JP7415917B2 - Composition and method for producing organic electroluminescent device - Google Patents

Description

The present invention relates to a composition suitably used for forming a functional film, which is an organic film made of a functional material, in the production of an organic electroluminescent device, and a method for producing an organic electroluminescent device using this composition.

The common method for manufacturing organic electroluminescent devices is to form organic materials into films by vacuum evaporation and laminate them, but in recent years, organic materials in solution form have been developed as a manufacturing method that is more efficient in material usage. Research on manufacturing methods using wet film formation, in which films are formed by an inkjet method or the like and laminated, is becoming more active.

In manufacturing organic electroluminescent devices, especially organic EL displays, by wet film formation, each pixel is divided by partition walls called banks, and the organic film that makes up the organic electroluminescent device is formed in a minute area within the bank. A method of forming a film by discharging an ink, which is a composition for forming an organic electroluminescent element, using an inkjet method has been studied. At this time, a technique has been proposed to obtain a flatter film within the area surrounded by the bank by mixing various surface modifiers with the ink (Patent Documents 1 and 2).

However, in the conventional method, the flatness of the film within the region surrounded by the bank was not sufficient.

Patent Document 3 discloses a technique using two or more types of solvents having different boiling points for the purpose of forming a functional layer having a substantially flat cross-sectional shape after drying and solidification.

International Publication No. 2010/104183 JP2002-056980A Japanese Patent Application Publication No. 2015-185640

When coating with an inkjet device, ink with too high a viscosity has problems with ejection properties, and ink with too low a viscosity cannot be held in the head, so there is a certain range of appropriate viscosity. On the other hand, in the process of drying a liquid film, there are various flows such as liquid movement due to concentration gradient and Marangoni convection, so the shape of the dry film tends to become complicated. In order to control this complex film shape, the viscosity of the ink can be increased to a certain extent and the flow speed can be slowed down. However, the high viscosity may exceed the viscosity range that can be properly ejected as an inkjet ink, making it difficult to adjust the viscosity to an appropriate range. In particular, if the solute dissolved in the ejected ink is mainly a low-molecular material, the viscosity of the ink is about the same as the viscosity of the solvent, so even if the solvent evaporates to a certain extent, the viscosity of the ink will change significantly. Therefore, the problem that the dried film is difficult to flatten due to the flow of the liquid tends to occur.

Even when a plurality of solvents having different boiling points are used as in Patent Document 3, there is still room for improvement in the flatness of the edge of the panel coated with ink.

The present invention improves the uniformity of the film thickness within a region surrounded by banks when forming an organic film constituting an organic electroluminescent device by wet film formation, and further improves the uniformity of the film thickness in the region surrounded by banks, and further improves the uniformity of the film thickness in the region surrounded by banks. It is an object of the present invention to provide a composition that can improve flatness not only at the edges but also at the edges, and a method for manufacturing an organic electroluminescent device using this composition.

When forming an organic film constituting an organic electroluminescent element in a region surrounded by banks by wet film formation, the present inventor uses a mixed solvent of two or more solvents with different boiling points and a functional material. By using a solvent with high temperature dependence of viscosity (flow activation energy) as the solvent with a high boiling point in a composition containing It has been found that the uniformity of thickness can be improved. It has also been found that by setting the boiling point of the solvent with a lower boiling point to 245° C. or higher, flatness can be improved not only at the center of the panel but also at the edges.

That is, the present invention has the following configuration.

[1] A composition comprising a functional material, a first solvent, and a second solvent, wherein the first solvent is a water-insoluble aromatic solvent, and the boiling point of the first solvent is lower than that of the second solvent. higher than the boiling point, the difference in boiling point between the first solvent and the second solvent is 10° C. or more, the first solvent has a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less, and the first solvent has a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less, A composition in which the content of the solvent is 5 to 50% by weight based on the total amount of the first solvent and the second solvent, and the second solvent has a boiling point of 245° C. or higher.

[2] The composition according to [1], wherein the total content of the first solvent and the second solvent in the composition is 50% by weight or more.

[3] The composition according to [1] or [2], wherein the functional material has a molecular weight of 50,000 or less.

[4] The composition according to any one of [1] to [3], wherein the second solvent has a viscosity of 5 mPas or less at 23°C.

[5] The composition according to any one of [1] to [4], wherein the difference between the boiling point of the first solvent and the boiling point of the second solvent is 30° C. or more.

[6] The composition according to any one of [1] to [5], wherein the flow activation energy of the first solvent is 5 kJ/mol or more greater than the flow activation energy of the second solvent.

[7] The composition according to any one of [1] to [6], wherein the first solvent has a surface tension of 30 mN/m or more.

[8] Any one of [1] to [7], wherein the first solvent and the second solvent are naphthalene, benzoic acid ester, or aromatic ether, each of which may have a substituent. The composition described in.

[9] The first solvent is 2-ethylhexyl benzoate, benzyl benzoate, acetylnaphthalene, dimethyl phthalate, diethyl phthalate, ethyl biphenyl, isopropylbiphenyl, diisopropylbiphenyl, triisopropylbiphenyl, 2-phenoxyethyl isobutyrate. The second solvent is any one of methylnaphthalene, ethylnaphthalene, isopropylnaphthalene, methoxynaphthalene, butyl benzoate, pentyl benzoate, isopentyl benzoate, diphenylmethane, and benzyltoluene [1] to [7]. ] The composition according to any one of.

[10] A method for producing an organic electroluminescent device, comprising a step of forming a wet film using the composition according to any one of [1] to [9].

According to the composition of the present invention, it is possible to improve the uniformity of the thickness of the functional film within the region surrounded by the bank. Moreover, the flatness can be improved not only at the center portion of the panel coated with ink but also at the edge portions.

1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device of the present invention. 3 is a diagram showing profiles of a light emitting layer and a blank of Reference Example 1. FIG. FIG. 3 is a diagram showing profiles of a light-emitting layer and a blank of Reference Example 2. 3 is a diagram showing profiles of a light emitting layer and a blank of Comparative Example 1. FIG. 3 is a diagram showing profiles of a light-emitting layer and a blank of Comparative Example 2. FIG. 3 is a diagram showing profiles of a light-emitting layer and a blank of Comparative Example 3. FIG. 3 is a diagram showing a profile of flatness evaluation of measurement point 1 in Example 1. FIG. 3 is a diagram showing a profile of flatness evaluation of measurement point 2 in Example 1. FIG. 3 is a diagram showing a profile of flatness evaluation of measurement point 1 in Example 2. FIG. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 2 in Example 2. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 1 in Example 3. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 1 of Comparative Example 4. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 2 of Comparative Example 4. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 1 of Comparative Example 5. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 2 of Comparative Example 5. FIG. 7 is a diagram showing a profile of flatness evaluation of measurement point 1 of Comparative Example 6. FIG. 6 is a diagram showing a profile of flatness evaluation of measurement point 2 of Comparative Example 6.

〔Composition〕
The composition of the present invention is a composition comprising a functional material, a first solvent, and a second solvent, wherein the first solvent is a water-insoluble aromatic solvent, and the boiling point of the first solvent is higher than the boiling point of the second solvent, the difference in boiling point between the first solvent and the second solvent is 10°C or more, and the first solvent has a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less. , the content ratio of the first solvent is 5 to 50% by weight based on the total amount of the first solvent and the second solvent, and the boiling point of the second solvent is 245° C. or higher.

The solvent contained in the composition of the present invention is such that the boiling point of the second solvent is 245°C or higher and the boiling point of the first solvent is higher than the boiling point of the second solvent, that is, the boiling point of both solvents is 245°C or higher. , it can be used as ink that can be ejected from minute nozzles. The composition of the present invention exhibits a moderately low viscosity at room temperature, but when the temperature drops due to the heat of vaporization during vacuum drying, the viscosity rapidly increases. This slows down the flow rate of the liquid, making it possible to control the shape of the film, resulting in a flat film. This effect is more pronounced in compositions in which the solute is of a low molecular weight, and the viscosity does not easily increase even when the solid content of the liquid increases due to evaporation of the solvent. Further, since the boiling point of the second solvent having a lower boiling point is also 245° C. or higher, it is possible to prevent the solvent from vaporizing before the vacuum drying process even at the panel edges where drying is particularly fast. Therefore, the temperature can be lowered sufficiently during the vacuum drying process, and a flat film can be obtained.

In this specification, when the composition of the present invention is used as an ink ejected from a nozzle of an inkjet device, it may be simply referred to as an ink.
When the composition of the present invention is used as an ink ejected from a nozzle of an inkjet device and applied to an area surrounded by banks, the ink in the area surrounded by banks becomes a liquid or a liquid film. Ink ejected from a nozzle is sometimes called a droplet.
A liquid film in which the solvent composition ratio of the liquid film changes by drying the liquid film in the area surrounded by the bank and evaporating the solvent may also be referred to as a liquid or a liquid film.
A film containing a functional material obtained by coating the composition of the present invention, evaporating the organic solvent, and drying the film is referred to as a functional film. Furthermore, a film containing an organic compound that does not contain a solvent or is dried by substantially volatilizing the solvent is referred to as an organic film. A functional film is a type of organic film.

[solvent]
<Type of solvent>
In the present invention, both the first solvent and the second solvent have a boiling point of 245° C. or higher, from the viewpoint of improving flatness due to temperature reduction and rapid increase in viscosity, and ensuring flatness at the edge of the panel.
Solvents with a boiling point of 245°C or higher are not particularly limited, but are preferably water-insoluble aromatic solvents such as aromatic hydrocarbon solvents, aromatic ester solvents, aromatic ether solvents, and aromatic ketone solvents. can be mentioned.

As the aromatic hydrocarbon solvent, benzene derivatives, naphthalene derivatives, hydrogenated naphthalene derivatives, and biphenyl derivatives are preferred.

As the benzene derivative, a benzene derivative having a total carbon number of 5 or more and 12 or less and having a linear, branched, or alicyclic alkyl group as a substituent is preferable, such as n-octylbenzel, n-nonylbenzene, etc. , n-decylbenzene, and dodecylbenzene.

The naphthalene derivative is not particularly limited, but naphthalene derivatives substituted with an alkyl group are preferred, and examples include 1-methylnaphthalene, 2-ethylnaphthalene, 2-isopropylnaphthalene, 2,6-dimethylnaphthalene, and 1-methoxynaphthalene. It will be done.

Examples of hydrogenated naphthalene derivatives include tetralin, 1,2-dihydronaphthalene, 1,4-dihydronaphthalene, etc., which may be substituted with an alkyl group having 1 to 6 carbon atoms.

The biphenyl derivative is not particularly limited, but biphenyl derivatives substituted with an alkyl group having 1 to 6 carbon atoms are preferred, such as 3-ethylbiphenyl, 4-isopropylbiphenyl, and the like.

Other preferred aromatic hydrocarbon solvents include diphenylmethane and methyldiphenylmethane.

Examples of aromatic ester solvents include benzoic acid ester solvents, phenylacetic acid ester solvents, and phthalic acid ester solvents.

The benzoic acid ester solvent is a compound having an ester bond with benzoic acid, and a compound in which benzoic acid, which may have a substituent, and an alcohol having 2 to 12 carbon atoms are ester bonded can be used. . The optional substituent is preferably a straight-chain or branched alkyl group having 1 to 6 carbon atoms, or a straight-chain or branched alkoxy group having 1 to 6 carbon atoms. There may be a plurality of these substituents, and in the case of a plurality of substituents, the total number of carbon atoms as the substituents is preferably 6 or less. Examples of the benzoate ester solvent include butyl benzoate, n-pentyl benzoate, isoamyl benzoate, n-hexyl benzoate, 2-ethylhexyl benzoate, benzyl benzoate, and ethyl 4-methoxybenzoate.

Examples of the phenylacetate-based solvent include ethyl phenylacetate.

Examples of phthalate ester solvents include dimethyl phthalate, diethyl phthalate, and dibutyl phthalate.

Other preferred aromatic ester solvents include 2-phenoxyethyl acetate, 2-phenoxyethyl isobutyrate, and the like.

Aromatic ether solvents are compounds having an aromatic ring and an ether bond, and include the following.
Examples of diphenyl ether derivatives optionally substituted with a linear or branched alkyl group having 1 to 6 carbon atoms include diphenyl ether, 2-phenoxytoluene, 3-phenoxytoluene, 4-phenoxytoluene;
Examples of benzene derivatives having two ether bonds with a linear or branched alkyl group having 1 to 6 carbon atoms include 1,4-diethoxybenzene, 1-ethoxy-4-hexyloxybenzene;
Examples of benzene derivatives having a linear or branched alkyl group having 4 to 12 carbon atoms and one ether bond include phenylhexyl ether;
As a benzyl ether solvent, for example, dibenzyl ether;
Other aromatic ether solvents include 2-phenoxyethanol:

The aromatic ketone solvent is a compound having an aromatic ring and a ketone structure, such as 1-acetylnaphthalene.

The solvent used in the present invention may be a water-insoluble non-aromatic solvent with a boiling point of 245°C or higher, and examples of the water-insoluble non-aromatic solvent include ether solvents and glycol ester solvents. Can be mentioned.
However, a water-insoluble aromatic solvent is used as the first solvent.

<Boiling point>
The first solvent is a water-insoluble aromatic solvent whose boiling point is 10° C. or more higher than the second solvent, which has a boiling point of 245° C. or more, and whose flow activation energy is 22 kJ/mol or more and 35 kJ/mol or less.
Among the solvents contained in the composition of the present invention, all water-insoluble aromatic solvents with a boiling point of 245°C or higher and a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less are used as the first solvent. The first solvent is all solvents corresponding to the first solvent.

The boiling points of both the first solvent and the second solvent used in the present invention are 245° C. or higher, and the boiling point of the first solvent is 10° C. or higher higher than the boiling point of the second solvent. Therefore, during the drying process after coating, the second solvent, which has a lower boiling point, usually evaporates earlier than the first solvent. As will be described later, when a liquid film is formed by the composition discharged into the bank and the liquid film is dried by vacuum drying or the like, the second solvent having a lower boiling point evaporates first. At this time, the temperature of the liquid film decreases as the heat of vaporization is removed. At this time, if the flow activation energy of the first solvent remaining in the liquid film is within the above range, the viscosity will rapidly increase, the flow rate of the liquid will slow down, and the film shape will be able to be controlled. A flat film can be obtained.

Among the solvents contained in the composition of the present invention, (a) a boiling point of 245°C or higher, (b) a solvent other than the first solvent, and (c) all solvents corresponding to the first solvent Solvents that satisfy all three conditions (a) to (c) of a solvent having a boiling point lower than the boiling point of the solvent are all solvents that correspond to the second solvent, and the second solvent corresponds to the second solvent. All solvents.
When the composition of the present invention contains a plurality of solvents corresponding to the first solvent, all the solvents corresponding to the plurality of first solvents are the first solvent, and the boiling point of the first solvent is the first solvent. The weighted average boiling point of all solvents corresponding to Similarly, when a plurality of solvents corresponding to the second solvent are included in the composition of the present invention, all the solvents corresponding to the plurality of second solvents are the second solvent, and the boiling point of the second solvent is This is the weighted average boiling point of all solvents corresponding to the second solvent.
The weighted average boiling point is the sum of the boiling points of individual solvents multiplied by the weight blending ratio of the solvents. In the present invention, unless otherwise specified, the boiling point of the first solvent is the weighted average boiling point of all solvents corresponding to the first solvent, and the boiling point of the second solvent is the weighted average boiling point of all solvents corresponding to the second solvent. It is the average boiling point.

The difference between the boiling point of the first solvent and the boiling point of the second solvent is 10°C or more, preferably 15°C or more, more preferably 20°C or more. Since it tends to volatilize faster than single solvent, it is more preferable, more preferably 30°C or higher, particularly preferably 35°C or higher. When the boiling point difference is above this value, it is easy to adjust the drying conditions, especially the vacuum drying conditions, so that a large amount of the second solvent is evaporated first and then the first solvent is evaporated during the drying process, especially during vacuum drying. preferable.
More preferably, in addition to the boiling point difference, when a plurality of solvents corresponding to the first solvent are included, the boiling point of the solvent with the highest weight blending ratio, and when a plurality of solvents corresponding to the second solvent are included, the boiling point of the solvent with the highest weight blending ratio. The difference between the boiling point of the solvent with a high ratio is also 10°C or more, preferably 15°C or more, more preferably 20°C or more, and when the temperature is 25°C or more, the second solvent is more likely to react faster than the first solvent. The temperature is more preferably 30°C or higher, particularly preferably 35°C or higher because it tends to volatilize. Since the drying process tends to reflect the volatility of the solvent with the highest weight blending ratio, it is preferable that the boiling point difference of the solvent with the highest weight blending ratio is greater than or equal to the above value.

From the viewpoint of easy volatilization of the solvent in the drying process, particularly from the viewpoint of easy volatilization of the solvent in vacuum drying, the boiling point of the first solvent is preferably 400°C or lower, and the boiling point of the second solvent is preferably 370°C or lower. Therefore, the upper limit of the boiling point difference between the first solvent and the second solvent is 155°C.

The second solvent may be a water-insoluble aromatic solvent with a boiling point of 245°C or higher, or may be a water-insoluble non-aromatic solvent with a boiling point of 245°C or higher. The second solvent is particularly preferably a water-insoluble aromatic solvent having a boiling point of 245° C. or higher. By having a boiling point of 245° C. or higher, it is possible to prevent the solvent from vaporizing before the vacuum drying process even at the edges of the panel where drying is quick. Therefore, the temperature can be lowered sufficiently during the vacuum drying process, and a flat film can be obtained even at the edges of the panel. The boiling point of the second solvent is preferably 250°C or higher, more preferably 255°C or higher, and most preferably 260°C or higher. Since it is preferable that the second solvent volatilizes earlier than the first solvent during the drying process, the boiling point of the second solvent is preferably 320°C or lower, more preferably 300°C or lower, and particularly preferably 280°C or lower.

The number of solvents corresponding to the first solvent contained in the first solvent is preferably 5 or less, more preferably 3 or less, and particularly preferably occupies 80% by weight or more of the first solvent. is 2 or less. When the number of first solvents is within this range, the composition can be easily managed. Further, it is considered that the drying process of the first solvent can be easily controlled and a flat film can be easily obtained.
The number of solvents corresponding to the second solvent contained in the second solvent is preferably 5 or less, more preferably 3 or less, and particularly preferably occupies 80% by weight or more of the second solvent. is 2 or less, most preferably 1. When the number of second solvents is within this range, the composition can be easily managed. In addition, by having the number of second solvents in this range, it is easy to control the initial stage of the drying process, and it is easy to volatilize most of the second solvents in the early stage of drying, resulting in a decrease in temperature due to heat of vaporization and an increase in the viscosity of the first solvent. It is considered that it is easy to control.

In addition, in this invention, the boiling point of a solvent is the value measured under atmospheric pressure.

<Flow activation energy>
Flow activation energy is E in the following formula (I). The flow activation energy is determined by measuring the viscosity of the solvent at different temperatures, plotting the logarithm of the viscosity against the reciprocal of the temperature, and determining the slope.
η=Aexp(E/RT) (I)
η: Viscosity (cP)
A: Constant E: Flow activation energy (kJ/mol)
R: gas constant (8.314J/K/mol)
T: Temperature (K)

The flow activation energy of the first solvent is 22 kJ/mol or more and 35 kJ/mol or less. The lower limit of the flow activation energy of the first solvent is preferably 23 kJ/mol or more, more preferably 24 kJ/mol or more. The upper limit of the flow activation energy of the first solvent is preferably 34 kJ/mol or less, more preferably 32 kJ/mol or less, and even more preferably 30 kJ/mol or less.

When the flow activation energy of the first solvent is equal to or higher than the above lower limit, the viscosity increases appropriately and quickly when the temperature decreases, making it easy to control the flatness of the functional film. It is preferable that the flow activation energy of the first solvent is equal to or less than the above upper limit value, because the rate of increase in viscosity when the temperature decreases is not too fast, the viscosity reached is not too high, and the flatness of the functional film can be easily controlled.

The flow activation energy of the first solvent is preferably 5 kJ/mol or more greater than the flow activation energy of the second solvent. In other words, the flow activation energy of the second solvent is preferably 5 kJ/mol or more lower than the flow activation energy of the first solvent. Within this range, the flow activation energy of the first solvent and the role of the second solvent can be clarified, making design easier.

When coating a composition in a bank and drying it to form a film, if the amount of liquid in the bank is relatively large and the amount gradually decreases as the solvent evaporates, the heat of vaporization is taken away. Even if the liquid temperature decreases, since a certain amount of the second solvent with low flow activation energy is present, thickening is difficult to occur and the fluidity of the liquid is maintained. During a drying process such as vacuum drying, when the solvent evaporates inside the bank and the liquid level is decreasing, if the fluidity of the liquid is maintained, the liquid on the side of the bank will also wet out as the liquid level decreases. , liquid does not easily remain on the side of the bank. As a result, it is thought that it becomes easier to make the film thickness uniform in the bank edge area. Conversely, if the difference in flow activation energy between the first solvent and the second solvent is small, even if some amount of the second solvent remains, each may be cooled by the heat of vaporization and thicken. In the present invention, it is desirable that the increase in viscosity be within an appropriate range, so by using one solvent as a solvent that is difficult to thicken and the other solvent as a solvent that is easy to thicken, the optimum thickening state can be achieved. Since this can be easily selected depending on the film thickness, material, drying profile, etc., it is preferable to provide a difference in flow activation energy between the first solvent and the second solvent as described above.

In the early stage of drying, from the viewpoint that the composition maintains fluidity and easily wets down the side of the bank, the flow activation energy difference between the first solvent and the second solvent is particularly 5.2 kJ/mol or more, particularly 5.5 kJ/mol or more. It is preferably 21.0 kJ/mol or less, particularly preferably 20.0 kJ/mol or less.

Examples of water-insoluble aromatic solvents with flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less suitable as the first solvent include 2-ethylhexyl benzoate (23.4 kJ/mol), benzyl benzoate (24. 5 kJ/mol), diethyl phthalate (27.5 kJ/mol), 2-phenoxyethyl acetate (28.6 kJ/mol), and isopropylbiphenyl (24.0 kJ/mol).
In addition, as a second solvent whose flow activation energy is 5 kJ/mol or more lower than such a first solvent, dibenzyl ether (18.7 kJ/mol), 3-phenoxytoluene (20.1 kJ/mol) , diphenyl ether (18.3 kJ/mol), and the like.

<Viscosity>
The second solvent preferably has a viscosity of 5 mPas or less at 23°C. When the viscosity of the second solvent is below the above upper limit, when preparing the composition, it becomes possible to select a first solvent with a higher viscosity and a functional material that can easily increase the viscosity. The range of selection of functional materials and ink density is expanded.
The viscosity of the second solvent is particularly preferably 4.5 mPas or less. On the other hand, the viscosity of the second solvent is preferably 1.0 mPas or more from the viewpoint of easily retaining the ink within the head when filled into the inkjet head.
In the present invention, the viscosity of the solvent can be measured using an E-type viscometer RE85L (manufactured by Toki Sangyo) at a cone plate rotation speed of 20 rpm to 100 rpm in an environment of 23°C.
The viscosity of the first solvent is preferably 3 mPas or more and 20 mPas or less.

<Surface tension>
The surface tension of the first solvent is preferably 30 mN/m or more, and preferably 45 mN/m or less. It is thought that by having the surface tension of the first solvent within this range, the surface tension of the ink as a whole can be maintained within an appropriate range, and stable ejection with an inkjet device is possible. Furthermore, it is considered preferable that the surface tension of the first solvent is within this range because it facilitates flattening of the liquid surface within the bank. When the surface tension of the first solvent is equal to or higher than the above lower limit, a certain level of tension is generated on the liquid surface during drying, and the surface area tends to be reduced, so that wrinkles are less likely to occur on the film. On the other hand, if the surface tension of the first solvent is less than or equal to the above upper limit, a difference in surface tension is less likely to occur during drying, and unnecessary Marangoni convection is less likely to occur, making it easier to form a flat film, which is preferable. .
In the present invention, the surface tension of a solvent can be measured by a plate method using a platinum plate in an environment of 23.0°C.

<Solvent combination>
The first solvent and the second solvent contained in the composition of the present invention may each be one type or a plurality of types.
In particular, it is preferable that two or more types of first solvents are included, since the surface tension that facilitates the generation of solvent convection can be adjusted, and the flatness can be further improved.
It is preferable that both the first solvent and the second solvent contained in the composition of the present invention are water-insoluble solvents, and it is more preferable that both the first solvent and the second solvent are water-insoluble aromatic solvents. .

In particular, from the viewpoint that the functional material dissolves well and does not easily precipitate during the drying process, the first solvent and the second solvent are naphthalene, benzoic acid ester, which may have a substituent, respectively. , aromatic ether.

Further, among the above-mentioned solvents, preferred combinations of the first solvent and the second solvent include the following.

First solvent: preferably 2-ethylhexyl benzoate, benzyl benzoate, 1-acetylnaphthalene, dimethyl phthalate, diethyl phthalate, ethyl biphenyl, isopropylbiphenyl, diisopropylbiphenyl, triisopropylbiphenyl, 2-phenoxyethyl isobutyrate. At least one of them, more preferably one or more of 2-ethylhexyl benzoate, benzyl benzoate, 1-acetylnaphthalene, dimethyl phthalate, and 2-phenoxyethyl isobutyrate.

Second solvent: Preferably methylnaphthalene, ethylnaphthalene, isopropylnaphthalene, methoxynaphthalene, butyl benzoate, pentyl benzoate, isopentyl benzoate, diphenylmethane, benzyltoluene, more preferably methylnaphthalene, ethylnaphthalene, benzoic acid. One or more types of butyl acid.

Furthermore, preferred combinations of the first solvent and the second solvent include 2-ethylhexyl benzoate and methylnaphthalene, 2-ethylhexyl benzoate and ethylnaphthalene, 2-ethylhexyl benzoate and isopropylnaphthalene, and 2-ethylhexyl benzoate and isopropylnaphthalene. Butyl benzoate, 2-ethylhexyl benzoate and isopentyl benzoate, benzyl benzoate and methylnaphthalene, benzyl benzoate and ethylnaphthalene, benzyl benzoate and isopropylnaphthalene, benzyl benzoate and butyl benzoate, benzyl benzoate and isopentyl benzoate A combination of these can be mentioned.

When the composition of the present invention contains two or more first solvents, preferred combinations include, for example, 2-ethylhexyl benzoate and benzyl benzoate, 2-ethylhexyl benzoate and dimethyl phthalate, and 2-ethylhexyl benzoate and dimethyl phthalate. - Combinations of acetylnaphthalene, etc.

[Content of first solvent and second solvent]
The content of the first solvent is 5 to 50% by weight based on the total amount of solvent in the composition of the present invention. In order to efficiently lower the temperature of the first solvent by volatilization of the second solvent, it is necessary to increase the volatile component, so the content of the first solvent is 50% by weight or less, preferably It is 40% by weight or less, more preferably 30% by weight or less. In order to maintain the functional material in a dissolved state when the second solvent evaporates, the content of the first solvent is 5% by weight or more, preferably 10% by weight or more, and more preferably 15% by weight or more.

The total content of the first solvent and the second solvent with respect to the total amount of solvents contained in the composition is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and 85% by weight or more. is particularly preferred, particularly preferably 90% by weight or more, most preferably 95% by weight or more, and the upper limit is 100% by weight. When the total content of the first solvent and the second solvent is equal to or higher than the above lower limit, the ink can be used as an ink that can be ejected from a micro nozzle, the drying of the solvent can be easily controlled, and the effects of the present invention can be easily obtained. .

<Other solvents>
The composition of the present invention may contain a solvent other than the first solvent and the second solvent.
As the solvent other than the first solvent and the second solvent, one or more solvents having a boiling point of less than 245°C may be used, such as dibenzyl ether with low flow activation energy or benzyltoluene as a high boiling point component. .
Including these other solvents has the advantage of being able to adjust the thickening effect associated with a temperature drop depending on the material, but in order to reliably obtain the effects of the present invention by including the first and second solvents, The content of the other solvents other than the first solvent and the second solvent is preferably 50% by weight or less, more preferably 30% by weight or less, and 20% by weight or less based on the total solvent contained in the composition of the present invention. It is more preferably 15% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less.

[Functional materials]
The functional material in the present invention preferably has a molecular weight of 50,000 or less. The functional material in the present invention may be a low-molecular material or a high-molecular material, but more remarkable effects can be obtained when it is a low-molecular material. Here, the low molecular weight material preferably has a molecular weight of 10,000 or less, more preferably 5,000 or less.

As the functional material in the present invention, a material for a light emitting layer, a material for a hole injection layer, a material for a hole transport layer, or a material for an electron transport layer, which will be described later, can be used, and preferably a material for a light emitting layer, It is a material for an injection layer or a material for a hole transport layer, and particularly preferably a low-molecular material for a light emitting layer.

The composition of the present invention may contain only one type of functional material, or may contain two or more types of functional materials.

[Content of solvent and functional materials]
The content of the functional material in the composition of the present invention is not particularly limited, but is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 1.0% by weight or more. The content is preferably 20% by weight or less, more preferably 15% by weight or less, and even more preferably 10% by weight or less.

Specific examples of the composition of the present invention include a composition for forming a light emitting layer, a composition for forming a hole injection layer, a composition for forming a hole transport layer, and a composition for forming an electrical transport layer, which will be described later. The preferable content of the solvent is as described below for each layer-forming composition. In addition, regarding the content of functional materials, the contents of the luminescent layer material, hole injection layer material, hole transport layer material, and electron transport layer material described later in each layer forming composition apply. do.

[Film formation by wet film formation method]
The composition of the present invention is suitably used for forming a functional film in the production of organic electroluminescent devices. The structure of the organic electroluminescent device is as described below.
The organic electroluminescent device according to the present invention usually has a substrate provided with electrodes, and a micro region in which light-emitting pixels are partitioned by partition walls called banks. A functional film is formed by discharging the composition of the present invention into a micro region defined by the bank, drying it, and heating it appropriately.

The ejection method is a method of ejecting droplets smaller than a micro area defined by a bank from a micro nozzle, and by ejecting a plurality of droplets, the micro area defined by a bank is coated with the composition of the present invention. It is preferable to meet the requirements. The ejection method is preferably an inkjet method.

In the wet film forming method, a micro region defined by banks is filled with the composition of the present invention and then vacuum dried. Vacuum drying means evaporating the solvent by reducing the pressure. In the present invention, since the first solvent has a higher boiling point than the second solvent, the second solvent usually has a higher vapor pressure and evaporates before the first solvent. When the second solvent evaporates, the heat of vaporization is taken away, and the temperature of the composition in the bank gradually decreases. It is preferable that the viscosity of the second solvent does not increase significantly due to a decrease in temperature. Therefore, as described above, the flow activation energy of the second solvent is preferably lower than the flow activation energy of the first solvent. In this case, the viscosity does not increase much while a certain amount of the second solvent remains, but when most of the second solvent evaporates, the temperature of the composition further decreases, and the first solvent with high flow activation energy remains in the composition. As a result, the viscosity of the composition increases rapidly, making it difficult for the liquid to flow. Therefore, liquid movement due to a concentration gradient, Marangoni convection, etc. are less likely to occur within the composition within the microregion partitioned by the bank. This makes it possible to suppress the disturbance of the liquid surface shape due to the flow of the composition while the solvent is volatilizing, and to control the drying conditions so that the surface of the dried film becomes uniform after the solvent volatilizes. becomes possible.

Most of both the first solvent and the second solvent can be volatilized by vacuum drying, but in order to dry them sufficiently, heat drying is then performed. The heating temperature is preferably a temperature and time at which the functional film does not crystallize or aggregate.

When the functional material is a low molecular material, the heating temperature is usually 50°C or higher, preferably 80°C or higher, more preferably 100°C or higher, more preferably 120°C or higher, and usually 200°C or lower, preferably 180°C. The temperature below is more preferably 150°C or below. The heating time is usually 1 minute or more, preferably 3 minutes or more, more preferably 5 minutes or more, and usually 120 minutes or less, preferably 90 minutes or less, more preferably 60 minutes or less.

When the functional material is a polymeric material, the heating temperature is usually 80°C or higher, preferably 100°C or higher, more preferably 150°C or higher, more preferably 200°C or higher, and usually 300°C or lower, preferably 270°C. The temperature below is more preferably 240°C or below. The heating time is usually 1 minute or more, preferably 3 minutes or more, more preferably 5 minutes or more, and usually 120 minutes or less, preferably 90 minutes or less, more preferably 60 minutes or less.

The heating method can be carried out using a hot plate, an oven, infrared irradiation, or the like. In the case of infrared irradiation that directly gives molecular vibrations, a heating time close to the lower limit above is sufficient; in the case of hot plate heating, where the substrate is in direct contact with the heat source or the heat source and the substrate are placed extremely close, the heating time is longer than infrared irradiation. requires a long time. In the case of oven heating, that is, in the case of heating with a gas in the oven, usually air or an inert gas such as nitrogen or argon, it takes time for the temperature to rise, so a heating time close to the upper limit of the above heating time is preferred. The heating time is appropriately adjusted depending on the heating method.

[Functional membrane]
The functional material contained in the functional film is usually 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and substantially 100% by weight. Most preferably, the upper limit is 100% by weight. Substantially 100% by weight means that the functional membrane may contain trace amounts of additives, residual solvents, and impurities. When the content of the functional material in the functional film is within this range, the function of the functional material can be expressed more effectively.

[Layer structure and formation method of organic electroluminescent device]
Preferred examples of the layer structure of an organic electroluminescent device manufactured using the composition of the present invention (hereinafter sometimes referred to as "organic electroluminescent device of the present invention") and the method for forming the same are as follows: This will be explained with reference to FIG.

FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device 10 of the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is a hole blocking layer, 7 is an electron transport layer, 8 is an electron injection layer, 9 each represents a cathode.

The organic electroluminescent device of the present invention has an anode, a light-emitting layer, and a cathode as essential constituent layers, but if necessary, as shown in FIG. There may be other functional layers in between.

[substrate]
The substrate 1 serves as a support for the organic electroluminescent device. As the substrate 1, a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, etc. are used. Particularly preferred is a glass plate; a plate made of transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, polysulfone, or the like. When using a synthetic resin substrate, it is preferable to pay attention to gas barrier properties. The gas barrier property of the substrate is preferably large because the organic electroluminescent element is unlikely to be degraded by outside air passing through the substrate. For this reason, one preferable method is to provide a dense silicon oxide film or the like on at least one side of the synthetic resin substrate to ensure gas barrier properties.

[anode]
The anode 2 is an electrode that plays the role of injecting holes into the layer on the light emitting layer 5 side.
The anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, or platinum, metal oxide such as indium and/or tin oxide, metal halide such as copper iodide, carbon black, or polyamide. (3-methylthiophene), polypyrrole, polyaniline, and other conductive polymers.

The anode 2 is usually formed by a method such as a sputtering method or a vacuum evaporation method.
When forming the anode 2 using metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., these fine particles are mixed with appropriate materials. The anode 2 can also be formed by dispersing it in a binder resin solution and applying it on the substrate 1.
In the case of a conductive polymer, a thin film can also be formed directly on the substrate 1 by electrolytic polymerization.
The anode 2 can also be formed by coating a conductive polymer on the substrate 1 (Appl. Phys. Lett., vol. 60, p. 2711, 1992).

The anode 2 usually has a single layer structure, but it can also have a laminated structure made of a plurality of materials if desired.

The thickness of the anode 2 may be appropriately selected depending on the required transparency and the like. 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 about 5 nm or more, preferably about 10 nm or more, and usually about 1000 nm or less, preferably about 500 nm or less. As long as it is opaque, the thickness of the anode 2 is arbitrary. A substrate 1 having the function of the anode 2 may also be used. It is also possible to laminate different conductive materials on the anode 2 described above.

In order to remove impurities attached to the anode 2, adjust the ionization potential, and improve hole injection properties, the surface of the anode 2 is subjected to ultraviolet (UV)/ozone treatment, oxygen plasma, or argon plasma treatment. It is preferable to do so.

[Hole injection layer]
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5. When providing the hole injection layer 3, the hole injection layer 3 is usually formed on the anode 2.

The method for forming the hole injection layer 3 may be a vacuum evaporation method or a wet film formation method, and is not particularly limited. The hole injection layer 3 is preferably formed by a wet film formation method from the viewpoint of reducing dark spots.
The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

(hole transport material)
The composition for forming a hole injection layer usually contains a hole transport material and a solvent as constituent materials of the hole injection layer 3.

The hole transport material is usually a compound having a hole transport property used in the hole injection layer 3 of an organic electroluminescent device, even if it is a polymer compound such as a polymer, or a monomer, etc. It may be a low-molecular compound, but a high-molecular compound is preferable.

As the hole transport material, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transport materials include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked with fluorene groups, hydrazone derivatives, silazane derivatives, and silanamine derivatives. , phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon, and the like.

In the present invention, the derivative includes, for example, an aromatic amine derivative, the aromatic amine itself and a compound having an aromatic amine as its main skeleton, and even if it is a polymer, it may be a monomer. There may be.

The hole transport material used as the material for the hole injection layer 3 may contain any one type of such compounds alone, or may contain two or more types of such compounds. When containing two or more hole transport materials, the combination is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two or more other hole transport materials are used. It is preferable to use them together.

Among the above-mentioned examples, aromatic amine compounds are preferable as the hole transport material, and aromatic tertiary amine compounds are particularly preferable from the viewpoint of amorphous property and visible light transmittance. The aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and also includes a compound having a group derived from an aromatic tertiary amine.

The type of aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, polymer compounds (polymerized compounds with repeating units) having a weight average molecular weight of 1,000 or more and 1,000,000 or less are preferred. preferable. Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds having repeating units represented by the following formula (1) or the following formula (11).

(In formula (1),
Ar ³ represents an aromatic hydrocarbon group or an aromatic heterocyclic group, which may have a substituent,
Ar ⁴ is a divalent aromatic hydrocarbon group or a divalent aromatic heterocyclic group which may have a substituent, or the aromatic hydrocarbon group and the aromatic heterocyclic group are directly or Represents a divalent group in which multiple groups are connected via a linking group. )

In the above formula (1), when a plurality of aromatic hydrocarbon groups and aromatic heterocyclic groups are connected via a connecting group, the connecting group is a divalent connecting group, for example -O- 1 to 30, preferably 1 to 5, groups selected from a group, a -C(=O)- group, and a -CH ₂ - group (which may have a substituent) in any order, and further Preferably, a group formed by linking 1 to 3 groups is mentioned.
Among the linking groups, aromatic carbide in which a plurality of Ar ⁴ 's in formula (1) are linked via a linking group represented by the following formula (2) is superior in hole injection into the light emitting layer. A hydrogen group or an aromatic heterocyclic group is preferred.

(In formula (2),
d represents an integer from 1 to 10,
R ⁸ and R ⁹ each independently represent a hydrogen atom or an alkyl group, an aromatic hydrocarbon group, or an aromatic heterocyclic group which may have a substituent.
When a plurality of R ⁸ and R ⁹ are present, they may be the same or different. )

In the above formula (11), j, k, l, m, n, and p each independently represent an integer of 0 or more. However, l+m≧1. Ar ¹¹ , Ar ¹² and Ar ¹⁴ each independently represent a divalent aromatic ring group having 30 or less carbon atoms which may have a substituent. Ar ¹³ represents a divalent aromatic ring group having 30 or less carbon atoms which may have a substituent or a divalent group represented by the following formula (12), and Q ¹¹ and Q ¹² are each independently represents a hydrocarbon chain having 6 or less carbon atoms which may have an oxygen atom, a sulfur atom, and a substituent, and S ¹ to S ⁴ are each independently a group represented by the following formula (13). expressed.
In addition, the aromatic ring group here refers to an aromatic hydrocarbon ring group and an aromatic heterocyclic group.

Examples of the aromatic ring group for Ar ¹¹ , Ar ¹² and Ar ¹⁴ include a monocyclic ring, 2 to 6 condensed rings, or a group in which two or more of these aromatic rings are connected. Specific examples of monocyclic or 2-6 fused ring aromatic ring groups include 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, biphenyl group, terphenyl group, quaterphenyl group, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring 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, Divalent groups derived from a pyridazine ring, a pyrimidine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a shinoline ring, a quinoxaline ring, a phenanthridine ring, a benzimidazole ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, or an azulene ring. . Among these, a divalent group derived from a benzene ring, a naphthalene ring, a fluorene ring, a pyridine ring, or a carbazole ring or a biphenyl group are preferred because they efficiently delocalize negative charges and are excellent in stability and heat resistance.
Examples of the aromatic ring group for Ar ¹³ are the same as those for Ar ¹¹ , Ar ¹² , and Ar ¹⁴ .

In the above formula (12), R ¹¹ represents an alkyl group, an aromatic ring group, or a trivalent group consisting of an alkyl group having 40 or less carbon atoms and an aromatic ring group, and these may have a substituent. R ¹² represents an alkyl group, an aromatic ring group, or a divalent group consisting of an alkyl group having 40 or less carbon atoms and an aromatic ring group, and these may have a substituent. Ar ³¹ represents a monovalent aromatic ring group or a monovalent crosslinking group, and these groups may have a substituent. q represents 1 to 4. When q is 2 or more, a plurality of R ^12s may be the same or different, and a plurality of Ar ^31s may be the same or different. The asterisk (*) indicates the bond with the nitrogen atom in formula (11).

The aromatic ring group for R ¹¹ is preferably one monocyclic or condensed aromatic ring group having 3 or more and 30 or less carbon atoms, or a group in which 2 to 6 of these are linked. Specific examples include benzene. trivalent groups derived from rings, fluorene rings, naphthalene rings, carbazole rings, dibenzofuran rings, dibenzothiophene rings, and groups in which 2 to 6 of these are linked.
The alkyl group for ^R11 is preferably a linear, branched, or ring-containing alkyl group having 1 to 12 carbon atoms, and specific examples include methane, ethane, propane, isopropane, butane, isobutane, pentane, and hexane. , groups derived from octane, and the like.
The group consisting of an alkyl group having 40 or less carbon atoms and an aromatic ring group for ^R11 is preferably a straight chain, branched, or ring-containing alkyl group having 1 or more carbon atoms and 12 or less carbon atoms, and a monomer group having 3 or more carbon atoms and 30 or less carbon atoms. Examples include a group in which one ring or fused ring aromatic ring group or 2 to 6 linked groups are connected.

Specific examples of the aromatic ring group for ^R12 include a benzene ring, a fluorene ring, a naphthalene ring, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, and a divalent group derived from a connecting ring having 30 or less carbon atoms. It will be done.
Specific examples of the alkyl group for R ¹² include divalent groups derived from methane, ethane, propane, isopropane, butane, isobutane, pentane, hexane, and octane.

Specific examples of the aromatic ring group of Ar ³¹ include monovalent groups derived from benzene rings, fluorene rings, naphthalene rings, carbazole rings, dibenzofuran rings, dibenzothiophene rings, and connecting rings having 30 or less carbon atoms. It will be done.

Examples of preferable structures of formula (12) include the following structures, and the main chain benzene ring or fluorene ring in the structure below, which is a partial structure of R ¹¹ , may further have a substituent.

Examples of the bridging group for Ar ³¹ include a group derived from a benzocyclobutene ring, a naphthocyclobutene ring, or an oxetane ring, a vinyl group, an acrylic group, and the like. In view of the stability of the compound, a group derived from a benzocyclobutene ring or a naphthocyclobutene ring is preferred.

In the above formula (13), x and y represent integers of 0 or more. Ar ²¹ and Ar ²³ each independently represent a divalent aromatic ring group, and these groups may have a substituent. Ar ²² represents a monovalent aromatic ring group which may have a substituent, R ¹³ represents an alkyl group, an aromatic ring group, or a divalent group consisting of an alkyl group and an aromatic ring group; It may have a substituent. Ar ³² represents a monovalent aromatic ring group or a monovalent crosslinking group, and these groups may have a substituent. The asterisk (*) indicates the bond with the nitrogen atom in formula (11).

Examples of the aromatic ring group for Ar ²¹ and Ar ²³ are the same as those for Ar ¹¹ , Ar ¹² and Ar ¹⁴ .

Examples of the aromatic ring group for Ar ²² and Ar ³² include a monocyclic ring, 2 to 6 condensed rings, or a group in which two or more of these aromatic rings are connected. Specific examples include 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, biphenyl group, and terphenyl group. , quaterphenyl group, 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, benzisoxazole ring, benziisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline Examples include monovalent groups derived from a ring, a shinoline ring, a quinoxaline ring, a phenanthridine ring, a benzimidazole ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, or an azulene ring. Among these, a monovalent group derived from a benzene ring, a naphthalene ring, a fluorene ring, a pyridine ring, or a carbazole ring or a biphenyl group are preferred because they efficiently delocalize negative charges and are excellent in stability and heat resistance.

Examples of the alkyl group or aromatic ring group for R ¹³ are the same as those for R ¹² .

The crosslinking group for Ar ³² is not particularly limited, but preferable examples include a group derived from a benzocyclobutene ring, a naphthocyclobutene ring, or an oxetane ring, a vinyl group, an acrylic group, and the like.

Each of the above Ar ¹¹ to Ar ¹⁴ , R ¹¹ to R ¹³ , Ar ²¹ to Ar ²³ , Ar ³¹ to Ar ³² , Q ¹¹ , and Q ¹² further has a substituent as long as it does not go against the spirit of the present invention. You can leave it there. The molecular weight of the substituent is preferably 400 or less, and more preferably 250 or less. The types of substituents are not particularly limited, but examples include one or more types selected from the following substituent group W.

[Substituent group W]
Alkyl groups having 1 or more carbon atoms, preferably 10 or less, and more preferably 8 or less, such as methyl and ethyl groups; Alkyl groups having 2 or more carbon atoms, preferably 11 or less, and more preferably 5 or less, such as vinyl groups; Alkenyl group; an alkynyl group having 2 or more carbon atoms, preferably 11 or less, more preferably 5 or less, such as an ethynyl group; a methoxy group, an ethoxy group, etc. having 1 or more carbon atoms, preferably 10 or less, more preferably Alkoxy group of 6 or less; aryloxy group having 4 or more carbon atoms, preferably 5 or more, preferably 25 or less, more preferably 14 or less, such as phenoxy group, naphthoxy group, pyridyloxy group; methoxycarbonyl group, ethoxycarbonyl group an alkoxycarbonyl group having 2 or more carbon atoms, preferably 11 or less, more preferably 7 or less; such as a dimethylamino group, diethylamino group, etc. having 2 or more carbon atoms, preferably 20 or less, more preferably 12 or less dialkylamino group; diarylamino group having 10 or more carbon atoms, preferably 12 or more, preferably 30 or less, more preferably 22 or less carbon atoms, such as diphenylamino group, ditolylamino group, N-carbazolyl group; phenylmethylamino group, etc. An arylalkylamino group having 6 or more carbon atoms, more preferably 7 or more, preferably 25 or less, still more preferably 17 or less; an acetyl group, a benzoyl group, etc. having 2 or more carbon atoms, preferably 10 or less, and Acyl group preferably having 7 or less; halogen atom such as fluorine atom or chlorine atom; haloalkyl group having 1 or more carbon atoms, preferably 8 or less, and more preferably 4 or less carbon atoms such as trifluoromethyl group; methylthio group, ethylthio group Alkylthio groups having 1 or more carbon atoms, preferably 10 or less, more preferably 6 or less carbon atoms, such as; phenylthio groups, naphthylthio groups, pyridylthio groups, etc., having 4 or more carbon atoms, preferably 5 or more carbon atoms, preferably 25 or less; More preferably an arylthio group with 14 or less; a silyl group with 2 or more carbon atoms, preferably 3 or more, preferably 33 or less, more preferably 26 or less, such as a trimethylsilyl group or triphenylsilyl group; a trimethylsiloxy group, triphenyl A siloxy group having 2 or more carbon atoms, preferably 3 or more, preferably 33 or less, more preferably 26 or less, such as a siloxy group; a cyano group; a phenyl group, a naphthyl group, etc. having 6 or more carbon atoms, preferably 30 More preferably an aromatic hydrocarbon group having 18 or less carbon atoms; an aromatic heterocyclic group having 3 or more carbon atoms, preferably 4 or more carbon atoms, preferably 28 or less carbon atoms, and more preferably 17 or less carbon atoms, such as a thienyl group or a pyridyl group.

Among the substituent group W, an alkyl group or an alkoxy group is preferable from the viewpoint of improving solubility, and an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable from the viewpoint of charge transportability and stability.

In particular, among polymer compounds having repeating units represented by formula (11), those having repeating units represented by formula (14) below have extremely high hole injection and transport properties. preferable.

In the above formula (14), R ²¹ to R ²⁵ each independently represent an arbitrary substituent. Specific examples of the substituents R ²¹ to R ²⁵ are the same as the substituents described in [Substituent Group W] above.
s and t each independently represent an integer of 0 or more and 5 or less.
u, v, and w each independently represent an integer of 0 or more and 4 or less.

Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds containing repeating units represented by the following formula (15) and/or formula (16).

In the above formulas (15) and (16), Ar ⁴⁵ , Ar ⁴⁷ and Ar ⁴⁸ each independently have a monovalent aromatic hydrocarbon group which may have a substituent or a substituent. represents a monovalent aromatic heterocyclic group. Ar ⁴⁴ and Ar ⁴⁶ each independently represent a divalent aromatic hydrocarbon group which may have a substituent or a divalent aromatic heterocyclic group which may have a substituent. R ⁴¹ to R ⁴³ each independently represent a hydrogen atom or an arbitrary substituent.

Specific examples, preferred examples, examples of optional substituents, and preferred examples of Ar ⁴⁵ , Ar ⁴⁷ and Ar ⁴⁸ are the same as those for Ar ²² , and specific examples and preferred examples of Ar ⁴⁴ and Ar ⁴⁶ are as follows. Examples, examples of substituents that may be present, and examples of preferable substituents are the same as those for Ar ¹¹ , Ar ¹² and Ar ¹⁴ . R ⁴¹ to R ⁴³ are preferably a hydrogen atom or a substituent listed in the above-mentioned [substituent group W], and more preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group, an aromatic hydrocarbon group or aromatic heterocyclic group.

Preferred specific examples of repeating units represented by formula (15) and formula (16) applicable to the present invention are listed below, but the present invention is not limited thereto.

(electron-accepting compound)
It is preferable that the composition for forming a hole injection layer contains an electron-accepting compound as a constituent material of the hole injection layer 3.

The electron-accepting compound is preferably a compound that has oxidizing power and has the ability to accept one electron from the above-mentioned hole-transporting material. Specifically, as the electron-accepting compound, a compound having an electron affinity of 4.0 eV or more is preferable, and a compound having an electron affinity of 5.0 eV or more is more preferable.

Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples include one or more compounds selected from the following. More specifically, as electron-accepting compounds, onium salts substituted with organic groups (International Publication 2005/089024, International Publication No. 2017/164268); high-valent inorganic compounds such as iron(III) chloride (JP 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris( Examples include aromatic boron compounds such as (pentafluorophenyl)borane (JP 2003-31365A); fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ion, alkylbenzene sulfonate ion, and camphor sulfonate ion.

The electron-accepting compound can improve the electrical conductivity of the hole-injecting layer 3 by oxidizing the hole-transporting material.

(Other constituent materials)
In addition to the hole transport material and electron-accepting compound described above, the material for the hole injection layer 3 may contain other components as long as the effects of the present invention are not significantly impaired.

(solvent)
It is preferable that at least one of the solvents in the composition for forming a hole injection layer used in the wet film forming method is a compound that can dissolve the constituent material of the hole injection layer 3 described above.

When the composition for forming a hole injection layer is the composition of the present invention, the solvents are the first solvent and the second solvent of the present invention.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, and amide solvents.

Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, Aromatic ethers such as phenetol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole, and the like can be mentioned.

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

Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, and methylnaphthalene.

Examples of the amide solvent include N,N-dimethylformamide and N,N-dimethylacetamide.
In addition, dimethyl sulfoxide and the like can also be used.
Among them, aromatic esters and aromatic ethers are preferred.

One type of these solvents may be used alone, or two or more types may be used in any combination and ratio.

The concentration of the hole transport material in the composition for forming a hole injection layer is arbitrary as long as it does not significantly impair the effects of the present invention. The concentration of the hole transport material in the composition for forming a hole injection layer is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and even more preferably 0. .5% by weight or more. The concentration of the hole transport material in the composition for forming a hole injection layer is preferably 70% by weight or less, more preferably 60% by weight or less, even more preferably 50% by weight or less. This concentration is preferably small in that film thickness unevenness is less likely to occur. Further, this concentration is preferably large in that defects are less likely to occur in the formed hole injection layer.

(Formation of hole injection layer by wet film formation method)
When forming the hole injection layer 3 by a wet film forming method, the material constituting the hole injection layer 3 is usually mixed with an appropriate solvent (solvent for hole injection layer) to form a film forming composition ( A composition for forming hole injection layer 3 is prepared, and this composition for forming hole injection layer 3 is applied onto a layer corresponding to the lower layer of the hole injection layer (usually anode 2) by an appropriate method. The hole injection layer 3 is formed by forming a film and drying it.

(Formation of hole injection layer 3 by vacuum evaporation method)
When forming the hole injection layer 3 by vacuum evaporation, the hole transport layer 3 can be formed, for example, as follows. One or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transport material, electron-accepting compound, etc.) are placed in a crucible placed in a vacuum container (if two or more materials are used, (into each crucible) and evacuate the inside of the vacuum container to about 10 ^-4 Pa using an appropriate vacuum pump. After this, the crucible is heated (if two or more materials are used, each crucible is heated) to control the amount of evaporation (if two or more materials are used, the amount of evaporation is controlled independently of each other). (controlled evaporation) to form a hole injection layer 3 on the anode 2 of the substrate 1 placed facing the crucible. When using two or more types of materials, the hole injection layer 3 can also be formed by placing a mixture of them in a crucible, heating and evaporating them.

The degree of vacuum during vapor deposition is not limited as long as it does not significantly impair the effects of the present invention. The degree of vacuum during vapor deposition is usually 0.1×10 ⁻⁶ Torr (0.13×10 ⁻⁴ Pa) or more and 9.0×10 ⁻⁶ Torr (12.0× ⁻⁴ Pa) or less. The deposition rate is not limited as long as it does not significantly impair the effects of the present invention. The deposition rate is usually 0.1 Å/sec or more and 5.0 Å/sec or less. The film forming temperature during vapor deposition is not limited as long as it does not significantly impair the effects of the present invention. The film forming temperature during vapor deposition is preferably 10°C or higher and 50°C or lower.

[Hole transport layer]
The hole transport layer 4 is a layer that transports from the anode 2 to the light emitting layer 5. The hole transport layer 4 is not an essential layer for the organic electroluminescent device of the present invention, but when the hole transport layer 4 is provided, the hole transport layer 4 is usually formed when the hole injection layer 3 is provided. is formed on the hole injection layer 3, or on the anode 2 if there is no hole injection layer 3.

The method for forming the hole transport layer 4 may be a vacuum evaporation method or a wet film formation method, and is not particularly limited. The hole transport layer 4 is preferably formed by a wet film forming method from the viewpoint of reducing dark spots.

The material forming the hole transport layer 4 is preferably a material that has high hole transport properties and can efficiently transport injected holes. For this reason, the material forming the hole transport layer 4 has a low ionization potential, high transparency to visible light, high hole mobility, and excellent stability, so that impurities that can become traps are eliminated during manufacturing. It is preferable that it is unlikely to occur during use. In many cases, the hole transport layer 4 is in contact with the light-emitting layer 5, so it does not quench the light emitted from the light-emitting layer 5 or form an exciplex with the light-emitting layer 5, thereby reducing efficiency. preferable.

The material for the hole transport layer 4 may be any material that has been conventionally used as a constituent material for the hole transport layer 4. Examples of materials for the hole transport layer 4 include arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, and silole derivatives. , oligothiophene derivatives, fused polycyclic aromatic derivatives, metal complexes, and the like.

Examples of materials for the hole transport layer 4 include polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, and polyarylene vinylene. derivatives, polysiloxane derivatives, polythiophene derivatives, poly(p-phenylenevinylene) derivatives and the like. These may be alternating copolymers, random polymers, block polymers or graft copolymers. It may also be a polymer whose main chain is branched and has three or more terminal parts, or a so-called dendrimer.

Among these, as the material for the hole transport layer 4, polyarylamine derivatives and polyarylene derivatives are preferable.
Specific examples of polyarylamine derivatives and polyarylene derivatives include those described in JP-A No. 2008-98619.
As the polyarylamine derivative, it is preferable to use the aromatic tertiary amine polymer compound described above.

When forming the hole transport layer 4 by a wet film forming method, a composition for forming a hole transport layer is prepared in the same manner as in the formation of the hole injection layer 3 described above, and then dried after wet film formation.
The composition for forming a hole transport layer contains a solvent in addition to the hole transport material described above. The solvent used is the same as that used for the hole injection layer forming composition. Further, the film forming conditions, drying conditions, etc. are the same as those for forming the hole injection layer 3.
When the composition for forming a hole transport layer is the composition of the present invention, the solvents are the first solvent and the second solvent of the present invention.
When the hole transport layer 4 is formed by vacuum evaporation, the conditions for forming the film are the same as those for forming the hole injection layer 3 described above.

The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 300 nm or more, taking into consideration factors such as penetration of the low-molecular material in the light-emitting layer and swelling of the hole transport material. It is 200 nm or less.

[Light-emitting layer]
The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between the electrodes to which an electric field is applied, and becomes a main light emission source. Generally, the light-emitting layer 5 is on the hole-transporting layer 4 when there is the hole-transporting layer 4, and on the hole-injecting layer 3 when there is no hole-transporting layer 4 and when there is the hole-injecting layer 3. If neither the hole transport layer 4 nor the hole injection layer 3 is present on the anode 2, it is formed on the anode 2.

<Material for light emitting layer>
The material for the light emitting layer usually includes a light emitting material and a charge transport material serving as a host.

<Light-emitting material>
As the light-emitting material, any known material that is usually used as a light-emitting material for organic electroluminescent devices can be used, and there are no particular limitations, as long as it emits light at a desired emission wavelength and has good luminous efficiency. Just use substances. The luminescent material may be a fluorescent material or a phosphorescent material, but from the viewpoint of internal quantum efficiency, it is preferably a phosphorescent material. More preferably, the red-emitting material and the green-emitting material are phosphorescent materials, and the blue-emitting material is a fluorescent material.

When the composition of the present invention is a composition for forming a light-emitting layer, it is preferable to use the following phosphorescent materials, fluorescent materials, and charge transport materials.

<Phosphorescent material>
A phosphorescent material refers to a material that emits light from an excited triplet state. For example, a typical example is a metal complex compound containing Ir, Pt, Eu, etc., and the structure of the material preferably includes a metal complex.

Among metal complexes, phosphorescent organometallic complexes that emit light via the triplet state are known from the long period periodic table (hereinafter, unless otherwise specified, when we refer to the periodic table, we refer to the long period periodic table). ) Examples include Werner type complexes or organometallic complexes containing a metal selected from Groups 7 to 11 as a central metal. Examples of such phosphorescent materials include the phosphorescent materials described in International Publication No. 2014/024889, International Publication No. 2015-087961, International Publication No. 2016/194784, and JP2014-074000. Preferably, a compound represented by the following formula (201) or a compound represented by the following formula (205) is preferable, and a compound represented by the following formula (201) is more preferable.

In formula (201), ring A1 represents an aromatic hydrocarbon ring structure which may have a substituent or an aromatic heterocyclic structure which may have a substituent.
Ring A2 represents an aromatic heterocyclic structure which may have a substituent.
R ²⁰¹ and R ²⁰² are each independently a structure represented by formula (202), and "*" represents the bonding position with ring A1 or ring A2. R ²⁰¹ and R ²⁰² may be the same or different, and when a plurality of R ²⁰¹ and R ²⁰² exist, they may be the same or different.

Ar ²⁰¹ and Ar ²⁰³ each independently represent an aromatic hydrocarbon ring structure that may have a substituent or an aromatic heterocyclic structure that may have a substituent.
Ar ²⁰² is an aromatic hydrocarbon ring structure that may have a substituent, an aromatic heterocyclic structure that may have a substituent, or an aliphatic hydrocarbon structure that may have a substituent. represents.
Substituents bonded to ring A1, substituents bonded to ring A2, or substituents bonded to ring A1 and substituents bonded to ring A2 may bond to each other to form a ring.

B ²⁰¹ -L ²⁰⁰ -B ²⁰² represents an anionic bidentate ligand. B ²⁰¹ and B ²⁰² each independently represent a carbon atom, an oxygen atom, or a nitrogen atom, and these atoms may be atoms constituting a ring. L ²⁰⁰ represents a single bond or an atomic group that constitutes a bidentate ligand together with B ²⁰¹ and B ²⁰² . When a plurality of B ²⁰¹ -L ²⁰⁰ -B ²⁰² exist, they may be the same or different.

Note that in equations (201) and (202),
i1 and i2 each independently represent an integer between 0 and 12,
i3 represents an integer of 0 or more with an upper limit of the number that can be replaced with Ar ²⁰² ,
i4 represents an integer of 0 or more with an upper limit of the number that can be replaced with Ar ²⁰¹ ,
k1 and k2 each independently represent an integer of 0 or more with an upper limit of the number that can be substituted in ring A1 and ring A2,
z represents an integer from 1 to 3.

(substituent)
Unless otherwise specified, the substituent is preferably a group selected from the following substituent group S.

<Substituent group S>
・Alkyl group, preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms, still more preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 6 carbon atoms .
-Alkoxy group, preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, still more preferably an alkoxy group having 1 to 6 carbon atoms.
-Aryloxy group, preferably an aryloxy group having 6 to 20 carbon atoms, more preferably an aryloxy group having 6 to 14 carbon atoms, even more preferably an aryloxy group having 6 to 12 carbon atoms, particularly preferably an aryloxy group having 6 to 12 carbon atoms Aryloxy group.
- Heteroaryloxy group, preferably a heteroaryloxy group having 3 to 20 carbon atoms, more preferably a heteroaryloxy group having 3 to 12 carbon atoms.
- An alkylamino group, preferably an alkylamino group having 1 to 20 carbon atoms, more preferably an alkylamino group having 1 to 12 carbon atoms.
- An arylamino group, preferably an arylamino group having 6 to 36 carbon atoms, more preferably an arylamino group having 6 to 24 carbon atoms.
-Aralkyl group, preferably an aralkyl group having 7 to 40 carbon atoms, more preferably an aralkyl group having 7 to 18 carbon atoms, even more preferably an aralkyl group having 7 to 12 carbon atoms.
・Heteroaralkyl group, preferably a heteroaralkyl group having 7 to 40 carbon atoms, more preferably a heteroaralkyl group having 7 to 18 carbon atoms,
・Alkenyl group, preferably an alkenyl group having 2 to 20 carbon atoms, more preferably an alkenyl group having 2 to 12 carbon atoms, still more preferably an alkenyl group having 2 to 8 carbon atoms, particularly preferably an alkenyl group having 2 to 6 carbon atoms .
- An alkynyl group, preferably an alkynyl group having 2 to 20 carbon atoms, more preferably an alkynyl group having 2 to 12 carbon atoms.
-Aryl group, preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 24 carbon atoms, still more preferably an aryl group having 6 to 18 carbon atoms, particularly preferably an aryl group having 6 to 14 carbon atoms .
・Heteroaryl group, preferably a heteroaryl group having 3 to 30 carbon atoms, more preferably a heteroaryl group having 3 to 24 carbon atoms, still more preferably a heteroaryl group having 3 to 18 carbon atoms, particularly preferably a heteroaryl group having 3 to 30 carbon atoms 14 heteroaryl groups.
- An alkylsilyl group, preferably an alkylsilyl group in which the alkyl group has 1 to 20 carbon atoms, more preferably an alkylsilyl group in which the alkyl group has 1 to 12 carbon atoms.
- An arylsilyl group, preferably an arylsilyl group in which the aryl group has 6 to 20 carbon atoms, more preferably an arylsilyl group in which the aryl group has 6 to 14 carbon atoms.
- An alkylcarbonyl group, preferably an alkylcarbonyl group having 2 to 20 carbon atoms.
-Arylcarbonyl group, preferably an arylcarbonyl group having 7 to 20 carbon atoms.

In the above groups, one or more hydrogen atoms may be replaced with a fluorine atom, or one or more hydrogen atoms may be replaced with a deuterium atom.
Unless otherwise specified, aryl is an aromatic hydrocarbon ring and heteroaryl is an aromatic heterocycle.
-Hydrogen atom, deuterium atom, fluorine atom, cyano group, or -SF5 _.

Among the substituent group S, preferred are alkyl groups, alkoxy groups, aryloxy groups, arylamino groups, aralkyl groups, alkenyl groups, aryl groups, heteroaryl groups, alkylsilyl groups, arylsilyl groups, and groups thereof. is a group in which one or more hydrogen atoms of is replaced with a fluorine atom, a fluorine atom, a cyano group, or _-SF5 ,
More preferred are alkyl groups, arylamino groups, aralkyl groups, alkenyl groups, aryl groups, and heteroaryl groups, and groups in which one or more hydrogen atoms of these groups are replaced with fluorine atoms, fluorine atoms, cyano group, or _-SF5 ,
More preferred are alkyl groups, alkoxy groups, aryloxy groups, arylamino groups, aralkyl groups, alkenyl groups, aryl groups, heteroaryl groups, alkylsilyl groups, and arylsilyl groups,
Particularly preferred are alkyl groups, arylamino groups, aralkyl groups, alkenyl groups, aryl groups, and heteroaryl groups,
Most preferred are alkyl groups, arylamino groups, aralkyl groups, aryl groups, and heteroaryl groups.

These substituent groups S may further have substituents selected from the substituent groups S as substituents. Preferable groups, more preferable groups, still more preferable groups, particularly preferable groups, and most preferable groups of the substituents that may be present are the same as the preferable groups in substituent group S.

(Ring A1)
Ring A1 represents an aromatic hydrocarbon ring structure which may have a substituent or an aromatic heterocyclic structure which may have a substituent.

The aromatic hydrocarbon ring is preferably an aromatic hydrocarbon ring having 6 to 30 carbon atoms. Specifically, a benzene ring, a naphthalene ring, an anthracene ring, a triphenyl ring, an acenaphthene ring, a fluoranthene ring, and a fluorene ring are preferred.

The aromatic heterocycle is preferably an aromatic heterocycle having 3 to 30 carbon atoms and containing any one of a nitrogen atom, an oxygen atom, or a sulfur atom as a heteroatom. More preferred are a furan ring, a benzofuran ring, a thiophene ring, and a benzothiophene ring.
Ring A1 is more preferably a benzene ring, a naphthalene ring, or a fluorene ring, particularly preferably a benzene ring or a fluorene ring, and most preferably a benzene ring.

(Ring A2)
Ring A2 represents an aromatic heterocyclic structure which may have a substituent.
The aromatic heterocycle is preferably an aromatic heterocycle having 3 to 30 carbon atoms and containing any one of a nitrogen atom, an oxygen atom, or a sulfur atom as a heteroatom. Specifically, pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, imidazole ring, oxazole ring, thiazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, quinazoline ring, Examples include naphthyridine ring and phenanthridine ring, preferably pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, benzothiazole ring, benzoxazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, and quinazoline ring, and more preferably is a pyridine ring, an imidazole ring, a benzothiazole ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, or a quinazoline ring, most preferably a pyridine ring, an imidazole ring, a benzothiazole ring, a quinoline ring, a quinoxaline ring, or a quinazoline ring. .

(Combination of ring A1 and ring A2)
Preferred combinations of ring A1 and ring A2, expressed as (ring A1-ring A2), are (benzene ring-pyridine ring), (benzene ring-quinoline ring), (benzene ring-quinoxaline ring), (benzene ring- (quinazoline ring), (benzene ring-benzothiazole ring), (benzene ring-imidazole ring), (benzene ring-pyrrole ring), (benzene ring-diazole ring), and (benzene ring-thiophene ring).

(Substituents on ring A1 and ring A2)
The substituents that ring A1 and ring A2 may have can be arbitrarily selected, but are preferably one or more substituents selected from the above substituent group S.

(Ar ²⁰¹ , Ar ²⁰² , Ar ²⁰³ )
Ar ²⁰¹ and Ar ²⁰³ each independently represent an aromatic hydrocarbon ring structure that may have a substituent or an aromatic heterocyclic structure that may have a substituent.
Ar ²⁰² is an aromatic hydrocarbon ring structure that may have a substituent, an aromatic heterocyclic structure that may have a substituent, or an aliphatic hydrocarbon structure that may have a substituent. represents.

When any of Ar ²⁰¹ , Ar ²⁰² , and Ar ²⁰³ is an aromatic hydrocarbon ring structure which may have a substituent, the aromatic hydrocarbon ring structure is preferably an aromatic hydrocarbon ring structure having 6 to 30 carbon atoms. It is a group hydrocarbon ring. Specifically, a benzene ring, a naphthalene ring, an anthracene ring, a triphenyl ring, an acenaphthene ring, a fluoranthene ring, and a fluorene ring are preferred, a benzene ring, a naphthalene ring, and a fluorene ring are more preferred, and a benzene ring is most preferred.

When either Ar ²⁰¹ or Ar ²⁰² is a benzene ring which may have a substituent, it is preferable that at least one benzene ring is bonded to an adjacent structure at the ortho or meta position, and at least one More preferably, two benzene rings are bonded to adjacent structures at meta positions.

When any of Ar ²⁰¹ , Ar ²⁰² , and Ar ²⁰³ is a fluorene ring that may have a substituent, the 9- and 9'-positions of the fluorene ring have a substituent or are bonded to an adjacent structure. It is preferable that

When any of Ar ²⁰¹ , Ar ²⁰² , and Ar ²⁰³ is an aromatic heterocyclic structure which may have a substituent, the aromatic heterocyclic structure preferably contains a nitrogen atom, an oxygen atom, or An aromatic heterocycle having 3 to 30 carbon atoms and containing any sulfur atom, specifically a pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, imidazole ring, oxazole ring, thiazole ring, benzothiazole ring , a benzoxazole ring, a benzimidazole ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a quinazoline ring, a naphthyridine ring, a phenanthridine ring, a carbazole ring, a dibenzofuran ring, and a dibenzothiophene ring, preferably a pyridine ring or a pyrimidine ring. , triazine ring, carbazole ring, dibenzofuran ring, and dibenzothiophene ring.

When any of Ar ²⁰¹ , Ar ²⁰² , and Ar ²⁰³ is a carbazole ring which may have a substituent, the N-position of the carbazole ring may have a substituent or be bonded to an adjacent structure. preferable.

When Ar ²⁰² is an aliphatic hydrocarbon structure that may have a substituent, it is an aliphatic hydrocarbon structure having a linear, branched, or cyclic structure, and preferably has 1 to 24 carbon atoms. More preferably, the number of carbon atoms is 1 or more and 12 or less, and more preferably 1 or more and 8 or less.

(i1, i2, i3, i4, k1, k2)
i1 and i2 each independently represent an integer of 0 to 12, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 6. By being within this range, it is expected that solubility and charge transport properties will be improved.
i3 preferably represents an integer of 0 to 5, more preferably 0 to 2, more preferably 0 or 1.
i4 preferably represents an integer of 0 to 2, more preferably 0 or 1.
k1 and k2 each independently preferably represent an integer of 0 to 3, more preferably 1 to 3, more preferably 1 or 2, particularly preferably 1.

(Preferred substituents for Ar ²⁰¹ , Ar ²⁰² , Ar ²⁰³ )
The substituents that Ar ²⁰¹ , Ar ²⁰² , and Ar ²⁰³ may have can be arbitrarily selected, but are preferably one or more substituents selected from the above substituent group S, and preferred groups are also the above substituents. As shown in group S, more preferred are unsubstituted (hydrogen atoms), alkyl groups, and aryl groups, particularly preferred are unsubstituted (hydrogen atoms), alkyl groups, and most preferred are unsubstituted (hydrogen atoms). ) or a tert-butyl group, where the tert-butyl group is substituted by Ar ²⁰³ when Ar ²⁰³ is present, Ar ²⁰² when Ar ²⁰³ is absent, and Ar ²⁰¹ when Ar ²⁰² and Ar ²⁰³ are absent. It is preferable that you do so.

(Preferred embodiment of the compound represented by formula (201))
The compound represented by the formula (201) is preferably a compound that satisfies any one or more of the following (I) to (IV).
(I) Phenylene linked formula The structure represented by formula (202) is a structure having a group in which benzene rings are linked, that is, a benzene ring structure, i1 is 1 to 6, and at least one benzene ring is in the ortho or meta position. It is preferable that the structure is bonded to an adjacent structure at the position.
Such a structure is expected to improve solubility and charge transport properties.

(II) (phenylene)-aralkyl (alkyl)
A structure having an aromatic hydrocarbon group or an aromatic heterocyclic group to which an alkyl group or an aralkyl group is bonded to ring A1 or ring A2, that is, Ar ²⁰¹ is an aromatic hydrocarbon structure or an aromatic heterocyclic structure, and i1 is 1 ~6, Ar ²⁰² is an aliphatic hydrocarbon structure, i2 is 1 to 12, preferably 3 to 8, Ar ²⁰³ is a benzene ring structure, and i3 is 0 or 1, preferably Ar ²⁰¹ is the aromatic hydrocarbon structure It has a hydrogen structure, more preferably a structure in which 1 to 5 benzene rings are connected, and more preferably one benzene ring.
Such a structure is expected to improve solubility and charge transport properties.

(III) Dendron A structure in which a dendron is bonded to ring A1 or ring A2, for example, Ar ²⁰¹ and Ar ²⁰² are benzene ring structures, Ar ²⁰³ is a biphenyl or terphenyl structure, i1 and i2 are 1 to 6, i3 is 2, j is 2.
Such a structure is expected to improve solubility and charge transport properties.

(IV) B ²⁰¹ -L ²⁰⁰ -B ²⁰²
The structure represented by B ²⁰¹ -L ²⁰⁰ -B ²⁰² is preferably a structure represented by the following formula (203) or the following formula (204).

In formula (203), R ²¹¹ , R ²¹² , and R ²¹³ each independently represent a substituent.
In formula (204), ring B3 represents an aromatic heterocyclic structure containing a nitrogen atom, which may have a substituent. Ring B3 is preferably a pyridine ring.

(Preferred phosphorescent material)
The phosphorescent material represented by the above formula (201) is not particularly limited, but the following are preferred.

Further, a phosphorescent material represented by the following formula (205) is also preferable.

[In formula (205), M ² represents a metal, and T represents a carbon atom or a nitrogen atom. R ⁹² to R ⁹⁵ each independently represent a substituent. However, when T is a nitrogen atom, R ⁹⁴ and R ⁹⁵ are absent. ]

In formula (205), specific examples of M ² include metals selected from Groups 7 to 11 of the periodic table. Among these, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, or gold is preferred, and divalent metals such as platinum and palladium are particularly preferred.

In addition, in formula (205), R ⁹² and R ⁹³ are each independently 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 an alkoxy group, an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group, or an aromatic heterocyclic group.

Further, 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, when T is a nitrogen atom, R ⁹⁴ or R ⁹⁵ directly bonded to T does not exist. Furthermore, R ⁹² to R ⁹⁵ may further have a substituent. As the substituent, the above-mentioned substituents can be used. Furthermore, any two or more groups among R ⁹² to R ⁹⁵ may be linked to each other to form a ring.

(molecular weight)
The molecular weight of the phosphorescent material is preferably 5,000 or less, more preferably 4,000 or less, particularly preferably 3,000 or less. Further, the molecular weight of the phosphorescent material is preferably 800 or more, more preferably 1000 or more, and still more preferably 1200 or more. It is thought that by having a molecular weight in this range, the phosphorescent materials do not aggregate with each other and are uniformly mixed with the charge transporting material, thereby making it possible to obtain a luminescent layer with high luminous efficiency.

The molecular weight of the phosphorescent material is high in Tg, melting point, decomposition temperature, etc., the phosphorescent material and the formed light emitting layer have excellent heat resistance, and the film quality due to gas generation, recrystallization, molecular migration, etc. A larger value is preferable in that it is less likely to cause a decrease in the concentration of impurities or an increase in impurity concentration due to thermal decomposition of the material. On the other hand, the molecular weight of the phosphorescent material is preferably small in terms of ease of purification of the organic compound.

<Charge transport material>
The charge transport material used in the light emitting layer is a material having a skeleton with excellent charge transport properties, and may be selected from electron transport materials, hole transport materials, and bipolar materials capable of transporting both electrons and holes. preferable.

Specific examples of skeletons with excellent charge transport properties include aromatic structures, aromatic amine structures, triarylamine structures, dibenzofuran structures, naphthalene structures, phenanthrene structures, phthalocyanine structures, porphyrin structures, thiophene structures, benzylphenyl structures, Examples include a fluorene structure, a quinacridone structure, a triphenylene structure, a carbazole structure, a pyrene structure, an anthracene structure, a phenanthroline structure, a quinoline structure, a pyridine structure, a pyrimidine structure, a triazine structure, an oxadiazole structure, and an imidazole structure.

As the electron-transporting material, compounds having a pyridine structure, a pyrimidine structure, or a triazine structure are more preferable from the viewpoint of being a material with excellent electron-transporting properties and a relatively stable structure. is even more preferable.

The hole-transporting material is a compound having a structure with excellent hole-transporting properties, and among the central skeletons with excellent charge-transporting properties, a carbazole structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure, or A pyrene structure is preferred as a structure with excellent hole transport properties, and a carbazole structure, dibenzofuran structure, or triarylamine structure is more preferred.

The charge transport material used in the light emitting layer preferably has a fused ring structure of 3 or more rings, and is a compound having two or more fused ring structures of 3 or more rings or a compound having at least one fused ring of 5 or more rings. is even more preferable. These compounds increase the rigidity of molecules, making it easier to obtain the effect of suppressing the degree of molecular motion in response to heat. Further, the fused rings of 3 or more rings and the fused rings of 5 or more rings preferably have an aromatic hydrocarbon ring or an aromatic heterocycle from the viewpoint of charge transportability and material durability.

Specifically, the fused ring structure of three or more rings includes an anthracene structure, a phenanthrene structure, a pyrene structure, a chrysene structure, a naphthacene structure, a triphenylene structure, a fluorene structure, a benzofluorene structure, an indenofluorene structure, an indrofluorene structure, Examples include a carbazole structure, an indenocarbazole structure, an indolocarbazole structure, a dibenzofuran structure, and a dibenzothiophene structure. From the viewpoint of charge transport properties and solubility, at least one selected from the group consisting of a phenanthrene structure, a fluorene structure, an indenofluorene structure, a carbazole structure, an indenocarbazole structure, an indolocarbazole structure, a dibenzofuran structure, and a dibenzothiophene structure. Preferably, a carbazole structure or an indolocarbazole structure is more preferable from the viewpoint of durability against charges.

In the present invention, from the viewpoint of durability against charges of the organic electroluminescent device, it is preferable that at least one of the charge transport materials in the light emitting layer is a material having a pyrimidine skeleton or a triazine skeleton.

The charge transport material of the light emitting layer is preferably a polymer material from the viewpoint of excellent flexibility. A light-emitting layer formed using a material with excellent flexibility is preferable as a light-emitting layer of an organic electroluminescent device formed on a flexible substrate. When the charge transporting material contained in the light-emitting layer is a polymeric material, the molecular weight is preferably 5,000 or more and 1,000,000 or less, more preferably 10,000 or more and 500,000 or less, and even more preferably 10,000 or more and 500,000 or less. 000 or more and 100,000 or less.

In addition, the charge transport material for the light emitting layer should be selected from the viewpoints of ease of synthesis and purification, ease of designing electron transport performance and hole transport performance, and ease of adjusting viscosity when dissolved in a solvent. Preferably, it is a low molecule. When the charge transport material contained in the light emitting layer is a low molecular weight material, the molecular weight is preferably 5,000 or less, more preferably 4,000 or less, particularly preferably 3,000 or less, and most preferably 2,000 or less. ,000 or less, preferably 300 or more, more preferably 350 or more, still more preferably 400 or more.

<Fluorescent material>
The fluorescent material is not particularly limited, but a compound represented by the following formula (211) is preferred.

In the above formula (211), Ar ²⁴¹ represents an aromatic hydrocarbon condensed ring structure which may have a substituent, Ar ²⁴² and Ar ²⁴³ each independently an alkyl group which may have a substituent, Represents an aromatic hydrocarbon group, an aromatic heterogroup, or a group in which these are bonded. n41 is an integer from 1 to 4.

Ar ²⁴¹ preferably represents an aromatic hydrocarbon condensed ring structure having 10 to 30 carbon atoms, and specific ring structures include naphthalene, acenaphthene, fluorene, anthracene, phenathrene, fluoranthene, pyrene, tetracene, chrysene, perylene, etc. Can be mentioned.
Ar ²⁴¹ is more preferably an aromatic hydrocarbon condensed ring structure having 12 to 20 carbon atoms, and specific ring structures include acenaphthene, fluorene, anthracene, phenathrene, fluoranthene, pyrene, tetracene, chrysene, and perylene. .
Ar ²⁴¹ is more preferably an aromatic hydrocarbon condensed ring structure having 16 to 18 carbon atoms, and specific examples of the ring structure include fluoranthene, pyrene, and chrysene.

n41 is 1 to 4, preferably 1 to 3, more preferably 1 to 2, and most preferably 2.

The alkyl group for Ar ²⁴² and Ar ²⁴³ is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms.
The aromatic hydrocarbon group for Ar ²⁴² and Ar ²⁴³ is preferably an aromatic hydrocarbon group having 6 to 30 carbon atoms, more preferably an aromatic hydrocarbon group having 6 to 24 carbon atoms, and most preferably a phenyl group. , is a naphthyl group.
The aromatic heterogroup of Ar ²⁴² and Ar ²⁴³ is preferably an aromatic heterogroup having 3 to 30 carbon atoms, more preferably an aromatic hydrocarbon group having 5 to 24 carbon atoms, specifically a carbazolyl group, A dibenzofuranyl group and a dibenzothiophenyl group are preferred, and a dibenzofuranyl group is more preferred.

The substituent that Ar ²⁴¹ , Ar ²⁴² , and Ar ²⁴³ may have is preferably a group selected from the substituent group S, more preferably a hydrocarbon group included in the substituent group S, and even more preferably is a hydrocarbon group among the groups preferable as the substituent group S.

The charge transport material used together with the fluorescent material is not particularly limited, but is preferably one represented by the following formula (212).

In the above formula (212), R ²⁵¹ and R ²⁵² are each independently a structure represented by formula (213), and R ²⁵³ represents a substituent, and when there is a plurality of R ²⁵³ , they may be the same or different. and n43 is an integer from 0 to 8.

In the above formula (213), * represents a bond with the anthracene ring of formula (212), and Ar ²⁵⁴ and Ar ²⁵⁵ each independently represent an aromatic hydrocarbon structure that may have a substituent, or a substituted Represents a heteroaromatic ring structure which may have a group, Ar ²⁵⁴ and Ar ²⁵⁵ each may be the same or different when there is a plurality of them, n44 is an integer of 1 to 5, and n45 is 0 to 5. It is an integer of 5.

Ar ²⁵⁴ is preferably a monocyclic or fused ring aromatic hydrocarbon structure having 6 to 30 carbon atoms, which may have a substituent, and more preferably has a substituent. , a monocyclic or fused ring aromatic hydrocarbon structure having 6 to 12 carbon atoms.

Ar ²⁵⁵ is preferably a monocyclic or fused ring aromatic hydrocarbon structure having 6 to 30 carbon atoms, which may have a substituent, or an aromatic hydrocarbon structure having 6 to 30 carbon atoms, which may have a substituent. It is an aromatic heterocyclic structure that is a condensed ring of. Ar ²⁵⁵ is more preferably a monocyclic or fused ring aromatic hydrocarbon structure having 6 to 12 carbon atoms, which may have a substituent, or an aromatic hydrocarbon structure having 12 carbon atoms, which may have a substituent. It is an aromatic heterocyclic structure that is a fused ring.

n44 is preferably an integer of 1 to 3, more preferably 1 or 2.
n45 is preferably an integer of 0 to 3, more preferably 0 to 2.

The substituent that R ²⁵³ , Ar ²⁵⁴ and Ar ²⁵⁵ may have is preferably a group selected from the above-mentioned substituent group S. More preferably, it is a hydrocarbon group included in the substituent group S, and still more preferably a hydrocarbon group among the groups preferable as the substituent group S.

The molecular weight of the fluorescent material and the charge transport material is preferably 5,000 or less, more preferably 4,000 or less, particularly preferably 3,000 or less, and most preferably 2,000 or less. Moreover, it is preferably 300 or more, more preferably 350 or more, and still more preferably 400 or more.

[Hole blocking layer]
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8, which will be described later. The hole blocking layer 6 is a layer of the electron transport layer that also plays the role of blocking holes moving from the anode 2 from reaching the cathode 9. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has the roles of blocking holes moving from the anode 2 from reaching the cathode 9 and efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. have

The physical properties required of the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, large energy gap (difference between HOMO and LUMO), and excited triplet energy level (T1 ) is high. Examples of materials for the hole blocking layer 6 that meet these conditions include bis(2-methyl-8-quinolinolato)(phenolato)aluminum, bis(2-methyl-8-quinolinolato)(triphenylsilanolate)aluminum, etc. mixed ligand complexes, metal complexes such as bis(2-methyl-8-quinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum dinuclear metal complexes, distyrylbiphenyl derivatives, etc. Styryl compounds (JP-A-11-242996), triazole derivatives such as 3-(4-biphenylyl)-4-phenyl-5(4-tert-butylphenyl)-1,2,4-triazole (JP-A-7 -41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Application Laid-Open No. 10-79297). Furthermore, a compound having at least one pyridine ring substituted at the 2, 4, and 6 positions described in International Publication No. 2005/022962 is also preferable as a material for the hole blocking layer 6.

There are no restrictions on the method of forming the hole blocking layer 6. The hole blocking layer 6 can be formed by a wet film formation method, a vapor deposition method, or other methods.
The thickness of the hole blocking layer 6 is arbitrary as long as it does not significantly impair the effects of the present invention. The thickness of the hole blocking layer 6 is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

[Electron transport layer]
The electron transport layer 7 is a layer provided between the light emitting layer 5 and the cathode 9 for transporting electrons.

The electron transport material for the electron transport layer 7 is usually one that has high electron injection efficiency from the cathode 9 or an adjacent layer on the cathode 9 side, has high electron mobility, and can efficiently transport the injected electrons. Use compounds that can be used. Compounds that satisfy these conditions include, for example, metal complexes such as aluminum complexes and lithium complexes of 8-hydroxyquinoline (Japanese Patent Application Laid-open No. 194393/1983), metal complexes of 10-hydroxybenzo[h]quinoline, and oxadioxide. Azole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound (JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N,N'-dicyanoanthraquinone diimine, triazine compound derivative, n-type hydrogen Examples include amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

The electron transport material used in the electron transport layer 7 includes electron transport organic compounds such as nitrogen-containing heterocyclic compounds such as bathophenanthroline and metal complexes such as an aluminum complex of 8-hydroxyquinoline, as well as sodium, potassium, and cesium. By doping with alkali metals such as lithium, rubidium, etc. (described in JP-A-10-270171, JP-A-2002-100478, JP-A-2002-100482, etc.), excellent film quality and electron injection transport properties can be achieved. This is preferable because it makes it possible to achieve both. It is also effective to dope the above-mentioned electron-transporting organic compound with an inorganic salt such as lithium fluoride or cesium carbonate.

There are no restrictions on the method for forming the electron transport layer 7. The electron transport layer 7 can be formed by a wet film formation method, a vapor deposition method, or other methods.

The thickness of the electron transport layer 7 is arbitrary as long as it does not significantly impair the effects of the present invention. The thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[Electron injection layer]
In order to efficiently inject electrons injected from the cathode 9 into the light emitting layer 5, an electron injection layer 8 may be provided between the electron transport layer 7 and the cathode 9, which will be described later. The electron injection layer 8 is made of inorganic salt or the like.

Examples of materials for the electron injection layer 8 include lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium (II) carbonate (CsCO ₃ ), etc. (Applied Physics Letters , 1997, Vol. 70, pp. 152; JP-A-10-74586; IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.) .

Since the electron injection layer 8 often does not have charge transport properties, in order to efficiently inject electrons, it is preferable to use it as an extremely thin film, and the film thickness is usually 0.1 nm or more, preferably 5 nm or less. be.

[cathode]
The cathode 9 is an electrode that serves to inject electrons into the layer on the light emitting layer 5 side.

The materials for the cathode 9 are usually metals such as aluminum, gold, silver, nickel, palladium, and platinum, metal oxides such as indium and/or tin oxides, metal halides such as copper iodide, carbon black, Alternatively, conductive polymers such as poly(3-methylthiophene), polypyrrole, and polyaniline may be used. Among these, metals with a low work function are preferred in order to efficiently inject electrons, and suitable metals such as tin, magnesium, indium, calcium, aluminum, silver, or alloys thereof are used. Specific examples include alloy electrodes with low work functions such as magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy, and the like.

Only one type of material may be used for the cathode 9, or two or more types may be used in combination in any combination and ratio.

The film thickness of the cathode 9 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 cathode 9 is usually about 5 nm or more, preferably about 10 nm or more, and usually about 1000 nm or less, preferably about 500 nm or less. The thickness of the cathode 9 may be arbitrary as long as it is opaque, and the cathode may be the same as the substrate.

It is also possible to layer different conductive materials on the cathode 9.
For the purpose of protecting the cathode, which is made of low work function metals such as alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium, the It is preferable to stack metal layers because this increases the stability of the device. Metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used for this purpose. These materials may be used alone or in any combination and ratio of two or more.

[Other layers]
The organic electroluminescent device of the present invention may have another configuration without departing from the spirit thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers described above, and layers that are not essential among the layers described above may be included. May be omitted.

In the layered structure described above, it is also possible to laminate components other than the substrate in the reverse order. For example, with the layer configuration shown in FIG. The injection layer 3 and the anode 2 may be provided in this order.

The organic electroluminescent device of the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array, and the anode and cathode are It may also be applied to a configuration arranged in a Y matrix.

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.

<Organic electroluminescent device>
Two or more organic electroluminescent elements that emit light in different colors can be provided to provide an organic electroluminescent device such as an organic EL display device or an organic EL lighting device. In this organic electroluminescent device, by using at least one, preferably all the organic electroluminescent elements as the organic electroluminescent element of the present invention, a high quality organic electroluminescent device can be provided.

<Organic EL display device>
There are no particular limitations on the type or structure of an organic EL display device using the organic electroluminescent device of the present invention, and it can be assembled using the organic electroluminescent device of the present invention according to a conventional method.
For example, an organic EL display device can be formed by the method described in "Organic EL Display" (Ohmsha, published August 20, 2004, written by Shizuka Tokito, Chinaya Adachi, and Hideyuki Murata). can.

<Organic EL lighting>
There are no particular restrictions on the type or structure of organic EL lighting using the organic electroluminescent device of the present invention, and it can be assembled using the organic electroluminescent device of the present invention according to a conventional method.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to the following examples, and the present invention can be implemented with arbitrary changes without departing from the gist thereof.

[Solvent used]
The physical properties of the solvents used in the following Examples and Comparative Examples are as shown in Table 1 below.

[Evaluation I: Evaluation of flatness of panel center]
<Preparation of substrate I>
On a glass substrate with a thickness of 0.7 mm, an indium tin oxide (ITO) film was formed using a sputtering method, and then a liquid-repellent acrylic resin was applied to a thickness of 1.7 μm using a spin coating method. The film was coated, and openings were created using a general photolithography method. The size of the opening is about 170 μm on the long axis and about 50 μm on the short axis.

<Coating base layer 1>
A composition for base layer 1 is prepared by dissolving a base layer containing an arylamine polymer as a main component in a solvent, and is applied to the above opening of substrate I using an inkjet printer (DMP-2831 manufactured by Fujifilm). The composition for base layer 1 was applied, vacuum dried and baked to form a film having a thickness of about 30 nm.

<Coating base layer 2>
A composition for base layer 2 is prepared by dissolving a base layer containing an arylamine polymer as a main component in a solvent, and is applied onto base layer 1 in the opening using an inkjet printer (DMP-2831 manufactured by Fujifilm). The composition for base layer 2 was applied, vacuum dried and fired to form a film having a thickness of about 20 nm.

<Preparation of solid content for forming light emitting layer>
Compounds (H-1) and (H-2), which are charge injection and transport materials shown below, and (D-1), which is a luminescent material, are mixed in a weight ratio of 30:70:20 to form a luminescent layer. The solid content was set as I-1.

<Definition of flatness>
A cross-sectional view of the organic film formed in the opening when the organic film is divided along a plane perpendicular to the plane of the organic film is defined as a cross-sectional profile of the organic film. In the organic film cross-sectional profile, the average film thickness Da of the organic film at a length of 25% to 75% of the opening length is calculated, and the film thickness Do(x) of the organic film at a certain position x is calculated using the following formula. Let X1 be an area that satisfies the following.
Da-Da×5%<Do(x)<Da+Da×5% (Formula 1)
When the length of the opening is X2, the definition of flatness is X1/X2×100 (%).

<Reference example 1>
Diethyl phthalate and cyclohexylbenzene were mixed at a weight ratio of 15:85 to obtain organic solvent I-1. Solid content I-1 for forming a light-emitting layer was dissolved in organic solvent I-1 to a concentration of 1.7% by weight to obtain a composition I-1 for forming a light-emitting layer.
On the base layer 2 of the opening, using an inkjet printer (DMP-2831 manufactured by Fuji Film Corporation), the composition I-1 for forming a light-emitting layer was applied in an amount of 5 drops. Thereafter, the organic solvent was removed by vacuum drying to dry the luminescent layer forming composition I-1, and the composition was baked at 120° C. for 3 minutes to form a functional film, the luminescent layer I-1.

In order to evaluate the flatness of the light-emitting layer I-1, the ITO substrate on which the organic film was formed was measured using a stylus type surface step meter (ET200, manufactured by Kosaka Institute). To measure the surface level difference, scanning was performed in the long axis direction of the opening, and two level difference profiles of the light emitting layer I-1 near the center of the substrate were obtained and averaged to obtain the level difference profile of the light emitting layer I-1. . In the same way, two profiles of the opening portion where no coating was applied were also obtained and averaged to obtain a blank profile. Next, the two profiles of the light-emitting layer I-1 and the blank were displayed superimposed to provide a cross-sectional view of how the organic film was formed in the opening. When the flatness was calculated according to the above definition, it was 93.8%. The profiles of the light-emitting layer I-1 and the blank are shown in FIG.

<Reference example 2>
2-phenoxyethyl acetate and ethyl benzoate were mixed at a weight ratio of 30:70 to obtain organic solvent I-2. Solid content I-1 for forming a light-emitting layer was dissolved in an organic solvent I-2 to a concentration of 1.7% by weight to obtain a composition I-2 for forming a light-emitting layer.

A light-emitting layer I-2 was formed in the same manner as in Reference Example 1, except that the composition I-2 for forming a light-emitting layer was used instead of the composition I-1 for forming a light-emitting layer, and its flatness was similarly evaluated. When calculated using the above definition, it was 96.2%. FIG. 2 shows the profiles of the light-emitting layer I-2 and the blank.

<Comparative example 1>
Dibenzyl ether and cyclohexylbenzene were mixed at a weight ratio of 20:80 to obtain organic solvent I-3. Solid content I-1 for forming a light emitting layer was dissolved in organic solvent I-3 to a concentration of 1.7% by weight to obtain a composition I-3 for forming a light emitting layer.

A light-emitting layer I-3 was formed in the same manner as in Reference Example 1 except that the composition I-3 for forming a light-emitting layer was used instead of the composition I-1 for forming a light-emitting layer, and its flatness was similarly evaluated. When calculated using the above definition, it was 50.1%. FIG. 3 shows the profiles of the light-emitting layer I-3 and the blank.

<Comparative example 2>
3-phenoxytoluene and cyclohexylbenzene were mixed at a weight ratio of 20:80 to obtain organic solvent I-4. Solid content I-1 for forming a light emitting layer was dissolved in organic solvent I-4 to a concentration of 1.7% by weight to obtain a composition I-4 for forming a light emitting layer.

A light-emitting layer I-4 was formed in the same manner as in Reference Example 1 except that the composition I-4 for forming a light-emitting layer was used instead of the composition I-1 for forming a light-emitting layer, and its flatness was similarly evaluated. When calculated using the above definition, it was 67.7%. FIG. 4 shows the profiles of the light-emitting layer I-4 and the blank.

<Comparative example 3>
2-phenoxyethanol and cyclohexylbenzene were mixed at a weight ratio of 20:80 to obtain organic solvent I-5. Solid content I-1 for forming a light emitting layer was dissolved in organic solvent I-5 to a concentration of 1.7% by weight to obtain a composition I-5 for forming a light emitting layer.

A light emitting layer I-5 was formed in the same manner as in Reference Example 1 except that the light emitting layer forming composition I-5 was used instead of the light emitting layer forming composition I-1, and its flatness was evaluated in the same manner. When calculated using the above definition, it was 42.4%. FIG. 5 shows the profiles of the light-emitting layer I-5 and the blank.

<Results of Reference Examples 1 and 2 and Comparative Examples 1 to 3>
Table 2 shows the solvent combinations and flatness of Reference Examples 1 and 2 and Comparative Examples 1 to 3.

<Consideration>
As is clear from the profiles, in Reference Examples 1 and 2, in addition to improving the flat area, wetting up to the partition wall portion of the opening (hereinafter referred to as meniscus) is extremely small, and the area that is effective as a light emitting element is You can see that it is getting wider. By selecting the flow activation energy within an appropriate range, wasteful flow of the liquid can be suppressed and a flat organic film can be obtained.
In Comparative Examples 1 and 2, since the solvents were designed to have very low flow activation energy, the liquid flowed during the drying process and moved toward the partition wall, resulting in a meniscus. has gained weight. In addition, because the liquid moved from the center toward the partition wall, the film thickness was thinner than in Reference Examples 1 and 2, even though the same droplets were placed.

In Comparative Example 3, an organic solvent is designed in which the flow activation energy is set to a very high value. In this case, although it is possible to suppress the flow, it is presumed that the meniscus is thickened because the liquid film does not wet down during the drying process. In other words, in order to obtain a flat organic film, it is necessary to have enough fluidity in the early stage of drying to allow the liquid to become wet, while in the final stage of drying, it is necessary to eliminate fluidity to eliminate unnecessary movement of the liquid. There is.

From the comparison between Reference Examples 1 and 2 and Comparative Examples 1 to 3 above, Reference Examples 1 and 2 are excellent in the flatness of the opening, but these Reference Examples 1 and 2 have a boiling point of 245°C as the second solvent. As a result, as in Comparative Example 4, which will be described later, the flatness of the panel edges is significantly inferior.

[Evaluation II: Evaluation of flatness in the center of the panel]
<Preparation of board II>
Similar to the preparation of substrate I in evaluation I, substrate II was prepared having at least 21 openings in the major axis direction and 65 openings in the minor axis direction, each having a major axis of approximately 170 μm and a minor axis of approximately 50 μm.

<Preparation of solid content>
Solid content II-1 was prepared by mixing hole transport material P-1 shown below and electron-withdrawing dopant D-2 at a weight ratio of 100:10.

<Definition of flatness>
When the length of the opening is La, calculate the average film thickness Da in a region where the distance x from the opening end is 0.25<x/La<0.75, and calculate the average film thickness Da of the organic film at a certain position x. Let Lb be a region where the film thickness Do(x) satisfies the following formula 2.
Da-Da×5%<Do(x)<Da+Da×5% (Formula 2)
The flatness was defined as Lb/La×100 (%) with respect to the length La of the opening.

<Example 1>
The ratio of solid content II-1 was adjusted to 5% by weight based on 2-isopropylnaphthalene, and heated at 110°C for 3 hours while stirring at 420 rpm using a stirrer to form standard composition II-1. 1 was produced.
Standard composition II-1, 2-isopropylnaphthalene and 2-ethylhexyl benzoate were mixed in a weight ratio of 50:20.75:29.25, and after stirring for a certain period of time, a membrane with a pore size of 0.2 μm was prepared. The mixture was filtered to prepare Composition II-1. Composition II-1 has a solid content II-1 concentration of 2.5% by weight and a weight ratio of 2-isopropylnaphthalene and 2-ethylhexyl benzoate of 70:30.

Composition II-1 was applied to the opening of substrate II using an inkjet printer (DMP-2831 manufactured by Fuji Film Corporation) and dried under vacuum to obtain an organic film. The organic film was fired on a hot plate at 130° C. for 3 minutes and then on a hot plate at 230° C. for 30 minutes to obtain organic film II-1. The coating amount was adjusted so that the dry film thickness was approximately 100 nm. Pixel group 1 is applied in a pattern such that 21 apertures are applied in the long axis direction and 65 apertures are applied in the short axis direction. And so. As a result, the pixel group 1 has a periodic structure in which coated openings and uncoated openings are repeated at a period of six openings in the short axis direction.

In order to evaluate the flatness, the film thickness profile of the organic film II-1 in the short axis direction was measured using a stylus-type surface step meter (ET200, manufactured by Kosaka Institute). The openings to be measured were at the following two locations within the plane of the 21×65 pixel group 1.
Measurement point 1: The 11th aperture on the long axis and the 33rd aperture on the short axis counting from both ends of the long axis and short axis (center area of pixel group 1)
Measurement point 2: Location of the third opening on the long axis and the ninth opening on the short axis counting from both ends of the long axis and short axis (edge area of pixel group 1)

The flatness evaluation results for measurement point 1 are shown in FIG. 7, and the flatness evaluation results for measurement point 2 are shown in FIG. From the definition of flatness in Equation 2, the flatness of the organic film 1 at the above two locations was calculated to be 81.0% at measurement location 1 and 84.3% at measurement location 2, which resulted in good flatness. . Furthermore, the shapes of the membranes at measurement location 1 and measurement location 2 were approximately the same.

<Example 2>
The ratio of solid content II-1 to butyl benzoate was adjusted to 5% by weight, and heated at 110°C for 3 hours while stirring at 420 rpm using a stirrer to form standard composition II-2. was created.
Composition II-2 was prepared by mixing standard composition II-2, butyl benzoate, and 2-ethylhexyl benzoate in a weight ratio of 50:20.75:29.25, respectively. Composition II-2 has a solid content II-1 concentration of 2.5% by weight and a weight ratio of butyl benzoate to 2-ethylhexyl benzoate of 70:30.

Organic film II-2 was formed using composition II-2 in the same manner as in Example 1, and its flatness was evaluated.
The flatness evaluation results for measurement point 1 are shown in FIG. 9, and the flatness evaluation results for measurement point 2 are shown in FIG. From the definition of flatness in Equation 2, the flatness of organic film II-2 at the two locations above is calculated to be 55.8% at measurement location 1 and 58.7% at measurement location 2, which is relatively good flatness. was gotten. Furthermore, the shapes of the membranes at measurement location 1 and measurement location 2 were approximately the same.

<Example 3>
Standard composition II-1, 2-isopropylnaphthalene, 2-ethylhexyl benzoate, and benzyl benzoate were mixed in a weight ratio of 50:20.75:29.25, and after stirring for a certain period of time, the pore size was 0. The mixture was filtered through a 2 μm membrane filter to prepare Composition II-3. Composition II-3 has a solid content II-1 concentration of 2.5% by weight, and a weight ratio of 2-isopropylnaphthalene, 2-ethylhexyl benzoate, and benzyl benzoate of 70:20:10.

Organic film II-3 was formed using composition II-3 in the same manner as in Example 1, and its flatness was evaluated.
The flatness evaluation results of measurement point 1 are shown in FIG. When the flatness of the organic film II-3 was calculated from the definition of flatness in Equation 2, good flatness of 90.2% was obtained at measurement point 1.

<Comparative example 4>
Standard composition II-1, 2-isopropylnaphthalene and dibenzyl ether were mixed in a weight ratio of 50:20.75:29.25, stirred for a certain period of time, and filtered through a membrane filter with a pore size of 0.2 μm. It was filtered to prepare composition II-4. Composition II-4 has a solid content II-1 concentration of 2.5% by weight and a weight ratio of 2-isopropylnaphthalene and dibenzyl ether of 70:30.

Organic film II-4 was formed using composition II-4 in the same manner as in Example 1, and its flatness was evaluated.
The flatness evaluation results for measurement location 1 are shown in FIG. 12, and the flatness evaluation results for measurement location 2 are shown in FIG. 13. From the definition of flatness in Equation 2, the flatness of the organic film II-4 at the two locations above is calculated to be 16.2% at measurement location 1 and 31.5% at measurement location 2, indicating that a flat film was obtained. There wasn't. The shapes of the membranes at measurement point 1 and measurement point 2 were similar in shape, with the center being depressed.

<Comparative example 5>
The ratio of solid content II-1 to cyclohexylbenzene was adjusted to 5% by weight, and heated at 110°C for 3 hours while stirring at 420 rpm using a stirrer to prepare standard composition II-3. Created.
Composition II-5 was prepared by mixing standard composition II-3, cyclohexylbenzene, and 2-ethylhexyl benzoate in a weight ratio of 50:20.75:29.25, respectively. Composition II-5 has a solid content II-1 concentration of 2.5% by weight and a weight ratio of cyclohexylbenzene and 2-ethylhexyl benzoate of 70:30.

Organic film II-5 was formed using Composition II-5 in the same manner as in Example 1, and its flatness was evaluated.
The flatness evaluation results of measurement point 1 are shown in FIG. 14, and the flatness evaluation results of measurement point 2 are shown in FIG. From the definition of flatness in Equation 2, we calculated the flatness of the organic film II-5 at the two locations.At measurement location 1, a good flatness of 68.9% was obtained, but at measurement location 2, it was 4.9%. 1%, a flat film could not be obtained.

<Comparative example 6>
The proportion of solid content II-1 was adjusted to 2.5% by weight based on 2-ethylhexyl benzoate, and heated at 110°C for 3 hours while stirring at 420 rpm using a stirrer to form a composition. II-6 was prepared.

Organic film II-6 was formed using Composition II-6 in the same manner as in Example 1, and its flatness was evaluated.
The flatness evaluation results for measurement point 1 are shown in FIG. 16, and the flatness evaluation results for measurement point 2 are shown in FIG. 17. From the definition of flatness in Equation 2, the flatness of the organic film II-6 at the two locations above is calculated to be 43.3% at measurement location 1 and 53.4% at measurement location 2, indicating that a flat film was obtained. There wasn't. The shapes of the membranes at measurement location 1 and measurement location 2 were approximately the same.

The results of Examples 1 to 3 and Comparative Examples 4 to 6 are summarized in Table 3. From these results, it was found that when the boiling point of the second solvent was 245° C. or higher, equivalent flatness could be obtained at the center and edges of the panel. In particular, it has been found that when the boiling point of the second solvent is 260° C. or higher, flatness of more than 80% can be obtained at both the center and edges of the panel.

Although the invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various changes can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2018-088327 filed on May 1, 2018, which is incorporated by reference in its entirety.

1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Organic electroluminescent element

Claims (7)

A composition comprising a functional material, a first solvent and a second solvent,
The first solvent is a water-insoluble aromatic solvent,
The boiling point of the first solvent is higher than the boiling point of the second solvent, and the difference in boiling point between the first solvent and the second solvent is 10° C. or more,
The first solvent has a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less,
The flow activation energy of the first solvent is 5 kJ/mol or more greater than the flow activation energy of the second solvent,
The content ratio of the first solvent is 5 to 50% by weight based on the total amount of the first solvent and the second solvent,
The total content of the first solvent and the second solvent with respect to the total amount of solvents contained in the composition is 95 % by weight or more,
The boiling point of the second solvent is 245°C or higher,
A composition in which the first solvent and the second solvent are naphthalene, benzoic acid ester, or aromatic ether, each of which may have a substituent . A composition comprising a functional material, a first solvent and a second solvent,
The first solvent is a water-insoluble aromatic solvent,
The boiling point of the first solvent is higher than the boiling point of the second solvent, and the difference in boiling point between the first solvent and the second solvent is 10° C. or more,
The first solvent has a flow activation energy of 22 kJ/mol or more and 35 kJ/mol or less,
The flow activation energy of the first solvent is 5 kJ/mol or more greater than the flow activation energy of the second solvent,
The content ratio of the first solvent is 5 to 50% by weight based on the total amount of the first solvent and the second solvent,
The total content of the first solvent and the second solvent with respect to the total amount of solvents contained in the composition is 95 % by weight or more,
The boiling point of the second solvent is 245°C or higher,
The first solvent is any one of 2-ethylhexyl benzoate, benzyl benzoate, acetylnaphthalene, dimethyl phthalate, diethyl phthalate, ethyl biphenyl, isopropylbiphenyl, diisopropylbiphenyl, triisopropylbiphenyl, and 2-phenoxyethyl isobutyrate. can be,
The second solvent is any one of methylnaphthalene, ethylnaphthalene, isopropylnaphthalene, methoxynaphthalene, butyl benzoate, pentyl benzoate, isopentyl benzoate, diphenylmethane, and benzyltoluene . The composition according to claim 1 or 2 , wherein the functional material has a molecular weight of 50,000 or less. The composition according to any one of claims 1 to 3, wherein the second solvent has a viscosity of 5 mPas or less at 23°C. The composition according to any one of claims 1 to 4 , wherein the difference between the boiling point of the first solvent and the boiling point of the second solvent is 30°C or more. The composition according to any one of claims 1 to 5 , wherein the first solvent has a surface tension of 30 mN/m or more. A method for producing an organic electroluminescent device, comprising a step of wet film formation using the composition according to any one of claims 1 to 6 .

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