JP2001287392A - Print head and image forming apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a print head 4 and an image forming apparatus capable of preventing a tailing phenomenon or clogging of toner 1 in a toner passing hole 6. SOLUTION: This image forming apparatus comprises a toner carrier body 2 for conveying the toner 1 by carrying it and the print head 4 that has the plurality of toner passing holes 6 for passing the toner 1 therethrough and controls the passing of the toner 1 by applying an image signal to a control electrode provided to the periphery of each of the toner passing holes 6. A control electrode 7 and a deflection electrode 10a, 10b are provided to both faces of an insulation substrate 12 forming the print head 4, respectively. The toner passing hole 6 is formed in a tapered shape such that the diameter at the side of the deflecting electrode 10a, 10b is greater than that at the side of the control electrode 7. As a result, since the speed of the toner 1 is not reduced by preventing the toner 1 from colliding with the inner wall face of the toner passing hole 6, the length of the toner flow is not enlarged so that the tailing phenomenon can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head applied to a copying machine, a facsimile, a printer, and the like, and an image forming apparatus using the print head, and more particularly to a flying of a developer from a developer carrier to an image receiving member. And performs image formation by attaching a developer to an image receiving member.

[0002]

2. Description of the Related Art In recent years, with the improvement of personal computer capabilities and the advancement of network technology, there has been a demand for a printer or copier having a high processing capability capable of handling a large number of documents (or capable of handling color documents). It is getting stronger. However, an image forming apparatus that can output satisfactory high-quality black and white or color documents and has a high processing speed is under development and is expected to appear.

As one of them, for example, Japanese Patent Publication No. Sho 4
No. 4,26,333, U.S. Pat. No. 3,689,935.
No. (JP-B-60-20747), Tokuheihei 9
As disclosed in -500842 and the like, by the action of an electric field, a developer such as a toner is caused to fly on an image receiving member such as a recording paper or an image carrying belt through a developer passage opening in which electrodes are disposed around the developer, 2. Description of the Related Art An image forming technique of a direct printing method for forming an image is known.

A method in which a plurality of dots are formed from a single developer passage port by deflecting and converging a flying developer is disclosed in Japanese Patent Publication No. 59-38908 and the Journal of the Electrophotographic Society, Vol. No. (1997) p. 114-1
17 and the like.

[0005] Here, the principle of the above method is shown in Figs.
This will be described below. FIG. 9 schematically illustrates an example of the image forming apparatus. The image forming apparatus includes a toner carrier 102 that carries and conveys a toner 101 as a negatively charged developer and a toner carrier 102. And a print head 10 that is disposed between the toner carrier 102 and the counter electrode 103 and that controls the flying of the toner 101.
4 is provided. An image receiving member 105 such as a recording paper or an image carrying belt is transferred between the counter electrode 103 and the print head 104. The print head 104 has an insulating substrate as a base material, a plurality of toner passage openings 106 through which the toner 101 passes, and control electrodes 10 disposed around the toner passage openings 106, respectively.
7 are provided.

The toner carrier 102 is grounded, and the counter electrode 103 is connected to a counter electrode power supply 108 for applying a counter electrode voltage to the counter electrode 103. When a counter electrode voltage is applied to the toner carrier 102, an electric field for moving the toner 101 toward the counter electrode 103 is formed between the toner carrier 102 and the counter electrode 103.

The control electrode 107 is connected to a control electrode power supply 109. The control electrode power supply 109 repeatedly supplies a control voltage to the control electrode 107 in accordance with an external image signal. When the voltage is the same polarity (negative polarity) as the charging polarity of the toner 101, the toner carrier 102
The toner 101 does not fly from the toner carrier 102 because electrostatic force acts in the direction. On the other hand, when the control voltage has the opposite polarity (positive polarity) to the charging polarity of the toner 101,
The toner 101 separates from the toner carrier 2 and flies by the action of electrostatic adhesion toward the control electrode 107. The flying toner 101 passes through the toner passage 106 due to the electric field formed between the toner carrier 102 and the counter electrode 103 by the application of the counter electrode voltage to the counter electrode 103, and eventually onto the image receiving member 105. Lands in dot form.

The counter electrode 10 of the print head 107
On the surface on the third side, the deflection electrodes 110a and 110 divided into two parts are provided.
b are arranged facing each other with the toner passage opening 106 as a center, and deflection electrode power supplies 111a and 111b are connected to the two divided deflection electrodes 110a and 110b, respectively. The deflection electrodes 110a and 110b are arranged so as to be located on both sides of the image receiving member 105 in the transfer direction with the toner passage opening 106 interposed therebetween. Then, the deflection electrode power supply 111 is supplied to both deflection electrodes 110a and 110b.
When different voltages are supplied in synchronism with the above-mentioned control voltage by the a and 111b, respectively, the toner passage port 1 of the electric field is supplied.
06, the symmetry centered on the toner passage 106 is broken.
Is deflected from the center of the toner passage opening 106 and flies, thereby forming a dot on the image receiving member 105 at a position deflected from the center of the toner passage opening 106. On the other hand, both deflection electrodes 110a, 110b
, The symmetry of the electric field around the toner passage 106 is maintained, and a dot is formed on the central axis of the toner passage 106. This deflection electrode 110a,
By controlling the voltage supplied to 110b, a plurality of dots can be formed in one toner passage 106 in the direction in which the deflecting electrodes 110a and 110b on the image receiving member 105 face each other. It is possible to form an image with increased resolution without increasing the number of toner passage openings 106 or increasing the number of toner passage openings 106.

FIG. 10 shows an example of voltage control of the control electrode 107 and the deflection electrodes 110a and 110b, and how the toner 101 flies. FIG. 10B is a time chart of the voltage supplied to the control electrode 107. FIG. 1C is a time chart of the voltage supplied to the deflection electrode 110b in FIG.
0 (d) shows a time chart of the voltage supplied to the deflection electrode 110a.

As shown in FIG. 10B, the control voltage is
A pulsed voltage Vb having a polarity opposite to the charging polarity of the toner 101
And a voltage Vw having the same polarity as the charging polarity of the toner 101. The voltage Vb promotes the passage of the toner 1 to the toner passage 6, while the voltage Vw causes the toner passage 6
Of the toner 1 is suppressed.

[0011] The left part of FIG.
0b is supplied to the deflection electrode 110a and the voltage Vh higher than the voltage VL is supplied to the deflection electrode 110a. In this case, the flight trajectory of the negatively charged toner 101 becomes , 110b are deflected to the left as indicated by the arrows.

The central portion of FIG. 10A shows a case where the voltages supplied to the two deflection electrodes 110a and 110b are both Vc. In this case, the toner 10
1 passes straight through the toner passage 106 and reaches a position on the image receiving member 105 corresponding to the toner passage 106.

Further, the right part of FIG. 10A shows a case where the voltage VL is supplied to the deflection electrode 110a and a voltage Vh higher than the voltage VL is supplied to the deflection electrode 110b. In this case, Since an electrostatic field is generated between the deflection electrodes 110a and 110b in a direction opposite to the above, the trajectory of the negatively charged toner 101 is deflected to the right.

The deflection process of the flight trajectory of the toner 101 as described above, that is, the left deflection process (hereinafter referred to as left deflection process), the straight traveling process and the right deflection process (hereinafter referred to as right deflection process), The toner image is formed on the image receiving member 5 continuously and repeatedly with the transfer of the image receiving member 105.

In the following description, a series of deflection steps from the left deflection step to the right deflection step is referred to as a full deflection step.
The distance between two dots formed on the image receiving member 105 in the left deflection process or right deflection process and the straight traveling process is referred to as a deflection distance.

[0016]

However, in the image forming apparatus having the above-described structure, the toner 101 at the trailing end of the flying toner stream lands at a position shorter than the normal deflection distance, and the dot is formed. There is a problem that a phenomenon (tailing phenomenon) occurs as if the image receiving member 105 is trailed in the lateral direction. The reason is that the toner 101 in flight and the inner wall surface of the toner passage opening 106 come into contact with each other. In other words, the toner 1
01 comes into contact with the inner wall surface, the toner 1
The flying speed of 01 is reduced. For this reason, the difference in the flying speed between the toner 101 in contact with the inner wall surface and the toner 101 not in contact increases, and the length of the toner flow passing through the toner passage port 106 increases. As a result, before the trailing end of the toner flow lands on the image receiving member 105, the direction of the deflecting electric field by the deflecting electrodes 110a and 110b is switched, and the landing position of the trailing end of the toner flow deviates from the normal position. As a result, a trailing dot is formed on the image receiving member 105.

The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a print head and an image forming apparatus that suppress the above-described tailing phenomenon. .

[0018]

In order to achieve the above object, in the present invention, the tailing phenomenon is suppressed by forming the developer passage opening into an appropriate shape.

More specifically, according to the first aspect of the present invention, there is provided a developer carrying member for carrying and transporting a developer, an image receiving member provided opposite to the developer carrying member and receiving a developer image, and A plurality of developer passages are provided between the developer carrying member and the image receiving member, and the developer carried by the developer carrying member passes through the image receiving member. A print head made of a substrate, a first electrode disposed around each of the developer passages on one surface of the insulating substrate of the print head, and a surface provided with the first electrode. A second electrode group disposed in a divided state around the developer passage openings on the opposite side of the insulating substrate surface so as to sandwich the developer passage openings; Supply a predetermined voltage to the electrodes according to the image signal. A voltage supply means, the plurality of electrodes constituting the second electrode group, directed to an image forming apparatus and a second voltage supply means for supplying respectively different voltages.

The developer passage is formed in such a shape that the length of the developer flowing through the developer passage is prevented from increasing in the developer passage.

With the above arrangement, the developer flow passing through the developer passage opening of the print head flies toward the image receiving member with its length being short, so that the rear end of the developer flow reaches the vicinity of the image receiving member. After that, the direction of the deflection electric field is switched.
Therefore, the rear end of the developer flow lands on the surface of the image receiving member almost without being affected by the switching of the direction of the deflection electric field.
The occurrence of the tailing phenomenon is suppressed.

According to a second aspect of the present invention, there is provided a developer carrying member for carrying and transporting a developer, an image receiving member provided to face the developer carrying member and receiving a developer image, and the developer carrying member. A print head having a plurality of developer passage ports provided between the image receiving member and the developer carried by the developer carrier to pass toward the image receiving member, and having a base made of an insulating substrate A first electrode disposed around the developer passage on one surface of the insulating substrate of the print head, and an insulation on a side opposite to the surface on which the first electrode is provided. A second electrode group arranged in a state of being divided into a plurality of parts so as to sandwich each of the developer passage ports, around the respective developer passage ports on the surface of the conductive substrate;
A first voltage supply unit for supplying a predetermined voltage to the first electrode in accordance with an image signal; and a second voltage for supplying different voltages to a plurality of electrodes constituting the second electrode group, respectively. And an image forming apparatus having a supply unit.

The developer passage opening is formed in a shape that suppresses the developer passing through the developer passage opening from contacting the inner wall surface of the developer passage opening.

As a result, the developer in flight passes through the developer passage without deceleration due to contact with the inner wall surface of the developer passage, so that the length of the developer flow becomes longer. Is suppressed. As a result, similarly to the first aspect of the present invention, the trailing end of the developer lands on the image receiving member without being largely affected by the switching of the direction of the deflection electric field, so that the occurrence of the tailing phenomenon is suppressed. .

According to a third aspect of the present invention, there is provided a developer carrying member for carrying and transporting a developer, an image receiving member provided opposite to the developer carrying member for receiving a developer image, and the developer carrying member. A print head having a plurality of developer passage ports provided between the image receiving member and the developer carried by the developer carrier to pass toward the image receiving member, and having a base made of an insulating substrate A first electrode disposed around the developer passage on one surface of the insulating substrate of the print head, and an insulation on a side opposite to the surface on which the first electrode is provided. A second electrode group arranged in a state of being divided into a plurality of parts so as to sandwich each of the developer passage ports, around the respective developer passage ports on the surface of the conductive substrate;
A first voltage supply unit for supplying a predetermined voltage to the first electrode in accordance with an image signal; and a second voltage for supplying different voltages to a plurality of electrodes constituting the second electrode group, respectively. And an image forming apparatus having a supply unit.

The developer passage is formed such that the diameter in the vicinity of the second electrode group is larger than the diameter on the first electrode side.

According to the present invention, a large space can be taken in a region where the trajectory of the developer is easily deflected inside the developer passage, so that the chance that the developer during the flight contacts the inner wall surface of the developer passage is reduced. I do. This reduces the chance that the flying speed of the developer is reduced, so that the length of the developer flow is prevented from being increased during the passage through the developer passage. As a result, as in the case of the first aspect, the developer flow reaches the image receiving member in a short state, so that the tailing phenomenon is reduced.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the first electrode is provided on the surface of the insulating substrate on the developer carrier side.

As a result, even if the flight trajectory of the developer is deflected in the developer passage, the developer can pass through the developer passage with almost no contact with the inner wall of the developer passage.
The degree of freedom of the deflection distance is increased, so that the developer can accurately land on a predetermined position of the image receiving member even at a long deflection distance. Further, since the chance that the developer comes into contact with the inner wall surface of the developer passage after being deflected in the developer passage is reduced, the problem that the length of the developer flow becomes longer can be solved. Furthermore, since the opening diameter of the developer passage opening on the image receiving member side can be increased, the area of the print head surface on the image receiving member side, in particular, the area from the opening edge to the deflection electrode decreases. As a result, the area of the region where the developer charged in the opposite polarity to the normal polarity (reverse polarity developer) is apt to be deposited is reduced, so that even if printing is performed continuously for a long period of time, the reverse deposited on the print head surface. The influence of the polar developer on the developer flight trajectory can be reduced.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the inner wall surface of the developer passage is formed by a second electrode from the first electrode side.
Are formed in a tapered shape whose diameter increases toward the electrode group side.

By doing so, there is no step on which the developer easily accumulates on the inner wall surface of the developer passage. Therefore, even if the developer contacts the inner wall surface of the developer passage, the developer does not stop in the developer passage. Can pass through. As a result, clogging of the developer passage opening by the developer is suppressed. 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.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the taper angle α of the inner wall surface of the developer passing port is such that the developer on the developer carrying member facing the developer passing port has Assume that β is the angle formed between the flight trajectory immediately before entering the passage opening and the central axis of the developer passage opening, and α / 2 ≧ β is satisfied.

That is, the developer flying from the developer carrying member is sucked by the first electrode provided around the developer passage, and is inclined at an angle β with respect to the central axis of the developer passage. Into the developer passage. However, in the present invention, the inner wall surface of the developer passage is inclined by α / 2 with respect to the central axis of the developer passage, and the value of α / 2 is equal to or more than β. The developer that has entered obliquely passes through almost without contacting the inner wall surface of the developer passage opening, and the deceleration of the developer is reliably suppressed. Therefore, the effect of reducing the tailing phenomenon can be further enhanced.

According to a seventh aspect of the present invention, in the fifth aspect of the present invention, the taper angle α of the inner wall surface of the developer passage is defined by a deflection distance p, and the opening diameter of the developer passage through the second electrode group. Is set to D, and the distance between the print head and the image receiving member is set to L, it is assumed that the setting is made so as to satisfy L · tan (α / 2) + D / 2 ≧ p.

That is, in the deflection step, the developer is deflected by the second electrode group and is discharged obliquely from the developer passage opening. At this time, the developer is obliquely deflected so as to land on the image receiving member at a position separated by a deflection distance p from a position on the central axis of the developer passage opening. However, in the present invention, the position separated by the deflection distance p on the image receiving member is a position where the inner wall surface of the developer passage opening intersects the image receiving member when the inner wall surface is extended to the image receiving member (the developer passage opening). (The position separated by Ltan (α / 2) + D / 2 from the position on the central axis of the liquid crystal), the developer to be discharged obliquely from the developer passage port is The developer is ejected almost without contacting the inner wall surface, and the deceleration of the developer is reliably suppressed. Therefore, the same function and effect as the sixth aspect of the invention can be obtained.

According to the invention of claim 8, in claim 5, 6, or 7,
In the invention, the developer passage port is formed by irradiating a laser from the mounting side of the mask in a state where the mask is mounted on the surface of the insulating substrate on which the second electrode group is formed. I do.

Thus, the tapered developer passage can be easily formed, so that the cost of the image forming apparatus can be reduced.

According to a ninth aspect of the present invention, there is provided an insulating substrate, a plurality of through-holes penetrating the insulating substrate, and first through-holes provided around the respective through-holes on one surface of the insulating substrate. And a second electrode group arranged around the through hole on the other surface of the insulating substrate and divided into a plurality of electrodes so as to sandwich the through hole. It is an invention of a head.

In the present invention, the through hole is formed such that the diameter in the vicinity of the second electrode group is larger than the diameter on the first electrode side.

When such a print head is used in an image forming apparatus and the through-hole is used as a developer passage, the length of the developer flowing through the through-hole can be suppressed from being lengthened. An image in which the pulling phenomenon is reduced is output. Therefore, the same function and effect as the third aspect of the invention can be obtained.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the inner wall surface of the through hole is formed in a tapered shape in which the diameter increases from the first electrode side toward the second electrode group side. Shall be. By doing so, the same operation and effect as the invention of claim 5 can be obtained.

According to an eleventh aspect of the present invention, in the tenth aspect of the present invention, the through-hole is provided with a laser from a mounting side of the mask while the mask is mounted on the surface of the insulating substrate on which the second electrode group is formed. To be irradiated.

Thus, by controlling the laser irradiation intensity, a tapered through-hole can be easily formed, and the taper angle can be freely controlled. Thereby, a print head in which the tailing phenomenon is reduced can be easily manufactured.

[0044]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus using a print head 4 according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a toner as a developer. In this embodiment, a non-magnetic toner using a polyester resin as a binder resin is used. The binder resin used for the toner 1 may be a styrene-acrylic copolymer, a styrene-butadiene copolymer, an epoxy resin, or the like.
These mixed resins are suitable. Further, a magnetic toner containing a magnetic powder may be used.In this case, as the magnetic powder, an alloy, a compound, or the like containing ferromagnetic elements such as ferrite, magnetite, iron, cobalt, and nickel is used. It is valid. Magnetic powder holding power is 7900 to 395
The amount of the magnetic powder is preferably 100 A / m, and the ratio of the magnetic powder to the resin is suitably 20 to 40% by weight based on 100 parts by weight of the toner particles. In addition, silica (SiO ₂ ), titanium oxide (Ti)
It is preferable to add 0.1 to 5% by weight of O ₂ ) and a metal salt of stearic acid. In particular, silica greatly affects the fluidity, and can prevent the toner 1 from being clogged in the toner passage 6 of the print head 4 described later. Further, since silica has a small diameter and a high chargeability, it is easily attracted to an electric force and easily adheres to the inner wall surface of the toner passage opening 6.
However, the toner 1 adhering to the inner wall surface of the toner passage 6 plays a role of a roller for promoting the movement when passing through the toner passage 6, so that clogging of the holes can be prevented. Then, the silica has a specific surface area by nitrogen adsorption (according to the BET method) is appropriately in a range of 100 to 300 m ² / g, the use of small diameter silicas such as less than 100 m ² / g, shredding resin It is not possible to obtain a sufficient fixing property to mix them together.

Reference numeral 2 denotes a toner carrier (developer carrier) that carries and transports the toner 1. The toner carrier 2 in this embodiment is formed using an aluminum cylinder having an outer diameter of 20 mm and a thickness of 1 mm, and the toner carrier 2 is grounded. The toner carrier 2 is configured to be rotatable around its central axis, and carries the toner 1 by this rotation. The material of the toner carrier 2 may be a material other than aluminum, such as a metal or alloy such as iron, or a member obtained by winding a rubber material such as silicon rubber or urethane rubber around a core shaft. Alternatively, a belt-shaped or drum-shaped one may be used. In addition to the grounding of the toner carrier 2, a DC voltage or an AC voltage may be applied. When applying an AC voltage, a DC voltage may be superimposed.

The toner 1 is layered on a toner carrier 2 by a regulating blade (not shown: attached to a mounting member in a cantilever shape, and a leading end thereof is pressed against the toner carrier 2). It is formed. This regulating blade is formed of an elastic member such as urethane or silicon, and has a hardness of 40 to 80 degrees (JIS K6301 A 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 suitably 4.9 to 39.2 N / m, and one to three layers of toner are formed on the toner carrier 2 by pressing the regulating blade. The regulating blade is used by electrically applying a float state, a ground state, or a DC or AC voltage. In the present embodiment, the regulating blade is used in a float 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 and charge the toner.

The toner 1 is supplied to a supply roller (not shown).
At the surface of the toner carrier 2. This supply roller is mounted on a metal shaft such as iron (in this embodiment, a diameter of 8 mm).
A synthetic rubber such as foamable urethane is formed with a thickness of about 2 to 6 mm. The hardness of the surface of the supply roller is 30 degrees (measured by a method according to JIS K6301 A scale when processed into a roller shape). 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 supply amount of the toner 1 to the toner carrier 2 and assists the charging of the toner 1. The charge polarity of the toner 1 may be either positive or negative, but in the present embodiment, a negatively charged toner is used. The charge amount of the toner 1 is-
It is preferable to adjust the type and amount of the charge control agent internally added to the toner 1 so as to be 5 to −30 μC / g. When the absolute value of the charge amount of the toner 1 is smaller than the above range,
Toner 1 charged to a polarity (positive polarity) opposite to a normal polarity (negative polarity) increases. For this reason, the toner 1 adheres to the periphery of the toner passage 6 of the print head 4, causing clogging of the toner passage 6, or deflecting the deflection electric field so that the toner 1 cannot be deflected in a normal direction. . On the other hand, if the absolute value of the charge amount of the toner 1 is larger than the above range, the image force between the toner 1 and the toner carrier 2 becomes strong, and even if a predetermined voltage is applied to the control electrode 7, the toner 1 cannot be removed from the toner carrier 2.

Reference numeral 3 denotes a counter electrode. In the present embodiment, the counter 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 10 ² to 10 ¹⁰ Ω · cm. Then, an image receiving member 5 such as a recording sheet or an image carrying belt, which receives the toner image, is transferred onto the counter electrode 3, and the toner 1 is attached to the image receiving member 5 to form a toner image. The counter electrode 3 may be formed by processing the film into an endless shape using the above-described film, and the toner 1 may be directly recorded on the film, and then transferred to the image receiving member 5. . The distance between the counter electrode 3 and a print head 4 described later is preferably in the range of 50 to 1000 μm.

Reference numeral 8 denotes a power supply for the counter electrode for applying a constant voltage to the counter electrode 3. The voltage applied to the counter electrode 3 is +
500 V to +2000 V is preferable, and +80 V is more preferable.
0V to + 1500V is more preferable. If the voltage applied to the counter electrode 3 is higher than the above range, the print head 4 and the counter electrode 3 are electrically short-circuited, and there is a possibility that both of them are destroyed by discharge. On the other hand, when the applied voltage is lower than the above range, the force for electrostatically attracting the toner 1 to the counter electrode 3 side is weakened,
A sufficient amount of toner 1 for printing high-density dots cannot be attracted to the image receiving member 5 side.

Reference numeral 4 denotes a print head. Reference numeral 12 denotes an insulating substrate (insulating substrate). The thickness of the insulating substrate 12 is suitably from 10 to 100 μm, and the material is a flexible material such as polyimide or polyethylene terephthalate, or a hard material such as an insulating ceramic substrate. Is used.

Reference numeral 13 denotes an insulating protective layer provided on the front and back surfaces of the insulating base material 12, and its thickness is suitably 5 to 30 μm. Of course, the material, thickness, number of constituent layers, and the like of the insulating base material 12 and the insulating protective layer 13 are not limited thereto, and may be arbitrarily designed.

Reference numeral 6 denotes a toner passage opening (developer passage: through-hole) having a circular cross section formed so as to penetrate the print head 4. The processing for forming the toner passage 6 in the print head 4 is preferably performed by forming holes using an excimer laser, a YAG laser, a CO ₂ laser or the like, and then performing an etching process for forming electrodes, as described later. . A plurality of the toner passage openings 6 are arranged along the length direction of the toner carrier 2 (a direction perpendicular to the plane of FIG. 1) to form a toner passage opening array.

Reference numeral 7 denotes a control electrode serving as a first electrode provided on the surface of the insulating base material 12 on the side of the toner carrier 2 so as to surround the toner passage opening 6.

Reference numerals 10a and 10b denote toner passage openings 6 around the toner passage opening 6 on the surface of the insulating base material 12 on the side of the counter electrode 3 (the image receiving member 5 side: the side opposite to the surface on which the control electrode 7 is provided). And a pair of deflection electrodes (a second electrode group that is divided and arranged so as to sandwich the toner passage opening 6). This deflection electrode 10
The control electrodes 7a and 10b are made of a copper foil or an aluminum foil having a thickness of about 2 to 30 μm.

The inner wall surface of the toner passage opening 6 is moved from the control electrode 7 side to the deflection electrodes 10a, 10b so that the diameter near the deflection electrodes 10a, 10b becomes larger than the diameter on the control electrode 7 side.
It is formed in a tapered shape whose diameter increases toward the 10b side. That is, the toner passage opening 6 has a shape that suppresses the length of the toner flow passing through the toner passage opening 6 from increasing in the toner passage opening 6, in other words, the toner 1 passing through the toner passage opening 6 It is formed in a shape that suppresses contact with the inner wall surface of the toner passage opening 6. As described above, any method may be used for forming the toner passage port 6 having the tapered inner wall surface. Among them, a mask is preferably formed on the surface of the insulating base material 12 on which the deflection electrodes 10a and 10b are provided. It is preferable to form a toner passage 6 by irradiating a laser from the mounting side of the mask in the mounted state. This is because only adjusting the irradiation intensity of the laser, the deflection electrode 10
This is because it is possible to easily form the tapered toner passage port 6 in which the aperture on the sides a and 10b is larger than the aperture on the control electrode 7 side.

The toner passage opening 6 is connected to the deflection electrode 10
If the apertures near a and 10b are formed larger than the aperture on the control electrode 7 side, they need not be formed in a tapered shape.
It may be formed in a shape in which the diameter gradually increases toward the b side. However, if there is a step in the toner passage 6, the toner 1 easily accumulates at the position of the step. Therefore, the toner passage 6 may be clogged, or the electric field of the accumulated toner 1 may cause distortion of the deflection electric field. The flying trajectory of the toner 1 may be different from the normal one. Then, the electric field tends to concentrate on the convex portion of the step, and there is a possibility that the inner wall surface of the toner passage opening 6 is destroyed by discharge. On the other hand, by forming the tapered shape as described above, the toner 1 deposited on the inner wall surface of the toner passage 6 can be reduced, and the electric field does not concentrate in the toner passage 6. The discharge breakdown in the passage 6 can be suppressed.

In this embodiment, a film having a 10 μm-thick copper foil provided on both sides of an insulating substrate 12 made of a 50 μm-thick polyimide resin is prepared, and the control electrode 7 and the deflection electrode are provided on each surface by etching. The electrodes 10a,
10b was formed by patterning. After that, the deflection electrode 1
Insulating base material 12 on which patterning of Oa and 10b is formed
A glass mask was placed on the top, and an excimer laser was irradiated from above to form a toner passage 6. Thereafter, plasma cleaning was performed to remove smear (carbide) generated by irradiation with excimer laser. Then, a polyparaxylylene resin was chemically vapor-deposited (CVD) on the entire surface of the insulating base material 12 to form an insulating protective layer 13 having a thickness of 15 μm.

Reference numeral 9 denotes a control electrode power supply as first voltage supply means connected to the control electrode 7, and supplies a control voltage to the control electrode 7 in accordance with an externally supplied image signal. The control electrode power supply 9 includes a voltage generator (not shown) for generating a voltage, and a switching element (not shown) for switching the voltage. One of the switching elements has about 32, 64 or 128 channels for controlling the voltage supplied to the control electrode 7 respectively. For example, 300 per inch (25.4 mm)
When recording at a dot recording density (300 dpi), if a switching element of 64 channels is used,
In order to supply a control voltage to the control electrodes 7 corresponding to the 300 toner passage openings 6, five switching elements having 64 channels are required.

11a and 11b are the deflection electrodes 10a and
A deflection electrode power supply as a second voltage supply means connected to the deflection electrodes 10a and 10b in synchronization with the supply of the control voltage to the control electrode 7 by the control electrode power supply 9. Supply each.

Next, the print head 4 (insulating base material 12)
The configuration of the control electrode 7 and the deflecting electrodes 10a and 10b provided in the first embodiment will be described with reference to FIG. FIG. 2 shows the print head 4
FIG. 2A is a plan view showing the relationship between each electrode provided on the surface and the toner passage opening 6. FIG. 2A shows a control electrode 7 provided on the surface of the print head 4 on the side of the toner carrier 2. FIG. 2B shows the deflection electrodes 10 a and 10 b provided on the surface on the counter electrode 3 side together with the toner passage port 6.

As shown in FIG. 2A, the shape of the control electrode 7 is a circle concentric with the toner passage port 6,
The shape may be an oval or an ellipse. The control electrode 7 does not need to surround the entire periphery of the toner passage 6, and the print head 4 of the toner carrier 2 is
The control electrode 7 may be provided only on the side where the vicinity moves by rotation or only on the opposite side. In the present embodiment, the control electrode 7 having a circular shape concentric with the toner passage 6 and having an inner diameter of 110 μm and an outer diameter of 150 μm is used. 14
Is a lead wire provided on the print head 4 so as to connect the control electrode 7 and the control electrode power supply 9, and the control voltage generated by the control electrode power supply 9 is supplied to the control electrode 7 via the lead wire 14. Supplied.

On the other hand, as shown in FIG. 2B, the pair of deflection electrodes 10a and 10b are arranged obliquely with respect to the transfer direction of the image receiving member 5 indicated by the arrow A with the toner passage opening 6 interposed therebetween. . This is for causing the toner 1 to sequentially fly in an oblique direction on the image receiving member 5 being transferred, and finally forming a horizontal line. A straight line passing through the center of the toner passage opening 6 and orthogonal to the transport direction A of the image receiving member 5 is defined as l1, and a straight line connecting the centers of the deflection electrodes 10a and 10b in the length direction is defined as l1.
Assuming that the angle is 2, the angle θ between the straight lines 11 and 12 is obtained by the following equation: tan θ = 1 / N.

In the above equation, N is the number of flight trajectories of the toner 1 obtained in the deflection process. For example, in the case shown in FIG. 10, three types of toner flight trajectories of left, center and right are formed. N = 3. In the present embodiment, since three types of toner trajectories are configured as in FIG.
8.3 degrees. In the adjacent toner passage 6, the deflection electrodes 10a and 10b around each of them are shared.

In the present embodiment, the cross-sectional shape of each toner passage 6 is circular throughout the thickness of the print head 4, but may be oval or elliptical. Further, the sectional shape of the toner passage opening 6 in the vicinity of the control electrode 7 is formed in a circular shape, and the sectional shape of the portion in the vicinity of the deflecting electrodes 10a and 10b is changed in the direction in which the deflecting electrodes 10a and 10b face each other (the direction of the straight line 12). The shape may be an ellipse, an ellipse, or the like that extends to the right side. In this case, it is preferable that the diameter (short diameter) in the direction perpendicular to the straight line l2 in the vicinity of the deflection electrodes 10a and 10b forming an oval or the like is equal to or larger than the diameter in the vicinity of the control electrode 7 forming a circle. Deflection electrode 10
It is desirable that the boundary between the portions a and 10b and the portion near the control electrode 7 be formed in a shape that smoothly connects the two portions so that no step is formed.

FIG. 3 is a voltage supply time chart of a voltage supply sequence to each electrode, and FIG. 3A is a voltage supply time chart of a control voltage to the control electrode 7.
(B) and (c) show deflection electrodes 10a and 10b, respectively.
3 is a voltage supply time chart of a deflection voltage to the control circuit.

In FIGS. 3A to 3C, the Tt period indicates the time required to form one line, and corresponds to the entire deflection process period. Tt is determined by the resolution of the image receiving member 5 in the transport direction A. For example, 300dp
In order to form a horizontal line at a pitch of i, dividing 1 inch of 25.4 mm by 300 dots gives a line pitch of about 84.6 μm. It is sufficient that the image receiving member 5 moves by one pitch while forming one line. Therefore, when the speed of the image receiving member 5 is, for example, 60 mm / s, the Tt period is about 1390 μs. In this embodiment, the resolution is 600 dpi, and the transfer speed of the image receiving member 5 is 100 mm / s.
And Therefore, the Tt period is 423 μs.

Further, TL, TC and TR are control electrodes 7
Is a control voltage supply time required to form a dot by supplying a control voltage to the image forming apparatus, and corresponds to a developer passage control step (toner passage control step). TL is a control voltage supply time required to form one dot by the left deflection process, and TC and TR are control voltage supply times to form one dot by the straight travel process and the right deflection process, respectively.

In the present embodiment, all control voltage supply times are made equal. That is, TL = TC = TR is set, and Tt = 423 μs.
= TR = Tt / 3 = 141 μs. Each of the control voltage supply times TL, TC, and TR corresponds to the toner 1
Period T consisting of pulse voltage Vc for promoting the passage of
B (pulse voltage width TB) and a suppression period Tw for suppressing passage of the toner 1 to the toner passage opening 6. Further, the promotion period TB is made variable in accordance with an image signal supplied from the outside. That is, when forming low-density dots, TB is set short, and when forming high-density dots, TB is set long. Further, by setting TB to zero (not supplying the pulse voltage Vc), the toner 1 cannot pass through the toner passage 6, so that a non-printing area is formed. As a result, image formation with excellent gradation can be realized. In the present embodiment, the variable range of TB is 0 to 80 μs. Then, the suppression period Tw is supplied from the end of the promotion period TB to the start of the next control voltage supply. During the suppression period Tw, the voltage Vw supplied to the control electrode 7
Was set to −50 V, and the pulse voltage Vc was set to 300 V.
Note that the voltage Vw supplied to the control electrode 7 during the suppression period Tw and the pulse voltage Vc superimposed on the voltage Vw during the promotion period TB are not limited to the above values, and the toner 1 may pass through the toner passage opening 6. An electric field to be suppressed or promoted may be formed between the toner carrier 2 and the print head 4. In the present embodiment, the voltage Vw is supplied to the control electrode 7 during the suppression period Tw. However, Vw is set to the ground level of the image forming apparatus, and a voltage having a polarity opposite to that of the toner 1 is applied to the toner carrier 2. Even when the toner is supplied, it is possible to suppress the toner 1 from passing through the toner passage port 6 during the Tw period.

As shown in FIGS. 3B and 3C, the deflection electrode power supplies 11a and 11b for supplying deflection voltages to the deflection electrodes 10a and 10b respectively have three voltage levels VL, VM and VH. Output is possible, and each deflection voltage level is switched in response to supply of a control voltage for one dot.
In this embodiment, VL = −50 V, VM = + 50 V, V
H = + 150V.

Next, the overall operation of the image forming apparatus according to the present embodiment will be described with reference to FIGS.

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

Subsequently, the image receiving member 5 is conveyed to a position facing the toner passage 6, that is, a print execution position. At the same time that the image receiving member 5 is transported to the print execution position,
As shown in (a), a control voltage pulse voltage Vc is selectively supplied from the control electrode power supply 9 to the control electrode 7. Thus, an attraction electric field is formed between the toner carrier 2 and the control electrode 7 to attract the toner 1 on the toner carrier 2 toward the control electrode 7 to which the pulse voltage Vc is supplied.
The toner 1 detached from the toner carrier 2 by the suction electric field is further attracted by the electric field formed between the toner carrier 2 and the counter electrode 3, and enters the toner passage 6 and passes.

On the other hand, the deflection electrodes 10a and 10b are supplied with deflection voltages from the deflection electrode power supplies 11a and 11b, respectively, in synchronization with the pulse voltage Vc supplied to the control electrode 7.
As a result, the flight trajectory of the toner 1 passing through the toner passage opening 6 is deflected by the deflecting electric field in which distortion occurs near the deflection electrodes 10a and 10b. The toner 1 whose flight trajectory is deflected is electrostatically attracted to the counter electrode 3 and eventually lands on the image receiving member 5 to form a dot. At this time, in the left deflecting step, dots are formed in the image receiving member 5 at positions distant to the left by a deflection distance p from the position on the central axis of the toner passage opening 6. In the straight traveling step, dots are formed at positions on the central axis of the toner passage port 6 in the image receiving member 5. Further, in the right deflection step, dots are formed on the image receiving member 5 at positions separated by a deflection distance p to the right from the position on the central axis of the toner passage opening 6.

The image receiving member 5 on which the dots are formed as described above is transported to a fixing unit (not shown), and the toner 1 on the image receiving member 5 is heated and melted and fixed by the fixing unit. After the completion of the fixing step, the image receiving member 5 is discharged out of the image forming apparatus, and a toner image fixed to the image receiving member 5 is finally obtained.

When the toner 1 passes through the toner passage 6, the inner wall surface of the toner passage 6 is formed in a tapered shape whose diameter increases from the control electrode 7 toward the deflection electrodes 10a and 10b. Therefore, the chance that the flying toner 1 comes into contact with the inner wall surface of the toner passage 6 is reduced.
Opportunities to reduce the flying speed of the toner 1 are also reduced. As a result, an increase in the length of the toner flow while passing through the toner passage 6 is also suppressed. Therefore, since the toner flow reaches the image receiving member 5 in a short state, the tailing phenomenon is reduced.

As described above, the inner wall surface of the toner passage port 6 is
When the taper shape is such that the diameter increases from the control electrode 7 side toward the deflection electrodes 10a and 10b, the taper angle α of the inner wall surface is set as shown in FIG. Flight trajectory of the toner 1 on the body 2 immediately before the toner 1 enters the toner passage 6 and the toner passage 6
It is desirable to set α / 2 ≧ β, where β is the angle formed by the center axis X of the above. That is, the toner 1 flying from the toner carrier 2 is sucked by the control electrode 7 provided around the toner passage 6, and the angle β with respect to the central axis X of the toner passage 6 (simulation in the later-described embodiment). As a result, the toner enters the toner passage opening 6 at an angle of about 5 °. However, if the taper angle α is set as described above, the inner wall surface of the toner passage 6 is inclined by α / 2 with respect to the center axis of the toner passage 6,
Since the value of α / 2 is equal to or larger than β, the toner 1 that has entered the toner passage opening 6 at an angle passes without contacting the inner wall surface of the toner passage opening 6 and the deceleration of the toner 1 is reliably suppressed. Is done. Therefore, the effect of reducing the tailing phenomenon can be further enhanced.

Further, as shown in FIG. 5, the taper angle α of the inner wall surface is set to be equal to the deflection electrodes 10a and 1a of the toner passage port 6.
The print head 4 and the image receiving member 5
L is the distance between L and tan (α / 2) +
It may be set so as to satisfy D / 2 ≧ p. That is,
In the deflecting step, the toner 1 is deflected by the deflecting electrodes 10 a and 10 b and is discharged obliquely from the toner passage 6. At this time, the toner 1 is deflected from the position on the central axis X of the toner passage port 6 (the position C in FIG. 5) on the image receiving member 5 by a deflection distance p.
It is obliquely deflected so as to land at a position (Q position) that is only a distance away. However, if the taper angle α is set as described above, the position (the Q position) separated by the deflection distance p on the image receiving member 5 is moved to the inner wall surface of the toner passage port 6 by the image receiving member 5.
(Refer to the two-dot chain line) where the inner wall surface and the image receiving member 5 intersect (R position: L · tan (α / 2) + D / 2 from the position on the central axis X of the toner passage port 6) ), The toner passage opening 6
The toner 1 which is about to be discharged obliquely is discharged almost without contacting the inner wall surface of the toner passage opening 6, and the deceleration of the toner 1 is surely suppressed. Therefore, similarly to the above, the effect of reducing the tailing phenomenon can be further enhanced.

Here, the print head 4 (Example) having the toner passage opening 6 formed thereon according to the embodiment of the present invention,
In an image forming apparatus using the print head 4 (Comparative Examples 1 and 2) having a different shape of the toner passage opening 6, the analysis results of the flight trajectory of the toner 1 and the image quality at the time of actual printing are as follows. Is shown in comparison with.

(Embodiment) According to the above-described method of forming the toner passage port 6, the taper shape (α = 11.1) is such that the opening diameter on the toner carrier 2 side is 60 μm and the opening diameter D on the image receiving member 5 side is 80 μm. 4 °> 2β = 10 °) was formed in the print head 4. Using the above dimensions, a simulation of the flight trajectory of the toner 1 was performed.

In the above simulation, a two-dimensional analysis was performed using analysis software ADAMS Ver8.2 (manufactured by Mechanical Dynamics). In this analysis, the forces acting on the toner 1 were defined as electrostatic force, mirror image force and air resistance due to an external electrostatic field. The toner 1 was assumed to be a true sphere having a diameter of 7.5 μm, the charge amount per unit weight was −20 μC / g, and the density was 1.0 × 10 ³ kg / m ³ . Then, two layers of the toner 1 were laminated on the toner carrier 2 and arranged at a position facing the toner passage 6. Further, the viscosity coefficient η of air is set to 1.8 × 10 ⁻⁵ Pa · s.
ec. Further, assuming that the toner carrier 2 and the counter electrode 3 are both parallel flat plates, the distance between the print head 4 and the toner carrier 2 is 30 μm, and the distance L between the print head 4 and the counter electrode 3 is The thickness was 200 μm. further,
The inner diameter of the control electrode 7 and the inner diameter of the deflection electrodes 10a and 10b were 90 μm and 130 μm, respectively. Then, assuming that the total thickness of the print head 4 is 100 μm,
2. The thicknesses of the insulating protective layer 13 and each electrode were the same as those in the above embodiment. Further, the insulating base material 12 of the print head 4
It is assumed that the relative dielectric constant of the insulating protective layer 13 is 3. Further, it is assumed that a voltage of +250 V is supplied to the control electrode 7 for 60 μs and then switched to −50 V. The deflection electrode 10a, the deflection electrode 10b, the counter electrode 3, and the toner carrier 2 have -50 V, 150 V, 1 kV, 0 V, respectively.
It was assumed that a voltage of V was constantly applied.

FIG. 6 shows the results of analysis of the flight trajectory of the toner 1 obtained by the above simulation. In addition, FIG.
0.25 ms after applying voltage pulse to control electrode 7
4 shows the flight trajectory of the toner 1 until the time elapses and the position of the toner 1 when 0.25 ms elapses. As is apparent from FIG. 6, it is understood that all the toner 1 has reached the image receiving member 5 when 0.25 ms has elapsed after the application of the voltage pulse to the control electrode 7.

From the result of the analysis under the above conditions, a value is obtained by dividing the number of toners 1 colliding with the inner wall surface of the toner passage opening 6 by the number of toners 1 passing through the toner passage opening 6. The probability of collision with the inner wall surface of the mouth 6 was used. Table 1 shows the probability of collision with the inner wall surface of the toner passage opening 6 in the first embodiment. As shown in Table 1, the probability of the toner 1 colliding with the inner wall surface of the toner passage 6 was about 33.3%.

Further, the above-described image forming apparatus is equipped with the print head 4 to print an image of a vertical line parallel to the transfer direction of the image receiving member 5 (image receiving paper), and to determine whether the tailing phenomenon has occurred. Was visually evaluated. The results are shown in Table 1 above. That is, in this embodiment, no tailing phenomenon was observed on the printed image.

Comparative Example 1 A toner passage 6 was formed in the print head 4 in the same manner as in the above embodiment.
However, in this comparative example 1, the shape of the toner passage port 6 is different from that of the above-described embodiment, the inner wall surface is not formed in a tapered shape, and the diameter is constant (70 μm) over the entire thickness of the print head 4. Of the shape.

The flying trajectory of the toner 1 was analyzed under the same conditions as in the first embodiment except for the shape of the toner passage opening 6. Further, in the same manner as in the first embodiment, the image forming apparatus is equipped with the print head 4 to print an image of a vertical line parallel to the transfer direction of the image receiving member 5 (image receiving paper), thereby causing a tailing phenomenon. Was visually evaluated to determine whether or not the occurrence of blemishes occurred.

FIG. 7 shows the flight trajectory of the toner 1 based on the above analysis result and the position of the toner 1 0.25 ms after the application of the voltage pulse to the control electrode 7. Table 1 shows the probability of collision with the inner wall surface of the toner passage 6 and the presence or absence of the tailing phenomenon in Comparative Example 1.

As is apparent from FIG.
It can be seen that some toner 1 that has not reached the image receiving member 5 even after 0.25 ms has passed. Further, it can be seen that the toner 1 collides with the inner wall surface of the toner passage 6. Then, as shown in Table 1, the probability that the toner 1 collides with the inner wall surface of the toner passage 6 was about 53.8%, which was higher than that of the first embodiment. In addition, a tailing phenomenon was visually observed on the image actually printed on the image receiving member 5.

Comparative Example 2 A toner passage 6 was formed in the print head 4 in the same manner as in the above embodiment.
However, in Comparative Example 2, the toner passage opening 6 was tapered so that the opening diameter on the toner carrier 2 side was 80 μm and the opening diameter on the image receiving member 5 side was 60 μm, contrary to the above embodiment. . Further, the same analysis and printing test as those of the above-described example and comparative example 1 were performed.

FIG. 8 shows the flight trajectory of the toner 1 based on the above analysis result and the position of the toner 1 0.25 ms after the application of the voltage pulse to the control electrode 7. Table 1 shows the probability of collision with the inner wall surface of the toner passage opening 6 and the presence or absence of the tailing phenomenon in Comparative Example 2.

As is clear from FIG. 8, the toner passage port 6
It can be seen that some toner 1 that has not reached the image receiving member 5 even after 0.25 ms has passed. Further, it can be seen that the toner 1 collides with the inner wall surface of the toner passage 6. Further, as shown in Table 1, the probability that the toner 1 collides with the inner wall surface of the toner passage 6 was about 52.9%, which was higher than that of the first embodiment. In addition, a tailing phenomenon was visually observed on the image actually printed on the image receiving member 5.

[0092]

[Table 1]

As can be seen from the above results, the probability that the toner 1 collides with the inner wall surface of the toner passage 6 is reduced by increasing the diameter of the opening of the toner passage 6 on the side of the deflection electrodes 10a and 10b. . It can also be seen that the tailing phenomenon is reduced in the printed image. The reason why the tailing phenomenon is reduced from the above results will be discussed below. That is, since the probability that the toner 1 collides with the inner wall surface of the toner passage 6 is reduced, the number of the toner 1 decelerated in the toner passage 6 is reduced. As a result, it is considered that the number of the toners 1 contained in the trailing end of the toner flowing through the toner passage opening 6 is reduced, so that the trailing phenomenon is less likely to occur. As can be seen by comparing FIG. 6 with FIGS. 7 and 8, as a result of the reduced probability that the toner 1 collides with the inner wall surface of the toner passage 6, the toner 1 that repeatedly collides with the inner wall surface of the toner passage 6 is also reduced. Reduced.
Accordingly, it is considered that the length of the toner flow passing through the toner passage opening 6 is also reduced, and as a result, the trailing phenomenon is less likely to occur.

In the above embodiment, it is considered that the effect that the toner 1 lands on the image receiving member 5 with high accuracy can be obtained in addition to suppressing the occurrence of the tailing phenomenon.

That is, when the toner 1 accumulates on the surface of the print head 4 on the image receiving member 5 side, the deflection electric field is distorted by the electric charge of the accumulated toner 1, and as a result, the flight trajectory of the toner 1 also changes. In addition, the toner 1 passing through the print head 4 while being deflected is landed on the image receiving member 5 without being sufficiently deflected by the toner 1 accumulated around the toner passage opening 6.

On the other hand, in the above embodiment, since the diameter of the toner passage opening 6 on the image receiving member 5 side is large, the toner passage opening 6 from the deflection electrodes 10a and 10b is formed.
Print head 4 to which toner 1 easily accumulates up to the opening edge
The surface area of the surface is reduced. As a result, the amount of the toner 1 deposited on the surface of the print head 4 on the image receiving member 5 side is reduced, and the trajectory of the deflected toner 1 is accurately maintained.

In the above embodiment (example), the surface of the print head 4 on the control electrode 7 side is opposed to the toner carrier 2 (the control electrode 7 is placed on the surface of the insulating base 12 on the toner carrier 2 side). Provided), but the deflection electrodes 10a, 10b
(A deflection electrode 10).
a, 10b are provided on the surface of the insulating base material 12 on the side of the toner carrier 2).
The opening diameter on the 10b side may be formed to be larger than that on the control electrode 7 side. However, in this case, after the trajectory of the toner 1 is changed by the deflecting electrodes 10a and 10b, the toner 1 must pass through the narrowed toner passage 6. The probability of collision with the inner wall increases compared to the above embodiment. Therefore, it is preferable that the print head 4 is arranged such that the surface on the control electrode 7 side faces the toner carrier 2 as in the above embodiment.

In the above-described embodiment, the insulating protective layers 13 are provided on both surfaces of the print head 4.
An antistatic electrode may be provided on the surface. This allows
The charge of the print head 4 due to the contact between the toner 1 and the print head 4 is prevented, and the charge amount of the toner 1 on the toner carrier 2 can be stabilized. The material of the antistatic electrode is preferably a hard material such as conductive amorphous carbon. This is to prevent wear due to direct contact with the image receiving member 5 and the toner 1. The surface resistance is 10 ⁸ to 10 ¹¹ Ω
The degree is preferred. This is because, if it exceeds the above range, the effect of removing the charged charges is reduced, while if it is less than the above range, there is a possibility that an electrical short circuit will occur with the counter electrode 3.

The diameter of the toner passage port 6 is not limited to the dimension shown in the above embodiment, but may be the same as that of the deflection electrodes 10a and 10a.
The opening diameter on the 10b side may be further increased. Especially 15
In an image forming apparatus that forms a low-resolution image of 0 dpi to 300 dpi, it is desirable to further increase the opening diameter on the side of the deflection electrodes 10a and 10b. This is because the deflection distance is long in low resolution printing, so if the aperture diameter is small,
The toner 1 whose flight trajectory is deflected in the toner passage 6 is
This is because a sufficient deflection distance cannot be obtained by colliding with the inner wall surface of the toner passage opening 6. However, the deflection electrode 10
If the opening diameters on the sides a and 10b are too large, the distance from the inner wall surface of the toner passage 6 to the deflecting electrodes 10a and 10b becomes short, so that the insulating insulating protective layer 13 covering the deflecting electrodes 10a and 10b accordingly. Becomes thinner. For this reason, the deflection electrodes 10 a and 10 opposed to each other via the toner passage port 6.
There is a possibility that an electrical short circuit may occur between b.

[0100]

As described above, according to the print head and the image forming apparatus of the present invention, the diameter of the developer passage opening near the second electrode group is larger than the diameter on the first electrode side. (A shape that suppresses the length of the developer flow passing through the developer passage opening from increasing in the developer passage opening, or a shape that suppresses the developer flow from contacting the inner wall surface of the developer passage opening. ), The chance of the flying developer colliding with the inner wall surface of the developer passage, that is, the chance of reducing the flying speed of the developer is reduced, so that the developer flow during the passage in the developer passage is reduced. An increase in length is suppressed.
As a result, an image with less tailing phenomenon is formed.

Further, by disposing the first electrode on the surface of the insulating substrate on the side of the developer carrying member, the developer deflected in the developer passage is almost in contact with the inner wall surface of the developer passage. Since the developer can pass through the developer passage opening without any trouble, the degree of freedom of the deflection distance is expanded, and the developer can be accurately landed on the image receiving member even at a long deflection distance. Further, since the chance of the developer contacting the inner wall surface of the developer passage is reduced, an image with less tailing phenomenon is formed.

Further, the inner wall surface of the developer passage is formed in a tapered shape in which the diameter increases from the first electrode side to the second electrode group side. Since there is no step that easily accumulates, clogging of the developer passage opening due to the developer and distortion of the deflection electric field due to charge of the developer accumulated inside the developer passage opening are suppressed. As a result, an image having no developer landing position error due to white streaks due to clogging or distortion of the deflection electric field is formed.

When the taper angle α of the inner wall surface of the developer passage is defined as β, the angle between the flight trajectory immediately before the developer enters the developer passage and the central axis of the developer passage is defined as β. ,
α / 2 ≧ β, or the deflection distance is p, the opening diameter of the developer passage opening on the second electrode group side is D, and the distance between the print head and the image receiving member is L. By setting L · tan (α / 2) + D / 2 ≧ p, the contact of the developer with the inner wall surface of the developer passage can be reliably suppressed. The deceleration of the agent is reliably suppressed, and the effect of reducing the tailing phenomenon can be further enhanced.

[Brief description of the drawings]

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

FIG. 2 is a plan view of each surface on a toner carrier side and a counter electrode side of a print head according to an embodiment of the present invention.

FIG. 3 is a voltage supply time chart showing respective supply timings of a control voltage and a deflection voltage.

FIG. 4 is a diagram showing the relationship between the taper angle of the inner wall surface of the toner passage and the flight trajectory immediately before the toner enters the toner passage.

FIG. 5 is a diagram illustrating a relationship among a taper angle of an inner wall surface of a toner passage, a deflection distance, a diameter of a toner passage opening on a deflection electrode side, and a distance between a print head and an image receiving member.

FIG. 6 is a diagram illustrating a flight trajectory of toner obtained by a simulation analysis in the example.

FIG. 7 is a diagram illustrating a flying trajectory of toner obtained by a simulation analysis in Comparative Example 1.

FIG. 8 is a diagram illustrating a flight trajectory of toner obtained by a simulation analysis in Comparative Example 2.

FIG. 9 is a schematic configuration diagram illustrating a conventional example of an image forming apparatus.

FIG. 10 is an explanatory diagram illustrating voltage control of a control electrode and a deflection electrode and a state of toner flying in a conventional image forming apparatus.

[Explanation of symbols]

Reference Signs List 1 toner (developer) 2 toner carrier (developer carrier) 4 print head 5 image receiving member 6 toner passage (developer passage) (through hole) 7 control electrode (first electrode) 9 power supply for control electrode (First voltage supply means) 10a, 10b Deflection electrode (second electrode group) 11a, 11b Power supply for deflection electrode (second voltage supply means) 12 Insulating base material (insulating substrate)

 ──────────────────────────────────────────────────の Continuation of the front page (71) Applicant 597063831 Owneds Brygga 13 421 57 Vestro Fround a Sweden (72) Inventor Taichi Ito 1006 Odakadoma, Kadoma City, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F-term (reference) 2C162AE25 AE31 AE47 AF70 AH25 CA02 CA12 CA24 CA28 2H029 DB04

Claims (11)

[Claims] A developer carrying member for carrying and transporting the developer; an image receiving member provided to face the developer carrying member for receiving a developer image; A print head provided between the plurality of developer passages, the plurality of developer passage ports through which the developer carried by the developer carrier passes toward the image receiving member, and the base material being formed of an insulating substrate; A first electrode disposed around each of the developer passage openings on one surface of the insulating substrate, and an insulating substrate surface on a side opposite to the surface on which the first electrode is provided. A second electrode group disposed in the vicinity of each developer passage opening in a state of being divided into a plurality of parts so as to sandwich each developer passage opening; and a predetermined electrode corresponding to the first electrode in accordance with an image signal. First voltage supply means for supplying a voltage; And a second voltage supply unit for supplying different voltages to the plurality of electrodes constituting the electrode group, respectively, wherein the developer passage opening is formed by a developer passing through the developer passage opening. An image forming apparatus, which is formed in a shape that suppresses a length of a developer flow from increasing in a developer passage opening. A developer carrying member for carrying and transporting the developer; an image receiving member provided to face the developer carrying member for receiving a developer image; A print head provided between the plurality of developer passages, the plurality of developer passage ports through which the developer carried by the developer carrier passes toward the image receiving member, and the base material being formed of an insulating substrate; A first electrode disposed around each of the developer passage openings on one surface of the insulating substrate, and an insulating substrate surface on a side opposite to the surface on which the first electrode is provided. A second electrode group disposed in the vicinity of each developer passage opening in a state of being divided into a plurality of parts so as to sandwich each developer passage opening; and a predetermined electrode corresponding to the first electrode in accordance with an image signal. First voltage supply means for supplying a voltage; And a second voltage supply unit for supplying different voltages to the plurality of electrodes constituting the electrode group, respectively, wherein the developer passage opening is formed by a developer passing through the developer passage opening. An image forming apparatus, wherein the image forming apparatus is formed in a shape that suppresses contact of an agent with an inner wall surface of a developer passage opening. A developer carrying member for carrying and transporting the developer; an image receiving member provided to face the developer carrying member for receiving a developer image; A print head provided between the plurality of developer passages, the plurality of developer passage ports through which the developer carried by the developer carrier passes toward the image receiving member, and the base material being formed of an insulating substrate; A first electrode disposed around each of the developer passage openings on one surface of the insulating substrate, and an insulating substrate surface on a side opposite to the surface on which the first electrode is provided. A second electrode group disposed in the vicinity of each developer passage opening in a state of being divided into a plurality of parts so as to sandwich each developer passage opening; and a predetermined electrode corresponding to the first electrode in accordance with an image signal. First voltage supply means for supplying a voltage; An image forming apparatus comprising: a second voltage supply unit configured to supply different voltages to a plurality of electrodes constituting the electrode group, wherein the developer passage port has a diameter in the vicinity of the second electrode group. Is formed so as to be larger than the aperture on the first electrode side. 4. The image forming apparatus according to claim 3, wherein the first electrode is provided on a surface of the insulating substrate on the side of the developer carrier. 5. The image forming apparatus according to claim 4, wherein the inner wall surface of the developer passage is formed in a tapered shape in which the diameter increases from the first electrode side to the second electrode group side. An image forming apparatus comprising: 6. The image forming apparatus according to claim 5, wherein the taper angle α of the inner wall surface of the developer passage is the developer passage of the developer on the developer carrier facing the developer passage. An image forming apparatus characterized in that α / 2 ≧ β is satisfied, where β is an angle between a flight trajectory immediately before entering the developer and a central axis of the developer passage. 7. The image forming apparatus according to claim 5, wherein the taper angle α of the inner wall surface of the developer passage port has a deflection distance of p.
When the opening diameter of the developer passage opening on the second electrode group side is D and the distance between the print head and the image receiving member is L, Ltan (α / 2) + D / 2 ≧ p An image forming apparatus characterized by being set to satisfy. 8. The image forming apparatus according to claim 5, 6 or 7, wherein the developer passage port is provided with the mask placed on a surface of the insulating substrate on which the second electrode group is formed. An image forming apparatus formed by irradiating a laser from a setting side. 9. An insulating substrate, a plurality of through-holes penetrating the insulating substrate, first electrodes provided around one of the through-holes on one surface of the insulating substrate, A print head comprising: a second electrode group arranged in a state of being divided into a plurality of parts so as to sandwich each of the through-holes around the through-hole on the other surface of the insulating substrate; The print head, wherein the through hole is formed such that a diameter near the second electrode group is larger than a diameter on the first electrode side. 10. The print head according to claim 9, wherein the inner wall surface of the through hole is formed in a tapered shape in which the diameter increases from the first electrode side to the second electrode group side. And print head. 11. The print head according to claim 10, wherein the through-hole irradiates a laser from the mounting side of the mask while the mask is mounted on the surface of the insulating substrate on which the second electrode group is formed. The print head characterized by being formed by the above.