JP2002367771A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element, and its manufacturing method, which can enough and stably restrain enlargement with time of dark spots. SOLUTION: With the organic electroluminescent element comprising a first electrode 2 formed on a substrate 1, a thin-film layer including a luminous layer 6 at least made of an organic compound formed on the first electrode, a second electrode 8 formed on the thin-film layer, and a sealing plate 21 with an adhesive and a substrate pasted together, Ia/Ib in an infrared ray absorption spectrum is to be not more than 3, provided, absorption intensity derived from alkane appearing between 2,800 and 3,000 cm<-1> is Ia, and absorption intensity derived from amine, amide appearing between 3,200 and 3,500 cm<-1> is Ib.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device that can be used in fields such as display devices, flat panel displays, backlights, and interiors, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An organic electroluminescent device emits light when holes injected from an anode and electrons injected from a cathode are recombined in an organic light emitting layer sandwiched between both electrodes.
A typical structure is a transparent first electrode (anode), hole transport layer, organic light emitting layer, and second electrode (cathode) on a glass substrate.
The light emission generated by the driving is extracted to the outside through the first electrode and the glass substrate. Further, a display device can be configured using an organic electroluminescent element. Such an organic electroluminescent device is thin,
High luminance light emission under low voltage driving and multicolor light emission by selecting an organic light emitting material are possible, and studies on application to light emitting devices, displays, and the like are being actively conducted.

One of the problems in the organic electroluminescent device is that the area of a non-light-emitting portion called a dark spot increases with time. It is known that the cause of such characteristic deterioration is moisture.
That is, moisture enters the organic thin film layer due to a defect of the second electrode or the like, and inactivates the element.

[0004] In order to prevent such dark spots from expanding, it is necessary to keep the organic electroluminescent device in a low humidity atmosphere. Usually, the organic electroluminescent device is sealed for the purpose of protecting the device from an external environment such as moisture. Stop means are used. The means include a method of bonding an element and a sealing plate via an adhesive, a method of forming a protective film having a moisture shielding property such as an oxide or a fluoride on a thin film layer, and a method of sealing a desiccant. There is a wide variety of methods, such as encapsulation inside the device. As the adhesive, a method using a moisture-resistant photocurable resin (JP-A-5-182759), a method of heating and melting a low-melting glass with a laser beam (JP-A-10-74583), a cation-curing type ultraviolet curing Method using epoxy resin
233283).

[0005]

However, in the prior art, the penetration of water into the inside of the device due to a decrease in the moisture shielding capability of the adhesive, the deterioration of the device due to heat or ultraviolet rays added for curing the resin, and the moisture shielding capability are reduced. The inorganic protective film has many problems such as easy damage to the element at the time of film formation, and the enlargement of dark spots cannot be sufficiently suppressed.

It is an object of the present invention to solve such a problem and to provide an organic electroluminescent device capable of sufficiently and stably suppressing the temporal expansion of a dark spot.

[0007]

SUMMARY OF THE INVENTION The present invention provides a first electrode formed on a substrate, a thin film layer formed on the first electrode, the light emitting layer comprising at least an organic compound, and a thin film layer formed on the thin film layer. An organic electroluminescent device including the second electrode thus formed and a sealing plate bonded to the substrate with an adhesive, wherein the cured adhesive has an infrared absorption spectrum of 2800 to 3
The absorption intensity derived from the alkane appearing at 000 cm ^-1
a, where the absorption intensity derived from amines and amides appearing at 3200 to 3500 cm ⁻¹ is represented by Ib, the Ia / Ib ratio is 3 or less.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below, but the present invention is not limited to a method of manufacturing an organic electroluminescent device having the exemplified form and structure. Therefore,
Single light emitting element, segment type, simple matrix type, active matrix type and other light emitting element types, colors,
The present invention can be applied to an organic electroluminescent device having an arbitrary structure irrespective of the number of emission colors such as monochrome.

The components of the organic electroluminescent device according to the present invention include, for example, a substrate 1 and a sealing plate 2 in the device shown in FIG.
1, all the members in contact with the sealing internal space 23, such as the bonding means 22, are included. Depending on the element configuration, a wiring, a connector, a lead electrode, a protective film covering the element surface, and the like may be included, and the constituent members are not particularly limited.

The sealing adhesive of the present invention has an infrared absorption spectrum of 2800 to 3
The absorption intensity derived from the alkane appearing at 000 cm ^-1
a, when the absorption intensity derived from amines and amides appearing at 3200 to 3500 cm ⁻¹ is defined as Ib, the Ia / Ib ratio needs to be 3 or less. More preferably 2.7
It is as follows. The Ia / Ib ratio is an index of the density of amino groups and amide groups in the cured resin. The higher the amino group and amide group densities, the better the heat resistance, chemical resistance, and adhesive strength of the cured resin, and exhibit extremely excellent properties as a sealing resin for an organic electroluminescent device. For example, when the adhesive is a two-liquid mixed type, the main agent is an epoxy resin, and the curing agent is an amine resin, the amount of the curing agent added to 100 (g) of the main agent
The calculation is (amine equivalent / epoxy equivalent) × 100 (g)
However, the heat resistance and flexibility of the cured resin can be adjusted by adjusting the amount of the curing agent added. Specifically, the addition amount (g) of the curing agent is preferably within a range of ± 20% of the value calculated by the equivalent.

In the present invention, a resin that maintains stable adhesive strength at room temperature or higher is used as the adhesive, and a two-pack type epoxy resin is preferred. A two-component epoxy resin is a very suitable adhesive as an adhesive for sealing an organic electroluminescent element because it does not generate moisture during a curing reaction and has a high adhesive strength to a metal or a glass substrate.
As the epoxy resin of the main agent, there are various resins such as bisphenol A type, novolak type, polyphenol type, polyhydroxybenzene type, vinyl polymer type, aromatic carboxylic acid type, and cyclohexene type. Any of them can be used.

Examples of the curing agent include amines such as aliphatic amines, aromatic amines, secondary and tertiary amines, modified heterocyclic diamines, and (poly) amidoamines. It is preferable to use an amidoamine-based curing agent.

The (poly) amidoamine-based curing agent in the present invention is an amide-based curing agent having an active amino group in a molecule synthesized from a (poly) amine and a (poly) carboxylic acid and having a molecular weight extending from an oligomer to a polymer region. Refers to a curing agent.

The curing agent according to the present invention may be used as a curing accelerator in addition to the (poly) amidoamine, or to improve the physical properties of the cured product such as mechanical strength and heat resistance.
Aliphatic amines, aromatic amines, secondary and tertiary amines,
Amines such as modified heterocyclic diamines, phthalic anhydride,
An acid anhydride such as maleic anhydride, a polysulfide resin having a mercaptan group, or the like may be contained.

[0015] The (poly) amidoamine curing agent has both hydrophobic and hydrophilic groups, so that it has high wettability on non-adhesives.
Good adhesion. For this reason, when a (poly) amidoamine-based curing agent is used for the sealing adhesive, the adhesion between the sealing plate or the substrate and the adhesive is increased, and it is necessary to prevent water from entering the sealing space from the outside. It can be suppressed effectively. Further, since it has a hydrophobic group, it has excellent moisture shielding properties as compared with ordinary amine-based cured products and the like, and can effectively suppress the diffusion of moisture in the resin. Furthermore, since curing with an epoxy resin (main agent) is possible at room temperature, there is no need for heating for curing the resin, and there is no risk of thermal damage to the organic thin film layer.

Further, in the present invention, means for applying pressure in the direction in which the substrate and the sealing plate are bonded to each other when the resin is cured can be used to improve the resin adhesion. Is effective for improving the adhesiveness of the film. By applying pressure, the resin penetrates into minute irregularities on the surface of the adherend, and the adhesion is improved. The size of the additional pressure is preferably at least 0.01 kg / cm ² or more 10 kg / cm ² or less. As a method for applying pressure, any method such as a method for applying pressure mechanically or a method for applying hydrostatic pressure to a medium such as a gas or a liquid filling a processing chamber for sealing may be used.

The state of the interface between the substrate or the sealing plate and the resin is very important. In many cases, a stress is generated at the bonding interface when the resin is cured, and the bonding stress causes the separation of the bonding interface. There is. Therefore, a process for improving the adhesion at the bonding interface becomes important.

In addition to the above-mentioned method of applying pressure, as a method for improving the resin adhesion, it is effective to apply a primer treatment to the substrate and the sealing plate. The primer treatment means that the surface of the substrate or the sealing plate is preliminarily treated with an adhesive in order to increase the affinity of the interface between the resin and the substrate and between the resin and the sealing plate.

Preferred examples of the primer include those obtained by diluting a silane coupling agent with a solvent. As the solvent, alcohols, toluene, xylene, ethyl acetate, methyl ethyl ketone, acetone and the like can be used, and when diluting the silane coupling agent, 1 to
What was diluted about 20% can be used as a suitable thing. As for the primer treatment method, it is only necessary to apply the primer on the substrate or the sealing plate surface and dry it,
If the substrate and the sealing plate are cleaned with a solvent or the like before applying the primer, the adhesion is further improved.

The silane coupling agent preferably has at least two or more types of functional groups in order to have an affinity for the resin and the adherend. Particularly when the resin contains an epoxy resin, it is preferable that at least one of the functional groups has an epoxy group.When the substrate or the sealing plate is an inorganic compound such as glass or metal, an alkoxy group such as a methoxy group or an ethoxy group is preferably used. It is preferable to have.

In order to further reduce the water permeability and the water absorption of the resin, a filler can be mixed into the adhesive resin. The filler is a fine particle made of an inorganic material such as silica, and the size, shape, and mixing ratio of the particle are not particularly limited, and are optimized as needed.

The curing condition of the sealing resin is not limited to the curing at room temperature, but it is needless to say that the temperature condition can be selected as needed within a range that does not deteriorate the organic electroluminescent element. In order to further improve the adhesion between the resin and the sealing plate, the sealing plate may be washed with an appropriate solvent,
A method of performing a V treatment to clean the surface of the sealing plate is effective.

The sealing method in the present invention is not particularly limited as long as the substrate and the sealing plate are bonded together. Therefore, the sealed internal space can be filled with a low-humidity liquid or gas. Examples of the former include inert liquids such as silicone oil, grease, and fluorocarbon oil. Examples of the latter include rare gases such as helium and argon, and inert gases such as nitrogen and carbon dioxide. Further, the inside of the sealed space can be kept at a vacuum.

The above method of filling the sealing space with a low-humidity gas can be easily achieved by bonding the substrate and the sealing plate in a low-humidity atmosphere. In order to obtain a sufficient sealing effect, the dew point in a low humidity atmosphere is preferably -30 ° C or lower, -60 ° C or lower, and more preferably -1 ° C or lower.
It is more preferable that the temperature is not higher than 00 ° C.

As the sealing plate, a plate or film formed of a material having low moisture permeability such as glass, resin, or a metal such as aluminum or stainless steel can be used. These may be a single type or a composite type obtained by depositing a metal such as aluminum on a resin film such as polyethylene.

In the present invention, the shape of the sealing plate 21 is not particularly limited, and the sealing plate 21 may be sealed with the substrate by forming a recess 24 as shown in FIG. 2 or a leg 25 as shown in FIG. The position to be bonded to the stop plate can be defined. By doing so, it is also possible to secure a volume for filling the sealing internal space 23 with gas or oil or for providing a moisture absorbent. Similar effects can be obtained by increasing the thickness of the bonding means. Furthermore, if the sealing method of the present invention is used, a getter film having a moisture absorbing effect or the like, or a black film or a light absorbing film having an anti-reflection effect is formed on the surface of the sealing plate in advance as necessary. You can also. As the hygroscopic agent, silica gel, zeolite, activated carbon, calcium oxide, germanium oxide, barium oxide, magnesium oxide, phosphorus pentoxide, calcium chloride and the like, and as the getter film aluminum, magnesium, barium, titanium and other metal deposited film. Examples can be given.

The bonding position between the substrate and the sealing plate is not particularly limited, and the bonding means may be positioned so as to cover the entire device. However, from the viewpoint of light emission stability, the bonding means is in contact with the light emitting region. It is preferable that they are not located. Furthermore, from the viewpoint of power supply, it is preferable that each of the first electrode and the second electrode is sealed so as to be exposed to the outside. Further, it is also possible to take out the electrode through a through hole provided in the substrate.

The material of the substrate is not particularly limited as long as it has optical transparency, mechanical strength, heat resistance and the like suitable for functioning as a display or a light emitting element. Although plastic plates and films such as polymethyl methacrylate, polycarbonate and amorphous polyolefin can be used, it is most preferable to use a glass plate. As the glass material, non-alkali glass, soda lime glass coated with a barrier coat such as a silicon oxide film, or the like can be used. Since the thickness only needs to be sufficient to maintain the mechanical strength, it is sufficient that the thickness is 0.2 mm or more. In addition, an antireflection function can be added to the first electrode or the substrate by using a known technique.

The thin film layers included in the organic electroluminescent device include 1) a hole transport layer / a light emitting layer, 2) a hole transport layer / a light emitting layer / an electron transport layer, 3) a light emitting layer / an electron transport layer, and 4) And e) a light-emitting layer in which the above-mentioned combined substances are mixed in a single layer. That is, if a light-emitting layer made of an organic compound is present as an element configuration, a light-emitting material alone or a light-emitting material and a hole-transport material or an electron-transport, as described in 4), in addition to the multi-layer structure of 1) to 3) above Only one light-emitting layer containing a material may be provided.

The hole transporting layer is formed of a hole transporting substance alone or a hole transporting substance and a polymer binder.
As the hole transporting substance, N, N'-diphenyl-N,
N'-di (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine (TPD) and N, N'-diphenyl-N, N'-dinaphthyl-1,1'-diphenyl-
Triphenylamines represented by 4,4'-diamine (NPD), N-isopropylcarbazole, biscarbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, oxadiazole derivatives and phthalocyanine derivatives Heterocyclic compounds, in the polymer system, polycarbonate and polystyrene derivatives having the monomer in the side chain, polyvinyl carbazole, polysilane, polyphenylene vinylene and the like are preferable,
There is no particular limitation.

The material of the light emitting layer formed by patterning on the first electrode is anthracene, pyrene, and 8-hydroxyquinoline aluminum, for example, bisstyrylanthracene derivative, tetraphenylbutadiene derivative, coumarin derivative, Oxadiazole derivatives,
A distyrylbenzene derivative, a pyrrolopyridine derivative, a perinone derivative, a cyclopentadiene derivative, a thiadiazolopyridine derivative, and a polymer system such as a polyphenylenevinylene derivative, a polyparaphenylene derivative, and a polythiophene derivative can be used. As the dopant to be added to the light emitting layer, rubrene, quinacridone derivative, phenoxazone 660, DCM1, perinone, perylene, coumarin 540, diazaindacene derivative, and the like can be used as they are.

As the electron transporting substance, it is necessary to efficiently transport electrons from the cathode between the electrodes to which an electric field is applied, and it is desirable to have a high electron injection efficiency and to efficiently transport the injected electrons. . For this purpose, it is required that the material has a high electron affinity, a high electron mobility, a high stability, and a small amount of impurities serving as traps during production and use. As materials satisfying such conditions, 8-hydroxyquinoline aluminum (Alq ₃ ), hydroxybenzoquinoline beryllium, 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiene Azole (t-Bu
Oxadiazole derivatives such as PBD) and 1,3 oxadiazole dimer derivatives having improved thin film stability
-Bis (4-t-butylphenyl-1,3,4-oxadizolyl) biphenylene (OXD-1), 1,3-bis (4-t-butylphenyl-1,3,4-oxadizolyl) phenylene (OXD- 7), triazole derivatives, phenanthroline derivatives and the like.

The above materials used for the hole transporting layer, the light emitting layer and the electron transporting layer can be used alone to form each layer. As the polymer binder, polyvinyl chloride, polycarbonate, polystyrene, poly (N- (Vinyl carbazole), polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene ether, polybutadiene, hydrocarbon resins, ketone resins, phenoxy resins, polyurethane resins, and other solvent-soluble resins, phenol resins, xylene resins, petroleum resins,
Urea resin, melamine resin, unsaturated polyester resin,
It is also possible to use the resin dispersed in a curable resin such as an alkyd resin, an epoxy resin, and a silicone resin.

The method of forming the organic layers such as the hole transport layer, the light emitting layer, and the electron transport layer includes resistance heating evaporation, electron beam evaporation, and sputtering. Although not particularly limited, an evaporation method such as resistance heating evaporation or electron beam evaporation is usually preferable in terms of characteristics. The thickness of the layer cannot be limited because it depends on the resistance value of the organic layer.
It is selected from between 1000 nm.

The cathode serving as the second electrode is not particularly limited as long as it can efficiently inject electrons into the light emitting layer of the device. Therefore, it is possible to use a low work function metal such as an alkali metal, but considering the stability of the electrode, platinum, gold,
Preferable examples include metals such as silver, copper, iron, tin, aluminum, magnesium and indium, and alloys of these metals with low work function metals. In addition, a stable electrode can be obtained while maintaining high electrode injection efficiency by doping the organic layer with a small amount of a low work function metal in advance and then forming a film of a relatively stable metal as a cathode. These electrodes are also manufactured by resistance heating evaporation,
Dry processes such as electron beam evaporation, sputtering, and ion plating are preferred.

[0036]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 An ITO substrate having a 130 nm thick ITO transparent electrode film formed on a 1.1 mm thick non-alkali glass surface by sputtering was prepared. After patterning this ITO film using the photolithography method, 46 mm × 38
mm, and a 12 mm wide I
A substrate was fabricated by patterning so that a TO film (first electrode) was present.

After washing the substrate, it was set in a vapor deposition machine and evacuated to a vacuum of 2 × 10 ⁻⁴ Pa. With the shadow mask for the light emitting layer having an opening of 15 mm square arranged, copper phthalocyanine 10 nm, N, N'-diphenyl-N, N'-
Dinaphthyl-1,1′-diphenyl-4,4′-diamine (α-NPD) 50 nm and tris (8-quinolinolato) aluminum (Alq ₃ ) 50 nm were deposited. After that, the thin film layer was exposed to lithium vapor to dope (0.5 nm in equivalent film thickness). Next, the mask was replaced with a second electrode shadow mask having four 5 × 12 mm openings, and aluminum was vapor-deposited to a thickness of 120 nm at a degree of vacuum of 3 × 10 ⁻⁴ Pa to pattern the second electrode. Thus, an organic electroluminescent device having four green light emitting regions on the substrate was manufactured.

After taking out the above-mentioned element from the vapor deposition machine and holding it for 20 minutes in a reduced pressure atmosphere by a rotary pump,
The sample was transferred under an argon atmosphere at a dew point of -90 ° C. Under the dry atmosphere, as a sealing resin, a phenol novolak type epoxy resin ("Epicoat" 152, manufactured by Japan Epoxy Resin Co., Ltd.) as a main component, and a polyamidoamine-based curing agent ("Versamide" JP161, manufactured by Cognis Japan Co., Ltd.) as a curing agent.
Were mixed in a weight ratio of 100: 52 and stirred sufficiently. The infrared absorption spectrum of the cured mixed resin was measured, the absorption peak derived from an alkane absorption peak and 2923cm ^-1 derived from 3305cm ^-1 amine, an amide is observed, the absorption peak intensity derived from the alkane Is Ia, and the absorption peak intensity derived from the amine is Ia
Assuming b, Ia / Ib = 2.5. The mixed resin was applied as an adhesive to a position surrounding the light emitting portion on the substrate, and a sealing plate made of non-alkali glass was bonded and sealed. At this time, a pressure of 0.2 kg / cm ² was applied in the direction of bonding the substrate and the sealing plate. When the obtained device was left in a moist heat atmosphere at a temperature of 80 ° C. and a relative humidity of 80% RH, the non-light-emitting portion (dark spot) observed immediately after sealing did not expand even after 150 hours, and the initial light emission The characteristics were maintained.

Example 2 As a sealing resin, a phenol novolak type epoxy resin ("Epicoat" 152, manufactured by Japan Epoxy Resin) was used as a main component, and a polyamidoamine-based curing agent ("Versamide" JP1460, manufactured by Cognis Japan) was used as a curing agent. An experiment was conducted in the same manner as in Example 1 except that was used. The mixing ratio was such that the weight ratio of the base material to the curing agent was 100: 40. The infrared absorption spectrum of the cured mixed resin was measured, the absorption peak derived from an alkane absorption peak and 2930 cm ^-1 derived from 3350 cm ^-1 amine, an amide is observed, the absorption peak intensity derived from the alkane Is Ia, and the absorption peak intensity derived from the amine is Ib, and Ia / Ib = 2. The mixed resin was applied as an adhesive to a position surrounding the light emitting portion on the substrate, and a sealing plate made of non-alkali glass was bonded and sealed.

The obtained device was subjected to a temperature of 80 ° C. and a relative humidity of 80.
When left in a moist heat atmosphere of% RH, the non-light-emitting portion (dark spot) observed immediately after sealing did not expand even after 200 hours, and the initial light-emitting characteristics were maintained.

Comparative Example 1 As a sealing resin, a bisphenol A type epoxy resin (Araldite Standard, manufactured by Ciba Specialty Chemicals) was used as a main component, and a polyamidoamine-based curing agent (Araldite Standard, manufactured by Ciba Specialty Chemicals) was used as a curing agent. The experiment was performed in the same manner as in Example 1 except that the above method was used. The mixing ratio was equal in weight ratio. Measurement of the infrared absorption spectrum after curing of the mixed resin, the absorption peak derived from an alkane absorption peak and 2925 cm ^-1 derived from amine 3300 cm ^-1 was observed, the absorption peak intensity derived from the alkane Ia ,
When the absorption peak intensity derived from the amine is Ib, I
a / Ib = 3.3. The mixed resin was applied as an adhesive to a position surrounding the light emitting portion on the substrate, and a sealing plate made of non-alkali glass was bonded and sealed.

The obtained device was subjected to a temperature of 80 ° C. and a relative humidity of 80.
When left in a moist heat atmosphere of% RH, the non-light-emitting portion (dark spot) observed immediately after sealing expanded within 50 hours, and the initial light-emitting characteristics could not be maintained.

[0044]

According to the organic electroluminescent device of the present invention, expansion of the non-light emitting region can be suppressed, and good reproducibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an organic electroluminescent device manufactured according to the present invention.

FIG. 2 is a cross-sectional view showing another example of the organic electroluminescent device manufactured by the present invention.

FIG. 3 is a cross-sectional view showing another example of the organic electroluminescent device manufactured by the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st electrode 3 Drive source 5 Hole transport layer 6 Light emitting layer 8 2nd electrode 21 Sealing plate 22 Adhesive resin 23 Sealing internal space 24 Depression 25 Leg

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB11 AB13 AB18 BB01 CA01 CB01 DA01 DB03 EB00 FA02 4J040 EG021 GA14 MA02 MA05 MA10 NA17 NA19

Claims (3)

[Claims] A first electrode formed on a substrate, and a first electrode
The light-emitting layer made of at least an organic compound formed on the
Including the thin film layer, the second electrode formed on the thin film layer,
Organic electroluminescence including a sealing plate bonded to a substrate with an agent
Infrared absorption spectrum of the adhesive after curing
, 2800-3000cm ^-1Arca appearing on
Ia, 3200-3500c
m^-1The absorption intensity derived from amine and amide appearing in
Where the Ia / Ib ratio is 3 or less.
Organic electroluminescent device. 2. The organic electroluminescent device according to claim 1, wherein the adhesive contains at least one of an amidoamine resin and a polyamideamine resin. 3. A display device using the organic electroluminescent device according to claim 1.