TWI707933B - Organic el element and method of producing same - Google Patents

Abstract

The present invention discloses an organic electroluminescence element. The organic electroluminescence element includes: a sealing substrate having a main surface opposed to the element substrate; and a desiccant layer provided on the main surface. A desiccant layer is provided in an area away from the outer periphery of the main surface. When viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer relative to the area of the main surface is 50% or more.

Description

Organic electroluminescence element and manufacturing method thereof

The present invention relates to an organic electroluminescence element (organic EL element) and its manufacturing method.

In order to prevent the light-emitting part of the organic electroluminescence element from decreasing the light-emitting life due to moisture, sometimes the light-emitting part that has been provided on the substrate is sealed by a sealing substrate, and then a water-absorbing material is provided on the sealing substrate (for example, Japanese Patent Application 2006-331766 Bulletin).

[The problem to be solved by the invention] When an organic electroluminescence element having a desiccant layer provided on a sealing substrate is to be manufactured, in order to avoid mixing of moisture, it is necessary to form a desiccant layer on the sealing substrate under a dry atmosphere such as an inert gas. However, from the viewpoint of simplification of steps and equipment, it is desirable to be able to form the desiccant layer in an atmospheric atmosphere without requiring a drying atmosphere. By using a desiccant with a large water absorption capacity, it is expected that the desiccant layer can maintain sufficient water absorption capacity even if the desiccant layer is formed in the atmosphere. However, it is clear that even if a desiccant with a large water absorption capacity is used, if the desiccant layer is formed on the sealing substrate in an air atmosphere, the light-emitting area ratio of the organic electroluminescent element is likely to be insufficient from the early stage immediately after its manufacture.

[Technical means to solve the problem] Therefore, an object of one aspect of the present invention is to provide an organic electroluminescent element that can maintain sufficient levels even when manufactured by a method including a step of forming a desiccant layer in an atmospheric atmosphere. The initial light emitting area ratio.

One aspect of the present invention relates to an organic electroluminescence element, which includes: an element substrate; a light-emitting portion provided on the element substrate; a sealing substrate having a main surface opposed to the element substrate; and, a desiccant layer , Which is set on the aforementioned main surface.

Another aspect of the present invention relates to a method of manufacturing the above-mentioned organic electroluminescence device. The method includes: forming a desiccant layer on the main surface of a sealing substrate; forming a light-emitting portion on an element substrate; and adhering the sealing substrate to the element in a direction in which the main surface faces the element substrate Steps on the substrate. The sealing substrate is bonded to the element substrate by the sealant between the element substrate and the sealing substrate. An airtight space surrounded by the element substrate, the sealing substrate and the sealant is formed, and the light-emitting part and the desiccant layer are arranged in the airtight space.

The light-emitting part has a pair of electrodes arranged opposite to each other and an organic layer arranged between them. The desiccant layer is arranged in an area away from the outer periphery of the aforementioned main surface. When viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer relative to the area of the main surface is 50% or more.

[Effects of the invention] If the area ratio of the desiccant layer is 50% or more, the organic electroluminescence element can easily maintain a sufficient initial light-emitting area ratio even when the desiccant layer is formed in an air atmosphere. In addition, a desiccant layer is provided in an area away from the outer periphery of the main surface of the sealing substrate, whereby the sealing substrate can be easily fixed to the element substrate.

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

Fig. 1 is a cross-sectional view showing an embodiment of an organic electroluminescence device. The organic electroluminescence element 20 shown in FIG. 1 includes an element substrate 1, a light-emitting part 7 provided on the element substrate 1, a sealing substrate 3, a desiccant layer 10 and a sealing agent 5.

The sealing substrate 3 has: a top plate portion 3A having a rectangular or square flat main surface 3S opposed to the element substrate 1; and a side wall portion 3B which is perpendicular to the main surface 3S along the outer peripheral end of the top plate portion 3A The direction extends. The top plate part 3A and the side wall part 3B form a recessed part having the main surface 3S as a bottom surface. The desiccant layer 10 is formed on the main surface 3S of the sealing substrate 3.

The sealant 5 is interposed between the side wall portion 3B of the sealing substrate 3 and the element substrate 1, and at the same time, the sealing substrate 3 and the element substrate 1 are bonded together. Thereby, an airtight space 30 surrounded by the element substrate 1, the sealing substrate 3, and the sealant 5 is formed. The light emitting unit 7 and the desiccant layer 10 are arranged in the airtight space 30. The sealing substrate 3 may be a flat plate-shaped body without the side wall portion 3B. In this case, the sealant 5 is usually interposed between the top plate portion 3A of the sealing substrate 3 and the element substrate 1. In any case, the "main surface facing the element substrate" refers to the surface facing the element substrate in the airtight space where the light-emitting portion is arranged.

Fig. 2 is a plan view showing an embodiment of a sealing substrate and a desiccant layer. The top view of FIG. 2 shows the form of the sealing substrate 3 and the desiccant layer 10 viewed from a direction perpendicular to the main surface 3S of the sealing substrate 3. As shown in FIG. 2, the desiccant layer 10 is provided in an area away from the outer periphery of the main surface 3S of the sealing substrate 3 toward the inner side thereof. In the plan view of FIG. 2, the area ratio of the desiccant layer 10 with respect to the area of the main surface 3S is 50% or more. The area ratio can be 60% or more, 70% or more, or 75% or more. It is considered that if the area ratio of the desiccant layer 10 is increased, the moisture adhering to the main surface 3S of the sealing substrate 3 in the air atmosphere will not easily affect the light-emitting portion 7. If the area ratio is 50% or more, even after the desiccant layer is formed, when the sealing substrate is left in the air atmosphere, for example, for 3 hours or more, it is easy to obtain organic electroluminescence with a light-emitting area ratio of 98% or more. element. In addition, from the viewpoint of ensuring stable adhesion between the sealing substrate and the element substrate, the area ratio of the desiccant layer 10 may be less than 90%. The thickness of the desiccant layer 10 may be 50 μm or more and 200 μm or less.

Regarding the desiccant layer 10, as shown in FIG. 2, it may be a single film, and as shown in FIG. 3, it may include linear portions. In the case of the embodiment of FIG. 3, the desiccant layer 10 includes a plurality of linear portions extending in a certain direction. The area ratio of the desiccant layer 10 when the desiccant layer 10 includes linear portions may be in the same range as the above-mentioned range exemplified for a single film. The linear portion may extend along any side of the rectangular or square main surface 3S. As shown in Fig. 3, the adjacent linear parts can be separated, or partly or wholly contacted. Generally, since each linear portion has a surface that is gently inclined with respect to the main surface 3S, even if adjacent linear portions are in contact, each linear portion can be distinguished. Regarding the width of each linear portion, for example, it may be 0.5 mm or more and 50 mm or less, or 1 mm or more and 10 mm or less. Here, "the width of the linear portion" is the width of the linear portion in the direction perpendicular to the longitudinal direction. The thickness of the linear portion may be 50 μm or more and 200 μm or less. The linear portion of the desiccant layer 10 does not necessarily need to extend linearly, and may include a curved portion. The linear portion may extend in a straight line or a curved line without crossing. For example, the linear portion may be curved or may extend in a spiral shape. Fig. 4 is a plan view showing an example of a desiccant layer having linear portions extending in a spiral shape. The spiral linear portion of the desiccant layer 10 shown in FIG. 4 is composed of a plurality of linear portions along each side of the main surface 3S.

Regarding the desiccant layer 10 having linear portions, since the surface area is large, it can exhibit a larger water absorption capacity than a single film. In addition, particularly, when the area of the main surface 3S is large, the desiccant layer 10 having linear portions is advantageous compared to the point that a single film can be easily formed.

The desiccant layer 10 contains, for example, oxide particles containing oxides of alkaline earth metals and a binder resin. The desiccant layer 10 can be formed, for example, by a method including coating the desiccant composition containing these on the main surface 3S of the sealing substrate.

The oxide particles in the desiccant layer 10 contain oxides of alkaline earth metals that can impart water absorption properties to the oxide particles. Taking the mass of the oxide particles as a reference, the oxide particles usually contain 80% by mass or more or 90% by mass or more of oxides of alkaline earth metals. The oxide particles can contain one kind or two or more kinds of oxides of alkaline earth metals with different components.

Examples of alkaline earth metal oxides include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO). The oxide of alkaline earth metal may be magnesium oxide, calcium oxide or a combination thereof.

Taking the mass of the desiccant layer as a reference, the content of oxide particles in the desiccant layer 10 may be 40 to 80% by mass. If the content of oxide particles is large, the water absorption capacity increases. Therefore, even when the desiccant layer 10 is formed in an air atmosphere, it is easy to maintain sufficient water absorption capacity. From the same viewpoint, the content of oxide particles may be 50% by mass or more, 55% by mass or more, or 60% by mass or more based on the mass of the desiccant layer.

The average particle diameter of the oxide particles is not particularly limited, but may be 0.01 to 30 μm, for example. If the average particle diameter of the oxide particles is in this range, higher water absorption 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, and may be 20 μm or less, 10 μm or less, or 5 μm or less. In this specification, the average particle size of oxide particles refers to the median value of the volume distribution measured by a dynamic light scattering particle size distribution meter. The average particle diameter is a value measured using a dispersion prepared by dispersing oxide particles in a predetermined dispersion medium.

The binder resin may include silicone resin, for example. The binder resin in the desiccant layer may include a cross-linked polymer formed of a polymerizable compound. The polymerizable compound may be modified silicone having (meth)acryloxy groups, for example. When the modified silicone is polymerized, the desiccant composition is hardened, and as a result, a desiccant layer is formed, which contains a cross-linked polymer as a silicone resin.

The modified polysiloxane having (meth)acryloxy groups is represented by the following formula (I), for example. In the formula (I), R ³ and R ⁴ each independently represent a divalent organic group, R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group, and x represents an integer of 1 or more. R ³ and R ⁴ may be alkylene groups.

The desiccant composition may also contain other polymerizable compounds capable of copolymerizing with the modified polysiloxane having (meth)acryloxy groups. The other polymerizable compound may be a (meth)acrylic compound having one or more (meth)acrylic groups. From the viewpoint of the effect of improving the stability of viscosity, the content of the modified silicone can be 80-100% by mass or 90-100% by mass relative to the total amount of the modified silicone and other polymerizable compounds.

With respect to the total mass of the desiccant composition, the total amount of the modified polysiloxane having (meth)acryloxy groups and other polymerizable compounds in the desiccant composition may be 20 to 90% by mass. If the content of the polymerizable compound is within this range, it tends to be easier to ensure more excellent coatability and water absorption performance. From the same point of view, relative to the total mass of the desiccant composition, the total amount of modified polysiloxane with (meth)acryloxy groups and other polymerizable compounds can be 20% by mass or more or 50% by mass % Or more, and may be 90% by mass or less or 70% by mass or less.

For light curing, the desiccant composition may further contain a photo radical polymerization initiator. As the photoradical polymerization initiator, for example, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) -1-butanone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-methyl-1[4-(methylthio)phenyl]-2-methyl Linopropane-1-one and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one. In the case where the desiccant composition contains the photoradical polymerization initiator, the content thereof can be, for example, 0.01 to 10% by mass relative to the mass of the polymerizable compound in the desiccant composition.

If necessary, the desiccant layer and the desiccant composition used to form it may also contain other ingredients. For example, for the purpose of adjusting the viscosity or improving the dispersibility of oxide particles, the desiccant layer and the desiccant composition may contain a polysiloxane compound that does not have a polymerizable group.

The desiccant composition can be pasty at 25°C. The viscosity of the desiccant composition at 25°C can range from 5 to 500 Pa•s. If the viscosity of the desiccant composition at 25° C. is within this range, the desiccant layer can be formed more easily by coating. The viscosity here is the value measured by a rotary viscometer such as a B-type viscometer or rheometer.

The element substrate 1 constituting the organic electroluminescence element 20 is not particularly limited, but is typically a glass substrate having insulating and translucent properties and having a rectangular main surface. The electrode 51 is formed on the element substrate 1 by a transparent conductive material ((for example, ITO (Indium Tin Oxide)). The electrode 51 is formed by, for example, the following method including: by a vacuum deposition method, A PVD (Physical Vapor Deposition) method such as a sputtering method, a step of forming an ITO film on the element substrate 1; and a step of forming an ITO film into a predetermined pattern shape by etching using a photoresist method. The electrode 51 can be led out to the outside of the airtight space 30, whereby the electrode 51 can be connected to the driving circuit.

The light emitting unit 7 has a pair of electrodes 51 and 52 arranged to face each other, and an organic layer 40 provided between the electrode 51 and the electrode 52. The electrode 51 may be an anode, and the electrode 52 may be a cathode. The organic layer 40 has a hole injection layer 41, a hole transport layer 42, a light emitting layer 43, and an electron transport layer 44, and these are laminated in order from the electrode 51 side.

The hole injection layer 41 is formed of copper phthalocyanine (CuPc) with a film thickness of several tens of nm, for example. The hole transport layer 42 is composed of, for example, bis[N-(1-naphthyl)-N-phenyl]benzidine (α -NPD) formation. The light-emitting layer 43 is formed of, for example, tris(8-quinolinolato)aluminum (Alq3) with a film thickness of several tens of nm. The electron transport layer 44 is formed of, for example, lithium fluoride (LiF) with a film thickness of several nm.

An electrode 52 is laminated on the upper surface of the organic layer 40. The electrode 52 may be a metal thin film formed by a PVD method such as a vacuum evaporation method. Examples of the material of the metal thin film include simple metal elements with small work functions such as Al, Li, Mg, and In, and alloys with small work functions such as Al-Li and Mg-Ag. The electrode 52 is formed, for example, with a film thickness of several tens to several 100 nm or 50 nm to 200 nm. The electrode 52 can be led out to the end of the element substrate 2 so that the electrode 52 can be connected to the driving circuit.

The sealing substrate 3 may be a glass substrate. The moisture in the atmosphere is relatively easy to adhere to the surface of the glass substrate. Therefore, in the case where the desiccant layer 10 is formed on the glass substrate as the sealing substrate 3 in an air atmosphere, it is advantageous to apply the method of controlling the area ratio of the desiccant layer 10 as in this embodiment.

The sealant 5 can be formed using a material generally used for sealing of organic electroluminescent devices. For example, the sealant 5 can be formed of ultraviolet curable resin.

The organic electroluminescence element 20 can be manufactured, for example, by a method including: a step of forming a desiccant layer 10 on the main surface 3S of the sealing substrate 3; a step of forming a light-emitting portion 7 on the element substrate 1; and, A step of disposing the sealing substrate 3 in a direction in which the main surface 3S faces the element substrate 1 to thereby form the organic electroluminescent element 20 including the element substrate 1, the light-emitting portion 7, the desiccant layer 10, and the sealing substrate 3.

The desiccant layer 10 may be formed on the main surface 3S in an atmospheric atmosphere. The "atmospheric atmosphere" mentioned in this manual can be an environment in which temperature and humidity are controlled by general air conditioning equipment. For example, the atmospheric atmosphere may be an atmosphere of 15-30°C and a relative humidity of 40-80%. In this case, the desiccant composition is applied on the main surface 3S of the sealing substrate 3 in an air atmosphere. Then, if necessary, the coating film of the desiccant composition is cured in the air atmosphere. The desiccant composition can be applied using a dispenser, for example.

The other steps can be performed according to the methods generally used in the manufacture of organic electroluminescent devices. The step of bonding the sealing substrate to the device substrate is usually carried out in a dehumidified and dry atmosphere.

>Examples> Hereinafter, the present invention will be explained in more detail with examples. However, the present invention is not limited to these Examples.

1. Desiccant composition Calcium oxide particles, liquid modified polysiloxane represented by formula (I), polysiloxane for viscosity adjustment (Dimethyl silicone), dispersant and photo-radical polymerization initiator are mixed . The obtained mixture was centrifuged and stirred at 1000 rpm for 5 minutes to obtain a white paste-like desiccant composition. Taking the mass of the desiccant composition as a reference, the content of calcium oxide particles in the desiccant composition is 60% by mass.

2. Manufacture and evaluation of organic electroluminescence devices (Example) By sputtering, an ITO film (with a thickness of 140 nm) was formed on the element substrate. The ITO film is patterned into a predetermined pattern shape by etching based on the photoresist method to form the anode. By the resistance heating method, a copper phthalocyanine (CuPc) film (with a thickness of 70μm) as a hole injection layer and a bis[N-(1-naphthyl) as a hole transport layer were sequentially formed on the upper surface of the anode. )-N-phenyl]benzidine (α-NPD) film (film thickness: 30 nm), and tris(8-quinolinolato) aluminum (Alq3) film (film thickness: 50 nm) as a light-emitting layer. Furthermore, by physical vapor deposition, a lithium fluoride (LiF) film (film thickness of 7 nm) as an electron transport layer and an aluminum film (film thickness of 150 nm) as a cathode were formed on the upper surface of the light-emitting layer.

As the sealing substrate, a glass substrate having recesses was prepared. The recessed part of the glass substrate is formed by the main surface of the glass substrate and the side wall part surrounding it. The main surface in the recess is a square of 18 mm×18 mm. Under an atmosphere of 25° C. and a relative humidity of 45%, the desiccant composition is applied in a line on the main surface of the recess by dispensing. Thereby, 12 linear coating films with a width of 1.4 mm and a length of 15 mm were formed. The coating film is cured by ultraviolet radiation, thereby forming a desiccant layer. The area ratio of the desiccant layer to the area of the main surface in the recess was 78%. Prepare a total of 4 sealing substrates with a desiccant layer formed by the same method, and place the sealing substrate immediately after the desiccant layer is formed, or after the desiccant layer is formed, in an environment at 25°C and a relative density of 45% The sealing substrate after being left for 1 hour, 2 hours or 3 hours was bonded to the element substrate.

In the glove box replaced with dry nitrogen, the sealing substrate and the device substrate on which the anode, the organic layer and the cathode were laminated were bonded with a sealant. The sealant is cured by ultraviolet irradiation and heating at 85°C for 1 hour. In this way, an organic electroluminescence element with a light-emitting part sealed in an airtight space is obtained.

(Comparative example) Except that six linear coating films having a width of 1.4 mm and a length of 10 mm were formed, an organic electroluminescence element for evaluation was produced in the same manner as in the examples. The area ratio of the desiccant layer to the area of the main surface in the recessed portion was 36%.

(Ratio of luminous area) The light-emitting area ratio (the area ratio of the area where light emission is observed to the area of the light-emitting portion) of each organic electroluminescence element was measured. FIG. 5 is a graph showing the relationship between the ratio of the light-emitting area of the organic electroluminescence element and the storage time of the sealing substrate. It has been confirmed that if the area ratio of the desiccant layer is 50% or more and less than 90%, even if the desiccant layer is formed in an air atmosphere, and then placed in an air atmosphere to a certain extent, it can maintain the state immediately after manufacturing. High luminous area ratio of electroluminescent elements.

According to one aspect of the present invention, it is possible to provide an organic electroluminescent device which can maintain a sufficient initial stage even when it is manufactured by a method including a step of forming a desiccant layer in an atmospheric atmosphere Luminous area ratio.

1.‧‧Component substrate 3‧‧‧Sealing substrate 3A‧‧‧Top plate of sealing substrate 3B‧‧‧Seal the side wall of the substrate 3S‧‧‧The main surface of the sealing substrate 5‧‧‧Sealant 7‧‧‧Lighting part 10‧‧‧Desiccant layer 20‧‧‧Organic electroluminescent element 30‧‧‧Airtight space 40‧‧‧Organic layer 41‧‧‧hole injection layer 42‧‧‧Hole Transmission Layer 43‧‧‧Light-emitting layer 44‧‧‧Electron Transport Layer 51、52‧‧‧electrode

Fig. 1 is a cross-sectional view showing an embodiment of an organic electroluminescence device. Fig. 2 is a plan view showing an embodiment of a sealing substrate and a desiccant layer. Fig. 3 is a plan view showing an embodiment of the sealing substrate and the desiccant layer. Fig. 4 is a plan view showing an embodiment of the sealing substrate and the desiccant layer. Fig. 5 is a graph showing the relationship between the light-emitting area ratio of the organic electroluminescence element and the storage time.

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1.‧‧Component substrate

3‧‧‧Sealing substrate

3A‧‧‧Top plate of sealing substrate

3B‧‧‧Seal the side wall of the substrate

3S‧‧‧The main surface of the sealing substrate

5‧‧‧Sealant

7‧‧‧Lighting part

10‧‧‧Desiccant layer

20‧‧‧Organic electroluminescent element

30‧‧‧Airtight space

40‧‧‧Organic layer

41‧‧‧hole injection layer

42‧‧‧Hole Transmission Layer

43‧‧‧Light-emitting layer

44‧‧‧Electron Transport Layer

51、52‧‧‧electrode

Claims (5)

An organic electroluminescence element, comprising: an element substrate; a light-emitting part, which is provided on the element substrate, and has a pair of electrodes arranged opposite to each other and an organic layer provided therebetween; and a sealing substrate having and The opposing main surface of the element substrate; a desiccant layer provided on the main surface; and, a sealant, which is interposed between the element substrate and the sealing substrate, whereby the element substrate and the sealing substrate are Bonding; wherein an airtight space surrounded by the element substrate, the sealing substrate, and the sealant is formed, and the light-emitting portion and the desiccant layer are arranged in the airtight space, and at a distance away from the main surface The area of the outer periphery is provided with the desiccant layer. When viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer relative to the area of the main surface in the airtight space is 50% or more. The layer includes linear portions. The organic electroluminescence device according to claim 1, wherein the desiccant layer contains oxide particles containing an oxide of alkaline earth metal and a binder resin, and the mass of the desiccant layer is used as a reference, the oxide particles The content is 40~80% by mass. A manufacturing method of an organic electroluminescence element, the method comprising: The step of forming a desiccant layer on the main surface of the sealing substrate; the step of forming a light-emitting portion on the element substrate, the light-emitting portion having a pair of electrodes arranged opposite to each other and an organic layer disposed between the two; and, as described above In the direction in which the main surface faces the element substrate, the step of bonding the sealing substrate to the element substrate by a sealant interposed between the element substrate and the sealing substrate, in which step, the element is formed An airtight space surrounded by the substrate, the sealing substrate, and the sealant, and the light-emitting part and the desiccant layer are arranged in the airtight space; and the desiccant layer is formed in an area away from the outer periphery of the main surface, from When viewed in a direction perpendicular to the main surface, the area ratio of the desiccant layer relative to the area of the main surface in the airtight space is 50% or more, and the desiccant layer includes linear portions. The method according to claim 3, wherein the desiccant layer is formed on the main surface of the sealing substrate in an atmosphere. The method according to claim 3 or 4, wherein the desiccant layer contains oxide particles containing oxides of alkaline earth metals and a binder resin, and the content of the oxide particles is based on the mass of the desiccant layer It is 40~80% by mass.

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