JP2971713B2 - Developing device - Google Patents

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 developing and visualizing an electrostatic latent image formed on an image carrier in an image forming apparatus utilizing an electrophotographic system or the like.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method, an electrostatic latent image formed on an image carrier is developed by a developing device and visualized as a toner image. FIG. 9 shows a main part of an example of an image forming apparatus provided with a conventional developing device.

This image forming apparatus includes a photosensitive drum 1 coated with a photosensitive layer made of an organic semiconductor as an image carrier.
In this example, the photosensitive drum 1 has a diameter of 30 mm, rotates at a speed of 60 mm per second in the direction of the arrow in the figure, and is uniformly charged to -600 V by a primary charger 5 disposed therearound. Next, the photosensitive drum 1 is exposed to light based on image information by a light emitting element 4 such as a laser or an LED, and the potential of the exposed portion changes to -100V. A formed electrostatic latent image is formed. The electrostatic latent image formed on the photosensitive drum 1 is developed by a developing device provided around the photosensitive drum 1.

In this developing device, a developing sleeve 2, a coating roller 3, and an elastic blade 7 as a developer carrier are provided in a developing container 6 containing a non-magnetic toner as a developer. The developing sleeve 2 has a diameter of 16 mm, and is rotatably arranged in the direction indicated by an arrow in an opening facing the photosensitive drum 1. An application roller 3 is arranged so as to abut on the lower oblique position of the developing sleeve 2. Have been. The application roller 3 has a diameter of 8 mm, and rotates in the direction of the arrow to rub the non-magnetic toner in the container 6 on the surface of the developing sleeve 2 to carry it.

The developing sleeve 2 carries the toner and transports the toner to a developing section facing the photosensitive drum 1. During the transport, the layer thickness of the toner is regulated by the elastic blade 7, and the toner is fixed on the developing sleeve 2. Is applied and formed. The elastic blade 7 is made of urethane or the like, is installed above the opening of the container 6, and hangs down from above to elastically contact the surface of the developing sleeve 2.

The toner applied to the thin toner layer on the developing sleeve 2 as described above is subjected to the elastic blade 7, the coating roller 3 and the developing sleeve 2 in the process up to that time.
, And a charged charge of −6 μC / g to −30 μC / g is applied.

The photosensitive drum 1 and the developing sleeve 2 have a gap of 50 to 500 μm, usually 30 μm, in the developing section.
It is arranged in a non-contact manner with an opening of 0 μm, and a frequency of 800 to 3500 Hz, an amplitude of 400 to 3000 V, and an integration of a waveform by a bias power supply 8 in a gap between the developing sleeve 2 and the photosensitive drum 1 (between SD) in the developing section. Average value Vdc:-
A developing bias in which a DC voltage of 50 to -550 V and an AC voltage are superimposed is applied, and a developing electric field is generated.

As the AC voltage, a sine wave shown in FIG. 10, a triangular wave shown in FIG. 11, a sawtooth wave shown in FIG. 12, a rectangular wave shown in FIG.
The difference between the binary value and the integrated average value Vdc is different, and as shown in FIG. 14, the time during which the first peak value (Vmax) for forming the electric field for urging the toner from the developing sleeve 2 toward the photosensitive drum 1 is applied. And a time during which a second peak value (Vmin) for forming an electric field for urging the toner from the photosensitive drum 1 toward the developing sleeve 2 is applied. DUTY bias)) is conventionally known.

The charged toner on the developing sleeve 2 is transferred from the surface of the developing sleeve 2 to the surface of the photosensitive drum 1 by the force received from these developing electric fields in the developing section, and the electrostatic latent on the photosensitive drum 1 is changed. Image development takes place.

[0010]

By the way, in recent years, with the development of computer graphics technology, an image formed by an electrophotographic image forming apparatus is desired to have higher image quality.

However, when a 5 mm square electrostatic latent image is developed using a duty bias and a rectangular wave bias as a developing bias, as shown in FIG. A so-called sweeping phenomenon occurs in which the density of g becomes significantly higher than that of other portions, and a uniform image cannot be obtained. Further, when development is performed using a sine wave, a triangular wave, and a sawtooth wave, the density becomes low and a sufficient image density cannot be obtained.

As a method for increasing the image density, a method of increasing the amplitude of the AC component of the developing bias applied to the gap between the developing units and a method of changing the DC component have been conventionally known. However, if the amplitude of the AC component of the developing bias is increased or the DC component is changed, the developing sleeve 2
In addition to the possibility that spark discharge or the like may occur between the photosensitive drum 1 and the photosensitive drum 1 (between SDs), there is a possibility that ground fog may occur.

Therefore, conventionally, it has been extremely difficult to satisfy the demand for obtaining a high-quality image.

Further, in the case of a color image, the toner images of the respective colors are superimposed.
It is more difficult to obtain a higher quality image than in the case of a single color image.

An object of the present invention is to define a developing bias applied to a developer carrying member during development, thereby enabling a high-quality image to be easily obtained by sweeping and having a low density. It is to provide a device.

Another object of the present invention is to define a developing bias applied to a developer carrier during development with respect to a charge amount q / m per unit mass of toner carried on the developer carrier. Accordingly, it is an object of the present invention to provide a developing device capable of easily obtaining a high-quality image with no sweeping and low density without developing toner scattering or electric discharge.

Still another object of the present invention is to reduce a developing bias applied to a developer carrier during development by applying a developer mass m per unit area of a developer layer thinly applied on the developer carrier. An object of the present invention is to provide a developing device capable of easily obtaining a high-quality image with no sweeping and low density without causing toner scattering or electric discharge by defining the ratio to / s.

[0018]

The above object is achieved by a developing apparatus according to the present invention. In summary, the present invention provides a developer carrier that is provided facing an image carrier and carries and transports a developer, and the image carrier for developing a latent image formed on the image carrier. Electric field forming means for forming an alternating electric field between the developer and the developer carrier, wherein the alternating electric field continues for a predetermined time and at a predetermined intensity for directing the developer toward the image carrier. In a developing device having a first electric field and a second electric field that continues at a predetermined intensity for a predetermined time for causing a developer to flow toward the developer carrier, the first electric field of the first electric field in one cycle of the alternating electric field is provided. Time to continue T11,
And a time T for transition from the second electric field to the first electric field.
The developing device 12 satisfies 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0, and the transition time from the first electric field to the second electric field is 40 μsec or less.

In the present invention, preferably, one of the alternating electric fields
In the cycle, the time T11 during which the first electric field lasts, and the time T12 during which the second electric field transitions to the first electric field.
Satisfies 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0.

According to another aspect of the present invention, a developer carrier provided opposite to the image carrier for carrying and transporting a developer, and developing the latent image formed on the image carrier is provided. Electric field forming means for forming an alternating electric field between the image carrier and the developer carrier, wherein the alternating electric field is provided for a predetermined time for causing the developer to move toward the image carrier. And a second electric field which continues at a predetermined intensity for a predetermined time for moving the developer toward the developer carrier.
In a developing device having an electric field, a time period during which the first electric field lasts in one cycle of the alternating electric field is T11,
T12 is a transition time from the second electric field to the first electric field,
Assuming that the time of one cycle of the alternating electric field is T and the charge amount per unit mass of the developer is q / m [μC / g], T11 /
(T11 + T12) is (T11 + T12) / T × 100 = B, and the following expression 6.0 [μC / g] ≦ | q / m | ≦ 18.0 [μC / g] 0 ≦ T11 / (T11 + T12) × 100 ≦ − (− 1.25 × | q / m | +22.5) × B / 100 + 90.0 18.0 [μC / g] ≦ | q / m | ≦ 26 0.0 [μC / g] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 26.0 [μC / g] ≦ | q / m | ≦ 35.0 [μC / g] When (−0.89 × | q / m | +18.7) × (B / 100−1.0) + 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 Is provided.

More preferably, T11 / (T11 + T12)
Is given by the following equation: 6.0 [μC / g] ≦ | q / m | ≦ 18.0 [μC / g] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ − (− 1.25 × | q / m | +22.5) × B / 100 + 60.0 When 18.0 [μC / g] ≦ | q / m | ≦ 26.0 [μC / g] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0 26.0 [μC / g] ≦ | q / m | ≦ 35.0 [μC / g] (−0.89 × | q / m | +18.7) × ( B / 100−1.0) + 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0.

According to still another aspect of the present invention, there is provided a developer carrier provided opposite to an image carrier for carrying and transporting a developer, and developing a latent image formed on the image carrier. To form an alternating electric field between the image carrier and the developer carrier, the alternating electric field comprising:
A first electric field that continues at a predetermined intensity for a predetermined time for moving the developer toward the image carrier, and a second electric field that continues at a predetermined intensity for a predetermined time to move the developer toward the developer carrier A developing device having an electric field.
In the cycle, the time during which the first electric field lasts is T11, and the time when the second electric field shifts to the first electric field is T11.
12. The time of one cycle of the alternating electric field is T, and the mass of the developer per unit area of the surface of the developer carrier is m / s [mg / cm].
² ], T11 / (T11 + T12) becomes (T11 + T12
) / T × 100 = B, and the following equation: 0.6 [mg / cm ² ] ≦ m / s ≦ 1.5 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ (−16.7 × m / s + 10.0) × B / 100 + 90.0 0.35 [mg / cm ² ] ≦ m / s ≦ 0.6 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 0.2 [mg / cm ² ] ≦ m / s ≦ 0.35 [mg / cm ² ] − (− 53.3 × m / s + 18.7) × (B / 100-1.0) + 10 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 A developing device is provided.

More preferably, T11 / (T11 + T12)
When the following equation is satisfied: 0.6 [mg / cm ² ] ≦ m / s ≦ 1.5 [mg / cm ² ] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ (−16.7 × m / s + 10.0) × B / 100 + 60.0 0.35 [mg / cm ² ] ≦ m / s ≦ 0.6 [mg / cm ² ] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0 0.2 [mg / cm ² ] ≦ m / s ≦ 0.35 [mg / cm ² ] − (− 53.3 × m / s + 18.7) × (B / 100-1. 0) + 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted intensive studies in order to obtain a good image without sweeping and low density by development. As a result, regarding the developing bias applied between the photosensitive drum and the developing sleeve, as shown in FIG.
That is, a process of forming an electric field for urging toner in a direction from the photosensitive drum to the developing sleeve in one cycle of the alternating electric field (toner energizing process in the developing sleeve direction) (A)
(B) (potential Vmax) during the transition from (potential Vmin) to the process of forming an electric field for urging toner in the direction from the developing sleeve to the photosensitive drum (toner biasing process in the direction of the photosensitive drum) When the developing bias (hereinafter referred to as a falling specified bias) that defines the fall of the AC component is used for the development by defining the state of the process (C), it is possible to obtain a good image with no sweeping and low density. Images were obtained.

This will be further described by a development experiment conducted by the present inventors. FIG. 17 shows an apparatus used in a development experiment. The waveform generator 21 is connected to a developing apparatus 23 via an amplifier 22, and the waveform is generated in the generator 21 by an oscilloscope 24 connected between the amplifier 22 and the developing apparatus 23. While monitoring the waveform of the developing bias to be performed, a developing bias was generated and applied to the developing device 23 to perform development. The configuration of the developing device 23 is the same as that of the conventional developing device shown in FIG.

As shown in FIG. 18, in one cycle of the AC component of the developing bias, the rise during the transition from the toner energizing process (B) toward the photosensitive drum to the toner energizing process (A) toward the developing sleeve. Is the process (D), the sum of the times of the processes (A) and (D) is T2, and the sum of the time T11 of the process (B) and the time T12 of the process (C) is T1.
The duty percentage (%) = T1 / (T1
+ T2) × 100, percent slope (%) = T11 / T1
× 100 = T11 / (T11 + T12) × 100.

FIG. 19 shows the relationship between the gradient percentage and the duty percentage of the AC component of the developing bias used for development in the above experiment in one cycle, and the state of sweeping of the obtained 5 mm square image and the occurrence of low density. FIG. Duty percentage is 5.0-9
5.0%, and at each duty percentage, the slope percentage is 0.5-99.5%.
Changed.

As can be seen from FIG. 19, 5.0 to 95.0.
% For all duty percentages (6% in the figure)
0% or more is mainly displayed, but the same applies to 60% or less). When the slope percentage is set to 60.0 to 90.0%, the sweeping of the image is reduced to a level at which there is no practical problem, The slope percentage is 0.5-60. In the% range, sweeping was completely eliminated. Also, the slope percentage is 1
When the density was set to 0.0 to 20.0%, the density of the image was low enough to have no practical problem, and when the density was 20.0 to 99.5%, a sufficient density was obtained.

Although the reason is not clear, it is considered as follows. First, the mechanism by which sweeping occurs will be described.

FIG. 20 is a sectional view showing lines of electric force between the developing sleeve to which the developing bias is applied and the photosensitive drum. As shown in FIG. 20, the electric line of force h is substantially linear at the center 13 where the space between the SD between the developing sleeve 2 and the photosensitive drum 1 is narrow in the lateral direction (moving direction). The line of electric force h is distorted at the end 14 where the distance between both sides is large. FIG. 21 shows that the surface of the photosensitive drum 1 facing the developing sleeve 2 has an image portion Rb (see FIG. 22).
FIG. 5 is an explanatory diagram schematically showing the direction of movement of toner due to the force of an electric field at the lateral end portion 14 between SDs when.

As shown in FIG. 21, toner flying from the developing sleeve 2, at the point a ₁ on the electric lines of force h ₁ distorted at the end 14 on the horizontal direction between SD, vector velocity tangentially It has V1. When the next moment the toner comes to a point a _2, the toner has a vector velocity V ₂ in the tangential direction of the electric force lines h ₂ at the point a _2. Then, the toner obtains a vector (V ₁ + V) obtained by combining these vector velocities from the point a _2.
2 ) Fly in the direction. Therefore, at the end 14 between the SDs, FIG.
As shown in FIG. 2, the toner t from the developing sleeve 2 does not fly along the line of electric force h, but shifts outward with respect to the photosensitive drum 1 as shown by a flight locus Q1 in the drawing. Reciprocate.

As shown in FIG. 23, the non-image portion Ra (photosensitive drum surface potential: -600 V) of the photosensitive drum 1 and the following upstream image portion Rb (photosensitive drum surface potential: -1)
00V), the toner t on the developing sleeve 2 on the downstream side of the image portion Rb when the image leading edge portion Rc, which is the boundary with the image portion Rb, comes to the end portion 14 between the SD where the electric lines of force are distorted
Flies and moves to the image portion Rb side as indicated by the locus Q2. As a result, the toner t concentrates on the image leading edge Rc, and the concentrated toner returns to the upstream side of the developing sleeve 2. Therefore, the toner t is located on the upstream side of the developing sleeve 2 corresponding to the end 14 between SD. Large pool M is formed.

Next, as shown in FIG. 24, when the image portion Rb is located at the end portion 14 between the SDs, the toner t on the developing sleeve 2 reciprocates outwardly displaced like a locus Q3. . As a result, regardless of the rotation of the developing sleeve 2, the toner pool M is continuously formed at a certain position on the upstream side of the developing sleeve 2, and the amount of the toner t accumulated further increases.

Then, as shown in FIG.
When the image rear end edge Re, which is the boundary between the image portion Rb and the subsequent non-image portion Rd on the upstream side, comes to the end portion 14 between the SDs, the electric field concentrates on the image rear end edge Re. Then, the toner t in the toner pool M on the developing sleeve 2 is drawn to the image rear edge portion Re. As a result, the toner t in the toner reservoir M reciprocates between the SDs, moves downstream with the movement of the image rear edge Re, and passes between the SDs.

Finally, as shown in FIG. 26, at the point where the width between the SDs is widened, the toner t of the toner pool M adheres to the rear end of the image portion Rb, and thus the toner image formed on the photosensitive drum 1 is formed. A sweep Rf is formed at the rear end of R.

From the above, it is effective to suppress the reciprocating movement of the toner at the end between the SD where the lines of electric force are distorted in order to prevent the sweeping of the image from occurring. In order to obtain a sufficient image density in the non-contact developing method, it is effective to make a sufficient reciprocating movement of the toner in the central portion between the SDs.

In general, assuming that the distance between SD is dSD, the potential of the developing sleeve 2 is Vs, and the charge amount of the toner is Qt, the toner receives a force Ft of FttQt × Vs / dSD from the electric field by the developing bias. Moving.

As shown in FIG. 27, the charge amount per unit mass of the toner on the developing sleeve has a non-uniform distribution, and the force from the electric field received by the toner and the reflection force received from the developing sleeve Varies depending on the charge amount of each toner. Since the toner having a small amount of charge has a small reflecting power, it is possible to reciprocate between SDs even when the force received from the electric field is weak, but in this case, the speed of the reciprocating motion is low due to low acceleration. Conversely, a toner having a large charge amount has a large mirroring power, and therefore cannot reciprocate between SDs unless the force received from the electric field is strong. However, the speed of the reciprocation is high because the acceleration is large.

FIG. 28 is an explanatory diagram showing the relationship between the potential at the end between the SDs of the developing sleeve to which the falling bias has been applied and the moving time of the toner from the developing sleeve in the direction of the photosensitive drum. It is. That is, as shown in FIG.
When the surface of the photosensitive drum 1 facing the developing sleeve 2 is an image area, the developing sleeve 2 and the photosensitive drum 1
4 shows the time during which the toner separated from the developing sleeve 2 under the prescribed falling bias is moved by receiving a force in the direction of the photosensitive drum 1 at the wide end portion 14 between SD.

In FIG. 28, the potential of the developing sleeve is V
a, the force from the electric field due to the developing bias between the SDs with respect to the toner having a small charge amount (hereinafter referred to as ta) becomes stronger than the mirroring force of the toner ta received from the developing sleeve. From the developing drum, the potential of the developing sleeve immediately becomes the same as the image portion potential Vc.
Is short.

On the other hand, a toner having a large charge amount (this is referred to as tb
In order for the force received from the electric field due to the developing bias to be stronger than the mirroring force from the developing sleeve, the potential of the developing sleeve must be larger Vb in the negative direction. Inability to separate from sleeve.

Therefore, regardless of the amount of charge of the toner, the reciprocating motion at the wide end between the SDs can be suppressed for all the toners, and the occurrence of sweeping can be prevented.

FIG. 29 is an explanatory diagram showing the relationship between the potential at the central portion between the SDs of the developing sleeve to which the falling specified bias is applied, and the moving time of the toner from the developing sleeve in the direction of the photosensitive drum. It is.

In FIG. 29, when the potential of the developing sleeve is V
At a, the force from the electric field due to the developing bias between the SDs with respect to the toner ta having a small charge amount becomes stronger than the mirror force of the toner ta received from the developing sleeve, and the toner ta moves from the developing sleeve toward the photosensitive drum. Start. In this case, since the time from the start of movement of the toner ta to the potential of the developing sleeve at the potential Vc is long, the movement time Ta of the toner ta is long, and the reciprocating movement between SD can be sufficiently performed.

The toner tb having a large charge amount starts to move to the photosensitive drum 1 when the potential of the developing sleeve becomes Vb. Although the movement time Tb of the toner tb is shorter than Ta, the acceleration of the toner tb is as described above.
The speed of the toner tb is faster than that of the toner ta, so that the toner can reciprocate sufficiently in a short time.

As described above, according to the developing bias of the falling specified bias, the falling edge of the AC component of the developing bias causes the S component corresponding to the toner of each charge amount to fall.
By controlling the reciprocating motion between D, the reciprocating motion of the toner at the wide end between the SDs is suppressed for all the toners irrespective of the amount of charge of the toner, and the reciprocating motion of the toner at the narrow central portion between the SDs is sufficient. Therefore, it is possible to suppress the occurrence of sweeping and low density in an image obtained by development.

As can be seen from FIG. 19, in the present invention, as described above, in order to prevent sweeping of images and low density,
T1 of time T11 in one cycle of the development bias (= T11
+ T12) as a percentage of the slope (T11 / T12)
1 × 100) is set so as to satisfy the relationship of 10.0 ≦ T11 / T1 × 100 ≦ 90.0, preferably 20.0 ≦ T11 / T1 × 100 ≦ 60.0.

In the above description, when the rise time of the developing bias becomes longer as shown by a dotted line in FIG.
The movement time of the toner ta having a small charge amount is from Ta to Ta '.
, The reciprocating movement of the toner occurs at the end between the SDs, causing sweeping. Therefore, the shorter the rise time, the better. That is, FIG.
As shown in FIG. 2, a first electric field that continues at a predetermined strength for a predetermined time for moving the toner to the photosensitive drum at a predetermined strength, and a second electric field that continues at a predetermined strength for a predetermined time to move the toner to the developing sleeve. Time to shift to electric field is 40μsec
It is as follows.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

Embodiment 1 In this embodiment, a developing device as shown in FIG.
A black toner for CLC200 commercially available from Canon Sales Co., Ltd. was used, and a falling bias shown in FIG. 1 was used as a developing bias.

That is, the falling bias is defined as follows: frequency: 1000 Hz, integrated average value Vdc of waveform: -200
V, amplitude: 1600 V, duty percentage: 30
%, Slope percentage: 66.7%. In FIG. 1, in order to clarify a difference from a conventionally known duty bias, the conventional duty bias is also written by a dotted line.

As a result of forming an image by using the above-mentioned falling bias for development, a good image without sweeping and low density could be obtained.

In the above description, a non-magnetic toner of a one-component developer was used as a developer, but the present invention is not limited to this, and a magnetic toner may be used, and a two-component developer may be used. It is possible to obtain various effects. In addition, instead of negatively charged toner, positively charged toner can also be used. In this case, the positive and negative polarities of the developing bias may be set to reverse. Furthermore, although the reversal development method was used for development, a regular development method may be used, and the same effect can be obtained.

Embodiment 2 In this embodiment, the falling specified bias shown in FIG. 2 was used as the developing bias, and the other conditions were the same as in Embodiment 1.

The prescribed bias for falling is frequency: 10
00 Hz, waveform integrated average value Vdc: -200 V, amplitude: 1600 V, duty percentage: 30%, slope percentage: 33.3%, and only the slope percentage is different from the falling regulation bias of the first embodiment. The developing bias indicated by the dotted line in FIG. 2 is the same as the conventionally known duty bias as in the first embodiment.

Even when an image was formed using the above-described falling bias for development, a good image without sweeping and low density could be obtained.

Next, the results of experiments conducted by the present inventors in more detail will be described with reference to FIG.

FIG. 3 shows the relationship between the inclination percentage and the duty percentage in one cycle of the AC component of the developing bias used for the development and the fog of the obtained 5 mm square image, together with the state of occurrence of sweeping and low density. FIG.

As can be seen from FIG. 3, when the duty percentage is 95% and 90%, the inclination percentage is
When it is set to 56%, the fog level is improved, and 0.5 to 5
At 0% the fog level was very good.

The duty percentage is 80%, 70%
In the case of, the fog level was improved when the inclination percentage was 53 to 57%, and the fog level was extremely improved when the inclination percentage was 0.5 to 51%.

The duty percentage is 60%, 50
% And 40%, the fog level was improved when the slope percentage was 54 to 58%, and the fog level was significantly improved when the slope percentage was 0.5 to 52%.

The duty percentage is 30%, 20%
In this case, the fog level was improved when the slope percentage was 56 to 59%, and the fog level was significantly improved when the slope percentage was 0.5 to 53%.

When the duty percentage was 10% and 5%, the fog level was improved when the slope percentage was 56-60%, and the fog level was very good when the inclination percentage was 0.5-54%.

Therefore, according to the above-mentioned experiment conducted by the present inventors in more detail, the slope percentage = T11 / T1 × 10
0 = A, duty percentage = T1 / (T1 + T2)
) × 100 = B, where A and B satisfy the following formula: 1.0 ≦ A ≦ −0.05 × B + 60.0, preferably 20.0 ≦ A ≦ −0.05 × B + 55.0, It has been found that not only an image without sweeping and light density can be obtained, but also fog in a non-image area can be reduced.

The developing bias used in the present embodiment is
The duty percentage A and the inclination percentage B satisfy the above relational expressions. Therefore, in this embodiment, not only the sweeping and the light density were not caused but also the image without the fogging of the non-image portion could be obtained.

Embodiment 3 In this embodiment, as shown in FIG. 4, the toner biasing process (A) (potential V
min) to the photosensitive drum direction (B) (potential Vmax) during the toner energizing process (potential Vmax). Conditions were set so as to satisfy the relational expression shown in Example 2. Otherwise, the procedure was the same as in Example 1.

As a result, it is possible to obtain an image having no sweeping, low density and no fog, and the effect of the present invention can be obtained even if the falling process of the prescribed falling bias is not a linearly falling waveform. I can do it.

In the above description, the falling waveform of the falling prescribed bias is stepped, but the same effect can be obtained by using a sine wave, a rectangular wave, a sawtooth wave, a triangular wave, an exponential function waveform, a logarithmic function waveform, or the like. it can. Further, the waveform in the rising process (D) of FIG. 4 may be a sine wave or the like.

As shown in FIG. 4, the waveforms in the toner urging process (A) in the direction of the developing sleeve and in the toner urging process (B) in the direction of the photosensitive drum are desirably linear, but the amplitude is small. As long as the waveform approaches a flat waveform, a sine wave, a triangular wave or the like may be used, and the same effect can be obtained.

Embodiment 4 FIG. 5 is a diagram showing a configuration in which the developing device of the present invention is installed in a color image forming apparatus.

This image forming apparatus includes a photosensitive drum 1 coated with a photosensitive layer made of an organic semiconductor as an image carrier,
The photosensitive drum 1 has a diameter of 80 mm and is rotated at a speed of 60 mm per second in the direction of the arrow in the figure. Around the photosensitive drum 1, a primary charger 5, a light emitting element 4 such as a laser or an LED, a four-color developing device 12 a, 12 b, 12 c, 12 d, a transfer drum 9 and a cleaner 10 are arranged. The fixing device 11 is installed at a location remote from the developing devices 12a to 12d.

Developing units 12a, 12b, 12c and 12d
Are cyan, magenta, yellow and black developing units in which cyan toner, magenta toner, yellow toner and black toner are stored in developing containers 6a, 6b, 6c and 6d, respectively. These developing containers 6a,
6b, 6c and 6d, developing rollers 2a, 2b, 2c and 2d each having a diameter of 16 mm, and application rollers 3a, 3b and 3 each having a diameter of 8 mm for applying toner to the developing sleeve.
c, 3d and elastic blades 7a, 7b, 7 made of urethane rubber for regulating the toner applied on the developing sleeve.
c and 7d are installed.

In this embodiment, the developing sleeves 2a to 2a
The distance between d and the photosensitive drum 1 was 300 μm. The toner of each color of the developing devices 2a to 2d is provided by Canon Sales Co., Ltd.
A commercially available non-magnetic toner for CLC200 was used.

The developing sleeves 2a, 2a, 2
b, 2c and 2d are connected to a developing bias power source 8,
According to the present invention, a falling specified bias was applied as a developing bias during development. As the falling regulation bias, the frequency shown in FIG.
z, integrated average value Vdc of waveform: -200 V, amplitude: 16
00V, duty percentage: 30%, gradient percentage: 33.3% were used.

The photosensitive drum 1 is kept at -6 by the primary charger 5.
The light-emitting element 4 performs exposure based on the image information of the first color cyan, and the potential of the exposed portion changes to -100 V. An electrostatic latent image for cyan was formed as an image area to be adhered. The electrostatic latent image formed on the photosensitive drum 1 was developed by the cyan developing device 12a.

At the time of development, the above-mentioned falling bias is applied to the developing sleeve 2a of the developing device 12 by the power source 8 to generate a developing electric field between the photosensitive drum 1 and the developing sleeve 2a. The negatively charged cyan toner is transferred from the surface of the developing sleeve 2a to the surface of the photosensitive drum 1 by the force received from the electric field, whereby the electrostatic latent image on the photosensitive drum 1 is developed to form a cyan toner image. did.

On the other hand, transfer paper (both not shown) is fed from a paper feed cassette to the transfer drum 9 and held in advance. The cyan toner image formed on the photosensitive drum 1 is At the timing when the transfer drum 1 and the transfer drum 9 reach the image transfer section facing each other, the transfer is performed on transfer paper by transfer means (not shown).

After the transfer of the photosensitive drum 1 is completed, the transfer residual toner on the photosensitive drum 1 is removed by a cleaner 10.
Thereafter, primary charging is uniformly performed again by the primary charger 5, and exposure is performed by the light emitting element 4 based on magenta image information of the second color to form an electrostatic latent image for magenta on the photosensitive drum 1.
The latent image is developed by the magenta developing device 12b into the developing sleeve 2.
b was developed under the above-specified falling bias to form a magenta toner image. The obtained magenta toner image was transferred onto the transfer paper on the transfer drum 9 from the cyan toner image in a superimposed manner.

The same applies to the third and fourth colors, yellow and black, after cleaning by the cleaner 10.
Primary charging by the primary charger 5 of the photosensitive drum 1, formation of a latent image for yellow and black by exposure with the light emitting element 4, latent image formation by applying the falling specified bias by the yellow developing unit 12 c and the black developing unit 12 d. A color image obtained by developing the image, transferring the yellow toner image and the black toner image obtained by the development onto a transfer paper, and superimposing and transferring four color toner images of cyan, magenta, yellow and black on the transfer paper. I got

The transfer paper on which the four color toner images have been transferred is then discharged from the transfer drum 9 by a static eliminator (not shown), and then sent to a fixing device 11 for fixing. The color mixture of the toner image and the fixation of the toner image to the transfer paper were performed to form a full-color permanent image, and the image was discharged out of the image forming apparatus.

In the above-described color image, since a plurality of color toner images are superimposed on each other, if the toner images of the respective colors are swept together, if the density is low or fogging occurs, a high-quality image cannot be obtained when a single color image is obtained. It was even more difficult than
In the present invention, since the development is performed using the falling specified bias in which the inclination percentage is set, it is possible to eliminate the sweeping of the toner images of each color, the occurrence of the low density and the fogging, and even the color image can be easily formed. A high quality image could be obtained.

In the above, a color image was formed using a non-magnetic toner of a one-component developer as a developer.
As in the case of the above, a magnetic toner or a two-component developer may be used, and not only a negatively charged toner but also a positively charged toner can be used (positive or negative of the developing bias). The polarity may be set to reverse.) Further, for the development, a reversal development method or a regular development method may be used. In any case, a similar effect can be obtained.

The image forming apparatus includes developing units 12a to 12d
Is fixedly arranged around the photosensitive drum 1, but the image forming apparatus to which the developing device of the present invention can be applied is not limited to this. As shown in FIG. 6, the developing devices 12a to 12d
Is used as a cartridge to form a rotary developing device 12, and the rotary developing device 12 is rotated by a cartridge selecting mechanism to transfer the developing devices 12a to 12d to a developing position opposed to the photosensitive drum 1 and to perform image development. It may be a device. 6, the same reference numerals as those shown in FIG. 5 indicate the same members.

Further, in the present embodiment, a color image is formed by a multiple transfer system in which toner images of respective colors are superimposedly transferred on a transfer material. However, as shown in FIG. Even if a color image is formed by a multiple development method in which the color images are superposed and developed, a color image is formed by an intermediate transfer method in which toner images of respective colors are superimposed and transferred on the intermediate transfer body 16 as shown in FIG. An image forming apparatus may be used.

As described above, according to the first to fourth embodiments, the falling specified bias is adopted as the developing bias obtained by superimposing the DC voltage and the AC voltage applied to the developer carrying member at the time of development. Since the gradient percentage of the falling process in one cycle of the AC component is defined and used so as to be within a predetermined range, it is possible to easily obtain a good image without sweeping and low density during development.

Embodiment 5 Next, an embodiment in which the charge amount of the developer is grasped to obtain a higher quality image will be described. In this embodiment, the charge amount per unit mass of the toner carried on the developing sleeve q /
By defining the slope percentage and the duty percentage in the AC component of the falling specified bias with respect to m, it is possible to easily obtain a good image without sweeping and low density without causing toner scattering or discharge in development. The feature is that it was made possible.

In general, there is a close relationship between the quality of a toner image and the amount of charge per unit mass q / m (μC / g) of the toner that forms the toner image, and | for obtaining a high-quality image. It is conventionally known that the range of q / m | is 6.0 to 35.0 μC / g.

By reducing | q / m |, it is possible to obtain a sufficient image density even when development is performed using a sine wave, a triangular wave, or a sawtooth wave as a developing bias, but toner scattering may occur. This is likely to occur and causes contamination of the image forming apparatus. When | q / m | is large, a sufficient image density cannot be obtained even when the duty bias and the rectangular wave are used.

As a method of increasing the image density in a state where | q / m | is large, a method of increasing the amplitude of the AC component of the developing bias applied to the gap (between SD) of the developing units and a method of increasing the DC component A method of increasing the peripheral speed of the developing sleeve has been conventionally known.

However, when the amplitude of the AC component of the developing bias is increased or the DC component is increased, as described above, the distance between the developing sleeve and the photosensitive drum (between SD) is increased.
Not only may cause spark discharge or the like, but also may cause ground fog. In the case of the method in which the peripheral speed of the developing sleeve is increased, the toner is scattered by the air flow in the developing device due to the increased peripheral speed, so that this method is not practical.

If the charge amount of the toner is reduced so as not to cause discharge and the like and | q / m | is set to 2.0 to 5.0 μC / g, toner scattering, fogging and the like are caused, which is not practical.

Therefore, in this embodiment, as described below, the falling specified bias is changed and used for development in accordance with the charge amount q / m of the toner, and the sweeping and the discharging are performed without causing the toner scattering and discharge. A development experiment was conducted in which a prescribed falling bias was determined according to the charge amount q / m of the toner, which can easily obtain a good image without a low density.

In the experiment, the same developing device as the conventional one shown in FIG. 9 was assembled with the experimental device shown in FIG. 17 and used for development. An image of 5 m square was formed by development, and the image was swept. Alignment and light concentration were examined. The developing device uses a black toner for CLC200 commercially available from Canon Sales Co., Ltd., and the toner amount (coating amount) m / s of the toner layer formed and applied on the developing sleeve 2 in a thin layer is as follows. 0.4mg / c
m ² .

FIG. 31 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias used in the experiment and the state of occurrence of sweeping of the obtained 5 mm square image. .

The charge amount q / m of the toner is -6.0 μC / g
-35.0 μC / g, the duty percentage is changed from 5.0% to 95.0%, and the slope percentage is changed from 0.5% to 99.5% at each of the duty percentages. Was.

As can be seen from FIG. 31, the toner charge amount q /
When m is −18 μC / g to −35 μC / g, 5.0 to 5.0
At all duty percentages of 95.0%,
If you set the slope percentage to 60.0-90.0%,
The sweeping of the image disappears to a level at which there is no practical problem, and the inclination percentage is 0.5 to 60. In the% range, sweeping was completely eliminated.

When q / m is -14.0 μC / g,
(1) The duty percentage is 95.0%, 90.0%
%, The slope percentage is set to 55.5 to 85.5%, sweeping stops at a level where there is no practical problem, and when the slope percentage is set to 0.5 to 55.5%, sweeping is completely completed. lost. (2) If the duty percentage is set to 80.0% and 70.0%, and the slope percentage is set to 56.0 to 86.0%, sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.
At 56.0%, sweeping was completely eliminated. (3) The duty percentage is 60.0%, 5
0.0%, 40.0%, and the slope percentage is 5
When 7.5 to 87.5% is set, sweeping is reduced to a level where there is no practical problem, and the slope percentage is set to 0.5 to 5%.
At 7.5%, sweeping was completely eliminated.
(4) The duty percentage is 30.0%, 20.0
%, The slope percentage is 59.0 to 89.0%, sweeping is reduced to a level at which there is no practical problem, and when the slope percentage is 0.5 to 59.0%, sweeping is completely completed. lost. (5) When the duty percentage is set to 10.0% and 5.0% and the inclination percentage is set to 59.7 to 89.7%, the sweeping is reduced to a level having no practical problem, and the inclination percentage is set to 0.1%. 5
At ５９59.7%, sweeping was completely eliminated.

When q / m is -10.0 μC / g,
(1) The duty percentage is 95. %, 90.0%
When the slope percentage is set to 51.0 to 81.0%, sweeping disappears to a level having no practical problem, and when the slope percentage is set to 0.5 to 55.5%, sweeping completely disappears. Was. (2) When the duty percentage is set to 80.0% and 70.0%, and the slope percentage is set to 52.5 to 82.5%, sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.
At 5-52.5%, sweeping was completely eliminated. (3) The duty percentage is 60.0%, 5
0.0%, 40.0%, and the slope percentage is 5
When it is 5.0 to 85.0%, sweeping disappears to a level where there is no practical problem, and the slope percentage is 0.5 to 5%.
At 5.0%, sweeping was completely eliminated.
(4) The duty percentage is 30.0%, 20.0
% And the slope percentage is 57.5 to 87.5%, sweeping is reduced to a level at which there is no practical problem. When the slope percentage is 0.5 to 57.5%, sweeping is completely completed. lost. (5) When the duty percentage is set to 10.0% and 5.0% and the inclination percentage is set to 59.5 to 89.5%, sweeping is reduced to a level having no practical problem, and the inclination percentage is set to 0.1%. 5
At ５９59.5%, sweeping was completely eliminated.

When q / m is -6.0 μC / g, (1)
95. Duty percentage %, 90.0%, and the slope percentage of 46.5-76.5%,
The sweeping disappeared to a level where there was no problem in practical use. When the slope percentage was set to 0.5 to 46.5%, the sweeping completely disappeared. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 4
When it is 9.0 to 79.0%, sweeping is reduced to a level where there is no practical problem, and the slope percentage is 0.5 to 4%.
At 9.0%, sweeping was completely eliminated.
(3) The duty percentage is 60.0%, 50.0%
%, 40.0%, and the slope percentage is 52.5-
When it is set to 82.5%, the sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.5 to 52.5%.
The sweep was completely gone. (4) Set the duty percentage to 30.0% and 20.0%,
When the slope percentage was set to 56.5 to 86.5%, sweeping disappeared to a level at which there was no practical problem. When the slope percentage was set to 0.5 to 56.5%, sweeping was completely stopped. (5) Set the duty percentage to 10.
0% and 5.0%, and the slope percentage is 59.0 to 59.0%.
When it is set to 89.0%, sweeping disappears to a level where there is no problem in practical use, and the slope percentage is 0.5 to 59.0%.
The sweep was completely gone.

FIG. 32 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias used in the experiment and the state of occurrence of low density of the obtained 5 mm square image. .

Similarly, the charge amount q / m of the toner is
Varying from 6.0 to 35.0 μC / g, the duty percentage varying from 5.0% to 95.0%,
At each of the duty percentages, the slope percentage was varied from 0.5% to 99.5%.

As can be seen from FIG. 32, the toner charge amount q /
When m is −6.0 μC / g to −26.0 μC / g,
When the slope percentage is set to 10.0 to 20.0% at all duty percentages of 5.0 to 95.0%, the density is reduced to a level at which there is no practical problem, and the slope percentage is 20.0 to 99. In the range of 0.5%, a sufficient concentration was obtained.

When q / m is −29.0 μC / g,
(1) The duty percentage is 95.0%, 90.0%
%, And the gradient percentage was 10.3 to 20.3%, the density was low to a level at which there was no problem in practical use. When the gradient percentage was 20.3% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the concentration was 0.8 to 20.8%, the concentration was not reduced to a level having no practical problem. When the gradient percentage was 20.8% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the slope percentage is set to 11.5 to 21.5%, the density is reduced to a level having no practical problem. When the slope percentage was set to 21.5% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
%, 20.0%, and the slope percentage is 12.3 to
At 22.3%, the concentration was reduced to a level at which there was no practical problem, and when the slope percentage was 22.3% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 12.6 to 22.6%, the density is not reduced to a level having no practical problem. 6
%, A sufficient concentration was obtained.

When q / m is -32.0 μC / g,
(1) The duty percentage is 95.0%, 90.0%
%, The gradient percentage was set to 10.7 to 20.7%, and the density was reduced to a level at which there was no practical problem. When the gradient percentage was set to 20.7% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the content was 1.5 to 21.5%, the concentration was not reduced to a level causing no practical problem. When the gradient percentage was 21.5% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the gradient percentage is set to 12.8 to 22.8%, the density is reduced to a level at which there is no practical problem. When the slope percentage was 22.8% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
%, 20.0%, and the slope percentage from 14.3 to
At 24.3%, the concentration was reduced to a level at which there was no problem in practical use, and when the slope percentage was 24.3% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 15.3 to 25.3%, the density density is reduced to a level having no practical problem. 3
%, A sufficient concentration was obtained.

When q / m is −35.0 μC / g,
(1) The duty percentage is 95.0%, 90.0%
%, The gradient percentage was set to 11.0 to 21.0%, and the density was reduced to a level at which there was no practical problem. When the gradient percentage was set to 21.0% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the concentration was 2.0 to 22.0%, the concentration was not reduced to a level causing no practical problem. When the gradient percentage was 22.0% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the gradient percentage is set to 14.0 to 24.0%, the density is reduced to a level at which there is no practical problem. When the slope percentage was 24.0% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
% And 20.0%, and the slope percentage is 16.5 to
At 26.5%, the concentration was reduced to a level at which there was no problem in practical use, and when the slope percentage was 26.5% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 17.0 to 27.0%, the density is reduced to a level having no practical problem, and the gradient percentage is set to 27. 0
%, A sufficient concentration was obtained.

Therefore, as understood from FIGS. 31 and 32, the slope percentage (%) = A = T11 / T1 × 10
0, duty percentage (%) = B = T1 / (T1
+ T2) × 100 is divided according to the range of the toner charge amount q / m. When −18.0 μC / g ≦ q / m ≦ −6.0 μC / g, 10.0 ≦ A ≦ − (− 1.25) × | q / m | +22.
5) × B / 100 + 90.0 -26.0 μC / g ≦ q / m ≦ −18.0 μC / g 10.0 ≦ A ≦ 90.0−35.0 μC / g ≦ q / m ≦ −26. In the case of 0 μC / g, (−0.89 × | q / m | +18.7) × (B / 100
By satisfying the relationship of -1.0) + 10.0 ≦ A ≦ 90.0, it was possible to obtain an image without sweeping and low density without toner scattering and discharge.

Preferably, the above relational expression is: 20.0 ≦ A ≦ − (− 1.25 × | q / m | + 22.times.18.0 μC / g ≦ q / m ≦ −6.0 μC / g)
5) xB / 100 + 60.0 -26.0 μC / g ≦ q / m ≦ −18.0 μC / g 20.0 ≦ A ≦ 60.0−35.0 μC / g ≦ q / m ≦ −26. In the case of 0 μC / g, (−0.89 × | q / m | +18.7) × (B / 100
−1.0) + 20.0 ≦ A ≦ 60.0.

Although the reason is not clear, first, as described above, according to the developing bias having the prescribed falling bias, the process of falling of the AC component of the developing bias corresponds to the toner of each charge amount. By controlling the reciprocating motion between the SDs, the reciprocating motion of the toner at the wide end between the SDs is suppressed and the reciprocating motion of the toner at the narrow central portion between the SDs is sufficient for all the toners regardless of the toner charge amount. Therefore, sweeping and low density of an image obtained by development can be suppressed. Further, sweeping of an image and low density can be suppressed by the following mechanism.

FIG. 33 shows the relationship between the moving time of the toner from the developing sleeve toward the photosensitive drum and the amount of charge of the toner at the end between SD when the falling specified bias applied to the developing sleeve is different. FIG.

In FIG. 33, when the charge amount q / m of the toner is small, the toner ta having the small charge amount starts to move from the developing sleeve to the photosensitive drum when the potential of the developing sleeve becomes Va. When the charge amount q / m of the toner is large, the toner tb having a large charge amount starts moving from the developing sleeve to the photosensitive drum when the potential of the developing sleeve becomes Vb. In the drawing, when the developing bias B1 having a large gradient percentage represented by a solid line is used, the movement time of the toner ta having a small charge amount and the movement time of the toner tb having a large charge amount are times Ta1 and Tb1, respectively. In the case of the developing bias B1, the toner tb having a large charge does not sweep, but the toner ta having a small charge has a moving time Ta.
Therefore, as described above, the end portion between the SDs moves outward and moves toward the toner reservoir M, and sweeping occurs. Accordingly, it is necessary to use a developing bias B2 having a small inclination percentage represented by a dotted line in the drawing for the toner ta having a small charge amount, thereby shortening the moving time of the toner ta from Ta1 to Ta2,
It is possible to prevent the occurrence of sweeping of the image.

In the above description, if the rise time of the developing bias becomes longer as shown by the dotted line in FIG.
Since the movement time of the toner ta having a small amount of charge changes and becomes longer, the toner reciprocates at the end between the SDs and sweeping occurs. Therefore, the shorter the rise time, the better.

FIG. 34 shows the relationship between the moving time of the toner from the developing sleeve toward the photosensitive drum and the charge amount of the toner at the center between the SDs when the prescribed falling bias applied to the developing sleeve is different. FIG.

In FIG. 34, when the electric charge q / m of the toner is small and the potential of the developing sleeve becomes Va, the toner ta having the small electric charge starts to move from the developing sleeve to the photosensitive drum. When the electric charge q / m of the toner is large and the potential of the developing sleeve becomes Vb, the toner tb having the large electric charge starts to move from the developing sleeve to the photosensitive drum. In the figure, when the developing bias B4 having a small inclination percentage represented by a solid line is used, the movement time of the toner ta having a small charge amount and the toner tb having a large charge amount is as follows.
The times are Ta4 and Tb4, respectively. Development bias B4
In the case of (1), the toner tb having a small charge does not cause a low density, but the toner tb having a large charge has a short moving time Tb4, so that a low density occurs. Therefore, for the toner tb having a large charge amount, it is necessary to use a developing bias B3 having a large gradient percentage represented by a dotted line in the figure, thereby moving the movement time of the toner tb from Tb4 to Tb4.
The length can be reduced to 3, and the occurrence of low image density can be prevented.

As described above, the image density can be improved by (1) increasing the amplitude of the AC component of the developing bias or changing the DC component, and (2) charging the toner q / m. In the method (1), discharge occurs, and in the method (2), toner is scattered. In the present invention, as described above, the density is adjusted by optimizing the time of the falling process (C) of the specified falling bias and the time of the toner energizing process (B) (potential Vmax) in the direction of the photosensitive drum. Since the density is improved, it is possible to improve the density by preventing discharge and toner scattering.

Embodiment 6 In this embodiment, as the developing bias, the falling specified bias in which the waveform in the falling process shown in FIG. Were set so as to satisfy the relational expression of Example 5. Electric charge q / of black toner (for CLC200)
m was -20.0 μC / g. The coating amount m / s of the toner layer on the developing sleeve was 0.4 mg / cm ² . Otherwise, the procedure was the same as in Example 5.

As a result, it was possible to obtain a swept image and an image having a low density without causing spark discharge and toner scattering. As described above, the falling process of the falling regulation bias is not limited to the waveform falling linearly,
It can be seen that the effects of the present invention can be obtained.

In the present embodiment, the falling waveform of the falling bias is stepwise, but the same effect can be obtained by using a sine wave, a rectangular wave, a sawtooth wave, a triangular wave, an exponential function waveform, a logarithmic function waveform, or the like. be able to. Further, the waveform in the rising process may be such a sine wave or the like.

As shown in FIG. 4, the waveforms in the toner energizing process (B) (potential Vmax) in the direction of the photosensitive drum and the toner energizing process (A) (potential Vmin) in the direction of the developing sleeve are linear. However, a sine wave, a triangular wave, or the like may be used as long as the amplitude is reduced to approximate a flat waveform, and the same effect can be obtained.

Embodiment 7 In this embodiment, the present invention is applied to the developing devices 12a to 12d in the color image forming apparatus shown in FIG.

In this embodiment, the developing devices 12a to 12a shown in FIG.
A toner layer having an application amount m / s of 0.4 mg / cm ² is applied and formed on the 12d developing sleeves 2a to 2d under the control of the elastic blades 7a to 7d in the same manner as in the sixth embodiment. Is the electric charge q / m at -20.0 μC / g
Was charged.

As the developing bias, a falling bias was applied so as to satisfy the relational expression of the fifth embodiment.
The falling bias is a frequency: 1000 Hz, V
dc: -200 V, amplitude: 1600 V, duty percentage: 30%, gradient percentage: 66.7%.

In this embodiment, the other points are the same as those of the fourth embodiment.
The image was formed by developing in the same manner as described above. as a result,
A color image without sweeping and low density could be obtained without causing toner scattering or discharge.

As in the case of the fourth embodiment, in this embodiment, the image forming apparatus also includes the developing device 1 as shown in FIG.
2a to 12d are formed as cartridges in the rotary developing device 12, and the rotary developing device 1 is
The image forming apparatus may be of a type in which the developing unit 12 is rotated to rotate the developing units 12 a to 12 d to a developing position opposed to the photosensitive drum 1 and developed.

Further, a color image was formed by a multiple transfer system in which toner images of respective colors were superimposed and transferred on a transfer material. Similarly, as shown in FIG. An image forming apparatus that forms a color image by an intermediate transfer method in which toner images of respective colors are superimposed and transferred on an intermediate transfer body 16 even when a color image is formed by a multiple development method of It may be.

In any case, it is possible to form a color image without sweeping and low density without causing toner scattering or electric discharge.

As described above, according to Examples 5 to 7, the falling specified bias is adopted as the developing bias in which the DC voltage and the AC voltage applied to the developer carrying member at the time of development are superimposed. Since the gradient percentage and the duty percentage of the falling process in one cycle of the AC component are defined so as to be within a predetermined range with respect to the toner charge amount q / m, good results are obtained without sweeping and low density during development. A good image can be easily obtained without causing toner scattering and discharge.

Embodiment 8 Next, an embodiment in which a higher quality image is obtained by grasping the amount of the developer will be described. In this embodiment, the gradient percentage and the duty percentage in the AC component of the falling specified bias are defined for the toner amount of the toner layer applied and formed on the thin layer on the developing sleeve, that is, the toner application amount m / s. Thus, a characteristic feature is that it is possible to easily obtain a good image without sweeping and low density without causing toner scattering or discharge in development.

In general, the quality of the toner image and the amount m of the toner forming the toner image on the developing sleeve per unit area
/ S (mg / cm ² ), and the range of m / s for obtaining a high-quality image is 0.2 to 1.
It is conventionally known that it is 5 mg / cm ² .

By increasing m / s, it is possible to obtain a sufficient image density even when development is performed using a sine wave, a triangular wave, or a sawtooth wave as a developing bias, but toner scattering occurs. This easily causes contamination of the image forming apparatus. If m / s is reduced, a sufficient image density cannot be obtained even if a duty bias and a rectangular wave are used.

As a method of increasing the image density in a state where m / s is small, there are a method of increasing the amplitude of the AC component of the developing bias applied to the gap (between SD) of the developing units, a method of increasing the DC component, and a method of developing. Methods for increasing the peripheral speed of the sleeve and the like are conventionally known.

However, if the amplitude of the developing bias AC component is increased or the DC component is increased, as described above, spark discharge or the like may occur between the developing sleeve and the photosensitive drum (between SD). Not only is there a possibility that ground fog will occur. In the case of the method in which the peripheral speed of the developing sleeve is increased, the toner is scattered by the air flow in the developing device due to the increased peripheral speed, so that this method is not practical.

If the amount of the applied toner is increased so as not to cause electric discharge and the m / s is set to 2.0 to 3.0 mg / cm ² , toner scattering, fogging and the like are caused to be impractical.

Therefore, in the present embodiment, as described below, the falling specified bias is changed according to the toner application amount m / s and used for development, and sweeping and discharging are performed without causing toner scattering and discharge. A development experiment was conducted in which a prescribed falling bias in accordance with the toner application amount m / s, which can easily obtain a good image without low density, was obtained.

In the experiment, as in the past, the same developing device as the conventional one shown in FIG. 9 was assembled in the experimental device shown in FIG. 17 and used for development, and a 5 m square image was formed by development. Then, the sweeping of the image and the low density were examined. The developing device includes CLC20 commercially available from Canon Sales Co., Ltd.
A black toner for 0 was used, and the charge q / m of the toner was set to −20.0 μC / g.

FIG. 35 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias used in the experiment and the state of occurrence of sweeping of the obtained 5 mm square image. .

The toner application amount m / s is set to 0.2 mg / cm
^{2 to} 1.5 mg / cm ² , the duty percentage is changed from 5.0% to 95.0%, and the slope percentage is changed from 0.5% to 99.5% at each duty percentage. I let it.

As can be seen from FIG. 35, the toner application amount m /
When s is 0.6 mg / cm ² or less, 5.0 to 95.0
% For all duty percentages, the sweeping of the image is reduced to a level at which there is no practical problem, and the gradient percentage is 0.5 to 60.%. In the% range, sweeping was completely eliminated.

When m / s is 0.9 mg / cm ² ,
(1) The duty percentage is 95.0%, 90.0%
%, The slope percentage is set to 55.5 to 85.5%, sweeping stops at a level where there is no practical problem, and when the slope percentage is set to 0.5 to 55.5%, sweeping is completely completed. lost. (2) If the duty percentage is set to 80.0% and 70.0%, and the slope percentage is set to 56.0 to 86.0%, sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.
At 56.0%, sweeping was completely eliminated. (3) The duty percentage is 60.0%, 5
0.0%, 40.0%, and the slope percentage is 5
When 7.5 to 87.5% is set, sweeping is reduced to a level where there is no practical problem, and the slope percentage is set to 0.5 to 5%.
At 7.5%, sweeping was completely eliminated.
(4) The duty percentage is 30.0%, 20.0
%, The slope percentage is 59.0 to 89.0%, sweeping is reduced to a level at which there is no practical problem, and when the slope percentage is 0.5 to 59.0%, sweeping is completely completed. lost. (5) When the duty percentage is set to 10.0% and 5.0% and the inclination percentage is set to 59.7 to 89.7%, the sweeping is reduced to a level having no practical problem, and the inclination percentage is set to 0.1%. 5
At ５９59.7%, sweeping was completely eliminated.

When m / s is 1.2 mg / cm ² ,
(1) The duty percentage is 95. %, 90.0%
When the slope percentage is set to 51.0 to 81.0%, sweeping disappears to a level having no practical problem, and when the slope percentage is set to 0.5 to 51.0%, sweeping completely disappears. Was. (2) When the duty percentage is set to 80.0% and 70.0%, and the slope percentage is set to 52.5 to 82.5%, sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.
At 5-52.5%, sweeping was completely eliminated. (3) The duty percentage is 60.0%, 5
0.0%, 40.0%, and the slope percentage is 5
When it is 5.0 to 85.0%, sweeping disappears to a level where there is no practical problem, and the slope percentage is 0.5 to 5%.
At 5.0%, sweeping was completely eliminated.
(4) The duty percentage is 30.0%, 20.0
% And the slope percentage is 57.5 to 87.5%, sweeping is reduced to a level at which there is no practical problem. When the slope percentage is 0.5 to 57.5%, sweeping is completely completed. lost. (5) When the duty percentage is set to 10.0% and 5.0% and the inclination percentage is set to 59.5 to 89.5%, sweeping is reduced to a level having no practical problem, and the inclination percentage is set to 0.1%. 5
At ５９59.5%, sweeping was completely eliminated.

When m / s is 1.5 mg / cm ² ,
(1) The duty percentage is 95. %, 90.0%
When the slope percentage is set to 46.5 to 76.5%, sweeping stops at a level where there is no practical problem, and when the slope percentage is set to 0.5 to 46.5%, sweeping completely stops. Was. (2) If the duty percentage is set to 80.0% and 70.0% and the slope percentage is set to 49.0 to 79.0%, the sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.
At 5-49.0%, sweeping was completely eliminated. (3) The duty percentage is 60.0%, 5
0.0%, 40.0%, and the slope percentage is 5
When it is set to 2.5 to 82.5%, the sweeping is reduced to a level having no practical problem, and the slope percentage is set to 0.5 to 5%.
At 2.5%, sweeping was completely eliminated.
(4) The duty percentage is 30.0%, 20.0
%, The slope percentage is set to 56.5 to 86.5%, sweeping stops at a level where there is no problem in practical use, and when the slope percentage is set to 0.5 to 56.5%, sweeping is completely completed. lost. (5) When the duty percentage is set to 10.0% and 5.0% and the inclination percentage is set to 59.0 to 89.0%, sweeping is reduced to a level having no practical problem, and the inclination percentage is set to 0.1%. 5
At ５９59.0%, sweeping was completely eliminated.

FIG. 36 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias used in the experiment, and the state of occurrence of low density in the obtained 5 mm square image. .

Similarly, the toner application amount m / s is set to 0.1.
Varied between 2~1.5mg / cm ^2, the duty percentage is varied from 5.0% 95.0%, varying from 0.5% to 99.5% inclination percentage in their respective duty percent I let it.

As can be seen from FIG. 36, the toner application amount m /
When s is 0.35 mg / cm ² or more, 5.0 to 95.
When the slope percentage is set to 10.0 to 20.0% at all duty percentages of 0%, the density is reduced to a level having no practical problem, and when the slope percentage is in the range of 20.0 to 99.5%. A sufficient concentration was obtained.

When m / s is 0.30 mg / cm ² ,
(1) The duty percentage is 95.0%, 90.0%
%, And the gradient percentage was 10.3 to 20.3%, the density was low to a level at which there was no problem in practical use. When the gradient percentage was 20.3% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the concentration was 0.8 to 20.8%, the concentration was not reduced to a level having no practical problem. When the gradient percentage was 20.8% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the slope percentage is set to 11.5 to 21.5%, the density is reduced to a level having no practical problem. When the slope percentage was set to 21.5% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
%, 20.0%, and the slope percentage is 12.3 to
At 22.3%, the concentration was reduced to a level at which there was no practical problem, and when the slope percentage was 22.3% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 12.6 to 22.6%, the density is not reduced to a level having no practical problem. 6
%, A sufficient concentration was obtained.

When m / s is 0.25 mg / cm ² ,
(1) The duty percentage is 95.0%, 90.0%
%, The gradient percentage was set to 10.7 to 20.7%, and the density was reduced to a level at which there was no practical problem. When the gradient percentage was set to 20.7% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the content was 1.5 to 21.5%, the concentration was not reduced to a level causing no practical problem. When the gradient percentage was 21.5% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the gradient percentage is set to 12.8 to 22.8%, the density is reduced to a level at which there is no practical problem. When the slope percentage was 22.8% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
%, 20.0%, and the slope percentage from 14.3 to
At 24.3%, the concentration was reduced to a level at which there was no problem in practical use, and when the slope percentage was 24.3% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 15.3 to 25.3%, the density density is reduced to a level having no practical problem. 3
%, A sufficient concentration was obtained.

When m / s is 0.20 mg / cm ² ,
(1) The duty percentage is 95.0%, 90.0%
%, The gradient percentage was set to 11.0 to 21.0%, and the density was reduced to a level at which there was no practical problem. When the gradient percentage was set to 21.0% or more, a sufficient density was obtained. (2) Duty percentage is 8
0.0% and 70.0%, and set the slope percentage to 1
When the concentration was 2.0 to 22.0%, the concentration was not reduced to a level causing no practical problem. When the gradient percentage was 22.0% or more, a sufficient concentration was obtained. (3) When the duty percentage is set to 60.0%, 50.0%, and 40.0%, and the gradient percentage is set to 14.0 to 24.0%, the density is reduced to a level at which there is no practical problem. When the slope percentage was 24.0% or more, a sufficient concentration was obtained. (4) The duty percentage is 30.0
% And 20.0%, and the slope percentage is 16.5 to
At 26.5%, the concentration was reduced to a level at which there was no problem in practical use, and when the slope percentage was 26.5% or more, a sufficient concentration was obtained. (5) When the duty percentage is set to 10.0% and 5.0% and the gradient percentage is set to 17.0 to 27.0%, the density is reduced to a level having no practical problem, and the gradient percentage is set to 27. 0
%, A sufficient concentration was obtained.

Therefore, as can be seen from FIGS. 35 and 36,
Slope percentage (%) = A = T11 / T1 × 100, duty percentage (%) = B = T1 / (T1 + T2)
× 100 is divided according to the range of toner application amount m / s, and when 0.6 mg / cm ² ≦ m / s ≦ 1.5 mg / cm ² 10.0 ≦ A ≦ (−16.7 × m /S+10.0)×B
/100+90.0 0.35 mg / cm ² ≦ m / s ≦ 0.6 mg / cm ² 10.0 ≦ A ≦ 90.0 0.2 mg / cm ² ≦ m / s ≦ 0.35 mg / cm ² Time − (− 53.3 × m / s + 18.7) × (B / 100−
1.0) + 10.0 ≦ A ≦ 90.0 By satisfying the following relationship, it became possible to obtain an image without sweeping and low density without toner scattering and discharge.

Preferably, the above relational expression is: 20.0 ≦ A ≦ (−16.7 × m / s + 10.0) × B when 0.6 mg / cm ² ≦ m / s ≦ 1.5 mg / cm ²
/100+60.0 0.35 mg / cm ² ≦ m / s ≦ 0.6 mg / cm ² When 20.0 ≦ A ≦ 60.0 0.2 mg / cm ² ≦ m / s ≦ 0.35 mg / cm ² Time − (− 53.3 × m / s + 18.7) × (B / 100−
1.0) + 20.0 ≦ A ≦ 60.0.

Although the reason is not clear, first, similarly to the above, according to the developing bias of the falling specified bias, the toner of each charge amount is generated by the process of falling of the AC component of the developing bias. By controlling the reciprocating motion between the SDs, the reciprocating motion of the toner at the wide end between the SDs is suppressed and the reciprocating motion of the toner at the narrow central portion between the SDs for all the toners irrespective of the toner charge amount. Can be sufficiently performed, so that sweeping and low density of an image obtained by development can be suppressed. Further, sweeping of an image and low density can be suppressed by the following mechanism.

Generally, the reflection force Fm of the toner on the developing sleeve is represented by FmmQ ² / r ² where Q is the charge amount of the toner particles and r is the distance between the center of the toner particles and the surface of the developing sleeve. And therefore the amount of toner applied to the developing sleeve m / s
When the thickness of the toner layer increases due to the increase in the distance, the distance r of the toner in the uppermost layer of the toner layer from the surface of the developing sleeve increases, so that the mirror force Fm received by the toner in the uppermost layer from the developing sleeve decreases. Therefore, even when the potential difference between the photosensitive drum and the developing sleeve is small and the developing electric field between the SDs is small, the toner can move from the developing sleeve to the photosensitive drum.

FIG. 37 shows the relationship between the moving time of the toner from the developing sleeve toward the photosensitive drum at the end between SD and the amount of applied toner when the falling bias applied to the developing sleeve is different. FIG.

In FIG. 37, when the applied amount m / s of the toner is large, the toner (tc) when the applied amount is large moves from the developing sleeve to the photosensitive drum when the potential of the developing sleeve becomes Va. start. When the applied amount m / s of the toner is small, the toner (td) when the applied amount is small starts to move from the developing sleeve to the photosensitive drum when the potential of the developing sleeve becomes Vb. In the drawing, when the developing bias B1 represented by the solid line and having a large inclination percentage is used, the toner tc having a large coating amount is used.
The movement time of the toner td with a small amount of application is time Tc1, Td1, respectively. When the developing bias B1 is used, the toner td having a small application amount does not sweep, but the toner tc having a large application amount has a moving time as long as Tc1, so that sweeping occurs. Therefore, it is necessary to use a developing bias B2 having a small inclination percentage represented by a dotted line in the figure for the toner tc having a large application amount, thereby shortening the moving time of the toner tc from Tc1 to Tc2, It is possible to prevent the occurrence of sweeping of the image.

In the above description, if the rise time of the developing bias becomes longer as shown by the dotted line in FIG.
Since the movement time of the toner tc having a small amount of application changes and becomes longer, the toner reciprocates at the end between the SDs and sweeping occurs. Therefore, the shorter the rise time, the better.

FIG. 38 shows the relationship between the moving time of the toner from the developing sleeve toward the photosensitive drum and the amount of the applied toner at the center between SD when the falling bias applied to the developing sleeve is different. FIG.

In FIG. 38, when the applied amount m / s of the toner is large, the toner tc when the applied amount is large is:
When the potential of the developing sleeve becomes Va, the developing sleeve starts moving to the photosensitive drum. When the applied amount m / s of the toner is small, the toner td when the applied amount is small starts moving from the developing sleeve to the photosensitive drum when the potential of the developing sleeve becomes Vb. In the drawing, when the developing bias B4 having a small inclination percentage represented by the solid line is used, the movement time of the toner tc when the coating amount is large and the movement time of the toner td when the coating amount is small are time Tc4 and Td4, respectively.
Becomes When the developing bias B4 is used, the toner tc when the amount of application is small does not cause a low density, but when the amount of application of the toner td is large, the movement time of the toner td becomes small as Td4, and the toner does not reciprocate sufficiently. , Low concentration occurs. Therefore, for the toner td when the application amount is large, it is necessary to use the developing bias B3 having a large inclination percentage represented by the dotted line in the figure, and thereby the movement time of the toner td can be extended from Td4 to Td3. ,
It is possible to prevent the occurrence of low image density.

As described above, in this embodiment, the time of the falling process (C) of the specified falling bias and the toner energizing process in the direction of the photosensitive drum (B) with respect to the toner application amount m / s on the developing sleeve. By optimizing the time of (potential Vmax), discharge and toner scattering can be prevented and the density can be improved.

Embodiment 9 In this embodiment, as the developing bias, the falling specified bias in which the waveform in the falling process shown in FIG. Were set so as to satisfy the relational expression of Example 8. Application amount of black toner (for CLC200) m /
s was 0.4 mg / cm ² . Otherwise, the procedure was the same as in Example 8.

As a result, it was possible to obtain a swept image and an image having a low density without causing spark discharge and toner scattering. As described above, the falling process of the falling regulation bias is not limited to the waveform falling linearly,
The effects of the present invention can be obtained.

In this embodiment, the falling waveform of the prescribed falling bias is stepped, but the same effect can be obtained by using a sine wave, a rectangular wave, a sawtooth wave, a triangular wave, an exponential function waveform, a logarithmic function waveform, or the like. be able to. Further, the waveform in the rising process may be such a sine wave or the like.

As shown in FIG. 4, the waveforms in the toner energizing process (B) (potential Vmax) in the direction of the photosensitive drum and the toner energizing process (A) (potential Vmin) in the direction of the developing sleeve are linear. However, a sine wave, a triangular wave, or the like may be used as long as the amplitude is reduced to approximate a flat waveform, and the same effect can be obtained.

Embodiment 10 In this embodiment, the present invention is applied to the developing devices 12a to 12d in the color image forming apparatus shown in FIG.

In this embodiment, the developing devices 12a to 12a shown in FIG.
A toner layer having a toner amount m / s of 0.4 mg / cm ² is applied on the 12d developing sleeves 2a to 2d under the control of the respective elastic blades 7a to 7d as in the ninth embodiment.
Formed.

As the developing bias, a falling specified bias was applied so as to satisfy the relational expression of the eighth embodiment.
The falling bias is a frequency: 1000 Hz, V
dc: -200 V, amplitude: 1600 V, duty percentage: 30%, gradient percentage: 66.7%.

In this embodiment, the other points are the same as those of the fourth embodiment.
The image was formed by developing in the same manner as described above. as a result,
A color image without sweeping and low density could be obtained without causing toner scattering or discharge.

As in the case of the fourth embodiment, also in this embodiment, the image forming apparatus employs the developing device 1 as shown in FIG.
2a to 12d are formed as cartridges in the rotary developing device 12, and the rotary developing device 1 is
The image forming apparatus may be of a type in which the developing unit 12 is rotated to rotate the developing units 12 a to 12 d to a developing position opposed to the photosensitive drum 1 and developed.

A color image was formed by a multiple transfer method in which toner images of respective colors were transferred on a transfer material in a superimposed manner. Similarly, as shown in FIG. An image forming apparatus that forms a color image by an intermediate transfer method in which toner images of respective colors are superimposed and transferred on an intermediate transfer body 16 even when a color image is formed by a multiple development method of It may be.

In any case, it is possible to form a color image without sweeping and low density without causing toner scattering or electric discharge.

As described above, according to the eighth to tenth embodiments, the falling specified bias is adopted as the developing bias obtained by superimposing the DC voltage and the AC voltage applied to the developer carrying member at the time of development. Since the gradient percentage and the duty percentage of the falling process in one cycle of the AC component are defined so as to be within a predetermined range with respect to the toner application amount m / s, good results without sweeping and low density during development. A good image can be easily obtained without causing toner scattering and discharge.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made within the technical concept of the present invention.

[0170]

As described above, according to the present invention,
A developer carrying member provided opposite to the image carrying member for carrying and transporting the developer, between the image carrying member and the developer carrying member for developing a latent image formed on the image carrying member; An electric field forming means for forming an alternating electric field, wherein the first electric field is maintained at a predetermined intensity for a predetermined time for causing the developer to move toward the image carrier; And a second electric field that continues at a predetermined strength for a predetermined time for moving the first electric field in one cycle of the alternating electric field, and the second electric field changes from the second electric field to the first electric field. The transition time T12 satisfies 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0, and the transition time from the first electric field to the second electric field is 4
Since it is configured to be 0 μsec or less, the developer with a higher charge amount has a shorter flight time than the developer with a lower charge amount, and therefore, the developer that flies at the rear end of the development region is reduced. A development pool is not formed, a sweeping phenomenon does not occur, and a good image free of sweeping and low density can be easily obtained by development.

In another embodiment of the present invention, in particular, the duration of the first electric field in one cycle of the alternating electric field is T11,
Assuming that the time required for transition from the second electric field to the first electric field is T12, the time of one cycle of the alternating electric field is T, and the charge per unit mass of the developer is q / m [μC / g], T11 / (T11 + T12)
Assuming that (T11 + T12) / T × 100 = B, when the following expression is 6.0 [μC / g] ≦ | q / m | ≦ 18.0 [μC / g], 10.0 ≦ T11 / ( T11 + T12) × 100 ≦ − (− 1.25 × | q / m | +22.5) × B / 100 + 90.0 18.0 [μC / g] ≦ | q / m | ≦ 26.0 [μC / g] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 26.0 [μC / g] ≦ | q / m | ≦ 35.0 [μC / g] (−0. 89 × | q / m | +18.7) × (B / 100−1.0) + 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 It is possible to easily obtain a good image without a shift and a low density without causing toner scattering and discharge.

In still another aspect of the present invention, one of the alternating electric fields
In the cycle, the duration of the first electric field is T11, the transition time from the second electric field to the first electric field is T12, the time of one cycle of the alternating electric field is T, and the developer per unit area of the developer carrier surface. If the mass is m / s [mg / cm ² ], T11
/ (T11 + T12) is (T11 + T12) / T × 100 = B
When the following equation is satisfied: 0.6 [mg / cm ² ] ≦ m / s ≦ 1.5 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ (−16.7 × m / s + 10.0) × B / 100 + 90.0 0.35 [mg / cm ² ] ≦ m / s ≦ 0.6 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 When ≦ 90.0 0.2 [mg / cm ² ] ≦ m / s ≦ 0.35 [mg / cm ² ] − (− 53.3 × m / s + 18.7) × (B / 100-1. 0) + 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0 Therefore, in the same manner, a good image without sweeping and low density can be formed by toner scattering and discharge. Can be easily obtained without raising.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a developing bias used in Embodiment 1 of the developing device of the present invention.

FIG. 2 is a waveform chart showing a developing bias used in Example 2 of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a duty ratio and a gradient percentage of a developing bias and a state of an image in a second embodiment.

FIG. 4 is a waveform chart showing a developing bias used in Example 3 of the present invention.

FIG. 5 is a configuration diagram illustrating a color image forming apparatus provided with the developing device of the present invention.

FIG. 6 is a configuration diagram illustrating another example of an image forming apparatus to which the developing device of the present invention can be applied.

FIG. 7 is a configuration diagram showing still another example of the image forming apparatus.

FIG. 8 is a configuration diagram illustrating still another example of the image forming apparatus.

FIG. 9 is a configuration diagram showing a conventional developing device.

FIG. 10 is a waveform chart showing a developing bias used in the developing device of FIG. 9;

FIG. 11 is a waveform chart showing another example of the developing bias.

FIG. 12 is a waveform chart showing still another example of the developing bias.

FIG. 13 is a waveform chart showing still another example of the developing bias.

FIG. 14 is a waveform chart showing still another example of the developing bias.

FIG. 15 is an explanatory diagram showing that sweeping has occurred in a toner image obtained when development is performed using the developing bias or the like in FIG. 14;

FIG. 16 is a waveform chart showing a falling specified bias used as a developing bias in the present invention.

FIG. 17 is a block diagram showing an apparatus used in a development experiment in the present invention.

18 is a waveform chart in which each element process in one cycle of an AC component of a developing bias used for development in an experiment using the apparatus of FIG. 17 is written.

FIG. 19 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias, and the state of sweeping of the obtained 5 mm square image and the occurrence of low density.

FIG. 20 is a cross-sectional view showing lines of electric force between a developing sleeve to which a developing bias is applied and a photosensitive drum between SD.

FIG. 21 is a view showing a state where a developing bias is applied when the surface of the photosensitive drum facing the developing sleeve is an image area;
FIG. 9 is an explanatory diagram schematically showing the direction of movement of toner due to the force of an electric field at the upper end in the horizontal direction between D.

FIG. 22 is a cross-sectional view illustrating a part of a mechanism in which an image sweeps due to toner behavior between SDs to which a developing bias is applied.

FIG. 23 is a cross-sectional view illustrating a part of the mechanism.

FIG. 24 is a cross-sectional view illustrating a part of the mechanism.

FIG. 25 is a cross-sectional view illustrating a part of the mechanism.

FIG. 26 is a cross-sectional view illustrating a part of the mechanism.

FIG. 27 is a graph showing a charge amount distribution per unit mass of toner on the developing sleeve.

FIG. 28 is an explanatory diagram showing a relationship between a potential at an end portion between SDs of a developing sleeve to which a falling specified bias is applied, and a moving time of toner from the developing sleeve in a direction of the photosensitive drum.

FIG. 29 is an explanatory diagram showing a relationship between a potential at a central portion between SDs of a developing sleeve to which a falling specified bias is applied, and a moving time of toner from the developing sleeve in a direction of a photosensitive drum.

FIG. 30 is a waveform diagram showing a developing bias having a long rise time.

FIG. 31 shows a relationship between a gradient percentage and a duty percentage in one cycle of an AC component of a developing bias used in a development experiment in Example 5 of the present invention, and a state of occurrence of sweeping of an obtained 5 mm square image. FIG.

FIG. 32 is an explanatory diagram showing the relationship between the gradient percentage and the duty percentage in one cycle of the AC component of the developing bias, and the state of occurrence of low density of the obtained 5 mm square image.

FIG. 33 is a diagram illustrating a relationship between a moving time of toner from the developing sleeve toward the photosensitive drum and an amount of charge of the toner at the end between SDs when a prescribed falling bias applied to the developing sleeve is different. FIG.

FIG. 34 is an explanatory diagram showing the relationship between the moving time of the toner from the developing sleeve toward the photosensitive drum at the center between the SDs and the charge amount of the toner.

FIG. 35 shows a relationship between a gradient percentage and a duty percentage in one cycle of an AC component of a developing bias used in a development experiment in Example 8 of the present invention, and a state of occurrence of sweeping of an obtained 5 mm square image. FIG.

FIG. 36 is an explanatory diagram showing a relationship between a gradient percentage and a duty percentage in one cycle of an AC component of a developing bias, and a state of occurrence of low density of an obtained 5 mm square image.

FIG. 37 is a diagram illustrating a relationship between a moving time of toner from the developing sleeve toward the photosensitive drum at an end portion between the SDs and an amount of applied toner when the falling bias applied to the developing sleeve is different. FIG.

FIG. 38 is an explanatory diagram showing the relationship between the moving time of toner from the developing sleeve in the direction of the photosensitive drum and the amount of applied toner at the center between the SDs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Developing sleeve 3 Coating roller 6 Developing container 7 Elastic blade 8 Bias power supply 12 Developing device 12a-12d Developing device 21 Waveform generator 23 Developing device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Sasame 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tatsuya Kobayashi 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Masao Nakano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuhisa Tsurugimo 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Moto Kato 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (72) Inventor Akihiko Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Haruo Fujii 3-30-2 Shimomaruko, Ota-ku, Tokyo JP-A-64-44468 (JP, A) JP-A-4-315181 (JP, A) JP-A-3-145664 (JP, A) JP-A-63-314568 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/06 101 G03G 15/08-15/09

Claims (17)

(57) [Claims] An image bearing member provided to face the image bearing member for carrying and transporting the developer; and a developing device for developing a latent image formed on the image bearing member. Electric field forming means for forming an alternating electric field with the developer carrier, wherein the alternating electric field continues for a predetermined time and at a predetermined intensity for causing the developer to move toward the image carrier. An electric field,
A second electric field that continues at a predetermined intensity for a predetermined time for causing the developer to flow toward the developer carrier, and wherein a time period T11 during which the first electric field lasts in one cycle of the alternating electric field, The time T12 for shifting from the second electric field to the first electric field satisfies 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0, and the time for shifting from the first electric field to the second electric field is , 40 μsec or less. 2. A time period T11 during which the first electric field lasts and a time period T12 when the second electric field is shifted to the first electric field in one cycle of the alternating electric field are 20.0 ≦ T11 / (T11 + T12). 2. The developing device according to claim 1, wherein the following condition is satisfied. 3. The developing apparatus according to claim 1, wherein a waveform of a voltage applied to said developer carrier when said second electric field shifts to said first electric field has a stepped shape. 4. The developing device according to claim 1, wherein a voltage applied to said developer carrier for forming said alternating electric field is a DC voltage superimposed on an AC voltage. 5. The developing device according to claim 1, wherein the developer on the developer carrier is not in contact with the image carrier at a developing position. 6. A developer carrying member provided opposite to the image carrying member for carrying and transporting a developer, and the image carrying member for developing a latent image formed on the image carrying member. Electric field forming means for forming an alternating electric field with the developer carrier, wherein the alternating electric field continues for a predetermined time and at a predetermined intensity for causing the developer to move toward the image carrier. An electric field,
A second electric field that continues at a predetermined intensity for a predetermined time for causing the developer to flow toward the developer carrier, wherein a period during which the first electric field lasts in one cycle of the alternating electric field is T11. T12 is the time required for the transition from the second electric field to the first electric field, T is the time of one cycle of the alternating electric field,
The charge amount per unit mass of the developer is q / m [μC / g].
Then, T11 / (T11 + T12) becomes (T11 + T12) /
Assuming that T × 100 = B, the following expression 6.0 [μC / g] ≦ | q / m | ≦ 18.0 [μC / g] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ − (−1.25 × | q / m | +22.5) × B / 100 + 90.0 18.0 [μC / g] ≦ | q / m | ≦ 26.0 [μC / g] 10.0 ≦ When T11 / (T11 + T12) × 100 ≦ 90.0 26.0 [μC / g] ≦ | q / m | ≦ 35.0 [μC / g] (−0.89 × | q / m | +18) 0.7) × (B / 100−1.0) + 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0. 7. T11 / (T11 + T12) is more preferably the following formula: 6.0 [μC / g] ≦ | q / m | ≦ 18.0 [μC / g] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ − (− 1.25 × | q / m | +22.5) × B / 100 + 60.0 18.0 [μC / g] ≦ | q / m | ≦ 26.0 When [μC / g] 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0 26.0 [μC / g] ≦ | q / m | ≦ 35.0 [μC / g] −0.89 × | q / m | +18.7) × (B / 100−1.0) + 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0 Item 6. The developing device according to Item 6. 8. The developing device according to claim 6, wherein a waveform of a voltage applied to said developer carrier when changing from said second electric field to said first electric field is stepwise. 9. The developing device according to claim 6, wherein the developing device is applied to an image forming apparatus that forms a color image. 10. The developing device according to claim 6, wherein a voltage applied to said developer carrier for forming said alternating electric field is a DC voltage superimposed on an AC voltage. 11. The developing device according to claim 6, wherein the developer on the developer carrier is not in contact with the image carrier at the developing position. 12. A developer carrier provided opposite to the image carrier, for carrying and transporting a developer, and the image carrier for developing a latent image formed on the image carrier. Electric field forming means for forming an alternating electric field with the developer carrier, wherein the alternating electric field continues for a predetermined time and at a predetermined intensity for causing the developer to move toward the image carrier. In a developing device having an electric field and a second electric field that continues at a predetermined intensity for a predetermined time for causing a developer to flow toward the developer carrier, the first electric field is maintained during one cycle of the alternating electric field. Let T11 be the time, T12 be the time of transition from the second electric field to the first electric field, T be the time of one cycle of the alternating electric field, and m / s the mass per unit area of the developer carrier surface of the developer. mg / cm ² ], T11 / (T11 +
T12) is (T11 + T12) / T × 100 = B,
When the following formula is 0.6 [mg / cm ² ] ≦ m / s ≦ 1.5 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ (−16.7 × m / s + 10.0) × B / 100 + 90.0 0.35 [mg / cm ² ] ≦ m / s ≦ 0.6 [mg / cm ² ] 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90 0.0 0.2 [mg / cm ² ] ≦ m / s ≦ 0.35 [mg / cm ² ] − (− 53.3 × m / s + 18.7) × (B / 100−1.0) + 10.0 ≦ T11 / (T11 + T12) × 100 ≦ 90.0. 13. T11 / (T11 + T12) is more preferably 20.0 ≦ when the following expression is satisfied: 0.6 [mg / cm ² ] ≦ m / s ≦ 1.5 [mg / cm ² ] T11 / (T11 + T12) × 100 ≦ (−16.7 × m / s + 10.0) × B / 100 + 60.0 0.35 [mg / cm ² ] ≦ m / s ≦ 0.6 [mg / cm ² 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0 0.2 [mg / cm ² ] ≦ m / s ≦ 0.35 [mg / cm ² ] − (− 53. 13. The developing device according to claim 12, wherein 3 × m / s + 18.7) × (B / 100−1.0) + 20.0 ≦ T11 / (T11 + T12) × 100 ≦ 60.0. 14. The developing device according to claim 12, wherein a waveform of a voltage applied to said developer carrier when changing from said second electric field to said first electric field is stepwise. 15. The image forming apparatus according to claim 1, wherein the developing device is applied to an image forming apparatus that forms a color image.
2 developing device. 16. The developing apparatus according to claim 12, wherein a voltage applied to said developer carrier for forming said alternating electric field is a DC voltage superimposed on an AC voltage. 17. The developing device according to claim 12, wherein the developer on the developer carrier is not in contact with the image carrier at a developing position.