JP2003217834A - Self-light emitting display device and manufacturing method for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of keeping stable display performance over a long period of time, and having a structure reduced in thickness so as to attain high manufacturing yield and low costs, and a manufacturing method for the display device. <P>SOLUTION: An array base plate 100 includes an organic EL element 40 formed by a first electrode 60 formed like an independent island in each pixel arranged in a matrix, a second electrode 66 disposed opposite to the first electrode 60 and formed in common to all pixels, and a light emitting layer 64 held between the first electrode 60 and the second electrode 66. A sealing base plate 200 is disposed opposite to the array base plate 100, and has an organic EL element 40 stored in a closed space formed with the array base plate 100. The surface of the organic EL element 40 is provided with a drying agent 70 formed by an oxide film of alkali metal or alkaline earth metal to dehumidify the interior of the closed space. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a manufacturing method thereof, and more particularly to an active matrix type self-luminous display device having a switching element for each pixel and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, attention has been paid to organic electroluminescence (EL) display devices as flat display devices. Since this organic EL display device is a self-luminous element, it has a wide viewing angle, can be thinned without requiring a backlight, has low power consumption, and has a high response speed. ing.

From these characteristics, the organic EL display device is
It is attracting attention as a promising candidate for next-generation flat panel display devices that will replace liquid crystal display devices. However, the life τ of the organic EL display device is still at an unsatisfactory level, as compared with the liquid crystal display device, the luminance is halved in about 10,000 hours at present.

This organic EL display device is constructed by arranging organic EL elements in a matrix on an array substrate in which an organic light emitting layer containing an organic compound having a light emitting function is sandwiched between an anode electrode and a cathode electrode. . Organic E
The absolute amount P of the number of photons emitted from the L element to the atmosphere is P = φ _EXT · A · J / e, where J is the current density per unit area flowing through the organic EL element and φ _EXT is the external quantum efficiency. ... (1) In addition, A is an effective area of the organic EL element, and e is an elementary amount of electricity.

The life τ tends to extend as the current density J decreases. Since the number P of photons is proportional to the luminance, the external quantum efficiency φ _EXT must be increased in order to obtain a long-lifetime device with a smaller drive current I (= A · J). The external quantum efficiency φ _EXT is represented by φ _EXT = χ · φ _PL · φ _OUT · φ _POL (2). χ is the injection balance of electrons and holes, φ _PL is the PL emission efficiency of the light emitting layer constituent material, φ _OUT is the light extraction efficiency, and φ _POL is the transmittance of the polarizing plate (provided for the purpose of preventing reflection of external light). Is.

The organic EL element is a light-emitting element driven by current injection, and electron-hole pairs are formed in the light-emitting layer with a probability of injection balance χ, and recombine and emit light with efficiency φ _PL . The implantation balance χ has been realized as χ≈1 which is close to the theoretical limit by improving the electrode structure.

However, this organic EL element is very sensitive to moisture, and when moisture enters from the outside, the injection balance of electrons and holes is disturbed. Further, the PL light emission efficiency is also lowered due to the influence of moisture. This makes it impossible to maintain sufficient display performance as a display device.

To realize a long life of the organic EL element,
It is necessary to control the amount of water in the closed space that houses the organic EL element, and for that purpose, a desiccant is essential. For example, when disposing the desiccant on the sealing substrate, it is necessary to secure a space for disposing the desiccant on the sealing substrate, which may hinder thinning, which is one of the features.

[0009]

As described above, in the organic EL display device, the light emitting element is deteriorated with the passage of time due to the moisture contained in the sealed space in which the organic EL element is housed, and is stable for a long period of time. There is a problem that it is difficult to maintain the display performance.

When the desiccant is placed on the sealing substrate,
It is necessary to secure a space for arranging the desiccant, which hinders thinning. Further, there is a problem that a separate manufacturing process for disposing the desiccant is required, which causes a decrease in manufacturing yield. Moreover, the manufacturing cost also rises.

The present invention has been made in view of the above problems, and an object thereof is to provide a display device capable of maintaining stable display performance for a long period of time. Another object of the present invention is to provide a low-cost display device that has a structure that can be thinned and has a high manufacturing yield, and a method for manufacturing the display device.

[0012]

According to a first aspect of the present invention, there is provided a display device comprising a first substrate, a first substrate arranged in a matrix on a main surface of the first substrate and formed in an island shape.
A plurality of display elements each including an electrode, a second electrode arranged to face the first electrode, and a light emitting layer held between the first electrode and the second electrode; A desiccant formed so as to continuously cover the outermost surface of the display device, the desiccant being an oxide film of an alkali metal or an alkaline earth metal, and the main substrate of the first substrate. A second substrate that houses the display element between
It is characterized by having.

According to a second aspect of the present invention, there is provided a method of manufacturing a display device, comprising: a first substrate, a first electrode formed in an island shape for each pixel arranged in a matrix, and the first electrode. A step of forming a display element including a second electrode facing each other and a light emitting layer held between the first electrode and the second electrode; and a step of forming an alkali on the surface of the display element. A step of disposing a desiccant formed of an oxide film of a metal or an alkaline earth metal, and an inactive layer formed between the second substrate and the first substrate so as to face the first substrate. A step of housing the display element in a closed space in a gas atmosphere.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A display device and a method for manufacturing the same according to an embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, a self-luminous display device, for example, an organic EL (electroluminescence) display device will be described as an example of the display device.

That is, as shown in FIGS. 1 and 2, the organic EL display device 1 includes an array substrate 1 as a first substrate in which organic EL elements as display elements are arranged in a matrix.
00 and a sealing substrate 200 as a second substrate for sealing the array substrate 100. This array substrate 100
The display area 102 for displaying the image of 3 is configured to include three types of light emitting units that emit light in red, green, and blue, that is, the organic EL element 40.

The organic EL element 40 has a first electrode 60 formed in an island shape for each element, and a second electrode 66 arranged so as to face the first electrode 60 and continuously formed in common for each element.
And an organic light emitting layer 64 as a light emitting layer held between these electrodes.

This array substrate 100 has a display area 10
2, the pixel switch 10 and the driving element 20, the storage capacitor element 30, and the organic EL element 40 are provided.
Here, as an example, the pixel switch 10 is composed of an n-type thin film transistor, and the driving element 10 is composed of a p-type thin film transistor. Each organic EL element 40 is selected via the pixel switch 10, and the excitation power for the organic EL element 40 is
It is controlled by the drive element 20.

The array substrate 100 also has a plurality of scanning lines Y arranged along the row direction of the organic EL elements 40 and a plurality of signal lines X arranged along the column direction of the organic EL elements 40. A power supply line P for supplying power to the first electrode side of the organic EL element 40. Further, the array substrate 100 includes a scanning line driving circuit 107 that supplies a driving signal to the scanning line Y and a signal line driving circuit 108 that supplies a driving signal to the signal line X in the peripheral area thereof.

The scanning line Y is connected to the scanning line drive circuit 107, and the signal line Y is connected to the signal line drive circuit 108. The pixel switch 10 is arranged near the intersection of the scanning line Y and the signal line X. The drive element 20 is an organic EL
It is connected in series with the element 40. In addition, the storage capacitor element 30 is connected in series with the pixel switch 10 and the driving element 20.
And the two electrodes of the storage capacitor element 30 are connected to the gate electrode and the source electrode of the driving element 20, respectively.

The power supply line P is connected to a first electrode power line (not shown) arranged around the display area 102. The second electrode side end of the organic EL element 40 is the display area 1
A common potential, which is arranged around 02, is connected to a second electrode power supply line (not shown) that supplies a ground potential.

More specifically, the pixel switch 10
The gate electrode is connected to the scanning line Y, the source electrode is connected to the signal line X, and the drain electrode is connected to one end of the storage capacitor element 30 and the gate electrode of the driving element 20.
The source electrode of the drive element 20 is connected to the power supply line P, and the drain electrode thereof is the first electrode 60 of the organic EL element 40.
It is connected to the. The other end of the storage capacitor element 30 is connected to the source electrode of the driving element 20.

When selected through the corresponding scanning line Y, the pixel switch 10 writes the video signal of the corresponding signal line X into the storage capacitor element 30 and controls the driving of the drive element 20.
The gate voltage of the drive element 20 is adjusted based on the video signal, the source-drain current of the drive element 20 is controlled,
A desired drive current is supplied to the organic EL element 40.

FIG. 2 is a schematic sectional view of a part of the organic EL display device, the drive element 20 and the organic EL element 40.

The driving element 20 is, for example, p as described above.
Type thin film transistor, and a polysilicon semiconductor layer 20P arranged on an insulating support substrate 120 having a light transmitting property such as a glass substrate, a gate electrode 20G arranged via a gate insulating film 52, and a gate insulating film. The source electrode 20S, which is in contact with the source region 20PS of the polysilicon semiconductor layer 20P through the contact hole 93 penetrating 52 and the interlayer insulating film 54, and the gate insulating film 52.
And the drain region 20 of the polysilicon semiconductor layer 20P through the contact hole 94 penetrating the interlayer insulating film 54.
And a drain electrode 20D that is in contact with the PD.

The organic EL element 40 is arranged on the insulating film 56 arranged on the interlayer insulating film 54. The organic EL element 40 for one pixel is partitioned by the partition walls 130 arranged in a grid pattern. The partition wall 130 is formed of a hydrophilic film such as hydrophilic SiO and a resin resist having water repellency. This organic EL element 40
Is configured to include the organic light emitting layer 64 sandwiched between the first electrode 60 and the second electrode 66 that is arranged so as to face the first electrode 60.

That is, the first electrode 60 is disposed on the insulating film 56 and the contact hole 9 penetrating the insulating film 56.
It is connected to the drain electrode 20D of the drive element 20 through the line 5. The first electrode 60 functions as an anode here, and is made of ITO (Indium Tin Oxide) or IZO (Indium.
It is formed of a light-transmissive conductive member such as zinc oxide.

The organic light emitting layer 64 may be composed of a three-layered stack of a hole transporting layer, an electron transporting layer formed commonly for each color, and a light emitting layer formed for each color. It may be composed of a layer or a single layer. For example, the hole transport layer is arranged between the anode and the light emitting layer, and is formed of a thin film of an aromatic amine derivative, a polythiophene derivative, a polyaniline derivative or the like. The light emitting layer is
The organic compound is disposed between the cathode and the hole transport layer and emits red, green, or blue light. This light emitting layer is made of P, for example, when a polymer material is used.
It is formed by laminating PV (polyparaphenylene vinylene), a polyfluorene derivative or a precursor thereof.

The second electrode 66 functions here as a cathode.
The organic EL element 40 is commonly connected to the organic light emitting layer 64.
It is arranged continuously. The second electrode 66 is, for example, C
a (calcium), Al (aluminum), Ba (burrs)
Um), Ag (silver), BaF _Two, LiF_TwoSuch as light reflection
Formed of a conductive metal film.

The desiccant 70 is closely arranged on the surface of each organic EL element 40 and adsorbs oxygen and moisture in the closed space formed between the array substrate 100 and the sealing substrate 200. That is, the desiccant 70 is formed of an alkali metal or alkaline earth metal oxide film such as barium oxide (Ba).
O) and calcium oxide (CaO). Such a desiccant 70 absorbs water that comes out of the organic EL element 40 and the like.

Thus, the organic EL element 40 and the desiccant 7
Since 0 and 0 are closely arranged, deterioration of the organic EL element 40 can be effectively suppressed as compared with the case where they are arranged separately.

The array substrate 100 and the sealing substrate 200 as described above are sealed by a sealing material 400. The sealing material 400 is made of, for example, an ultraviolet curable resin. The sealed space formed in the predetermined gap between the array substrate 100 and the sealing substrate 200 is filled with an inert gas such as nitrogen gas, and is maintained in a dry state that does not adversely affect the organic EL element 40. ing.

For example, the desiccant 70 may be barium oxide (Ba).
When formed by O), barium oxide chemically reacts with water to form barium hydroxide (Ba (OH) ₂ ). As a result, the inside of the closed space is quickly dehumidified, and the organic EL element 4
It is possible to prevent destruction due to moisture of 0, and it is possible to reliably maintain stable display performance for a long period of time.

In this embodiment, the desiccant 70 is the same as that shown in FIG.
As shown in FIG. 3, the organic EL element 40 is disposed on the second electrode 66 disposed on the outermost surface. More specifically, the desiccant 70 includes the second electrode 6 including the end portion 66A of the second electrode 66.
6 is arranged so as to cover the whole. Therefore, organic E
Since the second electrode 66 forming the L element 40 is not exposed in the closed space and is covered with the desiccant 70, it is possible to prevent the second electrode 66 from being chemically changed due to the influence of moisture. This makes it possible to maintain stable display performance for a long period of time.

Further, since the desiccant 70 is closely arranged on the outermost surface of the organic EL element 40, the desiccant 70 is formed on the sealing substrate 200.
It is no longer necessary to secure a space for placing
It is possible to reduce the thickness of the entire device. Further, since the desiccant 70 can be continuously formed in the vacuum chamber after the second electrode disposed on the outermost surface of the organic EL element 40 is formed by vapor deposition or the like, the number of manufacturing steps can be significantly reduced. It is possible to suppress the manufacturing cost and improve the manufacturing yield without increasing the manufacturing cost.

Further, since the desiccant 70 is disposed in close contact with the organic EL element 40, the number of parts can be reduced and the mechanical strength of the device can be increased.

In the organic EL element 40 thus constructed, electrons and holes are injected into the organic light emitting layer 64 sandwiched between the first electrode 62 and the second electrode 66, and these are recombined to re-combine them. Excitons are generated, and light is emitted by light emission of a predetermined wavelength generated when the excitons are deactivated. This EL
Light is emitted from the lower surface side of the array substrate 100, that is, the first electrode 6
It is emitted from the 0 side.

Next, a method of manufacturing this organic EL display device will be described.

That is, first, a process of forming and patterning a metal film and an insulating film is repeated to form a TFT, a capacitor and the like, and the pixel switch 1 is formed on the first substrate 100.
0, the driving element 20, the storage capacitor element 30, the scanning line driving circuit 107, the signal line driving circuit 108, and the like on the insulating substrate 120.
They are integrally formed on the top in the same process. Further, various wirings such as the signal line X, the scanning line Y, and the power supply line P are also formed. Then, an insulating film 56 is formed so as to cover these.

Subsequently, a contact hole 95 penetrating to the drain electrode 20D of the driving element 20 is formed in the insulating film 56 by etching. Then, the transparent electrode member, for example, ITO is arranged in the shape of an independent island for each pixel on the insulating film 56 to form the first electrode 60.

Then, the first electrode 60 is formed on the first substrate 100.
A partition wall 130 is formed to separate each of the above.

Then, an organic light emitting layer 64 is formed on the first electrode 60 by depositing a conductive polymer PEDOT (polyethylenedioxythiophene) film, a polymer EL film, or the like by, for example, an inkjet method.

Further, the second electrode 6 is formed on the organic light emitting layer 64.
6 is formed. In this embodiment, barium (Ba) is deposited as a cathode material to a thickness of 90 angstroms, and then silver (Ag) is continuously deposited as a protective film to a thickness of 1500 angstroms. This allows organic E
The L element 40 is formed.

A plurality of display elements 40 surrounded by the partition wall 130
Emits the same color for each column, for example.

Further, the second of the organic EL element 40 is continued.
On the electrode 66, barium oxide (Ba) is used as a desiccant 70.
O) to a thickness of 5 to 5000 angstroms (please replenish).

At this time, the film forming rate of Ba is set to 5 angstroms / sec in the first half and 20 angstroms / se in the second half.
c and the Ag film formation rate was set to 50 Å / sec. As a result, an alloy of Ba and Ag was formed at the interface between the two layers of Ba and Ag. Also,
BaO could be brought into close contact with the organic EL element 40 as the desiccant 70.

Subsequently, in order to seal the organic EL element 40 on the array substrate 100, an ultraviolet-curable sealing material 400 is applied along the outer circumference of the sealing substrate 200, and an atmosphere of an inert gas such as nitrogen gas is applied. Inside, the array substrate 100 and the sealing substrate 200 are bonded together. This allows organic E
The L element 40 is enclosed in a closed space of an inert gas atmosphere. After that, ultraviolet rays are irradiated to cure the sealing material 400.

In the color display type active matrix organic EL display device thus formed, the amount of drive current flowing through the organic EL element 40 is adjusted to obtain an initial luminance of 100 cd /
As a result of a life test performed under the condition of m ² , the life of this device in which the luminance is reduced by half was about 20,000 hours, and sufficient life characteristics were obtained.

The present invention is not limited to the above-described embodiments, but can be variously modified without departing from the scope of the invention.

For example, the hole-junction material TPD (N, N'biphenyl N, N'bismethylphenyl-biphenyldiamine) and the EL material Alq are formed on the first electrode 60 of the array substrate 100 similar to the case of the above-described embodiment. ₃ (trishydroxyquinone aluminum) is continuously vapor-deposited to form the organic light emitting layer 64.

Further, the second electrode 6 is formed on the organic light emitting layer 64.
6 is formed. Here, the second electrode 66 is formed by depositing calcium (Ca) as a cathode material to a film thickness of 350 Å and then continuously depositing silver (Ag) as a protective film. Further, after silver, calcium oxide (CaO) as a desiccant 70 is added to 5 to 5000.
The film is formed by continuous vapor deposition with a film thickness of angstrom. Further, BaF ₂ as a cathode material may be vapor-deposited on the second electrode in the range of 5 to 100 Å, and then Ca may be deposited in the range of 50 to 500 Å and Al 1500 to 3000 Å in this order. Also, LiF instead of BaF _2
2 may be vapor-deposited in the same film thickness.

The organic EL display device thus formed was subjected to a life test under the same conditions as those of the above-described embodiments, and as a result, the brightness of the device was reduced by half to a life of about 30,
It was 000 hours, and sufficient life characteristics were obtained.

Further, the desiccant 70 may be formed by reacting the alkali metal or alkaline earth metal formed on the second electrode with oxygen contained in the closed space to form an oxide film. Good.

As shown in FIG. 4, the desiccant 70 is
You may arrange | position so that the whole main surface of the array substrate 100 exposed in the enclosed space may be covered. That is, in the structure shown in FIG. 4, the partition wall 130 is arranged so as to cover the wiring portion 700 such as the drive circuit and various wirings arranged around the display area. The second electrode 66 is arranged on the partition wall 130.

In the case of such a structure, the desiccant 70 is applied to the exposed main surface of the array substrate 100, that is, the partition wall 13.
The zero electrode and the second electrode 66 are arranged so as to cover the whole including the end portions. As a result, all the components on the array substrate including the organic EL element 40 are dried by the desiccant 70.
Covered by. Therefore, the organic EL element 40 is not affected by moisture, and stable display performance can be maintained for a long period of time.

Moreover, the desiccant 70 is only interposed between the seal material 400 and the first substrate 100 to the extent that it covers the partition wall 130, and the seal material 400 and the first substrate 10 are included.
There is no intervening area between 0 and 0. In other words,
At least a part of the sealing material 400 and the first substrate 100 are in direct contact with each other without interposing the desiccant 70. Therefore, the adhesiveness between the sealing material 400 and the first substrate 100 is not hindered.

Further, in the structure shown in FIG.
Are arranged so as to cover the wiring portion 700 such as a drive circuit and various wirings arranged around the display area. A power supply line 800 for supplying a common potential to the second electrode 66 is arranged further on the outer periphery of the partition wall 130. The second electrode 66 is disposed on the partition wall 130 and is in contact with the power supply line 800 on the outer periphery.

In the case of such a structure, the desiccant 70 is arranged so as to cover the exposed main surface of the array substrate 100, that is, the whole of the second electrode 66 and the power supply line 800 including the respective end portions. As a result, all the components on the array substrate, including the organic EL element 40, are dried by the desiccant 7.
Covered by 0. Therefore, the organic EL element 40 is not affected by moisture, and stable display performance can be maintained for a long period of time.

Moreover, the desiccant 70 covers the second electrode 66 and the power supply line 800 so that the sealant 400 and the first substrate 1 are covered.
It is only interposed between the sealing material 4 and
00 and the first substrate 100 are not interposed. Therefore, the adhesiveness between the sealing material 400 and the first substrate 100 is not hindered.

As described above, according to the present invention, the organic EL device has a structure capable of easily removing water which deteriorates the life of the organic EL device, and can be made thin. Also,
A substrate having a special shape is not required for disposing the desiccant, and the desiccant can be formed by extension of vapor deposition of electrodes for disposing the desiccant on the outermost surface of the organic EL element in terms of process. It is advantageous for thinning, which is one of the characteristics of 1., and it is also possible to improve the manufacturing yield.

In the above embodiment, the bottom emission method for extracting light from the first electrode side has been described as an example. However, when the cathode material and the desiccant have a light transmitting property, the light is emitted from the second electrode side. It is also possible to adopt a top emission method in which For example, it can be achieved by forming a thin film of Ba, which is a cathode material, to the extent that it has a light-transmitting property, for example, a film having a thickness of about 10 nm, and also forming a thin film of BaO as a desiccant.

[0062]

As described above, according to the present invention, it is possible to provide a display device capable of maintaining stable display performance for a long period of time. Further, it is possible to provide a low-cost display device having a structure that can be made thin and having a high manufacturing yield, and a method for manufacturing the display device.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an organic EL display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure of one pixel of the organic EL display device shown in FIG.

3 is a cross-sectional view schematically showing a structure of a peripheral portion of the organic EL display device shown in FIG.

4 is a cross-sectional view schematically showing another structure of the peripheral portion of the organic EL display device shown in FIG.

5 is a cross-sectional view schematically showing another structure of the peripheral portion of the organic EL display device shown in FIG.

[Explanation of symbols]

1 ... Organic EL display device 10 ... Pixel switch 20 ... Drive element 40 ... Organic EL element 60 ... First electrode 64 ... Organic light emitting layer 66 ... Second electrode 70 ... Desiccant 100 ... Array substrate 130 ... Partition wall 200 ... Sealing substrate 400 ... Sealing material

Claims (7)

[Claims] 1. A first substrate, a first electrode arranged in a matrix on the main surface of the first substrate and formed in an island shape, and a second electrode arranged so as to face the first electrode. A plurality of display elements constituted by electrodes, a light emitting layer held between the first electrode and the second electrode, and formed so as to continuously cover the outermost surface of the display element,
And a desiccant formed of an oxide film of an alkali metal or an alkaline earth metal, a second substrate which is disposed so as to face the main surface of the first substrate and accommodates the display element between the first substrate and the second substrate, A self-luminous display device comprising: 2. The self-luminous display device according to claim 1, wherein the desiccant is made of barium oxide. 3. The second electrode is arranged continuously to a plurality of the display elements, and the desiccant is arranged so as to cover the entire second electrode including an end portion of the second electrode. The self-luminous display device according to claim 1, which is characterized in that. 4. The self-luminous display device according to claim 1, wherein a wiring circuit unit is integrally formed with the first substrate in a peripheral region of a display region in which the display element is arranged. Self-luminous display device. 5. The self-luminous display device comprises barrier ribs that electrically insulate each of the first electrodes and are disposed on the wiring circuit section, and the desiccant is the barrier ribs and the barrier ribs. The self-luminous display device according to claim 4, wherein the entire second electrode disposed in the area is covered. 6. The self-luminous display device according to claim 4, wherein the desiccant covers the wiring circuit section and the entire second electrode. 7. A first electrode formed on the first substrate in an island shape for each pixel arranged in a matrix, a second electrode arranged to face the first electrode, and the first electrode. A step of forming a display element constituted by a light emitting layer held between one electrode and the second electrode; and an oxide film of an alkali metal or an alkaline earth metal formed on the surface of the display element. Disposing a desiccant, disposing a second substrate facing the first substrate, and
And a step of housing the display element in a closed space in an inert gas atmosphere formed between the display element and the substrate.