EP2118049A1

EP2118049A1 - Arylamine-substituted divinyl fluorenes and their use for electrophotographic applications, and for oleds (organic light emitting devices)

Info

Publication number: EP2118049A1
Application number: EP07856528A
Authority: EP
Inventors: Rene Csuk; Gunter Mattersteig; Marc Herm
Original assignee: Sensient Imaging Technologies GmbH
Current assignee: Sensient Imaging Technologies GmbH
Priority date: 2006-12-13
Filing date: 2007-12-11
Publication date: 2009-11-18
Also published as: KR20090107032A; JP2010529946A; US8629300B2; WO2008071376A1; US20100094056A1; CN101641321A; DE102006059215A1; JP5385789B2

Abstract

The invention relates to arylamine-substituted divinyl fluorenes. The invention is based on the object of providing photoconductors having good durability, high sensitivity, and low residual potential. The task is to detect new perforated conductors, which can be used in electrophotography, for copying, and in the OLED field. The task is solved by the production of the title compounds, particularly of the formula (11).

Description

Arylamine-substituted divinylfluorenes and their use for electrophotographic applications and for OLEDs (Organic Light Emitting Devices)

The invention relates to novel arylamine derivatives of divinylfluorine and their use for electrophotographic applications and for organic light-emitting diodes and for new materials and active ingredients.

The use of triarylamines in electrophotography is well known. Furthermore, it has been found that triarylamine-derivatized hole-extended hole-hole promoters (defect-electron conductors) obtained by the incorporation of vinyl, butadienyl and styryl groups often have a much higher hole mobility than those without extension (EP795791 to Mitsubishi Chemical). Increasing hole mobility in charge transport materials is fundamental to increasing the efficiency of electrophotography in laser printers and copiers as well as electroluminescence in OLEDs.

It has been found that a small hole mobility in the charge transport layer reduces the sensitivity of the imaging unit of laser printing and copying machines and raises the residual potential (DE19829055). By decreasing the sensitivity and increasing the residual potential, a reduced print density is achieved. It is also known that the hole mobility in the charge transport layer is lowered when the concentration of the charge transport agent in the binder material, which is usually a polycarbonate, is lowered. To circumvent this, the concentration of charge transport material is increased, but this causes faster erosion of the charge transport layer. It has been found that the stated difficulties can be overcome by using a high molecular weight binder resin. However, high molecular weight resins have limited solubility in most solvents, causing defects such as clouding in the photoconductive film when formed by the dipping method. This considerably reduces the productivity of the photoconductor.

It is therefore obvious, hole conductor materials with a much higher hole mobility than the standard hole conductors such as TPD (N ₁ N'-diphenyl-N, N'-di-m-to! Yl-benzidine) or N, N'-diphenyl-N, N'-di-naphth-1-yl-benzidine (α-NPD). Thus, the concentration of charge transport material can be reduced and thus the stability of the hole transport layer can be increased. It is also advantageous that the printing speed is increased by using hole guides with high mobility.

Efficient electroluminescence in heterostructure OLEDs requires balanced hole and electron current densities in the respective charge transport materials. The recombination probability and thus the quantum efficiency of the electroluminescence could be increased considerably if the hole mobility in the hole transport layer is accompanied by the electron mobility in the electron transport layer. The incorporation of additional vinyl, butadienyl and styryl groups in the basic structure of the hole conductors should cause fine tuning of the hole mobility and thus an optimal adaptation to the electron mobilities.

θ.-Dialkyl-NNN'.N'-tetraryl-ΘH-fluorene-1-J-diamines in which the triarylamine group is part of the fluorene backbone and which have bulky sterically demanding substituents to obtain a high glass transition temperature are disclosed in US 2005 / 0067951A1 (Richter, Lischewski, Sensient) claims. These are suitable as hole conductor materials for electrophotography and for OLED applications. New divinylfluorene compounds which find use as optical brighteners, sensitizers for photosensitive materials, or starting materials for polymeric electroluminescent materials are claimed in US2006 / 0022193A1. The subject of this patent is also the synthesis of divinyl fluorene compounds. Starting from fluorene, dialkylation of the C-9 atom is carried out by means of alkyl bromide and sodium hydride. This is followed by reaction with paraformaldehyde and hydrogen bromide in acetic acid to give the corresponding 2,7-bis (bromomethyl) -9,9-dialkylfluorene. This is reacted by means of triethyl phosphite to give 2,7-bis (diethylphosphonatomethyl) -9,9-dialkylfluorene. In a subsequent Wittig-Horner olefination, these are reacted with an aldehyde or ketone in the presence of a base to give the corresponding 9,9-dialkyl-2,7-divinyl-9 / - / - fluorenes.

In DE 102005036696 already carbaldehyde and acrylaldehyde-substituted arylamines and their acetals. as precursors especially for electrophotographic Applications and for OLEDs as well as for new materials and active ingredients.

The aim of the invention is a wear-resistant photoconductor with excellent durability, high sensitivity and low residual potential

The object of the invention is to produce compounds and to propose their use as a hole conductor with substantially improved hole conductor mobility. These compounds should be new as substances or, if known, have not previously been considered for the intended purpose.

The invention is based on the scientific idea of creating new potential hole conductors by introducing groups with readily polarizable π-electrons - such as vinyl groups - into arylamino structures which are in direct conjugation with a fluorene molecule, with high hole conductor mobility and suitability for electrophotographic applications.

Suitable candidates are triarylamine derivatives of divinylfluorene.

The present invention claims as compounds compounds of formula 1 and their use in electrophotography, in OLEDs and for new drugs and materials.

The following definitions apply:

The group Ar in the general chemical formula 1 represents a homoaromatic or heteroaromatic group which may optionally be benzoannelated, for example phenylene, naphthylene, thienylene, furylene or anthracenylene units, if appropriate substituted by alkyl, aryl or arylalkyl groups, biphenylene units according to formula 6, fluorenylene, dibenzofuranylene, dibenzothiophenylene, carbazolylene or dibenzosilolylene units according to formula 7, wherein the unit A is selected from the following structures.

R ¹ and R ² are independently of one another a branched or linear alkyl group (C ¹ to C ² _O alkyl group), a branched or linearly unsaturated hydrocarbon group, a cycloalkyl group (eg cyclohexyl group) or an aryl group (eg phenyl, alkylphenyi, naphthyl, alkylnaphthyl). Biphenylyl, alkylbiphenylyl, stilbenyl or tolanyl group), a branched or linear alkoxy group.

R ³ and R ⁴ are each independently phenyl, alkylphenyi, in particular methylphenyl, biphenylyl, alkylbiphenyl, naphthyl, alkylnaphthyl, phenanthrenyl, alkylphenanthrenyl, anthracenyl, alkylanthracenyl, fluorenyl, alkylfluorenyl, triarylmethyl-aryl or triarylsilyl-aryl.

The compounds can be synthesized according to formula scheme 1.

Paraformaldehyde, HBr P (OEt) ₃

Formula Scheme 1

9,9-Dialkylfluorene 2 is 2,7-bishalomethylated using paraformaldehyde and HBr. The intermediate 3 is reacted in the second step with triethyl phosphite to give the corresponding 2,7-bis (dialkylphosphonatomethyl) -9,9-dialkylfluorene 4, which provides the desired 2,7-divinylfluorene 1 in the third step by reaction with an aromatic aldehyde. These reactions are carried out analogously to the specification in US2006 / 0022193A1. Thus, no procedural protection for the synthesis be raised by divinylfluorenes. However, there is a substance protection for the accessible in this way triarylamine derivatives of 2,7-divinyl-9H-fluorene 1, which are not claimed in US2006 / 0022193A1. For the reactions of Wittig-Horner described therein, no differently substituted diarylaminobenzaldehydes 5, in particular differently substituted diphenylaminobenzaldehyde claimed.

The following applies to the aldehydes of triarylamine 5:

The group Ar in the general chemical formula 5 represents a homoaromatic or heteroaromatic group which may optionally be benzoannelated, for example phenylene, naphthylene, thienylene, furylene or anthracenylene units, optionally substituted by alkyl, aryl or arylalkyl groups, biphenylene units according to formula 6, fluorenylene, dibenzofuranylene, dibenzothiophenylene, carbazolylene or dibenzosilolylene units according to formula 7, wherein the unit A is selected from the following structures.

R ³ and R ⁴ are each independently phenyl, alkylphenyl, in particular methylphenyl, biphenylyl, alkylbiphenyl, naphthyl, alkylnaphthyl, phenanthrenyl, alkylphenanthrenyl, anthracenyl, alkylanthracenyl, fluorenyl, alkylfluorenyl, triarylmethyl-aryl or triarylsilyl-aryl.

In a first embodiment, compounds of formula 8 are claimed:

Where: R ¹ and R ² are each independently a branched or linear alkyl group (C ¹ to C ² _O alkyl group), a branched or linear unsaturated hydrocarbon group, a cycloalkyl group (eg cyclohexyl group) or an aryl group (eg phenyl, alkylphenyl, naphthyl, alkylnaphthyl). Biphenylyl, alkylbiphenylyl, stilbenyl or tolanyl group), a branched or linear alkoxy group.

In a first preferred embodiment, compounds of formula 9 are claimed:

9

Where:

More preferred are compounds of formula 10:

R ¹¹ and R ¹² are each independently H, a branched or linear alkyl group (C 1 to C ₂₀ alkyl group), a branched or linear unsaturated hydrocarbon group, a cycloalkyl group (eg cyclohexyl group) or an aryl group (eg, phenyl, alkylphenyl, naphthyl, alkylnaphthyl, biphenylyl, alkylbiphenylyl, stilbenyl or tolanyl group), a branched or linear alkoxy group.

Even more preferred are compounds of formula 11, wherein:

R ¹¹ and R ¹² are each, independently of one another, H or a methyl group which may be in the ortho-, metha- and para-position to the amino group.

Most preferred is the compound of formula 12 wherein R ¹¹ and R ¹² each represents a methyl group in para position to the amino group.

The invention will be explained by examples.

Example 1: 2,7-bis (bromomethyl) -9,9-dimethylfluorene 3:

Finely powdered 9,9-dimethylfluorene (Sensient, 20.0 g, 102.9 mmol) and paraformaldehyde (15.0 g, 500 mmol) were placed in a 250 ml sulfonation flask with internal thermometer. Then, 100 ml of 33% HBr in glacial acetic acid and a magnetic stir bar were added. The flask was stoppered and stirred for 30 h at 45 ⁰ C. The white solid that formed was filtered off with suction and washed with a little ice-cold water (2 × 25 ml) and ice-cold methanol (2 × 20 ml). Finally, it was recrystallized from glacial acetic acid. After cooling, it was allowed to stand overnight, filtered off with suction and washed again with ice-cold methanol (2 × 20 ml). To standing at room temperature overnight and 8 hours in a drying oven at 70 ^° C., 25.02 g (65.8 mmol, 64%) of a white solid were obtained (TLC: cyclohexane: dichloromethane = 5: 1, R _f = 0, 45).

Example 2: 2,7-bis (diethoxyphosphinylmethyl) -9,9-dimethylfluorene 4:

2,7-Bis (bromomethyl) -9,9-dimethylfluorene (25.00 g, 66 mmol) and 25 ml of triethyl phosphite (150 mmol) are in a 100 ml three-necked flask with cross stirring, argon inlet, internal thermometer and distillation with Vigreux column under Argon purge entered. It is heated under standing oil bath carefully to 120-125 ⁰ C. At 65-70 ⁰ C began gas evolution and it formed a clear, stirrable mixture. The ethyl bromide was distilled off at 75-80 ° C. under a gentle stream of argon. After the distillation of the main amount of ethyl bromide was heated to 160 ° C for one hour. After cooling to 100 ° C oil bath temperature and with continued stirring, the argon flow was stopped and a membrane pump connected to remove excess triethyl phosphite. For this purpose, the oil bath temperature was increased to 150-160 ⁰ C. After no more triethyl phosphite distilled over, the oil pump was removed and argon was again flushed over. After cooling to 7O ⁰ C was poured into a crystallizing dish. A viscous, syrupy, clear liquid formed (31.2 g, 63.1 mmol, 95.6%). As crystallization did not occur after several hours of standing and rubbing with the glass rod and seeding, this crude product was used for the subsequent reaction.

Example 3: 2,7-Bis- (4-di-p-tolylaminophenylethenyl) -9,9-dimethyl-9H-fluorenene (MH15) 1:

In an 11-necked two-necked flask equipped with magnetic stirrer core, gas inlet tube and drying tube, 2, 7-bis (diethoxyphosphinylmethyl) -9, 9-dimethylfluorene (31, 2 g, 63.1 mmol) and dimethylformamide (431 ml) are introduced successively and stirred under flowing argon for 10 minutes. With continued stirring and argon purge, the aldehyde (Sensient, 38.1 g, 126.3 mmol) was added. After complete dissolution, ice was cooled from the outside and then te / f-BuOK (16.94 g, 151.0 mmol) was added in portions. Under continuous argon purge was under Ice cooling for 45 minutes and then further stirred at room temperature for 20 hours. In this case, the reaction mixture first turns dark red-brown, later green and forms a suspension with time. The target compound was then precipitated with three times the volume of methanol (1100 ml). It was stirred for one hour under ice cooling. It is filtered off with suction through a large frit, washed three times with 150 ml of methanol and dried overnight at 50 ^° C. in a drying oven. There was obtained 44.2 g (56 mmol) (89%) of a yellow solid (crude product), which was then subjected to column chromatography. For this purpose, a chromatography column 100 cm x 12 cm from Neubert and Kieselgel 60 (0.063-0.2 mm) Merck was used. The eluent was a mixture of cyclohexane and toluene (2: 1). To fill the column about 4 kg of silica gel with 9 liters of eluent mixture were mixed in several portions. Then a layer of sea sand (2 cm) was carefully applied. In the meantime, the crude product was dissolved in 1.5 liters of toluene and mixed with 300 g of silica gel. It was rotary evaporated to dryness on a rotary evaporator and the solid silica gel mixture was carefully positioned over the sand layer. Thereafter, further eluent mixture (cyclohexane: toluene = 2: 1) was added and finally a second layer of sand (2 cm) was applied. The column was carefully made up with further eluent. The runtime of the column was 4 hours and it was 22 liters of cyclohexane and 11 liters of toluene consumed. Fractions of 1 liter each were taken. The target product had an R _f value of 0.89. Only those fractions were collected which showed a distinct yellow spot on thin layer chromatography. The preliminary fractions with a slightly brownish spot, which was directly superimposed on the main spot, were discarded. Removal of the solvent by evaporation gave 37.4 g of a yellow solid, which was then dried for 12 hours at 100 ⁰ C in a drying oven. Finally, 36.4 g (73%) of a yellow crystalline solid (m.p. 242-245 ⁰ C).

Example 4:

Solubility studies and cleaning:

Compound 12 meets the industry-specified solubility criterion of 1 g of substance / 6 ml of methylene chloride or THF. From this compound, scale up to 35 g was performed. The compound was replaced by conventional Ie cleaning method such. B. recrystallization or column chromatography to a HPLC purity of> 99.5%.

Example 5:

Production of the hole conductor layers and electrophotographic tests

The electrophotographic properties of the produced hole conductor were determined in a double layer system by the cooperation partner. For this purpose, an aluminized polyester substrate was coated with a dispersion of Y-titanyl phthalocyanine in polycarbonate / methylene chloride. The charge generation layer thus formed after drying was coated with a solution of the corresponding hole conductor in polycarbonate / methylene chloride and measured after drying.

To determine the electrophotographic characteristics, the layer sequence to be tested was negatively charged in the dark with a corotron wire (Uo). After a defined time, the device is exposed with a defined amount of light. The voltage drop until exposure is referred to as dark decay (U _D ). The electrophotographic sensitivity results from the half-life of the discharge cycle multiplied by the irradiated light intensity. A typical discharge curve is shown in Figure 1. For commercial use, an electrophotographic sensitivity of at least 0.5 μJ / cm ² must be achieved with the layer sequence used.

Claims

claims

1. Arylamine-substituted divinylfluorene of the general formula 1

in which the substituents have the following meaning:

Ar is a homoaromatic or heteroaromatic group, if appropriate benzoannelated, phenylene, naphthylene, thienylene, furylene or anthracenylene, optionally substituted by alkyl, aryl or arylalkyl groups,

Biphenylene, fluorenylene, dibenzofuranylene, dibenzothiophenylene, carbazolylene or dibenzosilolylene units

R ¹ and R ² are independently a branched or linear alkyl group (Ci to C ₂ o alkyl group), a branched or linear unsaturated hydrocarbon group, a cycloalkyl group such as a cyclohexyl group or an aryl group such as phenyl, alkylphenyl, naphthyl, alkylnaphthyl -

Biphenylyl, alkylbiphenylyl, stilbenyl or tolanyl group, a branched or linear alkoxy group,

R ³ and R ⁴ are independent of each other

Phenyl, alkylphenyl such as methylphenyl, biphenylyl, alkylbiphenyl, naphthyl, alkylnaphthyl, phenanthrenyl, alkylphenanthrenyl, anthracenyl, alkylanthra- nyl, fluorenyl, alkylfluorenyl, triarylmethyl-aryl or triarylsilyl-aryl.

2. Compounds of the formula 8

R ¹ and R ² are each independently a branched or linear alkyl group C ¹ to C ₂₀ a branched or linearly unsaturated hydrocarbon group, a cycloalkyl group such as a cyclohexyl group or an aryl group such as phenyl, alkylphenyl, naphthyl, alkylnaphthyl

Biphenylyl, alkylbiphenylyl, stilbenyl or tolanyl group, a branched or linear alkoxy group.

R ³ and R ⁴ are independent of each other

Phenyl, alkylphenyl, in particular methylphenyl, biphenylyl, alkylbiphenyl, naphthyl, alkylnaphthyl, phenanthrenyl, alkylphenanthrenyl, anthracenyl, alkylanthracenyl, fluorenyl, alkylfluorenyl, triarylmethyl-aryl or triarylsilyl-aryl.

3. Compounds of the formula 9

where the following applies to the substituents:

R ³ and R ⁴ are independent of each other

4. Compounds of the formula 10

R ¹¹ and R ¹² are independent of each other

H, a branched or linear alkyl group C ₁ to C 20, a branched or linearly unsaturated hydrocarbon group, a cycloalkyl group such as cyclohexyl or an aryl group such as phenyl, alkylphenyl, naphthyl, alkylnaphthyl-.biphenylyl, alkylbiphenylyl-.stylbenyl or tolanyl group, a branched or linear alkoxy group.

5. Compounds of the formula 11

R ¹¹ and R ¹² are independent of each other

H or a methyl group which may be ortho, meta and para to the amino group.

6. Compounds according to claim 5, described by formula 12

in which R ¹¹ and R ¹² each represent a methyl group in the para position to the amino group represents

7. A process for the preparation of the compounds according to claims 1 to 6, characterized in that according to the formula scheme. 1

Paraformaldehyde, HBr P (OEt) ₃

Formula Scheme 1

9,9-dialkylfluorene 2,7-bishalomethylated using paraformaldehyde and HBr, the intermediate 3 in the second step is reacted with triethyl phosphite to give the corresponding 2,7-bis (dialkylphosphonatomethyl) -9,9-dialkylfluorene 4, which in the third step by reaction with an aromatic aldehyde yields the desired 2,7-divinylfluorene 1.

8. A process for the preparation of the compounds according to claims 1 to 7, characterized in that as the aromatic aldehyde differently substituted Diarylaminobenzaldehyde 5, in particular differently substituted diphenylamino benzaldehyde be used, wherein in the formula:

Ar is a homoaromatic or heteroaromatic group, if appropriate benzoanneliert such as phenylene, naphthylene, thienylene, furylene or anthracenylene, optionally substituted by alkyl, aryl or arylalkyl groups, biphenylene units wherein the unit A is selected from the following structures

and R ³ and R ^{4 are} independently

Phenyl, alkylphenyl, especially methylphenyl, biphenylyl, alkylbiphenyl, naphthyl, alkylnaphthyl, phenanthrenyl, alkylphenanthrenyl, anthracenyl, alkylanthracenyl, fluorenyl, alkylfluorenyl, triarylmethyl-aryl or triarylsilyl-aryl

9. Use of compounds of claims 1 to 6 in electrophotography.

10. Use of compounds of claims 1 to 6 in laser printing

11. Use of compounds of claims 1 to 6 in copying systems.

12. Use of compounds of claims 1 to 6 in OLEDs.