U.S. patent application number 09/759324 was filed with the patent office on 2001-09-06 for electrophotographic photosensitive member and process for producing the same.
This patent application is currently assigned to MITSUBISHI CHEMICAL CORPORATION. Invention is credited to Chouda, Takahiro, Kurihara, Syunichiro.
Application Number | 20010019804 09/759324 |
Document ID | / |
Family ID | 26414446 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019804 |
Kind Code |
A1 |
Kurihara, Syunichiro ; et
al. |
September 6, 2001 |
Electrophotographic photosensitive member and process for producing
the same
Abstract
An electrophotographic photosensitive member, including: a
conductive substrate; an undercoat layer formed on the conductive
substrate, which contains a binder resin and metal oxide particles
treated with an organic metal compound represented by formula (1):
1 where M is --SiR.sup.3, --TiR.sup.3 or Al; R is a hydrogen atom
or a C.sub.1 to C.sub.6 alkyl group; R.sup.1 and R.sup.2 are each,
independently, a C.sub.1 to C.sub.6 alkyl group; R.sup.3 is a
C.sub.1 to C.sub.6 alkyl group which may be substituted with an
alkoxy group or a C.sub.1 to C.sub.6 alkoxy group which may be
substituted with an alkoxy group; and a photosensitive layer formed
on the undercoat layer.
Inventors: |
Kurihara, Syunichiro;
(Yokohama-shi, JP) ; Chouda, Takahiro;
(Yokohama-shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
MITSUBISHI CHEMICAL
CORPORATION
5-2, Marunouchi 2-chome Chiyoda-ku
Tokyo
JP
|
Family ID: |
26414446 |
Appl. No.: |
09/759324 |
Filed: |
January 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09759324 |
Jan 16, 2001 |
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09361997 |
Jul 28, 1999 |
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6214506 |
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Current U.S.
Class: |
430/60 ; 430/131;
430/63; 430/65; 524/497 |
Current CPC
Class: |
G03G 5/142 20130101;
C01P 2006/82 20130101; C09C 1/3669 20130101; G03G 5/102 20130101;
C01P 2004/64 20130101; G03G 5/104 20130101; C09C 1/3692 20130101;
G03G 5/14704 20130101; G03G 5/144 20130101; C09C 1/3684
20130101 |
Class at
Publication: |
430/60 ; 430/131;
430/65; 430/63; 524/497 |
International
Class: |
G03G 005/14; C08K
003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 1998 |
JP |
10-215203 |
Mar 18, 1999 |
JP |
11-73292 |
Claims
What is claimed is:
1. An electrophotographic photosensitive member, comprising: a
conductive substrate; an undercoat layer on the conductive
substrate, comprising a binder resin and metal oxide particles
treated with an organic metal compound represented by formula (1);
12wherein M is --SiR.sup.3, --TiR.sup.3 or Al; R is a hydrogen atom
or a C.sub.1 to C.sub.6 alkyl group; R.sup.1 and R.sup.2 are each,
independently, a C.sub.1 to C.sub.6 alkyl group; R.sup.3 is a
C.sub.1 to C.sub.6 alkyl group which may be substituted with an
alkoxy group or a C.sub.1 to C.sub.6 alkoxy group which may be
substituted with an alkoxy group; and a photosensitive layer on the
undercoat layer.
2. The electrophotographic photosensitive member of claim 1,
wherein the organic metal compound is an organic silicon compound
represented by formula (2): 13wherein R.sup.4 and R.sup.5 are each,
independently, methyl or ethyl; and R.sup.6 is selected from the
group consisting of methyl, ethyl, methoxy and ethoxy.
3. The electrophotographic photosensitive member of claim 1,
wherein the metal oxide particles are titanium oxide particles.
4. The electrophotographic photosensitive member of claim 1,
wherein the metal oxide particles have an average primary particle
size of not more than 100 nm when measured from a TEM
micrograph.
5. The electrophotographic photosensitive member of claim 1,
wherein the binder resin is an alcohol-soluble resin.
6. The electrophotographic photosensitive member of claim 1,
wherein M is --SiR.sup.3.
7. The electrophotographic photosensitive member of claim 1,
wherein R.sup.3 is a C.sub.1 to C.sub.6 alkyl group.
8. The electrophotographic photosensitive member of claim 1,
wherein the weight ratio of the metal oxide particles treated with
the organic metal compound to the binder resin is 0.5:1 to
10:1.
9. The electrophotographic photosensitive member of claim 1,
wherein the binder resin is selected from the group consisting of
thermoplastic resins, cellulose-based resins, polyamide resins,
epoxy resins, urethane resins, acrylic acid-based resins,
methacrylic acid-based resins, thermosetting resins, and
photo-curable resins.
10. The electrophotographic photosensitive member of claim 1,
wherein the photosensitive layer is a laminate comprising a
charge-generating layer on the undercoat layer and a and a
charge-transport layer on the charge-generating layer.
11. The electrophotographic photosensitive member of claim 1,
wherein the conductive substrate is aluminum, stainless steel,
copper, nickel, or is a coated substrate obtained by forming a
conductive layer comprising aluminum, copper, palladium, tin oxide,
indium oxide on an insulating substrate
12. The electrophotographic photosensitive member of claim 1 1,
wherein the insulating substrate is a polyester film, paper, or
glass.
13. The electrophotographic photosensitive member of claim 1,
wherein the binder resin is a polyamide resin.
14. The electrophotographic photosensitive member of claim 1,
wherein the binder resin is a polyamide resin containing a diamine
component represented by formula (3): 14wherein 15and 16are each,
independently, a substituted or unsubstituted cyclohexyl ring; and
R.sup.7 and R.sup.8 are each, independently, a hydrogen atom, an
alkyl group, am alkoxy group or an aryl group.
15. A process for producing the electrophotographic photosensitive
member of claim 1, comprising forming the undercoat layer on the
conductive substrate by coating.
16. The process of claim 15, wherein the binder resin is an
alcohol-soluble resin, and a coating solution comprising the binder
resin and an alcohol as a main solvent is coated on the conductive
substrate.
17. A process for producing the electrophotographic photosensitive
member of claim 1, comprising: applying the undercoat layer on the
conductive substrate, and applying the photosensitive layer on the
undercoat layer.
18. A coating film, comprising: a binder resin; and metal oxide
particles treated with an organic metal compound represented by
formula (1) or formula (2): 17wherein M is --SiR.sup.3, 'TiR.sup.3
or Al; R is a hydrogen atom or a C.sub.1 to C.sub.6 alkyl group;
R.sup.1 and R.sup.2 are each, independently, a C.sub.1 to C.sub.6
alkyl group; R.sup.3 is a C.sub.1 to C6 alkyl group which may be
substituted with an alkoxy group or a C.sub.1 to C.sub.6 alkoxy
group which may be substituted with an alkoxy group; or 18wherein
R.sup.4 and R.sup.5 are each, independently, methyl Or ethyl; and
R.sup.6is selected from the group consisting of methyl, ethyl,
methoxy and ethoxy.
19. The coating film of claim 18, wherein the metal oxide is
titanium oxide.
20. Titanium oxide treated with an organic metal compound
represented by formula (1) or formula (2): 19wherein M is
--SiR.sup.3, --TiR.sup.3 or Al: R is a hydrogen atom or a C.sub.1
to C.sub.6 alkyl group; R.sup.1 and R.sup.2 are each,
independently, a C.sub.1 to C.sub.6 alkyl group; R.sup.3 is a
C.sub.1 to C.sub.6 alkyl group which may be substituted with an
alkoxy group or a C.sub.1 to C.sub.6 alkoxy group which may be
substituted with an alkoxy group; or 20wherein R.sup.4 and R.sup.5
are each, independently, methyl or ethyl; and R.sup.6 is selected
from the group consisting of methyl, ethyl, methoxy and ethoxy.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of tie Invention
[0002] The present invention relates to an electrophotographic
photosensitive member having an undercoat layer, a process for
producing the electrophotographic photosensitive member, and to
titanium oxide which is surface-treated so as to impart
hydrophobicity thereto.
[0003] 2. Description of the Background
[0004] In recent years, electrophotographic techniques have been
extensively applied to not only copying machines but also various
printers, because of, for example, high printing speed and
formation of high-quality images. As photosensitive members
constituting the main component of electrophotographic apparatuses,
organic photoconductive materials (OPC) have become predominately
used instead of inorganic photoconductive materials, such as
selenium, arsenic-selenium alloy, cadmium sulfide or zinc oxide,
because of the ease in selection of exposure light wavelength
range, facilitated production (producible by coating), use of
harmless materials from the standpoint of safety, among others..
There have been developed various type OPCs such as single layer
type OPCs obtained by dispersing a charge-generation substance and
a charge-transport substance in a binder, laminated type OPCs
comprising two function-separating layers, i.e., a
charge-generation layer and a charge-transport layer, and the like.
Among these OP Cs, the laminated-type OPCs having such a structure
that the charge-generation layer and the charge-transport layer are
successively laminated on a substrate, have been ordinarily
used.
[0005] Further, recently, in order to enhance electrophotographic
properties, image-forming properties and mechanical properties of
the photosensitive member, electrophotographic photosensitive
members obtained by successively laminating an undercoat layer and
a photosensitive layer on a substrate have been widely used.
[0006] As preferable binder resins for the undercoat layer, there
have been studied and frequently used alcohol-soluble resins,
especially alcohol-soluble polyamide resins, from the standpoints
of adhesion to the substrate, solvent resistance (resistance to
solvents used in the charge-generation and charge-transport
layers), coating property and electric barrier property.
[0007] Further, in order to satisfy the requirements for the
undercoat layer, inorganic particles such as metal oxide particles,
especially titanium oxide particles, have been used in the
undercoat layer. Besides, in order to enhance the performance of
the undercoat layer, there has been developed such a technique that
the metal oxide particles are treated with an organic compound. In
particular, there is known a method of treating the particles with
a metal-containing organic compound such as an organic silicon
compound CU.S. 5,612,158).
[0008] As metal oxide particles treated with such an organic
compound, there is ordinarily known those treated with
polysiloxanes such as dimethyl polysiloxane or methyl hydrogen
polysiloxane, stearic acid or the like.
[0009] Meanwhile, when a coating solution containing metal oxide
particles treated with an organic compound is prepared, the organic
compound is usually liberated in the coating solution upon
dispersion- and heat-treatments or the like, In addition, after the
production of the coating solution, the organic compound is
liberated over time. At present, it has been difficult to
completely prevent the liberation of the organic compound as a
treating agent.
[0010] For this reason, in the case where the layer containing
metal oxide particles treated with an organic compound, is formed
by coating, the organic compound liberated from the metal oxide
particles tends to be associated with each other in the coating
solution, so that defects such as crawling tend to occur upon
coating. As a result, a good coating film is difficult to produce.
Especially in the case of electrophotographic photosensitive
members, the defects, such as crawling in the undercoat layer tend
to cause image defects, resulting in problems such as deteriorated
yield.
[0011] In order to solve these problems, there has been proposed,
for example, a method of preventing an organic compound from being
liberated in a coating solution by previously washing the organic
compound-treated metal oxide particles with an organic solvent,
thereby inhibiting defects such as crawling of the undercoat layer
(Japanese Patent Application Laid-open (KOKAI) No. 10-282502).
[0012] However, this method requires additional steps such as
washing with the organic solvent, separating between the organic
solvent and the metal oxide particles, drying of the metal oxide
particles or the like. As a result, the method becomes
disadvantageous in productivity and costs.
[0013] Accordingly, there remains a need for electrophotographic
photosensitive members which overcome the disadvantages described
above.
SUMMARY OF THE INVENTION
[0014] It is an object of the present invention to provide an
electrophotographic photosensitive member having an undercoat
layer, which has excellent functional properties and can be
produced without defects, such as crawling, during formation of the
undercoat layer.
[0015] It is another object of the invention to provide a method of
making the electrophotographic photosensitive member.
[0016] It is another object of the invention to provide modified
titanium oxide particles which can be used in the manufacture of
electrophotographic photosensitive members.
[0017] The present invention is based in the inventors' discovery
that when an undercoat layer is formed by a coating method and the
undercoat layer comprises a binder resin and metal oxide particles
treated with an organic metal compound represented by the following
general formula (1): 2
[0018] where M is --SiR.sup.3, --TiR.sup.3 or Al; R is a hydrogen
atom or a C.sub.1 to C.sub.6 alkyl group; R.sup.1 and R.sup.2 are
individually a C.sub.1 to C.sub.6 alkyl group; R.sup.3 is a C.sub.1
to C.sub.6 alkyl group, a C.sub.1 to C.sub.6 alkoxy group, a
C.sub.2 to C.sub.6 alkoxyalkyl group or a C.sub.2 to C.sub.6
alkoxyalkoxy group, defects such as crawling of the undercoat-layer
can be avoided, and the obtained electrophotographic photosensitive
member has superior properties.
[0019] Accordingly, the objects of the invention, and others, may
be accomplished with an electrophotographic photosensitive member
comprising:
[0020] a conductive substrate,
[0021] an undercoat layer formed on the conductive substrate which
comprises a binder resin and metal oxide particles treated with an
organic metal compound represented by formula (1), and
[0022] a photosensitive layer formed on the undercoat layer.
[0023] The objects of the invention may also be accomplished with a
process for producing the electrophotographic photosensitive member
described above,
[0024] The objects of the invention may also be accomplished with a
coating film which comprises a binder resin and metal oxide
particles treated with the organic metal compound represented by
formula (1).
[0025] The objects of the invention may also be accomplished with
titanium dioxide treated with the organic metal compound
represented by formula (1). The treated titanium oxide is
particularly useful for manufacturing the inventive
electrophotographic photosensitive member.
[0026] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The photosensitive member according to the present invention
includes a conductive substrate. As the conductive substrates,
there may be exemplified metal substrates comprising, for example,
aluminum, stainless steel, copper, nickel or the like, or coated
substrates obtained by forming a conductive layer comprising
aluminum, copper, palladium, tin oxide, indium oxide, etc., on an
insulating substrate such as a polyester film, paper, glass or the
like. Among these conductive substrates, those produced by cutting
an endless metal pipe comprising aluminum or the like into an
appropriate length, are preferred. The surface of the conductive
substrate may be subjected to various treatments such as, for
example, oxidation treatment or chemical treatment, provided that
these treatments do not adversely affect a quality of obtained
images.
[0028] In the present invention, the undercoat layer is provided
between the conductive substrate and the photosensitive layer. The
undercoat layer used in the present invention comprises a binder
resin and metal oxide parades treated with the organic compound
represented by formula (1). As the binder resins, there may be
exemplified thermoplastic resins such as polyvinyl acetal, e.g.,
polyvinyl butyral, cellulose-based resins, polyarnide resins, epoxy
resins, urethane resins, acrylic acid-based resins, methacrylic
acid-based resins or the like; thernosetting resins; or
photo-curable resins. From the standpoints of adhesion to the
substrate, solvent resistance, electric barrier property, coating
property, dryability, etc., S alcohol-soluble resins, especially
alcohol-soluble polyamide resins are preferred. Among these, from
the standpoints of enhancing the performance of the undercoat layer
and stability of the coating solution, copolymerized polyamide
resins containing a diaamine component represented by the following
general formula (3), are more preferred. 3
[0029] where 4
[0030] and 5
[0031] are individually a substituted or unsubstituted cyclohexyl
ring; and R.sup.7 and R.sup.8 are individually a hydrogen atom, an
alkyl group, an alkoxy group or an aryl group. The rings denoted A
and B may be substituted with alkyl groups, having, for example, 1
to 6 carbon atoms. Preferably, such groups are saturated. Each ring
may have one or more substituent. R.sup.7 and RE may have, for
example, 1 to 10 carbon atoms. In embodiments where an
alcohol-soluble resin is used as a binder resin, as a matter of
course, the main solvent used to apply the undercoat layer is
alcohol.
[0032] The metal oxide particles are another constituent of the
undercoat layer, and may be treated with the organic metal compound
represented by formula (1). Specific examples of R in formula (1),
include a hydrogen atom, methyl, ethyl, n-propyl, i-propyl,
n-butyl,: sec-butyl, tetra-butyl, n-hexyl or the like. Among these
groups, a hydrogen atom is more preferred. R.sup.1 and R.sup.2 are
individually a linear or branched C.sub.1 to C.sub.6 alkyl group.
In consideration of reactivity with the metal oxide particles upon
the surface treatnent, C.sub.1 to C.sub.4 alkyl groups are
preferred. Among them, methyl and ethyl are more preferred. M is
--SiR.sup.3, --TiR.sup.3 or Al, where R.sup.3 is a C.sub.1 to
C.sub.6 alkyl group, a C.sub.1 to C.sub.6 alkoxy group, a C.sub.2
to Cs alkoxyalkyl group or a C.sub.2 to C.sub.6 alkoxyalkoxy group.
Specific examples of R.sup.3 include alkyl groups such as methyl,
ethyl, n-propyl, i-propyl, butyl, heptyl, hexyl or the like; alkoxy
groups such as methoxy, ethoxy, propoxy, butoxy or the like;
alkoxyalkyl groups such as methoxymethoxy, methoxyethoxy,
ethoxymethoxy, ethoxyethoxy or the like. Among these groups,
methyl, ethyl, methoxy and ethoxy are preferred.
[0033] Among the organic metal compounds represented by the above
general formula (1), organic silicon compounds represented by the
following general formula (2) are especially preferred. 6
[0034] where R.sup.4 and R.sup.5 are individually methyl or ethyl;
and R.sup.6 is a group selected from the group consisting of
methyl, ethyl, methoxy and ethoxy.
[0035] The surface treatment of the metal oxide particles with the
above surface-treating agent may be conducted by either a dry
method or a wet method. In the case of the dry method, the metal
oxide particles as a base material are charged into a high-speed
stirrer such as a Henschel mixer, a supermixer, etc., and then
while stirring the metal oxide particles at a high speed, a
solution of the surface-treating agent is dropped or sprayed
thereto so as to uniformly deposit on the surfaces of the
particles, or spray-added thereto so as to uniformly mix with the
particles. Thereafter, the thus coated particles are dried. On the
other hand, in the wet method, titanium oxide as a base material
and the surface-treating agent are added into a solvent and
dispersed therein by a ball mill, Coball Mill, a sand grill mill, a
bead mill such as pearl mill or the like, and then the solvent is
evaporated from the mixture. In both the dry and wet methods, it is
preferred that the obtained particles are baked at a temperature of
about 100.degree. C. to about 200.degree. C. during or after the
surface treatment to strengthen the bond between the metal oxide
and the surface-treating agent. The amount of the surface-treating
agent used is usually 0.01 to 100 parts by weight, preferably 0.1
to 10 parts by weight, based on 100 parts by weight of the metal
oxide. These ranges include all specific values and subranges
therebetween, including 0.02, 0.05, 0.2, 0.5, 1, 2, 5, 10, 25, 50
and 75 parts by weight of the surface-treating agent, based on 100
parts by weight of the metal oxide.
[0036] Among the above metal oxides, titanium oxide particles are
preferred from the standpoint of enhancing properties of the
undercoat layer. In addition, from the standpoint of enhancing
properties of the undercoat layer and dispersion stability of the
coating solution, titanium oxide particles have an average primary
particle size of not more than 100 nm are more preferred. The
titanium oxide particles may be either crystalline or amorphous.
Most ordinary crystalline titanium oxide has a rutile structure.
However, the titanium oxide used in the present invention may be in
the form of anatase or brookite. The metal oxide particles treated
with the organic metal compound as descried above may be further
treated with, for example, inorganic materials such as alumina,
silica, zirconia or the like.
[0037] The weight ratio of the metal oxide particles treated with
the organic metal compound to the binder resin in the undercoat
layer can be optionally selected. However, from the standpoint of
enhancing properties of the undercoat layer and dispersion
stability of the coating solution, the weight ratio is preferably
0.5:1 to 10:1, more preferably 2:1 to 5:1.
[0038] These ranges include all specific values and subranges
therebetween, such as 1:1, 3:1 and 8:1.
[0039] Further, various surfactants may be added in order to
improve the coating property of the coating solution and the
dispersibility of the particles therein. In addition, the coating
solution for the undercoat layer may further contain other
additives, such as leveling agents or anti-oxidizing agents.
[0040] The coating solution for the undercoat layer (hereinafter
referred to as "undercoating solution") may be produced by the
following method. The metal oxide particles, treated with the
organic metal compound, are dispersed using a ball mill, Coball
Mill, a sand mill or the like, and then diluted into an appropriate
concentration, thereby preparing a slurry. The slurry is mixed with
a binder solution previously prepared by dissolving the binder in a
solvent, thereby producing an undercoating solution. Alternatively,
binder pellets or powder may be directly added to the slurry, and
the mixture is mixed and stirred together to dissolve the binder in
the slurry, thereby producing the undercoating solution.
Alternatively, the undercoating solution may be produced by adding
the metal oxide particles treated with the organic compound to the
binder solution and then dispersing the particles therein. In these
production processes, various additives may be optionally added,
and the metal oxide particles may be subjected to various
treatments such as heat treatment or ultrasonic treatment, if
required or desired.
[0041] The undercoating solution may then be applied onto the
substrate and then dried, thereby forming the undercoat layer. As
the coating methods, there may be used any of a spray coating
method, a nozzle coating method, a blade coating method, a spin
coating method, an immersion coating method and the like. Among
these coating methods, the immersion coating method has been used
most often.
[0042] The photosensitive layer is formed on the undercoat layer.
The photosensitive layer may be in the form of a single layer.
However, the photosensitive layer preferably has a laminated layer
structure comprising two separate layers, i.e., a charge-generation
layer and a charge-transport layer. In the case where the
photosensitive layer has such a laminated layer structure, the
charge-generation layer and the charge-transport layer are
preferably successively formed on the undercoat layer in this
order.
[0043] As charge-generation substances used in the
charge-generation layer, there may be exemplified inorganic
photoconductive materials such as selenium or alloys thereof,
arsenic-selenium, cadmium sulfide, zinc oxide or the like; various
organic pigments or dyes such as phthalocyanine, azo dyes, e.g.,
monoazo, bisazo or trisazo, quinacridon, polycyclic quinone,
pyrylium salt, indigo, thioindigo, anthanthrone, pyranthrone or
cyanine; or the like. Among these materials, those containing
organic pigments are preferred. Further, metal-free
(non-metallo)phthalocyanines, or metallophthalocyanines having a
ligand comprising metal, metal oxide or metal chloride such as
copper, indium chloride, gallium chloride, tin, oxytitanium, zinc,
vanadium, hydroxy silicon or the like, are more preferred.
Especially, oxytitanium phthalocyanine is particularly
preferred.
[0044] The charge-generation layer may be produced by applying a
coating solution obtained by dissolving or dispersing fine
particles of these charge-generation substances and a binder
polymer in a solvent, and then drying the coating solution applied.
As the binders, there may be exemplified polymers or copolymers of
vinyl compounds such as styrene, vinyl acetate, vinyl chloride,
acrylic esters, methacrylic esters, vinyl alcohol, ethylvinyl
ether; polyvinyl acetals; polycarbonates; polyesters; polyamides;
polyurethanes; cellulose ethers; phenoxy resins; silicon resins;
epoxy resins; or the like.
[0045] The ratio of the charge-generation substance to the binder
polymer is not particularly restricted, but the binder polymer may
be used in an amount of usually 5 to 500 parts by weight,
preferably 20 to 300 parts by weight based on 100 parts by weight
of the charge-generation substance. These ranges include all
specific values and subranges therebetween, such as 10, 15, 25, 50,
75, 100, 200, 300 and 400 parts by weight of the binder polymer,
based on 100 parts by weight of the charge-generation
substance.
[0046] The charge-generation layer may also be constituted by a
vapor-deposited film comprising the charge-generation
substance.
[0047] The thickness of the charge-generation layer is usually 0.05
to 3 .mu.m, preferably 0.1 to 1 .mu.m. These ranges include all
specific values and subranges therebetween, such as 0.075, 0.15,
0.2 and 0.25 .mu.m.
[0048] The charge-transport layer may be produced by applying a
coating solution obtained by mixing a charge-transport substance
with a known excellent binder, dissolving the mixture in a solvent,
and adding an electron attractive compound or other additives such
as plasticizers or pigments, if required, onto the above
charge-generation layer. The thickness of the charge-transport
layer is usually 5 to 50 preferably 10 to 35 .mu.m. These ranges
include all specific values and subranges therebetween, such as 15,
20, 20, 30, 40 and 45 .mu.m.
[0049] As the charge-transport substances contained in the
charge-transport layer, there may be used high-molecular compounds
such as polyvinyl carbazole, polyvinyl pyrene, polyacenaphthylene
or the like; or low-molecular compounds such as various pyrazoline
derivatives, oxazole derivatives, hydrazone derivatives, stilbene
derivatives, arylamine derivatives or butadiene derivatives.
[0050] As the binder polymers, there may be preferably used those
polymers which have a good compatibility with the above
charge-transport substance, and are free from recrystallization of
the charge-transport substance and the phase separation after the
formation of coating film. Examples of the preferred binder
polymers may include polymers or copolymers of vinyl compounds such
as styrene, vinyl acetate, vinyl chloride, acrylic esters,
methacrylic esters, vinyl alcohol or ethylvinyl alcohol; polyvinyl
acetals; polycarbonates; polyesters; polysulfones; polyphenylene
oxides; polyurethanes; cellulose esters; cellulose ethers; phenoxy
resins; silicon resins; epoxy resins; or the like. Among these
binder polymers, polycarbonate resins are especially preferred.
Also, these resins may be partially cross-linked.
[0051] As to the ratio of the charge-transport substance to the
binder resin, the charge-transport substance may be used in an
amount of usually 10 to 200 parts by weight, preferably 20 to 150
parts by weight based on 100 parts by weigh of the binder resin.
These ranges include all specific values and subranges
therebetween, such as 15, 25, 50, 75, 100 and 175 parts by weight
of the charge-transport substance, based on 100 parts by weight of
the binder resin.
[0052] As the electron attractive compounds which may be optionally
added to the charge-transport layer, there may be exemplified cyano
compounds of aromatic esters or the like having a
tetracyano-quino-dimethane group, a dicyano-quino-methane group or
a dicyano-quino-vinyl group; nitro compounds such as 2,4,6-trinitro
fluorene; condensed polycyclic aromatic compounds such as perylene;
diphenoquinone derivatives; quinones; aldehydes; ketones; esters;
acid anhydrides; phthalides; metal complexes of substituted or
unsubstituted salicylic acid; metal salts of substituted or
unsubstituted salicylic acid; metal complexes of aromatic
carboxylic acids; or metal salts of aromatic carboxylic acids.
Among these electron attractive compounds, cyano compounds, nitro
compounds, condensed polycyclic aromatic compounds, diphenoquine
derivatives, metal complexes of substituted or unsubstituted
salicylic acid, metal salts of substituted or unsubstituted
salicylic acid, metal complexes of aromatic carboxylic acids and
metal salts of aromatic carboxylic acids, are preferably eased.
[0053] Organic pigments, resin particles, metal oxides or the like
may be added to the charge-transport layer in order to enhance
mechanical strength thereof. When the metal oxide is added to the
charge-transport layer, it is preferable to use metal oxide
particles treated with the organic metal compound represented by
formula (1) for the same reason as described as to the formation of
the undercoat layer.
[0054] The photosensitive layer of the electrophotographic
photosensitive member according to the present invention may
further contain various known additives such as plasticizers,
anti-oxidizing agents, ultra-violet light absorbing agents,
leveling agents or the like, in order to improve film-forming
property, flexibility, coating property and mechanical strength
thereof.
[0055] Further, an overcoat layer may be formed on the
photosensitive layer in order to enhance mechanical strength and
resistance to gases such as ozone, NO.sub.x or the like. In the
case where metal oxide particles are to be contained in the
overcoat layer for enhancing mechanical strength thereof, it is
also preferable to use metal oxide particles treated with the
organic metal compound represented by formula (1) for the same
reason as described above. As a matter of course, thin
photosensitive member may be further provided with an adhesive
layer, an intermediate layer, a transparent insulating layer or the
like, if required or desired.
[0056] The photosensitive layer, the overcoat layer, etc., may be
produced by an immersion coating method, a spray coating method, a
nozzle coating method, or the like.
[0057] The electrophotographic photosensitive member produced
according to the present invention may be subjected to various
electrophotographic copying processes mainly including charging,
exposure, development and transfer. As the charging method, there
may be used any conventional method, for example, a corotron- or
scorotron-charging method utilizing corona discharge, a contact
charging method using a conductive roller or brush, or paper, or
the like, in the charging method utilizing corona discharge, the
scorotron-charging method has been frequently used in order to keep
a dark potential constant. As the developing method, there may be
used ordinary developing methods of bringing a magnetic or
nonmagnetic one-component developer or two-component developer,
etc., into contact or non-contact with the photosensitive member.
As the transfer method, there may be used any conventional method
using corona discharge, a transfer roller or the like. In addition,
the electrophotographic process may usually include a fixing
process for affixing the developer onto paper or the like. As the
fixing methods, there may be used an ordinary heat- or
pressure-fixing method or the like. The electrophotographic process
may further include other processes such as cleaning, erasing or
the like.
[0058] Without being limited to any particular theory, a possible
explanation for the reason why the undercoat layer according to the
present invention, which comprises at least a binder resin and
metal oxide particles treated with the above-described
surface-treating agent, can improve properties of the
electropbotographic photosensitive member, and is free from coating
defects such as crawling even when being formed by coating, is set
forth below. However, the effects are not completely
understood.
[0059] That is, in the metal oxide particles treated with the
above-described surface-treating agent, the metal oxide particles
as a base material tend to be more strongly bonded to the
surface-treating agent as compared to conventional metal oxide
particles treated with polysiloxane or the like. Therefore, the
surface-treating agent used in the present invention is less
liberated in a coating solution as compared to conventional
surface-treating agents, so that coating defects such as crawling
upon the formation of coating film can be effectively
prevented.
[0060] Without being limited to any particular theory, a possible
explanation for the reason why the strong bond between the metal
oxide particles and the above surface-treating agent tends to is
set forth below. However, the effects are not completely
understood.
[0061] That is, it is currently believed that the bond between
polysiloxane and metal oxide particles is mainly caused by physical
absorption. Therefore, the bonding force therebetween is weak, so
that the conventional surface-treating agent tends to be liberated
from the metal oxide particles. Even in the case where there is
used methyl hydrogen polysiloxane which tends to form a chemical
bond with the metal oxide particles as a base material, the ratio
of chemically bonded polysiloxane to whole siloxane units is
extremely small due to steric hindrance, etc., because polysiloxane
is a high-molecular weight compound. As a result, even though
polysiloxane is used, the surface-treating agent tends to be
liberated from the metal oxide particles as a base material.
Whereas, the surface-treating agent used in the present invention
comprises a single-molecular compound and has an alkoxy group which
is considered to react with the metal oxide particles as a base
material. Further, the alkyl group or the alkoxy group bonded to
metal is small in steric size and, therefore, causes no steric
hindrance upon the reaction with hydroxy groups on the surfaces of
the metal oxide particles. As a result, since the surface-treating
agent can be readily chemically bonded to the metal oxide
particles, it is considered that the bond between the metal oxide
particles as a base material and the surface-treating agent is
strengthened.
[0062] In addition, since the above surface-treating agent used in
the present intention has one or more alkyl groups, if reactive
groups such as alkoxy groups are sufficiently reacted with the
metal oxide particles, there can be obtained metal oxide particles
showing a hydrophobic property similar to that obtained by treating
with siloxanes such as methyl hydrogen polysiloxane. This is
considered to be effective for improving an environmental
capability of the undercoat layer.
EXAMPLES
[0063] The present invention will now be explained in more detail
by examples, but these examples are not intended to limit the scope
of the present invention. The "part" used in Examples and
Comparative Examples indicates "part by weight" unless otherwise
specified. In the following Examples and Comparative Examples, a
copolymerized polyamide A represented by the following general
formula was used as the binder resin of the undercoat layer: 7
[0064] Production of Dispersion (P) (Present Invention)
[0065] Titanium oxide (tradename: TTO-55N, produced by Ishihara
Sangyo Co., Ltd.; average primary particle size: about 40 nm) was
previously dispersed together with titania treated with 3% by
weight of methyl dimethoxysilane by a ball mill. The obtained
titanium oxide slury was mixed with a solution of the copolymerized
polyamide A, and then the mixture was subjected -to an ultrasonic
dispersion treatment, thereby obtaining a dispersion (P) having a
solvent composition ratio of methanol to n-propanol of 7:3, a ratio
of titanium oxide to polyamide of 3:1 and a solid content of 16% by
weight.
[0066] Production of Dispersion (O) (Corresponding to U.S. Pat. No.
5.612 15)
[0067] Titanium oxide (tradename: TTO-55N, produced by Ishihara
Sangyo Co., Ltd.) was previously dispersed together with titania
treated with 3% by weight of methyl hydrogen polysiloxane by a ball
mill. The obtained titanium oxide slurry was mixed with a solution
of the copolymerized polyamide A, and then the mixture was
subjected to an ultrasonic dispersion treatment, thereby obtaining
a dispersion (Q) having a solvent composition ratio of methanol to
n-propanol of 7:3, a ratio of titanium oxide to polyamide of 3:1
and a solid content of 16% by weight.
Example 1
[0068] A surface-planished aluminum cylinder having an outer
diameter of 60 mm, a length of 350 mm and a thickness of 1.0 mm was
immersed in the dispersion (P) and coated therewith, thereby
forming an undercoat layer having a dry thickness of 0.75 .mu.m
thereon. The procedure was repeated to produce two drums. The
number of crawling defects on the drums was counted. As a result,
it was confirmed that no crawling was caused on these drums.
Comparative Example 1
[0069] A surface-planished aluminum cylinder having an outer
diameter of 60 mm, a length of 350 mm and a thickness of 1.0 mm was
immersed in the dispersion (Q) and coated therewith, thereby
forming an undercoat layer having a dry thickness of 0.75 gm
thereon. The procedure was repeated to produce two drums. The
number of crawling defects on the drums was counted. As a result,
it was confirmed that 664 crawling defects per one drum were
caused.
Reference Example 1
[0070] (Present Invention)
[0071] A surface-planished aluminum cylinder having an outer
diameter of 60 mm, a length 25 of 254 mm and a thickness of 1.0 mm
was immersed in the dispersion (P) and coated therewith, thereby
forming an undercoat layer having a dry thickness of 0.75 .mu.m
thereon.
[0072] Next, 10 parts of oxytitanium phthalocyanine having a
specific peak at a Bragg angle of 27.3.degree.
(2.theta..+-.0.2.degree.) in a powder X-ray diffraction pattern
measured using a CuK.alpha. ray, 5 parts of polyvinyl butyral
(tradenarne: #6000-C, produced by Denki Kagaku Kogyo Co., Ltd.)
were mixed with 500 parts of 1,2-dimethoxy ethane, and then the
mixture was pulverized and dispersed by a sand grind mill. The
aluminum cylinder on which the undercoat layer was formed, was
immersed in the obtained dispersion and coated therewith, thereby
forming a charge-generation layer having a dry thickness of 0.3
g/m.sup.2 (about 0.3 .mu.m) on the undercoat layer.
[0073] Next, the thus obtained aluminum cylinder was immersed in
and coated with a solution prepared by dissolving in a mixed
solvent comprising 1,4-dioxane and tetrahydrofuran, 56 parts by
weight of a hydrazone compound represented by the formula: 8
[0074] 14 parts by weight of a hydrazone compound represented by
the formula: 9
[0075] 1.5 parts by weight of a cyanogen compound represented by
the formula: 10
[0076] and 100 parts by weight of a polycarbonate resin produced by
a production method described in Examples of Japanese Patent
Application Laid-Open (KOKAI) No. 3-221962, incorporated herein by
reference, and having two repeating units (molar ratio between
monomers: 1:1) represented by the formula: 11
[0077] As a result, a charge-transport layer having a dry thickness
of 17 .mu.m was formed on the charge-generation layer, thereby
obtaining a drum as a photosensitive member A1.
Reference Example 2
Comparative Example
[0078] The same procedure as defined in Reference Example 1 for
production of the photosensitive member A1 was conducted except
that the dispersion (P) was changed to the dispersion (Q), thereby
producing a drum as a photosensitive member A2.
Reference Example 3
Comparative Example
[0079] The same procedure as defined in Reference Example 1 for
production of the photosensitive member A1 was conducted except
that--no undercoat layer was formed, thereby producing a as a
photosensitive member A3.
[0080] Evaluation
[0081] Next, these photosensitive members were set on a laser
printer (LASER JET 4 Plus manufactured by Hewlett Packard Corp.)
and subjected to formation of blank (white) images thereon under
various environmental conditions. The obtained images were
evaluated. As a result, in the case where the photosensitive
members A1 and A2 obtained in Reference Examples 1 and 2,
respectively, were used, it was confirmed that blank images having
a good quality could be obtained under any of environmental
conditions (temperature/humidity) of 5.degree. C./10% (LL),
25.degree. C./50% (NN) and 35.degree. C./85% (HH). However, in the
case where the photosensitive member A3 obtained in Reference
Example 3 was used, there were observed many fine black spots on
blank images under all of the above environmental conditions.
[0082] Next, these electrophotographic photosensitive members were
set onto a measuring apparatus for measuring properties of
photosensitive members, and charged so as to have a surface
potential of -700V, Thereafter, the half-decay exposure intensity
obtained when 780 nm light was irradiated on the photosensitive
members, the potential-retention percentage after the
photosensitive member was charged to -700V and allowed to stand for
5 seconds (DDRS), and the residual potential after erase by 660 nm
LED light, were measured. The results are shown in Table 1.
1TABLE 1 Photo- Half-decay exposure Residual sensitive intensity
(.mu.J/cm.sup.2) Potential (-V) DDR5 (%) member LL NN HH LL NN HH
LL NN HH A1 0.15 0.11 0.15 34 12 14 96 97 92 A2 0.16 0.11 0.16 44
19 17 97 97 93 A3 0.15 0.13 0.15 29 13 15 93 93 90
[0083] In general, when the undercoat layer was provided, the
potential-retention percentage could be improved (the value was
increased), but the residual potential was deteriorated (the value
was increased). In addition, when an inappropriate undercoat layer
was formed, the sensitivity was deteriorated (the value of
half-decay exposure intensity was increased). As is understood from
the above Table 1, the photosensitive member A1 according to the
present invention had B sensitivity substantially identical to
those of the photosensitive member A2 which is provided with an
undercoat layer containing titania treated with methyl hydrogen
polysiloxane and the photosensitive member A3 having no under coat
layer; a residual potential equal to or higher than that of the
photosensitive member A2 having another type undercoat layer; and a
potential-retention percent-age higher than that of the
photosensitive member A3 having no undercoat layer. Accordingly, it
was confirmed that the photosensitive member according to the
present invention as a whole showed enhanced electrophotographic
properties as compared to the conventional photosensitive
members.
[0084] From the above results, the electrophotographic
photosensitive member according to the present invention was
determined to be a good photosensitive member capable of showing
excellent electrophotographic properties and image properties under
various environmental conditions. In addition, even though the
undercoat layer was formed by coating, the occurrence of defects
such as crawling during coating could be remarkably prevented,
resulting in increased yield upon the production of
electrophotographic photosensitive members and reduction in
production costs. Accordingly, the electrophotographic
photosensitive member and the process for producing the
electrophotographic photosensitive member according to the present
invention are outstanding.
[0085] As to the titanium oxide according to the present invention,
in the above descriptions of the electrophotographic photosensitive
member and the process for producing the electrophotographic
photosensitive member according to the present invention, it has
been suggested that a rigid bond can be established between the
surface-treating agent and titanium oxide, so that the obtained
undercoat layer tends to show a good hydrophobic property. These
facts are explained in more detail by the Examples and Comparative
Examples described below.
Example 2
[0086] 100 parts by weight of titanium oxide (TTO-55N, produced by
Ishihara Sangyo Co., Ltd.; rutile type; primary particle size: 0.03
to 0.05 .mu.m), 3 parts by weight of methyl dimethoxysilane
(TSL8117, produced by Toshiba Silicone Co., Ltd.) and 267 parts by
weight of methanol were charged into a ball mill, and dispersed
together therein. After evaporating methanol, the mixture was baked
at 140.degree. C., thereby obtaining titanium oxide surface-treated
with methyl dimethoxysilane.
Comparative Example 2
[0087] The same procedure as defined in Example 2 was conducted
except that diphenyl dimethoxysilane (TSL8172, produced by Toshiba
Silicone Co., Ltd.) was used instead of methyl dimethoxysilane,
thereby obtaining titanium oxide surface-treated with diphenyl
dimethoxysilane.
Comparative Example 3
[0088] The same procedure as defined in Example 2 was conducted
except that polymethylhydrodiene siloxane (KF-99, produced by
Shinetsu Kagaku Co., Ltd.) was used instead of methyl
dimethoxysilane, thereby obtaining titanium oxide surface-treated
with polymethylhydrodiene siloxane.
[0089] Elution Test of Surface-Treating Agent
[0090] The surface-treated titanium oxide obtained above was placed
in a Soxhlet extractor, and 100 g of toluene was added thereto. The
mixture was extracted under reflux for 7 hours. The Si
concentration of the obtained extract was measured by a fluorescent
X-ray analysis. As a reference solution for calculating the
concentration, there was used a solution prepared by dissolving
polymethylhydrodiene siloxane (KF-99) in toluene. The results are
shown in Table 2.
2TABLE 2 Si concentration in extract Si concentration (ppm) Example
2 2.3 Comparative Example 2 183 Comparative Example 3 39.5
[0091] Table 2 showed that the surface-treating agent according to
the present invention was liberated to a lesser degree from the
surface-treated titanium oxide.
[0092] Water-Absorption Test
[0093] The surface-treated titanium oxide obtained above and
untreated titanium oxide (TTO-55N) were allowed to stand in an
atmosphere having a temperature of 35.degree. C. and a relative
humidity of 85% for 4 hours. The water content was measured by the
Karl Fischer's test (coulometric titration method), The results are
shown in Table 3.
3TABLE 3 Water content of titanium oxide Water content (%) Example
1 0.46 Comparative Example 1 0.53 Comparative Example 2 0.50
TTO-55N 1.73
[0094] As seen from Table 3, it was confirmed that the
surface-treated titanium oxide according to the present invention
showed a sufficient hydrophobic property.
[0095] Thus, titanium oxide according to the present invention
shows a hydrophobic property and is believed to be strongly bonded
to the surface-treating agent. For this reason, the titanium oxide
according to the present invention can be readily used in a coating
solution or cosmetics.
[0096] In accordance with the present invention, there is provided
an electrophotographic photosensitive member capable of producing
images having a good quality under whole environmental conditions
including low-temperature and low-humidity conditions
normal-temperature and normal-humidity conditions and
high-temperature and high-humidity conditions.
[0097] In addition, the present invention also provides titanium
oxide having a desirable hydrophobic property and which strongly
bonds to the surface-treating agent.
[0098] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
[0099] This application is based on Japanese Patent Application
Serial No. 10-215203 and 11-73192, filed on Jul. 30, 1998 and Mar.
18, 1999, respectively, both of which are incorporated herein by
reference in their entirety.
* * * * *