JPWO2018190043A1 - Coating liquid, method for producing coating liquid, coating film, and organic electroluminescence device - Google Patents

Abstract

An object of the present invention is to provide a coating solution having excellent preservability and excellent preservability and functionality of the coating film when dried to form a coating film, a method for producing the coating solution, and drying and solidifying the coating solution. It is an object of the present invention to provide a coating film comprising the above-mentioned coating film and an organic electroluminescent device provided with the coating film as an organic functional layer. The coating liquid of the present invention is a coating liquid containing a plurality of compounds for an organic electroluminescent device and an organic solvent, wherein at least two of the plurality of compounds for an organic electroluminescent device are isomers of each other. In a relationship.

Description

  The present invention relates to a coating solution, a method for producing the coating solution, a coating film, and an organic electroluminescence device. More specifically, the present invention provides a coating solution having excellent storage stability and excellent storage stability and functionality of a coating film when dried to form a coating film, a method for producing the coating solution, and drying the coating solution. The present invention relates to a solidified coating film and an organic electroluminescence device having the coating film as an organic functional layer.

2. Description of the Related Art An organic electroluminescence element (hereinafter, also referred to as an “organic EL element”) is a technology expected as a display or lighting. Applications of devices have been advanced, and commercialization of display devices such as mobile phones and displays has been progressing.
At present, a vapor deposition method is mainly used as a method for manufacturing an organic EL device. However, the vapor deposition method requires a high vacuum, so that the cost is high and it is difficult to make the layer thickness uniform when the area is increased. .

Therefore, a coating method is expected as a film forming method replacing the vapor deposition method. The coating method is superior in cost in comparison with the vapor deposition method, and it is easy to enlarge the area technically.
In general, as a coating type organic EL element, an example of a coating type polymer organic EL element using a polymer material for a light emitting layer (for example, see Patent Document 1) is given.

However, in the coating type polymer organic EL device, there are concerns about performance and production stability because it is difficult to purify the material and it is difficult to control the molecular weight distribution. ing.
Therefore, in recent years, a coating-type low-molecular organic EL element using a low-molecular material for a light-emitting layer has attracted attention.

However, the coating type low molecular organic EL element has a problem that the driving voltage increases. The cause of the increase in the driving voltage is the presence of microcrystals contained in the thin film.
Conventionally, the preservability of a coating solution or a coating film is insufficient, and a coating solution and a coating film having excellent preservability capable of maintaining a state in which microcrystals are not present for a long time are required. I have.

  In addition, it is known that films deposited by a general vapor deposition method and polymer films formed by a wet process are amorphous. Tends to be a problem with the low molecular weight organic EL device.

JP-A-6-33048

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is to provide a coating film having excellent storage stability and excellent storage stability and functionality when dried to form a coating film. It is an object of the present invention to provide a liquid, a method for producing the coating liquid, a coating film obtained by drying and solidifying the coating liquid, and an organic electroluminescence element including the coating film as an organic functional layer.

The present inventors have studied to improve the preservability of a coating solution from a thermodynamic point of view in order to solve the above problems. Specifically, the storage stability of the coating solution can be expressed by the magnitude of the free energy change (ΔG) of Gibbs as the coating solution from the viewpoint of thermodynamics. It is stable. ΔG is represented by the following equation. In the present invention, as a means for increasing ΔG to a negative value, it was conceived to achieve the object by positively utilizing the effect of entropy change (ΔS).
Formula: ΔG = ΔH−TΔS

Thus, the present inventors have conducted intensive studies based on the concept of actively utilizing the entropy change (ΔS). When at least two of the plurality of compounds for an organic electroluminescence device are in an isomer relationship with each other, ΔS is increased without substantially changing the physicochemical properties of the coating solution, and It has been found that it is possible to greatly improve the stability of, and the present invention has been achieved.
That is, the above object according to the present invention is solved by the following means.

1. A coating solution containing a plurality of types of compounds for an organic electroluminescence device and an organic solvent,
A coating liquid in which at least two of the plurality of compounds for an organic electroluminescence device have an isomer relationship with each other.

  2. 2. The coating liquid according to claim 1, wherein the content (molar ratio) of each of the compounds for an organic electroluminescence element in the isomer relationship is different from each other.

  3. 3. The coating liquid according to claim 1 or 2, wherein the number of isomers of the compound for an organic electroluminescence device having the isomer relationship is 3 or more.

  4. 4. The method according to any one of items 1 to 3, wherein the content of the plurality of compounds for an organic electroluminescence device is in the range of 0.5 to 5.0% by mass based on the total amount of the coating solution. The coating solution according to the above.

5. The method for producing a coating liquid according to any one of items 1 to 4, wherein
A method for producing a coating liquid, comprising a step of bringing the plurality of types of compounds for an organic electroluminescence device into contact with a supercritical or subcritical fluid.

  6. 5. A coating film formed by drying and solidifying the coating solution according to any one of items 1 to 4.

  7. An organic electroluminescence device comprising the coating film according to claim 6 as an organic functional layer.

  By the above means of the present invention, a coating solution having excellent preservability and excellent preservability and functionality of the coating film when dried to form a coating film, a method for producing the coating solution, a coating film, and organic electroluminescence An element can be provided.

  Although the mechanism of manifesting or acting the effects of the present invention has not been clarified, it is speculated as follows.

If the coating solution containing the organic material does not change during storage, the storage stability of the coating solution is infinite. Here, the preservability of the coating solution is determined by the change (ΔG) of Gibbs free energy of the second law of thermodynamics. That is, the more negative this ΔG, the greater the stability of the film, ie, the less likely it is to be subject to fluctuations due to disturbance requirements during use. ΔG can be expressed by the following equation by applying the temperature to the change in enthalpy (ΔH) and the change in entropy (TΔS).
Formula: ΔG = ΔH−TΔS

  The essence of the present invention is to increase the stability of a coating solution by effectively utilizing the effect of entropy change (ΔS) as a means for increasing ΔG to a negative value, and as a result, the coating solution is dried and solidified. This is a technology that can suppress fluctuations in physical properties of the film.

The coating solution of the present invention contains a plurality of types of compounds for organic electroluminescence devices (hereinafter also referred to as “compounds for organic EL devices”) and an organic solvent, and at least two of the plurality of types of compounds for organic EL devices. The species are in an isomeric relationship with each other. Although the isomers are different molecules, it is considered that the entropy change (ΔS) was increased without changing the physicochemical properties of the coating solution, and the effect of improving the storage stability of the coating solution could be effectively obtained.
That is, unlike the conventional coating liquid, the present application achieves a great effect by including in the coating liquid a compound of a combination that exerts an effect intentionally.

Next, entropy will be described.
Generally, gases are completely mixed. Mixes evenly with almost any molecule. The reason will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating an entropy change when two kinds of gases are mixed.

It is assumed that nitrogen molecules (component A) and oxygen molecules (component B) are contained at the same density in a box provided with a space at the center (see FIG. 1A, left). If this threshold is removed, oxygen molecules and nitrogen molecules are completely mixed (see FIG. 1A, right). Since both are gases, the enthalpy is considered to be almost zero. I do. That is, entropy increases. If the temperature is not absolute 0 degrees (0K (Kelvin)), TΔS will be positive and ΔG will be negative. That is, the gas is uniformly mixed by the effect of the entropy.
On the other hand, what if nitrogen molecules (component A) of the same density (= number of molecules) exist on both sides of the threshold? In this case, the entropy does not change before opening the threshold (see FIG. 1B, left) and after opening (see FIG. 1B, right) because the number of foreign molecules does not increase and the density does not change when viewed from the nitrogen molecule. In other words, it is important that different molecules coexist in order to exert the entropy effect.

An example in which this concept is applied to an ultraviolet absorber or the like is applied in the world of photographic materials, and an example is disclosed in JP-A-2014-229721.
As disclosed in Japanese Patent Application Laid-Open No. 2014-229721, it is possible to increase the Gibbs free energy in the initial state by effectively utilizing the entropy effect. It can be said that it is large enough to suppress fluctuations even under the severe deterioration condition of storage.

  Japanese Patent Application Laid-Open No. 2014-229721 refers to behavior in a solid state and a film state, but it goes without saying that the second law of thermodynamics is a concept applicable to all objects.

By the way, Japanese Patent Application Laid-Open No. 2014-229721 does not provide a sufficient description of the coating liquid and does not sufficiently disclose the effects.
Further, usually, the material used for the organic EL element is required to have high purity, and the purity is generally 99% or more. The isomer in the present application is regarded as one of impurities in the case of purity determination. For example, when one kind of organic material has an optical isomer and an L-form and an R-form exist, one of the isomers is used. In contrast to the optical isomer, the other optical isomer is often considered an impurity. Separation and purification of isomers including optical isomers requires a large number of steps, such as using a technique such as GPC (gel filtration chromatography) or HPLC (liquid chromatography).
In the present invention, when refining an organic material, a plurality of stereoisomers are regarded as the same component, and the isomer separation and purification as described above can be unnecessary. The benefits are great in terms of cost.

Furthermore, by preparing a coating film obtained by drying and solidifying the coating solution containing the isomer of the present invention, the coating film of the present invention containing the isomer is compared with the coating film of the comparative example not containing the isomer. Was found to have low cohesiveness and more excellent preservability. In addition, it was found that the organic EL device having the coating film of the present invention as an organic functional layer had excellent functionality such as a long light-emitting life and a small change in driving voltage.
This is because the coating solution of the present invention has excellent storage stability, and the coating solution obtained by drying and solidifying the coating film does not contain microcrystals that deteriorate the functionality of the coating film for a long time. It is thought that this was because it could be maintained.

Schematic diagram for explaining entropy change when two kinds of gases are mixed Schematic diagram for explaining entropy change when two kinds of gases are mixed Graph showing an example of a particle size distribution curve of a conventional vapor-deposited film and a coating film Schematic diagram of apparatus using packed column in supercritical or subcritical chromatography Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of the display unit A Schematic diagram showing the pixel circuit Schematic diagram of passive matrix type full color display device

  The coating liquid of the present invention is a coating liquid containing a plurality of compounds for organic electroluminescence devices and an organic solvent, wherein at least two of the plurality of compounds for organic electroluminescence devices are isomers of each other. It is characterized by having a relationship. This feature is a technical feature common or corresponding to the following embodiments.

In addition, as an embodiment of the coating liquid of the present invention, from the viewpoint of effectively obtaining the effects of the present invention, the contents (molar ratios) of the compounds for an organic electroluminescence element in the isomer relationship are different from each other. Is preferred. The following is presumed as such a reason.
Generally, it is considered that the crystal growth of an organic substance starts from a specific type of association. Specifically, a certain aggregate is generated, and another molecule interacts with the aggregate to increase the number of molecules of the aggregate. At this time, it is thought that if the molecule that joins the aggregate is the same as the molecule that formed the original aggregate, the aggregate grows faster, and if it is a different molecule, the aggregate growth is suppressed. It is known that such a growth model can be applied to isomers. As an example of the former, a recrystallization optical resolution method is known, which is performed by adding one chirality crystal to a supersaturated solution. As described above, it is known that isomer mixtures are formed by assembling and crystallizing molecules having the same chirality and steric structure. For example, the growth of microcrystals can be suppressed.

  Further, as an embodiment of the coating liquid of the present invention, the effect of the entropy change (ΔS) increases as the number of isomers increases, and thus the effect of the present invention can be effectively obtained by increasing the number of isomers. Therefore, it is preferable that the number of isomers of the compound for an organic electroluminescence device having the above-mentioned isomer relationship is 3 or more.

  Further, as an embodiment of the coating solution of the present invention, from the viewpoint of effectively obtaining the effects of the present invention, the content of the compound for the plurality of types of organic electroluminescent elements is 0.5% with respect to the total amount of the coating solution. It is preferable that it is within the range of 5.0 mass%.

  In addition, the method for producing a coating solution of the present invention includes, from the viewpoint of effectively obtaining the effects of the present invention, contacting the plurality of compounds for an organic electroluminescent device contained in the coating solution of the present invention with a supercritical or subcritical fluid. It is preferable to have a step of performing the following.

  Further, the coating film of the present invention is a film obtained by drying and solidifying the coating liquid of the present invention, and the organic electroluminescent element of the present invention includes the coating film as an organic functional layer.

  Hereinafter, the present invention, its components, and embodiments and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning including the numerical value described before and after it as a lower limit and an upper limit. In the present invention, ratios such as “%” and “ppm” are based on mass.

[Overview of coating film of the present invention]
The coating film of the present invention is a coating liquid containing a plurality of types of compounds for an organic EL device and an organic solvent, wherein at least two of the plurality of types of compounds for an organic EL device have an isomer relationship with each other. There is a feature.

  In the following, in order to facilitate understanding of the present invention, first, a basic policy and a history of research and development according to the present invention will be described, and then a specific technique of the present invention will be described.

The basic principle of the present invention is based on the following (1) to (5).
(1) The solute in the coating solution is preferably a low molecular compound.
(2) The coating method is preferable as the film forming method.
(3) The solvent in the coating solution is preferably a general-purpose solvent.
(4) Dissolution is preferably in a monomolecular state.
(5) It is preferable to utilize the adsorption-desorption equilibrium for the purification of the compound.

1. Superiority of low molecular weight compounds over high molecular weight compounds In forming an organic functional layer by a wet coating method, the superiority of low molecular weight compounds over high molecular weight compounds will be described.

(First Factor): Superiority of Purity It is preferable to apply sublimation purification to low molecular weight compounds because of their small molecular weight, and it is also desirable that recrystallization has a small molecular weight distribution. In addition, high-performance liquid chromatography (HPLC) or column chromatography with high purification efficiency can be used as a method for purifying a low-molecular compound, which is preferable.
In most cases, high-molecular compounds are purified by repetition of reprecipitation using a good solvent and a poor solvent. Purity and easy.
In addition, there are cases where a substituent having reactive activity remains at the polymerization terminal of the polymer compound, which is also one of the factors that make purification difficult.

(Second Factor): Superiority in Energy Level Specific to Molecules A light emitting polymer (LEP) is a π-conjugated polymer when its molecular weight increases, so it is conjugated to stabilize the molecule. The system is expanded, and in principle, the energy level difference between the singlet or triplet excited state and the ground state (also referred to as “energy level gap” or “band gap”) becomes narrower and blue. Light emission becomes difficult. For this reason, there is a problem that even when an attempt is made to use a light emitting polymer as a host, it is difficult to produce a compound having a high triplet energy (abbreviated as “high T ₁ compound”) due to the above-mentioned expansion of π conjugation.

On the other hand, low molecular compounds require aromatic compound residues to be π-conjugated units, but they can be selected arbitrarily and can be substituted at any position, and these do not require expansion of the conjugated system. . Therefore, in the case of a low-molecular compound, the energy level difference can be intentionally adjusted, and a blue phosphorescent substance can be produced, used as a host, and a compound that causes a TADF phenomenon can be constructed. .
As described above, the degree of expandability in which an arbitrary electronic state or an arbitrary level can be intentionally designed and synthesized is a factor of the second superiority of the low-molecular compound.

(Third factor): Ease of compound synthesis Similar to the second factor, the low molecular weight compound is not limited in the molecular structure that can be synthesized as compared with the light emitting polymer (LEP), and provides new functions and physical properties. (Tg, melting point, solubility, etc.) can be achieved by the molecular structure. This is the third advantage of low molecular weight compounds.

2. Issues in the formation of an organic functional layer by a wet coating method using a low molecular compound The formation of an organic functional layer by a wet coating method using a low molecular compound will be described.
In the material used for the organic EL element, electrons and holes must hop between molecules inside the organic EL element. Basically, electrons hop along the LUMO level, and holes hop using the HOMO level.
That is, unless the adjacent molecules always exist so that the π-conjugated system overlaps, such carrier conduction does not occur. Therefore, it is advantageous to form the molecular structure only with the π-conjugated unit as much as possible.
If a plurality of sterically bulky substituents (sec-butyl group, tert-octyl group, triisopropylsilyl group, etc.) are substituted in one molecule in order to improve the solubility in a solvent, The π-conjugated system between them becomes difficult to overlap, and hopping movement is hindered at the bulky substituent portion.

On the other hand, the organic EL element continuously flows current during light emission. Therefore, even if the quantum efficiency is 100% and the heat deactivation is 0%, the organic EL element continues to flow carriers. Therefore, it is necessary to provide a potential difference between the anode and the cathode to provide an electric field gradient, so that the equivalent circuit of the organic EL element is a series connection of a diode and a resistor.
That is, it is also known that Joule heat is generated inside the organic EL element during energized light emission, and that heat is generated at 100 ° C. or more inside the element, particularly in the light emitting layer where recombination occurs.

Further, since the organic layer thickness of the entire organic EL element is an extremely thin layer of about 200 nm, heat is conducted between the layers (films), and the high temperature state is maintained not only in the light emitting layer but also in all the layers. become.
An organic molecule exposed to such a state undergoes a phase transition from an amorphous state to a crystalline state when it exceeds its own glass transition point (Tg).
This crystal grows gradually, and if the thickness exceeds the layer thickness, the function separation by the layer as the organic EL element cannot be performed. As a result, the luminous efficiency decreases.

Further, when the crystal exceeds the entire organic layer (100 to 200 nm) of the organic EL element, the anode and the cathode are short-circuited. Then, an electric field concentration occurs in the short-circuited portion and a large current flows in a minute region, so that the organic compound in the portion is thermally decomposed and a dark spot is formed.
That is, the low molecular compound of the organic EL element is a molecule having no bulky non-aromatic substituent and having a glass transition point (Tg) of 100 ° C. or higher (preferably 150 ° C. or higher). There must be.
In order to construct such a molecule, usually, a π-conjugated system is increased or an aromatic group is simply connected, but the solubility in a solvent is extremely low. As a result, a coating liquid cannot be formed, or even if coating can be performed, crystal precipitation or uneven distribution of a substance occurs.

  As a means of solving this dilemma, we have developed a revolutionary technology that can form a stable amorphous film and hold it during energization (for example, see Japanese Patent No. 5403179 or No. 2014-196258). Specifically, it does not have a bulky, highly flexible branched alkyl group, etc., but connects only aromatic groups to form a biaryl structure, and has a large number of conformations due to rotational obstacles generated around its CC bond axis. By increasing the number of molecules and geometric isomers, or by allowing multiple molecules (eg, host and dopant) existing in the same layer to interact in various shapes and forms. Since the number of components can be increased, entropy in a thin film state can be increased, and a stable amorphous film can be formed.

The present inventors have improved the molecular structure of the low-molecular compound according to the above-described guidelines and optimized the drying conditions in the production of the organic EL device by the wet coating method. A dramatic improvement was achieved, with 95% of the device and a luminous life of 90%. As a result, even a device using a phosphorescent dopant as a light emitting dopant, especially a device using a blue phosphorescent dopant, which is considered to have the longest lifetime improvement, can achieve a basic characteristic comparable to that of a conventional vapor deposition method by a coating film forming method. Has been found to be able to demonstrate.
However, many problems still remain in the organic EL device with improved performance.

  These problems include, for example, the removal of the purity of the low-molecular compound, the trace amount of water adhering to the surface of the compound, the oxygen content of the solvent used, and the water content.

In addition, for example, even for a low molecular compound generally used for coating, in order to express the highest performance, after performing column chromatography and recrystallization, sublimation purification is performed, and further, an organic compound is used or stored. In this case, after a vacuum state, the atmosphere is replaced with a nitrogen atmosphere.
As described above, even when the organic EL device is manufactured by the coating method under extremely strict control, it is difficult to exceed the performance of the organic EL device manufactured by the vapor deposition method.

  Furthermore, in the first place, the low productivity of the vapor deposition method using a vacuum has an adverse effect on cost, so the coating method has attracted attention, and the coating method is also under such strict control. If it is performed, the productivity is lower and the cost is higher than the vapor deposition method.

3. Compound purification method (sublimation purification)
The advantage of a low molecular weight compound is that more purification means can be utilized than a high molecular weight compound and high purity can be achieved. However, after all, almost all of the organic compounds constituting the organic EL device are used through a purification means called sublimation purification.
Sublimation purification is a classical purification method, but its purification efficiency (theoretical plate number) is overwhelmingly smaller than purification methods such as recrystallization, column chromatography, and HPLC. It is used as a means to remove the solvent.

The main reason why the sublimation purification method is adopted for the organic compound for the organic EL is that the vacuum evaporation method is adopted for the production process of the organic EL element. If a very small amount of a solvent is contained in the organic compound, the solvent in the organic compound volatilizes when placed under vacuum in a vapor deposition apparatus, and the degree of vacuum is reduced. This makes serial production impossible and presents a manufacturing problem. Therefore, a sublimation purification method in which the solvent is completely removed during the purification is employed.
Therefore, when the production method of the organic EL element is changed from the vapor deposition method to the coating method, the purification of the organic compound by the sublimation purification method is not essential for the above-mentioned reason.

(Recrystallization)
Next, consider the most common recrystallization method for refining low molecular organic compounds.
This method is a purification method based on the second law of thermodynamics (the following formula).
Formula: −ΔG = −ΔH + TΔS

As the existence distance between substances becomes shorter, van der Waals force, hydrogen bonding force, π-π interaction force, dipole-dipole interaction force, etc. increase, and the enthalpy (−ΔH) increases.
On the other hand, when the substance is completely dispersed in the medium, the substance can move freely, so that the disorder increases and the entropy (ΔS) increases.
According to the second law of thermodynamics, all existing states shift to a direction in which the Gibbs free energy (−ΔG) is kept constant or increased.

That is, it can be reasonably explained that the compound A to be purified is purified by recrystallization, as follows.
When A is dissolved at a high temperature in a solvent called B in which A can be dissolved, A is present in a dispersed state. Therefore, the existence distance between A is large and it is difficult to interact with each other, so that the enthalpy (−ΔH) becomes extremely small.

On the other hand, the entropy (ΔS) is extremely large because A can move freely in the solution. When this high-temperature solution is cooled, TΔS at which the temperature T is applied becomes smaller than before cooling. At that time, in order to keep the Gibbs free energy (−ΔG) constant before and after cooling, the enthalpy (−ΔH) must be increased.
In other words, as TΔS decreases as the temperature decreases, A must reduce the distance from A to increase enthalpy. The extreme state is a crystal state in which the distance between A and A is minimum, whereby the enthalpy term (-ΔH) increases.
When the enthalpy increases in this way, the number of components in the system decreases, so the entropy decreases, and the enthalpy increases by reducing the entropy.

Thus, first, the entropy term (TΔS) decreases with a decrease in temperature, and the enthalpy (−ΔH) increases due to crystallization to make up for it, and the entropy term further decreases because the number of components decreases thereby. The recrystallization is achieved by repeating the thermodynamic equilibrium in which ΔS decreases and crystallization occurs to that extent.
However, attention must be paid to the interaction between the solute A and the solvent B. Since solute A is dissolved by being solvated in solvent B, A does not dissolve in B unless the interaction between AB is large. However, if the interaction is too large, the distance between A and A cannot be shortened enough to overcome the decrease in the entropy term that is reduced by cooling (because B is interposed between A and A). 2), which results in no recrystallization.

In other words, the purification method by recrystallization can be applied only when the interaction force between AA and the interaction force between A and B can be adjusted to a condition under which recrystallization occurs.
In such a method for recrystallization purification, it is possible to purify a large amount of several hundred kg or more at a time. Therefore, this method has long been used in the chemical industry.

(Column chromatography)
Next, column chromatography (hereinafter, also referred to as “chromatography”) will be considered.
The most typical type of column chromatography is to use fine silica gel as a stationary phase, adsorb Compound A thereon, and gradually elute it with a mobile phase (B) called an eluent.
At this time, when the interaction with the mobile phase (B) antagonizes the interaction (adsorption) between the silica gel surface and the compound A, A becomes an equilibrium between adsorption and desorption between silica and the mobile phase B. Is repeated earlier when the interaction with silica is small, and later when the interaction with silica is large.

At this time, since the number of theoretical plates (that is, purification efficiency) increases as the number of round trips of the adsorption-desorption equilibrium increases, the purification efficiency by the chromatographic method is proportional to the length of the stationary phase, and the passing speed of the mobile phase also increases. It is proportional to the surface area of the stationary phase.
This was realized by high performance liquid chromatography, which is widely used for component analysis and quality assurance of organic compounds.It is a rare method that can realize a high number of theoretical plates based on this theory. It is caused by that.
The reason that this chromatography method is superior to recrystallization is that the polarity of the mobile phase B can be arbitrarily changed. For example, the mobile phase may be a mixed solvent of a good solvent and a poor solvent from the beginning, or the number of theoretical plates may be further increased by using a gradient method in which the ratio of the good solvent is gradually increased during purification.

In addition, since the temperature can be arbitrarily changed, the most applicable feature is that the applicable range of the solute that can be purified is extremely wide, and the solute can be used as an almost universal purification method.
On the other hand, there is a disadvantage of the chromatographic method.
For example, when the chromatographic method is performed using only the solvent B '(that is, a good solvent) having a strong interaction with the compound A as the mobile phase, the interaction between A and the mobile phase B' is more than the interaction between A and silica gel. If the action is strong, the number of round trips of adsorption-desorption equilibrium is drastically reduced, and the purification effect is reduced.

In other words, in order to enhance the purification effect, it is necessary to mix a large excess of the poor solvent C in addition to the good solvent B 'to increase the number of times of adsorption-desorption equilibrium. However, in this case, the solution of compound A purified and collected contains a large excess of C, and the biggest problem is that it must be removed.
For example, in order to obtain 1 g of A, the mixing ratio of the good solvent B 'and the poor solvent C needs to be about 1:99 to 10:90, and generally about 10 L to 100 L of the poor solvent C You will need it. Therefore, HPLC fractionation is applied to research and development, but is not used for mass production.

Means for solving the problem of poor solvent concentration is HPLC using supercritical carbon dioxide. Supercritical carbon dioxide is obtained by converting carbon dioxide into a supercritical fluid at a high temperature and a high pressure, and can realize a supercritical state at a relatively low pressure and temperature. Therefore, carbon dioxide is mainly used in chromatography and extraction.
This supercritical carbon dioxide has characteristics different from ordinary fluids and liquids. That is, by changing the temperature and pressure, the polarity can be continuously changed in accordance with the polarity of the substance to be dissolved.
For example, this supercritical carbon dioxide is used for selective extraction of docosahexaenoic acid contained in fish heads, and sebum is dissolved and adhered to cleaning of special clothing using adhesives. The agent uses supercritical carbon dioxide which does not dissolve.

Although supercritical carbon dioxide can have various polarities as described above, the polarity of supercritical carbon dioxide formed in a relatively low temperature and pressure range is about the same as cyclohexane and heptane. In currently available supercritical HPLC, supercritical carbon dioxide of such a degree of polarity is produced in the apparatus, and it is mixed with a good solvent into the column, and the compound is formed by the same mechanism as ordinary HPLC. Purification is performed.
In a column chromatography system using supercritical carbon dioxide, the liquid enters a detector after passing through a column. However, usually, a high-temperature and high-pressure state is maintained until that stage, and carbon dioxide also exists as a supercritical fluid. Thereafter, the carbon dioxide is converted into a gas before being separated at normal temperature and normal pressure. At the time of separation, the carbon dioxide escapes from the solution by itself, so that it is not necessary to concentrate the poor solvent. At this time, carbon dioxide can be captured by a carbon dioxide capture device equipped with a liquid-liquid separation mechanism and the like described in a reference (Journal of the Society of Biotechnology, Vol. 88, No. 10, pp. 525-528, 2010). It can be used again as a supercritical fluid.

For this reason, in the drug discovery industry, where it is necessary to synthesize many high-purity newly synthesized compounds, recently, this supercritical HPLC has been actively utilized, and due to the influence, both analytical and preparative HPLC have been used. Selling prices have fallen and are becoming quite common.
Due to such characteristics and circumstances, we have utilized this supercritical HPLC for the purification of materials for organic EL devices requiring high purity (Japanese Patent No. 4389494).
As described above, there is a demand for improving the productivity of the organic EL industry, and there are various methods for purifying low-molecular-weight organic compounds. An appropriate purification method is selected depending on the availability of a residual solvent, and the like, and is used in combination.

4. Dissolution of Organic EL Compound First, what is dissolution? Usually, the solute A is surrounded by the interaction force of the solvent molecules B with the solvent molecules B, and the aggregates of A are separated so that B exists around A, that is, A is in an isolated single molecule state. That said, it's difficult to see if it really is.
For example, when A is a molecule having extremely low solubility or high crystallinity, if the crystal has a size equal to or larger than the wavelength of visible light, the fact that A is not dissolved can be easily detected by light scattering or the like. However, even if, for example, the solvent molecule B surrounds the microcrystal composed of several molecules of A, it looks as if it is dissolved. In an organic EL device, this may cause a serious problem later.
In other words, when forming thin layers (films) such as a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer by vapor deposition, the compounds constituting each layer are basically formed by vacuum deposition. In the state of a vaporized isolated single molecule, it lands on a substrate or an organic layer, and is formed as a solid thin film. Therefore, the film is basically formed of a random aggregate of single molecules, and becomes an ideal amorphous film.

On the other hand, in the case of the coating film forming method, when the coating liquid is a dispersion of microcrystals of the organic EL compound, even if it appears to be completely dissolved in appearance, the actual state of the obtained thin film is microcrystals. Becomes a thin film gathered. Therefore, for example, the level of HOMO or LUMO is not that of a single molecule but that of a stacked aggregate (crystalline state), which may be a factor of performance degradation.
Further, over time, the microcrystals become nuclei and grow into coarse crystals, so that not only the function separation between the layers cannot be performed but also the large crystals that short-circuit the anode and the cathode become dark. There is a big problem that spots are generated.
Regarding the coating film forming element using low molecules, from the above-mentioned long-term study, how to approximate the coating liquid in the initial state to a monomolecular dispersion state is first to achieve the same performance as the vapor deposition method. It is clear that this is a requirement.

Here, usually, how many molecules of the coating liquid that are supposed to be strictly dissolved are dispersed is analyzed by small angle X-ray scattering measurement (also referred to as “SAXS”). Let's think based on the results.
In FIG. 2, the broken line is the particle size distribution curve (horizontal axis: particle size (nm), vertical axis: frequency distribution) of the fine particles of the compound constituting the thin film produced by the vapor deposition method, and the solid line is the thin film produced by the coating method. 3 is a particle size distribution curve of fine particles of a constituent compound. Since both use the same compound, they can be directly compared.
In the particle size distribution of the fine particles of the compound in vapor deposition, the particle size at the position corresponding to the maximum peak is about 2 nm, which is a particle size close to monodispersion. This means that, in the case of vapor deposition, almost single molecules are randomly arranged to form an amorphous film because of the size of one or two molecules.
On the other hand, in the particle size distribution of the compound fine particles in the coating film formation, the particle size at the position corresponding to the maximum peak is about 4.5 nm, which is wider than the particle size distribution in the vapor deposition film formation.

As described above, since the same compound is used for the vapor deposition film formation and the coating film formation, the compound has the same crystallinity and cohesiveness. It is presumed that the dispersion state was not a single isolated molecule but a microcrystal dispersion.
Although this coating solution is a so-called clear solution, we misunderstand that a dispersion of several molecular microcrystals found by X-ray analysis is a dissolved solution.

5. Regarding Purity of Solvent of Organic EL Compound An organic EL element has a basic function of emitting light when a light emitting material in an excited state returns to a ground state.
In addition, it is necessary to transport between the electrode and the light emitting layer through a hopping phenomenon of electrons and holes.

First, with respect to the excited state, for example, in the case of an organic EL element doped with a 5% concentration of a light emitting material, to continuously emit light for one year at a luminance of 1000 cd / m ² , simply calculate: One dopant needs to be an exciton about 1 billion times.
At this time, even if the exciton reacts with the water molecule even once, it becomes a compound different from the original molecule. Further, when an exciton reacts with an oxygen molecule, some kind of oxidation reaction or coupling reaction occurs. This is the most typical phenomenon of a chemical change that causes a decrease in the function of the organic EL element.

In addition, even in materials other than the light emitting material, a radical state is almost the same number of times, and since the radical state is an active species as compared with the ground state, a chemical change which may cause a decrease in the function of the organic EL element may occur. There is.
In other words, water molecules and oxygen molecules must not be present in the coating solution at all, which is a prerequisite.
However, industrially, high-purity anhydrous solvents are expensive and difficult to handle. Therefore, in order to reduce the cost by the coating method, it is important to use a general-purpose solvent as a consumable agent.

6. Elemental technology according to the present invention [Coating liquid]
The coating liquid of the present invention is a coating liquid containing a plurality of compounds for an organic EL device and an organic solvent, wherein at least two of the plurality of compounds for an organic EL device have an isomer relationship with each other. There is a feature.

<Compound for organic electroluminescence device>
The “compound for an organic electroluminescence element” in the present invention refers to an organic compound that can be used for an organic functional layer constituting an organic electroluminescence element (also referred to as an “organic EL element”). Also referred to as "compound for organic EL device".
Further, the “organic functional layer” in the present invention refers to a layer containing an organic EL device compound formed between electrodes in an organic EL device.
The organic functional layer (also referred to as an “organic EL layer” or an “organic compound layer”) includes at least a light-emitting layer. In a broad sense, the light-emitting layer is formed by applying a current to an electrode including a cathode and an anode. Specifically, it refers to a layer containing a compound for an organic EL device that emits light when a current is applied to an electrode composed of a cathode and an anode.
The organic EL device according to the present invention may have a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer in addition to the light emitting layer, if necessary. The structure is sandwiched between the anode. Therefore, examples of the organic functional layer include a light emitting layer, a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer.
Hereinafter, the compound for an organic EL device that can be used for each of the above-described organic functional layers will be described in detail.

(1) Compound for Organic EL Device Used in Light-Emitting Layer The compound for organic EL device used in the light-emitting layer is not particularly limited, and a conventionally known light-emitting material for an organic EL device can be used. Such a light emitting material is mainly an organic compound, and according to a desired color tone, for example, Macromol. Symp. 125, pp. 17-26. Further, the light emitting material may be a polymer material such as p-polyphenylenevinylene or polyfluorene, and a polymer material having the light emitting material introduced into a side chain or a polymer material having the light emitting material as a polymer main chain. May be used. Note that, as described above, the light-emitting material may also have a hole-injection function and an electron-injection function in addition to the light-emitting performance. Can be used.
In a layer constituting an organic EL element, when the layer is composed of two or more kinds of organic compounds, a main component is called a host and other components are called a dopant. The mixing ratio of the dopant of the light emitting layer (hereinafter also referred to as the light emitting dopant) to the host compound is preferably 0.1 to less than 30% by mass.

The dopant used for the light emitting layer is roughly classified into two types: a fluorescent dopant that emits fluorescence and a phosphorescent dopant that emits phosphorescence.
Representative examples of fluorescent dopants include, for example, anthracene derivatives, diarylamine derivatives, pyrene derivatives, perylene derivatives, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squarium dyes, oxobenzanthracene dyes, Examples include fluorescein dyes, rhodamine dyes, pyrylium dyes, stilbene dyes, polythiophene dyes, rare earth complex fluorescent materials, and other known fluorescent compounds.

It is preferable that a phosphorescent compound is contained as a material used for the light emitting layer in the present invention.
The phosphorescent compound is a compound in which light emission from an excited triplet is observed, and a compound having a phosphorescence quantum yield of 0.001 or more at 25 ° C. The phosphorescence quantum yield is preferably at least 0.01, more preferably at least 0.1. The phosphorescence quantum yield can be measured by the method described in Spectroscopy II, 4th Edition, Experimental Chemistry Lecture 7, pp. 398 (1992 edition, Maruzen). The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescent compound used in the present invention only needs to achieve the above-mentioned phosphorescence quantum yield in any of the solvents.

  The phosphorescent dopant is a phosphorescent compound, a typical example of which is preferably a complex compound containing a metal belonging to Groups 8 to 10 in the periodic table of elements, and more preferably an iridium compound or an osmium compound. , A rhodium compound, a palladium compound, or a platinum compound (platinum complex compound), among which iridium compounds, rhodium compounds, and platinum compounds are preferable, and iridium compounds are most preferable.

  Examples of the dopant include compounds described in the following documents or patent publications. J. Am. Chem. Soc. 123, 4304-4312, WO 00/70655, 01/93642, 02/02714, 02/15645, 02/44189, 02/081488, JP-A-2002-280178, JP-A-2001-181616. JP-A-2002-280179, JP-A-2001-181617, JP-A-2002-280180, JP-A-2001-247859, JP-A-2002-299060, JP-A-2001-313178, JP-A-2002-302671, JP-A-2001-345183, JP-A-2002-324679, JP-A-2002-332291, JP-A-2002-50484, JP-A-2002-332292, JP-A-2002-83684, JP-T-2002-540572, JP-A-2002-117978, JP-A-2002-338588, JP-A-2002-170684, JP-A-2002-352960, JP-A-2002-50483, JP-A-2002-100476, JP-A-2002-173684, and JP-A-2002-173684. JP-A-2002-359082, JP-A-2002-175888, JP-A-2002-363552, JP-A-2002-184581, JP-A-2003-7469, JP-T-2002-525808, JP-A-2003-7471, JP-T-2002-525833, JP-A-2003-31366, JP-A-2002-226495, JP-A-2002-234894, JP-A-2002-2335076, JP-A-2002-241751, JP-A-2001-319779. , The 2001-319780, JP same 2002-62824, JP same 2002-100474, JP same 2002-203679, JP same 2002-343572, JP same 2002-203678 Patent Publication.

Hereinafter, specific examples of the phosphorescent dopant will be described, but the present invention is not limited thereto.

  Examples of the host compound include compounds having a basic skeleton such as a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, a furan derivative, and an oligoarylene compound. Materials and hole transport materials are also suitable examples. When applied to a blue or white light-emitting element, a display device, and a lighting device, the fluorescent maximum wavelength of the host compound is preferably 415 nm or less. More preferably, the 0 band is 450 nm or less. As the luminescent host, a compound which has a hole transporting ability and an electron transporting ability, prevents a long wavelength of light emission, and has a high Tg (glass transition temperature) is preferable.

As specific examples of the light emitting host, for example, compounds described in the following documents are suitable.
JP-A-2001-257076, JP-A-2002-308855, JP-A-2001-313179, JP-A-2002-319493, JP-A-2001-357977, JP-A-2002-334786, JP-A-2002-8860, JP-A-2002-334787, JP-A-2002-15871, JP-A-2002-334788, JP-A-2002-43056, JP-A-2002-334789, JP-A-2002-75645, JP-A-2002-338579, and JP-A-2002-338579. JP-A-2002-105445, JP-A-2002-343568, JP-A-2002-141173, JP-A-2002-352957, JP-A-2002-203683, JP-A-2002-363227, JP-A-2002-231453, and JP-A-2002-231453. No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002 JP-A-302516, JP-A-2002-305083, JP-A-2002-305084, JP-A-2002-308837 and the like.

(2) Compound for organic EL device used for hole injection layer and hole transport layer The compound for organic EL device (hole injection material) used for the hole injection layer has a property of injecting holes and blocking electrons. It has either one. Further, the compound (hole transporting material) used for the hole transporting layer has a function of transporting holes to the light emitting layer while having a barrier property against electrons. Therefore, in the present invention, the hole transport layer is included in the hole injection layer. These hole injection materials and hole transport materials may be organic or inorganic.
Specifically, for example, a triazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, oxazole derivative, styryl anthracene derivative, fluorenone derivative And hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, porphyrin compounds, and conductive polymer oligomers such as thiophene oligomers. Among these, an arylamine derivative and a porphyrin compound are preferred. Among the arylamine derivatives, aromatic tertiary amine compounds and styrylamine compounds are preferable, and aromatic tertiary amine compounds are more preferable.

Representative examples of the aromatic tertiary amine compound and styrylamine compound include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N' -Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1- Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl; 1,1-bis (4-di-p- Tolaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N -Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) biphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbene; N-phenylcarbazole, and two fused aromatic rings described in U.S. Pat. No. 5,061,569. In the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as α-NPD), JP-A-4-3 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which triphenylamine units described in JP-A-08688 are connected in a three-star burst type. MTDATA), etc. In addition, inorganic compounds such as p-type Si and p-type SiC can also be used as the hole injection material.
Further, the hole transporting material of the hole transporting layer preferably has a maximum fluorescence wavelength of 415 nm or less. That is, the hole transporting material is preferably a compound having a hole transporting property, preventing a long wavelength of light emission, and having a high Tg.

(3) Compound for Organic EL Device Used for Electron Injection Layer and Electron Transport Layer The electron injection layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer. As the compound for use), any compound can be selected from conventionally known compounds and used. Examples of compounds (electron injection materials) for organic EL devices used for the electron injection layer include heterocyclic tetracarboxylic anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, and carbodiimide. , Fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like.

A series of electron-transporting compounds described in JP-A-59-194393 are disclosed as materials for forming a light-emitting layer in the publication. It turned out that it can be used as a material. Further, in the oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as the electron injecting material.
Also, metal complexes of 8-quinolinol derivatives, such as tris (8-quinolinol) aluminum (abbreviated to Alq _3.), Tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8 Quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the center metal of these metal complexes is In. , Mg, Cu, Ca, Sn, Ga or a metal complex replaced with Pb can also be used as the electron injection material.
In addition, metal-free or metal phthalocyanine or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can be preferably used as an electron injection material. Further, similarly to the hole injection layer, an inorganic semiconductor such as n-type Si or n-type SiC can be used as the electron injection material.

  The preferred compound for an organic EL device used in the electron transport layer preferably has a maximum fluorescence wavelength at 415 nm or less. That is, the compound used for the electron transporting layer is preferably a compound having an electron transporting ability, preventing a long wavelength emission, and having a high Tg.

(Compound for organic EL element in coating liquid)
In the coating liquid of the present invention, from the viewpoint of effectively obtaining the effects of the present invention, the content of the compound for a plurality of types of organic EL devices contained in the coating liquid is 0.5 to 5. It is preferably within a range of 0% by mass, and more preferably 0.7 to 3.5%.
Further, from the viewpoint of effectively obtaining the effects of the present invention, the molecular weight of the compound for an organic EL device is preferably 5,000 or less, more preferably 3,000 or less, and still more preferably 1500 or less.

Further, from the viewpoint of effectively obtaining the effects of the present invention, it is preferable that each of the plurality of types of compounds for an organic EL device contained in the coating liquid is an organic compound containing only a non-metallic element as a constituent element.
As the compound for an organic EL device, an organic compound containing only a non-metal element as a constituent element and a complex compound containing a metal element are used as a material for an organic layer. The effects of the present invention are exhibited in any of the compound groups. In particular, in the coating film (especially, in the light-emitting layer), it is preferable that the organic compound containing only the non-metal element as a main component as a constituent element is in an isomer relationship. As described above, low-molecular compounds are often designed to have an aspect ratio of 1 or more, that is, a molecular structure on a flat plate, because they are designed by combining aromatic residues that become π-conjugated units. It is known that a compound having a π-plane and a molecular structure on a flat plate generally has high crystallinity due to its π-stacking property, and tends to become a microcrystal which becomes a problem in a coating solution. For these reasons, it is preferable that the organic compound containing only the nonmetallic element as a constituent element has a compound having an isomer relation.

  Further, the complex compound having a metal element is used as a dopant in the light emitting layer in a content of less than 50% by mass, and is used alone or in combination in an organic layer other than the light emitting layer. The complex compound has a structure including a metal atom and an organic ligand bonded to the metal atom, and has various structures such as a planar type and an octahedron depending on the coordination form. For this reason, in general, when comparing an organic compound having only a nonmetal element as a constituent element with a complex compound having a metal element, the molecular weight of the complex compound in particular tends to be larger than that of the organic compound. Therefore, in the complex compound, the aggregate and crystal growth derived from the large molecular weight are promoted. Since the effect of promoting crystal growth becomes more remarkable as the content of the complex compound in the coating solution or the coating film increases, the content of the solute in the coating solution and the content in the coating film exceed 50% by mass. It is particularly preferable that the complex compound containing a metal atom has a compound in an isomer relationship.

Further, it is preferable to increase the number of types of the compound for an organic EL device in the coating solution from the viewpoint of improving the storage stability of the coating solution. That is, when the plurality of components of the solute are considered thermodynamically as described in, for example, JP-T-2009-505154, at least one compound other than the compound for an organic EL device according to the present invention and the compound for an organic EL device is used. When mixing with another kind of compound for an organic EL device, a mixed Gibbs energy (ΔG _mix ), which is a value obtained by subtracting the Gibbs energy before mixing from the Gibbs energy after mixing, can be expressed as the following equation. it can.
Formula: ΔG _mix = RTΣ (X _n ln (X _n ))
In the above formula, R represents a gas constant. T represents an absolute temperature. _Xn represents a ratio in all components.
Here, since ΣX _n = 1, 0 <X _n <1 and ΔG _mix <0 from ln (X _n ) <0. Therefore, it is considered that by increasing the number of types of the compound for an organic EL device in the coating solution, an effect of excellent preservability can be obtained.

<Isomer>
At least two of the plural kinds of compounds for an organic EL device contained in the coating solution of the present invention have an isomer relationship with each other.
The “isomer” in the present invention refers to a compound having the same molecular formula and a different structure. As such isomers, structural isomers and stereoisomers are known, but from the viewpoint of effectively obtaining the effects of the present invention, stereoisomers are preferred.
The “number of isomers” in the present invention refers to the total number of isomers that can be considered from the structural formula of the compound for an organic EL device.

In addition, it is preferable that the contents (molar ratios) of the compounds for an organic EL element having an isomer relationship are different from each other from the viewpoint of effectively obtaining the effects of the present invention.
In addition, the number of isomers of the compound for an organic EL device having an isomer relationship is preferably 3 or more from the viewpoint of effectively obtaining the effect of entropy change (ΔS) and improving the storage stability of the coating solution. Preferably, it is set to 4 or more, more preferably 5 or more. Further, since the effect of the entropy change (ΔS) increases as the number of isomers increases, the upper limit of the number of isomers is not particularly limited, but is preferably 50 or less from the viewpoint of production efficiency.
The “number of isomers” in the present invention refers to the number obtained by adding the number of isomers for each of all the compounds for an organic EL device contained in the coating solution. However, in order to sufficiently exhibit the effects of the present invention, the number of isomers of the compound for an organic EL device having a specific molecular formula is preferably 3 or more, more preferably 4 or more, and preferably 5 or more. Is more preferred. The upper limit of the number of isomers is not particularly limited, but is preferably 20 or less.
Further, from the viewpoint of allowing a larger number of isomers to be contained in the coating liquid and effectively obtaining the effect of entropy change (ΔS), it is also preferable to contain both stereoisomers and structural isomers.

<Structural isomer>
In the present invention, the relationship between compounds having the same molecular formula and represented by different structural formulas is referred to as structural isomerism, and each compound is referred to as "structural isomer".
The structural isomer that can be used in the present invention is not particularly limited. For example, in the compound for an organic EL device, the position of the substituent bonded to the aromatic ring is different between the ortho position and the para position, and the alkyl group is linear. Compounds having a morphological or branched structure, compounds in which the methylene group of the alkyl group is replaced by oxygen at a different connection position, compounds in which the connection mode of the aromatic residue is ABA or AAB, and the like. It can be preferably used.

<Stereoisomer>
In the present invention, the compounds represented by the same planar structural formula are collectively referred to as stereoisomers when the spatial configuration (configuration) of atoms or atomic groups is different from each other. "Stereoisomers". In addition, stereoisomers are generally classified into enantiomers (enantiomers) and diastereomers, and from the viewpoint of effectively obtaining the effects of the present invention, diastereomers that are easy to design with a large number of isomers are preferable.
In the number of isomers in the present invention, the twist due to the bidentate ligand in the cis-trans isomer and hexacoordinate complex (M [AB] ₃ ) derived from the isomerization of the double bond is on the left. The surrounding Λ (lambda) body and the clockwise Δ (delta) body are not included. In M [AB] ₃ , M represents a metal atom, and [AB] represents a bidentate ligand coordinated to the metal atom.
The reason for excluding the cis-trans isomer derived from isomerization of the double bond is that the isomer of the cis isomer and the trans isomer are in equilibrium, and the equilibrium (existence ratio) changes depending on the temperature and solvent. This is because it is difficult to distinguish them. As described above, the cis-trans isomer is not included in the isomer in the present invention because the abundance ratio between the coating solution and the coating film is different. The reason for excluding the Λ- and Δ-forms in the hexacoordination complex is that due to the structural similarity, the effect of suppressing the formation of aggregates or microcrystals in the coating solution does not work, and the effect of the present application is sufficiently obtained. This is because they are not available, and separation by conventional methods is difficult.

<Enantiomers and diastereomers>
As described above, at least two of the plurality of types of compounds for an organic EL device contained in the coating solution of the present invention have an isomer relationship with each other. Here, by using a functional organic compound having a chirality generating site as an isomer, the entropy change (ΔS) is increased without substantially changing the physicochemical properties of the coating solution, and the stability of the coating solution is greatly improved. It is possible to do. From such a viewpoint, it is preferable to use an enantiomer or a diastereomer as an isomer. Further, by forming a substance having the same function as much as possible from many different molecules, it becomes possible to increase the above-mentioned Gibbs free energy to minus.
Here, the enantiomers and diastereomers will be described in detail.

  The main type having the chirality generating site described above is an asymmetric carbon compound in which the most common carbon atom (or an atom having an unpaired electron, such as nitrogen, sulfur, or phosphorus) is substituted with four different substituents. (I) a molecule having a bond axis imparting rotational isomerism (atropisomer axis) such as a biaryl group having a bulky substituent at the ortho position, a so-called axially asymmetric compound (II), and an aromatic ring surface. Plane asymmetric compound (III) having a chirality generating site due to inability to fix or rotate freely, helicity compound (IV) such as helicene having a defined twist direction, and complex formation (not shown) Compounds which exhibit asymmetry in the mirror image also belong to the scope of the present invention.

Enantiomers are isomers that appear when mirrored as a relation between right and left hands, which is also called enantiomers. In addition, (III), (IV) and other substances having a chirality generating site also refer to those having a mirror image relationship, and each of them can be said to be an enantiomer relationship.

  On the other hand, a diastereomer is a molecule that is expressed when two or more chirality-generating sites are present and that are not mirror images but have the same title when a planar molecular structure is written. It can also be called a ma relationship.

  Hereinafter, specific examples of the compound having three asymmetric carbons are shown.

  In this molecule, there are eight isomers, of which four mirror image pairs are enantiomers and the others are diastereoisomers. Solid double-headed arrows represent enantiomeric relationships, and dotted double-headed arrows represent diastereomeric relationships.

  Further, specific examples of the compound having one axial chirality and one asymmetric carbon are shown below. As described above, any type of chirality can be used in combination.

  Further, in a complex having a plurality of ligands, such as a trivalent hexacoordinate iridium complex, if one ligand has chirality, a complex having a plurality of chirality results. Also produces diastereomers.

  Furthermore, even if the ligand itself does not have chirality or the possibility of its existence, complex formation causes axial asymmetry, plane asymmetry and helicity, resulting in a complex having multiple chirality. Any of them can be applied to the present invention.

<Number of isomers>
About the example of the number of isomers of the compound for organic EL elements which concerns on this invention, the number of isomers of the compound H-19, H-21, D-2, D-3, and D-4 for organic EL elements shown below are concretely shown. This will be described using an example.

  The number of stereoisomers is, for example, the compound H-19 for an organic EL device, which has two unequal axial asymmetries. Therefore, when expressed in RS notation, a total of four types of RR, SS, RS and SR are provided. There are isomers. Here, “RR and SS” and “RS and SR” are each in an enantiomeric relationship. Further, two of RS and SR have a diastereomer relationship with respect to RR, and two of RR and SS have a diastereomer relationship with RS.

  Further, as another example, the compound H-21 for an organic EL device has three non-equivalent axial asymmetries. Therefore, when expressed in RS notation, RRR, SSS, RSR, SRS, SSR, RRS , RSS and SRR in total. Here, “RRR and SSS”, “RSR and SRS”, “SSR and RRS”, and “RSS and SRR” are each in an enantiomeric relationship. Six RRRs other than SSS have a diastereomeric relationship with respect to RRR. Similarly, RSR has six diastereomers other than SRS, and the same applies to other isomers.

Further, as another example, in the case of the compound D-2 for an organic EL device, the three ligands are the same, and the steric configurations of the three ligands are represented by R and S, and RRR, SSS, There are a total of four isomers, RSS and SRR. Here, since there are three ligands, it seems that there are actually 2 ³ = 8 combinations, but since the conformation of each ligand is not distinguished, “RSS, SRR” is replaced by “SSR, RRS ”And“ RSR, SRS ”cannot be distinguished from each other, so there are a total of four types. “RRR and SSS” and “RSS and SRR” are each in an enantiomeric relationship. Further, with respect to RRR, two of RSS and SRR are in a diastereomeric relationship, and the other is also the same.

  Further, as another example, in the case of the compound D-3 for an organic EL device, although the conformation of each ligand cannot be distinguished, one ligand has three chiral centers. , RRR, SSS, RSR, SRS, SSR, RRS, RSS and SRR, there are a total of eight isomers.

  Further, as another example, in the case of the compound D-4 for an organic EL device, the bidentate ligand coordinated to the above D-4 has one non-equivalent axial asymmetry. , And the two ligands are the same, so that when expressed in RS, there are a total of four isomers of RR, SS, RS and SR. Further, the bidentate ligand coordinated to the above D-4 has one non-equivalent axial asymmetry and one chiral center. There are a total of four isomers, SS, RS and SR. Therefore, in total, 4 × 4 = 16 isomers exist.

  In the above, an example of how to count the compounds for an organic EL device has been described with reference to five compounds, but other compounds for an organic EL device can be similarly calculated.

<Organic solvent>
The organic solvent contained in the coating liquid of the present invention refers to a liquid medium composed of an organic compound capable of dissolving or dispersing the compound for an organic EL device according to the present invention.
Examples of the liquid medium for dissolving or dispersing the compound for an organic EL device according to the present invention include ketones such as dichloromethane, methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, normal propyl acetate, isopropyl acetate and isobutyl acetate, chlorobenzene, Halogenated hydrocarbons such as chlorobenzene and 2,2,3,3-tetrafluoro-1-propanol (TFPO); aromatic hydrocarbons such as toluene, xylene, mesitylene and cyclohexylbenzene; cyclohexane, decalin and dodecane; Aliphatic hydrocarbons, alcohols of n-butanol, s-butanol, t-butanol, DMF (N, N-dimethylformamide), DMSO (Dimethyl sulfoxide), tetrahydrofuran (THF), dioxane, methyl butyl ether, propylene glycol And organic solvents such as ethers such as monomethyl ether, from the viewpoint of inhibiting a solvent amount contained in the device, the boiling point is preferably a solvent in the range of 50 to 180 ° C..

In particular, in the present invention, the interaction force between the compound for an organic EL device and the organic solvent is suppressed to a certain range or less and the driving force for drying is controlled by entropy. ° C), it is preferable to use an organic solvent in the range of 0.001 to 5% by mass.
Generally, a solvent with high solubility is used to dissolve the solute, but a solvent with high solubility generally has a high boiling point, such as chlorobenzene and glycerin, and requires a large amount of energy to dry the solvent. It is. Furthermore, a high solubility indicates that the interaction with the solute material is large, and the drying load is further increased due to a large interaction force between the solute and the solvent even during drying. Also, considering the drying process, if the interaction between the solute and the solute does not overcome the interaction between the solute and the solvent, the solvent will not be removed unless the interaction between the solute and the solvent is eliminated. Will be done. As a result, in the coating film after drying, the intermolecular interaction force is very strong, the film tends to have a large particle size, and when the intermolecular interaction force is remarkable, an aggregate is observed. Often. Therefore, by setting the solubility of the compound for an organic EL device within the range of 0.001 to 5% by mass, the interaction force between the compound for an organic EL device and the organic solvent can be suppressed to a certain range or less. Can be controlled by entropy.
As such an organic solvent, among the above-mentioned organic solvents, ester solvents, ether solvents and the like are preferably used.

[Production method of coating liquid]
The method for producing the coating liquid of the present invention can be produced by dispersing a plurality of types of compounds for an organic EL device according to the present invention in the organic solvent.
The method for producing the coating liquid of the present invention is not particularly limited. It can be produced by dispersing a compound.
From the viewpoint of effectively obtaining the effects of the present invention, the method for producing a coating liquid of the present invention preferably includes a step of bringing a plurality of types of compounds for an organic EL device into contact with a supercritical or subcritical fluid.
The step of bringing into contact with a supercritical or subcritical fluid is not particularly limited, and may be a method of stirring and mixing, or a method of mixing using supercritical or subcritical chromatography. As the mixing method, among these, from the viewpoint that the step of mixing and the step of increasing the purity of the compound for an organic EL device can be performed simultaneously, a method of mixing using supercritical or subcritical chromatography. It is preferable to use
In the method of stirring and mixing, the solution used for the coating solution of the present invention is purified in advance by using a gel permeation chromatography method or the like so that the solute has a high purity, and then the solution and the supercritical or subcritical state Mixing with a fluid is preferred.
Hereinafter, the supercritical or subcritical chromatography method will be described.

<Supercritical or subcritical chromatography>
The supercritical or subcritical chromatography method can use a packed column, an open column, or a capillary column.

(Chromatography column)
The column is not particularly limited as long as it has a separating agent capable of separating the target substance in the sample injected into the mobile phase.
The separating agent is selected from various separating agents according to the target substance. The form of the separating agent is not particularly limited. For example, the column may be packed in a state of being supported on a particulate carrier, or may be stored in a column in a state of being supported on an integrated carrier stored in a column, or may be separated. It may be housed in a column as an integral molded product of the agent.

  In the method using a packed column, as shown in FIG. 3, a supercritical fluid 11 containing an organic solvent (including carbon dioxide), a pump 12, a modifier 13 if necessary, and a compound for an organic EL device to be separated are used. A device comprising an injector 14 for injection, a column 15 for separation, a detector 17 if necessary, and a pressure regulating valve 18 can be used. The temperature of the column 15 is adjusted in a column oven 16. As the filler, silica that has been used in conventional chromatography methods, surface-modified silica, or the like can be appropriately selected.

In the present invention, the supercritical fluid is a substance in a supercritical state.
Here, the supercritical state will be described. A substance transitions between three states of gas, liquid, and solid due to changes in environmental conditions such as temperature, pressure (or volume), and the like, which is determined by a balance between intermolecular force and kinetic energy. The phase diagram (phase diagram) shows the transition between the gas-liquid-solid state by taking the temperature on the horizontal axis and the pressure on the vertical axis, in which the three phases of gas, liquid, and solid coexist. Is called the triple point. If the temperature is higher than the triple point, the liquid and its vapor are in equilibrium. The pressure at this time is a saturated vapor pressure and is represented by an evaporation curve (vapor pressure line). At a pressure lower than the pressure represented by this curve, all the liquid evaporates, and when a higher pressure is applied, all the vapor liquefies. Even if the pressure is kept constant and the temperature is changed, if the temperature exceeds this curve, the liquid becomes vapor and the vapor becomes liquid. The evaporation curve has an end point on the high temperature and high pressure side, which is called a critical point. The critical point is an important point that characterizes a substance, and the boundary between gas and liquid disappears in a state where the distinction between liquid and vapor cannot be made.
In a state where the temperature is higher than the critical point, it is possible to transfer between a liquid and a gas without causing a gas-liquid coexistence state.

  A fluid that is at or above the critical temperature and at or above the critical pressure is called a supercritical fluid, and a temperature / pressure region that provides the supercritical fluid is called a supercritical region. In addition, a state satisfying either the critical temperature or higher or the critical pressure or higher is referred to as a subcritical (expanded liquid) state, and a fluid in the subcritical state is referred to as a subcritical fluid. Supercritical fluids and subcritical fluids can be understood as high-density fluids having high kinetic energy, and exhibit liquid behavior in terms of dissolving solutes and gaseous properties in terms of density variability. Although the solvent properties of supercritical and subcritical fluids are numerous, it is important that they have low viscosity, high diffusivity, and excellent permeability to solid materials.

The supercritical state is, for example, a critical temperature (hereinafter, also referred to as Tc) of 31 ° C., a critical pressure (hereinafter, also referred to as Pc) of 7.38 × 10 ⁶ Pa, and propane (Tc = 96.7) in the case of carbon dioxide. ^{℃, Pc = 43.4 × 10 5} Pa), ethylene (Tc = 9.9 ℃, Pc = 52.2 × 10 5 Pa) , etc., in the region above the fluid becomes small large and viscous diffusion coefficient material Movement and reaching concentration equilibrium are quick and the density is high like a liquid, so that efficient separation is possible. In addition, the use of a substance that becomes a gas at normal pressure and normal temperature, such as carbon dioxide, allows quick recovery. In addition, there are no various obstacles due to the unavoidable trace of solvent remaining in the purification method using a liquid solvent.

As the solvent used as the supercritical fluid or subcritical fluid, carbon dioxide, nitrous oxide, ammonia, water, methanol, ethanol, 2-propanol, ethane, propane, butane, hexane, pentane, etc. are preferably used, Among them, carbon dioxide can be preferably used.
One type of solvent used as a supercritical fluid or a subcritical fluid can be used alone, or a substance called a modifier (entrainer) for adjusting the polarity can be added.

  Examples of the modifier include hydrocarbon solvents such as hexane, cyclohexane, benzene, and toluene; halogenated hydrocarbon solvents such as methyl chloride, dichloromethane, dichloroethane, and chlorobenzene; and alcohol solvents such as methanol, ethanol, propanol, and butanol. Solvents such as acetic acid, diethyl ether, tetrahydrofuran (THF), acetal solvents such as acetaldehyde diethyl acetal, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, formic acid, acetic acid and trifluoroacetic acid Carboxylic acid solvents such as acetonitrile, pyridine, N, N-dimethylformamide, etc .; sulfur compound solvents such as carbon disulfide, dimethyl sulfoxide; and water, nitric acid, sulfuric acid, etc. And the like.

  The use temperature of the supercritical fluid or the subcritical fluid is not particularly limited as long as it is not lower than the temperature at which the compound for an organic EL device according to the present invention dissolves. The solubility in a supercritical fluid or subcritical fluid may be poor, and if the temperature is too high, the compound for an organic EL device may be decomposed, so that the operating temperature range is from 20 to 600 ° C. Is preferred.

  The working pressure of the supercritical fluid or subcritical fluid is not particularly limited as long as the pressure is basically equal to or higher than the critical pressure of the substance used. However, if the pressure is too low, the compound for the organic EL device is put into the supercritical fluid or subcritical fluid. May be poor, and if the pressure is too high, there may be a problem in terms of durability of the manufacturing apparatus, safety at the time of operation, etc., so that the working pressure is in the range of 1 to 100 MPa. Is preferred.

  The device using a supercritical fluid or subcritical fluid is not limited as long as the device has a function of dissolving the compound for an organic EL device in contact with the supercritical fluid or subcritical fluid and in the supercritical fluid or subcritical fluid. It is not performed, for example, a batch system using a supercritical fluid or subcritical fluid in a closed system, a circulation system using a supercritical fluid or a subcritical fluid to circulate, a combination of a batch system and a circulation system It is possible to use a method or the like.

In the supercritical or subcritical chromatography method according to the present invention, after injecting the sample into the mobile phase, of the target substance, the tailing of the peak of the target substance, the elution of which is the slowest elution from the column, before the end of the following, before the end of the attenuation, Preferably, sample injection is performed.
At this time, after injecting the sample into the mobile phase, the composition of the mobile phase may be changed or the composition may be fixed. In particular, when performing a fractionation operation of a large number of compounds to be separated, it is preferable to change the composition of the mobile phase.

  The step of changing the composition of the mobile phase is to change the composition of the mobile phase containing a supercritical fluid or a subcritical fluid and a solvent. By changing the composition of the mobile phase in this step, the tailing of the peak can be attenuated faster. In column adsorption supercritical or subcritical chromatography, particularly when a preparative operation is performed in which a relatively large amount of a compound to be separated is loaded, peaks show remarkable tailing. If the next sample is injected before the tailing is attenuated, the tailing component will be mixed into the peak component of the next injected sample, which will lower the purity of the separated compound and cause inconvenience. Therefore, after the tailing has completely attenuated, the next sample injection must be performed. Therefore, the timing of the next sample injection can be accelerated by accelerating the tailing decay, but in the present invention, by changing the composition of the mobile phase, the extrusion of the peak component from the column is promoted, and the tailing is accelerated. Can be accelerated.

Changing the composition in the mobile phase produces the same effect as in the step gradient method in liquid chromatography, and promotes the extrusion of peak components from the column, thereby speeding up the tailing decay.
Since supercritical or subcritical chromatography uses a supercritical fluid or subcritical fluid with high diffusivity and low viscosity, the flow rate of the mobile phase is large and the equilibration of the column is fast. Therefore, even if the composition in the mobile phase changes temporarily, when the composition in the mobile phase is restored, the column quickly restores to the environment before the change, and the next sample immediately after tailing is attenuated. Can be injected. As a result, it is possible to increase the throughput of the sample per time, thereby improving efficiency and productivity.

The step of changing the composition of the mobile phase of the present invention may be performed by any method as long as it can be performed by a supercritical or subcritical chromatography apparatus. For example, the composition of the mobile phase can be changed by increasing the solvent ratio in the mobile phase, and the CO ₂ density in the mobile phase can be changed by significantly changing the pressure or the column temperature. And the change in the composition of the mobile phase.

  Although the mobile phase already contains a solvent, a solvent injection device is installed upstream of the column and downstream of the mobile phase generator separately from the solvent to be included in the mobile phase to increase the solvent ratio in the mobile phase. Can be done. The solvent injection device may be, for example, a solvent injection device including a loop pipe for holding a solvent to be injected, a flow path switching valve, and a solvent injection pump.

  The loop pipe used for the solvent injection device is a pipe having a predetermined volume. It is preferable to have a loop pipe because the quantitativeness of sample injection can be improved and a larger amount of sample can be injected. In the present invention, the volume of the loop pipe varies depending on conditions such as the type of column and the inner diameter of the column used in the supercritical or subcritical chromatography apparatus, the type of the target substance, the composition of the mobile phase, etc. Since it is necessary to inject a large amount of solvent, the loop pipe of the solvent injection apparatus is larger than the loop pipe of the sample injection apparatus, and is suitable to hold a large amount of solvent.

  The flow path switching valve used in the solvent injection device is not particularly limited as long as it is an openable / closable valve or cock provided in the mobile phase flow path. For example, a valve that uses a combination of a two-way valve and a butterfly valve, or switches a mobile phase flow path using a three-way valve is used. As the solvent injection pump used for the solvent injection device, a high-pressure pump used for sample injection of a supercritical or subcritical chromatography device can be used.

  When a solvent injection device is used, the solvent is injected by switching the flow path switching valve and sending the solvent to the mobile phase of the column by the solvent injection pump. In the solvent injection, it is preferable to instantaneously inject a solvent having a volume equal to or more than the sample injection volume, preferably twice or more, more preferably five times or more. As the upper limit, it is preferable to inject a solvent 30 times or less, preferably 20 times or less, more preferably 15 times or less the sample injection volume. By adopting such a solvent injection amount, the tailing of the peak is attenuated more quickly.

The solvent injected from the solvent injection device is not particularly limited, and may be, for example, the same solvent as the solvent contained in the mobile phase or a different solvent. The solvent to be injected may be one kind or two or more kinds.
In particular, a solvent having high polarity is preferable from the viewpoint of further facilitating tailing attenuation. Further, it is preferable to use a solvent having a higher polarity than the solvent contained in the mobile phase.

  Both the step of changing the composition of the mobile phase and the step of returning the composition of the mobile phase to the state before the change are preferably performed instantaneously. Here, the instant may be any time sufficient to cause a change in the mobile phase.

  Although there is no particular limitation on the method of peak detection, timing can be usually measured by a peak detected by a detector included in supercritical or subcritical chromatography, for example, an ultraviolet absorption spectrometer.

<Dry solidification process>
The drying and solidifying step is a step of applying the coating liquid obtained in the coating liquid preparation step and drying and solidifying the coating liquid.
Examples of the method of applying the coating liquid (method of forming a coating film) include a spin coating method, a casting method, an inkjet method, a spray method, a printing method, a slot coater method, and the like. From the viewpoint that a uniform film is easily obtained, and it is difficult to generate pinholes, preferably, an inkjet method, a spray method, a printing method, a coating method such as a slot type coater method, and among them, more preferably an inkjet method. It is preferable to use the method.

<Inkjet method>
The inkjet head used in the inkjet method may be an on-demand type or a continuous type. In addition, as a discharge method, an electric-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shared mode type, a shared wall type, etc.), an electric-thermal conversion method (for example, thermal Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (eg, an electric field control type, a slit jet type, etc.), and a discharge type (eg, a spark jet type, etc.). However, any discharge method may be used. As a printing method, a serial head method, a line head method, or the like can be used without limitation.

  The volume of the ink droplet ejected from the head is preferably in the range of 0.5 to 100 pL. It is more preferable that the thickness be in the range of 2 to 20 pL from the viewpoint of reducing coating unevenness and increasing the printing speed. In addition, the volume of the ink droplet can be appropriately adjusted by adjusting the applied voltage or the like.

  The printing resolution is preferably in the range of 180 to 10000 dpi (dots per inch), more preferably in the range of 360 to 2880 dpi, and can be appropriately set in consideration of the wet film thickness, the volume of ink droplets, and the like.

  In the present invention, the wet film thickness of the wet coating film at the time of inkjet coating (immediately after coating) can be appropriately set, but is preferably in the range of 1 to 100 μm, more preferably 1 to 30 μm, and most preferably 1 to 30 μm. In the range of ５5 μm, the effect of the present invention is more remarkably exhibited. The wet film thickness can be calculated from the application area, the printing resolution, and the volume of the ink droplet.

Ink jet printing methods include a one-pass printing method and a multi-pass printing method.
The one-pass printing method is a method of printing a predetermined print area by one head scan. On the other hand, the multi-pass printing method is a method of printing a predetermined print area by a plurality of head scans.
In the one-pass printing method, it is preferable to use a wide head in which nozzles are juxtaposed over the width of a desired coating pattern. When a plurality of independent application patterns whose patterns are not continuous with each other are formed on the same base material, a wide head having at least the width of each application pattern may be used.

  In the drying and solidifying step, the interaction force between the solute (compound for the organic EL device) and the solvent (organic solvent) is suppressed to a certain range or less and the driving force for drying is controlled by entropy. It is preferable to use an organic solvent having a solubility of the compound for an element in the range of 0.001 to 5% by mass at normal temperature (25 ° C.).

[Organic EL device]
The organic EL device of the present invention includes a coating film obtained by drying and solidifying the coating solution of the present invention as an organic functional layer.
The organic EL element has an anode, a cathode, and one or more organic functional layers (also referred to as an “organic EL layer” and an “organic compound layer”) sandwiched between these electrodes on a substrate. .

(substrate)
The substrate (hereinafter, also referred to as a base, a support substrate, a base, a support, or the like) that can be used for the organic EL element according to the present invention is not particularly limited, and a glass substrate, a plastic substrate, or the like can be used. And may be transparent or opaque. When light is extracted from the substrate side, the substrate is preferably transparent. As a transparent substrate preferably used, glass, quartz and a transparent plastic substrate can be exemplified.
Further, as a substrate, in order to prevent oxygen and water from entering from the substrate side, in a test according to JIS Z-0208, the thickness is 1 μm or more and the water vapor transmission rate is 1 g / (m ² · 24 h · atm. ) (25 ° C.) or lower.

  Specific examples of the glass substrate include non-alkali glass, low alkali glass, soda lime glass, and the like. Alkali-free glass is preferred from the viewpoint of low water absorption, but any of these may be used as long as it is sufficiently dried.

2. Description of the Related Art Plastic substrates have attracted attention in recent years because they are highly flexible, lightweight and hard to break, and can further reduce the thickness of organic EL elements.
The resin film used as the base material of the plastic substrate is not particularly limited. For example, polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, and cellulose triacetate (TAC) ), Cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose esters such as cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate , Norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone PES), polyphenylene sulfide, polysulfones, polyetherimides, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, may be mentioned organic-inorganic hybrid resin.
Examples of the organic-inorganic hybrid resin include those obtained by combining an organic resin and an inorganic polymer (eg, silica, alumina, titania, zirconia, etc.) obtained by a sol-gel reaction. Among these, a norbornene (or cycloolefin) resin such as ARTON (manufactured by JSR Corporation) or Apel (manufactured by Mitsui Chemicals, Inc.) is particularly preferable.

  A plastic substrate that is usually produced has a relatively high moisture permeability, and sometimes contains moisture inside the substrate. Therefore, when such a plastic substrate is used, it is preferable that a film (hereinafter, referred to as a “barrier film” or a “water vapor sealing film”) be provided on a resin film to suppress invasion of water vapor, oxygen, and the like.

The material constituting the barrier film is not particularly limited, and an inorganic or organic film, a hybrid of both, or the like is used. A film may be formed, and the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 0.01 g / ( preferably m ² · 24h) or less of the barrier film, and further, the measured oxygen permeability by the method based on JIS K 7126-1987 ^{is, 1 × 10 -3 mL / (} m 2 · 24h · atm) or less, the water vapor permeability is preferably ^{1 × 10 -5 g / (m} 2 · 24h) or less of the high barrier film.

The material constituting the barrier film is not particularly limited as long as it has a function of suppressing intrusion of those that cause deterioration of the element such as moisture and oxygen, and examples thereof include metal oxides, metal oxynitrides, and metal nitrides. An inorganic material, an organic material, a hybrid material of both, or the like can be used.
Metal oxides, metal oxynitrides or metal nitrides include metal oxides such as silicon oxide, titanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), aluminum oxide, and metal nitrides such as silicon nitride. And metal oxynitrides such as silicon oxynitride and titanium oxynitride.
In order to further improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and a layer made of an organic material. The order of laminating the inorganic layer and the organic layer is not particularly limited, but it is preferable that both layers are alternately laminated plural times.

The barrier film has a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) measured by a method according to JIS K 7129-1992. The following barrier film is preferable, and the oxygen permeability measured by a method based on JIS K 7126-1987 is 1 × 10 ⁻³ mL / (m ² · 24 h · atm) or less, the permeability is preferably ^{1 × 10 -5 g / (m} 2 · 24h) or less of the high barrier film.

The method of providing the barrier film on the resin film is not particularly limited, and any method may be used. For example, a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method Method, plasma polymerization method, atmospheric pressure plasma polymerization method, CVD method (chemical vapor deposition: for example, plasma CVD method, laser CVD method, thermal CVD method, etc.), coating method, sol-gel method and the like can be used. . Among these, a method by plasma CVD at or near atmospheric pressure is preferable because a dense film can be formed.
Examples of the opaque substrate include metal plates such as aluminum and stainless steel, films and opaque resin substrates, and ceramic substrates.

(anode)
As the anode of the organic EL device, a material having a large work function (4 eV or more), a metal, an alloy, an electrically conductive compound of a metal, or a mixture thereof is preferably used.
Here, the “metal conductive compound” refers to a compound of a metal and another substance having electrical conductivity, and specifically, for example, a metal oxide, a halide, or the like. Having electrical conductivity.

Specific examples of such an electrode material include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. The anode can be manufactured by forming a thin film made of these electrode materials on the substrate by a known method such as evaporation or sputtering.
Further, a pattern of a desired shape may be formed on the thin film by a photolithography method, and when pattern accuracy is not required much (about 100 μm or more), a desired shape is formed at the time of vapor deposition or sputtering of the electrode material. The pattern may be formed via a mask.
When taking out light emission from the anode, it is desirable to make the transmittance higher than 10%. The sheet resistance as an anode is several hundred Ω / sq. The following is preferred. Further, the thickness of the anode is selected in the range of usually 10 nm to 1 μm, preferably 10 to 200 nm, although it depends on the constituent material.

(Organic functional layer)
The organic functional layer (also referred to as an “organic EL layer” or an “organic compound layer”) includes at least a light-emitting layer. In a broad sense, the light-emitting layer is formed by applying a current to an electrode including a cathode and an anode. Specifically, it refers to a layer containing an organic compound which emits light when a current is applied to an electrode composed of a cathode and an anode.
The organic EL device according to the present invention may have a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer in addition to the light emitting layer, if necessary. The structure is sandwiched between the anode.
In particular,
(I) anode / light-emitting layer / cathode (ii) anode / hole injection layer / light-emitting layer / cathode (iii) anode / light-emitting layer / electron injection layer / cathode (iv) anode / hole-injection layer / light-emitting layer / electron Injection layer / cathode (v) anode / hole injection layer / hole transport layer / emission layer / electron transport layer / electron injection layer / cathode (vi) anode / hole transport layer / emission layer / electron transport layer / cathode, etc. The structure of is mentioned.
Further, a cathode buffer layer (eg, lithium fluoride) may be inserted between the electron injection layer and the cathode, and an anode buffer layer (eg, copper phthalocyanine, etc.) may be inserted between the anode and the hole injection layer. ) May be inserted.

(Light emitting layer)
The light-emitting layer according to the present invention is an electrode or an electron-transport layer, a layer that emits light by recombination of electrons and holes injected from the hole-transport layer, and a light-emitting portion is in the light-emitting layer. May be the interface between the light emitting layer and the adjacent layer. The light-emitting layer may be a layer having a single composition, or may have a laminated structure including a plurality of layers having the same or different compositions.
The light emitting layer itself may have functions such as a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer. That is, (1) an injection function capable of injecting holes from the anode or the hole injection layer and injecting electrons from the cathode or the electron injection layer when the electric field is applied to the light emitting layer; At least one of a transport function of transferring electric charges (electrons and holes) by the force of an electric field, and (3) a light-emitting function of providing a field of recombination of electrons and holes inside the light-emitting layer and connecting the same to light emission. A function may be provided. Note that the light-emitting layer may have a difference between the ease with which holes are injected and the ease with which electrons are injected, and may have a large or small transport function represented by the mobility of holes and electrons. It is preferable to have a function of transferring at least one of the charges.

Specific examples of the light-emitting material used in the light-emitting layer have already been described in “(1) Compound for organic EL element used in light-emitting layer”, and thus are omitted here.
Note that the light-emitting dopant used in the light-emitting layer may be only one kind described above, or a plurality of kinds may be used. By simultaneously extracting light from these plural kinds of dopants, a plurality of light emission maximum wavelengths may be obtained. A light emitting element having Further, for example, both a phosphorescent dopant and a fluorescent dopant may be added. When an organic EL device is formed by laminating a plurality of light-emitting layers, the light-emitting dopants contained in each layer may be the same or different, or may be a single type or a plurality of types. .
Further, a polymer material in which the light emitting dopant is introduced into a polymer chain or a polymer material in which the light emitting dopant is a polymer main chain may be used.
The light emitting dopant may be dispersed throughout the layer containing the host compound or may be partially dispersed. A compound having another function may be further added to the light emitting layer.

(Hole injection layer and hole transport layer)
Specific examples of the materials used for the hole injection layer and the hole transport layer have already been described in the above-mentioned “Compounds for Organic EL Devices Used for Hole Injection Layer and Hole Transport Layer”, and will not be described here.
The hole injecting layer and the hole transporting layer may be formed by coating the hole injecting material and the hole transporting material with, for example, a vacuum deposition method, a spin coating method, a casting method, an LB method, an inkjet method, a transfer method, a printing method, and the like. It can be formed by thinning by the method described above. The thickness of the hole injection layer and the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm. The hole injection layer and the hole transport layer may each have a single-layer structure composed of one or more of the above materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. Is also good. When both the hole injection layer and the hole transport layer are provided, different materials are usually used among the above materials, but the same material may be used.

(Electron injection layer and electron transport layer)
Specific examples of the materials used for the electron injection layer and the electron transport layer have already been described in the above “compounds for organic EL devices used for the electron injection layer and the electron transport layer”, and will not be described here.
The electron injection layer is formed by thinning the electron injection material by a known method such as a vacuum evaporation method, a spin coating method, a casting method, an LB method, an inkjet method, a transfer method, and a printing method. Can be.
The thickness of the electron injection layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. The electron injection layer may have a single-layer structure composed of one or more of these electron-injection materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
In this specification, among the electron injection layers, when the ionization energy is higher than that of the light emitting layer, the electron injection layer is particularly referred to as an electron transport layer. Therefore, in the present specification, the electron transport layer is included in the electron injection layer.
The electron transport layer is also called a hole blocking layer (hole blocking layer), and examples thereof include, for example, WO2000 / 70655, JP-A-2001-313178, JP-A-11-204258, No. 11-204359, and the description in page 237 of “Organic EL Device and Its Forefront of Industrialization” (published by NTT Corporation on November 30, 1998). In particular, in a so-called “phosphorescent light-emitting element” using an ortho-metal complex-based dopant for the light-emitting layer, it is preferable to adopt a configuration having an electron transport layer (hole blocking layer) as described in (v) and (vi) above.

(Buffer layer)
A buffer layer (electrode interface layer) may be present between the anode and the light emitting layer or the hole injection layer and between the cathode and the light emitting layer or the electron injection layer. The buffer layer is a layer provided between an electrode and an organic layer for lowering driving voltage and improving luminous efficiency. “The organic EL device and the forefront of industrialization thereof (November 30, 1998, published by NTT )), Vol. 2, Chapter 2, “Electrode Materials” (pages 123 to 166), and includes an anode buffer layer and a cathode buffer layer.
The details of the anode buffer layer are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. Specific examples thereof include a phthalocyanine buffer layer represented by copper phthalocyanine, and vanadium oxide. And a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
The details of the cathode buffer layer are also described in JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586. Specifically, a metal buffer layer represented by strontium, aluminum, or the like; Examples thereof include an alkali metal compound buffer layer represented by lithium fluoride, an alkaline earth metal compound buffer layer represented by magnesium fluoride, and an oxide buffer layer represented by aluminum oxide.
The buffer layer is preferably a very thin film, and its thickness is preferably in the range of 0.1 to 100 nm, depending on the material. Further, in addition to the above-mentioned basic constituent layers, layers having other functions may be appropriately laminated as needed.

(cathode)
As described above, as a cathode of an organic EL device, a metal having a small work function (less than 4 eV) (hereinafter, referred to as an electron injecting metal), an alloy, an electrically conductive compound of a metal, or a mixture thereof is generally used as an electrode material. Things are used.
Specific examples of such electrode materials include sodium, magnesium, lithium, aluminum, indium, rare earth metals, sodium-potassium alloys, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / Aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, and the like.

In the present invention, those listed above may be used as the electrode material of the cathode, but from the viewpoint of more effectively exhibiting the effects of the present invention, the cathode may contain a Group 13 metal element. preferable. That is, in the present invention, the cathode surface is oxidized with oxygen gas in a plasma state as described later to form an oxide film on the cathode surface, thereby preventing further oxidation of the cathode and improving the durability of the cathode. Can be done.
Therefore, the electrode material of the cathode is preferably a metal having a preferable electron injecting property required for the cathode, and a metal capable of forming a dense oxide film.

Specific examples of the cathode electrode material containing the Group 13 metal element include aluminum, indium, a magnesium / aluminum mixture, a magnesium / indium mixture, and an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture. And a lithium / aluminum mixture. The mixing ratio of each component of the mixture can be a conventionally known ratio for a cathode of an organic EL element, but is not particularly limited thereto. The cathode can be manufactured by forming a thin film of the electrode material on the organic compound layer (organic EL layer) by a method such as evaporation or sputtering.
The sheet resistance as a cathode is several hundred Ω / sq. The following is preferred, and the film thickness is usually selected in the range of 10 nm to 1 μm, preferably 50 to 200 nm. Note that it is preferable that one of the anode and the cathode of the organic EL element be transparent or translucent in order to transmit emitted light, because the luminous efficiency is improved.

[Method of Manufacturing Organic EL Element]
As an example of a method for manufacturing an organic EL device according to the present invention, a method for manufacturing an organic EL device including an anode / a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer / an electron injection layer / a cathode will be described.
First, a thin film made of a desired electrode material, for example, a material for an anode is formed on an appropriate substrate by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode. I do. Next, an organic compound thin film such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer is formed thereon.
As described above, as a method of thinning these organic compound thin films, there are a spin coating method, a casting method, an ink jet method, a vapor deposition method, a printing method, etc., but a uniform film is easily obtained, and a pinhole is formed. A vacuum deposition method or a spin coating method is preferred from the viewpoint of difficulty in generation.

Further, a different film formation method may be applied to each layer. The case of employing an evaporation method in the deposition, the deposition conditions may vary due to kinds of materials used, generally boat temperature 50 to 450 the degree of vacuum ¹⁰ -6 ^{to 10} -2 Pa, the deposition rate 0.01 It is desirable to appropriately select a temperature within a range of 50 nm / sec to 50 nm / sec, a substrate temperature of -50 to 300 ° C., and a thickness of 0.1 nm to 5 μm.
After forming these layers, a thin film made of a material for a cathode is formed thereon by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in a range of 50 to 200 nm, and a cathode is provided. As a result, a desired organic EL device is obtained. It is preferable that the organic EL element is manufactured from the hole injection layer to the cathode consistently by one evacuation, but it may be taken out and subjected to a different film forming method. At that time, it is necessary to consider that the operation is performed in a dry inert gas atmosphere.

[Sealing of organic EL element]
The sealing means of the organic EL element is not particularly limited. For example, after sealing the outer peripheral portion of the organic EL element with a sealing adhesive, a sealing member is formed so as to cover the light emitting region of the organic EL element. There is a method of arranging.

  Examples of the sealing adhesive include photo-curing and thermosetting adhesives having a reactive vinyl group of acrylic acid-based oligomer and methacrylic acid-based oligomer, and moisture-curable adhesives such as 2-cyanoacrylate. Can be mentioned. Further, a heat and chemical curing type (two-liquid mixing) of an epoxy type or the like can be used. In addition, hot melt type polyamide, polyester, and polyolefin can be used. In addition, a cation-curable ultraviolet-curable epoxy resin adhesive can be used.

  As the sealing member, a polymer film and a metal film can be preferably used from the viewpoint of making the organic EL element thinner.

  In the gap between the sealing member and the light emitting region of the organic EL element, in addition to the sealing adhesive, an inert gas such as nitrogen or argon, a fluorinated hydrocarbon, or a silicon oil in a gas phase or a liquid phase. An inert liquid can also be injected. Further, the gap between the sealing member and the display area of the organic EL element can be evacuated, or the gap can be filled with a hygroscopic compound.

[Display device]
In the multicolor display device using the organic EL element, a shadow mask is provided only when the light-emitting layer is formed, and the other layers are common. Therefore, patterning such as a shadow mask is unnecessary. The film can be formed by a method, an inkjet method, a printing method, or the like.
When patterning is performed only on the light emitting layer, the method is not particularly limited, but is preferably an evaporation method, an inkjet method, or a printing method. When using an evaporation method, patterning using a shadow mask is preferable.
In addition, it is also possible to reverse the manufacturing order to manufacture the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order.
When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Also, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The waveform of the applied alternating current may be arbitrary.

The multicolor display device can be used as a display device, a display, and various light emission light sources. In display devices and displays, full-color display is possible by using three types of organic EL elements emitting blue, red, and green light.
Examples of the display device and the display include a television, a personal computer, a mobile device, an AV device, a teletext display, an information display in a car, and the like. In particular, the display device may be used as a display device for reproducing a still image or a moving image, and when used as a display device for reproducing a moving image, the driving method may be either a simple matrix (passive matrix) method or an active matrix method.

Lighting sources include home lighting, interior lighting, backlights for watches and LCDs, advertising signs, traffic signals, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, and light sources for optical sensors. But not limited thereto.
Further, the organic EL device according to the present invention may be used as an organic EL device having a resonator structure.
The purpose of use of the organic EL device having such a resonator structure includes a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, a light source of an optical sensor, and the like. Not limited. In addition, laser oscillation may be used for the above purpose.

  The organic EL element according to the present invention may be used as a kind of lamp such as an illumination light source or an exposure light source, a projection device of a type for projecting an image, or a display of a type for directly recognizing a still image or a moving image. It may be used as a device (display). When used as a display device for reproducing moving images, a driving method may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more kinds of the organic EL elements of the present invention having different emission colors.

An example of a display device including the organic EL element according to the present invention will be described below with reference to the drawings.
FIG. 4 is a schematic diagram illustrating an example of a display device including an organic EL element. FIG. 2 is a schematic diagram of a display such as a mobile phone for displaying image information by light emission of an organic EL element. The display 41 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like. The control unit B is electrically connected to the display unit A, sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside, and the pixels for each scanning line are converted into an image data signal by the scanning signal. In response, the light is sequentially emitted, the image is scanned, and the image information is displayed on the display unit A.

FIG. 5 is a schematic diagram of the display unit A. The display unit A includes a wiring unit including a plurality of scanning lines 55 and data lines 56, a plurality of pixels 53, and the like on a substrate. The main members of the display unit A will be described below.
FIG. 5 shows a case where the light emitted from the pixel 53 is extracted in the direction of the white arrow (downward). The scanning lines 55 and the plurality of data lines 56 of the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a grid pattern, and are connected to the pixels 53 at orthogonal positions (details in FIG. Not shown). When a scanning signal is applied from the scanning line 55, the pixel 53 receives an image data signal from the data line 56 and emits light according to the received image data. By appropriately arranging pixels in a red region, pixels in a green region, and pixels in a blue region on the same substrate, full-color display is possible.

Next, a light emitting process of the pixel will be described.
FIG. 6 is a schematic diagram showing a circuit of a pixel. The pixel includes an organic EL element 60, a switching transistor 61, a driving transistor 62, a capacitor 63, and the like. Full-color display can be performed by using red, green, and blue light-emitting organic EL elements as the organic EL elements 60 for a plurality of pixels and juxtaposing them on the same substrate.
6, an image data signal is applied from a control unit B (not shown in FIG. 6, but shown in FIG. 4) to the drain of the switching transistor 61 via the data line 56. When a scanning signal is applied from the control unit B to the gate of the switching transistor 61 via the scanning line 55, the driving of the switching transistor 61 is turned on, and the image data signal applied to the drain is transferred to the capacitor 63 and the driving transistor 62. Transmitted to the gate.

By transmitting the image data signal, the capacitor 63 is charged according to the potential of the image data signal, and the driving of the drive transistor 62 is turned on. The driving transistor 62 has a drain connected to the power supply line 67, a source connected to the electrode of the organic EL element 60, and from the power supply line 67 to the organic EL element 60 according to the potential of the image data signal applied to the gate. Current is supplied.
When the scanning signal moves to the next scanning line 55 by the sequential scanning of the control unit B, the driving of the switching transistor 61 is turned off. However, even if the driving of the switching transistor 61 is turned off, the capacitor 63 holds the potential of the charged image data signal, so that the driving of the driving transistor 62 is kept on and the next scanning signal is applied. The light emission of the organic EL element 60 continues until this. When the scanning signal is applied next by the sequential scanning, the driving transistor 62 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 60 emits light. That is, the organic EL element 60 emits light by providing a switching transistor 61 and a driving transistor 62 as active elements for the organic EL element 60 of each of the plurality of pixels, thereby forming a plurality of pixels 53 (not shown in FIG. 6). , FIG. 5). Each organic EL element 60 emits light. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 60 may be light emission of a plurality of gradations by a multi-valued image data signal having a plurality of gradation potentials, or turning on and off a predetermined light emission amount by a binary image data signal. May be.
Further, the holding of the potential of the capacitor 63 may be continued until the next scanning signal is applied, or may be discharged just before the next scanning signal is applied.

  In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light in accordance with the data signal only when the scanning signal is scanned may be used.

  FIG. 7 is a schematic diagram of a display device using a passive matrix method. In FIG. 7, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a lattice shape so as to face each other with a pixel 53 interposed therebetween. When the scanning signal of the scanning line 55 is applied by the sequential scanning, the pixels 53 connected to the applied scanning line 55 emit light according to the image data signal. In the passive matrix method, there is no active element in the pixel 53, and the manufacturing cost can be reduced.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. Unless otherwise specified, each operation was performed at room temperature (25 ° C.). In addition, unless otherwise specified, each coating solution was prepared in a glove box under a nitrogen atmosphere without being brought into contact with the air.
The structural formulas of the compounds used in the examples are shown below. Table I shows the molecular formulas and the number of isomers of the following compounds for organic EL devices H-1 to H-21 and D-1 to D-4. The following compounds for organic EL devices H-1 to H-21 represent host compounds, and the following compounds for organic EL devices D-1 to D-4 represent dopants.

  Table I shows the molecular formula, structural isomer classification (compounds having the same alphabet have a structural isomer relationship with each other), the presence or absence of diastereomers, and the number of stereoisomers of each compound for an organic EL device. I have.

Example 1
≫Preparation of coating solution≫
[Preparation of coating liquid 1]
In a glove box filled with high-purity nitrogen, the compound for an organic EL device (H-1) was dissolved in terahydrofuran (THF, manufactured by Kanto Chemical Co., Ltd.) to a concentration of 2.0% by mass.

[Preparation of coating liquids 2 to 34]
Coating solutions 2 to 34 were prepared in the same manner as in coating solution 1, except that the compound for the organic EL device and the solvent were changed as shown in Table II below. The coating solution in which a plurality of compounds for an organic EL device were dissolved was adjusted to have the content (molar ratio) shown in Table II. The nPr acetate in Table II indicates normal propyl acetate.

[Preparation of coating liquid 35]
The solution obtained by concentrating the coating solution 1 under reduced pressure was subjected to supercritical chromatography under the following conditions, and only the portion where the peak of the compound for an organic EL device in the coating solution appeared was collected by an automatic preparative function. The obtained solution was concentrated so that the concentration of the compound for an organic EL device in the coating solution was 2.0% by mass, to obtain a coating solution 35.
In the supercritical chromatography treatment (SFC treatment), an organic solvent previously dehydrated was used as the organic solvent for the mobile phase. The solution after the SFC treatment was collected by connecting the elution portion to the inside of a glove box.

(Supercritical chromatography conditions (SFC treatment))
Equipment: Prep15 (Nippon Waters)
Column: Torus 2-PIC (particle size 5 μm, inner diameter 10.0 mm x length 150 mm)
Mobile phase: “Carbon dioxide: THF = 94: 6”
Mobile phase flow rate: 15 mL / min
Pressure: 18MPa
Temperature: 40 ° C
Detection: PDA (254 nm)

[Preparation of coating liquids 36 to 39]
In the preparation of the coating liquid 35, the coating liquid subjected to the supercritical chromatography treatment was changed from the coating liquid 1 to the coating liquids 10, 11, 18 and 21 in the same manner except that the mobile phase solvent was used as the respective coating solvent. And coating solutions 36, 37, 38 and 39 were prepared. In addition, in the supercritical chromatography treatment, only the portions where the peaks of the compounds for each organic EL element appeared in the coating solution were collected by the automatic preparative function. In the case of a coating solution containing a plurality of compounds for an organic EL device, only the portions where the peaks appeared were collected, and the collected solutions were mixed, so that the total concentration of the compound for an organic EL device in the coating solution was 2%. It concentrated so that it might be set to 0.0 mass%.

≫Evaluation of coating liquid≫
The following evaluation was performed about each coating liquid. The results are shown in Table II.
(1) Evaluation of storage stability of particle size distribution R _{1 was} obtained from the following evaluation (1-1) and R ₂ was obtained from the following evaluation (1-2), and the relative value of R ₂ when R ₁ was 100. R ₃ was calculated by the following equation, and the storage stability was evaluated according to the following criteria. Further, in the calculation of _{R 2} below (1-2), the half-width _{(R hw)} also calculates, when the half value width _{(R hw)} is 15nm or more was storability as "×". In the present invention, ◎, △, and Δ were judged to be acceptable.
Formula: R ₃ = (R ₂ / R ₁ ) × 100
：: R ₃ is 100 or more and less than 103 ：: R ₃ is 103 or more and less than 105 Δ: R ₃ is 105 or more and less than 110 ×: R ₃ is 110 or more or the half width (R _hw ) of R ₂ is 15 nm or more.

(1-1) small-angle X-ray scattering measurement and the particle size distribution analysis (calculation of _{R 1)}
Each coating solution was placed in an X-ray diffraction sample capillary (manufactured by WJM-Glas / Muller GmbH) to obtain a measurement sample. The solution sample was irradiated with X-rays using SPring-8 radiation at a wavelength of 0.1 nm. The measurement was performed using a HUBER multi-axis diffractometer, the X-ray incident angle θ was fixed at 0.2 °, and the solution sample was irradiated. The detector used a scintillation counter to set 2θ to scattered rays from 1 to 43 °. A measurement was made. From the obtained scattering diffraction data, a particle size distribution curve (horizontal axis: particle size (nm), vertical axis: distribution frequency (1 / nm)) was created using analysis software (NANO-Solver).
Specifically, in the present invention, for the gradient (slope) of the Guinier plot, using the particle size / pore size analysis software NANO-Solver manufactured by Rigaku Corporation, the pore size By performing analysis fitting, the particle size distribution of a single molecule or an aggregate thereof derived from the compound for an organic EL device in the coating film was obtained. For details of the small-angle X-ray scattering method, for example, the X-ray diffraction handbook, 3rd edition (published by Rigaku Denki Co., Ltd., 2000) can be referred to.
Further, the particle size distribution curve according to the present invention is created based on the small angle X-ray scattering measurement and analysis method, the horizontal axis is the axis representing the particle size, the vertical axis is the axis representing the frequency distribution, It is obtained by plotting the measured values of the frequency distribution with respect to the particle size and connecting the plots.
Then, the particle size corresponding to the maximum peak indicating the maximum frequency of distribution of particle size distribution in the curve at each coating solution was calculated as the particle size R _1.

(1-2) Small-angle X-ray scattering measurement and particle size distribution analysis (calculation of R ₂ and R _hw )
After keeping each coating solution in a sealed state for 30 days in an environment at a temperature of 25 ° C., a relative humidity of 3% or less and a pressure of 101325 Pa (1 atm), the same evaluation as in (1-1) was performed, and the particle size after 30 days had elapsed. I was asked to R _2. In the particle size distribution curve (horizontal axis: particle size (nm), vertical axis: distribution frequency (1 / nm)), the half width (R _hw ) of the maximum peak showing the maximum distribution frequency was calculated.

  As shown in Table II above, it was found that the coating solution of the present invention was excellent in storage stability. On the other hand, the coating liquid of the comparative example had poor storage stability.

Example 2
<< Preparation of coating film >>
[Preparation of Coating Films 2-1 (A) and 2-1 (B)]
To the coating liquid 2 obtained in Example 1, 2.0 mg (0.002% by mass) of the compound D-1 for an organic EL device was added and dissolved to obtain a coating liquid for forming a thin film.
A quartz substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. The quartz substrate was set on a spin coater, and the thin film forming coating liquid prepared above was formed by spin coating at 1500 rpm for 30 seconds, and then held at 100 ° C. for 30 minutes to form a coating film having a thickness of 40 nm. A film was formed on a quartz substrate to obtain a coating film 2-1 (A) which was a measurement sample before storage.
The residue of the coating liquid for forming a thin film is sealed, stored at a temperature of 25 ° C., a relative humidity of 3% or less and a pressure of 101325 Pa (1 atm) for 30 days, and then formed by the same film forming method as 2-1 (A). After storage, a coating film 2-1 (B) as a measurement sample was prepared.

[Production of Coated Films 2-2 (A) to 2-20 (A) and 2-2 (B) to 2-20 (B)]
In the preparation of the coating films 2-1 (A) and 2-1 (B), the same except that the coating solution obtained in Example 1 and the compound D-1 for an organic EL device were changed as shown in Table III below. Thus, coating films 2-2 (A) to 2-20 (A) which are measurement samples before storage and coating films 2-2 (B) to 2-20 (B) which are measurement samples after storage were prepared.
The compounds D-2 to D-4 for organic EL devices are hexacoordinate metal complexes having bidentate ligands, and have a structure that promotes generation of isomers in the bidentate ligand. Taking the compound D-2 for an organic EL device as an example, the number of isomers (the number of stereoisomers) in consideration of the coordination form is 4.

≫Evaluation of coating film≫
The following (1) evaluation of absolute quantum yield (hereinafter, also simply referred to as “PLQE”) and (2) evaluation of ultraviolet light resistance were performed as the preservation evaluation of each of the coating films. The results are shown in Table III.

(1) Evaluation of Coated Film According to the following method, PLQE and luminance residual ratio in a UV irradiation test using a HgXe light source were determined. As a UV irradiation test using a HgXe light source, a mercury xenon lamp UV irradiation device LC8 manufactured by Hamamatsu Photonics was used, and A9616-05 was attached to a UV cut filter.
A glass cover is placed on the coating film formed on the quartz substrate, and the light emitting surface of the irradiation fiber and the glass cover surface on the coating film are arranged horizontally. At a distance of 1 cm, the number of luminescent photons is reduced by half. Irradiated. The measurement was performed at room temperature (300K).
For the sample before storage, the number of emitted photons immediately after UV irradiation (within 30 seconds) was counted, and PLQE was determined by dividing by the number of absorbed photons.
Further, UV irradiation was continued, and the time required for reducing the number of emitted photons by half (half-time) was determined and used as an index of ultraviolet light resistance. The luminance was measured with a spectral radiance meter CS-1000 (manufactured by Konica Minolta) from an angle inclined by 45 degrees from the axis of the irradiation fiber.
For the sample after storage, PLQE and half-life were determined in the same manner as above and evaluated by the following formula.

(Evaluation of PLQE)
When the PLQE of the sample (2-1 (A) to 2-20 (A)) before storage is set to 100, the PLQE of the sample (2-1 (B) to 2-20 (B)) after storage is Relative values were calculated and evaluated according to the following criteria. In the present invention, ◎, △, and Δ were regarded as acceptable.

◎: Relative value is 95 or more and less than 100 ：: Relative value is 90 or more and less than 95 Δ: Relative value is 75 or more and less than 90 ×: Relative value is less than 75

(Evaluation of UV resistance)
Assuming that the luminance half-life of the sample (2-1 (A) to 2-20 (A)) before storage is 100, the sample (2-1 (B) to 2-20 (B)) after storage The relative value of the luminance half-life was calculated and evaluated according to the following criteria. In the present invention, ◎, △, and Δ were regarded as acceptable.

◎: Relative value is 95 or more and less than 100 ：: Relative value is 85 or more and less than 95 Δ: Relative value is 70 or more and less than 85 ×: Relative value is less than 70

As shown in the above III, the coating film of the present invention was found to be excellent in storage stability. On the other hand, the coating film of the comparative example had poor storage stability.

Example 3
≫Preparation of coating solution≫
[Preparation of coating liquid 3-1]
In a glove box filled with high-purity nitrogen, 2.0 mg of each of the compounds for organic EL devices H-1, H-8, H-14 and H-16 was added to terahydrofuran (Kanto Chemical (
2.4 g). Further, 1.7 mg of the compound D-1 for an organic EL device was added and dissolved to obtain a coating liquid 3-1 (0.4% by mass).

[Preparation of coating liquid 3-2]
In the preparation of the coating solution 3-1, the mass of each of the organic EL device compounds H-1, H-8, H-14, and H-16 was adjusted to 5.0 mg, and the organic EL device compound D-1 was used. Coating solution 3-2 (1.0% by mass) was obtained in the same manner except that the amount was 4.2 mg.

[Preparation of coating liquid 3-3]
In the above-mentioned preparation of the coating solution 3-1, the compounds H-8, H-9, and H-10 for the organic EL device are prepared.
And coating liquid 3-3 in the same manner except that H-11 was used.

[Preparation of coating solutions 3-4 to 3-9]
Coating solutions 3-4 to 3-9 were obtained in the same manner as in the preparation of coating solution 3-3, except that the total concentration (% by mass) of the compound for an organic EL device was changed as shown in Table IV. The compounds were dissolved in such a manner that the content ratio of each compound for an organic EL device was the same as that of the coating liquid 3-3.

[Preparation of coating liquid 3-10]
In the above-mentioned preparation of the coating liquid 3-3, the solvent was changed to toluene, the compound (dopant) for the organic EL device was changed to D-3, and the total concentration (% by mass) of the compound for the organic EL device was set in Table IV. The coating liquid 3-10 was obtained in the same manner except that the coating liquid was changed as shown in FIG.

[Preparation of coating solutions 3-11 and 3-12]
Coating solutions 3-11 and 3-12 were obtained in the same manner as in the preparation of coating solution 3-10, except that the total concentration (% by mass) of the compounds for organic EL devices was changed as shown in Table IV. In addition, it dissolved so that the content ratio of each compound for organic EL elements might be the same as that of the coating liquid 3-10.

≫Evaluation of coating liquid and coating film≫
<Evaluation of storage stability of coating liquid>
Each coating solution was evaluated in the same manner as in “(1) Evaluation of storage stability evaluation of particle size distribution” in Example 1 except that the storage period was changed from 30 days to 90 days. The storability of the particle size distribution was determined in the same manner as in “(1) Evaluation of storability evaluation of particle size distribution” in the evaluation of Example 1 except that the storage period was changed to 90 days as described above. R ₃ and half width (R _hw ) were calculated, and the storage stability was evaluated according to the following criteria. In the present invention, ◎, △, and Δ were regarded as acceptable. The results are shown in Table IV.
(Preservation of particle size distribution)
◎: _{R 3} is 100 or more, less than 105 ○: _{R 3} is 105 or more and less than 110 △: _{R 3} is 110 or more, 130 less ×: _{R 3} is 130 or more, or the half-width _{(R hw)} is more than 15nm

<Evaluation of storage stability of coating film>
By the following evaluation method, a film (coated film) obtained by drying and solidifying the obtained coating liquids 3-1 to 3-10 was evaluated. The coating film was produced in the same manner as in Example 2.

(Evaluation of storage stability of coating film: PLQE)
The PLQE before and after storage of the coating solution was determined in the same manner as in the PLQE in the UV irradiation test using the HgXe light source of Example 2 and evaluated by the following equation. In addition, in the same manner as in Example 2, the relative value of the PLQE of the sample after storage was calculated, assuming that the PLQE of the sample before storage was 100, and evaluated in the same manner as in Example 2. In the present invention, ◎, △, and Δ were regarded as acceptable. The results are shown in Table IV.

◎: Relative value is 90 or more and less than 100 ：: Relative value is 80 or more and less than 90 Δ: Relative value is 60 or more and less than 80 ×: Relative value is less than 60

  As shown in Table IV above, it was found that the coating solution and the coating film of the present invention had excellent storage stability. On the other hand, the coating liquid and the coating film of the comparative example were inferior in storage stability. In addition, it was found that when the compound for an organic EL device was in the range of 0.5 to 5.0% by mass based on the total amount of the coating solution, the storage stability was particularly improved.

Example 4
<< Preparation of organic EL device >>
An organic EL device having, as an organic functional layer, a film (coating film) obtained by drying and solidifying the coating solution of the present invention and a comparative example was produced by a wet film forming method. In the following examples, an organic EL element is manufactured by a spin coating method. However, the present invention is not limited to this. For example, a wet film forming method (wet coating method) such as an inkjet method, a die coating method, and a flexographic printing method. Method, a wet coating method). In the formation of the following light emitting layer, the coating liquid of the comparative example or the coating liquid of the present invention was used.

[Preparation of Organic EL Element 4-1]
After forming a first electrode layer (anode), a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode in this order on a flexible film, the organic EL is formed by sealing. Element 4-1 was produced.

(1.1) Production of flexible film having gas barrier properties As a flexible film, a polyethylene naphthalate film (manufactured by Teijin Dupont, hereinafter abbreviated as PEN) is formed on the entire surface on the side on which the first electrode is formed. Using an atmospheric pressure plasma discharge treatment apparatus having a configuration described in JP-A-2004-68143, an inorganic gas barrier film made of SiOx is continuously formed to a thickness of 500 nm on a flexible film. and oxygen permeability 0.001mL ^/ (m 2 · 24h) or less, to produce a water vapor permeability of 0.001g ^/ (m 2 · 24h) the following gas barrier properties of the flexible film.

(1.2) Formation of First Electrode Layer A 120 nm-thick ITO (indium tin oxide) film is formed on the above-prepared flexible film having gas barrier properties by sputtering, and is patterned by photolithography. Was performed to form a first electrode layer (anode).
The pattern was such that the light emitting area was 50 mm square.

(1.3) Formation of Hole Injection Layer The patterned ITO substrate was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. On this substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer Corporation, Baytron P Al 4083) to 70% with pure water at 3000 rpm for 30 seconds. After forming a film by the spin coating method, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 30 nm.

(1.4) Formation of Hole Transport Layer This substrate was transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and compound (HT-1) (Mw = 80000) as a hole transport material was converted to chlorobenzene. Was formed by spin coating at 1500 rpm for 30 seconds and then kept at 160 ° C. for 1 hour to form a hole transport layer having a thickness of 30 nm.

(1.5) Formation of light emitting layer <Coating solution for forming light emitting layer>
Compound for organic EL device: host compound (H-8) 45 parts by mass Compound for organic EL device: dopant (D-1) 9.0 parts by mass Solvent (normal propyl acetate) 2200 parts by mass Host which is a compound for organic EL device The compound (H-8) and the dopant (D-1) were dissolved in a solvent (normal propyl acetate) at the above ratio to prepare a coating solution for forming a light emitting layer. Next, the coating liquid for forming the light emitting layer was formed by spin coating at 2500 rpm for 30 seconds, and then held at 100 ° C. for 30 minutes to form a light emitting layer having a layer thickness of 40 nm. During application, a drying air was applied to the application liquid while maintaining the environmental temperature at 30 ° C.

(1.6) Formation of Electron Transport Layer Subsequently, a solution prepared by dissolving 20 mg of the compound (ET-1) in 4 mL of tetrafluoropropanol (TFP) was formed by spin coating at 1500 rpm for 30 seconds. At 120 ° C. for 30 minutes to form an electron transport layer having a thickness of 30 nm.

(1.7) Formation of Electron Injection Layer and Cathode Subsequently, the substrate was attached to a vacuum evaporation apparatus without exposing it to the atmosphere. Further, a molybdenum resistance heating boat charged with lithium fluoride was attached to a vacuum evaporation apparatus, the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁵ Pa, and the boat was energized and heated to reduce lithium fluoride to 0 × 10 ⁻⁵ Pa. An electron injection layer having a thickness of 2.0 nm was formed on the electron transport layer at a rate of 0.02 nm / sec.
Next, 100 nm of aluminum was deposited to form a cathode.

(1.8) Sealing Next, as a sealing member, a polyethylene terephthalate (PET) film (12 μm thick) is bonded to a flexible aluminum foil having a thickness of 30 μm (manufactured by Toyo Aluminum Co., Ltd.) for dry lamination. A laminate (adhesive layer thickness: 1.5 μm) was prepared by using an agent (two-component reaction type urethane adhesive).
Next, the following thermosetting adhesive is used as a sealing adhesive on the aluminum (cathode) surface, and is uniformly applied to the bonding surface (gloss surface) of the sealing member with a thickness of 20 μm using a dispenser. Was applied. This was dried under vacuum of 100 Pa or less for 12 hours. Further, the film was moved to a nitrogen atmosphere having a dew point of −80 ° C. or less and an oxygen concentration of 0.8 ppm, dried for 12 hours or more, and adjusted so that the moisture content of the sealing adhesive became 100 ppm or less.
An epoxy adhesive obtained by mixing the following (A) to (C) was used as the thermosetting adhesive.
(A) Bisphenol A diglycidyl ether (DGEBA)
(B) Dicyandiamide (DICY)
(C) Epoxy adduct curing accelerator

  Next, the sealing member is closely adhered and arranged so as to cover the joint between the take-out electrode and the electrode lead. The organic EL device 4-1 was manufactured by tightly sealing at 3 m / min.

[Preparation of Organic EL Element 4-2]
The coating solution for forming the light emitting layer used in the production of the organic EL device 4-1 was sealed for 7 days at a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm). An organic EL device 4-2 was produced in the same manner as in the production of the organic EL device 4-1 except that the stored light emitting layer coating solution for forming a light emitting layer was used.

[Production of Organic EL Devices 4-3 to 4-8]
In the formation of the light emitting layer in the method for producing the organic EL device 4-1, except that the host compound and the dopant of the light emitting layer forming coating solution were changed to the compounds shown in Table V below, the light emitting layer forming coating solution was used. Similarly, organic EL elements 4-3 to 4-8 were produced.

[Preparation of Organic EL Element 4-9]
The coating solution for forming the light emitting layer used in the production of the organic EL element 4-8 was sealed for 7 days at a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm). An organic EL device 4-9 was produced in the same manner as in the production of the organic EL device 4-8, except that the stored light-emitting layer coating solution for forming a light-emitting layer was used.

[Preparation of Organic EL Element 4-10]
The coating solution for forming the light emitting layer used in the production of the organic EL element 4-8 was sealed in an environment at a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm) and stored for 14 days. An organic EL device 4-10 was produced in the same manner as the production of the organic EL device 4-8, except that the stored light emitting layer coating solution for forming a light emitting layer was used.

[Production of Organic EL Element 4-11]
In the preparation of the organic EL device 4-5, when preparing the coating solution for forming the light emitting layer, the host compound was subjected to the supercritical chromatography treatment (SFC treatment) in the coating solution 38 prepared in Example 1. The organic EL element 4-11 was manufactured in the same manner except that the coating liquid 31 was used as a mother liquor as a dopant.
In the preparation of the coating solution, the same organic EL element as the coating liquid used in the organic EL element 4-5 was obtained by mixing the host compound and the dopant at a mass ratio of 45: 9 and then concentrating the mixture. A coating solution having a content (% by mass) of the compound for use was prepared.

[Production of Organic EL Element 4-12]
The coating solution for forming a light emitting layer used in the production of the organic EL element 4-11 was sealed in an environment of a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm) and stored for 7 days. An organic EL device 4-12 was produced in the same manner as in the production of the organic EL device 4-11, except that the saved coating solution for forming a light emitting layer was used.

[Preparation of Organic EL Element 4-13]
The coating solution for forming a light-emitting layer used in the production of the organic EL element 4-11 was sealed for 14 days at a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm). An organic EL element 4-13 was produced in the same manner as in the production of the organic EL element 4-11, except that the stored coating solution for forming a light emitting layer was used.

≫Evaluation of organic EL device≫
Each of the following (1) and (2) was evaluated for the organic EL elements 4-1 to 4-13. The results are shown in Table V below.

(1) Measurement of luminescence lifetime The luminescence lifetime was measured by continuously driving each organic EL element under the conditions of room temperature 25 ° C. and humidity 35% RH, and measuring the luminance using a spectral radiance meter CS-2000. The time at which the obtained luminance reached 75% was determined as a measure of the life. The driving conditions were such that the current value was 6000 cd / m ² at the start of continuous driving. The light emission life of each organic EL element was expressed as a relative value with the light emission life of the organic EL element 4-1 (Comparative Example) being 100.

(2) Measurement of voltage change In the measurement of voltage change, the drive voltage at 5 minutes after the start of measurement was set to the initial voltage (Vs) in the measurement of the light emission lifetime, and the drive was performed at the time when the luminance was reduced to half. The voltage was calculated as the post-deterioration voltage (Vf), and evaluated by the change rate of the drive voltage obtained by the following equation.
Formula: (Change rate of drive voltage) = {(voltage after deterioration (Vf)) / (initial voltage (Vs))} × 100
Table V shows the rate of change in voltage according to the following criteria. In the present invention, "O" was regarded as "pass".
：: Change rate of drive voltage is less than 1.2 〇: Change rate of drive voltage is 1.2 or more and less than 1.5 Δ: Change rate of drive voltage is 1.5 or more and less than 2.0 ×: Drive voltage Change rate of 2.0 or more

  As shown in Table V above, it was found that the organic EL element using the coating film of the present invention had a long light-emitting life and a small change rate of the driving voltage. It was also found that the organic EL element using the coating film formed with the coating solution of the present invention after storage for 7 days or 14 days also had a long luminescent life and a small change rate of the driving voltage. On the other hand, the organic EL device using the coating film of the comparative example was inferior in any of the evaluations of the emission life and the change rate of the driving voltage.

The coating solution of the present invention is excellent in storability and excellent in storability and functionality of the coating film when dried into a coating film, so that the wet coating method can be used for an electronic device such as an organic electroluminescent element. It can be used as a coating liquid for production.
Further, the method for producing a coating liquid of the present invention can be used as a method for producing a coating liquid when producing an electronic device such as an organic electroluminescence element.
Further, the coating film of the present invention can be suitably used for an organic functional layer constituting an organic EL element or a photoelectric conversion element.

Reference Signs List 11 supercritical fluid 12 pump 13 modifier 14 injector 15 column 16 column oven 17 detector 18 pressure regulating valve A display unit B control unit 41 display 53 pixel 55 scanning line 56 data line 60 organic EL element 61 switching transistor 62 drive transistor 63 Condenser 67 Power line

Claims (7)

A coating solution containing a plurality of types of compounds for an organic electroluminescence device and an organic solvent,
A coating liquid in which at least two of the plurality of compounds for an organic electroluminescence device have an isomer relationship with each other.   2. The coating liquid according to claim 1, wherein the content (molar ratio) of each of the compounds for an organic electroluminescence element in the isomer relationship is different from each other.   The coating liquid according to claim 1, wherein the number of isomers of the compound for an organic electroluminescence element having a relationship of the isomers is 3 or more. 4.   The content of the compound for a plurality of types of organic electroluminescence devices is in the range of 0.5 to 5.0% by mass based on the total amount of the coating solution. The coating solution according to the above. A method for producing a coating liquid according to any one of claims 1 to 4, wherein
A method for producing a coating liquid, comprising a step of bringing the plurality of types of compounds for an organic electroluminescence device into contact with a supercritical or subcritical fluid.   A coating film which is a film obtained by drying and solidifying the coating solution according to any one of claims 1 to 4.   An organic electroluminescence device comprising the coating film according to claim 6 as an organic functional layer.

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