JP2006135146A - Display element and organic material therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic material that is effective for increasing a lifetime, can also increase efficiency, is required for an element configuration, and has high carrier mobility. <P>SOLUTION: The organic material for display elements is represented by a general formula 1. The organic material is used for the display element clamping a light-emitting unit containing at least an organic light-emitting layer between a cathode and an anode, and is used in, for example, the light-emitting unit. In a stacked display element in which a plurality of light-emitting units are laminated, the organic material is used for the charge generation layer between the light-emitting units. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic material suitably used for a display element used in a color display or the like, and a self-luminous display element using the organic material.

  In recent years, the importance of human-machine interfaces has been increasing, including multimedia-oriented products. In order for humans to operate the machine more comfortably and efficiently, it is necessary to extract a sufficient amount of information from the machine being operated in a concise and instantaneous manner without any errors. Research has been conducted on such display elements.

  In addition, with the miniaturization of machines, the demand for miniaturization and thinning of display elements is increasing day by day. For example, downsizing of laptop information processing devices that are integrated with display elements, such as notebook personal computers and notebook word processors, has made remarkable progress, and as a result, technologies related to liquid crystal displays that are display elements Innovation is also great. Liquid crystal displays are used as interfaces for various products, and are often used in products we use daily, such as laptop TVs, watches, and calculators, as well as laptop information processing equipment.

  However, since a liquid crystal display is not self-luminous, it requires a backlight, and this backlight drive requires more power than driving a liquid crystal. Further, since the viewing angle is narrow, it is not suitable for a large display element such as a large display. Furthermore, since the display method is based on the alignment state of the liquid crystal molecules, the contrast changes depending on the angle even within the viewing angle. In addition, since the liquid crystal displays using the change in the molecular conformation in the ground state, the dynamic range cannot be widened. This is one of the reasons why the liquid crystal display is not suitable for displaying moving images.

On the other hand, plasma display elements, inorganic electroluminescent elements, organic electroluminescent elements and the like have been studied as self-luminous display elements.

  In addition, as for organic electroluminescent elements, research in combination with organic semiconductors has been energetically performed. If the present invention is used as a display element as well as an invention, this organic semiconductor is also covered by the claims. include.

  A plasma display element uses plasma light emission in a low-pressure gas for display and is suitable for an increase in size and capacity, but has problems in terms of thickness reduction and cost. In addition, a high voltage AC bias is required for driving, which is not suitable for portable devices.

  As for the inorganic electroluminescent element, a green light emitting display or the like has been commercialized. However, like the plasma display element, it is an AC bias drive and requires several hundred volts for the drive, and is not accepted by the user. However, due to technological development, the three primary colors of RGB required for color display display have been successfully emitted today, but no blue light-emitting material can emit light with high brightness and long life. Therefore, it is difficult to control the emission wavelength by molecular design.

  In 2000, a full-color display using inorganic electroluminescent elements was announced, but it uses a color conversion method, and it is difficult to make a device with an ideal independent three-primary-color driving method.

  On the other hand, electroluminescence due to organic compounds has been studied for a long time since the discovery of light emission due to carrier injection into anthracene single crystals that generate strong fluorescence by Helfrich et al. In the early 1960s. Since it was monochromatic and single crystal, it was conducted as a basic study of carrier injection into organic materials.

However, since Tang et al. Of Eastman Kodak in 1978 announced an organic electroluminescent device with a laminated structure having an amorphous light emitting layer that can drive at low voltage and emit high brightness, light emission and stability of RGB primary colors in various directions Research and development on brightness increase, laminated structure, manufacturing method, etc. are actively conducted. Hole transport as described in a research report published in Japanese Journal of Applied Physics Vol. 27, No. 2, pages L269-L271 (1988) by C. Adachi, S. Tokito, T. Tsutsui, S. Saito, etc. A three-layer structure (double heterostructure organic EL device) of materials, light-emitting materials, and electron transport materials has been developed. Furthermore, Journal of Applied Physics Vol. 65, No. 9, pages 3610-3616, such as CW Tang, SA Van Slyke, and CH Chen. As described in a research report published in (1989), an element structure in which a light emitting material is included in an electron transport material has been developed.

In addition, various new materials have been invented by molecular design, which is a characteristic of organic materials, and application research for color displays of organic electroluminescent elements having excellent characteristics such as direct current low voltage driving, thinness, and self-luminous properties has also been actively conducted. Has begun to be done.

  FIG. 4 shows a configuration example of such a display element (organic electroluminescent element). The display element 1 shown in this figure is provided on a transparent substrate 2 made of, for example, glass. The display element 1 includes an anode 3 made of ITO (Indium Tin Oxide: transparent electrode) provided on a substrate 2, an organic layer 4 provided on the anode 3, and a cathode 5 provided thereon. It is configured. The organic layer 4 has a configuration in which, for example, a hole injection layer 4a, a hole transport layer 4b, and an electron transporting light emitting layer 4c are sequentially stacked from the anode side. In the display element 1 configured as described above, light generated when electrons injected from the cathode and holes injected from the anode are recombined in the light emitting layer 4c is extracted from the substrate 2 side.

  In addition to such a configuration, the cathode 5, the organic layer 4, and the anode 3 are sequentially stacked from the substrate 2 side, and the upper electrode (upper electrode) is made of a transparent material. There is also a so-called top emission type display element in which light is extracted from the side opposite to the substrate 2. In particular, in an active matrix type display device in which a thin film transistor (hereinafter referred to as TFT) is provided on a substrate, a so-called top surface in which a top emission type display element is provided on the substrate on which the TFT is formed. The light emitting element structure is advantageous in improving the aperture ratio of the light emitting part.

In the display device having such a top light emitting element structure, when the upper electrode is a cathode, the upper electrode is constituted by an injection electrode using a metal fluoride or oxide layer such as LiF, Li ₂ O, or CsO. Is done. In some cases, an MgAg layer is laminated on these injection electrodes.

  In addition, in the top light emitting element structure, light can be extracted from both sides by using a transparent electrode such as ITO as an anode, but generally an opaque electrode is used to form a cavity structure. The organic layer thickness of the cavity structure is defined by the emission wavelength and can be derived from multiple interference calculations. In the top surface light emitting element structure, it is possible to improve the light extraction efficiency to the outside and control the emission spectrum by actively using the cavity structure.

  By the way, with regard to the practical application of organic electroluminescent elements, the actual number of manufacturers entering the market is increasing year by year, mainly in car audio, mobile phones, and digital cameras.

  The organic materials used have been improved year by year, and some fluorescent materials with external quantum efficiencies exceeding 5% have been reported, and values close to 20% for phosphorescent materials have also been reported. In general, the internal quantum efficiency can be estimated to be about 5 times that of the external quantum efficiency, and the phosphorescent material has reached a value close to the limit.

However, compared to the improved efficiency, the half life from the initial luminance of several hundred to several thousand cd / m ² is reached, depending on the emission color, until the continuous driving life is one of the guidelines for reliability. Is 1 to 40,000 hours, and the actual situation is that it does not extend as expected.

  This is one of the reasons why organic electroluminescent devices are said to be promising candidates for next-generation televisions, but cannot be increased in size and have not yet been put into practical use as products that require strict lifetimes.

  The lifetime of the organic electroluminescent device is generally determined by the injected electric charge, and this can be solved by reducing the initial luminance in driving. However, lowering the initial luminance limits applications in practical use and denies the potential of organic electroluminescence devices, making it impossible to realize next-generation television.

  In order to solve this problem, one of the means is to use a light emitting material or a peripheral material that has a more durable organic material and efficiently transports charges.

What is important here is that the hole drift mobility of OPC (Organic PhotoConductor = organic photoconductor) materials used in these organic electroluminescent devices and organic conductive materials used in organic semiconductor materials is at most. It is about 10 ⁻⁶ to 10 ⁻³ cm ² V ⁻¹ s ⁻¹ , which is closer to an insulator than a conductor.

  The reason why the organic electroluminescent device can use a large amount of current using such an organic material close to an insulator is that the conduction current can be explained by a space charge limited current (SCLC) mechanism.

The main factor that determines the magnitude of the current flowing in the organic thin film is not the equilibrium carrier density in the thin film but the carrier mobility. SCLC is described by J = 9/8 · (εε ₀ · μV ² ) / L ³ according to the child rule. In the child rule, only the carrier mobility μ is involved. Therefore, if μ increases, J can be increased. When J becomes large, the driving voltage can be lowered and a highly efficient element can be obtained.

When μ = 10 ⁻³ , which is a typical value of amorphous organic dye thin film, is used as carrier mobility μ, a large current of about 300 mAcm ⁻² flows when a voltage of 1.0 V is applied to a thin film with a thickness L = 100 nm. Become. In an actual organic electroluminescence device, the total thickness of the organic layer is set to about several tens of nanometers to increase the charge injection efficiency and to produce a device that can withstand practical use.

  Therefore, it is extremely important to use a material that can efficiently transport carriers (charges) in order to improve the characteristics of the organic electroluminescence device and achieve a long life.

  Although improving the carrier mobility of the material itself is one of the means, it can also be improved by separately forming a carrier hopping site using a technique such as doping.

  Further, as one means, it is possible to achieve a long life by reducing the load on the element. For this purpose, it is necessary to increase the luminance without changing the driving current, that is, to improve the efficiency, or to realize an element configuration that can obtain the same luminance even if the driving current is decreased.

  In order to increase the luminance without changing the drive current, that is, to improve the efficiency, the use of phosphorescent materials as the light emitting materials has been intensively researched and developed. Developing a light-emitting material is extremely difficult and impractical.

  As a technique for obtaining the same luminance even when the drive current is lowered, a stack type multi-photon emission element (MPE element) in which a plurality of organic light emitting elements are arranged in an overlapping manner has been proposed. In this case, for example, an element in which units of a plurality of organic light emitting elements are electrically connected in series via an intermediate conductive layer has been proposed (see Patent Document 1 below). The publication describes an element characterized in that a plurality of organic light emitting elements are electrically connected in series via an intermediate conductive layer.

  However, in an element configuration in which organic light emitting elements are stacked via an intermediate conductive layer, there is a concern about leakage current from the intermediate conductive layer when a display device is configured by arranging a plurality of elements in a plane, particularly for a passive matrix. May be a fatal defect in displaying images. Therefore, as shown in FIG. 5, a plurality of light emitting units 4-1, 4-2,... Made of an organic layer having at least a light emitting layer 4c are provided between the anode 3 and the cathode 5 as insulating charge generation layers. 6, a configuration of an MPE element (display element 1 ′) arranged in an overlapping manner via 6 is proposed.

Here, the charge generation layer 6 injects holes into the light emitting unit 4-2 disposed on the cathode 5 side of the charge generation layer 6 when a voltage is applied, while the anode 3 side of the charge generation layer 6 is present. The layer plays a role of injecting electrons into the light emitting unit 4-1, and is made of a metal oxide such as vanadium oxide (V ₂ O ₅ ) or rhenium 7 oxide (Re ₂ O ₇ ). It is configured.

  Further, in order to increase the electron injection efficiency from the charge generation layer 6 to the light emitting unit 4 on the anode 3 side, the electron injection layer 7 serving as an “in-situ reaction generation layer” is provided on the anode 3 side of the charge light emission layer 6. It is preferable to provide it. As such an “in-situ reaction generation layer”, for example, a mixed layer of bathocuproine (BCP) and metal cesium (Cs), or a laminated film of (8-quinolinolato) lithium complex and aluminum is used. Used.

  In the stack type organic electroluminescence device in which the light emitting units 4-1, 4-2,... Are stacked through the charge generation layer 6 as described above, when two light emitting units are stacked, ideally, When the luminous efficiency [lm / W] does not change and the luminance [cd / A] is doubled and three light emitting units are stacked, ideally [lm / W] does not change [cd] / A] can be tripled (see the following Patent Documents 2 and 3).

  In such a stack type organic electroluminescence device, there is a demand for an organic material capable of improving the charge injection efficiency in the material constituting the charge generation layer, in addition to the organic material having a high carrier mobility.

  In such a situation, in 1994, Haarer et al. Reported that by introducing a hexylthio group as a substituent into a triphenylene derivative, high hole mobility of 10-1 cm 2 / Vs was expressed (Non-Patent Document). 1). This triphenylene derivative, together with an azatriphenylene derivative, has been studied mainly as a discotic liquid crystal material because of its molecular structure symmetry. Since then, research to provide high charge mobility to discotic liquid crystal materials has been developed (see Non-Patent Document 2). In recent years, the application of torquexen compounds that serve as mesogens for discotic liquid crystals to optically functional materials is being developed (Non-patent Document 3). The non-patent document 1 of the invention report was deleted and the number of the non-patent document was shifted. Please check the correspondence between the document name and the document content.

Japanese Patent Laid-Open No. 11-329748 JP 2003-45676 A JP 2003-272860 A Nature, No. 371, p. 141, 1994 Advanced Materials (US), Vol. 13, No. 2, p.130-133, 2001 Journal of the American Chemical Society (USA), vol. 125, p. 9944-9945, 2003

  By the way, examples of the charge transport layer used in the organic electroluminescence device and the organic semiconductor include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. In general, in an organic electroluminescent device, by increasing the carrier mobility in these charge transport layers, the light emission efficiency is improved and low voltage driving becomes possible. On the other hand, for the light emitting layer, the combination of the host material and the guest material is important. In order to confine the generated excitons related to light emission, it is not always necessary to increase the mobility by focusing only on the charge transport property. It is not an improvement, but the balance between holes and electrons is important.

  As the development of organic electroluminescent devices began with the use of OPC materials, there are many materials with various variations and characteristics regarding hole injection materials and hole transport materials, whereas electron transport There are few types of materials and electron injection materials, and the current situation is that development is delayed. However, increasing the mobility of the hole injection material and the hole transport material is an important improvement item that leads to low voltage driving of the organic electroluminescent device. Part of the present invention has been made in view of such problems.

  Further, in the stack type organic electroluminescent device disclosed in Patent Documents 2 and 3, in order to increase the efficiency of electron injection from the charge generation layer 6 to the light emitting unit 4-1 shown in FIG. BCP) and metal cesium (Cs) mixed layer, or “in-situ reaction product layer (electron injection layer 7)” composed of a laminated film of (8-quinolinolato) lithium complex and aluminum is used as anode 3 of charge emitting layer 6 The structure provided in the side is disclosed. However, in the electron injection layer 7 constituted by these materials, the stoichiometric ratio of each material constituting the layer is important, and it is considered that the layer becomes unstable when this balance is lost.

  For example, BCP is rich in complex-forming ability, and when free components are matched, there is a high possibility of forming a complex with a peripheral material, and it is difficult to use it in consideration of the stability of the element. In addition, it is considered that the element using the BCP has poor reliability with respect to environmental resistance.

In such a stack type organic electroluminescent element, as disclosed in Patent Documents 2 and 3, a charge generation layer is formed using a metal oxide such as V ₂ O ₅ or Re ₂ O _7. 6, the efficiency of electrons injected by contacting a general electron transport layer such as Alq ₃ directly with the charge generation layer 6 is extremely low. In the stack type organic electroluminescent device, it is possible to efficiently inject electrons from the charge generation layer 6 to the light emitting unit 4-1 and holes into the light emitting unit 4-2. It becomes a very important point in the transformation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an organic material having a high carrier mobility, which is necessary for an element structure that is effective in extending the life and can improve efficiency, and is a repetitive (stacked) element. A display element capable of forming a charge generation layer, which is extremely important in constructing a display device, and capable of providing stable light emission for a long time by using this material is provided. It is intended to provide.

The organic material for display elements of the present invention for achieving the above object is represented by the following general formula (1).

However, in General Formula (1), R ^{1 to} R ⁶ are each independently hydrogen, halogen compound group, hydroxyl group, amino group, arylamino group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, carbon number A substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted alkoxyl group having 20 or less carbon atoms , A substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group. Further, adjacent R ^m (m = 1 to 6) may be bonded to each other through a ring structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom. The binding sites of Y ^{1 to} Y ³ are each independently any of the following general formulas (2) to (5).

ただし、一般式（２）および一般式（３）中において、Ａ¹〜Ａ³はそれぞれ独立に、水素、炭素数２０以下の置換あるいは無置換のアルキル基、炭素数２０以下の置換あるいは無置換のアルケニル基、炭素数３０以下の置換あるいは無置換のアリール基、炭素数３０以下の置換あるいは無置換の複素環基から選ばれる置換基である。

However, in General Formula (2) and General Formula (3), A ^{1 to} A ³ are each independently hydrogen, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, or a substituted or unsubstituted group having 20 or less carbon atoms. And a substituent selected from a substituted or unsubstituted aryl group having 30 or less carbon atoms and a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms.

  In the first display element of the present invention, a light emitting unit including at least an organic light emitting layer is sandwiched between a cathode and an anode, and the light emitting unit includes an organic material represented by the general formula (1). It is characterized by comprising at least one layer.

  Further, in the second display element of the present invention, a plurality of the light emitting units are laminated between the cathode and the anode via the charge generation layer, and in particular, the charge generation layer is an organic material represented by the general formula (1). It is characterized by comprising.

  The compound having a torquesen skeleton having the structure represented by the general formula (1) has very good carrier mobility.

  For this reason, the organic material represented by the general formula (1) is suitably used as a charge transport layer in a display device in which an organic light emitting layer or a charge transport layer is sandwiched as a light emitting unit between a cathode and an anode. Moreover, although the characteristics of the organic material of the general formula (1) vary depending on the nature of the skeleton, particularly the side chain, many of the organic materials have excellent hole transport characteristics, and many of them are hole injection layers in the charge transport layer. Or, it has excellent properties as a hole transport layer.

Furthermore, the organic material of the general formula (1) is very stable and has a charge injection efficiency in a stack type display element in which a plurality of light emitting units made of an organic material are stacked between a cathode and an anode via a charge generation layer. It was found that an excellent charge generation layer can be formed. In other words, since the organic material of the present invention has a torquesen skeleton in the molecule, it can take a stacking (columnar arrangement) in which the molecules overlap three-dimensionally or a nematic structure (random stacking in the plane direction). For this reason, it is considered that the formed charge can easily move between molecules under the application of an electric field, thereby functioning as an effective charge generation layer. In the Torquecene skeleton having nitrogen in X ^{1 to} X ⁶ or Y ^{1 to} Y ³ , the nitrogen portion is also a portion that controls charge generation. Therefore, the number and arrangement are appropriately adjusted in the molecular skeleton. Thus, a desired charge generation layer corresponding to the element can be formed.

  As described above, many of the organic materials of the general formula (1) mainly have hole transport performance. Depending on the skeleton, it is also measured when the intramolecular carrier is only holes. For this reason, even when the light emitting units are stacked in a state where the charge generation layer composed of this organic material is sandwiched, the leakage of charges that do not contribute to light emission between these optical units and the generated excitons Energy diffusion is not caused. Therefore, the superposed optical units can function efficiently and effectively independently to emit light. Thereby, low voltage driving in the stack type display element becomes possible.

  As described above, the organic material represented by the general formula (1) of the present invention is excellent in carrier mobility (particularly, hole transportability). Therefore, a light-emitting unit using such an organic material is used as a cathode-anode. By constructing the display element sandwiched between them, the light emission efficiency is improved and low-voltage driving is possible, as will be described later in the examples of the display element. Specifically, an organic electroluminescence device comparable to the conventional one can be produced, and the driving voltage is reduced to 1 V or more in a practical region as compared with the case of using a general hole injection material. As a result, power consumption as a display element can be reduced. In addition, since low voltage driving is possible, it is possible to extend the life of a display element in which a light emitting unit using such an organic material is sandwiched between a cathode and an anode.

  Further, as described above, the organic material of the general formula (1) is used as a charge transport layer in a stack type display element in which an organic light emitting layer or a charge transport layer is sandwiched between a cathode and an anode as a light emitting unit. In addition, the stack type display element can be driven at a low voltage.

  Hereinafter, embodiments of the present invention will be described in the order of an organic material for a display element, a synthesis method, and a display element.

<Organic materials for display elements>
The organic material for display elements of the present invention (hereinafter simply referred to as organic material) is an organic compound having a torquesen skeleton represented by the general formula (1). In the above-described general formula (1), R ^{1 to} R ⁸ are preferably electron-withdrawing substituents at positions other than the above-described substituents, excluding the sites where they are bonded to each other. Here, the electron-withdrawing substituent is a substituent having an effect of extracting an electron from the aryl nucleus, and the substituent constant (σ ⁺ ) in Hammett's rule is generally used as an index.

In the present compound, it is preferable that a substituent having a positive value for the substituent effect at the meta position relative to the atom Z, that is, the electrophilic substituent constant σ _m ^{+ at the} meta position is arranged. As the representative electrophilic substituent constant σ _m ^{+ at the} meta position, for example, a numerical value described in “Explanation of Organic Electronics (4th edition), Tokyo Chemical Dojin, 1992, page 291” can be used. Examples of such a substituent include a halogen compound group, a carbonyl group, a carbonyl ester group, a cyano group, a nitro group, an aryl group, or an alkoxy group.

  Among such electron-withdrawing substituents, a cyano group, a fluorine compound group (halogen compound group), and a methoxy group (alkoxy group) are more preferably used. Among these, specific examples of the fluorine compound group include, in addition to fluorine, a trifluoromethyl group, a pentafluoroethyl group, a pentafluorophenyl group, and the like.

  As described above, in the organic material in the general formula (1), it is possible to adjust the intermolecular interaction that controls the columnar arrangement by introducing the electron-withdrawing substituent as described above into the Torquesen-like skeleton. . For this reason, carrier mobility can be further increased. Further, this effect becomes more remarkable by using a cyano group, a fluorine compound group, or a methoxy group as the substituent.

  Next, more typical exemplary structures of the organic material of the present invention represented by the general formula (1) will be shown, but the organic material of the present invention is not limited to these molecular skeletons.

この一般式（６）中において、Ｒ¹〜Ｒ⁶、Ｘ¹〜Ｘ²、Ａ¹，Ａ²は、それぞれ上記一般式（１）および一般式（２）で定義したものと同じ意味を表す。 A) In the general formula (1), the following general formula (6) is shown as a structure in which the binding site of Y ^{1 to} Y ³ is the general formula (2).

In the general formula (6), R ^{1 to} R ⁶ , X ^{1 to} X ² , A ¹ and A ² represent the same meanings as defined in the general formula (1) and the general formula (2), respectively. .

Of these, Tables 1 and 2 below show typical structural examples in which X ^{1 to} X ⁶ are carbon in the general formula (6). The substituent represented by the structural formula (1) -2 represents a branched structure of an acyclic hydrocarbon group.

Tables 3 to 4 below show typical structural examples in which one of X ^{1 to} X ⁶ of the general formula (6) is nitrogen.

Tables 5 to 6 below show typical structural examples in which all of X ^{1 to} X ⁶ are nitrogen in the general formula (6).

この一般式（７）中において、Ｒ¹〜Ｒ^6、Ｘ¹〜Ｘ²，Ａ³は、それぞれ上記一般式（１）および一般式（３）で定義したものと同じ意味を表す。 B) In the general formula (1), the following general formula (7) is shown as a structure in which the binding site of Y ^{1 to} Y ³ is the general formula (3).

In the general formula (7), R ^{1 to} R ^6, X ^{1 to} X ² , and A ³ represent the same meanings as defined in the general formula (1) and the general formula (3), respectively.

Of these, Tables 7 to 8 below show typical structural examples in which X ^{1 to} X ⁶ of the general formula (7) are carbon.

Tables 9 to 10 below show typical structural examples in which one of X ^{1 to} X ⁶ of the general formula (7) is nitrogen.

Tables 11 to 12 below show typical structural examples in which all of X ^{1 to} X ⁶ are nitrogen in the general formula (7).

C) In the general formula (1), the structures where the binding sites Y ^{1 to} Y ³ are oxygen of the general formula (4) or sulfur of the general formula (5) are shown in Tables 13 to 14 below.

<Synthesis method>
The organic material of the present invention shown as an example above can be synthesized by various methods.

  For example, as a typical method for synthesizing the compounds shown in Tables 1 to 6 and Tables 13 to 14, a method of contacting arylpropionic acid with polyphosphoric acid (US Pat. No. 3,504,044, JP-A-10-29143), There is a reaction of indanone compounds (Japanese Patent Laid-Open No. 10-324648, Synthetic Communications, Vol. 27, p. 2021, 1997).

  Moreover, as a typical synthesis method of the compounds shown in Tables 7 to 12, for example, a method of forming a cyclized trimer in the presence of bromine from an indole derivative shown by N. Robertson et al. (Journal of Material Chemistry, Vol. 10, p.2043-2047, 2000). This method is shown in the following scheme (1).

From the brominated cyclized trimer thus obtained, substituents can be introduced under the conditions shown in Scheme (1).

  For example, in a nitrification reaction in which a cyano group is introduced, a hexacyanolated cyclized trimer can be synthesized by a Sandmeyer reaction using copper cyanide (Organic Synthesis, Collection Volume 3, p. 631).

  When arylboronic acid is used, a cyclized trimer that is hexa-arylated by the Suzuki-Miyaura reaction can be obtained.

  Furthermore, as a substitution reaction for the amine at the cyclized trimer site, for example, alkyl can be alkylated by reacting an alkyl halide as AX in the presence of sodium amide (Organic Synthesis, Collection Volume 5, p.769). .

  The organic material having a torquesen skeleton of the present invention is used as a material constituting the organic layer of a display element, in particular, an organic electroluminescent element, and increases the purity before being subjected to the manufacturing process of the organic electroluminescent element. The purity is preferably 95% or more, more preferably 99% or more. As a method for obtaining such a high-purity organic compound, in addition to a recrystallization method, a reprecipitation method, which is a purification after the synthesis of the organic compound, or a column purification using silica or alumina, a known method by a sublimation purification or a zone melt method is used. High purity methods can be used.

  Further, by repeating these purification methods or combining different purification methods, the mixture of unreacted substances, reaction by-products, catalyst residues, or residual solvents in the organic light-emitting material in the present invention is reduced. As a result, it is possible to obtain an organic electroluminescent element having better device characteristics.

Further, this compound is composed of the organic light-emitting material, particularly by suppressing the deterioration reaction from the oxidation and decomposition by taking the following storage methods a) to c) from the external factors such as light and oxygen. In the organic electroluminescence device, not only provides superior light emission characteristics, but also exhibits an effect in reducing the load on the manufacturing apparatus.
a) After synthesizing the organic light emitting material, immediately leave it in a cool place. The storage temperature is preferably in the range of -100 ° C to 100 ° C, more preferably in the temperature range of -50 ° C to 50 ° C.
b) After synthesizing the organic light emitting material, immediately store it in a light-shielding container.
c) After synthesizing the organic light emitting material, the synthesized organic light emitting material is stored in an inert gas atmosphere such as nitrogen, carbon dioxide, argon or the like.

<Display element-1>
Next, an embodiment of the first display element using the organic material for display element of the present invention will be described in detail with reference to FIG.

  The display element 10 shown in this figure includes an anode 13 provided on a substrate 12, a light emitting unit 14 made of an organic material layer provided on the anode 13, and a cathode 15 provided on the light emitting unit 14. An organic electroluminescent device provided.

  In the following description, the light emitted when the holes injected from the anode 13 and the electrons injected from the cathode 15 are combined in the light emitting unit 14 is extracted from the cathode 15 side opposite to the substrate 2. A structure of a top emission type display element will be described.

  First, the substrate 12 on which the display element 10 is provided is appropriately selected from a transparent substrate such as glass, a silicon substrate, and a film-like flexible substrate. When the driving method of a display device configured using the display element 10 is an active matrix method, a TFT substrate in which a TFT is provided for each pixel is used as the substrate 12. In this case, the display device has a structure in which the top emission type display element 10 is driven using a TFT.

The anode 13 provided as the lower electrode on the substrate 12 has a high work function from the vacuum level of the electrode material in order to efficiently inject holes, for example, chromium (Cr), gold (Au), An alloy of tin oxide (SnO ₂ ) and antimony (Sb), an alloy of zinc oxide (ZnO) and aluminum (Al), and oxides of these metals and alloys are used alone or in a mixed state. be able to.

  In the case where the display element 10 is a top emission type, it is possible to improve the light extraction efficiency to the outside by the interference effect and the high reflectance effect by configuring the anode 13 with a high reflectance material. As the electrode material, it is preferable to use an electrode mainly composed of Al, Ag, or the like. It is also possible to increase the charge injection efficiency by providing a transparent electrode material layer having a large work function such as ITO on these high reflectivity material layers.

  When the driving method of the display device configured using the display element 10 is an active matrix method, the anode 13 is patterned for each pixel provided with a TFT. An insulating film (not shown) is provided on the upper layer of the anode 13, and the surface of the anode 13 of each pixel is exposed from the opening of the insulating film.

  The light emitting unit 14 is formed by laminating a hole injection layer 14a, a hole transport layer 14b, a light emitting layer 14c, and an electron transport layer 14d in this order from the anode 13 side. Each of these layers is composed of an organic layer formed by, for example, a vacuum deposition method or another method such as a spin coating method. And the organic material demonstrated using General formula (1) of this invention is used for either of these layers 14a-14d.

  In particular, it is preferable that at least one of the hole injection layer 14a and the hole transport layer 14b is configured using an organic material represented by the general formula (1). In this case, the hole injection layer 14a or the hole transport layer 14b is configured as a layer made of a single material of the organic material of the general formula (1), or the organic material of the general formula (1) and the benzidine derivative Hole transport layer 14b or hole injection layer as a mixed layer using at least one material selected from, for example, materials having a tertiary amine skeleton such as styrylamine derivatives, triphenylmethane derivatives, and hydrazone derivatives 14a is configured. When the hole transport layer 14b and the hole injection layer 14a are mixed layers, these layers are formed by co-evaporating the organic material of the general formula (1) and other materials.

  For example, by using a material having a tertiary amine skeleton such as co-evaporation, the driving voltage of the display element 10 can be lowered, and an element having a thick film can be formed. This increase in film thickness is extremely advantageous in that it can prevent defects and short-circuits caused by non-light emitting points, and constitutes a highly reliable element in both passive and active elements. can do.

  In addition, the light emitting layer 14c is often configured by co-evaporation of trace molecules, and is configured as an organic thin film containing a trace amount of organic substances such as berylene derivatives, coumarin derivatives, pyran dyes, and triphenylamine derivatives. Is done. In particular, a luminescent center having a tertiary amine having a hole transporting characteristic in its molecular structure has a low intermolecular interaction and is difficult to quench the concentration, so that the luminescent layer 14c is highly doped. It becomes possible and functions as one of the optimal dopants.

  Each of the above organic layers, for example, the hole injection layer 14a and the hole transport layer 14b, may have a laminated structure including a plurality of layers.

  Furthermore, it does not prevent that each layer 14a-14d has other requirements, for example, the light emitting layer 14c can also be an electron transporting light emitting layer that also serves as the electron transporting layer 14d. The light-emitting layer 14c having a hole transport property may be used, and each layer may have a laminated structure. For example, the light emitting layer 14c may be a white light emitting element formed of a blue light emitting part, a green light emitting part, and a red light emitting part.

  Next, the cathode 15 has a three-layer structure in which a first layer 15a, a second layer 15b, and in some cases a third layer 15c are stacked in this order from the anode 13 side.

The first layer 15a is made of a material having a small work function and good light transmittance. Examples of such materials include Li ₂ O which is an oxide of lithium (Li), Li ₂ SiO ₃ which is a carbonate, Cs ₂ CO ₃ which is a carbonate of cesium (Cs), and these oxides. Mixtures can be used. Further, the first layer 15a is not limited to such a material. For example, alkaline earth metals such as calcium (Ca) and barium (Ba), and alkali metals such as lithium (Li) and cesium (Cs). Further, metals having a small work function such as indium (In), magnesium (Mg), silver (Ag), and further fluorides and oxides of these metals alone or these metals and fluorides, oxidation You may use it, improving stability as a mixture or alloy of a thing.

  The second layer 15b is composed of an electrode composed of an alkaline earth metal such as MgAg or an electrode composed of Al. When the cathode 15 is formed of a semi-transmissive electrode like a top light emitting device, light can be extracted by using a thin MgAg electrode or Ca electrode. By configuring the display element 10 with a material having optical transparency and good conductivity, the display element 10 emits light from the upper surface, which is constituted by a cavity structure that resonates and extracts emitted light between the anode 13 and the cathode 15 in particular. In the case of an element, the second layer 15b is formed using a semi-transmissive reflective material such as Mg-Ag. As a result, light emission is reflected at the interface of the second layer 15b and the interface of the anode 13 having light reflectivity to obtain a cavity effect.

  Furthermore, the third layer 15c can also be formed as a sealed electrode that can extract light emission by providing a transparent lanthanoid-based oxide for suppressing deterioration of the electrode. When the display element 10 is a “transmission type” that extracts emitted light from the substrate 12, the third layer 15c may be provided with a sealing electrode such as AuGe, Au, or Pt.

  The first layer 15a, the second layer 15b, and the third layer 15c described above are formed by a technique such as a vacuum deposition method, a sputtering method, or a plasma CVD method. When the driving method of the display device configured using this display element is an active matrix method, the cathode 15 is a laminated film of an insulating film and a light emitting unit 14 covering the periphery of the anode 13 (not shown). Thus, it may be formed as a solid film on the substrate 12 while being insulated from the anode 13, and may be used as a common electrode for each pixel.

  The electrode structure of the cathode 15 shown here is a three-layer structure. However, the cathode 15 may be formed of only the second layer 15b or between the first layer 15a and the second layer 15b as long as it is a laminated structure necessary when the functions of the layers constituting the cathode 15 are separated. In addition, it is possible to form a transparent electrode such as ITO, and it is needless to say that an optimal combination and laminated structure may be taken for the structure of the device to be produced.

  In the display element 10 having the above-described configuration, at least one of the hole injection layer 14a and the hole transport layer 14b is configured using the organic material represented by the general formula (1). The hole transport properties of the injection layer 14a and the hole transport layer 14 can be improved.

  In particular, in the organic material of the general formula (1), it is possible to adjust the intermolecular interaction that controls the columnar arrangement in the organic material by using one or more substitution sites as electron-withdrawing substituents. Thus, the carrier mobility can be increased, and the light emission efficiency and life characteristics can be improved.

<Display element-2>
Next, an embodiment of the second display element using the organic material for display element of the present invention will be described in detail with reference to FIG. It should be noted that the same components as those of the display element shown in FIG.

  A display element 11 shown in this figure is a stack type display element 11 formed by stacking light emitting units, and includes an anode 13 provided on a substrate 12 and a plurality of light emitting units 14 provided on the anode 13 in an overlapping manner. -1, 14-2,... (Two here), the cathode 15 provided on the uppermost light emitting unit 14-2, and the charge generation layer provided between the light emitting units 14-1 and 14-2. 16 is provided.

  In the display element 11 having such a configuration, the same substrate 12, anode 13 and cathode 15 as those of the display element 10 of the first embodiment are used.

  Each of the light emitting units 14-1 and 14-2 is the same as the light emitting unit 14 in the display element 10 of the first embodiment, that is, the hole injection layer 14a using the organic material represented by the general formula (1) The hole transport layer 14b may be provided. However, the light emitting units 14-1 and 14-2 described above may have exactly the same structure, but may have other structures. For example, when the light emitting unit 14-1 is formed as an organic layer structure for an orange light emitting element and the light emitting unit 14-2 is formed as an organic layer structure for a blue-green light emitting element, the emission color is white.

  The organic material of the general formula (1) of the present invention is used for the charge generation layer 16 provided between the light emitting unit 14-1 and the light emitting unit 14-2.

  Here, the charge generation layer 16 preferably has a structure in which, for example, an interface layer 16a and an intrinsic charge generation layer 16b are stacked in this order from the anode 13 side. The interface layer 16a serves as a cathode for the light emitting unit 14-1 provided in contact with the anode 13. Therefore, hereinafter, the interface layer 16a is referred to as an intermediate cathode layer 16a.

  Of these, the intermediate cathode layer 16a is preferably composed of at least one of an alkali metal oxide and an alkaline earth metal oxide. As the alkali metal oxide and alkaline earth metal oxide constituting the intermediate cathode layer 16a, general oxides and composite oxides are used. Specifically, metaborate, tetraborate, germane oxide, Molybdenum oxide, niobium oxide, silicic oxide, tantalum oxide, titanium oxide, vanadium oxide, tungsten oxide, zircon oxide, carbonate, soot oxide, subchromium oxide, chromium oxide, heavy chromium oxide At least one of ferrite, selenium oxide, selenium oxide, tin oxide, tellurium oxide, tellurium oxide, bismuth oxide, tetraborate, and metaborate is selected.

Among these, in particular, the intermediate cathode layer 16a is preferably made of Li ₂ SiO ₃ .

  Thus, by including at least one of an alkali metal oxide and an alkaline earth metal oxide as a material constituting the intermediate cathode layer 16a, the charge generation layer 16 to the light emitting unit 14-1 on the anode 13 side can be used. Electron injection efficiency is improved. In particular, materials such as alkali metal oxides and alkaline earth metal oxides constituting the intermediate cathode layer 16a in the charge generation layer 16 are supplied as stable materials from the film formation stage. For this reason, the intermediate cathode layer 16a using this, that is, the charge generation layer 15 is stabilized. Since the intermediate cathode layer 16a is composed of a single material of an alkali metal oxide and an alkaline earth metal oxide as a material constituting the intermediate cathode layer 16a, as shown in Patent Document 3, a conventional bathocproin (BCP) ) Compared to the intermediate cathode layer 16a (intermediate electron injection layer) made of a plurality of materials such as + Cs and Liq + Al, it is advantageous in terms of process and product yield.

  The organic material of the general formula (1) of the present invention is preferably used as the intrinsic charge generation layer 16b provided in contact with the light emitting unit 14-2. In this case, the intrinsic charge generation layer 16b may be composed only of the organic material of the general formula (1).

  The intermediate cathode layer 16a and the intrinsic charge generation layer 16b are not necessarily limited to a configuration that is clearly separated, and the material constituting the intrinsic charge generation layer 16b is contained in the intermediate cathode layer 16a. Or vice versa.

  The charge generation layer 16 is not limited to the above-described two-layer structure of the intermediate cathode layer 16a and the intrinsic charge generation layer 16b, and may have a stacked structure of three or more layers as necessary. However, the charge generation layer 16 contains the organic material of the general formula (1) of the present invention, and as a preferred form, there is a layer in contact with the light emitting unit 14-2 disposed on the cathode 15 side. The organic material represented by the general formula (1) of the present invention is used.

  When the intrinsic charge generation layer 16b of the charge generation layer 16 is formed using the organic material represented by the general formula (1), the intrinsic charge generation layer 16b also serves as the hole injection layer 14a. Also good. In this case, the hole injection layer 14 a is not necessarily provided in the light emitting unit 14-2 provided on the cathode 15 side with respect to the charge generation layer 16.

  Further, as described above, the organic material of the general formula (1) is used for the charge generation layer 16 and the organic material of the general formula (1) is used in the light emitting unit like the display element described with reference to FIG. It is also possible to combine the configuration. In this case, the organic material of the general formula (1) is used for each layer in the light emitting units 14-1 and 14-2 in the same manner as the light emitting unit in the display element described with reference to FIG.

  In particular, as the hole transport layer 14b or the hole injection layer 14a in the light emitting units 14-1 and 14-2, an organic material represented by the general formula (1), a benzidine derivative, a styrylamine derivative, a triphenylmethane derivative, and a hydrazone It is preferable to use a mixed film with at least one material selected from among derivatives. Particularly preferably, the mixed layer is preferably used as the hole injection layer 14a of the light emitting unit 14-2 in contact with the intrinsic charge generation layer 16b formed using the general formula (1).

  In the display element 11 of the second embodiment having the configuration described above, the light emitting units 14-1 and 14-2 are stacked by using the organic compound represented by the general formula (1) described above for the charge generation layer 16. It has become possible to suppress the increase in voltage due to this. This is because most of the organic material of the general formula (1) mainly has hole transport performance. And depending on the skeleton, even when the intramolecular carrier is measured only as a hole, even when the light emitting unit is stacked in a state of sandwiching the charge generation layer configured using this organic material, There is no charge leakage that does not contribute to light emission between these optical units, nor energy diffusion from the generated excitons. Therefore, the superposed optical units can function efficiently and effectively independently to emit light. This is considered to be due to the fact that the stack type display element can be driven at a low voltage.

  As a result, for example, when two units of the light emitting units 14-1 and 14-2 are stacked, the driving voltage has increased more than twice in the past, but the present invention makes it possible to suppress the increase of the driving voltage. Thus, an ideal stack type display element 11 can be obtained.

  In particular, in the organic material of the general formula (1), it is possible to adjust the intermolecular interaction that controls the columnar arrangement in the organic material by using one or more substitution sites as electron-withdrawing substituents. It is possible to achieve an effect on the charge transfer related to the charge generation layer 16 and to improve the light emission efficiency and the life characteristics.

Further, conventionally, it is possible to obtain a charge injection efficiency comparable to that in the case where V ₂ O ₅ is used as the layer (intrinsic charge generation layer 16b) in contact with the light emitting unit 14-2 side in the charge generation layer 16. In this case, since the intrinsic charge generation layer 16b can also serve as the hole injection layer, the hole injection layer is specially added to the light emitting unit 14-2 disposed on the cathode 15 side of the charge generation layer 16. 14a may not be provided, and the layer structure can be simplified.

Furthermore, V ₂ O ₅ that has been used heretofore has a high hygroscopic property, has a high reactivity with metal species, and is active, so that it is difficult to handle and it is difficult to stably use as a charge generation layer. However, the chemical stability of the charge generation layer 16 can be improved by using the organic material of the general formula (1) instead.

  Note that the display element of the present invention described in each of the above embodiments is not limited to a display element used for an active matrix type display device using a TFT substrate, but as a display element used for a passive type display device. Can be applied, and the same effect (improvement of long-term reliability) can be obtained.

  In each of the embodiments described above, the case of the “top emission type” in which light emission is extracted from the cathode 15 side provided on the side opposite to the substrate 12 has been described. However, the present invention is also applied to a “transmission type” display element in which the substrate 12 is made of a transparent material to extract emitted light from the substrate 12 side. In this case, in the laminated structure described with reference to FIG. 2, the anode 13 on the substrate 12 made of a transparent material is configured using a transparent electrode material having a large work function such as ITO. Thereby, emitted light is extracted from both the substrate 12 side and the opposite side of the substrate 12. In such a configuration, by forming the cathode 15 from a reflective material, emitted light is extracted only from the substrate 12 side. In this case, a sealing electrode such as AuGe, Au, or Pt may be attached to the uppermost layer of the cathode 6.

  Furthermore, the “transmission type” in which emitted light is extracted from the substrate 12 side even when the laminated structure described with reference to FIG. The display element can be configured. Also in this case, by changing the anode 13 serving as the upper electrode to a transparent electrode, emitted light is extracted from both the substrate 12 side and the opposite side of the substrate 12.

≪Synthesis of organic materials≫
A synthesis example of the organic material of the present invention will be described.

<Synthesis Example 1> Synthesis of Structural Formula (1) -18 First, after a 1000-ml three-necked flask equipped with a mechanical stirrer was sufficiently substituted with nitrogen, 3- (3,4-dicyanophenyl) propionic acid (20 g, 100 mmol) was added with polyphosphoric acid (500 g) and allowed to react at 140 ° C. for 2 hours with sufficient stirring. After cooling, 1000 mL of deionized water was added and stirred at room temperature for 2 hours. The obtained solid was removed by filtration, washed thoroughly with acetone and ethanol, yield, and then washed with acetone and ethanol to obtain 15.2 g (yield 31%) of the structural formula (1) -18. . It was confirmed from the result of measuring the solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS that the reaction product was structural formula (1) -18.

<Synthesis Example 2> Synthesis of Structural Formula (2) -10 In Synthesis Example 1, 3- (5,6-dimethoxypyridin-2-yl) propionic acid was used instead of 3- (3,4-dicyanophenyl) propionic acid. The reaction was performed in the same manner as in Synthesis Example 1 except that it was used. The obtained solid was measured by ¹ H-NMR, ¹³ C-NMR, and FD-MS, and as a result, it was confirmed that it was the structural formula (2) -10 which was the target product.

Synthesis Example 3 Synthesis of Structural Formula (3) -18 In Synthesis Example 1, 3- (5,6-dicyanopyrazin-2-yl) butanoic acid was used instead of 3- (3,4-dicyanophenyl) propionic acid. The reaction was performed in the same manner as in Synthesis Example 1 except that it was used. The obtained solid was measured by ¹ H-NMR, ¹³ C-NMR, and FD-MS, and as a result, it was confirmed to be the structural formula (3) -18 which is the target product.

<Synthesis Example 4> Synthesis of Structural Formula (4) -18 The compound represented by Structural Formula (4) -18 was synthesized by the procedure shown in the following Synthetic Formula (1) as follows.

  First, after thoroughly replacing a 500 ml three-necked flask equipped with a mechanical stirrer with nitrogen, 1-methylindole (13.1 g, 100 mmol) was dissolved in 250 ml of acetonitrile and bromine (48 g, 300 mmol) was added dropwise. And stirred for 24 hours at room temperature. After the reaction, the precipitated solid was filtered, washed with acetonitrile, and recrystallized from a DMSO / acetone mixed solvent to obtain 10.1 g of intermediate (C1) (yield 12%).

Subsequently, a 100 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, and then the intermediate (C1) obtained above (5.8 g, 6.7 mmol) and copper cyanide (3.9 g, 44 mmol) were obtained. ) And 50 ml of DMF was poured as a solvent. The reaction was carried out at reflux temperature for 8 hours. After completion of the reaction, the mixture was added to an ethylenediamine aqueous solution (ethylenediamine 100 ml, water 200 ml) and shaken, and then toluene was added to extract the organic layer. The solvent was removed by distillation under vacuum conditions, and then washed with acetone and ethanol to obtain 3.9 g of brown solid (yield 58%). As a result of measuring the obtained solid with ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed that it was the structural formula (4) -18 which was the target product.

<Synthesis Example 5> Synthesis of Structural Formula (5) -18 Except that 1-methyl-1H-pyrrolo [2,3-b] pyridine was used instead of 1-methylindole used in the first reaction in Synthesis Example 4. Reacted in the same manner as in Synthesis Example 1. The obtained solid was measured by ¹ H-NMR, ¹³ C-NMR, and FD-MS, and as a result, it was confirmed to be the structural formula (5) -18 which is the target product.

<Synthesis Example 6> Synthesis of Structural Formula (6) -18 Except that 5-methyl-5H-pyrrolo [3,2-b] pyrazine was used instead of 1-methylindole used in the first reaction in Synthesis Example 4. Reacted in the same manner as in Synthesis Example 1. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed that it was the structural formula (6) -18, which was the target product.

<Synthesis Example 7> Synthesis of Structural Formula (4) -7 As in Synthesis Example 4, except that 5-fluor-1-methylindole was used instead of 1-methylindole used in the first reaction in Synthesis Example 4. Reaction was performed. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed that it was the structural formula (4) -7, which was the target product.

≪Display element≫
Next, the manufacturing procedure in the display element of the example, the manufacturing procedure in the display element of the comparative example, and the evaluation results thereof will be described.

<Examples 1-7>
In each of Examples 1 to 7, the display element 10 having the configuration described with reference to FIG. 1 in the above-described embodiment was formed. However, in each Example, each material shown by General formula (1) was used as the hole injection layer 14a. Below, the manufacturing procedure of the display element 10 of Examples 1-7 is demonstrated.

An Ag alloy (film thickness of about 100 nm) was formed as the anode 13 on the substrate 12 made of a glass plate of 30 mm × 30 mm, and a light emitting region other than 2 mm × 2 mm was masked with an insulating film (not shown) by SiO ₂ vapor deposition. A cell for an organic electroluminescence device was produced.

Next, as the hole injection layer 14a, each material shown in Table 15 below was formed to a thickness of 10 nm (deposition rate: 0.2 to 0.4 nm / sec) by a vacuum evaporation method.

Next, α-NPD represented by the following structural formula 1 was formed as a hole transport layer 14b with a film thickness of 10 nm (deposition rate: 0.2 to 0.4 nm / sec) by a vacuum evaporation method.

Further, as the light-emitting layer 14c, ADN shown in the following structural formula 2 is used as a host, BD-052x (Idemitsu Kosan Co., Ltd .: trade name, blue dopant) is used as a dopant, and the dopant concentration is 5% in film thickness ratio. Furthermore, these materials were formed into a film with a total thickness of 28 nm by a vacuum deposition method.

Finally, as the electron transport layer 14d, Alq3 (8-hydroxy quinorine alminum) represented by the following structural formula 3 was deposited by vacuum deposition to a thickness of 12 nm.

After forming the organic layer 14 from the hole injection layer 14a to the electron transport layer 14d as described above, Li ₂ CO ₂ is deposited to about 0.3 nm (deposition rate by vacuum deposition) as the first layer 15a of the cathode 15. Then, MgAg was formed as a second layer 15b with a thickness of 10 nm by a vacuum deposition method, and the cathode 15 having a two-layer structure was provided.

<Comparative Example 1>
Except for forming HI-406 (made by Idemitsu Kosan Co., Ltd., trade name of hole injection material) as the hole injection layer 14a with a thickness of 10 nm (deposition rate: 0.2 to 0.4 nm / sec). The configuration was exactly the same as in Examples 1-7.

≪Evaluation result-1≫
As shown in Table 15, in the organic electroluminescent elements of Examples 1 to 7 in which the hole injection layer 14a is configured using the organic material (non-arylamine type) having a novel structure according to the present invention, the arylamine type hole is used. Equivalent luminous efficiency [cd / A] comparable to that of the organic electroluminescence device of Comparative Example 1 in which the hole injection layer 14a is configured using the injection material can be obtained, and the effect of the present invention can be confirmed. It was.

  In addition, in each of the non-arylamine organic materials used for the hole injection layer 14a in Examples 1 to 7, the arylamine material used as the hole injection layer 14a of Comparative Example 1 is 5 to 10 in thickness ratio. When% doping was applied, the driving voltage could be lowered by 0.5 V or more in the practical range. As a result, the lifetime of the organic electroluminescent device using the organic material having the novel skeleton of the present invention can be further increased by using a small amount of the arylamine-based material in the non-arylamine organic material in the present invention. It was confirmed that this could be achieved.

<Examples 8 to 14>
In each of Examples 8 to 14, the display element 11 having the configuration described with reference to FIG. 2 in the above-described embodiment was formed. However, in each Example, each material shown by General formula (1) was used as the intrinsic charge generation layer 16b. Below, the manufacturing procedure of the display element 11 of Examples 8-14 is demonstrated.

An Ag alloy (film thickness of about 100 nm) was formed as the anode 13 on the substrate 12 made of a glass plate of 30 mm × 30 mm, and a light emitting region other than 2 mm × 2 mm was masked with an insulating film (not shown) by SiO ₂ vapor deposition. A cell for an organic electroluminescence device was produced.

Next, as the hole injection layer 14a in the light emitting unit 14-1 of the first layer, an azatriphenylene-based material represented by the following structural formula 4 is 10 nm (deposition rate: 0.2 to 0.4 nm / sec) by vacuum evaporation. It was formed with a film thickness.

  Next, the structure from the hole transport layer 14b to the electron transport layer 14d was the same as in Examples 1-7. That is, α-NPDs of structural formula 1 were each formed with a film thickness of 10 nm (deposition rate: 0.2 to 0.4 nm / sec) by vacuum evaporation.

  Furthermore, as the light emitting layer 14c, ADN of Structural Formula 2 is used as a host, BD-052x (Idemitsu Kosan Co., Ltd .: trade name, blue dopant) is used as a dopant, and the dopant concentration is 5% in film thickness ratio. These materials were formed into a total film thickness of 28 nm by a vacuum deposition method.

  Next, as the electron transport layer 14d, Alq3 (8-hydroxy quinorine alminum) of the structural formula 3 was deposited to a thickness of 12 nm by a vacuum deposition method.

After the first light emitting unit 14-1 from the hole injection layer 14a to the electron transport layer 14d is formed as described above, Li ₂ CO _{3 is used} as the intermediate cathode layer (interface layer) 16a of the charge generation layer 16. Then, each material shown in Table 16 below was vapor-deposited with a thickness of 30 mm as the intrinsic charge generation layer 16b.

  Thereafter, as the hole injection layer 14a in the light emitting unit 14-2 of the second layer, an azatriphenylene material of the structural formula 4 is deposited to a film thickness of 50 nm (deposition rate: 0.2 to 0.4 nm / sec) by vacuum deposition. Formed with thickness. The reason why the film thickness is different from the hole injection layer 14a in the first light emitting unit 14-1 is to optically maximize the light extraction.

  Thereafter, the second layer light emitting unit 14-2 was formed with the same structure as the first layer (that is, the same structure as in Examples 1 to 7) from the hole transport layer 14b to the electron transport layer 14d.

  Next, about 0.3 nm (deposition rate: 0.01 nm / sec) of LiF was formed as a first layer 15a of the cathode 15 on the second layer light emitting unit 14-2 by a vacuum evaporation method. Next, 10 nm of MgAg was formed as the second layer 15b by vacuum deposition.

<Comparative example 2>
A single layer structure in which the cathode 15 is provided without providing the charge generation layer 16 and the second light emitting unit 14-2 on the first light emitting unit 14-1 formed in Examples 8-14. A light emitting element was manufactured.
≪Evaluation result-2≫

  As shown in Table 16, in the stack type organic electroluminescent elements of Examples 8 to 14 in which the charge generation layer 16 is configured using an organic material having a novel structure according to the present invention, one unit shown in Comparative Example 2 is used. The effect of the present invention was confirmed to obtain a luminous efficiency [cd / A] that is about twice that of the device.

FIG. 3 shows the results of life measurement of Example 14 and Comparative Example 2 under the driving conditions of an initial luminance of 2500 cd / m ² and a duty ratio of 50%. From this result, when the initial luminance was made the same, there was a long life effect by stacking, and the effect by applying the organic material having a novel structure in the present invention to the charge generation layer was confirmed.

  Further, in the configurations of Examples 8 to 14 described above, the configuration of the hole injection layer 14a in the second light emitting unit 14-2 is represented by the same general formula (1) as that used for the intrinsic charge generation layer 16b. By adopting a constitution in which the organic material is doped with the material used for the hole transport layer 14b in a film thickness ratio of 5 to 10%, the driving voltage in the practical region can be lowered by about 1V. As a result, when the charge generation layer 16 using each organic material represented by the general formula (1) is used, the hole injection layer 14a can be formed using the organic material of the general formula (1) and other materials (here, The effect of extending the life of the mixed layer with α-NPD was also confirmed.

It is a section lineblock diagram showing display element-1 of an embodiment. It is a section lineblock diagram showing display element-2 of an embodiment. It is a graph which shows the time change of the relative luminance of the display element of Example 14 and Comparative Example 2. It is a cross-sectional block diagram which shows an example of an organic electroluminescent element. It is a cross-sectional block diagram which shows an example of a stack type organic electroluminescent element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,11 ... Display element, 13 ... Anode, 14, 14-1, 14-2 ... Light emitting unit, 14a ... Hole injection layer, 14b ... Hole transport layer, 14c ... Light emitting layer (organic light emitting layer), 15 ... Cathode, 16 ... charge generation layer

Claims (18)

An organic material for a display element represented by the following general formula (1).

[In the general formula (1), R ^{1 to} R ⁶ are each independently hydrogen, a halogen compound group, a hydroxyl group, an amino group, an arylamino group, a substituted or unsubstituted carbonyl group having 20 or less carbon atoms, A substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted carbon group having 20 or less carbon atoms An alkoxyl group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group, and adjacent R ^m (m = 1 to 6) may be bonded to each other through a ring structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom, and the binding sites of Y ^{1 to} Y ³ are each independently any of the following general formulas (2) to (5). ]

[In the general formulas (2) and (3), A ^{1 to} A ³ are each independently hydrogen, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted group having 20 or less carbon atoms. It is a substituent selected from a substituted alkenyl group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, and a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms. ] The organic material for a display element according to claim 1,
The organic material for display elements, wherein at least one of X ^{1 to} X ^{8 in} the general formula (1) is nitrogen. The organic material for a display element according to claim 1,
Y < ¹ > -Y < ³ > in the said General formula (1) is General formula (2) or General formula (3). The organic material for display elements characterized by the above-mentioned. The organic material for a display element according to claim 1,
An organic material for a display element, wherein at least one of R ^{1 to} R ⁸ in the general formula (1) is an electron-withdrawing substituent. In the organic material for display elements according to claim 4,
The organic material for a display element, wherein the electron-withdrawing substituent is a cyano group, a fluorine compound group, or a methoxy group. In a display element in which a light emitting unit including at least an organic light emitting layer is sandwiched between a cathode and an anode,
The light emitting unit is configured by using at least one layer containing an organic material represented by the following general formula (1).

[However, in general formula (1), R ^{1 to} R ⁶ are each independently hydrogen, halogen compound group, hydroxyl group, amino group, arylamino group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, carbon A substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted alkoxyl having 20 or less carbon atoms A substituent selected from a group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group, and adjacent R ^m (M = 1 to 6) may be bonded to each other through a ring structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom, and the binding sites of Y ^{1 to} Y ³ are each independently any of the following general formulas (2) to (5). ]

[In the general formulas (2) and (3), A ^{1 to} A ³ are each independently hydrogen, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted group having 20 or less carbon atoms. It is a substituent selected from a substituted alkenyl group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, and a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms. ] The display element according to claim 6.
A display element, wherein at least one of X ^{1 to} X ^{8 in} the general formula (1) is nitrogen. The display element according to claim 6.
Y < ¹ > -Y < ³ > in the said General formula (1) is General formula (2) or General formula (3). The display element characterized by the above-mentioned. The display element according to claim 6.
A display element, wherein at least one of R ^{1 to} R ⁸ in the general formula (1) is an electron-withdrawing substituent. The display element according to claim 9, wherein
The display element, wherein the electron-withdrawing substituent is a cyano group, a fluorine compound group, or a methoxy group. The display element according to claim 6.
In the light emitting unit, at least one of a hole transport layer and a hole injection layer using the organic material represented by the general formula (1) is disposed. The display element according to claim 11, wherein
In the light emitting unit, there is a mixed film of the organic material represented by the general formula (1) and at least one material selected from a benzidine derivative, a styrylamine derivative, a triphenylmethane derivative, and a hydrazone derivative. The display element is arranged as at least one of the hole transport layer and the hole injection layer. In a display element in which a plurality of light emitting units including at least an organic light emitting layer are stacked between a cathode and an anode, and a charge generation layer is sandwiched between the light emitting units,
The charge generation layer is configured using an organic material represented by the following general formula (1).

[However, in general formula (1), R ^{1 to} R ⁶ are each independently hydrogen, halogen compound group, hydroxyl group, amino group, arylamino group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, carbon A substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted alkoxyl having 20 or less carbon atoms A substituent selected from a group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group, and adjacent R ^m (M = 1 to 6) may be bonded to each other through a ring structure. X ^{1 to} X ⁶ are each independently a carbon or nitrogen atom, and the binding sites of Y ^{1 to} Y ³ are each independently any of the following general formulas (2) to (5). ]

[In the general formulas (2) and (3), A ^{1 to} A ³ are each independently hydrogen, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted group having 20 or less carbon atoms. It is a substituent selected from a substituted alkenyl group, a substituted or unsubstituted aryl group having 30 or less carbon atoms, and a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms. ] The display element according to claim 13, wherein
A display element, wherein at least one of X ^{1 to} X ^{8 in} the general formula (1) is nitrogen. The display element according to claim 13, wherein
Y < ¹ > -Y < ³ > in the said General formula (1) is General formula (2) or General formula (3). The display element characterized by the above-mentioned. The display element according to claim 13, wherein
A display element, wherein at least one of R ^{1 to} R ⁸ in the general formula (1) is an electron-withdrawing substituent. The display element according to claim 16, wherein
The display element, wherein the electron-withdrawing substituent is a cyano group, a fluorine compound group, or a methoxy group. The display element according to claim 13, wherein
In the light emitting unit, there is a mixed film of the organic material represented by the general formula (1) and at least one material selected from a benzidine derivative, a styrylamine derivative, a triphenylmethane derivative, and a hydrazone derivative. The display element is arranged as at least one of the hole transport layer and the hole injection layer.

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