WO2006009050A1 - Organic electroluminescent device and method for manufacturing same - Google Patents

Abstract

Disclosed is an organic electroluminescent device wherein a short circuit between electrodes hardly occurs. The organic electroluminescent device comprises a first and second electrode layer arranged opposite to each other and an organic functional layer interposed between the first and second electrode layers and containing an organic compound. The organic functional layer includes a hole injection layer which is arranged in contact with the first electrode layer, and the hole injection layer is soluble in an organic solvent and contains a thermally decomposable low-molecular-weight compound having hole injection properties. The low-molecular-weight compound may be a phthalocyanine derivative.

Description

 TECHNICAL FIELD Organic electroluminescence device and manufacturing method thereof

 The present invention relates to an organic electroluminescent element and a method for manufacturing the same.

Background art

 An organic electroluminescent element (hereinafter referred to as “organic EL”) is a transparent first electrode made of a conductive material such as indium tin oxide (hereinafter referred to as “ITO”) on a main surface of a transparent substrate such as a glass substrate. An organic functional layer including a layer and a light emitting layer having an organic phosphor and a second electrode layer made of a metal such as A1 or Mg are sequentially formed.

 The organic functional layer includes a plurality of thin films and is formed by sequentially forming a first electrode layer, a hole injection layer, a hole transport layer, a light emitting layer, and an electron injection layer.

 When a DC electric field is applied between the first electrode layer and the second electrode layer, the holes injected from the first electrode layer and the electrons injected from the second electrode layer recombine in the light emitting layer, Upon receiving the energy, the phosphor in the light emitting layer emits light, and the light from the light emitting layer is extracted from the substrate or from the side opposite to the substrate. Such an organic EL element is self-luminous, has excellent power visibility, and can be driven at a low voltage of several V to several tens of V. Therefore, light weight including a driving circuit is possible. .

The organic EL device having the above-described configuration is roughly divided into a case where the organic functional layer has a low molecular weight and a composite force and a case where the organic functional layer is made of a high molecular weight compound. The former is called a low molecular weight organic EL device, and the latter. Is called a polymer organic EL device. Low in the case of low molecular organic EL devices The organic functional layer is formed using a vapor deposition method in which a molecular weight compound is vapor deposited. In the case of a high molecular weight organic EL device, by dissolving a high molecular weight compound in an organic solvent and then depositing the solution on the first electrode layer using a film forming method using a solution such as a spin coat method. Thus, an organic functional layer is formed.

Disclosure of the invention

 Among the organic functional layers described above, when the material of the hole injection layer has a low molecular weight compound force such as copper phthalocyanine, foreign substances are attached to the first electrode layer when forming the hole injection layer. The foreign matter acts as a mask for the first electrode layer. In other words, when a hole injection layer made of a low molecular weight compound is formed using a vapor deposition method, the foreign matter serves as a mask for the vapor deposition material flow, and the foreign matter and the first electrode layer come into contact with each other and In the vicinity thereof, a portion where the hole injection layer is not formed, that is, a defective portion of the hole injection layer is formed. As a result, the efficiency of hole injection into the light emitting layer is lowered, and the light emission efficiency of the pixel is lowered.

 In addition, since the hole injection layer is adjacent to the first electrode layer, when the above-described defect portion is formed in the hole injection layer, the first electrode layer and the second electrode layer are formed in the defect portion. May short circuit.

 When the material of the hole injection layer is made of a high molecular weight compound such as a conductive polymer, the hole injection layer can be formed by placing a solution of a high molecular weight compound. Even if it adheres, the solution covers the foreign matter. As a result, film defects in the hole injection layer and short circuit between the first electrode layer and the second electrode layer occur. However, the types of high molecular weight compounds that exhibit properties that can be used for the hole injection layer are limited.

In addition, since it is difficult to purify a hole injection layer material containing a high molecular weight compound, the content of impurities in the material is large, and the hole injection capability of the hole injection layer is not stable. More In addition, since the molecular weight distribution of the high molecular weight compound in the material differs depending on the production lot, the hole injection capability of the hole injection layer in each organic EL element is constant when multiple organic EL elements are formed. do not do.

 Furthermore, a thin film made of a high molecular weight compound easily retains a solvent in the thin film and easily adsorbs water, so that the organic EL element deteriorates due to the solvent and moisture. There is a problem of poor storage stability.

 An object of the present invention is to provide a means for solving various problems mentioned above as an example.

 An organic EL device according to a feature of the present invention includes an organic electroluminescence layer comprising a first and second electrode layers facing each other, and an organic functional layer containing an organic compound sandwiched between the first and second electrode layers. The organic functional layer includes a hole injection layer provided in contact with the first electrode layer, the hole injection layer being soluble in an organic solvent and having a hole injection property It contains a degradable low molecular weight compound.

 The method for producing an organic EL device according to the features of the present invention includes a step of forming a first electrode layer on a substrate, a step of forming an organic functional layer containing an organic compound on the first electrode layer, and the organic device. A step of forming a second electrode layer on the active layer, and the step of forming the organic functional layer is a step of forming a hole injection layer in contact with the first electrode layer. And forming the hole injection layer includes a step of preparing a solution containing a thermally decomposable low molecular weight compound that is soluble in an organic solvent and has a hole injection property, and the solution is used as the first electrode. And a step of arranging on the layer.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view of the organic EL device of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, an organic EL device manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings.

 An organic EL element 1 as shown in FIG. 1 has a substrate 2 made of a transparent material such as glass or resin, and a first electrode layer 3 made of a conductive material such as ITO provided on the substrate. The first electrode layer 3 is formed using a film forming method such as a sputtering method.

 A hole injection layer 4 is formed on the first electrode layer 3. The hole injection layer 4 is made of a low molecular weight compound that is soluble in an organic solvent and has hole injection properties. The molecular weight of such low molecular weight compounds is about 1000 or less. The low molecular weight compound is a special compound that decomposes when heated, that is, a compound having thermal decomposability, and the compound preferably causes thermal decomposition at a relatively low temperature of, for example, 500 ° C or lower. Masle.

 As a powerful low molecular weight compound, for example, there is a phthalocyanine derivative that is soluble in an organic solvent. The soluble phthalocyanine derivative is represented by the following general formula [Chemical Formula 1].

 [Chemical 1]

上記一般式 ίこおレ、て、 Meiま、 Al, Si, Ti, V, Cr， Mn, Fe， Co, Ni, Cu, Zn, Ga, Ge, Ru, Rh, Pd, In, Sn若しくは Pt等の金属原子を表す。 R1は、置換基を有してい ても良いアルキル基、水素原子、ハロゲン原子、水酸基、— OR3、— SR3、一 SeR3、 一 TeR3、一 OSiR4R5R6、 -OGeR4R5R6若しくは一 OPOR7R8を表す。 R3は、 置換基を有していても良いアルキル基、置換基を有していても良いアルコキシ基、置 換基を有していても良いシクロアルキル基若しくはポリエーテル基を表す。 R4， R5お よび R6は、互いに同一であっても異なっていても良ぐ置換基を有していても良いシク 口アルキル基、置換基を有していても良いァリール基、置換基を有していても良いアル コキシ基、置換基を有していても良いァリ一口キシ基あるいはポリエーテル基、水酸基 若しくは水素原子を表す。 R7, R8は、互いに同一であっても異なっていても良ぐ置 換基を有してレヽても良レ、アルキル基、置換基を有してレヽても良 ヽシクロアルキル基若し くは置換基を有してレヽても良レ、ァリール基を表す。

The above general formula ί, Mei, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Ru, Rh, Pd, In, Sn or Pt Represents a metal atom such as R1 represents an optionally substituted alkyl group, a hydrogen atom, a halogen atom, a hydroxyl group, —OR3, —SR3, one SeR3, one TeR3, one OSiR4R5R6, —OGeR4R5R6, or one OPOR7R8. R3 represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, a cycloalkyl group or a polyether group which may have a substituent. R4, R5 and R6 each have a cycloalkyl group which may have the same or different substituent, an aryl group which may have a substituent, and a substituent. Represents an alkoxy group which may be substituted, an aryloxy group which may have a substituent, a polyether group, a hydroxyl group or a hydrogen atom. R7 and R8 may be the same or different from each other and may have a substituent and may be substituted, an alkyl group, or a substituent and a cycloalkyl group or a cycloalkyl group. Represents a substituent having a substituent and represents an aryl group.

 R2 represents an alkyl group which may have a substituent, an alkoxy group which may have a substituent, a heterocyclic group which may have a substituent, a halogen atom, a nitro group, a cyan group or Represents a sulfonic acid group.

 In the phthalocyanine derivative having the chemical structure represented by the above general formula [Chemical Formula 1], the substituent of R1 is easily decomposed by heating, and the substituent of R2 contributes particularly to the solubility property in an organic solvent. Yes. That is, compared to phthalocyanine compounds such as copper phthalocyanine, the phthalocyanine derivative can be decomposed at a low temperature and becomes soluble in an organic solvent.

For the hole injection layer 4, an organic solution in which a low molecular weight compound such as the above phthalocyanine derivative is dissolved in an organic solvent is prepared, and then a film forming method such as a spin coating method is used. Then, the organic solution is placed on the first electrode layer, dried, and removed to remove the solvent.

 A hole transport layer 5 is provided on the hole injection layer 4. The hole transport layer 5 is composed of NPB (N, N, 1-di (naphthalene-1-yl) -1 N, N'-difuel-benzidine (N, N'-Di (naphth alene-1-yl) -Ν, Ν'-diphenyl-benzidme)), MTDATA (4, 4, 4, 4,

(3-methylphenylphenyl) triphenylamine (4,4 ', 4 "-tris (3-methylphenylphenyl) triphenylamine)) ^ TPD (N, N '-Bis (3-methylphenyl) -1,1, -1, biphenyl-1,4,4-diamine (ミ ン, Ν'-dipheny

材料 -Ν, Ν'-di (3-methylphenyl) -l, l * -biphenyl-4,4 ^, -diamine)) It can be formed using a method.

 On the hole transport layer 5, a light emitting layer 6 is provided. The light emitting layer 6 includes a material exhibiting light emitting characteristics such as Alq3 (tris (8-hydroxyquinoline) aluminum) and can be formed by using a film forming method such as a vapor deposition method. it can.

 An electron injection layer 7 is provided on the light emitting layer 6. The electron injection layer 7 contains, for example, lithium oxide and can be formed using a film forming method such as a vapor deposition method. As described above, the hole injection layer 4, the hole transport layer 5, the light emitting layer 6 and the electron injection layer 7 are formed in this order to constitute the organic functional layer 8.

 A second electrode layer 9 is provided on the electron injection layer 7. The second electrode layer 9 is made of a conductive material such as aluminum, aluminum lithium alloy, magnesium indium alloy, and magnesium silver alloy, and can be formed using a film forming method such as a vapor deposition method.

In the organic EL device having the above-described configuration, when an electric field is applied between the first electrode layer and the second electrode layer, the holes injected from the first electrode layer and the electrons injected from the second electrode layer And in the light emitting layer The light emitting layer emits light by recombination. When the first electrode layer and the second electrode layer are short-circuited, the short-circuited portion and the vicinity thereof are heated by Joule heat generated by the short-circuit, and this heat causes the low-molecular-weight coupling of the hole injection layer. Things decompose and vaporize. That is, when the low molecular weight compound contained in the hole injection layer is a phthalocyanine derivative, the R1 substituent portion in the above structural formula ([Chemical Formula 1]) is decomposed and vaporized. As a result, the hole injection layer in the vicinity of the short-circuited portion is expanded in volume and the short-circuited first electrode layer and second electrode layer are separated. In other words, the organic EL element configured as described above applies an electric field between the first electrode layer and the second electrode layer even if the first electrode layer and the second electrode layer are short-circuited. As a result, the hole injection layer has a self-healing function in which the short portion is repaired by thermal decomposition at a relatively low temperature and expansion. In addition, since a low-cost and high-purity phthalocyanine derivative can be obtained, the manufacturing cost of the organic EL device can be reduced.

 Since the hole injection layer as described above can be formed by placing a solution of a low molecular weight ionic compound on the first electrode layer, even if foreign matter adheres to the first electrode layer, it is covered. A hole injection layer can be formed. As a result, the defect portion of the hole injection layer is hardly formed in the portion where the foreign substance and the first electrode layer are in contact with each other and in the vicinity thereof. In addition, according to the film forming method, the generation of pinholes in the thin film can be suppressed as compared with the film forming method using the vapor deposition method. Therefore, a short circuit between the first electrode layer and the second electrode layer occurs. Furthermore, since thin films containing low molecular weight compounds can easily remove residual solvents and adsorbed moisture, they have high stability and can provide organic EL devices.

The low molecular weight compounds that can be used in the hole injection layer are not limited to soluble phthalocyanine derivatives. For example, soluble naphthalocyanine derivatives, soluble shear phthalates. Nin derivatives and soluble polyfunctional amine derivatives can be used as the material for the hole injection layer. As the polyfunctional amine derivative, for example, an arylamine derivative such as a triphenylamine derivative can be used.

 In addition, the hole injection layer is not limited to the case of being composed only of the above-described phthalocyanine derivative, and may include a compound having excellent hole injection properties as a dopant.

 The organic functional layer included in the organic EL element is not limited to the four-layer structure as described above, and may have a structure including at least a hole injection layer. For example, the organic functional layer may have a five-layer structure including a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

 An organic electroluminescent device comprising first and second electrode layers facing each other and an organic functional layer containing an organic compound sandwiched between the first and second electrode layers, wherein the organic functional layer comprises: A hole injection layer provided in contact with the first electrode layer, the hole injection layer including a thermally decomposable low molecular weight compound that is soluble in an organic solvent and has a hole injection property; According to the organic EL device of the present invention characterized by the above, when the first electrode layer and the second electrode layer are in contact with each other through a defect portion of the hole injection layer, Joule heat due to a short circuit is injected into the hole. When the layer is decomposed and expanded, the hole injection layer is adjacent to the first electrode layer, so that the first electrode layer and the second electrode layer can be effectively separated. As a result, the short part can be self-repaired.

Forming a first electrode layer on the substrate, forming an organic functional layer containing an organic compound on the first electrode layer, and forming a second electrode layer on the organic functional layer. In the method of manufacturing an organic EL element, the step of forming the organic functional layer includes a step of forming a hole injection layer in contact with the first electrode layer, and the step of forming the hole injection layer Organic solvent The present invention comprises a step of preparing a solution containing a thermally decomposable low molecular weight compound having a hole injection i4 and a step of disposing the solution on the first electrode layer. According to this organic EL device manufacturing method, the hole injection layer can be formed by disposing a solution containing a low molecular weight compound on the first electrode layer. Since it is difficult for defects in the hole injection layer due to the unevenness of the first electrode layer to occur, the risk of a short circuit between the first electrode layer and the second electrode layer is reduced.

Claims

The scope of the claims  1. An organic electroluminescent device comprising first and second electrode layers facing each other and an organic functional layer containing an organic compound sandwiched between the first and second electrode layers. The organic functional layer includes a hole injection layer provided in contact with the first electrode layer,  The organic electroluminescent device, wherein the hole injection layer contains a thermally decomposable low molecular weight compound that is soluble in an organic solvent and has a hole injection property.  2. The organic electroluminescence device according to claim 1, wherein the low molecular weight compound is a phthalocyanine derivative represented by the following general formula [Chemical Formula 1].  [Chemical 1]

[In the formula, Me is Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Ru, Rh, Pd In, Sn, or Pt, Rl is an alkyl group that may have a substituent, a hydrogen atom, a halogen atom, a hydroxyl group, —OR3, —SR3, —SeR3, one TeR3, one OSiR4R5R6, — OGe R4R5R6 or 1 OPOR7R8 (However, R3 may have a substituent, may be! /, An alkyl group, may have a substituent, may be! /, An alkoxy group, may have a substituent, Represents a good cycloalkyl group or a polyether group, and R4, R5 and R6 may be the same or different from each other, and may have a cycloalkyl group or a substituent which may have a substituent. Represents an aryl group, an alkoxy group which may have a substituent, an aryl group which may have a substituent, a polyether group, a hydroxyl group or a hydrogen atom, and R7 and R8 are the same as each other Alky, which may have different substituents R2 represents a cycloalkyl group or a substituent having a substituent, or a aryl group that may have a substituent, and R2 represents a group having a substituent. Re, an alkyl group, a substituent having a substituent may be selected, an alkoxy group, a heterocyclic group optionally having a substituent, a halogen atom, a nitro group, a cyan group or a sulfonic acid group. ]  3. The organic electroluminescence device according to claim 1, wherein the low molecular weight compound is a naphthalocyanine derivative, a cyanine derivative or a polyfunctional amine derivative. 4. forming a first electrode layer on the substrate; forming an organic functional layer containing an organic compound on the first electrode layer; forming a second electrode layer on the organic functional layer; A method for producing an organic electroluminescent device comprising:  The step of forming the organic functional layer includes the step of forming a hole injection layer in contact with the first electrode layer, The step of forming the hole injection layer includes a step of preparing a solution containing a thermally decomposable low molecular weight compound that is soluble in an organic solvent and has a hole injection property, and the solution is used as the first electrode. A method of producing an organic electroluminescent device, comprising a step of arranging on a layer.