U.S. patent application number 11/827115 was filed with the patent office on 2008-01-31 for oxo-titanylphthalocyanine crystal, method for producing the same, and electrophotographic photoreceptor.
Invention is credited to Jun Azuma, Yoshio Inagaki, Daisuke Kuboshima, Keiji Maruo, Junichiro Otsubo.
Application Number | 20080026310 11/827115 |
Document ID | / |
Family ID | 38692055 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080026310 |
Kind Code |
A1 |
Kuboshima; Daisuke ; et
al. |
January 31, 2008 |
Oxo-titanylphthalocyanine crystal, method for producing the same,
and electrophotographic photoreceptor
Abstract
The invention provides an oxo-titanylphthalocyanine crystal
which is stable, is superior in dispersibility in a photoreceptive
layer and efficiently contributes to improvements in sensitivity
and charge retention rate of an electrophotographic photoreceptor
when it is used as a charge generating agent, a method for
producing the oxo-titanylphthalocyanine crystal, and an
electrophotographic photoreceptor. The oxo-titanylphthalocyanine
crystal has predetermined optical characteristics and thermal
properties and is produced by a production method including the
following steps (a) to (d): (a) a step of dissolving a crude
oxo-titanylphthalocyanine crystal in an acid to obtain an
oxo-titanylphthalocyanine solution; (b) a step of adding the
oxo-titanylphthalocyanine solution dropwise in a poor solvent to
obtain a wet cake; (c) a step of washing the wet cake with an
alcohol having 1 to 4 carbon atoms; and (d) a step of stirring the
washed wet cake under heating in a nonaqueous solvent to obtain an
oxo-titanylphthalocyanine crystal.
Inventors: |
Kuboshima; Daisuke; (Osaka,
JP) ; Azuma; Jun; (Osaka, JP) ; Inagaki;
Yoshio; (Osaka, JP) ; Otsubo; Junichiro;
(Osaka, JP) ; Maruo; Keiji; (Osaka, JP) |
Correspondence
Address: |
ARTHUR G. SCHAIER;CARMODY & TORRANCE LLP
50 LEAVENWORTH STREET, P.O. BOX 1110
WATERBURY
CT
06721
US
|
Family ID: |
38692055 |
Appl. No.: |
11/827115 |
Filed: |
July 10, 2007 |
Current U.S.
Class: |
430/78 ; 117/70;
548/403 |
Current CPC
Class: |
G03G 5/0696 20130101;
C09B 67/0016 20130101; C09B 67/0026 20130101 |
Class at
Publication: |
430/78 ; 117/70;
548/403 |
International
Class: |
G03G 15/04 20060101
G03G015/04; C07D 207/50 20060101 C07D207/50; C30B 7/06 20060101
C30B007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2006 |
JP |
2006-208019 |
Claims
1. An oxo-titanylphthalocyanine crystal having a maximum
diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in a CuK.alpha.
characteristic X-ray diffraction spectrum and one peak in a
temperature range from 270 to 400.degree. C. other than the peak
derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by a production method comprising the
following steps (a) to (d): (a) a step of dissolving a crude
oxo-titanylphthalocyanine crystal in an acid to obtain an
oxo-titanylphthalocyanine solution; (b) a step of adding the
oxo-titanylphthalocyanine solution dropwise in a poor solvent to
obtain a wet cake; (c) a step of washing the wet cake with an
alcohol having 1 to 4 carbon atoms; and (d) a step of stirring the
washed wet cake under heating in a nonaqueous solvent to obtain an
oxo-titanylphthalocyanine crystal.
2. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the production method comprises the following inspection
steps (e) to (g) after the step (d): (e) a step of adding the
oxo-titanylphthalocyanine crystal in an amount by weight of 1.25
parts based on 100 parts by weight of a mixed solvent of methanol
and N,N-dimethylformamide (methanol:N,N-dimethylformamide=1:1 (by
weight ratio)) to prepare a suspension; (f) a step of filtering the
suspension with a filter to obtain a filtrate; and (g) a step of
confirming that the absorbance of the filtrate for light having a
wavelength of 400 nm is in a range from 0.01 to 0.08.
3. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the acid used in the step (a) is at least one type selected
from the group consisting of concentrated sulfuric acid,
trifluoroacetic acid and sulfonic acid.
4. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the poor solvent used in the step (b) is water.
5. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the alcohol having 1 to 4 carbon atoms which is used in the
step (c) is at least one type selected from the group consisting of
methanol, ethanol and 1-propanol.
6. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the wet cake was washed with the alcohol having 1 to 4
carbon atoms, and further washed with water in the step (c).
7. The oxo-titanylphthalocyanine crystal according to claim 1,
wherein the oxo-titanylphthalocyanine crystal has a maximum
diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum measured after it is
dipped in an organic solvent for 24 hours and no peak at
26.2.degree..
8. A method for producing an oxo-titanylphthalocyanine crystal, the
oxo-titanylphthalocyanine crystal having a maximum diffraction peak
at a Bragg angle (2.theta..+-.0.2.degree.)=27.2.degree. in a
CuK.alpha. characteristic X-ray diffraction spectrum and one peak
in a temperature range from 270 to 400.degree. C. other than the
peak derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the method comprising the following
steps (a) to (d): (a) a step of dissolving a crude
oxo-titanylphthalocyanine crystal in an acid to obtain an
oxo-titanylphthalocyanine solution; (b) a step of adding the
oxo-titanylphthalocyanine solution dropwise in a poor solvent to
obtain a wet cake; (c) a step of washing the wet cake with an
alcohol having 1 to 4 carbon atoms; and (d) a step of stirring the
washed wet cake under heating in a nonaqueous solvent to obtain an
oxo-titanylphthalocyanine crystal.
9. The method for producing an oxo-titanylphthalocyanine crystal
according to claim 8, the method comprising the following
inspection steps (e) to (g) after the step (d): (e) a step of
adding the oxo-titanylphthalocyanine crystal in an amount by weight
of 1.25 parts based on 100 parts by weight of a mixed solvent of
methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension; (f) a step of filtering the suspension with a filter to
obtain a filtrate; and (g) a step of confirming that the absorbance
of the filtrate for light having a wavelength of 400 nm is in a
range from 0.01 to 0.08.
10. An electrophotographic photoreceptor comprising a substrate and
a photoreceptive layer containing a charge generating agent, a
charge transfer agent and a binding resin, the photoreceptive layer
being formed on the substrate, wherein the charge generating agent
is an oxo-titanylphthalocyanine crystal having a maximum
diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in a CuK.alpha.
characteristic X-ray diffraction spectrum and one peak in a
temperature range from 270 to 400.degree. C. other than the peak
derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by a production method comprising the
following steps (a) to (d): (a) a step of dissolving a crude
oxo-titanylphthalocyanine crystal in an acid to obtain an
oxo-titanylphthalocyanine solution; (b) a step of adding the
oxo-titanylphthalocyanine solution dropwise in a poor solvent to
obtain a wet cake; (c) a step of washing the wet cake with an
alcohol having 1 to 4 carbon atoms; and (d) a step of stirring the
washed wet cake under heating in a nonaqueous solvent to obtain an
oxo-titanylphthalocyanine crystal.
11. The electrophotographic photoreceptor according to claim 10,
wherein the following relationship (1) is established between the
reflection absorbance (A/-) of the photoreceptive layer for light
having a wavelength of 700 nm, the film thickness (d/m) of the
photoreceptive layer and the concentration (C/wt %) of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer.
AC.sup.-1d.sup.-1>1.75.times.10.sup.-4 (1)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an
oxo-titanylphthalocyanine crystal formed from an
oxo-titanylphthalocyanine compound, a method for producing the
oxo-titanylphthalocyanine crystal, and an electrophotographic
photoreceptor. In particular, the invention relates to an
oxo-titanylphthalocyanine crystal which is stable, is superior in
dispersibility in a photoreceptive layer and efficiently
contributes to improvements in sensitivity and charge retention
rate in en electrophotographic photoreceptor, a method for
producing the oxo-titanylphthalocyanine crystal, and an
electrophotographic photoreceptor.
[0003] 2. Description of the Related Art
[0004] Generally, as electrophotographic photoreceptors for use in
electrophotographic devices such as copying machines and laser
printers, many organic photoreceptors have been used to cope with,
for example, demands for low costs and a resistance to
environmental pollution. As charge generating agents for use in
such organic photoreceptors, widely used are phthalocyanine type
pigments sensitive to infrared or near-infrared light emitted from
a semiconductor laser, infrared LED or the like.
[0005] Also, it is known that such phthalocyanine type pigments
include non-metal phthalocyanine compounds, copper phthalocyanine
compounds, titanylphthalocyanine compounds and the like depending
on their chemical structures, and also, each phthalocyanine
compound can take various crystal forms by a difference in
production conditions.
[0006] It is known that when an electrophotographic photoreceptor
using oxo-titanylphthalocyanine compound having a Y-type crystal
structure as the charge generating agent is produced in the
presence of many types of phthalocyanine compound crystals
differing in crystal type, electric characteristics in the
electrophotographic photoreceptor are more improved as compared
with the case of using oxo-titanylphthalocyanine having other
crystal types.
[0007] With regard to the Y-type oxo-titanylphthalocyanine crystal,
a method for producing an oxo-titanylphthalocyanine crystal having
a maximum diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.3.degree. with respect to CuK.alpha.
ray in an X-ray diffraction spectrum is disclosed, wherein an
organic compound capable of forming a phthalocyanine ring and a
titanium compound are made to react with each other at 130.degree.
C. for about 4 hours in dialkylamino alcohol to which urea or
ammonia is added (for example, refer to the following patent
document 1).
[0008] Also, a method for producing an oxo-titanylphthalocyanine
crystal is disclosed in which o-phthalonitrile is made to react
directly with titanium tetrabutoxide without using a urea compound
at 215.degree. C. for about 2 hours (for example, refer to the
following patent documents 2 and 3).
[0009] More specifically, disclosed is a method for producing an
oxo-titanylphthalocyanine crystal having a peak in a predetermined
range in a CuK.alpha. characteristic X-ray diffraction spectrum and
no temperature variation peak in a temperature range from 50 to
400.degree. C. in differential scanning calorimetric analysis.
[0010] However, in the case of the patent document 1, the addition
proportion of the titanium compound to the organic compound capable
of forming a phthalocyanine ring is small whereas the addition
proportion of urea and the like to the organic compound capable of
forming a phthalocyanine ring is excessive and also, reaction
temperature is low. There is therefore the problem that produced
Y-type oxo-titanylphthalocyanine crystals tend to undergo crystal
transition into .beta.-type or .alpha.-type crystals in a
photoreceptive layer application liquid. For this reason, the
photoreceptive layer application liquid is deteriorated in storage
stability, with the result that there is the problem that no
photoreceptive layer having good electric properties can be stably
formed.
[0011] On the other hand, in the case of using the
oxo-titanylphthalocyanine crystals described in the patent
documents 2 and 3, there is a problem concerning low dispersibility
in a photoreceptive layer though the crystal transition in the
photoreceptive layer application liquid can be suppressed to some
extent. As a result, there are problems concerning reduced
sensitivity and reduced charge retention rate in
electrophotographic photoreceptors using the
oxo-titanylphthalocyanine crystals as charge generating agents.
[Patent document 1] JP-A H08-176456 (examples)
[Patent document 2] JP 3463032 (claims)
[Patent document 3] JP-A 2004-145284 (claims)
SUMMARY OF THE INVENTION
[0012] In view of this situation, the inventors of the present
invention have made earnest studies concerning the above problems,
and as a result, found that an oxo-titanylphthalocyanine crystal
which is stable and is superior in dispersibility in a
photoreceptive layer can be obtained by washing a wet cake, which
is an intermediate product, with a predetermined alcohol in a
process of producing an oxo-phthalocyanine crystal having
predetermined optical characteristics and thermal stability.
[0013] Specifically, it is an object of the present invention to
provide an oxo-titanylphthalocyanine crystal which is stable, is
superior in dispersibility in a photoreceptive layer and
efficiently contributes to improvements in sensitivity and charge
retention rate of an electrophotographic photoreceptor when it is
contained in the electrophotographic photoreceptor as a charge
generating agent, a method for producing the
oxo-titanylphthalocyanine crystal, and an electrophotographic
photoreceptor.
[0014] According to an aspect of the present invention, there is
provided an oxo-titanylphthalocyanine crystal having a maximum
diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum and one peak in a
temperature range from 270 to 400.degree. C. other than the peak
derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by a production method including the
following steps (a) to (d), whereby the aforementioned problem can
be solved:
[0015] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0016] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0017] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0018] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0019] Crystal transition to an .alpha.-type crystal and
.beta.-type crystal can be efficiently suppressed even when the
oxo-titanylphthalocyanine crystal is dipped for a term as long as 7
days or more, for example, insofar as it has predetermined optical
characteristics and thermal characteristics.
[0020] The oxo-titanylphthalocyanine crystal can improve
dispersibility in the photoreceptive layer insofar as it is
produced through the predetermined process.
[0021] The effect of improving dispersibility is considered to be
obtained by washing the wet cake with a predetermined alcohol in
the step (c), thereby reforming the surface characteristics of the
oxo-titanylphthalocyanine crystal.
[0022] In any case, the oxo-titanylphthalocyanine crystal of the
present invention is stable and is superior in dispersibility in
the photoreceptive layer, and therefore, efficiently contributes to
improvements in sensitivity and charge retention rate of an
electrophotographic photoreceptor when it is contained in the
electrophotographic photoreceptor as a charge generating agent.
[0023] The wet cake shows the condition that oxo-phthalocyanine is
dispersed in a relatively small amount of, for example, water and
has a block form.
[0024] Also, when constituting the oxo-titanylphthalocyanine
crystal of the invention, the production method preferably includes
the following inspection steps (e) to (g) after the step (d):
[0025] (e) a step of adding the oxo-titanylphthalocyanine crystal
in an amount by weight of 1.25 parts based on 100 parts by weight
of a mixed solvent of methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension;
[0026] (f) a step of filtering the suspension with a filter to
obtain a filtrate; and
[0027] (g) a step of confirming that the absorbance of the filtrate
for light having a wavelength of 400 nm is a value in a range from
0.01 to 0.08.
[0028] Such a constitution ensures that when the absorbance of the
filtrate is measured, the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer can
be evaluated easily and quantitatively.
[0029] The reason why the absorbance for light having a wavelength
of 400 nm is measured as an index of dispersibility is that a
correlation among the absorbance for the light having such a
wavelength, the dispersibility of the oxo-titanylphthalocyanine
crystal and the electric characteristics of the electrophotographic
photoreceptor caused by the dispersibility has been empirically
found.
[0030] Also, such a correlation is considered to be created because
the condition of reformation of surface characteristics of the
oxo-titanylphthalocyanine crystal is reflected on the absorbance
for the light having a wavelength of 400 nm.
[0031] Further, when the oxo-titanylphthalocyanine crystal of the
invention is constituted, the acid used in the step (a) is
preferably at least one type selected from the group consisting of
concentrated sulfuric acid, trifluoroacetic acid and sulfonic
acid.
[0032] With such a constitution, impurities can be decomposed
efficiently by such an acid whereas the decomposition of the
oxo-titanylphthalocyanine compound can be suppressed with high
efficiency.
[0033] Furthermore, when constituting the oxo-titanylphthalocyanine
crystal of the invention, the poor solvent used in the step (b) is
preferably water.
[0034] With such a constitution, the surface area of the wet cake
obtained can be increased, which allows the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer to be
improved more efficiently in the subsequent washing step.
[0035] Moreover, when the oxo-titanylphthalocyanine crystal of the
invention is constituted, the alcohol having 1 to 4 carbon atoms
which is used in the step (c) is preferably at least one type
selected from the group consisting of methanol, ethanol and
1-propanol.
[0036] Such a constitution makes it possible to even more
efficiently improve the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer.
[0037] Also, when the oxo-titanylphthalocyanine crystal of the
invention is constituted, it is preferable that the wet cake is
washed with an alcohol having 1 to 4 carbon atoms and then, further
washed with water in the step (c).
[0038] Such a constitution effectively suppresses the crystal
transition of the oxo-titanylphthalocyanine crystal more
efficiently, so that a more stable oxo-titanylphthalocyanine
crystal can be obtained.
[0039] Also, when the oxo-titanylphthalocyanine crystal of the
invention is constituted, the oxo-titanylphthalocyanine crystal
preferably has a maximum diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum measured after the
crystal is dipped in an organic solvent for 24 hours and no peak at
26.2.degree..
[0040] Such a constitution enables a further improvement in the
stability of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer application liquid.
[0041] According to another aspect of the present invention, there
is provided a method for producing an oxo-titanylphthalocyanine
crystal, the oxo-titanylphthalocyanine crystal having a maximum
diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum and one peak in a
temperature range from 270 to 400.degree. C. other than the peak
derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the method including the following
steps (a) to (d):
[0042] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0043] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0044] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0045] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0046] Specifically, an oxo-titanylphthalocyanine crystal having
predetermined optical characteristics and thermal characteristics
is produced through predetermined steps, which results in the
production of an oxo-titanylphthalocyanine crystal which is stable
and is superior in dispersibility in a photoreceptive layer, and
therefore efficiently contributes to improvements in sensitivity
and charge retention rate of an electrophotographic photoreceptor
when it is contained in the electrophotographic photoreceptor as a
charge generating agent
[0047] Also, when executing the method for producing an
oxo-titanylphthalocyanine crystal according to the invention, the
method preferably includes the following inspection steps (e) to
(g) after the step (d):
[0048] (e) a step of adding the oxo-titanylphthalocyanine crystal
in an amount by weight of 1.25 parts based on 100 parts by weight
of a mixed solvent of methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension;
[0049] (f) a step of filtering the suspension with a filter to
obtain a filtrate; and
[0050] (g) a step of confirming that the absorbance of the filtrate
for light having a wavelength of 400 nm is a value in a range from
0.01 to 0.08.
[0051] Such a constitution ensures that when the absorbance of the
filtrate is measured, the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer can
be evaluated easily and quantitatively.
[0052] Accordingly, an oxo-titanylphthalocyanine crystal which is
stable and is superior in dispersibility in the photoreceptive
layer can be produced more stably.
[0053] According to a still another aspect of the present
invention, there is provided an electrophotographic photoreceptor
including a substrate and a photoreceptive layer containing a
charge generating agent, a charge transfer agent and a binding
resin formed on the substrate, wherein the charge generating agent
is an oxo-titanylphthalocyanine having a maximum diffraction peak
at a Bragg angle (2.theta..+-.0.2.degree.)=27.2.degree. in the
CuK.alpha. characteristic X-ray diffraction spectrum and one peak
in a temperature range from 270 to 400.degree. C. other than the
peak derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by the following steps (a) to (d):
[0054] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0055] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0056] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0057] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0058] Specifically, a predetermined oxo-titanylphthalocyanine
crystal which is stable and is superior in dispersibility in the
photoreceptive layer is contained as the charge generating agent,
which enables an electrophotographic photoreceptor having excellent
sensitivity and charge retention rate to be obtained.
[0059] Also, when the electrophotographic photoreceptor of the
invention is constituted, the following relationship (1) is
preferably established among the reflection absorbance (A/-) of the
photoreceptive layer for light having a wavelength of 700 nm, the
film thickness (d/m) of the photoreceptive layer and the
concentration (C/wt %) of the oxo-titanylphthalocyanine crystal in
the photoreceptive layer.
AC.sup.-1d.sup.-1>1.75.times.10.sup.-4 (1)
[0060] Such a constitution makes it possible to confirm with ease
the dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] FIG. 1 is a graph for explaining the relationship between
the absorbance and the sensitivity;
[0062] FIG. 2 is a graph for explaining the relationship between
the absorbance and the charge retention rate;
[0063] FIG. 3 is a graph for explaining the relationship between
the dispersibility and the sensitivity;
[0064] FIGS. 4A and 4B are views for explaining the configuration
of a monolayer type electrophotographic photoreceptor according to
the present invention;
[0065] FIGS. 5A and 5B are views for explaining a method for
measuring the reflection absorbance of a photoreceptive layer;
[0066] FIGS. 6A and 6B are views for explaining the configuration
of a laminate type electrophotographic photoreceptor according to
the present invention;
[0067] FIG. 7 is a CuK.alpha. characteristic X-ray diffraction
spectrum of an oxo-titanylphthalocyanine crystal used in examples;
and
[0068] FIG. 8 is a differential scanning analysis chart of an
oxo-titanylphthalocyanine crystal used in examples.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0069] A first embodiment of the present invention relates to an
oxo-titanylphthalocyanine crystal having a maximum diffraction peak
at a Bragg angle (2.theta..+-.0.2.degree.)=27.2.degree. in a
CuK.alpha. characteristic X-ray diffraction spectrum and one peak
in a temperature range from 270 to 400.degree. C. other than the
peak derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by a production method including the
following steps (a) to (d):
[0070] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0071] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0072] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0073] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0074] The oxo-titanylphthalocyanine crystal will be explained in
more detail. The steps (a) to (d) will be explained in the
subsequent second embodiment, and in this first embodiment, the
characteristics, etc. of the oxo-titanylphthalocyanine crystal
itself will be explained.
1. Oxo-Titanylphthalocyanine Compound
[0075] As an oxo-titanylphthalocyanine compound constituting the
oxo-titanylphthalocyanine crystal of the invention, compounds
represented by the following formula (1) are preferable.
[0076] This is because an oxo-titanylphthalocyanine compound having
such a structure not only enables further improvement in stability
of the oxo-titanylphthalocyanine crystal but also enables such an
oxo-titanylphthalocyanine crystal to be produced stably.
[0077] Also, particularly, the oxo-titanylphthalocyanine crystal
preferably has a structure represented by the following formula
(2). Among these compounds, unsubstituted oxo-titanylphthalocyanine
compounds represented by the following formula (3) are particularly
preferable.
[0078] This is because the use of an oxo-titanylphthalocyanine
compound having such a structure makes it possible to more easily
produce an oxo-titanylphthalocyanine crystal having more stable
qualities:
##STR00001##
(In the general formula (1), X.sup.1, X.sup.2, X.sup.3 and X.sup.4,
which may be the same or different substituents, each represents a
hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a
cyano group or a nitro group, and repeat units a, b, c and d, which
may be the same or different, each denote an integer from 1 to
4.)
##STR00002##
(In the general formula (2), X represents a hydrogen atom, a
halogen atom, an alkyl group, an alkoxy group, a cyano group or a
nitro group and a repeat unit e denotes an integer from 1 to
4.)
##STR00003##
[0079] 2. Oxo-Titanylphthalocyanine Crystal
(1) Optical Characteristics
[0080] The oxo-titanylphthalocyanine crystal of the present
invention is characterized by such optical characteristics that it
has a maximum diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum (first optical
characteristics).
[0081] It is preferable that the oxo-titanylphthalocyanine crystal
of the invention has no peak at 26.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum (second optical
characteristics).
[0082] It is also preferable that the oxo-titanylphthalocyanine
crystal of the invention has no peak at a Bragg angle
(2.theta..+-.0.2.degree.)=7.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum (third optical
characteristics).
[0083] This is because if an oxo-titanylphthalocyanine crystal
which is not provided with the first optical characteristics is
used, there is a tendency that the stability of crystals in an
organic solvent and charge generating ability are deteriorated more
significantly than in the case of using an
oxo-titanylphthalocyanine crystal provided with the first optical
characteristics. Conversely speaking, this is because if an
oxo-titanylphthalocyanine crystal is provided with the first
optical characteristics, more preferably, the second and third
characteristics, the stability of a crystal in an organic solvent
and charge generating ability can be improved.
[0084] It is preferable that the oxo-titanylphthalocyanine crystal
has a maximum diffraction peak at least at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. and no peak at a Bragg angle
(2.theta..+-.0.2.degree.)=26.2.degree. in the CuK.alpha.
characteristic X-ray diffraction spectrum measured after dipped for
24 hours in an organic solvent.
[0085] This reason is that when the oxo-titanylphthalocyanine
crystal has such characteristics, the stability of the crystal with
time and dispersibility of the crystal in the photoreceptive layer
application liquid can be more improved.
[0086] Specifically, this is because it can be confirmed that even
in the case of dipping the oxo-titanylphthalocyanine crystal for 24
hours in an organic solvent such as tetrahydrofuran in actual, the
crystal type is not transited to an .alpha. or .beta.-type but
retains a predetermined crystal type, and it is therefore possible
to control crystal transition in an organic solvent.
[0087] Note that the dipping experiment in an organic solvent for
evaluation, which is a criterion for the evaluation of the storage
stability of the oxo-titanylphthalocyanine crystal is preferably
made in the same condition that is used to actually store, for
example, a photoreceptive layer application liquid used to
manufacture the electrophotographic photoreceptor (hereinafter
referred to simply as photoreceptor application liquid). It is
therefore preferable to evaluate the storage stability of the
oxo-titanylphthalocyanine crystal in a closed system under the
condition of a temperature of 23.+-.1.degree. C. and a relative
humidity of 50 to 60% RH, for example.
[0088] Also, the organic solvent used when evaluating the storage
stability of the oxo-titanylphthalocyanine crystal is preferably at
least one type selected from the group consisting of
tetrahydrofuran, dichloromethane, toluene, 1,4-dioxane and
1-methoxy-2-propanol.
[0089] This is because when such an organic solvent is used as the
organic solvent in the photoreceptive layer application liquid, the
stability of the oxo-titanylphthalocyanine crystal can be estimated
more exactly, and also, the solvent is highly compatible with, for
example, the oxo-titanylphthalocyanine crystal, charge transfer
agent and binding resin. Accordingly, a photoreceptor that allows,
for example, the oxo-titanylphthalocyanine crystal and charge
transfer agent to exhibit their characteristics can be formed, and
an electrophotographic photoreceptor superior in electric
characteristics and image characteristics can be produced
resultantly.
(2) Thermal Characteristics
[0090] The oxo-titanylphthalocyanine crystal according to the
invention is also characterized by such thermal characteristics
that it has one peak in a temperature range from 270 to 400.degree.
C. other than the peak derived from vaporization of adsorbed water
in differential scanning calorimetric analysis.
[0091] This is because crystal transition of the crystal structure
to an .alpha.-type crystal and .beta.-type crystal can be
efficiently suppressed even when the oxo-titanylphthalocyanine
crystal is dipped in an organic solvent for a long term insofar as
it has the aforementioned optical characteristics and thermal
characteristics. Therefore, a photoreceptive layer application
liquid superior in storage stability can be obtained by using such
an oxo-titanylphthalocyanine crystal, with the result that an
electrophotographic photoreceptor superior in electric
characteristics and image characteristics can be stable
produced.
[0092] The aforementioned one peak which is a peak other than the
peak derived from the vaporization of adsorbed water and appears in
a temperature range from 270 to 400.degree. C. appears more
preferably in a temperature range from 290 to 400.degree. C., and
still more preferably in a temperature range from 300 to
400.degree. C.
[0093] A specific method for measuring the Bragg angle in the
CuK.alpha. characteristic X-ray diffraction spectrum and a specific
method of differential scanning calorimetric analysis will be
explained in detail in Examples described later.
Second Embodiment
[0094] A second embodiment of the present invention relates to a
method for producing an oxo-titanylphthalocyanine crystal having a
maximum diffraction peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. in a CuK.alpha.
characteristic X-ray diffraction spectrum and one peak in a
temperature range from 270 to 400.degree. C. other than the peak
derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the method including the following
steps (a) to (d):
[0095] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0096] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0097] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0098] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0099] The content which has already been explained in the first
embodiment will be properly omitted to explain the method for
producing an oxo-titanylphthalocyanine compound according to the
second embodiment.
1. Production of oxo-titanylphthalocyanine Compound
[0100] In the method for producing an oxo-titanylphthalocyanine
compound, production materials of this molecule, specifically,
o-phthalonitrile or its derivative, or 1,3-diiminoisoindoline or
its derivative, titanium alkoxide or titanium tetrachloride are
preferably made to rear with each other in the presence of a urea
compound to produce an oxo-titanylphthalocyanine compound.
[0101] Specifically, the method is preferably performed according
to the following reaction formula (1) or (2). In the reaction
formula (1) or (2), titanium tetrabutoxide represented by the
formula (5) is used as titanium alkoxide, by way of example.
(1) Reaction Formula
[0102] It is therefore preferable that o-phthalonitrile represented
by the formula (4) is made to react with titanium tetrabutoxide as
the titanium alkoxide represented by the formula (5) as shown in
the reaction formula (1) or 1,3-diiminoisoindoline represented by
the formula (6) is made to react with titanium tetrabutoxide as the
titanium alkoxide represented by the formula (5) as shown in the
reaction formula (2), to produce an oxo-titanylphthalocyanine
compound represented by the formula (3).
[0103] In this case, titanium tetrachloride may be used in place of
the titanium alkoxide such as titanium tetrabutoxide represented by
the formula (5).
##STR00004##
(2) Addition Quantity
[0104] The addition quantity of the titanium alkoxide such as
titanium tetrabutoxide represented by the formula (5) or titanium
tetrachloride is preferably a value ranging from 0.40 to 0.53 mol
based on 1 mol of o-phthalonitrile represented by the formula (4)
or its derivative or of 1,3-diiminoisoindoline represented by the
formula (6) or its derivative.
[0105] This is because when the titanium alkoxide such as titanium
tetrabutoxide represented by the formula (5) or titanium
tetrachloride is added in an amount exceeding 1/4 mol equivalents
to o-phthalonitrile represented by the formula (4) or its
derivative or to 1,3-diiminoisoindoline represented by the formula
(6) or its derivative, an interaction with a urea compound which
will be explained later is effected in an efficient manner. Such an
interaction will be described in detail in the paragraph as to the
urea compound.
[0106] Therefore, the addition quantity of the titanium alkoxide
such as titanium tetrabutoxide represented by the formula (5) or
titanium tetrachloride is more preferably a value ranging from 0.42
to 0.50 mol, and still more preferably a value ranging from 0.45 to
0.47 mol based on 1 mol of o-phthalonitrile represented by the
formula (4) or 1,3-diiminoisoindoline represented by the formula
(6), etc.
(3) Urea Compound
[0107] Also, the reaction represented by the above reaction
formulae (1) and (2) is preferably made in the presence of a urea
compound. This is because when an oxo-titanylphthalocyanine
compound produced in the presence of a urea compound is used, an
interaction between the urea compound and titanium alkoxide or
titanium tetrachloride is effected to thereby obtain a specific
oxo-titanylphthalocyanine crystal efficiently.
[0108] Specifically, the interaction means an action of the
materials concerned on promotion of the reaction represented by the
reaction formulae (1) and (2) wherein ammonia produced by the
reaction of the urea compound with the titanium alkoxide or
titanium tetrachloride further forms a complex with titanium
alkoxide or titanium chloride and the complex more promotes the
reaction. Such a promotion action makes it possible to efficiently
produce an oxo-titanylphthalocyanine crystal resistant to crystal
transition even in an organic solvent by reacting the raw
materials.
(3)-1 Type
[0109] The urea compound to be used in the reaction formulae (1)
and (2) is preferably at least one type selected from the group
consisting of urea, thiourea, O-methylisourea sulfate,
O-methylisourea carbonate and O-methylisourea hydrochloride.
[0110] This reason is that when such a urea compound is used as the
urea compound shown in the reaction formulae (1) and (2), ammonia
generated in the reaction process forms a complex in combination
with titanium alkoxide or titanium tetrachloride more efficiently
and the complex further promotes the reaction represented by the
reaction formulae (1) and (2).
[0111] Specifically, ammonia generated by the reaction between
titanium alkoxide or titanium tetrachloride as a raw material and a
urea compound further efficiently forms a complex compound in
combination with titanium alkoxide, etc. Therefore, the complex
compound further promotes the reaction represented by the reaction
formulae (1) and (2).
[0112] It has been clarified that such a complex compound tends to
be produced peculiarly when the reaction is made at a temperature
as high as 180.degree. C. or more. For this reason, it is more
effective to perform the reaction in a nitrogen-containing
compound, for example, quinoline (boiling point: 237.1.degree. C.)
or isoquinoline (boiling point: 242.5.degree. C.) or a mixture of
them (by weight ratio: 10:90 to 90:10).
[0113] Among the aforementioned urea compounds, urea is more
preferably used because ammonia which is a reaction accelerator and
the complex compound generated by the aid of ammonia are generated
more easily.
(3)-2 Addition Quantity
[0114] The addition quantity of the urea compound to be used in the
reaction represented by the reaction formulae (1) and (2) is
preferably a value in a range from 0.1 to 0.95 mol based on 1 mol
of o-phthalonitrile or its derivative or 1,3-diiminoisoindoline or
its derivative.
[0115] This is because the action of the urea compound described
above can be exhibited when the addition quantity of the urea
compound is made to fall in the above range.
[0116] Therefore, the addition quantity of the urea compound is
more preferably a value in a range from 0.2 to 0.8 mol, and still
more preferably a value in a range from 0.3 to 0.7 mol based on 1
mol of o-phthalonitrile or its derivative or 1,3-diiminoisoindoline
or its derivative.
(4) Solvent
[0117] Examples of the solvent to be used in the reaction
represented by the reaction formulae (1) and (2) include a single
compound or a combination of two or more compounds selected from
the group consisting of: hydrocarbon type solvents such as xylene,
naphthalene, methylnaphthalene, tetralin and nitrobenzene;
hydrocarbon halide type solvents such as dichlorobenzene,
trichlorobenzene, dibromobenzene and chloronaphthalene; alcoholic
solvents such as hexanol, octanol, decanol, benzyl alcohol,
ethylene glycol and diethylene glycol; ketone type solvents such as
cyclohexanone, acetophenone, 1-methyl-2-pyrrolidone and
1,3-dimethyl-2-imidazolidinone; amide type solvents such as
formamide and acetamide; and nitrogen-containing solvents such as
picoline, quinoline and isoquinoline.
[0118] Particularly, nitrogen-containing compounds having a boiling
point of 180.degree. C. or more, such as quinoline and
isoquinoline, are preferable solvents because ammonia produced by
the reaction of the titanium alkoxide or titanium tetrachloride as
the raw material with the urea compound tends to form a complex
with titanium alkoxide or the like more efficiently.
(5) Reaction Temperature
[0119] The temperature of the reaction represented by the reaction
formulae (1) and (2) is preferably designed to be a temperature as
high as 150.degree. C. or more. This is because if the reaction
temperature is less than 150.degree. C., particularly 135.degree.
C. or less, titanium alkoxide or titanium tetrachloride as the raw
material scarcely reacts with the urea compound, which makes it
difficult to form a complex compound. This gives difficulty in
producing the situation where the complex compound further promotes
the reaction represented by the reaction formulae (1) and (2). It
is therefore difficult to produce an oxo-titanylphthalocyanine
crystal which is resistant to crystal transition even in an organic
solvent in an efficient manner resultantly.
[0120] Accordingly, the temperature of the reaction represented by
the reaction formulae (1) and (2) is more preferably a value in a
range from 180 to 250.degree. C., and still more preferably a value
in a range from 200 to 240.degree. C.
(6) Reaction Time
[0121] The reaction time in the reaction represented by the
reaction formulae (1) and (2), though depending on the reaction
temperature, is preferably in a range from 0.5 to 10 hours. This is
because if the reaction time is less than 0.5 hours, the titanium
alkoxide or titanium tetrachloride as the raw material scarcely
reacts with the urea compound, thereby giving difficulty in forming
a complex compound. This makes it difficult for the complex
compound to further promote the reaction represented by the
reaction formulae (1) and (2), with the result of difficulty in
producing an oxo-titanylphthalocyanine crystal which is resistant
to crystal transition even in an organic solvent in an efficient
manner. If the reaction time exceeds 10 hours, on the other hand,
this may be economically disadvantageous or the produced complex
compound may be decreased.
[0122] Therefore, the reaction time in the reaction represented by
the reaction formulae (1) and (2) is more preferably a value in a
range from 0.6 to 3.5 hours, and still more preferably a value in a
range from 0.8 to 3 hours.
2. Method for Producing an oxo-titanylphthalocyanine Crystal
(1) Pre-Acid Treatment Step
[0123] Then, as a pre-stage prior to acid treatment for the
oxo-titanylphthalocyanine compound produced in the above step or
other steps, a pre-acid treatment step is preferably performed in
which the oxo-titanylphthalocyanine compound is added in an aqueous
organic solvent, the mixture is stirred under heating for a fixed
time and then the solution is allowed to stand at a temperature
lower than the stirring temperature for a fixed time, followed by
being subjected to stabilizing treatment.
[0124] Examples of the aqueous organic solvent used in the pre-acid
treatment include one type or two or more types of alcohols such as
methanol, ethanol and isopropanol, N,N-dimethylformamide,
N,N-dimethylacetamide, propionic acid, acetic acid,
N-methylpyrrolidone and ethylene glycol. A nonaqueous organic
solvent may be added to an aqueous organic solvent if its amount is
small.
[0125] Though no particular limitation is imposed on the condition
of the stirring treatment in the pre-acid treatment step, it is
preferable to perform stirring treatment in the condition of a
fixed temperature of about 70 to 200.degree. C. for about 1 to 3
hours.
[0126] Moreover, though there is no particular limitation to the
condition of the stabilizing treatment after the stirring
treatment, the solution is preferably allowed to stand in the
condition of a fixed temperature range of about 10 to 50.degree. C.
and particularly about 23.+-.1.degree. C. for 5 to 15 hours to
stabilize. The pre-acid treatment is executed in this manner to
obtain a crude oxo-titanylphthalocyanine crystal.
(2) Acid Treatment Step
[0127] Then, the acid treatment step is characterized in that the
crude oxo-titanylphthalocyanine crystal is dissolved in an acid to
obtain an oxo-titanylphthalocyanine solution.
[0128] This is because the crude oxo-titanylphthalocyanine crystal
is dissolved in an acid to enable to sufficiently decompose
impurities derived from substances left unremoved when the
oxo-titanylphthalocyanine compound is produced.
[0129] The acid to be used is preferably at least one type selected
from the group consisting of concentrated sulfuric acid,
trifluoroacetic acid and sulfonic acid.
[0130] This reason is that such an acid can decompose the
above-described impurities more efficiently whereas it can
efficiently suppress decomposition of the oxo-titanylphthalocyanine
compound.
[0131] Also, the reason is that after such an acid treatment,
components derived from these acids can be easily removed by
washing as will be explained later.
[0132] The acid treatment step is preferably executed usually at 0
to 10.degree. C. for 0.5 to 3.0 hours, though these conditions
differ depending on the acid to be used.
(3) Dropwise Addition Step
[0133] Then, the oxo-titanylphthalocyanine solution obtained in the
acid treatment step is added dropwise to a poor solvent to obtain a
wet cake.
[0134] This is because washing effect in the subsequent washing
step can be produced efficiently by adding the
oxo-titanylphthalocyanine solution dropwise to a poor solvent.
[0135] Specifically, this is because the wet cake of the
precipitated oxo-titanylphthalocyanine compound is put into an
amorphous state having a large surface area by the dropwise
addition, and therefore, the washing effect in the subsequent
washing step can be produced efficiently.
[0136] Also, the poor solvent to be used is preferably water.
[0137] This reason is that water can precipitate an
oxo-titanylphthalocyanine compound more easily from the viewpoint
of polarity and temperature control.
[0138] Consequently, the surface area of the wet cake of the
precipitated oxo-titanylphthalocyanine compound is increased to
perform the washing step more efficiently.
[0139] Other usable poor solvents may include methanol, ethanol or
a mixed solvent of methanol and water or a mixed solvent of ethanol
and water.
[0140] Note that the temperature of the poor solvent is usually
designed to be in a range from 0 to 20.degree. C., though it
differs depending on the type of the poor solvent to be used.
(4) Washing Step
[0141] Then, the wet cake of the oxo-titanylphthalocyanine compound
obtained in the dropwise addition step is washed with an alcohol
having 1 to 4 carbon atoms.
[0142] This is because washing the wet cake with an alcohol having
1 to 4 carbon atoms enables efficient improvement in the
dispersibility of the oxo-titanylphthalocyanine crystal obtained in
the subsequent crystal type transformation step in the
photoreceptive layer. The effect of improving the dispersibility is
considered to be obtained by reforming the surface properties of
the oxo-titanylphthalocyanine crystal.
[0143] In any case, the washing with a predetermined alcohol makes
it possible to stably obtain an oxo-titanylphthalocyanine crystal
which is superior in dispersibility in a photoreceptive layer and
contributes to improvements in sensitivity and charge retention
rate of an electrophotographic photoreceptor when the
oxo-titanylphthalocyanine crystal is added to the
electrophotographic photoreceptor as a charge generating agent.
[0144] The alcohol having 1 to 4 carbon atoms is preferably at
least one type selected from the group consisting of methanol,
ethanol and 1-propanol.
[0145] This reason is that any of these alcohols can improve the
dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer more efficiently.
[0146] It is also preferable that the wet cake is washed with an
alcohol having 1 to 4 carbon atoms, and then further washed with
water.
[0147] This is because when the wet cake is further washed with
water after washed with a predetermined alcohol, the crystal
transition of the oxo-titanylphthalocyanine crystal can be
suppressed to obtain a more stable oxo-titanylphthalocyanine
crystal.
[0148] The washing operations with an alcohol having 1 to 4 carbon
atoms and water are preferably repeated plural times,
respectively.
[0149] To mention the washing method in more detail, for example,
about 10 g of the wet cake may be dipped in about of 500 ml of a
predetermined alcohol or water and suspended by stirring or the
like to perform washing.
[0150] Also, the temperature of the predetermined alcohol or water
used in the washing is designed to be preferably in a range from 0
to 50.degree. C., and more preferably in a range from 10 to
40.degree. C. The washing time is designed to be preferably in a
range from 5 minutes to 10 hours, and more preferably in a range
from 0.5 to 8 hours.
(5) Crystal Type Transformation Step
[0151] Then, the wet cake obtained after the washing step is
stirred under heating in an nonaqueous solvent to obtain an
oxo-titanylphthalocyanine crystal.
[0152] This reason is that if the wet cake of the
oxo-titanylphthalocyanine crystal is stirred under heating in a
nonaqueous solvent, the crystal type can be transformed into a
predetermined crystal type having the optical characteristics and
thermal characteristics explained in the first embodiment.
[0153] In the above stirring under heating, the wet cake is
preferably dispersed in the nonaqueous solvent in the presence of
water and stirred at 30 to 70.degree. C. for 5 to 40 hours.
[0154] Examples of the nonaqueous solvent include halogen type
solvents such as chlorobenzene and dichloromethane.
(6) Inspection Step
[0155] The following inspection steps (e) to (g) are preferably
involved after the aforementioned crystal type transformation
step:
[0156] (e) a step of adding the oxo-titanylphthalocyanine crystal
in an amount by weight of 1.25 parts based on 100 parts by weight
of a mixed solvent of methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension;
[0157] (f) a step of filtering the suspension with a filter to
obtain a filtrate; and
[0158] (g) a step of confirming that the absorbance of the filtrate
for light having a wavelength of 400 nm is a value in a range from
0.01 to 0.08.
[0159] This reason is that if the absorbance of a predetermined
filtrate obtained through the above steps is measured, the
dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer can be evaluated easily and quantitatively,
and it is therefore possible to produce more stably an
oxo-titanylphthalocyanine crystal which is stable and is superior
in dispersibility in the photoreceptive layer.
[0160] Specifically, this is because when the absorbance of the
filtrate for light having a wavelength of 400 nm is less than 0.01,
a problem as to the formation of an oxo-titanylphthalocyanine
crystal itself may arise, whereas when the absorbance of the
filtrate for light having a wavelength of 400 nm exceeds 0.08, the
dispersibility of the oxo-titanylphthalocyanine crystal may tend to
decrease, which is a cause of a reduction in sensitivity and charge
retention rate in an electrophotographic photoreceptor.
[0161] Therefore, the absorbance of the filtrate for light having a
wavelength of 400 nm is more preferably a value in a range from
0.012 to 0.07, and still more preferably a value in a range from
0.012 to 0.05.
[0162] The reason why the absorbance for light having a wavelength
of 400 nm is measured as an index of dispersibility is that a
correlation among the absorbance for the light having such a
wavelength, the dispersibility of the oxo-titanylphthalocyanine
crystal and the electric characteristics of the electrophotographic
photoreceptor caused by the dispersibility has been empirically
found.
[0163] Also, such a correlation is considered to be created because
the condition of reformation of surface characteristics of the
oxo-titanylphthalocyanine crystal is reflected on the absorbance
for the light having a wavelength of 400 nm.
[0164] A method for measuring the absorbance of a predetermined
filtrate will be explained in Examples explained later.
[0165] As to the condition under which the suspension is obtained
in the step (e), a suspension obtained by stirring in the stirring
condition of a temperature of 23.+-.3.degree. C. and a rotational
speed of 100 rpm for 1 hour is used.
[0166] As to the amount of the mixed solvent used to suspend the
oxo-titanylphthalocyanine crystal, methanol and N-dimethylamide are
mixed in a total amount of 8 g (4 g each).
[0167] The amount of the oxo-titanylphthalocyanine crystal to be
suspended is designed to be 0.1 g.
[0168] Also, as the filter used to filter the suspension in the
step (f), a 0.1-.mu.m filter which is a PTFE type is used.
[0169] Moreover, the absorbing layer (filtrate) when the absorbance
is measured in the step (g) is designed to have a thickness of 10
mm (cell length).
[0170] Then, 1.25 parts by weight of a predetermined
oxo-titanylphthalocyanine crystal is added to 100 parts by weight
of a mixed solvent of methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension, and then, the suspension is filtered with a filter to
obtain a filtrate. With reference to FIG. 1, description will be
given to the relation between the absorbance of the filtrate for
light having a wavelength of 400 nm and the sensitivity of an
electrophotographic photoreceptor containing the
oxo-titanylphthalocyanine crystal as a charge generating agent.
[0171] Specifically, FIG. 1 shows a characteristic curve, in which
the abscissa is the absorbance (-) of the above predetermined
filtrate for light having a wavelength of 400 nm while the ordinate
is the absolute value (V) of the sensitivity of the
electrophotographic photoreceptor. For example, the configuration
of the electrophotographic photoreceptor and a method for measuring
the sensitivity will be described in Examples.
[0172] As is understood from the characteristic curve, the absolute
value (V) of the sensitivity increases with an increase in the
value of the absorbance (-) of the predetermined filtrate. Note
that a smaller absolute value (V) of the sensitivity means that the
electrophotographic photoreceptor has more excellent sensitivity
characteristics.
[0173] To explain more specifically, it is understood that as the
value of the absorbance (-) of the predetermined filtrate increases
0 to 0.08, the absolute value (V) of the sensitivity sharply
increases from about 40 V while the absolute value takes on a value
of about 60 V or less.
[0174] It is also understood that when the value of the absorbance
(-) of the predetermined filtrate exceeds 0.08 on the other hand,
the absolute value (V) of the sensitivity takes on a value as
higher as about 60 V or more, though an increase in the absolute
value (V) of the sensitivity is moderate.
[0175] Therefore, it is understood that in order to limit the
absolute value (V) of the sensitivity to about 60 V or less to
obtain excellent sensitivity characteristics, it is effective to
set the value of the absorbance (-) of the predetermined filtrate
to a value of 0.08 or less.
[0176] 1.25 parts by weight of a predetermined
oxo-titanylphthalocyanine crystal is added to 100 parts by weight
of a mixed solvent of methanol and N,N-dimethylformamide
(methanol:N,N-dimethylformamide=1:1 (by weight ratio)) to prepare a
suspension and then, the suspension is filtered with a filter to
obtain a filtrate. With reference to FIG. 2, description will be
given to the relation between the absorbance of the filtrate for
light having a wavelength of 400 nm and the charge retention rate
(%) of an electrophotographic photoreceptor containing the
oxo-titanylphthalocyanine crystal as a charge generating agent.
[0177] Specifically, FIG. 2 shows a characteristic curve, in which
the abscissa is the absorbance (-) of the above predetermined
filtrate for light having a wavelength of 400 nm while the ordinate
is the charge retention rate (%) of the electrophotographic
photoreceptor. For example, the configuration of the
electrophotographic photoreceptor and a method for measuring the
charge retention rate will be described in Examples.
[0178] As is understood from the characteristic curve, the value of
the charge retention rate (%) decreases with an increase in the
value of the absorbance (-) of the predetermined filtrate. Note
that a larger charge retention rate (%) means that an electrostatic
latent image formed on the surface of the electrophotographic
photoreceptor can be retained for a longer time and the
electrophotographic photoreceptor is superior in electric
characteristics.
[0179] To explain more specifically, it is understood that as the
value of the absorbance (-) of the predetermined filtrate increases
0 to 0.08, the value of the charge retention rate (%) slightly
sharply decreases from about 100% while the charge retention rate
(%) takes on a value of about 97.5% or more.
[0180] It is also understood that when the value of the absorbance
(-) of the predetermined filtrate exceeds 0.08 on the other hand,
the charge retention rate (%) takes on a value as low as about
97.5% or less, though a reduction in the value of the charge
retention rate (%) is moderate.
[0181] Therefore, it is understood that in order to keep the value
of the charge retention rate (%) at a level of about 97.5% or more
to obtain superior electric characteristics, it is effective to set
the value of the absorbance (-) of the predetermined filtrate to a
value of 0.08 or less.
[0182] Next, the relationship between the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer and
the sensitivity of the electrophotographic photoreceptor will be
explained with reference to FIG. 3.
[0183] Here, as the index of dispersibility, a parameter
(AC.sup.-1d.sup.-1) (unit: 1/(wt %m), the same as follows) is used
which is constituted of the reflection absorbance (A/-) for light
having a wavelength of 700 nm in the photoreceptive layer
containing the oxo-titanylphthalocyanine crystal, the film
thickness (d/m) of the photoreceptive layer and the concentration
(C/wt %) of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer. The parameter and a method for measuring the
reflection absorbance of the photoreceptive layer will be explained
later. Fundamentally, the parameter is used for the evaluation of
the dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer according to the Lambert-Beer's law.
[0184] Specifically, in FIG. 3, the abscissa is the value of
(AC.sup.-1d.sup.-1), the left ordinate is the absolute value (V) of
the sensitivity of the electrophotographic photoreceptor in
relation to a characteristic curve A and the right ordinate is the
dispersibility (relative evaluation) of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer in
relation to a characteristic curve B.
[0185] Also, the relative evaluation of the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer is
based on the results of observation using a microscope.
[0186] As is understood from the characteristic curve B, the
dispersibility (relative evaluation) of the
oxo-titanylphthalocyanine crystal is more improved with an increase
in the value of (AC.sup.-1d.sup.-1).
[0187] In other words, a larger value of (AC.sup.-1d.sup.-1) shows
that the dispersibility of the oxo-titanylphthalocyanine crystal in
the photoreceptive layer is higher.
[0188] Thus, it can be said that the dispersibility of the
oxo-titanylphthalocyanine crystal can be clearly evaluated by the
value of (AC.sup.-1d.sup.-1).
[0189] As is understood from the characteristic curve A, the
absolute value of the sensitivity is reduced with an increase in
the value of (AC.sup.-1d.sup.-1).
[0190] Therefore, when the results of the characteristic curves A
and B are evaluated overall, it can be said that the sensitivity of
the electrophotographic photoreceptor is more improved with an
increase in the dispersibility of the oxo-titanylphthalocyanine
crystal.
[0191] As a consequence, it can be said that the sensitivity of the
electrophotographic photoreceptor is improved more efficiently by
using the oxo-titanylphthalocyanine crystal superior in
dispersibility according to the present invention.
[0192] It has been separately confirmed that the charge retention
rate of the photographic photoreceptor is also clearly related with
the dispersibility of the oxo-titanylphthalocyanine crystal
similarly to the case of the sensitivity.
[0193] Note that when the electrophotographic photoreceptor is a
laminate type, the dispersibility of the oxo-titanylphthalocyanine
crystal may be evaluated by using its charge generating layer as
the subject.
Third Embodiment
[0194] A third embodiment of the present invention relates to an
electrophotographic photoreceptor including a substrate and a
photoreceptive layer containing a charge generating agent, a charge
transfer agent and a binding resin, the photoreceptive layer being
formed on the substrate, wherein the charge generating agent is an
oxo-titanylphthalocyanine crystal having a maximum diffraction peak
at a Bragg angle (2.theta..+-.0.2.degree.)=27.2.degree. in a
CuK.alpha. characteristic X-ray diffraction spectrum and one peak
in a temperature range from 270 to 400.degree. C. other than the
peak derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being produced by a production method including the
following steps (a) to (d):
[0195] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0196] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0197] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0198] (d) a step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine
crystal.
[0199] The contents which have been already explained in the first
and second embodiments are appropriately omitted, and the
electrophotographic photoreceptor of the third embodiment will be
explained by primarily taking a monolayer type photographic
photoreceptor as an example.
1. Basic Configuration
[0200] As shown in FIG. 4A, the basic configuration of an
electrophotographic photoreceptor 10 according to the invention
preferably includes a substrate 12 and a single photoreceptive
layer 14 formed on the substrate 12, the photoreceptive layer
containing a specific charge generating agent, a charge transfer
agent and a binding resin.
[0201] This reason is that the monolayer type electrophotographic
photoreceptor 10 can be applied to both positive and negative
charge types and also enables a simple layer structure, which makes
it possible to suppress coating film defects and to improve
productivity when the photoreceptive layer is formed.
[0202] This reason is also that optical characteristics can be
improved because the number of interfaces between layers is
small.
[0203] As is illustrated in FIG. 4B, a monolayer type photoreceptor
10' having an intermediate layer 16 formed between the
photoreceptive layer 14 and the substrate 12 may be adopted.
2. Substrate
[0204] Various materials having conductivity may be used as the
substrate 12 illustrated in FIG. 4. Examples of these materials
include metals such as iron, aluminum, copper, tin, platinum,
silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel,
palladium, indium, stainless steel and brass; plastic materials
coated with the above metal by deposition or lamination; and
glasses coated with, for example, alumite, aluminum iodide, tin
oxide or indium oxide.
[0205] The shape of the substrate may be any form including a
sheet-form and drum-form in accordance with the structure of an
image forming apparatus to be used. It is only required for the
substrate itself or its surface to have conductivity. In addition,
the substrate is preferably one having sufficient mechanical
strength upon use. In the case of a drum-form, the diameter of the
substrate is designed to be in a range from 10 to 60 mm, and more
preferably from 10 to 35 mm in view of developing a small-sized
device.
[0206] In order to prevent the generation of interference fringes,
the surface of the support substrate may be subjected to surface
roughing treatment using a method such as etching, anodic
oxidation, wet blasting method, sand blasting method, rough
abrasion and centerless cutting.
[0207] When the substrate is subjected to, for example, anodic
oxidation, the substrate may have nonconductive or semiconductive
characteristics. Even in such a case, it may be used as the
substrate insofar as it produces predetermined effects.
3. Intermediate Layer
[0208] As shown in FIG. 4B, an intermediate layer 16 containing a
predetermined binding resin may be formed on the substrate 12.
[0209] This is because the intermediate layer improves the adhesion
between the substrate and the photoreceptive layer and also, the
addition of the predetermined binding resin micropowder to the
intermediate layer ensures that incident light is scattered to
thereby suppress not only the generation of interference fringes
but also the injection of charges into the photoreceptive layer
during unexposed time, that is the cause of fogging and black
spots. Any material may be used as the micropowder without any
particular limitation insofar as it has light-scattering ability
and dispersibility. Examples of the micropowder include white
pigments such as titanium oxide, zinc oxide, zinc flower, zinc
sulfide, zinc white and lithopone; inorganic pigments as extenders
such as alumina, calcium carbonate and barium sulfate; fluororesin
particles; benzoguanamine resin particles; and styrene resin
particles.
[0210] The film thickness of the intermediate layer is preferably a
value in a range from 0.1 to 50 .mu.m. This is because if the
intermediate layer is too thick, residual potential may tend to
arise on the surface of the photoreceptor, which is a cause of
deteriorated electric characteristics, whereas if the intermediate
layer is too thin, the surface irregularities of the substrate can
be insufficiently flattened, thereby failing to obtain the adhesion
between the substrate and the photoreceptive layer.
[0211] For this reason, the thickness of the intermediate layer is
preferably a value in a range from 0.1 to 50 .mu.m, and more
preferably a value in a range from 0.5 to 30 .mu.m.
4. Photoreceptive Layer
(1) Binding Resin
[0212] No particular limitation is imposed on the type of the
binding resin to be used in the photographic photoreceptor of the
invention. Usable examples of the binding resin include, in
addition to a polycarbonate resin, thermoplastic resins such as a
polyester resin, polyarylate resin, styrene-butadiene copolymer,
styrene-acrylonitrile copolymer, styrene-maleic acid copolymer,
acryl copolymer, styrene-acrylic acid copolymer, polyethylene,
ethylene-vinyl acetate copolymer, polyethylene chloride, polyvinyl
chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate
copolymer, alkyd resin, polyamide, polyurethane, polysulfone,
diallyl phthalate resin, ketone resin, polyvinylbutyral resin and
polyether resin; crosslinking thermosetting resins such as a
silicone resin, epoxy resin, phenol resin, urea resin and melamine
resin; and photocurable resins such as epoxyacrylate and
urethaneacrylate.
(2) Charge Generating Agent
[0213] The charge generating agent to be used in the invention is
an oxo-titanylphthalocyanine crystal having a maximum diffraction
peak at a Bragg angle (2.theta..+-.0.2.degree.)=27.2.degree. in a
CuK.alpha. characteristic X-ray diffraction spectrum and one peak
in a temperature range from 270 to 400.degree. C. other than the
peak derived from vaporization of adsorbed water in differential
scanning calorimetric analysis, the oxo-titanylphthalocyanine
crystal being obtained by a production method including the
following steps (a) to (d):
[0214] (a) a step of dissolving a crude oxo-titanylphthalocyanine
crystal in an acid to obtain an oxo-titanylphthalocyanine
solution;
[0215] (b) a step of adding the oxo-titanylphthalocyanine solution
dropwise in a poor solvent to obtain a wet cake;
[0216] (c) a step of washing the wet cake with an alcohol having 1
to 4 carbon atoms; and
[0217] (d) A step of stirring the washed wet cake under heating in
a nonaqueous solvent to obtain an oxo-titanylphthalocyanine.
[0218] This is because such an oxo-titanylphthalocyanine crystal
has crystal stability and is also superior in dispersibility in the
photoreceptive layer, which enables to obtain an
electrophotographic photoreceptor having excellent sensitivity and
charge retention rate.
[0219] The details of the oxo-titanylphthalocyanine crystal as the
charge generating agent are overlapped on the descriptions in the
first and second embodiments, and are therefore omitted.
[0220] The addition quantity of the oxo-titanylphthalocyanine
crystal as the charge generating agent is preferably designed to be
in a range from 0.1 to 50 parts by weight based on 100 parts by
weight of the binding resin which will be explained later.
[0221] This reason is that if the addition quantity of the charge
generating agent is made to be in the above range, the charge
generating agent can generate charges efficiently when the
electrophotographic photoreceptor is exposed to light. In other
words, the reason is that if the addition quantity of the charge
generating agent is less than 0.1 part by weight based on 100 parts
by weight of the binding resin, the amount of the charge generating
agent may be not enough to form an electrostatic latent image on
the photoreceptor, whereas if the addition quantity of the charge
generating agent exceeds 50 parts by weight based on 100 parts by
weight of the binding resin, it may be difficult to disperse the
charge generating agent uniformly in the photoreceptive layer
application liquid.
[0222] For this reason, the addition quantity of the charge
generating agent is more preferably a value in a range from 0.5 to
30 parts by weight based on 100 parts by weight of the binding
resin.
(3) Hole Transfer Agent
[0223] Also, no particular limitation is imposed on the hole
transfer agent to be used in the invention, and conventionally
known various hole transfer compounds may be all used. Preferably
usable hole transfer compounds include a benzidine type compound, a
phenylenediamine type compound, a naphthylenediamine type compound,
a phenanethrylenediamine type compound, an oxadiazole type compound
(for example, 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), a
styryl type compound (for example,
9-(4-diethylaminostyryl)anthracene), a carbazole type compound (for
example, poly-N-vinylcarbazole), an organic polysilane compound, a
pyrazoline type compound (for example,
1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), a hydrazone type
compound, a triphenylamine type compound, an indole type compound,
an oxazole type compound, an isooxazole type compound, a thiazole
type compound, a thiadiazole type compound, an imidazole type
compound, a pyrazole type compound, a triazole type compound, a
butadiene type compound, a pyrene-hydrazone type compound, an
acrolein type compound, a carbazole-hydrazone type compound, a
quinoline-hydrazone type compound, a stilbene type compound, a
stilbene-hydrazone type compound and a diphenylenediamine type
compound. These compounds are used independently or may be used in
combinations of two or more.
[0224] Also, the addition quantity of the hole transfer agent is
preferably designed to be in a range from 1 to 120 parts by weight
of 100 parts by weight of the binding resin.
[0225] This is because if the addition quantity of the hole
transfer agent is less than 1 part by weight, the hole transfer
ability of the photoreceptive layer may be remarkably deteriorated
to thereby give an adverse influence on image characteristics,
whereas if the addition quantity of the hole transfer agent exceeds
120 parts by weight, this gives rise to the problem that the
dispersibility of the hole transfer agent is deteriorated and the
hole transfer agent is easily crystallized.
[0226] Therefore, the addition quantity of the hole transfer agent
is more preferably a value in a range from 5 to 100 parts by
weight, and still more preferably a value in a range from 10 to 90
parts by weight based on 100 parts by weight of the binding
resin.
(4) Electron Transfer Agent
[0227] No particular limitation is imposed on the electron transfer
agent to be used in the invention. Preferably usable electron
transfer agents include a benzoquinone type compound, a
naphthoquinone type compound, an anthraquinone type compound, a
diphenoquinone type compound, a dinaphthoquinone type compound, a
naphthalenetetracarboxylic acid diimide type compound, a fluorenone
type compound, a malononitrile type compound, a thiopyran type
compound, a trinitrothioxanthone type compound, a dinitroanthracene
type compound, a dinitroacridine type compound, a
nitroanthraquinone type compound, and a dinitroanthraquinone type
compound. These compounds are used independently or may be used in
combinations of two or more.
[0228] The addition quantity of the electron transfer agent is
preferably designed to be 1 to 120 parts by weight based on 100
parts by weight of the binding resin.
[0229] This is because if the addition quantity of the electron
transfer agent is less than 1 part by weight, the electron transfer
ability of the photoreceptive layer is remarkably deteriorated to
thereby give an adverse influence on image characteristics, whereas
if the addition quantity of the electron transfer exceeds 120 parts
by weight, this gives rise to the problem that the dispersibility
of the electron transfer agent is deteriorated and the electron
transfer agent is easily crystallized.
[0230] Therefore, the addition quantity of the electron transfer
agent is more preferably a value in a range from 5 to 100 parts by
weight, and still more preferably a value in a range from 10 to 90
parts by weight based on 100 parts by weight of the binding
resin.
(5) Thickness
[0231] The film thickness of the photoreceptive layer is preferably
designed to be in a range from 5.0 to 100 .mu.m.
[0232] This reason is that if the thickness of the photoreceptive
layer is less than 5.0 .mu.m, the mechanical strength required for
the electrophotographic photoreceptor may be insufficient, whereas
if the thickness of the photoreceptive layer exceeds 100 .mu.m, the
photoreceptive layer may tend to peel from the substrate and it may
be difficult to form the photoreceptive layer uniformly. For this
reason, the thickness of the photoreceptive layer is more
preferably a value in a range from 10 to 80 .mu.m, and still more
preferably a value in a range from 20 to 40 .mu.m.
(6) Relational Expression (1)
[0233] Also, the following relational expression (1) is preferably
established between the reflection absorbance (A/-) of the
photoreceptive layer for light having a wavelength of 700 nm, the
film thickness (d/m) of the photoreceptive layer and the
concentration (C/wt %) of the oxo-titanylphthalocyanine crystal in
the photoreceptive layer.
AC.sup.-1d.sup.-1>1.75.times.10.sup.-4 (1)
[0234] This reason is that in the case of a photoreceptive layer
satisfying the relational expression (1), the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer is
easily confirmed.
[0235] Specific reason is as follows: as explained with reference
to FIG. 3 in the second embodiment, there is a clear correlation
between the value of (AC.sup.-1d.sup.-1) (1/(wt %m)) which is the
left side of the relational expression (1) and the dispersibility
of the oxo-titanylphthalocyanine crystal in the photoreceptive
layer. Therefore, the dispersibility of the
oxo-titanylphthalocyanine crystal in the photoreceptive layer and
the electric characteristics of the electrophotographic
photoreceptor which are dependent on the dispersibility can be
easily confirmed by observing whether the value (AC.sup.-1d.sup.-1)
is in the predetermined range or not.
[0236] Here, the left side (AC.sup.-1d.sup.-1) of the relational
expression (1) is regarded as a parameter expressing the
dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer according to the Lambert-Beer's law.
[0237] Specifically, this reason is that when the film thickness
(d/m) of the photoreceptive layer and the concentration (C/wt %) of
the oxo-titanylphthalocyanine crystal in the photoreceptive layer
are fixed, incident light is scarcely absorbed and reflection
absorbance (A) for light having a wavelength of 700 nm tends to be
small if the dispersibility of the oxo-titanylphthalocyanine
crystal in the photoreceptive layer is insufficient, whereas if the
dispersibility of the oxo-titanylphthalocyanine crystal is
insufficient, incident light is easily absorbed and reflection
absorbance (A) of the photoreceptive layer for light having a
wavelength of 700 nm is large.
[0238] Therefore, it is understood from this reason that the
dispersibility of the oxo-titanylphthalocyanine crystal in the
photoreceptive layer can be evaluated from the value of the left
side (AC.sup.-1d.sup.-1) of the relational expression (1).
[0239] When the electrophotographic photoreceptor is a laminate
type, its charge generating layer is used as the subject to
evaluate the dispersibility of the oxo-titanylphthalocyanine
crystal.
[0240] With reference to FIG. 3, description will be given to the
relation between the value of AC.sup.-1d.sup.-1 (unit: 1/(wt %m),
the same as follows) which is the let side of the relational
expression (1)) and the sensitivity of the electrophotographic
photoreceptor.
[0241] Specifically, in FIG. 3, the abscissa is the value of
(AC.sup.-1d.sup.-1) and the ordinate (left axis) is the absolute
value (V) of the sensitivity to show a characteristic curve A.
[0242] As is understood from the characteristic curve A, as the
value of (AC.sup.-1d.sup.-1) is closer to 0, the absolute value (V)
of the sensitivity is larger, whereas as the value of
(AC.sup.-1d.sup.-1) is larger, the absolute value (V) of the
sensitivity is smaller. To mention in more detail, it is understood
that as the value of (AC.sup.-1d.sup.-1) is increased, the absolute
value (V) of the sensitivity sharply drops when the value of
(AC.sup.-1d.sup.-1) is in a range from 0 to 1.75.times.10.sup.4. It
is also understood that as the value of (AC.sup.-1d.sup.-1) is
increased, the absolute value (V) of the sensitivity gradually
drops and takes a value of 60 V or less when the value of
(AC.sup.-1d.sup.-1) is in a range above 1.75.times.10.sup.4.
[0243] The value of (AC.sup.-1d.sup.-1) is designed to be more
preferably 1.9.times.10.sup.4 or more and still more preferably
2.0.times.10.sup.4 or more.
[0244] The reflection absorbance (A/-) of the photoreceptive layer
for light having a wavelength of 700 nm may be measured, for
example, in the following manner.
[0245] First, the reflection absorbance (A.sub.1) of a support
substrate on which a photoreceptive layer (standard thickness:
2.5.times.10.sup.-5 m) is laminated, for light having a wavelength
of 700 nm is measured by a color difference meter (trade name:
Color Difference Meter CM1000, manufactured by Minolta Camera Co.,
Ltd.). Next, the reflection absorbance (A.sub.2) of a support
substrate on which no photoreceptive layer is laminated, for light
having a wavelength of 700 nm is measured in the same manner as
above.
[0246] More detailed explanations will be furnished with reference
to FIGS. 5A and 5B, in which FIG. 5A shows the condition of the
support substrate 12 on which the photoreceptive layer 14 is
laminated and FIG. 5B shows the condition of only the support
substrate 12 on which no photoreceptive layer 14 is laminated.
I.sub.0 in FIGS. 5A and 5B denotes the intensity of light (incident
light) applied to each support substrate, and I.sub.1 and I.sub.2
denote the intensities of the reflections of the lights incident to
the respective support substrates. In order to eliminate the
influence of the support substrate to obtain the reflection
absorbance of the photoreceptive layer, it is only necessary to
subtract the reflection absorbance A.sub.2 of the support substrate
from the reflection absorbance A.sub.1 in which the reflection
absorbances of the photoreceptive layer and support substrate are
intermingled.
[0247] Then, the reflection absorbance (A) of an intermediate layer
may be calculated from the following numerical formula (1) based on
the values (A.sub.1, A.sub.2) of the obtained reflection
absorbances.
[0248] The reflection absorbance (A.sub.1) in FIG. 5A is calculated
from the following numerical formula (2), and, similarly, the
reflection absorbance (A.sub.2) in FIG. 5B is calculated from the
following numerical formula (3).
A=A.sub.1-A.sub.2 (1)
A.sub.1=-Log I.sub.1/I.sub.0 (2)
A.sub.2=-Log I.sub.2/I.sub.0 (3)
5. Production Method
[0249] Though no particular limitation is imposed on the method for
producing a monolayer type photographic photoreceptor, the method
may be performed according to the following procedures. First, a
specific charge generating agent, charge transfer agent, binding
resin and other additives are added in a solvent to prepare an
application liquid. The obtained application liquid is applied to a
conductive substrate (aluminum preliminary pipe) by, for example, a
dip coat method, a spray coating method, a beads coating method, a
blade coating method and a roller coating method.
[0250] Thereafter, the coating layer is dried by hot air at
100.degree. C. for 30 minutes to obtain a monolayer type
photographic photoreceptor that includes a photoreceptive layer
having a fixed film thickness.
[0251] Various organic solvents may be used as the solvent used to
prepare the dispersion solution. Examples of the solvent include
alcohols such as methanol, ethanol, isopropanol and butanol;
aliphatic hydrocarbons such as n-hexane, octane and cyclohexane;
aromatic hydrocarbons such as benzene, toluene and xylene;
halogenated hydrocarbons such as dichloromethane, dichloroethane,
chloroform, carbon tetrachloride and chlorobenzene; ethers such as
dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol
dimethyl ether, diethylene glycol dimethyl ether, 1,3-dioxolan and
1,4-dioxane; ketones such as acetone, methyl ethyl ketone and
cyclohexanone; esters such as ethyl acetate and methyl acetate;
dimethylformaldehyde, dimethylformamide and dimethylsulfoxide.
These solvents may be used either singly or in combinations of two
or more. At this time, a surfactant, a leveling agent and the like
may be compounded in order to improve the dispersibility of the
charge generating agent and the smoothness of the surface of the
photoreceptive layer.
[0252] Also, it is preferable to form an intermediate layer on the
substrate before the photoreceptive layer is formed.
[0253] In the formation of this intermediate layer, the binding
resin and, according to the need, additives (organic micropowder or
inorganic micropowder) are mixed and dispersed using a known method
using a roll mill, a ball mill, an attritor, a paint shaker, an
ultrasonic dispersing machine or the like to prepare an application
liquid. The application liquid is applied to the substrate by known
measures, for example, a blade method, a dipping method or a
spraying method, followed by heat treatment to form an intermediate
layer.
[0254] A small amount of various additives (organic micropowder or
inorganic micropowder) may be added within a range free of problems
concerning precipitation in the production process, with the
intention of, for example, scattering light to thereby prevent the
generation of interference fringes.
[0255] Next, the obtained application liquid may be applied to, for
example, the surface of a support substrate (aluminum preliminary
pipe) by a coating method such as a dip coat method, a spray
coating method, a beads coating method, a blade coating method and
a roller coating method.
[0256] The subsequent step of drying the application liquid on the
substrate is performed at a temperature from 20 to 200.degree. C.
for 5 minutes to 2 hours.
[0257] Various organic solvents may be used as a solvent used to
prepare the application liquid. Examples of the solvent include
alcohols such as methanol, ethanol, isopropanol and butanol;
aliphatic hydrocarbons such as n-hexane, octane and cyclohexane;
aromatic hydrocarbons such as benzene, toluene and xylene;
halogenated hydrocarbons such as dichloromethane, dichloroethane,
chloroform, carbon tetrachloride and chlorobenzene; ketones such as
acetone, methyl ethyl ketone and cyclohexanone; esters such as
ethyl acetate and methyl acetate; dimethylformaldehyde,
dimethylformamide and dimethylsulfoxide. These solvents may be used
either singly or in combinations of two or more.
6. Laminate Type Electrophotographic Photoreceptor
[0258] When constituting the electrophotographic photoreceptor of
the present invention, as shown in FIG. 6, the photoreceptive layer
is also preferably a laminate type photoreceptive layer 20
including a charge generating layer 24 containing a specific charge
generating agent and a charge transfer layer 22 containing a charge
transfer agent and a binding resin.
[0259] The laminate type electrophotographic photoreceptor 20 may
be manufactured by forming a charge generating layer 24 containing
a specific charge generating agent on a substrate 12 by means of
vapor deposition or coating, and then applying an application
liquid containing a charge transfer agent and a binding resin on
the charge generating layer 24, followed by drying the application
liquid to form a charge transfer layer 22.
[0260] Contrary to the above structure, the charge transfer layer
22 is formed on the substrate 12 and the charge generating layer 24
may be formed on the charge transfer layer 22 as shown in FIG. 6B.
Because the charge generating layer 24 has a very lower thickness
than the charge transfer layer 22, it is preferable to form the
charge transfer layer 22 on the charge generating layer 24 to
protect the charge generating layer 24 as shown in FIG. 6A.
[0261] Also, an intermediate layer 25 is preferably formed on the
substrate in the same manner as in the case of the monolayer type
photoreceptor.
[0262] Also, the charge generating layer forming application liquid
and the charge transfer layer forming application liquid may be
prepared, for example, by dispersing/mixing predetermined
components such as a specific charge generating agent, a charge
transfer agent and a binding resin together with a dispersion
medium by using a roll mill, a ball mill, an attritor, a paint
shaker, an ultrasonic dispersing machine or the like.
[0263] Though no particular limitation is imposed on the thickness
of the photoreceptive layer (charge generating layer and charge
transfer layer) in the laminate type photoreceptive layer 20, the
thickness of the charge generating layer is preferably 0.01 to 5
.mu.m and more preferably 0.1 to 3 .mu.m and the thickness of the
charge transfer layer is preferably 2 to 100 .mu.m and more
preferably 5 to 50 .mu.m.
EXAMPLES
[0264] The present invention will be explained in detail by way of
Examples.
Example 1
1. Production of oxo-titanylphthalocyanine Compound
[0265] A flask in which the atmosphere was substituted with argon
was charged with 22 g (0.17 mol) of o-phthalonitrile, 25 g (0.073
mol) of titanium tetrabutoxide, 300 g of quinoline and 2.28 g
(0.038 mol) of urea, and the mixture was heated to 150.degree. C.
with stirring.
[0266] Then, the reaction system was heated to 215.degree. C. while
removing the vapor generated from the reaction system out of the
system and then the reaction was further continued for 2 hours with
stirring while keeping this temperature.
[0267] Then, after the reaction was finished, the reaction mixture
was cooled. When the mixture was cooled to 150.degree. C., the
reaction mixture was take out of the flask and subjected to
filtration using a glass filter. The obtained solid was washed with
N,N-dimethylformamide and methanol in this order, followed by
vacuum drying to obtain 24 g of a bluish violet solid.
2. Production of oxo-titanylphthalocyanine Crystal
(1) Pretreatment Prior to Pigmentation Treatment
[0268] 12 g of the bluish violet solid obtained in the above
production of the oxo-titanylphthalocyanine compound was added in
100 ml of N,N-dimethylformamide, and the mixture was heated to
130.degree. C. for 2 hours to perform stirring treatment.
[0269] Then, the heating was stopped after two hours passed, and
the mixture was cooled. When the mixture was cooled to
23.+-.1.degree. C., the stirring was also stopped, and in this
state, the solution was allowed to stand for 12 hours to perform
stabilizing treatment. Then, after stabilized, the supernatant was
separated by filtration using a glass filter, and the obtained
solid was washed with methanol and then dried under vacuum to
obtain 11.8 g of a crude crystal of an oxo-titanylphthalocyanine
compound.
(2) Pigmentation Treatment
[0270] 10 g of the crude crystal of the oxo-titanylphthalocyanine
compound obtained in the above pretreatment prior to pigmentation
treatment was added and dissolved in 100 g of 97% concentrated
sulfuric acid. This acid treatment was performed at 5.degree. C.
for one hour.
[0271] Next, the solution was added dropwise to 5 l of ice-cooled
purified water at a rate of 10 ml/min, and the mixture was stirred
at about 15.+-.3.degree. C. for 30 minutes and then allowed to
stand for 30 minutes. Then, the solution was subjected to
filtration using a glass filter to obtain a wet cake.
[0272] Subsequently, the obtained wet cake was suspended in 500 ml
of methanol to wash it, and after washing, methanol was removed by
filtration using a glass filter. Such washing was repeated four
times. Then, the obtained wet cake was suspended in 500 ml of
20.degree. C. purified water to wash it, and after washing, water
was removed by filtration using a glass filter.
[0273] 5 g of the washed wet cake was added to 0.75 g of water and
100 g of chlorobenzene, and the mixture was stirred under heating
at 50.degree. C. for 24 hours.
[0274] Then, the crystal obtained by subjecting the supernatant to
filtration using a glass filter was washed with 100 ml of methanol
on a funnel and then dried under vacuum at 50.degree. C. for 5
hours, to obtain 4.5 g of a crystal of unsubstituted
oxo-titanylphthalocyanine (blue powder) represented by the formula
(3).
3. Evaluation of oxo-titanylphthalocyanine Crystal
(1) Measurement of CuK.alpha. Characteristic X-Ray Diffraction
Spectrum
[0275] 0.3 g of the obtained oxo-titanylphthalocyanine crystal was
dispersed in 5 g of tetrahydrofuran, which was then stored in a
sealed system kept at a temperature of 23.+-.1.degree. C. under a
relative humidity of 50 to 60% for 24 hours in a sealed system, and
then tetrahydrofuran was removed. The mixture was charged in a
sample holder in a X-ray diffraction device (trade name: RINT1100,
manufactured by Rigaku Corporation to measure. The obtained
spectrum chart is shown in Table 7. The spectrum chart has the
characteristics that there is the maximum peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. and no peak at 26.2.degree..
It has been confirmed from this fact that the obtained
oxo-titanylphthalocyanine crystal has a stable and predetermined
crystal type. This is because the peak at a Bragg angle
(2.theta..+-.0.2.degree.)=27.2.degree. is specific to the above
predetermined crystal type and the peak at 26.2.degree. is specific
to a .beta.-type crystal.
[0276] The measuring condition was as follows.
X-ray tube globe: Cu Tube voltage: 40 kV Tube current: 30 mA Start
angle: 3.0.degree. Stop angle: 40.0.degree. Scanning speed:
10.degree./min
(2) Differential Scanning Calorimetric Analysis
[0277] The obtained oxo-titanylphthalocyanine crystal was subjected
to differential scanning calorimetric analysis using a differential
scanning calorimeter (trade name: TAS-200 model, DSC8230D,
manufactured by Rigaku Corporation). The obtained differential
scanning analysis chart is shown in FIG. 8. In this chart, other
than a peak derived from vaporization of adsorbed water, one peak
was confirmed at 296.degree. C.
[0278] The measuring condition was as follows.
Sample pan: made of aluminum Temperature rise rate: 20.degree.
C./min
(3) Measurement of Absorbance
[0279] 0.1 g (1.25 parts by weight) of the obtained
oxo-titanylphthalocyanine crystal was added to 8 g (100 parts by
weight) of a mixed solvent constituted of methanol and
N,N-dimethylformamide (methanol:N,N-dimethylformamide=1:1 (by
weight ratio). The mixture was stirred at a rotational speed of 100
rpm for one hour while keeping a temperature of 23.degree. C. to
obtain a suspension. Then, the obtained suspension was subjected to
filtration using a PTFE type 0.1-.mu.m membrane filter
(manufactured by Advantest Corporation) to obtain a filtrate.
Subsequently, the obtained filtrate was stored in a cell having a
length of 10 mm to measure absorbance of the filtrate for light
having a wavelength of 400 nm by using an absorptiometer (trade
name: Spectrophotometer U3000, manufactured by HITACHI, Ltd.) The
obtained results are shown in Table 1.
4. Production of an Electrophotographic Photoreceptor
(1) Formation of Intermediate Layer
[0280] 250 parts by weight of titanium oxide (trade name: MT-02,
manufactured by Tayca Corporation, surface treated with alumina,
silica and silicone, number average primary particle diameter: 10
nm), 100 parts by weight of a quaternary copolymer polyamide resin
(trade name: CM8000, manufactured by Toray Industries, Inc.) and a
solvent consisting of 1000 parts by weight of methanol and 250
parts by weight of n-butanol were mixed and dispersed for 5 hours.
The dispersion was further subjected to filtration using a 5-.mu.
filter to prepare an intermediate layer application liquid.
[0281] Then, an aluminum substrate (support substrate) of 30 mm in
diameter and 238.5 mm in length was dipped in the obtained
intermediate layer application liquid at a rate of 5 mm/sec in such
a manner that one end of the substrate faced upward, to apply the
application liquid. Thereafter, curing treatment was performed at
130.degree. C. for 30 minutes to form an intermediate layer having
a film thickness of 2 .mu.m.
(2) Formation of Charge Generating Layer
[0282] Then, 250 parts by weight of the oxo-titanylphthalocyanine
crystal produced in the above manner as a charge generating agent,
100 parts by weight of a polyvinylbutyral resin as a binding resin
and 8000 parts by weight of tetrahydrofuran as a dispersing medium
were mixed and dispersed for 48 hours by using a beads mill to
obtain a charge generating layer application liquid. The obtained
application liquid was subjected to filtration using a 3-.mu.
filter, and then the filtrate application liquid was applied to the
intermediate layer by a dip coat method, followed by drying at
80.degree. C. for 5 minutes to form a charge generating layer of
0.2 .mu.m in film thickness.
(3) Formation of Charge Transfer Layer
[0283] Next, stored in an ultrasonic dispersing machine are 55
parts by weight of a compound (HTM-1) represented by the following
formula (7) as a hole transfer agent, 5 parts by weight of
methaterphenyl as an additive, 60 parts by weight of a
polycarbonate resin having a viscosity average molecular weight of
20,000 and 40 parts by weight of a polycarbonate resin having a
viscosity average molecular weight of 50,000 as binding resins and
310 parts by weight of tetrahydrofuran and 310 parts by weight of
toluene as solvents. The mixture was subjected to dispersing
treatment performed for 10 minutes, to obtain a charge transfer
layer application liquid.
[0284] The obtained charge transfer layer application liquid was
applied to the surface of the charge generating layer in the same
manner as in the case of the charge generating layer application
liquid and dried at 120.degree. C. for 30 minutes to form a charge
transfer layer of 20 .mu.m in film thickness, thereby manufacturing
a laminate type electrophotographic photoreceptor.
##STR00005##
5. Evaluation
(1) Measurement of Sensitivity
[0285] The sensitivity of the obtained photographic photoreceptor
was measured.
[0286] Specifically, using a drum sensitivity tester (manufactured
by GENTEC Inc.), the electrophotographic photoreceptor was charged
such that the surface potential of the photoreceptor became -850 V.
Then, the surface of the electrophotographic photoreceptor was
exposed to monochromatic light (half value width: 20 nm, light
intensity: 1.0 .mu.J/cm.sup.2) having a wavelength of 780 nm which
light was extracted from white light by using a bandpass filter
(irradiation time: 50 msec). Subsequently, the potential of the
surface of the photoreceptor was measured as the sensitivity 350
msec after the surface of the photoreceptor was exposed to light.
The results are shown in Table 1. The measured potential takes on a
negative value and therefore, the absolute value of the measured
potential is described in Table 1.
(2) Measurement of Charge Retention Rate
[0287] The charge retention rate of the obtained photographic
photoreceptor was measured.
[0288] Specifically, using a drum sensitivity tester (manufactured
by GENTEC Inc.), the electrophotographic photoreceptor was charged
such that the surface potential of the photoreceptor became -850 V.
Then, the potential of the surface of the photoreceptor was
measured one second after the surface of the photoreceptor was
charged, to measure a charge retention rate (%). The results are
shown in Table 1.
Example 2
[0289] In Example 2, an oxo-titanylphthalocyanine crystal was
produced and also, an electrophotographic photoreceptor was
produced to evaluate in the same manner as in Example 1 except that
in the pigmentation treatment when the oxo-titanylphthalocyanine
crystal was produced, the wet cake was washed three times with
methanol and then twice with water. The obtained results are shown
in Table 1. The results of the CuK.alpha. characteristic X-ray
diffraction spectrum and differential scanning calorimetric
analysis of the obtained oxo-titanylphthalocyanine crystal were the
same as those of Example 1.
Example 3
[0290] In Example 3, an oxo-titanylphthalocyanine crystal was
produced and also, an electrophotographic photoreceptor was
produced to evaluate in the same manner as in Example 1 except that
in the pigmentation treatment when the oxo-titanylphthalocyanine
crystal was produced, the wet cake was washed twice with methanol
and then three times with water. The obtained results are shown in
Table 1. The results of the CuK.alpha. characteristic X-ray
diffraction spectrum and differential scanning calorimetric
analysis of the obtained oxo-titanylphthalocyanine crystal were the
same as those of Example 1.
Example 4
[0291] In Example 4, an oxo-titanylphthalocyanine crystal was
produced and also, an electrophotographic photoreceptor was
produced to evaluate in the same manner as in Example 1 except that
in the pigmentation treatment when the oxo-titanylphthalocyanine
crystal was produced, the wet cake was washed once with methanol
and then four times with water. The obtained results are shown in
Table 1. The results of the CuK.alpha. characteristic X-ray
diffraction spectrum and differential scanning calorimetric
analysis of the obtained oxo-titanylphthalocyanine crystal were the
same as those of Example 1.
Comparative Example 1
[0292] In Comparative Example 1, an oxo-titanylphthalocyanine
crystal was produced and also, an electrophotographic photoreceptor
was produced to evaluate in the same manner as in Example 1 except
that in the pigmentation treatment when the
oxo-titanylphthalocyanine crystal was produced, the wet cake was
not washed with methanol but washed five times with 60.degree. C.
water. The obtained results are shown in Table 1. The results of
the CuK.alpha. characteristic X-ray diffraction spectrum and
differential scanning calorimetric analysis of the obtained
oxo-titanylphthalocyanine crystal were the same as those of Example
1.
Comparative Example 2
[0293] In Comparative Example 2, an oxo-titanylphthalocyanine
crystal was produced and also, an electrophotographic photoreceptor
was produced to evaluate in the same manner as in Example 1 except
that in the pigmentation treatment when the
oxo-titanylphthalocyanine crystal was produced, the wet cake was
not washed with methanol but washed three times with 60.degree. C.
water. The obtained results are shown in Table 1. The results of
the CuK.alpha. characteristic X-ray diffraction spectrum and
differential scanning calorimetric analysis of the obtained
oxo-titanylphthalocyanine crystal were the same as those of Example
1.
Comparative Example 3
[0294] In Comparative Example 3, an oxo-titanylphthalocyanine
crystal was produced and also, an electrophotographic photoreceptor
was produced to evaluate in the same manner as in Example 1 except
that in the pigmentation treatment when the
oxo-titanylphthalocyanine crystal was produced, the wet cake was
not washed with methanol but washed three times with 20.degree. C.
water. The obtained results are shown in Table 1. The results of
the CuK.alpha. characteristic X-ray diffraction spectrum and
differential scanning calorimetric analysis of the obtained
oxo-titanylphthalocyanine crystal were the same as those of Example
1.
TABLE-US-00001 TABLE 1 Absolute value of Charge retention
Absorbance sensitivity rate .lamda. = 400 nm (V) (%) Example 1
0.012 47 99.4 Example 2 0.038 56 98.4 Example 3 0.052 55 98.6
Example 4 0.062 55 99.2 Comparative 0.095 63 96.9 Example 1
Comparative 0.110 68 95.6 Example 2 Comparative 0.201 65 95.7
Example 3
[0295] According to the present invention, an
oxo-titanylphthalocyanine crystal which is stable and has excellent
dispersibility can be obtained in such a manner that a wet cake
which is an intermediate product is washed with a predetermined
alcohol in the course of production of the
oxo-titanylphthalocyanine crystal having predetermined optical
characteristics and thermal characteristics.
[0296] According to the method for producing
oxo-titanylphthalocyanine crystal of the present invention, it is
possible to stably produce an oxo-titanylphthalocyanine crystal
which is stable and has excellent dispersibility in the
photoreceptive layer.
[0297] Therefore, the electrophotographic photoreceptor using the
oxo-titanylphthalocyanine crystal as the charge generating agent is
expected to contribute to improvement in electric properties and to
stabilization of qualities in various image forming devices such as
copying machines and printers.
* * * * *