JP2020021558A - Organic EL device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element capable of maintaining a sufficient initial emission area ratio even when manufactured by a method including a step of forming a desiccant layer in an air atmosphere. An organic EL device (20) including a sealing substrate (3) having a main surface (3S) facing the element substrate (1) and a desiccant layer (10) provided on the main surface (3S) is disclosed. The desiccant layer 10 is provided in a region away from the outer periphery of the main surface 3S. When viewed from the direction perpendicular to the main surface 3S, the area ratio of the desiccant layer 10 is 50% or more with respect to the area of the main surface 3S. [Selection diagram] Fig. 3

Description

  The present invention relates to an organic EL device and a method for manufacturing the same.

  In order to prevent the light emitting life of the light emitting portion of the organic EL element from being shortened by moisture, the light emitting portion provided on the substrate is sealed by the sealing substrate, and a water catching material is further provided on the sealing substrate. (For example, Patent Document 1).

JP 2006-331766 A

  In manufacturing an organic EL device having a desiccant layer provided on a sealing substrate, it is necessary to form the desiccant layer on the sealing substrate under a dry atmosphere such as an inert gas in order to avoid mixing of moisture. there were. However, from the viewpoint of simplification of the process and equipment, it is desirable that the desiccant layer can be formed under an air atmosphere without requiring a dry atmosphere. By using a desiccant having a large water capturing capacity, it is expected that the desiccant layer can maintain a sufficient water capturing ability even if the desiccant layer is formed in an air atmosphere. However, even if a desiccant having a large water-capturing capacity is used, it is clear that if the desiccant layer is formed on the sealing substrate in the air atmosphere, the luminous area ratio of the organic EL element tends to be insufficient from the initial stage immediately after the production. became.

  Therefore, an object of one aspect of the present invention is to provide an organic EL element capable of maintaining a sufficient initial light emitting area ratio even when manufactured by a method including a step of forming a desiccant layer in an air atmosphere. Is to do.

  One aspect of the present invention includes an element substrate, a light emitting portion provided on the element substrate, a sealing substrate having a main surface facing the element substrate, and a desiccant layer provided on the main surface. The present invention relates to an organic EL element provided.

  Another aspect of the present invention relates to a method for manufacturing the organic EL device. The method includes a step of forming a desiccant layer on a main surface of a sealing substrate, a step of forming a light emitting portion on an element substrate, and a step of forming the sealing substrate in a direction in which the main surface faces the element substrate. Bonding to the element substrate. The sealing substrate is bonded to the element substrate by a sealant interposed 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 unit and the desiccant layer are arranged in the airtight space.

  The light emitting section has a pair of electrodes arranged to face each other and an organic layer provided between them. The desiccant layer is provided in a region away from the outer periphery of the main surface, and when viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer is 50% of the area of the main surface. That is all.

  When the area ratio of the desiccant layer is 50% or more, the organic EL element can easily maintain a sufficient initial light emitting area ratio even when the desiccant layer is formed in an air atmosphere. Further, since the desiccant layer is provided in a region away from the outer periphery of the main surface of the sealing substrate, the sealing substrate is easily fixed to the element substrate.

  According to one aspect of the present invention, there is provided an organic EL element capable of maintaining a sufficient initial light emitting area ratio even when manufactured by a method including a step of forming a desiccant layer in an air atmosphere. .

FIG. 2 is a cross-sectional view illustrating one embodiment of an organic EL element. It is a top view which shows one Embodiment of a sealing substrate and a desiccant layer. It is a top view which shows one Embodiment of a sealing substrate and a desiccant layer. It is a top view which shows one Embodiment of a sealing substrate and a desiccant layer. 5 is a graph showing a relationship between a light emitting area ratio of an organic EL element and a standing time.

  Hereinafter, some 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 sectional view showing an embodiment of the organic EL device. The organic EL element 20 shown in FIG. 1 includes an element substrate 1, a light emitting unit 7 provided on the element substrate 1, a sealing substrate 3, a desiccant layer 10, and a sealant 5.

  The sealing substrate 3 has a top plate 3A having a flat rectangular or square main surface 3S facing the element substrate 1, and a side wall extending from the outer peripheral end of the top plate 3A in a direction perpendicular to the main surface 3S. 3B. The top plate 3A and the side wall 3B form a recess 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 sealing agent 5 adheres the sealing substrate 3 and the element substrate 1 while interposing between the side wall 3B of the sealing substrate 3 and the element substrate 1. As a result, 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-like body having no side wall portion 3B. In this case, the sealing agent 5 is usually provided between the top plate portion 3A of the sealing substrate 3 and the element substrate 1. Intervenes. In any case, the “main surface facing the element substrate” means a surface facing the element substrate in an airtight space in which the light emitting unit is arranged.

  FIG. 2 is a plan view showing one embodiment of the sealing substrate and the desiccant layer. The plan view of FIG. 2 shows a form in which the sealing substrate 3 and the desiccant layer 10 are 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 a region separated from the outer periphery of the main surface 3 </ b> S of the sealing substrate 3 to the inside thereof. In the plan view of FIG. 2, the area ratio of the desiccant layer 10 is 50% or more with respect to the area of the main surface 3S. This area ratio may be 60% or more, 70% or more, or 75% or more. It is considered that when the area ratio of the desiccant layer 10 increases, the moisture attached to the main surface 3S of the sealing substrate 3 in the air atmosphere hardly affects the light emitting unit 7. When the area ratio is 50% or more, even after the desiccant layer is formed, the sealing substrate is left in the air atmosphere, for example, for 3 hours or more, and has a sufficiently large light emitting area ratio of 98% or more. An organic EL element is easily obtained. 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 desiccant layer 10 may be a single film as shown in FIG. 2 or may include a linear portion as shown in FIG. In the case of the embodiment of FIG. 3, the desiccant layer 10 includes a plurality of linear portions extending along a certain direction. The linear portion may extend along any side of the rectangular or square main surface 3S. Adjacent linear portions may be separated as shown in FIG. 3, or may be partially or wholly in contact. Normally, each linear portion has a surface that is gently inclined with respect to the main surface 3S. Therefore, even when adjacent linear portions are in contact with each other, each linear portion can be distinguished. The width of each linear portion may be, for example, 0.5 mm or more and 50 mm or less, or 1 mm or more and 10 mm or less. The “width of the linear portion” here is a width in a direction perpendicular to the longitudinal direction of the linear portion. 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 portions may extend linearly or curvedly without intersecting. For example, the linear portion may meander, or may extend spirally. FIG. 4 is a plan view showing an example of a desiccant layer having a spirally extending linear portion. 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.

  Since the desiccant layer 10 having a linear portion has a large surface area, the desiccant layer 10 can exhibit a greater water-trapping ability than a single membrane. The desiccant layer 10 having a linear portion is also advantageous in that it can be formed more easily than a single film, particularly when the area of the main surface 3S is large.

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

  The oxide particles in the desiccant layer 10 include an oxide of an alkaline earth metal that can impart water-capturing performance to the oxide particles. The oxide particles usually contain at least 80% by mass or 90% by mass or more of an alkaline earth metal oxide based on the mass of the oxide particles. The oxide particles may include one or two or more alkaline earth metal oxides having different components.

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

  The content of the oxide particles in the desiccant layer 10 may be 40 to 80% by mass based on the mass of the desiccant layer. When the content of the oxide particles is large, the water capturing capacity increases, so that even when the desiccant layer 10 is formed in the air atmosphere, a sufficient water capturing capacity is easily maintained. From the same viewpoint, the content of the oxide particles may be 50% by mass or more, 55% by mass or more, or 60% by mass or more.

  The average particle size of the oxide particles is not particularly limited, but may be, for example, 0.01 to 30 μm. When the average particle size of the oxide particles is in this range, higher water-trapping 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 the present specification, the average particle size of the oxide particles means a median value of a volume distribution measured by a dynamic light scattering type particle size distribution meter. The average particle size is a value measured using a dispersion prepared by dispersing oxide particles in a predetermined dispersion medium.

  The binder resin may include, for example, a silicone resin. The binder resin in the desiccant layer may include a crosslinked polymer formed from a polymerizable compound. The polymerizable compound may be, for example, a modified silicone having a (meth) acryloyloxy group. When the modified silicone is polymerized, the desiccant composition is cured, and as a result, a desiccant layer containing a crosslinked polymer which is a silicone resin is formed.

The modified silicone having a (meth) acryloyloxy group is represented, for example, by the following formula (I). In 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 an alkylene group.

  The desiccant composition may further contain another polymerizable compound copolymerizable with the modified silicone having a (meth) acryloyloxy group. The other polymerizable compound may be a (meth) acryl compound having one or two or more (meth) acryloyl groups. From the viewpoint of the effect of improving the stability of viscosity, the content of the modified silicone may be 80 to 100% by mass, or 90 to 100% by mass based on the total amount of the modified silicone and other polymerizable compounds. .

  The total amount of the modified silicone having a (meth) acryloyloxy group and other polymerizable compounds in the desiccant composition may be 20 to 90% by mass based on the total mass of the desiccant composition. When the content of the polymerizable compound is in this range, there is a tendency that more excellent coating properties and water-capturing performance are easily ensured. From the same viewpoint, the total amount of the modified silicone having a (meth) acryloyloxy group and the other polymerizable compound may be 20% by mass or more or 50% by mass or more, and 90% by mass or less or 70% by mass or less. It may be.

  The desiccant composition may further contain a photoradical polymerization initiator for photocuring. Examples of the photoradical polymerization initiator include 1-hydroxy-cyclohexyl-phenyl-ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, and 2,2-dimethoxy-1 , 2-Diphenylethan-1-one, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]- 2-hydroxy-2-methyl-1-propan-1-one is exemplified. When the desiccant composition contains a photoradical polymerization initiator, the content may be, for example, 0.01 to 10% by mass based on the mass of the polymerizable compound in the desiccant composition.

  The desiccant layer and the desiccant composition for forming the desiccant layer may further contain other components as necessary. For example, the desiccant layer and the desiccant composition may contain a silicone compound having no polymerizable group for the purpose of adjusting viscosity or improving dispersibility of oxide particles.

  The desiccant composition can be in the form of a paste at 25 ° C. The viscosity at 25 ° C. of the desiccant composition may be 5 to 500 Pa · s. When the viscosity at 25 ° C. of the desiccant composition is in this range, the desiccant layer can be more easily formed by coating. The viscosity here is a value measured by a rotational viscometer such as a B-type viscometer or a rheometer.

  The element substrate 1 constituting the organic EL element 20 is not particularly limited, but is typically a glass substrate having an insulating property and a light-transmitting property and having a rectangular main surface. An 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, forming an ITO film on the element substrate 1 by a PVD (Physical Vapor Deposition) method such as a vacuum evaporation method and a sputtering method, and patterning the ITO film into a predetermined pattern shape by etching using a photoresist method. And forming the same. The electrode 51 may be extended to the outside of the airtight space 30, and the electrode 51 may be connected to a driving circuit.

  The light emitting section 7 includes a pair of electrodes 51 and 52 disposed to face each other, and an organic layer 40 provided between the electrodes 51 and 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, which are stacked in this order from the electrode 51 side.

The hole injection layer 41 is formed of, for example, copper phthalocyanine (CuPc) having a thickness of several tens nm. The hole transport layer 42 is formed of, for example, bis [N- (1-naphthyl) -N-phenyl] benzidine (α-NPD) having a thickness of several tens nm. The light emitting layer 43 is formed of, for example, tris (8-quinolinolato) aluminum (Alq ₃ ) having a thickness of several tens nm. The electron transport layer 44 is formed of, for example, lithium fluoride (LiF) having a thickness of several nm.

  The 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. As the material of the metal thin film, for example, a simple metal having a small work function such as Al, Li, Mg, and In, and an alloy having a small work function such as Al-Li and Mg-Ag are exemplified. The electrode 52 is formed to have a thickness of, for example, several tens nm to several hundreds nm, or 50 nm to 200 nm. The electrode 52 may be extended to the end of the element substrate 2, and the electrode 52 may be connected to a drive circuit.

  The sealing substrate 3 may be a glass substrate. Atmospheric moisture is relatively easy to adhere to the surface of the glass substrate. Therefore, when the desiccant layer 10 is formed on a glass substrate as the sealing substrate 3 in an air atmosphere, there is a great advantage in applying the method of controlling the area ratio of the desiccant layer 10 as in the present embodiment. .

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

  The organic EL element 20 includes, for example, a step of forming a desiccant layer 10 on the main surface 3S of the sealing substrate 3, a step of forming the light emitting unit 7 on the element substrate 1, and Is disposed in a direction facing the element substrate 1, thereby forming an organic EL element 20 including the element substrate 1, the light-emitting portion 7, the desiccant layer 10, and the sealing substrate 3. Can be.

  The desiccant layer 10 may be formed on the main surface 3S under an air atmosphere. The “atmosphere” referred to in this specification may be an environment in which the temperature and humidity are controlled by ordinary air conditioning equipment. For example, the atmosphere may be an atmosphere of 15 to 30 ° C. and a relative humidity of 40 to 80%. In this case, the desiccant composition is applied to the main surface 3S of the sealing substrate 3 in an air atmosphere. Thereafter, the coating of the desiccant composition is cured, if necessary, in an air atmosphere. The desiccant composition can be applied using, for example, a dispenser.

  Other steps can be performed according to a method usually employed in the manufacture of an organic EL device. The step of bonding the sealing substrate to the element substrate is usually performed in a dehumidified dry atmosphere.

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

1. Desiccant Composition The calcium oxide particles, the liquid modified silicone represented by the formula (I), the viscosity adjusting silicone (dimethyl silicone), the dispersant, and the photo-radical polymerization initiator are mixed, and the mixture is mixed at a rate of 1,000 rpm for 5 minutes. The mixture was centrifuged for minutes to obtain a desiccant composition in the form of a white paste. The content of the calcium oxide particles in the desiccant composition is 60% by mass based on the mass of the desiccant composition.

2. Fabrication of organic EL device and its evaluation (Example)
An ITO film (140 nm thick) was formed on the element substrate by a sputtering method, and this was patterned into a predetermined pattern by etching by a photoresist method, thereby forming an anode. A copper phthalocyanine (CuPc) film (thickness: 70 μm) as a hole injection layer and Bis [N- (1-naphthyl) -N-phenyl] benzidine (α-) as a hole transport layer are formed on the upper surface of the anode by resistance heating. A film (thickness: 30 nm) of NPD) and a film (thickness: 50 nm) of tris (8-quinolinolato) aluminum (Alq3) as a light emitting layer were sequentially formed. Further, a lithium fluoride (LiF) film (thickness: 7 nm) as an electron transport layer and an aluminum film (thickness: 150 nm) as a cathode were formed on the upper surface of the light emitting layer by physical vapor deposition with a thickness of 7 nm.

A glass substrate having a concave portion was prepared as a sealing substrate. The concave portion of the glass substrate is formed by the main surface of the glass substrate and the side wall surrounding the main surface. The main surface in the recess is a square of 18 mm × 18 mm. The desiccant composition was linearly applied to the main surface in the concave portion by dispensing under an atmosphere of 25 ° C. and a relative humidity of 45%. As a result, 12 linear coating films having a width of 1.4 mm and a length of 15 mm were formed. The desiccant layer was formed by curing the coating by ultraviolet irradiation. The area ratio of the desiccant layer to the area of the main surface in the recess was 78%.
A total of four sealing substrates on which a desiccant layer is formed are prepared in the same manner, and the sealing substrate immediately after the desiccant layer is formed, or the desiccant layer is formed, and then at 25 ° C. and a relative density of 45% The sealing substrate left for 1 hour, 2 hours, or 3 hours in the above environment was bonded to the element substrate by the following procedure.

  The sealing substrate and the element substrate on which the anode, the organic layer, and the cathode were stacked were bonded via a sealant in a glove box replaced with dry nitrogen. The sealant was cured by ultraviolet irradiation and heating at 85 ° C. for 1 hour. As a result, an organic EL device in which the light emitting portion was sealed in the airtight space was obtained.

(Comparative example)
An organic EL device for evaluation was produced in the same manner as in Example except that six linear coating films having a width of 1.4 mm and a length of 10 mm were formed. The area ratio of the desiccant layer to the area of the main surface in the recess was 36%.

(Emission area ratio)
The light emission area ratio (area ratio of the portion where light emission was observed to the area of the light emitting portion) of each organic EL element was measured. FIG. 5 is a graph showing a relationship between a light emitting area ratio of the organic EL element and a leaving time of the sealing substrate. When 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 left to some extent in an air atmosphere, the organic EL element immediately after manufacturing has a high level. It was confirmed that the emission area ratio was maintained.

  DESCRIPTION OF SYMBOLS 1 ... Element substrate, 3 ... Sealing substrate, 3A ... Top plate part of sealing substrate, 3B ... Side wall part of sealing substrate, 3S ... Main surface of sealing substrate, 5 ... Sealing agent, 7 ... Light emitting part, 10 ... desiccant layer, 20 ... organic EL element, 30 ... airtight space, 40 ... organic layer, 51, 52 ... electrode.

Claims (7)

An element substrate,
A light-emitting portion, which is provided on the element substrate and has a pair of electrodes arranged opposite to each other and an organic layer provided therebetween.
A sealing substrate having a main surface facing the element substrate,
A desiccant layer provided on the main surface,
A sealant interposed between the element substrate and the sealing substrate, thereby bonding the element substrate and the sealing substrate,
With
An airtight space surrounded by the element substrate, the sealing substrate, and the sealant is formed, and the light emitting unit and the desiccant layer are arranged in the airtight space,
The desiccant layer is provided in a region separated from the outer periphery of the main surface, and when viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer is the main surface in the hermetic space. 50% or more of the area of the organic EL device.   The organic EL device according to claim 1, wherein the desiccant layer includes a linear portion. The desiccant layer contains oxide particles containing an oxide of an alkaline earth metal, and a binder resin,
3. The organic EL device according to claim 1, wherein the content of the oxide particles is 40 to 80% by mass based on the mass of the desiccant layer. 4. Forming a desiccant layer on the main surface of the sealing substrate,
Forming a light-emitting portion having a pair of electrodes disposed opposite to each other and an organic layer provided therebetween, on the element substrate;
A step of bonding the sealing substrate to the element substrate with a sealing agent interposed between the element substrate and the sealing substrate in a direction in which the main surface faces the element substrate; Forming an airtight space surrounded by the sealing substrate and the sealant, wherein the light emitting unit and the desiccant layer are disposed in the airtight space,
With
The desiccant layer is formed in a region away from the outer periphery of the main surface, and when viewed from a direction perpendicular to the main surface, the area ratio of the desiccant layer is the area of the main surface in the hermetic space. 50% or more,
A method for manufacturing an organic EL device.   5. The method according to claim 4, wherein the desiccant layer comprises a linear portion.   The method according to claim 4, wherein the desiccant layer is formed on a main surface of the sealing substrate under an air atmosphere. The desiccant layer contains oxide particles containing an oxide of an alkaline earth metal, and a binder resin,
The content of the oxide particles is 40 to 80% by mass based on the mass of the desiccant layer,
A method according to any one of claims 4 to 6.

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