JP2004066701A - Electrostatic inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a good print image quality stably even when the ambient temperature varies variously. <P>SOLUTION: In the electrostatic inkjet print head 15, ink flows from an ink supply slit 31 into a housing 30 and passes between a plurality of ejection electrodes 20 before being discharged from an ink discharge slit 32. When a potential difference is present between the ejection electrode 20 and an auxiliary electrode 21, an ink liquid drop from an ink ejecting part 20a passes through an ink ejection slit 33 thence passes between a pair of auxiliary electrodes 21 before being ejected to a sheet. A heater 35 is disposed on the surface of the housing 30 in order to control the temperature of ink in the vicinity of the ink ejecting part 20a within a specified range between the ambient temperature and the evaporation point of ink. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrostatic inkjet printer that discharges ink containing pigment particles charged by Coulomb force.
[0002]
[Prior art]
An electrostatic ink jet printer forms an image on paper by applying a coulomb force by applying a predetermined pulse voltage to ink to eject ink droplets. The ink used here has a configuration in which charged pigment or resin solid particles are mixed in a liquid medium called a carrier. In addition, a large number of ejection electrodes for applying a pulse voltage are arranged in a print head of an electrostatic ink jet printer, and ink is normally ejected by maintaining a proper meniscus between adjacent ejection electrodes. It has become so.
[0003]
[Problems to be solved by the invention]
However, in the conventional electrostatic ink jet printer, there is a problem that when the ambient temperature changes, the quality of a printed image fluctuates, and it is difficult to stably obtain good print image quality.
[0004]
Accordingly, a main object of the present invention is to provide an electrostatic inkjet printer capable of stably obtaining good print quality even when the ambient temperature changes variously.
[0005]
[Means for Solving the Problems]
The present inventor has found that the reason why stable print quality cannot be obtained when the ambient temperature changes is due to the fact that the viscosity, surface tension, and conductivity of the ink vary with temperature. Was. Specifically, the viscosity and surface tension of the ink affect the shape of the meniscus in the ink ejection section, and the viscosity and the surface tension tend to increase as the temperature decreases. If the viscosity and the surface tension increase, the shape of the meniscus becomes unstable, and it becomes difficult to properly discharge the ink. Further, since the viscosity of the ink is inversely proportional to the electrophoretic velocity, the increase in the viscosity with a decrease in temperature not only makes the shape of the meniscus unstable but also reduces the electrophoretic velocity of the ink. If the electrophoretic speed of the ink decreases, the response to the pulse voltage decreases, so that high-speed printing cannot be performed. Further, the conductivity of the ink affects the degree of concentration of the pigment particles in the ink, and tends to increase in proportion to the temperature. At low temperatures, the conductivity is low, and the concentration of the pigment particles is promoted, so that the concentration of the pigment particles in the ejected ink increases. However, when the concentration is excessive, the ink becomes difficult to eject. Conversely, at high temperatures where the conductivity increases, the concentration of the pigment particles in the ink is suppressed, so that the ink is easily ejected.However, the ejected ink has a low pigment particle concentration, so that printing with a low concentration can be performed. Will be done. That is, if the temperature is too low, the ink is not ejected smoothly due to fluctuations in the conductivity of the ink, and if the temperature is too high, an image with a high density cannot be printed.
[0006]
In view of the above problems, the electrostatic inkjet printer according to claim 1, an ink holding unit that holds an ink containing a liquid medium and charged pigment particles, a plurality of ink ejection units that communicate with the ink holding unit, A discharge head disposed in the vicinity of each of the ink discharge units, and a print head having an auxiliary electrode spaced apart from the discharge electrode, and controlling a potential at each of the discharge electrode and the auxiliary electrode by controlling a potential at the discharge electrode and the auxiliary electrode. In an electrostatic inkjet printer that discharges ink from an ink discharge unit, a temperature control device for controlling the temperature of ink in the vicinity of the ink discharge unit of the print head to be within a predetermined range is provided.
[0007]
As described above, by controlling the temperature of the ink in the vicinity of the ink ejection portion of the print head within a predetermined range by a temperature control device, the viscosity, surface tension, and conductivity of the ink are kept within appropriate ranges, and the ambient temperature is controlled. , The print quality can be stably obtained.
[0008]
It should be noted that since the temperature suitable for ink ejection varies depending on the composition of the ink and the like, the predetermined range of the temperature controlled by the temperature control device is determined for each type of ink.
[0009]
According to a second aspect of the present invention, there is provided the electrostatic ink jet printer according to the first aspect, wherein the temperature control device is provided near the ink discharge unit.
[0010]
Conventionally, when performing color printing, at least four or more colors of ink are conventionally used, and independent print heads are generally provided for each color. However, the ambient temperature of these print heads is not necessarily constant, and the temperature between print heads is not always constant. Thermal expansion may differ. If the thermal expansion differs between the print heads as described above, the dot positions of the respective colors will not be aligned, causing a color shift and deteriorating the print image quality. Therefore, by installing a temperature control device near the ink ejection portion of the print head of each color as in the configuration of claim 2, the temperature of the ink near the ink ejection portion is controlled and the viscosity, surface tension, and conductivity of the ink are controlled. Not only can the ratio be kept in an appropriate range, but also the problem of color misregistration caused by the difference in thermal expansion of the material forming the print head of each color can be eliminated. Therefore, it is possible to stably obtain good print image quality in color printing. In addition, compared to a case where the temperature control device is installed at a distance from the ink ejection unit, an effect that the temperature of the ink in the vicinity of the ink ejection unit can be easily controlled within a predetermined range can be obtained.
[0011]
According to a third aspect of the present invention, in the electrostatic inkjet printer according to the first or second aspect, the temperature control device is a heater.
[0012]
According to the above configuration, by using the heater as the temperature control device, it is possible to control the temperature while suppressing the cost.
[0013]
The electrostatic ink-jet printer according to claim 4, wherein the predetermined range of the temperature of the ink controlled by the temperature controller is equal to or higher than the ambient temperature and equal to or lower than the volatilization temperature of the ink. There is a feature.
[0014]
According to the above configuration, by setting the temperature of the ink in the vicinity of the ink ejection portion to be equal to or higher than the ambient temperature and equal to or lower than the volatilization temperature of the ink, the volatilization of the ink is suppressed to a minimum, and the volatility causes the ink density to fluctuate with time. Is reduced. In addition, by controlling the ink to a temperature as high as possible below the volatilization temperature, it is possible to suppress the volatilization of the ink, reduce the viscosity and surface tension of the ink, stabilize the shape of the meniscus, and realize good print image quality. Can be. In addition, when the temperature of the ink becomes high, the electrophoresis speed increases, and the response to the pulse voltage increases, thereby enabling high-speed printing. In addition, if the temperature is too high or too low, there is a disadvantage that the ink cannot be smoothly discharged or a high-density printing cannot be performed due to fluctuations in the conductivity of the ink. By controlling the temperature within a predetermined range equal to or lower than the permissible temperature, such inconvenience can be solved and good print quality can be obtained.
[0015]
According to a fifth aspect of the present invention, in the electrostatic ink jet printer according to any one of the first to fourth aspects, when the ink is not ejected for a predetermined time or more, the temperature of the ink is controlled to be equal to or lower than the ambient temperature by the temperature controller. It is characterized by the following.
[0016]
Ink has the property of evaporating little by little over time even at room temperature, so if the ink is left at room temperature when printing is not performed for a long time, the ink concentration is promoted due to the accelerated volatilization of the ink. It is thought that it fluctuates extremely. Therefore, when the ink is not ejected for a predetermined time or longer as in the above configuration, by controlling the temperature of the ink to be equal to or lower than the ambient temperature, the volatilization of the ink is suppressed when printing is not performed for a long time. Fluctuations in ink density can be minimized.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0018]
First, the configuration of an electrostatic inkjet printer according to an embodiment of the present invention will be described with reference to FIG. The electrostatic inkjet printer 1 according to the present embodiment includes an ink tank 10, a pump 11, an ink reservoir 12, and a print head 15. The pump 11 and the print head 15 are connected to a controller 40, and power supplies 50 and 51 are arranged between the print head 15 and the controller 40. Each part is connected so that a first circulation circuit including the ink tank 10, the pump 11, the ink reservoir 12, and the print head 15 and a second circulation circuit including the ink tank 10, the pump 11, and the ink reservoir 12 are formed. Connected by
[0019]
In the ink tank 10, the ink 2 containing the liquid medium 2b and the pigment particles 2a is stored. The pigment particles 2a in the present embodiment are charged with a positive charge, and are in a state of being mutually dispersed. The ink 2 in the ink tank 10 is circulated by the pump 11 in the first and second circulation circuits described above. In the first circulation circuit, the ink 2 in the ink tank 10 is supplied to the ink reservoir 12 by the pump 11, a part of the ink 2 supplied to the ink reservoir 12 is supplied to the print head 15, and then supplied to the print head 15. A part of the discharged ink 2 is discharged onto the paper, and the ink 2 not discharged is returned to the ink tank 10 again. In the second circulation circuit, the ink 2 in the ink tank 10 is supplied to the ink reservoir 12 by the pump 11, and the ink 2 not supplied to the print head 15 out of the ink 2 supplied to the ink reservoir 12 is returned to the ink tank 10. Is returned to.
[0020]
The ink 2 circulates in the first and second circulation circuits without being ejected from the print head 15 to the paper while the electrostatic inkjet printer 1 is turned on and printing is not performed.
[0021]
The ink reservoir 12 prevents the pulsation of the ink 2 caused by the pump 11 from being transmitted to the print head 15, and also includes a fixed filter (not shown) disposed therein to compare the pigment particles 2 a in the ink 2. It has the function of removing objects having a relatively large diameter. That is, the amount and components of the ink 2 are controlled in the ink reservoir 12, and a part of the ink 2 flowing into the ink reservoir 12 is supplied to the print head 15, and the ink 2 not supplied is returned to the ink tank 10. It has become.
[0022]
Next, the configuration of the print head 15 in the electrostatic inkjet printer 1 of the present embodiment will be described with reference to FIGS. FIG. 2 is a partial perspective view of the print head 15 in the electrostatic inkjet printer of FIG. As shown in FIG. 2, the print head 15 includes a housing 30 for holding ink, a plurality of ejection electrodes 20 arranged in parallel in the housing 30, and a pair of auxiliary electrodes spaced outside the housing 30. And an electrode 21.
[0023]
The housing 30 is a hollow member having a substantially rectangular parallelepiped shape, and has an ink supply slit 31, an ink discharge slit 32, and an ink discharge slit 33 formed therein. The ink supply slit 31 is an opening through which the ink 2 supplied from the ink tank 10 to the print head 15 via the ink reservoir 12 passes. The ink discharge slit 33 is provided at a position corresponding to a space between the pair of auxiliary electrodes 21 that are spaced apart from each other, and has an opening for discharging a part of the ink 2 flowing into the housing 30 to the paper. It is. The ink discharge slit 32 is opened on a surface facing the ink supply slit 31, and allows the ink 2 that has not flown out of the ink discharge slit 33 to flow through the ink 2 that has flowed into the housing 30. The ink 2 that has passed through the ink discharge slit 32 and has reached the outside of the housing 30 is returned to the ink tank 10 again.
[0024]
Each of the ejection electrodes 20 arranged in parallel in the housing 30 is formed of an elongated plate member having a sharp tip, and the tip is located in the direction of the ink ejection slit 33 formed in the housing 30 and the plate surface is They are arranged at predetermined intervals so as to face each other. The ink 2 flowing from the ink supply slit 31 of the housing 30 passes through the gap between the adjacent ejection electrodes 20, and a meniscus is formed between the tips of the ejection electrodes 20 arranged linearly. Then, the ink 2 is ejected from each of the tips (ink ejection section 20a) of the ejection electrode 20. The length of the ink ejection section 20a in the arrangement direction is substantially the same as the width of a sheet on which an image is formed, and an image can be formed over substantially the entire width of the sheet.
[0025]
In the present embodiment, a heater 35 is provided on each of the surfaces of the housing 30 where the ink supply slit 31 and the ink discharge slit 32 are opened (the ink discharge slit 32 is opened in the drawing). Only the surface heater 35 is shown). The temperature of the housing 30 is controlled by the heaters 35 as described later in detail, and the temperature of the ink 2 in the housing 30 is controlled to be within a predetermined range. Note that various types of heaters such as a rubber heater made of silicon or the like and a ceramic heater can be used as the heater 35.
[0026]
Next, FIG. 3 shows a schematic configuration of the print head 15 of FIG. As shown in FIG. 3, the ink 2 discharged from the ink discharge unit 20 a of each discharge electrode 20 reaches the paper 5 through a space between the pair of auxiliary electrodes 21. Here, each ejection electrode 20 is connected to the controller 40 via a power supply 50, and the pair of auxiliary electrodes 21 are connected to the controller 40 via a power supply 51. The controller 40 controls the potentials of the ejection electrodes 20 and the auxiliary electrodes 21 individually.
[0027]
Here, the operation of the print head 15 and the controller 40 in the electrostatic inkjet printer 1 of the present embodiment when an image is printed on the paper 5 will be described.
[0028]
First, a positive pulse voltage having a predetermined peak voltage value and a predetermined pulse voltage width corresponding to image data to be printed is applied to the ejection electrode 20 and the auxiliary electrode 21 of the print head 15 from the controller 40 via the power supplies 50 and 51. Is supplied. When the pulse voltage is supplied, a potential difference is generated between the ejection electrode 20 and the auxiliary electrode 21, and a Coulomb force acts on a predetermined amount of the liquid medium 2b and the ink 2 droplets including the pigment particles 2a in the housing 30. As a result, two ink droplets are ejected toward the paper 5. The pulse voltage is selectively supplied only to the ejection electrodes 20 corresponding to the width direction position of the paper 5 on which an image is to be printed, among the plurality of ejection electrodes 20 arranged linearly over substantially the entire width of the paper 5. Thus, a desired image is printed on the paper 5. Here, the density of the image formed on the sheet 5 can be adjusted by changing the peak voltage value and the pulse voltage width of the pulse voltage supplied to the ejection electrode 20 and the auxiliary electrode 21.
[0029]
The paper 5 arranged to face the print head 15 in the present embodiment is placed on a grounded transfer table 6, and the paper 5 is similarly grounded. Note that the sheet 5 and the transport table 6 do not necessarily need to be grounded, and may be charged with a negative charge.
[0030]
Next, the temperature control of the ink 2 ejected by the heaters 35 installed on the upper surface and the lower surface of the housing 30 will be described. As shown in FIG. 3, the heater 35 is connected to the controller 40 via the power supply 52, and the temperature of the heater 35 is controlled by outputting a signal for changing the current amount of the heater 35 from the controller 40. . The original purpose of the temperature control of the heater 35 by the controller 40 is to control the ink 2 in the vicinity of the ink ejection unit 20a in the housing 30 within a predetermined range. The temperature of the ink 2 suitable for ejection is determined for each type of the ink 2 in consideration of differences in viscosity, surface tension, and the relationship between conductivity and temperature, which will be described later, depending on the composition of the liquid medium 2a and the pigment particles 2a included. Shall be determined.
[0031]
Here, as described above, the higher the temperature of the ink 2, the more easily the contained pigment particles 2a move, the lower the viscosity and the surface tension, the more stable the meniscus shape, and the smoother the ejection of the ink 2, In addition, the higher the temperature, the higher the electrophoretic speed of the ink 2 becomes, the greater the response to the pulse voltage becomes, and high-speed printing becomes possible. Therefore, it is considered preferable to keep the temperature of the ink 2 as high as possible. However, as described above, when the temperature of the ink 2 is high, the electric conductivity also increases, and when the electric conductivity is too high, the concentration of the pigment particles 2a in the ink 2 is increased. Therefore, although the ink 2 can be easily ejected, the density of the pigment particles 2a of the ejected ink 2 is low, and printing with a low density is performed. Further, in consideration of the volatility of the ink 2, it is preferable to set the temperature of the ink 2 to a temperature equal to or lower than the volatilization temperature (depending on the composition of the ink 2).
[0032]
For the above reasons, the predetermined range of the temperature of the ink 2 to be controlled in the present embodiment is set to be equal to or higher than the ambient temperature and equal to or lower than the volatilization temperature of the ink 2. In addition, from the viewpoint of stabilizing the ejection of the ink 2, it is preferable that the predetermined range is not widened but set as narrow as possible, for example, about 5 degrees at a certain temperature. According to the knowledge of the inventor, it is particularly preferable that the temperature of the general ink 2 used in the electrostatic ink jet printer is controlled in a range of 55 degrees or more and 60 degrees or less.
[0033]
Next, a modification of the print head 15 of the electrostatic inkjet printer 1 shown in FIG. 2 will be described with reference to FIG. The print head 115 in FIG. 4 is different from the print head 15 in FIG.
[0034]
An ink supply nozzle 131 protrudes from one side in the width direction of the housing 130, which is a thin rectangular hollow member, and an ink discharge nozzle 132 protrudes from the opposite side. An ink ejection slit 133 is provided on one side along the longitudinal direction. From the ink ejection slits 133, sharp tips toward the outside of the housing 130 are alternately formed at predetermined intervals in the longitudinal direction.
[0035]
The ink flows from the ink supply nozzle 131 into the hollow portion inside the housing 130 in the direction of the arrow in the drawing, and a part of the ink flows from the ink discharge slit 133, more specifically, a plurality of tip portions provided in the ink discharge slit 133. (Ink ejection unit 120a). The ink not discharged from the ink discharge unit 120a is discharged from the ink discharge nozzle 132.
[0036]
The plurality of ink ejection portions 120a provided in the ink ejection slit 133 communicate with the lower surface inside the housing 130. Elongated ejection electrodes 120 are arranged in parallel along the width direction at positions corresponding to the respective ink ejection portions 120a on the lower surface in the housing 30, and each ejection electrode 120 is similar to that shown in FIG. By generating a potential difference between the auxiliary electrode 21 and the ink droplet, the Coulomb force acts on the ink droplet to discharge the ink, as in the above-described example. In this modification, the meniscus is formed in a depression between the adjacent ink ejection units 120a.
[0037]
Further, in the modification shown in FIG. 4, the heater 135 is installed on the upper surface and the lower surface of the housing 130 (only the heater 135 on the upper surface is shown in the drawing). The temperature of the body 130 is controlled, and the temperature of the ink in the vicinity of the ink ejection unit 120a is controlled.
[0038]
FIGS. 2 to 4 show examples of the print head of the electrostatic inkjet printer 1 according to the present invention. In the case of performing color printing, at least four or more colors of ink are used, and independent printing is performed for each color. Generally, heads 15 and 115 are provided.
[0039]
As described above, in the electrostatic inkjet printer 1 according to the embodiment of the present invention described above, the ejection electrodes 20, 120 arranged corresponding to the ink ejection units 20a, 120a from which ink is ejected, respectively. And print heads 15 and 115 having the discharge electrodes 20 and 120 and the auxiliary electrodes 21 spaced apart from each other. The temperature of the ink 2 in the vicinity of the ink discharge units 20 a and 120 a is controlled within a predetermined range by heaters 35 and 135. It is configured to This makes it possible to maintain the viscosity, surface tension, and conductivity of the ink 2 in appropriate ranges, and to stably obtain good print image quality even when the ambient temperature changes variously.
[0040]
Further, as described above, when performing color printing, it is general that independent print heads 15 and 115 are provided for each color. However, when the thermal expansion between the print heads 15 and 115 is different, each color is different. Since the dot positions are not aligned, color misregistration occurs, and the print quality deteriorates. Therefore, by installing the heaters 35 and 135 on the surfaces of the housings 30 and 130, that is, relatively close to the ink ejection units 20a and 120a as in the above-described embodiment, the temperature of the ink 2 near the ink ejection units 20a and 120a is increased. Not only keeps the viscosity, surface tension, and conductivity of the ink 2 within appropriate ranges, but also eliminates the problem of color misregistration caused by the difference in thermal expansion between the materials forming the print heads 15 and 115 for each color. can do. Therefore, it is possible to stably obtain good print image quality in color printing.
[0041]
In addition, compared to the case where the heaters 35 and 135 are installed in a portion other than the print heads 15 and 115, such as the reservoir 12, away from the ink ejection units 20a and 120a, the ink 2 near the ink ejection units 20a and 120a is compared. Is also easily controlled within a predetermined range.
[0042]
Further, in the above-described embodiment, the heaters 35 and 135 are used as temperature control devices, so that temperature control can be performed while suppressing costs.
[0043]
Further, by setting a predetermined range of the temperature of the ink 2 controlled by the heaters 35 and 135 to be equal to or higher than the ambient temperature and equal to or lower than the volatilization temperature of the ink 2, volatilization of the ink 2 is suppressed to a minimum. The problem of fluctuating concentrations is reduced.
[0044]
Further, by controlling the temperature of the ink 2 as high as possible below the volatilization temperature, the volatility of the ink 2 is suppressed, the viscosity and surface tension of the ink 2 are reduced, the shape of the meniscus is stabilized, and good print quality is obtained. Can be realized.
[0045]
Further, when the temperature of the ink 2 becomes high, the electrophoresis speed increases, the response to the pulse voltage increases, and high-speed printing becomes possible.
[0046]
Also, if the temperature is too high or too low, the conductivity of the ink 2 fluctuates, which causes inconveniences such as the inability to discharge smoothly and the inability to print at a high density. By controlling the temperature within a predetermined range that is equal to or higher than the ambient temperature and equal to or lower than the allowable volatilization temperature of the ink, it is possible to eliminate such inconvenience and obtain good print image quality.
[0047]
The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made within the scope of the claims. For example, the heaters 35 and 135, which are temperature control devices, need only be able to control the temperature of the ink 2 in the vicinity of the ink ejection units 20a and 120a of the print heads 15 and 115 within a predetermined range. Instead of the vicinity of the ink ejection units 20a and 120a other than the surfaces of the housings 30 and 130, and not the vicinity of the ink ejection units 20a and 120a, there are various types such as an ink tank 10, a pump 11, an ink reservoir 12, and a pipe connecting each unit. May be.
[0048]
In addition, the predetermined range in which the temperature of the ink 2 is controlled is not limited to the ambient temperature or more and the volatilization temperature of the ink 2 or less, and may be a degree that does not hinder the ejection of the ink 2.
[0049]
As a temperature control device for controlling the temperature of the ink 2 within a predetermined range, in addition to a device having only a heating function such as the heaters 35 and 135, for example, a device using a Peltier module capable of heating and cooling is used. And so on.
[0050]
When the ink 2 is not ejected for a predetermined time or more, the control may be performed so that the temperature of the ink 2 becomes equal to or lower than the ambient temperature. Here, the data of the ambient temperature required to control the temperature of the ink 2 may be set in advance in consideration of the environment in which the printer is used, or may be obtained by a sensor. The predetermined time may be appropriately determined according to the type of the printer, the type of the ink 2 to be used, the ambient temperature, the environment in which the printer is used, and the like, for example, for several tens of minutes.
[0051]
As described above, by controlling the temperature of the ink 2 to be equal to or lower than the ambient temperature when the ink 2 is not ejected for a predetermined time or more, the volatilization of the ink 2 while printing is not performed for a long time is suppressed, and the ink density is reduced. Fluctuations can be minimized. This is because the ink 2 has the property that it evaporates little by little with time even at room temperature. If the ink 2 is kept at room temperature when printing is not performed for a long time, the evaporation of the ink 2 is accelerated. This is in consideration of the possibility that the ink density may fluctuate extremely.
[0052]
In order to control the temperature of the ink 2 to be equal to or lower than the ambient temperature, when the heater 35 is used as a temperature controller as in the above-described embodiment, for example, the power supply 52 of the heater 35 is stopped by the controller 40 for a certain period of time. It is considered that the temperature of the ink 2 can be made substantially the same as the ambient temperature. On the other hand, when a device capable of heating and cooling is used as the temperature control device, the ink 2 is usually controlled within a predetermined range by a heating action, and the ink 2 is controlled by a cooling action when the ink 2 is not ejected for a predetermined time or more. It can be below ambient temperature.
[0053]
Further, the voltage signal supplied to the ejection electrode 20 and the auxiliary electrode 21 of the print head 15 need not be a pulse signal, but may have an arbitrary waveform.
[0054]
In the above-described embodiment, the pigment particles 2a included in the ink 2 are charged to a positive charge. However, the pigment particles 2a may be charged to a negative charge.
[0055]
Further, the print medium is not limited to the sheet 5, and various media such as plastic may be used.
[0056]
【The invention's effect】
According to the first aspect, it is possible to stably obtain good print image quality even when the ambient temperature changes variously.
[0057]
According to the second aspect, it is possible to solve the problem of color misregistration in color printing and to stably obtain good print image quality.
[0058]
According to the third aspect, by using the heater as the temperature control device, it is possible to control the temperature while suppressing the cost.
[0059]
According to the fourth aspect, the problem that the ink concentration fluctuates with the passage of time due to the suppression of the volatilization of the ink is reduced, and the shape of the meniscus can be stabilized to realize good print image quality. High-speed printing is possible.
[0060]
According to the fifth aspect, when printing is not performed for a long time, the volatilization of the ink can be suppressed and the fluctuation of the ink density can be minimized.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an electrostatic inkjet printer according to an embodiment of the present invention.
FIG. 2 is a partial perspective view showing a print head in the electrostatic inkjet printer of FIG.
FIG. 3 is a configuration diagram illustrating a schematic configuration of the print head of FIG. 2;
FIG. 4 is an overall perspective view showing a modified example of the print head of FIG. 2;
[Explanation of symbols]
1 electrostatic inkjet printer
2 ink
2a Pigment particles
2b Liquid medium
15,115 print head
20, 120 ejection electrode
20a, 120a Ink ejection unit
21 Auxiliary electrode
30, 130 case (ink holding unit)
35,135 heater (temperature control device)

Claims (5)

An ink holding unit that holds an ink containing a liquid medium and charged pigment particles, a plurality of ink ejection units that communicate with the ink holding unit, an ejection electrode disposed near each of the ink ejection units, An electrostatic inkjet printer that includes a print head having electrodes and auxiliary electrodes spaced apart from each other, and discharges ink from the ink discharge unit by controlling a potential at each of the discharge electrodes and the auxiliary electrodes.
An electrostatic inkjet printer comprising a temperature control device for controlling the temperature of the ink in the vicinity of the ink ejection portion of the print head within a predetermined range. 2. The electrostatic ink jet printer according to claim 1, wherein the temperature control device is installed near the ink discharge unit. 3. The electrostatic inkjet printer according to claim 1, wherein the temperature control device is a heater. The electrostatic ink jet according to any one of claims 1 to 3, wherein a predetermined range of the temperature of the ink controlled by the temperature control device is equal to or higher than an ambient temperature and equal to or lower than a volatilization temperature of the ink. Printer. 5. The electrostatic ink jet printer according to claim 1, wherein when the ink is not ejected for a predetermined time or more, the temperature of the ink is controlled to be equal to or lower than an ambient temperature. 6. .

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