Triphenylamine derivative and use therefor

Abstract

A triphenylamine derivative represented by formula (1) exhibits good solubility in an organic solvent and allows an organic EL element having excellent luminance characteristics to be achieved when formed into a thin film and applied to a positive hole injection layer. ##STR00001##
(In the formula, R.sup.1 to R.sup.17 mutually independently represent a hydrogen atom, a halogen atom, a nitro group, a cyano group, an amino group, an aldehyde group, a hydroxyl group, a thiol group, a carboxylic acid group, and the like; and l, m, and n mutually independently represent an integer 1 to 5.)

Claims

1. A triphenylamine derivative characterized by having formula (1) ##STR00014## wherein R.sup.1 to R.sup.17 are each independently a hydrogen atom, a halogen atom, a nitro group, a cyano group, an amino group, an aldehyde group, a hydroxyl group, a thiol group, a carboxyl group, an alkyl group of 1 to 20 carbons which may be substituted with Z.sup.1, an alkenyl group of 2 to 20 carbons which may be substituted with Z.sup.1, an alkynyl group of 2 to 20 carbons which may be substituted with Z.sup.1, an aryl group of 6 to 20 carbons which may be substituted with Z.sup.2, a heteroaryl group of 2 to 20 carbons which may be substituted with Z.sup.2, —NHY.sup.1, —NY.sup.2Y.sup.3, —C(O)Y.sup.4, —OY.sup.5, —SY.sup.6, —C(O)OY.sup.7, —OC(O)Y.sup.8, —C(O)NHY.sup.9 or —C(O)NY.sup.10Y.sup.11, Y.sup.1 to Y.sup.11 are each independently an alkyl group of 1 to 20 carbons which may be substituted with Z.sup.1, an alkenyl group of 2 to 20 carbons which may be substituted with Z.sup.1, an alkynyl group of 2 to 20 carbons which may be substituted with Z.sup.1, an aryl group of 6 to 20 carbons which may be substituted with Z.sup.2, or a heteroaryl group of 2 to 20 carbons which may be substituted with Z.sup.2, in which Z.sup.1 is a halogen atom, a nitro group, a cyano group, an amino group, an aldehyde group, a hydroxyl group, a thiol group, a sulfonic acid group, a carboxyl group, an aryl group of 6 to 20 carbons which may be substituted with Z.sup.3, or a heteroaryl group of 2 to 20 carbons which may be substituted with Z.sup.3; Z.sup.2 is a halogen atom, a nitro group, a cyano group, an amino group, an aldehyde group, a hydroxyl group, a thiol group, a sulfonic acid group, a carboxyl group, an alkyl group of 1 to 20 carbons which may be substituted with Z.sup.3, an alkenyl group of 2 to 20 carbons which may be substituted with Z.sup.3, or an alkynyl group of 2 to 20 carbons which may be substituted with Z.sup.3; Z.sup.3 is a halogen atom, a nitro group, a cyano group, an amino group, an aldehyde group, a hydroxyl group, a thiol group, a sulfonic acid group or a carboxyl group; and the letters l, m, and n are each independently integers from 1 to 5.

2. The triphenylamine derivative of claim 1, wherein R.sup.1 to R.sup.17 are all hydrogen atoms.

3. A charge-transporting substance consisting of the triphenylamine derivative of claim 1 or 2.

4. A charge-transporting material comprising the charge-transporting substance of claim 3.

5. A charge-transporting varnish comprising the charge-transporting substance of claim 3, a dopant substance and an organic solvent.

6. A charge-transporting thin-film produced using the charge-transporting varnish of claim 5.

7. An electronic device comprising a positive electrode, the charge-transporting thin-film of claim 6 stacked on said positive electrode, and a hole transport layer or an emissive layer stacked on said charge-transporting thin-film.

8. An organic electroluminescence device comprising a positive electrode, the charge-transporting thin-film of claim 6 stacked on said positive electrode, and a hole transport layer or an emissive layer stacked on said charge-transporting thin-film.

9. A method of producing a charge-transporting thin-film, characterized by coating the charge-transporting varnish of claim 5 onto a substrate and evaporating off the solvent.

10. A method of producing the triphenylamine derivative of claim 1, comprising the step of reacting the triphenylamine compound of formula (2) with compounds having the diphenylamine structures of formulas (3) to (5) ##STR00015## wherein X.sup.1 to X.sup.3 are each independently a halogen atom or a pseudo-halogen group, and R.sup.1 to R.sup.17 and the letters l, m and n are as defined above in the presence of a catalyst.

Description

EXAMPLES

(1) Synthesis Examples and Working Examples are given below to more concretely illustrate the invention, although the invention is not limited by these Examples. The equipment used was as follows.

(2) (1) .sup.1H-NMR Measurement:

(3) JNM-ECP300 FT NMR System, from JEOL, Ltd.
(2) Substrate Cleaning: Substrate cleaning machine (reduced-pressure plasma system), from Choshu Industry Co., Ltd.
(3) Varnish Coating: MS-A100 Spin Coater, from Mikasa Co., Ltd.
(4) Film Thickness Measurement: Surfcorder ET-4000 microfigure measuring instrument, from Kosaka Laboratory, Ltd.
(5) EL Device Fabrication: C-E2L1G1-N Multifunction Vapor Deposition System, from Choshu Industry Co., Ltd.
(6) Measurement of EL Device Brightness, etc.: I-V-L Measurement System from Tech World, Inc.
(7) EL Device Lifetime Measurement (half-life measurement): PEL-105S Organic EL Brightness Life Evaluation System, from EHC K.K.

[1] Synthesis of Compounds

[Synthesis Example 1] Synthesis of Arylsulfonic Acid Compound A

(4) The Arylsulfonic Acid Compound A (formula (11)) used in the Examples was synthesized by the following reaction, based on the description provided in International Disclosure WO 2006/025342.

(5) ##STR00011##

(6) That is, 4.797 g (14.36 mol) of perfluorobiphenyl, 4.167 g (30.15 mol) of potassium carbonate and 100 mL of N,N-dimethylformamide were successively added to 11 g (31.59 mmol) of thoroughly dried sodium 1-naphthol-3,6-disulfonate and the reaction system was flushed with nitrogen, following which six hours of stirring was carried out at an internal temperature of 100° C.

(7) The system was allowed to cool to room temperature, then an additional 500 mL of N,N-dimethylformamide was added and 90 minutes of stirring was carried out at room temperature in order to re-dissolve the Arylsulfonic Acid Compound A that had precipitated out following the reaction. After stirring at room temperature, this solution was filtered to remove the potassium carbonate residue, and was concentrated under reduced pressure. In addition, to remove remaining impurities, 100 mL of methanol was added to the residue and room temperature stirring was carried out. After 30 minutes of stirring at room temperature, the suspension was filtered, giving a residue. The residue was then dissolved by adding thereto 300 mL of ultrapure water, and the resulting solution was ion-exchanged by column chromatography using Dowex 650C cation-exchange resin (from Dow Chemical; about 200 mL of H-type; distillation solvent: ultrapure water).

(8) The fraction at or below pH 1 was concentrated to dryness in vacuo and the residue was dried to hardness in vacuo, giving 11 g of a yellow powder (yield, 85%).

(9) .sup.1H-NMR (300 MHz, DMSO-d6):

(10) δ 7.18 (1H, s, Ar—H), 7.89 (1H, d, Ar—H), 8.01 (1H, s, Ar—H), 8.23 (1H, s, Ar—H), 8.28 (1H, d, Ar—H)

Synthesis Example 2

(11) The 4′-bromo-N-phenyl-[1,1′-biphenyl]-4-amine (formula (12)) used in Synthesis Example 3 was synthesized by the following reaction.

(12) ##STR00012##

(13) A flask was charged with 20 g of 4-bromo-4′-iodo-1,1′-biphenyl, 3.2 g of tetrakis(triphenylphosphine)palladium and 6.4 g of sodium t-butoxide and flushed with nitrogen, following which 200 mL of toluene and 6.1 g of aniline were added and stirring was carried out for 6.5 hours under refluxing conditions. The system was allowed to cool to room temperature, after which ion-exchanged water and chloroform were added and liquid-liquid extraction was carried out. The resulting organic phase was dried over sodium sulfate and then concentrated. The resulting residue was dissolved by adding chloroform thereto, then was separated and purified by column chromatography. The fractions containing the target substance were collected and concentrated. The powder thus obtained was re-crystallized, giving 11 g of 4′-bromo-N-phenyl-[1,1′-biphenyl]-4-amine.

(14) .sup.1H-NMR (300 MHz, CDCl.sub.3):

(15) δ 7.53-7.40 (m, 6H), 7.32-7.26 (m, 2H), 7.11 (d, d=8.6 Hz, 4H), 6.99-6.94 (t, d=7.4 Hz, 1H), 5.78 (s, 1H)

Synthesis Example 3

(16) Triphenylamine Derivative B (formula (13)) used in the Examples was synthesized by the following reaction.

(17) ##STR00013##

(18) A flask was charged with 0.81 g of tris(4-aminophenyl)-amine, 3.0 g of 4′-bromo-N-phenyl-[1,1′-biphenyl]-4-amine, 0.24 g of bis(dibenzylideneacetone) palladium, 0.35 g of 1,1′-bis(diphenylphosphino)ferrocene (DPPF) and 1.1 g of sodium t-butoxide, then flushed with nitrogen, after which 73 mL of toluene was added and stirring was carried out for 5 hours at 80° C. The system was allowed to cool to room temperature, and then was filtered. The residue thus obtained was dissolved in THF, the solution was filtered to remove impurities, and the resulting filtrate was concentrated. The residue was dissolved by adding 15 mL of THF thereto, and 2.6 g of the target triphenylamine derivative was obtained by re-precipitation.

(19) .sup.1H-NMR (300 MHz, DMSO-d6):

(20) δ 8.18 (s, 3H), 8.09 (s, 3H), 7.49-7.45 (m, 12H), 7.25-7.20 (m, 6H), 7.12-7.04 (m, 24H), 6.94 (d, d=8.6, 6H), 6.81 (t, d=7.1 Hz, 3H).

[2] Preparation of Charge-Transporting Varnish

Example 1-1

(21) Triphenylamine Derivative B (0.074 g) and 0.297 g of phosphotungstic acid (abbreviated below as “PTA”) were dissolved in 4 g of 1,3-dimethyl-2-imidazolidinone (abbreviated below as “DMI”) under a nitrogen atmosphere. Cyclohexanol (6 g; abbreviated below as “CHA”) and 2 g of propylene glycol (abbreviated below as “PG”) were added to the resulting solution and stirring was carried out, thereby preparing a charge-transporting varnish.

Examples 1-2 to 1-4

(22) Aside from setting the amounts in which Triphenylamine Derivative B and PTA were used to, respectively, 0.620 g and 0.309 g (Example 1-2), 0.053 g and 0.318 g (Example 1-3), and 0.034 g and 0.337 g (Example 1-4), charge-transporting varnishes were prepared in the same way as in Example 1-1.

Example 1-5

(23) Triphenylamine Derivative B (0.210 g) and 0.279 g of Arylsulfonic Acid Compound A were dissolved in 8 g of DMI under a nitrogen atmosphere. CHA (12 g) and 4 g of PG were added to the resulting solution and stirring was carried out, thereby preparing a charge-transporting varnish.

Example 1-6

(24) Triphenylamine Derivative B (0.123 g) and 0.245 g of Arylsulfonic Acid Compound A were dissolved in 6 g of DMI under a nitrogen atmosphere. CHA (9 g) and 3 g of PG were added to the resulting solution and stirring was carried out, thereby preparing a charge-transporting varnish.

Examples 1-7 and 1-8

(25) Aside from setting the amounts in which Triphenylamine Derivative B and Arylsulfonic Acid Compound A were used to, respectively, 0.101 g and 0.267 g (Example 1-7), and 0.085 g and 0.282 g (Example 1-8), charge-transporting varnishes were prepared in the same way as in Example 1-6.

Examples 1-9

(26) Triphenylamine Derivative B (0.124 g) and 0.619 g of PTA were dissolved in 8 g of DMI under a nitrogen atmosphere. CHA (12 g) and 4 g of PG were added to the resulting solution and stirring was carried out, after which 0.022 g of pentafluorophenyltriethoxysilane was added and further stirring was carried out, thereby preparing a charge-transporting varnish.

Example 1-10

(27) Aside from using 0.025 g of 3,3,3-trifluoropropyltrimethoxysilane and 0.049 g of phenyltrimethoxysilane instead of 0.022 g of pentaphenyltriethoxysilane, a charge-transporting varnish was prepared in the same way as in Example 1-9.

[3] Fabrication of Organic EL Devices and Evaluation of Device Characteristics

Example 2-1

(28) The varnish obtained in Example 1-1 was coated onto an ITO substrate using a spin coater, then dried at 50° C. for 5 minutes and baked in an open-air atmosphere at 230° C. for 10 minutes, thereby forming a uniform 30 nm thin-film on the ITO substrate. A 25 mm×25 mm×0.7 mm (t) glass substrate with indium-tin oxide (ITO) patterned on the surface to a film thickness of 150 nm was used as the ITO substrate. Prior to use, impurities on the surface were removed with an O.sub.2 plasma cleaning system (150 W, 30 seconds).

(29) Next, using a vapor deposition system (degree of vacuum, 1.0×10.sup.−5 Pa), thin-films of N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (α-NPD), tris(8-quinolinolate)aluminum(III) (Alq.sub.3), lithium fluoride and aluminum were successively deposited on the ITO substrate on which a thin-film had been formed, thereby giving an organic EL device. Vapor deposition was carried out at a rate of 0.2 nm/s for α-NPD, Alq.sub.3 and aluminum, and at a rate of 0.02 nm/s for lithium fluoride. The film thicknesses were set to, respectively, 30 nm, 40 nm, 0.5 nm and 120 nm.

(30) To prevent the device characteristics from deteriorating due to the influence of oxygen, moisture and the like in air, the organic EL device was sealed with sealing substrates, after which the characteristics were evaluated. Sealing was carried out by the following procedure.

(31) The organic EL device was placed between sealing substrates in a nitrogen atmosphere having an oxygen concentration of not more than 2 ppm and a dew point of not more than −85° C., and the sealing substrates were laminated together using an adhesive (XNR5516Z-B1, from Nagase ChemteX Corporation). A desiccant (HD-071010W-40, from Dynic Corporation) was placed, together with the organic EL device, within the sealing substrates at this time.

(32) The laminated sealing substrates were irradiated with UV light (wavelength, 365 nm; dosage, 6,000 mJ/cm.sup.2), then annealed at 80° C. for 1 hour to cure the adhesive.

Examples 2-2 to 2-8

(33) Aside from using the varnishes obtained in Examples 1-2 to and 1-8 instead of the varnish obtained in Example 1-1, organic EL devices were fabricated in the same way as in Example 2-1.

Example 2-9

(34) Aside from baking at 150° C. for 10 minutes instead of baking at 230° C. for 10 minutes, an organic EL device was fabricated in the same way as in Example 2-1.

Examples 2-10 to 2-13

(35) Aside from using the charge-transporting varnishes obtained in Examples 1-2, 1-3, 1-9 and 1-10 instead of the varnish obtained in Example 1-1, organic EL devices were fabricated in the same way as in Example 2-9.

(36) The current densities and brightnesses of the devices fabricated in each of the above Examples were measured at a driving voltage of 5 V. The results are shown in Table 1. As shown in Table 1, when a charge-transporting varnish according to the invention was used, EL devices having excellent brightness characteristics were obtained, not only when baked at a relatively high temperature of 230° C., but even when baked at a relatively low temperature of about 150° C.

(37) TABLE-US-00001 TABLE 1 Current Charge- Baking Current Bright- effi- transporting temper- density ness ciency varnish ature (mA/cm.sup.2) (cd/m.sup.2) (cd/A) Example 2-1 Example 1-1 230° C. 80 2,223 2.8 Example 2-2 Example 1-2 230° C. 86 2,371 2.8 Example 2-3 Example 1-3 230° C. 86 2,359 2.8 Example 2-4 Example 1-4 230° C. 73 2,054 2.8 Example 2-5 Example 1-5 230° C. 120 3,280 2.7 Example 2-6 Example 1-6 230° C. 67 2,001 3.0 Example 2-7 Example 1-7 230° C. 67 2,030 3.0 Example 2-8 Example 1-8 230° C. 62 1,788 2.9 Example 2-9 Example 1-1 150° C. 80 2,299 2.9 Example 2-10 Example 1-2 150° C. 87 2,546 2.9 Example 2-11 Example 1-3 150° C. 87 2,525 2.9 Example 2-12 Example 1-9 150° C. 179 4,609 2.6 Example 2-13 Example 1-10 150° C. 157 3,873 2.5

(38) Durability tests (for measuring lifetime) were carried out on the devices fabricated in Examples 2-1 to 2-6 and 2-9. Table 2 shows the brightness half-lives (initial brightness, 5,000 cd/m.sup.2). As shown in Table 2, organic EL devices provided with charge-transporting thin-films obtained from the charge-transporting varnishes of the invention had excellent durabilities.

(39) TABLE-US-00002 TABLE 2 Half-life (hours) Example 2-1 355 Example 2-2 335 Example 2-3 358 Example 2-4 207 Example 2-5 197 Example 2-6 181 Example 2-9 240