TWI619690B - Organic compound and organic electroluminescence device using the same - Google Patents

Abstract

The present invention discloses a novel organic material containing indenotriphenylene derivatives and an organic EL device using the organic material. More specifically, the present invention relates to an organic material and an organic EL device applying the organic material to a fluorescent light-emitting host or a phosphorescent light-emitting host. The aforementioned organic EL device can have a long life and high efficiency.

Description

Organic compound and organic electroluminescence element using the same

The present invention generally relates to an organic compound and an organic electroluminescence (hereinafter referred to as "organic EL") device related to the compound. Specifically, the present invention relates to an organic compound having the structure of formula (I) and an organic electroluminescence device and related device, flat panel, etc. that apply the aforementioned organic compound to a fluorescent light-emitting host or a phosphorescent light-emitting host.

Organic electroluminescence (organic EL) is a light-emitting diode (LED) in which the light-emitting layer is a film made of an organic compound, which emits light under a corresponding current. The light emitting layer of the organic compound is sandwiched between the two electrodes. Organic EL is used in flat panel displays because of its high illumination, low weight, ultra-thin shape, self-illumination without backlight, low power consumption, wide viewing angle, high contrast, simple manufacturing method, and fast response time.

The first observation of the phenomenon of electroluminescence of organic materials was carried out by Andre Bernanose and colleagues at Nancy Université in France in the early 1950s. Martin Pope of New York University and colleagues first observed direct current (DC) electrical excitation light on a single pure crystal doped with naphthacene under vacuum in 1963.

The first diode element was published by Eastman Kodak's Ching W. Tang and Steven Van Slyke in 1987. The device uses a two-layer structure with a hole transport layer and an electron transport layer separately provided, which reduces the operating voltage and improves efficiency, leading the organic EL research and device production of today's era.

Typically, an organic EL is composed of an organic material layer between two electrodes, which includes a hole transporting layer (HTL), an emitting layer (EML), and an electron transporting layer (electron transporting layer , ETL). The basic mechanism of organic EL involves carrier injection, carrier transport, reorganization, and the formation of exciton to emit light. When an external voltage is applied to the organic light-emitting element, electrons and holes are injected from the cathode and anode, respectively, electrons will be injected from the cathode into the lowest unoccupied molecular orbital (LUMO), and holes will be injected from the anode To the highest occupied molecular orbital (HOMO). When electrons and holes recombine in the light-emitting layer, excitons are formed and then emit light. When the luminescent molecule absorbs energy and reaches the excited state, depending on the spin combination of the electron and the hole, the exciton can assume a singlet state or a triplet state. 75% of excitons are formed by the reorganization of electrons and holes to reach triplet excited states. Decay from the triplet state is self forbidden. Therefore, the fluorescent element has only 25% internal quantum efficiency (internal quantum efficiency). Compared to fluorescent photoluminescence devices, phosphorescent organic EL devices use spin-orbit interaction to promote intersystem crossing between singlet and triplet states, thus obtaining singlet states from singlet states. And triplet light, and the internal quantum efficiency of the electro-excited light element has increased from 25% to 100%.

In recent years, Professor Adachi and his colleagues have developed a new type of fluorescent organic EL device that combines a thermally activated delayed fluorescence (TADF) mechanism by reverse intersystem crossing , RISC) mechanism, a promising way to convert spin-forbidden triplet excitons to singlet energy levels to obtain high efficiency of exciton formation.

Both triplet and singlet excitons can be used by organic EL. Because triplet excitons have a longer half-life and diffusion length compared to singlet excitons, phosphorescent organic EL generally requires an additional hole blocking layer (HBL) between the light-emitting layer and the electron transport layer Or an electron blocking layer (EBL) between the light emitting layer and the hole transport layer is required. The purpose of using a hole blocking layer or an electron blocking layer is to limit the recombination between injected holes and electrons, and to relax the excitons generated in the light emitting layer, thereby improving the efficiency of the device. In order to satisfy these effects, hole blocking materials or electron blocking materials must have HOMO and LUMO energy levels suitable for blocking the transmission of holes or electrons from the luminescent layer to the electron transport layer or to the hole transport layer.

There is a continuing need for organic EL materials that can effectively transport electrons or holes and block holes, yet have good thermal stability and high luminous efficiency. Based on the above reasons, the object of the present invention is to solve these problems of the prior art and provide an organic EL device that is quite excellent in thermal stability, high brightness, and long half-life time. The present invention uses a diaryl substituted arylene group to connect to positions 5, 6, 7 and 8 of the indenotriphenylene core skeleton, and provides a material with more excellent heat resistance, high luminous efficiency, Organic light-emitting device with high brightness and long half-life time.

The present invention provides a compound that can be used for a fluorescent light-emitting host or a phosphorescent light-emitting host of an organic EL device. The aforementioned organic compounds can overcome the lack of materials disclosed in the prior art such as US Patent Publication No. 20140131664, US Patent Publication No. 20140175384, and US Patent Publication No. 20140209866, such as low efficiency, short half-life time, and high power consumption. .

An object of the present invention is to provide a compound that can be used in a fluorescent light-emitting host or a phosphorescent light-emitting host in an organic EL device, or other materials having similar functions.

Still another object of the present invention is to provide an organic electroluminescence device, which includes the following compounds. The organic electroluminescence device of the present invention can be widely applied or installed in various organic light emitting devices (organic light emitting devices), lighting panels and / or backlight panels with organic light emitting functions.

The invention has economic advantages in industrial practice. Accordingly, a compound for an organic EL device is disclosed. The organic compound includes a structure represented by the following formula (I): Formula (I) where A represents a phenyl group or a substituted or unsubstituted fused ring hydrocarbon unit having two to four rings, and L represents a single bond or a group having 6 to 30 ring carbon atoms Substituted or unsubstituted divalent arylene group; Ar ₁ and Ar ₂ independently represent selected from substituted or unsubstituted phenyl group, substituted or unsubstituted Naphthyl group, substituted or unsubstituted anthracenyl group, substituted or unsubstituted phenanthrenyl group, substituted or unsubstituted pyrenyl group, and Substituted or unsubstituted chrysenyl group; R ₁ to R ₃ independently represent a substituted or unsubstituted alkyl group selected from a hydrogen atom having 1 to 20 carbon atoms , Substituted or unsubstituted aryl groups with 6 to 30 carbon atoms, and substituted or unsubstituted aralkyl groups with 6 to 30 carbon atoms, and 3 to 30 A group of substituted or unsubstituted heteroaryl groups of one carbon atom.

The invention also discloses an organic electroluminescence device, which includes a pair of electrodes, at least one light-emitting layer and one or more organic thin film layers, wherein the electrode is composed of a cathode and an anode, and the light-emitting layer and the organic thin film layer are both provided Between the cathode and the anode, and at least one layer of the light-emitting layer includes the compound as described above.

The aforementioned organic compound contained in the light-emitting layer can also be used as a light-emitting host material; alternatively, it can also be used as a fluorescent emitter. In addition, the light emitted by the light-emitting layer may be blue light or green light.

The present invention further discloses an organic light emitting device (organic light emitting device), which includes the organic electroluminescence device as described above.

The invention further discloses a lighting panel including the organic electroluminescence element as described above.

The present invention further discloses a backlight panel including the organic electroluminescence element as described above.

The present invention is to explore a compound and an organic EL device using the compound. In the following, a detailed description of production, structure and elements will be provided to fully understand the present invention. Obviously, the application of the present invention is not limited to the specific details familiar to those skilled in the art. On the other hand, the known common elements and procedures are not described in detail in the present invention, and should not unnecessarily limit the present invention. Some preferred embodiments of the present invention will now be described in more detail below. However, it should be recognized that the present invention can be widely practiced in various other embodiments besides the explicitly described embodiments, that is, the present invention can also be widely applied to other embodiments, except as specified in the scope of the appended patent application In addition, the scope of the present invention is not specifically limited.

The present invention discloses a compound having the structure shown in formula (I). In a preferred embodiment, the organic compound can be used for a fluorescent light-emitting host or a phosphorescent light-emitting host in a light-emitting layer of an organic EL device. Formula (I) has the following structure: Formula (I) where A represents a phenyl group or a substituted or unsubstituted fused ring hydrocarbon unit having two to four rings, and L represents a single bond or a substituted or unsubstituted group having 6 to 30 ring carbon atoms Ar ₁ and Ar ₂ independently represent a group selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthryl, Substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, and substituted or unsubstituted ketyl; R ₁ to R ₃ independently represent a group selected from the group consisting of hydrogen atoms, Substituted or unsubstituted alkyl groups of 1 to 20 carbon atoms, substituted or unsubstituted aryl groups of 6 to 30 carbon atoms, substituted or unsubstituted groups of 6 to 30 carbon atoms Aralkyl groups and substituted or unsubstituted heteroaryl groups having 3 to 30 carbon atoms.

In some preferred embodiments, according to the compound represented by the aforementioned formula (I), L can be further represented as one of the group selected from the group consisting of: .

In some preferred embodiments, according to the compound represented by the aforementioned formula (I), Ar ₁ may be further represented as one of the group selected from the group consisting of: .

In some preferred embodiments, according to the compound represented by the aforementioned formula (I), Ar ₂ may be further represented as one selected from the group consisting of the following groups: .

In some preferred embodiments, according to the compound represented by the aforementioned formula (I), it may further have a structure represented by the following formula (II) or formula (III): Formula (II) Formula (III) where L represents a single bond or a substituted or unsubstituted divalent arylene group having 6 to 30 ring carbon atoms, and Ar ₁ and Ar ₂ independently represent a group selected from substituted or unsubstituted Phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthracenyl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, and substituted or unsubstituted R ₁ to R ₃ independently represents a group selected from the group consisting of hydrogen atoms, halogens, substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, substituted groups having 6 to 30 carbon atoms or The group consisting of an unsubstituted aryl group, a substituted or unsubstituted aralkyl group having 6 to 30 carbon atoms, and a substituted or unsubstituted heteroaryl group having 3 to 30 carbon atoms.

In some preferred embodiments, according to the compound represented by the aforementioned formula (II) or formula (III), L is further represented as one selected from the group consisting of the following groups: .

In some preferred embodiments, according to the compound represented by the aforementioned formula (II) or formula (III), Ar _{1 is} further represented as one selected from the group consisting of the following groups: .

In some preferred embodiments, according to the compound represented by the foregoing formula (II) or formula (III), Ar _{2 is} further represented as one selected from the group consisting of the following groups: .

In some preferred embodiments, the compound represented by the foregoing formula (I) to formula (III) further has one of the groups consisting of the structures represented by the following general formulas: .

On the other hand, the present invention relates to an organic electroluminescence device, which may include a pair of electrodes composed of a cathode and an anode, at least one light-emitting layer, and one or more organic thin-film layers, both of which are provided Between the cathode and the anode of the pair of electrodes, at least one layer of the light-emitting layer contains the organic compound of the present invention.

Please refer to FIG. 1. In a preferred embodiment, such an organic electroluminescence device may include a transparent electrode 6, a hole injection layer 7, a hole transmission layer 8, a light-emitting layer 9, and a hole blocking layer 10 , The electron transport layer 11, the electron injection layer 12, and the metal electrode 13. In the device, the hole injection layer 7 is provided between the transparent electrode 6 and the metal electrode 13, the hole transmission layer 8 is provided between the hole injection layer 7 and the metal electrode 13, and the light emitting layer 9 is provided on the hole transmission layer 8 Between the metal electrode 13, the hole blocking layer 10 is disposed between the light emitting layer 9 and the metal electrode 13, the electron transport layer 11 is disposed between the hole blocking layer 10 and the metal electrode 13, and the electron injection layer 12 is disposed between the electrons Between the transmission layer 11 and the metal electrode 13. In addition, the light-emitting layer can emit phosphorescence, fluorescent light, or other light that can be generated by electrical excitation of organic materials; in a preferred embodiment, the light emitted from the light-emitting layer can be fluorescent light; in a preferred embodiment For example, the fluorescent light emitted from the self-luminous layer may be blue or green fluorescent light.

The detailed preparation of the organic material according to the present invention can be illustrated by exemplary embodiments, but it is not limited to the exemplary embodiments. Examples 1 to 5 show the preparation of some examples of the compounds in the present invention. Examples 6 and 7 show the I-V-B and half-life time of organic EL device manufacturing and organic EL device test reports.

Example 1: Synthesis of compound EX7

Synthesis of 2-phenyl-4-nitrobromobenzene

Add 2.6g (12.14mmol) 2-phenyl-4-nitroaniline (2-phenyl-4-nitroaniline) at 0 ~ 5 ℃ to 0.92g (13.35mmol) sodium nitrite (sodium nitrite), 8ml sulfuric acid (sulfuric acid, H ₂ SO ₄ ) and 9ml of acetic acid (acetic acid) mixed solution and also stirred at 0 ~ 5 ℃ for 2 hours, then add water to the mixed solution and stirred at room temperature for 1 hour. Take 4.3g (19.42mmol) of copper (II) bromide (copper (II) bromide) dissolved in 9.3ml of 2M hydrochloric acid solution, add to the mixed solution, stir at room temperature for 20 minutes to form a mixture, and then the mixture at 60 The reaction was heated at ℃ for 1 hour. The organic layer was extracted with ether and water, the organic layer was washed with brine, and the organic layer was dried with magnesium sulfate to evaporate the solvent to form a crude product. The crude product was purified by column chromatography filled with silica gel to obtain 1.5 g (5.39 mmol) of white solid product with a yield of 45.5%.

Synthesis of 2- (5-nitro- [1,1'-biphenyl] -2-yl) -9,9-dimethyl-9H-fluorene (2- (5-nitro- [1,1'-bipheny ] -2-yl) -9,9-dimethyl-9H-fluorene)

40g (14.38mmol) 2-phenyl-4-nitrobromobenzene, 27.7g (15.82mmol) 9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (9,9-dimethyl- 9H-fluoren-2-yl-2-boronic acid), 1.8g (0.16mmol) tetrakis (triphenylphosphine) palladium, Pd (PPh ₃ ) ₄ ), 119ml 2M sodium carbonate, 150ml ethanol And a mixture of 450 ml of toluene was degassed and placed under nitrogen, followed by heating at 90 ° C. overnight for reaction. After the reaction was completed, the mixture was cooled to room temperature, and the organic layer was extracted with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 43.1 g (110.1 mmol) of the product with a yield of 69.6%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 7.93 (s, 1H), 7.71 (d, 1H), 7.50 (d, 1H), 7.38 ~ 7.21 (m, 6H), 7.16 ~ 6.92 (m , 4H), 6.83 ~ 6.65 (m, 2H), 1.15 (s, 6H).

Synthesis of 2- (5-amino- [1,1'-biphenyl] -2-yl) -9,9-dimethyl-9H-fluorene (2- (5-amino- [1,1'-bipheny ] -2-yl) -9,9-dimethyl-9H-fluorene)

10.4g (26.56mmol) 2- (5-nitro- [1,1'-biphenyl] -2-yl) -9,9-dimethyl-9H-fluorene, 8.5g (159.36mmol) iron powder (iron powder) and a mixture of 10ml of concentrated hydrochloric acid (conc.HCl) in 100ml of alcohol and 30ml of water in an aqueous alcohol solution, heated at 85 ℃ for 2 hours under reflux to react. The mixture after the completion of the reaction was filtered, the filtrate was collected, and the filtrate was extracted with ethyl acetate and water. The extracted organic layer was taken out, dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure to form a solid. The solid was washed with hexane to obtain 8.2g (22.68mmol) of product with a yield of 85%. ¹ HNMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 7.71 (d, 1H), 7.64 (d, 1H), 7.42 (d, 1H), 7.29 ~ 7.12 (m, 7H), 7.06 (d, 2H) , 6.89 (s, 1H), 6.80 (d, 1H), 6.78 (s, 1H), 1.12 (s, 6H).

Synthesis of 2- (4-bromo- [1,1'-biphenyl] -2-yl) -9,9-dimethyl-9H-fluorene (2- (4-bromo- [1,1'-bipheny] -2-yl) -9,9-dimethyl-9H-fluorene)

Add 1g (2.76mmol) corresponding to 2- (4-amino- [1,1'-biphenyl] -2-yl) 9,9-dimethyl-9H-fluorene slowly add more than 1 hour at 0.34g (3.32mmol) tert-butyl nitrite (tert-butyl nitrite), 0.6g (2.76mmol) anhydrous copper (II) (anhydrous copper (II) bromide) and anhydrous acetonitrile (acetonitrile) in the mixture, thus The reaction is initiated by vigorous foaming and evolution of nitrogen gas. After the reaction was completed, the mixture was cooled to room temperature and poured into an aqueous HCl solution, and a crude product was precipitated. The crude product was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 0.3 g (0.70 mmol) of white solid product with a yield of 25%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 7.81 (d, 1H), 7.40 ~ 7.65 (m, 1H), 7.66 ~ 7.68 (m, 1H), 7.61 ~ 7.63 (m, 1H), 7.35 ~ 7.37 (m, 1H), 7.24 ~ 7.32 (m, 4H), 7.15 ~ 7.22 (m, 4H), 7.09 ~ 7.12 (m, 2H), 6.93 (d, 1H), 1.20 (s, 6H).

Synthesis of 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene (6-bromo-10,10-di-methyl-10H-indeno [2,1-b] triphenylene )

In a 100ml three-necked flask degassed and filled with nitrogen, 2.9g (0.68mmol) 2- (4-bromo- [1,1-biphenyl] -2-yl) -9,9-dimethyl- 9H-fluorene was dissolved in anhydrous dichloromethane (180 ml), and then 5.5 g (3.40 mmol) of iron (III) chloride was added to form a mixture, and the mixture was stirred for one hour to react. Quench the reaction with methanol and water, separate the organic layer and remove the solvent to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 1.7 g (0.81 mmol) of white solid product with a yield of 58.6%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.01 (s, 1H), 8.94 (d, 2H), 8.78 (s, 1H), 8.58 (s, 1H), 8.49 (s, 1H), 7.98 (d, 1H), 7.78-7.85 (m, 2H), 7.43 ~ 7.63 (m, 4H), 1.69 (s, 6H).

Synthesis of 10,10-dimethyl-6- (10- (naphthalen-2-yl) anthracene-9-yl) -10H-indeno [2,1-b] triphenylene (10,10-dimethyl-6- (10- (naphthalen-2-yl) anthracen-9-yl) -10H-indeno [2,1-b] triphenylene)

8.6g (20.3mmol) 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene (6-bromo-10,10-dimethyl-10H-indeno [2,1 -b) triphenylene), 7.8g (22.3mmol) 10- (naphthalen-2-yl) anthracen-9-ylboronic acid (10- (naphthalen-2-yl) anthracen-9-ylboronic acid), 0.5g (0.4mmol ) A mixture of tetrakis (triphenylphosphine) palladium, 21ml 2M sodium carbonate, 17ml ethanol and 70ml toluene was degassed and placed under nitrogen, followed by heating at 100 ° C for 12 hours for reaction. After the completion of the reaction, the mixture was cooled to room temperature, and the organic layer was extracted with ethyl acetate and water. The organic phase was dried over anhydrous magnesium sulfate to remove the solvent, and a residue was formed. The residue was purified by column chromatography filled with silica gel to obtain 6.5 g (10 mmol) of light yellow solid product with a yield of 50%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.06 (s, 1H), 9.01 (d, 1H), 8.81 ~ 8.88 (m, 3H), 8.60 (d, 1H), 7.93 ~ 8.11 (m , 5H), 7.76 ~ 7.86 (m, 5H), 7.64-7.73 (m, 2H), 7.54 ~ 7.63 (m, 4H), 7.40 ~ 7.48 (m, 2H), 7.34 ~ 7.31 (m, 4H), 1.71 (s, 6H).

Example 2: Synthesis of compound EX9

Synthesis of 10,10-dimethyl-6- (4- (10- (naphthalen-2-yl) anthracene-9-yl) phenyl) -10H-indeno [2,1-b] triphenylene (10, 10-dimethyl-6- (4- (10- (naphthalen-2-yl) anthracen-9-yl) phenyl)-10H-indeno [2,1-b] triphenylene)

Combine 8.6g (20.3mmol) 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene, 9.5g (22.3mmol) 4- (10- (naphthalen-2-yl ) Anthracene-9-yl) phenylboronic acid (4- (10- (naphthalen-2-yl) anthracen-9-yl) phenylboronic acid), 0.5g (0.4mmol) tetrakis (triphenylphosphine) palladium, 21ml 2M A mixture of sodium carbonate, 17 ml of ethanol, and 70 ml of toluene was degassed and placed under nitrogen, followed by heating at 100 ° C. for 12 hours for reaction. After the completion of the reaction, the mixture was cooled to room temperature, and the organic layer was extracted with ethyl acetate and water. The organic phase was dried over anhydrous magnesium sulfate to remove the solvent, and a residue was formed. The residue was purified by column chromatography filled with silica gel to obtain 7.3 g (10 mmol) of a yellow solid product with a yield of 50%. ¹ HNMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.06 (s, 1H), 9.01 (d, 1H), 8.81 ~ 8.88 (m, 3H), 8.60 (d, 1H), 7.93 ~ 8.11 (m, 5H), 7.76 ~ 7.86 (m, 5H), 7.64-7.73 (m, 2H), 7.54 ~ 7.63 (m, 4H), 7.40 ~ 7.48 (m, 2H), 7.34 ~ 7.25 (m, 8H), 1.71 ( s, 6H).

Example 3: Synthesis of compound EX17

Synthesis of 2- (10,10-dimethyl-10H-indeno [2,1-b] triphenylene-12-yl) quinoxaline (2- (10,10-dimethyl-10H-indeno [2,1 -b] triphenylen-12-yl) quinoline)

In a 500 ml three-necked flask degassed and filled with nitrogen, 10 g (21.7 mmol) of 9-bromo-10- (4- (naphthalen-1-yl) cyclohex-1,3-dienyl) anthracene ( 9-bromo-10-4- (naphthalen-1-yl) cyclo-hexa-1,3-dienyl) anthracene) was dissolved in anhydrous tetrahydrofuran (150ml), cooled to -78 ℃, and then 10.4ml (26.1mmol) was added ) 2.5M n-butyllithium, stir for 1 hour, then add 3.4g (32.6mmol) trimethyl borate and hexane-dichloromethane and stir overnight. After the reaction was completed, the organic layer was extracted with 300 ml of ethyl acetate and 200 ml of water, and the organic layer was dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure to obtain 7.4 g of yellow solid product. The rate is 80%.

Synthesis of 10,10-dimethyl-6- (10- (4- (naphthalen-1-yl) phenyl) anthracene-9-yl) -10H-indeno [1,2-b] triphenylene (10, 10-dimethyl-6- (10- (4- (naphthalen-1-yl) phenyl) anthracen-9-yl)-10H-indeno [2,1-b] triphenylene)

Combine 8.6g (20.3mmol) 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene, 9.5g (22.3mmol) 10- (4- (naphthalen-1-yl ) Cyclohex-1,3-dienyl) anthracene-9-ylboronic acid (10- (4- (naphthalen- 1-yl) cyclohexa-1,3-dienyl) anthracen-9-ylboronic acid), 0.5g ( A mixture of 0.4 mmol) tetrakis (triphenylphosphino) palladium, 21 ml of 2M sodium carbonate, 17 ml of ethanol, and 70 ml of toluene was degassed and placed under nitrogen, followed by heating at 100 ° C. for 12 hours for reaction. The mixture after the completion of the reaction was cooled to room temperature, and the organic layer was extracted with ethyl acetate and water, and the extracted organic layer was dried over anhydrous magnesium sulfate to remove the solvent to form a residue. The residue was purified by column chromatography filled with silica gel to obtain 5.9 g (8.1 mmol) of yellow solid product with a yield of 40%. ¹ HNMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.06 (s, 1H), 9.02 (d, 1H), 8.83 ~ 8.88 (m, 3H), 8.61 (d, 1H), 8.19 ~ 8.21 (m, 1H), 8.03 ~ 7.92 (m, 5H), 7.87 ~ 7.84 (m, 3H), 7.78 ~ 7.70 (m, 3H), 7.70 ~ 7.54 (m, 8H), 7.48 ~ 7.35 (m, 6H), 1.71 ( s, 6H).

Example 4: Synthesis of compound EX26

Synthesis of 4,4,5,5-tetramethyl-2- (6-phenylpyrene-1-yl) -1,3,2-dioxaborolane (4,4, 5,5-tetramethyl -2- (6-phenylpyren-1-yl) -1,3,2-dioxaborolane)

13.1g (37mmol) 1-bromo-6-phenylpyrene (1-bromo-6-phenylpyrene), 11.25g (44.3mmol) double-linked pinacol borate (bis (pinacolato) diboron), 0.44g ( A mixture of 0.38 mmol) tetrakis (triphenylphosphino) palladium, 10.8 g (110 mmol) potassium acetate and 440 ml 1,4-dioxane was degassed and placed under nitrogen, then heated at 90 ° C React for 16 hours. After the reaction was completed, the mixture was cooled to room temperature, the organic phase was separated and washed with ethyl acetate and water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under vacuum to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 10.5 g (26 mmol) of light yellow solid product with a yield of 70%.

Synthesis of 1- (4-bromophenyl) -6-phenylpyrene (1- (4-bromophenyl) -6-phenylpyrene)

10.5g (26mmol) 4,4,5,5-tetramethyl-2- (6-phenylpyrene-1-yl) -1,3,2-dioxaborolane, 12g (52mmol) A mixture of 1,4-dibromobenzene (1,4-dibromobenzene), 0.58g (0.5mmol) tetrakis (triphenylphosphine) palladium, 39ml 2M sodium carbonate, 40ml ethanol and 80ml toluene was degassed and placed in The reaction was carried out under nitrogen, followed by heating at 90 ° C overnight. After the reaction was completed, the mixture was cooled to room temperature, the organic phase was separated and washed with 250 ml of ethyl acetate and 1000 ml of water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 5.6 g (13 mmol) of light yellow solid product with a yield of 50%.

Synthesis of 4,4,5,5-tetramethyl-2- (4- (6-phenylpyrene-1-yl) phenyl) -1,3,2-dioxaborolane (4,4 , 5,5-tetramethyl-2- (4- (6-phenylpyren-1-yl) phenyl) -1,3,2-dioxaborolane)

5.6g (13mmol) 1- (4-bromophenyl) -6-phenylpyrene (1- (4-bromophenyl) -6-phenylpyrene), 4.9g (19.5mmol) double-linked pinacol borate 1 , 4-dibromobenzene (1,4-di-bromobenzene), 0.15g (0.13mmol) tetrakis (triphenylphosphine) palladium, 3.8g (39mmol) potassium acetate and 180ml 1,4-dioxane After degassing and placing under nitrogen, the reaction was then carried out by heating at 90 ° C for 16 hours. After the reaction was completed, the mixture was cooled to room temperature, the organic phase was separated and washed with ethyl acetate and water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under vacuum to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 4.36 g (9.1 mmol) of light yellow solid product with a yield of 70%.

Synthesis of 10,10-dimethyl-6- (4- (6-phenylpyrene-1-yl) phenyl) -10H-indeno [2,1-b] triphenylene (10,10-dimethyl-6 -(4- (6-phenylpyren-1-yl) phenyl) -10H-indeno [2,1-b] triphen ylene

4.36g (9.1mmol) 4,4,5,5-tetramethyl-2- (4- (6-phenylpyrene-1-yl) phenyl) -1,3,2-dioxaborolane Pentane, 3.8g (9.1mmol) 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene, 0.1g (0.09mmol) tetrakis (triphenylphosphine) palladium, A mixture of 14 ml of 2M sodium carbonate, 28 ml of ethanol, and 56 ml of toluene was degassed and placed under nitrogen, followed by heating at 90 ° C. overnight for reaction. The mixture after completion of the reaction was cooled to room temperature, the organic phase was separated and washed with 250 ml of ethyl acetate and 1000 ml of water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 4.43 g (6.37 mmol) of light yellow solid product with a yield of 70%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.01 (s, 1H), 8.85 ~ 8.73 (m, 4H), 8.33 ~ 8.19 (m, 4H), 8.07 ~ 7.96 (m, 8H), 7.64 ~ 7.83 (m, 6H), 7.57 ~ 7.41 (m, 6H), 1.69 (s, 6H).

Example 5: Synthesis of compound EX31

Synthesis of 4,4,5,5-tetramethyl-2- (6- (naphthalene-1-yl) pyrene-1-yl) -1,3,2-dioxaborolane (4,4, 5,5-tetramethyl-2- (6- (naphthalen-1-yl) pyren-1-yl) -1,3,2-dioxaborolane)

15g (37mmol) 1-bromo-6- (naphthalen-1-yl) pyrene (1-bromo-6- (naphthalen-1-yl) pyrene), 11.25g (44.3mmol) double pinacol borate , 0.44g (0.38mmol) tetrakis (triphenylphosphine) palladium, 10.8g (110mmol) potassium acetate and 440ml 1,4-dioxane mixture was degassed and placed under nitrogen, then heated at 90 ℃ React for 16 hours. After the reaction was completed, the mixture was cooled to room temperature, the organic phase was separated and washed with ethyl acetate and water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under vacuum to form a residue. The residue was purified by column chromatography (hexane-dichloromethane) filled with silica gel to obtain 11.8 g (26 mmol) of light yellow solid product with a yield of 70%.

Synthesis of 1- (4-bromophenyl) -6- (naphthalene-1-yl) pyrene (1- (4-bromophenyl) -6- (naphthalen- 1-yl) pyrene)

11.8g (26mmol) 4,4,5,5-tetramethyl-2- (6- (naphthalen-1-yl) pyrene-1-yl) -1,3,2-dioxaborolane , A mixture of 12g (52mmol) 1,4-dibromobenzene (1,4-dibromobenzene), 0.58g (0.5mmol) tetrakis (triphenylphosphine) palladium, 39ml 2M sodium carbonate, 40ml ethanol and 80ml toluene was degassed Treat and place under nitrogen, then heat at 90 ° C overnight to react. After the reaction was completed, the mixture was cooled to room temperature, the organic layer was separated and washed with 250 ml of ethyl acetate and 1000 ml of water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to form a residue. The residue was purified by silica gel-filled column chromatography (hexane-dichloromethane) to obtain 6.3 g (13 mmol) of light yellow solid product with a yield of 50%.

Synthesis of 4,4,5,5-tetramethyl-2- (4- (6- (naphthalene-1-yl) pyrene-1-yl) phenyl) -1,3,2-dioxaborolane Alkanes (4,4,5,5-tetramethyl-2- (4- (6- (naphthalen-1-yl) pyren-1-yl) phenyl) -1,3,2- dioxaborolane)

6.3g (15mmol) 1- (4-bromophenyl) -6- (naphthalene-1-yl) pyrene (1- (4-bromophenyl) -6- (naphthalene-1-yl) pyrene), 5.7g ( 22.5 mmol) a mixture of double pinacol borate, 0.17 g (0.15 mmol) tetrakis (triphenylphosphine) palladium, 4.4 g (45 mmol) potassium acetate and 180 ml 1,4-dioxane were degassed and It was placed under nitrogen and then heated at 90 ° C for 14 hours to carry out the reaction. After the reaction was completed, the mixture was cooled to room temperature, the organic phase was separated and washed with ethyl acetate and water, and then dried over anhydrous magnesium sulfate, and the solvent was removed under vacuum to form a residue. The residue was purified by silica gel-filled column chromatography (hexane-dichloromethane) to obtain 6.4 g (12 mmol) of light yellow solid product with a yield of 80%.

Synthesis of 10,10-dimethyl-6- (4- (6- (naphthalen-1-yl) pyrene-1-yl) phenyl) -10H-indeno [2,1-b] triphenylene (10, 10-dimethyl-6- (4- (6- (naphthalen-1-yl) pyren-1-yl) phenyl) -10H-ind- eno [2,1-b] triphenylene

6.4g (12mmol) 4,4,5,5-tetramethyl-2- (4- (6- (naphthalen-1-yl) pyrene-1-yl) phenyl) -1,3,2-di Oxaborolane, 5g (12mmol) 6-bromo-10,10-dimethyl-10H-indeno [2,1-b] triphenylene, 0.14g (0.12mmol) tetrakis (triphenylphosphine) A mixture of palladium, 18 ml of 2M sodium carbonate, 20 ml of ethanol, and 40 ml of toluene was degassed and placed under nitrogen, followed by heating at 90 ° C. overnight for reaction. After the reaction was completed, the mixture was cooled to room temperature, the organic layer was extracted with 250 ml of ethyl acetate and 1000 ml of water, and dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to form a residue. The residue was purified by silica gel-filled column chromatography (hexane-dichloromethane) to obtain 6.26 g (8.4 mmol) of light yellow solid product with a yield of 70%. ¹ H NMR (CDCl ₃ , 400MHz): Chemical shift (ppm) 9.01 (d, 1H), 9.00 (s, 1H), 8.88 ~ 8.81 (m, 3H), 8.74 (s, 1H), 8.7 (d, 1H ), 8.28 (d, 1H), 8.22 (d, 1H), 8.15 (d, 1H), 8.08 ~ 7.99 (m, 8H), 7.92 (d, 1H), 7.83 (d, 1H), 7.75 ~ 7.63 ( m, 5H), 7.55 ~ 7.39 (m, 5H), 7.30 ~ 7.27 (m, 1H), 1.69 (s, 6H).

General method of producing organic EL elements

According to the present invention, an indium tin oxide (ITO) coated glass (hereinafter ITO substrate) is provided, which has a resistance of 9 ohm / square to 12 ohm / square and a thickness of 120 nm to 160 nm, and use multiple cleaning steps (for example: detergent, deionized water) to clean in an ultrasonic bath. Before the vapor deposition process of the organic layer, the cleaned ITO substrate is further treated by UV and ozone. All pretreatment processes for ITO substrates are performed in a clean room (Class 100) environment.

In a high vacuum unit (10 ^-7 torr) such as resistively heated quartz boats, these organic layers are sequentially coated on the ITO substrate by vapor deposition. The thickness of the corresponding layer and the vapor deposition rate (0.1 nm / sec to 0.3 nm / sec) are accurately monitored or set by the quartz-crystal monitor. As mentioned above, individual layers may also be composed of more than one compound, meaning a host material that is generally doped with a dopant material. This type of material can be achieved by co-vaporization from two or more sources.

More specifically, in a preferred embodiment, in the organic EL device of the present invention, dipyrazino [2,3-f: 2,3-] quinoxaline-2,3,6, 7,10,11-hexacarbonitrile (Dipyrazino [2,3-f: 2,3-] quinoxaline-2,3,6,7,10,11-hexacarbonitrile, HAT-CN) can be used for hole injection layer, N , N-bis (naphthalene-1-yl) -N, N-bis (phenyl) -benzidine (N, N-bis (naphthalene-1-yl) -N, N-bis (phenyl) -benzidine, NPB ) Most commonly used in the hole transport layer, 10,10-dimethyl-12- (4- (pyrene-1-yl) phenyl) -10H-indeno [1,2-b] triphenylene (10,10 -dimethyl-12- (4- (pyren-1-yl) phenyl)-10H-indeno [1,2-b] triphenylene) (hereinafter referred to as PT-312, refer to US Patent Publication No. 20140175384) or 10, 10-dimethyl-12- (10- (naphthalene-2-yl) anthracene-9-yl) -10H-indeno [2,1-b] triphenylene (10,10-dimethyl-12- (10- ( naphthalen-2-yl) anthracen-9-yl) -10H-indeno [2,1-b] triphenylene) (hereinafter referred to as PT-313, refer to US Patent Publication No. 20140209866) can be used for blue light emitting host, N ¹ , N ¹ , N ⁶ , N ⁶ -tetratolylpyrene-1,6-diamine (N ¹ , N ¹ , N ⁶ , N ⁶ -tetram-tolylpyrene-1,6-diamine) (hereinafter referred to as D1) Can be used for blue luminescent guests; 2- (10,10-dimethyl-10H-indeno [2,1-b] triphenylene-13-yl) -9-phenyl-1,10-morpholine (2 -(10,10-dimethyl-10H-indeno [2,1-b] triphenylen-13-yl) -9-phenyl-1,10-phenanthroline) (hereinafter referred to as ET1) can be used with 5% lithium metal (Li) Co-deposition, and 2- (10,10-dimethyl-10H-indeno [2,1-b] triphenylene-12-yl) -4,6-diphenyl-1,3,5-triazine (2- (10,10-dimethyl-10H- indeno [2,1-b] triphenylen-12-yl) -4,6-diphenyl-1,3,5-triazine) (hereinafter referred to as ET2) , 2- (10,10-dimethyl-10H-indeno [2,1-b] triphenylene-13-yl) -4,6-bis (5-phenylbiphenyl-3-yl) -1 , 3,5-triazine (2- (10,10-dimethyl-10H-indeno [2,1-b] triphenylen-13-yl) -4,6-bis (5-phenylbiphenyl-3-yl) -1 , 3,5-triazineto) (hereinafter referred to as ET3) or 2,9-bis (naphthalen-2-yl)-4,7-diphenyl-1,10-morpholine (2,9-di (naphthalen- 2-yl) -4,7-diphenyl-1,10-phenanthrol -ine) (hereinafter referred to as ET4) and can be used with 8-hydroxyquinolato-lithium (LiQ), ET1, ET2 above , ET3, ET4 can be used for electron transport materials (ETM); tris (2-phenylpyridine) iridium (III) (tris (2-phenylpyridina-to) iridium (III)) (hereinafter referred to as D2) can be used for phosphorescent doping Miscellaneous agent; 4- (10,10-dimethyl-10H-indeno [2,1-b] triphenylene-13-yl) dibenzo [b, d] thiophene (4- (10,10-dimethyl -10H-indeno [2,1-b] triphenylen-13-yl) dibenzo [b, d] thio-phene) (hereinafter referred to as H1) can be used for hole blocking materials (HBM) or luminescent hosts. The above-mentioned prior art OLED materials that can be used to produce a standard organic EL element control group and the comparative materials in the present invention are shown in the following chemical structures: .

A typical organic EL device is composed of a low work function metal material containing Al, Mg, Ca, Li, and K, and is used as a cathode by thermal evaporation. The low work function metal material can assist electron injection from the cathode to the electron transport layer . In addition, in order to reduce the barrier of electron injection and improve the performance of the organic EL element, a thin-film electron injection layer is introduced between the cathode and the electron transport layer. The conventional material of the electron injection layer is a metal halide or metal oxide with a low work function, for example: LiF, LiQ, MgO, or Li ₂ O. On the other hand, after the organic EL element is manufactured, EL spectra and CIE coordinates are measured by using a PR650 spectrum scan spectrometer. In addition, Keithley 2400 programmable voltage-current source (Keithley 2400 programmable voltage-current source) is used to obtain current / voltage, luminescence / voltage and yield / voltage characteristic data. The above equipment is operated at room temperature (about 25 ° C) and atmospheric pressure.

Example 6

Using a procedure similar to the above general method, a blue fluorescent organic EL device with the following device structures I and II is produced, device structure I: ITO / HAT-CN (20nm) / NPB (130nm) / doped with 5% D1 Fluorescent host (30nm) / ET2 (10nm) / ETM (35nm) / Al (160nm) co-deposited with 5% Li; device structure II: ITO / HAT-CN (20nm) / NPB (130nm) / doped 5 The fluorescent body of% D1 (30nm) / ET2 (10nm) / ETM (35nm) / LiQ (1nm) / Al (160nm) co-deposited with 50% LiQ. The IVB (under 1000 nits) and half-life time of the fluorescent organic EL device test report are shown in Table 1 and Table 2. The half-life time is defined as the time when the initial brightness of 1000 cd / m ² drops to half.

Table 1

Table 2

Example 7

Using a procedure similar to the above general method, a phosphorescent organic EL element with the following element structure is produced, element structure: ITO / HAT-CN (20nm) / NPB (130nm) / phosphorus host (PHhost) + 12% D2 (30nm) / H1 (15nm) / ET2 (35nm) / LiQ (1nm) / Al (160nm) co-deposited with 50% LiQ. The IVB (under 1000 nits) and half-life time of the phosphorescent organic EL device test report are shown in Table 3. The half-life time is defined as the time when the initial brightness of 3000cd / m ² drops to half.

table 3

Please refer to Table 1 to Table 3. In the above preferred embodiments of the organic EL device test report, it is shown that the compound of formula (I) of the present invention is applied to the fluorescent host of the organic EL device and other application purposes (Compound EX1 can be used for phosphorescent host), compared with the prior art OLED materials such as US Patent Publication No. 20140131664, US Patent Publication No. 20140175384 and US Patent Publication No. 20140209866, the device can achieve better performance The performance is more particularly used in combination with compound H1 (for hole blocking layer or phosphorescent host), ET1, ET2, or ET3 (for hole transmission layer). Compared with the prior art material ET4, it can make Organic components reduce power consumption, increase efficiency and half-life time.

In summary, the present invention discloses a compound that can be used in organic EL elements. The invention also discloses an organic EL device, which can be applied to a fluorescent light-emitting host, a phosphorescent light-emitting host, etc. using the aforementioned compound. The mentioned organic compounds have the chemical structure represented by formula (I): Formula (I) where A represents a phenyl group or a substituted or unsubstituted fused ring hydrocarbon unit having two to four rings, and L represents a single bond or a substituted or unsubstituted group having 6 to 30 ring carbon atoms Ar ₁ and Ar ₂ independently represent a group selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthryl, Substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, and substituted or unsubstituted ketyl; R ₁ to R ₃ independently represent a hydrogen atom with 1 to 20 carbons Substituted or unsubstituted alkyl groups of atoms, substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, substituted or unsubstituted aralkyl groups having 6 to 30 carbon atoms and having A group of substituted or unsubstituted heteroaryl groups of 3 to 30 carbon atoms.

The above is only the preferred embodiments of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed in the preferred embodiments as above, it is not intended to limit the present invention. As a general knowledge person, within the scope of not departing from the technical solution of the present invention, equivalent embodiments with slight alterations or equivalent changes can be made using the technical content disclosed above, but any content that does not depart from the technical solution of the present invention is based on this Any simple modifications, equivalent changes, and modifications made to the above embodiments by the technical essence of the invention still fall within the scope of the technical solution of the present invention.

6‧‧‧Transparent electrode

7‧‧‧hole injection layer

8‧‧‧Electric tunnel transmission layer

9‧‧‧luminous layer

10‧‧‧hole barrier

11‧‧‧Electronic transmission layer

12‧‧‧Electron injection layer

13‧‧‧Metal electrode

FIG. 1 shows a schematic diagram of an embodiment of the organic EL device of the present invention.

Claims (18)

A compound having the structure represented by the following formula (I):

Where A represents a phenyl group or a substituted or unsubstituted fused ring hydrocarbon unit having two to four rings, and L represents a single bond or a substituted or unsubstituted divalent subvalent group having 6 to 30 ring carbon atoms Aryl; Ar ₁ and Ar ₂ independently represent selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthryl, substituted or unsubstituted Substituted phenanthrenyl, substituted or unsubstituted pyrenyl, and substituted or unsubstituted chrysenyl group, and when L is a single bond, at least one of Ar ₁ and Ar ₂ is substituted Or unsubstituted anthracenyl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, or substituted or unsubstituted ketyl; R ₁ to R ₃ independently represent selected from The group consisting of hydrogen atoms, halogens, and substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms. The compound according to claim 1, wherein L is further represented as one selected from the group consisting of:

The compound according to claim 1, wherein Ar _{1 is} further represented as one selected from the group consisting of:

The compound according to claim 1, wherein Ar _{2 is} further represented as one selected from the group consisting of:

The compound according to claim 1, further having a structure represented by the following formula (II) or formula (III):

Where L represents a single bond or a substituted or unsubstituted divalent arylene group having 6 to 30 ring carbon atoms, Ar ₁ and Ar ₂ independently represent a group selected from substituted or unsubstituted phenyl, Substituted or unsubstituted naphthyl, substituted or unsubstituted anthryl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, and substituted or unsubstituted ketyl ( chrysenyl group), and when L is a single bond, at least one of Ar ₁ and Ar ₂ is substituted or unsubstituted anthryl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted Pyrene, or substituted or unsubstituted ketyl; R ₁ to R ₃ independently represent selected from the group consisting of hydrogen atoms, halogens, and substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms Formed groups. The compound according to claim 5, wherein L is further represented as one selected from the group consisting of:

The compound according to claim 5, wherein Ar _{1 is} further represented as one selected from the group consisting of:

The compound according to claim 5, wherein Ar _{2 is} represented as one selected from the group consisting of the following groups:

The compound according to any one of claims 1 to 8, which is further expressed as one of the structures represented by the following general formulas:

as well as

An organic electroluminescence element, comprising a pair of electrodes, at least one light-emitting layer and one or more organic thin film layers, wherein the pair of electrodes is composed of a cathode and an anode, the at least one light-emitting layer and the one or more organic thin films The layer is provided between the cathode and the anode of the pair of electrodes, and the at least one light-emitting layer includes a compound as described in any one of claims 1 to 9. The organic electroluminescence device according to claim 10, wherein the at least one light-emitting layer is a host material. The organic electroluminescence device according to claim 10, wherein the at least one light-emitting layer is a fluorescent emitter. The organic electroluminescence device according to claim 10, wherein the light emitted by the at least one light-emitting layer includes blue or green fluorescent light. The organic electroluminescence device according to claim 10, wherein the one or more organic thin film layers are electron transport layers, and include at least one selected from the group consisting of the following compounds:

The organic electroluminescence device according to claim 10, wherein the at least one light-emitting layer includes a phosphorescent host, and the phosphorescent host includes the following compounds:

An organic light-emitting device comprising the organic electroluminescence element according to any one of claims 10 to 15. A light-emitting panel comprising the organic electroluminescence element according to any one of claims 10 to 15. A backlit flat panel comprising the organic electroluminescence element according to any one of claims 10 to 15.