JP2000015861A - Direct printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a good image by preventing a missing part of the formed image due to accumulated toner. SOLUTION: This printer comprises a printing particle holding means 30 that holds printing particles 38 each being charged in a predetermined pole, a rear face electrode 44 provided in opposition to the printing particle holding means 30 and a print head 50. The print head 50 is provided between the printing particle holding means 30 and rear face electrode 44 and includes a plurality of holes 56 through which the printing particles 38 can pass and electrodes 68, 70 provided around the holes 56. The printing particles 38 are directly adhered to a printing medium 8 which is conveyed between the rear face electrode 44 and print head 50. The surface of the print head is coated with a compound including fluorine. Or, a surface of a spacer which is provided between the printing particle holding means 30 and print head 50 is coated with a compound including fluorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct printing apparatus used for a color or monochrome copying machine, a printer, a facsimile machine, a micro machine, a multifunction machine thereof, and the like.

[0002]

2. Description of the Related Art US Pat. No. 5,477,250 discloses a direct printing apparatus. In this direct printing apparatus, a toner carrier that holds toner as print particles on the outer periphery, a back electrode facing the toner carrier, and a plurality of holes disposed between the back electrode and the toner carrier are provided. A printing station with a print head having electrodes surrounding these holes is arranged. Further, the back electrode is connected to a power supply, thereby forming an electric field between the toner carrier and the back electrode to suck the toner on the toner carrier and fly through the holes of the print head toward the back electrode. I have. A passage for a sheet as a printing medium is formed between the print head of the printing station and the back electrode.

In the direct printing apparatus, when an on-voltage is applied to the electrode of the print head of the printing station, the toner on the toner carrier flies due to the toner suction force due to the electric field between the toner carrier and the back electrode, and a hole is formed. And adheres on the sheet. When an off-voltage is applied to the electrodes of the print head, the toner suction force does not reach the toner on the toner carrier, and the toner does not fly. When the on / off voltage applied to the electrodes of the print head is controlled based on a desired image signal, an image corresponding to the image signal is printed on a sheet.

In the step of causing the toner to fly, in the print head, the toner flying in a trajectory that does not pass through the hole adheres to the surface on the developing roller side, or the oppositely charged toner adheres to the surface on the sheet passage side. There was a problem of doing. In order to solve this problem, conventionally, as a cleaning means, for example, AC between the print head and the back electrode is used.
By applying a bias, toner attached to the surface of the print head is removed.

[0005]

However, in the above-mentioned cleaning method, it is not possible to remove the dirt on the print head accumulated during the printing operation on the sheet, and it is necessary to remove the toner adhering only after the printing operation is completed. There was a problem that it could not be done. Further, there is a problem that the toner adhered to the surface of the print head on the sheet passage side can be reliably removed, but the toner adhered to the surface on the developing roller side cannot be reliably removed.

Therefore, particularly when an image having a high image ratio, that is, an image in which a large amount of toner needs to be adhered to a sheet, is formed, the surface of the developing roller at the end of the formed image is formed. A phenomenon occurs in which the accumulated toner enters the holes during the printing operation and clogging occurs. Due to such a phenomenon, there is a problem that a portion where toner is not attached to a formed image is generated and a defect occurs.

Accordingly, it is an object of the present invention to prevent a formed image from being lost due to accumulated toner and to form a good image.

[0008]

In order to solve the above-mentioned problems, a direct printing apparatus according to the present invention comprises a printing particle holding means for holding printing particles charged to a predetermined polarity, and a printing particle holding means opposed to the printing particle holding means. A back electrode provided, a print head having a plurality of holes disposed between the print particle holding means and the back electrode, through which the print particles can pass, and an electrode disposed around the holes; In a direct printing apparatus that directly adheres the printing particles to a printing medium conveyed between an electrode and a printing head, the surface of the printing head,
It is coated with a fluorine-containing compound.

Alternatively, a printing particle holding means for holding printing particles charged to a predetermined polarity, a back electrode arranged opposite to the printing particle holding means, and a space between the printing particle holding means and the back electrode A print head having a plurality of holes that are arranged and through which the print particles can pass and an electrode arranged around the holes, and the print particles are transferred to a printing medium transported between the back electrode and the print head. In a direct printing apparatus for direct attachment, a spacer is provided between the printing particle holding means and the print head, and the surface of the spacer is coated with a fluorine-containing compound.

Here, as the fluorine-containing compound,
Polytetrafluoroethylene (PEFT), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), fluorine resins such as tetrafluoroethylene-perfluoroacrylvinylether copolymer (PFA), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVdF), and polyvinyl fluoride (PVF). No.

According to the direct printing apparatus, the surface of the print head or sleeve facing the print particle holding means is coated with the fluorine-containing compound, so that the print particles hardly adhere to these members. As a result, it is possible to prevent these print particles from accumulating and to prevent the print head from being stained, so that the image formed on the printing medium is not stained or defective. Can be prevented.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a direct printing apparatus 2 according to a first embodiment of the present invention. The direct printing apparatus 2 has a sheet supply station indicated by reference numeral 4. The sheet supply station 4 has a cassette 6 in which sheets 8 such as paper are stacked and stored as a medium to be printed. A sheet supply roller 10 is disposed above the cassette 6, rotates while contacting the uppermost sheet 8, and sends out the sheet 8 to the inside of the printing apparatus 2. A pair of timing rollers 12 is arranged near the sheet supply roller 10, and the sheet 8 sent from the cassette 6 is formed of a printing material on the sheet 8 along a sheet path 14 indicated by a dashed line. The image is supplied to a printing station (generally designated by reference numeral 16). The printing device 2 also has a fixing station 18 for permanently fixing the image of the printing material to the sheet 8 and a stack station 20 for receiving the sheet 8 to which the image of the printing material has been fixed.

As shown in FIG.
Has a developing device generally indicated by reference numeral 24 on the sheet passage 14. The developing device 24 has a container 26 in which an opening 28 facing the sheet passage 14 is formed. Inside the container 26 and near the opening 28, a developing roller 30 as a printing material holding means is supported so as to be rotatable in the direction of arrow 32. The developing roller 30 is made of a conductive material and is grounded. On the outer peripheral surface of the developing roller,
A blade 36 is placed in contact with the blade 36,
It is preferably made of a plate made of rubber or stainless steel.

The container 26 contains a printing material, ie, toner particles 38. In the present embodiment, the toner particles 38
A negatively charged one is used.

Below the sheet passage 14, the whole is denoted by reference numeral 4.
The electrode mechanism denoted by reference numeral 0 is the developing roller 30 of the developing device 24.
And are arranged to face. This 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 DC power supply 46 for supplying a voltage of a predetermined polarity (positive in this embodiment) to the back electrode 44, and a voltage of, for example, +1200 volts is applied. Thus, an electric field E is formed between the back electrode 44 and the developing roller 30 so that the negatively charged toner particles 38 on the developing roller 30 are electrically attracted to the back electrode 44. It has become.

A print head, generally designated by the reference numeral 50, is fixed between the developing device 24 and the electrode mechanism 40 and above the sheet passage 14. The print head 50 is preferably made of a flexible printed circuit board 52 having a thickness of about 100-200 μm. As shown in FIG. 2, the portion of the print head 50 located in the print area where the developing roller 30 faces the back electrode 44 has an average particle size of the toner particles 38 (about several μm).
It has a plurality of holes 56 having an inner diameter of about 25 to 200 μm, which is substantially larger than m to 10 μm.

As shown in FIG. 3, in the present embodiment, the holes 56 are equally spaced extending in the direction of an arrow 64 (a direction parallel to the axis of the developing roller 30 and orthogonal to the direction 66 in which the sheet 8 is conveyed). Parallel lines 58, 60 and 62 located at
Are provided along the line, and the print head has a resolution of 600 dpi. The holes 56 on the lines 58, 60 and 62 are formed at equal intervals at a distance D (127 μm in the present embodiment).
(56a) and 56 (56c) are distances (D / D) in different directions with respect to the hole 56 (56b) on the center line 60, respectively.
n) (where n is the number of rows and is 3 in the present embodiment), so that when viewed from the sheet conveying direction 66, the holes 56 appear to be arranged at equal intervals as a whole. It is like that. The distance D and the number of columns are appropriately set according to the resolution.

As shown in FIG. 4, the flexible printed circuit board 52 also surrounds each of the holes 56 and is disposed in the axial direction of the holes 56 in a donut-shaped first electrode 68.
And a second electrode 70. The first electrode 68 is disposed on one side facing the developing roller 30, and the second electrode 70
Are arranged on the side facing the back electrode.

The first electrode 68 is electrically connected to the first driver 72 via the printed wiring 74, and the second electrode 70 is connected to the second driver 72.
The driver 72 is electrically connected to the driver 76 via a printed wiring 78.
8 and the second electrode 70 are configured to transmit image signals. The first driver 72 and the second driver 76 are connected to the controller 8 for outputting image data created by the printing apparatus.
0 is electrically connected.

The image signals transmitted to the first electrode 68 and the second electrode 70 include a DC component voltage constantly applied to these electrodes and image data from the controller 80 for forming dots on the sheet 8. And the voltage of the pulse component applied to these electrodes in response to

More specifically, in the present embodiment, for the first electrode 68, for example, the base voltage V1 (B) of the DC component is about -50 volts, and the pulse voltage V1 (P) of the pulse component is about +300. There is as a bolt. Second electrode 7
For 0, for example, the base voltage V2 of the DC component
(B) is about -100 volts, the pulse voltage V of the pulse component
2 (P) is about +200 volts.

The developing roller 3 of the print head 50
On the surface on the 0 side, a fluororesin layer 100 formed by coating a fluororesin which is a fluorine-containing compound is provided. PET, PCTFE, F
EP, PFA, ECTFE, PVdF, PVF and the like can be mentioned. Here, these fluororesins are characterized by having special non-adhesiveness and low abrasion, in addition to heat resistance, chemical resistance, electrical insulation and the like.

Next, the operation of the direct printing apparatus 2 having the above configuration will be described.

In the printing station 16, as shown in FIG. 2, the developing roller 30 is driven to rotate in a direction indicated by an arrow 32. The toner particles 38 are supplied to the developing roller 30 and conveyed to a contact area between the blade 36 and the developing roller 30, where a negative electrostatic charge is applied to the toner particles 38 by contact with the blade 36. Thus, as shown in FIG. 4, the outer peripheral portion of the developing roller 30 that has passed through the contact area holds a thin layer of the charged toner particles 38.

When the toner does not fly, the print head 50 receives a first voltage 68 and a second voltage V2 (B) of about -50 volts and a base voltage V2 (B) of about -100 volts, respectively. 70. Therefore, the negatively charged toner particles 38 on the developing roller 30 are
8 and the second power supply 70, and accumulate on the developing roller 30 without flying toward the hole 56.

The controller 80 outputs image data corresponding to an image to be reproduced to the first driver 72 and the second driver 76. In response to the image data, the first driver 72 and the second driver 76 form a pair of first electrodes 68.
And the second electrode 70, the pulse voltage V1 (P) (about +300
Volts) and pulse voltage V2 (P) (about +200 volts)
Is applied. As a result, the toner particles 38 at the portion of the developing roller 30 facing the electrode to which the pulse voltage is applied
Is electrically attracted to the first electrode 68 and the second electrode 70.

Next, when the toner particles 38 reach the vicinity of the first electrode 68 and the second electrode 70, the voltages applied to the first electrode 68 and the second electrode 70 are pulsed at respective timings. Switching from V1 (P), V2 (P) to base voltages V1 (B), V2 (B). As a result, the toner particles 38 propelling the holes 56 are urged radially inward from the surroundings by the first and second electrodes 68 and 70 to which the base voltages V1 (B) and V2 (B) are applied, respectively. Have converged.

At this time, some of the toner particles 38 fly in an orbit that does not pass through the hole 56 of the print head 50 as in the related art. However, in the present embodiment, since the fluororesin layer 100 is provided on the surface of the print head 50 on the side of the developing roller 30, the toner particles 38 whose trajectory is deviated may adhere to the surface of the print head 50. Instead, it enters the hole 56 so as to slide by electric suction, and is urged radially inward from the surroundings by the first and second electrodes 68 and 70 to converge.

Then, the condensed mass of the toner particles 38 adheres to the sheet 8 supplied from the sheet supply station 4 to the printing area 54, and an image is formed on the sheet 8. The above-described second electrode 70 is provided mainly for the purpose of converging the lump of the toner particles 38. Therefore, the second electrode 70 may be omitted as necessary.

The sheet 8 on which the image has been formed is conveyed to a fixing station 18 where the toner particle layer is heated and permanently fixed on the sheet 8, and finally discharged onto a stack station 20 or a catch tray.

As described above, in the direct printing apparatus 2 of the present invention, the surface of the print head 50 on the side of the developing roller 30 is coated with the fluorine-containing compound. It becomes difficult to adhere to the surface. Therefore, the accumulation of such toner particles 38 can be prevented. In particular, when an image having a high image ratio is formed, the accumulated toner particles 38 enter the holes 56 and clogging occurs. The inconvenience of causing a defect in the formed image can be reliably prevented. As a result, a good image can be formed.

FIGS. 5 to 7 show modifications of the direct printing apparatus 2 of the first embodiment. In the direct printing device 2 of FIG.
The print head 50 differs from the first embodiment only in that the fluororesin layer 100 is provided on the surface on the sheet passage 14 side. This makes it difficult for the toner particles 38 charged to the opposite polarity to adhere to the surface of the print head 50 on the sheet passage 14 side, so that accumulation of the toner particles 38 can be prevented in the same manner as described above.

In the direct printing apparatus 2 shown in FIG.
At 0, the fluororesin layers 100 are formed on both surfaces of the developing roller 30 and the sheet passage 14. FIG.
In the direct printing apparatus 2 shown in FIG.
Fluororesin layers 100 are formed on both surfaces of the developing roller 30 and on the inner peripheral surface of the hole 56. In this way, the print head 50 can be provided with toner particles 38 on any surface.
Can be prevented from adhering, so that a better image can be formed.

FIG. 8 shows a direct printing apparatus 2 according to the second embodiment. The second embodiment is different from the first embodiment in that a spacer 90 is provided between the developing roller 30 and the print head 50, and the fluororesin layer 100 is formed on the surface of the spacer 90. Are different.

The printing station 16 includes a sleeve 30a as a holding member for printing material and a driving roller 30b.
Is provided. Sleeve 3
Reference numeral 0a is an endless shape made of a conductive material such as nickel or nylon having a thickness of 0.15 mm and a diameter of 20 mm. The drive roller 30b is
a and is rotatably supported in the direction of arrow 32. The drive roller 30b has an outer diameter smaller than the inner diameter of the sleeve 30a, whereby a slack portion 31 is formed in the sleeve 30a as shown in FIG. It comes into contact. The drive roller 30b is made of a conductive material and is grounded. Note that the sleeve 30a may be grounded.

The spacer 90 is made of stainless steel, PE
It is formed of a material such as T or PEN. Spacer 90
Is provided on the upper surface of the print head 50 on the developing roller 30 side, and a slit 92 extending in the main scanning direction (a direction perpendicular to the paper surface) is provided at a position facing the portion of the print head 50 where the hole 56 is formed. Are formed. This spacer 9
The slack portion 31 of the sleeve 30 a of the developing roller 30 is in contact with the upper surface of the developing roller 30, and faces the slit 92 in a flat state. For this reason, the distance S between the sleeve 30a and the print head 50 is the same as that of the above-described embodiment.
It is kept constant regardless of the eccentricity and rattling of b.

In this embodiment, the surface of the spacer 90 on the side of the developing roller 30 and the slit 9
By coating the inner peripheral surface of No. 2, the fluororesin layer 100 is formed on the surface.

In the direct printing apparatus 2 of the second embodiment,
The voltage applied to the first electrode 68 and the second electrode 70 is changed from the pulse voltages V1 (P) and V2 (P) to the base voltage V1.
(B) and V2 (B), the developing roller 3
The toner particles 38 held in the sleeve 30 a are guided through the slits 92 into the holes 56 of the print head 50, and push the holes 56. At this time, since the sleeve 90 is provided on the developing roller 30 side of the print head 50,
The toner particles 38 do not accumulate on the surface of the print head 50. Further, in the sleeve 90, since the fluororesin layer 100 is formed on the surface,
Accumulation of the toner particles 38 on the surface of itself can be prevented.

Although the above embodiment has been described with respect to a monochrome direct printing apparatus having a single developing device, the present invention relates to a tandem type color direct printing apparatus in which a plurality of printing stations are arranged in a sheet conveying direction. Can also be applied.

In the illustrated embodiment, the printing station 1
In No. 6, the printing material used is a one-component system using only the toner particles 38, but the printing material can also be applied to a two-component system having a toner carrier.

Further, as the printing particle holding means, a hard roller sleeve and a flexible sleeve are applied, but the printing roller holding means can also be applied to a double roller type.

Further, although the electrodes (holes) formed in the print head 50 are provided in three rows along the longitudinal direction of the developing roller 30, at least one row may be provided. When a plurality of rows are provided, the pitch of the holes 56 may be set according to the required resolution.

As described above, the present invention has been described with reference to the specific embodiments. However, it is obvious that modifications and variations may be made without departing from the scope of the invention described in the claims. .

[0045]

EXPERIMENTAL EXAMPLE The present inventor conducted an experiment under the following conditions in order to confirm the effect of the direct printing apparatus 2 of the first embodiment shown in FIGS.

Fluororesin: Modified TFE paint (TC enamel) Binder resin type Film thickness: 30 μm Baking temperature: 180 ° C. Equipment setting conditions; System speed: 38 mm / sec Distance between developing roller surface and print head surface: 80 μm Hole diameter: 100 microns Total number of holes: 2480 dots (A4 width)-arranged in 6 rows Developing roller potential Vr = 0 (volt) Control electrode potential Printing Vb = 350 (volt) Non-printing Vw = 0 (volt) Back electrode potential VBE = 1300 (volt) One line printing time Ttotal = Tb (Vb application time) + Tw (Vw application time) where Tb = 700 μsec Tw = 1530 μsec toner; volume average particle diameter 8 μm (negatively chargeable toner) Printing station; 1-component developing unit using nylon (resistance 1 × 10E6Ω.m) sleeve

Under the above-mentioned conditions, when one sheet of a chart having an image ratio of 100% (so-called black solid in which all areas are painted black) is printed, several defects that are not problematic in use with the conventional apparatus are obtained. In contrast to this, the direct printing apparatus 2 of the present invention was able to print a good image without any loss. Further, in the case where ten sheets are continuously printed, conventionally, several tens or more places are lost and cannot be used. On the other hand, in the direct printing apparatus 2 according to the present invention, only a few places that do not cause a problem in use are used. Images could be printed.

[0048]

As is apparent from the above description, in the direct printing apparatus of the present invention, since the surface of the print head or the sleeve is coated with the fluorine-containing compound, the printing is performed on the print head by the characteristics of the fluorine-containing compound. Since particles are prevented from adhering and accumulating, even in an image having a high image ratio, occurrence of image defects or the like due to toner contamination can be prevented, and good image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a direct printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a printing station.

FIG. 3 is a partially enlarged plan view of a print head.

FIG. 4 is an enlarged sectional view showing a print head, a developing roller, and a back electrode.

FIG. 5 is an enlarged sectional view showing a modification of the direct printing apparatus according to the first embodiment.

FIG. 6 is an enlarged sectional view showing another modification of the direct printing apparatus according to the first embodiment.

FIG. 7 is an enlarged sectional view showing another modification of the direct printing apparatus according to the first embodiment.

FIG. 8 is an enlarged sectional view of a direct printing apparatus according to a second embodiment.

[Explanation of symbols]

2 ... printing device, 8 ... sheet (medium to be printed), 16 ... printing station, 30 ... developing roller (print particle holding means), 34 ... power supply, 38 ... toner particles (print particles), 4
4 ... Back electrode, 46 ... Power supply, 50 ... Print head, 56 ...
Holes, 68: first electrode, 70: second electrode, 90: spacer, 100: fluororesin layer.

Continued on the front page (72) Inventor Hirokatsu Shimada 2-13-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. (reference) 2C162 AE74 AE84 AJ02 CA02 CA12 CA24 2H029 AE02

Claims (2)

[Claims] 1. A printing particle holding means for holding printing particles charged to a predetermined polarity, a back electrode arranged to face the printing particle holding means, and a printing material holding means disposed between the printing particle holding means and the back electrode. A print head having a plurality of holes that are arranged and through which the print particles can pass and an electrode arranged around the holes, and the print particles are transferred to a printing medium transported between the back electrode and the print head. A direct printing apparatus for directly attaching, wherein a surface of the print head is coated with a fluorine-containing compound. 2. A printing particle holding means for holding printing particles charged to a predetermined polarity, a back electrode arranged to face the printing particle holding means, and a printing electrode holding means between the printing particle holding means and the back electrode. A print head having a plurality of holes that are arranged and through which the print particles can pass and an electrode arranged around the holes, and the print particles are transferred to a printing medium transported between the back electrode and the print head. A direct printing apparatus for directly attaching, wherein a spacer is provided between the printing particle holding means and a print head, and the surface of the spacer is coated with a fluorine-containing compound.