TWI671113B - Desiccant, sealing structure and organic electroluminescent element - Google Patents

Abstract

The invention discloses a desiccant, which contains a binder resin and oxide particles dispersed in the binder resin. At least a portion of the oxide particles form secondary particles, the secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles is 4 μm or less. The specific surface area of the oxide particles is 5 to 60 m ² / g.

Description

Desiccant, sealing structure and organic electroluminescence element

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

An organic EL (Electroluminescence) element generally includes a light-emitting portion including a thin film containing an organic light-emitting material, that is, an organic layer, and a pair of electrodes sandwiching the organic layer. Organic EL devices are self-emitting devices that inject holes and electrons into a thin film and recombine them to generate excitons and use the excitons to deactivate light (fluorescent or phosphorescent) that is emitted when they are deactivated. .

Regarding the organic EL element, it is expected to prevent generation and growth of a non-light emitting portion of an organic layer called a black dot. As the main cause of the black spots, it is known that the influence of moisture and oxygen is large. In particular, the presence of a small amount of moisture can greatly affect the generation of black spots.

Therefore, various studies have been made on methods for preventing moisture and oxygen from entering the organic EL element. For example, a hollow sealing structure is proposed in which an organic layer and an electrode are sealed in a hermetic container in a dry inert gas environment, and a desiccant is sealed in the hermetic container. For example, Patent Document 1 discloses an organic EL element including a desiccant-containing layer on the inner surface of a sealing cap, the desiccant-containing layer containing a powder of phosphorus pentoxide and a low-temperature curing epoxy-based adhesive.

On the other hand, as a dehumidifier, quicklime (calcium oxide) is sometimes used. For example, Patent Document 2 describes that quicklime preferably contains 50% by mass or more of particles having a particle diameter of 75 μm or more.

(Patent Document) Patent Document 1: Japanese Patent Application Laid-Open No. 2001-035659. Patent Document 2: Japanese Patent Application Laid-Open No. 2005-335987.

The main object of the present invention is to provide a desiccant which can effectively suppress the generation of black spots in an organic EL element for a longer period of time.

In one aspect of the present invention, a desiccant is provided, which comprises a binder resin and oxide particles dispersed in the binder resin. At least a part of the oxide particles forms a secondary particle including a plurality of primary particles. The oxide particles The average particle diameter is 4 μm or less, and the specific surface area of the oxide particles is 5 to 60 m ² / g. According to the desiccant, it is possible to effectively suppress the occurrence of black spots in the organic EL element for a longer period of time.

The present invention can also provide a composition which is used as a desiccant (application) and used to prepare a desiccant (application). The foregoing composition comprises a binder resin and oxide particles dispersed in the binder resin, and oxidizes. At least a part of the material particles form secondary particles including a plurality of primary particles, the average particle diameter of the oxide particles is 4 μm or less, and the specific surface area of the oxide particles is 5 to 60 m ² / g.

The specific surface area of the oxide particles may be 5 to 35 m ² / g. When the specific surface area of the oxide particles is within the above range, the water-capturing performance of the desiccant can be improved. From the same viewpoint, the binder resin may also include a silicone resin.

In another aspect of the present invention, there is provided a sealing structure including: a pair of substrates disposed opposite to each other; a sealant that seals an outer peripheral portion of the pair of substrates; and a desiccant layer that is inside the sealant and is sealed by the sealant. It is provided between the aforementioned pair of substrates and contains the aforementioned desiccant.

According to still another aspect of the present invention, there is provided an organic EL element including: an element substrate; a sealing substrate that is disposed opposite to the element substrate; a sealant that seals the element substrate and an outer peripheral portion of the sealing substrate; and a laminated body , Which is located inside the sealant and is disposed on the aforementioned element substrate, and has an organic layer and a pair of electrodes sandwiching the organic layer; a desiccant layer, which is located inside the sealant and is disposed on the sealing substrate, It also contains the aforementioned desiccant.

According to the desiccant according to one aspect of the present invention, it is possible to effectively suppress the generation of black spots in the organic EL element for a longer period of time. Since the oxide particles are dispersed in the binder resin, it is possible to uniformly disperse and arrange the oxide particles as a water-capturing component.

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

In the present specification, the "primary particle" means a particle that is integrally formed into a single particle when judged from the apparent geometric form. "Secondary particles" includes a plurality of primary particles. Generally, secondary particles are formed by aggregating a plurality of primary particles.

(Desiccant) An embodiment of the desiccant includes a binder resin and oxide particles dispersed in the binder resin.

[Oxide particles] At least a part of the oxide particles contained in the desiccant form secondary particles including a plurality of primary particles. The formation of secondary particles of the oxide particles can be confirmed by observing the oxide particles with a scanning electron microscope (SEM) or the like. Among the oxide particles contained in the desiccant, for example, 10 to 100% by mass or 50 to 100% by mass may form secondary particles. According to the findings of the present inventors, the case where the oxide particles form secondary particles helps to suppress the generation of black spots. In addition, it is difficult for the oxide particles forming the secondary particles to have a large volume, which helps achieve a sufficient water-capturing performance with a smaller volume of the desiccant.

The average particle diameter of the oxide particles may be 4 μm or less. When the average particle diameter of the oxide particles is 4 μm or less, it contributes to suppressing the generation of black spots in the organic EL element. From the same viewpoint, the average particle diameter of the oxide particles may be 3.9 μm or less or 3.8 μm or less. The lower limit of the average particle diameter of the oxide particles is not particularly limited, and may be, for example, 0.5 μm or more or 1 μm or more. For example, the average particle diameter of the oxide particles can be controlled by adjusting the calcination temperature, the calcination time, and the pulverization conditions of the oxide particles.

In the present specification, the average particle diameter of the oxide particles refers to the median of the volume distribution measured by a dynamic light scattering particle size analyzer. The average particle diameter is an average particle diameter of the entire oxide particles including the primary particles and the secondary particles, and the average particle diameter is performed using a dispersion liquid prepared by dispersing the oxide particles in a predetermined dispersant. measuring.

The average particle diameter of the primary particles of the oxide particles is not particularly limited, and may be, for example, 0.5 μm or less or 0.1 μm or less. The average particle diameter of the primary particles of the oxide particles may be 0.01 μm or more. The average particle diameter of the primary particles of the oxide particles may be an average value of the particle diameter (maximum width) of the primary particles existing in the observation field when the oxide particles are observed with an electron microscope or the like.

The oxide particles include an inorganic oxide that can impart water-capturing properties to the oxide particles. Based on the mass of the oxide particles, the oxide particles usually contain 80% by mass or more or 90% by mass of an inorganic oxide. The desiccant may include one kind of oxide particles or two or more kinds of oxide particles having different components. The oxide particles include, for example, selected from the group consisting of phosphorus pentoxide (P ₄ O ₁₀ ), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and aluminum oxide (Al ₂ O ₃ ). At least one inorganic oxide in the group. The oxide particles may include at least one alkaline earth metal oxide selected from the group consisting of magnesium oxide, calcium oxide, strontium oxide, and barium oxide, and may also include calcium oxide.

The specific surface area of the oxide particles is 5 to 60 m ² / g, and may be 5 to 35 m ² / g. When the specific surface area is 5 to 60 m ² / g, the desiccant can have more excellent water-capturing performance. From the same viewpoint, the specific surface area of the oxide particles may be 10 m ² / g or more or 15 m ² / g or more, or may be 50 m ² / g or less, 40 m ² / g or less, or 35 m ² / g or less.

In this specification, the specific surface area of the oxide particles refers to the total specific surface area of the oxide particles including the primary particles and the secondary particles, and is measured by the BET method.

The content of the oxide particles in the desiccant may be 10% by mass or more, 20% by mass or more, or 30% by mass or more of the total mass of the desiccant. The content of the oxide particles may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

The oxide particles containing calcium oxide can be obtained, for example, by the following method. The method includes the following steps: hydrated quick lime (CaO) to obtain hydrated lime (Ca (OH) ₂ ); And crush the quicklime. The temperature at which slaked lime is torrefied can be 300 ~ 600 ° C. The simmering time can be from 1 to 20 hours.

By pulverizing the quicklime, the average particle diameter of the oxide particles can be adjusted to a desired range. For example, quicklime can be dispersed in a solvent such as heptane and pulverized with a ball mill or the like.

The diameter of primary particles including oxide particles of calcium oxide tends to depend on the primary particles of slaked lime. By subjecting quicklime to a hydroxide treatment, the diameter of the primary particles of the oxide particles can be adjusted to a desired range.

[Binder resin] The binder resin is not particularly limited as long as it can disperse the oxide particles. When mixing with the oxide particles, a binder resin capable of forming a paste can be used. By using a paste of a desiccant, a desiccant layer in which oxide particles are uniformly dispersed can be easily formed.

The binder resin may include, for example, at least one resin selected from the group consisting of a polyvinyl chloride resin, a phenol resin, a silicone resin, an epoxy resin, a polyester resin, a urethane resin, an acrylic resin, and an olefin resin. The binder resin may include a silicone resin.

The mass ratio of the oxide particles and the binder resin in the desiccant is not particularly limited, and may be 1: 4 ~ 4: 1 or 1: 2 ~ 2: 1. When the mass ratio of the oxide particles and the binder resin is within the above range, there is a tendency that a desiccant layer described later can be easily formed.

The desiccant may contain components such as an organometallic compound and a curable resin in addition to the oxide particles and the binder resin.

The desiccant can be produced by a method including a step of mixing oxide particles and a binder resin. The mixing operation can be performed by centrifugation or the like. The rotation speed of centrifugation can be, for example, 100 to 3000 revolutions per minute. The centrifugation time can be from 1 to 60 minutes.

(Sealing Structure) The sealing structure of this embodiment includes a pair of substrates disposed opposite to each other, a sealant sealing the outer peripheral portion of the pair of substrates, and a drying provided inside the sealant and disposed between the pair of substrates.剂 层。 The agent layer. The desiccant layer may include a desiccant according to the above embodiment. The desiccant layer may fill the sealed space (the space between the aforementioned pair of substrates and inside the sealant).

The sealing structure of this embodiment is particularly suitable for use when packaging equipment that is easily affected by 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. The organic EL element 1 shown in FIG. 1 is a so-called hollow-sealed organic EL element, and is composed of an element substrate 2, a sealing substrate 3 disposed opposite to the element substrate 2, and provided on the element. A laminate on the substrate 2 (the laminate having an organic layer 4 and an anode 5 and a cathode 6 sandwiching the organic layer 4), a sealing element substrate 2, and a sealant 8 sealing the outer peripheral portion of the substrate 3; Is provided inside the desiccant layer 7 on the sealing substrate 3. The desiccant layer 7 may include a desiccant of the above-mentioned embodiment.

In the organic EL element 1, a conventionally known structure can be used for the elements other than the desiccant layer 7. An example of the organic EL element 1 will be briefly described below.

The element substrate 2 is made of a rectangular glass substrate having insulation and light transmission properties. On the element substrate 2, an anode 5 (electrode) is formed of a transparent conductive material, that is, ITO (Indum Tin Oxide). The anode 5 is formed by, for example, forming an ITO film formed on the element substrate 2 by a PVD (Physical Vapor Deposition) method such as a vacuum evaporation method or a sputtering method by etching using a photolithography method to form a predetermined electrode. Pattern shape, thereby forming the anode 5. A part of the anode 5 as an electrode is drawn out to an end of the element substrate 2 and is connected to a driving circuit (not shown).

On the upper surface of the anode 5, a thin film containing an organic light-emitting material, that is, an organic layer 4 is laminated by a PVD method such as a vacuum evaporation method or a resistance heating method. The organic layer 4 may be formed of a single layer or 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 sequentially stacked from the anode 5 side. The hole injection layer 4 a is formed of, for example, copper phthalocyanine (CuPc) having a film thickness of several tens of nanometers. The hole transport layer 4b is made of, for example, bis [N- (1-naphthyl) -N-phenyl] benzidine with a film thickness of tens of nanometers, α-NPD). The light emitting layer 4 _c is formed of, for example, tris (8-hydroxyquinoline) aluminum (Alq ₃ ) having a film thickness of several tens of nanometers. The electron transport layer 4d is formed of, for example, lithium fluoride (LiF) having a thickness of several nanometers. A laminate in which the anode 5, the organic layer 4, and a cathode 6 described later are sequentially stacked constitutes a light-emitting portion.

A cathode 6 (electrode), which is a metal thin film, is formed on the upper surface of the organic layer 4 (electron transport layer 4d) by a PVD method such as a vacuum evaporation method. Examples of the material of the metal thin film include a metal monomer having a small work function such as Al (aluminum), Li (lithium), Mg (magnesium), and In (indium), or Al-Li (aluminum-lithium), Mg- Alloys with smaller work functions such as Ag (magnesium-gold). The thickness of the cathode 6 is, for example, tens of nanometers to hundreds of nanometers (preferably 50 nm to 200 nm). A part of the cathode 6 is drawn out to an end of the element substrate 2 and is connected to a driving circuit (not shown).

The sealing substrate 3 is arranged 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 sealant 8. As the sealant, for example, an ultraviolet curable resin can be used. The desiccant layer 7 is provided on the inside of the sealant 8 on a part of the sealing substrate 3 or on the entire sealing substrate 3. The desiccant layer 7 is formed by applying the desiccant of the embodiment described above. The desiccant layer 7 has a film thickness of 1 to 300 μm.

(Manufacturing method of an organic EL element) First, the laminated body which laminated | stacked the organic layer 4 etc. (electrode not shown) on the element substrate 2 is prepared.

Next, a desiccant layer 7 is formed by applying a desiccant of this embodiment on a separately prepared sealing substrate 3 using a coater. Then, the sealant 8 is applied using a coater so as to surround the desiccant applied to the seal substrate 3. These operations are preferably performed in a glove box replaced with nitrogen having a dew point of -76 ° C.

Next, the element substrate 2 on which the organic layer 4 and the like are laminated and the sealing substrate 3 are bonded together. The bonded substrates are irradiated with UV (ultraviolet rays) and heated to about 80 ° C. for sealing, so that the organic EL element 1 of this embodiment is manufactured.

(Examples) Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to these examples.

1. Synthesis of oxide particles [oxide particles 1] Commercially available oxide particles are used as the oxide particles 1. The oxide particles 1 do not form secondary particles. The average particle diameter of the oxide particles 1 was 2.5 μm, and the specific surface area was 2.5 m ² / g. The oxide particles are dispersed in a dispersant (alcohol) to prepare a dispersion for measurement, and the median volume distribution of the dispersion obtained through a dynamic light scattering particle size analyzer is used as the average of the oxide particles. The particle size is recorded. Then, the oxide particles were dried at 120 ° C. for 8 hours or more under an environment where the pressure was reduced to 500 Pa or less, and then only the isothermal adsorption line on the nitrogen adsorption side at the liquid nitrogen temperature was obtained. The isothermal adsorption line was analyzed by the BET method to determine the specific surface area of the oxide particles. The average particle diameter and specific surface area of other oxide particles were also measured in the same manner.

[Oxide Particle 2] A quicklime powder (purity: 99% by mass) having a specific surface area of 17.1 m ² / g was dispersed in a solvent (heptane) and pulverized with a ball mill. After the pulverization, the solvent was removed by distillation to obtain the oxide particles 2. Observing the oxide particles 2 with a scanning electron microscope (SEM), it was found that almost all oxide particles formed secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 2 was 2.5 μm, and the specific surface area was 5.3 m ² / g.

[Oxide Particle 3] A slaked lime powder (purity: 73.2% by mass) having a specific surface area of 47 m ² / g was placed in an incinerator and calcined at a temperature of 450 ° C. for 3 hours to prepare a raw lime powder. The obtained quicklime powder was dispersed in a solvent (heptane) and pulverized with a ball mill. After the pulverization, the solvent was removed to obtain the oxide particles 3. Observing the oxide particles 3 with a scanning electron microscope (SEM), it was found that almost all of the oxide particles formed secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 3 was 3.8 μm, and the specific surface area was 34.6 m ² / g.

[Oxide Particle 4] A slaked lime powder (purity: 73.2% by mass) having a specific surface area of 47 m ² / g was placed in an sintering furnace, and the pressure was set to 5 × 10 ^-3 Pa or lower by a vacuum pump, and the temperature was measured at 450 ° C. The temperature was calcined for 3 hours, thereby preparing the oxide particles 4. The oxide particles 4 form secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 4 was 4.1 μm, and the specific surface area was 82.5 m ² / g.

[Oxide Particle 5] A slaked lime powder (purity: 73.3% by mass) having a specific surface area of 35 m ² / g was placed in an sintering furnace, and the pressure was set to 5 × 10 ^-3 Pa or less by a vacuum pump, and the temperature was measured at 450 ° C. The temperature was calcined for 3 hours, thereby preparing oxide particles 5. The oxide particles 5 form secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 5 was 5 μm, and the specific surface area was 76.1 m ² / g.

[Oxide Particle 6] A slaked lime powder (purity: 73.3% by mass) with a specific surface area of 35 m ² / g was replaced with a slaked lime powder (purity: 74.7% by mass) with a specific surface area of 15 m ² / g. The oxide particles 6 were prepared in the same manner as the material particles 5. The oxide particles 6 form secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 6 was 5 μm, and the specific surface area was 68.9 m ² / g.

[Oxide Particle 7] The slaked lime powder (purity: 73.3% by mass) with a specific surface area of 35 m ² / g was replaced with the slaked lime powder (purity: 74.2% by mass) with a specific surface area of 12 m ² / g. The oxide particles 7 are prepared by the same method for preparing the particles 5. The oxide particles 7 form secondary particles including a plurality of primary particles. The average particle diameter of the oxide particles 7 was 5 μm, and the specific surface area was 67.2 m ² / g.

2. Preparation of the desiccant The oxide particles 1 to 7 and the silicone resin were respectively mixed at a mass ratio of 1: 1, and the mixture was centrifuged and stirred at a rotation speed of 1000 rpm for 5 minutes to obtain Example 1 shown in Table 1. 2 and the desiccants of Comparative Examples 1 to 5.

3． Evaluation The sputtering method was used to form a film having a thickness of 140 nm on the element substrate from ITO, which is a conductive material having transparency. The ITO film is etched by photolithography to form a predetermined pattern shape, thereby forming an anode. Use resistance heating method. Copper phthalocyanine (CuPc) was formed on the upper surface of the formed anode to a thickness of 70 nm to form a hole injection layer, and di [N- (1-naphthyl) was formed on the upper surface of the hole injection layer. -N-phenyl] benzidine (α-NPD) forms a film with a thickness of 30 nm to form a hole transport layer, and then on the top surface of the hole transport layer, tris (8-hydroxyquinoline) aluminum (Alq ₃ ) A film having a film thickness of 50 nm is formed to form a light emitting layer. Next, lithium fluoride (LiF) was formed on the upper surface of the light-emitting layer into a 7-nm-thick film to form an electron-transporting layer, and aluminum was physically vapor-deposited on the surface of the electron-transporting layer with a thickness of 150 nm as a cathode. Thereby, a stacked body in which an anode, an organic layer (hole injection layer / hole transport layer / light emitting layer), an electron transport layer, and a cathode are sequentially stacked on the element substrate is formed. Next, in the glove box replaced with nitrogen having a dew point of -76 ° C, the desiccant of each of the examples or comparative examples was applied to the central portion of the sealing substrate by a coater to form a desiccant layer. Then, a sealant made of an ultraviolet curable resin is applied to the sealing substrate with a coater so as to surround the applied desiccant. Then, the element substrate and the sealing substrate are bonded so that the laminate, the desiccant layer, and the sealant are located inside. In this state, the element substrate and the outer peripheral portion of the sealing substrate are sealed by irradiating ultraviolet rays and heating to 80 ° C., thereby obtaining an organic EL element having a hollow sealing structure in which a desiccant is provided in an air-tight space surrounded by the sealing agent. The obtained organic EL element was placed in a high-temperature, high-humidity environment at 85 ° C. and 85% RH, and the change in light-emitting area ratio with respect to elapsed time was tracked.

FIG. 2 is a graph showing the relationship between the light-emitting area ratio and the elapsed time of the organic EL element in a high-temperature and high-humidity environment. The organic EL element including the desiccants of Examples 1 and 2 showed a light emitting area ratio of 80% or more after 500 hours, and the light emitting area ratio was maintained at 75% or more after 1000 hours. On the other hand, in the organic EL element including the desiccants of Comparative Examples 1 to 5, the light emitting area ratio decreased to less than 80% at the elapse of 500 hours. From this result, it is understood that the desiccant of the present invention can sufficiently suppress the occurrence of black spots in the organic EL element.

1‧‧‧Organic EL element

2‧‧‧Element substrate

3‧‧‧sealed substrate

4‧‧‧ organic layer

4a‧‧‧ Hole injection layer

4b‧‧‧hole transmission layer

4c‧‧‧Light-emitting layer

4d‧‧‧ electron transmission layer

5‧‧‧ anode

6‧‧‧ cathode

7‧‧‧ Desiccant layer

8‧‧‧ Sealant

FIG. 1 is a schematic cross-sectional view showing an organic EL element according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the light-emitting area ratio and the elapsed time of the organic EL element in a high-temperature and high-humidity environment.

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Claims (4)

A desiccant comprising a binder resin and oxide particles dispersed in the binder resin; wherein the oxide particles include calcium oxide; at least a part of the oxide particles form secondary particles, and the secondary particles include a plurality of Primary particles; the average particle size of the oxide particles is 4 μm or less; the specific surface area of the oxide particles is 5 to 60 m ² / g; the binder resin includes a silicone resin; the oxide particles and the binder resin The mass ratio is 1: 4 ~ 4: 1. The desiccant according to claim 1, wherein the specific surface area of the oxide particles is 5 to 35 m ² / g. A sealing structure includes: a pair of substrates disposed opposite to each other; a sealant that seals an outer peripheral portion of the pair of substrates; and a desiccant layer that is provided inside the sealant and is provided on the pair of substrates Between, and contains the desiccant described in claim 1 or 2. An organic electroluminescence element includes: an element substrate; a sealing substrate that is disposed opposite to the element substrate; a sealant that seals the element substrate and an outer peripheral portion of the sealing substrate; and a laminated body that is sealed in the aforementioned seal. And an organic layer and a counter electrode sandwiching the organic layer; and a desiccant layer provided inside the sealant and provided on the sealing substrate, and Contains the desiccant described in claim 1 or 2.