KR101030012B1 - Organic electroluminescent display using the same - Google Patents

Abstract

The present invention provides an organic electroluminescent device comprising an organic film between a pair of electrodes, wherein the organic film comprises at least one selected from the group consisting of UV absorbers, antioxidants and singlet oxygen quenchers. An organic electroluminescent device is provided. According to the present invention, at least one selected from among UV absorbers, antioxidants, and singlet oxygen quencher may be deposited or coated on top of each organic film and / or electrode including a light emitting layer individually or simultaneously, thereby forming a thin film. The stability and lifespan characteristics of the organic electroluminescent device are improved by increasing the stability and inhibiting oxidation by oxygen, in particular singlet oxygen.

Description

Organic electroluminescent display using the same}

1 is a view schematically showing the structure of an organic EL device according to an embodiment of the present invention.

The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device having improved stability and lifespan characteristics.

A general organic electroluminescent device has an anode in which an anode is formed on a substrate, and a hole transporting layer, a light emitting layer, an electron transporting layer and a cathode are sequentially formed on the anode. Here, the hole transport layer, the light emitting layer, and the electron transport layer are organic thin films made of an organic compound.

The driving principle of the organic EL device having the structure as described above is as follows.

When a voltage is applied between the anode and the cathode, holes injected from the anode are moved to the light emitting layer via the hole transport layer.

On the other hand, electrons are injected into the light emitting layer from the cathode via the electron transport layer, and carriers are recombined in the light emitting layer to generate excitons. The exciton is changed from the excited state to the ground state, whereby the fluorescent molecules in the light emitting layer emit light to form an image. At this time, the excitation state is emitted to the ground state through the singlet excited state is called fluorescence, and the emission is emitted to the ground state through the triplet excited state is called phosphorescence. In the case of fluorescence, the probability of singlet excited state is 25% (triple state 75%) and there is a limit of luminous efficiency, whereas phosphorescence can be used to triplet 75% and singlet excited state 25%. Internal quantum efficiencies up to 100% are possible.

As a phosphorescent material, Ir (ppy) ₃ , a phosphorescent pigment having the same spin-orbit coupling with a heavy element such as Ir and Pt as a dopant, is used as a dopant to effectively emit light even in the triplet state (phosphorescence). Developed organic electroluminescent device. At this time, CBP (4,4'-N, N'-dicarbazole-biphenyl) was used as a host.

However, the above-mentioned organic electroluminescent element is insufficient in view of commercial use because its lifetime is short, such as 150 hours or less. The reason for this is that the glass transition temperature of CBP is lower than 110 degrees and crystallization easily occurs. In addition to the problems of the organic material itself, various external factors such as photooxidation reaction by ultraviolet irradiation due to outdoor use, thermal decomposition reaction by Joule heat generated in the device during long time use, oxidation reaction by oxygen and moisture infiltration into the device Etc., the stability of the organic electroluminescent element is reduced and the lifetime is reduced.

Accordingly, the technical problem to be achieved by the present invention is to provide an organic EL device having improved stability and lifespan by solving the above problems.

In the present invention to achieve the first technical problem, in the organic electroluminescent device comprising an organic film between a pair of electrodes,

It provides an organic electroluminescent device characterized in that the organic film comprises at least one selected from the group consisting of UV absorbers, antioxidants and singlet oxygen quencher.

The first technical problem of the present invention includes an organic film between a pair of electrodes,

At least one electrode of the pair of electrodes is made of an organic electroluminescent device further comprises an antioxidant layer containing at least one selected from among UV absorbers, antioxidants and singlet oxygen quencher.

The organic layer is at least one selected from the group consisting of a light emitting layer, a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

An antioxidant layer containing at least one selected from among a UV absorber, an antioxidant, and a singlet oxygen quencher may be further included on at least one electrode of the pair of electrodes. And an organic film containing at least one selected from among the UV absorber, the antioxidant, and the singlet oxygen quencher, between two adjacent layers selected from among the light emitting layer, the hole injection layer, the hole transport layer, the light emitting layer, the hole blocking layer, the electron transport layer and the electron injection layer. Can be stacked.                     

Hereinafter, the present invention will be described in more detail.

The organic electroluminescent device of the present invention is a UV absorber for increasing device stability in outdoor use, an antioxidant for preventing oxidation, and a singlet oxygen quencher for improving stability by singlet oxygen. ) Is included in each organic film including a light emitting layer in the organic electroluminescent device, or deposited or coated on the organic film and / or the electrode to form a thin film to improve the stability and life characteristics.

As the UV absorber, both an organic UV absorber and an inorganic UV absorber can be used. As the organic UV absorber, both a benzotriazole phenol compound having a structure of Formula 1 and a 2-hydroxybenzophenone compound of Formula 2 may be used.

 [Formula 1]

Wherein R ₁ and R ₂ are each independently hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group Selected from the group consisting of

[Formula 2]

Wherein R ₃ is selected from the group consisting of hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group.

Specific examples of the compound of Formula 1 may include 2 (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol and 2 (2H-benzotriazole-2- 1) -4,6-di-tert-pentylphenol, or 2 (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol, and the like, and specific examples of the compound of formula (2) 2-hydroxybenzophenone (HBP) etc. are mentioned as this.

When exposed to sunlight for a very long time, UV absorbers will slowly decompose and lose their protective effect. There may also be a loss of the UV absorber due to the effects of moisture and high temperatures. In contrast, inorganic UV absorbers such as titanium dioxide, cerium dioxide, zinc oxide do not have the disadvantages mentioned for the organic UV absorbers, are not photochemically decomposed and are not affected under high temperatures. If the particle size of the inorganic UV absorber used is sufficiently small, highly transparent coatings can be produced, in principle organic and inorganic binders can be used for this purpose. However, when the above UV absorbers are used, photochemical damage may occur due to the large surface area of the titanium dioxide, cerium dioxide and zinc oxide nanoparticles, which can be prevented by using a sol-gel material.

In order to form the sol-gel material, in the present invention, RxM (OR) zx disclosed in US Pat. No. 4,799,963, where R is an organic radical, x may be 0 but is less than z (valence of metal), and M is Si, Al, Transparent coating compositions consisting of partially hydrolyzed alkoxides and colloidal cerium dioxide, or mixtures thereof, of Ti or Zr. Specific examples of RxM (OR) z-x include γ-glycidoxypropyl trimethoxysilane and methyl triethoxysilane.

The antioxidant used in the organic electroluminescent device of the present invention is a metal carbon represented by the following Chemical Formulas 3 to 5 known as antioxidants for optical recording dyes, information recording dyes, and triphenylmethane dyes sensitive to the presence of oxygen and moisture. Use a carboxylate.

(3)

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N),

[Formula 4]

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N),

[Chemical Formula 5]

In the formula, M represents a transition metal.

Specific examples of the transition metal in Chemical Formulas 3 to 5 include nickel, zinc, copper, cobalt, and manganese.

In the present invention, a singlet oxygen quencher is used to suppress photobleaching of organic materials and light emitting materials and to improve light stability. As such singlet oxygen quencher, carotene, amines, phenols, metal complexes and the like are used. Preferably, the 1,2-benzenedithiolate compound represented by the following formula (6) and bis (dithiobenzyl) represented by the formula (7) Metal complexes can be used.

[Formula 6]

Wherein M represents a transition metal, Y represents hydrogen, chlorine or fluorine, Bu represents a butyl group, M and NBu ₄ form an ionic bond,

[Formula 7]

In the formula, M represents a transition metal.

In the formulas (3) to (7), M is preferably a transition metal, particularly nickel, zinc, copper, cobalt, or the like.

The organic electroluminescent device of the present invention is prepared by adding a UV absorber, an antioxidant and / or a singlet oxygen quencher to an organic film formed between a pair of electrodes, a hole injection layer (HIL), a hole transport layer (HTL), Emission layer (EML), hole blocking layer (HBL), electron transport layer (ETL), an electron injection layer (EIL) is formed by further stacking a separate antioxidant layer between two adjacent layers or an antioxidant layer on the electrode It can be produced by further lamination.

The UV absorber, the antioxidant and / or the singlet oxygen quencher are applied to the organic film in the organic EL device (hole injection layer (HIL), hole transport layer (HTL), light emitting layer (EML), hole blocking layer (HBL), electron transport layer). (ETL), electron injection layer (EIL)), vacuum deposition, spin coating, casting, etc. can be used. Among them, when the organic film material is low molecular weight, vacuum deposition is used for uniform film quality. It is easy to obtain, and since pinhole generation can be suppressed, it is preferable. And if the organic film material is a polymer, it is preferable to use a spin coating method.

When the organic film is formed by vacuum deposition, the deposition conditions vary depending on the structure and thermal properties of the film forming material, but in general, the deposition temperature is 50 to 500 ° C., the vacuum degree is 10 to ⁸ to 10 ⁻³ torr, and the deposition rate is 0.01 to 100 mW /. sec.

In the case of common deposition by adding a UV absorber, an antioxidant and / or a singlet oxygen quencher together when forming the organic film, the at least one total doping concentration selected from the UV absorber, the antioxidant and the singlet oxygen quencher is not particularly limited, but the organic film is formed. It is preferably 0.001 to 10 parts by weight, in particular 0.01 to 5 parts by weight based on 100 parts by weight of the material (for example, the electron transport material in the case of the electron transport layer).                     

If UV absorbers, antioxidants and / or singlet oxygen quenchers are used in the formation of the organic layer, the mixing ratios of the antioxidants are 5 to 200 parts by weight based on 100 parts by weight of UV absorbers and singlet oxygen. The content of the quencher is preferably 5 to 200 parts by weight based on 100 parts by weight of the UV absorber.

1 illustrates an organic electroluminescent device according to an embodiment of the present invention.

Referring to this, the antioxidant layer is formed by using each or all of the above UV absorbers, antioxidants, singlet oxygen quencher on the second electrode (for example, the cathode). At this time, the antioxidant layer may be formed by a method such as vacuum deposition, spin coating, casting, LB, etc., but it is preferable to use a vacuum deposition method. It is because there exists an advantage that it is easy and pinhole generation is suppressed. When the antioxidant layer is formed by vacuum deposition, the deposition conditions vary depending on the type of UV absorber, antioxidant, singlet oxygen quencher compound, structure and thermal properties, etc., but are generally deposited at a deposition temperature of 50 to 500 ° C. and a vacuum degree of 10. It is preferable that it is ^-8 to 10 ^-3 torr and the deposition rate is 0.01 to 100 mW / sec.

In the present invention, formed on the electrode or adjacent to the hole injection layer (HIL), hole transport layer (HTL), light emitting layer (EML), hole blocking layer (HBL), electron transport layer (ETL), electron injection layer (EIL) The thickness of the anti-oxidation layer formed between the two layers is preferably 10 kPa to 5 mu m, and each material may be formed by common vacuum deposition alone or in two or more compositions, preferably all three materials. Will be used together. At this time, the mixing ratio of the UV absorber, the antioxidant and the singlet oxygen quencher is the same as the case described in the case of adding them to the organic film.

Alternatively, the antioxidant layer may be formed by spin coating or casting using a polymer binder in addition to the UV absorber, the antioxidant, and / or the singlet oxygen quencher. The polymer binder used at this time is not limited and may be selected and used among commercially available polymer binders. Specific examples thereof include (polycarbonate (PC) and polyvinyl butyral (PVB)). And the content of the polymer binder is preferably 50 to 500 parts by weight based on 100 parts by weight of one or more total content selected from UV absorbers, antioxidants and singlet oxygen quencher.

Referring to Figure 1 describes a method for manufacturing an organic EL device according to an embodiment of the present invention.

First, an anode is formed on a substrate by coating an anode material, which is a first electrode. Herein, a substrate used in a conventional organic electroluminescent device is used, and an organic substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness is preferable. As the anode material, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like, which are transparent and have excellent conductivity, are used.

The hole injection layer is vacuum-heat deposited or spin coated on the anode to selectively form the hole injection layer. The hole injection layer material is not particularly limited, and copper phthalocyanine (CuPc) or starburst type amines such as TCTA, m-MTDATA, IDE406 (Idemitsu Corp.), and the like may be used as the hole injection layer.

The hole transport layer is vacuum-deposited or spin-coated on the hole injection layer formed according to the above process to selectively form the hole transport layer. The hole transport layer material is not particularly limited, and N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4'-diamine (TPD), N, N'-di (naphthalen-1-yl) -N, N'-diphenyl benzidine, N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benxidine: α-NPD) , IDE320 (Idemitsu Co., Ltd.), etc. are used. A light emitting layer is then introduced over the hole transport layer, and the light emitting layer material is not particularly limited (oxadiazole dimer dyes (Bis-DAPOXP), spiro compounds (Spiro-DPVBi, Spiro-6P), triarylamine compounds, bis (styryl) amine (DPVBi, DSA). ) (More than blue), Coumarin 6 , C545T, Quinacridone, Ir (ppy) ₃ (more than green), DCM2, PtOEP, AAAP, DCDDC, PCJMTB, etc. (more than red) can be used.

An electron transport layer is formed on the light emitting layer by a vacuum deposition method or a spin coating method. It does not restrict | limit especially as an electron carrying layer material, Alq3 can be used.

In addition, an electron injection layer may be selectively stacked on the electron transport layer. As the electron injection layer forming material, materials such as LiF, NaCl, CsF, Li ₂ O, BaO, and Liq can be used.

An electron injection layer is selectively formed on the electron injection layer. Herein, (organic metal complexes such as Alq ₃ , Balq, Liq, and Zn (ODZ) ₂ ) are used as the total self-adhesion layer forming material.

Subsequently, a cathode is formed by vacuum thermal evaporation of a cathode metal, which is a second electrode, on the electron injection layer.

The organic electroluminescent device is completed by forming an antioxidant layer on the cathode using a UV absorber, an antioxidant, and / or a singlet oxygen quencher.

The cathode metal is lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag ) And the like are used. In addition, a transmissive cathode using ITO and IZO may be used to obtain a top emitting device.

The organic electroluminescent device of the present invention may further form an intermediate layer of one or two layers according to the needs of the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, and the cathode. In addition to the above-mentioned layers, a hole blocking layer and an electron blocking layer may also be included.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1

The anode cuts a corning 15Ω / cm ² (1200Å) ITO glass substrate to 50mm x 50mm x 0.7mm and ultrasonically cleans for 5 minutes in isopropyl alcohol and pure water, followed by UV and ozone cleaning for 30 minutes. Was used.

IDE406 (Idemitsu Kosan Co., Ltd.) was vacuum deposited on the substrate to form a hole injection layer having a thickness of 600 mm 3. Subsequently, IDE320 (Idemitsu Kosan Co., Ltd.) was vacuum deposited on the hole injection layer to a thickness of 300 GPa to form a hole transport layer.

The light emitting layer was formed on the hole transport layer by vacuum co-deposition of CBP, a green phosphorescent host material, and Ir (ppy) ₃ , a dopant material, on the hole transport layer. Thereafter, Alq3 was vacuum deposited on the emission layer to form an electron transport layer having a thickness of 200 kHz.

LiF 10kV (electron injection layer) and Al 3000kV (cathode) were sequentially vacuum deposited on the electron transport layer to form a LiF / Al electrode.

Subsequently, on the LiF / Al electrode, an anti-oxidation layer (thickness :) using 2-hydroxybenzophenone (HBP) as a UV absorber, zinc carboxylate as an antioxidant, and bis (dibenzobenzyl) nickel as a singlet oxygen quencher. 200 μs) was formed to manufacture an organic electroluminescent device as shown in FIG. 1.

Comparative Example 1

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that an antioxidant layer was not formed on the LiF / Al electrode.

In the organic EL device manufactured according to Example 1 and Comparative Example 1, the lifetime and stability were investigated, and the results are shown in Table 1 and FIG. 2.

Time (Hr) Example 1 Comparative Example 1 One 7601 7850 24 6258 6786 144 5983 6357 192 5806 6202 384 5602 6039 504 5386 6003 552 5135 5907 696 4326 5853 840 3896 5643

As shown in Table 1, Figure 2 it can be seen that the organic EL device of Example 1 is much improved the life and stability of the device compared to the case of Comparative Example 1.

As described above, according to the present invention, a thin film is formed by depositing or coating one or more selected from among UV absorbers, antioxidants, and singlet oxygen quencher separately or simultaneously on top of each organic film and / or electrode including a light emitting layer. Formation improves stability to light and suppresses oxidation by oxygen, in particular singlet oxygen, thereby improving stability and lifespan characteristics of the organic EL device.

Claims (11)

In an organic electroluminescent element comprising an organic film between a pair of electrodes, The organic film comprises an antioxidant, The antioxidant, An organic electroluminescent device, characterized in that at least one selected from metal carboxylates represented by the following formulas (3) to (5). (3)

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N), [Formula 4]

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N), [Chemical Formula 5]

In the formula, M represents a transition metal. An organic film between the pair of electrodes, Further comprising an antioxidant layer containing an antioxidant on at least one electrode of the pair of electrodes, The antioxidant, An organic electroluminescent device, characterized in that at least one selected from metal carboxylates represented by the following formulas (3) to (5). (3)

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N), [Formula 4]

In the formula, M represents a transition metal, X represents carbon (C) or nitrogen (N), [Chemical Formula 5]

In the formula, M represents a transition metal. The organic electroluminescent device according to claim 1 or 2, wherein the organic layer is at least one selected from the group consisting of a light emitting layer, a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. delete delete The method of claim 1, wherein the organic film further comprises a singlet oxygen quencher, The singlet oxygen quencher, An organic electroluminescent device, characterized in that at least one selected from the group consisting of keratin, amines, phenols, 1,2-benzenedithiolate of formula (6) and bis (dithiobenzyl) metal complex of formula (7). [Formula 6]

Wherein M represents a transition metal, Y represents hydrogen, chlorine or fluorine, Bu represents butyl, [Formula 7]

In the formula, M represents a transition metal. The organic electroluminescent device according to claim 1, further comprising an antioxidant layer on at least one electrode of the pair of electrodes, the antioxidant layer containing at least one selected from a UV absorber, an antioxidant, and a singlet oxygen quencher. The method of claim 1, wherein the organic film, An organic electroluminescent device, which is laminated between two adjacent layers selected from among a light emitting layer, a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer and an electron injection layer. The method of claim 1, wherein in the organic film, At least one UV absorber selected from the group consisting of a benzotriazole phenolic compound of formula 1, a 2-hydroxybenzophenone compound of formula 2, titanium dioxide, cerium dioxide, zinc oxide, partially hydrolyzed organic alkoxide and colloidal cerium dioxide An organic electroluminescent device further comprising. [Formula 1]

Wherein R ₁ and R ₂ are each independently hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group Selected from the group consisting of [Formula 2]

Wherein R ₃ is selected from the group consisting of hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group. The method of claim 2, wherein the antioxidant layer, At least one UV absorber selected from the group consisting of a benzotriazole phenolic compound of formula 1, a 2-hydroxybenzophenone compound of formula 2, titanium dioxide, cerium dioxide, zinc oxide, partially hydrolyzed organic alkoxide and colloidal cerium dioxide An organic electroluminescent device further comprising. [Formula 1]

Wherein R ₁ and R ₂ are each independently hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group Selected from the group consisting of [Formula 2]

Wherein R ₃ is selected from the group consisting of hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, and a substituted or unsubstituted C2-C20 heteroaryl group. The method of claim 2, wherein the antioxidant layer, Organic, characterized in that it further comprises at least one singlet oxygen quencher selected from the group consisting of keratin, amines, phenols, 1,2-benzenedithiorate of formula (6) and bis (dithiobenzyl) metal complex of formula (7) EL device. [Formula 6]

Wherein M represents a transition metal, Y represents hydrogen, chlorine or fluorine, Bu represents butyl, [Formula 7]

In the formula, M represents a transition metal.

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