JP2009058897A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display device which does not need to form a bank. <P>SOLUTION: A pixel electrode 13 is connected with an SD line 10 via a contact hole part 18 formed on a flattened film 12. The tapered angle θ of the edge part of the pixel electrode 13 is formed to be 40° or less. Accordingly, an organic EL layer 15 does not cause disconnection caused by a step on the edge part of the pixel electrode 13 and, therefore, an upper electrode 19 and the pixel electrode 13 are not short-circuited. At the contact hole part 18, organic EL layers 15, 16, 17 of three colors are formed so as to be superimposed on one another and, as the result, short-circuiting between the upper electrode 19 and the pixel electrode 13 due to the disconnection caused by the step of the organic EL layer 15 can be avoided. Thereby, the formation of the bank can be omitted in the organic EL display device and the manufacturing cost of the organic EL display device can be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to an organic EL display device including an organic EL light emitting layer.

  In the organic EL display device, light emitted from the organic EL layer is extracted in the direction opposite to the glass substrate on which the organic EL layer is formed, and the bottom emission type in which the light is emitted toward the glass substrate on which the organic EL layer is formed. There is a top emission type. The top emission type has an advantage that the brightness of the display can be increased because a large area of the organic EL layer can be taken.

  In an organic EL display device, an organic EL layer is sandwiched between a pixel electrode (lower electrode) and an upper electrode, a constant voltage is applied to the upper electrode, and a data signal voltage is applied to the lower electrode to emit light from the organic EL layer. An image is formed by controlling. The data signal voltage is supplied to the lower electrode through a thin film transistor (TFT). In the top emission type organic EL display device, since the organic EL layer can be formed on the TFT and the like, the light emission area can be increased.

  The organic EL layer is formed from a plurality of layers. The total thickness of the plurality of layers is 100 nm to 300 nm, although it varies depending on the color emitted by the organic EL layer. Since such a thin layer is sandwiched between the upper electrode and the lower electrode, if there is a defect in the organic EL layer, the upper electrode and the lower electrode are short-circuited. This short-circuit between the upper electrode and the lower electrode tends to occur at the end of the lower electrode.

  In order to prevent a short circuit between the upper electrode and the lower electrode that occurs at the end, a bank is provided between each organic EL layer to prevent disconnection of the organic EL layer at the end of the lower electrode. This bank is formed of a resin such as acrylic or polyimide. Banks are formed by photolithography, but at this time, etching residues such as resin are likely to occur. When an etching residue or the like occurs, a defect of the organic EL layer occurs at that portion.

  “Patent Document 1” describes a technique for solving the problems when a resin is used for a bank by forming the bank with an inorganic film such as SiN.

JP 2000-91082 A

  In the technique described in “Patent Document 1”, an inorganic material is used for the bank to solve problems such as etching residue when a resin is used for the bank. is there. The formation of the bank requires a photolithography process, and this photolithography process increases the manufacturing cost of the organic EL display device.

  In addition, when a bank is present, irregularities are formed on the surface, so that scattering of external light increases and the contrast is lowered. Furthermore, there is a problem in that light emitted from the organic EL layer becomes guided light and is emitted from the bank, resulting in smearing in the image.

  However, if the bank is omitted, a short circuit between the upper electrode and the lower electrode becomes a problem. An object of the present invention is to obtain an organic EL display device having a configuration in which a short circuit between an upper electrode and a lower electrode does not occur even if a bank is omitted.

  The top emission type organic EL display device includes a top anode type in which an anode is disposed on an upper electrode and a top cathode type in which a cathode is disposed on an upper electrode. The present invention is not limited to the top anode type and the top cathode type in a top emission type organic EL display device, and a taper of 40 degrees or less is formed at the end of the pixel electrode by using a metal pixel electrode. Here, the pixel electrode corresponds to the lower electrode of the organic EL layer. Accordingly, it is possible to prevent a short circuit between the upper electrode and the lower electrode at the end portion of the pixel electrode due to the disconnection of the organic EL layer at the end portion.

  In addition, in the present invention, in order to prevent the upper electrode and the lower electrode from being short-circuited due to the disconnection of the organic EL layer in the contact hole formed in the planarization film, the contact hole portion includes the three colors of organic EL layers. Two or more layers are superimposed. The specific configuration is as follows.

  An organic EL display device in which an organic EL layer that emits at least a first color or a second color and TFTs corresponding to each organic EL layer are formed in a matrix on a substrate, and the organic EL layer includes: The flattening film is sandwiched between a lower transparent conductive film that covers a pixel electrode formed on a planarizing film made of resin and an upper electrode that is a transparent electrode, and the flattening film is a wiring that connects the TFT and the TFT The pixel electrode and the wiring are connected via a contact hole formed in the planarizing film, and a taper is formed at an end of the pixel electrode. An organic EL display device, wherein the organic EL layers of the first color and the second color are formed to overlap each other.

  (2) The display device according to (1), wherein the taper is 40 degrees or less.

  (3) The display device according to (1), wherein the wiring is an SD wiring.

  (4) An organic EL display device in which organic EL layers emitting red, green, or blue light and TFTs corresponding to each organic EL layer are formed in a matrix on a substrate, and the organic EL layer is made of resin Sandwiched between a lower transparent conductive film covering the pixel electrode formed on the planarizing film formed in step 1 and an upper electrode which is a transparent electrode, and the planarizing film includes the TFT and a wiring connected to the TFT. The pixel electrode and the wiring are connected via a contact hole formed in the planarization film, and a taper of 40 degrees or less is formed at an end portion of the pixel electrode. In the hole, an organic EL display device, wherein a plurality of the organic EL layers of red, green, or blue are overlapped.

  (5) The organic EL display device according to (4), wherein the red, green, and blue organic EL layers are all superimposed in the contact hole.

  (6) The red, green, and blue organic EL layers are all superimposed in the contact hole, and the blue organic EL layer is sandwiched between the organic EL layers of other colors. (4) The organic EL display device according to (4).

  (7) The organic EL display device according to (4), wherein two layers of the red, green, and blue organic EL layers are overlapped in the contact hole.

  (8) The organic EL display device according to (4), wherein the lower transparent conductive film is made of IZO.

(9) The lower transparent conductive film has a resistivity of 1 to 10 ⁵ ohm · cm, a film thickness of 20 nm or less, and is formed on the entire surface of the substrate. Organic EL display device.

  (10) The organic EL display device according to (4), wherein the pixel electrode is made of an Al—Ni alloy.

  (11) An organic EL display device in which an organic EL layer emitting at least a first color or a second color and TFTs corresponding to each organic EL layer are formed in a matrix on a substrate, and the organic EL display The layer is sandwiched between the pixel electrode formed on the planarizing film made of resin and the upper electrode which is a transparent electrode, and the planarizing film covers the TFT and the wiring connected to the TFT. The pixel electrode and the wiring are connected via a contact hole formed in the planarization film, and an end portion of the pixel electrode is tapered, and in the contact hole, the first electrode The organic EL display device is characterized in that the organic EL layer of the second color and the second color are overlapped.

  (12) The display device according to (11), wherein the taper is 40 degrees or less.

  (13) The display device according to (11), wherein the wiring is an SD wiring.

  (14) An organic EL display device in which organic EL layers emitting red, green, or blue light and TFTs corresponding to the respective organic EL layers are formed in a matrix on a substrate, and the organic EL layer is made of resin Sandwiched between the pixel electrode formed on the planarizing film formed in step 1 and the upper electrode, which is a transparent electrode, the planarizing film covers the TFT and the wiring connected to the TFT, and the pixel The electrode and the SD wiring are connected via a contact hole formed in the planarization film, and a taper of 40 degrees or less is formed at the end of the pixel electrode. Or an organic EL display device, wherein a plurality of the green or blue organic EL layers are overlapped.

  (15) The organic EL display device according to (14), wherein the red, green, and blue organic EL layers are all superimposed in the contact hole.

  (16) The red, green, and blue organic EL layers are all superimposed in the contact hole, and the blue organic EL layer is sandwiched between the organic EL layers of other colors. (14) The organic EL display device according to (14).

  (17) The organic EL display device according to (14), wherein two layers of the red, green, and blue organic EL layers are superimposed in the contact hole.

  (18) The organic EL display device according to (14), wherein the pixel electrode is made of an Al—Nd alloy.

  According to the present invention, since the bank can be omitted, the manufacturing cost of the organic EL display device can be reduced. In addition, according to the present invention, since a bank is not formed, it is possible to prevent a pixel defect or the like due to an etching residue problem caused by a process of forming a bank.

  In addition, since it is not necessary to form a bank according to the present invention, the surface of the organic EL display device can be flattened. If the surface is flat, scattered light is reduced, so that contrast under external light can be improved. Furthermore, according to the present invention, since the bank can be eliminated, emission of the guided light from the bank portion can be prevented, and the image quality can be improved.

  The detailed contents of the present invention will be disclosed according to the embodiments.

FIG. 1 is a sectional view of a top emission type organic EL display device according to the present invention. In FIG. 1, a base film 2 for blocking impurities from glass is formed on a glass substrate 1. The base film 2 may have a single layer of SiN film or the like, but may have a two-layer structure of a SiN film and a SiO ₂ film. A semiconductor layer 3 for forming a TFT is formed on the base film 2, and a gate insulating film 4 is formed so as to cover the semiconductor layer 3. In the present embodiment, the semiconductor layer 3 converts the a-Si film into a poly-Si film by laser annealing. A gate electrode 5 which is a part of the gate wiring 5 is formed on the gate insulating film 4. The TFT in FIG. 1 is a top gate type TFT.

  An interlayer insulating film 6 is formed to cover the gate electrode 5, and source / drain wiring (SD wiring 10) is formed on the interlayer insulating film 6. In this specification, SD wiring refers to both a source wiring connected to the source region of the TFT and a drain wiring connected to the drain region of the TFT. A passivation film 11 for covering the SD wiring 10 and protecting the entire TFT is formed. A planarizing film 12 made of resin is formed on the passivation film 11. The planarizing film 12 is formed as thick as about 2 μm. The surface on which the TFT or the like is formed is uneven. In a top emission type organic EL display device, an organic EL layer is also formed on a TFT or the like, but the organic EL layer needs to be formed on a flat film. By forming the resin thick, the surface on which the organic EL layer is formed is flattened.

  A pixel electrode 13 is formed on the planarizing film 12. The pixel electrode 13 is made of an Al—Ni alloy having good reflectivity. The pixel electrode 13 is connected to the SD wiring 10 through the contact hole 18. A data signal is supplied from the SD wiring 10 to the pixel electrode 13, and a voltage corresponding to the data signal is applied to the organic EL layer, thereby forming an image. On the pixel electrode 13 serving as the lower electrode, IZO, which is a transparent conductive film 14 for contacting the organic EL layer, is deposited. An organic EL layer composed of a plurality of layers is formed on the transparent conductive film 14. An upper electrode 19 made of IZO, which is a transparent conductive film 14, is formed on the organic EL layer. The upper electrode 19 is formed by IZO.

  The structure of FIG. 1 is a top cathode structure in which the lower electrode is an anode and the upper electrode 19 is a cathode. Since it is necessary to inject holes into the lower electrode, a metal such as an Al alloy having a relatively small work function is unsuitable. Therefore, an IZO layer is deposited on the pixel electrode 13 made of Al—Ni to increase the work function. This is the anode.

  As described above, no bank is formed in the present invention. Problems when the bank is not formed are the E portion and the H portion in FIG. FIG. 2 shows a problem of the E portion when the bank is not formed with the conventional structure. In FIG. 2, the pixel electrode 13 is formed on the planarizing film 12. Since the pixel electrode 13 is formed only in the pixel portion, it is patterned by photolithography to form an edge portion.

  An organic EL layer is deposited on the pixel electrode 13. Since the total thickness of the deposited layer is as thin as 100 nm to 300 nm, the stepped portion as shown in FIG. An upper electrode 19 is formed on the organic EL layer. As shown in FIG. 2, when the organic EL layer is disconnected at the end of the pixel electrode 13, the upper electrode 19 and the lower electrode are short-circuited at the disconnected portion. Then, no voltage is applied to the organic EL layer, and the organic EL layer does not emit light. Therefore, this pixel becomes defective.

  Another problem when the bank is not formed is the H portion of FIG. FIG. 3 shows another problem when the bank portion is not formed with the conventional structure. FIG. 3 is an enlarged view of the contact hole portion 18. In FIG. 3, a passivation film 11 is formed on the SD wiring 10, and a planarization film 12 is formed thereon. A pixel electrode 13 is formed on the planarizing film 12. Since the pixel electrode 13 needs to be connected to the SD wiring 10, a contact hole 18 is formed in the passivation film 11 and the planarizing film 12 to establish electrical connection between the pixel electrode 13 and the SD wiring 10.

  An organic EL layer is formed on the pixel electrode 13, and an upper electrode 19 is formed thereon. The problem here is that the contact hole 18 formed in the planarization film 12 and the passivation film 11 is very deep as 2 μm or more, whereas the total thickness of the organic EL layer is about 100 nm to 300 nm. It is thin. Therefore, as shown in FIG. 3, the organic EL layer easily breaks in the contact hole portion 18. Then, as shown in FIG. 3, a phenomenon occurs in which the pixel electrode 13 and the upper electrode 19 are short-circuited in the contact hole portion 18. When the contact hole 18 is short-circuited, the pixel becomes defective.

  With respect to the problem in the portion E shown in FIG. 1, in this embodiment, as shown in FIG. 1, IZO is formed on the pixel electrode 13 made of an Al—Ni alloy. Then, taper etching is applied to the Al—Ni alloy to prevent disconnection at the end of the organic EL layer. In addition, with respect to the problem in the H portion of FIG. 1, in this embodiment, the organic EL layer is deposited not only on a single monochrome layer but also on two or three layers on the contact hole portion 18 to form the organic EL layer. The step is prevented by increasing the thickness.

  FIG. 4 is an enlarged schematic view showing the vicinity of the pixel electrode 13 of FIG. 1 and 4, the position of the pixel electrode 13 with respect to the contact hole 18 is reversed. In FIG. 4, the SD electrode is formed on the glass substrate 1, but this is for simplifying the drawing. Actually, the interlayer insulating film 6, below the SD electrode, A gate insulating film 4, a base film 2, etc. are present.

  In FIG. 4, a passivation film 11 and a planarizing film 12 are formed so as to cover the SD wiring 10. A pixel electrode 13 is formed on the planarizing film 12. The pixel electrode 13 is patterned by photolithography. The pixel electrode 13 is electrically connected to the SD electrode through a contact hole 18 formed in the planarizing film 12 and the passivation film 11. On the pixel electrode 13, IZO, which is a transparent electrode, is thinly deposited to a thickness of about 20 nm by sputtering. Since the present embodiment is a top cathode, if IZO is used as the pixel electrode 13, Al-Ni which is a metal is not necessary. However, in order to make the end of the pixel electrode 13 into a tapered shape, a metal pixel is intentionally made. The electrode 13 is used.

  That is, taper etching can be performed even with IZO. However, since the transparent conductive film 14 made of a metal oxide such as IZO is hard and fragile, if the taper is formed, the taper portion is destroyed and eventually a sharp edge is formed. In this embodiment, the tapered edge can be stably formed by using a sticky Al alloy for the pixel electrode 13. A thin IZO is formed on the pixel electrode 13 to serve as an anode.

  An organic EL layer is formed on the IZO film by vapor deposition, and an upper electrode 19 is formed on the IZO film by IZO. An auxiliary electrode 20 is formed on the upper electrode 19 corresponding to the contact hole 18. The auxiliary electrode 20 has a role of assisting conduction of the upper electrode 19 and a role of preventing emission of guided light from the contact hole portion 18.

  Al-Ni is used for the pixel electrode 13 because the reflectance of Ai-Ni is high and the contact resistance with IZO (In-Zn-O) is low. The pixel electrode 13 is formed as follows. That is, a thickness of 120 nm is formed by sputtering, a pattern is formed using a photoresist, and etching is performed using a mixed acid of phosphoric acid, acetic acid, and nitric acid.

  In order to prevent the pixel electrode 13 and the upper electrode 19 from being short-circuited because the organic EL layer, which is a vapor deposition film, is not completely covered with the step at the end of the pixel electrode 13, the taper at the end of the pixel electrode 13 is prevented. The angle θ was kept below 40 degrees. In general, the end portion is tapered in a just-etched state. In order to maintain the taper, it is necessary to perform rinsing after etching quickly. By spraying a large amount of water in a shower shape, the etching solution was quickly removed to maintain the taper angle.

  A 20 nm thick IZO thin film was formed thereon by sputtering. The discharge gas was adjusted to an IZO film having a resistivity of 10 to 300 Ω · cm by introducing 2.5% oxygen by volume with respect to Ar. Although the variation of the resistance value is considerably large, the resistance of the organic EL layer is much larger than this, so that there is no problem within this range.

  IZO is formed on the entire surface of the substrate, and is deposited on the substrate surface, between the pixels, on the terminals and between the terminals, and everywhere on the substrate surface, such as a sealing portion. Must not. FIG. 5 is a cross-sectional view of the terminal portion. In FIG. 5, the terminal wiring 50 is obtained by drawing the SD wiring 10 or the gate wiring 5 to the end of the substrate. When the current flowing through the terminal portion is large, the SD wiring 10 having a small resistance is used as the terminal wiring 50. A passivation film 11 and a planarizing film 12 are deposited so as to cover the terminal wiring 50, and openings are provided in these films. The same Ai-Ni as that of the pixel electrode 13 is applied to the opening and is panned to the shape of the terminal. Thereafter, IZO is thinly deposited to protect the Ai-Ni film from the atmosphere.

The IZO film is deposited between the terminal portions, and if the thickness of the IZO film is 10 to 20 nm and the resistivity is in the range of 1 to 10 ⁵ Ω · cm, the resistance in the terminal portion is There is no such phenomenon that it is too high or the resistance between the terminal portions becomes small and insulation cannot be maintained. For this reason, thin IZO is applied to the entire surface of the substrate in this embodiment.

  Returning to FIG. 4, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are formed as an organic EL layer on the thinly deposited IZO by mask vapor deposition. Thereafter, the upper electrode 19 was formed by IZO, and the auxiliary wiring 20 was formed so as to cover the contact hole portion 18. Each film is formed as follows. That is, the Al—Ni layer to be the pixel electrode 13 is 120 nm, the IZO layer thereon is 20 nm, and the hole transport layer 120 nm is formed in common for each color. Thereafter, the blue portion 17 forms a light emitting layer of 40 nm, the green portion 16 forms a hole transport layer of 60 nm and a light emitting layer of 40 nm, and the red portion 15 forms a hole transport layer of 130 nm and a light emitting layer of 30 nm. Therefore, the thickness of the hole transport layer is 120 nm for the blue portion 17, 180 nm for the green portion 16, and 250 nm for the red portion 15. On top of that, an electron transport layer of 10 nm, an electron injection layer of 60 nm, and an upper electrode 19 of IZO of 30 nm were deposited in common for each color.

  A hole transport layer and a light emitting layer formed separately for each color are formed so as to overlap each other at the boundary between the colors, and a contact hole 18 is provided in the overlapping portion 21 of the organic EL layer. As a result, the organic EL layer in the contact hole portion 18 becomes thick, and disconnection is prevented, so that a short circuit between the upper electrode 19 and the pixel electrode 13 can be prevented. When the red, green, and blue organic EL layers are stacked, if the blue organic EL layer is placed in the middle, it becomes difficult for current to flow, and thus an increase in power consumption can be prevented.

  FIG. 6 is a schematic cross-sectional view when organic EL layers are stacked, and FIG. 7 is a plan view. FIG. 6 shows that the organic EL layers overlap in the contact hole portion 18. In FIG. 6, when the organic EL layer is only blue, the thickness is about 100 nm, and the contact hole 18 easily breaks, but when the three color organic EL layers overlap, the total thickness is about 600 nm. No breakage occurs. Incidentally, the thickness of each color organic EL layer is about 100 nm for blue, about 200 nm for green, and about 300 nm for red. Thus, by superimposing the organic EL layers of the three colors, the resistance of the organic EL layer is increased, the current in the contact hole 18 becomes difficult to flow, and an increase in power consumption can be suppressed. The organic EL layer can overlap three colors depending on the location, but only two colors overlap depending on the location. Even in this case, the risk of disconnection in the contact hole 18 is much smaller than in the case of only one color.

  Returning to FIG. 4, the contact hole portion 18 is not flattened even if the organic EL layer is stacked. Since the contact hole portion 18 is not flat, guided light from the light emitting layer is emitted. Of the light emitted from the organic EL layer, the light directed to the upper electrode 19 contributes to image formation. However, light traveling in a direction parallel to the upper electrode 19 does not contribute to image formation. The light traveling in the direction parallel to the upper electrode 19 is referred to as guided light, and this guided light is visually refracted or reflected in the contact hole 18. Since guided light has a strong intensity and a different wavelength, the image quality is deteriorated. In order to prevent the guided light from being emitted to the outside, an auxiliary wiring 20 is provided in the contact hole portion 18.

  FIG. 7 is a plan view showing the arrangement of the pixel electrode 13, the organic EL layer, and the like. In FIG. 7, the pixel electrodes 13 and the organic EL layers are arranged in a mosaic pattern. The organic EL layer is formed to be larger than the pixel electrode 13, and a plurality of colors of organic EL layers are overlapped in a portion where the contact hole 18 exists. In the contact hole 183 portion, the three color organic EL layers overlap, and in the contact hole 182 portion, the two color organic EL layers overlap. The contact hole 18 is covered with an auxiliary wiring 20 made of metal.

  FIG. 8 is a circuit diagram of the pixel portion. In FIG. 8, when the reset line RES becomes High, T1 is turned ON, and the gate of T2 is initialized to the same potential as the drain of T2. In this state, the capacitor C is charged with a charge corresponding to the image signal from the data line DATA. When the control line ILUM becomes High, T3 is turned ON, and a current corresponding to the electric charge charged in the capacitor by the driving transistor T2 flows from the power supply line VSS to the organic EL layer OLED to form an image.

  FIG. 9 is an example of a process diagram for realizing the pixel structure of FIG. The layer structure shown in FIG. 9 is different from the general layer structure of the organic EL display device shown in FIG. In FIG. 9A, SD wiring SD was formed on the glass substrate 1. For the SD wiring SD, Mo was sputtered at 250 nm, and a wiring pattern was formed by photolithography. The electrode on one side of the capacitor in FIG. 8 was formed in the same layer as the SD wiring. Next, as shown in FIG. 9B, a-Si was formed to a thickness of 50 nm by CVD, converted into a poly-Si film by laser annealing, and patterned by photolithography.

A SiO ₂ film was formed to 100 nm thereon by CVD, and subsequently, as shown in FIG. 9C, Mo was sputtered to 150 nm and a gate wiring pattern G was formed by photolithography. The other electrode of the capacitor in FIG. 8 was formed in the same layer as the gate wiring pantan G. Boron is doped by ion plating, and a SiN film of 300 nm is deposited by CVD. Thereafter, activation annealing was performed at about 500 ° C., and hydrogenation annealing was further performed at 400 ° C.

  After the photosensitive acrylic resin was applied and planarized, a pattern of the contact hole 18 was formed by photolithography. As it is, SiN and the gate insulating film 4 were etched by CF4 + H2 plasma to penetrate the contact hole 18 to the lower wiring. This state is shown in FIG.

  On top of this, the Al—Ni alloy of the pixel electrode 13 described in FIG. 4 was sputtered, and a pixel pattern was formed by photolithography. An IZO film having a controlled resistivity was formed thereon to complete. This state is shown in FIG. The photolithography process is performed 5 times in total. When a positive voltage was applied to the anode of the pixel circuit thus formed and a negative voltage was applied to the cathode of the upper electrode 19, current flowed, and the organic EL layer emitted light.

  The organic EL layer is composed of a plurality of layers, and the configuration is as follows.

  The electron transporting layer is not particularly limited as long as it exhibits electron transporting properties and is easily formed into a charge transfer complex by co-evaporation with an alkali metal. For example, tris (8-quinolinolato) aluminum, tris (4-methyl-8- Quinolinolato) aluminum, bis (2-methyl-8-quinolinolato) -4-phenylphenolate-aluminum, bis [2- [2-hydroxyphenyl] benzoxazolate] zinc and other metal complexes and 2- (4-biphenylyl) ) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 1,3-bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazole- 2-yl] benzene or the like can be used.

  The electron injection layer is formed by co-evaporation of a material having an electron donating property with respect to the substance used for the electron transport layer, for example, an alkali metal such as lithium and cesium, an alkaline earth metal such as magnesium and calcium, and They may be selected from metals such as rare earth metals, or their oxides, halides, carbonates, etc., and used as substances exhibiting electron donating properties.

  The hole transport layer includes, for example, a tetraarylbenzidine compound (triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, a polythiophene derivative, Copper phthalocyanine derivatives and the like can be used.

  The light emitting layer material is not particularly limited as long as it can be formed as a light emitting layer by co-evaporation by adding a dopant that emits fluorescence or phosphorescence by recombination to a host material having electron and hole transport capability. For example, 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-quinolinolato aluminum, tris ( , 7-dibromo-8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane] -like complexes, anthracene derivatives, carbazole derivatives, and the like. .

  In addition, dopants are those that capture electrons and holes in the host and recombine to emit light. For example, a red light emitting substance such as a pyran derivative, a green coumarin derivative, a blue anthracene derivative, or an iridium complex. Further, it may be a phosphorescent substance such as a pyridinate derivative.

  The uppermost layer may be a transparent conductive film 14 for extracting light. In this embodiment, IZO is used, but ITO may be used.

  FIG. 10 is a cross-sectional view of a pixel portion showing a second embodiment of the present invention. The first embodiment is a so-called top cathode in which the pixel electrode 13 is an anode and the upper electrode 19 is a cathode, but this embodiment is a so-called top anode in which the pixel electrode 13 is a cathode and the upper electrode 19 is an anode. This is the case.

  FIG. 10 shows the contact hole portion 18 to the upper electrode 19 in an organic EL display device configured to supply current from the TFT formed on the glass substrate 1 to the pixel electrode 13 and the organic EL layer through the contact hole 18. It is. The omitted TFT circuit portion is almost the same as that shown in FIG. 9, but since the top cathode structure was used in Example 1, the TFT was a p-MOS doped with boron. In the top anode structure, an n-MOS doped with phosphorus is used.

  The pixel electrode 13 is made of an Al—Nd alloy having a high reflectance. A thin film having a thickness of 150 nm was formed by sputtering, a pattern was formed using a photoresist, and etching was performed using a mixed acid of phosphoric acid, acetic acid, and nitric acid to form the pixel electrode 13. As in Example 1, the end of the pixel electrode 13 has a tapered shape of 40 degrees or less.

  The surface of Al is usually covered with a natural oxide film of about 10 nm, and this oxide film needs to be removed for use as the cathode electrode of the organic EL layer. In this embodiment, the natural oxide film is removed by reverse sputtering. After removing the natural oxide film, LiF was deposited in a thickness of 0.5 nm, and an organic EL layer was sequentially deposited thereon by mask deposition with an electron transport layer, a light emitting layer, and a hole transport layer. Thereafter, IZO was formed as the upper electrode 19 serving as the anode, and the auxiliary wiring 20 was formed so as to cover the contact hole 18.

  Finally, an IZO thin film having a thickness of 20 nm was deposited by sputtering for the purpose of protecting the terminal portion. The discharge gas was introduced with 2.5% oxygen by volume relative to Ar, and the resistivity was adjusted to 10 to 300 Ω · cm. In the same manner as in the first embodiment, such an IZO film can achieve the resistance of the terminal portion and the insulation between the terminals even if it is deposited on the entire surface of the substrate.

  Regarding the thickness of the organic EL layer, the electron transport layer is 20 nm in blue, the light-emitting layer is 40 nm, the green is electron transport layer 25 nm, the light-emitting layer 100 nm, the red is electron transport layer 20 nm, and the light-emitting layer 60 nm. Each of these layers was deposited using a mask that overlapped on the contact hole 18. As for the order of stacking, if blue is placed in the center, it becomes difficult for the current to flow due to the band structure, so that wasteful power consumption can be suppressed. The hole transport layer was 60 nm in common for each color.

  When a negative voltage was applied to the cathode that is the pixel electrode 13 of the organic EL display device thus formed and a positive voltage was applied to the anode that was the upper electrode 19, current flowed, and the organic EL layer emitted light. The planar arrangement of the pixels described in the present embodiment is similar to the first embodiment, in which each color is arranged in a mosaic.

  In Example 1 and Example 2, IZO is used as the transparent conductive film 14, but the transparent conductive film 14 need not be limited to IZO. It is also possible to use ITO (In-Tin-Oxide), ATO (Sb-Tin-Oxide) or the like as the transparent conductive film 14. In the first and second embodiments, the case where the pixels are arranged in a mosaic shape has been described. However, it goes without saying that the present invention can be applied not only to a mosaic pixel arrangement but also to other pixel arrangements.

  FIG. 11 shows a case where pixels of each color are formed in a stripe shape. In FIG. 11, the pixel electrode 13 is formed for each pixel, but the organic EL layer is deposited in stripes for each color. The organic EL layer is formed larger than the pixel electrode 13. In FIG. 11, the reason why the blue stripe width is large is to compensate for the area because the light emission efficiency of blue is smaller than that of other colors.

  In FIG. 11, two color organic EL layers are formed to overlap each other on the side. In the arrangement of FIG. 11, two colors are overlapped instead of three colors. A contact hole 18 is formed in a portion where each color organic EL layer overlaps. An auxiliary wiring 20 is formed in the vertical direction so as to cover the contact hole 18. The auxiliary wiring 20 prevents the guided light from being emitted from the contact hole portion 18.

  FIG. 12 shows another example in which pixels of each color are formed in a stripe shape. The arrangement relationship between the pixel electrode 13, the organic EL layer, and the contact hole 18 is the same as in FIG. In FIG. 12, the auxiliary wiring 20 extends in the horizontal direction. Even when the auxiliary wiring 20 extends in the lateral direction, most of the contact holes 18 can be covered, but some of the contact holes 18 are not covered. The influence on the image quality of some uncovered contact holes 18 is negligible.

  11 and 12, the organic EL layer in the contact hole 18 is an overlap of two colors. However, since the organic EL layer is formed by vapor deposition, it is possible to design the vapor deposition mask so that the three color organic EL layers overlap only on the contact hole portion 18. Therefore, even in a stripe type pixel arrangement, the organic EL layers of three colors can be overlapped by the contact hole portion 18.

  As described above, according to the present invention, it is possible to prevent a short circuit between the upper electrode 19 and the pixel electrode 13 due to the disconnection of the organic EL layer without forming a bank. Therefore, the manufacturing cost of the organic EL display device can be reduced, and the problem of etching residue accompanying the process of forming the bank, the problem of guided light generated from the bank, and the like can be eliminated.

  In the above description, the organic EL layer has been described as emitting red, green, or blue light. However, in the organic EL display device, for example, two colors of organic EL layers are prepared without using three organic EL layers, and a full color can be displayed by using a color filter. Even in this case, disconnection at the contact hole portion can be prevented by overlapping the organic EL layers for two colors in the contact hole portion. In this case also, it is necessary to form a taper on the lower electrode made of metal.

It is sectional drawing of the display apparatus of this invention. It is a schematic diagram which shows a problem when a bank is abbreviate | omitted by a prior art. It is a schematic diagram which shows the other problem when a bank is abbreviate | omitted by a prior art. 1 is a cross-sectional view of a main part of Example 1. FIG. FIG. 3 is a cross-sectional view of a terminal portion according to the first embodiment. 3 is a cross-sectional view of a contact hole portion of Example 1. FIG. FIG. 3 is a pixel arrangement diagram according to the first exemplary embodiment. This is a pixel drive circuit. It is a process diagram corresponding to the drive circuit of a pixel. 6 is a cross-sectional view of Example 2. FIG. It is another example of pixel arrangement. It is a further another example of pixel arrangement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Base film, 3 ... Semiconductor layer, 4 ... Gate insulating film, 5 ... Gate wiring, 6 ... Interlayer insulating film, 10 ... SD wiring, 11 ... Passivation film, 12 ... Planarization film, 13 ... Pixel electrode, 14 ... Transparent conductive film, 15 ... Red organic EL layer, 16 ... Green organic EL layer, 17 ... Blue organic EL layer, 18 ... Contact hole, 19 ... Upper electrode, 20 ... Auxiliary electrode, 21 ... Organic EL layer 50, terminal wiring.

Claims (18)

An organic EL display device in which an organic EL layer emitting at least a first color or a second color and TFTs corresponding to each organic EL layer are formed in a matrix on a substrate,
The organic EL layer is sandwiched between a lower transparent conductive film that covers a pixel electrode formed on a planarizing film made of a resin and an upper electrode that is a transparent electrode,
The planarization film covers the TFT and a wiring connected to the TFT, and the pixel electrode and the wiring are connected via a contact hole formed in the planarization film,
A taper is formed at an end of the pixel electrode, and the organic EL layer of the first color and the second color is formed to overlap in the contact hole. Organic EL display device.   The display device according to claim 1, wherein the taper is 40 degrees or less.   The display device according to claim 1, wherein the wiring is an SD wiring. An organic EL display device in which organic EL layers that emit red, green, or blue on a substrate and TFTs corresponding to each organic EL layer are formed in a matrix,
The organic EL layer is sandwiched between a lower transparent conductive film that covers a pixel electrode formed on a planarizing film made of a resin and an upper electrode that is a transparent electrode,
The planarization film covers the TFT and a wiring connected to the TFT, and the pixel electrode and the wiring are connected via a contact hole formed in the planarization film,
A taper of 40 degrees or less is formed at the end of the pixel electrode, and a plurality of the red, green, or blue organic EL layers are overlapped in the contact hole. An organic EL display device comprising:   5. The organic EL display device according to claim 4, wherein the red, green, and blue organic EL layers are all superimposed in the contact hole.   In the contact hole, the red, green, and blue organic EL layers are all superimposed, and the blue organic EL layer is sandwiched between the organic EL layers of other colors. The organic EL display device according to claim 4.   5. The organic EL display device according to claim 4, wherein two layers of the red, green, and blue organic EL layers are overlapped in the contact hole.   The organic EL display device according to claim 4, wherein the lower transparent conductive film is formed of IZO. 5. The organic EL display according to claim 4, wherein the lower transparent conductive film has a resistivity of 1 to 10 ⁵ ohm · cm, a film thickness of 20 nm or less, and is formed on the entire surface of the substrate. apparatus.   The organic EL display device according to claim 4, wherein the pixel electrode is made of an Al—Ni alloy. An organic EL display device in which an organic EL layer emitting at least a first color or a second color and TFTs corresponding to each organic EL layer are formed in a matrix on a substrate,
The organic EL layer is sandwiched between a pixel electrode formed on a planarizing film made of resin and an upper electrode which is a transparent electrode,
The planarization film covers the TFT and a wiring connected to the TFT, and the pixel electrode and the wiring are connected via a contact hole formed in the planarization film,
A taper is formed at an end of the pixel electrode, and the organic EL layer of the first color and the second color is formed to overlap in the contact hole. Organic EL display device.   The display device according to claim 11, wherein the taper is 40 degrees or less.   The display device according to claim 11, wherein the wiring is an SD wiring. An organic EL display device in which organic EL layers that emit red, green, or blue on a substrate and TFTs corresponding to each organic EL layer are formed in a matrix,
The organic EL layer is sandwiched between a pixel electrode formed on a planarizing film made of resin and an upper electrode which is a transparent electrode,
The planarization film covers the TFT and a wiring connected to the TFT, and the pixel electrode and the SD wiring are connected via a contact hole formed in the planarization film,
A taper of 40 degrees or less is formed at the end of the pixel electrode, and the contact hole is formed by overlapping a plurality of the red, green, or blue organic EL layers. An organic EL display device comprising:   15. The organic EL display device according to claim 14, wherein the red, green, and blue organic EL layers are all superimposed in the contact hole.   In the contact hole, the red, green, and blue organic EL layers are all superimposed, and the blue organic EL layer is sandwiched between the organic EL layers of other colors. The organic EL display device according to claim 14.   The organic EL display device according to claim 14, wherein two layers of the red, green, and blue organic EL layers are overlapped in the contact hole.   The organic EL display device according to claim 14, wherein the pixel electrode is made of an Al—Nd alloy.

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