JP2008198365A - Manufacturing method of organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an organic electroluminescent element of long life and high luminous efficiency. <P>SOLUTION: In the manufacture of the organic electroluminescent element 10a provided with an anode 2 as well as a cathode 6 and with a hole injection layer 3 and an organic layer 4 formed between the anode 2 and the cathode 6 by a wet film-forming method, the organic layer 4 is formed with the use of ink of a viscosity of 1 to 20 cp containing at least one kind of solvent with a boiling point of 200°C or more, and at the same time, the organic layer 4 is formed after the hole injection layer 3 is heated at 200 °C or more and yet at not less than 'a boiling point of the solvent minus 10°C'. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an organic electroluminescent device, and more specifically, has a hole injection layer formed by a wet film formation method and an organic layer formed by a wet film formation method on the hole injection layer. The present invention relates to a method for manufacturing an organic electroluminescent element.

  Since the announcement of Kodak's stacked organic electroluminescence (EL) element using vacuum deposition, organic EL displays have been actively developed and are now in practical use. It's getting on.

  In such a stacked organic EL element, a plurality of organic layers (such as a light emitting layer, a hole injection layer, a hole transport layer, and an electron transport layer) are stacked between an anode and a cathode. In many cases, these organic layers are formed by vacuum-depositing organic layer materials such as low molecular weight dyes. However, it is difficult to obtain a thin film that is homogeneous and free of defects by the vacuum deposition method, and it takes a long time to form several organic layers.

On the other hand, a technique for forming a plurality of organic layers of a stacked organic EL element by a wet film forming method has been reported. For example, in Patent Document 1, after forming a hole injection transport layer by applying a polymer type hole injection transport material or a hole injection transport material and a polymer binder, The thing etc. which formed the light emitting layer by apply | coating a molecular binder are mentioned.
In Patent Document 2, an ink containing a polymer hole transporting compound is applied to form a hole injection layer, and then an ink containing a low molecular light emitting material is applied to form a light emitting layer. Etc. are mentioned.

JP-A-4-2096 International Publication No. 2006/095539 Pamphlet

However, in any of the techniques described in Patent Documents 1 and 2, there is a problem that an element in which a plurality of organic layers are formed by a wet film forming method cannot have a sufficiently long lifetime.
The present invention was devised in view of the above problems, and an organic electroluminescent device in which a hole injection layer and an organic layer formed on the hole injection layer are both formed by a wet film formation method. An object of the present invention is to provide a method for producing an organic electroluminescent device having a long lifetime and high luminous efficiency.

  As a result of intensive studies to solve the above problems, the present inventors have conventionally determined the temperature at which the hole injection layer is heated and the physical properties of the ink deposited on the hole injection layer. In comparison, the inventors have found that an organic electroluminescent device having a long lifetime and high luminous efficiency can be obtained, and the present invention has been completed.

  That is, the gist of the present invention is to have an anode and a cathode, and between the anode and the cathode, a hole injection layer formed by a wet film-forming method and on the hole injection layer by a wet film-forming method. A method for producing an organic electroluminescent element having an organic layer formed, wherein the organic layer is formed using an ink having a viscosity of 1 to 20 cp containing at least one solvent having a boiling point of 200 ° C. or higher, and An organic electroluminescent element manufacturing method is characterized in that the organic layer is formed after heating the hole injection layer at 200 ° C. or higher and “boiling point of the solvent −10 ° C.” or higher (claim 1).

At this time, the hole injection layer preferably contains a hole transporting compound and an electron accepting compound (claim 2).
Moreover, it is preferable that at least one of the solvents can dissolve the hole transporting compound or the electron accepting compound (claim 3).
Further, the organic layer is preferably a light emitting layer.

  According to the method for producing an organic electroluminescent element of the present invention, an organic electroluminescent element having a long lifetime and high luminous efficiency can be obtained.

  Hereinafter, the present invention will be described in detail with reference to examples and embodiments. However, the present invention is not limited to the following examples and embodiments, and may be arbitrarily changed without departing from the gist of the present invention. Can be implemented.

[I. Manufacturing method of organic electroluminescence device]
The method for producing an organic electroluminescent element (that is, organic EL element) of the present invention (hereinafter referred to as “the production method of the present invention” as appropriate) has an anode and a cathode, and at least holes between the anode and the cathode. A method for producing an organic EL device having an injection layer and an organic layer, wherein the formation of the organic layer is performed at a viscosity of 1 to at least one solvent having a boiling point of 200 ° C. or higher (hereinafter, appropriately referred to as “solvent for organic layer”). While using 20 cp of ink, the hole injection layer is heated to 200 ° C. or higher and “the boiling point of the organic layer solvent—10 ° C.” or higher to form the organic layer. In the organic EL device according to the present invention, the hole injection layer is a layer that exists between the anode and the cathode and is formed by a wet film-forming method, while the organic layer is formed between the anode and the cathode. It is a layer that exists between and on the hole injection layer and is formed by a wet film formation method.

  Hereinafter, the hole injection layer forming step and the heating step, and the organic layer forming step, which are the main features of the production method of the present invention, will be described first. On the other hand, the specific configuration and the like of the organic EL element to which the production method of the present invention is applied will be described again (in the column of [II. Organic electroluminescent element] described later).

[I-1. Formation process of hole injection layer]
The method for forming the hole injection layer according to the present invention is not particularly limited as long as the hole injection layer can be formed by a wet film formation method, and is arbitrary. The wet film forming method is an excellent forming method having advantages such as that a thin film that is homogeneous and free from defects can be easily obtained, and that the time for forming can be shortened.

  In the case of forming a hole injection layer by a wet film formation method, a composition for film formation (hole injection layer) is usually prepared by mixing the material of the hole injection layer with an appropriate solvent (solvent for the hole injection layer). Composition), and by applying this composition for a hole injection layer on a layer corresponding to the lower layer of the hole injection layer (usually an anode) by a suitable technique, forming a film, and drying To form a hole injection layer. In this case, the hole injection layer formed from the hole injection layer composition may be formed as a layer containing the compound contained in the hole injection layer composition as it is. It may be a layer containing a compound obtained by reaction of a compound contained in the product.

[I-1-1. Material of hole injection layer]
The material of the hole injection layer is contained in the hole injection layer and the hole injection layer composition, and is not particularly limited as long as the hole injection layer can be formed by a wet film forming method. However, a hole transporting compound and an electron accepting compound are usually used as the material for the hole injection layer. Further, other components may be used as the material for the hole injection layer. Hereinafter, materials of these hole injection layers will be described.

[I-1-1-1. High molecular weight hole transport compound]
The kind of the hole transporting compound used as the material for the hole injection layer is arbitrary as long as the effects of the present invention are not significantly impaired. However, among them, a polymer having a hole transporting property (a high molecular weight hole transporting compound, hereinafter referred to as “hole transporting polymer” as appropriate) is preferable, and an ionization potential of 4.5 eV to 5.5 eV is particularly preferable. It is preferable that it is a compound which has. The ionization potential is defined as the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of a material to the vacuum level, and can be measured directly by photoelectron spectroscopy or electrochemically. It is also obtained by correcting the oxidized potential with respect to the reference electrode. In the case of the latter method, for example, when a saturated sweet potato electrode (SCE) is used as a reference electrode, it is represented by the following formula ("Molecular Semiconductors", Springer-Verlag, 1985, pp. 98).
Ionization potential = oxidation potential (vs. SCE) + 4.3 eV

  Examples of the hole transporting polymer include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, and the like. Of these, aromatic amine compounds are preferred from the viewpoints of amorphousness, solubility in solvents, and visible light transmittance.

Of the aromatic amine compounds, aromatic tertiary amine compounds are particularly preferable. In addition, the aromatic tertiary amine compound here is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.
The type of the aromatic tertiary amine compound is not particularly limited, but a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less is more preferable from the viewpoint of the surface smoothing effect.

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

(In the formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. X represents a linking group selected from the following linking group group X1.)

Linking group group X1:

(In the formula, each of Ar ^{11 to} Ar ²⁸ independently represents an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group. R ¹ and R ² each independently represents hydrogen. Represents an atom or any substituent.)

In the formula (I), as Ar ^{1 to} Ar ⁵ and Ar ^{11 to} Ar ²⁸ , any monovalent or divalent group derived from any aromatic hydrocarbon ring or aromatic heterocyclic ring is applicable. That is, each of Ar ¹ , Ar ² , Ar ¹⁶ , Ar ^21, and Ar ²⁶ can be a monovalent group. Ar ^{3 to} Ar ⁵ , Ar ^{11 to} Ar ¹⁵ , Ar ^{17 to} Ar ²⁰ , Ar ²² to A divalent group can be applied to each of Ar ²⁵ , Ar ^27, and Ar ²⁸ . These may be the same or different from each other. Moreover, you may have arbitrary substituents.

  Examples of the aromatic hydrocarbon ring include a 5- or 6-membered monocyclic ring or a 2-5 condensed ring. Specific examples thereof include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, fluoranthene ring, fluorene ring and the like.

  Examples of the aromatic heterocycle include a 5- or 6-membered monocyclic ring or a 2-4 condensed ring. Specific examples thereof include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring. , Thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline Ring, cinolin ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like.

Ar ^{3 to} Ar ⁵ , Ar ^{11 to} Ar ¹⁵ , Ar ^{17 to} Ar ²⁰ , Ar ^{22 to} Ar ²⁵ , Ar ²⁷ , Ar ²⁸ may be one type or two or more types of aromatic hydrocarbon rings exemplified above. And / or two or more divalent groups derived from an aromatic heterocycle may be linked and used.

Furthermore, the group derived from the aromatic hydrocarbon ring and / or aromatic heterocycle of Ar ^{1 to} Ar ⁵ and Ar ^{11 to} Ar ²⁸ may further have a substituent unless it is contrary to the gist of the present invention. Good. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. The type of the substituent is not particularly limited, and examples thereof include one or more selected from the following substituent group W. In addition, as for a substituent, 1 piece may be substituted independently and 2 or more may be substituted by arbitrary combinations and ratios.

[Substituent group W]
An alkyl group having usually 1 or more, usually 10 or less, preferably 8 or less, such as a methyl group or an ethyl group; an alkenyl group having usually 2 or more, usually 11 or less, preferably 5 or less, such as a vinyl group An alkynyl group having usually 2 or more, usually 11 or less, preferably 5 or less, such as an ethynyl group; an alkoxy having a carbon number of usually 1 or more, usually 10 or less, preferably 6 or less, such as a methoxy group or an ethoxy group; A group; an aryloxy group such as a phenoxy group, a naphthoxy group, a pyridyloxy group, etc., usually 4 or more, preferably 5 or more, usually 25 or less, preferably 14 or less; a carbon such as a methoxycarbonyl group or an ethoxycarbonyl group An alkoxycarbonyl group having a number of usually 2 or more, usually 11 or less, preferably 7 or less; a dimethylamino group, a diethylamino group or the like, and usually having 2 or more carbon atoms Usually 20 or less, preferably 12 or less dialkylamino group; diphenylamino group, ditolylamino group, N-carbazolyl group, etc., and usually diarylamino having 10 or more carbon atoms, preferably 12 or more, usually 30 or less, preferably 22 or less Group: an arylalkylamino group having 6 or more carbon atoms, preferably 7 or more, usually 25 or less, preferably 17 or less, such as a phenylmethylamino group; an acetyl group, a benzoyl group or the like, and usually having 2 or more carbon atoms, Usually an acyl group of 10 or less, preferably 7 or less; a halogen atom such as a fluorine atom or a chlorine atom; a haloalkyl group having a carbon number of usually 1 or more, usually 8 or less, preferably 4 or less, such as a trifluoromethyl group; An alkylthio group having 1 to 10 carbon atoms, preferably 6 or less, preferably 6 or less; An arylthio group having usually 4 or more, preferably 5 or more, usually 25 or less, preferably 14 or less, such as a ruthio group, a naphthylthio group, or a pyridylthio group; Or more, preferably 3 or more, usually 33 or less, preferably 26 or less silyl group; trimethylsiloxy group, triphenylsiloxy group, etc., the carbon number is usually 2 or more, preferably 3 or more, usually 33 or less, preferably 26 or less. A siloxy group; a cyano group; an aromatic hydrocarbon ring group having usually 6 or more, usually 30 or less, preferably 18 or less, such as a phenyl group or a naphthyl group; a carbon number such as a thienyl group or a pyridyl group. An aromatic heterocyclic group of 3 or more, preferably 4 or more, usually 28 or less, preferably 17 or less.

Among those described above, Ar ¹ and Ar ² are 1 derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, and a pyridine ring from the viewpoint of the solubility, heat resistance, and hole injection / transport properties of the polymer compound. Is more preferably a phenyl group or a naphthyl group.

Among the above, Ar ^{3 to} Ar ⁵ are divalent benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings from the viewpoint of heat resistance and hole injection / transport properties including redox potential. Group is preferable, and a phenylene group, a biphenylene group, and a naphthylene group are more preferable.

In the formula (I), as R ¹ and R ² , a hydrogen atom or an arbitrary substituent is applicable. These may be the same or different from each other. The type of the substituent is not particularly limited as long as it is not contrary to the gist of the present invention. However, if applicable substituents are exemplified, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a silyl group, a siloxy group, an aromatic group A hydrocarbon group and an aromatic heterocyclic group are mentioned. Specific examples thereof include the groups exemplified above in the substituent group W.

Among the polymer compounds having a repeating unit represented by the formula (I), a polymer compound having a repeating unit represented by the following formula (I ′) is particularly preferable because the hole injection / transport property is very high. .

In the formula (I ′), R ^{41 to} R ⁴⁵ each independently represents an arbitrary substituent. Specific examples of the substituents of R ^{41 to} R ⁴⁵ are the same as the substituents that Ar ^{1 to} Ar ⁵ of formula (I) may have (that is, the substituents described in [Substituent group W]). It is. In the formula (I ′), p and q each independently represent an integer of 0 or more and 5 or less, and r, s, or t each independently represents an integer of 0 or more and 4 or less.

In the formula (I ′), Y ′ represents a linking group selected from the following linking group group Y2.

In the above formulas, Ar ^{31 to} Ar ³⁷ each independently represents a monovalent or divalent group derived from an aromatic hydrocarbon ring or aromatic heterocycle which may have a substituent. Specific examples of Ar ^{31 to} Ar ³⁷ are the same as Ar ^{1 to} Ar ⁵ described above. That is, Ar ^{31 to} Ar ³⁵ and Ar ³⁷ can be the same as Ar ^{3 to} Ar ^5, and Ar ³⁶ can be the same as Ar ¹ and Ar ² . Moreover, the substituent which may have is the same as said Ar < ¹ > -Ar < ⁵ >.

  Hereinafter, preferred specific examples of the repeating unit represented by the formula (I) or the formula (I ′) that can be applied in the present invention will be given, but the present invention is not limited thereto.

  In addition, preferred examples of other aromatic tertiary amine polymer compounds include polymer compounds containing a repeating unit represented by the following formula (III-1) and / or formula (III-2).

(In the formulas (III-1) and (III-2), Ar ⁴⁵ , Ar ⁴⁷ and Ar ⁴⁸ each independently have an aromatic hydrocarbon group which may have a substituent, or a substituent. Ar ⁴⁴ and Ar ⁴⁶ each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or may have a substituent. And represents a good divalent aromatic heterocyclic group, R ^{41 to} R ⁴³ each independently represents a hydrogen atom or an arbitrary substituent.)

Examples of Ar ⁴⁵ , Ar ⁴⁷ and Ar ⁴⁸ , and Ar ⁴⁴ and Ar ⁴⁶ , preferred examples, examples of substituents that may be included and examples of preferred substituents are Ar ²¹ and Ar ²² , respectively. Moreover, it is the same as Ar ^{23 to} Ar ²⁵ . R ^{41 to} R ⁴³ are preferably a hydrogen atom or a substituent described in [Substituent group W], more preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group, an aromatic hydrocarbon group, It is an aromatic hydrocarbon group.

  Although the preferable specific example of the repeating unit represented by Formula (III-1) and (III-2) applicable in this invention is given to the following, this invention is not limited to these.

Moreover, as a preferable example of the aromatic amine polymer compound applicable in this invention, the polymer compound which has the following repeating unit is mentioned. Therefore, the aromatic tertiary amine compounds exemplified as the preferred high molecular weight hole transporting compounds also particularly preferably have the following repeating units. However, the present invention is not limited to these examples.

  The aromatic amine compound may be a homopolymer composed of any one of the various repeating units described above, and is a copolymer containing two or more kinds in any combination and ratio. There may be. In the latter case, the form of the copolymer may be block copolymerization or random copolymerization.

  Moreover, only 1 type may be used for the positive hole transport compound used as a material of a positive hole injection layer, and it may use 2 or more types together by arbitrary combinations and a ratio. Accordingly, only one kind of hole transporting polymer may be used, or two or more kinds may be used in any combination and ratio. Further, only one of the high molecular weight hole transporting compound and the low molecular weight hole transporting compound (described later) may be used, or both may be used in combination.

  The weight average molecular weight of the hole transporting polymer used as the material of the hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 100 or more, preferably 500 or more, more preferably 1000 or more, Preferably it is 1,000,000 or less. If the weight average molecular weight is too small, it may be dissolved by the ink used in the layer laminated thereon, and if it is too large, it may be difficult to dissolve in the ink solvent used to form the hole injection layer. is there.

  The ratio of the hole transporting polymer in the hole injection layer is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 10% by weight or more, preferably 30 in terms of the weight ratio with respect to the whole hole injection layer. % By weight or more, usually 99.9% by weight or less, preferably 99% by weight or less. In addition, when using together 2 or more types of hole transportable polymers, it is preferable to make these total content contain in the said range.

[I-1-1-2. Electron-accepting compound]
The kind of the electron accepting compound used as the material for the hole injection layer is arbitrary as long as the effects of the present invention are not significantly impaired. Examples thereof include onium salts substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pendafluorophenyl) borate and triphenylsulfonium tetrafluoroborate; No. 251067), high-valence inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris (pendafluorophenyl) borane (JP-A-2003-31365); fullerene derivatives ; Iodine etc. are mentioned. Of the above compounds, an onium salt substituted with an organic group is preferable in terms of having strong oxidizing power, and an inorganic compound having a high valence is preferable, and an onium salt substituted with an organic group in terms of being soluble in various solvents, A cyano compound and an aromatic boron compound are preferable. Furthermore, an onium salt substituted with an organic group is most preferable from the viewpoint of achieving both strong oxidizing power and high solubility, and particularly preferably a compound represented by the following formulas (II-1) to (II-3). .

(In the above formulas (II-1) to (II-3), R ¹¹ , R ²¹ and R ³¹ each independently represents an organic group bonded to A ^{1 to} A ³ via a carbon atom. R ¹² , R ²² , R ²³ and R ^{32 to} R ³⁴ each independently represents an arbitrary group, and two or more adjacent groups of R ^{11 to} R ³⁴ may be bonded to each other to form a ring. A ¹ -A ³ are all elements in the long period type periodic table (hereinafter, unless otherwise specified, the term “periodic table” refers to the long period type periodic table). A ¹ represents an element belonging to Group 17 of the long periodic periodic table, A ² represents an element belonging to Group 16 of the long periodic periodic table, and A ³ represents 15th element of the long periodic periodic table. Z ₁ ^{n1- to} Z ₃ ^n3- each independently represents a counter anion, and n _{1 to} n ₃ each independently represents an ionic value of the counter anion.)

In the above formulas (II-1) to (II-3), R ¹¹ , R ²¹ and R ³¹ each independently represents an organic group bonded to A ^{1 to} A ³ via a carbon atom. Therefore, as R ¹¹ , R ^21, and R ³¹ , the type is not particularly limited as long as it is an organic group having a carbon atom at the bond portion with A ^{1 to} A ³ unless it is contrary to the gist of the present invention.

The molecular weights of R ¹¹ , R ²¹ and R ³¹ are each a value including the substituent, and are usually 1000 or less, preferably 500 or less.
Preferred examples of R ¹¹ , R ²¹ and R ³¹ include alkyl groups, alkenyl groups, alkynyl groups, aromatic hydrocarbon groups, and aromatic heterocyclic groups from the viewpoint of delocalizing positive charges. Among them, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable because it delocalizes positive charges and is thermally stable.

  The alkyl group includes, for example, a linear, branched or cyclic alkyl group having a carbon number of usually 1 or more and usually 12 or less, preferably 6 or less. Specific examples include methyl group, ethyl group, n-propyl group, 2-propyl group, n-butyl group, isobutyl group, tert-butyl group, cyclohexyl group and the like.

  Examples of the alkenyl group include those having usually 2 or more, usually 12 or less, preferably 6 or less carbon atoms. Specific examples include a vinyl group, an allyl group, and a 1-butenyl group.

  Examples of the alkynyl group include those having usually 2 or more, usually 12 or less, preferably 6 or less. Specific examples include ethynyl group and propargyl group.

  Examples of the aromatic hydrocarbon group include a monovalent group derived from a 5- or 6-membered monocyclic ring or a 2 to 5 condensed ring, and a group in which a positive charge is delocalized on the group. . Specific examples thereof include monovalent groups derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, fluorene ring, and the like. Can be mentioned.

  Examples of the aromatic heterocyclic group include a monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-4 condensed ring, and a group in which a positive charge is delocalized on the group. . Specific examples thereof include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, triazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, Pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline And monovalent groups derived from a ring, an isoquinoline ring, a sinoline ring, a quinoxaline ring, a phenanthridine ring, a benzimidazole ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, an azulene ring, and the like.

In the above formulas (II-1) to (II-3), R ¹² , R ²² , R ²³ and R ^{32 to} R ³⁴ each independently represents an arbitrary substituent. Accordingly, the types of R ¹² , R ²² , R ²³ and R ^{32 to} R ³⁴ are not particularly limited as long as they are not contrary to the spirit of the present invention.
The molecular weights of R ¹² , R ²² , R ²³ and R ^{32 to} R ³⁴ are each a value including the substituent, and are usually 1000 or less, preferably 500 or less.

Examples of R ¹² , R ²² , R ²³ and R ^{32 to} R ³⁴ are alkyl groups, alkenyl groups, alkynyl groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, amino groups, alkylamino groups, arylamino groups. , Acylamino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylcarbonyloxy group, alkylthio group, arylthio group, sulfonyl group, alkylsulfonyl group, arylsulfonyl group, sulfonyloxy group cyano group , Hydroxyl group, thiol group, silyl group and the like. Among them, like R ¹¹ , R ^21, and R ³¹ , an organic group having a carbon atom at the bond portion with A ^{1 to} A ³ is preferable from the viewpoint of high electron acceptability. Examples include an alkyl group, an alkenyl group, Alkynyl groups, aromatic hydrocarbon groups, and aromatic heterocyclic groups are preferred. In particular, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable because it has a large electron accepting property and is thermally stable.

As described above, the groups exemplified as R ¹¹ , R ²¹ , R ³¹ , R ¹² , R ²² , R ²³ , and R ^{32 to} R ³⁴ are further substituted with other substituents unless they are contrary to the spirit of the present invention. It may be. The type of the substituent is not particularly limited, and examples thereof include a halogen atom in addition to the groups exemplified as R ¹¹ , R ²¹ , R ³¹ , R ¹² , R ²² , R ²³ , and R ^{32 to} R ³⁴ . A cyano group, a thiocyano group, a nitro group, etc. are mentioned. Among these, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group are preferable from the viewpoint of not hindering heat resistance and electron accepting property. In addition, the substituent to be further substituted may be substituted with only one, or two or more may be substituted with any combination and ratio.

In the formulas (II-1) to (II-3), two or more adjacent groups out of R ^{11 to} R ³⁴ may be bonded to each other to form a ring.

In formulas (II-1) to (II-3), A ^{1 to} A ³ are all elements from the third period (third to sixth periods) of the periodic table, and A ¹ is a long-period type An element belonging to Group 17 of the periodic table is represented, A ² represents an element belonging to Group 16 and A ³ represents an element belonging to Group 15.

Among these, from the viewpoint of electron acceptability and availability, elements before the fifth period (third to fifth periods) of the periodic table are preferable. That is, A ¹ is preferably any ^one of an iodine atom, a bromine atom, and a chlorine atom, A ² is preferably any one of a tellurium atom, a selenium atom, and a sulfur atom, and A ³ is preferably an antimony atom, an arsenic atom, Any of the phosphorus atoms is preferred.

In particular, from the viewpoints of electron acceptability and compound stability, a compound in which A ¹ in formula (II-1) is a bromine atom or an iodine atom, or A ² in formula (II-2) is a selenium atom or a sulfur atom. Of these, a compound in which A ¹ in Formula (II-1) is an iodine atom is particularly preferable.

In formulas (II-1) to (II-3), Z ₁ ^{n1- to} Z ₃ ^n3- each independently represents a counter anion. The type of the counter anion is not particularly limited, and may be a monoatomic ion or a complex ion. However, the larger the size of the counter anion, the more the negative charge is delocalized, and the positive charge is also delocalized thereby increasing the electron accepting ability. Therefore, the complex ion is preferable to the monoatomic ion.

In formulas (II-1) to (II-3), n _{1 to} n ₃ are each independently any positive integer corresponding to the ionic valence of counter anions Z ₁ ^{n1 to} Z ₃ ⁿ³⁻ . The values of n _{1 to} n ₃ are not particularly limited, but all are preferably 1 or 2, and particularly preferably 1.

Specific examples of Z ₁ ^{n1- to} Z ₃ ^n3- include hydroxide ion, fluoride ion, chloride ion, bromide ion, iodide ion, cyanide ion, nitrate ion, nitrite ion, sulfate ion, sulfite. Ion, perchlorate ion, perbromate ion, periodate ion, chlorate ion, chlorite ion, hypochlorite ion, phosphate ion, phosphite ion, hypophosphite ion, borate ion , Isocyanate ion, hydrosulfide ion, tetrafluoroborate ion, hexafluorophosphate ion, hexachloroantimonate ion; carboxylate ion such as acetate ion, trifluoroacetate ion, benzoate ion; methanesulfonate ion, trifluoro Sulfonate ions such as romethanesulfonate ion; Alkoxy ions such as methoxy ion and t-butoxy ion For example.

In particular, the counter anions Z ₁ ^{n1 to} Z ₃ ⁿ³ are preferably complex ions represented by the following formulas (II-4) to (II-6) from the viewpoint of the stability of the compound and the solubility in a solvent. In view of the large size, the negative charge is delocalized, and the positive charge is also delocalized to increase the electron accepting ability. Therefore, a complex ion represented by the following formula (II-6) is more preferable.

In formulas (II-4) and (II-6), E ¹ and E ³ each independently represents an element belonging to Group 13 of the long-period periodic table. Of these, a boron atom, an aluminum atom, and a gallium atom are preferable, and a boron atom is preferable from the viewpoint of stability of the compound and ease of synthesis and purification.

In formula (II-5), E ² represents an element belonging to Group 15 of the long-period periodic table. Among these, a phosphorus atom, an arsenic atom and an antimony atom are preferable, and a phosphorus atom is preferable from the viewpoint of stability of the compound, ease of synthesis and purification, and toxicity.

  In the formulas (II-4) and (II-5), X represents a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom, and is a fluorine atom in terms of stability of the compound, ease of synthesis and purification, A chlorine atom is preferable, and a fluorine atom is particularly preferable.

In formula (II-6), Ar ^{61 to} Ar ⁶⁴ each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group. Examples of the aromatic hydrocarbon group and aromatic heterocyclic group are derived from the same 5- or 6-membered monocyclic ring or 2-5 condensed ring as those exemplified above for R ¹¹ , R ²¹ and R ³¹ . A monovalent group is mentioned. Among these, a monovalent group derived from a benzene ring, a naphthalene ring, a pyridine ring, a pyrazine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a quinoline ring, or an isoquinoline ring is preferable from the viewpoint of stability and heat resistance of the compound.

The aromatic hydrocarbon group and aromatic heterocyclic group exemplified as Ar ^{61 to} Ar ⁶⁴ may be further substituted with another substituent as long as not departing from the gist of the present invention. The type of the substituent is not particularly limited, and any substituent can be applied, but an electron-withdrawing group is preferable.

Especially, it is more preferable that at least one group among Ar ^{61 to} Ar ⁶⁴ has one or two or more fluorine atoms or chlorine atoms as substituents. In particular, it is particularly a perfluoroaryl group in which all the hydrogen atoms of Ar ^{61 to} Ar ⁶⁴ are substituted with fluorine atoms from the viewpoint of efficiently delocalizing negative charges and having a suitable sublimation property. preferable. Specific examples of the perfluoroaryl group include a pentafluorophenyl group, a heptafluoro-2-naphthyl group, and a tetrafluoro-4-pyridyl group.
In addition, as for the said substituent, only one may be substituted and two or more may be substituted by arbitrary combinations and ratios.

  The formula amount of the complex ions represented by the formulas (II-4) to (II-6) is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 100 or more, preferably 300 or more, more preferably 400 or more. Moreover, it is usually 5000 or less, preferably 3000 or less, more preferably 2000 or less. If the formula amount of the complex ion is too small, delocalization of the positive charge and the negative charge is insufficient, so that the electron accepting ability may be decreased, and if the formula amount of the complex ion is too large, The compound itself may interfere with charge transport.

  Specific examples of complex ions represented by formulas (II-4) to (II-6) are shown below, but the present invention is not limited to these.

  As the material for the hole injection layer, any one of the various electron-accepting compounds described above may be used alone, or two or more may be used in any combination and ratio. When two or more kinds of electron-accepting compounds are used, two or more kinds of electron-accepting compounds corresponding to any one of the formulas (II-1) to (II-3) may be combined. Two or more electron-accepting compounds corresponding to different formulas may be combined.

  The content of the electron-accepting compound in the hole-injecting layer and the composition for the hole-injecting layer is arbitrary as long as the effect of the present invention is not significantly impaired. % By weight or more, preferably 1% by weight or more, and usually 100% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. A larger amount of the electron-accepting compound is preferable because it is easier to insolubilize, and the heating time can be insolubilized in a short time. In addition, when using together 2 or more types of electron-accepting compounds, it is made for the total content of these to be contained in the said range.

  In addition, when the hole-injecting layer is formed or after the formation, the hole-transporting compound reacts with the electron-accepting compound, so that a cation radical and an ionic compound of the hole-transporting compound are formed in the formed hole-injecting layer. May be generated.

[I-1-1-3. Low molecular weight hole transport compound]
As a material for the hole injection layer, it is preferable to use a low molecular weight hole transporting compound as necessary.
The low molecular weight hole transporting compound can be appropriately selected from various compounds conventionally used as a hole injection / transport thin film forming material in an organic EL device. Among them, those having high solubility in a solvent are preferable.

  Preferable examples of the low molecular weight hole transporting compound include aromatic amine compounds. Of these, aromatic tertiary amine compounds are particularly preferred. Preferable specific examples of the aromatic tertiary amine compound include binaphthyl compounds represented by the following formula (IV).

In the formula (IV), Ar ^{51 to} Ar ⁵⁸ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ⁵¹ and Ar ⁵² , Ar ⁵⁵ and Ar ⁵⁶ may be bonded to each other to form a ring. Specific examples, preferred examples of Ar ^{51 to} Ar ⁵⁸ , examples of substituents that may be present, and examples of preferred substituents are the same as those exemplified above for Ar ^{1 to} Ar ⁵ , respectively. That is, examples of embodiment, preferred examples, examples of the substituent which may have and preferred substituents of Ar ⁵¹ to Ar ⁵⁶ are the same as those exemplified above for Ar ¹ and Ar ^2, Ar ⁵⁷ And specific examples and preferred examples of Ar ⁵⁸ , examples of substituents that may be present, and examples of preferred substituents are the same as those exemplified above for Ar ^{3 to} Ar ⁵ .

In formula (IV), u and v each independently represent an integer of 0 or more and 4 or less. However, u + v ≧ 1. Particularly preferred are u = 1 and v = 1.
In formula (IV), Q ¹ and Q ² each independently represent a direct bond or a divalent linking group.

In addition to-(Q ¹ NAr ⁵³ Ar ⁵⁷ (NAr ⁵¹ Ar ⁵² )) and-(Q ² NAr ⁵⁴ Ar ⁵⁸ (NAr ⁵⁵ Ar ⁵⁶ )), the naphthalene ring in formula (IV) has an optional substituent. You may have only 1 type or 2 types or more by arbitrary combinations and ratios. Further, these substituents — (Q ¹ NAr ⁵³ Ar ⁵⁷ (NAr ⁵¹ Ar ⁵² ) and — (Q ² NAr ⁵⁴ Ar ⁵⁸ (NAr ⁵⁵ Ar ⁵⁶ )) may be substituted at any position of the naphthalene ring. However, among them, binaphthyl compounds substituted on the 4-position and 4′-position of the naphthalene ring in formula (IV) are more preferred.

  The binaphthylene structure in the compound represented by the formula (IV) preferably has a substituent at the 2,2′-position. As the substituent bonded to the 2,2′-position, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an alkenyl group which may have a substituent, The alkoxycarbonyl group etc. which may have a substituent are mentioned. In addition, these substituents may be substituted by only one and two or more may be substituted by arbitrary combinations and ratios.

  In the compound represented by the formula (IV), the binaphthylene structure may have an arbitrary substituent other than the 2,2′-position. Examples of the substituent include the groups described above as substituents at the 2,2′-position. The compound represented by the formula (IV) has a substituent at the 2-position and the 2'-position, so that the two naphthalene rings are twisted so that the solubility is improved. In addition, these substituents may be substituted by only one and two or more may be substituted by arbitrary combinations and ratios.

  The molecular weight of the binaphthyl compound represented by the formula (IV) is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 500 or more, preferably 700 or more, and usually 2000 or less, preferably 1200 or less. is there.

  The preferred specific examples of the binaphthyl-based compound represented by the formula (IV) that can be applied in the present invention are shown below, but the present invention is not limited to these.

  Other examples of the aromatic amine compound that can be used as a low-molecular-weight hole-transporting compound include conventionally known compounds that have been used as a hole-injecting / transporting layer-forming material in organic EL devices. . Specific examples thereof include an aromatic diamine compound in which a tertiary aromatic amine unit such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane is linked (Japanese Patent Laid-Open No. 59-194393); Aromatics containing two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms Amines (Japanese Patent Laid-Open No. 5-234681); derivatives of triphenylbenzene and aromatic triamines having a starburst structure (US Pat. No. 4,923,774); N, N′-diphenyl-N, N′-bis (3 Aromatic diamines such as (methylphenyl) biphenyl-4,4′-diamine (US Pat. No. 4,764,625); α, α, α ′, α′-tetramethyl-α, α′- (4-di-p-tolylaminophenyl) -p-xylene (JP-A-3-2699084); sterically asymmetric triphenylamine derivative as a whole molecule (JP-A-4-129271); pyrenyl group A compound in which a plurality of aromatic diamino groups are substituted (Japanese Patent Laid-Open No. 4-175395); an aromatic diamine in which a tertiary aromatic amine unit is linked by an ethylene group (Japanese Patent Laid-Open No. 4-264189); having a styryl structure Aromatic diamines (Japanese Patent Laid-Open No. 4-290851); those obtained by linking aromatic tertiary amine units with thiophene groups (Japanese Patent Laid-Open No. 4-304466); Starburst type aromatic triamines (Japanese Patent Laid-Open No. 4-308688) ); Benzylphenyl compound (JP-A-4-364153); a tertiary amine linked by a fluorene group (JP-A-5-25473); Triamine compounds (JP-A-5-239455); Bisdipyridylaminobiphenyl (JP-A-5-320634); N, N, N-triphenylamine derivatives (JP-A-6-6) 1972); aromatic diamines having a phenoxazine structure (JP-A-7-138562); diaminophenylphenanthridine derivatives (JP-A-7-252474); hydrazone compounds (JP-A-2-311591). ); Silazane compounds (US Pat. No. 4,950,950); silanamine derivatives (JP-A-6-49079); phosphamine derivatives (JP-A-6-25659); quinacridone compounds and the like. These aromatic amine compounds may be used in combination of two or more as required.

  Other specific examples of the aromatic amine compound that can be used as a low molecular weight hole transporting compound include metal complexes of 8-hydroxyquinoline derivatives having a diarylamino group. In the above metal complex, the central metal is alkali metal, alkaline earth metal, Sc, Y, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Al, Ga, In, Si, Ge, Sn , Sm, Eu, Tb, and the ligand 8-hydroxyquinoline has at least one diarylamino group as a substituent, but may have any substituent other than the diarylamino group .

  Moreover, as a preferable specific example of a phthalocyanine derivative or a porphyrin derivative applicable as a low molecular weight hole transporting compound, porphyrin, 5,10,15,20-tetraphenyl-21H, 23H-porphyrin, 5,10,15 , 20-tetraphenyl-21H, 23H-porphyrin cobalt (II), 5,10,15,20-tetraphenyl-21H, 23H-porphyrin copper (II), 5,10,15,20-tetraphenyl-21H, 23H-porphyrin zinc (II), 5,10,15,20-tetraphenyl-21H, 23H-porphyrin vanadium (IV) oxide, 5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphyrin 29H, 31H-phthalocyanine copper (II), phthalocyanine zinc (II), Russia Nin titanium, phthalocyanine oxide magnesium, phthalocyanine lead, phthalocyanine copper (II), 4,4 ', 4' ', 4' '' - tetraaza-29H, 31H-phthalocyanine, and the like.

  Moreover, as a preferable specific example of an oligothiophene derivative applicable as a low molecular weight hole transporting compound, α-sexithiophene and the like can be mentioned.

  The molecular weights of these low molecular weight hole transporting compounds are arbitrary as long as the effects of the present invention are not significantly impaired, but are usually 200 or more, preferably 400 or more, more preferably 600 or more, and usually 5000 or less. The range is preferably 3000 or less, more preferably 2000 or less, still more preferably 1700 or less, and particularly preferably 1400 or less. If the molecular weight is too small, the heat resistance tends to be low, whereas if the molecular weight of the low molecular weight hole transporting compound is too large, synthesis and purification tend to be difficult.

  In addition, a low molecular weight hole transportable compound may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the low molecular weight hole transporting compound in the hole injection layer and the hole injection layer composition is arbitrary as long as the effects of the present invention are not significantly impaired. However, when used in combination with a hole transporting polymer, the content of the low molecular weight hole transporting compound is usually 0.01% by weight or more, preferably 0.1% by weight, based on the value of the hole transporting polymer. % Or more, more preferably 1% by weight or more, and usually 80% by weight or less, preferably 70% by weight or less, and more preferably 50% by weight or less. If the amount of the low molecular weight hole transporting compound is too small, the hole transporting property may be lowered. If the amount is too large, the hole transporting compound may be eluted into the layer laminated thereon. In addition, when using together 2 or more types of low molecular weight hole transportable compounds, content of these is made to be contained in the said range.

  By the way, in the manufacturing method of the present invention, a hole transporting compound such as a hole transporting polymer and a low molecular weight hole transporting compound, and an electron accepting property are provided in the hole injection layer composition and the hole injection layer. It is preferable to contain it in combination with a compound. Thereby, a high hole injection / transport property can be obtained.

[I-1-1-4. Other ingredients]
As a material for the hole injection layer, in addition to the above-described hole transporting polymer, electron accepting compound and low molecular weight hole transporting compound, other components may be used as long as the effects of the present invention are not significantly impaired. It may be included. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, coatability improving agents, and the like. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and ratios.

[I-1-2. Formation of hole injection layer]
The hole injection layer according to the present invention is formed by a wet film formation method. In this case, the composition for hole injection layer is applied on the layer (usually the anode) corresponding to the lower layer of the hole injection layer by a method such as spin coating or dip coating, and dried to correct the composition. A hole injection layer is formed.

  As the hole injection layer solvent to be contained in the composition for hole injection layer, any solvent can be used as long as the hole injection layer can be formed. However, among the aforementioned hole transporting polymer, electron accepting compound and low molecular weight hole transporting compound, those capable of dissolving at least one, particularly two or more, and particularly all three. preferable. Specifically, the hole-transporting polymer is usually 0.005% by weight or more, preferably 0.5% by weight or more, and particularly preferably 1% by weight or more at room temperature and normal pressure. It is preferable to dissolve 0.001% by weight or more, particularly 0.1% by weight or more, particularly 0.2% by weight or more, and a low molecular weight hole transporting compound is usually 0.005% by weight or more. Among them, it is preferable to dissolve 0.5% by weight or more, particularly 1% by weight or more.

  Moreover, as a solvent for hole injection layers, there is a possibility of deactivating free carriers (cation radicals) generated from hole transporting polymers, electron accepting compounds, low molecular weight hole transporting compounds, and mixtures thereof. A solvent that does not contain a deactivating substance or a substance that generates a deactivating substance is preferred.

  Preferable examples of the hole injection layer solvent include ether solvents and ester solvents. Specifically, examples of the ether solvent include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (hereinafter abbreviated as “PGMEA” as appropriate). Aliphatic ether; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole Aromatic ethers and the like. On the other hand, examples of ester solvents include aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate, and n-butyl lactate; phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, And aromatic esters such as n-butyl benzoate. In addition, these may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of solvents that can be used in addition to the ether solvents and ester solvents described above include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Solvent, dimethyl sulfoxide and the like. In addition, these may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio. Moreover, you may use 1 type, or 2 or more types among these solvents in combination with 1 type or 2 or more types among the above-mentioned ether type solvent and ester type solvent. In particular, aromatic hydrocarbon solvents such as benzene, toluene and xylene have a low ability to dissolve the electron-accepting compound and the hole-transporting polymer. Therefore, it is preferable to use a mixture with an ether solvent and an ester solvent. .

  The concentration of the solvent for the hole injection layer relative to the composition for the hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50%. It is in the range of not less than weight, usually 99.999% by weight or less, preferably 99.99% by weight or less, and more preferably 99.9% by weight or less. In addition, when mixing and using 2 or more types of solvents as a solvent for positive hole injection layers, it is made for the sum total of these solvents to satisfy | fill this range.

  In addition, since the organic EL element is usually formed by laminating layers (organic layers) made of a large number of organic compounds, each layer is preferably a uniform layer. Here, when a layer is formed by a wet film formation method, if a certain amount or more of water is present in the composition for forming each layer, moisture is mixed into the coating film and the uniformity of the film is impaired. It is preferable that the water content is as low as possible. In general, since organic EL elements use many materials such as a cathode that are remarkably deteriorated by moisture, the presence of moisture is preferably as small as possible from the viewpoint of deterioration of the elements. For the above reasons, the amount of water contained in the composition for hole injection layer is usually 1% by weight or less, preferably 0.1% by weight or less, and more preferably 0.05% by weight or less.

  Examples of methods for reducing the amount of water in the composition for hole injection layer include use of a nitrogen gas seal, use of a desiccant, dehydration of the solvent in advance, use of a solvent with low water solubility, etc. The method is mentioned. Especially, it is preferable to use a solvent with low water solubility from the viewpoint of preventing the phenomenon that the coating film absorbs moisture in the air and whitens when applying the composition for hole injection layer. Specifically, the composition for a hole injection layer is a solvent having low water solubility, specifically, for example, a solvent having water solubility at 25 ° C. of 1% by weight or less, preferably 0.1% by weight or less. Is usually 10% by weight or more, preferably 30% by weight or more, and particularly preferably 50% by weight or more based on the whole composition for a hole injection layer.

  There is no particular limitation on the method for coating and forming the hole injection layer composition by a wet film formation method. As an example of the coating / film forming method, various known methods such as spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, and ink jet method can be selected and used.

  After the application / film formation of the composition for hole injection layer, the resulting coating film is dried and the solvent for hole injection layer is removed to form a hole injection layer. The method for drying is not particularly limited, and examples thereof include heat drying and drying under reduced pressure. Specific conditions for drying are arbitrary as long as the effects of the present invention are not significantly impaired. For example, the temperature condition is usually 80 ° C. or higher, preferably 100 ° C. or higher, and usually 350 ° C. or lower, preferably It is 280 degrees C or less. The pressure is usually 1.3 Pa or more, preferably 13.3 Pa or more, and usually 101325 Pa or less, preferably 1013 Pa or less. Furthermore, the drying time is usually 1 minute or longer, preferably 10 minutes or longer, and usually 12 hours or shorter, preferably 6 hours or shorter.

  The thickness of the hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

[I-2. Hole injection layer heating process]
In the production method of the present invention, an organic layer is formed on the hole injection layer after a heating step of heating the formed hole injection layer. Here, heating means raising the temperature of the heating atmosphere. As a result, the hole injection layer is insolubilized with respect to the organic layer solvent used when forming the organic layer formed on the hole transport layer, and the hole injection layer is formed by the penetration of the organic layer solvent. Swelling and elution of the material contained in the hole injection layer into the organic layer solvent can be suppressed.

  However, in the production method of the present invention, the heating temperature in the heating step satisfies both the following heating condition (1) and heating condition (2). Here, the heating temperature refers to the temperature of the atmosphere, for example, the temperature in the oven or the temperature of the hot plate.

[Heating condition (1)]
The heating temperature in the heating step is 200 ° C. or higher, preferably 210 ° C. or higher, more preferably 230 ° C. or higher. If the heating temperature is too low, insolubilization in the organic layer solvent may be insufficient. In addition, there is no restriction | limiting in particular in the upper limit of heating temperature, Usually, 350 degrees C or less, Preferably it is 280 degrees C or less. If the heating temperature is too high, a part of the material of the hole injection layer may be decomposed. According to the study by the present inventors, it is presumed that when the above decomposition occurs, the acceptor in the hole injection layer disappears and the drive voltage of the organic EL element increases.

[Heating condition (2)]
When the boiling point of the organic layer solvent is represented by “T _bp ”, the heating temperature in the heating step is “T _bp −10 ° C.” or higher, preferably “T _bp −8 ° C.” or higher, more preferably “T _bp ”. ” _Or more, more preferably“ T _bp + 10 ° C. ”or more, and particularly preferably“ T _bp + 20 ° C. ”or more. The upper limit of the heating temperature is preferably 350 ° C. or lower. If the heating temperature is too low, insolubilization in the organic layer solvent may be insufficient. When two or more organic layer solvents are used, the heating temperature in the heating step is determined by setting the boiling point of the organic layer solvent having the lowest boiling point as T _bp .

  The time for heating at the heating temperature in the heating step is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 30 minutes or longer, preferably 1 hour or longer, and usually 5 hours or shorter, especially 3 hours or shorter. Is preferred. If the heating time is too short, insolubilization to the organic layer solvent may be insufficient, and if the heating time is too long, the production cost may increase.

  The atmosphere in the heating step is arbitrary as long as the effects of the present invention are not significantly impaired. However, from the viewpoint of reliably insolubilizing the hole injection layer, oxygen is preferably present in the atmosphere. Specifically, the oxygen concentration is usually 1% or more, preferably 10% or more, more preferably 15% or more, and usually 99% or less, especially 50% or less, and more preferably 30% or less. It is preferable to do. Therefore, the atmosphere is preferably in the air or in dry air.

In the heating step, the heating may be performed continuously or intermittently.
There is no restriction | limiting in particular in the heating means used in a heating process. Examples of the heating means include a clean oven, a hot plate, infrared rays, a halogen heater, and microwave irradiation. Among these, a clean oven and a hot plate are preferable.

In addition, you may perform a post-processing as needed after a heating process.
In addition, when the element is stored for a long time after the heating step, it is preferably stored in an inert gas atmosphere such as nitrogen.
Further, the heating step may be performed as a step integrated with the drying of the hole injection layer.

  Even if the hole injection layer obtained in this way is immersed in an organic layer solvent used for forming an upper layer for 10 minutes, the decrease in film thickness is usually 10% or less, preferably It is a suitable film of 5% or less, more preferably 3% or less.

[I-3. Organic layer deposition process]
After the heating step, an organic layer is formed on the hole injection layer. The type of organic layer formed on the hole injection layer differs depending on the layered structure of the target organic EL element, but there are other restrictions as long as the layer contains an organic compound and is formed by a wet film formation method. No. For example, an organic light emitting layer, a hole blocking layer, a hole transport layer, an electron transport layer and the like can be mentioned. Among them, a light emitting layer (organic light emitting layer) or a hole transport layer is more preferable, and a light emitting layer. It is particularly preferred. However, it is necessary that the hole injection layer and the organic layer are in direct contact with each other at least in part and preferably on the entire surface thereof.

  In the production method of the present invention, the organic layer is formed by a wet film formation method. Specifically, an organic layer is formed by dissolving an organic layer material in an appropriate organic layer solvent to prepare an ink (application solution), applying the ink to form a film, and drying the film. .

  However, as the organic layer solvent, a solvent having a boiling point of 200 ° C. or higher, preferably 210 ° C. or higher is used. If the boiling point of the organic layer solvent is too low, the drying speed is high and the film quality may be deteriorated. In addition, although the upper limit of the boiling point of the solvent for organic layers is arbitrary unless the effect of this invention is impaired remarkably, it is usually 350 degrees C or less, and it is preferable that it is 260 degrees C or less especially. If the boiling point of the organic layer solvent is too high, the solvent may remain in the organic layer in the drying step.

  Examples of suitable organic layer solvents include cyclohexyl benzene, isoamyl benzoate, diphenyl ether, benzene having an alkyl chain having 5 or more carbon atoms (for example, pentyl, hexyl, heptyl, octyl, etc.), tetralin, 1 , 4-butanediol, glycerin, nitrobenzene and the like. Among these, a hydrocarbon solvent containing no hetero atom is preferable.

  Moreover, only 1 type may be used for the solvent for organic layers, and it is preferable to use 2 or more types together by arbitrary combinations and ratios. In addition, when 2 or more types of organic layer solvents are contained in the ink, it is sufficient that at least one of the organic layer solvents has a boiling point in the above range.

  Further, at least one of the organic layer solvents may be a solvent capable of dissolving a hole transporting compound (including a hole transporting polymer and a low molecular weight hole transporting compound) or an electron accepting compound. preferable. Here, the solvent for the organic layer can dissolve the hole transporting compound or the electron accepting compound means that the solvent for the organic layer contains the hole transporting compound or the electron accepting compound usually at 0.001 weight at room temperature. % Or more, preferably 0.05% by weight or more, more preferably 0.5% by weight or more. Even when a solvent for an organic layer capable of dissolving a hole transporting compound or an electron accepting compound is used as described above, the hole injection layer is insolubilized by the heating step described above, so that an organic layer is formed. In this case, it is possible to suppress swelling of the hole injection layer due to permeation of the organic layer solvent and elution of the material contained in the hole injection layer into the organic layer solvent.

  The ink used for forming the organic layer has a viscosity of 1 cp or more, preferably 1.5 cp or more, more preferably 1.8 cp or more, and 20 cp or less, preferably 15 cp or less, more preferably 12 cp or less. It is. If the viscosity of the ink is too low or too high, there is a possibility that, for example, in the ink jet method, the ejectability is lowered, or the film thickness is difficult to control in the spin coating method. The viscosity can be measured with a rotary viscometer. Usually, it is carried out at 25 ° C., a rotor rotational speed of 100 rpm, and a shear rate of 750 (1 / sec).

  There is no limitation on the method for adjusting the viscosity of the ink. For example, it can be adjusted by using a solvent having a high viscosity or by containing a thickener.

  The concentration of the material for the organic layer in the ink is arbitrary as long as the effects of the present invention are not significantly impaired, but it is usually 0.002% by weight or more, preferably 0.02% by weight or more, and particularly preferably 0.2% by weight or more. Further, it is usually 20% by weight or less, preferably 10% by weight or less, and particularly preferably 5% by weight or less. If the concentration of the material of the organic layer is too low, the film thickness may be thin and the film quality may be deteriorated. If the concentration is too large, the film thickness may be increased and the driving voltage may be increased.

  There is no limitation on the method of applying and forming the ink, and an appropriate method may be arbitrarily adopted. Examples thereof include spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, and ink jet method.

  After the ink application and film formation, the obtained coating film is dried and the organic layer solvent is removed to form the organic layer. The method for drying is not particularly limited, and examples thereof include heat drying and drying under reduced pressure. Specific conditions for drying are arbitrary as long as the effects of the present invention are not significantly impaired. For example, the temperature condition is preferably 20 ° C. or higher, and is usually a glass of a material contained in the organic layer. Below the transition temperature. The pressure is usually 1.3 Pa or more, preferably 13.3 Pa or more, and usually 101325 Pa or less, preferably 1013 Pa or less. Further, the drying time is usually 10 minutes or longer, preferably 13.3 minutes or longer, and usually 12 hours or shorter, preferably 3 hours or shorter.

[I-4. Advantages of the manufacturing method described above]
By performing the hole injection layer forming step and the heating step, and the organic layer forming step described above, the manufacturing method of the present invention can manufacture an organic EL element having a long lifetime and high luminous efficiency. In addition to the above advantages, the organic EL device manufactured by the manufacturing method of the present invention usually has an advantage that the driving voltage of the device can be reduced. The reason why such an excellent advantage can be exhibited is not clear, but according to the study by the present inventors, it is presumed as follows.

  Conventionally, in wet film formation methods represented by spin coating, ink jet, printing, etc., it has been required to precisely control ink application characteristics and drying speed. Use was considered preferable. However, these high-boiling solvents have a slow drying rate, and when the ink containing these high-boiling solvents is wet-deposited on the hole injection layer, the surface of the hole injection layer is kept in contact with the solvent for a long time. Is done. As a result, it is considered that the hole injection layer swelled due to the permeation of the solvent and the material constituting the hole injection layer was eluted. This is considered to have caused a significant decrease in light emission efficiency and a decrease in element driving life.

  Therefore, in the production method of the present invention, the hole injection layer is subjected to a baking treatment at a temperature of 200 ° C. or higher and “solvent boiling point−10 ° C.” or higher. Thereby, it is considered that the interaction between the hole transporting compound and the electron accepting compound in the hole injection layer becomes stronger. This is presumably because more acceptor-derived radicals are generated in the hole injection layer. As a result, the electrostatic bonding force between the molecules of the material constituting the hole injection layer is greatly increased, and the hole injection layer swells due to the penetration of the solvent contained in the upper ink into the hole injection layer ( It is considered that the deterioration of the film quality and the charge transporting property) or the elution of the material of the hole injection layer (mixing of impurities into the organic layer) is significantly suppressed. As a result, it is estimated that the luminous efficiency and driving life of the obtained organic EL element are improved.

[II. Organic electroluminescent device]
An organic EL device manufactured by the manufacturing method of the present invention (hereinafter, abbreviated as “organic EL device of the present invention” as appropriate) has an anode and a cathode, and the hole injection layer between the anode and the cathode. And an organic layer. In addition, the organic EL device of the present invention usually includes a substrate, and has a laminated structure laminated on the substrate.

  FIG. 1 is a cross-sectional view schematically showing an example of the structure of the organic EL element of the present invention. An organic EL element 10a shown in FIG. 1 is configured by laminating an anode 2, a hole injection layer 3, an organic light emitting layer 4, an electron injection layer 5 and a cathode 6 in this order on a substrate 1. In the case of this configuration, the hole injection layer 3 usually corresponds to the above-described hole injection layer, and the organic light emitting layer 4 corresponds to an organic layer formed on the hole injection layer.

[II-1. substrate]
The substrate 1 serves as a support for the organic EL element 10a. For example, a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. However, it is preferable to pay attention to gas barrier properties when using a synthetic resin substrate. This is because if the gas barrier property of the substrate 1 is too small, the organic EL element 10a may be deteriorated by the outside air that has passed through the substrate 1. For this reason, a method of securing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also one of preferable methods.

[II-2. anode]
An anode 2 is provided on the substrate 1. The anode 2 plays a role of hole injection into a layer on the organic light emitting layer 4 side (hole injection layer 3 or organic light emitting layer 4 or the like).
This anode 2 is usually made of a metal such as aluminum, gold, silver, nickel, palladium, or platinum; a metal oxide such as an oxide of indium and / or tin; a metal halide such as copper iodide; a carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline. In addition, only 1 type may be used for the material of the anode 2, and 2 or more types may be used together by arbitrary combinations and a ratio.

Although there is no restriction | limiting in the formation method of the anode 2, Usually, it carries out by sputtering method, a vacuum evaporation method, etc. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by dispersing them and applying them onto the substrate 1. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).
In addition, the anode 2 is usually a single layer structure, but may be a laminated structure made of a plurality of materials if desired.

  The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more. Also, it is usually 1000 nm or less, preferably 500 nm or less. On the other hand, when the anode 2 may be opaque, the thickness of the anode 2 is arbitrary. The anode 2 may be configured the same as the substrate 1, and the anode 2 may also serve as the substrate 1. Further, it is possible to laminate different conductive materials on the anode 2.

Further, for the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is subjected to ultraviolet (UV) / ozone treatment, oxygen plasma, argon plasma. It is preferable to process.
Furthermore, a known anode buffer layer is inserted between the hole injection layer 3 and the anode 2 for the purpose of further improving the efficiency of hole injection and improving the adhesion of the whole organic layer to the anode. Also good.

[II-3. Hole injection layer]
The hole injection layer 3 is a layer that transports holes from the anode 2 to the organic light emitting layer 4. About the detail of the component contained in the positive hole injection layer 3, [I-1-1. As described in the column “Material of hole injection layer”. Moreover, about the formation method of the positive hole injection layer 3, [I-1. As described in the column of “Hole injection layer forming step”.
Furthermore, in the organic EL element of the present invention, as described above, the hole injection layer 3 is insolubilized by the heating process.

[II-4. Organic light emitting layer]
On the hole injection layer 3, an organic light emitting layer 4 is provided as an organic layer according to the present invention. The organic light emitting layer 4 is excited by recombination of holes injected from the anode 2 through the hole injection layer 3 and electrons injected from the cathode 6 through the electron injection layer 5 between the electrodes to which an electric field is applied. Thus, it is a layer that becomes a main light emitting source.

  The organic light emitting layer 4 contains at least a material having a light emitting property (light emitting material) as a constituent material, and preferably a compound having a hole transporting property (hole transporting compound) or an electron. And a compound having a transport property (electron transporting compound). Furthermore, the organic light emitting layer 4 may contain other components as long as the effects of the present invention are not significantly impaired. As these materials, it is preferable to use low molecular weight materials from the viewpoint of forming the organic light emitting layer 4 by a wet film forming method.

Any known material can be applied as the light emitting material. For example, a fluorescent material or a phosphorescent material may be used, but a phosphorescent material is preferable from the viewpoint of internal quantum efficiency.
For the purpose of improving the solubility in a solvent, it is preferable to reduce the symmetry and rigidity of the molecules of the luminescent material, or to introduce a lipophilic substituent such as an alkyl group.

Hereinafter, although the example of a fluorescent dye is mentioned among light emitting materials, a fluorescent dye is not limited to the following illustrations.
Examples of the fluorescent dye that gives blue light emission (blue fluorescent dye) include perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof.
Examples of fluorescent dyes that give green light emission (green fluorescent dyes) include quinacridone derivatives and coumarin derivatives.
Examples of fluorescent dyes that give yellow light (yellow fluorescent dyes) include rubrene and perimidone derivatives.
Examples of fluorescent dyes that give red luminescence (red fluorescent dyes) include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzoates. Examples thereof include thioxanthene derivatives and azabenzothioxanthene.

  Next, phosphorescent materials among the light emitting materials will be described. Examples of the phosphorescent material include an organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table.

  Examples of preferable metals selected from Groups 7 to 11 of the periodic table contained in the phosphorescent organometallic complex include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. . Preferred examples of these organometallic complexes include compounds represented by the following formula (V) or formula (VI).

｛式（Ｖ）中、Ｍは金属を表わし、ｑは上記金属の価数を表わす。また、Ｌ及びＬ’は二座配位子を表わす。ｊは０、１又は２の数を表わす。｝

{In Formula (V), M represents a metal, and q represents the valence of the metal. L and L ′ represent bidentate ligands. j represents a number of 0, 1 or 2. }

｛式（VI）中、Ｍ⁷は金属を表わし、Ｔは炭素原子又は窒素原子を表わす。Ｒ⁹²〜Ｒ⁹⁵は、それぞれ独立に置換基を表わす。但し、Ｔが窒素原子の場合は、Ｒ⁹⁴及びＲ⁹⁵は無い。｝

{In Formula (VI), M ⁷ represents a metal, and T represents a carbon atom or a nitrogen atom. R ^{92 to} R ⁹⁵ each independently represents a substituent. However, when T is a nitrogen atom, R ⁹⁴ and R ⁹⁵ are absent. }

Hereinafter, the compound represented by the formula (V) will be described first.
In formula (V), M represents an arbitrary metal, and specific examples of preferable ones include the metals described above as metals selected from Groups 7 to 11 of the periodic table.

上記Ｌの部分構造において、環Ａ１”は、置換基を有していてもよい、芳香族炭化水素基又は芳香族複素環基を表わす。 In the formula (V), the bidentate ligand L represents a ligand having the following partial structure.

In the partial structure of L, ring A1 ″ represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.

  Examples of the aromatic hydrocarbon group constituting the ring A1 ″ include a 5- or 6-membered monocyclic ring or a 2-5 condensed ring. Specific examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene. And a monovalent group derived from a ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, and a fluorene ring.

  Examples of the aromatic heterocyclic group constituting the ring A1 ″ include a 5- or 6-membered monocyclic ring or a 2-4 condensed ring. Specific examples thereof include a furan ring, a benzofuran ring, a thiophene ring, and a benzoic ring. Thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring , Benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, cinnoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring , Perimidine ring, key Gelsolin ring, quinazolinone ring, and a monovalent group derived from azulene ring.

In the partial structure of L, ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.
Examples of the nitrogen-containing aromatic heterocyclic group constituting the ring A2 include a 5- or 6-membered monocyclic ring or a 2-4 condensed ring. Specific examples thereof include pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, furopyrrole ring, thienofuran ring, benzoisoxazole Ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, And monovalent group derived from a quinazolinone ring.

Examples of the substituent that each ring A1 ″ or ring A2 may have include: a halogen atom such as a fluorine atom; an alkyl group such as a methyl group and an ethyl group; an alkenyl group such as a vinyl group; a methoxycarbonyl group and an ethoxy group Alkoxycarbonyl groups such as carbonyl groups; alkoxy groups such as methoxy groups and ethoxy groups; aryloxy groups such as phenoxy groups and benzyloxy groups; dialkylamino groups such as dimethylamino groups and diethylamino groups; diarylamino groups such as diphenylamino groups Carbazolyl group; acyl group such as acetyl group; haloalkyl group such as trifluoromethyl group; cyano group; aromatic hydrocarbon group such as phenyl group, naphthyl group, phenanthyl group and the like.
In addition, as for the said substituent, only 1 may be substituted and 2 or more may be substituted by arbitrary combinations and ratios.

In formula (V), bidentate ligand L ′ represents a ligand having at least one of the following partial structures. In the following formulae, “Ph” represents a phenyl group.

Among these, as L ′, the following ligands are preferable from the viewpoint of the stability of the complex.

  More preferred examples of the compound represented by the formula (V) include compounds represented by at least one of the following formulas (Va), (Vb) and (Vc).

{In Formula (Va), M ⁴ represents the same metal as M, w represents the valence of the metal, and ring A1 ″ represents an aromatic hydrocarbon group which may have a substituent. Ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.}

{In Formula (Vb), M ⁵ represents the same metal as M, w represents the valence of the metal, and ring A1 ″ represents an aromatic hydrocarbon group which may have a substituent or Represents an aromatic heterocyclic group, and ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.}

{In the formula (Vc), M ⁶ represents the same metal as M, w represents the valence of the metal, j represents 0, 1 or 2, ring A1 "and ring A1 'represent Each independently represents an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group, and ring A2 and ring A2 ′ are each independently a nitrogen-containing optionally substituted group. Represents an aromatic heterocyclic group.}

  In the above formulas (Va), (Vb) and (Vc), preferred examples of the ring A1 ″ and the ring A1 ′ include a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a thienyl group, a furyl group, a benzothienyl group, A benzofuryl group, a pyridyl group, a quinolyl group, an isoquinolyl group, a carbazolyl group, and the like can be given.

  In the above formulas (Va), (Vb) and (Vc), preferred examples of ring A2 and ring A2 ′ include pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, and benzimidazole group. Quinolyl group, isoquinolyl group, quinoxalyl group, phenanthridyl group and the like.

  Examples of the substituent that the compound represented by any one of the formulas (Va), (Vb), and (Vc) may have include a halogen atom such as a fluorine atom; an alkyl group such as a methyl group and an ethyl group Alkenyl groups such as vinyl groups; alkoxycarbonyl groups such as methoxycarbonyl groups and ethoxycarbonyl groups; alkoxy groups such as methoxy groups and ethoxy groups; aryloxy groups such as phenoxy groups and benzyloxy groups; dimethylamino groups and diethylamino groups A diarylamino group such as a diphenylamino group; a carbazolyl group; an acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; a cyano group and the like.

  The carbon number of the substituent is arbitrary as long as the effects of the present invention are not significantly impaired. However, when the substituent is an alkyl group, the carbon number is usually 1 or more and 6 or less. When the substituent is an alkenyl group, the carbon number is usually 2 or more and 6 or less. When the substituent is an alkoxycarbonyl group, the carbon number is usually 2 or more and 6 or less. Moreover, when a substituent is an alkoxy group, the carbon number is 1 or more and 6 or less normally. Moreover, when a substituent is an aryloxy group, the carbon number is 6 or more and 14 or less normally. Moreover, when a substituent is a dialkylamino group, the carbon number is 2 or more and 24 or less normally. Moreover, when a substituent is a diarylamino group, the carbon number is 12 or more and 28 or less normally. When the substituent is an acyl group, the carbon number is usually 1 or more and 14 or less. Moreover, when a substituent is a haloalkyl group, the carbon number is 1 or more and 12 or less normally.

  The above substituents may be linked to each other to form a ring. As a specific example, whether the substituent of the ring A1 ″ and the substituent of the ring A2 are bonded, or the substituent of the ring A1 ′ and the substituent of the ring A2 ′ are bonded, One condensed ring may be formed, such as a 7,8-benzoquinoline group.

  Among the substituents described above, the substituents of ring A1 ″, ring A1 ′, ring A2 and ring A2 ′ are more preferably alkyl groups, alkoxy groups, aromatic hydrocarbon groups, cyano groups, halogen atoms, haloalkyl groups. , Diarylamino group, and carbazolyl group. In addition, as for the substituents of ring A1 ″, ring A1 ′, ring A2 and ring A2 ′, only one may be substituted or two or more may be in any combination. And may be substituted with a ratio.

Further, the formula (Va), as preferred examples of M ⁴ ~M ⁶ in (Vb) and (Vc) include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold.

  Specific examples of the organometallic complex represented by any one of the above formulas (V), (Va), (Vb) and (Vc) are shown below. However, it is not limited to the following compounds.

  Further, among the organometallic complexes represented by the above formula (V), in particular, as the ligand L and / or L ′, a 2-arylpyridine-based ligand (that is, 2-arylpyridine, an arbitrary substituent group) And a compound having an arbitrary group condensed thereto) are preferable.

  The compounds described in International Patent Publication No. 2005/019373 can also be used as the light emitting material.

Next, the compound represented by formula (VI) will be described.
In the formula (VI), M ⁷ represents a metal. Specific examples include the metals described above as the metal selected from Groups 7 to 11 of the periodic table. Among these, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold is preferable, and divalent metals such as platinum and palladium are particularly preferable.

In the formula (VI), R ⁹² and R ⁹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, It represents at least one selected from the group consisting of an alkoxy group, an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. Each R ⁹² and R ⁹³ may be the same or different.

Further, in the formula (VI), when T is a carbon atom, R ⁹⁴ and R ⁹⁵ each independently represent a substituent represented by the same examples as R ⁹² and R ⁹³ . Further, in the formula (VI), when T is a nitrogen atom, R ⁹⁴ and R ⁹⁵ are absent. Each T may be the same or different.

In the formula (VI), R ^{92 to} R ⁹⁵ may further have a substituent. When it has a substituent, there is no restriction | limiting in particular in the kind, Arbitrary groups can be made into a substituent. Moreover, as for the substituent, only 1 may be substituted and 2 or more may be substituted by arbitrary combinations and ratios.
Furthermore, in the formula (VI), any two or more groups of R ^{92 to} R ⁹⁵ may be connected to each other to form a ring.

  Specific examples (T-1, T-10 to T-15) of the organometallic complex represented by the formula (VI) are shown below. However, it is not limited to the following examples. In the following chemical formulae, Me represents a methyl group, and Et represents an ethyl group.

  The molecular weight of the compound used as the light emitting material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, Preferably it is 200 or more, More preferably, it is 300 or more, More preferably, it is the range of 400 or more. If the molecular weight is too small, the heat resistance may be significantly reduced, gas may be generated, the film quality may be deteriorated when the film is formed, or the morphology of the organic electroluminescent element may be changed due to migration, etc. There is a case. On the other hand, if the molecular weight is too large, it tends to be difficult to purify the organic compound, or it may take time to dissolve the organic compound.

  In addition, any 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.

  The ratio of the light emitting material in the organic light emitting layer 4 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.001% by weight or more, preferably 0.01% by weight or more, more preferably 0.1% by weight. In addition, it is usually 50% by weight or less, preferably 30% by weight or less, and more preferably 20% by weight or less. If the amount of the light emitting material is too small, other materials may emit light. If the amount is too large, the light emission efficiency may be lowered due to concentration quenching or the like. In addition, when using together 2 or more types of luminescent material, it is made for the total content of these to be contained in the said range.

  Further, the organic light emitting layer 4 may contain a hole transporting compound as a constituent material. As the hole transporting compound, only one of the hole transporting polymer and the low molecular weight hole transporting compound may be used, or both may be used in combination. Here, among the hole transporting compounds, examples of the low molecular weight hole transporting compound include [I-1-1-3. In addition to the various compounds exemplified in the column of “low molecular weight hole transporting compound”, for example, two represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl Aromatic diamines containing the above tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234861), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) Aromatic amine compounds having a starburst structure such as triphenylamine (Journal of Luminescence, 1997, Vol. 72-74, pp. 985), aromatic amine compounds composed of tetramers of triphenylamine (Chemical Communications, 1996, pp. 2175), 2,2 ′, 7,7′-tetrakis- (diphenyla Mino) -9,9′-spirobifluorene, etc. (Synthetic Metals, 1997, Vol. 91, pp. 209), etc. In the organic light emitting layer 4, the hole transporting compound is Only 1 type may be used and 2 or more types may be used together by arbitrary combinations and a ratio.

  The ratio of the hole transporting compound in the organic light emitting layer 4 is arbitrary as long as the effects of the present invention are not significantly impaired.

  The organic light emitting layer 4 may contain an electron transporting compound as a constituent material. Here, among the electron transporting compounds, examples of low molecular weight electron transporting compounds include 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND), 2,5, -Bis (6 '-(2', 2 "-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7 -Diphenyl-1,10-phenanthroline (BCP, bathocuproin), 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 4 , 4′-bis (9-carbazole) -biphenyl (CBP), etc. In the organic light emitting layer 4, only one kind of electron transporting compound may be used, and two or more kinds are arbitrarily selected. In combination and ratio may be used in combination.

  The ratio of the electron transporting compound in the organic light emitting layer 4 is arbitrary as long as the effects of the present invention are not significantly impaired.

  When the organic light emitting layer 4 is formed by a wet film formation method, an ink is prepared by dissolving the above-described materials in an appropriate organic layer solvent, and this is applied onto the hole injection layer 3 after the heating step. Form by forming a film and drying to remove the solvent. The details are described in [I-3. The contents are the same as those described in the column of “Organic layer formation step”.

  Although the film thickness of the organic light emitting layer 4 is arbitrary as long as the effect of the present invention is not significantly impaired, it is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the thickness of the organic light emitting layer 4 is too thin, defects and dark spots may occur, and if it is too thick, the driving voltage may increase.

[II-5. Electron injection layer]
The electron injection layer 5 plays a role of efficiently injecting electrons injected from the cathode 6 into the organic light emitting layer 4. In order to perform electron injection efficiently, the material for forming the electron injection layer 5 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually preferably from 0.1 nm to 5 nm.

Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.
In addition, the material of the electron injection layer 5 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

There is no restriction | limiting in the formation method of the electron injection layer 5. FIG. The charge injection layer 5 is usually formed by laminating on the organic light emitting layer 4 by a wet film forming method or a vacuum deposition method.
The details of forming the electron injection layer 5 by the wet film forming method can be formed in the same manner as the method described in the organic film forming step.

On the other hand, when the electron injection layer 5 is formed by the vacuum deposition method, for example, the deposition source is put in a crucible or a metal boat installed in the vacuum vessel, and the inside of the vacuum vessel is about 10 ⁻⁴ Pa by an appropriate vacuum pump. Then, the crucible or metal boat is heated and evaporated to form an electron injection layer 5 on the organic light emitting layer 4 on the substrate placed facing the crucible or metal boat.

The alkali metal is usually deposited using an alkali metal dispenser in which nichrome is filled with an alkali metal chromate and a reducing agent. By heating the dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal is evaporated. When the organic electron transport compound and alkali metal are co-evaporated, the organic electron transport compound is put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump. Preferably, each crucible and dispenser are simultaneously heated and evaporated to form the electron injection layer 5 on the substrate placed facing the crucible and dispenser. At this time, co-evaporation is uniformly performed in the film thickness direction of the electron injection layer 5, but there may be a concentration distribution in the film thickness direction.

[II-6. cathode]
The cathode 6 plays a role of injecting electrons into a layer (such as the electron injection layer 5 or the organic light emitting layer 4) on the organic light emitting layer 4 side.
As the material of the cathode 6, the material used for the anode 2 can be used. However, in order to perform electron injection efficiently, a metal having a low work function is preferable, and tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy. In addition, the material of the cathode 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The film thickness of the cathode 6 is usually the same as that of the anode 2.
Further, for the purpose of protecting the cathode 6 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

[II-7. Other layers]
As described above, the organic EL element having the layer configuration shown in FIG. 1 has been mainly described. However, the organic EL element of the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 6 in addition to the layers described above, and an arbitrary layer may be omitted. .

  FIG. 2 is a cross-sectional view schematically showing another example of the structure of the organic EL element of the present invention. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  An organic EL element 10b shown in FIG. 2 has a hole transport layer 7 between the hole injection layer 3 and the organic light emitting layer 4 in addition to the same configuration as the organic EL element 10a of FIG. In the case of this configuration, the hole transport layer 7 corresponds to an organic layer formed on the hole injection layer 3.

  Examples of the material for forming the hole transport layer 7 include the same compounds as those exemplified as the hole transport compound that may be used by mixing with the hole injection layer 3. In addition, for example, polymer materials such as polyarylene ether sulfone containing polyvinyl carbazole, polyvinyl triphenylamine, and tetraphenylbenzidine can be used. Further, when the hole transport layer 7 is formed using a polymer material, the hole transport layer 7 may be formed from a polymerized polymer material after a wet transporting monomer is wet-formed. Good. In addition, the material of the positive hole transport layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The hole transport layer 7 can be formed by laminating these materials on the hole injection layer 3 by a wet film formation method or a vacuum deposition method. However, when this hole transport layer 7 is formed on the hole injection layer 3 as an organic layer according to the present invention, the hole transport layer 7 is [I-3. The organic layer is formed by a wet film formation method as described in the section “Deposition process of organic layer”. Thereby, the same advantages as described above, such as long life and high luminous efficiency, can be obtained.
The thickness of the hole transport layer 7 formed in this manner is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10 nm or more, preferably 30 nm or more. However, it is usually 300 nm or less, preferably 100 nm or less.

  FIG. 3 is a cross-sectional view schematically showing another example of the structure of the organic EL element of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The organic EL element 10c shown in FIG. 3 has an electron blocking layer 8 between the hole injection layer 3 and the organic light emitting layer 4 in addition to the same configuration as the organic EL element 10a shown in FIG. In the case of this configuration, the electron blocking layer 8 corresponds to an organic layer formed on the hole injection layer 3.

  The electron blocking layer 8 increases the recombination probability of holes and electrons in the organic light emitting layer 4 by preventing electrons moving from the organic light emitting layer 4 from reaching the hole injection layer 3, There are a role of confining the generated excitons in the light emitting layer 4 and a role of efficiently transporting holes injected from the hole injection layer 3 in the direction of the organic light emitting layer 4. In particular, it is effective when a phosphorescent material or a blue light emitting material is used as the light emitting material.

  The characteristics required for the electron blocking layer 8 include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the organic light emitting layer 4 is produced by the wet film formation method as the organic layer according to the present invention, the electron blocking layer 8 is also required to be compatible with the wet film formation. Examples of the material used for the electron blocking layer 8 include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (described in International Publication No. 2004/084260). In addition, the material of the electron blocking layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  When the electron blocking layer 8 is formed on the hole injection layer 3 as an organic layer according to the present invention, [I-3. The organic layer is formed by a wet film formation method as described in the section “Deposition process of organic layer”. Thereby, the same advantages as described above, such as long life and high luminous efficiency, can be obtained. However, when the electron blocking layer 8 is not formed on the hole injection layer 3, it can also be formed by a vacuum deposition method. Details of the procedure of the vacuum deposition method are the same as those of the electron injection layer 5.

As described above, in addition to the configurations described with reference to FIGS. 1 to 3, various modifications can be considered as the configuration of the organic EL element of the present invention.
For example, an electron transport layer may be provided between the organic light emitting layer 4 and the electron injection layer 5. The electron transport layer is provided for the purpose of further improving the light emitting efficiency of the device, and efficiently transports electrons injected from the cathode 6 between the electrodes to which an electric field is applied in the direction of the organic light emitting layer 4. Formed from a compound capable of

  As the electron transporting compound used for the electron transport layer, usually, the electron injection efficiency from the cathode 6 or the electron injection layer 5 is high, and the injected electrons having high electron mobility can be efficiently transported. Use possible compounds. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3- or 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound No. 207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type sulfide Zinc, n-type zinc selenide, etc. . In addition, only 1 type may be used for the material of an electron carrying layer, and 2 or more types may be used together by arbitrary combinations and a ratio.

There is no restriction | limiting in the formation method of an electron carrying layer. Therefore, the electron transport layer can be formed by a wet film formation method, as in the case of the hole injection layer 3 and the organic light emitting layer 4, but is usually formed by a vacuum deposition method. Details of the procedure of the vacuum deposition method are the same as those of the electron injection layer 5.
The thickness of the electron transport layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

  For example, a hole blocking layer may be provided between the organic light emitting layer 4 and the electron injection layer 5. The hole blocking layer is a layer stacked on the organic light emitting layer 4 so as to be in contact with the interface of the organic light emitting layer 4 on the cathode 6 side. The hole blocking layer has a role of blocking holes moving from the anode 2 from reaching the cathode 6 and a role of efficiently transporting electrons injected from the cathode 6 toward the organic light emitting layer 4. Have

  The physical properties required for the material constituting the hole blocking layer include high electron mobility, low hole mobility, large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). It is expensive. As a material for the hole blocking layer satisfying such conditions, for example, bis (2-methyl-8-quinolinolato), (phenolato) aluminum, bis (2-methyl-8-quinolinolato), (triphenylsilanolato) Mixed ligand complexes such as aluminum, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives Styryl compounds such as JP-A-11-242996 and triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole Kaihei 7-41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297). It is. Furthermore, compounds having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 are also preferable as the material for the hole blocking layer. In addition, the material of a hole-blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

There is no restriction | limiting in the formation method of a hole-blocking layer. Therefore, the hole blocking layer can be formed by using a wet film forming method as in the case of the hole injecting layer 3 and the organic light emitting layer 4, but is usually formed by a vacuum deposition method. Details of the procedure of the vacuum deposition method are the same as those of the electron injection layer 5.
The thickness of the hole blocking layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

Further, at the interface between the cathode 6 and the organic light emitting layer 4 or the electron transport layer, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ Inserting an ultra-thin insulating film (0.1 to 5 nm) formed by the above method is also an effective method for improving the efficiency of the device (Applied Physics Letters, 1997, Vol. 70, pp. 152; JP-A-10-74586; see IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.).

  Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the layer configuration of FIG. 1, other components are provided on the substrate 1 in the order of the cathode 6, the electron injection layer 5, the organic light emitting layer 4, the hole injection layer 3, and the anode 2.

  Furthermore, the organic EL element of the present invention can be configured by laminating components other than the substrate between two substrates, at least one of which is transparent.

Further, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

  Furthermore, the organic EL element of the present invention may be configured as a single organic EL element, or may be applied to a configuration in which a plurality of organic EL elements are arranged in an array, and the anode and cathode are X- You may apply to the structure arrange | positioned at Y matrix form.

In addition, each layer described above may contain components other than those described as materials as long as the effects of the present invention are not significantly impaired.
Furthermore, unless the effects of the present invention are significantly impaired, other steps are performed before, after, and during each step in the hole injection layer forming step, the heating step, and the organic layer forming step described above. May be.

[Comparative Example 1]
As a comparative example with respect to the examples of the present invention, an organic electroluminescence element was produced by the following production method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 150 nm (sputtered film; sheet resistance: 15Ω) is patterned into a 2 mm wide stripe using normal photolithography and hydrochloric acid etching. To form an anode.
The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  On this anode, as a material for the hole injection layer, a hole transporting polymer PB-1 having an aromatic amino group having the structural formula shown below was spin-coated with the electron accepting compound A-1 under the following conditions, A heating step was performed.

Spin coating conditions Solvent Ethyl benzoate Concentration of PB-1 2 [% by weight]
PB-1: A-1 10: 4
Spinner speed 1500 [rpm]
Spinner rotation time 30 [seconds]
Heating condition 230 [° C] 180 [min]

  A thin film having a uniform hole injection layer thickness of 30 nm was formed by the above spin coating.

Next, materials E-1, H-1, and D-1 shown below as materials for the light emitting layer (organic layer) were spin-coated under the following conditions.

Spin coating conditions Solvent (ink solvent) Diphenyl ether (boiling point 259 ° C)
Solid content 2 [wt%]
E-1: H-1: D-1 10: 10: 1
Spinner speed 1500 [rpm]
Spinner rotation time 30 [seconds]
Drying conditions 130 [° C] 60 [min]

  A thin film having a uniform light emitting layer thickness of 30 nm was formed by the above spin coating.

On the obtained light emitting layer, a compound HB-1 shown below as a hole blocking layer is formed by a vacuum deposition method with a film thickness of 5 nm, and then an aluminum 8-hydroxyquinoline complex ET-1 shown below is used as an electron transport layer. The layers were sequentially laminated so as to have a thickness of 30 nm.

Here, the element that has been deposited up to the electron transport layer 7 is once taken out from the vacuum deposition apparatus into the atmosphere, and used as a mask for cathode deposition, as a 2 mm-wide stripe having a shape orthogonal to the ITO stripe as the anode. A shadow mask is brought into close contact with the element, placed in another vacuum deposition apparatus, and a lithium fluoride (LiF) film having a thickness of 0.5 nm as the cathode buffer layer is formed by the same vacuum deposition method as the organic layer, and then aluminum as the cathode. Were stacked so as to have a film thickness of 80 nm.
As described above, an organic EL element having a light emitting area portion having a size of 2 mm × 2 mm was obtained.

[Comparative Example 2]
Next, as a comparative example for the examples of the present invention, a comparison was made except that isoamyl benzoate (boiling point 262 ° C.) was used instead of diphenyl ether as a solvent (ink solvent) in the spin coating conditions when forming the light emitting layer. In the same manner as in Example 1, an organic EL device was produced.

[Example 1]
An organic EL device was produced in the same manner as in Comparative Example 2 except that the heating temperature after application of the hole injection layer was changed to 260 ° C. under the spin coating conditions for forming the hole injection layer.

[Example 2]
Comparative example except that cyclohexylbenzene (boiling point 238 ° C.) was used instead of diphenyl ether as the solvent (ink solvent) and the solid content concentration was 3 [wt%] in the spin coating conditions for forming the light emitting layer. In the same manner as in Example 1, an organic EL device was produced.

[Example 3]
An organic EL device was produced in the same manner as in Example 2 except that the heating temperature after applying the hole injection layer was 260 ° C. under the spin coating conditions for forming the hole injection layer.

[Example 4]
An organic EL device was produced in the same manner as in Example 2 except that the heating temperature and heating time after applying the hole injection layer were set to 260 ° C. and 1 hour under the spin coating conditions for forming the hole injection layer. did.

[Summary]
Table 1 summarizes the characteristics of the organic electroluminescent elements obtained in Comparative Examples 1 and 2 and Examples 1 to 4.
Here, the light emission start voltage, the maximum luminance, the luminance-current efficiency, and the luminance-power efficiency were measured by connecting a LS-110 type luminance meter manufactured by Minolta to a Hewlett-Packard 4140B type pA METER.
The viscosity was measured using a rotary viscometer (DV-III- + (digital rheometer) manufactured by Brookfield) under the conditions of a temperature of 25 ° C., a rotor rotational speed of 100 rpm, and a shear rate of 750 (1 / sec). .

In Table 1, T _A represents the heating temperature during the formation of the hole injection layer, the boiling point of the solvent T _B is an ink solvent used in forming the hole layer on the hole injection layer Represent. In Table 1, the numerical value in the viscosity column represents the viscosity of the light emitting layer forming ink (that is, the composition of the light emitting layer material and the solvent).

  The present invention relates to various fields where an organic EL optical element is used, for example, a light source (for example, a light source of a copying machine, a flat panel display (for example, for an OA computer or a wall-mounted television) or a surface light emitter). It can be suitably used in the fields of liquid crystal displays and backlights of instruments), display panels, indicator lamps and the like.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Organic light emitting layer 5 Electron injection layer 6 Cathode 7 Hole transport layer 8 Electron blocking layers 10a to 10c Organic EL element

Claims (4)

Organic having an anode and a cathode, and having a hole injection layer formed by a wet film formation method and an organic layer formed on the hole injection layer by a wet film formation method between the anode and the cathode A method for manufacturing an electroluminescent device, comprising:
The organic layer is formed using an ink having a viscosity of 1 to 20 cp containing at least one solvent having a boiling point of 200 ° C. or higher, and
A method for producing an organic electroluminescent device, comprising forming the organic layer after heating the hole injection layer at 200 ° C. or higher and “boiling point of the solvent −10 ° C.” or higher. The method of manufacturing an organic electroluminescent element according to claim 1, wherein the hole injection layer contains a hole transporting compound and an electron accepting compound. The method for producing an organic electroluminescent device according to claim 2, wherein at least one of the solvents can dissolve the hole transporting compound or the electron accepting compound. The method for producing an organic electroluminescent element according to claim 1, wherein the organic layer is a light emitting layer.

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