JPH0939248A - Ink jet apparatus and ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of the time required for the preheating step to a recording speed by providing head drive means for giving a main signal to ink discharge continued to a preheat signal not to the ink discharge to an energy generating element. SOLUTION: When the time from the start of giving at least one preheat signal relative to one time ink discharge operation to the start of giving a main signal is Δt and the time from the start of giving the preheat signal to the reset of an ink meniscus to an ink discharge port is Δts2, head drive means is driven for the same ink discharge port in the case of Δts2<Δt. More particularly, at the time of recording in the ink jet apparatus, a main controller 612 controls the drive of a carriage feed motor 616A via a motor driver A, and controls the drive of a sheet feed motor 616B via a motor driver B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet device and an inkjet recording method, and more particularly to an ink ejection method.

[0002]

2. Description of the Related Art The ink jet system is a system in which ink is ejected as minute liquid droplets from an ejection port of an ink jet head, and is generally used in a recording apparatus for recording characters, figures and the like. The recording apparatus using this method has excellent advantages as a means for outputting a high-definition image and high-speed recording.

Among the ink jet methods, bubbles are generated in the ink by utilizing the heat energy generated by an electrothermal conversion element (hereinafter also referred to as a heater), and the ink is generated by using the pressure accompanying the generation of the bubbles. Discharge method (bubble jet method; for example, Japanese Patent Publication No. 61-5991)
1 to 4), the downsizing of the device,
It has features that it is easy to increase the image density.

FIG. 1 is a diagram for explaining a preferable discharge state of liquid drops in the bubble ink jet system.

As shown in FIG. 1A, when the ink path 106 of the ink jet head is filled with ink,
For example, when a pulsed ejection signal is applied to the heater 101 to apply heat energy to the ink near the heater 101 from the heater 101, a bubble 102 is formed (FIG. 1B). As the bubble 102 grows, the ink meniscus 104 near the ejection portion projects from the ejection port (orifice) 103 (see FIG. 1).
(C)) After that, the meniscus 104 retracts as the droplet 105 is ejected and the bubble 102 contracts (FIG. 1D).
In addition, it takes some time after the bubble disappears to let meniscus 1
04 moves forward (FIG. 1 (e)) and returns to the vicinity of the orifice 103 (FIG. 1 (f)).

In the above-mentioned discharge behavior, in order to obtain a preferable discharge state, it is desirable that initial bubbling (not shown) is formed on the heater 101 at various portions of the heater within an extremely short time. Then, after that, FIG.
Bubbles 102 are formed as shown in (c) to (c), and after the ejection is completed, the heater is covered with ink again.

Further, an ink jet system (hereinafter referred to as a bubble continuous ejection system) which ejects the above-mentioned bubbles generated for ejection as a kind of the bubble jet system by communicating with the outside air at a part of the edge of the ejection port. For example, a method disclosed in Japanese Patent Application Laid-Open No. 4-10940 is known, which causes less ink splash and mist and is different from the thermal bubble jet method described above.
Even if the temperature of the inkjet head itself changes, it is possible to perform stable ejection of the ejection amount.

FIG. 2 is a diagram for explaining a preferable discharge state by the bubble communication system.

As shown in FIG. 1C, the bubble 102 grown by applying heat energy is an ink droplet 105.
After being separated and communicating with the atmosphere at a part of the edge of the discharge port 103 (not shown), the ink droplet 105 is separated and discharged.

In order to obtain stable ejection in this bubble communication system, it is usually necessary to increase the thermal energy applied per unit volume of ink for ejection, as compared with the system shown in FIG.

As another method of the bubble jet method described above, for example, Japanese Patent Application Laid-Open No. 5-1993
There is also known one using an ordinary temperature solid ink described in Japanese Patent No. 96733. According to this method, the inkjet method using the water-based ink having water as a main component as described above causes image fixing failure or blurring at the boundary between image patterns of different colors depending on the combination of ink and recording paper. Although the quality may be deteriorated, a more stable image can be obtained without fear of fixing failure.

By the way, in the bubble jet method using the solid ink at room temperature, it is necessary to keep the ink in a melted state in the ink passage at least at the time of ejection, so that the ink and the periphery of the ink passage are heated to a melting temperature or higher during recording. . The higher the heat retention temperature is, the better in order to lower the viscosity so as to be advantageous for ejection. However, depending on the ink composition,
In some cases, overheating for a long time accelerates the deterioration of the ink, and the foaming becomes unstable, resulting in a non-ejection state.

Further, according to the study by the present inventors, ink-jet recording is possible even at room temperature solid ink which can be used in the bubble jet method already known in the above-mentioned JP-A-5-96733. In some practical environments, the droplet ejection performance is inferior to that of the water-based ink. This is because when solid ink is used, the bubble pressure during foaming may be insufficient. The room-temperature solid ink suitable for the bubble jet method has significantly smaller bubbles formed on the heater than the water-based ink, as compared with the same inkjet head. This means that the bubble pressure of the ink fixed at room temperature is relatively small.

In order to solve the problem in the case of using the solid ink, the pressure at the time of bubble growth may be set large so as to sufficiently overcome the viscosity of the ink in the ink passage in a practical environment. For this reason, in the case of the bubble jet method using the solid ink at room temperature, it is necessary to apply a larger thermal energy to the ink than in the case of using the aqueous ink. That is, supplementing the low bubble pressure, heating to a high temperature for low viscosity, and preventing ink deterioration due to holding at a high temperature are problems peculiar to bubble jet recording of normal temperature solid ink.

As one method for solving this problem, heat energy is applied to the ink immediately before the application of the ejection signal to preheat only the ink in the vicinity of the heater (hereinafter, this operation is referred to as preheating), It is possible to apply a discharge signal in this state to form bubbles. It is known that preheating can generate a larger bubble pressure for the same ink. Japanese Examined Patent Publication No. 3-75037 describes the basic concept of preheating in the bubble jet method. Also U
SP5065167 discloses a configuration in which preheating is used in a bubble jet method that uses solid ink at room temperature.

FIG. 3 shows an example of an ejection signal when preheating is used.

At the time of preheating, by applying preheat signals P1, P2, ..., P20 to the heater, which gives thermal energy to the ink to the extent that foaming does not occur in the ink, 20
The pre-heating process is repeated, and immediately after the pre-heating process is finished, the main signal Pmain is applied to form bubbles on the heater to eject liquid droplets.

At this time, the pulse width of the preheat signal and the main signal, the application time interval, the number of repetitions, etc. are set to predetermined values depending on the combination of the ink jet head and the ink. For example, even when an inkjet head having the same structure is used, in order to stably eject a room temperature solid ink containing a foaming medium such as lauric acid and ethylene carbonate, when an inkjet head having the same structure is used, a water-based ink is usually used. It is necessary to apply the preheat several times to several tens of times as in the case of ink.

[0019]

Generally, one of the factors that determines the recording speed of an ink jet recording apparatus is the ink refill time. This is because the ink is supplied into the ink path by the capillary force after the ink is ejected.
It refers to the time required for the meniscus to return to a predetermined position near the orifice, and the ejection interval is often determined by the length of this refill time tr. Therefore, the recording speed is determined by this.

On the other hand, the time tpr required for the preheating process
(Hereinafter, preheat time, see FIG. 3) is sufficiently smaller than the refill time tn, for example, tr = 200 μm
If sec and tpr = 4 μsec, the preheating time tpr has almost no effect on the recording speed. do not do. However, when the preheating time tpr is long as in the case of using the solid ink at room temperature, the preheating operation causes the recording speed to decrease with the refill time.

For example, as described in Japanese Examined Patent Publication No. 3-75037, in a structure in which preheating is always started after refilling is completed, the discharge interval is (t
(n + tpr) or more, the ejection frequency becomes 1 / (tr
+ Tpr) Hz or less. this is,
This is because stable ejection may not be continuously obtained when the operation of ejecting ink is repeated before the meniscus returns to the vicinity of the orifice.

As one trial, the inventors of the present invention used the discharge signal shown in FIG. 4 in which the time interval of each preheat signal shown in FIG. 3 was set to about 0 sec and the time tpr of the preheat process was shortened. However, in spite of the total amount of thermal energy imparted to the ink by the ejection signal shown in FIG. 4 being substantially equal to the ejection signal shown in FIG. 3, in many cases, the ejection stability by the ejection signal of FIG. It was below the ejection stability by the ejection signal of FIG. That is, when the discharge state at this time is visually observed using strobe light emission, in the signal form of FIG. 4, a small bubble is generated on the heater during the preheating process, which becomes a core and the ink does not warm sufficiently. It turns out that a bubble is formed in. in this way,
It is difficult to perform stable and high-speed recording by simply compressing the preheat signal interval. The above U
SP5065167 does not disclose a configuration for solving the above problems.

As described above, when the solid ink is used, the time required for the preheating process becomes long, and the recording speed is lowered in combination with the refill time. It should be noted that the problem of the decrease in recording speed due to such preheating time is not limited to the case of using solid ink. For example, even when the liquid ink is ejected in a relatively low temperature environment, there is a problem in that there is a difference in the degree.

The present invention has been made in view of the above problems, and an object thereof is an ink jet apparatus and an ink jet recording capable of reducing the influence of the time required for the preheating process on the recording speed. To provide a method.

[0025]

Therefore, according to the present invention,
An ink ejecting operation is performed in which ink having an ink ejecting port is used to generate bubbles for the ink supplied to the vicinity of the ink ejecting port by using thermal energy generated by an energy generating element and the ink is ejected based on the generation of the bubbles. In an inkjet apparatus that ejects ink onto a medium using an inkjet head, regarding the ink ejection operation, at least one preheat signal that does not result in ink ejection and a main signal that leads to the ink ejection subsequent to the preheat signal are provided as the energy generating element. The head drive means for applying to at least one of the at least one
When the time from the start of application of one preheat signal to the start of application of the main signal is Δt, and the time from the start of application of the at least one preheat signal until the ink meniscus substantially returns to the ink ejection port is Δts2 , The same ink ejection port is driven with Δts2 <Δt.

Further, with respect to the ink which has an ink ejection port and is supplied to the vicinity of the ink ejection port, bubbles are generated by utilizing the thermal energy generated by the energy generating element, and the ink is ejected based on the generation of the bubbles. In an inkjet recording method of ejecting ink onto a recording medium using an inkjet head that performs an ink ejection operation, at least one preheat signal that does not result in ink ejection and a main signal that leads to the ink ejection subsequent to the preheat signal are used as the energy. Ink is ejected by applying it to the generating element, where Δt is the time from the start of applying the at least one preheat signal to the start of applying the main signal for one ink ejection operation, and the at least one preheat From the start of signal application, the ink meniscus will reach the ink outlet. The time to qualitatively return Δts2
In this case, the same ink ejection port is driven with Δts2 <Δt.

According to the above configuration, the meniscus by the previous ejection is restored between the preheat start time and the application of the main signal, so that when the ink is continuously ejected, the ink supply caused by the preceding ink ejection is performed. The subsequent preheating is started before the position of the ink meniscus in the operation or before reaching the ink ejection port, the ink can be heated during the so-called ink refill, and the main signal is immediately given when the meniscus is restored. As a result, even when a very long preheat is required as in the case of a bubble jet type room temperature solid inkjet, high-speed continuous ejection is possible without being restricted by the time required for the preheat.

Further, preferably, since the main signal is applied after the bubble related to the preceding ink ejection is eliminated, the bubble generation due to the main signal application is not hindered by the bubble related to the preceding ejection.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

(Embodiment 1) FIG. 5 is an exploded perspective view of an ink jet head used in one embodiment of the present invention.

In FIG. 5, a liquid chamber 509 and a predetermined number of ink paths arranged at predetermined intervals are formed on a substrate 508 on which a heater 501 and electrode wiring (not shown) for sending an electric signal to the heater are formed. The top plate 5 is provided with a partition wall 507 for further operation and further has a supply port 510 in this substrate.
An ink jet head is formed by joining 11 together. That is, the above-mentioned joining forms the liquid passage 509, the ink passage 506 including the heater 501, and the ejection port (orifice) 503. The room temperature solid ink is heated and melted in an ink supply path (not shown), is supplied to the liquid chamber 509 via the supply port 510 in the melted state, and is further supplied to the ink by a capillary force or the like. Further, at the time of recording, the substrate 508 is kept at a temperature higher than the ink melting temperature by a substrate heater (not shown).

FIG. 6 is a block diagram showing the control arrangement of the ink jet apparatus according to this embodiment using the above ink jet head.

The ink jet system is not only used in such a generally well-known recording device, but also a printing device for printing a pattern or the like on a cloth, or the like.
It is also used for ejecting ink onto various media and adhering it to the media. Hereinafter, such adhering processing is referred to as recording.

The main controller 612 receives an image data signal from a host computer 615 such as an image reader or the like, and a frame memory 61 for buffering in units of one frame.
Store in 3. During recording, main controller 612
Carriage motor 616 via motor driver A
The drive of A is controlled, and the drive of the paper feed motor 616B is controlled via the motor driver B. With this,
Based on the image data read from the frame memory 613, the ejection signal control of the inkjet head 618 is performed via the driver controller 617 and the head driver 614. As will be described later, this control includes control of signal application timing according to the embodiment of the present invention.

If the current amount changes when the discharge signal is supplied to the heater, the discharge stability may be impaired. Therefore, when an ejection port group is divided into a plurality of blocks in an inkjet head having a plurality of ejection ports as in the present embodiment and ejection is performed simultaneously from each ejection port for each block, the preheat signal Pi in the preheating process is The pulse width Wpi and the signal pause time ti immediately after the application of the preheat signal Pi are set to, for example, ti ≧ n × tmod ≧ n × Wpi. As a result, it is possible to control the voltage drop of the circuit in the inkjet head or the inkjet recording device to be a predetermined value or less. Where tmod is (tdelay
÷ Wpi) remainder, tdelay, is a drive time interval between two blocks that are continuously driven.

FIG. 7 is a waveform diagram showing the ejection signal of this embodiment.

In the present embodiment, the ejection signal shown in FIG. 7 is used in the ejection method shown in FIG. 1, and as shown in the figure, 20 preheat pulses P1, P2, ... Immediately before the main pulse is applied. , P20 is applied, the first preheat pulse P1 is applied before the meniscus retracted toward the liquid chamber by the immediately preceding ejection is returned to the vicinity of the orifice.

In FIG. 7, the time Δt = 41.6 μsec required from the start of the application of the preheat pulse to the application of the main pulse Pmain. Further, (0.56 / 1.52) × 20 in FIG. 7 indicates that in preheating, a preheat pulse having a pulse width of 0.56 μsec is repeatedly applied 20 times at each pause time interval of 1.52 μsec. Further, the preheat pulse Pi (i = 1 to 20) sets the voltage VH pulse width so that foaming does not occur by itself.

In the present embodiment, a study will be given below regarding the adoption of the timing of applying the first preheat pulse before the meniscus returns to the vicinity of the orifice as described above.

In this embodiment, a room-temperature solid ink having the following composition is used, and when ejected, the ink is heated to 80 ° C., which is higher than the melting temperature of the ink, to hold the ink in a liquid state.

Ink composition: ethylene carbonate 47% by weight 1.12 dodecanediol 50% by weight dye 3% by weight The main part of the inkjet head used in the present embodiment has an orifice area of about 930 μm ² and a heater is provided. Ink path width about 50 μm, heater area about 36
50 μm ² , distance between heater center and orifice is about 187
μm. The heater is made of SiO 2.75 μm thick.
Hf constituting the heater resistor layer on the _two- layer substrate
Each of the thin film layers of B ₂ , SiO ₂ forming the protective layer, etc., and Ta forming the cavitation-resistant layer is about 0.1 μm.
m, 2.0 μm, and 0.6 μm in this order, and the layers are formed by etching in a predetermined pattern. The resistance value of the heater is about 80Ω.

When the above ink and ink jet head were used, first, the defoaming time and the meniscus recovery time of bubbles generated due to ejection were examined.

That is, the ejection signal shown in FIG.
When applied at 00 Hz, that is, at a period of 10 msec and continuously ejected, the position of the meniscus in the ink passage changed in each ejection as shown in FIG.

In the figure, the starting point of time is the rising time of the main pulse, and the negative value of the meniscus position means the amount of retreat into the ink path. As is clear from the figure, time t at which the meniscus returns to the vicinity of the orifice
2 is about 110 μsec.

The bubble disappearance time t1 is about 40-5.
It was 0 μsec. Here, the time t1 is not fixed because the defoaming phenomenon fluctuates instability in the case of the normal temperature solid ink as compared with the water-based ink.

Next, in the above continuous ejection, the application time (and main pulse application time) of the preheat pulse P1 for the subsequent ejection performed after each preceding ejection.
However, as shown in FIG. 9, the ejection performance under each condition indicated by the relative relationship between the defoaming time t1 and the meniscus recovery time t2 was compared. In addition, the condition 4 is, for example, Japanese Patent Fairness 3-
This is the conventionally known ejection timing control described in Japanese Patent Publication No. 75037, which starts preheating after the meniscus is restored. That is, FIG. 9 shows the conditions 1 to 5 when the preheat start time tsk (k = 1, 2, 3, 4, 5) is based on the application time of the preceding main pulse of the ejection (t = 0). The results are shown in Table 1 below, in which the discharge state is measured and compared under each condition.

[0047]

[Table 1]

In Table 1, the results of comprehensive evaluation of the ejection performance including the stability of the ejection speed under the respective conditions shown in FIG. 9 are shown by ◯, Δ, and ×, respectively.

In Table 1, when conditions 1 to 4 are compared with each other, when condition 3 is applied, that is, when the application of the preheat signal is started at time ts3 = 90 usec between the defoaming time t1 and the meniscus recovery time t2, It can be seen that it is possible to obtain the ejection stability that is substantially the same as the condition 4 which is the timing control of (1) in the shortest required time (the time from the application of the preceding main pulse to the application of the main pulse; shown in FIG. 9).

Condition 2 is a control for starting preheating at the timing of almost defoaming. The required time is shorter than that of Condition 3, but the ejection performance is less than that of Conditions 3 and 4. Further, the condition 1 required the shortest time, but bubbles remained in the ink passage, and continuous ejection thereafter was not possible. This is because the application of heat energy in the preheating process causes the bubbles for preceding ejection to grow as nuclei immediately before defoaming and form bubbles that do not dissolve in the ink in a short time.

Condition 5 for applying the main signal before the meniscus recovery time t2 required a shorter time than condition 3, but ejection was often unstable. In particular, when continuously driven under the condition 5, the discharge volume was not stable, and the dot size on the recording paper varied. Therefore, Condition 5 cannot be said to be more stable than Condition 3 for obtaining stable ejection.

As described above, as is clear from the above comparison result, the most preferable ejection timing control is the control under Condition 3, that is, the preheat signal is applied between the defoaming time t1 and the meniscus recovery time t2. The main pulse is applied immediately after the start of the process and after the meniscus is recovered. This makes it possible to perform higher-speed recording while maintaining the same ejection performance as the conventional method (condition 4).

In this way, high-speed recording is possible, and preheating contributes to stable ejection because more ink near the heater is heated to a higher temperature below the bubbling temperature by preheating before the main signal is applied. It is considered that the temperature can be kept warm and a larger foaming pressure can be obtained once by applying the main signal. That is, in order to sufficiently obtain the effect of preheating, the ink covers the heater at the time of preheating, and there is no bubble in the ink near the heater that becomes a nucleus of foaming with a small energy during preheating. It is necessary. Therefore, the preheat start time for the subsequent ink ejection is set to the time when the bubbles disappear from the heater and the surroundings after the preceding ink ejection, and the meniscus receding toward the liquid chamber due to the ejection returns to a predetermined position near the orifice. Try to set it during the time.

As shown in Condition 3, the main pulse is applied after the meniscus is restored. The time from the start of preheat application to the start of main pulse application is Δt, and the time from the preheat start time ts to the meniscus return time t2. Is expressed as Δts2, it can be expressed as Δts2 <Δt. Further, if the variation in the ejection volume can be allowed to some extent, the ejection timing control as in Condition 5, that is, the main pulse may be applied before the meniscus return time.

From the viewpoint of increasing the recording speed, it is more preferable that the preheating for the next ink ejection can be started immediately after the bubble disappears. Further, it is more preferable that the preheating is started immediately after the reheated ink covers the substantially heat-generating portion on the heater, and the preheating for ink ejection is started.

In the bubble jet method used in this embodiment, the bubbles generated on the heater often disappear in the process shown in FIG.

That is, after the bubble 1202 reaches its maximum growth (FIG. 10 (a)), it is rapidly contracted by stopping the supply of thermal energy from the heater 1201 to the ink (FIG. 10).
(B)) It eventually disappears (Fig. 10 (c)). At this time, in the ink path 1206 around the heater 1201, extremely small micro bubbles 1219 may remain as compared with the above bubbles for ejection. Also, often immediately after the bubbles disappear, so-called rebound bubbles 1220 are temporarily formed on the heater due to a cavitation phenomenon (see FIG. 10).
(D)) When these are redissolved in the ink, the bubble disappearance (defoaming) process ends.

Therefore, in order to sufficiently obtain the effect of the discharge timing control described in the present embodiment, the defoaming time t1 used in the control is shown in FIG. 10 (e) where the bubble 1202 and other bubbles disappear. It is sufficient to set the time when the state is reached.

(Embodiment 2) This embodiment shows an example in which the present invention is applied to the discharge control of the bubble communication system described with reference to FIG. FIG. 11 is a schematic diagram showing a heater drive signal related to the ejection timing control of this embodiment.

As shown in the figure, preheat pulses P1, P2, ..., P 30 times immediately before the main pulse signal is applied.
In the case where 30 is applied, the present embodiment is control of the condition that the first preheat pulse P1 is applied before the meniscus return related to the ejection immediately before that.

In this embodiment, a room-temperature solid ink having the following composition is used, and when the droplets are ejected, the ink is heated to 100 ° C., which is higher than the melting temperature of the ink, and the ink is held in a liquid state.

Ink composition: 67% by weight of lauric acid Carnauba wax 30% by weight Dye 3% by weight The size of the main part of the inkjet head used in this embodiment is such that the opening area of the discharge port is about 1080 μm ² and the ink path width of the heater part is About 40μm, heater area about 1280μ
m ² , the distance between the center of the heater and the discharge port is about 25 μm. Further, the heater is made of 1.0 μm SiO 2 on the substrate.
HfB on the layer ₂ (resistor), SiO _2, about Ta each thin film layer, respectively 0.08μm, 1.0μm, 0.1μ
It is formed by laminating with a thickness of m.

The frequency shown in FIG. 11 is 100 Hz.
When continuously ejected, the time t4 at which the meniscus returns to the vicinity of the orifice was about 350 μsec. Also,
After the bubble on the heater communicates with the outside air, the time t3 at which the ink covers the substantially heat-generating portion on the heater again is about 180 μsec.
Met.

Under these discharge conditions, the start time of the preheat signal P1 was set as shown in FIG. 12 (conditions 6 and 7), and the discharge performance under each condition was compared, and the results in Table 2 were obtained. The condition 8 shown in the figure is the conventional ejection timing control in which preheating is started after the meniscus is restored.

[0065]

[Table 2]

According to Table 2, the discharge state is stable under the conditions 7 and 8, of which time ts7 = 2.
According to the condition 7 in which the preheat is started at 80 usec, the recording can be performed at a higher speed than the condition 8. Further, the ejection states under Conditions 7 and 8 were more stable than those in the first embodiment.

Condition 6 is that the preheat start time is time t3.
Although it was the method set previously, continuous discharge was difficult due to bubbles remaining in the ink path. Also from this example, it is important to set the application times of P1 and Pmin so that the meniscus is restored between the preheat start time and the main signal application time.

As described above, in the bubble communication system as shown in FIG. 2, the application of the preheat signal is started between the time t3 at which the ink re-covers the substantial heat generating portion on the heater after the ink is ejected and the meniscus recovery time t4. Therefore, it is understood that higher-speed recording is possible while maintaining the same ejection performance as the conventional method.

As is clear from the above description, when the normal temperature solid ink is ejected by the bubble jet method, the bubble communication method as shown in FIG. 2 is used.
Discharge performance superior to that using the discharge method shown in FIG. 1 can be obtained.

(Third Embodiment) In this embodiment, a water-based ink is used in a bubble communication type ejection method, and application of a preheat signal is started before the meniscus is restored. FIG. 13 is a schematic diagram showing the preheat signal P′1 and the main signal Pmain according to this embodiment.

In this embodiment, the ink having the following composition was used, and the ink was kept at about 40 ° C. when the ink was ejected.

Ink composition: Diethylene glycol 15.0% by weight Ethanol 5.0% by weight Water 78.0% by weight Dye (Cl.FB ₂ ) 2.0% by weight The ink jet head used in this embodiment is the same as that in the above-described embodiment. It is structurally the same as that used in 2.

When the drive signal shown in FIG. 13 was applied at 100 Hz, continuous ejection was possible, and at this time, the meniscus recovery time t6 was about 70 μsec. Further, after the bubble on the heater communicates with the outside air, the time t5 at which the ink covers the substantial heat-generating portion on the heater again is about 40 to 45 μsec.
Met.

That is, in the present embodiment, the preheat signal P'1 shown in FIG. 13 is set to the time ts = 60 μsec before the meniscus return time t6, whereby the time t6 is set.
Thereafter, it is possible to perform higher-speed recording while maintaining the same ejection performance as the conventional method of starting preheating.

In order to actually know the relationship between the application of preheat and the defoaming of bubbles and the return of meniscus, for example, in a head composed of an oscilloscope for measuring a preheating signal and a transparent material, defoaming and meniscus positions can be determined. It becomes possible by the strobe light emission trigger to be observed.

The present invention is not limited to the shape of the ink jet head of the above embodiment and other specific numerical values. Further, the specific composition of the ink is not limited to that described in the above embodiment, and for example, an ordinary temperature solid ink containing various compositions described in Japanese Patent Application No. 3-249217 already proposed by the present applicant can be used. You may choose as a discharge medium. For example, the water-based ink may contain various alcohols, additives such as surface active agents or pigment substances in a predetermined ratio.

Further, it is not necessary to limit the specific shapes and configurations of the pre-signal and the main signal to the above-described embodiment as long as they are in accordance with the idea of the present invention. Further, the pre signal and the main signal do not have to be limited to pulse signals. Further, it is possible to eject the liquid droplets by the main process composed of a plurality of signals and the rest time after the end of the preheating.

In view of the fact that the time required for refilling changes depending on the ink temperature, it may be possible to control the preheating start time according to the temperature of the inkjet head or the ink in the present invention in order to obtain more stable ejection. For example, it is conceivable to delay the preheat start time when raising the temperature.

The method of the present invention is also effective when preheating is performed by combining pre-signals having different waveforms such as pulse width and voltage value and different pause times of pre-signals, or when the voltage values of the pre-signal and the main signal are different. Is.

[0080]

As is apparent from the above description, according to the present invention, when ink is continuously ejected, before the position of the ink meniscus or the ink ejection port in the ink supply operation caused by the preceding ink ejection. By starting the subsequent preheating and immediately after or after the meniscus return, the main signal is applied to reduce the viscosity of the ink in the ink path by heating to a degree that does not cause ink deterioration, and the bubble pressure related to the unique physical properties of the ink material. It becomes possible to generate a larger bubble pressure for compensating for the low level of the ink, and to eject ink at higher speed without being restricted by the length of preheating.

Further, preferably, since the application of the main signal is carried out after the defoaming of the bubble relating to the preceding ink ejection, the bubble generation due to the application of the main signal is not hindered by the bubble relating to the preceding ejection.

As a result, it becomes possible to perform stable and high-speed ejection which could not be obtained by the conventionally known preheating operation.

In particular, the present invention is effective when a larger amount of heat energy is input for stable ejection, for example, a bubble jet method as a bubble communication ejection method or a bubble jet method that uses room temperature solid ink as an ejection medium.

[Brief description of drawings]

1A to 1F are schematic diagrams illustrating an example of an ink ejection process in a bubble jet method.

FIGS. 2A to 2F are schematic diagrams illustrating another example of an ink ejection process in the bubble jet method.

FIG. 3 is a schematic diagram showing a conventional example of an ejection signal for performing preheating.

FIG. 4 is a schematic diagram showing another conventional example of an ejection signal for performing preheating.

FIG. 5 is a schematic exploded perspective view for explaining the structure of a bubble jet type inkjet head.

FIG. 6 is a block diagram illustrating a control system of the inkjet recording apparatus according to the embodiment of the invention.

FIG. 7 is a schematic diagram showing ejection signals used in an embodiment of the present invention.

FIG. 8 is a diagram for explaining a moving state of a meniscus.

FIG. 9 is a diagram for explaining the application timing of the ejection signal according to the embodiment of the present invention.

FIG. 10 is a schematic diagram for explaining a process of disappearing bubbles on a heater.

FIG. 11 is a schematic diagram showing ejection signals used in another embodiment of the present invention.

FIG. 12 is a diagram for explaining application timings of ejection signals according to another embodiment of the present invention.

FIG. 13 is a schematic diagram showing an ejection signal used in still another embodiment of the present invention.

[Explanation of symbols]

 101, 201, 501, 1201 Heater 102, 202, 1202 Bubble 103, 203 Discharge port 104, 204 Meniscus 105, 205 Ink drop 106, 206, 1206 Ink path 507 Partition wall 508 Substrate 509 Liquid chamber 510 Supply port 511 Top plate 512 Main Controller 513 Frame memory 514 Head driver 518 Inkjet head 1219 Micro bubbles 1220 Rebound bubbles P1, P'1 First preheat signal Pmain Main signal

Claims (8)

[Claims] 1. A bubble is generated by using thermal energy generated by an energy generating element for ink having an ink ejection port and supplied to the vicinity of the ink ejection port, and the ink is ejected based on the generation of the bubble. In an inkjet device that ejects ink onto a medium using an inkjet head that ejects ink, in regard to the ink ejecting operation, at least one preheat signal that does not result in ink ejection and a main signal that leads to the ink ejection following the preheat signal. A time period from the start of applying the at least one preheat signal to the start of applying the main signal for one time of the ink ejection operation to Δt, the at least one preheat signal. From the start of application of the ink, the ink meniscus ejects the ink Jet apparatus characterized by time to time to substantially return Derutats2, the drive for the same ink discharge ports in Δts2 <Δt is made to. 2. The ink jet apparatus according to claim 1, wherein the application of the at least one preheat signal is started after the disappearance of the bubble related to the preceding ink ejection. 3. The ink jet head is an ink ejection system in which generated air bubbles communicate with the outside air through the ink ejection ports, and the start of application of the at least one preheat signal is ink supply generated by preceding ink ejection. The inkjet apparatus according to claim 1, wherein the ink covers at least a substantially heat-generating portion of the energy generating element during operation. 4. The ink according to claim 1, wherein the ink is in a substantially solid state at room temperature, and the ink is held in a state of being at least heated and melted when the ink is ejected. Inkjet device. 5. A bubble is generated by using thermal energy generated by an energy generating element with respect to ink having an ink ejection port and supplied to the vicinity of the ink ejection port, and the ink is ejected based on the generation of the bubble. In an inkjet recording method of ejecting ink onto a recording medium using an inkjet head that ejects ink, at least one preheat signal that does not result in ink ejection and a main signal that leads to the ink ejection subsequent to the preheat signal are used as the energy. Ink is ejected by applying it to the generating element, where Δt is the time from the start of applying the at least one preheat signal to the start of applying the main signal in one ink ejection operation, and the at least one preheat From the start of signal application, the ink meniscus is substantially at the ink ejection port. When the Derutats2 the time to return to the ink jet recording method characterized in that for driving the same ink discharge ports in Δts2 <Δt. 6. The ink jet recording method according to claim 5, wherein the application of the at least one preheat signal is started after the disappearance of the bubbles related to the preceding ink ejection. 7. The ink jet head is an ink ejection system in which generated air bubbles communicate with the outside air through the ink ejection ports, and the start of application of the at least one preheat signal is ink supply generated by preceding ink ejection. The ink jet recording method according to claim 5, wherein the ink has covered at least a substantially heat-generating portion of the energy generating element in operation. 8. The ink according to claim 5, wherein the ink is in a substantially solid state at room temperature, and the ink is held in a state of being at least heated and melted when the ink is ejected. Inkjet recording method.