JP6879361B2 - Coating liquid, manufacturing method of coating liquid, coating film and organic electroluminescence element - Google Patents

Description

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

Organic electroluminescence devices (hereinafter, also referred to as "organic EL devices") are technologies expected for displays and lighting. The application of devices is progressing, and commercialization in display devices such as mobiles and displays is progressing.
Currently, the thin-film deposition method is the mainstream method for manufacturing organic EL devices, but since the thin-film deposition method requires a high vacuum, there is a problem 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 an alternative film forming method to the vapor deposition method. The coating method has an advantage in terms of cost as compared with the vapor deposition method, and it is technically easy to increase the area.
In general, examples of the coating type organic EL element include a coating type polymer organic EL element (see, for example, Patent Document 1) in which a polymer material is used for the light emitting layer.

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 thereof. ing.
Therefore, in recent years, a coating-type low-molecular-weight organic EL device using a low-molecular-weight material for the light emitting layer has attracted attention.

However, the coating type low molecular weight organic EL element has a problem that the driving voltage increases. The cause of this increase in drive voltage is the presence of microcrystals contained in the thin film.
Further, conventionally, the storage stability of the coating liquid or the coating film is insufficient, and there is a demand for a coating liquid and a coating film having excellent storage stability that can maintain the state in which no microcrystals are present for a long time as described above. There is.

Further, it is known that the film deposited by a general vapor deposition method and the polymer film formed by a wet process are amorphous, and the problem of the presence of microcrystals in the thin film is particularly a coating type. Low molecular weight organic EL elements are likely to cause problems.

Japanese Unexamined Patent Publication No. 6-33048

The present invention has been made in view of the above problems and situations, and the problem to be solved is that the coating film is excellent in 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 device provided with the coating film as an organic functional layer.

In order to solve the above problems, the present inventors have studied to improve the storage stability of the coating liquid from a thermodynamic point of view. Specifically, the storage stability of the coating liquid can be expressed by the magnitude of the Gibbs free energy change (ΔG) as the coating liquid from the viewpoint of thermodynamics, and the larger ΔG is, the more the coating liquid becomes. It can be said that it is stable. ΔG is expressed by the following equation, but in the present invention, as a means for increasing ΔG to a negative value, it is considered to positively utilize the effect of the entropy change (ΔS) to achieve the object.
Equation: ΔG = ΔH−TΔS

Therefore, the present inventors diligently studied based on the idea of positively utilizing the entropy change (ΔS), and found that the coating liquid contained a plurality of kinds of compounds for organic electroluminescence elements and an organic solvent. When at least two of the plurality of types of compounds for an organic electroluminescence device have an isomer relationship with each other, ΔS is increased and the coating liquid is increased with almost no change in the physicochemical properties of the coating liquid. We have found that it is possible to greatly improve the stability of the above, and have arrived at the present invention.
That is, the above-mentioned problem according to the present invention is solved by the following means.

1. 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 types of compounds for an organic electroluminescence device are isomers having an asymmetric carbon or an atropic isomer axis.
2. The coating liquid according to item 1, wherein the plurality of types of compounds for an organic electroluminescence element are organic compounds containing only non-metal elements as constituent elements.

3 . The coating solution according to Item 1, wherein the content (molar ratio) of each of the compounds for an organic electroluminescent device having an isomer relationship is different.

4 . The coating solution according to any one of items 1 to 3 , wherein the number of isomers of the compound for an organic electroluminescent device having an isomer relationship is 3 or more.

5 . Any one of the items 1 to 4 in which the content of the plurality of types of compounds for an organic electroluminescent device is in the range of 0.5 to 5.0% by mass with respect to the total amount of the coating liquid. The coating solution described in.

6 . The method for producing a coating liquid according to any one of paragraphs 1 to 5, wherein the coating liquid is produced.
A method for producing a coating liquid, which comprises a step of bringing the plurality of types of compounds for an organic electroluminescence device into contact with a supercritical or subcritical fluid.
7. The method for producing a coating liquid according to Item 6, wherein the step of contacting with the supercritical or subcritical fluid is a method of mixing using supercritical chromatography.

8 . A coating film obtained by drying and solidifying the coating liquid according to any one of items 1 to 5.

9 . An organic electroluminescence device including the coating film according to item 8 as an organic functional layer.

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

Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.

If the coating liquid containing the organic material does not change during storage, the storage stability of the coating liquid becomes infinite. Here, the storage stability of the coating liquid is determined by the change (ΔG) of the Gibbs free energy according to the second law of thermodynamics. That is, the larger this ΔG becomes negative, the more stable the film becomes, that is, the less susceptible it is to fluctuations due to disturbance requirements during use. ΔG can be expressed by the following equation by multiplying the change in enthalpy (ΔH) and the change in entropy by temperature (TΔS).
Equation: ΔG = ΔH−TΔS

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

The coating liquid of the present invention contains a plurality of types of compounds for an organic electroluminescence device (hereinafter, also referred to as "compounds for an organic EL device") and an organic solvent, and at least two of the plurality of types of compounds for an organic EL device. The species are isomers of each other. Although the isomers are different molecules, it is considered that the effect of improving the storage stability of the coating liquid could be effectively obtained by increasing the entropy change (ΔS) without changing the physicochemical properties of the coating liquid.
That is, unlike the conventional coating liquid, in the present application, a large effect is obtained by containing a combination of compounds that intentionally exerts an effect in the coating liquid.

Next, entropy will be described.
Generally, gases are completely mixed with each other. Almost any molecule is used to mix uniformly. The reason will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a change in entropy when two kinds of gases are mixed.

It is assumed that nitrogen molecules (component A) and oxygen molecules (component B) are contained in a box provided with a cutout in the center at the same density (see the left side of FIG. 1A). If this limit is removed, oxygen molecules and nitrogen molecules are completely mixed (see the right side of FIG. 1A). Since both are gases, the enthalpy is considered to be almost zero, but for example, when viewed from the nitrogen molecule, the disorder increases due to the coexistence of oxygen molecules, which are different molecules, before and after opening the limit. To do. That is, the entropy increases. Unless the temperature is absolutely 0 degrees (0K (Kelvin)), TΔS is positive, so ΔG is negative. In other words, the gas is uniformly mixed by the effect of this 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 between before opening the threshold (see the left in FIG. 1B) and after opening (see the right in FIG. 1B) because the number of different molecules does not increase and the density does not change when viewed from the nitrogen molecule. That is, in order to exert the entropy effect, it is important that different molecules coexist.

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

Although Japanese Patent Application Laid-Open No. 2014-229721 mentions behavior in a solid state and a film state, it goes without saying that the second law of thermodynamics is an idea that can be applied to all objects.

By the way, in Japanese Patent Application Laid-Open No. 2014-229721, the coating liquid is not sufficiently described, and the effect is not sufficiently disclosed.
Further, the material used for the organic EL element is usually required to have high purity, and the purity is generally 99% or more. The isomer in the present application is regarded as one kind of impurities in the case of purity determination. For example, when one kind of organic material has an optical isomer and L-form and R-form are present, one of them is present. In contrast to the optical isomer, the other optical isomer is often regarded as an impurity. Further, separation and purification of isomers including optical isomers requires a great deal of manpower, such as using a method such as GPC (gel filtration chromatography) or HPLC (liquid chromatography).
In the present invention, when purifying an organic material, a plurality of three-dimensional isomers are regarded as the same component, and the above-mentioned isomer separation and purification can be omitted. The merit is also great from the viewpoint of cost.

Further, by producing 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 containing no isomer. Was found to have low cohesiveness and better storage stability. Further, it was found that the organic EL element provided with the coating film of the present invention as an organic functional layer has excellent functionality such as a long emission life and a small change in driving voltage.
This is because the coating liquid of the present invention has excellent storage stability, and a state in which there are no microcrystals that reduce the functionality of the coating film in the coating liquid and in the coating film obtained by drying and solidifying the coating film for a long time. It is probable that it was possible to maintain it.

Schematic diagram illustrating the change in entropy when two types of gas are mixed Schematic diagram illustrating the change in entropy when two types of gas are mixed Graph showing an example of particle size distribution curve in conventional vapor deposition film and coating film Schematic of an apparatus using a packed column in a supercritical or subcritical chromatography method Schematic diagram showing an example of a display device composed of an organic EL element Schematic diagram of display unit A Schematic diagram showing a pixel circuit Schematic diagram of a passive matrix full-color display device

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

Further, as an embodiment of the coating liquid of the present invention, the content (molar ratio) of each of the compounds for an organic electroluminescence device having an isomer relationship is different from the viewpoint of effectively obtaining the effect of the present invention. Is preferable. The following is presumed as the reason for this.
In general, the crystal growth of organic matter is considered to originate from a specific association format. Specifically, one aggregate is formed, and another molecule interacts with the aggregate to increase the number of molecules of the aggregate. At this time, if the molecule that joins the aggregate is the same as the molecule that formed the original aggregate, the aggregate growth is considered to be fast, and if it is a different molecule, the aggregate growth is suppressed. It is known that such a growth model can also be applied to isomers. As an example of the former, a recrystallization optical resolution method is known, and the method is performed by adding one of the chirality crystals to a supersaturated solution. In this way, it is known that molecules having the same chirality and three-dimensional structure are aggregated and crystallized in the isomer mixture, and the content of the compound having an isomer relationship is different, so that the aggregate grows, in other words. For example, it is possible to suppress the growth of microcrystals.

Further, as an embodiment of the coating liquid of the present invention, since the effect of the entropy change (ΔS) increases as the number of isomers increases, the viewpoint of effectively obtaining the effect of the present invention by increasing the number of isomers. Therefore, it is preferable that the number of isomers of the compound for an organic electroluminescence device having an isomer relationship is 3 or more.

Further, as an embodiment of the coating liquid of the present invention, from the viewpoint of effectively obtaining the effects of the present invention, the content of the plurality of types of compounds for organic electroluminescence devices is 0.5 with respect to the total amount of the coating liquid. It is preferably in the range of ~ 5.0% by mass.

Further, in the method for producing a coating liquid of the present invention, from the viewpoint of effectively obtaining the effects of the present invention, the plurality of types of compounds for organic electroluminescence elements contained in the coating liquid of the present invention are brought into contact with a supercritical or subcritical fluid. It is preferable to have a step of causing the reaction.

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

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value. Further, in the present invention, the ratios such as "%" and "ppm" are based on mass.

[Overview of the 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 organic EL devices and an organic solvent, and at least two of the plurality of types of compounds for organic EL devices are isomers of each other. It is characterized by being.

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

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

1. 1. Superiority of low molecular weight compounds over high molecular weight compounds The superiority of low molecular weight compounds over high molecular weight compounds in the formation of organic functional layers by the wet coating method will be explained.

(First factor): Superiority of purity It is preferable to apply sublimation purification to a low molecular weight compound because it has a small molecular weight, and recrystallization also has a small molecular weight distribution and is desirable. Further, as a method for purifying a low molecular weight compound, high performance liquid chromatography (HPLC) or column chromatography having high purification efficiency can be used, which is preferable.
In most cases, the purification of high molecular weight compounds is carried out by repeating the reprecipitation method using a good solvent and a poor solvent, but the purification efficiency is low, and the low molecular weight compounds are higher from the viewpoint of the purification method. Easy to purify.
In addition, there are cases where a substituent having a 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 regarding energy level peculiar to the molecule Since the light emitting polymer (LEP) is a π-conjugated polymer when the molecular weight is increased, it is conjugated in order to stabilize the molecule. The system will be expanded, and in principle the energy level difference between the excited state of the singlet or triplet and the ground state (also referred to as "energy level gap" or "band gap") will become narrower and blue. Light emission becomes difficult. Again for the light-emitting polymer as the attempts to use as the host, (abbreviated as "high T ₁ compound".) Compounds with high triplet energy by expansion of said π-conjugated there is a problem that it is difficult to.

On the other hand, low molecular weight compounds require aromatic compound residues to be π-conjugated system units, but they can be selected arbitrarily, and they can be replaced at arbitrary positions, and these do not require extension of the conjugated system. .. Therefore, with low molecular weight compounds, the energy level difference can be intentionally adjusted, and it is possible to make a blue phosphorescent substance, to host it, or to build a compound that causes the TADF phenomenon. ..
As described above, the magnitude of extensibility at 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 weight compound.

(Third factor): Ease of compound synthesis Although it is similar to the second factor, the low molecular weight compound has no limitation on the molecular structure that can be synthesized as compared with the luminescent polymer (LEP), and has new functions and physical properties. It is possible to achieve the adjustment (Tg, melting point, solubility, etc.) by the molecular structure. This is the third factor of superiority of low molecular weight compounds.

2. Problems in Forming Organic Functional Layer by Wet Coating Method Using Low Molecular Compounds The formation of organic functional layer by wet coating method using low molecular weight compounds will be described.
In the material used for the organic EL device, electrons and holes must move by hopping between molecules inside the organic EL device. Basically, electrons are hopping along the LUMO level, and holes are hopping using the HOMO level.
That is, if adjacent molecules do not exist so that the π-conjugated systems overlap each other, such carrier conduction does not occur. Therefore, it is advantageous to form a molecular structure with only the π-conjugated system units as much as possible.
If a plurality of sterically bulky substituents (sec-butyl group, tert-octyl group, triisopropylsilyl group, etc.) are substituted into one molecule in order to improve the solubility in a solvent, the molecule The π-conjugated system between them becomes difficult to superimpose, and the hopping movement is hindered at the bulky substituent portion.

On the other hand, since the organic EL element constantly flows a current during light emission, the organic EL element continues to flow carriers even if the quantum efficiency is 100% and the heat deactivation is 0%. Therefore, it is necessary to provide a potential difference between the anode and the cathode to provide an electric current 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 higher 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.
When an organic molecule exposed to such a state exceeds its own glass transition point (Tg), it undergoes a phase transition from an amorphous state to a crystalline state.
This crystal gradually grows, and when it exceeds the layer thickness, the functions cannot be separated by the layer as an organic EL element, and as a result, the luminous efficiency is lowered.

Further, when this 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 is concentrated in the short-circuited portion, and a large current flows in a minute region, so that the organic compound in that portion undergoes thermal decomposition and a dark spot is formed.
That is, the low molecular weight compound of the organic EL device is a molecule that does not have a bulky non-aromatic substituent and has a glass transition point (Tg) of 100 ° C. or higher (preferably 150 ° C. or higher). There must be.
To construct such a molecule, the π-conjugated system is usually increased or aromatic groups are simply linked, but the solubility in a solvent is extremely low. As a result, it may not be a coating liquid, or even if it can be coated, crystal precipitation and uneven distribution of substances will occur.

As a means to solve this dilemma, we have developed an epoch-making technology that can form a stable amorphous film and retain it even during energization (for example, Japanese Patent No. 5403179 and Japanese Patent Application Laid-Open No. 5403179). 2014-196258, etc.). Specifically, it has a bulky and highly flexible branched alkyl group, and only aromatic groups are linked to form a viaaryl structure, and many conformations are formed due to rotation obstacles generated around the CC bond axis. And geometric isomers are actively increased, or multiple molecules (for example, a host and a dopant) existing in the same layer interact with each other in various shapes and morphologies in the membrane. Since the number of components can be increased, the entropy in the thin film state can be increased and a stable amorphous film can be formed.

In the production of an organic EL device by a wet coating method, the present inventors improved the molecular structure of a low molecular weight compound in accordance with the above-mentioned guidelines and optimized the drying conditions, etc., and found that the luminous efficiency was vapor deposition. A dramatic improvement was achieved, with 95% of the element and 90% of the luminous life. As a result, even devices that use phosphorescent dopants, especially blue phosphorescent dopants, which are considered to be the most difficult to improve the life of light-emitting dopants, have basic characteristics that are almost comparable to conventional vapor deposition deposition methods in the coating film formation method. I have found that I can demonstrate.
However, many problems still remain in the organic EL device whose performance has been improved in this way.

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

Further, for example, even a low molecular weight compound generally used for coating is subjected to column chromatography and recrystallization, sublimation purification, and further using or storing an organic compound in order to exhibit the highest performance. After passing through a vacuum state, the compound is replaced with a nitrogen atmosphere.
Even when the organic EL element produced by the coating method is produced under extremely strict control as described above, it is difficult to exceed the performance of the organic EL element produced by the vapor deposition method.

Furthermore, in the first place, the low productivity of the thin-film deposition method using vacuum adversely affects the cost, so the coating method is attracting attention, and the coating method is also under such strict control. If this is done, the productivity will be lower and the cost will be higher than the vapor deposition method.

3. 3. Compound purification method (sublimation purification)
The advantage of low molecular weight compounds is that they can utilize more purification means than high molecular weight compounds and can achieve high purity. 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 (the number of theoretical stages) is overwhelmingly lower than that of purification methods such as recrystallization, column chromatography, and HPLC, and it effectively removes metals and inorganic substances. It is used as a means for removing solvents.

The main reason why the sublimation purification method is adopted for organic compounds for organic EL is that the manufacturing process of the organic EL element adopts the vacuum vapor deposition method. If the organic compound contains even a very small amount of solvent, the solvent in the organic compound volatilizes when placed under vacuum in the vapor deposition apparatus, and the degree of vacuum is lowered. That makes continuous production impossible and becomes a manufacturing problem. Therefore, a sublimation purification method is adopted in which the solvent is completely removed during purification.
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 indispensable for the above reason.

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

As the distance between substances becomes shorter, the van der Waals force, hydrogen bond 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 around freely, so that the disorder increases and the entropy (ΔS) increases.
In the second law of thermodynamics, all states of existence shift toward keeping the Gibbs free energy (-ΔG) constant or increasing it.

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

On the other hand, A has an extremely large entropy (ΔS) because it can move around freely in the solution. When this high temperature solution is cooled, TΔS to which the temperature T is applied becomes smaller than that 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.
That is, as the temperature decreases and TΔS decreases, A must decrease the distance from A and increase the enthalpy. The extreme state is a crystalline state in which the distance between A and A is minimized, whereby the enthalpy term (−ΔH) increases.
As the enthalpy increases in this way, the number of components in the system decreases, so the entropy decreases, and by the amount of the decrease, crystals are formed and the enthalpy increases.

In this way, the entropy term (TΔS) decreases as the temperature decreases, and the enthalpy (−ΔH) increases due to crystallization to compensate for it, and the entropy term further increases due to the decrease in the number of components. Recrystallization is achieved by repeating the thermodynamic equilibrium in which the decrease in ΔS causes the size to decrease and crystallization occurs accordingly.
However, it should be noted that the interaction between the solute A and the solvent B. Since the solute A is dissolved by being solvated in the solvent B, A is not dissolved in B in the first place unless the interaction between A and B 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 cools and decreases (because B intervenes between A and A). The result is that recrystallization does not occur.

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

(Column chromatography)
Next, consider column chromatography (hereinafter, also referred to as "chromatography").
The most typical part of column chromatography is to use fine silica gel as a stationary phase, adsorb compound A there, and gradually elute it with a mobile phase (B) called an eluent.
At this time, when the interaction (adsorption) between the silica gel surface and the compound A is antagonized by the interaction with the mobile phase (B), A is an adsorption-desorption equilibrium between the silica gel and the mobile phase B. When the interaction with silica gel is small, it elutes quickly, and when the interaction with silica gel is large, it elutes slowly.

At this time, the larger the number of round trips between adsorption and desorption equilibrium, the greater the number of theoretical plates (that is, purification efficiency). Therefore, the purification efficiency by the chromatographic method is proportional to the length of the stationary phase and also the passing speed of the mobile phase. It will be proportional and will also be proportional to the surface area of the stationary phase.
High performance liquid chromatography has made this possible, and it is also widely used for component analysis and quality assurance of organic compounds, which is a rare method that can realize a high number of theoretical plates backed by this theory. It is due to the fact that.
The reason why this chromatographic method is superior to recrystallization is that the polarity of mobile phase B can be changed arbitrarily. For example, the number of theoretical plates can be further increased by using a gradient method in which the ratio of good solvents is gradually increased during purification, as well as the mobile phase being a mixed solvent of a good solvent and a poor solvent from the beginning.

In addition, since the temperature can be changed arbitrarily, the range of application of the solute that can be purified is extremely wide, and the greatest feature is that it can be used as an almost general-purpose purification method.
On the other hand, there are also drawbacks of the chromatographic method.
For example, when the chromatography method is performed using only the solvent B'(that is, a good solvent) that strongly interacts with the compound A in the mobile phase, the interaction between A and the mobile phase B'rather than the interaction between A and silica gel. If the action is strong, the number of round trips of the adsorption-desorption equilibrium is drastically reduced, and the purification effect is lowered.

That is, 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 adsorption-desorption equilibrium. However, in this case, the solution of the purified and separated compound A contains a large excess of C, and the biggest problem is that this 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 is used. It will be necessary. Therefore, although HPLC preparative is applied to research and development, it is not used for mass production.

A means for solving the problem of poor solvent concentration is HPLC using supercritical carbon dioxide. Supercritical carbon dioxide is a supercritical fluid made from carbon dioxide at high temperature and high pressure, and since it can realize a supercritical state at a relatively low pressure and temperature, carbon dioxide is exclusively used for 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 according to the polarity of what is desired to be melted.
For example, this supercritical carbon dioxide is also used when selectively extracting docosahexaenoic acid contained in fish heads, and when cleaning special clothing using an adhesive, the sebum is melted and adhered. Supercritical carbon dioxide, which does not dissolve, is used as the agent.

Although supercritical carbon dioxide can have various polarities in this way, the polarity of supercritical carbon dioxide formed in a region of relatively low temperature and pressure is about cyclohexane or heptane. In supercritical HPLC currently on the market, supercritical carbon dioxide of this degree of polarity is produced in the apparatus, mixed with a good solvent and entered into the column, and the compound is prepared by a mechanism similar to that of ordinary HPLC. Purification is performed.
In a column chromatography system using supercritical carbon dioxide, it enters the detector after passing through the column, but usually the high temperature and high pressure state is maintained until that stage, and carbon dioxide also exists as a supercritical fluid. After that, carbon dioxide becomes a gas until it is separated at normal temperature and pressure, and at the time of separation, it escapes from the solution by itself, so that concentration of a poor solvent becomes unnecessary. At this time, it is possible to recover carbon dioxide by a carbon dioxide recovery device equipped with a machine-liquid separation mechanism or the like described in References (Journal of the Society of Biotechnology, Vol. 88, No. 10, pp. 525-528, 2010). It can also be used as a supercritical fluid again.

Therefore, in the drug discovery industry, where it is necessary to synthesize a large number of new high-purity synthetic compounds, this supercritical HPLC has recently been actively utilized, and due to this effect, both for analysis and for preparative use. The selling price has dropped and it has become quite common.
From these characteristics and background, we have utilized this supercritical HPLC for the purification of materials for organic EL devices that require high purity (Patent No. 4389494).
As described above, while improvement in productivity in the organic EL industry is desired, there are various purification methods for low molecular weight organic compounds, but each has advantages and disadvantages, the characteristics of the produced compound, and the required purity of the compound. , Appropriate purification methods are selected and used in combination depending on the availability of residual solvent.

4. Dissolution of Organic EL Compounds First, let us consider what dissolution is. Normally, the solute A is surrounded by the solvent molecule B by the interaction force between A and B, and the aggregate of A is separated and B is present around A, that is, A is made into an isolated single molecule state. That said, it's hard to tell if it really is.
For example, when A is a molecule having extremely low solubility or high crystallinity, if it is a crystal having a size equal to or larger than the wavelength of visible light, it can be easily detected by light scattering or the like that it is not dissolved. However, for example, even if the solvent molecule B surrounds a microcrystal consisting of several molecules of A, it seems to be dissolved. For organic EL devices, this can cause major problems later.
That is, in the thin-film deposition film formation, when forming thin layers (films) such as a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, the compounds constituting each layer are basically vapor-deposited. It lands on a substrate or an organic layer in the state of a vaporized isolated single molecule, which becomes a solid thin film and is formed into a film. Therefore, basically, a film is formed by a random aggregate of single molecules, and an ideal amorphous film is obtained.

On the other hand, in the case of the coating film formation method, when the coating liquid is a dispersion of microcrystals of an organic EL compound, the actual state of the obtained thin film is microcrystals even if it seems to be completely dissolved. Is a thin film that is gathered together. Therefore, for example, the level of HOMO or LUMO is not that of a single molecule, but that of a stacked aggregate (crystal state), which may cause a decrease in performance.
In addition, over time, the microcrystals become nuclei and grow into coarse crystals, so it is not possible to separate the functions between the layers, and if it becomes a large crystal that short-circuits the anode and cathode, it becomes dark. There is a big problem of generating spots.
Regarding the coating film formation element using low molecules, from the above-mentioned many years of study, how to approximate the coating liquid in the initial state to the single molecule dispersion state is first to obtain the same performance as the vapor deposition method. It is clear that it is a requirement.

Here, it is usually analyzed by small-angle X-ray scattering measurement (also referred to as "SAXS") how much molecular dispersion the coating liquid intended to be strictly dissolved is. 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. It is a particle size distribution curve of the fine particles of the constituent compound. Since both use the same compound, they can be compared directly.
In the particle size distribution of the fine particles of the compound in the vapor deposition film formation, the particle size at the position corresponding to the maximum peak is about 2 nm, which is close to monodisperse. This means that since the size of one or two molecules is one or two, in the vapor deposition film formation, almost single molecules are randomly arranged to form an amorphous film.
On the other hand, in the particle size distribution of the fine particles of the compound 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 mentioned earlier, since the same compound is used for the vapor deposition film formation and the coating film formation, the original crystallinity and cohesiveness of the compound are the same, and this difference is due to the difference in the molecules in the state of the coating liquid. It is speculated that the dispersed state was not a single isolated molecule but a dispersion of microcrystals.
This coating liquid is a so-called clear solution, but we misunderstand the dispersion of crystallites of several molecules, which is found by analysis with X-rays, as a dissolved solution.

5. Purity of the solvent of the organic EL compound The organic EL element has a basic function of emitting light when the excited luminescent material returns to the ground state.
Further, it is necessary to transport electrons and holes from the electrode to the light emitting layer through a hopping phenomenon.

First, regarding the excited state, for example, in the case of an organic EL device doped with a light emitting material having a concentration of 5%, in order to continue emitting light for one year at a brightness of ^{1000 cd / m 2, a simple calculation is performed.} One dopant needs to be an exciton about 1 billion times.
At this time, if the exciton reacts with the water molecule even only once, it becomes a compound different from the original molecule. Moreover, when excitons react with oxygen molecules, some kind of oxidation reaction or coupling reaction occurs. This is the most typical phenomenon of chemical changes that cause functional deterioration of organic EL devices.

In addition, materials other than the luminescent material also enter the radical state about the same number of times, and since the radical state is also an active species as compared with the ground state, chemical changes that cause functional deterioration of the organic EL device may occur. There is sex.
In other words, water molecules and oxygen molecules should not be present in the coating liquid at all, which is a prerequisite.
However, industrially, a high-purity anhydrous solvent is expensive and difficult to handle. Therefore, in order to reduce the cost by the coating method, it is important how a general-purpose solvent can be used as a consumable.

6. Elementary Techniques Related to the Present Invention [Coating Liquid]
The coating liquid of the present invention is a coating liquid containing a plurality of types of compounds for organic EL devices and an organic solvent, and at least two of the plurality of types of compounds for organic EL devices have an isomer relationship with each other. It is characterized by being.

<Compounds for organic electroluminescence devices>
The "compound for an organic electroluminescence device" in the present invention refers to an organic compound that can be used in an organic functional layer constituting an organic electroluminescence device (also referred to as an "organic EL device"), and in the present invention, the "compound for an organic electroluminescence device" Also referred to as "compound for organic EL device".
Further, the "organic functional layer" in the present invention means a layer containing a compound for an organic EL element formed between electrodes in an organic EL element.
The organic functional layer (also referred to as "organic EL layer" or "organic compound layer") includes at least a light emitting layer, but in a broad sense, the light emitting layer is when an electric current is passed through an electrode composed of a cathode and an anode. Specifically, it refers to a layer containing a compound for an organic EL element that emits light when a current is passed through 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, and these layers serve as a cathode. It has a structure sandwiched between the anode and 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 compounds for organic EL devices that can be used for each of the above-mentioned organic functional layers will be described in detail.

(1) Compounds for Organic EL Devices Used in Light-emitting Layers The compounds for organic EL devices used in light-emitting layers are not particularly limited, and conventionally known light-emitting materials for organic EL devices can be used. Such light emitting materials are mainly organic compounds, and depending on the desired color tone, for example, Macromol. Symp. Examples include the compounds described in Vol. 125, pp. 17-26. Further, the light emitting material may be a polymer material such as p-polyphenylene vinylene or polyfluorene, and further, a polymer material in which the light emitting material is introduced into a side chain or a polymer material in which the light emitting material is used as a main chain of a polymer is used. You may use it. As described above, since the light emitting material may have a hole injection function and an electron injection function in addition to the light emission performance, most of the hole injection materials and electron injection materials described later can also be used as the light emitting material. Can be used.
In the layer constituting the organic EL element, when the layer is composed of two or more kinds of organic compounds, the main component is called a host, the other components are called dopants, and when the host and the dopant are used together in the light emitting layer, the main component. The mixing ratio of the dopant of the light emitting layer (hereinafter, also referred to as the light emitting dopant) with respect to the host compound is preferably 0.1 to 30% by mass by mass.

Dopants used in the light emitting layer are roughly classified into two types: a fluorescent dopant that emits fluorescence and a phosphorescent dopant that emits phosphorescence.
Typical examples of fluorescent dopants include anthracene derivatives, diarylamine derivatives, pyrene derivatives, perylene derivatives, coumarin dyes, pyrane dyes, cyanine dyes, croconium dyes, squalium dyes, and oxobenzanthracene dyes. Examples thereof include fluorescein dyes, rhodamine dyes, pyrylium dyes, stylben dyes, polythiophene dyes, rare earth complex fluorescent compounds, and other known fluorescent compounds.

The material used for the light emitting layer in the present invention preferably contains a phosphorescent compound.
The phosphorescent compound is a compound in which light emission from the excited triplet is observed, and is a compound having a phosphorescence quantum yield of 0.001 or more at 25 ° C. The phosphorus photon yield is preferably 0.01 or more, more preferably 0.1 or more. The phosphorus photon yield can be measured by the method described on page 398 (1992 edition, Maruzen) of Spectroscopy II of the 4th edition Experimental Chemistry Course 7. The phosphorescent quantum yield in a solution can be measured using various solvents, but the phosphorescent compound used in the present invention may achieve the above phosphorescent quantum yield in any of any solvents.

The phosphorescent dopant is a phosphorescent compound, and as a typical example thereof, it is preferably a complex compound containing a metal of Group 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-based compound), preferably an iridium compound, a rhodium compound, or a platinum compound, and most preferably an iridium compound.

Examples of dopants are the compounds described in the following literature or patent gazettes. J. Am. Chem. Soc. Vol. 123, pp. 4304 to 4312, WO00 / 70655, 01/93642, 02/02714, 02/15645, 02/44189, 02/081488, 2002-280178, 2001-181616 , 2002-280179, 2001-181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178, 2002-302671. 2001-345183, 2002-324679, 2002-332291, 2002-50484, 2002-332292, 2002-83648, 2002-540572, JP-A-2002-117978, No. 2002-338588, No. 2002-170684, No. 2002-352960, No. 2002-50483, No. 2002-100476, No. 2002-173674, 2002-359082, 2002-175884, 2002-363552, 2002-184582, 2003-7469, 2002-525808, 2003-7471. , Japanese Patent Application Laid-Open No. 2002-525833, JP-A-2003-31366, JP-A-2002-226495, JP-A-2002-234894, JP-A-2002-23507, JP-A-2002-241751, No. 2001-319779. Japanese Patent Publication No. 2001-319780, No. 2002-62824, No. 2002-100474, No. 2002-203679, No. 2002-343572, No. 2002-203678, etc.

Specific examples of phosphorescent dopants are given below, but the present invention is not limited thereto.

Examples of the host compound include those 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, and electron transport described later. Materials and hole transporting materials are also examples of suitable examples. When applied to a blue or white light emitting element, display device and lighting device, the fluorescence maximum wavelength of the host compound is preferably 415 nm or less, and when a phosphorescent dopant is used, 0- of the phosphorescence of the host compound is used. It is more preferable that the 0 band is 450 nm or less. As the light emitting host, a compound having hole transporting ability and electron transporting ability, preventing the wavelength of light emission from being lengthened, and having a high Tg (glass transition temperature) is preferable.

As a specific example of the light emitting host, for example, the compounds described in the following documents are suitable.
JP 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002. 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003 -3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002- 302516, 2002-305083, 2002-305084, 2002-308837, etc.

(2) Compounds for organic EL devices used in hole injection layers and hole transport layers Compounds for organic EL devices (hole injection materials) used in hole injection layers have hole injection and electron barrier properties. It has either. Further, the compound (hole transport material) used for the hole transport layer has an electron barrier property and also has a function of transporting holes to the light emitting layer. Therefore, in the present invention, the hole transport layer is included in the hole injection layer. The hole injection material and the hole transport material may be either an organic substance or an inorganic substance.
Specifically, for example, triazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, oxazole derivative, styrylanthracene derivative, fluorenone derivative. , Hydrazone derivatives, stylben derivatives, silazane derivatives, aniline-based copolymers, porphyrin compounds, thiophene oligomers and other conductive polymer oligomers. Of these, arylamine derivatives and porphyrin compounds are preferred. Among the arylamine derivatives, aromatic tertiary amine compounds and styrylamine compounds are preferable, and aromatic tertiary amine compounds are more preferable.

Typical examples of the above aromatic tertiary amine compound and styrylamine compound are 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-) Trillaminophenyl) -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] stilben; 4-N, N-diphenylamino -(2-Diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostylben; N-phenylcarbazole, as well as the two condensed aromatics described in US Pat. No. 5,061569. Those having a ring in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as α-NPD), described in JP-A-4-308688. Examples include 4,4', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) in which the triphenylamine units are linked in a three-star burst type. Further, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material.
Further, the hole transport material of the hole transport 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 ability, preventing the wavelength of light emission from being lengthened, and having a high Tg.

(3) Compounds for Organic EL Elements Used for Electron Injection Layer and Electron Transport Layer The electron injection layer may have a function of transmitting electrons injected from the cathode to the light emitting layer, and the material thereof (organic EL element). As the compound), any compound can be selected and used from conventionally known compounds. Examples of compounds for organic EL devices (electron injection materials) used in this electron injection layer include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyranjioxide derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthalene perylene, and carbodiimides. , Freolenilidene methane derivative, anthraquinodimethane and antron derivative, oxadiazole derivative and the like.

Further, 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, but as a result of examination by the present inventors, electron injection It was found that it could be used as a material. Further, among the oxadiazole derivatives, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is replaced with a sulfur atom, and a quinoxalin derivative having a quinoxalin ring known as an electron-withdrawing group can also be used as an electron injection material.
Further, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum ( _{abbreviated as Alq 3} ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-). Kinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metal of these metal complexes are In. , Mg, Cu, Ca, Sn, Ga or 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 also be preferably used as the electron injection material. Further, similarly to the hole injection layer, inorganic semiconductors such as n-type-Si and n-type-SiC can also be used as the electron injection material.

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

(Compounds for organic EL devices in coating liquid)
From the viewpoint of effectively obtaining the effects of the present invention, the coating liquid of the present invention has a content of a plurality of types of compounds for organic EL devices contained in the coating liquid of 0.5 to 5. It is preferably in the range of 0% by mass, and more preferably 0.7 to 3.5%.
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 5000 or less, more preferably 3000 or less, and further 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 organic EL elements contained in the coating liquid is an organic compound containing only a non-metal element as a constituent element.
As the compound for an organic EL element, 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 compound group. In particular, in the coating film (particularly the light emitting layer), it is preferable that an organic compound containing only a non-metal element as a main component is an isomer. As described above, since low molecular weight compounds are designed by combining aromatic residues that serve as π-conjugated units, they often have an aspect ratio of 1 or more, that is, a molecular structure on a flat plate. A compound having a π plane and a molecular structure on a flat plate is generally known to have high crystallinity due to its π stacking property, and tends to be a problematic microcrystal in a coating liquid. For these reasons, it is preferable that the organic compound containing only a non-metal element as a constituent element has a compound having an isomer relationship.

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

Further, it is preferable to increase the types of compounds for organic EL devices in the coating liquid from the viewpoint of improving the storage stability of the coating liquid. That is, when the plurality of components of the solute are considered thermodynamically as described in, for example, Japanese Patent Application Laid-Open No. 2009-505154, at least one of the compound for an organic EL element according to the present invention and the compound for an organic EL element thereof When mixing with other compounds for organic EL elements of the species, the mixed Gibbs energy (ΔG _mix ), which is the value obtained by subtracting the Gibbs energy before mixing from the Gibbs energy after mixing, can be expressed by the following formula. it can.
Formula: ΔG _mix = RTΣ (X _n ln (X _n ))
In the above equation, R represents the gas constant. Further, T represents an absolute temperature. Further, X _n represents the ratio in all the components.
Here, since ΣX _n = 1, 0 <X _n <1, and from ln (X _n ) <0, ΔG _mix <0. Therefore, it is considered that the effect of excellent storage stability can be obtained by increasing the types of the compound for the organic EL device in the coating liquid.

<Isomer>
At least two kinds of compounds for a plurality of kinds of organic EL devices contained in the coating liquid of the present invention are isomers of each other.
The "isomer" in the present invention refers to a compound having the same molecular formula but a different structure. Structural isomers and stereoisomers are known as such isomers, but from the viewpoint of effectively obtaining the effects of the present invention, stereoisomers are preferable.
Further, the "number of isomers" in the present invention means the total number of isomers that can be considered from the structural formula of the compound for an organic EL device.

Further, the content (molar ratio) of each of the compounds for an organic EL device having an isomer relationship is preferably different from the viewpoint of effectively obtaining the effect of the present invention.
Further, the number of isomers of the compound for an organic EL device having an isomer relationship may be 3 or more from the viewpoint of effectively obtaining the effect of the entropy change (ΔS) and improving the storage stability of the coating liquid. It is preferably 4 or more, more preferably 5 or more, and even 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 from the viewpoint of production efficiency, it is preferably 50 or less.
Further, the "number of isomers" in the present invention means the total number of isomers for each of all the compounds for organic EL devices contained in the coating liquid. However, in order to fully exert the effect 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, preferably 4 or more, and 5 or more. Is even more preferable. The upper limit of the number of isomers is not particularly limited, but is preferably 20 or less.
Further, from the viewpoint of containing a larger number of isomers in the coating liquid and effectively obtaining the effect of the entropy change (ΔS), it is also preferable to contain both the stereoisomer and the structural isomer.

<Structural isomer>
In the present invention, the relationships between compounds having the same molecular formula but represented by different structural formulas are referred to as structural isomers, and each compound is referred to as a "structural isomer".
The structural isomers that can be used in the present invention are not particularly limited. For example, a compound in which the position of the substituent bonded to the aromatic ring in the compound for an organic EL element is different between the ortho position and the para position, and the alkyl group is linear. Compounds with a shape or branch, compounds with different linking positions in which some methylene groups of alkyl groups are replaced with oxygen, compounds in which the linking mode of aromatic residues is ABA or AAB, etc. It can be preferably used.

<Three isomers>
In the present invention, the isomers generated by different spatial arrangements (three-dimensional arrangements) of atoms or atomic groups among compounds represented by the same planar structural formula are referred to as steric isomers, and each compound is referred to as "stereoisomer". It is called "three-isomer". 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 with a large number of isomers are preferable.
Further, in the number of isomers in the present invention, the twist due to the bidentate ligand in the cis-trans isomer and the 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 a metal atom.
The reason for excluding the cis-trans isomer derived from the isomerization of the double bond is that the cis and trans isomers are in an equilibrium relationship, and the equilibrium relationship (presence 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 in the coating liquid and the coating film is different. Further, the reason for excluding the Λ-form and the Δ-form in the hexacoordinate complex is that the effect of suppressing the formation of aggregates or microcrystals in the coating liquid does not work due to the structural similarity, and the effect of the present application can be sufficiently obtained. This is because there is no such thing and it is difficult to separate them by the conventional method.

<Enantiomer and diastereomer>
As described above, at least two kinds of compounds for a plurality of kinds of organic EL devices contained in the coating liquid of the present invention are isomers of each other. Here, by using a functional organic compound having a chirality generation site as an isomer, the entropy change (ΔS) is increased and the stability of the coating liquid is greatly improved without changing the physicochemical properties of the coating liquid. It is possible to make it. From this point of view, it is preferable to use an enantiomer or a diastereomer as the isomer. Further, by forming a substance having the same function as much as possible with a large number of different molecules, it becomes possible to negatively increase the free energy of Gibbs described above.
Here, enantiomers and diastereomers will be described in detail.

As the main type having the above-mentioned chirality generation site, an asymmetric carbon compound formed by substituting four different substituents with the most common carbon atom (or an atom having an unpaired electron, such as nitrogen, sulfur, or phosphorus). (I), a molecule having a bond axis (atorop isomer axis) that imparts rotational isomerism, such as a biaryl group having a bulky substituent at the ortho position, a so-called axis asymmetric compound (II), an aromatic ring surface. A plane asymmetric compound (III) having a chirality generation site due to its inability to fix or rotate freely, a helicity compound (IV) such as helisene in which the direction of twist is defined, and, although not shown, forming a complex. Compounds that exhibit asymmetry in the mirror image also fall within the scope of the present invention.

Enantiomers, also known as enantiomers, are isomers that are expressed when reflected in a mirror, such as the relationship between a right hand and a left hand, and this applies not only to asymmetric carbon compounds but also to type (II). Furthermore, (III), (IV) and other substances having chirality generation sites also refer to those having a mirror image relationship with each other, and each can be said to have an enantiomer relationship.

On the other hand, diastereomers are molecules that are expressed when there are two or more chirality generation sites and have the same title when writing a planar molecular structure that is not in a mirror image relationship, and each is a diastereomer. It can be said that it is a relationship of Ma.

Specific examples of compounds having three asymmetric carbons are shown below.

There are eight types of isomers in this molecule, of which four pairs that are in a mirror image relationship are enantiomeric isomers, and the others are diastereomeric isomers. The solid double-headed arrow represents the enantiomeric relationship, and the dotted double-headed arrow represents the diastereomer relationship.

Further, specific examples of compounds having one axial asymmetric and one asymmetric carbon are shown below. In this way, any combination of chirality types can be used.

Further, in a complex having a plurality of ligands, such as a trivalent 6-coordinated iridium complex, if one ligand has chirality, the result is a complex having a plurality of chirality, and of course, it. Also expresses diastereomers.

Furthermore, even if the ligand itself does not have chirality or the possibility of its existence, forming a complex causes axial asymmetry, surface asymmetry, and helicity, resulting in a complex having a plurality of chirality. Anything can be applied to the present invention.

<Number of isomers>
Regarding an example of the number of isomers of the compound for an organic EL device according to the present invention, the number of isomers of the compounds for organic EL devices H-19, H-21, D-2, D-3, and D-4 shown below is specified. Let's take an example.

For example, the number of steric isomers of the compound H-19 for an organic EL device has two non-equivalent axial asymmetry. Therefore, when expressed in RS notation, there are a total of four types of RR, SS, RS and SR. There is an isomer. Further, here, "RR and SS" and "RS and SR" are in an enantiomeric relationship, respectively. Further, RS and SR have a diastereomer relationship with RR, and RR and SS have a diastereomer relationship with RS.

Further, as another example, since the compound H-21 for an organic EL device has three non-equivalent axial asymmetry, when expressed in RS notation, RRR, SSS, RSR, SRS, SSR, RRS , RSS and SRR, a total of eight isomers exist. Further, here, "RRR and SSS", "RSR and SRS", "SSR and RRS", and "RSS and SRR" are in an enantiomeric relationship, respectively. In addition, six other than SSS have a diastereomer relationship with RRR. Similarly, six other than SRS have a diastereomeric relationship with RSR, 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 when the configuration of the three ligands is represented by R and S, RRR, SSS, There are a total of four isomers, RSS and SRR. Since the ligand is three, actually seems also to have 2 ^{3 =} 8 combinations, they do not distinguish conformation of the ligand "RSS, SRR" are "SSR, RRS "And" RSR, SRS "cannot be distinguished from each other, so there are a total of four types. In addition, "RRR and SSS" and "RSS and SRR" are in an enantiomeric relationship, respectively. In addition, RSS and SRR have a diastereomer relationship with RRR, and the same applies to the others.

Further, as another example, in the case of compound D-3 for an organic EL element, the conformation of each ligand cannot be distinguished, but since one ligand has three chiral centers, RS notation is used. , RRR, SSS, RSR, SRS, SSR, RRS, RSS and SRR, a total of eight isomers exist.

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

In the above, five compounds have been shown and described as examples of how to count the compounds for organic EL devices, but other compounds for organic EL devices can be calculated in the same manner.

<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 and di. Chlorobenzene, halogenated hydrocarbons such as 2,2,3,3-tetrafluoro-1-propanol (TFPO), aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, cyclohexane, decalin, dodecane and the like. Alcohols of aliphatic hydrocarbons, n-butanol, s-butanol, t-butanol, DMF (N, N-dimethylformamide), DMSO (Dimethyl sulfoxide), tetrahydrofuran (THF), dioxane, methylbutyl ether, propylene glycol monomethyl ether Examples thereof include organic solvents such as ethers such as, and a solvent having a boiling point in the range of 50 to 180 ° C. is preferable from the viewpoint of suppressing the amount of the solvent contained in the device.

In particular, in the present invention, the interaction force between the compound for the organic EL device and the organic solvent is suppressed to a certain range or less, and the driving force for drying is controlled by the entropy. Therefore, the solubility of the compound for the organic EL device is room temperature (25). ℃), it is preferable to use an organic solvent in the range of 0.001 to 5% by mass.
Generally, a highly soluble solvent is used to dissolve the solute, but a highly soluble solvent generally has a high boiling point such as chlorobenzene or glycerin, and requires a large amount of energy to dry the solvent. Is. Furthermore, the high solubility indicates that the interaction with the material which is the solute is large, and the interaction force between the solute and the solvent is large even during drying, so that the drying load is further increased. In addition, considering the drying process, the solvent is not removed unless the interaction between the solute and the solute overcomes the interaction between the solute and the solvent, so that the enthalpy of intermolecular interaction is inevitably strong. Will be done. As a result, in the coated film after drying, the intermolecular interaction force is very strong and tends to be a film having a large particle size, and when the intermolecular interaction force is remarkable, aggregates are observed. Often. Therefore, by setting the solubility of the compound for the organic EL device within the range of 0.001 to 5% by mass, the interaction force between the compound for the organic EL device and the organic solvent can be suppressed to a certain range or less, and drying can be performed. The driving force of is dominated by entropy.
As such an organic solvent, among the above-mentioned organic solvents, an ester solvent, an ether solvent and the like are preferably used.

[Manufacturing method of coating liquid]
As a method for producing a coating liquid of the present invention, it can be produced by dispersing a plurality of types of compounds for an organic EL device according to the present invention in the above organic solvent.
The method for producing the coating liquid of the present invention is not particularly limited, but for example, for a plurality of types of organic EL devices in the coating liquid by using various methods such as chromatography, ultrasonic wave or microwave irradiation, and electrophoresis. It can be produced by dispersing the compound.
Further, the method for producing a coating liquid of the present invention preferably includes a step of contacting a plurality of types of compounds for an organic EL device with a supercritical or subcritical fluid from the viewpoint of effectively obtaining the effects of the present invention.
The step of contacting with the 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. Further, as a mixing method, a method of mixing using supercritical or subcritical chromatography 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 at the same time. Is preferably used.
Further, in the method of stirring and mixing, the solution used for the coating liquid of the present invention is previously purified by gel permeation chromatography or the like so that the solute has high purity, and then is in a supercritical or subcritical state with the solution. It is preferable to mix with a fluid.
Hereinafter, the supercritical or subcritical chromatography method will be described.

<Supercritical or subcritical chromatography method>
For supercritical or subcritical chromatography methods, packed columns, open columns, and capillary columns can be used.

(Column for chromatography)
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, it may be packed in the column while being supported on a particulate carrier, may be contained in the column while being supported on an integrated carrier housed in the column, or may be separated. It may be housed in a column as an integral molded product made of an 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 consisting of 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 the column oven 16. As the filler, silica used in a conventional chromatography method, 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 changes between three states of gas, liquid, and solid due to changes in environmental conditions such as temperature and pressure (or volume), which is determined by the balance between intermolecular force and kinetic energy. The horizontal axis represents the temperature and the vertical axis represents the transition of the three gas-liquid solid states, which is called the state diagram (phase diagram). In it, the three phases of gas, liquid, and solid coexist and are balanced. The point in 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 the saturated vapor pressure and is represented by the evaporation curve (vapor pressure line). If the pressure is lower than the pressure represented by this curve, all the liquid is vaporized, and if a pressure higher than this is applied, all the vapor is liquefied. Even if the pressure is kept constant and the temperature is changed, when this curve is exceeded, the liquid becomes vapor and the vapor becomes liquid. This evaporation curve has an end point on the high temperature and high pressure side, and this is called a critical point. The critical point is an important point that characterizes a substance, and the interface between gas and liquid disappears when the liquid and vapor are indistinguishable.
In a state where the temperature is higher than the critical point, it is possible to move between a liquid and a gas without causing a gas-liquid coexistence state.

A fluid that is above the critical temperature and above the critical pressure is called a supercritical fluid, and a temperature / pressure region that gives the supercritical fluid is called a supercritical region. Further, a state in which either the critical temperature or higher or the critical pressure or higher is satisfied 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 with high kinetic energy, and exhibit liquid behavior in terms of dissolving solutes and gaseous characteristics in terms of density variability. There are many solvent properties of supercritical and subcritical fluids, but it is important that they have low viscosity, high diffusivity, and excellent permeability to solid materials.

In the supercritical state, for example, in the case of carbon dioxide, the critical temperature (hereinafter, also referred to as Tc) is 31 ° C., the critical pressure (hereinafter, also referred to as Pc) is 7.38 × 10 ⁶ Pa, and propane (Tc = 96.7). ° C., Pc = 43.4 × 10 ⁵ Pa), ethylene (Tc = 9.9 ° C., Pc = 52.2 × 10 ⁵ Pa), etc. Above this region, the fluid has a large diffusion coefficient and low viscosity, and is a substance. Since it moves quickly and reaches the concentration equilibrium and has a high density like a liquid, efficient separation is possible. Moreover, recovery is speeded up by using a substance such as carbon dioxide that becomes a gas at normal pressure and room temperature. In addition, there are no various obstacles due to the residual trace amount of solvent that is unavoidable in the purification method using a liquid solvent.

As the solvent used as the supercritical fluid or the subcritical fluid, carbon dioxide, dinitrogen monoxide, ammonia, water, methanol, ethanol, 2-propanol, ethane, propane, butane, hexane, pentane and the like are preferably used. Of these, 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. , Diethyl ether, ether solvent such as tetrahydrofuran (THF), acetal solvent such as acetaldehyde diethyl acetal, ketone solvent such as acetone and methyl ethyl ketone, ester solvent such as ethyl acetate and butyl acetate, formic acid, acetic acid, trifluoroacetic acid. Examples thereof include carboxylic acid solvents such as acetonitrile, pyridine, nitrogen compound solvents such as N, N-dimethylformamide, sulfur compound solvents such as carbon disulfide and dimethyl sulfoxide, and water, nitric acid, sulfuric acid and the like.

The operating temperature of the supercritical fluid or the subcritical fluid is basically not particularly limited as long as it is equal to or higher than the temperature at which the compound for the organic EL element according to the present invention melts, but if the temperature is too low, the compound for the organic EL element The operating temperature range is within the range of 20 to 600 ° C. because the solubility in supercritical fluid or subcritical fluid may be poor and the compound for organic EL element may be decomposed if the temperature is too high. It is preferable to do so.

The working pressure of the supercritical fluid or subcritical fluid is not particularly limited as long as it is equal to or higher than the critical pressure of the substance to be used, but if the pressure is too low, it enters the supercritical fluid or subcritical fluid of the compound for organic EL elements. If the pressure is too high, there may be problems in terms of durability of the manufacturing equipment, safety during operation, etc., so the working pressure should be in the range of 1 to 100 MPa. It is preferable to do so.

The device using the supercritical fluid or the subcritical fluid is limited as long as the compound for the organic EL element has a function of contacting the supercritical fluid or the subcritical fluid and dissolving in the supercritical fluid or the subcritical fluid. For example, a batch method in which a supercritical fluid or a subcritical fluid is used in a closed system, a distribution method in which a supercritical fluid or a subcritical fluid is circulated and used, and a combination of a batch method and a distribution method are combined. It is possible to use a method or the like.

In the supercritical or subcritical chromatography method according to the present invention, after injecting a sample into the mobile phase, the following before the tailing of the peak of the target substance having the slowest elution from the column is completely attenuated is as follows. It is preferable to inject the sample.
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 constant. In particular, when a large amount of the compound to be separated is 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 by this step, the attenuation of peak tailing can be accelerated. In column adsorption supercritical or subcritical chromatography, the peaks show remarkable tailing, especially when performing a preparative operation in which a relatively large amount of the compound to be separated is loaded. If the next sample is injected before the tailing is attenuated, the tailing component will be mixed with the peak component of the next injected sample, and the purity of the separated compound will decrease, resulting in inconvenience. Therefore, the next sample must be injected after waiting for the tailing to completely decay. Therefore, it is possible to accelerate the timing of the next sample injection by accelerating the attenuation of tailing. However, in the present invention, by changing the composition of the mobile phase, the extruding of the peak component from the column is promoted, and tailing is performed. Can accelerate the decay of.

Changing the composition in the mobile phase produces the same effect as the step gradient method in liquid chromatography, and promotes the extrusion of peak components from the column, thereby accelerating the attenuation of tailing.
Since supercritical or subcritical chromatography uses a supercritical fluid or subcritical fluid having high diffusivity and low viscosity, the flow velocity of the mobile phase is high and the column equilibration is fast. Therefore, even if the composition in the mobile phase changes temporarily, the column quickly returns to the environment before the change when the composition in the mobile phase is restored. Therefore, the next sample immediately after the tailing is attenuated. Can be injected. As a result, the amount of sample processed per hour can be increased, and efficiency and productivity are improved.

The step of changing the composition of the mobile phase of the present invention may be carried out by any method as long as it can be performed by a supercritical or subcritical chromatography apparatus. For example, increasing the solvent ratio in the mobile phase can cause changes in the composition of the mobile phase, and significant changes in pressure and column temperature also change _{the CO 2 density in the mobile phase.} , These are included in the composition change of the mobile phase.

The solvent is already contained in the mobile phase, but in addition to the solvent contained in the mobile phase, a solvent injection device is provided upstream of the column and downstream of the mobile phase generator to increase the solvent ratio in the mobile phase. Can be made to. The solvent injection device can be, for example, a solvent injection device including a loop pipe for holding the solvent to be injected, a flow path switching valve, and a solvent injection pump.

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

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 a cock provided in the flow path of the mobile phase. For example, a valve that uses a combination of a two-way valve and a butterfly valve, or a valve that switches the flow path of the mobile phase by using a three-way valve can be mentioned. As the solvent injection pump used in 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. For the injection of the solvent, it is preferable to instantly inject the solvent in an injection volume of the sample or more, preferably 2 times or more, more preferably 5 times or more. As the upper limit value, it is preferable to inject a solvent 30 times or less, preferably 20 times or less, more preferably 15 times or less the injection volume of the sample. With such a solvent injection amount, the attenuation of peak tailing is further accelerated.

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. Further, the solvent to be injected may be one kind or two or more kinds.
In particular, a highly polar solvent is preferred in that it further accelerates tailing decay. Further, it is preferable to use a solvent having a higher polarity than the solvent contained in the mobile phase.

It is preferable that both the step of changing the composition of the mobile phase and the step of returning the composition of the mobile phase to before the change are performed instantaneously. The term "instantaneous" as used herein may be any time sufficient to cause a change in the mobile phase.

The method of peak detection is not particularly limited, but usually, timing can be measured by a peak detected by a detector possessed by supercritical or subcritical chromatography, for example, an ultraviolet absorption spectrometer.

<Drying and solidifying process>
The dry solidification 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 coating method (coating film forming method) of the coating liquid include a spin coating method, a casting method, an inkjet method, a spray method, a printing method, a slot type coater method, and the like. From the viewpoint that a homogeneous film can be easily obtained and pinholes are less likely to be formed, a coating method such as an inkjet method, a spray method, a printing method, or a slot type coater method is preferable, and among them, an inkjet method is more preferable. It is preferable to use the method.

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

The volume of ink droplets ejected from the head is preferably in the range of 0.5 to 100 pL. It is more preferably in the range of 2 to 20 pL from the viewpoint of less coating unevenness and high printing speed. The volume of the ink droplet can be appropriately adjusted by adjusting the applied voltage or the like.

The print 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 in the range of 1 to 30 μm, and most preferably 1. In the range of ~ 5 μm, the effect of the present invention is more prominently exhibited. The wet film thickness can be calculated from the coating area, the print resolution, and the volume of ink droplets.

Inkjet 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 with 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 arranged side by side over a width equal to or larger than a desired coating pattern width. When forming a plurality of independent coating patterns whose patterns are not continuous with each other on the same substrate, a wide head having at least the width of each coating pattern may be used.

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

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

(substrate)
The substrate (hereinafter, also referred to as a substrate, a support substrate, a substrate, a support, etc.) 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. Also, it may be transparent or opaque. When light is taken out from the substrate side, the substrate is preferably transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent plastic substrate.
Further, as the substrate, to prevent oxygen and water from entering from the substrate side, JIS Z-0208 in test according to, the thickness of the water vapor transmission rate at 1μm or more ^{1g / (m 2 · 24h ·} atm ) (25 ° C.) or less is preferable.

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

Plastic substrates have been attracting attention in recent years because of their high flexibility, light weight, and resistance to cracking, and their ability to further reduce the thickness of organic EL elements.
The resin film used as the base material of the plastic substrate is not particularly limited, and 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 acetate phthalate, Cellulose acetate and other cellulose esters or derivatives thereof, Polyvinylidene chloride, Polyvinyl alcohol, Polyethylene vinyl alcohol, Syndiotactic polystyrene, Polycarbonate , Norbornen resin, polymethylpentene, polyether ketone, polyimide, polyether sulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or poly Examples thereof include allylates and organic-inorganic hybrid resins.
Examples of the organic-inorganic hybrid resin include those obtained by combining an organic resin with an inorganic polymer (for example, silica, alumina, titania, zirconia, etc.) obtained by a sol-gel reaction. Of these, norbornene (or cycloolefin-based) resins such as Arton (manufactured by JSR Corporation) or Appel (manufactured by Mitsui Chemicals, Inc.) are particularly preferable.

The plastic substrate usually produced has a relatively high moisture permeability, and may contain moisture inside the substrate. Therefore, when such a plastic substrate is used, it is preferable to provide a film (hereinafter referred to as "barrier film" or "water vapor sealing film") that suppresses the intrusion of water vapor, oxygen, etc. on the resin film.

The material constituting the barrier film is not particularly limited, and an inorganic substance, an organic film, or a hybrid of both of them 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 is a material that causes deterioration of the element such as moisture and oxygen but has a function of suppressing infiltration, and is, for example, a metal oxide, a metal oxynitride, a metal nitride, etc. Inorganic substances, organic substances, or hybrid materials of both can be used.
Metal oxides, metal oxynitrides or metal nitrides include silicon oxide, titanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), metal oxides such as aluminum oxide, and metal nitrides such as silicon nitride. , Metallic oxynitrides such as silicon oxynitride and titanium oxynitride.
Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The stacking order of the inorganic layer and the organic layer is not particularly limited, but it is preferable to stack the inorganic layer and the organic layer alternately a plurality of times.

Barrier film was measured by the method based on JIS K 7129-1992, the water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is 0.01g ^/ (m 2 · 24h) preferably less a 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 the permeability is preferably ^{1 × 10 -5 g / (m} 2 · 24h) or less of the high barrier film.

The method for providing the barrier film on the resin film is not particularly limited, and any method may be used. For example, a vacuum vapor deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, or an ion plating method may be used. 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, etc. can be used. .. Of these, the method by plasma CVD treatment at atmospheric pressure or in the vicinity of atmospheric pressure is preferable from the viewpoint that a dense film can be formed.
Examples of the opaque substrate include a metal plate such as aluminum and stainless steel, a film or opaque resin substrate, and a ceramic substrate.

(anode)
As the anode of the organic EL element, a metal having a large work function (4 eV or more), an electrically conductive compound of a metal, or a mixture thereof as an electrode material is preferably used.
Here, the "metal electrically 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. Refers to those 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 produced by forming a thin film made of these electrode substances on the substrate by a known method such as thin film deposition or sputtering.
Further, a pattern having a desired shape may be formed on this thin film by a photolithography method, and if pattern accuracy is not required so much (about 100 μm or more), the desired shape may be formed during vapor deposition or sputtering of the electrode material. The pattern may be formed through a mask.
When extracting light from the anode, it is desirable to increase the transmittance to more than 10%. The sheet resistance as an anode is several hundred Ω / sq. The following is preferable. Further, the film thickness of the anode depends on the constituent material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

(Organic functional layer)
The organic functional layer (also referred to as "organic EL layer" or "organic compound layer") includes at least a light emitting layer, but in a broad sense, the light emitting layer is when an electric current is passed through an electrode composed of a cathode and an anode. Specifically, it refers to a layer containing an organic compound that emits light when an electric current is passed through 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, and these layers serve as a cathode. It has a structure sandwiched between the anode and 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 / light emitting layer / electron transport layer / electron injection layer / cathode (vi) anode / hole transport layer / light emitting layer / electron transport layer / cathode, etc. The structure of.
Further, a cathode buffer layer (for example, lithium fluoride) may be inserted between the electron injection layer and the cathode, and an anode buffer layer (for example, copper phthalocyanine or the like) 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 a layer in which electrons and holes injected from an electrode or an electron transporting layer and a hole transporting layer are recombined to emit light, and the light emitting portion is in the layer of the light emitting layer. May also 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 composed of a plurality of layers having the same or different compositions.
The light emitting layer itself may be provided with 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 through the anode or hole injection layer and electrons being injected from the cathode or electron injection layer when an electric field is applied to the light emitting layer, (2) injection. At least one of the transport function of moving electric charges (electrons and holes) by the force of an electric field, and (3) the light emitting function of providing a field of recombination of electrons and holes inside the light emitting layer and connecting this to light emission. Functions may be added. The light emitting layer may have a difference in the ease of injecting holes and the ease of injecting electrons, and may have different transport functions represented by the mobility of holes and electrons. , Which has a function of transferring at least one of the charges is preferable.

A specific example of the light emitting material used for the light emitting layer has already been described in "(1) Compound for organic EL device used for the light emitting layer", and thus is omitted here.
As the light emitting dopant used for the light emitting layer, only one kind described above may be used, or a plurality of kinds may be used, and by simultaneously extracting light emission from these plurality of kinds of dopants, a plurality of emission maximum wavelengths may be used. It is also possible to configure a light emitting element having. Further, for example, both a phosphorescent dopant and a fluorescent dopant may be added. When a plurality of light emitting layers are laminated to form an organic EL element, the light emitting dopants contained in each layer may be the same or different, or may be of 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 the light emitting dopant is used as a main chain of a polymer may be used.
The luminescent dopant may be dispersed throughout the layer containing the host compound, or may be partially dispersed. A compound having yet another function may be 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 "Compound for organic EL device used for the hole injection layer and the hole transport layer", and thus are omitted here.
As the hole injection layer and the hole transport layer, the hole injection material and the hole transport material are known, for example, vacuum deposition method, spin coating method, casting method, LB method, inkjet method, transfer method, printing method and the like. It can be formed by thinning the film according to the above method. 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 have a one-layer structure composed of one or more of the above materials, respectively, and may have a laminated structure composed of a plurality of layers having the same composition or a different composition. May be 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-mentioned "Compound for organic EL device used for the electron injection layer and the electron transport layer", and thus are omitted here.
The electron injection layer is formed by thinning the electron injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, an inkjet method, a transfer method, or a printing method. Can be done.
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 one-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 a different composition.
In the present specification, among the electron injection layers, when the ionization energy is larger than that of the light emitting layer, it is 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 referred to as a hole blocking layer (hole block layer), and examples thereof include International Publication No. 2000/70655, JP-A-2001-313178, and JP-A-11-204258. Examples thereof include those described in JP-A-11-204359 and page 237 of "Organic EL Element and Its Industrialization Frontline (November 30, 1998, published by NTS Co., Ltd.)". In particular, in a so-called "phosphorescent light emitting device" that uses an orthometal 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 the electrode and the organic layer in order to reduce the driving voltage and improve the luminous efficiency. "Organic EL element and its forefront of industrialization (published by NTS on November 30, 1998)" ) ”, Volume 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, 9-2660062, 8-288609, etc., and specific examples thereof include a phthalocyanine buffer layer typified by copper phthalocyanine and vanadium oxide. Examples thereof include an oxide buffer layer represented by the above, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
The details of the cathode buffer layer are described in JP-A-6-325871, No. 9-17574, No. 10-74586, etc., and specifically, a metal buffer layer typified by strontium, aluminum, or the like. Examples thereof include an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, and an oxide buffer layer typified by aluminum oxide.
The buffer layer is preferably a very thin film, and although it depends on the material, the thickness thereof is preferably in the range of 0.1 to 100 nm. Further, in addition to the above basic constituent layers, layers having other functions may be appropriately laminated, if necessary.

(cathode)
As described above, as the cathode of the organic EL element, a metal having a small work function (less than 4 eV) (hereinafter referred to as an electron-injectable metal), an alloy, an electrically conductive compound of the 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 alloy, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, 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 exerting the effect of the present invention, the cathode may contain a Group 13 metal element. preferable. That is, in the present invention, as will be described later, the surface of the cathode is oxidized with oxygen gas in a plasma state to form an oxide film on the surface of the cathode, thereby preventing further oxidation of the cathode and improving the durability of the cathode. Can be made to.
Therefore, the electrode material of the cathode is preferably a metal having preferable electron injection properties required for the cathode and capable of forming a dense oxide film.

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

[Method for manufacturing organic EL elements]
As an example of the method for manufacturing the organic EL device according to the present invention, a method for manufacturing the organic EL device including the anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode will be described.
First, a thin film made of a desired electrode substance, for example, an anode substance is formed on a suitable substrate by a method such as thin film deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, to prepare an anode. To do. Next, for example, an organic compound thin film of 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 on this.
As a method for thinning these organic compound thin films, as described above, there are a spin coating method, a casting method, an inkjet method, a thin film deposition method, a printing method and the like, but a uniform film can be easily obtained and pinholes are formed. The vacuum vapor deposition method or the spin coating method is preferable because it is difficult to generate.

Further, a different film forming 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 in the range of ~ 50 nm / sec, substrate temperature -50 to 300 ° C., and thickness 0.1 nm to 5 μm.
After forming these layers, a thin film made of a material for a cathode is formed on the layer so as to have a thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided by a method such as vapor deposition or sputtering. Therefore, a desired organic EL element can be obtained. The organic EL element is preferably manufactured from the hole injection layer to the cathode by one vacuuming, but it may be taken out in the middle and a different film forming method may be applied. At that time, consideration must be given to performing the work in a dry inert gas atmosphere.

[Encapsulation of organic EL element]
The sealing means for the organic EL element is not particularly limited, but for example, after sealing the outer peripheral portion of the organic EL element with a sealing adhesive, the 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 acrylic acid-based oligomers, photocurable and thermosetting adhesives having a reactive vinyl group of methacrylic acid-based oligomers, and moisture-curable adhesives such as 2-cyanoacrylic acid ester. Can be mentioned. In addition, heat and chemical curing type (two-component mixture) such as epoxy type can be mentioned. Further, hot melt type polyamide, polyester and polyolefin can be mentioned. In addition, a cation-curable type ultraviolet-curable epoxy resin adhesive can be mentioned.

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

In the gap between the sealing member and the light emitting region of the organic EL element, in addition to the sealing adhesive, in the gas phase and liquid phase, an inert gas such as nitrogen or argon, fluorinated hydrocarbon, silicon oil, etc. It is also possible to inject a non-active liquid. Further, the gap between the sealing member and the display region of the organic EL element can be evacuated, or a hygroscopic compound can be sealed in the gap.

[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, and a vapor deposition method, a casting method, and a spin coating method are used on one surface. A film can be formed by a method, an inkjet method, a printing method, or the like.
When patterning only the light emitting layer, the method is not limited, but a vapor deposition method, an inkjet method, or a printing method is preferable. When the vapor deposition method is used, patterning using a shadow mask is preferable.
It is also possible to reverse the production order and produce 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. Further, 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 alternating current to be applied may be arbitrary.

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

Light sources include household lighting, interior lighting, backlights for clocks and liquid crystals, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. It can be mentioned, but it is not limited to this.
Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.
Examples of the purpose of use of the organic EL element having such a resonator structure include 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. Further, it may be used for the above-mentioned applications by oscillating a laser.

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

An example of a display device composed of an organic EL element according to the present invention will be described below with reference to the drawings.
FIG. 4 is a schematic view showing an example of a display device composed of an organic EL element. It is a schematic diagram of the display of a mobile phone or the like which displays 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 scans an image 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 a plurality of pixels based on image information from the outside, and the scanning signal converts the pixels of each scanning line into an image data signal. In response to this, light is emitted in sequence, image scanning is performed, and image information is displayed on the display unit A.

FIG. 5 is a schematic view of the display unit A. The display unit A has a wiring unit including a plurality of scanning lines 55 and data lines 56, a plurality of pixels 53, and the like on the 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 taken out 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 pixel 53 at orthogonal positions (details are shown 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. Full-color display is possible by appropriately arranging pixels in the red region, pixels in the green region, and pixels in the blue region of the emission color on the same substrate.

Next, the light emitting process of the pixel will be described.
FIG. 6 is a schematic view showing a pixel circuit. The pixel includes an organic EL element 60, a switching transistor 61, a drive transistor 62, a capacitor 63, and the like. As the organic EL element 60 for a plurality of pixels, red, green, and blue light emitting organic EL elements are used, and by arranging them side by side on the same substrate, full-color display can be performed.
In FIG. 6, an image data signal is applied from the 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. Then, 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 the capacitor 63 and the driving transistor 62. It is transmitted to the gate of.

By transmitting the image data signal, the capacitor 63 is charged according to the potential of the image data signal, and the drive transistor 62 is driven on. In the drive transistor 62, the drain is connected to the power supply line 67, the source is connected to the electrode of the organic EL element 60, and the power supply line 67 is connected 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 is transferred 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, since the capacitor 63 retains the potential of the charged image data signal even when the drive of the switching transistor 61 is turned off, the drive of the drive transistor 62 is kept on and the next scan signal is applied. The light emission of the organic EL element 60 continues until. 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, for the light emission of the organic EL element 60, the switching transistor 61 and the drive transistor 62, which are active elements, are provided for the organic EL element 60 of each of the plurality of pixels, and the 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 on / off of a predetermined light emission amount by a binary image data signal. It may be.
Further, the potential of the capacitor 63 may be continuously maintained until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

The present invention is not limited to the active matrix method described above, and may be a passive matrix type light emitting drive in which the organic EL element emits light in response to the data signal only when the scanning signal is scanned.

FIG. 7 is a schematic view of a display device based on the passive matrix method. In FIG. 7, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a grid pattern so as to face each other with the pixel 53 interposed therebetween. When the scanning signal of the scanning line 55 is applied by the sequential scanning, the pixel 53 connected to the applied scanning line 55 emits light according to the image data signal. In the passive matrix method, the pixel 53 does not have an active element, and the manufacturing cost can be reduced.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, each operation was performed at room temperature (25 ° C.). Unless otherwise specified, each coating liquid was prepared in a glove box in a nitrogen atmosphere without contact with the atmosphere.
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 D-1 to D-4 for organic EL devices represent dopants.

Table I shows the molecular formulas of the compounds for each organic EL element, the classification of structural isomers (compounds having the same alphabet have a structural isomer relationship with each other), the presence or absence of diastereomers, and the number of stereoisomers. There is.

Example 1
≪Preparation of coating liquid≫
[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 terrorahydrofuran (manufactured by Kanto Chemical Co., Ltd., THF) in an amount of 2.0% by mass.

[Preparation of coating liquids 2-34]
In the preparation of the coating liquid 1, the coating liquids 2 to 34 were prepared in the same manner except that the compounds and solvents for the organic EL device were changed as shown in Table II below. Further, the coating liquid in which a plurality of compounds for organic EL devices were dissolved was adjusted to have the content (molar ratio) in Table II. In addition, nPr acetate in Table II shows normal propyl acetate.

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

(Supercritical chromatography conditions (SFC treatment))
Equipment: Prep15 (manufactured by Japan Waters Corp.)
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: 18 MPa
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 supercritical chromatography treatment was changed from the coating liquid 1 to the coating liquids 10, 11, 18 and 21, and the mobile phase solvent was changed to each coating solvent in the same manner. , Coating liquids 36, 37, 38 and 39 were prepared. Further, in the supercritical chromatography treatment, only the portion of the coating liquid in which the peak of each organic EL element compound appeared was recovered by the automatic preparative function. In the coating liquid containing a plurality of compounds for organic EL devices, only the portion where the peak appears is recovered, and the recovered solutions are mixed, and the total concentration of the compounds for organic EL devices in the coating liquid is 2. Concentrated to 0.0% by mass.

≪Evaluation of coating liquid≫
The following evaluation was performed for each coating liquid. The results are shown in Table II.
(1) Evaluation of storage stability of particle size distribution R _{1 is obtained from the evaluation of (1-1) below, and R 2} is obtained from the evaluation of (1-2) below, and the relative value _{of R 2 when R 1} is 100. R ₃ was calculated by the following formula, and the storage stability was evaluated according to the following criteria. _{Further, in the calculation of R 2 in} (1-2) below, the full width at half maximum (R _hw ) was also calculated, and when the full width at half maximum (R _hw ) was 15 nm or more, the storage stability was set to “x”. Further, in the present invention, ⊚, ◯ and Δ were accepted.
Formula: R ₃ = (R ₂ / R ₁ ) x 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 of _{R 2 (R hw} ) 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 liquid was placed in a capillary for an X-ray diffraction sample (manufactured by WJM-Glas / Muller GmbH) to prepare a measurement sample. As X-rays, synchrotron radiation of SPring-8 was used, and the solution sample was irradiated with a wavelength of 0.1 nm. A multi-axis diffractometer manufactured by HUBER is used for the measurement, the X-ray incident angle θ is fixed at 0.2 ° and the solution sample is irradiated, and the detector uses a scintillation counter to scatter 2θ from 1 to 43 °. Measurements were 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, with respect to the gradient (slope) of the Guinier plot, the particle size / pore size analysis software NANO-Solver manufactured by Rigaku Co., Ltd. is used, and the pores and particle size are assumed to be spheres. By performing analytical fitting, the particle size distribution of a single molecule derived from the compound for an organic EL element or an aggregate thereof in the coating film was determined. 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.
The particle size distribution curve according to the present invention was created based on the above-mentioned small-angle X-ray scattering measurement and analysis method, with the horizontal axis representing the particle size and the vertical axis representing the frequency distribution. It was obtained by plotting the measured values of the frequency distribution with respect to the particle size and connecting each plot.
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 the particle size distribution analysis (calculation of _{R 2} and _{R hw)}
After storing each coating liquid in a tightly sealed environment at a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm) for 30 days, the same evaluation as in (1-1) was performed, and the particle size after 30 days passed. R ₂ was calculated. Further, in the particle size distribution curve (horizontal axis: particle size (nm), vertical axis: distribution frequency (1 / nm)), the half width ( _Rhw ) of the maximum peak showing the maximum distribution frequency was calculated.

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

Example 2
≪Preparation of coating film≫
[Preparation of coating films 2-1 (A) and 2-1 (B)]
2.0 mg (0.002% by mass) of compound D-1 for an organic EL device was added to the coating liquid 2 obtained in Example 1 and dissolved to obtain a coating liquid for thin film formation.
A quartz substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and washed with UV ozone for 5 minutes. The quartz substrate is placed in a spin coating machine, and the coating liquid for thin film formation prepared above is formed by the spin coating method at 1500 rpm and 30 seconds, respectively, and then held at 100 ° C. for 30 minutes to form a coating film having a film thickness of 40 nm. A film was formed on a quartz substrate to obtain a coating film 2-1 (A) as a measurement sample before storage.
The residue of the coating liquid for thin film formation is sealed, stored for 30 days 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 then by the same film forming method as in 2-1 (A). A coating film 2-1 (B), which is a measurement sample after storage, was prepared.

[Preparation of coating films 2-2 (A) to 2-20 (A) and 2-2 (B) to 2-20 (B)]
The same applies to the preparation of the coating films 2-1 (A) and 2-1 (B) except that the coating liquid obtained in Example 1 and the compound D-1 for an organic EL device are changed as shown in Table III below. Then, 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 hexa-coordinated metal complexes having a bidentate ligand, and have a structure that promotes the generation of isomers in the bidentate ligand. Taking compound D-2 for an organic EL device as an example, the number of isomers (number of steric isomers) in consideration of the coordination form is 4.

≪Evaluation of coating film≫
As the storage stability evaluation of each of the above coating films, the following (1) absolute quantum yield (hereinafter, also simply referred to as “PLQE”) was evaluated and (2) ultraviolet light resistance was evaluated. The results are shown in Table III.

(1) Evaluation of Coating Film The PLQE and luminance residual rate in a UV irradiation test using an HgXe light source were determined according to the following method. As a UV irradiation test using an 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.
Place the glass cover on the coating film formed on the quartz substrate, arrange so that the irradiation fiber emission surface and the glass cover surface on the coating film are horizontal, and at a distance of 1 cm, until the number of luminescent photons is halved. Irradiated. The measurement was performed at room temperature (300K).
For the sample before storage, the number of luminescent photons immediately after UV irradiation (within 30 seconds) was counted and divided by the number of absorbed photons to obtain PLQE.
Further, UV irradiation was continued, and the time required for the number of luminescent photons to be halved (half time) was determined and used as an index of ultraviolet light resistance. The brightness 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, the PLQE and half time were calculated by the same method as above and evaluated by the following formula.

(Evaluation of PLQE)
When the PLQE of the sample before storage (2-1 (A) to 2-20 (A)) is 100, the PLQE of the sample after storage (2-1 (B) to 2-20 (B)) Relative values were calculated and evaluated according to the following criteria. In the present invention, ⊚, ◯ and Δ were accepted.

⊚: 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)
The sample after storage (2-1 (B) to 2-20 (B)) when the luminance half time of the sample before storage (2-1 (A) to 2-20 (A)) is 100. The relative value of the luminance half time was calculated and evaluated according to the following criteria. In the present invention, ⊚, ◯ and Δ were accepted.

⊚: 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 III above, it was found that the coating film of the present invention has excellent storage stability. On the other hand, the coating film of the comparative example was inferior in storage stability.

Example 3
≪Preparation of coating liquid≫
[Preparation of coating liquid 3-1]
In a glove box filled with high-purity nitrogen, 2.0 mg of each of the compounds H-1, H-8, H-14 and H-16 for organic EL devices was added to terrorahydrofuran (Kanto Chemical Co., Inc. (Kanto Chemical Co., Inc.).
Co., Ltd.) Dissolved in 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 liquid 3-1 described above, the mass of each of the compounds H-1, H-8, H-14 and H-16 for the organic EL device was set to 5.0 mg, and the compound D-1 for the organic EL device was used. A 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 preparation of the coating liquid 3-1 described above, the compounds for organic EL devices H-8, H-9, H-10.
And H-11, a coating liquid 3-3 was obtained in the same manner.

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

[Preparation of coating liquid 3-10]
In the 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 shown in Table IV. A coating liquid 3-10 was obtained in the same manner except that the changes were made as shown in.

[Preparation of coating liquids 3-11 and 3-12]
In the above preparation of the coating liquid 3-10, coating liquids 3-11 and 3-12 were obtained in the same manner except that the total concentration (mass%) of the compounds for the organic EL device was changed as shown in Table IV. The content ratio of each compound for the organic EL device was dissolved so as to 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 liquid was evaluated in the same manner except that the storage period was changed from 30 days to 90 days in "(1) Evaluation of storage stability evaluation of particle size distribution" in the evaluation of Example 1 above. The storage stability of the particle size distribution is a relative value in the same manner as in "(1) Evaluation of storage stability evaluation of particle size distribution" in the evaluation of Example 1 above, except that the storage period is changed to 90 days as described above. R ₃ and the full width at half maximum (R _hw ) were calculated, and the storage stability was evaluated according to the following criteria. In the present invention, ⊚, ◯ and Δ were accepted. The results are shown in Table IV.
(Preservation of particle size distribution)
⊚: R ₃ is 100 or more and less than 105 ○: R ₃ is 105 or more and less than 110 Δ: R ₃ is 110 or more and less than 130 ×: R ₃ is 130 or more or half width (R _hw ) is 15 nm or more

<Evaluation of storage stability of coating film>
A film (coating film) obtained by drying and solidifying the obtained coating liquids 3-1 to 3-10 was evaluated by the following evaluation method. The coating film was prepared 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 liquid was obtained in the same manner as the PLQE in the UV irradiation test using the HgXe light source of Example 2, and evaluated by the following formula. As for the evaluation, as in Example 2, the relative value of the PLQE of the sample after storage was calculated when the PLQE of the sample before storage was 100, and the evaluation was performed according to the following criteria. In the present invention, ⊚, ◯ and Δ were accepted. 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 liquid and coating film of the present invention have excellent storage stability. On the other hand, the coating liquid and the coating film of the comparative example were inferior in storage stability. Further, it was found that the storage stability was particularly improved when the compound for the organic EL device was in the range of 0.5 to 5.0% by mass with respect to the total amount of the coating liquid.

Example 4
≪Manufacturing of organic EL element≫
An organic EL device including a film (coating film) obtained by drying and solidifying the coating liquid of the present invention and the comparative example as an organic functional layer was produced by a wet film forming method. In the following examples, the organic EL device is manufactured by the spin coating method, but the present invention is not limited to this, and a wet film forming method (wet coating method) such as an inkjet method, a die coating, or flexographic printing is used. The organic functional layer may be prepared by the method (wet coating method). Further, in the formation of the following light emitting layer, the coating liquid of Comparative Example or the coating liquid of the present invention was used.

[Manufacturing of organic EL element 4-1]
An organic EL is formed by 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 and then sealing the flexible film. Element 4-1 was manufactured.

(1.1) Preparation of Gas Barrier Flexible Film As a flexible film, the entire surface of a polyethylene naphthalate film (film manufactured by Teijin DuPont, hereinafter abbreviated as PEN) on the side where the first electrode is formed is formed. , JP-A-2004-68143 is used to continuously form an inorganic gas barrier film made of SiOx on a flexible film so as to have a thickness of 500 nm. 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 ITO (indium tin oxide) having a thickness of 120 nm is formed on the prepared gas barrier flexible film by a sputtering method and patterned by a photolithography method. To form the first electrode layer (anode).
The pattern was set so that the light emitting area was 50 mm square.

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

(1.4) Formation of Hole Transport Layer This substrate is transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and the hole transport material compound (HT-1) (Mw = 80000) is mixed with chlorobenzene. A solution dissolved in 0.5% was formed by a spin coating method at 1500 rpm for 30 seconds, and then held at 160 ° C. for 1 hour to prepare a hole transport layer having a layer thickness of 30 nm.

(1.5) Formation of light emitting layer <Coating liquid for forming light emitting layer>
Compound for organic EL element: Host compound (H-8) 45 parts by mass Compound for organic EL element: Dopant (D-1) 9.0 parts by mass Solvent (normal propyl acetate) 2200 parts by mass Host which is a compound for organic EL element The compound (H-8) and the dopant (D-1) were dissolved in a solvent (normal propyl acetate) at the above ratios to prepare a coating liquid for forming a light emitting layer. Next, the coating liquid for forming a light emitting layer was formed into a film by a spin coating method 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 coating, the coating liquid was blown with dry air 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. , 120 ° C. for 30 minutes to prepare an electron transport layer having a layer thickness of 30 nm.

(1.7) Formation of electron injection layer and cathode Subsequently, the substrate was attached to a vacuum vapor deposition apparatus without exposure to the atmosphere. Further, a molybdenum resistance heating boat containing lithium fluoride is attached to a vacuum vapor deposition apparatus, the vacuum tank is ^{depressurized to 4 × 10-5} Pa, and then the boat is energized and heated to reduce lithium fluoride to 0. An electron injection layer having a layer thickness of 2.0 nm was formed on the electron transport layer at .02 nm / sec.
Next, 100 nm of aluminum was vapor-deposited to form a cathode.

(1.8) Sealing Next, as a sealing member, a polyethylene terephthalate (PET) film (12 μm thickness) is adhered to a flexible aluminum foil (manufactured by Toyo Aluminum K.K. Co., Ltd.) with a thickness of 30 μm for dry lamination. A laminated product (adhesive layer thickness 1.5 μm) was prepared using an agent (two-component reaction type urethane-based adhesive).
Next, the following thermosetting adhesive was applied as a sealing adhesive on the aluminum (cathode) surface to the adhesive surface (glossy surface) of the sealing member using a dispenser with a thickness of 20 μm. Was applied to. This was dried under a vacuum of 100 Pa or less for 12 hours. Further, the dew point temperature was moved to −80 ° C. or lower and the oxygen concentration was 0.8 ppm in a nitrogen atmosphere, and the mixture was dried for 12 hours or more to adjust the water content of the sealing adhesive to 100 ppm or less.
As the thermosetting adhesive, an epoxy-based adhesive in which the following (A) to (C) were mixed was used.
(A) Bisphenol A Diglycidyl Ether (DGEBA)
(B) Dicyanodiamide (DICY)
(C) Epoxy adduct-based curing accelerator

Next, the sealing member is closely adhered and arranged so as to cover the joint portion of the take-out electrode and the electrode lead, and thick coating conditions are used using a crimping roll, the crimping roll temperature is 120 ° C., the pressure is 0.5 MPa, and the device speed is 0. The organic EL element 4-1 was manufactured by tightly sealing at 3 m / min.

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

[Manufacturing of organic EL elements 4-3 to 4-8]
In the formation of the light emitting layer in the method for producing the organic EL element 4-1 except that the light emitting layer forming coating liquid in which the host compound and the dopant of the light emitting layer forming coating liquid were changed to the compounds shown in Table V below was used. In the same manner, organic EL elements 4-3 to 4-8 were manufactured.

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

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

[Manufacturing of organic EL element 4-11]
In the production of the organic EL element 4-5, when the coating liquid for forming the light emitting layer was prepared, the coating liquid 38 prepared by preparing the host compound in Example 1 (supercritical chromatography treatment (SFC treatment) in the preparation step of the coating liquid) was performed. The organic EL element 4-11 was produced in the same manner except that the coating liquid 31 was used as the mother liquor.
In the preparation of the coating liquid, the host compound and the dopant are mixed so as to have a mass ratio of 45: 9, and then concentrated to be the same organic EL element as the coating liquid used in the organic EL element 4-5. A coating liquid having a content (% by mass) of the compound for use was prepared.

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

[Manufacturing of organic EL element 4-13]
The coating liquid for forming a light emitting layer used in the production of the organic EL element 4-11 was sealed and stored for 14 days in an environment of a temperature of 25 ° C., a relative humidity of 3% or less, and a pressure of 101325 Pa (1 atm). The 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 liquid for forming a light emitting layer was used.

≪Evaluation of organic EL element≫
Each of the following evaluations (1) and (2) was performed on the organic EL elements 4-1 to 4-13. These results are shown in Table V below.

(1) Measurement of light emission life The light emission life is measured by continuously driving each organic EL element under the conditions of room temperature 25 ° C. and humidity 35% RH, and measuring the brightness using a spectral radiance meter CS-2000. The time at which the radiance became 75% was determined as a measure of life. The drive condition was a current value ^{of 6000 cd / m 2} at the start of continuous drive. The emission lifetime of each organic EL element is represented by a relative value with the emission lifetime of the organic EL element 4-1 (Comparative Example) as 100.

(2) Measurement of voltage change In the measurement of voltage change, in the above (1) measurement of light emission life, the drive voltage 5 minutes after the start of measurement is set as the initial voltage (Vs), and the drive is performed when the brightness is halved. The voltage was calculated as the deteriorated voltage (Vf) and evaluated by the rate of change of the drive voltage obtained by the following formula.
Equation: (rate of change in 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, ◯ was regarded as acceptable.
⊚: Drive voltage change rate is less than 1.2 〇: Drive voltage change rate is 1.2 or more and less than 1.5 Δ: Drive voltage change rate 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 device using the coating film of the present invention has a long emission life and a small rate of change in the drive voltage. It was also found that the organic EL device using the coating film formed with the coating liquid of the present invention after being stored for 7 or 14 days also has a long emission 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 either the evaluation of the light emission lifetime and the evaluation of the rate of change of the drive voltage.

Since the coating liquid of the present invention has excellent storage stability and also has excellent storage stability and functionality when dried to form a coating film, a wet coating method can be used to obtain an electronic device such as an organic electroluminescence element. It can be used as a coating liquid during 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 manufacturing 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.

11 Supercritical fluid 12 Pump 13 Modifier 14 Injector 15 Column 16 Column oven 17 Detector 18 Pressure control valve A Display B Control 41 Display 53 Pixels 55 Scan line 56 Data line 60 Organic EL element 61 Switching transistor 62 Drive transistor 63 Condenser 67 power line

Claims (9)

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 types of compounds for an organic electroluminescence device are isomers having an asymmetric carbon or an atropic isomer axis. The coating liquid according to claim 1, wherein the plurality of types of compounds for an organic electroluminescence element are organic compounds containing only a non-metal element as a constituent element. The coating solution according to claim 1 or 2 , wherein the content (molar ratio) of each of the compounds for an organic electroluminescence device having an isomer relationship is different. The coating solution according to any one of claims 1 to 3, wherein the number of isomers of the compound for an organic electroluminescence device having an isomer relationship is 3 or more. Any one of claims 1 to 4 , wherein the content of the plurality of types of compounds for an organic electroluminescence device is in the range of 0.5 to 5.0% by mass with respect to the total amount of the coating liquid. The coating liquid described in. The method for producing a coating liquid according to any one of claims 1 to 5.
A method for producing a coating liquid, which comprises a step of bringing the plurality of types of compounds for an organic electroluminescence device into contact with a supercritical or subcritical fluid. The method for producing a coating liquid according to claim 6, wherein the step of contacting with the supercritical or subcritical fluid is a method of mixing using supercritical chromatography. A coating film obtained by drying and solidifying the coating liquid according to any one of claims 1 to 5. An organic electroluminescence device including the coating film according to claim 8 as an organic functional layer.

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