Electrophotographic apparatus
The electrophotographic apparatus includes: an electrophotographic photosensitive member; a charging unit; an image-exposing unit; a charge transfer amount-sensing unit for sensing the amount of charge transferred to the electrophotographic photosensitive member; and an exposed portion potential-controlling unit for controlling the potential of each of the exposed portions of the electrophotographic photosensitive member based on a sensing result, which is obtained by charging the electrophotographic photosensitive member with the charging unit, performing image exposure with the image-exposing unit in at least one light amount weaker than a light amount in which the normalized radius of curvature R of the electrophotographic photosensitive member represented by the following equation (E1), the normalized radius of curvature being obtained by a method of measuring an EV curve, shows a minimum, and in at least two light amounts stronger than the light amount in which the normalized radius of curvature shows the minimum. R = [ 1 + ( dy dx ) 2 ] 3 / 2 ❘ "\[LeftBracketingBar]" d 2 y dx 2 ❘ "\[RightBracketingBar]" ( E 1 )
1. An electrophotographic apparatus, comprising:
an electrophotographic photosensitive member comprising, in this order, (i) a support, (ii) an undercoat layer containing a polyamide resin and metal oxide particles, (iii) a charge-generating layer containing a charge-generating substance, the charge-generating substance comprising a titanyl phthalocyanine pigment or a hydroxygallium phthalocyanine pigment, and (iv) a charge-transporting layer containing a charge-transporting substance;
a charging unit configured to charge the electrophotographic photosensitive member;
an image-exposing unit configured to irradiate a surface of the electrophotographic photosensitive member with image exposure light to form an electrostatic latent image on the surface of the electrophotographic photosensitive member;
a developing unit configured to develop the electrostatic latent image with toner to form a toner image on the surface of the electrophotographic photosensitive member;
a transferring unit configured to transfer the toner image from the surface of the electrophotographic photosensitive member onto a transfer material;
a charge transfer amount-sensing unit configured to sense an amount of charge transferred to the electrophotographic photosensitive member by discharge per unit time; and
an exposed portion potential-controlling unit configured to control a potential of each of exposed portions of the electrophotographic photosensitive member based on a sensing result obtained by (i) charging the electrophotographic photosensitive member with the charging unit, (ii) performing image exposure with the image-exposing unit in a first light amount (μJ/cm 2 ) weaker than a light amount in which a normalized radius of curvature R of the electrophotographic photosensitive member represented by equation (E1) shows a minimum, and in second light amounts (μJ/cm 2 ) stronger than the light amount in which the normalized radius of curvature R shows the minimum, and (iii) sensing an amount of charge transferred to the electrophotographic photosensitive member per unit time at a time of charging of the exposed portion with the charge transfer amount-sensing unit, wherein
the normalized radius of curvature R of the electrophotographic photosensitive member has a minimum of 0.24 or less, which is calculated from the following equation (E1) in a graph whose axis of abscissa and axis of ordinate indicate an “x” and a “y”, respectively, as described below:
when at a temperature of 23.5 (° C.) and a relative humidity of 50 (% RH)
(1) a surface potential of the electrophotographic photosensitive member is set to 0 (V),
(2) the electrophotographic photosensitive member is charged for 0.005 second so that an absolute value of an initial surface potential of the electrophotographic photosensitive member becomes 500 (V),
(3) the electrophotographic photosensitive member is exposed to light having a wavelength of 805 (nm) and an intensity of 25 (mW/cm 2 ) in a light amount I exp (μJ/cm 2 ) for “t” seconds continuously 0.02 second after a start of the charging, and
(4) an absolute value of the surface potential of the electrophotographic photosensitive member after the exposure obtained through measurement 0.06 second after the start of the charging is represented by V exp (V),
in a graph whose axis of abscissa and axis of ordinate indicate the I exp and the V exp , respectively, the graph being obtained by repeatedly performing the measurements (1) to (4) while changing the I exp from 0.000 to 1.000 (μJ/cm 2 ) at intervals of 0.001 (μJ/cm 2 ) through a change in “t”,
when a light amount when the V exp of the graph=250 (V) is represented by I 1/2 (μJ/cm 2 ), a normalized light amount obtained by normalizing the axis of abscissa I exp so that 10·I 1/2 becomes 1 is represented by “x”, and a normalized surface potential obtained by normalizing the axis of ordinate V exp so that a value 500 (V) of the axis of ordinate of the graph becomes 1 and a value thereof when x=1 becomes 0 is represented by “y”:
R
=
[
1
+
(
dy
dx
)
2
]
3
/
2
❘
"\[LeftBracketingBar]"
d
2
y
dx
2
❘
"\[RightBracketingBar]"
(
E
1
)
the titanyl phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 9.8°±0.3° and 27.1°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 50 to 150 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 100 nm or less, and
the hydroxygallium phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 30 to 50 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 50 nm or less.
2. The electrophotographic apparatus according to claim 1 , wherein the normalized radius of curvature R has a minimum of 0.21 or less.
3. The electrophotographic apparatus according to claim 1 , wherein when at a temperature of 23.5 (° C.) and a relative humidity of 50 (% RH),
(1) a surface potential of the electrophotographic photosensitive member is set to 0 (V),
(2) the electrophotographic photosensitive member is charged for 0.005 second so that an absolute value of an initial surface potential of the electrophotographic photosensitive member becomes 500 (V),
(3) the electrophotographic photosensitive member is exposed to light having a wavelength of 805 [nm] and an intensity of 25 (mW/cm 2 ) in a light amount I exp (μJ/cm 2 ) for “t” seconds continuously 0.02 second after a start of the charging, and
(4) an absolute value of the surface potential of the electrophotographic photosensitive member after the exposure obtained through measurement 0.06 second after the start of the charging is represented by V exp (V),
in a graph whose axis of abscissa and axis of ordinate indicate the I exp and the V exp , respectively, the graph being obtained by repeatedly performing the measurements (1) to (4) while changing the I exp from 0.000 to 1.000 (μJ/cm 2 ) at intervals of 0.001 (μJ/cm 2 ) through a change in “t”,
when a normalized light amount “x” when a normalized surface potential “y” of the graph=0.5 is represented by Is 0.5 (μJ/cm 2 ), a quadruple light amount of the light amount Is 0.5 is represented by 4Is 0.5 (μJ/cm 2 ), a quintuple light amount thereof is represented by 5Is 0.5 (μJ/cm 2 ), the y when x=4Is 0.5 is represented by y4, and the y when x=5Is 0.5 is represented by y5,
slopes S2 and S3 of the electrophotographic photosensitive member satisfy S2≥3.0 and S3≤0.41 when
S
2
=
0.5
I
s
0.5
and
S
3
=
|
y
4
-
y
5
|
❘
"\[LeftBracketingBar]"
4
I
s
0.5
-
5
I
s
0
5
❘
"\[RightBracketingBar]"
.
4. The electrophotographic apparatus according to claim 3 , wherein S3 is 0.21 or less.
5. The electrophotographic apparatus according to claim 3 , wherein S3 is 0.15 or less.
6. The electrophotographic apparatus according to claim 1 , wherein the exposed portion potential-controlling unit is a unit for controlling a potential of each of exposed portions of the electrophotographic photosensitive member based on a sensing result obtained by
performing image exposure with the image-exposing unit in at least “n” light amounts where “n” represents an integer of 2 or more, the light amounts being weaker than the light amount in which the normalized radius of curvature R of the electrophotographic photosensitive member shows the minimum, and in at least “m” light amounts where “m” represents an integer of 3 or more, the light amounts being stronger than the light amount in which the normalized radius of curvature R shows the minimum, and
sensing an amount of charge transferred to the electrophotographic photosensitive member per unit time at a time of charging of the exposed portion with the charge transfer amount-sensing unit.
7. The electrophotographic apparatus according to claim 1 , wherein the metal oxide particles are titanium oxide particles, and the titanium oxide particles have an average primary particle diameter of 10 to 100 nm.
8. The electrophotographic apparatus according to claim 1 , wherein the undercoat layer has a thickness of 0.5 to 3.0 μm.
9. The electrophotographic apparatus according to claim 1 , wherein the charge-generating substance comprises the titanyl phthalocyanine pigment.
10. The electrophotographic apparatus according to claim 1 , wherein the charge-generating substance comprises the hydroxygallium phthalocyanine pigment.
11. The electrophotographic apparatus according to claim 1 , wherein the charge-generating layer has a thickness of 0.16 μm or more.
12. An electrophotographic apparatus, comprising:
an electrophotographic photosensitive member comprising a support, an undercoat layer, a charge-generating layer and a charge-transporting layer, in this order;
a charging unit configured to charge the electrophotographic photosensitive member;
an image-exposing unit configured to irradiate a surface of the electrophotographic photosensitive member with image exposure light to form an electrostatic latent image on the surface of the electrophotographic photosensitive member;
a developing unit configured to develop the electrostatic latent image with toner to form a toner image on the surface of the electrophotographic photosensitive member;
a transferring unit configured to transfer the toner image from the surface of the electrophotographic photosensitive member onto a transfer material;
a charge transfer amount-sensing unit configured to sense an amount of charge transferred to the electrophotographic photosensitive member by discharge per unit time; and
an exposed portion potential-controlling unit configured to control a potential of each of exposed portions of the electrophotographic photosensitive member based on a sensing result obtained by (i) charging the electrophotographic photosensitive member with the charging unit, (ii) performing image exposure with the image-exposing unit in first light amount (μJ/cm 2 ) weaker than a light amount in which a normalized radius of curvature R of the electrophotographic photosensitive member represented by the following equation (E1) shows a minimum, and in second light amount (μJ/cm 2 ) stronger than the light amount in which the normalized radius of curvature R shows the minimum, and (iii) sensing an amount of charge transferred to the electrophotographic photosensitive member per unit time at a time of charging of the exposed portion with the charge transfer amount-sensing unit, wherein
the normalized radius of curvature R of the electrophotographic photosensitive member has a minimum of 0.24 or less, which is calculated from the following equation (E1) in a graph whose axis of abscissa and axis of ordinate indicate an “x” and a “y”, respectively, as described below:
when at a temperature of 23.5 (C) and a relative humidity of 50 (% RH)
(1) a surface potential of the electrophotographic photosensitive member is set to 0 (V),
(2) the electrophotographic photosensitive member is charged for 0.005 second so that an absolute value of an initial surface potential of the electrophotographic photosensitive member becomes 500 (V),
(3) the electrophotographic photosensitive member is exposed to light having a wavelength of 805 (nm) and an intensity of 25 (mW/cm 2 ) in a light amount I exp (μJ/cm 2 ) for “t” seconds continuously 0.02 second after a start of the charging, and
(4) an absolute value of the surface potential of the electrophotographic photosensitive member after the exposure obtained through measurement 0.06 second after the start of the charging is represented by V exp (V),
in a graph whose axis of abscissa and axis of ordinate indicate the I exp and the V exp , respectively, the graph being obtained by repeatedly performing the measurements (1) to (4) while changing the I exp from 0.000 to 1.000 (μJ/cm 2 ) at intervals of 0.001 (μJ/cm 2 ) through a change in “t”,
when a light amount when the V exp of the graph=250 (V) is represented by I 1/2 (μJ/cm 2 ), a normalized light amount obtained by normalizing the axis of abscissa I exp SO that 10·I 1/2 becomes 1 is represented by “x”, and a normalized surface potential obtained by normalizing the axis of ordinate V exp so that a value 500 [V] of the axis of ordinate of the graph becomes 1 and a value thereof when x=1 becomes 0 is represented by “y”:
R
=
[
1
+
(
d
y
d
x
)
2
]
3
/
2
|
d
2
y
d
x
2
|
,
(
E1
)
the undercoat layer contains metal oxide particles,
the charge-generating layer contains a charge-generating substance comprising a titanyl phthalocyanine pigment or a hydroxygallium phthalocyanine pigment,
the titanyl phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 9.8°±0.3° and 27.1°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 50 to 150 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 100 nm or less, and
the hydroxygallium phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 30 to 50 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 50 nm or less.
13. The electrophotographic apparatus according to claim 12 , wherein the charge-generating substance comprises the titanyl phthalocyanine pigment.
14. The electrophotographic apparatus according to claim 12 , wherein the charge-generating substance comprises the hydroxygallium phthalocyanine pigment.
15. An electrophotographic apparatus, comprising:
an electrophotographic photosensitive member comprising a support, an undercoat layer, a charge-generating layer and a charge-transporting layer, in this order;
a charging unit configured to charge the electrophotographic photosensitive member;
an image-exposing unit configured to irradiate a surface of the electrophotographic photosensitive member with image exposure light to form an electrostatic latent image on the surface of the electrophotographic photosensitive member;
a developing unit configured to develop the electrostatic latent image with toner to form a toner image on the surface of the electrophotographic photosensitive member;
a transferring unit configured to transfer the toner image from the surface of the electrophotographic photosensitive member onto a transfer material;
a charge transfer amount-sensing unit configured to sense an amount of charge transferred to the electrophotographic photosensitive member by discharge per unit time; and
an exposed portion potential-controlling unit configured to control a potential of each of exposed portions of the electrophotographic photosensitive member based on a sensing result obtained by (i) charging the electrophotographic photosensitive member with the charging unit, (ii) performing image exposure with the image-exposing unit in first light amount (μJ/cm 2 ) weaker than a light amount in which a normalized radius of curvature R of the electrophotographic photosensitive member represented by the following equation (E1) shows a minimum, and in second light amount (μJ/cm 2 ) stronger than the light amount in which the normalized radius of curvature R shows the minimum, and (iii) sensing an amount of charge transferred to the electrophotographic photosensitive member per unit time at a time of charging of the exposed portion with the charge transfer amount-sensing unit, wherein
the normalized radius of curvature R of the electrophotographic photosensitive member has a minimum of 0.24 or less, which is calculated from the following equation (E1) in a graph whose axis of abscissa and axis of ordinate indicate an “x” and a “y”, respectively, as described below:
when at a temperature of 23.5 (C) and a relative humidity of 50 (% RH)
(1) a surface potential of the electrophotographic photosensitive member is set to 0 (V),
(2) the electrophotographic photosensitive member is charged for 0.005 second so that an absolute value of an initial surface potential of the electrophotographic photosensitive member becomes 500 (V),
(3) the electrophotographic photosensitive member is exposed to light having a wavelength of 805 (nm) and an intensity of 25 (mW/cm 2 ) in a light amount I exp (μJ/cm 2 ) for “t” seconds continuously 0.02 second after a start of the charging, and
(4) an absolute value of the surface potential of the electrophotographic photosensitive member after the exposure obtained through measurement 0.06 second after the start of the charging is represented by V exp (V),
in a graph whose axis of abscissa and axis of ordinate indicate the I exp and the V exp , respectively, the graph being obtained by repeatedly performing the measurements (1) to (4) while changing the I exp from 0.000 to 1.000 (μJ/cm 2 ) at intervals of 0.001 (μJ/cm 2 ) through a change in “t”,
when a light amount when the V exp of the graph=250 (V) is represented by I 1/2 (μJ/cm 2 ), a normalized light amount obtained by normalizing the axis of abscissa I exp SO that 10·I 1/2 becomes 1 is represented by “x”, and a normalized surface potential obtained by normalizing the axis of ordinate V exp so that a value 500 [V] of the axis of ordinate of the graph becomes 1 and a value thereof when x=1 becomes 0 is represented by “y”:
R
=
[
1
+
(
d
y
d
x
)
2
]
3
/
2
|
d
2
y
d
x
2
|
,
(
E1
)
the charge-transporting layer contains a charge-transporting substance comprising a compound represented by the formulae
the charge-generating layer contains a charge-generating substance comprising a titanyl phthalocyanine pigment or a hydroxygallium phthalocyanine pigment,
the titanyl phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 9.8°±0.3° and 27.1°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 50 to 150 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 100 nm or less, and
the hydroxygallium phthalocyanine pigment comprises crystal particles having a crystal form showing peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using a CuKα ray, and has a peak at 30 to 50 nm in a crystal particle size distribution measured by using small-angle X-ray scattering, and a half-width of the peak is 50 nm or less.
16. The electrophotographic apparatus according to claim 15 , wherein the charge-generating substance comprises the titanyl phthalocyanine pigment.
17. The electrophotographic apparatus according to claim 15 , wherein the charge-generating substance comprises the hydroxygallium phthalocyanine pigment.