formed at this time and is electrically connected to the gate electrode 307. This top view is shown in a region indicated by 503 in FIG.
[0055]
In the region indicated by 503, the gate wiring 502 has a convex portion because of a redundant design for securing a portion that does not get over the gate electrode 307. By doing so, even if the gate wiring 502 is disconnected at the portion over the gate electrode 307, it is possible to prevent the gate wiring 502 from being electrically disconnected there. In addition, the gate electrode 307 is processed into a U-shape, which is a redundant design for ensuring that a voltage is applied to both gate electrodes.
[0056]
The current supply line 317 and the gate wiring 502 are formed of a metal film having a lower resistance than the connection wiring 309 and the gate electrode 307. A metal film containing aluminum, copper or silver is preferably used. That is, a highly processable metal film is used for a gate electrode that requires fine pattern accuracy, and a low resistance is required for a bus line that requires low resistivity (gate wiring and current supply line in this embodiment). A simple metal film is used.
[0057]
After the gate wiring 502 and the current supply line 317 are formed, a first interlayer insulating film 318 made of a silicon oxide film is formed to a thickness of 800 nm. A plasma CVD method may be used as a formation method. As the first interlayer insulating film 318, another inorganic insulating film may be used or a resin (organic insulating film) may be used.
[0058]
Next, as illustrated in FIG. 3E, contact holes are formed in the first interlayer insulating film 318 to form wirings 319 to 322. In this embodiment, metal wirings having a three-layer structure of titanium / aluminum / titanium are used as the wirings 319 to 322. Of course, any material may be used as long as it is a conductive film. The wirings 319 to 322 are TFT source wirings or drain wirings.
[0059]
Further, the drain wiring 322 of the current control TFT is electrically connected to the connection wiring 309. As a result, the drain of the current control TFT 402 and the current supply line 317 are electrically connected.
[0060]
In this state, the switching TFT 401 and the current control TFT 402 are completed. In this embodiment, both TFTs are formed by p-channel TFTs, but both or one of them may be n-channel TFTs.
[0061]
The switching TFT 401 is formed such that the gate electrode crosses the active layer at two locations, and has a structure in which two channel formation regions are connected in series. With such a structure, an off-current value (current that flows when the TFT is turned off) can be effectively suppressed.
[0062]
Further, a storage capacitor 504 is formed in the pixel as shown in FIG. FIG. 6 shows a cross-sectional view of the storage capacitor 504 (a cross-sectional view taken along line BB ′ in FIG. 5A). The storage capacitor 504 is formed by a semiconductor layer 505, a gate insulating film 306, and a capacitor wiring 506 that are electrically connected to the drain of the current control TFT 402. In other words, the semiconductor layer 505 and the capacitor wiring 506 are insulated by the gate insulating film 306 to form a capacitor (retention capacitor).
[0063]
The capacitor wiring 506 is formed at the same time as the gate wiring 502 and the current supply line 317, and also serves as a wiring for electrically connecting the gate electrode 308 and the connection wiring 507. Note that the connection wiring 507 is electrically connected to the drain wiring (which may function as a source wiring) 320 of the switching TFT 401.
[0064]
The advantage of the storage capacitor shown in this embodiment is that the capacitor wiring 506 is formed after the active layer is formed. That is, in this embodiment, the semiconductor layer 505 is a p-type impurity region and can be used as an electrode as it is.
[0065]
After the wirings 319 to 322 are formed, a passivation film 323 made of a silicon nitride film or a silicon nitride oxide film is formed to a thickness of 200 nm. By performing a hydrogenation process before or after the formation of the passivation film 323, the electrical characteristics of the TFT can be improved.
[0066]
Next, as shown in FIG. 4A, an acrylic resin is formed to a thickness of 1 μm as the second interlayer insulating film 324, a contact hole 325 is opened, and then an anisotropic conductive film 326 is formed. In this embodiment, an acrylic resin in which silver particles are dispersed is used as the anisotropic conductive film 326. In addition, the anisotropic conductive film 326 is desirably formed with a thickness sufficient to flatten the contact hole 325. In this embodiment, the film is formed by a spin coating method with a thickness of 1.5 μm.
[0067]
Next, the anisotropic conductive film 326 is etched by plasma using oxygen gas. This process is continued until the second interlayer insulating film 324 is exposed. When the etching is completed, the conductor plug 327 is formed in a shape as shown in FIG. Note that when the second interlayer insulating film 324 is exposed, the conductor plug 327 may have a step due to a difference in etching rate with the second interlayer insulating film 324, but the step is 100 nm or less (preferably 50 nm or less). If there is no particular problem.
[0068]
After the conductor plug 327 is formed, a pixel electrode 328 made of an aluminum film to which scandium or titanium is added and an ITO film (compound film of indium oxide and tin oxide) are stacked and etched to form the aluminum film to which scandium or titanium is added. Then, a first transparent electrode 329 made of an ITO film is formed. In this embodiment, the pixel electrode 328 and the first transparent electrode 329 form an anode 340.
[0069]
In this embodiment, the thickness of the aluminum film is 200 nm, and the thickness of the ITO film is 100 nm. The ITO film can be etched with ITO-04N (trade name of an etching solution for ITO film of Kanto Chemical Co., Ltd.), and the aluminum film is carbon tetrachloride (SiCl _Four ) And chlorine (Cl ₂ ) Can be etched by a dry etching method using a mixed gas.
[0070]
The cross-sectional structure in FIG. 4B thus obtained corresponds to the cross-sectional structure cut along AA ′ in FIG.
[0071]
Next, as shown in FIG. 4C, an insulating film 330 is formed as a bank. In this embodiment, the bank 330 is formed using an acrylic resin, but it can also be formed using a silicon oxide film. After the bank 330 is formed, the first transparent electrode 329 is irradiated with ultraviolet light in an oxygen atmosphere to perform surface treatment of the first transparent electrode 329. This has the effect of increasing the work function of the first transparent electrode 329, and also has the effect of removing surface contamination.
[0072]
Then, the organic EL films 331 and 332 are each formed to a thickness of 50 nm. The organic EL film 331 is an organic EL film that emits blue light, and the organic EL film 332 is an organic EL film that emits red light. Although not shown, an organic EL film that emits green light simultaneously is also formed. In this embodiment, an organic EL film is separately formed for each pixel by an evaporation method using a shadow mask. Of course, it is also possible to make them separately using a printing method or an inkjet method.
[0073]
In this embodiment, an example in which the organic EL films 331 and 332 are used as a single layer is shown, but it is also effective to have a stacked structure using CuPc (copper phthalocyanine) as the hole injection layer. In this case, a copper phthalocyanine film is first formed on the entire surface, and then an organic EL film that emits red light for each pixel corresponding to red, green, and blue, an organic EL film that emits green light, and an organic EL film that emits blue light Form.
[0074]
When forming a green organic EL film, Alq is used as a base material of the organic EL film. _Three (Tris-8-quinolinolato aluminum complex) is used and quinacridone or coumarin 6 is added as a dopant. When forming a red organic EL film, Alq is used as a base material of the organic EL film. _Three And DCJT, DCM1 or DCM2 is added as a dopant. Further, when forming a blue organic EL film, BAlq is used as the organic EL film of the light emitting layer. _Three (5-coordinate complex having a mixed ligand of 2-methyl-8-quinolinol and a phenol derivative) and perylene is added as a dopant.
[0075]
Of course, in the present invention, it is not necessary to limit to the organic EL film, and it is possible to use a known low-molecular organic EL film or high-molecular organic EL film. When a polymer organic EL film is used, a coating method (spin coating method, ink jet method or printing method) can also be used.
[0076]
When the organic EL films 331 and 332 are formed as described above, a 20 nm-thick MgAg film (a metal film in which 1 to 10% silver (Ag) is added to magnesium (Mg)) is used as the second transparent electrode 333. Further, an ITO film having a thickness of 250 nm is formed as the third transparent electrode 334. In this embodiment, the second transparent electrode 333 and the third transparent electrode 334 form a cathode 341.
[0077]
Thus, an EL element 400 including the anode 340, the organic EL film 331 (or the organic EL film 332), and the cathode 341 is formed. In this embodiment, this EL element functions as a light emitting element.
[0078]
Next, as shown in FIG. 4D, an auxiliary electrode 336 made of a transparent conductive film is provided over the sealing body 335 with a thickness of 250 nm, and a conductor 337 made of an anisotropic conductive film is formed in the third shape. The transparent electrode 334 is provided. And the board | substrate 301 and the sealing body 335 are bonded together using a sealing material (not shown).
[0079]
Note that the bonding step is performed in an argon atmosphere. As a result, the space 338 is filled with argon. Of course, the gas to be sealed may be an inert gas, and a nitrogen gas or a rare gas may be used. The space 338 is preferably provided with a substance that adsorbs oxygen or water. Moreover, it is also possible to fill the resin instead of the space.
[0080]
Through the manufacturing process described above, a switching TFT (p-channel TFT in this embodiment) 401 and a current control TFT (p-channel TFT in this embodiment) 402 are formed in the pixel. In this embodiment, since all TFTs are p-channel TFTs, the manufacturing process is very simple.
[0081]
Further, the level difference is flattened by the second interlayer insulating film 324, and the drain wiring 321 of the current control TFT 402 and the pixel electrode 328 are electrically connected using the conductor plug 327 embedded in the contact hole 325. Therefore, the flatness of the anode 340 is high. Accordingly, the uniformity of the film thickness of the organic EL film 332 can be improved, so that the light emission of the pixels can be made uniform.
[0082]
[Example 2]
In this embodiment, an EL light-emitting device having pixels having a structure different from that of the EL light-emitting device shown in FIG. 2 will be described with reference to FIG. Note that this embodiment can be manufactured by making a slight modification to the structure of FIG. 2, and will be described with a focus on differences from FIG. Therefore, for the description of the parts denoted by the same reference numerals as those in FIG. 2, the “embodiment of the invention” may be referred to.
[0083]
In this embodiment, when a contact hole is formed in the interlayer insulating film 205, the pixel electrode 701 and the first transparent electrode 702 are formed in that state, and the insulating film 703 is formed so as to fill the concave portion due to the contact hole. In this embodiment, this insulating film 703 is referred to as a buried insulating film. Since the buried insulating film 703 can be formed at the same time as the bank 209, the number of steps is not particularly increased.
[0084]
The buried insulating film 703 is for preventing a short circuit between the cathode and the anode caused by the concave portion due to the contact hole, like the conductor plug 206 of FIG. At this time, the height between the upper surface of the buried insulating film 703 and the upper surface of the second transparent electrode 702 is preferably set to 100 to 300 nm. If this height exceeds 300 nm, the step may cause a short circuit between the cathode and the anode. Further, when the thickness is 100 nm or less, there is a possibility that the action of the simultaneously formed bank 209 (the action of suppressing the influence of the electric field concentration at the edge portion of the pixel electrode) is lowered.
[0085]
In this embodiment, after the second transparent electrode 702 is formed, an acrylic resin is formed to a thickness of 500 nm by a spin coating method, and oxygen gas is converted into plasma to form an acrylic film thickness (thickness outside the contact hole). Etching is performed until 200 nm becomes 200 nm. In this manner, the bank 209 and the buried insulating film 703 are formed by patterning after reducing the film thickness.
[0086]
Here, the top structure of the pixel of this embodiment is shown in FIG. In FIG. 8, a cross-sectional view cut along AA ′ corresponds to FIG. Note that the sealing body 215 and the conductor 217 are not shown in FIG. The basic pixel structure is the same as that shown in FIG.
[0087]
In FIG. 8, the bank 209 is formed so as to hide the steps at the ends of the pixel electrode 701 and the anode 702, and the embedded insulating film 703 is formed so that a part of the bank 209 protrudes. This protruding insulating film has a structure in which a concave portion by a contact hole of the pixel electrode 701 is embedded.
[0088]
Note that the EL light-emitting device of this example can be easily manufactured by combining the manufacturing method of Example 1 with the method for forming the buried insulating film.
[0089]
Example 3
Although only the structure of the pixel portion is shown in the EL light emitting device shown in the embodiment of the invention and in Example 1, a driving circuit for driving the pixel portion may be integrally formed on the same substrate. At that time, the driver circuit can be formed of an nMOS circuit, a pMOS circuit, or a CMOS circuit. Of course, only the pixel portion may be formed of TFTs, and an external drive circuit, typically a drive circuit including an IC chip (TCP, COG, or the like) may be used.
[0090]
In the first embodiment, the pixel portion is formed only by the p-channel TFT to reduce the manufacturing process. In this case, a driver circuit is formed by a pMOS circuit, and an IC chip is included as a driver circuit that cannot be manufactured by a pMOS. A drive circuit can also be used.
[0091]
Note that the configuration of this embodiment can be implemented in combination with the configuration of Embodiment 1 or Embodiment 2 freely.
[0092]
Example 4
In this embodiment, an example in which an amorphous silicon film (amorphous silicon film) is used as an active layer of a switching TFT and a current control TFT formed in a pixel portion is shown. An inversely staggered TFT is known as a TFT using an amorphous silicon film, but an inversely staggered TFT can also be used in this embodiment.
[0093]
Although the TFT using an amorphous silicon film is easy to manufacture, there is a drawback that the element size becomes large. However, in the EL light emitting device of the present invention, the size of the TFT affects the effective light emitting area of the pixel. do not do. Therefore, a cheaper EL light emitting device can be manufactured by using an amorphous silicon film as an active layer.
[0094]
In addition, the structure of a present Example can be implemented in combination freely with any structure of Example 1- Example 3. However, when combined with Example 3, it is difficult to produce a drive circuit having a high operation speed with a TFT using an amorphous silicon film. Therefore, it is desirable to provide an external drive circuit including an IC chip.
[0095]
Example 5
In Embodiments 1 to 4, the active matrix EL light-emitting device has been described. However, the present invention can also be applied to an EL element of a passive matrix EL light-emitting device.
[0096]
In addition, the structure of a present Example can be implemented in combination freely with any structure of Example 1- Example 3. However, when combined with the third embodiment, a driving circuit including an IC chip is externally attached.
[0097]
Example 6
A light emitting device formed by implementing the present invention can be used as a display portion of various electric appliances. Note that the display in which the light emitting device is incorporated in the housing includes all information display displays such as a personal computer display, a TV broadcast reception display, and an advertisement display.
[0098]
As other electrical appliances of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a music playback device (car audio, audio component, etc.), a notebook type personal computer, a game machine, Examples thereof include portable information terminals (mobile computers, mobile phones, portable game machines, electronic books, etc.), and image playback devices (devices having a display unit that plays back images recorded on a recording medium and displays the images). . Specific examples thereof are shown in FIGS.
[0099]
FIG. 10A illustrates an EL display which includes a housing 2001, a support base 2002, and a display portion 2003. The light emitting device of the present invention can be used for the display portion 2003. Since the EL display is a self-luminous type, a backlight is not necessary, and a display portion thinner than a liquid crystal display can be obtained.
[0100]
FIG. 10B illustrates a video camera, which includes a main body 2101, a display portion 2102, an audio input portion 2103, operation switches 2104, a battery 2105, and an image receiving portion 2106. The light emitting device of the present invention can be used for the display portion 2102.
[0101]
FIG. 10C illustrates a digital camera, which includes a main body 2201, a display portion 2202, an eyepiece portion 2203, and operation switches 2204. The light emitting device of the present invention can be used for the display portion 2202.
[0102]
FIG. 10D shows an image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2301, a recording medium (CD, LD, DVD, etc.) 2302, an operation switch 2303, and a display unit (a). 2304 and a display unit (b) 2305. The display unit (a) mainly displays image information, and the display unit (b) mainly displays character information. The light emitting device of the present invention can be used for these display units (a) and (b). Note that the image reproducing device provided with the recording medium may include a CD reproducing device, a game machine, and the like.
[0103]
FIG. 10E illustrates a portable (mobile) computer, which includes a main body 2401, a display portion 2402, an image receiving portion 2403, operation switches 2404, and a memory slot 2405. The electro-optical device of the present invention can be used for the display portion 2402. This portable computer can record information on a recording medium in which a flash memory or a non-volatile memory is integrated, and can reproduce the information.
[0104]
FIG. 10F illustrates a personal computer, which includes a main body 2501, a housing 2502, a display portion 2503, and a keyboard 2504. The light emitting device of the present invention can be used for the display portion 2503.
[0105]
If the emission brightness of the EL material is increased in the future, it is possible to enlarge and project the light including the output image information with a lens or the like and use it for a front type or rear type projector.
[0106]
In addition, the electronic devices often display information distributed through an electronic communication line such as the Internet or CATV (cable television), and in particular, opportunities for displaying moving image information are increasing. Since the response speed of the EL material is very high, it is suitable for displaying such a moving image.
[0107]
In addition, since the light emitting device consumes power in the light emitting portion, it is desirable to display information so that the light emitting portion is minimized. Therefore, when a light emitting device is used for a display unit mainly including character information such as a portable information terminal, particularly a mobile phone or a car audio, it is driven so that character information is formed by the light emitting part with a non-light emitting part as a background. It is desirable.
[0108]
Here, FIG. 11A shows a mobile phone, which includes a main body 2601, an audio output portion 2602, an audio input portion 2603, a display portion 2604, operation switches 2605, and an antenna 2606. The light-emitting device of the present invention can be used for the display portion 2604. Note that the display portion 2604 can suppress power consumption of the mobile phone by displaying white characters on a black background.
[0109]
FIG. 11B shows a car audio, which includes a main body 2701, a display portion 2702, and operation switches 2703 and 2704. The light emitting device of the present invention can be used for the display portion 2702. Moreover, although the vehicle-mounted car audio is shown in this embodiment, it may be used for a stationary car audio. Note that the display portion 2704 can suppress power consumption by displaying white characters on a black background.
[0110]
Furthermore, it is effective to provide a function of modulating the light emission luminance in accordance with the brightness of the usage environment by incorporating a photosensor and providing means for detecting the brightness of the usage environment. The user can recognize the image or the character information without any problem if the brightness of 100 to 150 can be secured in the contrast ratio as compared with the brightness of the usage environment. That is, when the usage environment is bright, it is possible to increase the brightness of the image for easy viewing, and when the usage environment is dark, the brightness of the image can be suppressed to reduce power consumption.
[0111]
As described above, the application range of the present invention is extremely wide and can be used for electric appliances in various fields. Moreover, you may use the light-emitting device of any structure shown in Examples 1-5 for the electric appliance of a present Example.
[0112]
【The invention's effect】
In the present invention, an electrode made of a transparent conductive film provided on the sealing body side is electrically connected to an electrode made of a transparent conductive film formed after forming an organic EL film by using an anisotropic conductive film. There is a feature in the point to connect to. Thereby, the resistance value of the transparent conductive film formed after the organic EL film is formed can be substantially lowered, and a uniform voltage can be applied.
[0113]
Further, in the present invention, the effective light emitting area of the pixel is greatly increased by combining with a light emitting device in which the cathode is transparent or translucent and a reflection electrode is provided under the EL element to extract light to the cathode side. An improved light-emitting device that is bright and has good image quality can be obtained. In addition, an electric appliance with good image quality using the light emitting device of the present invention as a display portion can be obtained.
[Brief description of the drawings]
FIG. 1 illustrates a cross-sectional structure of a light-emitting device.
FIG. 2 illustrates a cross-sectional structure of a light-emitting device.
3A and 3B illustrate a manufacturing process of a light-emitting device.
4A and 4B illustrate a manufacturing process of a light-emitting device.
FIG 5 illustrates a top structure and a circuit configuration of a pixel of a light-emitting device.
FIG. 6 shows a cross-sectional structure of a storage capacitor.
FIG 7 illustrates a cross-sectional structure of a light-emitting device.
FIG 8 illustrates a top structure of a light-emitting device.
FIG. 9 shows a cross-sectional structure of a conventional light emitting device.
FIG. 10 is a diagram showing a specific example of an electric appliance.
FIG. 11 is a diagram showing a specific example of an electric appliance.

Claims (6)

A first electrode on a first substrate;
An EL layer on the first electrode;
A second electrode on the EL layer;
A conductor on the second electrode;
A third electrode on the conductor;
A second substrate on the third electrode;
The second electrode and the third electrode have translucency,
The second electrode and the third electrode are electrically connected via the conductor,
The conductor is disposed at a position overlapping with a stacked structure including only the first electrode, the EL layer, and the second electrode ,
The light emitting device, wherein the third electrode is formed on the second substrate side . A TFT on a first substrate;
An insulating film on the TFT;
A contact hole provided in the insulating film;
An anisotropic conductive film embedded in the contact hole; a first electrode on the anisotropic conductive film and on the insulating film;
An EL layer on the first electrode;
A second electrode on the EL layer;
A conductor on the second electrode;
A third electrode on the conductor;
A second substrate on the third electrode;
The second electrode and the third electrode have translucency,
The second electrode and the third electrode are electrically connected via the conductor,
The first electrode, the EL layer, and the second electrode constitute an EL element,
The contact hole is disposed at a position overlapping the effective light emitting region of the EL element,
The first electrode and the TFT are electrically connected via the anisotropic conductive film embedded in the contact hole ,
The light emitting device, wherein the third electrode is formed on the second substrate side . A TFT on a first substrate;
An insulating film on the TFT;
A contact hole provided in the insulating film;
A first electrode provided on the insulating film and electrically connected to the TFT through the contact hole;
A buried insulating film on the first electrode;
An EL layer on the first electrode and on the buried insulating film;
A second electrode on the EL layer;
A conductor on the second electrode;
A third electrode on the conductor;
A second substrate on the third electrode;
The second electrode and the third electrode have translucency,
The second electrode and the third electrode are electrically connected via the conductor,
The first electrode, the EL layer, and the second electrode constitute an EL element,
The contact hole is disposed at a position surrounded by an effective light emitting region of the EL element,
The buried insulating film is provided so as to fill a concave portion of the first electrode formed due to the contact hole ;
The light emitting device, wherein the third electrode is formed on the second substrate side . In claim 2 or claim 3,
A bank that covers a step formed at an end of the first electrode;
The light emitting device, wherein the conductor is disposed at a position overlapping the bank. A method for manufacturing a light-emitting device in which an EL element includes a first electrode, an EL layer, and a second electrode,
Forming a TFT on the first substrate, an insulating film on the TFT, and a contact hole provided in the insulating film;
Forming an anisotropic conductive film on the insulating film and in the contact hole;
Etching the anisotropic conductive film until the insulating film is exposed to form a conductive material embedded in the contact hole,
Forming the first electrode on the conductive material and on the insulating film;
Forming the EL layer on the first electrode;
Forming the second electrode on the EL layer;
A second substrate provided with a third electrode is attached to face the first substrate so as to sandwich the conductor, whereby the second electrode and the third electrode are bonded to the conductor. Electrically connected through
The second electrode and the third electrode have translucency,
The contact hole is disposed at a position overlapping the effective light emitting region of the EL element,
The method for manufacturing a light-emitting device, wherein the first electrode and the TFT are electrically connected through the conductive material embedded in the contact hole. A method for manufacturing a light-emitting device in which an EL element includes a first electrode, an EL layer, and a second electrode,
Forming a TFT on the first substrate, an insulating film on the TFT, and a contact hole provided in the insulating film;
Forming the first electrode electrically connected to the TFT on the insulating film and in the contact hole;
Forming a buried insulating film provided on the first electrode and a bank provided so as to cover a step formed at an end of the first electrode;
Forming the EL layer on the first electrode, on the buried insulating film, and on the bank;
Forming the second electrode on the EL layer;
A second substrate provided with a third electrode is attached to face the first substrate so as to sandwich the conductor, whereby the second electrode and the third electrode are bonded to the conductor. Electrically connected through
The second electrode and the third electrode have translucency,
The contact hole is disposed at a position surrounded by an effective light emitting region of the EL element,
The method for manufacturing a light-emitting device, wherein the buried insulating film is provided so as to fill a concave portion of the first electrode formed due to the contact hole.

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