US3703371A - Photoconductive elements containing polymeric binders - Google Patents

Abstract

PHOTOCONDUCTIVE ELEMENTS CONTAINING A PHOTOCONDUCTOR AND A BINDER FOR THE PHOTOCONDUCTOR COMPRISING A POLY(ALKYLIDENEBISARYLOXYALKYL-CO-ALKYLENE ISOPHTHALATE) ARE DESCRIBED. THE DESCRIBED ELEMENTS CAN BE SENSITIZED AND CHARGED EITHER NEGATIVELY OR POSITIVELY AND USED TO PREPARE IMAGES ELECTROPHOTOGRAPHICALLY.

Description

U d St Paten .Qfi

US; crab-1.6 16 can,

ABSTRACT OF THE DISCLOSURE Photoconductive elements containing a photoconductor and a binder for the photoconductor comprising a poly- (alkylidenebisaryloxyalkyl-co-alkylene isophthalate) are described. The described elements can besensitized and charged either negatively or positively and usedto prepare images electrophotographically.

Patented Nov. 21 1972 speeds. In particular, substantial increases in speeds are obtained as compared to Ispeeds attainable with many other polymeric binder compositions. Thesejncreases in speed are observed when the coating accepts a suitable potential (e.g., 500-600 volts) and the relative speed o the coating is determined on the basis of the reciprocal of. the exposure required to reduce the potential ofv the surface charge by 100 volts (shoulder speed) or to 100 volts (toe speed). The reduction of the surface potential to 100 volts or below is significant in that it represents a requirement for suitable broad area development of a latent image. The relative speed at 100 volts is a measure of the ability to produce and henceforth to develop or otherwise utilize the latent image. When the photoconductor is absent from the coating and only a coi'lventional binder is used, the surface potential does not'fdroptoor below l00 volt's and therefore no speed jeanibeiassigned This is a continuation of application Ser. No. 772,370, I

filed Oct. 16, 1968, and now abandoned.

.',This inventionirelates to novel electrophotographic ele-' ments having coatings of binder-containing photoconduc: tive compositions.

, Binder-containing photoconductive compositions have been widely used in the preparation of electrophotographic elements. In 'electrophotographic reproduction processes, these elements are utilized in the formation of latent elec-' trostatic images. In some applications the photoconductive compositions contain an organic photoconductor and a sensitizer uniformly admixed in an inert resinous binder. (B)

Many binders are currently used in'connection with awide va'rietyyof available organic photoconductor compounds and compositions. Typical binders are ordinary polymeric materials, e.g., phenolic resins, ketone resins, acrylic ester resins, polystyrene, etc. However, these binders usually do I not impartany particular improvement in light sensitivity to'the system. The light sensitivity as indicated by the electrical speed ofthese particular systems is ordinarily due wholly to the organic photoconductor and sensitizer. Other binders have been found to contribute significantly to the light sensitivity of the system."However, the selection of these'polymers for incorporation into photoconductive compositions to form electrophotographic layers has proceeded on a compound-by-compound basis. Nothing has yet been discovered from thenumerous binders tested which permits efiective prediction and selection of particular polymers exhibiting the desired properties.

It is, therefore, an object of this invention to provide improved novel binder-containing photoconductive compositions which exhibit high light sensitivities.

It is another object to provide transparent electrophotographieelements having the high speed characteristic of the novel photoconductive compositions of this invention.

These and other objects of this invention are accomplished by a photoconductive composition which contains a photoconductor admixedwith a binder therefor which is a poly(alkylidenebisaryloxyalkyl-co-alkylene isophthalate (wherein the alkylene moiety contains 2 to 10 carbon atoms. It has been discovered that such compositions exhibit increased light sensitivities as evidenced by greater to such a composition. When a photo'c'ondu'c'tor is par't'of the coating in many conventional polymeric hinders, the surface potentials of such resultant compositions usually drop below 100 volts, and thus, a definite speed can be ascertained. However, these speeds are improved when the binders of this invention are employed.

i The poly(alkylidenebisaryloxyalkyl co alkylene isophthalate) copolyes'ters of this invention include those consisting essentially of the following repeating units:

and"

wherein Z is an alkylene group having 2 to 10 carbon atoms including substituted as well as unsubstituted alkylene radicals such as g (a)- A straight chain or branched chain alkylene hydrocarbon radical, e.g., those represented by the formula:

I TZ T where R, and R are either hydrogen'or an alkyl radical having 1 to 5 carbon atoms, 1 is an integer from 1 to 7 and s is an integer from zero to 7, including a trimethylene radical, a tetramethylene radical, a pentamethylene radical, a neopentylene radical, an ethylene radical, a

, hexamethylene radical, a propylene radical, etc.;

('b)- An ox'y'dialkyleneradical or a thiadialkylene radical, e.g.,those represented by the formula where each of and R is an alkylene radical including a branched 'chain alkylene CHCH2" etc. where- D is an oxygen or sulfur atom and n and o are integers from 2 to 7 including an oxydiethylene radical, a thiadiethylene radical, etc.;

(c) An alkylene bis(o xyalkylene) radical or an alkylerie bisfihiaalkylenradical, e.g.,those"represented by the formula where Q is the atoms necessary to complete a 3 to 6 carbon cycloalkylene radical and u and v are integers from to 5, including a cyclohexylenedimethylene radical, a cyclopentylenedimethylene radical, a cyclobutylene-dini'ethyleneradical, a' cyclobutylenediethylene radical, a

is coated on an electrically conducting support in a wellknown manner, such as swirling, spraying, doctor blade coating, and the like.

The novel binders of this invention improve the electrical speeds of compositions containing a wide variety of photoconductors.including inorganic photoconductors such as zinc oxide, titanium dioxide, cadmium sulfide and the like and organic photoconductors including organometallic photoconductors.

Typical photoconductors useful with the binders of this invention are described below.-

(A) Arylamine photoconductors including substituted and unsubstituted arylamines, diarylamines, nonpolymeric triarylamines and polymeric triarylamines such as those cyclobutylene radical, 2,2,4,4-te.tramethyl 1,3-cyclobutylene radical, etc.;

' (e) *D and E each can be ahydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group or an .aryloxy group. I The copolyester binders of this invention suitably contain'2"to 80% and preferably 30 to 60% of repeating unit A. The binder also suitably contains from about 20 to 98% and preferably 40 to 70% of repeating unit B. The polymer contains these units arranged in a random, linear fashion. Binders comprising such polymers improve the electrical speed of the photoconductive composition.

Exemplary of a few of the many polymers useful as binders in this invention are: I

( 1 Poly(4,4-isopropylidenebisphenoxyethyl-co-tri- .methylene isophthalate) (2) Poly(4,4-isopropylidenebisphenoxyethyl-co-tetramethylene isophthalate) (3) Poly(4,4'-isopropylidenebisphenoxyethyl-co-ethylene isophthalate) (4) Poly(4,4'-isopropylidcnebisphenoxyethyl-co-oxy- --diethylene isophthalate) e (5) Poly(4,4'-isopropylidenebisphenoxyethyl-co-neopentyl isophthalate) (6) Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclohexylenedimethylene isophthalate) (7) Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclobutylenedimethylene isophthalate) (8) Poly(4,4'-isopropylidenebisphenoxyethyl-co-thiadiethylene isophthalate) (9) Poly[4,4'-isopropylidenebisphenoxyethyl-co-ethyl enebis(oxyethylene) isophthalate] 10) Poly [4,4-isopropylidenebisphenoxyethyl-coethylenebis(thiaethylene) isophthalate] (1 1) Poly(4,4'-isopropylidenebisphenoxyethyl-co- 2,2,4,4 -tetramethyl-1,3-cyclobutylene isophthalate) (l2) Poly(4,4'-isopropylidenebisphenoxyethyl-co-tetramethylene-4-bromoisophthalate) 7 13) Poly(4,4'-isopropylidenebisphenoxyethyl-cd tetramethylene-5-phenoxyisophthalate) (14) Poly(4,4'-isopropylidenebisphenoxyethyl-copropylene isophthalate) 15) Poly(4,4-isopropylidenebisphenoxyethyl-cotetramethylene-Z,S-dichloroisophthalate) l 6) Poly(4,4'-isopropylidenebisphenoxyethyl'cotetramethylene-5-methoxyisophthalate) 17) Poly( 4,4'-isopropylidenebisphenoxyethyl-cotetramethylene-5-phenylisophthalate) In preparing typical electrophotographic elements utilizing the polymeric binders of this invention, an organic photoconductor is dissolved in a solution of binder and solvent and then, after thorough mixing, the composition described in US. Pats. 3,240,597 and 3,180,730.

(B) Photoconductors represented by the formula wherein A represents a nononuclear or polynuclear divalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, p entoxy, etc.), or a nitro group; A represents a mononuclear or polynuclear monovalent or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro group; Q can represent a hydrogen atom or an aromatic amino group, such as A'NH; b represents an integer from 1 to about 12, and L represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4'-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom of the phenyl group, these materials being more fully described in US. Pat. 3,265,496.

(C) Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials; and also other polyarylalkanes included by the formula:

I) J-d-E wherein each of D, E and G is an aryl group and I is a hydrogen atom, and alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, the aryl groups attached to the central carbon atom being preferably phenyl groups, although naphthyl groups can also be used, including substituted aryl groups containing substituents such as alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy, halogen, etc. in the ortho, meta or para positions, ortho-substituted phenyl being preferred; the aryl groups can also be joined together or cyclized to form a fiuorene moiety, for example; the amino substituent can be represented by the formula wherein each R can be an alkyl group typically having 1 toj8 carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group 'typically havingi to 6 atoms 'in the ring such as "morpholi'nof py'ridyl, pyrryl, etc.'; at least one of D, E and G" preferably being a p-dialkylami'nophenyl group," when I is an alkyl group, such an alkyl group more generally has to" 7 carbon atoms, "these materials being more fully described in U.S. Pat-3,274,000, French 'Pat. 1,383,- 46 1 and iIlZUZS. Ser.1No. 627,857 filed Apr. 3, ,1967 by Seus aiiq Goldman now US. 3,542,544. Photoconductors comprising 4-diarylamino sub- 'st'ituted chalcones'havingthe formula: i t

' \Nfli JD wherein R and R are each phenyl, radicals including ubstitutedphenyl radicals" and particularly whenR is a phenyl radical W.herein R and R areeach aryl radicals, aliphatic resi- .-dues of H012 carbon atoms such .as alkyl radicals prefer- :ablyhaving v1 to 4 carbon atoms, or hydrogen; particularly advantageousaresults being obtained-when R; is a vphenyl radical including-a substituted phenyl radical and where ;;R ,is diphenylaminophenyl, dimethylaminophenyl or ty is a conjugated triene with no aromatic structure fused thereto. However, if there isat least one aromatic structure fused tothe cycloheptenyl moiety, then the substituents are attached to a saturated carbon atom. Additional photoconductors within this class are included'in one of the following formulae: Y

6 where E and G can be either:

(a) A phenyl radical,

(b) A naphthyl radical,

(c) A heterocyclic radical having 5 to 6 atoms in the heterocyclic nucleus and at least one hetero nitrogen atom,

(d) A hydroxyl radical, or

(e) An oxygen containing radical having a structure such that the resultant cycloheptenyl compound is a symmetrical ether;

D can be any of the substituents defined for E and G above and is attached to a carbon atom in the cycloheptenyl nucleus having a double bond; (R and R (R and R (R and Re), and R and R are together the necessary atoms to complete a benzene ring fused to the cycloheptenyl nucleus; these compounds being more fully described in U.S. Ser. No. 654,091 filed July 18, 1967 now U.S. 3,533,786.

.' (F) Compounds containing an nucleus including (1) unsubstituted and substituted N,N- bicarbazyls containing substituents in either or both carbazolyl nuclei such as (a) An alkylradical including a substituted alkyl radical such as a haloalkyl or an alkoxyalkyl radical,

(b) A phenyl radical including a substituted phenyl radical such as a naphthyl, an aminophenyl or a hydroxyphenyl radical,

(c) A halogen atom,

(d) An amino radical including substituted as well as unsubstituted amino radicalssuch as an alkylamino or a phenylalkylamino radical,

"'(e) An 'alkoxy radical, (f) A hydroxyl radical,

. (g) A cyano radical,

NN El ill where D E G and" J are each either i (a) A substituted phenyl radical such as a naphthy radical, an alkylphenyl radical, a halophenyl radical, a hydroxyphenyl radical, a haloalkylphenyl radical or a hydroxyalkylphenyl radical or (b) A heterocyclic radical such as an imida zolyl radical, a furyl radical'ora pyrazoline radical. In addition, J and E can also be (c) An unsubstituted phenyl radical. Especially preferred are those tetra-substituted hydrazines wherein both D and G are either substituted phenyl'radicals or heterocyclic radicals. These compounds are more fully described in U.S. Ser. No. 673,962 filed Oct. 9, 1967 now U.S. 3,542,546.

(G) Organic compounds having a 3,3'-bis-aryl2F pyrazoline nucleus which is substituted in either fivemember ring with the same or dilferent substituents. The 1 and 5 positions on both pyrazoline rings can be substituted by an aryl moiety including unsubstituted as well as substituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl, carboxyaryl, hydroxyaryl and haloaryl. The 4 position can contain hydrogen or unsubstituted as well as substituted alkyl and aryl radicals such asralkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl, alkoxyalkyl, aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Other photoconductors in this class are represented by the following structure:

wherein D D 1;, and J can be either a phenylradical including a substituted phenyl radical such as a tolyl radical or a naphthyl radical including a substituted naphthyl radical, I

E E G G L and L can be any of the substituents set forth above and in addition can beeither a hydrogen atom or an alkyl radical containing 1-8 carbon atoms. These organic photoconductors are more fully described in US. Ser. No. 664,642 filed Aug. 31, 1967 now US. 3,527,602.

(H) Triarylamines in which at least one of the aryl radicals is substituted by either a vinyl radical or a vinylene radical having at least one active hydrogencontaining group. The phrase vinylene radical includes substituted as well as unsubstituted vinylene radicals and also includes those radicals having at least one and as many as three repeating units of vinylene groups such as wherein n is an integer of from one to three. Groups which contain active hydrogen are well known in the art, the definition of this term being set forth in several text books such as Advanced Organic Chemistry, R. C. Fuson, pp. 154-157, John Wiley & Sons, 1950. The term active hydrogen-containing group as used herein includes those compounds encompassed by the discussion in the textbook cited above and in addition includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups substituted on the vinylene radical of the triarylamine include:

(a) Carboxy radicals, (b) Hydroxy radicals, (c) Ethynyl radicals, (d) Ester radicals (e.g.,

wherein R is alkyl or aryl) including cyclic ester radicals (e.g.,

l? CCl etc.), and

(i) Amido radicals (e.g.,

ll -CN wherein R is a hydrogen atom, an alkyl group or an aryl group). Other active hydrogen-containing groups include substituted and unsubstituted alkylidyne oximido radicals. Photoconductors included in this class can be represented by the following structure: I

NAr o=o X Ag ie 17)n wherein: (a) Ar and Ar are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical, an alkyl phenyl radical or an aminophenyl radical;

(b) Ar is an arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical,

(c) R and R are each hydrogen, a phenyl radical including a substituted phenyl radical or a lower alkyl radical preferably having 1-8 carbon atoms;

(d) X is either (I) an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a hydroxy radical, a semicarbazono radical, an ethynyl radical, or a methylidyne oximido radical, or (2) hydrogen, provided that when X is hydrogen R and R are also hydrogen; and

(e) n is an integer of one to three.

The arylene nucleus can be substituted in any position by the vinyl or vinylene moiety. However, when Ar is phenylene, particularly good results are obtained if the substitution occurs in the para position. These materials are more fully described in US. Ser. No. 706,800 filed Feb. 20, 1968 now US. 3,567,450.

(I) Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogen-containing group. The term active hydrogen-containing group has the same meaning as set forth above and again includes those compounds encompassed by the discussion in the textbook and additionally includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogencontaining groups which are substituted on an aryl radical of the triarylamine include:

(a) Carboxy radicals;

(b) Hydroxy radicals;

(c) Ethynyl radicals;

(d) Ester radicals (e.g.,

wherein R is an alkyl or an aryl group);

(e) Lower alkylene hydroxy radicals (e.g., having 1-8 carbon atoms);

(f) Carboxylic acid anhydride radicals;

(g) Lower alkylene carboxy radicals (e.g., having 2-8 carbon atoms);

(h) Cyano radicals;

(i) Acyl halide radicals (e.g.,

etc.);

(j) Amido radicals (e.g.,

0 io t wherein R is a hydrogen atom, an alkyl group or an aryl group);

(k) Lower alkylidyne oximido radicals having 1-8 carbon atoms including substituted alkylidyne oximido radicals (e.g.,

wherein R is hydrogen or a lower alkyl radical);

(l) semicarbazono radicals; and

(m) Arylene carboxy radicals including.- substituted arylene carboxy radicals (e.g.,

wherein R; and B are phenyl or lower alkyl radicals. Photocond'uc'tor's included in this classcan be represented by the following structure: r

- -frxn wherein:

(a) An; and Ar are each a' phenyl radical including a substituted phenyl radical such asa halophenyl radical, an alkyl phenyl radical or'an" aminophenyl radical;

(b) Ar is an arylene radical'in'cluding 'a"'substitute'd arylene radical such as a phenyle'ne radical or-va naphthylene radical; and

(c) X is an active hydrogen-containing'groupsuch as a carboX'y radical, an acyl halide-radical, an amido radical, a carboxylic acid'anhydride'radical, an ester radical, a cyano radical, a semicarbazono radical, a hydroxy radical, an ethynyl radical, a methylidyine oximido radical or a phenylene carbox'y radical. These materials are more fully'described in U.S. Ser'.-'No.- 706,780 filed Feb. 20, 1968. r

(J) Organo met'allic compounds having at least one amino-aryl substituent attached to a: Group IVa or Group Va metal atom; The metallicsubstituents of this class of organic photoconductbrs are:Gr'oup- IVa orGroup Va metals in accordance'iwithlhe Periodic- Table of the Elements (Handbook of Chemistry and Physics, 38th edition, pp: 394-95) and include silicon, germanium,1tin and lead from Group Na and phosphorus, arsenic,.antimony arid bismuth from Group Va.x ;[hese materials can be substituted in the metallo nucleus-with a wide variety of substituents but at leasti'one of thesubstituents must be an amino-aryl radical; The amino radical can bepositioned anywhere on the aromatic 'nucleus,:but best results are obtained if the aryl 'moiety is aphenyl radical ha ving the amino group in the 4 or paraposition: 'Iypicalsubstituents, attached to the' -metal---nucleus include ;.the following: :1 s,

(a) A hydrogen, sulfurlor oxygenatom,"-

(c) An aryl radical-includingunsubstituted aswwell as substituted aryl radicals such as aminoaryl, alkylar'yland haloaryl, I 1

, (d) An.oxygen-containing.radicalisuch as-an-alkoxy or aryloxy radical, r

(e) An amino radical includingiunsubstituted.and substituted amino radicals such ast-monoand-diarylamino and monoand dialkylamino radicals,- r g (f) Aheterocyclic radicaland r 1 (g) A GroupdVaor Vaorgano metallicradical; Photoconductors included in? this class can'be represented by the following structures: r

or I

cti m v fl T-Ar-lYhr G L where E G L and Q can be wherein R and R can be hydrogen atomsor alkyl radicals having 1. to 8 carbon at0ms, or

(g) A heterocyclic radical having 5 to 6 atoms in the hetero nucleus including at least one nitrogen atom such as a triazolyl, a pyridyl radical, etc.;

T is an amino radical such as an alkylamino radical having 1 to 8 carbon atoms or-an arylamino radical such as a phenylamino radical; l

Ar is an aromatic radical such as phenyl or naphthyl;

M and M 2 are the same or ditferentGroup, lVa metals; 3

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and in addition can be a Group Iva organo-metallic radical or whenytaken atom or a sulfur atom;

J can be any of the substituents p E G L and Q andin addition cambeuwhen taken with B, an oxygen atom or-waisulfur atom-,Theise materials are described in U.S. Ser. No. 650,664fi1ed1uly 13,1967.

(K) Any other organic compound awhich exhibits photoconductiye properties such as those-;se't forth in Australian Pat. 248,402.? L v t Representative organic photoconductors useful in'this invention include the compounds listed below: y TABLE I diphenylamine dinaphthylamine N,N'-diphenylbenz idine N-phenyl-l-naphthylamine N-phenyl-2-naphthylamine I N,N'-diphenyl-p-phenylenediamine 2-carboxy-S-chloro-4'-methoxydiphenylarnine p-anilin'ophen'ol I N,N-di-2-naphthyl-p-phenylenediamine f r 4,4-benzylidene-bis-(N,N-dimethyl m-toluidine) triphenylamine N,N,N,N'-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine "I 4-hexanoyltriphenylamine 3 4-lauroyltriphenylamine 1 4-hexyltriphenylamine 4-dodecyltriphenylamine 4,4'-bis(diphenylarnino)benzil 4,4-bis(diphenylamino)benzophenonev poly[N,4"-(N,N',N'-triphenylbenzi dine) polyadipyltriphenylamine polysebacyltriphenylamine anine including. carbocyanine dyes.

, binder and organic photocond s sst hqto raphi e e ,rnix a. suitable amount of ,the coating. composition so 1 3 1-(p-'dipheiiylaminophe'nyl)ethanol 'dr oxytriph'enylamine Z h'YdTOXytfiphenyIamihe 4-formyltriphenylamine oxime H 4-acetyltriphenylamine oximq ,w 5 1-(p-diphenylaminophenyl')hexanol l=(p diphenylam'inophenyl)dodecanol p-diphenylaminoberizlo ic ac'idanhydride 4-cyanotripheriylamine--"' p diphenylaminobenzoic acid N,N-diphenylamide"- p-diphenylaminobenzoic acid-= p-diphenylaminobenzoylchloride 3 p-diphenylaminophenylpropionic acid 4-f'ormyltriphenylamine"semicarhazone' triphenyl-' -diethylaminophenylsilane methyl-diphenylp-diethylamino'phenylsila tripheny1+p-diethylaminophenylgermane. tr-iphenyl-p=dimethylaminophenylstanriane triphenylip-diethylaminophenylstannane diphenyl-di+(p=diethylaminophenybstannari triphenyl-p-diethylaminophenylplumbanetetra-p-diethylaminophe'nylplumbane 1 =1 1? pheny-l-di-(p-diethylaminophenyl) phosphine" .bis (p-diethylaminophenyl)phosphineioxide l tri-pdimethylaminophenylarsine tri=pdiethy1aminophenylarsine ,2yamethyl-4edirnethylaminophenylarsine trirp-diethylaminophenylbismuthine 1, m lhyl-d -lp-diethylaminophenyl)arsine, methyldi-(paiiethylaminophenyl)phosphine phenyl-triip-diethylaminophenyl.)stannane, methyl-tri(.p diethylaminophenyl)stannane oXidew e -pe st n op ieny serman diph y -phyl m nqpheny p:di y n pheny ts ne. tetrakis-[diphenyl -.(prdiethylaminophenyl)plumbyl] p methane 1, v r tetrakis-[diphenyl-(p diethylaminophenyl) stannyll; stannane i 1-1 r bis- [phenyletp-diethylaminophenyl )J dibismuthine' T -(pe ylam no h )p osptli sulfide d -(prtl inqphstlyl)t x t n The photoconductive-layers of theinvention can also 'be sensitized by the addition 'of effective amountsof sensitizing compounds to exhibit improved electropho- 4'5 tosensitivity. sensitizing compounds useful with the photoconductive compounds of the present invention can be selected fro'm a" wide variety of materials,"-including such materials as pyrylium' including 'thiapyrylium and "Selena- Pat. 3,250,615; fluorenes," such as" 7,12-dioxo-13-dibenzo(a,h)fluorene, 5,10-odioxo-4a,1l-diazabenzo(b)fluorene, 3,l3-dioxo-fioxadibenzo(b,g)fluorene, ,1 and. the 1 like; aromatic nitro compounds oft-the kinds :described' inwU.S.Pat. 2,610,120; anthronesylike. those disclosed in! U.'S.Pat-. 112,670,284, :quinones, 1U;S., Pat. 2,670,286; benzophenones US. Pat. =-2,67 =,0,28-7j; thiazoles US. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid dichloroacetie'acid, -andsalicyclicacid;

lsulfonic and phosphoric acids; and various dyes, such as iicvanina (in uding c b syanine2;..19 rqw pigedim -methane, thiazine, azine, oxazine, xanthene phthalein,

acridine, azo, anthraguin one' is and the like and mi tures thereof. The sensitizers referred for fisewith the compounds of this invention" are 'selected'from" pyrylium including selenapyrylium'anduthiapyrylium salts, and cy- Wh'ere a, sensitizing comp pin the sensitizing "com oim 14 coated element; Other methods of incorporating the sensi tizer or the effect of the sensitizer may, however, be employed con'sistent with the practice of this invention. In preparing the photoconductive layers, no sensitizing compound is required to give photoconductivity in the layers which contain the photoconducting substance therefore, no sensitizer is required in a particular photoconductive layer. Howev'en-"since relatively minor amounts of sensitizing compound give substantial improvement in speed in such layers, the sensitizer is preferred. The amount of sensitizer that canbe added to a photoconductor-incorporating layer to give effective increases in speed can vary widely. The optimum concentration in any given case will vary with .the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where 'an appropriate sensitizer is added in a concentration 'r'ange from about 0.0001 to about 30 percent by weightbased on the weight of the film-forming coating composition Normally, a sensitizer is added to the coating composition in an amount by weight from about 0.005 to about 5.0 percent by weight of the total coating composition.

Solvents usefulfor preparing coating compositions with'the binders of the present invention can include a wide variety of organic solvents for the components of the' -coating' composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride; ethylene chloride; and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

rlnipreparinguthe coating compositions utilizing the binders disclosed herein useful results are obtained Where theiphotoconductive substance is present in an amount equal toat least about 1 weight percent of the coating compositiom'l'he upper limit in the amount of photoconductive material present can be widely varied in accordance with usual practice. .It is normally required that the photoconductive material be present in an amountranging from about 1 weight percent of the coating-composition to about 99 weight percent of the coating composition. A preferred, .weight range for the conductivelayrs "of the presentinventio'n can include any of the electrically "conducting supports," for example,

paper (at a relative humidity above 20 percent); aluminum-paper 'lamintes; metal foils, such as aluminum 'foil, zinc' foil,-t-etc-'.; metal plates, such as aluminum, copper, zinc, brass,-'and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethy1ene terephthalate),= polystyrene and the like conducting sup- POrtsr-Y'i An especially usefulconducting support can be prepared by coating a film support material such as poly- (ethylene terephthalate)'-with a layer containing a semiconductor dispersed in a resin. A suitable conducting coating can be prepared from the sodium saltofa carboxy- .este'r' lactone 'of maleic-anhydride and a vinyl acetate the well known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a process of this type, an electrophotographic element held in the dark, is given'a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained byvthe layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively'dissipated from the surface of the layer by irnagewise exposure to light by means of a conventional exposure operation such as for example, by a contact-printing technique, or by lens projection of an image, or reflex or bireflex techniques and the like, to thereby form a latent electrostatic image in the photoconductvie layer. Exposin-g'the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.

The charge pattern produced by exposure is then'developed or transferred to another surface and developed there, i.e., either the charge or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density.- The developing electrostatically responsive particles can be in the form of a dust, or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to a latent electrostatic image for solid area development is by theme of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S. patents: 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,- 874,063; 2,984,163; 3,040,704; 3,117,884; and reissue Re. 25,779. Liquid development of the latent electrostatic image may also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier.'Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Pat. 2,297,691 and in Australian Pat. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a lowmelting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing respectively. Techniques of the type indicated are well known in the art and have been described in a number of U.S. and foreign patents, such as U.S. Pats. 2,297,691 and 2,551,582, and in RCA Review, vol. 15 (1954), pages 469-484.

The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconductive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting support. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material between layers or overcoated or interposed between the photoconductive layer or sensitizing layer and the conducting layer. It is also possible to adjust the position of the support and the conducting layer placing a photoconductor layer over a support. and coating the exposed face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations differing from those contained in the examples can be useful oreven preferred for the same or different application for the electrophotographic element.

The following examples are included for a further understanding of this invention. 1

Example' l 1.5 grams of poly(4,4-isopropylidenebisphenoxyethylco-tetramethylene isophthalate) binder cointaining 0.5 gram of 4,4'-benzylidine-bis(N,N-diethyl-m-toluidine) photoconductor-and .04 gram of 2,4 (4-ethoXyphenyl)-6-. (4-n-amlyoxystyryl) pyrylium fluoroborate sensitizer are dissolved in 15.6 grams of methylene'chloride by stirring the solids in the solvent'for one hour at room temperature. The resulting solution is hand coated at a wet coating thickness of 0.004 inch on a conducting layer'comprising the sodium salt of=a carboxyester lactone, such as described in U.S. 3,120,028, which in turn is coated on' a cellulose acetate film base. The coating block ismaintained at a temperature of F. 'After drying, the electrophotographic element is charged under positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts. It is then subjected to exposure from behind a stepped density gray scale to a 3000 K. tungsten source. The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential, V to some lower potentail, V, whose exact value depends on the actual amount of'exposure in meter-candle-seconds received by the area.'The results of the measurements are plotted on a graph of surface potentialV vs. log exposure for each step. The shoulder speed is the numerical expression of 10 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential by volts. The toe speed is the numerical expression of 10 multiplied by the'reciproc'al of the exposure in meter-candleseconds required to reduce the 600 volt charged surface potential to 100 volts. This coating is found to" have a positive 100 v. toe speed of 250. Similar results are obtained when 0.5 gram-of bis(4-diethylamino)-1,1,1-triphenylethaneor 0.5 gram of bis(4-diethylamino)tetraphenylmethane are used as photoconductors in place of the 4,4-benzylidine bis(N,N-diethyl-m-toluidine) for both positive and negative charging.

I Example 2 Example lis repeated except .that binder employed is poly(4,4'- isopropylidenebisphenoxyethyl co ethylene terephthalate). This binder does not fall within the scope of the inventionin that the terephthalate is used instead of the isophthalate and is included for comparison purposes only. The coating has a positive 100 volt toe speed of 128.

The following Examples 3 and 4 are identicalto Example 1 except for the binder employed. 1.5 grams of various binders are used in each of the following examples. In each case a significant improvement is noted in the 100 v. toe speeds over binders of the type described in the preceding example. I

TABLE II V Positive 100 v. toe Example Binder speed 3- Poly'(4-4'-is0propylideneblsphenoxyethyl-co- '20o -'ethYienolsophthalate); 4 Poly(4,4'-lsopropylldenebisphenoxyethyl-co- 200 neopentyl isophthalate).

Example 5 The coating compositions of Examples. 1, 3 and 4 are .again coated iu the manner described inExample 1. In

a darkened room, the surface of each of the photoconducopaque and light transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 meter-candles for 12 seconds. The resulting electrostatic latent image is developed in the usual manner by cascading over the surface of the layer a mixture of negatively charged black thermoplastic toner particles and glass beads. A good reproduction of the pattern results in each instance.

Example 6 The copolyesters described herein are made by standard melt condensation techniques. Poly(4,4'-isopropylidenebisphenoxyethyl co ethylene isophthalate) is prepared by miXing 0.15 mole of dimethyl isophthalate, 0.075 mole of 4,4 isopropylidenebisphenoxyethanol, 0.10 mole of ethylene glycol and 0.05 gram of tetrabutyl orthotitanate. Nitrogen is bubbled through the mixture,

and -98% of CHz-OHg-OGigQO-OHpCHg-O-ii- E O and it is heated at 200 C. for 2 hours to distill off methanol. The temperature is raised to 250 C. and vacuum applied until complete polymerization is completed. The resultant polymer contains 50% of repeating unit A and 50% B. The other polymers are prepared by the same method by replacing ethylene glycol with the appropriate compound. For example, trimethylene glycol would be used to prepare polymer 1, tetramethylene glycol for polymer 2, diethylene glycol for compound 4, etc.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can 'be effected within the spirit and scope of the invention as described hereina-bove and as defined in the appended claims.

I claim:

1. An electrophotographic element capable of reproducing continuous tones comprising a support having coated thereon a photoconductive composition comprising a photoconductor and a binder for said photoconductor comprising a polyester having 2-80% repeating and 20-98% of wherein Z is an alkylene group having 2 to 10 carbon atoms, and D and E are each selected from the group consisting of a hydrogen atom, a halogen atom, an aryl group, an alkyl group, an aryloxy group and an alkoxy wherein Z is an alkylene group having 2 to 10 carbon atoms, and D and E are each selected from the group consisting of a hydrogen atom, a halogen atom, an aryl group, an alkyl group, an aryloxy group and an alkoxy group.

5. The electrophotographic element of claim 4 wherein Z is selected from the group consisting of t is an integer from 1 to 7;

n and 0 are each integers from 2 to 7;

s is an integer from zero to 7;

u and v are each integers from 0 to 5;

p, q and r are each integers from 2 to 6;

D is selected from the group consisting of an oxygen atom and a sulfur atom;

Q represents the atoms necessary to complete a carbon atom cycloalkyl radical;

R and R are each selected from the group consisting of hydrogen and an alkyl radical having 1 to 5 carbon atoms; and

R and R are each alkylene radicals.

6. The electrophotographic element of claim 4 wherein the sensitizer is selected from the group consisting of carbocyanine, pyrylium, thiapyrylium and selenapyrylium dye salts.

7. The electrophotographic element of claim 4 wherein the organic photoconductor is 4,4-benzylidenebis(N,N-

diethyl-m-toluidine) ethyl-co-ethylene isophthalate) as a binder for said photoconductive composition.

16. In an electrophotographic process wherein an electrostatic charge pattern is formed on an electrophotographic element by applying a uniform charge to the surface of the photoconductive layer and exposing to a light image, the improvement characterized in that said electrographic element has a photoconductive layer containing a binder having 2-80% repeating units of and 20-98% of l CH: (I?

(N,N-diethyl-rn-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(4,4-isopropylidenebisphenoxyethyl-co-trimethylene isophthalate) as a binder for said photoconductive composition.

13. An electrophotographic element capable of reproducing continuous tones comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4'-benzylidinebis(N,N- diethyl-m-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(4,4-isopropylidenebisphenoxyethylco-tetramethylene isophthalate) as a binder for said photoconductive composition.

14. An electrophotographic element capable of reproducing continuous tones comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4'-benzylidinebis (N,N-diethyl-m-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(4,4-isopropylidenebisphenoxyethyl-co-neopentyl isophthalate) as a binder for said photoconductive composition.

15. An electrophotographic element capable of reproducing continuous tones comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4'-benzylidinebis (N,N-diethyl-m-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(4,4-isopropylidenebisphenoxywherein Z is an alkylene group having 2 to 10 carbon atoms, and D and E are each selected from the group consisting of a hydrogen atom, a halogen atom, an aryl group, an alkyl group, an aryloxy group and an alkoxy group.

The British Journal of Photography (September 1964), pp. 784-787.

Conix, Thermoplastic Polyesters from Bisphenols, Industrial and Engineering Chemistry, vol 51, No. 2 (February 1959), pp. 147-150.

CHARLES E. VAN HORN, Primary Examiner US. Cl. X.R.

( 58 @E'HMEAEE W @QRKEQTWN P t 3,7 3,37 me a November 21, 1972 Inventor(s) stwalt H. Merrill It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 7, "l6 should read --3l---; m? line 23, "16" should read ---3l--..

Signed and sealed tfiis 12th day Of June 19 73.

(SEAL) Attes't:

EDW M.PLETQHER,JR. ROBERT GOTTSCHALK Attest ng Offlcer I Commissioner of Patents: