JP2001117509A - Organic el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the emission luminance of an organic EL display device and to obtain a long life of the device. SOLUTION: After a driving substrate 1-9 for driving an active matrix to increase the light emission time of a single pixel by a memory effect and an EL element substrate 11-14 for the emission of EL light are produced as completely separated from each other, the substrates are laminated by pressing by using indium columns 10 or the like as a glue.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an organic EL display which is one of flat panel displays.

[0002]

2. Description of the Related Art As a method for driving an organic EL display, there are a simple matrix method and an active matrix method. The simple matrix method is the simplest driving method, and has a structure in which an EL thin film is sandwiched between a lower electrode formed in a stripe shape and an upper electrode formed in a stripe shape perpendicular to the lower electrode. This is a method of driving an EL display by sequentially switching the voltages of the stripe-shaped electrodes.

As another driving method, there is an active matrix method. This is a thin film transistor (Thin Flim Tr)
An EL device is formed on a pixel substrate composed of an anistor (TFT) or the like. The drive waveform of the voltage applied to the unit pixel structure composed of TFTs enables memory drive that cannot be realized by the simple matrix structure, and has the characteristic that the light emission time of a single pixel can be lengthened.

[0004]

The organic EL display of a simple matrix method [0006] is, already have been the prototype, for example EL international conference was held in 1998 (9 ^th Int. Worksh
op on Inorganic and Organic Electroluminescence) by Pioneer S. Miyaguchi et al. (“Extended Abstrct of EL 98”, (1998) 137). The problem of the simple matrix method is that the luminance required for a single pixel is extremely large because the response speed of the organic EL element to the applied voltage of light emission is very fast (usually 1 μsec or less).

For example, if an EL display is manufactured using an organic EL element and 100 stripe electrodes are driven, the duty ratio is 1/100, and a display luminance of 100 (cd / m ² ) is obtained. In such a case, the organic EL element forming each single pixel needs a luminance of 10,000 (cd / m ² ) instantaneously. In this EL display, the time during which each single pixel emits light is, as shown in FIG.
Since there is only a 1/100 frame period, the temporal utilization of light emission is extremely low.

In addition, since the EL element must be driven at a very high luminance instantaneously, the individual EL elements constituting each single pixel deteriorate, and the life of the element is greatly reduced. Furthermore, the organic EL element has a problem in that the applied voltage increases as the pixel emits light with high luminance. Further, the organic EL device has a problem that the luminous efficiency is reduced by half under the luminous condition where the luminance increases 100 times from 100 (cd / m ² ) to 10,000 (cd / m ² ). As described above, the simple matrix method causes a decrease in the life of the EL element, an increase in applied voltage, and a decrease in luminous efficiency.

On the other hand, for example, the SID (The So
(Ciety for Information Display) As presented by T. Shimoda of Seiko Epson at an international conference, an organic EL display with a TFT mounted on each pixel has already been prototyped (SID99 Digest, (1999) 372) . In this method, each pixel has a memory function due to the mounted TFT, and the light emission time of each pixel can be greatly increased by this memory function. Therefore, it is intended to increase the brightness of the display. .

However, since the light emitting layer of the organic EL element uses an organic material, it is easily decomposed and deteriorated by an organic solvent or water. Processing technology)
Cannot be used for EL element processing. The anode and the cathode of the EL element are parallel to each other and have no irregularities. In addition, since the TFT and the EL element are arranged side by side, the ratio of the light emitting area to the display screen is reduced. For this reason, high definition of the EL display is restricted, and the aperture ratio is significantly reduced (an aperture ratio of 15% or less).

Therefore, in this EL display, although each single pixel can emit light continuously for one frame period, the light emission intensity per single pixel in consideration of the aperture ratio as shown in FIG. Significantly lower. Further, when light is extracted on the EL element side, it is difficult to make the cathode electrode made of a metal material having a small work function transparent, which further lowers the light emission utilization rate. For this reason, the brightness of the organic EL display using the TFT tends to be hardly improved as compared with the brightness of the simple matrix method, but rather to be lowered.

Accordingly, an object of the present invention is to provide an organic EL display device which solves the above-mentioned conventional problems and which can improve the light emission luminance by improving the aperture ratio of the light emitting element while maintaining the memory effect by active matrix driving. It is something you want to do.

[0011]

In order to achieve this object, an organic EL display device according to the present invention comprises an active matrix driving substrate for driving the EL element, and an organic EL display device.
It has a structure in which an EL element substrate that emits light from an element is bonded.

Further, in the present invention, a thin film transistor may be used as a driving substrate of the active matrix, and a MOS field effect transistor may be used. Still further, in the present invention, the bonding portion may be made of indium, gold, nickel, silver, or a metal containing solder, and the bonding portion may be made of an anisotropic conductive material, a photocurable insulating material, or a conductive resin. A ball may be used, and a cathode metal material of the EL element may be used as a metal material for the bonding. Further, in the device of the present invention, a flexible substrate may be used as the drive substrate of the active matrix and the substrate of the EL element.

[0013]

According to the present invention, as a means for increasing the luminance of an organic EL display device, an active matrix drive substrate and an EL element substrate are completely separated and manufactured.
Since the display device is formed by bonding the two substrates, each single pixel of the EL display device emits light continuously over one frame period, and the aperture ratio is greatly improved. As shown in FIG. 1C, the emission intensity per single pixel is greatly improved as compared with the conventional active matrix method (FIG. 1B).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 shows the organic EL of the present invention.
1 shows a structural cross-sectional view of one embodiment according to a specific example of a display device. TFTs constituting an active matrix circuit are formed on the first glass substrate 1. In FIG.
1 is a first glass substrate, 2 is a gate electrode of molybdenum-tantalum alloy or aluminum, 3 is a first (gate) insulating film of silicon nitride, 4 is a semiconductor layer of amorphous silicon,
5 is a source electrode of titanium or aluminum, 6 is a drain electrode of titanium or aluminum, 7 is a second insulating film of silicon nitride, 8 is an aluminum electrode which is electrically connected to the source electrode 5 and provided independently for each pixel. Reference numeral 9 denotes a pixel electrode, and reference numeral 9 denotes an aluminum light-shielding film. On the pixel electrode 8, an indium column 10 having a columnar structure is formed by a vapor deposition method and a lift-off method or by plating and a lift-off method.

On the other hand, 12 transparent electrode (ITO) films are formed on 11 second glass substrate, and 13
A light-emitting layer is formed, and a cathode metal electrode 14 of an EL element separated for each unit pixel is patterned thereon.
For these two glass substrates, the pixel electrode 8 and the EL
The indium pillars 10 are used as glue and pressed to perform bonding while aligning the elements with the cathode metal electrodes 14.

Therefore, light emitted from the EL element is extracted not from the TFT side but from the organic EL light emitting layer side (upper side in FIG. 2). At this time, each of the cathode metal electrodes 14 corresponds to a unit pixel of the EL display device, and the aperture ratio of the organic EL display is increased to almost 100% by patterning at a minimum interval at which the pixels can be separated. Can be.

FIG. 3 shows an embodiment of another embodiment according to the present invention. FIG. 3 is a sectional structural view of the active matrix substrate shown in FIG. 2 when a silicon substrate is used instead of glass.

On the silicon substrate shown in FIG. 3, MOSFETs (Metal-Oxide-
Semiconductor Field-Effect Transistor (MOS field effect transistor) has been manufactured. Here, in FIG. 3, 15 is a p-type silicon substrate, 16 and 17 are n ⁺ source and drain regions of a MOSFET formed on the semiconductor substrate 15, 18 is a p ⁺ pixel separation region, and 19 is this pixel separation region. This is a field insulating film made of silicon oxide formed on 18. 20 is a gate insulating film of silicon oxide, 21 is a gate electrode of polysilicon, 22 is a first insulating film of silicon oxide, and 23 is electrically connected to the drain region 17 through a contact hole provided in the first insulating film 22. The first aluminum electrode 25 is electrically connected to the source region 16 through a contact hole provided in the second insulating film 24 made of silicon oxide, and the second aluminum electrode 25 is provided independently for each pixel. It is a metal electrode. 26 is P
An SG (phosphosilicate glass) third insulating film 27 is an aluminum pixel metal electrode formed on the third insulating film and electrically connected to the second metal electrode 25.

On the other hand, 29 transparent electrode (ITO) films are formed on a glass substrate 28, 30 organic EL light emitting layers are further formed, and further, a unit pixel 31 is formed thereon.
The metal electrode for a cathode of the EL element is patterned. While positioning the pixel electrode 27 and the metal electrode 30 for the cathode of the EL element on these two substrates, an anisotropic conductive material in which metal fine particles 33 are dispersed in a binder material 32 is sandwiched as glue and pressed. Stick together. Also in this case, light emitted from the EL element is extracted not from the MOSFET side but from the organic EL light emitting layer side (upper side in FIG. 3). At this time, each of the metal electrodes for cathode 31 is EL
The aperture ratio of the organic EL display device can be increased to almost 100% by patterning at a minimum interval that corresponds to a unit pixel of the display and can be separated from each other.

Although the embodiment in which a glass or silicon substrate is used as the driving substrate of the active matrix has been described above, the present invention can be applied to a case where a plastic substrate having flexibility is used. In this case, a TFT is formed on a plastic substrate in the same manner as in FIG. 2, and an EL element is also formed on another plastic substrate, and the two plastic substrates are connected to a metal bump or an anisotropic conductive material. Thus, a flexible EL display device can be manufactured. Also in this case, each of the metal electrodes for the cathode corresponds to a unit pixel of the EL display device, and the aperture ratio of the organic EL display is reduced to almost 100% by patterning at a minimum interval capable of separating pixels. Can be enhanced.

In the above-described embodiment, the case where metal bumps and anisotropic conductive material are used for bonding substrates has been described. The substrates can be attached to each other using an insulating resin material or the like.

As for the material of the metal bump, in addition to indium, a metal containing gold, nickel, silver, solder, or the like can be used. In particular, a bump material for bonding a cathode metal material of an EL element as it is can be used. It is also possible to use as.

Although the embodiments of the present invention have been described with reference to some specific examples, the present invention is not limited to these embodiments, and various kinds of various embodiments may be included within the scope of the invention defined in the appended claims. It is obvious that modifications and changes are possible.

[0024]

According to the present invention, not only the memory effect by the active matrix driving is exerted, but also the aperture ratio becomes close to 100%, so that the aperture ratio is reduced as shown in FIG. The light emission intensity per single pixel taken into consideration is remarkably improved, and luminance substantially equal to the luminance of a single EL element can be obtained as the luminance of the entire display device.

Further, a rise in the voltage applied to the EL element of each pixel does not occur, and a decrease in luminous efficiency is suppressed. In addition, the light emission of the EL element of each pixel is always maintained at about the same level as the luminance of the display device during one frame period, the duty ratio becomes almost 1, and the state of continuous light emission can be maintained. The instantaneous light emission is not used, and the reduction in element life is greatly suppressed.

Further, in manufacturing an EL element, the EL
Since a driving part such as a TFT is not formed on the element substrate, the EL film is not affected by the unevenness of the TFT, and a wet process using an organic solvent that decomposes the organic EL material must be used for the EL element production. Since there is no structure and the TFT and the EL element are not juxtaposed, fine processing becomes easy, and a high-definition display device can be manufactured. In addition, since the entire organic EL element is completely covered with the active matrix substrate by bonding, it is not directly exposed to the atmosphere,
Conventionally, the sealing operation, which is indispensable for the organic EL element, is unnecessary or simplified.

[Brief description of the drawings]

FIG. 1 is a comparison of light emission intensity per single pixel in consideration of an aperture ratio in an organic EL display device using different driving methods.
(B) shows the light emission luminance in the case of the conventional active matrix driving method, and (c) shows the light emission luminance in the case of the active matrix driving method of the present invention.

FIG. 2 is a structural sectional view of an EL display device according to the present invention when an active matrix drive substrate using a TFT and an EL element substrate are bonded to each other.

FIG. 3 is a structural sectional view of an EL display device according to the present invention when an active matrix drive substrate using a MOSFET and an EL element substrate are bonded to each other.

[Explanation of symbols]

 1,11,28 Glass substrate 2,21 Gate electrode 3,20 Gate insulating film 4 Semiconductor layer 5 Source electrode 6 Drain electrode 7,22,24,26 Insulating film 8,27 Pixel electrode 9 Light shielding film 10 Indium pillar 12,29 Transparent electrode 13,30 Organic EL light-emitting layer 14,31 Metal electrode for cathode 15 Semiconductor substrate 16 Source region 17 Drain region 18 Pixel separation region 19 Field insulating film 23,25 Metal electrode 32 Binder material 33 Metal fine particles

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/14 H01L 29/78 612Z 33/26 (72) Inventor Yoji Inoue 1-10 Kinuta, Setagaya-ku, Tokyo No. 11 Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Isao Tanaka 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Shinji Okamoto 1 Kinuta, Setagaya-ku Tokyo 10-10-11 Japan Broadcasting Corporation Broadcasting Research Institute F term (reference) 3K007 AB02 BA07 CA01 DA02 EB05 5C094 AA07 AA37 BA29 CA19 EB01 FB01 5F110 AA30 BB01 CC07 DD02 DD05 EE03 EE06 EE09 FF02 FF03 GG03 NN03 NN24 NN25 NN47 NN62

Claims (7)

[Claims] In a display device using an organic EL material, the display device has a structure in which an active matrix driving substrate for driving an EL element and an EL element substrate for emitting light from the EL element are bonded to each other. Characteristic organic EL display device. 2. The organic EL display device according to claim 1, wherein a thin film transistor is used for a driving substrate of the active matrix. 3. The organic EL display device according to claim 1, wherein a MOS field effect transistor is used as a drive substrate of said active matrix. 4. The organic EL display device according to claim 1, wherein the bonding portion is made of indium, gold, nickel, silver, or a metal containing solder. 5. The organic EL display device according to claim 1, wherein an anisotropic conductive material, a photocurable insulating material, or a conductive resin ball is used for the bonded portion. . 6. The organic EL device according to claim 1, wherein a cathode metal material of the EL element is used as a metal material for the bonding.
Display device. 7. The device according to claim 1, wherein
An organic EL display device, wherein a flexible substrate is used for the active matrix drive substrate and the EL element substrate.