JPS6095557A - Developing method - Google Patents

Abstract

PURPOSE:To obtain a developed image which is faithful to an original image and has no negative characteristics or negative characteristics improved greatly by performing development by using an area including an area wherein the surface potential V on a latent image holding member and image density D after the development are in relation dD/dV>0. CONSTITUTION:The latent image holding member 1 rotates in a direction (a) and is charged electrostatically uniformly by a corona charger 2 and exposed 3 to an image, and a latent image is made by a developing device 4 into a visible image, which is transferred to a transfer material 6 by a transfer charger 5. A developing bias for forming an alternating electric field is applied to the sleeve 10 of the developing device 4 from an oscillator which generates a sine-wave alternating current and a bias power source 15 composed of a DC superposing circuit. Then when the charging potential of the latent image holding member (photosensitive drum) 1 is lowered so that a dark surface potential VD is -300V and a light part potential VL is 0V, the area wherein dD/dV>0 in a V-D curve is used and an area E showing that dD/dV<0 is excluded, so that a developed image has no negative characteristics or negative characteristics improved greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method. This relates to the developing method used.

Conventionally, a developer holding member having a thin layer of dry developer formed on its surface and a latent image holding section 4A are opposed to each other in a developing section with a development gap larger than the thickness of the developer thin layer. A developing method in which an alternating electric field is continuously formed to repeatedly transfer and reverse transfer of the developer and perform 'C development was published in the Japanese Patent Publication No. 8. Z) known from Publication No. 32375.

According to this developing method, there is no ground strength and the gradation is excellent.
, a good image with no thin lines can be obtained. Curve of image 11NFID after development (V-1
, 1 curve) is generally a curve like that shown in FIG. 1 (a).

However, when a thin layer of non-magnetic developer is applied onto the developer holding member and development is performed by continuously forming an alternating electric field in the development gap in the development section, the V −
It was found that a D curve was obtained. This is different from the general V-1) curve (a) mentioned above, in which development is abnormally accelerated in the intermediate potential area B, and γ (the gradient of image density with respect to the latent image potential) increases, and the high potential area A This is a characteristic in which the image density I) decreases (hereinafter, this characteristic will be referred to as a negative characteristic). In this case, the image density of the solid black part becomes lighter than the image fIM density of the halftone part, and it cannot be used for compensation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing method that eliminates the above-mentioned conventional drawbacks and prevents the occurrence of negative characteristics that appear in reproduced images during the developing process.

To achieve the above object, the present invention provides a developing method in which developer is held on the surface of a developer holding member and is conveyed to a position facing the latent image holding member to perform development, as shown in FIG. 1(b). The region E which does not significantly show the negative characteristics of the V-D curve shown is used, and as a specific example, the Iw
The stop holding part keeps the developer. As a result, it is possible to realize a V-1) curve that does not exhibit negative characteristics to the extent that the developed image gives a bad impression, and to obtain a reproduced image that is faithful to the original image.

By the way, the above-mentioned negative characteristic is caused by the fact that when an alternating electric field is formed in the development gap to cause reciprocating motion of the non-magnetic developer, the developer becomes a powder cloud, and the developer becomes powder cloud. It is estimated that this occurs as a singular development. t), the developer repeats reciprocating motion in response to the frequency of the image bias; The image agent cannot respond to changes in bias and is prone to a butterfly cloud condition. A type of electric field curtain is formed within the development area in the gap between the latent image holding member and the developer carrying member at the high potential portion A, and this curtain allows the developer to reciprocate over a relatively wide width. It is thought that the developer is hard to escape from the curtain because it is sealed inside, and the occurrence of dirt is small. It is thought that the width of the electric field curtain at the low potential part I3 is narrow, and the developer easily separates from this curtain, resulting in a large number of clouds. When we actually apply an alternating electric field during copying and observe the width of the development area, we find that the developed area width is wider in the area B than in ViA between the area A where the potential is high and the area B where the potential is low, as mentioned above. This is a development performed due to the occurrence of clouds. 1 in terms of image quality
In some areas, the edge effect peculiar to powder cloud development becomes noticeable. It is considered that the phenomenon in area A continues in area C where the potential is higher than area A, and the image density increases depending on the latent image potential.

As a result, in the intermediate potential area shown in B in Figure 1, the area to be developed, that is, the development width, is widened and a developed image with high density is obtained, but in the high potential area A, it is affected by the electric field curtain described above. It is thought that this causes the image density to decrease.

According to experiments, negative characteristics did not occur when a direct current or a low frequency bias with sufficient frequency response was used as the developing bias. Therefore, in order to prevent such negative characteristics, it is sufficient to reduce the number of reciprocating movements of the developer. but,
Merely reducing the frequency of the developing bias results in the disadvantage that the image density is low and that the image quality is degraded due to the occurrence of ground curl.

Therefore, in the present invention, without changing the frequency of the applied developing bias, the area where a developed image with a high intermediate potential as shown in B in FIG. 1 is obtained corresponds to the highest density part of the original image. By setting an alternating electric field between the latent image holding member and the developer carrying member, a developed image that does not exhibit negative characteristics or has significantly improved negative characteristics and is faithful to the original image can be obtained. It became possible to obtain.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram of a copying apparatus to which the present invention is applied, in which a latent image holding member l having a photoconductive layer rotates in the direction of arrow a, and after being uniformly charged by a corona charger 2, The latent image is made into a visible image by the developing device 4. Thereafter, the visible image on the latent image holding member is transferred onto a transfer material 6 such as paper by a transfer charger 5, and fixed onto the transfer material by a fixing device (not shown). Further, the latent image holding member after the transfer is cleaned by a cleaning device 7.

Here, the developing device 4, which is the main part of the present invention, will be described in detail. The nine magnetic particles in the developer container 8 are attracted to the sleeve surface by the magnetic force of the magnetic roller 11 included in the sleeve 1 (l), which is a developer holding member, and are transported by the rotation of the sleeve 10 in the direction of the arrow. The magnetic particles 8 are formed into a regulating blade made of a magnetic material]2
The leakage from the developer container 8 is prevented by the magnetic force of the magnetic pole N of the magnet roller 11, and the developer is pushed back in the direction of arrow C by gravity. Therefore, only the non-magnetic toner 13 is uniformly applied in a thin layer on the sleeve 10, and this non-magnetic toner 13 is conveyed on the sleeve in the direction of the arrow and is developed in the developing section facing the latent image holding member l. Served. On the other hand, the magnetic particles 9Il-1 circulating in the direction of arrow C take in the non-magnetic toner 13 during this circulation, and the above-mentioned circulation is repeated. The method for applying a thin layer of non-magnetic toner is detailed in Japanese Patent Application No. 73231/1983 filed by the applicant of the present application, and therefore a detailed explanation will be omitted.

1411 in the figure: A sealing member made of a magnetic material, which prevents leakage of magnetic particles to the outside of the developer container 8 by the magnetic force of the magnetic pole S of the magnet row 211 and this member.

Further, 15 is a bias power supply for applying a developing bias voltage to the sleeve 10.

A developing bias for forming an alternating electric field was applied from the bias power supply 15 to the sleeve lO of the developing device 4 as described above. The bias power supply 15 consists of an oscillator that generates a string wave alternating current and a direct current superimposition circuit, and the developing bias has a frequency of 1. fl 1cllz , a peak-to-peak value of 1.3 kVp-p, and a DC component superimposed thereon was applied. In other words, an alternating electric field was applied between the bias in which a direct current was superimposed on the above-mentioned alternating current conditions and the m-image potential.

The V-D curve shown in FIG. 1(b) had a superimposed direct current division of -100 V under the above-mentioned developing bias conditions.

At this time, the dark area surface potential of the latent image holding part is VD=-55
The bright area potential was set to 0 V and the bright area potential L = 0. Under the above-mentioned AC conditions, the region F of the V-D curve shown in 0)) in FIG. 1 is used, which includes the region 11 that shows a markedly negative characteristic.

However, by lowering the charging potential of the latent image holding member (photosensitive drum), the dark area surface potential of the latent image holding member is reduced to VD=-30Q.
The developed image does not include the region H which is clearly shown, where the bright area potential is set as . At this time, there is no practical problem even if the area E' is included.

As another means, the DC component superimposed on the developing bias is set to -300cm, and the bright area potential of the latent image holding member is set to VL.
--200■, similar effects can be obtained.

In general, the configuration of the developing device (in this example, the photosensitive drum diameter is 6'0φ, the sleeve diameter is 20<6.
50μ), and when using a developer with a certain charging characteristic and setting AC conditions for the developing bias, the difference between the dark area potential VD and bright area potential VL of the latent image holding member, and the DC voltage VDC of the developing bias. , B: The concentration is M at the midpoint potential of the V-D curve in Figure 1 Q))
At the point indicating AX? +II potential on the image holding member;
Potential difference between the DC component of the developing bias and the potential difference between the potential on the latent image holding member and the DC component of the developing bias at the point where the pink latent image is not formed in the low potential area ( ) in Figure 1. , the above v 1., v 1., V
l) C is set, and an alternating electric field is applied between the latent image holding member and the developer holding member. rlIl
A developed image faithful to the original image and rich in gradation can be obtained11.

Note that the developing device is not limited to the embodiment shown in FIG. 2, and the present invention can be applied to any developing device that generates negative characteristics. Similarly, in this embodiment, an example of non-magnetic toner is shown, but magnetic toner can also be applied to a developing device exhibiting negative characteristics.

As described above, in the present invention, ■-1) the odor and the developed image are reduced by setting an alternating electric field between the latent image carrier and the developer carrier so as to use the region not shown in the curve; Negativity f
Improved the occurrence of 1. By lowering the frequency (41° in case of 7 Jjη), we were able to prevent any deterioration in image quality, including the occurrence of background fog.

[Brief explanation of drawings]

Figure 1 shows normal V-1) [111m negative ft:
FIG. 2 is a schematic diagram of a copying machine showing an embodiment of the present invention. In the figure, an IVi latent image holding unit, 4 VJ developing device,
8 developer container, 9 magnetic particles, 10 sleeve, 11
12 represents a magnetic net roller, 12 represents a non-magnetic toner, 14 represents an fd seal member, and 15 represents a bias power source. Applicant Canon Co., Ltd. C1D1I IfL (V)

Claims (2)

[Claims] (1) The image density after development [1] for VK of the latent image holding section is negative. (2) Using the above region dD/dV>O,
2. The developing method according to claim 1, wherein an alternating electric field for developing bias is applied between the latent image holding member and the developer holding member.