JPH0885227A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable the formation of an image with a sufficient print density by conveying the insulating toner 18 to a position near the control electrode 13 in the electrode array 1 and applying a low control voltage. To do. [Structure] An electrode array 1 having a plurality of openings 12 is arranged between a back electrode body 2 with which an image recording medium 3 abuts and a toner carrying roller 16. When the surface of the toner carrying roller 16 is formed of the conductive porous layer 16b and a part of the surface of the conductive porous layer 16b is brought into contact with the insulating sheet 11 in the electrode array 1, the conductive porous layer 16b is formed. The insulating toner 18 is positively opened by the holes of the quality layer 16b.
As a result, the distance between the surface of the conductive porous layer 16b and the control electrode 13 of each opening 12 can be shortened, because it can be transported to the vicinity,
An image having a sufficient print density can be formed by applying a low control voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an image forming apparatus which can be used in a copying machine, a facsimile machine, a printer, etc., and more specifically, an image forming apparatus for forming an image by flying charged toner by an electric field. It is about.

[0002]

2. Description of the Related Art Heretofore, as one type of image forming apparatus, the applicant of the present invention has previously disclosed, in Japanese Patent Application Laid-Open No. 3-215874, an opening for charged toner by an electrode array having a plurality of openings. An image forming apparatus for controlling passage and forming an image on an image recording medium located on the opposite side of the toner supply means with the electrode array interposed therebetween, wherein the toner is one side of an insulating sheet in the electrode array. A reference electrode is formed on the side facing the supply means, and a control electrode is arranged on each side facing the image recording medium so as to be divided for each opening. It has been proposed that a plurality of rotating toner carriers are planted on the peripheral surface and a blade for contacting the brush to splash the toner into a cloud shape (smoke shape).

[0003]

However, in the image forming apparatus, the region affected by the electric field can be formed only in the narrow space between the reference electrode and the control electrode in the opening of the electrode array. Further, the brush and the blade do not play a role of forming an electric field, but only form a cloud of toner. Moreover, since the location where the cloud of toner is generated is a position away from the opening, the electrode The cloud-shaped toner cannot be positively conveyed and guided into the electric field in the opening between the reference electrode and the control electrode of the array, and the toner concentration in the electric field becomes insufficient, resulting in a sufficient print density. There was a problem that it could not be thickened.

In order to solve this drawback, in order to increase the flying amount of toner and to make the printing density sufficient, the strength of the electric field in the opening is increased, so that the potential difference between the reference electrode and the control electrode is increased. However, the drive circuit must be able to withstand a high voltage, resulting in an increase in manufacturing cost. SUMMARY OF THE INVENTION It is an object of the present invention to achieve these technical problems and to provide an image forming apparatus capable of obtaining a sufficient print density with a low control voltage.

[0005]

In order to achieve the above object, an image forming apparatus according to the invention of claim 1 is provided with an electrode array having a plurality of openings, each opening having a control electrode. Toner supply means for supplying toner to the openings of the electrode array, an image recording medium arranged on the side opposite to the toner supply means with respect to the electrode array, and each control electrode of the electrode array are independently controlled. By doing so, an image forming apparatus comprising control electrode driving means for selectively flying the toner from the toner supply means onto the image recording medium through the opening, the toner supply means also serving as an electrode. It is composed of a conductive porous material,
At least a part of the toner supply unit is configured to come into contact with one surface of an electrically insulating sheet carrying a control electrode in the electrode array.

According to a second aspect of the present invention, the toner supply means in the first aspect is constituted by a toner carrier roller having a conductive porous material at least on the outer peripheral side so as to also serve as an electrode. It is configured such that a part of the outer peripheral surface of the roller and one surface of the electrically insulating sheet near the opening in the electrode array are elastically brought into contact with each other.

[0007]

Next, an embodiment of the present invention will be described. FIG. 1 shows an outline of an image forming apparatus of the present invention. Above the electrode array 1 as toner flow control means, about 1
A cylindrical back electrode roller 2 serving as a back electrode body is rotatably supported by a frame (not shown) with an interval of mm, and is rotated in the direction of arrow A by a drive device (not shown). An image recording medium 3 such as a printing sheet inserted in a gap between the electrode array 1 and the back electrode roller 2 can be conveyed in the direction of arrow B by the sheet feeding device 4. A fixing device 5 including a heating roller 6 and a pressing roller 7 for fixing an image is arranged on the downstream side of the image recording medium 3 in the conveying direction.

The electrode array 1 is attached to the upper surface of a toner case 9 of a toner supply device 8 described later.
Next, the respective components will be described in detail. As shown in FIGS. 1 and 2, the electrode array 1 includes a polyimide insulating sheet 11 as an insulating base material having a thickness of approximately 25 μm and a diameter of approximately 100 μm. A plurality of openings 12 are formed in a row, and control electrodes 13 are formed on the side facing the image recording medium 3 so as to be divided into the openings 12.

That is, for each opening 12 having a round hole shape formed through the insulating sheet 11, an annular electrode portion 13a is provided on the upper side of the insulating sheet 11 along the circumferential edge of each opening 12.
And a lead portion 13b for connecting each electrode portion 13a to the control voltage applying circuit 21 of FIG.
Is formed of a metal such as copper and gold having a thickness of 1 μm. If the thickness of the insulating sheet 11 is too thin, the control electrode 1
Since it becomes difficult to form 3 and handle the electrode array 1 itself, a polyimide resin having a thickness of 25 μm is preferable.

Toner supply device 8 as toner supply means
Is a toner case 9 which also serves as a housing, a toner 18 accommodated in the toner case 9, and a supply roller 15.
And a sponge-like porous substance layer 16b made conductive by adding carbon to the outer periphery of an inner cylinder 16a made of a metal cylinder such as copper or aluminum, for example, carbon-containing porous polyurethane or the like. Conductive toner carrying roller 1
It is composed of 6 etc. The toner carrying roller 16 and the supply roller 15 each having an axis orthogonal to the direction in which the image recording medium 3 is conveyed have substantially the same length, and are rotated in the directions of arrows C and D by a rotation driving device (not shown). To be made.

A part of the outer peripheral surface of the toner carrying roller 16 is
The lower surface of the insulating sheet 11 of the electrode array 1 and the opening 1
It is arranged so as to contact the vicinity of the two rows. A DC power supply 22 is connected between the back electrode body 2 and the inner cylinder 16a of the toner carrying roller 16 so that a high voltage of about +1 kV is applied to the back electrode body 2, and A control voltage application circuit (IC, integrated circuit) 21 is connected between the inner cylinder 16a and the control electrode 13, and a voltage of 0 V or +50 V is applied to the control electrode 13 based on image forming data.

The toner 18 is an insulating toner having an electric insulation property, and is supplied to the surface of the toner carrying roller 16 by the supply roller 15. Since the outer peripheral surface of the toner carrying roller 16 is the sponge-like conductive porous material layer 16b, the toner carrying roller 16 has the same electric potential as a whole including the surface of the toner carrying roller 16 and the toner 18 attached in the minute holes.

Next, the recording operation (printing operation) of the image forming apparatus thus configured will be described. First, the toner carrying roller 16 and the toner supply roller 15 having substantially the same length as that of the toner carrying roller 16 are indicated by arrows C and D in FIG.
Insulating toner 18 sent from toner supply roller 15 inside toner case 9 by rotating in the direction
Are rubbed against the surface of the toner carrying roller 16. The toner 18 carried on the surface of the conductive porous layer 16b of the toner carrying roller 16 and in the minute holes is conveyed toward the electrode array 1 by the rotation of the toner carrying roller 16. The surface of the toner carrying roller 16 is rubbed against the insulating sheet 11 on the lower surface of the electrode array 1 and elastically deformed, and the surface of the toner carrying roller 16 and the electrode array 1 are brought into close contact with each other. At this time, a part of the toner 18 falls off from the toner carrying roller 16, forming a cloud shape and staying in the space in the minute hole of the conductive porous layer 16b below the opening 12. When the toner 18 comes off from the toner carrying roller 16, the toner 1
8 is negatively and greatly charged.

As described above, in a state where the negatively charged toner 18 is accumulated in the space below the opening 12 in the form of cloud, the control electrode 13 corresponding to the image portion corresponds to the image signal in accordance with the image signal. A voltage of + 50V is applied from the control voltage application circuit 21. As a result, in the vicinity of the opening 12 corresponding to the image portion, due to the potential difference between the control electrode 13 and the conductive toner carrying roller 16, an electric force line from the control electrode portion 13a toward the toner carrying roller 16 is formed. . The strength of the line of electric force at this time is proportional to the potential difference and inversely proportional to the distance between the control electrode 13 and the surface of the toner carrying roller 16.

Then, the negatively charged toner 18
Is subjected to an electrostatic force in the direction of higher potential by the line of electric force from the control electrode 13 toward the toner carrying roller 16, and is drawn out so as to pass through the opening 12. The toner 18 thus extracted is further subjected to an electric field formed between the image recording medium 3 and the electrode array 1 by the voltage (+1000 V) applied to the back electrode body 2 to cause the image recording medium 3 to move. The toner 18 flies toward and the toner 18 is deposited on the surface of the image recording medium 3 to form visible pixels.

A voltage of -10 V is applied from the control voltage applying circuit 21 to the control electrode 13 for the non-image portion. As a result, the toner carrying roller 16 and the control electrode 13
An electric field in the opposite direction to the electric field for the image forming portion is formed between the toner carrying roller 16 and the toner 18 on the toner carrying roller 16 and the toner 18 staying in the space below the opening 12. These toners 18 do not pass through the opening 12 due to the electrostatic force directed in the 16 directions.

Further, the opening 1 is formed on the surface of the image recording medium 3.
While one row of toner 18 is formed by the two rows, the image recording medium 3 is conveyed by one pixel in the direction perpendicular to the row of the openings 12 (direction of arrow B in FIG. 1). By repeating such an operation, a predetermined image is formed by the toner 18 on the surface of the image recording medium 3. After that, the toner image is fixed on the image recording medium 3 at the position of the fixing device 5.

In the image forming apparatus constructed as described above, when the insulating toner 18 is used, the toner carrying roller 16 having conductivity and the control electrode 1 in the electrode array 1 are used.
The electrical insulation between the openings 12 and 3 is maintained, and the opening 12 is not dielectrically broken. As described above, in the present invention, the toner 18 carried in the charged state on the surface of the carrier roller 16 having the conductive and porous surface layer 16b, and the electrode array 1 are provided.
The charged toner 18 in the cloud state due to the impact of the surface of the toner carrying roller 16 being rubbed by the insulating sheet 11 in FIG. Since the surface of the toner-carrying roller which is conveyed in a dark state and is elastic and porous such as a sponge is in close contact with the opening 12 of the electrode array 1 so as to be extremely close to the opening 12, the distance from the control electrode 13, in other words, 2 Since the distance between the two electrodes is extremely short, a sufficiently high print density can be obtained even with a low potential difference (control voltage).

Further, by using a drive circuit (IC) having a low output voltage as the control voltage applying circuit 21, the operation of image forming control can be executed, so that the manufacturing cost of the image forming apparatus can be reduced. You can do it. Further, when the thickness of the insulating sheet 11 is reduced in the conventional technique, wrinkles are likely to occur in the electrode array 1 and the influence of wrinkles appears in printing, but as in the present invention, the surface of the toner carrying roller 16 is affected. Is elastic and is brought into close contact with the electrode array, so that the influence of wrinkles of the electrode array 1 can be reduced, and uneven printing density does not occur.

In the present invention, as another example of the surface material of the toner carrying roller 16, electrically conductive metal whiskers, fine metal fibers and conductive metal powder are mixed in a soft sponge-like synthetic resin. It is possible to use a conductive porous material such as a soft silicone rubber resin mixed with carbon or a material. In addition to carbon, a metal filler or an organic conductive substance such as TCNQ (tetracyanoquinodimethane) -TTF (tetrathiafulvalene) complex may be used as the conductive material.

[0021]

As described above, claim 1
According to the invention described in claim 1, an electrode array in which a plurality of openings are formed, each opening having a control electrode, a toner supply unit for supplying toner to the openings of the electrode array, and By independently controlling the image recording medium arranged on the side opposite to the toner supply unit and each control electrode of the electrode array, the toner is selected on the image recording medium from the toner supply unit through the opening. In an image forming apparatus including a control electrode driving unit that causes the toner particles to fly, the toner supply unit is made of a conductive porous material that also serves as an electrode, and one surface of an electrically insulating sheet that carries the control electrode in the electrode array. In addition, since it is configured such that at least a part of the toner supply means is brought into contact with the surface of the conductive toner supply means, the conductive porous material is provided on the surface of the conductive toner supply means. The toner carried in the electrically charged state was rubbed by the electrically insulating sheet in the electrode array and formed into a cloud shape by the impact, and the clouded charged state toner entered the pores of the porous material. Since the surface of the toner supply means, which is elastic and porous such as sponge, is brought into close contact with the opening of the electrode array while being conveyed in the state of high density in the vicinity of the opening, the distance from the control electrode, in other words, 2 Since the distance between the two electrodes becomes extremely short, the remarkable effect that a sufficiently high print density can be obtained even with a low potential difference (control voltage) is exerted.

According to a second aspect of the present invention, the toner supply means is constituted by a toner carrying roller at least the outer peripheral side of which is made of a conductive porous material so as to also serve as an electrode. Since a part of the outer peripheral surface and one surface of the electric insulating sheet near the opening in the electrode array are elastically brought into contact with each other, the toner carried in a charged state on the surface of the conductive toner carrying roller is charged into the electrode. The impact of rubbing with an electrically insulating sheet in the array creates a cloud shape, and the charged toner is transported to the vicinity of the opening with a high density while remaining in the pores on the surface of the porous material. Since the distance between the part of the porous surface of the toner carrying roller made of the elastic conductive porous material and the control electrode in the electrode array can be shortened, the control in the electrode array is suppressed. Also the control voltage applied between the electrodes and the toner carrier roller is a low potential, a marked effect of being able to obtain a sufficiently dense printing density.

Further, since a part of the surface of the sponge-like elastic and porous toner carrying roller is brought into elastic contact with the electrode array, even if the electrode array is not thin plate-like and flat, the opening It is possible to provide an image forming apparatus capable of maintaining an extremely short distance between the surface of the toner carrier roller and the surface of the toner carrying roller and stably printing with a stable density.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an image forming apparatus.

FIG. 2 is a perspective view of an electrode array.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrode array 2 Rear electrode body 3 Image recording medium 8 Toner supply device 11 Insulating sheet 12 Opening 13 Control electrode 16 Toner carrier roller 16b as toner supplying means 16b Conductive porous material layer 18 Insulating toner 21 Control voltage application circuit 22 DC Power supply

Claims (2)

[Claims] 1. An electrode array in which a plurality of openings are formed, each opening having a control electrode, toner supply means for supplying toner to the openings of the electrode array, and the toner for the electrode array. By independently controlling the image recording medium arranged on the side opposite to the supply unit and each control electrode of the electrode array, the toner is selectively transferred onto the image recording medium from the toner supply unit through the opening. In the image forming apparatus including a control electrode driving unit that causes the control electrode driving unit to fly to the surface, the toner supply unit is made of a conductive porous material so as to also serve as an electrode, and is provided on one surface of an electrically insulating sheet that carries the control electrode in the electrode array. An image forming apparatus characterized in that at least a part of the toner supply unit is brought into contact with the toner supply unit. 2. The toner supply means is composed of a toner carrying roller having a conductive porous material at least on the outer peripheral side so as to also serve as an electrode, and a part of the outer peripheral surface of the toner carrying roller and the electrode array. 2. The image forming apparatus according to claim 1, wherein one side of the electrically insulating sheet near the opening is elastically contacted.