Developer regulating member and developing apparatus

A developer regulating member includes a thin plate having a spring property and a polyamide-containing rubber layer disposed on the thin plate. The polyamide-containing rubber layer contains a polyamide having the Shore D hardness between 25 and 65 both inclusive. A developing apparatus includes a developer container for containing a monocomponent developer of negative charging property, a developer carrying member provided in an opening portion of the developer container, for carrying the developer, and a regulating member for forming a nip together with the developer carrying member and regulating a thickness of a developer layer on the developer carrying member. A surface of the regulating member forming the nip is comprised of a polyamide-containing rubber layer containing a polyamide having the Shore D hardness between 25 and 65 both inclusive.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a developing apparatus used in image 
forming apparatus such as copiers and printers, and to a developer 
regulating member for regulating a developer, used in the developing 
apparatus. 
2. Related Background Art 
In the image forming apparatus of the electrophotographic method) the 
developing apparatus visualizes an electrostatic latent image formed on an 
image carrying member, in the form of a toner image. 
As one type of such developing apparatus, a variety of dry-type 
monocomponent developing apparatuses were proposed and are under practical 
use. It is, however, not easy to form a thin layer of toner as a 
monocomponent developer on a developer carrying member in either one of 
the developing apparatus. 
An improvement is demanded in resolution, visibility, and the like of image 
nowadays, and it is essential to develop a method and apparatus for 
forming the thin layer of toner. Some measures were proposed as to such 
method and apparatus. 
For example, as described in Japanese Laid-open Patent Application No. 
54-43038, there is a developing apparatus in which a rubber or metal 
elastic blade is set in contact with a developing sleeve of the developer 
carrying member and in which the toner is regulated as being passed 
through the contact portion between the elastic blade and the developing 
sleeve, whereby the thin layer of toner is formed on the developing sleeve 
and friction in the contact portion causes sufficient triboelectricity on 
the toner. 
For regulating non-magnetic toner by the above elastic blade, a separate 
toner supply member for supplying the toner onto the developing sleeve 
becomes necessary. The reason is that in the case of magnetic toner the 
toner can be supplied onto the developing sleeve by magnetism of a magnet 
in the developing sleeve, whereas in the case of the non-magnetic toner 
the toner cannot be supplied by magnetism. 
Thus, the developing apparatus shown in FIG. 4 was proposed in Japanese 
Laid-open Patent Application No. 58-116559. In this conventional 
developing apparatus proposed, an elastic roller 27 of fur brush structure 
in contact with the developing sleeve 26 is disposed at an upstream 
position in the rotating direction of the developing sleeve 26 with 
respect to the elastic blade 25 in a developer container 24 containing the 
nonmagnetic toner 23 as a monocomponent developer, and the elastic roller 
27 scrapes the residual toner 23 remaining on the developing sleeve 26 
without being consumed for development and also supplies new toner 23 onto 
the developing sleeve 26. 
The above-stated structure enabled the thin film of non-magnetic toner 23 
to be formed well on the developing sleeve 26 and thus enabled an 
electrostatic latent image to be developed well on the image carrying 
member. 
However, demands for a further improvement in quality of image and for a 
further reduction in consumption energy induced the need for use of toner 
with smaller particle sizes and with lower melting point. In repeating the 
developing operation with a such toner many times, the following problems 
arose. 
(1) When a thin metal plate of SUS, phosphor bronze, or the like is used as 
the elastic blade, longitudinal contact is likely to become nonuniform 
because of its too high hardness, so that coating unevenness of toner 
tends to occur on the developing sleeve. Further, the too high hardness 
causes excessive force to be applied locally on the toner and poor 
releasability of surface causes the toner to be fused on the surface of 
elastic blade in contact with the developing sleeve after repetition of 
the developing operation. This results in coating unevenness of toner or 
stripes on the developing sleeve, thus in turn resulting in poor quality 
of image. 
(2) If the elastic blade is a plate of conventional urethane rubber, 
silicone rubber, or the like used singly or one formed by bonding such 
rubber onto a metal thin plate in order to achieve stable contact 
throughout long-term operation, the problem of (1) will be avoided, but 
triboelectrification capability to the toner will become insufficient, 
making triboelectricity insufficient on the toner. This will result in fog 
as a problem of image, and in the worst case it raises the problem that 
the toner is scattered from the developing sleeve to contaminate the 
inside of image forming apparatus. 
Thus, the elastic blade itself needs to be made of a material with high 
triboelectrification capability. A material having high electron accepting 
property is selected for toner of positive polarity, while a material 
having high electron donating property is selected for toner of negative 
polarity. 
There were various proposals on use of materials in which a charge control 
material of high electron donating property was added in a base material 
of silicone rubber, urethane rubber, or the like, especially for the 
negative-polarity toner among the above, but they were not sufficient yet 
in terms of the triboelectricity given to the toner. They were not 
successful yet in preventing occurrence of a foggy image especially under 
high-humidity circumstances. 
In order to prevent this occurrence of a foggy image, materials of further 
higher electron donating property are effective, and for example, 
polyamide resins such as nylon are used. Since the polyamide resins do not 
have elasticity, it is of course impossible to use them in a plate shape 
singly. It is conceivable that they may be used in the form of a coating 
on a thin metal plate as a supporting layer for regulating pressure or in 
the form of a plate of resin bonded thereto. 
Employment of this structure was able to prevent the occurrence of a foggy 
image in the initial state of developing operation, but on the other hand 
it raised coating unevenness of toner on the developing sleeve in the 
initial state and occurrence of fusion of toner to the surface of elastic 
blade after repetition of the developing operation, as in the above case 
of using the metal thin plate singly. A cause of this is of course that 
excessive force is exerted on the toner passing the elastic blade because 
of the too high hardness of polyamide resin. For decreasing the hardness, 
the elastic blade was thus constructed in such structure that, for 
example, urethane rubber was bonded as an elastic layer onto a metal thin 
plate and that a thin coating of polyamide resin was formed as a charge 
giving layer on the surface of urethane rubber. This structure improved 
the stability of toner coating on the sleeve, as compared with the 
structure in which the polyamide resin was directly formed on the thin 
metal film, but after repetition of the developing operation under 
high-temperature circumstances, this structure also resulted in fusion of 
toner at a high-hardness portion, because the hardness of polyamide resin 
itself was high in the surface layer. Thus, this structure was not 
preferable. 
Accordingly, properties desired for the elastic blade are the excellent 
charge giving property to the toner and possession of appropriate hardness 
to allow the toner to pass in an appropriate layer thickness through the 
contact portion without exerting the excessive force thereon in the 
contact portion. The above conventional materials and structures failed to 
meet these properties sufficiently and thus failed to prevent fog and 
fusion of toner. 
It was proposed in Japanese Patent Application No. 7-155511 that the 
elastic blade was made of a polyamide elastomer containing a polyamide 
component of good triboelectrification capability to the negative toner 
and a polyether component having elasticity. 
It was, however, found that simply using this material was not enough to 
prevent the fog and fusion of toner and it was necessary to further define 
a proper range of hardness of the polyamide elastomer in use in order to 
draw the full performance. 
With too low hardnesses, the desired triboelectrification capability cannot 
be attained, so that the fog occurs especially under high-humidity 
circumstances. This is because low-hardness polyamide elastomers include 
low contents of the polyamide component in the formulation thereof and 
therefore the electron donating property of the elastic blade to the 
negative toner is too low. 
Too high hardnesses will cause coating unevenness due to fusion of toner, 
because the excessive force is exerted on the toner passing the elastic 
blade, as being the case with the polyamide resin of the conventional 
example described above. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a developer regulating 
member and a developing apparatus free from coating unevenness and 
occurrence of stripe. 
Another object of the present invention is to provide a developer 
regulating member and a developing apparatus that can give high 
triboelectricity to the developer. 
Still another object of the present invention is to provide a developer 
regulating member and a developing apparatus arranged to prevent fog and 
fusion of developer. 
Still another object of the present invention is to provide a developer 
regulating member comprising a thin plate having a spring property, and a 
polyamide-containing rubber layer disposed on the thin plate, said layer 
containing a polyamide having the Shore D hardness between 25 and 65 both 
inclusive, and also to provide a developing apparatus comprising the 
foregoing developer regulating member. 
Further objects of the present invention will become apparent in the 
description which follows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The embodiments of the present invention will be described. 
(Embodiment 1) 
FIG. 1 is a cross-sectional view of the image forming apparatus using the 
developing apparatus as an embodiment of the present invention and FIG. 2 
is a cross-sectional view of the developing apparatus. In FIG. 1, a 
photosensitive drum 1 as a latent image carrying member rotates in the 
direction of arrow A, the photosensitive drum 1 is uniformly charged by a 
charging device 2 for charging it, and the photosensitive drum 1 is 
exposed to laser light 3 emitted from a laser optical device being 
exposure means for writing an electrostatic, latent image thereon, thereby 
forming the electrostatic, latent image on the surface thereof. 
This electrostatic, latent image is developed by the developing apparatus 4 
disposed in the vicinity of the photosensitive drum 1 and detachably 
mounted in the form of a process cartridge on the image forming apparatus, 
so as to be visualized as a toner image. (In the present embodiment 
so-called reversal development is carried out to form a toner image in the 
exposed portion.) 
The toner image visualized on the photosensitive drum 1 is transferred to 
sheet 13 as a recording medium by a transfer roller 9, transfer-residue 
toner remaining on the photosensitive drum 1 without being transferred is 
scraped by a cleaning blade 10 to be stored in a waste toner container 11, 
and the thus cleaned photosensitive drum 1 repeats the above action to 
form images. 
On the other hand, the sheet 13 with the transferred toner image is 
subjected to a fixing process by a fixing device 12 and the sheet is then 
discharged to the outside of apparatus, thus completing the print 
operation. 
The developing apparatus 4 according to the present invention will be 
described in more detail referring to FIG. 2. 
In FIG. 2, reference numeral 14 designates a developer container for 
containing non-magnetic toner 8 of negative charge property as a 
monocomponent developer, and the present developing apparatus 4 is 
arranged to have a developing sleeve 5 as a developer carrying member 
located at an opening portion extending in the longitudinal direction in 
the developer container 14 and opposed to the photosensitive drum 1 and to 
develop the electrostatic, latent image on the photosensitive drum 1 to 
visualize it. 
In the above developing apparatus 4, the developing sleeve 5 laterally 
extends in the above opening portion so that the substantially right half 
peripheral surface as illustrated intrudes in the developer container 14 
while the substantially left half peripheral surface is exposed to the 
outside of the developer container 14. The exposed surface to the outside 
of this developer container 14 is opposed with a very small gap to the 
photosensitive drum 1 located left of the developing apparatus 4. The 
developing sleeve 5 is driven to rotate in the direction of arrow B and 
the surface thereof has proper roughness for raising a rubbing probability 
against the toner 8 and for good conveyance of toner 8. 
Above the developing sleeve 5 there is disposed an elastic blade 7 arranged 
to be supported by a stop plate 15 and to keep the vicinity of its tip on 
the free end side in surface contact with the outer peripheral surface of 
the developing sleeve 5. The contact direction is the so-called counter 
direction in which the tip side is located on the upstream side in the 
rotating direction of developing sleeve 5 with respect to the contact 
portion. 
This elastic blade 7 is one obtained by bonding a polyamide-containing 
rubber (hereinafter referred to as polyamide elastomer) as an elastic 
member 16 onto a thin metal film 17 of SUS or phosphor bronze having 
spring elasticity or one obtaining by injection-molding the 
polyamide-containing rubber on the metal thin plate 17. This metal thin 
plate maintains the pressing force of elastic blade 7 against the 
developing sleeve 5 and the polyamide elastomer secures the charging 
property to the negative-polarity toner 8. The material, a preparing 
process, etc. of this elastic blade 7 will be detailed hereinafter. 
An elastic roller 6 is in contact with the developing sleeve 5 on the 
upstream side in the rotating direction thereof with respect to the 
contact portion of the above elastic blade 7 with the surface of 
developing sleeve 5 and is supported rotatably. 
In the present developing apparatus 4 described above, in the developing 
operation the toner 8 in the developer container 14 is fed toward the 
elastic roller 6 with rotation of agitating member 18 in the direction of 
arrow C. 
Further, the toner 8 is carried to the vicinity of developing sleeve 5 with 
rotation of the elastic roller 6 in the direction of arrow D. In the 
contact portion between the developing sleeve 5 and the elastic roller 6, 
the toner 8 carried on the elastic roller 6 is rubbed by the developing 
sleeve 5 to be subject to triboelectrification, thereby coming to be 
deposited on the developing sleeve 5. 
After that, with rotation of the developing sleeve 5 in the direction of 
arrow B, the toner is carried under contact with the elastic blade 7, so 
that the toner is given appropriate triboelectricity (quantity of 
triboelectrification) and forms a thin layer on the developing sleeve 5. 
Then the toner is further conveyed to the developing section being the 
opposite part to the photosensitive drum 1. 
Undeveloped toner not consumed in the developing section is recovered from 
the bottom part of developing sleeve 5 with rotation thereof. In this 
recovering section a seal member 19 is provided to let the undeveloped 
toner pass into the developer container 14 and to prevent the toner 8 in 
the developer container 14 from leaking through the bottom part of 
developing sleeve 5. 
The undeveloped toner on the developing sleeve 5, thus recovered, is 
scraped from the surface of developing sleeve 5 in the contact portion 
between the elastic roller 6 and the developing sleeve 5. Most of toner 
thus scraped off is conveyed with rotation of the elastic roller 6 to be 
mixed with the toner 8 in the developer container 14 and the charge on the 
toner is dispersed. At the same time, new toner is supplied onto the 
developing sleeve 5 by rotation of the elastic roller 6 and the 
above-stated action is repeated. 
In the above developing section the latent image on the photosensitive drum 
1 is developed as a toner image by applying an alternating voltage with 
direct current being superimposed thereon (a development AC bias) between 
the developing sleeve 5 and the photosensitive drum 1 by power supply 20. 
Next described is a specific example of each constituent element in the 
developing apparatus 4 in the present embodiment. 
The developing sleeve 5 was the one obtained by subjecting a surface of an 
aluminum sleeve having the diameter of 16 mm to a regular blast treatment 
with spherical glass beads (#600) before surface roughness Rz thereof 
became about 3 .mu.m, and it was disposed as opposed to the photosensitive 
drum 1 with the gap of 300 .mu.m and was rotated at the tip speed 
(peripheral speed) of 80 mm/s a little faster than the tip speed 50 mm/s 
of the photosensitive drum 1. 
The toner 8 was a non-magnetic monocomponent developer, which had a mean 
particle size of 8 .mu.m. 
The elastic roller 6 is preferably of the sponge structure or of the fur 
brush structure in which fibers of rayon, nylon, or the like are planted 
on a core, in terms of supply of toner 8 onto the developing sleeve 5 and 
scraping of undeveloped toner. The present embodiment employed the elastic 
roller 6 of the diameter 12 mm in the structure wherein rubber sponge was 
disposed on a core. This elastic roller 6 was set in contact with the 
developing sleeve 5 and was driven by a driving means, not illustrated, to 
rotate in the same direction as the developing sleeve 5 was. 
The elastic blade 7 according to the present invention is described in 
detail below. 
The polyamide elastomer is a resultant from ester linkage or amide linkage 
between polyamide and polyether, as described previously. 
The polyamide component is selected from polyamide 6, polyamide 6/6, 
polyamide 6/12, polyamide 11, polyamide 12, polyamide 12/12; or 
copolyamides resulting from condensation polymerization of monomers 
thereof; and a preferred polyamide component may be selected from those 
obtained by carboxylating terminal amino groups of the foregoing 
polyamides with a dibasic acid or the like. Examples of the dibasic acid 
include aliphatic saturated dicarboxylic acids such as oxalic acid, 
succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic 
acid; aliphatic unsaturated dicarboxylic acids such as maleic acid; 
aromatic dicarboxylic acids such as phthalic acid and terephthalic acid; 
polydicarboxylic acids made of the foregoing dibasic acids and diols such 
as ethylene glycol, butanediol, hexanediol, and octanediol, and so on. 
The polyether component is one selected from polyetherdiols such as 
homopolymers or copolymers of polyethylene glycol, polypropylene glycol, 
polytetramethylene glycol, and the like; and polyetherdiamines with the 
both terminals aminated. 
In the present embodiment, the polyamide elastomer was molded as an elastic 
member 16 in the thickness of 1 mm on the metal thin film 17 of phosphor 
bronze 0.1 mm thick having the spring elastic property. Specifically, the 
polyamide elastomer was synthesized by using nylon 12 as the polyamide 
component, letting nylon 12 react with dodecanedioic acid as the dibasic 
acid, and using polytetramethylene glycol as the polyether component. The 
resultant was dried for a predetermined time and thereafter was injected 
by injection molding directly into the mold with the metal thin film 17 
set therein, at the melt temperature 200.degree. C. and at the mold 
temperature 30.degree. C., thereby fabricating the elastic blade 7. 
In order to clarify the proper hardness range of this polyamide elastomer, 
the present inventors prepared test samples obtained by forming polyamide 
elastomers of different hardnesses on the metal thin film 17 by the above 
method. The unit of hardness employed herein was the Shore D hardness 
(ASTM D2240), normally used for expressing the hardness of resin. 
For checking the proper Shore D hardness range, each test sample of elastic 
blade was set under contact pressure of 20 g in the developing apparatus 
of the present embodiment, print operations of 3000 sheets were carried 
out under the high-temperature and high-humidity circumstance (35.degree. 
C./90% RH), and the test sample was evaluated, especially, by observing 
fog on image and the toner coating condition on the developing sleeve 5. 
In the developing operation the development bias applied from the power 
supply 20 to the developing sleeve 5 was one obtained by superimposing the 
DC voltage of -400 V on the alternating voltage of the frequency 2000 Hz 
and the peak-to-peak voltage 1600 V, so that surface potentials of the 
latent image on the photosensitive drum 1 were -600 V in unexposed 
portions and -150 V in exposed portions, thereby performing the reversal 
development in the exposed portions. 
Results of evaluation are shown in the following table. 
______________________________________ 
Coating unevenness 
After 
Shore D 3000 
Material hardness Fog Initial 
prints 
______________________________________ 
polyamide 20 x .smallcircle. 
.smallcircle. 
elastomer 
polyamide 25 .smallcircle. 
.smallcircle. 
.smallcircle. 
elastomer 
polyamide 40 .smallcircle. 
.smallcircle. 
.smallcircle. 
elastomer 
polyamide 55 .smallcircle. 
.smallcircle. 
.smallcircle. 
elastomer 
polyamide 65 .smallcircle. 
.smallcircle. 
.smallcircle. 
elastomer 
polyamide 70 .smallcircle. 
.smallcircle. 
x 
elastomer 
polyamide 74 .smallcircle. 
x x 
resin 
______________________________________ 
As apparent from the table, in the case of the Shore D hardness being 20, 
fog occurred on the image from the initial stage of the print operation, 
whereas this fog did not appear in the case of the Shore D hardness being 
25 or more. The reason is that the polyamide elastomer of low Shore D 
hardness includes a low content of the polyamide component in the 
formulation thereof and exhibits the low electron donating property to the 
negative-polarity toner, as described previously. 
The preferred content of the polyamide component is 20% or more by weight 
with respect to the polyamide elastomer. 
In the case of the Shore D hardness being 70, toner coating unevenness and 
stripe appeared on the developing sleeve 5 after print operations of 3000 
sheets. In contrast, no coating unevenness occurred in the case of the 
Shore D hardness being 65 or less. The cause of this unevenness is the 
fusion of toner on the surface of elastic blade 7, which is caused by 
excessive force locally applied on the toner because of too high hardness 
of polyamide elastomer. The table further shows the evaluation result of 
the polyamide resin having the Shore D hardness 74 as a comparative 
example. The comparative example showed some coating unevenness on the 
developing sleeve 5 from the initial state and repetition of print 
operations of about 1000 sheets resulted in coating stripes. The reason 
why the coating unevenness occurred from the initial state as observed is 
the too high hardness and failure in obtaining a uniform contact nip in 
the longitudinal direction for lack of rubber elasticity. In addition, 
appearance of coating stripe after durability test is also due to the 
extreme fusion of toner caused by the high hardness. 
Accordingly, the proper range of the Shore D hardness of the polyamide 
elastomer is between 25 and 65 both inclusive, whereby the desired 
triboelectrification capability to the toner can be achieved under 
high-temperature and high-humidity circumstances and whereby fusion of 
toner can be prevented from occurring on the blade surface after 
repetition of print operations. As a result, the uniform toner coating was 
able to be attained stably from the initial state. 
(Embodiment 2) 
The second embodiment of the present invention will be described referring 
to FIG. 3 which is the schematic, cross-sectional view of developing 
apparatus 21. 
In the present embodiment, the elastic blade 22 is a plate blade 22 of 
polyamide elastomer 1.5 mm thick without the metal thin plate 17, 
different from Embodiment 1. 
Namely, the present embodiment is arranged to make the elastic blade 22 in 
contact with the developing sleeve 5 by the spring elasticity of the 
polyamide elastomer itself. Since the polyamide elastomer is provided with 
elasticity based on the polyether component as described in Embodiment 1, 
the structure can be simplified by omitting the thin metal plate for 
regulating the pressure, as in the present embodiment. 
The proper hardness range of polyamide elastomer is between 25 and 65 both 
inclusive of Shore D hardness as in Embodiment 1, whereby the same effect 
as in Embodiment 1 can be achieved. 
In this case, the thickness of the blade is preferably not less than 1.0 
mm. 
It is of course possible to select each of the members used in Embodiments 
1 and 2 as the occasion may demand, within the scope of the present 
invention. 
Although Embodiments 1 and 2 employed the process cartridge of the 
developing apparatus detachably mounted on the main body of image forming 
apparatus, the developing apparatus may be constructed in such structure 
that the developing apparatus is fixed in the main body of image forming 
apparatus and only the toner is replenished thereto. Further, the 
developing apparatus may be incorporated with the photosensitive drum, 
cleaning blade, waste toner receiving container, and charging device in 
the form of a process cartridge to be detachably mounted to the main body 
of image forming apparatus. 
The embodiments of the present invention were described above, but it 
should be understood that the present invention is by no means limited to 
these embodiments and that the invention may involve all modifications 
falling within the technical idea thereof.