JP2008227383A - Organic electroluminescent device and its fabrication process, electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent device in which emission efficiency, emission lifetime and manufacturability are improved. <P>SOLUTION: The organic electroluminescent device 10 comprises a function layer 7 including a hole block layer 6 and a light-emitting layer 5, and a first electrode 3 and a second electrode 8 for applying a voltage to the function layer 7 wherein the hole block layer 6 contains a copolymer of vinyl pyridine monomer, and vinyl monomer including an electron transportation unit contained in a light-emitting layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence device, a manufacturing method thereof, and an electronic apparatus.

In Patent Documents 1 and 2, in an organic EL (electroluminescence) device, a carrier blocking layer and an electron blocking layer are provided between the light emitting layer and the cathode, and between the light emitting layer and the anode, respectively, thereby regenerating the carrier. It is described that the number of carriers that do not contribute to the coupling and escape is reduced, and the luminous efficiency and the luminous lifetime are improved.
JP 2006-059878 A JP 2006-059879 A

  In Patent Documents 1 and 2, poly (2-vinylpyridine), poly (4-vinylpyridine), polyacrylic acid, polymethacrylic acid, poly (N, N-dimethylacrylamide), poly (ethylene glycol) are used as the hole blocking layer. ), Polypropylene glycol, poly (2-ethyl-2-oxazoline), poly (2-hydroxyethyl acrylate), poly (2-hydroxyethyl methacrylate), poly (tetramethylene ether) glycol, polyvinyl acetate, polyvinyl butyral Substituted polystyrene and poly-N-vinylpyrrolidone are preferred, and poly (2-vinylpyridine) is mainly used.

  By the way, poly (2-vinylpyridine) is an insulator in the first place, and has a carrier blocking property, but has a low electrical conductivity. For this reason, in Patent Documents 1 and 2, the film is formed with such a film thickness that the insulation can be ignored. However, if the hole blocking layer is thinned in this way, current leakage may occur. In addition, it is very difficult to control the film thickness of about 1 to 5 nm by the liquid layer method, and when it is laminated to a thickness exceeding 5 nm, not only holes but also electrons are blocked, and it hardly functions as a hole block and electron transport layer. there is a possibility.

  The present invention has been made in view of the above-mentioned problems of the prior art, and includes an organic electroluminescence device having a hole blocking layer that solves the above-described problems and improved in luminous efficiency, luminous lifetime, and manufacturability. The purpose is to provide.

In order to solve the above problems, an organic electroluminescence device of the present invention includes a functional layer including a hole blocking layer and a light emitting layer, and a first electrode and a second electrode that apply a voltage to the functional layer, The hole block layer includes a copolymer of a vinyl pyridine monomer and a vinyl monomer including an electron transport unit included in the light emitting layer.
According to this configuration, the polymer constituting the hole blocking layer has a skeleton structure of polyvinyl pyridine exhibiting a good hole blocking function, and further, the light emitting layer contains a vinyl monomer copolymerized with a vinyl pyridine monomer. Electron transportability is imparted by including an electron transport unit. Thereby, a hole block layer having both a hole block function and an electron transport function can be realized. Such a hole blocking layer can improve the confinement of holes to the light emitting layer, and can realize an organic electroluminescence device with high current efficiency and long life.

The copolymer is a polymer represented by Formula (1) or Formula (2) of Chemical Formula 1, and the ratio of the vinylpyridine monomer and the vinyl monomer in Formula (1) and Formula (2) is m: n. In this case, it is preferable that m and n satisfy the relationship of m ≧ n.
Polyvinylpyridine alone has the property that it dissolves only in a specific type of solvent. By using a material that dissolves in a specific organic solvent as a constituent material of the light-emitting layer, holes are formed on the light-emitting layer using a liquid phase method. Even when a liquid material for forming the block layer is applied, the light emitting layer can be prevented from being dissolved.
The copolymer of the hole block layer according to the present invention can also have such a dissolution property of polyvinyl pyridine, but the dissolution property is lost when the ratio of the vinyl monomer to be copolymerized increases. There is.
Therefore, by adjusting the ratio m: n of the vinyl pyridine monomer to the vinyl monomer so that m ≧ n, a copolymer having the solubility characteristics of polyvinyl pyridine can be obtained, and a liquid phase method is provided on the light emitting layer. It becomes possible to form a hole block layer simply using.

Further, it is preferable that m and n satisfy a relationship of m ≧ 3n. If it is set as such a range, the phase dissolution of a light emitting layer can be avoided more reliably.
If the ratio of the vinyl monomer having an electron transport unit is small, the electron transport property of the hole block layer is lowered, and when the hole block layer is formed thick, it may not function as a hole block layer. Therefore, if the ratio m: n of the vinyl pyridine monomer to the vinyl monomer is in the range of 3: 1 to 5: 1, it is preferable because the electron transport property of the hole block layer can be sufficiently secured.

  It is preferable that the electron transport unit of the vinyl monomer has a characteristic group including an aromatic ring having electron transport properties or a heterocycle having electron transport properties. Any characteristic group comprising an aromatic ring or a heterocyclic ring can be easily introduced into a vinyl monomer.

It is preferable that a spacer group is introduced between the electron transport unit introduced into the side chain of the copolymer and the main chain. That is, it is preferable that a spacer group is introduced between the vinyl group of the vinyl monomer and the electron transport unit.
With such a configuration, when a vinyl monomer and a vinyl pyridine monomer are polymerized to obtain a copolymer, the electron transport unit having a size larger than that of the vinyl pyridine monomer is prevented from becoming a steric hindrance, and a polymerization reaction is performed. Can be promoted.

  The spacer group is preferably an alkyl group or an aryl group. These functional groups are effective as the spacer group.

It is preferable that the vinyl monomer is a comonomer having a characteristic group represented by any one of formulas (3) to (6) of Chemical Formula 2.
The light emitting materials constituting the light emitting layer in the case of using the hole blocking layer containing the organic compound represented by the formulas (3) to (6) are those represented by the formulas (7) to (10) of Chemical formula 3, respectively. is there. Thus, in the present invention, as the hole blocking layer, a copolymer obtained by polymerizing a vinyl monomer having a characteristic group containing the same electron transport unit as the electron transport unit of the light emitting material with a vinyl pyridine monomer is used. . As a result, an organic electroluminescence device having a hole blocking layer having an appropriate electron transporting property according to the configuration of the light emitting layer is obtained, so that the electron transporting property from the hole blocking layer to the light emitting layer is improved and the current efficiency is increased. be able to.

The organic electroluminescence device of the present invention further includes a functional layer including a hole blocking layer and a light emitting layer, and a first electrode and a second electrode for applying a voltage to the functional layer, and the hole blocking layer includes vinyl pyridine. A copolymer of a monomer and a vinyl monomer having an electron transport unit including an aromatic ring having an electron transporting property or a heterocyclic ring having an electron transporting property is included.
In the present invention, the vinyl monomer constituting the hole block layer may be any one that includes at least an electron transport unit. Such an electron transport unit is preferably the same type as the electron transport unit included in the light emitting layer, but even if the electron transport unit does not coincide with the electron transport unit of the light emitting layer, the hole transport layer has an electron transporting property. Different types of electron transport units can be employed within the range that can be obtained.

According to another aspect of the present invention, there is provided a method for manufacturing an organic electroluminescent device comprising: a functional layer including a hole blocking layer and a light emitting layer; and a first electrode and a second electrode for applying a voltage to the functional layer. A manufacturing method, wherein the hole blocking layer is formed using a liquid material including a copolymer of a vinyl pyridine monomer and a vinyl monomer including an electron transport unit included in the light emitting layer. .
By setting it as such a manufacturing method, the hole block layer provided with the hole block function and the electron transport function can be formed easily.

The hole blocking layer is preferably formed using a liquid phase method such as an inkjet method or a spin coating method.
Conventionally, it is necessary to form the hole blocking layer with a thickness of 1 to 5 nm in order to ensure the electron transport property, and such a thin film is difficult to form by a liquid phase method such as an ink jet method or a spin coat method. It was. In contrast, in the present invention, since the hole blocking layer is made of a material having an electron transporting property, the hole blocking layer is formed with a film thickness (for example, 10 to 20 nm) that can be uniformly formed using a liquid phase method. it can.
Therefore, according to the manufacturing method of the present invention, an organic electroluminescence device including a hole blocking layer having good hole blocking property and electron transporting property can be easily and inexpensively manufactured by a liquid phase method.

  Next, an electronic apparatus according to the present invention includes the organic electroluminescence device according to the present invention described above. According to this configuration, it is possible to provide an electronic apparatus including a light emitting device with high reliability and excellent light emission characteristics.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

(Organic EL device)
FIG. 1 is a schematic configuration diagram of an organic EL device 10 of the present embodiment. The organic EL device 10 includes a base 2 made of glass, quartz, plastic, or the like. An anode (first electrode) 3, a hole injection layer 4, a light emitting layer 5, a hole blocking layer 6, and a cathode (second electrode) 8 are formed on the substrate 2. The hole injection layer 4, the light emitting layer 5, and the hole block layer 6 are all formed of an organic material, and the hole injection layer 4, the light emitting layer 5, and the hole block layer 6 form a functional layer 7. . The functional layer 7 is sandwiched between the anode 3 and the cathode 8, and the organic EL element 9, which is a light emitting element, is formed by the anode 3, the functional layer 7, and the cathode 8. A wiring for applying a driving voltage is connected to the anode 3 and the cathode 8 as conceptually shown in FIG.

  Holes from the anode 3 and electrons from the cathode 8 are injected into the light emitting layer 5 through the wiring. The holes and electrons injected into the light emitting layer 5 move through the light emitting layer 5 and recombine. The energy released during the recombination generates excitons, and when the excitons return to the ground state, energy is emitted in the form of fluorescence or phosphorescence. The light emitted from the organic EL element 9 is emitted from the base 2 made of a glass substrate or the like and taken out to the outside (bottom emission method). If the cathode 8 is formed of a transparent conductive film such as ITO, light emitted from the organic EL element 9 can be extracted from the cathode 8 side (top emission method). In the following description, electrons and holes injected into the light emitting layer 5 may be referred to as carriers.

  As the hole injection layer 4, an arylamine derivative, a phthalocyanine derivative, a polyaniline derivative + an organic acid, a polythiophene derivative + a polymer acid, or the like is used. In particular, a mixture (PEDOT / PSS) of polyethylene dioxythiophene and polystyrene sulfonic acid is suitable.

  The light emitting layer 5 includes a known light emitting material capable of emitting fluorescence or phosphorescence. Specifically, (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinyl carbazole (PVK), polythiophene derivative, polymethyl Polysilanes such as phenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as. Alternatively, a low molecular material such as carbazole (CBP) can be doped with these low molecular dyes to form a light emitting layer.

  In the present embodiment, a polymer light emitting material represented by the following formulas (7) to (10) of the following chemical formula 4 is used as the light emitting layer 5 in particular.

  The organic EL device 10 according to the present invention includes, as the hole blocking layer 6 formed between the light emitting layer 5 and the cathode 8, a vinyl pyridine monomer and a vinyl monomer including an electron transport unit included in the light emitting layer. A thin film made of the above copolymer is used. Specifically, a copolymer of the vinyl pyridine monomer represented by the formula (11) of the chemical formula 5 and the vinyl monomer having the electron transport unit Y represented by the formula (12) (the formula (1) of the chemical formula 6), or The hole blocking layer 6 is formed by using a copolymer of the vinyl pyridine monomer represented by the formula (11) and the vinyl monomer having the electron transport unit Y and the spacer group R represented by the formula (13) (formula (2) in the chemical formula 6). Forming. The polymerization method for producing the copolymer is not particularly limited, and any of radical polymerization, cationic polymerization, and anionic polymerization may be used.

  More specifically, examples of the copolymer constituting the hole blocking layer 6 include a copolymer obtained by polymerizing a vinyl monomer containing a characteristic group represented by Formula (3) to Formula (6) of Chemical Formula 7 together with a vinylpyridine monomer. be able to. Formulas (3) to (6) correspond to the side chain RY in Formula (2) of Chemical Formula 6, and a phenyl group as a spacer group R is interposed between the electron transport unit Y and the main chain. It has been introduced. Therefore, the electron transport unit Y in each characteristic group is obtained by omitting the phenyl group at the upper end of the figure in the formulas (3) to (6) of Chemical formula 7.

  In the formulas (3) to (6), the case where a phenyl group is used as the spacer group R is shown, but the spacer group R may be another aryl group or an alkyl group. By introducing such a spacer group R between the electron transport unit Y and the vinyl group, the distance between the electron transport unit Y and the vinyl group can be increased, and the size is larger than that of the vinylpyridine monomer. The electron transport unit Y can be prevented from becoming a steric hindrance during the polymerization, and the polymerization reaction can be promoted.

  The copolymer in which the characteristic groups represented by the formulas (3) to (6) are introduced is selected according to the configuration of the electron transport unit of the luminescent material constituting the luminescent layer 5. That is, as the copolymer constituting the hole block layer 6, a copolymer having an electron transport unit Y common to the electron transport unit of the light emitting layer 5 is selected. Therefore, when the luminescent material constituting the light emitting layer 5 is represented by the formula (7) of the chemical formula 5, the formula (3) having the same electron transport unit as the constituent repeating unit of the formula (7) A copolymer having an electron transport unit obtained by removing the phenyl group at the upper end of the figure from the characteristic group shown or the characteristic group of the formula (3) is used as the hole blocking layer 6. Similarly, for the luminescent materials represented by the formulas (8) to (10), the characteristic groups represented by the formulas (4) to (6) or those obtained by omitting the phenyl group in the characteristic groups are holes. Used for the block layer 6.

  When the light emitting layer 5 is configured using the light emitting material represented by the formulas (7) to (10) in Chemical formula 4, the injection barrier from the anode 3 and the cathode 8 to the light emitting layer 5 is large, and it is involved in carrier recombination. The number of carriers that escape easily increases, and the carrier mobility in the light emitting layer 5 greatly differs between holes and electrons, so that the carrier balance is likely to be lost. Therefore, in the present embodiment, as the hole blocking layer 6, a copolymer having the electron transport unit of the light emitting layer 5 in a vinyl monomer as described above is used. Thereby, since the electron transport system of the hole block layer 6 has the same configuration as the electron transport system of the light emitting layer 5, the electron transport from the hole block layer 6 to the light emitting layer 5 becomes smooth, and the current efficiency is improved. Can do.

  Note that the electron transport unit Y does not necessarily have to be the same as the constituent repeating unit of the light-emitting material as in the formula (3) to formula (6) of Chemical formula 7. For example, a derivative of a characteristic group represented by the formulas (3) to (6) including one or more aromatic rings having an electron transport property as shown in Chemical Formula 8 may be used as the electron transport unit Y. Alternatively, the electron transporting aromatic ring shown in Chemical formula 8 can be used as the electron transport unit Y in Chemical formula 6.

  By the way, a single polyvinyl pyridine is dissolved only in acetic acid, t-butanol, lower alcohol, DMF (dimethylformamide), DMSO (dimethyl sulfoxide). Therefore, by using a light-emitting material soluble in a halogen-containing organic solvent or an aromatic organic solvent as the constituent material of the light-emitting layer 5, phase dissolution occurs even when a liquid material containing polyvinylpyridine is applied on the light-emitting layer 5. There is no advantage. Therefore, in the copolymer according to the present embodiment, in order to obtain such advantageous characteristics of polyvinyl pyridine, the ratio of the vinyl monomer including the electron transport unit Y is equal to or less than the content ratio of the vinyl pyridine monomer. What should I do?

  Specifically, the vinyl pyridine monomer so that the ratios m and n of the vinyl pyridine monomer and the vinyl monomer represented by the formula (1) or the formula (2) in the chemical formula 6 satisfy the relationship of m ≧ n. The mixing ratio of vinyl monomer is adjusted. In order to develop the solubility characteristics of polyvinyl pyridine, it is preferable that the content ratio of the vinyl monomer is small. On the other hand, if the ratio of the vinyl monomer is decreased, the electron transport property is decreased. Therefore, the mixing ratio m: n is 5: The mixing ratio may be adjusted so as to be in the range of 1 to 3: 1. By setting it as this range, the copolymer which has the solubility characteristic similar to polyvinyl pyridine can be obtained, ensuring the electron transport property obtained by the vinyl monomer containing the electron transport unit Y.

  As described above, the copolymer used for the constituent material of the hole blocking layer 6 in this embodiment has a good hole blocking function because it contains a vinylpyridine monomer, and further, electron transport. By including a vinyl monomer having unit Y, electron transportability is imparted to polyvinyl pyridine, which is originally an insulator. By having such a configuration, the hole blocking layer 6 of the present embodiment has both an excellent hole blocking function and an electron transporting property.

  Here, FIG. 2 is an operation explanatory view of the organic EL device 10 including the hole block layer 6. 2A is an enlarged cross-sectional view showing the light emitting layer 5 and the hole blocking layer 6 in the organic EL device 10 according to the present invention, and FIG. 2B shows the hole blocking layer 60 made of polyvinylpyridine. FIG. 6 is a cross-sectional configuration diagram of a conventional configuration formed on a light emitting layer 5.

Since the hole block layer 60 in the conventional configuration is made of polyvinyl pyridine as an insulator, if it is formed thick, even the electrons injected from the cathode are blocked, and the hole block layer 60 does not function. Therefore, as shown in FIG. 2B, a hole blocking layer 60 is formed so as to transmit electrons while blocking holes by forming a very thin polyvinylpyridine film having a thickness of about 1 to 5 nm.
However, in such a thin film, the intended effect may not be obtained because the holes are not sufficiently blocked. In particular, when a liquid phase method such as an ink-jet method or a spin coating method is used, a portion 60d where the hole blocking layer 60 is locally thinned by unevenness on the surface of the light emitting layer 5 as shown in FIG. Easy to form. In addition, it is extremely difficult to form a thin film having a thickness of 5 nm or less in the liquid phase method with a uniform thickness, and variations in light emission characteristics due to uneven film thickness are likely to occur.

On the other hand, in the present invention, as described above, a copolymer of a vinyl monomer containing an electron transport unit and a vinylpyridine monomer is formed on the light emitting layer 5 as a hole blocking layer 6. And by using the copolymer which has an electron transport property in this way, the hole block layer 6 can be formed thickly (for example, thickness 10-20 nm) as shown to Fig.2 (a). Accordingly, the thin portion 60d shown in FIG. 2B can be formed on the light emitting layer 5 with a uniform thickness without being formed.
In addition, since it can be formed in this way, the hole block layer 6 can be formed by using a liquid phase method such as an ink-jet method or a spin coating method, which has been difficult to apply in the past, and the equipment cost can be reduced. The hole block layer 6 can be formed by a simple process.
In addition, since the hole blocking layer 6 can be formed with a thickness twice or more that of the conventional one, the hole blocking function of the hole blocking layer 6 can be improved, and the hole blocking layer 6 excellent in both the hole blocking function and the electron transporting property. Can be realized.

  As described above, in the organic EL device of the present invention, the hole blocking layer 6 excellent in both the hole blocking function and the electron transporting property is provided, so that the hole can be well confined in the light emitting layer 5, thereby improving the current efficiency. As a result, the light emission lifetime is also increased. Furthermore, since it can be manufactured by a simple liquid phase process, it is an organic EL device capable of reducing the manufacturing cost.

  In addition, since the electron transport unit included in the light emitting layer 5 and the electron transport unit included in the hole block layer 6 have a common configuration, a hole block layer having an appropriate electron transport property according to the configuration of the light emitting layer can be obtained. Since the provided organic electroluminescence device can be configured, the electron transport property from the hole blocking layer to the light emitting layer is improved, and the current efficiency can be increased.

  An electron injection layer may be provided between the hole block layer 6 and the cathode 8. As such an electron injection layer, polyfluorene derivatives, polyparaphenylene vinylene derivatives, polyparaphenylene derivatives, polyvinylcarbazole, polythiophene derivatives, polysilane-based high molecular organic materials such as polymethylphenylsilane are preferably used.

Next, a method for producing an organic compound that can be used as a material for forming the hole blocking layer 6 according to the embodiment will be briefly described. In the following, vinyl monomers constituting the copolymer represented by the formula (2) of the chemical formula 6 and the vinyl monomers 3A to 6A having the characteristic groups represented by the formula (3) to the formula (6) of the chemical formula 7 The manufacturing method will be described with reference to Chemical Formula 9 to Chemical Formula 12.
In addition, if vinyl monomers 3A-6A are manufactured by the following manufacturing method, the copolymer which has a structure shown to Formula (2) of Chemical formula 6 is obtained by making it copolymerize with the vinyl pyridine monomer prepared separately. For the polymerization step, any of radical polymerization, cationic polymerization, and anionic polymerization may be used.

  The vinyl monomer 3A containing the characteristic group shown in Formula (3) of Chemical Formula 7 can be produced by the reaction process shown in Chemical Formula 9 below. In the lower column of Chemical Formula 9, the main parts of the reaction conditions (catalyst, reaction environment, reaction temperature, etc.) in the reaction formulas (i) to (ii) are also shown.

  The vinyl monomer 4A containing the characteristic group represented by the formula (4) in Chemical Formula 7 is obtained through a reaction process represented by Chemical Formula 10 below. In the lower column of Chemical Formula 10, the main parts of the reaction conditions (catalyst, reaction environment, reaction temperature, etc.) in the reaction formulas (i) to (ii) are also shown.

  The vinyl monomer 5A containing the characteristic group represented by the formula (5) of Chemical Formula 7 is obtained through a reaction process represented by Chemical Formula 11 below. In the lower column of Chemical Formula 11, the main parts of the reaction conditions (catalyst, reaction environment, reaction temperature, etc.) in the reaction formulas (i) to (ii) are also shown.

  The vinyl monomer 6A containing the characteristic group represented by the formula (6) in Chemical formula 7 is obtained through the reaction process shown in the chemical formula 12 below. In the lower column of Chemical Formula 12, the main parts of the reaction conditions (catalyst, reaction environment, reaction temperature, etc.) in the reaction formulas (i) to (v) are also shown.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following description, the configuration and manufacturing process of the organic EL device shown in FIGS. 1 to 3 will be referred to as appropriate.

[Example 1]
In this example, an organic EL device 10 having a hole blocking layer 6 made of a copolymer containing a vinyl monomer having a characteristic group represented by the formula (3) of Chemical Formula 7 was produced.
First, an ITO film was patterned on the substrate 2 to form an anode 3.
Next, a liquid material containing a hole injection layer forming material is applied on the anode 3 to a layer thickness of 50 to 60 nm by a spin coating method, and then the substrate 2 coated with the liquid material is heated and fired at 150 ° C. Thus, the hole injection layer 4 was formed on the anode 3. As the hole injection layer forming material, 3,4-polyethylenedioxythiophene / polystyrenesulfonic acid (PEDOT / PSS), which is a polyolefin derivative, was used.

  Next, on the hole injection layer 4, a liquid material in which a light emitting material represented by the formula (7) of Chemical Formula 4 is used as a 1.8 wt% xylene solution is applied by spin coating to a layer thickness of 60 to 80 nm, and then The light emitting layer 5 was formed on the hole injection layer 4 by subjecting the substrate 2 coated with the liquid material to a baking treatment at 130 ° C. for 30 minutes in a nitrogen atmosphere.

  Next, a copolymer (number average molecular weight 50000) represented by the formula (2) of the chemical formula 6 obtained by copolymerizing a vinyl monomer having a characteristic group represented by the formula (3) of the chemical formula 7 with a vinylpyridine monomer, A liquid material in a 0.5 wt% 2-ethoxyethanol solution was prepared, and this liquid material was applied on the light emitting layer 5 by 10 to 20 nm by a spin coat method. Thereafter, the substrate 2 coated with the liquid material was baked at 200 ° C. for 60 minutes in a nitrogen atmosphere to form the hole blocking layer 6 on the light emitting layer 5.

Next, under a vacuum of 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa), a 4 nm thick LiF layer, a 10 nm thick Ca layer is formed on the hole blocking layer 6 by a vacuum deposition method. Then, an Al layer having a layer thickness of 200 nm was sequentially laminated to form the cathode 8.

[Example 2]
It is obtained by forming the light emitting layer 5 using the light emitting material represented by the formula (8) of Chemical formula 4 and copolymerizing the vinyl monomer having the characteristic group represented by the chemical formula (4) of the chemical formula 7 and the vinylpyridine monomer. An organic EL device according to Example 2 was fabricated in the same manner as in Example 1 except that the hole blocking layer 6 was formed using the copolymer represented by Formula (2) of Chemical Formula 6.

[Example 3]
It is obtained by forming the light emitting layer 5 using the light emitting material represented by the formula (9) of Chemical formula 4 and copolymerizing the vinyl monomer having the characteristic group represented by the chemical formula (5) of the chemical formula 7 and the vinylpyridine monomer. An organic EL device according to Example 3 was fabricated in the same manner as in Example 1 except that the hole blocking layer 6 was formed using the copolymer represented by Formula (2) of Chemical Formula 6.

[Example 4]
It is obtained by forming the light emitting layer 5 using the light emitting material represented by the formula (10) of Chemical Formula 4 and copolymerizing the vinyl monomer having the characteristic group represented by the formula (6) of Chemical Formula 7 and the vinylpyridine monomer. An organic EL device according to Example 4 was produced in the same manner as in Example 1 except that the hole block layer 6 was formed using the copolymer represented by Formula (2) of Chemical Formula 6.

[Comparative Example 1]
The organic EL device according to Comparative Example 1 was produced by the following procedure.
The organic EL device of Comparative Example 1 has the same layer structure as the organic EL device 10 shown in FIG. 1 except that the hole blocking layer 6 is not provided. That is, the organic EL device has a configuration in which an anode 3, a hole injection layer 4, a light emitting layer 5, and a cathode 8 are laminated on a substrate 2.
Further, the light emitting material constituting the light emitting layer 5 is as shown in the formula (7) of the chemical formula 4 as in the first embodiment.

First, an ITO film was patterned on the substrate 2 to form an anode 3.
Next, a liquid material containing a hole injection layer forming material is applied on the anode 3 to a layer thickness of 50 to 60 nm by a spin coating method, and then the substrate 2 coated with the liquid material is heated and fired at 150 ° C. Thus, the hole injection layer 4 was formed on the anode 3. As the hole injection layer forming material, 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS), which is a polyolefin derivative, was used.

  Next, a liquid material in which a light emitting material represented by the formula (7) of Chemical Formula 4 (the same light emitting material as that in Example 1) in 1.8 wt% xylene solution is formed on the hole injection layer 4 by spin coating. The light emitting layer 5 is formed on the hole injection layer 4 by applying a baking treatment at 130 ° C. for 30 minutes in a nitrogen atmosphere to the base 2 coated with a thickness of 60 to 80 nm and then coated with the liquid material. Formed.

Next, the cathode 8 was formed on the light emitting layer 5 without forming a hole block layer. Specifically, a LiF layer having a layer thickness of 4 nm, a Ca layer having a layer thickness of 10 nm, and a layer thickness of 200 nm are formed by vacuum deposition under a vacuum of 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa). The Al layer was sequentially laminated to form the cathode 8 on the light emitting layer 5.

[Comparative Example 2]
An organic EL device according to Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the light-emitting layer 5 was formed using the light-emitting material represented by Formula (8) of Chemical Formula 4 (the same light-emitting material as Example 2). did.

[Comparative Example 3]
An organic EL device according to Example 3 was fabricated in the same manner as Comparative Example 1 except that the light-emitting layer 5 was formed using the light-emitting material represented by Formula (9) in Chemical Formula 4 (the same light-emitting material as Example 3). did.

[Comparative Example 4]
An organic EL device according to Comparative Example 4 was produced in the same manner as in Example 1 except that the light emitting layer 5 was formed using the light emitting material represented by Formula (10) of Chemical Formula 4 (the same light emitting material as in Example 4). did.

[Evaluation results]
Regarding the organic EL devices according to Examples 1 to 4 and Comparative Examples 1 to 4 manufactured as described above, the organic EL devices of Examples 1 to 4 and the organics of Comparative Examples 1 to 4 are set to an initial luminance of 800 cd / cm ^2. The EL device was driven at a constant current, and the current efficiency and half time were measured for each organic EL device. Table 1 shows the measurement results.
The current efficiency is a current value required per luminance of 1 cd / cm ² , and the half time is an operation time until the light emission luminance becomes 1/2 of the initial luminance. Moreover, in Table 1, the current efficiency and the half-life value are displayed as relative values with the current efficiency and the half-life time of Comparative Examples 1 to 4 to be compared as 1, respectively.

  As shown in Table 1, organic ELs of Examples 1 to 4 in which a hole blocking layer made of a copolymer containing a vinyl monomer having the same electron transport unit as the light emitting material constituting the light emitting layer 5 was formed. As a result, the device was superior in both current efficiency and half time compared to the organic EL devices of Comparative Examples 1 to 4 having no hole blocking layer.

  Thus, by providing the hole block layer 6 including a copolymer of a vinyl monomer containing an electron transport unit included in the light emitting layer 5 and a vinyl pyridine monomer, a good hole block function and an electron transport property are obtained. Thus, it was confirmed that the current efficiency can be improved and the light emission life can be extended. In addition, since the hole blocking layer 6 according to this example has a good electron transporting property, it can be formed as thick as about 10 to 20 nm, thereby further improving the hole blocking function of the hole blocking layer 6. In addition, there is no problem of leakage current or the like when the hole block layer is thin.

[Image forming apparatus (electronic equipment)]
Next, an image forming apparatus which is a first embodiment of an electronic apparatus including the organic EL device of the present invention will be described.
FIG. 4 is a schematic configuration diagram illustrating a main part of the image forming apparatus 100 including the organic EL device as a line head.

  The image forming apparatus 100 includes a photosensitive drum 16 as an image carrier in the vicinity of the travel path of the transfer medium 22. Around the photosensitive drum 16, an exposure device 15, a developing device 18, and a transfer roller 21 are sequentially arranged along the rotation direction of the photosensitive drum 16 (indicated by an arrow in the drawing). The photosensitive drum 16 is rotatably provided around the rotation shaft 17, and a photosensitive surface 16 </ b> A is formed on the outer peripheral surface of the photosensitive drum 16 at the central portion in the rotation axis direction. The exposure device 15 and the developing device 18 are arranged in a long axis shape along the rotation shaft 17 of the photosensitive drum 16, and the width in the long axis direction substantially coincides with the width of the photosensitive surface 16A.

  In the image forming apparatus 100, first, in the process of rotating the photosensitive drum 16, the surface of the photosensitive drum 16 (photosensitive surface 16 </ b> A) is positive (+) by a charging device (not shown) provided on the upstream side of the exposure device 15. Then, the surface of the photosensitive drum 16 is exposed by the exposure device 15 to form an electrostatic latent image LA on the surface. Further, the toner (developer) 20 is applied to the surface of the photosensitive drum 16 by the developing roller 19 of the developing device 18, and the toner image corresponding to the electrostatic latent image LA is formed by the electric attractive force of the electrostatic latent image LA. It is formed. The toner particles are positively (+) charged.

  After the toner image is formed by the developing device 18, the toner image comes into contact with the transfer medium 22 by further rotation of the photosensitive drum 16, and the transfer roller 21 has a polarity opposite to that of the toner particles of the toner image from the back surface of the transfer medium 22. Charge (here, negative (−) charge) is applied, and accordingly, toner particles forming a toner image are attracted from the surface of the photosensitive drum 16 to the transfer medium 22, and the toner image is transferred to the surface of the transfer medium 22. Is transcribed.

  The exposure apparatus 15 includes a line head 1 having a plurality of organic EL elements 9 and an imaging optical element 12 having a plurality of lens elements 13 for imaging the light L emitted from the line head 1 at an erecting equal magnification. I have. The line head 1 and the imaging optical element 12 are held by a head case (not shown) while being aligned with each other, and are fixed on the photosensitive drum 16.

  The line head 1 includes a light emitting element array 110 in which a plurality of organic EL elements 9 are arranged along the rotation axis 17 of the photosensitive drum 16 and a drive element group including a drive element (not shown) that drives the organic EL elements 9. And a control circuit group 11 for controlling driving of these drive elements (drive element group). The organic EL element 9, the drive element group, and the control circuit group 11 are integrally formed on a long and thin element substrate (base) 2.

  The imaging optical element 12 is arranged (arranged) in a zigzag pattern in which the lens elements 13 having the same configuration as the SELFOC (registered trademark) lens element manufactured by Nippon Sheet Glass Co., Ltd. are arranged along the rotation axis 17 of the photosensitive drum 16. A lens element array 14 is provided.

  In this image forming apparatus 100, the organic EL element 9 formed on the line head 1 has the structure of the light emitting element of the present invention described above. Therefore, the image forming apparatus is provided with an exposure apparatus with high current efficiency, low power consumption, and long life.

[Organic EL display device (electronic equipment)]
Next, an organic EL display device that is a second embodiment of an electronic apparatus including the organic EL device of the present invention will be described. FIG. 5 is a schematic configuration diagram of an organic EL display device 200 including organic EL elements as pixels in a matrix.

  The organic EL display device 200 includes a circuit element unit 30 including a thin film transistor as a circuit element, a pixel electrode (first electrode) 3 serving as an anode, an organic functional layer 7 including a light emitting layer, and a counter electrode serving as a cathode. (Second electrode) 8, a sealing portion 32, and the like are provided.

  For example, a glass substrate is used as the substrate 2. As a substrate in the present invention, in addition to a glass substrate, various known substrates used for electro-optical devices and circuit substrates such as a silicon substrate, a quartz substrate, a ceramic substrate, a metal substrate, a plastic substrate, and a plastic film substrate are applied. The

  On the substrate 2, a plurality of pixel areas A as light emitting areas are arranged in a matrix, and when performing color display, for example, each color corresponds to red (R), green (G), and blue (B). The pixel area A to be formed is formed in a predetermined arrangement. In each pixel region A, a pixel electrode (anode) 3 is disposed, and in the vicinity thereof, a signal line 42, a common power supply line 43, a scanning line 41, scanning lines for other pixel electrodes (not shown), and the like are disposed. . As the planar shape of the pixel region A, an arbitrary shape such as a circle or an oval can be applied in addition to the rectangle shown in the figure.

  The sealing portion 32 prevents water and oxygen from entering and prevents the counter electrode 8 or the organic functional layer 7 from being oxidized, and includes a sealing substrate (or sealing can) 34 bonded to the base 2. The sealing substrate 34 is made of glass, metal, or the like, and the base 2 and the sealing substrate 34 are bonded together with a sealing agent. A desiccant is disposed inside the substrate 2, and an inert gas filling layer 33 filled with an inert gas is formed in a space formed between the substrates.

  In the pixel region A, a first thin film transistor 44 for switching in which a scanning signal is supplied to the gate electrode through the scanning line 41 and a holding for holding an image signal supplied from the signal line 42 through the thin film transistor 44. The capacitor cap, the driving second thin film transistor 45 to which the image signal held by the holding capacitor cap is supplied to the gate electrode, and the common supply line when electrically connected to the common power supply line 43 through the thin film transistor 45 A pixel electrode 3 into which a drive current flows from the electric wire 43 and a functional layer 7 sandwiched between the pixel electrode 3 and the counter electrode (cathode) 8 are provided. The functional layer 7 includes a light emitting layer and a hole blocking layer, and the organic EL element 9 which is a light emitting element includes the pixel electrode 3, the counter electrode 8, the functional layer 7, and the like.

  In the pixel area A, when the scanning line 41 is driven and the first thin film transistor 44 is turned on, the potential of the signal line 42 at that time is held in the holding capacitor cap, and the second capacitance is changed according to the state of the holding capacitor cap. The conductive state of the thin film transistor 45 is determined. In addition, a voltage is applied to the pixel electrode 3 from the common power supply line 43 through the channel of the second thin film transistor 45, and a current flows between the pixel electrode 3 and the counter electrode 8 through the functional layer 7 due to the potential difference. The functional layer 7 (light emitting layer) emits light according to the amount of current at this time.

  In the organic EL display device 200, light emitted from the functional layer 7 to the base 2 side is transmitted through the circuit element unit 30 and the base 2 and emitted to the lower side (observer side) of the base 2. The light emitted from 7 to the opposite side of the base 2 is reflected by the counter electrode 8, and the light passes through the circuit element portion 30 and the base 2 and is emitted to the lower side (observer side) of the base 2 (bottom). Emission type). Note that light emitted from the counter electrode can be emitted by using a transparent material as the counter electrode 8 (top emission type). In this case, ITO or the like can be used as the transparent material for the counter electrode.

  In this organic EL display device 200, the organic EL element 9 formed in the pixel region A has the structure of the light emitting element of the present invention described above. As a result, the organic EL display device has high current efficiency, low power consumption, and long life and bright display.

The cross-sectional block diagram which shows the organic EL apparatus of this invention. The figure which shows the manufacturing process of the organic electroluminescent apparatus of this invention. FIG. 3 is a diagram for explaining the operation of the organic EL device of the present invention. 1 is a diagram illustrating an image forming apparatus that is an example of an electronic apparatus. The figure which shows the organic electroluminescence display which is an example of an electronic device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Organic EL apparatus, 2 base | substrate, 3 anode (1st electrode), 4 hole injection layer, 5 light emitting layer, 6 hole block layer, 7 functional layer, 8 cathode, 9 organic EL element, 6a liquid material

Claims (11)

A functional layer including a hole blocking layer and a light emitting layer; and a first electrode and a second electrode for applying a voltage to the functional layer,
The organic electroluminescence device, wherein the hole blocking layer includes a copolymer of a vinyl pyridine monomer and a vinyl monomer including an electron transport unit included in the light emitting layer. The copolymer is a polymer represented by Formula (1) or Formula (2) of Chemical Formula 1,
When the ratio of the vinylpyridine monomer and the vinyl monomer in the formulas (1) and (2) is m: n,
The organic electroluminescence device according to claim 1, wherein the m and n satisfy a relationship of m ≧ n.

  3. The organic electroluminescence device according to claim 2, wherein m and n satisfy a relationship of m ≧ 3n.   4. The organic electroluminescence device according to claim 1, wherein the electron transport unit of the vinyl monomer includes an aromatic ring having an electron transport property or a heterocycle having an electron transport property. 5.   4. The organic electrophoretic device according to claim 1, wherein a spacer group is introduced between the electron transport unit introduced into the side chain of the copolymer and the main chain. 5. Luminescence device.   6. The organic electroluminescence device according to claim 5, wherein the spacer group is an alkyl group or an aryl group. The organic electroluminescent device according to claim 6, wherein the vinyl monomer is a comonomer having a characteristic group represented by any one of formulas (3) to (6) of Chemical Formula 2.

A functional layer including a hole blocking layer and a light emitting layer; and a first electrode and a second electrode for applying a voltage to the functional layer,
The hole blocking layer includes a copolymer of a vinyl pyridine monomer and a vinyl monomer having an electron transport unit including an aromatic ring having electron transport properties or a heterocycle having electron transport properties. Organic electroluminescence device. A method of manufacturing an organic electroluminescence device comprising: a functional layer including a hole blocking layer and a light emitting layer; and a first electrode and a second electrode for applying a voltage to the functional layer,
Production of an organic electroluminescence device, wherein the hole blocking layer is formed using a liquid material containing a copolymer of a vinyl pyridine monomer and a vinyl monomer containing an electron transport unit contained in the light emitting layer. Method.   The method of manufacturing an organic electroluminescence device according to claim 9, wherein the hole blocking layer is formed using a liquid phase method.   An electronic apparatus comprising the organic electroluminescence device according to claim 1.

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