Electrophotographic photosensitive member
View Patent ↗In an electrophotographic apparatus (e.g., a photocopier or laser printer), an electrophotographic photosensitive member (image-forming part) has a metal substrate roughened on its surface, a metal oxide-containing undercoat layer on the substrate, and an organic photosensitive layer over the undercoat. A coherent light source (e.g., laser) can cause interference fringes that degrade the printed image. Interference fringes are judged (or predicted) as follows: The surface reflectance is measured at intervals over the spectral width of the light source. The measured surface reflectance is corrected, using a mirror-surface conductive substrate as a reference, to obtain a reflectance of the photosensitive member. The reflectance is subjected to a discrete Fourier transformation, which generates a power spectrum, over the spectral width of the light source, from the reflectance as a function of the wavelength. Interference fringes are judged from the maximum peak value in the power spectrum, as compared to a predetermined value.
1. An electrophotographic photosensitive member, that is mountable in an electrophotographic apparatus including a coherent exposure light source, comprising:
a conductive substrate having a roughened surface which is roughened by a sand blasting process to provide a sand-blast-roughened surface;
a metal oxide-containing undercoat layer coated on the sand-blast-roughened surface and having a film thickness d within a range of 1.5 μm≦d≦3.5 μm; and
an organic photosensitive layer coated on the metal oxide-containing undercoat layer;
wherein the electrophotographic photosensitive member satisfies a condition Sp≦10, and Sp is determined by
(a) measuring a surface reflectance of coherent light from the electrophotographic photosensitive member at a plurality of predetermined wavelength intervals of width Δλ within a wavelength range of 750 nm≦λ≦812 nm to obtain a measured surface reflectance;
(b) correcting the measured surface reflectance to obtain a corrected reflectance I opc of the electrophotographic photosensitive member, by taking a mirror-surface conductive substrate reflectance as a reference, and subjecting the corrected reflectance to a discrete Fourier transformation according to a following equation (1) and calculating, from a result of the equation (1), a power spectrum |S(n/(N·Δλ)| 2 according to a following equation (2)
S
(
n
N
·
Δ
λ
)
=
∑
m
=
0
N
-
1
I
OPC
(
m
·
Δ
λ
)
exp
(
-
ⅈ2π
·
n
N
·
Δ
λ
·
m
·
Δ
λ
)
=
a
+
bi
(
1
)
wherein i represents √−1, n and m represent integers, and N represents N=2 s (s=1, 2, . . . , u);
S
(
n
N
·
Δλ
)
2
=
a
2
+
b
2
;
(
2
)
and
(c) determining a peak value of the power spectrum |S(n/(N·Δλ))| 2 within a frequency range of 0<n/(N·Δλ(Hz)≦2.5×10 8 ; and
(d) setting the peak value of the power spectrum |S(n/(N·Δλ))| 2 equal to Sp.
2. The electrophotographic photosensitive member according to claim 1 , wherein the photosensitive layer comprises, laminated in succession from the conductive substrate,
a charge generation layer including a charge generation material and a resinous binder, and
a charge transport layer including a charge transport material and a resinous binder.
3. The electrophotographic photosensitive member according to claim 1 , wherein the conductive substrate has an average surface roughness Ra within a range of 0.23 μm≦Ra≦0.35 μm, a maximum surface roughness R max within a range of 2.4 μm≦R max ≦2.7 μm, and a conductive-substrate reflectance I sb within a range of 0≦I sb ≦15%, where a surface reflectance of a mirror-surface conductive substrate for a monochromatic light of wavelength λ=780 nm is taken as a reference reflectance for I sb .
4. The electrophotographic photosensitive member according to claim 3 , wherein the photosensitive layer comprises, laminated in succession from the conductive substrate,
a charge generation layer including a charge generation material and a resinous binder, and
a charge transport layer including a charge transport material and a resinous binder.
5. The electrophotographic photosensitive member according to claim 3 , wherein I sb is determined according to a formula
I sb ={( I 0 −I dark )÷( I ref −I dark )}×100(%)
where I 0 is measured conductive-substrate reflectance, I ref is the reference reflectance, and I dark is a non-illuminated reflectance.
6. The electrophotographic photosensitive member according to claim 3 , wherein the undercoat layer has a film thickness d within a range of 2 μm≦d≦3.5 μm and an undercoat-layer reflectance I ucl within a range of 0<I ucl <17%, where a surface reflectance of a mirror-surface conductive substrate for a monochromatic light of a wavelength, λ=780 nm is taken as a reference reflectance.
7. The electrophotographic photosensitive member according to claim 6 , wherein the photosensitive layer comprises, laminated in succession from the conductive substrate,
a charge generation layer including a charge generation material and a resinous binder, and
a charge transport layer including a charge transport material and a resinous binder.
8. The electrophotographic photosensitive member according to claim 6 , wherein I ucl is determined according to a formula
I ucl ={( I 0 −I dark )÷( I ref −I dark )}×100(%),
where I 0 is a measured undercoat-layer reflectance, I ref is the reference reflectance, and I dark is a non-illuminated reflectance.
9. The electrophotographic photosensitive member according to claim 1 , wherein the undercoat layer has a film thickness d within a range of 2 μm≦d≦3.5 μm and an undercoat-layer reflectance I ucl within a range of 0<I ucl <17%, where a surface reflectance of a mirror-surface conductive substrate for a monochromatic light of a wavelength, λ=780 nm is taken as a reference reflectance.