JPH10109434A - Ink jet printer and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control the density of ink liquid droplets by selecting a signal corresponding to the density of dots to be printed from a plurality of preset signals and changing the ratio of ink and a solvent corresponding to the selected signal to mix the ink and the solvent. SOLUTION: When ink liquid proplets are emitted for the purpose of printing, at first, a drive signal is applied to a second heating element 26 according to density data and ink 14 is extruded to a mixing part 22 from a second orifice 27. The amt. of the extruded ink is controlled by the drive signal applied to the second heating element 26. Next, a constant drive signal is applied to a first heating element 19 and a solvent 11 begins to jet from the first orifice 20 and the ink 14 extruded to the mixing part 22 is mixed with a solvent 11. At this time, the drive signal of the second heating element 26 is turned OFF. Thereafter, by the turning-OFF of the drive signal to the first heating element 19, a constriction is generated in the solvent 11 mixed with the ink 14 to emit ink liquid droplets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet printer capable of printing halftones and a method of driving the same, and more particularly to a method of printing more tones by mixing ink and a solvent in advance. The present invention relates to an inkjet printer and a driving method thereof.

[0002]

2. Description of the Related Art An ink-jet printer is an on-demand type printer that discharges ink droplets from nozzles in accordance with a recording signal and records the recording on a recording medium such as paper or film. Therefore, it is rapidly spreading in recent years.

On the other hand, in recent years, document creation using a computer, that is, so-called desktop publishing has been actively performed especially in offices.
There is an increasing demand to output not only characters and figures but also color natural images such as photographs with characters and figures. In order to print such a high-quality natural image, it is important to reproduce halftones.

[0004] In an ink jet printer, a method using a piezoelectric element and a method using a heating element are mainly adopted as a method for discharging ink droplets. In the method using a piezoelectric element, a pressure is applied to ink by deformation of the piezoelectric element generated when a current is applied to the piezoelectric element, and the ink droplet is ejected from a nozzle by the pressure. In the method using the heating element, the ink is heated and boiled by the heating element to generate bubbles in the ink, and the ink droplets are ejected from the nozzles by the pressure generated by the generation of the bubbles.

Conventionally, in such an ink-jet printer, when printing halftones, for example, the size of a voltage applied to a piezoelectric element or a heating element or a pulse width is changed to control the size of a droplet to be ejected. The gradation of light and shade is expressed by making the diameter of the print dot variable. Alternatively, one pixel is constituted by a matrix composed of, for example, 4 × 4 dots, and the so-called dither method is used in units of the matrix to express a gray scale.

[0006]

However, when trying to express halftones by using a method of changing the magnitude and pulse width of the voltage applied to the piezoelectric element and the heating element, the magnitude and pulse width of the voltage are made too small. Then, the ink droplet is not discharged from the nozzle. For this reason, in the conventional inkjet printer, the minimum diameter of the ink droplet is limited, and the number of gradations that can be expressed is small. In particular, since there is a limit to the minimum diameter of an ink droplet, it is difficult to express a light-colored dot, and it is practically insufficient to print out a natural image or the like.

On the other hand, in the method of expressing gradation using the dither method, for example, when one pixel is constituted by a 4 × 4 matrix, 17 gradations of density can be expressed. However, when one pixel is formed of a 4 × 4 matrix using the dither method in this manner, when printing is performed at the same dot density as when the dither method is not used, the resolution is reduced to ４. For this reason, the image becomes coarse, and in this case, it is practically insufficient to print out a natural image.

In order to solve such a problem, the applicant of the present application disclosed in Japanese Patent Application Laid-Open No. Hei 5-201024 by discharging ink droplets obtained by quantitatively mixing a transparent solvent and ink. A two-liquid mixing type inkjet printer for printing was proposed.

In a two-liquid ink jet printer, one of a transparent solvent and an ink is quantified in accordance with a desired gradation and is mixed with the other liquid.
That is, for example, the ink is quantified in accordance with a desired gradation, and the thus quantified ink and the solvent are mixed. Then, printing is performed by discharging ink droplets composed of the liquids thus mixed. In such an ink jet printer, since the density of each ink droplet can be changed, each dot can be provided with a gradation of light and shade.

In such an ink jet printer of the two-liquid mixing type, it is natural that the density of ink droplets formed by mixing ink and a solvent is controlled with high accuracy in accordance with the density of dots to be printed. is important.

Accordingly, the present invention has been proposed in view of such a conventional situation, and is a two-liquid mixing system capable of accurately controlling the concentration of ink droplets formed by mixing ink and a solvent. And a method for driving the same.

[0012]

An ink jet printer according to the present invention, which has been completed to achieve the above object, selects a signal corresponding to the density of dots to be printed from a plurality of preset signals. Signal selecting means, mixing means for changing the ratio of ink and solvent in accordance with the signal selected by the signal selecting means to mix the ink and the solvent, and ink droplets made of the liquid mixed by the mixing means And discharge means for discharging the liquid.

Here, the signal is, for example, a pulse signal in which at least one of the number of pulses, the pulse width, and the pulse peak value is variable corresponding to the dot density.

The mixing means includes, for example, a pressure applying means for applying pressure to the ink or the solvent, and changes the mixing ratio between the ink and the solvent by changing the pressure by the pressure applying means in accordance with the signal. The one that changes is preferred. Here, the pressure applying unit applies a pressure to the ink or the solvent using, for example, a piezoelectric element. Alternatively, for example, pressure is applied to the ink or the solvent by heating the ink or the solvent with the heating element to generate bubbles.

It is preferable that the discharging means includes, for example, a piezoelectric element for applying pressure to the ink droplet, and discharges the ink droplet by the pressure of the piezoelectric element. Alternatively, for example, a device that includes a heating element that heats an ink droplet, heats the ink droplet with the heating element to generate a bubble, and discharges the ink droplet with a pressure generated by the bubble is also preferable. .

Further, the ink jet printer has a data processing means for performing processing based on a multi-tone dither method, and performs processing based on the multi-tone dither method on an image to be printed by the data processing means. The density of the dots to be printed may be set.

In the above-described ink jet printer, a signal corresponding to the density of the dot to be printed is selected from a plurality of preset signals by the signal selecting means, and is selected by the signal selecting means by the mixing means. The ink and the solvent are mixed by changing the ratio between the ink and the solvent according to the signal. Therefore, the ink and the solvent can be mixed by appropriately changing the ratio of the ink and the solvent according to the density of the dots to be printed.

Further, in the driving method of the ink jet printer according to the present invention, a signal corresponding to the density of the dot to be printed is selected from a plurality of preset signals, and the ink and solvent are selected according to the selected signal. The ink and the solvent are mixed by changing the ratio, and ink droplets composed of the mixed liquid are ejected and attached to a recording medium.

Here, the signal is, for example, a pulse signal in which at least one of the number of pulses, the pulse width, and the pulse peak value is variable corresponding to the dot density.

In this ink jet printer driving method, for example, the mixing ratio of the ink and the solvent is changed by changing the pressure applied to the ink or the solvent according to the signal. Here, when pressure is applied to the ink or the solvent, for example, pressure is applied to the ink or the solvent using a piezoelectric element. Alternatively, for example, pressure is applied to the ink or the solvent by heating the ink or the solvent with the heating element to generate bubbles.

In this ink jet printer driving method, when the ink droplets are ejected, for example, a pressure is applied to the ink droplets by a piezoelectric element, and the ink droplets are ejected by the pressure. . Alternatively, for example, a heating element heats ink droplets to generate bubbles,
The ink droplets are ejected by the pressure generated by the bubbles.

In the method of driving an ink jet printer, a process based on a multi-tone dither method may be performed on an image to be printed in advance to set the density of dots to be printed.

In the above-described method of driving an ink-jet printer, a signal corresponding to the density of a dot to be printed is selected from a plurality of preset signals, and the ratio between the ink and the solvent is determined according to the selected signal. By changing, the ink and the solvent are mixed. Therefore, the ink and the solvent can be mixed by appropriately changing the ratio of the ink and the solvent according to the density of the dots to be printed.

In another ink jet printer according to the present invention, a heating means heats ink or a solvent to generate bubbles, thereby applying pressure to the ink or the solvent to mix the ink and the solvent. And discharging means for discharging ink droplets composed of liquid mixed by the mixing means, and before the ink and the solvent are mixed by the mixing means, the heating element according to the density of dots to be printed. In this case, the ink or the solvent is preliminarily heated within a range in which bubbles do not occur.

Here, when the ink or the solvent is heated in advance, for example, the heat generation time of the heating element is changed according to the density of the dot to be printed, so that the heat generation amount of the heating element is changed. Alternatively, for example, the magnitude of the applied voltage applied to the heating element is changed in accordance with the density of the dot to be printed, thereby changing the amount of heat generated by the heating element.
Alternatively, for example, the number of voltage pulses applied to the heating element is changed in accordance with the density of the dot to be printed, thereby changing the amount of heat generated by the heating element. Alternatively, for example, the interval between voltage pulses applied to the heating element is changed in accordance with the density of dots to be printed, and the temperature change of the ink or the solvent heated by the heating element is controlled.

It is preferable that the discharging means includes, for example, a piezoelectric element for applying pressure to the ink droplet, and discharges the ink droplet by the pressure of the piezoelectric element. Alternatively, for example, a second heating element for heating the ink droplet is provided, and the ink droplet is heated by the second heating element to generate a bubble, and the ink droplet is ejected at a pressure generated by the bubble. Are also suitable.

Further, the ink jet printer includes a data processing means for performing processing based on a multi-tone dither method, and performs processing based on the multi-tone dither method on an image to be printed by the data processing means. The density of the dots to be printed may be set.

In the above-described ink jet printer, before the ink and the solvent are mixed by the mixing means, the ink or the solvent is preliminarily heated within a range where bubbles are not generated by the heating element according to the density of the dots to be printed. Accordingly, the ink and the solvent can be mixed by appropriately changing the ratio of the ink and the solvent according to the density of the dots to be printed.

In another driving method of an ink jet printer according to the present invention, the ink or the solvent is preliminarily heated by the heat generating element according to the density of the dot to be printed within a range in which bubbles are not generated. The ink or solvent is further heated by the heating element to generate air bubbles, pressure is applied to the ink or solvent, the ink and the solvent are mixed, and ink droplets composed of the mixed liquid are discharged. It is characterized by being attached to a recording medium.

Here, when the ink or the solvent is heated in advance, for example, the heat generation time of the heating element is changed according to the density of the dot to be printed to change the heat generation amount of the heating element. Alternatively, for example, the magnitude of the applied voltage applied to the heating element is changed in accordance with the density of the dot to be printed, thereby changing the amount of heat generated by the heating element.
Alternatively, for example, the number of voltage pulses applied to the heating element is changed in accordance with the density of the dot to be printed, thereby changing the amount of heat generated by the heating element. Alternatively, for example, the interval between voltage pulses applied to the heating element is changed in accordance with the density of dots to be printed, and the temperature change of the ink or the solvent heated by the heating element is controlled.

When the ink droplets are ejected,
For example, it is preferable that a pressure is applied to the ink droplet by a piezoelectric element, and the ink droplet is ejected by the pressure. Alternatively, for example, it is also preferable that the ink droplets are heated by the second heating element to generate bubbles, and the ink droplets are ejected at a pressure generated by the bubbles.

In the method of driving an ink jet printer, a process based on a multi-tone dither method may be performed on an image to be printed in advance to set the density of dots to be printed.

In the ink jet printer as described above, before the ink and the solvent are mixed, the ink or the solvent is preliminarily heated by the heat generating element according to the density of the dot to be printed within a range where bubbles are not generated. This makes it possible to mix the ink and the solvent by appropriately changing the ratio of the ink and the solvent according to the density of the dots to be printed.

[0034]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the following examples, and it goes without saying that the shape and the like can be arbitrarily changed without departing from the gist of the present invention.

First Embodiment An ink jet printer according to a first embodiment of the present invention is a two-liquid mixing type ink jet printer which mixes ink and a solvent and discharges the mixed ink. Is used to quantitatively mix the ink and the solvent, and the ink droplets formed by mixing the ink and the solvent are ejected using bubbles generated by driving the heating element.

FIGS. 1 and 2 show a main part of a printer head of this ink jet printer, and FIGS. 3 and 4 show enlarged views of the vicinity of a nozzle for discharging ink droplets.
Shown in

In this printer head, as shown in FIGS. 1 and 2, a head chip T1 is adhered to a base B1, and a transparent solvent 11 is supplied from a solvent reservoir 12 in the base B1 to the first of the head chip T1. While being supplied to the communication groove 13, the ink 14 is supplied from the ink reservoir 15 in the base B1 to the second communication groove 16 of the head chip T1.

In the head chip T1, the solvent 11
As shown in FIGS. 3 and 4, the first cavity 18 passes through the first communication groove 13 and further passes through the first supply groove 17.
Is filled. Here, a first heating element 19 is disposed so as to be in contact with the first cavity 18, and the solvent 11 in the first cavity 18 can be heated by the first heating element 19. I have. And solvent 1
1 is held by the capillary force in the first cavity 18, and a half-moon-shaped concave portion, a so-called meniscus M <b> 1 is formed on the surface of the first orifice 20.
The solvent 11 may have various configurations. In the present embodiment, a solvent obtained by adding a surfactant to pure water is used.

In the printer head, a mixing groove 23 is formed inside the orifice plate 21 as a passage for introducing the ink 14 into the mixing section 22.
The ink 14 is further filled from the second communication groove 16 into the mixing groove 23 through the second supply groove 24 and the second cavity 25. Here, a second heating element 26 is provided so as to be in contact with the second cavity 25, and the ink 14 in the second cavity 25 can be heated by the second heating element 26. I have. And ink 1
4 is held by capillary force and has a second orifice 2
At 7, a meniscus M2 is formed on the surface. Although various configurations can be used for the ink 14, an aqueous ink is used in the present embodiment.

In the above-mentioned printer head, the opening area of the second orifice 27 is smaller than the opening area of the first orifice 20, preferably smaller than 1/2. Thus, when the ink 14 is mixed with the solvent 11,
Can be determined more accurately.

The mixing section 2 of the orifice plate 21
The diameter of 2 is larger than the diameter of the first orifice 20. This prevents the solvent 11 from entering the mixing unit 22 during the standby time of the ejection of the ink droplets due to the capillary force, and the solvent 11 and the ink 14 come into contact during the standby time of the ejection and are naturally mixed. Disappears.

The orifice plate 21 is subjected to a water-repellent treatment by coating it with a fluorine resin or the like. That is, as shown in FIGS. 5 and 6, at least the surface C1 (hatched portion in the drawing) of the mixing section 22 of the orifice plate 21 is subjected to a water-repellent treatment, so that the meniscus M1 of the solvent 11 is stably placed in the first position. The ink can be formed in the orifice 20 and the meniscus M2 of the ink 14 can be stably formed in the second orifice 27, thereby preventing unnecessary natural mixing of the ink 11 and the solvent 14. The water-repellent treatment is performed on the orifice plate 2
1 may be applied not only to the surface C1 of the mixing section 22 but also to a slightly wider range than the mixing section 22 if it is provided so as to include the surface C1 of the mixing section 22. It may be applied to the entire surface.

In the present embodiment, the main dimensions of each member are the first heating element 19 and the second heating element 26.
Is 60 μm square, the diameter of the first orifice 20 is 30 μm, the second orifice 27 is 10 μm square, the diameter of the first cavity 18 and the second cavity 25 is 105 μm, and the depth is 35 μm. The cross section of the mixing groove 23 is 10 μm square, the diameter of the mixing section 22 is 75 μm,
The depth was 25 μm.

Next, the operation of ejecting ink droplets from the printer head as described above will be described with reference to FIG.

As shown in FIG. 7A, in the initial state, the solvent 11 is supplied to the first cavity 18 by capillary force.
And a meniscus M1 is formed at the first orifice 20 by surface tension. On the other hand, ink 14
Is filled into the mixing groove 23 through the second cavity 25 by capillary force, and forms a meniscus M2 at the second orifice 27.

When discharging ink droplets for printing, first, a drive signal according to the density data is given to the second heating element 26, and the second heating element 26 generates heat. As shown in FIG. 7B, the ink 14 undergoes film boiling, and bubbles B2 are generated on the second heating element 26. As a result, the internal pressure in the second cavity 25 increases, and the ink 14 moves from the second orifice 27 to the mixing section 2.
It is pushed out to 2. Here, the amount by which the ink 14 is pushed out is controlled by a drive signal given to the second heating element 26.

Next, a drive signal is given to the first heating element 19, and the first heating element 19 generates heat. As a result, as shown in FIG.
As shown in (C), the film of the solvent 11 is boiled and bubbles B1 are generated on the first heating element 19, so that the first cavity 1 is formed.
The internal pressure in 8 increases. As a result, the solvent 11 starts to protrude from the first orifice 20, and the ink 14 that has been pushed out by the mixing unit 22 is mixed with the solvent 11.

At this time or prior to this, the second
Is turned off, and as a result,
The bubble B2 disappears rapidly, and the internal pressure in the second cavity 25 decreases. As a result, as shown in FIG. 7C, the ink 14 is torn off near the second orifice 27 and drawn toward the second cavity 25.

Thereafter, as shown in FIG. 7D, the solvent 11 mixed with the ink 14 and projected from the first orifice 20 further grows as a liquid column. At this time, in the second cavity 25 and the mixing groove 23, the refilling of the ink 14 starts due to the capillary force.

Next, the drive signal to the first heating element 19 is turned off, and as shown in FIG. 7E, the bubble B1 starts to contract, whereby the solvent 11 is removed from the first cavity 18 The liquid column is constricted. On the other hand, the ink 14 is refilled into the mixing groove 23 by the capillary force.

Thereafter, as shown in FIG. 7 (F), the liquid column is torn off, and an ink droplet D1 in which the ink 14 and the solvent 11 are mixed is discharged, while the meniscus M1 of the solvent 11 is discharged.
Recedes into the first cavity 18. The ink droplets D1 thus ejected fly toward the recording medium and adhere to the recording medium, so that dots are printed by the ink droplets D1.

Thereafter, as shown in FIG. 7 (G), the solvent 11 is refilled into the first cavity 18 by capillary force, and returns to the initial state.

It is necessary that the ink 14 extruded as shown in FIG. 7B is all mixed with the ink droplets D 1 and ejected, and does not remain in the mixing section 22. In order to prevent the ink 14 from remaining in the mixing section 22, the mixing ratio of the ink 14 is usually preferably about 50% or less, although it depends on conditions such as the ejection frequency. Therefore, in order to obtain a sufficient maximum density, the ink 14 needs to have a sufficient density. Therefore, the mixing ratio of the ink 14 is 50
When the weight is%, the ink 14 contains a coloring agent such as a dye or a pigment to such an extent that the printing density is 1.5, preferably 2 or more as the reflection density.

In this embodiment, an aqueous ink is used as the ink 14 and a mixture of pure water and a surfactant is used as the solvent 11. For example, an oil-based ink or an oil-based solvent may be used. Can also be used.

In the above-described printer head, when driving the second heating element 26, a pulse voltage is applied to the second heating element 26 as a drive signal. Then, the ink 1 mixed with the solvent 11 by the pulse voltage
By controlling the mixing amount of No. 4, the density of the ejected ink droplet D1 is controlled. Therefore, the relationship between the voltage applied to the second heating element 26 and the mixing amount of the ink 14 mixed with the solvent 11 will be described below. In the following description, the mixing amount of the ink 14 is determined by the
1 was determined from the density when it was attached to the recording medium.

First, FIG. 8 shows the magnitude of the voltage applied to the second heating element 26 and the ink 1 mixed with the solvent 11.
4 shows the results of examining the relationship between No. 4 and the mixing amount. As shown in FIG. 8, when the voltage applied to the second heating element 26 is changed, the mixing amount of the ink 14 also changes, and as the applied voltage increases, that is, the heating value of the second heating element 26 increases. Accordingly, the mixing amount of the ink 14 also increases.

Therefore, in order to control the mixing amount of the ink 14 mixed with the solvent 11, for example, as shown in FIG. 9, the pulse peak value of the pulse voltage applied to the second heating element 26 in accordance with the density data Should be changed. That is, when printing a light dot, as shown in FIG. 9A, a pulse voltage having a small pulse peak value is applied to the second pulse voltage.
When a dark dot is printed by applying a voltage to the second heating element 26, a pulse voltage having a large pulse peak value may be applied to the second heating element 26 as shown in FIG. 9B.

FIG. 10 shows that when a constant voltage is applied to the second heating element 26, the voltage application time and the solvent 11
The result of examining the relationship with the mixing amount of the ink 14 to be mixed is shown. As shown in FIG. 10, when the voltage application time is changed, the mixing amount of the ink 14 also changes. As the voltage application time increases, that is, as the heat generation amount of the second heating element 26 increases, the mixing of the ink 14 increases. The amount also increases.

Therefore, in order to control the mixing amount of the ink 14 mixed with the solvent 11, for example, as shown in FIG. 11, the pulse width of the pulse voltage applied to the second heating element 26 is changed according to the density data. You only need to change it. That is, when printing a light dot, as shown in FIG. 11A, a pulse voltage with a narrow pulse width is applied to the second heating element 26, and when printing a dark dot, as shown in FIG.
As shown in (B), a pulse voltage having a wide pulse width is applied to the second pulse voltage.
May be applied to the heating element 26.

However, when the pulse width of the pulse voltage applied to the second heating element 26 is variable,
Of the drive signal to the second heating element 26, ie, when the pulse voltage applied to the second heating element 26 falls, and the start time of the drive signal to the first heating element 19, ie, the first time. The relative time from when the pulse voltage applied to the heating element 19 rises should be constant regardless of the density of the dots to be printed. Therefore, the second
When the pulse width of the pulse voltage applied to the second heating element 26 is made variable, it is preferable to change the time when the pulse voltage applied to the second heating element 26 rises.

When the number of voltage pulses applied to the second heating element 26 is changed when one ink droplet is ejected, the mixing of the ink 14 mixed with the solvent 11 is performed in accordance with the number of pulses. The amount also varies. in this way,
In response to one ink droplet, a plurality of voltage pulses are
When the voltage is applied to the heating element 26, the second heating element 26 generates heat every time each voltage pulse is applied, so that the ink 14 is pushed out to the mixing unit 22 for each voltage pulse.
The ink 14 pushed out to the mixing unit 22 remains in the mixing unit 22 even while the voltage pulse is in the OFF state, so that the ink 14 is accumulated in the mixing unit 22 for each voltage pulse. Therefore, by changing the number of voltage pulses applied to the second heating element 26, the amount of the ink 14 accumulated in the mixing unit 22 changes, and as a result, the mixing of the ink 14 mixed with the solvent 11 The amount changes.

Therefore, in order to control the mixing amount of the ink 14 mixed with the solvent 11, for example, as shown in FIG. 12, the number of pulses of the pulse voltage applied to the second heating element 26 is changed according to the density data. It should be done. That is, as shown in FIG. 12A, when printing light dots, the number of pulses of the pulse voltage applied to the second heating element 26 is reduced, and when printing dark dots, as shown in FIG. 12B. Thus, the number of pulses of the pulse voltage applied to the second heating element 26 may be increased.

As described above, as a method of controlling the density of the ejected ink droplet D1, a method of varying the pulse peak value of the drive signal supplied to the second heating element 26, a method of varying the pulse width, and Although the method of varying the number of pulses has been described, these methods use only one of the methods to control the density of the ink droplet D1, The density of the droplet D1 may be controlled.

The operation shown in FIG. 7 is a typical operation, and the timing and state of each operation, such as the shape of the liquid column and the operation at the time of refilling, are determined by structural elements such as the orifice size. It changes depending on physical factors such as viscosity and surface tension of the ink 14 and the solvent 11 and operating conditions such as a discharge frequency.

Then, the density of the ink droplet D1 is shown in FIG.
In (B), it is determined by the amount of the ink 14 pushed out from the second orifice 27, and this is controlled by the drive signal given to the second heating element 26 as described above. That is, the amount of the ink 14 pushed out from the second orifice 27 increases as the pulse peak value, the pulse width, and the number of pulses of the drive signal increase, and decreases as the pulse value decreases. Note that such control factors, that is, the pulse peak value, the pulse width, and the number of pulses of the drive signal are set in advance by experimentally obtaining optimum values.

Here, FIG. 13 shows a specific example of a drive signal applied to the first heating element 19 and the second heating element 26. In FIG. 13, the horizontal axis represents time and the vertical axis represents voltage, and the drive signal is shown. In addition, each time point in FIGS. 7A to 7G is plotted in correspondence with the drive signal.

In the example shown in FIG. 13, the first heating element 1
The cycle of applying the drive voltage to the reference numeral 9 is constant at 200 μsec. That is, the ejection cycle of the ink droplet D1 is
200 μsec (frequency 5 kHz), during which the operation of quantitatively mixing the ink 14 and the solvent 11 and the operation of the ink droplet D
1 is performed.

On the other hand, with respect to the drive signal applied to the second heating element 26, the timing for pushing out the ink 14, that is, the timing for turning on the drive signal applied to the second heating element 26 is made earlier or later, and The timing at which the drive signal is turned off is constant. As a result, the pulse width of the drive signal becomes variable, and the drive time of the second heating element 26 changes.

Next, a driving circuit of an ink jet printer having the above-described printer head will be described with reference to FIG.
This will be described with reference to FIG.

In this ink jet printer, prior to printing, the first heating element drive signal storage circuit 31 stores
An optimum pattern of a drive signal for driving the first heating element 19 used for discharging the ink droplet D1 is input and stored as drive signal pattern data. Here, since the drive signal of the first heating element 19 may always have the same pattern, the first heating element drive signal storage circuit 31
May be stored in a single pattern.

Similarly, prior to printing, the optimum pattern of the drive signal for driving the second heating element 26 used to push out the ink 14 is stored in the second heating element drive signal storage circuit 32. It is input and stored as signal pattern data. Here, since the drive signal of the second heating element 26 must be changed according to the density of the dot to be printed, a plurality of patterns are set so as to correspond to each gradation. That is, in this ink jet printer, the second color is adjusted so as to correspond to the density of the dot to be printed.
A plurality of patterns of driving signals are set in the heating element driving signal storage circuit 32.

Here, the number of tones that can be taken by the density data in the image signal input to the ink jet printer,
Compared with the number of gradations obtained by quantitatively mixing the solvent 11 and the ink 14, when the number of gradations that the density data can take is larger, that is, the number of density modulation steps in the dot of this inkjet printer is If the number is small, it is preferable to use a multi-tone dither method such as a multi-tone error diffusion method. This makes it possible to express all gradations in a pseudo manner. In the experiment by the present applicant, if the density modulation in the dot obtained by quantitatively mixing the solvent 11 and the ink 14 can obtain about 16 gradations, the multi-gradation dither processing corresponding thereto can be performed to achieve a sufficient image quality. Was able to print a good image.

When the multi-tone dither method is used together, it is not necessary to make the drive signal patterns correspond to all the gradations of the input density data. A plurality of drive signal patterns may be input to and stored in the second heating element drive signal storage circuit 32 to the extent that the density modulation within the dot can be stably performed.

When printing is actually performed by the above-described ink jet printer, digital halftone data including information on the density of dots to be printed and the like is supplied from another block as data of an image to be printed, and The halftone data is transmitted through the data transfer circuit 33 to the first
To the second heating element drive circuit 35 and the second heating element drive circuit 35.

Here, when it is necessary to perform multi-tone dither processing on image data to be printed, a function of multi-tone dither processing is added to the data transfer circuit 33 and the data transfer circuit 33 The multi-tone dither processing is performed on the input digital halftone data to set the density of dots to be printed. Note that the multi-tone dither processing may be executed at a stage before the multi-tone dither processing, instead of being executed by the data transfer circuit 33, and the result of the multi-tone dither processing may be input to the data transfer circuit 33. Even with this, the same effect can be obtained.

Then, at the timing for discharging the ink droplet D1, a discharge trigger is output from another block, and
The discharge trigger is detected by the timing control circuit 36. Timing control circuit 3 that detects discharge trigger
6 sends the second heating element enable signal to the second heating element drive circuit 35 and sends the first heating element enable signal to the first heating element drive circuit 34 at a predetermined timing.

Next, the second heating element drive circuit 35
Measures the timing to drive the second heating element 26 based on the second heating element enable signal sent from the timing control circuit 36, and when the timing to drive the second heating element 26 comes, A drive signal having a pattern corresponding to the digital halftone data sent from the data transfer circuit 33 is selected and read from the second heating element drive signal storage circuit 32. That is, the second heating element drive circuit 35 functions as a signal selection unit that selects a drive signal corresponding to the density of the dot to be printed from a plurality of preset signals.

Then, the second readout of the optimum drive signal
The heating element drive circuit 35 supplies the drive signal to the second heating element 26. As a result, the second heating element 26 generates heat, and a predetermined amount of the ink 14 is supplied from the second orifice 27 to the mixing section 22 of the orifice plate 21. The timing at which a drive signal is supplied from the second heating element drive circuit 35 to the second heating element 26 is as follows.
This is as shown in FIG.

Here, the second heating element drive circuit 35
However, when the optimum drive signal is read from the second heating element drive signal storage circuit 32, for example, the selection signal corresponding to the digital halftone data is transmitted from the second heating element drive circuit 35 to the second heating element. Element drive signal storage circuit 3
2 and the second heating element drive signal storage circuit 32
Selects a drive signal of an optimal pattern according to the selection signal, and transfers the drive signal to the second heating element drive circuit 3.
5 is output. Alternatively, for example, a plurality of patterns of drive signals stored in the second heating element drive signal storage circuit 32 are supplied from the second heating element drive signal storage circuit 32 to the second heating element drive circuit 35. , The second heating element drive circuit 35 selects a drive signal having an optimal pattern from the drive signals according to the digital halftone data.

On the other hand, the first heating element drive circuit 34
Measures the timing to drive the first heating element 19 based on the first heating element enable signal sent from the timing control circuit 36, and when the timing to drive the first heating element 19 comes, A drive signal for driving the first heating element 19 is read from the first heating element drive signal storage circuit 31, and the drive signal is supplied to the first heating element 19. As a result, a predetermined amount of the ink 14 previously supplied from the second orifice 27 to the mixing section 22 of the orifice plate 21 and the solvent 11 are mixed and discharged. The timing at which a drive signal is supplied from the first heating element drive circuit 34 to the first heating element 19 is as shown in FIG.

At this time, if the digital halftone data sent from the data transfer circuit 33 is equal to or smaller than a predetermined threshold value, the first heating element 19 and the second heating element 26
May not be supplied with the drive signal. That is,
For example, when the digital halftone data is equal to or less than a predetermined threshold value and the dot to be printed is white or a very pale color close to white, the ink droplet D1 may not be ejected at all. Thereby, the consumption of the solvent 11 can be reduced. However, the ink droplet D1 may always be ejected when the digital halftone data has any value. At this time, when the dots to be printed are white, only the solvent 11 is ejected without mixing the ink 14 with the solvent 11.

In the present embodiment, the first
The drive signal pattern data is input to and stored in the heating element drive signal storage circuit 31 and the second heating element drive signal storage circuit 32, but the drive signal pattern data may be printed in various forms such as environmental conditions. A new input and storage may be performed each time printing is performed in accordance with the conditions. That is, for example, every time each page is printed, a pattern optimal for various printing conditions such as an environmental condition at that time may be input and stored.

However, when it is not necessary to change the drive signal pattern, an optimum drive signal pattern is selected at the time of shipment from the factory, and the first heat-generating element drive signal storage circuit 31 and the second heat-generating element drive signal are stored. Stored in the signal storage circuit 32,
After that, the drive signal pattern may not be changed. When the drive signal pattern can be determined in advance when developing an ink jet printer, the drive signal pattern is stored in a read-only memory (ROM) or the like in advance and cannot be changed at the time of factory shipment or after shipment. You may do so.

Next, an example of the configuration of a multi-nozzle printer head in which a plurality of the above-described printer heads are used to form a multi-nozzle will be described.

This multi-nozzle printer head is shown in FIG.
As shown in FIG. 5 and FIG. 16, 16 printer heads as described above are arranged in line in parallel to form a printer head group, and two sets of the printer head groups are arranged on the left and right. That is, the multi-nozzle printer head includes a total of 32 printer heads as described above. The basic structure of each printer head is the same as the printer head shown in FIGS.

The pitch of each printer head is 170 μm as shown in FIG. 15, and each printer head of the right group of printer heads and each printer head of the left group of printer heads are half pitch from each other. Minutes, ie 85
They are shifted by μm. Thus, it is possible to record 32 dots with a width of about 2.7 mm at a rate of about 12 dots / mm (300 dpi) in one scan. In each of the left and right printer head groups, the first communication groove 13 provided in the head chip and the second communication groove 13 are provided.
The multi-nozzle printer head in which the communication groove 16 is a long hole, and the first supply groove 17 and the second supply groove 24 are respectively connected to the communication groove 16 in FIG. It operates in the same way as the printer head shown. In other words, this multi-nozzle printer head is shown in FIGS.
The driving signal is controlled as shown in FIG. 13 and operates according to the timing chart as shown in FIG. 13 to discharge the ink droplet D1 as shown in FIG.

Next, a drive circuit of an ink jet printer having the above-described multi-nozzle printer head will be described with reference to FIG.

In this ink jet printer, prior to printing, the first heating element drive signal storage circuit 41 stores
An optimum pattern of a drive signal for driving the first heating element 19 used for discharging the ink droplet D1 is input and stored as drive signal pattern data. Here, since the driving signal of the first heating element 19 may always have the same pattern, the driving signal storage circuit 41 for the first heating element may be used.
May be stored in a single pattern.

Similarly, prior to printing, the optimum pattern of the drive signal for driving the second heating element 26 used to push out the ink is stored in the second heating element drive signal storage circuit 42. It is input and stored as pattern data. Here, since the drive signal of the second heating element 26 must be changed according to the density of the dot to be printed, a plurality of patterns are set so as to correspond to each gradation. That is, in this ink jet printer, a plurality of pattern drive signals are set in the second heating element drive signal storage circuit 42 so as to correspond to the density of dots to be printed.

When printing is actually performed by this ink jet printer, digital halftone data including information on the density of dots to be printed and the like is supplied from another block as data of an image to be printed, and The halftone data is sent to the plurality of second heating element drive circuits 44 and the plurality of first heating element drive circuits 45 via the serial / parallel conversion circuit 43.

When the timing for discharging the ink droplet D1 comes, a discharge trigger is output from another block, and
The ejection trigger is detected by the timing control circuit 46. Timing control circuit 4 that detects discharge trigger
6 sends a second heating element enable signal to each second heating element drive circuit 44 and sends a first heating element enable signal to each first heating element drive circuit 45 at a predetermined timing. I do.

Next, each second heating element drive circuit 44
Measures the timing to drive the second heating element 26 driven by the second heating element drive circuit 44 based on the second heating element enable signal sent from the timing control circuit 46, and 2 heating elements 26
When the timing for driving is obtained, the drive signal of the pattern corresponding to the digital halftone data sent from the serial / parallel conversion circuit 43 is read out from the second heating element drive signal storage circuit 42, and the drive signal is read out. It is supplied to the second heating element 26. Thereby, the second heating element 2
6 generates heat, and a predetermined amount of the ink 14 is supplied from the second orifice 27 to the mixing section 22 of the orifice plate 21.

On the other hand, each first heating element drive circuit 45
Measures the timing to drive the first heating element 19 driven by the first heating element drive circuit 45 based on the first heating element enable signal sent from the timing control circuit 46, and 1 heating element 19
When it is time to drive the first heating element 1
9 is read out from the first heating element drive signal storage circuit 41, and the drive signal
Is supplied to the heating element 19. As a result, the first heating element 19 generates heat, and as a result, the second orifice 27
A predetermined amount of the ink 14 supplied to the mixing section 22 of the orifice plate 21 from the liquid and the solvent 11 are mixed and discharged.

Here, when the first heating element 19 and the second heating element 26 of each printer head are all driven at the same timing, the first heating element drive signal storage circuit 41 and the second heating element Only one element drive signal storage circuit 42 is required. At this time, the second heating element drive signal storage circuit 42 outputs an appropriate drive signal to each of the second heating element drive circuits 44 from the stored plurality of patterns of drive signals.

The printer head described in the above example is called a side shooter type because of the mounting form of the first heating element 19 and the second heating element 26.
The present invention relates to the first heating element 19 and the second heating element 26.
Can also be applied to those having an edge shooter type.

FIG. 18 shows a main part of an example of the configuration of an edge shooter type printer head, and FIG. 19 is an enlarged view of the vicinity of a nozzle for discharging ink droplets D1.

FIG. 18A is a view of an edge shooter type printer head viewed from the side.
FIG. 18B is a view of the edge shooter type printer head viewed from the direction of arrow B in FIG.
FIG. 18C is a view of the edge shooter type printer head viewed from the direction of arrow C in FIG. FIG.
9A is an enlarged view of the nozzle portion of the edge shooter type printer head of FIG. 18 viewed from the printing surface side, and FIG. 19B is a view taken along line BB of FIG. 19A. It is sectional drawing and FIG.19 (C) is sectional drawing in CC line | wire of FIG.19 (A).

In the edge shooter-type printer head, it is preferable that the orifice plate 21 is subjected to a water-repellent treatment, similarly to the side shooter-type printer head described above.

FIG. 20 shows an example of a multi-printer head in which a plurality of such edge shooter type printer heads are used to form a multi-nozzle. Here, FIG.
20A is a diagram of the multi-printer head viewed from the printing surface side, FIG. 20B is a diagram of the multi-printer head viewed from the side, and FIG.
FIG. 20D is a cross-sectional view taken along line CC of FIG.
20A is a cross-sectional view taken along line DD in FIG. 20A, and FIG. 20E is a cross-sectional view taken along line EE in FIG. Although FIG. 20 shows an example in which eight printer heads are used and the number of nozzles is eight, the number of nozzles is not limited to this.

FIG. 21 shows a multi-nozzle printer head that uses two multi-nozzle printer heads shown in FIG. 20 and is shifted from each other by a half pitch. This multi-nozzle printer head has two nozzles compared to the multi-nozzle printer head shown in FIG.
Since the resolution is doubled, the resolution is almost doubled.

Here, in the multi-nozzle printer head shown in FIG. 20, the pitch between orifices of each printer head is 170 μm. This corresponds to a resolution of about 6 dots / mm (150 dpi). on the other hand,
In the multi-nozzle printer head shown in FIG.
The resolution is twice that of the multi-nozzle printer head shown in FIG. 0, that is, about 12 dots / mm (300 dpi).

In the above description, the second heating element 2
The pressure is applied to the ink 14 by heating the ink 14 in step 6 to generate air bubbles, and the pressure is changed in accordance with the drive signal.
Has been changed. However, the means for applying pressure to the ink 14 is not limited to this, and for example, an electromechanical conversion element such as a piezoelectric element may be used. That is, for example, the mixing ratio of the ink 14 and the solvent 11 may be changed by applying a pressure to the ink 14 by a piezoelectric element and changing the pressure according to the drive signal.

In the above description, the first heating element 1
By heating the solvent 11 at 9 to generate bubbles,
Pressure is applied to the ink droplet D1 in which the ink 14 and the solvent 11 are mixed, and the ink droplet D1 is ejected by this pressure. However, the means for applying pressure to the ink droplet D1 is not limited to this.
An electromechanical transducer such as a piezoelectric element may be used. That is, for example, a pressure may be applied to the ink droplet D1 by a piezoelectric element, and the ink droplet D1 may be ejected by this pressure.

In the ink jet printer using the above-described printer head, the gradation of light and shade can be changed for each dot, and the density modulation can be performed very well from low density to high density. Therefore, very high-quality continuous tone recording can be performed. In conventional ink jet printers, density modulation is mainly performed by modulating the droplet size.However, in the modulation of the droplet size, there is a limit to reducing the size of the droplet, and especially the expressive power of the low density portion is reduced. It was very unsatisfactory. On the other hand, according to the present embodiment, since the concentration of the droplet itself can be freely changed, even if the droplet size is kept constant, very high quality including the high concentration part to the low concentration part is obtained. It is possible to perform various gradation recording. Further, in performing the gradation expression, there is no need to rely entirely on a pseudo area gradation method such as a so-called two-tone dither method, so that gradation recording can be performed without deteriorating the resolution.

Next, the overall configuration of an ink jet printer having the above-described printer head will be described.

FIGS. 22 to 24 show examples of the structure of an ink jet printer equipped with the above-described printer head. FIG. 22 is a configuration example of a drum rotation type ink jet printer. In this drum rotary type ink jet printer, a printing paper 222 as a printing object is wound around the outer circumference of a drum 223 and fixed at a predetermined position. A feed screw 224 is provided on the outer periphery of the drum 223 in the drum axis direction, and a printer head 221 is screwed to the feed screw 224. Then, the rotation of the feed screw 224 causes the printer head 221 to move in the axial direction.
The drum 223 includes a pulley 225, a belt 226,
It is rotationally driven by a motor 228 via a pulley 227. Further, the rotation of the feed screw 224 and the motor 228 and the driving of the printer head 221 are controlled by the drive control unit 22.
9, the drive is controlled based on the print data and the control signal 230.

In such a configuration, when the drum 223 rotates, the printer head 221 is synchronized with the rotation.
, An ink droplet is ejected from the ink to form an image on the print paper 222. The drum 223 makes one rotation and the print paper 2
When printing of one line in the circumferential direction on the print head 22 is completed, the feed screw 224 is rotated to move the printer head 221 by one line, and print the next line. In this case, there is a method in which the drum 223 and the feed screw 224 are simultaneously rotated to gradually move the printer head 221 while printing. In the case of a multi-nozzle printer head or a configuration in which the same location is printed several times, step feed is suitable.
Printing is performed in a spiral manner while simultaneously rotating the feed screw 224 in conjunction with the feed screw 23.

FIG. 23 shows a configuration example of a serial type ink jet printer. In this case, the structure is almost the same as that of the drum rotating type shown in FIG.
The drum 22 is not wound around the drum 223 and is provided with a paper pressure roller 231 provided in parallel with the axial direction.
3 is held by crimping. In this case, when the printer head 221 moves and prints one scan, the drum 2
23 is rotated by one scan, and printing for the next scan is performed. The movement of the printer head 221 may be in the same direction or in the reciprocating direction.

FIG. 24 shows a configuration example of a line type ink jet printer. In this case, instead of the printer head 221 and the feed screw 224 of the serial type inkjet printer shown in FIG.
A line head 232 in which 1 is arranged in a line is fixedly provided in the axial direction. In this configuration, printing for one line is performed simultaneously by the line head 232, and when printing is completed, the drum 223 is rotated by one line to perform printing for the next line. In this case, all lines can be printed at once, divided into a plurality of blocks, or alternately printed every other line.

FIG. 25 shows a configuration example of a printing and control system of an ink jet printer. Signal 251 such as print data
Are input to the signal processing control circuit 252, are arranged in the printing order in the signal processing control circuit 252, and are sent to the printer head 254 via the drive circuit 253. The printing order differs depending on the configuration of the printer head and the printing unit, and also has a relationship with the input order of the printing data. If necessary, a memory 25 such as a line buffer memory or one screen memory may be used.
Record once in 5 and remove. Printer head 254
Outputs a gradation signal and a discharge signal.

When the number of nozzles in a multi-printer head is very large, an IC is mounted on the printer head 254 to reduce the number of wires connected to the printer head 254. A correction circuit 256 is connected to the signal processing control circuit 252, and performs γ correction, color correction in the case of color, and variation correction of each printer head. The correction circuit 256 stores predetermined correction data in a ROM.
The information is stored in a map format, and is taken out according to external conditions, for example, a nozzle number, a temperature, an input signal, or the like.

The signal processing control circuit 252 includes, for example, a CP
Processing is performed by software as a U or DSP configuration. Then, the processed signal is sent to various control units 257.
In the various control units 257, the drum 223 and the feed screw 22
4 to control the driving and synchronization of the motor for driving the rotation of the printer 4, cleaning of the printer head, supply and discharge of the print paper 222, and the like. Note that the signal 251 includes an operation unit signal and an external control signal other than print data.

Second Embodiment Next, a description will be given of a second embodiment of the ink jet printer to which the present invention is applied.

The ink jet printer according to the present embodiment is a two-liquid mixing type ink jet printer that mixes ink and a solvent and then discharges the ink. The ink jet printer uses ink bubbles generated by driving a heating element. And the solvent are quantitatively mixed, and ink droplets formed by mixing the ink and the solvent are ejected using bubbles generated by driving the heating element.

FIGS. 26 and 27 show the main part of the printer head of this ink jet printer, and FIGS. 28 and 29 show enlarged views of the vicinity of the nozzle for discharging ink droplets.

This printer head is shown in FIGS. 26 and 27.
As shown in the figure, the head chip T2 is adhered to the base B2, and the transparent solvent 51 is placed in a solvent reservoir 52 in the base B2.
Is supplied to the first communication groove 53 of the head chip T2, and the ink 54 is supplied from the ink reservoir 55 in the base B2 to the second communication groove 56 of the head chip T2.

In the head chip T2, the solvent 51
Is further filled from the first communication groove 53 through the first supply groove 57 into the first cavity 58 as shown in FIGS. 28 and 29. Here, a first heating element 59 is provided so as to be in contact with the first cavity 58, and the solvent 51 in the first cavity 58 can be heated by the first heating element 59. I have. Then, the solvent 51 is held in the first cavity 58 by capillary force, and in the first orifice 60, a half-moon-shaped concave portion, a so-called meniscus M3, is formed on the surface. The solvent 51 may have various configurations. In the present embodiment, a solvent obtained by adding a surfactant to pure water is used.

In the printer head, a mixing groove 63 is formed inside the orifice plate 61 as a passage for introducing the ink 54 into the mixing section 62.
The ink 54 is further filled from the second communication groove 56 into the mixing groove 63 through the second supply groove 64 and the second cavity 65. Here, a second heating element 66 is provided so as to be in contact with the second cavity 65, and the ink 54 in the second cavity 65 can be heated by the second heating element 66. I have. And ink 5
4 is held by capillary force and has a second orifice 6
At 7, a meniscus M4 is formed on the surface. Although various configurations can be used for the ink 54, a water-based ink is used in the present embodiment.

In the above-mentioned printer head, the opening area of the second orifice 67 is smaller than the opening area of the first orifice 60, preferably smaller than 1/2. Thus, when the ink 54 is mixed with the solvent 51,
Can be determined more accurately.

The mixing section 6 of the orifice plate 61
The diameter of 2 is larger than the diameter of the first orifice 60. Accordingly, the solvent 51 does not enter the mixing unit 62 during the standby time of the ejection of the ink droplet due to the capillary force, and the solvent 51 and the ink 54 come into contact with each other during the standby time of the ejection, and they are naturally mixed. Disappears.

The orifice plate 61 is subjected to a water-repellent treatment by coating it with a fluorine resin or the like. That is, as shown in FIGS. 30 and 31, at least the surface C2 of the mixing portion 62 of the orifice plate 61 is provided.
By applying a water-repellent treatment to (shaded area in the figure), the solvent 51
Can be stably formed at the first orifice 60, and the meniscus M4 of the ink 54 can be stably formed at the second orifice 67. Unwanted natural mixing is prevented. If the water-repellent treatment is performed so as to include the surface C2 of the mixing section 62 of the orifice plate 61, not only the surface C2 of the mixing section 62 but also the mixing section 62.
It may be applied to a slightly wider range than that, or may be applied to the entire surface of the orifice plate 61.

In the present embodiment, the main dimensions of each member are the first heating element 59 and the second heating element 66.
Is 60 μm square, the diameter of the first orifice 60 is 30 μm, the second orifice 67 is 10 μm square, the diameter of the first cavity 58 and the second cavity 65 is 105 μm, and the depth is 35 μm. The cross section of the mixing groove 63 is 10 μm square, the diameter of the mixing section 62 is 75 μm,
The depth was 25 μm.

Next, the operation of discharging the ink droplets from the printer head as described above will be described with reference to FIG.

As shown in FIG. 32A, in the initial state, the solvent 51 is supplied to the first cavity 5 by capillary force.
8 and form a meniscus M3 at the first orifice 60 by surface tension. On the other hand, ink 5
4 is filled into the mixing groove 63 through the second cavity 65 by capillary force, and forms a meniscus M4 at the second orifice 67.

When ejecting ink droplets for printing, first, a drive signal in accordance with the density data is given to the second heating element 66, the second heating element 66 generates heat, and the ink 54 is discharged. Is warmed. At this time, the second heating element 66 controls the ink 5 so that air bubbles are not generated in the ink 54.
Heat 4 Thereafter, a drive signal is further supplied to the second heating element 66, and the second heating element 66 generates heat. As a result, as shown in FIG. A bubble B4 is generated on the heating element 66. Thereby, the internal pressure in the second cavity 65 increases, and the ink 54 is pushed out from the second orifice 67 to the mixing section 62.

Next, a drive signal is supplied to the first heating element 59, and the first heating element 59 generates heat. As a result, as shown in FIG.
As shown in FIG. 2 (C), the film boiling of the solvent 51 causes bubbles B3 to be generated on the first heating element 59, and the internal pressure in the first cavity 58 increases. Thereby, the solvent 51 becomes the first
The ink 54 that has begun to protrude from the orifice 60 and has been pushed out to the mixing section 62 is mixed with the solvent 51.

At this time or prior to this, the second
Is turned off, and as a result,
The bubble B4 disappears rapidly, and the internal pressure in the second cavity 65 decreases. As a result, as shown in FIG. 32C, the ink 54 is torn off near the second orifice 67 and is drawn toward the second cavity 65.

Thereafter, as shown in FIG. 32D, the solvent 51 mixed with the ink 54 and projected from the first orifice 60 further grows as a liquid column. At this time, the second
In the cavity 65 and the mixing groove 63, the refilling of the ink 54 starts due to the capillary force.

Next, the drive signal to the first heating element 59 is turned off, and as shown in FIG. 32 (E), the bubble B3 starts to contract, whereby the solvent 51 is removed from the first cavity 58. The liquid column is constricted. On the other hand, the ink 54 is refilled into the mixing groove 63 by the capillary force.

Thereafter, as shown in FIG. 32 (F), the liquid column is torn off, and an ink droplet D2 in which the ink 54 and the solvent 51 are mixed is ejected, while the meniscus M3 of the solvent 51 is discharged.
Recedes into the first cavity 58. Then, the ink droplets D2 thus ejected fly toward the recording medium and adhere to the recording medium, so that dots are printed by the ink droplets D2.

Thereafter, as shown in FIG. 32 (G), the solvent 51 is refilled into the first cavity 58 by the capillary force, and returns to the initial state.

By the way, all the extruded ink 54 as shown in FIG. 32 (B) must be mixed with the ink droplet D2 and discharged, so that it does not remain in the mixing section 62. In order to prevent the ink 54 from remaining in the mixing section 51, the mixing ratio of the ink 54 is usually preferably about 50% or less, depending on conditions such as the ejection frequency. Therefore, in order to obtain a sufficient maximum density, the ink 54 needs to have a sufficient density. Therefore, the mixing ratio of the ink 54 is 5
When the weight is 0% by weight, the ink 54 contains a coloring agent such as a dye or a pigment to such an extent that a printing density of 1.5, preferably 2 or more is obtained as a reflection density.

In the present embodiment, an aqueous ink is used as the ink 54, and a mixture of pure water and a surfactant is used as the solvent 51. For example, an oil-based ink or an oil-based solvent may be used. Can also be used.

In the above-described printer head, when driving the second heating element 66, a pulse voltage is applied to the second heating element 66 as a drive signal. Then, the second heating element 66 generates heat by the pulse voltage, whereby the ink 54 is heated to generate a bubble B4,
The ink 54 is pushed out to the mixing unit 62 by the pressure generated by the generation of the bubble B4. And
The ink 54 thus extruded into the mixing section 62 is mixed with the solvent 51 and discharged as an ink droplet D2.

In the printer head, the solvent 5
1, the amount of the ink 54, ie, the mixing unit 62
By controlling the amount of ink 54 extruded to
The density of the ink droplet D2 is controlled. Therefore, a method of controlling the amount of the ink 54 pushed out to the mixing unit 62 will be described below. In the following description, the solvent 51
The mixing amount of the ink 54 with respect to was determined from the density when the ejected ink droplet D2 was attached to the recording medium.

First, FIG. 33 shows that the magnitude of the electric power applied to the second heating element 66 and the temperature of the solvent 51 are determined by using the temperature of the ink 54 immediately before the bubble B4 is generated in the ink 54 and pushed out to the mixing section 62 as a parameter. The result of examining the relationship with the mixing amount of the ink 54 to be mixed is shown. As shown in FIG. 33, when the temperature of the ink 54 is changed, the mixing amount of the ink 54 also changes, and the mixing amount of the ink 54 increases as the temperature increases. Therefore, in order to control the amount of the ink 54 mixed with the solvent 51, it is only necessary to control the temperature of the ink 54 immediately before the bubble 54 is generated in the ink 54 and pushed out to the mixing unit 62.

The control of the temperature of the ink 54 is performed, for example, by applying a drive signal for generating a bubble B4 in the ink 54 to the second heating element 66 before applying the driving signal to the second heating element 66. This can be realized by applying a drive signal (hereinafter, referred to as a pre-pulse) to the extent that no bubbles are generated in the ink 54.

FIGS. 34 to 37 show specific examples of the method of applying the pre-pulse. The pre-pulse applied as follows only increases the temperature of the ink 54 existing near the second heating element 66, and does not vaporize the ink 54. Then, in a heated state, a drive signal for generating a bubble B4 is applied to the second heating element 66. As a result, the amount of the ink 54 according to the density data of the dot to be printed is supplied to the second orifice 6.
7 to the mixing section 62.

FIG. 34 shows a method of applying a low-voltage pulse as a pre-pulse before the drive signal for generating the bubble B4 with a pulse width corresponding to the density data of the dot to be printed. In this method, when printing a dark dot, as shown in FIG. 34A, the pulse width of the pre-pulse is increased, and when printing a light dot,
As shown in FIG. 34B, the pulse width of the pre-pulse is reduced. In this method, the end time of the prepulse,
Difference Ta from start time of drive signal for generating bubble B4
Is fixed so as to be always uniform, and the pulse width is changed by changing the start time of the pre-pulse. Here, Ta = 0 may be set.

FIG. 35 shows a method in which a pulse voltage having a short pulse width is applied as a pre-pulse a predetermined time before the drive signal for generating the bubble B4 with a voltage having a magnitude according to the density data of the dot to be printed. Is shown. In this method, when printing a dark dot, the pre-pulse voltage is increased as shown in FIG. 35 (A), and when printing a light dot, the pre-pulse voltage is reduced as shown in FIG. 35 (B). I do.

FIG. 36 shows a method of applying, as a pre-pulse, a pulse voltage having a short pulse width in a number corresponding to the density data of the dot to be printed, before the drive signal for generating the bubble B4. In this method, when printing a deep dot, the number of pre-pulse pulses is increased as shown in FIG. 36A, and when printing a light dot, the number of pre-pulse pulses is increased as shown in FIG. 36B. Less.

FIG. 37 shows that, as a pre-pulse, a pulse having a short pulse width is applied before the drive signal for generating the bubble B4, and after the end of the pre-pulse, the bubble B4
The method of changing the time until the start of the drive signal for generating the dot according to the density data of the dot to be printed is shown. In this method, the longer the time from the end of the pre-pulse to the start of the drive signal, the longer the second heating element 6
The temperature of the ink 54 near 6 will decrease. Therefore, when printing a dark dot, as shown in FIG. 37A, the time Tb from the end of the pre-pulse to the start of the drive signal is shortened, and when printing a light dot,
As shown in FIG. 37B, the time Tc from the end of the pre-pulse to the start of the drive signal is increased.

As described above, as a method of controlling the density of the ejected ink droplet D2, a method of varying the pulse width of the pre-pulse, a method of varying the magnitude of the voltage of the pre-pulse,
The method of varying the number of pre-pulses and the method of varying the interval between the pre-pulse and the drive signal have been described. In these methods, the density of the ink droplet D2 is controlled using only one of the methods. Alternatively, some methods may be combined to control the density of the ink droplet D2.

The operation shown in FIG. 32 is a typical operation. The timing and state of each operation, such as the shape of the liquid column and the operation at the time of refilling, are determined by structural elements such as the orifice size. It changes depending on physical factors such as viscosity and surface tension of the ink 54 and the solvent 51, and operating conditions such as the ejection frequency.

The density of the ink droplet D2 is shown in FIG.
In (B), it is determined by the amount of ink 54 pushed out from the second orifice 67, which is controlled by the pre-pulse applied to the second heating element 66 as described above. That is, the amount of the ink 54 pushed out from the second orifice 67 is determined by the pre-pulse.
4 increases when heated to a high temperature, and decreases when not heated too high. It should be noted that optimum values are experimentally obtained and set in advance for such control factors, that is, how to apply a pre-pulse.

Here, FIG. 38 shows a specific example of a drive signal applied to the first heating element 59 and the second heating element 66. In FIG. 38, the horizontal axis represents time, the vertical axis represents voltage, and the driving signal is shown.
Are plotted in correspondence with the drive signals.

In the case of the example shown in FIG. 38, the first heating element 5
The cycle of applying the drive voltage to the reference numeral 9 is constant at 200 μsec. That is, the ejection cycle of the ink droplet D2 is
200 μsec (frequency 5 kHz), during which the operation of quantitatively mixing the ink 54 and the solvent 51 and the ink droplet D
2 is performed.

On the other hand, as for the drive signal applied to the second heating element 66, after applying a pre-pulse which is variable according to the density, a drive signal for pushing out the ink 54 is applied. Here, the drive signal for pushing out the ink 54 is a constant signal in accordance with the ejection cycle of the ink droplet D2. The width is variable. This changes the prepulse application time,
The amount of heat generated by the second heating element 66 due to the pre-pulse changes.

Next, an operation when printing is performed by an ink jet printer having the above-described printer head will be described with reference to FIG. 39 showing an example of a drive circuit of such an ink jet printer.

When printing is performed by this ink jet printer, digital halftone data including information on the density of dots to be printed and the like is supplied from another block as data of an image to be printed, Data is sent to the first heating element drive circuit 72 and the second heating element drive circuit 73 via the data transfer circuit 71.

Here, when it is necessary to perform multi-tone dither processing on the image data to be printed, a function of multi-tone dither processing is added to the data transfer circuit 71 and the data transfer circuit 71 The multi-tone dither processing is performed on the input digital halftone data to set the density of dots to be printed. Note that the multi-tone dither processing may be executed at a stage before the multi-tone dither processing instead of being executed by the data transfer circuit 71, and the result of executing the multi-tone dither processing may be input to the data transfer circuit 71. Even with this, the same effect can be obtained.

When the timing for discharging the ink droplet D2 comes, a discharge trigger is output from another block, and
The discharge trigger is detected by the timing control circuit 74. Timing control circuit 7 that detects discharge trigger
4 sends the second heating element enable signal to the second heating element drive circuit 73 and sends the first heating element enable signal to the first heating element drive circuit 72 at a predetermined timing.

Next, the second heating element drive circuit 73
Measures the timing to drive the second heating element 66 based on the second heating element enable signal sent from the timing control circuit 74, and when the timing to drive the second heating element 66 comes, The pre-pulse corresponding to the digital halftone data sent from the data transfer circuit 71 is supplied to the second heating element 66. As a result, the second heating element 66 generates heat, and the ink 54 is heated. After that, the second heating element drive circuit 73 supplies a drive signal to the second heating element 66. As a result, the second heating element 66 further generates heat, and a bubble B4 is generated in the ink 54,
A predetermined amount of ink 54 corresponding to the digital halftone data is supplied from the second orifice 67 to the mixing section 62 of the orifice plate 61 by the pressure of the bubble B4. The second heating element drive circuit 73 outputs the second
The timing at which the drive signal is supplied to the heating element 66 is as shown in FIG.

On the other hand, the first heating element drive circuit 72
Measures the timing for driving the first heating element 59 based on the first heating element enable signal sent from the timing control circuit 74, and when the timing for driving the first heating element 59 has come, A drive signal for driving the first heating element 59 is supplied to the first heating element 59. As a result, the first heating element 59 generates heat, and the solvent 5
1, a bubble B3 is generated, and pressure is generated by the bubble B3. As a result, a predetermined amount of the ink 54 previously supplied from the second orifice 67 to the mixing section 62 of the orifice plate 61 and the solvent 51 are mixed and discharged. In addition,
From the first heating element drive circuit 72 to the first heating element 5
The timing at which the drive signal is supplied to 9 is as shown in FIG.

At this time, when the digital halftone data sent from the data transfer circuit 71 is equal to or less than a predetermined threshold, the first heating element 59 and the second heating element 66
May not be supplied with the drive signal. That is,
For example, when the digital halftone data is equal to or less than a predetermined threshold value and the dot to be printed is white or a very pale color close to white, the ink droplets may not be ejected at all. Thereby, the consumption of the solvent 51 can be reduced. However, the ink droplet D2 may always be ejected regardless of the value of the digital halftone data. At this time, when the dots to be printed are white, the solvent 5 is mixed with the solvent 51 without mixing the ink 54.
Only 1 is ejected.

The density number of the density data in the image signal input to the ink jet printer is compared with that obtained by quantitatively mixing the solvent 51 and the ink 54. When the number of possible gradations is larger, that is, when the number of density modulation steps in the dot of this inkjet printer is smaller than the density data, a multi-tone dither method such as a multi-tone error diffusion method is used together. Is preferred. This makes it possible to express all gradations in a pseudo manner. In our experiments,
If the density modulation in the dot obtained by quantitatively mixing the ink 54 and the solvent 51 can take about 16 gradations,
By performing the corresponding multi-tone dither processing, it was possible to print a sufficiently high-quality image.

Next, an example of the configuration of a multi-nozzle printer head in which a plurality of the above-described printer heads are used to form a multi-nozzle will be described.

This multi-nozzle printer head is shown in FIG.
As shown in FIG. 0 and FIG. 41, 16 printer heads as described above are arranged in line in parallel to form a printer head group, and two printer head groups are arranged on the left and right. That is, the multi-nozzle printer head includes a total of 32 printer heads as described above. The basic structure of each printer head is shown in FIG.
29 is similar to the printer head shown in FIG.

The pitch of each printer head is 170 μm as shown in FIG. 40, and each printer head of the right set of printer heads and each printer head of the left set of print heads are half pitch apart from each other. Minutes, ie 85
They are shifted by μm. Thus, it is possible to record 32 dots with a width of about 2.7 mm at a rate of about 12 dots / mm (300 dpi) in one scan. In each of the left and right printer head groups, the first communication groove 53 provided in the head chip and the second communication groove 53
The communication grooves 56 are elongated holes, and 16 first supply grooves 57 and 16 second supply grooves 64 are connected to them.

This multi-nozzle printer head is shown in FIG.
The operation is similar to that of the printer head shown in FIGS. That is, the multi-nozzle printer head is controlled by the pre-pulse as shown in FIGS. 34 to 37, operates according to the timing chart shown in FIG. 38, and operates as shown in FIG. Is discharged.

When printing is actually performed with the above-described multi-nozzle printer head, first, as shown in FIG.
As data of an image to be printed, digital halftone data including information on the density of dots to be printed and the like is supplied from another block, and the digital halftone data is supplied to a plurality of Are sent to the second heating element drive circuit 82 and the plurality of first heating element drive circuits 83, respectively.

Then, at the timing for discharging the ink droplet D2, a discharge trigger is output from another block, and
The discharge trigger is detected by the timing control circuit 84. Timing control circuit 8 that detects discharge trigger
4 sends a second heating element enable signal to each second heating element drive circuit 82 and sends a first heating element enable signal to each first heating element drive circuit 83 at a predetermined timing. I do.

Next, each second heating element drive circuit 82
Measures the timing to drive the second heating element 66 driven by the second heating element drive circuit 82 based on the second heating element enable signal sent from the timing control circuit 84, and 2 heating elements 66
When it is time to drive the second heating element 66, a pre-pulse of a pattern corresponding to the digital halftone data sent from the serial / parallel conversion circuit 81 and a drive signal are supplied. As a result, the second heating element 66 generates heat, and a predetermined amount of the ink 54 is supplied from the second orifice 67 to the mixing section 62 of the orifice plate 61.

On the other hand, each first heating element drive circuit 83
Measures the timing to drive the first heating element 59 driven by the first heating element drive circuit 83 based on the first heating element enable signal sent from the timing control circuit 84, and 1 heating element 59
When it is time to drive the first heating element 5
9 is supplied to the first heating element 59. As a result, the first heating element 59 generates heat, and as a result, a predetermined amount of the ink 54 previously supplied from the second orifice 67 to the mixing section 62 of the orifice plate 61.
And the solvent 51 are mixed and discharged.

The printer head described in the above example is of a so-called side shooter type because of the mounting form of the first heating element 59 and the second heating element 66.
The present invention provides a first heating element 59 and a second heating element 66.
Can also be applied to those having an edge shooter type.

FIG. 43 shows a main part of an example of the configuration of an edge shooter type printer head, and FIG. 44 is an enlarged view of the vicinity of a nozzle for discharging ink droplets D2.

FIG. 43 (A) is a side view of an edge shooter type printer head, and FIG.
FIG. 43B is a diagram of the edge shooter type printer head viewed from the direction of arrow B in FIG. 43A.
FIG. 43C is a diagram of the edge shooter type printer head viewed from the direction of arrow C in FIG. 43A. FIG.
4 (A) is an enlarged view of the nozzle portion of the edge shooter type printer head of FIG. 43 viewed from the printing surface side, and FIG. 44 (B) is a view taken along the line BB of FIG. 44 (A). FIG. 44C is a cross-sectional view taken along line CC of FIG. 44A.

In this edge shooter-type printer head, it is preferable that the orifice plate 61 be subjected to a water-repellent treatment, similarly to the side shooter-type printer head described above.

FIG. 45 shows an example of a multi-printer head in which a plurality of such edge shooter-type printer heads are used to form a multi-nozzle. Here, FIG.
(A) is a diagram of the multi-printer head viewed from the printing surface side, (B) of FIG. 45 is a diagram of the multi-printer head viewed from the side, and (C) of FIG.
FIG. 45 (A) is a sectional view taken along line CC, and FIG.
FIG. 45A is a cross-sectional view taken along a line DD in FIG. 45A, and FIG. 45E is a cross-sectional view taken along a line EE in FIG. 45A. Although FIG. 45 shows an example in which eight printer heads are used and the number of nozzles is eight, the number of nozzles is not limited to this.

FIG. 46 shows a multi-nozzle printer head using two multi-nozzle printer heads shown in FIG. 45 and displaced from each other by a half pitch. This multi-nozzle printer head has two nozzles compared to the multi-nozzle printer head shown in FIG.
Since the resolution is doubled, the resolution is almost doubled.

Here, in the multi-nozzle printer head shown in FIG. 45, the pitch between orifices of each printer head is 170 μm. This corresponds to a resolution of about 6 dots / mm (150 dpi). on the other hand,
In the multi-nozzle printer head shown in FIG.
The resolution is twice that of the multi-nozzle printer head shown in FIG. 5, that is, about 12 dots / mm (300 dpi).

In the above description, the first heating element 5
By heating the solvent 51 at 9 to generate bubbles,
A pressure is applied to the ink droplet D2 in which the ink 54 and the solvent 51 are mixed, and the ink droplet D2 is ejected by this pressure. However, the means for applying pressure to the ink droplet D2 is not limited to this.
An electromechanical transducer such as a piezoelectric element may be used. That is, for example, a pressure may be applied to the ink droplet D2 by a piezoelectric element, and the ink droplet D2 may be ejected by this pressure.

In the ink jet printer using the above-described printer head, the gradation of light and shade can be changed for each dot, and the density can be modulated very well from low to high. Therefore, very high-quality continuous tone recording can be performed. In conventional ink jet printers, density modulation is mainly performed by modulating the droplet size.However, in the modulation of the droplet size, there is a limit to reducing the size of the droplet, and especially the expressive power of the low density portion is reduced. It was very unsatisfactory. On the other hand, according to the present embodiment, since the concentration of the droplet itself can be freely changed, even if the droplet size is kept constant, very high quality including the high concentration part to the low concentration part is obtained. It is possible to perform various gradation recording. Further, in performing the gradation expression, there is no need to rely entirely on a pseudo area gradation method such as a so-called two-tone dither method, so that gradation recording can be performed without deteriorating the resolution.

The overall structure of the ink jet printer according to this embodiment is the same as that described in the first embodiment with reference to FIGS. Therefore, the description of the overall configuration of the inkjet printer will be omitted.

By the way, in the first and second embodiments, multi-tone printing is performed by modulating the ink density of the ink droplet, but the size of the ink droplet is modulated. You may use it combining methods. This can be realized by changing the pulse width, the number of pulses, the pulse peak value, etc. of the drive signal applied to the first heating element in the ink jet printer heads according to the first and second embodiments. Alternatively, as in the second embodiment, the pre-pulse is applied to the first heating element as in the case of applying the pre-pulse to the second heating element, and the pulse width, the number of pulses, the pulse peak value, and the like are changed. Can also be realized. As described above, by combining the method of modulating the ink concentration of the ink droplet and the method of modulating the size of the ink droplet, gradation recording with a wider dynamic range can be performed.

More specifically, for example, as shown in FIG. 47A, only the droplet size is sequentially reduced with the ink droplet concentration being maximized from the higher ink concentration, and the droplet size is further increased. If the density cannot be lowered, the density of the ink droplets is sequentially lowered from here. Or, FIG.
As shown in (B), the size of the ink droplets is reduced from the one with the highest ink concentration to the maximum, and only the ink concentration is reduced. So as to lower it. Alternatively, as shown in FIG. 47 (C), the size of the ink droplet and the ink density are reduced in parallel from the one with the higher ink density.

In the first and second embodiments, the case where the ink is quantitatively mixed with the solvent has been described. However, the ink and the solvent can be used interchangeably. That is, even if the solvent is quantitatively mixed with the ink to modulate the concentration of the ink droplet, the same effect as the above-described example can be realized. In this case, the configuration and operation of the ink jet printer are the same as in the above-described example.

However, when the amount of the solvent is determined and mixed with the ink, the mixing ratio of the solvent to the ink is usually set such that all the determined solvent is mixed with the ink and ejected as ink droplets. It is preferable that the maximum is about 50%. For this reason, when the solvent is quantitatively mixed with the ink, there is a limit to the expression of the light-colored dots, that is, the expression of the highlight portion. Conversely, however, the expression of a dark dot, that is, the expression of a shadow portion, is very advantageous because it is not necessary to previously darken the ink so that a sufficient density can be obtained in the shadow portion.

[0179]

As is apparent from the above description, according to the present invention, the density of the dot to be printed is adjusted so as to correspond to the density of the dot to be printed.
The ink and the solvent can be accurately determined and mixed, and the concentration of the ink droplet formed by mixing the ink and the solvent can be accurately controlled. Thus, according to the present invention,
It is possible to accurately perform density modulation over many gradations, and it is possible to print beautifully even an image including a halftone.

[Brief description of the drawings]

FIG. 1 is a front view of a printer head of an ink jet printer according to a first embodiment as viewed from a printing surface side.

FIG. 2 is a sectional view taken along line A1-A1 in FIG.

FIG. 3 is an enlarged front view showing a nozzle portion of the printer head of FIG. 1;

FIG. 4 is a sectional view taken along line A2-A2 in FIG.

FIG. 5 is a front view for explaining a water-repellent treatment of an orifice plate of the printer head of FIG. 1;

6 is a sectional view taken along line A3-A3 in FIG.

FIG. 7 is a sectional view schematically showing the operation of the printer head of FIG.

FIG. 8 is a diagram illustrating a relationship between a magnitude of a voltage applied to a second heating element and a mixing amount of ink.

FIG. 9 is a diagram illustrating a state in which a mixing amount of ink and a solvent is controlled by a magnitude of a pulse voltage to a second heating element.

FIG. 10 is a diagram illustrating a relationship between a voltage application time to a second heating element and an ink mixing amount.

FIG. 11 is a diagram showing a state in which the mixing amount of ink and a solvent is controlled by the pulse width of a pulse voltage applied to a second heating element.

FIG. 12 is a diagram illustrating a state in which a mixing amount of ink and a solvent is controlled by the number of pulses of a pulse voltage to a second heating element.

FIG. 13 is a time chart showing an example of a drive signal supplied to a first heating element and a second heating element in the first embodiment.

FIG. 14 is a block diagram illustrating a driving circuit of the printer head of FIG. 1;

FIG. 15 is a front view of the multi-nozzle printer head according to the first embodiment as viewed from a printing surface side.

16 is a sectional view taken along line A4-A4 in FIG.

FIG. 17 is a block diagram showing a drive circuit of the multi-nozzle printer head of FIG.

FIG. 18 is a diagram illustrating a configuration example of an edge shooter type printer head.

FIG. 19 is an enlarged view showing a nozzle portion of the edge shooter type printer head of FIG. 18;

FIG. 20 is a front view of a configuration example of an edge shooter type printer head having a multi-nozzle as viewed from a printing surface side.

21 is a front view showing a configuration example of a multi-nozzle printer head in which the nozzle pitch is narrowed by using two multi-nozzle printer heads of FIG. 20;

FIG. 22 is a diagram illustrating a configuration example of a drum rotation type ink jet printer.

FIG. 23 is a diagram illustrating a configuration example of a serial type inkjet printer.

FIG. 24 is a diagram illustrating a configuration example of a line-type inkjet printer.

FIG. 25 is a block diagram illustrating a configuration example of a signal processing and control system of the inkjet printer.

FIG. 26 is a front view of a printer head of an inkjet printer according to a second embodiment as viewed from a printing surface side.

FIG. 27 is a sectional view taken along line A5-A5 in FIG. 26;

FIG. 28 is an enlarged front view showing a nozzle portion of the printer head of FIG. 26;

29 is a sectional view taken along line A6-A6 of FIG.

FIG. 30 is a front view for describing a water-repellent treatment of an orifice plate of the printer head of FIG. 26;

FIG. 31 is a sectional view taken along line A7-A7 of FIG. 30;

FIG. 32 is a sectional view schematically showing the operation of the printer head of FIG. 26;

FIG. 33 is a diagram illustrating a relationship between electric power applied to a second heating element and a mixing amount of ink, using ink temperature as a parameter.

FIG. 34 is a diagram illustrating a state in which the mixing amount of ink and a solvent is controlled by the pulse width of a pre-pulse to a second heating element.

FIG. 35 is a diagram illustrating a state in which the mixing amount of ink and a solvent is controlled by the voltage level of a pre-pulse to a second heating element.

FIG. 36 is a diagram illustrating a state in which the mixing amount of ink and a solvent is controlled by the number of pre-pulses to the second heating element.

FIG. 37 is a diagram illustrating a state in which the mixing amount of ink and a solvent is controlled by the interval between a pre-pulse to a second heating element and a drive signal.

FIG. 38 is a time chart showing an example of a drive signal supplied to the first heating element and the second heating element in the second embodiment.

FIG. 39 is a block diagram showing a driving circuit of the printer head of FIG. 26;

FIG. 40 is a front view of the multi-nozzle printer head according to the second embodiment as viewed from the printing surface side.

FIG. 41 is a sectional view taken along line A8-A8 in FIG. 40;

FIG. 42 is a block diagram showing a driving circuit of the multi-nozzle printer head of FIG. 40;

FIG. 43 is a diagram illustrating a configuration example of an edge shooter type printer head.

44 is an enlarged view showing a nozzle portion of the edge shooter type printer head of FIG. 43.

FIG. 45 is a front view of a configuration example of an edge shooter type printer head having a multi-nozzle as viewed from a printing surface side.

FIG. 46 is a front view showing an example of the configuration of a multi-nozzle printer head in which the nozzle pitch is narrowed using two multi-nozzle printer heads of FIG. 45;

FIG. 47 schematically shows dots printed when a method of modulating the ink density of ink droplets and a method of modulating the size of ink droplets are combined using an inkjet printer to which the present invention is applied. FIG.

[Explanation of symbols]

11 solvent, 12 solvent reservoir, 13 first communication groove,
14 ink, 15 ink reservoir, 16 second communication groove, 17 first supply groove, 18 first cavity, 19 first heating element, 20 first orifice, 21 orifice plate, 22 mixing section,
23 mixing groove, 24 second supply groove, 25 second cavity, 26 second heating element, 27 second orifice, 31 first heating element drive signal storage circuit, 32 second heating element drive Signal storage circuit, 3
3 data transfer circuit, 34 first heating element drive circuit, 35 second heating element drive circuit, 36
Timing control circuit

Claims (32)

[Claims] 1. A signal selecting means for selecting a signal corresponding to the density of a dot to be printed from a plurality of preset signals, and the ratio of ink and solvent is determined according to the signal selected by the signal selecting means. An ink jet printer comprising: a mixing unit that changes the mixture of the ink and the solvent; and an ejection unit that ejects ink droplets made of the liquid mixed by the mixing unit. 2. The signal according to the density of a dot,
2. The ink jet printer according to claim 1, wherein at least one of the pulse number, the pulse width, and the pulse peak value is a variable pulse signal. 3. The mixing means includes pressure applying means for applying pressure to the ink or the solvent, and changes the mixing ratio between the ink and the solvent by changing the pressure by the pressure applying means in accordance with the signal. The ink jet printer according to claim 1, wherein: 4. An ink jet printer according to claim 3, wherein said pressure applying means applies pressure to the ink or the solvent by a piezoelectric element. 5. The method according to claim 3, wherein the pressure applying means applies pressure to the ink or the solvent by heating the ink or the solvent with the heating element to generate bubbles.
The ink-jet printer as described. 6. An ink jet printer according to claim 1, wherein said discharging means includes a piezoelectric element for applying pressure to the ink droplet, and discharges the ink droplet by the pressure of the piezoelectric element. 7. The discharging means includes a heating element for heating the ink droplet, wherein the heating element heats the ink droplet to generate a bubble, and discharges the ink droplet at a pressure generated by the bubble. The inkjet printer according to claim 1, wherein: 8. A data processing means for performing processing based on a multi-tone dither method, wherein the data processing means performs processing based on the multi-tone dither method on an image to be printed, and 2. The ink jet printer according to claim 1, wherein the density is set. 9. A signal corresponding to the density of dots to be printed is selected from a plurality of preset signals, and the ink and the solvent are mixed by changing the ratio of the ink and the solvent according to the selected signal. A method for driving an ink jet printer, comprising: ejecting ink droplets composed of the above-mentioned mixed liquid and attaching them to a recording medium. 10. The signal according to claim 9, wherein the signal is a pulse signal in which at least one of a pulse number, a pulse width, and a pulse peak value is variable in accordance with a dot density. Driving method of inkjet printer. 11. The method according to claim 9, wherein the mixing ratio of the ink and the solvent is changed by changing the pressure applied to the ink or the solvent according to the signal. 12. When applying pressure to the ink or the solvent,
The method according to claim 11, wherein a pressure is applied to the ink or the solvent using a piezoelectric element. 13. When applying pressure to the ink or the solvent,
The method according to claim 11, wherein pressure is applied to the ink or the solvent by generating bubbles by heating the ink or the solvent with the heating element. 14. The method according to claim 9, wherein a pressure is applied to the ink droplet by a piezoelectric element when the ink droplet is ejected, and the ink droplet is ejected by the pressure. . 15. The method according to claim 9, wherein, when discharging the ink droplet, the heating element heats the ink droplet to generate a bubble, and the ink droplet is discharged at a pressure generated by the bubble. Driving method of an ink jet printer. 16. The method according to claim 9, wherein a process based on a multi-tone dither method is performed on an image to be printed in advance to set the density of dots to be printed. 17. A mixing unit for mixing the ink and the solvent by applying pressure to the ink or the solvent by heating the ink or the solvent with the heating element to generate bubbles, and a liquid mixed by the mixing unit. Discharging means for discharging ink droplets comprising, before mixing the ink and the solvent by the mixing means, depending on the density of the dots to be printed, a range in which ink or solvent is not generated by the heating element according to the density of dots to be printed. An ink jet printer characterized by heating in advance. 18. When the ink or the solvent is pre-heated,
18. The ink jet printer according to claim 17, wherein a heat generation time of the heating element is changed according to a density of a dot to be printed to change a heat generation amount of the heating element. 19. When preheating the ink or the solvent,
18. The ink-jet printer according to claim 17, wherein a magnitude of an applied voltage applied to the heating element is changed according to a density of a dot to be printed to change a heating value of the heating element. 20. When heating the ink or the solvent in advance,
18. The ink jet printer according to claim 17, wherein the number of voltage pulses applied to the heating element is changed according to the density of dots to be printed to change the amount of heat generated by the heating element. 21. When heating the ink or the solvent in advance,
18. The method according to claim 17, wherein an interval of a voltage pulse applied to the heating element is changed according to a density of a dot to be printed to control a temperature change of the ink or the solvent heated by the heating element. Inkjet printer. 22. The ink jet printer according to claim 17, wherein said discharging means includes a piezoelectric element for applying a pressure to the ink droplet, and discharges the ink droplet by the pressure of the piezoelectric element. 23. The discharge means includes a second heating element for heating the ink droplet, and the second heating element heats the ink droplet to generate a bubble, and the ink is generated by a pressure generated by the bubble. 18. The ink jet printer according to claim 17, wherein the ink jet printer discharges droplets. 24. Data processing means for performing processing based on a multi-tone dither method, wherein the data processing means performs processing based on the multi-tone dither method on an image to be printed, and 18. The ink jet printer according to claim 17, wherein a density is set. 25. In accordance with the density of dots to be printed, the ink or the solvent is preliminarily heated by the heating element within a range where bubbles are not generated, and the heated ink or the solvent is further heated by the heating element to generate bubbles. By applying pressure to the ink or the solvent to mix the ink and the solvent, and ejecting the ink droplets composed of the mixed liquid to adhere to the recording medium. Drive method. 26. When heating the ink or the solvent in advance,
26. The driving method of an ink jet printer according to claim 25, wherein a heat generation time of the heating element is changed by changing a heat generation time of the heating element according to a density of a dot to be printed. 27. When heating the ink or the solvent in advance,
26. The method according to claim 25, wherein the amount of heat generated by the heating element is changed by changing the magnitude of an applied voltage applied to the heating element according to the density of dots to be printed. . 28. When heating the ink or the solvent in advance,
26. The driving method of an ink jet printer according to claim 25, wherein the number of voltage pulses applied to the heating element is changed according to the density of dots to be printed to change the amount of heat generated by the heating element. 29. When heating the ink or the solvent in advance,
26. The method according to claim 25, further comprising: changing an interval of a voltage pulse applied to the heating element in accordance with a density of a dot to be printed to control a temperature change of the ink or the solvent heated by the heating element. Driving method of an ink jet printer. 30. The method according to claim 25, wherein when ejecting the ink droplet, a pressure is applied to the ink droplet by a piezoelectric element, and the ink droplet is ejected by the pressure. . 31. The method according to claim 31, wherein, when discharging the ink droplet, the second heating element heats the ink droplet to generate a bubble, and discharges the ink droplet with a pressure generated by the bubble. Item 30. The method for driving an ink jet printer according to item 25. 32. The method according to claim 25, wherein a process based on a multi-tone dither method is performed on an image to be printed in advance to set the density of dots to be printed.