JP2017183153A - Manufacturing method of organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a manufacturing method capable of obtaining an organic light-emitting layer having flatness required as organic EL element.SOLUTION: In a manufacturing method of organic EL element for manufacturing an organic EL element by sandwiching an organic light-emitting layer 40, containing a polymer luminescent material having molecular weight of 100,000-130,000, between a positive electrode 20 and a negative electrode 50, i.e., two electrodes at least one of which is transparent or translucent, the organic light-emitting layer 40 is formed by coating or printing method, and the coating speed or printing speed onto a substrate 10 is 200-250 mm/s.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for manufacturing an organic EL element for manufacturing an organic EL (electroluminescence) element in which an organic functional layer containing a polymer material is sandwiched between two electrodes formed on a substrate.

  In general, in an organic EL element, for example, an anode, an organic light emitting layer, and a cathode are sequentially laminated on a base material, and at least one of the anode and the cathode is used as a transparent electrode, thereby emitting light from the organic light emitting layer as an anode. It is taken out from the side or the cathode side.

  Conventionally, as a method for manufacturing this type of organic EL element, the one described in Patent Document 1 has been proposed. In this conventional manufacturing method, the organic light emitting layer is formed by coating or printing, and the printing speed in the case of printing is set to 100 mm / s (millimeter / second).

JP 2012-204137 A

  By the way, the inventors of the present invention have studied the use of a polymer light emitting material constituting the organic light emitting layer having a molecular weight of 100,000 or more and 130,000 or less when developing the organic EL element. Then, the inventors have made a trial production of applying the film forming method by coating or printing as described in Patent Document 1 to the film formation of an organic light emitting layer using such a high molecular weight material. And examined.

  However, in the film forming method as described in Patent Document 1, film formation is performed at a coating speed or a printing speed of 100 mm / s, and according to studies by the present inventors, organic light emission for an organic EL element is performed. It was found that the layer had poor flatness and a film shape with a large unevenness difference.

  This invention is made | formed in view of the said problem, and it aims at implement | achieving the manufacturing method which can obtain the organic light emitting layer which has the flatness required as an organic EL element.

  In order to achieve the above object, in the invention according to claim 1, the molecular weight is 100,000 or more between two electrodes (20, 50) formed on the base material (10), at least one of which is transparent or translucent. An organic EL device manufacturing method for manufacturing an organic EL device comprising an organic light emitting layer (40) containing a polymer light emitting material of 130,000 or less, wherein the organic light emitting layer is formed by coating or printing. And the application | coating speed or printing speed on a base material is 200 mm / s or more and 250 mm / s or less, It is characterized by the above-mentioned.

  The present invention was created as a result of conducting an experimental study on coating speed or printing speed when coating or printing an ink containing a polymer light emitting material having a molecular weight of 100,000 or more and 130,000 or less that the inventor wants to use. It has been done.

  According to the production method of the present invention, an organic light-emitting layer having flatness necessary for an organic EL element can be obtained when the coating speed or printing speed on the substrate is in the range of 200 mm / s to 250 mm / s. Can do. Here, the coating speed and the printing speed mean the speed at which the ink spreads on the substrate during coating or printing.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a schematic sectional drawing of the pixel structure in the organic EL element concerning embodiment of this invention. It is a schematic plan view which shows the arrangement configuration of the pixel in the said embodiment. It is a graph which shows the result evaluated about the relationship between the generation rate of the said nonuniformity, and the printing speed when the unpainted which generate | occur | produces in a pixel is made nonuniform in the specific example of the said embodiment. It is a figure which shows typically the flat rate of the organic light emitting layer in the said pixel. It is a graph which shows the result evaluated about the relationship between the flat rate shown by FIG. 4, and the printing speed in the said specific example. It is a graph which shows the evaluation result of the relative brightness | luminance in the said specific example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

  The organic EL element according to the present embodiment is applied as an organic EL display, for example, and the configuration of the pixel G1 will be described with reference to FIGS. 1 and 2A. Note that the two pixels G1 shown as FIG. 2B indicate the states “OK (good example)” and “NG (bad example)” of the pixel G1 related to evaluation of printing unevenness, which will be described later.

  As shown in FIG. 2A, a plurality of pixels G1 are arranged on a substrate 10 as a base material, and display is performed by selectively controlling the light emission of each pixel G1. . Here, the pixels G1 are arranged in a matrix of m × n such that m in the X direction, which is the horizontal direction in FIG. 2A, and n in the Y direction, which is the vertical direction.

  On the substrate 10, an insulating bank (partition wall) 60 made of an insulating material such as a resin or an inorganic material is provided between the pixels G <b> 1. Each pixel G1 is an area surrounded by the bank, so that each pixel G1 is partitioned by the bank.

  FIG. 1 shows a cross-sectional configuration of one pixel G1, and each pixel G1 in FIG. 2A has the same configuration as that shown in FIG. As shown in FIG. 1, the pixel G <b> 1 is composed of a stacked body provided on a substrate 10, and this stacked body is formed of an anode 20 as an upper electrode, a bank 60, and a hole injection layer 30 from the substrate 10 side. The organic light emitting layer 40 and the cathode 50 as the lower electrode are sequentially laminated.

  Then, either one or both of the anode 20 and the cathode 50 are used as transparent or semi-transparent electrodes, so that light emitted from the organic light emitting layer 40 is extracted from the anode 20 side, the cathode 50 side, or both sides. Here, as each element which comprises the board | substrate 10 and the pixel G1, what is employ | adopted as a normal organic EL element can be used.

  The substrate 10 is a transparent substrate such as glass, but is not limited to glass, and various substrates such as a resin substrate with a barrier film and a metal substrate can be used.

  The anode 20 can be any conductive material capable of forming a transparent or translucent electrode. Specifically, the oxide includes indium tin oxide (ITO), indium zinc oxide (IZO), and the like, and these are formed as the anode 20 by sputtering or the like.

  After the anode 20 is formed, the banks 60 (both ends of the pixel G1) are formed by photolithography using an organic material such as a photosensitive material between adjacent anode patterns. More specifically, it includes at least a step of applying a photosensitive resin composition to a substrate and a step of forming a partition wall pattern by pattern exposure, development, and baking.

  The photosensitive material for forming the bank 60 may be either a positive type resist or a negative type resist, and may be a commercially available one, but it must have insulating properties. If the bank does not have sufficient insulation, a current flows to the adjacent pixel electrode through the bank and a display defect occurs. Also, proper display may not be possible due to TFT malfunction. Specific examples of the photosensitive material include, but are not limited to, polyimide, acrylic resin, novolac resin, and fluorene. Further, for the purpose of improving the display quality of the organic EL display, a light shielding material may be included in the photosensitive material.

  The photosensitive resin forming the bank 60 is applied using a known coating method such as a spin coater, bar coater, roll coater, die coater, or gravure coater. Next, in the step of forming a bank pattern by pattern exposure and development, a bank pattern can be formed by a conventionally known exposure and development method. Regarding firing, firing can be performed by a conventionally known method using an oven, a hot plate or the like.

  The bank 60 desirably has a film thickness in the range of 0.5 μm to 5.0 μm. It should be noted that if the bank film thickness is too low, the effect of preventing leakage current between the adjacent pixels via the hole transport layer, preventing short circuit, and preventing color mixture of the organic light emitting material may not be obtained. After the bank 60 is formed, the hole injection layer 30 is formed.

  The hole injection layer 30 can be made of a substance having a hole transporting property, and examples thereof include PEDOT (abbreviation of poly (3,4-ethylenediothiophene)). The hole injection layer 30 can be collectively applied using, for example, a spin coating method, a bar coating method, a protruding coating method, or a dip coating method.

  In the present embodiment, the organic light emitting layer 40 includes a polymer light emitting material having a molecular weight of 100,000 to 130,000. The polymer light emitting material is a material having a light emitting property, and preferably a material having a property of transporting carriers such as electrons and holes, that is, a carrier transporting material.

  As the polymer light emitting material, for example, a polyfluorene (PF) polymer, a polyphenylene vinylene (PPV) polymer, a polyvinyl carbazole (PVK) polymer, or the like can be used, and a fluorescent dye or a phosphorescent dye can be used. Those dispersed in the polymer, polystyrene polymer, polythiophene polymer, polymethyl methacrylate polymer, or the like can also be used.

  Such an organic light emitting layer 40 is formed by applying or printing an ink obtained by dissolving a polymer light emitting material in an organic solvent exemplified below. Although the viscosity of the ink composition varies depending on the printing method, the ink composition such as letterpress printing is adjusted to an appropriate viscosity in consideration of transfer from the anilox roll to the letterpress, and the viscosity of the ink is 2 to 120 mPa · It is desirable to set it as s. In the case of 2 mPa · s or less, mottling unevenness is likely to occur in the pixel, causing unevenness. In the case of 120 mPa · s or more, the ink does not level on the relief plate after the ink is transferred from the anilox roll to the relief plate, which causes unevenness. Further, the solution of the present invention may contain an additive in order to adjust the viscosity and / or surface tension. As the additive, a high molecular weight compound (thickener) for increasing the viscosity, a poor solvent, a low molecular weight compound for decreasing the viscosity, a surfactant for decreasing the surface tension, and the like are used in appropriate combination. You can also. When a poor solvent is used as a thickener, the viscosity can be increased by adding a small amount of a poor solvent relative to the solid content in the solution. In this case, what is necessary is just to select the kind and addition amount of a solvent in the range which solid content in a solution does not precipitate. The amount of the poor solvent is preferably 50 wt% or less with respect to the entire solution.

  As the solvent, ether solvents such as tetrahydrofuran and dioxane, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, isobutylbenzene, s-butylbenzene, anisole, methylanisole, tetralin , Aromatic hydrocarbon solvents such as ethoxybenzene, 1-methylnaphthalene, cyclohexylbenzene, cyclohexane, bicyclohexyl, methylcyclohexane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n -Aliphatic hydrocarbon solvents such as decane, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate, butyl acetate and ethyl cellosolve acetate, Polyhydric alcohols such as lenglycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dimethoxyethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerin, 1,2-hexanediol and the like Examples thereof include alcohol solvents such as methanol, ethanol, propanol, isopropanol and cyclohexanol, sulfoxide solvents such as dimethyl sulfoxide, and amide solvents such as N-methyl-2-pyrrolidone and N, N-dimethylformamide. . These organic solvents can be used alone or in combination. From the viewpoint of film formability, the solvent preferably has a boiling point of 100 ° C. or higher. Examples of the coating method include spin coating, bar coating, protruding coating, and dip coating, and examples of printing include letterpress printing, offset printing, gravure printing, and gravure offset printing.

  As the cathode 50, for example, a laminated structure of Al / Ca (light emitting layer side), Al / NaF (light emitting layer side) or the like can be adopted, and these laminated structures can be formed by, for example, a vacuum deposition method or the like. .

  As described above, the organic EL element has the organic light emitting layer 40 sandwiched between the two electrodes 20 and 50 formed on the substrate 10, but the hole injection layer 30 is omitted if possible. There may be. Moreover, in the organic EL element of this embodiment, the anode 20, the hole injection layer 30, and the cathode 50 are formed by a normal manufacturing method as described above.

  However, in this embodiment, when forming the organic light emitting layer 40 containing a polymer light emitting material having a molecular weight of 100,000 to 130,000 by coating or printing, the coating speed or printing speed on the substrate 10 is set to 200 mm / It is necessary to set it as the range of s-250 mm / s or less. This is obtained as a result of an experimental study conducted by the present inventor regarding the relationship between the molecular weight of the polymer light emitting material and the printing speed in the formation of the organic light emitting layer 40.

  Next, the present embodiment will be described in more detail by introducing a specific example related to this experimental study, but the present embodiment is not limited to the following specific example.

[Concrete example]
In the specific example of the present embodiment, the organic light emitting layer 40 was formed using a relief printing method as a desirable example among the above-described coating and printing methods. Here, the printing direction was set to the Y direction in FIG.

  In this specific example, in FIG. 2A, it is assumed that 108 pixels G1 are arranged in a matrix of 12 pixels in the X direction and 9 pixels in the Y direction. Here, the pixel width L in the Y direction was 37.5 μm, and the pixel pitch in the Y direction was 74.5 μm.

  First, an ITO film was formed on a glass substrate as the substrate 10 by using a sputtering method, and the ITO film was patterned by a photolithography method to form the anode 20 having the pixel width L and the pixel pitch. A polymer film made of PEDOT was formed thereon as a hole injection layer 30 by spin coating.

  Further, using an organic light emitting ink in which a polymer light emitting material was dissolved in tetralin, an organic light emitting layer 40 was printed and formed on the anode 20 and the hole injection layer 30 by a relief printing method. At this time, the Y direction shown in FIG. After printing and drying, a cathode 50 made of Al / NaF (light emitting layer side) was formed thereon by resistance heating vapor deposition.

  Here, in this example, as the polymer light emitting material of this embodiment, those having a molecular weight of 105,000 (hereinafter simply referred to as 105k) and those having a molecular weight of 126,000 (hereinafter simply referred to as 126k) were used. Further, as the polymer light emitting material of the comparative example, those having a molecular weight of 225,000 (hereinafter simply referred to as 225k) and 235,000 (hereinafter simply referred to as 235k) were used.

  These materials having different molecular weights can be easily obtained, for example, by changing the degree of polymerization in materials of the same kind. In this example, the above process was performed for each material having a different molecular weight to produce an organic EL element.

  Moreover, as printing conditions by the relief printing of the ink containing the polymer light emitting material, the doctoring speed was 10 mm / s, and the printing speed was changed in the range of 100 mm / s to 300 mm / s. Here, the printing direction is the Y direction in FIG. 2A as described above, and the printing speed is the speed at which ink is applied in this Y direction.

  Specifically, the printing speed was changed to 100, 150, 200, 250, 275, 300 mm / s. The printing speed: 100 mm / s is a conventional printing speed similar to the conditions described in Patent Document 1 described above.

  First, in this specific example, the relationship between the printing speed and the occurrence rate of printing unevenness will be described. As shown in FIG. 2B, this non-uniformity is an area where no ink is applied in the pixel G1 when no ink is applied to the entire pixel. That is, the occurrence of unevenness (NG) is indicated when “unpainted” exists.

  The unevenness was evaluated by causing the pixel G1 to emit light and observing the pixel G1, or observing the pixel G1 with a fluorescence microscope. Then, the unevenness was evaluated for the 108 pixels G1 described above. For example, when there were a pixels G1 in which unevenness occurred, (a / 108) × 100 (%) was defined as the unevenness occurrence rate. Then, the relationship between the printing speed and the unevenness occurrence rate was investigated in the case where the organic light emitting layer 40 was formed from the 105k and 126k polymer light emitting materials of this embodiment. The result is shown in FIG.

  As shown in FIG. 3, when the organic light emitting layer 40 of the present embodiment is formed by letterpress printing, unevenness occurs when the printing speed is less than 200 mm / s, but the unevenness generation rate increases as the printing speed increases. It was confirmed that there was almost no unevenness at 200 m / s or more. In the case of the polymer light emitting material of 225k and 235k as a comparative example, it was confirmed that there was almost no unevenness even at a conventional printing speed of 100 m / s.

  Next, in this specific example, the flatness of the organic light emitting layer 40 was investigated for each of the 108 pixels G1. This flatness is defined by FIG. In FIG. 4, the horizontal axis indicates the pixel width L shown in FIG. 2A, and the vertical axis indicates the film thickness of the organic light emitting layer 40. Furthermore, the horizontal axis of FIG. 4 indicates the pixel size in the Y direction, that is, the printing direction in FIG.

  FIG. 4 shows the film shape obtained by coating or printing. As shown in FIG. 4, the width of the portion thicker than the reference value by 10 nm within the pixel width L is defined as a flat portion that is a flat portion, and the width of the flat portion is H. Therefore, as a flatness parameter, a ratio of the width H of the flat portion in the pixel width L, that is, a flat rate represented by (H / L) × 100 (%) is provided. FIG. 4A shows a film shape in which the pixel width L and the flat portion width H are the same width, that is, a flat rate of 100%. On the other hand, FIG. 4B shows a so-called downward convex shape in which the central part of the pixel width is the thinnest, and FIG. 4C shows the thinnest end part of the pixel width and the central part being thicker than the end part. The so-called upward convex shape is shown. Such a film-shaped profile can be confirmed by a scanning white interferometer.

  Here, as shown in FIG. 4, the minimum value of the film thickness within the pixel width L is set as a reference value. The film thickness of this reference value is typically about 50 nm to 100 nm, for example, about 80 nm.

  Here, if the film thickness is 10 nm or less than the reference value within the pixel width L, that is, if the difference in film thickness from the reference value is 10 nm or less, the luminance change is 10 in the case of constant current driving. It has been confirmed that it can be suppressed to less than%. If the luminance change is less than 10%, it is a practically satisfactory level as an organic EL element. This can be said for both the present embodiment and the comparative example, that is, regardless of the molecular weight of the polymer light emitting material constituting the organic light emitting layer 40.

  Therefore, as a flatness parameter, a ratio of the width H of the flat portion in the pixel width L, that is, a flat rate represented by (H / L) × 100 (%) is provided. Then, in the case where the organic light emitting layer 40 is formed from the 105k and 126k polymer light emitting materials of the present embodiment, the relationship between the printing speed and the flatness was investigated. The result is shown in FIG.

  As shown in FIG. 5, when the organic light emitting layer 40 of this embodiment is formed by letterpress printing, it is confirmed that a flat rate of 70% or higher is exhibited when the printing speed is in the range of 200 mm / s to 250 mm / s. It was done. Here, even in the case of the polymer light emitting material of 225k and 235k as a comparative example, it has been confirmed that a flatness of 70% or more is realized at a conventional printing speed of 100 m / s.

  The flatness ratio of 70% or more means that a practically good luminance is secured as an organic EL element. That is, in the case where the organic light emitting layer 40 is formed with the polymer light emitting material of 105k and 126k in the present embodiment, the flatness is not good when the printing speed is less than 200 mm / s, but the printing speed is 200 mm / s or more and 250 mm / s or less. If so, it can be said that good flatness can be realized.

  Next, in this specific example, the luminance of the organic light emitting layer 40 of the present embodiment and the organic light emitting layer 40 made of a polymer light emitting material as a comparative example were evaluated. The result is shown in FIG. In FIG. 6, evaluation by relative luminance is performed. Here, relative luminance is normalized to 100 in the organic light emitting layer 40 made of a 235 k polymer light emitting material as a comparative example formed at a printing speed of 100 mm / s.

  As shown in FIG. 6, also in the organic light emitting layer 40 of the present embodiment made of polymer light emitting materials of 105k and 126k, the printing speed is in the range of 200 mm / s to 250 mm / s, and the printing speed is 100 mm / s. It was confirmed that the luminance equivalent to that of 225k and 235k printed in the above was realized.

  In the above specific examples, examples of the polymer light emitting material having the molecular weight of 100,000 to 130,000 constituting the organic light emitting layer 40 of the present embodiment are 105k and 126k, but are not limited thereto. If the molecular weight is 100,000 or more and 130,000 or less, the same result as the above specific example can be obtained.

  Thus, according to this embodiment, when forming the organic light emitting layer 40 containing the polymer light emitting material having a molecular weight of 100,000 to 130,000 by coating or printing, the coating speed or the printing speed is 200 mm / s or more and 250 mm. / S or less, a range not conventionally adopted. As a result, the organic light emitting layer 40 having flatness necessary for the organic EL element can be obtained, and practically sufficient luminance can be realized.

(Other embodiments)
The polymer light-emitting material constituting the organic light-emitting layer 40 is preferably a material having a light-emitting property and a carrier transporting property, but any material having a light-emitting property does not have a carrier transporting property. It may be.

  As described above, the organic EL element may be any element as long as the organic light emitting layer 40 is sandwiched between the two electrodes 20 and 50 formed on the substrate 10 as described above. In addition to the hole injection layer 30, a configuration in which layers such as an electron injection layer, an electron transport layer, and a successful transport layer employed in a normal organic EL element are inserted may be used.

  Further, the organic EL element is not limited to being applied to an organic EL display for multicolor display or single color display. Moreover, as a base material, what is necessary is just to be able to form the laminated body which has the electrodes 20 and 50 and the organic light emitting layer 40 on the said base material, It is not limited to said board | substrate 10, The shape is also a board. Not limited to the shape, it can be arbitrarily selected.

  Further, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope described in the claims. The above embodiments are not irrelevant to each other, and can be combined as appropriate unless the combination is clearly impossible, and the above embodiments are not limited to the illustrated examples. Absent. In each of the above-described embodiments, it is needless to say that elements constituting the embodiment are not necessarily essential unless explicitly stated as essential and clearly considered essential in principle. Yes. Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is clearly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to the specific number except for the case. Further, in each of the above embodiments, when referring to the shape, positional relationship, etc. of the component, etc., the shape, unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to the positional relationship or the like.

DESCRIPTION OF SYMBOLS 10 Substrate as base material 20 Anode 40 Organic light emitting layer 50 Cathode 60 Bank

Claims (3)

An organic light emitting layer (40) comprising a polymer light emitting material having a molecular weight of 100,000 to 130,000 between two electrodes (20, 50) formed on the substrate (10), at least one of which is transparent or translucent. ) Is an organic EL element manufacturing method for manufacturing an organic EL element,
A method for producing an organic EL device, wherein the organic light emitting layer is applied or formed by a printing method, and a coating speed or a printing speed on the substrate is 200 mm / s or more and 250 mm / s or less.   The method for producing an organic EL device according to claim 1, wherein the polymer light emitting material is a carrier transporting material.   The method for producing an organic EL element according to claim 1, wherein the organic light emitting layer is formed by a relief printing method.

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