JPH08179603A - Development device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a developing device that suppresses filming and increase in torque that occur as the number of printed sheets is piled up and that is stable over a long period of time. A supply bias applying means 22 is connected between the toner carrier 12 and the supply member 18 so as to generate a potential difference, and a predetermined relationship is established between the potential difference and the contact depth of the supply member 18 and the toner carrier 12. Was set, and a predetermined relationship between the average particle diameter of the toner 7 and the average bubble pore diameter on the surface of the foaming member 20 of the supply member 18, and the degree of compression of the toner 7 were defined. Further, the volume resistivity of the supply member 18 is specified, and the rotation direction of the supply member 18 and the peripheral speed with respect to the toner carrier 12 are specified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming an image using toner, and more particularly to a developing device for forming a uniform thin toner layer on a toner carrying member for development.

[0002]

2. Description of the Related Art A conventional developing device is disclosed in JP-A-61-240.
As disclosed in Japanese Patent No. 261, the potential difference is provided between the supply member and the toner carrier to improve the image quality. Further, as disclosed in Japanese Patent Laid-Open No. 3-41486, the pore diameter of the elastic supply member in contact with the toner carrying member is regulated to prevent the developer from being defectively charged and to reduce the density decrease and the density unevenness. .

[0003]

However, JP-A-61-161
In JP-A-240261, when black solid continuous printing is performed, the toner is continuously consumed, the number of times of rubbing with the supply member and the regulating member is small, and the charge amount of the toner does not sufficiently increase. The transportability is deteriorated, a strong mechanical stress is applied to the toner layer between the toner carrier and the regulating member, and toner having a small particle size is generated due to the deformation and crushing of the toner. The small particle size toner has a larger surface area per unit volume than ordinary toner, and therefore has a large adhesive force due to the image force with the toner carrier, resulting in a latent image formed on the latent image carrier from the toner carrier. It is not sufficiently developed and remains on the toner carrier. The residual toner on the toner carrier is peeled off by the supply member and accumulated on the supply member. When the amount of small particle toner accumulated on the supply member increases,
Many adhere strongly to the toner carrier, and at the contact portion of the regulating member, the toner adheres strongly to the regulating member due to the scraping force and the image force of the regulating member. The small particle size toner strongly adhered to the toner carrier and the regulation member is fixed by mechanical stress, frictional heat, etc. by being repeatedly rubbed (hereinafter, the toner is strongly adhered to the toner carrier and the regulation member). The phenomenon is called filming). As a result of filming, the adhered matter may impede the flow of toner and cause a remarkable decrease in image density. Moreover, the toner is likely to be clogged in the supply member, the elasticity of the supply member is lost, and the torque is increased.

By the way, in the above-mentioned Japanese Patent Laid-Open No. 3-41486, when the bubble hole diameter of the foam member of the supply member is small and the toner enters the bubble hole on the surface of the supply member, the surface of the supply member becomes apparently flat, and the toner In some cases, the supply delay was caused due to the loss of the mechanical transport force of the.

Therefore, the present invention is intended to solve the above problems, and an object of the present invention is to suppress filming that occurs as the number of printed sheets is piled up, prevent a remarkable decrease in image density, and suppress an increase in torque. It is to provide a developing device that is stable over a long period of time.

[0006]

A developing device according to the present invention comprises a toner carrier made of an elastic body, a supply member for supplying a toner to the toner carrier with a developer, and a thin toner layer on the toner carrier. In a developing device having a regulating member for forming a toner carrier, the supply member is pressed against the toner carrier, and the contact depth F (mm) between the supply member and the toner carrier and the toner carrier are Between the potential Vb (V) and the potential Vs (V) of the supply member, Vb and Vs have the same polarity and F ≦ 1.0. 1) When F ≦ 0.1 (F + 0.
1) × (| Vs−Vb | +100) ≧ 40 and | Vs−
Vb | ≦ 570, 2) 10 when 0.1 <F ≦ 0.6
0 × F + 90 ≦ | Vs−Vb | ≦ 570, 3) 0.6
<F ≦ 1.0, the relationship is 150 ≦ | Vs−Vb | ≦ 570.

Further, the developing device of the present invention is characterized in that the supply member has a volume resistivity of 10 ³ to 10 ⁹ Ωcm.

Further, in the developing device of the present invention, the supply member is made of an elastic foam, and 3 × dt ≦ ds between the average pore diameter ds of the surface portion and the average particle diameter dt of the developer.
It is characterized by having a relationship of ≦ 40 × dt.

Further, the developing device of the present invention is characterized in that the developer has a compressibility of 35.0% or less.

Further, in the developing device of the present invention, the surface of the supply member rotates in a direction opposite to that of the toner carrier, and the peripheral speed ratio thereof is 30 to 100% with respect to the toner carrier. Is characterized by.

[0011]

According to the present invention, filming is suppressed by providing a predetermined potential difference | Vs-Vb | between the toner carrier and the supply member and satisfying a predetermined relationship between the contact depth between the toner carrier and the supply member. , A good image can be obtained for a long time.

By providing the potential difference | Vs-Vb |, firstly, the force of the electric field enhances the toner transporting property, reduces the mechanical stress on the toner on the toner carrier by the regulating member, and the filming is performed. It suppresses the generation of small particle size toner that causes Secondly, the small particle size toner is also developed without selectively developing only new toner, and the effect of the small particle size toner accumulating on the supply member can be reduced, and the occurrence of filming can be suppressed.

However, the potential difference | Vs-Vb | is 570V.
When the value exceeds the above value, the discharge start voltage is reached, the transportability of the toner becomes unstable, significant density unevenness occurs, and other electric circuits are adversely affected by noise.

In the region where the contact depth F is F ≦ 0.1 mm,
Since the rotation torque is low and the increase rate of the rotation torque when printing is repeated is low, from the viewpoint of low torque, and because the mechanical force that the toner receives due to the friction between the toner carrier and the supply member is small, It is also a desirable region from the viewpoint of suppressing the generation of the diameter toner and reducing the filming. Further, by providing the potential difference | Vs−Vb |, the supplyability is improved, and (F + 0.1) × (| Vs−Vb
Since a sufficient image density can be obtained in the region of the hyperbolic function of | +100) ≧ 40, the good region spreads in the direction of shallow contact depth, and the rotational torque can be further reduced.

In the region of 0.1 <F ≦ 0.6, the toner carrier and the supply member are in sufficient contact with each other, and the chargeability of the toner is made uniform, so that a stable image can be formed without causing a supply delay. It is a desirable area from the viewpoint of obtaining. By providing a potential difference | Vs−Vb |, 100 × F
Filming is suppressed in the region of + 90 ≦ | Vs−Vb |. Further, the toner transportability is improved, and uniform and sufficient image density can be obtained.

In the region of 0.6 <F ≦ 1.0, the toner left undeveloped on the toner carrier due to the print pattern is scraped off by the supply member having a sufficient contact depth, and the print history is kept for a long time. It is a desirable area for obtaining stable printing without causing it over the entire length. By providing the potential difference | Vs−Vb |, filming does not occur in the region of 150 ≦ | Vs−Vb |. Contact depth is 1.0 mm
Is an upper limit value that does not cause jitter and image loss due to an increase in rotation torque.

Further, the volume resistivity of the supply member is 10 ³
By setting it to be 10 ⁹ Ωcm, the potential difference |
The effect of Vs-Vb | is guaranteed. When the resistance is lower than 10 ³ Ωcm, the charge is injected into the toner, and the toner is abnormally charged thereby, so that the good range is narrowed. 10 ⁹
When the resistance is higher than Ωcm, even if the potential difference | Vs−Vb | is set, the resistance of the supply member is large, so that a large voltage drop occurs in the supply member and the supply site between the supply member and the toner carrier is large. The effective potential difference becomes small, and the effect of the potential difference | Vs-Vb | diminishes. In the region where the volume resistivity of the supply member is 10 ³ to 10 ⁹ Ωcm, the potential difference | Vs−
This is desirable in that the effect of Vb | can be efficiently realized.

When the toner is accumulated on the supply member, the following problems occur. First, the elasticity of the foam member is lost, the mechanical stress applied to the toner between the supply member and the toner carrier increases, and small-sized toner particles tend to be generated. When the amount of small-sized toner increases, the pressure and the image force between the toner carrier and the regulation member cause the toner to adhere strongly to the toner carrier and the regulation member and are repeatedly rubbed, resulting in mechanical stress and friction heat. The so-called filming is apt to occur due to sticking due to such factors. Secondly, the elasticity of the supply member is lost and the torque increases. Therefore, the problems can be solved in the following points.

1) By setting the bubble pore diameter ds of the supply member to 3 × dt ≦ ds ≦ 40 × dt with respect to the average particle diameter dt of the toner, it is possible to obtain a structure in which the toner is less likely to be clogged with the supply member. . When the pore diameter is smaller than 3 times the toner particle diameter, the load of the initial rotation torque increases and the mechanical transportability of the toner cannot be sufficiently obtained. When the bubble pore diameter is larger than 40 times the toner particle diameter, the pressing force of the foaming member against the toner carrier becomes small, resulting in uneven density due to defective charging of the toner and delay in supply. Further, if the air holes are clogged with toner, the rate of increase in torque becomes remarkable. Therefore, the relationship of 3 × dt ≦ ds ≦ 40 × dt can solve the above problems.

2) By setting the degree of toner compression to 35.0% or less, it is possible to obtain a structure in which the toner is less likely to be clogged with the supply member. The degree of compression indicates the ratio between the density when the toner is put in a certain container (loose density) and the density when the toner is tapped a predetermined number of times (hard density),
{(Firm density)-(loose density)} / (firm density)
Is defined by The firm density has a correlation with the amount of toner clogging the foam member of the supply member, and the larger the density, the greater the amount of toner clogging. Depending on the ratio of firm density and loosening density,
The degree of toner clogging of the supply member can be regulated. If the toner has a degree of compression of more than 35.0%, when the printing is repeated, the toner has a tendency to increase in the degree of compression of the toner when small-sized toner particles are generated due to crushing of the toner or the like. The toner having a small particle size is more likely to be accumulated on the supply member at an accelerated rate. As a result, filming occurs, and in order to obtain a desired printing life, the toner compression degree 3
It is necessary to use toner of 5.0% or less.

3) By rotating the supply member in the direction opposite to the surface of the toner carrier, the toner on the surface of the supply member is efficiently supplied to the toner carrier and compared with the case of rotating in the same direction. The effect of the toner being pushed into the bubble holes of the supply member is reduced, and the accumulation of toner on the supply member is suppressed. The peripheral speed of the supply member relative to the toner carrier is 3
If it is slower than 0%, the ability to supply the toner required for printing to the toner carrier becomes insufficient, and the supply delay occurs. If it exceeds 100%, the driving torque increases and the number of times of rubbing between the supply member and the toner carrier increases, so that the supply member and the toner carrier are significantly worn, and it becomes difficult to obtain a uniform image for a long period of time.

The relationship between the average bubble pore diameter of the foaming member of the supply member and the average particle diameter of the toner, the fluidity of the toner, the rotating direction of the supply member and the peripheral speed with respect to the toner carrier, and the volume resistivity of the supply member are controlled. As a result, it is possible to obtain a structure in which the toner is less likely to be clogged in the supply member, to suppress filming, and also to suppress the rotation torque of the developing device, so that a good image can be obtained.

[0023]

1 is a cross-sectional schematic view of an image forming apparatus using a developing device according to a specific embodiment of the present invention. The latent image carrier 1 is formed by forming a photosensitive layer 3 made of an organic or inorganic photoconductive material on a conductive support portion 2. After charging the photosensitive layer 3 with a charging device 4 (charging roller in FIG. 1) such as a corona charging device or a charging roller,
The light emitted from the light source 5 such as a laser or an LED forms an image forming optical system 6
Through which light is selectively applied to the photosensitive layer 3 according to the image,
A potential contrast is obtained to form a desired electrostatic latent image pattern. On the other hand, the developing device 11 conveys and develops the toner 7 which is an image forming body. The toner carrier 12 that conveys the toner 7 is made of metal or conductive resin such that urethane can be applied to the outer circumference of the shaft 13 so as to be electrically biased.
A flexible layer 15 is formed by forming an elastic layer 14 of EPDM, silicon or the like, and further having a film thickness of about several to several hundreds μm on the outer periphery thereof.
Is formed. A blade-shaped or cylindrical-shaped regulating member 16 formed of a non-magnetic or magnetic metal or resin is pressed against the toner carrier 12 by a pressing means 17 using an elastic body such as a spring or rubber. The toner 7 is charged to a predetermined polarity at the deformed portion of the toner carrier 12 due to the pressing force of the regulation member 16, the toner layer is thinned, and the toner 7 is directly held and conveyed on the toner carrier 12. . Further, the supply member 18 separates or uniformizes the toner layer on the toner carrier 12 to supply the toner 7, and is provided on the shaft 19 made of metal or conductive resin so as to be electrically biased. The foamed member 20 having bubble holes on the outer periphery is formed. The supply member 18 is
Due to the deformation of the toner carrier 12 and the supply member 18, the toner carrier 12 is arranged so as to have a predetermined contact depth with respect to the toner carrier 12, and the toner carrier 12 and the toner carrier 12 rotate in the same rotation direction. By arranging and driving in this way,
It is possible to mechanically remove the unevenness of the residual toner layer that does not contribute to the development on the toner carrier 12 after the development and further supply the toner 7 sent from the toner storage container to the toner carrier 12. . The developing bias applying unit 8 and the supplying bias applying unit 22 are connected to the conductive shaft 13 of the toner carrier 12 and the conductive shaft 19 of the supply member 18 so as to apply and maintain a predetermined potential, respectively. The toner carrier 12 is in contact with the latent image carrier 1 at a predetermined pressure. At or near this contact portion, in addition to the potential contrast of the latent image carrier 1, the latent image carrier 1 and the toner carrier 12 and An electric field is formed by the developing bias applying unit 8 applied between the developing member and the supply member 18, and the toner 7 charged according to the electric field is transferred to the latent image carrier 1 to visualize the electrostatic latent image. . Further, a transfer device 9 (transfer roller in FIG. 1) such as a corona transfer device or a transfer roller is used to transfer the image of the toner onto the recording paper 10, and the toner is fixed to the recording paper 10 using heat or pressure.

In FIG. 1, the latent image carrier 1 and the toner carrier 12 are subjected to pressure development, but they have a sufficient electric field at the development site or a predetermined gap when a magnetic toner is used. It doesn't matter.

(Experimental Example 1) The configuration of the developing device of the present invention will be described. ASK is formed on the elastic layer 14 of the toner carrier 12.
Urethane rubber having a hardness of 65 degrees in ER-C hardness was used, and a conductive flexible layer 15 was formed on the outer periphery of the urethane rubber as a coating layer thickness of 10 μm.
m to form a urethane coat layer in which carbon is dispersed,
The toner carrier 12 has a volume resistivity of 10 ⁶ Ωcm or less. To achieve this volume resistivity,
The material of the flexible layer 15 on the surface of the toner carrier 12 is carbon, or a conductive resin such as ethylene or styrene in which carbon, organic or inorganic ion conductive agent is dispersed or melted, natural rubber, SBR, NBR, silicone rubber. It is also possible to use a conductive rubber material such as the above and appropriately combine it with the material of the elastic layer 14. The surface of the flexible layer 15 has an appropriate roughness so that a mechanical transport force can be obtained in addition to the electrostatic adhesion force due to toner charging. Desirably, the surface roughness R
It is desirable that max be equal to or smaller than the average particle size of the toner 7. The regulating member 16 was formed by bending the tip of a leaf spring material made of stainless steel and having a thickness of 0.1 mm into an L-shape, and press-contacting the toner carrying member 12. The regulating member 16 is made of a conductive material such as stainless steel or phosphor bronze, a resin such as silicon or urethane, or a conductive elastic material in which a conductive powder such as carbon is mixed with the resin as long as the chargeability of the toner can be made uniform. The plate spring may have a plate thickness of 0.05 to 3 mm.

The toner 7 may be a magnetic toner or a non-magnetic toner, and either resin-based toner or wax-based toner can be used, and the constitution of the developer is not limited to one component. From the viewpoint of image resolution, the average particle size is preferably in the range of 3 to 20 μm. From the viewpoint that the toner is less likely to be clogged in the supply member 18, the smaller the degree of compression is, the more difficult it is to clog, and the degree of compression is preferably 35.0% or less. In order to achieve this degree of compression, it can be achieved by controlling the particle size distribution in the toner manufacturing process, changing the type of external additive, adjusting the amount of external additive, and the like. In this experimental example, the toner 7 is a non-magnetic one-component toner that is negatively charged by frictional charging. The average particle size is 10 μm,
The degree of compression is 33%. The degree of compression of the toner was measured using a powder tester manufactured by Hosokawa Micron.

The foaming member 20 of the supply member 18 is formed of an electrically conductive, continuous foaming soft foaming member. For example, a sponge body of polyurethane, chloroprene rubber, or silicon rubber, which has an appropriate hardness and is easy to process, is used by impregnating or dispersing carbon, an organic or inorganic ion conductive agent as a conductive agent. The volume resistivity of the foamed member is set so as to be 10 ³ to 10 ⁹ Ωcm by appropriately combining a sponge body and a conductive agent. The foaming member 20 is not limited to open cells, and may be closed cells or a mixture of closed cells and open cells. Developing device 11
From the viewpoint of suppressing the rotational torque of No. 2 and preventing the supply delay, it is desirable that the open cell ratio, which is the ratio of the number of open cell holes on the surface of the foam member 20 to the total number of cell holes, is 40% or more. The bubble hole diameter ds of the foaming member 20 has a relationship of 3 × dt ≦ ds ≦ 40 × dt with respect to the average particle diameter dt of the toner 7, whereby the foaming member 20 is formed.
It is possible to obtain a structure in which the toner is unlikely to be clogged. The density of the foam member 20 is determined by the material and the bubble hole diameter,
It is 0.05 to 0.30 (g / cm ³ ). In this experimental example, the foam member 20 has an average pore diameter of 200 μm,
The supply member 18 is formed of an open-celled polyurethane foam having a wall thickness of 3 mm and is made conductive, and the volume resistivity of the supply member 18 is 10 ⁶ Ωcm. The density of the foam member 20 is 0.1 (g / cm ³ ).

The supply member 18 is the toner carrier 12
When the toner carrier 12 is contacted with the toner carrier 12 and is deformed, the toner carrier 12 has a predetermined contact depth. The contact depth is (radius of toner carrier 12) + (radius of supply member 18) − (toner carrier 12 and supply member 18).
Distance between axes). The outer diameter of the toner carrier 12 is 15 to 20 mm, and in the present experimental example, the outer diameter was 18 mm. The contact depth can be easily changed by changing the outer diameter of the supply member 18. Supply member 1 used
No. 8 has an outer diameter of 11 to 14 mm.

The operation of this embodiment will be described. The arrows in the figure indicate the rotation direction of each member, and the peripheral speed ratio between the latent image carrier 1 and the toner carrier 12 is 1: from the viewpoint that resolution can be obtained and sufficient image density can be obtained. 1-1: 5
Is desirable. Further, the supply member 18 is the toner carrier 12
By rotating in the direction opposite to the surface, the toner 7 becomes the foaming member 2
The effect of entering the bubble holes on the 0 surface is reduced, and the accumulation of the toner 7 on the supply member 18 is suppressed. Toner carrier 12
From the viewpoint of suppressing the rotational torque and ensuring the toner supply property, it is desirable that the peripheral speed ratio to be 30 to 100%.

Further, printing was performed by adjusting the developing bias applying means 8 and the supplying bias applying means 22 to change the potential of the toner carrier 12 and the potential of the supplying member 18. The potential of the developing bias applying means 8 is determined in relation to the latent image potential contrast on the photosensitive layer 3 in order to obtain a desired image density and resolution during development. In the configuration of this embodiment, the potential Vb of the toner carrier 12 is set to -350V. Therefore, in order to change the potential difference between the toner carrier 12 and the supply member 18, the voltage of the supply bias applying unit 22 is changed, the potential Vs of the supply member 18 is Vb and Vs have the same polarity, and | Vs |> | Vb | was set.

FIG. 2 shows the evaluation results of 10,000 black solid printings. The horizontal axis represents the contact depth between the toner carrier 12 and the supply member 18, and the vertical axis represents the absolute value | Vs−Vb | of the difference between the potential Vs of the supply member 18 and the potential Vb of the toner carrier 12.
Is. The area G is an area where there is no image problem even after printing 10,000 sheets, and the initial image quality is maintained as it is.
By setting the volume resistivity of the supply member 18 to 10 ³ to 10 ⁹ Ωcm, the effect of the potential difference | Vs-Vb | is guaranteed. When the resistance is lower than 10 ³ Ωcm, electric charges are injected into the toner and the toner is abnormally charged, so that the image density may become non-uniform and the good range becomes narrow. When the resistance is higher than 10 ⁹ Ωcm, even if the potential difference | Vs−Vb | is set, a large voltage drop occurs in the supply member due to the large resistance of the supply member, and the supply site between the supply member and the toner carrier is large. The effective potential difference becomes smaller, and the effect of the potential difference | Vs−Vb | diminishes. The volume resistivity of the supply member in the region of 10 ³ to 10 ⁹ Ωcm is desirable in terms of efficiently realizing the effect of the potential difference | Vs-Vb |.

In the region G, G1 and G2 are F ≦ 0.1.
Since the contact depth is mm and the contact depth is shallow, the rotation torque is low, and the increase rate of the rotation torque when printing is repeated is low. Therefore, from the viewpoint of low torque, and by the squeezing of the toner carrier 12 and the supply member 18. Since the toner receives less stress, G1 and G2 can be reduced from the viewpoint of reducing filming.
Area is desirable.

The contact depth of the G3 and G4 regions is 0.1 <F.
In the range of ≦ 0.6, the toner bearing member 12 and the supply member 18 have outer diameters, runouts, and mechanical tolerances such as an axial distance.
It is a desirable region from the viewpoint that a uniform contact depth is sufficient and the toner is uniformly charged to obtain a stable image without causing a supply delay.
Among them, in the G3 region, the potential difference | Vs−Vb | is small, and it is difficult to supply the poorly charged toner to the toner carrier 12.
The area of G3 is desirable from the viewpoint of reducing fog. Also,
The G4 region has a large potential difference | Vs-Vb | and a little fog, but it has an effect of suppressing the occurrence of filming, and is a region desirable for obtaining the developing device 11 having a long life.

Areas G5 and G6 are areas where 0.6 <F ≦ 1.0, and the toner remaining undeveloped on the toner carrier due to the print pattern is supplied by a supply member having a sufficient contact depth. It is a desirable area for obtaining stable printing without causing scraping and printing history for a long period of time. Above all, the G5 region has less fogging, and the G6 region has a filming suppressing effect. Therefore, it is better to set the condition in the region of G1, G3, or G5 when an image with less fog is produced in the region G, and to set the condition of G1 or G2 in the case of reducing the torque. It is possible to set the optimum conditions to obtain the characteristics.

In the area B, when black solid printing is performed, a density decrease occurs at the trailing edge of the image, that is, a so-called supply delay occurs. This is because the toner carrier 12 and the supply member 18 do not contact each other sufficiently and uniformly because the contact depth of the portion A in FIG. The reason is that the toner is not sufficiently conveyed to No. 12. Further, since the residual toner remaining on the toner carrier 12 and not used for development is not sufficiently scraped off by the supply member 18, a print history occurs due to the non-uniformity of the chargeability between the residual toner and the new toner. However, as | Vs−Vb | becomes larger, in the portion A of FIG. 1, the toner 7 that is negatively charged and has adhered to the supply member 18 by the image force moves from the supply member 18 to the toner carrier 12 is changed. Supply power is improved due to stronger power. Since the chargeability of the toner is not uniform and insufficient because the contact depth is shallow, the supplyability tends to improve as | Vs−Vb | increases, but at a certain value, it is almost saturated. The good supply property is that when the contact depth is 0.1 mm or less, the relationship between the contact depth F and the potential difference | Vs-Vb | is (F
+0.1) × (| Vs−Vb | +100) ≧ 40 In the hyperbolic function region, the supply member 18 and the toner carrier 12 are kept in contact with each other, and a sufficient image density is obtained at the lower limit of uniform rubbing. It turned out to be good. Further, in this region, the rotational torque is the smallest, and the rate of increase in torque when printing is repeated is low, so a contact depth of 0.1 mm or less is desirable from the viewpoint of low torque.

Region C is for toner carrier 12 and supply member 1.
Since the contact depth of No. 8 is large, the rotation torque is large, and it is affected by the bending of the developing device 11, etc., and the jitter, the image omission because the various rollers are not pressed uniformly, and the like are remarkable. The rotation torque has a first-order positive correlation with the contact depth amount. When the contact depth is set to 1.00 mm, the initial rotation torque is almost twice as much as when the contact depth is 0.1 mm. Became. When 10,000 sheets were printed, the toner clogged the foaming member 20 of the supply member 18, the elasticity of the supply member 18 was lost, and the rotational torque was increased, increasing by almost 20%.
Further, the toner clogging the supply member 18, the surface of the supply member 18 becomes apparently flat, the toner is not mechanically conveyed, and the image density is lowered.
The increase rate of the rotational torque after durability printing increases as the contact depth increases, and when the contact depth exceeds 1.0 mm,
Even if there was no problem in the initial printing, as the printing was repeated, the deterioration of the image such as the jitter due to the increase of the rotation torque and the image omission occurred.

In the area D, when black printing is performed on 10,000 sheets, the toner is filmed on the regulating member 16 and the toner carrier 12, so that the image density is remarkably lowered. When black solid continuous printing is performed, the toner continues to be consumed, and the number of times of rubbing with the supply member 18 and the regulation member 16 is small. Therefore, the charge amount of the toner does not sufficiently increase, and therefore the toner on the toner carrier 12 is not covered. Transportability drops. As a result, a strong stress is applied to the thin toner layer between the toner carrier 12 and the regulation member 16, and the toner having a small particle size is generated due to the deformation and crushing of the toner. Since the toner having a small particle size has a larger surface area per unit volume than the normal toner, the toner has a large adhesion force due to the image force with respect to the toner carrier 12 and is formed on the latent image carrier 1 from the toner carrier 12. The latent image is not sufficiently developed and remains on the toner carrier 12. The residual toner on the toner carrier 12 is peeled off by the supply member 18 and accumulated on the supply member 18. Supply member 18
As the amount of small-sized toner accumulated in the toner increases, more of the toner adheres strongly to the toner carrier 12. Further, at the abutting portion of the regulation member 16, the regulation member 16 scrapes off the image and the regulation force is applied to the regulation member. Strongly adheres to 16. The small particle size toner strongly adhered to the toner carrier 12 and the regulation member 16
By being rubbed many times, filming is caused by mechanical stress, frictional heat, etc., and the flow of the toner 7 is hindered.
This causes a marked decrease in image density. further,
At the non-filmed portion, the new toner is not sufficiently uniformly charged by the small particle size toner strongly adhered to the toner carrier 12 or the regulation member 16, so that density unevenness and supply delay occur. Toner carrier 12
The toner filming on the control member 16 and the regulating member 16 has a potential difference | V.
Without s-Vb |, it occurred on several hundred sheets, and the printing life was almost 1/10. This is because, by applying Vs, the small particle diameter toner accumulated in the foaming member 20 of the supply member 18 and adhered by the image force in the portion A of FIG. Since the force of the electric field moving to the body 12 works, the toner transportability is improved, the toner layer on the toner carrier 12 is made thicker, and stress due to the regulation member 16 is less likely to be applied. It has the effect of developing by consuming it little by little by mixing it with. When the contact depth is shallow, the stress applied to the toner is small, and the toner having a small particle size is less likely to be generated. Therefore, the potential difference between the supply bias and the developing bias | Vs
Even if -Vb | is small, the situation in which filming occurs can be suppressed, and the contact depth F and the potential difference | Vs-Vb |
Is correlated, and when 0.1 ≦ F ≦ 0.6, 100 × F
Filming did not occur in the region of + 90 ≦ | Vs−Vb | ≦ 570, and a good image could be obtained for a long period of time. When the contact depth increases, the stress applied to the toner increases, and filming easily occurs.
When 6 <F ≦ 1.0, 150 ≦ | Vs−Vb | ≦ 570
Filming did not occur in the area.

The area E is the toner carrier 12 and the supply member 1.
8. This is a potential difference region where discharge is started via the toner. Due to the discharge, the electric field at the portion A in FIG. 1 became unstable, the transportability of the toner became unstable, and remarkable density unevenness occurred. In addition, other electric circuits and the like are adversely affected by noise.

In the present experimental example, the developing bias applying means 8 and the supplying bias applying means 22 are connected in parallel to the conductive support portion 2 of the latent image carrier 1, but the toner carrier 12 and the toner carrier 12 are connected. A potential difference can be provided between the supply members 18, and within the range of the region G, it is also possible to connect in series to the conductive support portion 2 of the latent image carrier 1.
Further, similarly, a voltage may be divided by using an element such as a resistor.

In the above-mentioned embodiments, the example using the negative charging toner has been described. However, even if the positive charging toner is used, the potential difference | Vs-Vb | of the supply bias applying means 22 satisfies the predetermined condition. With such a configuration, the positive and negative polarities of the above action may be changed.

(Experimental Example 2) With the configuration of Experimental Example 1, toner 7 is used.
Having an average particle size of 10 μm, the bubble hole diameter on the surface of the foaming member 20 of the supply member 18 is 30 μm, the contact depth between the supply member 18 and the toner carrier 12 and the potential difference between the supply member 18 and the toner carrier 12 | A printing test was conducted with Vs-Vb | set within a predetermined range. Since the bubble hole diameter is small, the sponge partition wall portion forming the bubble hole is increased, and the foam member 2 when the supply member 18 is brought into contact with the toner carrier 12 is obtained.
The increase in load is large with respect to the strain of 0, and the rate of increase in rotational torque is large due to the contact depth. Bubble hole diameter is 30
At a contact depth of 1.0 mm at μm, the initial rotational torque increased by 30% as compared with Experimental Example 1. However, as a result of printing, the initial printed image was the same as in Experimental Example 1 without causing image dropout. 10,000 sheets durable printing,
The rotation torque did not change, and neither the jitter nor the image omission due to the bending of the developing device 11 occurred. In addition, there was no supply delay and no filming.

(Comparative Example 1) In the structure of Experimental Example 1, when the bubble hole diameter on the surface of the foaming member 20 of the supply member 18 is set to 20 μm, the load is increased largely, the rotating torque is large from the beginning, and the contact depth is 1. When it was 0.0 mm, it was almost doubled as compared with Experimental Example 1. Jitter and image dropout occurred in the initial printing. If the material of the foaming member 20 of the supply member 18 is changed and the hardness of the foaming member 20 is lowered, the initial rotation torque can be suppressed and the image defect due to the deflection of the developing device 11 can be improved, but if printing is repeated, a supply delay occurs. It was When the bubble pore diameter of the foaming member 20 is twice the average particle diameter of the toner, the surface of the supply member 18 tends to be apparently flat due to the adhesion of at most two toner particles, and the mechanical transport force is lost.
Supply delay will occur.

From the experimental example 2 and the comparative example 1 described above, the bubble hole diameter on the surface portion of the foaming member 20 is 3 of the average particle diameter of the toner 7.
The double is the lower limit for obtaining the load of the rotational torque and the mechanical carrying force of the toner, and a good image without jitter etc. can be obtained from the initial stage, and in order to maintain it for a long time, the surface portion of the foaming member 20 is The bubble pore size of 3 is the average particle size of toner 7
Double or more is desirable.

(Experimental Example 3) With the configuration of Experimental Example 1, the toner 7 is used.
Having an average particle size of 10 μm, the bubble pore diameter on the surface of the foaming member 20 of the supply member 18 is 400 μm, the contact depth between the supply member 18 and the toner carrier 12 and the potential difference between the supply member 18 and the toner carrier 12 | A printing test was conducted with Vs-Vb | set within a predetermined range. As a result of printing, when 10,000 sheets of durable printing were carried out, when the contact depth was 1.0 mm, the same printing as in Experimental Example 1 was obtained although the rotational torque increased by 40%.

(Comparative Example 2) With the structure of Experimental Example 1, when the bubble hole diameter on the surface of the foam member 20 of the supply member 18 was 450 μm, uneven density, supply delay, and print history occurred from the initial printing. This is because, since the bubble hole diameter is large, the pressing force of the foam member 20 against the toner carrier 12 is small, and the force of rubbing the toner 7 on the supply member 18 against the toner carrier 12 is small, so that the toner is triboelectrically charged. It is not performed uniformly and sufficiently, and uneven density and supply delay occur. Further, the force for scraping off the undeveloped toner remaining on the toner carrier 12 is small, and a developing memory occurs. Further, as the printing is repeated, the foaming member 20 is easily clogged with the toner 7, and the rotational torque is significantly increased. Further, filming is likely to occur on the toner carrier 12 and the regulating member 16, and filming and supply delay occur after about several hundred sheets.

From Experimental Example 3 and Comparative Example 2 described above, when designing the developing device 11, it is necessary to consider the increase in the rotational torque, and further, a good image is obtained without image deterioration due to filming. In order to maintain it for a long period of time, it is desirable that the bubble hole diameter on the surface portion of the foaming member 20 be 40 times or less the average particle diameter of the toner 7.

(Experimental Example 4) With the configuration of Experimental Example 1, toner 7 is used.
The printing test was conducted by changing the compression degree of 1% by 1%. The degree of compression can be changed by controlling the particle size distribution of the toner 7, changing the type of external additive, adjusting the amount of external additive, and the like. The evaluation results are shown in Table 1.

[0048]

[Table 1]

As the amount of small particle size toner increases as printing is performed, the fluidity of the entire toner decreases, so that the surface portion of the foaming member 20 of the supply member 18 is easily clogged with toner, and more clogged toner is generated. I tended not to go out. If a toner having a low compression rate is used, the toner is less likely to be clogged with the supply member 18, so that an increase in the rotational torque and the occurrence of filming are suppressed and the printing life is extended. When 35.0% was used, the rotation torque was increased, but the same printing as in Experimental Example 1 was stably obtained. When a printing test was conducted using a toner 7 having a compression ratio of 36.0%, the rotation torque was remarkably increased.
Further, filming and supply delay easily occur on the toner carrier 12 and the regulation member 16, and the printing life is reduced to 1/2.
It has become a degree.

From Experimental Example 4 described above, in order to maintain a good image without image deterioration for a long period of time, it is desirable that the compression ratio of the toner 7 is 35.0% or less.

Although the embodiments have been described above, the present invention is not limited to the above embodiments but can be widely applied to developing devices for electrophotography and the like, and is particularly effective when applied to printers, copying machines and facsimiles.

[0052]

In the developing device according to the present invention, a potential difference is provided between the supply member and the toner carrier, a predetermined relationship is satisfied between the potential difference and the contact depth, and the volume resistivity of the supply member is increased. By specifying, when black solid printing is performed, the charge amount of the toner is increased at the trailing edge of the image, and the toner is sufficiently conveyed to the toner carrier by the force of the electric field, so that a sufficient supply can be achieved without causing a supply delay. It was possible to provide a density image. Further, it was possible to prevent fogging and uneven density. Further, when continuous black solid printing is performed, the toner transportability is improved and the toner layer on the toner carrier is thickened to reduce the stress on the toner at the contact portion with the regulation member. In addition, the toner filming to the regulating member and the supply delay can be suppressed, and the initial printed image can be maintained for a long period of time without lowering the image density.

Further, a predetermined relationship is satisfied between the average cell pore size of the surface of the elastic foam of the supply member and the average particle size of the toner, and the toner compressibility is set to 35.0% or less.
Further, by regulating the rotation direction and speed of the supply member, the toner is less likely to be clogged with the supply member, and the following effects are obtained. First, it was possible to suppress filming of the toner on the regulating member and the toner carrier, and to stably obtain a good image for a long period of time without lowering image density and delaying supply. Secondly, it was possible to suppress an increase in the rotational torque due to the loss of elasticity of the supply member.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus using a developing device of the present invention.

FIG. 2 is a view showing an evaluation result of performing black solid durability printing with the developing device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Latent image carrier 4 ... Charging device 5 ... Light source 6 ... Imaging optical system 7 ... Toner 8 ... Development bias applying means 9 ... Transfer device 10 ... Recording paper 11 ... Developing device 12 ... Toner carrier 16 ... Regulation member 18 ... Supply member 22 ... Supply bias applying means

Claims (5)

[Claims] 1. A developing device having a toner carrier made of an elastic body, a supply member for supplying a developer with toner to the toner carrier, and a regulating member for forming a thin toner layer on the toner carrier. , The supply member is pressed against the toner carrier, the contact depth F (mm) between the supply member and the toner carrier, and the potential V of the toner carrier.
b (V) and the potential Vs (V) of the supply member, Vb
And Vs have the same polarity and F ≦ 1.0. 1) When F ≦ 0.1, (F + 0.1) × (| Vs−Vb
| +100) ≧ 40 and | Vs−Vb | ≦ 570 2) When 0.1 <F ≦ 0.6, 100 × F + 90 ≦ | V
s−Vb | ≦ 570 3) When 0.6 <F ≦ 1.0 150 ≦ | Vs−Vb |
A developing device satisfying ≦ 570. 2. The volume resistivity of the supply member is 10 ³ -1.
The developing device according to claim 1, wherein the developing device has a resistance of 0 ⁹ Ωcm. 3. The supply member is made of an elastic foam, and has an average pore diameter ds of the surface portion and an average particle diameter dt of the developer.
3. The developing device according to claim 2, wherein the developing device has a relationship of 3 × dt ≦ ds ≦ 40 × dt. 4. The developing device according to claim 2, wherein the developer has a degree of compression of 35.0% or less. 5. The surface of the supply member rotates in the opposite direction to the surface of the toner carrier, and the peripheral speed ratio thereof is 30 to 100% with respect to the toner carrier. The developing device according to claim 2, claim 3, or claim 4.