JP2014033134A - Composition for organic electroluminescent element, organic film, organic electroluminescent element, organic el display device and organic el lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for an organic electroluminescent element that can be driven at a low voltage, and an organic electroluminescent element using the composition for an organic electroluminescent element.SOLUTION: A composition for an organic electroluminescent element contains a hole-transporting compound having a crosslinking group and an electron-accepting compound. When the amount of the crosslinking group in 1 g of the composition is denoted as A (mol/g) and the amount of the electron-accepting compound in 1 g of the composition is denoted as B (mol/g), A/B is larger than 0 and less than 2.0.

Description

  The present invention relates to a composition for an organic electroluminescence device used for forming an organic layer of an organic electroluminescence device. The present invention also provides an organic electroluminescent device having an organic film formed using the composition for organic electroluminescent device, an organic layer formed using the composition for organic electroluminescent device, and the organic electroluminescent device. The present invention relates to an organic EL display having an element and organic EL lighting.

In recent years, an electroluminescent element (organic electroluminescent element) using an organic thin film has been developed. Examples of the method for forming the organic thin film in the organic electroluminescence device include a vacuum deposition method and a wet film formation method.
Among these, since the vacuum deposition method can be laminated, it has an advantage that the charge injection from the anode and / or the cathode is improved and the exciton light-emitting layer is easily contained. On the other hand, the wet film formation method does not require a vacuum process, and can easily increase the area, and it is easy to mix a plurality of materials having various functions in one layer (coating liquid).

  For example, Patent Document 1 discloses forming an organic layer of an organic electroluminescent element using a composition containing a hole transporting compound having a crosslinking group and an electron accepting compound. However, the drive voltage of the obtained element was still high.

JP 2010-239125 A

An object of the present invention is to provide a composition useful for obtaining an organic electroluminescent device that can be driven at a low voltage.
Moreover, this invention makes it a subject to provide the organic electroluminescent element which can be driven by a low voltage using this composition for organic electroluminescent elements.

As a result of intensive studies in view of the above problems, the present inventors have found that the amount of the crosslinking group and the amount of the electron-accepting compound in the composition greatly affect the driving voltage. This is because there is an interaction between the cross-linking group and the electron-accepting compound, and it is assumed that the electron-accepting compound does not function sufficiently when there are many cross-linking groups.
Furthermore, as a result of repeated studies, the present inventors have found that the above problem can be solved by setting the ratio of the crosslinking group and the electron-accepting compound within a specific range, and have reached the present invention.

That is, the gist of the present invention is as follows.
[1] A composition for an organic electroluminescent device comprising a hole transporting compound having a crosslinking group and an electron accepting compound,
The amount of crosslinking group in 1 g of the composition is A (mol / g),
When the amount of the electron-accepting compound in 1 g of the composition is B (mol / g),
A / B is larger than 0 and smaller than 2.0,
The composition for organic electroluminescent elements characterized by the above-mentioned.
[2] The composition for organic electroluminescent elements according to [1], wherein A / B is larger than 0 and smaller than 1.0.
[3] The composition for organic electroluminescent elements according to [1] or [2], wherein the hole transporting compound having a crosslinking group contains a repeating unit represented by the following formula (1).

(In the formula, m represents an integer of 0 or more and 3 or less,
Ar ¹ and Ar ² each independently represent a direct bond, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent,
Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.

However, Ar ¹ and Ar ² are not simultaneously a direct bond. )
[4] The composition for organic electroluminescent elements according to any one of [1] to [3], wherein the crosslinking group is represented by the following formula (2).

(The benzocyclobutene ring in the formula (2) may have a substituent. The substituents may be bonded to each other to form a ring.)
[5] The organic electroluminescent element according to any one of [1] to [4], wherein the electron-accepting compound is a salt containing an anion having a pentafluorophenyl group represented by the following formula (3): Composition.

[6] An organic film obtained by applying the composition for organic electroluminescent elements according to any one of [1] to [5] and then crosslinking the hole transporting compound contained in the composition.
[7] An organic electroluminescent device having an organic layer disposed between a positive electrode and a negative electrode and a positive electrode on the substrate,
The organic electroluminescent element in which an organic layer contains the organic film as described in [6].
[8] The organic electroluminescence device according to [7], wherein the organic film constitutes a hole injection layer.
[9] The organic electroluminescent element includes a hole injection layer, a hole transport layer, and a light emitting layer as an organic layer, and all of the hole injection layer, the hole transport layer, and the light emitting layer are formed by a wet film forming method. The organic electroluminescent element according to [7] or [8].
[10] An organic EL display comprising the organic electroluminescent element according to any one of [7] to [9].
[11] An organic EL illumination comprising the organic electroluminescent element according to any one of [7] to [9].

  According to the composition for organic electroluminescent elements of the present invention, an organic film having a low electrical resistivity can be obtained. From this, the organic layer containing the organic film obtained by crosslinking the hole transporting compound contained in the composition for organic electroluminescence elements after applying the composition for organic electroluminescence elements of the present invention has an electrical resistivity. Since it is low, the organic electroluminescent device having this layer can be driven at a low voltage.

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

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not specified in the contents.
<Composition for organic electroluminescence device>
The present invention is a composition for an organic electroluminescent device comprising a hole transporting compound having a crosslinking group and an electron accepting compound,
The amount of crosslinking group in 1 g of the composition is A (mol / g),
When the amount of the electron-accepting compound in 1 g of the composition is B (mol / g),
A / B is larger than 0 and smaller than 2.0,
The composition for organic electroluminescent elements characterized by the above-mentioned.

In the present invention, the driving voltage of the organic electroluminescent device greatly affects the amount of the cross-linking group and the amount of the electron-accepting compound in the composition for the organic electroluminescent device. This is the first discovery that a compound does not function sufficiently and the present invention has been completed.
As described above, when the amount of the cross-linking group in 1 g of the composition is A (mol / g) and the amount of the electron-accepting compound in 1 g of the composition is B (mol / g), A / B is larger than 0. The composition for organic electroluminescent elements is characterized by being smaller than 2.0.
Here, A / B is preferably smaller than 1.5 and more preferably smaller than 1.0 in that the electrical resistivity can be further reduced. On the other hand, when A / B is extremely small, it may be dissolved in an organic solvent even after the post-crosslinking reaction. Therefore, A / B is usually 0.1 or more, preferably 0.3 or more, and more preferably 0.5 or more in terms of sufficient insolubilization with respect to the organic solvent.

Hereinafter, the method for calculating A / B will be specifically described using the composition for an organic electroluminescent element used in Example 1 as an example.
The composition of the composition for organic electroluminescent elements used in Example 1 is as follows.
Coating solution concentration H1: 4.875 wt%
H2: 1.625% by weight
A1: 1.950% by weight

  In the polymer (H1), the molecular weight of the repeating unit excluding the terminal group is 499.73 × 0.95 × 0.95 + 736.08 × 0.05 × 0.95 + 345. 44 * 0.95 * 0.05 + 581.31 * 0.05 * 0.05 = 503.83 (g / mol). Since the polymer (H1) has 0.05 crosslinking groups per repeating unit, the number of crosslinking groups in the polymer (H1) is 0.05 / 503.83 = 0.000099 (mol / g).

  Similarly, in the polymer (H2), the molecular weight of the repeating unit excluding the terminal group is 522.72 × 0.95 × 0.7198 + 759.07 × 0.05 × 0. 7198 + 614.78 × 0.95 × 0.2802 + 851.13 × 0.05 × 0.2802 = 560.33 (g / mol). Since the polymer (H2) has 0.2802 × 2 = 0.5604 crosslinking groups per repeating unit, the number of crosslinking groups in the polymer (H2) is 0.5604 / 560.33 = 0.010 (mol / g).

Since the concentrations of (H1) and (H2) in the composition for organic electroluminescent elements are 4.875 wt% and 1.625 wt%, respectively, A = 0.04875 × 0.000099 + 0.01625 × 0. .0010 = 0.000021 (mol / g).
Since the concentration of the electron-accepting compound (A1) in the composition is 1.950% by weight and the molecular weight of (A1) is 1016.02 (g / mol), B = 0.01950 / 1016. It is calculated as 02 = 0.000019 (mol / g).
From the above, A / B of the composition for organic electroluminescent elements used in Example 1 is calculated as 1.1.

<Hole transporting compound having a crosslinking group>
The hole transporting compound having a crosslinking group in the present invention has a hole transporting site as a partial structure. Examples of the hole transport site include a triarylamine structure, a fluorene ring, an anthracene ring, a pyrene ring, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, a phenoxazine ring, and a phenanthroline ring, and a thiophene ring structure. Examples thereof include aromatic heterocyclic structures such as rings and silole rings, and metal complex structures.

Especially, it is preferable to have a triarylamine structure as a hole transport site in terms of improving electrochemical stability and hole transport ability.
Moreover, it is preferable that it is a polymer at the point which becomes easy to become insoluble in an organic solvent by a crosslinking reaction. In particular, a polymer containing a repeating unit represented by the following formula (1) is preferable from the viewpoint of improving electrochemical stability and hole transport ability.

(In the formula, m represents an integer of 0 to 3, inclusive,
Ar ¹ and Ar ² each independently represent a direct bond, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent,
Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.
However, Ar ¹ and Ar ² are not simultaneously a direct bond. )

[About Ar ^{1 to} Ar ⁵ ]
In formula (1), Ar ¹ and Ar ² are each independently a direct bond, an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocycle which may have a substituent. Represents a group, and Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.

Examples of the aromatic hydrocarbon group which may have a substituent include, for example, a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and acenaphthene. Examples thereof include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring and a fluorene ring.
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. ring It can be mentioned groups derived from 2-4 fused rings.

Ar ^{1 to} Ar ⁵ are each independently from 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 group derived from a ring selected from the group consisting of
Further, as Ar ^{1 to} Ar ⁵ , a group in which one or two or more rings selected from the above group are connected by a direct bond is preferable, and a biphenyl group, a biphenylene group, a terphenyl group, and a terphenylene group are more preferable.
Examples of the substituent that the aromatic hydrocarbon group that may have a substituent and the aromatic heterocyclic group that may have a substituent may have the following [Substituent group Z]. And the groups described.

[Substituent group Z]
For example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, tert-butyl group, n-hexyl group, cyclohexyl group, dodecyl group, etc. A linear, branched, or cyclic alkyl group having usually 1 or more carbon atoms and usually 24 or less, preferably 12 or less;
An alkenyl group having usually 2 or more carbon atoms and usually 24 or less, preferably 12 or less, such as a vinyl group;
An alkynyl group such as an ethynyl group, which usually has 2 or more carbon atoms and is usually 24 or less, preferably 12 or less;
For example, an alkoxy group having a carbon number of usually 1 or more and usually 24 or less, preferably 12 or less, such as a methoxy group or an ethoxy group;
For example, an aryloxy group having usually 4 or more, preferably 5 or more, usually 36 or less, preferably 24, such as a phenoxy group, a naphthoxy group, or a pyridyloxy group;
For example, an alkoxycarbonyl group having 2 or more carbon atoms, usually 24 or less, preferably 12 or less, such as a methoxycarbonyl group or an ethoxycarbonyl group;
For example, a dialkylamino group having 2 or more carbon atoms and usually 24 or less, preferably 12 or less, such as a dimethylamino group or a diethylamino group;
For example, a diarylamino group having a carbon number of usually 10 or more, preferably 12 or more, usually 36 or less, preferably 24 or less, such as a diphenylamino group, a ditolylamino group, or an N-carbazolyl group;
An arylalkylamino group having usually 7 carbon atoms, usually 36 or less, preferably 24 or less, such as a phenylmethylamino group;
For example, an acetyl group, a benzoyl group, etc., an acyl group having usually 2 carbon atoms and usually having 24 or less, preferably 12;
For example, a halogen atom such as a fluorine atom or a chlorine atom;
A haloalkyl group having usually 1 or more and usually 12 or less, preferably 6 or less, such as a trifluoromethyl group;
For example, an alkylthio group having a carbon number of usually 1 or more and usually 24 or less, preferably 12 or less, such as a methylthio group or an ethylthio group;
For example, an arylthio group having a carbon number of usually 4 or more, preferably 5 or more, usually 36 or less, preferably 24 or less, such as a phenylthio group, a naphthylthio group, or a pyridylthio group;
For example, a silyl group having a carbon number of usually 2 or more, preferably 3 or more, usually 36 or less, preferably 24 or less, such as a trimethylsilyl group or a triphenylsilyl group;
For example, a siloxy group having 2 or more, preferably 3 or more, usually 36 or less, preferably 24 or less, such as trimethylsiloxy group or triphenylsiloxy group;
A cyano group;
For example, an aromatic hydrocarbon ring group having usually 6 or more carbon atoms and usually 36 or less, preferably 24 or less, such as a phenyl group or a naphthyl group;
For example, an aromatic heterocyclic group having 3 or more, preferably 4 or more, usually 36 or less, preferably 24 or less, such as thienyl group or pyridyl group.

Among these substituents, an alkyl group having 1 to 12 carbon atoms and an alkoxy group having 1 to 12 carbon atoms are preferable from the viewpoint of solubility.
Each of the above substituents may further have a substituent, and examples thereof are selected from the groups exemplified in the section of the substituent group Z.
In terms of excellent hole transportability, Ar ^{1 to} Ar ⁵ , including a substituent, have usually 3 or more carbon atoms, preferably 5 or more, more preferably 6 or more, and usually 72 or less, preferably 48 or less, more preferably 25 or less.

[About m]
M in the formula (1) represents an integer of 0 or more and 3 or less, and m is preferably 0 in that the film formability is improved. Further, m is preferably 1 or more and 3 or less from the viewpoint of improving hole transport ability.
In addition, when m is 2 or more, the repeating unit represented by the formula (1) has two or more Ar ⁴ and Ar ⁵ . In this case, Ar ⁴ and Ar ⁵ may be the same or different from each other. Furthermore, Ar ⁴ and Ar ⁵ may be bonded to each other directly or via a linking group to form a cyclic structure.

[About the cross-linking group]
In the present invention, the hole transporting compound having a crosslinking group causes a large difference in solubility in a solvent before and after the reaction (insolubilization reaction) caused by irradiation with heat and / or active energy rays. Can be made.

The cross-linking group refers to 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 cross-linking group include groups shown in the cross-linkable group group T in that insolubilization is easy. The crosslinkable group according to the present invention is not limited to these.

(In the above formula, R ^{21 to} R ²³ each independently represents a hydrogen atom or an alkyl group which may have a substituent. Ar ²¹ represents an aromatic group which may have a substituent. .
X ¹ , X ² and X ³ each independently represent a hydrogen atom or a halogen atom.
R ²⁴ represents a hydrogen atom or a vinyl group.
The benzocyclobutene ring may have a substituent, and the substituents may be bonded to each other to form a ring. )
Examples of the alkyl group of R ^{21 to} R ²³ include alkyl groups having usually 1 or more, usually 24 or less, preferably 12 or less, such as a methyl group or an ethyl group.

Examples of the aromatic group of Ar ²¹ include the same groups as the aromatic groups constituting the Ar ^{1 to} Ar ⁵ .
As the R ²¹ to R ^23, and Ar ²¹ is a substituent which may have, it is not particularly limited, for example, such as a group selected from the substituent group Z can be mentioned.
A group that undergoes insolubilization 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 preferred in terms of high reactivity and easy insolubilization. Among these, an oxetane group is particularly preferable from the viewpoint that the rate of cationic polymerization can be easily controlled, and a vinyl ether group is preferable from the viewpoint that a hydroxyl group that may cause deterioration of the device during the cationic polymerization is hardly generated.

A group that undergoes a cycloaddition reaction, such as an arylvinylcarbonyl group such as a cinnamoyl group, or a group derived from a benzocyclobutene ring, is preferred from the viewpoint of further improving electrochemical stability.
Of the crosslinkable groups, a group derived from a benzocyclobutene ring is particularly preferable in that the structure after insolubilization is particularly stable.
Specifically, a group represented by the following formula (2) is preferable.

(The benzocyclobutene ring in the formula (2) may have a substituent. The substituents may be bonded to each other to form a ring.)
The crosslinkable group may be directly bonded to a monovalent or divalent aromatic group in the molecule, or may be bonded via a divalent group. As the divalent group, a group selected from an —O— group, a —C (═O) — group, or an (optionally substituted) —CH ₂ — group may be selected from 1 to 30 in any order. It is preferable to bind to a monovalent or divalent aromatic group via a divalent group formed by individual linking. Specific examples of the crosslinkable group via these divalent groups, that is, a group containing a crosslinkable group, are as shown in <Group group T ′ containing a crosslinkable group> below, but the present invention is not limited thereto. It is not something.

(In the above formula, m represents an integer of 0 to 12, and n represents an integer of 1 to 12.)
Specific examples of the group containing these crosslinkable groups include the following.

<Electron-accepting compound>
The electron-accepting compound in the present invention is a compound having an oxidizing power and an ability to accept electrons from the above-described hole-transporting compound. Specifically, a compound with an electron affinity of 4 eV or more is preferable, and a compound with a compound of 5 eV or more is more preferable.
Examples of the electron-accepting compound include onium salts substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, iron (III) chloride (Japanese Patent Laid-Open No. 11-251067). Publication), high valence inorganic compounds such as ammonium peroxodisulfate, cyano compounds such as tetracyanoethylene, aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365), fullerene derivatives, iodine Etc.

Of the above-mentioned compounds, an onium salt substituted with an organic group, a high-valence inorganic compound, 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.
In addition, from the viewpoint of being chemically stable and enhancing durability, and from the point of delocalizing holes and further increasing hole transportability, the electron-accepting compound is represented by the following formula (3). It is preferable that it is a salt containing the anion which has a pentafluorophenyl group represented, and it is especially preferable that it is a salt containing the anion represented by following formula (3-1) (3-2).

In addition, an electron-accepting compound may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio. When two or more types are used, the total amount is the amount of the electron-accepting compound.
<Solvent etc.>
The solvent contained in the composition for organic electroluminescent elements of the present invention is not particularly limited, but it is necessary to dissolve the hole transporting compound and the electron accepting compound having a crosslinking group. Preferably, 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 Aliphatic ethers such as ether acetate (PGMEA), 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethyl Aniso Ether solvents such as aromatic ethers such as 2,4-dimethylanisole; aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate and n-butyl lactate; phenyl acetate, phenyl propionate, methyl benzoate, Examples thereof include organic solvents such as ester solvents such as ethyl benzoate, isopropyl benzoate, propyl benzoate, and n-butyl benzoate. These may be used alone or in combination of two or more.

The concentration of the solvent contained in the composition for organic electroluminescent elements of the present invention is usually 10% by weight or more, preferably 50% by weight or more, more preferably 80% by weight or more.
In addition, it is widely known that moisture may promote deterioration of the performance of the organic electroluminescent element, particularly brightness reduction during continuous driving, in order to reduce moisture remaining in the coating film as much as possible. Among these solvents, those having a water solubility at 25 ° C. of 1% by weight or less are preferred, and solvents having a solubility of 0.1% by weight or less are more preferred.

Examples of the solvent contained in the composition for organic electroluminescent elements of the present invention include a solvent having a surface tension at 20 ° C. of less than 40 dyn / cm, preferably 36 dyn / cm or less, more preferably 33 dyn / cm or less.
Specific examples of such a low surface tension solvent include the aforementioned aromatic solvents such as toluene, xylene, methicylene and cyclohexylbenzene, ester solvents such as ethyl benzoate, ether solvents such as anisole, trifluoromethoxy, and the like. Anisole, pentafluoromethoxybenzene, 3- (trifluoromethyl) anisole, ethyl (pentafluorobenzoate) and the like can be mentioned.

The concentration of these solvents in the composition is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more.
Examples of the solvent contained in the composition for organic electroluminescence device of the present invention include a solvent having a vapor pressure at 25 ° C. of 10 mmHg or less, preferably 5 mmHg or less and usually 0.1 mmHg or more. By using such a solvent, it is possible to prepare a composition suitable for a process for producing an organic electroluminescent device by a wet film-forming method and suitable for the properties of the arylamine polymer of the present invention. Specific examples of such a solvent include the above-described aromatic solvents such as toluene, xylene, and methicylene, ether solvents, and ester solvents. The concentration of these solvents in the composition is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more.

  As a solvent contained in the composition for organic electroluminescent elements of the present invention, the vapor pressure at 25 ° C. is 2 mmHg or more, preferably 3 mmHg or more, more preferably 4 mmHg or more (however, the upper limit is preferably 10 mmHg or less). A mixed solvent of a certain solvent and a solvent having a vapor pressure at 25 ° C. of less than 2 mmHg, preferably 1 mmHg or less, more preferably 0.5 mmHg or less. By using such a mixed solvent, a homogeneous layer containing the arylamine polymer of the present invention and further an electron accepting compound can be formed by a wet film forming method. The concentration of the mixed solvent in the composition is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more.

  Since the organic electroluminescent element is formed by laminating a large number of layers made of an organic compound, it is very important that the film quality is uniform. When a layer is formed by a wet film forming method, a film forming method such as a coating method such as a spin coating method or a spray method, or a printing method such as an ink jet method or a screen method can be adopted depending on the material and properties of the base. For example, since the spray method is effective for forming a uniform film on a surface with unevenness, it is preferable when a layer made of an organic compound is provided on a surface where unevenness due to a patterned electrode or a partition between pixels remains. In the case of application by a spray method, it is preferable that the droplets of the application liquid sprayed from the nozzle to the application surface are as small as possible because uniform film quality can be obtained. For that purpose, a solvent with high vapor pressure is mixed with the coating liquid, and a part of the solvent is volatilized from the sprayed coating droplet in the coating atmosphere, so that fine droplets are generated immediately before adhering to the substrate. Is preferred. Also, in order to obtain a more uniform film quality, it is necessary to secure time for the liquid film generated on the substrate to be leveled immediately after coating. In order to achieve this purpose, a slower drying solvent, that is, a vapor A technique in which a solvent having a low pressure is contained to some extent is used.

Specific examples of the solvent having a vapor pressure of 2 mmHg to 10 mmHg at 25 ° C. include organic solvents such as xylene, anisole, cyclohexanone, and toluene. Examples of the solvent having a vapor pressure of less than 2 mmHg at 25 ° C. include ethyl benzoate, methyl benzoate, tetralin, and phenetole.
The ratio of the mixed solvent is such that the solvent having a vapor pressure of 2 mmHg or more at 25 ° C. is 5% by weight or more, preferably 25% by weight or more, but less than 50% by weight, and the vapor pressure at 25 ° C. is 25% by weight. The solvent which is less than 2 mmHg is 30% by weight or more, preferably 50% by weight or more, particularly preferably 75% by weight or more, but less than 95% by weight in the total mixed solvent.

  In addition, since an organic electroluminescent element is formed by laminating a plurality of layers made of organic compounds, each layer is required to be a uniform layer. In the case of forming a layer by a wet film forming method, moisture may be mixed into the coating solution (composition) for forming the layer, so that moisture may be mixed into the coating film and the uniformity of the film may be impaired. It is preferable that the water content is as low as possible. Specifically, the amount of water contained in the organic electroluminescent element composition is preferably 1% by weight or less, more preferably 0.1% by weight or less, and still more preferably 0.05% by weight or less.

  In addition, since organic electroluminescent devices use many materials such as cathodes that are significantly deteriorated by moisture, the presence of moisture is not preferable from the viewpoint of device degradation. Examples of the method for reducing the amount of water in the solution include nitrogen gas sealing, use of a desiccant, dehydration of the solvent in advance, use of a solvent with low water solubility, and the like. Among these, the use of a solvent having low water solubility is preferable because the solution coating film can prevent whitening by absorbing moisture in the atmosphere during the coating process.

From such a viewpoint, the composition for organic electroluminescent elements of the present invention contains, for example, a solvent having a water solubility at 25 ° C. of 1% by weight or less (preferably 0.1% by weight or less) in the composition. It is preferable to contain 10% by weight or more. The solvent satisfying the above solubility condition is more preferably 30% by weight or more, and particularly preferably 50% by weight or more.
In addition, as a solvent contained in the composition for organic electroluminescent elements of this invention, you may contain various other solvents other than the solvent mentioned above as needed. Examples of such other solvents include amides such as N, N-dimethylformamide and N, N-dimethylacetamide; dimethyl sulfoxide and the like.
Moreover, the composition for organic electroluminescent elements of this invention may contain various additives, such as coating property improving agents, such as a leveling agent and an antifoamer.

<Organic film>
The organic film of the present invention can be obtained by applying the composition for organic electroluminescent elements of the present invention and then crosslinking the hole transporting compound contained in the composition.

<Organic electroluminescent device>
The organic electroluminescence device of the present invention has an anode and a cathode on the substrate, an organic layer disposed between the anode and the cathode, and the organic layer is coated with the composition for an organic electroluminescence device of the present invention. Thereafter, an organic film (organic film of the present invention) obtained by crosslinking a hole transporting compound is included.
FIG. 1 is a cross-sectional view schematically showing an example of the structure of the organic electroluminescent element of the present invention. The organic electroluminescent device shown in FIG. 1 has an anode, a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode laminated in this order on a substrate. Configured. In the case of this configuration, the hole injection layer usually corresponds to an organic layer including the above-described organic film of the present invention.

[1] Substrate
The substrate serves as a support for the organic electroluminescence device, and quartz or glass plates, metal plates or metal foils, plastic films or sheets are used. Especially glass plates, polyester,
Transparent synthetic resin plates such as polymethacrylate, polycarbonate and polysulfone are preferred. 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.

[2] Anode
The anode plays a role of hole injection into a layer on the light emitting layer side (hole injection layer, light emitting layer, or the like) described later. This anode is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or poly It is composed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline. In general, the anode is often formed by a sputtering method, a vacuum deposition method, or the like. Also, in the case of fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., it is dispersed in an appropriate binder resin solution and placed on the substrate. An anode can also be formed by coating. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on a substrate by electrolytic polymerization, or an anode can be formed by applying a conductive polymer on a substrate (Applied Physics Letters, 1992, Vol. .60, pp. 2711). The anode can be formed by stacking different materials.

  The thickness of the anode varies depending on the required transparency. When transparency is required, it is desirable that the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 nm or more, preferably 10 nm or more, Usually, it is 1000 nm or less, preferably 500 nm or less. If it may be opaque, the anode may be the same as the substrate. Furthermore, it is also possible to laminate different conductive materials on the anode.

  In addition, the surface of the anode is treated with ultraviolet (UV) / ozone, oxygen plasma, or argon plasma for the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve the hole injection property. Is preferred.

[3] Hole injection layer
A hole injection layer is formed on the anode.
The hole injection layer is a layer that transports holes to a layer adjacent to the cathode side of the anode.
The organic electroluminescent device of the present invention may have a configuration in which the hole injection layer is omitted.
The hole injection layer preferably contains a hole transporting compound, and more preferably contains a hole transporting compound and an electron accepting compound. Further, the hole injection layer preferably contains a cation radical compound, and particularly preferably contains a cation radical compound and a hole transporting compound.

The hole injection layer may contain a binder resin and a coating property improving agent as necessary. The binder resin is preferably one that hardly acts as a charge trap.
The hole injection layer can be formed by depositing only the electron-accepting compound on the anode by a wet film-forming method, and directly applying and laminating the charge transport material composition thereon. In this case, a part of the charge transport material composition interacts with the electron-accepting compound, so that a layer excellent in hole injecting property is formed.

The hole injection layer preferably includes the organic film of the present invention because it has a low electrical resistivity and can be obtained to reduce the driving voltage of the device.
The hole injection layer is preferably formed by a wet coating method. After preparing a composition for forming a hole injection layer (preferably a composition for an organic electroluminescence device of the present invention), the composition is subjected to wet film formation to form a layer corresponding to the lower layer of the hole injection layer (usually an anode) The hole injection layer is formed by applying and drying.

The temperature in the film forming step is preferably 0 ° C. or higher, and preferably 50 ° C. or lower in order to prevent film loss due to the formation of crystals in the composition.
Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.
After coating, the film of the composition for forming a hole injection layer is usually dried by heating or the like. As a drying method, a heating step is usually performed. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

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

In the heating step, the heating temperature is preferably equal to or higher than the boiling point of the solvent of the composition for forming a hole injection layer. The heating time is not limited as long as the coating film does not sufficiently crosslink, but is preferably 10 seconds or longer and usually 180 minutes or shorter. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.
The thickness of the hole injection layer is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

[4] Hole transport layer
The hole transport layer can be formed on the hole injection layer. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.
The material for forming the hole transport layer is preferably a material having a high hole transport capability and capable of efficiently transporting the injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, since it is in contact with the light emitting layer, it is preferable not to quench the light emitted from the light emitting layer or to reduce the efficiency by forming an exciplex with the light emitting layer.

As the hole transporting compound, a material conventionally used as a constituent material of the hole transporting layer can be used. Examples of conventionally used materials include those exemplified as the hole transporting compound used in the above-described hole injection layer. In addition, 4,4′-bis [N
An aromatic diamine containing two or more tertiary amines typified by-(1-naphthyl) -N-phenylamino] biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234683) No. gazette), aromatic amine compounds having a starburst structure such as 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997). Year), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9 ′. -Spiro compounds such as spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), calories such as 4,4'-N, N'-dicarbazole biphenyl Such as tetrazole derivatives. Further, for example, polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), polyarylene ether sulfone (Polym. Adv. Tech., 7, 33, 1996) containing tetraphenylbenzidine, etc. Can be mentioned.

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

The hole transport layer is also preferably a layer formed by crosslinking a compound having a crosslinking group in that the light emitting layer can be laminated by a wet coating method. The compound having a crosslinking group forms a network polymer compound by crosslinking reaction.
Examples of such crosslinkable groups include cyclic ether groups such as oxetane groups and epoxy groups; groups containing unsaturated double bonds such as vinyl groups, trifluorovinyl groups, styryl groups, acrylic groups, methacryloyl groups, and cinnamoyl groups. A group derived from a benzocyclobutene ring;

The compound having a crosslinking group may be any of a monomer, an oligomer, and a polymer. The compound which has a crosslinking group may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.
The compound used for the hole transport layer preferably has a hole transport site as a partial structure. Examples of the hole transport site include a triarylamine structure, a fluorene ring, an anthracene ring, a pyrene ring, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, a phenoxazine ring, and a phenanthroline ring, and a thiophene ring structure. Examples thereof include aromatic heterocyclic structures such as rings and silole rings, and metal complex structures.
The thickness of the hole transport layer is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

(Light emitting layer)
The light-emitting layer is a layer that has a function of emitting light when excited by recombination of holes injected from the anode and electrons injected from the cathode when an electric field is applied between the pair of electrodes. The light emitting layer is a layer formed between the anode and the cathode. When the hole injection layer is on the anode, the light emitting layer is formed between the hole injection layer and the cathode and on the anode. When there is a hole transport layer, it is formed between the hole transport layer and the cathode.

The thickness of the light emitting layer is arbitrary as long as the effects of the present invention are not significantly impaired. However, a thicker layer is preferable from the viewpoint that defects are unlikely to occur in the film, and a thinner layer is preferable from the viewpoint that a low driving voltage is easily obtained. For this reason, it is preferably 3 nm or more, more preferably 5 nm or more, and on the other hand, it is usually preferably 200 nm or less, and more preferably 100 nm or less.
The light emitting layer contains at least a material having a light emitting property (light emitting material) and preferably contains a material having a charge transporting property (charge transporting material).

(Luminescent material)
The light emitting material emits light at a desired light emission wavelength, and is not particularly limited as long as the effect of the present invention is not impaired, and a known light emitting material can be applied. The light emitting material may be a fluorescent light emitting material or a phosphorescent light emitting material, but a material having good light emission efficiency is preferred, and a phosphorescent light emitting material is preferred from the viewpoint of internal quantum efficiency.

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

Examples of the fluorescent light-emitting material that gives yellow light (yellow fluorescent light-emitting material) include rubrene and perimidone derivatives.
Examples of fluorescent light-emitting materials (red fluorescent light-emitting materials) that emit red light include, for example, DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) -based compounds, benzopyran derivatives, rhodamine derivatives. Benzothioxanthene derivatives, azabenzothioxanthene and the like.

  Examples of the phosphorescent light-emitting material include seventh to eleventh long-period periodic tables (hereinafter referred to as long-period periodic tables when referred to as “periodic tables” unless otherwise specified). And organometallic complexes containing a metal selected from the group. Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

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

  Specific examples of preferred phosphorescent materials include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, and tris. Examples thereof include phenylpyridine complexes such as (2-phenylpyridine) osmium and tris (2-phenylpyridine) rhenium, and porphyrin complexes such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethyl palladium porphyrin, and octaphenyl palladium porphyrin.

Polymeric light-emitting materials include poly (9,9-dioctylfluorene-2,7-diyl), poly [(9,9-dioctylfluorene-2,7-diyl) -co- (4,4′- (N
-(4-sec-butylphenyl)) diphenylamine)], poly [(9,9-dioctylfluorene-2,7-diyl) -co- (1,4-benzo-2 {2,1'-3}- And polyfluorene-based materials such as poly [2-methoxy-5- (2-hexylhexyloxy) -1,4-phenylenevinylene].

(Charge transport material)
The charge transport material is a material having a positive charge (hole) or negative charge (electron) transport property, and is not particularly limited as long as the effect of the present invention is not impaired, and a known light emitting material can be applied.
As the charge transporting material, a compound or the like conventionally used in a light emitting layer of an organic electroluminescence device can be used, and a compound used as a host material of the light emitting layer is particularly preferable.

Specific examples of charge transporting materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which tertiary amines are linked by a fluorene group. , Hydrazone compounds, silazane compounds, silanamin compounds, phosphamine compounds, quinacridone compounds, and the like as examples of hole transporting compounds in the hole injection layer, anthracene compounds, pyrene compounds, Examples thereof include electron transporting compounds such as carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds and silole compounds.

In addition, for example, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are nitrogen atoms. Aromatic diamine (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1
-Aromatic amine compounds having a starburst structure such as naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), an aromatic amine comprising a tetramer of triphenylamine Compounds (Chem. Commun., 2175, 1996), 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9 ′
-Positive hole transport layers such as fluorene compounds such as spirobifluorene (Synth. Metals, 91, 209, 1997), carbazole compounds such as 4,4'-N, N'-dicarbazole biphenyl, etc. The compounds exemplified as the hole transporting compound can also be preferably used. In addition, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1-naphthyl)- Oxadiazole compounds such as 1,3,4-oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4- Examples include silole compounds such as diphenylsilole (PyPySPyPy) and phenanthroline compounds such as bathophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin).

<Formation of light emitting layer by wet film formation method>
The method for forming the light emitting layer may be a vacuum deposition method or a wet film formation method, but a wet film formation method is preferable and a spin coating method and an ink jet method are more preferable because of excellent film forming properties. When the light emitting layer is formed by a wet film forming method, the light emitting layer is usually used instead of the hole injection layer forming composition in the same manner as in the case of forming the hole injection layer by the wet film forming method. The resulting material is formed using a composition for forming a light emitting layer prepared by mixing a soluble solvent (solvent for the light emitting layer).

  Examples of the solvent include, for example, ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, alkane solvents, halogenated aromatic hydrocarbon solvents, aliphatic solvents, and the like mentioned for the formation of the hole injection layer. Examples thereof include alcohol solvents, alicyclic alcohol solvents, aliphatic ketone solvents, and alicyclic ketone solvents. Although the specific example of a solvent is given to the following, as long as the effect of this invention is not impaired, it is not limited to these.

For example, aliphatic ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2 -Aromatic ether solvents such as methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole, diphenyl ether; phenyl acetate, phenyl propionate, methyl benzoate, benzoic acid Aromatic ester solvents such as ethyl, ethyl benzoate, propyl benzoate, n-butyl benzoate; toluene, xylene, methicylene, cyclohexylbenzene, tetralin, 3-ilopropylbiphenyl, 1 Aromatic hydrocarbon solvents such as 2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene and methylnaphthalene; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; n
-Alkane solvents such as decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; halogenated aromatic hydrocarbon solvents such as chlorobenzene, dichlorobenzene, and trichlorobenzene; aliphatic alcohol solvents such as butanol and hexanol; cyclohexanol, Examples thereof include alicyclic alcohol solvents such as cyclooctanol; aliphatic ketone solvents such as methyl ethyl ketone and dibutyl ketone; and alicyclic ketone solvents such as cyclohexanone, cyclooctanone, and fenkon. Of these, alkane solvents and aromatic hydrocarbon solvents are particularly preferred.

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

There is no restriction | limiting in the formation method of the hole-blocking layer 6. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the hole blocking layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less. .

The electron transport layer is provided between the light emitting layer and the electron injection layer for the purpose of further improving the current efficiency of the device.
The electron transport layer is formed of a compound capable of efficiently transporting electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the light emitting layer. The electron transporting compound used in the electron transporting layer is a compound that has high electron injection efficiency from the cathode or the electron injection layer and has high electron mobility and can efficiently transport injected electrons. It is necessary.

The electron transporting compound used for the electron transporting layer is usually preferably a compound that has high electron injection efficiency from the cathode or the electron injection layer and can efficiently transport the injected electrons. Specific examples of the electron transporting compound 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 (JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous Silicon carbide, n-type zinc sulfide, n-type cere Zinc oxide and the like.
The film thickness of the electron transport layer is usually 1 nm or more, preferably 5 nm or more, and is usually 300 nm or less, preferably 100 nm or less.
The electron transport layer is formed by laminating on the hole blocking layer by a wet film formation method or a vacuum deposition method in the same manner as described above. Usually, a vacuum deposition method is used.

(Electron injection layer)
The electron injection layer plays a role of efficiently injecting electrons injected from the cathode into the electron transport layer or the light emitting layer.
In order to perform electron injection efficiently, the material for forming the electron injection layer is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually preferably from 0.1 nm to 5 nm.
Furthermore, an organic electron transport material represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.) also improves electron injection / transport and makes it possible to achieve both excellent film quality. preferable.

The film thickness is usually in the range of 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.
The electron injection layer is formed by laminating on the light emitting layer or the hole blocking layer thereon by a wet film formation method or a vacuum deposition method.
The details in the case of the wet film forming method are the same as those in the case of the light emitting layer described above.

(cathode)
The cathode plays a role of injecting electrons into a layer on the light emitting layer side (such as an electron injection layer or a light emitting layer).
As the material of the cathode, it is possible to use the material used for the above-mentioned anode, but it is preferable to use a metal having a low work function for efficient electron injection, for example, tin, magnesium, indium Further, metals such as calcium, aluminum, and silver, or alloys thereof are used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

From the viewpoint of device stability, it is preferable to protect a cathode made of a metal having a low work function by laminating a metal layer having a high work function and stable to the atmosphere on the cathode. Examples of the metal to be laminated include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum.
The thickness of the cathode is usually the same as that of the anode.

(Other layers)
The organic electroluminescent element of the present invention may further have other layers as long as the effects of the present invention are not significantly impaired. That is, any other layer described above may be provided between the anode and the cathode.
<Other element configuration>
In addition, it is also possible to laminate | stack a cathode, an electron injection layer, a light emitting layer, a positive hole injection layer, and an anode in order on a board | substrate contrary to the above-mentioned description.

<Others>
When the organic electroluminescent element of the present invention is applied to an organic electroluminescent device, it may be used as a single organic electroluminescent element, or may be used in a configuration in which a plurality of organic electroluminescent elements are arranged in an array, The anode and the cathode may be used in a configuration in which they are arranged in an XY matrix.

<Organic EL display device>
The organic EL display device of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic electroluminescent display apparatus of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display device of the present invention can be obtained by the method described in “Organic EL display” (Ohm, published on Aug. 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

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

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
[Synthesis example]
Synthesis of (H1)

4,4′-Dibromobiphenyl (4.23 g, 13.6 mol), 2-amino-9,9-
Dihexylfluorene (9.00 g, 25.7 mmol), 4- (3-aminophenyl) benzocyclobutene (0.265 g, 1.36 mmol), tert-butoxy sodium (10.1 g, 104.5 mmol), and toluene ( 48 ml) was charged, the inside of the system was sufficiently purged with nitrogen, and the mixture was heated to 65 ° C. (solution A1). Tri-t-butylphosphine (0.285 g, 2.16 mmol) was added to a 35 ml toluene solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.285 g, 0.275 mmol) and heated to 65 ° C. ( Solution B1). In a nitrogen stream, solution B1 is added to solution A1 and 2 hours.
The reaction was heated to reflux. Thereafter, 4,4′-dibromobiphenyl (3.51 g, 11.3 mmol) was additionally added. The mixture was heated under reflux for 2.0 hours, and 2,2-bis [4- (4-bromophenyl) phenyl] -4-methylpentane (0.669 g) was further added. After refluxing for 1 hour, 4,4′-dibromobiphenyl (0.053 g) was added. After refluxing for 1 hour, the reaction solution was allowed to cool, and the reaction solution was dropped into 1000 ml of ethanol to crystallize the crude polymer.

  The obtained crude polymer was dissolved in 250 ml of toluene and charged with N, N-diphenylamine (0.92 g) and tert-butoxy sodium (10.1 g). The system was sufficiently purged with nitrogen and heated to 65 ° C. (Solution C1). Tri-t-butylphosphine (0.219 g) was added to a 18 ml toluene solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.142 g) and heated to 65 ° C. (solution D1). In a nitrogen stream, the solution D1 was added to the solution C1, and heated to reflux for 4 hours. Bromobenzene (4.25 g) and re-prepared solution D1 were added to this reaction solution, and the mixture was further heated under reflux for 2 hours. The reaction solution was allowed to cool and added dropwise to 1000 ml of ethanol to obtain an end-capped crude polymer.

This end-capped crude polymer was dissolved in toluene, reprecipitated in acetone, and the precipitated polymer was separated by filtration. The filtered crude polymer was dissolved in toluene, washed with dilute hydrochloric acid, and reprecipitated with ammonia-containing ethanol. The polymer collected by filtration was purified by column chromatography to obtain a polymer (H1) (5.2 g).
Weight average molecular weight (Mw) = 84800
Dispersity (Mw / Mn) = 1.38
Synthesis of (H2)

sec-Butylaniline (5.30 g, 35.5 mmol), 4- (3-aminophenyl) benzocyclobutene (2.70 g, 13.8 mmol), 1,4-dibromobenzene (5.82 g, 24.7 mmol) , Tert-butoxy sodium (15.17 g, 157.9 mmol) and toluene (45 ml) were charged, and the system was sufficiently purged with nitrogen and heated to 60 ° C. (solution A2). Tri-t-butylphosphine (0.8 g, 3.95 mmol) was added to a 25 ml toluene solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.51 g, 0.49 mmol) and heated to 60 ° C. ( Solution B2). In a nitrogen stream, the solution B2 was added to the solution A2, and the mixture was heated to reflux for 2.0 hours. 4,4′-Dibromobiphenyl (6.945 g, 22.22596 mmol) was added. 1.
After 2-hour heating at reflux, 2,2-bis [4- (4-bromophenyl) phenyl] -4-methylpentane (0.642 g, 1.17 mmol) was added. After heating under reflux for 1.0 hour, 4,4′-dibromobiphenyl (0.24 g, 0.769 mmol) was further added. After 30 minutes, the reaction solution was allowed to cool, and the reaction solution was dropped into 1500 ml of ethanol to crystallize the crude polymer.

  The obtained crude polymer was dissolved in 300 ml of toluene, charged with N, N-diphenylamine (1.67 g) and sodium tert-butoxy (7.6 g), and the system was sufficiently purged with nitrogen and heated to 60 ° C. (Solution C2). Tri-t-butylphosphine (0.4 g) was added to a 20 ml toluene solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.255 g), and the mixture was heated to 60 ° C. (solution D2). In a nitrogen stream, the solution D2 was added to the solution C2, and heated to reflux for 2 hours. Bromobenzene (3.87 g) was added to the reaction solution. The reaction was heated to reflux for 4 hours. The reaction solution was allowed to cool and added dropwise to an ethanol / water (1500 ml / 100 ml) solution to obtain an end-capped crude polymer.

This end-capped crude polymer was dissolved in toluene, reprecipitated in acetone, and the precipitated polymer was separated by filtration. The crude polymer separated by filtration was dissolved in toluene, washed with dilute hydrochloric acid, and reprecipitated with ammonia-containing ethanol. The polymer collected by filtration was purified by column chromatography to obtain a polymer (H2) (3.9 g).
Weight average molecular weight (Mw) = 71200
Dispersity (Mw / Mn) = 1.39
Synthesis of (H3)

sec-butylaniline (7.285 g, 48.8 mmol), 4- (3-aminophenyl) benzocyclobutene (3.711 g, 19.0 mmol), 1,4-dibromobenzene (8.00 g, 33.9 mmol) , Tert-butoxy sodium (20.86 g, 217.0 mmol), and toluene (64 ml) were charged, the inside of the system was sufficiently purged with nitrogen, and the mixture was heated to 60 ° C. (solution A3). Tri-t-butylphosphine (1.10 g, 5.42 mmol) was added to a toluene 32 ml solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.70 g, 0.678 mmol) and heated to 60 ° C. ( Solution B3). In a nitrogen stream, the solution B3 was added to the solution A3, and heated and refluxed for 2.0 hours. 4,4′-Dibromobiphenyl (9.52 g, 30.5 mmol) was added. 1.0
After refluxing for 2 hours, 2,2-bis [4- (4-bromophenyl) phenyl] -4-methylpentane (0.558 g, 1.02 mmol) and 1,1-bis [4- (4-bromophenyl) Phenyl] -1- [1-methyl-1- [4- (4-bromophenyl) phenyl] ethyl] phenylethane (0.571 g, 0.678 mmol) was added. After heating under reflux for 1.0 hour, 4,4′-dibromobiphenyl (0.106 g, 0.339 mmol) was further added. After 30 minutes, the reaction solution was allowed to cool, and the reaction solution was dropped into 1500 ml of ethanol to crystallize the crude polymer.

  The obtained crude polymer was dissolved in 300 ml of toluene, charged with N, N-diphenylamine (1.15 g) and tert-butoxy sodium (20.9 g), and the system was sufficiently purged with nitrogen, and heated to 60 ° C. (Solution C4). Tri-t-butylphosphine (0.549 g) was added to a 20 ml toluene solution of tris (dibenzylideneacetone) dipalladium chloroform complex (0.351 g), and the mixture was heated to 60 ° C. (solution D4). In a nitrogen stream, the solution D4 was added to the solution C4, and heated to reflux for 2 hours. Bromobenzene (5.32 g) was added to the reaction solution. The reaction was heated to reflux for 4 hours. The reaction solution was allowed to cool and added dropwise to an ethanol / water (1500 ml / 100 ml) solution to obtain an end-capped crude polymer.

This end-capped crude polymer was dissolved in toluene, reprecipitated in acetone, and the precipitated polymer was separated by filtration. The crude polymer separated by filtration was dissolved in toluene, washed with dilute hydrochloric acid, and reprecipitated with ammonia-containing ethanol. The polymer collected by filtration was purified by column chromatography to obtain a polymer (H3) (5.9 g).
Weight average molecular weight (Mw) = 74000
Dispersity (Mw / Mn) = 2.17
Example 1
An element having a layer structure of (anode / hole injection layer / cathode) was produced.

  An anode is formed by patterning an indium tin oxide (ITO) transparent conductive film on a glass substrate with a thickness of 70 nm (sputtered film, sheet resistance 15 Ω) into a 2 mm-wide stripe by ordinary photolithography technology did. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  First, a polymer represented by the following structural formula (H1) (crosslinking group number 0.000099 (mol / g)), a polymer represented by structural formula (H2) (crosslinking group number 0.0010 (mol / g)), structural formula A coating solution for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate shown in (A1) was prepared. This coating solution was formed by spin coating on the anode under the following conditions to obtain a hole injection layer having a thickness of 200 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 4.875% by weight
H2: 1.625% by weight
A1: 1.950% by weight
<Film formation conditions for hole injection layer>
Spin coating atmosphere In air Heating condition In air 230 ° C. 1 hour After that, by vacuum deposition, aluminum as a cathode was laminated in a 2 mm width stripe shape orthogonal to the ITO stripe as the anode so as to have a film thickness of 80 nm. . As described above, an element having a current-carrying portion having a size of 2 mm × 2 mm was obtained. Table 1 summarizes the current density when a voltage of 1.4 V was applied to the device.

(Comparative Example 1)
A device was fabricated in the same manner as in Example 1 except that the composition of the coating solution for forming the hole injection layer in Example 1 was changed as follows. Table 1 summarizes the current density when a voltage of 1.4 V was applied to the device.
<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 1.625% by weight
H2: 4.875 wt%
A1: 1.950% by weight

As shown in Table 1, an element using an organic film formed using the composition for organic electroluminescent elements of the present invention as a hole injection layer has a large current density, and the composition for organic electroluminescent elements of the present invention is used. It can be seen that the organic film formed in this manner has a low electrical resistivity. For this reason, the organic electroluminescent element which uses the organic film formed using the composition for organic electroluminescent elements of this invention as a positive hole injection layer is considered that a drive voltage is low.

(Example 2)
A device having a layer structure of (anode / hole injection layer / hole transport layer / cathode) was produced.
An anode is formed by patterning an indium tin oxide (ITO) transparent conductive film on a glass substrate with a thickness of 70 nm (sputtered film, sheet resistance 15 Ω) into a 2 mm-wide stripe by ordinary photolithography technology did. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  First, a polymer represented by the following structural formula (H1) (number of cross-linking groups 0.000099 (mol / g)), 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate represented by the structural formula (A1) And a coating solution for forming a hole injection layer containing ethyl benzoate. This coating solution was formed on the anode by spin coating under the following conditions to obtain a hole injection layer having a thickness of 150 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 5.500% by weight
A1: 0.825 wt%
<Film formation conditions for hole injection layer>
Spin coating atmosphere In-air heating condition In-air 230 ° C. 1 hour Subsequently, a coating solution for forming a hole transport layer containing a polymer represented by the following formula (H4) was prepared, and a film was formed by spin coating under the following conditions. Then, a hole transport layer having a thickness of 10 nm was formed by polymerization by heating.

<Coating liquid for hole transport layer formation>
Solvent Cyclohexylbenzene Coating solution concentration 1.4% by weight
<Hole transport layer deposition conditions>
Spin coating atmosphere Nitrogen Heating condition Nitrogen 230 ° C. 1 hour After that, by vacuum deposition, aluminum was stacked in a 2 mm wide stripe shape orthogonal to the anode ITO stripe so as to have a film thickness of 80 nm as the cathode. . As described above, an element having a current-carrying portion having a size of 2 mm × 2 mm was obtained. 2V for this element
Table 2 summarizes the current density when the above voltage was applied.

(Example 3)
A device was prepared in the same manner as in Example 2 except that the hole injection layer was formed as follows.
A polymer represented by the following structural formula (H1) (crosslinking group number 0.000099 (mol / g)), a polymer represented by the structural formula (H3) (crosslinking group number 0.0010 (mol / g)) structural formula (A1) A coating solution for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate was prepared. This coating solution was formed on the anode by spin coating under the following conditions to obtain a hole injection layer having a thickness of 150 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 5.225% by weight
H3: 0.275% by weight
A1: 0.825 wt%
<Film formation conditions for hole injection layer>
Spin coating atmosphere In-air heating conditions In-air 230 ° C. for 1 hour Table 2 summarizes the current density when a voltage of 2 V was applied to the device.

Example 4
A device was prepared in the same manner as in Example 2 except that the hole injection layer was formed as follows.
A polymer represented by the following structural formula (H1) (crosslinking group number 0.000099 (mol / g)), a polymer represented by the structural formula (H3) (crosslinking group number 0.0010 (mol / g)) structural formula (A1) A coating solution for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate was prepared. This coating solution was formed on the anode by spin coating under the following conditions to obtain a hole injection layer having a thickness of 150 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 4.950% by weight
H3: 0.550% by weight
A1: 0.825 wt%
<Film formation conditions for hole injection layer>
Spin coating atmosphere In-air heating conditions In-air 230 ° C. for 1 hour Table 2 summarizes the current density when a voltage of 2 V was applied to the device.

(Comparative Example 2)
A device was prepared in the same manner as in Example 2 except that the hole injection layer was formed as follows.
A polymer represented by the following structural formula (H1) (crosslinking group number 0.000099 (mol / g)), a polymer represented by structural formula (H2) (crosslinking group number 0.0010 (mol / g)) structural formula (A1) A coating solution for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate was prepared. This coating solution was formed on the anode by spin coating under the following conditions to obtain a hole injection layer having a thickness of 150 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H1: 1.375% by weight
H2: 4.125% by weight
A1: 1.650% by weight
Table 2 summarizes the current density when a voltage of 2 V was applied to the device.

  As shown in Table 1, an element using an organic film formed using the composition for organic electroluminescent elements of the present invention as a hole injection layer has a large current density, and the composition for organic electroluminescent elements of the present invention is used. It can be seen that the organic film formed in this manner has a low electrical resistivity. For this reason, the organic electroluminescent element which uses the organic film formed using the composition for organic electroluminescent elements of this invention as a positive hole injection layer is considered that a drive voltage is low.

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 (11)

A composition for an organic electroluminescent device comprising a hole transporting compound having a crosslinking group and an electron accepting compound,
The amount of crosslinking group in 1 g of the composition is A (mol / g),
When the amount of the electron-accepting compound in 1 g of the composition is B (mol / g),
A / B is larger than 0 and smaller than 2.0,
The composition for organic electroluminescent elements characterized by the above-mentioned. The composition for organic electroluminescent elements according to claim 1, wherein A / B is larger than 0 and smaller than 1.0. The composition for organic electroluminescent elements according to claim 1 or 2, wherein the hole transporting compound having a crosslinking group contains a repeating unit represented by the following formula (1).

(In the formula, m represents an integer of 0 or more and 3 or less,
Ar ¹ and Ar ² each independently represent a direct bond, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent,
Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.
However, Ar ¹ and Ar ² are not simultaneously a direct bond. ) The composition for organic electroluminescent elements according to any one of claims 1 to 3, wherein the crosslinking group is represented by the following formula (2).

(The benzocyclobutene ring in the formula (2) may have a substituent. The substituents may be bonded to each other to form a ring.) The composition for organic electroluminescent elements as described in any one of Claims 1-4 whose electron-accepting compound is a salt containing the anion which has a pentafluorophenyl group represented by following formula (3).

  The organic film obtained by apply | coating the composition for organic electroluminescent elements as described in any one of Claims 1-5, and bridge | crosslinking the hole transportable compound contained in the said composition. An organic electroluminescence device having an organic layer disposed between an anode and a cathode, and the anode and the cathode on a substrate,
The organic electroluminescent element in which an organic layer contains the organic film of Claim 6.   The organic electroluminescent element according to claim 7, wherein the organic film constitutes a hole injection layer.   The organic electroluminescent device includes a hole injection layer, a hole transport layer, and a light emitting layer as an organic layer, and the hole injection layer, the hole transport layer, and the light emitting layer are all formed by a wet film formation method. Item 9. The organic electroluminescent device according to Item 7 or 8.   The organic electroluminescent display provided with the organic electroluminescent element as described in any one of Claims 7-9.   Organic EL illumination provided with the organic electroluminescent element as described in any one of Claims 7-9.

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