WO2001064446A1

WO2001064446A1 - Print head, and image forming device using the same

Info

Publication number: WO2001064446A1
Application number: PCT/JP2001/001535
Authority: WO
Inventors: Katsutoshi Ogawa
Original assignee: Matsushita Electric Industrial Co., Ltd.; Array Ab
Priority date: 2000-02-29
Filing date: 2001-02-28
Publication date: 2001-09-07
Also published as: AU2001236008A1

Abstract

A print head and an image forming device using the same, wherein in order to prevent occurrence of short-circuits between deflecting electrodes and to prevent occurrence of color mixing so as to improve reliability in recording, disposed on both surfaces of an insulation board (12) constituting a print head (4) are control electrodes (7) and deflecting electrodes (10a, 10b), and a toner passage hole (6) is formed which has a taper shape such that the inner diameter of the toner passage hole (6) on the control electrode (7) side is larger than the inner diameter on the deflecting electrode (10a, 10b) side. Also, the print head (4) is disposed such that the control electrode (7) is opposed to the toner carrier (2). Further, a print head (4) having a toner passage hole (6) of the above-mentioned shape is installed such that at least it corresponds to a toner carrier (2) disposed downstream in the direction of transfer of an image receiving member (5).

Description

Satsuki Itoda ¾ Print head and image forming apparatus using it (Technical field)

The present invention relates to a print head applied to a copier, a facsimile, a printer, and the like, and an image forming apparatus using the same, and more particularly to a print head controlled by an image signal from a developer carrier to a back electrode. The present invention relates to an image forming apparatus that controls the flight of a developer to an image receiving member and forms an image by attaching the developer to an image receiving member located between a print head and a back electrode.

(Background technology)

In recent years, with the improvement of personal computer capabilities and the advancement of network technology, there has been an increasing demand for printers and copiers that can handle a large amount of documents and have a high processing capability that can also handle single documents. . However, an image forming apparatus capable of outputting satisfactory high-quality black-and-white or color documents and having a high processing speed is under development and is expected to appear.

As one of them, conventionally, Japanese Patent Publication No. 44-263333 and US Patent No. 3,689,935 (see Japanese Patent Publication No. 60-207747) And developing a developer such as toner onto an image receiving member such as a recording paper or an intermediate image carrying belt by the action of an electric field, as disclosed in Japanese Unexamined Patent Application Publication No. 9-500842 An image forming technique of a direct printing method is known.

The principle of this method will be described with reference to FIGS. 10 and 11. FIG. 10 is a schematic diagram showing this image forming apparatus. For example, a print head 4 for controlling toner flight between a toner carrier 2 and a back electrode 3 that carries a negatively charged toner 1 and moves. The image receiving member 5 is arranged and transported between the print head 4 and the back electrode 3. The print head 4 has an insulating member as a base material, and has a plurality of toner passage holes 6 through which the toner passes, and a control electrode 7 disposed around each toner passage hole 6.

The toner carrier 2 is grounded, and the back electrode 2 is connected to a back electrode power supply 8. The control electrode 7 is connected to a control electrode power supply 9. The control electrode power supply 9 responds to external image signals. The pulsed control voltage is output repeatedly.

If the polarity of the control voltage supplied from the control electrode power supply 9 to the control electrode 7 is the same as the toner charging polarity, the toner on the toner carrier 2 exerts an electrostatic adhesion force in the direction of the toner carrier 2 Therefore, the toner 1 does not fly from the toner carrier 2. When the polarity of the control voltage supplied from the control electrode power supply 9 to the control electrode 7 is opposite to the toner charging polarity, the toner 1 acts on the toner carrier by the action of electrostatic adhesion toward the control electrode 7. Desorb from 2. Further, by supplying a voltage having a polarity opposite to the charged polarity of the toner to the back electrode 3 from the power supply 8 for the back electrode, an electrostatic adhesion force toward the back electrode 3 acts on the toner 1. As a result, the toner passes through the toner passage hole 6 and adheres to the image receiving member 5 transported between the print head 2 and the back electrode 3.

Further, as disclosed in Japanese Patent Publication No. 59-38908 and the Journal of the Institute of Electrophotography Vol. 36, No. 2 (issued in 1997), pages 114 to 117, etc., the flying toner is deflected and converged. Thus, a plurality of dots can be formed from one passage hole.

Fig. 11 is a principle diagram showing the state of deflection, (a) is a diagram showing the direction of deflection of toner 1, (b) is a time chart of the voltage (V7) applied to the control electrode 7, ( c) shows a time chart of the voltage (VIOb) applied to the right deflection electrode 1 Ob, and (d) shows a time chart of the voltage (VIOa) applied to the left deflection electrode 10a.

On the back electrode 3 side of the print head 2, the deflection electrodes 10 a and 10 b divided into two are arranged symmetrically with respect to the center of the through hole 6. Further, different voltages are applied to the two divided deflection electrodes 10a and 10b from the deflection power supplies 11a and 11b. As a result, the symmetry of the electric field around the toner passage hole 6 is broken, and the flight trajectory of the toner passing through the toner passage hole 6 is deflected from the center of the toner passage hole 6. As a result, the toner 1 lands on the image receiving member 5 at a position away from the central axis of the toner passage hole 6, and a dot is formed. Further, by applying the same voltage to the deflection electrodes 10a and 10b, the toner 1 lands on the center of the toner passage hole 6 and a dot is formed.

As described above, by controlling the deflection voltage applied to the deflection electrodes 10a and 10b, dots can be formed at a plurality of positions on the image receiving member 5 from one toner one passage hole 6. Therefore, a high-resolution toner image can be formed on the image receiving member 5 even if the number of the toner passage holes 6 provided in the print head 2 is small. 0

11 in FIG. 11, the voltage (Vh) applied to the deflecting electrode 10a disposed on the left side of the toner passage hole 6 when viewed in the direction orthogonal to the conveying direction of the image receiving member 5 is the bias on the right side. This shows a case where the voltage is relatively higher than the voltage (VL) applied to the counter electrode 10b. As a result, the flight trajectory of the negatively charged toner 5 is deflected to the left side by an electrostatic field (hereinafter, an electric field formed between the deflecting electrodes is abbreviated as a deflecting electric field) generated between the deflecting electrodes 10a and 10b. You. ② in the figure shows a case where the same voltage (Vc) is applied to both the deflection electrodes 10a and 1 Ob. As a result, the charged toner moves straight toward the image receiving member 5 as indicated by an arrow, and reaches a position on the image receiving member 5 opposite to the position of the toner passage hole. Further, (3) in the figure shows a case where the voltage (Vh) applied to the right deflection electrode 1 Ob is relatively higher than the voltage (VL) applied to the left deflection electrode 10a. As a result, a deflection electric field in the direction opposite to that of the left part of the figure is formed on the ίdeflection ΐί! Poles 10 a, 10 bR; j, and the flight trajectory of the charged toner 5 is deflected to the right.

The above-described deflection process of the flying trajectory of the toner, namely, the leftward deflection, the leftward deflection, the rightward deflection, and the rightward deflection are repeated successively with the transfer of the image receiving member 5, and the toner image is transferred onto the image receiving member 5. A toner image is formed. In the following description, each of the above ①, ②, and ③ is abbreviated as left deflection ί¾, ϋ'ί advancing, right deflection Γ-, respectively. In addition, the cycle in which the deviation from [1] to [3] is repeated from (1) to (3) is abbreviated as the entire deflection process cycle. In addition, the two dots formed on the image receiving member 5 by the left deflection 鍾 and the Zong energy を are changed to the left deflection “separation, and right deflection: The distance between the two dots formed is abbreviated to the French U distance.

However, the liiij image forming apparatus having the above configuration has the following two points, j i.

First, the first problem is an electrical short circuit between the deflection electrodes. In other words, when the potential difference between the two deflecting electrodes becomes ignited at the two deflecting electrodes facing each other across the through hole, a discharge phenomenon occurs between the two deflecting electrodes, and the print head is narrowed to the deflecting electrode. The problem is that the electric circuit is destroyed. Particularly in a high environment, the air insulation property of air is reduced, and an electrical short circuit is likely to occur. Also, if toner adheres to the periphery of the toner passage hole, an electric field is concentrated on the toner particles and an electric short circuit is likely to occur.

In order to suppress this electrical short circuit, there are two approaches: one is to increase the distance between the deflection electrodes, and the other is to increase the thickness of the insulating layer covering the deflection electrodes. However, In the case of the countermeasure, there is a problem that the intensity of the deflecting electric field is reduced and the trajectory of the toner cannot be sufficiently deflected. In the latter case, a thick insulating layer must be coated around the deflection electrode. As a result, the insulating layer covering the periphery of the control electrode is inevitably thicker, and the distance from the toner carrier to the control electrode is increased, so that the electric field formed between the toner carrier and the control electrode is reduced. The strength is also weakened. As a result, there is a problem that the toner detachment responsiveness, in which the toner detaches from the toner carrying member, decreases as the electric field strength between the two decreases.

The second problem is that, in the image forming apparatus using the above-described configuration, if the toner carriers of a plurality of colors are arranged along the conveying direction of the image receiving member, regular coloring cannot be performed. It is. This is caused by the following phenomena: In other words, toner having a polarity opposite to the normal charging polarity is mixed in the toner that has landed on the image receiving member on the upstream side in the image receiving member transport direction among the toner carriers of a plurality of colors. Also, if the back surface voltage applied to the back electrode is high, charges may flow into the toner particles through the image receiving member, inverting the negative electrode properties of the toner. When the opposite polarity toner is present on the image receiving member in this manner, the opposite polarity toner flies from the image receiving member toward the print head at the position facing the print head for the second color or later, which is a so-called reverse flight of toner. Problems arise. For this reason, a different color toner (hereinafter, abbreviated as a different color toner), which is referred to as the upstream toner carrier, adheres to the print head disposed on the downstream side. Of these, toner of another color that has entered the toner passage hole cannot be easily removed from the toner passage hole and remains in the passage hole as it is. When printing is performed in such a state, another color toner mixed with the normal color toner and stopped in the passage hole also blows out to the image receiving member, and as a result, an image in which a color different from the F-standard color is mixed is received. It is formed on the member.

In order to prevent such a problem from occurring, it is conceivable to reduce the opening diameter of the toner passage hole in order to prevent the toner particles of different colors from entering the toner passage hole. However, in the above-mentioned T-stage, since the toner particles detached from the toner carrier are prevented from entering the toner passage hole, not only the image density is reduced, but also the toner accumulates in the toner passage hole once. In such a case, there is a problem that the toner passage hole is easily clogged.

The present invention has been made in view of the above-described problems, and has as its object to reduce the possibility of an electrical short circuit between deflection electrodes and to suppress color mixing, and to provide a print head and an image form using the same. _e

0

It is an object of the present invention to provide an apparatus. (Disclosure of the Invention)

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention includes: a developer carrying member that carries and transports a developer; an image receiving member that is disposed to face the developer carrying member and receives the developer; An insulating substrate provided between the developer carrier and the image receiving member, the insulating substrate having a plurality of developer passage holes through which the developer carried by the developer carrier passes toward the image receiving member; A first electrode disposed on one surface of the substrate around each developer passage hole, and a first electrode disposed on the other surface of the insulating substrate around each developer passage hole, with the developer passage hole interposed therebetween. A print head including a second electrode group divided into a plurality of parts, a first voltage supply unit configured to supply a predetermined voltage to the first electrode according to an external image signal, A second voltage supply that supplies a different voltage to that of the second electrode group An image forming equipment and means, said Purintoe' de developer passage hole are those having a shape as to inhibit electrical shorting between the second electrode group.

As a result, even if the deflection electrodes are arranged in the print head as the second electrode group with the developer passage hole interposed therebetween, even if different voltages are applied to the respective deflection electrodes, an electrical short circuit between the two is suppressed. As a result, the discharge breakdown of the print head and the inflow of excessive current into the electric circuit that supplies the voltage to the deflection electrode can be suppressed.

Further, the image forming apparatus of the present invention is characterized in that the inner diameter of the developer passage hole in the print head on the second electrode group side is smaller than the inner diameter on the first electrode side.

As a result, when the deflecting electrode is used as the second electrode group, the insulating layer around the deflecting electrode is formed thick, so that even if the electric insulation of air is reduced in a high-humidity environment or the like, it is formed thick. The electrical resistance between the deflection electrodes is not greatly reduced by the insulating layer. As a result, the electric short circuit between the deflection electrodes, which occurs significantly in a high-humidity environment or the like, is suppressed by the configuration of the present invention. At the same time, when the control electrode is used as the first electrode, the amount of developer passing through the developer passage hole increases, so that printing with high image density can be performed.

Further, in the present invention, it is preferable that the print head is arranged such that the first electrode faces the developer carrier.

As a result, the first electrode is closer to the developer carrier than the second electrode group. „

0

The detachment of the developer particles from the surface of the developer carrier is performed in response to the voltage applied to the first electrode without being affected by the voltage applied to the second electrode group, so that an image on the image receiving member is formed. The reproduction will be performed faithfully.

Further, the inner wall surface of the developer passage hole is preferably tapered so that the inside diameter of the developer passage hole on the second electrode group side is smaller than the inside diameter of the first electrode side. As a result, since the corners of the step where the developer easily accumulates do not exist in the developer passage hole, even if the developer comes into contact with the inner wall of the developer passage hole, the developer does not stop inside the developer passage hole without stopping. You can have. As a result, an image without clogging of the developer passage hole by the developer is formed. In addition, since the distortion of the deflection electric field due to the accumulated charge of the developer is suppressed, a high-precision image having no variation in the deflection distance is formed.

Further, a mask having an opening corresponding to the developing hole is placed on the surface of the insulating substrate on which the first electrode is formed, and a laser beam is irradiated from the mounting side of the mask. It is preferable to use the print head formed by the above.

This makes it possible to easily form a developer passage hole having a tapered cross-sectional shape in the print head, thereby providing a low-cost image forming apparatus.

Furthermore, the opening provided in the mask preferably has an inner diameter larger than the inner diameter of the first electrode.

This allows the laser beam to be reflected by the first electrode even if the inner periphery of the first electrode is not covered by the mask. Even if the placement accuracy when placing on the head is reduced, a developer passage hole along the inner diameter of the first electrode is formed in the print head. This eliminates the need for a precise print head manufacturing process, and can provide an inexpensive image forming apparatus. An image forming apparatus having another configuration according to the present invention includes an image receiving member that receives a developer image, and is disposed so as to face the image receiving member and along the transport direction of the image receiving member. A plurality of developer carriers for carrying and transporting the developer, and a developer carrier disposed between the developing carrier and the image receiving member, wherein the developer carried by the developer carrier passes toward the image receiving member. A plurality of print heads each including an insulating substrate having a plurality of developer passage holes formed therein, and control electrodes disposed around the respective developer passage holes on the negative surface of the insulating substrate. A voltage supply stage for supplying a predetermined voltage to the control electrode according to an image signal from the unit. ^ PT / JP01 / 01535 An image forming apparatus using a print head, wherein the development of the print head arranged at least in correspondence with the developer carrying member located at the downstream side in the conveying direction of the image receiving member. The developer passage hole has a shape that suppresses the intrusion of the developer from the image receiving member into the developer passage hole.

As a result, the developer used in the image formation on the upstream side does not fly back and adhere to the inner wall of the developer passage hole of the print head used for the next color image formation. Therefore, when forming an image of the next color, toner of another color is not mixed and discharged from the developer passage hole, so that an image formed by only the normal color toner is received in an area formed only by the normal color toner. A toner image is formed on the member. For this reason, both color images of the color balance that should be obtained are faithfully reproduced. Further, since the π diameter of the developing passage on the side of the developer carrier is provided widely, sufficient developing particles for color development are supplied onto the image receiving member, and the passage hole is also clogged by the developing agent. Can be prevented.

Further, in the configuration of the image forming apparatus t according to the present invention, at least the developer passage hole of the print head arranged corresponding to the developer carrier positioned on the downstream side in the transport direction of the image receiving member includes an image receiving member. The inner diameter on the member side is smaller than the inner diameter on the developer carrying member side.

As a result, with a very simple configuration, the invasion of the other color J image agent into the developer passage hole due to the reverse flight can be easily suppressed.

Further, according to the present invention, the inner surface of the developing passage is tapered so that the inner surface of the developing passage is smaller than the inner surface of the developing support. Is preferred.

As a result, since the corners of the step where the developer easily accumulates do not exist in the developer passage hole, even if the developer comes into contact with the inner wall of the developer passage hole, the developer does not stop inside the developer passage hole without stopping. You can have. As a result, both images are formed without clogging of the developer passage hole by the developer. In addition, when a print head having a deflection electrode is used, the distortion of the deflection electric field due to the accumulated charge of the developer can be suppressed, so that a high-precision image without variation in the deflection distance can be formed.

Further, at least the developer passage hole of the print head arranged corresponding to the developer carrying member located on the downstream side in the conveying direction of the image receiving member is provided on the insulating substrate facing the developing member. It is preferably formed by mounting a mask on the g-plane and irradiating a laser beam from the mounting side of the mask.

Further, the opening provided in the mask corresponding to the developer passage hole of the print head preferably has an inner diameter larger than the interval between the control electrodes.

This allows the control electrode to reflect laser light even if the periphery of the inner edge of the control electrode is not covered by the mask, so that the position accuracy of the opening provided on the mask and the mask can be printed. Even if the Elf degree at the time of printing is lowered, a developer passage hole along the inner diameter of the control electrode is formed in the print head. This eliminates the need for a precise printhead manufacturing process, and reduces the cost of image forming equipment. ¾ can be provided.

Further, the print head according to the present invention includes an insulating S plate, a plurality of through holes passing through the insulating plate, and a through hole on one surface of the insulating plate. And a second polarizer, which is divided into a plurality of parts around the through-hole on the other side of the green substrate and sandwiches the through-hole. A printed head provided with an inner diameter in the vicinity of the second electrode group of the through holes, which is smaller than an inner diameter of the first electrode side.

As a result, it is possible to provide a print head in which an electrical short is hardly generated by the polarized electrode even when the polarized electrode is arranged as a two-pole group.

Further, in the print head according to the present investigation, it is preferable that the inside of the through hole has a tapered shape.

As a result, the step on the level where the developer easily accumulates does not exist in the through-hole. Can pass through. As a result, an image is formed in which the penetration by the developer is uniform. In addition, since the distortion of the deflection electric field due to the charge of the accumulated developer is suppressed, a high-precision image without variation in the deviation distance is formed.

Further, the through-hole is formed on the surface of the insulating substrate on which the first electrode is formed, corresponding to the through-hole.

By placing a mask having a Π ^portion; Boar it is preferable from the mask of the placement side and is formed Ri by the irradiation with laser. Thus, a through hole having a tapered cross-sectional shape can be easily formed in the print head, so that a low-cost print head can be provided.

Further, it is preferable that the opening provided in the mask corresponding to the through hole has an inner diameter wider than the interval between the first electrodes.

This allows the laser beam to be reflected by the first electrode even if the periphery of the inner edge of the first electrode is not covered by the mask, so that the position accuracy of the opening provided in the mask and the mask can be printed. Even if the placement accuracy when placing on the head is reduced, a through-hole along the inner diameter of the first electrode is formed in the print head. As a result, a precise print head manufacturing process is not required, so that an inexpensive print head can be provided.

(Simplified explanation of figure tffi)

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

FIG. 2A is a plan view of the print head surface on the toner carrier side according to the embodiment. C FIG. 2B is a plan view of the print head surface on the back electrode side according to the embodiment. FIG. 3A is a time chart of a voltage waveform applied to the control electrode according to the embodiment.

FIG. 3B is a time chart of a voltage waveform applied to one deflection electrode according to the embodiment.

FIG. 3C is a time chart of a voltage waveform applied to the other deflection electrode according to the embodiment.

FIG. 3D is a diagram illustrating a state in which the flying direction of the toner according to the embodiment is sequentially deflected.

FIG. 4A is a cross-sectional view of the vicinity of the toner passage hole in the print head according to the embodiment.

FIG. 4B is a cross-sectional view of the vicinity of a toner passage hole of a conventional print head.

FIG. 4C is a cross-sectional view of the vicinity of a toner passage hole of a conventional print head.

FIG. 5 is a diagram illustrating a procedure for manufacturing a toner passage hole according to the embodiment.

FIG. 6 is a cross-sectional view illustrating a schematic configuration of the color image forming apparatus according to the embodiment.

FIG. 7 is a diagram illustrating movement of toner between the print head and the image receiving member according to the embodiment. ^.

FIG. 8 is a diagram illustrating the movement of toner between a print head of a conventional configuration and an image receiving member.

FIG. 9 is a cross-sectional view illustrating a print head according to the example.

FIG. 10 is a schematic diagram showing a conventional image forming apparatus.

FIG. 11A shows the direction of deflection.

FIG. 11 (b) is a time chart of the voltage applied to the control electrode.

FIG. 11 (c) is a time chart of the voltage applied to the right deflection electrode.

FIG. 11D is a time chart of the voltage applied to the left deflection electrode.

(Best mode for carrying out the invention)

The best mode for carrying out the present invention will be described as an example with reference to the drawings.

(Example 1)

FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a toner. In Example 1, a magnetic toner using a polyester resin as a binder resin was used. In addition, a binder resin used for the toner is preferably a styrene-acrylic copolymer, a styrene-butadiene copolymer, an epoxy resin, or a mixed resin thereof. In addition, a magnetic toner containing a magnetic powder may be used. In this case, the magnetic powder may be an alloy containing an element exhibiting ferromagnetism such as iron, cobalt, and nickel, such as fluoride and magnesite. And compounds are effective. The holding power of the magnetic powder is suitably from 100 to 50 Oe, and the amount of the magnetic powder to the resin is suitably from 20 to 40% by weight based on 100 parts by weight of the toner particles. In addition, it is preferable to add 0.1 to 5% by weight of a metal salt such as silica (Si02), titanium oxide (Π02), or stearic acid to control the flowability of the charge control agent and the toner. In particular, silica greatly affects fluidity and can prevent toner from clogging a toner passage hole of a print head, which will be described later.Since silica has a small diameter and a high chargeability, it can be used for electric power. It is strongly pulled and easily attaches to the inner wall surface of the through hole. However, the toner adhering to the inner wall surface of the toner passage hole serves as an opening for promoting the movement when passing through the toner passage hole, so that clogging of the hole can be prevented. Silica has a BET specific surface area of 100 to 300 m ² / g by nitrogen adsorption ^ Some are appropriate. If silica having a small diameter of less than 100 m ² / g is used, sufficient fixability cannot be obtained because the resin is mixed so as to be shredded.

Next, reference numeral 2 denotes a toner carrier for carrying and transporting the toner 1. The toner carrier 2 was an aluminum cylinder having an outer diameter of 20 mm and a thickness of 1 mm, and the toner carrier 2 was configured to be grounded. The material of the toner carrier 2 may be made of a metal or alloy such as iron, a member obtained by winding a rubber material such as silicon rubber or urethane rubber around a core shaft, or the like, in addition to aluminum. Further, in addition to the roller shape, a belt shape or a drum shape may be used. In addition to the grounding of the toner carrier 2, a DC voltage or an AC voltage may be applied. When an AC voltage is applied, a DC voltage may be superimposed.

The toner 1 is formed on the toner carrier 2 with a regulating blade (not shown). The regulating blade is formed of an elastic member such as urethane or silicon, and has a hardness of 40 to 80 degrees (JISK631A scale).

The free end length (length of the portion protruding from the mounting member) of the regulating blade that regulates the toner layer with respect to the toner carrier 2 is 5 to 15 mm. The linear pressure applied to the toner carrier 2 by the regulating blade is preferably 5 to 40 g / cm. One to three layers of toner are formed on the toner carrier 2 by pressing the regulating blade. The regulating blade is used by applying a float state, a ground state, or an iS current or an AC voltage. In the first embodiment, the regulating blade is floated in a floating state. The toner 1 is sandwiched between the toner carrier 2 and the regulating blade, and receives a small charge from the toner carrier 2 to receive a charge there and charge.

The toner 1 is supplied to the toner carrier 2 by a supply roller (not shown). The supply roller is formed by forming a synthetic rubber such as foaming urethane to a thickness of about 2 to 6 mm on a metal shaft such as iron (diameter 8 mm in this embodiment). The hardness of the surface of the supply roller is 30 degrees (measured with a JISK 6301 mm scale method when processed into a roller). The amount of biting into the toner carrier 2 is preferably in the range of 0.1 to 2 mm. The supply roller is used by being grounded or applied with a DC or AC voltage. The supply roller controls the amount of toner supplied to the toner carrier 2 and assists in charging the toner 1. The polarity of the charged toner may be either positive or negative. However, in Example 1, a negatively charged toner was used. In addition, the charge control agent added to the toner is charged so that the charge iq / m of the toner is _5 to 130 ° C / g. ^ It is preferable to adjust the type and amount. If the absolute value of the charge amount is lower than the above, toner of the opposite polarity increases. As a result, the toner adheres to the periphery of the toner passage hole, causing clogging of the toner passage hole, or distorting the deflection electric field, so that the toner cannot be deflected in a normal direction. Also, when the absolute value of the charge amount is larger than the above, the image force between the toner particles and the toner carrier becomes stronger, and even when a predetermined voltage is applied to the control electrode, the toner particles are separated from the toner carrier. You will not be able to leave.

3 is a back electrode. In the first embodiment, the back electrode 3 is formed of a metal plate, but a film in which a conductive filler is dispersed in a resin may be used. In this case, the resistance of the film is preferably about ^{102 to 101ϋΩ} · cm. The toner image is recorded by directly attaching toner 1 on back electrode 3 or by placing an image receiving member on back electrode 3 and attaching toner on the image receiving member to form a toner image. May be. Further, the rear electrode 3 may be processed into an endless film shape as described above, and the toner may be directly recorded on the film and then transferred to the image receiving member. The distance between the back electrode 3 and a print head described later is preferably in the range of 50 to: L0000 / m.

Reference numeral 8 denotes a back electrode voltage supply for supplying a constant voltage to the back electrode 3. The voltage applied to the back electrode 3 is preferably from +500 V to +200 V, and more preferably from +800 V to +150 V. If the voltage applied to the back electrode 3 is higher than the above range, the print head 2 and the back electrode 3 may be electrically short-circuited and both may be discharged and destroyed. If the applied voltage is lower than the above range, the force for electrostatically attracting the toner 1 to the back electrode 3 is weakened, and sufficient toner is absorbed to the image receiving member 5 to print a high-density dot. 1 can not be done.

4 is a print head. Numeral 12 is an insulating base material constituting the print head 4, and its thickness is suitably from 10 to 100 / m, and materials such as polyimide and polyethylene terephthalate are preferable. Reference numeral 13 denotes an insulating protective layer, and the appropriate thickness is 5 to 30 microns. Of course, the material and thickness of the insulating base material 12 and the insulating protective layer, the number of constituent layers, and the like are not limited thereto, and may be arbitrarily designed as long as the structure according to the present invention described later.

Reference numeral 6 denotes a toner passage hole that passes through the print head 4. As will be described later, processing for forming the toner passage hole 6 in the print head 4 is performed by drilling with an excimer laser, a YAG laser, a C02 laser, or the like, and then performing an etching process for forming an electrode. Do this ^ Is preferred. A plurality of the toner passage holes 6 are arranged along the longitudinal direction of the print head 4 to form a toner passage hole array. The print head 4 described in this embodiment has two rows of toner passage holes.

Reference numeral 7 denotes a control electrode provided on the surface of the base material 12 on the side of the toner carrier 2 so as to surround the toner passage hole 6. Further, 10 a and 10 b are deflection electrodes provided around the toner passage hole 6 on the surface of the base material 12 on the back electrode 3 side. The control electrode 7 and the deflection electrodes 10a and 10b are made of a copper foil or an aluminum foil having a thickness of about 2 to 30 microns. The cross-sectional shape of the through hole 6 will be described later.

Reference numeral 9 denotes a control electrode voltage power supply connected to the control electrode 7, and supplies a voltage pulse to the control electrode 7 according to an image signal supplied from the outside. The control electrode voltage power supply 9 includes a voltage generator (not shown) for generating a voltage, and a switching element (not shown) for switching this voltage. One of the switching elements has about 32, 64, 128 channels for controlling the voltage supplied to the control electrode 7, respectively. For example, when recording at a recording density of 300 dots per inch (300 dpi), if a switching element of 64 channels is used, it is necessary to control 300 apertures. It requires five switching elements with four channels. In addition, 1 la and 1 lb are voltage power supplies for the deflection electrodes connected to the deflection electrodes 10 a and 1 O b, respectively, and the voltage is synchronized with the voltage pulse supplied from the control electrode voltage power supply 9. Is supplied to the deflection electrodes 10a and 10b.

Next, the configuration of the control electrode 7 provided on the print head 4 and the deflection electrodes 10a and 10b will be described with reference to FIG. FIG. 2 is a plan view showing the ^ i pole and the toner passage hole 6 provided on the surface of the print head 4, and FIG. 2A is provided on the print head 4 on the toner carrier 2 side. (B) shows the deflection electrodes 10a and 10b provided on the print head 4 on the back electrode 3 side and the toner passage hole 6. FIG.

Although the shape of each toner passage hole 6 shown in FIG. 2A is circular, it may be oval or elliptical. The diameter of the toner passage hole 6 is set to about 50 to 200 m. The shape of the control electrode 7 is a circle concentric with the toner passage hole 6, but may be a shape such as a good circle or an oval. Further, the control electrode 7 does not need to surround the entire periphery of the toner passage hole 6, and the control electrode may be provided only on the upstream or downstream side in the rotation direction of the toner carrier 2. .

14

No.

Reference numeral 14 denotes a lead wire provided on the print head for connecting the control electrode 7 and a voltage power supply for the control electrode. The voltage pulse generated by the control electrode voltage power supply is supplied to the control electrode 7 via the lead wire 14.

As shown in FIG. 2B, the deflection electrodes 10a and 10b are arranged obliquely with respect to the conveying direction of the image receiving member indicated by arrow A with the toner passage hole 6 interposed therebetween. This is for causing the toner to sequentially fly in an oblique direction on the image receiving member being conveyed, thereby finally forming a horizontal line. A straight line passing through the center of the bets Na one passage hole 6 perpendicular to the conveying direction of the image receiving member is a 1 i, equal to 1 ₂ the straight line connecting the center of the deflection electrodes 10 a, 1 O b, and 1 t The angle 0 between 1 and ₂ is obtained by the following equation.

t an0 = 1 / N

In the above equation, N is the number of toner trajectories obtained in the deflection process.For example, in the case shown in FIG. 11, three types of toner trajectories, left, center, and right, are formed, so that N = 3 . In this embodiment, as in FIG. 11, three types of toner trajectories are formed, and therefore, 0 is set to 18.3 degrees. Further, the deflection electrodes 10a and 10b are shared by the adjacent toner passage holes 6.

FIG. 3 shows the voltage waveform applied to the control electrode 7 and the deflection electrodes 10a and 10b and the flying direction of the toner. FIG. 3 (a) is a time chart of the voltage waveform applied to the control electrode. (b) and (c) show time charts of voltage waveforms applied to the deflection electrodes 10a and 10b, respectively. The toner is shown in Fig. 3 (a) to (c), the vertical axis is voltage, and the horizontal axis is time. FIG. 3D is a view showing a state in which the flying direction of the toner is sequentially deflected. The reference numerals given in FIG. 3 (d) are the same as those in FIGS.

3 (a) to 3 (c), the Tt period indicates the time required to form one line, and corresponds to the above-described entire deflection step period. Tt is determined by the resolution of the image receiving member in the transport direction. For example, to form a horizontal line at a pitch of 300 dpi (dot / inch), dividing one inch (inch) 25.4111111 by 300 dots (Dot) results in a line pitch of about 84.6 m. The image receiving member may be moved by one pitch while forming one line. Therefore, when the speed of the image receiving member is, for example, 60 mm / s, the Tt period is about 1390 / s. In the first embodiment, the resolution is 600 dpi and the conveying speed of the image receiving member is 1 _r

Fifteen

O Omm / s. Therefore, the Tt period is 423〃s.

TL, TC, and TR are control voltage supply times required to supply a voltage to the control electrode 7 and control the formation of one dot, and correspond to the above-described passage control step period. TL is the control voltage supply time required to form one dot by the left deflection process, and TCTRL is the control voltage supply time to form one dot by the right deflection process.

In the first embodiment, TL = TC = TR is set. That is, since Tt = 423〃s, TL = TC 二 TR 二 14 l〃s. Each control voltage supply time TL, TC, and TR is a pulse voltage width Tb that promotes the passage of toner 1 to the toner passage hole 6, and suppresses the passage of the toner 1 to the toner passage hole 6. Consists of the suppression period Tw. The pulse voltage width Tb corresponds to the acceleration step described above. Further, the pulse voltage width Tb is made variable according to the image signal supplied from the outside. That is, Tb is set short when forming a low-concentration dot, and long when forming a high-concentration dot. Further, by setting Tb to zero, the non-printing area is formed because the toner 1 cannot pass through the toner passage hole 6. As a result, it is possible to form an image with excellent gradation. Tw is supplied after the end of Tb until the next control voltage supply time. In the first embodiment, the variable range of Tb is set to 0〃s to 80〃s. Further, the voltage Vw applied to the control electrode 7 during the suppression period T was set to 150 V, and the pulse voltage Vc was set to 300 V.制御 Control during the suppression process period ^ The pressure level vw applied to the electrode and the voltage Vc superimposed on the voltage level Vw during the period are not limited to the value in the above 、 1, but the toner passage hole for toner 1 An electric field that suppresses or accelerates the passage of the ink 6 may be formed between the toner carrier 2 and the print head 4. In the first embodiment, the suppression voltage Vw is applied to the control electrode 7 during the suppression period TW.However, Vw is set to the ground level of the image forming apparatus, and the toner 1 and the toner 1 are attached to the toner carrier 2. Even if a voltage of the opposite polarity is applied, it is possible to suppress the toner 1 from passing through the toner passage hole 6 during the Tw period.

As shown in FIGS. 3 (b) and (c), the deflection electrode voltage power supply for supplying the deflection voltage to each of the deflection electrodes 10a and 10b can output three voltage levels of VL, VM and VH. , Each deflection voltage level is switched in synchronization with the supply time for one dot control. In the first embodiment, the VL knee is 50 V, VM = + 50 V, and VH = + 150 V. _{Λ Ο}

l b

Next, the print head in the first embodiment and the entire image forming operation of the image forming apparatus using the print head will be described with reference to FIGS.

First, the toner carrier 2 rotates and the toner 1 is transported to a position facing the toner passage hole 6. A voltage of +1000 V is applied to the back electrode 3 from the back electrode voltage power supply 8 in advance. At this time, a voltage of −50 V is applied to the control electrode 7. As a result, the electric field formed between the toner carrier 2 and the back electrode 3 is cut off by the voltage supplied from the back electrode voltage power supply, so that the toner 1 is still carried on the toner carrier 2. Become.

Next, the image receiving member 5 is conveyed to a position facing the toner passage hole 6, that is, a print execution position. At the same time as the image receiving member 5 is conveyed to the print execution position, a predetermined pulse voltage as shown in FIG. 3 is selectively supplied from the control electrode voltage power supply 9 to the control electrode 7. Thereby, an attraction electric field for attracting the toner 1 on the toner carrier 2 toward the control electrode 7 to which the pulse voltage is supplied is formed between the toner carrier 1 and the control electrode 7. The toner 1 detached from the toner carrier 2 due to the above-mentioned attracting electric field is further attracted by the electric field formed between the toner carrier 2 and the back electrode 3 and enters the toner passage hole 6.

In addition, a predetermined pressure is applied to the deflection electrodes 10a and 10b from the deflection electrode / U voltage power supplies 11a and 11b in synchronization with the pulse voltage applied to the control electrode 7. As a result, the flight trajectory of the toner 1 passing through the toner passage hole 6 is deflected by the deflecting electric field having distortion near the deflection electrodes 10a and 10b. After the flight track is deflected, the toner is electrically attracted to the back electrode 3 and lands on the moving image receiving member 5 to form a dot. The image-receiving member 5 having the dot formation formed thereon is conveyed to a fixing unit (not shown), and the toner on the image-receiving member 5 is heated and melted by a fixed means, and is fixed on the image-receiving member 5. After the completion of the aging process, the image receiving member 5 is discharged out of the image forming apparatus, and finally, a toner image fixed to the image receiving member 5 is obtained.

Next, the cross-sectional shape of the toner passage hole 6 will be described. FIG. 4 is a cross-sectional view showing the cross-sectional shape of the print head 4 in the vicinity of the toner passage hole. FIG. 4A is a cross-sectional view of the toner passage hole according to the present embodiment. The inner diameters of the toner passage holes on the side 2 and the back electrode 3 are 0 D and 0 d, respectively. Note that the relationship of (^ 0> 0 (1) holds between 0 0 and 0 (1. FIG. 4B is a cross-sectional view of a conventional toner passage hole, The inner diameter of the toner passage hole 6 on the side of the toner carrier 2 of the present embodiment is equal to the inner diameter øD of the entire through hole. ^ Things. FIG. 4 (c) is a cross-sectional view of the toner passage hole in the conventional example, which is equal to the inner diameter ød of the toner passage hole on the back electrode side in the present embodiment in the entire area of the toner passage hole.

In FIG. 4, reference numeral 12 denotes an insulating base material, and reference numeral 13 denotes an insulating protective layer. Reference numeral 7 denotes a control electrode disposed on the surface of the base material 12 on the side of the toner carrier 2 so as to surround the toner passage hole 6. 10 a and 10 b are deflection electrodes provided on the surface of the base material 12 on the side of the back electrode 3 and around the toner passage hole 6.

The present embodiment is characterized in that the opening diameter on the control electrode 7 side is larger than that on the deflection electrodes 10a and 10b side. With such a configuration, the following effects can be obtained. That is, comparing (a) and (b) in FIG. 4, although the distance between the deflection electrodes 10a and 1013 does not change, the insulating layer near the deflection electrode existing between the two is (a) ) Is thicker by D-d. Therefore, even if the electric resistance in the air decreases in a high humidity environment, since there is no insulating layer, an electric short circuit between the deflection electrodes 10a and 10b is suppressed. Also, comparing (a) and (c) in Fig. 4, the distance between the deflection ΐί! Poles 10a and 10b is equal in each case, but in (c), the diameter of the toner passage hole is As the size becomes smaller, toner tends to clog in the toner passage hole. On the other hand, in (a), a larger space is obtained in the toner passage hole on the control electrode side than in (c), so that toner clogging is less likely to occur than in (c).

In this embodiment, the toner passage hole 6 may have any cross-sectional shape as long as the I-diameter is different between the two electrode sides, as shown in FIG. 4 (a). It is preferable to have such a tapered shape. If there is a step in the opening, the toner tends to accumulate at the corners, resulting in clogging of the toner passage hole and distortion of the deflection electric field due to the electric charge of the accumulated toner so that the toner trajectory is normal. Will be different. Further, the electric field tends to concentrate on the convex portion of the step, and there is a possibility that the inner wall of the through hole of the toner may be destroyed by discharge. On the other hand, by providing a tapered shape, the amount of toner deposited on the inner wall of the toner passage hole can be reduced. Further, since the electric field does not concentrate due to the shape of the toner passage hole, discharge breakdown in the toner passage hole can be suppressed.

Regarding the method of forming the toner passage hole 6, it is preferable to form a toner passage hole by irradiating a laser from the surface of the insulating base material 12 on which the control electrode 7 is disposed. Laser irradiation intensity lo

This is because it is easy to form a toner passage hole such that the opening diameter on the deflection electrode side in this embodiment is smaller than the opening diameter on the control electrode side only by adjusting. Figure 4 shows the procedure for preparing the toner passage hole. The procedure for forming the toner passage hole 6 will be described below with reference to FIG.

First, as shown in FIG. 5 (a), a control electrode 7 and a deflection electrode 10a, 10b made of metal foil are formed on both surfaces of an insulating base material 12. As a means for forming both electrodes, a conventionally used electrode pattern forming means such as an etching method is used. Next, as shown in FIG. 5 (b), a metal mask 15 is placed on the surface of the insulating base material 12 on which the pattern of the control electrode 7 is formed, and from above (in the direction of the arrow in the figure). Irradiate an excimer laser. As a result, as shown in FIG. 5C, a toner passage hole 6 penetrating the insulating base material 12 is formed.

Note that the mouth portion corresponding to the toner passage hole 6 of the metal mask 15 may have a diameter larger than the inner diameter of the control electrode 7 as long as it covers the outer ring of the control electrode 7. Laser controlled! ! Even if it is directly irradiated on the pole 7, the laser light reflects on the control electrode 7, so that the control electrode 7 plays the role of a mask fl. Rather, since the metal mask 1 5 may be any degree of coating the outer ring of the control electrode 7, the metal mask 1 5 relative to the position of the toner passage hole 6 Dai Ah ¹ I degree and opening position accuracy of the mask 1 5 There is an advantage that the production method of the print head becomes easy because the second one is not required. In addition, since the opening position accuracy of the mask 15 does not need to be high accuracy, it is not necessary to flow a glass mask used for high-precision masking, and it is sufficient if the mask is made of gold. This is because even if the mask 15 is deteriorated by the laser irradiation, a new mask can be supplied at low cost.

Next, the insulating substrate 12 having the toner passage holes 6 formed thereon is subjected to plasma cleaning to remove smear generated by laser irradiation. Then, as shown in FIG. The surface is covered with an insulating protective layer 13. In order to cover the control electrode 7 exposed on the inner surface of the toner passage hole 6, it is preferable to form the insulating protective layer 13 using a chemical vapor deposition (CVD) method. The print head according to the present embodiment is manufactured by the procedure described above.

In this example, specifically, for example, a film was prepared in which a 10-μm thick copper foil was provided on both sides of an insulating substrate 12 made of a polyimide resin having a thickness of 50 μm. Then, a control electrode 7 and deflection electrodes 10a and 10b were formed on each surface by etching. After that, the metal on the film J: A mask 15 was placed, and an excimer laser was radiated from above the mask 15 to form a toner passage hole 6. Further, after performing plasma cleaning, a polyparaxylylene resin was chemically vapor-deposited (CVD) on the film surface to form an insulating protective layer 13 having a thickness of 10 μm. Through the above steps, finally, a tapered toner passage hole 6 having an inner diameter of 90 μm and an inner diameter of 60 / m at the side of the toner carrier 2 and the back electrode 3 was obtained.

(Example 2)

Next, an image forming apparatus using a print head according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus using a print head according to the second embodiment. In FIG. 6, 16Y, 16M, 16C, and 16BK are toner supply units for each color, and are arranged in the order of yellow, magenta, cyan, and black along the conveying direction of the image receiving member 5. The toner supply unit for each color includes a toner 1 and a toner carrier 2, a stirring member 17 for stirring the toner 1, a toner supply member 18 for supplying the toner 1 to the toner carrier 2, and a toner layer on the toner carrier 2. It comprises a toner layer regulating member 19 to be formed, a print head 4, and a print head holder 20 for holding the print head 4.

The print head 4 has a cross-sectional shape such that the inner diameter of the toner passage hole on the toner carrier 2 side is larger than that of the back electrode 3 side as described in the first embodiment. Note that a configuration in which the print head 4 and the print head holder 20 are separated from the toner supply unit may be used. Further, it is preferable that the toner supply units 16Y, 16M, 16C, and 16BK are configured to be detachable from the image forming apparatus main body. This configuration facilitates toner supply to the toner supply units 16Μ, 16Μ, 16C, 16 トナー and maintenance of the print head 4 and other components. is there.

Reference numeral 21 denotes a transport belt for carrying and transporting the image receiving member 5, which is made of a resin sheet having a medium-to-high resistivity. Reference numeral 22 denotes a belt support roller that stretches the transport belt 21 and drives it to rotate. Further, on the back surface of the conveyor belt 21, back electrodes 3 #, 3 #, 3C, 3 # are arranged to face the toner supply units of each color.

In FIG. 6, the back electrode of each color has a roller shape. However, the present invention is not limited to this. For example, a conductive plate may be provided, or a conductive elastic blade may be brought into contact with the rear surface of the conveyor belt 21. Is also good. 23 should remove toner adhering to the surface of the conveyor belt 21. ^ This is a tilt cleaning device. Reference numeral 24 denotes a registration roller that supplies the image receiving member 5 onto the conveyor belt 21 while adjusting the supply timing. Reference numeral 25 denotes a fixing device for fixing the toner image formed on the image receiving member. . Other configurations are the same as in the first embodiment.

Next, the image forming operation will be described with reference to FIG. First, an image signal is externally stored in the image forming apparatus. After the accumulation of the image signal is completed, a predetermined voltage is applied to the electrodes arranged on the print heads of each color in order to prevent clogging due to toner attached around the toner passage hole. Then, the rotation driving of the conveyor belt 21, the toner carrier 2, and the fixing device 25 is started. Also, a back voltage is supplied to the back electrode of each color. On the other hand, the image receiving member 5 is transported from a paper cassette (not shown) to the registration roller 24 and moves onto the transport belt 21 at a predetermined timing. When the image receiving member 5 is conveyed to a position f opposite to the toner supply unit 16Y, the control voltage of the print head 4 provided in the unit 16Y is applied to a control voltage corresponding to an external image signal. Is applied. Accordingly, the toner on the toner carrier 2 provided in the unit 16Y passes through a toner passage hole provided in the print head 4 and reaches the image receiving member 5. The image receiving member 5 continuously moves while being carried on the transport belt 21, and a predetermined voltage is sequentially supplied to the control electrode, so that a toner image of yellow toner is formed on the image receiving member 5. It is formed.

Then, when the image receiving member 5 is conveyed to a position facing the toner supply unit 16M, the toner image is converted into a yellow toner image through a process similar to that of the unit 16Y. Superimposed on In the toner supply units 16C and 16BK, four color toner images are finally formed on the image receiving member by the same process. The image receiving member 5 carrying the color toner image separates from the transport belt 21 and enters the constant-length device P # 25. In the fixing device 25, the color toner image is fixed and fixed on the image receiving member 5, and the image receiving member 5 is discharged to a discharge tray (not shown).

Through the above steps, a color image is printed on the image receiving member 5. On the other hand, in the toner supply unit of each color after the image receiving member 5 has passed, the rotation driving of the toner holder 2 is sequentially stopped, and thereafter, the voltage application to each electrode of the pudding head is stopped. After that, the voltage supply to the back electrode is also stopped. The surface of the conveyor belt 21 from which the image receiving member 5 has been separated is cleaned by the belt cleaning device 23, and attached to the surface of the conveyor belt 21. ^ The removed toner is removed from the belt 21 surface. When at least the surface of the conveyor belt 21 facing the toner supply unit of each color passes through the cleaning device 23, the rotation of the belt support rollers 22 is stopped, and the rotation of the conveyor belt 21 is stopped. Further, the driving of the fixing device is stopped. Thus, the printing operation by the present image forming apparatus is completed. Next, the reverse flight of the toner will be described in detail with reference to FIGS. 7 and 8, while comparing the configuration of the present invention with the conventional configuration.

7 and 8 are diagrams showing toner movement between the print head and the image receiving member. FIG. 7 shows the toner according to the present embodiment, and FIG. 8 shows the shape of a conventional toner passage hole. 4 shows the movement of the toner when a print head having the following formula is used. 7A and 8A are diagrams illustrating the movement of the toner when the image receiving member is transported to the toner supply units for the second and subsequent colors, and FIGS. 7B and 8B are diagrams illustrating the toner movement in the unit. FIG. 3C is a diagram illustrating a state in which the toner passes through the toner passage hole 6, and FIG. 4C is a diagram illustrating a state in which the toner of the unit reaches the image receiving member 5. 7 and 8, 1a indicates toner particles that have already landed on the image receiving member 5 on the upstream side in the moving direction of the conveyor belt, and 1b indicates toner particles of the second and subsequent colors. The other reference numerals are the same as those in FIGS.

In this embodiment, at least the toner passage hole 6 of the print head 4 disposed on the downstream side in the transport direction of the image receiving member 5 prevents the toner from entering the toner passage hole 6 from the image receiving member 5. It has a shape that suppresses it. To suppress the intrusion of the toner, as shown in FIG. 7, the toner passage hole 6 only needs to have a shape such that the opening diameter on the back electrode 3 side is smaller than that on the toner carrier 2 side. . The reason will be described below.

The toner arriving on the image receiving member 5 contains toner of the opposite polarity charged to the opposite polarity to the normal charge polarity (hereinafter, abbreviated as forward polarity). The first reason is that the bulk toner in which the forward polarity toner particles and the opposite polarity toner are aggregated separates from the toner carrier 2. The toner that has reached the image receiving member in a lump is broken by collision with the image receiving member 5. As a result, the opposite polarity toner is released from the lump and can move freely. The second cause is that when the electric resistance between the conveyor belt and the image receiving member 5 is low, charge flows into the toner from the back electrode 3. As a result, the charge amount of the charged toner gradually decreases. Further, when the electrical insulation of the toner is reduced in a high humidity environment, the toner is further charged with the opposite polarity, and eventually charged to the opposite polarity. ^ For the above reasons, the toner of the opposite polarity among the toner particles 1a carried on the image receiving member 5 passes through the toner passage hole 6 from the back electrode 3 when transported to the next image forming position. Then, due to the electrostatic field that reaches the toner carrier 2, the toner particles fly backward from the image receiving member 5 toward the print head 4 and adhere to the print head 4. At this time, if the opening diameter of the toner passage hole is the same on the toner carrier 2 side and the back electrode 3 side, or the opening diameter on the back electrode 3 side is larger, as in the print head of the conventional configuration, The toner that has flown backward enters the toner passage hole 6 and adheres to the inner wall surface of the toner passage hole 6 (FIG. 8 (a)). On the other hand, in the present embodiment, since the opening diameter on the back electrode 3 side is narrowed, penetration of the toner that has flown backward into the toner passage hole 6 is blocked. Therefore, the adhesion of the toner to the inner wall of the toner passage hole as shown in FIG. 8 (a) is suppressed (FIG. 7 (a)).

Next, at the stage of printing with the toner 1 b of the next color, the toner particle lb of the next color passes through the toner passage hole 6. At this time, as shown in FIG. 8A, if the toner particles 1a adhere to the inner wall of the toner passage hole 6, the toner particles 1a are repelled by the next color toner 1b. Further, since the toner particles 1b passing through the toner passage hole 6 are not sufficiently accelerated by the electrostatic field, the toner particles 1a having the opposite polarity adhere to the forward polarity toner particles 1b passing therethrough. As a result, the toner particles 1a adhering to the inner wall of the toner passage hole 6 exit the toner passage hole 6 together with the next color toner particles 1b (FIG. 8 (b)). In particular, in the case of a print head having a deflecting electrode, the flying trajectory of the toner is deflected even in the toner passage hole 6, so that the toner particles 1 b often contact the surface of the toner passage hole 6. As a result, the tendency that the toner particles 1 a of another color are mixed with the toner particles 1 b of the next color and the toner passing holes 6 are drawn out becomes remarkable. From the above, the toner image is formed on the image receiving member in a state where the toner 1a is mixed in the area where the next color toner 1b should be formed only (FIG. 8 (c)). If different color toners are mixed, not only will the color development balance be lost, but a poor quality color image will be created with a dark ground force pre-appearing on a light color.

On the other hand, in the embodiment of the present invention, since the toner passage hole 6 has such a shape that the adhesion of the toner particles 1a to the toner passage hole 6 is suppressed in advance, the toner passage hole 6 The resulting toner particles are occupied by the next-color toner 1b without being mixed with the next-color toner 1a (FIG. 7 (b)). Therefore, the toner image is formed on the image receiving member 5 "without mixing the toner particles la in the area originally formed only by the next color toner 1b (FIG. 7 (c)). this ₀ As a result, a color image having the originally obtained color balance is faithfully reproduced. Further, since the opening diameter on the side of the toner carrier 2 is wide, the effect of maintaining the image density and suppressing the occurrence of clogging is exhibited.

Note that the cross-sectional shape of the toner passage hole 6 according to the present embodiment is not limited to a taper shape as shown in FIG. For example, as shown in FIG. 9 (a), a step is provided inside the toner passage hole 6 of the insulating base material 12 so as to prevent the toner from entering by reverse flight, or as shown in FIG. 9 (b). Alternatively, the shape may be such that the opening diameter is narrowed in the toner passage hole 6. However, in the case of FIG. 9A, if there is a step in the toner passage hole 6, the toner is likely to be deposited at the corners of the step, and as a result, the toner passage hole 6 is likely to be clogged by the toner particles. . Further, in the case of FIG. 9 (b), in the case of the print head provided with the deflection electrode, the toner particles may come into contact with the taper surface on the back electrode 3 side of the toner passage hole 6. Therefore, it is not preferable to provide the toner passage hole 6 as shown in FIG. 8B in the print head having the deflection electrode.

Further, in order to form the toner passage hole shape shown in FIG. 9B by laser light irradiation, it is necessary to irradiate laser from both the toner carrier 2 side and the back electrode 3 side, and the toner passage hole 6 is formed. Not only the number of manufacturing steps increases, but also the associated masks need to be prepared, which increases the cost of the print head. From the above, in the present embodiment, it is preferable to have the cross-sectional shape of the through-hole of the toner as shown in FIG. Further, in the second embodiment, the metamorphic shape of the through hole 6 in the print head 4 corresponding to each color may be the same. Conversely, it may have a shape such that the inner diameter of the toner passage hole 6 on the front surface electrode 3 is reduced toward the downstream side in the transport direction of the image receiving member 5. This is because the amount of toner flying backward and adhering to the print head increases toward the downstream side.

FIG. 7 of the second embodiment shows a print head having the deflection electrodes 10a and 10b, but a print head without the deflection electrodes 10a and 10b is shown. Alternatively, instead of the deflection electrodes 10 a and 10 b, a voltage of the same polarity as that of the forward polarity toner is applied to converge the flight trajectory of the toner toward the center of the toner passage hole 6. A common focusing electrode may be arranged in the through hole 6 of the toner.

In the second embodiment, the configuration in which the toner images of the respective colors are directly recorded on the image receiving member 5 has been described. However, the present invention is not limited to this. For example, a configuration may be used in which toner images of each color are sequentially formed on a belt-like or drum-like intermediate transfer medium and then transferred to an image receiving member such as paper.

Incidentally, the dimension of the inner diameter of the toner passage hole is as follows.If D 1 is the toner carrier 2 side and D 2 is the back electrode 3 side, 0 1/0 2 is in the range of 1.2 to 2.0. Is preferred. Below the range, the effect of blocking the entry of reverse flying toner is not exhibited. In addition, when the ratio exceeds the above range, the toner supplied from the toner carrier 2 tends to cause clogging of the toner passage hole. Further, in order to obtain the effect of blocking the progress of the reverse flight toner, it is preferable that the value of (D 1 -D 2) / 2 be larger than the average particle size of the toner.

The quiet density of the toner used is preferably in the range of 0.2 to 0.4 kg / cm ³ . If the value is less than ffl, the cohesive force of the toner is increased, and the toner passage hole is likely to be clogged. Further, since the toner is easy to congeal, it is difficult to apply a tripolar charge to the toner by a regulating blade or the like. For this reason, the toner of the opposite polarity increases, and the toner which flies backward from the image receiving member also increases. In addition, when the distance exceeds the range, the cohesive force of the toner decreases, and the image receiving member easily separates from the other toner. Therefore, if the opposite polarity toner is present in the image receiving member, the toner easily flies back to the toner passage hole.

In addition, the toner formed on the image receiving member is formed of yellow, black, cyan, and black in terms of maintaining the clearness of the text and adjusting the color balance. Preferably. When a toner image of ^ r color is to be transferred to the image receiving member in the order of in the following manner in a configuration using a medium, the transfer of the toner image to the medium is the reverse of the above. That is, it is necessary to arrange the print heads of ^ color so that black, cyan, magenta, and yellow are in this order. However, in the case of this array of print heads, the color of the toner becomes lighter toward the downstream side in the moving direction of the intermediate transfer medium, and the color mixture of the different color toner on the upstream side is directly applied to the image receiving material. It is extremely つ ^ compared to the printing method. As described above, the configuration using the intermediate transfer medium is more affected by the color mixture, so that the configuration according to the present invention is preferably used.

In addition, at the end of the print head described in the projection examples 1 and 2, the grounding area is controlled by the conductive layer to which the predetermined? Stabilization and o

Role may be provided. The material of the antistatic layer is preferably a hard material such as conductive amorphous carbon. This is because the image receiving member is prevented from being worn by directly contacting the toner particles. The surface resistance is the order of 1 0 ⁸ Omega / mouth ~ 1 / mouth exceeds preferred _(above range, effect of removing the electric charge is reduced. Moreover, when less than the above range, the back electrode Between them, there is a risk of an electrical short circuit.

Further, the diameter of the toner passage hole and the material of the print head are not limited to the dimensions and materials shown in Embodiments 1 and 2, but may be any as long as the effects according to the present invention are exhibited. Of course, such dimensions and materials may be used.

(Industrial applicability)

The present invention relates to a print head used as a device for forming an image by controlling the flight of a developer from a developer carrier to an image receiving member by a deflection electrode, and an image forming apparatus using the same. It has high industrial applicability in that electrical short circuits can be suppressed and color mixing can be suppressed.

Claims

A developer carrier that carries and transports the developer;

An image receiving member disposed opposite to the developer carrier, for receiving the developer,

An insulating substrate provided between the developer carrier and the image receiving member, the insulating substrate having a plurality of developer passage holes through which the developer carried by the developer carrier passes toward the image receiving member; A first electrode disposed on one surface of the substrate around each developer passage hole, and a first electrode disposed on the other surface of the insulating substrate around each developer passage hole, with the developer passage hole interposed therebetween. A print head comprising a second electrode group divided and arranged;

First voltage supply means for supplying a predetermined voltage to the first electrode according to an external image signal;

An image forming apparatus comprising: a second voltage supply unit that supplies a different voltage to each of the second electrode groups.

An image forming apparatus, wherein the developer passage hole of the print head has a shape that suppresses an electrical short circuit between the second electrode groups. A developer carrying member that carries and transports the developer,

An image forming apparatus comprising: a second voltage supply unit that supplies a different voltage to each of the second electrode groups. An image forming apparatus, wherein an inner diameter of a developer passage hole in the print head on the second electrode group side is smaller than an inner diameter on the first electrode side. 3. The image forming apparatus according to claim 1, wherein the print head is arranged so that the first electrode faces the developer carrier. The inner wall surface of the developer passage hole is tapered so that the inside diameter of the developer passage hole on the second electrode group side is smaller than the inside diameter of the first electrode side. The image forming apparatus according to any one of claims 1 to 3. In the developer passage hole, a mask having an opening corresponding to the developer passage hole is placed on the surface of the insulating substrate on which the first electrode is formed, and a laser is irradiated from the placement side of the mask. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is formed by:

The image forming apparatus according to claim 5, wherein the opening provided in the mask has an inner diameter larger than the inner diameter of the first electrode. An image receiving member for receiving the developer image,

A plurality of developer carrying members arranged to face the image receiving member and along the carrying direction of the image receiving member and carrying and carrying the developer;

An insulating substrate provided between the developer carrier and the image receiving member, the insulating substrate having a plurality of developer passage holes through which the developer carried by the developer carrier passes toward the image receiving member; A plurality of printheads having a control electrode disposed on one surface of the substrate around each developer passage hole; and

An image forming apparatus using a print head, comprising: a voltage supply means for supplying a predetermined voltage to the control electrode according to an external image signal.

The developer passage hole of the print head arranged at least corresponding to the developer carrying member located on the downstream side in the transport direction of the image receiving member is provided between the image receiving member and the developer passage hole. An image forming apparatus having a shape that suppresses the intrusion of the developer into the image receiving device c for receiving a developer image;

An insulating substrate provided between the developer carrier and the image receiving member, the insulating substrate having a plurality of developer passage holes through which the developer carried by the developer carrier passes toward the image receiving member; A plurality of printheads having control electrodes disposed on one surface of the substrate around each developer passage hole; and

An image forming apparatus using a print head, comprising: a voltage supply means for supplying a predetermined voltage to the control electrode in accordance with an external image signal.

At least the developer passage hole of the print head arranged corresponding to the developer carrying member located on the downstream side in the transport direction of the image receiving member has an inner diameter on the image receiving member side smaller than an inner diameter on the developer carrying member side. An image forming apparatus characterized by being small. The inner wall surface of the developer passage hole has a tapered shape such that the inner diameter of the developer passage hole on the image receiving member side is smaller than the inner diameter of the developer / carrier member side. 8. The image forming apparatus according to 8. At least the developer passage hole of the print head arranged corresponding to the developer carrying member located at the downstream side of the image receiving member in the conveying direction is provided with a mask on the surface of the insulating substrate facing the developer carrying member. 10. The image forming apparatus according to claim 9, wherein the image forming apparatus is formed by irradiating a laser from a mounting side of the mask. 10. The method according to claim 10, wherein the opening provided in the mask corresponding to the developer passage hole of the print head has an inner diameter larger than the interval between the control electrodes. Image forming device. . An insulating substrate; A plurality of through holes penetrating the insulating substrate,

A first electrode provided around one of the through holes on one surface of the insulating substrate; and a first electrode provided around the through hole on the other surface of the insulating substrate. A print head comprising: a second electrode group disposed in a vertical direction; wherein the inner diameter of the through hole near the second electrode group is smaller than the inner diameter of the first electrode side. De. The inner wall surface of the through hole is tapered so that the inner diameter of the through hole near the second electrode group is smaller than the inner diameter of the first electrode side. Print head. The through-hole is formed by placing a mask having an opening corresponding to the through-hole on the surface of the insulating substrate on which the first electrode is formed, and irradiating a laser from the placement side of the mask. 14. The print head according to claim 13, wherein the print head is a printed head. 15. The printhead according to claim 14, wherein the opening provided in the mask corresponding to the through hole has an inner diameter larger than the interval between the first electrodes.