JP2003280556A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide light emitting elements or a light emitting device having both practical luminance and stability. <P>SOLUTION: The light emitting device is provided with light emitting elements in which an electric charge injection transport medium and a light emitting medium that include an organic or an inorganic compound are formed between a pair of electrodes. In the light emitting device, a resistor body is arranged between the light emitting elements and an active element that is a control means to apply a voltage to the light emitting elements and the voltage is applied through the resistor body. Since the resistor body holds a constant resistive value, even when light emitting element changes over time resulting in increase in the internal resistive value of the light emitting element, the influence of the increase is reduced at constant voltage drive. The resistor body is formed on the surface of the opposite side on which the electric charge injection and transport medium, and the light emitting medium are not formed, of at least one of the electrodes of the pair of the electrodes. <P>COPYRIGHT: (C)2004,JPO

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 including a light emitting element including a charge injecting and transporting medium containing an organic compound or an inorganic compound and a light emitting medium, and more particularly, to a voltage applied to the light emitting element by a field effect transistor. The present invention relates to a light emitting device of an active matrix driving method for controlling.

[0002]

2. Description of the Related Art A light emitting device including a light emitting body such as an organic electroluminescent medium contains an organic amine type hole transport layer between a pair of electrodes, and an organic compound such as Alq3 which exhibits electronic conductivity and emits light. By stacking layers and applying a direct current voltage of 6 to 8 V, a brightness of several hundred cd / cm ² can be obtained, and thus it has performance applicable to a display medium and the like.

Organic compounds used in many cases for the purpose of forming a light emitting device are roughly classified into low molecular weight organic compounds and high molecular weight organic compounds. An example of a low molecular weight organic compound is copper phthalocyanine (CuP) as a hole injection layer.
c), α-NPD (4,4′-bis- [N- (naphthyl) -N-phenyl-amino] biphenyl) which is an aromatic amine material,
MTDATA (4,4 ', 4 "-tris (N-3-methylphenyl-N-
Phenyl-amino) triphenylamine) etc. are known,
Examples of the light emitting layer include tris-8-quinolinolato aluminum complex (Alq ₃ ). Polyaniline and polythiophene derivatives (PEDO)
T) etc.

From the viewpoint of material diversity, low molecular weight organic compounds produced by the vapor deposition method are said to be remarkably diverse as compared with high molecular weight organic materials. Further, a light emitting element may be formed by combining such an organic compound material and an inorganic compound material. For example, Japanese Patent Laid-Open No. 2001-2001
Japanese Patent No. 230082 discloses a technique in which an inorganic electron injecting / transporting layer or an inorganic hole injecting / transporting layer is applied to achieve high luminous efficiency and a long life. In any case, it is known that there are various types of structures of light emitting elements.

An example of an active matrix drive type display device in which such a light emitting element is controlled by a field effect transistor is disclosed in JP-A-8-234683. The publication discloses a structure in which an organic electroluminescence layer is formed on an upper layer of a thin film transistor (TFT) using polycrystalline silicon via an insulating film made of silicon dioxide. Further, the passivation layer having the tapered end portion on the anode is located on the lower layer side of the organic electroluminescence layer. For the cathode, a material with a work function lower than 4 eV is selected.
An alloy of a metal such as g or Al and Mg is applied.

In Japanese Patent Laid-Open No. 2001-147659, a current mirror circuit is formed by a TFT in each pixel,
An example of a current-driven display device capable of preventing the influence of TFT characteristic variations is disclosed.

[0007]

However, such a conventional light emitting device has a problem that the emission brightness is deteriorated due to aging even if sufficient brightness is obtained immediately after fabrication. . In other words, the brightness decreases as the integrated time of light emission increases, and the time to reach the half-value (half-life) is short, so that the stability is poor and it is not practically usable.

The factors of deterioration of the light emitting device include chemical changes in the charge injecting and transporting medium containing an organic compound or an inorganic compound and the light emitting medium, its structural change due to heat generation during driving, and insulation caused by energization due to macroscopic defects. Factors such as breakdown, deterioration of electrode or electrode interface, structural instability based on amorphous structure of charge injection transport medium and light emitting medium containing organic compound or inorganic compound, irreversible breakdown due to stress or strain due to device structure There is.

It has been found that defects such as non-light emitting points (also called dark spots) appearing in pixels can be improved by improving the sealing method of the light emitting element. On the other hand, the decrease in emission brightness is a problem of the material itself used, and in addition to the direct cause of the flow of current, the structural change due to heat generation can be considered as the main factor. The heat generation inevitably results from the current flowing through the light emitting element as Joule heat. This is not only the heat generated by passing a current through the light emitting element,
Heat is also added to the active elements of the pixel. In particular, in a current drive type light emitting device in which a constant current is supplied by the active element of each pixel, this heat generation becomes a serious problem.

In any case, the irreversible decrease in brightness caused by the light emission of the light emitting element is a problem that must be solved before the light emitting device using the same is put into practical use. For this purpose, it is necessary to improve the materials for the charge injecting and transporting medium containing the organic compound or the inorganic compound and the light emitting medium itself, but it is also possible to solve it by improving the element structure, the structure of the light emitting device, or the driving method. It is necessary as a countermeasure.

The present invention has been made in view of the above problems, and an object thereof is to provide a light emitting element or a light emitting device having both practical brightness and stability.

[0012]

In order to solve the above problems, the present invention has a light emitting device in which a charge injection transport medium containing an organic compound or an inorganic compound and a light emitting medium are formed between a pair of electrodes, A light-emitting device in which a resistor is interposed between an active element that is a control unit that applies a voltage to the light-emitting element, and a voltage is applied through the resistor, and the resistor holds a constant resistance value. Even if the light emitting element changes with time and the internal resistance value increases, the influence thereof is reduced during constant voltage driving. The resistor is formed on at least one electrode of a light-emitting element containing an organic compound which becomes a light-emitting body between a pair of electrodes, on the opposite surface on which the charge injection transport medium containing the organic compound or the inorganic compound and the light-emitting medium are not arranged. Is.

As another structure, a light emitting element in which a charge injecting and transporting medium containing an organic compound or an inorganic compound and a light emitting medium are formed between a pair of electrodes, and at least one of the pair of electrodes is provided with a light emitting element. A resistor is provided on the opposite surface on which the charge injection transport medium containing an organic compound or an inorganic compound and the light emitting medium are not formed, and one electrode of the light emitting element connected to a common electrode for applying a constant potential is A light-emitting device connected to an active element that is a control means for applying a voltage. Even if the light-emitting element changes with time due to the resistor holding a constant resistance value and the internal resistance value increases, a constant voltage is maintained. The effect is reduced during driving.

In the structure of the invention described above, the active element included in the control means for applying a voltage to the light emitting element is a field effect transistor, an insulated gate transistor, or a thin film transistor, and a single drain, a low concentration drain, and a single gate. There is no particular limitation on the structure such as a multi-gate, a top-gate type, a bottom-gate (inverted stagger) type. These active elements may be formed by using a semiconductor layer on an insulating surface, or may be formed in a single crystal or polycrystal semiconductor substrate.

The resistor may be formed between the active element and one electrode of the light emitting element connected thereto or between the other electrode of the light emitting element and the common potential line. As a material for forming the resistor, an amorphous film selected from C, Si and Ge, a microcrystalline or polycrystalline film, an amorphous film of SiC and SiGe,
Microcrystalline or polycrystalline coatings or their oxides, nitrides, oxynitrides are applied. In order to control the resistivity, P, B or the like may be appropriately doped therein. Other applicable materials include Ti, Mo, Ta, Al,
An amorphous, microcrystalline or polycrystalline film selected from W, In and Zn or their oxides, nitrides and oxynitrides are applied.

Further, it is possible to interpose a two-terminal non-linear element in addition to simply using the resistor film. A straightforward example is a diode, which is a pin diode, a pn diode, or a p diode formed by appropriately using Si, SiGe, or SiC.
i diode, in diode, nin diode, p
An ip diode or the like can be applied.

The charge injecting and transporting medium and the light emitting medium containing an organic compound or an inorganic compound in the light emitting device are one or more layers selected from low molecular weight organic compounds, medium molecular weight organic compounds and high molecular weight organic compounds. It may be combined with an inorganic compound having an electron injecting / transporting property or a hole injecting / transporting property. As the light-emitting body, a phenylanthracene derivative, a tetraaryldiamine derivative, a quinolinol complex derivative, a distyrylbenzene derivative, or the like can be applied. good.
As the high molecular weight organic compound, there are polyparaphenylene vinylene type, polyparaphenylene type, polythiophene type, polyfluorene type, etc., and poly (paraphenylene vinylene) (poly (p-phenylene vinylene)): (PPV), poly (2,5-dialkoxy-1,4-phenylene vinylene) (poly (2,5-dialkoxy-1,4-phenylene vinylene)):
(RO-PPV), poly (2- (2'-ethyl-hexoxy) -5-methoxy-1,4-phenylene vinylene)
(poly [2- (2'-ethylhexoxy) -5-methoxy-1,4-phenylenevi
nylene]): (MEH-PPV), poly (2- (dialkoxyphenyl) -1,4-phenylenevinylene) (poly [2
-(dialkoxyphenyl) -1,4-phenylene vinylene]): (RO
Ph-PPV), polyparaphenylene (poly [p-phenyle
ne]): (PPP), poly (2,5-dialkoxy-
1,4-phenylene) (poly (2,5-dialkoxy-1,4-phenyle
ne)): (RO-PPP), poly (2,5-dihexoxy-1,4-phenylene) (poly (2,5-dihexoxy-1,4-pheny
lene)), polythiophene: (P
T), poly (3-alkylthiophene)
hiophene)): (PAT), poly (3-hexylthiophene): (PHT), poly (3
-Cyclohexylthiophene) (poly (3-cyclohexylthio
phene)): (PCHT), poly (3-cyclohexyl-
4-methylthiophene) (poly (3-cyclohexyl-4-methylt
hiophene)): (PCHMT), poly (3,4-dicyclohexylthiophene)
e)): (PDCHT), poly [3- (4-octylphenyl) -thiophene] (poly [3- (4octylphenyl) -thiophe
ne]): (POPT), poly [3- (4-octylphenyl) -2,2bithiophene] (poly [3- (4-octylphenyl)-
2,2-bithiophene]): (PTOPT), polyfluorene (polyfluorene): (PF), poly (9,9-dialkylfluorene) (poly (9,9-dialkylfluorene): (PDA
F), poly (9,9-dioctylfluorene) (poly (9,
9-dioctylfluorene): (PDOF) and the like.
As the inorganic compound material, diamond-like carbon (D
LC), Si, Ge, and oxides or nitrides thereof, which may be appropriately doped with P, B, N, or the like. Further, an oxide, a nitride or a fluoride of an alkali metal or an alkaline earth metal, or at least Z with the metal.
It may be a compound or alloy of n, Sn, V, Ru, Sm and In.

The materials listed above are examples, and by using these materials, a hole injecting and transporting layer, a hole transporting layer, an electron injecting and transporting layer,
A light emitting element can be formed by appropriately laminating functional layers such as an electron transport layer, a light emitting layer, an electron block layer, and a hole block layer. Moreover, you may form the mixed layer or mixed junction which combined each of these layers.

The light emitting device of the present invention can form a pixel including a light emitting element, an active element and a resistor, and can function as a display body.

The resistance value of the resistor should take into consideration the current-voltage and the characteristics of the light emitting element having nonlinearity. When the maximum rated voltage, that is, the maximum emission brightness for practical use is taken as a reference, the resistance value of the current-voltage characteristic. The internal resistance value is determined to be 0.05 to 50 times the internal resistance value. In the present invention, the resistance value required by the resistor is ((resistance of light emitting element formed in one pixel / area of light emitting element formed in one pixel) × 0.05) Ω or more, ((one pixel Resistance of the light emitting element formed in / the area of the light emitting element formed in one pixel) x 5
0) Ω or less.

Alternatively, the current-voltage and characteristics of the light emitting element having nonlinearity should be taken into consideration, and the maximum rated voltage,
That is, with reference to the maximum emission luminance for practical use, the resistance value of the resistor is ((electric field applied to one pixel / current density flowing in one pixel) × 0.00 in consideration of the current-voltage characteristic.
5) Ω or more and ((electric field applied to one pixel / current density flowing in one pixel) × 50) Ω or less.

The resistance value of the resistor thus defined is
If it is less than the lower limit value, the effect of inserting the resistor cannot be sufficiently obtained, and if it is more than the upper limit value, the driving voltage increases and the driving voltage of the active element increases, which is a burden. That is, the light emitting device cannot be operated with a practical drive voltage.

Of course, the influence of heat generation cannot be ignored by interposing the resistor in this way.
However, the effect is that the lower layer side, upper layer side,
It is alleviated by using an insulating material having a high thermal conductivity on at least one of the side walls. As a material having high thermal conductivity, aluminum oxynitride (AlO _x N _1-x : x = 0.
01 to 20 atomic%), aluminum nitride, silicon nitride, and DLC are selected. Further, in order to dissipate the heat and suppress the temperature rise of the light emitting element, it is desirable that the light emitting element is pulse-lighted or intermittently lighted. In particular, when functioning as a display body, it is desirable to apply the time-division gradation driving method.

When a constant voltage is applied to the light emitting element, there is a phenomenon that the brightness decreases with time, which means an increase in internal resistance. Therefore, as a means for apparently reducing the change in the internal resistance, it is realized by interposing a resistor between the active element and the light emitting element or between the light emitting element and the common potential line. Further, by forming the light emitting element in contact with an insulating material having high heat conductivity, heat dissipation can be improved, and deterioration in temperature can be suppressed by suppressing an increase in temperature of the light emitting element. With such a configuration of the present invention, the stability of the light emitting device can be improved.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. A typical aspect of the light-emitting device according to this embodiment is a light-emitting element in which a charge-injecting / transporting medium containing an organic compound or an inorganic compound and a light-emitting medium are formed between a pair of electrodes, a resistor, and the light-emitting element. An image display unit is formed by arranging pixels provided with at least one active element for controlling an applied voltage in a matrix. The light-emitting device is shown in a perspective view in FIG. 1A, and FIG. 1B is a vertical cross-sectional view taken along the line AA ′ in FIG.
(C) has shown the longitudinal cross-sectional view of the BB 'line.

As shown in these figures, the light emitting device is an element substrate 1 provided with an image display area 12, a scanning line driving circuit 13, a data line driving circuit 14, an input / output terminal 15, and the like.
0 and the counter substrate 11 provided with the color filter 18
Are fixed by a sealing material 19.

As the element substrate 10, glass, quartz, plastic, semiconductor, metal substrate or the like is used. The counter substrate 11 is similar, but at least one of them is a translucent substrate so that the light emission of the light emitting element can be visually recognized. Further, the sealing material 19 is formed along the peripheral portion of the counter substrate 11, but in the positional relationship with the element substrate, it overlaps with the scanning line driving circuit 13 and the data line driving circuit 14 via the interlayer insulating film 16. Is formed. The interlayer insulating film 16 is formed to have a flat surface, but the outermost surface and side surfaces are formed of aluminum oxynitride (AlO _x N _1-x : x = 0.0).
1 to 20 atomic%), aluminum nitride, silicon nitride,
It is formed of an inorganic insulating material such as DLC, silicon nitride, or silicon oxynitride.

In the image display unit 12, a matrix is formed by the scanning lines and the data lines extending from the scanning line driving circuit 13 and the data line driving circuit 14, and a switching element group appropriately arranged at each place and the switching element group are arranged. A pixel matrix is formed from the organic light emitting element group 17 that is electrically connected. Although the scanning line drive circuit 13 is configured to be driven from both sides of the image display area 12, only one side may be provided if the signal delay does not matter.

In order to perform multicolor display, the light emitting element group 17 changes the emission color for each individual pixel, for example, R (red) G (green) B
The (blue) colors are arranged in rows or columns or in a delta arrangement to form the image display unit 12. Alternatively, white light emitting elements are uniformly formed over the entire surface, a color filter 18 facing the image display section 12 is provided, and a predetermined colored layer is arranged corresponding to each pixel. Color filter 18 is R (red)
Even when combined with a light emitting element that emits each color of G (green) and B (blue), it has an effect of increasing the color purity.

An input terminal portion 15 is formed on the outer peripheral portion of the element substrate 10, and various signals are input from an external circuit and connected to a power source. Further, the space surrounded by the element substrate 10 and the counter substrate 11 and the sealing material 19 is filled with an inert gas to prevent the organic light emitting element group 17 from being corroded.
There may be a desiccant such as barium oxide in this space.

A light emitting element which is a basic constituent element of a pixel,
The mutual relationship between the resistor and the active element is shown in FIGS.
2 is shown.

In FIG. 11A, a light emitting element 300 is a stack in which a layer 302 containing a charge injection transport medium containing an organic compound or an inorganic compound and a light emitting medium is formed between a first electrode 301 and a second electrode 303. A resistor 304 having a type structure and having a specific resistance ρ is formed on the surface of the first electrode on which the layer 302 including the charge injection transport medium containing the organic compound or the inorganic compound and the light emitting medium is not formed. Resistor 30
An electrode or wiring 305 connected to the active element 305 is formed on one side of the first electrode 301 and the resistor 30.
By the area where 4 and the electrode or wiring 305 overlap,
The resistance value of the resistor 304 connected in series between the active element 310 and the light emitting element 300 is defined.

The resistor 304 is an amorphous, microcrystalline or polycrystalline film selected from C, Si and Ge, SiC and Si.
Amorphous, microcrystalline, or polycrystalline coatings of Ge or their oxides, nitrides, oxynitrides can be applied. Further, in order to control the resistivity, P, B or the like may be appropriately doped. Other applicable materials include amorphous, microcrystalline, or polycrystalline films selected from Ti, Mo, Ta, Al, W, In, and Zn, or oxides, nitrides, and oxynitrides thereof. and so on. Further, not only the film of the resistor is used, but a two-terminal non-linear element may be interposed. A simple example is a diode, S
A pin diode, a pn diode, a pi diode, an in diode, a nin diode, a pip diode, or the like formed using i, SiGe, or SiC as appropriate can be used.

As described above, the resistivity of the resistor can be freely set depending on the film thickness and the overlapping area of the laminated body. The value to be set is one in which the current-voltage and characteristics of the light emitting element having nonlinearity are taken into consideration, and the maximum rated voltage,
That is, based on the maximum emission brightness for practical use, the internal resistance value obtained from the current-voltage characteristics is 0.05 to
Within 50 times the range. Specifically, the resistance value required by the resistor is ((resistance of the light emitting element formed in one pixel /
Area of light emitting element formed in one pixel) × 0.05) Ω or more and ((resistance of light emitting element formed in one pixel / area of light emitting element formed in one pixel) × 50) Ω or less To do so.

Alternatively, the current-voltage and characteristics of the light emitting element having nonlinearity should be taken into consideration, and the maximum rated voltage,
That is, with reference to the maximum emission luminance for practical use, the resistance value of the resistor is ((electric field applied to one pixel / current density flowing in one pixel) × 0.00 in consideration of the current-voltage characteristic.
5) Ω or more and ((electric field applied to one pixel / current density flowing in one pixel) × 50) Ω or less.

When a constant voltage is applied to the light emitting element, there is a phenomenon that the brightness decreases with time, which means that the internal resistance increases. Therefore, as a means for apparently mitigating the change in the internal resistance, the stability of luminance can be improved by interposing a resistor between the active element and the light emitting element or between the light emitting element and the common potential line. .

FIG. 11B shows an equivalent circuit diagram thereof. The light emitting element 300 has a series resistance Rs that is considered to be caused by the electric resistance of the thin film forming the diode D and the light emitting element.
, Capacitance C, and parallel resistance Rsh when leakage current flows
It is represented by.

FIG. 12A shows an example in which a resistor is provided on the second electrode 303 side. The second electrode 303 is connected to a common electrode that applies a constant potential. The same effect can be obtained by connecting the resistor to the second electrode side. Figure 1
2 (B) shows an equivalent circuit diagram thereof.

FIG. 2 shows an example of a circuit diagram of an image display portion of a light emitting device formed with such a pixel structure. One pixel 200 has TFTs 201, 202, 20
3, the light emitting element 205, and the resistor 204 are included.
The TFT 201 is turned on based on the signal of the scanning signal line 207.
The TFT 203, which is an address selection unit that is turned off,
Is a driving unit for controlling the light emission of the light emitting element 205, and T
The FT 202 is a control unit that performs an on / off operation based on a signal on the erase signal line 208, controls conduction of the TFT 203, and forcibly causes light emission and non-light emission.

The resistor 204 inserted in series between the TFT 203 and the light emitting element 205 has a function of alleviating the influence of the resistance change of the light emitting element 205 and suppressing the change in the luminance, especially during constant voltage driving. You can

3 and 4 are diagrams for explaining this effect. FIG. 3 shows a conventional configuration without a resistor,
203 and the light emitting element 205 are directly connected. The light emitting element 205 is shown by its equivalent circuit, and is represented by a series resistance Rs, which is considered to be caused by the electric resistance of the thin film forming the diode D and the light emitting element, a capacitance C, and a parallel resistance Rsh when a leakage current flows. ing. In addition, here Rsh
>> Rs is considered by ignoring the influence of the parallel resistance.

Here, the power supply line 20 is passed through the TFT 203.
When the voltage V is applied from No. 9, the current I flowing through the light emitting element 205 is represented by V / Rs. After that, when the light emitting element deteriorates and the series resistance increases to Rs + r, the current value I ′ after deterioration becomes V / (Rs + r), and the series resistance change of the light emitting element directly affects. Assuming that the increase in resistance due to deterioration is r = Rs, the current value is halved.

On the other hand, when a resistor 204 having a resistance value Re is inserted in series between the TFT 203 and the light emitting element 205 as shown in FIG. 4, in order to obtain the same brightness, the voltage applied from the power source line 209 as V + V ′. Need to raise,
The current I becomes (V + V ') / (Rs + Re). After that, when the light emitting element deteriorates and the series resistance increases to Rs + r, the current value I ′ after deterioration is (V + V ′) / (Rs + r + R
e). Assuming that Rs = r = Re, the change in the current value is 2/3, and comparing the apparent fluctuation rates, the presence of the high resistance element is smaller.

An example of a specific structure of the pixel 200 shown in FIG. 2 is shown in FIG. FIG. 5 shows the main constituent elements of the circuit, and shows the positional relationship between the TFTs 201, 202, 203 and the scanning signal line 207, the erase signal line 208, and the power supply line 209.

The pixel structure shown in FIG. 5 is formed on an insulating surface formed on the main surface of glass, quartz, plastic, or a semiconductor or metal material as a substrate. In the manufacturing process, as shown in FIG. 6, after the semiconductor layers 103 and 104 which are divided into islands are formed, the scan signal line 207, the erase signal line 208, and the gate electrode are formed through a gate insulating film. Form 106. The scanning signal line 207 and the erasing signal line 208 overlap with the semiconductor layer 103 to form gates in separate TFTs. The semiconductor layer is preferably formed using crystalline silicon, and the source and drain regions, the low concentration drain region, and the like may be formed as appropriate. Further, the semiconductor layer and the wiring forming the gate may be laminated to form a bottom gate type (inverse stagger type) TFT by forming the wiring first on the insulating surface.

After that, an interlayer insulating film is formed, and the first electrode 211 of the light emitting element is formed. When the electrode 211 is used as a hole injecting electrode, a conductive material having a work function of 4 eV or more such as indium tin oxide alloy generally called ITO, ZnO, TiN, TaN is usually applied. Or this first
When the electrode 211 is used as an electron injection electrode, its surface is formed of an alloy containing an alkali metal or an alkaline earth metal, or various compounds such as oxides, fluorides and nitrides.

After that, as shown in FIG.
Pixels are formed by forming 6, 209, 210 and 212. In addition, a partition layer 213 that covers the outer peripheral portion of the first electrode 211 of the light emitting element is formed, and a layer containing an organic compound that serves as a light emitting body is formed thereover, so that the light emitting element is formed in a self-aligned manner. The first electrode 211 of the light emitting element and the TFT 20
A resistor is provided between the switch and the switch 3.
It is illustrated in a longitudinal section according to the line A '.

In one embodiment shown in FIG. 7, the base insulating film 102, the semiconductor layer 106, the gate insulating film 105,
A gate electrode 106, a first inorganic interlayer insulating film 107, an organic interlayer insulating film 108, and a second inorganic interlayer insulating film 109 are formed. In the source and drain regions 110 formed in the semiconductor layer 104, a power supply line 209 and a wiring 212 connected to a light emitting element are formed.

The first inorganic interlayer insulating film 107 is formed of silicon nitride or silicon oxynitride, and the alkali metal or alkaline earth metal, which is a constituent material of the electrode of the light emitting element, is used as the semiconductor layer 1.
It is prevented from spreading to 06. The organic interlayer insulating film 108 is made of acrylic, polyimide, polyimideamide, or the like by a coating method and has a flat surface to improve the coverage of the light emitting element formed in the upper layer. Second interlayer insulating film 10
For the purpose of forming a dense film on the organic interlayer insulating film 108, silicon nitride, aluminum nitride oxide, or aluminum nitride formed by a high frequency sputtering method is applied. From the viewpoint of dissipating the heat generated by the TFT and the light emitting element, it is preferable to apply an insulating material having a high thermal conductivity to this portion, and aluminum nitride, aluminum oxynitride and the like are suitable in this respect.

A resistor 215 is interposed between the first electrode 211 of the light emitting element and the wiring 212. Resistor is C, S
i, Ge, amorphous, microcrystalline, or polycrystalline film, SiC, SiGe amorphous, microcrystalline, or polycrystalline film, or oxides, nitrides, or oxynitrides thereof Thing is applied. In order to control the resistivity, P, B or the like may be appropriately doped therein. As other applicable materials, an amorphous, microcrystalline, or polycrystalline film selected from Ti, Mo, Ta, Al, W, In, and Zn or their oxides, nitrides, oxynitrides Is applied.

Of course, the actual resistance value can be adjusted by the area of the connecting portion and the thickness of the film, and the standard of the resistance value to be interposed is the internal resistance at the time of applying the maximum rated voltage applied to the light emitting element. It is defined by the resistivity such that the value is in the range of 0.05 to 50 times.

The advantage of providing the resistor will be described with reference to FIG. As shown in the inset diagram, FIG. 16 shows the current-voltage characteristics of both terminals of a fixed resistor Rd connected to the light emitting element. When Rd = 0, the current-voltage characteristic with a considerably large slope is shown. On the other hand, the slope becomes smaller as Rd is increased. The light emitting element shows the same tendency as the internal resistance value increases as the luminance deteriorates, but by connecting the fixed resistance in advance, the influence (variation rate) of the internal resistance change can be reduced, and The change over time can be reduced.

The resistance value of the light emitting element varies depending on the structure and area of the layer containing the organic compound which becomes the light emitting body. Light emitting elements are indium tin oxide alloy (ITO), zinc oxide (Zn oxide)
O), indium zinc oxide (IZO), etc., an organic compound formed to a thickness of 30 to 150 nm on the first electrode 211 formed to a thickness of 30 to 150 nm, and a thickness of 10 to 1000 nm, preferably 50 to 150 nm. Alternatively, a layer 112 including a charge injection transport medium containing an inorganic compound and a light emitting medium, and CsF, B
The second electrode 113 is made of a conductive material containing an alkali metal or an alkaline earth metal such as aF, CaF, MgAg, and AlLi.

The partition layer 111 has an opening above the first electrode 211 and is formed so as to surround the side surface thereof. For the purpose of relaxing the stress of the layer 112 containing the charge injecting and transporting medium containing the organic compound or the inorganic compound and the light emitting medium, which is formed in the upper layer of these members, 0.
It has a curvature of 2 to 3 μm, and the inclination angle of the side wall is 35 to 35
It may be formed at 70 degrees.

The layer 112 containing the charge injecting and transporting medium containing an organic compound or an inorganic compound and the light emitting medium is one or more layers selected from a low molecular weight organic compound, a medium molecular weight organic compound and a high molecular weight organic compound. And may be combined with an inorganic compound having an electron injecting / transporting property or a hole injecting / transporting property.
As the light emitter, a phenylanthracene derivative, a tetraaryldiamine derivative, a quinolinol complex derivative, a distyrylbenzene derivative, or the like can be applied, and using this as a host substance, a coumarin derivative, DCM, quinacridone,
Rubrene or the like may be added as a dopant. As the high molecular weight organic compound, there are polyparaphenylene vinylene type, polyparaphenylene type, polythiophene type, polyfluorene type, etc., and poly (paraphenylene vinylene) (poly (p-phenylene vinylene)): (PPV), poly (2,5-dialkoxy-1,4-phenylene vinylene) (poly (2,5-dialkoxy-1,4-phenylene vinylene)):
(RO-PPV), poly (2- (2'-ethyl-hexoxy) -5-methoxy-1,4-phenylene vinylene)
(poly [2- (2'-ethylhexoxy) -5-methoxy-1,4-phenylene v
inylene]): (MEH-PPV), poly (2- (dialkoxyphenyl) -1,4-phenylenevinylene) (poly
[2- (dialkoxyphenyl) -1,4-phenylene vinylene]): (R
OPh-PPV), polyparaphenylene (poly [p-pheny
lene]): (PPP), poly (2,5-dialkoxy-
1,4-phenylene) (poly (2,5-dialkoxy-1,4-phenyle
ne)): (RO-PPP), poly (2,5-dihexoxy-1,4-phenylene) (poly (2,5-dihexoxy-1,4-pheny
lene)), polythiophene: (P
T), poly (3-alkylthiophene)
hiophene)): (PAT), poly (3-hexylthiophene): (PHT), poly (3
-Cyclohexylthiophene) (poly (3-cyclohexylthio
phene)): (PCHT), poly (3-cyclohexyl-
4-methylthiophene) (poly (3-cyclohexyl-4-methylt
hiophene)): (PCHMT), poly (3,4-dicyclohexylthiophene)
e)): (PDCHT), poly [3- (4-octylphenyl) -thiophene] (poly [3- (4octylphenyl) -thiophe
ne]): (POPT), poly [3- (4-octylphenyl) -2,2bithiophene] (poly [3- (4-octylphenyl)-
2,2-bithiophene]): (PTOPT), polyfluorene (polyfluorene): (PF), poly (9,9-dialkylfluorene) (poly (9,9-dialkylfluorene): (PDA
F), poly (9,9-dioctylfluorene) (poly (9,
9-dioctylfluorene): (PDOF) and the like.
As the inorganic compound material, diamond-like carbon (D
LC), Si, Ge, and oxides or nitrides thereof, which may be appropriately doped with P, B, N, or the like. Further, an oxide, a nitride or a fluoride of an alkali metal or an alkaline earth metal, or at least Z with the metal.
It may be a compound or alloy of n, Sn, V, Ru, Sm and In.

In the low molecular weight organic compound, copper phthalocyanine (CuPc) and MTDA which is an aromatic amine material
A hole injecting and transporting layer formed of TA and α-NPD and an electron injecting layer and a light emitting layer formed of tris-8-quinolinolato aluminum complex (Alq ₃ ) can be formed by stacking. Alq ₃ enables light emission (fluorescence) from the singlet excited state. In order to increase the brightness, it is preferable to utilize the light emission (phosphorescence) from the triplet excited state. In this case, CuPc, which is a phthalocyanine-based material, and α-, which is an aromatic amine-based material, are used as the layer 21 including the charge injection transport medium containing an organic compound or an inorganic compound and the light emitting medium.
On the hole injecting and transporting layer formed of NPD, a light emitting layer is formed by using carbazole-based CBP + Ir (ppy) ₃ , and further, by using bathocuproine (BCP), a hole blocking layer and an electron injecting and transporting layer by Alq _3. It is also possible to have a laminated structure.

Although the above two structures are examples using low molecular weight organic compounds, it is also possible to realize an organic light emitting device in which a high molecular weight organic compound and a low molecular weight organic compound are combined. For example, from the anode side as the layer 21 containing a charge injection transport medium containing an organic compound or an inorganic compound and a light emitting medium,
Polythiophene derivative of high molecular organic compound (PEDO
T) hole injection / transport layer, α-NPD hole injection / transport layer, CBP + Ir (ppy) ₃ light-emitting layer, BC
A hole blocking layer made of P and an electron injection transport layer made of Alq ₃ may be laminated. By changing the hole injection layer to PEDOT, the hole injection characteristics are improved and the light emission efficiency can be improved.

An inorganic compound material may be used for the hole injecting / transporting layer and the electron injecting / transporting layer. As the inorganic compound material, diamond-like carbon (DLC), Si, G
e, and oxides or nitrides of these, P, B, N
Etc. may be appropriately doped. Further, oxides, nitrides or fluorides of alkali metals or alkaline earth metals, and at least Zn, Sn, V, Ru, and
It may be a compound or alloy of Sm and In.

Table 1 shows an example of the internal resistance value of the light emitting device obtained when the low molecular weight organic compound material is used and when the high molecular weight organic compound material is used. In Table 1, the area of the light emitting element is 0.1 mm ² . The structure of the light emitting element using the low molecular weight organic compound material is CuP on the first electrode 223.
c is 20 nm, α-NPD is 60 nm, Alq3: DMQd
Is laminated with 38 nm and Alq3 is laminated with 38 nm, and the second electrode is CaF.
Is 1 nm and Al is 200 nm. The structure of the light emitting device using the high molecular organic compound material is PEDOT of 30 nm, P
PV is formed to 80 nm and Ca is 20 nm as the second electrode, A
1 has a structure in which 100 nm is laminated.

As an example of a mode in which an inorganic compound material is combined with these organic compound materials, diamond-like carbon (DLC) of 2 to 3 nm is formed on PEDOT, and a layer containing a light emitting body is formed thereon. Or PEDO
A 2-3 nm DLC is formed on T to form a hole injecting and transporting layer and a light emitting layer. Or, 2-3nm D on PEDOT
The LC laminate is repeatedly laminated two or more times.
Alternatively, a light emitting layer that emits the same color or a different color and a DLC are stacked, and a plurality of stacked layers are stacked. Since DLC has a high thermal conductivity, by combining DLC as an inorganic compound material in this way, it is possible to impart an effect of suppressing a temperature rise due to heat generation of the light emitting element and reducing deterioration of brightness.

The resistance value per pixel is different between a low molecular weight element using a low molecular weight organic compound material and a high molecular weight element using a high molecular weight organic compound material, and it varies depending on driving conditions. The area of the light emitting element is 4.8 × 10 ^-5 cm ²
Resistance of 8MΩ~34MΩ is obtained when light is emitted at a luminance of 100cd / m ² ~200cd / m ² as. In the present invention, the resistance value required by the resistor is ((resistance of light emitting element formed in one pixel / area of light emitting element formed in one pixel) × 0.05) Ω or more, ((in one pixel (Resistance of formed light emitting element / area of light emitting element formed in one pixel)
× 50) Ω or less. Alternatively, the current-voltage and characteristics of the light-emitting element having non-linearity should be considered, and its maximum rated voltage, that is, the maximum emission brightness for practical use as a reference, in consideration of its current-voltage characteristics,
The resistance value of the resistor is ((electric field applied to one pixel / current density flowing in one pixel) × 0.05) Ω or more, ((electric field applied to one pixel / current density flowing in one pixel) × 50) Be less than Ω.

Based on the results of Table 1, it is sufficient to insert a resistance of 0.8 to 340 MΩ into one pixel in accordance with the resistivity of the light emitting element.

[0063]

[Table 1]

The resistance value suitable for connecting to the light emitting element is
Originally it depends on the driving conditions. The light emission brightness of the light emitting element is proportional to the current density flowing as shown in FIG.
As shown in FIG. 14, the applied voltage changes exponentially. That is, the current-voltage characteristics of the light emitting element show non-linearity as shown in FIG. 15, and the resistance value at that time changes continuously when the applied voltage changes. Therefore, the resistance value of the resistors inserted in series should be defined within a predetermined range within a range where practical brightness can be obtained.

If the resistance value of the resistor is sufficiently large in comparison with the resistance value of the light emitting element, it is possible to further stabilize the change in luminance with time. However, since the applied voltage for causing the light emitting element to emit light increases accordingly, it is necessary to select an appropriate resistance value in consideration of the driving voltage of the light emitting device.

By forming the resistor 215 between the TFT and the first electrode of the light emitting element, it is possible to function as a protective resistor for preventing the TFT from being destroyed by static electricity. That is, when the layer 112 including the charge injecting and transporting medium containing an organic compound or an inorganic compound and the light emitting medium and the cathode 113 are formed by a film forming method involving charged particles such as electron beam evaporation or sputtering, the first electrode 211 serves as an antenna. It is possible to prevent electrostatic breakdown of the TFT connected to it.

By forming the resistor in this way,
Although the number of heat generating points when the light emitting element is driven increases, by using a member having high thermal conductivity for the second inorganic interlayer insulating film 109 as shown in FIG. 7, heat is dissipated to the peripheral portion, The temperature rise of the light emitting element due to heat generation can be suppressed. In order to obtain such an effect, the second electrode 113
You may form the film of the same material on the top. Aluminum oxynitride (AlO _x N _1-x :
x = 0.01 to 20 atomic%), aluminum nitride, silicon nitride, DLC and the like can be selected.

An arrangement of resistors different from that of FIG. 7 is shown in FIG.
And a power line 209 is formed on the second inorganic interlayer insulating film 109.
After forming the wiring 212 connected to the light emitting element, the resistor 2
15 is formed on almost the entire surface. afterwards,
The first electrode 211 of the light emitting element is formed. At this time, the resistor
The resistance value substantially given by 215 is the same as the resistance of the wiring 212.
It is defined by the area where the body 215 and the first electrode 213 overlap.
It In addition, a third layer that covers the top surface and the side surface of the partition layer 111 is formed.
The inorganic insulating film 116 is formed of aluminum oxynitride (AlO
_xN_1-x: X = 0.01 to 20 atomic%), aluminum nitride
Light emission by forming it with silicon, silicon nitride, or DLC.
The heat generated by the element is dissipated and the temperature rises from that area.
A charge injection transport medium containing an organic compound or an inorganic compound, and
It is possible to prevent alteration of the luminescent medium. TFT203
Other components are the same as in FIG. 7.

Further, in the structure shown in FIG. 9, after forming the wiring 212 connecting the power source line 209 and the light emitting element on the second inorganic interlayer insulating film 109, the resistor 215 is left and the second organic interlayer insulating film is formed. A film 115 is formed to form a first light emitting device.
The electrode 211 is formed and electrically connected to the wiring 212. In this connection, the resistor 215 is interposed. That is, the substantial resistance value given by the resistor 215 is
It is defined by the area of the contact portion where the wiring 212, the resistor 215, and the first electrode 211 overlap.

An example of forming a resistor on the second electrode side is shown in FIG.
It is shown at 0. In FIG. 10, the first electrode 211 of the light emitting element and the partition layer 111 are formed as in FIG. 7, and then the layer 112 including the charge injection transport medium containing an organic compound or the inorganic compound and the light emitting medium is formed. After that, the second electrode 1
13 is formed in a predetermined pattern, and using this as an etching mask, the layer 112 containing the charge injection transport medium containing the organic compound or the inorganic compound and the light emitting medium on the lower layer side is removed.
After that, the resistor 215 and the wiring 115 are formed, so that the resistor can be formed on the electrode side to which the common potential is applied. The substantial resistance value given by the resistor 215 in this connection is defined by the area where the second electrode 113 and the resistor 215 overlap.

Various electronic devices can be completed by the light emitting device of the present invention described above. Examples thereof include personal digital assistants (electronic notebooks, mobile computers, mobile phones, etc.), video cameras, digital cameras, personal computers, television receivers, mobile phones, and the like. Examples of those are shown in FIG.

FIG. 17A shows an example in which the present invention is applied to complete a television receiver, and includes a housing 3001 and a support base 30.
02, a display unit 3003, and the like. The present invention makes it possible to complete a television receiver.

FIG. 17B shows an example in which a video camera is completed by applying the present invention. The main body 3011 and the display unit 30 are shown.
12, a voice input unit 3013, operation switches 3014, a battery 3015, an image receiving unit 3016, and the like. A video camera can be completed by the present invention.

FIG. 17C shows an example in which a notebook personal computer is completed by applying the present invention, which is composed of a main body 3021, a housing 3022, a display portion 3023, a keyboard 3024, and the like. According to the present invention, a personal computer can be completed.

FIG. 17D shows the PDA (Per
This is an example of the completion of a sonal digital assistant), and includes a main body 3031, a stylus 3032, a display portion 3033, operation buttons 3034, an external interface 3035, and the like. A PDA can be completed according to the present invention.

FIG. 17 (E) is an example in which the present invention is applied to complete a sound reproducing device, specifically, a vehicle-mounted audio device, which is a main body 3041, a display portion 3042, operation switches 3043, 3044. It is composed of. The present invention can complete an audio device.

FIG. 17F shows an example in which the present invention is applied to complete a digital camera. The main body 3051 and the display section are shown.
(A) 3052, eyepiece 3053, operation switch 305
4, a display unit (B) 3055, a battery 3056, and the like. According to the present invention, a digital camera can be completed.

FIG. 17G shows an example in which a mobile phone is completed by applying the present invention. The main body 3061 and the voice output section 30 are shown.
62, a voice input unit 3063, a display unit 3064, operation switches 3065, an antenna 3066, and the like. According to the present invention, a mobile phone can be completed.

In addition to the above, in addition to a navigation system, a sound reproducing device (car audio system, audio component system, etc.), a personal computer, a game machine, a portable information terminal (mobile computer, mobile phone, portable game machine, electronic book, etc.) Home appliances such as refrigerators, refrigerators, washing machines, rice cookers, landline phones, vacuum cleaners, and thermometers, hanging advertisements in trains, large-area information displays such as train station and airport arrival / departure information boards Can be applied to.

Although the structure in which the resistor is provided in the pixel portion including the light emitting element and the active element has been described with reference to FIGS. 7 to 10, the present invention is not limited to this embodiment, and these elements can be freely arranged. It can be implemented in combination. The preferred embodiments of the present invention have been described above, but it is understood by those skilled in the art that the modes and details can be variously changed without departing from the spirit and scope of the present invention. If so, it is easily understood.

[0081]

As described above, the resistor is connected in series between the light emitting element and the active element for controlling the light emission, or between the light emitting element and the common potential line for applying a constant potential. By providing the light emitting element, a change in luminance of the light emitting element with time can be reduced. That is, the structure of the present invention can improve the stability of the light emitting device. By forming the resistor as a thin film on the wiring connecting the active element and the light emitting element or on one surface of the electrode of the light emitting element, the resistor can be formed in each pixel without impairing the aperture ratio. Such an effect can be remarkably achieved during constant voltage driving.

[Brief description of drawings]

FIG. 1 is a perspective view and a vertical cross-sectional view illustrating a configuration of a light emitting device of the present invention.

FIG. 2 is an equivalent circuit diagram of an image display unit of the light emitting device of the present invention.

FIG. 3 is a diagram illustrating a conventional pixel configuration and an amount of change in luminance due to change over time.

FIG. 4 is a diagram illustrating the pixel configuration of the present invention and the amount of change in luminance due to change over time.

FIG. 5 is a top view showing a pixel configuration of a pixel of the present invention.

FIG. 6 is a top view illustrating a manufacturing process of a pixel of a pixel of the present invention.

FIG. 7 is a top view showing a pixel configuration of a pixel of the present invention, and is a vertical cross-sectional view showing one arrangement example of a resistor.

FIG. 8 is a top view showing a pixel configuration of a pixel of the present invention, and is a vertical cross-sectional view showing one arrangement example of a resistor.

FIG. 9 is a top view showing a pixel configuration of a pixel of the present invention, and is a vertical cross-sectional view showing one arrangement example of a resistor.

FIG. 10 is a top view showing a pixel configuration of a pixel of the present invention, and is a vertical cross-sectional view showing one arrangement example of a resistor.

FIG. 11 is a diagram illustrating a connection of a light emitting element, an active element, and a resistor, which is a configuration of a pixel according to the present invention.

FIG. 12 is a diagram illustrating a connection of a light emitting element, an active element, and a resistor, which is a configuration of a pixel according to the present invention.

FIG. 13 is a graph showing current vs. emission luminance characteristics of a light emitting device.

FIG. 14 is a graph showing voltage vs. emission luminance characteristics of a light emitting device.

FIG. 15 is a graph showing voltage-current characteristics of a light emitting device.

FIG. 16 is a graph showing voltage-current characteristics when a resistor is connected in series to a light emitting device.

FIG. 17 is a diagram showing a specific application example of a light emitting device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shunpei Yamazaki             398 Hase, Atsugi City, Kanagawa Prefecture, Ltd.             Conductor Energy Laboratory F-term (reference) 3K007 AB11 BB07 CC05 DB03 GA00                 5C094 AA23 AA42 BA03 BA23 BA27                       CA19 EA04 EA07

Claims (12)

[Claims] 1. A light emitting device having a charge injecting / transporting medium containing an organic compound or an inorganic compound and a light emitting medium formed between a pair of electrodes, the charge injecting / transporting medium of at least one of the pair of electrodes, and A light emitting device, wherein a resistor is provided on the opposite surface on which the light emitting medium is not formed, and a control means for applying a voltage to the light emitting element via the resistor is provided. 2. A charge injecting / transporting medium containing an organic compound or an inorganic compound and a light emitting element formed between a pair of electrodes, wherein the charge injecting / transporting medium of at least one electrode of the pair of electrodes and A resistor is provided on the opposite surface where the light emitting medium is not formed, one electrode of the light emitting element is connected to a control means for applying a voltage, and the other electrode applies a constant potential through the resistor. A light-emitting device characterized by being connected to a common electrode. 3. A light emitting device having a charge injecting and transporting medium containing an organic compound or an inorganic compound and a light emitting medium formed between a pair of electrodes, and a field effect transistor, wherein at least one electrode of the pair of electrodes. A resistor is provided on the opposite surface where the charge injection transport medium and the light emitting medium are not formed, and the field effect transistor controls the light emission by applying a voltage to the light emitting element via the resistor. A light-emitting device having a pixel. 4. A light emitting device, in which a charge injection transport medium containing an organic compound or an inorganic compound and a light emitting medium are formed between a pair of electrodes, and a field effect transistor, and at least one electrode of the pair of electrodes. A resistor is provided on the surface on the opposite side where the charge injection transport medium and the light emitting medium are not formed, one electrode of the light emitting element is connected to the source or drain of the field effect transistor, and the other electrode is A light-emitting device comprising: a pixel connected to a common electrode for applying a constant potential via a resistor and controlling light emission by applying a voltage to the light-emitting element by the field-effect transistor. 5. A light emitting device having a charge injecting and transporting medium containing an organic compound or an inorganic compound and a light emitting medium formed between a pair of electrodes, and a field effect transistor, wherein at least one electrode of the pair of electrodes. And a field-effect transistor, and a resistor is connected in series between the field-effect transistor and the field-effect transistor, and a pixel for controlling light emission by applying a voltage to the light-emitting element via the resistor by the field-effect transistor is provided. A light-emitting device characterized by being provided. 6. A light emitting device having a charge injection transport medium containing an organic compound or an inorganic compound and a light emitting medium formed between a pair of electrodes, a field effect transistor, and at least one of the pair of electrodes. A resistor is provided on the surface of the electrode of the light emitting element opposite to the side where the charge injection transport medium and the light emitting medium are not formed, and one electrode of the light emitting element is connected to the source or drain of the field effect transistor, and the other electrode Is connected in series to a common electrode that applies a constant potential via the resistor, and a pixel for controlling light emission by applying a voltage to the light emitting element via the resistor by the field effect transistor is provided. A light-emitting device characterized by being provided. 7. The method according to any one of claims 1 to 6,
The light emitting device, wherein the resistor includes one or more selected from C, Si and Ge. 8. The method according to any one of claims 1 to 6,
The resistor is made of Ti, Mo, Ta, Al, W, In, Z.
A light-emitting device comprising one or more kinds selected from oxides or nitrides of n. 9. The method according to any one of claims 1 to 6,
The resistance value of the resistor is 0.05 to 5 with respect to the value of the internal resistance when the maximum rated voltage applied to the light emitting element is applied.
A light-emitting device characterized by being in a range of 0 times. 10. The resistance value of the resistor according to claim 1, wherein the resistance value of the resistor is ((resistance of light emitting element formed in one pixel / area of light emitting element formed in one pixel) ×
0.05) Ω or more, ((resistance of light emitting element formed in one pixel / area of light emitting element formed in one pixel) × 50) Ω
The following is a light-emitting device. 11. The resistance value of the resistor according to claim 1, wherein the resistance value is ((electric field applied to one pixel / current density flowing in one pixel) × 0.05) Ω or more,
((Electric field applied to one pixel / current density flowing in one pixel)
× 50) Ω or less, a light emitting device. 12. The light emitting device according to claim 1, wherein the light emitting element emits light by applying a constant voltage based on a digital video signal.