United States Patent to 11, 4,018,606 Contois Et Al
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United States Patent to 11, 4,018,606 Contois et al. 45 Apr. 19, 1977 (54) ORGANIC AZO PIGMENT SENSITIZERS FOR PHOTOCONDUCTIVE LAYERS R ph C 2 x (75) Inventors: Lawrence E. Contois; Joseph Y. R2 NEN-C Kaukeinen; Stephen Michel; Thomas C M. Plutchak, all of Rochester, N.Y. R R (73) Assignee: Eastman Kodak Company, wherein X consists of the atoms necessary to complete Rochester, N.Y. a naphthalene, anthracene, or OH (22 Filed: May 3, 1974 C 2 N. -C N N (21) Appl. No.: 466,658 =N R (52) U.S. Cl. ...................................... 96/1.7; 96/1.6 ring; (51) Int. Cl”.......................................... G03G 5/09 (58) Field of Search ........................... 96/1, 1.5, 1.6 R', R', and R are hydrogen, halogen, alkoxy, NO, alkyl, SOH or alkali metal salts thereof, (56) References Cited O O UNITED STATES PATENTS rCNH NO, and -CNH 3,384,632 5/1968 Solodar ................................ 96/1.6 3,622,341 8/1969 Lee ....................................... 96/1.6 and COOH or alkali metal salts thereof, and Rand R8 3,684,548 8/1972 Contois ............................... 96/1.6 can comprise the atoms necessary to complete a 3,775,105 l/1973 Kukla ................................... 96/1.6 phenyl, naphthyl or anthryl ring; and R is selected from FOREIGN PATENTS OR APPLICATIONS the group consisting of 1,370,197 10/1974 United Kingdom .................. 96/1.5 O O H il H Primary Examiner-David Klein 8-i-O-No, 8-N-O). or COOM Assistant Examiner-John L. Goodrow Attorney, Agent, or Firm-Arthur H. Rosenstein where M is alkyl, alkali or alkaline earth metal are useful as sensitizers for photoconductive compositions in electrophotographic processes. 57 ABSTRACT A class of organic pigments having the formula 23 Claims, No Drawings 4,018,606 1. 2. sure time; it makes possible the recording of a wide ORGANIC AZO PIGMENT SENSITIZERS FOR range of colors in proper tonal relationship, and allows projection printing through various optical systems. By PHOTOCONDUCTIVE LAYERS increasing the speeds through the use of sensitizers, The process of xerography, as disclosed by Carlson in photoconductors which would otherwise have been U.S. Pat. No. 2,297,691, employs an electrophoto unsatisfactory are useful in processes where high graphic element comprising a support material bearing speeds are required such as document copying. a coating of a normally insulating material whose elec Various pigment particles are described in the prior trical resistance varies with the amount of incident art as useful photoconductors. The use of substituted actinic radiation it receives during an imagewise expo O 2,4-diaminotriazines as electrically photosensitive par sure. The element, commonly termed a photoconduc ticles in photoelectrophoretic imaging and in conven tive element, is first given a uniform surface adaptation. tional xerographic processes is described in U.S. Pat. It is then exposed to a pattern of actinic radiation which No. 3,445,227. U.S. Pat. Nos. 3,447,922 and 3,448,028 has the effect of differentially reducing the potential of describe the use of N-substituted-3,13-dioxodinaph the surface charge in accordance with the relative en 15 tho(2,1-b',2',3'-d)-furan-6-carboxamides as photosen ergy contained in various parts of the radiation pattern. sitive particles in xerographic processes. These photo The differential surface charge of electrostatic latent conductors in themselves are not sensitive at the longer image remaining on the electrophotographic element is wavelength portion of the visible spectrum. then made visible by contacting the surface with a A large number of acidic compounds have been de suitable electroscopic marking material. Such marking 20 scribed as sensitizers for photoconductive composi material or toner, whether contained in an insulating tions such as in U.S. Pat. No. 3,316,087 and French liquid or on a dry carrier, can be deposited on the Pat. No. 1,288,392. The search for materials which exposed surface in accordance with either the charge enhance the sensitization of a broad range of photocon pattern or the absence of charge pattern as desired. ductors is a continuing one. The deposited marking material may then be either 25 It is, therefore, an object of this invention to provide permanently fixed to the surface of the sensitive ele novel sensitized photoconductive compositions. ment by known means such as heat, pressure, solvent It is another object of this invention to provide novel vapor, or the like, or transferred to a second element to sensitized photoconductive elements. which it may similarly be fixed. Likewise, the electro It is a further object of this invention to provide a static latent image can be transferred to a second ele 30 process for using novel sensitized, photoconductive ment and developed there. elements. Various photoconductive insulating materials have These and other objects are accomplished with pho been employed in the manufacture of electrophoto toconductive compositions containing a photoconduc graphic elements. For example, vapors of selenium and tor and a sensitizing amount of a specific class of or vapors of selenium alloys deposited on a suitable sup 35 ganic pigments. Electrically insulating polymeric bind port and particles of photoconductive zinc oxide held ers are generally added with non-polymeric photocon in a resinous, film-forming binder have found wide. application in present-day document copying applica ductors. tions. The organic pigment sensitizers of this invention Since the introduction of electrophotography, a great 40 have the formula: many organic compounds have also been screened for their photoconductive properties. As a result, a very R1 ph large number of organic compounds are known to pos Cn 2 sess some degree of photoconductivity. Many organic R2 NEN-C X compounds have revealed a useful level of photocon 45 N duction and have been incorporated into photoconduc C tive compositions. Optically clear organic photocon R3 ductor containing elements having desirable electro photographic properties can be especially useful in electrophotography. Such electrophotographic ele SO wherein: ments may be exposed through a transparent base if X consists of the atoms necessary to complete a desired, thereby providing unusual flexibility in equip naphthalene, anthracene or ment design. Such compositions, when coated as a film or layer on a suitable support also yield an element gh which is reusable; that is, it can be used to form subse 55 2 N quent images after residual toner from prior images has -C N been removed by transfer and/or cleaning. N Although some of the photoconductors comprising C=N V. the materials described are inherently light-sensitive, R their degree of sensitivity is usually low and in the short 60 wavelength portion of the spectrum so that it is com mon practice to add materials to increase the speed and R, R', and Rare independently selected from the to shift the sensitivity toward the longer wavelength. group consisting of hydrogen, halogen, such as chlo portion of the visible spectrum. Increasing the speed rine, bromine, fluorine or iodine, alkoxy, preferably and shifting the sensitivity of such systems, into the 65 containing 1 to 8 carbon atoms such as methoxy, eth visible region of the spectrum has several advantages: it oxy, propoxy, and the like, including substituted alkoxy makes available inexpensive and convenient light such as aminoalkoxy, haloalkoxy, and the like; NO, sources such as incandescent lamps; it reduces expo alkyl, preferably containing from 1 to 8 carbon atoms 4,018,606 3 such as methyl, ethyl, propyl, butyl, isopentyl, hexyl NO, . and the like; SOH or alkali metal salts thereof such as SONa, SOK, and the like; and COOH or alkali metal, salts thereof such as COONa, COOK, and the like . OCH 5 (C)ON O R” and R can, taken together, also comprise the atoms necessary to complete a phenyl, naphthyl, or anthryl ring. The above organic pigments produce an enhanced R is selected from the group consisting of sensitization effect, when used in a photoconductive 15 composition containing photoconductors in compari son to the sensitization of (A) photoconductor compo sitions without the sensitizers, (B) photoconductive compositions containing only the pigments without an independent photoconductor, and (C) photoconduc on-G), co-(O) 20 tive compositions containing a photoconductor and similar pigments outside the scope of this invention. or COOm wherein M is alkyl preferably containing The enhanced sensitization is evidenced by greater from 1 to 8 carbon atoms such as methyl, ethyl, isopro electrical speeds. A suitable method of increasing elec pyl, butyl, hexyl, octyl, and the like; alkali metals such trical speed is described more fully in the appended as Li, Na, K, Rb and Cs; and alkaline earth metals such 25 examples. as Ca, Sr., Ba, and the like. Preferred binders for use in preparing the present It is noted that the term alkyl used throughout the photoconductive layers comprise polymers having specification and claims is meant to include substituted fairly high dielectric strength which are good electri alkyl such as chloroalkyl, aralkyl, and the like. Gener cally insulating film-forming vehicles. Materials of this ally, any substituent may be used on the alkyl that does 30 type comprise styrene-butadiene copolymers; silicon not adversely affect the sensitizing properties of the resins; styrene-alkyd resins; silicon-alkyd resins; soya pigment. alkyd resins; poly(vinyl chloride); poly(vinylidene Some preferred pigment sensitizers of this