JP2007335105A - Light-emitting element, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element with small distortion occurring at the interface with an organic material layer and a second conductive layer arranged on it, in which thickness of the light-emitting layer is maintained uniformly and loss of conductivity of the second conductive layer can be suppressed. <P>SOLUTION: The manufacturing method of a light-emitting element comprises a process in which a first jointing material is fabricated by forming a first conductive layer and an organic material layer in the order on a transparent first base material of flat-plate shape, a process in which a second jointing member is fabricated by coating a conductive paste so as to cover the inner face of a recessed part and a part of the peripheral part of the recessed part aperture on a second base material of a cap-shape which has the recessed part and in which at least the inner face has insulation property, a process in which the first jointing member and the second jointing member are superposed so that the recessed part may envelope the organic material layer, and a process in which heat treatment is applied on each jointing member superposed to cure the conductive paste, and by electrically connecting to the organic material layer, a light-emitting element is obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting device using organic electroluminescence, and more particularly to a light emitting device having excellent stability of light emitting characteristics and a manufacturing method capable of suppressing thermal or mechanical influence on the light emitting device in the manufacturing process. .

An organic electroluminescence element (hereinafter referred to as an organic EL element) is formed by laminating a first electrode (anode), an organic material layer, and a second electrode layer (cathode) in this order on the surface of a transparent glass or transparent substrate. It has the basic composition made.
Usually, the first electrode layer is made of a transparent conductive material typified by ITO (tin-added indium). The organic material layer is composed of at least a light emitting layer of an organic material, and if necessary, a hole injection layer or a hole transport layer is provided between the first conductive layer (anode) and the light emitting layer. The electron transport layer and the electron injection hole are provided between the light emitting layer and the second conductive layer (cathode), respectively. At that time, as the second conductive layer, a metal material such as magnesium (Mg), silver (Ag), aluminum (Al) or an alloy material mainly composed of these metals is preferably used.

In order to achieve the above-described configuration, two typical manufacturing methods described below are known.
The first manufacturing method is a method in which an organic material layer is formed on a first conductive layer, and then a second conductive layer is formed on the organic material layer. In that case, the metal film which comprises a 2nd conductive layer is the method of forming an organic EL element by forming by physical film-forming methods, such as a vapor deposition method and a sputtering method (for example, refer patent document 1).

In the second manufacturing method, a first substrate in which a first electrode layer and a hole transport layer are sequentially laminated on a first substrate, and a second conductive layer and a light emitting layer are sequentially laminated on the second substrate. A second substrate is prepared, and the two substrates are stacked so that the light emitting layer and the hole transport layer are in contact with each other, and bonded together by pressure bonding at a temperature at which the light emitting layer or the hole transport layer is softened. This is a method for producing an organic EL element (for example, see Patent Document 2).
JP 2003-45674 A Japanese Patent No. 2755216

However, the first manufacturing method uses a process in which particles collide and deposit on the organic material layer with high energy as the second conductive layer is formed, so that the organic material layer including the light emitting layer is damaged. And the organic material layer is thermally or mechanically destroyed, and as a result, the light emission quality of the organic EL element may be significantly reduced.
Further, when the second conductive layer is formed on the organic material layer by a physical film formation method, the internal stress tends to remain at the interface between the two because the properties of the materials are different. Therefore, depending on the thermal history that the organic EL element subsequently receives, distortion due to the interface occurs, and this distortion may adversely affect the light emission quality of the organic EL element.

  Further, in the second production method, in the formation of the second conductive layer, it is necessary to heat and pressure-bond the organic material layer to a temperature at which the organic material layer is softened. The thickness will be biased. Therefore, there is a possibility that the light emission characteristics that are uniformly excellent in the organic EL element are remarkably deteriorated.

  In addition, since a material capable of efficiently injecting electrons into an organic material is desirable for the cathode of the organic EL element, an alloy material containing a metal having a low work function and high activity as described above is preferably used. However, these alloy materials have the property that when exposed to oxygen, they are oxidized and their conductivity is easily impaired. Therefore, a cathode made of such an alloy material is affected by oxidation, and its conductivity is lost, the luminance of the light emitting element is lowered, or the cathode layer and the organic material layer are partially separated. As a result, a non-light emitting portion may occur in the light emitting element.

  The present invention has been made in view of the above circumstances, the strain generated at the interface between the organic material layer and the second conductive layer disposed thereon is small, the thickness of the light emitting layer is kept uniform, and the second conductive layer An object of the present invention is to provide a light-emitting element capable of suppressing the loss of conductivity of the.

  In order to achieve the above object, the present invention provides a flat transparent first base material, a first conductive layer provided on the first base material, and an organic material layer provided on the first conductive layer. A cap-shaped second base material having a concave portion, and at least the inner surface of the concave portion is insulative, and the inner surface of the concave portion and the peripheral edge of the concave portion of the second base material. And a second bonding member composed of a second conductive layer provided so as to cover the portion, and the first bonding member and the second bonding member are overlapped so that the concave portion wraps the organic material layer The light-emitting element is characterized in that the second conductive layer is made of a conductor obtained by curing a conductive paste.

  The present invention also includes a step of forming a first joining member by sequentially forming a first conductive layer and an organic material layer on a flat transparent first base material, having a recess, and at least the inner surface of the recess A step of applying a conductive paste to the cap-shaped second base material having an insulating property so as to cover a part of the inner surface of the concave portion and the peripheral edge of the concave portion, thereby producing a second bonding member, the concave portion Wrapping the first bonding member and the second bonding member so as to wrap the organic material layer, and applying heat treatment to the stacked bonding members to cure the conductive paste, thereby the organic material There is provided a method for manufacturing a light-emitting element, including a step of electrically connecting a layer to obtain a light-emitting element.

The light-emitting element of the present invention includes a first bonding member having an organic material layer, a second bonding member having a second electrode layer in the recess, and the first bonding member so that the recess wraps the organic material layer. The second bonding member is overlaid and has a second conductive layer made of a conductive material obtained by curing the conductive paste, so that the first bonding member and the second bonding are in an uncured state of the conductive paste. By superimposing the members, the conductive paste is sufficiently adhered to the outer surface of the organic material layer, and then the conductive paste is cured, so that the organic material layer and the first layer are not damaged without damaging the organic material layer. A light-emitting element in which the two electrode layers can be electrically connected and the organic material layer has a uniform thickness can be provided.
In addition, the electrical and mechanical bonding characteristics of the interface between the organic material layer and the second electrode layer are improved, and a light emitting element having excellent characteristics such as luminous efficiency and lifetime can be provided.

The method for manufacturing a light-emitting element of the present invention includes a first bonding member having an organic material layer and a second bonding member in which a conductive paste serving as a second electrode layer is applied in the recess, and the recess has the organic material layer. Since the first bonding member and the second bonding member are overlapped so as to wrap, and then the conductive paste is cured to form the second conductive layer, the first bonding member is in an uncured state. And the second bonding member are superposed on each other so that the conductive paste is sufficiently adhered to the outer surface of the organic material layer, and then the conductive paste is cured without damaging the organic material layer. A light-emitting element in which the organic material layer and the second electrode layer can be electrically connected and the thickness of the organic material layer is uniform can be manufactured with high yield.
In addition, the electrical and mechanical joining characteristics of the interface between the organic material layer and the second electrode layer are improved, and a light emitting element having excellent characteristics such as luminous efficiency and lifetime can be manufactured.

Hereinafter, as an embodiment of the present invention, a case where an organic material layer constituting a light emitting element functions as an organic EL element will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a process of superimposing the first joining member and the second joining member in the method for producing a light-emitting element of the present invention, and FIG. 2 is a schematic view showing an example of the light-emitting element of the present invention. FIG. In these drawings, reference numeral 1 is an organic material layer, 2 is a first substrate, 3 is a first conductive layer, 4 is a conductive paste, 5 is a second substrate, 6 is a first bonding member, and 7 is a second member. A joining member, 8 is an insulating layer, 9 is a second conductive layer, and 10 is a light emitting element.

  The light-emitting element 10 (organic EL element) shown in FIG. 2 includes a flat plate-like transparent first base material 2, a first conductive layer 3 (anode) provided on the first base material 2, and the first A first joining member 6 comprising an organic material layer 1 provided on the conductive layer 3; a cap-shaped second base material 5 having a recess; a bottom surface and side surfaces in the recess of the second base material 5; A second bonding member 7 comprising an insulating layer 8 provided so as to cover a part of the peripheral edge of the recess opening, and a second conductive layer 9 (cathode) provided so as to cover a part of the insulating layer 8. And the second conductive layer 9 is made of a conductor obtained by curing the conductive paste 4 so that the concave portion wraps the organic material layer 1. It is characterized by becoming.

  As the first base material 2, a plate-like transparent glass or resin substrate (hereinafter referred to as “glass substrate” or “resin substrate”, respectively) can be used. Examples of the glass substrate include quartz glass, BK7, and soda lime glass. Examples of the resin substrate include polycarbonate, polyimide, polyethylene terephthalate, and the like. The first joining member 6 has a structure in which a first conductive layer 3 and an organic material layer 1 are sequentially laminated on the first base material 2.

In addition, when a resin substrate is used as the first base material 2, since the resin substrate transmits moisture, one surface of the first base material 2 is interposed between the first base material 2 and the first conductive layer 3. It is necessary to provide a gas barrier layer so as to cover all of the above. As this gas barrier layer, for example, in addition to metals such as Au, Ag, Cu, Al, and Pt, or alloys thereof, oxides and nitrides such as SiO ₂ and Si ₃ N ₄ can be used. Further, the gas barrier layer is required to have a high transmittance for light emitted from the organic material layer 24 to the outside (hereinafter also referred to as “light emission”). The light transmittance is desirably 85% or more.

A method for forming such a gas barrier layer is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, a screen printing method, and a slit coating method. When a conductive material such as a metal is used for the gas barrier layer, it is necessary to provide an insulating layer between the gas barrier layer and the first conductive layer 3, so it is desirable to use an insulating material such as SiO ₂ or Si ₃ N _4. .

  The first conductive layer 3 is made of a material having high conductivity and high permeability, and generally, a plurality of first conductive layers 3 are provided on the first base material 2 so as to be separated from each other. Examples of the first conductive layer 3 include tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), and aluminum-doped zinc oxide (AZO). Materials can be used.

  A method for forming the first conductive layer 3 is not particularly limited, and for example, a sputtering method, an inkjet method, a spin coating method, or the like can be used. In the ink jet method and the spin coating method, a transparent conductive layer (anode) can be formed by dispersing fine particles of the first conductive material in a binder and heating and degreasing after coating. For example, when forming an ITO film, an ethanol solution of indium chloride and tin chloride may be applied and heated. At that time, the thickness of the first conductive layer 3 is preferably about 50 nm to 400 nm.

The organic material layer 1 is disposed so as to partially overlap with one of the plurality of first conductive layers 3 arranged, and includes at least a light emitting layer made of an organic material. Moreover, the organic material layer 1 includes a functional layer such as an electron injection layer, an electron transport layer, a hole transport layer, and a hole injection layer above and below the light emitting layer as necessary. Is done.
Therefore, the organic material layer 1 has a structure in which a hole transport layer, a light-emitting layer, and an electron transport layer are sequentially arranged on the first conductive layer 3, or on the first conductive layer 3. A hole injection layer, a hole transport layer, and a light emitting layer may be arranged in this order. This makes it possible to design and control various characteristics of the light emitting element, such as improving the light emission efficiency of the light emitting element and controlling the emission wavelength.

  A method for forming each layer of the organic material layer 1 is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, an ink jet method, a gravure printing method, a slit coating method, and a transfer method. In that case, if the inkjet method is used, the utilization efficiency of the material is high, and an expensive vacuum process is unnecessary, which is industrially advantageous.

  In the present invention, the uncured conductive paste 4 is adhered to the surface of the organic material layer 1 and then the conductive paste 4 is cured to form the second conductive layer 9. The surface may be flat or an uneven surface. As described above, according to the present invention, the influence of the surface roughness of the organic material layer 1 can be alleviated, and the generation of dark spots due to poor electrical connection between the organic material layer 1 and the second conductive layer 9 can be prevented. It can be greatly reduced.

  On the other hand, the second base member 5 of the second bonding member 7 is preferably a member having a cap shape with a recess, strong against corrosion, and excellent in gas barrier properties. For example, a can body made of stainless steel or glass ( Sealing cans) can be used. However, the 2nd base material 5 is not limited to this, For example, you may use a flexible sheet | seat body and a thin body (a film | membrane is also included).

  When the 2nd base material 5 is comprised with members which have electroconductivity, such as stainless steel, the form with which the 2nd base material 5 and the 2nd conductive layer 9 are electrically insulated is desirable. In that case, for example, a method of electrically insulating by forming an oxide or nitride such as Al, Si, Ti or the like as the insulating layer 8 on one surface of the second substrate 5 is suitable.

  The insulating layer 8 is disposed so as to cover all the bottom and side surfaces in the recess of the second base material 5 and the peripheral edge of the recess opening. Examples of the method for forming the insulating layer 8 made of oxide or nitride include an aerosol deposition method, a sputtering method, a CVD method, and the like. Further, the thickness of the insulating layer 8 is not limited as long as sufficient insulation can be ensured, but is desirably in the range of 10 to 1000 nm in order to reduce the thickness of the entire device.

Further, a hygroscopic material can be used as a member constituting the insulating layer 8. As specific materials, for example, oxides of alkaline earth metals such as Ca, Sr, Ba, Ra, Be, and Mg, and organometallic compounds such as aluminum oxide octylate can be used. As a method for forming such an alkaline earth metal oxide film, for example, a sputtering method or an electron beam evaporation method using an oxide as a target can be used. In addition, as a method of forming an organic metal compound such as aluminum oxide octylate, for example, a method of printing a solution in which an organic metal compound is dissolved in an organic solvent such as toluene or xylene can be used. The hygroscopic layer described above may be separately laminated as an intermediate layer in addition to the same form as the insulating layer 8.
Therefore, the second bonding member 7 may have a structure in which the insulating layer 8, the intermediate layer (not shown), and the second conductive layer 9 are sequentially laminated on one surface of the second base material 5.

  The second conductive layer 9 is disposed so as to cover a part of the insulating layer 8. Here, “part” means a partial region of the insulating layer 8 covering the entire upper surface of the insulating layer 8 covering the bottom surface of the recess and the inner surface of the recess and the peripheral edge of the recess opening, which is continuous from the upper surface. To do.

In the light emitting device of the present invention, the second conductive layer 9 is made of a material obtained by curing the conductive paste 4.
As the conductive paste 4 used for forming the second conductive layer 9, for example, an Ag paste, a Cu paste, a carbon-containing paste, or the like is used, and among these, an Ag paste is preferable. In the uncured state, this Ag paste has sufficient fluidity to apply the paste to the substrate surface, while the Ag paste applied to the substrate surface can be cured by heat treatment at a low temperature. It is desirable to have sufficient conductivity after curing, and examples include commercially available products such as silver paste and dotite. The method for applying the conductive paste to a part of the insulating layer 8 is not particularly limited, and examples thereof include screen printing, spin coating, and inkjet method.

  The thickness of the second conductive layer 9 is desirably about 50 nm to 400 nm. If the thickness of the second conductive layer 9 is less than the above range, it is not preferable because the possibility that the conductive layer is short-circuited is high, and if the thickness of the second conductive layer 9 exceeds the above range, coating becomes difficult. This is not preferable because the cost increases.

The light emitting device of the present invention includes a first bonding member 6 having the organic material layer 1 and a second bonding member 7 having the second electrode layer 4 in the recess, and the first so that the recess wraps the organic material layer 1. Since the joining member 6 and the second joining member 7 are overlapped and have the second conductive layer 9 made of a conductor obtained by curing the conductive paste, the first joining member is in an uncured state. The conductive paste 4 is sufficiently adhered to the outer surface of the organic material layer 1 by superimposing the second bonding member 7 and the second bonding member 7, and then the conductive paste 4 is cured to thereby cure the organic material layer 1. The organic material layer 1 and the second electrode layer 4 can be electrically connected without causing damage to the light-emitting element, and a light-emitting element having a uniform film thickness of the organic material layer 1 can be provided.
In addition, the electrical and mechanical joining characteristics of the interface between the organic material layer 1 and the second electrode layer 4 are improved, and a light emitting element having excellent characteristics such as luminous efficiency and lifetime can be provided.

  In the method for producing a light-emitting element of the present invention, first, a first bonding member 6 is produced by sequentially forming a first conductive layer 3 and an organic material layer 1 on a flat transparent first substrate 2. The conductive paste 4 is applied to the cap-shaped second base material 5 having a process and a recess, and at least the inner surface of the recess has an insulating property so as to cover a part of the inner surface of the recess and the peripheral edge of the recess. The process of apply | coating and producing the 2nd joining member 7 is performed. The process of manufacturing the first bonding member 6 and the second bonding member 7 can be performed by using the materials and manufacturing methods described for each component described above.

Next, as shown in FIG. 1, a step of overlapping the first bonding member 6 and the second bonding member 7 so that the concave portion of the second bonding member 7 wraps the organic material layer 1 of the first bonding member 6. Do.
The conductive paste 4 applied to the inner surface of the concave portion of the second bonding member 7 flows so as to wrap around the organic material layer 1 of the first bonding member 6 according to the pressure of the second bonding member 7, and the surface of the organic material layer 1 Adhere to. In addition, the conductive paste 4 applied to a part of the peripheral edge of the recess opening of the second bonding member 7 is bonded to a cathode-side wiring (not shown) on the first substrate 2.

  Next, a process of obtaining a light-emitting element 10 is performed by performing heat treatment on the overlapped bonding members to cure the conductive paste 4 to be electrically connected to the organic material layer 1. The temperature of this heat treatment is a temperature at which the conductive paste 4 to be used is cured, and is preferably as low as possible.

In this method of manufacturing an optical element, a first bonding member 6 having an organic material layer 1 and a second bonding member 7 in which a conductive paste 4 to be a second electrode layer 9 is applied in a concave portion, the concave portion is an organic material. Since the first bonding member 6 and the second bonding member 7 are overlapped so as to wrap the layer 1, and then the conductive paste 4 is cured to form the second conductive layer 9, the conductive paste 4 is not yet formed. By overlapping the first bonding member 6 and the second bonding member 7 in a cured state, the conductive paste 4 is sufficiently adhered to the outer surface of the organic material layer 1, and then the conductive paste 4 is cured. Accordingly, the organic material layer 1 and the second electrode layer 9 can be electrically connected without damaging the organic material layer 1, and a light-emitting element having a uniform thickness of the organic material layer 1 can be manufactured with high yield. it can.
In addition, the electrical and mechanical bonding characteristics of the interface between the organic material layer 1 and the second electrode layer 9 are improved, and a light emitting element having excellent characteristics such as luminous efficiency and lifetime can be manufactured.

[Example]
First, a first conductive layer (ITO 150 nm / a-NPD 130 nm / Coumarin 6: Alq ₃ 20 nm / Alq ₃ 40 nm) was formed on the glass substrate by a vapor deposition method to produce a first bonding member.
Moreover, Ag paste was apply | coated on another glass substrate, and it was set as the 2nd joining member. After superimposing these joining members, the Ag paste was cured by heat treatment to produce an organic EL device.

[Comparative example]
On the glass substrate, ITO 150 nm / a-NPD 130 nm / Coumarin 6: Alq ₃ 20 nm / Alq ₃ 40 nm / Ag 200 nm were formed by vapor deposition to produce an organic EL device.

  A voltage of 10 V was applied to each of the organic EL elements of Examples and Comparative Examples to emit light, and the luminance was measured. The results are shown in Table 1.

  From the results shown in Table 1, it was demonstrated that the organic EL elements of the examples according to the present invention have significantly superior light emission performance as compared with the comparative examples.

It is typical sectional drawing which shows the process of superimposing the 1st joining member and said 2nd joining member in the manufacturing method of the light emitting element of this invention. It is typical sectional drawing which shows an example of the light emitting element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Organic material layer, 2 ... 1st base material, 3 ... 1st electroconductive layer, 4 ... Conductive paste, 5 ... 2nd base material, 6 ... 1st joining member, 7 ... 2nd joining member, 8 ... Insulation Layer, 9 ... second conductive layer, 10 ... light emitting element.

Claims (2)

A first joining member comprising a flat transparent first base material, a first conductive layer provided on the first base material, and an organic material layer provided on the first conductive layer;
A cap-shaped second base material having a recess, and at least the inner surface of the recess has an insulating property, and a second base provided so as to cover the inner surface of the recess and a part of the peripheral edge of the recess opening. A light emitting device comprising a second bonding member composed of a conductive layer, wherein the first bonding member and the second bonding member are overlapped so that the concave portion wraps the organic material layer,
The light emitting device, wherein the second conductive layer is made of a conductor obtained by curing a conductive paste. A step of forming a first conductive layer and an organic material layer in order on a flat transparent first substrate to produce a first joining member,
A conductive paste is applied to a cap-shaped second base material having a recess and at least the inner surface of the recess having an insulating property so as to cover the inner surface of the recess and a part of the periphery of the opening of the recess. Producing a joining member;
A step of superimposing the first joining member and the second joining member so that the concave portion wraps the organic material layer, and heat-treating each superposed joining member to cure the conductive paste to form the organic And a step of obtaining a light emitting element by electrically connecting to a material layer.

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