JPS59184375A - Image forming method - Google Patents

Abstract

PURPOSE:To execute a compensation control of a picture density at an almost constant level with high accuracy extending over a long period of time in spite of a long period of time and also a developing property variation of a repeat varation property, by controlling an effective value of an AC bias impressed between a developing member and a latent image holding body, in accordance with a remaining quantity of a developer. CONSTITUTION:A toner T exists between a sleeve 22 and an electrode plate 25, and when the toner T in a hopper 21 is consumed, the toner quantity between them is decreased. Subsequently, an AC bias impressed to the sleeve 22 being a developing member is detected by the electrode plate 25 through the toner. The toner quantity in the hopper 21 is detected from an induced voltage value of the electrode plate 25, an induced voltage variation is led into a rectifying and smoothing circuit 26a of a circuit 26, led to a comparing circuit 26b, and by operating a switching circuit 26c, an effective value of an output AC bias of an AC voltage impressing means S is controlled stepwise in the direction for compensating a developing property time aging.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides electrophotographic method φ electrostatic recording on a latent image carrier.
The present invention relates to an improvement in an image forming method in which an electrostatic latent image is formed by an appropriate method such as an ion flow control method, and a high-resistance component developer is applied to the surface of the latent image to visualize the latent image.

High resistance component developer (volume resistance 1010Ωcm or more”)
As latent image development methods using , impression development methods (US Pat. No. 3,405,882, etc.), jumping development methods (JP-A-54-42141, etc.), and the like are known.

Figure 1 shows an example of such equipment. 1 is a photoreceptor such as a rotating drum type in transfer type electrophotography, an insulator such as a rotating drum type in transfer type electrostatic recording method, and an electrofax machine. A latent image carrier such as a photosensitive paper in a method or an electrostatic recording paper in a direct electrostatic recording method, and an electrostatic latent image is formed on its surface by a latent image forming process device or a process mechanism not shown in the figure. formed and is moving in the direction of the arrow.

2 is the overall code of the developing device, and 21 is the high-resistance component developer T.
(hereinafter referred to as toner) is accommodated in the hopper; 22 is a rotating cylindrical body (hereinafter referred to as sleeve) as a developing member (developer layer supporting member);
3 is built-in. In the drawing, the sleeve 22 is supported by a bearing with its substantially right half circumferential surface exposed inside the hopper 21 and its substantially left half circumferential surface exposed outside the hopper, and is driven to rotate in the direction of the arrow. Reference numeral 24 designates a doctor blade as a toner applying member disposed with the lower edge portion close to the upper surface of the sleeve 22, and 27 represents a stirring member for toner in the hopper.

The axis of the sleeve 22 is substantially parallel to the generatrix of the latent image holder 1, and the sleeve 22 faces the latent image holder 1 closely with a slight gap therebetween. The respective surface moving speeds (peripheral speeds) of the latent image holding member 1 and the sleeve 22 are approximately the same. Further, an alternating current voltage is applied between the latent image holding member 1 and the sleeve 22 by an alternating current voltage applying means S.

The substantially right half circumferential surface of the sleeve 22 is in constant contact with the toner pool in the hopper 21, and the toner near the sleeve surface forms a magnetic adhesion layer on the sleeve surface due to the magnetic force of the magnetism generating means 23 in the sleeve, and is also electrostatically charged. Sealed and held by force.

When the sleeve 22 is driven to rotate, the toner layer adhering to the sleeve surface passes through the position of the doctor blade 24 and is layered into a thin toner layer Tl having approximately uniform thickness at each portion. The toner is charged mainly by the rotation of the sleeve 22.
This is caused by the frictional contact between the sleeve surface and the toner in the toner pool near the sleeve surface.

The toner PI layer surface of the sleeve 22 rotates toward the latent image holder 1 side as the sleeve rotates, and passes through the development area A, which is the closest portion between the latent image holder 1 and the sleeve 22 .

During this passing process, the toner in the thin toner layer on the side of the sleeve 22 is blown away by the AC electric field caused by the AC voltage applied between the latent image carrier 1 and the sleeve 22, and the toner in the latent image carrier 1 in the development area A is blown away.
It reciprocates between the surface and the sleeve 22 surface. Finally, the toner on the sleeve 22 side selectively migrates and adheres to one surface of the latent image carrier according to the potential pattern of the latent image, resulting in a toner image T.
2 are formed sequentially.

The sleeve surface, on which toner has been selectively consumed after passing through the development area A, is rotated again to the toner reservoir of the hopper 21 and is resupplied with toner. The layer T1 surface rotates.

By the way, one of the problems when adopting such a developing method is a phenomenon in which the developability changes over time due to preferential adhesion of small particle size toner to the surface of the sleeve 22 serving as a developing member.

That is, the particle size distribution of the toner T is distributed with a certain spread on the large diameter side and the small diameter side with the standard particle size as the center. Among them, the toner having a smaller particle diameter tends to electrostatically preferentially adhere to the surface of the sleeve 22 than the toner having a larger diameter. Therefore, when toner T is replenished into the hopper 21 and development is executed, for a while after that, the toner with a small particle size preferentially adheres to the surface of the sleeve 22, as shown in FIG. 2(a). In this state, the surface of the sleeve 22 is completely covered with the layer Ta of the small particle size toner. As a result, the toner Tb in the vicinity of the sleeve surface as the sleeve 22 rotates.
The chance of direct frictional contact with the surface of the sleeve 22 decreases, and the amount of charge on the toner tends to be insufficient. and hopper 21
As the toner consumption progresses, the phenomenon of preferential adhesion of small-particle toner to the sleeve 22 surface tends to gradually weaken, and as shown in FIG. 2(b), the adhesion of small-particle toner to the sleeve 22 surface decreases. and this causes sleeve 2
The opportunity for the toner near the second surface, both small and large particles, to come into direct contact with the surface of the sleeve 22 increases, and a sufficient amount of charge is gradually secured to the toner.

As a result, in response to the change in toner charge amount,
As shown in the graph of FIG. 3, the obtained image density is initially at a relatively low level, and as the copy integration progresses, the image density level gradually increases. That is, a phenomenon in which the developability changes over time occurs. This phenomenon of change in developability over time occurs in hopper 2.
This occurs repeatedly every time toner T is newly replenished within 1 hour.

It is an object of the present invention to accurately compensate and control the image density level to a substantially constant level over a long period of time, regardless of the long-term and repeatedly fluctuating changes in developability as described above.

That is, the present invention provides an image forming method in which an electrostatic latent image is formed on a latent image holder, and a high-resistance component developer is applied to the surface of the latent image to visualize the latent image. The present invention is characterized in that the effective value of the AC bias applied between the developing member and the latent image holder is controlled according to the remaining amount of the developer.

Hereinafter, a detailed explanation will be given using the drawings.

In the above-mentioned developing method, a latent image holding member 1 and a developing member 2 are used.
There is a correlation between the frequency of the AC bias applied between the two and the image density as shown in the graph example in FIG.

When an AC bias is applied between the latent image holding member 1 and the developing member 22, the toner in the developing member 22-L is blown away by the electric field formed by the applied bias as described above, and the latent image in the developing area A is A reciprocating movement is performed between the holding body l and the developing member 22. Finally, the reciprocating toner is selectively transferred and adhered to one surface of the latent image holder according to the potential pattern of the latent image, forming a toner image. In order for the latent image to be sufficiently developed at this time, in addition to the fact that the toner itself has sufficient electrical charge, the toner that moves back and forth while the latent image surface passes through the development area A It is necessary that sufficient contact be made. To this end, one possibility is to make the passage time of the latent image surface to the development area sufficient, and the other is to increase the number of times the latent image contacts the toner.

In order to bring the toner from the developing member 22 to the latent image surface at a distance while the latent image surface passes through the development area A, the mass of the toner is m and the toner is given a surface within one hour.

a≧2 sentences/l', (1) t indicates that the latent image surface exists within a sufficient area for the latent image surface to be developed to be developed ξ by the toner on the developing member 22, that is, within the development area λ. Although it varies depending on the time or toner, it is determined by the time required for one contact when the latent image surface and toner need to contact each other multiple times in the development area.

The force F applied to the toner during development is expressed as F=ma, , , , , (2), but since the toner has a charge q and is placed in a charge E, F=E・q, , , , (3) Since it receives the force, ma=E * q... (4) -.

Therefore, from the relationship with equation (1), E・(q/m)=2J1/12=F/m,,,(
5) If the DC potential of the developing member 22 with respect to the latent image carrier l is V, c, and the latent image potential is VD, the electric field E is determined by the effective value V of the applied AC bias, E= (V+Vo Vo c)/l ---
(8), the toner acts on the developing member 22.
The force F that moves the latent image closer to the surface is F= (Q/m) (V”Vel VD C)m7 sentence.

(7) becomes. That is, the so-called tripoq/m (coulomb/q) force F acting on the toner depends on the effective value V of the applied AC bias when Vr3, Voc, m, and 1 are constant. This effective 4f
It is believed that iv controls the amount of toner on the developing member 22 that is carried to the latent image surface.

Therefore, the present invention makes use of the dependence of image density on the AC bias effective value (FIG. 4), and utilizes the dependence of the image density on the AC bias effective value (Fig. (Fig. 3), that is, detecting the temporal transition of the developability change phenomenon over time and correspondingly adjusting the latent image holding member l.
The effective value of the alternating current bias applied between the developing member 22 and the developing member 22 is controlled over time to maintain the image density level at a substantially constant level throughout.

The change in developability, as shown in the example in FIG. By detecting the remaining amount of toner, it is possible to approximately know the developing performance at that point.

There are various possible means for detecting the amount of toner remaining in the hopper 21, including mechanical, electrical, and optical.

FIG. 1 shows an example of an electrical detection means, in which an electrode plate 25 is disposed opposite to the sleeve 22 on the inside of the hopper wall on the opposite side to the side on which the sleeve 22 as a developing member is disposed. Toner T exists between the sleeve 22 and the electrode plate 25,
As the toner T in the hopper 21 is consumed, the amount of toner decreases.

The AC bias applied to the sleeve 22 as a developing member is detected by the electrode plate 25 via the toner present between the sleeve 22 and the electrode plate 25. In this case, the sleeve 22 and the electrode 25 form a capacitor with toner between them, the capacitance of which depends on the amount of toner present between the sleeve 22 and the electrode plate 25, and the voltage induced in the electrode plate 25 is approximately the fifth It will look like the example graph. That is, the absolute value of the induced voltage varies depending on the applied AC voltage, frequency, type of toner, shape of the electrode plate, etc., and changes depending on the amount of toner. Conversely, the amount of toner in the hopper 21 is detected from the induced voltage value of the electrode plate 25.

Therefore, the change in the induced voltage of the electrode plate 25 (that is, the change in the amount of toner remaining in the hopper) is rectified by a circuit 26 including a rectifier/smoothing circuit 26a, a comparator circuit 26b, a plurality of switching circuits 26c, etc. as shown in the example of FIG. - Introduced into the smoothing circuit 26a, passed through the circuit and led to the comparison circuit 26b, and operates the switching circuit 26c according to the output voltage to determine the effective value of the output AC bias of the AC voltage applying means S as shown in FIG. Gradually (
This example circuit performs control in three stages. For example, the AC bias applied to the sleeve is standard AC, 800Hz/1200V.
When using sine wave AC with PP (maximum amplitude 11), remaining amount of toner AC bias 1st stage control 200-140g 1500V p p
(Effective value toeov) 2nd stage control 140-100g 1300V p p
(tt920V) 3rd stage control 100~flog 1200V p
p (tt850V).

As a result, as shown in the graph example in FIG. 7, the image density level can be maintained at a substantially constant level over a long period of time, regardless of the phenomenon of changes in developability over time due to preferential adhesion of small-particle developer to the developing member 22. I can do it.

As described above, the effect of controlling the development characteristics according to the present invention is extremely excellent, and by increasing the number of control steps to more than the three steps of the embodiment, even more precise control becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an example of a developing device, Fig. 2 (a) is a schematic diagram showing a state in which the surface of the developing member is covered with a layer of small-particle developer, and Fig. 2 (b) is a schematic diagram of the small-particle developing valve. Figure 3 is a graph showing the phenomenon of changes in developability over time; Figure 4 is a graph showing the relationship between the effective value of AC/<Ias and image density; Figure 5 t ± A graph of the relationship between the amount of toner remaining in the hopper and the voltage of the electrode plate. Figure 6 is an example of a control circuit.
Figure 7 is a graph of development characteristics obtained from control sound. 2 is a latent image holder; 2 is a developing device; 211 is a toner hopper; 22 is a rotating snoop as a developing member; and 25 is an electrode plate. Figure 1 Figure 6 Figure 18 Figure 3 Happy Figure 4

Claims (1)

[Claims] (+) In an image forming method that forms an electrostatic latent image on a latent image holder and visualizes the latent image by applying a high-resistance component developer to the surface of the latent image, An image forming method characterized by controlling the effective value of an AC bias applied between a developing member and a latent image holder according to the remaining amount of developer.