WO2011019025A1 - Organic electroluminescent element, organic el display device, and organic el lighting device - Google Patents

Abstract

Disclosed is an organic electroluminescent element which contains a light-emitting layer produced by a wet-mode film formation method and has a long operation life. Specifically disclosed is an organic electroluminescent element, in which at least a light-emitting layer formed by a wet-mode film formation method is provided between a cathode and an anode. The organic electroluminescent element is characterized in that the light-emitting layer contains a charge-transporting material or charge-transporting materials, and at least one of the charge-transporting materials is an anthracene derivative having a molecular weight of 460 to 2000 and having a specific structure that fulfils formula (1): 0.01 = µe/µh = 6 (wherein µe represents the electron mobility of the charge-transporting material at an electric field strength of 0.16 MV/cm; and µh represents the hole mobility of the charge-transporting material at an electric field strength of 0.16 MV/cm).

Description

Organic electroluminescent device, organic EL display device, and organic EL lighting

The present invention relates to a composition for an organic electroluminescent element used for forming a light emitting layer of an organic electroluminescent element by a wet film forming method.
Moreover, this invention relates to the organic electroluminescent element using this composition for organic electroluminescent elements, the organic electroluminescent display apparatus using this organic electroluminescent element, and organic electroluminescent illumination.

In recent years, organic electroluminescence (organic EL) elements have been actively developed as a technology for manufacturing light-emitting devices such as displays and lighting, and put into practical use mainly for small to medium-sized display applications. Has begun.
The organic electroluminescence device obtains light emission by injecting positive and negative charges (carriers) into an organic layer between two electrodes and recombining the carriers.

Currently, organic electroluminescence devices in practical use are generally manufactured using a technique in which a relatively low molecular weight compound is heated under high vacuum conditions, and the evaporated compound is deposited on a substrate placed above.

For this vacuum deposition method, by adjusting the charge balance between holes and electrons injected into the light-emitting layer, various causes of deterioration due to the generation of excessively injected charges can be suppressed, and thus the organic electric field can be reduced. The idea of improving the driving life of the light emitting element has been proposed.

In Patent Document 1, an electron injection layer made of an inorganic compound is used for the purpose of lowering the voltage. In this case, in order to prevent the electron injection from becoming too good and reaching the hole transport layer. In addition, the mobility is adjusted to reduce the electron transport property of the host.

In Patent Document 2, an amorphous carbon film is disposed between the anode and the organic layer to improve the hole injection efficiency. Here, contrary to Patent Document 1, the electron mobility of the light emitting layer is increased.

In Patent Document 3, in an organic electroluminescence device having two stacked light emitting layers, the time required for electrons injected from the cathode and holes injected from the anode to reach the interface between the two light emitting layers is approximately the same. Techniques for making adjustments are disclosed.

In Patent Document 4, in order to balance the charge of holes and electrons of the device, the ratio of the electron mobility of the electron transport layer to the electron mobility of the light emitting layer, the hole mobility of the hole transport layer and the light emitting layer A technique for defining the ratio of hole mobility to be within a certain range is disclosed.

Patent Document 5 discloses a technique for defining the electron / hole mobility ratio of each of the light emitting layers of RGB to be within a certain range in a device in which RGB are arranged in parallel for display applications and the like.

Patent Document 6 relates to an element using an electron transport layer with a small energy gap for the purpose of causing a phosphorescent element to emit light at a low voltage, and the electron / hole mobility ratio between the electron transport layer and the light emitting layer is within a predetermined range. By defining, a technique for preventing the exciton from diffusing to the electron transport layer side by separating the recombination site from the interface with the electron transport layer is disclosed.

Japanese Unexamined Patent Publication No. 2000-164359 Japanese Unexamined Patent Publication No. 2001-176663 Japanese Unexamined Patent Publication No. 2006-107790 Japanese Unexamined Patent Publication No. 2006-270091 Japanese Unexamined Patent Publication No. 2008-205174 International Publication No. 2008/015949 Pamphlet International Publication No. 2004/018587 Pamphlet Japanese Unexamined Patent Publication No. 2008-124156

Each of these documents discloses a technique for recombination of holes and electrons at a desired position of the light emitting layer, and the excitons generated thereby efficiently contribute to light emission.
By the way, in recent years, there is an increasing need for increasing the size of organic electroluminescent elements. However, since it is difficult to uniformly deposit on a large area substrate by vacuum deposition, the vacuum deposition method is suitable for manufacturing large area organic EL panels such as large displays and large area surface emitting lighting. Not. Further, the vacuum vapor deposition method has a problem that the utilization efficiency of the organic material as the vapor deposition source is low and the manufacturing cost is likely to be high.

As a means for producing a large-area organic EL panel, a wet film forming method represented by a spin coating method, an ink jet method, a dip coating method, various printing methods and the like has been proposed.

However, an organic electroluminescent element having a light emitting layer formed by a wet film forming method has a problem that its lifetime is short. In addition, the physical properties of the organic electroluminescent element largely depend on the method of forming the light emitting layer. In particular, the lifetime of the organic electroluminescent element is not limited even if the composition of the light emitting layer is the same. It is known that the lifetime of the element having the light emitting layer is completely different between the case where the light emitting layer is formed and the case where the light emitting layer is formed. For example, in the device of Example 14 of Patent Document 7 and the device of Example 47 of Patent Document 8, the same compound is used as the host of the light-emitting layer, but the former half-life of forming the light-emitting layer by vapor deposition is lower. Although the length of 4500 hours is long, the latter half-time in which the light emitting layer is produced by the coating method is as short as 1600 hours.
An organic electroluminescence device having a long lifetime by a wet film forming method has not been proposed so far.

An object of the present invention is to provide an organic electroluminescent device having a long driving life in an organic electroluminescent device having a light emitting layer formed by a wet film forming method.

The inventors of the present invention do not improve the lifetime of an organic electroluminescent device having a light-emitting layer formed by a wet film formation method because the charge balance upon recombination of injected holes and electrons in the device is not good. We thought that it might be caused by the equilibrium, and studied diligently to solve these problems.

As a result, we found that the cause of this problem is not only the problem of simple charge balance obtained from the mobility ratio of the constituent material itself considered for the vapor deposition film, but also a problem peculiar to the wet film formation method. It was.
As a result of further investigation, by using an ink (film-forming composition) that satisfies a specific condition, holes and electrons injected in an organic electroluminescent device having a light-emitting layer formed by a wet film-forming method are used. As a result, it was found that the charge balance upon recombination in the device is balanced, and as a result, a long-life organic electroluminescent device can be obtained, and the present invention has been completed.

That is, the gist of the present invention resides in the following organic electroluminescence device, organic EL display device, and organic EL illumination.
[1] An organic electroluminescence device having at least a light emitting layer formed by a wet method between a cathode and an anode, the light emitting layer containing a charge transport material, and at least of the charge transport materials One is an anthracene derivative having a molecular weight of 460 to 2000 and represented by the following general formula (2) that satisfies the following formula (1):
0.01 ≦ μe / μh ≦ 6 (1)
(In formula (1), μe represents the electron mobility of the charge transport material at an electric field strength of 0.16 MV / cm, and μh represents the hole mobility of the charge transport material at an electric field strength of 0.16 MV / cm. )

(In Formula (2), each of Ring A and Ring B independently represents an aromatic group that is a 6-membered ring bonded to an anthracene ring and may be further condensed with 1 to 3 aromatic rings. To express.
Ar ^1A and Ar ^1B each independently represent a divalent aromatic group derived from a monocyclic to condensed ring.
m and n each independently represents an integer of 0 or more, and m + n is 8 or less.
When m and n are each 2 or more, the plurality of Ar ^1A and Ar ^1B contained in one molecule may be the same or different.
Of the ring A, ring B, Ar ^1A and Ar ^1B , when the number of those on the same plane as the anthracene ring is α and the number of others is β, the following formula (3) is satisfied.

For ring A, ring B, Ar ^1A and Ar ^1B , the total number of monocycles and the total number of condensed rings satisfy the following formula (4).

When at least one of ring A and ring B is a condensed ring having three benzene rings, the anthracene ring and the condensed ring having three benzene rings are bonded at positions other than the 9th and 10th positions. ing. )
[2] The organic electroluminescent element according to claim 1, wherein the charge transport material satisfies the following formulas (2a) and (2b).
μe ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2a)
μh ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2b)
(In formulas (2a) and (2b), μe and μh are synonymous with μe and μh in formula (1).)
[3] The organic electroluminescent element as described in [1] or [2] above, wherein the light emitting layer further contains a fluorescent light emitting material as a light emitting material.
[4] The organic electroluminescent element as described in [3] above, wherein the fluorescent light-emitting material is a substituted or unsubstituted condensed aromatic hydrocarbon compound having 10 to 40 nuclear carbon atoms.
[5] The above-mentioned [1], wherein a first organic layer is provided between the light emitting layer and the anode, and the first organic layer is a layer formed by a wet film forming method. ] The organic electroluminescent element of any one of [4].
[6] The organic electroluminescent element as described in [5] above, wherein the first organic layer is a layer formed by crosslinking a crosslinkable compound.
[7] The organic electric field according to [5] or [6] above, wherein a second organic layer containing an electron-accepting compound is provided between the anode and the first organic layer. Light emitting element.
[8] The organic electroluminescent element as described in [7] above, wherein the second organic layer is a layer containing no ether bond.
[9] An organic EL display device comprising the organic electroluminescent element as described in any one of [1] to [8].
[10] An organic EL illumination comprising the organic electroluminescence device as described in any one of [1] to [8].

According to the composition for an organic electroluminescent device according to the present invention, an organic electroluminescent device having an organic layer such as a luminescent layer formed by a wet film-forming method, in particular, an organic layer on an electrode, especially an organic layer on an electrode. Among them, in the organic electroluminescence device in which the light emitting layer is formed by the wet film forming method, the charge balance between injected holes and electrons is excellent. As a result, it is possible to provide an organic electroluminescent element having a long lifetime and high luminous efficiency, and using such an organic electroluminescent element, it is possible to provide a high-quality organic EL display device and organic EL illumination. .

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

Hereinafter, embodiments of the composition for organic electroluminescence device according to the present invention, the organic electroluminescence device of the present invention containing the composition, and the organic EL display and organic EL illumination will be described in detail. The description of the requirements is an example (representative example) of an embodiment of the present invention, and the present invention is not specified in these contents unless it exceeds the gist.

[Composition for organic electroluminescence device]
The composition for organic electroluminescent elements according to the present invention is a composition for organic electroluminescent elements containing a charge transport material, a luminescent material, and a solvent, and at least one of the charge transport materials is represented by the following formula (1): ) Is satisfied.
0.01 ≦ μe / μh ≦ 6 (1)
(In formula (1), μe represents the electron mobility of the charge transport material at an electric field strength of 0.16 MV / cm, and μh represents the hole mobility of the charge transport material at an electric field strength of 0.16 MV / cm). .)

In the following, the value of “μe / μh” may be referred to as “parameter value of the present invention” as appropriate.

{Charge transport material}
The composition for organic electroluminescent elements according to the present invention contains a charge transport material.

In the organic electroluminescence device, it is preferable that the light emitting material emits light upon receiving electric charge or energy from a host material having charge transport performance. Therefore, the charge transport material contained in the composition for organic electroluminescent elements according to the present invention is preferably a charge transport material used as this host material.

<Molecular weight>
In the present invention, the molecular weight of the compound used as the charge transport material is usually 2000 or less, preferably 1500 or less, more preferably 1200 or less, particularly preferably 1100 or less, and 460 or more, preferably 480 or more, more preferably 490 or more. Especially preferably, it is the range of 496 or more. If the molecular weight of the charge transporting material is equal to or higher than the above lower limit, the heat resistance, the difficulty of gas generation, the film quality when the film is formed, or the morphological change of the organic electroluminescence device due to migration, etc. preferable. On the other hand, when the molecular weight of the charge transporting material is not more than the above upper limit, the organic compound can be easily purified, and there is a tendency that it takes less time to dissolve in the solvent.

<Structure, etc.>
Charge transport materials are classified into hole transport compounds that mainly have hole transport ability, electron transport compounds that mainly have electron transport ability, and bipolar compounds that have the performance of both, based on the difference in charge transport properties. Is done.

The charge transport material in the present invention contains a compound having an anthracene ring of the following general formula (2) as a partial structure.

(In Formula (2), each of Ring A and Ring B independently represents an aromatic group that is a 6-membered ring bonded to an anthracene ring and may be further condensed with 1 to 3 aromatic rings. To express.
Ar ^1A and Ar ^1B each independently represent a divalent aromatic group derived from a monocyclic to condensed ring.
m and n each independently represents an integer of 0 or more, and m + n is 8 or less.
When m and n are each 2 or more, a plurality of Ar ^A and Ar ^B contained in one molecule may be the same or different.
Of the ring A, ring B, Ar ^1A and Ar ^1B , when the number of those on the same plane as the anthracene ring is α and the number of others is β, the following formula (3) is satisfied.

For ring A, ring B, Ar ^1A and Ar ^1B , the total number of monocycles and the total number of condensed rings satisfy the following formula (4).

When at least one of ring A and ring B is a condensed ring having three benzene rings, the anthracene ring and the condensed ring having three benzene rings are bonded at positions other than the 9th and 10th positions. ing. )

Ring A and ring B each independently represents an aromatic group in which the portion bonded to the anthracene ring is a 6-membered ring and may further be condensed with 1 to 3 aromatic rings.
In the present invention, the “aromatic group” represents a functional group having aromaticity, and includes both an aromatic hydrocarbon group and an aromatic heterocyclic group.

Specific examples when ring A and ring B are aromatic hydrocarbon groups include benzene rings, naphthalene rings, phenanthrene rings, anthracene rings, pyrene rings, chrysene rings, naphthacene rings, benzophenanthrene rings, and the like, Alternatively, a group derived from a condensed ring formed by condensation of 2 to 4 benzene rings may be mentioned.

Specific examples when ring A and ring B are aromatic heterocyclic groups include furan ring, benzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, Indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring , Pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc.

Ar ^1A and Ar ^1B each represent a divalent aromatic group derived from a monocyclic to a condensed 4-ring bonded to ring A and ring B.

As a specific example when Ar ^1A and Ar ^1B are aromatic hydrocarbon groups, those having 6 to 14 carbon atoms are preferable. Specific examples include groups derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, and the like.

Specific examples when Ar ^1A and Ar ^1B are aromatic heterocyclic groups are preferably those having 3 to 9 carbon atoms, such as a furan ring, a benzofuran ring, a dibenzofuran ring, a thiophene ring, a benzothiophene ring, and a pyrrole ring. , Pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring , Benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, quinaline Isoindolinone ring, an azulene ring, an acridine ring, a phenanthroline ring, and a group derived from a phenazine ring.

m and n each independently represents an integer of 0 or more, and m + n is 8 or less. m + n is the total number of aromatic groups substituted on ring A or ring B. A larger number tends to increase molecular weight and lower solubility, and is preferably 6 or less. The following is more preferable, and 2 or less is particularly preferable.
When m and n are each 2 or more, a plurality of Ar ^1A and Ar ^1B contained in one molecule may be the same or different, but the molecular symmetry is low and the solubility is likely to be high. Preferably they are different.

Of the ring A, ring B, Ar ^1A and Ar ^1B , when the number of those on the same plane as the anthracene ring is α and the number of others is β, the following formula (3) is satisfied.

Here, the aromatic group which is on the same plane as the anthracene ring is an odd number of aromatic groups between the anthracene ring and the anthracene ring among the aromatic groups bonded on the 9th and 10th extension lines of the anthracene ring. Say what you have.

Specifically, for example, in the case of the following compound (X), a total of three aromatic groups of monocyclic 1, monocyclic 2 and condensed ring 3 are in the same plane with respect to the central anthracene ring. It is considered that the total four other aromatic groups of condensed ring 1, single ring 3, condensed ring 2 and single ring 4 are on a different plane from the central anthracene ring. That is, in the case of this compound, β / (α + 1) = 4 / (3 + 1) = 1.

When the above formula (3) is satisfied, the reason why the lifetime of a device in which a light emitting layer containing this as a charge transport material is formed by a wet method is increased is that β / (α + 1) is 3 or more in the light emitting layer. It is considered that charge transport between the charge transport materials is easily performed efficiently, and that β / (α + 1) is 10 or less, the crystallization of the charge transport material in the light emitting layer is difficult to occur.

In ring A, ring B, Ar ^1A and Ar ^1B , the total number of monocycles and the total number of condensed rings satisfy the following formula (4).

Specifically, for example, in the case of the above-mentioned compound (5), since there are a total of 4 monocyclic rings and a total of 3 condensed rings, the total number of monocyclic rings / total number of condensed rings is 4/3. .
If the ratio of the monocyclic ring to the condensed ring is within the range of the above formula (4), the reason why the lifetime of the element in which the light emitting layer containing this as a charge transporting material is formed by the wet method is increased is the monocyclic ring to the condensed ring. If the ratio is 1.0 or more, crystallization of the charge transport material in the light-emitting layer is difficult to occur, and if the ratio of the single ring to the condensed ring is 2.0 or less, the charge-transport material in the light-emitting layer It is considered that charge transport is easily performed efficiently.

When at least one of ring A and ring B is a condensed ring having three benzene rings, the anthracene ring and the condensed benzene ring have three condensed rings at positions other than the 9th and 10th positions. Are connected. When an anthracene ring and three condensed rings of the benzene ring are bonded at positions other than the 9th position and the 10th position, the lifetime of a device in which a light emitting layer including this as a charge transporting material is formed by a wet method is increased. The reason for the increase is that bonding at a position other than the 9th and 10th positions results in crystallization of the charge transport material in the light emitting layer compared to bonding at a position other than the 9th and 10th positions. It is thought that it is hard to happen.

As the charge transport material used in the present invention, the above-mentioned anthracene derivative has high current efficiency, excellent durability, and long life of a device in which a light emitting layer containing this as a charge transport material is formed by a wet method. Further, these effects are particularly high when the light emitting material is a fluorescent light emitting material. The reason is estimated as follows.

In the movement of holes, the molecule in which holes exist (cation radical molecule) pulls out one electron from the neutral molecule HOMO and rearranges itself to become a neutral molecule. This time, the extracted molecule becomes a cation radical. It is thought to be caused by becoming a molecule. On the other hand, in the movement of electrons, the molecule in which the electron exists (anion radical molecule) gives one electron to the neutral molecule HOMO, and it rearranges itself to become a neutral molecule. This time, the given molecule becomes an anion radical molecule. It is thought that it is caused by becoming.

That is, the mobility can be controlled by controlling the orbital overlap of the HOMO on the neutral molecule and the SOMO of the cation radical molecule, and the LUMO on the neutral molecule and the SOMO of the anion radical molecule.

In the case of anthracene derivatives, in many cases, HOMO and LUMO are localized in the anthracene ring. For this reason, by changing the substituent of the anthracene ring, packing between molecules changes, thereby changing the overlap of orbits, and thus the mobility can be controlled.

In particular, it is considered that the anthracene derivative according to the present invention easily satisfies the formula (1).

[Specific examples of charge transport materials]
Specific preferred examples of the charge transport material in the present invention are shown below, but the present invention is not limited thereto.

In compound a of the above structural formula, α is 1 and β is 6, so β / (α + 1) = 3 and single ring / condensed ring = 4/3. In compound b of the above structural formula, α is 1 and β is 8, so β / (α + 1) = 4 and single ring / fused ring = 6/3 = 2. In compound c of the above structural formula, α is 0 and β is 4, so β / (α + 1) = 4 and single ring / fused ring = 2/2 = 1. In the compound d of the above structural formula, α is 0 and β is 4, so β / (α + 1) = 4 and single ring / fused ring = 2/2 = 1. In the compound e of the structural formula, α is 0 and β is 4, so β / (α + 1) = 4 and single ring / fused ring = 2/2 = 1. In the compound f of the above structural formula, α is 0 and β is 3, so β / (α + 1) = 3 and single ring / fused ring = 2/1 = 2. In compound g of the above structural formula, α is 1 and β is 8, so β / (α + 1) = 4 and single ring / fused ring = 5/4. In compound h of the above structural formula, α is 0 and β is 4, so β / (α + 1) = 4 and single ring / fused ring = 2/2 = 1. In compound i of the above structural formula, α is 1 and β is 6, so β / (α + 1) = 3 and single ring / fused ring = 4/3. In compound j of the above structural formula, α is 0 and β is 4, so β / (α + 1) = 4 and single ring / fused ring = 2/2. In compound k of the above structural formula, α is 1 and β is 6, so β / (α + 1) = 3 and single ring / fused ring = 4/3.

<Formula (1)>
At least one of the charge transport materials contained in the composition for organic electroluminescent elements according to the present invention satisfies the following formula (1). Hereinafter, the charge transport material satisfying the following formula (1) is appropriately referred to as “charge transport material (1)”.
0.01 ≦ μe / μh ≦ 6 (1)
(In the formula (1),
μe represents the electron mobility of the charge transport material at an electric field strength of 0.16 MV / cm, and μh represents the hole mobility of the charge transport material at an electric field strength of 0.16 MV / cm. )

In the present invention, the electron mobility and hole mobility of the charge transport material (herein referred to as “charge mobility”) can be measured by, for example, the TOF method (Time of flight). That is, the anthracene derivative according to the present invention can be selected by measuring the charge mobility of an anthracene derivative having a structure satisfying the above formulas (2) to (4).

The measurement method by the TOF method is shown below.

(Preparation of charge mobility measurement sample)
As a sample for charge mobility measurement, a single element is formed on a substrate in the order of an anode, a layer made of a compound whose charge mobility is to be measured (hereinafter referred to as “measurement target compound layer”), and a cathode. (Hereinafter referred to as “measurement sample”). In addition, in order to measure, the anode and the cathode use one that transmits light. When measuring from the substrate side, a transparent substrate is also used for the substrate.
The layer made of the compound that is the subject of charge mobility measurement may be formed by a wet film-forming method using a composition containing the charge transport material and the organic solvent that is the subject of charge mobility measurement, You may form the charge transport material which is a measuring object of charge mobility by the dry-type film-forming method (vapor deposition method). The organic solvent used for preparing the composition is not particularly limited as long as it dissolves the charge transport material well.
Although there is no restriction | limiting in particular in the wet film-forming method used when forming a measuring object compound layer, For example, the casting method etc. are mentioned.
The film thickness of the measurement target compound layer is not particularly limited as long as it can be measured, but is usually 1 μm.

(Measurement of charge mobility)
The measurement method and principle are as follows.
In order to measure charge mobility, for example, Brio (lamp excitation Nd: YAG pulse laser, manufactured by Quantel) is used as a pulse light source, and a TDS2022 type oscilloscope (manufactured by Tektronix) is used as an oscilloscope.
In the measurement of charge mobility in the present invention, a voltage (voltage at which the electric field strength becomes 0.16 MV / cm) is applied to the measurement sample prepared as described above at 25 ° C. In this state, pulse light is irradiated from the transparent electrode side of the measurement sample using, for example, Brio (lamp excitation Nd: YAG pulse laser, manufactured by Quantel).
At this time, the generated current is subjected to a current-voltage change by a shunt resistor, and a voltage waveform is observed using an oscilloscope.
Here, in order to further improve the measurement sensitivity, a voltage amplifier, for example, a DA1855A differential amplifier (manufactured by LeCroy) may be used.

Here, the time required for the charge to move from end to end in the organic layer, that is, between the electrodes, can be considered as the time from when the current is generated until the current disappears.
The time required for this charge to move in the measurement target compound layer is T (sec), and the voltage applied to the measurement target compound layer is V (V) (however, the voltage is 0.16 MV / cm. When the film thickness of the measurement target compound layer is d (cm), the charge mobility is μ = d / [T × (V / d)] as unit electric field strength and charge transfer rate per unit second. (Cm ² / V · s)
Can be calculated.

By this method, for example, charge mobility is calculated at a voltage of three or more points, and the Pool-Frenkel equation μ (E) = μ (0) × exp (β × E ^0.5 )
E = V / d
μ (0) = zero-field mobility
β: Poole-Frenkel factor
The charge mobility at an arbitrary electric field strength is calculated by fitting measured data by using the least square method.

Since the polarity of the charge moving from the transparent electrode surface to the counter electrode is reversed by reversing the polarity of the voltage applied to the measurement sample, the hole mobility and the electron mobility are measured by the same method.

Note that the measuring instrument used for measuring the charge mobility is not limited to the above-described measuring instrument as long as the same measurement as described above is possible. It is preferable to use equipment.

The μe / μh of the charge transport material (1) in the present invention is usually 0.01 or more, preferably 0.05 or more, more preferably 0.1 or more, and usually 6 or less, preferably 5 or less, more preferably 4 It is as follows.
When the parameter value of the present invention is within the above range, in the organic electroluminescence device in which the organic layer on the electrode, particularly the light emitting layer, is formed by a wet film forming method, the charge balance between injected holes and electrons is Since it is excellent, an organic electroluminescence device having a long lifetime and high luminous efficiency can be obtained.

<Formulas (2a), (2b)>
In the present invention, the charge transporting material (1) satisfying the formula (1) preferably satisfies the following formulas (2a) and (2b).
μe ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2a)
μh ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2b)

The electron mobility μe of the charge transport material (1) is usually 2.0 × 10 ⁻⁷ cm ² / V · s or more, preferably 1.0 × 10 ⁻⁶ cm ² / V · s or more, more preferably 1 0.0 × 10 ⁻⁵ cm ² / V · s or more, usually 1.0 × 10 ⁻¹ cm ² / V · s or less, preferably 1.0 × 10 ⁻² cm ² / V · s or less, more preferably Is 3.0 × 10 ⁻³ cm ² / V · s or less.
In addition, the hole mobility μh of the charge transport material (1) is usually 2.0 × 10 ⁻⁷ cm ² / V · s or more, preferably 1.0 × 10 ⁻⁶ cm ² / V · s or more, Preferably it is 1.0 × 10 ⁻⁵ cm ² / V · s or more, usually 1.0 × 10 ⁻¹ cm ² / V · s or less, preferably 1.0 × 10 ⁻² cm ² / V · s or less. More preferably, it is 1.0 × 10 ⁻³ cm ² / V · s or less.

When the electron mobility μe and the hole mobility μh of the charge transport material (1) are within the above ranges, when an organic electroluminescence device is produced, the charge is less than the thickness of a light emitting layer that is usually produced, which will be described later. Since the movement is fast, an organic electroluminescence device with a low driving voltage can be obtained.

<Content in composition>
The charge transport material contained in the composition for organic electroluminescent elements according to the present invention may be only one kind, or may be a combination of two or more kinds in any combination and ratio. At least one kind is a charge transport material (1) that satisfies the parameter values of the present invention.

The content of the charge transport material in the total solid content contained in the composition for organic electroluminescent elements of the present invention is usually 65% by weight or more, preferably 75% by weight or more, more preferably 85% by weight or more. It is 99.95 weight% or less, Preferably it is 99.5 weight% or less, More preferably, it is 99 weight% or less.
When the content of the charge transport material in the composition for organic electroluminescent elements is at least the lower limit, the drive voltage and the light emission efficiency are not easily increased due to a decrease in charge transport capability in the thin film. On the other hand, if the content of the charge transport material is less than or equal to this upper limit, film thickness unevenness is unlikely to occur.
In addition, when using together 2 or more types of charge transport materials, it is made for the total content of these to be contained in the said range.

Further, the content ratio of the charge transport material (1) in the total charge transport material contained in the composition for organic electroluminescent elements according to the present invention is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight. % Or more.
When the ratio of the charge transport material (1) in the total charge transport material is equal to or higher than the lower limit, the above-mentioned effect due to the use of the charge transport material (1) satisfying the parameter value of the present invention is easily exhibited.

In particular, it is preferable that all the charge transport materials in the composition for organic electroluminescent elements according to the present invention are the charge transport materials (1). The charge transport material (1) may be only one kind or two or more kinds of materials may be used in any combination and ratio, but two or more kinds of charge transport materials (1) are used in combination. In some cases, the total content of these is usually set to the above lower limit or more.

{Luminescent material}
The composition for organic electroluminescent elements according to the present invention is used for forming a light emitting layer of an organic electroluminescent element, but the composition for organic electroluminescent elements according to the present invention usually contains a luminescent material.

A luminescent material is a material having an emission quantum yield of 30% or more in a dilute solution at room temperature in an inert gas atmosphere, and is used based on comparison with a fluorescence or phosphorescence spectrum in the dilute solution. A part or all of the EL spectrum obtained when the organic electroluminescence device manufactured in this manner is energized is defined as a material attributed to the light emission of the material.

Here, the measurement methods of the emission quantum yield of the luminescent material, the fluorescence or phosphorescence spectrum in the solution, and the EL spectrum when the organic electroluminescence device is used are as follows.

(Measurement method of luminescence quantum yield)
The luminescence quantum yield of the luminescent material can be measured using, for example, an absolute PL quantum yield measuring apparatus C9920-02 (manufactured by Hamamatsu Photonics).
In the measurement, a solution obtained by diluting the luminescent material to about 0.01 mmol / L with respect to the solvent and sufficiently deoxidizing with an inert gas (for example, nitrogen) is used.

(Measurement method of fluorescence or phosphorescence spectrum in solution)
A solution similar to that used for the above-described measurement of the luminescence quantum yield is irradiated with light of an arbitrary wavelength using, for example, a spectrophotometer F-4500 (manufactured by Hitachi, Ltd.) to obtain a luminescent material. The spectrum obtained by excitation is measured.
Note that the measuring instrument to be used is not limited to the above measuring instrument as long as the same measurement as described above is possible, and other measuring instruments may be used.

(Measurement method of EL spectrum in case of organic electroluminescence device)
The EL spectrum of the organic electroluminescent element can be obtained by spectrally separating the spectrum. Specifically, a predetermined current is applied to the manufactured element, and the obtained EL spectrum is measured by an instantaneous multi-photometry system MCPD-2000 (manufactured by Otsuka Electronics Co., Ltd.).
Note that the measuring instrument to be used is not limited to the above measuring instrument as long as the same measurement as described above is possible, and other measuring instruments may be used.

Any known material can be applied as the light emitting material, and it is not limited as long as it is normally used as a light emitting material of an organic electroluminescent element. For example, a fluorescent material or a phosphorescent material may be used.
In principle, the emission efficiency of an organic electroluminescent device is lower than that of a phosphorescent material, but the energy gap in the excited singlet state is smaller than that of a phosphorescent material having the same emission wavelength, and the exciton lifetime is nano. Since it is very short, on the order of seconds, the load on the light emitting material is small and the drive life of the element tends to be long.
On the other hand, phosphorescent materials, in principle, have very high emission efficiency of organic electroluminescent devices, but the energy gap in the excited singlet state is larger than fluorescent materials with the same emission wavelength, and the exciton lifetime is from microseconds to milliseconds. Since the order is long, the driving life is likely to be shorter than that of the fluorescent light emitting material. Therefore, it is preferable to use a phosphorescent material for applications in which light emission efficiency is more important than lifetime. In addition, for example, blue may be used in combination, such as using a fluorescent material, and green and red using a phosphorescent material.

<Molecular weight>
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, still 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. When the molecular weight of the luminescent material is equal to or more than the above lower limit, the heat resistance is excellent, gas generation hardly occurs, the film quality when the film is formed is excellent, and the morphological change of the organic electroluminescence element due to migration or the like hardly occurs. On the other hand, when the molecular weight of the light emitting material is not more than the above upper limit, the organic compound can be easily purified, and it is difficult to take time when dissolved in a solvent.

<Structure, etc.>
As described above, any known material can be applied to the luminescent material. However, for the purpose of improving the solubility in a solvent, the symmetry and rigidity of the molecule of the luminescent material are reduced, or an alkyl group is used. It is preferable to introduce a lipophilic substituent.

<Phosphorescent material>
As the phosphorescent material, for example, a long-period type periodic table (hereinafter, unless otherwise specified, the term “periodic table” refers to a long-period type periodic table) selected from Group 7 to 11 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.

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 phosphorescent materials include tris (2-phenylpyridine) 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 porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

<Fluorescent material>
In the present invention, it is preferable to use a fluorescent light-emitting material as the light-emitting material since the driving life is particularly long when the element is used. The fluorescent light-emitting material is preferably a substituted or unsubstituted condensed aromatic hydrocarbon compound having 10 to 40 nuclear carbon atoms from the viewpoint of efficiently capturing holes in the light-emitting layer.

Hereinafter, examples of the fluorescent light emitting material will be given, but the fluorescent light emitting material that can be used in the present invention is not limited to the following examples.

Examples of the fluorescent light emitting material (green fluorescent dye) that gives green light emission include aluminum complexes such as quinacridone, coumarin, Al (C ₉ H ₆ NO) _3, and derivatives thereof.

Examples of the fluorescent material that gives yellow light (yellow fluorescent dye) include rubrene, perimidone and derivatives thereof.

Examples of fluorescent light emitting materials (red fluorescent dyes) that emit red light include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyrene) -4H-pyran) -based compounds, benzopyran, rhodamine , Xanthene such as benzothioxanthene, azabenzothioxanthene, and derivatives thereof.

Fluorescent materials (blue fluorescent dyes) that emit blue light include substituted or unsubstituted condensed aromatic hydrocarbon compounds having 10 to 40 nuclear carbon atoms. More specific examples include naphthalene, perylene, pyrene, chrysene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, arylamine, styrylamine, and derivatives thereof.

Among them, styrylamine compounds and arylamine compounds are preferable in terms of high blue color purity, high efficiency, and long life.

As the styrylamine compound, those represented by the following formula (A) are preferable in that holes are efficiently captured in the light emitting layer.

(In Formula (A), Ar ² is a group selected from a biphenyl group, a terphenyl group, a stilbene group, and a distyrylaryl group, and Ar ³ and Ar ⁴ each independently represent a hydrogen atom or a carbon number of 6 And Ar ² , Ar ³ and Ar ⁴ may have a substituent, p is an integer of 1 to 4. Preferably, at least one of Ar ³ or Ar ⁴ is styryl. Substituted with a group.)

Here, examples of the aromatic group having 6 to 20 carbon atoms include aromatic hydrocarbon groups such as a phenyl group, a naphthyl group, an anthranyl group, a phenanthryl group, and a terphenyl group.

Further, as the arylamine compound, those represented by the following formula (B) are preferable in that holes are efficiently captured in the light emitting layer.

(In the formula (B), Ar ⁵ is a substituted or unsubstituted aryl group having 10 to 40 nuclear carbon atoms, and Ar ⁶ and Ar ⁷ are each independently substituted or unsubstituted nuclear carbon atoms having 5 to 40 carbon atoms. Q is an integer of 1 to 4.)

Here, examples of the aryl group having 10 to 40 nuclear carbon atoms of Ar ⁵ include a naphthyl group, anthranyl group, phenanthryl group, pyrenyl group, chrysenyl group, coronyl group, biphenyl group, terphenyl group, diphenylanthranyl group, Examples thereof include a carbazolyl group, a benzoquinolyl group, a fluoranthenyl group, an acenaphthofluoranthenyl group, and a stilbene group.

Examples of the aryl group having 5 to 40 nuclear carbon atoms of Ar ⁶ and Ar ⁷ include a phenyl group, a naphthyl group, an anthranyl group, a phenanthryl group, a pyrenyl group, a chrysenyl group, a coronyl group, a biphenyl group, and a terphenyl group. , Pyrrolyl group, furanyl group, thiophenyl group, benzothiophenyl group, oxadiazolyl group, diphenylanthranyl group, indolyl group, carbazolyl group, pyridyl group, benzoquinolyl group, fluoranthenyl group, acenaphthofluoranthenyl group, stilbene group, etc. Can be mentioned.

When these aryl groups have a substituent, preferred substituents are alkyl groups having 1 to 6 carbon atoms (ethyl group, methyl group, i-propyl group, n-propyl group, s-butyl group, t-butyl group). Group, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group, etc.), alkoxy group having 1 to 6 carbon atoms (ethoxy group, methoxy group, i-propoxy group, n-propoxy group, s-butoxy group, t-butoxy group) A pentoxy group, a hexyloxy group, a cyclopentoxy group, a cyclohexyloxy group, etc.), an aryl group having 5 to 40 nuclear atoms, an amino group substituted with an aryl group having 5 to 40 nuclear atoms, and 5 to 5 nuclear atoms Examples include an ester group having a 40 aryl group, an ester group having an alkyl group having 1 to 6 carbon atoms, a cyano group, a nitro group, and a halogen atom.

<Content in composition>
Only 1 type may be sufficient as the luminescent material contained in the composition for organic electroluminescent elements which concerns on this invention, and 2 or more types may be used together by arbitrary combinations and ratios.

The proportion of the luminescent material in the total solid content contained in the composition for organic electroluminescent elements according to the present invention is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 0.05% by weight or more, more preferably Is 0.5% by weight or more, particularly preferably 1% by weight or more, preferably 35% by weight or less, more preferably 25% by weight or less, and particularly preferably 15% by weight or less. If the luminescent material is at least the above lower limit, uneven light emission is unlikely to occur, and if it is at most the above upper limit, the luminous efficiency tends to be good. In addition, when using together 2 or more types of luminescent material, it is preferable that these total content is included in the said range.

{solvent}
The composition for organic electroluminescent elements according to the present invention contains a solvent. Here, the solvent in the present invention is a liquid in an atmosphere of 20 ° C. and 1 atm, and can dissolve the light emitting material and the charge transporting material contained in the composition for organic electroluminescent elements according to the present invention. A compound.

The solvent is not particularly limited as long as it is a commercially available polar or nonpolar solvent, but among them, a substituted or unsubstituted aromatic such as benzene, toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, dichlorobenzene and the like. Aromatic hydrocarbon solvents; aromatic ether solvents such as anisole, benzoic acid ester, diphenyl ether, aromatic ester solvents; linear or cyclic alkane solvents such as hexane, heptane, cyclohexane; carboxylic acid ester solvents such as ethyl acetate Solvents; carbonyl-containing solvents such as acetone and cyclohexanone; water; alcohols; cyclic ethers and the like are preferable. Of these, aromatic hydrocarbon solvents are more preferable, and benzene, toluene, mesitylene, and cyclohexylbenzene are particularly preferable.

In the composition for organic electroluminescent elements according to the present invention, one type of solvent may be contained, or two or more types of solvents may be contained in any combination. The solvent is preferably contained in a combination of 1 or more, preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less.

Further, when two or more solvents are used in combination, the mixing ratio is not limited at all, but the solvent having the largest mixing ratio is preferably 1% by weight or more, more preferably 5% in all the solvents. It should be at least 10% by weight, particularly preferably at least 10% by weight. The solvent having the largest mixing ratio is preferably 100% by weight or less, more preferably 90% by weight or less, and particularly preferably 80% by weight or less in the total solvent. The solvent having the smallest mixing ratio is preferably 0.0001% by weight or more, more preferably 0.001% by weight or more, and particularly preferably 0.01% by weight or more in the total solvent. The solvent having the smallest mixing ratio is preferably 50% by weight or less in the total solvent.

{Other ingredients}
The composition for an organic electroluminescent device according to the present invention includes a coating agent such as a leveling agent, an antifoaming agent, a thickener, a charge transporting aid such as an electron accepting compound and an electron donating compound, and a binder resin. Etc. may be contained. The content of these other components in the composition for organic electroluminescent elements is preferably 50% by weight or less from the viewpoint of charge transfer of the thin film, light emitting property of the light emitting material, film quality of the thin film, and the like.

{Solvent concentration / Solid concentration}
When the composition for organic electroluminescent elements according to the present invention is used as a composition for forming a light emitting layer for forming a light emitting layer of the organic electroluminescent element of the present invention described later, a solvent in the composition for organic electroluminescent elements. The content of is arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 30% by weight or more, more preferably 50% by weight or more, and preferably 99.9999% by weight or less. In addition, when mixing and using 2 or more types of solvents as a solvent, it is preferable to make it the sum total of these solvents satisfy | fill this range.

In addition, the total solid concentration of the light emitting material, charge transporting material, and the like of the composition for organic electroluminescent elements according to the present invention is preferably 0.01% by weight or more, and preferably 70% by weight or less. If this concentration is less than or equal to the above upper limit, film thickness unevenness is less likely to occur, and if it is greater than or equal to the above lower limit, defects are less likely to occur in the film.

[Light emitting layer]
The light-emitting layer according to the present invention is a composition for an organic electroluminescent device according to the present invention by mixing a charge transport material containing the charge transport material (1), a light-emitting material, a solvent, and other components used as necessary. And is formed by a wet film formation method using the same. The method of the wet film forming method is not limited as long as the effect of the present invention is not significantly impaired, and any method described later can be used.
Specifically, the light emitting layer according to the present invention is formed by applying the organic electroluminescent element composition according to the present invention on the film formation surface in the same manner as in the hole injection layer described later, It can be formed by drying and removing the solvent.

The temperature at which the composition for organic electroluminescent elements according to the present invention is applied 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.
Further, the relative humidity in the coating step is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 0.01 ppm or more, and preferably 80% or less.

After coating, the organic electroluminescent element composition film 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 lower than the glass transition temperature of the charge transport material or luminescent material used in the composition for organic electroluminescent elements, unless the effects of the present invention are significantly impaired. Moreover, when two or more types of charge transport materials or luminescent materials used in the composition for organic electroluminescent elements are contained, at least one type is heated at a temperature lower than the glass transition temperature of the charge transport material or luminescent material. Is preferred.

In the heating step, the heating time is not limited, but is preferably 10 seconds or longer and usually 180 minutes or shorter. If the heating time is short, the luminous efficiency is excellent, and if it is long, the formed thin film tends to be homogeneous. Heating may be performed in two steps.

The thickness of the light emitting layer according to the present invention is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 3 nm or more, more preferably 5 nm or more, and preferably 200 nm or less, more preferably 100 nm or less. is there. If the thickness of the organic thin film is not less than the above lower limit, the film is less likely to be defective, and if it is not more than the above upper limit, the driving voltage tends to be low.

[Organic electroluminescence device]
The organic electroluminescent device of the present invention has a light emitting layer between an anode and a cathode, and this light emitting layer is formed by a wet film forming method using the above-mentioned composition for organic electroluminescent device according to the present invention. It is characterized by being a layer.

Moreover, the organic electroluminescent element of the present invention preferably has a first organic layer between the light emitting layer and the anode, and the first organic layer is preferably a layer formed by a wet film formation method, The first organic layer is preferably a layer formed by crosslinking a crosslinkable compound.

Furthermore, it is preferable to have a second organic layer containing an electron-accepting compound between the first organic layer and the anode, and this second organic layer is also a layer formed by a wet film formation method. Preferably there is.

The reason why the first organic layer and the second organic layer are preferably formed by a wet film forming method is as follows.

In the case of an element in which the organic layer existing between the anode and the light-emitting layer, in particular, the first organic layer and the second organic layer are formed by a wet film formation method, compared to an element formed by a vapor deposition method, Since these mixed layers are formed at the interface between the first organic layer and the second organic layer, the amount of holes injected and transported from the anode to the second organic layer to the first organic layer is deposited. Compared to devices formed by the method. At the same time, the amount of electrons injected and transported from the light emitting layer to the first organic layer to the second organic layer is large.

In the case of an element manufactured using the charge transport material (1) satisfying the formula (1), the injected holes and electrons are efficiently recombined in the light emitting layer, and the holes and electrons that do not contribute to the recombination are generated. The ratio of leakage to the adjacent hole blocking layer and the first organic layer is suppressed. For example, electrons that are not consumed in the light emitting layer and leak to the first organic layer easily reach the second organic layer by the mixed layer formed at the interface between the first organic layer and the second organic layer. The hole transporting compound and the electron accepting compound forming the second organic layer are reduced and deteriorated. As mentioned above, when the organic layer which has between an anode and a light emitting layer is formed by the wet film-forming method, the effect by using a charge transport material (1) is high.

In the present invention, the wet film forming method is a film forming method, that is, a coating method, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method. A method of forming a film by drying a coated film using a wet film forming method such as a capillary coating method, an ink jet method, a nozzle printing method, a screen printing method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, an ink jet method, and a nozzle printing method are preferable. This is a composition for organic electroluminescence device according to the present invention used as a coating composition in a wet film-forming method, a first organic layer forming composition, and a second organic layer forming composition described later. This is in order to meet the liquidity peculiar to

{First organic layer}
The 1st organic layer in this invention is an organic layer which exists between an anode and a light emitting layer in the organic electroluminescent element of this invention. When two or more layers are included between the anode and the light emitting layer, the layer adjacent to the light emitting layer on the anode side of the light emitting layer is defined as the first organic layer.
The first organic layer is preferably a layer containing a hole transporting compound. The first organic layer is preferably a layer formed by crosslinking a crosslinkable compound.

<Hole transporting compound>
The hole transporting compound may be a monomer (a compound having a single molecular weight) or an oligomer (a low molecular weight polymer compound having a repeating unit), or a polymer (a high molecular weight polymer compound having a repeating unit). ). The hole transporting compound is preferably a polymer compound having a repeating unit such as an oligomer or a polymer because it is excellent in film formability or heat resistance.

(Molecular weight)
When the hole transporting compound is a monomer, the molecular weight is preferably 5000 or less, more preferably 2500 or less, and preferably 300 or more, more preferably 500 or more. If the molecular weight is less than or equal to this upper limit, the impurities are hardly increased in molecular weight and purification is easy. Further, when the molecular weight is equal to or more than this lower limit, the heat resistance is hardly lowered due to a decrease in glass transition temperature, melting point, vaporization temperature and the like.

When the hole transporting compound is an oligomer or a polymer, its weight average molecular weight is preferably 3,000,000 or less, more preferably 1,000,000 or less, particularly preferably 500,000 or less, Preferably it is 1,000 or more, More preferably, it is 2,500 or more, Most preferably, it is 5,000 or more. If the molecular weight is lower than this upper limit, the impurities are hardly increased in molecular weight and purification is easy, and if the molecular weight is higher than this lower limit, the film formability is excellent and the glass transition temperature, melting point and vaporization temperature are lowered. Deterioration of heat resistance due to is difficult to occur.

When the hole transporting compound is an oligomer or a polymer, its dispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is preferably 3.0 or less, more preferably 2.5 or less, Particularly preferably, it is 2.0 or less, preferably 1.0 or more, more preferably 1.1 or more, and particularly preferably 1.2 or more. When the dispersity is less than or equal to this upper limit, purification is easy, and solvent solubility and film formability tend to be good.

The weight average molecular weight and the number average molecular weight in the present invention are determined by SEC (size exclusion chromatography) measurement. In SEC measurement, the elution time is shorter for higher molecular weight components and the elution time is longer for lower molecular weight components, but using the calibration curve calculated from the elution time of polystyrene (standard sample) with a known molecular weight, the elution time of the sample is changed to the molecular weight. By converting, the weight average molecular weight and the number average molecular weight are calculated.

(Construction)
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.

Examples of the material for the first organic layer include hole transporting compounds conventionally used for the hole injection layer of the organic electroluminescence device. 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.

In addition, 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.

Among these, the polyarylamine derivative is preferably a polymer compound containing a repeating unit represented by the following formula (II). In particular, the polymer compound is preferably 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 the formula (II), Ar ^A and Ar ^B each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)

Examples of the aromatic hydrocarbon group optionally having a substituent of Ar ^A and Ar ^B include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene A group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, a fluorene ring, or a group in which these 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 2-4 fused ring group derived from and these rings include a group formed by connecting a direct bond or two or more rings.

From the viewpoint 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 group, and an aromatic heterocyclic group.

In addition, as the polyarylene derivative, arylene groups such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, exemplified as Ar ^A and Ar ^B in the formula (II), are repeated. Examples thereof include a polymer compound contained in a unit.

As the polyarylene derivative, a polymer compound having a repeating unit consisting of at least one of the following formulas (III-1) and (III-2) is particularly preferable.

(In the 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 the formula (III-2), R ^e and R ^f are independently the same as R ^a , R ^b , R ^c or R ^d in the formula (III-1). Independently 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 include an oxygen atom, a boron atom which may have a substituent, a nitrogen atom which may have a substituent, a silicon atom which may have a substituent, and a substituent. A phosphorus atom which may be substituted, a sulfur atom which may have a substituent, a carbon atom which may have a substituent, or a group formed by bonding these.

The polyarylene derivative includes a repeating unit represented by the following formula (III-3) in addition to the repeating unit consisting of at least one of the above formula (III-1) and the following formula (III-2). It is preferable to have.

(In the formula (III-3), Ar ^g to Ar ^m 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 ^g to Ar ^m 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 Japanese Patent Application Laid-Open No. 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.

Furthermore, when the hole transporting compound in the present invention is a polymer, it is preferably a polymer containing a repeating unit represented by the following formula (5).

(In the formula (5), m represents an integer of 0 to 3, and Ar ¹¹ and Ar ¹² are each independently an aromatic hydrocarbon group or substituent which may have a direct bond or a substituent. Each of Ar ¹³ to Ar ¹⁵ may independently have an aromatic hydrocarbon group which may have a substituent or a substituent. Represents an aromatic heterocyclic group, provided that neither Ar ¹¹ nor Ar ¹² is a direct bond.)

Examples of the aromatic hydrocarbon group optionally having a substituent of Ar ¹¹ to Ar ¹⁵ include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene And groups derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, and a fluorene ring.

Examples of the aromatic heterocyclic group optionally having a substituent of Ar ¹¹ to Ar ¹⁵ include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, and an oxadiazole ring. , Indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole 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, azure Lysine ring, phenanthroline ring, and the like phenazine ring, and a single ring or 2 to 4 groups derived from fused ring of 5 or 6-membered ring.

Ar ¹¹ to Ar ¹⁵ are each independently a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a thiophene ring, a pyridine ring, and a fluorene ring from the viewpoint of solubility in a solvent and heat resistance. A ring-derived group selected from the group consisting of

Ar ¹¹ , Ar ¹² , and Ar ¹⁴ are also preferably a divalent group in which one or two or more rings selected from the above group are directly bonded or connected by a —CH═CH— group. A terphenylene group is more preferable.

The substituent that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ¹¹ to Ar ¹⁵ may have in addition to the crosslinkable group described later is not particularly limited. For example, the following <substituent group Z 1 type or 2 types or more selected from>.

<Substituent group Z>
An alkyl group having preferably 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methyl group or an ethyl group;
An alkenyl group having preferably 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a vinyl group;
An alkynyl group having preferably 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as an ethynyl group;
An alkoxy group having preferably 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methoxy group or an ethoxy group;
An aryloxy group having preferably 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms, such as a phenoxy group, a naphthoxy group, and a pyridyloxy group;
An alkoxycarbonyl group having preferably 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a methoxycarbonyl group and an ethoxycarbonyl group;
A dialkylamino group having preferably 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a dimethylamino group and a diethylamino group;
A diarylamino group having preferably 10 to 36 carbon atoms, more preferably 12 to 24 carbon atoms, such as a diphenylamino group, a ditolylamino group, or an N-carbazolyl group;
An arylalkylamino group having preferably 6 to 36 carbon atoms, more preferably 7 to 24 carbon atoms, such as a phenylmethylamino group;
An acyl group having preferably 2 to 24 carbon atoms, preferably 2 to 12 carbon atoms, such as an acetyl group or a benzoyl group;
Halogen atoms such as fluorine atoms and chlorine atoms;
A haloalkyl group having preferably 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group;
An alkylthio group having preferably 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methylthio group and an ethylthio group;
A phenylthio group, a naphthylthio group, a pyridylthio group and the like, preferably an arylthio group having 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms;
A silyl group having preferably 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsilyl group or a triphenylsilyl group;
A siloxy group having preferably 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsiloxy group and a triphenylsiloxy group;
A cyano group;
An aromatic hydrocarbon group having preferably 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms, such as a phenyl group and a naphthyl group;
An aromatic heterocyclic group having preferably 3 to 36 carbon atoms, more preferably 4 to 24 carbon atoms, such as thienyl group and pyridyl group

Each of the above substituents may further have a substituent, and examples thereof include the groups exemplified in the above <Substituent group Z>.

The molecular weight of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ¹¹ to Ar ¹⁵ may have in addition to the crosslinkable group described later is preferably 500 or less, including the substituted group, The following is more preferable.

From the viewpoint of solubility in a solvent, the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ¹¹ to Ar ¹⁵ may each independently have an alkyl group having 1 to 12 carbon atoms and An alkoxy group having 1 to 12 carbon atoms is preferred.

In addition, when m is 2 or more, the repeating unit represented by the formula (5) has two or more Ar ¹⁴ and Ar ¹⁵ . In that case, Ar ¹⁴ and Ar ¹⁵ may be the same or different. Further, Ar ¹⁴ and Ar ¹⁵ may be bonded to each other directly or via a linking group to form a cyclic structure.

The substituent that Ar ¹¹ to Ar ¹⁵ may have may be a crosslinkable group described later.
M in the formula (5) represents an integer of 0 or more and 3 or less, and m is preferably 0 in terms of enhancing the solubility in an organic solvent and the film formability. Further, p is preferably 1 or more and 3 or less from the viewpoint of improving the hole transport ability of the polymer.

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

<Crosslinkable compound>
The first organic layer is preferably a layer formed by crosslinking a crosslinkable compound, and in particular, the above hole transporting compound is a crosslinkable compound having a crosslinkable group. Or it is preferable at the point which can make a big difference in the solubility with respect to a solvent before and after the reaction (crosslinking reaction) which arises by irradiation of an active energy ray.

Here, the crosslinkable group means a group that reacts with the same or different group of another molecule located in the vicinity 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 following <crosslinkable group group T> in terms of easy crosslinking.

<Crosslinkable group T>

(Wherein R ¹ to R ⁵ each independently represents a hydrogen atom or an alkyl group. Ar ³¹ may have an optionally substituted aromatic hydrocarbon group or substituent. Represents an aromatic heterocyclic group.)

As the crosslinkable group, a group that undergoes a crosslinking reaction by cationic polymerization such as a cyclic ether group such as an epoxy group or an oxetane group, or a vinyl ether group is preferable in terms of high reactivity and easy crosslinking. 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.
In addition, as the crosslinkable group, a group that does not contain an ether bond is preferable because the conjugation of the charge transport unit becomes long and the mobility of the charge transport material is high. A group that undergoes a cycloaddition reaction, such as the above group, is preferred from the viewpoint of further improving the electrochemical stability.
Of the crosslinkable groups, a group derived from a benzocyclobutene ring is particularly preferable because the structure after crosslinking 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. A divalent group formed by individual linking is exemplified.

The crosslinkable compound may be any of a monomer, an oligomer, and a polymer, but is preferably a polymer in terms of excellent film formability. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

As the crosslinkable compound, it is preferable to use a hole transporting compound having a crosslinkable group as described above. Examples of the hole transporting compound include those exemplified above, and those having a crosslinkable group as described above bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer compound containing a repeating unit having a crosslinkable group, and the formula (II), the formulas (III-1) to (III-3), and the formula A polymer compound having a repeating unit in which the crosslinkable group is bonded directly or via a linking group to (5) is preferable.

In particular, in the case of a hole transporting compound having a crosslinkable group in the repeating unit represented by the formula (5), it may be a crosslinkable polymer having a repeating unit represented by the following formula (5 ′). preferable.

(In the formula (5 ′), n represents an integer of 0 to 3, and Ar ²¹ and Ar ²² are each independently a direct bond, an aromatic hydrocarbon group which may have a substituent, or a substituent. Each of Ar ²³ to Ar ²⁵ may independently have an aromatic hydrocarbon group which may have a substituent or a substituent. Represents an aromatic heterocyclic group, and T represents a group containing a crosslinkable group, provided that neither Ar ²¹ nor Ar ²² is a direct bond.

Specific examples of the aromatic hydrocarbon group which may have a substituent in Ar ²¹ to Ar ²⁵ and the aromatic heterocyclic group which may have a substituent include Ar ¹¹ to Ar ¹¹ in the formula (5). This is the same as the specific examples of the aromatic hydrocarbon group which may have a substituent of Ar ^{15 and} the aromatic heterocyclic group which may have a substituent. Moreover, a preferable example is also the same. Furthermore, the substituent which may have is the same.
The n is the same as m in the formula (5), and the preferred value is also the same.

<Specific example>
Specific examples of the hole transporting compound suitable as the hole transporting compound contained in the first organic layer are shown below, but the present invention is not limited thereto.

<Other ingredients>
The first organic layer may contain other components other than the hole transporting compound as long as the effects of the present invention are not impaired. Examples of other components include various electron-accepting compounds, luminescent materials, additives that promote a crosslinking reaction, binder resins, leveling agents, coating properties improving agents such as antifoaming agents, and the like. 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.
When the organic layer between the anode and the light emitting layer is a single layer, that is, only the first organic layer, the first organic layer preferably contains an electron-accepting compound described later.

<First organic layer forming composition>
When forming the first organic layer by a wet film-forming method, the hole-transporting compound constituting the first organic layer and, if necessary, the above-mentioned other components are mixed with an appropriate solvent for film formation. A composition (first organic layer forming composition) is prepared and used.

The content of the hole transporting compound in the first organic layer forming composition is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 50% by weight or less, more preferably 20% by weight or less. In addition, 2 or more types of hole transportable compounds may be contained in the 1st composition for organic layer formation, In that case, it is preferable that the sum total of 2 or more types becomes said range. When the content of the hole transporting compound is equal to or higher than the above lower limit, defects are hardly generated in the formed first organic layer, and when the content is equal to or lower than the above upper limit, film thickness unevenness is hardly generated.

The solvent contained in the first organic layer forming composition is not particularly limited, but the hole transporting compound is preferably 0.1% by weight or more, more preferably 0.5% by weight. As described above, a solvent capable of dissolving 1.0% by weight or more is particularly preferable.

The boiling point of this solvent is preferably 110 ° C. or higher, more preferably 140 ° C. or higher, particularly preferably 200 ° C. or higher, preferably 400 ° C. or lower, more preferably 300 ° C. or lower. When the boiling point of the solvent is not less than the above lower limit, the drying rate is not too fast and the film quality tends to be good. Moreover, since the temperature of a drying process may be low temperature as the boiling point of a solvent is below the said upper limit, possibility that it will have a bad influence on another layer or a board | substrate is low.

Specific examples of the solvent include aromatic compounds such as toluene, xylene, methicylene, cyclohexylbenzene; halogen-containing solvents such as 1,2-dichloroethane, chlorobenzene, o-dichlorobenzene; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol -1-monomethyl ether acetate (PGMEA) and other aliphatic ethers, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2 Ether solvents such as aromatic ethers such as 1,3-dimethylanisole and 2,4-dimethylanisole; aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate and n-butyl lactate; phenyl acetate, Phenyl propionate, methyl benzoate, ethyl benzoate, isopropyl benzoate, propyl benzoate, organic solvents such as ester solvents such as benzoic acid n- butyl. These may be used alone or in combination of two or more.

<Film formation method>
The first organic layer is preferably formed on the substrate or other layers by the wet film formation method using the first organic layer forming composition described above.
That is, the first composition for forming an organic layer is prepared, and this composition is formed into a wet film on a substrate or other layer, and the film after film formation is subjected to heat drying or reduced pressure as necessary. The solvent is removed by drying or the like.

When the hole transporting compound is a compound having a crosslinkable group, the crosslinkable compound undergoes a crosslinking reaction by heating and / or irradiation with active energy rays after film formation, whereby a cured film is obtained.

When this crosslinking reaction is by heating, the heating method is not particularly limited, but the heating condition is preferably 120 ° C. or higher, more preferably 400 ° C. or lower. Further, the heating time is preferably 1 minute or longer, more preferably 24 hours or shorter.

Further, 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 cross-linking reaction is based on irradiation with active energy rays, a method of direct irradiation using an ultraviolet, visible or 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 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. The irradiation time is preferably set to conditions necessary for reducing the solubility of the film, but is preferably 0.1 seconds or longer, and more preferably 10 hours or shorter.

Heating and / or irradiation with active energy rays may be performed alone or in combination. When combined, the order of implementation is not particularly limited.

In order to reduce the amount of moisture contained in the film and / or the amount of moisture adsorbed on the surface of the film after the heating and / or irradiation with active energy rays, the heating and / or irradiation with active energy rays is performed in an atmosphere not containing moisture such as a nitrogen gas atmosphere. preferable. In the case where heating and / or irradiation with active energy rays are performed in combination for the same purpose, it is particularly preferable to perform at least the step immediately before film formation in an atmosphere containing no moisture such as a nitrogen gas atmosphere.

<Film thickness>
The film thickness of the first organic layer is preferably 3 nm or more, more preferably 5 nm or more, particularly preferably 10 nm or more, preferably 100 nm or less, more preferably 80 nm or less, and particularly preferably 50 nm or less. When the film thickness is equal to or greater than the above lower limit, the ratio of electrons leaking from the first organic layer is small, and the element is formed by degrading the hole transporting compound and the electron accepting compound that form the second organic layer. Is less likely to affect the drive life of On the other hand, if it is below the above upper limit, the drive voltage tends to be low.
The first organic layer may be composed of a single layer, or may be composed of a plurality of layers stacked. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.

{Second organic layer}
The organic electroluminescent element of the present invention preferably has a second organic layer between the anode and the first organic layer. The second organic layer is preferably a layer containing a hole transporting compound and an electron accepting compound.

<Hole transporting compound>
As the hole transporting compound for forming the second organic layer, the compound having the crosslinkable group may be used as the hole transporting compound. In this case, as the hole transporting compound, a low molecular compound or a polymer compound may be used as long as it has a hole transporting ability. The crosslinkable group is preferably a group that does not contain an ether bond from the viewpoint that the conjugation of the charge transport unit becomes long and the mobility of the charge transport material becomes high.

The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV or more and 6.0 eV or less from the viewpoint of a charge injection barrier from the anode to the second organic layer. From this point of view, examples of hole transporting compounds include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazone compounds, Examples include silazane compounds, silanamine derivatives, phosphamine derivatives, quinacridone compounds, and phthalocyanine derivatives.

Of these, aromatic amine compounds are preferred as the hole transporting compound, and aromatic tertiary amine compounds are more preferred from the viewpoint of amorphousness and visible light transmittance. 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 kind 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 polymer in which repeating units are linked) is more preferable.

Preferred examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (IV).

(In the formula (IV), Ar ³⁵ and Ar ³⁶ each independently represent an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. Ar ³⁷ to Ar ³⁹ each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. Z represents a linking group selected from the following group of linking groups, and among Ar ³⁵ to Ar ³⁹ , two groups bonded to the same N atom are bonded to each other to form a ring. May be.)

(In the above formulas, Ar ⁴⁰ to Ar ⁴⁴ and Ar ⁴⁶ to Ar ⁴⁹ are each independently an aromatic hydrocarbon group which may have a substituent, or an aromatic which may have a substituent. Ar ⁴⁵ and Ar ⁵⁰ each independently represents an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. R ¹⁰ and R ¹¹ each independently represents a hydrogen atom or an arbitrary substituent.)

Ar ³⁵ to Ar ⁵⁰ each independently represents an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. These may be the same or different from each other. Moreover, these groups may further have a substituent. The molecular weight of the substituent is usually 400 or less, and preferably 250 or less.

Ar ³⁵ and Ar ³⁶ are each independently a benzene ring, naphthalene ring, phenanthrene ring, thiophene ring, pyridine, from the viewpoint of the solubility, heat resistance, and hole injection / transport properties of the aromatic tertiary amine polymer compound. A group derived from a ring is preferable, and a phenyl group (a group derived from a benzene ring) and a naphthyl group (a group derived from a naphthalene ring) are more preferable.

Ar ³⁷ to Ar ³⁹ are each preferably a group derived from a benzene ring, a naphthalene ring, a triphenylene ring, or a phenanthrene ring, from the viewpoint of heat resistance and hole injection / transport properties including a redox potential, A phenylene group (a group derived from a benzene ring), a biphenylene group (a group derived from a benzene ring), and a naphthylene group (a group derived from a naphthalene ring) are more preferable.

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (IV) include those described in International Publication No. 2005/089024 pamphlet.

In addition, the hole transporting compound may contain any one kind, and may contain two or more kinds. 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.

<Electron-accepting compound>
The second organic layer preferably contains an 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 having an electron affinity of 4 eV or more is preferable, and a compound of 5 eV or more is more preferable.

Examples of the electron-accepting compound include a triaryl boron compound, a metal halide, a Lewis acid, an organic acid, an onium salt, a salt of an arylamine and a metal halide, and a salt of an arylamine and a Lewis acid. 1 type, or 2 or more types of compounds etc. chosen from are mentioned. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (WO 2005/089024 pamphlet) Iron (III) chloride (Japanese Unexamined Patent Publication No. 11-251067), high-valent inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Unexamined Patent Publication) 2003-31365)) and the like; fullerene derivatives; iodine and the like. Since these electron-accepting compounds oxidize the hole-transporting compound, the conductivity of the second organic layer can be improved.

Among the above-mentioned compounds, onium salts substituted with organic groups, high-valence inorganic compounds, and the like are preferable because they have strong oxidizing power. In addition, an onium salt substituted with an organic group, a cyano compound, an aromatic boron compound, or the like is preferable because it is highly soluble in various solvents and can be applied to form a film by a wet film formation method.

Specific examples of onium salts substituted with organic groups, cyano compounds, and aromatic boron compounds suitable as electron-accepting compounds include those described in WO 2005/089024, and preferred examples thereof are also the same. is there. Examples thereof include compounds represented by the following structural formulas, but are not limited thereto.

In addition, an electron-accepting compound may be used individually by 1 type, and 2 or more types may be used for it in arbitrary combinations and ratios.

The ratio of the electron-accepting compound to the hole-transporting compound is preferably 0.1 mol% or more, more preferably 1 mol% or more, and preferably 100 mol% or less, more preferably 40 mol% or less. Used in

<Other ingredients>
The second organic layer may contain other components other than the hole transporting compound and the electron accepting compound as long as the effects of the present invention are not impaired. Examples of other components include various light-emitting materials, electron transport compounds, additives that promote a crosslinking reaction, binder resins, leveling agents, coating properties improving agents such as antifoaming agents, and the like. 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.

<Second organic layer forming composition>
When the second organic layer is formed by a wet film formation method, the hole transporting compound, electron accepting compound, and other components described above, if necessary, are mixed with an appropriate solvent. Then, a film forming composition (second organic layer forming composition) is prepared and used.

The concentration of the hole transporting compound in the second composition for forming an organic layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 0.01% by weight in terms of film thickness uniformity. More preferably, it is 0.1% by weight or more, particularly preferably 0.5% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less, and particularly preferably 50% by weight or less. If the concentration is too low, defects may occur in the formed second organic layer, and if the concentration is too high, film thickness unevenness may occur. In addition, 2 or more types of hole transportable compounds may be contained in the 2nd composition for organic layer formation, In that case, it is preferable that the sum total of 2 or more types becomes said range.

In addition, the content of the electron-accepting compound with respect to the hole-transporting compound is preferably 0.1 mol% or more, more preferably 1 mol% or more. However, it is preferably 100 mol% or less, more preferably 40 mol% or less, and the content of the electron-accepting compound in the second organic layer forming composition is preferably 0.01 wt% or more, more preferably Is 0.05% by weight or more, preferably 20% by weight or less, more preferably 10% by weight or less. In addition, 2 or more types of electron-accepting compounds may be contained in the 2nd composition for organic layer formation, In that case, it is preferable that the sum total of 2 or more types becomes said range.

The solvent contained in the second organic layer forming composition is not particularly limited, but at least one of the solvents contained in the second organic layer forming composition is a second organic layer. A solvent capable of dissolving the material of the layer is preferred.

The boiling point of the solvent is preferably 110 ° C. or higher, more preferably 140 ° C. or higher, particularly preferably 200 ° C. or higher, preferably 400 ° C. or lower, more preferably 300 ° C. or lower. When it is at least the above lower limit of the solvent, the drying speed of the formed film is slow, and the film quality tends to be good. Moreover, since the temperature of a drying process may be low as the boiling point of a solvent is below the said upper limit, possibility that it will have a bad influence on another layer and a board | substrate (for example, glass substrate) is low.

Examples of solvents include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like. Specifically, examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3 -Aromatic ethers such as dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole and the like. Examples of ester solvents include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Further, aromatic hydrocarbon solvents include, for example, toluene, xylene, cyclohexylbenzene, 3-iropropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, methylnaphthalene. Etc. Examples of the amide solvent include N, N-dimethylformamide and N, N-dimethylacetamide. In addition, dimethyl sulfoxide or the like can also be used as a solvent.

Among the solvents described above, a solvent having high ability to dissolve the material of the second organic layer (dissolution ability) or high affinity with the material is preferable. This is because the concentration of the second organic layer forming composition can be arbitrarily set to prepare a composition having a concentration excellent in the efficiency of the film forming process.

Note that one type of solvent may be used, or two or more types of solvents may be used in any combination and in any ratio.

<Film formation method>
The second organic layer is preferably formed by a wet film formation method using the above-described second organic layer forming composition. That is, the second organic layer-forming composition is applied on a layer (usually an anode) corresponding to the lower layer of the second organic layer and dried to form the second organic layer.

After the application, it is usually dried by heating or the like. The heating means used in the heating step is not limited as long as the effects of the present invention are not significantly impaired. Examples of the heating means include a clean oven, a hot plate, infrared rays, a halogen heater, and microwave irradiation. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.
When the hole transporting compound is a crosslinkable compound, the method for forming the second organic layer is the same as that described in the section {First organic layer} <film forming method>. The preferred embodiment is also the same.

In addition, when forming a 2nd organic layer by a vacuum evaporation method, first, 1 type or 2 types or more of materials (a hole transportable compound, an electron-accepting compound, etc.) are put into the crucible installed in the vacuum vessel. Put it in each crucible if two or more materials are used, and evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump. Then, the crucible is heated (each crucible is heated when two or more materials are used), and the evaporation amount is controlled to evaporate (when two or more materials are used, the evaporation amount is controlled independently). Evaporate) to form a second organic layer on the anode of the substrate placed facing the crucible. In addition, when using 2 or more types of materials, they can also be put into a crucible, can be heated and evaporated, and can be used for formation of a 2nd organic layer.

<Film thickness>
The thickness of the second organic layer is preferably in the range of 5 nm or more, more preferably 10 nm or more, and preferably 1000 nm or less, more preferably 500 nm or less. When the film thickness is not less than the above lower limit, the hole injection ability is excellent, and when it is not more than the above upper limit, the resistance tends to be low.
The second organic layer may be composed of a single layer, or may be composed of a plurality of layers. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.

{Configuration of organic electroluminescence device}
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 of 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, The 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.
In the case of the element shown in FIG. 1, the hole transport layer 4 corresponds to the first organic layer, and the hole injection layer 3 corresponds to the second organic layer. Each of the layers described below is formed by selecting a material that satisfies the above-described conditions as the conditions of the second organic layer, the first organic layer, and the light emitting layer, to which these correspond.

<Board>
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, and polyaniline.

The anode 2 is usually 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 1. Further, 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 subjected to ultraviolet (UV) / ozone treatment, oxygen plasma treatment, argon plasma treatment, etc. 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 hole injection layer can be formed by using the material and the film forming method described in {Second organic layer}. The same applies to preferred embodiments of the material and the film formation method.

<Hole transport layer>
The hole transport layer 4 is provided on the hole injection layer 3. The hole transport layer 4 can be formed by the material and the film forming method described in the above {first organic layer}. The same applies to preferred embodiments of the material and the film formation method.

<Light emitting layer>
When the hole injection layer 3 or the hole transport layer 4 is provided, the light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between electrodes to which an electric field is applied, and becomes a main light emitting source.
In this invention, the light emitting layer 5 is formed using the composition for organic electroluminescent elements which concerns on this invention containing the above-mentioned charge transport material (1), a luminescent material, and a solvent.

<Hole blocking layer>
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have

The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high. Examples of the hole blocking layer material satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Mixed ligand complexes of, such as metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyryl biphenyl derivatives, etc. Triazole derivatives such as styryl compounds (Japanese Patent Laid-Open No. 11-242996), 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (Japan) Japanese Patent Laid-Open No. 7-41759), phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297) Broadcast), and the like. Further, 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 the material of the hole blocking layer 6.
In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

There is no limitation on the formation method of the hole blocking layer 6. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

The film thickness of the hole blocking layer 6 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 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, oxadi Azole 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 Compound (Japanese Unexamined Patent Publication No. 6-207169), phenanthroline derivative (Japanese Unexamined Patent Publication No. 5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthraquinone diimine, n-type hydrogen Amorphous silicon carbide, n-type Examples thereof include zinc sulfide and n-type zinc selenide.

In addition, only 1 type may be used for the material of the electron carrying layer 7, and 2 or more types may be used together by arbitrary combinations and a ratio.

There is no limitation on the method of forming the electron transport layer 7. 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 ( Described in Japanese Laid-Open Patent Publication No. 10-270171, Japanese Laid-Open Patent Publication No. 2002-1000047, Japanese Laid-Open Patent Publication No. 2002-1000048, and the like, thereby improving electron injection / transport properties and achieving excellent film quality. It is preferable because it becomes possible. The film thickness in this case is preferably 5 nm or more, more preferably 10 nm or more, and preferably 200 nm or less, particularly preferably 100 nm or less.

In addition, only 1 type may be used for the material of the electron injection layer 8, and 2 or more types may be used together by arbitrary combinations and a ratio.

There is no limitation on the method of forming the electron injection layer 8. 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, a metal having a low work function is preferable for efficient electron injection. 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, only 1 type may be used for the material of the cathode 9, and 2 or more types may be used together by arbitrary combinations and a ratio.

The film thickness of the cathode 9 is usually the same as that of the anode 2.

Furthermore, 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. .

Examples of the layer that may be included in addition to the layers described above include an electron blocking layer.
The electron blocking layer is provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5 and prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3. Thus, the probability of recombination of holes and electrons in the light emitting layer 5 is increased, the excitons generated are confined in the light emitting layer 5, and the holes injected from the hole injection layer 3 are efficiently collected. There is a role to transport in the direction of. 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 5 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 ratios.

There is no limitation on the method of forming the electron blocking layer. Accordingly, the film can be formed by a wet film formation method, a vapor deposition method, or other methods, but from the viewpoint of charge balance, the wet film formation method is preferable in the present invention.

Further, at the interface between the cathode 9 and the light emitting layer 5 or the electron transport layer 7, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ). It is also an effective method to improve the efficiency of the element by inserting an ultra-thin insulating film (0.1 to 5 nm) formed by the above (Applied Physics Letters, 1997, Vol. 70, pp. 152; Japan) (See Japanese Patent Laid-Open No. 10-74586; IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154).

Also, in the layer configuration described above, it is possible to stack components other than the substrate in the reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate 1 are the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, the positive layer. The hole injection layer 3 and the anode 2 may be provided in this order.

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.

In addition, 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) (in the case where 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.

In addition, each layer described above may contain components other than those described as materials as long as the effects of the present invention are not significantly impaired.

[Organic EL display device and organic EL lighting]
The organic EL display device (organic EL display) and the organic EL illumination of the present invention use the organic electroluminescent element of the present invention as described above. There is no restriction | limiting in particular about the type and structure of the organic electroluminescent display of this invention, and organic electroluminescent illumination, 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.

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless it exceeds the gist.

[Example 1]
The organic electroluminescent element shown in FIG. 1 was manufactured.
On the glass substrate 1, an indium tin oxide (ITO) transparent conductive film with a thickness of 150 nm (sputtered film, sheet resistance 15Ω) is patterned into a 2 mm wide stripe by a normal photolithography technique, and the anode 2 Formed. The substrate 1 on which the anode 2 was formed was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning and the like.

A hole injection layer 3 was formed on the substrate after the treatment as follows.
As a hole injection material, an aromatic amine polymer compound PB-1 having a repeating structure shown below (weight average molecular weight: 52000, number average molecular weight: 32500), an electron accepting compound PI-1 having a structure shown below and a solvent A hole injection layer forming composition (second organic layer forming composition) containing ethyl benzoate was prepared. In the composition for forming the hole injection layer, the total concentration of the aromatic amine polymer compound PB-1 and the electron accepting compound PI-1 is 2% by weight, and the aromatic amine polymer compound PB-1 And the weight ratio of the electron-accepting compound PI-1 was (aromatic amine polymer compound PB-1) :( electron-accepting compound PI-1) = 10: 2.

The composition for forming a hole injection layer was spin-coated on the substrate after the above treatment at a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Then, it heat-dried at 230 degreeC for 60 minutes. The thin film of the uniform hole injection layer 3 with a film thickness of 30 nm was formed by the above operation.

Next, a hole transport layer 4 was formed on the formed hole injection layer 3 as follows.
Polymer composition HT-1 having a repeating structure shown below (weight average molecular weight: 60000, number average molecular weight: 33000) and a composition for forming a hole transport layer containing cyclohexylbenzene as a solvent (first organic layer forming composition) Prepared). The concentration of the polymer compound HT-1 in the composition for forming a hole transport layer was 1.4% by weight.

The composition for forming a hole transport layer was spin-coated on the hole injection layer 3 at a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Thereafter, the polymer compound was heated at 230 ° C. for 60 minutes to crosslink and cure the polymer compound. By the above operation, a uniform thin film of the hole transport layer 4 having a film thickness of 20 nm was formed.

Next, a light emitting layer was formed on the formed hole transport layer 4 as follows. For the formation of the light emitting layer, the composition for organic electroluminescent elements of the present invention was used. The compound D-1 having the structure shown below is used as the light emitting material (dopant material), the compound E-1 having the structure shown below is used as the charge transport material (host material), and cyclohexylbenzene is used as the solvent. It was.
The total concentration of Compound D-1 and Compound E-1 in the composition for organic electroluminescence device was 3.2% by weight. The weight ratio of Compound D-1 and Compound E-1 was (Compound D-1) :( Compound E-1) = 1: 10.

Compound E-1 has an electron mobility μe of 1.7 × 10 ⁻³ cm ² / V · s and a hole mobility μh of 2.1 × 10 ⁻³ cm ² / V at an electric field strength of 0.16 MV / cm. V · s, and μe / μh was 0.81.

The composition for organic electroluminescence device was spin-coated on the hole transport layer 4 with a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Thereafter, it was dried by heating at 130 ° C. for 60 minutes. The thin film of the uniform light emitting layer 5 with a film thickness of 40 nm was formed by the above operation.

Next, a compound HB-1 shown below was formed as a hole blocking layer 6 on the formed light emitting layer 5 by a vacuum deposition method so as to have a film thickness of 10 nm.

Next, the following compound ET-1 as an electron transport layer 7 was formed on the formed hole blocking layer 6 by a vacuum deposition method so as to have a film thickness of 30 nm.

Next, on the formed electron transport layer 7, lithium fluoride (LiF) is formed to a thickness of 0.5 nm as the electron injection layer 8 by vacuum deposition, and further, aluminum is formed to a thickness of 80 nm as the cathode 9. Thus, it was formed in a stripe shape having a width of 2 mm perpendicular to the anode 2.
As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained.

It was confirmed that blue light emission having a peak wavelength of 463 nm was obtained from this device.
In addition, as a result of performing a constant current driving test at room temperature under an initial luminance of 1000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) was 3700 hours. .

[Example 2]
As a charge transport material, instead of compound E-1, the following compound E-2 (electron mobility μe = 2.1 × 10 ⁻³ cm ² / V · s at electric field strength of 0.16 MV / cm, hole mobility) An organic electroluminescent element was obtained in the same manner as in Example 1 except that μh = 1.4 × 10 ⁻³ cm ² / V · s, μe / μh = 1.50) was used.

It was confirmed that blue light emission having a peak wavelength of 466 nm was obtained from this device.
In addition, as a result of performing a constant current driving test at room temperature under an initial luminance of 1000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) was 2800 hours. .

[Example 3]
As a charge transport material, instead of compound E-1, the following compound E-3 (electron mobility μe = 1.5 × 10 ⁻³ cm ² / V · s at electric field strength of 0.16 MV / cm, hole mobility) An organic electroluminescent device was obtained in the same manner as in Example 1 except that μh = 3.0 × 10 ⁻⁴ cm ² / V · s, μe / μh = 5.00) was used.

It was confirmed that blue light emission having a peak wavelength of 461 nm was obtained from this device.
In addition, as a result of performing a constant current drive driving test at room temperature under an initial luminance of 1000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) was 3300 hours. .

[Comparative Example 1]
As a charge transport material, instead of compound E-1, the following compound E-4 (electron mobility μe = 2.8 × 10 ⁻³ cm ² / V · s at electric field strength of 0.16 MV / cm, hole mobility) An organic electroluminescent device was obtained in the same manner as in Example 1 except that μh = 2.6 × 10 ⁻⁴ cm ² / V · s, μe / μh = 10.77) was used.

It was confirmed that blue light emission having a peak wavelength of 463 nm was obtained from this device.
Further, as a result of conducting a constant current drive driving test at room temperature under an initial luminance of 1000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) was as short as 1300 hours. .

[Comparative Example 2]
As a charge transport material, instead of the compound E-1, the following compound E-5 (electron mobility μe = 2.6 × 10 ⁻³ cm ² / V · s at electric field strength of 0.16 MV / cm, hole transport) The organic electroluminescence device was obtained in the same manner as in Example 1 except that the degree of microh = 4.0 × 10 ⁻⁴ cm ² / V · s, μe / μh = 6.50) was used.

It was confirmed that blue light emission having a peak wavelength of 465 nm was obtained from this device.
Further, as a result of performing a constant current drive driving test at room temperature under an initial luminance of 1000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) was as short as 1700 hours. .

From the above results, it can be seen that a long-life organic electroluminescence device can be produced using the composition for organic electroluminescence device of the present invention.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on Aug. 10, 2009 (Japanese Patent Application No. 2009-185733), the contents of which are incorporated herein by reference.

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 (10)

An organic electroluminescent element having at least a light emitting layer formed by a wet method between a cathode and an anode, wherein the light emitting layer contains a charge transport material, and at least one of the charge transport materials is An organic electroluminescent element characterized by being an anthracene derivative represented by the following general formula (2) having a molecular weight of 460 to 2000 and satisfying the following formula (1).
0.01 ≦ μe / μh ≦ 6 (1)
(In formula (1), μe represents the electron mobility of the charge transport material at an electric field strength of 0.16 MV / cm, and μh represents the hole mobility of the charge transport material at an electric field strength of 0.16 MV / cm. )

(In Formula (2), each of Ring A and Ring B independently represents an aromatic group that is a 6-membered ring bonded to an anthracene ring and may be further condensed with 1 to 3 aromatic rings. To express.
Ar ^1A and Ar ^1B each independently represent a divalent aromatic group derived from a monocyclic to condensed ring.
m and n each independently represents an integer of 0 or more, and m + n is 8 or less.
When m and n are each 2 or more, the plurality of Ar ^1A and Ar ^1B contained in one molecule may be the same or different.
Of the ring A, ring B, Ar ^1A and Ar ^1B , when the number of those on the same plane as the anthracene ring is α and the number of others is β, the following formula (3) is satisfied.

For ring A, ring B, Ar ^1A and Ar ^1B , the total number of monocycles and the total number of condensed rings satisfy the following formula (4).

When at least one of ring A and ring B is a condensed ring having three benzene rings, the anthracene ring and the condensed ring having three benzene rings are bonded at positions other than the 9th and 10th positions. ing. ) The organic electroluminescent element according to claim 1, wherein the charge transport material satisfies the following formulas (2a) and (2b).
μe ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2a)
μh ≧ 2.0 × 10 ⁻⁷ cm ² / V · s (2b)
(In formulas (2a) and (2b), μe and μh are synonymous with μe and μh in formula (1).) The organic electroluminescent device according to claim 1 or 2, wherein the light emitting layer further contains a fluorescent light emitting material as a light emitting material. 4. The organic electroluminescent device according to claim 3, wherein the fluorescent light-emitting material is a substituted or unsubstituted condensed aromatic hydrocarbon compound having 10 to 40 nuclear carbon atoms. The first organic layer is provided between the light emitting layer and the anode, and the first organic layer is a layer formed by a wet film forming method. The organic electroluminescent element of any one. The organic electroluminescent element according to claim 5, wherein the first organic layer is a layer formed by crosslinking a crosslinkable compound. The organic electroluminescence device according to claim 5 or 6, further comprising a second organic layer containing an electron-accepting compound between the anode and the first organic layer. The organic electroluminescent element according to claim 7, wherein the second organic layer is a layer not containing an ether bond. An organic EL display device comprising the organic electroluminescent element according to any one of claims 1 to 8. An organic EL illumination comprising the organic electroluminescent element according to any one of claims 1 to 8.

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