JP4487235B2 - Display element manufacturing equipment - Google Patents

Description

The present invention relates to apparatus for manufacturing a display element having a structure in which organic compound layers are laminated such hole blocking layer or an electron transporting layer on the light emitting layer.

  In recent years, in the field of display devices such as displays, an organic EL layer containing an organic light-emitting material is sandwiched between a pair of electrodes, and an organic EL is formed by injecting electrons and holes into the organic EL layer. An organic EL element that emits light by recombination within a layer has attracted attention. Here, the organic EL layer is composed of a plurality of types of organic materials such as a light emitting material for emitting RGB three colors, an electron transport material, a hole transport material, and the like. Some of these organic EL elements include a mixture of a light-emitting material, an electron transport material, and a hole transport material, and a light-emitting layer formed of a mixed layer formed by mixing these organic materials. Some have a structure in which a light emitting layer containing, an electron transport layer and a hole transport layer are separately formed and laminated.

  Further, when the mobility of holes injected from the anode into the light emitting layer is larger than the mobility of electrons injected from the cathode, the holes escape to the cathode side between the light emitting layer and the cathode or electron transport layer. In some cases, a hole blocking layer made of a low molecular weight organic material is provided. This hole blocking layer is also effective when a phosphorescent material is used as the light emitting material. In other words, when a phosphorescent material is used, electrons and holes are combined in the light emitting layer and excited from the ground state to the excited state, and then a non-radiative transition called intersystem crossing is first performed from the singlet excited state. Then, a transition is made to the triplet excited state, and then phosphorescence is emitted when the triplet excited state shifts to the ground state. In this way, the phosphorescent material emits light even when transitioning from the triplet excited state to the ground state, so the internal quantum efficiency of the phosphorescent material is higher than that of the fluorescent material, but it is generated by recombination of electrons and holes in the light emitting layer. If triplet excitons escape to the cathode side, the efficiency of generating phosphorescence in the light emitting layer is reduced. Therefore, by providing a hole blocking layer, triplet excitons are prevented from escaping to the cathode side.

Here, in order to form a light emitting layer and a layer made of a low molecular weight organic material such as an electron transport layer and a hole blocking layer on the light emitting layer, a vacuum deposition method (see, for example, Non-Patent Document 1), spin A method suitable for forming a smooth layer having a uniform thickness such as a coating method (for example, see Non-Patent Document 2) is widely used. However, in particular, in an organic EL device used for a full-color display, three types of solutions in which luminescent materials corresponding to three types of RGB dyes are dissolved are appropriately applied to predetermined positions where the three primary colors emit light. Since it is necessary to divide, an inkjet method suitable for forming the light emitting layer (for example, refer to Patent Document 1) may be used.
Japanese Patent Laid-Open No. 10-12377 (page 3, FIG. 1-2) Applied Physics Letters 51, 913-915, W. Tang and SAVan Slyke et al., 1987 Applied Physics Letters 69, 3117-3119, CC.Wu, JCSturm, RAPegister and METhmpson et al., 1996

  However, as described in Non-Patent Document 1, when a plurality of organic compound layers such as a light emitting layer and an electron transport layer are formed by a vacuum deposition method, a plurality of processes such as a mask, exposure, and etching are required. The manufacturing process becomes complicated.

In addition, an organic EL element having a structure in which a plurality of organic compound layers are stacked lacks the stability of the element at the layer interface as compared with an organic EL element formed by mixing a plurality of types of organic materials into a single mixed layer. However, as in the method described in Non-Patent Document 2, when a plurality of organic compound layers are formed using a spin coating method, it is possible to coat the RGB three-color light-emitting layers at predetermined positions. In addition, it is difficult to continuously form a plurality of organic compound layers without interruption, and a low molecular material layer such as a hole blocking layer is formed on the dried light emitting layer. In this case, when a low molecular material layer formed by subsequent application is dried, crystallization may occur and an element defect may occur. If the ink jet method is used, the light emitting layer can be easily applied separately, but there is a possibility that the low molecular material layer may be crystallized as in the case of the spin coating method.
The object of the present invention is to prevent crystallization when forming another organic compound layer by stacking on the light emitting layer, to improve the stability of the display element, and the like.

Apparatus for manufacturing a display device according to claim 1, in the production apparatus for producing a display device having a sandwiched luminous organic compound layer between a pair of electrodes and these pair of electrodes, the ink jet head and the spray An apparatus main body equipped with a separate head, wherein one electrode disposed below the apparatus main body and the apparatus main body are configured to be relatively movable in the separation direction of the ink jet head and the spray head; A first solution containing one or more organic compounds dissolved in a solvent is dropped on the one electrode to form a first organic compound layer containing a light-emitting material, and through the relative movement immediately after the dropping of the first solution, the second solution by spraying the first organic compound layer comprising one or more organic compounds is dissolved in a solvent by the spray head It is characterized in that the configuration was to form a second organic compound layer.

By dropping the first solution in the ink-jet head excellent in part component separately painting property on one of the electrodes is formed by painted in precisely the first organic compound layer containing a light emitting material in place on the electrode . Immediately after the first solution is dropped through the relative movement , the second solution is sprayed with a spray head having excellent film-forming properties, and the second organic compound layer is uniformly formed on the first organic compound layer. Now it forms smoothly.

Here, the ink jet head was dropped a first solution in electrostatic electrode to form a first organic compound layer, through the relative movement, immediately after the first solution added dropwise, the second solution by spray head since forming the second organic compound layer over the first organic compound layer by spraying, before the first organic compound layer has fully dried, the second organic compound layer thereon Can be formed. That is, the first and second organic compound layers partially penetrate and mix with each other in the vicinity of the interface to form a gradient layer. Accordingly, crystallization can be prevented when the second organic compound layer is formed on the first organic compound layer, and the stability of the manufactured display element can be improved.

According to a second aspect of the present invention, there is provided the display element manufacturing apparatus according to the first aspect of the invention, wherein the spray head injects the second solution before the first organic compound layer formed on one of the electrodes is dried. And forming a second organic compound layer. Accordingly, since the second solution is sprayed onto the first organic compound layer that has not yet been dried to form the second organic compound layer, the first and second organic compound layers are in the vicinity of the interface. , The other layer partially penetrates and becomes easy to mix, and a gradient layer is formed.

According to the present invention, to form a first organic compound layer by dropping a first solution to the electrodeposition best by the inkjet head, through the relative movement, immediately after the dropping of the first solution, spray The second solution is ejected by the head to form the second organic compound layer on the first organic compound layer. Therefore, before the first organic compound layer is completely dried , the second organic compound layer is formed on the first organic compound layer. Two organic compound layers can be formed. That is, the first and second organic compound layers partially penetrate and mix with each other in the vicinity of the interface, so that a gradient layer is easily formed. Accordingly, crystallization can be prevented from occurring when the second organic compound layer is formed, and the stability of the manufactured display element can be improved.

According to the invention of claim 2 , the spray head sprays the second solution to form the second organic compound layer before the first organic compound layer formed on the one electrode is dried. Therefore, since the second organic compound layer is formed by applying the second solution onto the first organic compound layer that has not yet been dried, the first and second organic compound layers are in the vicinity of the interface. In this case, the gradient layer is more easily formed by partially penetrating the other layer and mixing.

To prevent crystallization at the time of forming another organic compound layer is laminated on the light emitting layer, to increase the stability of the display device, such as to achieve the object of the present invention, a pair of electrodes and these A manufacturing apparatus for manufacturing a display element having a light emitting organic compound layer sandwiched between a pair of electrodes, comprising: an apparatus main body equipped with an inkjet head and a spray head spaced apart; A first solution containing one or more organic compounds dissolved in a solvent by the ink jet head, wherein the one electrode arranged on the device and the apparatus main body are configured to be relatively movable in the separation direction of the ink jet head and the spray head. and it was dropped on one of the electrodes to form a first organic compound layer containing a light emitting material, through a relative movement, immediately after the dropping of the first solution, dissolved in the solvent by spray head By injecting a second solution comprising one or more organic compounds it was realized by Rukoto be configured to form a second organic compound layer to the first organic compound layer.

Examples of the present invention will be described. The present embodiment is an example in which the present invention is applied to the manufacture of an organic EL element used for an organic EL display.
As shown in FIG. 1, an organic EL display 1 includes a glass substrate 2, a plurality of organic EL elements 3 (display elements) arranged in a grid pattern on the glass substrate 2, a current driving TFT 4, a horizontal driving circuit. 5, a vertical drive circuit 6 and a sealing layer 7 are provided. Each organic EL element 3 includes a display organic EL layer 10 (an organic compound layer for light emission), and an anode (ITO (indium-tin oxide) 11) and a cathode 12 that sandwich the organic EL layer 10 from above and below. ing.

  In each organic EL element 3, when a DC voltage is applied between ITO 11 serving as the anode and the cathode 12, the light emitting material in the organic EL layer 10 is excited and emits light, passes through the glass substrate 2, and passes downward in FIG. Irradiate light. On the other hand, when the voltage between the anode (ITO11) and the cathode 12 is OFF, the light is extinguished.

One current driving TFT 4 is provided for each organic EL element 3, and acts as a switch for controlling current supply to the corresponding organic EL element 3. The horizontal drive circuit 5 and the vertical drive circuit 6 perform independent light emission and extinction control of each organic EL element 3 by turning on or off the current drive TFT 4 corresponding to each organic EL element 3. Since these current drive TFT 4, horizontal drive circuit 5 and vertical drive circuit 6 are known techniques, their description is omitted.
The sealing layer 7 covers the organic EL element 3, the current drive TFT 4, the horizontal drive circuit 5, the vertical drive circuit 6 and the like from above and protects them.

Next, the organic EL element 3 will be described.
The organic EL element 3 includes a pair of electrodes (anode ITO 11 and cathode 12) and an organic EL layer 10 sandwiched between the pair of electrodes. The organic EL layer 10 is a light emitting layer 10a containing a light emitting material. (First organic compound layer) and a hole blocking layer 10b (second organic compound layer) formed on the light emitting layer 10a.

Hereinafter, the organic EL element 3 will be described according to its manufacturing process.
First, as shown in FIG. 2A, ITO 11 is vapor-deposited with a thickness of 150 nm on a glass substrate 2 to form an anode.
Then, as shown in FIG. 2B, an exposure resist is applied to the surface of the ITO 11 by a method such as spin coating, and then a desired electrode pattern is mask-exposed. Thereafter, the resist and ITO 11 in portions not exposed are removed by etching using aqua regia, which is a mixed solution of concentrated nitric acid and concentrated sulfuric acid, to form a desired electrode pattern. Further, the surface of the ITO 11 on which the electrode pattern is formed is sequentially cleaned by neutral detergent cleaning, acetone cleaning, IPA (isopropyl alcohol) cleaning, and UV ozone cleaning.

  Next, as shown in FIG. 2-3, a solution prepared by dissolving PMMA and polycarbonate in a hydrocarbon solvent is applied onto ITO 11 by an existing method such as a spin coating method or an ink jet method, and an insulating layer is formed. After the formation, the insulating layer at the position corresponding to the patterned ITO 11 is removed by light exposure, and the partition wall 13 is formed. The upper surface of the partition wall 13 is subjected to a coating process for repelling the two types of first and second solutions 15 and 16 applied in the next step. A coating treatment for improving the wettability with respect to the second solutions 15 and 16 is performed.

  Next, the organic EL layer 10 is formed on the patterned ITO 11. The organic EL layer 10 is formed on the light emitting layer 10a containing the light emitting material, and the light emitting layer 10a. The triplet excitons generated by recombination of holes and electrons in the light emitting layer 10a include A hole blocking layer 10b for preventing the light emitting layer 10a from flowing out to the cathode 12 side. Then, as will be described below, the light emitting layer 10a is successively formed on the ITO 11 sequentially by the ink jet method and the hole blocking layer 10b is formed by the spray method.

First, as a solution to be applied when forming the light emitting layer 10a, PVK (poly (N-vinylcarbazole)) as a hole transporting polymer, BND (2,5-bis (1-naphthyl)-as an electron transporting material, 1,3,4-oxadiazole) and TPD (N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine) as a luminescent material are dissolved in a hydrocarbon solvent (tetralin). A first solution is prepared. Furthermore, in order to increase the internal quantum efficiency of the organic EL element 3, iridium complex Ir (ppy) 3 (tris (2-phenylpyridine) iridium) is added to the first solution as a phosphorescent material.
On the other hand, as a solution to be applied when forming the hole blocking layer 10b, BCP (2,9-dimethyl-4,7-diphenyl-phenanthroline) is dissolved in a hydrocarbon solvent to prepare a second solution.

Thus, after producing the 1st solution 15 for light emitting layer 10a formation, and the 2nd solution 16 for hole blocking layer 10b formation, after applying the 1st solution 15 on ITO11 by the ink jet method, it continues. The second solution 16 is applied by the spray method, and a solution applying apparatus 20 used at that time is shown in FIG.

This solution coating apparatus 20 (display element manufacturing apparatus) includes an apparatus main body 21, and an inkjet head 22 and a spray head 23 provided on the apparatus main body 21 so as to be separated from each other in the left-right direction in FIG. 21 is moved relative to the glass substrate 2 to the left (separating direction) to drop the first solution 15 from the inkjet head 22 and at the same time, the second solution 16 is sprayed from the spray head 23.

  As shown in FIG. 4, the ink jet head 22 is a piezoelectric element type ink jet head including a piezoelectric element 22a, and from an orifice 22b formed in the ink jet head 22 in accordance with a signal from a driver 22c. A droplet of the first solution 15 is discharged and applied onto the ITO 11 (FIG. 2-4). Since the ink receiving elasticity from the ink jet head 22 is relatively poor, the distance from the ink jet head 23 to the ITO 11 is about 0.1 to 1.0 mm, and the distance is reduced.

  Next, an inert gas such as nitrogen or argon is supplied to the spray head 23, and the second solution 16 is sprayed from the spray head 23 together with the inert gas in the form of a mist, as shown in FIG. Two solutions 16 are apply | coated on the light emitting layer 10a. Here, since the particle diameter of the droplets ejected from the spray head 23 is very small (for example, several μm to several tens of μm), the hole blocking layer 10b is applied on the light emitting layer 10a with a uniform thickness. Easy to do. The distance from the spray head 23 to the glass substrate 2 is about 1.0 to 5.0 cm.

  Here, when the second solution 16 is applied onto the light emitting layer 10a from the spray head 23 after the light emitting layer 10a has dried after a lapse of time since the first solution 15 was applied onto the ITO 11, the second solution When the 16 solvent is dried, a needle-like crystal may be formed in the hole blocking layer 10 b, and this needle-like crystal is a major factor that decreases the stability of the organic EL element 3. Therefore, immediately after the first solution 15 is dropped onto the ITO 11 from the inkjet head 22, the second solution 16 is ejected from the spray head 23.

  Then, before the first solution 15 applied on the ITO 11 is dried, the second solution 16 is applied thereon, so that the first and second solutions 15 and 16 are partially mixed, as shown in FIG. As described above, the vicinity of the interface between the light emitting layer 10a and the hole blocking layer 10b is formed in the mixed gradation layer so that the degree of mixing gradually changes. As shown in FIG. 2-6, in the organic EL layer 10 thus formed, the interface between the light emitting layer 10a and the hole blocking layer 10b is stable, and when the hole blocking layer 10b is formed, acicular crystals are formed. Since it does not occur, the stability of the element is excellent, and the element life of the organic EL element 3 is also improved.

  Finally, as shown in FIG. 2-7, a cathode 12 made of LiF (lithium fluoride) as an electron injection layer and an Al layer is formed on the organic EL layer 10 by vacuum deposition. Here, the thicknesses of the LiF layer and the Al layer are 10 mm and 1000 mm, respectively, and are laminated continuously.

According to the organic EL element manufacturing method to which the organic EL element described above and the display element manufacturing apparatus of the present invention are applied , immediately after the first solution 15 for forming the light emitting layer 10a is dropped onto the ITO 11 from the inkjet head 22. Further, in order to eject the second solution 16 for forming the hole blocking layer 10b from the spray head 23, the second solution 16 is applied thereon before the first solution 15 applied on the ITO 11 is dried. Therefore, the first and second solutions 15 and 16 are partially mixed, and the vicinity of the interface between the light emitting layer 10a and the hole blocking layer 10b is mixed with the gradient layer so that the degree of mixing gradually changes. It is formed. Therefore, the interface between the light emitting layer 10a and the hole blocking layer 10b is stabilized, and when the hole blocking layer 10b is formed, device defects such as crystallization do not occur, the device is excellent in stability, and the device life is extended.

Next, modified examples in which various modifications are made to the above embodiment will be described.
1] The organic compound contained in the light emitting layer 10a is not limited to that of the above-described embodiment. First, as the light emitting material, for example, perylene, kunmarin, rubrene, Nile red, DCM (4-dicyanomethylene-2-methyl-6-dimethylaminostyryl-4-pyran), DCJTB (4-dicyanomethylene-6-C) Jurolidinostyryl-2-tert-butyl-4H-pyran), squarylium, aluminum complexes, and the like. Examples of phosphorescent materials include metal complexes of heavy metals such as platinum complexes and europium (Eu) complexes.

  Further, hole transport materials include hole transport materials such as oxadiazole, oxazole, triphenylmethane, hydrazoline, arylamine, hydrazone, and stilbene. Specifically, TPD, α-NPD (N , N′-di (1-naphthyl) -N, N′diphenylbenzidine), TAPC (1,1-bis (di4tolylaminophenyl) -cyclohexane), PPD (N, N′-di (9-phenanthryl) -N, N'-diphenylbenzidine), TRP, NPB (α-NPD dimer), etc.

  Further, examples of the electron transport material include electron transport materials such as an oxadiazole derivative, a triazole derivative, and an aluminum complex. Specifically, tBu-PBD (2- (4-biphenyl) -5- (para- Tert-butylphenyl) -1,3,4-oxadiazole), TAZ (3- (4′-tert-butylphenyl) -4-phenyl-5- (4 ″ -biphenyl) -1,2,4 -Triazole), AlQ3 (tris (8-quinolinolato) aluminum (III)), BND (2,5-bis (1-naphthyl) -1,3,4-oxadiazole), Bphen (vasophenanthroline), P- EtTAZ (3- (4′-tert-butylphenyl) -4- (paraethylphenyl) -5- (4 ″ -biphenyl) -1,2,4 triazole) etc. There is.

  2] The material constituting the partition wall 13 is not limited to that of the above embodiment. For example, there are PVK, polystyrene, nylon, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyarylate, polysulfone, polyphenylene sulfide, polyamideimide, polyimide, fluorine resin, and the like.

  3] A hole injection layer for injecting holes into the light emitting material in the light emitting layer 10a is formed on the ITO 11, and then the first solution 15 and the second solution 16 are continuously applied as described above. You may do it. In this case, as shown in FIG. 2B, after patterning the ITO 11 into a predetermined electrode pattern, it is applied onto the ITO 11 and dried by various methods such as a spin coating method, an ink jet method, or a spray method. . Thereafter, as described above, the organic EL layer 10 is formed by an inkjet method and a spray method. Examples of the material constituting the hole injection layer include, but are not limited to, polyethylene dioxythiophene polystyrene sulfonate (PEDOT / PSS), copper phthalocyanine, and triphenylamine derivatives.

4] As a material for forming the electron injection layer of the cathode 12, other materials such as lithium oxide and cesium fluoride may be used in addition to the LiF of the above embodiment.
5] In the above embodiment, the hole transport material and the electron transport material are dissolved in the solvent together with the light emitting material to produce the first solution 15, and the light emitting layer 10a in which the light emitting material, the hole transport material and the electron transport material are mixed is prepared. Although formed on the ITO 11, the hole transport layer and the electron transport layer are independently formed by various methods such as a spin coat method, an ink jet method, or a spray method, and the organic EL layer 10 is formed into a hole transport layer and a light emitting layer. A layer, a hole blocking layer, and an electron transport layer may be laminated.

Next, another embodiment of the present invention will be described.
In the above embodiment, the hole blocking layer 10b is formed by the spray method on the light emitting layer 10a formed by the ink jet method, but as shown in FIGS. 6-7, the electron transport layer 10c is laminated on the light emitting layer 10a. The present invention can also be applied to the organic EL element 3A having the above structure.

  That is, as shown in FIGS. 6-1 to 6-7, the ITO 11 is vapor-deposited (FIG. 6-1) and patterned (FIG. 6-2) in the same manner as in the previous embodiment, and the partition wall 13 is formed. After that (FIG. 6-3), a first solution 15 prepared by dissolving TPD as a light emitting material in a hydrocarbon solvent is applied onto the ITO 11 by an ink jet method to form the light emitting layer 10a (FIG. 6). 4). And immediately after apply | coating the 1st solution 15, as shown to FIGS. 6-5, the 2nd solution 16 produced by melt | dissolving BCP as an electron transport material in a hydrocarbon-type solvent is used for the light emitting layer 10a by the spray method. It is applied on top to form the electron transport layer 10c.

Then, before the light emitting layer 10a on the ITO 11 is completely dried, the second solution 16 is applied thereon, so that the light emitting layer 10a and the electron transport layer 10c are partially formed as shown in FIG. 6-6. As a result of mixing, the vicinity of the interface between the light emitting layer 10a and the electron transporting layer 10c is formed in a gradient layer mixed so that the degree of mixing gradually changes. Accordingly, the interface between the light emitting layer 10a and the electron transport layer 10c is stabilized, and crystallization can be prevented from occurring when the electron transport layer 10c is formed, so that the element life of the organic EL element 3 is improved.
Finally, as shown in FIGS. 6-7, the cathode 12 is formed on the organic EL layer 10A by vacuum vapor deposition, thereby completing the manufacture of the organic EL element 3A.

1 is an overall configuration diagram of an organic EL display according to an embodiment of the present invention. It is sectional drawing of the organic EL element in ITO vapor deposition. It is sectional drawing of the organic EL element in an ITO patterning process. It is sectional drawing of the organic EL element in a partition formation process. It is sectional drawing of the organic EL element in the 1st solution application | coating process by the inkjet method. It is sectional drawing of the organic EL element in the 2nd solution application | coating process by a spray method. It is sectional drawing of the organic EL element in an organic EL layer formation process. It is sectional drawing of the organic EL element in a cathode vapor deposition process. It is a schematic block diagram of a solution coating device. It is a schematic block diagram of an inkjet head. It is a principal part enlarged view of FIGS. 2-6. It is sectional drawing of the organic EL element of the ITO vapor deposition process in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the ITO patterning process in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the partition formation process in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the 1st solution application | coating process by the inkjet method in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the 2nd solution application | coating process by the spray method in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the organic EL layer formation process in the manufacturing process of another Example. It is sectional drawing of the organic EL element of the cathode vapor deposition process in the manufacturing process of another Example.

3, 3A Organic EL element 10, 10A Organic EL layer 10a Light emitting layer 10b Hole blocking layer 10c Electron transport layer 11 ITO
12 Cathode 15 First solution 16 Second solution

Claims (2)

In a manufacturing apparatus for manufacturing a display element having a pair of electrodes and an organic compound layer for light emission sandwiched between the pair of electrodes,
An apparatus main body equipped with an inkjet head and a spray head separated from each other,
One electrode arranged below the device main body and the device main body are configured to be relatively movable in the separation direction of the inkjet head and the spray head,
A first solution containing one or more organic compounds dissolved in a solvent is dropped on the one electrode by the inkjet head to form a first organic compound layer containing a light emitting material;
Via the relative movement, immediately after the dropping of the first solution, the first organic compound is sprayed with a second solution containing one or more organic compounds dissolved in a solvent by the spray head. Configured to form a second organic compound layer on the layer;
A display element manufacturing apparatus . 2. The spray head according to claim 1, wherein the second organic compound layer is formed by spraying the second solution before the first organic compound layer formed on the one electrode is dried. A display device manufacturing apparatus according to claim 1 .