WO2017221802A1 - Ink composition for organic light-emitting elements, and organic light-emitting element production method using same - Google Patents

Abstract

The purpose of the present invention is to provide an ink composition for organic light-emitting elements, which, when a compound having a pyrene skeleton and/or a compound having an anthracene skeleton is used as a host organic material, exhibits excellent inkjet discharge stability and is capable of achieving high emission efficiency. Provided is an ink composition for organic light-emitting elements, which comprises: a light-emitting host material containing a compound having a pyrene skeleton and/or a compound having an anthracene skeleton; and a solvent having a vapor pressure of 5 mmHg or less, wherein the three-dimensional distance (Ra) represented by formula (a) is 8 or less (in the formula, dD_host, dP_host, and dH_host represent a dispersion term, polarization term, and hydrogen bond term in the Hansen solubility parameter of the light-emitting host material, respectively; and dD_solvent, dP_solvent, and dH_solvent represent a dispersion term, polarization term, and hydrogen bond term in the Hansen solubility parameter of the solvent, respectively.)

Description

INK COMPOSITION FOR ORGANIC LIGHT EMITTING ELEMENT AND METHOD FOR PRODUCING ORGANIC LIGHT EMITTING ELEMENT USING THE SAME

The present invention relates to an ink composition for an organic light emitting device and a method for producing an organic light emitting device using the same.

Organic light emitting elements usually include an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode. When an electric field is applied to the organic light emitting device, holes are injected from the anode into the hole transport layer, electrons are injected from the cathode into the electron transport layer, and then holes and electrons are injected into the light emitting layer. In the light emitting layer, the injected holes and electrons are recombined, and the light emitting material in the light emitting layer emits light by the energy generated at this time. In some cases, the organic light emitting device does not have a hole transport layer and / or an electron transport layer. Moreover, other layers, such as a positive hole injection layer and an electron injection layer, may be included.

Organic light-emitting elements are suitable and are being put into practical use from the standpoint of display performance such as high visibility and low viewing angle dependence, as well as the ability to reduce the weight and thickness of displays. However, since there is still a demand for improvement in power consumption, research for further improvement in luminous efficiency is ongoing.

For example, Patent Document 1 describes an invention relating to a pyrene derivative represented by a predetermined chemical formula. Patent Document 1 describes that an organic EL element having high luminous efficiency can be produced by using the pyrene derivative.

Note that Patent Document 1 describes that when an organic EL element is produced using the pyrene derivative, the organic compound layer or the light emitting layer can be formed by vapor deposition or wet.

Patent Document 2 describes an invention related to an anthracene derivative represented by a predetermined chemical formula. Patent Document 2 describes that the use of the anthracene derivative can increase the light emission efficiency and extend the light emission lifetime.

In addition, it is described that the anthracene derivative described in Patent Document 2 may be used as a light emitting host material or a light emitting guest material.

Further, in Patent Document 2, although the formation method of the light emitting layer or the like is not clearly described, in the examples, it is described that the light emitting layer is formed by vapor-depositing an anthracene derivative.

International Publication No. 2011/0777690 JP 2006-306732 A

In recent years, from the viewpoints of high-definition patterning and high material utilization efficiency, it has been studied to form each layer constituting the organic light-emitting element by a wet film forming method, particularly an ink jet method.

However, when a light emitting layer or the like is formed by an ink jet method using a compound having a pyrene skeleton or a compound having an anthracene skeleton as described in Patent Documents 1 and 2, the ink jet ejection stability is not sufficient, and the light emission is high. It has been found that efficiency may not be obtained.

Therefore, the present invention provides an ink composition for an organic light emitting device that is excellent in inkjet ejection stability and can realize high light emission efficiency when at least one of a compound having a pyrene skeleton and a compound having an anthracene skeleton is used as an organic host material. The purpose is to provide goods.

The present inventors have conducted intensive research to solve the above problems. As a result, with respect to a compound having a pyrene skeleton and / or a compound having an anthracene skeleton, the above problem can be solved by controlling the solubility and solvent vapor pressure of the compound in the ink composition for an organic light emitting device. As a result, the present invention has been completed.

That is, the present invention relates to an ink composition for an organic light-emitting device comprising a light-emitting host material containing at least one of a compound having a pyrene skeleton and a compound having an anthracene skeleton, and one or more solvents having a vapor pressure of 5 mmHg or less. Related to things. At this time, the three-dimensional coordinate distance (Ra) of the Hansen solubility parameter represented by the following formula (a) is 8 or less.

In the above formula, dD _host , dP _host , and dH _host are respectively a dispersion term, a polarization term, and a hydrogen bond term of the Hansen solubility parameter of the light emitting host material, and dD _solvent , dP _solvent , and dH _solvent are These are the dispersion term, polarization term, and hydrogen bond term of the Hansen solubility parameter of the solvent.

According to the present invention, it is possible to obtain an ink composition for an organic light emitting device that is excellent in inkjet discharge stability and can realize high light emission efficiency.

It is a fragmentary sectional view which shows typically the process of forming a coating film by the inkjet method.

Hereinafter, embodiments for carrying out the present invention will be described in detail.

<Ink composition for organic light emitting device>
The ink composition for an organic light emitting device according to this embodiment includes a light emitting host material and a solvent. In addition, a light emitting dopant material, an additive, and the like may be further included as necessary. In this specification, “emission” includes emission by fluorescence and emission by phosphorescence.

According to the above-described ink composition for an organic light-emitting element, an ink composition for an organic light-emitting element that is excellent in inkjet ejection stability and can realize high light emission efficiency can be obtained. The reason for this is not necessarily clear, but is presumed to be due to the following mechanism.

That is, the light-emitting host material used in the present invention had good characteristics in an organic light-emitting device formed by vapor deposition. However, when an attempt is made to form a film by the inkjet method using the light-emitting host material used in the present invention, if the three-dimensional coordinate distance (Ra) of the Hansen solubility parameter exceeds 8, the compatibility of the solvent with the light-emitting host material Insufficient amount may cause aggregation of the light emitting host material in the ink composition for an organic light emitting device. For this reason, the light emitting host material is deposited in the vicinity of the ink jet nozzle, and the straightness of the liquid droplets deteriorates, thereby impairing the ink jet ejection stability. Furthermore, since the droplets that have landed on the support are further promoted to agglomerate during drying, the luminous efficiency can be reduced.

Also, when the vapor pressure of the solvent is 5 mmHg or more, the ink is dried in the vicinity of the ink jet nozzle, and the same problem as in the case of insufficient compatibility occurs.

On the other hand, the ink composition for an organic light emitting device according to the present invention has one or more kinds having a three-dimensional coordinate distance (Ra) of the Hansen solubility parameter of the light emitting host material and the solvent of 8 or less and a vapor pressure of 5 mmHg or less. Select a solvent. Thereby, compatibility is improved and aggregation of the luminescent host material is suppressed. That is, the inkjet discharge stability and the light emission efficiency can be improved. In addition, the above-mentioned mechanism is a thing guessed to the last, and even if it is a case where the effect of this invention is acquired by another mechanism, it is contained in the technical scope of this invention.

[Light emitting host material]
The light emitting host material usually has a function of transporting holes and electrons injected into the light emitting layer.

The light-emitting host material according to this embodiment includes at least one of a compound having a pyrene skeleton and a compound having an anthracene skeleton.

Specific examples of the compound having a pyrene skeleton and an anthracene skeleton as the light-emitting host material are not particularly limited, but include compounds represented by the following chemical formulas (1) and (2).

In this case, in the chemical formulas (1) and (2), A ₁ and A ₂ are each independently an alkyl group which may have a substituent, an alkenyl group which may have a substituent, An alkynyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an aryl group which may have a substituent, a substitution Represents a heteroaryl group which may have a group. At this time, in the chemical formulas (1) and (2), A ₁ and A ₂ are represented at any bond position except for Ar ₁ to Ar ₆ described later of the condensed polycycle constituting the pyrene skeleton or anthracene skeleton. It means that they may be combined.

Ar ₁ to Ar ₆ each independently represents a hydrogen atom, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent.

l is an integer of 0 to 8. When l is 2 or more, A ₁ may be the same or different.

m is an integer of 0 to 8. When m is 2 or more, A ₂ may be the same or different.

The alkyl group in the present invention is not particularly limited, but is methyl group, ethyl group, propyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl. Having 1 to 20 carbon atoms such as a group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, etc. Straight chain alkyl group; branched alkyl group having 3 to 20 carbon atoms such as isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group; cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclo Examples thereof include cyclic alkyl groups having 3 to 20 carbon atoms such as an octyl group. Of these, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, and a cyclic alkyl group having 3 to 10 carbon atoms are preferable, and a methyl group, an ethyl group, A propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, cyclopentyl group, cyclohexyl group, and cycloheptyl group are more preferable.

The alkenyl group in the present invention is not particularly limited, but vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, decenyl group, dodecenyl group, tetradecenyl group, hexadecenyl group, octadecenyl group, etc. Straight chain alkenyl group having 1 to 60 carbon atoms; branched chain alkenyl group having 4 to 60 carbon atoms such as methylpentenyl group; 3 to 60 carbon atoms such as cyclohexenyl group, cycloheptenyl group, and 4-methylcyclohexene group And cyclic alkenyl groups. Of these, a straight chain alkenyl group having 2 to 50 carbon atoms, a branched alkenyl group having 4 to 50 carbon atoms, and a cyclic alkenyl group having 3 to 50 carbon atoms are preferable, and 2 to 30 carbon atoms are preferable. Of these, a straight-chain alkenyl group, a branched alkenyl group having 4 to 30 carbon atoms, and a cyclic alkenyl group having 3 to 30 carbon atoms are more preferable.

The alkynyl group in the present invention is not particularly limited, but ethenyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 1-pentenyl group, 1-hexenyl group, 1-heptenyl group, 1-octenyl group 1-nonenyl group, 1-decenyl group, 1-undecenyl group, 1-dodecenyl group, 1-tridecenyl group, 1-tetradecenyl group, 1-pentadecenyl group, 1-hexadecenyl group, 1-heptadecenyl group, 1-octadecenyl group And alkynyl groups having 2 to 60 carbon atoms such as 1-nonadecenyl group. Of these, an alkynyl group having 2 to 50 carbon atoms is preferable, and an alkynyl group having 2 to 30 carbon atoms is more preferable.

The alkoxy group in the present invention is not particularly limited, and examples thereof include an alkoxy group having 1 to 60 carbon atoms such as a methoxy group, an ethoxy group, a propyl group, an isopropyloxy group, and a butoxy group. Among these, an alkoxy group having 1 to 20 carbon atoms is preferable, and an alkoxy group having 2 to 10 carbon atoms is more preferable.

The aryloxy group in the present invention is not particularly limited, and examples thereof include aryloxy groups having 6 to 60 carbon atoms such as a phenyloxymethyl group, a phenyloxyethoxy group, a naphthyloxymethyl group, and a naphthyloxyethoxy group. Of these, an aryloxy group having 6 to 30 carbon atoms is preferable, and an aryloxy group having 6 to 20 carbon atoms is more preferable.

The aryl group in the present invention is not particularly limited, but phenyl group, biphenyl group, terphenyl group, naphthyl group, anthryl group, phenanthryl group, pyrenyl group, chrysenyl group, fluorenyl group, 9,9-dimethylfluorenyl group, Examples thereof include aryl groups having 6 to 60 carbon atoms such as spirofluorenyl group and fluoranthenyl group. Of these, an aryl group having 6 to 50 carbon atoms is preferable, and an aryl group having 6 to 30 carbon atoms is more preferable.

The heteroaryl group in the present invention is not particularly limited, but thiophene, thiazole, furan, oxazole, pyran, pyrrole, imidazole, pyrazole, isothiazole, isoxazole, furazane, triazole, pyridine, pyrazine, pyrimidine, pyridazine, triazine, Benzothiophene, benzothiazole, thianthrene, isobenzofuran, benzoxazole, chromene, xanthene, phenoxathiin, indolizine, isoindole, indole, benzimidazole, indazole, benzotriazole, purine, quinolidine, isoquinoline, quinoline, phthalazine, naphthyridine, Quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, phenanthridine, acridine, Rimijin, phenanthroline, phenazine, phenothiazine, phenoxazine, or the like monovalent group formed by removing one hydrogen atom from dibenzodioxins and the like. Of these, a heteroaryl group having 5 to 50 carbon atoms is preferable, and a monovalent group formed by removing one hydrogen atom from carbazole, pyridine, pyrazine, pyrimidine, pyridazine, and triazine is more preferable.

The alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, aryl group and heteroaryl group in the present invention may have a substituent. Although it does not restrict | limit especially as said substituent, The above-mentioned alkyl group; The above-mentioned alkenyl group; The above-mentioned alkynyl group; The above-mentioned alkoxy group; The above-mentioned aryloxy group; The above-mentioned aryl group; Hydroxy group; thiol group; nitro group; sulfo group; cyano group; alkoxy group such as methoxy group, ethoxy group, propyl group, isopropyloxy group, butoxy group, phenyloxymethyl group, phenyloxyethoxy group; Examples thereof include alkylcarbonyl groups such as ethylcarbonyl group, propylcarbonyl group and butylcarbonyl group; and ester groups such as methyloxycarbonyl group, ethyloxycarbonyl group, propyloxycarbonyl group and butyloxycarbonyl group. Provided that when A ₁ and A ₂ and Ar ₁ to Ar ₆ are an alkyl group, an alkenyl group, an alkynyl group, or an alkoxy group, the substituent is an alkyl group, an alkenyl group, an alkynyl group, or an alkoxy group; Never become.

Specifically, when A ₁ and A ₂ are an alkyl group, an alkenyl group, or an alkynyl group, preferably an aryl group or a heteroaryl group can be a substituent. When A ₁ , A ₂ , Ar ₁ to Ar ₆ are an aryl group or a heteroaryl group, preferably an alkyl group, an alkenyl group, an alkynyl group, or a heteroaryl group can be a substituent.

A ₁ and A ₂ described above are preferably an aryl group having 6 to 50 carbon atoms which may have a substituent, and may have a phenyl group or a substituent which may have a substituent. It is more preferably a good naphthyl group, an anthryl group which may have a substituent, or a pyrenyl group which may have a substituent.

Ar ₁ to Ar ₆ are preferably an aryl group having 6 to 50 carbon atoms which may have a substituent, and may have a phenyl group or a substituent which may have a substituent. It is more preferably a good naphthyl group, an anthryl group which may have a substituent, or a pyrenyl group which may have a substituent.

The compound having a pyrene skeleton represented by the chemical formula (1) may include an anthracene skeleton in A ₁ , A ₂ , Ar ₁ to Ar ₆ , and the compound having an anthracene skeleton represented by the chemical formula (2) May contain a pyrene skeleton at A ₁ , A ₂ , and Ar ₁ to Ar ₆ . In such a case, it can be said that the light-emitting host material is a compound having an anthracene skeleton and a pyrene skeleton.

Hereinafter, specific examples of the pyrene compound and the anthracene compound of one embodiment of the present invention will be shown.

The above-mentioned luminescent host materials may be used alone or in combination of two or more.

The molecular weight of the light emitting host material according to the present invention is preferably 5000 g / mol or less, more preferably 2000 g / mol or less, and further preferably 300 to 2000 g / mol. The molecular weight of the luminescent host material is preferably 5000 g / mol or less because the luminescent host material can be easily dissolved in the solvent.

The light emitting host material may include other light emitting host materials in addition to the light emitting host materials represented by the above chemical formulas (1) and (2).

The other light-emitting host material is not particularly limited, but is a silane compound such as 1,4-bis (triphenylsilyl) benzene (UGH-2), 1,3-bis (triphenylsilyl) benzene; Phosphine compounds such as bis (diphenylphosphoryl) dibenzo [b, d] thiophene (PPT) and 2,7-bis (diphenylphosphoryl) -9,9′-spirofluorene (SPPO13); triphenylamine derivatives; benzimidazole derivatives Quinoline derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, triazine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like.

The content of the organic light emitting host material is preferably 0.1 to 50% by mass, and more preferably 0.1 to 10% by mass with respect to the total mass of the ink composition for organic light emitting elements. When the content of the organic light emitting host material is 0.1% by mass or more, it is preferable because a uniform film can be formed. On the other hand, it is preferable that the content of the organic light emitting host material is 10% by mass or less because precipitation of the organic light emitting host material can be suppressed.

[Luminescent dopant material]
Examples of luminescent dopant materials include aromatic amine derivatives, tetraphenylbutadiene derivatives, coumarin derivatives, bisstyrylarylene derivatives, oxadiazole derivatives, and tris (8-quinolinolato) aluminum complexes represented by the following formula (3) The aromatic amine derivative is more preferable. These luminescent dopant materials may be used alone or in combination.

In the above formula (3), Ar ₇ may have a substituent, such as benzene ring, naphthalene ring, fluorene ring, fluoranthene ring, phenanthrene ring, perylene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, etc. Represents a benzene ring or a group derived from a condensed polycycle formed by condensation of 2 to 6 benzene rings, or a styryl group. Ar ₈ to Ar ₁₁ each independently represents an aryl group which may have a substituent or a heteroaryl group which may have a substituent.

Among the aromatic amine derivatives represented by the above formula (3), Ar ₇ is preferably an anthracene ring, a phenanthrene ring, a pyrene ring, a group derived from a chrysene ring, or a styryl group, and is derived from a pyrene ring or a chrysene ring. It is more preferably a group or a styryl group.

The aromatic amine derivative in which Ar _{7 in the} above formula (3) is a group derived from a pyrene ring is preferably represented by the following formula (4), and as an aromatic amine derivative that is a group derived from a chrysene ring, It is preferable to be represented by the following formula (5).

As the aromatic amine derivative in which Ar _{7 in the} above formula (3) is a styryl group, those represented by the following formulas (6) and (7) are preferable.

At this time, in the chemical formulas (4) and (5), A ₃ and A ₄ are each independently an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkynyl group which may have a group, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an aryl group which may have a substituent, a substituent Represents a heteroaryl group which may have In this case, the notation of A ₃ and A ₄ in the chemical formulas (4) and (5) means that they may be bonded to any bonding position other than the position where the condensed polycyclic amine is bonded.

In the chemical formulas (4) to (7), Ar ₁₂ to Ar ₂₅ each independently represents an aryl group or a heteroaryl group which may have a substituent.

Specific examples of groups related to A ₃ and A ₄ , preferred carbon numbers, and substituents include those equivalent to those described for A ₁ and A ₂ among the specific examples shown in the description of the light emitting host material. Ar ₁₂ to Ar ₂₅ may be the same as those described for Ar ₁ to Ar ₆ and for the aryl group which may have a substituent and the heteroaryl group which may have a substituent. Can be mentioned.

x is an integer of 0-8. When x is 2 or more, A ₃ may be the same or different.

y is an integer of 0 to 8. When y is 2 or more, A ₄ may be the same or different.

Ar ₂₆ to Ar ₃₁ each independently represents an arylene group having 6 to 26 carbon atoms which may have a substituent, or a divalent heterocyclic group having a π-conjugated system. The arylene group is selected from divalent groups obtained by removing one aromatic hydrogen from the aryl group.

R ₁ to R ₈ each represents a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a substituent. An alkoxy group which may have, an aryloxy group which may have a substituent, an aryl group which may have a substituent, and a heteroaryl group which may have a substituent.

A is an integer of 0-2. When a is 2, the repeating unit may be the same or different.

b is an integer of 1 to 3. When b is 2 or 3, —N (Ar ₂₂ ) (Ar ₂₃ ) may be the same or different.

The alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, aryl group, heteroaryl group, and substituent are as described above.

Hereinafter, specific examples of the light-emitting dopant compound according to one embodiment will be shown.

The molecular weight of the luminescent dopant material is preferably 5000 g / mol or less, more preferably 2000 g / mol or less, and even more preferably 300 to 2000 g / mol. When the molecular weight of the light emitting host material is 5000 g / mol or less, it is preferable because the light emitting dopant material can be easily dissolved in the solvent.

The content of the light-emitting dopant material is preferably 0.1 to 50% by mass, and more preferably 0.1 to 10% by mass with respect to the mass of the light-emitting host material. It is preferable that the content of the light-emitting dopant material is 0.1% by mass or more because a uniform film can be formed. On the other hand, when the content of the light-emitting dopant material is 10% by mass or less, it is preferable because a decrease in light emission efficiency due to concentration quenching of the light-emitting dopant material can be suppressed.

[solvent]
In one embodiment, the solvent applied to the ink composition for an organic light-emitting device is not particularly limited, and a known solvent can be appropriately used depending on the layer to be formed. Specific examples include aromatic solvents, alkane solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, amide solvents, other solvents, and the like.

Examples of the aromatic solvent include cumene, tert-butylbenzene, pentylbenzene, hexylbenzene, cyclohexylbenzene, dodecylbenzene, diethylbenzene, mesitylene, diphenylmethane, cyclohexylbenzene, tetralin, naphthalene, 1-methylnaphthalene, 1-ethylnaphthalene, etc. Aromatic hydrocarbon solvents: Aromatic ester solvents such as phenyl acetate, phenyl propionate, ethyl benzoate, propyl benzoate, butyl benzoate, methyl 4-methylbenzoate; anisole, ethyl phenyl ether (phenetole), propylphenyl Aromatic ether solvents such as ether, butylphenyl ether, 4-methylanisole, 4-ethylanisole, dimethylanisole, dimethoxybenzene, diphenylether; Tofenon, propiophenone, butyl phenyl ketone, 1-phenyl-1-butanone, 1-phenyl-2-butanone, 4'-methylacetophenone, aromatic ketone solvents such as 4'-ethyl acetophenone.

Examples of the alkane solvent include nonane, decane, cyclononane, cyclodecane, decahydronaphthalene and the like.

Examples of the ester solvent include amyl acetate, hexyl acetate, methoxybutyl acetate, ethyl lactate, and butyl lactate.

Examples of the ether solvent include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and triethylene glycol dimethyl ether.

Examples of the ketone solvent include amyl methyl ketone, diisobutyl ketone, cyclohexanone, cycloheptanone, and isophorone.

Examples of the alcohol solvent include 1-hexanol, cyclohexanol, 1-heptanol, 2-ethylhexanol, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol and the like.

Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide and the like.

Examples of the other solvent include water, dimethyl sulfoxide, N-methyl-2-pyrrolidone, and γ-butyrolactone.

Of the above-mentioned solvents, it is preferable to include an aromatic solvent, more preferably to include an aromatic hydrocarbon, an aromatic ester, and an aromatic ketone. Diethylbenzene, cyclohexylbenzene, tetralin, 1-methylnaphthalene, 1-ethyl Naphthalene, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, methyl 4-methylbenzoate, 4'-methylacetophenone, 4'-ethylacetophenone, butylphenylketone, 1-phenyl-1-butanone, 1 More preferably, it includes -phenyl-2-butanone, and particularly preferably includes cyclohexylbenzene, tetralin, 1-methylnaphthalene, 1-ethylnaphthalene, butyl benzoate, 4'-methylacetophenone, and 4'-ethylacetophenone.

In addition, the above-mentioned solvent may be used independently or may be used in combination of 2 or more type.

The vapor pressure of the above-mentioned solvent is 5 mmHg or less, preferably 1 mmHg or less, more preferably 0.01 to 1 mmHg. When the vapor pressure exceeds 5 mmHg, the evaporation of the solvent in the drying process of the coating film after ink jet ejection becomes excessively fast, and aggregation of the compound having a pyrene skeleton or anthracene skeleton (light-emitting host material) may occur. In addition, the solvent may remain in the coating film even after drying, which may reduce the luminous efficiency and durability of the organic light emitting device. In the present specification, the value of “vapor pressure” means the vapor pressure of the solvent at 25 ° C. Vapor pressure measurement has various methods such as static method, boiling point method, isoteniscope, gas flow method, DSC method, etc., and the method applied depends on the properties of the sample, the sample amount, and the magnitude of the vapor pressure. In this specification, the “static method” having the widest application range was used, and the equilibrium vapor pressure at 25 ° C. was directly measured using a pressure gauge.

In addition, in the range which does not inhibit the effect of this invention, the solvent whose vapor pressure of a solvent is 5 mmHg or less and the solvent whose vapor pressure of a solvent is more than 5 mmHg can also be mixed.

The water solubility of the above-mentioned solvent at 20 ° C. is preferably 1% by weight or less, more preferably 0.9% by weight or less, and further preferably 0.7% by weight or less. When the solubility of water at 20 ° C. of the solvent is 1% or less, it is possible to prevent the occurrence of dark spots in the obtained organic light emitting device, and it is possible to prevent short circuit failure and durability deterioration. preferable.

The viscosity of the above-mentioned solvent is preferably 1.0 to 6.0 mPa · s, more preferably 1.2 to 5.0 mPa · s, and 1.5 to 4.5 mPa · s. Is particularly preferred. When the viscosity of the solvent is 1.0 mPa · s or more, the vapor pressure generally does not increase excessively from the viewpoint of molecular weight, and therefore, the nozzle of the inkjet head is less likely to be clogged. On the other hand, when the viscosity of the solvent is 6.0 mPa · s or less, the viscosity of the obtained ink composition does not become excessively high, so that it is easy to eject micro droplets of the ink composition for an organic light emitting element from the inkjet head. To preferred.

The surface tension of the solvent is preferably 20 to 45 mN / m, more preferably 25 to 43 mN / m, and particularly preferably 28 to 40 mN / m. When the surface tension of the ink composition is 20 mN / m or more, the wettability of the ink composition for an organic light emitting device on the nozzle surface is not excessively increased, and the ink composition for the organic light emitting device is attached around the nozzle. This is preferable because bending in the flying direction of the droplets is difficult to occur. On the other hand, when the surface tension of the ink composition is 45 mN / m or less, the shape of the meniscus at the nozzle tip is likely to be stable, and the discharge amount and discharge timing of the ink composition for an organic light emitting device can be easily controlled. To preferred.

In one embodiment of the present invention, when the ink composition for an organic light emitting device is used for forming a light emitting layer, a three-dimensional coordinate distance (Ra) represented by the following formula (a) relating to the relationship between the light emitting host material and the solvent. ) Is preferably 8 or less, more preferably 6 or less, and even more preferably 5 or less.

In the above formula, dD _host , dP _host , and dH _host are respectively a dispersion term, a polarization term, and a hydrogen bond term of the Hansen solubility parameter of the luminescent host material, and dD _solvent , dP _solvent , and dH _solvent are Hansen of the solvent, respectively. Dispersion term, polarization term, and hydrogen bond term of the solubility parameter.

When the three-dimensional coordinate distance (Ra) of the Hansen solubility parameter represented by the above formula (a) (hereinafter also referred to as “HSP-Ra”) is 8 or less, the light-emitting host material is dissolved in the solvent. It becomes suitable, and aggregation during drying hardly occurs.

The HSP-Ra can be an index for predicting the affinity between the light emitting host material and the solvent. The solubility characteristics of each substance are represented by three-dimensional coordinates having a dispersion term, a polarization term, and a hydrogen bond term as coordinate axes. From the difference in distance (HSP distance) between Hansen solubility parameter coordinates of the luminescent host material and the solvent. The solubility can be determined. At this time, the dispersion term represents van der Waals force, the polarization term represents dipole moment force, and the hydrogen bond term represents hydrogen bond force.

In order to make a specific determination of solubility, the solubility parameter of the luminescent host material and the three-dimensional values obtained by inputting the dispersion term, the polarization term, and the hydrogen bond term of the solubility parameter of the solvent into the above formula (a). A coordinate distance (Ra) is obtained. At this time, the closer the three-dimensional coordinate distance (Ra) is to 0, the better the compatibility between the light emitting host material and the solvent. In this specification, the value of “three-dimensional coordinate distance (Ra) (HSP−Ra)” is a value calculated using Hansen ’s solubility parameter calculation software HSPiP (ver. 4.1.07). It shall be.

The Hansen solubility parameters of the luminescent host material and the solvent are, specifically, the Hansen solubility parameter calculation software HSPiP, CAS and name, SMILLES notation (Simplicated Molecular input Entry syntax: The chemical structure of the molecule is an alphanumeric character of ASCII code. This can be obtained by inputting the notation of the character string structure without ambiguity. In the case of a substance whose Hansen solubility parameter is unknown, it can be calculated by various methods described in the e-book recorded in HSPiP, but an outline of two typical methods will be described below. As a first method, first, the solubility is examined using less than 20 solvents whose HSP values have been determined. All the three-dimensional points of the solvent in which the target substance is dissolved are encapsulated inside the sphere (this “sphere” is defined as Sphere in HSPiP), and the solvent points that do not dissolve are outside the sphere. Locate the sphere using the HSPiP Sphere search program. The center coordinate of the sphere can be defined as the Hansen solubility parameter of the target substance. As a second method, the calculation can be performed by inputting the SMILLES notation of the target substance into a program using a neural network method called Y-MB of HSPiP. In addition, when the molecule of the luminescent host material becomes larger, it may have a plurality of Hansen solubility parameters. In that case, the three-dimensional coordinate distance with the solvent is calculated for all Hansen solubility parameters of the luminescent host material, and the smallest value is adopted as Ra.

When mixing two kinds of solvents, the Hansen solubility parameters (dispersion term, polarization term, and hydrogen bond term) of the mixed solvent can be obtained from the following formula (b).

In the above formula, dD _m , dP _m , dH _m are the dispersion term, polarization term, and hydrogen bond term of the Hansen solubility parameter of the mixed solvent, respectively, and a, dD ₁ , dP ₁ , dH ₁ are the solvent 1 Volume ratio, Hansen solubility parameter dispersion term, polarization term, and hydrogen bond term, b, dD ₂ , dP ₂ , and dH ₂ are the solvent 2 volume ratio, Hansen solubility parameter dispersion term, polarization term, and hydrogen, respectively. It is a coupling term. In the case of mixing three or more kinds of solvents, the Hansen solubility parameter of the mixed solvent can be similarly determined using the volume ratio.

By mixing two or more kinds of solvents at a predetermined volume ratio (volume percent), a mixed solvent having a Hansen solubility parameter that a single solvent does not have can be prepared. As a result, by selecting an appropriate solvent type and mixing ratio, it is possible to reduce Ra obtained from the Hansen solubility parameter of the mixed solvent and the luminescent host material as compared with that of the single solvent. The solubility in a solvent can be further increased.
The volume ratio (volume percent) in the case of using a mixture of two kinds of solvents may be selected so as to be a ratio that results in a smaller Ra, and is not particularly limited. When the total is 100%, for example, it can be selected from 90/10 to 10/90.

[Additive]
The ink composition for an organic light emitting device of the present invention has additives such as a leveling agent and a viscosity adjusting agent as necessary for the purpose of improving the ink jet discharge property or the smoothness when drying the ink jet discharge. It may be contained.

Leveling agent Although it does not restrict | limit especially as a leveling agent, A silicone type compound, a fluorine-type compound, a siloxane type compound, a nonionic surfactant, an ionic surfactant, a titanate coupling agent etc. can be used. Of these, silicone compounds and fluorine compounds are preferred.

The silicone compound is not particularly limited, and examples thereof include dimethyl silicone, methyl silicone, phenyl silicone, methyl phenyl silicone, alkyl-modified silicone, alkoxy-modified silicone, and polyether-modified silicone. Of these, dimethyl silicone and methylphenyl silicone are preferred.

The fluorine-based compound is not particularly limited, and examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, fluoroalkyl methacrylate, perfluoropolyether, and perfluoroalkylethylene oxide. Of these, polytetrafluoroethylene is preferred.

The siloxane compound is not particularly limited, and examples thereof include dimethylsiloxane compounds (trade names: KF96L-1, KF96L-5, KF96L-10, KF96L-100, manufactured by Shin-Etsu Silicone Co., Ltd.).

Among the leveling agents described above, it is preferable to use a silicone compound, a fluorine compound, or a siloxane compound, and it is more preferable to use a siloxane compound.

The above leveling agents may be used alone or in combination of two or more.

The addition ratio of the leveling agent varies depending on the desired performance, but is preferably 0.001 to 5% by mass, and preferably 0.001 to 1% by mass with respect to the total mass of the ink composition for an organic light emitting device. It is more preferable that It is preferable that the addition ratio of the leveling agent is 0.001% by mass or more because the smoothness of the coating film can be improved. On the other hand, it is preferable that the addition rate of the leveling agent is 5% by mass or less because the luminous efficiency can be improved.

Viscosity modifier The viscosity modifier is not particularly limited, but poly (α-methylstyrene), polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene / acrylonitrile copolymer, polymethyl methacrylate, methacryl / styrene copolymer. A thermoplastic resin such as polycarbonate can be used. Of these, poly (α-methylstyrene), polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene / acrylonitrile copolymer, and polymethyl methacrylate are preferable.

The above-mentioned viscosity modifiers may be used alone or in combination of two or more.

The addition ratio of the viscosity modifier varies depending on the desired performance, but is preferably 0.001 to 5% by mass, and 0.01 to 1% by mass with respect to the total mass of the ink composition for an organic light emitting device. % Is more preferable. It is preferable that the addition ratio of the viscosity modifier is 0.001% by mass or more because aggregation of the light emitting host material can be suppressed and the light emission efficiency can be improved. On the other hand, when the addition rate of the viscosity modifier is 5% by mass or less, it is preferable because the flying shape of the inkjet droplet can be improved.

<Organic light emitting device>
According to an embodiment of the present invention, an organic light emitting device is provided. In this case, the organic light emitting device includes at least an anode, a light emitting layer, and a cathode. The organic light emitting device may include one or more other layers such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. Moreover, you may include well-known things, such as a sealing member.

Hereinafter, each configuration of the organic light emitting device will be described in detail.

[anode]
The anode is not particularly limited, and metals such as gold (Au), copper iodide (CuI), indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like can be used. These materials may be used alone or in combination of two or more.

The film thickness of the anode is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 10 to 200 nm.

The anode can be formed by a method such as vapor deposition or sputtering. At this time, pattern formation may be performed by a photolithography method or a method using a mask.

[Hole injection layer]
The hole injection layer is an optional component in the organic light emitting device and has a function of taking holes from the anode. Normally, holes taken from the anode are transported to the hole transport layer or the light emitting layer.

The hole injection material is not particularly limited, but is a phthalocyanine compound such as copper phthalocyanine; a triphenylamine derivative such as 4,4 ′, 4 ″ -tris [phenyl (m-tolyl) amino] triphenylamine; , 5,8,9,12-hexaazatriphenylenehexacarbonitrile, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane and other cyano compounds; vanadium oxide, molybdenum oxide, etc. Oxides; amorphous carbon; conductive polymers such as polyaniline (emeraldine), poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (PEDOT-PSS), polypyrrole, etc. The hole injecting material is preferably a conductive polymer, and PEDOT-PSS More preferably.

The thickness of the hole injection layer is not particularly limited, but is preferably 0.1 nm to 5 μm.

The hole injection layer may be a single layer or a laminate of two or more.

[Hole transport layer]
The hole transport layer is an optional component in the organic light emitting device and has a function of efficiently transporting holes. The hole transport layer may have a function of preventing hole transport. The hole transport layer usually takes holes from the anode or the hole injection layer and transports the holes to the light emitting layer.

The hole transport material that can be used for the hole transport layer is not particularly limited, but TPD (N, N′-diphenyl-N, N′-di (3-methylphenyl) -1,1′-biphenyl-4 , 4′diamine), α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), m-MTDATA (4,4 ′, 4 ″ -tris (3-methyl) Low molecular triphenylamine derivatives such as phenylphenylamino) triphenylamine), and the like, and polymer compounds such as diamine polymers polymerized by introducing substituents into polyvinylcarbazole and triarylamine derivatives. The transport material is preferably a polymer compound obtained by introducing a substituent into a triphenylamine derivative or triarylamine derivative and polymerizing the fluorene skeleton. And more preferably a diamine polymer.

The film thickness of the hole transport layer is not particularly limited, but is preferably 1 nm to 5 μm, more preferably 5 nm to 1 μm, and further preferably 10 to 500 nm.

[Light emitting layer]
The light emitting layer has a function of causing light emission by using energy generated by recombination of holes and electrons injected into the light emitting layer.

At this time, as described above, the light emitting layer includes a light emitting host material containing at least one of a compound having a pyrene skeleton and a compound having an anthracene skeleton. In addition, if necessary, a known light-emitting host material may be used in combination.

Further, the light emitting layer may contain a light emitting dopant material as necessary.

Since the above-mentioned materials can be used as the light emitting dopant material, description thereof is omitted here.

The thickness of the light emitting layer is not particularly limited, but is preferably 2 nm to 30 μm, more preferably 10 nm to 20 μm, further preferably 15 nm to 15 μm, and particularly preferably 15 to 200 nm. preferable. The above range is preferable because the film thickness can be controlled with high accuracy.

[Electron transport layer]
The electron transport layer is an optional component in the organic light emitting device and has a function of efficiently transporting electrons. The electron transport layer can have a function of preventing electron transport. The electron transport layer usually takes electrons from the cathode or the electron injection layer and transports the electrons to the light emitting layer.

The electron transport material that can be used for the electron transport layer is not particularly limited, but tris (8-quinolylato) aluminum (Alq), tris (4-methyl-8-quinolinolato) aluminum (Almq3), bis (10-hydroxybenzo). [H] quinolinato) beryllium (BeBq2), bis (2-methyl-8-quinolinolato) (p-phenylphenolate) aluminum (BAlq), bis (8-quinolinolato) zinc (Znq), 8-hydroxyquinolinolatolithium A metal complex having a quinoline skeleton or a benzoquinoline skeleton such as (Liq); a metal complex having a benzoxazoline skeleton such as bis [2- (2′-hydroxyphenyl) benzoxazolate] zinc (Zn (BOX) 2); Bis [2- (2′-hydroxyphenyl) ben Thiazolate] zinc (Zn (BTZ) 2) metal complex having benzothiazoline skeleton; 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (TAZ), 1,3-bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (OXD-7), 9- [4- (5-phenyl-1,3,4-oxadiazol-2-yl) phenyl] carbazole ( CO11), 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H-benzimidazole) (TPBI), 2- [3- (dibenzothiophen-4-yl) Phenyl] -1-phenyl-1H-benzimidazole (mDBTBIm-II) and other polyazole derivatives; benzimidazole derivatives; quinoline derivatives; perylene derivatives; pyridine derivatives; pyrimidine derivatives; triazine derivatives; quinoxaline derivatives; Derivatives and the like. Among these, the electron transport material is preferably a benzimidazole derivative, a pyridine derivative, a pyrimidine derivative, a triazine derivative, or a phenanthroline derivative.

The above-mentioned electron transport materials may be used alone or in combination of two or more.

The thickness of the electron transport layer is not particularly limited, but is preferably 5 nm to 5 μm, and more preferably 5 to 200 nm.

The electron transport layer may be a single layer or a laminate of two or more.

[Electron injection layer]
The electron injection layer is an optional component in the organic light emitting device and has a function of taking electrons from the cathode. Usually, electrons taken from the cathode are transported to the electron transport layer or the light emitting layer.

The electron injecting material that can be used for the electron injecting layer is not particularly limited; however, alkali metals such as lithium and calcium; metals such as strontium and aluminum; alkali metal salts such as lithium fluoride and sodium fluoride; 8-hydroxyquino Examples include alkali metal compounds such as lithium lithium; alkaline earth metal salts such as magnesium fluoride; oxides such as aluminum oxide. Among these, the electron injecting material is preferably an alkali metal, an alkali metal salt, or an alkali metal compound, and more preferably an alkali metal salt or an alkali metal compound.

The above-described electron injection materials may be used alone or in combination of two or more.

The thickness of the electron injection layer is not particularly limited, but is preferably 0.1 nm to 5 μm.

The electron injection layer may be a single layer or a laminate of two or more.

[cathode]
Examples of the cathode include, but are not limited to, lithium, sodium, magnesium, aluminum, sodium-potassium alloy, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, rare earth metal, and the like. . These materials may be used alone or in combination of two or more.

The cathode can be usually formed by a method such as vapor deposition or sputtering.

The film thickness of the cathode is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 10 to 200 nm.

<Method for producing organic light-emitting device>
According to an embodiment of the present invention, a method for manufacturing an organic light emitting device is provided. The method for producing an organic light-emitting device includes a step of forming a light-emitting layer by applying an ink composition for an organic light-emitting device onto a support by an inkjet method (hereinafter also referred to as “light-emitting layer forming step”).

[Light emitting layer forming step]
The light emitting layer forming step is a step of forming a light emitting layer by applying an ink composition for an organic light emitting element onto a support by an ink jet method.

Hereinafter, the light emitting layer forming step in one embodiment will be described with reference to the drawings.

More specifically, FIG. 1 is a partial cross-sectional view schematically showing a process of forming a coating film by an ink jet method. In FIG. 1, it has the board | substrate 1, the anode 2 arrange | positioned on the said board | substrate, and the positive hole transport layer 4 arrange | positioned on the said anode. At this time, a plurality of laminated bodies of the anode 2 and the hole transport layer 3 provided on the substrate are separated by the bank 3. When the ink composition for organic light emitting elements is ejected from the nozzle 6 of the ink jet head 7, a coating film 5 of the ink composition for organic light emitting elements is formed on the hole transport layer 3. A light emitting layer can be formed by drying the obtained coating film.

(Ink composition for organic light emitting device)
As the ink composition for an organic light-emitting element, the above-described one can be used, and thus the description thereof is omitted here.

(Support)
The support is a constituent layer of the organic light emitting device adjacent to the light emitting layer, and varies depending on the organic light emitting device to be manufactured. For example, when producing an organic light emitting device comprising an anode, a light emitting layer, and a cathode, the support is an anode or a cathode. In the case of manufacturing an organic light emitting device comprising an anode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode, the support is a hole injection layer or an electron transport layer. Thus, the support is an anode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, or a cathode, preferably an anode, a hole injection layer, a hole transport layer, A hole injection layer or a hole transport layer is more preferable, and a hole transport layer is still more preferable.

Note that a bank may be formed on the support. By having the bank, the light emitting layer can be formed only at a desired location.

The height of the bank is preferably 0.1 to 5.0 μm, more preferably 0.2 to 3.0 μm, and further preferably 0.2 to 2.0 μm.

The width of the bank opening is preferably 10 to 200 μm, more preferably 30 to 200 μm, and further preferably 50 to 100 μm.

Furthermore, the length of the bank opening is preferably 10 to 400 μm, more preferably 20 to 200 μm, and further preferably 50 to 200 μm.

Further, the taper angle of the bank is preferably 10 to 100 degrees, more preferably 10 to 90 degrees, and further preferably 10 to 80 degrees.

(Application)
Application is performed by an ink jet method. More specifically, the ink composition for an organic light-emitting element is discharged from the nozzle of the inkjet head to the support.

At this time, the discharge amount of the ink composition for an organic light emitting device is preferably 1 to 50 pL / time, more preferably 1 to 30 pL / time, and further preferably 1 to 20 pL / time.

The opening diameter of the inkjet head is preferably 5 to 50 μm and more preferably 10 to 30 μm from the viewpoint of nozzle clogging and ejection accuracy.

The temperature at which the coating film is formed is not particularly limited, but is 10 to 10 from the viewpoint of suppressing crystallization of the light emitting material (light emitting host material and / or light emitting dopant material) contained in the ink composition for an organic light emitting device. It is preferably 50 ° C., more preferably 15 to 40 ° C., and further preferably 15 to 30 ° C.

The relative humidity when forming the coating film is not particularly limited, but is preferably 0.01 ppm to 80%, more preferably 0.05 ppm to 60%, and more preferably 0.1 ppm to 15%. More preferably, it is 1 ppm to 1%, particularly preferably 5 to 100 ppm. It is preferable that the relative humidity is 0.01 ppm or more because the conditions for forming the coating film can be easily controlled. On the other hand, when the relative humidity is 80% or less, it is preferable because the amount of moisture adsorbed on the coating film that can affect the resulting light emitting layer can be reduced.

(Dry)
A light emitting layer can be formed by drying the obtained coating film.

The drying temperature is not particularly limited, but it may be performed at room temperature (25 ° C.) or by heating. When carried out by heating, the temperature is preferably 40 to 130 ° C, more preferably 40 to 80 ° C.

Further, the drying pressure is preferably performed under reduced pressure, and more preferably under reduced pressure of 0.001 to 100 Pa.

Furthermore, the drying time is preferably 1 to 90 minutes, more preferably 1 to 30 minutes.

[Formation process of other layers]
Other layers constituting the organic light-emitting device, specifically, the anode, the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer, and the cathode can be appropriately formed by known methods. .

For example, the anode and the cathode can be formed by a method such as vapor deposition or sputtering.

Further, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer can be formed by a vacuum deposition method, a spin coat method, a cast method, an ink jet method, an LB method, or the like.

Hereinafter, the present invention will be described using examples, but the present invention is not limited to the description of the examples.

[Example 1]
0.095 g of H-1 as a light-emitting host material represented by the following formula and 0.005 g of D-1 as a light-emitting dopant material represented by the following formula were combined with 9.9 g of tetralin (vapor pressure: By adding to 0.35 mmHg), an ink composition for an organic light emitting device was produced.

It should be noted that the three-dimensional coordinate distance (Ra) for tetralin and the luminescent host material H-1 is calculated using Hansen's solubility parameter calculation software HSPiP ver. It was 4.4 when it computed using 4.1.07.

[Example 2]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the light-emitting host material was changed to H-2 represented by the following formula.

Note that the Ra of the tetralin and H-2, which is the light-emitting host material, was calculated by the same method as in Example 1, and found to be 4.8.

[Example 3]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the light-emitting host material was changed to H-3 represented by the following formula.

It should be noted that Ra according to tetralin and H-3, which is the light-emitting host material, was calculated by the same method as in Example 1, and Ra was 3.5.

[Example 4]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the light-emitting host material was changed to H-4 represented by the following formula.

Note that the Ra for the tetralin and the light-emitting host material H-4 was calculated by the same method as in Example 1, and the Ra was 3.6.

[Example 5]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 2, except that the solvent was changed to 1-methylnaphthalene (vapor pressure: 0.05 mmHg).

Note that the Ra for the 1-methylnaphthalene and the luminescent host material H-2 was calculated by the same method as in Example 1, and the Ra was 4.8.

[Example 6]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 2 except that the solvent was changed to butyl benzoate (vapor pressure: 0.02 mmHg).

In addition, Ra according to the same method as in Example 1 was calculated for Ra related to butyl benzoate and H-2 as the light-emitting host material, and Ra was 7.3.

[Example 7]
An ink composition for an organic light emitting device was produced in the same manner as in Example 6 except that the light emitting host material was changed to H-3.

Note that the Ra for the butyl benzoate and the light-emitting host material H-3 was calculated by the same method as in Example 1, and the Ra was 7.3.

[Example 8]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the solvent was changed to phenetole (vapor pressure: 1.33 mmHg).

In addition, when Ra related to phenetol and the light-emitting host material H-1 was calculated in the same manner as in Example 1, Ra was 7.2.

[Example 9]
An ink composition for an organic light emitting device was produced in the same manner as in Example 8 except that the light emitting host material was changed to H-2.

In addition, Ra according to the same method as in Example 1 was calculated for Ra relating to phenetol and the light-emitting host material H-2, and Ra was 6.7.

[Example 10]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 2, except that the solvent was changed to 4-ethylanisole (vapor pressure: 0.33 mmHg).

It should be noted that Ra according to 4-ethylanisole and H-2 as the light-emitting host material was calculated by the same method as in Example 1, and Ra was 7.6.

[Example 11]
An ink composition for an organic light emitting device was produced in the same manner as in Example 10 except that the light emitting host material was changed to H-4.

It should be noted that Ra according to 4-ethylanisole and luminescent host material H-4 was calculated by the same method as in Example 1, and Ra was 7.4.

[Example 12]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 2 except that the solvent was changed to 4′-methylacetophenone (vapor pressure: 0.18 mmHg).

It should be noted that Ra according to 4'-methylacetophenone and H-2 as the light-emitting host material was calculated by the same method as in Example 1, and Ra was 7.2.

[Example 13]
The same as in Example 2 except that the solvent was changed to a mixed solvent of diphenyl ether (vapor pressure: 0.05 mmHg): 44 volume percent and 1-methylnaphthalene (vapor pressure: 0.05 mmHg): 56 volume percent. The ink composition for organic light emitting devices was manufactured by the method.

In the same manner as in Example 1, when Ra related to H-2 which is a mixed solvent of diphenyl ether: 44 volume percent and 1-methylnaphthalene: 56 volume percent and the luminescent host material was calculated, Ra was 4.5. Met.

[Example 14]
Except that the solvent was changed to a mixed solvent of cyclohexylbenzene (vapor pressure: 0.07 mmHg): 84 volume percent and diphenyl ether (vapor pressure: 0.05 mmHg): 16 volume percent, the same method as in Example 3 was used. An ink composition for an organic light emitting device was produced.

In the same manner as in Example 1, the Ra of the mixed solvent of cyclohexylbenzene: 84 volume percent and diphenyl ether: 16 volume percent and H-2, which is the light-emitting host material, was calculated to be 3.4. It was.

Each of the solvents used in Examples 1 to 14 has a water solubility at 20 ° C. of 0.7% by weight or less, and the viscosity of the solvent is in the range of 1.5 to 4.5 mPa · s. The surface tension of the solvent was in the range of 28-40 mN / m. Further, the surface tension of any ink composition for organic light emitting devices was in the range of 28 to 40 mN / m.

[Comparative Example 1]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the solvent was changed to toluene (vapor pressure: 28.40 mmHg) having a vapor pressure higher than 5 mmHg.

In addition, Ra according to the same method as in Example 1 was calculated for Ra and luminescence host material H-1, and Ra was 7.7.

[Comparative Example 2]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 2 except that the solvent was changed to toluene.

In addition, Ra according to the same method as in Example 1 was calculated for toluene and H-2, which is the luminescent host material, and Ra was 8.2.

[Comparative Example 3]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 3 except that the solvent was changed to toluene.

In addition, Ra according to the same method as in Example 1 was calculated for Ra and H-3, which is the luminescent host material, and Ra was 6.9.

[Comparative Example 4]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 4 except that the solvent was changed to toluene.

In addition, when Ra related to toluene and H-4, which is the luminescent host material, was calculated by the same method as in Example 1, Ra was 6.5.

[Comparative Example 5]
An ink composition for an organic light-emitting device was produced in the same manner as in Example 1 except that the solvent was changed to hexylbenzene (vapor pressure: 0.09 mmHg).

Note that the Ra for the hexylbenzene and the luminescent host material H-1 was calculated by the same method as in Example 1, and the Ra was 9.3.

[Evaluation]
Various performances were evaluated using the ink compositions for organic light emitting devices produced in Examples 1 to 12 and Comparative Examples 1 to 5.

(Inkjet (IJ) ejection properties)
Using an inkjet printer DMP2831 and a cartridge box DMC-11610 (manufactured by FUJIFILM Corporation), the ink composition for an organic light emitting device was discharged at 10 nozzles at a discharge amount of 10 pl, an operating temperature of 25 ° C., and a relative humidity of 50%. Discharging for 30 seconds, stopping discharging for 1 minute, and then discharging again. In addition, evaluation of IJ dischargeability was performed according to the following criteria.

◎: Re-ejectable, droplet bending nozzle number 0 places ○: Re-ejectable, droplet bending nozzle number 1 location △: Re-ejectable, droplet bending nozzle number 2-4 locations ×: Re-ejectable, More than 5 nozzles that generate droplet bending or re-discharge is not possible

At this time, nozzle cleaning was performed under the following conditions. That is, the head nozzle surface was slightly brought into contact with a cleaning pad mounted on the ink jet printer, and ink on the nozzle surface was sucked.

(Luminescence efficiency)
An organic light emitting device was fabricated and the luminous efficiency was evaluated.

Fabrication and Evaluation of Organic Light-Emitting Element UV / O ₃ was irradiated onto the cleaned ITO substrate, and poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (PEDOT-PSS) was deposited to 45 nm by spin coating. And heated in the atmosphere at 180 ° C. for 15 minutes to form a hole injection layer. Next, a 0.6 wt% xylene solution of HT-1 represented by the following formula was formed on the hole injection layer by spin coating to a thickness of 20 nm, and dried at 230 ° C. for 30 minutes in a nitrogen atmosphere. A hole transport layer was formed. Next, the ink composition for an organic light emitting device was formed into a film of 30 nm by spin coating on the hole transport layer, and the pressure was reduced to 10 ⁻¹ Pa, followed by drying at 110 ° C. for 15 minutes to form a light emitting layer. . Then, under a vacuum condition of 5 × 10 ⁻³ Pa, ET-1 represented by the following formula is 20 nm as an electron transport layer, and 8-hydroxyquinolinolatolithium (Liq) is 0.5 nm as an electron injection layer, As a cathode, aluminum was sequentially deposited to a thickness of 100 nm. Finally, the substrate was transported to a glove box and sealed with a glass substrate to produce an organic light emitting device.

With respect to the organic light emitting device thus manufactured, the light emission from the organic light emitting device is measured with BM-9 (manufactured by Topcon Co., Ltd.) by connecting to an external power source, and the luminous efficiency is obtained from the current value at 1000 cd / m ^2. Calculated.

The results obtained are shown in Table 1 below.

From the results in Table 1, it can be seen that the ink compositions for organic light-emitting elements produced in Examples 1 to 12 are excellent in inkjet discharge stability and exhibit high luminous efficiency. For example, as can be seen from the comparison between Example 8 and Example 1, when one type of solvent is used alone and the same luminescent host material is used, a solvent having a smaller Ra and a lower vapor pressure is selected and used. Thus, it is apparent that the light emission efficiency and the IJ discharge performance can be further improved.
As can be seen from the comparison between Example 13 and Example 5, when the same luminescent host material is used, a combination of two solvents is used so that Ra becomes smaller, so that one kind of solvent is used alone. It is clear that the luminous efficiency can be remarkably improved as compared with FIG.
As can be seen from the comparison between Example 14 and Example 3, in the case where two types of solvents are combined so as to have substantially the same Ra using the same luminescent host material, the luminous efficiency is higher than when a single type of solvent is used alone. It is clear that can be further improved. The storage stability of the ink composition at high temperature and / or long term in the sense that precipitation or aggregation of the light emitting host material is less likely to occur is more effective than that of Example 3 as a result of being able to further suppress the vapor pressure of the solvent. Example 14 was superior.

The ink composition for an organic light-emitting device of the present invention includes one or more solvents having a specific vapor pressure or less, and the three-dimensional coordinate distance (Ra) represented by a specific formula is 8 or less. In manufacturing an organic light-emitting device using a specific light-emitting host material, a light-emitting layer can be formed under excellent inkjet discharge stability, and the obtained organic light-emitting device can realize high light emission efficiency. For this reason, an organic light emitting device including at least an anode, a light emitting layer, and a cathode and further including one or more other layers such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer Can be manufactured.

1: Substrate 2: Anode 3: Bank 4: Hole transport layer 5: Coating film 6: Nozzle 7: Inkjet head.

Claims (5)

A light emitting host material comprising at least one of a compound having a pyrene skeleton and a compound having an anthracene skeleton;
One or more solvents having a vapor pressure of 5 mmHg or less;
Including
The following formula (a):

(In the above formula, dD _host , dP _host , and dH _host are the dispersion term, polarization term, and hydrogen bond term of the Hansen solubility parameter of the luminescent host material, respectively, and dD _solvent , dP _solvent , and dH _solvent are Hansen solubility parameter dispersion, polarization, and hydrogen bond terms.)
An ink composition for an organic light emitting device, wherein the three-dimensional coordinate distance (Ra) represented by The ink composition for an organic light-emitting element according to claim 1, wherein the solvent has a vapor pressure of 1 mmHg or less. The ink composition for an organic light-emitting element according to claim 1 or 2, wherein the solvent contains at least one selected from the group consisting of aromatic hydrocarbons, aromatic esters, and aromatic ketones. The ink composition for an organic light-emitting element according to any one of claims 1 to 3, wherein the three-dimensional coordinate distance (Ra) is 6 or less. A method for producing an organic light emitting device, comprising at least an anode, a light emitting layer, and a cathode,
A production method comprising a step of forming the light emitting layer by applying the ink composition for an organic light emitting device according to any one of claims 1 to 4 on a support by an ink jet method.

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