JP2007200801A - Top-emission type organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a top-emission type organic electroluminescent element which has superior display characteristics and in which manufacturing cost is inexpensive in the organic EL element in which an organic EL element base material and a sealing base material are stuck to each other. <P>SOLUTION: By installing second barrier ribs and by forming a getter layer by inkjet method between the second barrier ribs, a transparent getter layer can be made homogeneous on the sealing substrate which is the takeout side, and film thickness control of the transparent getter layer can be carried out easily. Moreover, cost can be suppressed lower in the case the second barrier rib is installed at the sealing substrate than in the case a recess is installed at the sealing container. Moreover, by making the getter layer transparent, it can be used for the top-emission type. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a top emission type organic electroluminescence element (hereinafter referred to as a top emission type organic EL element) which is expected to be used widely as a display such as an information display terminal or a surface emitting light source.

  2. Description of the Related Art Conventionally, a display using an electroluminescence (hereinafter also simply referred to as EL) display device has been developed for a display unit of a mobile device such as a mobile phone or a PDA or a personal computer.

  An EL display device includes a plurality of light emitting units having an EL layer (light emitting layer) in a substrate surface, and performs desired display by independently driving each light emitting unit. This EL display device can be classified into, for example, a bottom emission type in which light is extracted from the element substrate side and a top emission type in which light is extracted from the sealing member side, depending on the difference in the light extraction direction from the light emitting layer. For the reasons such as the degree of freedom of material selection, the bottom emission type structure has been mainly studied so far.

  On the other hand, in the field of display devices, there are high needs for enlargement, high definition, and high brightness, and research aimed at increasing the size of EL display devices is also actively conducted.

  However, when the above-mentioned bottom emission type EL display device is enlarged, it is necessary to control a wiring electrode that supplies a signal to the electrode or to make a transistor thick, which causes a problem that the aperture ratio of the pixel is lowered. there were. In addition, when the aperture ratio is reduced in this way, a problem arises that the product life is shortened as a result of flowing a large current through the light emitting layer in order to ensure the luminance of the pixel. For this reason, in recent years, a top emission type structure in which the aperture ratio of a pixel is not affected by the structure of a wiring or the like has attracted attention and has been actively studied.

  An organic EL element has a structure in which a functional layer including a light-emitting layer is sandwiched between two electrodes (anode and cathode), one of which has a light-transmitting property. A self-luminous display element that emits light in a layer. The functional layer is usually composed of a plurality of functionally separated layers. Typical examples thereof include copper phthalocyanine for the hole injection layer and N, N′-di (1-naphthyl) -N for the hole transport layer. , N′-diphenyl-1, 1′-biphenyl-4, 4′-diamine, a low molecular EL element in which tris (8-quinolinol) aluminum is laminated on the light emitting layer, a polythiophene derivative in the hole transport layer, and light emission There is a polymer EL element in which a polyalkylfluorene derivative is stacked on a layer. It is known that an organic EL element is deteriorated by moisture and oxygen in the atmosphere when the functional layer and the cathode layer are left exposed to the atmosphere. As a specific representative example, there is a phenomenon in which a non-light emitting region called a dark spot occurs and expands with time.

  As a method for solving this problem, a method of forming a getter layer as an adsorbent in a sealed container has been proposed. If a transparent getter layer is used, it can be used as a top emission type. (See Patent Document 1).

However, the above-described method has a problem that the sealing container is expensive because the sealing container is provided with a recess and the getter layer is formed. Moreover, as a method for applying the getter layer to the sealed container, generally, an injection method by a dispensing method is adopted. It also has the problem of being difficult.
JP 2003-142256 A

  The present invention has been devised in view of the above problems, and can uniformly form a transparent getter layer on the sealing substrate on the light extraction side, and can easily control the film thickness of the transparent getter layer. It aims at providing a top emission type organic EL element.

  The present invention according to claim 1 includes at least a support substrate, an organic EL element substrate including a light emitting region and a first partition on the substrate, and at least a sealing substrate and a getter layer on the sealing substrate. A top-emission organic electroluminescence element formed by bonding a sealing substrate, wherein a second partition is provided on a sealing substrate, and a transparent getter layer is formed between the second partitions by an inkjet method. The top emission type organic electroluminescence element.

  According to a second aspect of the present invention, in the top emission type organic electroluminescent element according to the first aspect, the second partition wall is formed by arranging an organic EL element base material and a sealing base material so as to face each other. It is a top emission type organic electroluminescent element characterized by being formed in the position corresponding to the light emission area | region of an element base material.

  According to the first aspect of the present invention, the second partition wall is provided on the sealing substrate, and the getter layer is formed between the second partition walls by the ink jet method, whereby the light extraction side is provided on the sealing substrate. The transparent getter layer can be made uniform, and the film thickness control of the transparent getter layer can be easily performed. In addition, the cost can be reduced by providing the second partition wall on the sealing substrate rather than providing the recess in the sealing container. Moreover, it can be used for a top emission type by making the getter layer transparent.

  According to the second aspect of the present invention, the second partition is formed at a position corresponding to the outside of the light emitting region of the organic EL element substrate when the organic EL element substrate and the sealing substrate are arranged to face each other. By being done, it can suppress that the 2nd partition inhibits the light emitted from a light emission area | region.

  According to the present invention, by providing the second partition wall and forming the getter layer between the second partition walls by the ink jet method, a transparent getter layer on the sealing substrate on the take-out side can be made uniform, and the transparent getter layer The film thickness can be easily controlled. In addition, the cost can be reduced by providing the second partition wall on the sealing substrate rather than providing the recess in the sealing container. Moreover, it can be used for a top emission type by making the getter layer transparent.

  Moreover, the 2nd partition is formed in the position corresponded out of the light emission area | region of an organic EL element base material, when an organic EL element base material and a sealing base material are opposingly arranged. Therefore, it is possible to suppress the second partition wall from inhibiting light emitted from the light emitting region, and it is possible to prevent display characteristics from being deteriorated by the second partition wall. For this reason, it becomes possible to provide a top emission type organic EL element excellent in display characteristics.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a partial schematic cross-sectional view showing an embodiment of the top emission type organic EL device of the present invention.

The top emission type organic EL element 30 of the present invention is:
An organic layer formed of a first electrode 12, a functional layer 13 including a light emitting layer, a transparent second electrode 14, and a first partition wall 15 on the support substrate 11 shown in FIG. An EL element substrate 10;
On the sealing substrate 21 shown in FIG. 2A, the sealing substrate 20 having transparency and flatness, in which the second partition wall 22, the getter layer 23, and the adhesive layer 24 are formed, is bonded, An integrated structure is formed by adhesive sealing. The functional layer 13 always includes a light emitting layer that emits light when a voltage is applied. Further, it may be a multilayer film including a layer such as a hole transport layer that assists light emission.
The light emitting region includes a first electrode 12 formed on the support substrate 11, a functional layer 13, and a transparent second electrode 14, and is partitioned by a first partition 15.

Hereinafter, a method for producing the organic EL element substrate 10 will be described.
First, the first electrode 12 is formed on the support substrate 11.

  As the support substrate 11, in addition to a light-transmitting base material such as glass, quartz, and a plastic sheet, a metal foil or sheet such as aluminum or stainless steel, a silicon substrate, the plastic film or sheet, aluminum, copper, nickel, stainless steel, or the like For example, a non-translucent base material in which the metal films are laminated can be used.

  Further, a thin film transistor (TFT) may be formed on the support substrate 11 as necessary, and used as a driving substrate. As a material of the TFT, an organic TFT such as polythiophene, polyaniline, copper phthalocyanine, or perylene derivative may be used, or amorphous silicon or polysilicon TFT may be used.

  When the first electrode 12 is used as an anode, a metal composite oxide such as ITO (indium tin composite oxide), indium zinc composite oxide or zinc aluminum composite oxide, or a metal material such as gold or platinum is used. Can do.

  The first electrode 12 can be formed by a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or a dry film forming method, or a metal oxide or metal material fine particle is epoxy. Examples thereof include a gravure printing method using a fine particle dispersion dispersed in a resin or an acrylic resin, and a wet film forming method such as a screen printing method.

  Next, the first partition 15 is formed on the support substrate 11 on which the first electrode 12 is formed.

  As the first partition 15, a photosensitive resin having an acrylic resin or a polyimide resin as a base resin can be used.

  In addition, the first partition 15 forms a photosensitive layer having a predetermined thickness by using a coating method such as roll coating, spin coating, screen printing, spray coating, or the like, and patterning such as pattern exposure and development. Processing is performed to form a predetermined position between the first electrodes 12. At this time, the height of the first partition 15 is, for example, about 1 μm.

  The first partition 15 is formed on the support substrate 11. Since the 1st partition 15 is formed with a fixed pattern at this time, the support substrate 11 can be divided equally. For this reason, it becomes possible to make the functional layer 13 formed in the section surrounded by the first partition wall 15 into a constant film thickness.

  Next, the functional layer 13 is formed by forming a single layer film or a multilayer film containing a light emitting substance.

  As a structural example when the functional layer 13 is formed of a multilayer film, a hole injection transport layer, an electron transport light emitting layer or a hole transport light emitting layer, a two-layer structure including an electron transport layer, a hole injection transport layer, Three layers consisting of a light emitting layer and an electron injecting and transporting layer. Furthermore, the injection layer and the transporting layer can be separated, or an electron blocking layer, a hole blocking layer, etc. can be inserted to form a multilayer. It is.

  Next, the second electrode 14 is formed on the functional layer 13 to obtain the organic EL element substrate 10.

  When the second electrode 14 is a cathode, a material having a high electron injection efficiency is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface in contact with the functional layer 13, and Al or Cu having high stability and conductivity is placed. It can be used by laminating. In order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function, stable Ag, An alloy system with a metal element such as Al or Cu may be used. Specific examples include alloys such as Mg, Ag, Al, Li, and Cu.

  As a method for forming the second electrode 14, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method can be used depending on the material. At this time, since the thickness of the second electrode 14 is used as a transparent electrode, after laminating these metal materials as a thin film of about 1 to 10 nm, ITO (indium tin composite oxide), indium zinc composite oxide, zinc It is preferable to stack 10 to 150 nm of a metal composite oxide such as an aluminum composite oxide so as to achieve both electron injectability and translucency.

Hereinafter, a method for producing the sealing substrate 20 will be described.
First, the second partition wall 22 is formed on the sealing substrate 21.

  As the sealing substrate 21, it is necessary to use a transparent and planar light-transmitting substrate. For example, glass, quartz, polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, poly Plastic films and sheets such as methyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, etc., or metal oxides such as silicon oxide and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, and nitriding on these plastic films and sheets A light-transmitting substrate in which a single layer or a layer of a polymer resin film such as a metal nitride such as silicon or aluminum nitride, a metal oxynitride such as silicon oxynitride, an acrylic resin, an epoxy resin, a silicon resin, or a polyester resin is used. be able to

  As the second partition wall 22, a photosensitive resin based on an acrylic resin or a polyimide resin can be used.

  The second partition wall 22 is formed by forming a photosensitive layer having a predetermined thickness on the sealing substrate 21 by using a coating method such as roll coating, spin coating, screen printing, spray coating, or the like with the photosensitive resin solution, It is formed by performing patterning processing such as pattern exposure and development. Since these methods can form the second partition wall 22 on the sealing substrate easily and in large quantities, the cost can be kept lower than providing a recess in the sealing container. At this time, the height of the second partition wall 22 is preferably in the range of 1 to 50 μm.

  The second partition 22 is formed on the sealing substrate 20. At this time, the second partition wall 22 may be formed at a position corresponding to the outside of the light emitting region of the organic EL element substrate 10 when the organic EL element substrate 10 and the sealing substrate 20 are disposed to face each other. desirable. Examples of the outside of the light emitting region of the organic EL element substrate 10 include a portion of the first partition 15 and a portion other than the EL element portion. Thereby, in the top emission type organic EL element 30, the second partition wall 22 can be disposed to such an extent that the getter layer 23 can be formed smoothly without shielding light emitted from the light emitting region. For this reason, it is possible to prevent the display characteristics from being deteriorated by the second partition.

  However, the second partition 22 is only required to be able to delimit and hold the getter layer 23. For this reason, the 2nd partition 22 does not necessarily need to be formed on the sealing base material 20 corresponded out of the light emission area | region of the organic EL element base material 10. FIG.

  Next, a getter layer 23 is formed between the second partition walls 22 on the sealing substrate 21.

  The getter layer 23 is a layer provided to obtain an effect of adsorbing or removing oxygen or moisture. Since the getter layer 23 is formed on the sealing substrate 21 on the light extraction side, the getter layer 23 is required to be transparent.

  As the getter layer 23, one or a combination of alkali metal, alkaline earth metal, alkaline earth metal oxide, alkali metal or alkaline earth metal hydroxide, silica gel, zeolite compound, or the like is used. It can be used and used after being dispersed or dissolved in a solvent.

  As the solvent for dispersing and dissolving the getter material used for the getter layer 23, a hydrocarbon-based organic solvent can be used, and examples thereof include toluene. When the getter material is dispersed and dissolved in the solvent, the concentration of the getter material is preferably in the range of 0.01 wt% to 10 wt%. The viscosity is preferably in the range of 1 to 20 cp.

  In the present invention, an ink jet method is used to form the getter layer 23.

  Conventionally, as a method of forming the getter layer 23, there are a dispensing method, a spin coating method, a printing method, and the like. However, in the case of the dispensing method, the discharge accuracy is low due to the air pulse method. For this reason, it is difficult to make the getter layer 23 formed on the sealing substrate 21 uniform. In the case of the spin coating method, a step of removing the desiccant applied to an undesired region after applying a getter material to the entire surface of the sealing substrate 21 is necessary. For this reason, it is not preferable in terms of cost. In the case of the printing method, since a blanket or a plate is used, the scale of the apparatus becomes large. It is desirable to form the getter layer 23 in a low dew point environment of −50 ° C. or lower so that the getter material does not absorb moisture. However, when the scale of the apparatus is large, it is difficult to handle in an artificially controlled environment. It is.

  In the case of the inkjet method, since the piezo method is used, the discharge amount can be controlled with picoliter scale accuracy. Therefore, the getter layer 23 can be formed more uniformly on the sealing substrate 21 than the dispensing method, and the film thickness control of the getter layer 23 can be easily performed. In addition, the apparatus used in the ink jet method is smaller in scale than the printing method. Therefore, handling is easy even under an artificially adjusted environment such as a low dew point environment of −50 ° C. or lower. In view of the above, the ink jet method is superior to other methods, the getter layer 23 on the sealing substrate 21 on the light extraction side can be made uniform, and the film thickness control of the getter layer 23 can be easily performed. .

  When the getter layer 23 is formed using an ink jet method, it is preferable that the getter material used for the getter layer 23 be formed in a low dew point environment of −50 ° C. or lower so that moisture is not absorbed.

  At this time, the film thickness of the getter layer 23 is preferably in the range of 0.1 to 50 μm, and more preferably in the range of 1 to 20 μm.

  Next, the adhesive layer 24 is formed on the end portion of the sealing substrate 21 to obtain the sealing substrate 20.

  Examples of the adhesive used as the adhesive layer 24 include an ultraviolet curable resin made of an epoxy resin, an acrylic resin, a silicon resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and acid-modified such as polyethylene and polypropylene. A thermoplastic adhesive resin made of a product can be used as a single layer or a laminated layer. Further, a desiccant such as barium oxide or calcium oxide is mixed to remove moisture contained in the adhesive layer 24, or an inorganic filler of about several percent is mixed to control the thickness of the adhesive layer 24. May be.

  As a method for forming the adhesive layer 24, a printing method, a nozzle coating method, or the like can be used. Alternatively, a transfer method in which the adhesive layer 24 is formed on another substrate in advance and transferred may be used. The adhesive layer 24 may be formed not on the sealing substrate 21 but on the support substrate 11.

  Hereinafter, a method for manufacturing the top emission type organic electroluminescence element 30 will be described.

  The organic EL element substrate 10 and the sealing substrate 20 are bonded together, the adhesive layer 24 is cured, and the organic electroluminescence element 30 is obtained.

  The adhesive layer 24 may be cured in a reduced pressure environment. Moreover, according to the used adhesive agent, you may perform ultraviolet irradiation, a heating, etc., and these may be performed simultaneously.

  A 150 nm thick ITO film was formed by sputtering indium-tin alloy oxide on a support substrate made of glass, and a first electrode was formed by patterning.

  Next, a photosensitive resin solution made of a polyimide resin is applied on the substrate on which the first electrode is formed by a spin coater to form a photosensitive layer, and a series of patterning processes such as pattern exposure and development are performed to obtain 1 μm. A thick first partition was formed.

  Next, a 20 nm hole transport layer made of a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid on the first electrode, and poly [2-methoxy-5- (2′-ethylhexene). A 100 nm-thick functional layer having a two-layer structure including an 80 nm-thick phosphor layer made of (siloxy) -1,4-phenylenevinylene] (MEHPPV) was formed.

  Next, an indium / tin alloy compound was sputtered onto the functional layer, an ITO film having a thickness of 60 nm was formed, and a second electrode was formed on the functional layer by patterning to produce an organic EL element substrate. .

  Next, a photosensitive resin solution made of polyimide resin is applied onto a sealing substrate made of glass with a slit coater to form a photosensitive layer, and a series of patterning processes such as pattern exposure and development are performed, and then the sealing substrate A second partition wall was formed on top. The thickness of the second partition wall was 20 μm.

  Next, an aluminum metal complex (manufactured by Futaba Electronics Co., Ltd., trade name: Oredry) as a getter material was dissolved in toluene so as to have a concentration of 5 wt% to prepare a solution.

  Next, the solution was applied to a region partitioned by the second partition on the sealing substrate by an inkjet method under a dew point atmosphere of −70 ° C., and dried at 180 ° C. to form a getter layer having a thickness of 5 μm. .

  Next, an ultraviolet curable epoxy adhesive was applied to the sealing substrate, and the organic EL element substrate and the sealing substrate were bonded together.

  Next, it was adhesively sealed by UV curing and heat curing to obtain a top emission type organic electroluminescence element.

  In the obtained top emission type organic electroluminescence element, the unevenness of the transparent getter layer could not be visually recognized. Therefore, a top emission type organic EL element excellent in display characteristics could be obtained.

1 is a schematic cross-sectional view showing one embodiment of a top emission type organic electroluminescence element of the present invention. (A) is a schematic cross section which shows one Example of a sealing base material. (B) is a schematic cross section which shows one Example of an organic EL element base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Organic EL element base material 11 ... Support substrate 12 ... 1st electrode 13 ... Functional layer 14 ... 2nd electrode 15 ... 1st partition 20 ... Sealing base material 21 ... Sealing substrate 22 …… Second partition wall 23 …… Getter layer 24 ...... Adhesive layer 30 …… Top emission type organic EL element

Claims (2)

An organic EL element substrate including at least a support substrate and a light emitting region and a first partition on the substrate;
It is a top emission type organic electroluminescence element formed by laminating at least a sealing substrate and a sealing substrate having a transparent getter layer on the sealing substrate,
A top emission type organic material having a second partition wall which partitions the sealing substrate into a plurality of regions on the sealing substrate, and the getter layer is formed by an inkjet method in a region partitioned by the second partition wall Electroluminescence element.   It is a top emission type organic electroluminescent element of Claim 1, Comprising: A 2nd partition is outside the light emission area | region of an organic EL element base material when an organic EL element base material and a sealing base material are opposingly arranged. A top emission type organic electroluminescence element characterized by being formed at a corresponding position.

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