JP4812602B2 - Organic thin film element and method for manufacturing the same - Google Patents

Description

  The present invention relates to an organic thin film element comprising a carrier transporting thin film or a light emitting thin film comprising an organic layer, and a method for producing the same.

  In recent years, attention has been focused on organic thin film elements using organic materials as active materials instead of conventional inorganic materials, in other words, organic electronic elements. The organic thin film element includes various elements such as an organic EL element and an organic transistor, all of which are characterized in that the organic thin film portion has a carrier transport function or a light emitting function.

  The organic thin film element materials can be broadly classified into low molecular weight materials and high molecular weight materials. Depending on applications, low molecular weight organic EL materials, high molecular weight organic EL materials, and low molecular weight organic transistor materials can be used. It is classified as a polymer organic transistor material. Since organic materials are inherently highly insulating, only a limited number of types of materials can be used for organic electronics.

  As a low molecular weight organic EL material, an organic material such as a hole injection material, a hole transport material, a light emitting material, an electron transport material, and an electron injection material is required. As the light emitting material, a red light emitting material, a green light emitting material, Blue light emitting materials, white light emitting materials, and the like are required. Often used as a hole injection material is copper phthalocyanine, a phenylamine derivative, or the like, and in some cases, a doping material for improving hole injection characteristics may be used. As the hole transport material, a phenylamine derivative is often used. As a light-emitting material, it is common to use a metal complex such as an aluminum quinolinol complex doped with a small amount of a light-emitting low-molecular material for improving light emission efficiency. For example, a method of improving luminous efficiency by using a light emitting material or a phenylamine based material as a host material and a light emitting low molecular weight material including a laser dye or a condensed ring aromatic as a guest material is used. As the electron transporting material and the electron injecting material, metal complex materials, other organic dye materials, materials obtained by doping these materials to improve electron injection characteristics, and the like are used.

  What is characteristic as a low molecular weight organic EL element is that a multilayer laminated structure such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer can be formed by a vacuum deposition method. By maintaining the proper injection balance of holes and electrons, confining the recombination sites of holes and electrons in the light-emitting layer, and realizing the performance of organic EL elements with high emission efficiency and long life. is there.

  On the other hand, in the polymer organic EL element, a solution process such as spin coating, ink jet, printing, etc., capable of high-speed film formation under atmospheric pressure is used instead of an organic thin film forming process using an expensive vacuum apparatus. Therefore, it is expected to form a large-area element at a low price.

  However, unlike the above-described low-molecular organic EL devices, the polymer organic EL device has a problem in terms of solvent efficiency and difficult to form a multilayer laminated structure, and has problems in terms of luminous efficiency and lifetime. . In general, a simple structure of “transparent electrode / buffer layer / light emitting layer / cathode” is used as the structure of the polymer organic EL element. In such a simple structure, the light emitting sites in the light emitting layer are not present. When shifted to the buffer layer side or the cathode side, the deactivation ratio at the interface increases, so that the light emission efficiency and the lifetime are likely to be reduced. In addition, it is said that specific chemical substances in the buffer layer diffuse into the light emitting layer, so that the light emission efficiency and life are likely to be impaired. Appearance was craving.

  As a general method for producing a polymer organic EL element, a polythiophene-based aqueous material is used as a buffer layer, and a polyfluorene-based or polyparaphenylenevinylene-based material is dissolved in an organic solvent as a light-emitting layer. Formed. Since the buffer layer is insoluble in an organic solvent after drying, the upper light-emitting layer can be formed by applying an organic solvent-based solution without breaking the shape of the layer. However, in order to further increase the number of layers, for example, if the following solution containing an organic solvent is applied on the light emitting layer from above, the light emitting layer that has already been formed will be dissolved. It is difficult to make it easier.

  As a method of increasing the number of layers in a polymer organic EL element, for example, after applying a soluble precursor polymer material, the polymer material is denatured and insolubilized by heating at a high temperature of about 200 degrees Celsius for several hours or longer. A method for forming the next layer has been reported by the University of Cambridge, etc. (Non-patent Document 1, Patent Document 1). However, since the process temperature is high and the heating time takes a long time, This method is not suitable as a manufacturing process, and is not desirable for a polymer organic EL device aiming at cost reduction.

  In addition, a method of forming a multilayer laminated structure by forming a low molecular weight organic EL material by vacuum deposition after forming a polymer organic EL element has been reported (Non-Patent Document 2). By including, it becomes impossible to differentiate from a low molecular organic EL element, and a merit in terms of cost reduction cannot be expected so much.

  On the other hand, a method using a crosslinkable hole transporting material has been reported (Patent Document 2). For hole injection materials, hole transport materials, light emitting materials of various colors, electron transport materials, and the like, Having a crosslinkable material having a complicated chemical structure leads to an increase in material cost and is a method contrary to cost reduction of the device. In addition, depending on the structure of the crosslinkable material, it may shrink after crosslinking to impair the morphology of the film, and it is not easy to determine the chemical structure and compounding ratio of the material to obtain a uniform thin film even after crosslinking. Absent. The uniformity and flatness of the film is a lifeline in the organic thin film element. If a part of the film is extremely thin, the resistance value becomes low, so the current is concentrated on the part and the film is burnt. Or leak current. Conversely, if the film has high uniformity and good morphology, an electric field is applied uniformly over the entire surface. If it is an organic EL device, uniform light emission can be obtained over the entire surface, and the reliability of the device can be greatly enhanced. .

  The problems described above apply to the organic transistor element which is the same organic thin film element. An organic transistor is formed of a gate electrode, a gate insulating film, an organic active layer made of an organic semiconductor, a source electrode, a drain electrode, and the like. In some cases, an inorganic film or a polymer film is used as the gate insulating film. is there. There are cases where low molecular vapor deposition materials are used as the organic active layer and polymer coating materials are used. For example, when a polymer film is used for the gate insulating film and a polymer coating material is used for the organic active layer As in the case of the polymer organic EL element, there is a problem of stacking, and it has been difficult for the prior art to easily form a stacked structure of high-quality polymer films.

  Next, the background regarding the manufacturing method of the polymer organic EL element and the conventional problems will be described. As a method for forming a polymer organic EL element, in addition to the spin coating method, an ink jet method has attracted attention as a method capable of colorization.

  The inkjet method has significantly higher material utilization efficiency than vacuum deposition and spin coating, and allows high-speed application of materials over a large area at normal pressure. Compared with the conventional low molecular organic EL device manufacturing method Therefore, it is expected as a manufacturing method that can reduce costs. The position accuracy of coating by the ink jet method is also increasing year by year, and it has become possible to increase the accuracy of 100 pixels or more per inch that can be applied to mobile phones, PDAs and the like. In addition to the method for producing a polymer organic EL element, attention has been paid in recent years as a technique for producing a flat panel display such as application to production of a color filter of a color liquid crystal panel.

  The ink jet technique is generally a technique for applying an aqueous ink to a paper recording medium, and a special ink jet technique is required to apply an organic solvent ink to a glass substrate.

  In the inkjet method, optimization is required for three points: hardware, ink, and printing substrate. First, the hardware has various conditions such as positioning accuracy, ejection amount accuracy, ejection angle control, and countermeasures against nozzle clogging. However, the condition becomes severe for a pixel size of several tens of micrometers or less. At present, a nozzle capable of ejecting a micro droplet having a minimum size of about 2 pl has been developed. As for the ink, an aqueous ink is generally used. However, in the case of an organic electronics element, it is often necessary to use an organic solvent, particularly an aromatic organic solvent. Therefore, hardware different from a commercially available inkjet printer is required.

  As for ink, first, it is necessary to consider the boiling point and solubility. When using an organic solvent-based ink, if a solvent with a very low boiling point such as chloroform or tetrahydrofuran is used, the drying speed of the solvent at the tip of the inkjet nozzle is too fast, causing the ink to solidify and causing nozzle clogging frequently It becomes. Therefore, although a solvent having a certain high boiling point is desired, it is necessary to ensure the solubility of the polymer material, and it is necessary to select the solvent in consideration of the boiling point and solubility of the solvent. In some cases, a mixed solvent in which two or more solvents are mixed may be used.

  In the inkjet, it is important to adjust the viscosity. In the offset printing and the screen printing, which are general printing methods, the viscosity of the ink is about 2000 cP to 30000 cP. In contrast, the inkjet uses 1 cP to 50 cP. A relatively low viscosity ink to the extent is used.

  The stability of the ink is also very important, and the viscosity should be kept constant during long-term storage, and it should be prevented that solids in the ink precipitate or change during storage. It is. Inks used for printing on general paper use dyes and pigment-based inks, but for organic electronics, synthetic polymers such as polyfluorene-based, polythiophene-based, and polyparaphenylene vinylene-based are used. In addition, it is necessary to develop a technique for improving the stability of ink. These synthetic polymers are highly hydrophobic and dissolve well in low-polarity aromatic organic solvents, but it is said that hydrophobic polymers tend to aggregate with each other, causing solid components to precipitate during long-term storage. Concerned. However, if additives are added, there is a risk that the carrier transport property and light emitting property on the organic electronics element may be impaired, and there have been almost no reports of examples in which a mixture other than a solvent has been added to the ink for forming the organic electronics element. It has not been.

  For the printing substrate, a surface treatment according to the ink is essential, and it is desirable that the ink is wet and stretched on the coated surface without stagnation. When a film made of an organic material is formed on a glass surface or a transparent electrode, a process of cleaning the substrate surface by UV-ozone treatment or plasma treatment using a gas containing oxygen is often used.

  In addition, as a phenomenon peculiar to inkjet, in the process of drying ink droplets, the solvent evaporation rate can be different between the periphery of the droplets and the center of the droplets. There are cases where the periphery of the droplet swells, or conversely, the center of the droplet swells, and it is necessary to optimize the combination of the solute and the solvent, the blending conditions of the solvent, the drying conditions, and the like.

  As a method for producing a polymer-based organic EL device using an inkjet method, due to the problem of a solvent system that can be used, as described above, an aqueous material is used to form the first buffer layer, and after drying, A method of forming a second light-emitting layer using a light-emitting polymer solution dissolved in an organic solvent system is common, and the maximum number of layering techniques is two layers.

  In Patent Document 3, as a method for producing an organic EL element, a liquid containing a polythiophene derivative and a silane coupling agent, or a liquid containing a precursor of polyparaphenylene and its derivative is formed by an ink jet method and cured by heating. A method of conjugating to form a layer is disclosed.

  However, in this method, the materials that can be handled are limited, and the same method cannot be used when a general carrier transporting material or a light emitting material is used. In addition, the manufacturing process includes a process having a very long time and a low throughput, such as heating at 200 ° C. for 2 hours in nitrogen, and thus there is a problem in adopting it as an industrial manufacturing process.

  As a problem when manufacturing a polymer organic EL element using an ink jet method on the device side, if an ink of an ink jet head through an aqueous material is not dried and an organic solvent ink is passed, Due to the principle of reprecipitation, there was a problem that the solid content in the organic solvent-based ink was deposited and could easily cause clogging. In other words, it is practically impossible to apply water-based ink and organic solvent-based ink alternately with a single ink-jet head. If manufacturing is considered, one ink-jet according to the type of solvent used. It was necessary to prepare the equipment.

In Patent Document 4, a coating film is formed using an ink containing a polymer having a carrier transporting property or a light emitting property and a low molecular crosslinking agent having a functional group, and the coating film is crosslinked with light or heat. Thus, it has been proposed to form a laminated structure in which two or more layers are laminated by applying a solution so that a coating film of a base layer does not dissolve even when a solution containing a solvent is applied thereon. However, the coating film formed by these methods has a problem that the film thickness becomes non-uniform due to shrinkage during drying and crosslinking.
Special Table 2000-51627 JP-A-10-195131 JP 2000-208254 A JP-A-2005-243300 NC Greenham, et al., Nature, 1993, Vol. 365, p. 628 T. Sano, AB Holmes, et al., Synthetic Metals, 2001, Vol. 121, p.1701

  It is an object of the present invention to form a laminated structure without using different solvent systems in an organic thin film element having a structure in which a plurality of organic layers are laminated, and a carrier transporting thin film with high film forming uniformity or An organic thin film element capable of forming a light-emitting thin film and a method for manufacturing the same are provided.

  The organic thin film element of the present invention has a plurality of aromatic rings or heterocyclic rings, a polymer compound exhibiting carrier transportability or luminescence, a plurality of crosslinkable functional groups, and a molecular weight / crosslinkable functional group. A carrier transporting thin film or a light emitting thin film obtained by crosslinking an ink containing a reactive oligomer or polymer having a value in the range of 180 to 2000 and a polymerization initiator is provided.

  In the present invention, the reactive oligomer or polymer is contained in the ink, and the carrier transporting thin film or the light emitting thin film is cross-linked. Therefore, even if an ink containing a solvent is applied thereon, the base layer is formed. The carrier transporting thin film or the light emitting thin film is not dissolved. For this reason, a thin film can be formed using the ink containing a solvent on it, without considering dissolution of a foundation layer.

  In the present invention, a reactive oligomer or polymer having a molecular weight / crosslinkable functional group value in the range of 180 to 2000 is used. When the value of molecular weight / crosslinkable functional group is less than 180, the effect of the present invention that a carrier transporting thin film or a light-emitting thin film with high film formation uniformity is formed may not be sufficiently obtained. On the other hand, if it exceeds 2000, the viscosity of the ink increases and it may be difficult to form a coating film using an inkjet head or the like.

  According to the present invention, since the carrier transporting thin film or the light emitting thin film is cross-linked, an organic thin film element capable of forming a film by applying ink thereon can be obtained.

  In the present invention, a reactive monomer having a plurality of crosslinkable functional groups and having a molecular weight / crosslinkable functional group value of less than 180 may be further contained in the ink. By containing the reactive monomer, ink characteristics such as ink viscosity can be adjusted.

  The viscosity of the reactive oligomer or polymer is, for example, 10 mPas / 10000 mPas, and the viscosity of the reactive monomer is, for example, 1 to 10 mPas.

  The molecular weight / crosslinkable functional group value of the reactive monomer is preferably in the range of 90 to 170.

  The reactive oligomer or polymer in the present invention preferably has a hydrophobic part, an ether bond or an ester bond in the molecular structure, is nonionic and has surface activity. By using such a reactive oligomer or polymer, it is excellent in affinity with a polymer compound having hydrophobicity and excellent in affinity with a solvent, so that the stability of the ink can be increased, for example, Stability at the time of ejection from an inkjet can be improved.

  Examples of the crosslinkable functional group of the reactive oligomer or polymer in the present invention include a radical polymerizable acryloyl group, a vinyl group, a cationic polymerizable vinyl ether group, a cationic polymerizable oxetane ring, and a cationic polymerizable oxirane ring. . When a reactive oligomer or polymer having a radical polymerizable acryloyl group or vinyl group is used, the crosslinking reaction can be carried out in a short time by adding a small amount of a polymerization initiator that generates radicals. When photocrosslinking is performed using a reactive oligomer or polymer having a cationic polymerizable vinyl ether group or the like, it is preferable to add a photo cationic polymerization initiator into the ink.

  The organic thin film element of the present invention has a structure in which at least two polymer films are laminated, and the lower layer of this laminated structure is preferably the carrier transporting thin film or the light emitting thin film of the present invention.

  Specifically as an organic thin film element of this invention, an organic electroluminescent element (organic EL element), an organic transistor element, etc. are mentioned.

  In the present invention, the band gap after crosslinking of the reactive oligomer or polymer is preferably larger than the band gap of the polymer compound exhibiting carrier transporting property or light emitting property. This makes it difficult for electrons and holes to be trapped in the organic thin film element, thereby preventing the electrical / electronic performance and optical performance of the organic thin film element from deteriorating.

  The polymer compound in the present invention has a plurality of aromatic rings or heterocyclic rings. It is sufficient if the total of the aromatic ring and the heterocyclic ring is plural. Examples of the polymer compound exhibiting carrier transport property or light emission property include a polymer compound conventionally used as a carrier transport material or a light emitting material in an organic EL device, a carrier transport material used in an organic transistor device, and the like. Can be used.

  In the present invention, the ink contains at least a polymer compound, a reactive oligomer or polymer, and a polymerization initiator. The content of the reactive oligomer or polymer is preferably in the range of 1: 0.01 to 1: 2 by weight ratio (polymer compound: reactive oligomer or polymer) to the polymer compound, more preferably Is 1: 0.05 to 1: 1. Moreover, it is preferable to use a polymerization initiator in the ratio of 0.1-20 weight% with respect to the total amount of a reactive oligomer polymer and a reactive monomer, More preferably, it is 1-10 weight%.

  When a reactive monomer is used, the content of the reactive monomer is in the range of 1: 0.01 to 1: 2 in weight ratio (polymer compound: reactive monomer) to the polymer compound. It is preferable that the ratio is 1: 0.05 to 1: 1.

  The crosslinkable ink of the present invention is an ink used for forming a carrier transporting thin film or a light emitting thin film of the organic thin film element of the present invention, and has a plurality of aromatic rings or heterocyclic rings, and has carrier transportability. Alternatively, a polymer compound exhibiting luminescence, a reactive oligomer or polymer having a plurality of crosslinkable functional groups, and having a molecular weight / crosslinkable functional group value in the range of 180 to 2000, a polymerization initiator, and a solvent It is characterized by containing.

  The solvent in the crosslinkable ink of the present invention is not particularly limited as long as it can dissolve or disperse a polymer compound, a reactive oligomer or polymer, and a polymerization initiator, and an organic solvent is generally used. Accordingly, an aqueous solvent may be used.

  The ratio of the solvent in the crosslinkable ink can be appropriately adjusted in consideration of the viscosity of the ink.

  The method for producing an organic thin film element of the present invention is a method for producing the organic thin film element of the present invention, wherein the crosslinkable ink of the present invention is ejected onto a substrate using a piezo inkjet head, A thin film on the substrate formed by discharging is cross-linked by light or heat to form the carrier transporting thin film or the light emitting thin film.

  According to the manufacturing method of the present invention, a carrier transporting thin film or a light emitting thin film can be formed in a predetermined region on a substrate using an ink jet head, and the thin film can be formed efficiently. In the present invention, since the thin film on the substrate is crosslinked by light or heat, the thin film is used as an underlayer, and an ink containing a solvent is further applied thereon to form a carrier transporting thin film or light emission. It can be formed by laminating organic thin films such as conductive thin films.

  Further, in the present invention, since a reactive oligomer or polymer having a molecular weight / crosslinkable functional group value in the range of 180 to 2000 is used, the film is more uniform than when only a conventional reactive monomer is used. It is possible to improve the properties and realize a good morphology. In addition, since a large crosslinked net can be formed, the quality of the film can be improved.

  According to the present invention, organic electronic elements such as organic EL elements and organic transistor elements can be formed in a short time and with good film quality.

  Examples of the general formula of the reactive oligomer or polymer that can be used in the present invention include the following.

In the following general formula, R, R ₁ , R ₂ , and Rn are hydrogen, an alkyl group, an alkoxy group, an ethylene glycol group, an ether group, a phenyl group, and a hydrocarbon group such as an alkyl group or an alkoxy group. In which a group, a cyclohexane group or the like is substituted, or a part of a hydrocarbon group is substituted with oxygen, nitrogen, sulfur, phosphorus or the like.

  G is carbon, methylene, alkane, alkene, ether, benzene, cyclohexane, naphthalene, other hydrocarbons, or a part of hydrocarbons substituted with oxygen, nitrogen, sulfur, phosphorus, or the like.

  As the reactive oligomer or polymer of the present invention, those having a crosslinkable functional group and a flexible alkyl chain or polyethylene glycol chain are preferably used. For example, a reactive oligomer / polymer represented by the following formula has an acryloyl group as a crosslinkable functional group and a flexible polyethylene glycol chain. The alkyl chain preferably has 4 or more carbon atoms, and the polyethylene glycol chain preferably has 2 or more repeating units. The reactive oligomer / polymer shown below has an aromatic ring, and the aromatic ring provides heat resistance and toughness.

  According to the present invention, in an organic thin film element having a structure in which a plurality of organic layers are laminated, a laminated structure can be formed without using different solvent systems and the like, and a carrier transporting thin film having high film forming uniformity or A luminescent thin film can be formed.

  The organic thin film element of the present invention can be formed using an inkjet method that can be applied to a large area, colored, etc. at low cost. Therefore, it is possible to obtain a multi-layered organic thin film element with high efficiency and long life.

  In addition, if the material is soluble in a solvent, there is no limitation on the types of the carrier transporting material and the light emitting material, and it is not necessary to use a different process in forming the thin film, so that the manufacturing efficiency can be improved.

  In the present invention, since a photocrosslinking process can be used, the film can be insolubilized in a shorter time. In addition, when a material having insufficient resistance to light such as ultraviolet light is used, crosslinking can be performed by heat. In this case, since it is not necessary to carry out the thermal denaturation reaction from the precursor as in the prior art, the crosslinking can be carried out in a relatively short time also serving as a process for evaporating the solvent.

  In the present invention, since a reactive oligomer or polymer having a molecular weight / crosslinkable functional group value in the range of 180 to 2000 is used, the uniformity of the thin film is improved as compared with the case of using a low molecular weight crosslinker. be able to. When a reactive monomer, which is a low molecular weight cross-linking agent, is used, a thick portion is formed in a ring shape, and when used in an organic EL element, different brightness is exhibited at the center and the periphery of the pixel. become. On the other hand, when the reactive oligomer / polymer of the present invention is used, the uniformity of the thin film is increased, and light emission with substantially uniform luminance can be obtained within the pixel.

<Reactive oligomers and polymers>
Specific examples of the reactive oligomer / polymer that can be used in the present invention are shown below. Further, under the chemical structural formula, the compound name, average molecular weight or molecular weight, number of crosslinkable functional groups, and molecular weight / crosslinkable functional group values are shown.

<Reactive monomer>
Specific examples of the reactive monomer that can be used in the present invention are shown below.

<Polymerization initiator>
Specific examples of the photopolymerization initiator that can be used in the present invention are shown below.

  Specific examples of the photocationic polymerization initiator that can be used in the present invention are shown below.

  Specific examples of the polymer compound exhibiting carrier transportability or light emission that can be used in the present invention are shown below.

  The polymer compound shown below can be synthesized by a Suzuki coupling method using a boronic acid ester compound corresponding to a chemical composition unit and a dibromo compound in a blending ratio corresponding to the chemical composition.

<Experiment 1>
(Production of polymer organic EL device)
An ITO (Indium Tin Oxide) film is formed on a 100 mm square, 0.7 mm thick glass substrate by sputtering, and then patterned on a stripe with a width of 100 micrometers and an interval of 50 micrometers. A grid-like pattern having an opening on 100 μm × 150 μm ITO was formed with a polyimide insulating film having a thickness of 2 μm by photolithography.

  As polymer ink 1, 1 g of poly [9,9-dioctylfluorene-amine-thiophene] derivative, 200 mg of acrylate oligomer 1 and 10 mg of benzoin ethyl ether are dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin to form a hole injection layer. Ink was used.

  As polymer ink 2, 1 g of poly [9,9-dioctylfluorene-diamine] derivative, 200 mg of acrylate oligomer 1 and 10 mg of benzoin ethyl ether are dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin, did.

  As polymer ink 3, 1 g of poly [9,9-dioctylfluorene-stilbene] derivative, 200 mg of acrylate oligomer 1 and 10 mg of benzoin ethyl ether were dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin to obtain an ink for a blue light emitting layer. .

  As polymer ink 4, 1 g of poly [9,9-dioctylfluorene-diamine-benzothidiazole] derivative, 200 mg of acrylate oligomer 1 and 10 mg of benzoin ethyl ether are dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin for a green light emitting layer. Ink.

  As polymer ink 5, 1 g of poly [9,9-dioctylfluorene-diamine-thiophene-benzothiazole] derivative, 200 mg of acrylate oligomer 1 and 10 mg of benzoin ethyl ether are dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin to emit red light. A layer ink was obtained.

  As polymer ink 6, 1 g of poly [9,9-dioctylfluorene-pyridine] derivative was dissolved in a mixed solvent of 50 mL of xylene and 50 mL of tetralin to obtain an ink for an electron transport layer.

  The molecular weight of the polyfluorene-based material used for the polymer inks 1 to 6 was about 10,000 to 200,000.

  For polymer inks 1 to 6, the viscosity is measured using a viscometer, and if the viscosity is too high so that the viscosity falls within the range of 7 to 10 mPas (7 to 10 cP), the ink viscosity is diluted with xylene. Adjusted.

  The glass substrate on which ITO and the polyimide insulating film were patterned was washed with pure water and an organic solvent in this order, and then baked at 150 ° C. for 1 hour in a clean oven to completely remove moisture. Thereafter, in a UV ozone treatment device, treatment is performed at 50 ° C. for 10 minutes to completely remove the organic matter on the ITO, so that the contact angle on the ITO is 10 degrees or less, and the affinity of the polymer ink is increased. After the ink was dropped, pre-processing was performed so that the ink spread in the pixel without spreading.

  An ink jet head capable of dropping about 40 pL is prepared as an ink jet device, and the glass substrate is adsorbed by a vacuum chuck on an XY stage where a precise XY movement with a movement error of 5 micrometers or less can be controlled from a personal computer. After adjusting the position and angle with the CCD camera, the polymer ink was dropped at the center of the grid in the following order under the control of a personal computer. The voltage applied to the inkjet head was adjusted so that the discharge speed of the polymer ink was about 4 to 6 m / s. The discharge frequency was 5 kHz.

First, the polymer ink 1 was dripped into the eyes of the whole grid, and UV light (40 mW / cm ² ) containing a wavelength of 365 nm was irradiated for 5 minutes to be crosslinked and cured.

Next, the polymer ink 2 was dropped into the eyes of the entire board, and UV light (40 mW / cm ² ) was irradiated for 5 minutes to be crosslinked and cured.

Next, the polymer ink 3 was dropped every two lines, and UV light (40 mW / cm ² ) was irradiated for 5 minutes to crosslink and cure.

Next, the polymer ink 4 was dropped every two lines so as to come to the pixel adjacent to the pixel where the polymer ink 3 was dropped, and UV light (40 mW / cm ² ) was irradiated for 5 minutes to crosslink and cure.

Next, polymer ink 5 is dropped every two lines so that it comes to the pixel next to the pixel where polymer inks 3 and 4 are dropped, and UV light (40 mW / cm ² ) is irradiated for 5 minutes to crosslink and cure. It was.

  Next, the polymer ink 6 was dripped into the eyes of the entire board.

  Next, using a metal shadow mask, lithium fluoride was deposited in a thickness of 1 nm, calcium was deposited in a thickness of 5 nm, and aluminum was deposited in a thickness of 200 nm by a vacuum deposition method.

  Finally, a glass cap having a desiccant previously attached to the inner surface was adhered and sealed with a UV curable adhesive.

  The device structure and the film thickness of each layer are [ITO (150 nm) / hole injection layer (40 nm) / hole transport layer (20 nm) / light emitting layer (each color 70 nm) / electron transport layer (20 nm) / LiF (1 nm) / Ca (5 nm) / Al (200 nm)].

  FIG. 1 is a schematic cross-sectional view showing the produced organic EL element. On the anode 1 made of ITO, a hole injection layer 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5, and a cathode 6 having a laminated structure of LiF / Ga / Al are formed.

In the organic EL device thus fabricated, when a voltage of 10 V was applied with the ITO side being plus and the aluminum side being minus, the blue portion was 400 cd / m ² , the green portion was 1000 cd / m ² , and the red portion was 100 cd / m. It showed m ² emission. Luminous efficiency was 1 cd / A in the blue part, 6 cd / A in the green part, and 0.4 cd / A in the red part.

(Comparative example)
In the above polymer ink, an ink not containing a crosslinking agent and a polymerization initiator was prepared, and a similar organic EL device was produced. When 10 V was applied, the luminous efficiency was 0.4 cd / A in the blue portion, and the green portion. 2.5 cd / A and 0.2 cd / A in the red part, and in any luminescent color, the results were lower than in the case of containing a crosslinking agent.

<Experiment 2>
(Production of organic transistors)
A tantalum film having a thickness of 1 nm was formed on a glass substrate with a thickness of 100 nm, and 30 nm was oxidized by anodic oxidation to make the surface tantalum pentoxide. On top of that, 500 mg of poly [3-hexylthiophene], 50 mg of acrylate oligomer 1 and 5 mg of benzoin ethyl ether dissolved in 50 mL of orthodichlorobenzene were dropped by an ink jet method, and then on a hot plate at 100 ° C. for 10 minutes. After applying heat, UV light was irradiated for 5 minutes to cure.

  The substrate is set in a vacuum deposition apparatus, and the gold source and drain electrodes are formed with a channel width of 1 mm and a channel width of 50 μm so that a channel is formed immediately above the tantalum pentoxide gate insulating film and on the polythiophene film. It was vapor-deposited and formed so that it might become.

  FIG. 2 is a schematic cross-sectional view showing the produced organic transistor. As shown in FIG. 2, a gate electrode 11 made of a tantalum film is provided on the substrate 1, and a gate insulating film 12 made of tantalum pentoxide is provided on the gate electrode 11, so that gate insulation is achieved. An organic semiconductor film 13 made of a polythiophene film is provided on the film 12, and a source electrode 14 and a drain electrode 15 are formed on the organic semiconductor film 13.

  In the organic transistor thus formed, when a voltage of 40 V is applied between the gold source and drain electrodes and a voltage of -40 V is applied to the tantalum gate electrode, a current of about 1 microampere flows between the source and drain, and the gate voltage Accordingly, the current flowing between the source and the drain is modulated, and the on / off operation of the transistor can be obtained.

<Experiment 3>
(Production of polymer organic EL device)
Here, an organic EL element was produced using an ink further added with a reactive monomer shown below and an ink using a reactive polymer.

(Example in which reactive monomer is further added)
Polyfluorene derivative (carrier transport / light-emitting polymer) 1g
Acrylate oligomer 1 (reactive oligomer) 200mg
Trimethylolpropane trimethacrylate (low molecular crosslinking agent) 100mg
Benzoin ethyl ether (photopolymerization initiator) 10mg
Anisole (solvent 1) 60mL
60 mL of xylene (solvent 2)
(Example using reactive polymer)
Polyfluorene derivative (carrier transport / light-emitting polymer) 1g
Acrylate polymer 1 (reactive polymer) 200 mg
Benzoin ethyl ether (photopolymerization initiator) 10mg
Anisole (solvent 1) 60mL
60 mL of xylene (solvent 2)
As a polyfluorene derivative, a poly [9,9-dioctylfluorene-amine-thiophene] derivative for a hole injection layer, a poly [9,9-dioctylfluorene-diamine] derivative for a hole transport layer, a blue light emitting layer As an example, a poly [9,9-dioctylfluorene-stilbene] derivative was used and an ink was prepared according to the above blending ratio. For the electron transport layer, 1 g of poly [9,9-dioctylfluorene-pyridine] derivative was dissolved in a mixed solvent of 50 mL of xylene and 50 mL of anisole to obtain an ink for an electron transport layer. The ink thus prepared was adjusted by diluting with xylene so that the viscosity was in the range of 7 to 10 mPas, and [ITO (150 nm) / hole injection layer (40 nm) was prepared by the same production method as in the above-mentioned Examples. An organic EL device having a structure of / hole transport layer (20 nm) / light emitting layer (70 nm) / electron transport layer (20 nm) / LiF (1 nm) / Ca (5 nm) / Al (200 nm)] was produced.

  The luminance-current-voltage characteristics of the organic EL devices thus prepared were measured. As a result, the luminous efficiency at 10 V was 1 cd / A or more, compared with 0.4 cd / A when no crosslinking agent was added. As a result, high luminous efficiency was obtained.

<Ink configuration example>
A polyfluorene derivative was used as the main functional material of the ink, but the same formulation can be used when other materials such as polyphenylene vinylene materials, phenylamine materials, and polythiophene materials are used.

  As for the compounding ratio, a reactive oligomer or a reactive polymer is used in a range of 0.01 to 2 with respect to the functional polymer 1. Preferably, the range is from 0.05 to 1.

  Similarly, the reactive monomer is used in the range of 0.01 to 2 with respect to the functional polymer 1. Preferably, the range is from 0.05 to 1. The polymerization initiator is used in a proportion of 0.1 to 20% by weight based on the total amount of the reactive oligomer / polymer / monomer. More preferably, it is used in the range of 1 to 10% by weight.

  As the solvent, toluene, xylene, ethylbenzene, alkylbenzene, cyclohexylbenzene, tetralin, anisole, and the like and mixed solvents thereof can be used mainly for aromatic solvents, but it is not limited as long as the solute can be dissolved.

  The viscosity is 2 to 20 mPas (2 to 20 cP) for inkjet. More preferably, it is adjusted to a range of 3 to 15 mPas.

  For other printing, it is adjusted to 50 to 500 mPas for gravure printing, 100 to 1000 mPas for letterpress printing, and 2000 to 30000 mPas for screen printing.

<Experiment 4>
In the following, each ink was prepared as shown in Tables 1 to 3, and the polyimide insulating film prepared in Experiment 1 was applied onto an ITO substrate formed in a grid pattern by inkjet, and UV light (365 nm peak, 40 mW) was applied. ) And then dried for 5 minutes at 120 ° C. in a nitrogen atmosphere, and the shape of the film was observed. In the film shape observation, after coating a gold thin film (several nm or less) on the entire surface, the film thickness state was measured by an optical interference type three-dimensional non-contact surface shape measurement system. As a general shape of the film after coating and drying, there are cases where the periphery swells in a caldera shape and the center swells. There was a case. As an evaluation, the ratio of the highest thickness portion to the lowest thickness portion in the pixel was obtained. Coating was performed so that the film thickness averaged about 70 nm.

Specific ink preparation example Functional polymer: 1 (weight ratio) (In the following examples, a poly [9,9-dioctylfluorene-diamine-benzothiazole] derivative, which is a green light-emitting material, was used.)
Reactive oligomer / reactive polymer: 0.2 (weight ratio)
Reactive monomer: 0.1 (weight ratio)
Polymerization initiator: 0.01 (weight ratio)
Solvent: 100 mL to 200 mL, adjusted to a viscosity of 8 mPas The mixing ratio of the mixed solvent is 1: 1
Tables 1 to 3 show the functional polymer (polymer compound), reactive oligomer / reactive polymer, reactive monomer, polymerization initiator, and solvent used in the ink. Tables 1 to 3 show the evaluation of the uniformity of the film formed from the ink as described above.

  The non-uniformity of inkjet droplets after drying is thought to be mainly due to the difference in drying speed between the droplet periphery and the center of the droplet. When the solute moves from the peripheral part to the peripheral part, a candela is obtained when a caldera-like shape in which the peripheral part of the droplet is raised is obtained. This shape is thought to be affected by the boiling point and viscosity of the solvent, the mixing ratio of the mixed solvent, the drying temperature, etc., but when the same solvent is used, a reactive oligomer or reactive polymer with a large molecular weight is used. It was found that the film thickness was easier to obtain than when a low molecular weight reactive monomer was added. From this result, it is presumed that this is because reactive oligomers and reactive polymers having a large molecular weight are likely to gel quickly at the time of drying, and the amount of solute moving to the periphery is small. In addition, since low molecular weight reactive monomers have a large amount of cross-linking per molecular weight, it is considered that there is a possibility that nonuniformity of the film may occur due to a change in volume or molecular bond.

  When both a reactive oligomer or reactive polymer having a large molecular weight and a reactive monomer having a low molecular weight are mixed, it is considered that both film uniformity and high crosslink density can be obtained.

  The uniformity of the ink-jet coating film greatly affects the uniformity of brightness during light emission and the lifetime. When the film thickness is non-uniform, current flows intensively in the thin film area, and the brightness of the portion is high, whereas the brightness of the thick film portion is very low. In addition, since the portion where a large amount of current flows accelerates and deteriorates, the lifetime of the device is shortened as a whole. On the other hand, when the uniformity of the film thickness is high, the luminance uniformity within the pixel is increased, and the uniformity of the current density contributes to the improvement of the lifetime. Therefore, the organic thin film element coated with the ink according to the blending ratio of the present invention can not only exhibit high luminous efficiency but also improve the uniformity of the light emitting surface and the lifetime.

1 is a schematic cross-sectional view showing an organic EL element of one embodiment according to the present invention. The schematic sectional drawing which shows the organic transistor element of other embodiment according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Anode 2 ... Hole injection layer 3 ... Hole transport layer 4 ... Light emitting layer 5 ... Electron transport layer 6 ... Cathode 10 ... Substrate 11 ... Gate electrode 12 ... Gate insulating film 13 ... Organic-semiconductor film 14 ... Source electrode 15 ... Drain electrode

Claims (9)

  A polymer compound having a plurality of aromatic rings or heterocyclic rings, exhibiting carrier transportability or luminescence, a plurality of crosslinkable functional groups, and a molecular weight / crosslinkable functional group value within the range of 180 to 2000 An organic thin film element comprising a carrier transporting thin film or a light emitting thin film obtained by crosslinking an ink containing a reactive oligomer or polymer and a polymerization initiator.   2. The organic thin film element according to claim 1, wherein a reactive monomer having a plurality of crosslinkable functional groups and having a molecular weight / crosslinkable functional group value of less than 180 is contained in the ink.   3. The organic thin film element according to claim 1, wherein the reactive oligomer or polymer has a hydrophobic portion and an ether bond or an ester bond in the molecular structure, and is nonionic and has surface activity.   The reactive oligomer or polymer has a radical polymerizable acryloyl group, a vinyl group, or a cationic polymerizable vinyl ether group as the crosslinkable functional group. Organic thin film element.   The organic thin film element according to any one of claims 1 to 4, wherein the reactive oligomer or polymer has a cationic polymerizable oxetane ring or oxirane ring as the crosslinkable functional group.   6. The structure according to claim 1, wherein at least two polymer films are laminated, and a lower layer of the laminated structure is the carrier-transporting thin film or the light-emitting thin film. The organic thin film element described in 1.   It is an organic electroluminescent element or an organic transistor element, The organic thin film element of any one of Claims 1-6 characterized by the above-mentioned.   A polymer compound having a plurality of aromatic rings or heterocyclic rings, exhibiting carrier transportability or luminescence, a plurality of crosslinkable functional groups, and a molecular weight / crosslinkable functional group value within the range of 180 to 2000 A crosslinkable ink comprising: a reactive oligomer or polymer, a polymerization initiator, and a solvent. A method for producing the organic thin film element according to any one of claims 1 to 7,
Discharging the crosslinkable ink according to claim 8 onto a substrate using a piezoelectric inkjet head;
And a step of forming a carrier transporting thin film or a light emitting thin film by crosslinking a thin film on a substrate formed by discharge with light or heat.

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