JPH1076664A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device, having a high recording frequency and capable of effecting stabilized recording, by a method wherein the particles of a coloring material in a recording liquid supplied to the vicinity of an opening are agglomerated and are separated from the insulating liquid to discharge and form an image on the medium for forming the image. SOLUTION: The crosslinking between ink meniscuses formed on respective openings 43a with each other is prevented by a bulkhead, specifying both sides of a recording liquid recovering groove 57, and an oil repelling surface, provided on the upper surface of the bulkhead, whereby undesired vibration and the disturbance of discharging direction of the ink meniscus 47, which are generated upon the flying of recording particle drops 76, are prevented and stabilized recording is permitted. Further, the diameter of the recording particle drop 76, flied out of the opening 43a, is changed by the value of discharging voltage and the impressing period of time of the voltage. When a recording liquid 70, containing the toner 71 of average grain size 1μm, is used, the diameter of the recording particle drop 76 is changed within the range of about 15-120μm when the discharging voltage is changed within the range of 150-600V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an electrostatic force acting on a recording liquid in which colorant particles are dispersed in an insulating liquid.
The present invention relates to an image forming apparatus that forms an image by flying colorant particles.

[0002]

2. Description of the Related Art In recent years, ink jet printers using an ink jet recording system have become widespread in the field of personal printers. However, conventional ink jet printers have problems such as poor image storability and light fastness due to the use of a dye recording liquid.

On the other hand, WO93 / 11866 discloses an image forming apparatus which enables the use of pigment particles as a coloring agent and solves the above-mentioned problems of the dye recording liquid. This apparatus includes a conductive recording liquid supply tube, and by applying a predetermined voltage to the recording liquid supply tube, a predetermined electric field is generated between the recording liquid supply tube and a counter electrode facing the tip. Form. Then, a recording liquid containing colorant particles charged to the same polarity as the potential of the recording liquid supply tube is supplied to the recording liquid supply tube. On this occasion,
A recording medium is interposed between the tip of the recording liquid supply tube and the counter electrode, and is conveyed in a predetermined direction.

[0004] The coloring agent particles in the recording liquid are discharged at a discharge point near the distal end of the recording liquid supply tube due to an electric field formed between the distal end of the recording liquid supply tube and the counter electrode.
Receiving the electrostatic attraction force from the counter electrode, a semicircular ink meniscus is formed near the tip of the recording liquid supply tube.
However, the colorant particles cannot fly from the ink meniscus due to the surface tension of the solvent of the recording liquid, and stay at the tip of the ink meniscus. In this way, many colorant particles collect at the tip of the ink meniscus and form aggregates.

When the recording medium is conveyed in a predetermined direction and the voltage applied to the recording liquid supply tube is further increased, the electric field from the tip of the recording liquid supply tube to the counter electrode is strengthened, and the electric field is higher than the surface tension of the recording liquid solvent. The electrostatic attraction acting on the aggregates prevails, and the aggregates are separated from the ink meniscus and fly toward a recording medium interposed between the aggregates. Then, a predetermined image is formed on the recording medium by the aggregate of the colorant particles flying from the ink meniscus.

In an image forming apparatus based on the above-described flying principle, since there is no nozzle for determining the size of a flying droplet as in the conventional ink jet recording using a dye recording liquid, pigment particles can be used. For this reason, problems such as image storability and light resistance, which were problems of the conventional ink jet printer, are solved.

[0007]

However, in the above-described conventional image forming apparatus, when the colorant particles are ejected toward the recording medium, the ejection points near the tip of the conductive recording liquid supply tube are often increased. Are once agglomerated. For this reason, in the conventional image forming apparatus, there is a problem that the coloring agent particles are easily fixed to the tip of the recording liquid supply tube, and the recording liquid is clogged.

Further, since the strongest electric field is formed at the tip of the recording liquid supply tube close to the counter electrode, the colorant particles hardly reach the ejection point, and the aggregation of the colorant particles becomes unstable, and the recording dots are formed. A defect such as a decrease in diameter occurs. Further, since the aggregation of the colorant particles becomes unstable, the recording frequency becomes extremely unstable, and there is a problem that a high quality image cannot be formed. The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus having a high recording frequency and capable of performing stable recording.

[0009]

In order to achieve the above-mentioned object, an image forming apparatus according to the present invention comprises a storage means for storing a recording liquid formed by dispersing charged colorant particles in an insulating liquid; An ink flow path for circulating the recording liquid, a first electrode provided in the ink flow path, and an ink flow path for arranging the opening at a predetermined distance from the image forming medium. A second electrode having a tip extending to substantially the same height as the opening, and a supply unit for supplying the recording liquid contained in the containing unit to the opening; By applying a voltage to the first and second electrodes according to a predetermined image signal, the colorant particles in the recording liquid supplied near the opening are aggregated, and the aggregated colorant particles are separated from the insulating liquid. Separated from the And a, and a voltage application means for forming an image on an image forming medium.

Further, the image forming apparatus of the present invention has a storage means for storing a recording liquid formed by dispersing charged colorant particles in an insulating liquid, and an opening. An ink flow path that is disposed at a predetermined distance and circulates the recording liquid; a first electrode provided in the ink flow path; and a tip protruding from the opening toward the image forming medium. An insulating guide member, and a second end provided on the guide member so as to face the first electrode and extending to substantially the same height as the opening.
An electrode, a supply unit that supplies the recording liquid in the storage unit to the opening, and a voltage applied to the first and second electrodes in accordance with a predetermined image signal to aggregate the colorant particles in the recording liquid. And a voltage applying unit that separates and discharges the aggregated colorant particles from the insulating liquid to form an image on the image forming medium.

Further, the image forming apparatus of the present invention has an insulating support member forming an opening at a position separated from the image forming medium by a predetermined distance, and forming a flow path communicating with the opening;
A first electrode provided to extend to the opening along the inner surface of the flow path, and a tip provided in the flow path and protruding from the opening toward the image forming medium by a predetermined length. An insulating guide member, a second electrode provided along the surface of the guide member and having a tip extending to substantially the same height as the opening, and charged colorant particles dispersed in an insulating liquid. Supply means for supplying a recording liquid to the opening through the flow path, forming a meniscus protruding from the opening toward the image forming medium from the opening by wetting of the recording liquid by the guide member, and a predetermined image signal By applying a voltage to the first and second electrodes according to the above, an electric field is formed from the center of the meniscus to the outside, and the colorant particles in the recording liquid are moved along the liquid surface of the meniscus to the tip of the meniscus. And an image forming means for forming an image on the image forming medium by separating and discharging the colorant particles aggregated at the tip of the meniscus from the insulating liquid. .

Further, according to the image forming apparatus of the present invention, a plurality of openings are formed in a plane separated from the image forming medium by a predetermined distance, and a plurality of insulating supports forming a plurality of flow paths communicating with the respective openings. A member, a plurality of first electrodes provided independently of each other along the inner surface of each of the flow paths, and having a tip extending to each of the openings; and a predetermined length from each of the openings toward the image forming medium. An insulating guide member having a plurality of protrusions projecting therefrom; and a plurality of second guides provided in the respective flow paths corresponding to the respective first electrodes and having tips extending to substantially the same height as the respective openings. Two electrodes, a supply means for supplying a recording liquid formed by dispersing charged colorant particles in an insulating liquid to each of the openings through each of the flow paths, and a supply means for all the first and second electrodes. 1 is applied to each of the openings. The colorant particles in the recording liquid were aggregated,
By selectively applying a second voltage higher than the first voltage to the first and second electrodes selected according to a predetermined image signal, the aggregated colorant particles are separated from the insulating liquid. Voltage applying means for ejecting and forming an image on the image forming medium.

Further, according to the image forming apparatus of the present invention, a plurality of openings are formed in a plane separated from the image forming medium by a predetermined distance, and a plurality of insulating supports forming a plurality of flow paths communicating with the respective openings. A member, a plurality of first electrodes provided independently of each other along the inner surface of each of the flow paths, and having a tip extending to each of the openings; and a predetermined length from each of the openings toward the image forming medium. An insulating guide member having a plurality of protrusions projecting therefrom; and a plurality of second guides provided in the respective flow paths corresponding to the respective first electrodes and having tips extending to substantially the same height as the respective openings. Two electrodes, supply means for supplying a recording liquid, which is obtained by dispersing charged colorant particles in an insulating liquid, to each of the openings through each of the flow paths, and Protruding toward the image forming medium,
A plurality of partitions for partitioning the recording liquid supplied to the openings by the supply unit; a collection unit for collecting the recording liquid supplied to the openings by the supply unit; A plurality of recovery paths for guiding the recording liquid supplied to the respective openings by the supply means to the recovery means, and applying a first voltage to all of the first and second electrodes. Thereby, the colorant particles in the recording liquid supplied near each of the openings are aggregated, and a second voltage higher than the first voltage is applied to the first and second electrodes selected according to a predetermined image signal. Voltage applying means for selectively applying the ink to separate and eject the aggregated colorant particles from the insulating liquid to form an image on the image forming medium.

Further, the image forming apparatus of the present invention has a plurality of grooves, a tip of each of the grooves forms a plurality of openings in a plane separated from the image forming medium by a predetermined distance, and First and second support members opposing each other having a plurality of first electrodes disposed on the surface extending to each of the openings, and projecting toward the image forming medium by a predetermined length from each of the openings. While having a plurality of projections at its upper end, while being sandwiched by the first and second support members, it is electrically connected to the first electrodes and extends to substantially the same height as the openings. A guide member having, on its surface, a plurality of second electrodes having a distal end and a base end having a plurality of connection terminals corresponding to the first electrodes formed outside the first and second support members; Dispersed colorant particles in an insulating liquid Supply means for supplying the recording liquid to the openings through the grooves, and projecting from the first and second support members toward the image forming medium between the openings. A plurality of partitions for partitioning the recording liquid supplied to the openings by the supply unit; a collection unit for collecting the recording liquid supplied to the openings by the supply unit; And a plurality of recovery paths for guiding the recording liquid supplied to each of the openings by the supply means to the recovery means, and the first and second electrodes to the first and second electrodes via the connection terminals. By applying the voltage of 1, the colorant particles in the recording liquid supplied in the vicinity of the opening are aggregated, and connected to the connection terminals that are connected to the first and second electrodes selected according to a predetermined image signal. A second voltage higher than the first voltage is selectively applied. And the comprises a voltage applying means for agglomerated colorant particles are separated discharged from the insulating liquid for forming an image on the target image forming medium.

Further, the image forming apparatus of the present invention has an opposing surface in which a plurality of grooves each having an end formed with an opening are formed at a position separated from the image forming medium by a predetermined distance, and the surface of each of the grooves is formed. An insulating support member having a plurality of first electrodes extending to the openings and exposed to the opposing surface, and a surface proximate to the opposing surface of the support member, and on this surface, A distal end electrically connected to each of the first electrodes and extending to substantially the same height as each of the openings, and a base end formed with a plurality of connection terminals corresponding to each of the first electrodes outside the support member. Having a plurality of second
An insulative guide member having electrodes and having a plurality of protrusions protruding toward the image forming medium by a predetermined length from each of the openings at an upper end opposed to the image forming medium; The recording liquid, which is obtained by dispersing agent particles in an insulating liquid, is supplied to each of the openings through the grooves, and the recording liquid is wetted by the projections of the guide member, and the image to be imaged from the openings. Supply means for forming a plurality of meniscuses projecting toward the forming medium; and projecting from the support member toward the image forming medium between the openings, and supplied to the openings by the supply means. A plurality of partition walls for partitioning the recording liquid, a recovery unit for recovering the recording liquid supplied to each of the openings by the supply unit, and provided between the adjacent partition walls; Up the recording liquid supplied to the opening A plurality of collection paths for guiding the collection means, the first and second above all through the respective connection terminals
By applying a first voltage to the electrodes, the colorant particles in the recording liquid are caused to migrate along the liquid surface of each of the meniscuses toward the tip of each of the meniscuses and aggregate, and according to a predetermined image signal Selectively applying a second voltage higher than the first voltage to the connection terminal that is electrically connected to the first and second electrodes selected in response to the first and second electrodes selected according to the image signal. Image forming means for forming an image on the image forming medium by separating and discharging the colorant particles aggregated at the tip of the meniscus corresponding to the two electrodes from the insulating liquid.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, an inkjet printer 1 as an image forming apparatus according to the present invention will be described.

As shown in FIG. 1, the ink jet printer 1 has a housing 2. At a substantially central predetermined position in the housing 2, a belt 3 (image forming medium) that runs endlessly in the direction of arrow a in the figure is provided.

Outer peripheral surface 3 as an image bearing surface of the belt 3
On a, a color image is formed by a recording device 10 described later. The image formed on the outer peripheral surface 3a of the belt 3 is moved to a predetermined transfer position along with the movement of the belt 3, and is transferred onto the recording paper P conveyed synchronously at this transfer position. That is, the belt 3 functions as an intermediate image carrier that temporarily holds the image from the recording device 10 and transfers the held image onto the recording paper P. The width of the belt 3 is set to be at least larger than the width of the recording paper P.

The belt 3 is wound and stretched around three rollers 4, 5, and 6 disposed at predetermined positions in the housing 2, respectively. The roller 4 located above the transfer roller 15 via the belt 3 at the transfer position where the image is transferred.
The rollers 5 and 6 positioned below the roller 5 and 6 are positioned such that the belt 3 between the rollers 5 and 6 runs in a substantially horizontal plane. Then, rollers 4, 5, 6 are driven by a motor (not shown).
, The belt 3 runs at a constant speed in the direction of arrow a in the figure.

The belt 3 is made of a metal having an appropriate roughness, silicon resin, silicon rubber, a fluororesin such as polyfluoroethylene, or a simple substance such as polyimide, or is formed on a metal belt such as stainless steel. It is formed by coating the applied resin or rubber with a predetermined thickness. The outer peripheral surface 3a of the belt 3 is formed of a material having excellent heat-resistance as well as excellent releasability from a recording liquid described later. In addition, the belt 3 is formed of a relatively durable material having excellent wear resistance in order to maintain a gap with a tip of a recording head described later incorporated in the recording apparatus 10 with high accuracy.

In the case of the belt 3 in which a resin or rubber is coated on a metal belt, the thickness of the coating layer is required to make the recording liquid held on the belt 3 releasable, uniform the pressure applied during transfer, and required. The thickness is set appropriately in consideration of the abrasion life and the like. For example, when coating with silicon rubber, it is preferable to set the layer thickness to about 50 to 200 μm.

In any case, if an insulating material is used for the outer peripheral surface 3a of the belt 3, the belt 3 may be charged with static electricity due to frictional charging or the like. As described above, when the belt 3 is charged with static electricity, the electric field at the time of image formation may be disturbed to cause an image defect. Therefore, when an insulating material is used for the belt 3, it is desirable to mix a conductive filler such as carbon, zinc oxide, and titanium oxide to lower the electric resistance of the material. Further, if the charging potential of the belt 3 is controlled by a corona charging device or the like, an insulating material in which a conductive filler is not mixed can be used.

At a predetermined position below the belt 3, the belt 3
A recording device 10 for forming a color image according to an image signal on the outer peripheral surface 3a of the recording medium 10 is provided. Recording device 10
Has four recording units 30a, 30b, 30c, 30d (to be described in detail later) provided side by side along the running direction of the belt 3. These recording units are prepared in accordance with the type of recording liquid to be recorded (black, cyan, magenta, yellow), and the tip of a recording head described later projects from the upper end of each recording unit. The leading end of each of these recording heads is provided at a discharge position separated by a predetermined distance below the belt 3 running between the rollers 5 and 6.

Each recording unit 30a, 30b, 30c,
As described in detail later, an insulating liquid (hereinafter referred to as 30d)
Carrier liquid), black, cyan, magenta, and yellow recording liquids in which charged colorant particles (hereinafter, referred to as toner) are dispersed, and are separated from a signal source (not shown). When the image signal is input to each recording unit, an electric field is formed from the leading end of each recording head toward the belt 3 according to the color-separated image signal, and the toner flies onto the outer peripheral surface 3a of the belt 3. Thus, an image for each color is formed. In this case, the color-separated 4
The two images are accurately overlapped on the outer peripheral surface 3a of the belt 3 to form one color image. still,
Each recording unit has the same configuration except that the color of the contained recording liquid is different. Therefore, in the following description, the recording unit 30 will be simply described.

Inside the belt 3, that is, on the side opposite to the recording apparatus 10, a grounded electrode plate 8 for forming a predetermined electric field between the recording heads 30 is provided. A predetermined voltage is applied to the electrode plate 8 by a power source (not shown) as necessary. The electrode plate 8 is provided substantially parallel to and close to the belt 3, and functions to suppress the vibration of the belt 3 and keep the gap between the belt 3 and the leading end of the recording head constant.

The electrode plate 8 is not necessarily provided by forming the belt 3 from a conductive material. That is, if the belt 3 is made conductive, and if necessary, any one of the rollers 4, 5, and 6 around which the belt 3 is wound functions as an electrode, the belt 3 and the recording head can be formed without the electrode plate 8. A predetermined electric field can be formed between the first electric field and the second electric field.

On the right side of the belt 3 in the drawing, paper feed cassettes 12a and 12b in which a plurality of recording papers P are stacked are provided. Recording papers P of different sizes are stored in the respective paper cassettes 12a and 12b.
The printers 2a and 12b are mounted on the housing 2 of the printer 1 such that the front ends are located inside the housing 2 and the rear ends are located outside the housing 2. Each paper cassette 12a, 1
2b, each paper cassette 12
Paper feed rollers 11 and 13 are provided, respectively, which roll near the top end of the uppermost recording paper P accumulated in a and 12b and take out one by one from the uppermost recording paper P in order.

The recording paper P on the downstream side of the paper feed rollers 11 and 13
, A pair of transport guides 11a, 11b, and 1 disposed opposite to each surface of the recording paper P.
3a and 13b are provided. In addition, the transport guide 11
On the downstream side of a, 11b, 13a, and 13b, a pair of recording papers P conveyed via the respective conveyance guides are nipped and conveyed toward a predetermined transfer position between the roller 4 and the transfer roller 15. Transport rollers 14a and 14b are provided.

The transfer roller 15 rolled into contact with the roller 4 is
Like the belt 3, the belt 3 is made of a material having excellent peelability and heat resistance. For example, a belt used in a conventional electrophotographic apparatus can be used. Inside the transfer roller 15, a heater 15a heated to 70 ° C. to 100 ° C. is provided. The heater 15a heats the transfer roller 15 to a predetermined temperature so that the toner image formed on the recording paper P by the recording device 10 can be melted or softened. Note that the heater 15a may be provided inside the roller 4.

The roller 4 and the transfer roller 15
The toner image on the belt 3 that has been passed through the belt 3 and melted or softened by the heater 15a is pressed against the recording paper P between the roller 4 and the transfer roller 15, and the toner image is transferred and fixed onto the recording paper P. It is supposed to be. That is, the outer peripheral surface 3a of the belt 3 is formed of a material having high releasability,
Since the recording paper P has a stronger adhesive force to the toner, the toner image formed on the outer peripheral surface 3a of the belt 3 is almost completely transferred onto the recording paper P.

Instead of providing the above-described heater 15a, a voltage having a polarity opposite to the charge polarity of the toner is applied to the transfer roller 15 so that the transfer roller 15 is placed on the belt 3 as in the conventional electrostatic transfer system using electrophotography. Can be transferred onto the recording paper P. In this case, the voltage applied to the transfer roller 15 may be about 500 to 1000 volts.

On the transport path on the downstream side of the transfer roller 15,
A pair of conveying rollers 16a and 16b are provided between the roller 4 and the transfer roller 15 to convey the recording paper P on which the toner image has been transferred. Transport roller 16
A heater plate 17 for drying the toner image transferred and fixed onto the recording paper P is provided further downstream of the heaters 16a and 16b.

The heater plate 17 is provided for drying an image transferred on the recording paper P, and employs an electrostatic transfer system in which a predetermined voltage is applied to the transfer roller 15 to transfer a toner image. In this case, it is necessary to fix the toner image transferred onto the recording paper P by increasing the temperature of the heater plate 17 to about 100 ° C.

The recording paper P passed above the heater plate 17 passes very close to the heater plate 17 without contact. Downstream of the heater plate 17, a pair of paper discharge rollers 18a, 18b for holding the recording paper P and discharging the recording paper P out of the housing 2.
Is provided. On the downstream side of the paper discharge rollers 18a, 18b and on the left side wall of the housing 2 in the drawing, a paper discharge on which the recording paper P discharged outside the housing 2 via the paper discharge rollers 18a, 18b is placed. A tray 19 protrudes.

Thus, in synchronization with the movement of the image formed by the recording apparatus 10, the recording paper P taken out of the predetermined paper feed cassette 12a or 12b by the paper feed roller 11 or 13 is transferred to the transport guides 11a and 11b. Or 13
The transfer roller 15 is fed to the transfer position between the roller 4 and the transfer roller 15 via the transfer rollers 14a and 14b. The recording paper P sent to the transfer position in synchronization with the toner image as described above is moved at the same speed as the belt 3 and passes through the transfer roller 15, so that the toner image formed on the outer peripheral surface of the belt 3 is formed. Is transferred to the transport roller 16
The paper is discharged onto the paper discharge tray 19 via the paper discharge rollers 19a and 16b and the paper discharge rollers 18a and 18b. At this time, the recording paper P on which the toner image has been transferred passes through the heater plate 17, and the carrier liquid attached to the toner is sufficiently dried.

Above the transfer roller 15, the transfer roller 1
A duct 21 is provided so as to surround the heater plate 5, and a duct 22 is provided above the heater plate 17 so as to surround the heater plate 17. Each duct 21, 22
The carrier liquid gas generated by the heating is collected and sent to a decomposition device 24 for decomposing the gas. The decomposer 24 functions in the same manner as a catalyst device that decomposes exhaust gas of an automobile, decomposes the gas into water and carbon dioxide gas, and discharges the gas to prevent generation of odor.

On the outer peripheral surface of the transfer roller 15, a cleaning blade 23 made of silicone resin for scraping off the toner adhered to the outer peripheral surface of the transfer roller 15 is disposed so as to contact the outer peripheral surface at an acute angle. I have.

Below the roller 6, a wiping device 25 for wiping toner adhered to the belt 3 is provided. The wiping device 25 has a felt or a brush which is disposed in contact with the roller 6 and is impregnated with a carrier liquid in the recording liquid, and rubs the belt 3 with such a felt or a brush. The toner attached to the surface is wiped off.

A dryer 26 for blowing hot air toward the outer peripheral surface 3a of the belt 3 is provided between the wiping device 25 and the recording device 10. That is,
When the toner is cleaned by the wiping device 25, the carrier liquid slightly wets the outer peripheral surface 3 a of the belt 3. If the degree of wetting of the belt 3 is high, an image defect may occur on the outer peripheral surface 3a of the belt 3 due to bleeding or flowing when an image is formed next. Therefore, it is necessary to sufficiently dry the belt 3 in preparation for the next recording operation.

Next, the recording unit 30 will be described in detail. FIG. 2 shows the details of the recording unit 30. The recording unit 30 includes a head unit 4 disposed below and facing the belt 3 as an intermediate recording medium.
0, a recording liquid tank 32 containing a recording liquid to be circulated to the head unit 40 and having a recording liquid concentration adjusting mechanism.
And Note that the recording liquid used here is formed by dispersing charged toner in an insulating carrier liquid, and the toner includes the above four colors (black, cyan, magenta, and yellow).

The head unit 40 has a substantially rectangular parallelepiped recording head 42 (see FIG. 4) disposed below the belt 3 and extending in a vertical plane. The recording head 42 has a front end 42 a which is opposed to the lower side of the belt 3 by a predetermined distance.
(Refers to a tip of a protruding plate described later).
a is arranged so as to extend in a direction crossing the conveying direction of the recording paper P, that is, in a direction crossing the running direction of the belt 3.
In the present embodiment, the leading end 42 a of the recording head 42 is 0.1 to 3 m from the outer peripheral surface 3 a of the belt 3.
m. The distance between the leading end 42a of the recording head 42 and the outer peripheral surface 3a of the belt 3 is determined according to the magnitude of a recording voltage applied to the recording head 42, which will be described later.

Near the tip 42a of the recording head 42, there are formed a plurality of openings 43a arranged in the longitudinal direction. Inside the recording head 42, the recording head 4
A plurality of recording liquid supply passages 43 extending vertically upward from the lower end 42b of each of the two toward each of the openings 43a and for independently flowing the recording liquid are formed. The recording liquid supply paths 43 are provided to extend in parallel with each other and in the vertical direction. Further, the recording head 42 has a projecting plate 50 to be described later, which extends to the leading end 42 a of the recording head 42 through substantially the center of each recording liquid supply path 43.

The head unit 40 has a guide member 44 that surrounds the side surface and the lower surface of the recording head 42. The guide member 44 supports the recording head 42 at a predetermined position, and forms a recording liquid recovery path 45 with the outer wall of the recording head 42. That is, the recording liquid supplied to the recording head 42 rises inside the recording head 42 via each recording liquid supply path 43 and overflows from each opening 43a formed near the tip 42a. And each opening 4
Excessive recording liquid overflowing from 3a flows down along the outer peripheral wall of the recording head 42 and is recovered through a recording liquid recovery path 45.

In a space below the guide member 44 and communicated with the recording liquid collecting passage 45, a filter 46 for passing the collected surplus recording liquid and removing foreign matters in the recording liquid is provided. I have. The filter 46 has openings so as not to hinder the flow of the toner in the recording liquid.

A sponge-like filter member (not shown) may be provided in the recording liquid recovery path 45 at a position close to each opening 43a of the recording head 42. The filter member has a plurality of holes having a diameter larger than the aperture of the filter 46. By setting the hole diameter to an appropriate value, the recovery speed of the recording liquid flowing to the recording liquid recovery path 45 can be adjusted. That is, by adjusting the pore diameter of the filter member, the capillary action of the filter member can be controlled, and the recovery speed of the recording liquid can be adjusted.

Further, the head unit 40 has a plurality of electrodes 41 (first electrodes) extending along the inner surface of each recording liquid supply passage 43 in the recording head 42 to the opening 43a at the upper end thereof. Each electrode 4 is provided on both surfaces of the projection plate 50.
A plurality of electrodes (second electrodes) to be described later corresponding to No. 1 are formed. A drive circuit 48 (voltage applying means or image forming means) for selectively applying a predetermined recording voltage in accordance with an image signal is connected to each electrode formed on the projection plate 50. It is possible to selectively apply a large voltage.

On the right side of the head unit 40 in the figure, a recording liquid tank 32 containing a recording liquid is provided. A recording liquid supply pipe 34 for supplying the recording liquid contained in the recording liquid tank 32 to each recording liquid supply path 43 in the recording head 42 is connected between the head unit 40 and the recording liquid tank 32. I have. In the middle of the recording liquid supply pipe 34, a pump P1 for pumping the recording liquid in the recording liquid tank 32 at a predetermined flow rate and pressure is provided.

Further, between the head unit 40 and the recording liquid tank 32, recording is performed to collect the excess recording liquid collected through the recording liquid recovery path 45 and passed through the filter 46 into the recording liquid tank 32. The liquid recovery pipe 36 is connected. A pump P <b> 2 is provided in the middle of the recording liquid recovery pipe 36 to feed surplus recording liquid overflowing from the tip of the recording head 42 to the recording liquid tank 32. In addition, pump P1,
The recording liquid supply pipe 34 and the recording liquid supply path 43 function as supply means of the present invention, and the recording liquid recovery path 45 (guide member 44), the recording liquid recovery pipe 36, and the pump P2
It acts as the collecting means of the present invention.

In the recording liquid tank 32, as a concentration adjusting mechanism, a concentration measuring device 31 for measuring the optical transmittance of the recording liquid contained in the recording liquid tank 32 to measure the toner concentration of the recording liquid; A toner storage chamber 33 storing a toner having a predetermined concentration, a carrier liquid storage chamber 35 storing a carrier liquid, and a stirring device 37 for stirring the recording liquid stored in the recording liquid tank 32 are provided. I have.

In the toner storage chamber 33, the density measuring device 31 is provided.
Is provided with a toner supply unit 33a for replenishing the recording liquid with the consumed toner in accordance with the toner concentration measured by the method described above, and a carrier liquid for replenishing the carrier liquid insufficient in the recording liquid is provided in the carrier liquid storage chamber 35. A feeder 35a is provided. Therefore, the recording liquid in the recording liquid tank 32 is constantly stirred by the stirring device 37, and the toner concentration is constantly monitored by the concentration measuring device 31, and the toner concentration is adjusted to a predetermined value. I have.

The recording unit 30 configured as described above
When the recording liquid is circulated inside the recording liquid, first, the recording liquid pumped up from the recording liquid tank 32 by the pump P1 is supplied to each recording liquid supply path 43 in the recording head 42 through the recording liquid supply pipe 34. The recording liquid supplied to each recording liquid supply path 43 rises in the recording liquid supply path 43 and overflows from the opening 43a near the tip 42a of the recording head 42.
At this time, a plurality of ink meniscuses 47 corresponding to the openings 43a of the respective recording liquid supply paths 43 are formed near the leading end 42a of the recording head 42. Tip 42a of recording head 42
Excessive recording liquid overflowing from the nearby opening 43 a flows downward through the recording liquid recovery path 45 and is guided to the filter 46. The recording liquid that has passed through the filter 46 is suctioned by the pump P2 after the foreign matter is removed, and
To be collected.

Here, the components of the recording liquid contained in the recording liquid tank 32 will be described. The recording liquid is configured by dispersing charged toner as colorant particles in a carrier liquid as an insulating liquid at a ratio of about 2 to 7% by weight.

The carrier liquid has an electric resistivity of at least 1
0 ⁹ ohm-cm or more, preferably an isoparaffinic solvent is a liquid insulating (e.g., 10 ¹¹ 10 ¹³ degree of Isopar G having electrical resistance, H, K, L, M (Esso Petroleum)) and silicone oil , Hexane, pentane,
It is a dispersion medium composed of an organic solvent such as octane. The above electric resistivity was measured using a precision LCR meter 4284A manufactured by Hewlett-Packard; a liquid test fixture 16452A as a measuring head.

The toner has a particle size of about 0.01 to 5 μm and has a predetermined potential (here, a positive potential) in the carrier liquid.
Thermoplastic resin particles containing metal soap for imparting charge, such as zirconium octylate or lithium octylate, or a coloring component.

The recording liquid is basically the same as the liquid developer used in electrophotography and the like, but is required to have a higher electric resistance than the liquid developer. In other words, when the electric resistance of the recording liquid is low, the electric field does not act only on the charged toner, resulting in a fatal disadvantage that the toner separating function is not weakened. Also, if the electric resistance of the recording liquid is low, the carrier liquid itself is energized as in the case of the conventional electrostatic ink jet, so that the entire recording liquid is charged and all of the liquid is discharged without distinction between the toner and the carrier liquid. However, the effect of the present invention is completely lost. For this reason, a recording liquid having a higher electric resistance is required.

Factors that undesirably lower the electric resistance include metal soaps such as naphthenic acid, octylic acid, and stearic acid (for example, zirconium naphthenate, octylic acid) which are generally added to improve toner dispersion or chargeability. It is conceivable to add zirconium) or various surfactants. Since these generally reduce the electric resistance of the recording liquid, it is necessary to take measures to minimize the amount.

The electrical resistance of the recording liquid that can be used in the recording apparatus 10 of the present embodiment to obtain good recording characteristics (a state in which only toner is mainly separated from the recording liquid and ejected) is 10 ⁸ ohm-cm or more. With this level of electrical resistance, flow and bleeding on the ordinary recording paper P are reduced, and
An electrical resistance of more than 0 ¹⁰ ohm-cm further improves the sharpness of the image contour. This indicates that it is desirable that the electric resistance of the recording liquid be as high as possible.

In order to obtain such a high electric resistance as the recording liquid, the electric resistance of the carrier liquid before the toner is dispersed needs to be higher. Considering the effects of the additives described above, the electric resistance of the carrier liquid is 10 ¹⁰
More than ohm centimeters is required. In order to disperse the toner in the carrier liquid having such an electric resistance, the above-mentioned additives are added to a necessary minimum, and the electric resistance is reduced to about 10 ⁸ ohm-cm. The term "required minimum" as used herein means that it is necessary to maintain a level at which there is no practical problem from the evaluation of the charging and dispersion stability of the toner, and the specific value differs depending on the material used. Therefore, the higher the electrical resistance of the base carrier liquid, the greater the degree of freedom in using a dispersing aid and a charge control agent when preparing the recording liquid.

As described above, the components of the recording liquid are basically the same as the liquid developers used in electrophotography and the like, but the electric resistance of the carrier liquid is required to be higher than these. Therefore, it is necessary to reduce the conductive component in the recording liquid in accordance with the object of the present invention.

As the recording liquid used in the present invention, a resin, a colorant, and a charge controlling agent are kneaded with heat, and after cooling, toner fine particles obtained by pulverizing to a desired particle diameter are coated with a small amount of a dispersing aid. If necessary, a small amount of a swellable solvent or the like is added and dispersed in a carrier liquid, which is suitable for producing a recording liquid having high electric resistance.

In the recording method according to the present embodiment, the toner is selectively fly on the outer peripheral surface 3a of the belt 3 as an intermediate image carrier to form an image on the outer peripheral surface 3a. As shown in the photograph, the entire surface of the image carrier (photoconductor) is not wet with the recording liquid. For this reason, in the recording method of the present invention, so-called "fogging" does not occur at all, so that the toner density can be set higher than that of the recording liquid used in the conventional electrophotographic technology. Thereby, the density of the recording liquid can be set in consideration of the dispersion stability of the toner, the dispersion stability of the toner can be increased, and precipitation and aggregation can be suppressed.

In the recording liquid in which the toner is dispersed in the carrier liquid, the toner is less likely to aggregate than the conventional dry toner, so that a resin having a lower softening temperature can be used, and the temperature of the transfer roller 15 can be lowered. can do. In this embodiment, the traveling speed of the belt 3 is set to 90 mm / s.
When the surface temperature of the transfer roller 15 is set to 80 ° C., good transfer can be performed. The transfer temperature is lower than the fixing temperature of the conventional dry toner (170 ° C. or higher).

Further, according to the recording method of the present invention, since the toner is discharged by utilizing the electric repulsion, the charge amount of the toner is required to be stable. The charge amount is preferably 60 millivolts or more. In addition, for the measurement of zeta potential, US P
A Laser Gee Meter M-501 manufactured by EN KEM was used.

On the other hand, as for the particle size of the toner, a large toner particle is suitable for a high electrophoretic speed, but has a disadvantage that precipitation tends to occur. When the average particle size of the toner is 0.01 μm or less, an image with bleeding, which is considered to be due to difficulty in separating from the carrier liquid, occurs. In order not to absorb liquid at all, for example, to prevent bleeding or flow even when recording on a metal surface, it is preferable that the toner particle size is 0.1 μm or more. Although large particles also depend on the sedimentation prevention mechanism in the recording apparatus, particles larger than about 5 micrometers sediment in an extremely short time, making it difficult to use. That is, the particle size of the toner needs to be appropriately selected according to the apparatus. For example, if it is used intermittently, it is preferable that it is 4 micrometers or less.

Next, the recording operation of the ink jet printer 1 configured as described above will be described. First, as an initializing operation, the heater 15a and the heater plate 17 are energized and heated to a predetermined temperature. Also,
As described above, the recording liquid is circulated in each of the recording units 30a, 30b, 30c, and 30d, and a predetermined ink meniscus 47 is formed in each of the openings 43a near the leading end 42a of each of the recording heads 42. And each opening 43
A bias voltage having a predetermined magnitude is applied as a bias voltage to each electrode formed on the projection plate 50 corresponding to a.
The toner in the recording liquid is aggregated in the meniscus according to the bias voltage.

When the color-separated image signals are respectively input to the drive circuits 48 of the recording units 30a, 30b, 30c, 30d from a signal source (not shown), the belt 3 runs at a constant speed in the direction of arrow a. At the same time, a recording voltage higher than the bias voltage previously applied to each electrode of each recording head 42 is selectively applied. Then, a predetermined electric field is formed between the belt 3 and the electrode selected according to the color-separated image signal, and this electric field separates and discharges the charged toner aggregate from the vertex of the ink meniscus 47. Aggregates fly toward the outer peripheral surface 3 a of the belt 3. Thereby, toner images corresponding to the colors of the respective recording liquids are sequentially formed on the outer peripheral surface 3a of the belt 3, and
A predetermined color image corresponding to the image signal is formed on the belt 3 by being superposed by a synchronization unit (not shown).

The toner image (color image) formed on the outer peripheral surface 3 a of the belt 3 is moved as the belt 3 runs, and is conveyed to a transfer position between the roller 4 and the transfer roller 15.

In synchronization with the movement of the image, the paper feed roller 1
1, 13 and the transport rollers 14a and 14b are operated, and the recording paper P stored in either the paper feed cassette 12a or 12b is taken out and sent to the transfer position.

The recording paper P sent to the transfer position in synchronization with the toner image is heated by the heater 15a and pressed and held between the roller 4 and the transfer roller 15 to melt or soften the toner image. Then, the image is transferred onto the recording paper P.

The recording paper P on which the toner image has been transferred is conveyed while being nipped by the conveying rollers 16a and 16b, passed through the heater plate 17, the toner image is sufficiently dried, and is nipped by the paper discharging rollers 18a and 18b. The paper is discharged onto the paper discharge tray 19.

The carrier liquid gas generated at the time of transfer and drying is collected by a duct 21 provided above the transfer roller and a duct 22 provided above the heater plate 17, and is subjected to water and carbon dioxide gas by a decomposition device 24. And is discharged outside the machine.

The toner adhering on the outer peripheral surface of the transfer roller 15 and the toner remaining on the outer peripheral surface 3a of the belt 3 are removed by the cleaning blade 23 and the wiping device 25, respectively. After the residual toner is removed by the wiping device 25, the belt 3
6 to prepare for the next recording operation.

Next, the recording head 42 according to the embodiment of the present invention incorporated in the head unit 40 will be described in detail with reference to FIGS. FIG. 3 is a sectional view of the recording head 42, and FIG. 4 is a perspective view of the recording head 42. The recording head 42 has a pair of substantially rectangular plate-shaped support members 51 and 52, and a projection plate 50 (guide member) sandwiched between the support members 51 and 52. One supporting member 51 (representatively described) is shown in FIG. 5, and the protruding plate 50 is shown in FIG.

The supporting member 51 is made of a material having a high electric resistivity, preferably a plastic having an insulating property of 10 ¹² ohm cm or more (the higher the electric resistance, the better, the polyetherketone suitable for high-precision machining) Polycarbonate or the like) or ceramics.
It is formed in a substantially rectangular plate shape having a thickness of 10 to 10 mm.

The projection plate 50 has a thickness of 30 to 200 μm.
m high-resistance material (eg, polyether siphon, polyester, polyethylene, fluororesin,
It is formed from a resin material such as polyimide or polypropylene, or various ceramics, etc., a material having an electrical resistance of 10 ¹¹ ohm-cm or more. Note that, as the protruding plate 50, a printed wiring board often used in the electric appliance industry may be used.

As shown in FIG. 5, the support member 51 has a plurality of rectangular grooves 51a extending parallel to each other on one surface thereof, that is, an inner surface facing the protruding plate 50. Groove 51a
The plurality of recording liquid supplies for flowing the recording liquid together with the grooves similarly formed in the other support member 52 (not shown) in the state where the recording head 42 is assembled (the state shown in FIG. 4). A path 43 is formed.

Each groove 51a is formed to have a depth of 50 to 500 μm and a width of 100 to 1000 μm. The front end of each groove 51a extends slightly before the upper end 511 of the support member 51. The base end of each groove 51a is 51 extends almost beyond the center. Each groove 5 extending to substantially the center of the support member 51
The base end of 1a is a substantially rectangular recess 51b deeper than the groove 51a.
Are in communication with each other. Also, this recess 51b
A recording liquid chamber 53 is formed together with a recess 52b (not shown) similarly formed in the other support member 52, and the recording liquid supply pipe 34 for supplying the recording liquid is formed in the recording liquid chamber 53. Is connected.

As described above, by forming a plurality of grooves 51a on the inner surface of the support member 51, a space between each groove 51a is provided.
A plurality of rectangular partitions 55 bordering each recording liquid supply path 43 are formed. The groove 51a extending between the partition walls 55
The top end of the (recording liquid supply path 43) is
a, that is, a predetermined distance (50 from the upper end 511 of the support member 51).
An opening 43a of the recording liquid supply path 43 is formed at a position where the recording liquid supply path 43 is retracted.

Further, between the adjacent partition walls 55, and at the edge of the opening 43a at the end of the recording liquid supply path 43, the recording liquid collecting groove 57 (downwardly inclined toward the outer peripheral surface 51c of the support member 51). 3 and 4) are formed. The width of each recording liquid collecting groove 57 is formed to be the same as the width of the opening 43a, and the inclination angle thereof is set to be an acute angle of 70 degrees or less.

Further, each groove 51 formed in the support member 51
a, ie, the inner surface of each recording liquid supply passage 43, is coated with an electrode 4 as a first electrode by a conductive paint or metal plating.
Numerals 1 each extend to the opening 43a and are formed with a thickness of about 2 to 30 μm. Each electrode 41 is, for example, gold,
It is formed of a metal such as copper, chromium, aluminum, nickel, or an alloy thereof. In addition, each electrode 41 has a groove 5
The supporting member 51 is provided independently for each la and has an end exposed on the same surface as the inner surface (opposing surface) of the supporting member 51 so as to contact a protruding plate 50 described later.

The other support member 52 combined with the support member 51 configured as described above is formed symmetrically with the support member 51, and faces each other so that the grooves of the support members 51 and 52 coincide with each other. And bonded together. In this case, a projecting plate 50 described below is provided between the support members 51 and 52.
Are formed to form the recording head 42.

As shown in FIG. 6, the projecting plate 50 has a front portion 501 formed in a substantially rectangular plate shape sandwiched between a pair of support members 51 and 52, and extends in a direction away from one end of the front portion. And a rear portion 502 that is not sandwiched by the support members 51 and 52. Projection plate 50
Has a width substantially equal to the width of the recording head 42,
And a length substantially equal to the height of the recording head 42,
The recording head 42 has an upper end 50a which is arranged at a height corresponding to the height of the plurality of openings 43a while being sandwiched by the pair of support members 51 and 52.

The projection plate 50 has a substantially triangular plate-like projection 59 having a sharp tip (the tip 42a of the recording head 42) projecting from the upper end 50a, and the number of grooves of the support members 51 and 52 along the upper end 50a. It has a corresponding number. That is, the plurality of protrusions 59 integrally formed on the upper end 50 a of the protrusion plate 50 are formed by the grooves 51 a formed on the support members 51 and 52.
Are provided at the same pitch.

Further, each projection 5 is provided on each surface of the projection plate 50.
A plurality of electrodes 60 as second electrodes provided corresponding to 9 are provided. The tip of each electrode 60 extends to the bottom of the corresponding projection 59, that is, the height of the upper end 50a of the projection plate 50, and the base end of each electrode 60 extends to the lower end 50b of the rear end portion 502 of the projection plate 50. A drive circuit 4 is provided at the base end of each electrode 60 extending to the lower end 50 b of the projection plate 50.
A pad 61 is formed as a connection terminal to be connected to 8.

The width of the electrode 60 formed on the front portion 501 of the protruding plate 50 is such that the supporting member 51 is opposed to each surface of the protruding plate 50 when sandwiched between the pair of supporting members 51 and 52. , 52 are formed slightly wider than the width of the electrode 41 so as to contact the electrode 41 formed in the grooves 51a, 52a. Therefore, the projecting plate 50 is supported by the supporting members 51, 5
2, each electrode 60 formed on the projection plate 50 is electrically connected to each electrode 41 formed on the support members 51 and 52 in pixel units. Therefore, the electrode 60
By selectively applying a voltage to each electrode 60 via the pad 61 formed in the recording liquid supply path 43, the same voltage is selectively applied to the electrode 41 in each recording liquid supply path 43.

The projection plate 50 formed as described above is arranged so that each projection 59 projects from the opening 43a at the end of each recording liquid supply path 43 by a predetermined length. In this case, the projection plate 50 is positioned and arranged so that the upper end 50a of the projection plate 50 does not protrude upward from the opening 43a and substantially matches the height of the opening 43a, and only the projection 59 projects from the center of the opening 43a. Is done.

The size of each projection 59 formed on the projection plate 50 depends on the amount of the recording liquid supplied through the recording liquid supply path 43, the size of the opening 43a of the recording liquid supply path 43, or The size is appropriately selected depending on the wettability of the projection 59 with the recording liquid, and is set to a size such that at least the tip of the projection 59 is not submerged by the ink meniscus formed near the opening 43a.

For example, when the width of the opening 43a is 500 μm, the length of the bottom of the projection 59 is 300 to 500 μm.
m, and the height of the protrusion 59 is 300 to 12
It is set within the range of 00 μm. When the recording characteristics of the recording head 42 were examined by variously changing the width and height of the projection 59, the length of the bottom of the projection 59 was set to be approximately half the width of the opening 43a and the same as the width of the opening 43a. By setting the length between the same length as the length of the base and three times the length, it was found that stable recording characteristics could be obtained.

Further, the shape of the projection 59 may be a so-called spire that is sharp from the bottom arranged on the upper end 50a of the projection plate 50 toward the tip. Further, the protrusion 59 is not limited to a plate shape, and may be a rotating body. In this case, the protrusion 59
It is necessary to form the recording liquid supply passage 43 so as not to block the opening 43a.

That is, when an electric field is applied to the recording liquid supplied through the recording liquid supply path 43 toward the belt 3, the toner in the recording liquid smoothly moves to the tip of the projection 59. Any material may be used as long as it has a movable outer shape and has good wettability (lipophilicity) with the recording liquid. In particular, the protrusion 59 has a critical surface tension indicating wettability of 2
It is desirable to use a material of 5 dyne / cm or more.

In view of the above, the projection plate 50 does not necessarily have to be formed by one plate as in the above-described embodiment, but includes a plurality of portions independently disposed in the respective recording liquid supply paths 43. It may be configured. Further, in this case, the projection plate disposed in each recording liquid supply path 43 may be composed of a metal part located below the opening 43a and an insulating part located above the opening 43a. That is, the opening 43a
Any structure may be used as long as it has an electrode portion up to substantially the same height as.

Further, in the above embodiment, the electrode 60 formed on the protruding plate 50 and the electrode 41 formed on the supporting members 51 and 52 are configured to be electrically connected. , 60 to each electrode 4
1 and 60 may be driven separately.

The ink meniscus 4 individually formed near each opening 43a along each projection 59 is provided between two adjacent projections 59, that is, between two adjacent openings 43a.
A partition 55 for separating the cells 7 from each other is provided.
Each partition 55 has an opening 43 a at the tip of each recording liquid supply path 43.
The upper end 55a (the upper ends 511, 5 of the support members 51, 52) projecting about 50 to
21).

It is desirable that the corners where the partition wall 55 faces the recording liquid supply passage 43 or the recording liquid recovery groove 57 are slightly chamfered or not chamfered at all. That is, by not chamfering the corners of the partition wall 55, the wetting and spreading of the recording liquid can be prevented at these corners, and the cross-linking of each ink meniscus 47 can be prevented.

An oil-repellent surface for repelling the recording liquid may be provided on the upper end 55a of each partition wall 55. The oil-repellent surface is made of a material having a critical surface tension of 20 dyne / cm or less, such as a fluorine resin, a fluorine paint, a silicone resin, a silicone paint, or a silicone resin, when an isoparaffin solvent is used as a recording liquid. Good oil repellency (wetting prevention property) can be exhibited. Thus, by providing the oil repellent surface on the upper end 55a of each partition wall 55, it is possible to prevent crosslinking of the adjacent ink meniscus. Further, by providing the oil-repellent surface, even when the height of the partition wall 55 is the same as the height of the opening 43a at the end of the recording liquid supply path 43, the ink meniscus 47 can be prevented from being crosslinked.

The partition wall 55 having the above-described structure is mounted on each of the projections 5.
9 can prevent cross-linking of the adjacent ink meniscus 47, can prevent disturbance of the ejection direction and ejection frequency of the recording particle droplet due to the crosslinking of the recording liquid, and can stably eject the recording particle droplet. be able to. Further, each partition 55 is separated from each edge of each opening 43a by each support member 51, 52.
Of the recording liquid collecting groove 57 provided to be inclined toward the outer peripheral surfaces 51c and 52c.

Next, the flying operation of the recording droplet by the recording head 42 configured as described above will be described. still,
Here, the flying operation of the recording liquid droplets will be described with reference to FIGS. 7 to 9 which show a simplified configuration corresponding to one pixel of the recording head 42.

FIG. 7 is a longitudinal sectional view showing a recording head 420 of one pixel, FIG. 8 is a longitudinal sectional view showing the recording head 420 of FIG. 7 rotated by 90 ° about a vertical axis, and FIG. FIG. 4 is a diagram showing a state in which a recording droplet is flying by 420.

First, the recording liquid tank 32 is operated by the pump P1.
The recording liquid 70 stored in the inside is pumped up through the recording liquid supply pipe 34, and the recording liquid 70 is supplied into the recording liquid chamber 53 of the recording head 42. When the inside of the recording liquid chamber 53 is filled with the recording liquid 70, the recording liquid 70 rises through each recording liquid supply path 43, and the opening 43 at the tip of each recording liquid supply path 43.
overflows from a.

The recording liquid 70 overflowing from the opening 43a of the recording liquid supply path 43 is separated from the partition walls 55 provided on both sides of the opening 43a.
Flows out through the recording liquid collecting groove 57 defined by
It flows downward along the outer peripheral walls 51c, 52c of the support members 51, 52. Then, the recording liquid 70 flowing along the outer peripheral walls 51c and 52c is collected by the recording liquid recovery path 45 and the filter 4
6, and the recording liquid tank 32 through the recording liquid collection pipe 36.
To be collected.

As described above, the recording liquid 70 is supplied to the head unit 4.
0, the opening 43a of each recording liquid supply path 43
In the vicinity, the recording liquid 70 wets up along the projection 59 of the projection plate 50, and the supply pressure of the recording liquid 70 and the recording liquid 70
The ink meniscus 47 shown in FIG. 9 is formed by the surface tension of the recording liquid and the capillary action of the recording liquid collecting groove 57.

In this case, the upper end 55a of the partition wall 55 provided between the openings 43a is made higher than the opening 43a,
By forming an oil-repellent surface on the surface 5a as required and not chamfering the corners of the partition wall 55, the ink meniscus 47 formed individually in each opening 43a is prevented from being bridged.

In the state where the ink meniscus 47 is formed near the opening 43a, the electrodes 60 formed on the protruding plate 50 are connected to the electrodes 60 through 1000 through the driving circuit 48.
When a bias voltage (first voltage) of about 0 volts is applied, the electrode 4 provided along the inner surface of the recording liquid supply path 43
1 is also energized, the same voltage is applied, and an electric field (first electric field) from the electrode 41 toward the outer peripheral surface 3a (recording paper P) of the belt 3
Is formed, and an electric field (second electric field) from the electrode 60 toward the outer peripheral surface 3a is formed.

Under the influence of the first electric field from the electrode 41 toward the belt 3, the toner 71 in the recording liquid 70 receives an electrostatic repulsive force from the electrode 41, and the toner 71 is moved to the ink meniscus 47.
, Ie, the top of the projection 59 of the projection plate 50. At this time, due to the influence of the second electric field from the electrode 60 toward the belt 3, the toner 71 migrated toward the apex of the protrusion 59 receives an electrostatic repulsive force from the electrode 60 and is urged in a direction away from the protrusion 59. You. That is, when the first and second electric fields are combined, an electric field that is directed vertically upward or slightly outward away from the projection plate 50 is formed.

Since the ink meniscus 47 tapers toward the top, the toner 71 in the recording liquid 70 that rises in the recording liquid supply path 43 under the influence of the first and second electric fields is replaced by the ink. The protrusion 59 is moved along the ink surface of the meniscus 47 toward the tip of the projection 59 and aggregates near the tip of the projection 59. That is, by providing the electrode 60 that generates the second electric field near the foot of the protrusion 59, the toner 71 in the recording liquid 70 does not move along the protrusion plate 50, and the toner aggregate 74 is formed at the tip of the protrusion 59. Can be formed.

As a result, it is possible to prevent the toner 71 in the recording liquid 70 from sticking to the projection plate 50, particularly to the tip of the projection 59, to prevent the recording liquid supply path 43 from being clogged by the adhered substance, and to agglomerate the toner. Efficiency can be greatly improved.

Further, by providing the electrode 60 for generating the second electric field near the foot of the projection 59, the number of lines of electric force passing through the inside of the ink meniscus 47 can be increased, and the aggregation efficiency of the toner can be greatly improved. The recording frequency of the recording head can be increased. It has been found that when the recording head 42 of the present embodiment is used, it is possible to achieve a recording frequency that is about two to three times as large as the case where no electrode is provided near the foot of the protrusion.

When the toner aggregate 74 is formed at the tip of the projection 59 as described above, a larger electrostatic force is applied to the aggregate 7.
4, the bias voltage is set so that the aggregates 74 do not fly from the ink meniscus 47. In addition, the distance between the tip of each electrode 41 and 60 and the electrode plate 8 (that is, the distance between the recording head 42 and the recording head 42) is set so that the aggregates 74 do not fly when a bias voltage is applied to each of the electrodes 41 and 60. (A distance between the front end 42a and the outer peripheral surface 3a of the belt 3).

As another method of forming an electric field from the tips of the electrodes 41 and 60 toward the outer peripheral surface 3a of the belt 3, a method of applying a voltage having a polarity opposite to that of the toner to the belt 3 or the electrode plate 8 can be considered. . Further, when the belt 3 in which the coating layer is coated on the metal belt is used, a desired electric field can be formed by charging the belt 3 to a predetermined potential in advance by corona charging or the like. in this case,
There is an advantage that a complicated circuit for superimposing and applying the ejection voltage to the bias voltage can be omitted.

On the other hand, the carrier liquid 72 separated from the toner 71 by applying a bias voltage to the electrodes 41 and 60
Is moved toward the vertex of the ink meniscus 47 without passing through the recording liquid collecting groove 57.
It flows out of the foot of 7. That is, the carrier liquid 72 has negative ions due to the mutual charging action with the toner 71 (positive), and is not raised by the electric field acting on the ink meniscus 47. Therefore, the carrier liquid 72 separated from the toner 71 is forced from the bottom of the ink meniscus 47 by the surface tension of the recording liquid 70 (capillary action of the recording liquid recovery groove 57), gravity, and a partially generated electrostatic attraction force. Is leaked out.

As a discharge path for the carrier liquid 72, the recording liquid recovery groove 57 formed adjacent to each opening 43a is desirably shaped so that the carrier liquid 72 separated by the aggregation of the toner 71 can be efficiently discharged. . Carrier liquid 7
By efficiently discharging the ink meniscus 4, the ink meniscus 4
7 can be stabilized, the ejection state of the toner can be stabilized, the recording speed can be increased, and the ejection frequency can be further increased.

The recording liquid collecting groove 57 may be provided on only one side without being provided on both sides of the opening 43a, but is preferably provided on both sides to maintain the symmetry of the ink meniscus. Further, in order to efficiently discharge the carrier liquid 72, it is desirable that the edge between the recording liquid supply path 43 and the recording liquid collecting groove 57 be chamfered. May be exposed. By exposing the tip of the electrode 41 at the edge of the opening 43a, a strong electric field can be generated.

As described above, the toner 71 and the carrier liquid 7
In a state where the electrodes 2 are separated from each other, the ejection voltage (second voltage) is selectively superimposed and applied from the drive circuit 48 to the electrode 60 (and 41) selected according to the image signal. The ejection voltage to be superimposed is about 100 to 800 volts,
In the ink meniscus 47 near the opening 43a having the electrode 60 (41) to which the ejection voltage is selectively applied, a stronger electric field is generated than when the bias voltage is applied.

Due to this electric field, an electrostatic force stronger than the binding force such as surface tension acting on the toner aggregate 74 acts on the toner aggregate 74, and the toner aggregate 7 as recording particles
The recording particles 4 are separated from the ink meniscus 47 and fly toward the outer peripheral surface 3 a of the belt 3 as recording droplets 76. As a result, dots (toner images) are formed by the recording particle droplets 76 on the outer peripheral surface 3a, and a desired image is formed on the outer peripheral surface 3a.

As described above, according to the recording head 42 of this embodiment, the electrodes 60 are provided near the foot of each of the projections 59 protruding from each of the openings 43a. The same voltage as that of the electrode 41 is applied. Therefore, it is possible to prevent an electric field from being generated toward the projection plate 50, particularly the tip of the projection 59, and to prevent the toner from sticking to the projection plate 50. Thereby, the aggregation efficiency of the toner can be improved, and a high recording frequency can be obtained.

Further, according to the recording head 42 of the present embodiment, the carrier liquid 72 separated from the toner 71 can be forcibly discharged through the recording liquid collecting groove 57.
1 can be efficiently separated from the carrier liquid 72, and the toner 7
1 can be increased, and the ejection frequency of the recording particle droplet 76 can be increased. For example, in the recording head 42 described above, an ejection frequency of 500 Hz to 1 kHz can be achieved. Note that this discharge frequency tends to increase as the diameter of the opening 43a of the recording liquid supply path 43 decreases, and the discharge frequency when the opening diameter is set to 100 μm shows 2 kHz.

Further, the partition wall 55 defining both sides of the recording liquid collecting groove 57 and the oil repellent surface provided on the upper surface 55a can prevent the ink meniscus 47 formed in each opening 43a from cross-linking each other. Undesired vibration of the ink meniscus 47 and disturbance of the ejection direction that occur when the particle droplet 76 flies can be prevented, and stable recording can be performed.
High quality images can be formed.

Further, it is known that the diameter of the recording particle droplet 76 flying from the opening 43a changes depending on the magnitude of the applied ejection voltage and the application time.
When the recording liquid 70 containing m toner 71 is used, when the ejection voltage is changed to 150 to 600 volts, the diameter of the recording particle droplet 76 changes in a range of about 15 to 120 μm.
Further, when the application time of the signal voltage is changed by 50 to 500 microseconds (at a recording frequency of 1 KHz), 10 μm is obtained.
m to 300 μm. As described above, by adjusting the applied voltage and time, the particle diameter of the recording particle droplet 76 can be changed, so that the recording particle droplet 76 having a small particle diameter can fly from the large opening 43a, and the recording liquid 70
Clogging of the recording liquid supply path 43 due to drying of the recording liquid can be prevented, and high-density recording can be performed.

Incidentally, the opening 43a of the recording head 42 described above.
Are provided at a density of about 1 or 2 per mm, but more openings 43a can be provided by overlapping a plurality of recording heads 42 while shifting the positions of the openings 43a. Thus, a recording head having a desired recording density can be achieved.

Further, according to the recording head 42, unlike a conventional ink jet printer, a solid or semi-solid component toner aggregate is separated from a recording liquid without forming a liquid as a recording image to form a recording image. Can be formed. For this reason, the recording particle droplets
a, the toner image formed on the recording paper P flows after the toner image reaches the recording paper P, and penetrates between the fibers of the recording paper P due to the capillary phenomenon, and causes image defects such as so-called feathering. Will not occur. Note that the carrier liquid and the toner are separated at the time of discharging the recording particle droplets, but are not completely separated by 100%, and the toner reaches the belt 3 in a state of being wetted by the carrier liquid. However, since the accompanying carrier liquid is small, the toner particles do not flow because the liquid droplets lose their fluidity when they reach the outer peripheral surface 3a of the belt 3. For this reason, a sharp image can be recorded even on a non-absorbing image receiving material such as metal or plastic, and when an image of each color is sequentially formed in accordance with a color-separated image signal, each color is Image 1
The next color can be superimposed immediately without having to dry for each color. Therefore, it is more suitable for high-speed printing than the conventional inkjet.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, an example in which the belt 3 is used as an image forming medium has been described. However, the present invention is also applicable to a recording apparatus that directly forms an image on recording paper or the like.

In the above embodiment, the projection plate 50 is sandwiched between the pair of support members 51 and 52. However, as shown in FIG. 10, the support member is provided only on one side of the projection plate 50. A configuration in which the support member is inclined toward the support member at an angle between the vertical direction and the lateral side may be employed. Also in this case, the same effects as those of the above-described embodiment can be obtained.

The opening 43 at the tip of the recording liquid supply path 43
The shape of “a” does not need to be square, and the cross-sectional shape of the electrode 41 forms a well-shaped or ring-shaped (doughnut-shaped) electric field in which the electric field at the center of the opening 43 a, that is, at the tip of the protrusion 59, is slightly lower than the peripheral part. Any structure is acceptable. In other words, it is sufficient that the protrusion 59 has a shape substantially surrounding the foot of the protrusion 59.
Specifically, any cross-sectional shape such as a circle (ring shape) and an ellipse is possible. Also, the electrode may not be entirely covered with the opening end, but may be a discontinuous (partial) electrode arrangement such as a U-shape, a parallel plate, or a stripe.

The tip of the electrode 60 formed on the protruding plate 50 does not necessarily need to be arranged at the same height as the upper end 50a of the protruding plate 50, but is arranged at a position slightly higher than the upper end 50a of the protruding plate 50. You may.

In each of the above embodiments,
Although the width (distance between adjacent openings) of the partition wall 55 is illustrated as having the same level as the size of the opening 43a, the present invention is not limited to this, and can be further reduced. In this case, in addition to making the height of the partition wall 55 sufficiently high, by sharpening all the corners of the partition wall 55, the effect of stopping the spread of the recording liquid is increased. In the case where the partition wall 55 is formed of a polycarbonate resin or the like using the recording liquid having a surface tension of about 18 to 30 millinewton / meter used in the present invention, the corner of the partition wall 55 has a chamfer of 100 μm or less and a curved surface. In this case, if the radius is 100 μm or less, the ink meniscus is not cross-linked between the adjacent openings 43a during normal recording.

Furthermore, the arrangement direction of the protrusion 59 may be set to a direction different from that of each of the above-described embodiments by 90 degrees, and the shape of the protrusion 59 can be appropriately selected. When the bottom of the protrusion 59 is made smaller, the spread of the foot of the ink meniscus formed around the protrusion becomes smaller, making it difficult for the recording liquid to crawl on the partition walls. However, since the amount of toner aggregation is reduced, it should be adjusted according to the purpose. It is. In the above embodiment,
Although the projections 59 are arranged with high accuracy by forming the projections 59 integrally with the projection plate 50, the projections 59 can be divided into a plurality of parts or various kinds of deformations can be made such that the projections 59 are sized and structured to be arranged only in the opening. . Further, in the embodiment, all the protrusions are arranged at the center of the electrode. However, this is shown as a preferable arrangement example, and although the recording effect is slightly reduced, one side of the groove is used to simplify the device structure. Arranging the projections on the surface is also included in the gist of the present invention.

Further, in this embodiment, the bias voltage is applied to the electrode 60. However, the bias voltage may be applied to the electrode plate 8 (or the belt 3) as the opposing electrode. It is sufficient that a bias voltage sufficient for recording between the electrodes 60 and 41 and the belt 3 is applied.

[0128]

As described above, since the image forming apparatus of the present invention has the above-described configuration and operation, a high recording frequency can be obtained, and stable recording can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an ink jet printer as an image forming apparatus of the present invention.

FIG. 2 is a schematic diagram showing a recording unit incorporated in the inkjet printer of FIG. 1;

FIG. 3 is a view showing a first unit incorporated in the recording unit of FIG. 2;
FIG. 2 is a schematic diagram showing a recording head according to the embodiment.

FIG. 4 is a perspective view showing the recording head knit of FIG. 3;

FIG. 5 is a perspective view showing a support member constituting the recording head of FIG. 4;

FIG. 6 is an exemplary plan view showing a projection plate incorporated in the recording head of FIG. 4;

FIG. 7 is a sectional view schematically showing a configuration corresponding to one pixel of the recording head of FIG. 4;

FIG. 8 is a cross-sectional view of the recording head of FIG. 7 rotated by 90 °.

FIG. 9 is a view for explaining a flying operation of a recording liquid droplet by the recording head of FIG. 7;

FIG. 10 is a sectional view showing a recording head according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ink-jet printer, 3 ... Belt, 3a ... Outer peripheral surface, 8 ... Electrode plate, 10 ... Recording device, 15 ... Transfer roller, 30 ... Recording unit, 41, 60 ... Electrode, 42 ... Recording head, 43 ... Recording liquid supply Road 43a Opening 47 Ink meniscus 48 Drive circuit 50 Protrusion plate 51 52 Support member 51a Groove 57 Recording liquid collecting groove 59 Protrusion.

Claims (7)

[Claims] A storage means for storing a recording liquid formed by dispersing charged colorant particles in an insulating liquid; and an opening, wherein the opening is disposed at a position separated from the image forming medium by a predetermined distance. An ink flow path for circulating the recording liquid; a first electrode provided in the ink flow path; and a first electrode provided in the ink flow path to face the first electrode;
A second electrode having a tip extending to substantially the same height as the opening; a supply unit for supplying the recording liquid stored in the storage unit to the opening; a first electrode and a second electrode in accordance with a predetermined image signal; By applying a voltage, the colorant particles in the recording liquid supplied near the opening are aggregated, and the aggregated colorant particles are separated and discharged from the insulating liquid to form an image on the image forming medium. An image forming apparatus comprising: a voltage application unit that forms 2. A storage means for storing a recording liquid formed by dispersing charged colorant particles in an insulating liquid, and an opening, wherein the opening is arranged at a position separated from the image forming medium by a predetermined distance. An ink flow path through which the recording liquid flows, a first electrode provided in the ink flow path, an insulating guide member having a tip protruding from the opening toward the image forming medium, Provided on the guide member so as to face the first electrode,
A second electrode having a tip extending to substantially the same height as the opening, a supply unit for supplying the recording liquid in the storage unit to the opening, and applying a voltage to the first and second electrodes according to a predetermined image signal A voltage application means for aggregating the colorant particles in the recording liquid, separating and aggregating the aggregated colorant particles from the insulating liquid to form an image on the image forming medium, An image forming apparatus comprising: 3. An insulating support member forming an opening at a position separated from the image forming medium by a predetermined distance and forming a flow path communicating with the opening, and extending to the opening along an inner surface of the flow path. A first electrode provided in the channel, an insulating guide member having a tip protruding from the opening toward the image forming medium by a predetermined length from the opening, and a surface of the guide member. And a second electrode having a tip extending to substantially the same height as the opening, and a recording liquid formed by dispersing charged colorant particles in an insulating liquid, through the flow path to the opening. Supply means for supplying the recording liquid to form a meniscus protruding from the opening toward the image forming medium when the recording liquid is wetted by the guide member; and applying a voltage to the first and second electrodes in accordance with a predetermined image signal. By doing Forming an electric field directed outward from the center of the meniscus, causing the colorant particles in the recording liquid to migrate along the liquid surface of the meniscus toward the tip of the meniscus and aggregate, and aggregate at the tip of the meniscus An image forming apparatus comprising: an image forming unit configured to form an image on the image forming medium by separating and discharging the colorant particles separated from the insulating liquid. 4. An insulating support member forming a plurality of openings in a plane separated from the image forming medium by a predetermined distance, forming a plurality of flow passages communicating with the respective openings, A plurality of first electrodes provided independently along the inner surface and having tips extending to the respective openings, and a plurality of protrusions projecting from the respective openings toward the image forming medium by a predetermined length. An insulating guide member having a plurality of second electrodes provided in each of the flow paths corresponding to the first electrodes and having tips extending to substantially the same height as the openings; Supply means for supplying a recording liquid formed by dispersing particles in an insulating liquid to the openings via the flow paths, and applying a first voltage to all the first and second electrodes. Aggregates colorant particles in the recording liquid supplied near each of the openings And selectively applying a second voltage higher than the first voltage to the first and second electrodes selected according to a predetermined image signal, thereby causing the agglomerated colorant particles to fall into the insulating liquid. And a voltage applying means for forming an image on the image forming medium by being ejected separately from the image forming medium. 5. An insulating support member forming a plurality of openings in a plane separated by a predetermined distance from an image forming medium, forming a plurality of flow passages communicating with the respective openings, A plurality of first electrodes provided independently along the inner surface and having tips extending to the respective openings, and a plurality of protrusions projecting from the respective openings toward the image forming medium by a predetermined length. An insulating guide member having a plurality of second electrodes provided in each of the flow paths corresponding to the first electrodes and having tips extending to substantially the same height as the openings; Supply means for supplying a recording liquid, which is obtained by dispersing particles in an insulating liquid, to each of the openings via the respective flow paths; and projecting from the support member toward the image forming medium between the respective openings. Recording liquid supplied to each opening by the supply means. A plurality of partitions for partitioning, a collecting means for collecting the recording liquid supplied to the openings by the supply means, provided between adjacent partitions, and supplied to the openings by the supply means. A plurality of recovery paths for guiding the collected recording liquid to the recovery means; and applying a first voltage to all of the first and second electrodes, thereby providing a color in the recording liquid supplied near each of the openings. By aggregating the colorant particles and selectively applying a second voltage higher than the first voltage to the first and second electrodes selected according to a predetermined image signal, An image forming apparatus comprising: a voltage application unit configured to form an image on the image forming medium by separating and discharging the insulating liquid. 6. A groove having a plurality of grooves, a tip of each of the grooves forms a plurality of openings in a plane separated by a predetermined distance from the image forming medium, and extends to a surface of each of the grooves to each of the openings. A first and a second support member facing each other, in which a plurality of first electrodes are arranged, and a plurality of protrusions protruding toward the image forming medium by a predetermined length from each of the openings at an upper end thereof. In addition, in a state of being sandwiched by the first and second support members,
A tip electrically connected to the first electrodes and extending to substantially the same height as the openings, and a plurality of connections corresponding to the first electrodes outside the first and second support members. A guide member having, on its surface, a plurality of second electrodes having a base end having terminals formed thereon, and a recording liquid obtained by dispersing charged colorant particles in an insulating liquid through each of the openings through the grooves. Supply means for supplying the paper toward the image forming medium, the recording medium being projected from the first and second support members toward the image forming medium between the respective openings, and supplied to the respective openings by the supply means. A plurality of partition walls for partitioning the liquid; a recovery unit for recovering the recording liquid supplied to each of the openings by the supply unit; a collection unit provided between the adjacent partition walls; A plurality of guides for guiding the supplied recording liquid to the recovery means. By applying a first voltage to all of the first and second electrodes via the respective connection terminals, the colorant particles in the recording liquid supplied near the opening are aggregated, By selectively applying a second voltage higher than the first voltage to a connection terminal that is conducted to the first and second electrodes selected according to a predetermined image signal, the aggregated colorant particles are removed. An image forming apparatus comprising: a voltage application unit configured to form an image on the image forming medium by separating and discharging the insulating liquid. 7. An opposing surface in which a plurality of grooves each having an end formed with an opening is formed at a position separated from the image forming medium by a predetermined distance, and each groove extends to the opening on a surface of the groove. And a plurality of first exposed on the facing surface.
An insulating support member having electrodes, and a surface close to and opposed to the opposing surface of the support member, on which surface the first electrodes are electrically connected;
A plurality of second electrodes having a distal end extending to substantially the same height as each of the openings, and a plurality of second electrodes having a plurality of connection terminals formed outside the support member and corresponding to the first electrodes; An insulating guide member having a plurality of protrusions protruding toward the image forming medium by a predetermined length from each of the openings at an upper end opposed to the forming medium; and charging the colorant particles into the insulating liquid. The dispersed recording liquid is supplied toward each of the openings through the respective grooves, and the plurality of projections projecting toward the image forming medium from the respective openings by the wetting of the recording liquid by the respective projections of the guide member. Supply means for forming a meniscus, and a plurality of projections projecting from the support member toward the image forming medium between the openings to partition recording liquid supplied to the openings by the supply means. And the above-mentioned supplier A collecting means for collecting the recording liquid supplied to each of the openings, and a collecting means provided between the adjacent partition walls for guiding the recording liquid supplied to each of the openings by the supplying means to the collecting means. By applying a first voltage to all of the first and second electrodes via the plurality of recovery paths and each of the connection terminals, the colorant particles in the recording liquid are moved along the liquid surface of each of the meniscuses. Then, electrophoresis is performed toward the tip of each of the meniscuses to cause aggregation, and a second voltage higher than the first voltage is applied to a connection terminal that is connected to the first and second electrodes selected according to a predetermined image signal. By selectively applying, the colorant particles agglomerated at the tip of the meniscus corresponding to the first and second electrodes selected according to the image signal are separated and discharged from the insulating liquid to form the image to be formed. Images that form images on media An image forming apparatus comprising: a forming unit.