JP2000307119A - Drive device of organic el element and organic el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous emission of light, reduction in contrast, and variability in brightness by a method wherein a switching element composed of a control electrode, and a set of control electrodes formed on a non-single crystal silicon substrate where an active layer is specified in thickness and an EL element equipped with an organic layer concerned in the function of light emission, are provided. SOLUTION: An insulated gate 3 is laminated on an island of a crystallized active layer (polysilicon layer) 2a above the surface of an insulating substrate 1. It is preferable that the active layer or an α-Si film is formed as thick as 100 to 800 Å, preferably 300 to 500 Å. A drain wiring electrode 12 and a source wiring electrode 13 are each formed in a drain connection part and a source connection part which are previously opened so as to be connected to a drain electrode and a source electrode. In this case, either the drain or the source electrode functions as the first or second electrode of an organic EL element or is connected to it. Furthermore, an insulating film 14 is formed on the drain wiring electrode 12, and an edge cover which covers a part other than a pixel part is provided for the formation of a switching element. An organic EL element electrode has a connection metal layer formed between a hole injection electrode 15 and the wiring electrode 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an organic EL device, and more particularly to a driving device for an organic EL device using a thin film transistor having a non-single-crystal semiconductor thin film as a base.

[0002]

2. Description of the Related Art Conventionally, in an organic EL display device (display), there has been known a technology for displaying an image by simply driving an XY matrix circuit (Japanese Patent Laid-Open No. 2-37).
385, JP-A-3-233891, etc.).
However, in such simple driving, line-sequential driving is performed, and when the number of scans is as large as several hundreds, the required instantaneous luminance is several hundred times the observed luminance. There was a problem.

(1) The driving voltage increases. Since the voltage is usually two to three times or more that under a DC steady voltage, the efficiency is reduced. Therefore, power consumption increases. (2) Since the amount of current flowing instantaneously becomes several hundred times, the organic light emitting layer is easily deteriorated. (3) As in the case of (2), since the flowing current is very large, a voltage drop in the electrode wiring becomes a problem.

The following active matrix drive has been proposed as a method for solving the above (1) to (3). That is, a display using ZnS, which is an inorganic substance, as a phosphor and further performing active matrix driving is disclosed (US Pat. No. 4,143,297).
issue). However, in this technique, since the inorganic phosphor is used, the driving voltage is as high as 100 V or more, which is a problem. A similar technique is IEEE Trans Electr.
on Devices, 802 (1971). On the other hand, recently, a large number of displays that perform active matrix driving using an organic phosphor have been developed (Japanese Patent Application Laid-Open Nos. 7-122360 and 7-122).
No. 361, JP-A-7-153576, JP-A-8-54836, JP-A-7-111341, JP-A-7-310290, JP-A-8-109
370, JP-A-8-129359, JP-A-8-241047 and JP-A-8-227276.
Issue publication). In the above technique, the driving voltage is drastically reduced to 10 V or less by using an organic phosphor, and the efficiency is 3 lm / w or higher when a highly efficient organic phosphor is used.
There were excellent features such as extremely high efficiency in the range of 15 lm / w, and the driving voltage of the high-definition display was reduced to 1/2 to 1/3 compared to the simple driving, and the power consumption could be reduced. However, the following points were problems.

One of the characteristics of the switching elements constituting a TFT is an off current Ioff that flows during non-operation. When the off-current Ioff increases, an erroneous light emission phenomenon or a decrease in contrast occurs, which significantly lowers the quality of the display device.

Another characteristic of the switching element is an S value (sub-threshold coefficient). Generally, in a switching element such as a TFT, it is considered that the smaller the S value, the better. This is because when the S value is small, the switching operation can be performed with a small change in voltage. However, when driving an organic EL element which is a current light emitting element, when the S value is large, the variation of the switching element is liable to occur as a change in light emission luminance as it is, and the light emission luminance varies between pixels and products.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic EL device which prevents erroneous light emission and lowering of contrast, does not cause variation in light emission luminance between pixels and products, and has a high operation speed. A driving device and an organic EL display device using the driving device.

[0008]

That is, the above object is achieved by the following constitutions. (1) A switching element in which a control electrode and a set of controlled electrodes are formed on a non-single-crystal silicon substrate, and an organic EL element driven by the switching element and having at least an organic layer involved in a light emitting function. The driving device for an organic EL element, wherein the switching element has an active layer made of a non-single-crystal silicon substrate having a thickness of 100 to 800 °. (2) The switching element has an S value of 0.8 (V / d
ecade) or more. (3) The off current of the switching element is 1 × 10
The driving device for an organic EL device according to the above (1) or (2), wherein the driving voltage is ^-8 A or less. (4) An organic EL display device in which the organic EL element driving devices according to any one of (1) to (3) are arranged in a matrix.

[0009]

[Function] Since the organic EL element is a current light emitting element, it is affected by current fluctuation due to variation of the switching element.
Light emission luminance tends to vary. In particular, an element having a large S value can switch the current on the controlled side by a slight change in the control voltage, but the on-state current varies due to a variation in the threshold value between the elements due to variations in element characteristics or changes over time. A large difference occurs.

Therefore, by setting the S value to a certain value or more and keeping the ratio of the change of the controlled current / the change of the threshold voltage small, the organic E due to the variation of the switching element is reduced.
Variations in light emission luminance among the L elements can be suppressed.

[0011] Here, the S value, referred to as a sub-threshold coefficient, for example, in the case of _{FET, S = ∂V gs / ∂log} 10 I ds (V / decade) V gs: drain - gate voltage I _ds: drain -It is expressed by the source-to-source current.

The relationship between the S value, the variation in Ion, and the electric field mobility is as shown in FIG. 9 of the embodiment of the present invention. As is clear from the graph of FIG. 9, when the S value decreases, the dispersion of Ion and the electric field mobility increase. And the S value is 0.8
As the temperature becomes lower, the variation of Ion becomes 40 or more, but the electric field mobility also becomes 40 or more. Here, the variation of Ion is shown as a percentage of the value obtained by dividing the standard deviation of the variation of Ion by the average value of Ion.

The relationship between the electric field mobility and the thickness of the active layer is as shown in FIG. 10, for example. The relationship between the electric field mobility and the thickness of the active layer depends on the method of forming the active layer, but as is clear from the graph of FIG. Also, it is difficult to make the electric field mobility 30 (cm ² / V · sec) or more.

The off current and the thickness of the active layer have a relationship as shown in FIG. 11, for example. As is clear from this graph, when the thickness of the active layer exceeds 1000 °, the off-current increases and the characteristics of the TFT deteriorate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic EL device driving apparatus according to the present invention comprises a switching element in which a control electrode and a set of controlled electrodes are formed on a silicon substrate, and is driven by the switching element to at least emit light. An organic EL element having an organic layer involved in the operation of the switching element, wherein the switching element has an active layer thickness of 100 to 1000
Å, and the S value is more than 0.8 (V / decade).

As described above, by restricting the thickness of the active layer of the silicon substrate, an increase in off current can be suppressed. Further, the S value is adjusted to 0.
By setting it to be more than 8 (V / decade), it is possible to suppress a variation in light emission luminance due to a variation in characteristics between elements.

In the switching element of the present invention, a control electrode and a set of controlled electrodes are formed on a silicon substrate, and
There is no particular restriction on the semiconductor as long as it is a semiconductor that directly drives the L element.
(Thin Film Transistor) type is preferable.

The substrate used in the present invention is preferably insulating and made of a transparent material such as quartz, sapphire or glass. Here, “transparent” means that the organic EL display device has a property of transmitting sufficient light for practical use in an organic EL display device. For example, a material that transmits 50% or more of light in a desired emission wavelength band is considered to be transparent.
Further, the low strain point glass refers to a glass that is warped at a temperature of about 700 ° C. or more.

In the present invention, the thin film transistor (T
FT) is used for driving an organic EL element.

The active layer of this switching element is, for example, a portion where an n + / i / n + region is formed,
Indicates an N-type doped portion, and i indicates an undoped portion. The doped portion of the active layer may be p + doped p-type. This active layer is preferably formed of polysilicon. Polysilicon shows a sufficient stability to energization compared to amorphous Si.

The α-Si layer as a polysilicon precursor can be laminated by various CVD methods, but is preferably laminated by a plasma CVD method. Then, KrF (248
nm) Anneal with an excimer laser such as a laser and crystallize. As a specific method, SID'9
6, Digest oftechnical paper
s It is good to use the method as shown in P17-28.

The annealing of the excimer laser is preferably performed at a substrate temperature of 100 to 300 ° C., and is preferably annealed with a laser beam having an energy amount of 100 to 300 mJ / cm ² .

In addition, crystallization may be performed by using a generally used thermal annealing method. Further, by using both the thermal annealing method and the laser annealing method, more preferable results can be obtained.

The activated polysilicon has 900
There is a silicon thin film (a so-called high-temperature polysilicon film) formed through a heat treatment at about ° C and a silicon thin film (a so-called low-temperature polysilicon film) formed at a relatively low temperature of 600 ° C or lower. The active layer of the present invention may be either high-temperature polysilicon or low-temperature polysilicon.

The active layer, that is, the film thickness of α-Si is 100
Å800 °, preferably 300〜500 °.

The active layer (polysilicon layer) is patterned into islands by photolithography so as to have a structure required as a switching element.

The substrate used is quartz having an insulating property,
Ceramic, sapphire, glass and the like can be used, but are preferably inexpensive materials such as low strain point glass. TFT-EL when a glass substrate is used
Avoids melting or distortion of the glass and out-diffusion of dopants in the active area.
On) is performed at a low process temperature to avoid on). In this way, all manufacturing steps on the glass substrate must be performed at 800 ° C. or less, preferably 600 ° C. or less.

In order to form a control electrode, an insulating gate material is preferably laminated on the polysilicon island and over the surface of the insulating substrate. The insulating material is preferably plasma CVD (PECVD) or low pressure CVD (L
Silicon dioxide (SiO ₂ ) deposited by chemical vapor deposition (CVD) such as PCVD. The thickness of the gate oxide insulating layer is preferably about 50-200 nm. The substrate temperature is preferably from 250 to 400 ° C., and in order to obtain a high-quality insulated gate material, annealing is preferably performed at from 300 to 6 ° C.
It is preferable to carry out at 00 ° C. for about 1 to 3 hours.

Further, as a control electrode, for example, a gate electrode is formed by vapor deposition or sputtering, and the gate electrode is patterned. The preferred thickness of the gate electrode is 100 to 500 nm.

As a preferable gate forming method, there is the following technique using polysilicon as a gate.

<N-type P-doped polysilicon> The gate electrode is formed by forming P-doped α-Si by a plasma CVD method.
This is polycrystallized by annealing at 600 ° C. to form n-type polycrystalline Si, which is patterned by photolithography.

If necessary, signal electrode lines and scanning electrode lines may be formed. A metal line such as an Al alloy, Al, Cr, W, and Mo is formed by photolithography.

When an Al gate is used, it is preferable to perform anodic oxidation twice for insulation.
Anodization is disclosed in detail in Japanese Patent Publication No. 8-15120.

Further, an n + or p + site is formed by ion doping.

The contacts such as the drain and the source as controlled electrodes are made at the positions where the insulating film is opened. Among the above insulating films, SiO ₂ is obtained by using, for example, TEOS (tetraethoxysilane) as a gas at a substrate temperature of 250 to 400 ° C.
And can be obtained by PECVD. In addition, it can be obtained by setting the substrate temperature to 100 to 300 ° C. by ECR-CVD.

The interlayer insulating film can be formed, for example, by the following method. Etchback method by plasma etching Various CVD methods, plasma CVD, PECVD
(Plasma Inhansudo CVD), LPCVD preferably a SiO ₂ silica and the like (vacuum CVD) method 0.
A film having a thickness of 2 μm to 3 μm is formed.

By this method, a flattened interlayer insulating film (SiO ₂ ) can be obtained. In this method, PSG, BSG (phosphorus silica glass, boron silica glass), or a silicon nitride-based compound such as Si ₃ N ₄ can be used in addition to silica. As described above, the switching element is formed.

The off current of the switching element is 1 × 10
^-8 A or less, especially 1 × 10 ^-10 A or less. The lower limit is not particularly limited and is preferably as small as possible, but is usually 1 × 10 ⁻¹³ A, preferably 1 × 10 ⁻¹⁴ A
It is about. An increase in off-state current causes erroneous light emission and a decrease in contrast.

The electric field mobility of the switching element is preferably 60 (cm ² / V · sec) or less, particularly 30 to 50 (cm ^2).
/ V · sec).

Next, a more specific configuration of the switching element of the present invention and a manufacturing process thereof will be described with reference to the drawings.

First, as shown in FIG. 1, an α-Si layer 2 is laminated on a substrate 1 by a sputtering method, various CVD methods, preferably a plasma CVD method.

After that, as shown in FIG. 2, annealing and crystallization are performed with an excimer laser 15 or the like to form an active layer 2a.
To form

Further, as shown in FIG. 3, the crystallized active layer (polysilicon layer) 2a is patterned into islands by photolithography.

Next, as shown in FIG. 4, an insulating gate 3 is laminated on the polysilicon island 2a and over the surface of the insulating substrate 1. The substrate temperature is 250-400 ° C
Preferably, annealing is performed at 300 to 600 ° C. for about 1 to 3 hours in order to obtain a higher quality insulated gate material.

Next, as shown in FIG. 5, a gate electrode 4 is formed by vapor deposition or sputtering.

Next, as shown in FIG.
Is patterned, ion doping 16 is performed on the patterned gate electrode 4 to form an n + or p + portion, and further, a signal electrode line and a scanning electrode line are formed by photolithography.

Next, contacts such as a drain and a source are formed. The contact is made at a location where the insulating film 11 is opened. First, an SiO ₂ film is formed as an interlayer insulating layer by a normal pressure CVD method. Next, the interlayer insulating layer is etched to form a contact hole, and a drain / source connection portion is opened.

A drain wiring electrode 12 and a source wiring electrode 13 are formed on the opened drain and source connecting portions, respectively, and connected to the drain and source electrodes. In this case, one of the drain and source electrodes functions as or is connected to the first electrode or the second electrode of the organic EL element. In the illustrated example, the hole injection electrode is ITO.
Connected to (15). Further, the drain wiring electrode 12
An insulating film 14 is formed thereon, and at the same time, an edge cover covering portions other than the pixel portion is formed to obtain a switching element as shown in FIG.

For connection with an electrode of an organic EL element such as a hole injection electrode, for example, as shown in FIG.
A connection metal layer 16 such as TiN may be formed between the third electrode 3 and the hole injection electrode 15 in order to improve the connection between them.

Next, the structure of the organic EL device of the present invention will be described. An organic EL element has an organic layer containing at least an organic substance involved in a light emitting function between a first electrode and a second electrode. Then, light is emitted when electrons and holes provided from the first electrode and the second electrode recombine in the organic layer.

Either of the first electrode and the second electrode may be a hole injection electrode or an electron injection electrode, but usually, the first electrode on the substrate side is a hole injection electrode and the second electrode is a second electrode.
Are used as electron injection electrodes.

As the electron injection electrode, a substance having a low work function is preferable. For example, K, Li, Na, Mg, La, C
e, Ca, Sr, Ba, Al, Ag, In, Sn, Z
It is preferable to use a single metal element such as n or Zr, or a two-component or three-component alloy system containing them for improving the stability. As an alloy system, for example, Ag · Mg (A
g: 0.1 to 50 at%), Al.Li (Li: 0.01)
１４14 at%), In · Mg (Mg: 50 to 80 at%),
Al.Ca (Ca: 0.01 to 20 at%) and the like. Note that the electron injection electrode can also be formed by an evaporation method or a sputtering method.

The thickness of the electron injecting electrode thin film may be a certain thickness or more for sufficiently injecting electrons.
The thickness is preferably 1 nm or more, more preferably 3 nm or more. The upper limit is not particularly limited, but the thickness may be generally about 3 to 500 nm. An auxiliary electrode or a protection electrode may be further provided on the electron injection electrode.

The pressure during the deposition is preferably 1 × 10 ⁻⁸ to 1
The heating temperature of the evaporation source is 100 to 1400 ° C. for a metal material and 100 to 50 ° C. for an organic material at × 10 ⁻⁵ Torr.
About 0 ° C. is preferable.

The hole injection electrode is preferably a transparent or translucent electrode for extracting emitted light. As the transparent electrode, ITO (tin-doped indium oxide), IZO
(Zinc-doped indium oxide), ZnO, SnO ₂ , I
Examples include n ₂ O ₃ , and preferably ITO (tin-doped indium oxide) and IZO (zinc-doped indium oxide). ITO usually contains In ₂ O ₃ and SnO in a stoichiometric composition, but the amount of O may slightly deviate from this. When transparency is not required, the hole injection electrode may be made of a known opaque metal material.

The thickness of the hole injecting electrode may be a certain thickness or more for sufficiently injecting holes, and is preferably 5 or more.
The range is preferably from 0 to 500 nm, more preferably from 50 to 300 nm. The upper limit is not particularly limited, but if the thickness is too large, there is a fear of peeling or the like. If the thickness is too small, there is a problem in the film strength at the time of manufacturing, the hole transport ability, and the resistance value.

This hole injecting electrode layer can be formed by a vapor deposition method or the like, but is preferably a sputtering method, especially a pulse D method.
It is preferable to form by the C sputtering method.

The organic layer of the organic EL structure can have the following configuration. The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The hole injecting and transporting layer has a function of facilitating the injection of holes from the hole injecting electrode, a function of stably transporting holes, and a function of preventing electrons.
The electron injection transport layer has a function of facilitating injection of electrons from the electron injection electrode, a function of stably transporting electrons, and a function of preventing holes. These layers increase and confine holes and electrons injected into the light emitting layer, optimize the recombination region, and improve luminous efficiency.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited and vary depending on the forming method.
It is preferable that the thickness be in the range of 10 to 300 nm.

The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer depend on the design of the recombination and light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. When the hole or electron injection layer and the transport layer are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 1 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and 500 nm for the transport layer.
It is about. Such a film thickness is the same when two injection / transport layers are provided.

The light emitting layer of the organic EL element contains a fluorescent substance which is a compound having a light emitting function. Examples of such a fluorescent substance include, for example, JP-A-63-26469.
No. 2 discloses at least one compound selected from compounds such as quinacridone, rubrene, and styryl dyes. Also, Tris (8
Quinolinol derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand, such as (quinolinolato) aluminum; tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, phenylanthracene derivatives described in JP-A-8-12600 (Japanese Patent Application No. 6-110569), tetraarylethene derivatives described in JP-A-8-12969 (Japanese Patent Application No. 6-114456), and the like are used. be able to.

Further, it is preferable to use in combination with a host substance capable of emitting light by itself, and it is preferable to use it as a dopant. In such a case, the content of the compound in the light emitting layer is preferably 0.01 to 20% by volume, more preferably 0.1 to 15% by volume. In particular, for a rubrene-based material, the content is preferably 0.01 to 20% by volume. By using in combination with the host substance,
The emission wavelength characteristic of the host material can be changed, light emission shifted to a longer wavelength becomes possible, and the emission efficiency and stability of the device are improved.

As the host substance, a quinolinolato complex is preferable, and an aluminum complex having 8-quinolinol or a derivative thereof as a ligand is preferable. Such an aluminum complex is disclosed in JP-A-63-26469.
No. 2, JP-A-3-255190, JP-A-5-7073
3, JP-A-5-258859, JP-A-6-2158
No. 74 and the like.

Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum Oxide, tris (8-quinolinolato) indium,
Tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-
8-quinolinolato) gallium, bis (5-chloro-8-
Quinolinolato) calcium, 5,7-dichloro-8-quinolinolatoaluminum, tris (5,7-dibromo-
8-hydroxyquinolinolato) aluminum and poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane].

Other host materials are disclosed in
Phenylanthracene derivative described in JP-A-12600 (Japanese Patent Application No. 6-110569) and JP-A-8-1296
No. 9 (Japanese Patent Application No. 6-114456) is also preferable.

The light emitting layer may also serve as the electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited.

The light emitting layer is preferably a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound, if necessary.
Further, it is preferable that a dopant is contained in the mixed layer. The content of the compound in such a mixed layer is 0.01 to 20% by volume, further 0.1 to 15% by volume.
% Is preferable.

In the mixed layer, a carrier hopping conduction path is formed, so that each carrier moves in a material having a favorable polarity, and injection of a carrier having the opposite polarity is unlikely to occur, so that the organic compound is less likely to be damaged. This has the advantage that the element life is extended. Further, by including the above-described dopant in such a mixed layer, the emission wavelength characteristics of the mixed layer itself can be changed, the emission wavelength can be shifted to a longer wavelength, and the emission intensity is increased, The stability of the device can be improved.

The hole injecting / transporting compound and the electron injecting / transporting compound used in the mixed layer may be selected from a compound for the hole injecting / transporting layer and a compound for the electron injecting / transporting layer described later. Among them, compounds for the hole injection transport layer include amine derivatives having strong fluorescence,
For example, it is preferable to use a triphenyldiamine derivative which is a hole transport material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring.

As the electron injecting and transporting compound, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). It is also preferable to use the above-mentioned phenylanthracene derivatives and tetraarylethene derivatives.

As the compound for the hole injecting and transporting layer, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is the above-described hole transporting material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is used. Is preferred.

The mixing ratio in this case depends on the respective carrier mobilities and carrier concentrations. In general, the weight ratio of the compound of the hole injecting / transporting compound / the compound having the electron injecting / transporting function is 1/99 to less. 99/1, more preferably 10/90 to 90/10, particularly preferably 20/80
It is preferable to set it to about 80/20.

The thickness of the mixed layer is preferably not less than the thickness corresponding to one molecular layer and less than the thickness of the organic compound layer. Specifically, the thickness is preferably 1 to 85 nm, more preferably 5 to 60 nm, particularly preferably 5 to 50 nm.

As a method for forming a mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are about the same or very close, they are mixed in advance in the same evaporation board. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

The hole injecting and transporting layer is described in, for example,
JP-A-3-295695, JP-A-2-191694, JP-A-3-792, JP-A-5-234681
JP, JP-A-5-239455, JP-A-5-5-2
JP-A-99174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100172
Various organic compounds described in JP-A No. 06509555 A1 and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine,
Examples include hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group, and polythiophene. These compounds may be used alone or in combination of two or more. When two or more kinds are used in combination, they may be stacked as separate layers or mixed.

When the hole injecting and transporting layer is divided into a hole injecting layer and a hole transporting layer, a preferable combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to laminate the compounds in order from the hole injecting electrode (ITO or the like) with the smallest ionization potential. Further, it is preferable to use a compound having a good thin film property on the surface of the hole injection electrode. Such a stacking order is the same when two or more hole injection transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In addition, in the case of forming an element, since a thin film of about 1 to 10 nm can be made uniform and pinhole-free because evaporation is used,
Even if a compound having a small ionization potential and having absorption in the visible region is used for the hole injection layer, it is possible to prevent a change in the color tone of the emission color and a decrease in efficiency due to reabsorption. The hole injecting and transporting layer can be formed by vapor deposition of the above compound in the same manner as the light emitting layer and the like.

The electron injecting / transporting layer includes a quinoline derivative such as an organometallic complex having 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof as a ligand, an oxadiazole derivative, a perylene derivative, or the like. A pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, or the like can be used. The electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the compounds in descending order of the electron affinity value from the electron injection electrode side. Such a stacking order is the same when two or more electron injection / transport layers are provided.

For forming the hole injection transport layer, the light emitting layer and the electron injection transport layer, a uniform thin film can be formed.
It is preferable to use a vacuum deposition method. When vacuum deposition is used, the amorphous state or the crystal grain size is 0.2 μm
The following homogeneous thin film is obtained. If the crystal grain size exceeds 0.2 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

The conditions for vacuum deposition are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to set it to about sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced, and the occurrence and growth of dark spots can be suppressed.

In the case where a plurality of compounds are contained in one layer when a vacuum evaporation method is used for forming each of these layers, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

The emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL element to optimize the extraction efficiency and the color purity.

If a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance of the element and the display contrast are improved.

An optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film to convert the color of the emitted light. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, a material having a high fluorescence quantum yield may be basically used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. In practice, laser dyes and the like are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalocyanines, etc.) naphthalimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds A styryl compound, a coumarin compound or the like may be used.

As the binder, basically, a material which does not extinguish the fluorescence may be selected, and a binder which can be finely patterned by photolithography, printing or the like is preferable. In the case where the hole injection electrode is formed on the substrate in contact with the hole injection electrode, a material which is not damaged when the hole injection electrode (ITO, IZO) is formed is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

The organic EL device of the present invention is generally used as a DC drive type or pulse drive type EL device.
The applied voltage is usually about 2 to 30V.

[0092]

EXAMPLE An amorphous silicon layer was formed on a Corning 1737 heat-resistant alkali-free glass substrate to a thickness of about 600 ° by a CVD method. The film forming conditions are as follows. Si ₂ H ₆ gas: 100 SCCM, pressure: 0.3 Torr, temperature: 480 ° C.

Then, the amorphous silicon layer was solid-phase grown to form an active layer (polysilicon layer). This solid phase growth used both thermal annealing and laser annealing. The conditions are as follows.

<Thermal annealing> N ₂ : 1 SLM, temperature: 600 ° C., processing time: 24 hours <Laser annealing> KrF: 254 nm, energy density: 200 mJ / cm ² ,
Number of shots: 50

Next, this polysilicon layer was patterned to obtain an active silicon layer: 500 °.

On this active silicon layer, an SiO ₂ layer serving as a gate oxide film was formed to a thickness of about 800 ° by, for example, a plasma CVD method. The film forming conditions are, for example, as follows.

Input power: 50 W, TEOS (tetraethoxysilane) gas: 50 SCCM, O ₂ : 500 SCCM,
Pressure: 0.1-0.5 Torr, temperature: 350 ° C.

On this SiO ₂ layer, a Mo—Si ₂ layer serving as a gate electrode was formed to a thickness of about 1000 ° by a sputtering method. Then, the Mo—Si ₂ layer and the SiO ₂ layer formed above were patterned by, for example, dry etching to obtain a gate electrode and a gate oxide film.

Then, using the gate electrode as a mask, an N-type impurity: P was doped by ion doping into portions of the silicon active layer that would become source / drain regions.

Next, this was heated at about 550 ° C. for 10 hours in a nitrogen atmosphere to activate the dopant. Further, hydrogenation was performed by heat treatment at about 400 ° C. for 30 minutes in a hydrogen atmosphere to reduce the defect state density of the semiconductor.

Then, an SiO ₂ layer serving as an interlayer insulating layer was formed on the entire substrate to a thickness of about 8000 mm. The conditions for forming the SiO ₂ film serving as the interlayer insulating layer are as follows. O ₂ / N ₂ : 10 SLM 5% SiH ₄ / N ₂ : 1 SLM 1% PH ₃ / N ₂ : 500 SCCM N ₂ : 10 SLM Temperature: 410 ° C. Pressure: atmospheric pressure

The SiO ₂ film serving as the interlayer insulating layer was etched to form a contact hole. Next, Al was deposited as a drain and source wiring electrode.

Also, except that the number of laser shots in laser annealing was 200 (comparative sample 1) when the thickness of the active layer was 300 °, and the number of laser shots in laser annealing was 200 (comparative sample 2) when the film thickness was 1000 °. A comparative sample was prepared in the same manner as described above.

When the S value of the obtained TFT array was evaluated, it was 1.0 (V / decade) for the sample of the present invention and 0.4 (V / decade) for Comparative Sample 1. Further, when the off current was measured, the sample of the present invention was found to be 4 × 10
^-10 A, Comparative Sample 1 was 1 × 10 ⁻¹⁰ A, and Comparative Sample 2 was 1 × 10 ⁻⁶ A or more.

Next, an ITO film serving as a hole injection electrode was formed in a region where the organic EL element was formed, and was connected to the wiring electrode.

An organic layer including a light emitting layer was formed by a vacuum evaporation method on the pixel region (on ITO) of the sample TFT thin film pattern of the present invention produced as described above. The materials formed are as follows. Here, only one example is given, but as is clear from the concept, the present invention can be applied irrespective of a film forming material as long as it can be formed by an evaporation method.

As the hole injection layer and the hole transport layer,
N, N'-bis (m-methylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (N,
N´-bis (m-methyl phenyl) -N, N´-diphenyl-1,1´-biph
enyl-4,4'-diamine; hereinafter abbreviated as TPD); tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq3) as an emission layer and an electron transport layer; Then, a cathode was successively formed as the second electrode 12.

As a film forming method, a vacuum injection method was selected for the hole injection layer and the hole transport layer, and a DC sputtering method was selected for the second electrode. As the second electrode, an Al / Li alloy (L
i concentration: 7 at%) with a gas pressure of 1 Pa, a power of 1 W / cm ² and a film thickness of 5 nm.
The film was laminated at a thickness of 200 nm with a power of 3 Pa and a power of 1 W / cm ² .

When a predetermined driving voltage was applied to the gate of the obtained TFT for driving each pixel of the organic EL display device and time-division driving was performed, an on-off operation (light emission) was confirmed according to the operation of the TFT. Was. In addition, the sample of the present invention had improved contrast as compared with Comparative Sample 1, and no erroneous light emission phenomenon was observed. The contrast ratio of Comparative Sample 2 was lower than that of the sample of the present invention by 以下 or less.

As is clear from the gist, the present invention is not limited to the organic EL element constituting films used in this embodiment and the order of lamination thereof, but includes a hole injection layer, a light emitting layer, a second electrode and a wiring electrode. May be used, and a hole injection layer, an electron transport layer, an electron injection layer, and the like may be further formed to form a multilayer structure. In other words, the type of material to be deposited,
Applicable regardless of the structure.

[0111]

As described above, according to the present invention, an erroneous light emission and a decrease in contrast are prevented, and there is no variation in light emission luminance between pixels or products, and an operation speed of an organic EL element is high. A driving device can be realized.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a manufacturing process of a driving device for an organic EL element of the present invention.

FIG. 2 is a partial cross-sectional view showing a manufacturing process of a driving device for an organic EL element of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a manufacturing process of a drive device for an organic EL element of the present invention.

FIG. 4 is a partial cross-sectional view showing a manufacturing process of the driving device for an organic EL element of the present invention.

FIG. 5 is a partial cross-sectional view showing a manufacturing process of the driving device for an organic EL element of the present invention.

FIG. 6 is a partial cross-sectional view showing a manufacturing process of the driving device for the organic EL element of the present invention.

FIG. 7 is a partial cross-sectional view showing a basic configuration example of a driving device for an organic EL element of the present invention.

FIG. 8 is a partial cross-sectional view showing a state of a connection metal layer formed between a wiring electrode and a hole injection electrode in order to improve the connection between them.

FIG. 9 is a graph showing a relationship between variation and electric field mobility and film thickness.

FIG. 10 is a graph showing a relationship between electric field mobility and film thickness for each annealing condition.

FIG. 11 is a graph showing a relationship between a film thickness and a leakage current (Ioff).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Amorphous silicon layer 2a Active layer 3 Gate oxide film 4 Gate electrode 5 Insulating film 6 Resist

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB00 AB02 AB04 AB06 AB17 BB06 CA01 CA02 CB01 DA00 DA01 DB03 EB00 FA01 FA03 GA00 5C094 AA06 AA07 AA13 AA60 BA03 BA27 CA19 DA09 EA05 EB02 5F110 AA06 BB01 DD02 DD02 DD02 DD02 EE03 EE04 EE05 EE06 EE09 EE34 EE43 EE44 EE45 FF02 FF24 FF30 FF32 FF36 GG02 GG13 GG25 GG35 GG45 HJ01 HJ12 HJ23 HL03 NN02 NN04 NN23 NN24 NN25 NN26 NN35 PP03 PP04 Q10 PP13

Claims (4)

[Claims] 1. An organic EL device comprising: a switching element in which a control electrode and a set of controlled electrodes are formed on a non-single-crystal silicon substrate; and an organic EL element driven by the switching element and having at least an organic layer involved in a light emitting function. The driving device for an organic EL device, wherein the switching element has an active layer made of a non-single-crystal silicon substrate having a thickness of 100 to 800 °. 2. The switching element has an S value of 0.8.
2. The driving device for an organic EL device according to claim 1, wherein the driving voltage is not less than (V / decade). 3. The off current of the switching element is 1
3. The driving device for an organic EL device according to claim 1, wherein the driving current is not more than × 10 ⁻⁸ A. 4. An organic EL display device, wherein the organic EL element driving devices according to claim 1 are arranged in a matrix.