JP2003053977A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder having high drying speed, high image quality and high productivity in which the ejection opening is prevented from being clogged with ink and blur is suppressed. SOLUTION: The imaging apparatus using ink 50 produced by dispersing charged particles A into a solvent and ejecting ink liquid drops 51 from an ejection head 10 using an ink ejecting means comprises means 21, 22 and 23 for supplying ink to the ejection head 10; means 12, 18a and 18b for controlling distribution of particles in ink in the ejection head 10; means for supporting/ carrying a recording medium 30 which receives ink liquid drops 51 ejected from the ejection head 10; and means 36, 42 and 44 for forming an electric field for accelerating flying ink liquid drops 51 wherein a heating element 14 is employed as the ejecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus that ejects ink by a heating element, and more particularly to an ink jet recording apparatus that uses ink in which particles are dispersed in a solvent.

[0002]

2. Description of the Related Art Currently used recording systems are a laser recording electrophotographic system, an LED recording electrophotographic system, a dot matrix impact recording system, a thermal paper recording system, a film recording system and a thermal wax recording system. , A dye dispersion thermal transfer recording method, an inkjet recording method, and the like. Among them, the ink jet recording method does not require processing such as toner transfer and developing process unlike the electrophotographic method, and the recording head can be downsized to reduce the size of the recording apparatus. It is widely used because it can print on plain paper. The conventional ink jet recording method uses a piezo element that deforms in response to an electric signal, uses a heating resistor that generates heat in response to an electric signal, and causes ink to fly by the pressure of steam due to heat. Some use electrostatic force. In the inkjet method that uses electrostatic force by electric signals, the IEICE Transactions'
83/1, Vol. J66-C, No. Due to electric field interference between adjacent channels at 1 and p51, there is a problem that the displacement amount of the recording pixel position becomes large when the recording electrode interval is narrow.

Therefore, a method has been developed in which the amount of change in the recording pixel position does not increase even if the recording electrode interval is narrow (Japanese Patent Publication No. 10-501490). This is a method of separating selected ink droplets from an ink body in a printing device by electrostatic attraction. In this method, an electric field is generated by applying an electric potential to the print head and another electric potential to the platen installed on the side facing the recording medium. Each electric field is modulated or discharged. Since it is not necessary to turn it on for each ink drop, a high voltage switching device is not required to generate the electric field and a very simple high voltage power supply can be used. Further, since it is not necessary to separate the electric field applied to the nozzles from the electric field applied to the adjacent nozzles, the distance between the nozzles can be narrowed. The magnitude of the electric field applied is set to a value that is not large enough to pull the ink droplets away from the printhead when the ink in the nozzle is in the rest position, and the ink in the nozzle causes the ink meniscus to move from the front of the printhead. It is large enough to pull the ink droplets away from the print head when in the protruding state.

In this ink drop selection method, the selected ink meniscus is projected from the front surface of the print head. Since the radius of the ink meniscus is small and is closest to the counter electrode, charges are accumulated in the protruding ink meniscus, and the accumulated charges concentrate the force generated by the electric field potential on the selected ink. This power is
Together with the pressure of the ink, it overcomes the surface tension of the ink, causing selected ink droplets to separate from the ink body.

The ink droplet selection means reduces the electrothermal force of the surface tension of the ink under pressure, generates an electric heating bubble due to a bubble volume insufficient to cause ejection of the ink droplet, and ejects the ink droplet. Piezoelectric, which has insufficient volume change to eject, and electrostatic attraction, which uses one electrode for each nozzle. In addition, the ink droplet separating means is close to (a recording medium close to the print head),
There are proximity by vibrating ink pressure, electrostatic attraction, magnetic attraction, etc.

However, in all of the ink jet recording methods, including the electrostatic type ink jet recording method capable of reducing the displacement amount, the ink viscosity rises due to the evaporation of the ink dispersion solvent from the ink ejection portion. There is a problem that drawing defects occur due to solidification of ink and ink. For this reason, the ink jet recording apparatus is provided with means for sealing the ink ejection port when printing is not performed, and means for cleaning the ejection port if necessary. To solve such a problem, Japanese Patent Laid-Open No. 11-1
According to Japanese Patent Publication No. 92732, a method of ejecting ink at regular intervals is disclosed in order to prevent clogging of ink regardless of drawing on the recording head, and Japanese Patent Laid-Open No. 2000-127417 discloses that method. A technique related to a method for cleaning a discharge port is disclosed. Due to the problems described above, the ink used in such an inkjet recording system contains a large amount of an aqueous solvent or an organic solvent containing a dye or a pigment as a coloring agent, and has a low ink viscosity and a low particle concentration. It was Therefore, such an inkjet recording method causes image bleeding, making it difficult to form a high-quality / high-resolution image.
Since it takes time to dry the image forming portion, it is difficult to improve productivity.

On the other hand, an ink in which particles are dispersed in a solvent is used in order to achieve an ink jet recording system with little image bleeding, fast drying speed, and high image quality and high productivity.
It is disclosed in Japanese Patent Laid-Open No. 000672 and Japanese Patent Laid-Open No. 2000-63723. It is effective to increase the particle concentration and decrease the concentration of the dispersion solvent in order to reduce the bleeding of the ink image and to improve the drying property. However, when an ink having a high particle concentration and a low dispersion solvent concentration is applied to the conventional inkjet recording method, the ink is clogged at the ejection portion, and good drawing cannot be performed.

As a solution to this, Japanese Patent Laid-Open No. 8-1
Japanese Patent No. 42331 discloses an ink jet recording apparatus with high image quality and high productivity, which has less bleeding and a high drying speed. It is configured to use an ink in which a coloring agent charged to a predetermined polarity is dispersed in a solvent and to regulate the flow of the coloring agent component in the ink by the force of the electric field to aggregate the coloring agent component. The aggregated coloring material component is ejected toward the recording medium by the force of the electric field. Further, by applying a voltage having the same polarity as the charging polarity of the colorant to the aggregation electrode on the upstream side in the ink transport direction with respect to the aggregation electrode on the downstream side in the ink transport direction of the pair of aggregation electrodes, It further comprises a removing unit that conveys and removes the coloring material component remaining between the aggregating electrodes toward the downstream side in the ink conveying direction.
Further, a collecting unit is provided for collecting the ink after the colorant components are aggregated by the aggregating unit through a recovery port provided near the aggregating electrode.

However, in this ink jet recording apparatus, a strong electric field is required in order to eject ink by an electric field. Therefore, when a strong electric field is used, electric field interference occurs between adjacent electrodes. Therefore, there was a fatal drawback that the resolution could not be increased. In addition, when the colorant component aggregated by the aggregating unit is discharged, the entire colorant component aggregated by the aggregating unit is discharged, so that there is a drawback that the density does not reach the intended density depending on the conditions. It was further,
The residual coloring material component removing means removes the coloring material component remaining between the aggregating electrodes, but this can clean only the inside of the ejection port. It was not possible to remove the residual coloring agent component at the tip of the ejection port, which is in contact with the air.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is an ink jet recording apparatus which ejects ink by a heating element, with less bleeding and a faster drying speed. An object of the present invention is to provide an ink jet recording apparatus with high image quality and high productivity that can increase the resolution.

[0011]

In order to achieve the above object, the invention of an inkjet image forming apparatus according to claim 1 uses an ink in which charged particles are dispersed in a solvent,
In an image forming apparatus that ejects ink droplets with an inkjet head (hereinafter referred to as “ejection head”) that uses a heating element as the ink ejection means, an ink supply means for supplying the ink to the ejection head and the ejection. Particle distribution control means for controlling the distribution of particles in the ink within the head, and recording medium support / transport means for supporting / transporting a recording medium for receiving ink droplets ejected from the ejection head and flying, Acceleration electric field forming means for forming an electric field for accelerating the velocity of the flying ink droplets. The invention described in claim 2 is claim 1
The inkjet image forming apparatus described above is characterized by including an accelerating electric field forming unit that forms an electric field for accelerating the velocity of the flying ink droplets. According to a third aspect of the present invention, in the inkjet image forming apparatus according to the first or second aspect, substantially only the solvent carrier is ejected using the particle distribution control means after image recording is completed or in a cleaning mode. . According to the above configuration, since the heating element ejects the ink, there is no electric field interference with the adjacent channel, and the ejection direction can be stably ejected even if the ejection port is formed with high density. Further, by accelerating the velocity of the flying ink droplets by the acceleration electrode, the distance between the ejection head and the image receiving sheet can be widened and the landing accuracy can be improved. In addition, the means for controlling the particle distribution in the ejection head increases the particle concentration in the ejected ink droplets by increasing the particle concentration in the vicinity of the ejection port during image recording, and after the image recording, the ejection port The discharge port can be cleaned by lowering the particle concentration in the vicinity and discharging substantially the solvent. As a result, it is possible to provide an ink jet recording apparatus with high image quality and high productivity, with less bleeding and quick drying.

In addition, other inventions described below are possible. A fourth aspect of the present invention is the inkjet image forming apparatus according to any one of the above aspects, further including an ink circulation unit that returns the ink from the ejection head. According to a fifth aspect of the present invention, in the inkjet image forming apparatus according to any one of the first to third aspects, the ejection port of the ejection head is provided only near the darkest position of the particle distribution formed by the particle distribution control means. .
According to a sixth aspect of the present invention, in the ink jet recording apparatus according to any one of the above aspects, a temperature detecting unit that detects the temperature of the ink in the ink tank, and the ink in the ink tank is heated or cooled according to the detected temperature. A temperature control means is provided. The seventh invention is
The ink jet recording apparatus according to any one of the above 1, wherein the drawing head is provided with a temperature detecting means for detecting the temperature of the drawing head, and a temperature adjusting means for heating or cooling the ink jet drawing head according to the detected temperature. To do.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a principle diagram of a first embodiment of the present invention. In FIG. 1, the inkjet recording apparatus continuously feeds the ink 50 from the ink tank 20 containing the ink 50 to the ejection head 10 via the pipe 21 to the ejection head 10 by the liquid feeding means 22. The ink used is an ink in which particles colored with a pigment and a dye are dispersed in a solvent. The particles used here are particles that have been charged in advance, but particles that are not charged may be charged by the charging means before they reach the ejection portion 10a of the ejection head 10. In addition, particles may be used that generate electric charge by irradiation with light, and the irradiation unit may generate electric charge.

The discharge port 1 is provided in the liquid delivery path in the discharge head 10.
0a is formed, and the ink ejecting means 14 is provided therein. The ink ejection unit 14 is a heating element described in detail in FIG. 2, and the ejection signal generation unit 13 applies an electric signal based on the image data signal. When an electric signal is applied to the heat generating element 14, the heat generating element 14 generates heat to rapidly generate bubbles, and the volume of the bubbles increases, so that ink in the heating element 14 portion is ejected from the ejection port 10a. Further, the ejection port head 10 is provided with a concentration distribution control electrode 18 as a concentration distribution forming means for controlling the concentration of particles, and the concentration distribution control electrode 18 has a concentration bias voltage control device (12 in FIG. 5) described later. ) Applies a voltage. During image formation, a voltage that forms an electric field E1 in the direction in which particles move to the vicinity 10a of the ejection port is applied to the concentration distribution control electrode by the concentration bias voltage control device. Outlet 10
The ink 50 is ejected by the heating element 14 which is the above-mentioned ink ejecting means in a state where the particle concentration near a is high. Further, a predetermined voltage is applied to the accelerating electrode 36 and the accelerating electrode 38, which will be described later, by bias voltage control devices 34 and C, respectively, so that a potential difference is generated between the accelerating electrode 36 and the accelerating electrode 38.

The ink 50 continuously sent to the ejection head 10 by the liquid sending means 22 is thus heated.
When ejected by means of No. 4, most of the particles in the ink 50 and a small amount of the dispersion solvent are ejected as droplets 51, and the remaining particles and most of the dispersion solvent are ejected by the return circulation means 25B through the return pipe 26B. Return to tank 20.
On the other hand, the ink 50 that has been delivered to the ejection head 10 but not ejected is recovered in the ink tank through the return pipe 26A by the circulation means 25A with the original concentration. In FIG. 1, in order to show that the ink that has not been ejected (original density) and the remaining ink that has been ejected (low density) are different, ink circulation means and return pipes 25A and 25B,
And 26A and 26B are shown separately, but in reality, there is one ink circulation means 25 and one return pipe 26, and they are the same.

During image formation, the image receiving sheet 30 is moved in a fixed state by means for fixing and moving the position of the image receiving sheet 30 (for example, recording drum, flat plate, etc.). An image is formed on the image receiving sheet 30 by ejecting ink droplets 51 while the main scanning of the head is appropriately performed on the moving image receiving sheet 30 (moving from top to bottom in the direction of the arrow in FIG. 1). To do.

2A and 2B are views showing an example of a liquid jet recording head used in the present invention. FIG. 2A is a front partial view from the orifice side of the head, and FIG. 2B is shown by a chain line XY in FIG. 2A. The cut surface partial view at the time of cutting in a part is shown. The recording head 201 shown in the figure is provided with a groove having a predetermined number of grooves with a predetermined linear density and a predetermined width provided on the surface of a substrate 203 on which the electrothermal converter 202 is provided. It has a structure in which the orifice 205 and the liquid discharge part 206 are formed by joining so as to cover the plate 204. In the case of the recording head shown in the figure, it is shown as having a plurality of orifices 205, but of course the present invention is not limited to this, and the application to the recording head in the case of a single orifice also applies to the present invention. It falls into the category. The liquid ejecting unit 206 has an orifice 205 for ejecting liquid droplets at its end, and thermal energy generated by the electrothermal converter 202 acts on the liquid to generate bubbles,
It has a heat acting portion 207, which is a place where a rapid state change is caused by the expansion and contraction of the volume.

The heat-acting portion 207 is located above the heat-generating portion 208 of the electrothermal converter 202, and has a heat-acting surface 209 that comes into contact with the liquid in the heat-generating portion 208 as its bottom surface. The heat generating unit 208 is a lower layer 210 provided on the substrate 203.
And a heating resistance layer 211 provided on the lower layer 210.
And electrodes 213 and 214 provided on the surface of the heat generating resistance layer 211 for energizing the heat generating resistance layer 211 to generate heat. The electrode 213 is an electrode common to the heat generating parts of the respective liquid ejecting parts, and the electrode 214
Is a selection electrode for selecting the heat generating portion of each liquid ejecting portion to generate heat. The upper layer 212 isolates the heat generating resistance layer 211 from the liquid in the liquid ejecting unit 206 in order to chemically and physically protect the heat generating resistance layer 211 from the liquid used, and also separates the electrodes 213 and 214 from each other through the liquid. It has a protective function of the heat generating resistance layer 211 for preventing a short circuit. The upper layer 212 has the above-mentioned function, but when the heating resistance layer 211 is liquid resistant and there is no fear of electrical short circuit between the electrodes 213 and 214 through the liquid. However, it is not necessarily provided, and may be designed as an electrothermal converter having a structure in which the liquid directly contacts the surface of the heating resistance layer 211.

The lower layer 210 mainly has a heat flow control function. That is, when the droplets are discharged, the heat generated in the heat generating resistance layer 211 is conducted to the heat acting portion 207 side rather than to the substrate 203 side.
After the liquid droplets are discharged, that is, the power supply to the heating resistance layer 211 is turned off.
After being heated, the heat in the heat acting portion 207 and the heat generating portion 208 is rapidly released to the substrate 203 side, and the heat acting portion 2
It is provided for the liquid at 07 and bubbles generated to be drastically reduced. As described above, when the droplets are ejected, the heat acting portion 2
The heat flow rate to the 07 side is as large as possible, and when the heating resistor layer 211 is turned off, the heat flow rate to the substrate 203 side is set to be as large as possible.
High efficiency of droplet discharge energy, improvement of thermal response and continuous repeated droplet discharge performance, improvement of droplet discharge frequency, uniform discharge droplet volume, stabilization of droplet discharge direction, droplet discharge speed In order to realize the uniformity of the above, and the improvement of the fidelity and certainty of the response to the recording signal, it is only necessary to execute the recording so that the above relationship is established in the bubble volume change curve.

This point will be described more specifically. FIG. 3 shows a temporal change in the bubble volume generated in the heat acting portion 207 when an electric signal having a pulse waveform indicated by the symbol P is input to the electrothermal converter 202 provided in the recording head. Now, when the pulsed electric signal P0 is input to the electrothermal converter 202 at time t0 and time tf, a bubble is generated in the heat acting portion 207 at time ti, and the volume Vv of this bubble is Start to increase from time ti,
The maximum volume Vvp is reached at time tp. Time tf
When the electric signal p is turned off at, the volume Vv of the bubble starts to decrease after the time tp. The rate of decrease of the bubble volume Vv when the electric signal P0 is turned off depends on the temporal change rate of the bubble volume Vv at time τ1.

FIG. 4 is a schematic vertical sectional view of an ink jet recording apparatus embodying the principle diagram of FIG. In FIG.
Reference numeral 10 denotes an ejection head of an ink jet recording apparatus, which has an ejection portion 10a at the upper right of the drawing, and a heating element 14 is disposed there. An electric signal based on the image data signal is applied from the ejection signal generating means 13 to the heating element 14. The interior of the ejection head 10 is hollow, and the flow path regulating member 10b is located in the center thereof to regulate the flow path of the ink 50. That is, the ink 5 is continuously fed from the ink tank 20 containing the ink 50 into the ejection head 10 via the pipe 21, the liquid feeding means 22, and the pipe 23.
0 advances to the upper left in the passage between the left wall surface of the ejection head 10 and the left surface of the flow path regulating member 10b, and moves to the ejection portion 10a side, and to the right wall surface of the ejection head 10 and the right surface of the flow path regulating member 10b. The flow path goes to the lower right, and returns to the ink tank 20 below the flow path regulating member 10b.

The flow path regulating member 10b has a stepped upper side, and the distance from the upper surface of the ejection head 10 is the ejection portion 10a.
Is wide on the opposite side and narrow on the discharge part 10a side. In this narrow region, the concentration distribution control electrode 1 is formed on the inside of the upper surface of the ejection head 10 and on the upper surface of the flow path regulating member 10b.
8 are provided. A pulse P1 is applied between the concentration distribution control electrodes 18 from the concentration bias voltage control device (electric field control means) 12 for a predetermined time, and the concentration distribution control electrodes 18 are
An electric field is formed between them. When ink in which charged particles are dispersed in a solvent passes through this electric field, the particles move to the concentration distribution control electrode 18 on the ejection port 10a side,
A voltage pulse is applied.

In this way, when an electric signal is applied to the heating element 14 in a state where the particle concentration near the ejection port 10a is high, an ink droplet 51 having an extremely high particle concentration is ejected from the ejection port 10a. It Particularly, in the present invention, the ejection port 10a is located at the darkest position in the color material distribution between the density distribution control electrodes 18 (the upper density distribution control electrode 18 in FIG. 5).
Since it is provided only in the vicinity, the ink droplet 51 having an extremely high particle concentration is ejected from the ejection port 10a.

Comparing the images when the discharged ink 50 is discharged and drawn as it is and when the discharged and drawn ink is drawn by increasing the particle concentration by using the density distribution control, the image when the particle concentration is high is higher. There was little bleeding and the drying time was fast. By intermittently applying the concentration bias voltage, the concentration bias voltage is gradually moved to prevent particles from being electrodeposited and fixed to the concentration distribution control electrode. Furthermore, by controlling the pulse width, it is possible to control the particle concentration in the vicinity of the ejection port 10a and the particle concentration of the ejected ink droplets, and it is possible to improve the gradation reproducibility of the drawn image. .

Further, in this ink jet image forming apparatus, since the residual ink ejected has a low density, it is temporarily returned from the ejection head 10 to the ink tank 20 and then returned to the ink tank 20 at a concentration close to the original density. It is better to use it after raising it to.

An accelerating electrode 36 is provided on the back surface of the image receiving sheet 30, and the accelerating electrode 3 provided in the ejection portion 10a.
8 and acceleration electrode 36 between the acceleration bias voltage controller 34 '
The voltage is applied by. Therefore, if a voltage is applied between the acceleration electrode 38 and the acceleration electrode 36 by this acceleration bias voltage control device 34 ', the ejection port 1
The charged ink droplets 51 discharged from 0a are accelerated by the acceleration bias electrodes 36 and 38 and land on the image receiving sheet 30. By providing the acceleration bias electrode 36 in this way, good landing position accuracy could be obtained even if the distance between the ejection head 10 and the image receiving sheet 30 was widened. The ink used is a dispersion of particles 4 in a solvent, and the particle concentration is preferably about 10% by mass or more. Here, particles that have been positively or negatively charged (charged) in advance are used, but uncharged particles may be charged by the charging means before reaching the ejection portion.

Here, the ink used in the present invention will be described in detail. The ink used in the present invention comprises at least particles dispersed in a solvent, and the dispersed particles may be organic particles or inorganic particles. The solvent used in the ink of the present invention is not particularly limited, but those having a specific electric resistance of 10 ⁴ Ωcm to 10 ¹⁵ Ωcm and a relative dielectric constant of 2.0 to 80 are preferable. This is because if the resistivity value becomes extremely low, it becomes difficult to maintain the particle concentration gradient due to the disappearance of the electric field formed after the power is cut off.In addition, if the dielectric constant becomes extremely high, the electric field relaxes due to the polarization of the solvent. Therefore, it becomes difficult to control the particle concentration. The solvent preferably has a viscosity of 1.0 cP to 20 cP and a surface tension of 19 to 74 dyne / cm (kN / m). The particles dispersed in the solvent may be colored particles or non-colored particles. When using colored particles, the coloring material itself may be dispersed as dispersed particles in a solvent, or may be contained in other dispersed particles such as resin particles. When it is contained, a pigment or the like is generally coated with a resin material of dispersed resin particles to obtain resin-coated particles, and a dye or the like is generally pigmented by dispersing resin particles into colored particles. There is.

As the coloring material, any pigment and dye conventionally used in the technical field of ink compositions or printing can be used. As a pigment,
What is generally used in the technical field of printing can be used regardless of whether it is an inorganic pigment or an organic pigment. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, viridian, cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment. , Quinacridone pigments, isoindolinone pigments, dioxazine pigments, slene pigments, perylene pigments, perinone pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments, etc. Can be used without.

As the dye, azo dye, metal complex salt dye,
Naphthol dye, anthraquinone dye, indigo dye,
Carbonyl dye, quinone imine dye, xanthene dye, aniline dye, quinoline dye, nitro dye, nitroso dye, benzoquinone dye, naphthoquinone dye, phthalocyanine dye, metal phthalocyanine dye and the like can be used without particular limitation. These pigments and dyes may be used alone or in appropriate combination.

In the ink used in the present invention, dispersed resin particles for improving the fixability of an image after printing may be used in addition to the above-mentioned colored particles. The average particle size of these particles including the colored particles dispersed in the solvent of the present invention and further the resin particles is 0.05 μm to 5 μm.
Is preferred. More preferably, 0.1 μm to 1.5 μm
And more preferably in the range of 0.1 μm to 1.0 μm.

The particles in the ink of the present invention are preferably positively or negatively charged electroscopic particles. It is possible to impart the electroscopic property to the particles by appropriately using the technique of the developer for wet electrostatic photography. Specifically, "Recent development and practical application of electrophotographic development system and toner material" 139
~ 148, "Basics and Applications of Electrophotography" edited by The Institute of Electrophotography, 497-505 (Corona Publishing Co., Ltd., 1988), Yuji Harasaki, "Electrophotography" 16 (No. 2), 44 (197).
7 years) and the like and the use of the electroscopic material and other additives. Examples of preferable electrophoretic materials include metal soaps, organic phosphoric acid or salts thereof, organic sulfonic acids or salts thereof, amphoteric surfactants and the like. For example, as metal soaps, fatty acids having 6 to 24 carbon atoms (for example, 2
-Ethylhexynoic acid, 2-ethylcaproic acid, lauric acid, paramitic acid, elaidic acid, linoleic acid, ricinoleic acid, oleic acid, stearic acid, enanthic acid, naphthenic acid, ethylenediaminetetraacetic acid, etc.), resin acid, dialkylsuccinic acid , Metal salts of alkyl phthalic acid, alkyl salicylic acid, etc. (as metal ion metal, Na, K,
Li, B, Al, Ti, Ca, Pb, Mn, Co, Z
n, Mg, Ce, Ag, Cd, Zr, Cu, Fe, B
a, etc.) (for example, US Pat. Nos. 3,411,936, 39;
00412, JP-B-49-27707, JP-A-51.
-37651, 52-38937, 52-10.
No. 7837, No. 53-123138, etc.).

Examples of the organic phosphoric acid or salts thereof include mono-, di-, or trialkyl phosphoric acid or dialkyldithiophosphoric acid having an alkyl group having 3 to 18 carbon atoms (for example, British Patent Nos. 1411739 and 1276363,
Etc.). Examples of the organic sulfonic acids or salts thereof include long-chain aliphatic sulfonic acids, long-chain alkylbenzene sulfonic acids, dialkyl sulfosuccinic acids and the like or metal salts thereof (for example, Japanese Patent Publication No. 47-37128,
JP-A-53-123138, JP-A-51-47437,
Nos. 50-79640 and 53-30340).

Examples of the amphoteric surfactant include phospholipids such as lecithin and kephalin (for example, Japanese Examined Patent Publication No. 51-47046).
No., etc.), β-containing an alkyl group having 8 or more carbon atoms
Alanines (for example, described in JP-A-50-17642, JP-B-51-47046, JP-A-49-17741, etc.), metal complexes of β-diketones (for example, JP-B-49-27707, Etc.), a copolymer having a maleic acid half amide component (for example, JP-B-6-19596).
No. 6-19595, etc.). These electrophoretic materials can be used alone or in combination of two or more kinds.

The electrophoretic material is a dispersion solvent 10 which is a carrier liquid.
It is preferable to use about 0.001 to 1.0 parts by mass with respect to 00 parts by mass. Further, various additives may be added if desired. The upper limit of the total amount of additives is limited by the specific electric resistance, viscosity, or surface tension of the ink. That is,
The specific electric resistance of the ink is about 10 ⁴ Ωcm to 10 ¹⁵ Ωcm, the relative dielectric constant is about 2.0 to 80, and the viscosity is about 1.0 cP.
About 30 cP, surface tension 19-74 dyne / cm
It is desirable to adjust it to be about (kN / m).

Next, a second embodiment of the present invention will be described. FIG. 5 shows a principle diagram of the second embodiment of the present invention (a recording medium and the like are omitted). The structure of the ink jet recording apparatus of FIG. 5 is the same as that of FIG. 5, except that the density bias voltage between the density distribution control electrodes 18 is applied. In FIG. 5, the particle concentration in the vicinity of the ejection port 10a is increased during image recording and the particles are ejected from the ejection port 10a. However, in FIG. Only the discharge port 10a is discharged to clean the tip of the discharge port 10a. That is, in FIG. 5, when the concentration bias voltage P2 between the concentration control electrodes 18 is reversed from that in FIG.
When the charged particles pass through this electric field, the particles move to the concentration control electrode 18 on the side of the flow path regulating member 10b, and conversely, the particle concentration in the vicinity of the ejection port 10a becomes extremely thin. When an electric signal is applied to the heating element 14 in this state, the ink droplets 51 'of only the solvent carrier having an extremely low particle concentration are ejected from the ejection port 10a, whereby the ejection port is cleaned. Becomes Thus, after the image formation is completed, a voltage is applied to the concentration distribution control electrode to form an electric field in which the particles move in a direction away from the ejection port, and ink droplets are ejected in a state where the particle concentration near the ejection port is low. Therefore, the concentration of particles in the ejected ink liquid is low, and the solvent is ejected, and the ejection port and the tip of the ejection port, which is likely to be clogged by contact with air, are cleaned. As a result, it was possible to prevent the ink from clogging at the ejection port.

In addition to the completion of image formation, a cleaning mode may be provided even during image formation. This is because the head that has not been ejected for a long time may also be dried and the ejection port may be clogged, so that the head is not fully ejected by the second embodiment at an appropriate time interval (that is, a time when the ejection port is not dried). Only the solvent is discharged from the outlet or the discharge port requiring cleaning to wash them.

The ejected ink droplets land on the recording medium conveyed by the recording medium conveying means (not shown),
Drawing is done. Ink is circulated between the ink tanks (not shown) to the recording head 41 by an ink circulation unit (not shown). Therefore, sufficient ink is supplied into the ink chamber even when drawing is performed. Further, sufficient particles are supplied to the ink 6 in the ink chamber 2 by having a replenishing means for replenishing the ink in accordance with the consumption of the particles in the ink. Further, since the temperature of the ink in the ink tank and the temperature of the drawing head are stably controlled, the liquid properties of the ink are also stable, and stable ejection can be performed.

[0038]

According to the present invention, at the time of drawing, ink droplets having a high particle concentration are ejected by increasing the particle concentration in the vicinity of the ejection port and ejecting the ink droplets at the end of image formation and during image formation. Also, by periodically lowering the particle concentration in the vicinity of the discharge port and discharging, it is possible to discharge the substantially solvent and clean the discharge port. That is, the nozzle clogging hardly occurs because the carrier-dispersing solvent is ejected at the end of the operation to clean the nozzle. Further, since the discharged ink density can be considerably increased by the particle distribution control means, the image density can be increased, so that the bleeding is small and the drying speed is high. The landing accuracy could be improved by the electric field that accelerates the particles in the direction perpendicular to the image receptor surface. Since the heating element has an orifice structure, there is no fear of crosstalk, and since the electrostatic field is not used, the channel density of the ejection port can be increased. As described above, according to the present invention, it is possible to provide an ink jet recording apparatus with high image quality and high productivity, in which ink is not clogged at the ejection port, bleeding is small, and the drying speed is fast. Become.

[Brief description of drawings]

FIG. 1 shows a principle diagram of a first embodiment of the present invention.

2A and 2B are views showing an example of a liquid jet recording head used in the present invention, FIG. 2A is a front partial view from the orifice side of the head, and FIG. 2B is a dashed-dotted line XY in FIG. 2A. The cutting surface partial view at the time of cutting in the part shown is shown.

FIG. 3 is a timing chart showing an electric signal input to the recording head and a temporal change in volume of bubbles generated in a heat acting portion.

FIG. 4 is a schematic vertical cross-sectional view of an inkjet recording apparatus that embodies the principle diagram of FIG.

FIG. 5 is a schematic vertical sectional view of an inkjet recording apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

10 Discharge head 10a discharge port 10b Flow path regulating member 12 Concentration bias voltage control device (electric field control means) 13 Discharge signal generating means 14 Ink ejection means (heating element) 18 Concentration distribution control electrode 20 ink tank 21 pipes 22 Liquid transfer means 25 Return circulation means 26 Return pipe 30 Image receiving sheet 34, 34 'Acceleration bias voltage control device 36 Accelerator electrode 38 Acceleration bias electrode 50 ink 51 dark ink droplets 51 'thin ink droplet A ink particles 201 Liquid jet recording head 202 electrothermal converter 203 substrate 204 grooved plate 205 Orifice 206 Liquid discharge part 207 Heat acting part 208 Heat generating part 209 Thermal surface 210 Lower layer 211 Heating layer 212 upper layer 213 common electrode 214 selection electrode

Claims (3)

[Claims] 1. An image in which ink droplets are ejected by an ink jet head (hereinafter referred to as “ejection head”) that uses an ink in which charged particles are dispersed in a solvent and uses a heating element as an ejecting means of the ink. In the forming apparatus, an ink supply unit that supplies the ink to the ejection head, a particle distribution control unit that controls the distribution of particles in the ink within the ejection head, and an ink droplet that ejects from the ejection head and flies. An inkjet image forming apparatus, comprising: a recording medium supporting / conveying means for supporting / conveying a recording medium that receives the recording medium. 2. The inkjet image forming apparatus according to claim 1, further comprising accelerating electric field forming means for forming an electric field for accelerating the velocity of the flying ink droplets. 3. The inkjet image forming apparatus according to claim 1, wherein substantially only the solvent carrier is ejected using the particle distribution control means after the image recording is completed or in the cleaning mode. apparatus.