JP4647134B2 - Organic EL display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device in which an organic EL (electroluminescent) layer is provided between a pair of electrodes, and an electric field is applied to the organic EL layer by the pair of electrodes to emit light.
[0002]
[Prior art]
In recent years, EL display devices using electroluminescence have been actively developed. The EL display device has a configuration in which a light emitting layer is provided between an anode and a cathode. In the EL display device, as in the liquid crystal display device, a passive driving method represented by a line sequential method is adopted in addition to an active driving method in which a switch such as a TFT is provided for each pixel to individually drive each pixel. Can do. Such an EL display device can be classified into an inorganic EL display device and an organic EL display device depending on the type of the luminescent compound used. In an organic EL display device, in order to efficiently confine holes supplied from the anode and electrons supplied from the cathode in the light emitting layer, the organic layer is sandwiched between the electron transport layer and the hole (hole) transport layer. It is common to configure.
[0003]
In an inorganic EL display device and an organic EL display device, there are pros and cons due to the type of luminescent compound. The inorganic EL display device has an advantage that the device life is long (half-life of luminance is 20000 hours or more), but has a disadvantage that the light emission efficiency, particularly blue light emission efficiency is small and the drive voltage is high. On the other hand, the organic EL display device has high light emission efficiency and requires a small voltage necessary for causing the light emitting compound to emit light, but has a drawback that the device life is short. Therefore, when used as a display such as a mobile phone, the organic EL display device is more promising. However, in consideration of practicality, it is necessary to extend the device life of the organic EL display device.
[0004]
[Problems to be solved by the invention]
There are various reasons why the life of the organic EL display device is short (cause of deterioration). One of them is due to thermal energy. In the organic EL display device, 5% of the electric energy supplied to the organic layer is used for light emission, and the remaining 95% is consumed as heat. For this reason, when a voltage is applied between the electrodes, a large amount of heat is generated in the organic layer or the like, and the following phenomenon occurs due to the heat and the organic EL display device is deteriorated.
[0005]
First, due to the mutual diffusion between the light emitting layer and the hole transport layer, the current-voltage characteristic is shifted to the high voltage side, and the luminance is lowered. Second, the anode is oxidized. Third, the organic layer is decomposed. The organic layer decomposes directly due to thermal energy and also due to the oxidation of the anode.
[0006]
Such thermal degradation appears more prominently in an organic EL display device adopting a passive drive method. In the passive drive method, for example, an anode or a cathode (scanning electrode) to which a high voltage is applied is sequentially switched, and a pixel (light emitting layer) to which the high voltage is applied is caused to emit light instantaneously. Therefore, in order to visually recognize that a certain pixel always emits light with a predetermined luminance, so that the luminance does not become lower than a predetermined value before the next high potential is applied after the high voltage is applied first. It is necessary to cause the pixel to emit light with a luminance considerably higher than the predetermined value. Therefore, when passive driving is adopted, it is necessary to repeatedly apply a large potential. As a result, the energization amount in each pixel, and hence the heat generation amount, increases, and the problem of thermal degradation becomes more prominent.
[0007]
The present invention has been conceived under such circumstances, and an object thereof is to suppress the thermal deterioration and extend the life of the organic EL display device.
[0008]
DISCLOSURE OF THE INVENTION
That is, the organic EL display device provided by the present invention includes a plurality of anodes (first electrodes) that extend in a strip shape on a transparent substrate and are formed in parallel independently of each other, and the respective anodes are sequentially independent. A plurality of hole injection layers and a hole transport layer that are stacked, a plurality of light emitting layers that are stacked on each of the hole transport layers and extend perpendicular to the respective anodes, and are formed independently of each other; An organic EL display device having a plurality of electron transport layers, an electron injection layer, and a cathode (second electrode), which are sequentially and independently stacked with respect to a light emitting layer, and is stacked on the plurality of cathodes to dissipate heat. A member is provided, and the heat dissipating member is bonded onto the plurality of cathodes via a silicone resin adhesive that is in contact with the plurality of cathodes in common .
[0009]
In this configuration, when a voltage is applied between the first and second electrodes (anode and cathode) , thermal energy is generated in an organic layer (hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer) or the like. Even if this occurs, the thermal energy is positively released to the outside of the apparatus through the heat radiating member. As a result, it becomes possible to extend the life of the device by suppressing the oxidation of the electrodes and the organic layer due to the temperature rise of the device and thermal energy, and hence the thermal degradation of the device. In this configuration, the silicone resin adhesive functions as a buffer layer. That is, even when an external load is applied to the heat radiating member, the load is alleviated by the silicone resin adhesive, so that the interface between the organic layer and the second electrode or the organic layer itself is caused by the external load. It becomes possible to suppress the situation of being damaged. Moreover, since the silicone resin adhesive has high thermal diffusivity, the heat transfer to the heat radiating member is not hindered.
[0010]
In order to enjoy the effect more reliably in this way, the heat radiating member is made of a metal having a higher thermal diffusibility than the transparent substrate, or the heat radiating member has a plurality of convex portions to ensure a large surface area. Is preferred.
[0011]
As described above, the thermal deterioration appears more prominently in the passively driven organic EL display device. Therefore, providing the heat dissipation member is more effective for an organic EL display device configured to be passively driven.
[0014]
Other advantages and features of the present invention will become more apparent from the following description of embodiments of the invention.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. Here, FIG. 1 is a partially broken perspective view showing an example of an organic EL display device according to the present invention, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. It is a whole perspective view.
[0016]
The organic EL display device X shown in FIG. 1 and FIG. 2 is configured to be passively driven by a line sequential method, and has a plurality of anodes 2, a plurality of organic layers 3, and a plurality of cathodes 4 on a transparent substrate 1. And the heat radiating member 5 is provided.
[0017]
The transparent substrate 1 is not clearly shown on the drawing, but is formed in a rectangular shape using, for example, transparent glass or a resin film. The anode 2 is formed in a strip shape extending in the direction of arrow AB in FIG. 1 on the surface 10 of the transparent substrate 1, and a plurality of anodes 2 are arranged in the width direction thereof. These anodes 2 can be formed by performing an etching process after forming a transparent conductor film having a thickness of 200 to 500 mm by a known method such as vapor deposition or sputtering using ITO or the like.
[0018]
The organic layer 3 includes a plurality of hole injection layers 30, a plurality of hole transport layers 31, a plurality of light emitting layers 32, a plurality of electron transport layers 33, and a plurality of electron injection layers 34.
[0019]
The hole injection layer 30 has a role of improving hole extraction efficiency from the anode 2, that is, hole injection efficiency into the organic layer 3. The hole transport layer 31 efficiently moves holes to the light emitting layer 32 and suppresses electrons from the cathode 4 from moving beyond the light emitting layer 32 to the anode 2. It has a role to increase the recombination efficiency.
[0020]
The hole injection layer 30 and the hole transport layer 31 are formed in a strip shape extending in the same direction as the anode 2 (the direction of arrow AB in FIG. 1). The hole injection layer 30 is formed on the anode 2 and the hole transport layer 31 is stacked on the hole injection layer 30, and a plurality of layers extend in parallel in the width direction of the anode 2 (arrow CD direction in FIG. 1). .
[0021]
The hole injection layer 30 and the hole transport layer 31 can be formed, for example, by sputtering or vapor deposition. The hole injection layer 30 is formed to have a thickness of several to 10 mm, and the hole transport layer 30 is formed to have a thickness of 100 to 1000 mm. The
[0022]
As a material constituting the hole injection layer 30, for example, copper phthalocyanine, metal-free phthalocyanine, aromatic amine (TPAC, 2Me-TPD, α-NPD, etc.) can be used. On the other hand, as a material constituting the hole transport layer 31, for example, 1,1-bis (4-di-p-aminophenyl) cyclohexane, galbazole and derivatives thereof, triphenylamine and derivatives thereof can be used.
[0023]
The light emitting layer 32 is formed in a strip shape extending in a direction (arrow CD direction in FIG. 1) orthogonal to the direction in which the anode 2 extends (arrow AB direction in FIG. 1). (In the direction of arrow AB) and extend parallel to each other. These light emitting layers 32 contain a light emitting substance, and are a place where excitons are generated by recombination of holes from the anode 2 and electrons from the cathode 4. The excitons move through the light emitting layer 32, and the light emitting material emits light in the process.
[0024]
The electron injection layer 34 has a role of improving the electron extraction efficiency from the cathode 4, that is, the electron injection efficiency into the organic layer 3. The electron transport layer 33 efficiently moves electrons to the light emitting layer 32 and suppresses movement of holes from the anode 2 beyond the light emitting layer 32 to the cathode 4. It has a role to increase the recombination efficiency.
[0025]
The electron transport layer 33 and the electron injection layer 34 are formed in a strip shape extending in the same direction as the light emitting layer 32 (the arrow CD direction in FIG. 1). The electron transport layer 33 is stacked on the light emitting layer 32, and the electron injection layer 34 is stacked on the electron transport layer 33. A plurality of layers are aligned in the width direction of the light emitting layer 32 (the arrow AB direction in FIG. 1) and are parallel to each other. It extends.
[0026]
The light emitting layer 32, the electron transport layer 33, and the electron injection layer 34 can be formed, for example, by sputtering or vapor deposition. The light emitting layer 32 and the electron transport layer 33 have a thickness of 100 to 1000 mm, and the electron injection layer 34 has a thickness. Is formed to several to 10 cm.
[0027]
Examples of the luminescent substance include tris (8-quinolinolato) aluminum complex, bis (benzoquinolinolato) beryllium complex, ditoluylvinylbiphenyl, tri (dibenzoylmethyl) phenanthroline europium complex (Eu (DBM) ₃ (Phen)), And fluorescent or phosphorescent emissive materials such as phenylpyridine iridium compounds can be used. Of course, polymer light-emitting substances such as poly (p-phenylene vinylene), polyalkylthiophene, polyfluorene, and derivatives thereof may be used.
[0028]
In the case where the organic EL display device X is configured for color display, for example, the three adjacent light emitting layers 32 are made up of an R light emitting layer, a G light emitting layer, and a B light emitting layer, and such a set is used. A plurality may be provided. In this case, the R light emitting layer, the G light emitting layer, and the B light emitting layer may contain a light emitting substance that emits light corresponding to each color, or emit light filters corresponding to each color. It may be provided between the layer 32 and the second substrate 12.
[0029]
On the other hand, as materials constituting the electron transport layer 33 and the electron injection layer 34, for example, anthraquinodimethane, diphenylquinone, perylenetetracarboxylic acid, triazole, oxazole, oxadiazole, benzoxazole, and derivatives thereof are used. be able to. The electron injection layer 34 can also be formed of an inorganic material such as LiF. In this case, the electron injection layer 34 is not a component of the organic layer 3.
[0030]
A plurality of cathodes 4 extend in parallel to each other along the width direction (arrow AB direction in FIG. 1) of the light emitting layer 32 in a strip shape extending in the same direction as the light emitting layer 32 (arrow CD direction in FIG. 1). . Such a cathode 4 can be formed by performing an etching process after forming a metal film such as aluminum by sputtering or vapor deposition, for example.
[0031]
As shown in FIGS. 1 to 3, the heat dissipating member 5 is formed with a plurality of bead-shaped convex portions 51 extending on the base 50 in the same direction as the direction in which the cathode 4 extends (the arrow CD direction in FIG. 1). The whole is made of a material having excellent thermal diffusivity such as aluminum.
[0032]
If the heat dissipating member 5 is provided, even if heat energy is generated in the organic layer 3 or the like when a voltage is applied between the anode 2 and the cathode 4, the heat energy is actively transmitted to the outside of the apparatus via the heat dissipating member 5. To be released. As a result, it is possible to extend the life of the device by suppressing the oxidation of the electrodes 2 and 4 and the organic layer 3 due to the temperature rise of the device and thermal energy, and consequently the thermal degradation of the device.
[0033]
The heat dissipating member 5 is bonded onto the plurality of cathodes 4 via an adhesive 6. As the adhesive 6, for example, a material having a large thermal diffusivity such as silicone is used. Thus, if the heat radiating member 5 is adhere | attached via the adhesive agent 6, the heat radiating member 5 will function as a buffering material. That is, even when an external load is applied to the heat dissipation member 5, the load is absorbed by the adhesive 6, and the force acting on the interface between the organic layer 3 and the cathode 4 and the organic layer 3 itself is applied. Alleviated. Further, if the heat radiating member 5 is bonded with an adhesive 6 having a high thermal diffusivity, the adhesive 6 does not hinder heat transfer to the heat radiating member 5.
[0034]
The plurality of anodes 2 and the plurality of cathodes 4 are electrically connected to a driver IC (not shown). From the driver IC, a scanning voltage is sequentially applied to the plurality of anodes 2 and a signal voltage corresponding to a display image is input to the plurality of cathodes 4 in synchronization with the clock pulse.
[0035]
When a voltage higher than a certain value is applied between the anode 2 and the cathode 4 corresponding to the selected pixel by the driver IC, holes are injected from the anode 2 into the hole injection layer 30 and electrons are transmitted from the cathode 4. Electrons are injected into the injection layer 3. The holes are transported to the light emitting layer 32 via the hole transport layer 31, and the electrons are transported to the light emitting layer 32 via the electron transport layer 33. In the light emitting layer 32, electrons and holes are recombined to generate excitons, and the excitons move through the light emitting layer 32. In the light emitting layer 32, light emission is generated by energy released when excitons move between predetermined bands in the luminescent material. The light at this time passes through the hole transport layer 33, the hole injection layer 34, the anode 2, and the transparent substrate 1 and is emitted to the outside of the organic EL display device X. In this way, an image is displayed when the selected pixel emits light.
[0036]
The heat dissipating member may be any member that efficiently releases heat to the outside of the apparatus. As in the heat dissipating member 5 ′ shown in FIG. 4, a plurality of prismatic protrusions 51 ′ are arranged in a matrix on the base 50 ′. In addition, a plurality of fins may be provided in addition to a plurality of conical or pyramidal or cylindrical convex portions.
[0037]
In this embodiment, the organic EL display device in which the organic layer is configured by the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, and the hole injection layer has been described as an example. It can be changed. For example, a two-layer structure including a hole transport layer and a light-emitting layer, or an electron transport layer and a light-emitting layer, or a three-layer structure including a hole transport layer, an electron transport layer, and a light-emitting layer may be used.
[Brief description of the drawings]
FIG. 1 is a partially broken perspective view showing an example of an organic EL display device according to the present invention.
2 is a cross-sectional view taken along line II-II in FIG.
FIG. 3 is an overall perspective view of a heat radiating member.
FIG. 4 is an overall perspective view showing another example of the heat radiating member.
[Explanation of symbols]
X Organic EL display device 1 Transparent substrate 2 Anode 3 Organic layer 4 Cathode 5 Heat dissipating member 50 Bead-shaped convex part (of heat dissipating member)

Claims (4)

A plurality of anodes extending in a strip shape and formed independently and parallel to each other on a transparent substrate, a plurality of hole injection layers and hole transport layers sequentially and independently stacked on each of the anodes, and each of the above A plurality of light-emitting layers that are stacked on the hole transport layer and extend perpendicular to the respective anodes and formed independently of each other; and a plurality of electron-transport layers that are sequentially stacked on each of the light-emitting layers, An organic EL display device having an electron injection layer and a cathode ,
A heat dissipation member is provided by laminating the plurality of cathodes , and
The organic EL display device, wherein the heat radiating member is bonded onto the plurality of cathodes via a silicone resin adhesive that is in contact with the plurality of cathodes in common .   The organic EL display device according to claim 1, wherein the heat radiating member is formed of a metal having a higher thermal diffusibility than the transparent substrate.   The organic EL display device according to claim 1, wherein the heat dissipation member has a plurality of convex portions.   The organic EL display device according to claim 1, wherein the organic EL display device is configured to be passively driven.

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