JP7801899B2 - Organic electroluminescent device and organic electroluminescent lighting using novel 1,10-phenanthroline compound - Google Patents

Description

The present invention provides organic electroluminescent devices using a novel 1,10-phenanthroline compound that has excellent heat resistance, good compatibility with deep-red dyes, and achieves high device efficiency, low voltage, and long life. It also contributes to improving the performance of phosphorescent or thermally activated organic EL devices that use triplet excitons, and relates to organic electroluminescent lighting that uses such devices.

Due to its lightweight, flexible, and energy-efficient features, organic electroluminescence (OLED) is beginning to be used in new flat-screen TVs to replace LCD TVs (see, for example, the Sony Bravia website (https://www.sony.jp/bravia/)), next-generation displays compatible with large 4K and 8K projectors, and displays in the medical field that require high resolution (see, for example, the JOELD website (https://www.j-oled.com/application/)), and it is also expected to be used in lighting. In fact, in recent years, OLED has become increasingly popular not only in TVs but also in displays for large projectors and as a light source for lighting. However, the challenge remains in achieving both a longer lifespan and lower power consumption to further improve reliability.

The key factors are smooth surface morphology, appropriate highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels, and high charge injection and transport properties. Compared to hole-transporting (p-type) organic semiconductors used in organic electroluminescence, electron-transporting (n-type) organic semiconductors are known to have mobility three orders of magnitude lower (see, for example, Non-Patent Documents 1 and 2).

The disadvantages of different mobilities include a decrease in luminous efficiency due to the inability of holes and electrons injected from the two electrodes to combine efficiently, resulting in the accumulation of charge at the interface of the organic film in the fabricated device; abnormal heat generation from the device because, when charges recombine within the device, they are converted into thermal energy rather than converted into luminescent energy; the heat generated causes the evaporated or coated amorphous organic compound to recrystallize, forming quenched areas known as dark spots; and the heat generated itself can destroy the organic compound itself, or the accumulated charge can cause the organic compound to undergo oxidation or reduction reactions, changing into a different compound, similar to thermal destruction.
These problems are known to have a significant impact on the lifespan of the device (see, for example, Non-Patent Document 3).

To avoid this problem, organic electroluminescence devices typically employ a multilayer structure with separate functions. These functions refer to hole injection, hole transport, light emission, electron transport, and electron injection. Each function may be independent, or a single layer may perform two or more of these functions. Furthermore, a single function may be performed using a single organic compound, or a single function may be performed using two or more organic compounds, or even a hybrid with an inorganic compound (see, for example, Non-Patent Document 4). Furthermore, a tandem structure may be employed, with multiple layers of these functions stacked together (see Patent Document 1).

Currently commercially available organic electroluminescence (hereinafter referred to as OLED) devices, such as mobile devices like smartphones and OLED televisions, almost all use OLED panels that apply technology for functionally dispersed elements or tandem elements.

Organic EL panels manufactured using this technology use a shadow mask to deposit light-emitting materials in the three primary colors of light: blue, green, and red. Alternatively, white-based light is extracted from the three primary colors and then converted to full color using color filters in the three primary colors. (See, for example, Non-Patent Document 5.)

Organic EL panels are also being used in the lighting field for indirect lighting, and some, when combined with phosphorescent materials, achieve an internal quantum efficiency of 100%, making them suitable for energy-saving lighting. (See, for example, Non-Patent Document 6.)

Light sources are important not only for home and industrial use, but also in primary industries such as agriculture. In the agricultural field, lighting is used as a light source for artificial cultivation in greenhouses and airtight rooms, and highly efficient organic electroluminescent devices, which emit light in the deep red region around 670 nm, are particularly expected to be used as light sources for plant cultivation.

Currently used functionally separated elements have many positive aspects, but of course there are also areas that need improvement. Specifically, the number of times vapor deposition or coating is performed to separate the functions increases. Needless to say, increasing the number of times increases the effort required to manufacture the element or display. In this case, effort refers to the time required for production. Requiring more time means a decrease in the number of light-emitting elements produced per unit time. Fewer units produced increases the production cost per unit. Furthermore, as the number of materials used increases, material costs also increase. These effects are reflected in the selling price of the final product.

Considering the above, it is necessary to separate functions, but in order to compete with liquid crystal (LCD) panels and light-emitting diode (LED) panels, it is necessary to combine functional parts and simplify the manufacturing of the element or display.

Abhishek P. Kulkarni, Christopher J. Tonzola, Amit Babel, and Samson A Jenekhe. , Chem. Mater. 2004, 16, 4556 Lixin Xiao, Zhijian Chen, Bo Qu, Jiaxiu Luo, Sheng Kong, Qihuang Gong and Junji Kido, Adv. Mater. 2011,23,926 Tatsuo Mori, "Material Design and Lifetime Extension Technology for Organic EL Devices," Surface Technology, Vol. 61, No. 10, 2011, p. 682 Akiyoshi Mikami, "Fundamentals of Organic EL Displays," Journal of the Institute of Image Information and Television Engineers, Vol. 67, No. 9, pp. 800, 2013 Electronic Device Industry News, September 28, 2018, "No. 268: LG's 8K OLED, Challenges for Further Higher Resolution" https://www.sangyo-times.jp/article.aspx?ID=2764 ITmedia, March 6, 2014, "Will Organic EL Lighting Overtake LED Lighting? Achieves 131 Lumens/Watt," https://www.itmedia.co.jp/smartjapan/articles/1403/06/news036.html

Patent No. 4925569

The object of the present invention is to provide an element that can achieve both long life, low power consumption, and efficient manufacturing, as well as a light-emitting element, including a deep-red light-emitting element, for which it is difficult to achieve both improved luminous efficiency and long life.

The above problems are solved by the following inventions 1) to 6).
1) A compound represented by the following general formula [1]:
[In the formula, ^R1 is hydrogen or a group independently selected from the group consisting of a methyl group, an ethyl group, a normal propyl group, and an isopropyl group.]
An organic electroluminescence device containing a 1,10-phenanthroline compound represented by the formula:
2) The following general formula [2]
[In the formula, ^R2 is hydrogen or a group independently selected from the group consisting of a methyl group, an ethyl group, a normal propyl group, and an isopropyl group.]
An organic electroluminescence device containing a 1,10-phenanthroline compound represented by the formula:
3) An organic electroluminescence device using the 1,10-phenanthroline compound according to 1) in an electron transport layer and/or a light emitting layer.
4) An organic electroluminescence device using the 1,10-phenanthroline compound according to 2) in an electron transport layer and/or a light emitting layer.
5) Organic electroluminescence lighting using the organic electroluminescence element according to 3).
6) Organic electroluminescence lighting using the organic electroluminescence element according to 4).
7) A deep red organic electroluminescent lighting device using the organic electroluminescent element according to 3).
8) A deep red organic electroluminescent lighting device using the organic electroluminescent element according to 4).

According to the organic electroluminescence device of the present invention, a new phenanthroline compound is used in which a 6-quinoline compound and a 4-isoquinoline compound, which are heteroaryl ring compounds, are introduced at the 2- and 9-positions of a 1,10-phenanthroline compound. This device has a long life, low power consumption, and efficient manufacturing. Furthermore, since the device has the ability to efficiently emit light from a deep red light-emitting material, it can also be used for deep red lighting.
Density functional theory calculations show that the newly invented compounds have a deeper lowest unoccupied molecular orbital (LUMO) level than the -2.16 eV of 2,9-di-2-naphthalenyl-4,7-diphenyl-1,10-phenanthrene (hereinafter abbreviated as NBPhen), a conventional electron transport material, and therefore are expected to have improved electron injection properties.In fact, the experimentally determined electron affinity is -3.6 eV, which is close to the work function of an electrode used as a cathode, such as aluminum metal, which has a work function of -4.1 eV, indicating that electrons can be easily injected from the cathode.
Regarding the heat resistance required for organic electroluminescence materials, the 1,10-phenanthroline compound of the present invention has a glass transition temperature of 130°C or higher, so it can fully withstand the heat generated in the device and is less likely to be degraded by heat.
Furthermore, due to its excellent electrochemical stability, when combined with a green light-emitting material, it has a longer lifespan than the conventional material NBphen at ^a luminance of 1000 cd/m2. When combined with a deep red light-emitting material, it has a high internal energy trapping effect, preventing energy leakage to surrounding materials and producing red light with high color purity.
Furthermore, by using the 1,10-phenanthroline compound of the present invention, which is resistant to crystallization, conventional organic electroluminescent devices can be easily fabricated, which contributes to time and economical effects.
Therefore, the present invention is considered to be extremely useful as an invention that can be applied industrially.

An example of the device fabricated in Example 1 is shown in FIG. The energy diagrams on the elements of 4iq-Bphen, 6q-Bphen and 3q-Bphen in Example 1 are shown in FIG. FIG. 3 shows the EL spectra of light emitted from devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen in Example 1 to which NBphen was added. The current density-voltage characteristics of Example 1 are shown in FIG. The brightness-voltage characteristics of Example 1 are shown in FIG. The power efficiency-luminance characteristics of Example 1 are shown in FIG. The external quantum efficiency-luminance characteristics of Example 1 are shown in FIG. The measurement of the driving life (half life) of Example 1 is shown in FIG. An example of the device fabricated in Example 2 is shown in FIG. FIG. 10 shows EL spectra of light emitted from devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen to which NBphen was added in Example 2. The current density-voltage characteristics of Example 2 are shown in FIG. The brightness-voltage characteristics of Example 2 are shown in FIG. The power efficiency-luminance characteristics of Example 2 are shown in FIG. The external quantum efficiency-luminance characteristics of Example 2 are shown in FIG. The measurement of the driving life (half life) of Example 2 is shown in FIG. FIG. 16 shows energy diagrams on the devices fabricated in Example 3 for 4iq-Bphen, 6q-Bphen, and 3q-Bphen. FIG. 17 shows EL spectra of light emitted from devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen of Example 3, respectively. The current density-voltage characteristics of Example 3 are shown in FIG. The brightness-voltage characteristics of Example 3 are shown in FIG. The external quantum efficiency-luminance characteristics of Example 3 are shown in FIG. The measurement of the driving life (half life) of Example 3 is shown in FIG. FIG. 22 shows EL spectra of light emitted from the devices prepared in Example 4 using 4iq-Bphen, 6q-Bphen, and 4DBT46TRZ, respectively. The current density-voltage characteristics of Example 4 are shown in FIG. The luminance-voltage characteristics of Example 4 are shown in FIG. The external quantum efficiency-luminance characteristics of Example 4 are shown in FIG. The measurement of the operating life (half life) of Example 4 is shown in FIG. A cross-sectional view of a preferred example of the organic EL element of the present invention is shown in FIG.

The present invention will now be described in detail.
The novel 1,10-phenanthroline compound of the present invention can be produced by Suzuki-Miyaura coupling (hereinafter abbreviated as Suzuki coupling), as shown in the following reaction scheme.

In the case of general formula [1]

In the case of general formula [2]

In the above-mentioned production methods of the general formula [1] and the general formula [2], ^X1 represents a halogen atom, such as chlorine, bromine or iodine.
also functions as a leaving group, so compounds in which X ¹ has such a substituent added thereto can also be used in this reaction.

In the above-mentioned production methods of the general formula [1] and the general formula [2], ^X2 is a boric acid compound.
Or boric acid ester
^{R 1'} and R ^2' are alkyl groups such as a methyl group and an isopropyl group, and R ^1' and R ^2' may be bonded together to form a ring.

Solvents that can be used include aromatic hydrocarbons such as toluene, xylene, and mesitylene, cyclic ethers such as tetrahydrofuran and 1,4-dioxane, aliphatic ethers such as 1,2-dimethoxyethane and ethylene glycol monomethyl ether, and alcohols such as ethanol, isopropyl alcohol, and n-butanol. These solvents can be used alone or in combination.

The base used in the reaction can be an alkali metal carbonate or phosphate. Examples include sodium carbonate, potassium carbonate, cesium carbonate, tripotassium phosphate, dipotassium phosphate, trisodium phosphate, and dibasic sodium phosphate. These are usually used alone, but two or more bases can also be used in combination without any problems.

A palladium-based catalyst is used. Because the reaction does not proceed smoothly with palladium alone, it is preferable to use a phosphorus-based co-catalyst in combination. An example of a catalyst that can be used alone is tetrakis(triphenylphosphine)palladium, which is a complex compound of palladium and triphenylphosphine.
Examples of palladium catalysts that can be used in combination with a phosphorus catalyst include palladium acetate, palladium chloride, trisbenzylideneacetonedipalladium, and bisbenzylideneacetonepalladium.
Examples of the phosphorus catalyst to be used in combination include triphenylphosphine, triorthotolylphosphine, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (X-phos), 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-phos), 2-dicyclohexylphosphino-2'-dimethylaminobiphenyl (Davephos), 2-dicyclohexylphosphino-2',6'-diisopropoxybiphenyl (Ruphos), and tricyclohexylphosphine.

Water is not absolutely necessary, and the reaction may be carried out anhydrous. If water is added, it should be added in an amount of about 1/2 to 1/3 of the amount of organic solvent used.

The reaction temperature is usually the reflux temperature of the solvent.

The reaction time is determined by monitoring the progress of the reaction using instruments such as gas chromatography, high-performance liquid chromatography, or thin-layer chromatography.

The raw material, 2,9-dichloro-4,7-diphenyl-1,10-phenanthroline, is available as an industrial product.

The other raw materials, 4-isoquinolineboronic acids and 6-quinolineboronic acids, are also available as industrial products.

If they are not available, the corresponding halides can be converted into Grignard or lithium reagents, then reacted with trimethylborane or triisopropylborane, and hydrolyzed with acidic water such as hydrochloric acid to obtain boronic acids.

If you want to obtain a boronic acid ester, you can treat the reaction in [0031] with water to obtain the corresponding methyl ester or isopropyl ester. Alternatively, you can dehydrate and condense the boronic acid obtained in [0031] with pinacol in toluene to obtain a cyclic pinacol ester. Cyclic boronic acids can also be obtained by reacting 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane with the Grignard reagent or lithium reagent synthesized in [0031], or by heating the corresponding halide and bispinacolatodiborane in a suitable solvent such as dimethylformamide in the presence of potassium acetate and a catalyst such as [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride.

The 1,10-phenanthroline compound obtained in the reaction has purity issues and must be purified before being used in devices. Recrystallization is an effective method for purification, but in some cases it can also be separated using silica gel column chromatography.

It is desirable to further purify the purified 1,10-phenanthroline compound by sublimation before proceeding to film formation. This is to minimize the generation of residues in the crucibles in which the product is placed during film formation. Chemically purified compounds may contain trace amounts of substances that are easily decomposed by heating, so the purpose is to physically remove them.
When sublimating, it is common to create a heating temperature gradient to achieve a purification effect. Also, since sublimation does not occur at atmospheric pressure, it is necessary to reduce the pressure using a vacuum pump. The status of sublimation purification is usually judged visually, as the time required varies depending on the material to be sublimated.

The 1,10-phenanthroline compound to be evaluated is formed into a film using a vacuum deposition machine, and an element for evaluation is prepared.
For the evaluation element, a square shape of about 2 mm on a side is prepared using a metal mask on a substrate such as quartz glass with a pre-treated electrode attached. One or more elements are prepared on the quartz glass. It is usually desirable to prepare multiple elements.

Pre-processing is generally carried out as follows: Pre-processing must be carried out thoroughly and carefully, as the degree of processing will affect accurate evaluation.
The substrate with the anode electrode is cut into pieces using a diamond cutter or similar to fit the size of the evaluation cell. The substrate will have fine debris remaining on it when the metal electrode was attached, so this is cleaned and removed. In particular, the metal often has a rough surface because it is attached to the substrate using methods such as sputtering. If used as an element in this state, the element may short-circuit or the evaporated film may not be evenly layered, resulting in non-emitting areas. This has a major impact on the evaluation of the element's lifespan.
Therefore, first, to smooth the surface of the metal electrode and degrease the entire substrate, the surface of the cut substrate is lightly polished with a non-woven wiper (for example, Bemcot (Bemcot is a registered trademark of Asahi Kasei Corporation (Registration No. 1153841 and six other trademarks))) soaked in acetone (for electronic materials). Next, the substrate is immersed in an ultrasonic cleaner filled with an aqueous solution of detergent (for example, Semico Clean (Semico Clean is a registered trademark of Furuuchi Chemical Co., Ltd. (Registration No. 6017459)) diluted with water, and ultrasonic cleaning is performed for about 10 minutes. This allows polishing residue and the like to be removed from the substrate.
In order to remove the detergent adhering to the substrate, the substrate is immersed in an ultrasonic cleaner filled with distilled water and subjected to ultrasonic cleaning for about 10 minutes.
Furthermore, since any moisture remaining on the substrate will affect film formation and its lifespan, the substrate is ultrasonically cleaned by immersing it in an ultrasonic cleaner filled with acetone (for the electronics industry) and then isopropyl alcohol (for the electronics industry) for approximately 10 minutes each.Finally, the substrate is immersed in a boiling solution of isopropyl alcohol (for the electronics industry) for 5 minutes, after which it is cleaned with ultraviolet light and ozone and dried under reduced pressure in a desiccator.
This series of operations is carried out in a fume hood due to the flammability of acetone and isopropyl alcohol.

The components of the organic EL element of the present invention will be explained below using as an example an element configuration consisting of an anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and cathode. The organic EL element of the present invention is preferably supported on a substrate. There are no particular restrictions on the material of the substrate, and examples include glass, quartz glass, transparent plastic, and the like commonly used in conventional organic EL elements.

The anode of the organic EL device of the present invention is preferably made of an electrode material that is a metal element having a large work function (4 eV or more), an alloy of metals having a large work function (4 eV or more), a conductive substance, or a mixture of these. Specific examples include metals such as gold, silver, and copper, conductive transparent materials such as ITO (indium tin oxide), tin oxide (SnO ₂ ), and zinc oxide (ZnO), and conductive polymer materials such as polypyrrole and polythiophene.
The anode can be formed using these electrode materials by methods such as vapor deposition, sputtering, and coating. The sheet electrical resistance of the anode is preferably several hundred Ω/ ^cm2 or less. The thickness of the anode varies depending on the material, but is generally about 5 to 1,000 nm, and preferably 10 to 500 nm.

The cathode is preferably made of an elemental metal with a low work function (4 eV or less), an alloy of metals with a low work function (4 eV or less), a conductive substance, or a mixture thereof, such as lithium, a lithium-indium alloy, sodium, a sodium-potassium alloy, magnesium, a magnesium-silver alloy, a magnesium-indium alloy, aluminum, an aluminum-lithium alloy, or an aluminum-magnesium alloy.
The cathode can be produced by using these electrode materials by a method such as vapor deposition or sputtering.
The sheet electrical resistance of the cathode is preferably several hundred Ω/ ^cm2 or less. The thickness of the cathode varies depending on the material, but is generally about 5 to 1,000 nm, preferably 10 to 500 nm. In order to efficiently extract light emitted from the organic EL element of the present invention, it is preferable that at least one of the anode and cathode electrodes is transparent or semi-transparent.

The cleaned electrode substrate is placed in a vapor deposition machine or spin coater to create the anode hole injection layer while minimizing exposure to air. Low molecular weight compounds that can be vapor deposited are prepared using a vacuum deposition machine, while compounds with large molecular weights that are not suitable for vapor deposition are prepared by dissolving them in an appropriate solvent and applying the coating.

A hole injection layer is laminated on the anode electrode.
A hole injection layer is a layer inserted to improve the injection of holes injected from the anode into the organic thin film. The metals used in the anode have a large work function, generally around -5 eV. Therefore, a hole injection layer is not necessary if the organic compound has a highest occupied molecular orbital (HOMO) close to this work function. However, there are few compounds that meet such conditions, and there is a slight difference between the work function of the anode and the highest occupied molecular orbital (HOMO) of the organic thin film, which acts as a barrier. This prevents holes generated at the anode from efficiently moving to the organic thin film. Therefore, this layer is provided to solve this problem.
Usually, the film is laminated to a thickness of 10 to 200 nm.

An example of a compound that can be used in the hole injection layer and that can be vapor deposited is copper phthalocyanine (CuPc) represented by the following formula.

Furthermore, DNTPD disclosed in Japanese Patent Application Laid-Open No. 9-301934 filed by the present applicant is also an example of a compound that can be vapor deposited as a hole injection layer.

An example of a hole injection layer that can be applied is PDOT-PSS (polymer mixture) which is a water-soluble polymer and is represented by the following chemical formula:

Similarly, PTPD-1 and PPBI shown in the following chemical formula can be used.

Similarly, PES-1 and PES-2 disclosed in Japanese Patent Application Laid-Open No. 9-188756 of the present applicant can also be used as a hole injection layer by adding an antimony complex called TBPAH, as exemplified below.

A hole transport layer is laminated on the hole injection layer.
The hole transport layer is made of a hole transport compound and has the function of transporting holes injected from the anode to the light-emitting layer. When the hole transport compound is disposed between two electrodes to which an electric field is applied and holes are injected from the anode, the hole transport compound preferably has a hole mobility of at least ^{10-6 cm2} /V-sec. Such a hole transport compound can be selected from materials conventionally used as charge injection materials for holes in photoconductive materials and known materials used in hole transport layers of organic EL devices.

An example of the hole transport material is N,N'-di(1-naphthyl)-N,N'-diphenyl-4,4-diaminophenyl (α-NPD).

Examples include BABP disclosed in JP-A-2004-115441, DTASi disclosed in JP-A-2005-220088, DNDPN disclosed in JP-A-2008-201676, and CzTDA and DBTDTA disclosed in JP-A-2010-254635, all of which are owned by the present applicant.

Other examples include 4DBFHPB and 4DBTHPB, as described in JP 2019-26556 A.

These compounds can be used alone or in layers, or multiple compounds can be co-deposited and mixed together.

The light-emitting layer of the organic EL device of the present invention can be made from any light-emitting material commonly used by those skilled in the art. Recently, phosphorescent materials and thermally activated delayed fluorescent materials with high quantum efficiency have been used as light-emitting materials. The novel 1,10-phenanthroline compound of the present invention has an energy level that allows them to emit light appropriately.

The light-emitting layer is formed from a host material and a light-emitting material (dopant) [Appl. Phys. Lett., 65 3610 (1989)]. The light-emitting material is used in combination with the host material to avoid concentration quenching and to efficiently transfer the emission energy to the light-emitting material. In general, the amount of the light-emitting material relative to the host material is preferably 0.01 to 40% by weight, more preferably 0.1 to 20% by weight.

Examples of blue phosphorescent materials include FIrpic, FIr6, FIrN4, and Ir(Fppy)3, as exemplified in JP-A-2010-251565.

Examples of green phosphorescent materials include Ir(ppy) ₂ acac described in Journal of the American Chemical Society (2001), 123(18), 4304-4312, and Ir(ppy) ₃ described in Pure and Applied Chemistry 71(11) 2095-2106 (1999).

As the red phosphorescent material, there is a compound of the following formula described in JP-A-2009-132688:
and phosphorescent materials represented by the following formula described in JP-A-2009-149607:

and phosphorescent materials represented by the following formula described in JP-A-2009-164614:

or a phosphorescent material represented by the following formula described in JP-A-2013-155153:

(Bu means a butyl group).

The deep red emitting material is (DPQ) ₂ Ir(dpm) represented by the following formula, which is described in Chemistry-a European Journal 25(30)7308-7314 published in 2019.

For this compound, which has a very deep lowest unoccupied molecular orbital (LUMO) (−3.8 eV), the host material is also required to have a similarly deep lowest unoccupied molecular orbital (LUMO).
Furthermore, the phenomenon of thermally activated delayed fluorescence has been confirmed since the 1930s to occur in eosin Y and other compounds. In 2010, a group led by Professor Adachi of Kyushu University began to seriously attempt to utilize this technology in this field.

Examples of blue thermally activated delayed fluorescent materials include ν-DABNA described in Nature Photonics 13, 678-692, (2019);

DABNA-1 and DABNA-2 described in Adv. Mater 2016, 28(14), 2777-2781;

2CzPN described in Nature 492, 234-238, (2012)
Examples include:

The green thermally activated delayed fluorescent substance is 4CzIPN, which is also described in Nature 492, 234-238, (2012).

PXZ-TRZ described in Chemical Communications (Cambridge, United Kingdom) (2012), 48, (93), 11392-11394.
Examples include:

As for the red thermally activated delayed fluorescent substance, HAP-3TPA described in U.S. Patent Application Publication No. 2019/0074449 is used.

Mater. Horiz., 2016, 3, 145-151
Examples include:

Furthermore, the novel 1,10-phenanthroline compound of the present invention can also be used in a new organic EL light-emitting technology called hyperfluorescence, which has been proposed by Professor Adachi of Kyushu University.
Hyperfluorescence technology is attracting attention both domestically and internationally as a technology that can achieve high efficiency and long life for organic EL devices by utilizing the advantages of fluorescent materials that use singlet excitons and thermally activated delayed fluorescent materials that use triplet excitons.

Currently, organic EL elements generally use phosphorescent materials for red and green, and fluorescent materials for blue. As for phosphorescent materials, there are no suitable blue materials, and although phosphorescent materials have better luminous efficiency than fluorescent materials, they face difficulties in terms of color purity and cost due to the use of rare metals such as iridium.
Therefore, thermally activated delayed fluorescent materials, which do not contain rare metals and can use triplet excitons like phosphorescent materials, can fully compensate for the disadvantages of phosphorescent materials, particularly in terms of cost.

For example, the following compound (HDT-1) is a blue delayed-activation fluorescent material described in Nature Photonics by Adachi et al. (doi.org/10.1038/s41566-020-00745-z) relating to hyperfluorescence devices.
The triplet exciton energy gap of the novel 1,10-phenanthroline compound of the present invention is 2.88 eV, but the triplet exciton energy gap of the novel 1,10-phenanthroline compound of the present invention is as large as 3.0 to 3.1 eV, and therefore has a sufficient charge trapping effect. In addition, the energy gap of the v-DABNA described in [Chemical Formula 31] that is used together with the compound is also 2.1 eV, and this compound can also trap charges.
Generally, red and green light-emitting materials do not have as large an energy gap as blue light-emitting materials, so that it is possible to sufficiently confine charges in light-emitting materials of either color.

The host material used together with these light-emitting materials is the following compound described in Japanese Patent No. 5683784:
Examples include:

In addition, the following compound described in Japanese Patent No. 5325402 of the present applicant:
Examples include:

The following compound described in JP-A-2010-13421 of the present applicant:
can also be exemplified.

The following compound described in Japanese Patent No. 5674266 of the present applicant:

Furthermore, the following compound described in Japanese Patent No. 5727237 of the present applicant:
Examples include:

A hole-blocking layer can also be inserted between the light-emitting layer and the electron-transporting layer. A hole-blocking layer is a layer that, as the name suggests, prevents holes that are unable to recombine with electrons during light emission from leaking into the electron-transporting layer. Hole leakage often occurs when the mobility of holes and electrons is affected, resulting in an imbalance of charge. If leaked holes recombine in the electron-transporting layer or at the interface between the light-emitting layer and the electron-transporting layer, light will be emitted from the recombination site, resulting in light of a different wavelength from the light obtained from the light-emitting layer.

A characteristic of materials used as hole-blocking materials is that they have a large highest occupied molecular orbital (HOMO) value. Because holes are injected from the anode, if a material with a HOMO value close to the work function of the anode electrode is used, holes can move easily, resulting in hole punch-through.

As described above, any material having a high HOMO value can be used as the hole-blocking material. Examples include DBF-TRZ described in the applicant's Japanese Patent No. 6580613,
DBT-TRZ
Examples include:

The highest occupied molecular orbital (HOMO) value of DBF-TRZ is -6.4 eV, while the highest occupied molecular orbital (HOMO) value of DBT-TRZ is -6.3 eV, which is much larger than the anode work function of -5.1 eV.

An electron transport layer is laminated next to the hole blocking layer. The electron transport material used here is an electron transport material represented by general formula [1] or general formula [2].

In the electron transport material represented by general formula [1], the two 4-isoquinoline compounds bonded to the 1,10-phenanthroline compound may be the same or different, but are preferably the same. Specific examples of the 4-isoquinoline compounds include the following:

In the electron transport material represented by general formula [2], the two 6-quinoline compounds bonded to the 1,10-phenanthroline compound may be the same or different, but are preferably the same. Specific examples of the 6-quinoline compounds include the following:

These compounds can be formed into thin films by themselves to form electron transport layers, but two or more compounds can also be mixed together to form a single layer by co-evaporation, or two or more electron transport layers can be formed by a single compound.

These compounds are also compounds described in Japanese Patent No. 5650114, such as the following compounds:
or,

The following compound described in J. Org. Chem., 1996, 61(9), 3017-3022:
It can also be used in combination with other compounds.

When used in a mixture with the above compounds, the total amount of general formula [1] and general formula [2] can be any ratio of 30% by weight or more, preferably 40% by weight or more, and more preferably 50% by weight or more of the mixture.

The method for forming the hole injection layer and hole transport layer of a device containing the novel 1,10-phenanthroline compound of the present invention is not particularly limited. For example, a dry film-forming method (e.g., vacuum deposition, ionization deposition, etc.) or a wet film-forming method [solvent coating method (e.g., spin coating, casting, inkjet method, etc.)] can be used. The electron transport layer is formed by a dry film-forming method (e.g., vacuum deposition, ionization deposition, etc.) because a wet film-forming method may cause dissolution of the underlying layer. The above film-forming methods may be used in combination to fabricate the device.
When forming each layer such as a hole transport layer, a light-emitting layer, and an electron transport layer by vacuum deposition, the vacuum deposition conditions are not particularly limited. Typically, deposition is preferably performed under a vacuum of about 10 ⁻⁵ Torr or less, with a boat temperature (evaporation source temperature) of about 50 to 500°C and a substrate temperature of about −50 to 300°C, at a rate of about 0.01 to 50 nm/sec. When forming each layer of a hole transport layer, a light-emitting layer, and an electron transport layer using multiple compounds, it is preferable to perform co-deposition while controlling the temperature of each boat containing the compounds.

When forming the hole injection layer and hole transport layer using a solvent coating method, the components that make up each layer are dissolved or dispersed in a solvent to form a coating solution. Examples of solvents include hydrocarbon solvents (e.g., heptane, toluene, xylene, cyclohexane, etc.), ketone solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), halogen-based solvents (e.g., dichloromethane, chloroform, chlorobenzene, dichlorobenzene, etc.), ester solvents (e.g., ethyl acetate, butyl acetate, etc.), alcohol solvents (e.g., methanol, ethanol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ether solvents (e.g., dibutyl ether, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc.), aprotic solvents (e.g., N,N'-dimethylacetamide, dimethyl sulfoxide, etc.), and water. A single solvent may be used, or multiple solvents may be used in combination.

The thickness of each layer, such as the hole transport layer, the light emitting layer, and the electron transport layer, is not particularly limited, but is usually set to 5 to 5,000 nm.
The organic EL element of the present invention can be protected by providing a protective layer (sealing layer) or encapsulating the element in an inert substance to block contact with oxygen, moisture, etc. Examples of inert substances include paraffin, silicone oil, and fluorocarbon. Materials used for the protective layer include fluororesins, epoxy resins, silicone resins, polyesters, polycarbonates, and photocurable resins.

The organic EL element of the present invention can be used as a DC-driven element. When a DC voltage is applied, light emission is observed when a voltage of about 1.5 to 20 V is typically applied with the anode as the positive polarity and the cathode as the negative polarity. The organic EL element of the present invention can also be used as an AC-driven element. When an AC voltage is applied, light emission occurs when the anode is positive and the cathode is negative. The organic EL element of the present invention can be used in full-color displays for televisions, mobile phones, game consoles, etc.; area color displays such as in-vehicle warning lights and safety devices; white backlights for copiers, printers, and liquid crystal displays; and various types of lighting, such as indoor or outdoor indirect lighting and desk lighting.

FIG. 27 shows a cross-sectional view of a preferred example of the organic EL element of the present invention.
Figure 27 shows an example in which an anode 2, a hole injection layer 7, a hole transport layer 5, an emissive layer 3, a hole blocking layer 9, an electron transport layer 6, an electron injection layer 8, and a cathode 4 are sequentially formed on a substrate 1. In this case, the hole injection layer 7 is provided to increase the adhesion between the anode 2 and the hole transport layer 5, improving hole injection from the anode and contributing to a reduction in the voltage required for the light-emitting device. This example also includes a hole blocking layer 9. This separates the functions of charge transport and light emission, increasing the freedom in material selection, thereby improving the efficiency of light emission and the freedom in the color of emitted light. The hole blocking layer 9 can be inserted between the emissive layer 3 and the electron transport layer 6.

Synthesis Example

The present invention will be explained in more detail below with reference to the following synthesis examples and working examples, but the present invention is not limited thereto in any way.

Synthesis Example 1: Synthesis of Compound No. (I)
A 300 ml four-necked round-bottom flask equipped with a nitrogen inlet tube, reflux condenser, thermometer, and mechanical stirrer is charged with 4.7 g (17.8 mmol x 2.5 equivalents) of sodium carbonate and 55 ml of water and stirred. Next, 110 ml of tetrahydrofuran, 10.0 g (17.8 mmol x 2.2 equivalents) of 4-isoquinolineboronic acid ester, and 7.1 g (17.8 mmol) of 2,9-dichloro-4,7-diphenylphenanthroline are added and nitrogen substitution is carried out for 15 minutes. Then, 0.1 g (17.8 mmol x 0.5%) of tetrakistriphenylphosphine is added and the mixture is stirred in a water bath at 65-67°C for 12 hours. As the reaction progresses, the target product precipitates as crystals.
After a predetermined time had passed, the mixture was cooled to room temperature, and the precipitated crystals were collected by suction filtration.
The obtained crystals were recrystallized by adding 200 ml of orthodichlorobenzene and 1 g of activated clay. Through this operation, 8.6 g of the target compound (I) was recovered. The yield was 82.4%.
Of this, 8 g was purified by sublimation. The sublimation conditions were heating at high temperature 310 °C, medium temperature 290 °C, and low temperature 230 °C under vacuum for 4.5 hours. After cooling to room temperature, 5.8 g of the target product was recovered. The recovery rate from this operation was 72.5%. The obtained crystals were used for device fabrication.
The compound after sublimation purification was identified by elemental analysis, the results of which are shown in Table 1. The purity confirmed by high performance liquid chromatography was 99.78%.

Synthesis Example 2: Synthesis of Compound No. (II)-2
A 300 ml four-neck round-bottom flask equipped with a nitrogen inlet tube, reflux condenser, thermometer, and mechanical stirrer was charged with 4.7 g (17.8 mmol x 2.5 equivalents) of sodium carbonate and 55 ml of water and stirred. Subsequently, 110 ml of tetrahydrofuran, 10.5 g (17.8 mmol x 2.2 equivalents) of 6-methyl-4-isoquinolineboronic acid ester (prepared from 6-methyl-4-bromoisoquinoline), and 7.1 g (17.8 mmol) of 2,9-dichloro-4,7-diphenylphenanthroline were added and the mixture was purged with nitrogen for 15 minutes. Then, 0.1 g (17.8 mmol x 0.5%) of tetrakistriphenylphosphine was added and the mixture was stirred in a water bath at 65-67°C for 12 hours. As the reaction progressed, the target product precipitated as crystals.
After a predetermined time had passed, the mixture was cooled to room temperature, and the precipitated crystals were collected by suction filtration.
The obtained crystals were recrystallized by adding 200 ml of orthodichlorobenzene and 1 g of activated clay. Through this operation, 8.8 g of the target compound (II)-2 was recovered. The yield was 80.4%.
Of this, 8 g was purified by sublimation. The sublimation conditions were heating at high temperature 310°C, medium temperature 290°C, and low temperature 230°C under vacuum for 4.5 hours. After cooling to room temperature, 5.4 g of the target product was recovered. The recovery rate from this operation was 67.5%.

Synthesis Example 3: Synthesis of Compound No. (II)-5
The target product was obtained in the same manner as in Synthesis Example 2, except that 10.5 g of 1-methyl-4-isoquinolineboronic acid ester (prepared from 1-methyl-4-bromoisoquinoline) was used.

Synthesis Example 4: Synthesis of Compound No. (III)-5
The target product was obtained in the same manner as in Synthesis Example 2, except that 11.1 g of 1-ethyl-4-isoquinolineboronic acid ester (prepared from 1-ethyl-4-bromoisoquinoline) was used.

Synthesis Example 5: Synthesis of Compound No. (IV)-5
The target product was obtained in the same manner as in Synthesis Example 2, except that 11.6 g of 1-normal propyl-4-isoquinolineboronic acid ester (prepared from 1-normal propyl-4-bromoisoquinoline) was used.

Synthesis Example 6: Synthesis of Compound No. (VI)
In a 300 ml four-necked round-bottom flask equipped with a nitrogen inlet tube, reflux condenser, thermometer, and mechanical stirrer, 4.7 g (17.8 mmol x 2.5 equivalents) of sodium carbonate and 55 ml of water were added and stirred. Next, 110 ml of tetrahydrofuran, 10.0 g (17.8 mmol x 2.2 equivalents) of 4-isoquinolineboronic acid ester, and 7.1 g (17.8 mmol) of 2,9-dichloro-4,7-diphenylphenanthroline were added and nitrogen substitution was carried out for 15 minutes. Then, 0.1 g (17.8 mmol x 0.5%) of tetrakistriphenylphosphine was added and the mixture was stirred in a water bath at 65-67°C for 18 hours. As the reaction progressed, the target product precipitated as crystals.
After a predetermined time had passed, the mixture was cooled to room temperature, and the precipitated crystals were collected by suction filtration.
The obtained crystals were recrystallized by adding 200 ml of orthodichlorobenzene and 1 g of activated clay. This procedure resulted in the recovery of 8.4 g of the target compound (VI). The yield was 80.4%.
Of this, 7.3 g was purified by sublimation. The sublimation conditions were heating at high temperature 330°C, medium temperature 310°C, and low temperature 250°C under vacuum for 3 hours. After cooling to room temperature, 6.2 g of the target product was recovered. The recovery rate from this operation was 84.9%. The obtained crystals were used for device fabrication.
The compound after sublimation purification was identified by elemental analysis, the results of which are shown in Table 2. The purity confirmed by high performance liquid chromatography was 99.63%.

Synthesis Example 7: Synthesis of Compound No. (VII)-2
A 300 ml four-neck round-bottom flask equipped with a nitrogen inlet tube, reflux condenser, thermometer, and mechanical stirrer was charged with 4.7 g (17.8 mmol x 2.5 equivalents) of sodium carbonate and 55 ml of water and stirred. Subsequently, 110 ml of tetrahydrofuran, 10.5 g (17.8 mmol x 2.2 equivalents) of 8-methyl-6-quinolineboronic acid ester (prepared from 8-methyl-6-bromoquinoline), and 7.1 g (17.8 mmol) of 2,9-dichloro-4,7-diphenylphenanthroline were added and the mixture was purged with nitrogen for 15 minutes. Then, 0.1 g (17.8 mmol x 0.5%) of tetrakistriphenylphosphine was added and the mixture was stirred in a water bath at 65-67°C for 18 hours. As the reaction progressed, the target product precipitated as crystals.
After a predetermined time had passed, the mixture was cooled to room temperature, and the precipitated crystals were collected by suction filtration.
The obtained crystals were recrystallized by adding 200 ml of orthodichlorobenzene and 1 g of activated clay. Through this operation, 8.3 g of the target compound (VII)-2 was recovered. The yield was 75.9%.
Of this, 7.5 g was purified by sublimation. The sublimation conditions were heating at high temperature 330°C, medium temperature 310°C, and low temperature 250°C under vacuum for 3 hours. After cooling to room temperature, 6.7 g of the target product was recovered. The recovery rate from this operation was 89.3%.

Synthesis Example 8: Synthesis of Compound No. (VII)-6
The target product was obtained in the same manner as in Synthesis Example 7, except that 10.5 g of 2-methyl-6-quinolineboronic acid ester (prepared from 2-methyl-6-bromoquinoline) was used.

Synthesis Example 9: Synthesis of Compound No. (VIII)-6
The target product was obtained in the same manner as in Synthesis Example 7, except that 11.1 g of 2-ethyl-6-quinolineboronic acid ester (prepared from 2-ethyl-6-bromoquinoline) was used.

Synthesis Example 10: Synthesis of Compound No. (IX)-6
The target product was obtained in the same manner as in Synthesis Example 7, except that 11.6 g of 2-n-propyl-6-quinolineboronic acid ester (prepared from 2-n-propyl-6-bromoquinoline) was used.

Comparative Example: Synthesis of 2,9-di(quinolin-3-yl)-4,7-diphenyl-1,10-phenanthroline
A 300ml four-necked round-bottom flask equipped with a nitrogen inlet tube, reflux condenser, thermometer, and mechanical stirrer is charged with 4.7g (17.8mmol x 2.5 equivalents) of sodium carbonate and 55ml of water and stirred. Next, 110ml of tetrahydrofuran, 10.0g (17.8mmol x 2.2 equivalents) of 3-quinolineboronic acid ester, and 7.1g (17.8mmol) of 2,9-dichloro-4,7-diphenylphenanthroline are added and nitrogen substitution is carried out for 15 minutes. Then, 0.1g (17.8mmol x 0.5%) of tetrakistriphenylphosphine is added and the mixture is stirred in a water bath at 65-67°C for 18 hours. As the reaction progresses, the target product precipitates as crystals.
After a predetermined time had passed, the mixture was cooled to room temperature, and the precipitated crystals were collected by suction filtration.
The obtained crystals were recrystallized by adding 200 ml of orthodichlorobenzene and 1 g of activated clay. 9.0 g of the target compound was recovered by this operation. The yield was 86.2%.
Of this, 5.5 g was purified by sublimation. The sublimation conditions were heating at high temperature 350°C, medium temperature 330°C, and low temperature 270°C under vacuum for 2 hours. After cooling to room temperature, 4.24 g of the target product was recovered. The recovery rate from this operation was 77.1%.
The compound after sublimation purification was identified by elemental analysis, the results of which are shown in Table 3. The purity confirmed by high performance liquid chromatography was 99.88%.

Example 1
A device was fabricated using the compound of Compound No. (I) in Synthesis Example 1 (hereinafter referred to as 4iq-Bphen), the compound of Compound No. (VI) in Synthesis Example 6 (hereinafter referred to as 6q-Bphen), and 2,9-di(quinolin-3-yl)-4,7-diphenyl-1,10-phenanthroline (hereinafter referred to as 3q-Bphen) of a comparative example, and NBphen described in [Chemical Formula 54] of [0098].
An example of the fabricated device is shown in Figure 1.
The energy diagrams for 4iq-Bphen, 6q-Bphen, and 3q-Bphen on the respective elements are shown in Figure 2.
EL spectra showing the light emitted from devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen with NBphen added are shown in FIG.
The current density-voltage characteristics are shown in Figure 4.
The brightness-voltage characteristics are shown in Figure 5.
The power efficiency-luminance characteristics are shown in Figure 6.
The external quantum efficiency vs. luminance characteristics are shown in Figure 7.
The operating life (half life) measurement is shown in FIG.
The results of the drive life measurement (calculated at a constant initial luminance of 1000 cd/m) are shown in Table 4 (with 20 wt% Liq addition) and Table 5 (without Liq addition). Liq (8-hydroxyquinolinolato-lithium), shown in Figure 1, can be added to materials used in the electron transport layer of organic EL elements to extend their lifespan, and is therefore widely used to improve the durability of organic EL elements. Tables 4 and 5 show that 4iq-Bphen and 6q-Bphen had long lifespans in organic EL elements without the addition of Liq, so Figures 2 to 8 all show the measurement results for organic EL elements without the addition of Liq.

As a result of evaluating each characteristic, the comparative compounds 3q-Bphen and NBphen have higher charge injection properties than the 4iq-Bphen and 6q-Bphen of the present invention, as shown in Figures 4 and 5. However, Figures 6 and 7 show that as the brightness increases, the power efficiency and external quantum efficiency decrease significantly. This is thought to be because charge retention occurs in devices using 3q-Bphen and NBphen, reducing charge recombination within the device.
On the other hand, the 4iq-Bphen and 6q-Bphen of the present invention show small changes in power efficiency and external quantum efficiency, regardless of the brightness. This is thought to be because charge retention is unlikely to occur in devices fabricated using these compounds, and the balance between charge injection, movement, and recombination is nearly stable.
Furthermore, in organic EL devices, the addition of Liq is thought to suppress recrystallization of the electron transport layer and enable a longer lifetime, but contrary to expectations, 4iq-Bphen and 6q-Bphen showed an operating lifetime of over 10,000 hours in organic EL devices without the addition of Liq. These results demonstrate that 4iq-Bphen and 6q-Bphen are resistant to recrystallization even without the addition of lithium complexes such as Liq, and can achieve an operating lifetime sufficient for practical use, thereby enabling the simplification of organic EL devices.

Example 2
Devices were fabricated using 4iq-Bphen, 6q-Bphen, and 3q-Bphen as a comparative example. The light-emitting layer used was Ir(pq) ₂ acac, which emits orange light at around 600 nm and is shown in Chemical Formula 67.
In addition, for the hole injection layer, PTPD-1:PPBI described in [Chemical Formula 11] and [Chemical Formula 12] was used to form a film in order to improve the hole injection property and the film quality at the ITO interface, and α-NPD described in [Chemical Formula 16] was used to form a film in the hole transport layer. A lithium complex (Liq) was used to improve the electron injection property, and Al was used for the cathode.

The fabricated device structure is as follows.
ITO (100 nm) (anode) / PTPD-1: PPBI (20 nm) (hole injection layer) / α-NPD (20 nm) (hole transport layer) / α-NPD: 4iq-Bphen or 6q-Bphen or 3q-Bphen (1:1), 3 wt. % Ir(pq) ₂ acac (40 nm) (emitting layer)/NBPhen (50 nm) (electron transport layer)/NBPhen: 20 wt. %Liq (20 nm) (electron transport layer)/Liq (1 nm) (electron injection layer)/Al (80 nm) (cathode)
An example of the fabricated element is shown in Figure 9.
EL spectra showing the light emitted from the devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen with NBphen added are shown in FIG.
The current density-voltage characteristics are shown in Figure 11.
The brightness-voltage characteristics are shown in Figure 12.
The power efficiency vs. brightness characteristics are shown in Figure 13.
The external quantum efficiency vs. luminance characteristics are shown in Figure 14.
The operating life (half life) measurement is shown in FIG.
Table 6 shows a summary of the device measurement results.

In the table, V _on indicates the voltage at 1 cdm- ² . V ₁₀₀₀ indicates the voltage at 1000 cdm- ² . EQE ₁₀₀₀ indicates the external quantum efficiency at 1000 cdm- ² . PE ₁₀₀₀ indicates the power efficiency at 1000 cdm- ² . LT ₅₀ indicates the 50% luminance decay time at a constant current density (25 mAm ^-2 ). LT ₅₀ (@1000 cdm- ² ) indicates the 50% luminance decay time at 1000 cdm- ² .

Example 3
Devices were fabricated using 4iq-Bphen, 6q-Bphen, and 3q-Bphen for comparison. The light-emitting layer used was (DPQ) ₂ Ir(dpm), which emits deep red light at around 670 nm and is shown in Chemical Formula 30.
As in Example 2, PTPD-1:PPBI described in [Chemical Formula 11] and [Chemical Formula 12] was formed in the hole injection layer to improve the hole injection property and the film quality at the ITO interface, and α-NPD described in [Chemical Formula 16] was formed in the hole transport layer. A lithium complex (Liq) was used to improve the electron injection property, and Al was used for the cathode.

The fabricated device structure is as follows.
ITO (130 nm) (anode) / PTPD-1:PPBI (20 nm) (hole injection layer) / α-NPD (20 nm) (hole transport layer) / α-NPD:4iq-Bphen or 6q-Bphen or 3q-Bphen (1:1), 1 wt. % (DPQ) _2Ir (dpm) (40 nm) (light-emitting layer) / 4iq-Bphen or 6q-Bphen or 3q-Bphen (50 nm) (electron transport layer) / 4iq-Bphen or 6q-Bphen or 3q-Bphen, 20 wt. % Liq (20 nm) (electron transport layer with improved electron injection) / Liq (1 nm) (electron injection layer) / Al (80 nm) (cathode)
The energy diagrams for the fabricated elements 4iq-Bphen, 6q-Bphen, and 3q-Bphen are shown in FIG.
EL spectra showing the light emitted from the devices using 4iq-Bphen, 6q-Bphen, and 3q-Bphen are shown in FIG.
The current density-voltage characteristics are shown in Figure 18.
The brightness-voltage characteristics are shown in FIG.
The external quantum efficiency vs. luminance characteristics are shown in Figure 20.
The operating life (half life) measurement is shown in FIG.
Table 7 shows a summary of the device measurement results.

As can be seen from the results in Table 7, the lifetimes of the devices using 4iq-Bphen and 6q-Bphen of the present application in the device configuration prepared in Example 3 were 67 and 87 times longer, respectively, than those of devices using 3q-Bphen, demonstrating that 4iq-Bphen and 6q-Bphen of the present application are materials that produce deep red light emission with extremely high efficiency.

Example 4
Devices using 4iq-Bphen and 6q-Bphen were fabricated.
In this case, instead of 3q-Bphen, the comparative compound used was 4DBT46TRZ, which is shown in [Chemical Formula 68] and is described in Japanese Patent No. 6580613, jointly filed by Yamagata University and the present applicant. NBPhen was used for the electron transport layer and electron injection layer.

The fabricated device structure is as follows.
ITO (130 nm) (anode) / PTPD-1:PPBI (20 nm) (hole injection layer) / α-NPD (20 nm) (hole transport layer) / α-NPD:4iq-Bphen or 6q-Bphen or 4DBT46TRZ (1:1), 1 wt. % (DPQ) _2Ir (dpm) (40 nm) (light emitting layer) / NBPhen (50 nm) (electron transport layer) / NBPhen, 20 wt. % Liq (20 nm) (electron transport layer with improved electron injection) / Liq (1 nm) (electron injection layer) / Al (80 nm) (cathode)
The EL spectra of the fabricated devices using 4iq-Bphen, 6q-Bphen, and 4DBT46TRZ are shown in FIG.
The current density-voltage characteristics are shown in Figure 23.
The brightness-voltage characteristics are shown in FIG.
The external quantum efficiency vs. luminance characteristics are shown in Figure 25.
The operating life (half life) measurement is shown in FIG.
Table 8 shows a summary of the device measurement results.

The fabrication conditions for the device produced in Example 4 were suitable for efficiently using 4DBT46TRZ in the light-emitting layer. For 6q-Bphen, the device conditions were not optimized, resulting in a shorter lifetime compared to 4DBT46TRZ. However, for 4iq-Bphen, even when used without optimizing the device configuration, a lifetime 1.6 times longer than when using 4DBT46TRZ was achieved.

1 Substrate 2 Anode (ITO)
3 Light-emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer 7 Hole injection layer 8 Electron injection layer 9 Hole blocking layer

Claims (8)

The following general formula [1]
[In the formula, ^R1 is hydrogen or a group independently selected from the group consisting of a methyl group, an ethyl group, a normal propyl group, and an isopropyl group.]
An organic electroluminescence device containing a 1,10-phenanthroline compound represented by the formula: The following general formula [2]
[In the formula, ^R2 is hydrogen or a group independently selected from the group consisting of a methyl group, an ethyl group, a normal propyl group, and an isopropyl group.]
An organic electroluminescence device containing a 1,10-phenanthroline compound represented by the formula: An organic electroluminescence device using the 1,10-phenanthroline compound according to claim 1 in an electron transport layer and/or an emitting layer. An organic electroluminescence device using the 1,10-phenanthroline compound according to claim 2 in an electron transport layer and/or an emitting layer. Organic electroluminescent lighting using the organic electroluminescent element according to claim 3. Organic electroluminescent lighting using the organic electroluminescent element according to claim 4. Deep red organic electroluminescent lighting using the organic electroluminescent element according to claim 3. Deep red organic electroluminescent lighting using the organic electroluminescent element according to claim 4.