JP4600880B2 - Sealing cap for organic EL element and method for producing the same - Google Patents

Description

  The present invention relates to a sealing cap for an organic EL element, and particularly relates to a sealing cap for an organic EL element having a composite moisture absorption function and a method for manufacturing the same.

Organic electroluminescence elements (hereinafter referred to as “organic EL elements” for short) have become possible to form high-purity, high-quality laminated films with a thickness of nm class due to recent advances in thin film formation technology, and have a thickness of about 5V. Low voltage operation is possible.
In this way, organic EL elements are attracting attention as elements for next-generation display systems that have low power consumption, high quality, are thin, and can display curved surfaces.

In an organic EL element, a plurality of films composed of predetermined organic molecular components are sequentially stacked to form an organic EL layer, and electrode layers are attached to both the upper and lower sides to form an OLED (organic light emitting diode). A predetermined voltage or current is applied to inject electrons and holes into the organic EL layer, and the phenomenon of light emission when electrons and holes recombine is utilized.
Therefore, in order to perform the display function by guiding the light emission to the outside, at least one of the upper and lower electrodes must be transparent.

  As this transparent electrode film, ITO (Indium Tin Oxide) is widely used as a material capable of achieving both electrical conductivity and transparency, but in general, annealing is required to reduce the electrical resistance of ITO, and Polishing is necessary to increase the smoothness of the ITO surface (to reduce the roughness).

Since the organic EL layer deteriorates when the ITO is annealed at a high temperature, the organic EL layer has to be formed after the ITO.
That is, the stacking order is [substrate-first electrode (ITO) -organic EL layer-second electrode (may be an opaque electrode)], a structure that emits light from the substrate side (bottom emission) is adopted, and the substrate must also be transparent. I must.

Further, as this transparent substrate, a glass substrate is usually used because it is required to be somewhat strong and airtight so that the organic EL layer and the like can be protected against physical and chemical stimulation from the outside.
Further, a sealing cap is necessary to protect the organic EL layer and the like from the second electrode side. For the same reason, a glass cap is usually used, and the substrate is sealed with a transparent substrate (glass substrate). A case is formed with a sealing cap.

In particular, the organic EL layer is altered even if there is a small amount of oxygen or moisture, and the light emitting ability is reduced. As described above, the organic EL layer is sealed with a transparent substrate (glass substrate) and a glass cap to block oxygen and moisture from the outside. In addition, it is necessary to remove moisture remaining inside the case that is emitted from each layer of the OLED, or a partition, an insulating layer, and a driving unit associated with the OLED.
Therefore, a hygroscopic material has been conventionally inserted into the case.

For example, Patent Document 1 discloses a technique for providing a hygroscopic material layer over the details of the structure of a color conversion type organic EL element.
Examples of the hygroscopic material include calcium oxide, calcium chloride, magnesium chloride, calcium sulfate, diphosphorus pentoxide, zeolite, silica gel, and aluminum oxide.

Patent Document 2 discloses a technique in which an adhesive support sheet is provided in a space surrounded by an air permeable sheet and an inner surface of a cap, and a powder moisture absorbent is provided therein.
Examples of the hygroscopic material include calcium oxide, barium oxide, magnesium oxide, aluminum oxide, phosphorus oxide, zeolite, silica gel, activated carbon and the like.

However, according to these methods, the moisture absorption capacity inside the case depends on the inserted moisture absorbent material, and a separate process for installing these moisture absorbent materials is required, and sealing is performed after the moisture absorbent material is installed. Since the process is limited so that the hygroscopic material does not deteriorate due to moisture absorption during the previous process, not only the cost is increased, but it is sufficient to increase the amount of the hygroscopic material and improve the micro shape of the hygroscopic material It may be difficult to obtain a proper moisture absorption capacity.
JP 2003-257666 A JP 2002-31557 A

  In order to solve the above-mentioned problems of the organic EL element, the present invention has a simple structure and does not require a separate process during the production of the organic EL element, and sufficient moisture absorption capability only by a normal sealing process. An object of the present invention is to provide a sealing cap for an organic EL device having a composite moisture absorption function capable of obtaining the above and a method for producing the same.

In order to achieve the above object, a sealing cap for an organic EL device according to the present invention comprises a plurality of organic light emitting diodes (OLEDs) comprising at least a transparent electrode film, an organic EL layer, and a cathode electrode. A sealing cap for an organic EL element having a size corresponding to the transparent substrate on which the array is mounted, having a leg portion on an edge portion, and a tip of the leg portion being hermetically bonded to the edge portion of the transparent substrate, The inner surface facing the OLED array has a hygroscopic property, and further, a moisture absorbing material having water permeability is installed on the inner surface, the inner surface is made of a magnesium alloy, and the outer surface and the surface of the leg portion are oxidized. It is characterized by comprising a magnesium alloy .

In addition, as described in claims 2 and 4 , the hygroscopic material is made of zeolite.

Further, as described in claim 3 , in order to achieve the above object, a method for producing a sealing cap of an organic EL element according to the present invention includes:
Step 1 of preparing a metal plate made of a magnesium alloy of a corresponding size for a transparent substrate on which an array of a plurality of organic light emitting diodes (OLEDs) comprising at least a transparent electrode film, an organic EL layer, and a cathode electrode is mounted. When,
Step 2 of selectively masking a predetermined portion of one side of the metal plate with a resist;
Step 3 of immersing the metal plate in a predetermined solution to form a magnesium hydroxide Mg (OH) ₂ layer on the entire surface of the metal plate not covered with the resist;
Removing the resist from one side of the metal plate; and
Screen printing a paste-like hygroscopic material at a predetermined location on one side of the metal plate, or selectively applying a hygroscopic material suspension with a dispenser to form a hygroscopic material film, step 5;
The metal plate to which the hygroscopic material is selectively attached is baked at a predetermined temperature, thereby firing the hygroscopic material and oxidizing the magnesium hydroxide Mg (OH) ₂ layer on the surface of the metal plate. Step 6 of chemically changing to a layer of magnesium MgO;
Step 7 of pressing the metal plate to form a sealing cap for the organic EL element comprising a lid portion and a leg portion at the periphery of the lid portion;
It is characterized by including.

  According to the sealing cap of the organic EL element according to the present invention, the moisture emitted from the OLED including the organic EL layer or the pixel driving unit thereof in the airtight case is not only the hygroscopic material but also the inner surface of the sealing cap. Therefore, the moisture absorption effect is effectively performed, and the alteration of the organic EL layer due to moisture is minimized.

  Since the sealing cap of the organic EL element is originally necessary to ensure the airtightness of the case of the organic EL element, the organic EL element sealing cap according to the present invention has a combined moisture absorption effect. Simple and economical.

Embodiments according to the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a sealing cap of an organic EL element in this embodiment and an organic EL element formed by sealing an organic EL substrate using the same, and FIG. 2 is an organic EL element in this embodiment. FIG. 3 is a schematic cross-sectional view showing a method for producing an element sealing cap, FIG. 3 is a flowchart showing a method for producing an organic EL element sealing cap in this embodiment, and a procedure for sealing an organic EL substrate using the same. 4 is a three-dimensional structural schematic diagram showing an example of zeolite installed as a hygroscopic material in this example.

  Referring to FIG. 1, a bottom emission type organic EL device using a sealing cap of an organic EL device according to the present invention is formed by the following procedure.

FIG. 1B shows a substrate of a bottom emission type organic EL element. First, a transparent electrode film 20 made of, for example, ITO (indium tin oxide) is formed on the upper surface of a transparent substrate (glass substrate) 10. The
The transparent substrate 10 is usually a glass substrate at present, but it may be a substrate made of transparent plastic or the like having a physically and chemically required strength.
In the case of a passive matrix drive type, the transparent electrode film 20 is composed of a plurality of strips and is arranged so as to run to the left and right in parallel with the depth direction of the figure.

Second, a plurality of pixels composed of a set of organic EL layers 30R, 30G, and 30B corresponding to the three primary colors R, G, and B are formed on the upper surface of the transparent electrode film 20, and a cathode electrode is further formed on the upper surface. 40 is formed.
The cathode electrode 40 is usually made of an Mg—Ag alloy, and is arranged so as to run in the depth direction in parallel with the left-right direction of the drawing.
The organic EL layers 30R, 30G, and 30B are arranged at each intersection of both strips of the transparent electrode film 20 and the cathode electrode 40 to form an OLED (organic light emitting diode).

FIG. 1A shows a sealing cap of a bottom emission type organic EL element according to the present invention, which includes a lid 51 and a metal matrix provided with legs 52 on the edge thereof.
As the material of the metal matrix, it is desirable that magnesium (Mg), aluminum (Al), or an alloy containing them is preferable because it has high workability and heat conductivity, high surface moisture adsorption efficiency, and is desirably economically available. In particular, an Mg alloy containing lithium (Li) is suitable.

The surface of the sealing cap is covered with insulating layers 50c and 50b until it reaches the outer surface of the lid 51, the inner and outer surfaces of the leg 52 and a part of the inner surface of the lid, and most of the inner surface of the lid is This is a metal base exposed surface 50a with high moisture adsorption efficiency.
The metal matrix exposed surface 50a may be roughened in order to increase the surface area and increase the moisture absorption efficiency described later, that is, the moisture adsorption efficiency.

Next, a hygroscopic material 60 made of a polycrystalline film or collected in a sheet form so as to be in contact with the exposed surface of the metal base 50a is installed to complete an organic EL sealing cap.
The hygroscopic material 60 is either adhered by printing or application, adhered by an adhesive (not shown), or engaged by a hook (not shown) provided on the inner surface of the leg portion. In this way, the metal base exposed surface 50a is arranged so as to be in direct contact with the OLED or the like so as not to damage the OLED or the like.
In FIG. 1A, the hygroscopic material 60 just covers the metal base exposed surface 50a. However, the hygroscopic material may cover the metal base exposed surface larger than the metal base exposed surface or conversely.

  Finally, as shown in FIG. 1C, the bottom emission type organic EL element substrate (OLED etc.) on which the tip of the leg portion 52 of the sealing cap (FIG. 1A) provided with the hygroscopic material 60 is mounted. The edge part of the transparent substrate 10 of FIG. 1 (B) is airtightly bonded through the bonding part 70 to complete the organic EL element.

  Here, the hygroscopic material 60 macroscopically covers the metal base exposed surface 50a as shown in the figure, but microscopically, the moisture absorption material 60, the gap between the powder, the polycrystalline grain boundary, or the There is water permeability that reaches the metal matrix exposed surface 50a from an OLED or the like through holes composed of a plurality of atoms or molecules in the crystal.

Since the completed organic EL device is hermetically sealed, there is no ingress of moisture from the outside, but there is particularly moisture diffusion from the internal OLED, etc., and if left unattended, the organic EL layer will be deteriorated. I will.
In this embodiment, since two types of adsorption functions of physical adsorption by the hygroscopic material 60 and chemical adsorption by the metal base exposed surface 50a work, the moisture that has been dissipated is more than in the case of relying solely on the hygroscopic material as in the prior art. Can be absorbed efficiently.

  Next, regarding a specific method for manufacturing a sealing cap of an organic EL element according to an embodiment of the present invention, when an Mg alloy containing Li is used as the material of the metal base of the sealing cap, and zeolite is used as the hygroscopic material Particularly suitable manufacturing methods, including the sealing procedure between the sealing cap and the substrate of the organic EL element, are shown in FIG. 2 (sectional schematic diagram showing the manufacturing method of the sealing cap) and FIG. 3 (the manufacturing method of the sealing cap, and This will be described with reference to a flowchart showing a procedure for sealing an organic EL element substrate using this.

  In step 1 (FIG. 3 (S1)), referring to FIG. 2 (A), a transparent substrate on which an array of a plurality of organic light emitting diodes (OLEDs) comprising at least a transparent electrode film, an organic EL layer, and a cathode electrode is mounted. A metal plate 50 made of an Mg alloy containing a predetermined amount of Li having a size corresponding to 1 is prepared.

  In step 2 (FIG. 3 (S2)), referring to FIG. 2 (A), a predetermined portion to be the metal base exposed surface 50a on one side of the metal plate 50 is selectively masked by the alkali resistant resist 110.

In step 3 (FIG. 3 (S3)), referring to FIG. 2 (B), the metal plate 50 is immersed in a solution in which NaOH and NaCl are mixed and dissolved at a predetermined ratio, and the entire metal plate is immersed. Magnesium hydroxide (Mg (OH) ₂ ) layers 51b and 51c are formed on portions of the surface other than the metal base exposed surface 50a covered with the resist.

  In step 4 (FIG. 3 (S4)), the resist 110 is removed from one surface of the metal plate 50 in FIG.

In step 5 (FIG. 3 (S5)), referring to FIG. 2 (C), a screen mask 120 is applied to a portion of one side of the metal plate 50 other than the metal base exposed surface 50a, which is a predetermined location, and pasted. The zeolite film forming the hygroscopic material 60 is formed by screen printing on the metal matrix exposed surface 50a.
Alternatively, a zeolite membrane may be formed by selectively applying a suspension of zeolite to the predetermined portion 50a with a dispenser.

In step 6 (FIG. 3 (S6)), in FIG. 2C, the screen mask 120 is removed, and the metal plate 50 on which the zeolite film is selectively formed is baked at a temperature of 390 ° C. or higher and 410 ° C. or lower.
With reference to FIG. 2 (D), this baking baked the zeolite film forming the moisture absorbent 60 and chemically changed the magnesium hydroxide (Mg (OH) ₂ ) layers 51b and 51c in the surface of the metal plate 50. Insulating layers 50b and 50c made of magnesium oxide (MgO) layers.

  In step 7 (FIG. 3 (S7)), referring to FIG. 2 (E), the metal plate 50 is pressed using the press dies 130 and 135, and the lid 51 and the peripheral leg 52 are removed. A metal base exposed surface 50a made of an Mg alloy containing Li, with a moisture absorbent 60 made of a zeolite film attached to the inner surface of the lid, and a portion other than the metal base exposed surface covered with Mg oxide The sealing cap of the organic EL element by invention is obtained.

  The stopper 136 of the press die 135 abuts on the press die 130 during the press working, and prevents the press die 135 from being pushed further and damages the moisture absorbent 60 and the like.

  In step 8 (FIG. 3 (S8)), the sealing cap of the completed organic EL element is once dried and stored.

In step 9 (FIG. 3 (S9)), the sealing cap of the organic EL element is baked immediately before use.
That is, it is heated and dried at a temperature of 390 ° C. or higher and 410 ° C. or lower.

  In step 10 (FIG. 3 (S10)), the sealing cap of the organic EL element is carried into a glove box filled with high-purity nitrogen gas.

  In step 11 (FIG. 3 (S11)), referring to FIG. 1C again, the tip of the leg portion 52 of the sealing cap of the organic EL element and the edge of the transparent substrate 10 of the organic EL element substrate are bonded to each other. The organic EL element is completed by being hermetically bonded via 70.

  In this way, the moisture absorbing material inside the organic EL element and the exposed surface of the metal base of the sealing cap are both dehydrated and dried, so that moisture generated from the inside of the organic EL element can be efficiently absorbed after the sealing is completed. it can.

In the present embodiment, the hygroscopic material 60 is typically arranged so as to contact only the metal base exposed surface 50a of the sealing cap, but in addition to this, the hygroscopic material is placed in other places such as the edge of the transparent substrate 10. You may arrange.
For example, the hygroscopic material may be distributed between the OLEDs directly or via a suitable insulating protective layer.

  In addition, in addition to the OLED, in actuality, for example, a filter is additionally provided in the case of color conversion or the like, and in the case of the active matrix drive type, a pixel drive unit including a TFT transistor is additionally provided. However, in forming them, the hygroscopic material may be distributed and disposed in necessary places.

  Further, a part of the metal base exposed surface 50a of the sealing cap may be exposed without being covered with the hygroscopic material 60. In that case, the metal base exposed surface of the sealing cap can naturally adsorb moisture directly.

  Next, in the present example (Example 2), the reason why Mg alloy containing Li is selected as the material of the metal base of the sealing cap and zeolite is selected as the hygroscopic material will be described in more detail.

  When an alloy such as aluminum (Al) or magnesium (Mg) is selected as the material of the metal base of the sealing cap, the exposed surface of the metal base not only functions as a suitable moisture adsorbent, but is required for other surfaces. Such an insulating layer can be formed by oxidation of a metal matrix.

At that time, in the case of Al, anodization, that is, electrical conversion, is required to form alumina, whereas in the case of Mg, for example, it is dipped in a ₂ to 5% solution of magnesium dichloride MgCl _2. It only needs to be fired, and can be manufactured inexpensively and simply.
The film thickness of the formed Mg oxide is as thin as 50 to 100 nm, but is stable and sufficiently clears the withstand voltage of 15 V required for the organic EL element.

In the case of MgCl ₂ immersion, unevenness and bleed may occur on the surface, but it has been reported that this problem can be solved by dipping (immersing) in appropriate concentration NaOH + NaCl and baking.
(A. Yamamoto and H. Tsubakino, Materials Trans., 44-4 (2003), pp511-517, Jpn. Inst. Metals)

  Further, when an appropriate amount of lithium (Li) is mixed with Mg as an alloy as an alloy, an even better moisture absorption performance can be obtained easily and inexpensively.

As the material of the hygroscopic material, there can be a wide variety of examples which have been conventionally mentioned. According to this embodiment, zeolite is suitable.
Due to recent technological advancements, it is possible to produce zeolites with a stable, high purity, homogeneous, controlled microstructure so that moisture can be adsorbed efficiently without emitting harmful substances to the organic EL layer at low cost. Based on the knowledge that it has become.

Referring to FIG. 4, it is a schematic diagram showing an example of the three-dimensional structure of zeolite.
As is well known, in zeolite, Al or Si is arranged at the vertices, and the ridges between the vertices indicate bonds through oxygen atoms O.
Usually, Al and Si are arranged at the vertices where the three ridges and the four ridges gather, respectively, but there are cases where, for example, Al ⁻ Na ⁺ is arranged at the four ridge vertices instead of Si. In this case, Na ⁺ It is said that ions can move freely to some extent.

What is characteristic here is that it passes through an octagon shown in the center front of the figure, a relatively large hole extending in the rear direction (depth direction) in the figure, and two squares shown in the front right end of the figure, These are relatively small holes each extending in the left direction in the figure, and both form an isolated space extending in the vertical direction, the front-rear direction, and the horizontal direction.
The size of both pores is several angstroms each. However, the selective adsorption of water molecules and the inhalation direction of water molecules are determined by the difference, the difference in shape, and the difference in the arrangement position of the Al ^- ion. Said.

  Accordingly, in FIG. 1C, when a zeolite having an appropriate structure, such as polycrystalline powder, is selected, water molecules emitted from an OLED or the like are not only physically adsorbed by the zeolite 60 but also the zeolite 60 It reaches the metal base exposed surface 50a of the sealing cap through the large pores or small pores composed of a plurality of atoms in the powder gap, polycrystalline grain boundary, or crystal, and chemically adsorbs there. Is done.

It is a cross-sectional schematic diagram which shows the sealing cap of the organic EL element in a present Example, and the organic EL element formed by sealing an organic EL board | substrate using this. It is a cross-sectional schematic diagram which shows the manufacturing method of the sealing cap of the organic EL element in a present Example. It is a flowchart which shows the manufacturing method of the sealing cap of the organic EL element in a present Example, and the procedure which seals an organic EL board | substrate using this. It is a three-dimensional structure schematic diagram which shows the example of the zeolite installed as a hygroscopic material in a present Example.

Explanation of symbols

10 Transparent substrate (glass substrate)
20 Transparent electrode film 30R, 30G, 30B Organic EL layer 40 Cathode electrode 50 Metal plate 50a Metal base exposed surface 50b, 50c Insulating layer 51 Lid 51b, 51c Magnesium hydroxide layer 52 Leg 60 Hygroscopic material 70 Adhesive 110 Resist 120 Screen mask 130, 135 Press die 136 Stopper

Claims (4)

It has a size corresponding to a transparent substrate on which an array of a plurality of organic light emitting diodes (OLEDs) consisting of at least a transparent electrode film, an organic EL layer, and a cathode electrode is mounted, and has a leg portion at an edge portion and a tip of the leg portion Is an organic EL element sealing cap that is hermetically bonded to the edge of the transparent substrate, wherein the inner surface facing the OLED array is hygroscopic, and the hygroscopic material has water permeability on the inner surface Is installed ,
A sealing cap for an organic EL element, wherein the inner surface is made of a magnesium alloy, and the outer surface and the surfaces of the legs are made of an oxidized magnesium alloy .   The said hygroscopic material consists of zeolite, The sealing cap of the organic EL element of Claim 1 characterized by the above-mentioned. Step 1 of preparing a metal plate made of a magnesium alloy of a corresponding size for a transparent substrate on which an array of a plurality of organic light emitting diodes (OLEDs) comprising at least a transparent electrode film, an organic EL layer, and a cathode electrode is mounted. When,
Step 2 of selectively masking a predetermined portion of one side of the metal plate with a resist;
Step 3 of immersing the metal plate in a predetermined solution to form a magnesium hydroxide Mg (OH) ₂ layer on the entire surface of the metal plate not covered with the resist;
Removing the resist from one side of the metal plate; and
Screen printing a paste-like hygroscopic material at a predetermined location on one side of the metal plate, or selectively applying a hygroscopic material suspension with a dispenser to form a hygroscopic material film, step 5;
The metal plate to which the hygroscopic material is selectively attached is baked at a predetermined temperature, thereby firing the hygroscopic material and oxidizing the magnesium hydroxide Mg (OH) ₂ layer on the surface of the metal plate. Step 6 of chemically changing to a layer of magnesium MgO;
Step 7 of pressing the metal plate to form a sealing cap for the organic EL element comprising a lid portion and a leg portion at the periphery of the lid portion;
The manufacturing method of the sealing cap of the organic EL element characterized by including. The method for producing a sealing cap for an organic EL element according to claim 3 , wherein the hygroscopic material is made of zeolite.

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