JP2001291595A - Light emission device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emission device of a high brightness and a high reliability. SOLUTION: On a reflecting electrode 101, an anode 102, an EL layer 103, a cathode 104 and an auxiliary electrode 105 are sequentially laminated. In addition, the anode 102, the cathode 104 and the auxiliary electrode 105 are transparent or translucent to visible rays. In such a structure, because almost all the emitted light generated in the EL layer 103 is radiated to the cathode 104 side, an effective light emission area of pixel is greatly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using a thin film made of a light emitting material. Further, the present invention relates to an electric appliance using the light emitting device as a display portion or a light source.

[0002]

2. Description of the Related Art In recent years, a light-emitting device (hereinafter, referred to as an EL device) using 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). Device). The EL light emitting device has an EL element having a structure in which an EL film is interposed between an anode and a cathode, and emits light by applying a voltage between the anode and the cathode. In particular, a film using an organic film as the EL film is called an organic EL film. Note that the light-emitting material from which EL is obtained includes a light-emitting material that emits light through singlet excitation and a light-emitting material that emits light through triplet excitation.

As the cathode, a metal having a small work function (typically, a metal belonging to Group 1 or 2 of the periodic table) is often used. As the anode, a compound film (ITO) of indium oxide and tin oxide is used. Such a transparent oxide conductive film is often used. Therefore, the obtained light emission passes through the anode and is visually recognized.

[0004] Recently, active matrix EL light-emitting devices that control light emission of EL elements provided in each pixel using TFTs (thin film transistors) have been developed, and prototypes have been announced. Each of these prototypes has a pixel electrode as an anode, and the light emitted from the EL element is emitted to the TFT side.

However, in such a structure, the TFT
In addition, since light does not pass through the region where the wiring is formed, a light-emitting area that can be visually recognized (hereinafter, referred to as an effective light-emitting area) is significantly reduced. Therefore, in order to obtain a bright image, it is necessary to increase the light emission luminance, and this has resulted in accelerated deterioration of the organic EL film.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a bright and highly reliable light emitting device. Another object is to provide a highly reliable electric appliance using such a light-emitting device as a display portion or a light source.

[0007]

The present invention is characterized in that an EL element 100 having the structure shown in FIG. 1 is used.
In FIG. 1, reference numeral 101 denotes a reflective electrode made of a metal film. The reflective electrode 101 is preferably formed using a metal film having high reflectance, and an aluminum film (including an aluminum alloy film and an aluminum film containing an additive) or a silver thin film is preferably used. A conductive film plated with aluminum or silver may be used.

Next, reference numeral 102 denotes an anode of the EL element 100, which is made of a conductive film transparent to visible light (hereinafter, referred to as a transparent conductive film). In addition, being transparent to visible light (light in the visible light range) means transmitting visible light at a transmittance of 80 to 100%. When an oxide conductive film (typically, a compound film of indium oxide and tin oxide or a compound film of indium oxide and zinc oxide) is used as the transparent conductive film,
The thickness of the transparent conductive film is 10 to 200 nm (preferably 50 nm).
１００100 nm).

At this time, it is the work function of the anode 102 that determines the hole injection barrier, and the reflective electrode 101 reflects light emitted from the EL element and simultaneously applies a uniform voltage to the anode 102.

Reference numeral 103 denotes an EL layer, which includes a single layer or a plurality of layers. Note that the EL film may be an organic EL film or an inorganic EL film, or may be formed by stacking an organic EL film and an inorganic EL film. Also, the EL layer 10
The structure of No. 3 may be any known structure. That is,
In this specification, an EL layer refers to a layer formed by freely combining a charge injection layer, a charge transport layer, or an EL film (also referred to as a light-emitting layer). Of course, the EL film may be of a low molecular weight or a high molecular weight.

Reference numeral 104 denotes a cathode of the EL element 100, which is a metal film having a small work function (about -3.5 to -3.8 e).
V) is used. As a metal film having such a work function, a metal film containing an element belonging to Group 1 or 2 of the periodic table may be used. Therefore, in the present invention, it is desirable to use a metal film containing an element belonging to Group 1 or 2 of the periodic table with a thickness of 10 to 70 nm (preferably 20 to 50 nm).

Since the thin metal film as described above can transmit visible light, the cathode 104 can be used as an electrode transparent to visible light.

Reference numeral 105 denotes an electrode made of a transparent conductive film in contact with the cathode (hereinafter, referred to as an auxiliary electrode). As the auxiliary electrode 105, an oxide conductive film typified by a compound film of indium oxide and tin oxide or a compound film of indium oxide and zinc oxide may be used. The film thickness is 10-2
It may be 00 nm (preferably 50 to 100 nm). At this time, the work function of the cathode 104 determines the electron injection barrier, and the auxiliary electrode 105 applies a uniform voltage to the cathode 104.

In the case of the EL device having the above structure, light generated in the EL layer (strictly, an EL film included in the EL layer) is observed from the auxiliary electrode 105 side (upward in FIG. 1). . This can be easily understood by considering that most of the light emitted to the anode 102 side is reflected by the reflective electrode 101.

An advantage of the present invention is that light emission of the EL light emitting device, which has conventionally been difficult to extract from the cathode side, can be easily extracted from the cathode side. This effect is particularly remarkable when an active matrix EL light emitting device is formed.

[0016]

FIG. 2 shows an embodiment of the present invention.
This will be described with reference to FIG. In FIG. 2, reference numeral 201 denotes a substrate on which an element is formed (hereinafter, referred to as an element formation substrate). In the present invention, any material may be used for the substrate, and glass (including quartz glass), crystallized glass, single crystal silicon, ceramics, metal, or plastic can be used.

A pixel 202 is formed on an element forming substrate 201. The pixel 202 has a structure including a switching TFT 203 and a current controlling TFT 204. Note that FIG. 2 shows three pixels, and pixels corresponding to red, green, and blue, respectively, are formed. The switching TFT 203 functions as a switch for capturing a video signal into a pixel, and the current control TFT 204 is an EL.
It functions as a switch for controlling the current flowing through the element. At this time, the drain of the switching TFT 203 is electrically connected to the gate of the current control TFT 204.

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. Further, both TFTs may be n-channel TFTs or p-channel TFTs.

The switching TFT 203 and the current control TFT 204 are covered with an interlayer insulating film 205, on which the pixel electrode 207a and the drain of the current control TFT 204 are electrically connected via a conductor 206. I have. An anode 207b made of a transparent conductive film is stacked on the pixel electrode (corresponding to the reflective electrode 101 in FIG. 1) 207a. Note that as the conductor 206, a resin in which metal particles are dispersed to have conductivity (typically, an anisotropic conductive film) may be used. Of course, the pixel electrode 207a
May be directly connected to the drain of the current control TFT 204.

In the present embodiment, the use of the conductor 206 prevents the pixel electrode 207a from being formed with a recess due to the contact hole. Such a concave portion is not preferable because it can cause deterioration of the organic EL layer.
That is, by flattening the pixel electrode 207a with the conductor 206 as in this embodiment, deterioration of the organic EL layer can be suppressed and uniform light emission can be obtained.

Next, reference numeral 208 denotes an adjacent pixel electrode 207a.
It is an insulating film provided in a gap between them, and is formed so as to cover a step formed at an end portion of the pixel electrode 207a. Insulating film 2
08 has an effect of suppressing the influence of electric field concentration at the end of the pixel electrode 207a by keeping the organic EL layer away from the end of the pixel electrode 207a.

In this specification, the insulating film 208 is called a bank. As the bank 208, a resin, a silicon oxide film, a silicon nitride film, or a silicon oxynitride film can be used. In particular, since the resin has a low relative dielectric constant, the electric field concentration at the end of the pixel electrode 207a can be effectively suppressed.

Next, reference numeral 209 denotes an organic EL emitting red light.
Reference numeral 210 denotes an organic EL layer that emits green light, and 211 denotes an organic EL layer that emits blue light. Organic EL layers 209-21
The structure 1 may be a known structure. As in the present embodiment,
When an organic EL layer is separately formed for each pixel, it is preferable to form the organic EL layer using an evaporation method.

The cathode 212 provided so as to cover the organic EL layers 209 to 211 is an alloy film obtained by co-evaporating aluminum and lithium (hereinafter referred to as an Al-Li film).
And a film thickness of 10 to 70 nm (typically 20 to 50 nm).
nm). In addition, 10 to 200 nm
An auxiliary electrode 213 (preferably 50 to 100 nm) is provided.

A spacer 215 made of resin and a passivation film 216 are provided on a substrate (hereinafter, referred to as a counter substrate) 214 provided to face the element forming substrate, and the element forming substrate is formed by a sealing material (not shown). 20
It is attached to 1. The height of the spacer 215 is not particularly limited, but may be 1 to 3 μm. Further, the passivation film 216 is preferably an insulating film having a high transmittance which can suppress outgassing from the spacer 215, and is a silicon nitride film, a silicon nitride oxide film, a tantalum oxide film, or a carbon film (preferably a diamond-like carbon film).
Is used.

The element forming substrate 201 and the opposing substrate 21
It is preferable that a nitrogen gas or a rare gas is sealed in a space 217 formed between the space 217 and the space 217. This space 217
Is provided with an adsorbent (a substance having a hygroscopic property),
It is desirable to adsorb water, oxygen or gas generated from the resin mixed in the water.

The EL element 218 thus formed
FIG. 2 (B) shows the detailed structure of FIG. The pixel electrode 207a also serves as a reflective electrode, and has a structure similar to that of the EL element of the present invention shown in FIG.

With the structure shown in this embodiment, EL
The light emitted from the element 218 is emitted in the direction of the arrow (the direction indicated by the light emission direction). Therefore, even if the area of the TFT and the wiring occupying the pixel is large,
The effective light emitting area is defined by the area of the pixel electrode 207a, and can be sufficiently large. That is, a sufficiently bright image can be obtained without increasing the emission luminance.

This means that the power consumption of the EL light emitting device can be reduced by setting the drive voltage of the EL element low. Similarly, by setting the driving voltage low, it is possible to suppress the deterioration of the organic EL film and increase the reliability of the EL light emitting device.

[0030]

[Embodiment 1] This embodiment will be described with reference to FIGS. Note that FIGS. 3 and 4 are cross-sectional views illustrating 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.
This corresponds to the code used in.

First, as shown in FIG. 3A, a glass substrate 301 is prepared as an element forming substrate, and an insulating film 302 made of a silicon oxide film is formed thereon to a thickness of 200 nm. The insulating film 302 may be formed by a low-pressure thermal CVD method, a plasma CVD method, a sputtering method, or an evaporation method.

Next, a crystalline silicon film 303 is formed on the insulating film 302 to a thickness of 50 nm. Known methods can be used as a method for forming the crystalline silicon film 303. The amorphous silicon film may be laser-crystallized using a solid-state laser or excimer laser, or the amorphous silicon film may be crystallized by heat treatment (furnace annealing). In this embodiment, XeCl
Crystallization is performed by irradiating an excimer laser using a gas.

Next, as shown in FIG. 3B, the crystalline silicon film 303 is patterned to form island-like crystalline silicon films (hereinafter, referred to as active layers) 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 active layer. further,
Gate electrodes 307 and 308 are formed over the gate insulating film 306. In this embodiment, a 350 nm-thick tungsten film or a tungsten alloy film is used as a material of the gate electrodes 307 and 308. Of course, other known materials can be used as the material of the gate electrode.

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.

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 a mask. A known method may be used for the addition method. Thus, an impurity region exhibiting a p-type conductivity (hereinafter referred to as a p-type impurity region) 310 to 3
14 are formed. Further, 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.

Next, a heat treatment is performed to activate the added element belonging to Group 13 of the periodic table. This activation may be performed by furnace annealing, laser annealing, lamp annealing, or a combination thereof. In this embodiment, the heat treatment at 500 ° C. for 4 hours is performed in a nitrogen atmosphere.

However, in this activation step, it is desirable that the oxygen concentration in the processing atmosphere be 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, which makes it difficult to make electrical contact with a gate wiring or a current supply line to be formed later.

It is effective to perform a hydrogenation treatment after the activation is completed. The hydrogenation treatment may use a known hydrogen annealing technique or a plasma hydrogenation technique.

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 (the top view is in a region denoted by 501 in FIG. 5A), the connection wiring 309 and the current supply line 317 are electrically connected. Although not shown, a gate wiring (a 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.

In the region denoted by reference numeral 503, the reason why the gate wiring 502 has a projection is that the gate electrode 307
This is a redundant design to secure a part that does not survive. By doing so, the gate wiring 502 is connected to the gate electrode 30.
Even if the wire breaks at the part that goes over 7, the gate wiring 50
2 can be prevented from being electrically disconnected there. The processing of the gate electrode 307 in a U-shape is also a redundant design to ensure that a voltage is applied to both gate electrodes.

The current supply line 317 and the gate wiring 50
2 is formed of a metal film having lower resistance than the connection wiring 309 and the gate electrode 307. It is preferable to use a metal film containing aluminum, copper, or silver. That is, a metal film having high workability is used for a gate electrode requiring fine pattern accuracy, and a low resistance is used for a bus line (gate wiring and current supply line in this embodiment) requiring low resistivity. Use a suitable metal film.

After the gate wiring 502 and the current supply line 309 are formed, the first interlayer insulating film 3 made of a silicon oxide film is formed.
18 is formed to a thickness of 800 nm. As a forming method, a plasma CVD method may be used. First interlayer insulating film 31
As 8, another inorganic insulating film may be used, or a resin (organic insulating film) may be used.

Next, as shown in FIG. 3E, a contact hole is formed in the first interlayer insulating film 318 to form a wiring 319.
To 322. In this embodiment, the wirings 319 to 322 are used.
A metal wiring having a three-layer structure of titanium / aluminum / titanium is used. Of course, any material may be used as long as it is a conductive film. The wirings 319 to 322 serve as a source wiring or a drain wiring of the TFT.

The drain wiring 3 of the current controlling TFT
Reference numeral 22 is electrically connected to the connection wiring 309. As a result, the drain of the current control TFT 402 and the current supply line 3
17 are electrically connected.

In this state, the switching TFT 401 and the current controlling TFT (EL driving TFT) 402 are completed. In this embodiment, both TFTs are p-channel type TFs.
It is formed of T. However, the switching TFT 401 has a structure in which a gate electrode is formed so as to cross an active layer at two places, and two channel forming regions are connected in series. With such a structure, an off-current value (a current flowing when the TFT is turned off) can be effectively suppressed.

Further, a storage capacitor 504 is formed in the pixel as shown in FIG. The storage capacitor 504 is formed by the semiconductor layer 505 electrically connected to the drain of the current control TFT 402, the gate insulating film 306, and the capacitor wiring 506. The capacitor wiring 506 is formed simultaneously with 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 a drain wiring (which may function as a source wiring) of the switching TFT 401.
20 is electrically connected.

After forming the wirings 319 to 322, 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 the hydrogenation treatment before or after the formation of the passivation film 323, the electrical characteristics of the TFT can be improved.

Next, as shown in FIG. 4A, acrylic is formed to a thickness of 1 μm as the second interlayer insulating film 324,
After opening the contact hole 325, the anisotropic conductive film 32
6 is formed. In this embodiment, acrylic in which silver particles are dispersed is used as the anisotropic conductive film 326. Further, it is preferable that the anisotropic conductive film 326 be formed with a sufficient thickness so that the contact hole 325 can be flattened.
In the present embodiment, it is formed by a spin coating method with a thickness of 1.5 μm.

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 327 is formed in a shape as shown in FIG.

After the formation of the conductor 327, an aluminum film to which scandium or titanium is added and an ITO film (a compound film of indium oxide and tin oxide) are laminated.
The pixel electrode 328 and the anode 329 are formed by batch etching. In this embodiment, the thickness of the aluminum film is 20
0 nm, and the thickness of the ITO film is 100 nm. The ITO film is made of ITO-04N (Kanto Chemical Co., Ltd.
The aluminum film can be etched by a dry etching method using a mixed gas of carbon tetrachloride (SiCl ₄ ) and chlorine (Cl ₂ ).

The cross-sectional structure of FIG. 4B obtained in this way corresponds to the cross-sectional structure taken along the line AA ′ in FIG.

Next, as shown in FIG. 4C, a bank 330 made of an insulating film is formed. In this embodiment, the bank 330 is formed using acrylic, but it is also possible to form the bank 330 using a silicon oxide film. After the bank 330 is formed, the anode 329 is irradiated with ultraviolet light in an oxygen atmosphere to perform a surface treatment on the anode 329. This has the effect of increasing the work function of the anode 329 and also has the effect of removing surface contamination.

Then, each of the organic EL layers 331 and 332 is formed to a thickness of 50 nm. Note that the organic EL layer 331 is an organic EL layer that emits blue light, and the organic EL layer 332 is an organic EL layer that emits red light. Although not shown, an organic EL layer which emits green light at the same time is also formed. In this embodiment, an organic EL layer 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 ink jet method.

In this embodiment, the organic EL layers 331, 3
32 is formed in a laminated structure, and specifically, CuPc (copper phthalocyanine) is used as a hole injection layer. In this case, first, a copper phthalocyanine film is entirely formed, and then a red light emitting layer, a green light emitting layer, and a blue light emitting layer are formed for each pixel corresponding to red, green, and blue.

When a green light emitting layer is formed, Alq ₃ (tris-8-quinolinolato aluminum complex) is used as a base material of the light emitting layer, and quinacridone or coumarin 6 is added as a dopant. When a red light emitting layer is formed, Alq _{3 is} used as a base material of the light emitting layer.
, And DCJT, DCM1 or DCM2 is added as a dopant. When forming a blue light-emitting layer, BAlq ₃ (2-methyl-
Perylene is added as a dopant using a 5-coordinate complex having a mixed ligand of 8-quinolinol and a phenol derivative.

Of course, in the present invention, it is not necessary to limit to the above-mentioned organic materials, and it is possible to use known low-molecular-weight organic EL materials, high-molecular-weight organic EL materials, or inorganic EL materials. When a polymer organic EL material is used, a coating method can be used.

As described above, the organic EL layers 331, 33
2 is formed, a cathode 333 having a thickness of 20 nm
gAg film (magnesium (Mg) with 1-10% silver (A
g) -added metal film), and the auxiliary electrode 33
As No. 4, an ITO film having a thickness of 150 nm is formed. Thus, an EL element 400 including the anode 329, the organic EL layer 332, and the cathode 333 is formed. In this embodiment, this E
The L element functions as a light emitting element.

Next, as shown in FIG. 4D, a spacer 336 made of a resin and an opposing passivation film 337 made of a tantalum oxide film or a diamond-like carbon film are formed on the opposing substrate 335, and a sealing material (not shown) is formed. The element forming substrate 301 and the opposing substrate 335 are bonded to each other by using. The opposing passivation film 337 has an effect of preventing outgassing from the spacer 336 made of resin. In this embodiment, an element formed substrate includes an element formed on the substrate. The term “opposite substrate” includes the spacer formed on the substrate and the opposing passivation film.

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 filled may be an inert gas, and a nitrogen gas or a rare gas may be used. In addition, space 33
8 is preferably provided with a substance that adsorbs oxygen or water. Further, instead of forming a space, it is also possible to fill with a resin.

By the manufacturing process described above, the switching TFT (the p-channel type TF in this embodiment) is provided in the pixel.
T) 401 and a current controlling TFT (p-channel TFT in this embodiment) 402 are formed. In this embodiment, since all the TFTs are p-channel TFTs, the manufacturing process is very simple. Of course, the switching TFT and / or
Alternatively, an n-channel TFT can be used as the current control TFT. A known technique may be used for manufacturing the n-channel TFT, and the structure is not particularly limited.

The level difference is flattened by the second interlayer insulating film 324, and the drain wiring 321 and the pixel electrode 328 of the current controlling TFT 402 are electrically connected to each other by using the conductor 327 embedded in the contact hole 325. , The flatness of the pixel electrode 328 is high. Therefore, the uniformity of the film thickness of the organic EL layer 332 can be improved, and the light emission of the pixel can be made uniform.

The most significant feature of the present invention is that light emission from the EL element 400 is emitted toward the counter substrate 335 side. Thus, almost the entire area of the pixel becomes an effective light emitting area, and the area of the pixel electrode 328 substantially determines the effective light emitting area. Therefore, it is possible to realize a high aperture ratio of 80 to 95%.

[Embodiment 2] In this embodiment, an EL light emitting device having a pixel 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 only by making some changes to the structure of FIG.
A description will be given focusing on the differences from FIG. Therefore, the description of the portions denoted by the same reference numerals as in FIG. 2 may be referred to “Embodiments of the Invention”.

In this embodiment, after a contact hole is formed in the interlayer insulating film 205, a pixel electrode 601a and an anode 601b are formed in that state, and an insulating film 602 is formed so as to fill a recess formed by the contact hole. In this embodiment, the insulating film 602 is called a buried insulating film. Since the buried insulating film 602 can be formed simultaneously with the bank 208, the number of steps is not particularly increased.

The buried insulating film 602 is for suppressing the deterioration of the organic EL layer caused by the concave portion due to the contact hole, similarly to the conductor 206 of FIG. At this time, the height between the top of the buried insulating film 602 and the anode 601b is preferably set to 100 to 300 nm.
If this height exceeds 300 nm, the step may cause deterioration of the organic EL layer. Also, 10
There is a possibility that the function of the bank 208 (the function of suppressing the influence of the electric field concentration at the edge of the pixel electrode) formed at the same time as the thickness becomes 0 nm or less may be reduced.

In this embodiment, after forming the anode 601a, acryl was coated to 500 nm by spin coating.
Oxygen gas is turned into plasma, and the thickness of acrylic (the thickness outside the contact hole) is 200 nm.
Etch until. After the film thickness is reduced in this way, patterning is performed to form the bank 208 and the buried insulating film 6.
02 is formed.

FIG. 7 shows the top structure of the pixel of this embodiment. 7 is a sectional view taken along line AA ′ in FIG.
Is equivalent to Note that the counter substrate 214 and the spacer 215 are not shown in FIG. In addition, since the basic pixel structure is the same as that of FIG. 5, detailed description will be omitted.

In FIG. 7, the bank 208 is a pixel electrode 6
The buried insulating film 602 is formed so that a part of the bank 208 protrudes. The protruding insulating film serves as the pixel electrode 6
The structure is such that a recess formed by the contact hole 01a is buried.

The EL light emitting device of this embodiment can be easily manufactured by combining the manufacturing method of Embodiment 1 with the method of forming the buried insulating film.

[Embodiment 3] Although only the structure of the pixel portion is shown in the EL light emitting device shown in Embodiment 1, a drive circuit for driving the pixel portion may be integrally formed on the same substrate. At that time, the driving circuit can be formed by an nMOS circuit, a pMOS circuit, or a CMOS circuit. Of course, only the pixel portion may be formed of TFTs, and a driving circuit including an IC chip may be used as an external driving circuit.

In the first embodiment, the pixel portion is formed only of the p-channel TFT to reduce the number of manufacturing steps. In this case, however, the driving circuit is formed by a pMOS circuit, and the driving circuit cannot be manufactured by the pMOS. A driving circuit including a chip can also be used.

The structure of this embodiment can be implemented by freely combining with the structure of the first or second embodiment.

Embodiment 4 In this embodiment, 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.
Here is an example of using. An inverted staggered TFT is known as a TFT using an amorphous silicon film, but such a TFT can be used in this embodiment.

Although a TFT using an amorphous silicon film has a simple manufacturing process, it has a disadvantage that the element size is increased.
The size of T does not affect the effective light emitting area of the pixel. Therefore, a less expensive EL light emitting device can be manufactured by using an amorphous silicon film as an active layer.

The structure of this embodiment can be implemented by freely combining with any of the structures of the first to third embodiments. However, when combined with the third embodiment,
Since it is difficult to manufacture a driver circuit with a high operation speed using a TFT using an amorphous silicon film, it is preferable to externally provide a driver circuit including an IC chip.

Fifth Embodiment In the first to fourth embodiments, the active matrix type EL light emitting device has been described.
It is also possible to carry out for the L element.

The passive matrix type EL light emitting device is formed so as to include a structure in which an organic EL layer is interposed between an anode and a cathode provided in a stripe shape so as to be orthogonal to each other. At this time, the structure shown in FIG. 1 may be used.

The structure of this embodiment can be implemented by freely combining with any of the structures of the first to third embodiments. However, when combined with the third embodiment, a driving circuit including an IC chip is externally provided.

[Embodiment 6] This embodiment shows an example in which the EL light emitting device of the present invention is used as a light source for a backlight used in a liquid crystal display or a fluorescent display lamp. In this case, it is not necessary to divide the EL element for each pixel, and the EL element embodying the present invention may be used as a light emitting element that emits light in a planar manner.

Further, light emission of different colors for each area may be obtained by dividing the area into a plurality of areas on the substrate surface. The production of the EL element is performed according to the organic E of Example 1.
What is necessary is just to refer to the manufacturing process of an L layer.

Since the EL element of this embodiment basically corresponds to the case where one pixel is enlarged in the first embodiment, refer to the first embodiment for measures such as covering the end of the anode with an insulating film. It is desirable to do this.

[Embodiment 7] A light emitting device formed by carrying out the present invention can be used as a display portion of various electric appliances. For example, to watch TV broadcasts, etc.
It is preferable to use a display in which the light-emitting device of the present invention having a size of 0 inches is incorporated in a housing. In addition, displays incorporating a light emitting device in a housing include a display for a personal computer and a TV.
All displays for displaying information such as a display for broadcast reception and a display for advertisement display are included.

Other electric appliances of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a music reproducing device (car audio, audio component, etc.), a notebook personal computer, Game devices, portable information terminals (mobile computers, mobile phones, portable game machines, electronic books, etc.), image reproducing devices (devices having a display unit for reproducing images recorded on a recording medium and displaying the images) Is mentioned. 8 and 9 show specific examples of these electric appliances.

FIG. 8A shows a display in which a light emitting device is incorporated in a housing.
A display unit 2003 and the like are included. The light emitting device of the present invention has a display unit 2
003. Since such a display is a self-luminous type, it does not require a backlight and can be a display portion thinner than a liquid crystal display.

FIG. 8B shows a video camera,
101, display unit 2102, voice input unit 2103, operation switch 2104, battery 2105, image receiving unit 2106
And so on. The light emitting device of the present invention can be used for the display portion 2102.

FIG. 8C shows a part (right side) of a head-mounted EL display, which includes a main body 2201, a signal cable 2202, a head fixing band 2203, and a display unit 22.
04, an optical system 2205, a light emitting device 2206, and the like. The present invention can be used for the light emitting device 2206.

FIG. 8D shows an image reproducing apparatus (specifically, a DVD reproducing apparatus) provided with a recording medium.
1, recording medium (DVD or the like) 2302, operation switch 23
03, a display unit (a) 2304, a display unit (b) 2305, and the like. 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 includes a home game machine and the like.

FIG. 8E shows a portable computer, which includes a main body 2401, a camera section 2402, an image receiving section 2403, operation switches 2404, a display section 2405, and the like. The light emitting device of the present invention can be used for the display portion 2405.

FIG. 8F shows a personal computer, which includes a main body 2501, a housing 2502, a display portion 2503, a keyboard 2504, and the like. The light-emitting device of the present invention can be used for the display portion 2503.

If the light emission luminance further increases in the future, it becomes possible to use the front light or rear light projector by enlarging and projecting the light containing the output image information with a lens or an optical fiber.

In the light emitting device, since the light emitting portion consumes power, it is desirable to display information so that the light emitting portion is reduced as much as possible. Therefore, when a light emitting device is used for a portable information terminal, particularly a display portion mainly for character information such as a mobile phone or a music reproducing device, the character information is driven by the light emitting portion with the non-light emitting portion as a background. It is desirable to do.

FIG. 9A shows a mobile phone, which includes a main body 2601, an audio output unit 2602, an audio input unit 2603,
Display unit 2604, operation switch 2605, antenna 26
06. The light emitting device of the present invention can be used for the display portion 2604. Note that the display portion 2604 can display power of the mobile phone by displaying white characters on a black background.

FIG. 9B shows a music reproducing apparatus, specifically, a car audio system.
02, including operation switches 2703 and 2704. The light-emitting device of the present invention can be used for the display portion 2702. In this embodiment, an in-vehicle car audio device is shown, but the present invention may be applied to a portable or home music playback device. Note that the display portion 2704 can suppress power consumption by displaying white characters on a black background. This is particularly effective in a portable music player.

Further, the light emitting device of the present invention can be used as a backlight light source of a liquid crystal display device (liquid crystal module). The liquid crystal display device can be used as a display unit in all of the above-described electric appliances, similarly to the light emitting device of the present invention. The light emitting device of the present invention is provided in an electric appliance together with a liquid crystal display device.

As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electric appliances in various fields. Further, the electric appliance of the present embodiment may use the light emitting device having any configuration shown in the first to sixth embodiments.

[0096]

According to the present invention, in an EL device including an anode, a cathode and an EL layer, the cathode is made transparent to visible light,
Further, by providing a reflective electrode under the EL element, light can be extracted to the cathode side. As a result, the effective light emitting area of the pixel is significantly improved, and bright light emission can be obtained without increasing the driving voltage of the EL element.

Then, since the drive voltage is lowered, E
It is possible to suppress deterioration of the L layer and reduce power consumption of the light emitting device. That is, a bright and highly reliable light-emitting device can be provided. Further, the reliability of an electric appliance using the light emitting device of the present invention as a display portion or a light source can be improved.

[Brief description of the drawings]

FIG. 1 illustrates a cross-sectional structure of an EL element.

FIG. 2 illustrates a cross-sectional structure of a light-emitting device.

FIG. 3 illustrates a manufacturing process of a light-emitting device.

FIG. 4 illustrates 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 illustrates a cross-sectional structure of a light-emitting device.

FIG. 7 illustrates a top structure of a light-emitting device.

FIG. 8 illustrates an example of an electric appliance.

FIG. 9 illustrates an example of an electric appliance.

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Claims (15)

[Claims] 1. A light emitting device comprising an anode, a cathode, an EL layer between the anode and the cathode, and a reflective electrode in contact with the anode. 2. A light emitting device comprising an anode on a reflective electrode, an EL layer on the anode, and a cathode on the EL layer. 3. The light emitting device according to claim 1, wherein the anode and the cathode are transparent to visible light. 4. A light emitting device comprising an anode, a cathode, an EL layer between the anode and the cathode, a reflective electrode in contact with the anode, and an auxiliary electrode in contact with the cathode. 5. An anode on a reflective electrode, and an EL on the anode.
A light-emitting device comprising: a layer, a cathode on the EL layer, and an auxiliary electrode on the cathode. 6. The light emitting device according to claim 4, wherein the anode, the cathode, and the auxiliary electrode are transparent to visible light. 7. The light emitting device according to claim 4, wherein said auxiliary electrode is an oxide conductive film. 8. The light emitting device according to claim 1, wherein the anode is an oxide conductive film, and the cathode is a metal film transparent to visible light. 9. A light emitting device according to claim 1, wherein a semiconductor element is electrically connected to said reflection electrode. 10. An electric appliance using the light emitting device according to claim 1 as a display unit or a light source. 11. A method for forming a reflective electrode, forming an anode on the reflective electrode, forming an EL layer on the anode, and forming a cathode on the EL layer. Method for manufacturing a light emitting device. 12. A light emitting device according to claim 11, wherein said anode is formed of an oxide conductive film transparent to visible light, and said cathode is formed of a metal film transparent to visible light. Method of manufacturing. 13. A reflective electrode is formed, an anode is formed on the reflective electrode, an EL layer is formed on the anode, a cathode is formed on the EL layer, and an auxiliary is formed on the cathode. A method for manufacturing a light-emitting device, including a method for forming an electrode. 14. The method according to claim 13, wherein said anode and said auxiliary electrode are formed of an oxide conductive film transparent to visible light, and said cathode is formed of a metal film transparent to visible light. Method for manufacturing a light emitting device. 15. The method for manufacturing a light-emitting device according to claim 11, wherein the reflective electrode is formed by electrically connecting the reflective electrode to a TFT.