DE4422332A1 - Oligomeric liquid crystalline triphenylene derivatives and their use as charge transport substances in electrophotography - Google Patents

Abstract

Compounds have the general formula (I) Z[-Y<1>-(A-Y<2>)m-X]n, in which the variables have the following meanings: Z stands for an n-valent aliphatic residue with 2 to 20 C atoms or for an n-valent three to seven-membered saturated or unsaturated carbocyclic or heterocyclic residue that may also be benzocyclised, or for an n-valent siloxane or cyclosiloxane residue with up to 10 Si atoms; Y<1>, Y<2> stand for a chemical bond, oxygen, sulphur or a group -CO-O-, -O-CO-, -N(R)-CO- or -CO-N(R)-; m equals 0 or 1; A stands for an alkylene group with 2 to 20 C atoms in which non-adjacent C atoms may be substituted by oxygen, sulphur, -CO-O-, -O-CO- or -N(R)-; n equals 2 to 6; R stands for hydrogen or C1-C4-alkyl; and X stands for a substituted triphenylene residue. Because they recur n times in the compounds, A, Y<1>, Y<2>, m and X may be the same or different. These compounds are useful as charge carriers.

Description

Organic photoconductors have been known for a long time and are used primarily in xerography as electrophotographic recording materials (Schaffert, IBM J. Res. Develop., 1971, 75). Organic photoconductors are currently used in molecular dispersion in a neutral binder in photocopiers and laser printers (Borsenberger, J. Phys. Chem., 1993, 11314). Such arrangements have a typical maximum carrier mobility of 10 ^-5 cm² / Vs. A further increase in the mobility of the charge carriers in doped films can no longer be achieved (Baessler, Adv. Mat. 1993, 662). Charge carrier mobility in this order of magnitude, however, limits the printing or copying speed of electrophotographic devices, so that a further increase in speed only appears possible by increasing the charge carrier mobility. However, this cannot be achieved with the conventional methods currently used.

(Poly-N-Vinylcarbazol, PVK) is the oldest commercially used Photoconductor polymer in a single layer arrangement (Hoegl, J. Phys. Chem., 1965, 755). However, such amorphous materials have apparently an intrinsic limitation on charge carrier mobility and unloadability under radiation points that can only be remedied with structurally new substances leaves.

In work by Closs et al. (Liquid Crystals, 14 (3) 1 629 (1993), Bengs et al. (Liquid Crystals, 15 (5), 565 (1993) and Adam et al., Phys. Rev. Lett., 70 (4), 457 (1993) could be shown be that hexapentyloxytriphenylene in the liquid crystalline Phase has photoconductive properties. Since the usage temperatures of a photocopier in a temperature interval The observed transport must also be between 20 ° C and 50 ° C phenomena are in this interval. This is with hexapentyl oxytriphenylene is not the case.

Furthermore, a photoconductor layer must have a certain can withstand mechanical stress, which is their cause in individual process steps (concreting the charge pattern, about wearing the toner image).

The object of the present invention was therefore to liquid new ones to provide crystalline materials that besides photoconductive properties in a liquid crystalline phase Have temperature range between 20 ° C and 50 ° C and mechanical are resilient.

Surprisingly, new oligomeric triphenylene derivatives Charge transport substance for electrophotography of general my formula I

C- (A) _m - (X) _n I,

in the C a central unit, n one of the numbers 2 to 6, m 0 or 1, A is a spacer and X is the same or different Substituted triphenylene residues are the desired ones shafts, photoconductive properties, liquid crystalline phase in the temperature range between 20 ° C and 50 ° C as well as a high mechanical stability.

The linking unit C is two for n, preferably an alkylene radical or a siloxane radical with 2 to 20 chain links, for n equal to 3 preferably an alkylene radical, a cycloalkylene residue, an aromatic or heteroaromatic residue or a Cy closiloxane residue, for n is four, five or six A is preferred a cyclosiloxane residue or a triphenylene residue.

Preferred groups C are, for example:

1,3,5-cyclohexane tricarboxylic acid, 1,3,5-benzene tricarboxylic acid, Maleic acid, fumaric acid, oxalic acid, malonic acid, succinic acid, Glutaric acid, adipic acid, pimelic acid, suberic acid, ethylene glycol, Propylene glycol, 1,3-dihydroxypropylene, 1,4-dihydroxybutylene, 1,5-dihydroxypentylene, 1,6-dihydroxyhexylene, 1,8-dihydroxy octylene, 1,10-dihydroxydecylene or sebacic acid.  

Spacer A is preferably an alkyl or alkyloxy group with 2 to 30, preferably 3 to 20 and particularly preferably 4 to 11 carbon atoms, with non-neighboring carbon atoms due to oxygen, Sulfur, -NH-, -N (CH₃) -, -COO- or -OCO- in not adjacent position can be replaced.

For n equal to 2, A is preferably an alkyl group with 2 to 20, preferably 2 to 12 C atoms, where C atoms are caused by oxygen, Sulfur, -NH-, -N (CH₃) -, -COO- or -OCO- in not adjacent position can be replaced.

If the linking unit C is an alkyl group, the Spacer preferred and there is a direct bond between linking unit and the rest X.

If the linking unit C is a cyclic or linear Is siloxane, spacer A is preferably an alkyl group with 2 to 12 carbon atoms, carbon atoms by oxygen, NH, N (CH₃), COO or OCO can be replaced in a non-adjacent position.

Preferred groups A are for example:

z¹ preferably 2 to 12, z² preferably 2 to 10 and z³ preferred 2 to 11 means.

The same or different substituted triphenylene radicals X preferably have the following structure

The radicals R¹ to R⁵ independently of one another represent an alkoxy, Alkanoyloxy or alkylthio radical with 1 to 20, preferably 1 to 20 and particularly preferably 4 to 12 carbon atoms, not adjacent beard C atoms through oxygen, sulfur, -NH, -N (CH₃) -, -COO- or -OCO- can be replaced.

In addition, other radicals R are also radicals which have a polymerizable group P. These residues R have preferably has a structure of the formula II,

- (- Y¹-) _p - (- A²-) _q -Y¹-P II,

being the variables
Y¹ is a direct bond, O, S, COO or OCO,
A² is a spacing unit containing 2 to 10 methylene groups,
P is a polymerizable group of the formula

correspond, wherein R is an alkylene group and p, q are independently 0 or 1.

The compounds are prepared by customary methods. The production of differently substituted triphenyls derivate is for example at w. Kreuder, H. Ringsdorf, Makromol. Chem. Rap. Commun, 4, 807 (1983). The introduction of Spacers and polymerizable groups can be analogous to literature regulations, such as those in DE-A-39 17 196 and literature cited there are carried out.

Examples

The examples are synthesized according to the above writings. The phase behavior became polarization microscopic in a Leitz polarizing microscope (Leitz Ortholux II®) in Connection with a Mettler heating table determined. Verified was the optically determined phase sequence by differential Scanning calorimetry with a Mettler DSC 7.

The photoconductive properties were measured in an apparatus determined as described in Closs et al. (Liquid Crystals, 14 (3), 629 (1993)).

The following abbreviations are used throughout:
I isotropic phase
D _ho discotic hexagonal phase
K¹, K₂, K different crystalline phases
G Glass condition.

example 1 2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxydecyl] - 3 ′, 6 ′, 7 ′, 10 ′, 11′-pentakis (pentyloxy) triphenylene a) 6- [3,6,7,10,11-Pentakis (pentyloxy) -2-triphenylenyloxy] decyl bromide

15 g (49.98 mmol) of 1,10-dibromohexane and 5 g (7.41 mmol) of 3,6,7,10,11-pentakispentyloxy-2-hydroxy-triphenylene are dissolved in 12 ml of 2-pentanone and after addition of 6 g (43.41 mmol) of potassium carbonate was stirred at 70 ° C. for 15 h. The reaction mixture is then allowed to cool, and potassium bromide which has precipitated and excess potassium carbonate are suctioned off. After the first flash chromatography (CH₂Cl₂ / PE 1/2), 5.1 g of crude product are obtained, which are subjected to a further flash chromatography. Recrystallization from acetonitrile / acetone (1/1) gives the pure product.
Yield: 5.21 g (= 78.8% of theory)

b) Di-2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy] - 1,10-decane

1.5 g (2.22 mmol) monohydroxytriphenylene and 2.0 g (2.24 mmol) 6- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenyl enyloxy] decyl bromide are obtained in 15 ml of methyl propyl ketone dissolved under argon. After adding 4 g (28.94 mmol) of potassium carbonate and the potassium iodide (50 mg), the mixture is heated to boiling for 20 h. After the reaction mixture has cooled, the product is filtered off with suction. The dimer is isolated by twice flash chromatography (CH₂Cl₂ / PE 1/1) and after subsequent recrystallization from acetone.
Yield: 2.58 g (= 76.2% of theory).

Example 2 a) 2- [3,6,7,10,11-Pentakis (pentyloxy) -2-triphenylenyloxy] butene

5 g (6.97 mmol) of 3,6,7,10,11-pentakispentyloxy-2-acetyl-tri phenylene and 1.41 g (10.46 mmol) of bromobutene are dissolved in 10 ml of toluene. After the addition of 2 g (35.71 mmol) of potassium hydroxide and 0.2 ml of tetrabutylammonium hydroxide, the mixture is stirred at 40 ° C. for 20 h. It is then filtered with 50 ml of water and 50 ml of petroleum ether. The organic phase is extracted with 2N H₂SO₄ saturated NaCl solution and water. Drying over sodium sulfate and distilling off the solvent gives the crude product, which can be purified by repeated recrystallization from ethanol or acetonitrile. Flash chromatography (CH₂Cl₂ / PE 1/1) is carried out for highly pure product before recrystallization.
Yield: 4.33 g (= 85.2% of theory)

b) Di- [2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy butyl]] - 1 ′, 3′-1 ′, 1 ′, 3 ′, 3′tetramethyldisiloxane (3)

200 mg (0.274 mmol) of 2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy) -butene and 18.42 mg (0.137 mmol) of tetra methyldisiloxane become 1 ml of absolute toluene under argon in one Polymerization vessel dissolved. After adding the catalyst (2 μl SLM 86005, catalyst solution from Wacker Chemie Burghausen), the mixture is stirred at 50 ° C. for 48 h. It is then precipitated in 100 ml of toluene. The crude product obtained is subjected to flash chromatography (CH₂Cl₂ / PE 1/1) to separate the excess monomers. Finally, the dimer is dissolved in 1 ml of methylene chloride, filtered through a white rim filter (pore diameter = 0.2 μm) and precipitated in 100 ml of methanol.
Yield: 65 mg (= 29.8% of theory)
Phase behavior: D _ho 110 i.

Example 3 Di- [2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxybutyl)] - 1′5′-1 ′, 1 ′, 3 ′, 3 ′, 5 ′, 5 ′, - hexamethyltrisiloxane

200 mg (0.274 mmol) of 2- [3,6,7,10,11-pentakis (pentyloxy) -2- triphenylenyloxy] -butene and 28 mg (0.137 mmol) of hexamethyltrisiloxane become 1 ml of absolute toluene under argon in a polymerisation vessel solved. After adding the catalyst (2 μl SLM 86005, catalyst solution from Wacker Chemie Burghausen), the mixture is stirred at 60 ° C. for 48 h. It is then precipitated in 100 ml of toluene. The crude product obtained is subjected to flash chromatography (CH₂Cl₂ / PE 1/1) to remove the excess monomer. Finally, the dimer is dissolved in 1 ml of methylene chloride using a white edge filter (pore diameter = 0.2 µm)
filtered and precipitated in 100 ml of methanol.
Yield: 149 mg (= 65.2% of theory)
Phase behavior: k₁ 7 k₂ 27.5 D _ho 90 i.

Example 4 1,3,5,7-tetra- [3 ′, 6 ′, 7 ′, 10 ′, 11′-pentakis (pentyloxy) -2- triphenylenyloxybutyl) -1,3,5,7-tetramethylcyclosiloxane

500 mg (0.68 mmol) of 2- [3,6,7,10,11-pentakis (pentyloxy) -2-tripheny lenyloxy] -butene and 41.23 mg (1.71 mmol) of tetramethylcyclosiloxane become 1 ml of absolute toluene dissolved under argon in a polymerization vessel. After adding the catalyst (2 μl SLM 86005, catalyst solution from Wacker Chemie Burghausen), the mixture is stirred at 60 ° C. for 24 h. It is then precipitated in 100 ml of toluene. The crude product obtained is subjected to flash chromatography (CH₂Cl₂ / PE 3/1) to remove the excess monomer. Finally, the cyclosiloxane is dissolved in 1 ml of methylene chloride, filtered through a white rim filter (pore diameter = 0.2 μm) and precipitated in 100 ml of methanol.
Yield: 402.2 mg (= 77.65% of theory)
Phase behavior: g - 48 D _ho 141 i.

Example 5 1,3,5,7-tetra- [3 ′, 6 ′, 7 ′, 10 ′, 11′-pentakis (pentyloxy) -2- triphenylenyloxyoctyl] -1,3,5,7-tetramethylcyclosiloxane a) 2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy] octene

The following were used as in Example 2a:
6 g (8.37 mmol) 3,6,7,10,11-pentakispentyloxy-2-acetyl triphenylene
3 g (15.7 mmol) bromoctene
2 g (35.71 mmol) potassium hydroxide
0.2 ml tetrabutylammonium hydroxide.

The reaction and working up corresponded to the procedure given in Example 2.a).
Yield: 5.29 g (= 80.5% of theory).

b) 1,3,5,7-tetra- [3 ′, 6 ′, 7 ′, 10 ′, 11′-pentakis (pentyloxy) -2- triphenylenyloxyoctyl] -1,3,5,7-tetramethylcyclosiloxane

400 mg (0.509 mmol) of 2- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy] octene and 30.63 mg. (1.27 mmol) tetra methylcyclosiloxane, 1 ml of absolute toluene is dissolved under argon in a polymerization vessel. After adding the catalyst 2 ul SLM 86005 is stirred at 60 ° C for 18 h. It is then precipitated in 100 ml of toluene. The crude product obtained is subjected to flash chromatography (CH₂Cl₂ / PE 3/1) to remove the excess monomer. Finally, the cyclosiloxane is dissolved in 1 ml of methylene chloride, filtered through a white edge filter (pore diameter = 0.2 µm) and precipitated in 100 ml of methanol.
Yield: 357 mg (= 85.4% of theory)
Phase behavior: g - 50 D _x 98.5 i.

Example 6 2,3,6,7,10,11-hexakis [3,6,7,10,11-pentakis (pentyloxy) -2- triphenylenyloxyhexyloxycarbonylmethyleneoxy] triphenylene a) 6- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenyleneoxy] hexanol

1.88 g (2.79 mmol) monohydroxytriphenylene, 0.51 g (2.79 mmol) bromohexanol, 1.07 g (8.37 mmol) finely powdered, freshly chilled potassium carbonate and 0.46 g (2.79 mmol ) Potassium iodide in 25 ml of pentanone-2 are refluxed under argon for 2 days. The cooled mixture is filtered, washed with dichloromethane and the crude product obtained is purified by flash chromatography twice (CH₂Cl₂).
Yield: 1.52 g (= 70% of theory)

b) 2,3,6,7,10, l1-hexakis [3,6,7,10,11-pentakis (pentyloxy) -2- triphenylenyloxyhexyloxycarbonylmethyleneoxy] triphenylene

30 mg (0.0354 mmol) triphenylene hexaacetate and 246.9 mg (0.3185 mmol) 6- [3,6,7,10,11-pentakis (pentyloxy) -2-tripheny lenoxy] hexanol become dry after adding a little Dichloromethane (molecular sieve 4Å) mixed in a Schlenk vessel. The homogeneous solution is stirred for a few minutes and then ßend the solvent as completely as possible with nitrogen (dried over P₂O₅) distributed. The apparatus becomes short flushed early with argon (dried over P₂O₅) and at 110 ° C heated. Also under argon are 2 drops of the Kataly Sator solution (10 vol .-% tetra (isopropyl) orthotitanate (Merck) in dry diethenglycol dimethyl ether (molecular sieve 4 Å) to the Given melt. The beginning blistering indicates that Escape of ethanol and thus the start of the transesterification at. It is one hour at 120 ° C under normal pressure, 1.5 h at 125 ° C in a water jet vacuum and 12 h in an oil pump vacuum (0.007 mbar) condensed, the temperature after a Hour in an oil pump vacuum must be increased to 140 ° C in order to To prevent freezing of the melt. Although an association tents blistering that is not fully reflected on a concludes a closed reaction, can be observed the condensation is stopped after a total of 15 hours.

The residue is dissolved in absolute THF and the heptamer via preparative GPC from the excess monomer Triphenylene alcohol separated (column material Sephadex LH 60, Eluens = THF distilled over potassium). With the first The desired product is obtained with a high-intensity peak.  

Immediately afterwards, the elugram shows several, very intimate weak peaks that are not fully converted can be assigned to low molecular weight oligomers; as the excess triphenylene alcohol is eluted.

The heptamer is obtained as pure substance by spinning in the corresponding fractions. Since even after drying for several days in an oil pump vacuum, residues of THF are still occluded in the glassy oligomer, ge must be freeze-dried from benzene to remove the remaining THF.
Yield: 154.8 mg (= 83.2% of theory).

Example 7 a) 6- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy] nonanol

The reaction was carried out analogously to Example 6.a).
Approach:
10,087 g (14.94 mmol) 3,6,7,10,11-pentakispentyloxy-2-hydroxy-triphenylene
3.334 g (14.94 mmol) bromononanol
6.2 g (44.85 mmol) potassium carbonate
2.48 g (2.09 mmol) potassium iodide
40 ml pentanone-2
Yield: 7.61 g (= 62.3% of theory).

b) 2,3,6,7,10,11-hexakis [3,6,7,10,11-pentakis (pentyloxy) -2- triphenylenyloxynonyloxycarbonylmethyleneoxy] triphenylene

Approach:
71.10 mg (0.0846 mmol) triphenylene hexaacetate
510.4 mg (0.6246 mmol) of 6- [3,6,7,10,11-pentakis (pentyl oxy) -2-triphenylenyloxy] nonanol
Drop of catalyst solution (10 vol% tetra (isopropyl) ortho titanate in dry diethylene glycol dimethyl ether (molecular sieve 4 Å).

The reaction was carried out analogously to Example 6.b), but at a somewhat elevated temperature.
Yield: 428.8 mg (= 92.8% of theory).

Example 8 a) 6- [3,6,7,10,11-pentakis (pentyloxy) -2-triphenylenyloxy] undecanol

The reaction was carried out analogously to Example 6.a).
Approach:
1.412 g (2.09 mmol) 3,6,7,10,11-pentakispentyloxy-2-hydroxy triphenylene
0.525 g (2.09 mmol) bromundecanol
0.87 g (6.27 mmol) potassium carbonate
0.347 g (2.09 mmol) potassium iodide
25 ml pentanone-2
Yield: 1.28 g (= 72.3% of theory).

b) 2,3,6,7,10,11-hexakis [3,6,7,10,11-pentakis (pentyloxy) -2- triphenylenyloxyundecyloxycarbonylmethyleneoxy] triphenylene

The reaction was carried out analogously to Example 6.b) at a slightly elevated temperature compared to those given in 6.b). He was
20.0 mg (0.0236 mmol) triphenylene hexaacetate
174.2 mg (0.1572 mmol) of 6- [3,6,7,10,11-pentakis (pentyl oxy) -2-triphenylenyloxy] -undecanol
2 drops of catalyst solution (10 vol% tetra (isopropyl) ortho titanate in dry diethylene glycol dimethyl ether (molecular sieve 4 Å)
used.
Yield: 120.1 mg (= 90.3% of theory).

For application examples 9 to 10, these became discotic liquid crystalline compounds between two indium tin oxides (ITO) coated glass plates. The electrode area is 2 mm². The layer thickness of the sample is approx. 10 µm, adjusted by a spacer film of 6 µm. To this cell a voltage of 9 V is applied. The temperature control of the sample follows in a special heating table operated with direct current. For photocurrent measurement, the sample is periodically Light signal exposed at a frequency of 10 Hz and the Difference between light and dark current using lock-in technology measured.  

Example 9

For this example, the compound from Example 1 was used in accordance with prepared and on the general rule given above investigated photoconductive properties. The result is in the Table 1 summarized.

Table 1

Example 10

For this example, the compound from Example 2 was made according to prepared and on the general rule given above investigated photoconductive properties. The result is in the Table 2 summarized.

Table 2

Example 11

For this example, the compound from Example 4 was made according to prepared and on the general rule given above investigated photoconductive properties. The result is in the Table 3 summarized.

Table 3

Claims (14)

1. Use of compounds of the general formula I C- (A) _m - (X) _n I, in which C is a central unit, n is one of the numbers 2 to 6, m 0 or 1, A is a spacer and X is the same or differently substituted Triphenylene residues are compounds as charge transport. 2. Use of compounds according to claim 1, in which n is 2, 3, 4 or 6. 3. Use of compounds according to claim 1, in which C for n = 2 an alkylene or siloxane radical with 2 to 20 chains structure, for n = 3 a cycloalkylene radical, an aromatic or heteroaromatic radical or a cyclosiloxane radical and for n = 4 or 6 are a cyclosiloxane or triphenylene radical. 4. Use of compounds according to claim 1, in which X is a tri substituted by alkoxy, alkanoyloxy or alkylthio is phenylene radical, where the alkyl radicals have 1 to 20 carbon atoms and can be interrupted and given by oxygen if substituted by a polymerizable group. 5. Use of compounds according to claim 1 and 4, in which n is 2 and m is 0. 6. Use of compounds according to claim 1 and 4, in which n is 2 and C is a siloxane radical and A is one spacing group is with 2 to 20 methylene groups, of which up to six non-contiguous methylene groups can be replaced by O, S, NH, N (CH₃), COO, OCO. 7. Use of compounds according to claim 1 and 4, in which n = 3, 4, 5 or 6 and A is a spacing group with 2 to 20 methylene groups, up to six of which are not neighboring methylene groups by O, S, NH, N (CH₃), COO, OCO can be replaced.   8. Compounds of the general formula I C- (A) _m - (X) _n I, in which C is a central unit, n is one of the numbers 2 to 6, A is a spacer and X is the same or different substituted triphenylene radicals. 9. Compounds according to claim 8, in which C is a siloxane, Cyclosiloxane, cycloaliphatic or aromatic group or having an α, ω-dihydroxyalkyl group or α, ω-dicarboxylic acids 2 to 6 carbon atoms. 10. Compounds according to claim 9, in which C 1,3,5-cyclohexane tricarboxylic acid, 1,3,5-benzenetricarboxylic acid, maleic acid, fumaric acid, ethylene glycol, propylene glycol, 1,3-dihydroxypropylene, 1,4-dihydroxybutylene, 1,5-dihydroxy pentylene, 1,6-dihydroxyhexylene, oxalic acid Corresponds to malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid or sebacic acid and n is an integer from 1 to 20 and m is 3, 4, 5 or 6. 11. Compounds according to claim 8, in which A is an alkyl group with 2 to 20 carbon atoms, whereby not neighboring C atoms can be replaced by O, S, COO, OCO, NH or N (CH₃) can. 12. Compounds according to claim 8, in which X is an alkoxy, Alkanoyloxy or alkylthio radical with 1 to 20 carbon atoms optionally interrupted by O, S, COO, OCO, NH or N (CH₃) means triphenylene radical.   13. Compounds according to claims 8 and 12, in which the triphenylene radicals are substituted by at least one polymerizable group of the general formula II - (- Y¹-) _p - (- A²-) _q Y¹-P II, the variables
Y¹ is a direct bond, O, S, COO or OCO,
A² is a spacing unit containing 2 to 10 methylene groups,
P is a polymerizable group of the formula correspond, where R is an alkylene group having 1 to 5 carbon atoms and
p, q are independently 0 or 1. 14. Use of the compounds of formula I according to claim 8 to 13 as a compensation layer in display technology.