Apparatus for producing a substrate for a photoconductive members

An apparatus suitable for fabricating a substrate suitable for photoconductive members has a cylindrical rotating vessel surrounded by a housing which contains a plurality of rigid spheres therein. A substrate supporting means is placed within the cylindrical rotating vessel so as to be rotatable coaxially therewith. A supplying means for a surface coating liquid, such as polybutene, is placed at an upper position over the external wall face of the cylindrical rotating vessel. A reservoir for the surface coating liquid is placed at a lower position below the external wall face of the cylindrical rotating vessel. A means to circulate the surface coating liquid to the supplying means is employed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for treating the surface of a body 
to produce a surface-treated material which is suitably used as a 
constituting member for electric devices, electron devices, or especially 
as a substrate for the light receiving member in electrophotography. 
2. Description of the Prior Art 
There have been used metal bodies in plate form, cylindrical form, 
endless-belt form or the like as a substrate for photoconductive members 
such as the light receiving member in electrophotography. And for such 
metal bodies, they are required to have an appropriate surface to be 
suited for their uses. 
Because of this, a surface treatment by the grinding work with means of a 
diamond cutting tool using lathe, milling cutter, etc. has been carried 
out for the surface of a metal body. As the metal body, there has been 
generally used aluminum alloy as the most preferable one. And in the 
conventional technique, aluminum alloy is subjected to said surface 
treatment, and an appropriate light receiving layer is formed on the 
treated surface of the aluminum alloy in accordance with the use purpose. 
However, there exist various problems in the conventional surface treating 
technique. That is, during the surface treatment by grinding work with 
means of a diamond cutting tool using lathe, milling cutter, etc. in the 
conventional surface treating technique, intermetallic compounds such as 
Si-Al-Fe series compounds, Fe-Al series compounds, TiB.sub.2 and the like, 
oxides of Al, Mg, Ti, Si and Fe and/or air holes due to H.sub.2 gas are 
often generated within the alloy texture. In addition to these problems, 
there is another kind problem that a surface defect such as level 
difference at grain boundary which generates between adjacent aluminum 
textures having different crystal orientations is often brought about. 
Further, in the conventional technique, as for the aluminum alloy for use 
in obtaining an appropriate substrate, it is necessary to have an 
extremely clean surface. However, a film composed of oxides having a 
thickness of up to 30 .ANG. is apt to be easily formed on the surface of 
such kind aluminum alloy since its surface still remains active even under 
ultra-high vacuum condition of 10.sup.-9 mmHg. 
Under these circumstances, a surface-treated material obtained in 
accordance with the known manner eventually becomes such that is likely to 
invite various problems and defects to the functions of a photoconductive 
member prepared by depositing a light receiving layer thereon. 
For instance, in the case where it is a light receiving member for 
electrophotography, a light receiving layer formed on the surface of such 
material is apt to become such that is poor in layer uniformity and 
constituent homogeneity, and is unstable in electric, optical and 
photoconductive characteristics thereby bringing about defects in the 
images obtained. 
This tendency is remarkable in the case where the light receiving layer is 
composed of an amorphous material consisting of silicon atoms or 
containing silicon atoms as the main constituent. 
SUMMARY OF THE INVENTION 
The present inventors have conducted extensive studies in order to solve 
the problems in the aforementioned conventional techniques and in order to 
develop a new manner for effectively and simply producing a 
surface-treated material which has a desirable surface shape to be suited 
as a constituting member for electric devices, electron devices, and 
especially as a substrate for the light receiving member in 
electrophotography. 
As a result, the present inventors finally have found a manner that enables 
one to efficiently and stably produce said surface-treated material having 
a particular uneven surface shape provided with irregularities composed of 
a plurality of fine spherical dimples in simplified particular procedures 
as detailed below. 
It is therefore an object of this invention to provide an apparatus for 
producing a desirable surface-treated material which is usable as a 
constituting member for electric devices, electron devices, and especially 
as a substrate for the light receiving member in electrophotography. 
Another object of this invention is to provide an apparatus for producing a 
surface-treated substrate having a particular uneven-shaped surface 
provided with irregularities composed of a plurality of fine spherical 
dimples which enables one to prepare a desirable photoconductive member 
having a photoconductive layer being wealthy in practically applicable 
characteristics; being free from any problem due to rest potential, being 
constantly stable in electric, optical and photoconductive properties, 
having a high light fatigue resistance, a high durability and a high 
moisture resistance, and being not deteriorated upon repeating use. 
Further object of this invention is to provide an apparatus for producing a 
surface-treated substrate having a particular uneven-shaped surface 
provided with irregularities composed of a plurality of fine spherical 
dimples which enables one to prepare a desirable light receiving member 
for electrophotography having a light receiving layer composed of an 
amorphous material containing silicon atoms as a main constituent and, if 
necessary, hydrogen atoms(H) and/or halogen atoms (X) [hereinafter 
referred to as "a-Si(H,X)"] which is replete in the above-mentioned 
practically applicable characteristics and has a function of effectively 
preventing the occurrence of interference fringe in the formed images due 
to the interference phenomenon thereby forming visible images of excellent 
quality even in the case of using coherent laser beams possible producing 
interference as a light source.

DETAILED DESCRIPTION OF THE INVENTION 
The present inventors have made earnest studies for overcoming the 
foregoing problems on the conventional substrate (support) for electric 
devices, electron devices, and especially for the light receiving member 
in electrophotography and attaining the objects of this invention as 
described above and, as a result, have accomplished this invention based 
on the findings as below described. 
That is, one of the findings is that when rigid true spheres are dropped 
gravitationally onto the surface of a relevant aluminum alloy body to be a 
substrate, for instance, for the light receiving member in 
electrophotography, there can be obtained a desirable surface-treated 
material having an uneven-shaped surface provided with irregularities 
composed of a plurality of fine spherical dimples which is accompanied 
with neither any intermetallic compound nor any metal oxide, which has not 
any presence of a hole due to H.sub.2 gas and which has not any occurrence 
of surface defects such as level difference at grain boundary respectively 
observed in the conventional substrate. 
Another finding is that when the above surface treating process is carried 
out in the presence of a liquid containing a long chain molecular 
hydrocarbon such as polybutene, no oxide film is formed on the surface of 
the aluminum alloy body. 
Further finding is that when a light receiving layer composed of a-Si(H,X) 
is deposited on the thus resulting substrate to obtain a light receiving 
member for use in electrophotography by glow discharging manner, there can 
be obtained a desirable light receiving member having a uniform and 
homogeneous light receiving layer being wealthy in practically applicable 
characteristics. That is, in the light receiving member thus obtained, 
lights passed through the light receiving layer reflect on the layer 
interface and at the surface of the substrate and interfere each other to 
effectively prevent images to be obtained from being accompanied with 
interference fringe patterns thereby enabling one to make images excellent 
in quality. 
This invention has been completed on the basis of the above findings, and 
it provides an apparatus for producing a surface-treated material having a 
particular surface shape provided with irregularities composed of a 
plurality of fine spherical dimples which is indeed suitable for use in 
electric devices, electron devices and especially suitably usable as a 
substrate for the light receiving member in electrophotography, 
characterized in that a plurality of rigid spheres of even surface or 
uneven surface having almost the same diameter or different diameters are 
let falling from almost the same height onto the surface of a body to be 
said surface-treated material in the state of having been entirely coated 
with a liquid containing polybutene (hereinafter referred to as "coating 
liquid") to make the body surface to be in an uneven shape provided with 
irregularities composed of a plurality of fine spherical dimples. 
The body for use in surface treatment by the apparatus of this invention 
may be either electroconductive or electrically insulative. 
The electroconductive body can include, for example, metals such as NiCr, 
stainless steels, Al, Cr, Mo, Au, Nb, Ta, V, Ti, Pt and Pb or the alloys 
thereof. 
The electrically insulative body can include, for example, films or sheets 
of synthetic resins such as polyester, polyethylene, polycarbonate, 
cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene 
chloride, polystyrene, and polyamide, glass, ceramic and paper. It is 
preferred that the electrically insulative support is applied with 
electroconductive treatment to at least one of the surfaces thereof and 
disposed with a light receiving layer on the thus treated surface. 
In the case of glass, for instance, electroconductivity is applied by 
disposing, at the surface thereof, a thin film made of NiCr, Al, Cr, Mo, 
Au, Ir, Nb, Ta, V, Ti, Pt, Pd, In.sub.2 O.sub.3, SnO.sub.2, ITO (In.sub.2 
O.sub.3 +SnO.sub.2), etc. In the case of the synthetic resin film such as 
a polyester film, the electroconductivity is provided to the surface by 
disposing a thin film of metal such as NiCr, Al, Ag, Pv, Zn, Ni, Au, Cr, 
Mo, Ir, Nb, Ta, V, Tl and Pt by means of vacuum deposition, electron beam 
vapor deposition, sputtering, etc. or applying lamination with the metal 
to the surface. The support may be of any configuration such as 
cylindrical, belt-like shape, which can be properly determined depending 
on the application uses. For instance, in the case of using the light 
receiving member as image forming member for use in electronic 
photography, it is desirably configurated into an endless belt or 
cylindrical form in the case of continuous high speed reproduction. The 
thickness of the support member is properly determined so that the light 
receiving member as desired can be formed. In the case flexibility is 
required for the light receiving member, it can be made as thin as 
possible within a range capable of sufficiently providing the function as 
the substrate. However, the thickness is usually greater than 10 um in 
view of the fabrication and handling or mechanical strength of the 
substrate. 
The rigid sphere of even surface or uneven surface (usually .phi.=0.4-2.0 
mm) to be used for forming the uneven shape as described above at the 
support surface can include, for example, various kinds of rigid spheres 
made of stainless steels, aluminum, steels, nickel and brass and like 
other metals, ceramics and plastics. Among all, rigid spheres of stainless 
steels or steels are preferred in view of the durability and the reduced 
cost. The hardness of such sphere may be higher or lower than that of the 
support. 
However, in the case of using the rigid sphere repeatedly used, it is 
desired that the hardness is higher than that of the support. 
As for the coating liquid to be used for coating the body, it is required 
to uniformly coat the entire surface of the body with a thinner liquid 
coat as much as possible. Then the liquid coat is necessary to be easily 
solidified. The solidified liquid coat is necessary to be easily and 
completely washed out in washing process. Further, in dry-finishing 
process it is necessary that neither any dry unevenness nor any residue be 
left to bring about a surface-treated material in the absolute clean 
state. 
In this connection, the coating liquid is required to satisfy the following 
(a) to (e) conditions; (a) that is a viscous liquid, (b) that has an 
insulative property, (c) that has a coating action, (d) that the resulting 
coat can be easily washed out with a solvent and (e) that after the 
removal of the solidified coat the surface of the surface-treated material 
is in an absolute clean state. 
As the coating liquid to satisfy all the above conditions, a liquid 
prepared by dissolving a long chain molecular hydrocarbon in a relevant 
solvent can be mentioned as a preferred example. 
As typical examples for the long chain molecular hydrocarbon, there are 
polybutenes. Among the polybutenes, those represented by the following 
general formula are preferred; 
##STR1## 
wherein n is an integral number of 3 to 40. And among the polybutenes 
represented by the above general formula, those of which n is 3 to 20 are 
most preferred. 
Further, among the most preferred polybutenes there are some which satisfy 
all the foregoing conditions themselves. In that case, the coating liquid 
can be substantially consisted of that kind polybutene. 
As for the solvent to be used for preparing the coating liquid, any organic 
solvent can be employed as long as it disolves the long chain molecular 
hydrocarbon to obtain the coating liquid which satisfies the foregoing (a) 
to (e) conditions. 
Usable as the organic solvent are, for example, ether, heptane, toluene, 
trichloroethylene, trichloroethane and the like. And among these organic 
solvents, trichloroethane is most preferable. That is, when 
trichloroethane is used, the foregoing polybutene can be easily and 
effectively dissolved therein to obtain a desirable coating liquid which 
is malleable and coats the entire body surface uniformly with an even and 
extremely thin liquid coat which does not give any hindrance for the 
formation of an uneven shape composed of a plurality of fine spherical 
dimples at the body surface by the falling rigid spheres thereonto and 
brings about sooner solidification of the liquid coat after the uneven 
shape formation toward the body surface. And using said coating liquid in 
washing process results in washing out the solidified coat effectively and 
completely to lead to obtaining a desirable surface-treated material 
having an absolute clean uneven shaped surface provided with 
irregularities composed of a plurality of fine spherical dimple without 
any unevenness and any residue due to the coat in the successive drying 
process. 
And, as for the coating liquid composed of said polybutene and 
trichloroethane, the constituting ratio of the two substances is an 
important factor. The constituting ratio of said polybutene versus 
trichloroethane is preferably in the range of 1:4 to 4:1 and most 
preferably 1:1. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Explanation will be then made to embodiments of the apparatus of this 
invention for producing a surface-treated material having an uneven shaped 
surface provided with irregularities composed of fine spherical dimples 
which referring to the drawings, but this invention is not intended to 
limit only thereto. 
FIGS. 1(A) through 1(C) show several typical embodiments of substrates 
formed with the uneven shape composed of a plurality of spherical dimples 
at the surface according to this invention, in which explanation on the 
coating liquid is omitted for simplification purpose. 
In the embodiments shown in FIG. 1(A), a plurality of dimples pits 104, 104 
. . . substantially of an identical radius of curvature and substantially 
of an identical width are formed while being closely overlapped with each 
other thereby forming an uneven shape regularly by causing to fall a 
plurality of spheres 103, 103, . . . regularly substantially from an 
identical height to different positions at the surface 102 of the body 
101. In this case, it is naturally required for forming the dimples 104, 
104, . . . overlapped with each other that the spheres 103, 103, . . . are 
gravitationally dropped such that the times of collision of the respective 
spheres 103 to the surface 102 are displaced from each other. 
Further, in the embodiment shown in FIG. 1(B), a plurality of dimples 104, 
104', . . . having two kinds of radius of curvature and two kinds of width 
are formed being densely overlapped with each other to the surface 102 of 
the body 101 thereby forming an unevenness with irregular height at the 
surface by dropping two kinds of spheres 103, 103', . . . of different 
diameters from the heights substantially identical with or different from 
each other. 
Furthermore, in the embodiment shown in FIG. 1(C) (front elevational and 
cross-sectional views for the body surface), a plurality of dimples 104, 
104, . . . substantially of an identical radius of curvature and plural 
kinds of width are formed while being overlapped with each other thereby 
forming an irregular unevenness by causing to fall a plurality of spheres 
103, 103, . . . substantially of an identical diameter from substantially 
identical height irregularly to the surface 102 of the body 101. 
As described above, uneven shape composed of the spherical dimples can be 
formed by dropping the rigid spheres onto the support surface. In this 
case, a plurality of spherical dimples having desired radius of curvature 
and width can be formed at a predetermined density on the support surface 
by properly selecting various conditions such as the diameter of the rigid 
spheres, falling height, hardness for the rigid true sphere and the body 
surface or the amount of the fallen spheres. That is, the height and the 
pitch of the uneven shape formed on the support surface can optionally be 
adjusted depending on the purpose by selecting various conditions as 
described above thereby enabling to obtain a substrate having a desired 
uneven shape on the surface. 
FIG. 2(A) is a cross-sectional view schematically illustrating a 
constitutional example of the apparatus for producing a surface-treated 
substrate according to this invention, and FIG. 2(B) is an enlarged 
portion view of the surrounding wall of the cylindrical rotating vessel of 
the apparatus shown in FIG. 2(A). 
FIG. 3(A) is a cross-sectional portion view schematically illustrating a 
modified example of the apparatus as shown in FIG. 2(A); and FIG. 3(B) is 
an enlarged portion view of the surrounding wall of the cylindrical 
rotating vessel in the apparatus as shown in FIG. 3(A). 
FIG. 4(A) is a cross-sectional portion view schematically illustrating a 
modified example of the apparatus as shown in FIG. 3(A); and FIG. 4(B) is 
an enlarged portion view of the surrounding wall of the cylindrical 
rotating vessel in the apparatus as shown in FIG. 4(A). 
Referring to FIGS. 2(A) and 2(B), surrounding wall 1 has upper part 11 in 
oval form of a cross section which is forming space A of an oval form in 
the inside and lower part 12 in a round form of a cross section which is 
forming space B of a round form in the inside. In the middle at the bottom 
part of the space B, there is provided a downward projected semicircular 
part 13 which is forming space C. The surrounding wall 1 is unitedly 
formed while being completely sealed by a metal plate such as stainless 
steel which has a resistance against pressure, heat and chemicals. 
The entire of the surrounding wall 1 makes a housing being long from side 
to side at the external appearance and the both sides of the housing are 
fixedly sealed by appropriate side walls (not shown). 
The device is supported by supporting base 2 wherein the downward projected 
semicircular part 13 is buried in the supporting base 2 so as to fixedly 
support the entire of the device thereby. 
In the middle of the space B, there is installed cylindrical rotating 
vessel 3 which is made up unitedly of a perforated metal plate such as 
panching metal. Both sides of the rotating vessel 3 are respectively 
rotatably supported by the corresponding side wall of the housing. One 
side of the rotating vessel 3 is connected to an appropriate drive means 
such as a motor (not shown) so that it can be rotated around the axial 
center. The rotating vessel 3 contains rigid true spheres or rigid spheres 
of an uneven surface shape 4, 4, . . . , which are carried while riding on 
the inner face of the surrounding wall of the rotating vessel up to the 
rotation top part by the action of perforated irregularities of the 
surrounding wall and the centrifugal force of the rotating vessel then 
gravitationally dropped onto the surface of a body (aluminum cylinder for 
a substrate) in cylindrical form 5 as shown in FIG. 3(A). The body is 
supported on rotating shaft 6 being connected to a drive means such as 
motor coaxially with the rotating vessel 3 at the side wall of the housing 
(not shown). At the upper middle position in the space A, there is placed 
coating liquid spraying pipe 7 having holes 71, 71, . . . to allow the 
coating liquid to be jetting-like downward sprayed, which is extended 
linearly crossing the horizontal length of the space A above and over the 
rotating vessel 3. 
An opening 8 coating liquid conveying pipe 81 is provided to the space C. 
The coating liquid conveying pipe 81 is connected to the coating liquid 
spraying pipe 7 through an appropriate pump means. Liquid storing tank 82 
is employed with which exhausting pipe 84 having an appropriate valve 
means 84' is provided at the bottom part. In the storing tank 82, the 
coating liquid conveyed from the device is clarified by settling sediments 
such as fine metal particles caused during the surface treatment 
operation, which are exhausted together with a liquid through the 
exhausting pipe 84. A new coating liquid in the amount of the exhausted 
liquid is supplied into the system from reservoir 83 through conduit 83' 
having an appropriate valve means. 
The coating liquid is necessary to be replaced entirely after a 
predetermined number of cycles. In that case, the entire used coating 
liquid is exhausted through the exhausting pipe 84 by opening the valve 
means 84' while closing valve means 82', and thereafter a new coating 
liquid in a predetermined amount is supplied into the system from the 
reservoir 83 in the same way as previously described. 
An example of producing a surface-treated material by operating the 
apparatus as shown in FIG. 2(A) is now explained. 
Firstly, a body in cylindrical form such as aluminum alloy cylinder 5 is 
placed on the rotating shaft 6 in the rotating vessel 3 containing a 
plurality of the rigid spheres 4, 4, . . . , then a coating liquid [for 
example, composed of polybutene and trichloroethane (1:1)] in a 
predetermined amount is introduced into the system from the reservoir 83 
and sprayed over the surrounding wall of the rotating vessel 3 through the 
spraying holes 71, 71, . . . of the spraying pipe 7 in the way as shown in 
FIG. 2(A) in which the spraying situation of the coating liquid is 
represented by numerical number 9. The coating liquid thus supplied is 
successively passed through the perforations of the surrounding wall of 
the rotating vessel 3 and flowed down onto the surface of the body 5 
thereby coating it with a thin liquid coat. The residual coating liquid is 
further flowed down to soak the rigid spheres existing in the bottom part 
of the rotating vessel 3 then passed through the perforations of the 
surrounding wall of the rotating vessel 3 into the space C. The coating 
liquid gathered therein is conveyed into the liquid storing tank 82 then 
recycled to the spraying pipe by the action of the pump means. It is a 
matter of course that after the introduction of the coating liquid in a 
predetermined amount into the system, the valve means 83' is closed to 
stop the supply of the coating liquid from the reservoir 83. Then the 
rotation of the rotating vessel 3 and that of the rotating shaft are 
started, wherein the former is rotated in the opposite direction to the 
latter respectively in the way as shown by the arrow mark in FIG. 2(A). 
The rotating speed of the rotating vessel 3 is properly determined and 
controlled while considering that the rigid spheres 4, 4, . . . can be 
appropriately lifted up to the top part along the inner face of the 
surrounding wall of the rotating vessel 3 to allow those rigid spheres to 
be gravitationally fallen onto the surface of the body 5. On the other 
hand, the rotating speed of the rotating shaft 6 is properly determined 
and controlled while considering the density of the spherical dimples to 
be formed and the amount of rigid spheres supplied. 
As above explained, the formation of an even shape provided with 
irregularities composed of fine spherical dimples to the surface of the 
body is carried out while coating the entire surface of the body with a 
thinner liquid coat. The operation of the surface treatment may be carried 
out at room temperature under atmospheric pressure condition. However in 
the case when it is desired to make the rigid spheres strongly collided 
against the surface of the body, said operation is preferred to carry out 
under reduced pressure condition. 
After the passage of a predetermined time period, when the rotation of the 
rotating vessel and that of the rotating shaft are stopped and at the same 
time the supply of the coating liquid is stopped, there is brought about a 
surface-treated product having an uneven shaped surface provided with 
irregularities composed of fine spherical dimples which is entirely coated 
with a thinner solidified coat. The product is taken out from the 
apparatus, and may be stored in stable state without having any problem 
even at an appropriate open place even in the case of an aluminum alloy 
cylinder until it is used since its entire surface is prevented from being 
contacted with air by the solidified coat placed thereon. 
In the apparatus of this invention, a desirable surface treated can be 
continuously produced by placing a new body to be treated in the system 
and commencing the above operation after the once obtained product has 
been taken out from the apparatus. 
The above example is directed to the case of one body, but it is possible 
for the apparatus of this invention to be so structured that plural bodies 
may be treated at the same time. 
Further, for practical use of the surface-treated product having a thinner 
solidified coat thereon resulted from the apparatus, it is first subjected 
to washing with an appropriate solvent to remove the solidified coat 
therefrom followed by dryness, and the material thus obtained is brought 
into a deposition chamber (not shown) for forming a light receiving layer 
on its absolutely clean uneven-shaped surface in any case. 
Therefore, in the case where necessary, the above washing process may be 
conducted in the apparatus as shown in FIG. 2(A). In that case, after the 
surface treatment operation having been terminated, the entire coating 
liquid remaining in the system is exhausted therefrom, and a washing 
liquid such as trichloroethane is supplied from a reservoir (not shown) to 
the spraying pipe 7 through the liquid conveying pipe 81 to be downward 
jetting-like sprayed through spraying holes 71, 71, . . . while the 
rotation of the rotating vessel being stopped but the rotating shaft on 
which a surface treated body coated with a thinner liquid coat or a 
thinner solidified coat being placed being rotated properly. The washing 
liquid gathered in the space C can be recycled for repeated use. Otherwise 
it is exhausted outside the system through the exhausting pipe 84 while 
the valve means 82' being closed and the valve means 84' being opened. 
FIG. 3(A) is a cross-sectional portion view schematically illustrating a 
modified example of the apparatus as shown in FIG. 2(A); and FIG. 3(B) is 
an enlarged portion view of the surrounding wall of the cylindrical 
rotating vessel in the apparatus as shown in FIG. 3(A). 
In the apparatus of this invention as shown in FIGS. 3(A) and 3(B), liquid 
flow stopping bars 32, 32, . . . are fixedly disposed horizontally in the 
longitudinal direction on the external surface of the surrounding wall of 
the rotating vessel 3 and rigid sphere holding bars 31, 31, . . . are 
fixedly disposed horizontally in the longitudinal direction on the inner 
surface of said surrounding wall. 
The operation of the apparatus of this invention as shown in FIGS. 3(A) and 
3(B) is conducted in the same way as in the apparatus as shown in FIGS. 
2(A) and 2(B) except that the inflow of the coating liquid into the 
rotating vessel 3 is more effectively proceeded by the actions of the 
liquid flow stopping bars 32, 32, . . . and lifting the rigid spheres 4, 
4, . . . is more effectively proceeded by the actions of the rigid sphere 
holding bars 31, 31, . . . 
FIG. 4(A) is a cross-sectional portion view schematically illustrating a 
modified example of the apparatus as shown in FIG. 3(A); and FIG. 4(B) is 
an enlarged portion view of the surrounding wall of the cylindrical 
rotating vessel in the apparatus as shown in FIG. 4(A). 
In the apparatus of this invention as shown in FIGS. 4(A) and 4(B), the 
rigid sphere holding bars 31, 31, . . . in the apparatus as shown in FIGS. 
3(A) and 3(B) are replaced by blade-like form bars 31', 31', . . . 
In this apparatus, lifting the rigid spheres 4, 4, . . . are further 
effectively proceeded and at the same time releasing those rigid spheres 
at the rotation top part of the rotating vessel 3 and their falling can be 
more properly conducted. 
As above detailed, according to the apparatus of this invention there can 
be obtained a desirable surface-treated material that fine spherical 
dimples following the shape of a rigid spheres are formed with the surface 
without leaving plane part and the surface is entirely coated with a solid 
coat caused by the coating liquid so that the surface provided with 
irregularities composed of fine spherical dimples is prevented from being 
in contact with air thereby it being always kept in a stable state. 
Washing with a solvent such as trichloroethane invites an effective 
elution of the solid coat and the result after dryness gives a desirable 
surface-treated material having an absolute clean surface provided with 
irregularities composed of a plurality of fine spherical dimples which is 
indeed suitable as a substrate for photoconductive members. 
In fact, it has been found as a result of the comparative test that the 
surface-treated substrate obtained in accordance with the apparatus is 
superior to another kind surface-treated substrate having an uneven-shaped 
surface provided with irregularities composed of fine spherical dimples 
which was obtained in accordance with the apparatus of this invention 
without using any coating liquid. 
In the comparative test, a film composed of a-Si : H : X was formed on the 
surface of each substrate, and the resulting two members were subjected to 
imagewise exposure by irradiating laser beams at 780 nm wavelength and 
with 80 .mu.m of spot diameter using known image exposing device and 
images were obtained by subsequent development and transfer. The state of 
the occurrence of an interference fringe on thus obtained images was 
observed and evaluated for each member. As a result, it was found that the 
former member is superior to the latter member.