JPH11129521A - Method and apparatus for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for forming images whereby a reverse fly of toners is eliminated, cleaning of adhering toners is facilitated, the apparatus is reduced in cost and a print speed is enhanced. SOLUTION: An intensity and an application time of an electric field applied between a toner control member 3 and a counter electrode member 2 are controlled, thereby setting an injection amount of charges of a reverse polarity to a charging polarity of a toner 7 which are to be injected to the toner 7 adhering on the counter electrode member 2 or on a paper 6 in a range whereby the toner 7 doest not start flying in a reverse direction because of the injected charges. As a result, the intensity and application time of the electric field between a first electrode layer 22 and a rear electrode 23 are reduced. A time for the paper 6 to pass a strong electric field area becomes not larger than 1 msec, and the quantity of toners flying reverse is reduced to 1/10 or smaller. A reverse fly of adhering toners because of the injection of electric charges to the toners is thus eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium on which a toner carried on a toner carrier is selectively caused to fly, and the toner carrier and a counter electrode facing the toner carrier or a recording member on the counter electrode. And an image forming method for forming an image by attaching the toner.

[0002]

2. Description of the Related Art Conventionally, as a powder image forming method, an image forming method called direct toning or toner projection has been known. In this image forming method, an electric field is applied to a charged toner layer or toner cloud by applying a voltage to a control electrode portion provided around a hole or a slit,
This is to selectively fly toner at a specific position and move the toner through holes or slits to directly form an image on a recording member such as paper.

An image forming apparatus adopting such an image forming method includes a sleeve-shaped toner carrier for carrying a toner, a counter electrode member as a counter electrode arranged to face the toner carrier 1, and a toner. It is composed of a toner control member having minute holes to be passed and a control electrode.
The toner carrier is disposed inside a toner container containing the toner, and the toner is applied to the surface of the toner carrier by a known technique employed when the toner carrier is carried by a known electrophotographic image forming apparatus. Carry.

The toner control member is mounted so as to close an opening formed at an appropriate position in the toner container, and is provided between the toner carrier and the counter electrode member to transfer toner from the toner carrier to the counter electrode member. Control flight. Then, a flying electric field for causing the toner carried on the toner carrier to fly toward the opposite electrode member is formed between the toner carrier and the opposing electrode member provided opposite to the toner carrier.

In such an image forming apparatus, for example, a negatively charged toner is used, the toner carrier is grounded, a high DC voltage is applied to a counter electrode member, and an image signal is applied to a control electrode of a toner control member. When voltage is applied,
An electric field acts on the toner on the toner carrier. As a result of the action of the electric field, the Coulomb force applied to the toner exceeds the sum of the adhesive force and the image force acting between the toner and the toner carrier, and the toner starts to fly toward the counter electrode member. As a result, the toner passes through the minute holes of the toner control member and continues to fly by being attracted by the flying electric field formed by the voltage applied to the counter electrode member. For example, the toner is transported on the counter electrode member in a predetermined direction. Stop on the paper
An image is recorded on the paper.

Conventionally, as shown in FIGS. 11 and 12, a plurality of (four in the illustrated example) image forming apparatuses are provided in parallel to form a multicolor image. One is known ("Multicolor image generating apparatus" described in JP-A-6-234233). 11 and 12, reference numerals 10, 11, 12, and 13 denote developing units for forming images of different colors, 14 denotes a developing roll (corresponding to a toner carrier in the image forming apparatus), 15 denotes a toner container, Reference numeral 22 denotes a first electrode layer (corresponding to a toner control member in the above-described image forming apparatus), and reference numeral 23 denotes a rear electrode (corresponding to a counter electrode member in the above-described image forming apparatus) which also serves as a belt 41 for sucking and conveying the sheet 54.

[0007]

However, when the test pattern was made into a pudding using a non-magnetic insulating toner by the above-described multicolor image forming apparatus, the developing roller as a toner carrier was moved from a developing roller to a counter electrode member. Of the toner flying toward the rear electrode, 5% to 10% of the toner flew in the direction opposite to the original flight direction (hereinafter, the phenomenon that the toner flies in the reverse direction is referred to as “reverse flying"
). As a result of continuous printing without cleaning the toner that has flown in the reverse direction, the number of prints is 5 to 50 (this number is the image area ratio of the test pattern: the pattern image of the test pattern paper). (Depending on the occupying ratio), clogging occurred in the toner passage hole of the first electrode layer as the toner control member, and white stripes appeared on the entire image portion of the printed paper. Also, even in the case of paper on which white streaks did not appear, the image line corresponding to the above-described clogged portion became thin, or the white background of the paper became dusty, resulting in poor print image quality. Decreased. In this experiment, the average particle size of the toner was 7.0 μm, and the average charge amount on the developing roller was −10 μC / g.

For this reason, in order to maintain the print quality of the image forming apparatus based on the above-described image forming method at the highest level, every time printing on one sheet is completed in the image forming process. It is necessary to clean the first electrode layer serving as the toner control member to prevent the toner passage holes of the first electrode layer from being clogged.

However, in this image forming apparatus, for example, when an image having a resolution of about 300 dpi can be recorded, a toner passage hole having a diameter of 0.140 mm and a pitch of 0.084 mm are formed in the toner control member.
It is formed at intervals of 5 mm. Therefore, in order to remove the toner clogged in such an extremely small toner transmission hole, it is necessary to use a special cleaning device having a high cleaning performance, and there is a problem that the cost of the device is increased. Further, in the multicolor image generation device,
In order to be able to clean the toner passage hole, every time printing on the paper is completed, the opposite electrode belt also serving as a conveyance means of the paper is moved from the portion of the first electrode layer as the toner control member. It is necessary to retreat and move the cleaning device closer to the toner control member. For this reason, in an image forming apparatus equipped with such a cleaning device, the configuration is complicated, and the moving process of the toner control member and the cleaning device is added to the image forming process. Is significantly reduced.

The present invention has been made in view of the above background, and has as its object to eliminate reverse flight of toner, facilitate cleaning of adhered toner, reduce the cost of the apparatus, and improve printing. An object of the present invention is to provide an image forming method and an image forming apparatus capable of increasing the speed.

[0011]

According to one aspect of the present invention, there is provided a toner carrier for supporting a toner, a counter electrode facing the toner carrier, and a counter electrode facing the toner carrier. Forming a monochromatic image, comprising a toner control member disposed between the electrodes and having a plurality of independent or a series of minute openings and a plurality of control electrodes for controlling toner passage through each minute opening; By applying a voltage to the control electrode section of the toner control member in accordance with an image signal by using one image forming unit or a plurality of image forming units that form different multicolor images, The toner carried on the carrier is selectively fly, and the toner transferred to the counter electrode side through the minute opening is attached to the counter electrode or a recording member on the counter electrode to form a monochromatic image or In the image forming method for forming a color image, the electric field strength and application time of the applied electric field between the control electrode portion and the counter electrode are controlled to inject the toner adhering to the counter electrode or the recording member. The injection amount of the injected charge having the opposite polarity to the charge polarity of the toner is set in a range where the injected charge does not cause the toner to start flying in the reverse direction.

In this image forming method, the electric field strength and the application time of the electric field applied between the control electrode portion and the counter electrode are controlled so as to inject the toner adhering to the counter electrode or the recording member. The amount of injected charge having the opposite polarity to the charged polarity of the toner is set to a range where the injected charge does not cause the attached toner to start flying in the reverse direction. This eliminates reverse flight of the attached toner due to charge injection into the attached toner with charges having a polarity opposite to the charge polarity of the attached toner.

According to a second aspect of the present invention, in the image forming method of the first aspect, the minute opening between the control electrode portion and the counter electrode, which is added to the toner adhered to the counter electrode or the upper recording member. The application time of the electric field having the same level as the applied electric field formed in the vicinity is set to 1 msec or less.

In this image forming method, the toner adhered to the counter electrode or the upper recording member has the same level of strength as the applied electric field formed near the minute opening between the control electrode and the counter electrode. Application time of 1 m
sec. As a result, the time during which the toner adhering to the counter electrode or the upper recording member is exposed to a strong electric field is a short time of 1 msec or less, and the amount of charge that causes the toner to fly backward into the adhering toner is reduced. Reverse flight of the attached toner is suppressed.

According to a third aspect of the present invention, there is provided a toner carrier for carrying a toner, a counter electrode facing the toner carrier, and a plurality of independent electrodes disposed between the toner carrier and the counter electrode. A plurality of fine openings and a toner control member having a plurality of control electrodes for controlling the passage of toner through each of the fine openings, using a plurality of image forming units that form mutually different multicolor images, By applying a voltage to the control electrode portion of the toner control member in accordance with an image signal, the toner carried on the toner carrier is selectively caused to fly, and is shifted to the counter electrode side through the minute opening. In the image forming method for forming a multicolor image by adhering the made toner onto the counter electrode or a recording member on the counter electrode, the image forming method includes the steps of: Professional The pair to the attached toner on the recording member on the counter electrode or counter electrode by the scan, is characterized in applying an electric field of electric field polarity opposite that applied by the image forming unit of the front stage.

In this image forming method, the image of the counter electrode or the toner adhered to the recording member on the counter electrode is attached to the toner of the preceding stage by the image forming process of the preceding image forming unit. An electric field of opposite polarity to the electric field applied by the imaging unit is applied. Thereby, before the attached toner is exposed to the electric charge by the next image forming unit, the electric field of the opposite polarity applied to the attached toner causes
The charge injected into the attached toner is neutralized, and the attached toner is prevented from flying backward.

According to a fourth aspect of the present invention, in the image forming method of the first aspect, the toner adheres to the toner adhering to the counter electrode or the upper recording member in a range excluding the vicinity of the minute opening in the image forming unit. The electric field is a weak electric field having the same polarity as the electric field near the minute opening.

In this image forming method, the electric field applied to the opposite electrode or the toner deposited on the upper recording member in a range excluding the vicinity of the minute opening in the image forming unit is the same as the electric field near the minute opening. Since it is a weakly polarized electric field,
The electric charge injected into the attached toner at a portion that does not contribute to image formation is weakened, and the backward flight of the attached toner is suppressed.

According to a fifth aspect of the present invention, there is provided a toner carrier for carrying a toner, a counter electrode opposed to the toner carrier, and a plurality of independent electrodes disposed between the toner carrier and the counter electrode. Having a plurality of image forming units for forming mutually different multicolor images, comprising a plurality of minute openings and a toner control member having a plurality of control electrodes controlling the passage of toner through each minute opening. In the forming apparatus, the charge injected into the position facing the counter electrode between the respective image forming units by the image forming process of the preceding image forming unit with respect to the toner on the counter electrode or the recording member on the counter electrode. Characterized in that a neutralizing electrode for neutralizing is provided.

In this image forming apparatus, the counter electrode or the recording member on the counter electrode is attached between the plurality of image forming units by the image forming process of the preceding image forming unit. An electric field is applied to the toner to neutralize the electric field applied by the preceding imaging unit. Thus, before the attached toner is exposed to the electric charge from the next image forming unit, the charge injected into the attached toner is neutralized by the opposite polarity electric field applied to the attached toner by the neutralizing electrode. In this way, the reverse flight of the attached toner is suppressed.

According to a sixth aspect of the present invention, there is provided a toner carrier for carrying a toner, a counter electrode opposed to the toner carrier, and a plurality of independent electrodes disposed between the toner carrier and the counter electrode. One image forming unit for forming a single-color image, or a multi-color image forming unit for forming a single-color image, comprising a plurality of minute openings and a toner control member having a plurality of control electrodes for controlling the passage of toner through each minute opening. In an image forming apparatus including a plurality of image forming units for forming an image, a weak electric field having the same polarity as the electric field near the minute opening is provided in a range excluding the vicinity of the minute opening facing the counter electrode of the toner control member. Characterized in that a shield electrode for applying a voltage is applied.

In this image forming apparatus, the shield electrode applies an electric field near the minute opening to the adhering toner on the counter electrode or the upper recording member in a range excluding the vicinity of the minute opening in the image forming unit. And a weak electric field having the same polarity as that of. As a result, the charge injected into the attached toner at a portion that does not contribute to image formation is weakened without causing a side effect as described below, and the reverse flight of the attached toner is suppressed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] Hereinafter, an embodiment in which the present invention is applied to an image forming apparatus will be described. FIG. 1 is a perspective view showing a schematic configuration of a main part of a conventional image forming apparatus employing such an image forming method. The image forming apparatus includes a sleeve-shaped toner carrier 1 that carries a toner, a counter electrode member 2 as a counter electrode that is arranged to face the toner carrier 1, a toner control member 3, and the like. The toner carrier 1 is disposed inside a toner container 4 for storing toner. The toner carrier 1 is provided on the surface of the toner carrier 1 when a known electrophotographic image forming apparatus carries toner on the toner carrier. The toner can be carried by a known technique. In the present image forming apparatus, the toner that is negatively charged by friction between the doctor blade 5 or a toner supply member (not shown) and the toner carrier 1 is carried on the toner carrier 1 by electrostatic force. Thus, the toner layer is formed.

The toner control member 3 is mounted so as to close an opening formed in the lower wall of the toner container 4. As shown in FIG. 2, the toner control member 3 is provided between the toner carrier 1 and the counter electrode member 2.
In order to control the flying of the toner from the nozzle to the counter electrode member 2, a toner passage hole (hereinafter referred to as “hole”) 31 as a plurality of minute openings and an inner diameter φ formed around each hole
Have a ring-shaped control electrode 32 of 0.160 mm. The diameter φ of the holes 31 and the pitch Ph between the holes 31 in a direction (axial direction of the toner carrier 1) orthogonal to the conveying direction of the paper 6 as a recording medium (recording member) are images to be recorded on the paper 6. Is set according to the resolution of. In this image forming apparatus, a hole 31 having a diameter φh of 0.140 mm is provided on a substrate made of polyimide having a thickness of 0.075 mm so that an image having a pitch Ph of 0.0845 mm can be formed so that an image having a resolution of about 300 dpi can be recorded. It is formed by. The holes 31 are formed in eight rows (31-1 to 31-8) in a region where the width W of the paper 6 in the conveying direction is about 2 mm, and the total number of the holes 31 is 2,300. A ring-shaped control electrode 32 having an inner diameter φ of 0.160 mm, which is electrically independent from each other, is formed around each hole 31. Each control electrode 32 is a power supply circuit for applying a voltage corresponding to image information. It is connected to the.

FIG. 3 is an enlarged schematic diagram of an image recording section of an image forming apparatus employing such an image forming method. The toner carrier 1 carrying the toner 7 is grounded, and the toner 7 carried on the toner carrier 1 is placed between the toner carrier 1 and the opposing electrode member 2 provided opposite thereto. A power supply 8 is connected as a flying electric field forming means for forming a flying electric field for flying toward. This power supply 8 applies a DC high voltage having a polarity opposite to the average charging polarity of the toner 7 to the counter electrode member 2. (Hereinafter, margin)

Further, between the toner carrier 1 and the counter electrode member 2, a toner control having a toner passage hole 31 as a minute opening and a control electrode 32 provided around the toner passage hole 31. A toner control member 3 as a member is provided. A power supply (hereinafter, referred to as an “image power supply”) that applies a control voltage generated based on image information to each control electrode 32 is provided between the toner carrier 1 and each control electrode 32 of the toner control member 3. 9) is connected. The image power supply 9 controls each control electrode 32 based on image information.
Are applied to each other.

In the illustrated apparatus, the distance Li between the control electrode 32 of the toner control member 3 and the counter electrode member 2 is 0.5 mm, and the distance L between the control electrode 32 and the toner carrier 1 is L.
k is 0.05 mm, and the peripheral speed of the toner carrier 1 is 300 mm
/ Sec, and the transport speed of the paper 6 is 100 mm / sec.

FIG. 4 is a schematic diagram showing the flying state of the toner. For example, when the toner carrier 1 is grounded using a negatively charged toner, a high DC voltage of +0.9 kV is applied to the counter electrode member 2, and an image signal voltage Vblack of +325 V is applied to the control electrode 32 for 200 μsec, the toner An electric field of 6 × 10 ⁶ V / m acts on the toner 7 on the carrier 1. As a result of the action of the electric field, the Coulomb force applied to the toner 7 exceeds the sum of the adhesion force and the mirror image force acting between the toner 7 and the toner carrier 1, and the toner 7 moves toward the counter electrode member 2. Begins to fly, the toner control member 3
Through the hole 31, is continuously attracted by the flying electric field formed by the voltage applied to the opposing electrode member 2, and hits the paper 6 being conveyed on the opposing electrode member 2 in a predetermined direction by conveying means (not shown). Stopping, and the image is recorded on the paper 6. In this apparatus, the control electrode 32 corresponding to the non-image portion where the toner on the paper 6 does not adhere is applied with -50V.
Is applied.

By the way, in order to know the cause of the above-mentioned reverse flight of the adhered toner, the charge amount of the reverse flight toner was measured using a well-known Faraday gauge, and found to be +3 μmsec. The state of the toner during flight and after landing is 27,000 per second.
When a top frame was photographed and observed with a high-speed camera, the toner lands on the opposing electrode member 2 immediately after the toner lands on the opposing electrode member 2. It has been found that the reverse flight of the adhered toner starts after 1.2 to 3.7 msec.

From this result, after the toner 7 charged to the normal polarity (here, the negative polarity) lands on the counter electrode member 2, the charging polarity of the toner 7 is reversed to the opposite polarity after the above-mentioned time has elapsed. It is clear that we did. However, according to the video image captured by the above high-speed camera, the flying toner jumps or rolls slightly at the time of landing, but it is known that the toner stays in a short time, so it is frictionally charged within the above time. This does not mean that the polarity has changed.

Therefore, it is considered that such a reversal phenomenon of the charged polarity of the toner occurs due to the injection of the charge of the opposite polarity from the counter electrode member 2 within the above-mentioned time. However, the base of the toner 7 is made of a polyester resin and is a complete insulator. Therefore, the counter electrode member 2 and the toner control member 3 are attached to the toner base made of the insulator.
And the charge of the opposite polarity cannot be injected due to the action of the electric field between the toner and the polarity control agent (C) embedded in the toner.
It is difficult to imagine that the charges of CA), dyes, pigments and the like have moved.

From the above, the present inventors have paid attention to silica externally added to the surface of the toner for the purpose of weakening the adhesion of the toner and improving the fluidity of the toner. The diameter of the fine silica powder is as small as 0.1 μm or less, but is large enough to eliminate van der Waals force which is a main factor of the adhesion of the toner.

Then, a toner-like powder having an average particle size of 7.0 μm, which is made of only the polyester resin from which the coloring material such as the polarity control agent (CCA) and dyes and pigments has been removed, is prepared by a known pulverizing method. Three types of pseudo toners A, B, and C were prepared by externally adding three types of silicas a, b, and c to the surface by a known hybridization method. The addition amount of the silica was 1 wt% and 3 wt% with respect to the polyester resin of the toner base.

Then, these three types of pseudo toners A,
B and C are set in the electrostatic flying experiment apparatus 100 shown in FIG. 5, and the applied voltage Vt to each of the pseudo toners A, B and C is
By changing the application time Tv, each pseudo toner A, B,
The flying amount of C and the charge amount of the flying toner were measured by a known method. The electrostatic flying experiment apparatus 100 forms a crater-shaped depression 101a having a depth d = 0.1 m and a diameter φD = 10 mm at substantially the center of a grounded metal plate 101 corresponding to the toner carrier 1. Then, the pseudo toner is squeezed with a rubber blade into the recess 101a and filled in a planar shape, and a gap of L = 1.0 mm is maintained above the metal plate 101 in parallel with the metal plate 101. hand,
It is configured by disposing a counter electrode plate 102 corresponding to the counter electrode member 2. Then, a pulse of ± 400 to ± 2 kV is applied to the counter electrode plate 102 of the electrostatic flying experiment apparatus 100 from a high-voltage pulse power supply (not shown) for 100 μsec.
The counter electrode plate 1 is applied for a time of c to 1000 μsec.
The weight and charge amount of the pseudo toners A, B, and C flying and adhering to No. 02 were measured.

FIG. 6 shows the pseudo toners A,
The relationship between the flying amounts of B and C and the applied voltage is shown. FIG.
Is a conductive toner measured under the same conditions for comparison with the pseudo toners A, B, and C. FIG.
As is clear from FIG. 3, the flying amounts of the pseudo toners A, B, and C differ depending on the type of silica added. It can be seen that the flying amounts are almost equal. At this time, the charge amounts of the pseudo toners A, B, and C varied, but when the positive voltage was applied,-
Around 10 μc / g, +10 μm when negative charge is applied
c / g. This experimental result clearly shows that charge injection occurred from the grounded conductive metal plate 101 to the pseudo toners A, B, and C. Therefore, when the recording material on which the toner has landed is a conductive member, charge is injected from the conductive recording member into the silica of the adhered toner, the charge polarity of the toner is reversed, and the toner flies backward. Occur. When the recording material on which the toner has landed is an insulating member such as paper, the moisture or the like contained in the insulating member serves as a medium, and the toner adhering from the side of the counter electrode on which the recording material is placed is attached. Charge injection into silica occurs, the charge polarity of the toner is reversed, and the toner flies backward.

Tables 1 and 2 show that the applied voltage is constant (+2 k
V, the electric field formed at this time is kept at 2 × 10 ⁶ V / m), and the data of the flying amount of each pseudo toner when the pulse width of the applied voltage is varied are shown. The amount of silica added to the polyester resin of the toner matrix of each pseudo toner was 1
FIG. 7 shows the relationship between the flying amount of each of the pseudo toners A, B, and C and the pulse width in the case of wt%. As is clear from Tables 1 and 2 and FIG. 7, although there is a slight difference depending on the type of silica, it can be seen that in any of the pseudo toners, almost no flight occurs when the pulse width of the applied voltage is 100 μsec or less. . At this time, each of the pseudo toners A, B,
The charge amount of C was ± 10 μc /
g.

[0037]

[Table 1] (Hereinafter, margin)

[0038]

[Table 2]

As is clear from Tables 1 and 2, the flying amount of each of the pseudo toners A, B, and C was such that the amount of silica added was 3%.
It can be seen that the case where the amount of silica added is 1% is smaller than the case of (1). Therefore, the amount of silica added to toner actually used for image formation is 0.5% to 1%.
%, The flying amount is considered to be almost zero in the case of the toner having the silica addition amount of about 0.5%. Further, since the triboelectric charge of the toner is geometrically separated by silica added thereto, it does not disappear unless there is a charge flying in the air.

Therefore, in order to inject a charge of the opposite polarity into the silica added to the toner, neutralize the triboelectric charge of the toner, and invert the charge polarity of the toner to cause the toner to fly backward. It is considered that about three times the electric charge must be injected when the electric charge is injected into the non-charged pseudo toner and the ink is caused to fly. Considering these points, it can be estimated that the reverse flight of the toner in the actual image forming process starts when the voltage application time to the toner is 1 msec or more. This is the result of shooting the flying state of the actual toner by the high-speed camera described above, that is,
Voltage application time to toner is 1.2 to 3.7 msec
This substantially coincides with the start of the reverse flight of the toner after the elapse.

For example, in the multicolor image forming apparatus shown in FIGS. 11 and 12, the first electrode layer 22 as a toner control member is provided below the developing devices 10, 11, 12, and 13 of the respective colors. Are each stretched in a width of 50 mm in parallel with the rear electrode 23 as a counter electrode member. The first electrode layer 22 has a voltage of +1.2 kV
Is constantly applied. Further, the first electrode layer 22
The ring-shaped electrode and its lead wire formed at
A voltage of 5 V or -50 V is applied. As a result, the gap between the ring-shaped electrode and its lead wire is 05 mm, and the gap between them is 1.8 to 2.5 mm.
A strong electric field of × 10 ⁶ V / m is always formed. In addition, since the moving speed of the rear electrode 23 which also serves as the suction conveyance belt 41 of the paper 54 is 100 mm / sec, the toner of the color for which an image is formed first is exposed to the above-mentioned strong electric field for about 2 msec. Become. Therefore, in this device,
It is considered that sufficient charge injection occurred into the silica added to the surface of the toner, and as a result, a large amount of the toner flies back as described above.

Therefore, in the image forming method according to the present embodiment, the electric field intensity and the application time of the electric field applied between the toner control member 3 and the counter electrode member 2 are controlled to control the counter electrode member 2 or the paper 6. The injection amount of the injected charge having the opposite polarity to the charge polarity of the toner 7 to be injected into the toner 7 adhered thereon was set to a range in which the injected charge did not cause the toner to start flying in the reverse direction. In other words, as shown in FIG. 8, the first toner control member 3 in each color developing device
Rear electrode 23 of electrode layer 22 corresponding to counter electrode member 2
The width W1 of the portion parallel to is reduced. Specifically, the width W
1 was changed to a half width (25 mm) of the conventional width W0 = 50 mm of the part.

As a result, the electric field intensity and the application time of the applied electric field between the first electrode layer 22 and the rear electrode 23 are reduced, and the passing time of the paper 6 in the strong electric field region becomes 1 msec or less. The toner amount decreased to 1/10 or less. This eliminates the reverse flight of the attached toner due to the charge injection into the attached toner. Therefore, in this image forming method, the cleaning interval of the first electrode layer 22 is set to
The ratio can be set to one for every 10 or more prints, and a decrease in print speed when printing 10 or less prints can be eliminated. In addition, in this image forming method, since the toner is prevented from flying backward, the number of times of cleaning of the toner can be reduced, and the cleaning device can have a simple configuration such as a vacuum system.

As another image forming method according to this embodiment, the rear electrode 23 or the rear electrode 23 is formed between a plurality of image forming units as shown in FIGS. An electric field having a polarity opposite to that of the electric field applied by the preceding image forming unit was applied to the toner adhered on the paper 54 on the rear electrode 23. Specifically, as shown in FIG. 9, the rear electrode 2 between the image forming units
3, a neutralizing electrode 103 for neutralizing the charge injected into the toner by the image forming process of the preceding image forming unit is provided to the toner. An electric field having a polarity opposite to that of the electric field applied by the image unit is applied.

Here, the width W2 of the neutralizing electrode 103 along the paper transport direction is set to 20 mm, the applied voltage is set to +2.7 kV, and the charging polarity of the toner is set between the neutralizing electrode 103 and the rear electrode 23. -3.0 × 10 ⁶ V / m of opposite polarity
When the reverse polarity electric field was formed, the reverse flying toner was greatly reduced. In this image forming method, before the attached toner is exposed to the electric charge from the next image forming unit, the toner is injected into the attached toner by the electric field of the opposite polarity applied to the attached toner by the neutralizing electrode 103. Since the charge is neutralized, the backward flight of the attached toner is suppressed. This is because, in FIG. 9, the positive (+) charge injected during 0.5 sec when the toner of each color passes through the first electrode layer 22 having the width W0 is changed by the neutralizing electrode 103 for 0.2 sec. , By injecting a negative (−) charge of the opposite polarity to a considerable extent.

Next, still another image forming method and apparatus according to the present embodiment will be described. In this image forming apparatus, as shown in FIG. 10, the minute opening (toner passage hole 31) facing the rear electrode 23 of the first electrode layer 22 as the toner control member is located in a range excluding the vicinity of the minute opening. A shield electrode 104 for applying a weak electric field having the same polarity as a nearby electric field is provided. Then, the shield electrode 104
Accordingly, a weak electric field having the same polarity as the electric field near the minute opening is applied to the toner adhered on the rear electrode 23 or the paper 54 in a range excluding the vicinity of the minute opening in the image forming unit.
For example, +0.6 kV is applied.

As a result, the electric charge injected into the adhered toner at a portion that does not contribute to image formation is weakened, and the reverse flight of the adhered toner is greatly reduced. This is because the electric field acting on the toner under the shield electrode 104 is weakened, so that the charge injected into the toner when the toner passes through the first electrode layer 22 is reduced, and the reverse of the toner is reduced. It is considered that the flight was suppressed. Here, if a higher voltage is applied to the shield electrode 104, the charge injection into the toner is made zero or the negative charge is injected into the toner to neutralize the positive charge injected in the previous stage. It is also possible to do. However, actually, the lead wire 34 wired to the developing roller 14 side with the 75 μm thick polyimide film of the first electrode layer 22 being
Since a voltage of 50 V is applied, when a high voltage is applied to the shield electrode 104 as described above,
Since there is a possibility that dielectric breakdown may occur between the lead wire 34 and the lead wire 34, practical use is difficult. In addition, the shield electrode 10
By forming the electrode 4 apart from the ring-shaped electrode 34, the influence of the shield electrode 104 on the image forming electric field is reduced, and the image forming is not adversely affected.

In the image forming method and apparatus according to the above-described embodiment, the most basic image forming process has been described as an example. However, this image forming method and apparatus is not limited to the toner charging method and the configuration of the control electrode plate. Can be applied to a direct-toning type image forming method and apparatus in which toner charged by an electric field formed by an image signal voltage is separated from a toner carrier by electrostatic force and toner is caused to fly by the electrostatic force. Needless to say.

Further, in the image forming apparatus according to the above-described embodiment, an example in which a sheet such as paper 6 is used as a recording member and an image is formed by attaching toner onto the recording material has been described. An electrode layer (for example, an aluminum foil layer) that functions as the counter electrode on the back of the paper, in addition to insulators such as paper and paper
May be formed. Further, the counter electrode may be formed of a rotating endless belt-shaped metal thin film, and may be configured to transfer the attached toner to a recording member such as paper.

[0050]

According to the first to sixth aspects of the present invention, by controlling the electric field intensity and the application time of the electric field applied between the control electrode portion and the counter electrode, a polarity opposite to the charging polarity of the attached toner is controlled. Since the reverse flight of the adhered toner due to charge injection into the adhered toner can be eliminated, the number of times of cleaning the adhered toner can be reduced, the image forming speed can be improved, and the cleaning device can be simplified to reduce the cost of the device. There is an excellent effect that it can be reduced.

In particular, according to the second aspect of the present invention, the time during which the toner adhering to the counter electrode or the upper recording member is exposed to a strong electric field is as short as 1 msec or less. This has an excellent effect that the amount of the toner adhering to the adhered toner can be reduced to suppress the backward flight of the adhered toner.

Further, according to the third aspect of the present invention, before the attached toner is exposed to the electric charge by the next image forming unit, the toner is injected into the attached toner by the electric field of the opposite polarity applied to the attached toner. Since the charge can be neutralized, there is an excellent effect that the backward flight of the attached toner can be suppressed.

According to the fourth aspect of the present invention, the electric field applied to the opposite electrode or the toner adhered on the upper recording member in a range excluding the vicinity of the minute opening in the image forming unit is reduced.
Since an electric field having the same polarity as that of the electric field in the vicinity of the minute opening can be obtained, the electric charge injected into the adhered toner at a portion not contributing to image formation can be weakened, and the reverse flight of the adhered toner can be suppressed. effective.

Further, according to the invention of claim 5, a neutralizing electrode is provided, and the counter electrode or the counter electrode on the counter electrode is provided between the plurality of image forming units by the image forming process of the preceding image forming unit. Since an electric field for neutralizing the electric field applied by the preceding image forming unit is applied to the toner adhered on the recording member, the neutralizing electrode is applied before the adhered toner is exposed to the charge by the next image forming unit. Thus, an electric field of opposite polarity applied to the attached toner neutralizes the charge injected into the attached toner, and has an excellent effect that the attached toner can be prevented from flying backward.

According to the sixth aspect of the present invention, the shield electrode is provided, and the opposite electrode or the toner adhering on the upper recording member in the area excluding the vicinity of the minute opening in the image forming unit is provided. Since a weak electric field having the same polarity as the electric field near the minute opening is applied, the electric charge injected into the attached toner at a portion that does not contribute to image formation is weakened, and the reverse flight of the attached toner can be suppressed. Has an effect.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a main part of an image forming apparatus according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a pattern of a control electrode in a toner control member of the image forming apparatus.

FIG. 3 is an enlarged schematic diagram of an image recording unit of the image forming apparatus.

FIG. 4 is a schematic diagram illustrating a flying state of toner in the image forming unit.

FIG. 5 is a schematic diagram of an experimental device for measuring reverse flying toner in the image forming unit.

FIG. 6 is a graph showing a relationship between an applied electric field and a flying amount of toner.

FIG. 7 is a graph showing a relationship between a pulse width of an applied electric field and a flying amount of toner.

FIG. 8 is an enlarged schematic diagram of an image recording unit of the image forming apparatus according to the embodiment.

FIG. 9 is an enlarged schematic diagram of an image recording unit of another image forming apparatus according to the embodiment.

FIG. 10 is an enlarged schematic diagram of an image recording unit of still another image forming apparatus according to the embodiment.

FIG. 11 is an exploded perspective view showing a configuration of a conventional multicolor image forming apparatus.

FIG. 12 is a schematic sectional view illustrating a configuration of an image forming unit of the multicolor image forming apparatus.

[Explanation of symbols]

 Reference Signs List 1 toner carrier 2 counter electrode member 3 toner control member 22 first electrode layer 23 rear electrode 31 toner passage hole 32 control electrode 34 lead wire 103 neutralizing electrode 104 shield electrode

Claims (6)

[Claims] 1. A toner carrier for carrying a toner, a counter electrode facing the toner carrier, and a plurality of minute openings independent of each other or arranged in series between the toner carrier and the counter electrode. One image forming unit for forming a single-color image, or a plurality of image forming units for forming different multi-color images from each other, comprising: a toner control member having a plurality of control electrode portions for controlling toner passage through each minute opening. Using an image unit, a voltage is applied to the control electrode section of the toner control member in accordance with an image signal, so that the toner carried on the toner carrier is selectively caused to fly, and passes through the minute opening. An image forming method for forming a single-color image or a multicolor image by adhering the toner transferred to the counter electrode side onto the counter electrode or a recording member on the counter electrode, wherein the control electrode unit and the control electrode unit By controlling the electric field intensity and the application time of the applied electric field between the counter electrodes, the injection amount of the injection charge of the opposite polarity to the charge polarity of the toner to be injected into the toner attached to the counter electrode or the recording member, An image forming method, wherein the injection charge is set to a range in which the toner does not start flying in the reverse direction. 2. The image forming method according to claim 1, wherein an applied electric field is formed near the minute opening between the control electrode and the counter electrode, which is applied to the toner adhered to the counter electrode or the upper recording member. An application time of an electric field having the same level of strength as that of the image forming method is set to 1 msec or less. 3. A toner carrier for carrying a toner, a counter electrode facing the toner carrier, and a plurality of micro-openings independently or mutually arranged between the toner carrier and the counter electrode. And controlling the toner control member by using a plurality of image forming units for forming different multicolor images, each of the plurality of image forming units comprising a plurality of control electrode portions for controlling the passage of toner through each minute opening. By applying a voltage to the electrode portion in accordance with an image signal, the toner carried on the toner carrier is selectively caused to fly, and the toner transferred to the counter electrode side through the minute opening is moved toward the counter electrode. In an image forming method for forming a multicolor image by adhering to a recording member on an electrode or the counter electrode, between the plurality of image forming units, the counter electrode or An image forming method, wherein an electric field having a polarity opposite to that of the electric field applied by the preceding image forming unit is applied to the toner adhered on the recording member on the counter electrode. 4. The image forming method according to claim 1, wherein an electric field applied to the toner adhered to the counter electrode or the upper recording member in a range excluding the vicinity of the minute opening in the image forming unit is applied to the minute opening. An image forming method, wherein a weak electric field having the same polarity as a nearby electric field is used. 5. A toner carrier for carrying a toner, a counter electrode facing the toner carrier, and a series of a plurality of minute openings which are provided between the toner carrier and the counter electrode and are independent from each other or a series of fine openings. An image forming apparatus comprising a plurality of image forming units for forming different multicolor images, each of the plurality of image forming units comprising a toner control member having a plurality of control electrode portions for controlling toner passage through each minute opening; A neutralizing electrode for neutralizing the charge injected by the image forming process of the preceding image forming unit for the counter electrode or the toner on the recording member on the counter electrode at a position facing the counter electrode between the image units; An image forming apparatus comprising: 6. A toner carrier for carrying a toner, a counter electrode facing the toner carrier, and a plurality of minute openings independently or in series provided between the toner carrier and the counter electrode. One image forming unit for forming a single-color image, or a plurality of image forming units for forming different multi-color images from each other, comprising: a toner control member having a plurality of control electrode portions for controlling toner passage through each minute opening. In an image forming apparatus provided with an image unit, a shield electrode for applying a weak electric field having the same polarity as the electric field near the minute opening is arranged in a range excluding the vicinity of the minute opening facing the counter electrode of the toner control member. An image forming apparatus, comprising: