CA1108914A

CA1108914A - Hydrazone containing charge transport element and photoconductive process of using same

Info

Publication number: CA1108914A
Application number: CA313,483A
Authority: CA
Inventors: Howard W. Anderson; Michael T. Moore
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1977-10-17
Filing date: 1978-10-16
Publication date: 1981-09-15
Also published as: JPS5459143A; AU3719478A; AR222158A1; AU520312B2; EP0001599B1; JPS5542380B2; US4150987A; EP0001599A1; DE2861209D1

Abstract

HYDRAZONE CONTAINING CHARGE TRANSPORT ELEMENT
AND PHOTOCONDUCTIVE PROCESS OF USING SAME
Abstract of the Disclosure A process for electrophotographic reproduction, and a layered electrophotographic plate having a conven-tional charge generation layer and a p-type hydrazone con-taining charge transport layer, in which the surface of the charge transport layer is selectively discharged by actinic radiation as a result of the migration through the transport layer of charges generated in the charge generation layer as a result of the actinic radiation and injected into the transport layer, the hydrazone having the composition;

n=0,1 R1 = -O(CH2)yCH3 y=0, 1 X=0,1,2,3 R3 =-H
R4 =-H

R2 = -OCH2CH3 R5 =-H

-H

R6 = R7 = R6 & R7 =

Description

Back~round of the Invention 16 1. Field of the Invention 17 This invention relates in general to electro~ -18 photographic reproduction, and in particular to electro- -19 photographic reproduction utilizing hydrazone materlals of - ~ -20 the composition; -22 Rl~(C ~)n C = N - I n = () 1 24 R~L 2 :
26 Rl = ~ (CH2) yCH3 y=0 ,1 .
27 ~ /(CH2)xCH3 x = 0,1,2,3

2 8 -N 0 -N
29 2 x H3 ,~ , . .

" ~ , ~ ~ , . ' ' , ~ -OC~I2CH3

3 -N ~ R4 = -H

4 -C~12C~3 6 R2 = -OCH2CH3 R5 = -H

7 -CH3 ~ -CH3 11 CH~C 2 2 3 12 R7 = -~

17 R6 & R7 =

19 r~
~
21 as the active material in the p-typ~ charge transport layer 22 of a multi-layer photoconductor system.

23 2. Description of the Prior ~rt 24 Electrophotographic processes and materials~ such as xerograph~y, are of course well known. Fundamentally, 26 such processes involve the forma~:ion of a un:iforrn electro-27 static charge upon a norMall~ insula-tirlg plate or element 28 under "dark" conditions. Thereafter, the element is exposed B0977049 -3~

.
,- . . :

~ ,.f~ gt 1 to light in an imagewise manner to render the ligh-t struck 2 portions oE the element conductive thereby permitting the 3 electrostatic charge to be conducted Erom -the surface of the 4 element. Thus a latent image in the form of charyed surface areas are formed on the portions of the surface not struck 6 by light. The latent electrostatic image on the surface of 7 the element is -then typically developed by exposure to an 8 oppositely charged powder, i.e, a toner which is held -to the 9 charged portion of the element by the affinity of the toner for the opposite charge. The discharged portion of the 11 element displays no such affinity for -the toner. The thus 12 formed image of toner is thereafter transferred to another 13 surface, such as paper, and adhered thereto by, for ln-14 stance, pressure sensitive, heat sensitive, etc, adhesives admixed with the toner.
16 A particularly useful electrophotographic element 17 is that in which a charge generation layer, which is re-18 sponsive to actinlc radiation to generate electron-hole 19 pairs, is utilized in conjunction with a _-type charge transport layer adjacent thereto. Numerous charge genera-21 tion layers responsive to selected actinic radiation are 22 known. The charge transport layer is nct responsive to 23 actinic radiation under the operating conditions, but serves 24 to transport the positive charge from the charge generation layer, to, depending upon the particular system involved, 26 the surface of the negatively charged transport layer at 27 which the image is formed, or alternatively, to a conductor 28 in a positively charyed ~y~tem. U.S. Letters Patent 3,837,851 B09770~9 _4_ ~3~

l discusses an electrophotographic plate u-tilizing as the 2 active material in the charye transport layer a -tri-aryl 3 pyrazoline compound.
4 Hydrazones of a differing nature than those with which the instant invention is concerned have been employed 6 in photoconduc~ors essentially as a material responsive to 7 actinic radiation. U.S. Letters Paten-t 3,717,462, issued 8 ~February 20, 1973, discloses such use of a hydrazone com-g pound. Other similar uses of hydrazone compounds, in gene-ral are to be found in U.S~ Letters Patent 3,765,884.
11 In summary, the prior art has recognized the use 12 of charge transport layers in conjunction with distinct 13 charge generating layers, but has not suggested the use of 14 hydrazones in general, and particularly the hydrazones of lS the instant invention, for use as the active ma~erial in a 16 charge transport layer. On khe other hand, hydrazones 17 differing from the specific hydrazones of the instant in-18 vention have been employed as lic3ht responsive materials as 19 opposed to charge transport materials.
Summary of the Invention 21 The present invention, which provides a sur-22 prising and heretofore unavailable improvement in multi-23 layer electrophotographic elements, comprises an element 24 having, as its fundamental parts, a conductor, a charge ~eneration layer, which i5 substantially conventional in 26 nature, and a novel p-type charge transport layer adjacen-t 27 thereto including, as the active material, a hydrazone 28 having the general formula;
' .

''.',, ' ' ' .' ,'.

1~ ( c = f, --C = N - ~ n = 0, 1 3 ~l ~7 6 Rl = -O (CH2 ) yCH3 y=0, 1 r~/(CH2)xcH3 x=0,1,2,3 9 (CH2 ) xCH3 R3 = -H

11 -N~ ~ R4 - -H

14 R2 = -OCH2CH3 R5 = -H
-CEI3 R ~ Cf~3 16 CN2CH3 6 ~=~
17 -H -CH2 ~\=/

19 ~--~ C 2CH2CH2C 3 2 0 R7 = ~) ~) 22 .
23 R6 & R7- ~/

26 ~
27 A particularly prefe.rred char~Je transport materlal ls p-28 diethylaminobenzaldehyde-~diphenylhydrazone),i.e., ' , .

. .

N _ ~ I = M - N /

4 Other preferred charge transport materials are; o-ethoxy-p-diethylaminobenzaldehyde-(diphenylhydrazone), i.e., 9 OCH2cH3 _-methyl-p-diethylaminobenzaldehyde-(diphenylhydrazone), 11 i.e., 13 CH3 C ~ I = N - N /

14 CH3 CH2 ~ 0 16 o-methyl-p-dimethylaminobenzaldehyde-(diphenylhydrazone), 17 i.e., 8 ~N ~--C = N - N

22 p-dipropylaminobenzaldehyde-(diphenylhydrazone~, i.e., 23 CH3-CH2-C ~ ~ C = ~ - N

26 p-diethylaminobenzaldehyde-(be~zylphenylhydrazone), i.e., 27 C~3C~2 Hl / CH2-0 28 ~ > N ~ C = N - N \
9 CH3C~12 0 B0977049 _7_ , .
, .
-, 1 p-dibutylaminobenzaldehyde-(diphenylhydrazone)~ i.e., 2 CH3-CH2-CH2-C~ C = N - M/

p-dimethylaminobenzaldehyde-(diphenylhydrazone),i.e , 7 C~N~3 I N <

g Multilayer electrophotographic elements are, in general, known- The charge generation layer, which may be organic or 11 inorganic, is responsive to actinic radiation falling there 12 upon to generate an electron-hole pair. While the charge 13 generation layer may be self-supporting, preferably a pliant 14 support such as a polymeric film having a metalized surface is employed. Biaxially oriented polyethylene ~erephthalate 16 is a preferred pliant support. As discussed above, the 17 charge generation layer must be in electrical communication 18 with a conductor to facilitate selective discharge of the 19 element. Again with regard to the preferred but conven-tional aspect of the instant invention, an aluminized Mylar 21 (polyethylene terephthalate film) i5 conveniently employed 22 with the aluminum constituting the conducting layer. The 23 charge generation layer is preferably formed on the support 24 and in contact with the conduct:ing layer. While not criti-25 cal, the charye generation layer is yenerally between 0.05 26 microns to 0 20 microns thick. Inorganic charge generating 27 materials include selenium, telluriurn and compounds ~rom 28 groups IIb and VIa of the periodic table, i.e., cadmium . ;~ t~ V~
, , .
_ ~L'L~ 3P4 1 sulfo-selenide. Organic charge generation materials includ-ing cyanine compounds such as those disclosed in U.S. Patent No. 3,887,366, issued June 3, 1975, disazo compounds such as those described in Canadian Patent No. 980,160, issued December 23, 1975, ar;d U.S. Patent No. 4,123,270, issued October 31, 1978, or phthalocyanine compounds are generally operable. Useful results are ob-tainable with charge gen-erating materials comprising methine dye derived from squaric acid. Materials of this type are discussed in U.S.
Patent No. 3,824,099, issued July 16, 1974.
Chlorodiane Blue, methyl squarylium and hydroxy squarylium are particularly preferred charge generating materials.
More specifically, these preferred materials are;
4-4" - (3,3'-dichloro - 4,4' - biphenylylene) bis(azo) bis 3-hydroxy -2- naphthanilide , i.e., H
N - C OH Cl Cl Oli C-N~0 0 ~N=N~_N=N ~) H

22 2,4 - bis- ~2-methyl-4-dimethylaminophenyl)-1,3-cyclobuta-dienediylium-1,3-diolate, i.e., C ~ ~ CH3 ~, Ctl~ ~ / CH3 C O~ Cl13 27 2~4-bis-(2-hydroxy-4-dimethylaminophenyl)-l~3-cyclobuta dienediylium-1,3-diolate, i.e., .~ ` , -:

.

3L dL~

l CH3 O~l 1~ Oll CH3 2 ~ ~ CH3 4 but will, for convenience, be hereafter identi.fied as Chlorodiane Blue, methyl squarylium and hydroxy squarylium, 6 respectively.
7 In summary, a broad ranye o~ inorganic and organic 8 charge generation materials are operable with the charge 9 transport material of the instant invention. However, since the charge transport material must, in most embodiments of ll the invention, be substantially transparent to the actinic 12 radiation which activates the charge generation ma-terial, it 13 is preferred that the charge generation material be re-14 sponsive to actinic radiation in the visible light and longer wave lengths, i.e., longer than 3900 angstroms. This 16 requirement is of concern in the preferred embodiment where-17 in the charge transport material is interposed between -the 18 charge generation material and the source of actinic radia-l9 tion, i.e., as in a negative charging system. Howe~er, in a positive charging system, the charge generation material may 21 be~directly exposed to the actinic radiation and the charge 22 transport materi~al interposed between the charge generation 23 material~and the conductor. In the latter case, charge 24 generation materials and actinic radiation sources operating at shorter than visible light wave lengths are suitable for 26 use with the charge transport material oP the instant inven-27 tion~
28 Ill the preferred embodiment of the instant in-B0977049 -lO-.

, , .
.

f~3~

1 vention in which organic charge generation rna-terials are 2 employed, such materials are, as is conventional, coated 3 onto the metalized support utilizing, for instance, meniscus 4 coating, doctor blade coating or dip coating. Preferably, an adhesive layer is provided on the support to aid in 6 bonding the charge genera-tion layer thereto. Polyester 7 resins are a preferred adhesive layer.
8 The novel charge ~ransport layer according to the 9 instant invention is preferably coated onto the charge generation layer to form the top or exposed layer of the 11 element. Preferably, the charge transport layer is between 12 7 microns and 35 microns thick; but may be thicker, and 13 operably may be less than 7 microns, i.e., 5 microns thick.
14 Though the following discussion will primarily address this preferred embodiment, it is to be understood that, with 16 regard to positive charging systems, the charge transport 17 layer can be interposed between the charge generation layer 18 and the support in the manner illustrated in the drawing and 19 discussed below.
The active material of the _-type charge transport 21 layer of the instant invention is a hydrazone of the generic 22 structure;
23 ~R3 Hl J~5 l6 24 Rl- ~ (C = lC)n C = N - I n = 0,1 2!i R~ x2 HR7 26 Rl = -O(CH2)yCH3 y=0,1 27 ~ /(CII2)xCH3 x = 0,1,2,3 ~ \
29 (CH~)xCH3 .

Rl ~3 = ~
2 ~ C 2 C 3 3 -N R~ H
4 ~ CH2~-H3 6 R2 = -OCH2CH3 ~5 = -H
7 -CH3 ~ C113 8 -CH2CH3 R6=
9 -H -C~2 --l O -CH3 12 R7 =--(~ -CH2CH2C~l2cH3 \--l7 R6 & R7 =

19 r~.
~
21 A particularly preferred charge transport material is p-22 diethylaminobenzaldehyde-(diphenylhydraæone3,i.e., 23 CH3 C~ 0 24 ~ ~N ~ C -- N~N

27 Other preferred charge transport rnaterials are; o-ethoxy-p-28 diethylaminobenzaldehyde~(~liphenylhydrazone), i.e., g~

2 > N ~ C - N-N
3 CH3 ~ CH2 ~ \ 0 4 CH2c~3 o-methyl-p-diethylaminobenzaldehyde-~diphenylhydrazone~, 6 i.èO, CH3 C ~ ~ H / 0 8 / N ~ ~ C = N-~
9 CH3 C 2 ~ 0 11 _-methyl-p-dimethylaminobenzaldehyde-(diphenylhydrazone), i.e., 12 CH H ,0 13 ~ N~ = N-N
14 Cf~3 \ 0 16 p-dipropylaminobenzaldehyde-(diphenylhydrazone~, i.e., 17 CH3-CH2-C ~ I / 0 18 / N- ~ C = N - N

p-diethylaminobenzaldehyde-(benzylphenylhydrazone), i.e., 21 CH3 CE12 ~ H ~ CH2 0 22 > N ~ C = N - N "' 24 p-dibutylaminobenzaldehyde-(diphenylhydrazone), i.e., CH3-CH2-CH2 C ~ ~ 7 - 26 / N ~ C = N ~ M
27 CH3-CEI2-cH2 CH2 28 p-dimethylaminobenzaldehyde-(dipherlylhydrazon~), i.~., .
B0977049 -lI-,:
, ~, ' , ......... .
. .

2 ~ N - ~ - C = N - N /

4 In use, the hydrazone material is admi~ed with a binder in an organic solvent, coated onto the charge generation layer 6 and dried in a forced air oven. While numerou.s polymeric 7 binders will be apparent to -those skilled in the art, typi-8 cal binders include polycarbonate resins, i.e., M-60 avail-9 able from Mobay Chemical Company, polyester resins such as PE-200 available from Goodyear, and acrylic resins such as 11 A-ll available from Rohm and Haas. Various other resins are 12 also operable as will be demonstrated below. ~he resins, 13 which may be used singularly or in combination, are admixed 14 with an organic solvent or solvents, preferably tetrahydro-furan and toluene, though other appropriate solvents will be 16 apparent to those skilled in the art.
17 - Various other constituents for lubrication, 18 stability, enhanced adhesion, coating quality, etc, may be 19 included in the charge transport layer to accomplish pur-poses evident to those skilled in the art. For instance, a 21 silicon oil, such as that available under the trademark DC-22 200 from Dow Corning, is included in the charge transport 23 layer solution.
24 Brief Description of the Drawings In the Drawing:
26 FIGURE 1 is a simplified sect:ional view of the 27 charge generation and charye transport layers of the pre-28 ferred embodiment of the ins-tan-t invention illustrating the 1 response to exposure vf a neyatively charged e],ement -to 2 actinic radiationi 3 FIGUR~ 2 is a view similar to -that of Fiyure 1 4 illustrating the resul-ting negative charge on the element surface;
6 FIGURE 3 is a view similar to tha-t of Figure 1 7 illustrating a positive charginy element; and 8 FIGURE 4 is a view similar to that of Figure 2 9 illustratiny the resulting positive charge on the surface of ,, the positive charged element.
11 Detailed Description of the Drawinys 12 Turniny now to the drawing, wherein like cornpo-13 nents and constituents are designated by like reference 14 numerals throughout the various figures, a multilayer electro~
lS ~photographic element is depicted in Figure 1 and generally 16 designated by the reEerence numeral 10.
17 ~lement 10 includes charge generation layer 12 and 18 charge transport layer 14. As illustrated, a ne~ative 19 charge exists on the surface of charge transport layer 14.
20 ~ positive charge is provided adjacent charge generation ', 21 layer 12, i.e., in a conducting layer (not shown). ~ctinic 22 radiatlon 16 is shown passing through charge transport layer 23 14 at area 18 and inducing charye generation layer 12 to 24 produce the electron-hole pair charges. The hole is at-25 tracted to the negative charge on ~he surface of charye 26 transport layer 14. Thus, as sho~n in F:igure 2, the hole is 27 injected into and travels -throuyh charge transport la~er 14 28 to discharge area 18. Charge tr~nsport layer 14 is es-"
Bo977049 -15-i 1 sentially an insulating materia] relative to the neyative 2 charge thereon. Thus, localized discharge is maintained a-t 3 area 18. The electron, of course, is attrac-ted to the 4 positive charge at the conducting layer (not shown).
A similar result is illustrated in Figu~e 3 and 6 Figure 4. However, element 10', while including the same 7 layers, is arranged di~ferently. Charge generation layer 12 8 is positively charged and exposed directly to actinic radia-9 tion 16. Charge transport layer 14 is interpcsed between charge generation layer 12 and the negative charge, usually Il carried at a conductive layer ~not shown). Again actinic 12 radiation 16 develops electron-hole pair charges. Area 18 13 of charge generation layer 12 is discharged by the electrons 14 while the corresponding holes pass through charge transport layer 14 in response to the attraction of the negative 16 charges. Element 10' has the advantage of not requiring 17 that actlnia radiation 16 pass through charye transport 18 layer 14, but charge generation layer 12 is not protected.
19 Other embodiments are contemplated but not il-lustrated. For instance, element 10 of Figure 1 could be 21 exposed to actinic radiation from the opposite side, i.e., 22 through the conducting layer.
23 ~ Detailed ~xamples of the Invention 24 ~The illustrative examples below are provided to permit those skilled in the art to practice the preferred 26 embodiment of the instant invention as well as to illustrate 27 the operable variations in the invention. ~lowever, it is 28 not contemplated that the illu~trative examples will extend .

~ ~rr~ 4 l to all operable combinations, or specify the various alter-2 native components apparent to those skilled in the art.
3 Example 1 4 A support appropriate for the instant invention was prepared by coating an aluminized Mylar (duPont Trade-~ mark for polyethylene tereph-thalate) subs-trate with a solu-7 tion of polyester resin (PE 200 available from Goodyear) 8 dissolved in tetrahydrofuran:toluene solvent system in a 9:1 g ratio (0.7~ to 1.4% solids, weight:weight). The polyester coating was meniscus coated and dried in a forced air oven.
11 Chlorodiane Blue (0.73~ solids by weight) was then dissolved 12 in 1.2:1.0:2.2 (by weight) mix-ture of ethylenediamine, n-13 butylamine and tetrahydrofuran. Silicon oil (available 14 under the Trademark DC-200 from Dow Corning) was then added in the amount of 2.3~ by weight relative to the Chlorodiane 16 Blue. The resulting solution was meniscus coated onto the 17 polyester coated substrate, and the resulting coated sub-18 strate dried in a forced air o~en. Thus a relatively con-19 ventional Chlorodiane Blue charge generation layer was produced on an again conventional polyester support.

21 The novel charge transport layer of the instant ~2 invention was formed by admixing a polycarbonate resin 23 binder (M-60 available from Mobay Chemical Company) in the 24 amount of 7.65 grams, a polyester resin (PE-200 available from Goodyear) in the amount of 3.60 grams, and an acrylic 26 resin (A-ll available from Rohm and ~laas) in the amount of 27 2.25 grams in 86.5 grams of tetrahydrGfuran and toluene 2~ solvent, the solvents being present in a ratio of approxi-1 mately 9:1 by weight. A preferred hydrazone accordiny -to 2 the instant in~ention, i~e., p-diethylaminobenzaldehyde-3 (diphenylhydrazone) was then added in the amount of 9.0 4 grams in conjunction with 0.02 grams o~ silicon oil (DC-200). Additional tetrahydroEuran may then be added to 6 adjust the viscosity to that appropriate or the chosen 7 coating technique. In the instant example, the resulting 8 solution was meniscus coated onto the charge generation 9 layer as formed abo~e and the entire film again dried in a forced air oven to form a multilayered electrophotographic 11 element. The electrophotographic element was tested by 12 first charging the surface thereof to -870 volts in the 13 dark, exposing the charged electrophotographic element to 14 light typical of that utilized in commercial electrophoto-graphic apparatus under various light intensity conditions, 16 and determining the light intensity necessary to discharge 17 the element to a voltage of ~150 volts after 454 millise-18 conds under such conditions. It was determined that the 19 element of the instant example required 1.10 microjoules per square centimeter for such discharge. Such value is 21 indicative of excellent hole transport. Electrophotographic 22 elements essentially identical to that of the instant 23 examples w~re tested in commercially designed copying ~ 24 equipment and provided excellent results as to charge ., ' transport, resistance to toner filming, physical resistance 26 to wear, long-term stability o~ electr:Lcal and physical 27 properties, and low temperature operation~
28 Example 2a-f .

.

Bo977049 - 18 -. ~ .

: :, , 1 Multilayered electrophotoyraphic elements similar 2 to those of example 1 were prepared with varied transport 3 layer resins in differing amounts.
4 Binder Resins Example M-60 (_ms) ~ A-ll (gms) 6 2a 13.5 0 7 2b 0 13.5 0 8~ 2c 9.0 2.25 2.25 9' 2d 10.12 2.25 1.13 10 2e 9-90 3.60 :
11 2f 7.65 2.25 3.60 12 :Testing in the manner set forth in Example 1 13 yielded the following resuLts.
14 : Discharge Exposure ~ Response Energy Time Dark . Discharge (microjoules/
16 (milliseconds) Volta~e Voltaye centimeter2) 17 2a 454 -870 -150 1.38 18 2b 454 -870 -190 1.34 19 . 2c 45~ -870 -150 1.10 2d 454 -870 -150 1.15 21 2e 454 -870 -150 1.10 22 2f 454 -870 -150 1.03 23 Example 3 24 A multilayered electrophotographic element similar to that of Example 1 was prepared with the exception that a transport layer solution containing 14.5 grarn~ of acr~llc 27 r~sin ~A-ll) as the ~ole binder and 14.5 grams o~ ~-dieth~l-28 aminoben~aldehyde~(diphenylhydrazone) was employed. When .
.

1 tested as set forth in Example 1, 3.0 microjoules per square 2 centimeter of light energy were required to discharge the 3 element from a dark voltage of -870 volts to -150 volts at a 4 discharge response time of 454 milliseconds.
Example 4 6 A multilayered electrophotographic element similar 7 to that of Example 1 was prepared with the exception that 8 the acrylic resin employed was B-50, a proprietary resin g available from Rohm and Haas, in place of the A-ll acrylic resin. When tested as set forth in Example 1, 1.16 micro-11 joules per square centimeter of light energy were required 12 to discharge the element from a dark voltage of -870 volts 13 to -150 at a discharge response time of 454 milliseconds.
14 Example 5a-e Multilayered electrophotographic elements similar 16 to that of Example 2e were prepared with the exception that 17 ~ the following polyester resins were substituted in the same 18 amount for the PE200 polyester resin.
19 Example Polyester 5a PE222 (Goodyear) 21 ~ 5b 49000 (duPont) 22 ~ Sc PE207 (Goodyear) 23 Sd VPE5545 (Goodyear) 24 5e PE307 (Goodyear) 25~ Results substantially similar to those of Example 2e were 26 obtained in each instance.
27 Example 6a-k 28 ~ Mu]tilayered electrophotographic elements similar :

1 to that of Example 1 were prepared wi~h the exceptj.on that 2 the initial adhesive coatings were prepared with the fol-3 lowing resins in place of the polyester (PE200) in similar 4 amounts. Each element was charged to -870 volts and dis~
charged to -150 volts in 146 milliseconds. The indicated 6 light energy in microjoules per square centimeter was required, 7 Example Trademark Resin Exposure Eneryy 8 6a PE 222 polyester 1.14 9 6b PE 207 polyester 1.28 6c 49000 polyester 1.28 11 6d A-ll acrylic 1.34 12 6e B-66 acrylic 1.51 13 6f M-60 polycarbonate 1.48 14 6g polysulfone 1.36 6h 15/95S orm~ar F~r~af 1.28 16 6i B-72A ~utv~r~ B~t~r 1.22 ~
17 ~j B-76- formv~r For~ar 1.26 18 ~ 6k polyvinyl carbazo].e 1.23 19 ~a9c~9 ~ Vb Multilayer electrophotographic elements similar to ~1 that of example 2e were prepared with the exception that 22 ~5.78 grams of p-dieth-ylaminobenzaldehyde-(diphenylhydrazone) 23 were substituted in the transport layer sslution in Éxample 24 7a, and 7.27 grams were s.imilarly substituted in Example 7b.
When tested under the same discharge voltages and discharge 26 response time as in Example 1, it was found that the element 27 ~ Of ExampIe 7a requixed 1.4 microjoules per square centimeter 28 of light energy and that oE Example 7b required 1.3 micro-29 ~oules per square centimeter oE light energy.
* t~ade~k .
,, .

, .

l Example 8 -2 A multilayered electrophotographic element similar 3 to that of Example 2a was prepared with the exception that 4 13.5 grams of p-diethylaminobenzaldehyde-(diphenylhydrazone) was employed in the charge transport layer solution. When 6 tested as set forth in Example 1, 1.37 microjoules per 7 square centimeter of light energy were required to discharge 8 the element from a dark voltage of -870 volts to ~150 vol-ts 9 at a discharge response time of 146 milliseconds.
Example 9 ll A multilayered electrophotographic element similar 12 to that of Example 2a was prepared with the exception -that 13 20.25 grams of p-diethylaminobenzaldehyde-(diphenylhydrazone) 14 was employed in the charge transport layer solution. When lS tested as set orth in Example 1, 1.37 microjoules per 16 square centimeter of Iight energy were required to discharge 17 the element from a dark voltage of -870 volts to -150 volts 18 at a discharge ~esponse time of 146 milliseconds.
l9 Example lO a-d -20 ~ Multilayered electrophotographic elements wPre 21 prepared sirnilar to that of Example 2a with the excep~ion 22 that the following alternative hydrazone compounds were 23 employed in the same quantity in the charge transport solu-24 tion.
E mple 26 lOa o-methyl-~-dimethylaminobenzaldehyde-(diphenylhydrazone) 27 lOb o-ethoxy-~-diethylaminoberlzaldehyde-(diphenylhydrazone~
23 lOc o-methyl-~-diethylaminobenzaldehyde-(diphenylhydrazone) 29 lOd p-dirnethylamir~obenzaldehyde-(diphenylhydrazone) B097704g -22-.

1 The follo~ing results were obtained.
2 Discharge Exposure Response Energy 3 Time Dark Discharge (microjoules/
Example~ (milllseconds) Voltage Voltdge centimeter2) lOa 146 -800 -190 1~71 6 lOb 146 -800 -190 1.24 7 lOc 1~6 -800 -190 1O64 8 lOd 146 800 -190 1.65 g Example 11 a-c Multilayered electxophotographic elements were 11 prepared similar to that of Example 2a with the exception 12 that 13.5 grams of the following hydrazones were employed in 13 the transport layer solution.
14 Example lla o-methyl-p-dime-thylaminobenzaldehyde-(diphenylhydra20ne) 16 llb _-ethoxy-p-diethylaminobenzaldehyde-(diphenylhydrazone) 17 llc _-methyl-p-diethylaminobenzaldehyde-(diphenylhydrazone) 18 The following results were obtained.
19 Discharge Exposure ~esponse Energy Time Dark Discharge (microjoules/
Example ~(milliseconds) Voltage Vol-tage centimeter2) 22 lla 146 -870 -150 1.56 23 llb 146 -870 -150 1.21 24 llc 146 -870 -150 1.60 ~xample 12 a-c 26 ~ Multilayered electrophotoyraphic elements were 27 prepared similar to that of Example 1 with the exception 28 that the ~ransport layer ~olution contained 6 . 75 grams of ` B0977049 -23-`

l polyester resin (PE200), 6.75 grams of polycarbona-te resin 2 (M60) and 13.5 grams of the ~ollowing hydrazone compounds;
3 Example 4 12a p-dimethylaminoben~aldehyde-(diphenylhydrazone) 12b p-dipropylaminobenzaldehyde-(diphenylh~drazone) 6 12c p-dibutylaminoben~aldehyde-tdiphenylhydrazone) 7 The following results were obtained.
8 Discharge Exposure Response Energy 9 Time Dark Discharge (microjoul~s/ - -Example (milliseconds) Voltage Voltage centimeter ) 11 12a 146 -800 -190 1.81 12 12b 146 -800 -l90 .92 13 12c 146 -800 -190 1.51 14 Example 13 In a manner generally similar to that of Example 16 l, hydroxy squarylium in the amount of 1 gram in a solvent 17 mixture of l milliliter of ethylenediamine, 5 milliliters 18 propylamine, and 24 milliliters of tetrahydrofuran was 19 meniscus coated on an aluminized polyester substrate (~Iylar) ~to form a charge ge~eration layer and dried. A novel trans-21 port layer in accord with the instant invention was for~ed 22 by~meniscus coating a solution of polycarbonate resin (M60) 23 in the amount of 8.12 grams and 8.12 grams of _-diethylamino-24 benzaldehyde-(diphenylhydrazone) in a 9:1 mixture of tetra-hydrofuran and toluene on the coated support and drying to , 26 form a multilayered electrophotographic element. When 27 ~tested as set forth in Example 1, 1.40 microjoules per ~28 square centimeter o~ light eneryy were required to discharge .

~Bo977049 - 24 -.

1 the element from a dark volt~ge of -870 volts to -150 volts 2 at a discharge response time of 146 millisecon~s.
3 Example 14 4 A multilayered electrophotographic element similar to that of Example 13 was prepared with the exception that 6 o-ethoxy-p-diethylaminobenzaldehyde-(diphenylhydrazone) was 7 employed in the transport layer solution. When tested as 8 set forth in Example 1, 1.02 rnicrojoules per square centi-g meter of light energy were required to discharge the element from a dark voltage of -870 volts to -150 volts at a dis-11 charge response time of 146 milliseconds, 12 Example 15 13 A multilayered electrophotographic element similar 14 to that of Example 13 was prepared with the exception that the charge generation layer solution contained 0.85 grams of 16 hydroxy squarylium and 0.15 grams of methyl squarylium.
17 When tested as set forth in Example 1, 0.86 microjoules per 18 square centimeter of light energy were required to discharge 19 the element from a dark voltage of -870 volts to -150 volts at a discharge responae time o~ 146 milliseconds.
21 Example 16 22 ~ A multllayered electrophotographic element similar 23 to that of Example 13 was prepared with the exception that ~4 the charge generation solution contained 0.85 grams of hydroxy squarylium and 0.15 ~rams of methyl .squarylium, and 26 the charge transport layer solution contained 8.12 grams of 27 polycarbonate resin (M60) and 5.42 grams of ~-diethy:Lamino-28 benzaldehyde-(diphenylhydrazone). When tested a5 set forth B0977049 ~5~

-1 in Example 1, 1.10 microjoules per square c~ntimeter of 2 light energy were required to discharge the element from a 3 dark voltage of ~870 volts to -150 volts at a discharge 4 response time of 146 milliseconds.
Example 17 6 A multilayered electrophotographlc element was 7 prepared by coating onto a charge yeneration layer (formed 8 of vacuum deposited selenium and tellurium) a charge trans-9 port layer from a solution of 6.75 grams of polyester resin (PE200), 6.75 grams of polycarbonate resin (M 60) and 13.5 11 grams of ~-diethylaminobenzaldehyde-(diphenylhydrazone).
12 When tested as set forth in Example 1, 2.0 microjoules per 13 square centimeter of light energy were required to discharge 14 the element from a dark voltage of ~800 volts to -300 volts at a discharge response time of 454 mill.iseconds.
16 From the above examples, it is apparent that the 17 p-type charge transport system of the instant invention is .

18 operable with varying types of resin binders as well as a 19 substantial number of hydrazone compounds of the designated type. ~Both organic and inorganic charge generation layers 21 are suitable for use with the charge generation layer of the , . .
22 instant invention, and various combinations of solvents, 23 polymeric binders etc. may he employed as is known in the 24 art. When used in relatively high concentrations, certain of the hydrazones display a tenclency to crystallize, thereby 26 degrading the charge transpor~ function. llow~ver, when 27 lesser amounts are usedl operable results are obka:irlahle.

28 Such adjustment will be readily accomplished by those skillecl 29 in the art.

1 The electropho-tographic elements utilizing the 2 charge transport layer in accord with the ins-tant invention 3 display an excellent balance between sensitivity, particu-4 larly at low temperatures, adhesion to adjacent layers and resistance to physical wear again at varying temperatures.
6 The elements have been found to age well and display remark-7 able resistance to toner filming.
8 Although in view of the wide usage to which -the 9 present invention can be put, only limited embodiments of the in~ention have been described for purposes of illustra-11 tion, it is, however, anticipated that various changes and 12 modifications will be apparent to those skilled in the art, 13 and that such changes and modif.ications may be made wi-thout 14 departing from the scope of the invention as defined by the following claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A electrophotographic element comprising;

an electrically conductive layer;

a charge generation layer responsive to actinic radiation to generate an electron-hole pair; and a p-type charge transport layer adjacent the charge generation layer, the charge transport layer com-prising a hydrazone of the composition;

n = 0,1 R1 = -O(CH2)yCH3 y = 0,1 x = 0,1,2,3 R3 = -H
R4 = -H

R2 = -OCH2CH3 R5 = -H

-CH2CH3 R6 = -H

-CH2 R7 =
-CH3 R6 & R7 =

and a polymeric binder;
whereby holes generated by photoelectric phe-nomenon in the charge generation layer may be transported through the charge transport layer to facilitate localized selective discharge of charged surfaces of the element.

2. An electrophotographic element as set forth in Claim 1 in which the p-type charge transport layer comprises a hydrazone selected from the group consisting of p-diethyl-aminobenzaldehyde-(diphenylhydrazone), o-ethoxy-p-diethyl-aminobenzaldehyde-(diphenylhydrazone), o-methyl-p-diethyl-aminobenzaldehyde-(diphenylhydrazone), o-methyl-p-dimethyl-aminobenzaldehyde-(diphenylhydrazone), p-dipropylamino-benzaldehyde-(diphenylhydrazone), p-diethylaminobenzalde-hyde-(benzylphenylhydrazone), p-dibutylaminobenzaldehyde-(diphenylhydrazone), and p-dimethylaminobenzaldehyde-(di-phenylhydrazone).

3. An electrophotographic element as set forth in Claim 1 in which the p-type charge transport layer includes p-diethylaminobenzaldehyde-(diphenylhydrazone).

4. An electrophotographic element as set forth in Claim 1 in which the charge generation layer is positioned between the electrically conductive layer and the p-type charge transport layer, with the p-type charge transport layer forming an exposed surface of the electrophotographic element.

5. An electrophotographic element as set forth in Claim 4 in which the charge generation layer is responsive to actinic radiation of a wave length greater than 3,900 angstroms to generate an electron-hole pair.

6. An electrophotographic element as set forth in Claim 1 in which the charge generation layer is of a thick-ness between 0.05 microns to 0.2 microns, and the p-type charge transport layer is at least 5 microns thick.

7. An electrophotographic element as set forth in Claim 6 in which the p-type charge transport layer is be-tween 7 and 35 microns thick.

8. An electrophotographic element as set forth in Claim l in which the charge generaton layer comprises a photoconductor selected from the group consisting of se-lenium and its alloys, tellurium and its alloys, compounds of an element from Group IIb and an element from Group VIa of the Periodic Table, cyanine compounds, disazo compounds, phthalocyanine compounds, and methine dyes derived from squaric acid.

9. An electrophotographic element as set forth in Claim 8 in which the photoconductive material selected from the group consisting of Chlorodiane Blue, methyl squarylium and hydroxy squarylium.

10. An electrophotographic element as set forth in Claim 1 in which the polymeric binder is selected from the group consisting of polycarbonate resins, polyester resins, acrylic resins, and mixtures thereof.

11. An electrophotographic process comprising the steps of;
electrostatically charging in the dark the surface of an electrophotographic plate comprising; a conductive substrate, a charge generation layer responsive to actinic radiation to generate an electron-hole pair, and a p-type eharge transport layer adjacent the charge generation layer, the charge transport layer comprising a hydrazone of the composition;

n - 0,1 R1 = -O(CH2)y CH3 y=0,1 x=0,1,2,3, R3 = -H

R4 = -H

R2 = -OCH2CH3 R5 = -H

R6 = R7 = R6 & R7 = and a polymeric binder;
exposing the electrophotographic element to an image-wise pattern of actinic radiation;
generating an electron-hole pair in the charge generation layer at the portion struck by the actinic radia-tion;
injecting the hole generated in the charge genera-tion layer into the charge transport layer; and discharging the surface of the electrophotographic element in an image-wise fashion corresponding to the pattern of the actinic radiation to produce a latent elec-trostatic image thereon.

12. An electrophotographic process as set forth in Claim 11 in which the charge generation layer is positioned between the conductive substrate and the charge transport layer and in electrical contact with each, the charge transport layer has an exposed surface layer which is initially negatively charged, the actinic radiation passes through the charge transport layer to strike the charge generation layer, and the resulting holes are injected into and transported through the charge transport layer to discharge negative charges on the surface of the charge transport layer thus producing the latent electrostatic image.

13. An electrophotographic process as set forth in Claim 11 in which the charge transport layer is inter-posed between the charge generation layer and tile conductive substrate, the charge generation layer is positively charged, and holes generated as a result of actinic radiation strik-ing the charge generation layer are injected into and trans-ported through the charge transport layer to the conductive substrate while electrons discharge the surface of the charge generation layer to produce the electrostatic image.

14. An electrophotographic process as set forth in Claims 11, 12 or 13 in which the p-type charge transport layer com-prises a hydrazone selected from the group consisting of p-diethylaminobenzaldehyde-(diphenylhydrazone), o-ethoxy-p-diethylaminobenzaldehyde-(cliphenylhydrazone), o-methyl-p-diethylaminobenzaldehyde-(diphenylhydrazone), o-me-thyl-p-dimethylaminobenzaldehyde-(diphenylhydrazone), p-dipropyl-aminobenzaldehyde-(diphenylhydrazone), p-diethylaminobenz-aldehyde-(benzylphenylhydrazone), p-dibutylaminobenzalde-hyde-(diphenylhydrazone), and p-dimethylaminobenzaldehyde-(diphenylhydrazone).

15. An electrophotographic process as set forth in Claims 11, 12 or 13 in which p-type charge transport layer includes p-diethylaminobenzaldehyde-(diphenylhydrazone).

16. An electrophotographic element as set forth in Claim 11 in which the charge generation layer includes a photoconductor selected from the group consisting of selenium and its alloys, tellurium and its alloys, compounds of an element from Group IIb and an element from Group VIa of the Periodic Table, cyanine compounds, disazo compounds, phtha-locyanine compounds, and methine dyes derived from squaric acid.

17 . An electrophotograhic process as set forth in claim 16 in which the photoconductive material is selected from the group consisting of Chlorodiane Blue, methyl squarylic and hydroxy squarylium.