JP3416307B2 - 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 an electrophotographic system,
Displays the electrostatic latent image formed on the image carrier by recording
Copier, printer, recording image
Also relates to image forming devices such as image display devices and facsimile machines.
It is. [0002] 2. Description of the Related Art Conventionally, carrier particles are formed on the surface of a developer carrier.
And a two-component developer mainly composed of two components of toner and toner particles.
Holding the developer with the image carrier carrying the electrostatic latent image.
The developer is transported to the developing section facing the
A brush is formed to allow an exchange between the image carrier and the developer carrier.
The electrostatic latent image can be developed while applying an alternating electric field.
A visualization developing method is known. This developing method is generally called a magnetic brush developing method.
Often done. Further, the above-mentioned developer carrier is generally
Often used as a developing sleeve for developing devices
Therefore, in the following description, it is referred to as a developing sleeve.
The image carrier is generally used for a photosensitive drum.
Therefore, in the following description, they are collectively referred to as photosensitive drums.
And The above-described magnetic brush developing method will be further described.
In this developing method, a two-component developer is carried on a developing sleeve.
Transported to the developing section, and the developer
Magnetic brush on the surface of the developing sleeve
And a small gap is maintained between the developing sleeve and the developing sleeve.
Rub or close the magnetic brush on the oriented photosensitive drum
And continuously between the developing sleeve and the photosensitive drum.
Apply an alternating electric field to remove toner particles from the developing sleeve side.
Transfer to the photosensitive drum side and reverse in the opposite direction
And development is performed by repeating
Nos. 55-3260 and 59-165082). [0005] As a magnetic brush developing method, there are other simple methods.
Non-contact alternating power supply for color and multiple development
A field development method is also known (for example, Japanese Patent Application Laid-Open No. 56-1426).
No. 8, 58-68051, 56-144452, 5
9-181362 and 60-176069). On the other hand, a magnetic brush developing method is used for a developing device.
High-speed, low-noise printers
Laser beam printers that use the electrophotographic method
is there. Typical applications of this printer include text and graphics.
It is binary recording of such an image, corresponding to the image signal to be recorded
Scans the photosensitive drum while emitting and extinguishing the laser beam
That is, so-called binary recording is performed. Statement like this
Since the recording of characters and figures does not require halftones,
The structure becomes simple. This binary recording laser
As a device that can reproduce halftones with a beam printer,
Well-known methods such as the laser method and density pattern method are well known.
ing. However, as is well known, dithering and concentration
High resolution can be obtained with printers that use the turn method, etc.
hard. Therefore, in recent years, high recording density has not been reduced.
A method for forming a halftone image while obtaining resolution has been proposed.
ing. In this method, a laser is driven by an image signal.
By modulating the width of the pulse signal
The formation is performed. That is, one pixel of the laser
The luminous flux emission time length is controlled according to the image density.
Therefore, one pixel of the laser beam scanning the photosensitive drum
The photosensitive drum irradiation time per hit is controlled according to the image density.
Is controlled. Specifically, for a low density image portion,
Reduce the pulse width of the pulse signal to irradiate the photosensitive drum.
The pulse width for high-density image parts.
To lengthen the irradiation time length of the photosensitive drum. In such a pulse width modulation (PWM) system,
According to this, a high-resolution and high-gradation image can be formed.
Leverage method is an image type that requires high resolution and high gradation.
And indispensable for color image forming equipment.
Has become. [0010] SUMMARY OF THE INVENTION
When an image is output by the image forming apparatus, the reflection density
In the halftone area of 0.3 or less,
It has happened. This roughness is often found in text documents, etc.
Does not occur so much in low density areas such as photographic images
Many occurred. [0011] Then, the cause of the occurrence of the rust was examined.
At this time, the following was found. Normally, dot distribution latent images
When forming a latent image in a highlight area,
Then, the latent image on the photosensitive drum
It is not a latent image but a local latent image. Further
If you try to reproduce a lower density,
The dot latent image is dull due to the effect of the optical film thickness, as shown in FIG.
In addition, the maximum contrast Vo gradually decreases
U. For example, trying to reproduce an image with a reflection density of about 0.2
Then, Vo of the dot latent image at that time is 150 to 200
About V. In the case of reversal development, to remove fog
The surface potential of the non-image area is equal to the DC component of the developing bias voltage.
Is set 100 to 200V higher than
Trust V₀Is between 150 and 200 V, the dot latent image
Potential difference V from developing bias DC component of light exposure part_contIs
It will be about 0-100V. When Vcont is 0 to 100 V,
Reaches the photosensitive drum or remains on the developing sleeve
Or a very unstable contrast potential. for that reason
Then, the above-described dot latent image is developed with a two-component developer.
The contact state of the magnetic brush with the photosensitive drum
Dots that greatly affect and correspond to unevenness of the magnetic brush ears
Missing (where the magnetic brush is in contact with the photosensitive drum)
Is not developed, but is developed in areas that are not in contact)
According to this, it is easy to cause roughness. Further, for the purpose of eliminating the roughness,
The alternating voltage is superimposed on the image bias, and the bias is set to 6 k.
Hz or higher, toner does not reciprocate in one pulse
A way to do this has been proposed. According to this method,
The toner flows between SD (between the developing sleeve and the photosensitive drum).
Makes an oscillating motion that does not end. Photosensitive drum surface
The potential difference Vcont between the potential and the DC component of the developing bias is Vco
If nt <0, the DC component is
And the toner is biased toward the developing sleeve.
You. When Vcont is greater than 0, the DC component is
Works to attract toner to the photosensitive drum according to the position.
The amount of toner corresponding to the latent image potential
I am attracted. This tendency is due to the intermittent application of alternating voltage.
This becomes more noticeable. When developed under such conditions, photosensitive
The toner that reaches the drum vibrates on the photosensitive drum.
Return and concentrate on the latent image area. Therefore, the dot shape
It is possible to obtain a uniform and good image without unevenness
became. However, this developing method is applied to toner.
Vibration caused by an electric field causes the flying toner to vibrate.
Because the method of developing while returning is used, toner
If the camera does not vibrate enough, the highlight
Can not be completely removed, and sufficient uniformity of concentration can be obtained.
There was a problem that was not. An object of the present invention is to provide an image bearing member formed on an image carrier.
The distributed electrostatic latent image is formed by a magnetic brush of a two-component developer.
Develop into a developed image with reduced roughness to obtain a high quality image.
To provide a developing device capable of obtaining an image.
You. [0018] SUMMARY OF THE INVENTION The above objects are attained by the present invention.
This is achieved with a developing device. In summary, the present invention relates to a toner
And a two-component developer having a magnetic carrier and a magnet inside.
The developer is supported on the stored developer carrier and faces the image carrier.
The developer is transported to the image area, and the developer
While forming a brush and rubbing against the surface of the image carrier,
Apply a developing bias to the developer carrier to
Dot distribution electrostatic latent formed on image carrier by developer
In a developing device for developing an image, the developing bias is:
Voltage V that attracts toner from image carrier to developer carrier
₁(V) is applied to the developer carrier for a time T₁(Seconds)
Voltage V that causes toner to fly from developer carrier to image carrier
_Two(V) is applied to the developer carrier for a time T₁(Seconds)
A process of alternating a plurality of times, followed by a voltage V
_Three(V) is applied to the developer carrier for a time T_Two(Seconds)
From one cycle, and the time of one cycle is T
_Three(Seconds), where the voltage V_ThreeIs the image of the electrostatic latent image.
V of the image area_L(V), the voltage V of the non-image portion_D(V)
When ｜ V_L| <| V_Three| <| V_D| And V_Three= (V₁+ V_Two) / 2 And the above T₁And T_TwoBut, T₁<8.94d / | V_Two-V₁|^1/2 T_Two> 133d^Two/ (| V_Two-V₁｜ ・ T₁) -T₁/ 2 Here, d is the closest distance between the developer carrier and the image carrier.
Satisfies the relationship of the distance (m), and the distance d is 1.5
Of the developing nip in the circumferential direction of the image carrier
The length is L (m), and the peripheral speed of the image carrier is v (m / sec).
When the T_ThreeBut, T_Three<1/40 · L / v Is a developing device that satisfies the following relationship: [0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 2 is a configuration diagram illustrating a developing device. This developing device is an electronic
Formed on the surface of a photosensitive drum 1 having an outer diameter of 80 mm
The dot distribution latent image obtained by the magnetic brush of the two-component developer is used.
It is developed and visualized. In the developing device, a developing chamber (second
(1 chamber) R1 and a stirring chamber (2nd chamber) R2
A container 16 is provided, and a toner storage chamber R is provided above the stirring chamber R2.
3 is provided in the toner storage chamber R3.
(Non-magnetic toner) 18 is accommodated therein. Toner storage room
A supply port 20 is provided below R3, and is consumed in development.
The replenishing toner 18 is supplied in an amount corresponding to the
, Is dropped into the stirring chamber R2 and supplied. On the other hand, the developing chamber R1 and the stirring chamber R2
Inside, two components consisting of non-magnetic toner and magnetic carrier
The developer 19 is stored. Tona of two-component developer 19
The mixing ratio of toner and carrier is about 5% by weight of toner.
It was to so. Non-magnetic toner has a volume average particle size of about 8 μm.
Those having a diameter were used. The magnetic carrier is made of resin
Ferrite particles (maximum magnetization 60 emu /
g) having a weight average particle size of about 50 μm and an electrical resistor.
Resistance value is 10⁸ Ωcm or more was used. Career transparency
The magnetic susceptibility was about 5.0. A portion of the developing container 16 close to the photosensitive drum 1
An opening is provided at the position, and is rotatably assembled to the developing container 16.
The developing sleeve 11 into which the photosensitive drum 1
It is arranged to protrude toward. Developing sleeve
11 is made of a non-magnetic material and has an outer diameter of 32 mm.
The peripheral speed was 280 mm / sec. With developing sleeve 11
The distance from the photosensitive drum 1 was 500 μm. Development Three
A roller-shaped magnet 12 is arranged in a non-rotating manner
ing. This magnet 12 has a developing magnetic pole S₁ And its current
Magnetic pole N located downstream of image sleeve 11 in the rotation direction_Three When,
Sequentially located further downstream for transporting the developer 19
Magnetic pole N_Two , S_Two And N₁ And The magnet 12 is
Image pole S₁ Of the developing drum so as to face the photosensitive drum 1.
It is positioned in the probe 11. Development magnetic pole S₁ Is the current
In the vicinity of the developing section between the image sleeve 11 and the photosensitive drum 1
A magnetic field is formed, and the magnetic field
A magnetic brush is formed on the held two-component developer 19. Above the developing sleeve 11, a developing container 1 is provided.
6, the developer regulating blade 15 is fixed to the developing sleeve.
11 and a predetermined interval. Regulation blade
15 is a non-magnetic material such as aluminum and SUS316
In this example, the distance from the developing sleeve 11 is 80
It was set to 0 μm. The regulating blade 15 is used for the developing sleeve 11.
The layer thickness of the developer 19 carried thereon is regulated. A transport screw 13 is provided in the developing chamber R1.
And is driven by the rotation of the transport screw 13.
While the developer 19 in the image chamber R1 is being stirred, the developing three
The belt 11 is conveyed in the longitudinal direction. In the stirring chamber R2
A transfer screw 14 is also installed, and this transfer screw
The developer 19 in the stirring chamber R2 is
While the supplied toner 18 is being stirred, the developing
The tube 11 is conveyed in the longitudinal direction. This transfer screen
The transfer direction by screw 14 is that by screw 13.
Is the opposite direction. The partition 17 of the developing container 16 has a near side and a far side
Is provided with an opening, and is conveyed by the screw 13.
Developer passes from one of these openings to screw 14
The developer conveyed by the screw 14 is opened by another opening.
Delivered from the mouth to the screw 13 and stirred as described above.
It is transported while being stirred. Magnetic carrier by this stirring
, The toner is charged to the polarity to develop the latent image
Is done. The developing sleeve 11 is provided with a magnetic pole N of the magnet 12._Two
The developer 19 is carried at a position near the developer, and the carried developer
Is transported toward the developing section with the rotation of the developing sleeve 11.
Is done. When the developer 19 reaches the vicinity of the developing section, the developing
Magnetic pole S₁ Magnetic force in the developer
While rising from the surface of the developing sleeve 11 and developing.
A magnetic brush of developer is formed on the sleeve surface. So
Of the magnetic brush rubs the surface of the photosensitive drum 1,
Between the developing sleeve 11 and the photosensitive drum 1
The photosensitive drum 1 formed on the photosensitive drum 1 by applying
The electrostatic latent image is developed. Here, the developing sleeve 11 is not shown.
As shown in FIG.
By applying a voltage, the highlight area is smooth and
There is no roughness and the T / T + C ratio of the developer (toner
In the concentration (wt%), T is the toner weight, and C is the carrier weight.
T / T + C ratio = T / (T + C) × 100
High-quality images with little fluctuations
Was. The operation of the developing bias will be described with reference to FIG.
I will tell. In FIG. 3, first, the developing bias is pulled back.
Voltage V₁Is T₁When the time is applied, the toner on the photosensitive drum 1
Indicates that the toner in the image area and the toner in the non-image area are uniformly developed.
It receives the force of flying to the sleeve 11 side. Next, the developing voltage V
_TwoIs applied for the same length of time, T1.
-Receives the force to fly both the image part and the non-image part. Further
In addition, the voltage corresponding to the DC bias considering fog removal
V_Three= (V₁+ V_Two) / 2 (blank voltage) to T_TwoTime application
Then, the toner in the non-image area is pulled back onto the developing sleeve.
Is applied to the image area (the highlight area in FIG. 6).
On the photosensitive drum.
The power to approach is given. Perform this step at least during development.
When the process is repeated 50 times or more, as described above,
Normally especially uniform development due to uneven vibration of toner
Highly uniform image areas that are difficult to highlight
And a smooth image is obtained. Here, a uniform T / T + C ratio with little variation
To obtain a good image, the potential difference of the developing bias, SD
Gap (between the developing sleeve of the developing section and the photosensitive drum)
Distance) and voltage application time T₁ , T_Two Relationship is important
You. The following describes the movement of the toner for this.
State. FIG. 2 is a view showing the state of the developer in the developing section.
It is. During the development, the carrier magnetically moves between the photosensitive drum 1 and the photosensitive drum 1.
The brush brush ears are formed sparsely as shown in the figure,
More than half the toner is free to reciprocate
You. Therefore, the following description is based on a form that ignores the existence of carriers.
I will tell. It is unreasonable to ignore the existence of carriers
Is not supported in many experiments.
You. In FIG. 2B, the symbol q indicates the toner charge.
Load (C / kg), m is mass (kg), a is acceleration (N
Per second^Two ), ΔV is the potential difference (V) between SD and d, and d is SD
The gap between them (m). First, the features of the present invention will be described.
The toner adhering to the photosensitive drum 1 causes a pull-back voltage
V₁ Time T during which₁ During the return to the developing sleeve 11
By setting conditions that do not allow the toner to
Repeat the biased behavior on the drum. Here, the potential of the image portion of the photosensitive drum is considered.
Lead to the condition that is not returned to the developing sleeve,
The latent image when reproducing the image of about 0.2 is developed
DC component of the sleeve (fly on the image part, or
Voltage in the direction of pulling back). Therefore, in the present invention, the pull-back voltage V₁
The developer from the developing sleeve to the photosensitive drum
Voltage V_Two Of the voltage of the intermediate value (DC component) of (V_Two + V₁ )
/ 2 is the potential of the highlight image portion of the photosensitive drum.
Then, the pull-back voltage V of the developing sleeve₁ Mark
Toner is pulled back to the developing sleeve
You only have to give the time that is not     1/2 aT₁ ^Two        = 1/2 · ｛| q | / m · | 1/2 · (V_Two + V₁ ) -V₁ | / D｝         ・ T₁ ^Two        = 1/4 · | Q | · | V_Two -V₁ │ / d ・ T₁ ^Two <D ... (1) Given by Here, the toner is charged with its triboelectric charge Q
The larger absolute value | Q | is affected by the electric field,
It will be cool. In the present invention, even when the toner having a large Q
Selected conditions that will not be returned to the Charge Q of toner
The maximum value of
5.0 × 10^-2C / kg, so T
₁ The following equation (2) is obtained as a condition of From equation (1), T₁ ^Two <4d^Two / (| Q |
・ ｜ V_Two -V₁ ｜) | Q | = 5.0 × 10^-2And assign     T₁ ^Two <80d^Two / | V_Two -V₁ |     Ｔ T₁ <8.94d / | V_Two -V₁ |^1/2               ... (2) According to the present invention, the toner is applied to the developing sleeve.
The voltage to pull back and the voltage to fly from the developing sleeve
After applying multiple times, in the image area,
In the image area, the voltage in the pullback direction (the DC component voltage described above)
Pressure) to T_Two The time is applied, but as shown below,_Two time
The length is also characterized. When obtaining the condition of the above equation (2), the friction
Highly charged toner has a latent potential of almost the same potential as the developing sleeve.
If it adheres to the image, it will again develop by
Selected a condition that does not return to the
Low-toner toner is charged between the developing sleeve and the photosensitive drum.
Image voltage V_Two And blank voltage V_Three Only applied time
Then fly from the top of the developing sleeve to the highlight image area
The conditions were determined. If the toner having a low triboelectric charge flies,
Sufficient developability is obtained with low selectivity up to the highlight area
Become so. for that purpose,     1/2 · | Q | · (1/2 · | V_Two -V₁ |) / D · T₁ ^Two            + | Q | · (1/2 · | V_Two -V₁ |) / D · T₁ T_Two > D     1/2 · | Q | · | V_Two -V₁ │ / d ・ T₁ ・ (T₁ / 2 + T_Two )> D     Ｔ T_Two > 2d^Two / (| Q | · | V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2                                                           ... (3) Here, transfer of the toner having a low triboelectric charge is performed before transfer.
, The minimum value of the triboelectric charge Q is 1.5 × 10
^-2At C / kg, if we put it into equation (3),     T_Two > 133d^Two / (| V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2 (4) Becomes T shown above_Two To apply more than time
As a result, an image having a small variation in the T / T + C ratio can be obtained. Sa
In addition, in the present invention, vibration due to a sufficient electric field is developed during development.
It is provided to the image agent, which includes a developing section,
Specifically, the AC bias is applied to the development nip as described above.
Must be repeated for more than 40 cycles
There is. If the number of cycles is less than 40, the development will be insufficient.
If you request high image quality,
In this case, it is not possible to sufficiently obtain the uniformity of the part. In the present invention, the developing nip is as follows.
You. In other words, depending on the amount of the developer and the developing bias,
Although different, as in the present invention, the two-component
Forming a thin layer of imaging agent and developing bias including AC bias
In the case of using the development method with
Within 1.5 times the closest distance d between the sleeve and the photosensitive drum.
It was found that development took place in the box. Therefore,
With the length of the development nip within 1.5 times the closest distance,
The length is defined as L (m) (≦ 1.5d). Therefore, the peripheral speed of the photosensitive drum is defined as v (m / sec).
Then, the developing time T becomes T (second) = L / v It is represented by Therefore, in the present invention, one cycle of the developing bias is used.
Icle T_Three age, T_Three <1/40 · L / v Satisfies the condition of
Now you can get perfect images. Hereinafter, reference examples and examples of the present invention will be described.
This will be described specifically. Reference Example 1 The image was formed by developing under the following conditions. For development
Uses the developing device shown in FIG.
Was performed. Outer diameter of photosensitive drum: 80 mm Developing sleeve outer diameter: 32mm Developing sleeve peripheral speed: 280 mm / sec Photosensitive drum peripheral speed v: 160 mm / sec SD distance d: 500 μm Development nip L: 5 μm 1/40 · L / v: 7.81 × 10^-Four As the toner of the two-component developer, a positive toner is used.
Was. The developing bias shown in FIG. 3 was used. FIG.
, Each voltage and application time were as follows. [0048] V_D : 600V V_L : 50V V_Two : 1450V V₁ : -550V V_Three : 450V T₁ : 6.25 × 10^-Fivesec (→ T₁ <8.94d / |
V_Two -V₁ |^1/2 ) T_Two : 3.75 × 10^-Foursec (→ T_Two > 133d^Two /
(| V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2) T_Three : 2T₁ + T_Two = 5.0 × 10^-Foursec (→ T_Three <1
/ 40 · L / v) Development was performed under the above conditions to form an image.
However, the reproducibility of the highlight part is also good, and the T / T + C ratio
An image with little fluctuation was obtained. Reference Example 2 In Reference Example 1, the developing bias and the charging polarity of the toner
changed. Otherwise, develop and apply the image in the same manner as in Reference Example 1.
Image formation was performed. A negative toner is used for the toner of the two-component developer.
Was. The developing bias is shown in FIG.
The addition time was as follows. [0052] V_D : -600V V_L : -50V V_Two : -1450V V₁ : -50V V_Three : -550V T₁ : 5.0 × 10^-Fivesec (→ T₁ <8.94d / | V
_Two -V₁ |^1/2 ) T_Two : 4.0 × 10^-Foursec (→ T_Two > 133d^Two / (|
V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2) T_Three : 2T₁ + T_Two = 5.0 × 10^-Foursec (→ T_Three <1
/ 40 · L / v) As a result, a highlight equal to or higher than that of Reference Example 1 was obtained.
The image shows the reproducibility of the G part and the fluctuation of the T / T + C ratio is small
Obtained. Embodiment 1 Same as Reference Example 2 except that the developing bias shown in FIG. 4 was used
I made it. The value of each voltage of this developing bias was the same as that of Reference Example 2.
However, the waveform patterns are different. In FIG. 4, the application time of each voltage is as follows.
Caught.     T₁: 4.16 × 10^-Fivesec (→ T₁<8.94d / | V_Two-V₁|^1/2)     T_Two: 4.99 × 10^-Foursec (→ T_Two> 133d^Two/ (| V_Two-V₁|                                   ・ T₁) -T₁/ 2)     T_Three: 4T₁+ T_Two= 6.65 × 10^-Foursec (→ T_Three<1/40 L / v) As a result, the image quality, density, and highlight reproduction of Reference Example 2 or higher
And stable images with low T / T + C ratio
Was. T₁ : 4.16 × 10^-Fivesec (→ T₁ <
8.94d / | V_Two -V₁ |^1/2 ) T_Two : 4.99 × 10^-Foursec (→ T_Two > 133d^Two /
(| V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2) T_Three : 4T₁ + T_Two = 6.65 × 10^-Foursec (→ T_Three <
1/40 · L / v) As a result, the image quality, density, and highlight reproduction of Example 2 or higher
And stable images with low T / T + C ratio
Was. Embodiment 2 Same as Reference Example 2 except that the developing bias shown in FIG. 5 was used
I made it. The value of each voltage of this developing bias was the same as that of Reference Example 2.
However, the waveform patterns are different. In FIG. 5, the application time of each voltage is as follows.
Caught.     T₁: 3.57 × 10^-Fivesec (→ T₁<8.94d / | V_Two-V₁|^1/2)     T_Two: 4.99 × 10^-Foursec (→ T_Two> 133d^Two/ (| V_Two-V₁|                                   ・ T₁) -T₁/ 2)     T_Three: 6T₁+ T_Two= 7.13 × 10^-Foursec (→ T_Three<1/40 L / v) As a result, the image quality, density, and highlight
The image showing the realism and having a small T / T + C ratio was obtained stably.
Was. T₁ : 3.57 × 10^-Fivesec (→ T₁ <
8.94d / | V_Two -V₁ |^1/2 ) T_Two : 4.99 × 10^-Foursec (→ T_Two > 133d^Two /
(| V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2) T_Three : 6T₁ + T_Two = 7.13 × 10^-Foursec (→ T_Three <
1/40 · L / v) As a result, the image quality, density, and highlight
The image showing the realism and having a small T / T + C ratio was obtained stably.
Was. Comparative example In Reference Example 2, the application time T of the developing bias shown in FIG._Two
Was changed outside the scope of the present invention. Otherwise the same as in Reference Example 2.
To form an image. Application time of each voltage
Is as follows. T₁ : 6.25 × 10^-Fivesec (→ T₁ <
8.94d / | V_Two -V₁ |^1/2 ) T_Two : 1.25 × 10^-Foursec (→ T_Two <133d^Two /
(| V_Two -V₁ ｜ ・ T₁ ) -T₁ / 2) T_Three : 2T₁ + T_Two = 2.5 × 10^-Foursec (→ T_Three <1
/ 40 · L / v) As a result, the highlighted portion is uniform
Is the voltage V_Three Application time T_Two Does not satisfy the condition
In addition, the density fluctuation due to the T / T + C ratio is large, and
Only a stable image was obtained. [0063] As described above, according to the present invention,
T / T + C ratio by applying a developing bias
High quality with no irregularities in highlights regardless of fluctuations
An image can be obtained stably.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing a developing device used in an embodiment of the present invention. FIG. 2 is a diagram illustrating a state of a developer in a developing unit. FIG. 3 is a diagram showing a voltage waveform of a developing bias as a reference example of the present invention. FIG. 4 is a diagram showing a voltage waveform of a developing bias used in the present invention. FIG. 5 is a diagram showing a voltage waveform of another developing bias used in the present invention. FIG. 6 is a surface potential diagram showing latent images of a solid portion and a highlight portion. [Description of Signs] 1 photosensitive drum 11 developing sleeve 12 magnet 15 regulating blade 18 replenishing toner 19 two-component developer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Kenjo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-60-134262 (JP, A) JP-A Sho 55-133059 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G03G 15/06 101 G03G 15/08 G03G 15/09

Claims (1)

(57) [Claim 1] A two-component developer having a toner and a magnetic carrier is carried on a developer carrying member having a built-in magnet, and is conveyed to a developing section facing the image carrying member. In the developing section, a magnetic brush of developer is formed by a magnet and rubbed against the surface of the image carrier, and a developing bias is applied to the developer carrier to form the developer on the image carrier with the developer of the magnetic brush. In the developing device for developing the formed dot distribution electrostatic latent image, the developing bias applies a voltage V ₁ (V) for attracting toner from the image carrier to the developer carrier to the developer carrier for a time T _1.
(Second) The process of applying and applying a voltage V ₂ (V) for causing the toner to fly from the developer carrier to the image carrier for a time T ₁
(Second) A process of alternately repeating the application process a plurality of times, followed by applying a voltage V ₃ (V) to the developer carrier for a time T.
₂ (second) application process, one cycle is constituted, and one cycle time is T ₃ (second). Here, the voltage V ₃ is the voltage V _L of the image portion of the electrostatic latent image. (V) and the voltage V _D (V) of the non-image portion, the relationship of | V _L | <| V ₃ | <| V _D | and V ₃ = (V ₁ + V ₂ ) / 2 is satisfied. , the T ₁ and T _{2 is, T 1 <8.94d / | V} 2 -V 1 | 1/2 T 2> 133d 2 / (| V 2 -V 1 | · T 1) -T 1/2 However , D: satisfy the relationship of the closest distance (m) between the developer carrier and the image carrier, and further satisfy 1.5
Assuming that the length of the developing nip in the circumferential direction of the image carrier is L (m) and the peripheral speed of the image carrier is v (m / sec), T ₃ is T ₃ < A developing device satisfying a relationship of 1/40 · L / v.