JP2006114844A - Selecting method of organic el device material, organic el device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a selecting method of organic EL device materials for fully, efficiently obtaining the organic EL devices having sufficient luminescent properties for practical use. <P>SOLUTION: A selecting method of organic EL device materials solving the problem is the selecting method of the organic EL device materials selecting dopant materials used with predetermined host materials contained in the light emitting layer of the organic EL device, from two or more kinds of dopant materials having the same main skeleton. The selecting method has a dopant determining process of determining on the basis of the correlation between the ratio of the molecular weight of each dopant material to the molecular weight of the host material, and the luminous efficiency of the organic EL devices provided with the light emitting layer containing the host materials and the dopant materials. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for selecting an organic EL (Electroluminescence) element material, a method for manufacturing an organic EL element, and an organic EL element.

  An organic EL element used for an organic EL display, for example, has a light emitting layer containing a light emitting organic compound such as a fluorescent organic compound or a phosphorescent organic compound sandwiched between a hole injection electrode (anode) and an electron injection electrode (cathode). It is an element that is excited and emits light by applying an electric field from the electrode to the light emitting organic compound. Such an organic EL element is superior in element characteristics such as luminance and light emission efficiency (quantum yield) as compared with an inorganic EL element, and is now in the stage of practical use.

  The light emission principle of this organic EL element is generally considered as follows. That is, first, holes (holes) injected from the hole injection electrode into the light emitting layer and electrons injected from the electron injection electrode into the light emitting layer recombine in the light emitting layer. Excitons are generated. Subsequently, when the exciton is deactivated, it is considered that energy is emitted by being released as a light (fluorescence, phosphorescence) component.

  The light-emitting layer of the organic EL element is roughly classified into one that contains one kind of light-emitting organic compound alone and one that has excellent film-forming properties (hereinafter referred to as “host material”). Some of them contain a relatively high light-emitting organic compound (hereinafter referred to as “dopant material”) by doping (for example, see Non-Patent Document 1). Among these, the latter light-emitting layer can improve the light-emitting efficiency of the organic EL device and can use various light-emitting organic compounds. A host material and a dopant material have been proposed (see, for example, Patent Document 1).

  Such an organic EL element needs to sufficiently reduce the driving voltage in practical use. Therefore, in order to achieve a sufficient decrease in the driving voltage, carriers (holes and electrons) are injected into a region where the molecules of the host material exist (hereinafter referred to as “host region”) in the light emitting layer or the carrier transport layer. There has been a demand for further improvements in performance and mobility. In order to meet such demands, and further to improve the amorphous nature of the light emitting layer, conventionally, organic compounds having a higher molecular weight have tended to be used as host materials.

  For example, Patent Document 2 intends to provide an organic electroluminescent device that can emit light with high luminous efficiency and can be stably driven, and has an electron transport layer having a molecular weight of 400 or more and a molecular weight of less than 400. An organic EL element containing a dopant material and having an electron mobility of the dopant material higher than that of the host material has been proposed.

On the other hand, when determining the combination of the host material and the dopant material used for the light emitting layer of the organic EL element, the organic EL element is actually manufactured using a plurality of combinations of these materials, and the emission characteristics (emission efficiency, driving) Lifetime, driving voltage, chromaticity, etc.) were measured to determine which combination was practical.
JP 2003-26616 A JP 2002-1000047 A CW Tang et al., Journal of Applied Physics, American Institute of Physics, 1989, 65, p. 3610

  However, the present inventors have studied the conventional organic EL element described in Patent Document 2 in detail. However, such a conventional organic EL element does not yet have sufficient light emission characteristics for practical use. I found out.

  For example, the present inventors have found that the organic EL element proposed in Patent Document 2 can reduce the driving voltage but also the light emission efficiency with respect to the applied current. When the luminous efficiency decreases, the amount of current injected into the element must be increased in order to obtain the same level of luminance, and as a result, the power consumption required to drive the organic EL element increases. Therefore, it has been clarified that the organic EL element described in Patent Document 2 cannot be said to have sufficient light emission characteristics for practical use.

  In addition, for all combinations of host materials and dopant materials that may be used for the light emitting layer, it is inefficient to inhibit the rapid development of materials by producing organic EL elements and measuring their light emission characteristics. Instead, this results in a delay in the commercialization of various products using organic EL elements.

  Accordingly, the present invention has been made in view of the above circumstances, and a method for selecting an organic EL element material for sufficiently efficiently obtaining an organic EL element having light emission characteristics sufficient for practical use, and an organic method using the selection method. It is an object of the present invention to provide an EL device manufacturing method and an organic EL device having light emission characteristics sufficient for practical use, particularly light emission efficiency sufficient for practical use.

  As a result of intensive studies to achieve the above object, the present inventors have found that the light emission characteristics of the organic EL element are affected by the correlation between the molecular weights of both the host material and the dopant material used in the light emitting layer. As a result, the present invention has been completed.

  That is, in the method for selecting an organic EL element material of the present invention, a dopant material used in combination with a predetermined host material contained in the light emitting layer of the organic EL element is selected from two or more dopant materials having the same main skeleton. A method for selecting an organic EL element material, the ratio of the molecular weight of each of the dopant materials to the molecular weight of the host material, and the luminous efficiency of an organic EL element comprising a light-emitting layer containing the host material and the dopant material It has the dopant determination process determined based on correlation of these, It is characterized by the above-mentioned. Here, “two or more types of dopant materials having the same main skeleton” are two or more types of dopant materials having a common skeleton in the molecules of the respective dopant materials, and the common skeleton is the terminal of the molecule. Rather, it refers to something that is near the center of the molecule.

  Such a method for selecting an organic EL element material is based on known information on molecular weight of some combinations of host materials and dopant materials, and information on organic EL element samples using the combinations. Use correlation with emission characteristics. Therefore, the molecular weights of the host material and the dopant material for which the organic EL element sample is not actually manufactured are also known. Therefore, in light of the above correlation, the organic EL element using the combination is used. The light emission characteristics can be easily predicted. As a result, it is not necessary to prepare an organic EL element sample for all of the enormous combinations of host materials and dopant materials and to measure the light emission characteristics thereof, so that the organic EL elements having desired light emission characteristics are sufficiently efficient. Can be obtained.

  The method for selecting an organic EL element material of the present invention particularly uses a correlation relating to a dopant material having the same main skeleton. In the dopant material having the same main skeleton, the spread of the π electron cloud contributing to the light emission of the organic EL element is presumed to depend on the molecular weight. Therefore, it is considered that the reliability of the correlation between the molecular weight of the dopant material having the same main skeleton and the light emission characteristics of the organic EL element is extremely high. Therefore, it is estimated that the organic EL element obtained by using the method for selecting an organic EL element material of the present invention has sufficiently excellent light emission characteristics.

In this method of selecting the organic EL element material, it is preferable that the dopant material used in combination with the host material is determined so as to satisfy the condition represented by the following formula (A) in the dopant determination step.
(DMW / HMW) ≧ α (A)
In the above formula (A), HMW and DMW indicate the molecular weights of the host material and the dopant material, respectively, and α indicates a specific value. α is a specific value obtained experimentally, and varies depending on the type of the main skeleton of the dopant material. This α may be, for example, a DMW / HMW value such that a tendency of increasing luminous efficiency with increasing DMW / HMW is hardly recognized. Alternatively, it may be a DMW / HMW value at which the luminous efficiency is equal to or higher than a certain value.

  By selecting and deciding the combination of host material and dopant material so that DMW / HMW is equal to or higher than the specific value α, the combination can be uniquely selected. The combination of the host material and the dopant material can be determined.

  In the method for selecting an organic EL element material of the present invention, α is preferably 1.

  It has been confirmed by experiments of the present inventors that an organic EL element obtained by using such a method for selecting an organic EL element material has a further excellent luminous efficiency. Although the reason is not clarified in detail at present, the present inventors consider as follows. However, the factors are not limited to these.

  Conventionally, materials for light-emitting layers that have been selected and synthesized when developing organic EL elements have an increased molecular weight from the viewpoint of improving the thermal characteristics and driving life of the layers. There was a trend. This tendency was particularly remarkable when selecting a host material that is a main component of the light emitting layer. When the molecular weight of the host material is increased, the molecular weight of the dopant material is relatively reduced. When the content ratio of these materials in the light emitting layer is controlled on a mass basis, the number of molecules (number of moles) is the number of molecules of the dopant material (number of moles). Hereinafter, the number of “dopant molecules”) is relatively large.

  However, if the number of dopant molecules in the light-emitting layer increases, the dopant molecules that should function as carrier trap sites become hopping sites, and carriers cannot be efficiently trapped there. Probability will be reduced. Further, it is considered that when the number of dopant molecules in the light emitting layer increases, the dopant molecules hardly emit light due to so-called concentration quenching. As a result, it is estimated that the luminous efficiency of the organic EL element provided with such a light emitting layer is lowered.

  On the other hand, the organic EL element obtained by using the organic EL element material selection method of the present invention described above functions as the above-mentioned hopping site or concentration quenching occurs because the number of dopant molecules is relatively small. It seems that there is little tendency to do. As a result, it is estimated that the organic EL element has a further excellent luminous efficiency.

  In addition, such an organic EL element has a higher carrier recombination probability as compared with the conventional one, so that deterioration of the organic EL element due to carriers not involved in recombination is further suppressed. The driving life tends to be improved.

  In the method for selecting an organic EL element material of the present invention, a host material used in combination with a predetermined dopant material contained in a light emitting layer of an organic EL element is selected from two or more kinds of dopant materials having the same main skeleton. A method for selecting an organic EL element material, wherein a correlation between a ratio of a molecular weight of each of the host materials to a molecular weight of the dopant material and a luminous efficiency of an organic EL element including a light emitting layer containing the dopant material and the host material And a host determining step for determining based on.

  This organic EL element material selection method may be caused by the same factors as described above, whereby an organic EL element having light emission characteristics sufficient for practical use can be obtained sufficiently efficiently.

The method for selecting the organic EL element material is preferably such that the host material used in combination with the dopant material is determined so as to satisfy the condition represented by the following formula (B) in the host determination step.
(HMW / DMW) ≦ β (B)
In the above formula (B), DMW and HMW represent the molecular weights of the dopant material and the host material, respectively, and β represents a specific value. β is a specific value obtained experimentally, and differs depending on the type of the main skeleton of the host material. This β may be, for example, a value of HMW / DMW such that a tendency to decrease the luminous efficiency due to a decrease in HMW / DMW is hardly recognized. Alternatively, it may be a value of HMW / DMW at which the light emission efficiency is a certain value or less.

  By selecting and deciding the combination of dopant material and host material so that HMW / DMW is below a specific value β, the combination can be uniquely selected, making it more suitable for practical use. The combination of dopant material and host material can be determined.

  In the method for selecting an organic EL element material described above, the host material is preferably an anthracene derivative. Here, the “anthracene derivative” includes an anthracene multimer having a plurality of anthracene skeletons. Anthracene derivatives are relatively excellent in carrier transportability among compounds used as host materials. Therefore, an organic EL element obtained by using an anthracene derivative as a host material has a further excellent luminous efficiency.

  Furthermore, in the method for selecting an organic EL element material of the present invention, the dopant material is preferably one or more compounds selected from the group consisting of naphthacene derivatives, benzofluoranthene derivatives, diindenoperylene derivatives and perylene derivatives. . These compounds are relatively excellent in carrier trapping properties among compounds used as dopant materials. Therefore, the organic EL element obtained by using these compounds as the dopant material is further excellent in luminous efficiency and driving life.

  The method for producing an organic EL element of the present invention includes a step of determining a host material and a dopant material used for a light emitting layer by the above-described method for selecting an organic EL element material. Since the method for producing an organic EL element of the present invention uses the above-described method for selecting an organic EL element material, it is possible to produce an organic EL element having light emission characteristics that are sufficiently suitable for practical use.

  In the organic EL device of the present invention, the light emitting layer provided between the electrodes arranged opposite to each other contains a host material and a dopant material, and the ratio of the molecular weight of the dopant material to the molecular weight of the host material is 1 or more. It is characterized by that.

  It has been confirmed by experiments of the present inventors that the organic EL device of the present invention is further excellent in luminous efficiency. Although the reason is not clarified in detail at present, the present inventors consider as follows. However, the factors are not limited to these.

  Conventionally, a material used for a light emitting layer of an organic EL device has a tendency to increase its molecular weight from the viewpoint of improving the thermal characteristics and driving life of the layer. This tendency was particularly remarkable in the host material that is the main component of the light emitting layer. When the HMW is increased, the DMW is relatively decreased. When the content ratio of these materials in the light-emitting layer is adjusted on a mass basis, the number of molecules (number of moles) is the number of molecules of the dopant material (hereinafter referred to as “dopant molecules”). Number) is relatively large.

  However, if the number of dopant molecules in the light-emitting layer increases, the dopant molecules that should function as carrier trap sites become hopping sites, and carriers cannot be efficiently trapped there. It is estimated that the probability decreases. It is also considered that when the number of dopant molecules in the light emitting layer increases, the emission of the dopant molecules becomes weak due to so-called concentration quenching. As a result, it is estimated that the luminous efficiency of the organic EL element provided with such a light emitting layer is not sufficient for practical use.

  On the other hand, the organic EL element of the present invention has a DMW / HMW of 1 or more in the light emitting layer, so that the number of dopant molecules is relatively smaller than that of the conventional one. Or it is thought that there is a tendency for concentration quenching to occur little. As a result, the organic EL device of the present invention is presumed to have a further excellent luminous efficiency.

  In addition, since the organic EL element of the present invention has a higher carrier recombination probability than the conventional one, deterioration of the organic EL element due to carriers not involved in recombination is further suppressed. The driving life tends to be improved.

  In the organic EL device of the present invention, the host material and / or dopant material is preferably a hydrocarbon compound. Compared with other compounds that can be used for the light emitting layer, the hydrocarbon compound tends to suppress deterioration of the material due to the light emission process, and thus its driving life tends to be extended.

  In the organic EL device of the present invention, the host material is more preferably an anthracene derivative and the luminous efficiency tends to be further improved.

  Furthermore, in the organic EL device of the present invention, when the dopant material is at least one compound selected from the group consisting of a naphthacene derivative, a benzofluoranthene derivative, a diindenoperylene derivative and a perylene derivative, the luminous efficiency is further improved. This is preferable because it tends to be excellent. In the present specification, “benzofluoranthene derivative” does not include a diindenoperylene derivative, and “perylene derivative” does not include a diindenoperylene derivative.

  In the organic EL device of the present invention, the molecular weight of the host material described above is preferably 500 to 1500 from the viewpoints of improving the light emission characteristics and improving the film formability.

  From the same viewpoint, in the organic EL device of the present invention, the dopant material preferably has a molecular weight of 500 to 1500.

  According to the present invention, a method for selecting an organic EL element material for sufficiently efficiently obtaining an organic EL element having light emission characteristics sufficient for practical use, a method for producing an organic EL element using the selection method, and sufficient for practical use. It is possible to provide an organic EL element having excellent light emission characteristics, particularly light emission efficiency sufficient for practical use.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  First, a method for selecting an organic EL element material according to a preferred embodiment of the present invention will be described.

  In the method for selecting an organic EL element material of the present embodiment, two or more kinds of dopant materials having the same main skeleton as the molecular weight (HMW) of the host material are used together with the host material contained in the light emitting layer of the organic EL element. And a dopant determination step of determining based on the correlation between the molecular weight (DMW) of the dopant material and the organic EL element material having a light emitting layer containing these materials.

  In this method for selecting an organic EL element material, first, a host material used for a light emitting layer is selected and determined. Although the organic compound selected as the host material will not be specifically limited if it is conventionally contained in the light emitting layer of an organic EL element as a host material, It is preferable in the molecular weight being 500-1500. If the HMW is less than 500, the light emitting layer tends to be inferior in film formability and amorphousness, and the carrier injecting property and transporting property tend to be lowered. Tend to. On the other hand, when the HMW exceeds 1500, it tends to be impossible to form a film by a dry film forming method such as an evaporation method or a sputtering method.

  Furthermore, it is preferable to employ a hydrocarbon compound as the host material used for the light emitting layer. The host material has a role of transporting carriers in the light emitting layer. At this time, the host material repeats a redox reaction. Since hydrocarbon compounds tend to be less prone to deterioration even if the oxidation-reduction reaction is repeated as compared with compounds used for other host materials, organic EL elements using hydrocarbon compounds as the host material of the light emitting layer Tends to be excellent in each light emission characteristic including a driving life. From such a viewpoint, it is more preferable to employ a polycyclic aromatic compound as a host material used in the light emitting layer.

  Further, it is more preferable to select an anthracene derivative as the host material. An organic EL device containing an anthracene derivative as a host material in a light emitting layer tends to be excellent in luminous efficiency and driving life. From the same viewpoint, as this anthracene derivative, an anthracene multimer is particularly preferable, and those represented by the following formulas (1) to (12) are very preferable.

  Commercially available host materials such as these anthracene derivatives may be used or synthesized. As a method for synthesizing the host material, a method described in Japanese Patent Application Laid-Open No. 2004-2351 and Japanese Patent Application Laid-Open No. 8-12600, or a method based thereon can be used.

  Next, the main skeleton of the compound used as a dopant material to be contained in the light emitting layer together with the host material is selected and determined. At this time, since it tends to hardly deteriorate, it is preferable to select a main skeleton in which the compound used as the dopant material is a hydrocarbon compound, and it is more preferable to select a polycyclic aromatic compound. Further, this main skeleton is divided into a main skeleton represented by the following formula (13) which is the main skeleton of the naphthacene derivative, a main skeleton represented by the following formula (14) which is the main skeleton of the benzofluoranthene derivative, It is more preferable to select from the main skeleton represented by the following formula (15) which is the main skeleton of the noperylene derivative and the following formula (15A) which is the main skeleton of the perylene derivative. Compounds having these main skeletons tend to have excellent emission characteristics, particularly emission efficiency.

  Commercially available dopant materials including these compounds may be used or synthesized. The method for synthesizing the dopant material is described in JP-A No. 2003-104916, JP-A No. 2003-26616, JP-A No. 2000-268964, JP-A No. 2000-26337, and JP-A No. 2000-26334. Or a similar method can be used.

  Subsequently, for a plurality of dopant materials having the same main skeleton, the correlation of the molecular weight with the host material is examined. For example, the ratio (DMW / HMW) of the molecular weight (DMW) of each dopant material to the molecular weight (HMW) of the host material is calculated.

  At the same time, an organic EL element sample having the same configuration as that of the organic EL element described later is prepared using the host material and the dopant material whose molecular weight ratios are calculated as the constituent material of the light emitting layer. Next, light emission characteristics such as luminous efficiency (luminance), driving life (luminance half-life), and driving voltage of the obtained organic EL element sample are measured. Then, the above-mentioned DMW / HMW is taken on the horizontal axis, and the value of the light emission characteristic is taken on the vertical axis, and the correlation between DMW / HMW and the light emission characteristic is examined.

  Thereby, information on how the combination of the host material and the dopant material used for the light emitting layer can be selected from the viewpoint of molecular weight, and an organic EL element exhibiting optimal light emission characteristics can be obtained. Is possible.

  Based on the correlation thus obtained, a dopant material used in combination with the host material contained in the light emitting layer is selected and determined (dopant determination step). In this case, the compound selected as the dopant material may be a compound different from the dopant material as long as it has the same main skeleton as the dopant material used when the correlation of the molecular weight was examined. That is, the compound contained as a dopant material in the said organic EL element sample may be sufficient, and the compound which is not contained as the dopant material may be sufficient. Thereby, the optimal combination can be selected as needed for all the enormous combinations of the host material and the dopant material without producing an organic EL element containing them.

Moreover, the selection criteria for the dopant material may be changed as necessary depending on the obtained correlation. For example, when the luminous efficiency of the organic EL element sample tends to increase simply relative to DMW / HMW, in order to obtain an organic EL element with higher luminous efficiency, the dopant material should have as high DMW / HMW as possible. May be selected. Alternatively, the dopant material may be selected so as to satisfy the following formula (A) from the viewpoint that light emission efficiency of a certain level or more should be obtained, and from the viewpoint of considering other factors such as light emission characteristics and film formability. Good.
(DMW / HMW) ≧ α (A)
Here, in the formula (A), α represents a specific value obtained experimentally, for example, a value specified by the method described above.

  In addition, when the luminous efficiency of the organic EL element tends to be as shown in FIG. 6 with respect to DMW / HMW, it is preferable to select and determine a dopant material in which DMW / HMW is in the vicinity of r or higher. By selecting and determining a dopant material to be used for the light emitting layer based on such a criterion, an organic EL element having excellent light emission efficiency tends to be obtained more efficiently and reliably.

  When selecting a compound to be used as a dopant material in the dopant determination step, it is preferable to select from compounds having a molecular weight of 500 to 1500 from the same viewpoint as the host material. Furthermore, from the viewpoint of more effectively obtaining an organic EL device having more excellent luminous efficiency and driving lifetime, the naphthacene derivative in which the dopant material has the main skeletons of the above formulas (13) to (15) and (15A), It is preferably one or more compounds selected from the group consisting of benzofluoranthene derivatives, diindenoperylene derivatives and perylene derivatives, and more preferably one or more compounds selected from the group consisting of multimers of the above derivatives. preferable.

  Examples of the compound having such a main skeleton include naphthacene derivatives represented by the following formulas (16) to (29), benzofluoranthene derivatives represented by the following formulas (30) to (36), and the following formulas Examples include diindenoperylene derivatives represented by (37) to (44) and perylene derivatives represented by the following formulas (44A), (44B), (44C), and (44D).

  The organic EL device manufacturing method according to a preferred embodiment of the present invention is conventional except that the light emitting layer is formed using the host material and the dopant material of the light emitting layer selected in the above-described organic EL device material selection method. This is performed in the same manner as the method for producing an organic EL element. Therefore, the manufacturing method of the organic EL element of this embodiment is performed as follows, for example.

  First, a hole injection electrode is formed on a prepared substrate by a method such as sputtering, vapor deposition, or coating. Next, an inorganic hole injection layer is formed on the hole injection electrode by sputtering, vapor deposition, coating, or the like. Subsequently, a light emitting layer is formed on the inorganic hole injection layer using a sputtering method, a vapor deposition method, a coating method, or the like. Then, an inorganic electron injection layer is formed on the light emitting layer by a method such as a vapor deposition method, a sputtering method, or a coating method, and an electron injection electrode is further formed thereon using a vacuum vapor deposition method, an EB method, a sputtering method, or the like. Thereby, the organic EL element (5-layer type organic EL element) of this embodiment is obtained.

  Next, an organic EL element according to a preferred embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view showing a first embodiment (single-layer organic EL) of an organic EL element according to the present invention. An organic EL element 100 shown in FIG. 1 has a structure in which a light emitting layer 10 is sandwiched between two electrodes (a first electrode 1 and a second electrode 2) arranged to face each other.

  FIG. 2 is a schematic cross-sectional view showing a second embodiment (two-layer organic EL) of an organic EL element according to the present invention. An organic EL element 200 shown in FIG. 2 has a structure in which a hole transport layer 11 is provided between the first electrode 1 and the light emitting layer 10 of the organic EL element 100 in FIG.

  FIG. 3 is a schematic cross-sectional view showing a third embodiment (three-layer organic EL) of an organic EL element according to the present invention. The organic EL element 300 shown in FIG. 3 has a structure in which the electron transport layer 12 is provided between the second electrode 2 and the light emitting layer 10 of the organic EL element 200 in FIG.

FIG. 4 is a schematic cross-sectional view showing a fourth embodiment (four-layer organic EL) of an organic EL element according to the present invention. An organic EL element 400 shown in FIG. 4 includes a hole injection layer 14, a hole transport layer 11, a light emitting layer 10, and two electrodes (a first electrode 1 and a second electrode 2) arranged to face each other. The electron injection layer 13 is sandwiched. The hole injection layer 14, the hole transport layer 11, the light emitting layer 10, and the electron injection layer 13 are all organic layers, and are stacked in this order from the first electrode 1 side. The electron injection layer 13 can be an inorganic layer (metal layer, metal compound layer, etc.) (the same applies hereinafter).

  FIG. 5 is a schematic cross-sectional view showing a fifth embodiment (five-layer type organic EL) of the organic EL element according to the present invention. An organic EL element 500 shown in FIG. 5 has a structure in which an electron transport layer 12 is provided between the electron injection layer 13 and the light emitting layer 10 of the organic EL element 400 in FIG.

  Further, although not shown, a plurality of light emitting layers containing different constituent materials (type of material, content ratio of materials) may be provided as a light emitting layer.

  In the first to fifth embodiments, the first electrode 1 is formed on the substrate 4.

  In the said embodiment, the 1st electrode 1 and the 2nd electrode 2 function as a hole injection electrode (anode) and an electron injection electrode (cathode), respectively, and by application of the electric field by the power supply P, in 1st Embodiment Holes (holes) are injected from the first electrode 1 into the light emitting layer 10 (the hole transport layer 11 in the second to third embodiments, the hole injection layer 14 in the fourth to fifth embodiments), and the light emission is performed. Electrons are injected from the second electrode 2 into the layer 10 (the light emitting layer 10 in the second embodiment, the electron transport layer 12 in the third embodiment, and the electron injection layer 13 in the fourth to fifth embodiments), Based on these recombination, the compound for organic EL elements in the light emitting layer emits light.

  The preferred thicknesses of the light emitting layer, hole transport layer, electron transport layer, hole injection layer, and electron injection layer are all 0.1 to 100 nm.

(substrate)
Examples of the substrate 4 include amorphous substrates such as glass and quartz, crystal substrates such as Si, GaAs, ZnSe, ZnS, GaP, and InP, metal substrates such as Mo, Al, Pt, Ir, Au, Pd, and SUS, and polyolefins. A resin substrate such as PET can be used. Further, a thin film made of a crystalline or amorphous ceramic, metal, organic substance or the like formed on a predetermined substrate may be used.

  When the substrate 4 side is the light extraction side, it is preferable to use a transparent substrate made of glass, quartz or the like, or a resin such as polyolefin or PET as the substrate 4, and in particular, an inexpensive glass or resin transparent substrate is used. Is preferred. The transparent substrate may be provided with a color filter film, a color conversion film containing a fluorescent material, a dielectric reflection film, or the like for adjusting the color light.

(First electrode)
The first electrode 1 functions as a hole injection electrode (anode). Therefore, the material of the first electrode 1 is not particularly limited as long as it is provided in the conventional organic EL element, but it can be efficiently applied to a layer adjacent to the first electrode 1 and A material that can uniformly apply an electric field is preferable.

  When the substrate 4 side is the light extraction side, the transmittance at a wavelength of 400 to 700 nm, which is the emission wavelength region of the organic EL element, particularly the transmittance of the first electrode 1 at the wavelength of each RGB color is 50% or more. Preferably, it is 80% or more, more preferably 90% or more. When the transmittance of the first electrode 1 is less than 50%, the light emission from the light emitting layer 10 is attenuated, and it is difficult to obtain the luminance necessary for image display.

The 1st electrode 1 with comparatively high light transmittance can be comprised using the transparent conductive film comprised with various oxides. As such a material, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO) and the like are preferable. It is particularly preferable in that a thin film having a uniform in-plane specific resistance can be easily obtained.

  The film thickness of the first electrode 1 is preferably determined in consideration of the above-described light transmittance. For example, when using an oxide transparent conductive film, the film thickness is preferably 10 to 500 nm, more preferably 30 to 300 nm. When the film thickness of the first electrode 1 exceeds 500 nm, the light transmittance may be insufficient and the first electrode 1 may be peeled off from the substrate 4 in some cases. Further, although the light transmittance is improved as the film thickness is decreased, when the film thickness is less than 10 nm, the resistivity is increased and the driving voltage of the organic EL element tends to be increased.

(Second electrode)
The second electrode 2 functions as an electron injection electrode (cathode). The material of the second electrode 2 is not particularly limited as long as it is provided in a conventional organic EL element, and examples thereof include a metal material, an organometallic complex, a metal compound, and the like. In order to efficiently and reliably inject electrons into the layer 10, it is preferable to use a material having a relatively low work function, and it may be transparent.

  Specific examples of the metal material constituting the second electrode 2 include alkali metals such as Li, Na, K or Cs, alkaline earth metals such as Mg, Ca, Sr or Ba, or Al (aluminum). . Alternatively, a metal having properties similar to those of an alkali metal or an alkaline earth metal such as La, Ce, Sn, Zn, or Zr can be used. Furthermore, oxides or halides of the above metal materials can also be used. Further, it may be a mixture or alloy containing the above materials, and a plurality of these may be laminated.

  The film thickness of the second electrode 2 only needs to be such that electrons can be uniformly injected, and may be 0.1 nm or more.

  An auxiliary electrode may be provided on the second electrode 2. Thereby, the electron injection efficiency to the light emitting layer 10 grade | etc., Can be improved, and the penetration | invasion of the water | moisture content or the organic solvent to the light emitting layer 10 or the electron injection layer 13 can be prevented. As a material for the auxiliary electrode, a general metal can be used because there is no restriction on work function and charge injection capability. However, it is preferable to use a metal having high conductivity and easy handling. In particular, in the case where the second electrode 2 includes an organic material, it is preferable to select appropriately according to the type and adhesion of the organic material.

  Examples of the material used for the auxiliary electrode include Al, Ag, In, Ti, Cu, Au, Mo, W, Pt, Pd, and Ni. Among them, when a low-resistance metal such as Al and Ag is used, electrons are used. The injection efficiency can be further increased. Moreover, higher sealing properties can be obtained by using a metal compound such as TiN. These materials may be used alone or in combination of two or more. Moreover, when using 2 or more types of metals, you may use as an alloy. Such an auxiliary electrode can be formed by, for example, a vacuum deposition method or the like.

(Light emitting layer)
For the light emitting layer 10, a host material and a dopant material selected and determined by the above-described organic EL element material selection method are used. An organic EL device including such a light emitting layer 10 exhibits sufficiently excellent light emission characteristics suitable for practical use.

  Such a combination of the host material and the dopant material is preferably a combination of the host material and the dopant material such that DMW / HMW is 1 or more. The organic EL element provided with the light emitting layer 10 containing such a combination of materials tends to be more excellent in luminous efficiency. More specifically, when the combination is expressed as (host material-dopant material), (the compound represented by the above formula (1) (referred to as “compound (1)”; hereinafter the same) —compound (18)). (Compound (4) -Compound (20)), (Compound (6) -Compound (21)), (Compound (1) -Compound (28)), (Compound (6) -Compound (36)) and the like. Can be mentioned.

  The mass ratio of the host material and the dopant material in the light-emitting layer 10 is preferably 1: 1 to 1: 4 in terms of (host material: dopant material), although it varies depending on the type of compound selected as each material. Is more preferably 1: 1 to 1: 3, and further preferably 1: 1 to 1: 2. When the mass ratio of the host material is smaller than that described above, the dopant material molecules function as hopping sites, and the molecules tend to be unable to trap carriers efficiently, so the carrier recombination probability decreases, There exists a tendency for the luminous efficiency of an organic EL element to reduce. Further, when the mass ratio of the host material is larger than that described above, the number of molecules of the dopant material that should function as a carrier trap site is excessively decreased, and thus the light emission efficiency tends to be lowered.

  Moreover, the light emitting layer 10 may be composed of a plurality of light emitting layers having different types of constituent materials or different proportions of constituent materials. In this case, at least one of the plurality of light emitting layers may be a light emitting layer containing a combination of the host material and the dopant material described above. In the other light emitting layers, the constituent material is an organic compound that generates excitons by recombination of electrons and holes, and emits light when the excitons release energy to return to the ground state. It can use without being specifically limited.

  Specifically, for example, organometallic complex compounds such as aluminum complex, beryllium complex, zinc complex, iridium complex, or rare earth metal complex, anthracene, naphthacene, benzofluoranthene, naphthofluoranthene, styrylamine, tetraaryldiamine, or These derivatives, low molecular organic compounds such as perylene, diindenoperylene, quinacridone, coumarin, DCM or DCJTB, or π-conjugated polymers such as polyacetylene derivatives, polyphenylene vinylene derivatives, polyfluorene derivatives or polythiophene derivatives, or polyvinyl Dyes on non-π-conjugated side chain polymers or main chain polymers such as compounds, polystyrene derivatives, polysilane derivatives, polyacrylate derivatives or polymethacrylate derivatives And high molecular organic compounds such as those containing.

  As the host material, among the above-mentioned compounds, aromatic carbonization such as 1,10-phenanthroline derivative, organometallic complex compound, naphthalene, anthracene, naphthacene, perylene, diindenoperylene, benzofluoranthene or naphthofluoranthene Hydrogen compounds and their derivatives, styrylamine or tetraaryldiamine derivatives are preferred. As the dopant material, among the above-mentioned compounds, aromatic hydrocarbon compounds such as organometallic complex compounds, naphthalene, anthracene, naphthacene, perylene, diindenoperylene, benzofluoranthene, naphthofluoranthene, and derivatives thereof, Furthermore, styrylamine or tetraaryldiamine derivatives, or quinacridone, coumarin, DCM, and derivatives thereof are preferable.

  The light emitting layer may be a mixed layer of at least one kind of hole transporting compound and at least one kind of electron transporting compound, if necessary, and may contain a dopant in the mixed layer. In the mixed layer, a carrier hopping conduction path is generated, and each carrier moves in a polar dominant substance, so that it is considered that carrier injection in the reverse direction is unlikely to occur. This makes it difficult for the organic material constituting the light emitting layer to be damaged, and thus has the advantage of extending the drive life of the organic EL element.

  Examples of the hole transporting compound and electron transporting compound used in the mixed layer include 1,10-phenanthroline derivatives, organometallic complex compounds, aromatic hydrocarbon compounds such as anthracene, naphthacene, benzofluoranthene, naphthofluoranthene, and the like. It is preferable to use a derivative of As the hole transporting compound, an amine derivative having strong fluorescence is preferably used, and examples of such an amine derivative include a triphenyldiamine derivative, a styrylamine derivative, and an amine derivative having an aromatic condensed ring.

  In this case, the preferred mixing ratio of the hole transporting compound and the electron transporting compound varies depending on the carrier mobility and the carrier concentration, but generally, the mixing ratio of the hole transporting compound and the electron transporting compound ( (Mass ratio) is preferably 1:99 to 99: 1, more preferably 10:90 to 90:10, and even more preferably about 20:80 to 80:20.

(Hall transport layer)
For the hole transport layer, any of hole transport materials such as low molecular materials and polymer materials can be used. Examples of the hole transporting low molecular weight material include pyrazoline derivatives, arylamine derivatives, stilbene derivatives, and triphenyldiamine derivatives. Also, hole transporting polymer materials include polyvinyl carbazole (PVK), polyethylene dioxythiophene (PEDOT), polyethylene dioxythiophene / polystyrene sulfonic acid copolymer (PEDOT / PSS), polyaniline / polystyrene sulfonic acid copolymer. (Pani / PSS). One of these hole transport materials may be used alone, or two or more thereof may be used in combination.

(Electron transport layer)
For the electron transport layer, any of electron transport materials of low molecular materials and polymer materials can be used. Examples of electron transporting low molecular weight materials include aluminum complexes having quinolinol and benzoquinolinol as ligands, beryllium complexes, zinc complexes, oxadiazole derivatives, anthraquinodimethane and derivatives thereof, benzoquinones and derivatives thereof, and naphthoquinones. And derivatives thereof, anthraquinone and derivatives thereof, tetracyanoanthraquinodimethane and derivatives thereof, fluorene and derivatives thereof, diphenyldicyanoethylene and derivatives thereof, phenanthroline and derivatives thereof, and metal complexes having these compounds as ligands Can be mentioned. Examples of the electron transporting polymer material include polyquinoxaline and polyquinoline.

  As the constituent material of the electron transport layer described above, one kind may be used alone, or two or more kinds may be used in combination.

(Hole injection layer)
The material of the hole injection layer is not particularly limited as long as it is used for the hole injection layer of the conventional organic EL device, and organic materials such as arylamine, phthalocyanine, polyaniline / organic acid, polythiophene / polymer acid, etc. A compound material, a metal such as germanium or silicon, or an oxide of a metalloid can be used. These hole injecting materials may be used singly or in combination of two or more.

  Moreover, when providing both a hole transport layer and a hole injection layer, it is preferable to laminate | stack in order of the layer of a compound with a small ionization potential from the hole injection electrode side. Further, it is preferable to use a compound having a good thin film property on the surface of the hole injection electrode. By adopting such a stacking order, the driving voltage is lowered, and it tends to be possible to prevent the occurrence of current leakage and the generation / growth of dark spots. In addition, in the case of elementization, since vapor deposition is used, a thin film of about 1 to 10 nm can be made uniform and pinhole-free, so that the ion injection potential is small in the hole injection layer and the visible portion has absorption. Even if such a compound is used, it is possible to prevent a decrease in efficiency due to a change in color tone of light emission and reabsorption. The hole injecting and transporting layer can be formed by evaporating the above compound in the same manner as the light emitting layer and the like.

  An alkali metal such as lithium, lithium fluoride, lithium oxide, or the like can be used for the electron injection layer.

  Moreover, when providing both an electron injection layer and an electron carrying layer, it is preferable to laminate | stack in order of the compound with a large value of an electron affinity from the electron injection electrode side.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in another embodiment of the method for selecting an organic EL element material of the present invention, first, a compound used as a dopant material for the light emitting layer may be selected and determined. In this case, next, the main skeleton of the host material to be included in the light emitting layer together with the dopant material is selected and determined. Subsequently, for a plurality of host materials having the same main skeleton, the molecular weight correlation with the dopant material may be examined. This also provides information on how the combination of the host material and the dopant material used in the light emitting layer can be selected from the viewpoint of molecular weight to produce an organic EL element exhibiting optimal light emission characteristics. It becomes possible.

  Based on the correlation thus obtained, a host material used in combination with the dopant material contained in the light emitting layer is selected and determined (host determination step). In this case, the compound selected as the host material may be any compound having the same main skeleton as that used as the dopant material of the light emitting layer of the organic EL element sample prepared when the molecular weight correlation is examined. Therefore, it may be a compound contained as a host material in the organic EL device sample, or a compound not contained as a host material. Thereby, the optimal combination can be selected as needed for all the enormous combinations of the host material and the dopant material without producing an organic EL element containing them.

  In addition, the suitable (preferable) aspect in the selection method of this organic EL element material is the same as the case where the compound used as a host material of a light emitting layer mentioned above is first selected and determined.

  Further, when selecting the combination of the host material and the dopant material contained in the light emitting layer, in addition to / instead of investigating the correlation of the molecular weights of these materials, the π-conjugated electron clouds of these materials (compounds) The above combination may be selected and determined based on the spread of, the intermolecular distance of the dopant material (compound), the electron density of the dopant material (compound), and the like. The spread of the π-conjugated electron cloud, the intermolecular distance of the dopant material, and the electron density of the dopant material can be determined using a conventionally known molecular orbital calculation method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Production Example 1 of Organic EL Element)
A glass substrate having an ITO transparent electrode (hole injection electrode) having a thickness of 100 nm was subjected to ultrasonic cleaning using a neutral detergent and pure water and dried. Next, the surface of the transparent electrode was washed with UV / O ₃ and then fixed to a substrate holder of a vacuum deposition apparatus (VPC-410, Vacuum Kiko Co., Ltd., trade name), and the pressure was reduced to 1 × 10 ⁻⁴ Pa or less. . Next, while maintaining the reduced pressure state, the compound represented by the following formula (45) was deposited to a thickness of 100 nm at a deposition rate of 0.2 nm / second to form a hole injection layer.

Subsequently, a compound represented by the following formula (46) (referred to as “compound (46)”, hereinafter the same) was deposited to a thickness of 30 nm at a deposition rate of 0.2 nm / second to form a hole transport layer.

  Furthermore, while maintaining the reduced pressure state, the compound (1) as the host material and the compound (16) as the dopant material were mixed at a mass ratio of 50: 1 with a total deposition rate of 0.2 nm / sec. It evaporated to thickness and was set as the light emitting layer. Since the molecular weight (HMW) of compound (1) was 506 and the molecular weight (DMW) of compound (16) was 380, the molecular weight ratio (DMW / HMW) was 0.75.

Next, while maintaining the reduced pressure state, the compound (47) was deposited to a thickness of 20 nm at a deposition rate of 0.2 nm / second to form an electron transport layer.

  Next, LiF was deposited to a thickness of 0.3 nm at a deposition rate of 0.01 nm / second to form an electron injection electrode, and further, Al was deposited to 150 nm as a protective electrode, whereby the four-layer organic EL element of Production Example 1 was obtained. Obtained.

When a direct current voltage was applied to the organic EL element of Preparation Example 1 and a current was passed, the organic EL element emitted light, and the driving voltage, luminance, and chromaticity coordinates at 10 mA / cm ² were as shown in Table 1.

(Production Examples 2 to 6 of the organic EL element)
Organic EL elements of Production Examples 2 to 6 were obtained in the same manner as in Production Example 1 except that the compounds (17) to (21) as the dopant material were used in place of the compound (16) as the dopant material. Table 1 shows information on the molecular weights and measurement results of the respective light emission characteristics. FIG. 7 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 1 to 6.

(Production Examples 7 to 12 of an organic EL element)
Organic EL elements of Preparation Examples 7 to 12 were obtained in the same manner as Preparation Examples 1 to 6, except that the compound (4) as the host material was used instead of the compound (1) as the host material. Table 2 shows information relating to their molecular weights and measurement results of the respective light emission characteristics. 8 is a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 7 to 12.

(Preparation Examples 13-18 of Organic EL Element)
Organic EL elements of Preparation Examples 13 to 18 were obtained in the same manner as Preparation Examples 1 to 6, except that the compound (6) as the host material was used instead of the compound (1) as the host material. Table 3 shows the information on the molecular weights and the measurement results of the emission characteristics. Moreover, about the organic EL element of the manufacture examples 13-18, the graph which shows the correlation with DMW / HMW (X-axis) and a brightness | luminance (Y-axis) is shown in FIG.

(Preparation Examples 19-24 of Organic EL Element)
Organic EL elements of Preparation Examples 19 to 24 were obtained in the same manner as Preparation Examples 1 to 6, except that the compound (9) as the host material was used instead of the compound (1) as the host material. Table 4 shows information on the molecular weights and measurement results of the respective luminescence characteristics. Moreover, about the organic EL element of the manufacture examples 19-24, the graph which shows the correlation with DMW / HMW (X-axis) and a brightness | luminance (Y-axis) is shown in FIG.

(Organic EL device fabrication examples 25 to 28)
Organic EL elements of Preparation Examples 25 to 28 were obtained in the same manner as Preparation Example 1, except that the compounds (22) to (25) as dopant materials were used in place of the compound (16) as the dopant material. Table 5 shows the information on the molecular weights and the measurement results of the respective light emission characteristics. FIG. 11 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 25 to 28.

(Production Examples 29 to 32 of the organic EL element)
Organic EL elements of Preparation Examples 29 to 32 were obtained in the same manner as Preparation Example 7 except that the compounds (22) to (25) as the dopant material were used instead of the compound (16) as the dopant material. Table 6 shows information on the molecular weights and measurement results of the respective light emission characteristics. FIG. 12 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 29 to 32.

(Preparation examples 33 to 36 of organic EL elements)
Organic EL elements of Preparation Examples 33 to 36 were obtained in the same manner as Preparation Example 13 except that the compounds (22) to (25) as dopant materials were used in place of the compound (16) as the dopant material. Table 7 shows information on the molecular weights and emission characteristics. FIG. 13 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 33 to 36.

(Organic EL device production examples 37 to 40)
Organic EL elements of Preparation Examples 37 to 40 were obtained in the same manner as Preparation Example 19 except that the compounds (22) to (25) as dopant materials were used instead of the compound (16) as the dopant material. Table 8 shows the information on the molecular weight and the emission characteristics. FIG. 14 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 37 to 40.

(Preparation examples 41 to 47 of organic EL elements)
Organic EL elements of Preparation Examples 41 to 47 were obtained in the same manner as Preparation Example 1, except that the compounds (30) to (36) as dopant materials were used instead of the compound (16) as the dopant material. Table 9 shows the information on the molecular weight and the emission characteristics. 15 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 41 to 47.

(Examples 48 to 54 for producing organic EL elements)
Organic EL elements of Production Examples 48 to 54 were obtained in the same manner as in Production Example 7 except that the compounds (30) to (36) as the dopant material were used instead of the compound (16) as the dopant material. Table 10 shows the information on the molecular weight and the emission characteristics. FIG. 16 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 48 to 54.

(Organic EL device production examples 55-61)
Organic EL elements of Preparation Examples 55 to 61 were obtained in the same manner as Preparation Example 13 except that the compounds (30) to (36) as dopant materials were used instead of the compound (16) as the dopant material. Table 11 shows the information on the molecular weight and the emission characteristics. FIG. 17 is a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 55 to 61.

(Preparation examples 62 to 68 of organic EL elements)
Organic EL elements of Preparation Examples 62 to 68 were obtained in the same manner as Preparation Example 19 except that the compounds (30) to (36) as the dopant material were used instead of the compound (16) as the dopant material. Table 12 shows information on the molecular weights and the respective emission characteristics. FIG. 18 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 62 to 68.

(Preparation examples 69 to 75 of organic EL element)
Instead of the compound (1) as the host material, the compound (18) as the host material is used, and instead of the compound (16) as the dopant material, the compounds (37), (38), (39 ) To (43) were used, and the organic EL elements of Preparation Examples 69 to 75 were obtained in the same manner as Preparation Example 1. Table 13 shows the information on the molecular weight and the emission characteristics. FIG. 19 shows a graph showing the correlation between DMW / HMW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 69 to 75.

(Preparation examples of organic EL elements 76 to 82)
Organic EL elements of Preparation Examples 76 to 82 were obtained in the same manner as Preparation Examples 69 to 75 except that the compound (24) as the host material was used instead of the compound (48) as the host material. Table 14 shows the information on the molecular weight and the emission characteristics. 20 shows a graph showing the correlation between D _MW / H _MW (X axis) and luminance (Y axis) for the organic EL elements of Production Examples 76 to 82.

It is a schematic cross section which shows the organic EL element which concerns on 1st Embodiment. It is a schematic cross section which shows the organic EL element which concerns on 2nd Embodiment. It is a schematic cross section which shows the organic EL element which concerns on 3rd Embodiment. It is a schematic cross section which shows the organic EL element which concerns on 4th Embodiment. It is a schematic cross section which shows the organic EL element which concerns on 5th Embodiment. It is a graph which shows typically an example of correlation with DMW / HMW and the luminous efficiency (luminance) of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element. It is a graph which shows the correlation with DMW / HMW which concerns on the Example of this invention, and the brightness | luminance of an organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st electrode, 2 ... 2nd electrode, 4 ... Substrate, 10 ... Light emitting layer, 11 ... Hole transport layer, 13 ... Electron injection layer, 14 ... Hole injection layer, 100 ... Organic according to the first embodiment EL element 200 ... Organic EL element according to the second embodiment 300 ... Organic EL element according to the third embodiment 400 ... Organic EL element according to the fourth embodiment 500 ... Organic EL element according to the fifth embodiment , P ... Power supply.

Claims (14)

A method for selecting an organic EL element material, wherein a dopant material used in combination with a predetermined host material contained in a light emitting layer of an organic EL element is selected from two or more dopant materials having the same main skeleton,
The ratio of the molecular weight of each of the dopant materials to the molecular weight of the host material;
Luminous efficiency of an organic EL device comprising a light emitting layer containing the host material and the dopant material,
A method for selecting an organic EL element material, comprising a dopant determination step of determining based on the correlation of 2. The method for selecting an organic EL element material according to claim 1, wherein in the dopant determination step, the dopant material to be used in combination with the host material is determined so as to satisfy a condition represented by the following formula (A). .
(DMW / HMW) ≧ α (A)
(In the formula, HMW and DMW indicate the molecular weights of the host material and the dopant material, respectively, and α indicates a specific value.)   In the said Formula (A), (alpha) is 1, The selection method of the organic EL element material of Claim 2 characterized by the above-mentioned. A method of selecting an organic EL element material, wherein a host material used in combination with a predetermined dopant material contained in a light emitting layer of an organic EL element is selected from two or more kinds of dopant materials having the same main skeleton,
The ratio of the molecular weight of each of the host materials to the molecular weight of the dopant material;
Luminous efficiency of an organic EL device comprising a light emitting layer containing the dopant material and the host material,
A method for selecting an organic EL element material, comprising a host determination step of determining based on the correlation of 5. The method for selecting an organic EL element material according to claim 4, wherein in the host determination step, the host material used in combination with the dopant material is determined so as to satisfy a condition represented by the following formula (B). .
(HMW / DMW) ≦ β (B)
(In the formula, DMW and HMW represent molecular weights of the dopant material and the host material, respectively, and β represents a specific value.)   The method for selecting an organic EL element material according to any one of claims 1 to 5, wherein the host material is an anthracene derivative.   The said dopant material is 1 or more types of compounds chosen from the group which consists of a naphthacene derivative, a benzofluoranthene derivative, a diindenoperylene derivative, and a perylene derivative, The any one of Claims 1-6 characterized by the above-mentioned. The method for selecting an organic EL element material described in 1.   A method for producing an organic EL element, comprising a step of determining a host material and a dopant material used for a light emitting layer by the method for selecting an organic EL element material according to claim 1.   A light-emitting layer provided between electrodes arranged opposite to each other contains a host material and a dopant material, and the ratio of the molecular weight of the dopant material to the molecular weight of the host material is 1 or more. element.   The organic EL device according to claim 9, wherein the host material and / or the dopant material is a hydrocarbon compound.   The organic EL device according to claim 9, wherein the host material is an anthracene derivative.   The organic material according to any one of claims 9 to 11, wherein the dopant material is at least one compound selected from the group consisting of a naphthacene derivative, a benzofluoranthene derivative, and a diindenoperylene derivative. EL element.   The organic EL element according to any one of claims 9 to 12, wherein the host material has a molecular weight of 500 to 1500. The organic EL element according to claim 9, wherein the dopant material has a molecular weight of 500 to 1500.

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