JP2000185429A - Direct recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner particles on a recording roller from dropping to an edge part of a hole on a substrate and at the upstream side in a transfer direction of the toner. SOLUTION: The apparatus includes a recording roller 30 for holding and transferring charged toner particles 38 in a transfer direction, a back electrode 44 opposite to the recording roller 30 for electrostatically attracting the toner particles 38, a substrate 50 of an insulating material which is arranged between the recording roller 30 and back electrode 44 so as to form a path for a recording sheet 8 between the substrate and the back electrode 44 and which has a plurality of holes 56 where the toner particles 38 can path, a plurality of control electrodes 58 disposed in the periphery of each hole 56 of the substrate 50 for controlling toner particles 38 held by the recording roller 30 to fly to the back electrode 44 upon receipt of selective impression of a predetermined voltage, and restraint electrodes set at the upstream side in the transfer direction for each hole 56 of the substrate 50 for restraining the toner particles 38 held by the recording roller 30 from flying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for recording an image on a recording sheet by causing recording particles to fly and directly attaching to a recording sheet such as paper.

[0002]

2. Description of the Related Art A conventional recording apparatus is disclosed in U.S. Pat. No. 5,477,250. This recording apparatus has a rotating cylindrical toner holding member for holding charged toner particles on the outer peripheral surface, and a back electrode spaced from the toner holding member. The back electrode is electrically connected to a power supply, and forms an electric field for electrostatically attracting charged toner particles on the toner holding member toward the back electrode.
An insulating plate having a plurality of holes through which toner particles can pass is disposed between the toner holding member and the back electrode. The insulating plate has a ring-shaped electrode surrounding the hole.

In the above recording apparatus, when a voltage corresponding to the image data is applied to the electrode, the toner particles at a position facing the electrode on the toner holding member are peeled off and fly to the corresponding hole, and pass through the hole. Then, the image adheres to the recording sheet, and an image corresponding to the image data is recorded on the recording sheet.

[0004]

However, in the above recording apparatus, when the toner particles are caused to fly toward the hole by applying a voltage to the electrode, the toner holding member corresponds to the ring-shaped electrode larger than the hole. Since an electric field is formed between the toner particles, toner particles are peeled off in a region larger than the size of the hole on the toner holding member. Some of the separated toner particles do not fly into the holes but fall to the edge of the holes on the insulating plate. To continuously use the toner particles dropped on the edge of the hole and located on the upstream side of the toner holding member in the toner conveying direction for the next image formation, the voltage applied to the electrodes is turned off to insulate the toner particles. It is necessary to temporarily return the toner particles on the conductive plate to the toner holding member, and there is a problem that the image forming speed is reduced by the time required for the return.

Further, when the toner particles are returned to the toner holding member from the insulating plate in this way, the toner particles are unevenly adhered to the toner layer compared to the uniform toner particle layer before flying. When the toner particle layer in the disturbed state is used for image formation, there is a problem that the uniformity of image formation density is impaired.

Further, when an attempt is made to obtain a dark gradation by increasing the voltage application time to the electrode, if the toner particles on the upstream side of the toner holding member with respect to the hole have already been separated, Since the toner flying amount to the hole immediately becomes the saturation density without increasing in proportion to the voltage application time, the maximum density could not be sufficiently obtained, and it was difficult to obtain a wide gradation.

[0007]

In order to solve the above-mentioned problems, a direct recording apparatus according to the present invention comprises a holding member for conveying charged recording particles in a conveying direction while holding the recording particles, and a holding member which faces the holding member. A back electrode for electrostatically attracting the recording particles, and a recording medium disposed between the holding member and the back electrode so as to form a passage between the back electrode and the recording particles. A substrate made of an insulating material having a plurality of holes through which the recording particles are arranged around each of the holes in the substrate and selectively received a predetermined voltage to be held by the holding member. A plurality of control electrodes for controlling the flight toward the back electrode; and a flight of the recording particles held on the holding member, provided on the substrate on the upstream side in the transport direction with respect to the holes. A suppression electrode deterrence to, those having a.

In the direct recording apparatus of the present invention, it is preferable that each of the control electrodes has a shape in which an upstream portion in the transport direction is missing. In this case, the upstream portion of each of the control electrodes may be completely missing, or the upstream portion of each of the control electrodes may be formed thinner than other portions.

In the direct recording apparatus according to the present invention, it is preferable that a lead-out line for applying a voltage to each of the control electrodes on the substrate is provided downstream in the transport direction.

Further, in the direct recording apparatus of the present invention, the above-mentioned suppression electrode may be provided in common for a plurality of holes.

[0011]

According to the direct recording apparatus of the present invention, since the flight suppression electrode is provided on the upstream side of the hole in the predetermined direction, the electric field acting on the holding member on the upstream side of the opposing portion of the hole is weak. That is, the recording particles held on the holding member do not peel or fly before reaching the opposing portion of the hole.
This eliminates the need for returning the recording particles once dropped on the substrate to the holding member when performing subsequent image formation as in the related art, so that the time required for continuous dot image formation is reduced, and the image formation speed is reduced. Can be speeded up.

Further, since the recording particles do not separate from the holding member until the recording particles reach the opposed portion of the hole, the recording particles on the holding member when used for image formation can maintain a uniform state, As a result, the supply amount of the recording particles used for forming each dot can be made uniform, and an image having a uniform density without unevenness can be formed.

Further, at the moment when the voltage is applied to the control electrode, not only the opposing portion of the hole but also the recording particles on the upstream side can be prevented from peeling off from the holding member, so that the voltage application time to the control electrode can be reduced. If the length is made longer, it is possible to create a state in which the recording particles fly continuously toward the holes in proportion thereto. This enables the highest density dot imaging,
A wide gradation can be obtained.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a direct recording apparatus of the present invention indicated by reference numeral 2 as a whole. The recording device 2 has a sheet supply station indicated generally by the reference numeral 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 recording 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 a recording station (generally indicated by reference numeral 16) for forming an image composed of recording particles on the sheet 8. The recording device 2 also comprises a fixing station 18 for permanently fixing the image of recording particles and a final stacking station 20 for receiving the sheet 8 on which the image of recording particles has been fixed.
And

In this embodiment, an example in which a toner image is directly formed on the recording sheet 8 as a recording medium from the recording station 16 has been described. It is not limited to. For example, the toner image may be formed on the intermediate transfer member (for example, an insulating belt) from the recording station 16 and the toner image may be transferred from the intermediate transfer member to a recording sheet. In this case, the intermediate transfer member may be regarded as a recording medium.

Referring to FIG. 2, the recording station 16
Has a recording particle supply section indicated generally by reference numeral 24 on the sheet passage 14. The recording particle supply unit 24 has a container 26, in which an opening 28 facing the sheet passage 14 is formed. A recording roller (holding member) 30 is supported near the opening 28 so as to be rotatable in the direction of arrow 32. The recording roller 30 is made of a conductive material, and is electrically grounded via 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 recording roller 30. The recording roller 30 may be directly grounded without passing through the DC power supply 34.

The container 26 contains recording particles, that is, toner particles 38. The toner particles 38
The recording roller 30 is supplied to the outer peripheral surface of the recording roller 30 by a supply roller (not shown) provided therein, and is conveyed as the recording roller 30 rotates. Subsequently, the toner particles 38 held by the recording roller 30 are transported to a contact area between the recording roller 30 and the blade 36, where the toner particles 38 are brought into frictional contact with the blade 36 and charged to a predetermined polarity. In the present embodiment, the toner particles 38 that are negatively charged are used. Therefore, the outer peripheral surface of the recording roller 30 that has passed through the contact area between the recording roller 30 and the blade 36 carries the negatively charged toner particles 38 in a uniform thin layer. As shown in the figure, the recording roller 30 is supplied with a positive voltage from a power supply 34, thereby electrically adsorbing the negatively charged toner particles 38 to the recording roller 30. When the recording roller 30 is directly grounded, the toner particles 38 are held on the recording roller 30 by a mirror image.

Behind the sheet passage 14 and below the recording particle supply unit 24, an electrode mechanism indicated generally by reference numeral 40 is arranged. 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, whereby the negatively charged toner on the recording roller 30 is electrostatically charged toward the back electrode 44. It is made to be sucked. However, the voltage applied from the power supply 46 to the back electrode 44 does not cause the toner particles 38 held on the recording roller 30 to fly by only the electric field formed between the back electrode 44 and the recording roller 30. It is as size.

A substrate, generally designated by the reference numeral 50, is fixed between the recording particle supply unit 24 and the electrode mechanism 40 and above the sheet passage 14. The substrate 50 has a thickness of about 100
Preferably, it is made of a flexible printed circuit board 52 made of an insulating material of about 200 μm. As shown in FIGS. 2 and 3,
The portion of the substrate 50 where the recording roller 30 is located in the recording area 54 facing the back electrode 44 has a size that is substantially larger than the average particle size of the toner particles 38 (about several μm to about ten several μm). A plurality of holes 56 having an inner diameter of 200 μm
have. These holes 56 are uniformly arranged at predetermined intervals in a direction orthogonal to the sheet conveying direction.

As shown in FIG. 3, the flexible printed circuit board 52 has a control electrode 58 and a toner flying suppression electrode 64 embedded around each hole 56. As shown in FIG. 4A, the control electrode 58 is located on the upstream side of the conventional ring-shaped electrode 59 (see FIG. 4D) in the toner particle transport direction by the recording roller 30 (hereinafter simply referred to as the upstream side). Is a C-shaped shape completely missing. The control electrode 58 is connected to an image signal output unit 60 via a lead-out line 66, and a predetermined voltage is applied to the control electrode 58 from the signal output unit 60. In the example of FIG. 4, the toner flying suppression electrode 64 is provided on the upstream side of the hole 56. This toner flying suppression electrode 64
Is grounded without passing through a power supply, for example, and prevents or reduces the generation of an electric field (hereinafter, referred to as a peeling electric field) that encourages the toner particles to peel from the recording roller 30 on the upstream side of the hole 56. . The toner flying suppression electrode 64 may be grounded via a power supply having a polarity opposite to the polarity (negative in this embodiment) of the toner particles 38.

In this embodiment, the control electrode 58 is formed in a C-shape by omitting the upstream portion.
As shown in the figure, the two control electrodes 5 divided on both sides of the hole 56 completely lacking not only the upstream part but also the downstream part thereof.
8a and 58b, or a control electrode in which the upstream portion of the conventional ring-shaped electrode 59 is partially thinned by cutting off the upstream portion as shown in FIG. 58c.

Next, the operation of the recording apparatus 2 will be described. In the recording particle supply section 24, as shown in FIG. 2, the recording roller 30 rotates in the direction of arrow 32. Toner particles 38
Is supplied to the recording roller 30 and is conveyed to a contact area between the blade 36 and the recording roller 30, where a negative electrostatic charge is given to the toner particles 38 by friction with the blade 36. Thus, as shown in FIG. 3, the outer peripheral portion of the recording roller 30 that has passed through the contact area holds the charged toner particles 38 in a uniform thin layer state.

During non-image formation, a negative base voltage is applied to the control electrode 58. As a result, the negatively charged toner particles 38 on the recording roller 30 are removed from the control electrode 5.
8 and is stably held on the recording roller 30 without flying toward the hole 56.

At the time of image formation, a voltage is applied from the signal output unit 60 to the control electrode 58 according to the image to be formed. This voltage forms an electric field between the control electrode 58 and the recording roller 30, and the action of the electric field causes the negatively charged toner particles 38 held on the recording roller 30 to be combined with the suction force of the back electrode 44. It is more strongly attracted electrostatically, is separated from the recording roller 30, and flies toward the corresponding hole 56.

At this time, the conventional ring-shaped control electrode 59
In the case of (FIG. 4D), an electric field is formed between the recording roller 30 and the ring-shaped control electrode 59 larger than the hole 56, so that as shown in FIG. Then, the toner particles 38 are separated from the recording roller 30 in a region larger than the size of the hole 56. Of the separated toner particles 38, the toner particles 38 held at the position on the recording roller 30 facing the holes 56 pass through the holes 56 and adhere to the sheet 8 to form dots 62. The toner particles 38 held at a position on the recording roller 30 facing the control electrode 59 fall to an edge portion of the hole 56 of the substrate 50 and an upstream portion 51. In order to continuously use the toner particles 38 which have fallen on the edge portion 51 of the hole 56 for forming the next dot, as shown in FIG.
It is necessary to once return the toner particles 38 dropped on the substrate 50 to the recording roller 30 by turning off the voltage application to the recording roller 30, and a time required for this recovery (hereinafter, referred to as a toner recovery time) takes, for example, about 100 μsec. .
This toner recovery time imposes a heavy burden on high-speed image formation of at most 200 μsec, which is the time required for one-dot image formation.

Then, as shown in FIG.
After the toner particles 38 that have fallen on the recording roller 30 return to the recording roller 30, the next voltage is applied to the ring-shaped control electrode 59 to form the next dot 62.
Since the toner particles 38 fall on the edge 51 of the recording roller 30, the operation of returning the toner particles 38 to the recording roller 30 and then performing the next dot image is repeated. As described above, since the toner recovery time is required for each dot image formation, the conventional ring-shaped control electrode 59 has a problem that the image formation speed is reduced. Further, since the toner particle layer on the recording roller 30 after the toner recovery is non-uniform and disturbed, if the toner particle layer in the disturbed state is used for the next image formation, the uniformity of the image forming density is impaired. There was also a problem.

In a recording apparatus having a low image forming speed, the next dot image can be formed after the recording roller 30 is sufficiently rotated after forming one dot, so that the toner return time has no effect. In reality, since high-speed image formation is required, the toner recovery time cannot be ignored.

On the other hand, the control electrode 58 of the present embodiment has a C-shaped shape lacking the upstream portion in the toner conveying direction. The peeling electric field becomes weak. The state in which the toner peeling electric field has become weak is shown in the graph of FIG.
In this graph, the horizontal axis indicates the position on the substrate 50, positions 0 to 130 correspond to the holes 56, and 0 or less correspond to the holes 5
6 is upstream of the toner particle transport direction. on the other hand,
The vertical axis indicates the toner peeling electric field on the recording roller 30. In this graph, 36 completely surrounds the periphery of the hole 56.
In the case of the 0-degree ring-shaped control electrode 59, as shown by the dotted line in the graph, since the electric field is larger on the upstream side than the position facing the hole 56, the toner particles 38 at the position facing the hole 56 At the same time, the toner particles 38 on the upstream side are separated from the recording roller 30. Similarly, in the case of the C-type control electrode 58 that surrounds the periphery of the hole 56 within a range of 300 °, similarly, as shown by a dashed line in the graph, the peeling electric field becomes larger on the upstream side than the position facing the hole 56. Therefore, the toner particles 38 at the upstream side of the recording roller 30 together with the toner particles 38 at the position facing the hole 56 are separated. On the other hand, in the case of the C-type control electrode 58 that surrounds the periphery of the hole 56 within a range of 240 °, as shown by the solid line in the graph, the peeling electric field is weaker on the upstream side than the position facing the hole 56. The recording roller 3
The toner particles 38 on 0 are not peeled off until the toner particles 38 come to a position facing the hole 56. In addition to the above, since the toner flying suppression electrode 64 is provided on the upstream side of the hole 56, formation of a peeling electric field on the upstream side of the hole 56 is efficiently prevented or reduced, and The toner particles have holes 56
Is reliably prevented from being separated on the upstream side.

As shown in FIG. 7A, the control electrode 58 is formed in a C-shape in which the upstream portion is chipped, and the peeling electric field on the recording roller 30 on the upstream side of the hole 56 is weakened. When a voltage is applied to 58 to turn it on, the toner particles 38 separate from the recording roller 30 and fly toward the holes 56 only when they come to the position opposing the holes 56, and the toner particles 38 passing through the holes 56 8 and form dots 62. At this time, since the toner particles 38 do not fall on the substrate 50 and on the upstream side of the edge of the hole 56, it is not necessary to consider the toner recovery time. Therefore, as shown in FIG.
By immediately applying the next voltage to 8 and turning it on, the next dot image formation can be performed, thereby increasing the image formation speed. FIG. 7B shows a state in which the dots 62 are formed so as to partially overlap each other. However, this is not the case in practice.
The conveying speed of the sheet 8 can be made higher than before so that the sheets 2 and 62 are formed adjacent to each other without overlapping, thereby achieving a higher image forming speed.

Further, since the toner particles 38 do not separate from the recording roller 30 until the toner particles 38 come to a position facing the hole 56, the toner particles 38 on the recording roller 30 when used for image formation come into contact with the blade 36. The same uniform state as when passing through the area is maintained. As a result, the supply amount of the toner particles 38 used for forming each dot becomes uniform, and it is possible to form an image with uniform density without unevenness.

Further, at the moment when a voltage is applied to the control electrode 38, not only the position facing the hole 56 but also the toner particles 38 on the upstream side can be prevented from peeling off from the recording roller 30. By lengthening the voltage application time, a state can be created in which the toner particles 38 fly continuously toward the holes 56 in proportion thereto. As a result, dot image formation with the highest density becomes possible, and a wide gradation can be obtained.

In the direct recording apparatus 2, the toner flying suppression electrodes 6 are individually provided corresponding to the holes 56 of the substrate 50.
4, the toner flying suppression electrode 64 may be provided in common to the plurality of holes 56 as shown in FIG. By adopting such a configuration, the toner flying suppression electrode 6
The number of lead wires for grounding 4 can be reduced, and the circuit configuration can be simplified.

As shown in FIG. 9, it is preferable that the lead-out line 66 for applying a voltage to the control electrode 58 is drawn out to the downstream side of the substrate 50 in the toner particle transport direction. This causes a slight toner particle peeling electric field to be formed between the lead-out wiring 66 and the recording roller 30. Therefore, when the toner particle 38 is pulled out to the upstream side, the peeling / flying of the toner particles 38 occurs on the upstream side of the hole 56. Because it can cause it.

In the direct recording apparatus 2 described above, one electrode 58 is provided for one hole 56 of the substrate 50. In the present invention, the hole 56 is provided on the back electrode 44 side of the control electrode 58. It can be applied to the case where two electrodes are provided.
When a voltage having the same polarity as that of the toner particles 38 is applied to the second electrode, the aggregation of the toner particles 38 passing through the holes 56 can be converged by an electric repulsive force. Can be formed. This second
Is farther from the recording roller 30 than the control electrode 58, the toner particle peeling electric field formed by applying a voltage to the second electrode has a negligible effect. Therefore, the second electrode may have a ring shape surrounding the entire circumference of the hole 56, but in order to more reliably prevent the toner particles from peeling and flying upstream of the hole 56,
Like the control electrode 58, the second electrode may have a shape lacking the upstream portion.

Further, the second electrode is divided into two right and left electrodes, and two or three dots are separated by one hole 56 by turning on or off the left and right second electrodes (so-called dot). The present invention can be applied to a recording apparatus that performs (deflection control).

Further, the recording particle supply section 24 is not limited to the above-described one, and any type of developing device used in the electrophotographic image forming apparatus can be used in place of the recording particle supply section.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a direct recording apparatus according to a preferred embodiment.

FIG. 2 is a schematic sectional view of a recording station.

FIG. 3 is a partially enlarged view of a substrate, a recording roller, and a back electrode when a thin layer of toner particles is carried on the recording roller.

4A is a diagram illustrating a shape of a control electrode according to the present embodiment, FIGS. 4B and 4C are variations of the shape of the control electrode, FIG.
(D) is a diagram showing a conventional ring-shaped control electrode.

FIGS. 5A to 5C are diagrams showing a process of forming dots on a sheet by flying toner particles on a recording roller using a conventional ring-shaped control electrode.

FIG. 6 is a graph showing a peeling electric field on a recording roller when a ring-shaped control electrode and two types of C-type control electrodes are used.

FIGS. 7A and 7B are diagrams showing a process of forming dots on a sheet by flying toner particles on a recording roller using a C-type control electrode of the embodiment. FIGS.

FIG. 8 is a diagram showing a modification of the toner flight suppression electrode.

FIG. 9 is a diagram illustrating a state in which a lead wire of a control electrode is drawn to a downstream side in a toner conveying direction.

[Explanation of symbols]

2: Direct recording device, 8: Recording sheet, 30: Recording roller (holding member), 38: Toner particles (Recording particles), 44:
Back electrode, 50: substrate, 56: hole, 58: control electrode, 6
4 ... toner flying suppression electrode, 66 ... lead-out wiring.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Shibata 2-3-13-1 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. (reference) 2C162 AE04 AE25 AE31 AE74 AE81 AF14 AF19 AH40 CA02 CA03 CA12 CA13 CA19 CA24 2H029 AA01 AB03 AB08 AB10 AB16 AB21 AC02 AC05

Claims (6)

[Claims] 1. A holding member for conveying charged recording particles in a conveying direction while holding the recording particles, a back electrode facing the holding member for electrostatically attracting the recording particles, and a back electrode. A substrate made of an insulating material having a plurality of holes through which the recording particles can pass, the substrate being arranged between the holding member and the back electrode so as to form a passage through which a recording medium passes; A plurality of control electrodes disposed around and controlling the recording particles held by the holding member to fly toward the back electrode by selectively receiving a predetermined voltage application; and A direct recording apparatus, comprising: a suppression electrode provided on the upstream side in the transport direction with respect to each hole, for suppressing flying of recording particles held by the holding member. 2. The direct recording apparatus according to claim 1, wherein each of the control electrodes has a shape in which a portion on an upstream side in the transport direction is missing. 3. The direct recording apparatus according to claim 2, wherein an upstream portion of each of the control electrodes is completely missing. 4. The direct recording apparatus according to claim 2, wherein an upstream portion of each of the control electrodes is formed thinner than other portions. 5. The direct recording apparatus according to claim 1, wherein a lead wire for applying a voltage to each of the control electrodes is provided on the substrate at a downstream side in the transport direction. 6. The direct recording apparatus according to claim 1, wherein the suppression electrode is provided commonly to a plurality of holes.