Display device and light emitting device

Display device and light emitting device

[Technical field to which the invention belongs]

The present invention relates to a display device having a light-emitting layer such as an electroluminescence (EL) element on a substrate, and in particular to a packaging structure of an organic EL display element.

[Technology of learning]

In recent years, display devices using organic EL elements have attracted attention as display devices that can replace CRT or LCD. Figure 1A is a plan view of a conventional organic EL display device, and Figure 1B is a cross-sectional view of AA'. On the transparent substrate 1, a plurality of selection drive circuits 2 are arranged in each pixel. A planarization insulating film 3 is formed to cover the selection driving circuit 2, and a contact hole is formed in the area of each selection driving circuit 2 opposite to the planarization insulation film 3 to connect the pixel electrode 4 to the selection driving circuit 2. The light emitting layer 5 and the counter electrode 6 are arranged to cover these. Around the display area where the selective drive circuit 2, the pixel electrode 4, the light-emitting layer 5, and the counter electrode 6 are formed, display drive circuits 7a and 7b are arranged to control the selective drive circuit 2, or to apply a predetermined voltage to the pixel electrode 4. Drive the display area. The driving circuit 7 is connected to the terminal 9 by a wiring 8. The protective frame 10 made of metal such as aluminum is covered and arranged. The protective frame 10 is fixed on the transparent substrate 1 with an adhesive 11 of ultraviolet curable resin. The packaging space between the protective frame 10 and the transparent substrate 1 is filled with dry nitrogen gas, and the inner surface of the protective frame 10 is provided with a desiccant sheet 12.

The selective driving circuit 2 has a large number of semiconductor elements, such as thin film transistors (TFTs). The first TFT is switched on and off in response to the output of the driving circuit 7a. The output of the driving circuit 7a makes the first TFT of the selection driving circuit 2 a conductive pixel electrode 4. A voltage corresponding to the output of the driving circuit 7b is applied via the second TFT, and a current can flow between it and the counter electrode 6. Here, the light-emitting layer 5 is configured to emit light by passing current, and emits light according to the intensity of the current flowing between the pixel electrode 4 and the counter electrode 6. The luminous light will be seen through the transparent substrate 1 towards the bottom of the cross-sectional view.

In addition, the organic EL element recombines the holes injected from the anode and the electrons injected from the cathode in the light-emitting layer to excite organic molecules forming the light-emitting layer to generate excitation electrons. The excitation electrons emit light from the light-emitting layer during the de-excitation process. This light is emitted from the transparent anode to the outside through the transparent insulating substrate to emit light.

However, it is well known that the organic EL layer 5 will be degraded by moisture. For example, if there are defects such as pinholes in the counter electrode 6, the moisture soaked will oxidize the counter electrode 6 or cause the light emitting layer 5 to contact the counter electrode 6. The peeling or the like between the electrodes 6 generates dark spots, and the display quality is extremely deteriorated. The protective frame 10 protects the display area and the drive circuit 7 from physical impacts, and has a function of preventing moisture intrusion. Therefore, the disk shape is formed to cover the display area. In addition, in order to solve the immersion of moisture, the space is filled with inert gas such as dry nitrogen or helium, and a desiccant sheet 12 is arranged. In addition, in order to arrange the desiccant sheet 12, there is a step in the arrangement. These structures are disclosed in, for example, the announcement of Japanese Patent Laid-Open No. 9-148066.

However, the conventional sealing structure directly coats the adhesive 11 on the transparent substrate 1 to bond the protective frame 10. Therefore, when the sealant 11 is hardened, due to the difference in thermal expansion rate between the transparent substrate 1 and the protective frame 10, The adhesive 11 may peel off, resulting in incomplete sealing. In addition, the sealant 11 is applied to the wiring 8 in the area where the wiring 8 is arranged. However, due to the stress when the sealant 11 is hardened, the wiring 8 may be disconnected.

[Object of the invention]

Therefore, the object of the present invention is to provide an EL display device that has a structure in which the transparent substrate 1 and the protection frame 10 are not easily peeled off even if there is a difference in thermal expansion between the transparent substrate 1 and the protective frame 10, or the wiring 8 The structure is not easy to break.

In order to solve the above problems, the present invention disposes the display device in the display field between the first and second substrates of different materials, and includes a package for bonding between the first and second substrates. 1 or (and) a display device with a buffer layer between the second substrates.

The buffer layer is an insulating film.

In addition, the display area is a structure in which a plurality of thin films including an insulating film are laminated. The insulating film extends between the sealing member and the first or (and) second substrate to form a buffer layer.

In addition, the display field has a selection drive circuit provided for each pixel; a planarization insulating film formed to cover the selection drive circuit; and pixel electrodes provided on the planarization insulation film corresponding to each selection drive circuit, and the buffer layer is Planarize the insulating film.

In addition, the first substrate is a transparent insulating substrate, and the second substrate is a protective frame formed to cover the display area.

In addition, the first substrate is made of glass or resin, and the second substrate is made of metal.

The planarization insulating film extends between the first substrate and the package.

In addition, the planarization insulating film is made of a material softer than the package and the first substrate.

Furthermore, there are terminals connected to the display area via wires and exposed to the outside of the display device, and a buffer layer is arranged between the wires or the terminals and the package.

Another feature of the present invention is that the light-emitting device according to item 12 of the scope of patent application has a light-emitting field with light-emitting elements sealed between a first substrate and a second substrate with different thermal expansion rates, wherein

The first and second substrates are bonded to each other with a sealant at the position surrounding the light-emitting area,

A buffer layer is formed between the sealant and the first and/or second substrate.

In addition, another feature is that a desiccant is incorporated in the aforementioned package of the above-mentioned device.

Furthermore, in the present invention, the device located in the display field or the light-emitting field is an organic electroluminescent device containing an organic light-emitting material.

Due to the presence of the above buffer layer, the present invention can absorb the stress generated in the sealing part due to the difference in thermal expansion coefficients of the first and second substrates by this buffer layer, and can reliably prevent the peeling of the sealant from causing the first Poor adhesion of the first and second substrates.

In addition, the display area has a structure of a plurality of thin film layers including an insulating film, and the insulating film is formed as a buffer layer, so there is no need to form a buffer layer separately, and it can be formed at the same time when forming the display area. Therefore, the manufacturing process can be simplified.

In addition, the buffer layer is a flattening insulating film, and the thickness of the flattening insulating film It is thicker than the gate insulating film or the interlayer insulating film, and its material is also softer than glass or packaging. Among the insulating films formed in the display field, it is the most suitable as a buffer layer.

In addition, it has terminals connected to the display area via wiring and exposed to the outside of the display device. A buffer layer is arranged between the wiring or the terminal and the package to prevent the wiring from breaking due to stress when the sealant is hardened.

<p>1 Transparent substrate 2 Selection drive circuit (switching element) 3, 21 Flattening insulating film 4 Pixel electrode 5, 5c Light emitting layer 5a First hole transport layer 5b Second hole transport layer 5d Electron current carrying layer 6 Counter electrode 7, 7a , 7b Drive circuit 8 Wiring 9 Terminal 10 Protective frame 11 Adhesive (package) 12 Desiccant sheet 41 Gate 42 Gate insulating film 43 Active layer 43c Channel 43d Drain 43s Source 44 Blocking insulating film 45 Interlayer insulation Film 46 drive power cord</p>

Figures 1A and 1B are plan views and cross-sectional views of conventional display devices. 2A, 2B, and 2C are plan views and cross-sectional views of the display device of the present invention.

[Implementation form of invention]

Fig. 2A is a plan view of the organic EL display device according to the first embodiment of the present invention, and Fig. 2B is a cross-sectional view of AA'. The same structure as the conventional one is attached with the same number and its detailed description is omitted. A selection driving circuit 2 and a pixel electrode 4 are arranged on the transparent substrate 1 for each pixel, and the light-emitting layer 5 and the opposite electrode 6 are arranged to cover the arrangement. Around the display area where the selection driving circuit 2, the pixel electrode 4, the light-emitting layer 5, and the counter electrode 6 are formed, driving circuits 7a, 7b for controlling the selection driving circuit 2 or applying a predetermined voltage to the pixel electrode 4 are arranged. The drive circuit 7 is connected to the terminal 9 via the wiring 8. The protective frame 10 is also configured to cover the display area. In the present invention, the substrate refers to the one that includes the protective frame 10.

The feature of this embodiment is that a buffer layer is provided between the sealant and the substrate. Specifically, in this embodiment, the planarization insulating film 21 formed to cover the selection drive circuit 2 is extended to the outside of the display area, and the sealant A planarization insulating film 21 is arranged between 11 and the substrate 1.

The planarization insulating film 21 is located between the sealant 11 and the substrate 1. Since the flattening insulating film 21 is softer than the sealant 11 and the substrate 1, even when the sealant 11 is hardened, the package 11 will be stressed due to the difference in thermal expansion coefficient between the substrate 1 and the protective frame 10 Since the planarization insulating film 21 serves as a buffer layer and absorbs the stress, it is possible to prevent the substrate 1 and the protective frame 10 from peeling off.

The gist of the present invention is to arrange a buffer layer softer than the sealant 11 between the sealant 11 and the substrate 1, and is not limited to the planarization insulating film 21. As long as the material is softer than the sealant 11, any material can be used. But because The wiring is connected to the terminal 9 which crosses under the package 11 and is exposed to the outside. Therefore, when this structure is formed, the buffer layer needs to be at least an insulating film.

In addition, the buffer layer may be formed in addition to the film used in the laminated structure in the display field. However, the display field contains a multi-layer insulating film, and if any one or more layers are extended to the field of the package 11, the buffer layer can be formed without additional manufacturing steps, which is very efficient.

In addition, among most insulating films formed in the display field, the planarizing insulating film 21 has the function of a film that planarizes the unevenness caused by the structure formed in the lower layer, and the gate insulating film 42 of 500 to 2000 Compared with the interlayer insulating film 45, for example, a thickness of 1 μm to 2 μm can be formed. If so, the planarization insulating film 21 has a sufficient thickness and is most suitable as a buffer layer.

The material of the planarization insulating film 21 can be acrylic resin, silicon oxide film, silicon oxide film, positive resist material, etc. However, the display device is formed on most of the mother glass in the same step at the same time. In order to divide it, compared with the spin coating material used for semiconductor wafers, that is, the SOG film, the above-mentioned acrylic resin is more suitable for large-area processing, or Positive resist materials are more suitable. In addition, the material of the planarization insulating film 21 is preferably selected as the water penetration amount is smaller. The organic EL with a light-emitting layer is significantly degraded by moisture. This is because when moisture penetrates into the packaging space formed by the substrate 1 and the protective frame 10, the display quality will be degraded.

As the thickness of the flattening insulating film 21 increases in principle, the function as a buffer layer increases, but on the other hand, the area exposed to the outside increases, and the amount of penetration of water increases accordingly. Therefore, within the scope of the buffer layer function, Try to be as thin as possible.

If any of the materials of the planarization insulating film 21 are used, some moisture will penetrate. Therefore, if the desiccant powder is mixed into the package 11, the moisture permeating the planarization insulating film 21 will be absorbed, and the deterioration of the organic EL can be surely prevented. The planarization insulating film 21 is 1 μm to 2 μm as described above. Therefore, as long as the desiccant is stirred and mixed into the sealant 11, even if the desiccant is not stirred and mixed into the planarization insulating film 21, it can prevent moisture from penetrating into the planarizing insulating film 21 and entering the package. In the space. If the desiccant is mixed before the sealant 11 is hardened, and the resin is hardened after being fully stirred, it can be uniformly mixed into the sealant 11. The desiccant is a chemically adsorbing substance. The chemical adsorption desiccant may, for example, be oxides of alkaline earth metals such as calcium oxide and barium oxide, halides of alkaline earth metals such as calcium chloride, and phosphorus pentoxide. However, the physical adsorption ratio of silica gel (Silikagel) is not suitable because it will release the absorbed moisture at high temperature.

FIG. 2C is an example of the cross-sectional structure of each pixel of the active matrix type organic EL display of this embodiment. On an insulating substrate 1 made of quartz glass, alkali-free glass, etc., a gate 41 made of high melting point metals such as Cr and Mo is arranged. SiO is sequentially laminated on the gate 41₂The gate insulating film 42 and the active layer 43 formed by the p-Si film. The active layer 43 is a channel 43c (Channel) above the gate 41, and on both sides of the channel 43c, the stopper insulating film 44 on the channel 43C is used as a mask to perform ion doping. (ion doping), and then cover both sides of the gate 41 with resist and apply ion doping. There are low-concentration areas on both sides of the gate 41, and a high-concentration area source 43s and drain are arranged on the outside of the gate 41.pole43d. The structure of the gate 41, the gate insulating film 42, and the active layer 43 is a TFT, which is a part of the selective driving circuit. TFT is the so-called LDD constructor.

Thus, on the entire surface of the gate insulating film 42, the active layer 43 and the blocking insulating film 44, SiO₂Film, SiN film, and SiO₂An interlayer insulating film 45 is formed by forming an interlayer insulating film 45, and a contact hole (ContactHoll) provided corresponding to the drain 43d is filled with metal such as Al and connected to the driving power line 46. Furthermore, a flattening insulating film 3 made of, for example, an organic resin and flattened the surface is formed on the entire surface. Then, a contact hole is formed at the position corresponding to the source electrode 43s of the planarized insulating film 3, and a transparent electrode made of ITO indium tin oxide (Indium Tin Oxide) etc. which is in contact with the source electrode 13s through the contact hole is arranged 4.

The light-emitting layer 5 is the first hole intercepting layer 5a formed by MTDATA (4,4-bis(3-methylphenylanilino)biphenyl), TPD(4,4,4-see (3-methyl) Phenylanilino) triphenylamine) formed by the second hole intercepting layer 5b, and Bebq containing quinacridone derivative₂The light-emitting layer 5c and Bebq formed by (10-benzene[h]p-carbophthalic acid-beryllium complex)₂A light-emitting element layer composed of the formed electron intercepting layer 5d. The above configuration is described in Japanese Patent Application Publication No. 11-22183 and Japanese Patent Application No. 11-22184, for example.

Furthermore, the TFT is an example of a Botton gate TFT whose gate is located more on the substrate side than the active layer. However, the key is to selectively apply a voltage to one of the pixel electrodes. Yes, for example, a top gate TFT whose active layer is located on the substrate side more than the gate electrode may be used.