KR20190111919A - An organic electroluminescent element containing a composition for forming a light emitting layer and the composition for forming a light emitting layer. - Google Patents

Abstract

An object of the present invention is to provide an organic electroluminescent device having a long driving life and excellent storage stability, and to provide a composition for forming a light emitting layer suitable for the same, specifically, a light emitting material, a non-light emitting material and an organic solvent. As a composition for light emitting layer formation of the organic electroluminescent element containing, 1 type or multiple types of this light emitting material may be sufficient, The said non-luminescent material is a high Tg compound whose glass transition temperature is 130 degreeC or more, and glass transition temperature is 100 degrees C or less. A low Tg compound, the content of the low Tg compound in all non-luminescent materials is 10 to 70% by weight, and at least one of the non-luminescent materials is a material having a pyrimidine skeleton or a triazine skeleton It is providing a composition for forming a light emitting layer.

Description

An organic electroluminescent element containing a composition for forming a light emitting layer and the composition for forming a light emitting layer.

This invention relates to the composition for light emitting layer formation, and the organic electroluminescent element containing this composition for light emitting layer formation.

Organic electroluminescent devices have been actively developed as a technique for manufacturing light emitting devices such as displays and lighting in recent years, since they can emit light in various colors with a simple device configuration.

An organic electroluminescent element injects holes and electrons from an anode and a cathode, reaches each electric charge in a light emitting layer, and charges are recombined in this light emitting layer, and light emission is obtained. From this principle, improving the luminous efficiency by forming a light emitting layer using the light emitting layer forming composition containing not only a light emitting material but a charge transport material and making a charge remain in a light emitting layer is examined (refer patent document 1). ).

On the other hand, keeping the charge in the light emitting layer deteriorates the current-voltage characteristics of the organic electroluminescent element. In order to retain charge in one layer, it is usually performed by a method of trapping charge in the film to retain charge. According to these methods, it is possible to increase the luminous efficiency by keeping the charge in the light emitting layer, but at the same time, it leads to a deterioration of the current-voltage characteristic, that is, a rise in the driving voltage of the organic electroluminescent element. Since the power consumption increases when the drive voltage becomes high, the technique which reduces drive voltage reduction is proposed by making three or more types of the total number of the charge transport materials contained in the composition for light emitting layer formation, for example (patent document) 2).

However, when the kind of charge transport material is increased, it is considered that the method of improving the drive life which is an important characteristic of an organic electroluminescent element and the method of maintaining the storage stability at high temperature are still inadequate.

Japanese Patent Publication No. 2005-219513 International Publication WO2013 / 069338 Pamphlet

An object of this invention is to provide the organic electroluminescent element which has long drive life and was excellent in storage stability, and makes it a subject to provide the composition for light emitting layer formation suitable for it.

As a result of earnest examination by the present inventors about this subject, the drive lifetime is long and high temperature storage is carried out by using the compound whose glass transition temperature is higher than predetermined temperature, and the compound lower than predetermined temperature for the composition for light emitting layer formation. It was found that an organic electroluminescent element which hardly decreases the driving life is obtained afterwards.

This invention is achieved based on this knowledge, and makes the following a summary.

[1] A composition for forming a light emitting layer of an organic electroluminescent device, comprising a light emitting material, a non-light emitting material, and an organic solvent, wherein the non-light emitting material has a high Tg compound having a glass transition temperature of 130 ° C or higher and a glass transition temperature of 100 ° C. Including the low Tg compound below, the content rate of the said low Tg compound with respect to all the said non-luminescent materials is 8-70 mass%, At least 1 is a material which has a pyrimidine skeleton or a triazine skeleton among the said non-luminescent materials, Composition for forming a light emitting layer.

[2] The composition for forming a light emitting layer according to [1], wherein the content of all of the non-luminescent materials having a content ratio of 1.0% by mass or more with respect to the total amount of all the non-luminescent materials contained in the composition for forming a light emitting layer is 5000 or less.

[3] The composition for forming a light emitting layer according to [1] or [2], wherein a molecular weight of all the light emitting materials is 5000 or less.

[4] The light emitting layer according to any one of [1] to [3], wherein the material having a pyrimidine skeleton or a triazine skeleton contained in the composition for forming a light emitting layer is the high Tg compound and / or the low Tg compound. Formation composition.

[5] The composition for forming a light emitting layer according to any one of [1] to [4], wherein a weighted average glass transition temperature of all of the non-light emitting materials included in the composition for forming a light emitting layer is 100 ° C or more.

[6] The light emitting layer forming composition according to [1] to [5], wherein the low Tg compound is a compound in which monocyclic compounds are bonded to each other via a direct bond and / or a linking group.

[7] The light emitting layer forming composition according to any one of [1] to [6], in which the low Tg compound contains only a compound in which aromatic hydrocarbon monocyclic compounds are bonded to each other via a direct bond and / or a linking group.

[8] The light emitting layer forming composition according to any one of [1] to [7], wherein the low Tg compound is a compound represented by the following structural formula (A).

[In Formula (A), R <^1> -R <^15> respectively independently represents the monovalent compound which the hydrogen atom or the C6-C30 phenyl group or aromatic hydrocarbon monocyclic compound couple | bonded.]

[9] An organic electroluminescent device having a light emitting layer wet formed using the light emitting layer forming composition according to any one of [1] to [8].

According to the present invention, after high temperature storage, an organic electroluminescent element having a long driving life and high luminous efficiency can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows an example of embodiment of the organic electroluminescent element of this invention.
It is typical sectional drawing which shows another example of embodiment of the organic electroluminescent element of this invention.

EMBODIMENT OF THE INVENTION Although the embodiment of the composition for light emitting layer formation of this invention, the organic electroluminescent element, and its manufacturing method is demonstrated in detail below, the following description is an example (representative example) of embodiment of this invention, and this invention is the summary. Unless exceeded, these contents are not specific.

[Composition for Forming Light Emitting Layer]

The light emitting layer formation composition of this invention is used for formation of the light emitting layer of an organic electroluminescent element, Comprising a light emitting material, a non-light emitting material, and an organic solvent, As a non-light emitting material, it is glass transition temperature (it describes as Tg hereafter). It contains a high Tg compound whose 130 degreeC or more and a low Tg compound whose Tg is 100 degrees C or less.

(Luminescent material)

As the light emitting material, any known material used as a light emitting material of an organic electroluminescent element can be generally applied, and there is no particular limitation, and a light emitting material having a light emission efficiency with good luminous efficiency may be used. The light emitting material may be a fluorescent light emitting material or a phosphorescent light emitting material, but is preferably a phosphorescent light emitting material from the viewpoint of low internal quantum efficiency and low heat generation.

As the phosphorescent light emitting material, for example, a long-period periodic table (hereinafter, referred to as a "periodic periodic table" unless otherwise specified) shall be referred to as a long-period periodic table.) A metal selected from Groups 7 to 11 is included as the center metal. Werner complex, organometallic complex, etc. which are mentioned are mentioned.

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 metal selected from Groups 7 to 11 of the periodic table, iridium and platinum are more preferable.

As the ligand of the complex, an aryl group such as an arylpyridine ligand, a heteroarylpyridine ligand, an arylpyrazole ligand, a heteroarylpyrazole ligand, or a ligand having a pyridine, pyrazole, or phenanthroline bound to a heteroaryl group is preferable. In particular, a phenylpyridine ligand and a phenylpyrazole ligand are preferable.

Specific examples of the phosphorescent light emitting material include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum and tris (2-phenyl Pyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, etc. are mentioned.

In particular, as an organometallic complex of a phosphorescence emitting material, Preferably, the compound represented by following formula (I) is mentioned.

ML _(qj) L ' _j (I)

(In formula (I), M represents a metal and q represents the valence of the metal. In addition, L and L 'represent a bidentate ligand. J represents a number of 0, 1 or 2. L or L In the case where a plurality of '' s are present, a plurality of L's or L's may be the same or different, respectively.)

In formula (I), M represents arbitrary metals. Specific examples of preferred M include the metals described above as metals selected from Groups 7 to 11 of the periodic table.

In addition, in Formula (I), the bidentate ligand L represents a ligand having the following partial structure.

In the partial structure of L, ring A1 represents an aromatic ring group which may have a substituent. An aromatic hydrocarbon group may be sufficient as the aromatic ring group in this invention, and an aromatic heterocyclic group may be sufficient as it.

In addition, in the said L partial structure, ring A2 represents the nitrogen containing aromatic heterocyclic group which may have a substituent.

In addition, in Formula (I), as a bidentate ligand L ', the ligand shown below is mentioned.

As the organometallic complex of the phosphorescent light emitting material in the present invention, from the viewpoint of easily interacting with the non-light emitting material coexisting in the light emitting layer, the above formula (I) having a bidentate ligand is relatively three-dimensional and bulky. The compound represented is preferable.

Further, for example, blue may be used in combination with a fluorescent light emitting material and a phosphorescent light emitting material, such as a fluorescent light emitting material and green and a red phosphorescent light emitting material.

Moreover, in order to improve the solubility with respect to the solvent used for preparation of the composition for light emitting layer formation used when forming a light emitting layer by a wet film forming method, the symmetry and rigidity of the molecule | numerator of a light emitting material is reduced, or an alkyl group etc. It is preferable to introduce lipophilic substituents.

Any 1 type may be used for a luminescent material, and may use 2 or more types together by arbitrary combinations and a ratio.

The molecular weight of the light emitting material in the present invention is preferably 5000 or less, more preferably 4000 or less, and particularly preferably 3000 or less. Moreover, the molecular weight of the light emitting material in this invention is 400 or more normally, Preferably it is 600 or more, More preferably, it is 800 or more, Especially preferably, it is 1000 or more. By this molecular weight range, it is thought that a light emitting layer with high luminous efficiency can be obtained by mixing uniformly with a non-light-emitting material, without light-emitting material condensing.

The molecular weight of the light emitting material is high in Tg, melting point, decomposition temperature, etc., and is excellent in heat resistance of the light emitting material and the formed light emitting layer, and is accompanied by a decrease in film quality or thermal decomposition of the material due to gas generation, recrystallization and migration of molecules. A large thing is preferable at the point which an increase of an impurity concentration hardly arises. On the other hand, the molecular weight of a luminescent material is preferable in the point which is easy to refine | purify an organic compound, and is easy to melt | dissolve in a solvent.

(Non-luminescent material)

The non-luminescent material in this invention shall refer to all nonvolatile materials other than a luminescent material. A nonvolatile material is materials other than the organic solvent in the composition for light emitting layer formation, and means the thing of the material contained in a light emitting layer when forming a light emitting layer. As a non-light emitting material, although the high Tg compound and low Tg compound mentioned later are included at least, materials other than these may be included.

In the present invention, at least one of the non-luminescent materials is a material having a pyrimidine skeleton or a triazine skeleton from the viewpoint of durability to charge of the organic electroluminescent element, and at least one of the high Tg compound or the low Tg compound described later. It is preferable that it is a material which has a pyrimidine skeleton or a triazine skeleton. Furthermore, it is more preferable that any of the non-luminescent materials is a material having a triazine skeleton, and particularly preferably at least one of the high Tg compound or the low Tg compound described later is a material having a triazine skeleton, and the low Tg compound described later. It is most preferable that it is a material which has this triazine skeleton.

In the light emitting layer forming composition of the present invention, the molecular weight of each of the non-light emitting materials having a content of 1.0% by mass or more relative to the total amount of all the non-light emitting materials included in the light emitting layer forming composition is preferably 5000 or less, and more preferably. It is 4000 or less, Especially preferably, it is 3000 or less, Most preferably, it is 2000 or less, Usually 300 or more, Preferably it is 350 or more, More preferably, it is 400 or more.

<High Tg Compound>

The high Tg compound of this invention is a compound in which Tg shows 130 degreeC or more. As a high Tg compound, what is necessary is just to select suitably the thing whose Tg is 130 degreeC or more from the compound normally used for formation of the light emitting layer of an organic electroluminescent element, but it is preferable that it is a charge transport material normally contained in a light emitting layer as a high Tg compound.

As a compound whose Tg is 130 degreeC or more, it is preferable that it is a compound which couple | bonds tricyclic or more condensed ring structure with respect to the center skeleton excellent in charge transportability. In particular, it is preferable that it is a compound which has 2 or more of tricyclic or more condensed ring structures, and / or a compound which has at least one condensed ring of 5 or more rings. By these compounds, the rigidity of the molecule is increased, and the effect of suppressing the degree of molecular motion in response to heat is easily obtained.

Moreover, it is preferable from the point of charge transport property and the durability of a material that the tricyclic or more condensed ring and 5 or more rings condensed ring which a high Tg compound has have an aromatic hydrocarbon ring or an aromatic heterocycle.

Specific examples of the central skeleton having excellent charge transport properties include aromatic structure, aromatic amine structure, triarylamine structure, dibenzofuran structure, naphthalene structure, phenanthrene structure, phthalocyanine structure, porphyrin structure, thiophene structure, benzylphenyl structure, Fluorene structure, quinacridone structure, triphenylene structure, carbazole structure, pyrene structure, anthracene structure, phenanthroline structure, quinoline structure, pyridine structure, pyrimidine structure, triazine structure, oxadiazole structure or imidazole The structure etc. are mentioned.

Especially, the compound which has a pyridine structure, a pyrimidine structure, and a triazine structure is more preferable from a viewpoint of the material which is excellent in electron transport property and a structure is comparatively stable, and it is still more preferable that it is a compound which has a pyrimidine structure and a triazine structure. .

It is preferable that the high Tg compound in the present invention is a material having a structure excellent in electron transportability in that the light emitting material itself can suppress deterioration of the light emitting material due to transporting electrons and thus increase the driving life. Do.

Moreover, the compound which has a structure excellent in hole transportability is also preferable, and a carbazole structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure, or a pyrene structure is a hole transport property also in the center skeleton excellent in the said charge transportability. It is preferable as an excellent structure, and a carbazole structure, a dibenzofuran structure, or a triarylamine structure is more preferable.

It is preferable that the high Tg compound in the present invention is a material having a structure having excellent hole transporting properties in that the light emitting material itself can suppress deterioration of the light emitting material due to transporting holes and further increase the driving life. Do.

As described above, the high Tg compound of the present invention preferably has a tricyclic or more condensed ring structure, and is a compound having two or more tricyclic or more condensed ring structures and / or a compound having at least one condensed ring of five or more rings. More preferred. Specific examples of the tricyclic or more condensed ring structure include anthracene structure, phenanthrene structure, pyrene structure, chrysene structure, naphthacene structure, triphenylene structure, fluorene structure, benzofluorene structure, indenofluorene structure, An indolofluorene structure, a carbazole structure, an indenocarbazole structure, an indolocarbazole structure, a dibenzofuran structure, a dibenzothiophene structure, and the like. From the viewpoint of charge transportability and solubility, a phenanthrene structure, fluorene structure, indenofluorene structure, carbazole structure, indenocarbazole structure, indolocarbazole structure, dibenzofuran structure and dibenzothiophene structure At least one selected from the group is preferable, and a carbazole structure or an indolocarbazole structure is more preferable in view of durability to charge.

The molecular weight of the high Tg compound in this invention is 5000 or less normally, Preferably it is 4000 or less, More preferably, it is 3000 or less, Most preferably, it is 2000 or less. In addition, the molecular weight of the high Tg compound in this invention is 300 or more normally, Preferably it is 350 or more, More preferably, it is 400 or more.

It is preferable that the molecular weight of the high Tg compound is large in that the decrease in film quality due to gas generation, recrystallization, migration of molecules, etc. is unlikely to occur. On the other hand, the molecular weight of a high Tg compound is preferable in the point which is easy to refine | purify an organic compound, and is easy to melt | dissolve in a solvent.

If Tg of the high Tg compound in this invention is 130 degreeC or more, it is arbitrary, unless the effect of this invention is impaired remarkably. The Tg of the high Tg compound in the present invention is preferably 135 ° C or more, more preferably 140 ° C or more, from the viewpoint that the film at the time of high temperature storage is stabilized. In addition, since Tg of the high Tg compound in this invention has high solubility with respect to the organic solvent, it is 250 degrees C or less normally, Preferably it is 200 degrees C or less, More preferably, it is 180 degrees C or less, More preferably, it is 160 degreeC It is as follows.

For example, in the case of using an organic electroluminescent element for a vehicle-mounted display, if the vehicle is parked under summer salt, the vehicle-mounted display may exceed 80 ° C. Therefore, the vehicle-mounted display exceeds 100 ° C. Reliability in the high temperature storage test to be required is required. Therefore, the general high temperature storage test of an organic electroluminescent element is normally performed at 100 degreeC or more, and is about 120 degreeC high. In addition, the change in the film properties and morphology near Tg actually occurs gradually before and after Tg. As mentioned above, Tg of the high Tg compound in this invention is 130 degreeC or more which is temperature higher than a storage test. Moreover, higher Tg is more preferable from a viewpoint of suppressing the change of the film | membrane physical property and morphology in a long-term high temperature storage test more. On the other hand, the Tg of the high Tg compound is preferably low from the viewpoint of device solubility by solvent solubility and suppression of crystallization in the film.

Although at least 1 type of high Tg compound should just be included in the light emitting layer formation composition of this invention, it may be contained in multiple numbers.

<Low Tg compound>

The low Tg compound of this invention is a compound in which Tg shows 100 degrees C or less. As a low Tg compound, it is preferable that monocyclic compounds are compounds which couple | bonded through the direct bond and / or the coupling group. Although the said compound may have a substituent and this substituent is not specifically limited, It is preferable at the point which an alkyl group or an aralkyl group is excellent in solubility and storage stability of an ink.

Although it will not specifically limit, if it is an atom and a substituent which can be used as a material for organic electroluminescent elements normally as a coupling group, Specifically, as a bivalent coupling group, Oxygen atom, a sulfur atom, an alkylene group, a sulfo group, a carbonyl group; Nitrogen atom as a trivalent linking group; As a tetravalent coupling group, a silicon atom is preferable. Here, a linking group means that a monocyclic compound couple | bonds with all the bonding hands. In addition, these coupling groups may connect monocyclic compounds, or may connect the compound which monocyclic compounds couple | bonded through the direct bond. In addition, the monocyclic compound to connect at this time, or the compound which monocyclic compounds couple | bonded through the direct bond may be the same structure, or a different structure may be sufficient as it. For example, when a nitrogen atom is a coupling group and the compound which monocyclic compounds couple | bonded through the direct bond is an aryl group, it points to a triarylamine, and three substituents of a triarylamine may be same or different. As a linking group, a nitrogen atom or an alkylene group is more preferable at the point that the twist of an adjacent ring becomes larger, the planarity of a molecule is low, and it is hard to cause crystallization by molecular packing. In addition, from the viewpoint of durability to charge, a compound containing only direct bonds is more preferable.

As a low Tg compound, what is necessary is just to select suitably the thing which satisfy | fills the said conditions from the compound used for the light emitting layer formation of an organic electroluminescent element normally, Specifically as a low Tg material, monocyclic compounds mutually couple | bond directly and / or At least one selected from the group consisting of an aromatic structure, aromatic amine structure, thiophene structure, benzylphenyl structure, pyridine structure, pyrimidine structure, triazine structure, oxadiazole structure and imidazole structure The compound which has a structure of is preferable. Aromatic-hydrocarbon monocyclic compounds are compounds which couple | bonded through the direct bond and / or the coupling group, and the compound which has an aromatic structure, an aromatic amine structure, or the benzyl phenyl structure is more preferable at the point which is more excellent in charge transport property.

As a low Tg compound, since the planarity as a molecule | numerator is low and it is hard to cause crystallization by molecular packing, the compound which monocyclic compounds couple | bonded through the direct bond and / or the coupling group is preferable. On the other hand, the compound which aromatic hydrocarbon monocyclic compounds couple | bonded through the direct bond and / or the coupling group is more preferable at the point that the influence of a hydrogen bond is small, it is easy to keep a bond rotation, and the planarity of a molecule can be made low. Furthermore, it is preferable that the low Tg compound contained in the composition for light emitting layer formation of this invention contains only the compound which aromatic hydrocarbon monocyclic compounds couple | bonded directly, from the point which is excellent in durability to an electric charge.

In particular, as a low Tg compound which the aromatic hydrocarbon monocyclic compounds couple | bonded directly, the compound represented by following formula (A) is preferable.

In Formula (A), R <^1> -R <^15> respectively independently represents the monovalent compound which the hydrogen atom or the C6-C30 phenyl group or aromatic hydrocarbon monocyclic compound couple | bonded.

The low Tg compound which has a structure of Formula (A) is a structure with high durability with respect to electric charge, and is easy to make stability and molecular motion by heat etc. compatible. Moreover, since the structure of Formula (A) is a compound which only the monocyclic ring of aromatic hydrocarbon couple | bonded, it is easy to fill the clearance gap between high Tg compounds, and it is preferable. In addition, the structure of Formula (A) is preferable when the high Tg compound has a condensed ring structure of three or more rings or a condensed ring structure of five or more rings, since the gap between the high Tg compounds generated by the condensed ring is easily filled. Do.

Moreover, when the condensed ring contains an aromatic hydrocarbon ring or an aromatic heterocycle, the structure of Formula (A) becomes high in affinity with Formula (A) which is an aromatic hydrocarbon compound, and the state which filled the clearance gap between high Tg compounds is It is considered that it is more stable, and it is preferable.

Moreover, the preferable low Tg compound in this invention is a compound which monocyclic compounds couple | bonded through the direct bond and / or the coupling group. Among these, it is preferable that they are a pyridine type compound, a pyrimidine type compound, a triazine type compound, etc. which are materials which are excellent in electron transport property and a comparatively stable structure. By these compounds, it becomes possible to suppress the deterioration of the light emitting material due to the transport of electrons of the light emitting material itself and to prolong the driving life.

The low Tg compound in the present invention is a material having excellent electron transport properties and a relatively stable structure in that the light emitting material itself can suppress deterioration of the light emitting material due to electrons transport and thereby increase the driving life. It is preferable.

On the other hand, the low Tg compound in the present invention is a material having a structure having excellent hole transporting properties in that the light emitting material itself can suppress the deterioration of the light emitting material due to transporting holes and thus increase the driving life. It is preferable.

As a structure excellent in hole transportability, a dicycloalkylarylamine structure, a cycloalkyldiarylamine structure, and a triarylamine structure are preferable. Among them, the triarylamine structure is more preferable from the viewpoint of durability.

The molecular weight of the low Tg compound in this invention is 5000 or less normally, Preferably it is 4000 or less, More preferably, it is 3000 or less, Most preferably, it is 2000 or less. Moreover, the molecular weight of the low Tg compound in this invention is 300 or more normally, Preferably it is 350 or more, More preferably, it is 400 or more.

It is preferable that the molecular weight of the low Tg compound is large in that it is difficult to reduce the film quality due to gas generation, recrystallization, migration of molecules, or the like. On the other hand, the molecular weight of a low Tg compound is preferable in the point which is easy to refine | purify an organic compound, and is easy to melt | dissolve in a solvent.

The Tg of the low Tg compound in the present invention is arbitrary as long as it is 100 ° C. or lower unless the effects of the present invention are remarkably impaired. Tg of the low Tg compound in this invention becomes like this. Preferably it is 95 degrees C or less, More preferably, it is 90 degrees C or less. Moreover, Tg of the low Tg compound in this invention is 60 degreeC or more normally, Preferably it is 70 degreeC or more, More preferably, it is 80 degreeC or more, More preferably, it is 85 degreeC or more.

It is preferable that Tg of the low Tg compound in this invention is low from a viewpoint of the solubility with respect to a solvent, and element stability by suppression of crystallization in a film | membrane. On the other hand, the Tg of the low Tg compound is preferably high from the viewpoint of ensuring nonvolatileness, thermal stability in the device fabrication process and the storage of the device.

Although at least 1 type of low Tg compounds should just be contained in the light emitting layer formation composition of this invention, it may be contained in multiple numbers.

(Organic solvent)

It is preferable to form the light emitting layer formation composition of this invention as a light emitting layer using wet film-forming methods, such as an inkjet method. As an organic solvent used by this invention, if light emitting layer materials, such as a light emitting material and a non-light emitting material, melt | dissolve or disperse | distribute favorably, it will not specifically limit.

As solubility of an organic solvent, it is preferable to melt | dissolve a luminescent material, a non-luminescent material, etc. normally at 25 degreeC and 1 atmosphere, respectively 0.01 mass% or more normally, Preferably it is 0.05 mass% or more, More preferably, it is preferable to melt | dissolve 0.1 mass% or more. Do. Although the specific example of an organic solvent is given to the following, an organic solvent is not limited to these, unless the effect of this invention is impaired.

As an organic solvent, For example, Alkanes, such as n-decane, cyclohexane, ethylcyclohexane, decalin, bicyclohexane; Aromatic hydrocarbons such as toluene, xylene, methiylene, cyclohexylbenzene, tetramethylcyclohexanone and tetralin; Halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene and trichloro benzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phentol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2, Aromatic ethers such as 4-dimethylanisole and diphenyl ether; Aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate and n-butyl benzoate; Alicyclic ketones such as cyclohexanone, cyclooctanone and phencone; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); Etc. can be mentioned.

Among the above, preferably, they are at least one selected from the group consisting of alkanes and / or aromatic hydrocarbons, more preferably toluene, xylene and cyclohexylbenzene. These are non-polar, are less likely to be affected by moisture, and the material is easy to dissolve, making it easy to stably store the ink.

These organic solvents may be used individually by 1 type, and may use two or more types by arbitrary combinations and a ratio.

In addition, in order to obtain a more uniform film | membrane, it is preferable that an organic solvent evaporates at a suitable speed | rate from the liquid film immediately after film-forming. For this reason, the boiling point of an organic solvent is 80 degreeC or more normally, Preferably it is 100 degreeC or more, More preferably, it is 120 degreeC or more. The boiling point of the organic solvent is usually 270 ° C or lower, preferably 250 ° C or lower, and more preferably 230 ° C or lower.

(About composition ratio of composition for light emitting layer formation)

The light emitting layer formation composition of this invention may contain other components suitably as long as it contains the said high Tg compound and the low Tg compound as above-mentioned as a non-light emitting material. However, it is necessary that the content of the low Tg compound (hereinafter simply referred to as the content of the low Tg compound) of all the non-luminescent materials included in the composition for forming the light emitting layer is 8 to 70% by mass, and that it is 10 to 70% by mass. More preferred. The content rate of the low Tg compound is 8 mass% or more, 10 mass% or more is preferable, and 15 mass% or more is more preferable. Moreover, the content rate of a low Tg compound is 80 mass% or less, 70 mass% or less is preferable, 50 mass% or less is more preferable, 40 mass% or less is more preferable, 35 mass% or less is especially preferable.

It is preferable that the content rate of the low Tg compound is high in the solubility with respect to a solvent, the ink storage stability after melt | dissolution, crystallization of a light emitting layer hardly arise, and a light emitting surface becomes uniform and stable. On the other hand, it is preferable that the content rate of the low Tg compound is low in the point that the change of the morphology of the film | membrane in high temperature storage of an element does not occur easily.

10 mass% or more is preferable, as for the content rate of the high Tg compound with respect to all the non-luminescent materials contained in the light emitting layer formation composition hereafter (it is simply described as content rate of a high Tg compound), 15 mass% or more is more preferable, and also 90 mass% or less is preferable, and 70 mass% or less is more preferable.

Contrary to the low Tg compound, the content rate of the high Tg compound is low in terms of solubility in solvents, storage stability after dissolution, crystallization of the light emitting layer hardly occurs, and the light emitting surface is uniform and stable, and the high temperature of the device is preferable. High is preferable at the point which the change of the morphology of a film | membrane in preservation hardly occurs.

Moreover, 5 mass% or more is preferable, as for the content rate of the luminescent material in all the nonvolatile materials contained in the composition for light emitting layer formation, 10 mass% or more is more preferable, Furthermore, 40 mass% or less is preferable, and 30 mass % Is more preferable.

(The mechanism of action of the present invention)

By including a high Tg compound, the heat resistance of a film improves, and it is guessed that a uniform film can be formed at the time of film-forming by including a low Tg compound.

Since a high Tg compound is easy to crystallize at the time of film-forming, and is a rigid compound, since high Tg compounds are hard to be close in molecular level, it reduces the charge transport property of a film | membrane. However, if the low Tg compound is present, it is assumed that the low Tg compound is in the form of filling the gap between the rigid high Tg compounds, thereby suppressing crystallization of the high Tg compound and forming a uniform film.

When the composition containing the low Tg compound and the high Tg compound is wet formed, the low Tg compound and the high Tg compound are dried in a uniformly mixed state. That is, it is thought that the film | membrane which filled the space | interval of rigid high Tg compounds with a low Tg compound can be easily formed, and it becomes easy to form the uniform film | membrane which is excellent in transportability. In the conventional vacuum heating vapor deposition method, since materials are clustered and deposited, it is considered that a low Tg compound is difficult to fill a gap between high Tg compounds.

Moreover, in a film | membrane, since a low Tg compound exists between high Tg compounds, it is thought that the film | membrane with high heat resistance in which the crystallization of a high Tg compound was suppressed is determined.

In general, when only a low Tg compound is used for the organic electroluminescent element, heat resistance is insufficient, and therefore, it is considered that deterioration of the organic electroluminescent element is accelerated by high temperature storage or accelerated by energization driving. Surprisingly, in the present invention, by mixing the low Tg compound and the high Tg compound, an unexpected effect of improving the heat resistance of the organic EL device by the interaction of the low Tg compound and the high Tg compound was found. This is presumably because the thermal movement of the low Tg compound due to heat during high temperature storage and heat generation in the energization driving is suppressed by the high Tg compound present in the vicinity of the low Tg compound.

By including a low Tg compound, the solubility in an organic solvent can be improved, and the storage stability of a composition can be ensured, and crystallization in the film | membrane of an organic electroluminescent element can be suppressed, and the drive life in room temperature is improved. I can lengthen it. In addition, by including the high Tg compound, it is possible to suppress the change of the film properties and the morphology under the high temperature storage around 100 ° C., which is concerned by the low Tg compound, and to obtain a stable long driving life without changing after high temperature storage. .

The reason why the Tg of the high Tg compound is 130 ° C. or more is as described above.

Moreover, since the Tg of a low Tg compound is 100 degrees C or less, interaction with a high Tg compound is suppressed, and there exists a tendency for the effect of the crystallization suppression of a low Tg compound to be easy to be expressed. When there exists a difference of 30 degreeC or more like this invention, it is thought that the effect derived from each other Tg is fully expressed.

Although the difference in Tg of a high Tg compound and a low Tg compound is not specifically limited, 30 degreeC or more is preferable, 40 degreeC or more is more preferable, and 50 degreeC or more is more preferable. Moreover, 70 degrees C or less is preferable, and 65 degrees C or less is more preferable. The Tg difference becomes larger to some extent than the above lower limit, and the high Tg compound is less likely to be affected by the molecular motion of the low Tg compound, making the film morphology difficult to change even at high temperatures. Moreover, since it is below the said upper limit, it becomes easy to mix a high Tg compound and a low Tg compound more uniformly in a film | membrane.

The content rate of the low Tg compound is 8-70 mass% as mentioned above. It is 8 mass% or more, and there exists an influence which the intermolecular interaction of a high Tg compound has, and it is easy to suppress crystallization in a film | membrane and an organic solvent. Moreover, since it is 70 mass% or less, the change in the crystallinity at the time of high temperature storage resulting from a low Tg compound can be absorbed by the other less than 30 mass%, and the tendency which can suppress the morphology change of the whole film | membrane is have.

Any of the high Tg compound and the low Tg compound is a pyrimidine skeleton or a triazine skeleton having high electron transportability and excellent structural stability, so that the probability of electrons localizing on the light emitting material is low, and stable light emission can be obtained. Therefore, the effect of the long life can be sufficiently obtained.

If the low Tg compound is a compound in which monocyclic compounds are bonded to each other via a direct bond and / or a linking group, the planarity as a molecule is lowered, which makes it more difficult to cause crystallization by molecular packing. Therefore, the effect of the said crystallization suppression can be acquired further.

As for the molecular weight of each non-light emitting material whose content rate with respect to the total amount of all the non-light emitting materials contained in the composition for light emitting layer formation of this invention is 1.0 mass% or more, 5000 or less are preferable. The said molecular weight is in this range, and it is preferable to form into a film in the state which the most non-luminescent material mixed uniformly.

When there are few compounds of high molecular weight in a film | membrane, entanglement of a three-dimensional molecule | numerator is suppressed and a high Tg compound and a low Tg compound will become easy to mix uniformly. As a result, generation | occurrence | production of the micro area | region where low Tg compounds gathered is suppressed, and stability at the time of high temperature storage becomes easy to be obtained. In addition, a small region in which high Tg compounds are collected at the time of film formation is generated, and crystallization at the time of film formation is suppressed, so that a uniform film is easily obtained, and the characteristics of the organic EL device are improved.

In addition, the solubility of the compound in the solvent or the entanglement of the molecular chain in the solvent is suppressed by being below the upper limit of the molecular weight, so that impurities (that is, deterioration substances) are easily removed.

In this invention, it is preferable that it is 100 degreeC or more, and, as for the weighted average glass transition temperature of all the non-luminescent materials contained in the composition for light emitting layer formation, it is more preferable that it is 115 degreeC or more. Moreover, weighted average glass transition temperature becomes like this. Preferably it is 150 degrees C or less, More preferably, it is 145 degrees C or less. Since the weighted average glass transition temperature is 100 ° C. or more, the morphology of the film is less likely to change due to the influence of heat during high temperature storage or heat generated in the organic electroluminescent element during energization, that is, the driving life becomes longer. Moreover, when the weighted average glass transition temperature is 150 degrees C or less, the clearance gap between molecules becomes easy to fill up, and the charge transport property in a film | membrane, and the drive life improves.

(Other non-luminescent materials)

As a non-light-emitting material which the composition for light emitting layer formation of this invention may contain other than the said high Tg compound and low Tg compound, additives, such as a charge transport material and antioxidant, are mentioned.

<Third charge transport material>

The composition for light emitting layer formation of this invention may contain the charge transport material which does not belong to any of the said high Tg compound or the said low Tg compound. For convenience, this is called a third charge transport material. As the third charge transport material, a material having a skeleton excellent in charge transport property is preferable.

Specific examples of the skeleton having excellent charge transport properties include an aromatic structure, an aromatic amine structure, a triarylamine structure, a dibenzofuran structure, a naphthalene structure, a phenanthrene structure, a phthalocyanine structure, a porphyrin structure, a thiophene structure, a benzylphenyl structure, and a flu Orene structure, quinacridone structure, triphenylene structure, carbazole structure, pyrene structure, anthracene structure, phenanthroline structure, quinoline structure, pyridine structure, pyrimidine structure, triazine structure, oxadiazole structure, imidazole structure Etc. can be mentioned.

Among them, at least one selected from the group consisting of a compound having a pyridine structure, a pyrimidine structure and a triazine structure, from the viewpoint of excellent material for electron transport and a relatively stable structure, a pyrimidine structure, and / Or a compound having a triazine structure.

The third charge transport material according to the present invention is a material having a structure having excellent electron transport properties in that the light emitting material itself can suppress deterioration of the light emitting material due to transporting electrons and thus increase the driving life. It is preferable.

Moreover, the compound which has a structure excellent in hole transportability is also preferable, and a carbazole structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure, or a pyrene structure is a hole transport property also in the center skeleton excellent in the said charge transportability. It is preferable as an excellent structure, and a carbazole structure, a dibenzofuran structure, or a triarylamine structure is more preferable.

The third charge transport material according to the present invention is a material having a structure having excellent hole transport properties in that the light emitting material itself can suppress deterioration of the light emitting material due to transporting holes and thus prolong the driving life. It is preferable.

The molecular weight of the third charge transport material in the present invention is arbitrary as long as the effect of the present invention is not impaired remarkably. The molecular weight of the 3rd charge transport material in this invention is 5000 or less normally, Preferably it is 4000 or less, More preferably, it is 3000 or less, Most preferably, it is 2000 or less. Moreover, the molecular weight of the 3rd charge transport material in this invention is 300 or more normally, Preferably it is 350 or more, More preferably, it is 400 or more.

It is preferable that the molecular weight of the third charge transport material is large, in that the decrease in film quality due to gas generation, recrystallization, migration of molecules, etc. is unlikely to occur. On the other hand, since the molecular weight of a 3rd charge transport material is easy to refine | purify an organic compound, and is easy to melt | dissolve in a solvent, it is preferable that it is small.

It is preferable that the composition for light emitting layer formation of this invention contains the 3rd charge transport material which does not belong to either the said high Tg compound or the said low Tg compound. The third charge transport material may be two or more kinds.

[Formation of Light-Emitting Layer]

The light emitting layer which concerns on this invention is formed by the wet-film-forming method using the light emitting layer formation composition of this invention mentioned above.

(Method for Forming Light Emitting Layer by Wet Film Formation)

In the present invention, the wet film forming method is a film forming method, that is, a method of applying a wet film forming method as a coating method, and means a method of drying the coated film to form a film. As the coating method, for example, the spin coating method, the dip coating method, the die coating method, the bar coating method, the blade coating method, the roll coating method, the spray coating method, the capillary coating method, the inkjet method, the nozzle printing method, the screen A printing method, the gravure printing method, the flexographic printing method, etc. are mentioned. Among these film forming methods, the spin coating method, the spray coating method, the ink jet method, the nozzle printing method and the like are preferable.

When forming a light emitting layer by the wet film-forming method, the light emitting layer formation composition prepared by melt | dissolving the above-mentioned light emitting material, a high Tg compound, a low Tg compound, and other material used as needed in an appropriate organic solvent is normally used, It forms by forming into a film and removing an organic solvent by heating, pressure reduction, etc.

As a method of removing the organic solvent, heating or reduced pressure can be used. As a heating means used in a heating method, a clean oven, a hot plate, etc. are preferable at the point which heat | fever is uniformly given to the whole film | membrane.

The heating temperature in the heating step is arbitrary as long as the effect of the present invention is not impaired remarkably, but the higher temperature is preferable in terms of shortening the drying time, and the lower temperature is preferable in terms of less damage to the material. .

An upper limit is 250 degrees C or less normally, Preferably it is 200 degrees C or less, More preferably, it is 150 degrees C or less. The lower limit is usually 30 ° C or higher, preferably 50 ° C or higher, and more preferably 80 ° C or higher. By the temperature below an upper limit, decomposition | disassembly and crystallization of the charge transport material or phosphorescence emitting material used normally can be suppressed. Moreover, the removal time of a solvent can be shortened because it is more than the said minimum. The heating time in a heating process is suitably determined according to the solvent boiling point and vapor pressure in the light emitting layer formation composition, the heat resistance of a material, and heating conditions.

[Measurement Method of Glass Transition Temperature (Tg)]

The measuring method of Tg in this invention is as follows.

Using the differential scanning calorimeter, it measured by the temperature increase rate of 10 degree-C / min to room temperature 25 degreeC-300 degreeC, and made the center temperature of the inflection point which shows the glass transition in the DSC curve obtained by it as Tg. Measurement conditions are shown below.

<Glass transition point temperature measurement conditions>

Differential Scanning Calorimeter (DSC): Shimadzu DTA-50

Sample volume: about 4 mg

Sample vessel: aluminum pan

Atmosphere: atmospheric

Temperature range: room temperature 25 ° C. to 300 ° C.

Temperature rise rate: 10 ℃ / min

The weighted average glass transition temperature is the sum of Tg of each non-luminescent material obtained by the said method and multiplying the weight ratio of each non-luminescent material with respect to all the non-luminescent materials.

[Layer Structure and Manufacturing Method of Organic Electroluminescent Device]

EMBODIMENT OF THE INVENTION Below, an example of embodiment, such as a general layer structure of the organic electroluminescent element which concerns on this invention, its manufacturing method, etc. is demonstrated with reference to FIG.

1 is a schematic view of a cross section showing a structural example of an organic electroluminescent element 10 according to the present invention, in which 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, and 5 is 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.

As the material to be applied to these structures, a known material can be applied, and there is no particular limitation, but typical materials and manufacturing methods for each layer are described below as an example. In addition, when citing a publication, a paper, etc., it is assumed that the content can be appropriately applied and applied within the scope of common sense of those skilled in the art.

(Substrate (1))

The board | substrate 1 becomes a support body of an organic electroluminescent element, Usually, a plate of quartz or glass, a metal plate, metal foil, a plastic film, a sheet, etc. are used. Among these, plates of transparent synthetic resins such as glass plates and polyesters, polymethacrylates, polycarbonates, and polysulfones are preferable. The substrate 1 is preferably made of a material having a high gas barrier property in that deterioration of the organic electroluminescent element due to outside air is unlikely to occur. For this reason, especially when using a material with low gas barrier property, such as a synthetic resin board | substrate, it is preferable to provide a dense silicon oxide film etc. in at least one surface of the board | substrate 1, and to raise gas barrier property.

(Anode (2))

The anode 2 is responsible for injecting holes into the layer on the light emitting layer side. The anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium or platinum; Metal oxides such as oxides of indium and / or tin; Metal halides such as copper iodide; Carbon black and conductive polymers such as poly (3-methylthiophene), polypyrrole, and polyaniline. The formation of the anode 2 is usually carried out by a dry method such as sputtering or vacuum evaporation. In addition, in the case of forming the anode 2 using metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, and the like, it is dispersed in a suitable binder resin solution and formed on a substrate. It can also form by apply | coating to. In the case of the conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or the anode 2 can be formed by applying the conductive polymer on the substrate (Appl. Phys. Lett., Vol. 60, 2711). Page, 1992).

The anode 2 is usually a single layer structure, but may be a laminated structure as appropriate. In the case where the anode 2 has a laminated structure, another conductive material may be laminated on the anode of the first layer. What is necessary is just to determine the thickness of the anode 2 according to transparency, material, etc. which are required. When especially high transparency is needed, the thickness which the transmittance | permeability of visible light becomes 60% or more is preferable, and the thickness which becomes 80% or more is more preferable. The thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. On the other hand, when transparency is unnecessary, the thickness of the anode 2 may be arbitrarily set according to the required strength or the like, and in this case, the anode 2 may have the same thickness as the substrate 1.

In the case of forming the film on the surface of the anode 2, before the film formation, treatment with ultraviolet light + ozone, oxygen plasma, argon plasma, and the like removes impurities on the anode, and adjusts the ionization potential to adjust hole injection properties. It is preferable to improve.

(Hole injection layer 3)

The layer which is responsible for transporting holes from the anode side to the light emitting layer side is usually called a hole injection transport layer or a hole transport layer. And when there are two or more layers which play a function of transporting a hole from an anode side to a light emitting layer side, the layer closer to the anode side may be called the hole injection layer 3. The hole injection layer 3 is preferably used in that it enhances the function of transporting holes from the anode to the light emitting layer side. When using the hole injection layer 3, the hole injection layer 3 is normally formed on an anode.

The film thickness of the hole injection layer 3 is usually 1 nm or more, preferably 5 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

The method of forming the hole injection layer 3 may be a vacuum vapor deposition method or a wet film formation method. It is preferable to form by the wet film-forming method from the point which is excellent in film-forming property.

It is preferable that the hole injection layer 3 contains a hole transporting compound, and more preferably contain a hole transporting compound and an electron accepting compound. Furthermore, it is preferable to include a cationic radical compound in a hole injection layer, and it is especially preferable to contain a cationic radical compound and a hole transporting compound.

<Hole transporting compound>

The composition for forming a hole injection layer usually contains a hole transporting compound serving as the hole injection layer 3. In addition, in the case of a wet film-forming method, a solvent is also contained normally. It is preferable that the composition for forming a hole injection layer has high hole transporting properties and can transport the injected holes efficiently. For this reason, it is preferable that hole mobility is large and it is hard to generate | occur | produce the impurity which becomes a trap at the time of manufacture, use, etc. In addition, it is desirable to have excellent stability, small ionization potential, and high transparency to visible light. In particular, when the hole injection layer 3 is in contact with the light emitting layer 5, it is preferable not to extinguish the light emission from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 so as not to reduce the light emission efficiency. .

As the hole transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable from the viewpoint of the charge injection barrier from the anode 2 to the hole injection layer 3. Examples of the hole-transporting compound include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzyl phenyl compounds, compounds in which tertiary amines are linked with fluorene groups, and hydrazone compounds And silazane-based compounds, quinacridone-based compounds and the like.

Among the above-mentioned exemplary compounds, from the viewpoint of amorphousness and visible light transmission, an aromatic amine compound is preferable, and an aromatic tertiary amine compound is particularly preferable. Here, an aromatic tertiary amine compound is a compound which has an aromatic tertiary amine structure, and also includes the compound which has group derived from aromatic tertiary amine.

Although the kind of aromatic tertiary amine compound is not specifically limited, Since it is easy to obtain uniform luminescence by surface smoothing effect, the polymer compound (polymerization compound which a repeating unit carries out) a weight average molecular weight is 1000 or more and 1000000 or less. It is preferable to use. As a preferable example of an aromatic tertiary amine high molecular compound, the high molecular compound etc. which have a repeating unit represented by following formula (II) are mentioned.

(In Formula (II), Ar <^1> and Ar <^2> respectively independently represent the aromatic group which may have a substituent, or the heteroaromatic group which may have a substituent. Ar <^3> -Ar <^5> may each independently have a substituent. A heteroaromatic group which may have an aromatic group or a substituent is represented Y represents a linking group selected from the following group of linking groups In addition, in Ar ¹ to Ar ⁵ , two groups bonded to the same N atom are bonded to each other to form a ring; You may also

The linking group is shown below.

(In each said formula, Ar <^6> -Ar <^16> respectively independently represents the aromatic group which may have a substituent, or the heteroaromatic group which may have a substituent. R <^105> and R <^106> respectively independently represent a hydrogen atom or an arbitrary substituent Indicates.)

As the aromatic group and the heteroaromatic group of Ar ¹ to Ar ¹⁶ , a group derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, or a pyridine ring is preferable from the viewpoint of the solubility, heat resistance, and hole injection transport property of the polymer compound. , Group derived from a benzene ring or a naphthalene ring is more preferable.

As a specific example of the aromatic tertiary amine high molecular compound which has a repeating unit represented by Formula (II), the thing described in the international publication 2005/089024 pamphlet, etc. are mentioned.

<Electron-accepting compound>

Since the conductivity of the hole injection layer 3 can be improved in the hole injection layer 3 by oxidation of the hole transport compound, it is preferable that the hole injection layer 3 contains an electron accepting compound.

As the electron-accepting compound, a compound having an oxidizing power and having the ability to accept one electron from the hole-transporting compound described above is preferable, specifically, a compound having an electron affinity of 4 eV or more is preferable, and a compound having an electron affinity of 5 eV or more is more preferable. Do.

Examples of such an electron-accepting compound include one selected from the group consisting of triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, salts of arylamines and Lewis acids, or 2 or more types of compounds, etc. are mentioned. Specifically, substituted onium salts of organic groups such as 4-isopropyl-4'-methyldiphenyl iodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (international publication 2005 / 089024 pamphlet); High-valent inorganic compounds such as iron chloride (III) (JP-A-11-251067) and ammonium peroxodisulfate; Cyano compounds such as tetracyanoethylene; Aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365); Fullerene derivative, iodine, etc. are mentioned.

<Cation Radical Compound>

As a cationic radical compound, the ionic compound containing the cationic radical which is a chemical species removed 1 electron from the hole transport compound, and a large anion is preferable. However, when a cationic radical is derived from a hole-transporting high molecular compound, a cationic radical becomes a structure remove | eliminated one electron from the repeating unit of a high molecular compound.

As a cationic radical, it is preferable that it is a chemical species removed 1 electron from the compound mentioned above as a hole transport compound. It is suitable from the viewpoint of amorphousness, transmittance of visible light, heat resistance, solubility, etc. that it is the chemical species removed 1 electron from the compound suitable as a hole-transport compound.

Here, a cationic radical compound can be produced by mixing the above-mentioned hole transporting compound and an electron accepting compound. That is, by mixing the hole-transporting compound and the electron-accepting compound described above, electrons move from the hole-transporting compound to the electron-accepting compound, and a cationic ion compound containing the cationic radical and the large anion of the hole-transporting compound is produced.

Cationic radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, Vol. 12, p. 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, vol. 94, p. 7716), It is also produced by oxidative polymerization (dehydrogenation polymerization).

Oxidation polymerization here means oxidizing a monomer chemically or electrochemically using peroxodisulfate etc. in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is oxidized to polymerize, and a cationic radical removed by one electron from the repeating unit of the polymer, wherein the anion derived from the acidic solution is used as the anion.

<Formation of Hole Injection Layer 3 by Wet Film Forming Method>

In the case of forming the hole injection layer 3 by the wet film formation method, a composition for forming a film (for hole injection layer formation) is usually prepared by mixing a material used as the hole injection layer 3 with a soluble solvent (solvent for a hole injection layer). The composition is prepared, and the composition for forming a hole injection layer is applied by forming a film on a layer corresponding to the lower layer of the hole injection layer 3 (typically, the anode 2), and forming a film.

The concentration of the hole-transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired. However, the lower one is preferable from the point of uniformity of film thickness, and on the other hand, the hole injection layer In the point which is hard to produce a defect in (3), the higher one is preferable. It is preferable that it is specifically 0.01 mass% or more, It is more preferable that it is 0.1 mass% or more, It is especially preferable that it is 0.5 mass% or more, On the other hand, It is preferable that it is 70 mass% or less, It is more preferable that it is 60 mass% or less, It is especially preferable that it is 50 mass% or less.

As a solvent, an ether solvent, an ester solvent, an aromatic hydrocarbon solvent, an amide solvent, etc. are mentioned, for example.

Examples of the ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA), and 1,2-dimethoxybenzene and 1,3-dimethoxy. And aromatic ethers such as benzene, anisole, phentol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole. .

Examples of the ester solvents include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.

Examples of the aromatic hydrocarbon solvents include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, methylnaphthalene, and the like. Can be. Examples of the amide solvents include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.

In addition to these, dimethyl sulfoxide and the like can also be used.

Formation of the hole injection layer 3 by the wet film-forming method is usually carried out after preparation of the composition for forming a hole injection layer, and this is a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2). It is performed by coating into a film and drying on it. The hole injection layer 3 usually dries the coating film by heating, reduced pressure drying, or the like after film formation.

<Formation of hole injection layer 3 by vacuum deposition method>

In the case of forming the hole injection layer 3 by the vacuum deposition method, one or two or more kinds of constituent materials (hole transporting compound, electron-accepting compound, and the like) of the hole injection layer 3 are usually placed in a vacuum container. Put them in the installed crucible (when using two or more kinds of materials, usually put them in separate crucibles), exhaust the inside of the vacuum container to about 10 ^-4 kPa with a vacuum pump, and then heat the crucible (two or more kinds). In the case of using a material, each crucible is usually heated) and evaporated while controlling the evaporation amount of the material in the crucible (when using two or more kinds of materials, the evaporation is usually performed while independently controlling the evaporation amount). A hole injecting layer 3 is formed on the anode on the substrate facing away from the substrate. In the case where two or more kinds of materials are used, the hole injection layer 3 may be formed by placing these mixtures in a crucible, and heating and evaporating them.

The degree of vacuum during deposition is not limited so long as the effects of the present invention are not impaired significantly, but is usually at least 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) and 9.0 × 10 ⁻⁶ Torr (12.0 × 10 ⁻⁴⁾ Iii) below. The vapor deposition rate is not limited as long as the effect of the present invention is not impaired remarkably, but is usually 0.1 ms / sec or more and 5.0 ms / sec or less. Although the film-forming temperature at the time of vapor deposition is not limited, unless the effect of this invention is impaired remarkably, Preferably it is carried out at 10 degreeC or more and 50 degrees C or less.

(Hole transport layer (4))

The hole transport layer 4 is a layer responsible for transporting holes from the anode side to the light emitting layer side. Although the hole transport layer 4 is not an essential layer in the organic electroluminescent device of the present invention, it is preferable to use this layer in that it enhances the function of transporting holes from the anode 2 to the light emitting layer 5. . When the hole transport layer 4 is used, the hole transport layer 4 is usually formed between the anode 2 and the light emitting layer 5. In addition, when the hole injection layer 3 mentioned above exists, it is formed between the hole injection layer 3 and the light emitting layer 5.

The film thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and on the other hand, is usually 300 nm or less, preferably 100 nm or less.

The method of forming the hole transport layer 4 may be a vacuum vapor deposition method or a wet film formation method. It is preferable to form by the wet film-forming method from the point which is excellent in film-forming property.

The hole transport layer 4 usually contains a hole transport compound to be the hole transport layer 4. As a hole-transporting compound contained in the hole-transporting layer 4, 2 or more tertiary amines especially represented by 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are included. And starburst structures such as aromatic diamines in which two or more condensed aromatic rings are substituted with nitrogen atoms (JP-A-5-234681) and 4,4 ', 4 "-tris (1-naphthylphenylamino) triphenylamine Aromatic amine compounds (J. Lumin., Vol. 72-74, 985, 1997), aromatic amine compounds containing tetramers of triphenylamine (Chem. Commun., Page 2175, 1996), 2, Spiro compounds such as 2 ', 7,7'-tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), 4,4'- Carbazole derivatives such as N, N'-dicarbazole biphenyl, and the like, for example, polyvinylcarbazole, polyvinyltriphenylamine (JP-A-7-53953) and tetraphenylbenzidine Containing polyarylene ether sulfone, which can be preferably used also (. Polym Adv. Tech., 7, pp. 33, 1996).

<Formation of Hole Transport Layer 4 by Wet Film Forming Method>

In the case of forming the hole transporting layer 4 by the wet film forming method, the composition for forming a hole transporting layer is generally used in place of the composition for forming the hole injection layer in the same manner as the case of forming the hole injection layer 3 described above by the wet film forming method. To form.

When forming the hole transport layer 4 by the wet film-forming method, the composition for hole transport layer formation usually contains a solvent further. The solvent used for the composition for hole transport layer formation can use the solvent similar to the solvent used for the composition for hole injection layer formation mentioned above.

The concentration of the hole transporting compound in the composition for forming a hole transporting layer can be in the same range as the concentration of the hole transporting compound in the composition for forming a hole injection layer.

Formation by the wet film-forming method of the hole transport layer 4 can be performed similarly to the film-forming method of the hole injection layer 3 mentioned above.

<Formation of Hole Transport Layer 4 by Vacuum Evaporation Method>

Also in the case of forming the hole transport layer 4 by the vacuum deposition method, the composition for forming the hole transport layer is generally used in place of the composition for forming the hole injection layer in the same manner as in the case of forming the hole injection layer 3 described above by the vacuum deposition method. Can be used. Film-forming conditions, such as the vacuum degree, vapor deposition rate, and temperature at the time of vapor deposition, can be formed on the conditions similar to the vacuum vapor deposition of the said hole injection layer 3 at the time.

(Light emitting layer 5)

The light emitting layer 5 is a layer which is excited by the recombination of the holes injected from the anode 2 and the electrons injected from the cathode 9 when an electric field is applied between the pair of electrodes, and is a layer responsible for emitting light. The light emitting layer 5 is a layer formed between the anode 2 and the cathode 9, and the light emitting layer 5 is the hole injection layer 3 and the cathode when the hole injection layer 3 is provided on the anode 2. It is formed between (9), and when there is a hole transport layer 4 on the anode 2, it is formed between the hole transport layer 4 and the cathode (9).

The film thickness of the light emitting layer 5 is arbitrary as long as it does not significantly impair the effects of the present invention. However, the film thickness is preferably thick in that defects are unlikely to occur in the film, and preferably thin in view of low driving voltage. Do. Specifically, it is usually in the range of 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less.

In addition, you may provide two or more light emitting layers in an organic electroluminescent element.

The detail of the light emitting layer 5 is as above-mentioned.

When forming light emitting layers other than the light emitting layer which concerns on this invention by the vacuum vapor deposition method, it forms as follows.

<Method of Forming Light Emitting Layer by Vacuum Vapor Deposition Method>

In the case of forming a light emitting layer by a vacuum deposition method, the normal, of the light-emitting layer constituent material (the above-described light emitting material, a non-light-emitting material, etc.), placed into separate crucibles, respectively installed in the vacuum container, the inside of the vacuum vessel by a vacuum pump 10 ^- After exhausting to about ⁴ kPa, each crucible is heated to evaporate while controlling the evaporation amount of the material in each crucible independently, thereby forming a light emitting layer on a substrate or the like placed on each crucible. In addition, a mixture of the constituent materials may be placed in one crucible, and heated and evaporated to form a light emitting layer.

The degree of vacuum during deposition is not limited so long as the effects of the present invention are not impaired significantly, but is usually at least 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) and 9.0 × 10 ⁻⁶ Torr (12.0 × 10 ⁻⁴⁾ Iii) below. The deposition rate is not limited as long as the effects of the present invention are not impaired remarkably, but is usually 0.1 ms / sec or more and 5.0 ms / sec or less. Although the film-forming temperature at the time of vapor deposition is not limited, unless the effect of this invention is impaired remarkably, Preferably it is carried out at 10 degreeC or more and 50 degrees C or less.

(Hole blocking layer (6))

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

The hole blocking layer 6 serves to prevent the holes 9 moving from the anode 2 from reaching the cathode 9, and efficiently transports electrons injected from the cathode 9 in the direction of the light emitting layer 5. Has a role to play. The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, large energy gap (difference between HOMO and LUMO), and high excitation triplet level (T1). It can be mentioned.

As a material of the hole-blocking layer 6 which satisfy | fills these conditions, bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato), for example Mixed ligand complex such as (triphenylsilanolato) aluminum, bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinolato) aluminum binuclear metal Styryl compounds such as metal complexes such as complexes and distyryl biphenyl derivatives (JP-A-11-242996) and 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) Triazole derivatives such as -1,2,4-triazole (JP-A-7-41759) and phenanthroline derivatives such as vasocuproin (JP-A-10-79297) Can be. Moreover, the compound which has at least 1 the pyridine ring by which 2nd, 4th, and 6th positions substituted in the international publication 2005/022962 pamphlet is also preferable as a material of the hole-blocking layer 6.

There is no restriction | limiting in the formation method of the hole blocking layer 6, It can form in the same way as the formation method of the light emitting layer 5 mentioned above.

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. to be.

(Electron transport layer 7)

The electron transport layer 7 is provided between the light emitting layer 5 and the electron injection layer 8 for the purpose of further improving the current efficiency of the device.

The electron transport layer 7 is a compound capable of efficiently injecting electrons from the cathode 9 or the electron injection layer 8 between the electrodes provided with an electric field and efficiently transporting the electrons in the direction of the light emitting layer 5. Is formed.

As the electron transporting compound used for the electron transporting layer 7, a compound having a high electron injection efficiency from the cathode 9 or the electron injection layer 8 and capable of transporting the injected electrons efficiently is preferable. 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, and oxa. Diazole derivatives, distyryl biphenyl derivatives, silol derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzenes 5645948), quinoxaline compound (Japanese Patent Laid-Open Publication No. Hei 6-207169), phenanthroline derivative (Japanese Patent Laid-Open Publication No. Hei 5-331459), 2-t-butyl-9,10-N, N ' -Dicyano anthranimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, etc. are mentioned.

The film thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and on the other hand, is usually 300 nm or less, preferably 100 nm or less.

The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a wet film formation method or a vacuum deposition method in the same manner as above. Usually, the vacuum vapor deposition method is used.

(Electron injection layer 8)

The electron injection layer 8 may be provided between the cathode 9 and the electron transport layer 7 or the light emitting layer 5. The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the electron transport layer 7 or the light emitting layer 5.

In order to perform electron injection efficiently, the material which forms the electron injection layer 8 is preferably a metal having a low work function. As an example, alkali metals, such as sodium and cesium, and alkaline-earth metals, such as barium and calcium, are used. As for the film thickness, 0.1 nm or more and 5 nm or less are preferable normally.

Furthermore, alkali metals, such as sodium, potassium, cesium, lithium, and rubidium, are dope to the organic electron transport material represented by metal complexes, such as nitrogen-containing heterocyclic compounds, such as vasophenanthroline, and aluminum complex of 8-hydroxyquinoline. (Described in Japanese Patent Application Laid-open No. Hei 10-270171, Japanese Patent Application Laid-Open No. 2002-100478, Japanese Patent Application Laid-Open No. 2002-100482, etc.) can also improve electron injection and transport properties, thereby achieving excellent film quality. It is preferable because it becomes.

The film thickness is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 8 is formed by laminating on the light emitting layer 5 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 in the case of the light emitting layer 5 described above.

(Cathode (9))

The cathode 9 refers to a role of injecting electrons into a layer (electron injection layer 8 or light emitting layer 5, etc.) on the light emitting layer side. As the material of the cathode 9, it is possible to use a material used for the anode 2, but in performing electron injection efficiently, it is preferable to use a metal having a low work function, for example, tin, Metals such as magnesium, indium, calcium, aluminum, silver, or alloys thereof are used. As a specific example, alloy electrodes of low work function, such as a magnesium silver alloy, a magnesium indium alloy, and an aluminum lithium alloy, etc. are mentioned, for example.

In view of the stability of the device, it is preferable to stack a metal layer having a high work function on the cathode 9 and stable to the atmosphere, and to protect the cathode 9 containing a metal of low work function. As a metal to laminate | stack, metals, such as aluminum, silver, copper, nickel, chromium, gold, and platinum, are mentioned, for example.

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

(Other layers)

The organic electroluminescent element of this invention may have another layer, unless the effect of this invention is impaired remarkably. That is, you may have the other arbitrary layers mentioned above between the anode 2 and the cathode 9.

<Other device configurations>

It is also possible to laminate the structure opposite to the above description, that is, in order of a cathode, an electron injection layer, a light emitting layer, a hole injection layer, and an anode on a substrate.

Example

Next, although an Example demonstrates this invention further more concretely, this invention is not limited to the following Example description, unless the summary is exceeded.

(Example 1)

The organic electroluminescent element of the structure shown in FIG. 1 was produced.

<Anode>

Forming an indium tin oxide (ITO) transparent conductive film with a thickness of 70 nm on a substrate 1 made of glass (sputter film formation product, sheet resistance 15Ω) is patterned on a 2 mm wide stripe by conventional photolithography techniques. Thus, the anode 2 was formed. The substrate 1 (ITO substrate) on which the anode 2 was formed was washed in the order of ultrasonic washing with pure water and washing with water with pure water, followed by drying with nitrogen blow, and finally ultraviolet ozone washing.

<Hole injection layer>

Next, the hole injection layer 3 was formed by the wet film-forming method as follows.

As a hole-transporting compound, 4-isopropyl-4'-methyldiphenyl iodonium tetrakis is 2.0 mass% and a high molecular weight compound (weight average molecular weight 52000) which has a repeating structure represented by following formula (P1) is an electron-accepting compound. A composition for forming a hole injection layer in which (pentafluorophenyl) borate was dissolved in 0.4% by mass of ethyl benzoate was prepared, and the composition for forming a hole injection layer was formed on the ITO substrate by spin coating. By heating and drying, the hole injection layer 3 with a film thickness of 32 nm was formed. Film-forming conditions were as follows.

<Film forming condition>

Spin coat condition: Spinner rotational speed 500rpm / 2s → 2100rpm / 30s

Heat-drying condition: left in a clean oven at 230 ° C for 1 hour

<Hole transport layer>

Next, the hole transport layer 4 was formed on the formed hole injection layer 3 by the wet film-forming method as follows.

As a crosslinking | crosslinked compound, the high molecular compound (HT-1) (weight average molecular weight: 53000) of the repeating structure shown below was made into the solvent, melt | dissolved in cyclohexylbenzene, and the composition for hole transport layer formation was prepared. The concentration of the high molecular compound (HT-1) in the composition for forming a hole transport layer was 2.0% by mass.

The composition for forming a hole transport layer is formed on the hole injection layer 3 by spin coating and further heated and dried to crosslink the cured polymer compound (HT-1), thereby curing a hole having a thickness of 21 nm. The transport layer 4 was formed. Film-forming conditions were as follows.

<Film forming condition>

Spin coat condition: Spinner rotational speed 500rpm / 2s → 2900rpm / 120s

Heat-drying condition: left on hot plate at 230 ° C. for 1 hour

<Light emitting layer>

Subsequently, the light emitting layer 5 was formed on the formed hole transport layer 4 as follows. Compounds (HH-1), (HH-2), (H-1), (LH-1) and (D-1) shown below are mixed in a mass ratio of 35: 20: 35: 10: 15, The light emitting layer formation composition which melt | dissolved in xylene was prepared so that this mixture might be 3.45 mass%, and this light emitting layer formation composition was formed into a film on the said hole transport layer 4 by the spin coat method in nitrogen atmosphere, and also heat-dried. And the light emitting layer 5 having a thickness of 59 nm was formed. Film-forming conditions were as follows.

<Film forming condition>

Spin coat condition: Spinner speed 500rpm / 2 sec → 1700rpm / 120 sec

Heat drying condition: 20 minutes on a hot plate at 120 ℃

In addition, Tg of the said compound (HH-1), (HH-2), (H-1), and (LH-1) is 159 degreeC, 142 degreeC, 113 degreeC, and 90 degreeC, respectively, and is a non-luminescent material, In this regard, (HH-1) and (HH-2) correspond to the high Tg compound of the present invention, and (LH-1) corresponds to the low Tg compound of the present invention. (LH-1), which is a low Tg compound, has a pyrimidine skeleton, and monocyclic compounds are bonded to each other via a direct bond and / or a linking group.

The molecular weight of each compound is (HH-1), (HH-2), (H-1), (LH-1) and (D-1) are 968.4, 866.3, 636.3, 841.4 and 1363.9, respectively. 5000 or less. Moreover, the content rate of the low Tg compound with respect to the total amount of all the non-luminescent materials contained in the composition for light emitting layer formation was 10 mass%, and the weighted average glass transition temperature of all the non-luminescent materials was 133 degreeC.

<Hole blocking layer>

Subsequently, the compound (HB-1) shown below was formed as a hole blocking layer 6 on the formed light emitting layer 5 so that it might become 10 nm in thickness by the vacuum evaporation method.

<Electron transport layer>

Subsequently, on the formed hole blocking layer 6, the compound (ET-1) shown below was formed as a film thickness of 20 nm as the electron carrying layer 7 by the vacuum evaporation method.

<Electron injection layer, cathode>

Here, an element which has been deposited up to the electron transport layer 7 is once taken out into the atmosphere in the vacuum deposition apparatus, and has a 2 mm-wide striped shadow having a shape orthogonal to the ITO stripe as an anode as a mask for cathode deposition. The mask was brought into close contact with the element and placed in a separate vacuum deposition apparatus, and lithium fluoride (LiF) was deposited as an electron injection layer 8 with a thickness of 0.5 nm and then the cathode 9 by a vacuum deposition method similar to the electron transport layer 7. ) Were laminated so as to have a film thickness of 80.0 nm.

<Sealing>

Subsequently, in order to prevent the element from deteriorating with moisture in the air or the like during storage, the sealing treatment was performed by the method described below.

In the nitrogen glove box connected to the vacuum vapor deposition apparatus, the photocurable resin was apply | coated with the width of about 1 mm to the outer peripheral part of the 23 mm x 23 mm size glass plate, and the moisture getter sheet was installed in the center part. The board | substrate which completed cathode formation on this was bonded together so that the vaporized surface might face the desiccant sheet. Then, ultraviolet light was irradiated only to the area | region to which the photocurable resin was apply | coated, and the resin was hardened. This obtained the organic electroluminescent element which has the light emitting area part of a 2 mm x 2 mm size.

(Example 2)

In Example 1, compounds (HH-2), (LH-1), (LH-2), (H-1) and (D-1) as non-light-emitting materials and light-emitting materials included in the light-emitting layer-forming composition. ) Was prepared in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 15: 15: 15: 55: 15. In addition, compound (LH-2) is a compound which has a structure shown below, Tg was 87 degreeC and molecular weight was 762.3. Moreover, the content rate of the low Tg compound with respect to the total amount of all the non-luminescent materials contained in the composition for light emitting layer formation was 30 mass%, and the weighted average glass transition temperature of all the non-luminescent materials was 110 degreeC.

(Example 3)

In Example 1, compounds (HH-1), (H-2), (H-3), (LH-1) and (D-1) as non-light-emitting materials and light-emitting materials included in the light-emitting layer-forming composition. ) Was prepared in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 35: 15: 35: 15: 15. In addition, compound (H-2) and (H-3) are compounds which have a structure shown below, Tg was 129 degreeC and 109 degreeC, respectively, and molecular weight was 791.3 and 1157.5, respectively. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the light-emitting layer-forming composition was 15% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 127 ° C.

(Example 4)

In Example 1, compounds (HH-1), (LH-1) and (D-1) are mixed in a mass ratio of 70:30:15 as the non-light-emitting material and the light-emitting material included in the composition for forming a light-emitting layer. The organic electroluminescent element was produced similarly to Example 1 except having changed to what was made. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the light-emitting layer-forming composition was 30% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 138 ° C.

(Example 5)

In Example 1, (HH-1), (H-2), (LH-1), and (D-1) as non-light-emitting materials and light-emitting materials included in the light-emitting layer-forming composition, 70:15: An organic electroluminescent element was produced in the same manner as in Example 1, except that the mixture was mixed at a mass ratio of 15:15. The content rate of the low Tg compound was 15 mass% with respect to the total amount of all the non-luminescent materials contained in the composition for emitting layer formation, and the weighted average glass transition temperature of all the non-luminescent materials was 144 ° C.

(Example 6)

In Example 1, (HH-1), (H-3), (LH-1), and (D-1) as the non-light-emitting material and the light-emitting material included in the light-emitting layer-forming composition, 35:35: An organic electroluminescent element was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 30:15. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the light-emitting layer-forming composition was 30% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 121 ° C.

(Comparative Example 1)

In Example 1, (LH-1), (LH-2), (H-3) and (D-1) as the non-light-emitting material and the light-emitting material included in the light-emitting layer-forming composition, 30:35: An organic electroluminescent element was produced in the same manner as in Example 1 except that the mixture was mixed at a mass ratio of 35:15. The weighted average glass transition temperature of all the non-luminescent materials was 96 ° C.

(Comparative Example 2)

In Example 1, (HH-1), (HH-2), and (D-1) were mixed at a mass ratio of 70:30:15 as the non-light-emitting material and the light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 1 except having changed to the thing. The weighted average glass transition temperature of all the non-luminescent materials was 154 ° C.

<Evaluation of driving life of organic electroluminescent element>

After storing each organic electroluminescent element obtained in Examples 1-6 and Comparative Examples 1 and 2 for 72 hours in a 100 degreeC thermostat, it was driven by 15 mA / cm <2>, and 15% when converted into luminance 7000 cd / m <2>. The attenuation life (LT85) was calculated. And the comparative value (henceforth a "heating LT85" hereafter) when LT85 of Comparative Example 2 in which LT85 was long was 1 in the comparative example was calculated | required. Table 1 shows the composition ratio of the light emitting layer forming composition of each Example and the comparative example, and the evaluation result of the drive life.

(Example 7)

The organic electroluminescent element of the structure shown in FIG. 2 was produced.

<Light emitting layer>

The non-light-emitting material and the light-emitting material which are formed from the anode to the hole transport layer 4 and included in the light-emitting layer-forming composition as in Example 1, are (HH-3), (H-1), (LH-2) and ( A light emitting layer was formed in the same manner as in Example 1 except that D-1) was mixed with a mass ratio of 35: 35: 30: 15. In addition, compound (HH-3) is a compound which has a structure shown below, Tg was 132 degreeC and molecular weight was 868.1. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the composition for forming the light-emitting layer was 30% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 112 ° C.

<Electron transport layer>

Subsequently, the mixture which mixed the compound ET-2 and compound 1 shown below by the mass ratio of 2: 3 as the electron carrying layer 7 by the vacuum evaporation method was formed on the formed light emitting layer 5 so that it might become a film thickness of 20 nm. In addition, unlike Example 1, the hole blocking layer 6 was not formed.

<Cathode, sealing>

Subsequently, aluminum was laminated as the cathode 9 so as to have a film thickness of 80.0 nm, and then sealing was performed in the same manner as in Example 1. In addition, unlike Example 1, the electron injection layer 8 was not formed.

(Example 8)

In Example 7, Compounds (HH-1), (LH-3) and (D-1) were mixed in a mass ratio of 70:30:15 as a non-light-emitting material and a light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 7 except having changed to the thing. In addition, compound (LH-3) is a compound which has a structure shown below, Tg was 95 degreeC and molecular weight was 586.2. Moreover, the content rate of the low Tg compound with respect to the total amount of all the non-luminescent materials contained in the composition for light emitting layer formation was 30 mass%, and the weighted average glass transition temperature of all the non-luminescent materials was 140 degreeC.

(Example 9)

In Example 7, Compounds (HH-1), (LH-1), (LH-3), and (D-1) were used as non-luminescent materials and luminescent materials included in the light-emitting layer-forming composition, 70:15: The organic electroluminescent element was produced like Example 7 except having changed into the thing mixed by the mass ratio of 15:15. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the composition for forming a light emitting layer was 30% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 139 ° C.

(Example 10)

In Example 7, compounds (HH-1), (LH-1) and (D-1) were mixed in a mass ratio of 70:30:15 as a non-light-emitting material and a light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 7 except having changed to the thing. The content rate of the low Tg compound with respect to the total amount of all the non-light-emitting materials contained in the light-emitting layer-forming composition was 30% by mass, and the weighted average glass transition temperature of all the non-light-emitting materials was 138 ° C.

(Comparative Example 3)

In Example 7, Compounds (HH-1), (LH-4) and (D-1) were mixed in a mass ratio of 70:30:15 as a non-light-emitting material and a light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 7 except having changed to the thing. In addition, compound (LH-4) is a compound which has a structure shown below, Tg was 95 degreeC and molecular weight was 930.2. In addition, the weighted average glass transition temperature of all the non-luminescent materials was 140 degreeC.

(Comparative Example 4)

In Example 7, Compounds (HH-1), (LH-5) and (D-1) were mixed in a weight ratio of 70:30:15 as a non-light-emitting material and a light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 7 except having changed to the thing. In addition, compound (LH-5) is a compound which has a structure shown below, Tg was 86 degreeC and molecular weight was 612.8. In addition, the weighted average glass transition temperature of all the non-luminescent materials was 137 degreeC.

(Comparative Example 5)

In Example 7, compounds (HH-1), (LH-1) and (D-1) were mixed in a mass ratio of 95: 5: 15 as a non-light-emitting material and a light-emitting material included in the light-emitting layer-forming composition. The organic electroluminescent element was produced like Example 7 except having changed to the thing. In addition, the weighted average glass transition temperature of all the non-luminescent materials was 156 degreeC.

<Evaluation of driving life of organic electroluminescent element>

After storing each organic electroluminescent element obtained in Examples 7-10 and Comparative Examples 3-5 for 72 hours in a 100 degreeC thermostat, it was driven by 15 mA / cm <2>, and converted into luminance of 7000 cd / m <2> by 15%. The attenuation life (LT85) was calculated. And "LT85 after heating" was calculated | required as a relative value in the case where LT85 of the comparative example 5 which LT85 was longest was 1 in the comparative example. Table 2 shows the composition ratios of the light emitting layer forming compositions and the evaluation results of the drive life of the respective examples and comparative examples.

In Examples 1 to 6, which include a high Tg compound and a low Tg compound as the non-luminescent material, in Table 1, Comparative Example 1 and Comparative Example 2 containing only either the high Tg compound or the low Tg compound as the non-luminescent material On the other hand, LT85 is large and the voltage is also low even after heating.

In Table 2, LT85 is large in Examples 7-10 which contain the material which has a pyrimidine skeleton or a triazine skeleton as a non-luminescent material, and whose content rate of a low Tg compound is a specific range. On the other hand, in the comparative examples 3 and 4 which do not include both the material having a pyrimidine skeleton and the material having a triazine skeleton as non-luminescent materials, LT85 after heating is small. In addition, although the material which has a pyrimidine frame | skeleton or a triazine frame | skeleton is included as a non-light emitting material, the comparative example 5 which the content rate of a low Tg compound deviates from a specific range has the high voltage after heating.

As mentioned above, it turns out that Examples 1-10 are the outstanding organic electroluminescent element even after heating, and the high characteristic is acquired even after heating.

INDUSTRIAL APPLICABILITY The present invention is a light emitting layer-forming composition of an organic electroluminescent element, and is used in various fields in which an organic electroluminescent element is used, for example, a light source utilizing characteristics as a flat panel display (for example, for OA computers or wall-mounted televisions) or surface light emitting bodies. (For example, it can be used suitably in the field | area, such as a light source of a copy machine, a backlight light source of a liquid crystal display, or a measuring instrument), a display panel, a beacon, an illuminating device.

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
10: organic electroluminescent element

Claims (9)

A composition for forming a light emitting layer of an organic electroluminescent device, comprising a light emitting material, a non-light emitting material, and an organic solvent,
The non-luminescent material includes a high Tg compound having a glass transition temperature of 130 ° C. or higher and a low Tg compound having a glass transition temperature of 100 ° C. or less,
The content rate of the said low Tg compound with respect to all the said non-luminescent materials is 8-70 mass%,
At least one of the non-luminescent materials is a composition for forming a light emitting layer, which is a material having a pyrimidine skeleton or a triazine skeleton. The composition for forming a light emitting layer according to claim 1, wherein the molecular weight of each non-luminescent material having a content ratio of 1.0% by mass or more with respect to the total amount of all the non-light emitting materials contained in the composition for forming a light emitting layer is 5000 or less. The light emitting layer formation composition of Claim 1 or 2 whose molecular weight of all the said light emitting materials is 5000 or less. The light emitting layer formation in any one of Claims 1-3 whose material which has a pyrimidine skeleton or a triazine skeleton contained in the said composition for light emitting layer formation is the said high Tg compound and / or the said low Tg compound. Composition The light emitting layer forming composition according to any one of claims 1 to 4, wherein the weighted average glass transition temperature of all of the non-light emitting materials included in the light emitting layer forming composition is 100 ° C or more. The composition for forming a light emitting layer according to any one of claims 1 to 5, wherein the low Tg compound is a compound in which monocyclic compounds are bonded to each other via a direct bond and / or a linking group. The composition for forming a light emitting layer according to any one of claims 1 to 6, wherein the low Tg compound includes only a compound in which aromatic hydrocarbon monocyclic compounds are bonded to each other via a direct bond and / or a linking group. The light emitting layer forming composition according to any one of claims 1 to 7, wherein the low Tg compound is a compound represented by the following structural formula (A).

[In Formula (A), R <^1> -R <^15> respectively independently represents the monovalent compound which the hydrogen atom or the C6-C30 phenyl group or aromatic hydrocarbon monocyclic compound couple | bonded.] The organic electroluminescent element which has a light emitting layer wet-formed using the light emitting layer formation composition of any one of Claims 1-8.

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