JP2000306680A - Driving device for organic EL element and organic EL display device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent erroneous light emission and decrease in contrast, without causing variation in light emission luminance between pixels or products.
In addition, a driving device for an organic EL element having a high operation speed is realized. A switching element in which a control electrode and a set of controlled electrodes are formed on a non-single-crystal silicon substrate;
An organic EL element driven by the switching element and having at least an organic layer involved in a light emitting function,
The switching element is an organic EL element driving device in which the L / W value representing the ratio of the length (L) 2 to the width (W) 1 of the control electrode exceeds 1.

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 TransElectro.
n 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 Laid-Open Nos. 7-122360 and 7-1223).
No. 61, JP-A-7-153576, JP-A-8-158
-54836, JP-A-7-111341,
JP-A-7-310290, JP-A-8-10937
0, JP-A-8-129359 and JP-A-8-129.
JP 241047 and JP-A-8-227276). 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 to 15 liter when a highly efficient organic phosphor is used.
The efficiency is extremely high in the range of m / w, and the driving voltage of the high-definition display is 1/2 to 1 as compared with the simple driving.
/ 3, which is an excellent feature that power consumption can be reduced, but has the following problems.

When an organic EL element is driven by a TFT, 1
The current flowing per pixel is about 1 μA. However, if the current of this level is controlled by the TFT, the current is controlled near the change point of the VGS-IDS characteristic, as shown in FIG. In addition, the controlled current IDS fluctuates greatly, for example, to I1 and I2, and is susceptible to variations in element characteristics. For this reason, variation in light emission luminance occurs between pixels, which is one of the factors that cause display quality deterioration such as uneven light emission.

One of the factors that determine the performance of a display device is the problem of gradation control. Usually, it is said that eight or more gradations are necessary to obtain a high-definition display. However, most display devices using conventional TFTs have S / N ratios.
In many cases, the ratio is less than 20 dB, making it difficult to control eight or more gradations, which has been a major obstacle to obtaining a high-definition display. The S / N of the organic EL display device
A major factor that determines the ratio is the variation in Ion of the TFT, and reducing the variation in Ion has been an important issue.

[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. It is an object to realize a driving device and a high-quality organic EL display device using the driving device.

[0008]

Another characteristic of the switching element is an L / W value which is a ratio of the length L of the gate electrode to the width W. Generally, in a switching element such as a TFT, a smaller L / W value is more preferable. This is because when the L / W value is small, a switching operation (a large change in the controlled current) can be performed with a small voltage change, and it is generally considered that a TFT is preferably about 1/3 to 1/1. However, when driving an organic EL element that is a current light emitting element, if the L / W value is reduced, the variation of the switching element is likely to occur as a change in the emission luminance as it is, and the emission luminance varies between pixels and products. I will.

Therefore, by making the L / W value larger than a certain value, for example, the VGS-IDS characteristic curve shown in FIG. 11 becomes gentle as shown in FIG. By driving at a voltage V1 distant from the change point, even if the element characteristics fluctuate, the difference between the fluctuations I1 and I2 of the controlled current IDS is small, and the effect of the fluctuation of the element characteristics is reduced.

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 L / W value representing a ratio of a length (L) to a width (W) of the control electrode exceeding 1. (2) An organic EL display device in which the driving device of the organic EL element of (1) is arranged in a matrix.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A driving device for an organic EL device according to the present invention is a switching device in which a control electrode and a set of controlled electrodes are formed on a non-single-crystal silicon substrate, and is driven by the switching device. An organic EL element having at least an organic layer involved in a light emitting function, wherein the switching element has an L / W value representing a ratio of a length (L) to a width (W) of the control electrode exceeding 1 It is.

The L / W value of this switching element is, for example, as shown in FIG. 1, the ratio L / W of the length L to the width W of the gate electrode 1 which is the controlled electrode. FIG. 1 is a schematic partial enlarged view of a TFT element such as the TFT 1 shown in FIG. 2, and shows a state in which a gate electrode 1 is formed on a silicon substrate 2 (21). This L / W ratio can also be considered as the ratio between the channel length and the channel width.

The L / W value of the switching element exceeds 1, preferably 2 to 100, more preferably 2 to 10.

As described above, by setting the L / W value of the switching element to be larger than a predetermined value, it is possible to suppress a variation in light emission luminance due to a variation in characteristics between the elements.

According to the switching element of the present invention, a control electrode and a set of controlled electrodes are formed on a silicon substrate,
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.

FIG. 2 shows the switching element of the present invention.
This will be described more specifically with reference to FIG. Figure 2 shows the organic EL
FIG. 3 is a plan view showing an example of a TFT array for driving elements.

In FIG. 1, a source electrode 13 is connected to a source bus 11 and is connected to a source portion formed on a silicon substrate 21 via a contact hole 13a. On the silicon substrate 21, a gate bus 12 commonly connected to a TFT element of another pixel (not shown)
And the gate bus 12 is formed on the silicon substrate 2
A gate electrode is formed at a portion that intersects 1.

A drain wiring 14 is connected to a drain part formed on the silicon substrate with the source part and the gate electrode interposed therebetween through a contact hole 14a. The drain wiring 14 is connected to a gate line 15 via a contact hole 14b. The gate line 15 is formed on a silicon substrate 22 constituting the TFT 2 and is connected to one electrode of a capacitor 18. The other electrode of the capacitor 18 is connected to the ground bus 23.
And the source electrode 17 is connected to the source electrode 17 via a contact hole 17a.
Connected to the source part of FT1. Gate line 1
A gate electrode is formed at a portion where 5 intersects the silicon body 22.

A drain wiring 16 is connected through a contact hole 16a to a drain part formed on the silicon substrate with the source part and the gate electrode 15 interposed therebetween.
The drain wiring 16 forms one electrode of an organic EL element serving as a pixel or is connected thereto.

TFT1 for directly driving this organic EL element
Is the switching element in the present invention, and this TFT
FIG. 1 is a simplified representation of the gate portion of FIG.

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 the 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, Digestoftechnicalpapers
It is preferable to use a method as shown on pages 17 to 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 configuration 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 preferred gate forming method, there is the following technique using polysilicon as a gate.

<N-type P-doped polysilicon> A 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 locations 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. Etch-back method by plasma etching Various CVD methods, plasma CVD, PECVD (plasma enhanced CVD), LPCVD (low pressure CV
D) The SiO ₂ silica is preferably 0.2 μm by a method or the like.
m 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 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. 3, a sputtering method, various CVD methods, preferably a plasma CVD
The α-Si layer 102 is stacked by a method or the like.

Thereafter, as shown in FIG. 4, annealing and crystallization are performed by an excimer laser 115 or the like to form an active layer 102a. At that time, thermal annealing may be used together.

Further, as shown in FIG. 5, the crystallized active layer (polysilicon layer) 102a is patterned into islands by photolithography.

Next, as shown in FIG.
3 over the polysilicon island 102a and the surface of the insulating substrate 101. The substrate temperature is 25
Annealing is preferably performed at 300 to 600 ° C. for about 1 to 3 hours in order to obtain a high quality insulated gate material.

Next, as shown in FIG.
4 is formed by vapor deposition or sputtering.

Next, as shown in FIG.
04 is patterned, ion doping 116 is performed on the patterned gate electrode 104 to form an n + or p + site, 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 111 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 112 and a source wiring electrode 113 are formed on the opened drain and source connection portions, respectively, and connected to the drain and source electrodes. In this case, one of the drain and source electrodes is an organic EL.
Functions or is connected to a first electrode or a second electrode of the element. In the illustrated example, it is connected to ITO (115) which is a hole injection electrode. Further, an insulating film 114 is formed on the drain wiring electrode 112, 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.

The connection with an electrode of the organic EL element such as a hole injection electrode is made between the wiring electrode 113 and the hole injection electrode 115 as shown in FIG. , TiN or other connecting metal layer 116 may be formed.

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 the first electrode or 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 capable of 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 that can sufficiently inject 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 injection electrode layer can be formed by a vapor deposition method or the like.
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 / 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.

The host substance is preferably a quinolinolato complex, and more preferably an aluminum complex having 8-quinolinol or a derivative thereof as a ligand. 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 include those 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 an 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 hopping conduction path of carriers is formed, so that each carrier moves in a substance having a favorable polarity, and injection of a carrier having the opposite polarity is less likely 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 and transporting compound and the electron injecting and transporting compound used in the mixed layer may be selected from the compounds for the hole injecting and transporting layer and the compounds for the electron injecting and transporting layer, respectively. 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 compound capable of injecting and transporting electrons, 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 as 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 the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately 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 laminated separately into a hole injecting and 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.

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, etc. 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 preferred 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 luminescent 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 fluorescent conversion filter film absorbs EL light and emits light from the phosphor in the fluorescent 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, basically, a material having a high fluorescence quantum yield may be 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, a material which basically does not quench 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-driven or pulse-driven EL device.
The applied voltage is usually about 2 to 30V.

[0094]

EXAMPLE An amorphous silicon layer having a thickness of about 600 DEG was formed on a 1737 heat-resistant alkali-free glass substrate manufactured by Corning by low pressure CVD (LPCVD). 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: 200

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
Toxisilane) gas: 50 SCCM, O _Two: 500 SCCM, pressure
Force: 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.

At this time, the length (L) of the gate electrode is 15
μm, width (W) 5 μm, and L / W value was 3.

Next, using the gate electrode as a mask, an N-type impurity: P was doped by ion doping in portions to be the source / drain regions of the silicon active layer.

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 at 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.

The length (L) of the gate electrode is 5 μm,
Comparative samples were prepared in the same manner as above except that the width (W) was 15 μm and the L / W value was reduced to 1/3.

The drain current of each element of the obtained TFT array with respect to a specific gate voltage (5 V) was measured, and the fluctuation rate of the drain current was obtained. As a result, the sample of the present invention was within ± 8%. On the other hand, the comparison sample was ± 12% 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 connected to the wiring electrode. Then, in order to emit light only in the light emitting region (pixel portion), the interlayer insulating film SiO ₂ is formed in a thickness of 4000
A film was formed, and a portion serving as a light emitting region was opened.

An organic layer including a light emitting layer was formed by a vacuum deposition 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 a hole injection layer and a 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 or abbreviated as TPD), and tris (8-hydroxyquinoline) aluminum (hereinafter A)
lq3), the second electrode 1 without breaking the vacuum.
As No. 2, a cathode was continuously formed.

As a film forming method, a vacuum evaporation 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 .

Each pixel of the obtained organic EL display device is set to 1
When a constant current drive of 0 mA / cm ² was performed, an on-off operation (light emission) was confirmed according to the operation of the TFT. Further, when the light emission luminance of each element at the time of constant current driving was measured, the variation of the light emission luminance was within ± 8% in the sample of the present invention, but was ± 12% or more in the comparative sample.

Further, the S / N ratio of the display device of the present invention was determined to be 20 dB or more, and it was found that gradation control of 8 or more gradations was possible.

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.

[0115]

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 schematic enlarged view of a gate portion of a driving device of an organic EL element of the present invention.

FIG. 2 is a plan view showing an example 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 manufacturing process of the driving device for the organic EL element of the present invention.

FIG. 8 is a partial cross-sectional view showing a manufacturing process of the drive device for the organic EL element of the present invention.

FIG. 9 is a partial cross-sectional view showing a manufacturing process of the drive device for an organic EL element of the present invention.

FIG. 10 is a partial cross-sectional view showing a step of manufacturing an organic EL element driving device according to the present invention.

FIG. 11 is a graph showing a VGS-IDS characteristic curve when the L / W value is small.

FIG. 12 is a graph showing a VGS-IDS characteristic curve when the L / W value is large.

[Explanation of symbols]

 Reference Signs List 1 gate 2 silicon base 11 source bus 12 gate bus 13 source electrode 14 drain electrode 15 gate line 16 drain electrode 17 source electrode 18 capacitor 21, 22 silicon base 101 substrate 102 amorphous silicon layer 102a active layer 103 gate oxide film 104 gate electrode 105 Insulating film 106 resist

Continued on the front page F term (reference) 3K007 AB00 AB02 AB17 BB06 CA00 CA01 CA02 CB01 DA00 DB03 EB00 FA01 FA03 GA00 5C094 AA06 AA07 AA55 AA60 BA27 CA19 GA10

Claims (2)

[Claims] An organic EL element having a control electrode and a set of controlled electrodes formed on a non-single-crystal silicon substrate, and an organic layer 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 L / W value representing a ratio of a length (L) to a width (W) of the control electrode exceeding 1. 2. An organic EL display device in which the organic EL element driving devices according to claim 1 are arranged in a matrix.