WO1994024612A1

WO1994024612A1 - Chemical compounds

Info

Publication number: WO1994024612A1
Application number: PCT/GB1994/000765
Authority: WO
Inventors: Stephen James Reynolds; Raymond Stevenson Gairns; Paul Andrew Simpson
Original assignee: Zeneca Limited
Priority date: 1993-04-15
Filing date: 1994-04-12
Publication date: 1994-10-27
Also published as: GB9307749D0

Abstract

An organic photoconductor comprising an electrically conducting support, a charge generation layer and a charge transport layer wherein the charge generation layer contains a boron subphthalocyanine such as that obtainable by reacting phenyldichloroborane with tetra-4-methylthiophenylphthalonitrile.

Description

CHEMICAL COMPOUNDS This invention relates to chemical compounds, to compositions and to an organic photoconductor for use as the photosensitive element of an electrophotographic device such as a copier or printer.

Organic photoconductor (OPC) or photoreceptor devices used in electrophotographic copiers and printers generally comprise an electrically conducting support, a charge generation layer (CGL) containing a charge generation compound, which may be a dye or pigment, and a charge transport layer (CTL) containing a charge transport material which may be either an n-type or a p-type semiconductor.

It has now been found that high performance OPC devices may be obtained using boron subphthalocyanine charge generation compounds in the charge generation layer thereof.

Thus, according to the invention, there is provided an organic photoconductor comprising an electrically conducting support, a charge generation layer and a charge transport layer, characterised in that the charge generation layer contains a boron subphthalocyanine.

The boron subphthalocyanine preferably comprises three optionally substituted isoindole units surrounding a boron atom. Each optional substituent, hereinafter referred to as R, which may be present in the isoindole units is preferably an alkyl, aryl, ether, thioether, halo, nitro, cyano, ester, acyl, sulpho, sulphonamide, carboxy or carbonamide group. When R is alkyl it is preferably C.__₄-alkyl. The preferred aryl substituents represented by R is optionally substituted naphthyl or phenyl. Preferred ethers and thioethers represented by R are alkyl and aryl ethers and thioethers, more preferably C₁.₄-alkyl, naphthyl, phenyl and tolyl ethers and thioethers.

When R is optionally substituted naphthyl or phenyl the optional substituents are preferably selected from halo, especially chloro;

C-.₈-alkyl, especially methyl; nitro; C-^-alkoxy, especially methoxy and cyano.

When R is an ester group it is preferably -C0₂T^*- wherein T¹ is C-_^.-alkyl or phenyl. When R is an acyl group it is preferably -COT¹ wherein T¹ is as hereinbefore defined. When R is a carbonamide group it is preferably -CCNT²T³ wherein T² and T³ are each independently H, C..₄-alkyl or phenyl.

Preferably the boron subphthalocyanine is unsubstituted or has from 1 to 12, more preferably 3, 6, 9 or 12, substituents represented by R which are different to each other or the same as each other.

Examples of optional substituents represented by R include methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, phenyl, methoxy, ethoxy, -SCH₃, -SCH₂CH₃, naphthyloxy, naphthylthio, phenoxy, phenylthio, chloro, fluoro, bromo, nitro, cyano, methylphenylthio, methylphenoxy, methoxyphenoxy, methoxyphenylthio, nitrophenoxy, t-octylphenoxy, butoxyphenoxy and di-t-butyiphenoxy.

A preferred boron subphthalocyanine is a compound cf the Formula (1) :

wherein:

Z is optionally substituted boron; and R¹, R², R³, R\ R^s, R^β, R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are each independently H or a substituent. Z is preferably boron substituted by a halogen, hydroxy or alkoxy, more preferably by an alkyl, aryl or aryloxy group. The preferred halogen is Cl, F or Br; the preferred alkoxy group is C_x__β- alkoxy; the preferred alkyl group is C₁.₆-alkyl especially C_x_₄-alkyl; the preferred aryl group is phenyl; the preferred aryloxy group is phenoxy. Examples of boron substituted by the aforementioned groups include B-Cl, B-F, B-CH₃, B-OCH₃, B-Phenyl, B-Br, B-OH and B-OCH₂CH₃. R¹, R², R³, R⁴, R^s, R^β, R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are preferably each independently H or a substituent selected from those mentioned above for R.

It is preferred that R¹ is identical to R^s, R⁸, R⁹ or R¹². Preferably R² is identical to R^s, R⁷, R¹⁰ or R¹¹. R³ is preferably identical to R^s, R⁷, R¹⁰ or R¹¹. R⁴ is preferably identical to R^s, R^s, R⁹ or R¹².

In one embodiment of the present invention R¹, R⁴, R⁵, R⁸, R⁹ and R¹² are identical to each other. In a second embodiment R¹ to R¹² are identical to each other. In a third embodiment R², R³, R⁶, R⁷, R¹⁰ and R¹¹ are identical to each other and different from R¹, R⁴, R^s, R⁸, R⁹ and R¹².

The thickness of the electrically conductive support will depend on many factors, for example its cost, and may be of substantial thickness (e.g. over 2,500μM) or lower thickness providing there are no adverse effects on the OPC. Preferably the support is from 50 to 250μM thick, more preferably 75 to 200μM thick.

The electrically conducting support may be a metal support preferably in the form of a drum or a composite material comprising an insulating supporting material such as a sheet of polymeric material, e.g. a polyester sheet or film, coated with a thin film of a conducting material, e.g. a metal such as aluminium or nickel, in the form of a drum or a continuous belt.

The CGL may consist essentially of the boron subphthalocyanine but preferably the CGL comprises a solution or dispersion thereof in a resin. Preferably the CGL is from 0.05 to 20μM thick, more preferably 0.1 to lOμM thick. Examples of suitable resins for use in the charge generation layer are polycarbonate, polyester, polystyrene, polyurethane, epoxy, acrylic, styrene-acrylic, melamine and silicone resins. Where the resin does not have good adhesive properties with respect to the substrate, e.g. a polycarbonate resin, adhesion between the resin and the substrate may be improved by the use of an adhesive resin. Specific examples of suitable resins for use in the charge generating phase are LEXAN 141 Natural (available from General Electric Plastics, Europe) and VITEL PE200 polyester. A suitable adhesive resin for bonding the charge generation layer to the substrate is VMCA (available from Union Carbide) . Particularly preferred resins have a number average molecular weight (MW) from 20,000 to 150,000, more preferably from 50,000 to 100,000, especially those mentioned above.

Examples of resins include polystyrenes; silicone resins such as DC-801, DC-804 and DC-997 all manufactured by the Dow Corning

Corporation; and Lexan, a polycarbonate resin, SR-82 manufactured by the General Electric Company; acrylic and methacrylic ester polymers such as Acryloid A10 and Acryloid B72, polymerized ester derivatives of acrylic and alpha-acrylic acids both supplied by Rohm and Haas Company and Lucite 44, Lucite 45 and Lucite 46 polymerized butyl methacrylates supplied by the E.I. du-Pont de Nemours & Company; chlorinated rubber such as Parlson supplied by the Hercules Powder Company; vinyl polymers and copolymers such as polvinyl chloride, polyvinyl acetate, etc including Vinylite VYHH and VMCH manufactured by the Bakelite Corporation; cellulose esters and ethers such as ethyl cellulose, nitro-cellulose, etc; alkyd resins such as Glyptal 2469 manufactured by the General Electric Company, etc; and polyester resins such as those available from Goodyear under the tradename Flexclad. In addition, mixtures of such resins with each other or with plasticizers so as to improve adhesion, flexibility, blocking, etc of the coating may be used. Thus, Rezyl 869 (a linseed oil- glycerol- alkyd manufactured by American Cyanamid Company) may be added to chlorinated rubber to improve its adhesion and flexibility. Similarly, Vinylites VYHH and VMCH (polyvinyl chloride-acetate copolymers manufactured by the Bakelite Company) may be blended together. Plasticizers include phthalates, phosphates and adipates.

Particularly preferred resins are poly(4,4 ' -isopropylidene- diphenylene carbonate) with an MW of from about 35,000 to about 40,000, available as Lexan 145 from General Electric Company; poly- (4,4 ' -isopropylidene-diphenylene carbonate) with an MW of from about 40,000 to 45,000, available as Lexan 141 from the General Electric Company; a polycarbonate resin having an MW of from about 50,000 to about 100,000, available as Makrolon from Farbenfabricken Bayer A.G. and a polycarbonate resin having an MW of from about 20,000 to about 50,000, available as Merlon from Mobay Chemical Company.

The CTL preferably comprises resin and a charge transport material, for example an oxazole, oxadiazole, enamine or a leuco di- or tri-arylmethane, a hydrazone, a tetraarylbenzidine or a triarylamine, especially those described in US Patent No 5,085,961 column 2, line 23 to column 6, line 27 which is incorporated herein by reference thereto. The CTL preferably has a thickness from 1 to 50μM and more preferably from 5 to 30μM. Examples of suitable resins for use in the CTL include those mentioned above for the CGL.

The charge transport materials may be included in the CTL and the OPC may be prepared using analogous methods to those described in the art for the phthalocyanine CTMs . The OPC may be in the form of an aggregate organic photo conductor, for example analogous to those described in J.Appl.Phys. 49(11) , 1978 pp 5543-5554 and 5555-5564. Such aggregate OPCs show high sensitivity, a broad spectral response and excellent stability of electrical characteristics when rapidly recycled through the steps employed in electrostatic electrophotography.

The boron subphthalocyanines may be prepared by condensing approximately three equivalents of an optionally substituted orthodicyanobenzene with a compound of formula BX-.Y-, wherein X is F, Cl or Br, Y is a substituent (preferably as defined herein for R) and n and m each independently have a value of 0 to 3 and provided m and n is less than or equal to 3. The condensation is preferably performed in high boiling inert solvent, e.g. 1-chloronaphthalene, preferably at a temperature of 180 to^*280°C, more preferably 210 to 260°C. A reaction time of 10 minutes to 1 hour, preferably 15 minutes to 45 minutes is usually sufficient.

Compounds of Formula (1) wherein Z is B-H or boron substituted by alkyl, aryl or aryloxy and R¹ to R¹² are as hereinbefore defined form a further aspect of the present invention.

Further compounds according to the invention are of Formula (l) wherein Z and R¹ to R¹² are as hereinbefore defined with the proviso that when Z is boron substituted by halo or alkoxy at least one of R¹ to R¹², preferably at least there of R¹ to R¹², is, or are each independently, selected from C_x.₃-alkyl, C_x.₃-alkoxy, aryloxy, thioether, cyano, ester, acyl, sulpho, sulphonamide, carboxy and carbonamide.

The boron subphthalocyanines described herein may also be used as colorants for textiles, resins or for inks, especially inks used in hot melt ink jet printing.

A further feature of the present invention is a composition comprising resin and a boron subphthalocyanine as hereinbefore described, preferably of Formula (1) as hereinbefore defined. The preferred resin is electrically non-conductive. Particularly preferred resins are as hereinbefore described.

The weight ratio of resin to boron subphthalocyanine preferably lies in the range 99:1 to 1:99, more preferably 20:1 to 1:20, more especially about 1 to 1. The invention is illustrated but not limited by the following examples in which all parts are by weight unless otherwise indicated. Ph is phenyl.

Example 1 Preparation of the compounds of Formula (1) wherein R¹ to R¹² are 4- methylphenylthio and Z is B-Ph, B-Cl, B-OCH-, or B-OH

Phenyldichloroborane (3.86g, 0.0243mol) was added dropwise to a stirred solution of tetra-4-methylphenylthiophthalonitrile (preparable by condensation of 4-methylphenglthiol and tetrachlorophthalonitrile) (10g, 0.0162mol) in 1-chloronaphthalene (20ml) at 200°C under an atmosphere of nitrogen. The mixture was stirred at 250°C under nitrogen for 30 minutes and then allowed to cool to room temperature. The mixture was drowned out into methanol (200ml) and the supernatant liquid decanted off to leave a bluish-green gum. The gum was triturated with methanol (2 x 200ml) to give a solid which was placed in a soxhlet thimble and extracted under reflux with methanol for 30 hours. The remaining solid was collected by filtration as a mixture of differently substituted boron subphthalocyanines. The individual components were separated by column chromatography on silica eluting with:

(i) hexane 3:1 dichloromethane to give a mixture of the title compounds wherein Z is B-Ph/B-Cl (0.5g, 5%) as a bluish-green solid, m.p. 155-165°C (dec); and lambda max (CH₂C1₂) 640nm (E max 97800); (ii) hexane 1:1 dichloromethane gave the title compound wherein Z is B-OCH. (1.39g, 14%) as a bluish-green solid, m.p. 130-140°C; lambda max (CH²C1₂) 635nm (E max 99500) ; (iii) dichloromethane 10:1 hexane gave the title compound wherein Z is 3-OH ( 0 . 3g , 3 % ) as a greenish-blue solid , m . p . 140 - 160 °C ; lambda max ( CH₂C1₂ ) 630nm ( E max 98100 ) .

Example 2 Preparat ion of the compound of Formula ( 1 ) wherein R¹ to R¹² are 2 - naphthyloxy and Z is B- Cl

Stage a

A mixture of tetrachlorophthalonitrile (26.5g, O.lmol),

2-naphthol (86g, 0.6mol) and potassium carbonate (55.5g, 0.4mol) in dimethylformamide (200ml) was stirred and heated at 120°C for 2 hours.

The mixture was cooled, drowned out into water (500ml) and extracted using dichloromethane (2x200ml) . The combined organic extracts were washed with aqueous 5% potassium hydroxide and water. The organic layer was dried (MgS0₄) , carbon screened and evaporated to dryness in vacuo to leave a solid. The solid was crystallised from acetone/water to yield tetra(2-naphthyloxy)phthalonitrile (42.64g, 69.6%) as a pale yellow powder, m.p. 196-198⁰C.

Stage b Phenyldichloroborane (0.29g, l.δmmol) was added dropwise to a stirred solution of tetra(2-naphthyloxy)phthalonitrile (5g, 7.i8mmol) in 1-chloronaphthalene (12ml) at 200°C under an atmosphere of nitrogen. The resultant mixture was stirred at 250°C under nitrogen for 10 minutes then allowed to cool to room temperature. The mixture was drowned out into methanol (100ml) and the resultant precipitate collected by filtration and washed with methanol to leave a blue solid. The solid was purified by column chromatography on silica eluting with hexane 3:2 dichloromethane to give the title compound (0.175g, 1.1'%) as a reddish-blue gum,- lambda max (CH₂C1₂) 608.4nm (E max 71000) .

Example 3

Preparation of the compounds of Formula (1) wherein Z is B-OCH-, or a mixture of -B-Cl/-B-Ph and R². R³, R⁶. R⁷. R¹⁰ and R¹¹ are 2- naphthylthio Stage a

2-Thionaphthol (16.98g, 0.106mol) was added to a stirred solution of sodium methoxide (6.05g, 0.112mol) in methanol (50ml) under nitrogen. The mixture was stirred for 1 hour and then added dropwise over 1 hour to a stirred solution of 4 , 5-dichlorcphthalo- nitrile (lOg, 0.0507mol) in methanol (100ml) . The resultant suspension was stirred and heated under reflux for 2 hours and then cooled and drowned out into water (300ml) . The solid was collected by filtration, filtered through a pad of silica, eluting with toluene, and the filtrate evaporated to dryness in vacuo to give a solid which was crystallised from acetone/ water to yield 4- (2-thionaphthyl) -5- chlorophthalonitrile (11.2g, 68%) as a white solid, m.p. 209-212°C.

Stage b

2-Thionaphthol (11.09g, 0.069mol) was added to a stirred solution of sodium methoxide (3.92g, 0.073mol) in methanol (50ml) under nitrogen. The mixture was stirred for 1 hour and then added dropwise over 1 hour to a stirred solution of 4- (2-thionaphthyl) -5- chlorophthalo nitrile (llg, 0.0345mol) in methanol (100ml) . The resultant suspension was stirred and heated under reflux for 3 hours and then cooled and drowned out into water (400ml) . The solid was collected by filtration, dissolved in dichloromethane (41) and washed with 10% aqueous potassium hydroxide (2 x 11) , then water (11) and dried (MgS0₄) and evaporated to dryness n vacuo to leave an off-white solid which was recrystallised from toluene to give 4,5-di(2- thionaphthyl) hthalonitrile (12.3g, 80%) as a white fluffy solid, m.p. 244-246°C.

Stage c

Phenyldichloroborane (1.22g, 7.71mmol) was added dropwise to a stirred solution of 4, 5-di (-2-thionaphthyl) -phthalonitrile (2.l6g, 4.86mmol) in 1-chloronaphthalene (10ml) at 200°C under an atmosphere of nitrogen. The resultant mixture was stirred at 250°C for 10 minutes and then allowed to cool to room temperature. The mixture was drowned out into methanol (100ml) and the resultant precipitate collected by filtration and washed with methanol to leave a blue solid. The solid was placed in a soxhlet thimble and washed with refluxing methanol for 18 hours. The remaining solid was purified by column chromatography on silica eluting with hexane 1:1 dichloromethane to give the title mixture where Z is -B-Cl/-3-Ph as a reddish-blue solid, m.p. 160-170°C (dec); lambda max (CH₂C1₂) 605nm (e max 64000) . Elution with hexane 1:3 dichloromethane gave the title compound wherein Z is B-OCH, (0.03g) as a reddish-blue solid, m.p. 135-140°C (dec) lambda max 600nm (e max 80000) .

Example 4

Preparation of a compound of Formula (1) wherein R², R³, R⁶, R⁷, R¹⁰ and R¹¹ are 4-nitrophenoxy and Z is B-Ph A mixture of 4,5-dichlorophthalonitrile (15g, 0.076mol) ,

4-nitrophenol (21.29g, 0.153mol) , potassium carbonate (21.2g, 0.153mol) in dimethylformamide (100ml) was stirred at 120°C for 2 hours and cooled to room temperature before adding to water (250ml) . The mixture was extracted using dichloromethane (2 x 100ml) and the combined organic extracts washed with water, with 5% potassium hydroxide and water (2 x 100ml) . The organic phase was dried (MgS0₄) , carbon screened and evaporated to dryness in vacuo. The resultant solid was crystallised from acetone and water to yield 4,5-di(4- nitrophenoxy) hthalonitrile (8.21g, 36.5%) as a yellow solid. Phenyldichloroborane (0.9g, 5.6mmol) was added dropwise to a stirred solution of 4, 5-di (4-nitrophenoxy) hthalonitrile (1.5g, 3.73mmo^'l) in 1-chloronaphthalene (5ml) at 200°C under an atmosphere of nitrogen. The resultant solution was stirred and heated at 250°C under nitrogen for 30 minutes, allowed to cool to room temperature and then drowned out into methanol (100ml) . The resultant solid was purified by column chromatography on alumina eluting with dichloromethane to yield the title compound as a magenta solid, m.p. 235-255°C (dec) ; lambda max (CH₂C1₂) 569nm.

Example 5

Preparation of the compound of Formula (1) wherein R¹ to R¹² are chloro and Z is a mixture of B-Ph and B-Cl

Phenyldichloroborane (1.3mls, 0.013mol), was added dropwise to a stirred solution of tetrachlorophthalonitrile (lOg, 0.038mol) in 1- chloronaphthalene (20ml) at 240°C under an atmosphere of nitrogen.

The mixture was then stirred and heated for 2^">_ hours at 240°C. The mixture was allowed to cool to room temperature and drowned into methanol (200mls) . The product precipitated along with unreacted starting material and was filtered off under vacuum.

Starting material was removed from the crude mixture by column chromatography on silica, eluting with dichloromethane. A bluish-red solid was isolated and found to be a mixture of 3 differently substituted sub-phthalocyanines all of which gave fluorescent bands on t.l.c. (eluting with 1:1 hexane:dichloromethane) , r.f. values (1) 0.84 major product (isolated); (2) 0.66 minor product; and (3) 0.54 minor product. The major product (1) was isolated by column chromatography on silica, eluting with 1:1 hexane:dichloromethane as a bluish-red solid (0.5g, 6.2%); m.p. 184-188°C; lambda max (CH₂C1₂) 587nm_; the major product being Z = B-Cl, with minor amounts of Z = B-Ph.

Example 6

Preparation of a compound of Formula (1) wherein R¹ to R¹² are H and Z is B-Ph

Phenyldichloroborane (3.1g, 0.02mol) was added dropwise to a stirred solution of diiminoisoindoline (11.32g, 0.078mol) in 1-chloro naphthalene (20ml) at 200°C under an atmosphere of nitrogen. The mixture was stirred and heated to 260°C for 1 hour and then allowed to cool to room temperature. The mixture was drowned into methanol (400ml) and the precipitated starting material filtered off to leave a dark red filtrate which was extracted with n-hexane (5 x 250ml) . Solvent was evaporated from the combined extract to give a crude product which contained some 1-chloronaphthalene. The crude product was dissolved in dichloromethane (40ml) and purified by column chromatography on silica, eluting with dichloromethane to yield the title product as a magenta solid (0.20g, 2.4%), m.p. 122-124°C, lambda max (CH₂C1₂) 560nm, m/z 472 (M"^*(Ph), 52%) .

Examples 7 and 8

Sub-phthalocyanine (0.2g) from the above examples and polyester resin (VITEL PE200 from Goodyear) (0.2g) were added to a bottle containing 3mm glass beads (lOg) and dichloromethane 4:1 toluene

(DCM/T) (4.5ml) and shaken for 1 hour on a Red Devil paint shaker. The dispersion was diluted with 4:1 DCM/T (4ml), coated onto 100 micron aluminised polyester film (MELINEX from ICI) , using a 6 micron (wet thickness) wire-wound bar and dried to form a charge generation layer (CGL) . The polyester film had been precoated with a 2% wt/v solution of an adhesive polymer in tetrahydrofuran 9:1 toluene using a 6 micron (wet thickness) wire- ound bar. The CGL was overcoated with a solution of 4- (diethylamino)benzaldehydediphenylhydrazone (0.3g) and polycarbonate binder (0.24g, VITEL PE200) in DCM/T (9:1, 3.24g) using a 150 micron (wet thickness) wire-wound bar, dried at 70°C for 3 hours to form an OPC comprising a CGL and a CTL. Each OPC was tested using a Kawaguchi Electric Works Model SP428

Electrostatic Paper Analyser, in the dynamic mode. The following properties were measured:

V_x Surface potential (volt) of sample after 10 seconds charging with a 6kV corona. V₂ Surface potential (volt) after 5 seconds in dark conditions. DD Dark decay (%) given by the expression: Vχ-V₂ DD = x 100

V. S Sensitivity (lux sec) : the product of the light intensity (lux) and the time (sec) taken to reduce the surface potential by 50%. V_r Residual Potential (volt) remaining on surface after illumination for 10 sec.

The results are set out in Table 1:

Table 1

Example CGC V_x (volts) v₂ (volts) DD (%) S (lux sec) v_r

(volt)

7 Ex 6 1550 1256 19 10.8 160

8 Ex 1 1240 980 21 30.0 360

* - wherein Z is B-OCH₃.

Claims

1. An organic photoconductor comprising an electrically conducting support, a charge generation layer and a charge transport layer, characterised in that the charge generation layer contains a boron subphthalocyanine.

2. A composition comprising a resin and a boron subphthalocyanine.

3. Use of a compound of Formula (1) in an organic photoconductor:

wherein:

Z is optionally substituted boron; and R¹, R², R³, R⁴, R^s, R⁶. R⁷, R^β, R⁹, R¹⁰, R¹¹ and R¹² are each independently H or a substituent.

4. A compound of Formula (1) , as shown in Claim 3, wherein Z is B-H or boron substituted by alkyl, aryl or aryloxy and R¹ to R¹² are as defined in Claim 3.

5. A compound of Formula (1), as shown in Claim 3, wherein Z and R¹ to R¹² are as defined in Claim 3 with the proviso that when Z is boron substituted by halo or alkoxy at least one of R¹ to R¹² is selected from C_x.₃-alkyl, C_x.₃-alkoxy, aryloxy, thioether, cyano, ester, acyl, sulpho, sulphonamide, carboxy and carbonamide.