JP4513800B2 - Manufacturing method of organic EL element - Google Patents

Description

  The present invention relates to a method for producing an organic EL element which is an electroluminescent element used for a display, a display light source and the like, an organic EL element, and an ink composition used for forming a hole injection layer and a light emitting layer thereof.

  In recent years, development of light-emitting elements using organic substances in a light-emitting layer has been accelerated as a spontaneous emission type display replacing a liquid crystal display. As a process for forming a light emitting layer made of an organic substance in an organic EL (electroluminescence) element, Appl. Phys. Lett. 51 (12), 21 September 1987, page 913, a method of depositing a low molecular weight material by vapor deposition, and Appl. Phys. Lett. 71 (1), 7 July 1997, page 34, a method of applying a polymer material has been mainly developed.

  In the case of using a low molecular weight material as a means for coloring, a method of depositing and forming a light emitting material having a different light emission color on a desired pixel corresponding portion through a mask having a predetermined pattern is performed. On the other hand, when a polymer material is used, colorization using an inkjet method has attracted attention because patterning can be performed minutely and easily. The production of an organic EL element by the ink jet method is disclosed in, for example, JP-A-7-235378, JP-A-10-12377, JP-A-10-153987, JP-A-11-40358, and JP-A-11-54270.

  Further, it has been proposed that in an organic EL device, a hole injection layer or a hole transport layer is formed between an anode and a light emitting layer in order to improve luminous efficiency and durability (Appl. Phys. Lett. 51). , 21 September 1987, page 913). Conventionally, a conductive polymer such as a polythiophene derivative or a polyaniline derivative (Nature, 357, 477, 1992) is used as the buffer layer or the hole injection layer, and the film is formed by a coating method such as spin coating. In many cases, a phenylamine derivative is formed by vapor deposition and used as a hole injection layer or a hole transport layer of a low molecular material.

  In organic EL devices, when forming a laminated structure of a hole injection layer and a light emitting layer, the organic thin film constituting the hole injection layer and the light emitting layer is formed by simply and finely patterning without wasting materials. Means to do this are required.

  The ink jet method is very effective. However, it is a very difficult problem to prepare an ink composition that can be formed as a functional film without sacrificing the characteristics of the material while satisfying stable ejection properties by the ink jet method. In the production of organic EL devices, ink compositions are described in JP-A-11-40358 and JP-A-11-54270. These publications describe compositions using DMF (dimethylformamide) or a high-boiling solvent such as glycerin or diethylene glycol as a wetting agent from the viewpoint of dischargeability. DMF has problems with stability against heat, acid and alkali, and higher alcohols such as glycerin and diethylene glycol react with PPV precursors in the process of conjugation when polyparaphenylene vinylene (PPV) is used as a green light emitting material. There is a problem that will inhibit. In particular, glycerin is difficult to remove.

  In addition, if the nozzle diameter is reduced to form a smaller inkjet droplet in order to increase the patterning resolution, there is a problem that the ink becomes easier to dry as the droplet becomes smaller.

  Further, when the organic layer is laminated not only by the ink jet method but also by a coating method, so-called compatibility in which the solvent of the composition dissolves the organic film of the base layer becomes a problem. Specifically, the light emitting layer is formed on the hole injection layer (or hole transport layer).

  Accordingly, an object of the present invention is to provide a method for producing an organic EL device composed of an organic laminated film having excellent characteristics in a simple, short time, low cost, and an ink composition enabling the method.

  According to this invention, the manufacturing method of the organic EL element of following (1)-(5) is provided.

  (1) A method for producing an organic EL device having a structure in which a hole injection layer and a light emitting layer are sandwiched between an anode and a cathode, and an ink composition containing a hole injection material made of an organic compound in a predetermined region on a substrate An organic material comprising: a step of applying a material by an ink jet method to form a hole injection layer; and a step of applying an ink composition containing a light emitting material made of an organic compound by an ink jet method to form a light emitting layer. Manufacturing method of EL element.

  In this method, both the hole injection layer and the light emitting layer made of an organic compound are formed by an ink jet method. With this method, all organic layers can be formed by a simple method, High performance can be achieved.

  In the present invention, the hole injection layer is a layer that can effectively inject holes into the light emitting layer from the anode side, and also has a hole transport function. In addition to the hole injection layer, a hole transport layer having a hole transport function may be provided as a separate layer.

  (2) The organic EL element is an element having a plurality of pixels on a substrate, a partition wall is provided on the substrate to separate the pixels, and the hole injection layer and the light emitting layer are formed in a region between the partition walls. (1) The manufacturing method of the organic EL element characterized by these.

  By the method (2), a multicolor and high-definition organic EL element can be easily obtained without mixing different light-emitting layers.

  (3) The organic EL element is an element having a plurality of pixels on a substrate, a partition wall is provided on the substrate to separate the pixels, and the hole injection layer is subjected to a continuous treatment process of oxygen gas plasma and fluorocarbon gas plasma. And the light emitting layer is formed. (1) A method for producing an organic EL device according to (1).

  By the method (3), a difference in wettability of droplets can be imparted on the substrate, and fine patterning of inkjet droplets becomes possible.

  (4) After applying an ink composition containing a hole injection material made of the organic compound by an ink jet method, the solvent of the ink composition is removed to obtain a hole injection layer, and the ink composition is made of the organic compound (1) The method for producing an organic EL device according to (1), wherein an ink composition containing a light emitting material is applied by an ink jet method, and then the solvent of the ink composition is removed to obtain a light emitting layer.

  By the method (4), an organic solid thin film as a hole injection layer and a light emitting layer having desired characteristics can be formed.

  (5) After applying an ink composition containing a hole injection material made of the organic compound by an ink jet method, the material of the ink composition is further cured or conjugated by heat treatment to obtain a hole injection layer; and (1) The organic material according to (1), wherein an ink composition containing a light emitting material composed of the organic compound is applied by an ink jet method, and then the light emitting layer is obtained by further curing or conjugating the material of the ink composition by heat treatment. Manufacturing method of EL element.

  By the method (5), a hole injection layer and a light emitting layer having excellent functions can be formed.

  According to the invention, the following ink compositions (6) to (15) are provided. (6) An ink composition containing a hole injection material or a light emitting material applied by an inkjet method in the manufacture of an organic EL device, wherein the viscosity is 1 to 20 mPa · s, the surface tension is 20 to 70 mN / m, and the inkjet head An ink composition having a contact angle with respect to a material constituting the nozzle surface of 30 to 170 °.

  According to the ink composition of (6), particularly when applied by the ink jet method, the nozzle hole is clogged, the flying bend of the ink droplet is suppressed, the discharge is smoothed, and the discharge amount and the discharge timing can be controlled. Thus, stable ejection by the ink jet method becomes possible.

  (7) The ink composition according to (6), wherein the solid content concentration is 0.01 to 10.0 wt%.

  According to the ink composition of (7), it is possible to obtain a desired film thickness without impairing the discharge property when applied by an ink jet method.

  (8) The ink composition according to (6) or (7), comprising at least one solvent having a vapor pressure of 0.001 to 50 mmHg (room temperature).

  According to the ink composition (8), the ink can be prevented from drying when applied by inkjet, and clogging in the nozzle holes can be eliminated. (9) The ink composition according to any one of (8), wherein the solvent of the ink composition is an aprotic cyclic polar solvent.

  The ink composition (9) can be stably dispersed or dissolved without impairing the properties of the hole injection material or the light emitting material, and can be stably ejected when applied by the ink jet method.

  (10) The ink composition according to any one of (6) to (9), comprising glycol ether acetic acid.

  According to the ink composition of (10), it is possible not only to suppress ink drying, but also to improve film formability.

  (11) The ink composition according to any one of (6) to (10), which contains 20 wt% or less of a lower alcohol.

  According to the ink composition of (11), it is possible to adjust the surface tension and the viscosity to desired values without impairing the ink ejection property, particularly when applied by the ink jet method.

  (12) The ink composition according to (6), wherein the ink composition includes a hole injection material, and the hole injection material includes a mixture of a polythiophene derivative and polystyrene sulfonic acid.

  According to the ink composition of (12), particularly when applied by the ink jet method, the discharge property and the film forming property are excellent, and a high-performance hole injection layer can be obtained in the organic EL element.

  (13) The ink composition according to (12), further comprising a silane coupling agent as a thermosetting agent.

  When the ink composition (13) is used, a hole injection layer that does not cause compatibility with the light emitting layer in the organic EL element can be formed by applying the ink composition particularly by an ink jet method.

  (14) The ink composition according to (6), wherein the ink composition includes a light emitting material, and the light emitting material includes a precursor of poly (paraphenylene vinylene) and a derivative thereof.

  According to the ink composition of (14), the ink composition for a green or red light-emitting layer, which has excellent discharge properties and film-forming properties particularly when applied to an ink jet method and has excellent light emission characteristics in an organic EL device, is provided. Can do.

  (15) The ink composition according to (14), wherein a light-emitting material doped with a low molecular dye is used.

  According to the ink composition of (15), it is possible to obtain a green or red light emitting layer ink composition excellent in dischargeability, film formability and light emission characteristics particularly when applied to an ink jet method.

  The ink compositions (6) to (15) can be suitably used in the step of forming a hole injection layer or a light emitting layer in the method for producing an organic EL device of (1) to (5), respectively.

  Moreover, according to this invention, the high performance organic EL element obtained by the said method is provided.

  Hereinafter, embodiments of the present invention will be described in detail.

  The method for producing an organic EL device by the ink jet method of the present invention is to eject an ink composition in which a hole injection material made of an organic material and a light emitting material made of an organic material are dissolved or dispersed in a solvent from an ink jet head. In this method, for example, a transparent electrode is formed and applied onto a substrate constituting a pixel to form a hole injection layer and a light emitting layer. According to such an ink jet method, fine patterning can be performed easily and in a short time, and multi-coloring is possible. Further, since a necessary amount of material may be applied to a necessary place, the material is not wasted even if the substrate has a large area.

  The structure of an ink jet head used in the manufacturing method for the organic EL device of the present invention is shown in FIGS. The inkjet head 10 includes, for example, a stainless steel nozzle plate 11 and a diaphragm 13, and both are joined via a partition member (reservoir plate) 15. A plurality of ink chambers 19 and liquid reservoirs 21 are formed between the nozzle plate 11 and the diaphragm 13 by the partition member 15. The interiors of the ink chamber 19 and the liquid reservoir 21 are filled with the ink composition of the present invention, and the ink chamber 19 and the liquid reservoir 21 communicate with each other via the supply port 23. Further, the nozzle plate 11 is provided with nozzle holes 25 for ejecting the ink composition from the ink chamber 19 in a jet form. On the other hand, the ink jet head 10 is formed with an ink introduction hole 27 for supplying an ink composition to the liquid reservoir 21. A piezoelectric element 29 is bonded to the surface of the vibration plate 13 opposite to the surface facing the ink chamber 19 in correspondence with the position of the space 19.

  The piezoelectric element 29 is located between the pair of electrodes 31 and bends so that the piezoelectric element 29 protrudes outward when energized. As a result, the volume of the ink chamber 19 increases. Accordingly, the ink composition corresponding to the increased volume flows into the ink chamber 19 from the liquid reservoir 21 through the supply port 23. Next, when the energization to the piezoelectric element 29 is released, both the piezoelectric element 29 and the diaphragm 13 return to their original shapes. As a result, the space 19 also returns to its original volume, so that the pressure of the ink composition inside the ink chamber 19 rises, and the ink composition is ejected from the nozzle hole 25 toward the substrate.

  An ink repellent layer 26 is provided around the nozzle hole 25 in order to prevent the ink composition from being bent or clogged. That is, an ink repellent layer 26 made of, for example, a Ni-tetrafluoroethylene eutectoid plating layer is provided in the peripheral portion of the nozzle hole 25 as shown in FIG.

  In the method for producing an organic EL element of the present invention, an ink composition containing a hole injection material or a light emitting material used by being discharged from the inkjet head has the following characteristics.

  The viscosity of the ink composition is preferably 1 to 20 mPa · s, and particularly preferably 2 to 8 mPa · s. When the viscosity of the ink composition is less than 1 mPa · s, not only is it difficult to control the discharge amount, but the solid concentration is too low to form a sufficient film. If it exceeds 20 mPa · s, the ink composition may not be smoothly ejected from the nozzle holes, and it may be necessary to change the specifications of the apparatus such as enlarging the nozzle holes. Further, when the viscosity is large, the solid component in the ink composition is likely to precipitate, and the nozzle hole is clogged frequently.

  The surface tension of the ink composition is preferably 20 to 70 mN / m, particularly preferably 25 to 45 mN / m. By setting the surface tension within this range, it is possible to suppress the flight bending during ink ejection. When the surface tension is less than 20 mN / m, the wettability of the ink composition on the nozzle surface increases. Therefore, when the ink composition is ejected, the ink composition may adhere asymmetrically around the nozzle holes. is there. In this case, since an attractive force acts between the composition adhering to the nozzle hole and the adhering substance to be ejected, the ink composition is ejected by non-uniform force, and so-called flight bending that cannot reach the target position. Of course, and the frequency of that will increase. On the other hand, if it exceeds 70 mN / m, the shape of the meniscus at the nozzle tip is unstable, and it becomes difficult to control the discharge amount and discharge timing of the ink composition.

  The contact angle with respect to the material constituting the nozzle surface for discharging the ink composition provided on the inkjet head is preferably 30 ° to 170 °, particularly preferably 35 ° to 65 °. When the ink composition has a contact angle in this range, the flight bending of the ink composition can be controlled, and precise patterning becomes possible. When the contact angle is less than 30 °, the wettability of the ink composition with respect to the material constituting the nozzle surface increases, and thus flight bending occurs as in the case of surface tension. Also. If the angle exceeds 170 °, the interaction between the ink composition and the nozzle holes becomes minimal, and the shape of the meniscus at the tip of the nozzle is not stable, making it difficult to control the ejection amount and ejection timing of the ink composition.

  Here, the flight curve means that when the ink composition is ejected from the nozzle, the dot landing position causes a deviation of 50 μm or more from the target position. This occurs mainly due to non-uniform wettability of the nozzle holes or clogging due to adhesion of solid components of the ink composition.

  The solid content concentration of the ink composition is preferably 0.01 to 10.0 wt%, more preferably 0.1 to 5.0 wt%, based on the entire composition. If the solid content concentration is too low, the number of ejections increases to obtain the required film thickness, and the mass production efficiency deteriorates. On the other hand, if it is too high, the viscosity becomes high and the dischargeability is affected.

  The solid component is preferably dissolved or dispersed in at least one solvent having a vapor pressure at room temperature of 0.005 to 50 mmHg. By using a solvent that does not easily thirst, it is possible to prevent the ink composition from being dried at the nozzle holes, thereby causing thickening, aggregation, and solid adhesion. However, a solvent having a vapor pressure lower than 0.005 mmHg is not suitable because it is difficult to remove the solvent during the film formation process.

  Examples of such solvents include aprotic cyclic polar solvents such as γ-butyrolactone, N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) and derivatives thereof, or carbitol acetate ( And glycol ether acetic acid such as butyl carbitol acetate (BCA). Solvents such as CA and BCA are also effective in improving the film formability.

  On the other hand, lower alcohols such as methanol (MeOH), ethanol (EtOH), and propyl alcohol are effective in adjusting the surface tension and viscosity, but are desirably 20 wt% or less because of high volatility.

  In addition, the above-mentioned characteristic is suitable also as a characteristic of the positive hole transport material which comprises the same layer in the case of forming a positive hole transport layer in an organic EL element.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
Example 1 relates to an ink composition for forming a hole injection layer applied by an inkjet method in the production of an organic EL device.

  In the present invention, as a hole injection material, PEDT (polyethylenedioxythiophene) which is a polythiophene derivative

  And PSS (polystyrene sulfonic acid)

  Was used. These can be purchased from Bayer as Vitron P. Examples of the hole injection material (or hole transport material used as a material for the hole transport layer) include polyaniline, porphyrin compounds, pyridine derivatives, etc., which are thermally durable polymers and polar such as water. Vitron P that can be dispersed in a solvent is suitable for the ink jet system. Using Vitron P, ink compositions shown in Table 1 were prepared.

  In order to prevent compatibility with the light emitting layer, γ-glycidyloxypropyltrimethoxysilane was used as a silane coupling agent that crosslinks by heat treatment, and the same weight as the conductive polymer was added. The final solid concentration of the ink composition was 0.16 wt%.

  Table 2 shows the results of evaluating the viscosity, surface tension, contact angle with respect to the material constituting the ink ejection nozzle surface of the inkjet head, ejection properties, patterning properties, and film-forming properties. The physical properties and ejection characteristics of the ink composition were evaluated by the following methods.

  Viscosity: A value at 20 ° C. was measured with an E-type viscometer.

  Surface tension: The value at 20 ° C. was also measured by the plate method.

  Contact angle: Measured as a static contact angle on the material (Ni-tetrafluoroethylene eutectoid plated water repellent layer) constituting the ink discharge nozzle surface of the inkjet head.

  Discharge characteristics: An inkjet printer head (MJ-930C manufactured by Epson Corporation) was used. The flying bend was measured by variation in landing of ink droplets on the substrate when the distance between the head and the substrate was 0.6 mm. As the nozzle clogging frequency, the time required for the ink composition to be ejected continuously (frequency: 7200 Hz) until the nozzle hole is clogged due to the solid component of the deposited ink composition and the ejection becomes impossible. Was measured.

  Patterning property, film forming property: A film formed by discharging to the test cell shown in FIGS. 3A and 3B, removing the solvent at room temperature in a vacuum, and then heat-treating in the atmosphere at 200 ° C. for 10 minutes. The film quality (aggregation, flatness, etc.) was observed with a microscope. The test cell has a pixel (40 μm pitch) in which a 2 μm thick polyimide 40 formed on the ITO substrate 41 is opened with a diameter of 30 μm. Before discharge, a continuous treatment of oxygen gas plasma and fluorocarbon gas plasma was performed, and the polyimide surface was made water repellent and the ITO surface was made hydrophilic. The plasma treatment may be performed in any atmosphere in vacuum or air. And the ink composition 44 was discharged from the inkjet head 43 of the inkjet apparatus 42 to the opening part, and the film was obtained and evaluated. The results are shown in Table 2 below.

  As shown in Table 2, the discharge property, the patterning property, and the film forming property are all sufficiently practical. In the composition of Table 1, for example, a composition in which the addition amount of methanol (MeOH) and isopropyl alcohol (IPA) exceeds 20% was prepared and evaluated in the same manner as described above, or 1,3- A composition in which dimethyl-2-imidazolidine (DMI) was not added and replaced with water was prepared and evaluated by forming a film in the same manner as described above. Even if the physical value was satisfied, the ink composition was depleted. Clogging occurred during discharge.

(Example 2)
Example 2 relates to an ink composition for a light emitting layer.

  In the present invention, poly (paraphenylene vinylene) (PPV) is used as the green light emitting material.

  As an organic compound capable of forming a light emitting layer, in addition to PPV, polyalkylthiophene such as PTV (poly (2,5-thienylene vinylene)), PFV (poly (2,5-furylene vinylene)), poly Examples include polyarylene vinylenes such as paraphenylene and polyalkylfluorene, pyrazoline dimer, quinolidinecarboxylic acid, benzopyrylium perchlorate, benzopyranoquinolidine, phenanthroline europium complex, and one or more of these. It can be used by mixing. Among these, those made of a polymer organic compound are preferable. The polymer organic compound is excellent in film formability, and the durability of the light emitting layer is very good. Polymeric materials have a wide range of freedom in molecular design, and rational design of EL light-emitting elements is possible. In addition, it has a forbidden band width in the visible region and relatively high conductivity, and among these, conjugated polymers tend to have such a tendency. As the light emitting layer material, a conjugated polymer itself or a conjugated polymer precursor that is conjugated (film-formed) by heating or the like is used. Among these, PPV or a derivative thereof is particularly preferable. As precursors of PPV derivatives, MO-PPV (poly (2,5-dimethoxy-1,4-phenylenevinylene)) precursor, CN-PPV (poly (2,5-bishexyloxy-1,4-phenylene-) (1-cyanovinylene))) precursor and the like. The precursor before conjugation (film formation) of PPV or a derivative thereof is soluble in water or a polar solvent, and is suitable for pattern formation by an ink jet method. In addition, PPV or its derivatives have strong fluorescence, and the PPV thin film also functions as a hole injecting and transporting layer because it is a conductive polymer in which π electrons of double bonds are delocalized on the polymer chain. A high-performance organic EL element can be obtained.

  Ink compositions shown in Table 3 were prepared using a poly (paraphenylene vinylene) precursor (water / MeOH = 5/95 mixed solution). The solid content concentration was 0.3 wt%.

  Table 4 shows the results of evaluating the viscosity, surface tension, contact angle with respect to the material constituting the ink ejection nozzle surface of the inkjet head, ejection properties, patterning properties, and film-forming properties. The physical properties and ejection characteristics of the ink composition were evaluated in the same manner as in Example 1. The film forming property was evaluated by removing the solvent in vacuum at room temperature after discharge and treating it at 150 ° C. for 4 hours in a nitrogen atmosphere.

  As shown in Table 4, the ejection property, the patterning property, and the film forming property were sufficiently high and reached practical levels. On the other hand, for example, when an ink composition in which DMI was replaced with dimethylformamide (DMF) or butyl carbitol acetate (BCA) was replaced with glycerin and film formation and evaluation similar to those described above were performed, ejection properties were determined. However, the light emission efficiency was low and the emission color was shifted to the short wavelength side. If the solid content concentration is desired to be higher than 0.3 wt%, adding 20 wt% or more of the precursor solution will increase the MeOH content, tend to cause ink thirst, and cause flight bending and clogging. The concentrated product was used.

(Example 3)
Example 3 relates to an ink composition for a light emitting layer.

  In this example, the PPV precursor ink composition used in Example 2 was added with rhodamine 101, which is a low molecular fluorescent dye, as a red light emitting material.

  The method of doping with a low molecular weight fluorescent dye can change the light emission characteristics of the light emitting layer, and is very effective as a means for improving the light emission efficiency or changing the light emission wavelength, for example. Red and green light emission with high color purity can be obtained by doping with a fluorescent dye.

  As the fluorescent dye used for the red light emitting layer, DCM, a rhodamine or rhodamine derivative, perylene, or the like, which is a laser dye, can be used. Since these fluorescent dyes are low in molecule, they are soluble in a solvent, have good compatibility with PPV and the like, and can easily form a uniform and stable light emitting layer. Examples of the rhodamine derivative fluorescent dye include rhodamine B, rhodamine B base, rhodamine 6G, rhodamine 101 perchlorate and the like, and a mixture of two or more thereof may be used.

  Examples of the fluorescent dye used for the green light emitting layer include quinacridone, rubrene, DCJT, and derivatives thereof. These fluorescent dyes, like the above-mentioned red fluorescent dyes, have low molecular weight and are therefore soluble in a solvent, and are compatible with PPV and the like, so that a light emitting layer can be easily formed.

  In this example, ink compositions for red light emitting layers shown in Table 5 below were prepared.

  Table 6 shows the results of evaluating the viscosity, surface tension, contact angle with respect to the material constituting the ink discharge nozzle surface of the inkjet head, discharge property, patterning property, and film forming property. The physical properties, ejection characteristics, and film formability of the ink composition were evaluated in the same manner as in Example 2.

  As shown in Table 6, the discharge property, the patterning property, and the film forming property were sufficiently reached the practical level. When the doping amount of rhodamine 101 was 1.5 wt% with respect to the PPV precursor, red light emission was most efficiently exhibited.

Example 4
Example 4 relates to a method for manufacturing an organic EL element by an inkjet method. FIG. 4 shows a manufacturing process of a three-color full-color organic EL element.

  The transparent substrate 104 functions as a support and a surface from which light is extracted. Therefore, the transparent substrate 104 is selected in consideration of light transmission characteristics and thermal stability. Examples of the transparent substrate material include a glass substrate and a transparent plastic, but a glass substrate is preferable because of excellent heat resistance.

  First, pixel electrodes 101, 102, and 103 were formed on the transparent substrate 104. Examples of the forming method include photolithography, vacuum deposition, sputtering method, pyrosol method and the like, and it is preferable to use photolithography. A transparent pixel electrode is preferable as the pixel electrode, and examples of the material constituting the transparent pixel electrode include a tin oxide film, an ITO film, and a composite oxide film of indium oxide and zinc oxide.

  Next, partition walls (banks) 105 were formed of photosensitive polyimide, and the gaps between the transparent pixel electrodes were filled. Accordingly, it is possible to improve contrast, prevent color mixing of light emitting materials, and prevent light leakage from between pixels.

  The material constituting the partition wall 105 is not particularly limited as long as it has durability against the solvent of the EL material. However, since it can be made Teflon (registered trademark) by fluorocarbon gas plasma treatment, for example, acrylic resin, epoxy resin, photosensitive resin, and the like. Organic materials such as conductive polyimide are preferred. The laminated partition which made inorganic materials, such as liquid glass, the lower layer may be sufficient. The partition wall 105 may be a black resist by mixing carbon black or the like with the above material. Examples of the method for forming the partition wall 105 include photolithography.

  Immediately before applying the ink composition for the hole injection layer (further hole transport layer), the substrate was subjected to continuous plasma treatment with oxygen gas and fluorocarbon gas plasma. Thereby, the polyimide surface becomes water repellent and the ITO surface becomes hydrophilic, and the wettability on the substrate side for finely patterning the ink jet droplets can be controlled. As an apparatus for generating plasma, an apparatus for generating plasma in a vacuum or an apparatus for generating plasma in the atmosphere can be used similarly.

  Next, the hole injection layer ink composition described in Example 1 is ejected from the head 110 (MJ-930C manufactured by Epson Corporation) of the inkjet printing apparatus 109, and patterning coating is performed on each of the pixel electrodes 101, 102, and 103. went. After coating, the solvent was removed under the conditions of vacuum (1 torr), room temperature, and 20 minutes, and then heat treatment at 200 ° C. (on a hot plate) in the atmosphere for 10 minutes, whereby the light emitting layers described in Examples 2 and 3 were used. A hole injection layer 120 that is incompatible with the ink composition was formed. The film thickness was 40 nm. In this embodiment, a common hole injection layer is formed in each pixel, but in some cases, each light emitting layer may be formed using a hole injection material (or hole transport material) suitable for the light emitting layer. .

  Furthermore, the red light emitting layer ink composition mentioned in Example 3 and the green light emitting layer ink composition mentioned in Example 2 were patterned on the pixel electrodes 101 and 102 via the hole injection layer 120 by the inkjet method. It was applied to the shape. After coating, the solvent was removed in vacuum (1 torr) at room temperature for 20 minutes, followed by conjugation by a heat treatment at 150 ° C. for 4 hours in a nitrogen atmosphere to form a red light emitting layer 106 and a green light emitting layer 107. . The film thickness was 50 nm. The light-emitting layer conjugated by heat treatment is insoluble in the solvent.

  According to such an ink jet method, fine patterning can be performed easily and in a short time. Further, the film thickness can be changed by changing the solid content concentration and the ejection amount of the ink composition.

  Further, before the light emitting layer is formed, the hole injection layer 120 may be subjected to continuous plasma treatment with oxygen gas and fluorocarbon gas plasma. As a result, a fluoride layer is formed on the hole injection or hole transport layer 120 and the ionization potential is increased, so that the hole injection efficiency is increased, and an organic EL device with high light emission efficiency can be provided.

  Next, a blue light emitting layer 108 was formed on the pixel electrode 103 through the red light emitting layer 106, the green light emitting layer 107 and the hole injection layer 120. Thereby, not only the three primary colors of red, green, and blue can be formed, but also the step between the red light emitting layer 106 and the green light emitting layer 107 and the partition wall 105 can be filled and flattened. Thereby, a short circuit between the upper and lower electrodes can be reliably prevented. By adjusting the film thickness of the blue light emitting layer, the blue light emitting layer functions as an electron injecting and transporting layer in the laminated structure of the red light emitting layer and the green light emitting layer, and does not emit blue light.

  A method for forming the blue light emitting layer 108 is not particularly limited, and the blue light emitting layer 108 can be formed by a general spin coating method or an ink jet method as a wet method. In this example, a blue light emitting layer 108 having a film thickness of 45 nm was formed by spin coating a xylene solution of polydioctylfluorene.

  Other examples of the blue light-emitting layer include polydihexylfluorene, which is a polyfluorene derivative, and copolymers with other polymerization groups, and a blue fluorescent dye or an organic compound having an electron injecting and transporting ability may be added.

  Examples of organic compounds that can form an electron injecting and transporting layer include oxadiazole derivatives such as PBD and OXD-8, DSA, aluminum quinol complexes, Bebq, triazole derivatives, azomethine complexes, porphine complexes, and the like.

  Even if the light emitting material is not suitable for the ink jet method by forming two colors of the organic light emitting layer by the ink jet method and forming the other color by the conventional coating method as in this embodiment, the ink jet method Since a full-color organic EL element can be formed by combining with other organic light emitting materials used in the above, the degree of freedom in element design is increased. Examples of conventional coating methods other than the inkjet method include a printing method, a transfer method, a dipping method, a spin coating method, a casting method, a capillary method, a roll coating method, and a bar coating method.

  Finally, a cathode (counter electrode) 113 was formed. The cathode 113 is preferably a metal thin film electrode, and examples of the metal constituting the cathode include Mg, Ag, Al, Li, and the like. In addition to these, materials having a small work function can be used. For example, alkali metals, alkaline earth metals such as Ca, and alloys containing them can be used. Metal fluorides can also be applied. Such a cathode 113 can be formed by vapor deposition or sputtering. In this example, Ca was deposited to 100 nm by vacuum heating vapor deposition, and Al was further deposited to 1200 nm by sputtering to form a cathode.

  Further, a protective film may be formed on the cathode 113. By forming the protective film, it was possible to prevent the cathode 113 and the light emitting layers 106, 107, 108 from being deteriorated, damaged, peeled off, and the like.

  Examples of the constituent material of such a protective film include epoxy resin, acrylic resin, liquid glass, and the like. Examples of methods for forming the protective film include spin coating, casting, dipping, bar coating, roll coating, and capillary methods.

In the organic EL element obtained in this example, a luminance of 100 cd / m ² or more was obtained for each color pixel even at a low voltage of 5 V or less. In addition, the red and green pixels formed by the inkjet method have luminous efficiencies of 0.15 lm / W and 0.25 lm / W, respectively, and an emission lifetime (initial luminance when a constant current is applied and continuous emission is performed). The time until the decrease by 50% was 2000 hours or more.

  The same material as described above was used, and the same level as that of a red light emitting element and a green light emitting element in which a hole injection layer and a light emitting layer were formed by spin coating with the same laminated structure. Thus, an excellent characteristic was exhibited even in the ink jet system, and an element not inferior to a spin coat product could be formed.

  As described above, according to the present invention, both the hole injection layer and the light emitting layer are formed by the ink jet method, and an organic EL element can be obtained easily and quickly at low cost. In addition, it was possible to provide a hole injection ink composition and a light emitting material layer ink composition excellent in ejection property, patterning property, and film forming property. In addition, a high-definition full-color organic EL element having a laminated structure and excellent in characteristics can be formed easily and easily by patterning the hole injection or hole transport layer and the light-emitting layer by the ink jet method using the ink composition. Can do.

It is a top perspective view which shows an example of the structure of the printer head for inkjet used for manufacture of the organic thin film EL element of this invention. It is sectional drawing which shows an example of the structure of the nozzle part of the inkjet printer head used for manufacture of the organic thin-film EL element of this invention. In the Example of this invention, it is a figure which shows the test cell used for the patternability of an ink composition, and film formability evaluation. It is sectional drawing which shows an example of the manufacturing method of the organic EL element of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Head for inkjet, 11 ... Nozzle plate, 13 ... Diaphragm, 15 ... Partition member, 19 ... Ink chamber, 21 ... Liquid reservoir, 23 ... Supply port, 25 ... Nozzle hole, 26 ... Ink-repellent layer, 27 ... Ink Introducing hole, 29 ... piezoelectric element, 31 ... electrode, 33 ... nozzle surface, 40 ... polyimide partition, 41 ... ITO, 42 ... inkjet printing apparatus, 43 ... inkjet head, 44 ... ink composition, 101 ... pixel electrode (red) , 102 ... Pixel electrode (green), 103 ... Pixel electrode (blue), 104 ... Transparent substrate, 105 ... Partition, 106 ... Light emitting layer (red), 107 ... Light emitting layer (green), 108 ... Light emitting layer (blue), 109: Inkjet printing apparatus, 110: Inkjet head, 113 ... Cathode, 120 ... Hole injection layer.

Claims (5)

A method for producing an organic EL device having a structure in which a hole injection layer and a light emitting layer are sandwiched between an anode and a cathode,
Applying an ink composition containing a hole injection material made of an organic compound to a predetermined region on the substrate by an inkjet method to form a hole injection layer;
After forming the hole injection layer, applying an ink composition containing a light emitting material made of an organic compound by an inkjet method to form a light emitting layer, and
The method for producing an organic EL device, wherein the ink composition containing the hole injection material contains γ-glycidyloxypropyltrimethoxysilane as a thermosetting agent. The organic EL element is an element having a plurality of pixels on a substrate, a partition wall for separating the pixels is provided on the substrate, and the hole injection layer and the light emitting layer are formed in a region between the partition walls. The manufacturing method of the organic EL element of Claim 1 . The method for manufacturing an organic EL device according to claim 1 or claim 2, wherein the ink composition contains a glycol ether acetate. As the luminescent material, at least a poly (para-phenylene vinylene) or derivatives of the poly (p-phenylene vinylene) or the poly any one of claims 1 to 3, characterized in that it comprises a precursor of (paraphenylene vinylene), The manufacturing method of the organic EL element of description. The method for manufacturing an organic EL device according to any one of claims 1 to 4, characterized by using a material obtained by doping the small molecule dye as the luminescent material.

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