JP2005310465A - Manufacturing method of organic el element and organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an organic EL element capable of forming an organic layer having the excellent linearity of the end of a pattern on a substrate without causing a transfer defect that a part of an ink layer to be transferred and removed is left on a blanket, in a manufacturing method of an organic EL element using letterpress reversing offset printing. <P>SOLUTION: A relief printing plate having linear or dashed line-like cut-out parts 7 at upper surface ends of its projecting parts 6 for incising an ink layer is used as a relief printing plate 3 for transferring and removing unnecessary parts of the ink layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic EL element, and more particularly, to an organic EL element manufacturing method and an organic EL element in which an organic layer of an organic EL element is formed in a pattern by a letterpress reverse offset printing method.

  An organic EL element has a structure in which a thin organic layer containing a fluorescent or phosphorescent organic compound is sandwiched between a cathode forming an electron injection electrode and an anode forming a hole injection electrode. This is a display element that performs display by utilizing the emission of light (fluorescence / phosphorescence) when excitons are generated by injecting and recombining and exciton is generated.

Organic materials used for the light emitting layer of the organic EL element are classified into low-molecular materials and high-molecular materials. The method for forming the light emitting layer varies depending on the material. For low molecular weight materials, a method of forming a film mainly by vapor deposition is used, and for high molecular weight materials, a method of dissolving or dispersing in a solvent and applying on a substrate is performed.
In addition, as a means for patterning the light emitting layer in order to make the organic EL element full color, when using a low molecular weight material, a mask having a pattern according to a desired pixel shape is used, and different light emitting colors are used. A method of depositing and forming a light emitting material on a portion corresponding to a desired pixel is performed.
This method is an excellent method for uniformly forming a thin film in a desired shape, but there is a problem that it is difficult to form a pattern when the substrate to be deposited becomes large in terms of mask accuracy.

On the other hand, in the case of using a polymer material, a pattern formation mainly by an ink jet method and a pattern formation method by printing have been proposed. For example, the ink jet method disclosed in Japanese Patent Application Laid-Open No. 10-12377 is a method of obtaining a desired pattern by ejecting a light emitting layer material dissolved in a solvent from an ink jet nozzle onto a substrate and drying it on the substrate. .
However, since the ink droplets ejected from the nozzle are spherical, the ink spreads in a circular shape when landing on the substrate, the shape of the formed pattern lacks linearity, or the landing accuracy is poor. There is a problem that linearity cannot be obtained.

On the other hand, for example, in Japanese Patent Application Laid-Open No. 2002-305077, a bank is previously formed on a substrate with a material having ink repellency by using photolithography, and ink droplets are landed on the bank. A method is disclosed in which ink repels according to the shape and a linear pattern is obtained.
However, when a pattern is formed using the ink jet method, there remains a problem that the area where the ink jet nozzle performs drawing processing per unit time is small, and the pattern formation throughput is low.

As a method for forming a light emitting layer pattern with a polymer material on a substrate by a printing method without using an ink jet method, for example, Japanese Laid-Open Patent Publication No. 2003-17261 proposes a relief reversal offset printing method. In the letterpress reverse printing method, when the light emitting layer is formed by patterning by printing, first, an ink (hereinafter also referred to simply as ink) in which the material of the light emitting layer is dissolved or dispersed in a solvent is placed on a blanket with a slit coater or cap coater. Apply an ink layer using a dip coater, etc., and then press the negative relief plate against the target pattern (positive part) to remove the unnecessary ink layer (negative part). Is transferred and removed, and then the ink layer pattern (positive portion) remaining on the blanket is transferred onto the substrate on which the element is formed.

  Patterning of the light emitting layer by such a relief reversal offset printing method is preferable because it uses few devices, uses materials efficiently, has high throughput, and leads to cost reduction. However, in the process of transferring and removing an unnecessary portion from the blanket on which the ink layer is formed against the target pattern by pressing the relief plate that is a negative plate, as shown in FIG. When the convex portion 6 of the relief plate 3 comes into contact with the ink layer 2 and is peeled off, the end portion of the ink layer pattern (the portion remaining on the blanket) formed on the substrate as shown in FIG. A and the end portion B of the portion of the ink layer that has been transferred and removed from the relief printing plate are those where the ink has been torn off at the boundary, so the end portion A of the pattern of the ink layer formed on the substrate is a straight line There was a drawback of poor nature.

In addition, when transferring the ink layer from the blanket to the relief printing plate, the ink adhesion to the blanket surface or the relief printing surface may vary depending on the slight difference in the physical properties of the ink material and the slight drying conditions of the ink layer. Since the ink adhesion to the ink and the strength of the ink layer film in the semi-dry state are different, when the part of the ink layer on the blanket where the convex part of the relief plate is pressed is peeled off, the ink layer In some cases, the ink layer is not separated well at the end portion and the ink layer is not transferred and removed from the convex portion. That is, there may occur a transfer defect in which a portion of the ink layer to be transferred and removed on the convex portion of the relief plate remains on the blanket. For this reason, there is a problem that the physical properties of the material of the ink layer and the process conditions at the time of transfer removal must be strictly controlled.
JP 2002-305077 A JP 2003-17261 A

The present invention has been made in view of the above problems, and in the method for manufacturing an organic EL element in which an organic layer is formed by a letterpress reversal offset printing method, the edge of the pattern on the substrate is excellent in linearity. It is an object of the present invention to provide a method for manufacturing an organic EL element capable of forming an organic layer without a transfer defect such that a portion of an ink layer to be transferred and removed remains on a blanket.
It is another object of the present invention to provide an organic EL element manufactured using the method for manufacturing an organic EL element.

  The present invention relates to a method for producing an organic EL element using a letterpress reverse offset printing method, as a letterpress for transferring and removing an unnecessary portion of an ink layer, a line or a broken line for cutting an ink layer into an upper surface end of the convex part. It is a manufacturing method of the organic EL element characterized by using the relief plate which has a shape-shaped cut | notch part.

  Moreover, this invention is an organic EL element manufactured using the manufacturing method of the organic EL element by the said invention.

The present invention relates to a method for producing an organic EL element using a letterpress reverse offset printing method, as a letterpress for transferring and removing an unnecessary portion of an ink layer, a line or a broken line for cutting an ink layer into an upper surface end of the convex part. Uses a relief plate with a cut-out in the shape of a plate, so it has excellent linearity at the edge of the pattern on the substrate, and there is no transfer defect such that the portion of the ink layer to be transferred and removed remains on the blanket. It becomes the manufacturing method of the organic EL element which can form a layer.
Moreover, since this invention is an organic EL element manufactured using the manufacturing method of the said organic EL element, it is excellent in the linearity of the edge part of a pattern, and becomes an organic EL element without a transfer defect.

Below, the manufacturing method of the organic EL element by this invention is demonstrated in detail based on the embodiment.
FIG. 2A is a schematic view of an example of a relief printing plate used in the method for producing an organic EL element according to the present invention. As shown in FIG. 2A, the relief plate 3 has a linear or broken cut portion 7 for making a cut in the ink layer at the upper end portion of the convex portion 6.

  In the process of transferring and removing an unnecessary part (negative part) of the ink layer by pressing a negative relief plate against the target pattern (positive part) from the blanket on which the ink layer is formed, FIG. As shown in (b), since the upper or lower end of the convex portion has a linear or broken cut portion 7, the cut portion 7 is moved to the ink layer 2 when pressed against the blanket on which the ink layer is formed. You can bite into the ink layer.

  Accordingly, when the blanket and the letterpress are separated, a cut along the edge is formed in the ink layer, and the ink layer is cut as shown in FIG. 2C according to the shape of the cut. That is, the linearity of the end portion of the ink layer pattern formed on the substrate is good. Further, there is no transfer defect such that the portion of the ink layer to be transferred and removed remains on the blanket.

  The material of the blanket is not particularly limited as long as it can be used in this method, but it is silicone in consideration of resistance to ink solvent, swelling property, shape stability, adhesion to ink and wettability. It is preferable to use rubber or fluorinated silicone rubber.

The material of the relief plate is not particularly limited as long as it can be used in this method, but a glass plate, a quartz plate, a metal plate, a resin plate, etc. are used in consideration of pattern pitch accuracy, ink wettability and adhesion. In view of surface properties and pattern accuracy, a glass plate or a quartz plate is preferably used. In addition, the surface of these materials may be subjected to surface treatment for the purpose of imparting adhesion with ink or the like, or an appropriate material may be applied to form an adhesion layer.
The method for forming the concave portions of the relief plate is not particularly limited, but it is preferable to form a resist pattern by photolithography and form the concave portions by a method such as dry etching, wet etching or sand blasting. If the depth of the recess is too shallow, the ink layer on the surface of the blanket will come into contact with the bottom surface of the recess when the blanket is pressed.

The method of forming the cut portion 7 in the convex portion is not particularly limited as long as it is a method capable of forming the cut portion, but the linearity of the cut portion becomes the linearity of the ink layer to be patterned as it is. As a method for forming the cut portion, a method of forming a resist layer on the plate using photolithography and etching the relief plate portion while leaving the cut portion is preferable.
Further, when etching, the relief printing substrate may be etched as it is, or another material is formed on the relief printing substrate for the height of the cut portion, and desired by using photolithography. The cut portion may be formed by removing the film by etching while leaving the cut portion. In addition, the notch may be formed before forming the relief groove, or the notch may be formed after forming the groove.

The shape of the cut portion 7 is not particularly limited as long as it can be cut appropriately according to the thickness of the ink layer, but the cross-sectional shape of the cut portion is the height of the cut portion. If it is too high, when the blanket is pressed against the convex part, the leading edge of the cut portion penetrates the ink layer and damages the underlying blanket layer. If the height of the cut portion is too low, the ink layer cannot be sufficiently cut, which is also not preferable.
As the planar shape of the cut portion, it is preferable that the cut portion has a high linearity because the pattern needs to be cut in a straight line. However, if the transferred ink layer can form a linear end portion, the cut portion is formed. A broken line with a notch may be used. By using the broken line-shaped cut portion, the force applied to the cut portion is concentrated, so that the cut of the ink layer can be formed with less pressing pressure.

  The material of the ink layer is usually obtained by dispersing a pigment or resin kneaded in a dispersion resin in a solvent, dispersing it in a solvent using a dispersant, or dissolving a dye and a binder resin in a solvent. However, if necessary, an additive may be added to improve adhesion, drying property, flexibility of the ink layer film, and the like.

  As shown in the figure, the organic EL element includes at least a first electrode, an organic layer including a light emitting layer, and a second electrode on a substrate. Further, from the viewpoint of contrast, it is preferable that a polarizing plate is provided outside the substrate. From the viewpoint of reliability, a sealing film or a sealing layer is formed on the second electrode of the organic EL element. It is preferable to provide a substrate.

The substrate was subjected to a barrier treatment with an inorganic material substrate such as a quartz substrate or a glass substrate, a resin substrate such as an acrylic substrate, a polyethylene terephthalate substrate, a polyether sulfone substrate, or a polyimide substrate, or SiO ₂ or SiN _x . A flexible film or the like is preferably used, but the present invention is not limited to these.

  Here, the organic layer has a structure having at least one light emitting layer, and may have a single layer structure of the light emitting layer or a multilayer structure of the charge transport layer and the light emitting layer. Here, each of the charge transport layer and the light emitting layer may have a multilayer structure. Moreover, you may provide a buffer layer between a light emitting layer and an electrode as needed.

  In addition, as an organic layer, at least one of them has a pattern formed by a relief reversal offset printing method, and a plurality of light emitting layers that usually emit different colors are patterned according to the pixel shape. The relief printing plate used at this time has a linear or broken cut portion for cutting the ink layer at the upper end portion of the convex portion. Thereby, the pattern of the light emitting layer which is excellent in the linearity of the edge part of a pattern and has no transfer defect can be obtained.

Further, among organic layers, a layer that does not require patterning is deposited by spin coating method, bar coating method, dip coating method, spray coating method using an organic EL coating liquid, or by using an organic material. It can be formed by a known process such as a method.
In the case of producing an organic EL element composed of a multilayer laminated film, the solvent used for the layer to be produced later does not dissolve the underlying layer formed in order to prevent mixing of materials between the films in contact with each other. preferable.

  As the first electrode and the second electrode that sandwich the organic layer, in the organic EL element, when the substrate and the first electrode are transparent, light emission from the organic layer is emitted from the substrate side, so that the light emission efficiency is increased. Therefore, it is preferable that the second electrode has a reflective electrode or a reflective layer.

As a transparent electrode, a transparent electrode such as ITO, SnO ₂ or ZnO can be used as an anode,
Reflective electrodes include metals such as Al, Ca and Ag, alloys such as Mg—Ag and Li—Al, laminated films of metals such as Ca / Ag and Mg / Ag, insulators such as LiF / Al and metals However, the present invention is not particularly limited to these.

  Moreover, when these materials are formed on a substrate or an organic EL layer, it is possible to use a method such as sputtering, EB vapor deposition, resistance heating vapor deposition, etc., but the present invention is not particularly limited to these. Absent.

  The connection method between the first electrode and the second electrode corresponding to each pixel may be configured such that the first electrode and the second electrode corresponding to the organic EL layer become stripe-shaped electrodes orthogonal to each other. The first electrode or the second electrode may be connected to a common electrode (source bus line, gate bus line) via one or more thin film transistors (TFTs).

  Next, the coating liquid for organic EL elements used in the relief reversal offset printing method in the present invention will be described. The organic EL device coating liquid in the present invention can be broadly classified into a light emitting layer forming coating liquid and a charge transport layer forming coating liquid. Here, as the light emitting layer forming coating liquid, known polymer light emitting materials for organic EL elements (for example, poly (p-phenylene) (PPP), poly (p-phenylene vinylene) (PPV), poly (p -Naphthalene vinylene (PNV), poly (2-decyloxy-1,4-phenylene) (DO-PPP), poly [2,5-bis [2- (N, N, N-triethylammonium) ethoxy] -1 , 4-phenylene-alt-1,4-phenylene] dibromide (PPP-NEt3 +), poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylenevinylene] (MEH-PPV), Poly (5-methoxy- (2-propanoxysulfonide) -1,4-phenylenevinylene) (MPS-PPV), poly [2,5-bis (hexyloxy-1,4-fluoro) Nylene)-(1-cyanovinylene)] (CN-PPV), poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylene- (1-cyanovinylene)] (MEH-CN-PPV) and , Poly (dioctylfluorene) (PDF) and the like, but the present invention is not particularly limited thereto, and a coating solution in which a known solvent is dissolved or dispersed can be used. The solvent may be a single solvent or a mixture of a plurality of solvents. Moreover, you may add the additive for viscosity adjustment, a leveling agent, etc. to these liquids as needed.

  As a coating liquid for forming a charge transport layer, known polymer charge transport materials (for example, polyaniline (PANI), 3,4-polyethylenedioxythiophene (PEDOT), polycarbazole (PVCz), poly (triphenylamine derivatives) (Poly-TPD), poly (oxadiazole derivative) (Poly-OXZ), etc., but the present invention is not particularly limited to these.) Or for organic EL elements, for organic photoconductors And a precursor of a known polymer charge transport material (for example, Pre-PPV, Pre-PNV, etc., but the present invention is not particularly limited thereto) is dissolved or dispersed in a known solvent. However, viscosity adjusting additives, leveling agents, and the like may be added to these liquids as necessary.

Examples of the solvent for dissolving these polymer materials include ethylene glycol, propylene glycol, triethylene glycol, ethylene glycol monomethyl ether, ethylene glycol moethyl ether, triethylene glycol monomethyl ether, triethylene glycol moethyl ether, Ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol diacetate, diethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, N-dimethylformamide, N-methyl-2-pyrrolidone, cyclohexanone, 1- Propanol, isopropanol, octane, nonane Decane, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, nitrobenzene, there is anisole, the present invention is not particularly limited thereto. Further, if necessary, two or more kinds of solvents may be mixed and used.

Hereinafter, specific examples will be described.
(Substrate formation)
A glass substrate with ITO having a film thickness of 150 nm formed by sputtering is used as a first electrode to produce an ITO transparent stripe electrode with a line and space of 100 μm as a first electrode, and then a photosensitive polyimide resin 0 is formed on this substrate. The film was applied to a thickness of 0.7 μm, and was patterned by photolithography so as to cover the space part of the ITO electrode pattern and 10 μm at both ends of the ITO electrode to form an insulating layer. Further, this substrate was immersed in pure water, subjected to ultrasonic cleaning for 30 minutes, and after IPA drying, the substrate surface was cleaned by UV ozone treatment.

Next, a PEDOT / PSS water / IPA solution was applied onto the substrate using a slit coater to form a hole transport layer having a dry film thickness of 50 nm.
(Formation of notch in relief)
A positive photoresist OFPR-800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to a glass substrate approximately the same size as the substrate size of the organic EL element with a film thickness of 1.5 μm, prebaked, exposed and developed. After forming the resist pattern 4 as shown in FIG. 3A, etching was performed to a depth of 1 μm with buffered hydrofluoric acid to form a cut portion 7 in the convex portion as shown in FIG.
(Formation of concave parts on letterpress)
Further, in the same manner, as shown in FIG. 3C, the photoresist was patterned by photolithography so as to expose a recess of 100 μm in line and space, thereby forming a resist pattern 4 ′. As shown in FIG. 3 (d), etching was performed with buffered hydrofluoric acid to a depth (D) of 10 μm to produce a relief of a relief plate having a line and space (L / S) of 100 μm.
(Ink from luminescent materials)
Next, a coating solution in which poly (dioctylfluorene) is dissolved in a 5: 5 mixed solvent of o-xylene and nitrobenzene is used as a blue light emitting layer forming ink, and poly (p-phenylene vinylene) is used as a green light emitting layer forming ink. ) In a 5: 5 mixed solvent of methanol and ethylene glycol, and poly (2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylene- ( 1-cyanovinylene)] in a 5: 5 mixed solvent of o-xylene and nitrobenzene was used.

  Next, a silicone rubber plate having a thickness of 1 mm was wound around a metal cylinder to form a blanket cylinder. This was attached to a remodeled commercial printer, and a slit coater was attached as a coater for applying the light emitting layer forming ink to the blanket.

Next, the blue light emitting layer forming ink is applied onto the blanket from the slit coater so as to have a dry film thickness of 100 nm, and transferred and removed as it is with the negative of the relief plate, and then the blanket cylinder is pressed against the substrate. The substrate was rolled, the light emitting layer was transferred onto the hole transport layer of the substrate, and a pattern was formed, followed by heat drying at 100 ° C. under a reduced pressure of 1 × 10 ⁻³ Torr for 1 hour. Thereafter, the green and red light-emitting layers were similarly applied and transferred with a dry film thickness of 100 nm, and then heat-dried at 100 ° C. for 1 hour under a reduced pressure of 1 × 10 ⁻³ Torr to form a light-emitting layer pattern. did.
(Cathode formation and sealing)
Furthermore, silver was vapor-deposited to a film thickness of 200 nm using a metal mask in which a pattern perpendicular to the ITO ITO stripe of the anode was formed on this substrate to form a cathode. Finally, the element was bonded and sealed using a UV curable adhesive using a glass sealing can.

  When the cathode and anode of the organic EL device prepared by the above method were connected to a DC power source and a voltage of 10 V was applied, uniform light emission was observed with no missing pixels. Further, when the substrate on which the cathode was not formed and the device was not observed was observed with a microscope, the pixels of each light emitting layer were patterned with good linearity.

  The organic EL element of Example 2 was created using a technique substantially similar to that of Example 1. The difference from Example 1 is that the cut portion was not formed when the negative relief was produced. When a voltage of 10 V was applied to the sample of Comparative Example 1, some parts were missing and no light was emitted. Further, when the substrate on which the cathode was not formed and the device was not observed was observed with a microscope, the pattern edge of the pixel of each light emitting layer was found to be jagged, and a part not transferred was seen.

It is explanatory drawing of the bad linearity of the edge part of a pattern in a relief reverse printing method. (A) is the schematic of an example of the letterpress used in the manufacturing method of the organic EL element by this invention. (B) is explanatory drawing of the manufacturing method of the organic EL element by this invention. (C) is explanatory drawing of the manufacturing method of the organic EL element by this invention. (A)-(d) is explanatory drawing of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Blanket 2 ... Ink layer 3 ... Letterpress 4, 4 '... Resist pattern 5 ... Substrate base material 6 ... Projection convex part 7 ... Notch part

Claims (2)

  In a method for manufacturing an organic EL element using a relief reversal offset printing method, as a relief plate for transferring and removing an unnecessary portion of an ink layer, a linear or broken cut portion for making a cut in the ink layer at the upper end of the convex portion The manufacturing method of the organic EL element characterized by using the relief printing plate | board which has.   An organic EL device manufactured using the method for manufacturing an organic EL device according to claim 1.

Images