KR100466494B1 - Organic electroluminescent device - Google Patents

Abstract

The present invention relates to an organic electroluminescent device comprising a polyarylamine-based polymer having the formula (1) in the hole transport layer. The organic electroluminescent device according to the present invention has excellent durability due to the hole transport polymer described below.

In Chemical Formula 1,

R ₁ and R ₂ are each independently C _1-12 hydrocarbyl, C _1-12 alkoxy, C _1-12 thioalkoxy, C _1-12 aryloxy, C _1-12 thioaryloxy, or —CO ₂ R ₃ Where R ₃ is hydrogen or C _1-12 alkyl, Ar is a carbazole, phenothiazine, phenoxazine moiety, X is independently hydrogen or halogen, and x is a positive number between 0 and 1 ( x + y = 1), a and b are each independently an integer between 0 and 4, and m is an integer between 1 and 1000.

Description

Organic electroluminescent device {ORGANIC ELECTROLUMINESCENT DEVICE}

The present invention relates to an organic electroluminescent device comprising a polyarylamine compound as a hole transporting polymer. More specifically, the present invention relates to an organic electroluminescent device comprising a polyarylamine hole transporting polymer having excellent stability in the hole transport layer of the organic electroluminescent device.

The structure of a general organic electroluminescent device is mostly the form shown in FIG. The anode of a typical organic electroluminescent device consists of indium tin oxide (ITO), followed by N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4, 4'-diamine (TPD) is vacuum deposited to form a hole transport layer. The electron transport layer and the light emitting layer are then formed by vacuum deposition of aluminum tris-8-hydroxyquinoline (Alq 3). Finally, the cathode is made by vacuum evaporation with magnesium and silver (9: 1), and then a protective layer is made by UV curing, and a voltage is applied to measure the emission of green light. In addition to the above methods, many studies have been conducted, such as introducing various single molecules or changing the structure of devices. Such examples are known in the following documents. United States Patent 4,356,429 (Tang et al.), United States Patent 4,539,507 (VanSlyke et al.), United States Patent 5,047,687 (VanSlyke et al.), United States Patent 5,059,862 (VanSlyke et al.), Jounal of Applied Physics 65 (9), 1989 , 3610 and the like.

One of the problems of the present organic electroluminescent device is the lifetime of the device. In general, the organic electroluminescent device takes only about 30 hours before the light emission disappears. Therefore, many studies have been conducted to overcome these problems and obtain a better life. For example, Adachi et al. Used an aromatic tertiary amine in the hole transport layer to confirm that the lifetime of the device ranges from several hours to 500 hours depending on the amine type. (AppliedPhysics Letters 66, 1995, 2679-2681) Adachi et al. The device using the amine with the smallest energy gap between the anode and the hole transport layer has been reported to have the longest lifetime. Similar examples can be found in US Patent 4,885,211 (Tang et al.), US Patent 5,059,862 (Vanslyke et al.), US Patent 5,374,489 (Imai et al.), And the like.

As another method for improving the life span, U.S. Patent No. 5,306,572 (Oshashi et al.) Focuses on the junctions between the various layers of the organic electroluminescent device to improve the smoothness of the anode layer and the adhesion between the layers. It has been proposed to treat the coupling material in one layer of the device to form a new intermediate layer between the anode and the hole transport layer. Devices treated with these materials have been reported to have lifetimes between 5000 and 8000 hours. However, the reproducibility of such work is uncertain and the cost is very high when applied to production. In addition, U.S. Patent No. 5,719,467 (Antoniadis et al.) Proposes an organic electroluminescent device incorporating a conductive polymer such as polyaniline doped with a camphor-sulphonic acid between the anode and the hole transport layer to improve the lifetime, or the conductive polymer itself as an anode. Also disclosed is a method of use. However, many organic electroluminescent devices have a problem in that the intensity or life of the emitted light is reduced in a high temperature environment, for example, when a device mounted in a car parks for a long time in the summer sun.

The present invention is to solve the above problems and to provide an economical and durable organic electroluminescent device, the object of which is to provide a novel polyarylamine hole transporting polymer having excellent stability to the hole transport layer of the organic electroluminescent device Can be achieved by introduction.

1 is a view schematically showing the structure of a general organic electroluminescent device,

2 is a view showing the structure of an organic electroluminescent device according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11, 21 Substrate 12, 22 ... Anode Transparent Electrode Layer

13 ... hole transport layer 14, 24 ... electron transport layer

15, 25 ... light emitting layer 16, 26 ... metal electrode layer

23.Hole transport polymer 17, 27 ... protective layer

Referring to FIG. 2, the organic electroluminescent device according to the present invention includes a transparent anode electrode, a hole transport layer made of a hole transport polymer, an electron transport layer and a light emitting layer, and a cathode on a substrate. The cathode blocks moisture or oxygen as a protective layer.

The substrate is preferably a glass substrate, the indium tin oxide (ITO) is preferred for the transparent anode, and magnesium or other metal having a work function of less than 5 eV is preferred for the cathode. Aluminum, silver, and gold may be used as the protective layer, and an insulator such as SiO 2, SiN x, or an insulating polymer may be used.

As the electron transport layer and the light emitting layer, an oxynoid compound in which a metal is chelated may be used. In particular, it is more preferable to use aluminum tris-8-hydroxyquinoline (Alq3) which emits green light. For the luminous efficiency of the device, a suitable fluorescent material such as quinacridone may be doped into the electron transport layer and the light emitting layer.

In order to improve the life of the device, the hole transporting polymer of Formula 1 having arylamine having excellent hole transporting capacity in the hole transporting layer of the organic electroluminescent device according to the present invention is employed.

In Formula 1, R ₁ and R ₂ are each independently C _1-12 hydrocarbyl, C _1-12 alkoxy, C _1-12 thioalkoxy, C _1-12 aryloxy, C _1-12 thioaryloxy, or -CO ₂ R ₃ , wherein R ₃ is hydrogen and C _1-12 alkyl. Preferably R 1 is C _1-5 alkoxy, C _1-5 thioalkoxy, C _1-6 hydrocarbyl or —CO ₂ R ₃ , wherein R ₃ is C _1-5 alkyl. More preferably R ₁ is where methoxy, methyl, s-butyl, and —CO ₂ R _{3 is} where R ₃ is methyl, ethyl. Preferably R ₂ is C _1-5 alkoxy, C _1-5 thioalkoxy, C _1-6 hydrocarbyl, more preferably hydrogen, methoxy, methyl, most preferably hydrogen. Ar is preferably a carbazole, phenothiazine or phenooxazine residue, more preferably a carbazole, phenothiazine residue. Each X is independently hydrogen or halogen, preferably hydrogen, chlorine, and bromine. x is a positive number between 0 and 1 (x + y = 1), a and b are each independently an integer between 0 and 4, preferably a is 0 and b is 1. m is an integer between 1 and 1000, preferably between 5 and 500, and more preferably between 5 and 100 yarns.

Arylamine polymers that can be used as the hole transporting polymers of the present invention exhibit strong photoluminescence in diluents or in the solid phase. Exposure of these materials to wavelengths of 300 to 700 nm emits light in the range of 400 to 800 nm. More preferably, these materials absorb light at 350-400 nm and emit light in the 400-650 nm range. Such arylamine polymers are readily soluble in conventional solvents. These can be processed into a thin film or a coating film by conventional techniques.

The arylamine polymer of the present invention has a weight average molecular weight of at least 1000 Daltons, preferably at least 5000 Daltons, more preferably at least 10,000 Daltons, even more preferably at least 15,000 Daltons, most preferably at least 20,000 Daltons Preferably it is 1,000,000 Daltons or less, More preferably, it is 500,000 Daltons or less, Most preferably, it is 100,000 Daltons or less. Molecular weights are determined by gel permeation chromatography using polystyrene standards.

Preferably the polydispersity (Mw / Mn) of the arylamine polymer is at most 5, more preferably at most 4, even more preferably at most 3 and most preferably at most 2.

As used herein, "hydrocarbyl" means a specific organic moiety containing only hydrogen and carbon unless otherwise specified, and those containing one or more aromatic, aliphatic and cycloaliphatic residues and aromatic, aliphatic and cycloaliphatic residues. It may include.

The monomers used for the synthesis of the arylamine polymers are preferably formulas (2) and (3).

In Chemical Formulas 2 and 3, R ₁ , R ₂ , Ar, a, and b are as described above, and X is halogen. The monomer may be prepared by the halogenation reaction of Chemical Formulas 4 and 5 below.

R ₁ , R ₂ , Ar, a and b are as described above.

Formulas 4 and 5 may be prepared by contacting a diarylamine and a haloaromatic compound in the presence of a catalyst. Conditions for this reaction can be found in the literature: Gauthier et al. Synthesis p. 383 (1987), Guram et al. Angewandte Chemie international Edition in English, vol 34, p. 1348 (1995). The diarylamines and haloaromatic compounds are prepared by reacting in the presence of copper powder and potassium carbonate or by contacting them under a catalyst consisting of sodium t-butoxide with palladium and tri-o-tolylphosphine. Preferably, when using copper powder and potassium carbonate, an iodoaromatic compound is used as a reactant. When using a catalyst consisting of sodium t-butoxide, palladium and tri-o-tolylphosphine, it is preferable to use a bromoaromatic compound as a reactant.

The preparation of the arylamine polymer which is preferably used as the hole transporting polymer of the organic electroluminescent device according to the present invention can be represented by Scheme 1.

The arylamine polymers include divalent nickel salts, at least stoichiometric amounts of zinc powder and trisubstituted phosphines, compounds capable of fast reaction in polar solvents, and addition of co-solvents of aromatic hydrocarbons or ethers by addition. It can be prepared through a halide coupling reaction ('polymerization reaction') to be carried out under. Nickel (zero valent) catalyst is formed during the reaction by contacting a divalent nickel salt with a reducing agent in the presence of a substance capable of further reaction with a substance capable of acting as a ligand.

Such arylamine polymers are preferably described in Colon et al., Journal of Polymer Science, Part A, Polymer Chemistry edition, vol 28, p. 367 (1990), Journal of Organic Chemistry, 51, p. 2627 (1986). According to the experimental method of)] may be prepared by contacting the monomers under a nickel catalyst.

The polymerization reaction is carried out under a polar solvent, preferably dimethylformamide, N, N-dimethylacetamide, N-cyclohexylpyrrolidone, or N-methylpyrrolidone. Cosolvents other than amides can be up to 50% by volume. Preferred cosolvents are tetrahydrofuran, aromatic hydrocarbons. The reaction should preferably be carried out in an environment free of oxygen and moisture. Because oxygen destroys the catalyst, moisture can end the polymerization prematurely. More preferably the reaction should be carried out under an inert atmosphere such as nitrogen or argon.

The catalyst is preferably produced in divalent nickel salts. Nickel salts are salts that can be changed to zero valence under reaction conditions. Preferred nickel salts are nickel halides and more preferred are nickel chloride, nickel bromide. The divalent nickel salt is at least 0.01 mole percent, more preferably at least 0.1 mole percent and most preferably 1.0 moleset relative to the monomer. The divalent nickel salt is preferably at most 30 mole percent, more preferably at most 15 mole percent, relative to the monomer.

The nickel catalytic polymerization reaction is carried out under a compound which reduces divalent nickel salts to zero salts. Preferred metals are zinc, magnesium, calcium and lithium. More preferred pill is zinc powder. At least a stoichiometric amount of the reducing agent relative to the nickel amount is necessary to keep the nickel in the zero state throughout the reaction. Preferably the reducing agent is at least about 150 mole percent, more preferably at least 200 mole percent, most preferably at least about 250 mole percent. Preferably the reducing agent is about 500 mole percent or less, more preferably 400 mole percent or less and most preferably about 300 mole percent or less.

The polymerization reaction should have a substance that acts as a ligand. Preferred ligand is trihydrocarbylphosphine. More preferably triaryl or trialkyl, most preferably triphenylphosphine. Preferred amounts are at least about 10 mole percent, more preferably at least 20 mole percent, preferably at most about 100 mole percent, more preferably at most 50 mole percent, most preferably at most about 40 mole percent.

The polymerization reaction is carried out under a temperature at which the reaction proceeds at a reasonable rate. The reaction temperature is preferably about 25 ° C. or more, more preferably 50 ° C. or more, most preferably about 70 ° C. or more, preferably the reaction temperature is about 200 ° C. or less, more preferably 150 ° C. or less, most preferably Is approximately 125 ° C. or less. At temperatures above 200 ° C. the catalyst can be destroyed. The reaction time depends on the reaction temperature, the amount of catalyst and the concentration of the reactants. Preferably it is about 1 hour or more, More preferably, it is 10 hours or more. Preferably the reaction time is about 100 hours or less, more preferably 72 hours or less and most preferably about 48 hours or less.

Alternatively, arylamine polymers can be prepared by the methods described in Ioyada et al., Bulletin of the Chemical Society of Japan, vol 63, p. 80 (1990). This method is similar to the method described below. In particular the catalyst is a divalent nickel salt introduced as a nickel halide bis-triphenylphosphine complex. The reaction can be carried out in a variety of solvents including acetone, dimethylformamide, tetrahydrofuran and acetonitrile. The reaction can be promoted by adding 10 mol% of organic soluble iodide such as tetraethylammonium iodide. This reaction is carried out for 1 to 24 hours at a temperature of 20 to 100 ℃.

In another embodiment, the polymer can be prepared by the method described by Yamamotto et al., Progress in Polymer Science, vol. 17, p. 1153 (1992). In this process, the dihalodiarylamine monomer is at least a stoichiometric amount of a nickel catalyst in the form of a nickel (1,5-cyclooctadiene) complex and at least a stoichiometric amount of 1,5-cyclooctadiene as a ligand. Contact in an inert solvent such as tetrahydrofuran. The reaction is preferably carried out at 70 ° C. or higher for at least 2 days.

In another embodiment, the polymer is described in Miyaura et al., Synthetic Communication, vol. 11, p. 513 (1981) and other documents by Wallow et al., American Chemical Society polymer Preprint vol. 34, (1), p. 1009 (1993). In this method, the dihalodiarylamine monomer is converted to the corresponding diboronic acid by converting it to dirithio- or digrinaddiarylamine and then reacting with trialkylborate. This is described by Rehalin et al., Makromoleculaire Chemie, vol. 191, p. 199-2003 (1990). Dibronic acid is then reacted with dihalodiarylamine monomer in an inert solvent (such as toluene ethanol) for 10 to 100 hours at 70 ° C. or higher in the presence of a catalytic amount of tetrakistriphenylphosphine palladium and the presence of an aqueous base.

The arylamine polymer synthesized by all the above-mentioned methods can be recovered by conventional techniques. Preferred techniques are precipitation and filtration using nonsolvents.

The polyarylamines above form pinholes and grooveless films. Such films may be formed by conventional methods such as spin coating, dip coating, roller coating, draw bar coating, and the like. The composition applied to the substrate by this coating method may be an arylamine polymer dissolved in a conventional organic solvent. Preferred solvents are aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, ketones, ethers and the like. The lower the polarity, the more preferable the solvent. Preferably the composition solution comprises 0.5 to 10 weight percent of the polyarylamine polymer. 0.5 to 5.0 weight percent is preferred for thinner films. This composition is applied to a suitable substrate in a desired manner. The resulting film is even in thickness and is in a preferred form without pinholes.

The following examples are included for illustrative purposes only and do not limit the scope of the claims. Unless stated otherwise, all parts and percentages are parts by weight and percent by weight.

Example 1

N- [4- (N ', N'-diphenylamino) phenyl] carbazole synthesis

Carbazole (2.9 g, 0.017 mol), 4-iodophenyl diphenyl amine (6.65 g, 0.018 mol), copper powder (0.44 g), potassium carbonate (3.05 g), 18-crown-6-ether (0.4 g And nitrobenzene (30 ml) are placed in a reactor with a stirrer and heated at 200 ° C. for 90 hours under nitrogen atmosphere. The hot reaction solution is filtered through celite and evaporated under reduced pressure. The product obtained after evaporation is placed in a column filled with silica gel and passed through hexane to remove color. The product was recrystallized from acetone to give 4.19 g (60%) of the compound.

Example 2

N- [4- {N ', N'-di (bromophenyl) amino} phenyl] carbazole synthesis

A solution of N-bromosuccimid (19.0 g, 0.11 mol) in dimethylformamide (150 ml) was slowly dropped into a solution of the compound (21.73 g, 0.053 mol) in dimethylformamide (150 ml). The reaction temperature does not exceed 50 ° C. Stir for 30 minutes after the addition is complete. The reaction mixture is slowly dropped into 150 ml of water to precipitate the product. After filtration the product was recrystallized in ethanol to give 21.1 g (70%) of the compound.

Example 3

Hole Transport Polymer Synthesis (PDPA-CZ)

Triphenylphosphine (3.9 g, 15 mmol), zinc fine (5.9 g, 90 mmol), nickel chloride-2,2'-bipyridine complex (NiCl ₂ -Bipy) (0.26 g, 0.9 mmol) and N- [4- {N ', N'-di (bromophenyl) amino} phenyl] carbazole (17.0 g, 30 mmol) was added. Vacuum 0.2 mmHg with a vacuum device, and then inject nitrogen. Repeat seven times. N, N'-dimethylacetamide (DMAc) (45 ml) is placed in the reactor. The reaction was stirred at 80 ° C. for two days, and then dichloromethane (100 ml) was added thereto. The reaction solution was filtered through Celite, the filtrate was washed with 3N aqueous HCl solution (300ml) and water (3 × 300ml), dried over MgSO ₄ and distilled under reduced pressure with a rotary evaporator. The residue was dropped in methanol to obtain a yellow precipitate, filtered and washed, and dried in a vacuum oven at 60 ° C. for one day to obtain a hole transport polymer (PDPA-CZ) (8.3 g).

Example 4

Hole Transport Polymer Synthesis (Copolymer)

Triphenylphosphine (3.9 g, 15 mmol), zinc powder (5.9 g, 90 mmol), nickel chloride-2,2'-bipyridine complex (NiCl ₂ -Bipy) (0.26 g, 0.9 mmol) and N- [4- {N ', N'-di (bromophenyl) amino} phenyl] carbazole (8.5 g, 15 mmol) and N, N-di (bromophenyl) -p-anizidine (6.52 g, 15 mmol) is added. Vacuum 0.2 mmHg with a vacuum device, and then inject nitrogen. Repeat seven times. N, N'-dimethylacetamide (DMAc) (45 ml) is placed in the reactor. The reaction was stirred at 80 ° C. for two days, and then dichloromethane (100 ml) was added thereto. The reaction solution was filtered through Celite, the filtrate was washed with 3N aqueous HCl solution (300ml) and water (3 × 300ml), dried over MgSO ₄ and distilled under reduced pressure with a rotary evaporator. The residue was dropped in methanol to obtain a yellow precipitate, filtered and washed, and dried in a vacuum oven at 60 ° C. for one day to obtain a hole transporting polymer (7.5 g). NMR confirmed the 1: 1 copolymer.

Example 5

Hole Transport Polymer Synthesis (PDPA-PT)

Triphenylphosphine (3.9 g, 15 mmol), zinc fine (5.9 g, 90 mmol), nickel chloride-2,2'-bipyridine complex (NiCl ₂ -Bipy) (0.26 g, 0.9 mmol) and N- [4- {N ', N'-di (bromophenyl) amino} phenyl] phenothiazine (18.0 g, 30 mmol) was added. Vacuum 0.2 mmHg with a vacuum device, and then inject nitrogen. Repeat seven times. N-methylpyrrolidone (50 ml) is placed in the reactor. The reaction was stirred at 80 ° C. for two days, and then dichloromethane (100 ml) was added thereto. The reaction solution was filtered through Celite, the filtrate was washed with 3N aqueous HCl solution (300ml) and water (3 × 300ml), dried over MgSO ₄ and distilled under reduced pressure with a rotary evaporator. The residue was dropped in methanol to obtain a yellow precipitate, filtered and washed, and dried in a vacuum oven at 60 ° C. for one day to obtain a hole transporting polymer (PDPA-PT) (6.5 g).

Example 6

General organic electroluminescent device fabrication

The ITO transparent positive electrode coated on the organic substrate is photolithographically patterned according to the patterned form, followed by washing with detergent, acetone and ethanol. The TPD hole transport terminal molecule was vacuum deposited to 600 kPa on the ITO electrode. Then, Alq3 was vacuum deposited to 600 Å thick with the electron transport layer and the light emitting layer. Finally, 1000 Å of magnesium is used as the cathode, and 1000 은 of silver is used as the protective layer.

When the organic electroluminescent device was operated under a constant direct current of 40 mA / cm 2 in a nitrogen dry box, the initial luminance was 1200 cd / m 2 and the voltage was 5.2 V. However, the durability of the device was only about 5 hours.

Example 7

Same as Example 6 except vacuum deposition of TPD. In the hole transport layer, the hole transport polymer (PDPA-CZ) was spin-coated on the ITO electrode at about 1000 mW. In order to remove the remaining solvent was heated for 10 minutes at 120 ℃ and Alq3 was vacuum-deposited.

When the organic electroluminescent device was operated under a constant direct current of 40 mA / cm 2 in a nitrogen dry box, the initial luminance was 400 cd / m 2 and the voltage was 10V. The efficiency of the device was reduced, but no sudden device breakdown was found in approximately 100 hours of continuous operation. The initial luminance was reduced to about 60% and the voltage rose to about 14V. As a result, the efficiency of the device was reduced, but the durability was improved.

By introducing the polyarylamine hole transporting polymer having excellent stability according to the present invention into the hole transporting layer of the light emitting device, there is an advantage that an organic electroluminescent device having economical durability and excellent durability can be manufactured.

Claims (10)

In an organic electroluminescent device comprising a substrate, a transparent electrode, a hole transport layer, an electron transport layer, an organic light emitting layer, and a metal electrode, the hole transport layer is represented by the following Chemical Formula 1 having a weight average molecular weight of 15,000 Daltons or more and 100,000 Daltons or less An organic electroluminescent device comprising an arylamine polymer, wherein the electron transport layer and the light emitting layer comprise a fluorescent dye together with aluminum tris-8-hydroxyquinoline: In Chemical Formula 1, R ₁ and R ₂ are each independently C _1-12 hydrocarbyl, C _1-12 alkoxy, C _1-12 thioalkoxy, C _1-12 aryloxy, C _1-12 thioaryloxy, or —CO ₂ R ₃ Where R ₃ is hydrogen or C _1-12 alkyl, Ar is a carbazole, phenothiazine, phenooxazine moiety, X is halogen, x is a positive integer between 0 and 1 (x + y = 1 a, b are each independently 0 or 1 (where a is 0, all of the substituents on which R ₂ is substituted benzene ring are hydrogen, and when b is 0, R ₁ is a substituent of substituted benzene ring) Is all hydrogen), m is an integer from 5 to 100. The compound of claim 1, wherein R ₁ is methyl, s-butyl, methoxy or —CO ₂ R ₃ , wherein R ₃ is hydrogen, methyl or ethyl, R ₂ is hydrogen, Ar is carbazole, phenoti Are azine residues, each X is independently hydrogen, chlorine or bromine, x is a positive number between 0 and 1 (x + y = 1), a is 0 and b is 0 or 1 (where a is 0) Means that all substituents of R ₂ substituted benzene rings are hydrogen, and when b is 0, all substituents of R ₁ substituted benzene rings are hydrogen), and m is an organic electroluminescent device having an integer between 5 and 100. . The organic electroluminescent device according to claim 1, wherein the arylamine polymer of Chemical Formula 1 is prepared by the following Scheme 1. In Scheme 1, R ₁ , R ₂ , Ar, X, x, a, b and m are as defined in Formula 1 of claim 1. delete delete delete delete delete delete delete