GB2322866A - Crystalline form of a titanyl phthalocyanine obtained by treatment of Type X polymorphic form with substituted aromatic hydrocarbon(s) - Google Patents

Abstract

There is disclosed a crystalline form of a titanyl phthalocyanine characterised by having an XRD pattern showing a maximum peak at a Bragg angle (20Œ0.2‹) of about 27.3‹ and further diffraction peaks in decreasing order of intensity at Bragg angles (20Œ0.2‹) of about 9.0‹, about 9.5‹, about 24.1‹ and about 14.3‹. Its use in charge generating materials, photoconductive members and electroreprographic devices is also disclosed. A process for its preparation comprises the following steps: a) reacting an optionally substituted phthalonitrile with ammonia in the presence of alkali metal alkoxide (eg sodium or potassium methoxide) to form a diiminoisoindoline; b) reacting the diiminoisoindoline obtained from step 'a)' with titanium tetraalkoxide (eg the tetrabutoxide) to form a titanyl phthalocyanine of the polymorphic crystal form known as Type I; c) dissolving the Type I titanyl phthalocyanine obtained from step 'b)' in a mixture of alkane sulphonic acid (eg methanesulphonic acid) and halogenated aliphatic hydrocarbon (eg dichloromethane) to form a titanyl phthalocyanine of the polymorphic crystal form known as Type X; and d) treating the Type X titanyl phthalocyanine obtained form step 'c)' with substituted aromatic hydrocarbon (eg methoxybenzene) until a titanyl phthalocyanine is formed having the XRD pattern stated above and then collecting the titanyl phthalocyanine from the substituted aromatic hydrocarbon.

Description

TITANYL PHTHALOCYANINE AND ITS USE The present invention relates to particular crystalline forms of certain metal phthalocyanines, particularly those of titanium and to the use of such phthalocyanines and compositions comprising such phthalocyanines in electroreprography.

Electroreprography is any process in which an image is reproduced by means of electricity and incident radiation, usually electromagnetic radiation more usually visible light. Electroreprography includes the technology of electrophotography which encompasses photocopying and laser printing technologies. In both these technologies a latent electrostatic image in charge is produced by exposure of a photoconductive drum to light. This can be either reflected light from an iiluminated image (photocopying) or by scanning the drum with a laser usually under instnrction from a computer (laser printing).

Once a latent image has been produced in charge it must be developed with colorant so that a visible image can be printed onto paper.

Phthalocyanines and their metal complexes have been used for many years in electroreprography because generally they exhibit good photoconduction. Recently organic photoconductors based on various dyes and pigments such as methine, cyanine, pyrylium, phthalocyanine and azo dyes have been used in high speed, high quality printing and copying. whilst the photoconducting properties of such dyes can be readily tuned for specific applications such dyes are unsuitable because they tend to lack the stability needed for the repeated use required in modem copiers and printers.

More recently many crystalline forms of phthalocyanines and their metal complexes have been disclosed and patented but none of these have satisfactorily fulfilled all the requirements necessary to provide charge generating materials. The requirements for a good charge generating material include: i) a high spectral sensitivity to LED's or semiconductor lasers; ii) a high charge acceptance which gives better electrical contrast between charged and uncharged areas and thus provides better print quality; iii) a low dark decay; iv) a high photodischarge sensitivity so the minimum amount of energy may be used to discharge the photoconductor; v) a low residual potential after exposure of the photoconductor to radiation vi) long term stability of the material to many thousand repeat cycles of charging and discharging.

Therefore according to the present invention there is provided a crystalline form of a titanyl phthalocyanine (also abbreviated to TiOPc) characterised by having an X-ray diffraction (abbreviated to XRD) pattern showing a maximum peak at a Bragg angle (20i0.2 ) of about 27.30 and further diffraction peaks in decreasing order of intensity at Bragg angles (28s0.2") of about 9.0 , about 9.5 , about 24.1 and about 14.3 .

Titanyl phthalocyanines showing the preceding XRD peaks [as well as titanyl phthalocyanine obtained or obtainable as the end product of the process of the present invention comprising steps a) to d) as described below] are referred to herein as "Zeneca type titanyl phthalocyanine" [also abbreviated to TiOPc(Za)]. Without wishing to be bound by theory it is believed that TiOPc(Za) may comprise a previously unknown polymorphic crystal form of titanyl phthalocyanine and/or may comprise an improved form of the titanyl phthalocyanine of the polymorphic crystal form known as Type IV.

Preferred titanyl phthalocyanines are those which are unsubstituted or carry fluoro groups on the periphery of the ring structure. An unsubstituted titanyl phthalocyanine is especially preferred.

The precise nature of the synthetic process used to prepare the titanyl phthalocyanines as well as subsequent solvent treatments to the pigments are critical in determining the polymorphic form of the crystals obtained.

Thus broadly according to the present invention there is provided a process for preparing titanyl phthalocyanine comprising the following steps: a) reacting an optionally substituted phthalonitrile with an ammonia in the presence of an alkali metal alkoxide to form a diiminoisoindoline; b) reacting the diiminoisoindoline obtained from step 'a)' with a titanium tetraalkoxide to form a titanyl phthalocyanine of the polymorphic crystal form known as Type c) dissolving the Type I titanyl phthalocyanine obtained from step 'b)' in a mixture of an alkane sulphonic acid and a halogenated aliphatic hydrocarbon to form a titanyl phthalocyanine of the polymorphic crystal form known as Type X; and d) treating the Type X titanyl phthalocyanine obtained form step 'c)' with substituted aromatic hydrocarbon until a titanyl phthalocyanine is formed having an XRD pattern showing a maximum peak at a Bragg angle (20+0.2 ) of about 27.3 and further diffraction peaks in decreasing order of intensity at Bragg angles (20i0.20) of about 9.0 , about 9.5 , about 24.1 and about 14.3 , and then collecting the titanyl phthalocyanine from the substituted aromatic hydrocarbon.

A group which comprises a chain of three or more atoms signifies a group in which the chain may be straight or branched or the chain or part of the chain may form a ring.

For example, an alkyl group may comprise: propyl which includes n-propyl and isopropyl; butyl which includes n-butyl, sec-butyl, isobutyl and tert-butyl; and an alkyl group of three or more carbon atoms may comprise a cycloalkyl group. The total number of certain atoms is specified herein for certain substituents, for example C1 n alkyl, signifies an alkyl group having from 1 to n carbon atoms. The term 'aryl' as used herein signifies a radical which comprises an aromatic hydrocarbon ring, for example phenyl, naphthyl, anthryl and phenanthryl radicals.

Unless the context clearly indicates otherwise, as used herein plural forms of the terms herein are to be construed as including the singular form and vice versa.

In step 'a)' the phthalonitrile is preferably unsubstituted. The alkali metal alkoxide may comprise an alkali metal Cr - C6 - alkoxide. Preferably the alkali metal alkoxide comprises a sodium alkoxide andlor a potassium alkoxide, more preferably sodium methoxide.

In step 'b)' the titanium tetraalkoxide may comprise a titanium tetra (Cr - C6 alkoxide), preferably titanium tetrabutoxide.

In step 'c)' the alkane sulphonic acid may comprise a C1 0ic - alkane sulphonic acid, preferably a Oj - C4 - alkane sulphonic acid and more preferably methane sulphonic acid. The halogenated aliphatic hydrocarbon may comprise one or more halo atoms selected from fluoro-, chloro- and bromo- and may comprise different halo atoms on the same molecule. Preferably the halogenated aliphatic hydrocarbon comprises a chlorinated aliphatic hydrocarbon, more preferably dichloromethane.

In step 'd)' the substituted aromatic hydrocarbon may comprise an aryloxybenzene and/or alkoxybenzene, preferably methoxybenzene (also known as anisole).

Step 'a)' of the present process may be carried out at a temperature from about 20"C to about 120"C, preferably from about 50"C to about 75"C. The solvent used in step 'a)' may comprise C1-C10 alcohols, preferably Cr-C4 alcohols. The alkali metal alkoxide used will have the same alkoxy group as the alcohol.

Step 'b)' of the present process may be carried out at a temperature from about 130"C to about 230. C, preferably from about 190"C to about 210 C. The solvent used in step 'b)' may comprise suitable high boiling solvents such as aromatic or aliphatic alcohols and/or aromatic or aliphatic hydrocarbons (optionally comprising a hetero atom).

Preferably the solvent may comprise chloronapthalene, methyl naphthalene and/or quinoline.

Step 'c)' of the present process may be carried out at a temperature between 20"C to +20"C, preferably between -10 C to +100C. Preferably the solvent used in step 'c)' comprises a mixture of methane suiphonic acid and dichloromethane.

Step 'd)' of the present process may be carried out at a temperature from about -25 C to about +250C, preferably from about -10 C to about +10 C, more preferably from about -5 C to about +5"C. Preferably step 'd)' is carried under an inert atmosphere, more preferably under nitrogen which is substantially free from water.

A preferred method for collecting the solid product from one or more of steps 'b)', 'c)' and/or 'd)' comprises the further steps of: forming a slurry with the solid in a suitable liquid; allowing the solid to settle from the slurry; decanting the mother liquor from the slurry to leave a solid residue, optionally repeating the preceding steps one or more times; dissolving the solid residue in a suitable solvent; and collecting the solid by filtration.

This collection method has the advantage that if the process of the present invention uses large quantities collection is quicker than filtration only. Also it has been found that if the solid is initially collected by filtration alone solid impurities (such as tars) in the reaction mixture may settle on the solid during filtration which may impair the electrical properties of the TiOPc collected. Forming a slurry and decanting the mother liquor as described above substantially removes any solid impurities prior to collection of the solid by filtration. Thus TiOPc collected in this way may exhibit improved electrical properties for use in electroreprography and/or is useful as purer starting material for use in subsequent steps in the process of the present invention.

A further aspect of the present invention comprises the titanyl phthalocyanine obtained or obtainable as the end product of the process comprising steps a) to d) as described herein.

A still further aspect of the present invention provides a charge generating material comprising a Zeneca type titanyl phthalocyanine optionally together with a suitable binder andlor carrier.

According to a yet further aspect of the present invention there is provided a photoconductive member comprising a substrate, a charge generating layer and a charge transport layer characterised in that the charge generating layer comprises the charge generating material of the present invention.

The charge generating layer comprising the titanyl phthalocyanine is preferably in a binder and is coated on the substrate followed by the charge transport layer which is again preferably in a binder. Coating may be conveniently carried out by dissolving or dispersing the charge generating material or charge transport material as appropriate in a liquid medium followed by evaporating the liquid medium. Suitable liquid media may be selected from one or more of the following and any suitable mixtures thereof: alkylacetates, alkyl propionates, butanol, pentanol, cyclohexanone, cyclopentanone, xylene, toulene, mesitylene and cumene.

The charge generating layer may also contain one or more additional charge generating materials which may be selected from one or more of the following and any suitable mixtures thereof: phthalocyanines, polyazo compounds, perylene compounds, dihaloanthanthrone compounds and azonapthol compounds.

Suitable binders for the charge generating layer and the charge transport layer may be selected from one or more of the following and any suitable mixtures thereof: polyesters, polywarbonates, polyamides, polyurethanes, polybutyrol, poly(estercarbonates), poly(ether-carbonates), polyvinyl acetals, polyvinyl chloride coploymers, stryene-butadiene copolymers, cellulose derivatives, and polyimides.

Preferably the titanyl phthalocyanine is present in the charge generating layer in an amount of from about 30% to about 80%, more preferably from about 50% to about 75%, by weight of the composition forming the charge generating layer.

Preferably the binder is present in the charge generating layer in an amount of from about 20% to about 70%, more preferably from about 25% to about 50%, by weight of the composition forming the charge generating layer.

Preferably the respective weight ratio of the titanyl phthalocyanine to binder in the charge generating layer is from about 3/7 to about 4, more preferably from about 1 to about 3.

The substrate for the photoconductive member may be any electrically conducting substrate commonly used in electrophotography. The substrate may be a metal or metallised sheet or the curved surface of a substantially cylindrical drum. Preferred metals comprise aluminium, stainless steel, copper, more preferably aluminium.

Metallised sheets preferably comprise aluminised polyester film.

The charge transport layer may comprise one or more compounds which may act as a charge transport material selected from one or more of the following and any suitable mixtures thereof: arylamines, aryl hydrazones, stilbenes, pyrazolines, di- and triarylmethanes, heterocyclic aminoaryl compounds and oxadiazoles. Preferred charge transport materials comprise arylamines of Formula I;

Formula I in which R', R2, R3 and R4 are each independently H or alkyl.

Preferred compounds of Formula I are those in which R1 and R2 are each independently C1-lo alkyl and R3 and R4 are both H. More preferred compounds of Formula I are those in which R and R2 are methyl and R3 and R4 are both H.

The photoconductive member may also comprise additional layers which improves its electrical, mechanical or stability characteristics. Adhesive layers, blocking layers and/or protective layers may also be added.

A further aspect of the present invention comprises an electroreprographic device comprising a Zeneca type titanyl phthalocyanine, a charge generating composition as described herein and/or a photoconductive member as described herein. Preferably the electroreprographic device is selected from: a photocopier and a laser printer.

Broadly a still further aspect of the present invention provides for a method of manufacturing of one of more of the following: a charge generating composition as described herein; a photo-conductive member as described herein; and/or an electroreprographic device as described herein: using a Zeneca type titanyl phthalocyanine.

A specific embodiment of the process of the present invention will now be described which it will be understood is illustrative only and should not be construed as limiting the disclosure of the present invention.

Example 1 Preparation of titanyl phthalocyanine S Preparation of diiminoisoindoline C6H4(CN)2 Di3 One kg of phthalonitrile, 3.5 litres of methanol and 100 ml of a solution of 25 % by weight of sodium methoxide in methanol (obtained from Aldrich) were mixed together with stirring in an open vessel. The mixture was heated at 3040"C for 2 hours whilst 280 g of ammonia was bubbled through the mixture, after which the mixture was heated at 600C under reflux for a further 2 hours. The reaction mixture was filtered whilst hot. The filtrate was allowed to cool to ambient temperature to form crystals which were collected by filtration. The crude crystals were purified using liquid chromatography at high pressure, with methanol as the eluent, to obtain 895 g of diiminoisoindoline which was used in stage I b as described below.

PreDaration of TiOPc (I)

581 g of diiminoisoindoline (also known as Dl3 - prepared as described in stage la) was mixed with 3.176 kg of chloronapthalene in a closed reaction vessel. The air in the reaction vessel was replaced by dry nitrogen and 340 g of titanium tetrabutoxide was added to the mixture. Still in an inert nitrogen atmosphere, the mixture was heated to 200"C as rapidly as possible (over 1 hour 30 minutes) using an oil bath and held at that temperature for a further 2 hours 30 minutes whilst the reaction vessel was purged with fast flowing N2 gas to remove butanol and ammonia gas. The reaction mixture was left to cool to 175"C without being stirred and was allowed to settle for about 20 minutes. The upper mother liquors were decanted to leave a solid residue in the reaction vessel. One litre of boiling dimethylformamide (DMF) was added to this solid whilst heating at 150"C for 15 minutes to form a slurry which was then allowed to settle for 15 minutes and the upper liquors were decanted to leave a solid residue. A slurry was formed from solid residue a further three times as described before, except the third time the DMF slurry was filtered to obtain a pale blue/green filtrate. This filtrate was allowed to cool to room temperature and a purple solid precipitate was formed which was collected by filtration.

The purple solid was washed thrice with one litre of DMF at room temperature until the washings were a very pale green colour. The solid was then washed thrice with 500 ml of methanol and finally was dried at 70"C until the solid was approximately a constant weight (about 400 g). The TiOPc(l) obtained was used in stage Ic as described below.

1 c) Conversion of TiOPc(l) to TiOPc(X)

Two litres of a mixture of methane sulphonic acid and dichloromethane (in a respective volume ratio of 1:4) was chilled to 0 C. To this mixture was added 200 g of TiOPc(l) prepared as described in stage 1 b above. The mixture was stirred for 5 minutes to dissolve the TiOPc(l) in the acid The solution was filtered through glass-fibre filter paper to remove insoluble impurities and any undissolved TiOPc(l). The filtrate was diluted by being added drop-wise from a dropping funnel (500 ml at a time to keep the solution cold) over about 1 hour 30 minutes to the centre of the vortex of a stirred cold solution (at -10"C) comprising 10 litres of methanol, 2.5 kg of de-ionised ice and 7.5 kg of de-ionised water. The resultant suspension (at a temperature of -5 C after the dilution was completed) was filtered to collect a blue solid which was then washed with 4 litres of methanol. This blue solid was added to 8 litres of de-ionised water to form a slurry which was heated for 2 hours at 75"C. This sluny was then filtered as before to collect a solid which was then washed with methanol in 1 litre quantities until the conductivity of the solid measured 20 I1S or less, which typically required about 8 litres of methanol. The resultant TiOPc(X) was used in stage I c as described below.

Id) Conversion of TiOPc(X) to TlOPc(Za!

300 g of TiOPc (X) prepared as described in stage Ic, was mixed with 4 litres of anisole at 3-5"C for one hour to form a slurry, which was then filtered over a total of 5-6 hours through glass-fibre paper. The collected solid was washed with 3 litres of ethylated industrial alcohol followed by 4 litres of de-ionised water. The washed bright blue solid was dried at 75 C overnight to give 1709 of TiOPc(Za). The XRD pattern of this TiOPc (Za) was measured using a Cu-Kct beam of wavelength 1.541 A and showed a maximum peak at a Bragg angle (20) of 27.3 and further diffraction peaks in decreasing order of intensity at Bragg angles (20) of 9.0 , 9.5 , 24.1 and 14.3 .

Claims (38)

1. A process for preparing titanyl phthalocyanine comprising the following steps: a) reacting an optionally substituted phthalonitrile with ammonia in the presence of alkali metal alkoxide to form a diiminoisoindoline; b) reacting the diiminoisoindoline obtained from step 'a)' with titanium tetraalkoxide to form a titanyl phthalocyanine of the polymorphic crystal form known as Type I; c) dissolving the Type I titanyl phthalocyanine obtained from step 'b)' in a mixture of alkane sulphonic acid and halogenated aliphatic hydrocarbon to form a titanyl phthaiocyanine of the polymorphic crystal form known as Type X; and d) treating the Type X titanyl phthalocyanine obtained form step 'c)' with substituted aromatic hydrocarbon until a titanyl phthalocyanine is formed having an XRD pattern showing a maximum peak at a Bragg angle (20i0.20) of about 27.3 and further diffraction peaks in decreasing order of intensity at Bragg angles (28±0.2") of about 9.0 , about 9.5 , about 24.1 and about 14.3",.and then collecting the titanyl phthalocyanine from the substituted aromatic hydrocarbon.

2. A process as claimed in claim 1, in which in step a) the alkali metal alkoxide comprises one or more C-C6 alkoxide of sodium or potassium.

3. A process as claimed in claim 2, in which in step a) the alkali metal alkoxide comprises sodium methoxide.

4. A process as claimed in any preceding claim, in which in step a) the reaction is carried out at a temperature from about 20"C to about 1200C.

5. A process as claimed in claim 4, in which in step a) the reaction is carried out at a temperature from about 500C to about 750C.

6. A process as claimed in any preceding claim, in which in step b) the titanium tetraalkoxide comprises one or more C1-C6 alkoxide of titanium.

7. A process as claimed in claim 6, in which in step b) the titanium alkoxide comprises titanium tetrabutoxide.

8. A process as claimed in any preceding claim, in which in step b) the reaction is carried out at a temperature from about 1 30 C to about 230"C.

9. A process as claimed in claim 8, in which in step b) the reaction is carried out at a temperature from about 19000 to about 210"C.

10. A process as claimed in any preceding claim, in which in step c) the alkane sulphonic acid comprises one or more C,-C,0 alkane sulphonic acid.

11. A process as claimed in any preceding claim, in which in step c) the alkane sulphonic acid comprises one or more C1-C4 alkane sulphonic acid.

12. A process as claimed in any preceding claim, in which in step c) the alkane sulphonic acid comprises methane sulphonic acid.

13. A process as claimed in any preceding claim, in which in step c) the halogenated aliphatic hydrocarbon comprises one or more chlorinated aliphatic hydrocarbon.

14. A process as claimed in any preceding claim, in which in step c) the halogenated aliphatic hydrocarbon comprises dichloromethane.

15. A process as claimed in any preceding claim, in which in step c) the dissolution is carried out at a temperature from about -20 C to about +20"C.

16. A process as claimed in claim 15, in which in step c) the dissolution is carried out at a temperature from about -10 C to about +10 C.

17. A process as claimed in any preceding claim, in which in step d) the substituted aromatic hydrocarbon comprises one or more: aryloxybenzene, alkoxybenzene or suitable mixtures thereof.

18. A process as claimed in claim 17, in which in step d) the substituted aromatic hydrocarbon comprises methoxybenzene.

19. A process as claimed in any preceding claim, in which in step d) the treatment is carried out at a temperature from about -25 C to about +25"C.

20. A process as claimed in claim 19, in which in step d) the treatment is carried out at a temperature from about -100C to about +10 C.

21. A process as claimed in claim 20, in which in step c) the treatment is carried out at a temperature from about -5 C to about +5"C.

22. A process as claimed in any preceding claim, in which step d) is carried out substantially in an inert atmosphere.

23. A process as claimed in claim 22, in which the inert atmosphere comprises nitrogen gas which is substantially free of water.

24. A process as claimed in any preceding claim in which the solid product from one or more of steps b), c) and/or d) is collected by a method comprising the further steps of: forming a slurry with the solid in a suitable liquid; allowing the solid to settle from the slurry; decanting the upper liquor from the slurry to leave a solid residue, optionally repeating the preceding steps one or more times, dissolving the solid residue in a suitable solvent; and collecting the solid by filtration.

25. A process substantially as described herein with reference to Example 1.

26. A crystalline form of a titanyl phthalocyanine obtained or obtainable by a process as claimed in any preceding claim.

27. A crystalline form of a titanyl phthalocyanine characterised by having an XRD pattern showing a maximum peak at a Bragg angle (20+0.2 ) of about 27.3 and further diffraction peaks in decreasing order of intensity at Bragg angles (2()j0.20) of about 9.0 , about 9.5 , about 24.1 and about 14.3 .

28. A crystalline form of a titanyl phthalocyanine obtained or obtainable substantially as described herein with reference to Example 1.

29. A charge generating material comprising a crystalline form of titanyl phthalocyanine as claimed in any of claims 26 to 28 together with a suitable binder and/or carrier.

30. A photo-conductive member comprising a substrate, a charge generating layer and a charge transport layer characterised in that the charge generating layer comprises a crystalline form of titanyl phthalocyanine as claimed in any of claims 26 to 28.

31. A photo-conductive member as claimed in claim 30, which comprises the curved surface of a substantially cylindrical photoconductive drum.

32. A photo-conductive member as claimed in either claim 30 or 31, in which the charge transport layer comprises one or more compounds which may act as a charge transport material selected from one or more of the following and any suitable mixtures thereof: arylamines, aryl hydrazones, stilbenes, pyrazolines, di and tri-arylmethanes, heterocyclic aminoaryl compounds and oxadiazoles.

33. A photo-conductive member as claimed in claim 32, in which the charge transport material comprises arylamines of Formula I:

Formula I in which R1, R2., R3 and R4 are each independently H or alkyl.

34. A photo-conductive member as claimed in claim 33, in which the charge transport material comprises arylamines of Formula I where R1 and R2 are each independently Cl.lo alkyl and R3 and R4 are both H.

35. A photo-conductive member as claimed in claim 34, in which the charge transport material comprises arylamines of Formula I where R1 and R2 are both methyl.

36. An electroreprographic device comprising a crystalline form of titanyl phthalocyanine as claimed in any of claims 26 to 28, a charge generating material as claimed in claim 29 and/or a photoconductive member as claimed in any of claims 30 to 35.

37. An electroreprographic device as claimed in claim 36, which is selected from: a photocopier and a laser printer.

38. A method of manufacturing of one of more of the following: a) a charge generating material as claimed in claim 29; b) a photoconductive member as claimed in any of claims 30 to 35; and/or c) an electroreprographic device as claimed in either claim 36 or 37; comprising use of a crystalline form of titanyl phthalocyanine as claimed in any of claims 26 to 28.