JP2010192474A - Organic electroluminescent element, organic el display, and organic el lighting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can be driven at a low voltage, has high light-emitting efficiency and long drive service life, and to provide an organic EL display and an organic EL lighting equipped with the element. <P>SOLUTION: The organic electroluminescent element includes a substrate; an anode provided on the substrate, a plurality of organic layers and a cathode, wherein the plurality of organic layers include a first organic layer; and a second organic layer formed by a wet film forming method, where halogen atom concentration (wt.%) of the first organic layer is ≥2 wt.%, and not less than 20 times the halogen atom concentration (wt.%) of the second organic layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element, an organic EL display, and organic EL lighting.

  In recent years, electroluminescent devices using organic thin films (that is, organic electroluminescent devices) have been developed. Examples of the method for forming the organic thin film in the organic electroluminescence device include a vacuum deposition method and a wet film formation method. Since the vacuum deposition method is easy to stack, it has an advantage that the charge injection from the anode and / or the cathode is improved, and the exciton light-emitting layer is easily contained. In addition, the wet film formation method is easier to increase in area than the vacuum deposition method, and it is easy to mix a plurality of materials having various functions in one layer (coating liquid). There are advantages.

For example, Patent Document 1 and Patent Document 2 disclose that all organic layers are formed using a material having a low halogen atom concentration as a method for manufacturing an organic electroluminescent element including a layer formed by a vacuum deposition method. .
In the preparation of an organic electroluminescent element including a layer formed by a wet film formation method, in Patent Document 3 and Patent Document 4, a material having a low halogen atom concentration is used even when a layer is formed by a wet film formation method. It is disclosed.

JP 2004-327454 A JP 2004-327455 A JP 2007-220772 A International Publication No. 2006-37458 Pamphlet

  An object of the present invention is to provide an organic electroluminescence device that can be driven at a low voltage, has high luminous efficiency, and has a long driving life, and an organic EL display and organic EL illumination including the organic electroluminescence device.

As a result of intensive studies to solve the above problems, the inventors of the present invention have determined that the halogen atom concentration (% by weight) of the organic layer is relatively specified or higher in the specific organic layer formed by the wet film forming method. The present inventors have found that the above-mentioned problems can be solved by setting the value of.
That is, the present invention is an organic electroluminescent device comprising a substrate, an anode provided on the substrate, a plurality of organic layers, and a cathode, wherein the plurality of organic layers are formed by a wet film formation method. The first organic layer and the second organic layer, the halogen atom concentration (wt%) of the first organic layer is 2 wt% or more, and the halogen atom concentration (wt%) of the second organic layer The organic electroluminescent element, and the organic EL display and the organic EL illumination provided with the organic electroluminescent element.

  The organic electroluminescence device of the present invention can be driven at a low voltage, has high luminous efficiency, and has a long driving life. In addition, a decrease in light emission luminance, a voltage increase, generation of a non-light emitting portion (dark spot), a short circuit defect, and the like during constant current driving are suppressed.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention. It is a figure which shows the current-voltage characteristic measured in the reference example 1 and the reference comparative example 1 of this invention. The vertical axis represents current density [A / cm ² ], and the horizontal axis represents voltage [V]. It is a figure which shows the measurement result by TOF-SIMS of the element produced in Example 1 of this invention. The vertical axis represents ion detection intensity, and the horizontal axis represents measurement time [s]. It is a figure which shows the measurement result by TOF-SIMS of the element produced by the comparative example 3 of this invention. The vertical axis represents ion detection intensity, and the horizontal axis represents measurement time [s].

The embodiment of the organic electroluminescent element of the present invention, and the organic EL display and organic EL illumination will be described in detail. The description of the constituent elements described below is an example (representative example) of the embodiment of the present invention. The present invention is not limited to these contents unless it exceeds the gist.
<Basic configuration>
The organic electroluminescent device of the present invention is an organic electroluminescent device comprising a substrate and an anode, an organic layer, and a cathode provided on the substrate, wherein the organic layer is formed by a wet film formation method. The first organic layer and the second organic layer, the first organic layer and the second organic layer being provided adjacent to each other in this order from the anode side, and the halogen atoms of the first organic layer The organic electroluminescent device is characterized in that the concentration (% by weight) is 2% by weight or more and further 20 times or more the halogen atom concentration (% by weight) of the second organic layer.

[Halogen atom concentration]
In the present invention, the absolute value of the halogen atom concentration of the organic layer is calculated by the method described in the following section (1. Calculation method of halogen atom concentration). Further, the ratio between layers, for example, the ratio of the halogen atom concentration in the first organic layer to the halogen atom concentration in the second organic layer is described in the following section (2. Method for measuring the ratio of halogen atom concentration between organic layers). It is calculated from the measurement method described in 1.

(1. Calculation method of halogen atom concentration)
The halogen atom concentration contained in the first organic layer is calculated from the state after forming the layer.
Specifically, the composition used in Reference Example 1 will be described. A composition in which a compound (H1) (4.5% by weight) represented by the following structural formula and a compound (A1) (0.09% by weight) represented by the following formula are dissolved in ethyl benzoate as a solvent. Is used to form a layer.

When a layer is formed using the said composition, it is estimated that the structure in a layer is as follows.

From this, the halogen atom concentration in the layer is calculated as follows.
The halogen content contained in the anion portion of the formula (A1) is calculated as {(atomic weight of fluorine) / (molecular weight of the anion portion of (A1))} × 100 = 380/679 = 56%.

Here, 0.09% by weight of (A1) first contains 0.601% by weight of (A1) anion portion, and further in this (A1) anion portion, 0.336% by weight Of halogen atoms (fluorine atoms).
From this, the concentration (wt%) of the halogen atoms contained in the layer is calculated as {0.336 wt% / (4.5 wt% + 0.601 wt%)} × 100 = 6.6 wt%. The
(The total halogen atom concentration (% by weight) of each organic layer of the organic electroluminescence device is 0.5% by weight or more)
The organic electroluminescent device of the present invention comprises an organic layer between an anode and a cathode, and the halogen atom concentration (wt%) in the organic layer is 0.5 wt% or more. It is an organic electroluminescent element.

The halogen atom concentration in the organic layer is 0.5% by weight or more as follows.
When the total thickness of the organic layer is x (nm), the layer containing halogen atoms is one layer, and the thickness of the layer having a halogen atom concentration of a (wt%) is y (nm) The total concentration of halogen atoms in each of the plurality of organic layers is calculated as a × y / x (% by weight).
A specific description will be given below with reference to Example 1 described later.

  The film thicknesses of the organic layers in the device produced in Example 1 are the hole injection layer (first organic layer / 30 nm), the hole transport layer (second organic layer / 20 nm), and the light emitting layer (40 nm), respectively. The hole blocking layer (10 nm) and the electron transport layer (30 nm) are 130 nm in total. Here, the layer containing halogen is only the hole injection layer, and the halogen atom concentration is 6.6% by weight. From this, the total of the halogen atom concentration of each of the plurality of organic layers is calculated as 6.6 × (30/130) = 1.52 wt%.

(2. Measurement method of halogen atom concentration ratio between organic layers)
Next, the fact that the halogen atom concentration (wt%) of the first organic layer is 20 times or more the halogen atom concentration (wt%) of the second organic layer is defined by the TOF-SIMS method.
The TOF-SIMS method performs measurement using TOF-SIMS IV (manufactured by ION-TOF).

In the measurement method, a measurement sample is etched with sputter ions, and the TOF-SIMS spectrum of secondary ions emitted from the sample by irradiation with primary ions after etching is measured in a negative ion mode. Bivalent positive ions of bismuth trimer clusters are used as primary ions, and argon positive ions are used as sputter ions. The etching area is 300 μm ² and the sputter analysis area is 150 μm ² . By repeating etching and TOF-SIMS measurement, the distribution of halogen ions in the depth direction from the sample surface is evaluated.

In addition, about the boundary of a 1st organic layer and a 2nd organic layer, it can obtain | require as follows with the spectrum of the said TOF-SIMS method.
The detected intensity of halogen ions in the first organic layer is X1, and the detected intensity of halogen in the second organic layer is X2. At this time, at the interface between the first organic layer and the second organic layer, the depth at which the detected intensity of the halogen ion is ((X1-X2) / 2) is set to the first organic layer and the second organic layer. The boundary.

Note that the measuring device used for specifying the present invention is not limited to the above measuring device as long as the same measurement as described above is possible, and other measuring devices may be used. Is preferably used.
The first organic layer in the present invention has a halogen atom concentration (% by weight) of usually 2% by weight or more, preferably 4% by weight or more, more preferably 6% by weight or more, and usually 60% by weight or less, preferably 40%. % By weight or less, more preferably 20% by weight or less. Within this range, a layer that is thermally and electrically stable and has a high charge transporting ability can be obtained.

In the organic electroluminescent device of the present invention, the halogen atom concentration of the first organic layer relative to the second organic layer is usually 20 times or more, preferably 50 times or more, more preferably 100 times or more, and usually 1, It is 1,000,000 times or less, preferably 10,000 times or less.
Within the above range, charge injection from the first organic layer to the second organic layer is good, and halogen atoms are present at the interface between the second organic layer and the second organic layer and the layer above it. Since there are few trap sites and quench sites, the resulting device has a low drive voltage, high current efficiency, and a long drive life.

(2. Contained as a halogen atom)
The halogen atom contained in the first organic layer may be any of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, but is thermally and electrically stable and further has a charge transporting ability. A fluorine atom is preferable in that a high layer can be obtained.
In addition, there is no restriction | limiting in particular as an aspect containing a halogen atom, unless the effect of this invention is impaired, You may contain by the halide ion, complex ion, and the electrically neutral molecule | numerator.

In addition, when contained as a halide ion, an electron accepting compound is particularly preferable.
(Electron-accepting compound)
As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound is preferable. Specifically, a compound with an electron affinity of 4 eV or more is preferable, and a compound with a compound of 5 eV or more is more preferable.

Examples of the compound satisfying the above include aromatic compounds having a halogen atom, triaryl boron compounds, triaryl boron compounds, onium salts, aminium salts, metal halides, halogen-containing polymers, and organic acids.
Specific examples of the electron-accepting compound are shown below, but the present invention is not limited to these.

  <Aromatic compound having halogen atom>

<Triaryl boron compound>

<Onium salt>

<Aminium salt>

<Metal halide>

<Halogen-containing polymer>

<Organic acid>

Furthermore, examples of the electron-accepting compound not containing a halogen atom include those described in the following <Halogen-free electron-accepting group>, but are not limited to these unless the effects of the present invention are impaired. is not.

  <Halogen-free electron-accepting compound group>

[Organic layer]
In the present invention, the “organic layer” refers to a layer containing an organic compound.
In the organic electroluminescent element of the present invention, the organic layer refers to each layer disposed between the anode and the cathode.

Examples of the organic layer in the organic electroluminescence device of the present invention include a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.
Of these organic layers, the layer containing the halogen atom concentration of 2% by weight or more (first organic layer) and the second organic layer are limited as long as they are two adjacent layers. Any layer may be used.

By forming two adjacent layers of these organic layers as the first organic layer and the second layer, there is little increase in drive voltage during constant current energization or decrease in brightness during energization, and excellent drive life. An organic electroluminescent device can be obtained.
However, the first organic layer is preferably present as close as possible to the anode in that charge injection from the anode can be promoted and the driving voltage can be further reduced.

Specifically, as schematically shown in FIG. 1, the first organic layer is present on the opposite side of the light emitting layer 5 with the second layer interposed therebetween, that is, the first organic layer, the second organic layer, The organic layer and the light emitting layer are preferably arranged in this order.
More specifically, the hole injection layer is the first organic layer, and the hole transport layer is the second organic layer.

Further, since the hole transport layer may be omitted, the hole injection layer may be the first organic layer and the light emitting layer may be the second organic layer.
(First organic layer)
The first organic layer in the present invention preferably contains a hole transport material in the layer.
The hole transport material is not particularly limited as long as the effect of the present invention is not impaired, and a known compound can be used, but has an insolubilizing group in that lamination by a wet film forming method can be easily performed. A compound (hereinafter sometimes referred to as “insoluble compound”) is preferred.

[Insolubilized group]
The insolubilizing compound in the present invention is a compound having a group containing an insolubilizing group.
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.

(Dissociable group)
The hole transport material in the present invention preferably has a dissociation group as an insolubilizing group in terms of excellent charge transport ability after insolubilization (after dissociation reaction).
Here, the dissociating 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.

Such a dissociating group is preferably a group that thermally dissociates without forming a polar group on the aromatic hydrocarbon ring side, and more preferably a group that dissociates thermally 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.

Specific examples of the dissociating group are as follows, but the present invention is not limited thereto.
A specific example in the case where the dissociating group is a divalent group is as shown in <Divalent dissociating group group A> below. <Divalent dissociation group A>

A specific example in the case where the dissociating group is a monovalent group is as shown in <Monovalent dissociating group B> below. <Monovalent dissociation group B>

(Crosslinkable group)
In addition, the hole transport material in the present invention has a crosslinkable group as an insolubilizing group, and is soluble in a solvent before and after a reaction (insolubilizing reaction) caused by irradiation with heat and / or active energy rays. It is preferable in that a large difference can be generated.

Here, the crosslinkable group refers to a group that reacts with the same or different groups of other molecules located nearby by irradiation with heat and / or active energy rays to form a new chemical bond.
Examples of the crosslinkable group include groups shown in the crosslinkable group group T in that it is easily insolubilized.
[Crosslinkable group T]

(In formula, R < ¹ > -R < ⁵ > represents a hydrogen atom or an alkyl group each independently. Ar < ³¹ > may have the aromatic hydrocarbon group or substituent which may have a substituent. Represents an aromatic heterocyclic group.)
Groups that are insolubilized by cationic polymerization, such as cyclic ether groups such as epoxy groups and oxetane groups, and vinyl ether groups are preferred because they are highly reactive and easily insolubilized. Among these, an oxetane group is particularly preferable from the viewpoint that the rate of cationic polymerization can be easily controlled, and a vinyl ether group is preferable from the viewpoint that a hydroxyl group that may cause deterioration of the device during the cationic polymerization is hardly generated.

A group that undergoes a cycloaddition reaction, such as an arylvinylcarbonyl group such as a cinnamoyl group, or a group derived from a benzocyclobutene ring, is preferred from the viewpoint of further improving electrochemical stability.
Among the crosslinkable groups, a group derived from a benzocyclobutene ring is particularly preferable in that the structure after insolubilization is particularly stable.
The crosslinkable group may be directly bonded to the aromatic hydrocarbon group or aromatic heterocyclic group in the molecule, but may be bonded via a divalent group. As the divalent group, a group selected from an —O— group, a —C (═O) — group, or an (optionally substituted) —CH ₂ — group may be selected from 1 to 30 in any order. It is preferable to bind to an aromatic hydrocarbon group or an aromatic heterocyclic group via a divalent group formed by connecting them individually.

(Structure of hole transport material)
The material forming the first organic layer is preferably a material having a high hole transport capability 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, since it is in contact with the light emitting layer, it is preferable not to quench the light emitted from the light emitting layer or to reduce the efficiency by forming an exciplex with the light emitting layer.

  As the material of the first organic layer, any material that has been conventionally used as a constituent material of the first organic layer may be used. For example, the hole transport property used in the above-described hole injection layer may be used. What was illustrated as a compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives, metal complexes and the like.

  Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of alternating copolymer compounds, random polymer compounds, block polymer compounds, and graft copolymer compounds. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer compound containing a repeating unit represented by the following formula (II). In particular, it is preferably a polymer compound composed of a repeating unit represented by the following formula (II). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In Formula (II), Ar ^a and Ar ^b may each independently have a substituent,
Represents an aromatic hydrocarbon group or an aromatic heterocyclic group. )
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and an acenaphthene. Examples thereof include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, a fluorene ring, and a group in which two or more rings are connected by a direct bond.

  Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. Or a group and the rings of from 2-4 fused rings include groups formed by connecting a direct bond or two or more rings.

In view of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, and fluorene ring. A group derived from a selected ring or a group formed by linking two or more benzene rings (for example, a biphenyl group or a terphenyl group) is preferable.
Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of the substituent that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as its repeating unit. The high molecular compound which has is mentioned.
As the polyarylene derivative, a polymer compound having a repeating unit composed of the following formula (III-1) and / or the following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In Formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in Formula (III-1) above. Independently, it represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)
Specific examples of X are —O—, —BR—, —NR—, —SiR ₂ —, —PR—, —SR—, —CR ₂ — or a group formed by bonding thereof. R represents a hydrogen atom or an arbitrary organic group.

  The polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the following formula (III-1) and / or the following formula (III-2). Is preferred.

(In the formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent. Independently represents 0 or 1.)
Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).

Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.
The structure of the hole transporting compound is not particularly limited, but is preferably a compound having a structure represented by the following formula (4) as a partial structure.

Further, when the hole transport material in the present invention is a compound having no insolubilizing group, for example, PEDOT / PSS (Adv. Mater., 2000, Vol. 12, p. 481) or emeraldine hydrochloride (J. Phys) Chem., 1990, Vol. 94, p. 7716), and the like, and high molecular compounds obtained by oxidative polymerization (dehydrogenation polymerization). The oxidative polymerization referred to here is a method in which a monomer is chemically or electrochemically oxidized using peroxodisulfate or the like in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is polymerized by being oxidized, and a polymer containing a cation radical is generated with an anion derived from an acidic solution as a counter anion. In this oxidative polymerization, when an acid containing a halogen atom is used, a polymer containing a cation radical having a counter anion containing a halogen atom is obtained, which is preferable because of excellent thermal and electrical stability.

[Film formation method]
In the organic electroluminescent element of the present invention, the first organic layer and the second organic layer are formed by a wet film forming method.
In the present invention, the wet film forming method includes, 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.

When forming a layer by a wet film formation method, usually, a material for hole injection layer is mixed with an appropriate solvent to prepare a composition for film formation, and the composition is applied to the lower layer by an appropriate method. It forms into a film by apply | coating on the applicable layer and drying. This drying may be heat drying or reduced pressure drying.
When forming a film using an insolubilizing compound, the insolubilizing compound undergoes an insolubilizing reaction and forms a layer by heating and / or irradiation with active energy rays after application as described above.

When the insolubilization method is heating, the heating method is not particularly limited, but the heating condition is that a film formed at 120 ° C. or higher, preferably 400 ° C. or lower is heated. 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 substrate or a laminate having the formed film 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.

  When the insolubilization method is based on irradiation with active energy rays, direct irradiation using an ultraviolet, visible or infrared light source such as an ultra high pressure mercury lamp, high pressure mercury lamp, halogen lamp or infrared lamp, or the aforementioned light source Examples include a mask aligner incorporated and a method of irradiation using a conveyor type light irradiation device. Further, for example, there is a method of irradiating using a so-called microwave oven that irradiates a microwave generated by a magnetron. 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.

You may perform a heating and / or irradiation of an active energy ray individually or in combination, respectively. When combined, the order of implementation is not particularly limited.
In order to reduce the amount of moisture contained in the layer and / or the amount of moisture adsorbed on the surface of the layer after the heating and / or irradiation with active energy rays, it is performed in an atmosphere not containing moisture such as a nitrogen gas atmosphere. preferable. When performing heating and / or irradiation with active energy rays for the same purpose, it is particularly preferable to perform at least the process immediately before the formation of the upper layer in an atmosphere containing no moisture such as a nitrogen gas atmosphere.

The thickness of the insolubilized film thus formed in the present invention is usually 3 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and usually 100 nm or less, preferably 80 nm or less, more preferably 50 nm or less.
(Second organic layer)
In the present invention, the second organic layer is appropriately selected depending on the desired configuration of the element, but may be a layer formed using the hole transport material, or may be a light emitting layer. .

When the second organic layer is formed using the hole transport material, the specific example and the film forming method are the same. The same applies to preferred embodiments.
(Light emitting layer)
The light emitting layer is preferably formed by forming a film using a composition (light emitting layer composition) containing a light emitting low molecular weight compound, a charge transporting low molecular weight compound and a solvent.

The composition for light emitting layer contains a light emitting low molecular weight compound and a charge transporting compound.
[Luminescent low molecular weight compound]
The organic electroluminescent element of the present invention preferably has a light emitting layer between an anode and a cathode, and the light emitting layer preferably contains a light emitting low molecular weight compound.
The light emitting low molecular compound is not particularly limited as long as it is a compound having a light emitting property defined by a single molecular weight, and a known material can be applied. For example, it may be a fluorescent low molecular weight compound or a phosphorescent low molecular weight compound, but from the viewpoint of internal quantum efficiency, it is preferably a phosphorescent low molecular weight compound.

In order to improve the solubility in a solvent, it is preferable to reduce the symmetry and rigidity of the molecule of the light-emitting low molecular weight compound or to introduce a lipophilic substituent such as an alkyl group.
Hereinafter, examples of the fluorescent light-emitting low molecular compound among the light-emitting low molecular compounds will be described, but the fluorescent light-emitting low molecular compound is not limited to the following examples.

Examples of the fluorescent light-emitting low molecular compound that gives blue light emission (blue fluorescent light-emitting low molecular compound) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis (2-phenylethenyl) benzene, and their Derivatives and the like.
Examples of the fluorescent low-molecular compound that gives green light emission (green fluorescent low-molecular compound) include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al (C ₉ H ₆ NO) _3, and the like.

Examples of the fluorescent luminescent low molecular weight compound that gives yellow luminescence (yellow fluorescent luminescent low molecular weight compound) include rubrene and perimidone derivatives.
Examples of the fluorescent light-emitting low molecular compound that gives red light (red fluorescent light-emitting low molecular compound) include, for example, DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) -based compound Benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

Examples of the phosphorescent low molecular weight compound include, for example, a long-period periodic table (hereinafter, unless otherwise specified, the term “periodic table” refers to a long-period periodic table). And an organometallic complex containing a metal selected from the group.
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.

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

  Specific examples of the phosphorescent low molecular weight compound include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, and tris. (2-phenylpyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

  The molecular weight of the compound used as the light-emitting low molecular compound 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, still more preferably 3000 or less, and usually The range is 100 or more, preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more. If the molecular weight of the light-emitting low molecular weight compound is too small, the heat resistance is remarkably lowered, gas generation is caused, the film quality is deteriorated when the film is formed, or the organic electroluminescent device is caused by migration or the like. It may cause morphological changes. On the other hand, if the molecular weight of the luminescent low molecular weight compound is too large, it tends to be difficult to purify the luminescent low molecular weight compound, or it may take time to dissolve in the solvent.

In addition, only 1 type may be used for the luminescent low molecular weight compound mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.
[Charge transporting low molecular weight compounds]
The charge transporting low molecular weight compound in the present invention is a compound having a charge transporting property such as a hole transporting property or an electron transporting property, and is a compound defined by a single molecular weight.

In the present invention, only one kind of charge transporting low molecular weight compound may be used, or two or more kinds may be used in any combination and ratio.
In the light emitting layer, it is preferable to use a light emitting low molecular weight compound as a dopant material and a charge transporting low molecular weight compound as a host material.
The charge transporting low molecular weight compound may be a compound that has been conventionally used in a light emitting layer of an organic electroluminescence device, and particularly a compound that is used as a host material of the light emitting layer.

  Specific examples of charge transporting low molecular weight compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which tertiary amines are linked by a fluorene group. , Hydrazone compounds, silazane compounds, silanamine compounds, phosphamine compounds, quinacridone compounds, anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, silole compounds Etc.

For example, 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 (J. Lumin, etc.) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, etc. , 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′, 7, 7 ′. -Fluorene compounds such as tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4'-N, N'- Carbazole compounds such as carbazole biphenyl, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1- Oxadiazole compounds such as naphthyl) -1,3,4-oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3 , 4-diphenylsilol (PyPySPyPy) and other silole compounds, bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin) and other phenanthroline compounds It is done.

(solvent)
Moreover, a solvent will not be specifically limited if it is a solvent in which a luminescent low molecular weight compound and a charge transporting low molecular weight compound dissolve favorably.
The solubility of the solvent is usually 0.01% by weight or more, preferably 0.05% by weight or more, and more preferably 0% of the light-emitting low-molecular compound and the charge-transporting low-molecular compound at normal temperature and normal pressure, respectively. It is preferable to dissolve 1% by weight or more.

Although the specific example of a solvent is given to the following, as long as the effect of this invention is not impaired, it is not limited to these.
For example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated aroma such as chlorobenzene, dichlorobenzene, and trichlorobenzene Group hydrocarbons: 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethyl Aromatic ethers such as anisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; Alicyclic ketones such as Sanone, Cyclooctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene And aliphatic ethers such as glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA).

Of these, alkanes and aromatic hydrocarbons are preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.
In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 80 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher, and usually 270 ° C or lower, preferably 250 ° C or lower, more preferably 230 ° C or lower.

The amount of the solvent used is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably with respect to 100 parts by weight of the composition for the light emitting layer. 80 parts by weight or more, preferably 99.95 parts by weight or less, more preferably 99.9 parts by weight or less, and particularly preferably 99.8 parts by weight or less. When the content is lower than the lower limit, the viscosity becomes too high, and the film forming workability may be lowered. On the other hand, if the value exceeds the upper limit, the film thickness obtained by removing the solvent after film formation cannot be obtained, so that film formation tends to be difficult. In addition, when mixing and using 2 or more types of solvents as a composition for light emitting layers, it is made for the sum total of these solvents to satisfy | fill this range.

Moreover, the composition for light emitting layers in this invention may contain various additives, such as a leveling agent and an antifoamer, for the purpose of improving film formability.
(Method for forming light emitting layer)
The method for forming a light emitting layer in the present invention is preferably performed by a wet film forming method from the viewpoint of excellent film forming properties.

  After application of the composition for the light emitting layer for producing the light emitting layer, the obtained coating film is dried and the solvent for the light emitting layer is removed to form the light emitting layer. The method of the wet film formation method is not limited as long as the effect of the present invention is not significantly impaired. For example, the wet film formation method in the present invention described in the above [Film formation method] can be mentioned. Coating method and inkjet method.

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 light emitting layer is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.
<Configuration of organic electroluminescent element>
Below, the layer structure of the organic electroluminescent element manufactured with the method of this invention, its general 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 serves as a support for the organic electroluminescence device, and quartz or glass plates, metal plates or metal foils, plastic films, sheets, or the like are 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, 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. 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, conductive polymer fine powder, etc., an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate (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. 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 is a layer that transports holes from the anode 2 to the light emitting layer, and is usually formed on the anode 2.

The method for forming the hole injection layer according to the present invention may be a vacuum vapor deposition method or a wet film formation method, and is not particularly limited. However, from the viewpoint of reducing dark spots, the hole injection layer may be formed by a wet film formation method. preferable.
The thickness of the hole injection layer 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 is formed by wet film formation, the material for forming the hole injection layer is usually mixed with an appropriate solvent (hole injection layer solvent) to form a composition for film formation (hole injection). Layer forming composition), and applying this hole injection layer forming composition onto a layer corresponding to the lower layer of the hole injection layer (usually an anode) by an appropriate technique, A hole injection layer is formed by drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.
As long as the hole transporting compound is a compound having a hole transporting property, which is usually used in a hole injection layer of an organic electroluminescence device, a monomer or the like may be a polymer compound or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

As the hole transporting compound, 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 is preferable.
Therefore, the hole transporting compound is preferably formed using the above hole transporting material. In the case of using a material other than the above-described hole transporting material, examples of the hole transporting compound include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, and fluorene groups that are tertiary. Examples include amine-linked compounds, hydrazone derivatives, silazane derivatives, silanamine derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, and carbon.

In the present invention, the derivative includes, for example, an aromatic amine derivative and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.
The hole transporting compound used as the material for the hole injection layer may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. 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 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.))
As the aromatic hydrocarbon group and the aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property 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 an alkyl group, an alkenyl group, an alkoxy group, a silyl group, a siloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. .

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.
In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), which is a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  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 as described in the section (2-1. Electron accepting compound). The preferable example is also the same.

(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 a ratio.

(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 step, 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 ether solvents 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 the composition for forming the hole injection layer is prepared, the composition is coated on the layer corresponding to the lower layer of the hole injection layer (usually the anode 2) by wet film formation, and dried to form the composition. A hole injection layer 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 in 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.

[Hole transport layer]
The hole transport layer can be formed by the material and the film forming method described in the section [Second organic layer]. The preferred materials and methods are similar.
{Light emitting layer}
The light emitting layer can be formed by the material and film forming method described in the above section [Light emitting layer]. The preferred materials and methods are similar.

{Hole blocking layer}
A hole blocking layer may be provided between the light emitting layer and an electron injection layer 8 described later. The hole blocking layer is a layer stacked on the light emitting layer so as to be in contact with the cathode side interface of the light emitting layer.
This hole blocking layer has a role of blocking holes moving from the anode 2 from reaching the cathode and a role of efficiently transporting electrons injected from the cathode toward 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. Examples of the material for the hole blocking layer that satisfies such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Mixed-ligand complexes, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Triazole derivatives such as styryl compounds (JP-A-11-242996), 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7 -41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), and the like. That. Furthermore, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer.

In addition, the material of a hole-blocking layer 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 a hole-blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the hole blocking layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

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

  As the electron transporting compound used for the electron transport layer, usually, the electron injection efficiency from the cathode or the electron injection layer 8 is high, and the injected electrons can be efficiently transported with high electron mobility. Use compounds. 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 zinc Such as emissions of zinc, and the like.

In addition, only 1 type may be used for the material of an electron carrying layer, and 2 or more types may be used together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of an electron carrying layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the electron transport layer 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 into the light emitting layer. 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 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer) on the light emitting layer side.

  As the cathode material, the material used for the anode 2 can be used. However, a metal having a low work function is preferable for efficient electron injection. For example, tin, magnesium, indium, calcium A suitable metal such as aluminum or 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, only 1 type may be used for the material of a cathode, and 2 or more types may be used together by arbitrary combinations and a ratio.
The thickness of the cathode is usually the same as that of the anode 2.
Further, for the purpose of protecting the cathode 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 in addition to the layers described above, and an arbitrary layer may be omitted.
<Electron blocking layer>
Examples of the layer that may be included include an electron blocking layer.

  The electron blocking layer is provided between the hole injecting layer or the hole transporting layer and the light emitting layer, and prevents electrons moving from the light emitting layer from reaching the hole injecting layer. Increases the recombination probability of holes and electrons, and has the role of confining the generated excitons in the light-emitting layer, and the role of efficiently transporting holes injected from the hole injection layer toward the light-emitting layer. . In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer is formed as an organic layer according to the present invention by a wet film formation method, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

In addition, the material of an electron blocking layer 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 an electron blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
Further, at the interface between the cathode and the light emitting layer or the electron transport layer, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), etc. are formed. It is also an effective method to improve the efficiency of the device by inserting a very thin insulating film (0.1 to 5 nm) (Applied Physics Letters, 1997, Vol. 70, pp. 152; No. 74586; see IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.).

Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate are cathode, electron injection layer 8, electron transport layer, hole blocking layer, light emitting layer, hole transport layer, hole injection layer, anode 2 You may provide in order.
Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention 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), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

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 EL display and organic EL lighting]
The organic EL display and the organic EL illumination of the present invention are provided with the organic electroluminescent element of the present invention as described above. There is no restriction | limiting in particular about the model and structure of an organic electroluminescent display, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display and the organic EL display of the present invention can be obtained by the method described in “Organic EL display” (Ohm, August 20, 2004, published by Shizushi Tokito, Chiba Adachi, Hideyuki Murata). EL illumination can be formed.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention can be arbitrarily modified and implemented without departing from the gist thereof.
[Evaluation of current-voltage characteristics]
(Reference Example 1)
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate to a thickness of 120 nm (manufactured by Sanyo Vacuum Co., Ltd., sputtered film) using ordinary photolithography technology and hydrochloric acid etching An anode was formed by patterning into a stripe 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.

Arylamine polymer (4.5% by weight) represented by the following formula (H1) and 0.09% by weight (aryl) of 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate represented by the following formula (A1) 20 wt% with respect to the amine polymer) was dissolved in ethyl benzoate as a solvent, and then filtered using a PTFE (polytetrafluoroethylene) membrane filter having a pore size of 0.2 μm to prepare a coating composition. This coating composition was spin coated on the substrate. The spin coating was performed in an air atmosphere at a temperature of 23 ° C. and a relative humidity of 60%, the spinner rotation speed was 1500 rpm, and the spinner time was 30 seconds. After spin coating, it was heated at 230 ° C. for 1 hour in an oven at atmospheric pressure. In this way, a hole injection layer of about 100 nm was formed.

The compound forming the hole injection layer is represented by the formula (H2), and the halogen atom concentration calculated from the charging ratio is 6.6% by weight.

Subsequently, a 2 mm wide striped shadow mask was brought into close contact with the element so as to be orthogonal to the anode ITO stripe as a mask for cathode vapor deposition. After roughly evacuating the apparatus with an oil rotary pump, the apparatus was evacuated with a cryopump until the degree of vacuum in the apparatus was 3 × 10 ⁻⁴ Pa or less.

Aluminum was heated as a cathode by a molybdenum boat, and an aluminum layer having a thickness of 80 nm was formed by controlling the deposition rate at 0.5 to 5 liters / second and the degree of vacuum at 2 to 3 × 10 ⁻⁴ Pa. The substrate temperature during vapor deposition of the cathode was kept at room temperature.
As described above, a single layer element having an element area of 2 mm × 2 mm was obtained.
The obtained single layer element was connected to a 2400 type source meter (manufactured by Keithley), and voltage was sequentially applied to read the current value.

The current-voltage characteristic of this element is shown in FIG.
As shown in FIG. 2, the device of Reference Example 1 having a layer having a halogen atom concentration of 2% by weight or more passed a current at a lower voltage than the device of Reference Comparative Example 1. From this, it became clear that the resistance of the layer can be reduced by increasing the halogen atom concentration.
[Comparative Reference Example 1]
A device having a hole injection layer was prepared in the same manner as in Reference Example 1 except that the concentration of the compound represented by the formula (A1) was changed to 3% by weight of the compound represented by the formula (H1). Voltage characteristics were measured.

The halogen atom concentration calculated from the charge ratio of the hole injection layer is 1.1% by weight. The current-voltage characteristics of this element are shown in FIG.
<Production of organic electroluminescence device>
Example 1
The organic electroluminescent element shown in FIG. 1 was produced.

  An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 with a thickness of 120 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.

First, a hole transporting polymer material having a repeating structure represented by the following structural formula (P1) (weight average molecular weight (Mw) = 63600, number average molecular weight (Mn) = 35100, dispersity (Mw / Mn) = 1 .81), a composition for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate represented by the structural formula (A1) and ethyl benzoate was prepared. This composition was formed into a film on the anode 2 by spin coating under the following conditions and insolubilized by heating to obtain a hole injection layer 3 (first organic layer) having a thickness of 30 nm.

<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition 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 coating atmosphere In-air heating conditions In-air 230 ° C. 3 hours Subsequently, an organic electroluminescent element composition containing the following hole-transporting polymer material (P2) was prepared, and the conditions were as follows: A hole transport layer 4 (second organic layer) having a thickness of 20 nm was formed by film formation by spin coating and insolubilization by heating.

<Composition for forming hole transport layer>
Solvent Toluene Solid concentration 0.4 wt%
<Film formation conditions for hole transport layer 4>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere In nitrogen Heating condition In nitrogen, 230 ° C., 1 hour Next, in forming the light emitting layer 5, the following is shown using the organic compounds (C1) and (D1) shown below An organic electroluminescent element composition was prepared and spin coated on the hole transport layer 4 under the conditions shown below to obtain a light emitting layer 5 with a film thickness of 40 nm.

<Composition for light emitting layer formation>
Solvent Toluene Composition concentration C1: 0.80 wt%
D1: 0.08% by weight
<Film-forming conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere Nitrogen Heating conditions Under reduced pressure (0.1 MPa), 130 ° C., 1 hour Here, the substrate on which the light emitting layer 5 has been deposited is in a vacuum deposition apparatus connected to a nitrogen glove box Evacuated until the degree of vacuum in the apparatus becomes 1.7 × 10 ⁻⁴ Pa or less, and then BA
lq (C2) was laminated by a vacuum deposition method to obtain a hole blocking layer 6. The deposition rate was controlled in the range of 0.5 to 1.1 liters / second, and the hole blocking layer 6 having a film thickness of 10 nm was formed by being laminated on the light emitting layer 5. The degree of vacuum at the time of deposition was 2.5 to 4.0 × 10 ⁻⁵ Pa.

Then, Alq3 (C3) was heated and vapor-deposited, and the electron carrying layer 7 was formed into a film. The degree of vacuum during deposition is 2.8 to 3.7 × 10 ⁻⁵ Pa, the deposition rate is controlled in the range of 0.7 to 1.2 Å / sec, and a film with a thickness of 30 nm is formed on the hole blocking layer 6. To form an electron transport layer 7.

Here, the element that has been vapor-deposited up to the electron transport layer 7 is transported in a vacuum to a chamber connected to the hole blocking layer 6 and the chamber in which the electron transport layer 7 is vapor-deposited, and 2 mm as a mask for cathode vapor deposition. A stripe-shaped shadow mask having a width was brought into close contact with the element so as to be orthogonal to the ITO stripe of the anode 2.

First, lithium fluoride (LiF) is controlled as the electron injection layer 8 at a deposition rate of 0.08 to 0.15 liters / second and a degree of vacuum of 2.5 to 5.5 × 10 ⁻⁵ Pa using a molybdenum boat. , 0
. A film having a thickness of 5 nm was formed on the electron transport layer 7. Next, aluminum is similarly heated by a molybdenum boat as the cathode 9 and controlled at a deposition rate of 0.5 to 1.5 liters / second and a degree of vacuum of 2.0 to 5.5 × 10 ⁻⁵ Pa to a film thickness of 80 nm. An aluminum layer was formed. 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 Three Bond) 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. A device that can be driven at a low voltage, has high luminous efficiency, and has a long lifetime was obtained.
Table 2 shows the normalized drive life when the drive life of Comparative Example 3 is 1.
Furthermore, the measurement result by TOF-SIMS method is shown in FIG.

(Example 2)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the hole injection layer 3 (first organic layer) was formed as follows.
<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition concentration P1: 2.0% by weight
A1: 0.8% by weight
Table 1 shows the characteristics of this element. A device that can be driven at a low voltage, has high luminous efficiency, and has a long lifetime was obtained.

(Example 3)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the hole injection layer 3 was formed as follows.
<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition concentration P1: 2.0% by weight
A1: 0.2% by weight
Table 1 shows the characteristics of this element. An element capable of being driven at a low voltage and having high luminous efficiency was obtained.

(Comparative Example 1)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the hole injection layer 3 was formed as follows.
<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition concentration P1: 2.0% by weight
A1: 0.06% by weight
Table 1 shows the characteristics of this element.

(Comparative Example 2)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the hole injection layer 3 was formed as follows.
<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition concentration P1: 2.0% by weight
A1: 0.1% by weight
Table 1 shows the characteristics of this element.

(Comparative Example 3)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the hole injection layer 3 was formed as follows.
<Composition for forming hole injection layer>
Solvent Ethyl benzoate Composition concentration P2: 2.0% by weight
A1: 0.8% by weight

(Weight average molecular weight: 26500, number average molecular weight: 12000)
The driving life of this element is shown in Table 2.
Furthermore, the measurement result by TOF-SIMS method is shown in FIG.

  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 of instruments), display panels, indicator lamps 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)

An organic electroluminescent device comprising a substrate and an anode, an organic layer, and a cathode provided on the substrate,
The organic layer includes a first organic layer and a second organic layer formed by a wet film formation method,
The first organic layer and the second organic layer are provided adjacent in this order from the anode side,
The halogen atom concentration (% by weight) of the first organic layer is 2% by weight or more,
Furthermore, it is 20 times or more of the halogen atom concentration (weight%) of a 2nd organic layer, The organic electroluminescent element characterized by the above-mentioned.   The organic electroluminescent device according to claim 1, wherein the first organic layer is a hole injection layer, and the second organic layer is a hole transport layer.   3. The organic electroluminescent element according to claim 1, wherein a concentration (% by weight) of halogen atoms in the organic layer is 0.5% by weight or more.   The organic electroluminescent element according to claim 1, wherein the halogen atom contained is a fluorine atom. A light emitting layer between the anode and the cathode;
The organic electroluminescent element according to any one of claims 1 to 4, wherein the light emitting layer contains a light emitting low molecular weight compound.   The organic electroluminescent element according to claim 1, wherein the first organic layer contains an insoluble polymer compound. An organic EL display comprising the organic electroluminescent element according to claim 1.   An organic EL illumination comprising the organic electroluminescent element according to claim 1.