JP2010212354A - Composition for organic electroluminescent element and manufacturing method thereof, organic electroluminescent element, organic el display, and organic el illumination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide composition for organic electroluminescent element, forming the organic electroluminescent element with no occurrence of pin holes and dark spots by a wet film forming method. <P>SOLUTION: The composition for an organic electroluminescent element is used for forming a layer, by a dry film forming method, which is arranged between a positive electrode and a negative electrode of the organic electroluminescent element, containing electric charge transportation material and solvent. The composition is manufactured through a heating step and a filtering step or an ultrasonic processing step, with its volume average particle size (d50) in particle size distribution being 400 nm or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a composition for an organic electroluminescent element used for forming an organic electroluminescent element by a wet film forming method and a method for producing the same.
The present invention also relates to an organic electroluminescent element using the composition for organic electroluminescent elements, an organic EL display device using the organic electroluminescent element, and organic EL illumination.

  Organic electroluminescent devices are usually formed by providing a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and the like between an anode and a cathode, and materials suitable for each layer are being developed. In addition, the light emission colors of organic electroluminescent elements are being developed in red, green and blue, respectively.

  As a method for forming each constituent layer of the organic electroluminescent element, there are a vacuum vapor deposition method and a wet film formation method. Among these, the vacuum deposition method has a problem in terms of yield when manufacturing a medium- or large-sized full-color panel for a television or a monitor. Therefore, the wet film-forming method is suitable for these large area applications.

  However, in order to form an organic layer of an organic electroluminescent element by a wet film formation method, the material for forming the organic layer is dissolved in a solvent, and the high performance required as a component layer of the element after the wet film formation is obtained. It is desirable to have. In particular, in an organic electroluminescent element in which an organic layer is formed by a wet film forming method, the generation of pinholes and dark spots has been a problem.

In order to solve such a problem, it is conceivable to filter the composition for organic electroluminescent elements used in the wet film-forming method.
In addition, in patent document 1, regarding the composition for forming a hole injecting and transporting layer of an organic electroluminescent element, it is stated that the particle size distribution is reduced by measuring the particle size distribution before filtration and performing ultrasonic treatment. However, there is no description about the particle size distribution after filtration, and it did not provide a means for verifying whether filtration was performed properly.

JP 2000-106278 A

  An object of the present invention is to provide a composition for an organic electroluminescence device capable of forming an organic electroluminescence device free from pinholes and dark spots by a wet film formation method.

  As a result of intensive studies to solve the above problems, the present inventors have measured the volume average particle size (d50) of the particle size distribution of the composition for organic electroluminescent elements, and this value is an organic electric field whose value is not more than a predetermined value. It has been found that an organic electroluminescent device free from the generation of pinholes and dark spots can be produced by a wet film-forming method if it is a composition for a light emitting device.

  That is, the gist of the present invention is for an organic electroluminescent device used for forming a layer disposed between an anode and a cathode of an organic electroluminescent device containing a charge transporting material and a solvent by a wet film forming method. An organic electroluminescent device characterized in that the composition is produced through a heating step and a filtration step, and the volume average particle size (d50) of the particle size distribution is 400 nm or less. A composition for use (claim 1).

  Another gist of the present invention is a composition for an organic electroluminescent device used for forming a layer disposed between an anode and a cathode of an organic electroluminescent device, comprising a charge transport material and a solvent. The composition is manufactured through a heating process and an ultrasonic treatment process and then a filtration process, and the volume average particle size (d50) of the particle size distribution is 400 nm or less. It exists in the composition for light emitting elements (Claim 2).

  Another gist of the present invention is an organic electroluminescence device having an anode, a cathode, and a layer disposed between the anode and the cathode, wherein the layer disposed between the anode and the cathode The present invention resides in an organic electroluminescent device (Claim 6), which is a layer formed using the composition for an organic electroluminescent device.

  Another gist of the present invention resides in an organic EL display device (Claim 7) characterized by using the organic electroluminescent element of the present invention.

  Another gist of the present invention resides in an organic EL illumination (Claim 8) characterized by using the organic electroluminescence device of the present invention.

  Another gist of the present invention is a method for producing the composition for an organic electroluminescent element of the present invention, wherein a heating step of heating a solution containing a charge transport material and a solvent, and the solution after the heating are performed. A composition for forming an organic electroluminescence device, comprising: a filtration step for filtration, and measuring a particle size distribution between 0.0000001 seconds (in situ measurement in the filtration step) and 2678400 seconds after filtration. The manufacturing method (Claim 9).

  Another gist of the present invention is a method for producing the composition for an organic electroluminescence device of the present invention, wherein the solution containing a charge transport material and a solvent is heated and subjected to an ultrasonic treatment step. An organic electroluminescence device comprising: a filtration step of filtering the solution, and measuring the particle size distribution between 0.0000001 seconds (in situ measurement in the filtration step) and 2678400 seconds after filtration A method for producing a forming composition (claim 10).

  The composition for organic electroluminescent elements of the present invention is produced through a heating step and a filtration or ultrasonic treatment step, and the volume average particle size (d50) of the particle size distribution is 400 nm or less, and pinholes and dark spots. It is an extremely uniform composition free from the precipitation of foreign matter and materials that cause the above. For this reason, using this composition for organic electroluminescent elements, a high-performance organic electroluminescent element free from problems of occurrence of pinholes and dark spots can be produced by a wet film forming method. A high-quality organic EL display device and organic EL illumination can be stably provided using the organic electroluminescent element.

It is typical sectional drawing which showed an example of the organic electroluminescent element of this invention. It is explanatory drawing of the measurement principle of the particle size distribution by a dynamic light scattering method.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not specified in the contents.

[Composition for organic electroluminescence device]
The composition for an organic electroluminescent device of the present invention is an organic material that is used for forming a layer disposed between an anode and a cathode of an organic electroluminescent device containing a charge transporting material and a solvent by a wet film forming method. A composition for an electroluminescent device, which is produced through a heating step and a filtration step or an ultrasonic treatment step, and a volume average particle size (d50) of particle size distribution is 400 nm or less. It is characterized by that.

  Such a composition for an organic electroluminescent device of the present invention is obtained by dissolving the charge transporting material in a solvent under heating using a charge transporting material and a solvent described later, or further ultrasonicating after the dissolution by heating. Thereafter, filtration is performed, and the volume average particle size (d50) of the particle size distribution is measured to confirm that this value is 400 nm or less. Alternatively, by preparing the composition under each condition in heating followed by heating and sonication, which can achieve the volume average particle size (d50) ≦ 400 nm of the particle size distribution obtained in advance by experiment, The composition for organic electroluminescent elements of the present invention can be obtained.

  Note that the heating step may be performed together with the ultrasonic treatment step, and in that case, the heating step is preferably performed after the ultrasonic treatment step. Furthermore, an ultrasonic treatment step may be performed after the heating step, and it is also preferable to use ultrasonic treatment in combination in the filtration step.

  Below, the manufacturing method of the composition for organic electroluminescent elements of this invention is demonstrated for every process.

{Heating process}
The heating step of heating the solution containing the charge transporting material and the solvent is performed by putting the charge transporting material and the solvent, which will be described later, into a container at a predetermined ratio, and preferably heating with stirring.

  The degree of heating in the heating step is appropriately determined according to the vapor pressure and boiling point of the solvent used, the solubility of the organic electroluminescent element material, etc., but is usually 30 ° C. or higher, particularly 80 ° C. or higher and lower than the boiling point of the solvent used. In particular, the temperature is preferably 30 ° C. or more lower than the boiling point. If the heating temperature is too low, the effect of promoting dissolution due to heating cannot be obtained sufficiently, and if it is too high, there may be a safety problem due to the relationship between the boiling point of the solvent and the vapor pressure.

  In addition, when stirring is performed in the heating step, the stirring conditions are not particularly limited and are appropriately determined according to the solubility of the charge transporting material used in the solvent. It is preferably 0.01 rpm or more, particularly 10 rpm or more, and 2000 rpm or less, particularly 200 rpm or less. If the number of rotations during stirring is too small, it may take time to dissolve the charge transport material, the amount of undissolved material may increase, and the production yield may deteriorate. Further, if the number of revolutions during stirring is too large, the contents may be scattered outside the container, stirring efficiency may be reduced, power consumption required for stirring may be adversely affected, and the like.

  This heating step is usually performed until it is confirmed by visual observation that the charge transport material is dissolved in the solvent. Accordingly, the time required for the heating step is the time until confirmation of dissolution, and usually varies from 1 minute to 750 hours, although it varies depending on the solubility of the charge transport material used in the solvent, heating conditions, and stirring conditions. is there.

  After visually confirming the dissolution of the charge transport material by this heating step, that is, after observing the obtained solution visually and observing the presence of undissolved material and fine particles, the next filtration is performed. It moves to a process or an ultrasonic treatment process.

{Filtering process}
Although there is no restriction | limiting in particular as a filtration means of the solution obtained at the heating process, For example, the following are mentioned.

  Examples of the filtering means include natural filtration and vacuum filtration using Nutsche and filter paper carried out in a normal chemical laboratory, pressure filtration by compression / compression performed in a factory, and centrifugal filtration by a centrifuge. Furthermore, the filtration at the time of heating which heats at the time of filtration, the filtration which uses an ultrasonic wave together, the ultrafiltration by which the opening (filter filter pore diameter) of the filter medium was close to the molecular size, etc. are mentioned.

  Examples of the filter medium include natural fibers, synthetic fibers, glass fibers, and metal materials, but a material whose porosity is not easily changed by water pressure is suitable. For example, a metal mesh made of stainless steel mesh Examples of synthetic fibers such as copper mesh nets include low hygroscopic nylon nets and molded products punched into synthetic resins. In addition, a porous film filter made of a polymer material called a membrane filter (having a hole structure in which holes close to a circle are connected to each other) and a housing made of metal, glass, plastic, etc. ( A membrane filter unit (an integral molded product is also called a syringe filter) that is incorporated in a filter holder) or integrally molded with the housing can also be used. Examples of the polymer material include cellulose mixed ester, cellulose acetate, polycarbonate, PTFE (polytetrafluoroethylene), and polyester nonwoven fabric coated with cellulose acetate. A commercial item can be used for these various filter media.

Moreover, although there is no restriction | limiting in particular as the filtration conditions of this filtration process, The following conditions are employable.
When the pressure applied during filtration is expressed as a differential pressure from the atmospheric pressure, the value is positive and 1 hPa or more, preferably 200 MPa or less, particularly preferably 0.2 MPa or less. If the applied pressure at the time of filtration is too small, it may take a long time from the start of filtration of the charge transport material to the end of filtration, the solvent may volatilize during that time, and the properties of the solution may change. is there. In addition, if the applied pressure during filtration is too large, there are adverse effects such as breaking the filtration membrane, reducing the filtration performance (passing particles larger than the specification of the filtration membrane), and increasing the power consumption required for filtration. It may occur. At this time, a means for reducing the pressure at the filtration outlet may be used in combination, and the pressure reducing force is preferably 0.001 Pa or more, particularly 1 Pa or more, 1013 hPa or less, particularly 900 hPa or less. Such pressure reduction at the time of filtration may not be used, but if it is used, if the pressure at the time of filtration is too large, the solvent will volatilize and the properties as a solution will change. There is a possibility that adverse effects such as a decrease in performance (passing through particles larger than the specification of the filtration membrane) and an increase in power consumption required for filtration may occur.

  The temperature at the time of filtration is preferably a temperature not lower than the freezing point of the solvent to be used, particularly not lower than 5 ° C. from the freezing point of the solvent and not higher than the boiling point of the solvent, particularly not lower than 20 ° C. from the boiling point. If the temperature at the time of filtration is too low, the viscosity of the solution increases, and it takes a long time from the start of filtration of the charge transport material to the end of filtration. There is a risk of destruction. If the temperature during filtration is too high, the solvent volatilizes and the properties of the solution change, the filtration performance deteriorates (particles larger than the specification of the filtration membrane pass), and the power consumption required for filtration increases. May cause adverse effects such as

  As described above, an ultrasonic treatment step may be performed before the filtration step. In this case, the filtration step is performed on the solution after the following ultrasonic treatment step. Furthermore, it is also preferable to use an ultrasonic treatment process together with the filtration process.

{Ultrasonic treatment process}
Although there is no restriction | limiting in particular as an ultrasonic treatment means used at the ultrasonic treatment process of the solution obtained at the heating process, For example, the following are mentioned.

  Generally, when a solution is irradiated with ultrasonic waves, countless vacuum bubbles are generated in the solution. The vacuum bubbles are called cavitation, and crushing, crushing, dispersing, emulsifying, etc. are performed using the force when the cavitation is crushed. As an example, an ultrasonic disperser (also called an ultrasonic homogenizer) is set directly to touch the solution (composition for organic electroluminescence device) before being put into the filtration step, and ultrasonic waves are applied to the composition. Filtration method, a method of attaching an ultrasonic oscillator to the input container of the filtration step and exciting the solution from the outside of the container, a method of attaching an ultrasonic oscillator to the filter unit housing of the filtration device, and the solution being filtered The method of exciting from the outside is mentioned.

Moreover, although there is no restriction | limiting in particular as an ultrasonic treatment condition of this ultrasonic treatment process, The following conditions are employable.
As a frequency at the time of ultrasonic treatment, a range that can be used from a technical viewpoint is 20 kHz or more, 20 MHz or less, particularly 500 kHz or less. If the frequency during sonication is too low, the dissolution of the solute will not proceed, and in the subsequent filtration step, it may take a long time from the start of filtration of the charge transport material to the end of filtration. is there. In addition, if the frequency at the time of ultrasonic treatment is too high, the power consumption required for the treatment increases. When ultrasonic treatment is used in combination with the filtration step, the filtration membrane is destroyed, and the filtration performance is reduced (the specification of the filtration membrane). May cause adverse effects such as the passage of larger particles.

  The output at the time of ultrasonic processing is obliged to be used within the output specified in the Radio Law, but the range that can be used only from a technical point of view is usually 1 W or more, especially 30 W. From the above, it is possible to list usually 100 kW or less, particularly 1 kW or less. If the frequency is constant, the output of the ultrasonic wave is determined by the amplitude. If the output during sonication is too low, solute disintegration will not proceed, and it may take a long time from the start of filtration of the charge transport material to the end of filtration in the subsequent filtration step. is there. In addition, if the output during sonication is too high, the charge transport material and the light-emitting material itself are decomposed by receiving ultrasonic energy, and the power consumption required for the treatment increases. In such a case, there is a possibility that harmful effects such as destruction of the filtration membrane and deterioration of the filtration performance (passing through particles larger than the specification of the filtration membrane) may occur.

  The treatment time during ultrasonic treatment is usually 0.1 seconds or longer, particularly 1 minute or longer, and usually 10,000 minutes or shorter, particularly 240 minutes or shorter. If the treatment time during sonication is too short, solute disintegration will not proceed, and it may take a long time from the start of filtration of the charge transport material to the end of filtration in the subsequent filtration step. There is. In addition, if the treatment time at the time of ultrasonic treatment is too long, the charge transport material or the light emitting material itself is decomposed by receiving ultrasonic energy, the solvent volatilizes in the meantime, and the property as a solution changes. When ultrasonic treatment is used in combination, there is a risk that the filtration membrane will be destroyed, the filtration performance will be reduced (particles larger than the specification of the filtration membrane will pass), and the power consumption required for filtration will increase. .

  The treatment temperature at the time of ultrasonic treatment is preferably set to a temperature not lower than the freezing point of the solvent to be used, particularly not lower than 5 ° C. from the freezing point of the solvent and not higher than the boiling point of the solvent, particularly not lower than 20 ° C. from the boiling point. If the treatment temperature during sonication is too low, solute disintegration will not proceed, and it will take a long time from the start of filtration of the charge transport material to the end of filtration in the subsequent filtration step. When ultrasonic treatment is used in combination, the filtration membrane may be destroyed, the yield may decrease, the solute concentration after filtration may decrease, and the like. In addition, if the treatment temperature during sonication is too high, the solvent will volatilize and the properties of the solution will change, the filtration performance will deteriorate (particles larger than the specification of the filtration membrane will pass), the consumption required for filtration There is a risk of adverse effects such as an increase in power.

{Measurement of volume average particle size (d50) of particle size distribution}
In the present invention, the volume average particle size (d50) of the particle size distribution is measured for the solution obtained through the filtration step after the heating step or the heating step and the ultrasonic treatment step. The composition for organic electroluminescent elements confirmed to be 400 nm or less by measuring the volume average particle diameter (d50) is appropriately subjected to heating or a dissolution process by heating and ultrasonic treatment. It is a composition for organic electroluminescent elements that can form an organic electroluminescent element that does not contain foreign matters or precipitates during the filtration step, and therefore has no problem of generating pinholes or dark spots.
Thus, the measurement of a particle group having a nanoscale size particle size of volume average particle size (d50) ≦ 400 nm is performed using the following principle.

<Measurement principle: Dynamic light scattering method (FFT power spectrum method)>
Particles having a size of several μm or less undergo Brownian motion under the influence of solvent molecular motion. The speed of this movement depends on the particle size (exactly mass, which is proportional to the volume of the particle if the density of the particle is constant), and small particles are fast and large. The particles move slowly. When these Brownian particles are irradiated with laser light, a phenomenon (Doppler shift) occurs in which the phase of the scattered light changes according to the speed. Since this Doppler shift includes particle movement speed, that is, particle diameter information, it is possible to detect it and obtain the particle size distribution.

FIG. 2 is an explanatory diagram showing this measurement principle, and shows a process from detection of particle diameter information to particle size distribution conversion.
As shown in FIG. 2, the measurement of the particle size distribution by the dynamic light scattering method is performed according to the following procedure.
(1) A sample is irradiated with laser diode light through an optical fiber.
(2) The scattered light including the particle diameter information is also transmitted to the detection unit using the reflected light as a reference.
(3) Phase change including particle diameter information is detected and analog / digital (A / D) conversion is performed.
(4) The digitized information is converted into frequency components by FFT (Fast Fourier Transformer).
(5) A particle size distribution is obtained from the frequency component converted data using a special algorithm (for example, specification of the device manufacturer).

  According to the above measurement principle, if the density of the sample particles is known, the volume (frequency, cumulative) distribution can be measured. Therefore, assuming that the particles are spherical, the volume distribution can be converted into the relationship between the particle diameter and the frequency, that is, the particle size distribution. This is called volume particle size distribution. Here, the median value of the volume particle size cumulative distribution is exclusively used as the average particle size. This is referred to as a volume average particle diameter and is abbreviated as d50.

  In addition, in the measurement of the particle size distribution, the filter for filtration used was assumed with respect to the particle size distribution of the composition after filtration, assuming that particles larger than the opening of the filter pass through due to a defect in the filter, etc. The measurement range must be selected appropriately according to the mesh size. For example, when a 0.2 μm aperture filter is used, the measurement range must be at least in the range of 10 nm to 200 nm. More preferably, it is in the range of 0.1 nm to 800 nm. In other words, the measurement range is preferably such that the maximum measurable particle diameter is 4 times or more the opening of the filter for opening.

The particle size distribution of the composition for organic electroluminescent elements is from 0.0000001 seconds (in situ measurement in the filtration step) to 2678400 seconds after the production of the composition for organic electroluminescent elements, that is, preferably after filtration. In between, it is preferable to measure. It may be technically difficult to set the measurement time after filtration to less than 0.0000001 seconds, and if it exceeds 2678400 seconds, the production cost will increase greatly, which is extremely disadvantageous for practical use of ink production. There is a case.
When the particle size distribution is not measured in situ in the filtration step, the particle size distribution is measured by 2678400 seconds after obtaining the organic electroluminescent element composition by filtration. Usually, the measurement is carried out using a solution obtained by diluting the composition with an appropriate magnification using the same solvent filtered through the above filter. This dilution is performed in order to prevent measurement errors from occurring when the composition has a particle size distribution that is too high.

  The composition for organic electroluminescent elements of the present invention is characterized in that the volume average particle size (d50) of the particle size distribution measured in this way is 400 nm or less. When the volume average particle size (d50) exceeds 400 nm, there is a problem of precipitation of foreign matters and dissolved materials, and an organic electroluminescent device free from pinholes and dark spots cannot be produced. The volume average particle size (d50) is preferably as small as possible. Therefore, it is particularly preferable that the volume average particle size (d50) is 200 nm or less, and particularly 5 nm or less. In short, it will not be commensurate with the processing cost. Therefore, the volume average particle diameter (d50) of the composition for organic electroluminescent elements is usually 100 nm or more.

  In addition, when the volume average particle diameter (d50) is confirmed to exceed 400 nm by measuring the volume average particle diameter (d50) of the particle size distribution, the heating process, the filtration process, and the ultrasonic treatment described above are further performed. A process is performed and the composition for organic electroluminescent elements of volume average particle diameter (d50) <= 400nm is obtained.

{Usage}
The composition for an organic electroluminescent device of the present invention is a layer disposed between the anode and the cathode of the organic electroluminescent device, that is, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, etc. It is used to form functional layers such as charge transport layers and light emitting layers by a wet film forming method. In particular, wet film forming methods such as a light emitting layer, a hole transport layer, a hole injection layer, etc. It is preferably applied to the layer formed by

  In the present invention, the wet film forming method includes, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, nozzle printing. This method is a wet film formation method such as a printing method, a screen printing method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable. This is because the liquid property specific to the composition for organic electroluminescent elements of the present invention used as a film forming composition in the wet film forming method is met.

  In addition, the composition for organic electroluminescent elements of the present invention has a volume average particle size (d50) of particle size distribution of 400 nm or less. A high-performance organic electroluminescent device free from the problem of spot generation can be produced. As a method for evaluating the occurrence of such pinholes and dark spots, the following method can be used.

Evaluation of dark spots caused by pinholes and foreign matters is possible by measuring the surface roughness of a thin film layer formed using the composition. For example, the surface roughness of the base substrate before forming the thin film layer is measured by a measuring means capable of measuring on the sub-nm scale, and the magnitude of the surface roughness value of the thin film layer formed on the base substrate is small or large. It is possible to adopt a method of comparing the two. As a measuring means capable of measuring the surface roughness on the sub-nm scale, for example, Bart scan manufactured by Ryoka System Co., Ltd. can be cited.
Therefore, when a thin film layer is formed on the base substrate using the obtained composition, when this thin film layer is applied to an organic electroluminescence device, the pin resulting from the surface roughness of the electrode, adhesion of foreign matter, etc. It is possible to evaluate whether the generation of holes or dark spots can be suppressed. That is, in this evaluation, when the surface roughness of the thin film layer is the same as or smaller than the surface roughness of the base substrate, it can be determined that the generation of pinholes and dark spots can be suppressed.
In particular, as an indicator of surface roughness, crests and troughs of the surface shape, that is, values obtained by performing some kind of statistical processing on the target measurement surface (for example, an average value measured many times) ) Can be used as Rmax. When the value is larger than Rmax of the base substrate, it suggests that a pinhole or a foreign substance exists, and the occurrence of a short circuit of the element or generation of a dark spot on the light emitting surface is predicted.

{Blend composition}
Hereinafter, blending components such as a charge transporting material and a solvent contained in the composition for an organic electroluminescence device of the present invention and the composition thereof will be described.

  Although the composition for organic electroluminescent elements of this invention contains a charge transport material and a solvent as an essential component, according to a use, it further contains a luminescent material and another component. Hereinafter, the light emitting material and the charge transport material are collectively referred to as “organic electroluminescent element material”.

<Organic electroluminescent material>
The content of the organic electroluminescent element material in the composition for organic electroluminescent elements of the present invention is usually 0.0001 wt% or more, preferably 0.001 wt% or more, more preferably 0.1 wt% or more, and usually 90 wt%. Hereinafter, it is preferably 70 wt% or less, more preferably 50 wt% or less. If this content is less than the above lower limit, the film thickness of the thin film formed by the wet film formation method becomes thin, and when it is used as an element, it may cause black spots or short circuits. If this content is higher than the above upper limit, the film thickness of the thin film formed by the wet film forming method becomes thick, and when it is used as an element, the driving voltage is likely to increase or film non-uniformity (coating unevenness) is likely to occur. And uneven brightness may occur.

  The organic electroluminescent element material in the present invention may be either a low molecule or a polymer, and is arbitrarily selected according to the application as long as the effects of the present invention are not significantly impaired. When the organic electroluminescent material is a low molecule, its molecular weight is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, preferably 200 or more, more preferably The range is 300 or more, more preferably 400 or more. When the organic electroluminescent element material is a polymer, the molecular weight (hereinafter, unless otherwise specified, the molecular weight of the polymer refers to the weight average molecular weight) is usually 1000000 or less, preferably 500000 or less, more preferably 300000. In the following, it is usually in the range of 2000 or more, preferably 5000 or more, more preferably 10,000 or more.

When the organic electroluminescent element material is a low molecule, if the molecular weight is too small, the glass transition temperature, melting point, decomposition temperature, etc. tend to be low, and the heat resistance of the organic electroluminescent element material and the organic thin film to be formed is significantly reduced. In some cases, the device performance may be deteriorated due to a decrease in film quality due to recrystallization or molecular migration, or an increase in impurity concentration due to thermal decomposition of the material. In the case of a polymer, although it is not so remarkable as a low molecule, if the molecular weight is too small, the same problem may be caused due to a decrease in heat resistance.
On the other hand, if the molecular weight of the organic electroluminescent element material is too large, the organic electroluminescent element with respect to the solvent depends on the structure of the organic electroluminescent element material and the type of solvent used for preparing the composition (ink). The solubility of the material may become too small, for example, purification in the material manufacturing process may be difficult. In addition, there is a problem that a portion where a thin film is not formed during film formation or a film thickness of the formed organic thin film becomes too thin, which may cause black spots or short-circuiting when used as an element. .

(Luminescent material)
The composition for organic electroluminescent elements of the present invention may contain a luminescent material as an organic electroluminescent element material. In this case, the composition for organic electroluminescent elements of the present invention is usually used for forming a light emitting layer of an organic electroluminescent element.

  A light-emitting material is a material having a fluorescence quantum yield or phosphorescence quantum yield of 30% or more in a dilute solution at room temperature in an inert gas atmosphere. A part or all of an EL spectrum obtained when an organic electroluminescence device manufactured using is energized is defined as a material attributed to light emission of the material.

  The light emitting material is not limited as long as it is usually used as a light emitting material of an organic electroluminescent element. For example, a fluorescent material or a phosphorescent material may be used, but a phosphorescent material is preferable from the viewpoint of internal quantum efficiency. In addition, a fluorescent material may be used for the blue light emitting material, and a phosphorescent light emitting material may be used for the green light emitting material and the red light emitting material.

  As the light emitting material, for the purpose of improving the solubility in a solvent, a material in which the symmetry or rigidity of the molecule is reduced or a lipophilic substituent such as an alkyl group is introduced is used. preferable.

  Hereinafter, examples of the fluorescent light emitting material among the light emitting materials will be described, but the fluorescent light emitting material is not limited to the following examples.

  Examples of the fluorescent light-emitting material (blue fluorescent dye) that emits blue light include naphthalene, chrysene, perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof. Of these, anthracene, chrysene, pyrene, and derivatives thereof are preferable.

Examples of the fluorescent light emitting material (green fluorescent dye) that gives green light emission include aluminum complexes such as quinacridone, coumarin, diaminoanthracene, Al (C ₉ H ₆ NO) _3, and derivatives thereof.

  Examples of the fluorescent material that gives yellow light (yellow fluorescent dye) include rubrene, perimidone and derivatives thereof.

  Examples of fluorescent light-emitting materials (red fluorescent dyes) that emit red light include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyrene) -4H-pyran) -based compounds, benzopyran, and rhodamine. , Xanthenes such as benzothioxanthene and azabenzothioxanthene, and derivatives thereof.

  As the phosphorescent material, for example, a long-period type periodic table (hereinafter referred to as a long-period type periodic table when referred to as “periodic table” unless otherwise specified) is selected from the seventh to eleventh groups. A Werner type complex or a non-Werner type organometallic complex containing a metal as a central metal.

  Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Among these, iridium, palladium, and platinum are more preferable.

  As the ligand of the complex, a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or a (hetero) arylpyrazole ligand and a pyridine, pyrazole, phenanthroline, or the like is connected is preferable. A pyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of the phosphorescent material include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2- Phenylpyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

  The molecular weight of the compound used as the luminescent material is preferably a low molecular weight, and is arbitrary as long as the effects of the present invention are not significantly impaired. Usually, it is 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, The range is usually 100 or more, preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more. If the molecular weight of the luminescent material is too small, the heat resistance will be significantly reduced, gas generation will be caused, the film quality will be reduced when the film is formed, or the morphology of the organic electroluminescent element will be changed due to migration, etc. Sometimes come. On the other hand, if the molecular weight of the luminescent material is too large, it may cause a decrease in luminescent color purity due to an increase in the π conjugate length, it will be difficult to purify the organic compound, and it will take time to dissolve in the solvent. There is a tendency to.

  In addition, only 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio. Moreover, you may mix and use the charge transport material mentioned later by arbitrary ratios.

When the composition for organic electroluminescent elements of the present invention contains a luminescent material, the content of the luminescent material contained in the composition for organic electroluminescent elements is preferably 0.000001 wt% or more, more preferably 0.0001 wt% or more. 0.01 wt% or more is particularly preferable, 25 wt% or less is preferable, 15 wt% or less is more preferable, and 15 wt% or less is particularly preferable.
When the content of the light emitting material in the composition for organic electroluminescent elements is less than this lower limit, a portion where a thin film is not formed during film formation occurs due to insufficient solid content in the composition for organic electroluminescent elements, Or the problem that the film thickness of the formed thin film becomes too thin may occur, and it may not be possible to obtain the desired function sufficiently, such as generation of black spots or short circuit in the finally obtained device. is there. In addition, the relative value of the concentration with respect to the charge transport material contained in the composition for organic electroluminescent elements is decreased, the transfer of charge or energy from the charge transport material is insufficient, and the power consumption is reduced due to an increase in reactive current. In addition, there may be a color shift due to light emission from the charge transport material itself.
On the other hand, if the content of the luminescent material in the composition for organic electroluminescent elements exceeds this upper limit, the thickness of the thin film obtained at the time of film formation becomes too thick, and the driving voltage of the element rises, and uneven coating tends to occur. Thus, the desired function may not be sufficiently obtained, such as causing luminance unevenness on the light emitting surface of the element. In addition, quenching phenomenon due to increased interaction between light emitting material molecules, generally called concentration quenching, aggregation of the light emitting material during drying, and increase in driving voltage due to the light emitting material acting as a trap for charges injected into the light emitting layer In some cases, the durability of the device may be reduced.
When there are a plurality of light emitting materials contained in the composition for organic electroluminescent elements of the present invention, the content represents the total amount.

(Charge transport material)
In an organic electroluminescent device, it is desirable to efficiently extract and transport positive and negative charges (hereinafter sometimes referred to as carriers) from an anode and a cathode, and efficiently supply them to the above-described luminescent materials as necessary. Therefore, the composition for organic electroluminescent elements of the present invention contains such a charge transport material as an essential component as an organic electroluminescent element material. Examples of the charge transporting material include a hole transporting compound and an electron transporting compound. These charge transport materials may be used alone, or may be used by mixing with the above-described light emitting material at an arbitrary ratio. When mixed with a light-emitting material, the light-emitting material preferably emits light by receiving charge or energy from the charge transport material.

  Here, examples of the charge transport material include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, thiophene compounds, benzylphenyl compounds, fluorene compounds, hydrazone compounds, silazane compounds, silanamine compounds, Phosphamine compounds, quinacridone compounds, triphenylene compounds, carbazole compounds, pyrene compounds, benzidine compounds, anthracene compounds, phenanthroline compounds, quinoline compounds, pyridine compounds, triazine compounds, oxadiazole compounds, Examples include imidazole compounds. These may be low molecules, but may be polymers in which a plurality of arbitrary compounds are linked.

  More specifically, two or more condensed aromatic rings containing two or more tertiary amines represented by 4,4-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are nitrogen. Aromatic amine compounds having a starburst structure, such as aromatic amine compounds substituted with atoms (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (Journal of Luminescence, 1997, Vol. 72-74, pp. 985), an aromatic amine compound consisting of a tetramer of triphenylamine (Chemical Communications, 1996, pp. 2175), 2, 2 ′, Fluorene series such as 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene Compound (Synthetic Metals, 1997, Vol. 91, pp. 209), 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND), 2,5-bis (6 ′ -(2 ', 2 "-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10- Phenanthroline (BCP, bathocuproine), 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 4,4′-bis (9- Carbazole) -biphenyl (CBP), polyvinyl carbazole, polyaniline, polyalkylthiophene and the like.

The charge transport material in the present invention may be a low molecule or a polymer, and is arbitrarily selected according to the use unless the effects of the present invention are significantly impaired. When the charge transport material is a low molecule, its molecular weight is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, preferably 200 or more, more preferably 300 or more. More preferably, the range is 400 or more. When the charge transport material is a polymer, the molecular weight (hereinafter, unless otherwise specified, the molecular weight of the polymer refers to the weight average molecular weight) is usually 1000000 or less, preferably 500000 or less, more preferably 300000 or less, Moreover, it is 2000 or more normally, Preferably it is 5000 or more, More preferably, it is the range of 10,000 or more.
If the charge transport material is a low molecule, if its molecular weight is too small, the glass transition temperature, melting point, decomposition temperature, etc. tend to be low, and the heat resistance of the charge transport material and the organic thin film to be formed is significantly reduced, and recrystallization occurs. In some cases, the film quality deteriorates due to molecular migration or the like, or the impurity concentration increases due to thermal decomposition of the material, thereby degrading the device performance. In the case of a polymer, although it is not so remarkable as a low molecule, if the molecular weight is too small, the same problem may be caused due to a decrease in heat resistance.
On the other hand, if the molecular weight of the charge transport material is too large, the solubility of the charge transport material in the solvent decreases depending on the structure of the charge transport material and the type of solvent used to prepare the composition (ink). In some cases, for example, purification in the material production process may be difficult. In addition, there is a problem that a portion where a thin film is not formed during film formation or a film thickness of the formed organic thin film becomes too thin, which may cause black spots or short-circuiting when used as an element. .

  Note that only one of the charge transport materials described above may be used, or two or more of them may be used in any combination and ratio.

  The content of the charge transport material contained in the composition for organic electroluminescent elements of the present invention is preferably 0.000001 wt% or more, more preferably 0.0001 wt% or more, and still more preferably 0.01 wt% or more. Moreover, 50 wt% or less is preferable, 30 wt% or less is more preferable, and 15 wt% or less is still more preferable. If the content of the charge transport material in the composition for organic electroluminescent elements is less than this lower limit, it may cause an increase in driving voltage due to a decrease in charge transport capability in the formed thin film, or a decrease in luminous efficiency. is there. In addition, the solid content in the composition for organic electroluminescent elements is insufficient, resulting in a problem that a thin film is not formed at the time of coating film formation, or the formed thin film is too thin. This is not preferable because the desired function may not be sufficiently obtained, such as the occurrence of black spots or short-circuiting in the finally obtained device, while the content of the charge transport material is not limited to this upper limit. The film thickness of the thin film obtained at the time of film formation is too thick, the drive voltage of the element rises, coating unevenness is likely to occur, and brightness unevenness of the light emitting surface of the element is caused. Since it may not be obtained sufficiently, it is not preferable.

  Moreover, when the composition for organic electroluminescent elements of this invention contains a luminescent material with a charge transport material, the ratio of content of the luminescent material with respect to content of the charge transport material in the composition for organic electroluminescent elements is 0. 0.01 wt% or more is preferable, 0.1 wt% or more is more preferable, and 1 wt% or more is more preferable. Moreover, 50 wt% or less is preferable, 30 wt% or less is more preferable, and 10 wt% or less is still more preferable. If the ratio of the content of the light-emitting material to the content of the charge-transporting material in the composition for organic electroluminescent elements is below this lower limit, the transfer of charge or energy from the charge-transporting material becomes insufficient, resulting in an increase in reactive current. A decrease in power consumption or a color shift due to light emission from the charge transport material itself occurs. On the other hand, if this ratio exceeds the above upper limit, quenching phenomenon due to an increase in interaction between light emitting material molecules, generally called concentration quenching, aggregation of the light emitting material during drying, trapping of charges injected into the light emitting layer. As a result, the driving voltage increases and the durability of the element decreases.

<Solvent>
The composition for organic electroluminescent elements of the present invention contains a solvent. Here, the solvent in the present invention is a compound that is a liquid in an atmosphere of 20 ° C. and 1 atm, and that can dissolve the light emitting material and the charge transporting material contained in the composition for organic electroluminescent elements of the present invention. It is.

  The solvent is not particularly limited as long as it is a commercially available polar or nonpolar solvent. Among them, a substituted or unsubstituted aromatic such as benzene, toluene, xylene, mesitylene, cyclohexylbenzene, dodecylbenzene, tetralin, etc. Aromatic hydrocarbon solvents, aromatic ether solvents such as anisole, benzoic acid ester, diphenyl ether, aromatic ester solvents, linear or cyclic alkane solvents such as hexane, heptane, cyclohexane, and carboxylic acid ester solvents such as ethyl acetate Solvents, carbonyl-containing solvents such as acetone and cyclohexanone, water, alcohols, cyclic ethers, etc. are preferable. The boiling point is 180 ° C. Aromatic hydrocarbon solvents are more preferred, especially trimethyl Benzene, cyclohexylbenzene, dodecylbenzene, tetralin, cyclohexanone, ethyl benzoate is preferred.

  In the composition for organic electroluminescent elements of the present invention, one type of solvent may be contained, or may be contained in a combination of two or more types of solvents, but usually one or more types, preferably Are preferably contained in combinations of 2 or more, usually 10 or less, preferably 8 or less, more preferably 6 or less.

  In addition, when two or more solvents are used as a mixture, the mixing ratio is not limited at all, but the solvent having the largest mixing ratio is usually 1 wt% or more, preferably 5 wt% in all the solvents. Or more, more preferably 10 wt% or more, and usually 100 wt% or less, preferably 90 wt% or less, more preferably 80 wt% or less, and the solvent having the smallest mixing ratio is usually 0.0001 wt% or more, preferably The mixing ratio is preferably 0.001 wt% or more, more preferably 0.01 wt% or more, and usually 50 wt% or less.

<Other ingredients>
The composition for an organic electroluminescent device of the present invention includes the above-described charge transporting material, luminescent material, solvent, coating property improving agent such as a leveling agent, antifoaming agent, thickener, electron accepting compound, and electron donating property. You may contain charge transport adjuvants, such as a compound, binder resin. The content of these other components in the composition for organic electroluminescent elements does not significantly inhibit the charge transfer of the formed thin film, does not inhibit the light emission of the luminescent material, and does not deteriorate the film quality of the formed thin film. In view of the above, it is usually 50 wt% or less.

<Solvent concentration / solid content concentration>
Although content of the solvent in the composition for organic electroluminescent elements of this invention is arbitrary unless the effect of this invention is impaired remarkably, it is 50 wt% or more normally, and is 99.9999 wt% or less normally. In addition, when mixing and using 2 or more types of solvents as a solvent, it is made for the sum total of these solvents to satisfy | fill this range.
Further, the total solid content concentration of the light emitting material, the charge transporting material, etc. is usually 0.01 wt% or more and usually 70 wt% or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.

[Organic electroluminescence device]
The organic electroluminescent element of the present invention is an organic electroluminescent element having an anode, a cathode, and a layer disposed between the anode and the cathode, wherein the layer disposed between the anode and the cathode is the above-mentioned book. It is a layer formed using the composition for organic electroluminescent elements of the invention. The layer formed using the composition for organic electroluminescent elements of the present invention is not particularly limited as long as it is a layer between the anode and the cathode, but as described above, the light emitting layer, the hole injection layer In addition, one or more of the hole transport layers are preferable.

Below, the layer structure of the organic electroluminescent element of this invention, its general formation method, etc. are demonstrated with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent element 10 of the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

{substrate}
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

{anode}
The anode 2 serves to inject holes into the layer on the light emitting layer side.

  This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

  The anode 2 is usually formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate 1. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

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

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

  For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.

{Hole injection layer}
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.

  In the method for forming the hole injection layer 3 according to the present invention, the hole injection layer 3 is preferably formed by a wet film formation method from the viewpoint of reducing dark spots. In particular, a layer containing a hole transporting compound and an electron accepting compound, which will be described in detail below, is preferably formed by a wet film-forming method, and is particularly formed by the composition for organic electroluminescent elements of the present invention. It is preferred that the layer be a layer.

  The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When the hole injection layer 3 is formed by a wet film formation method, a material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (a solvent for hole injection layer) to form a film-forming composition ( A composition for forming a hole injection layer, preferably a composition for an organic electroluminescent device of the present invention) is prepared, and this composition for forming a hole injection layer corresponds to the lower layer of the hole injection layer 3 by an appropriate technique. The hole injection layer 3 is formed by coating on a layer (usually an anode) to be formed, forming a film, and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.

  The hole transporting compound may be a high molecular compound or a low molecular compound as long as it is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device. .

The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzidine compounds, benzylphenyl compounds, and tertiary amines linked by fluorene groups. Compounds, hydrazone compounds, silazane compounds, silanamine compounds, phosphamine compounds, quinacridone compounds, low molecular or high molecular materials that are arbitrarily combined with these, and the like.
Moreover, it is also preferable to use the crosslinkable compound illustrated as a compound used for the below-mentioned hole transport layer 4, and the structure conversion type compound by a heat | fever as a hole transportable compound.

  The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more of aromatic tertiary amine polymer compounds and one of other hole transporting compounds or Two or more types are preferably used in combination.

  Among the above examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

  The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

[In Formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. . Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Y represents a linking group selected from the following linking group group. Moreover, among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

（上記各式中、Ａｒ^６〜Ａｒ^１６は、それぞれ独立して、置換基を有していてもよい芳香族炭化水素基または置換基を有していてもよい芳香族複素環基を表す。Ｒ^２１およびＲ^２２は、それぞれ独立して、水素原子または任意の置換基を表す。）］

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents each independently the aromatic hydrocarbon group which may have a substituent, or the aromatic heterocyclic group which may have a substituent. R ²¹ and R ²² each independently represent a hydrogen atom or an arbitrary substituent.

As the aromatic hydrocarbon group and the aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property of the polymer compound A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of this substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.

When R ²¹ and R ²² are optional substituents, examples of the substituent include alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

  Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the above formula (I) include those described in WO2005 / 089024.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01 wt% or more in terms of film thickness uniformity, preferably It is 0.1 wt% or more, more preferably 0.5 wt% or more, and usually 70 wt% or less, preferably 60 wt% or less, more preferably 50 wt% or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron-accepting compound as well as a hole-transporting compound as a constituent material of the hole injection layer.

  The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

  Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, triphenylsulfonium tetrafluoroborate (WO2005 / 089024); iron chloride (Only one of them may be used, or two or more may be used in any combination and ratio.) (Japanese Patent Laid-Open No. 11-251067), high-valent inorganic compounds such as ammonium peroxodisulfate A cyano compound such as tetracyanoethylene; an aromatic boron compound such as tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365); a fullerene derivative; iodine and the like.

  These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.

  The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component, and 2 or more types may be used together by arbitrary combinations and ratios, but the hole injection property from an anode and the hole transport property to a cathode side are good. From the viewpoint of ensuring, the content in the hole injection layer is preferably 80 wt% or less.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying process, which may adversely affect other layers and the substrate.

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

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

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

Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.
Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.

In addition, dimethyl sulfoxide and the like can also be used.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.

(Film formation method)
After preparing the composition for forming a hole injection layer, the composition is formed on a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by a wet film formation method, and dried. The hole injection layer 3 can be formed.

  The temperature in the film forming step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film loss due to the formation of crystals in the composition.

  Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.

  After the film formation, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming the hole injection layer and sufficient insolubilization of the thin film does not occur, but preferably 10 seconds or longer, usually 180 minutes. It is as follows. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by a vacuum deposition method, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are contained in a vacuum container. (If two or more materials are used, put them in each crucible), evacuate the vacuum vessel to about 10 ⁻⁴ Pa with an appropriate vacuum pump, and then heat the crucible (2 When using more than one kind of material, heat each crucible) and evaporate by controlling the amount of evaporation (when using more than two kinds of materials, evaporate by controlling the amount of evaporation independently) A hole injection layer 3 is formed on the anode 2 of the substrate placed face to face. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

{Hole transport layer}
The organic electroluminescent element of the present invention preferably has a hole transport layer 4.

  The method for forming the hole transport layer 4 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.

  In particular, in the organic electroluminescent device of the present invention in which the luminescent layer is formed using the composition for organic electroluminescent device of the present invention, the hole injection barrier between the hole injection layer and the luminescent layer is relaxed. In addition, it has a hole transport layer from the viewpoint of reducing driving voltage, suppressing deterioration of materials due to accumulation of holes at the layer interface, and improving luminous efficiency by improving efficiency of hole injection into the light emitting layer. In addition, this hole transport layer uniformly coats the hole injection layer, and further, from the viewpoint of washing or covering fine foreign matters due to the projections derived from the anode and particles, etc., by a wet film formation method, Preferably, it is preferably formed by a wet film forming method using the composition for organic electroluminescent elements of the present invention.

  The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. However, the organic electroluminescent element of the present invention may have a configuration in which the hole transport layer is omitted.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

  The material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are substituted with nitrogen atoms. Aromatic amine compounds having a starburst structure (J. Lumin., 72) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234811), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine -74, 985, 1997), an aromatic amine compound consisting of a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2,2 ', 7,7'-tetrakis- ( Spiro compounds such as diphenylamino) -9,9′-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4′-N, N′-dica Examples thereof include carbazole derivatives such as vazole biphenyl, and polyarylene ether sulfone (Polym. Adv. Tech.) Containing, for example, polyvinyl carbazole, polyvinyl triphenylamine (JP-A-7-53953), and tetraphenylbenzidine. 7, Vol. 33, 1996).

  In the case of forming the hole transport layer 4 by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3 and then heated and dried after the wet film formation. .

  The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.

  When the hole transport layer is formed by vacuum deposition, the film forming conditions are the same as those for forming the hole injection layer 3.

  The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.

  The hole transport layer 4 may be a layer formed by crosslinking a crosslinkable compound. Here, the crosslinkable compound is a compound having a crosslinking group, and forms a polymer by crosslinking. The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

  Examples of the crosslinking group of the crosslinking compound include cyclic ethers such as oxetane and epoxy; unsaturated double bonds such as vinyl group, trifluorovinyl group, styryl group, acrylic group, methacryloyl and cinnamoyl; benzocyclobutane and the like. It is done.

  The number of crosslinkable groups possessed by the crosslinkable compound, that is, the monomer, oligomer or polymer having a crosslinkable group is not particularly limited, but is generally less than 2.0, preferably 0.8 or less, more preferably 0 per unit charge transport unit. A number that is .5 or less is preferred. This is to adjust the relative dielectric constant of the hole transport layer forming material to a suitable range. Moreover, when the number of crosslinking groups is too large, reactive active species are generated, which may adversely affect other materials. Here, when the material forming the crosslinkable polymer is a monomer body, the unit charge transport unit is a monomer body itself, and indicates a skeleton (main skeleton) excluding a crosslinking group. Even when other types of monomers are mixed, the main skeleton of each monomer is shown. When the material forming the crosslinkable polymer is an oligomer or polymer, in the case of repeating a structure in which conjugation is broken organically, the repeated structure is defined as a unit charge transport unit. In the case of a structure in which conjugation is widely connected, a minimum repeating structure exhibiting charge transporting property or a monomer structure is shown. For example, polycyclic aromatics such as naphthalene, anthracene, phenanthrene, tetracene, chrysene, pyrene, perylene, fluorene, triphenylene, carbazole, triarylamine, tetraarylbenzidine, 1,4-bis (diarylamino) benzene, etc. It is done.

  Furthermore, as the crosslinkable compound, it is preferable to use a hole transporting compound having a crosslinkable group. Examples of hole transporting compounds in this case include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; Examples include phenylamine derivatives; silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes, and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

  In particular, the crosslinkable compound is preferably a crosslinkable compound having a group represented by the following formula from the viewpoints of a high reaction rate, a low reaction temperature, and a small number of side reactions.

  In addition, the hole transport layer according to the present invention may be formed using a heat-converted compound having a structure represented by the following formula (U1) or (U2), and the reaction speed and reaction temperature. Is preferable in view of low C and low side reaction.

(In the formula (U1), ring A ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. A ring may be formed directly or via a divalent linking group.
S ¹ , S ² and R ^{1 to} R ⁶ are each independently a hydrogen atom, a hydroxyl group, an alkyl group which may have a substituent, an aromatic hydrocarbon ring group which may have a substituent, An aromatic heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy which may have a substituent A group, an acyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an acyloxy group which may have a substituent, It represents an arylamino group which may have a substituent, a heteroarylamino group which may have a substituent, or an acylamino group which may have a substituent.
In formula (U2), ring B ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. Further, the substituents may form a ring directly or via a divalent linking group.
S ^{11 to} S ¹⁴ and R ^{11 to} R ¹⁶ are each independently the same as those shown as S ¹ , S ² , and R ^{1 to} R ⁶ . )

  The molecular weight of the crosslinkable compound is usually 5000 or less, preferably 2500 or less, preferably 300 or more, more preferably 500 or more.

  In order to form a hole transport layer 4 by crosslinking a crosslinkable compound, a composition for forming a hole transport layer in which a crosslinkable compound is dissolved or dispersed in a solvent is usually prepared and deposited by a wet film formation method. Then, the crosslinkable compound is crosslinked.

  This composition for hole transport layer formation may contain the additive which accelerates | stimulates a crosslinking reaction other than a crosslinkable compound. Examples of additives that accelerate the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds. One of these may be used alone, or two or more may be used in any combination and ratio.

  Further, the composition for forming a hole transport layer may further contain a coating property improver such as a leveling agent and an antifoaming agent, an electron accepting compound, a binder resin, and the like.

  In this composition for forming a hole transport layer, the crosslinkable compound is usually 0.01 wt% or more, preferably 0.05 wt% or more, more preferably 0.1 wt% or more, usually 50 wt% or less, preferably 20 wt% or less, More preferably, it contains 10 wt% or less.

  After forming a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on the lower layer (usually the hole injection layer 3), the composition is crosslinked by heating and / or irradiation with electromagnetic energy such as light. Are polymerized by crosslinking.

  Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.

  The heating method after film formation is not particularly limited, and examples thereof include heat drying and reduced pressure drying. The heating temperature condition in the case of heat drying is usually 120 ° C. or higher, preferably 400 ° C. or lower.

  The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a deposited layer on a hot plate or heating in an oven is used. For example, a means such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be employed.

  In the case of irradiation with electromagnetic energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp, an infrared lamp, etc. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

  Heating and irradiation of electromagnetic energy such as light may be performed individually or in combination. When combined, the order of implementation is not particularly limited.

  The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Light emitting layer}
When the hole injection layer 3 or the hole transport layer 4 is provided, the light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between electrodes to which an electric field is applied, and becomes a main light emitting source.

<Light emitting layer material>
The light emitting layer 5 contains at least a material having a light emitting property (light emitting material) as a constituent material, and preferably a compound having a hole transporting property (hole transporting compound) or an electron transport. A compound (electron transporting compound) having the following properties: A light emitting material may be used as a dopant material, and a hole transporting compound, an electron transporting compound, or the like may be used as a host material. There is no particular limitation on the light-emitting material, and a material that emits light at a desired light emission wavelength and has favorable light emission efficiency may be used. Furthermore, the light emitting layer 5 may contain other components as long as the effects of the present invention are not significantly impaired. In addition, when forming the light emitting layer 5 with a wet film-forming method, it is preferable to use a low molecular weight material in any case.

  In the organic electroluminescent element of the present invention, the light emitting layer 5 is preferably formed by a wet film forming method using the above-described composition for organic electroluminescent elements of the present invention. Therefore, as specific examples of the light emitting material and the charge transporting compound contained in the light emitting layer 5 according to the present invention, as specific examples of the light emitting material and the charge transporting material included in the organic electroluminescent element composition of the present invention described above. These are the same as those exemplified, and each of these may be used alone, or two or more may be used in any combination and ratio.

  In order to form the light emitting layer 5 using the composition for organic electroluminescent elements of the present invention, the obtained thin film is dried and the solvent is removed after the organic electroluminescent element composition is wet-formed. Here, the method of the wet film forming method is not limited as long as the effects of the present invention are not significantly impaired, and any of the above-described methods can be used. A specific method of the wet film formation is the same as the method described in the formation of the hole injection layer 3.

  The thickness of the light-emitting layer 5 thus formed is arbitrary as long as the effects of the present invention are not significantly impaired, but are usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. It is. If the thickness of the light emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

  Further, the content ratio of the light emitting material in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.05 wt% or more and usually 35 wt% or less. If the amount of the light emitting material is too small, uneven light emission may occur. If the amount is too large, the light emission efficiency may be reduced. In addition, when using together 2 or more types of luminescent material, it is made for the total content of these to be contained in the said range.

  When the light emitting layer 5 contains an electron transporting compound, the content ratio of the electron transporting compound in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1 wt% or more, usually 65 wt. % Or less. If the amount of the electron transporting compound in the light emitting layer is too small, it may be easily affected by a short circuit, and if it is too large, the film thickness may be uneven. In addition, when using together 2 or more types of electron transport compounds in a light emitting layer, content of these is made to be contained in the said range.

  Moreover, when the light emitting layer 5 contains a hole transporting compound, the ratio of the hole transporting compound in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired. 65 wt% or less. If the amount of the hole transporting compound in the light emitting layer is too small, it may be easily affected by a short circuit, and if it is too large, film thickness unevenness may occur. In addition, when using together 2 or more types of hole transportable compounds in a light emitting layer, it is made for the total content of these to be contained in the said range.

{Hole blocking layer}
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

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

The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high. Examples of the material of the hole blocking layer 6 satisfying such conditions include, for example, bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum. Mixed ligand complexes such as, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Of styryl compounds (JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole 7-41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), and the like. It is. Further, a compound having at least one pyridine ring substituted at positions 2, 4, and 6 described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer 6.

  In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  There is no restriction | limiting in the formation method of the hole-blocking layer 6, A wet film-forming method, a vapor deposition method, and another method are employable.

  The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

{Electron transport layer}
An electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.

  The electron transport layer 7 is provided for the purpose of further improving the light emission efficiency of the device, and efficiently transports electrons injected from the cathode 9 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. Formed from a compound capable of

  As an electron transport compound used for the electron transport layer 7, usually, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons are transported efficiently with high electron mobility. The compound which can be used is used. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like.

  In addition, the material of the electron carrying layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the electron carrying layer 7, A wet film-forming method, a vapor deposition method, and another method are employable.

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

{Electron injection layer}
The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the film thickness is preferably from 0.1 nm to 5 nm.

  Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium or rubidium ( As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, and the like, it is possible to improve electron injection / transport properties and achieve both excellent film quality. Therefore, it is preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron injection layer 8, A wet film-forming method, a vapor deposition method, and another method are employable.

{cathode}
The cathode 9 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer 5) on the light emitting layer 5 side.

  As the material of the cathode 9, the material used for the anode 2 can be used. However, a metal having a low work function is preferable for efficient electron injection. For example, tin, magnesium, indium, A suitable metal such as calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

  In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The film thickness of the cathode 9 is usually the same as that of the anode 2.

  Further, for the purpose of protecting the cathode 9 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element according to the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers described above, and an arbitrary layer may be omitted. .

Examples of the layer that may be included in addition to the layers described above include an electron blocking layer.
The electron blocking layer is provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5 and prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3. Thus, the probability of recombination of holes and electrons in the light emitting layer 5 is increased, the excitons generated are confined in the light emitting layer 5, and the holes injected from the hole injection layer 3 are efficiently collected. There is a role to transport in the direction of. In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer 5 is produced by a wet film formation method using the composition for organic electroluminescence elements of the present invention, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (described in International Publication No. 2004/084260).

  In addition, the material of an electron blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of an electronic blockage | prevention layer, A wet film-forming method, a vapor deposition method, and another method are employable.

Further, at the interface between the cathode 9 and the light emitting layer 5 or the electron transport layer 7, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ). It is also an effective method to improve the efficiency of the element by inserting an ultrathin insulating film (0.1 to 5 nm) formed by the method (Applied Physics Letters, 1997, Vol. 70, pp. 152; (Kaihei 10-74586; IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.).

  Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate 1 are the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, the positive layer. The hole injection layer 3 and the anode 2 may be provided in this order.

  Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention by laminating components other than the substrate between two substrates, at least one of which is transparent.

Further, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, (when the anode is ITO, the cathode is Al, these two layers) interfacial layer between the respective stages (between emission units) Alternatively, for example, a charge consisting of five vanadium oxide (V 2 _{O 5),} etc. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

  Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.

  Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

[Organic EL display device]
The organic EL display device of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic electroluminescent display apparatus of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display device of the present invention can be obtained by the method described in “Organic EL display” (Ohm, published on Aug. 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

[Organic EL lighting]
The organic EL illumination of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic EL illumination of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

  Examples The present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless it exceeds the gist.

<Example 1>
A composition for forming a hole transport layer (a composition for an organic electroluminescence device of the present invention) was prepared as follows.
The following compound (A-1) (molecular weight 20000-30000) is used as the hole transporting compound (charge transporting material), and cyclohexylbenzene is used as the solvent. The concentration of the hole transporting compound in the composition is 4 wt. %, Each was weighed and placed in a flask, the flask was stoppered, and the mixture was stirred with a stirrer at 300 rpm for 1 hour under heating at 130 ° C.

  After visually confirming that the hole-transporting compound has not dissolved yet, transfer the solution to a pressure dispenser and filter the solution using a 0.2 μm aperture filter while applying pressure at 0.2 MPa. Thus, a composition for forming a hole transport layer was obtained.

  Using the obtained composition for forming a hole transport layer, a film was formed on a glass substrate (surface roughness Rmax = 4 nm) on which ITO (indium tin oxide) was formed to a thickness of 150 nm by an inkjet method at 230 ° C. A hole transport layer having a thickness of 20 nm was formed by firing in a nitrogen atmosphere for 1 hour.

  One day after obtaining the hole transport layer forming composition by filtration, the composition was diluted 40-fold with cyclohexylbenzene filtered through a 0.2 μm aperture filter, and Nanotrac UPA manufactured by Nikkiso Co., Ltd. -When the particle size distribution was measured with a measurement range of 0.8 to 800 nm using UT151, the volume average particle size (d50) was 180 nm.

About this formed hole transport layer, when the surface roughness was measured by the Ryoka System Co., Ltd. bart scan, it was Rmax = 4nm.
From this result, using the obtained composition for forming a hole transport layer, a surface smooth hole transport layer that eliminates the surface roughness of the base substrate can be formed. Is applied to organic electroluminescence devices, it has been found that the generation of pinholes and dark spots due to the planar roughness of the anode can be suppressed.

<Comparative Example 1>
In Example 1, a composition for forming a hole transport layer was prepared in the same manner except that filtration was performed using a filter having an opening of 1 μm instead of a filter having an opening of 0.2 μm. When the particle size distribution of the composition for transport layer formation was measured and the hole transport layer was formed, the volume average particle size (d50) of the composition for hole transport layer formation was 800 nm. The surface roughness of the layer was Rmax = 10 nm, and the surface roughness of the underlying substrate could not be eliminated, and it was predicted that problems of pinholes and dark spots could occur in the organic electroluminescence device.

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

Claims (10)

An organic electroluminescent device composition used for forming a layer disposed between an anode and a cathode of an organic electroluminescent device, comprising a charge transporting material and a solvent, by a wet film-forming method,
The composition is manufactured through a heating step and a filtration step,
The composition for organic electroluminescent elements, wherein the volume average particle size (d50) of the particle size distribution is 400 nm or less. A composition for an organic electroluminescent device used for forming a layer disposed between an anode and a cathode of an organic electroluminescent device, comprising a charge transport material and a solvent,
The composition is manufactured through a filtration step after a heating step and an ultrasonic treatment step,
The composition for organic electroluminescent elements, wherein the volume average particle size (d50) of the particle size distribution is 400 nm or less.   The composition for organic electroluminescent elements according to claim 1 or 2, wherein the charge transport material is a material for forming a light emitting layer.   The composition for an organic electroluminescent element according to claim 1, wherein the charge transport material is a material for forming a charge transport layer.   The composition for organic electroluminescent elements according to any one of claims 1 to 4, wherein the wet film-forming method is an inkjet method. An organic electroluminescent device having an anode, a cathode, and a layer disposed between the anode and the cathode,
An organic electric field characterized in that the layer disposed between the anode and the cathode is a layer formed using the composition for an organic electroluminescent element according to any one of claims 1 to 5. Light emitting element.   An organic EL display device using the organic electroluminescent element according to claim 6.   An organic EL illumination comprising the organic electroluminescence device according to claim 6. It is a manufacturing method of the composition for organic electroluminescent elements as described in any one of Claims 1 thru | or 5, Comprising:
A heating step of heating a solution containing the charge transport material and the solvent;
Filtering the solution after the heating,
A method for producing a composition for forming an organic electroluminescent element, wherein the particle size distribution is measured from 0.0000001 seconds (in situ measurement in a filtration step) to 2678400 seconds after filtration. It is a manufacturing method of the composition for organic electroluminescent elements according to any one of claims 1 to 5,
After undergoing a heating step and a sonication step for heating the solution containing the charge transport material and the solvent,
Filtering the solution.
A method for producing a composition for forming an organic electroluminescent element, wherein the particle size distribution is measured from 0.0000001 seconds (in situ measurement in a filtration step) to 2678400 seconds after filtration.

Images