The electroluminescent material containing an organic luminescent substance

 

(57) Abstract:

The invention relates to electroluminescent materials containing organic fluorescent substance. Describes a new electroluminescent material consisting of e an injecting layer, an active luminescent layer based on chelate complex of a metal, a hole-transport layer and the hole-an injecting layer, characterized in that the luminescent layer contains a complex of metal and its derivative N,N'-bis (2-hydroxybenzylidene)-1,2-phenylenediamine of the formula /I/, where M = Zn, Cd, Mg; R1- R4independently from each other - H, C1- C5- n-alkyl, isopropyl, tert-butyl, phenyl, unsubstituted or substituted with halogen, stands, tert-bootrom, a methoxy group, ethoxypropane, dimethylaminopropoxy, diethylaminopropyl, 1-naphthyl, 2-naphthyl, nitrile group; R5- H, C1- C5- n - alkyl; R6- H, C1- C4- n - alkyl; R7- R8independently from each other - H, C1- C18- n-alkyl, unsubstituted phenyl, C1- C8- n-alkoxygroup, dimethylaminopropan; R7+ R8= -(CH2)nwhere n = 3 to 5; R7+ R8= C(CH3)2- (CH2)2- C (CH3spectrum with increased thermostability. 2 C. p. F.-ly.

The invention relates to electroluminescent material containing an organic fluorescent substance.

Known electroluminescent material (ELM), containing a luminescent layer evaporated layer of organic compounds - 8- aluminum [C. W. Tang, S. A. Van Slike, Appl. Phys. Letter v.51, pp. 913-915 (1987)] . At the same time as the hole-an injecting layer (anode) is applied transparent low-resistance layer based on a mixed oxide of indium and tin, In2O3- SnO2(ITO), and as electron-an injecting layer (cathode) - alloy Mg-Ag.

The closest to the technical nature of the present device is ELM, consisting of electron-an injecting layer (cathode) (alloy Mg-In, in a mass ratio of 10: 1), an active luminescent layer, hole-transport layer containing N,N'-diphenyl-N,N'-(3-were)-1,1'-biphenyl-4,4'- diamine (TPD) and hole-an injecting layer (anode) (In2O3- SnO2), which contains as an active luminescent layer chelate zinc bis-salicylaldimine ligands (1-AZM-Hex).

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1AZM-Hex is a chelate salt, which is sublimated in a vacuum without lady blue electroluminescence with a maximum at 462 nm, which is proportional to the current density in the range of 10-102mA/cm2and spectra of photo- (max= 461 nm) and electroluminescence are almost identical. [Y. Hamada et al., Blue electroluminescence in thin films of azomethin-zinc complexes, Japanese Journal of Applied Physics, Part 2, vol. 32, no.4 A, 1 April 1993, pp.L511-L513]. Though fluorescent substance 1-AZM-Hex has a high heat resistance (melting point 360oC), but the morphology of the hole-transport layer, consisting of TPD varies even at room temperature due to a low glass transition temperature (< 60oC). Heating during operation of the device leads to a change in the electrical transport properties of the layer and, as a consequence, the loss of the electroluminescence device, i.e. the loss of life of the device.

The present invention is the creation of electroluminescent material with radiation in the green region of the spectrum with increased thermostability.

The problem is solved by the fact that according to the invention the electroluminescent material consisting of electron-an injecting layer, an active luminescent layer containing a complex of the metal and its derivative N,N'-bis(2-hydroxybenzylidene)- 1,2-phenylenediamine, hole-transport layer and hole-injecti the Loy

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where M= Zn, Cd, Mg, R1-R4independently from each other H, C1-C5- n-alkyl, isopropyl, tert-butyl, phenyl, unsubstituted or substituted by: halogen, stands, tert.bootrom, a methoxy group, ethoxypropane, dimethylaminopropoxy, diethylaminopropyl, 1-naphthyl, 2-naphthyl, nitrile group;

R5- H, C1-C5- n-alkyl;

R6- H, C1-C4- n-alkyl;

R7-R8- independently from each other - H, C1-C18- n-alkyl, unsubstituted phenyl, C1-C8- n-alkoxygroup, dimethylaminopropan;

R7+ R8= - (CH2)n-, where n=3-5;

R7+ R8= C(CH3)2-(CH2)2- C(CH3)2-

Introduction disubstituted phenyl ring between the nitrogen atoms, instead of the alkyl chain in the prototype increases the coupling and leads to the shift of the maximum radiation in the long wavelength region. Group R1-R8do not change the ability of a substance to the electroluminescence, but affect its solubility in organic solvents and allow small shift of the maximum wavelength of the photo - and electroluminescence, that is, to fine-tune electroluminescent properties.

PR of triphenylamine (PTA) with the General formula

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where n= 8-9, when the molecular-mass distribution: Mn=2332, Mw=3586 and polydispersity Mw/Mn= 1.54, with a high glass transition temperature 185oC compared with TPD, which ensures the preservation of the morphology of the hole-transport layer even at elevated temperatures [Yakushenko I. K., Kaplunov M,, Shamayev S. N., Efimov, O. N., Nikolaev, C., Belov, M. J., Marchenko, E. P., A. Skvortsov,, Voronin, C. A. "a Method for obtaining a mixture of oligotrophication and 3-(4-biphenylyl)-4-(4 - tertbutylphenyl)-5-(4-dimethylaminophenyl)-1,2,4-triazole as materials for electroluminescent devices and electroluminescent device on the basis of their Application for the patent of the Russian Federation N 97118798/04 from 20.11.97, a positive decision from 2.06.98.]

Example 1.

Synthesis of N,N'-bis(2-hydroxybenzylidene)-1,2-phenylenediamine.

In a round bottom flask with a capacity of 150 ml, equipped with a reflux condenser, was placed a solution of 2.7 g (0,0025 mol) of 1,2-phenylenediamine in 65 ml of ethanol, to which was then added a solution of 6.2 g (0,051 mol) of salicylic aldehyde in 10 ml of ethanol. The reaction mixture was heated under reflux to boiling and kept at this temperature for 1 hour. After cooling stood a yellow crystalline precipitate. It at. The output 76% of theoretical (including 1,2-phenylenediamine). TPL163-164oC.

Synthesis of N, N'-bis(2-hydroxybenzylidene)-1,2-phenylenediamine zinc (II), Zn(OB-PDA)

In a round bottom flask with a capacity of 250 ml, equipped with a reflux condenser, magnetic stirrer and addition funnel, was placed a solution of 4.74 g (0.015 mol) of N,N'-bis(2 - hydroxybenzylidene)-1,2-phenylenediamine in 50 ml of ethanol. Then in an inert atmosphere (argon) under continuous stirring to this mixture was added at once a solution of 1.68 g (0.03 mol) of potassium hydroxide in 25 ml of ethanol. The mixture was stirred for 10 min, and then thereto was added dropwise a solution of 3.26 g ZnCl21,5 H2O (0.02 mol) in 20 ml of ethanol. She rolled a yellow precipitate. It was stirred for 20 minutes while heating the mixture to 45-50oC. After cooling the mixture to room temperature the precipitate was filtered, washed successively with ethanol (20 ml), water (3h20 ml), dried in vacuo over potassium hydroxide. Got 4.63 g of the complex of N,N'-bis(2-hydroxybenzylidene)-1,2-phenylenediamine zinc (II). Output 81.2% of theoretical (counting on the ligand). TPL=354-355oC. the IR spectrum (KBr tablet) contains absorption bands with maxima (cm-1): 3075 SL, SL 3050, 3012 Wed, 1615 O., 1610 O., 1584, 1529, 1484 SL, 1462 O. C, 1P, 971 Wed, 942 O. SL, 931 O. SL, 920, 853 Wed, 844 Wed, 786 Wed, 763 CL, 758, 749 O., 739 SL, 700 Wed, 638 sq, 634 Wed, 601 Wed, 586 O. SL, 551 square, 540 sq, 531 Wed, 510 Wed, 493 SL, SL 479, 420 SL. Qualitative denote the intensities of the bands in the IR spectra: acting with - very strong, s - strong, Wed - medium, SL - weak, acting with a very weak PL - shoulder. The presence of bands of stretching vibrations of C-H in the region 3000-3100 cm-1and bands of vibrations of double bond C=C in the field 1500-1600 cm-1confirms the existence of a system of interconnected relations of the carbon-carbon bonds.

Absorption maxima in the UV region for film of Zn(OB-PDA), deposited at 350oC: 243, 297, 398 nm. The maximum photoluminescence (deposited film, stimulating emission 460 nm) is observed at 550 nm, half-width of the spectrum of photoluminescence 70 nm.

Example 2. Synthesis of a mixture of oligomers of triphenylamine for hole-transport layer.

The scheme of synthesis of a mixture of oligomers of triphenylamine(I)

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1) Synthesis of monomer.

4-Methyldiphenylamine received according to [1].

The mixture 66.68 g (30.6 mol) 4-iodine-toluene, 43.94 g (0.26 mol) of diphenylamine, 41.4 g (0.30 mol) of anhydrous K2CO3and 2.0 g of copper powder was heated in 75 ml of nitrobenzene to a boil with continuous stirring boiled under reflux in the course is ltrate by distillation under reduced pressure to remove the benzene, nitrobenzene, the remains of a 4-iodotoluene, and the residue was distilled in vacuum, collecting the fraction boiling at 180-200oC / 3 mm RT. Art. cooling substance was secretarypantyhose. It was purified by chromatographytandem on a short column with Al2O3, eluent benzene : hexane (1: 1), with subsequent crystallization from 90% aqueous acetic acid. Received 47.2 g of pure substances. Output 70.1% of theoretical. So pl. 68.0oC (lit. so pl. 68.8oC [2]).

2) 4,4'-Dibromo-(4"-methyl)triphenylamine was obtained according to the method similar to [3]:

To a solution 28.72 g (0.11 mol) of 4-methyldiphenylamine in 140 ml of diethyl ether, cooled to -10oC, was added in small portions during 2 hours 55 g (0.22 mol) of deoxyribose (receipt, see [4]) with continuous stirring. Initial temperature (-10oC) supported the entire period of addition of the reagent and forth, until the termination of allocation of gaseous HBr (only 2.5-3 hours), after which the mixture was heated to room temperature and left for 24 hours. Then the reaction mixture was treated with 20% aqueous NaOH solution (to pH 8-9 aqueous phase). Separated organic layer was separated by washing with 5% aqueous acetic acid, then water, then drove the solvent under reduced pressure the (1:4 vol.), followed by recrystallization from 90% aqueous acetic acid. Received 38.2 g of the product. Output 82.6% of theoretical. So pl. 107oC. Elemental analysis: found, %: C: 57.37; H: 3.69; Br: 37.22. C19H15NBr2. Calculated, %: C: 57.71; H: 3.62; Br: 38.31.

3) Synthesis of oligomers.

Oligomerization of the monomer [4,4'-dibromo-(4"-methyl)triphenylamine] were conducted according to a modified method [1].

Oligo(4,4'-(4"-methyl)triphenylamine (promoterami), (I).

5.21 g (0.133 mol) of potassium metal was added in small pieces to a solution of 5.54 g (0.058 mol) MgCl2anhydrous 300 ml of dry THF in an atmosphere of dry argon for 0.5 hours. The mixture is then boiled under reflux with continuous stirring for 2 hours (until the formation of fine metal magnesium). The mixture was cooled to room temperature and over a period of 0.5 hours was added a solution 24.52 g (0.059 mol) of 4,4'-dibromo-(4"-methyl)triphenylamine in 50 ml of dry THF. The mixture was stirred at room temperature for 3 hours, then was added 0.35 g of catalyst ([1,3 - bis(diphenylphosphino)propane] Nickel(II)chloride) (dpppNiCl). The mixture spontaneously heated up to the boiling point, which is then maintained for a further 2 hours. By Oh ethanol. Formed small flocculent precipitate yellowish-brown color. It was filtered, washed with portions 4x100 ml of 2% hydrochloric acid, then with water until neutral wash water, dried in vacuum at 50oC. Received 15.95 g of the crude product. It was dissolved in 60 ml of benzene, was filtered from the insoluble residue was poured into 350 ml of hexane. Fallen yellow precipitate was filtered, dried in vacuum at 50oC. Received 6.35 g of the product. The yield of the pure product 39% of theoretical. So pl. 183-187oC. Elemental analysis: found, %: C: 82.18; H: 4.87; N: 5.15; Br: 7.03. Brutto-formula (C18.6H13.2NBr0.24)n. Calculated, %: C: 82.29; H: 5.45; N: 5.05; Br: 7.20. For gross formula (C19H15N)8Br2. Molecular weight distribution: Mn= 1812, Mw= 2802, the polydispersity Mn/Mw= 1.55V. The glass transition temperature (measured on a differential scanning calorimeter DTAS-1300) is equal to 175oC.

5) Dibromononane of oligomer (I):

Oligo(4,4'-(4"-methyl)triphenylamine (dimethylsiloxane) (II)

To a suspension of 4.13 g (0.17 mol) of metallic magnesium in 60 ml of dry THF was added in an argon atmosphere and with continuous stirring 16.1 g (0.11 mol) of methyl iodide with such scores.15 g of the catalyst ([1,3-bis(diphenylphosphino)propane] Nickel(II)chloride) (dpppNiCl2) and a solution of 6.0 g (about 0.003 mol) prosteradlo of oligomer (I) in 95 ml of THF. The reaction mixture was stirred at room temperature for 24 hours, then boiled under reflux for a further 2 hours. Upon cooling the reaction mass was carefully poured into 1.5 l of a 2% solution of hydrochloric acid. Fell precipitate a light yellow color. It was washed successively with 2% hydrochloric acid, water, ammonium hydroxide, water, then dried in vacuum at 50oC. Received 5.54 g of dry product. Cleaning: previously obtained product was dissolved in 60 ml of benzene and was chromatographically on a short column of silica gel (eluent benzene). The collected eluate was concentrated to a volume of about 40 ml and poured with stirring into 100 ml of hexane. Fell light yellow precipitate. It was filtered, washed with hexane, dried in vacuum at 50oC. Received 3.47 g of substance. The yield of the pure product 61.4% of theoretical. Melting point 206-210oC. the glass transition Temperature by the method of differential thermal analysis 185oC. Elemental analysis: found, %: C: 88.47; H: 5.71; N: 5.83. For gross formula (C17.7H13.6N)ncalculated, %: C: 88.56; H: 6.08, N: 5.36. For gross formula (C19H15N)8(CH3w/Mn=1.54. UV absorption spectrum (solution in chloroform) 313.372 nm.

Example 3. The electroluminescent material is ITO/PTA/Zn(OB-PDA)/Mg:Ag.

For the manufacture of electroluminescent devices with the structure ITO/PTA/Zn(OB-PDA)/Mg:Ag, where ITO - hole-an injecting layer, PTA - hole-transport layer, Zn(OB-PDA) - electroluminescent layer and Mg:Ag - electron-an injecting layer, use a glass substrate with a transparent layer of a mixed oxide of indium and tin with resistance 20-25 Ohms/square, which by centrifuging from a solution in toluene put a layer of PTA thickness of 0.05-0.1 μm. Then, by vacuum evaporation of Zn(OB-PDA) obtained in example 1, at a temperature of about 350oC and a base pressure of 5 10-6mm RT. Art. cause the active electroluminescent layer thickness of 0.02-0.05 micron. The sample is placed in a vacuum installation VUP-4, pump out in a dynamic mode to vacuum 5 10-6mm RT.article and sprayed metal electrode by evaporation of an alloy containing magnesium (90 wt%), and silver (10 wt.%). The thickness of the metal electrode is about 0.1 μm. The area of the illuminated surface of 4-5 mm2. Received ELU has the following parameters: brightness 480 CD/m2is achieved at a voltage of 11.8 V and PLA material, containing electroconductive layer, an active luminescent layer based on chelate complex of a metal, a hole-transport layer and hole-an injecting layer, characterized in that the luminescent layer contains a complex of metal and its derivative N, N1bis(2-hydroxybenzylidene)-1,2-phenylenediamine of the formula

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where M is Zn, Cd, Mg;

R1- R4independently from each other - H, C1- C5-n-alkyl, isopropyl, tert-butyl, phenyl, unsubstituted or substituted with halogen, stands, tert-bootrom, a methoxy group, ethoxypropane, dimethylaminopropoxy, diethylaminopropyl, 1-naphthyl, 2-naphthyl, nitrile group;

R5- H, C1- C5-n-alkyl;

R6- H, C1- C4-n-alkyl;

R7and R8independently from each other - H, C1- C18-n-alkyl, unsubstituted phenyl, WITH1- C8-n-alkoxygroup, dimethylaminopropan;

R7+ R8= -(CH2)-nwhere n=3-5, R7+ R8= C(CH3)2- (CH2)2- C(CH3)2-.

2. The electroluminescent material under item 1, characterized in that n,N1bis(2-hydroxybenzylidene)-1,2-phenylendiamin the layer contains a mixture of oligomers of triphenylamine formula

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where n = 8 - 9

when the molecular-mass distribution Mn= 2332, Mw= 3586.

 

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