JPH11165427A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which print particles on a print roller are activated sufficiently to form a high density image and an image can be formed at high speed. SOLUTION: An image forming apparatus comprises a print roller 30 for supporting print particles 38, and a back face electrode 44 for forming an electric field between the print roller 30 and the electrode 44. A head 52 having holes 56 is interposed between the print roller 30 and the electrode 44. The head 52 is provided with two electrodes 58a, 58b arranged closely to the holes 56 in order to increase the field strength thus flying the print particles toward a sheet 8 while passing between the head 52 and the back face electrode 44. Since the print particles 38 are attracted with a stronger force as compared with a case where an image signal is applied only to one electrode, a high density image can be obtained even if the duration of the image signal is short.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for forming an image on a recording medium such as paper by causing the printing material to fly from a holding member for the printing material and adhere to the recording medium.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus, an image is formed on a recording medium such as paper by flying a printing material from a holding member of the printing material and attaching the printing material to a recording medium such as paper. A rotating cylinder that holds the charged printing material, i.e., the printing particles; a back electrode that is arranged at a distance from the rotating cylinder and forms an electric field that attracts the charged printing particles on the rotating cylinder; An insulating substrate having a plurality of holes arranged between the body and the back electrode and having a plurality of holes arranged at predetermined intervals in a direction orthogonal to the rotation direction of the rotating cylinder, and activating the printing particles on the rotating cylinder. There has been proposed one provided with a single flying electrode that flies toward the recording medium through the hole.

[0003]

However, the single flying electrode cannot activate a sufficient amount of the printing material on the rotating cylinder, so that a high-density image is obtained on the recording medium. It was difficult. Further, in order to increase the image forming speed, a pulse signal having a short duration must be applied in a short period, but in such a case, the printing material on the rotating cylinder cannot be sufficiently activated, and the charge amount cannot be reduced. If high printing particles are used, the suction of the printing material by the back electrode must be increased.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention can sufficiently activate a printing material on a printing material holding member, and as a result, can produce a high-density image and can cope with high-speed image formation. It is an object to provide an image forming apparatus. In order to achieve this object, an image forming apparatus according to the present invention includes a printing material holding member that holds a printing material and a portion of the printing material holding member that faces the printing material holding portion and that is located between the printing material holding member and the portion. A back electrode that forms an electric field that attracts the printing material, and the printing material held by the printing material holding member toward a recording medium that passes between the insulating member and the back electrode. To fly through the hole,
At least two flying electrodes for forming an electric field for attracting the printing material were arranged near the holes.

Another embodiment of the image forming apparatus of the present invention has a focusing electrode disposed near the hole and for urging a printing material passing through the hole toward the center of the hole.

[0006]

In this image forming apparatus, at least two flying electrodes are arranged in the vicinity of the hole formed in the insulating member, so that only one flying electrode is provided as in the prior art. The printing material on the holding member can be more strongly and more activated than the image forming apparatus that does not include the printing material, and can fly on the recording medium. As a result, a high-density image can be obtained on a recording medium, and a required-density image can be secured even if a short-duration pulse is applied to the flying electrode in a short cycle. Is possible. In addition, in the case where the focusing electrode is provided in the vicinity of the hole in addition to the flying electrode, the printing material passing through the hole can be focused at the center of the hole, so that a group of flying printing materials can be recorded without being dispersed. It can fly to the medium, resulting in well-defined dots and images.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an image forming apparatus of the present invention indicated by reference numeral 2 as a whole. Image forming apparatus 2
Has a sheet supply station, generally designated 4. The sheet supply station 4 has a cassette 6 which is detachable, and sheets 8 such as paper are stacked and stored therein. The sheet supply roller 10 is disposed on the cassette 6, rotates while contacting the uppermost sheet 8, and sends out the sheet 8 to the inside of the image forming apparatus 2. A pair of timing rollers 12 is disposed near the sheet supply roller 10, and the sheet 8 fed from the cassette 6 is
Is supplied along a sheet path 14 indicated by a dashed line to an image forming station (generally indicated by reference numeral 16) for forming an image of a printing material on the sheet 8. The image forming apparatus 2 also has a fixing station 18 for permanently fixing the image of the printing material to the sheet 8 and a final stacking station 20 for receiving the sheet 8 to which the image of the printing material has been fixed.

Referring to FIG. 2, the printing station 16
Has a printing material supply section indicated generally by reference numeral 24 on the sheet path 14. The printing material supply unit 24 has a container 26, and an opening 28 is formed in a portion of the container 26 facing the sheet passage 14. A printing roller 30 is supported near the opening 28, and is rotatable in the direction of arrow 32. The print roller 30 is made of a conductive material, and is electrically connected to a DC power supply 34. The blade 36 is preferably made of a plate made of rubber or stainless steel, and is arranged in contact with the printing roller 30.

The container 26 is made of printing material or printing particles 38.
Is housed. The print particles 38 are supplied to the outer peripheral surface of the print roller 30 by a supply unit, that is, a supply roller (not shown) accommodated in the container 26, and are conveyed according to the rotation of the print roller 30. The print particles 38 held by the print roller 30 are then conveyed to a contact area between the print roller 30 and the blade 36, where the print particles 38 are brought into frictional contact with the blade 36 and charged to a predetermined polarity.
In the present embodiment, the negatively charged print particles 38 are used. Therefore, the printing roller 30 and the blade 3
Each outer circumferential portion of the print roller 30 that has passed through the contact area with the carrier 6 carries a thin layer of negatively charged print particles 38. Further, as shown in the drawing, the printing roller 30 is
4, a positive voltage is supplied, and the negatively charged print particles 38 are electrically attracted to the print roller 30.

An electrode mechanism, generally designated by the reference numeral 40, is disposed below the printing material supply section 24 beyond the sheet path 14. The electrode mechanism 40 has a support 42 made of an insulating material and a back electrode 44 made of a conductive material. The back electrode 44 is connected to a power supply 46 that supplies a voltage of a predetermined polarity (positive in this embodiment) to the back electrode 44, thereby electrically attracting the negatively charged toner on the print roller 30 to the back electrode 44. I have to do it. But,
The voltage applied from the power supply 46 to the back electrode 44 is held by the printing roller 30 only by the electric field formed between the back electrode 44 and the printing roller 30 by applying a voltage from the power supply 46 to the back electrode 44. Printed particles 38
There is a degree that does not fly.

A printing head, generally designated by the reference numeral 50, is fixed between the printing material supply unit 24 and the electrode mechanism 40 and above the sheet path 14. The print head 50 is a flexible printed circuit board 5 having a thickness of about 100-200 μm.
It is preferable to make it with 2. As shown in FIGS. 2 and 3, the printing area 54 where the printing roller 30 is opposed to the back electrode 44.
The portion of the print head 50 located at about 50 to 200 μm inner diameter, which is substantially larger than the average particle size of the print particles 38 (about several μm to several tens μm).
The holes 56 are arranged at regular intervals at predetermined intervals in a direction orthogonal to the sheet conveying direction.

As shown in FIG. 3, the flexible printed circuit board 52 has three donut-shaped electrodes surrounding each hole 56, that is, a first electrode (first electrode) from the printing roller 30 side to the back electrode 44 side. A first flying electrode) 58a, a second electrode (second flying electrode) 58b, and a third electrode (converging electrode) 58c, which are connected to an image signal output unit 60, and A predetermined signal is applied from the output unit 60 to each of the electrodes 58a, 58b and 58c.

The operation of the printing apparatus 2 configured as described above will be described. First, in the printing material supply unit 24, the printing roller 30 rotates in the direction indicated by the arrow 32 as shown in FIG. The printing particles 38 are supplied to the printing roller 30 and conveyed to a contact area between the blade 36 and the printing roller 30, where the contact with the blade 36 imparts a negative electrostatic charge to the printing particles 38. Thus, as shown in FIG. 3, the outer peripheral portion of the print roller 30 that has passed the contact area carries a thin layer of the charged print particles 38.

At the time of printing, the first electrode 58a and the second electrode 5
8b, a predetermined image signal (positive pulse signal) is applied from the signal output unit 60. As a result, as shown in FIG. 4, the negatively charged charged particles 3 held on the print roller 30 at a position facing the electrode to which the image signal is applied.
8 is electrically attracted to the first electrode 58a and the second electrode 58b, and flies toward the corresponding hole 56 in combination with the attraction force of the back electrode 44.

Next, when the flying printing particles 38 reach the vicinity of the exit of the hole 56, a negative voltage is applied to the third electrode 58c. As a result, the flying printing particles 38 having the negative charge are electrically biased radially inward from the surroundings and converge. Then, the condensed mass of the printing particles 38 is transferred from the sheet supply station 4 to the printing area 54.
The dots are formed on the sheet 8 by adhering to the sheet 8 supplied to the sheet 8. Thus, the dots formed by the converged printing particles 38 have a sharp contour on the sheet 8 and are of high density. In addition, the switching of the voltage applied to the electrodes at the timing described above stops the flying of the printing particles from the printing roller 30.

Then, the sheet 8 to which the printing particles 38 are attached
Is transported to the fixing device 18 where the print particles 38 are heated and permanently fixed on the sheet 8 and finally discharged onto the stack station 20 or catch tray.

As described above, according to the present invention, a positive voltage is applied to the two electrodes 58a and 58b at the same time, and the printing particles 38 at the corresponding positions apply image signals to only one of the electrodes. Since the suction is performed with a larger force than in the case of applying, a sufficient number of printing particles 38 fly to obtain a high-density image even if the duration and period of the image signal (pulse signal) are short. Further, a sufficient amount of print particles can be caused to fly without increasing the voltage applied to the back electrode 44. Further, by applying a voltage having the same polarity as the charged polarity of the printing particles to the third electrode 58c,
The clusters of printed particles can be converged to create well-defined dots and images.

It is not necessary to apply an image signal to the first and second electrodes 58a and 58b at the same time. First, an image signal is applied to the first electrode 58a, and then, after a lapse of a predetermined time, the second electrode 58b May be applied with an image signal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a partial cross-sectional view of the image forming apparatus shown in FIG.

FIG. 3 is an enlarged sectional view of an image forming area in the image forming apparatus shown in FIG.

FIG. 4 is an enlarged sectional view of an image forming area in the image forming apparatus shown in FIG. 1, as in FIG.

[Explanation of symbols]

2 ... image forming apparatus, 24 ... printing material supply unit, 30 ... printing roller, 38 ... printing material, 44 ... back electrode, 50 ... head, 54 ... image forming area, 56 ... holes, 58a, 58b,
58c: first, second, third electrodes, 60: image signal output unit.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Koji Uno 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Keikatsu Shimada Azuchi, Chuo-ku, Osaka-shi, Osaka 2-13-13, Machimachi-cho, Osaka International Building Minolta Co., Ltd. (72) Inventor Satoshi Shibata 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd. (72) Inventor Toshio Yamaki Osaka 2-13-13 Azuchicho, Chuo-ku, Osaka City, Osaka International Building Minolta Co., Ltd.

Claims (2)

[Claims] 1. A printing material holding member for holding a printing material, and an electric field for attracting the printing material is formed between the printing material holding member and a portion of the printing material holding member which holds the printing material. A back electrode; and an insulating member disposed between the printing material holding member and the back electrode, the insulating member having at least one hole facing the portion, and passing between the insulating member and the back electrode. In order to cause the printing material held by the printing material holding member to fly through the hole toward the recording medium to be printed, at least two flying electrodes for forming an electric field for attracting the printing material are provided near the hole. An image forming apparatus, wherein: 2. The image forming apparatus according to claim 1, further comprising a converging electrode disposed near the hole and for urging a printing material passing through the hole toward the center of the hole.