JP2017208235A - Desiccant, sealing structure, and organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a desiccant capable of suppressing an organic layer in an organic EL element from being dissolved while containing a binder.SOLUTION: There is disclosed a desiccant containing a binder and oxide particles that are dispersed in the binder and contain an alkaline earth metal oxide. The binder contains fluorine-modified silicone having a silicon atom and a fluorinated alkyl group bonded to the silicon atom.SELECTED DRAWING: None

Description

  The present invention relates to a desiccant, a sealing structure, and an organic EL element.

  An organic EL (Electroluminescence) element generally has a light emitting portion including an organic layer which is a thin film containing an organic light emitting material and a pair of electrodes sandwiching the organic layer. The organic EL device generates excitons by injecting holes and electrons into a thin film and recombining them, and emits light (fluorescence or phosphorescence) when the excitons are deactivated. It is a self-luminous element to be used.

  Regarding organic EL elements, it is desired to prevent the occurrence of non-light-emitting portions of organic layers called dark spots and their growth. It is known that the main causes of dark spots are the influence of moisture and oxygen. In particular, it is known that even if the amount of moisture is extremely small, the generation of dark spots is greatly affected.

  Thus, various methods for preventing moisture and oxygen from entering the organic EL element have been studied. For example, a hollow sealing structure has been proposed in which an organic layer and an electrode are sealed in an airtight container in an inert gas atmosphere and a desiccant is sealed in the airtight container. For example, Patent Documents 1 and 2 disclose an organic EL element including, as a desiccant, an inert liquid made of fluorine oil or a mixture of a fluorine gel and a predetermined amount of adsorbent. Patent Document 2 also discloses an organic EL element provided with a desiccant prepared by mixing a predetermined amount of an adsorbent with an inert liquid made of silicone oil.

JP 2003-163076 A JP 2007-012372 A

  However, in a conventional organic EL device provided with a desiccant containing a silicone-based oil or the like as a binder, the organic layer in the organic EL device may dissolve during long-term storage. This is thought to be because the binder oozes out of the desiccant layer and dissolves the organic layer.

  Then, this invention makes it the main objective to provide the desiccant which can suppress melt | dissolution of the organic layer in an organic EL element, including a binder.

  One aspect of the present invention provides a desiccant containing a binder and oxide particles containing an alkaline earth metal oxide dispersed in the binder. The binder includes a fluorine-modified silicone having a silicon atom and a fluorinated alkyl group bonded to the silicon atom.

  According to this desiccant, dissolution of the organic layer of the organic EL element can be effectively suppressed.

  The content of the oxide particles may be 5 to 70% by mass based on the total amount of the desiccant. When the content of the oxide particles is within this range, the viscosity adjustment of the desiccant tends to be easier.

  The viscosity of the desiccant at 25 ° C. may be 5 to 500 Pa · s. When the viscosity of the desiccant at 25 ° C. is within this range, the desiccant layer can be more easily formed by coating.

  In another aspect, the present invention is provided between a pair of substrates opposed to each other, a sealing sealant that seals an outer peripheral portion of the pair of substrates, and between the pair of substrates inside the sealing sealant. Moreover, a sealing structure provided with the desiccant layer containing the said desiccant is provided.

  In yet another aspect, the present invention provides an element substrate, a sealing substrate disposed opposite to the element substrate, a sealing sealant that seals the outer periphery of the element substrate and the sealing substrate, and a sealing seal. A laminate having an organic layer and a pair of electrodes sandwiching the organic layer provided on the element substrate inside the agent, and the desiccant provided on the sealing substrate inside the sealing sealant. An organic EL device comprising a desiccant layer is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the desiccant which can suppress melt | dissolution of the organic layer in an organic EL layer is provided, including a binder. Since the oxide particles are dispersed in the binder, the oxide particles as the water replenishing component can be uniformly dispersed and arranged. Since the dispersibility of the oxide particles in the binder is good, the desiccant of the present invention has a form suitable for easily forming the desiccant layer by a method such as coating, such as a paste. Can do.

It is a schematic cross section which shows the organic EL element which concerns on one Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

Desiccant The desiccant according to one embodiment contains a binder and oxide particles dispersed in the binder and containing an alkaline earth metal oxide. The binder includes fluorine-modified silicone.

[Fluorine-modified silicone]
The fluorine-modified silicone has a siloxane containing a silicon atom and an oxygen atom, which are alternately bonded, and a fluorinated alkyl group bonded to a silicon atom in the siloxane. The fluorine-modified silicone is represented, for example, by the following general formula (1).

  In the general formula (1), R represents a fluorinated alkyl group having 1 to 4 carbon atoms or an alkyl group having 1 to 4 carbon atoms, and a plurality of R in one molecule may be the same or different. At least one of the plurality of Rs therein is a fluorinated alkyl group. n represents an integer of 0 or more.

  The fluorinated alkyl group as R is a group in which at least a part of hydrogen atoms of the alkyl group is substituted with fluorine atoms. The fluorinated alkyl group may be a group in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms. Examples of the fluorinated alkyl group include trifluoromethyl group, 2,2,2-trifluoroethyl group, 3,3,3-trifluoropropyl group, 4,4,4-trifluorobutyl group, 6,6. , 6-trifluorohexyl group and 8,8,8-trifluorooctyl group.

  The alkyl group as R can be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group.

  N in the general formula (1) can be set, for example, in such a range that the viscosity of the fluorine-modified silicone at 25 ° C. is 10 mPa · s to 100 Pa · s. The specific range of n may vary depending on the structure such as R, but may be 10 to 1000, for example.

  Fluorine-modified silicone can be synthesized by a usual method or can be obtained as a commercial product. Suitable commercial products include, for example, FL-5, X-22-821, X-22-822, FL-100-100CS, FL-100-450CS, FL-100-1,000CS (product names, both Shin-Etsu Chemical Co., Ltd.). These fluorine-modified silicones can be used alone or in combination of two or more.

  The viscosity of the fluorine-modified silicone at 25 ° C. may be 10 mPa · s to 100 Pa · s. When the viscosity is within this range, it tends to be easier to adjust the viscosity of the desiccant. From the same viewpoint, the viscosity of the fluorine-modified silicone may be 50 mPa · s or more, 100 mPa · s or more, or 50 Pa · s or less, or 10 Pa · s or less.

[Oxide particles]
The oxide particles include an alkaline earth metal oxide that can impart water replenishment performance to the oxide particles. The oxide particles usually contain 80% by mass or more, or 90% by mass or more of an alkaline earth metal oxide based on the mass of the oxide particles. The oxide particles can contain one kind or two or more kinds of alkaline earth metal oxides having different components.

  Examples of the alkaline earth metal oxide include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and the like. The alkaline earth metal oxide may be magnesium oxide and / or calcium oxide.

  The average particle diameter of the oxide particles is not particularly limited, but may be, for example, 0.01 to 30 μm. When the average particle diameter of the oxide particles is within this range, more sufficient water replenishment performance tends to be obtained. From the same viewpoint, the average particle diameter of the oxide particles may be 0.1 μm or more, 0.5 μm or more, or 1 μm or more, or 20 μm or less, 10 μm or less, or 5 μm or less.

  In the present specification, the average particle size of the oxide particles means the median value of the volume distribution measured with a dynamic light scattering particle size distribution meter. This average particle diameter is a value measured using a dispersion prepared by dispersing oxide particles in a predetermined dispersion medium.

  The content of the oxide particles in the desiccant is 5 to 70% by mass based on the total amount of the desiccant. When the content of the oxide particles is within this range, more sufficient water replenishment performance is obtained, and the viscosity adjustment of the desiccant tends to be easier. From the same viewpoint, the content of the oxide particles may be 10% by mass or more, 20% by mass or more, or 30% by mass or more, or 65% by mass or less or 60% by mass or less.

The oxide particles containing calcium oxide are, for example, a process of obtaining a slaked lime (Ca (OH) ₂ ) by hydroxylating quick lime (CaO), a process of baking slaked lime to obtain quick lime, and a process of pulverizing quick lime. Can be obtained by a method comprising: 300-600 degreeC may be sufficient as the temperature which bakes slaked lime. The firing time may be 1 to 20 hours.

  The desiccant may contain silica particles such as Aerosil (registered trademark) as a component other than the binder and oxide particles.

  The desiccant can be pasty at 25 ° C. When the desiccant is in a paste form, the desiccant layer can be more easily formed by coating in the minute airtight space of the organic EL element. The viscosity of the desiccant at 25 ° C. may be 5 to 500 Pa · s. When the viscosity of the desiccant at 25 ° C. is within this range, the desiccant layer can be more easily formed by coating. From the same viewpoint, the viscosity of the desiccant may be 10 Pa · s or more, 30 Pa · s or more, or 400 Pa · s or less or 200 Pa · s or less. Application can be performed by a dispenser or the like. The viscosity of the desiccant can be adjusted by the viscosity of the fluorine-modified silicone and the content of oxide particles. The viscosity here is a value measured by a rotational viscometer such as a B-type viscometer or a rheometer.

  The desiccant can be manufactured by a method including mixing oxide particles and fluorine-modified silicone. Mixing can be performed by centrifugation or the like. The rotation speed of the centrifugation may be, for example, 100 to 3000 rotations / minute. The centrifugation time may be 1 to 60 minutes.

Sealing structure The sealing structure of the present embodiment includes a pair of substrates disposed opposite to each other, a sealing sealant that seals the outer peripheral portion of the pair of substrates, and a pair of substrates inside the sealing sealant. And a provided desiccant layer. The desiccant layer can include the desiccant according to the above-described embodiment. The desiccant layer may fill the sealed space (the space inside the sealing sealant between the pair of substrates).

  The sealing structure of this embodiment can be particularly suitably used when encapsulating a device that is susceptible to moisture. Examples of such devices include organic electronic devices such as organic EL elements, organic semiconductors, and organic solar cells.

Organic EL Element FIG. 1 is a schematic cross-sectional view showing an embodiment of an organic EL element. An organic EL element 1 shown in FIG. 1 sandwiches an element substrate 2, a sealing substrate 3 disposed opposite to the element substrate 2, and an organic layer 4 and an organic layer 4 provided on the element substrate 2. A laminated body having an anode 5 and a cathode 6, a sealing sealant 8 that seals the outer periphery of the element substrate 2 and the sealing substrate 3, and provided on the sealing substrate 3 inside the sealing sealant 8. This is an organic EL element having a so-called hollow sealing structure constituted of the desiccant layer 7. The desiccant layer 7 can contain the desiccant of the above embodiment. After a long period of storage or use, there is a possibility that the binder that has oozed out of the desiccant layer 7 reaches the organic layer 4 and dissolves the organic layer 4, but the desiccant layer 7 uses the desiccant of the above embodiment. By including, the melt | dissolution of the organic layer 4 by a binder can be suppressed. However, the organic EL element is not limited to the hollow sealing structure as shown in FIG. 1, and includes, for example, a desiccant layer filled in an airtight space surrounded by the element substrate, the sealing substrate, and the sealing seal layer. An organic EL element having a filling structure may be used.

  In the organic EL element 1, a normal configuration can be applied to elements other than the desiccant layer 7, and an example thereof will be briefly described below.

  The element substrate 2 is made of a rectangular glass substrate having insulating properties and translucency, and an anode 5 (electrode) is formed on the element substrate 2 by ITO (Indium Tin Oxide) which is a transparent conductive material. Yes. The anode 5 is formed by, for example, patterning an ITO film formed on the element substrate 2 into a predetermined pattern shape by etching using a photoresist method by a PVD (Physical Vapor Deposition) method such as a vacuum deposition method or a sputtering method. Is done. A part of the anode 5 as an electrode is drawn to the end of the element substrate 2 and connected to a drive circuit (not shown).

On the upper surface of the anode 5, an organic layer 4, which is a thin film containing an organic light emitting material, is laminated by, for example, a PVD method such as a vacuum evaporation method or a resistance heating method. The organic layer 4 may be formed from a single layer, or may be formed from a plurality of layers having different functions. The organic layer 4 in this embodiment has a four-layer structure in which a hole injection layer 4a, a hole transport layer 4b, a light emitting layer 4c, and an electron transport layer 4d are stacked in this order from the anode 5 side. The hole injection layer 4a is made of, for example, copper phthalocyanine (CuPc) having a thickness of several tens of nm. The hole transport layer 4b is formed of, for example, bis [N- (1-naphthyl) -N-phenyl] benzidine (α-NPD) having a thickness of several tens of nm. The light emitting layer 4c is made of, for example, tris (8-quinolinolato) aluminum (Alq ₃ ) having a thickness of several tens of nm. The electron transport layer 4d is made of, for example, lithium fluoride (LiF) having a thickness of several nm. And the light emission part is formed by the laminated body in which the anode 5, the organic layer 4, and the cathode 6 mentioned later were laminated | stacked in this order.

  On the upper surface of the organic layer 4 (electron transport layer 4d), a cathode 6 (electrode) which is a metal thin film is laminated by a PVD method such as a vacuum deposition method. Examples of the material for the metal thin film include a simple metal having a low work function such as Al, Li, Mg, and In, and an alloy having a low work function such as Al—Li and Mg—Ag. The cathode 6 is formed with a film thickness of, for example, several tens nm to several hundreds nm (preferably 50 nm to 200 nm). A part of the cathode 6 is pulled out to the end of the element substrate 2 and connected to the drive circuit.

  The sealing substrate 3 is disposed so as to face the element substrate 2 with the organic layer 4 interposed therebetween, and the outer peripheral portions of the element substrate 2 and the sealing substrate 3 are sealed with a sealing sealant 8. As the sealing agent, for example, an ultraviolet curable resin can be used. Furthermore, the desiccant layer 7 is provided on a part or all of the sealing substrate 3 inside the sealing sealant 8. The desiccant layer 7 is formed by applying the desiccant of the above embodiment. The desiccant layer 7 is formed with a film thickness of 1 to 300 μm.

Method for Manufacturing Organic EL Element First, a laminate in which an organic layer 4 or the like (electrodes not shown) is laminated on the element substrate 2 is prepared.

  Next, the desiccant of this embodiment is applied on the separately prepared sealing substrate 3 with a dispenser to form the desiccant layer 7. Further, the sealing sealant 8 is applied with a dispenser so as to surround the desiccant applied on the sealing substrate 3. These operations are preferably performed in a glove box substituted with nitrogen having a dew point of -76 ° C or lower. The applied desiccant may contain a solvent, but is typically substantially solvent-free.

  Next, the element substrate 2 and the sealing substrate 3 on which the organic layer 4 and the like are laminated are bonded together. The organic EL element 1 of this embodiment is manufactured by sealing the bonded substrates by UV irradiation and heating at about 80 ° C.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

1. Preparation of desiccant Calcium oxide particles having an average particle diameter adjusted to 2 μm, fluorine-modified silicone as a binder (product name having methyl group and 3,3,3-trifluoropropyl group as R in formula (1)) : FL-100-1000CS, manufactured by Shin-Etsu Chemical Co., Ltd., viscosity: 1.3 Pa · s (25 ° C.)), perfluoropolyether (product name: demnum S-20, manufactured by Daikin Industries, Ltd.), or dimethyl silicone (Product name: Element14 PDMS 10K-JC, manufactured by Momentive Performance Materials Co., Ltd.), and stirred for 5 minutes at 1000 rpm, and Examples 1-3 and Comparative Examples 1-4 shown in Table 1 A desiccant was obtained. Table 1 shows the content of calcium oxide particles based on the total amount of the desiccant, the form of the desiccant, and the viscosity. The viscosity at 25 ° C. of the desiccant is a value measured under the condition of a shear rate of 5 s ⁻¹ using a rheometer as a measuring device.

  The desiccant of Examples 1 to 3 containing fluorine-modified silicone as a binder and the desiccant of Comparative Example 4 containing dimethyl silicone as a binder became paste. On the other hand, the desiccants of Comparative Examples 1 to 3 containing perfluoropolyether as a binder did not form a paste due to the low dispersibility of the calcium oxide particles.

2. Evaluation [Production of Organic EL Device]
ITO, which is a conductive material having transparency, was formed to a thickness of 140 nm on the element substrate by sputtering. The ITO film was patterned into a predetermined pattern shape by etching using a photoresist method to form an anode.
A hole injection layer is formed by depositing copper phthalocyanine (CuPc) with a thickness of 70 nm on the upper surface of the formed anode by resistance heating, and Bis [N- (1-naphthyl) is formed on the upper surface of the hole injection layer. -N-phenyl] benzidine (α-NPD) is formed to a thickness of 30 nm to form a hole transport layer, and a film of tris (8-quinolinolato) aluminum (Alq ₃ ) is formed on the top surface of the hole transport layer to a thickness of 50 nm. A light emitting layer was formed by forming a film with a thickness. Further, lithium fluoride (LiF) was formed to a thickness of 7 nm on the upper surface of the light emitting layer to form an electron transport layer, and aluminum was physically vapor-deposited to a thickness of 150 nm as a cathode on the surface of the electron transport layer. As described above, a laminate in which the anode, the organic layer (hole injection layer / hole transport layer / light emitting layer / electron transport layer), and the cathode were laminated in this order was formed on the element substrate.
Next, in the glove box substituted with nitrogen having a dew point of −76 ° C. or less, the desiccant of Example 2 or Comparative Example 4 was applied to the central portion of the sealing substrate by a dispenser to form a desiccant layer. . A sealing sealant made of an ultraviolet curable resin was applied onto the sealing substrate with a dispenser so as to surround the desiccant layer.
Then, the element substrate and the sealing substrate were bonded together in a direction in which the laminate, the desiccant layer, and the sealing sealant were inside. In this state, the outer periphery of the element substrate and the sealing substrate is sealed by ultraviolet irradiation and heating at 80 ° C., and a hollow sealing structure in which a desiccant layer is provided in an airtight space surrounded by the sealing sealant. An organic EL device was obtained.

[Change in emission area ratio with respect to elapsed time]
The obtained organic EL device was left in a high-temperature and high-humidity environment of 85 ° C. and 85% RH, and the change in the light emission area ratio with respect to the elapsed time was traced. Table 2 shows changes in the light emission area ratio.

[Solution distance of organic layer to elapsed time]
Except that the desiccant of Example 2 or Comparative Example 4 was applied by dispensing only a capacity that can be filled in a sealed container surrounded by a sealing sealant, in the same manner as in [Preparation of organic EL element] above, An organic EL device having a filled and sealed structure including a desiccant layer filled in an airtight container was obtained.
A hole was formed in the cathode of the obtained organic EL device with a laser, and the organic EL device was allowed to stand at 85 ° C., and the dissolution distance of the organic layer was observed and measured with an optical microscope. The dissolution distance is shown in Table 3. The dissolution distance indicates the distance from the center of the hole to the end of the portion where the dissolution of the organic layer has occurred, and the larger the value, the more the dissolution of the organic layer proceeds.

  The organic EL device containing the desiccant of Example 2 exhibited a light emission area ratio of 90% or more after 100 hours, and maintained a light emission area ratio of 85% or more even after 170 hours. Furthermore, in the organic EL device containing the desiccant of Example 2, the dissolution of the organic layer hardly progressed. On the other hand, the organic EL element containing the desiccant of Comparative Example 4 maintained the same light emitting area ratio as the organic EL element containing the desiccant of Example 2, but the organic layer in the organic EL element was dissolved. Progressed. From these results, it was confirmed that the desiccant of the present invention can effectively suppress dissolution of the organic layer even when the binder oozes out.

  DESCRIPTION OF SYMBOLS 1 ... Organic EL element, 2 ... Element substrate, 3 ... Sealing substrate, 4 ... Organic layer, 4a ... Hole injection layer, 4b ... Hole transport layer, 4c ... Light emitting layer, 4d ... Electron transport layer, 5 ... Anode, 6 ... cathode, 7 ... desiccant layer, 8 ... sealing sealant.

Claims (5)

A binder, and oxide particles containing an alkaline earth metal oxide dispersed in the binder,
The desiccant in which the binder contains a fluorine-modified silicone having a silicon atom and a fluorinated alkyl group bonded to the silicon atom.   The desiccant according to claim 1, wherein the content of the oxide particles is 5 to 70% by mass based on the total amount of the desiccant.   The desiccant of Claim 1 or 2 whose viscosity in 25 degreeC of the said desiccant is 5-500 Pa.s. A pair of opposed substrates;
A sealing sealant that seals the outer periphery of the pair of substrates;
A desiccant layer containing the desiccant according to any one of claims 1 to 3, provided between the pair of substrates inside the sealing sealant;
A sealing structure comprising: An element substrate;
A sealing substrate disposed opposite to the element substrate;
A sealing sealant for sealing the outer periphery of the element substrate and the sealing substrate;
A laminate having an organic layer and a pair of electrodes sandwiching the organic layer provided on the element substrate inside the sealing sealant;
A desiccant layer containing the desiccant according to any one of claims 1 to 3, provided on the sealing substrate inside the sealing sealant;
An organic EL device comprising:

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