INFRARED SENSITIVE PHOTOCONDUCTOR COMPOSITION

COMPOSE PHOTOCONDUCTEUR SENSIBLE A L'INFRAROUGE

English Abstract

ABSTRACT OF THE DISCLOSURE
Electrophotographic plates and process of use thereof
are provided wherein the plates contain a
photoconductive layer in contact with at least one layer
containing a squaric acid methine dye. The plates are
sensitive to infrared light.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrophotographic plate comprising a conduc-
tive substrate, and a photoconductive layer in contact
with at least one layer containing a squaric acid
methine dye.
2. A plate according to Claim 1 wherein said plate is
sensitive to infrared light.
3. A plate according to Claim l wherein said plate is
negatively or positively charged.
4. A plate according to Claim 1 wherein said squaric
acid methine dye is selected from the group consisting
of
<IMG>
wherein A and B are independently,
wherein X1 = NR1R2, OH; wherein
R1,R2 are alkyl of 1-6 carbons,
<IMG>
and X2,X3 = H, OH, alkyl of
1-6 carbons,
<IMG>

<IMG> wherein R3,R4 - alkyl of 1-6 carbons,
H, and R5 is independently H,
OCH3 or halogen;
<IMG> wherein R9,R6,R7,R8 = H, OH,
wherein 10, R11 and
R12 are independ-
<IMG> ently alkyl of 1 to 6
carbon atoms and R13
is independently H,
or OR14, or halogen,
wherein R14 is alkyl
of 1 to 6 carbon
atoms.
5. An electrophotographic imaging process comprising
subjecting a photoconductive layer in contact with at
least one layer comprising squaric acid methine dye, to
an applied electric field and exposing at least one of

said dye layers to an image pattern of radiation to
which said dye layer is photosensitive, characterized in
that at least a portion of said dye layer contains a
material of the structure
<IMG>
wherein A and B are independently,
wherein X1 = NR1R2, OH; wherein
R1,R2 are alkyl of 1-6 carbons,
<IMG> and X2,X3 = H, OH, alkyl 1-6 carbons,
<IMG>
wherein R3,R4 = alkyl of 1-6 carbons,
H and R5 is independently H, OCH3 or
halogen;
<IMG>
wherein R9,R6,R7,R8 = H, OH
11

wherein R10, R11
and R12 are
independently
alkyl of 1 to 6
carbon atoms and
R13 is indepen-
dently H or
<IMG> OR14, or halogen
wherein R14 is
alkyl of 1 to
6 carbon atoms.
6. A plate according to Claim 4 wherein said photo
conductive layer comprises selenium or selenium alloy.
7. A method according to Claim 5 wherein said photo
conductive layer comprises selenium or selenium alloy.
8. A plate according to Claim 4 wherein A and B are
phenyl, X1 is dialkylamino, X2 is alkyl and X3 is
hydrogen.
9. A plate according to Claim 8 wherein X1 is
dimethylamino and X2 is methyl.
12

10. A process according to Claim 5 wherein A and B are
phenyl, X1 is dialkylamino, X2 is alkyl and X3 is hydrogen.
11. A process according to Claim 10 wherein X1 is dimethyl
amino and X2 is methyl.
13

Description

i2~ 7
61051-1745
The present invention is directed to infrared photo-
sensitive photoconductor materials and the mekhods of using æame.
In partlcular, the present invention is directed to electrophoto-
graphic plates having a photoconductive layer, preferably
comprising salenium, adjacent to one or two layers comprising a
squaric acid methine dye.
United States Patent No. 3,617,270 discloses the u~e of
squaric acid methine dyes for the optical sensitization of zinc
oxide. United States Patent Nos. 3,824,099, 3,837,851, 4,123,270
and 4,150,987 disclose the use of squaric acid methine dyes for a
conventional charge generation layer with a p-type charge
transport layer in a layered electrophotographic plate. Squaric
acid methine dyes have been disclosed as useful in electrophoretic
migration imaging process in United States Patent No. 4,175,956.
It is an object of the present invention to provide
novel and improved electrophotographic plates for use in an
electrophotographic imaging process.
It is another object of the invention to provide
improved electrophotographic plates sensitive in the infrared
region of the spectrum.
~! *rt

The accompanying FIGURE 1 shows the time-voltage
response of positively and negatively charged plates
according to the embodiment of the present invention
shown in FIGURE 2 under conditions of charging, dark
decay and discharging.
FIGURES 2, 3 and 4 illustrate various embodiments of
layers containing photoconductor materials according to
the present invention.
The electrophotographic plates of the present invention
comprise, in addition to a conductive substrate, a
photoconductive layer disposed between two layers
containing the squaric acid methine dye. Electrophoto-
graphic plates having the above structure display
improved sensitivity to infrared light when charged
either positively or negatively.
To obtain the infrared sensitivity of the present
invention a conventional photoconductive layer, such as
selenium or selenium alloy, is disposed adjacent to one
or two squaric acid methine dye-containing layers.
In the electrophotographic plates, according to the
present invention both upper and lower layers containing
squaric acid methine dye may vary in thickness generally
between 0.01 to about 30 microns thick, preferably being
from about 0.1 to about 10 microns thick. The
photoconductive layer located between the squaric acid
methine layers is preferably selenium having a thickness
of about 20-70 microns, preferably from about 50-60
microns. The photoconductive layer may also comprise
selenium alloys. The substrate may be a conventional
conductive substrate, such as aluminum, aluminum coated

~ Z S~ ~i7
polyester resin and the like, and may be opaque ox
transparent.
In forming a preferred electrophotographic plate accord-
ing to FIGURE 2, the lower (first) squaric acid methine
layer 10 may be applied to the substrate 11 in any
convenient manner such as by coating from a slurry.
Preferably the dye composition may be mechanically
brushed onto the substrate. The first squaric acid
methine dye layer may then be over-coated with the
selenium or selenium alloy layer 12 in a conventional
manner, with the second (upper) squaric acid dye layer
13 being applied in a manner similar to that used for
the first layer.
Referring to FIGURE 3, a plate may be found having a
single squaric acid methine dye-containing layer 10 upon
a selenium or selenium alloy layer 12. The substrate 11
may be a conventional material as described aboveO
Referring to FIGURE 4, the single squaric acid methine
dye-containing layer 10 may be located between the
selenium alloy layer 12 and substrate 11.
The dyes may be applied through evaporation, in binders,
as a coating in a micronized slurry, in solution or a
combination of all of the above methods. The squaric
acid methine dye may be used alone or in conjunction
with a binder wh,en the layer is formed by coating from a
slurry. The optimum ratio of dye to binder may gener-
ally be from about 2:1 to 1:10. Binderless layers may
be formed by vacuum evaporation. Many types of binder
material known in the axt, such as polyester resins, may
be utilized as binder materials.

~Z6~i7
61051~1745
The solvent, to prepare the squaric acid methine dye
layer is selected on the basis of polymer-binder solubility and
volatility. Solvents which may be utilized to prepare the dye
layer include ethers, cyclic ethers, halogenated hydrocarbons,
ketones, aliphatic solvents and aromatic solvents. A preferred
class of solvents comprises tetrahydrofuran, chloroform, methylene
chloride, carbon te~rachloride, acetone, benzene and toluene.
Tetrahydrofuran and methylene chloride are particularly preferred
solvents because of excellent dispersive characteristics and high
volatility.
The photosensitive layer of squaric acid methine dye
according to the present invention can be prepared as a suspension
of squaric acid methine dye in a solution of an appropriate
binder. The binder may be selected from a variety of polymers,
for example, Epoxy-~pon~ 1007 F (a 4,4'-isopropylidene diphenol-
epichlorohydrin resin manufactured by Shell Chemical Co.),
Acryloid*-B66 (a me~hyl/butyl methacrylate copolymer ~anufactured
by Rohm and Haas Co~), Vylon*-200 (a polyester resin manufactured
by Toyob Co., Japan), Panlite* L-1250 and K1300 (a polycarbonate
resin manufactured by Teijin Co., Japan), polyurethane, poly-
styrene and Luvican* (a polyvinylcarbazole manufactured by BASF).
The dye to b~nder ratio in the photosensitive layer may
be in the range from about 1:1 to 1:40. Preferably, the dye to
binder ratio should be in the range of from about 1:2 to 1:10,
most preferably at 1:6. Concentration of the dye-binder
*Trade Mark

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61051~17~5
suspension may be adjusted to viscosities whlch insure suitable
coating characteristics. For example, generally in dye-binder
ratios varying from 1:3 to 1:10, the solvent concentrations used
to prepare the
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~lurries vary from approximately 90~ to 78~, respec-
t~vely.
- The squaric.acid ~ethine dye u~eful in accordance with
the present invention ~ay be those of the following
~ormula:
B
~ II)
wherein A and B are independently,
X2 wherein Xl = NRlR2, OH;
\ Rl,R2 alkyl o~ 1 6 carbons,
~xl~
X3 and X2,X3 ~ ~, O~, alkyl of 1-6 carbons,
~ / ~3
`!' ~wheréin R3,R4 = alkyl of 1-6 caxbons,
~R R5 iz independently H, OCH3 or halogen
R8 ~ R7 wherein Rg~6'~7'~8

1~52~
10' 11
R12 are independ-
ently alkyl of 1 to
10 / / Rl 6 carbon atoms and R13
- CH-~ ~ ~ is independently H, OR14 ,
N ~ ~ or halogen, wherein R14
I is alkyl of 1 to 6 carbon
R12 atoms
A particularly preferred class of squaric acid methine
dyes comprises those of the above formula wherein A and
B are phenyl, wherein Xl is dialkylamino, particularly
dimethylamino, X2 is alkyl, preferably methyl, and X3 is
hydrogen.
General methods for the preparation of squaric acid
methine dyes are known and are disclosed in, for exam-
ple, Treibs et al., Angew. Chem. Internat. Ed. 4, 695
(1965); Sprenger et al., Angew. Chem. Internat. Ed. 5,
894 (1966); and Treibs et al., Leibiq's ~nn Chem., 712,
123 tl968). Generally, squaric acid is reacted with the
desired carbocy'clic or heterocyclic compound in a
suitable solvent with heating. The product is isolated
by cooling the reaction mixture to obtain crystals or by
adding thereto a non-solvent for the dye.
The following examples are given for the purpose of
illustration and are not deemed to be a limitation on
the invention.

EXAMPLE 1
2,4 bis-~2-methyl-4-dimethylaminophenyl)-1,3-cyclobutad-
iene diylium~1,3 dio]ate was deposited onto a .005 inch
thick aluminum foil and then overcoated with a layer of
60 micron thick selenium. On the upper surface of the
selenium another layer of dye was deposited.
Two electrophotographic plates were charged by corona.
One was charged with 100 micro amps-negative, and
another with 15 micro amps-positive. Each plate was
- 10 charged for a period of about 13 seconds, placed in the
dark for about 10 seconds then discharged by exposure to
light filtered through an 800 nm filter. The results
are shown in FIG. 1.
EXAMPLE 2
Referring to Fig. 3, a 50 ~m Selenium layer 12 was
evaporated onto aluminum substrate 11 and then
overcoated with a suspension of reprecipitated
2,4-bis-(2-methyl-4-dimethylaminophenyl) 1,3
cyclobutadiene diylium - 1,3- diolate in polyvinyl
butyral tratio by wt. 1:3) 10 at a wet gap of 50 ~m to
give a total film thickness of 51 ~m.
The following sensitometric results are obtained:
,
Charge acceptance: 1387 volts
Charge retained (after 0.5 sec): 98%
Sensitivity (800 nm~ : 0.78 ~J/cm
* Energy required to discharge from 800 volts to
400 volts.
. : .

12~ t
EXAMPLE 3
Referring to Fig. 4, a 300 to 400 A layer 10 of
2,4-bis-(2-methyl-4-dimethylaminophenyl)-1,3-cyclobuta-
diene diylium-1,3-diolate was vacuum deposlted onto
aluminum su~strate 11. Evaporated on this layer was 50
~m selenium 12.
The following sensitometric results are obtained:
Charge acceptance: 1183 volts
Charge retained (after 0.5 sec): 99%
Sensitivity (800,nm) : 4.54 ~Jtcm2
* Energy required to discharge from 400 volts to
100 volts.