JP2010212676A - Organic light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light emitting device having high efficiency and long service life for any of emission colors in an organic EL display device having at least two or more colors of organic electroluminescent elements. <P>SOLUTION: In the organic EL display device having at least two or more colors of organic electroluminescent elements, the organic light emitting device has a structure in which a hole blocking layer of each of the two or more colors of organic electroluminescent elements contains the same hole blocking material, and the hole blocking material is a compound included in a light emitting layer of the two or more colors of organic electroluminescent elements and having the same ring structure as that of a condensed polycyclic hydrocarbon and/or aromatic heterocyclic ring owned by at least any one of compounds, as a partial structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic light emitting device.

In recent years, organic electroluminescent elements have been actively developed as light emitting devices such as displays and lighting. This organic electroluminescent element injects positive and negative charges into an organic thin film between electrodes and takes out an excited state generated by recombination as light.
For the purpose of increasing the luminous efficiency of the organic electroluminescent element, an element using phosphorescence (emission by triplet excitons) instead of fluorescence (emission by singlet excitons) has been studied. When phosphorescence is used, it is considered that the efficiency is improved about three times as compared with an element using fluorescence, and it has been reported that europium complex, platinum complex or the like is used as phosphorescent molecule. However, conventional organic electroluminescent devices using phosphorescent molecules are highly efficient, but are insufficient for practical use in terms of driving stability, and it is difficult to realize a display device with high efficiency and long life. It was.

  In an organic electroluminescent element, light emission is basically obtained by a combination of a hole transport layer and an electron transport layer. That is, the holes injected from the anode move through the hole transport layer, recombine with the electrons injected from the cathode and moving through the electron transport layer near the interface between the two layers, and the hole transport layer and The principle is that the electron transport layer is excited to emit light, and the light emitting layer is provided between the hole transport layer and the electron transport layer to improve the light emission efficiency. is there.

In the case of a phosphorescent organic electroluminescent device, a hole blocking layer is generally provided on the cathode side of the light emitting layer in order to increase its efficiency and lifetime. By confining excitons in the light-emitting layer, the efficiency can be increased (Patent Document 1), and the deterioration of the layer on the cathode side of the light-emitting layer due to holes can be prevented, and its lifetime is reduced. It is because it is thought that it improves.
Further, in the case of a fluorescent organic electroluminescent device, it is sometimes prevented that the hole blocking layer is not formed to prevent luminance characteristics and lifetime from being reduced (Patent Document 2). In addition, it is considered that there are cases where it is advantageous not to form the hole blocking layer from the viewpoint of voltage. For these reasons, when an organic EL display device having organic electroluminescent elements of red, green and blue is produced, the light emission is phosphorescence in order to effectively achieve a long life, high efficiency, and low voltage. In some cases, it is considered optimal to use a hole blocking layer and not to use a hole blocking layer when the emission is fluorescent (Patent Document 3).

  However, in such a division method, when an organic EL display device in which phosphorescence and fluorescence are mixed is produced, it is necessary to pattern each of them in a vacuum vapor deposition method using a shadow mask. Vapor deposition using a shadow mask is accompanied by problems such as insufficient pattern accuracy and insufficient pattern position accuracy when the corresponding metal mask is enlarged along with the large screen of the substrate (Patent Document 4). Further, when patterning, there may be problems such as a decrease in yield due to the generated particles and an increase in cost. As described above, vacuum deposition using a shadow mask has a problem that mass production and enlargement are disadvantageous.

Based on this, when aiming to manufacture an organic EL display device that achieves higher efficiency and longer life, a hole blocking layer made of the same material is deposited and laminated on a position adjacent to the cathode side of each light emitting layer. It would be advantageous to do so.
In addition, when viewed as a display / lighting, it is also important that the lifetime of each emission color is complete. This is because if only one color undergoes a rapid luminance drop, the pixel will be out of color. In particular, in an organic EL display device in which phosphorescence and fluorescence are mixed, the hole blocking layer suitable for phosphorescence in the hole blocking layer so far has a poor charge injection property with respect to fluorescence, and the hole blocking layer suitable for fluorescence. Then, there was a problem that triplet energy was insufficient for phosphorescence.

JP 2001-284056 A JP 2006-156848 A JP 2005-158668 A Japanese Patent Application Laid-Open No. 2003-077660

  An object of the present invention is to provide an organic light-emitting device having high efficiency and a long lifetime without accumulating holes at the interface with the light-emitting layer.

  As a result of intensive studies by the present inventors, in an organic light emitting device having organic electroluminescent elements of at least two colors, at least one of the organic electroluminescent elements of two or more colors uses a phosphorescent light emitting material as a light emitting material. When each of the organic electroluminescent elements of two or more colors has a layer formed of the same (that is, common) material adjacent to the cathode side of the light emitting layer, I found that the problem could be solved.

  More specifically, the layer adjacent to the cathode side of the light emitting layer includes the same ring structure as the condensed polycyclic hydrocarbon and / or aromatic heterocyclic ring included in the light emitting material contained in the light emitting layer as a partial structure. By adopting a hole blocking material, it becomes possible to provide a hole blocking layer having a composition common between light emitting layers showing different emission colors, and as a result, no holes are retained near the cathode side interface of the light emitting layer, In addition, the present inventors have found that an organic light-emitting device having high efficiency and a long lifetime can be obtained, and the present invention has been achieved.

  That is, the present invention relates to an organic light emitting device having organic electroluminescent elements of at least two colors, wherein the organic electroluminescent elements of two or more colors are adjacent to the light emitting layer and the cathode side of the light emitting layer, respectively. The organic electroluminescent element of two or more colors includes at least one organic layer formed by a wet film forming method, and at least one of the organic electroluminescent elements of the two or more colors is a light emitting layer. The hole blocking layer of the organic electroluminescent element of the two or more colors containing a phosphorescent light emitting material contains the same hole blocking material, and the hole blocking material is an organic electroluminescent of the two or more colors. An organic light-emitting device characterized in that it is a compound having, as a partial structure, the same ring structure as the condensed polycyclic hydrocarbon and / or aromatic heterocyclic ring contained in any one compound contained in the light-emitting layer of the element Exist.

  The “organic light-emitting device” in the present invention refers to both “organic EL display device” and “organic EL lighting”. The “organic electroluminescent element” in the present invention represents not only a pixel in a display device but also a minimum light emitting unit (light emitting part) in an organic light emitting device.

  The organic light emitting device of the present invention has high luminous efficiency, has a long driving life, and can suppress an increase in driving voltage in any element of at least two colors.

The example of sectional drawing of the organic electroluminescent element of this invention is shown.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the content is not limited to these.
The organic light emitting device of the present invention has organic electroluminescent elements of at least two colors,
The organic electroluminescent elements of two or more colors each have a light-emitting layer and a hole blocking layer adjacent to the cathode side of the light-emitting layer,
The organic electroluminescent element of two or more colors includes at least one organic layer formed by a wet film formation method,
At least one of the organic electroluminescent elements of the two or more colors contains a phosphorescent material in the light emitting layer,
Each of the hole blocking layers of the organic electroluminescent elements of two or more colors contains the same hole blocking material,
The hole blocking material has the same structure as the condensed polycyclic hydrocarbon and / or aromatic heterocycle of any one of the compounds contained in the light emitting layer of the organic electroluminescent element of two or more colors (that is, the same ring It is an organic light-emitting device characterized by being a compound having a structure) as a partial structure.
By using the hole blocking layer of the present invention, it is possible to stably extend the life and suppress an increase in voltage in any element of at least two colors.

<Hole blocking layer>
The hole blocking layer in the present invention is laminated on the light emitting layer so as to be in contact with the interface on the cathode side of the light emitting layer, and has a role of preventing holes moving from the anode from reaching the cathode. And formed from a compound capable of efficiently transporting electrons injected from the cathode in the direction of the light emitting layer.
The physical properties required for the material constituting the hole blocking layer include high electron mobility, low hole mobility, large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). It is expensive.

[Hole blocking material]
The hole blocking material in the present invention is a compound having, as a partial structure, the same structure as that of a condensed polycyclic hydrocarbon and / or an aromatic heterocyclic ring, which is included in the light emitting layer, and any one compound is included as a partial structure. is there.

In addition, any one compound contained in the light emitting layer means the light emitting material, the hole transporting compound, or the electron transporting compound described in the section of <Light emitting layer material> described later.
The hole-blocking layer plays a role of efficiently injecting electrons into the light-emitting layer in addition to the role of hole blocking, and is therefore a condensed polycyclic hydrocarbon and / or aromatic compound possessed by the electron-transporting compound contained in the light-emitting layer. It is preferable that a structure similar to the group heterocycle (that is, the same ring structure) is included as a partial structure.

In the present invention, the hole blocking material has the same structure as the condensed polycyclic hydrocarbon and / or the aromatic heterocyclic ring, which is included in the phosphorescent light emitting material as a partial structure, in that the driving voltage of the phosphorescent device can be reduced. It is preferable to have a partial structure.
Furthermore, in the present invention, the hole blocking material has the same structure as the condensed polycyclic hydrocarbon and / or aromatic heterocyclic ring that the fluorescent light emitting material contains as a partial structure in that the driving voltage of the fluorescent element can be reduced. It is preferable to have as a partial structure.

(About structure)
Examples of the condensed polycyclic hydrocarbon include naphthalene, anthracene, tetracene, phenalene, phenanthrene, fluoranthene, fluorene, pyrene, chrysene, perylene, triphenylene, and the like. Is preferred.

  An aromatic heterocycle refers to a ring structure composed of both carbon and other elements. It may be a single ring or a condensed ring. Examples of the aromatic heterocycle include pyrrole, imidazole, pyrazole, furan, dibenzofuran, carbazole, oxazole, thiophene, thiazole, pyridine, pyridazine, pyrimidine, pyrazine, phenanthroline, quinoline, and isoquinoline. In particular, pyridine, pyrimidine, triazine, quinoline, phenanthroline, and imidazole are preferable.

In the case of the aromatic heterocyclic ring containing a nitrogen atom, it is preferable that all o-position and p-position are substituted with an aromatic ring.
In this case, the o-position and p-position of a 6-membered ring containing a nitrogen atom are active sites, and electrons are delocalized by substitution with an aromatic ring group. This makes it more stable with electrons.

A plurality of aromatic heterocycles may be included in the hole blocking material. At that time, it is sufficient that at least one aromatic heterocyclic ring has the same ring structure as the aromatic heterocyclic ring included in any one compound included in the light emitting layer. The plurality of aromatic heterocycles preferably have the same ring structure as the aromatic heterocycle of any one compound contained in the light emitting layer.

Further, the hole blocking material may have the same structure as any one compound contained in the light emitting layer. In this case, charge transfer between the same compounds is preferable because charge transfer between different compounds having the same partial structure is further improved.
In the present invention, a compound used as a hole blocking material, that is, a structure similar to a condensed polycyclic hydrocarbon and / or an aromatic heterocyclic ring, which is included in the light emitting layer and includes any one compound as a partial structure, Although the preferable specific example of the compound which has as a partial structure is shown below, this invention is not limited to these.

  <Specific example>

(Molecular weight)
The molecular weight of the hole blocking material is usually 10,000 or less, preferably 5000 or less, and usually 100 or more, preferably 200 or more.
When it is within the above range, film formation by vacuum deposition and purification are easy, and heat resistance is excellent.

<Light emitting layer>
When a hole injection layer is provided on the hole injection layer or a hole transport layer, a light emitting layer is provided on the hole transport layer. The light emitting layer is a layer which is excited by recombination of holes injected from the anode and electrons injected from the cathode between the electrodes to which an electric field is applied, and becomes a main light emitting source.
[Light emitting layer material]
The light emitting layer contains at least a material having a light emitting property (light emitting material) as a constituent material, and preferably a compound having a hole transporting property (hole transporting compound) or an electron transporting material. Contains a compound having properties (electron transporting compound). A light emitting material may be used as a dopant material, and a hole transporting compound, an electron transporting compound, or the like may be used as a host material.

  In the present invention, the compound having the same structure as the condensed polycyclic hydrocarbon and / or aromatic heterocyclic group contained in the hole blocking material may be a charge in the light emitting layer even if it is a light emitting material. It may be a transport material. However, it is easy to deliver charges, the drive voltage of the resulting device is likely to decrease, and it is difficult for electrons to accumulate at the interface between the light emitting layer and the hole blocking layer, and the drive life of the resulting device is extended. It preferably has the same partial structure as the charge transport material.

(Luminescent material)
As the light emitting material, it is preferable that at least one of the at least two colors is a phosphorescent light emitting material, yellow is used when the light emitting color is two colors, and red is a phosphorescent light emitting material when there are three or more colors. And blue is preferably fluorescent.
For the purpose of improving the solubility in a solvent, it is preferable to reduce the symmetry and rigidity of the molecules of the luminescent material, or to introduce a lipophilic substituent such as an alkyl group.

Examples of fluorescent dyes among fluorescent light emitting materials are given, but the fluorescent dyes are not limited to the following examples.
Examples of the fluorescent dye that gives blue light emission (blue fluorescent dye) include naphthalene, chrysene, perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof.

Examples of fluorescent dyes that give green light emission (green fluorescent dyes) include quinacridone derivatives, coumarin derivatives, and aluminum complexes such as Al (C ₉ H ₆ NO) ₃ .
Examples of fluorescent dyes that give yellow light (yellow fluorescent dyes) include rubrene and perimidone derivatives.
Examples of fluorescent dyes (red fluorescent dyes) that emit red light include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyrene) -4H-pyran) -based compounds, benzopyran derivatives, rhodamines. Derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

As the phosphorescent material, for example, a long-period type periodic table (hereinafter referred to as a long-period type periodic table when referred to as “periodic table” unless otherwise specified) is selected from the seventh to eleventh groups. And an organometallic complex containing a metal.
Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

The ligand of the complex is preferably a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or (hetero) arylpyrazole ligand is linked to pyridine, pyrazole, phenanthroline, etc. A pyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of phosphorescent materials include tris (2-phenylpyridine) iridium, tris {2- (4-n-propylphenyl) pyridine} iridium, tris {2- (4-n-butylphenyl) isoquinoline} iridium. , Tris {2- (4-n-hexylphenyl) pyridine} iridium, tris {2- (4-n-hexylphenyl) isoquinoline} iridium, tris [5-methyl- {3- (4'-n-hexylphenyl) ) Phenyl} pyridine] iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2-phenylpyridine) osmium, tris (2-phenylpyridine) Rhenium, octaethyl platinum porphyrin, octaphenyl platinum poly Firin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and their derivatives. The molecular weight of the compound used as the light emitting material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, more preferably 3000 or less, and usually 100 or more, Preferably it is 200 or more, More preferably, it is 300 or more, More preferably, it is the range of 400 or more. If the molecular weight of the luminescent material is too small, the heat resistance will be significantly reduced, gas generation will be caused, the film quality will be reduced when the film is formed, or the morphology of the organic electroluminescent element will be changed due to migration, etc. Sometimes come. On the other hand, if the molecular weight of the luminescent material is too large, it tends to be difficult to purify the organic compound, or it may take time to dissolve in the solvent.

In addition, any 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.
The ratio of the light emitting material in the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.05% by weight or more and usually 35% by weight or less. If the amount of the light emitting material is too small, uneven light emission may occur. If the amount is too large, the light emission efficiency may be reduced. In addition, when using together 2 or more types of luminescent material, it is made for the total content of these to be contained in the said range.

(Hole transporting compound)
The light emitting layer may contain a hole transporting compound as a constituent material. Here, among the hole transporting compounds, examples of the low molecular weight hole transporting compound include low molecular weight hole transporting compounds used in the hole injection layer, for example, 4,4′- An aromatic diamine represented by bis [N- (1-naphthyl) -N-phenylamino] biphenyl containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms No. 5-234681, an aromatic amine compound having a starburst structure such as 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (Journal of Luminescence, 1997, Vol. 72-74). , Pp. 985), an aromatic amine compound consisting of a tetramer of triphenylamine (Chemical Communications, 1996, pp. 21). 5), 2,2 ', 7,7'-tetrakis - (diphenylamino) -9,9'-spirobifluorene spiro compounds such as fluorene (Synthetic Metals
1997, Vol. 91, pp. 209) and the like.

In the light emitting layer, only one hole transporting compound may be used, or two or more hole transporting compounds may be used in any combination and ratio.
The ratio of the hole transporting compound in the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1% by weight or more and usually 65% by weight or less. If the amount of the hole transporting compound is too small, it may be easily affected by a short circuit, and if it is too large, the film thickness may be uneven. In addition, when using together 2 or more types of hole transportable compounds, it is made for the total content of these to be contained in the said range.

(Electron transporting compound)
The light emitting layer may contain an electron transporting compound as a constituent material. Here, among the electron transporting compounds, examples of low molecular weight electron transporting compounds include 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND), 2,5, -Bis (6 '-(2', 2 "-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySP)
yPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproine), 2- (4-biphenylyl) -5- (p-tert-butyl) Phenyl) -1,3,4-oxadiazole (tBu-PBD), 4,4′-bis (9-carbazole) -biphenyl (CBP), and the like. In the light emitting layer, only one type of electron transporting compound may be used, or two or more types may be used in any combination and ratio.

  The ratio of the electron transporting compound in the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1% by weight or more and usually 65% by weight or less. If the amount of the electron transporting compound is too small, it may be easily affected by a short circuit, and if it is too large, the film thickness may be uneven. In addition, when using together 2 or more types of electron transport compounds, it is made for the total content of these to be contained in the said range.

<Formation of light emitting layer>
When the light emitting layer is formed by the wet film forming method according to the present invention, the above material is dissolved in an appropriate solvent to prepare a light emitting layer forming composition, and the film is formed using the composition.
As the light emitting layer solvent to be contained in the light emitting layer forming composition for forming the light emitting layer by the wet film forming method according to the present invention, any solvent can be used as long as the light emitting layer can be formed.

The ratio of the light-emitting layer solvent to the light-emitting layer-forming composition for forming the light-emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, usually 70% by weight or less, It is. In addition, when using 2 or more types of solvents as a solvent for light emitting layers, it is made for the sum total of these solvents to satisfy | fill this range.
The solid content concentration of the light emitting material, hole transporting compound, electron transporting compound and the like in the composition for forming a light emitting layer is usually 0.01% by weight or more and usually 70% by weight or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.

  After wet forming the composition for forming a light emitting layer, the obtained coating film is dried and the solvent is removed to form a light emitting layer. The thickness of the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the thickness of the light emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

  The organic EL display device of the present invention is basically characterized by having the hole blocking layer and the light emitting layer described above, and the red, green and blue organic electroluminescent elements are each further provided with a hole injection layer. It is preferable to have a hole transport layer and an electron transport layer, and these layers are laminated in order of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer and an electron transport layer from the anode side. Is particularly preferred.

In addition, the hole injection layer, the hole transport layer, and the light emitting layer are layers formed by a wet film formation method, and the hole blocking layer and the electron transport layer are layers formed by a vapor deposition film formation method. Is particularly preferred. It is very advantageous in terms of cost to form a light-emitting layer by a wet film formation method, and since the light-emitting layer formed by this wet film formation method does not dissolve and the film quality can be kept uniform, It is preferable to form the blocking layer and the electron transport layer by a vacuum deposition method.

  Furthermore, the hole transport layer preferably contains an insolubilized polymer formed by insolubilizing a compound having an insolubilizing group. A method for forming a compound having an insolubilizing group, an insolubilizing polymer formed by insolubilizing the compound having an insolubilizing group, and a hole transporting layer containing the insolubilizing polymer will be described later in <Organic electroluminescence device> It is the same as that described in the section of (hole transport layer).

  Moreover, it is preferable that a positive hole injection layer contains dope material. In the present invention, the dope material refers to a material containing a hole transporting compound and an electron accepting compound, or a material containing an electron transporting compound and an electron donating compound. That is, including a doping material in the hole injection layer means that the hole injection layer includes a hole transporting compound and an electron accepting compound, or includes an electron transporting compound and an electron donating compound. means. Of course, in the hole injection layer, even if the hole transporting compound and the electron accepting compound, or the compound produced by the reaction of the electron transporting compound and the electron donating compound is contained. Good.

About the formation method of the positive hole injection layer containing a positive hole transport compound, an electron-accepting compound, and dope material, it is the same as that of what was described in the term of the <organic electroluminescent element> (hole injection layer) mentioned later. is there.
In the present invention, the wet film forming method refers to, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing. This method is a wet film formation method such as a method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable. This is because the liquid property specific to the coating composition used for the organic electroluminescent element is matched.

<Reason for the effect of the present invention>
The reason why the effect is obtained by using the configuration of the present invention is estimated as follows.
Conventionally, a compound having an electron affinity (EA) close to that of a light emitting material has been selected as a hole blocking material.
In other words, the hole blocking material is required to have an ion or potential deeper than that of the light emitting material and have an EA close to that of the light emitting material.

However, when preparing an organic EL display device having red, green and blue organic electroluminescent elements, red, green and blue organic electroluminescent elements have a hole blocking layer in common. The difference in electron affinity between the light emitting layer and the hole blocking layer of any one of the electroluminescent elements becomes large.
Here, when the hole blocking material has a partial structure similar to that of the condensed polycyclic hydrocarbon and / or the aromatic heterocyclic ring included in the light emitting material, it is considered that electrons are transferred smoothly.

In other words, even if the difference in electron affinity between the light emitting layer and the hole blocking layer becomes large, the hole blocking material is the same part as the condensed polycyclic hydrocarbon and / or aromatic heterocyclic ring that the light emitting material has. By having the structure, since an electron is transferred, an organic EL display device having a long driving life and a low driving voltage can be obtained.
<Configuration of organic electroluminescent element>
Below, the layer structure of the organic electroluminescent element of this invention, its formation method, etc. are demonstrated with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device according to the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

(substrate)
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

(anode)
The anode 2 serves to inject holes into the layer on the light emitting layer side.
This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, or platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

  In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate 1. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.
For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.

(Hole injection layer)
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.
The method for forming the hole injection layer 3 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When the hole injection layer 3 is formed by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a film-forming composition (positive The hole injection layer forming composition) is prepared, and this hole injection layer forming composition is applied onto a layer corresponding to the lower layer of the hole injection layer 3 (usually an anode) by an appropriate technique. The hole injection layer 3 is formed by coating and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as a constituent material of the hole injection layer.
The hole transporting compound may be a polymer compound or a monomer as long as it is a compound having a hole transporting property that is usually used for a hole injection layer of an organic electroluminescence device.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazones Compounds, silazane compounds, silanamin compounds, phosphamine compounds, quinacridone compounds, and the like.

  The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. In the case of containing two or more kinds of hole transporting compounds, the combination is arbitrary, but one or more kinds of aromatic tertiary amine polymer compounds and one or two kinds of other hole transporting compounds. It is preferable to use the above in combination.

Among the above-mentioned examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.
The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

(In the formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Represents a linking group selected from the group of linking groups, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents each independently the aromatic hydrocarbon group which may have a substituent, or the aromatic heterocyclic group which may have a substituent. R ¹ and R ² each independently represents a hydrogen atom or an arbitrary substituent.))
The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ include a benzene ring, a naphthalene ring, a phenanthrene ring, and a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport properties of the polymer compound. A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.
When R ¹ and R ² are optional substituents, examples of the substituent include alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024.
The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.
The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (International Publication No. WO 2005/089024); High valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds; fullerene derivatives; iodine and the like.

These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.
The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and ratios.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying process, which may adversely affect other layers and the substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.
Examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.
Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.

Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.
In addition, dimethyl sulfoxide and the like can also be used.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.

(Film formation method)
After preparing the composition for forming the hole injection layer, the composition is applied on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried. The hole injection layer 3 is formed.
The temperature in the film forming step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film loss due to the formation of crystals in the composition.

Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.
After the film formation, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used for the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C or higher, preferably 410 ° C or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using more than 2 kinds of materials, put them in each crucible), evacuate the vacuum vessel to about 10-4 Pa with a suitable vacuum pump, and then heat the crucible (2 or more kinds) When using these materials, heat each crucible) and control the amount of evaporation to evaporate (if more than one material is used, control the amount of evaporation independently) and face the crucible. A hole injection layer 3 is formed on the anode 2 of the placed substrate. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

[Hole transport layer]
The method for forming the hole transport layer 4 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

Such a material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are substituted with nitrogen atoms. Aromatic amine compounds having a starburst structure such as aromatic diamines (Japanese Patent Laid-Open No. Hei 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (J. Lumin. 72-74, 985, 1997), aromatic amine compounds consisting of tetramers of triphenylamine (Chem. Commun., 2175, 1996), 2,2 ′, 7,7′-tetrakis. Spiro compounds such as-(diphenylamino) -9,9'-spirobifluorene (Synth. Metals,
91, 209, 1997), and carbazole derivatives such as 4,4′-N, N′-dicarbazolebiphenyl. Further, for example, polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), polyarylene ether sulfone (Polym. Adv. Tech., 7, 33, 1996) containing tetraphenylbenzidine, etc. Can be mentioned.

In the case of forming the hole transport layer 4 by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3 and then heated and dried after the wet film formation. .
The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.

In the case where the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer 3.
The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.
The hole transport layer 4 is preferably a layer formed by insolubilizing a compound having an insolubilizing group (hereinafter referred to as “insolubilizing compound”) from the viewpoint of heat resistance or film formability. The insolubilizing compound is a compound having an insolubilizing group, and forms an insolubilizing polymer by insolubilization.

The insolubilizing group is a group that reacts by irradiation with heat and / or active energy rays, and is a group having an effect of lowering solubility in an organic solvent or water after the reaction than before the reaction.
In the present invention, the insolubilizing group is preferably a dissociating group or a crosslinkable group.
The leaving group refers to a group that dissociates from a bonded aromatic hydrocarbon ring at 70 ° C. or more and is soluble in a solvent. Here, being soluble in a solvent means that the compound is dissolved in toluene at 0.1% by weight or more at room temperature in a state before reacting by irradiation with heat and / or active energy rays. The solubility in toluene is preferably 0.5% by weight or more, more preferably 1% by weight or more.

The leaving group is preferably a group that is thermally dissociated without forming a polar group on the aromatic hydrocarbon ring side, and more preferably a group that is thermally dissociated by a reverse Diels-Alder reaction.
Furthermore, it is preferably a group that thermally dissociates at 100 ° C. or higher, and preferably a group that thermally dissociates at 300 ° C. or lower.
Examples of the crosslinkable group include cyclic ethers such as oxetane and epoxy; unsaturated double bonds such as vinyl group, trifluorovinyl group, styryl group, acrylic group, methacryloyl and cinnamoyl; benzocyclobutane and the like. .

The insolubilizing compound may be any of a monomer, an oligomer and a polymer. The insolubilizing compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.
As the insolubilizing compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

In order to form the hole transporting layer 4 by insolubilizing the insolubilizing compound, usually a composition for forming a hole transporting layer in which the insolubilizing compound is dissolved or dispersed in a solvent is prepared and formed by wet film formation. Insolubilize.
In addition to the insolubilizing compound, the hole transport layer forming composition may contain an additive that promotes the insolubilization reaction. Examples of additives that accelerate the insolubilization reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.

Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;
In the composition for forming a hole transport layer, the insoluble compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained by weight% or less, more preferably 10% by weight or less.

After forming a composition for forming a hole transport layer containing an insolubilizing compound at such a concentration on a lower layer (usually the hole injection layer 3), the insolubilizing compound is heated and / or irradiated with electromagnetic energy such as light. Are cross-linked to form an insolubilized polymer.
Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.
The heating method after film formation is not particularly limited, and examples thereof include heat drying and reduced pressure drying. The heating temperature condition in the case of heat drying is usually 120 ° C. or higher, preferably 400 ° C. or lower.

The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a deposited layer on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.
In the case of irradiation with electromagnetic energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp or an infrared lamp, or the above-mentioned light source is incorporated. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

Irradiation of electromagnetic energy such as heating and light may be performed individually or in combination. When combined, the order of implementation is not particularly limited.
The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

(Light emitting layer)
The light emitting layer is a layer that is excited by recombination of holes injected from the anode and electrons injected from the cathode between the electrodes to which an electric field is applied (anode and cathode) and becomes a main light emitting source. is there.
The material for forming the light emitting layer and the film forming method are the same as those described in the section of <Light emitting layer>. The same applies to preferable materials and film formation methods.

(Hole blocking layer)
It is preferable to have a hole blocking layer between the light emitting layer and the electron transport layer. The hole blocking layer can be formed by the material and the film forming method described in the above section [Hole blocking layer]. The same applies to preferred embodiments of the material and the film formation method.

{Electron transport layer}
An electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.
The electron transport layer 7 is provided for the purpose of further improving the light emission efficiency of the device, and efficiently transports electrons injected from the cathode 9 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. Formed from a compound capable of

As an electron transporting compound used for the electron transport layer 7, usually, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons having high electron mobility are efficiently transported. The compound which can be used is used. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type Sele Zinc oxide and the like.

In addition, the material of the electron carrying layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron carrying layer 7. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The film thickness of the electron transport layer 7 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Electron injection layer}
The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the film thickness is preferably from 0.1 nm to 5 nm.

  Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

{cathode}
The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer 5 side (such as the electron injection layer 8 or the light emitting layer 5).
As the material of the cathode 9, the material used for the anode 2 can be used. However, in order to perform electron injection efficiently, a metal having a low work function is preferable. For example, tin, magnesium, indium, A suitable metal such as calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.
In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The film thickness of the cathode 9 is usually the same as that of the anode 2.
Further, for the purpose of protecting the cathode 9 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element according to the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers described above, and an arbitrary layer may be omitted. .

Furthermore, the organic electroluminescence device according to the present invention can be configured by laminating components other than the substrate between two substrates, at least one of which is transparent.
Further, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), a charge generation layer (for example, vanadium pentoxide (V2 O5)) ( The provision of Carrier Generation Layer (CGL) is more preferable from the viewpoint of light emission efficiency and driving voltage because the barrier between the stages is reduced.

Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.
Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

<Organic light emitting device>
The organic light emitting device of the present invention is produced using the organic electroluminescent element. Organic light emitting devices include organic EL display devices and organic EL lighting.
[Organic EL display device]
The organic EL display device of the present invention is produced using the organic electroluminescent element. The organic EL display device of the present invention is, for example, a method described in “Organic EL display” (Ohm Co., Ltd., issued on August 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

<Organic EL lighting>
The organic EL illumination of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic EL illumination of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
[Production of organic electroluminescence device]
(Example 1-1)
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 with a thickness of 150 nm (manufactured by Sanyo Vacuum Co., Ltd., sputtered film product) using ordinary photolithography technology and hydrochloric acid etching Then, the anode 2 was formed by patterning into stripes having a width of 2 mm. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with an aqueous surfactant solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water, followed by drying with compressed air, and finally UV irradiation. Ozone cleaning was performed. This ITO functions as the transparent electrode 2.

  Next, hole injection containing an arylamine polymer represented by the following structural formula (P1), 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate represented by the structural formula (A1), and ethyl benzoate A layer forming coating solution was prepared. This coating solution was formed by spin coating on the anode under the following conditions to obtain a hole injection layer 3 having a thickness of 30 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration P1: 2.0% by weight
A1: 0.4% by weight
<Film formation conditions for hole injection layer 3>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coat atmosphere In-air heating conditions In-air 230 ° C. 1 hour Next, a hole transport layer forming coating solution containing the compound (H1) having the structure shown below was prepared, and the conditions were as follows: A hole transport layer 4 having a film thickness of 15 nm was formed by film formation by spin coating and polymerization by heating.

<Coating liquid for hole transport layer formation>
Solvent Cyclohexylbenzene Coating solution concentration 1.0% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coating atmosphere In-air heating condition In-air 230 ° C. 1 hour Next, compounds (C1) and (C2) represented by the following structural formula and (D1) having the following structure are contained. A coating solution for forming a light emitting layer was prepared, a film was formed by spin coating under the following conditions, and the light emitting layer 5 having a thickness of 40 nm was formed by heating.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C1: 3.40% by weight
D1: 0.34% by weight
<Film-forming conditions of the light emitting layer 5>
Spinner speed 1200rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Here, the substrate on which the light-emitting layer has been formed is transferred into a vacuum deposition apparatus, exhausted until the degree of vacuum in the apparatus becomes 2.0 × 10 ⁻⁴ Pa or less, and then the organic compound (C1) is subjected to vacuum deposition. Then, the deposition rate was controlled in the range of 0.8 to 1.2 liters / second and laminated on the light emitting layer to obtain a hole blocking layer 6 having a thickness of 10 nm. In this embodiment, both the light emitting layer 5 and the hole blocking layer 6 have an anthracene skeleton, which satisfies the requirements of the present invention.

Subsequently, an organic compound (Alq ₃ ) having the structure shown below is deposited on the hole blocking layer 6 by controlling the deposition rate within a range of 0.8 to 1.2 liters / second by a vacuum deposition method. An electron transport layer 7 having a thickness of 20 nm was formed.

Here, the element on which vapor deposition up to the electron transport layer 7 has been taken out is once taken out and placed in another vapor deposition apparatus, and a 2 mm wide striped shadow mask is orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. In this way, exhaustion was performed until the degree of vacuum in the apparatus was 2.3 × 10 ⁻⁴ Pa or less.
As the electron injection layer 8, lithium fluoride (LiF) was first formed on the electron transport layer 7 at a deposition rate of 0.1 Å / sec and a film thickness of 0.5 nm using a molybdenum boat. The degree of vacuum at the time of vapor deposition was 2.6 × 10 ⁻⁴ Pa. Next, aluminum was similarly heated by a molybdenum boat as the cathode 9, and the deposition rate was controlled in the range of 1.0 to 4.9 kg / sec to form an aluminum layer having a thickness of 80 nm. The degree of vacuum at the time of vapor deposition was 2.6 × 10 ⁻⁴ Pa. The substrate temperature during the above two-layer deposition was kept at room temperature.

Subsequently, in order to prevent the element from being deteriorated by moisture in the atmosphere during storage, sealing treatment was performed by the method described below.
In a nitrogen glove box, a photocurable resin 30Y-437 (manufactured by ThreeBond) is applied to the outer periphery of a 23 mm × 23 mm size glass plate with a width of about 1 mm, and a moisture getter sheet (manufactured by Dynic) is applied to the center. ) Was installed. On this, the board | substrate which completed cathode formation was bonded together so that the vapor-deposited surface might oppose a desiccant sheet. Thereafter, only the region where the photocurable resin was applied was irradiated with ultraviolet light to cure the resin.
As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. Table 1 shows the characteristics of this element.

(Example 1-2)
In Example 1-1, the organic electroluminescent element shown in FIG. 1 was produced in the same manner as in Example 1 except that the light emitting layer 5 was formed as follows.
A coating solution for forming a light emitting layer containing the compounds (C2), (C3), (D2), and (D3) having the structure shown below is prepared, film-formed by spin coating under the following conditions, and heated. Thus, the light emitting layer 5 having a thickness of 60 nm was formed.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C2: 1.25 wt%
C3: 3.75% by weight
D2: 0.25% by weight
D3: 0.35% by weight
<Film-forming conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Table 1 shows the characteristics of the obtained organic electroluminescent element.

(Example 1-3)
In Example 1-1, the organic electroluminescent element shown in FIG. 1 was prepared in the same manner as in Example 1 except that the light emitting layer 5 was formed as follows.
A coating solution for forming a light emitting layer containing compounds (C4), (C5), and (D2) having the structure shown below is prepared, and film formation is performed by spin coating under the following conditions, followed by heating. A light emitting layer 5 of 60 nm was formed.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C4: 1.25% by weight
C5: 3.75% by weight
D2: 0.50% by weight
<Film-forming conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Table 1 shows the characteristics of the obtained organic electroluminescent element.

In addition, the device which has the organic electroluminescent element obtained in these Examples 1-1 to 1-3 corresponds to an example of the organic light emitting device of the present invention.
(Comparative Examples 1-1 to 1-3)
In Examples 1-1 to 1-3, the hole blocking layer 6 was formed using the compound (C6) having the following structure, except that the hole blocking layer 6 was formed. Thus, the organic electroluminescent element shown in FIG. 1 was prepared.

Table 1 shows the characteristics of the obtained organic electroluminescent element.
In addition, the organic electroluminescent element obtained in the comparative examples 1-1 to 1-3 uses (C6) for the hole blocking layer 6, and the (C6) is a condensation contained in the host of the light emitting layer. It does not have polycyclic hydrocarbons or aromatic heterocycles. Therefore, the device having the organic electroluminescent element obtained in Comparative Examples 1-1 to 1-3 is outside the scope of the present invention.

As shown in Table 1, it can be seen that the organic EL device of the present invention has low driving voltage, high current efficiency, and long driving life in each color element.
That is, in a plurality of elements having different emission colors, the hole blocking layer provided on the light emitting layer cathode side can be formed of a common material, so that the productivity is high, and an organic EL device having such an element is In any color, since low driving voltage, high luminous efficiency, and long driving life are shown, it can be seen that light can be emitted for a long time without causing color shift.

  The present invention relates to various fields in which organic electroluminescent elements are used, for example, light sources (for example, light sources of copiers, flat panel displays (for example, for OA computers and wall-mounted televisions) and surface light emitters). It can be suitably used in the fields of liquid crystal displays and backlights for instruments, display panels, marker lamps, lighting devices, and the like.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode

Claims (8)

In an organic light emitting device having organic electroluminescent elements of at least two colors,
The organic electroluminescent elements of two or more colors each have a light-emitting layer and a hole blocking layer adjacent to the cathode side of the light-emitting layer,
The organic electroluminescent element of two or more colors includes at least one organic layer formed by a wet film formation method,
At least one of the organic electroluminescent elements of the two or more colors contains a phosphorescent material in the light emitting layer,
Each of the hole blocking layers of the organic electroluminescent elements of two or more colors contains the same hole blocking material,
The hole blocking material has the same ring structure as that of the condensed polycyclic hydrocarbon and / or aromatic heterocyclic ring contained in any one of the compounds contained in the light emitting layer of the organic electroluminescent element of two or more colors. An organic light-emitting device, which is a compound having At least one of the organic electroluminescent elements having two or more colors includes an electron transporting compound in the light emitting layer,
The organic light-emitting device according to claim 1, wherein the hole blocking material includes the same ring structure as the condensed polycyclic hydrocarbon and / or the aromatic heterocyclic ring included in the electron transporting compound.   2. The organic light-emitting device according to claim 1, wherein the hole blocking material includes the same ring structure as the condensed polycyclic hydrocarbon and / or the aromatic heterocycle included in the phosphorescent material. At least one of the organic electroluminescent elements of two or more colors includes a fluorescent light emitting material in a light emitting layer,
2. The organic light-emitting device according to claim 1, wherein the hole blocking material includes the same ring structure as a condensed polycyclic hydrocarbon and / or an aromatic heterocyclic ring included in the fluorescent material. Each of the organic electroluminescent elements of two or more colors further has a hole injection layer, a hole transport layer and an electron transport layer,
It is laminated | stacked in order of the positive hole injection layer, the positive hole transport layer, the light emitting layer, the positive hole blocking layer, and the electron carrying layer from the anode side, The characteristic as described in any one of Claims 1-4 characterized by the above-mentioned. Organic light emitting device.   The hole injection layer, the hole transport layer, and the light emitting layer are all formed by a wet film formation method, and the hole blocking layer and the electron transport layer are formed by an evaporation film formation method. The organic light-emitting device according to claim 5, wherein the organic light-emitting device is a patterned layer.   The organic light-emitting device according to claim 5, wherein the hole transport layer contains an insolubilized polymer formed by insolubilizing a compound having an insolubilizing group.   The organic light-emitting device according to claim 5, wherein the hole injection layer contains a doped material.

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