U.S. patent number 3,784,376 [Application Number 05/223,770] was granted by the patent office on 1974-01-08 for photoconductive element containing furans, indoles, or thiophenes.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Charles J. Fox.
United States Patent |
3,784,376 |
Fox |
January 8, 1974 |
PHOTOCONDUCTIVE ELEMENT CONTAINING FURANS, INDOLES, OR
THIOPHENES
Abstract
Organic photoconductive elements of improved electrophotographic
speed are prepared by coating on an electrically conducting support
a photoconductive layer containing a 1,3-diarylisobenzofuran or
1,3-diaryl-4,7-dihydroisobenzofuran or the corresponding isoindole
or isobenzothiophene derivatives.
Inventors: |
Fox; Charles J. (Rochester,
NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
22837908 |
Appl.
No.: |
05/223,770 |
Filed: |
February 4, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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73257 |
Sep 16, 1970 |
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Current U.S.
Class: |
430/78;
430/75 |
Current CPC
Class: |
G03G
5/0674 (20130101); G03G 5/067 (20130101); G03G
5/0629 (20130101) |
Current International
Class: |
G03G
5/06 (20060101); G03g 005/00 () |
Field of
Search: |
;96/1.5 ;252/501 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
CA., Vol. 57, p. 1743 I..
|
Primary Examiner: Torchin; Norman G.
Assistant Examiner: Goodrow; John L.
Attorney, Agent or Firm: Robert W. Hampton et al.
Claims
I claim:
1. A photoconductive element comprising an electrically conducting
support and having thereon a layer comprising a polymeric binder
with an organic photoconductive compound of the formula
##SPC4##
where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrogen, alkyl,
aryl, -COOR, -CON(R).sub.2, CN, halogen, -OR, -R'-COOR, or
-R'-CON(R).sub.2 wherein R is hydrogen or alkyl and R' is an
alkylene radical; Ar and Ar.sub.1 are aryl groups; X is O, S, or
NR; and n and m are integers from 0 to 4.
2. An element according to claim 1 in which R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 are hydrogen or lower alkyl.
3. An element according to claim 2 in which a sensitizing dye is
incorporated with the organic photoconductor compound.
4. An element according to claim 3 in which the organic
photoconductor compound is 1,3-diphenylisobenzofuran.
5. An element according to claim 3 in which the organic
photoconductor compound is
1,3-diphenyl-5,6-dimethylisobenzofuran.
6. An element according to claim 3 in which the organic
photoconductor compound is
1,3-diphenyl-4,7-dihydroisobenzofuran.
7. An element according to claim 1 comprising a photoconductive
layer coated on an electrically conducting support, said layer
comprising (a) a photoconductive compound selected from the group
consisting of 1,3-diphenylisobenzo-furan,
1,3-diphenyl-5,6-dimethylisobenzofuran and
1,3-diphenyl-4,7-dihydroisobenzofuran, (b) a sensitizing dye and
(c) a polymeric binder.
8. An element according to claim 7 in which the polymeric binder is
a major component of the photoconductive layer and is a
terephthalic polyester.
9. An element according to claim 7 in which the polymeric binder is
a major component of the photoconductive layer and is a bisphenol-A
polycarbonate.
10. An element according to claim 3 in which the organic
photoconductor compound is 1,2,3-triphenylisoindole.
Description
This invention relates to electrophotography and more particularly
to novel organic photoconductive materials.
Electrophotographic processes employ an electrophotographic or
photoconductive element comprising a coating of a photoconductive
insulating material on a conductive support. The element is given a
uniform surface charge in the dark and then is exposed to an image
pattern of activating electromagnetic radiation such as light or
X-rays. The charge on the photoconductive element is dissipated in
the illuminated area to form an electrostatic charge pattern which
is then developed by contact with an electroscopic marking
material. The marking material or toner, as it is also called,
whether carried in an insulating liquid or in the form of a dry
powder, deposits on the exposed surface in accordance with either
the charge pattern or the discharge pattern, as desired. Then, if
the photoconductive element is of the non-reusable type, the
developed image is fixed by fusion or otherwise to the surface of
the photoconductive element. If the element is of the reusable
type, e.g., a selenium-coated drum, the image is transferred to
another surface such as paper and then fixed to provide a copy of
the original.
All of this is well known and has been described in many patents
and other literature, for example, in the patent of Carlson, U. S.
Pat. No. 2,297,691, and in more recent works such as
"Electrophotography" by R. M. Scaffert, published by Focal Press
Ltd., 1965.
It is also known that many organic materials can be used as
photoconductors. The organic photoconductors have a number of
advantages over the inorganic photoconductors such as zinc oxide,
which are presently more widely used. For instance, the organics
are more resistant to abrasion than the inorganics. They can be
charged to either high negative or positive potential while the
inorganics often saturate at low potential and are less versatile
in that characteristically they accept only a positive or a
negative charge. Also the organics usually offer greater exposure
latitude, can be spectrally sensitized more effectively and have
other advantages over zinc oxide and other inorganics.
These useful properties which organic photoconductors possess in
greater or lesser degree have lead to a widespread interest in
them. However, they also have certain disadvantages which render
them less desirable than zinc oxide for some uses. For example,
many organic photoconductors have low xerographic speed or
sensitivity and those that have adequate speed often have poor
light stability and form colored materials by photodegradation.
Among the many organic photoconductors that have been proposed are
various 2,5-diarylfurans and 2,3-benzofurans, as disclosed, for
example, in German Pat. No. 1,105,714 and Belgian Pat. No. 585,450.
Although these furan derivaties have a number of advantages as
organic photoconductors a problem has been that their sensitivity
or electrophotographic speed has not been as high as desired.
In accordance with the present invention I have discovered that
certain isobenzofurans and related compounds have unexpectedly
higher electrophotographic speed than the furan derivaties which
are reported in the prior art as photoconductors and also have
better light stability than high speed organic photoconductors.
Based on this discovery, the photoconductive elements of the
present invention, in general, comprise (a) an electrically
conductive support and (b) a 1,3-diarylisobenzofuran or
1,3-diaryl-4,7-dihydroisobenzofuran or the corresponding
isobenzothiophene and isoindole compounds. These compounds are
characterized by the presence of a fused 6-membered unsaturated
ring in the 4,5-position of the furan, thiophene or pyrrole ring
and aryl substituents in the 1 and 3 positions. The aryl groups can
be separated from the heterocyclic nucleus by conjugated linear
carbon chains of 2,4,6 or 8 carbon atoms, i.e., --CH=CH--.sub.n,
where n = 0 to 4. Therefore, in referring broadly to the 1,3-diaryl
substituted compounds herein, it is intended to include vinylogs in
which one or both of the 1,3-aryl groups is separated from the
heterocyclic nucleus by one or more vinylene groups. The term aryl
is thus used with respect to the 1,3-substituents to include not
only phenyl, naphthyl and the like but also styryl,
naphthylvinylene and the like.
Such compounds can be represented by the formulae: ##SPC1##
wherein X is -O-, -S- or -NR; R is H or alkyl of 1 to 18 carbon
atoms, preferably lower alkyl; Ar and Ar.sub.1 are aryl groups;
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrogen atoms or
substituents, and n and m are integers from 0 to 4. As substituens,
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 can be essentially any
electropositive or electronegative radicals such as alkyl, aryl,
-COOR, -CONR.sub.2, -CN, halogen, -OR, -R' -COOR or -R'
-CONR.sub.2, wherein R is hydrogen or alkyl of 1 to 18 carbon atoms
and preferably is lower alkyl and R' is an alkylene radical of 1 to
18 carbon atoms, preferably lower alkyl (i.e., 1 to about 6 carbon
atoms). The aryl groups, Ar and Ar.sub.1 include, for example,
phenyl, naphthyl, etc, and such radicals having substituents on the
aromatic rings.
The photoconductive elements of the invention can employ any of the
described isobenzofuran and analogous compounds having the
indicated broad range of substituents. Advantageously, however,
compounds are employed in which R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 and the values of n and m are such that the compounds are
soluble in convenient solvents and are compatible with the most
effective binder resins. Best results in these respects are
obtained when n and m are 0 or 1 and R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 are hydrogen atoms or alkyl groups of 1 to 18 carbon atoms,
especially lower alkyl groups (i.e., 1 to about 6 carbon
atoms).
Examples of the compounds of particular interest include the
following: 1,3-diphenylisobenzofuran;
1,3-diphenyl-5,6-dimethylisobenzofuran;
1,3-diphenyl-4,7-dihydroisobenzofuran;
1-mesityl-3-phenylisobenzofuran; 1,3-dimesitylisobenzofuran;
1,3-diphenyl-4,7-diethylisobenzofuran;
1,3-diphenyl-5,6-dimethyl-isobenzothiophene;
1,3-diphenyl-4,7-dimethylisoindole;
1,3-bis(m-bromostyryl)isobenzothiophene;
1,3-bis(p-dimethylamino-styryl)isobenzofuran;
1-(2-naphthyl)-3-styryl-5,6-dimethylisobenzofuran;
1,3-di(m-tolyl)-4-dimethylamino-7-ethylisobenzothiophene;
1,3-bis-(4-phenyl-1,3-butadienyl-1)-2-methylisoindole;
1,3-bis-(2-naphthylvinylene-1)isobenzofuran;
1,3-diphenyl-5-methylisoindole; 1,3-diphenyl-2-methylisoindole;
1,3-diphenyl-5,6-dimethyl-4,7-dihydroisobenzothiophene and
1,3-diphenyl-2-methyl-4,7-dihydroisoindole.
Isobenzofurans and dihydroisobenzofurans of the types suitable in
the compositions of the invention and methods of preparing such
compounds are described, for example, by M. S. Newman, J. Org.
Chem., 26, 2630 (1960) and by Adams et al., J. Am. Chem. Soc., 62,
56 (1940). The isobenzothiophene and isoindole compounds, i.e.,
where X in the formulae above is -S- or -NH-, can be prepared, for
example, by the procedure of Mann et al., Chem. Commun. 1969,
420.
When employed as photoconductors in accordance with the present
invention these compounds are mixed in an amount of 1 to 75 parts
by weight with 25 to 99 parts by weight of a polymeric binder and
are coated from a suitable solvent on a conducting support to
provide the photoconductive layer of the electrophotographic
element.
Preferred binders for admixture with the photoconductive compounds
in preparing the photoconductive layers of the present invention
include polymers having fairly high dielectric strength which are
good electrically insulating film-forming vehicles. Materials of
this type include styrene-butadiene copolymers; silicone resins;
styrene-alkyd resins; silicone-alkyd resins; soya-alkyd resins;
poly(vinyl chloride); poly(vinylidene chloride); vinyl
chloride-vinylidene chloride copolymers; vinylidene
chloride-acrylonitrile copolymers; poly(vinyl acetate); vinyl
acetate-vinyl chloride copolymers; poly(vinyl acetals), such as
poly(vinyl butyral); polyacrylic and methacrylic esters, such as
poly(methyl methacrylate), poly(n-butyl methacrylate),
poly(isobutyl methacrylate), etc.; polystyrene; nitrated
polystyrene; polymethylstyrene; isobutylene polymers; polyesters,
such as
copoly[ethylene-co-alkylenebis(alkyleneoxyaryl)phenylene-dicarboxylate],
e.g.,
poly[ethylene-co-isopropylidene-2,2-bis-(ethyleneoxyphenyl)terephthalate];
phenolformaldehyde resins; ketone resins; polyamides;
polycarbonates; polythiocarbonates; copolymers of vinyl
haloarylates and vinyl acetate such as
poly(vinyl-m-bromobenzoate-co vinyl acetate); waxes, chlorinated
polyethylene, etc. Especially preferred are thermoplastic resins.
Suitable resins are sold under such trademarks as Vitel PE-101,
Cymac, Piccopale 100, Saran F-220, Lexan 145 and Geon 222. Also
mixtures of these binders can be used.
The photoconductive compositions formed by blending a polymeric
binder such as a polyester or polycarbonate with a monomeric
organic photoconductor of the type described are preferred
embodiments of the invention, because they provide a wide choice of
binders and ratios of binder to photoconductor. It is well known,
however, to use polymerizable photoconductors that require no
separate polymeric binder. It should be understood therefore that
it is within the scope of the present invention to use species of
the described photoconductors that contain the active nuclei
depicted above but that are polymerizable and require no separate
polymeric binder, although even in this event a polymer of the
polymeric binder type can also be blended with the polymeric
photoconductor if desired.
The polymeric photoconductors are prepared by polymerizing monomers
which contain the described photoconductive nuclei (i.e.,
1,3-diarylisobenzofuran or 1,3-diaryl-4,7-dihydroisobenzofuran or
corresponding isobenzothiophene or isoindole) and which are
polymerizable to form either addition or condensation polymers.
Addition polymers can be formed when the monomeric photoconductor
contains one or more vinylene groups as, for example, when n or m
or both in I or II above is a positive integer of 1 to 4. The
addition polymerization can be carried out by known catalytic
techniques for polymerization of vinyl monomers.
Condensation polymers can be formed when, for example, in formulae
I and II, two or more of the substituents R.sub.1 through R.sub.6
are radicals that condense with other radicals to form esters,
amides, urethanes, carbonates, etc. These include radicals such as
-OH, -COOH. -COOalkyl, -NH.sub.2 and the like. Conventional
catalytic procedures for forming such condensation polymers can be
used. For example, if R.sub.1 and R.sub.2 are carboxyl groups the
isobenzofuran compound can be reacted with a glycol such as
ethylene glycol in the presence of a catalyst such as an oxide of
tin or titanium to form a polyester. The preferred condensation
polymers are polycarbonates and polyurethanes and especially
preferred are those formed from monomers I or II when R.sub.1 and
R.sub.9 are the polymer-forming functional groups such as hydroxyl
groups, n and m are zero, and the monomer is reacted with phosgene
or a diisocyanate.
Solvents useful for preparing coating compositions with the
photoconductors of the present invention can include a wide variety
of organic solvents for the components of the coating composition.
For example, benzene; toluene; acetone; 2-butanone; chlorinated
hydrocarbons such as methylene chloride; ethylene chloride; and the
like; others, such as tetrahydrofuran and the like, or mixtures of
such solvents can advantageously be employed in the practice of
this invention.
Sensitizing compounds usful with the photoconductive elements of
the present invention can be selected from a wide variety of
materials, including such materials as pyrylium dye salts including
thiapyrylium dye salts and selenapyrylium dye salts disclosed in
VanAllen et al. U. S. Pat. No. 3,250,615; fluorenes, such as
7,12-dioxo-13-dibenzo(a,h)fluorene,
5,10-dioxo-4a,11-diazabenzo(b)fluorene,
3,13-dioxo-7-oxadibenzo-(b,g)fluorene, and the like; aggregate-type
sensitizers of the type described in Belgian Pat. No. 705,117 dated
Apr. 16, 1968; aromatic nitro compounds of the kind described in U.
S. Pat. No. 2,610,120; anthrones like those disclosed in U. S. Pat.
2,670,284; quinones, U. S. Pat. No. 2,670,286; benzophenones U. S.
Pat. No. 2,670,287; thiazoles U. S. Pat. No. 2,732,301; mineral
acids; carboxylic acids, such as maleic acid, di- and
tri-chloroacetic acids, and salicyclic acid; sulfonic and
phosphoric acids; and other electron acceptor compounds as
disclosed by H. Hoegl, J. Phys. Chem., 69, No. 3, 755-766 (March,
1965), and U. S. Pat. No. 3,232,755.
The amount of sensitizer that can be added to a photoconductor
layer to give effective increases in speed can vary widely. The
optimum concentration will vary with the specific photoconductor
and sensitizing compound used. In general, substantial speed gains
can be obtained where an appropriate sensitizer is added in a
concentration range from about 0.0001 to about 10 weight percent or
more based on the weight of the coating composition. Normally,
sensitizers are added to the coating composition in an amount of
about 0.005 to about 5.0 percent by weight of the total coating
composition.
Coating thicknesses of the photoconductive composition on a support
can vary widely. Normally, a coating in the range of about 1.mu. to
about 500.mu. after drying is useful for the practice of this
invention. The preferred range of coating thickness is found to be
in the range from about 5.mu. to about 200.mu. after drying
although useful results can be obtained outside of this range.
Suitable supporting materials for the photoconductive layers of the
present invention can include any of a wide variety of electrically
conducting supports, for example, various conducting papers;
aluminum coated paper; aluminum-paper laminates; metal foils such
as aluminum foil, zinc foil, etc.; metal plates, such as aluminum,
copper, zinc, brass, and galvanized plates; varpor deposited metal
layers such as silver, nickel or aluminum on conventional film
supports such as cellulose acetate, poly-(ethylene terephthalate),
polystyrene and the like conducting supports. An especially useful
conducting support can be prepared by coating a support material
such as poly(ethylene terephthalate with a layer containing a
semiconductor dispersed in a resin as described in U. S. Pat. No.
3,245,833 or vacuum deposited on the support. Likewise, a suitable
conducting coating can be prepared from the sodium salt of a
carboxyester lactone of a malaic anhydride-vinyl acetate copolymer.
Such kinds of conducting layers and methods for their optimum
preparation and use are disclosed in U. S. Pat. Nos. 3,007,901;
3,245,833 and 3,267,807.
The electrophotographic elements of the invention are used for
making xerographic images in the following manner: The
electrophotographic element is held in the dark and given a blanket
electrostatic charge by placing it under a corona discharge. This
uniform charge is retained by the photoconductive layer because the
substantial dark insulating property of the layer, i.e., the low
conductivity of the layer in the dark. The electrostatic charge
formed on the surface of the photoconductive layer is then
selectively dissipated from the surface of the layer by image-wise
exposure to light by means of a conventional exposure operation
such as, for example, by a contact-printing technique, or by lens
projection of an image, and the like, to thereby form a latent
electrostatic image in the photoconductive layer. Exposing the
surface in this manner forms a pattern of electrostatic charge by
virtue of the fact that light energy striking the photoconductor
causes the electrostatic charge in the light struck areas to be
conducted away from the surface in proportion to the intensity of
the illumination in a particular area.
The charge pattern produced by exposure is then developed or
transferred to another surface and developed there, i.e., either
the charged or uncharged areas rendered visible, by treatment with
a medium comprising electrostatically responsive particles having
optical density. The developing electrostatically responsive
particles can be in the form of a dust, i.e., powder, or a pigment
in a resinous carrier, i.e., toner. A preferred method of applying
such toner to a latent electrostaic image for solid area
development is by the use of a magnetic brush. Methods for forming
and using a magnetic brush toner applicator are described in the
following U. S. Pat. Nos: 2,786,439; 2,786,440; 2,786,441;
2,811,465; 2,874,063; 2,984,163; 3,040,704; 3,117,884; and Reissue
25,779. Liquid development of the latent electrostatic image may
also be used. In liquid development, the developing particles are
carried to the image-bearing surface in an electrically insulating
liquid carrier. Methods of development of this type are widely
known and have been described in the patent literature, for
example, U. S. Pat. No. 2,907,674 and in Australian Pat. No.
212,315. In dry developing processes, the most widely used method
of obtaining a permanent record is achieved by selecting a
developing particle which has as one of its components a
low-melting resin. Heating the powder image then causes the resin
to melt or fuse into or on the element. The powder is, therefore,
caused to adhere permanently to the surface of the photoconductive
layer. In other cases, a transfer of the electrostatic charge image
formed on the photoconductive layer can be made to a second support
such as paper which would then become the final print after
development and fusing. Techniques of the type indicated are well
known in the art and have been described in a number of U. S. and
foreign patents, such as U. S. Pat. Nos. 2,297,691 and 2,551,582
and in "RCA Review" Vol. 15 (1954) pages 469-484.
The following example further illustrates the principles of the
invention.
EXAMPLE 1
Electrophotographic elements or plates are prepared in the
following manner: To a solution of 0.15 grams of the organic
photoconductive compound and 0.002 grams of a sensitizing dye in 5
ml. of methylene chloride is added 0.050 grams of Vitel PE-101*
*Vitel PE-101 is a trademark of Goodyear Tire & Rubber Company
for a copolyester of terephthalic acid with a glycol mixture having
a 9:1 molar ratio of ethylene glycol and
2,2-bis-(4-.beta.-hydroxyethoxyphenyl) propane. polyester. The
mixture is agitated to obtain a clear viscous solution or dope
which is knife-coated on aluminum foil at about 125.degree. F. and
a wet thickness of 0.004 inches. The coated product is dried and
dark-conditioned by heating for fifteen hours in a dark oven at
47.degree. C. Samples of the resulting xerographic element are
charged in total darkness by means of a negative corona and then
exposed through a step tablet to the light of a tungsten lamp at an
illumination intensity of about 19 foot-candles for 12 seconds. The
step tablet is of the carbon-grain-in-gelatin type with density
increments of 0.15. An inlay of 2.0 density covers one half of the
tablet to extend the range of exposure. A photographic film
positive carrying printed text and numbers identifying the steps
lies between the photoconductive layer and the tablet.
The resulting electrostatic latent image is developed by cascading
over the surface of the photoconductive layer a mixture of
negatively charged thermoplastic toner particles and plastic
beads.
Following the described procedure a series of electrophotographic
elements is prepared using the furan compounds I through V and
sensitizers (or no sensitizers) as indicated in the following lists
of furan compounds and sensitizers and the table hereinafter.
Elements are also prepared which contain a furan compound but no
sensitizer and a control element is prepared which contains only
the polyester binder resin and the sensitizer B. ##SPC2##
SENSITIZERS
A. No sensitizer added.
B. 4-(4-n-amyloxyphenyl)-2,6-bis(4-ethylphenyl)-thiapyrylium
perchlorate
C. 2,4,7-trinitrofluorenone
D. Crystal violet
E. Rhodamine B
F. 2,4-bis-(4-ethoxyphenyl)-6-(4-amyloxystyryl) pyrylium
fluoroborate
The table below records the results of the described xerographic
exposure of plates containing the organic photoconductors and
sensitizers indicated in the table. (Except that the data for the
element containing compound IV are from a test with positive
charging. In a negative charging test, which possibly failed for
other reasons, the element containing this compound yielded no
image.). The speed designations in the table are relative speeds
indicating the multiple by which the particular xerographic element
is faster than the control that contains only the polyester binder
resin and sensitizer B. With the procedure described the control
gives a detectable image to about step 10.
Table ______________________________________ Photoconductor
Sensitizer Image Formed Speed Rating
______________________________________ I A (None) Yes 24 I B Yes
200 I C Yes 48 I D Yes 98 I E Yes 200 II A (None) Yes 78 II E Yes
120 III C Yes 150 IV B Yes 57 IV C Yes 20 IV D No -- IV E Yes 15 V
A (None) No -- V B Yes 38 V C Yes 6 V D No -- V E Yes 5 None A
(None) No -- (Control) B Yes 5 C No -- D No -- E No --
______________________________________
The results recorded in the table show that the described
isobenzofuran compounds I, II and III are photoconductors of good
sensitivity. They are unexpectedly superior to a simple diaryl
substituted furan such as compound V. In these particular
comparisons compound IV, (1,3,4,7-tetraphenyl-isobenzofuran, which
is also a 1,3-diarylisobenzofuran of the type contemplated herein)
is not as markedly superior to photoconductor V and the control
element as are compounds I, II and III. An explanation for these
results which are not as good as can be obtained with compound IV
is that some crystallization of the compound occurred in this
particular coating. The following example describes a coating in
which substantially better results are obtained with compound
IV.
EXAMPLE 2
The crystallization of the 1,3,4,7-tetraphenylisobenzo-furan
encountered in Example 1 is eliminated or reduced in a
photoconductive element prepared substantially as in Example 1 but
using bisphenol-A polycarbonate (Lexan 145 polycarbonate) as the
binder instead of polyester and using approximately 15 percent
concentration of the compound in the coating instead of
approximately 20 percent. Testing of such compositions containing
compound IV and either sensitizer B or sensitizer F for positive
and negative charging gives the following results:
______________________________________ speed Photoconductor
Sensitizer Positive Negative ______________________________________
IV B 120 71 IV F 170 160 ______________________________________
The next example illustrates the use of the following
thiobenzofuran and isoindole compounds in photoconductive elements
of the invention: ##SPC3##
EXAMPLE 3
Photoconductive elements of the invention containing a
thiobenzofuran (compound VI) or an isoindole (compound VII) are
prepared as in Example 1, using the following basic
formulation:
Photoconductor -- 0.25 g.
Vitel 101 polyester -- 1.00 g.
Sensitizer -- 0.01 g.
Methylene chloride -- 9.60 g.
Results obtained with these compositions positively charged and
tested as in Example 1 are as follows:
______________________________________ Photoconductor Sensitizer
Image Formed Speed Rating ______________________________________ VI
B Yes 200 E Yes 100 VII B Yes 50 E Yes 50
______________________________________
Compounds of somewhat related structure which appear to have some
utility as organic photoconductors, although not having the
surprisingly high sensitivity of the 1,3-diarylisobenzofurans,
include the following isoindoles:
1-(4-dimethyl-aminophenylisoindole, 1-phenylisoindole and
1-(4-methoxyphenyl) isoindole.
The invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *