JP3404757B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
Photographic image forming method, especially using contact charging device
To an image forming method. [0002] 2. Description of the Related Art In electrophotographic image formation, static
A charging device for uniformly charging the surface of the electrostatic latent image carrier has been developed.
Used. Such charging devices are roughly classified into rollers.
There are a charging device and a contact charging device.
And fixed or rotating brush chargers and rollers
Charging device, blade charging device, magnetic brush charging device, etc.
Are known. By the way, in electrophotographic image formation,
Toner charged to the original charge polarity in developing devices
In addition, toner particles that are charged to the opposite polarity are generated.
May adhere to the surface of the electrostatic latent image carrier,
In addition, there are cases where the cleaning device cannot
You. Also, the electrostatic latent polarity is opposite to the original charge polarity of the toner.
Image carrier shavings are generated, and this is the cleaning device.
May not be removed. For example, prior to forming an electrostatic latent image,
A contact-type charging device was used to charge the surface of the carrier
In such a case, the toner particles of the opposite polarity or the electrostatic latent image carrier is scraped.
Powder or the like adheres to the charging device, resulting in poor charging.
And image noise called brush streak noise
Live. As a means to solve this problem,
No. 43750 discloses that a charging device is charged with an electrostatic latent image during charging.
Apply a voltage containing a DC component of the same polarity as the charging polarity of the carrier
When not charged, the polarity is opposite to the charged polarity of the electrostatic latent image carrier
Of the charging device
Teaches the removal of fine dust adhered to the surface. Japanese Patent Application Laid-Open No. 58-42067 discloses
Non-image area on electrostatic latent image carrier passes through brush charger
The voltage applied to the brush charging device
Transfer the dirt attached to the brush to the electrostatic latent image carrier
Teaches to let go and remove. In addition, Shokai 5
Japanese Patent Application Laid-Open No. 7-65347 discloses that the toner adheres to a charging brush roller.
Cleaning dirt with another cleaning roller
Is taught. [0006] [Problems to be solved by the invention]
JP-A-63-43750 and JP-A-58-42067.
According to the conventional technology disclosed in the report,
The surface of the electrostatic latent image carrier is
It will be charged to the opposite polarity to its original charge polarity.
The charge of the opposite polarity at that time is transferred to the surface of the electrostatic latent image
It is stored inside, and as a result,
When charging the surface of the electrostatic latent image carrier to the original charging polarity
In addition, this charge cancels the original charge, and the charge amount
Problems occur, and uneven charging occurs. Further, Japanese Utility Model Laid-Open No. 57-65347 discloses the above.
As you teach, if you adopt another cleaning roller
In this case, the image forming apparatus becomes large-scale and the production cost is high.
Cling. Therefore, the present invention provides an image using a contact-type charging device.
In the forming method, the fine powder stain adhered to the charging device is
Reduce the amount of charge on the surface of the electrostatic latent image carrier, or
Easy removal without inconvenience such as
The title. [0008] The present inventor has solved the above-mentioned problems.
When image formation is performed as a result of repeated research to solve
Before, after, or between the images, the electrostatic latent image carrier
The same polarity as the original charging polarity on the surface
Voltage that is absolutely lower than the applied normal voltage (contact type
(Charging width of charging device / electrostatic latent image carrier speed)
If applied, the original band of toner attached to the charging device
Fine powder of the opposite polarity to the electrode properties is effective in a short cleaning time
And eventually moved to the electrostatic latent image carrier side.
Ming completed. That is, the present invention uses a contact-type charging device.
Before, after or during image formation
The charging device has the same polarity as the charging polarity of the electrostatic latent image carrier.
The absolute value of the normal voltage applied to the charging device.
Apply a low voltage for 0.1 msec or more (charging width / electrostatic latent image
Pulse in the following cycleApply the pulse
The voltage application time (period x pulse voltage application frequency)
0.01 seconds or more and 20 seconds or lessImage characterized by the following:
The present invention provides a forming method. In the present specification, the term “band of the electrostatic latent image carrier” is used.
Normal voltage applied to the charging device with the same polarity as the electrode
0 V, that is, the ground potential
included. The charging width is, as shown in FIG.
Of the portion where the charging member B is in contact with the electrostatic latent image carrier PC
Is the width L, and the speed of the electrostatic latent image carrier is
The speed of movement of the carrier surface,
In the case of the ram type, it is the peripheral speed. The "before" at the time of image formation is defined as
This is before forming, and during continuous printing (copying), the next
The part corresponding to the front of the copying material tip is also included. At the time of image formation
"After" means after image formation and continuous printing
(Copying), including the part corresponding to the back of the previous transfer material
No. "Between images" refers to the transfer material during continuous printing (copying).
A portion corresponding to a space between transfer materials. When the power of the image forming apparatus is turned on, "image forming"
Before Time ". Also, when clearing jams, etc.
Provide a means to monitor the position, and
When applying a pulse voltage, the user switch
The cleaning process for the user.
In the case, before or after the image formation, any
Crab included. Further, the “period” is one pulse.
The time from the start of voltage application to the start of the next pulse voltage application is
Say. The time for applying the pulse voltage according to the cycle,
(Period x number of pulse voltage applications) is one print (or
20 seconds or less per copy), preferably 0.01 seconds or more
No. This shortens the cleaning time for charging device contamination.
In addition, this is from the viewpoint of enhancing the stain removal effect.Ma
In addition, as is clear from the experimental results described below,
Is desirably 0.1 msec or more. So book
In the present invention, such a period is set to 0.1 msec or more.
You. The aforementioned "(charging width / electrostatic latent image carrier speed)"
The following cycle and the number of pulse applications must be changed each time
Therefore, the “cycle” and “number” can be averaged.
Typical "cycle" and "number of times" are also included. Also, the pulse waveform
May be a rectangular wave, a sine wave, a triangular wave, or the like. In addition,
JP-A-3-174561 discloses that two voltage values are alternately set.
A vibration pulse voltage with a predetermined duty ratio
Teaches a contact charging device.
With the aim of improving the charging performance of
The application of the loose voltage is performed at the time of charging.
Are different. [0015] According to the image forming method of the present invention, an image is formed
When a normal charging voltage is applied to the
The absolute potential of the device is higher than the absolute potential of the surface of the electrostatic latent image carrier.
Extremely high, reverse polarity to the original charge polarity of the toner
Charged toner debris and electrostatic latent image carrier shavings
Adhere to the device. However, before or after image formation or between images
The charging device has the same polarity as the charging polarity of the electrostatic latent image carrier.
The absolute value of the normal voltage applied to the charging device.
A voltage that is low and lower than the surface potential of the electrostatic latent image
By applying pulses in the above cycle,In addition,
Set the pulse voltage application time (period x pulse voltage application frequency) to 0.
By setting the time between 01 seconds and 20 seconds,Attached to the charging device
Toner fragments charged to the opposite polarity to the charged polarity
Move to the electrostatic latent image carrier side where the electric charge exists, and thus
Fine powder stains on the charging device are removed. Also, the image
Before or after formation or between images, the charging device is charged with an electrostatic latent.
The same polarity as the charging polarity of the image carrier, and applied to the charging device
The absolute voltage is lower than the normal voltage, and the electrostatic latent image carrier
A voltage higher than the surface potential is applied in the form of a pulse in the above cycleAnd
Further, the pulse voltage application time (cycle × pulse voltage application time)
Number) from 0.01 to 20 secondsBy
Also, the toner fragments are partially removed. This is the charging device
When the voltage applied to the charging device is switched, the charging device and the electrostatic latent
The electrostatic attraction between the image carrier surfaces changes, and the
It is thought that the knuckle fragments vibrate and are thrown away
You. In cleaning the fine powder, an electrostatic latent
Make sure that a voltage of the opposite polarity to the charging polarity of the image carrier is applied.
Reverse polarity memory, which is inconvenient for the electrostatic latent image carrier
No
When the charging voltage of
It is charged uniformly at a predetermined potential. [0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, one embodiment (embodiment 1) of the present invention will be described with reference to the drawings.
It will be described with reference to FIG. FIG. 1 shows a pudding implementing the method of the present invention.
1 shows an example of the data. This printer has an electrostatic latent
A photosensitive drum 1 as an image carrier is provided.
Is rotated in the direction of arrow CW by the main motor M1.
It is. Around the drum 1, a fixed brush charging device 2,
Image device 3, transfer device 4, cleaning device 5, residual charge
Are sequentially arranged. An optical system 7 is arranged above the photosensitive drum 1.
This optical system has a semiconductor laser in a housing 71.
Laser generator, polygon mirror, toroidal lens,
Mirror, spherical mirror, folding mirror, reflection mirror
The exposure slide on the floor of the housing 71
The photosensitive drum 1 can be image-exposed from a cartridge. The timing on the right side of the photosensitive drum 1 in FIG.
Roller pair 81, intermediate roller pair 82 and paper feed cassette 83
Are sequentially arranged, and the paper feed cassette 83 has a paper feed roller.
84 is facing. Also, on the left side of the photosensitive drum 1 in the drawing,
Indicates that a fixing roller pair 91 and a discharge roller pair 92 are sequentially arranged.
The discharge tray 93 faces the discharge roller pair 92.
You. The system speed of the printer (photosensitive drum
The peripheral speed of the system 1 is 3.5 cm / sec. Also, photosensitive
The diameter of the body drum 1 is 30 mm. Therefore, drum 1
One rotation takes 2.7 seconds. The charging device 2 is shown in FIG.
As shown in FIG.
Connected or grounded. Applied to the charging device 2
The voltage Vc is Vc = -1.1K when the power supply 220 is used.
V and Vc = 0 V when grounded. In the first embodiment,
As shown in the enlarged view of part (A) of FIG.
Is maintained at Vc = -1.1 KV, and is
Five times in a cycle of 200 msec (frequency 5 Hz)
Subsequently, Vc = 0 V is applied in a pulse form. In addition, Pal
When applying the power voltage, the power supply 220 is replaced with the ground potential.
A voltage power supply whose absolute value is lower than the voltage (the charging polarity of the drum 1 and
(Same polarity). The developing device 3 is a contact type using a one-component developer.
A developing device, as shown in FIG.
Is connected to a power supply PW1 via a switch 31.
Or grounded. Bias applied to developing device
The voltage Vb is Vb = −250 when using the power supply PW1.
V and Vb = 0 V when grounded. This developing device 3
In normal image formation, a developing bias Vb = −250 V mark
Of the same polarity as that of the drum 1
The reversal development is performed by a toner. The transfer device 4 is of a roller type,
As shown in (C) of FIG.
1 connected to the power supply PW2 or grounded
You. Voltage V applied to transfer roller 40_TIs on the photoconductor
When transferring the toner image of_T= + 1.1K
V, V when grounded_T= 0V. Figure 3 shows the pudding
FIG. 3 is a block diagram showing the main points of a control circuit of the data processor. This control
The circuit consists of a read only memory ROM and a random access
Microprocessor CPU1 including access memory RAM
The operation of the entire printer is
It is controlled by the processor CPU1. The microprocessor CPU1 has an interface
-Rotation control of the photosensitive drum 1 via the face circuit I / O
Control unit 10a, the control unit 10b of the transfer device 4, and the
Control unit 10c, developing bias control unit 10d, eraser system
The control unit 10h and the other control unit 10e are connected, and
Is connected to a print command input unit 10f. My
The processing program of the microprocessor CPU1 is stored in a memory in advance.
It is stored in the ROM. Print command input unit 10f
Is an external computer CP such as a personal computer
Receiving the printer control signal from the microprocessor C
It works to send to PU1. A print command is stored in the memory ROM.
Time to start rotating photoreceptor drum 1 after force / stop
During the stop time, the voltage V is applied to the transfer roller 40._TTime to apply
/ Voltage V_TVoltage Vc is applied to the charging device 2 during the time when
Application time / time when voltage Vc is set to ground potential,
Time for applying the bias Vb / time for turning off the voltage Vb;
The time for turning on / off the racer 6 is stored in advance.
On / off switching
The signal is transmitted through the interface I / O,
Control unit 10a, transfer device control unit 10b, charging device control unit 1
0c, developing bias controller 10d, eraser controller 10
h. Therefore, the voltage applied to the charging device 2
Switching of Vc is performed by the instruction of the control unit 10c, and the developing device 3
Of the developing bias Vb to the instruction of the control unit 10d.
The voltage V applied to the transfer roller 40_TSwitching is controlled
The instruction of the unit 10b and the on / off of the eraser 6 are controlled by the control unit 10
h. Also, the microprocessor CPU1 has:
An operation panel 10g is also connected.
Print key K etc. to allow lint start
You. In this embodiment, the photosensitive drum 1 is a τ-type metal-free phthalocyanine.
Charge generation layer containing nin and polyvinyl butyral resin
On a cylindrical aluminum substrate with an outer diameter of 30 mm and a length of 240 mm
And a hydrazone compound and a poly
Formed by forming a charge transport layer containing a carbonate resin
Negatively charged function-separated type with sensitivity to long wavelength light
Organic photoreceptor. Note that an electrostatic latent image to which the present invention can be applied
The carrier is not limited to this photoconductor. The toner used in the developing device 3
Is a polyester-based negatively charged toner having an average particle size of
Is 10 μm, and 80% by weight is in the range of particle diameter of 7 to 13 μm.
Distribute. The fixed brush charging device 2 is shown in FIG.
Yes, conductive carbon powder of 18 wt% based on the total weight
Included thickness 6 denier, electric resistance 1 × 10^FiveΩcm
The conductive rayon fiber 21 is a bundle of 100 fibers.
W-woven on the warp of the base fabric 22 having a thickness of about 1 mm,
5000 pieces / cm^TwoAnd conductive on the back surface of the base cloth 22
The base cloth 22 is coated with aluminum adhesive.
Fixed to the back plate 23 made of
You. Length L of brush part 20 = 240 mm, width W = 7 m
m, height H = 5 mm. In addition, the present invention can be applied.
Contact type charging device is limited to this brush charging device
is not. The transfer roller 40 of the transfer device 4 has the electric resistance 1
0^FiveΩ conductive urethane rubber roller.
The ram 1 is pressed at a linear pressure of 30 g / cm. This printer
According to the above, in normal image formation, the surface of the photosensitive drum 1
The power supply 220 is set to a predetermined potential by the charging device 2 connected thereto.
And the image is exposed from the optical system 7 to the charged area.
An electrostatic latent image is formed. The electrostatic latent image thus formed is
The toner image is developed by the developing device 3 and the transfer image is transferred.
Then, the process proceeds to the transfer area facing the frame 40. On the other hand, from the sheet cassette 83 to the sheet feeding roller 8
4, the transfer paper is pulled out and passed through the intermediate roller pair 82.
The timing roller pair 81 is reached.
The image is sent to the transfer area in synchronization with the toner image. Hide
On the drum 1 by the action of the transfer roller 40 in the transfer area
Is transferred onto the transfer paper, and the transfer paper is
To 91, where the toner image is fixed and then discharged.
The sheet is discharged to a sheet discharge tray 93 by the roller pair 92. By the way, in the printing operation, charging is performed.
A normal charging voltage (Vc =-
1.1KV) is applied to a developing device or the like.
Positively charged toner fragments and the charging device 2
Positive photosensitivity caused by contact with the surface of ram 1
Of the fine powder such as body shaving powder, it adheres to the drum 1 and
Those not removed by the cleaning device 5
As it arrives at the charging device 2 as it is, it adheres to the brush bristles 21.
Because the potential of the charging device brush bristle by the power supply 220 is
Negative potential and more negative than the negative potential on the surface of the photosensitive drum 1
This is because it is high in value. Therefore, in this printer, the timing shown in FIG.
Print as follows at the timing shown in the chart
Is performed. First, the printer turns on the print key K
State and print command by external computer CP
After the receipt, the rotation of the photosensitive drum 1 is started. afterwards
Start applying voltage Vc = -1.1 KV to contact charger 2
Then, the drum 1 is charged. Voltage Vc = -1.1KV mark
The developing bias is applied to the developing device 3 at the same time as the start of application.
Start applying 50V and transfer to transfer roller 40
Voltage V_T= + 1.1 KV is applied. In addition,
The sub 6 is also turned on. The oblique lines shown in the timing chart (for example,
(The line indicated by (a)) is a place where attention is focused on one point of the drum 1.
One point of each is on each element (charging, developing, transfer device)
Are connected by a straight line. (A) Part
Is the space between the images.
Thus, the voltage Vc applied to the charging device 2 has a cycle of 200 msec.
Switch to ground potential (Vc = 0V) 5 times continuously with c
Then, a pulse voltage of Vc = 0 V is applied. This pulse
Due to the application of the voltage, the voltage applied to the brush of the charging device 2
Charged dirt migrates to the negatively charged portion of drum 1
Electric field works in the direction. In this way, brush dirt is cleaned
Is In the cleaning of the fine powder, a charging device
2 shows a positive polarity with respect to the charging polarity (negative) of the photosensitive drum 1.
No pressure is applied, so the positive
Memory is not created, and
When a regular charging voltage is applied, the photosensitive drum
The surface is uniformly charged with a predetermined charge amount. in this way
As a result, the adhesion of the charging device 2 is removed,
Charging device-specific poor charging due to dirt,
In addition, it is possible to prevent the occurrence of the streak-like image noise. The B / W ratio is calculated by the printing method described above.
Perform 5% print output (A4 size vertical) and evaluate next
1-4 were performed. Evaluation 1 (Evaluation of toner consumption) Weigh the toner consumption by printing 5000 sheets,
The ranking is performed according to the amount. [0033] Evaluation of toner consumption Less than 90g ○ 90g or more × Evaluation 2 (Evaluation of the amount of dirt attached to the brush of the charging device) Fine dust adhered to the charging brush after printing 5,000 sheets
The quantities are weighed and ranked according to the quantity. However
The amount is shown by the amount of fine dust adhered to one charging brush. [0034] Evaluation 3 (Evaluation of the amount of charge of brush adhesion dirt) Fine dust adhered to the charging brush after printing 5,000 sheets
Is measured, and ranking is performed based on the measured value. However
And the amount of charge per unit weight. [0035] Evaluation 4 (Regarding generation of brush streak image noise) The evaluation of streak noise is based on the evaluation of fine powder stains on the brush charger.
Do also to assess if it has been successfully removed
It is. That is, in the charging device 2,
If there is fine powder dirt, the surface of the photosensitive drum 1
Unevenness occurs in the direction perpendicular to This charged unevenness is exposed
Even after this, the potential (Vi) after the image exposure remains uneven.
You. That is, the potential immediately after being charged by the charging device
Part of (Vo) having a partially higher potential is image exposure
The post-potential (Vi) is also partially high. When the reversal development is performed, a portion having a low Vi
A minute amount of toner adheres. That is, Vo unevenness
Is in the spot of Vi,AndEventual image unevenness, especially streaks
It becomes noise. Therefore, the fine dust of the charging device 2
The evaluation is performed by evaluating streak noise. Streak
The size is evaluated by the following method. Pudding in Fig. 1
After charging on the drum 1 using a
Toon (lights up), 2 dots off (lights out)
Is written with a laser. The same applies to the secondary inspection direction 2
Write dot on (lit), 2 dot off (unlit)
Adjust the laser extinguishing timing so as to form a pattern.
Thereafter, through the reversal development, transfer, and fixing processes, as shown in FIG.
Get a print image like The minimum of 2 dots × 2 dots on the image
The maximum width of the solid black pattern in the main scanning direction is W_MAnd
W of 30 minimal black solid patterns continuous in the main scanning direction
_MΣ is the standard deviation of
Linking is performed as follows. Standard deviation σ Evaluation symbol σ <30 μm ○ 30 μm ≦ σ × In the evaluation, the mark ○ indicates no or no noise.
The state that can be done is the state where there is a streak noise that can not be ignored.
Is shown. That is, when σ is large, the main scanning direction
The width of the fine black solid varies widely in the main scanning direction
Means that. Evaluation 5 (Comprehensive evaluation) Evaluation 1 (toner consumption), evaluation 4 (stroke noise)
Perform a comprehensive evaluation based on the results. × Not good △ favorable ○ More preferred Evaluations 2 and 3 examine the cause of the occurrence of brush streak noise.
Here is the final comprehensive review for an intermediate evaluation
The price was not reflected. According to the printing method of the first embodiment described above.
As shown in Table 1, all the items were ○. Next
The above-mentioned printer is used for the charging brush width of the charging device 2 (brush).
Latch width) W, peripheral speed (speed) of photosensitive drum 1, charging brush
Apply pulse voltage (Vc = 0) to remove stains
Pulse position (between images, before or after image), applied pulse
Pulse period, pulse frequency (1 / pulse period)
Period), the number of pulses applied per print
Degree, total time related to pulse application per print
(Number × period) was changed variously, and
Printing was performed, and the evaluations 1 to 4 were performed. together,
Comparative Examples 1 to 12 were performed as Comparative Examples, and the same evaluation was performed.
Was. These are shown in Table 1 together with Example 1 described above.
Are shown in Table 4. However, in Examples 40 and 4 shown in Table 4,
1. In Comparative Example 12, the number of pulses was
It is displayed in the number of times. Examples 2 to 11, Comparative Examples2-4about By changing the pulse period (frequency) and the number of pulses,
And the pulse application time (number of pulses x period) is constant
Then, printing and evaluation were performed. Other conditions are the same as in the first embodiment. pulse
If the period is less than 0.1 msec, the amount of dirt on the charging brush is large.
Undesirably, resulting in streak noise
Was. If the pulse cycle is 5 msec or more, the charging brush sticks
The effect of removing the noise is great, so that
It did not occur almost and was very good. This is because when the pulse period becomes short, the pulse
Is applied to the charging brush even if a reverse electric field is formed.
Because the fine powder cannot respond and cannot move to the photosensitive drum side
it is conceivable that. Also, the pulse cycle is 2 of brush width / speed.
When the time exceeds 00 msec, the toner consumption increases sharply.
Therefore, it was not preferable. This is because the pulse period exceeds the brush width / speed.
Then, there is a place where the photosensitive drum surface potential is extremely low between the images.
It is considered that the toner is formed and the toner is developed. About Comparative Example 1 No charging brush applied pulse inserted between images
Is the case. Otherwise, print under the same conditions as in Example 1.
And evaluated. As a result, both the dirt amount and the dirt charge amount are large,
Brush streak noise occurred. From this, to the charging brush
It is understood that the application of the pulse voltage is necessary. Examples 12 and 13 Under the same conditions as in Example 1, but before the image, not between the images, or
Was printed and evaluated by applying a pulse after the image. As a result, the same result as in Example 1 was obtained. Examples 14 to 22 and Comparative Examples 5 to 9 Photoconductor drum peripheral speed 140mm/ SOthers raised to
Printing and evaluation were performed under the same conditions as in Examples 1 to 11 and Comparative Examples 2 to 4.
Value. It is preferable that the pulse period is less than 0.1 msec.
It didn't work. Very good with a pulse period of 5 msec or more
It was good. Pulse period is 50mse of brush width / speed
When c exceeds c, toner consumption increases, which is not preferable. Comparative Examples 10 and 11 and Examples 23 to 34
Stay Examples 1 to 1 except that the charging brush width was increased to 21 mm
1. Perform printing and evaluation under the same conditions as Comparative Examples 2 to 4.
Was. It is not preferable if the pulse period is less than 0.1 msec
Was. Very good with a pulse period of 5 msec or more
Was. Pulse period exceeds 600msec of brush width / speed
As a result, toner consumption increased, which was not preferable. Examples 35 to 41 and Comparative Example 12 Except that the number of pulses was changed in various ways,
And evaluation. Number of pulses per print
Less than 0.1 times (once per 10 prints)
The noise was terrible and unfavorable. Pre-pulse count
Particularly favorable results are obtained at least once per sheet.
Was. This is due to the decrease in the number of cleanings,
The fine powder adhered was not completely removed, and the streak noise was generated.
it is considered as. [0048] [Table 1][0049] [Table 2][0050] [Table 3][0051] [Table 4]The present invention is not limited to the above-described embodiment.
It can be implemented in various ways. In each of the above embodiments,
The pulse voltage Vc for removing the charging brush dirt is all
Is 0 V, but the voltage used for charging (-1.
Any voltage between 1KV) and 0V can be selected.
You. In short, a reverse electric field is applied between the electrostatic latent image carrier and the contact charging device.
What is necessary is just to form. In the above embodiment, the contact type charging device is used.
Although a fixed brush charging device was used, the method of the present invention
Rotary brush charging device, roller charging device, blade charging
Equipment, magneticMindUse a contact charging device such as a brush charging device
It is also applicable to cases where However, the method of the present invention
It is particularly effective in a brush charging device using a contact in the shape of a brush. In the above embodiment, the electrostatic latent image carrier is used.
Therefore, a negatively charged photoconductor was used, but a positively charged photoconductor was also used.
It goes without saying that it can be used. Further, the above embodiment
Now, we adopt reversal development, so-called negative-positive development.
However, the method of the present invention can also be applied to positive-positive development. You
In other words, the charging device is operated by an electric field opposite to that during normal charging.
Can be cleaned. For regular development,
That is, the polarity of the charging voltage to the electrostatic latent image carrier and the transfer device
If the applied voltage is the same polarity and the toner has the opposite polarity,
Charging device carries toner with the same polarity as toner and electrostatic latent image
Fine particles are attached, but the same as in reversal development.
In addition, a contact charging device for cleaning
After charging the image carrier with normal polarity, the contact charging device
Cleaning by applying a small voltage or 0V to the
I can do it. [0054] As described above, according to the present invention, the connection
Image formation using tactile charging deviceMethodIn the charging device
The amount of fine dust adhering to the electrostatic latent image carrier
Inconvenience, such as lowering the charge and causing uneven charging
And it can be easily removed with less toner consumption.
Wear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a schematic configuration of an example of a printer for performing a method of the present invention. FIG. 2A is an explanatory diagram of a voltage applying unit to a charging device, FIG. 2B is an explanatory diagram of a voltage applying unit to a developing device, and FIG. 2C is an explanatory diagram of a voltage applying unit to a transfer device. FIG. 3 is a block diagram illustrating a control circuit of the printer of FIG. 1; FIG. 4 is a perspective view of a charging device. [5] printed in the printer 1 command, the rotation of the photosensitive drum, switching the applied voltage Vc to the charging device, switching the bias voltage Vb applied to the developing device, and the switching state of the voltage V _T applied to the transfer device FIG. FIG. 6 is a diagram showing an image pattern for performing image noise evaluation. FIG. 7 is an explanatory diagram of a charging width by a charging device. DESCRIPTION OF REFERENCE NUMERALS 1 photoconductor drum 2 brush charging device 220 charging voltage power supply 210 changeover switch 3 developing device 30 developing sleeve 31 changeover switch PW1 developing device power supply 4 transfer device 40 transfer roller 41 changeover switch PW2 transfer device power supply 5 cleaning device Reference Signs List 6 Eraser 7 Optical system 81 Timing roller pair 82 Intermediate roller pair 83 Paper feed cassette 91 Fixing roller pair 92 Paper discharge roller pair 93 Paper discharge tray

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Issei Osawa 2-3-1, Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-62-168174 (JP, A) JP-A-2-278273 (JP, A) JP-A-62-239183 (JP, A) JP-A-55-134863 (JP, A) JP-B-63-3313 (JP, B1) Jiko-Sho-63 -23715 (JP, Y1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02

Claims (1)

(57) Claims 1. In an image forming method using a contact-type charging device, an electrostatic latent image carrier is charged to the charging device before, after, or between images during image formation. A voltage having the same polarity as the charging polarity and having an absolute value lower than a normal voltage applied to the charging device is defined as 0.
When the pulse voltage is applied at a cycle of 1 msec or more (charging width / electrostatic latent image carrier speed) or less and the pulse voltage is applied.
Duration (period x number of pulse voltage application) is 0.01 seconds or more and 20
Image forming method , wherein the time is less than seconds .