JP2002151269A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align light-emitting intensity of EL elements of different emission colors and enhance emission intensity of the EL elements in a pixel part of a light-emitting device. SOLUTION: Emission intensity of EL elements formed in plural can be aligned by combining EL elements having EL layers including triplet compounds and EL elements having EL layers including singlet compounds at a pixel part. Further, EL elements of higher emission intensity can be formed by making hole transport layers in lamination structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus (hereinafter, referred to as a light emitting device) having an element (hereinafter, referred to as a light emitting element) having a light emitting material interposed between electrodes. In particular, the present invention relates to a light-emitting device having a light-emitting element using an organic compound capable of obtaining EL (Electro Luminescence) as a light-emitting material (hereinafter, referred to as an EL element).

[0002]

2. Description of the Related Art In recent years, research on EL elements having a structure in which a thin film (EL layer) made of an organic compound capable of obtaining EL is sandwiched between an anode and a cathode has been advanced, and a light emitting device utilizing the light emitting characteristics of the EL elements has been developed. Is being developed.

The EL layer usually has a laminated structure. Typically, the EL layer has a laminated structure of “hole transport layer / light emitting layer / electron transport layer” proposed by Tang et al. Of Kodak Eastman Company. Is mentioned. This structure has a very high luminous efficiency, and almost all EL displays currently under research and development adopt this structure.

In addition, a hole injection layer / hole transport layer / light-emitting layer / electron transport layer, or a hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer is provided on the anode. A structure in which layers are sequentially stacked may be used. The light emitting layer may be doped with a fluorescent dye or the like.

In this specification, all layers provided between a cathode and an anode are collectively called an EL layer. Therefore, the above-described hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and the like are all included in the EL layer.

[0006] When a predetermined voltage is applied to the EL layer having the above structure from a pair of electrodes, recombination of carriers occurs in the light emitting layer, and light emission is obtained. In this specification, a light-emitting element formed of an anode, an EL layer, and a cathode is referred to as an EL element.
It is called an element.

In an EL device, when the driving voltage is increased, the deterioration of the EL layer is promoted. Therefore, an organic compound which emits light by a singlet exciton (singlet), which is a usual light emitting material (hereinafter, referred to as a singlet compound). In addition, an organic compound that emits light by a triplet exciton (triplet) that provides high emission luminance at a low drive voltage (hereinafter, referred to as an organic compound)
Known as triplet compounds).

[0008] In this specification, a singlet compound refers to a compound that emits light only through singlet excitation, and a triplet compound refers to a compound that emits light via triplet excitation.

[0009]

The light emission luminance of an EL element is controlled by a voltage applied to the EL layer.
Light emission luminance with respect to voltage is different. That is, when a light-emitting material with low light emission luminance is used, it is necessary to apply a high voltage to obtain higher luminance. However, when a high voltage is applied, there is a problem that the light emitting material is deteriorated. Further, in the case where EL elements formed on the same substrate show different light emission luminance for each voltage, different voltages are applied to make the luminance uniform, which results in a difference in the life of the EL element. Problems arise.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and forms an EL device having a long life and a desired emission luminance at a low voltage.

According to the present invention, among the plurality of EL elements formed in the pixel portion on the same substrate, not only an EL element having an EL layer containing a light-emitting material (singlet compound) having low light emission luminance but also a high voltage at a low voltage. By successfully combining and using an EL element having an EL layer containing a triplet compound capable of obtaining emission luminance, it is possible not only to reduce the power consumption of the EL element but also to control and align the emission luminance of a plurality of EL elements. I do.

FIG. 1A shows a circuit configuration of a pixel portion which can be used in the present invention. 101 is a gate line, 102a to 102c are source lines, 103a to 1
03c is a current supply line. Then, three pixels a (104a) and three pixels b (1
04b) and the pixel c (104c) are formed.

Reference numeral 105 denotes a switching transistor, which is formed in each of three pixels. In addition,
Although a structure having two channel formation regions between the source region and the drain region is illustrated here, two or more or one channel formation region may be provided.

Reference numeral 106 denotes a current control transistor. In each pixel, the gate is connected to the switching transistor, the source is connected to the current supply line, and the drain is connected to the EL element. Reference numeral 107 denotes a capacitor which holds a voltage applied to the gate of the current control transistor 106. However, the capacitor 107 can be omitted.

The pixel a (104a) and the pixel b (10
4b) and the pixel c (104c) are connected to the EL element a (108).
a), EL element b (108b) and EL element c (108
c).

These EL elements have an element structure as shown in FIG. EL element 111
The EL layer 114 is formed by the cathode 112, the anode 113, and the EL layer 114. When a voltage is applied to the cathode 112 or the anode 113, the EL layer 114 emits light.

The EL layer 114 is composed of a plurality of layers. The EL layer 114 is made of a luminescent material, and is sandwiched between the cathode 112 and the luminescent layer 115 to improve the injection property of electrons from the cathode. The injected electrons are emitted from the light emitting layer 115.
An electron transport layer 117 having a role of transporting the electrons is formed.

A hole injection layer 118 sandwiched between the anode 113 and the light emitting layer 115 to improve the injection property of holes (holes) from the anode.
The hole transport layer 119 having a role of transporting the H.15 to the H.15 is formed.

In general, light is obtained by recombination of electrons injected from the cathode 112 and holes injected from the anode 113 in the light-emitting layer 115. In this structure, a hole transport layer is provided. That is, layers other than the cathode 112, the anode 113, the light emitting layer 115, and the hole transport layer may be provided as needed.

In the present invention, the EL shown in FIG.
Of the layers 114, an EL element using a triplet compound for the light-emitting layer 115 or an E element using a singlet compound
An L element is formed. Then, pixels a to a shown in FIG.
By forming these EL elements in combination with the pixel c (104a to 104c), the emission luminance of a plurality of EL elements can be uniformed, and deterioration of only specific EL elements can be prevented.

For example, when a three-color pixel display is performed, the luminous luminance of the luminescent material of the color displaying the pixel a (104a) is changed to the pixel b (104b) or the pixel c (10) displaying the other two colors.
4c), the EL element a (108
a) using a triplet compound for the light-emitting layer,
A singlet compound is used for the light emitting layer of the L element.

In the case where the light emission luminance of the color for displaying two types of pixels a (104a) and b (104b) is lower than the light emission luminance of the color for displaying one type of pixel c (104c). Are two types of EL elements a (108a) and E
A triplet compound is used for the light emitting layer of the L element b (108b), and a singlet compound is used for the light emitting layer of the EL element c (108c).

In addition, all of the three types of pixels a (104a), b (104b), and c (104c) have low luminous luminance, and if it is desired to obtain high luminous luminance at a lower voltage, three types of pixels are used. EL element a (108a), EL element b
A triplet compound may be used for all the light emitting layers of (108b) and the EL element c (108c).

As the triplet compound, organic compounds described in the following articles can be mentioned as typical materials. (1) T.Tsutsui, C.Adachi, S.Saito, Photochemical
Processes in Organized Molecular Systems, ed.K. Hon
da, (Elsevier Sci. Pub., Tokyo, 1991) p. 437. (2) MABaldo, DFO'Brien, Y. You, A. Shoustikov,
S. Sibley, METhompson, SRForrest, Nature 395
(1998) p.151. (3) MABaldo, S.Lamansky, PEBurrrows, METho
mpson, SRForrest, Appl. Phys. Lett., 75 (1999) p. 4. (4) T. Tsutsui, MJYang, M. Yahiro, K. Nakamura,
T.Watanabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Mayagu
chi, Jpn.Appl.Phys., 38 (12B) (1999) L1502.

It is considered that not only the luminescent material described in the above paper but also a luminescent material represented by the following molecular formula (specifically, a metal complex or an organic compound) can be used.

[0026]

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[0027]

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In the above chemical formula, M is 8 to 1 in the periodic table.
It is an element belonging to Group 0, and n is 2 or 3. In the above paper, platinum and iridium are used. Further, nickel, cobalt or palladium is preferable because of its similar physical properties to platinum and iridium. In particular, nickel is preferable as the central metal because it easily forms a complex.

Besides, europium, terbium,
A rare-earth complex in which a rare-earth element ion such as cerium forms a ligand can also be used as a triplet compound.

Since the triplet compound has a higher luminous efficiency than the singlet compound, the operating voltage (the voltage required to cause the EL element to emit light) can be reduced to obtain the same emission luminance.

Further, in the present invention, as shown in FIG. 2, by providing a plurality of hole transport layers between the anode and the light emitting layer 125, the mobility of carriers (electrons and holes) injected from the anode can be improved. Can be increased. Note that, in this specification, only the case where the hole transport layer is stacked is shown, but the electron transport layer is also provided with an energy level between the cathode and the electron transport layer (similar to the hole transport layer). The present invention can be practiced by using a compound that reduces the difference in the LUMO level).

FIG. 2A shows the same EL as in FIG. 1B.
1 shows the structure of an element. A light emitting layer 125 is provided between the cathode 123 and the anode 124.
An electron injection layer 126 and an electron transport layer 127 are provided between the anode and the light emitting layer 125.
8 and the hole transport layer 1 (129).

On the other hand, FIG. 2B shows that the hole transport layer 2 is located between the hole transport layer 1 (129) and the hole injection layer 128.
The layered structure has another layer of (130).

These laminated structures can be shown by the band structure in FIG. Here, FIG.
The same reference numerals as those used in FIG. 2A and FIG. 2B are used. That is, the hole transport layer 1 (129) and the hole injection layer 12
8 and the hole transport layer 2 (130) is formed between the hole injection layer and the hole transport layer.
The difference between MO levels can be reduced. This facilitates the movement of holes between the hole injection layer and the hole transport layer, and as a result, achieves high luminance of the EL element at a low voltage.

Here, as an example, the hole transport layer 1
(129) and the hole transport layer 2 (130) are shown as being formed in a laminated structure. These laminated structures are formed between the hole injection layer and the hole transport layer as described above. The hole transport layer may be formed of two or more different materials as long as the difference in the HOMO levels can be reduced, but it is preferable that the hole transport layer has a laminated structure of two to five layers.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the following examples.

[0037]

[Embodiment 1] In this embodiment, a method of manufacturing a pixel portion and a driving circuit provided around the pixel portion on the same insulator will be described. However, for simplicity,
Regarding the driver circuit, a CMOS circuit combining an n-channel transistor and a p-channel transistor is illustrated.

First, as shown in FIG. 3A, a glass substrate 201 is prepared as an insulator. In this embodiment, a protective film (carbon film, specifically, a diamond-like carbon film) (not shown) is provided on both surfaces (front and back surfaces) of the glass substrate 201. Further, a material other than glass (eg, plastic) may be used as long as it transmits visible light.

Next, a base film 202 is formed on the glass substrate 201 to a thickness of 300 nm. In this embodiment, the base film 20 is used.
2 is used by stacking silicon nitride oxide films. At this time, the nitrogen concentration of the layer in contact with the glass substrate 201 is 10 to 25 wt.
%, And it is better to contain nitrogen more than other layers.

Next, an amorphous silicon film (not shown) having a thickness of 50 nm is formed on the base film 202 by a sputtering method. Note that the present invention is not limited to an amorphous silicon film, and may be any semiconductor film including an amorphous structure (including a microcrystalline semiconductor film).
As the amorphous semiconductor film, an amorphous silicon film or an amorphous silicon germanium film (germanium is 1 × 10 ¹⁸ to 1
(A silicon film containing a concentration of × 10 ²¹ atoms / cm ³ ). The thickness may be 20 to 100 nm.

Then, the amorphous silicon film is crystallized by using a known laser crystallization method, and a crystalline silicon film 203 is formed. In this embodiment, a solid-state laser (specifically, the second harmonic of a Nd: YAG laser) is used, but an excimer laser may be used. Further, a furnace annealing method may be used as a crystallization method.

Next, as shown in FIG. 3B, the crystalline silicon film 203 is etched by a first photolithography step to form island-like crystalline silicon films 204 to 207. These are crystalline silicon films which will later become the active layers of the transistors.

Although a crystalline silicon film is used as an active layer of a transistor in this embodiment, an amorphous silicon film can be used as an active layer.

Here, in this embodiment, a protective film (not shown) made of a silicon oxide film is formed on the island-like crystalline silicon films 204 to 207 to a thickness of 130 nm by sputtering, and the semiconductor is made of p-type. An impurity element to be a semiconductor (hereinafter, referred to as a p-type impurity element) is added to the island-shaped crystalline silicon films 204 to 207. As the p-type impurity element, an element belonging to Group 13 of the periodic table (typically, boron or gallium) can be used. Note that this protective film is provided to prevent the crystalline silicon film from being directly exposed to plasma when adding an impurity and to enable fine concentration control.

The concentration of the p-type impurity element added at this time is 1 × 10 ^{15 to} 5 × 10 ¹⁷ atoms / cm ³ (typically, 1 × 10 ¹⁶ to 1 × 10 ¹⁷ atoms / cm ³ ). It is good. The p-type impurity element added at this concentration is used for adjusting the threshold voltage of the n-channel transistor.

Next, island-shaped crystalline silicon films 204 to 207 are formed.
Wash the surface. First, the surface is cleaned using pure water containing ozone. At this time, since a thin oxide film is formed on the surface, the thin oxide film is further removed using a hydrofluoric acid aqueous solution diluted to 1%. By this treatment, contaminants attached to the surfaces of the island-shaped crystalline silicon films 204 to 207 can be removed.
At this time, the concentration of ozone is preferably 6 mg / L or more. These series of processes are performed without opening to the atmosphere.

The island-shaped crystalline silicon films 204 to 20
7, a gate insulating film 208 is formed. As the gate insulating film 208, 10 to 150 nm, preferably 50 to 150 nm
An insulating film containing silicon having a thickness of about 100 nm may be used. This may have a single-layer structure or a laminated structure. In this embodiment, a silicon nitride oxide film having a thickness of 80 nm is used.

In this embodiment, the island-shaped crystalline silicon film 204 is used.
Steps 207 to 207 are performed without opening to the atmosphere to form a gate insulating film 208 to reduce contaminants and interface states at the interface between the semiconductor film and the gate insulating film. In this case, a multi-chamber (or in-line) apparatus having at least a cleaning chamber and a sputtering chamber may be used.

Next, the first conductive film 209 is formed to a thickness of 30 nm.
A thick tantalum nitride film is formed, and a second conductive film 21 is formed.
A tungsten film of 370 nm is formed as 0. Alternatively, a combination using a tungsten film as the first conductive film and an aluminum alloy film as the second conductive film, or a combination using a titanium film as the first conductive film and a tungsten film as the second conductive film may be used. good.

These metal films may be formed by a sputtering method. When an inert gas such as Xe or Ne is added as a sputtering gas, the film can be prevented from peeling due to stress. Further, the purity of the tungsten target is set to 99.
By setting the content to 9999%, a low-resistance tungsten film having a resistivity of 20 mΩcm or less can be formed.

Further, the steps from the surface cleaning of the semiconductors 204 to 207 to the formation of the second conductive film 210 can be performed without opening to the atmosphere. In this case, a multi-chamber (or in-line) apparatus having at least a cleaning chamber, a sputtering chamber for forming an insulating film, and a sputtering chamber for forming a conductive film may be used.

Next, resists 211a to 211e are formed, and the second conductive film 210 is etched. This etching condition is preferably performed by dry etching using ICP (Inductively Coupled Plasma). As an etching gas, a mixed gas of carbon tetrafluoride (CF ₄ ) gas, chlorine (Cl ₂ ) gas, and oxygen (O ₂ ) is used.

As typical etching conditions, the gas pressure is set to 1 Pa, and in this state, 500 W is applied to the coil type electrode.
Is applied to generate RF power (13.56 MHz). In addition, the stage on which the substrate is mounted has a self-bias voltage of 150 W RF power (13.56 MHz).
To apply a negative self-bias to the substrate. At this time, the flow rate of each gas was set to 2.5 × 10 ⁻⁵ m ³ / min for carbon tetrafluoride gas and 2.5 × 10 ⁻⁵ m ³ / min for chlorine gas.
^-5 m ³ / min and oxygen gas at 1.0 × 10 ⁻⁵ m ³ / min (FIG. 3C).

As a result, the second conductive film (tungsten film) 210 is selectively etched, and electrodes 212 to 216 made of the second conductive film are formed. The reason that the second conductive film 210 is selectively etched is that the progress of the etching of the first conductive film (tantalum nitride film) is extremely slowed by adding oxygen to the etching gas.

Here, there is a reason why the first conductive film 209 is left. At this time, it is possible to etch the first conductive film at the same time, but if the first conductive film is etched, the gate insulating film 208 is also etched in the same step to reduce the film thickness. At this time, if the thickness of the gate insulating film 208 is 100 nm or more, there is no problem. However, if the thickness is less than that, a part of the gate insulating film 208 is removed during a subsequent process, and the semiconductor film thereunder is exposed. This is because a semiconductor film serving as a source region or a drain region of the transistor may be removed.

However, the problem described above can be solved by leaving the first conductive film 209 as in this embodiment.

Next, an n-type impurity element (phosphorus in this embodiment) is added in a self-aligned manner using the resists 211a to 211e and the electrodes 212 to 216 as a mask. At this time, phosphorus is added through the first conductive film 209. In the impurity regions 217 to 225 thus formed, an n-type impurity element is contained in an amount of 1 × 10 ²⁰ to 1 × 10 ²¹ atoms / cm ³ (typically,
× 10 ^{20 to} 5 × 10 ²¹ atoms / cm ³ ).

Next, the first conductive film 209 is etched using the resists 211a to 211e as a mask. This etching is performed by a dry etching method using ICP, and carbon tetrafluoride (C
A mixed gas of F ₄ ) gas and chlorine (Cl ₂ ) gas is used.
Typical etching conditions are as follows: gas pressure is 1 Pa, and in this state, 500 W of RF power (13.
56 MHz) to generate plasma. In addition, the stage on which the substrate is mounted has a self-bias voltage of 20 W
RF power (13.56 MHz) to apply a negative self-bias to the substrate. At this time, the flow rate of each gas was set to 3.0 × 10 ⁻⁵ m ³ / carbon tetrafluoride gas.
min, and chlorine gas is preferably 3.0 × 10 ⁻⁵ m ³ / min. Thus, the electrodes 226 to 2 made of the first conductive film
30 are formed (FIG. 3D).

Next, as shown in FIG. 3E, the electrodes 212 to 216 made of the second conductive film are selectively etched using the resists 211a to 211g as they are. This etching is performed by a dry etching method using ICP, and a mixed gas of carbon tetrafluoride (CF ₄ ) gas, chlorine (Cl ₂ ) gas, and oxygen (O ₂ ) is used as an etching gas. Under typical etching conditions, a gas pressure is set to 1 Pa, and in this state, RF power (13.56 MHz) of 500 W is applied to the coil-type electrode to generate plasma.
Also, 20 W of RF power (13.56 MHz) was applied as a self-bias voltage to the stage on which the substrate was placed,
A negative self-bias is applied to the substrate. At this time, the flow rate of each gas was set to 2.5 × 1
0 ^-5 m ³ / min, chlorine gas 2.5 × 10 ^-5 m ³ / mi
n and oxygen gas are preferably 1.0 × 10 ⁻⁵ m ³ / min. Due to the presence of this oxygen, the etching rate of the tantalum nitride film is suppressed. Thus, the second gate electrode 231
To 235 are formed.

Next, an n-type impurity element (phosphorus in this embodiment) is added. In this step, the second gate electrode 231
To 235 function as a mask, phosphorus is added through part of the electrodes 226 to 230 formed of the first conductive film,
N-type impurity regions 236 to 245 containing phosphorus at a concentration of 2 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ (typically, 5 × 10 ^{17 to} 5 × 10 ¹⁸ atoms / cm ³ ) are formed.

The addition conditions here are such that the accelerating voltage is 70 to 120 kV (90 kV in this embodiment) so that phosphorus reaches the island-shaped crystalline silicon film through the first conductive film and the gate insulating film. ) And higher.

Next, as shown in FIG. 4A, the electrodes 226 to 230 made of the first conductive film are etched to form a first conductive film.
Gate electrodes 246 to 250 are formed. This etching is performed by dry etching using ICP or RI
The etching is performed by a dry etching method in an E (Reactive Ion Etching) mode, and a mixed gas of carbon tetrafluoride (CF ₄ ) gas and chlorine (Cl ₂ ) gas is used as an etching gas. Under typical etching conditions, a gas pressure is set to 1 Pa, and in this state, RF power (13.56 MHz) of 500 W is applied to the coil-type electrode to generate plasma.
Also, 20 W of RF power (13.56 MHz) was applied as a self-bias voltage to the stage on which the substrate was placed,
A negative self-bias is applied to the substrate. At this time, the flow rate of each gas was set to 2.5 × 1
0 ^-5 m ³ / min, chlorine gas 2.5 × 10 ^-5 m ³ / mi
n and oxygen gas are preferably 1.0 × 10 ⁻⁵ m ³ / min.

At this time, the first gate electrodes 246 to 25
0 is etched so as to partially overlap the n-type impurity regions (b) 236 to 245 via the gate insulating film 208.
For example, the n-type impurity region (b) 236 is divided into a region 236a not overlapping the first gate electrode 246 and an overlapping region 236b via the gate insulating film 208, and the n-type impurity region (b) 237 It is divided into a region 237a which does not overlap with the first gate electrode 246 and a region 237b which overlaps with the first gate electrode 246 through the film 208.

Next, resists 251a and 251b are formed, and an impurity element which makes a semiconductor a p-type semiconductor (hereinafter, referred to as a p-type impurity element) is added. An element belonging to Group 13 of the periodic table (typically, boron) may be added as the p-type impurity element. Here, the first gate electrode 2 is made of boron.
The acceleration voltage is set so as to reach the semiconductor film through the gate insulating film 208 and the gate insulating film 208. Thus, p-type impurity regions 252 to 255 are formed.
(B)).

Next, as shown in FIG. 4C, a silicon nitride film or a silicon nitride oxide film having a thickness of 30 to 100 nm is formed as the first inorganic insulating film 256. Thereafter, the added n-type and p-type impurity elements are activated. As an activating means, furnace annealing, laser annealing, lamp annealing or a combination thereof can be used.

Next, as shown in FIG. 4D, a second inorganic insulating film 2 made of a silicon nitride film or a silicon nitride oxide film is formed.
57 are formed to a thickness of 50 to 200 nm. After the formation of the second inorganic insulating film 257, heat treatment is performed in a temperature range of 350 to 450 ° C. The second inorganic insulating film 25
It is effective to perform a plasma treatment using hydrogen (H ₂ ) gas or ammonia (NH ₃ ) gas before forming 7.

Next, a resin film transmitting visible light is formed as the organic insulating film 258 to a thickness of 1 to 2 μm. As the resin film, a polyimide film, a polyamide film, an acrylic resin film, or a BCB (benzocyclobutene) film may be used. It is also possible to use a photosensitive resin film.

In this embodiment, the first inorganic insulating film 25
6, the laminated film of the second inorganic insulating film 257 and the organic insulating film 258 is generically called an interlayer insulating film.

Next, as shown in FIG. 5A, a pixel electrode (anode) 259 made of an oxide conductive film having a large work function and transparent to visible light is formed on the organic insulating film 258.
It is formed to a thickness of about 120 nm. In this embodiment, an oxide conductive film in which gallium oxide is added to zinc oxide is formed.
Further, as another oxide conductive film, an oxide conductive film made of indium oxide, zinc oxide, tin oxide, or a compound thereof can be used.

Note that, after forming the oxide conductive film, patterning is performed to form the pixel electrode 259. Before the patterning, the surface of the oxide conductive film may be flattened. The flattening process may be a plasma process or a CM process.
P (chemical mechanical polishing) processing may be used.

Next, contact holes are formed in the interlayer insulating film, and wirings 260 to 266 are formed. At this time, the wiring 266 is formed so as to be connected to the pixel electrode 259. In this embodiment, the wiring is a three-layer laminated film in which a 150-nm titanium film, a 300-nm aluminum film containing titanium, and a 100-nm titanium film are continuously formed by sputtering from the lower layer side.

At this time, the wirings 260 and 262 are CMOS
The source wiring 261 of the circuit functions as a drain wiring. The wiring 263 is a source wiring of the switching transistor, and the wiring 264 is a drain wiring of the switching transistor. Reference numeral 265 denotes a source wiring of the current control transistor (corresponding to a current supply line), and 266 denotes a drain wiring of the current control transistor.
59.

Next, as shown in FIG.
7 is formed. The bank 267 may be formed by patterning an insulating film or an organic resin film containing 100 to 400 nm of silicon. The bank 267 is formed so as to fill between pixels (between pixel electrodes). Another object is to prevent an organic EL film such as a light emitting layer to be formed next from directly touching the edge of the pixel electrode 259.

Since the bank 267 is an insulating film,
Attention must be paid to electrostatic breakdown of the element during film formation.
When carbon particles or metal particles are added to the insulating film serving as the material of the bank 267 to reduce the resistivity, generation of static electricity during film formation can be suppressed. In that case, bank 267
Resistivity 1 × of the material insulating film 10 ⁶ ~1 × 10 ^{1 2}
The added amount of carbon particles or metal particles may be adjusted so as to be Ωm (preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ Ωm).

Further, when carbon particles or metal particles are added to the bank 267, the light absorbency increases and the transmittance decreases. That is, since light from the outside of the light emitting device is absorbed, E
It is possible to avoid such a problem that an external scene is reflected on the cathode surface of the L element.

Next, an EL layer 268 is formed by an evaporation method. In this embodiment, a stacked body of the hole injection layer and the light emitting layer is called an EL layer. That is, a laminate in which a hole-injecting layer, a hole-transporting layer, a hole-blocking layer (or a hole-blocking layer), an electron-transporting layer, or an electron-injecting layer is combined with a light-emitting layer is described in this specification. Then, among these, a laminate including at least a light emitting layer and a hole transport layer is referred to as an EL layer.

Here, a method for forming a layer that emits green light by using a triplet compound for the light emitting layer as the EL layer will be described.

In this embodiment, first, a copper phthalocyanine (CuPc) film is formed to a thickness of 20 nm as a hole injection layer. Next, as a hole transport layer, MTDATA of an aromatic amine called a starburst amine is 20 nm, and α-NPD, which is also an aromatic amine compound, is 10 nm.
To a thickness of That is, the present embodiment describes a case where the hole transport layer is formed of two layers, MTDATA and α-NPD.

The material for forming the hole transport layer is roughly classified into a hole transporting low molecular weight compound and a hole transporting high molecular weight compound. can do. Specifically, compounds such as TPAC, PDA and TPD can be used as the hole transporting low molecular weight compound. As the hole transporting polymer compound, polyvinyl carbazole (PVK) or T
Various polymer compounds in which PD is incorporated in the main chain or side chain of the polymer can be used.

The hole transporting layer can be formed by laminating a plurality of materials. The total thickness of the hole transporting layer is preferably about 20 to 100 nm. It is necessary to reduce the film thickness per layer. Therefore, the number of layers is preferably about 2 to 4 layers.

Further, CBP and Ir (pp
y) ₃ is deposited to a thickness of 20 nm by co-evaporation. After forming the light emitting layer, BC was used as a hole blocking layer.
P is formed to a thickness of 10 nm, and an aluminum quinolylato complex (Alq ₃ ) is formed to a thickness of 40 nm as an electron transport layer.

Although the case where the EL layer which emits green light is formed has been described above, the green light-emitting material may be aluminum quinolylato complex (Alq ₃ ), which has been previously mentioned as a material for forming the electron transport layer. Benzoquinolinolatoberylium complex (BeBq) can also be used. Furthermore, an aluminum quinolylato complex (Alq ₃ ) using a material such as coumarin 6 or quinacridone as a dopant can also be used as a light emitting material.

Further, when an EL layer that emits red light is formed, the Eu complex (Eu (DCM) ₃ (Phen)
In addition to aluminum quinolylato complex (Alq ₃ ), DCM-1
Can be used as a light-emitting material.

In the case of forming an EL layer that emits blue light, in addition to the distyryl derivative DPVBi,
Zinc complex having azomethine compound as ligand and DPVB
A light-emitting material in which i is doped with perylene can be used.

In the practice of the present invention, for example, when forming red, blue and green EL layers, the above-mentioned light emitting materials can be used. Further, as a light emitting material, a singlet compound and a triplet compound can be freely combined and used as needed. The material introduced in the section of the invention can be used for the triplet compound.

However, since the formation of the red, blue and green EL layers is one of the embodiments, the present invention is not limited to this. It is also possible to form a combination of a plurality of other colors. .

After forming the EL layer 268, a cathode 269 made of a conductive film having a small work function is formed to a thickness of 300 nm. As the conductive film having a small work function, a conductive film containing an element belonging to Group 1 or 2 of the long-periodic periodic table or a transition element belonging to Group 3 to 11 may be used. In this embodiment, a conductive film made of ytterbium (Yb) is used. Alternatively, a conductive film made of a compound of lithium and aluminum can be used. Thus, the EL including the pixel electrode (anode) 259, the EL layer 268, and the cathode 269
An element 270 is formed.

After forming the cathode 269, the passivation film 27 is completely covered with the EL element 270.
It is effective to provide 1. Passivation film 27
1 is made of an insulating film including a carbon film, a silicon nitride film, or a silicon nitride oxide film, and the insulating film is used as a single layer or a stacked layer in combination.

At this time, a film having good coverage is preferably used as a passivation film, and a carbon film, particularly, a D film is preferably used.
It is effective to use an LC (diamond-like carbon) film. Since the DLC film can be formed in a temperature range from room temperature to 100 ° C. or less, it can be easily formed above the EL layer 268 having low heat resistance. Further, the DLC film has a high blocking effect against oxygen, and the EL layer 268
Can be suppressed. Therefore, the problem that the EL layer 268 is oxidized during the subsequent sealing step can be prevented.

Further, a seal member (not shown) is provided on the substrate 201 (or the base film 202) so as to surround at least the pixel portion, and a cover member 272 is attached. As a sealant, an ultraviolet curable resin which is less degassed and hardly permeates water or oxygen may be used. The space 273 may be filled with an inert gas (nitrogen gas or rare gas), a resin (ultraviolet curable resin or epoxy resin), or an inert gas.

It is effective to provide a material having a moisture absorbing effect or a material having an antioxidant effect in the space 273. The cover material 272 is a glass substrate, a metal substrate (preferably a stainless steel substrate), a ceramic substrate or a plastic substrate (including a plastic film).
May be used. When a plastic substrate is used, it is preferable to provide a carbon film (preferably a diamond-like carbon film) on the front and back surfaces to prevent oxygen and water from permeating.

Thus, a light emitting device having a structure as shown in FIG. 5B is completed. After forming the bank 267,
It is effective to continuously process the steps up to the formation of the passivation film 271 without exposing to the atmosphere using a multi-chamber (or in-line) film forming apparatus. Further, by further developing, it is also possible to continuously perform processing up to the step of bonding the cover material 272 without releasing it to the atmosphere.

Thus, the n-channel transistor 601, the p-channel transistor 602,
A switching transistor (transistor functioning as a switching element for transmitting a video data signal into a pixel) 603 and a current control transistor (transistor functioning as a current control element for controlling a current flowing through the EL element) 604 are formed.

At this time, the driving circuit includes a CMOS circuit in which an n-channel transistor 601 and a p-channel transistor 602 are complementarily combined as a basic circuit.
The pixel portion is formed by a plurality of pixels including a switching transistor 603 and a current control transistor 604.

The photolithography process required in the above manufacturing process is seven times, which is smaller than that of a general active matrix type light emitting device. That is, the manufacturing process of the transistor is greatly simplified, and an improvement in yield and a reduction in manufacturing cost can be realized.

Further, as described with reference to FIG. 4A, by providing an impurity region overlapping the first gate electrode with a gate insulating film interposed therebetween, an n-channel transistor resistant to deterioration due to the hot carrier effect is provided. Can be formed. Therefore, a highly reliable light-emitting device can be realized.

Further, a light emitting device of this embodiment, which has been performed up to a sealing (or enclosing) step for protecting the EL element, will be described with reference to FIGS. 6 (A) and 6 (B). In addition, the code | symbol used in FIGS. 3-5 is quoted as needed.

FIG. 6A is a top view showing a state in which the process up to sealing of the EL element has been performed, and FIG.
It is sectional drawing cut | disconnected by A '. Reference numeral 501 shown by a dotted line denotes a pixel portion, 502 denotes a source side driver circuit, and 503 denotes a gate side driver circuit. 504 is a cover material, 505 is a first seal material, and 506 is a second seal material.

Reference numeral 507 denotes wiring for transmitting signals input to the source-side driving circuit 502 and the gate-side driving circuit 503, and a video signal or a clock signal from an FPC (flexible print circuit) 508 serving as an external input terminal. Receive. Although only the FPC is shown here, this FPC has a printed wiring board (P
WB) may be attached.

Next, the cross-sectional structure will be described with reference to FIG. A pixel portion 501 and a source side driver circuit 502 are formed above the substrate 201. The pixel portion 501 is formed by a plurality of pixels including a current control transistor 604 and a pixel electrode 259 electrically connected to a drain of the transistor 604. Is done. The source side driver circuit 502 includes an n-channel transistor 601 and a p-channel transistor
2 (see FIG. 5B). Note that a polarizing plate (typically, a circular polarizing plate) may be attached to the substrate 201.

The pixel electrode 259 functions as an anode of the EL element. Further, banks 267 are provided at both ends of the pixel electrode 259.
Are formed, and an EL layer 268 and a cathode 269 of an EL element are formed on the pixel electrode 259. The cathode 269 also functions as a common wiring for all pixels, and is electrically connected to the FPC 508 via the connection wiring 507. further,
All elements included in the pixel portion 501 and the source-side driver circuit 502 are covered with the passivation film 271.

Further, the cover member 504 is bonded by the first seal member 505. Note that a spacer may be provided to secure an interval between the cover member 504 and the EL element. The space 27 is provided inside the first sealing material 505.
3 are formed. Note that the first sealant 505 is desirably a material that does not transmit moisture or oxygen. Further, it is effective to provide a substance having a moisture absorbing effect or a substance having an antioxidant effect in the space 273.

Note that carbon films (specifically, diamond-like carbon films) 509a and 509b are preferably provided as protective films on the front and back surfaces of the cover member 504 to a thickness of 2 to 30 nm. Such a carbon film has a role of preventing oxygen and water from entering and mechanically protecting the surface of the cover member 504.

After bonding the cover member 504, the first
The second sealing material 50 is so formed as to cover the exposed surface of the sealing material 505.
6 are provided. The second sealing material 506 is the first sealing material 5
The same material as 05 can be used.

By enclosing the EL element with the above structure, the EL element can be completely shut off from the outside, and a substance which promotes deterioration of the EL layer due to oxidation, such as moisture or oxygen, enters from the outside. Can be prevented. Therefore,
A highly reliable light-emitting device can be obtained.

As shown in FIGS. 6A and 6B, an FPC having a pixel portion and a driving circuit on the same substrate
The light emitting device mounted up to this point is particularly referred to as a light emitting device with a built-in drive circuit in this specification.

The light emitting device manufactured by carrying out this embodiment can be operated by a digital signal or an analog signal.

[Embodiment 2] In this embodiment, a plurality of EL layers which can be used in carrying out the present invention are formed, and the characteristics of an EL element using these are shown. Note that the structure of the EL layer manufactured in this embodiment is shown in FIG.

FIG. 7A shows the structure of the EL element a.
First, α-NPD is formed with a thickness of 40 nm as a hole transport layer by an evaporation method on an anode made of a compound of indium oxide and tin oxide. As a light-emitting material for forming a light-emitting layer thereon, a triplet compound Ir
(Ppy) ₃ and CBP are deposited to a thickness of 20 nm by a co-evaporation method. Further, BCP was added on the light emitting layer as an electron transporting layer.
After forming each of nm and Alq ₃ by a vapor deposition method, EL element a is formed by vapor-depositing Yb to a thickness of 400 nm as a cathode. The EL element a
Is emission utilizing triplet excitation energy by a triplet compound.

FIG. 7B shows the structure of the EL element b.
First, 20 nm of copper phthalocyanine as a hole injection layer and 20 n of MTDATA as a hole transport layer were formed on an anode composed of a compound of indium oxide and tin oxide.
m and α-NPD are each formed to a thickness of 10 nm by a vapor deposition method. A singlet compound, Alq ₃ , is formed as a light emitting material for forming a light emitting layer thereon to a thickness of 50 nm by an evaporation method. Then, the EL element b is formed by depositing Yb as a cathode to a thickness of 400 nm. In addition,
Light emission obtained from the EL element b utilizes singlet excitation energy by a singlet compound.

FIG. 7C shows the structure of the EL element c.
First, α-NPD was deposited as a hole transport layer on an anode composed of a compound of indium oxide and tin oxide as a hole transport layer.
It is formed by a nm evaporation method. A singlet compound, Alq ₃ , is formed as a light emitting material for forming a light emitting layer thereon to a thickness of 50 nm by an evaporation method. And Y as a cathode
b was deposited to a thickness of 400 nm to obtain an EL element c.
To form Note that the light emission obtained by the EL element c is:
This utilizes singlet excitation energy by a singlet compound. In the EL element c, the EL layer is formed only of the light emitting layer and the hole transport layer.

FIG. 7D shows the structure of the EL element d.
First, PEDOT, which is a polythiophene derivative, was formed on an anode composed of a compound of indium oxide and tin oxide as a hole injection layer by spin coating to a thickness of 30 nm.
Is formed with a film thickness of Further, polyparaphenylene vinylene (hereinafter, referred to as PPV) is formed as a light-emitting material thereon to a thickness of 80 nm by spin coating. And
The EL element d is formed by forming Yb as a cathode to a thickness of 400 nm by an evaporation method. Note that light emission obtained by the EL element d utilizes singlet excitation energy by a singlet compound. Also, E
The L element d is different from the other EL elements shown so far in that a polymer material is used for the light emitting layer.

Next, electrical characteristics were evaluated using the EL device described with reference to FIG. The result is shown in FIG. First, FIG. 8A shows luminance characteristics with respect to current density. Broadly, EL using a triplet compound
There was a difference in the characteristics with respect to the current density between the device and the EL device using the singlet compound. That is, for the EL element a using the triplet compound, 60 mA / cm ²
Although the luminance of about 6000 cd / m ² was obtained with respect to the current density of the EL element b, the EL element b, the EL element c, and the EL element d using the singlet compound were about one-third 200.
Only a luminance of about 0 cd / m ² was obtained.

FIG. 8B shows the result of measuring the external quantum efficiency with respect to the current density. As for the external quantum efficiency, the EL element a using the triplet compound for the EL element showed overwhelmingly good characteristics as in the luminance characteristic. At the place where the difference is the largest, a high quantum efficiency of about 7 times is obtained.

As shown in the results of FIG. 8, light emission can be obtained more efficiently by using a triplet compound for an EL element.

Therefore, FIG. 7 using a triplet compound was used.
In order to further improve the light emission obtained by the EL element a of (A), another layer was provided.

FIG. 9A shows the same EL element a as shown in FIG. 7A. Then, in FIG. 9B, EL
Copper phthalocyanine was deposited on the anode of device a by vapor deposition.
It was formed with a thickness of nm. Although the electrical characteristics at this time are shown in FIG. 10, as shown in FIG. 10A, the luminance itself of the EL element did not change much by providing copper phthalocyanine on the anode, but the luminance was maintained. Time has become longer.

Further, from FIG. 10B, although the value of the current flowing at the initial stage is different due to the further increase of the film, it becomes almost the same over time.
(A) and FIG. 10 (B) show that the durability of the EL element when the same amount of current is applied is improved. Usually, copper phthalocyanine is known as a hole injecting material for improving the hole injecting property from the anode, but here,
It can be said that the material improves the durability of the EL element. Note that the results were obtained by continuously lighting the EL element under a low voltage of 6.5 V and measuring the luminance of the EL element and the amount of current flowing through the EL element over time. Further, instead of the copper phthalocyanine shown in this embodiment, a polythiophene-based material, for example, PEDOT (poly
(3,4-ethylene dioxythiophene)) can also be used.

Thus, an EL device as shown in FIG. 9C was manufactured. Α-NPD as the hole transport layer in FIG. 9 (B)
(40 nm) instead of MTDATA at 20 nm, α-
NPD was formed to a thickness of 10 nm by an evaporation method. That is, the conventional copper phthalocyanine and the hole transport layer
Another hole transport layer is provided between the layers, and the HOM between the two layers is provided.
The energy difference at the O level is reduced. In addition,
In this specification, the element in FIG. 9C is referred to as an EL element a ′.

FIG. 11 shows the electric characteristics of the EL element shown in FIG. 9C. FIG. 11A shows the currents of EL element a shown in FIG. 9A and EL element a ′ in which a hole injection layer made of copper phthalocyanine and a hole transport layer made of MTDATA are formed. It is the result of having measured light emission luminance with respect to density. This shows that lamination of copper phthalocyanine and MTDATA does not affect the emission luminance of the EL element.

FIG. 11B shows the result of measurement of the light emission luminance when a voltage is applied to the EL element. The luminance is improved by stacking copper phthalocyanine and MTDATA. Since the luminance when the same voltage is applied is improved, the same light emission luminance can be performed at a lower voltage.

FIG. 11C shows the result of measurement of the amount of current when a voltage is applied to the EL element. Here, the amount of current with respect to the applied voltage is larger in the EL element a 'than in the EL element a when viewed at the same voltage.

The above results show that the EL element a 'was formed by laminating copper phthalocyanine and MTDATA on the EL element a, thereby achieving a lower voltage of the EL element.

Further, the response speed of the EL element a ′ was measured. Measurement can be performed with any power supply, DC
(DC current) is applied and switched between ON and OFF. Note that ON is a selection period and refers to a period during which a voltage is applied. OFF is a non-selection period, and the voltage is 0V. Each of these periods is 250 μs.

Specifically, a photomultiplier (Photomultiplier) was installed on the microscope, and the output of the photomultiplier was evaluated using a value read by an oscilloscope. In this measurement, switching from OFF to ON is defined as rising, and switching from ON to OFF is defined as falling. Then, from the moment when the power supply voltage is switched from OFF to ON, the optical response following the power supply becomes 100%.
The time required to show the emission luminance increased to 90% with respect to the emission luminance of% was defined as the rise response time. Further, from the moment when the voltage of the power supply is switched from ON to OFF, the time required for the optical response to follow it to show the emission luminance reduced to 10% from the emission luminance of 100% up to that point is set to fall. Response time.

FIG. 25 shows the state of the measurement at this time. In FIG. 25, the arrow (a) indicates the output (voltage) of the power supply, and the arrow (b) indicates the optical response to the output. Further, since the photomultiplier tube uses a negative output type, a negative potential is output when the photomultiplier is switched from OFF (0 V) to ON (here, an example of 6 V is shown).

In FIG. 25, the point at which 90% of the luminance was obtained is indicated by an arrow c.
s. In this embodiment, the output of the power supply is 6
When the voltage is V, although there is some variation depending on the EL element, the response time of the rise and fall can be in the range of 1 to 100 μs, preferably 1 to 50 μs. Further, Table 1 shows the results (rise time and fall time) measured by changing the voltage at ON from 6 V to 10 V in steps of 1 V.

[0128]

[Table 1]

Table 1 shows that the response speed in these voltage ranges is very high, and that it can be used without any problem even in ordinary digital driving.

[Embodiment 3] FIG. 12 shows a sectional structure of a pixel portion in an active matrix light emitting device of this embodiment. In FIG. 12, 10 is an insulator, and 11 is FIG.
Current control transistors (TFTs) 604 and 12 are pixel electrodes (anodes), 13 is a bank, 14 is a known hole injection layer, 15 is a red light emitting layer, 16 is a green light emitting layer, and 17 is a green light emitting layer. A light emitting layer that emits blue light, 18 is a known electron transport layer, and 19 is a cathode.

At this time, in this embodiment, a triplet compound is used as the light emitting layer 15 emitting red light and the light emitting layer 17 emitting blue light, and a singlet compound is used as the light emitting layer 16 emitting green light. That is, an EL element using a singlet compound is an EL element that emits green light,
The EL element using the triplet compound is an EL element that emits red light and an EL element that emits blue light.

When a low molecular weight organic compound is used as the light emitting layer, the life of the light emitting layer that emits red light and the light emitting layer that emits blue light are shorter than those of the light emitting layer that emits green light. This is because, since the luminous efficiency is inferior, the operating voltage must be set high in order to obtain the same luminous luminance as that of green, and the progress of deterioration is accelerated accordingly.

However, in this embodiment, since the triplet compound having high luminous efficiency is used for the light emitting layer 15 emitting red light and the light emitting layer 17 emitting blue light, the same light emission luminance as the light emitting layer 16 emitting green light is obtained. However, it is possible to make the operating voltages uniform. Accordingly, the deterioration of the light emitting layer 15 that emits red light and the light emitting layer 17 that emits blue light are not extremely accelerated, and color display can be performed without causing a problem such as color shift. The fact that the operating voltage can be kept low is also preferable from the viewpoint that the margin of the withstand voltage of the transistor can be set low.

In this embodiment, an example is shown in which a triplet compound is used as the light emitting layer 15 that emits red light and the light emitting layer 17 that emits blue light, but the triplet compound is further added to the light emitting layer 16 that emits green light. It is also possible to use.

Next, FIG. 13 shows a circuit configuration of a pixel portion when the present embodiment is implemented. Here, a pixel (pixel (red)) 20a including an EL element that emits red light, and a pixel (pixel (green)) 20b including an EL element that emits green light
3 and a pixel (pixel (blue)) 20c including an EL element that emits blue light, all of which have the same circuit configuration.

In FIG. 13A, 21 is a gate wiring, 22a to 22c are source wirings (data wirings), 23a
23c are current supply lines. The current supply line 23 is a wiring that determines the operating voltage of the EL element, and
0a, green light emitting pixel 20b and blue light emitting pixel 20c
The same voltage is applied to any of the pixels. Therefore, the line width (thickness) of the wiring may be the same design.

Further, reference numerals 24a to 24c are switching transistors, which are formed here by n-channel transistors. Although a structure having two channel formation regions between a source region and a drain region is illustrated here, two or more or one channel formation region may be provided.

Reference numerals 25a to 25c denote current control transistors, and gates of the switching transistors 24a to 24c.
24c, the sources are current supply lines 23a to 23c.
And the drain is connected to any of the EL elements 26a to 26c. Here, 27a to 27c are capacitors, which hold voltages applied to the gates of the current supply lines 25a to 25c, respectively. However, the capacitors 27a to 27c can be omitted.

In FIG. 13A, the switching transistors 24a to 24a made of n-channel transistors are used.
Although an example is shown in which current control transistors 25a to 25c including 4c and p-channel transistors are provided,
As shown in FIG. 13B, each of the pixel (red) 30a, the pixel (green) 30b, and the pixel (blue) 30c has a switching transistor 2 composed of a p-channel transistor.
It is also possible to provide current control transistors 29a to 29c composed of 8a to 28c and n-channel transistors.

Further, FIGS. 13A and 13B show an example in which two transistors are provided in one pixel, but the number of transistors is two or more (typically three to three).
Six). In that case, the n-channel transistor and the p-channel transistor may be provided in any combination.

In this embodiment, the EL element 26a is a red-emitting EL element, the EL element 26c is a blue-emitting EL element, and both use a triplet compound as a light-emitting layer. The EL element 26b is a green light emitting EL element, and uses a singlet compound as a light emitting layer.

By selectively using the triplet compound and the singlet compound in this manner, the operating voltages of the EL elements 26a to 26c are all the same (10 V or less, preferably 3 to 10 V).
V). Therefore, since the power supply required for the light emitting device can be unified at, for example, 3 V or 5 V, there is an advantage that circuit design becomes easy.

The structure of this embodiment can be implemented in combination with any of the structures of Embodiment 1 and Embodiment 2.

[Embodiment 4] In this embodiment, a case will be described in which the pixel portion and the driving circuit are all formed of n-channel transistors. Note that the manufacturing process of the n-channel transistor may be in accordance with the first embodiment, and the description is omitted.

FIG. 14 shows a sectional structure of the light emitting device of this embodiment. Note that the basic structure is the same as that shown in FIG.
Since the cross-sectional structure is the same as that of (B), only the differences will be described here.

In this embodiment, an n-channel transistor 1201 is provided instead of the p-channel transistor 602 in FIG. 5B, and a current control transistor 1202 made of an n-channel transistor is provided instead of the current control transistor 604. Have been.

A wiring 266 connected to the drain of the current control transistor 1202 functions as a cathode of the EL element, and an EL layer 1203, an anode 1204 made of an oxide conductive film, and a passivation film 1205 are provided thereon. . At this time, the wiring 266 is formed using a metal film containing an element belonging to Group 1 or 2 of the periodic table, or at least a surface in contact with the EL layer 1203 is a metal film containing an element belonging to Group 1 or 2 of the periodic table. It is desirable to be formed with.

The n-channel transistors used in this embodiment may be all enhancement transistors or all depletion transistors. Of course, it is also possible to separately use both of them and use them in combination.

FIG. 15 shows a circuit configuration of a pixel. 13 are the same as those in FIG.
Please refer to the description.

As shown in FIG. 15, the pixels (red) 35a,
The switching transistors 24a to 24c and the current control transistors 36a to 36c provided in each of the pixel (green) 35b and the pixel (blue) 35c are all formed by n-channel transistors.

According to the structure of this embodiment, in the manufacturing process of the light emitting device of the first embodiment, a photolithography process for forming a p-channel transistor, and a process for forming a pixel electrode (anode) in the first embodiment. Since the photolithography process can be omitted, the manufacturing process can be further simplified.

The structure of this embodiment can be implemented in combination with any of the structures of the first to third embodiments.

[Embodiment 5] In this embodiment, a case where the pixel portion and the driving circuit are all formed by p-channel transistors will be described. FIG. 16 shows a cross-sectional structure of the light emitting device of this embodiment. Note that the description of the first embodiment may be referred to for the portions denoted by the same reference numerals as those in FIG. 5B shown in the first embodiment.

In this embodiment, the driving circuits are p-channel transistor 1401 and p-channel transistor 1
The pixel portion includes a switching transistor 1403 formed of a p-channel transistor and a current control transistor 1404 formed of a p-channel transistor. In addition,
The active layer of the p-channel transistor 1401 includes a source region 41, a drain region 42, and LDD regions 43a and 43b.
And a channel forming region 44. The structure of the active layer is
The same applies to the p-channel transistor 1402, the switching transistor 1403, and the current control transistor 1404.

Here, the manufacturing process of the p-channel transistor of this embodiment will be described with reference to FIG. First,
The steps up to the step of FIG.

Next, the electrodes 212 to 216 made of the second conductive film are formed using the resists 211a to 211e.
Then, using the resists 211a to 211e and the electrodes 212 to 216 made of the second conductive film as masks,
An element belonging to Group 3 (boron in this embodiment) is added to the semiconductor film, and a region containing boron at a concentration of 1 × 10 ²⁰ to 1 × 10 ²¹ atoms / cm ³ (hereinafter referred to as a p-type impurity region (a)) )
Steps 301 to 309 are formed (FIG. 17A).

Next, the electrodes 212 to 216 made of the second conductive film are formed using the resists 211a to 211e as shown in FIG.
The second gate electrodes 310 to 314 are formed by etching under the same etching conditions as described above (FIG. 17B).

Next, using the resists 211a to 211e and the second gate electrodes 310 to 314 as a mask, the first conductive film 209 is etched under the same etching conditions as in FIG. 319 are formed.

Then, using the resists 211a to 211e and the second gate electrodes 310 to 314 as a mask, an element belonging to Group 13 of the periodic table (boron in this embodiment) is added to the semiconductor film, and 1 × 10 ¹⁶ to 1 × 10 ¹⁹ atoms / cm ³ region containing boron at a concentration of (typically ^{1 × 10 17 ~1 × 10 1} 8 atoms / cm 3 in) (hereinafter, p-type impurity region (b) hereinafter)
320 to 329 are formed (FIG. 17C).

Subsequent steps may follow the steps in FIG. 4C of the first embodiment and thereafter. Through the above steps, a light emitting device having a structure shown in FIG. 16 can be formed.

Further, all the p-channel transistors used in this embodiment may be enhancement type transistors, or all may be depletion type transistors. Of course, it is also possible to separately use both of them and use them in combination.

FIG. 18 shows a circuit configuration of a pixel. 13 are the same as those in FIG.
Please refer to the description.

As shown in FIG. 18, pixels (red) 50a,
The switching transistors 51a to 51c and the current control transistors 52a to 52c provided in the pixel (green) 50b and the pixel (blue) 50c are all formed by p-channel transistors.

According to the structure of this embodiment, one photolithography step can be omitted in the manufacturing process of the light emitting device of the first embodiment, so that the manufacturing process can be simplified as compared with the first embodiment. It is.

The structure of this embodiment can be implemented in combination with any of the structures of the first to fourth embodiments.

[Embodiment 6] In the active matrix type light emitting device of the present invention, a MOS (Metal Ox
ide Semiconductor) transistors can also be used. In that case, a MOS transistor formed on a semiconductor substrate (typically, a silicon wafer) by a known method may be used.

The configuration other than the semiconductor element in the present embodiment can be implemented in combination with the configurations of the first to fifth embodiments.

[Embodiment 7] In Embodiment 1, the light emitting device with a built-in drive circuit shown in FIG. 6 is an example in which a pixel portion and a drive circuit are integrally formed on the same insulator. It is also possible to provide an external IC (integrated circuit). In such a case, the structure is as shown in FIG.

The module shown in FIG. 19A has an active matrix substrate 60 (pixel portion 61, wirings 62a and 62a).
2b), the FPC 63 is attached to the
A printed wiring board 64 is attached via 63. Here, a functional block diagram of the printed wiring board 64 is shown in FIG.
This is shown in FIG. 9 (B).

As shown in FIG. 19B, at least I / O ports (also referred to as input or output units) 65 and 68 and a source-side drive circuit 66 are provided inside a printed wiring board 64.
Further, an IC functioning as the gate side drive circuit 67 is provided.

As described above, a module having a configuration in which an FPC is mounted on an active matrix substrate having a pixel portion formed on a substrate surface, and a printed wiring board having a function as a driving circuit is mounted via the FPC, In the specification, the light emitting module will be referred to as a drive circuit external light emitting module.

The module shown in FIG.
Light emitting device with built-in driving circuit 70 (pixel portion 71, source side driving circuit 72, gate side driving circuit 73, wirings 72a, 73a
Is attached to the FPC 74, and the FPC 74
The printed wiring board 75 is attached via the. Here, a functional block diagram of the printed wiring board 75 is shown in FIG.
It is shown in (B).

As shown in FIG. 20B, at least I / O ports 76, 79,
An IC functioning as the control unit 77 is provided. Although the memory unit 78 is provided here,
It is not necessary. Also, the control unit 77
This is a part having a function for controlling a drive circuit, correcting image data, and the like.

In this specification, a module having a configuration in which a printed circuit board having a function as a controller is attached to a light emitting device with a built-in driving circuit in which a pixel portion and a driving circuit are formed on a substrate surface is described. It will be referred to as an external light emitting module.

[Embodiment 8] A light emitting device formed by carrying out the present invention (including a module having the form shown in Embodiment 9)
Is built in various electric appliances, and the pixel portion is used as a video display portion. Examples of the electric appliance of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, an audio device, a notebook personal computer, a game device, and a portable device (mobile computer, mobile phone, and portable game machine). Or an electronic book), and an image reproducing apparatus provided with a recording medium. Specific examples of these electric appliances are shown in FIGS.

FIG. 21A shows a display device,
01, the support base 2002, and the display unit 2003. The light emitting device of the present invention can be used for the display portion 2003. In the case where a light-emitting device having an EL element is used for the display portion 2003, a thin display portion can be provided without a backlight because the EL element is a self-luminous type.

FIG. 21B shows 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 210.
6 inclusive. The light emitting device of the present invention can be used for the display portion 2102.

FIG. 21C shows 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 or the liquid crystal display device of the present invention can be used for the display portion 2202.

FIG. 21D shows an image reproducing apparatus (specifically, a DVD reproducing apparatus) provided with a recording medium.
1, a recording medium (CD, LD, DVD, etc.) 2302,
An operation switch 2303, a display unit (a) 2304, and a display unit (b) 2305 are included. 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 employs these display units (a) and (b).
Can be used. Note that the image reproducing device provided with the recording medium may include a CD reproducing device, a game machine, and the like.

FIG. 21E shows a portable (mobile) computer having a main body 2401, a display portion 2402, an image receiving portion 2403, operation switches 2404, and a memory slot 24.
05 inclusive. The light emitting 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 nonvolatile memory is integrated, and can reproduce the information.

FIG. 21F shows a personal computer, which includes a main body 2501, a housing 2502, a display portion 2503,
A keyboard 2504 is included. The light-emitting device of the present invention can be used for the display portion 2503.

Further, the above-mentioned electric appliances are available on the Internet or C
Information distributed through an electronic communication line such as an ATV (cable television) is frequently displayed, and in particular, opportunities to display moving image information are increasing. In the case where a light-emitting device having an EL element in a display portion is used, a moving image can be displayed without delay because the response speed of the EL element is extremely high.

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 the light emitting device is used for a portable information terminal, particularly a display portion mainly for character information such as a mobile phone or an audio device, the character information is driven by the light emitting portion with the non-light emitting portion as a background. It is desirable.

FIG. 22A shows a mobile phone, and the main body 26 is provided.
01, audio output unit 2602, audio input unit 2603, display unit 2604, operation switch 2605, antenna 2606
including. 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. 22B also shows a mobile phone.
Unlike (A), it is a two-fold type. Body 26
11, an audio output unit 2612, an audio input unit 2613, a display unit a2614, a display unit b2615, and an antenna 2616. Note that this type of mobile phone does not have an operation switch, but one of the display units a and b is provided on one of the display units as shown in FIGS. 22C, 22D, and 22E. It displays the character information and provides its function. The other display unit mainly displays image information. Note that the light emitting device of the present invention has a display portion a26.
14 or the display unit b2615.

In the case of the mobile phone shown in FIG. 22B, the light emitting device used for the display portion is provided with a CMOS circuit using a sensor (CMO).
S sensor), and can be used as an authentication system terminal that authenticates a user by reading a fingerprint or palm. In addition, external brightness (illuminance) can be read and light can be emitted so that information can be displayed with the set contrast.

Further, the power consumption can be reduced by lowering the luminance when the operation switch 2605 is used and increasing the luminance when the operation switch has been used. Further, power consumption can be reduced by increasing the luminance of the display portion 2604 when an incoming call is received and decreasing the luminance during a call. In addition, when the device is continuously used, the power can be reduced by providing a function of turning off the display by time control unless resetting is performed. In addition,
These may be manually controlled.

FIG. 22 (F) shows a sound reproducing device, specifically, an audio for vehicle, which comprises a main body 2621 and a display portion 262.
2, including operation switches 2623 and 2624. The light-emitting device of the present invention can be used for the display portion 2622. In this embodiment, the in-vehicle audio is shown, but the present invention may be applied to a portable or home-use audio reproducing apparatus. The display unit 2
Reference numeral 622 indicates power consumption by displaying white characters on a black background. This is particularly effective in a portable sound reproducing device.

Further, in the portable electric appliance shown in this embodiment, as a method for reducing power consumption, a sensor unit for sensing external brightness is provided, and when used in a dark place, a display unit is provided. To add a function such as lowering the brightness of the image.

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, any configuration shown in the first to eighth embodiments may be applied to the electric appliance of the present embodiment.

[Embodiment 9] In the embodiment 1, the case where the transistor (hereinafter, referred to as TFT) has a top gate type structure has been described. However, the present invention is not limited to the TFT structure. 23, a bottom gate type TFT (typically, an inverted stagger type TFT) may be used. Further, the inverted staggered TFT may be formed by any means.

FIG. 23A shows a bottom gate type T
In manufacturing a light-emitting device using FT, the formed EL
It is a top view of a module. Source-side drive circuit 300
1, a gate side driving circuit 3002 and a pixel portion 3003 are formed. In FIG. 23A, xx ′
Area a30 of the pixel portion 3003 when the light emitting device is turned off at
FIG. 23B shows a cross-sectional view of No. 04.

In FIG. 23B, only the current control TFT among the pixel TFTs will be described. Reference numeral 3011 denotes a substrate, and 3012 denotes an insulating film serving as a base (hereinafter, referred to as a base film). As the substrate 3011, a light-transmitting substrate, typically, a glass substrate, a quartz substrate, a glass ceramic substrate,
Alternatively, a crystallized glass substrate can be used. However, it must withstand the maximum processing temperature during the manufacturing process.

The base film 3012 is particularly effective when a substrate containing mobile ions or a substrate having conductivity is used, but need not be provided on a quartz substrate. Base film 30
As 12, an insulating film containing silicon (silicon) may be used. In this specification, “an insulating film containing silicon”
Specifically, oxygen or nitrogen is contained at a predetermined ratio with respect to silicon such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film (SiOxNy: x and y are represented by arbitrary integers). Refers to an insulating film.

Reference numeral 3013 denotes a current control TFT, which is formed by a p-channel TFT. As shown in this embodiment, when the EL emission direction is the upper surface of the substrate (the surface on which the TFT and the EL layer are provided), the switching TFT is formed of an n-channel TFT, and the current control TFT is also an n-channel TFT. It is preferable that it is the structure formed by. However, the present invention is not limited to this configuration. Switching T
The FT and the current control TFT may be either n-channel TFTs or p-channel TFTs.

The current control TFT 3013 is connected to the source region 3
014, drain region 3015 and channel formation region 3
An active layer including 016, a gate insulating film 3017, a gate electrode 3018, a first interlayer insulating film 3019, a source wiring 3020, and a drain wiring 3021 are formed. In this embodiment, the current control TFT 3013 has n
It is a channel type TFT.

The drain region of the switching TFT is connected to the gate electrode 3018 of the current control TFT 3013. Although not shown, specifically, the gate electrode 3018 of the current control TFT 3013 is connected to the switching T
It is electrically connected to a drain region (not shown) of the FT via a drain wiring (not shown). Note that the gate electrode 3018 has a single-gate structure, but may have a multi-gate structure. In addition, current control TFT
Source wiring 3020 of 3013 is connected to a current supply line (not shown).

The current control TFT 3013 is an element for controlling the amount of current injected into the EL element, and a relatively large amount of current flows. Therefore, it is preferable that the channel width (W) is designed to be larger than the channel width of the switching TFT. It is preferable that the channel length (L) is designed to be long so that an excessive current does not flow through the current control TFT 3013. Desirably 0.5 to 2μ per pixel
A (preferably 1 to 1.5 μA).

Further, the thickness of the active layer (particularly, the channel formation region) of the current control TFT 3013 is increased (preferably 50 to 100 nm, more preferably 60 to 80 n).
m), deterioration of the TFT may be suppressed.

After forming the current control TFT 3013, a first interlayer insulating film 3019 and a second interlayer insulating film (not shown) are formed, and a pixel electrode 3023 electrically connected to the current control TFT 3013 is formed. . In this embodiment, the pixel electrode 3023 made of a conductive film functions as a cathode of the EL element.

Specifically, an alloy film of aluminum and lithium is used, but a conductive film made of an element belonging to Group 1 or 2 of the periodic table or a conductive film to which those elements are added may be used.

After the pixel electrode 3013 is formed, a third interlayer insulating film 3024 is formed. Note that the third interlayer insulating film 3024 functions as a so-called bank.

Next, an EL layer 3025 is formed. Note that FIG. 23B is a cross-sectional view in which pixel columns in which the same EL layer is formed are arranged.

The EL layer in this example used Alq3 as the electron injection layer, BCP as the electron transport layer, and CBP doped with Ir (ppy) 3 as the light emitting layer. Further, a hole transport layer was formed using α-NPD.

Next, an anode 3026 made of a transparent conductive film is formed on the EL layer. Thereby, the EL element 30
27 are formed. In the case of this example, a compound of indium oxide and tin oxide or a transparent conductive film,
A conductive film including a compound of indium oxide and zinc oxide is used.

Further, by forming a passivation film made of an insulating material on the anode, an inversely staggered TFT is formed.
An EL module having a structure can be formed.
Note that the light emitting device manufactured according to this example is the same as that shown in FIG.
Light can be emitted in the direction (upper surface) of the arrow (B).

The inverted staggered TFT has a structure in which the number of steps is easily reduced as compared with that of the top gate type TFT. Therefore, it is very advantageous to reduce the manufacturing cost, which is an object of the present invention.

The structure of this embodiment can be implemented by freely combining with any of the structures of Embodiments 1 to 8.

[Embodiment 10] In this embodiment, a case where an SRAM is introduced in a pixel portion will be described. FIG. 24 is an enlarged view of the pixel 3104. In FIG. 24, 310
5 is a switching TFT. Switching TFT3
The gate electrode 105 is a gate signal line 3 which is one of the gate signal lines (G1 to Gn) for inputting a gate signal.
106. Switching TFT3105
One of the source region and the drain region is connected to a source signal line 3107 which is one of the source signal lines (S1 to Sn) for inputting signals, and the other is connected to the input side of the SRAM 3108. The output side of the SRAM 3108 is connected to the gate electrode of the current control TFT 3109.

One of the source region and the drain region of the current control TFT 3109 has one of the current supply lines (V1 to Vn).
, And the other is connected to the EL element 3111.

[0211] The EL element 3111 includes an anode and a cathode, and an EL layer provided between the anode and the cathode. When the anode is connected to the source region or the drain region of the current control TFT 3109, in other words, when the anode is a pixel electrode, the cathode is a counter electrode. Conversely, the cathode is a current control TFT
When connected to the source or drain region 3109, in other words, when the cathode is a pixel electrode, the anode serves as the counter electrode.

The SRAM 3108 has two p-channel TFTs and two n-channel TFTs. The source region of the p-channel TFT is Vddh on the high voltage side, and the source region of the n-channel TFT is the low voltage side. Vss. One p-channel TFT and one n-channel TFT are paired, and one SR
Two pairs of a p-channel TFT and an n-channel TFT exist in the AM.

Further, a pair of p-channel TFT and n
The channel type TFT has drain regions connected to each other. The gate electrodes of the paired p-channel TFT and n-channel TFT are connected to each other. The drain region of one pair of the p-channel TFT and the n-channel TFT is kept at the same potential as the gate electrode of the other pair of the p-channel TFT and the n-channel TFT. I'm dripping.

The drain region of one pair of p-channel and n-channel TFTs is an input side to which an input signal (Vin) enters, and the other pair of p-channel and n-channel TFTs The drain region of the channel type TFT is an output side where an output signal (Vout) is output.

The SRAM is designed to hold Vin and output Vout which is a signal obtained by inverting Vin. That is, if Vin is Hi, Vout becomes a Lo signal equivalent to Vss, and if Vin is Lo, Vout becomes Vd.
It becomes a Hi signal equivalent to dh.

As shown in this embodiment, in the case where one SRAM is provided in the pixel 3104, since the memory data in the pixel is held, the still image is stored in a state where most of the external circuits are stopped. Can be displayed. Thereby, low power consumption can be realized. Also,
It is also possible to provide a plurality of SRAMs for a pixel,
When a plurality of AMs are provided, a plurality of data can be held, so that a gray scale display based on a time gray scale can be performed.

The structure of this embodiment can be implemented by freely combining with any structure of the first to ninth embodiments.

[0218]

By practicing the present invention, it is easy to equalize the light emission luminance of the EL elements formed on the same substrate, and furthermore, a light emitting device with low power consumption that can emit light with high luminance at a low voltage. Can be manufactured. In addition, by using these light-emitting devices for a display portion, an electric appliance with low power consumption can be provided.

[Brief description of the drawings]

FIG. 1 illustrates a light-emitting device.

FIG. 2 illustrates a stacked structure of an EL element.

FIG. 3 is a diagram showing a manufacturing process of the light emitting device.

FIG. 4 is a diagram showing a manufacturing process of the light emitting device.

FIG. 5 is a diagram showing a manufacturing process of the light emitting device.

FIG. 6 illustrates a top structure and a cross-sectional structure of a light-emitting device.

FIG. 7 is a diagram illustrating a stacked structure of an EL element.

FIG. 8 illustrates element characteristics of an EL element.

FIG. 9 is a diagram illustrating a stacked structure of an EL element.

FIG. 10 illustrates element characteristics of an EL element.

FIG. 11 illustrates element characteristics of an EL element.

FIG. 12 illustrates a cross-sectional structure of a light-emitting device.

FIG. 13 illustrates a circuit configuration of a pixel of a light-emitting device.

FIG. 14 illustrates a cross-sectional structure of a light-emitting device.

FIG. 15 illustrates a circuit configuration of a pixel of a light-emitting device.

FIG. 16 illustrates a cross-sectional structure of a light-emitting device.

FIG. 17 illustrates a manufacturing process of a light-emitting device.

FIG. 18 illustrates a circuit configuration of a pixel of a light-emitting device.

FIG. 19 is a diagram illustrating a structure of a light emitting device with an external drive circuit.

FIG. 20 is a diagram illustrating a structure of a light-emitting device with an external controller.

FIG. 21 illustrates a specific example of an electric appliance.

FIG. 22 illustrates a specific example of an electric appliance.

FIG 23 illustrates a top view and a cross-sectional structure of a light-emitting device.

FIG. 24 illustrates a circuit configuration of a pixel of a light-emitting device.

FIG. 25 illustrates element characteristics of an EL element.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B33 / 22 H05B33 / 22 DZ (72) Inventor Toshio Ikeda 398 Hase, Atsugi-shi, Kanagawa Pref. 3K007 AB02 AB04 AB06 AB11 AB17 BA06 BB01 BB05 CB01 DA01 DB03 EB00 GA04 5C094 AA07 AA08 AA22 AA24 BA03 BA12 BA27 CA19 CA24 CA25 DA09 DA13 DB01 DB02 DB04 EA04 EA05 EA10 FB10 FB10 GB10 HA10

Claims (15)

[Claims] 1. A light-emitting device having a plurality of EL elements in a pixel portion on a substrate, wherein the plurality of EL elements has at least one EL element having an EL layer containing a triplet compound, and the EL layer has A light-emitting device comprising a plurality of hole transport layers. 2. A light-emitting device having a plurality of EL elements in a pixel portion on a substrate, wherein the plurality of EL elements is a first EL element having a first EL layer containing a triplet compound;
And at least one second EL element having a second EL layer containing a singlet compound, wherein the first and second EL layers have a plurality of hole transport layers. Light emitting device. 3. A light emitting device having a plurality of EL elements in a pixel portion on a substrate, wherein the plurality of EL elements are a first EL element having a first EL layer containing a triplet compound;
And a second EL element having a second EL layer containing a singlet compound. The first EL element has a hole injection layer formed in contact with an anode, and a second EL element in contact with the hole injection layer. A hole transport layer formed in contact with the hole transport layer, a light emitting layer formed in contact with the hole transport layer, a hole blocking layer formed in contact with the light emitting layer, and a hole blocking layer formed in contact with the hole blocking layer. A light emitting device having an electron transporting layer and a cathode formed in contact with the electron transporting layer, the light emitting device having a plurality of the hole transporting layers. 4. The hole injection layer according to claim 3, wherein the hole injection layer is formed of a layer containing copper phthalocyanine, and the hole transport layer is formed of MT.
The light emitting layer is composed of a layer containing CBP and Ir (ppy) ₃ , the hole blocking layer is composed of a layer containing BCP, and the electron transport layer is composed of Alq. _3. A light-emitting device comprising a layer containing ₃ . 5. The light-emitting device according to claim 2, wherein the first EL element emits red light, and the second EL element emits blue or green light. 6. The light-emitting device according to claim 2, wherein the first EL element emits blue light, and the second EL element emits red or green light. 7. The light-emitting device according to claim 2, wherein the first EL element emits green light, and the second EL element emits red or blue light. 8. The light-emitting device according to claim 2, wherein the first EL element emits red or blue light, and the second EL element emits green light. 9. The light-emitting device according to claim 2, wherein the first EL element emits red or green light, and the second EL element emits blue light. 10. The device according to claim 2, wherein the first EL element emits blue or green light and the second EL element emits blue or green light.
Wherein the EL element emits red light. 11. The light emitting device according to claim 1, wherein the hole transport layer has a laminated structure of two to four layers. 12. The hole transporting layer according to claim 1, wherein the hole transporting layer comprises a layer containing MTDATA and an α
A light emitting device comprising: a layer containing NPD. 13. The light emitting device according to claim 12, wherein the layer containing α-NPD is formed between the light emitting layer and the layer containing MTDATA. 14. An electric appliance using the light emitting device according to claim 1. Description: 15. The light-emitting device according to claim 1, wherein the light-emitting device is a display device, a video camera, a head-mounted display, an image reproducing device provided with a recording medium, a goggle-type display, a personal computer, and a portable device. A light-emitting device, which is a type selected from a telephone, a sound reproducing device, and a digital camera.