JPH0557907A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To record a high-quality, half-tone image even on plain printing paper by discharging the heat-meltable ink which is solid at room temp. and becomes liquid in a head upon heating in a manner to control the ink dot diameter, while increasing the printing speed. CONSTITUTION:The ink jet recorder is provided with a head 2 having an ink chamber 3 filled with an electrically conductive heat-meltable ink 1 and an ink discharge orifice 4 formed in communication with the ink chamber 3 for each picture element density, an ink heating means 5 adapted to heat the heat- meltable ink 1 in the ink chamber 3 of the head 2 to such an extent as to melt a part of the ink near at least the orifice 4 and a control electrode 7 near each orifice 4. The recorder is further provided with an electrostatic force control means 6 which directs a variable electrostatic force S toward a recording material 8 provided facing toward each orifice 4 according to multiple gradient image information with the control voltage changeable in response to the multiple gradient image information applied to each control electrode 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called ink jet recording apparatus for ejecting ink corresponding to image information toward a recording medium such as paper, and more particularly, an ink jet type ink ejecting ink by electrostatic attraction. Relating to improvement of recording device.

[0002]

2. Description of the Related Art Ink jet printers that eject ink from an orifice or slit to record an ink image on a recording medium are widely used because of their simplicity and high speed. Various methods have been proposed for this type of ink jet recording apparatus. Among them, an electrostatic field is formed between the control electrode inside the print head and the back electrode on the back surface of the recording medium, and electrostatic discharge The so-called electrostatic attraction type inkjet recording device, which draws out the ink in the print head by an attractive force and prints, has a particularly simple structure, that the head can be easily manufactured to easily create a page width head, and high-speed printing is possible. Is possible, and the dot diameter can be controlled by pulse width modulation.

In such a type, for example, an ink jet recording apparatus disclosed in Japanese Patent Laid-Open No. 1-297618 uses a low-viscosity, high-resistance oil-based ink having good flying properties. However, in order to realize low viscosity with good flying property, coloring with a dye is necessary, but since the main solvent of the ink is oil, an oil-soluble dye has to be used.
When this oil-soluble dye is ingested by the human body, it is difficult to dissolve in water, and therefore, there is a high risk of accumulation without being discharged to the outside of the body. Further, since the body viscosity ink easily penetrates along the paper fibers and forms bleeding dots to cause so-called feathering, an ink absorbing layer such as clay is provided on the surface for performing this inkjet recording. There is no choice but to use special paper, and it is not suitable for plain paper. When a low-viscosity ink is prepared by dispersing the pigment, the dispersion stability is poor, and the pigment tends to settle during storage.

As a means for solving such a technical problem, for example, POD (Pulse On Demand) using a hot-melt ink as disclosed in JP-A-60-228163.
There is an inkjet recording method. In this method, the ink that becomes solid at room temperature and becomes liquid when heated in the recording head is ejected by the pressure wave generated by the piezoelectric element, so that the ink is cooled and fixed before flowing along the paper fibers to prevent feathering. It has the characteristic of being suitable for plain paper without causing it.

[0005]

However, in this method, since the piezoelectric elements cannot be arranged at a high density, a recording head having a page width cannot be produced, and as a result, the printing speed is slow. There are challenges. Furthermore, in order to eject a small amount of ink with a pressure wave, it is necessary to apply a relatively large pressure wave to a small nozzle, which makes it difficult to process the nozzle in order to secure the nozzle strength. There is also a technical problem that the piezoelectric element becomes large. Furthermore,
Despite being able to form good dots without feathering on plain paper, the size of the droplet is roughly determined by the nozzle diameter, and it is difficult to control the size of the dot by an electrical signal. There is a technical problem that a high quality halftone image cannot be recorded.

Further, there are a POD ink jet recording method using a water-based ink and an ink jet recording method in which droplets are ejected by utilizing pressure fluctuation when water is boiled. In these methods, ink is ejected from the nozzle tip. The water in the ink may evaporate, and the colorant may deposit on the peripheral surface of the nozzle, which may deteriorate the ejection characteristics of the ink and may even clog the nozzle. Therefore, a number of additional devices such as capping of ink ejection holes, blank ejection, forced suction of ink, and wiping of ink ejection holes are indispensable, which is a fundamental technical problem that prevents simplification of the device. There is.

The present invention has been made in order to solve the above technical problems, and is based on a heat-melting ink which is solid at room temperature and becomes liquid when heated in the head, and has a high printing speed. It is an object of the present invention to provide an ink jet recording apparatus capable of recording a high quality halftone image even on plain paper which is a recording medium while controlling the ejection diameter of the ink. Another object of the present invention is to provide an ink jet recording apparatus that does not have nozzle clogging even if it is left for a long time without providing a special clogging preventing means. Another object of the present invention is to provide an ink jet recording apparatus that can use a pigment-dispersed ink that can be stored for a long time.

[0008]

That is, the present invention is
As shown in FIG. 1, a head body 2 having an ink chamber 3 filled with a conductive hot-melt ink 1 and an ink ejection orifice 4 communicating with the ink chamber 3 is provided for each pixel density. Ink heating means 5 for heating the ink 1 to such an extent that at least a portion of the heat-meltable ink 1 filled in the ink chamber 3 of the head main body 2 located near the orifice 4 is melted, and in the vicinity of each orifice 4. A control voltage 7 is provided, and a control voltage that changes in accordance with multi-tone image information is applied to each control electrode 7 to provide a multi-tone image toward the recording pair 8 side, which is arranged to face each orifice four times. An electrostatic attraction force variable control means 6 for applying a variable electrostatic attraction force S according to information is provided.

In such technical means, the heat-meltable ink 1 is a material which is heated and melted by the ink heating means 4 and has sufficient hardness at room temperature so as to exhibit sufficient fixing property. Is selected. At the same time, a material having a low melt viscosity is selected so that the yarn can easily fly from the orifice 4. For example, ink containing wax as a main component may be used. Further, if the ink 1 is insulative, it is impossible to inject charges from the control electrode 7, and if it is excessively conductive, it is difficult for the ink to be pulled, and it is difficult for the towed to fly. Therefore, it is necessary to appropriately adjust the degree of conductivity.

Further, as the ink heating means 5, since the ink can be ejected if the ink 1 near the orifice 4 is melted, the head main body 2 is at least within a range where the ink 1 near the orifice 4 can be melted. It may be designed so as to be heated, and it is not always necessary to heat the entire head body 2. However, when only a part of the ink is heated and melted, in order to promptly re-supply the consumed ink, open a part of the liquid surface to atmospheric pressure air and It is necessary to devise the shape of the ink chamber so that it can be automatically replenished by dropping it.

Further, as the electrostatic attraction force variable control means 6, the electrostatic attraction force may be continuously changed by appropriately changing the voltage applied to the control electrode 7, or may be changed stepwise. However, it is possible to set the degree of change in consideration of the degree of change in the ink dot diameter and the fact that excessive drawing of ink does not result in coalescence with an adjacent towing string. is necessary.

Further, the recording medium 8 includes not only a final recording medium such as plain paper or a film made of an ink impermeable material, but also an intermediate transfer medium. In this case, as the intermediate transfer member, for example, one that holds and conveys the ink 1 ejected from the head main body 2 and pressure-transfers it to the final recording medium is used. From the viewpoint of ensuring good quality, it is necessary to design so that the surface temperature of the intermediate transfer member is maintained near the softening temperature of the heat-meltable ink by a predetermined heating means.

From the viewpoint of reducing the change in the dot diameter due to the change in the thickness of the recording medium 8, the ink string raised from the orifice 4 flows toward the recording medium 8 by the flow of the gas A. It is preferable to add an air flow transporting means 9 that transports the air straightly. In this case, the electrostatic attraction force formed by the electrostatic attraction force variable control means 6 may be set to such an extent that the ink is raised in the form of a string, and the ink 1 is ejected to the recording medium 8. You don't need a degree.

Further, when the recording medium 8 is made of an ink permeable material, from the viewpoint of further improving the fixing property of the ink on the recording medium 8, the ink is ejected from the head main body 2. To the extent that the ink 1 is formed as flat dots having deep roots on the recording medium 8, the recording medium 8
It is preferable to add a recording medium heating means 10 for heating the recording medium. In this case, if the temperature of the recording medium 8 is too high, the ink 1 flows more than necessary on the recording medium 8 and permeates between the fibers of the ink permeable material such as paper more than necessary. Since bleeding and print-through (a phenomenon in which ink penetrates to the back) occur, the recording medium heating means 10
It is necessary to properly adjust the set temperature of.

[0015]

According to the above-mentioned technical means, the ink heating means 5 has such a degree that at least the portion of the hot-melt ink 1 filled in the ink chamber 3 of the head body 2 located near the orifice 4 is melted. Ink 1 is heated. In this state, the electrostatic attraction force variable control means 6 controls the orifices 4
When a control voltage that changes according to multi-gradation image information is applied to each control electrode 7 arranged in the vicinity, each orifice 4
A variable electrostatic attraction force S corresponding to the multi-gradation image information is formed toward the recording medium 8 side which is arranged so as to face. Then, the melted ink 1 in the head main body 2 is pulled by the variable electrostatic attraction S, extends in the form of a string toward the recording body 8 side, and flies, and after reaching the recording body 8, it is solidified and fixed. To do. At this time, since the pulling state of the ink is changed by the variable electrostatic attraction S, the diameter of the ink dot on the recording medium 8 is changed and a halftone image corresponding to each dot diameter is formed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. Example 1 FIG. 2 is a schematic configuration diagram of Example 1 of an inkjet recording apparatus to which the present invention is applied. In the figure, reference numeral 20
Is a head main body, has an ink chamber 21 for accommodating the heat-meltable ink 11, and an orifice plate 22 configured as one side wall of the ink chamber 21 has orifices 23 in a pixel density unit in a direction perpendicular to the paper surface. Many were opened. An ink heater 25 as an ink heating means for melting the heat-meltable ink 11 contained in the ink chamber 21 is provided outside the side wall 24 of the head body 20 facing the orifice plate 22. .. A surface liquid-repellent layer 26 is provided on the outer surface of the orifice plate 22 so that a convex ink meniscus can be formed. Then, the ink 11 consumed by an ink supply device (not shown) is automatically supplied, and the ink pressure in the orifice 23 is set to be higher than the atmospheric pressure by about 400 Pa by an ink supply pressure adjusting device (not shown).

Further, an individual control electrode 31 is arranged around each of the orifices 23, and each control electrode 3 is provided.
A control voltage corresponding to a multi-gradation image signal is applied to 1 by an individual control electrode drive circuit 32. On the other hand, a roll-shaped electrode back surface 33 that also serves as a conveying member for the recording medium 40 such as recording paper is provided at a portion facing the orifice 23, and one back electrode driving circuit 3 is provided.
A predetermined control voltage is applied by means of 4. Reference numeral 27 is an insulating protective layer that covers the extraction electrode portion of the control electrode 31. In this embodiment, the pulse voltage and pulse width applied to the back electrode 33 are selected as large as possible within a range in which the ink 11 is held by surface tension and does not reach the recording medium 40. In addition, the control electrode 3
The polarity of the control voltage applied to No. 1 is selected to be opposite to that of the voltage applied to the back electrode 33. By this,
The ink 11 does not fly only by the voltage applied to the back electrode 33, but it can be adjusted so that the ink 11 flies when the control voltage is added to it, and with a relatively small control voltage,
The flight operation of the ink 11 is controlled.

The specific printing operation according to this embodiment is performed in the following steps. (1) A voltage is applied to the back electrode 33. Almost at the same time, a control voltage is applied to the control electrode 31 in accordance with the image signal, and the ink 11 is drawn out from the orifice 23 in a thread shape in accordance with the image and reaches the surface of the recording medium 40. (2) The back electrode applied voltage and the control electrode applied voltage are turned off at substantially the same time after an electrostatic field having a width sufficient to form dots is applied. (3) The string of the ink 11 becomes thin due to the surface tension,
After a lapse of time required for cutting, the recording medium 40
Is step fed. (4) The next cycle is started after the time required for the ink consumed by the flight to be re-supplied by the surface tension and to return to the initial meniscus height. That is, the procedure returns to (1).

The ink used in this embodiment is a black ink obtained by stirring and dispersing carbon black having an average primary particle diameter of 0.05 μm in a state where linear paraffin having a molecular weight of about 1,000 is melted by heating. Is used. This ink has a viscosity of about 13 mPas at 140 ° C. and is suitable for flying by the electrostatic attraction type inkjet method. Surface tension is 26 dy at 140 ° C
It showed ne / cm.

Image recording was carried out under the following conditions, and a good image having a dot diameter of about 100 μm was obtained. Recording density 8 dot / mm (vertical and horizontal) Recording repetition frequency 200 Hz Head temperature approx. 140 ° C Orifice diameter 80 μm Orifice arrangement 2 rows zigzag Control voltage +400 V Back electrode applied voltage −2,000 V Pulse width 1 msec Recording medium Our standard paper (L paper) Recording material thickness: approx. 100 μm Distance from head surface to paper: approx. 250 μm

The state of ink flying was observed using a microscope observation device and a strobe exposure device. The strobe exposure device repeatedly emits light in synchronization with the flight (driving) of ink. Figure 3 (a) showing how ink draws a towing thread and flies.
It shows in (b). When the hot-melt ink of this example is used, the viscosity at the time of melting can be kept low, so that the melt viscosity is 1
At 3 mpas, the thickness of the towline remains at most 10 μm.
Therefore, fine dots with a diameter of 10 μm can be printed by adjusting the pulse width and the acting electric field. This is important when performing halftone recording by pulse width modulation or higher density recording. Further, since the string is thin, the amount of ink returning to the head side after the electrostatic field is turned off and the amount of ink scattered as satellite dots on the paper side are small, and reliability is reduced due to ink stains on the surface of the orifice plate 22. , Distortion of image quality due to satellite dots is extremely small.

Another feature of this embodiment is that the type of the recording medium 40 is not selected. That is, the printed recording medium 40 was a standard copy paper, which was not coated with a surface or the like, but formed substantially circular dots without bleeding. This is because the melted ink quickly cools and solidifies after reaching the surface of the paper. The image was good with no feathering, paper warpage, or show-through. Although the diameter of the dot is about 100 μm, the dot is formed in a shape that is raised by about 30 μm from the paper surface, but the rise is hardly visible to the naked eye. In some cases, when touching, the swelling of the dots may be felt, and when printing on both sides, the paper may be slightly lifted from the back electrode 33 by the dot printed earlier, and the flying characteristics may be slightly changed. , PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), etc. can be suppressed very easily by using a heating roll coated with a fluororesin. There is no problem.

Next, all the power sources including the ink heater 25 were turned off, left for one week, and then turned on again to print. While the power is off, of course, the heat-meltable ink 11 is solidified, so that it is extremely stable and does not cause sedimentation or secondary agglomeration of the pigment, and the orifice 23 is dried to dry like the water-based ink. It won't clog.
Normal printing was possible even after being left for one week. Of course, the orifice 23 is not capped. Furthermore, in order to check the deterioration due to the storage of the ink, 30 ° C, 80% humidity
%, The solid ink was allowed to stand for one month and then supplied to the print head, and a printing experiment was conducted. As a result, normal printing was possible.

The ink used has a molecular weight of about 5,
000 alpha olefin / maleic acid ester copolymer in a state of being melted by heating, the average primary particle diameter is about 0.
A black ink made by stirring and dispersing carbon black of 05 μm was manufactured. This ink is about 50 at 100 ° C
It is a low-viscosity ink showing a viscosity of mpas and suitable for flying by an electrostatic attraction type inkjet recording system. The surface tension was about 30 dyne / cm at 100 ° C. When a printing test similar to that described above was conducted using this ink, good printing results were obtained.

The ink material applied in the present invention is not limited to the linear paraffin and alpha olefin / maleic acid ester copolymer. For example, any material may be used, such as stearic acid, stearic acid amide, zinc stearate, oleic acid amide, etc., as long as it is a solid at room temperature, has a suitable melting point, and has a low melt viscosity as the main solvent, and the pigment is dispersed therein. The dispersed pigment is not limited to carbon black.

(Comparative Example) Even if it is attempted to achieve the same flight with a conventional oil-based ink, it is not possible to achieve both dispersion stability and viscosity of carbon black as a pigment. Pigmentation will not occur if pigmented,
Although there is no thickening due to coloring, the oil-soluble pigment accumulates in the human body, which is not preferable in terms of safety. In our consideration,
200 mpas is the lowest viscosity ink that can secure dispersion stability by dispersing the pigment in the oily main solvent. 4 (a) and 4 (b) show, for reference, the results of observing a towing thread when the ink 11 'was made to fly with a similar head.

As shown in the figure, the shape of the towing thread is substantially conical. This is because the electric field concentrates on the tip of the towing thread, but the viscosity increases with the surrounding ink, and the towing thread becomes thick. The observation timing (strobe light emission timing) is when the electrostatic field is turned off. After that, the knots of the towing thread move to the head side according to the ink permeation of the paper, and the towing threads are cut at approximately the midpoint between the head and the paper surface, and each heads toward the head and the paper. In the case of this oil-based ink, since the amount of ink returning to the head is large, it takes time until the surface of the orifice plate 22 is contaminated with ink or returns to the initial state, although the surface of the orifice plate 22 is liquid-repellent. There is a drawback that it costs. Compared to this,
It can be clearly seen how good the flying state of the embodiment shown in FIG. 3 is. Further, in the case of the oil-based ink, the voltage applied to the back electrode was -2,400V, whereas in the case of the example, sufficient printing was possible at -1,800V.

Example 2 FIG. 5 shows Example 2 of the ink jet recording apparatus to which the present invention is applied. In the figure, reference numeral 50 denotes a head main body, and this head main body has an ink chamber 51 for accommodating the heat-meltable ink 11, and an ink nozzle plate 52 configured as a top wall of the ink chamber 51 has a paper surface. A large number of nozzle holes (orifices) 53 are opened in the vertical direction. In this embodiment, the ink nozzle plate 52 has a nozzle hole 53 made of photosensitive glass, a cylindrical convex portion 54 made of photosensitive polyimide on the upper portion, and electron beam vacuum evaporation of gold on the lower portion. The control electrode 61 was made by photoetching. Then, an amorphous fluororesin (manufactured by Asahi Glass Co., Ltd., trade name CYTOP) was applied to the end of the ink nozzle plate 52. This makes it possible to eliminate the instability of flight due to ink stains on the end of the ink nozzle plate 52.

An ink heater 56 is provided on the inner surface of the glass side plate 55 forming one side wall of the ink chamber 51 of the head body 50. The ink heater 56 is formed by printing a thick film resistor on the inner surface of the glass side plate 55 in a band shape by silk printing and firing, and the ink heater 56 is overcoated with a glass protective layer (not shown) for protection and insulation. There is. An ink temperature detector (not shown) is provided in the ink chamber 51. Based on the detection result, an ink heater control circuit (not shown) intermittently communicates with the ink heater 56 to maintain the ink temperature near the set temperature. To do. The glass side plate 55 and the ink nozzle plate 52 are adhered to each other with an epoxy resin adhesive.

Further, the air nozzle plate 70 was formed by forming an air nozzle hole 71 by exposure and development at a position corresponding to the nozzle hole 53 of the photosensitive glass, and sputtering an aluminum common electrode 62 on the surface. The side wall 73 of the air flow passage 72 was formed by injection molding of polysulfone resin, and was bonded to the air nozzle plate 70 with an epoxy resin adhesive. Then, the air pressurized by an air pump (not shown) flows into the air nozzle hole 71 through the air flow passage 72.

A control voltage according to a multi-gradation image signal is applied between the control electrode 61 and the common electrode 62.

A hot support 80 for heating and supporting the recording medium 40 is provided at a portion facing the air nozzle plate 70.
This hot support 80 is a ceramic PTC thermistor (Positive Thermal Coeff) held by, for example, a stainless steel frame.
Abbreviation of icient. (Manufactured by TDK) was used.

Further, the hot-melt ink used in this example was prepared by adding straight-chain polyester as a main component, carbon black, a dye, and an antioxidant.
The melting point is 90 ° C. and the color tone is black.

When the ink jet recording apparatus thus prepared was operated with the following parameters, the resolution was higher than that in Example 1, and stable and good images were not affected by the material and thickness of the recording medium. Got Dot density 200 spi Head scan speed 400 mm / sec Number of integrated nozzles 24 nozzle Ink heater set temperature 140 ° C Recorded object set temperature 40 ° C Flying repetition frequency 2 KHz Control electrode applied voltage +400 V Common electrode applied voltage −500 V Air pressure 10 KPas

Analysis of the image recording operation in this embodiment shows that when a voltage is applied between the control electrode 61 and the common electrode 62, electric charge is injected from the control electrode 61 into the ink 11 and the ink meniscus 11a. The electric charge reaches the surface of the ink meniscus 11a so that the surface of the ink meniscus 11a is substantially controlled.
It becomes equipotential to 1. At this time, the electrostatic field formed is directed from the ink nozzle plate 52 toward the recording medium 40 side.
Therefore, due to the Coulomb force, the ink meniscus 11
Part of "a" is pulled out to form an ink string. The air A pressurized by an air pump (not shown) flows into the air nozzle hole 71 through the air flow passage 72. Carried by this air flow, the ink string 11b is substantially straight and the recording medium 40
Since the ink droplet flies in the direction, the variation in the ink dot position can be suppressed to be smaller than that in the first embodiment. During this time, the ink string 11 is cooled during flight, but does not reach the solidification temperature because the ink temperature in the ink chamber 51 is high.

On the other hand, the recording medium 40 is conveyed to the printing position by a conveying mechanism (not shown). Then, at the print position, the hot support 80 heats the recording medium 40 to control it at an appropriate temperature. In this state, the recording medium 40
In the case of paper, as shown in FIG. 6, the ink that has reached the recording medium 40 appropriately flows on the recording medium 40 and appropriately permeates into the fibers of the paper, so that the solidification of the ink occurs. The dots 90 are smooth, have deep roots 91, and have good fixability. On the other hand, when the hot support 80 is not provided or the set temperature of the hot support 80 is too low, the phenomenon shown in FIG. 7 occurs. That is, the ink string 11b
Is rapidly cooled by coming into contact with the recording medium 40, and immediately solidifies immediately before flowing, so that the raised dots 92 are formed on the recording medium 40. Further, when the recording medium 40 is paper, the ink solidifies immediately after the surface tension between the fibers of the paper penetrates due to the surface tension, so that the roots are not fully lowered into the paper and the dots 92 of the shallow roots 93 are formed. Poor fixability.

[Embodiment 3] FIG. 8 is an explanatory view showing the overall configuration of Embodiment 3 of the color ink jet recording apparatus to which the present invention is applied. In the figure, a four-color recording head 100 for color printing,
Specifically, a K head (for black) 111, a Y head (for yellow) 112, an M head (for magenta) 113,
A C head (for cyan) 114 is arranged in parallel to face the intermediate transfer member 115. The four-color recording head 111
Denoted at 114 are image transfer inks of the respective color components in accordance with an image signal from a host computer (not shown).
15 output. Reference numeral 116 is the intermediate transfer member 11.
The recording medium 117 on which the image-like ink on the recording medium 5 is transferred conveys the recording medium 116, and the recording medium 1 is transferred to the intermediate transfer member 115.
16 is a back surface roll for pressing, and 118 is an intermediate transfer member 11.
5 A cleaner that removes residual ink, paper dust, foreign matter, and dust on the surface.

FIG. 9 shows the structure of the recording head 100 for each color, and FIG. 10 shows the operation of the recording head 100. In this embodiment, the powder ink 120 is supplied to the ink chamber 121 in the recording head 100 by a powder ink supply device (not shown). The powder ink 120 is formed by adding straight-chain polyethylene as a main component to each color dye as a colorant, an antioxidant, a viscosity modifier, and the like.

The head heater 122 is a thick film resistor formed on a PI (polyimide) flexible substrate 123, and is energized by a head heater driving circuit (not shown) during the standby of the printer and the printing operation. The powder ink 120 is heated above its melting point to form the ink 120a. On the other hand, the PI flexible substrate 123
An orifice 124 is formed in the substrate. In this embodiment, the PI flexible substrate 123 is made of photosensitive polyimide, and the orifice 124 is formed by a photosensitive polyimide developing process. Then, the PI flexible substrate 123
A liquid-repellent layer (not shown) is formed on the surface facing the intermediate transfer member 115 to prevent the molten ink 120a from flowing out of the recording head 100 due to gravity and surface tension.

A control electrode 125 is provided on the surface opposite to the PI flexible substrate 123 (the surface inside the recording head 100), and the orifice 124 and the control electrode 125 are dots desired by the printer. A large number of recording media are lined up in the vertical direction with respect to the paper surface over the maximum recording medium width at intervals, and they operate in parallel to contribute to the improvement of the printing speed. Further, in this embodiment, one control electrode 125 is provided so as to communicate with one orifice 124,
It is processed into a shape surrounding the circular orifice 124. The control electrode 125 is formed by adhering a copper foil to the PI flexible substrate 123 with an epoxy resin adhesive and applying a photoetching process.

Further, the control electrode 125 is the pixel driving board 1
It is pressed against 26 via an anisotropic conductive film. here,
The pixel drive board 126 drives a large number of control electrodes 125 with a high voltage (+400 V in this embodiment) whose pulse width changes in accordance with a multi-gradation image signal. In this embodiment, on the glass substrate. Thin film transistor (TFT)
The technology is to form a high withstand voltage drive element array and a shift register for serial-parallel conversion of image data.

The intermediate transfer body 115 is composed of an intermediate transfer body drum base material 131 made of an aluminum tube and an intermediate transfer body drum surface layer 132. Here, the intermediate transfer body drum surface layer 132 is made by mixing carbon filler into silicon rubber to prevent charging. Since the surface tension of the molten ink 120a is 26 dyne / cm, the silicone rubber having a surface energy close to this is selected.

Furthermore, a bias pulse of -1 KV is applied to the intermediate transfer body drum base material 131, and the pixel drive board 126 causes the control electrode 125 to be + in response to the image signal.
When a pulse of 400 V is applied, the molten ink 120a
In the vicinity of the orifice 124, the Coulomb force is received to form the towing thread 120b of the ink 120a and fly toward the intermediate transfer body 115. The intermediate transfer body drum surface layer 132 is coated with the ink 1 by the intermediate transfer body heater 133.
It is maintained at a softening temperature of 20. Particularly, in this embodiment, the surface tension of the ink and the intermediate transfer drum surface layer 132
Since the surface energy of the ink is substantially equal to that of the ink,
The dots formed by b continue to expand slowly,
The image-shaped ink 120c changes to a relatively flat image.

Subtractive color mixing is performed on the intermediate transfer member 115. Since the intermediate transfer member 115 is configured to have less dimensional change due to disturbance than paper or the like, registration (registration) of each color is significantly easier and more accurate than subtractive color mixing on paper. Is high.

FIG. 11 shows the state of transfer and fixing from the intermediate transfer member 115 to the recording medium 116. In the figure, an intermediate transfer member heater 133 heats the intermediate transfer member 115 and controls the temperature so that the surface of the intermediate transfer member 115 is close to the softening temperature of the hot-melt ink 120. Then, the recording medium 116 made of plain paper is transferred to the intermediate transfer member 1 by a paper feeding device (not shown).
It is fed between 15 and the back roll 117.

Then, the image formed by the recording head 100 of each color is pressed against the recording medium 116 while being kept on the intermediate transfer member 115 while being kept near the softening temperature. In this embodiment, the intermediate transfer drum surface layer 1
The material of the surface energy of 32 is selected so as to be substantially equal to the surface tension of the molten ink 120a and sufficiently lower than the surface energy of the recording medium 116. For this reason,
Due to the difference in surface energy between the intermediate transfer body 115 and the recording medium 116, ink is transferred from the intermediate transfer body 115 to the recording medium 11.
Move to 6.

At this time, since the temperature of the ink is near the softening temperature and the pressure is applied by the back roll 117, the ink 120d is deformed and the surface of the dot is not only substantially flat, but also the recording medium 116. Is plain paper, the crushed ink 120d covers the base material of the paper. For this reason, the amount of ink peeled off due to rubbing is reduced, and the optical density of the ink portion is ensured to be sufficiently high. Further, in this embodiment, since the intermediate transfer drum surface layer 132 is made of silicon rubber and a relatively soft material, the back roll 117 is a metal roll made of an iron pipe plated with chrome. The intermediate transfer member 11
Even if the 5th side is made of a hard material and the back roll 117 side is made of a relatively soft material, substantially the same operation is achieved.

In addition, the intermediate transfer member 115 to the recording medium 11
Since the transfer rate to 6 is substantially 100%, it is not necessary to clean the transfer residual ink. However, the recording medium 116 often removes fibers, dust, etc. from the intermediate transfer member 11.
There is a possibility that it will be attached to No. 5. The gap between the recording head 100 of each color and the intermediate transfer member 115 is several tens of μm to several hundreds.
Since it is μm, it is not preferable to send the intermediate transfer body 115 with these relatively large dusts attached to the printing position. The cleaner 118 traps the large dust of several tens of μm or more.

As described above, according to the present embodiment, it was possible to form a flat heat-meltable ink image having a simple structure and excellent fixability and color developability on a transparent film sheet. Furthermore, according to the present embodiment, since the smooth surface of the intermediate transfer body drum surface layer 132 is transferred to form the smooth dot, the dot excellent in color reproducibility is formed even in the reflection image on the recording medium 116. We were able to.

As described above, according to the invention described in any one of claims 1 to 4, the ink in the molten state of the head main body is pulled by the variable electrostatic attraction force according to the multi-tone image information, Since the ink that extends toward the recording medium is made to fly while changing the threading state and solidifies and solidifies when it reaches the recording medium, an ink dot with a diameter corresponding to the multi-tone image information is recorded on the recording medium. The image can be formed with a high fixing strength, and even if plain paper is used as the recording medium, a high-quality halftone image having a good fixing property can be recorded. Further, according to the present invention, even if the nozzle is left for a long time, the nozzle is not clogged without providing a special means for preventing clogging, stable recording operation can be realized, and further, it can endure long-term storage. Pigment-dispersed ink can be used, and image recording can be realized with a relatively low driving voltage.

In particular, according to the second aspect of the invention, since the ink tow thread raised from the inside of the orifice is conveyed straight to the recording medium side by the flow of gas, the ink tow thread is transferred onto the recording medium. The flying position accuracy of the recording medium can be improved, and the resolution of the ink image on the recording medium can be further increased by that amount, and stable printing can be performed against changes in the recording medium material and thickness. You can

According to the third aspect of the invention, the recording medium made of the ink permeable material is appropriately heated, and the ink ejected from the head main body is made into flat dots having deep roots on the recording medium. Since the ink is formed, the fixing property of the ink can be made more reliable.

Further, according to the invention of claim 4, a heated intermediate transfer member is provided, on which the image-like ink is temporarily placed in a softened state, and thereafter, pressure transfer or application is performed on the recording medium. By pressure transfer fixing, a flat heat-meltable ink image is squeezed and formed on the recording medium, so the ink does not easily peel off due to rubbing, and a substantially sufficient fixing degree is achieved. In addition, since the amount of the ink portion impregnated in the recording medium is reduced, the optical density of the ink image portion can be increased,
The ink image quality on the recording medium can be kept good for a long time. Further, even if color printing is performed on the transparent film sheet, a flat ink image can be obtained, so that the coloring property on the transparent film sheet can be kept extremely excellent. Furthermore, the ink image from the recording head is temporarily placed on the intermediate transfer body, and then,
Since the pressure transfer is performed on the recording medium, the distance between the recording head and the intermediate transfer member can be made constant, so that the ink dot diameter can be made constant without being affected by the thickness of the recording medium. Therefore, it is possible to effectively prevent the deterioration of the image quality due to the variation of the ink dot diameter. In addition, if the intermediate transfer member has an accurate feed amount, and a certain environmental setting is made by the heating means so that the expansion and contraction due to the environmental change can be substantially ignored, when a color image is formed, a recording medium is formed. It is possible to easily realize registration (registration) between colors as compared with a type in which ink images of a plurality of colors are superposed on each other.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an inkjet recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of an inkjet recording apparatus according to a first embodiment.

FIG. 3 is an explanatory diagram showing an operation of the inkjet recording apparatus according to the first embodiment.

FIG. 4 is an explanatory diagram showing an operation of an inkjet recording apparatus according to a comparative example.

FIG. 5 is an explanatory diagram showing a configuration of an inkjet recording apparatus according to a second embodiment.

FIG. 6 is an explanatory diagram showing the operation of the hot support according to the second embodiment.

FIG. 7 is an explanatory diagram showing an operation when the temperature of the hot support of Example 2 is low.

FIG. 8 is an explanatory diagram showing an overall configuration of a color inkjet recording apparatus according to a third embodiment.

FIG. 9 is an explanatory diagram showing details of a recording head used in a third embodiment.

FIG. 10 is an explanatory diagram showing the operation of the recording head used in the third embodiment.

FIG. 11 is an explanatory view showing the action of the intermediate transfer member of Example 3.

[Explanation of symbols]

1 ... Thermal melting ink, 2 ... Head body, 3 ... Ink chamber,
Reference numeral 4 ... Orifice, 5 ... Ink heating means, 6 ... Electrostatic attraction variable control means, 7 ... Control electrode, 8 ... Recording medium, 9 ... Air flow conveying means, 10 ... Recording medium heating means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 9012-2C B41J 3/04 103 G

Claims (4)

[Claims] 1. An ink chamber (3) filled with a conductive heat-meltable ink (1), and an ink ejection orifice (4) communicating with the ink chamber (3) is provided for each pixel density. The head main body (2) and the heat-meltable ink (1) filled in the ink chamber (3) of the head main body (2) are melted to such an extent that at least a portion located near the orifice (4) is melted. An ink heating means (5) for heating the ink (1) and a control electrode (7) are arranged in the vicinity of each orifice (4), and each control electrode (7) changes according to multi-tone image information. A control voltage is applied to each orifice (4)
And an electrostatic attraction force variable control means (6) for exerting a variable electrostatic attraction force (S) corresponding to the multi-tone image information toward the recording medium (8) side that is arranged opposite to. An inkjet recording device characterized by the above. 2. The air flow transporting means (9) according to claim 1, wherein the ink string raised from the inside of the orifice (4) is transported straight to the recording medium (8) by the flow of the gas (A). An ink jet recording apparatus characterized by being added with. 3. The ink (1) ejected from the head body (2) when the recording medium (8) according to claim 1 or 2 is made of an ink permeable material.
An ink jet recording apparatus, wherein a recording medium heating means (10) for heating the recording medium (8) is added to the extent that the dots are formed as flat dots having deep roots on the recording medium (8). Recording device. 4. The recording medium (8) according to claim 1 or 2, wherein the recording medium (8) is an intermediate transfer medium, and the intermediate transfer medium holds and conveys the ink ejected from the head main body and applies it to the final recording medium. An ink jet recording apparatus characterized by being pressure-transferred.