JP6228626B2 - Method for manufacturing organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescent element, a display device, a light emitting device, and a method for manufacturing an organic electroluminescent element.

As a method for forming the organic layer constituting the organic electroluminescence element, a vacuum deposition method, a spin coating method, a coating method using an ink jet method or the like is widely used. Among these, the coating method has the advantages of being excellent in mass productivity and easy process control.
The coating method includes a step of applying a solution obtained by dissolving a material for forming an organic thin film in a solvent onto an organic thin film serving as a base. In this step, if a part of the organic thin film serving as a base for coating is dissolved in the solvent, the layer structure as designed cannot be obtained.

  For this reason, attempts have been made to increase the solvent resistance by constituting the organic thin film with a crosslinked resin material. Non-Patent Document 1 discloses such a technique. Non-Patent Document 1 describes that after applying a solution in which a crosslinkable resin composed of a diamine derivative and a photopolymerization initiator are dissolved, the resin is reacted by light irradiation to form a hole transport layer. Yes. And the organic thin film containing a luminescent material is formed by the apply | coating method on the hole transport layer formed in this way.

  However, when the hole transport layer is formed using the technique described in Non-Patent Document 1, sufficient performance as an organic electroluminescence element may not be obtained. For example, Patent Document 1 describes that there is a problem that the driving life is shortened when an organic layer is formed by polymerizing a polymerizable compound by the technique of Non-Patent Document 1. In order to solve such a problem, the technique described in Patent Document 1 includes a hole transport layer formed by polymerizing a polymerizable compound, and a polymerization reaction start provided adjacent to the hole transport layer. And a hole injection layer containing an agent.

JP 2008-227483 A

Advanced Materials 2006, 18, 948-954.

In the organic electroluminescence element, it is important to improve the light emission efficiency. On the other hand, realization of a structure excellent in mass productivity is also required. However, both Non-Patent Document 1 and Patent Document 1 have made it difficult to realize an organic electroluminescence element that is excellent in mass productivity and has good light emission characteristics.
The problem to be solved by the present invention includes the above-described problem as an example.

According to the invention described in claim 1, the step of forming an organic layer on the anode;
Forming a light emitting layer on the organic layer;
Forming a cathode on the light emitting layer;
With
The step of forming the organic layer includes:
Preparing a first solution containing a polymerizable compound (a) containing a ring-opening polymerizable group and a second solution containing a polymerization initiator (b);
Cooling the first solution and the second solution;
The manufacturing method of the organic electroluminescent element containing this is provided.

It is sectional drawing which shows the organic electroluminescent element which concerns on this embodiment. It is sectional drawing which shows the light-emitting device containing the organic electroluminescent element shown in FIG. It is a flowchart explaining the formation method of the positive hole transport layer shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.
In this specification, “provided” above a certain layer means both the case where the layer is provided in contact with the layer and the case where the layer is provided above the layer via another layer. including.

FIG. 1 is a cross-sectional view showing an organic electroluminescence element 100 according to this embodiment. FIG. 1 is a schematic diagram for illustrating the organic electroluminescence element 100, and the configuration of the organic electroluminescence element 100 according to the present embodiment is not limited to that illustrated in FIG.
1A shows a case where the hole injection layer is not included, and FIG. 1B shows a case where the hole injection layer 21 is included. In the present embodiment, the organic electroluminescence element 100 shown in FIG.

In the organic electroluminescence device 100 according to this embodiment, a hole transport layer 22 (organic layer), a light emitting layer 24, an electron transport layer 26, an electron injection layer 28, and a cathode 30 are sequentially formed on the anode 20. The hole transport layer 22 is formed of a resin composition obtained by ring-opening polymerization of a polymerizable compound (a) containing a ring-opening polymerizable group in the presence of a polymerization initiator (b). The maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole transport layer 22 are both 14 nm or less.
Hereinafter, the configuration of the organic electroluminescence element 100 according to this embodiment will be described in detail.

The organic electroluminescence element 100 is provided on the substrate 10.
Examples of the material constituting the substrate 10 include quartz, glass, metal or metal oxide, and resin. When the substrate 10 is made of a resin, examples of the resin material include polyester, poly (meth) acrylate, polycarbonate, polysulfone, and the like. One of these resin materials may be used alone, or two or more arbitrary combinations may be used.
Although the thickness of the board | substrate 10 is not specifically limited, For example, they are 1 micrometer or more and 50 mm or less, Preferably they are 50 micrometers or more and 3 mm or less. By setting the thickness of the substrate 10 within the range, sufficient mechanical strength can be obtained while reducing the weight of the organic electroluminescence element.

As shown in FIG. 1A, the anode 20 is provided on the substrate 10.
The material constituting the anode 20 is preferably a conductive material having a work function larger than that of the cathode 30.
The anode 20 is made of a metal material such as aluminum, gold, silver, nickel, palladium, or platinum, a metal oxide obtained by oxidizing a metal material such as indium, zinc, tin, or an alloy thereof, or a metal halide such as copper iodide. , Carbon black, or a conductive polymer such as polypyrrole, polyaniline, poly (3-methylthiophene), or PEDOT: PSS (Poly (3,4-ethylenedithiophene) poly (styrenesulfonate)). Among these, indium tin oxide (ITO: Indium-Tin-Oxide), indium zinc oxide (IZO: Indium-Zinc-Oxide), zinc oxide, or tin oxide is particularly preferable. One of these materials may be used alone, or two or more arbitrary combinations may be used. The material of the anode 20 can be appropriately selected depending on the transparency required for the anode 20, for example.

When the emitted light is configured to be extracted from the anode 20 side, the anode 20 is transparent or translucent to the wavelength of the emitted light. In this case, the transmittance of light of the emission wavelength at the anode 20 is, for example, 60% or more, and preferably 80% or more.
When the anode 20 is transparent or translucent, the film thickness of the anode 20 is, for example, 5 nm to 1000 nm, preferably 10 nm to 500 nm. Thereby, the increase in electrical resistance resulting from the thin film thickness can be suppressed while ensuring transparency.

The hole transport layer 22 is provided on the anode 20.
In this embodiment, the hole transport layer 22 is made of a resin composition obtained by ring-opening polymerization of a polymerizable compound (a) containing a ring-opening polymerizable group in the presence of a polymerization initiator (b). Is formed. Specifically, after applying a layer forming material containing both the polymerizable compound (a) and the polymerization initiator (b), the components (a) and (b) are reacted to form a hole transport layer 22. Is forming.

As described above, the polymerizable compound (a) has a ring-opening polymerizable group in the molecular structure. The ring-opening polymerizable group is a group having a heterocyclic structure in which ring-opening polymerization proceeds by the action of a cation, an anion, a radical or the like. As the polymerization mode, cationic or anionic ring-opening polymerization is preferable. Examples of the heterocyclic ring constituting the ring-opening polymerizable group include an epoxy ring, an oxetane ring, a tetrahydrofuran ring, a lactone ring, a carbonate ring, an oxazoline ring, and an episulfide ring. Among these, an epoxy ring and an oxetane ring are preferably used. Thus, when an epoxy group or an oxetanyl group is selected as the ring-opening polymerizable group, the hole transport layer 22 having excellent solvent resistance can be formed.
Since the polymerizable compound (a) has a ring-opening polymerizable group, a resin having a three-dimensional network structure is formed by a crosslinking reaction. For this reason, the hole transport layer 22 excellent in chemical stability insoluble in the organic solvent can be formed.
The ring-opening polymerizable group is ring-opened by the polymerization initiator (b), whereby the polymerization of the polymerizable compound (a) proceeds to form a resin cured product having a three-dimensional network structure. Since such a polymerization mode is employed, water is not generated during the polymerization reaction, and it is possible to suppress a decrease in luminous efficiency due to the polymerization reaction.

The number of ring-opening polymerizable groups in one molecule of the polymerizable compound (a) is preferably 2 or more. That is, the polymerizable compound (a) preferably contains a bifunctional or polyfunctional (trifunctional or higher) polymerizable compound. By doing so, it is possible to form the hole transport layer 22 having a high crosslinking density and particularly excellent in chemical stability such as solvent resistance.
Here, when a bifunctional or polyfunctional (trifunctional or higher) polymerizable compound is used, in general, the chemical and mechanical properties of the cured resin are improved, while the reactivity of the polymerizable compound (a) is increased. The pot life of the layer forming material tends to be shortened. For this reason, various compounds can also be mixed and used as the polymerizable compound (a) from the viewpoint of balancing the improvement of the crosslinking density and the reactivity. For example,
A mixture of monofunctional and bifunctional polymerizable compounds;
A mixture of monofunctional and polyfunctional polymerizable compounds,
A mixture of bifunctional and polyfunctional polymerizable compounds;
Any mixture of monofunctional, bifunctional and polyfunctional polymerizable compounds can be used.
In addition, as a resin material which comprises the positive hole transport layer 22, polymeric compounds other than the above-mentioned polymeric compound (a) may be used together.

As the polymerizable compound (a), triarylamine derivatives, carbazole derivatives, fluorene derivatives, 2,4,6-triphenyl pyridine derivatives, C ₆₀ derivatives, oligothiophene derivatives, phthalocyanine derivatives, porphyrin derivatives, condensed polycyclic aromatic Derivatives, metal complex derivatives and the like. Among these, a triarylamine derivative having high electrochemical stability and charge transportability is preferable. That is, the polymerizable compound (a) is preferably a compound containing a triarylamine structure.

As the polymerizable compound (a), the following compounds having no repeating unit can be used.

Moreover, as a polymeric compound (a), the polymerizable oligomer which has a repeating unit shown below can be used.

In addition, as a polymeric compound (a), 1 type selected from either of the above may be used independently, and 2 or more types may be used in arbitrary combinations.
When the polymerizable compound (a) is a compound having no repeating unit, the weight average molecular weight of the polymerizable compound (a) is, for example, 300 or more and 5000 or less, and preferably 500 or more and 2500 or less. Thereby, the solubility with respect to a solvent is securable, implement | achieving sufficient electric charge transportability.
When the polymerizable compound (a) is a polymerizable oligomer, the weight average molecular weight of the polymerizable compound (a) is, for example, 500 or more and 2 million or less, preferably 2000 or more and 500,000 or less, more preferably It is 4000 or more and 200,000 or less. By setting it to the above lower limit or more, the film formability of the hole transport layer 22 can be improved. Moreover, the fall of glass transition temperature, melting | fusing point, and vaporization temperature can be suppressed, and heat resistance can also be ensured. On the other hand, by setting it to the upper limit value or less, purification of the polymerizable compound (a) can be facilitated.
In addition, a weight average molecular weight is obtained from the conversion value by the comparison with standard polymers, such as a polystyrene measured using GPC (Gel Permeation Chromatography).

As a polymerization initiator (b) in this embodiment, the compound which produces | generates an anion and a cation is mentioned, for example. The cation contributes to the polymerization reaction of the polymerizable compound (a) and then converts to a steady state, and performs charge transport as a part of the hole transport layer. For this reason, by using the compound which produces | generates an anion and a cation as a polymerization initiator (b), the hole transport property of the hole transport layer 22 is improved, having a function as a polymerization initiator (b). be able to.
An organic onium salt is mentioned as a compound which produces | generates an anion and a cation. In the present embodiment, organic onium salts represented by the following formulas (1) to (3) are preferably used.

In the above formulas (1) to (3), R ¹¹ , R ²¹ and R ³¹ each represents an organic group bonded to A ¹ , A ² and A ³ via a carbon atom. Examples of R ¹¹ , R ²¹ , and R ³¹ in this embodiment include an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, or an aromatic heterocyclic group. Among these, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable from the viewpoint of delocalizing positive charges and from the viewpoint of thermal stability.

As the alkyl group constituting R ¹¹ , R ²¹ , and R ³¹ , a linear, branched, or cyclic alkyl group can be used. The alkyl group has, for example, 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. Examples of the alkyl group in this embodiment include a methyl group, an ethyl group, an n-propyl group, a 2-propyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and a cyclohexyl group.
The carbon number of the alkenyl group constituting R ¹¹ , R ²¹ , and R ³¹ is, for example, 2 or more and 12 or less, and preferably 2 or more and 6 or less. Examples of the alkenyl group in this embodiment include a vinyl group, an allyl group, and a 1-butenyl group.
The carbon number of the alkynyl group constituting R ¹¹ , R ²¹ , and R ³¹ is, for example, 2 or more and 12 or less, and preferably 2 or more and 6 or less. Examples of the alkynyl group in this embodiment include an ethynyl group and a propargyl group.

The aromatic hydrocarbon group constituting R ¹¹ , R ²¹ , and R ³¹ is, for example, a monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-5 condensed ring, and has a positive charge on the group. Can be delocalized by. Examples of the aromatic hydrocarbon group in the present embodiment include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, and fluorene ring. Monovalent group derived from the above.
The aromatic heterocyclic group constituting R ¹¹ , R ²¹ , and R ³¹ is, for example, a monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-4 condensed ring, and has a positive charge. Those that are more delocalized on the base are mentioned. Examples of the aromatic heterocyclic group in the present embodiment include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, triazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrrolo Imidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, One derived from pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, or azulene ring It includes the groups.

In said formula (1)-(3), R < ¹² >, R <^22> , R < ^{23 >} , R ^{< 32>} , R ^<33> , and R ^<34 > represent arbitrary groups each independently. R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ in the present embodiment include an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an amino group, an alkoxy group 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 or a silyl group. Among these, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable from the viewpoints of electron acceptability and thermal stability. The molecular weight of R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is a value including a substituent, for example, 1000 or less, preferably 500 or less.

The alkyl group, alkenyl group, alkynyl group, aromatic hydrocarbon group, and aromatic heterocyclic group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ include R ¹¹ , R ²¹ , And those similar to R ³¹ can be used.

Examples of the amino group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ include an alkylamino group, an arylamino group, and an acylamino group.
The alkylamino group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is an alkyl having one or more alkyl groups having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. An amino group is mentioned. Examples of the alkylamino group in this embodiment include a methylamino group, a dimethylamino group, a diethylamino group, and a dibenzylamino group.

The arylamino group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is an aromatic hydrocarbon group or aromatic group having 3 to 25 carbon atoms, preferably 4 to 15 carbon atoms. An arylamino group having one or more heterocyclic groups can be mentioned. Examples of the arylamino group in the present embodiment include a phenylamino group, a diphenylamino group, a tolylamino group, a pyridylamino group, and a thienylamino group.
As the acylamino group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ , an acylamino group having one or more acyl groups having 2 to 25 carbon atoms, preferably 2 to 15 carbon atoms Is mentioned. Examples of the acylamino group in this embodiment include an acetylamino group and a benzoylamino group.

The number of carbon atoms of the alkoxy group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is, for example, 1 or more and 12 or less, preferably 1 or more and 6 or less. Examples of the alkoxy group in this embodiment include a methoxy group, an ethoxy group, and a butoxy group.
The aryloxy group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is an aromatic hydrocarbon group or aromatic group having 3 to 25 carbon atoms, preferably 4 to 15 carbon atoms. An aryloxy group having a heterocyclic group is exemplified. Examples of the aryloxy group in the present embodiment include a phenyloxy group, a naphthyloxy group, a pyridyloxy group, such as a thienyloxy group.

The number of carbon atoms of the acyl group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is 1 or more and 25 or less, preferably 1 or more and 15 or less. Examples of the acyl group in this embodiment include a formyl group, an acetyl group, or a benzoyl group.
The alkoxycarbonyl group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ has 2 to 10 carbon atoms, preferably 2 to 7 carbon atoms. Examples of the alkoxycarbonyl group in the present embodiment include a methoxycarbonyl group or an ethoxycarbonyl group.

The aryloxycarbonyl group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is an aromatic hydrocarbon group or aromatic group having 3 to 25 carbon atoms, preferably 4 to 15 carbon atoms. Having a heterocyclic group. Examples of the aryloxycarbonyl group according to this embodiment include a phenoxycarbonyl group and a pyridyloxycarbonyl group.
The carbon number of the alkylcarbonyloxy group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is 2 or more and 10 or less, preferably 2 or more and 7 or less. Examples of the alkylcarbonyloxy group in the present embodiment include an acetoxy group and a trifluoroacetoxy group.

The carbon number of the alkylthio group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ is 1 or more and 12 or less, preferably 1 or more and 6 or less. Examples of the alkylthio group according to this embodiment include a methylthio group and an ethylthio group.
The arylthio group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ has 3 or more and 25 or less, preferably 4 or more and 14 or less. Examples of the arylthio group in the present embodiment include a phenylthio group, a naphthylthio group, and a pyridylthio group.

Examples of the alkylsulfonyl group and arylsulfonyl group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ include a mesyl group or a tosyl group.
Examples of the sulfonyloxy group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ include a mesyloxy group or a tosyloxy group.
Examples of the silyl group constituting R ¹² , R ²² , R ²³ , R ³² , R ³³ , and R ³⁴ include a trimethylsilyl group or a triphenylsilyl group.

In the above formulas (1) to (3), A ¹ is an iodine atom, bromine atom, or chlorine atom, A ² is a tellurium atom, selenium atom, or sulfur atom, and A ³ is an antimony atom or arsenic. An atom or a phosphorus atom.

In the above formulas (1) to (3), Z ₁ ^n1- , Z ₂ ^n2- , and Z ₃ ^n3- are complex ions represented by the following formulas (4), (5), and (6), respectively. is there.

In formulas (4) and (6), E ¹ and E ³ are each independently a boron atom, an aluminum atom, a gallium atom, or the like. In formula (5), E ² represents a phosphorus atom, an arsenic atom, an antimony atom, or the like.

In the above formulas (4) and (5), X represents a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom.
In said formula (6), Ar < ⁶¹ > -Ar < ⁶⁴ > represents an aromatic hydrocarbon group or an aromatic heterocyclic group each independently. Ar ^{61 to} Ar ⁶⁴ in this embodiment are the same as R ¹¹ , R ²¹ , and R ³¹ , such as a monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-5 condensed ring. Ar ^{61 to} Ar ⁶⁴ may be substituted with any group including an electron-withdrawing group.

^{Examples of} Z ₁ ^n1- , Z ₂ ^n2- , and Z ₃ ^n3- constituting the organic onium salt in the present embodiment include the following.

As the organic onium salt in the present embodiment, an organic iodonium salt, an organic sulfonium salt, or the like can be suitably used.
In the present embodiment, an organic onium salt represented by the following formula (7) can be particularly preferably used as the polymerization initiator (b). By using the polymerization initiator (b) of the following formula (7), the film quality of the formed hole transport layer 22 can be improved.

Moreover, as a polymerization initiator (b), the metal complex which has acetylacetonate as a bidentate ligand can also be used, for example. In this case, it is possible to realize an organic electroluminescence device having good luminance and light emission lifetime while promoting polymerization of the polymerizable compound (a).
Examples of the metal constituting the metal complex include molybdenum, titanium, vanadium, and the like. Further, the methyl group constituting acetylacetonate may be another alkyl group. Examples of other alkyl groups include a tert-butyl group. Thereby, bulkiness can be improved and the solubility to a solvent can be improved.
In the present embodiment, the metal complex shown below can be used as the polymerization initiator (b).

In addition, as a polymerization initiator (b), 1 type selected from either of the above may be used independently, and 2 or more types may be used in arbitrary combinations.
The molecular weight of the polymerization initiator (b) is, for example, 100 or more and 10,000 or less, preferably 200 or more and 3000 or less. Thereby, the solubility in a solvent can be sufficiently ensured while suppressing the volatility during the formation of the coating film.

In the present embodiment, both the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole transport layer 22 are 14 nm or less, and preferably 10 nm or less. Here, the maximum peak height Rp is the maximum value of the peak height of the contour curve at the reference length defined by JISB0601. The mountain height means the height from the average line to the summit. Moreover, the maximum valley depth Rv is the maximum value of the valley depth of the contour curve at the reference length defined by JISB0601. The valley depth means the depth from the average line to the valley bottom.
The maximum peak height Rp and the maximum valley depth Rv of the upper surface of the hole transport layer 22 may be determined by a method such as Alpha Step IQ (manufactured by KLA-Tencor), SEM (Scanning Electron Microscope), or AFM (Atomic Force Microscope). Can be measured.

It is important for the present inventor to precisely control the smoothness of the upper surface of the organic layer constituting the organic electroluminescence element in order to improve the light emission characteristics (emission efficiency, emission unevenness, etc.) of the organic electroluminescence element. I found out. Based on this knowledge, in this embodiment, the smoothness of the upper surface of the hole transport layer 22 is precisely controlled. And the maximum peak height Rp and the maximum valley depth Rv are employ | adopted as a parameter | index showing smoothness. It has been confirmed by experiments of the present inventor that these indicators are good indicators for controlling the light emission characteristics of the organic electroluminescence element.
That is, in the present embodiment, the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole transport layer 22 are set to the upper limit value or less. Thereby, the unevenness | corrugation in the upper surface of the positive hole transport layer 22 can be made minute so that the light emission characteristic may not be affected. Therefore, it is possible to realize good light emission characteristics.
Further, by setting the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole transport layer 22 to be equal to or lower than the above upper limit values, the unevenness on the upper surface of each organic layer formed on the hole transport layer 22 is also as follows. It can be made minute so as not to affect the light emission characteristics.
The lower limit values of the maximum peak height Rp and the maximum valley depth Rv are not particularly limited, but are, for example, 0.1 nm. In this case, the adhesion with the light emitting layer 24 provided on the hole transport layer 22 can be improved.

  In the present embodiment, as shown in FIG. 1B, a hole injection layer 21 may be provided between the hole transport layer 22 and the anode 20. As the hole injection layer 21, for example, a layer in which the difference in work function between the hole conduction level and the anode 20 is smaller than that of the organic layer 22 is used. Thereby, hole injection from the anode 20 can be facilitated.

As a material constituting the hole injection layer 21, a compound having a hole transporting property can be used. Examples of the material constituting the hole injection layer 21 in the present embodiment include an aromatic amine compound, a phthalocyanine derivative, a porphyrin derivative, or an oligothiophene derivative. Among these, it is preferable to use an aromatic amine compound from the viewpoints of amorphousness, solubility in a solvent, and translucency.
As the aromatic amine compound constituting the hole injection layer 21, an aromatic tertiary amine compound or the like is used. Thereby, high hole transportability can be realized. The aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure and includes a compound having a group derived from an aromatic tertiary amine.

  The hole injection layer 21 may have an electron accepting compound. Examples of the electron-accepting compound include onium salts, triarylboron compounds, metal halides, Lewis acids, organic acids, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. By including these electron-accepting compounds, the conductivity of the hole injection layer 21 can be improved.

  The thickness of the hole injection layer 21 is, for example, not less than 1 nm and not more than 1000 nm, preferably not less than 10 nm and not more than 500 nm. Thereby, it is possible to reduce the resistance while ensuring the hole injection property.

In this embodiment, the hole injection layer 21 is a resin cured product obtained by ring-opening polymerization of a polymerizable compound (a) containing a ring-opening polymerizable group in the presence of a polymerization initiator (b). It may be formed of an object. In this case, the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole injection layer 21 are both 14 nm or less.
Further, in this case, the hole transport layer 22 is not particularly limited, but is made of, for example, a material containing the above-described polymerizable compound (a) and the polymerization initiator (b) in the same manner as the hole injection layer 21.

  As shown in FIG. 1A, the light emitting layer 24 is provided on the hole transport layer 22. In the present embodiment, the light emitting layer 24 is provided in contact with, for example, the hole transport layer 22.

The light emitting layer 24 in this embodiment has a light emitting material. As the light emitting material, either a fluorescent light emitting material or a phosphorescent light emitting material can be used, but a phosphorescent light emitting material may be used from the viewpoint of improving the internal quantum efficiency.
As the phosphorescent material, one kind of heavy atom having an atomic weight of 100 to 200 is selected from iridium, platinum, osmium, rhenium, gold, tungsten, ruthenium, hafnium, eurobium, terbium, rhodium, palladium, silver, and the like. Alternatively, a phosphorescent organometallic complex containing two or more kinds is used.

  In the present embodiment, as described above, the light emitting layer 24 includes a light emitting material composed of heavy atoms having an atomic weight of 100 or more and 200 or less. Thereby, a repulsive force caused by the heavy atom effect acts between the cation and anion contained in the polymerization initiator (b) in the hole transport layer 22 and the heavy atom in the light emitting layer 24. For this reason, it can suppress that the exciton in the light emitting layer 24 lose | disappears because the cation or anion which comprises a polymerization initiator (b) diffuses in the light emitting layer 24. FIG.

  The light emitting layer 24 in the present embodiment includes, for example, a hole transporting compound or an electron transporting compound. Examples of the hole transporting compound include the same materials as those constituting the hole injection layer 21 such as an aromatic amine compound, a phthalocyanine derivative, a porphyrin derivative, or an oligothiophene derivative. Examples of the electron transporting compound include 2,5-bis (1-naphthyl) -1,3,4-oxadiazole, 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl)). -1,1-dimethyl-3,4-diphenylsilole, bathophenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2- (4-biphenylyl) -5- (p-tersal Butylphenyl) -1,3,4-oxadiazole, 4,4′-bis (9-carbazole) -biphenyl, bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum, etc. It is done.

  The thickness of the light emitting layer 24 is, for example, 5 nm or more and 1000 nm or less, preferably 20 nm or more and 100 nm or less. Thereby, it is possible to improve the light emission efficiency and the light emission lifetime while suppressing the voltage of the organic electroluminescence element.

As shown in FIG. 1A, an electron transport layer 26 is provided on the light emitting layer 24. The electron transport layer 26 is made of, for example, a compound having an electron transport property. Moreover, as a material which comprises the electron carrying layer 26, the thing which has a function which blocks | prevents the hole which moves from the anode 20, for example reaching | attaining the cathode 30 can be used.
As a material constituting the electron transport layer 26 in the present embodiment, bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, or tris Mixed ligand complexes such as (8-quinolinolato) aluminum, and metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes , Styryl compounds such as distyrylbiphenyl derivatives, triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole, or phenanthrolines such as bathocuproine Derivatives.

In addition, as a material which comprises the electron carrying layer 26, 1 type selected from either of the above may be used independently, and 2 or more types may be combined arbitrarily.
The thickness of the electron transport layer 26 is, for example, not less than 0.5 nm and not more than 100 nm, preferably not less than 1 nm and not more than 50 nm. Thereby, the drive efficiency of an organic electroluminescent element can be improved, ensuring the thickness which can fully suppress the hole inject | poured from the anode 20, and suppressing the fall of luminous efficiency.

As shown in FIG. 1A, an electron injection layer 28 is provided on the electron transport layer 26. As the electron injection layer 28, for example, a metal having a low work function or a compound thereof is used in order to improve the electron injection efficiency in the organic electroluminescence device 100.
In the present embodiment, the material constituting the electron injection layer 28 is an alkali metal such as lithium, sodium or cesium, an alkaline earth metal such as barium or calcium, or CsF, Cs ₂ CO ₃ , Li ₂ O, Alternatively, a compound such as LiF can be used. These materials may be used individually by 1 type, and may be used together by arbitrary combinations of 2 or more types.
The thickness of the electron injection layer 28 is, for example, not less than 0.1 nm and not more than 5 nm, preferably not less than 0.5 nm and not more than 2 nm.

  As shown in FIG. 1A, the cathode 30 is formed on the light emitting layer 24. In the present embodiment, the cathode 30 is provided above the light emitting layer 24 via, for example, an electron transport layer 26 and an electron injection layer 28 provided on the light emitting layer 24.

As the cathode 30, for example, a conductive material having a work function smaller than that of the anode 20 is selected.
In the present embodiment, the material constituting the cathode 30 is not particularly limited as long as it is a conductive material having a work function smaller than that of the anode 20. The cathode 30 is made of tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof. One of these materials may be used alone, or two or more arbitrary combinations may be used.
The film thickness of the cathode 30 is, for example, 5 nm to 1000 nm, preferably 10 nm to 500 nm. Thereby, it is possible to suppress an increase in electrical resistance due to the thin film thickness while reducing the manufacturing cost by reducing the film thickness.

In the present embodiment, both the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the cathode 30 are 10 nm or less, preferably 6 nm or less. Thereby, the unevenness | corrugation in the upper surface of the cathode 30 can be made minute so that the light emission efficiency is not affected. Accordingly, it is possible to suppress a decrease in light emission efficiency.
Note that the lower limit values of the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the cathode 30 are not particularly limited. However, for example, when the thickness is in the range of 0.1 nm or more, the light emission efficiency of the organic electroluminescence element can be sufficiently improved.

FIG. 2 is a cross-sectional view showing a light emitting device 200 including the organic electroluminescence element 100 shown in FIG. 2 is a schematic diagram for showing the light emitting device 200, and the configuration of the light emitting device 200 according to the present embodiment is not limited to that shown in FIG. The light emitting device 200 is configured using the organic electroluminescence element 100. The light emitting device 200 according to the present embodiment can be used as, for example, a display device or a light emitting device.
The organic electroluminescent element 100 according to the present embodiment is sealed with a sealing can 40 made of, for example, metal or glass. The sealing can 40 is provided on the substrate 10, for example. Further, the sealing can 40 is bonded to the substrate 10 by a sealing material 44, for example. With this sealing material 44, the inside of the sealing can 40 can be sealed. The inside of the sealing can 40 is filled with an inert gas such as nitrogen gas. Thereby, it can suppress that the organic electroluminescent element 100 in the sealing can 40 deteriorates with oxygen.
In the sealing can 40, for example, a desiccant 42 is disposed. Thereby, it can suppress that the element characteristic of the organic electroluminescent element 100 deteriorates with the water | moisture content which remained in the sealing can 40. FIG.

Next, a method for manufacturing the organic electroluminescence element 100 according to this embodiment will be described.
The manufacturing method of the organic electroluminescent element 100 according to the present embodiment includes a step of forming the hole transport layer 22 on the anode 20, a step of forming the light emitting layer 24 on the hole transport layer 22, and the light emitting layer 24. Forming a cathode 30 on the substrate. The step of forming the hole transport layer 22 includes a step of preparing a first solution containing a polymerizable compound (a) containing a ring-opening polymerizable group and a second solution containing a polymerization initiator (b). , A step of preparing a coating solution by mixing the first solution and the second solution, a step of forming a coating film by applying the coating solution, and a polymerizable compound in the presence of the polymerization initiator (b) ( a) ring-opening polymerization to cure the coating film.
Hereinafter, the manufacturing method of the organic electroluminescent element 100 will be described in detail.

First, the anode 20 is formed on the substrate 10. The anode 20 is formed using a sputtering method, a vacuum evaporation method, or the like.
Also, when using metal fine particles, metal halide fine particles, carbon material fine particles, metal oxide fine particles, conductive polymer fine powder, or the like as the anode 20, for example, these materials are dispersed in a binder resin solution. Then, the anode 20 is formed by coating on the substrate 10. Further, when a conductive polymer is used as the material of the anode 20, the anode 20 is formed using electrolytic polymerization, a coating method, or the like.

Next, the hole transport layer 22 is formed on the anode 20. In the present embodiment, the hole transport layer 22 is formed as follows, for example.
FIG. 3 is a flowchart illustrating a method for forming the hole transport layer 22 shown in FIG.
First, a first solution containing a polymerizable compound (a) containing a ring-opening polymerizable group and a second solution containing a polymerization initiator (b) are prepared (S01, S02). That is, the first solution and the second solution are prepared separately. The first solution is prepared by dissolving the polymerizable compound (a) in the first solvent. The second solution is prepared by dissolving the polymerization initiator (b) in the second solvent. In the present embodiment, either the first solution or the second solution may be prepared first.

In the step of preparing the first solution (S01), for example, the polymerizable compound (a) is dissolved in the first solvent under the temperature condition of the boiling point of the first solvent + 30 ° C. or less. When xylene is used as the first solvent, the polymerizable compound (a) is dissolved in the first solvent under a temperature condition of 165 ° C. or lower. Thereby, it can suppress that the 1st solvent volatilizes and solid content concentration in the 1st solution changes. Therefore, it becomes easy to prepare a coating solution described later.
Also in the step of preparing the second solution (S02), for example, the polymerization initiator (b) is dissolved in the second solvent under the temperature condition of the boiling point of the second solvent + 30 ° C. or less. When xylene is used as the second solvent, the polymerization initiator (b) is dissolved in the second solvent under a temperature condition of 165 ° C. or lower. Thereby, it can suppress that the 2nd solvent volatilizes and solid content concentration in the 2nd solution changes. Therefore, it becomes easy to prepare a coating solution described later.

  In this embodiment, the polymerizable compound (a) and the polymerization initiator (b) are each dissolved in a separately prepared solvent. For this reason, in the process of melt | dissolving polymeric compound (a), since polymerization initiator (b) does not exist in a solvent, it can suppress that ring-opening polymerization of polymeric compound (a) advances. Therefore, a wide process margin can be taken with respect to the melting temperature and the melting time.

Examples of the first solvent include aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, ester solvents, ether solvents, amide solvents, dimethyl sulfoxide, and the like. Examples of the aliphatic hydrocarbon solvent include bicyclohexyl, trimethylcyclohexane, Fencon, menthone, cis-decalin, and the like. Examples of the aromatic hydrocarbon solvent include benzene, trimethylbenzene, dodecylbenzene, cyclohexylbenzene, toluene, xylene, tetralin, or 1,5-dimethyltetralin. Examples of ester solvents include ethyl acetate, 2-phenoxyethyl acetate, n-butyl acetate, ethyl lactate, n-butyl lactate, methyl benzoate, ethyl benzoate, ethyl 4-fluorobenzoate, isopropyl benzoate, and benzoic acid. Examples include butyl, isopentyl benzoate, and benzyl benzoate. Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, or propylene glycol-1-monomethyl ether acetate, or 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, diphenyl ether. , Aromatic ethers such as phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole and 2,4-dimethylanisole. Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide and the like. In addition, these solvents may be used individually by 1 type, and may be used in combination of 2 or more type.
As the second solvent, for example, the same solvent as the first solvent can be used.
Note that the first solvent and the second solvent may be different from each other. In this case, the solubility of the polymerizable compound (a) and the polymerization initiator (b) in the solvent can be controlled. Moreover, the film-forming property can also be improved by adjusting the difference between the boiling points of the first solvent and the second solvent.

In this embodiment, after the step of preparing the first solution and the second solution (S01, S02) and before the step of forming the coating solution by mixing the first solution and the second solution (S03) The first solution and the second solution may be cooled. The cooling method may be natural cooling or forced cooling by air cooling or a refrigerant.
In the present embodiment, the first solution and the second solution are cooled to, for example, 60 ° C. or lower, preferably 40 ° C. or lower. By carrying out like this, in the process of mixing a 1st solution and a 2nd solution, progress of superposition | polymerization of a polymeric compound (a) can be suppressed more reliably.

  Next, the first solution containing the polymerizable compound (a) and the second solution containing the polymerization initiator (b) are mixed to prepare a coating solution (S03). From the viewpoint of more reliably suppressing the progress of the polymerization of the polymerizable compound (a), this mixing step is preferably performed without heating or under heating conditions of, for example, 60 ° C. or lower.

In the prior art, both the polymerizable compound (a) and the polymerization initiator (b) are dissolved in the same solvent. According to the study of the present inventor, it has been clarified that the following problems occur in this case.
First, when the ring-opening polymerization of the polymerizable compound (a) proceeds to a certain degree in the presence of the polymerization initiator (b) in the preparation stage of the coating solution, the resulting organic layer has an absorption band in the visible light region. To have. In this case, the light emission characteristics of the organic electroluminescence element are impaired.
When the method of adjusting the coating solution by dissolving both the polymerizable compound (a) and the polymerization initiator (b) in the same solvent is taken, the polymerizable compound (a ) Progresses in the ring-opening polymerization, and the coating solution may be slightly colored. In this case, as described above, the obtained organic layer has an absorption band in the visible light region. On the other hand, even if the coating solution is not colored enough, at first glance, it may have an absorption band in the visible light region if the polymerization proceeds to some extent even if it is colorless at first glance.
Secondly, when an organic layer is formed by applying, drying and curing a coating solution in which both the polymerizable compound (a) and the polymerization initiator (b) are dissolved in the same solvent, a minute size of nanometer size is obtained. Unevenness occurs. Since the minute irregularities cause a decrease in light emission characteristics, it is difficult to stably realize good light emission characteristics.

In contrast, in the present embodiment, as described above, it is possible to avoid the reaction between the polymerizable compound (a) and the polymerization initiator (b) in the coating liquid preparation stage. For this reason, the transparency in the coating liquid containing a polymeric compound (a) and a polymerization initiator (b) can be maintained. In this case, the transparency of the hole transport layer 22 formed by the coating liquid is also ensured. Therefore, it is possible to suppress the deterioration of the light emission characteristics of the organic electroluminescence element due to the discoloration of the organic layer.
Further, according to the present embodiment, the unevenness on the upper surface of the hole transport layer 22 formed by the coating solution containing the polymerizable compound (a) and the polymerization initiator (b) is not affected to the light emission efficiency. It can be very small. Therefore, it can also suppress that the light emission characteristic of an organic electroluminescent element falls by the unevenness | corrugation formed in the organic layer upper surface.
The fact that such an effect can be obtained by the present embodiment will be shown by examples described later.

  Moreover, according to the manufacturing method of the organic electroluminescent element which concerns on this embodiment, as above-mentioned, before a coating liquid is apply | coated, a polymeric compound (a) and a polymerization initiator (b) will react. Can be avoided. For this reason, it can suppress that the viscosity of a coating liquid rises before a coating liquid is apply | coated. Therefore, for example, it is possible to suppress the occurrence of a problem that the coating liquid is clogged with the nozzles when coating is performed by the ink jet method.

  In the present embodiment, the mixing of the first solution and the second solution may be performed while controlling the temperature of the first solution and the second solution to 40 ° C. or less. By controlling the temperature condition at the time of mixing the first solution and the second solution in this way, it is possible to reliably suppress the reaction between the polymerizable compound (a) and the polymerization initiator (b) during mixing. Is possible.

Next, a coating film is formed by applying a coating solution obtained by mixing the first solution and the second solution (S04). In the present embodiment, the coating liquid is applied on, for example, the anode 20. The coating liquid is applied by spin coating or ink jet.
In this embodiment, after the step (S04) of forming the coating film, before the step of curing the coating film by ring-opening polymerization of the polymerizable compound (a) in the presence of the polymerization initiator (b). In (S05), the coating film can be dried. The coating film is dried, for example, in a pressure atmosphere of less than 2 Pa using a vacuum dryer. By drying the coating film, it is possible to suppress unnecessary reactions from being accelerated by the polarity of the solvent when the polymerizable compound (a) is polymerized in the presence of the polymerization initiator (b). Therefore, it becomes possible to ensure the transparency of the organic layer formed by the coating film.

Next, the polymerizable compound (a) is polymerized in the presence of the polymerization initiator (b) to cure the coating film (S05). Thereby, the hole transport layer 22 is formed.
In the present embodiment, for example, the polymerizable compound (a) is polymerized in the presence of the polymerization initiator (b) by heating the coating film. The heating conditions at this time are, for example, 200 ° C. or more and 250 ° C. or less and 5 minutes or more and 60 minutes or less. In the present embodiment, the polymerizable compound (a) and the polymerization initiator (b) are contained in one coating solution. For this reason, a sufficient reaction is possible even by firing for a short time as described above. Therefore, the manufacturing cost of the organic electroluminescence element can be reduced.

  In the present embodiment, when the coating film is cured, curing by light irradiation is not performed, and a heat curing method is employed. For this reason, it is suppressed that the part which has the function to convey a hole among polymeric compounds (a) will be oxidized by light irradiation. Accordingly, a decrease in light emission characteristics of the organic electroluminescence element due to the coating film curing step is suppressed.

  In the present embodiment, a step of forming a hole injection layer may be provided before the step of forming the hole transport layer 22 and after the step of forming the anode 20. In this case, the coating liquid for forming the hole transport layer 22 is applied onto the hole injection layer. The hole injection layer is formed on the anode 20 by a coating method such as spin coating or ink jet.

Next, the light emitting layer 24 is formed on the hole transport layer 22.
In the present embodiment, the light emitting layer 24 is formed as follows, for example. First, the material constituting the light emitting layer 24 is dissolved in a solvent to prepare a coating solution. As the solvent, for example, aromatic solvents such as toluene and xylene are used. Next, this coating solution is applied onto the hole transport layer 22 to form a coating film on the hole transport layer 22. The coating liquid is applied by a coating method such as spin coating or ink jet. Next, this coating film is dried. The coating film is dried, for example, in a pressure atmosphere of less than 2 Pa using a vacuum dryer. Thereby, the light emitting layer 24 is formed.

  Next, the electron transport layer 26 is formed on the light emitting layer 24. The electron transport layer 26 is formed on the light emitting layer 24 by a coating method, a vacuum deposition method, or the like. When using the vacuum vapor deposition method, the electron transport layer 26 is formed by putting the vapor deposition source in the vacuum vapor deposition machine, reducing the pressure inside the vacuum vapor deposition machine to the set pressure, and then heating and evaporating the vapor deposition source. This is the same when the anode 20, the light emitting layer 24, and the cathode 30 are formed by vacuum deposition.

  Next, the electron injection layer 28 is formed on the electron transport layer 26. The electron injection layer 28 is formed on the electron transport layer 26 by a coating method, a vacuum deposition method, or the like.

Next, the cathode 30 is formed on the electron injection layer 28. The cathode 30 is formed on the electron injection layer 28 by a vacuum vapor deposition method or a sputtering method.
According to this embodiment, the unevenness on the upper surface of the hole transport layer 22 can be controlled in a minute range. For this reason, the organic layer formed on the hole transport layer 22 and the unevenness on the upper surface of the cathode 30 are also controlled in a minute range. Accordingly, it is possible to suppress a decrease in light emission characteristics due to the unevenness formed in the cathode 30.
In this way, the organic electroluminescence element 100 shown in FIG. 1A is formed.

  As shown in FIG. 2, the formed organic electroluminescence element 100 is sealed with, for example, a sealing can 40. In the present embodiment, the organic electroluminescence element 100 is sealed with a sealing can 40 in a glove box in an inert gas atmosphere such as nitrogen gas. At this time, a desiccant 42 may be disposed in the sealing can 40.

Next, the operation and effect of this embodiment will be described.
In the present embodiment, a resin obtained by subjecting the hole transport layer 22 (organic layer) to ring-opening polymerization of a polymerizable compound (a) containing a ring-opening polymerizable group in the presence of a polymerization initiator (b). It is formed of a cured product. Therefore, the hole transport layer 22 can be formed using a coating method. Therefore, it is possible to realize an organic electroluminescence element excellent in mass productivity and manufacturing stability.

On the other hand, when the hole transport layer 22 is formed using such components (a) and (b), the present state is that the light emission characteristics as expected are not obtained. In addition, there is a problem that the light emission characteristics vary.
As a result of intensive studies on this cause, the present inventor has found that the micro smoothness of the upper surface of the hole transport layer 22 affects the light emission characteristics.
In the coating method, a solution obtained by dissolving a layer forming material containing a polymerizable compound (a) and a polymerization initiator (b) in an organic solvent is applied onto a substrate. Since the solution has such a low viscosity that there is no problem in the operation in the application process, the surface immediately after application is smooth. However, when the organic solvent is dried and the reaction of the resin proceeds, and further crosslinking proceeds by heating or the like, minute irregularities are generated on the surface of the organic layer. Thus, although the surface of the thin layer formed by the coating method seems to have sufficient smoothness at first glance, there are minute irregularities on the nm level. Conventionally, the existence of such minute irregularities has not been known and has not been a problem. The inventor of the present invention has determined that such minute irregularities cause a decrease in light emission characteristics.
The reason why the minute irregularities formed on the upper surface of the organic layer cause a decrease in the light emission characteristics is not necessarily clear, but is estimated as follows. That is, when minute irregularities are formed on the upper surface of the organic layer, an electric field strength distribution is generated in the light emitting surface. If unevenness in light emission occurs due to this electric field intensity distribution, the light emission characteristics deteriorate. In addition, the light generated from the light emitting layer is scattered by the minute unevenness formed on the upper surface of the organic layer, thereby reducing the light emitting characteristics.
In the present embodiment, based on such knowledge, the maximum peak height Rp and the maximum valley depth Rv on the upper surface of the hole transport layer 22 (organic layer) are both set to 14 nm or less. Thereby, sufficiently good light emission characteristics are stably realized.

  As described above, according to this embodiment, an organic electroluminescent element having excellent light emission characteristics as well as excellent mass productivity and manufacturing stability can be realized.

  In addition, the structure of the organic electroluminescent element 100 which concerns on this embodiment is not restricted to what is shown to Fig.1 (a). For example, as shown in FIG. 1B, a hole injection layer 21 may be provided between the anode 20 and the hole transport layer 22.

  Hereinafter, the present embodiment will be described in detail with reference to examples. In addition, this embodiment is not limited to description of these Examples at all.

Example 1
An anode made of ITO (Indium-Tin-Oxide) having a thickness of 110 nm was formed on a transparent glass substrate. The anode was formed by a vacuum evaporation method.
Next, a hole transport layer was formed on the anode. The hole transport layer was formed by the following method.
First, a first solution containing a polymerizable compound (a) represented by the following formula (8) was produced. The first solution was obtained by dissolving the polymerizable compound (a) in a xylene solvent at 160 ° C. for 10 minutes. Next, the prepared first solution was cooled to room temperature (25 ° C., unless otherwise specified, “room temperature” means 25 ° C.).

  Next, separately from the first solution, a second solution containing a polymerization initiator (b) represented by the following formula (7) was prepared. The second solution was obtained by dissolving the polymerization initiator (b) in a xylene solvent at 160 ° C. for 10 minutes. Next, the prepared second solution was cooled to room temperature.

  Next, the first solution and the second solution were mixed to prepare a coating solution. The mixing of the first solution and the second solution was performed at room temperature. A coating solution was prepared so that the content of the polymerization initiator (b) in the entire solid content excluding the solvent was 7.6% by weight. Next, the coating solution was applied on the anode, and a coating film having a thickness of 45 nm was formed on the anode. The coating solution was applied by a spin coating method.

  Next, the coating film was dried at room temperature under an atmosphere of less than 2 Pa using a vacuum dryer. Next, the coating film was heat-treated at 230 ° C. for 15 minutes under normal pressure. As a result, in the coating film, the ring-opening polymerization of the polymerizable compound (a) proceeded in the presence of the polymerization initiator (b) to form a hole transport layer composed of a resin composition having a three-dimensional crosslinked structure. .

  Next, a light emitting layer was formed on the hole transport layer by the following method. First, a coating liquid containing bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum as an electron transporting compound and a light emitting material represented by the following formula (9) is coated on the hole transporting layer. Then, a coating film having a thickness of 40 nm was formed on the hole transport layer. This coating solution was prepared by dissolving bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum and a luminescent material represented by the following formula (9) in a toluene solvent. In addition, the coating liquid was prepared so that content of a luminescent material might be 6 weight% among the whole solid content except a solvent.

Next, this coating solution was applied onto the hole transport layer to form a coating film having a thickness of 40 nm on the hole transport layer. The coating solution was applied by a spin coating method.
Next, the coating film was dried under a pressure atmosphere of less than 2 Pa using a vacuum dryer. Next, a heat treatment was performed on the coating film formed on the hole transport layer. In this way, a light emitting layer was formed.

Next, an electron transport layer having a thickness of 30 nm was formed on the light emitting layer. The electron transport layer was formed by depositing tris (8-quinolinolato) aluminum on the light emitting layer by vacuum evaporation. Next, an electron injection layer having a thickness of 1 nm was formed on the electron transport layer. The electron injection layer was formed by depositing LiF on the electron transport layer by a vacuum evaporation method. Next, a cathode having a thickness of 80 nm was formed on the electron injection layer. The cathode was formed by depositing Ag on the electron injection layer by vacuum evaporation. In addition, the process of forming an electron carrying layer, an electron injection layer, and a cathode was performed continuously in a vacuum evaporation machine.
Thus, the organic electroluminescent element provided with the some organic layer between the anode and the cathode was obtained.

  Next, the organic electroluminescence element obtained above was taken out from the vacuum vapor deposition machine. Next, the organic electroluminescence element was sealed with a metal (glass) sealing can. Sealing with a sealing can was performed in a glove box in an inert gas atmosphere. Thereby, a light emitting device was obtained.

(Comparative Example 1)
An organic electroluminescence element and a light emitting device were obtained in the same manner as in Example 1 except for the method for forming the hole transport layer. The hole transport layer was formed as follows.
First, a polymerizable compound (a) represented by the above formula (8) and a polymerization initiator (b) represented by the above formula (7) were placed in a xylene solvent. Next, the xylene solvent containing the polymerizable compound (a) and the polymerization initiator (b) is heated at 160 ° C. for 2 minutes, so that the polymerizable compound (a) and the polymerization initiator (b) are converted into a xylene solvent. Dissolved in. This obtained the coating liquid containing a polymeric compound (a) and a polymerization initiator (b). A coating solution was prepared so that the content of the polymerization initiator (b) in the entire solid content excluding the solvent was 7.6% by weight.

Next, the coating solution was applied on the anode, and a coating film having a thickness of 45 nm was formed on the anode. The coating solution was applied by a spin coating method.
Next, the coating film was dried under a pressure atmosphere of less than 2 Pa using a vacuum dryer. Next, the coating film was subjected to heat treatment at 230 ° C. for 15 minutes under normal pressure. As a result, in the coating film, the ring-opening polymerization of the polymerizable compound (b) proceeded in the presence of the polymerization initiator (b) to form a hole transport layer made of a cured resin having a three-dimensional crosslinked structure. .

(Comparative Example 2)
An organic electroluminescence element and a light-emitting device were obtained in the same manner as in Comparative Example 1 except for a method for preparing a coating liquid containing a polymerizable compound (a) and a polymerization initiator (b). The coating solution was prepared as follows.
First, a polymerizable compound (a) represented by the above formula (8) and a polymerization initiator (b) represented by the above formula (7) were placed in a xylene solvent. Next, the xylene solvent containing the polymerizable compound (a) and the polymerization initiator (b) is heated at 160 ° C. for 10 minutes, so that the polymerizable compound (a) and the polymerization initiator (b) are converted into a xylene solvent. Dissolved in. This obtained the coating liquid containing a polymeric compound (a) and a polymerization initiator (b). A coating solution was prepared so that the content of the polymerization initiator (b) in the entire solid content excluding the solvent was 7.6% by weight.

  About the Example and each comparative example, it evaluated as follows. The evaluation results are shown in Table 1.

(Smoothness of hole transport layer surface)
The maximum peak height Rp and the maximum valley depth Rv on the surface of the hole transport layer were measured.
The measurement was performed as follows. First, after forming a positive hole transport layer, several places of the film | membrane formed into a film on the glass substrate were shaved with the cutter so that the glass substrate surface might be exposed. Subsequently, the height from each exposed location on the glass substrate surface to the surface of the hole transport layer located in the vicinity of each location was measured. Based on the measured heights from the respective locations, the film thicknesses at several locations of the film formed on the glass substrate were calculated. And the maximum peak height Rp and the maximum valley depth Rv in the surface of a positive hole transport layer were calculated | required from the calculated film thickness. The height from the exposed surface of the glass substrate to the surface of the hole transport layer located in the vicinity of the surface is a needle pressure of 3.0 ± 0.2 mg, scan using an alpha step IQ (manufactured by KLA-Tencor). The measurement was performed under conditions of a range of 300 μm and a single scan.
In Table 1, the larger one of the maximum peak height Rp or the maximum valley depth Rv in the measurement range is shown. The unit of the measured value shown in Table 1 is nm.

(Smoothness of cathode surface)
The maximum peak height Rp and the maximum valley depth Rv on the surface of the cathode were measured.
The measurement was performed as follows. First, after forming the cathode, several portions of the film formed on the glass substrate were shaved with a cutter so that the glass substrate surface was exposed. Subsequently, the height from each exposed location on the glass substrate surface to the surface of the cathode located in the vicinity of each location was measured. Based on the measured heights from the respective locations, the film thicknesses at several locations of the film formed on the glass substrate were calculated. Then, from the calculated film thickness, the maximum peak height Rp and the maximum valley depth Rv on the surface of the cathode were obtained. The height from the exposed surface of the glass substrate to the surface of the cathode located in the vicinity thereof is alpha step IQ (manufactured by KLA-Tencor) using a needle pressure of 3.0 ± 0.2 mg, a scanning range of 300 μm, It was measured under the condition of one scan.
In Table 1, the larger one of the maximum peak height Rp or the maximum valley depth Rv in the measurement range is shown. The unit of the measured value shown in Table 1 is nm.

(Relative brightness)
The relative luminance of the obtained light emitting device was measured. Luminance meter (LS-110, manufactured by Konica Minolta Holdings Co., Ltd.) and current power source (236 type source-measure unit, manufactured by Keithley), current-voltage-luminance measurement, light emitting devices in each example and each comparative example The brightness of was calculated. Table 1 shows the relative luminance in each example and each comparative example when the luminance in Example 1 is set as a reference (100%).

(Relative life)
The relative lifetime of the obtained light emitting device was measured. The relative lifetime was calculated from the change in relative luminance under a constant current density of about 20 mA / cm ² . In Table 1, the relative lifetime in each Example and each comparative example when the lifetime in Example 1 is set as a reference (100%) is shown.

(Light emission unevenness)
While making the obtained organic electroluminescence element emit light, the presence or absence of light emission unevenness was observed by light microscopic observation using Eclipse L150 (manufactured by Nikon Corporation). The input voltage was 3 to 4 V at which the organic electroluminescence element emits light.

As shown in Table 1, in Example 1, the maximum peak height Rp and the maximum valley depth Rv on the hole transport layer surface are 14 nm or less. Further, the maximum peak height Rp and the maximum valley depth Rv on the cathode surface are 10 nm or less. Example 1 showed good results for all of relative luminance, relative lifetime, and light emission unevenness.
On the other hand, in Comparative Example 1, the maximum peak height Rp and the maximum valley depth Rv on the surface of the hole transport layer exceed 14 nm. Further, the maximum peak height Rp and the maximum valley depth Rv on the cathode surface exceed 10 nm. In such Comparative Example 1, light emission unevenness occurred as compared with Example 1. That is, a decrease in light emission characteristics was observed.
In Comparative Example 2, the maximum peak height Rp and the maximum valley depth Rv on the hole transport layer surface exceed 14 nm. Further, the maximum peak height Rp and the maximum valley depth Rv on the cathode surface exceed 10 nm. In Comparative Example 2 as described above, the light emission efficiency was reduced as compared with Example 1, and light emission unevenness occurred. That is, a decrease in light emission characteristics was observed.

Claims (3)

Forming an organic layer on the anode;
Forming a light emitting layer on the organic layer;
Forming a cathode on the light emitting layer;
With
The step of forming the organic layer includes:
Preparing a first solution containing a thermally polymerizable polymerizable compound (a) containing a ring-opening polymerizable group and a second solution containing a polymerization initiator (b);
Cooling the first solution and the second solution to 60 ° C. or lower and room temperature ;
Performed after the cooling step, mixing the first solution and the second solution to create a coating solution;
The manufacturing method of the organic electroluminescent element containing this. In the manufacturing method of the organic electroluminescent element of Claim 1,
After the step of preparing the coating liquid by mixing the first solution and the second solution,
A step of forming a coating film by applying the coating solution;
Curing the coating film by ring-opening polymerization of the polymerizable compound (a) in the presence of the polymerization initiator (b);
The manufacturing method of the organic electroluminescent element containing this. In the manufacturing method of the organic electroluminescent element of Claim 1 or 2,
In the process of cooling the first solution and the second solution to 60 ° C. or lower, the method for manufacturing an organic electroluminescence element, wherein the first solution and the second solution are cooled to 40 ° C. or lower.

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