JP2962294B2 - Driving method of inkjet printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an ink jet printer which discharges a solvent by mixing a certain amount of ink with a solvent.

[0002]

2. Description of the Related Art As a conventional two-liquid mixing type ink jet print head capable of halftone recording, an on-demand type thermal ink jet head that mixes two liquids on the upper surface of a heating element and two liquids are mixed in a discharge unit. A continuous type charge control inkjet head and the like are known.

[0003]

However, in the conventional ink jet print heads described above, the function of preventing the two liquids from mixing when unnecessary is not perfect, and the two liquids are always in contact in the mixing section. . For this reason, it is difficult to prepare a mixed liquid having an accurate mixing ratio at the start of the operation, and the mixed liquid mixed in the mixing section up to that time has to be discharged once as a dummy. In addition, since the two liquids were always in contact, the respective liquids were liable to cause long-term chemical and physical reactions, and the characteristics of the two liquids were liable to change. As a result, there is a problem that the density control tends to be unstable during printing, and the printing quality is degraded.

[0004] The present invention has been made in view of such circumstances, and it is possible to reliably contact ink ejected from an ink ejection hole with a solvent ejected from the solvent ejection hole outside each of the ejection holes. It is another object of the present invention to provide a method of driving an ink jet printer capable of obtaining a good density gradation in a dot unit by mixing two liquids.

[0005]

According to the present invention, an ink ejection hole for ejecting ink and a solvent ejection hole for ejecting a solvent are arranged close to each other, and the ink ejected from the ink ejection hole and the solvent ejection hole are arranged. The method for driving an ink jet printer in which the solvent ejected from the ink comes in contact with the outside of each of the ejection holes, and the ink and the solvent are ejected, for ejecting the solvent after the completion of voltage application for pushing out the ink. The voltage application is terminated.

Further, according to the present invention, an ink ejection hole for ejecting ink and a solvent ejection hole for ejecting a solvent are arranged close to each other, and ink ejected from the ink ejection hole and ink ejected from the solvent ejection hole are arranged. In the method of driving an ink jet printer in which the solvent is ejected after the solvent comes into contact with the end surface of each of the ejection holes, the voltage application for ejecting the solvent is completed after the voltage application for pushing out the ink is completed. It is characterized by doing.

In the method of driving an ink jet printer according to the present invention, for example, voltage application for discharging a solvent is started after voltage application for pushing out ink is completed.

In the method for driving an ink jet printer according to the present invention, for example, the time from the end of the voltage application for pushing out the ink to the start of the voltage application for discharging the solvent is independent of the amount of ink pushed out. It is constant.

In the method of driving an ink jet printer according to the present invention, for example, after the voltage application for discharging the solvent is completed, the voltage application for pushing out the next ink starts.

In the method of driving an ink jet printer according to the present invention, for example, the time from when the voltage application for ejecting the solvent is completed to when the voltage application for extruding the next ink is started is reduced. It changes according to the quantity.

Further, in the method for driving an ink jet printer according to the present invention, for example, the time required for applying the voltage for ejecting the solvent and the time for starting the application of the voltage for pushing out the next ink may be reduced by the time when the solvent is applied. Is refilled.

Further, in the method for driving an ink jet printer according to the present invention, for example, the time from when the voltage application for ejecting the solvent is completed to when the voltage application for pushing out the next ink is started is reduced. Longer than the time required for refilling.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The present invention is applied to, for example, an ink jet printer having a configuration as shown in FIGS.

FIG. 14 shows an example of the configuration of a drum rotary type ink jet printer. A printing paper 52 as a printing medium is wound around the outer periphery of a drum 53 and fixed at a predetermined position. A feed screw 54 is provided on the outer periphery of the drum 53 in parallel with the drum axis direction, and the head 51 is screwed to the feed screw 54. The rotation of the feed screw 54 causes the head 51 to move in the axial direction. The drum 53 includes a pulley 55, a belt 56,
It is rotationally driven by a motor 58 via a pulley 57.
Further, the rotation of the feed screw 54 and the motor 58 and the head 5
The drive 1 is controlled by the drive control unit 59 based on the print data and the control signal 60.

In the above configuration, when the drum 53 rotates, ink is ejected from the head 51 in synchronization with the rotation, and an image is formed on the printing paper 52. Drum 5
After one rotation of 3 causes printing of one line in the circumferential direction on the printing paper 52 to be completed, the feed screw 54 rotates to move the head 51 by one line and print the next line. In this case, there is a method of simultaneously rotating the drum 53 and the feed screw 54 and gradually moving the head 51 while printing. In the case of a multi-nozzle head or a configuration in which the same location is printed several times, step feed is suitable. However, when the number of single nozzles or multi-nozzles is small, the drum 53 and the feed screw 5 are used.
4 is simultaneously performed and rotated simultaneously to perform spiral printing.

FIG. 15 shows a configuration example of a serial type ink jet printer. In this case as well, the configuration is substantially the same as that of the drum rotating type shown in FIG. 14, but the printing paper 52 is not wound around the drum 53, and is rotated by a paper pressure roller 61 provided in parallel in the axial direction. 53 is held by pressure bonding. In this case, the head 51 moves to 1
When a line is printed, the drum 53 is rotated by one line and the next line is printed. The head 51 moves in the same direction or in the reciprocating direction.

FIG. 16 shows a configuration example of a line type ink jet printer. In this case, instead of the serial type head 51 and the feed screw 54 shown in FIG. 15, a line head 6 in which many heads 51 are arranged in a line.
2 are provided fixed in the axial direction. In this configuration,
Printing of one line is simultaneously performed by the line head 62,
When the printing is completed, the drum 53 is rotated by one line to perform printing on 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. 17 is a block diagram showing the configuration of a printing and control system. Signals 71 such as print data are
The signal processing / control circuit 72
And is sent to the head 74 via the driver 73. The printing order differs depending on the configuration of the head and the printing unit, and also has a relationship with the input order of the printing data. If necessary, the printing order is temporarily recorded in a memory 75 such as a line buffer memory or a one-screen memory and then taken out. The head 74 outputs a gradation signal and an ejection signal.

When the number of nozzles is very large in the multi-head, an IC is mounted on the head 74 to reduce the number of wirings connected to the head 74. A correction circuit 76 is connected to the signal processing / control circuit 72, and performs γ correction, color correction in the case of color, and variation correction of each head. Generally, predetermined correction data is stored in the correction circuit 76 in the form of a ROM map, and is taken out according to external conditions such as a nozzle number, a temperature, and an input signal.

The signal processing / control circuit 72 is generally processed by a CPU using software, and the processed signal is sent to various control units 77. The various control units 77 drive a motor that rotationally drives the drum 53 and the feed screw 54,
Control such as synchronization, head cleaning, and supply and discharge of the print paper 52 is performed. Needless to say, the signal 71 includes an operation unit signal and an external control signal other than the print data.

Here, the configuration of the ink jet print head used in the above ink jet printer will be described.

The ink jet print head shown in FIGS. 1 and 2 is a single head using a so-called Kaiser type ink jet print head. In FIG. 1, a head 1 is provided with a liquid chamber 3 filled with a transparent solvent 2 and an ink quantification unit 5 for quantifying the ink 4 in parallel. A transparent solvent supply path 6 and an ink supply path 7 are connected to one end of the liquid chamber 3 and one end of the ink metering section 5, respectively, and the other end is connected to a mixing nozzle section 8, respectively.
Further, a one-way valve 9 is provided in the transparent solvent supply path 6, and a flat type vibrator 11 is attached to the outer periphery of the liquid chamber 3 via a vibrating plate 10. Further, the mixing nozzle section 8
In FIG. 2, a cylindrical transparent solvent discharge port 12 for communicating the liquid chamber 3 with the outside and a tubular ink discharge port 13 for communicating the ink metering section 5 with the outside are provided concentrically, as shown in FIG. As described above, the transparent solvent nozzle 14 and the ink nozzle 15 are formed at the tips of the discharge holes 12 and 13, respectively. The end faces of both nozzles 14 and 15 are arranged so as to be on the same plane.

The ink metering section 5 is divided into two chambers by an electroosmotic membrane 16 formed of a porous diaphragm. One chamber 5a is connected to the ink supply path 7, and the other chamber 5b is connected to the ink discharge port. 13. Further, mesh electrodes (not shown) are provided on both sides of the electroosmotic membrane 16, and by applying a pulsed DC voltage between the mesh electrodes, the ink 4 penetrates the electroosmotic membrane 16 and the two chambers 5a, 5a.
Move between b. The direction and amount of movement of the ink 4 can be accurately controlled by the polarity of the voltage applied between the electrodes and the amount of current, respectively.

On the other hand, the electrostrictive vibrator 11 has electrodes 11a adhered to both surfaces of an electrostrictive substance such as lead zirconate titanate, and by applying a predetermined voltage between the electrodes 11a, The electrostrictive vibrator 11 is polarized so as to be displaced in a direction in which the volume of the liquid chamber 3 changes.

Next, the operation of the ink jet print head will be described with reference to FIGS. First, the transparent solvent 2 is supplied from the transparent solvent supply path 6, and the liquid chamber 3 and the inside of the transparent solvent discharge hole 12 are filled with the transparent solvent 2. Similarly, the ink 4 is supplied from the ink supply path 7, and the inside of the ink metering section 5 and the ink ejection holes 13 are filled with the ink 4. At this time,
Ensure that no air remains inside each. FIG. 3A shows a state in which the mixing solvent 8 is filled with the transparent solvent 2 and the ink 4.

Next, when it is time to mix the transparent solvent 2 and the ink 4, printing is started in step S101 shown in FIG. Next, in step S102, the ink metering unit 5 is controlled to supply a desired amount of the ink 4 supplied from the ink supply path 7 to the ink ejection holes 13 of the mixing nozzle unit 8. At the orifice of the ink nozzle 15, as shown in FIG. 3B, the amount of the supplied ink 4 is pushed out of the orifice. At this time, the extruded ink 4 does not jump out of the ink nozzle 15 and remains in a spherical shape 4a at the outlet. This spherical state depends on the contact angle between the ink 4 and the ink nozzle 15, the ink 4
And the surface tension.

Next, in step S103 shown in FIG. 4, when a predetermined voltage is applied between the electrodes 11a of the vibrator 11, the vibrator 11 is displaced and the volume in the liquid chamber 3 is reduced. As shown in FIG.
4. Discharge outside. At this time, the adjacent ink nozzle 1
The ink bulb 4a extruded from 5 and the transparent solvent 2a in the discharging process come into contact with each other, and the two liquids tend to be united by the surface tension. As a result, as shown in FIG. 3D, the ink bulb 4a is drawn by the movement of the transparent solvent 2a, and the two are integrated to form a mixed liquid 17, and as shown in FIG. Is discharged from the mixing nozzle section 8. And
The ink 4 and the transparent solvent 4 mix with each other, and eventually fly as a mixed solution 17 having a desired concentration, and adhere to recording paper (not shown).

When the transparent solvent 2 is discharged, the liquid chamber 3
The pressure and the volume decrease applied to the liquid are efficiently transmitted to the mixing nozzle unit 8 without affecting the supply path 6 by the one-way valve 9 provided in the transparent solvent supply path 6. When the displacement of the vibrator 11 is returned to the original position, the transparent solvent 2 is supplied from the transparent solvent supply path 6 into the liquid chamber 3 via the one-way valve 9.

Next, in step S104 shown in FIG. 4, the presence or absence of the next dot printing is determined, and if there is, the flow returns to step S102 to repeat the above operation. If there is no next dot printing, the process returns to step S101 and waits.

According to this embodiment, when the head 1 is not performing a printing operation, the ink 4 in the ink nozzle 15 and the transparent solvent 2 in the transparent solvent nozzle 14 And the respective liquid levels are inside the ends of both nozzles 15 and 14 due to surface tension. Therefore, the transparent solvent 2 and the ink 4 do not mix. As a result, long-term contact between the transparent solvent 2 and the ink 4 can be prevented, so that chemical and physical reactions between the transparent solvent 2 and the ink 4 can be completely prevented, and the density control during printing can be reliably performed. Thus, it is possible to realize halftone printing with uniform image quality.

FIG. 5 shows a modification of the mixing nozzle section 8, and FIG. 6 shows the discharge operation of the transparent solvent 2 and the ink 4, respectively. In these figures, parts corresponding to the parts shown in FIGS. 2 and 3 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The mixing nozzle portion 8 shown in FIG. 5A has the tip of the ink nozzle 15 of the mixing nozzle portion 8 shown in FIG. A material 18 having a small wettability to the transparent solvent 2 and a large contact angle was coated on a region outside the ink nozzle 15 on the inner periphery. According to this modification, when the head 1 is not performing a printing operation, the transparent solvent 2 is located inside the tip of the ink nozzle 15, so that the transparent solvent 2 and the ink 4 do not naturally mix.

The mixing nozzle 8 shown in FIG. 5B is an example in which the tip of the ink nozzle 15 of the mixing nozzle 8 shown in FIG.

In the mixing nozzle section 8 shown in FIG. 5C, an ink discharge hole 13 and a transparent solvent discharge hole 12 are provided in parallel and adjacent to each other. This is an example in which it is configured to be located on the same plane.

The mixing nozzle section 8 shown in FIG. 5D includes the ink nozzle 15 and the transparent solvent nozzle 1 shown in FIG.
4 is an example in which the tip of the ink nozzle 15 is cut obliquely so that the tip of the ink nozzle 15 protrudes from the tip of the transparent solvent nozzle 14.

The mixing nozzle section 8 shown in FIG. 5E connects the ink discharge hole 13 and the transparent solvent discharge hole 12 at a certain angle θ.
The ink nozzle 15 and the transparent solvent nozzle 14
This is an example in which the front ends are opposed to each other.

The mixing nozzle section 8 shown in FIG. 5F has an ink ejection hole 13 at the center, a plurality of transparent solvent ejection holes 12 arranged in parallel around the ink ejection hole 13, and an ink nozzle 15. This is an example in which the transparent solvent nozzle 14 and the tip end face of the transparent solvent nozzle 14 are located on the same plane.

FIGS. 6 (a), (b), (c), (d),
(E) and (f) correspond to (a), (b) and (b) of FIG.
Mixing nozzle section 8 shown in (c), (d), (e), (f)
FIG. 9 is an explanatory diagram showing the discharge operation of the modified example, but the operation is almost the same as the discharge operation shown in FIG.

The same effects as in the case of the ink jet print head shown in FIGS. 1 and 2 can also be obtained by each of the modifications shown in FIG.

In the ink jet print head shown in FIG. 1, the ink jet print head 1 using the flat type electrostrictive vibrator 11 has been described. However, as shown in FIG. 8 and a stem-type ink jet print head in which a liquid chamber 3 is composed of two chambers 3a and 3b using a flat electrostrictive vibrator 11 as shown in FIG. The same effect can be obtained by applying.

In each of the above-described ink jet print heads, the electrostrictive vibrator 11 is used as a means for discharging the transparent solvent 2.
Although the description has been given of the case where is used, the present invention may be applied to an ink nozzle of a thermal inkjet type inkjet print.

There are two types of thermal ink jet print heads, an edge shooter type thermal ink jet print head and a side shooter type thermal ink jet print head, depending on the width direction of the nozzle.

FIGS. 9 and 11 show examples of the structure of an edge shooter type and side shooter type thermal ink jet print head, respectively. The basic principle of ink ejection is exactly the same in both systems. 9 and 11, a heater 23 is provided on a substrate 21 via an insulating film 22 such as SiO ₂ . A pair of Al electrodes 24 and 25 are provided on the heater 23 so as to face each other, and the upper surfaces of the heater 23 and the electrodes 24 and 25
27 and 28. An opening 28a is formed in the uppermost protective film 28 made of polyimide at a position where the electrodes 24 and 25 face each other, and an orifice plate 29 is provided above the protective film 28. I have. Then, ink 31 is supplied to a liquid chamber 30 formed in the orifice plate 29 from an ink supply path (not shown).

Here, in the edge shooter type head shown in FIG. 9, the liquid chamber 30 is opened in a direction parallel to the heater 23. In the side shooter type head shown in FIG.
A liquid chamber 30 is opened in a direction perpendicular to 3 and forms nozzles 32 and 33, respectively. In the side shooter head, two protective films 26 and 28 are provided.

In the edge shooter type thermal ink jet print head having the above-described configuration, the heater 23 is used.
When a predetermined voltage pulse is applied for a certain period of time, a nuclear bubble 41 is generated on the surface of the heater 23 as shown in FIG. The nuclear bubbles 41 coalesce as shown in FIG. 10B to form a film bubble 42, and the film bubbles 42 grow by adiabatic expansion to become bubbles 43 as shown in FIG. Next, when the application of the voltage to the heater 23 is stopped, the surrounding ink 31 takes heat as shown in FIG. 10D, and the bubble 43 contracts, and as shown in FIG. 43 disappears. And (c) of FIG.
The ink 31 is ejected from the nozzle 32 to the outside as ink droplets 31a by the ejection force of the film boiling phenomenon generated in the processes (d) and (e).

In the thermal ink jet print head of the side shooter type shown in FIG. 11, the ink droplets 31a are discharged by the same operation as shown in FIG. In FIG. 12, a plurality of liquid chambers 30 are provided in parallel with the orifice plate 29, and a common ink supply path 44 is provided.
Supplies the ink 31. Further, the ink supply path 44
Is provided with a barrier 45 for partitioning each liquid chamber 30.

FIG. 13 shows an example in which the side shooter type thermal ink jet print head shown in FIG. 11 is a two-liquid mixing chamber. That is, the liquid chamber 30 shown in FIG.
The ink metering section 5 was provided on the upper part of the nozzle 9, and the ink ejection hole 13 was opened on the outer periphery of the nozzle 33. This embodiment is shown in FIG.
(E) is applied to a side shooter type ink jet print head.

In the above-described ink jet print heads, the case of a single head has been described. The same effect can be obtained by applying to a multi-color multi-head in which a plurality of multi-heads are provided for the number of colors.

Next, a description will be given of an ink-jet printer which is multiplexed by disposing a plurality of the above-mentioned side shooter type thermal ink jet print heads or edge shooter type thermal ink jet print heads.

FIGS. 18 to 20 are a schematic overall view, a cross-sectional view and a vertical cross-sectional view of a multi-sided shooter type thermal ink jet print head.

The side shooter type thermal ink jet print head includes an ink outlet 101 and a transparent solvent ejector 102.
And an ink constant-pressure pumping unit 103. The ink 4 is filled in the ink quantifying units 112 and 112 ′ divided into two by the electroosmotic membrane 113 in the ink quantifying pressure feeding unit 103. On the front and back of the electroosmotic membrane 113, mesh electrodes 114 through which ink can pass,
114 'is fixed.

On the other hand, in the transparent solvent discharging section 102,
The transparent solution 2 is led from a transparent solution tank (not shown),
The liquid chamber 109 and the common liquid chamber 109 'are filled.
Further, a heater 110 is provided below the liquid chamber 109. The transparent solvent 2 extruded from the transparent solvent ejection hole 111
And the ink 4 pushed out from the ink ejection hole 106,
The ink is mixed in the mixed ink ejection hole 116 in the ink outlet 101.

The ink 4 is supplied to the ink metering units 112 and 112 '.
The electro-osmosis for more constant-pressure feeding is the same as the case of the ink jet print head shown in FIGS. 1 and 2, and the description thereof will be omitted.

The amount of the ink 4 is controlled by the pulse width of the voltage pulse applied to the mesh electrodes 114 and 114 ′ by electroosmosis. The voltage pulse for pushing out the ink 4 and the voltage pulse for discharging the transparent solvent 2 are: It is given at a predetermined timing. At this time, when the amount of the extruded ink 4 is large, the ink 4 may come into contact with the transparent solvent 2 before discharging. At this time, the ink 4 is discharged together with the transparent solvent 2 immediately after a predetermined amount of the ink 4 is extruded so that the ink 4 is not diffused and mixed into the transparent solvent 2.

FIG. 22 shows the timing at which an electroosmotic voltage pulse for ejecting the ink 4 and a discharge voltage pulse are generated by electroosmosis. The voltage pulse width t _ei of the electro-osmosis is t according to the amount of the ink 4 mixed.
It changes like _e1 , t _e2 , t _e3 . Intervals for ejecting ink 4 T, the time t _d to width t _p and the voltage pulses of electroosmosis voltage pulse discharge generates a voltage pulse of the discharge from the end is constant. Therefore, the density of the print dots, that is, the amount of the ink 4, is adjusted at the timing of generating the voltage pulse for electroosmosis.

The voltage pulse of the electroosmosis and the actual movement of the ink 4 are not completely synchronized, and the ejection of the ink 4 is delayed. This delay, that is, the response, changes depending on the characteristics of the head and the ink. The value of the time t _d is determined by the time of the delay is set to be slightly longer than the delay time.

The interval t _x from the stop of the discharge voltage pulse to the generation of the electroosmotic voltage pulse varies depending on the timing at which the electroosmotic voltage pulse is generated. Although during this period the refilling of the transparent solvent 2 is performed, since it depends on the diameter of the transparent solvent 2 of the ink 4 is time to refill the viscosity and surface tension and mixed ink discharge hole, the interval t _x is the transparent It is set to be longer than the refill time of the solvent 2.

FIG. 21 shows the discharge operation of the transparent solvent 2 and the ink 4 of the side shooter type thermal ink jet print head.
Shown in FIG. 21A shows a discharge standby state, in which the ink 4 determined by electroosmosis is supplied to the ink discharge holes 106.
It is in a state of being extruded and raised. Transparent solvent 2
Since the surface tension and the external pressure are in an equilibrium state, the meniscus surface 115 is formed by the transparent solvent discharge holes 111. The diameter of the transparent solvent ejection hole 111 is smaller than that of the mixed ink ejection hole 116, and a liquid repellency treatment using polytetrafluoroethylene or the like is performed in the vicinity thereof. Therefore, in the standby state, the transparent solvent 2 does not reach the mixed ink ejection hole 116 due to the capillary phenomenon.

FIG. 21 (b) shows that the transparent solvent 2
The boiling phenomenon starts at the interface between the heater and the heater 110, and minute air bubbles 117 are scattered.

When the rapidly heated transparent solvent 2 is instantaneously vaporized, a so-called film boiling phenomenon occurs as shown in FIG. Since the pressure in the liquid chamber 109 increases by the amount of the growth of the bubbles 117, the state of equilibrium with the external force on the meniscus surface 115 is broken, and the column of the transparent solvent starts to grow from the transparent solvent discharge hole 111. Therefore, the ink 4 that has been extruded from the ink ejection holes 106 and the transparent solvent 2 that has started to grow contact and coalesce to form a mixed ink column 118, and the growth continues.

Thereafter, as shown in FIG. 21D, the bubbles 117 are in a state of maximum growth, and the volume of the transparent solvent 2 corresponding to the volume of the bubbles 117 plus the ink 4 which is quantitatively mixed is added. Is ejected from the mixed ink ejection hole 116. At this time, no current is flowing through the heater 110, and the surface temperature of the heater 110 is decreasing. The volume of the bubble 117 reaches its maximum slightly after the timing at which the electric pulse to the heater 110 is cut off.

Next, the bubble 1 as shown in FIG.
17 is cooled by the transparent solvent 2 or the like, and starts to contract. At the front end of the mixed ink column 118, it advances at the pushed speed, and at the rear end, the bubble 117 contracts and the liquid chamber 1
09 is reduced, the mixed ink ejection holes 1
The transparent solvent 2 flows backward from 16 to the transparent solvent ejection hole 111, and constriction occurs in the mixed ink column 118. Since almost all of the ink 4 is present at the leading end of the mixed ink column 118, the trailing end is substantially only the transparent solvent 2. Therefore, the liquid chamber 1
The ink 4 flows back to 09 and does not mix with the transparent solvent 2. In addition, since the transparent solvent 2 is heated, and the transparent solvent does not contain a dye, the transparent solvent 2 is heated on the surface of the heater 110, such as an ink jet print head using the conventional ink film boiling phenomenon to discharge mixed ink droplets. Adhesion of foreign matter due to thermal decomposition of the dye, so-called scorching, does not occur.

All of the ink 4 mixed in the transparent solvent 2 is contained in the flying mixed ink droplet and does not remain in the transparent solvent 2 drawn into the liquid chamber 109 but is pushed out by the force of discharging the transparent solvent 2. The amount of the transparent solvent 2 to be ejected is a certain amount or more with respect to the amount of the ink 4 to be mixed, so that the amount of the transparent solvent 2 to be mixed can be sufficiently fly to the printing material together with the ink 4 thus mixed.

The mixing ratio for the ink 4 not to be mixed with the transparent solvent 2 in the liquid chamber 109 and to be able to fly sufficiently is 50% or less of the transparent solvent 2 but is preferably about 30%. desirable. Therefore, in order to obtain a sufficient maximum density, the ink 4 should have a sufficient density, and the print density of the mixed ink should be 2 or more in reflection density.
The ink 4 contains a dye.

The size of the mixed ink droplet varies depending on the amount of the ink 4 to be mixed. Therefore, the gradation of the printed image is controlled by the density of the mixed ink droplet and the area of the print dot. For example, when the mixing ratio of the ink 4 at the maximum density is 30% by volume ratio, the volume ratio of the mixed ink droplet ejected at the minimum density, that is, when the ink 4 is not mixed at all, and at the maximum density is 7:10. The volume of the mixed ink droplet and the print dot diameter are almost proportional. Therefore, in consideration of the change in the print dot diameter, the amount of the ink 4 to be mixed is controlled so as to obtain a desired print density.

Further, the bubble 117 contracts and the liquid chamber 109
When the transparent solvent 2 is in contact with the surface of the heater 110 on the side and cooling proceeds, the external pressure at the transparent solvent discharge hole 111 becomes higher than the internal pressure of the liquid chamber 109, and as shown in FIG. The surface 115 enters the liquid chamber 109.

Thereafter, as shown in FIG. 21 (g), the transparent solvent 2 is refilled by capillary action, and the state returns to the state where the meniscus surface 115 is formed at the transparent solvent discharge hole 111. At this time, the bubbles 117 have completely disappeared.

The ink 4 has an electro-osmotic property with respect to the electro-osmotic film 113. Aqueous and non-aqueous ones can be used, but in the case of aqueous ones, the driving voltage must be set below the decomposition voltage (around 1 V) to cause electrolysis.
Not preferred.

As the transparent solvent 2, a solvent compatible with the ink is used. For example, with respect to the ink having the above-described structure, chlorooctane and an ink obtained by adding a humectant, a vehicle agent, and the like thereto can be used. When a material having compatibility is used as the transparent solvent, the ink is well diffused in the transparent solvent, so that the concentration of the mixed ink droplets becomes uniform. Therefore, the image is expressed in gradation by the density of dots, and a higher quality image can be obtained. However, since the size of the mixed ink droplet changes depending on the amount of mixed ink, it is necessary to perform gradation control taking this into account.

Further, as the transparent solvent, water and a non-compatible solvent obtained by adding a wetting agent, a vehicle agent and the like thereto can also be used. When a material having no compatibility is used as the transparent solvent, the diffusion of the ink into the transparent solvent is incomplete, so that the transparent solvent serves as a carrier for transporting the ink to a non-printed material. Therefore, the image is close to an image expressed in gradation by the change in the size of the ink dot, that is, the area. However, since the ink is not mixed with the transparent solvent, it is less likely that the ink will be mixed into the liquid chamber when the ink is pushed out to the mixed ink ejection hole.

For the electroosmotic membrane 113, for example, a microporous membrane filter is used. As the material thereof, celluloses such as nitrocellulose, acetylcellulose, and regenerated cellulose, plastics such as polytetrafluoroethylene, polycarbonate, polyamide, and polyethylene, and ceramics such as glass and alumina can be used. It is necessary that the ink be electroosmotic without swelling or erosion. For example, when nitrocellulose is used as the electroosmotic membrane, for example, chlorooctane is used as a solvent, a quaternary ammonium salt of dodecylbenzenesulfonic acid is dissolved as an electrolyte in a weight ratio of 1 to 5%, and a dye, a wetting agent, and a vehicle are further dissolved. An ink containing an agent or the like can be used.

In addition, mesh electrodes 114 and 114 ′
Is preferably an inert metal that does not react with the substance in the ink, for example, a thickness of 50 μm, a pitch of 100 μm,
It is suitable to apply nickel plating to a μm iron mesh and then to platinum or gold plating. Alternatively, it is also possible to deposit, for example, gold directly on the front and back of the electroosmotic membrane 113 and use this as an electrode.

The head body must have solvent resistance to the solvent used for the ink and the transparent solvent. Examples of the head body include plastics such as polyethylene, polypropylene, and polytetrafluoroethylene; ceramic materials such as glass and alumina; It is made of a metal such as nickel.

FIGS. 23 to 25 are a schematic overall view, a cross-sectional view and a vertical cross-sectional view of a multi-edged edge shooter type thermal ink jet print head.

The edge shooter type thermal ink jet print head, like the side shooter type thermal ink jet print head, comprises an ink lead-out section 101, a transparent solvent discharge section 102, and an ink constant pressure feed section 103. The ink 4 is filled in the ink quantifying units 112 and 112 ′ divided into two by the electroosmotic membrane 113 in the ink quantifying pressure feeding unit 103. On the front and back of the electroosmotic membrane 113, a mesh electrode 1 through which ink can pass
14, 114 'are fixed.

On the other hand, in the transparent solvent discharging section 102,
The transparent solution 2 is guided from a transparent solution tank (not shown) to the transparent solvent supply path 108 and is filled in the liquid chamber 109. The ink 4 is guided from an ink tank (not shown) to the ink supply path 105, and is supplied to the ink quantifying units 112 and 11.
Sent to 2 '. A heater 110 is provided below the liquid chamber 109. The transparent solvent 2 extruded from the transparent solvent ejection hole 111 and the ink 4 extruded from the ink ejection hole 106 are mixed with the mixed ink ejection hole 1 in the ink outlet 101.
Mix at 16. The liquid chamber 109 is a barrier 13
It is divided by zero. This prevents interference between the adjacent liquid chambers 109 when bubbles are generated, and the pressure of the bubbles is concentrated in the direction of the transparent solvent discharge hole 111. Further, the barrier 130 is provided between the heater 110 and the transparent solvent discharge hole 1.
It also serves as a spacer for keeping the distance to 11 constant.

The ink 4 is supplied to the ink quantifying units 112 and 112 ′.
The electro-osmosis for more constant-pressure feeding is the same as the case of the ink jet print head shown in FIGS. 1 and 2, and the description thereof will be omitted.

The amount of the ink 4 by the edge shooter type thermal ink jet print head is controlled and discharged by the electroosmosis as described above. The timing at which the electroosmotic voltage pulse for ejecting the ink 4 and the ejection voltage pulse for extruding the ink 4 due to electroosmosis are the same as in the case of the side shooter type thermal inkjet print head using FIG.

FIG. 26 shows the discharge operation of the transparent solvent 2 and the ink 4 of the edge shooter type thermal ink jet print head.
Shown in The above-described ejection operation is the same as the ejection operation of the transparent solvent 2 and the ink 4 of the thermal inkjet type side shooter type thermal inkjet print head. FIG. 26A shows an ejection standby state, which is determined by electroosmosis. The ink 4 is extruded from the ink ejection holes 106 and is in a raised state.

FIG. 26 (b) shows the case where the heater 110 is heated and its surface temperature rises sharply.
The boiling phenomenon has started at the interface between the heater and the heater 110, and fine bubbles 117 are scattered.

When the rapidly heated transparent solvent 2 is instantaneously vaporized, a so-called film boiling phenomenon occurs as shown in FIG. 26 (c). Therefore, the ink 4 that has been extruded from the ink ejection holes 106 and the transparent solvent 2 that has started to grow contact and coalesce to form a mixed ink column 118, and the growth continues.

Thereafter, as shown in FIG. 26 (d), the bubbles 117 are in a state of maximum growth, and the volume of the ink 4 which is quantitatively mixed with the transparent solvent 2 corresponding to the volume of the bubbles 117 is added. The mixed ink is pushed out from the mixed ink ejection hole 116.

Next, a bubble 1 as shown in FIG.
17 is cooled by the transparent solvent 2 or the like, and starts to contract. It is the transparent solvent 2 that is heated, and the transparent solvent does not contain a dye. Therefore, like a conventional ink jet print head that uses the film boiling phenomenon of an ink to discharge mixed ink droplets, the dye is heated at the surface of the heater 110. Adhesion of foreign matter due to thermal decomposition, so-called burning does not occur.

Further, the bubbles 117 contract and the liquid chamber 109
When the transparent solvent 2 comes into contact with the surface of the heater 110 on the side and cooling proceeds, the external pressure at the transparent solvent discharge hole 111 becomes higher than the internal pressure of the liquid chamber 109, and as shown in FIG. The surface 115 enters the liquid chamber 109.

Thereafter, as shown in FIG. 26 (g), the transparent solvent 2 is refilled by capillary action, and the state returns to the state where the meniscus surface 115 is formed at the transparent solvent discharge hole 111. At this time, the bubbles 117 have completely disappeared.

The configuration of an ink jet printer equipped with the above-described multi-edge shooter type thermal ink jet print head or side shooter type thermal ink jet print head and a description of its printing and control system are as follows.
Since the contents are the same as those described with reference to FIGS. 14 to 17, the description here is omitted.

The control method of the multi-head is as shown in the block diagram of FIG. The digital halftone data is supplied to the serial / parallel conversion circuit 121 by the signal processing control circuit 72 in FIG.

At the print timing, a print trigger is output from the signal processing control circuit 72, the timing control circuit 122 detects this, and outputs an ink quantitative unit enable signal at a predetermined timing to the ink quantitative unit driver 12.
3 outputs a transparent solvent discharge section Enable signal to the transparent solution discharge section driver 124. The respective Enable signals are output at timings as shown in FIG.

The ink quantifying unit driver 123 controls the corresponding ink quantifying unit 125 according to the above-described ink quantifying unit Enable signal, whereby a predetermined amount of ink is pressure-fed from the ink ejection holes 106 of the plurality of heads. You.

On the other hand, the above-mentioned transparent solvent discharge section Enable having a predetermined time delay from the ink quantitative section Enable signal.
The transparent solvent ejection unit driver 124 controls each transparent solvent ejection unit 126 according to the e signal. Thereby, the transparent solvent is ejected while being mixed with the ink.

[0092]

As described above, according to the method of driving an ink jet printer according to the present invention, the ink ejection holes for ejecting ink and the solvent ejection holes for ejecting the solvent are arranged close to each other. After the ink extruded from the hole and the solvent ejected from the solvent ejection hole come in contact with the outside of each of the ink ejection holes, the ink and the solvent are ejected in the ink jet printer driving method, in which the ink is extruded. Since the voltage application for discharging the solvent is completed after the completion of the voltage application, the ink extruded from the ink discharge holes is reliably brought into contact with the solvent discharged from the solvent discharge holes outside the ink discharge holes. By mixing the two liquids, it is possible to obtain good density gradation in dot units. Further, it is possible to prevent the two liquids from being mixed when the head is not operating. As a result, long-term contact between the two liquids can be prevented, so that chemical and physical reactions between the two liquids can be completely prevented, and density control during printing can be reliably performed, and uniform image quality can be achieved. Halftone printing can be realized.

According to the method of driving an ink jet printer according to the present invention, the ink ejection holes for ejecting ink and the solvent ejection holes for ejecting the solvent are arranged close to each other, and the ink ejected from the ink ejection holes can be used. After the solvent discharged from the solvent discharge hole comes into contact with the end surface of each of the ink discharge holes, the method for driving an ink jet printer in which the ink and the solvent are discharged is performed. Since the voltage application for discharging the ink is completed, the ink extruded from the ink discharge holes can be reliably brought into contact with the solvent discharged from the solvent discharge holes outside each of the ink discharge holes. By mixing, it is possible to obtain a good density gradation in dot units. Further, it is possible to prevent the two liquids from being mixed when the head is not operating. As a result, long-term contact between the two liquids can be prevented, so that chemical and physical reactions between the two liquids can be completely prevented, and density control during printing can be reliably performed, and uniform image quality can be achieved. Halftone printing can be realized.

In the driving method of the ink jet printer according to the present invention, since the voltage application for discharging the solvent is started after the voltage application for pushing out the ink is completed, the ink is prevented from being diffused and mixed into the solvent. In addition, chemical and physical reactions of both solutions can be completely prevented. Further, the time from the end of the voltage application for pushing out the ink to the start of the voltage application for ejecting the solvent can be constant regardless of the amount of ink pushed out. Further, after the application of the voltage for ejecting the solvent is completed, the application of the voltage for pushing out the next ink is started, so that the ink is not diffused and mixed into the solvent, and the chemical and physical The reaction can be completely prevented.

Further, in the driving method of the ink jet printer according to the present invention, the time period between the end of the application of the voltage for discharging the solvent and the start of the application of the voltage for pushing out the next ink, the time for the solvent of the solvent is reduced. Refilling can be performed. Further, the time from the end of the voltage application for discharging the solvent to the start of the voltage application for pushing out the next ink is longer than the time required for refilling the solvent, Refilling can be performed reliably.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an ink jet print head used in an ink jet printer embodying the present invention.

FIG. 2 is an enlarged sectional view showing a configuration of a mixing nozzle section of the inkjet print head.

FIG. 3 is an explanatory diagram showing an operation of discharging ink and a transparent solvent in the ink jet print head.

FIG. 4 is a flowchart illustrating the operation of the inkjet print head.

FIG. 5 is an explanatory diagram showing a configuration of a modified example of the mixing nozzle portion of the ink jet print head used in the ink jet printer embodying the present invention.

FIG. 6 is an explanatory diagram showing an operation of discharging the ink and the transparent solvent of the mixing nozzle section shown in FIG.

FIG. 7 is a longitudinal sectional view illustrating a schematic configuration of an example of a glued type inkjet print head.

FIG. 8 is a longitudinal sectional view showing a schematic configuration of an example of a stem type inkjet print head.

FIG. 9 is a longitudinal sectional view showing a configuration of an example of an edge shooter type thermal inkjet print head.

10 is an explanatory diagram showing a droplet forming process by the head shown in FIG.

FIG. 11 is a vertical cross-sectional view in a direction perpendicular to the multi direction showing a configuration of an example of a side shooter type thermal inkjet print head.

FIG. 12 is a longitudinal sectional view along the multi-direction of FIG. 11;

FIG. 13 is a longitudinal sectional view showing a configuration of an example of a two-liquid mixing type side shooter type thermal inkjet print head.

FIG. 14 is an explanatory diagram illustrating a configuration of an example of a drum rotary inkjet printer.

FIG. 15 is an explanatory diagram illustrating a configuration of an example of a serial type inkjet printer.

FIG. 16 is an explanatory diagram illustrating a configuration of an example of a line-type inkjet printer.

FIG. 17 is a block diagram illustrating a configuration example of a signal processing and control system of the inkjet printer.

FIG. 18 is an overall view showing a configuration of an example of a multi-sided side shooter type thermal inkjet print head.

19 is a longitudinal sectional view of the inkjet print head shown in FIG. 18 taken along a multi-direction.

20 is a longitudinal sectional view of the inkjet print head shown in FIG. 18 in a direction perpendicular to the multiple directions.

FIG. 21 is an explanatory diagram illustrating an operation of discharging the ink and the transparent solvent of the inkjet print head illustrated in FIG. 18;

FIG. 22 is a diagram illustrating timings of driving voltage pulses of the inkjet print head illustrated in FIG. 18;

FIG. 23 is an overall view illustrating a configuration of an example of a multi-edge thermal shooter type ink jet print head.

24 is a longitudinal sectional view of the inkjet print head shown in FIG. 23 in a direction perpendicular to the multiple directions.

FIG. 25 is a longitudinal sectional view of the inkjet print head shown in FIG. 23, taken along a multi-direction.

FIG. 26 is an explanatory diagram showing the operation of discharging the ink and the transparent solvent of the inkjet print head shown in FIG.

FIG. 27 is a diagram schematically showing a driving operation of the thermal inkjet print head.

[Explanation of symbols]

1,51 print head, 2 transparent solvent, 3,109
Liquid chamber, 4 inks, 5,112,112 'ink metering section, 7,105 ink supply path, 11 electrostrictive vibrator,
12,111 transparent solvent ejection holes, 13,106 ink ejection holes, 16,113 electroosmotic membrane, 18 substances, 52
Printing paper (substrate), 53 drum, 54 feed screw (drive member), 58 motor (drive member), 110
heater

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masayuki Sato 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Masao Shinya 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo (56) References JP-A-6-71883 (JP, A) JP-A-6-71887 (JP, A) JP-A-6-87214 (JP, A) (58) Fields investigated ( Int.Cl. ⁶ , DB name) B41J 2/205

Claims (14)

(57) [Claims] An ink ejection hole for ejecting ink and a solvent ejection hole for ejecting a solvent are arranged in close proximity to each other, and the ink ejected from the ink ejection hole and the solvent ejected from the solvent ejection hole are formed by the solvent. In the method of driving an ink jet printer in which the ink and the solvent are ejected after contacting outside each ejection hole, the voltage application for ejecting the solvent is terminated after the voltage application for pushing out the ink is terminated. Method for driving an inkjet printer. 2. The method according to claim 1, wherein a voltage application for discharging the solvent is started after the voltage application for pushing out the ink is completed. 3. The method according to claim 2, wherein the time from the end of the application of the voltage for pushing out the ink to the start of the application of the voltage for ejecting the solvent is constant regardless of the amount of ink pushed out. The driving method of the ink jet printer described in the above. 4. The method according to claim 1, wherein after the voltage application for discharging the solvent is completed, the voltage application for pushing out the next ink is started. 5. The method according to claim 1, wherein the time from the end of the application of the voltage for discharging the solvent to the start of the application of the voltage for pushing out the next ink changes according to the amount of ink pushed out. 5. The driving method of the inkjet printer according to 4. 6. The method according to claim 1, wherein the refilling of the solvent is performed during a period from the end of the application of the voltage for discharging the solvent to the start of the application of the voltage for pushing out the next ink. 5. The driving method of the inkjet printer according to 4. 7. The method according to claim 1, wherein the time from the end of the voltage application for discharging the solvent to the start of the voltage application for pushing out the next ink is longer than the time required for refilling the solvent. The method for driving an ink jet printer according to claim 6. 8. An ink ejection hole for ejecting ink and a solvent ejection hole for ejecting a solvent are arranged in close proximity to each other, and the ink ejected from the ink ejection hole and the solvent ejected from the solvent ejection hole are formed. In the method for driving an ink jet printer, in which the ink and the solvent are ejected after the contact on each of the ejection hole end faces, the voltage application for ejecting the solvent is terminated after the voltage application for pushing out the ink is completed. Characteristic driving method of an ink jet printer. 9. The driving method of an ink jet printer according to claim 8, wherein a voltage application for discharging the solvent is started after the voltage application for pushing out the ink is completed. 10. The time from when the voltage application for pushing out the ink is completed to when the voltage application for ejecting the solvent starts is constant regardless of the amount of ink pushed out. 10. The driving method of the ink jet printer according to item 9. 11. The driving method of an ink jet printer according to claim 8, wherein after the voltage application for discharging the solvent is completed, the voltage application for pushing out the next ink is started. 12. The method according to claim 1, wherein the time from the end of the application of the voltage for discharging the solvent to the start of the application of the voltage for pushing out the next ink changes according to the amount of ink pushed out. 12. The method for driving an ink jet printer according to item 11. 13. The method according to claim 1, wherein the refilling of the solvent is performed during a time period from the completion of the application of the voltage for discharging the solvent to the start of the application of the voltage for pushing out the next ink. 12. The method for driving an ink jet printer according to item 11. 14. The method according to claim 1, wherein the time from the end of the voltage application for discharging the solvent to the start of the voltage application for pushing out the next ink is longer than the time required for refilling the solvent. The method for driving an ink jet printer according to claim 13.