CA1129426A - Photoconductive compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Photoconductive compositions and elements comprising a film forming electrically insulating polymer and a dye material having an absorption spec-trum which changes when a binderless coating of said dye material is treated with solvent vapors; wherein said composition has an absorption spectrum which is similar to the changed absorption spectrum of said binderless coated dye material are disclosed.

Description

11;~ 9~26 r PHOTOCONDUCTIVE C MPOSITIONS

This invention relates to electrophotography and particularly to light sensitive materials for photo-- conductive compositions.
BACKGROUND OF THE INVENTION
Electrophotographic imaging processes and techniques have been extensively described in the prior art. Generally~ such processes have in common the steps of employing a photoconductive element which is prepared to respond to image-wise exposure to electro-magnetic radiation thereby forming a latent-electrostatic-charge image. A variety of subsequent operations, nowwell-known in the art, can then be employed to produce a permanent record of the image.
One type of photoconductive element particu-; larly useful in electrophotography employs a composition 23 containing a photoconductive material and optionally an electrlcally insulating, film-forming, resinous binding material. An lntegrated electrophotographic element incorporating such a compositlon is generally produced in a multi-layer type Or structure by coating a layer of the above described composition onto a support previously overcoated with a layer of an electrically conducting material. Alternatively, the above-descrlbed composltion can be coated dlrectly onto a conductlve support made of metal or other sultable conductlve 3 materials.
Usually, the desired electrophotographic properties are dictated by the end use contemplated for the photoconductive element. In many such applications, it is desirable for the photoconductive element to exhibit high speed, as measured by an electrical speed ; or characteristic curve, a low residual potential after exposure and resistance to electrical fatigue. Various . other applications specifically require that the 1~294;~

photoconductive element be capable of accepting a high surface potential with a low dark decay rate.
In many other applications, it is desirable that the photoconductive element be capable of high speeds and relatively high resolution as measured in terms o~ lines per millimeter. Typical applications where high resolution images are necessary are one to one microfilm reproductions, and the production of microimages from regular sized images. Ideally, a microfilm duplicating system should provide exact micro-duplicates of existing microfilm frames or micro-images of normal-sized copy with no loss in resolution from the original.
High speed "heterogeneous" or "aggregate"
15 photoconductive systems have been developed which exhibit many of the desirable qualities mentioned above. I'hese aggregate compositions are the sub~ect matter of William A. Light, U.S. Patent 3,615,414 issued October 26, 1971 and Gramza et al., U.S. Patent 3,732,180 issued May 8, 1973. These heterogeneous or aggregate photoconductive elements comprise photocon-ductive compositions containing a continuous polymer phase having dispersed therein co-crystalline particles composed of a pyrylium or thiopyrylium salt and a 25 polymer. However, the resolutlon obtainable with heterogeneous or aggregate photoconductive elements is not as hlgh as the resolution obtainable with some other types of photoconductive elements having much lower speeds such as the elements disclosed in U.S.
Patent 3,542,547.
The use of thiopyrylium dye salts in photo-conductive compositions is also disclosed in Contois et al., U.s. 3,973,962, issued August 10, 1976, and Van Allan et al., U.S. 3,250,615 issued May 10, 1966. Certain 35 monomethine thiopyrylium dye salts are also disclosed as sensitizers for photoconductive compositions in Reynolds et al., U.S. 3,938,994 issued February 17, 1976.

SUMMARY OF THE INVENTION
The present invention provides photoconductive compositions and elements which comprise a film forming electrically insulating polymer, a dye material having an absorption spectrum which changes when a binderless coating of said dye material is treated with a solvent vapor and, if desired, an organic photoconductor mater-ial; wherein said composition has an absorption spectrum which is substantially similar to the changed absorption spectrum of said binderless coated dye material.
The present invention also provides a method of making the photoconductive compositions of the present invention.
The photoconductive compositions of the present invention are obtained by treating a composition com-prising a dye material of the type described above and an electrically insulating polymer with solvent vapors of the type described hereinafter. The vapor treatment causes a transformation of the photoconductive composi-tion that is evidenced by a speed increase and a changein the absorption spectrum of said photoconductive composition. As stated above the changed absorption spectrum of the photoconductive composition is substan-tially similar to the absorption spectrum of the dye material used therein when a binderless coating of said dye material is treated with solvent vapors.
Any dye material which has (1) an absorption spectrum which changes when a binderless coating of the dye is treated with a solvent vapor and (2) exhibits an absorptlon spectrum substantially similar to said changed absorption spectrum in a solvent vapor treated photoconductive composition comprising said dye material and an electrically insulating polymer will be useful in forming the compositions of the invention. Thus, useful dye materials can be easily identified by first combining the dye material being considered with a coating solvent of the type disclosed hereinafter and secondly, incorporating said dye material in a photo-conductive composition which includes an electrically insulating polymer. The resulting mixtures are then llZ94Z6 coated on separate transparent supports of the type disclosed hereinafter. After the coatings dry, the abæorption spec~rum of each coating is determined in a conventional manner, one being tested before sol-S vent vapor treatment of the coating and the othertested during such treatment. If the dye material being tested is suitable for use in forming the com-positions of the present invention, (1) the absorp-tion spectrum of the binderless coating during sol-vent vapor treatment will be different from theabsorption spectrum of the same coating before sol-vent treatment and (2) the absorption spectrum of a solvent vapor-treated photoconductive composition comprising said dye material and an electrically insulating polymer will be sub6tantially similar to the changed absorption spectrum of the binderless coated dye material.
The foregoing test also serves to distin-guish the photoconductive compositions of the present invention from the aggregate photoconductive composi-tions disclosed and claimed in the aforementioned Light and Gramza patents. The latter aggregate pho-toconductive compositions appear to result from dye-polymer co-crystallization induced by solvent treatment. This dye-polymer co-crystallization is evidenced by the co-crystals of dye and polymer which are present in aggregate photoconductive compositions.
It is believed that the change in absorption spectrum exhibited by vapor-treated binderless coat-ings of the dye materials useful in the presentinvention results from dye-dye interaction rather than dye-polymer co-crystallization. Dye-dye inter-action refers to interaction between individual mole-cules or groups of molecules of the same or similar dye materials. The absorption spectra of the pyr-ylium dye salts used to form the aforementioned aggregate photoconductive compositions also change when a binderless coating of such dye salts is treated with solvent vapors. However, the absorption spectra of vapor-treated compositions comprising an electrically insulating polymer and the aforemen-tioned pyrylium dyes are different from that of a vapor-treated binderless coating of the pyrylium dye.

~29426 Figure 1 shows the absorption spectrum of one of the photoconductive compositions of the present invention before and after transformation.
Preferred Embodiments .. ...
In a preferred embodiment of the present invention there are provided photoconductive compositions and elements comprising a film forming electrically insulating polymer and a dye material which has (a) an absorption spectrum which changes when a binderless coating of said dye material is treated with a solvent and (b) a structure according to the formula \ ~ C\ /; ~c6H5 (I) . C H C6H5 wherein Z and zl may be the same or different, repre-~r~ sent 0, Se and S and X represents an anion such as O~ 15 perchlorate or fluoroborate; wherein said compositions have after transformation an absorption spectrum which is similar to the changed absorption spectrum of said binderless coated dye material.
According to another embodiment of the present invention photoconductive compositions are provided as ~ust described which also contain an organic photocon-ductive material.
Useful materials included within the scope of general Formula I lnclude the materials shown in Table I.

T_A B L E
~Z ~ ~ Dye MateriaI Name v~
1. 4-[(2,6-diphenyl-4H-thiopyran-4-ylidene)-I ~ methyl]-2,6-diphenylthiopyrylium per-chlorate

2. 4-[(2,6-diphenyl-4H-thiopyran-4-ylidene)-methyl]-2,6-diphenylselenopyrylium per-chlorate

3. 4-[(2,6-diphenyl-4H-thiopyran-4-ylidene)-methyl]-2,6-diphenylthiopyrylium fluoro-borate !

~ llZ94Z6 ~~ T A B L E I Cont'd.

4. 4-[(2 ,6-diphenyl-4H-pyran-4-ylidene)-methyl]-2,6-diphenylthiopyrylium per-chlorate

5 ~ 5. 4-[(2,6-diphenyl-4H-pyran-4-ylidene)-,~p methyl~-2,6-diphenylselenopyrylium per-chlorate

6. 4-[(2,6-diphenyl-4H-pyran-4-ylidene)-methyl~-2,6-diphenylpyrylium perchlo-rate The symetrical pyrylium and thiopyrylium monomethine dyes of Formula I may be prepared according to the procedure described in U.S. Patent 3,938 ,994. The prep~ration of the sulfur-oxygen unsymetrical monomethine pyrylium dyes is taught by G. A. Reynolds and J. A. VanAllan, J. Heterocyclic Chem., 9, 1105 (1972). The preparation of symetrical monomethine selenopyrylium, as well as thiopyrylium dyes, iB taught by A. J. Tolmachev and M. A.
Kudinova, Khimiya Geterotsiklicheskikh Soedinenii, 49 (1974)-The unsymetricsl selenopyrylium dyes are new _ compoæitions of matter prepared a8 follows: In Structures III and IV, Z represents 0 or S.

25H C~0~5~ ~C HH C~ ~ \C~H~

(II) (III) . 3( ~
~ F o ~ Z C l o~

~o H~C ~ C H
(IY) f A mixture of 0.31 B of (II) and 0.35 g of (III) in 10 ml of acetic anhydride was refluxed for 30 minutes and cooled to room temperature, during which time glistening needles of the desired material formed.

As stated above, the photoconductive composi-tions of the present invention are obtained by treating compositions comprising a dye material as previously described and an electrically insulating polymer with a solvent vapor. The treatment can be carried out in several ways. For example, a solution containing the selected dye material, the electrically insulating polymer and, if desired, a material which is an organic photoconductor can be coated in the form of a layer in a conventional manner onto a suitable support. Treat-ment is then achieved in situ by contact of the coating with the vapors of a solvent until a color change is noted in the coating. Also treatment can be achieved by inhibition of solvent removal in an otherwise normal coating operation of a solvent dope containing the dye and polymer and when desired, an organic photoconductor Similarly, coating such a layer from a solvent mixture which also contains a higher boiling solvent which per-sists in the coating during drying is among the methods for the desired treatment.
In general, the photoconductive compositions of the examples have been prepared by mixing together separate solutions of the selected dye material and the electrically insulating polymer and then, if desired, adding an organic photoconductor. The solution is then coated on a conductive support, such as a nickel-coated poly(ethylene terephthalate) film support, and dried in air or under vacuum at about 60C for about one hour.
The coated composition is then treated with a solvent 3 vapor ~or a few minutes and then redried under vacuum for about one hour at about 60C.
The organic coating solvents useful for preparing coating dopes can be selected from a variety of materials. Useful liquids include substituted hydrocarbon solvents, wlth preferred materials being halogenated hydrocarbon solvents. The requisite pro-perties of the solvent are that it be capable of dis-solving the selected dye material and be capable of dissolving or at least highly swelling or solubilizing 4 the polymeric ingredient of the composition. In 11~9426 addition, it is helpful if the solvent is volatile, preferably having A bo~ling point of less than about 200 C. Particularly useful solvent6 include halogenated lower alkanes having from about 1 to about 3 carbon atoms.
The solvents useful in obtaining the photo-conductive compositions of the invention include,among others, dichloromethane, toluene, tetrahydro-furan, ~-dioxane, chloroform and l,l,l-trichloroeth-ane. Such solvents may be used alone or in combina-tion, in which case each component of the combina-tion need not be a solvent for the particular dye material used. The particular solvent(s) used will, in some cases, be determined by the particular com-bination of electrically insulating polymer, dyematerial and the material used as the organic photo-conductor. For example, in some cases one solventmay cause ~ particular polymer, organic photoconduc-tor or dye material to precipitate out of the coated composition while other solvents will result in the desired photoconductive compo6itions.
After treatment according to one of the above procedures, a transformation occurs in thecomposition being treated. The desired transforma-tion is indicated by increased speed and a change inthe absorption spectrum of the solvent treated coated composition. In other words, the now trans-formed composition possesse6 increased speed and an absorption spectrum that is different from that of the same composition before transformation. In general, one observes a new absorption spectrum in the now transformed composition. In one embodiment of the present invention, an absorption peak appears in the treated composition in the region of 560 nm, while such peak is not present in the same composi-tion which has not been treated. In th~ embodi-ment, the color of the layers shifts from a blue-green to a blue, which is consistent with the change in the absorption spectrum.
~0 1129~26 g The amount of the selected dye material incorporated into photoconductive compositions and elements of the present invention can be varied over a relatively wide range. When such compositions do not include an organic photoconduct~ve material, the selected dye material may be present in an amount of about 0.1 to about 50.0 percent by weight of the coating composition on a dry basis. Larger or smaller amounts of the selected dye material, such as monomethine pyrylium dye salts, may also be employed, although best results are generally obtained when using an amount within the aforemen-tioned range. When the compositions include anorganic photoconductive material, useful results are obtained by using the selected dye material in amounts of about 0.1 to about 30 percent by weight of the photoconductive coating composition. The upper limit in the amount of dye material present in a sensitized layer is determined as a matter of choice and the total amount of any dye msterial used will vary widely depending on the material selected, the electrophotographic response desired, the pro-posed structure of the photoconductive element and the mechanical properties desired in the element.
Most electrically insulating film-forming polymers are useful in the present invention. Such polymers include polystyrene, polyvinylethers, poly-olefins, polythiocarbonates, polycarbonates and phe-nolic resins such as those disclosed in U.S. Patent 3,615,414. Mixtures of such polymers are also use-ful.
P~rticularly useful polymers have recurringunits as shown in Table II.

B~

1~2~2~

TABLE II

Polymers O O
(1) ~C--\ O \--C-O--~ O ~ ' 0 ,--o~
t~

Poly[4,4'-(hexahydro-4,7-methanolndan-5-ylidene)-diphenylene terephthalate]
O O CH
(2) ~C-.\ 0 \~-O-~ O ~-C-O-~ o ~-t-~ ~-~~

Poly[4,4'-(lsopropylldene)dlphenylene 4,4'-oxydlbenzoate]

Cl\ ~CI O

cl t~; cl Poly~4,4'-(2-norbornylldene)bls(2,6-dlchloro-phenylene)carbonate]
.j O
(4) ~0-~ 0 ~ O \~-O-C~
t~ ,l-.

Poly~4,4'-(he~ahydro-4,7-methanolndan-5-ylldene)-diphenylene carbonate~

O _ 15 (5) ~o--~OO ~ O ~--O-C~
1~ ,!

Poly~4,4'-(2-norbornylldene)dlphenylene carbonate]

~1 ' ~2~6 ( 6 ) ~CH--Cl 12~
I~O,I

P~lystyrene CH O

(7) ~o--~ 0 \-- C --~ 0 \--o-C~
CH

Poly(4,4'-lsopropylldenedlp~enylene carbonate) U6eful orgsnic photoconductive material6 sre generally electron acceptor or electron donor~
for the dye materials. Such material6 may be selected from materials de6ignated as organic photo-conductors in the patent literature 6uch a6 those di6clo6ed in U.S. Patent6 3,615,414, 3,873,311 and 3,873,312 and Research Disclosure, item 10938, Vol-ume 109, May, 1973. Typical materials include aro-matic amines such as tri-p-tolylamine and (di-~tol-ylaminophenyl)cyclohexane.
In general, organic photoconductive materi-al6, when used, are present in the composition in an amount equal to at lea6t about 1 weight percent of the coating composition on a dry ba6e. The upper limit in the amount of photoconductor substance pre5ent can be widely varied in accordance with u6ual practice. It is normally required that the organic photoconductor materisl be present, on a dry basis, in an amount of from about 1 weight percent of the coating composition to the limit of its solu-bility in the polymeric binder. A polymeric organlcphotoconductor may also be employed. A preferred weight range for the organic photoconductor in the coating composition ~8 from about 10 weight percent to about 40 weight percent on a dry basis.

B, 1~2942~

Suitable supporting materials for the photo-conductive compositions of this invention may include any of a wide variety of electrically conducting supports, for example, paper (at a relative humidity above 20 percent); aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc; metal plates such as aluminum, copper, zinc, brass and galvanized plates, vapor-deposited metal layers such as silver, chromium, nickel, aluminum, cermet materials and the like coated on paper or conventional photographic film bases such as cellulose acetate, polystyrene. Such conducting materials as nickel can be vacuum deposited on transparent film supports in sufficiently thin layers to allow electrophotographic elements prepared therewith to be exposed from either side of such elements. An espe-cially useful conducting support can be prepared by coating a support material such as poly(ethylene tere-phthalate) with a conducting layer containing a semi-conductor dispersed in a resin. Such conducting layers 20 both with and without insulating barrier layers are described in U.S. Patent 3,245,833 and U.S. Patent 3,880,657. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer.
25 Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in U.S.
Patent 3,007,901 and 3,262,807.
The photoconductive compositions of this invention can be coated, if desired, directly on a 30 conducting substrate. In some cases, it may be desir-able to use one or- more intermediate subbing layers between the conducting substrate to improve adhesion to the conducting substrate and/or to act as an electrical barrier layer between the coated composition and the 35 conducting substrate. Such subbing layers, if used, typically have a dry thickness in the range of about 0.1 to about 5 microns. Typical subbing layer materials which may be used are described, for example, in U.S.
Patents 3,143,421; U.s. Patent 3,640,708 and U.S.
40 Patent 3,501,301.

Optional overcoat layers may be used in the present invention if desired. For example, to improve surface hardness and resistance to abrasion, the surface layer of the element of the invention may be overcoa~ed with one or more electrically insula-ting, organic polymer coatings or electrically insu-lating, inorganic coatings. A number of such coat-ings are well known in the art and, accordingly, extended discussion thereof is unnecessary. Typical useful such overcoats are disclosed, for example, in Research Disclosure, "Electrophotographic Elements, Materials, and Processes", Volume 109, page 63, Paragraph V, May, 1973.
Coating thicknesses of the photoconductive composition on the support can vary widely. Nor-mally, a coating in the range of about 0.5 micron to about 300 microns before drying is useful for the practice of this invention. The preferred range of coating thickness is found to be in the range from about 1.0 micron to about 150 microns before drying, although useful results can be obtained outside of this range. The resultant dry thickness of the coat-ing is preferably between about 2 microns and about 50 microns, although useful results can be obtsined with a dry coating thickness between about 1 andabout 200 microns.
The elements of the present invention can be employed in any of the well-known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a pro-cess of this type, an electrophotographic element is held in the dark and given a blanket electrostatic charge by treatin8 it with a corona discharge. This uniform charge is retained by the layer because of the substantial dark insulating property of the layer, i.e., the low electrical conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissip$ted from the surface of the layer by imagewise exposure to light by means of a conven-tional exposure operation such as, for example, by a contact-printing ~' 9~26 technique, or by pro~ection of an image, and the like, to thereby form a latent electrostatic image in the photoconductive layer.
The latent electrostatic image produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas are 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 dust, i.e., powder, or a pigment in a resinous carrier, i.e., toner. A preferred method of applying such toner to a latent electrostatic image for solid area development is by the use of a magnetic brush.
Methods of forming and u~ing a magnetic brush toner applicator are described in the following U.S. Patents:
Young, U.S. 2,786,439 issued March 26, 1957; Giaimo, u.S. 2,786,440 issued March 26, 1957; Young, U.S.
2,786,441 issued March 26, 1957; Greig, U.S. 2,874,063 issued February 17, 1959. 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, Metcalfe et al., U.S. Patent 2,907,674 issued October 6, 1959. In dry developing processes, the most widely used method of obtaining a permanent record utilizes a developing partlcle which has as one of its components a thermoplastic resin.
Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, thus caused to adhere permanently to the surface of the photoconductive layer.
The following examples are included for a further understanding of the invention. Each of the exemplified dye materials exhibits (1) a change in absorption spectrum when a binderless coating thereof is treated with a solvent vapor and (2) substantially 4 the same changed absorption spectrum in a solvent vapor treated photoconductive composition which includes said dye material and an electrically insulating polymer.
Example 1 24.2 mg of dye material 5 were dissolved in 4 ml of dichloromethane and 0.1 ml 1,1,1,3,3,3-hexafluoro-isopropanol (HFIP). This solution was coated on poly-(ethylene terephthalate) at 50C. The visible spectrum of the film, as coated, has absorption maxima at 630 nm, and at 600 nm and another band at 415 nm.
Transformation of dye material 5 to the enhanced photoconductive state was spectrally observed in the presence of tetrahydrofuran vapor. The prepared film was fumed by suspending it in a Dewar flask which was saturated with the vapors. The flask, fitted for optical access, was placed into a conventional Cary 14 spectrometer and the film's optical spectrum was re-corded. ~he amount of time required to form the en-hanced photoconductive state of the dye is dependent on the concentration of solvent fumes in contact with the film surface.
The spectrum recorded during the fuming of a binderless coating of dye material 5, Table I, has an absorption maximum at 615 nm, a shoulder at 550 nm and a band at 415 nm. The spectrum of the enhanced photo-conductive state in a polymer matrix was substantially the same as the spectrum of the vapor treated binderless coating.
Example 2 - Preparation and testing of photoconductive films containing dye material 1, Table I.
3 To 12.8 mg of dye material 1, Table I, was added 1 ml of dichloromethane, 0.1 ml of HFIP and 5 ml dichloromethane containing Lexan 145 (0.1 g/ml). Lexan 145 is a polycarbonate polymer supplied by General Electric Co., having structure 7 in Table II. The solution was stirred and heated for 5 minutes and then 327 mg of tri-p-tolylamine was added. The final solu-tion was coated on an unsubbed nickel coated poly-(ethylene terephthalate) support and air-dried at 55C
for 5 minutes. The film was then dried in a vacuum oven at 60C for one hour after vapor treatment. Dry film thickness was 6.o~.

~i~9426 The untreated film appeared blue-green by transmitted light. Upon solvent treatment for one minute with the vapors of methylene chloride, the films turned blue. The optical absorption spectrum for this film before and after vapor treatment is shown in Fig.
1. The spectrum was determined in a conventional manner using for example a Cary 14 spectrophotometer.
The spectrum 1 for the untreated film has a peak at about 650 nm and a shoulder at 60o nm. The spectrum 2 for the methylene chloride treated film 2 is shifted with narrow band peaks at 635 nm and 560 nm. The peak at about 560 nm is absent from the untreated film.
The photosensitivity and the electrical speed of each coating was determined as follows: the front surface of the coating was electrostatically charged negatively under a corona source until the surface potential as measured by a capacitively coupled probe attached to an electrometer attained an initial dark value, VO of -500 volts. The rear surface of the charged coating was then exposed to monochromatic visible radiation at a wavelength equivalent to a peak in the optical absorption maximum of the dye material.
The exposure caused reduction of the surface potential of the element from -500 volts to -100 volts. The photosensitivity of the element can be considered equivalent to the exposure in ergs/cm2 necessary to discharge the element from -500 to -100 volts, after correction for light absorption and reflection by the film support.
3 The photosensitivities (at 640 nm) of control and fumed films of the above composition are listed in the following table.
Photosensitivity Photosensitivity Exposureof Fumed Film of Control 35 Configuration(ergs/cm ) (ergs/cm2) Negative Charge 8 189 Rear Exposure Example 3 A photoconductive film containing dye material 4 3, Table I was tested as in Example 2. Upon vapor treatment the films changed from blue-green to blue and exhibited the same absorption and speed characteristics as material 1.
Example 4 15.5 mg of dye material 2 was dissolved in 2 ml CH2C12 and 0.2 ml HFIP. To this was added 5 ml of poly[4,4'-(2-norbornylidene)diphenylene carbonate]
(polymer material 5, Table II) solution(0.075 g of polymer/ml CH2C12) and 297.8 mg of tri-p-tolylamine.
This solution was warmed, coated on nickel coated poly(ethylene terephthalate) at 25C, and allowed to air dry 2-3 minutes at 50C. The film was then vapor treated for 5 minutes with toluene and oven dried at 55C for 1-1/2 hours. The control was an untreated film of dye material 2. It had maximum absorption at 660 nm and a shoulder at 620 nm. The transformed films (i.e., vapor treated to form the enhanced photoconductive state) had maximum absorption at 655 nm and a smaller peak at 580 nm.
The photosensitivity values shown in Table III of the control and the vapor treated film was determined as in Example 2 for negative charging, front and rear exposures.
TABLE III
PhotosensitivitylPhotosensitivity of the of the ExposureTransformed Film Control Confi~ tlon(ergs/cm2) (ergs/cm2) Negative Charge 30 498 3 Front Exposure Negative Charge 20 145 Rear Exposure y Photosensitivity was calculated for a discharge from -308V to -58V at A = 650 nm.
Exa_ple 5 16.1 mg of dye material 2 was dissolved in 2 I ml dichloromethane and 0.2 ml HFIP. To this 5 ml of a Lexan 145 solution (0.1 ~ Lexan/ml CH2C12) and 299.0 mg tri-p-tolylamine were added. The solution was heated, coated on Ni/Estar at 25C, and allowed to air dry at 1~94Z6 50C. The rilm was then vapor treated wlth tetrahy-drofuran for 2 mlnutes and oven drled at 55C ror 1-1/2 hours.
The photosensltlvlty Or the treated rilm and 5 untreated control ~llm was determlned as ln Example 2 for negative charglng front and rear exposure. Results are shown ln Table IY.
TABLE IV
Photosensitlvltyl Photosensltlvity of the of the ExposureTransrormed Fllm Control Configuratlon(ergs/cm2) _(er~s/cm2) Negatlve Charge 22 975 Front Exposure Negatlve Charge 35 220 Rear Exposure lThe ph~tosensltlvlty was calculated for -500V to -lOOV
dlgcharge at A ~ 650 nm.
ExamPle 6 Thls example was prepared to show the comblna-tion Or hlgh speed and good resolutlon possessed by photoconductlve rllms of the present lnventlon compared to the speed and resolutlon of typlcal homogenous photoconductlve rllms such as those descrlbed ln U.S.
Patent 3,542,547 and conventlonal aggregate photoconduc-tive ~llms such as those descrlbed ln ~.S. Patent 3,615,414 and U.S. Patent 3,873,311.
Three photoconductlve ~llms were prepared.
3 Fllm A was a homogenous rllm Or the type descrlbed ln U.S. Patent 3,542,547. Fllm B was an aggregate rllm Or the type descrlbed in V.S. Patent 3,873,311. Fllms C
and D lnclude dye materlal 1, Table I. Each rllm lncluded the rollowln~ llsted materlals.
Fllm A
(a) CH2C12 17.6 g (b) 2,4-bls(4-ethoxyphenyl)-6- 0.04 g (4-pentyloxystyryl)pyrylium tetra~luoroborate (c) 2,6-blst4-amyloxyphenyl)-4~2-(4 0.01 g amyloxyphenyl)-~-phenyl-4H-pyran-4-yllden~lmethy~ pYrylium-per chlorate' ~2 -D~

1~9426 Fllm A Cont'd.
(d) Vltel PE 101~ (Goodyear) 1.8 g (e) 4,4'-bis(dlethylamlno)-2,2'- o.6 g dimethyltrlphenyl methane ~llm B
(a) CH2C12 10.2 g (b) 1,1,2-tr~chloroethane ~.8 g (c) Lexan 145 polycarbonate 1.8 g (d) 4-(p-dimethylamlnophenyl)- 0.09 g lG 2,6-dlphenylthlopyryllum tetra~luoroborate (e) 4,4'-bls(dlethylamlno)-2,2'- 1.2 g dlmethyltrlphenylmethane Fllm C
; 15 (a) CH2C12 3~:32 g (b) Hexafluorolsopropanol o.84 g (c) 4-~2,6-Dlphenyl-4H-thlopyran-4- 0.126g ylldene)methyl]-2,6-dlphenyl-thlopyryllum perchlorate (d) Lexan 145 polycarbonate 3.0 g (e) Trl-p-tolylamlne l.BB g (f) Poly[(oxycarbonylethylene-1,4- 0.15 g phenylene-2-cyanovlnylene-1,4-phenylene-l-cyanovlnylene-1,4-phenylene(phenylamlno)-1,4-phenylene ethylenecarbonyl-oxydecamethylene]
(g) Toluene 5.64 g Fllm D
(a) CH2C12 34.32 g (b) Hexa~luoro~sopropanol 0.84 g (c) 4-t2,6-Dlphenyl-4H-thlopyran-4- 0.126g ylldene)methyl]-2,6-dlphenyl-thlopyrylium perchlorate (d) Lexan 145 polycarbonate 3.0 g (e) 4,4'-dlethylamlno-2,2'- l.B8 g dlmethyltrlphenylmethane (g) Toluene 5.64 g ~ Each coating composltlon was made 24 hours prlor to coatlng by dlssolvlng the components ln the order llsted, allowlng surrlclent time between addltlons ror complete solvatlon. Each composltlon was coated on a transparent nlckel or cuprous lodlde conductive support.

1~2~4Z~

Coating A was made at a coverage of 7.5 gms/m2. Coating B was made at a coverage of 11.3 gms/m2. Coatings C
and D were made at a coverage of 7.5 gms/m2. The coatings were then dried.
Photosensitivity and resolution data are presented in Table V. Photosensitivity was determined as in Example 2 for negative charging at a wavelength where the optical density of the film equals l.O.
Discharge was from -600V to -lOOV. The data in this table shows that photoconductive elements comprising the composition of the present invention have a better speed resolution product than the photoconductive elements A and B which are representative of the prior art.

-21- 11;294Z6 C
C o o C~ 0 ~ U~ o 0 ~ ~ t~
1~ 0 Cl 0 5 I ~ ~e ~ ~ ,~
~ _ bO
C~
J~ ~
OCC

O

~a ~ ~ I a: o , co ~ ~ 'I
¦ E ~'¦ I 11' " ~ o ~ C

~ o b~
I I I I
O~ O o o O
S ~.
~ e , ~ ~ 5 o C
~ a~ ~ ~ ~ 4 E
S C~
~ C~ ~
a) ~ o o o o ~ ~ c ,1 ~ a~ o o ~ s~ o ~ ~n ` ~ ~ 0 ~ o o 3, U~
v o '' e~ a o~ .
B ~ I

1~2942~

Examples 7-12 Six different polymers having the recurring units 1, 2, 3, 4~ 5 and 6 from Table II were used to ma~e six photoconductive films, each containing a different polymer. Each film contained the dye material 1, Table I. The films were prepared substantially in accordance with Example 2. Each film was found to have greater photosensitivity after vapor treatment than before such treatment. Each vapor treated film also 10 had a spectral peak at about 560 nm which did not appear in the film before vapor treatment. These Examples 7-12 also show that the change in absorption spectrum and enhanced speed is independent of the polymer material .
Hence, the transformation probably results from dye-dye 15 interaction instead of dye-polymer co-crystallization.
Example 13 To 12.8 mg of dye material 4 was added 1 ml of dlchloromethane, 0.1 ml of hexafluoroisopropanol and ~ 5 ml dichloromethane containlng Lexan 145 (0.1 g/ml).
O 20 The solution was stirred and heated for 5 minutes and 2 then 327 mg of tri-p-tolylamine was added. The final solution was coated on an unsubbed nickel coated poly-(ethylene terephthalate) support and air-dried at 55C
for 5 minutes. Transformation occurred upon vapor 25 treatment with warmed dioxane. The film was dried in a vacuum oven at 60C for one hour after vapor treatment.
The absorption spectrum of this film after vapor treat~
ment had a shoulder at 578 nm and a peak at 605 nm.
The spectrum of the untreated film was different from 30 that of the treated film.
Q Photosensitivity measurements were made as in Example 2 for rear exposure discharge from -500V to -lOOV.
The photosensitivity was 13 erg/cm2.
'_ xample 14 17.0 mg of dye material 5 was dissolved in 2 I ml CH2C12 and 0.2 ml HFIP. To this was added 5 ml of Y Lexan solution (0.1 g of polymer/ml of CH2C12) and _ 302.1 mg tri-_-tolylamine. This solution was heated to drive off excess HFIP, coated on nickel coated poly-4 (ethylene terephthalate) at 25C and allowed to air dry ~1~94Z6 2-3 minutes at 5OC. The film was then fumed for one minute with tetrahydrofuran and oven dryed 1/2 hour at 58C. Photosensitivity measurements were made according to Example 2. The results are presented in Table VI.
TABLE VI

PhotosensitivityPhotosensitivity Exposure of the fumed filmof the control Configuration (ergs/cm2) (ergs/cm2) Front 19.2 3O9 Rear 13.6 83 Photosensitivity in this example is the energy required to discharge the film from -500V to -lOOV at 610 nm.
The invention has been described in detail with particular reference to certain preferred embodi-ments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of the invention.

Claims (19)

We claim:

1. A photoconductive composition compris-ing a film-forming electrically insulating polymer and a dye material having an absorption spectrum which changes when a binderless coating of said dye material is treated with solvent vapors and having a structure according to the formula:

wherein Z and Z1, which may be the same or differ-ent, represent O, Se and S; X? represents an anion; wherein said composition has an absorption spectrum which is similar to the changed absorption spectrum of said binderless coated dye material.

2. A photoconductive composition as in Claim 1, wherein X is a perchlorate of a fluorobo-rate anion.

3. A phtooconductive composition according to Claim 1 wherein said composition also contains an organic photoconductor.

4. A photoconductive composition according to Claim 3 wherein said composition comprises an organic photoconductor selected from the group con-sisting of tri-p-tolylamine and (di-p-tolylamino-phenyl) cyclohexane.

5. A photoconductive composition as in Claim 1 wherein said dye material is present in said composition in an amount of about 0.001 to about 30 weight percent on a dry basis.

6. A photoconductive composition as in Claim 1 wherein said polymer is selected from the group consisting of poly[4,4'-(hexahydro-4,7-methanoindan-5-ylidene)diphenylene terephthalate];
poly[4,4'-(isopropylidene)diphenylene 4,4'-oxydiben-zoate]; poly[4,4'-(2-norbornylidene)bis-(2,6-dichlo-rophenylene) carbonate]; poly[4,4'-hexahydro-4,7-methanoindan-5-ylidene)diphenylene carbonate]; poly-[4,4'-(2-norbornylidene)diphenylene carbonate];
polystyrene, and poly(4,4'-isopropylidenediphenylene carbonate).

7. A photoconductive composition compris-ing a film-forming electrically insulating polymer, tri-p-tolylamine and a dye material selected from the group consisting of 4-[(2,6-diphenyl-4H-thiopy-ran-4-ylidene)methyl]-2,6-diphenylthiopyrylium per-chlorate; 4-[2,6-diphenyl-4H-thiopyran-4-ylidene)-methyl]-2,6-diphenylselenopyrylium perchlorate; 4-[(2,6-diphenyl-4H-thiopyran-4-ylidene)methyl]-2,6-diphenylthiopyrylium fluoroborate, 4-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl]-2,6-diphenylthiopyrylium perchlorate; 4-[(2,6-diphenyl-4H-pyran-4-ylidene)-methyl]-2,6-diphenylselenopyrylium perchlorate and 4-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl]-2,6-di-phenylpyrylium perchlorate; said composition being characterized by an absorption spectrum which is substantially similar to the absorption spectrum of a solvent-treated binderless coating of said dye material.

8. A photoconductive composition as in Claim 7 wherein said polymer is selected from the group consisting of poly[4,4'-(hexahydro-4,7-meth-anoindan-5-ylidene)diphenylene terephthalate]; poly-[4,4'-(isopropylidene)diphenylene 4,4'-oxydibenzo-ate]; poly[4,4'-(2-norbornylidene)bis(2,6-dichloro-phenylene)carbonate]; poly[4,4'-(hexahydro-4,7-meth-anoindan-5-ylidene)diphenylene carbonate]; poly-[4,4'-(2-norbornylidene)diphenylene carbonate];
polystyrene, and poly(4,4'-isopropylidenediphenylene carbonate).

9. An electrophotographic element compris-ing a conductive support and a layer of a trans-formed photoconductive composition which comprises a film-forming electrically insulating polymer and a dye material which has an absorption spectrum which changes when a binderless costing of said dye mate-rial is treated with solvent vapors and having a structure according to the formula:

wherein Z and Z', which may be the same or differ-ent, represent O, Se or S; X? represents an anion;
wherein said composition has an absorption spectrum which is substantially similar to the changed absorption spectrum of said binderless coated dye material.

10. An electropotographic element as in Claim 9, wherein X is a perchlorate or a fluorobo-rate anion.

11. An electrophotographic element as in Claim 9, wherein said composition also contains an organic photoconductor for said dye material.

12. An electrophotographic element as in Claim 11, wherein said composition comprises an organic photoconductor material selected from the group consisting of tri-p-tolylamine and (di-p-tol-ylaminophenyl)cyclohexane.

13, An electrophotographic element as in Claim 9, wherein said dye material is present in said composition in an amount of about 0.001 to about 30 weight percent on a dry basis.

14. An electrophotographic element as in Claim 9, wherein said electrically insulating poly-mer is selected from the group consisting of poly-[4,4'-(hexahydro-4,7-methanoindan-5-ylidene)diphen-ylene terephthalate]; poly[4,4'-(isopropylidene)-diphenylene 4,4'-oxydibenzoate]; poly[4,4'-(2-nor-bornylidene)bi6-(2,6-dichlorophenylene) carbonate];
poly[4,4'-hexahydro-4,7-methanoindan-5-ylidene)-diphenylene carbonate]; poly[4,4'-(2-norbornyli-dene)diphenylene carbonate], polystyrene, and poly-(4,4'-isopropylidenediphenylene carbonate).

15. An electrophotographic element compris-ing a support and a photoconductive composition which comprises a film-forming electrically insulat-ing polymer, tri-p-tolylamine and a dye material selected from the group consisting of 4-[(2,6-diphenyl-4H-thiopyran-4-ylidene)methyl]-2,6-diphenyl-thiopyrylium perchlorate; 4-[2,6-diphenyl-4H-thiopy-ran-4-ylidene)-methyl]-2,6-diphenylselenopyrylium perchlorate; 4-[(2,6-diphenyl-4H-thiopyran-4-yli-dene)methyl]-2,6-diphenylthiopyrylium fluoroborate;
4-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl]-2,6-diphenylthiopyrylium perchlorate, 4-[(2,6-diphenyl-4H-pyran-4-ylidene)-methyl]-2,6-diphenylselenopyr-ylium perchlorate and 4,[(2,6-diphenyl-4H-pyran-4-ylidene)methyl]-2,6-diphenylpyrylium perchlorate;
said composition having an absorption spectrum which is substantially similar to the abrasion spectrum of a solvent-treated binderless coating of said dye material.

16. An electrophotographic element as in Claim 15, wherein said electrically insulating poly-mer is selected from the group consisting of poly-[4,4'-(hexahydro-4,7-methanoindan-5-ylidene)diphenyl-ene terephthalate]; poly[4,4'-(isopropylidene)-diphenylene 4,4'-oxydibenzoate], poly[4,4'-(2-nor-bornylidene)bis(2,6-dichlorophenylene)carbonate];
poly[4,4'-(hexahydro-4,7-methanoindan-5-ylidene)-diphenylene carbonate]; poly[4,4'-(2-norbornyli-dene)diphenylene carbonate], polystyrene, and poly-(4,4'-isopropylidenediphenylene carbonate).

17. A compound having the structure:

wherein Z is O or S.

18. A method of making a photoconductive composition containing an electrically insulating polymer and a dye msterial, said method comprising the step of treating said composition with solvent vapors, thereby causing a transformation in said composition characterized in that the dye has the structure:

wherein Z and Z1, which may be the same or differ-ent, represent O, Se and S; X? represents an anion; wherein said composition has an absorption spectrum which is similar to the changed absorption spectrum of said binderless coated dye material and the absorption spectrum of (a) a solvent vapor-treated binderless coating of said dye material and (b) said transformed composition are similar.

19. A method as in Claim 18 wherein said photoconductive composition also contains an organic photoconductor.