JPS641013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developing method, and more specifically, to an electrophotographic developing method using a one-component developer, and in particular, to an electrophotographic developing method that uses a one-component developer, and in particular, an electrophotographic developing method that uses a one-component developer. The present invention relates to an electrophotographic developing method that makes it possible to obtain a visual image.

Conventionally, electrophotographic development methods using a one-component developer include the powder cloud method, in which toner particles are sprayed, and electrostatic imaging, in which a uniform toner layer is formed on a toner support member such as a web or sheet. A contact development method in which development is performed by bringing the toner layer into contact with a holding surface, a jumping development method in which the toner layer is not brought into direct contact with the electrostatic image holding surface and the toner is selectively flown onto the holding surface by the electric field of the electrostatic image; Forming a magnetic brush using conductive magnetic toner,
A magneto-dry method, etc., in which development is performed by contacting an electrostatic image holding surface, are known.

Among the various one-component development methods mentioned above, powder and
In the cloud method, contact development method, and MagneDry method, toner is applied to the electrostatic image holding surface without distinguishing between image areas (areas to which toner should originally adhere) and non-image areas (areas of the background to which toner should not originally adhere). Because of the contact, toner adhesion occurs even in non-image areas to some extent, making it impossible to avoid the occurrence of so-called background fog. However, in the jumping development method (for example, the method described in Japanese Patent Publication No. 41-9475), development is performed with a gap between the toner layer and the electrostatic image holding surface without contact, which prevents background fogging. This is an extremely effective method in this respect. However, since the phenomenon of toner flight caused by the electric field of an electrostatic image is utilized during development, the resulting visible image generally has the following drawbacks.

The first problem is that the sharpness decreases at the edges of the image area. The electric field of an electrostatic image at the edge of the image is as shown in FIG. 1 in the case of an electrostatic latent image formed on an electrophotographic photoreceptor. That is, if a conductive member S is used as a developer support near the center m of the image area, electric lines of force will emanate from the image area,
Since the toner has reached the toner support, the toner moves along the lines of electric force, adheres to the surface of the photoreceptor, and is developed. However, at the edge of the image area, the lines of electric force do not reach the toner support S due to charges induced in the non-image area and wrap around to the back electrode of the electrostatic image holder. The adhesion of the toner that has been applied is extremely uncertain, and if it is just barely adhering, it may not even adhere. As a result, the resulting image lacks sharpness and is unclear at the edges of the image portion, and when developing a line image, there is a problem that the image is developed to appear thinner than the original image.

In order to avoid this in the normal jumping development method, the gap between the electrostatic image holding surface and the developer carrier surface must be made sufficiently small (for example, 100μ or less), and in practice, the gap between the two surfaces is It is easy to cause press-contact accidents due to developer or foreign matter. Furthermore, maintaining such a small gap often involves difficulties in device design.

The second problem is that images obtained by the jumping development method generally lack gradation.
In jumping development, the toner only flies when the electric field of the electrostatic image overcomes the restraining force on the toner support. The force that binds the toner to the toner support is based on the Van der Waals force between the toner and the toner support, the adhesion force between the toners, and the fact that the toner is electrically charged. It is the resultant force of the reflection force between Therefore, the potential of the electrostatic image is a certain value (hereinafter referred to as
Only when the toner transfer threshold (referred to as the toner transfer threshold) is exceeded, and the resulting electric field exceeds the toner restraining force, toner flight occurs and toner adhesion to the electrostatic image holding surface occurs. However, the binding force of the above-mentioned toner to the support varies depending on the individual toner or the particle size of the toner, even if the toner is manufactured and mixed according to a certain recipe, but it is still approximately the same. It is thought that the electrostatic image surface potential is narrowly distributed around a certain value, and correspondingly, the threshold value of the electrostatic image surface potential at which toner flight occurs is also thought to be narrowly distributed around a certain value. In this way, when the toner flies from the support, there is a threshold value, so toner adhesion occurs in image areas that have a surface potential exceeding this threshold value.
On the contrary, the result is that almost no toner adheres to image areas with a surface potential below the threshold, resulting in a gradation characteristic with a so-called γ (gamma = slope of the characteristic curve of image density versus electrostatic image potential). The result is that only a blurry image is obtained.

The present invention was made to eliminate the problems of the various one-component developing methods described above, and its main purpose is to improve the reproducibility of image edges in a relatively large development gap (for example, 200μ or more). An object of the present invention is to provide an electrophotographic developing method which makes it possible to obtain a visible image with excellent tonality and rich gradation.

In order to achieve the above object, the present invention has the following features.

In a developing section, a latent image carrier having an electrostatic latent image formed on its surface and a developer carrier carrying a developer layer on its surface are faced to each other with a gap maintained in the developing section.
A developing method that performs development by forming an alternating electric field that causes the developer released from the developer carrier to adhere to the surface of the latent image holder and also causes the developer attached to the surface of the latent image holder to separate from the surface of the latent image holder. The potential difference (peak-to-peak) between the maximum potential and the minimum potential of the waveform forming the alternating electric field is equal to the gap d (unit: micron) in the developing section between the latent image carrier and the developer carrier. On the other hand, the developing method is characterized in that it is larger than (1.5×d) V (volts) and smaller than (1.5×d+1500) V (volts).

The present invention provides a potential difference relationship for reliably performing a developing method in which the developer attached to the surface of the latent image carrier is removed from the surface of the latent image carrier by satisfying the potential difference relationship of the alternating electric field with respect to the gap d. Since the focus is only on the reciprocating motion of the developer, the dependence on the frequency of reciprocating the developer can be reduced and the tolerance range can be increased.
According to the present invention, there is provided a developing method that can improve gradation or line image reproducibility with respect to the development gap d and prevent background fog.

Hereinafter, embodiments and examples according to the present invention will be described in detail with reference to the drawings.

This will be explained using FIG. 2 as an example. The voltage waveform applied to the toner carrier is shown in the lower row, and although it is a rectangular wave here, it is not limited to this as will be described later. In a time interval t ₁ a bias voltage of magnitude Vmin is applied, and in a time interval t ₂ a bias voltage of magnitude
A bias voltage of Vmax is applied. Vmin,
The size of Vmax is Vmin when the image area charge formed on the image surface is positive and this is to be developed with negatively charged toner, the image area potential is V _D and the non-image area potential is V _L. ＜V _L ＜V _D ＜Vmax ......Select so as to satisfy (1). So chosen, during the time interval t ₁ the bias voltage Vmin tends to transfer the toner and accelerate development, which is referred to as the toner transfer phase. In the time interval t ₂ , the bias voltage Vmax inhibits development and tends to return the toner transferred to the latent image surface in the time interval t ₁ to the toner carrier, which is called a toner reverse transfer stage.

Vth・f and Vth・r in FIG. 2 are potential thresholds for toner to transfer from the toner carrier to the latent image surface and from the latent image surface to the toner carrier, respectively, and the curves shown in the figure It is considered that the potential value is extrapolated by a straight line from the point where the slope of the rise is the largest.
In the upper part of FIG. 2, the amount of toner transfer at _t1 and the degree of toner reverse transfer at _t2 are modeled blotted against the latent image potential.

In the toner transfer stage, the amount of toner transferred from the toner carrier to the electrostatic image holder is as shown by curve 1 shown by a broken line in FIG. The slope of this curve is approximately equal to the slope of the curve when the alternating bias voltage that periodically repeats Vmin and Vmax at a low frequency is not applied as described above. This slope is large, and the amount of toner transfer tends to be saturated at an intermediate value between V _L and V _D , resulting in poor halftone image reproduction and poor gradation. The second broken line curve shown in FIG. 2 represents the establishment of the degree of toner reverse transition.

One of the features of the developing method according to the present invention is that the toner transfer stage and the toner reverse transfer stage are alternately repeated, and a second feature is that towards the latter half of the developing process, The purpose of this invention is to change the strength of the electric field acting in the gap between the toner carrier and the electrostatic image holder, that is, the development gap, in a unique manner by the method described below. In other words, by adjusting the electric field strength, the transfer of toner can be controlled, and the amount of transferred toner, which ultimately transfers and adheres to the surface of the electrostatic image holder and contributes to development, can be controlled by adjusting the electric field strength. The purpose is to achieve a phenomenon in which the toner transfer amount changes in a small slope and is almost uniform from V _L to V _D by convergence according to the potential, as shown by curve 3 in FIG. Therefore, in the non-image area, the final toner adhesion is virtually non-existent, while toner adhesion to the halftone image area is an excellent visible image with extremely high gradation in accordance with the surface potential. is obtained.

As a method for adjusting the electric field strength during the development interval, there is a method in which the applied alternating voltage is gradually converged to an appropriate constant DC value, but the present invention proposes a method in which the development interval itself is increased during the development process. We are hiring. The method will be described in detail below.

An example of the development process in this method is shown in Figure 3A.
Shown in B and C. As shown in Figure 3A and B,
The electrostatic image holder 4 moves in the direction of the arrow, during which time it passes through areas with different development gaps.
5 is a toner carrier. Therefore, the gap between the electrostatic image holding surface and the toner carrier gradually widens starting from the closest position in the developing section. Figure A shows the state of the electric field in the image area of the electrostatic image carrier, and Figure B shows the state of the electric field in the non-image area of the respective toner carriers during transfer and countertransference. Further, C in the same figure shows the waveform of the alternating voltage applied to the toner carrier, and when the electrostatic image charge is positive, |Vmax−V _L |>|V _L −Vmin| |Vmax−V _D |< |V _D −Vmin| ………(2) is set.

In the areas shown in FIG. 3A and B, the first process described later is carried out, and in the area shown in the second process described later,
process is occurring.

It is important that the effects of toner transfer and countertransference in the image area and non-image area in the first process and the second process change. This pattern will be explained phenomenologically. First, in the image part, as illustrated in FIG. 3A, in the first process,
Since Vmax > V _D > Vmin, a relatively strong toner transfer electric field occurs from the toner carrier 5 toward the image area of the electrostatic image carrier 4 during the period t ₁ (applied voltage Vmin), and the toner transfers to the image area. arrive at and adhere there. On the other hand, in the period t ₂ (applied voltage Vmax),
A relatively weak toner reverse transition electric field is applied to the electrostatic image carrier 4.
This occurs from the image area toward the toner carrier 5, and a portion of the toner is returned to the toner carrier 5 from the image area. Each time the periods t ₁ and t ₂ are repeated in this manner, toner transfer and countertransference occur between the toner carrier 5 and the image area of the electrostatic image carrier 4. This is because the relationship between the applied voltages Vmin and Vmax and the image area potential V _D is set as |Vmax−V _D |<|V _D −Vmin| as shown in equation (2), so in this first process, Since the amount of toner transferred from the toner carrier to the image area is much larger than the amount of toner reverse transfer, it is not a practical problem that the toner reverse transfer reduces the toner transfer, that is, the development effect.

Next, as shown in FIG. 3A, the gap between the toner carrier and the electrostatic image carrier increases over time, and the electric field strength in this gap due to the applied bias voltage increases continuously or intermittently. decrease,
When it becomes equal to the threshold value |Vth·r|, the amount of toner once attached to the electrostatic image carrier during period t ₂ that is reversely transferred to the toner carrier side becomes zero. Here, |Vth・r| is the minimum absolute potential difference between the electrostatic image forming surface and the surface of the toner carrier, which allows the toner to separate from the electrostatic image forming surface and reverse transfer to the toner carrier. This is called the potential threshold.

Further, when the potential becomes lower than this potential threshold, reverse transfer no longer occurs, but the amount of toner transferred from the toner carrier to the electrostatic image holder is smaller than the amount of toner transferred during period _t1 . An electric field is generated that promotes the transition.

In this region, neither transition nor countertransference occurs anymore, and development is completed.

Next, the process of toner movement in the non-image area (potential V _L ) of the electrostatic image holder will be explained with reference to FIG. 3B. In the first process shown above,
Since Vmal> _VL >Vmin, a relatively weak toner transfer electric field occurs from the toner carrier 5 to the non-image area of the electrostatic image carrier 4 during the period _t1 (applied voltage Vmin), and the toner transfers to the non-image area. It adheres to the parts. On the other hand, t ₂
During the period (applied voltage Vmax), a relatively strong toner reverse transition electric field occurs from the non-image area toward the toner carrier, and the toner is returned from the non-image area to the toner carrier. It is considered that each time periods t ₁ and t ₂ are repeated in this way, toner transfer and countertransference occur between the toner carrier and the toner, and the toner reciprocates between them. This is the applied voltage Vmin,
As mentioned earlier, the relationship between Vmax and non-image area potential V _L is set as |Vmax−V _L |>|V _L −Vmin|, so the amount of reverse transfer of toner is more stochastic than the amount of transfer. is considered to be large. In this case, of course, more toner than has actually adhered will not be reversely transferred.

Next, as shown in FIG. 3B, when the gap between the electrostatic image carrier and the toner carrier widens and the electric field acting there becomes lower than the threshold |Vth・f|, the static electricity is no longer removed from the toner support. No toner transfer occurs toward the image carrier. period instead
Although it is smaller than the toner backtransfer at t ₂ , an electric field is generated that promotes the tendency of the toner to backtransfer from the electrostatic image carrier toward the toner carrier.
Therefore, the toner transferred to the non-image area in the first step is completely removed in this second step and returned to the toner support. In this region, neither transition nor countertransference occurs anymore, and development is completed. Regarding the reproduction of halftones, the final amount of toner transferred to the latent image surface is determined by the magnitude of the toner transfer amount and the reverse transfer amount depending on the potential, but in the end, the slope is as shown in curve 3 in Figure 2. A microscopic image with small gradation and therefore high gradation can be obtained. Furthermore, due to the effect of the external alternating bias described above in the development-promoting toner transfer stage, the electric lines of force emitted from the edge of the image surface do not wrap around toward the back electrode and are directed to the surface of the developer carrier. This makes it possible to perform clear development to the edges of the image. The extent of this wrap-around of electric lines of force increases as the distance between the electrostatic image holding surface and the developer carrier surface increases.
This can be minimized by increasing the applied voltage.

The amplitude of the external alternating voltage has an appropriate value depending on the latent image potential under a constant development gap. When the development gap is increased, the amplitude must be increased in order to maintain the bias effect at the same level. For example, if the electric field caused by an external voltage is to be kept constant, the amplitude must be increased in proportion to the development gap.
However, if this ratio is increased, the effect of the external electric field becomes too large compared to the latent image potential contrast, and background fog is likely to occur.To prevent this, the DC component of the external voltage is shifted to the reverse transition side. As a result, the image density decreases.

As a result of experiments using the apparatus described later in Examples (FIGS. 6 and 7), when the gap in the developing section between the latent image carrier and the developer support is d (unit: μ), the external The amplitude (peak-to-peak, Vpp) of the alternating voltage (unit: V) is 1.5[V/μ]・d[μ]≦Vpp≦1.5[V/μ]・d[
μ〕 +1500〔V〕 It was found that V that satisfies (3) is appropriate. this
The appropriate range of Vpp is the area surrounded by two straight lines a and b as a function of the development gap d as follows: Vpp=1.5d......(3) Vpp=1.5d+1500......(4) be. This area is A on the graph in Figure 4.
It is represented as a region. These are (3) and (4) above.
It is expressed by the formula. The amplitude value (V) is the development gap
Straight line graphs a and b are drawn as a function of (d), and the area is divided by both straight lines. Other areas are (B)(C)
It is expressed as In region (B), background fog is difficult to avoid and the image contrast is low. In addition, the region (C) has poor gradation and line image reproducibility, and both regions are unsuitable for the amplitude of external voltage.

From this graph, it can be seen that when developing with a specific latent image potential and a specific development gap, the external voltage amplitude value with respect to the latent image potential in the development gap exceeds the threshold value mentioned above. If the development gap is set at one point and then changed, the voltage value may be set at a point moved approximately parallel to the straight lines a and b.

Furthermore, this result indicates that the latent image potential contrast is 200V.
~900V, external voltage frequency is for 50Hz ~ 1KHz. The former covers the potential range in general electrophotography;
Regarding the latter, an appropriate bias effect cannot be obtained at a frequency of 1 KHz or higher. As mentioned above, the appropriate external voltage value varies depending on these values, and the appropriate area in FIG. 4 has a width.
When the latent image potential contrast is high and when the frequency is high, a larger amplitude is more effective.

Examples will be described below.

Example This will be explained with reference to FIG.

11 is a photosensitive drum having a Se film, and 12 is a toner carrier made of a conductive rubber sheet, which is driven by a metal roller 13. Toner carrier 12
The moving speed is approximately the same as the peripheral speed of the electrostatic image holder 11, which is 200 mm/sec. Reference numeral 15 denotes a non-magnetic insulating toner stored in a container 17, which is transported by the frictional force with the toner carrier 12 and the Van der Waals force, and whose thickness is regulated to about 60μ by an elastic coating member 16. , a negative charge is applied by a corona charger 18 before development. The toner consists of a sterene maleic acid resin, 2% by weight of a charge control agent, and 3% by weight of carbon black. Although the gap between the members 11 and 12 is maintained at a minimum of 200μ, as the members 11 and 12 rotate,
The gap gradually becomes larger, forming a development area having the first and second processes described above. Reference numeral 14 denotes a sliding electrode that contacts the metal core of the rotating member 13, and is connected to the electrically conductive support of the grounded member 11 by the power supply 1.
Alternate voltages are applied to members 12, 13, and 14 by means of 9. The waveform of the alternating electric field is rectangular, and the frequency is 500Hz.
It is. The electrostatic image potential is +750V in the image area and +50V in the non-image area, and the potential of the member 12 is the maximum value Vmax.
= +900V, minimum value Vmin = -300V, amplitude (peak-to-peak) Vpp = 1200V. With the above configuration, a clear image with high gradation could be obtained. Under this configuration, if the gap between member 11 and member 12 is set to 400μ, the potential of member 12 is maximum value Vmax = 1050V, minimum value Vmin = -450V,
Appropriate images were obtained with an amplitude (peak-to-peak) of 1500V.

Embodiment 2 FIG. 6 shows still another embodiment of a developing device employing the above-described method according to the present invention.

21 is a photosensitive drum with a radius of 40 mm and has a CdS layer and an insulating layer; 22 is a photosensitive drum with a radius of 15 mm containing a permanent magnet 23;
mm non-magnetic sleeve, both members 21 and 22
rotates in the same direction at a constant circumferential speed of 100 mm/sec.
25 is an insulating magnetic toner whose components are 60% by weight of styrene resin, 35% by weight of magnetite,
It consists of 3% by weight of carbon black and 2% by weight of a negative charge control agent. Additionally, 0.3% by weight of colloidal silica is externally added to improve fluidity. The toner is transported by a sleeve 22, and a magnetic blade 26 close to the sleeve reduces the coating thickness to approximately 70 μm.
regulated by. Further, the toner is given a negative charge by frictional charging with the sleeve 22. Member 27 is a toner container. The gap between the members 21 and 22 is maintained at a minimum of 200 μm, but as the members 21 and 22 rotate, the moving speed of both members and the width of the gap are set so as to satisfy the conditions described above with reference to FIG. 3. Member 21 and member 22 are maintained in electrical continuity, and alternating voltages are applied to the conductive support member of member 21 by power supply 29. The alternating voltage was a sine wave and the frequency was 200 Hz, and the relationship between the voltage value and the electrostatic image potential was as shown in FIG.

The electrostatic image potential is +500V in the image area and OV in the non-image area, and a DC voltage +200V is superimposed on a sine wave with an amplitude of 400V (800Vpp). Based on the above configuration, a clear image with high gradation could be obtained.
Furthermore, based on the above configuration, if the gap between the members 21 and 22 is set to a minimum of 500μ, the external voltage is set to an amplitude of 600V.
(1200Vpp) and a DC voltage of +200V.

FIG. 7 illustrates a positioning mechanism for changing the developing gap between the sleeve and the electrostatic image carrier in the embodiment shown in FIG. 6. In the figure, 3
Reference numeral 1 denotes rollers at both ends of the developing device that abut against and position the electrostatic image carrier, and arm 3
It is rotatably supported by 2. This arm 32 is adjustable by a piston rod in the direction toward or away from the electrostatic image carrier, and is finally attached to the side plate 27 of the developing device by a fixing screw 32a. This developing device has a fixed shaft 3 attached to the main body of the image forming device.
4, 35 and a fixed spring 36, it is stationary and supported in a three-point manner. 33a is a pin installed on the side plate, and is engaged with the fixing spring. As a developing gap adjusting means, a slidable locking member 37 having a groove that engages with the fixed shaft 34, and a screw 39 that comes into contact with the rear end of the locking member 37 and adjusts the amount of sliding of the locking member are provided. ing. The sliding direction of this sliding locking member 37 is determined by a long groove 37a that fits into a fixing pin 38 provided on the developing device side. Therefore, in order to change the development gap, adjust the adjusting screw 39 and slide the locking member 37.
This is done by slightly rotating the developing device integrated therewith about the screw 32a as a fulcrum. Positioning in a predetermined development gap can be detected by a thickness gauge. As mentioned above, it is possible to change the development gap in this way and select the appropriate amplitude of the applied bias voltage accordingly. For example, when the thickness of the developer layer formed on the developer support changes, this is usually corrected. For example, if the thickness of the developer layer that is formed increases or decreases due to changes in conditions such as the type of developer used, the environment in which the machine is used, especially changes in temperature and humidity, or wear of the positioning rollers due to frequency of use, the development gap is changed to form a developer layer of a desired thickness, and at this time, the amplitude of the applied bias is adjusted as described above so that it is within the region A in FIG.

In the above description, the case where the image area potential V _D is positive has been described in detail, but the present invention is not limited to this case, and can also be applied when the image area potential is negative. It can be applied in the same way if the positive direction of is made small and the negative direction is made large. Therefore, when the image area charge is negative, the above-mentioned (1) and (2) are expressed as the following (1)' and (2)'.

Vmax＞V _L ＞V _D ＞Vmin ……(1)′ ｜Vmin−V _L ｜＞｜V _L −Vmax｜ ｜Vmin−V _D ｜＜｜V _L −Vmax｜ ……(2)′ It goes without saying that the invention is not limited to the above embodiments, and can be applied to methods of developing latent images of other forms or properties.

As explained above, the present invention provides a development system in which a latent image carrier having an electrostatic latent image formed on its surface and a developer carrier carrying a developer layer on its surface face each other with a gap maintained in a developing section. In the section, an alternating electric field is formed to cause the developer released from the developer carrier to adhere to the surface of the latent image carrier and to separate the developer attached to the surface of the latent image carrier from the surface of the latent image carrier. A developing method in which the potential difference (peak-to-peak) between the maximum potential and the minimum potential of the waveform forming the alternating electric field is determined by the gap d (unit: (1.5 x d) V (volts)
×d+1500) Since this developing method is characterized by being smaller than V (volts), it not only does not cause background fog, but also provides a microscopic image with excellent gradation and line image (line copy) reproducibility. . Furthermore, by applying a low-frequency alternating electric field, the transfer of developer to the non-image area and the reverse transfer to developer carrying are alternately and reliably repeated in the gap between the developer carrier and the non-image area in the development area. Such reciprocating movement of the developer enables development with extremely excellent gradation. Furthermore, when a magnetic developer layer is supported on a non-magnetic sleeve containing a magnet, the magnetic developer uniformly increases the binding force of the developer onto the sleeve due to the action of the magnetic field, thereby preventing developer transfer. Potential threshold Vth・f
Since the value of can be taken sufficiently large, it is possible to suppress the adhesion of the developer to the non-image area to a small amount, and it is possible to minimize background fog.

The developing method for performing developer transfer and reverse transfer using the developer according to the present invention is as follows:
By applying a low frequency alternating bias electric field having an appropriate amplitude, it was possible to obtain an image with high gradation, clear edges of the image, and beautiful fog and dirt.

In an electrophotographic development method, an electrostatic image carrier and a toner carrier are faced to each other with a gap between them, and a constant high-frequency pulse bias (frequency of 10 kilocycles/second to 3000 kilocycles/second) is applied to this gap. , a technique is known in which toner is attached to the image area but not to the non-image area (UK Patent No. 1,458,766 and US Pat. No. 3,890,929). In this known example, there is no technical idea of placing the magnetic developer under the action of a magnetic field and applying a low-frequency alternating voltage to the development gap in order to improve gradation as in the present invention; By adjusting and changing the electric field strength during the development process, the magnetic developer is transferred to the non-image area under the required magnetic restraint, and the development of the low potential area of the image can also be adjusted, and there is no development failure at the edge of the image.
The technical concept of reproducing faithful gradation is not described.

Other developing methods similar to the above-mentioned known techniques have been described (e.g., U.S. Pat. No. 3,866,574;
No. 3,893,418, etc.), both of which apply high-frequency pulses, the present invention has a different technical idea for the same reason as mentioned above.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of electric lines of force generated from an electrostatic image, Fig. 2 is a graph illustrating the principle of the developing method according to the present invention, and an explanatory diagram showing an example of the applied voltage waveform, and Figs. 3 A and B. is a process explanatory diagram showing the first, second, and third steps of the developing method according to the present invention, FIG. 3C is a waveform diagram schematically showing an example of the applied voltage waveform, and FIG. 4 is a diagram showing the development gap. 5 and 6 are cross-sectional views respectively showing embodiments of implementing the developing method according to the present invention, and FIG. FIG. 8 is a sectional view showing the mechanism of development gap change, and is a waveform diagram showing an example of an alternating voltage waveform applied in the embodiment shown in FIG. 6. 4, 11, 21...electrostatic image carrier, 5, 12,
22...Developer carrier.

Claims (1)

[Scope of Claims] 1. In a developing section, a latent image carrier having an electrostatic latent image formed on its surface and a developer carrier carrying a developer layer on its surface face each other with a gap maintained in the developing section, A developing method that performs development by forming an alternating electric field that causes the developer released from the developer carrier to adhere to the surface of the latent image holder and also causes the developer attached to the surface of the latent image holder to separate from the surface of the latent image holder. And,
The potential difference (peak-to-peak) between the maximum potential and the minimum potential of the waveform forming the alternating electric field is the gap d in the developing area between the latent image carrier and the developer carrier.
(unit: micron), (1.5 x d) V (volt)
A developing method characterized by being larger than (1.5×d+1500) and smaller than V (volt). 2. The developing method according to claim 1, wherein the potential difference is 800 volts or more.