JPH0410940A - Liquid jet method and recorder equipped with same method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention provides a liquid jetting method that can be suitably used for liquid jet recording in which recording is performed by making ejected liquid adhere to a recording medium using thermal energy. and a recording device using the method.

<Prior art> The liquid jet recording method, in which an image is formed by depositing a liquid or a solid recording medium (ink) that can be melted by heat onto a recording medium using thermal energy, is capable of high-resolution, high-speed printing. It has excellent features such as high recording quality, low noise, easy color image recording, the ability to record on plain paper, etc., and the ability to easily downsize the recording head and the entire device. are doing.

2. Description of the Related Art Many recording methods and apparatuses using the same are already known as recording methods in which recording liquid is ejected using thermal energy.

Among them, for example, JP-A No. 54-161935, JP-A No. 61-185455, JP-A No. 61-24
Publication No. 9768 discloses that by applying heat to the recording liquid (ink), the recording liquid is gasified or a bubble is generated in the recording liquid, and the gas or the gas forming the bubble is ejected together with the recording liquid. It describes how to perform the recording.

That is, Japanese Patent Laid-Open No. 54-161935 discloses that ink in a liquid chamber is gasified by a heating element, and the gas is ejected from an ink ejection port along with ink droplets.

Furthermore, in JP-A-61-185455, liquid ink filled in a small gap between a plate-shaped member having a small opening and a heating element head is heated by the heating element head, and the generated bubbles cause ink to flow through the small opening. As the drops fly,
It is shown that the gas forming the bubble is also ejected from the small opening to form an image on the recording paper.

Furthermore, Japanese Patent Application Laid-Open No. 61-249768 discloses a method in which bubbles are formed by applying thermal energy to liquid ink, and ink droplets are formed and flown based on the expansion force of the bubbles, and at the same time, the gas forming the bubbles is released. It is also described that an image is formed by ejecting it into the atmosphere from a large opening.

Further, according to the above-mentioned publications, it is possible to prevent clogging of orifices and openings by ejecting gas together with the recording liquid.

Furthermore, Japanese Patent Application Laid-Open No. 197246/1983 describes a recording device that uses thermal energy, in which ink supplied to a plurality of holes provided in a recording medium is heated by a recording head having a heat generating element to cover ink droplets. A recording device that makes a recording material fly is shown. However, in the recording apparatus, it is difficult to bring the heating element and the recording medium into complete contact with each other, and the thermal efficiency may not be as good as expected. Therefore, there were cases where it was not possible to adequately support high-speed recording. Further, although it is described that the pressure of the generated bubbles is used to make ink fly, the specific principles thereof are not disclosed, and therefore no guidelines for solving such problems are provided.

<Problems to be Solved by the Invention> However, in the above-mentioned JP-A-54-161935, JP-A-61-185455, and JP-A-61-249768, the gas forming bubbles is removed from ink droplets. Because the gasified ink is compressed into the atmosphere as it flies, it causes splashes and mist of the recording liquid, which can cause background stains on the recording paper and cause dirt inside the device. In some cases, problems such as

Furthermore, in the recording device described in JP-A-61-197246, it is difficult to bring the heating element and the recording medium into complete contact with each other, and the thermal efficiency may not be as high as expected. In addition, although it is described that the ink is ejected using the pressure of the generated bubbles, the specific principles etc. are not shown, so there are many I couldn't even get a concrete policy.

The present invention was made in view of the above-mentioned problems, and its purpose is to stabilize the volume and speed of ejected droplets, and further suppress the generation of splash and mist. In addition to preventing background smudges on images and dirt inside the device when used as a device, it also improves ejection efficiency, prevents clogging, and extends the life of the recording head, making it possible to print high-quality images. The purpose of this invention is to propose a liquid injection method.

〈Means for solving problems〉 A liquid jetting method of the present invention achieves the above object.

Bubbles are created by heating the liquid.

The liquid ejecting method for performing recording by ejecting at least a portion of the liquid using the bubbles is characterized in that the bubbles are communicated with the outside air under a condition that the internal pressure of the bubbles is equal to or lower than the outside air pressure.

A recording apparatus of the present invention that achieves the above object includes a recording head having an ejection port for heating ink with an ejection energy generating means to generate air bubbles and ejecting at least a portion of the ink using the air bubbles; A drive circuit for driving the ejection energy generating means so as to communicate the air bubbles with the outside air under the condition that the internal pressure of the air bubbles is lower than the outside air pressure, and is provided at a position where the ejection opening and the recording medium face each other. The platen is characterized in that it has a flat platen.

<Example> Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(e) are schematic cross-sectional views for explaining liquid ejection by the liquid ejecting method of the present invention, respectively.

In FIG. 1(a) to FIG. 1(e), 1 is a base, 2
3 is a heater, 3 is ink, 4 is a top plate, 5 is an ejection port, 6 is a bubble, 7 is a droplet, and 101 is a recording medium. In addition,
The liquid path is formed by the base 1, the top plate 4, and a wall (not shown).

FIG. 1(a) shows the initial state, in which the inside of the liquid path is filled with ink 3. Ink 3 First, when a current is instantaneously applied to the heater (for example, an electrothermal converter) 2 and the ink 3 near the heater is rapidly heated in a pulsed manner, bubbles 6 are generated on the heater 2 due to so-called film boiling of the ink. , it begins to expand rapidly (Fig. 1(b)). Further, the bubble 6 continues to expand, growing mainly toward the outlet port 5 side where the inertial resistance is smaller, and finally exceeds the outlet port 5, and the bubble 6 communicates with the outside air (FIG. 1(C)). At this time, the outside air is in equilibrium with the inside of the bubble 6 or flows into the bubble 6.

Until this moment, the ink 3 pushed out from the ejection port 5 continues to fly forward due to the momentum given by the expansion of the bubble 6, and finally becomes an independent droplet and lands on a recording medium 101 such as paper. (Fig. 1(d))
). Furthermore, the gap formed at the tip of the ejection port 5 side is supplied with ink 3 toward the right in the drawing due to the surface tension of the ink 3 at the rear and wetting with the member forming the liquid path (Fig. 1(e)), and returns to the initial state. return. The recording medium 101 is conveyed along the platen to a position facing the ejection port 5 by a platen, a roller, a belt, or any combination thereof. Alternatively, the recording medium 101 may be fixed and the ejection ports 5 may be moved (the recording head may be moved), or these may be combined. In short, the ejection port 5 and the recording medium are relatively movable,
A desired ejection port may be opposed to a desired position on the recording medium.

Now, in Fig. 1 (C), when the bubble 6 communicates with the outside air, there is no movement of gas between the outside air and the inside of the bubble, and in order for the outside air to flow into the bubble, the internal pressure of the bubble must be equal to the outside pressure. It is necessary to communicate the bubble with the outside air under conditions lower than or equal to

Therefore, in order to satisfy the above condition, ink is ejected as the second length increases, so that the graph of the relationship between the bubble internal pressure or volume and time becomes as shown in FIG. 2(b). That is, in FIG. 2(b), t=tb
The bubble may be communicated with the outside air at a time when (tl≦tb).

When a droplet is ejected under these conditions, compared to the case where the internal pressure of the bubble is higher than the outside pressure and the bubble is communicated with the outside air and the droplet is ejected (gas is ejected into the atmosphere), the ink is This prevents the recording paper and the inside of the device from becoming dirty due to mist and splash. Further, since the bubble is communicated with the outside air while the volume of the bubble increases, sufficient kinetic energy can be transmitted to the ink, resulting in the effect of increasing the ejection speed.

Furthermore, it is more desirable to communicate the bubble with the outside air under conditions where the internal pressure of the bubble is lower than the outside pressure because the above effect can be made more pronounced.

In other words, communicating the bubble with the outside air under conditions where the internal pressure of the bubble is lower than the outside air pressure will prevent the unstable liquid near the discharge port from scattering, which would occur if the bubble was connected under conditions where the internal pressure of the bubble was higher than the outside air pressure. Moreover, since the force of drawing the unstable liquid into the liquid path is stronger than when the pressures are equal, it is possible to discharge the liquid more stably and prevent unnecessary liquid from scattering. can be achieved.

The recording head used in the present invention is provided at a position where the heater 2 is close to the ejection port 5. This is the simplest method for communicating the bubble with the outside air.

However, simply moving the heater closer to the discharge port does not satisfy the above conditions of the present invention. Therefore, in order to satisfy the above conditions of the present invention, the amount of thermal energy generated by the heater (the configuration of the heater, the forming material, the driving conditions, the area, the heat capacity of the substrate on which the heater is installed, etc.), the physical properties of the ink, each part of the recording head, etc. By selecting the thickness (distance between the discharge port and heater, width and height of the discharge port and liquid path) as desired, the bubble can be communicated with the outside air in a desired state.

As mentioned above, the shape of the liquid path can be cited as a condition for achieving the present invention more effectively. Although the width of the liquid path shape is almost determined by the shape of the thermal energy generating element used, the specific relationship is only a rule of thumb. In the present invention, it has been found that the shape of the liquid path has a large effect on the growth of bubbles, and that it is effective for the above conditions in the liquid path.

In other words, it has been found that the communication state of the bubbles can be changed by utilizing the height of the liquid path. In order to be less susceptible to other influences such as the environment, and to achieve further stability, it is preferable that the height H of the liquid path is lower than the width W of the liquid path (H x W).

In addition, it is not possible to allow the bubble to communicate with the outside air when the volume is at least 70%, more preferably at least 80%, of the maximum volume of the bubble that would be reached if the bubble did not communicate with the outside air. This is preferable.

In addition to the conditions of the present invention, there is a condition in which the bubble communicates with the outside air under the condition that the first differential value of the moving speed of the tip of the bubble in the direction of the discharge port is negative, or a condition in which the bubble communicates with the outside air, or the discharge port side of the discharge energy generating means The distance β from the end of the bubble to the end on the side of the discharge port, and the distance Cゎ from the end of the discharge energy generating means opposite to the discharge port to the end of the bubble opposite to the discharge port are ff,
It is more preferable to communicate the bubble with the outside air under the condition that /ffI, ≧1, or both conditions.

Next, a method of measuring the relationship between the internal pressure of the bubble and the external atmospheric pressure will be explained.

Since it is difficult to directly measure the pressure inside the bubble, the magnitude relationship between the internal pressure of the bubble and the external pressure can be determined by the method described below or by appropriately combining these methods.

First, a method of determining the magnitude relationship between the internal pressure of the bubble and the external pressure by measuring the time change in the volume of the bubble or the volume of ink outside the ejection port will be described.

(Method of determining from the bubble volume) By measuring the bubble volume ■ during the time from when the ink starts foaming until the bubble communicates with the outside air, and finding the second derivative of ■ d"V/dt" It is possible to know the magnitude relationship between the internal pressure and external pressure of the bubble. That is, d
If ``V/dt''> 0, the internal pressure of the bubble is higher than the external pressure, and if d2V/dt''≦O, the internal pressure of the bubble is less than the external pressure. From t=to until t=t+, the internal pressure of the bubble is higher than the external pressure by <d"V/dt2>O, and 1 =
1 + time until the bubble communicates with the outside air 1 = 1
Until 1, the internal pressure of the bubble is less than the external pressure, and d” V/
dt2≦O. As mentioned above, the second derivative d” V of ■
/dt", it is possible to know the magnitude relationship between the internal pressure of the bubble and the external pressure.

Note that in this case, it is necessary that the bubble be visible from the outside of the recording head. In order to observe bubbles from the outside of the print head, it is desirable that a portion of the print head be formed of a transparent member so that bubble formation, growth, etc. can be observed from the outside of the print head. If the constituent members of the recording head are non-transparent, for example, the top plate of the recording head or the like may be replaced with a transparent member. At this time,
It is desirable to select the same hardness, elasticity, etc. of the replaced member and the replaced member as much as possible.

As for replacing components, if the top plate of the recording head is made of metal, opaque ceramic, or colored plastic, for example, it may be replaced with transparent plastic (for example, transparent acrylic), glass, etc. The replacement location and the materials used therein are not limited to those described above. .

However, in order to avoid differences in foaming properties due to differences in the physical properties of the members, it is desirable to select a material whose physical properties, such as wettability to ink, are as close to those of the original member as possible. Whether or not the foamed state is equivalent to that of the original member can be confirmed by discharging it and checking whether the discharge speed and discharge volume are the same as the original state.

If it is made of a transparent member in advance, the above operation is not necessary.

Furthermore, even if the constituent members of the recording head are not replaced with other members, or even if the constituent members of the recording head cannot be replaced, the magnitude relationship between the internal pressure and external pressure of the bubble can be determined by the following method. .

(Method of determining from the volume of ejected ink) During the time from the start of bubbling until the ink droplets fly, measure the volume of ink ejected outward from the ejection port (6),
■Second derivative of d”V.

/d t", it is possible to know the magnitude relationship between the internal pressure of the bubble and the external pressure. That is, d2Va /d
If t” > O, the internal pressure of the bubble is higher than the external pressure,
If a tv a / dt ”≦0, the internal pressure of the bubble is less than the external pressure. Figure 2 (d) shows that when the bubble is communicated with the internal pressure higher than the external pressure, the bubble pops out from the discharge port. -th differential dV, /d of the volume of ink ■.
The diagram shows the time change of t, and the start of foaming t = t
The time it takes for the bubble to communicate with the outside air from o = 1. Until, the internal pressure of the bubble is higher than the external pressure (, d” Vd
/dt"> O. On the other hand, Fig. 2(e) shows the time change of the first derivative dV, /dt of ■ when the bubble is communicated with the outside air with the internal pressure of the bubble being lower than the outside pressure. From the same figure, the internal pressure of the bubble is higher than the external pressure until 1=1+ from the start of foaming t = t o.
” Va /d, t” > o, but t ” t +
Therefore, until t=tIl, the internal pressure of the bubble is lower than the external pressure, and d' Va /dt''≦0.

As described above, by obtaining the second derivative d''V, , /dt'' of V, the magnitude relationship between the internal pressure of the bubble and the external pressure can be known.

A method for measuring the volume Vd of ink existing outside the ejection port will be explained. The shape of the droplet at each time after ejection can be determined using a microscope 3 while illuminating the droplet ejecting from the ejection port using a light source β1 such as a strobe, LED, or laser.
It can be measured by observing at 2. In other words, by emitting pulsed light in synchronization with the drive pulse of a recording head that is continuously discharging at a constant frequency and with a predetermined delay time, a unidirectional recording after a predetermined period of time has elapsed from the ejection. It is possible to measure the projected shape of a droplet as seen from above. At this time, the measurement can be performed more accurately if the pulse width of the pulsed light is as small as possible within a range that can ensure a sufficient amount of light for measurement. Although it is possible to roughly estimate the droplet volume from this unidirectional measurement, it is desirable to measure it by the following method in order to obtain it more accurately.

As shown in Figure 3, the ejection direction of the droplet is set to X, and as described above, the droplet is projected simultaneously from two directions, y, z, orthogonal to the X axis while illuminating with pulsed light. Measure the shape using a microscope.

At this time, the measurement direction y or Z using the microscope is preferably parallel to the direction in which the ejection ports are arranged. Regarding one image measured in this way from two directions, Fig. 4(a) and Fig. 4(
As shown in b), the width a (
x), b(x). By calculating from these values according to the following equation, the volume Vd of the droplet after a predetermined time can be determined. Note that this formula is y
The −z cross section is approximated by an ellipse, and can be determined with sufficient accuracy for calculating the volume of droplets and bubbles described below.

■, = (π/4) S a(x)-b(x)dx
Furthermore, by changing the lighting delay time of this pulsed light sequentially from O, it is possible to determine the change in Vd after application of the drive pulse.

The bubble volume in the liquid path can also be measured by applying the method described above.

As described above, after the bubbles in the liquid path are made observable, the projected shape is measured from two directions while being illuminated with pulsed light, similar to the droplet volume measurement method described above, and the above calculation formula is applied. Its volume can be found.

Since the behavior of droplets and bubbles both require a time resolution of about 0.1 μsec, infrared LEDs are used as pulsed light sources.
Using a pulse width of 50 nsec, connect an infrared camera to the microscope to capture an image, calculate the above a (x) and b (x) from the image, and measure by applying the above calculation formula. Bye.

In addition to the above, it is also possible to know the magnitude relationship between the internal pressure of the bubble and the external pressure from the airflow.

(Method of determining from airflow (gas movement)) A method of detecting airflow (gas movement) caused by the pressure difference inside and outside the bubble at the moment of communication between the bubbles will be explained.

In order to find out the magnitude relationship between the internal pressure of a bubble and the external pressure from the airflow, there are two methods: installing a minute tuft near the discharge port and observing the movement of the tuft caused by changes in the airflow using a microscope, and Changes in air density near the exit are measured using the Schlieren method, Matsuha-Zehnder interferometry,
A detection method using an optical method such as a hologram method can be used.

Using these methods, if an airflow is observed from the liquid path side to the outside at the moment the bubble communicates with the outside air, this indicates that the bubble has communicated with the internal pressure higher than the outside pressure, and the inside of the liquid path If airflow flowing into the bubble is observed, it indicates that the bubble has communicated with the internal pressure lower than the external pressure.

Next, one configuration of a recording head suitably used in the present invention will be described.

FIGS. 5(a) and 5(b) show a schematic assembled perspective view and a schematic top view of one suitable recording head. In addition,
FIG. 5(b) shows a state in which the top plate shown in FIG. 5(a) is not provided.

The structure of the recording head shown in FIGS. 5(a) and 5(b) will be briefly described.

In the recording head shown in FIGS. 5(a) and 5(b), a wall 8 is provided on a base 1, a top plate 4 is joined to cover the wall 8, and a common liquid chamber 10 and A liquid path 12 is formed. The top plate 4 has a supply port 11 for supplying ink.
is provided, and ink can be supplied into the liquid path 12 through the common liquid chamber 10 with which the liquid path 12 communicates.

Furthermore, heaters 2 are provided in the base 1, and liquid paths are provided corresponding to each of these heaters 2. Heater 2
has a heating resistor layer and an electrode (both not shown) electrically connected to the heating resistor layer, and is energized by this electrode in accordance with a recording signal. This energization causes the heater 2 to generate thermal energy, which can be applied to the ink supplied into the liquid path. This thermal energy can generate bubbles in the ink according to the recording signal.

Further, another configuration of the recording head suitable for use in the present invention will be explained.

FIGS. 6(a) and 6(b) show a schematic cross-sectional view and a schematic plan view of the recording head, respectively. The difference between this print head and the print head shown in Fig. 5 is that in the print head shown in Fig. 5, the ink supplied into the liquid path is ejected straight or substantially straight along the liquid path. In contrast, in the case shown in Figure 6, the supplied inlet is bent along the liquid path (in the figure, one outlet is formed directly above the heater). ).

In addition, in FIG. 6(a) and FIG. 6(b), the fifth
The same numbers as shown in FIG. 5(a) and FIG. 5(b) refer to the same components.

In FIG. 6(a) and FIG. 6(b), 16 is an orifice plate in which discharge ports 5 are formed, and here, the wall 9 provided between each discharge port 5 is also formed integrally. There is.

The present invention will be explained below using specific examples.

[Example 1] In this example, a recording head shown in FIG. 5 was used. In this embodiment, the top plate 6 is made of glass. In addition, the dimensions of the liquid path 12 and the heater 2 of the recording head used are such that the height of the liquid path 12 is 20 μm + the width − is 5 μm.
The size of the heater was 28 μm wide x 18 μm long, and the position where the heater was provided was 20 μm long from the end of the heater 2 closest to the discharge port to the discharge port.

48 liquid channels 12 were arranged at a density of 360 channels per inch.

To this recording head, C, 1, Food black 2 3.0% by weight diethylene glycol 15.0% by weight N-methyl-2-pyrrolidone 5.0% by weight ion-exchanged water 77.
0% by weight of each component was stirred in a container, mixed and dissolved uniformly, and then filtered through a Teflon filter with a pore size of 0.45 μm.The resulting ink had a viscosity of 2.0 cps (at 20°C). An attempt was made to supply the liquid to the liquid chamber 10 from the port 11 and discharge it.

When driving the heater 2 of the recording head, a pulsed electric signal was applied to the heater 2. Also, the voltage of the applied pulse wave was 9. The OV and pulse width were set to 5.0 μsec, and this was applied to the heater 2 at a frequency of 2 kHz.

First, when we used a strobe microscope to observe the situation in which ink was ejected from successive ejection ports 5 among the ejection ports 5, we found that bubbles generated by heating communicated with the outside air about 2 μSec after the start of bubbling. The situation was confirmed.

Further, the volume (6) of the ink ejected from the ejection port and the first derivative dV, /dt of the volume (2) of the ink show temporal changes as shown in FIG.
Second derivative of the volume of the bubble from 5 μsec until the bubble communicates with the outside air after about 2 μsec d” V, +
/dt" was negative, and it was confirmed that the bubble internal pressure was lower than the external pressure.

Separately, when looking at the magnitude relationship between the bubble's internal pressure and the external pressure based on the bubble's volume V, the relationship d"V/dt"≦0 is also satisfied in this case, indicating that the bubble's internal pressure is less than the external pressure. confirmed.

Incidentally, the volume of the flying droplets at this time was within the range of 14±1 pβ together with the volume of the flying droplets discharged from each discharge port 5. Furthermore, the speed of the flying droplets is approximately 14 m/sec.
c, which was sufficient to record excellent flight speed.

Then, an electric signal is applied to the six heaters 2 in the front so that a checkered pattern is formed for each pixel, and the ink is ejected.
1 When it was attached to recording paper, a desired checkered pattern with no uneven printing was drawn on the recording paper. When this image was enlarged and observed, it was clear that there was no excess ink scattering or background smearing.

[Example 2] Next, image formation was performed using the recording head shown in FIG. 6. Note that in this example, transparent glass was used as the orifice plate 14.

In this example, the discharge port 5 is a circle with a diameter of 36 μm on the surface side of the orifice plate, and the length from the heater surface to the discharge port is 20 LLm.
4 μm x 24 μm, number of discharge ports per inch: 36
48 discharge ports were arranged at a density of 0.

The same ink as in Example 1 was supplied to this recording head, and ejection was attempted.

The heating conditions for the heater 12 of the recording head are 7. OV, 4.
．． It was set to 5 μsec and was driven at 2 KHz.

First, when ink was ejected from 16 consecutive ejection ports 5 out of the ejection ports 5 and observed using a strobe microscope, it was found that about 2.5 seconds after the start of foaming. After 1 μsec, it was confirmed that the bubbles generated by heating were communicating with the outside air.

In addition, the bubble volume V and the first derivative dV/dt of the bubble volume (■) from the start of foaming until the bubble communicates with the outside air show changes over time as shown in FIG. It was confirmed that the second derivative of the bubble volume d" V/dtt from 5 μSeC until the bubble communicated with the outside air after about 2.1 μSeC was negative, and the bubble internal pressure was lower than the outside pressure.

Further, when the volume of the flying droplets at this time was measured, it fell within the range of 18±lpl for each nozzle. Additionally, the droplet speed was approximately 10 m/sec.

Therefore, in the same manner as in Example 1, an electrical signal was applied to the 16 heaters 2 to form a checkered pattern for each pixel, and ink was ejected and deposited on the recording paper. The desired checkerboard pattern was drawn without any blemishes. When this image was enlarged and observed, it was clear that there was no excess ink scattering or background smearing.

[Example 3] Using the recording head used in Example 1, C, 1, Direct Black 1543.5% by weight glycerin
, 5.0% by weight diethylene glycol 2
After stirring each component consisting of 5.0% by weight polyethylene glycol 28.0% by weight (average molecular weight 300) and 38.5% by weight ion-exchanged water to uniformly mix and dissolve,
The magnitude relationship between the bubble internal pressure and the external pressure was measured in the same manner as in Example 1, except that ink with a viscosity of 10.5 cps (20°C) obtained by filtration with a Teflon filter with a pore size of 0545 μm was used, and the ink discharge was measured. I did it. As a result, it was found that in this example as well, the bubble communicates with the outside air in a state where the internal pressure of the bubble is lower than the outside pressure when the bubble communicates with the outside air. Although the ink ejection speed was 7 ml sec, which was lower than in Example 1, the ejection itself was extremely stable.

[Examples 4 to 12] Recording was performed by using a recording head with a bent liquid path similar to the recording head used in Example 2, and by supplying the same ink as in Example 2.

Table 1 shows the outline of each recording head and the ejection results. Further, schematic diagrams of each recording head are shown in FIGS.

As can be seen from Table 1, the volume of the ejected liquid and the ejection speed of the droplets were extremely stable in all cases, and the recording was also extremely excellent.

[Examples 13 to 15] Recording was carried out by using a recording head in which the liquid path was not bent, similar to the recording head used in Example 1, and by supplying the same ink as in Example 1.

Table 2 shows an outline of each recording head and the ejection results. Further, schematic diagrams of each recording head are shown in FIGS.

As can be seen from Table 2, the volume of the ejected liquid and the ejection speed of the droplets were extremely stable in all cases, and the recording was also extremely excellent.

[Comparative Example 1] For the recording head shown in FIG. 5, the end face of the heater 2 on the ejection port side was placed at a position 3 μm from the ejection port 5, and the bubble communicated with the outside air in a state where the bubble internal pressure was higher than the outside air pressure. A recording head thus constructed was manufactured and the recording state was evaluated.

When this recording head was supplied with each of the inks used in Example 1.2 and driven to perform checkered pattern recording in the same manner as in Example 1.2, the ejection itself was able to be performed. However, continuous and stable ejection was not achieved. Furthermore, when the image recorded on the recording paper was observed, it was found that the image had many fine background stains, so this phenomenon was analyzed in more detail.

First, as in Example 1, we used a strobe microscope to observe the process from when a bubble is formed by heating the heater 2 to when a droplet is ejected from the ejection port 5. Droplets were ejected due to the bubbles formed. However, this droplet was not a droplet like in Example 1, but a collection of many minute droplets 21 as shown in FIG. The remaining ink without being given momentum blocks the ejection port 5. At this time, the inside of the nozzle is once in communication with the outside air, so the second
As shown in FIG. 0(b), air 22 became bubbles and was taken into the nozzle and remained there. No droplets were ejected in this state.

In addition, the volume V of the bubble from the time the bubble is formed until it communicates with the outside air, the first derivative d of the bubble volume V,
V/dt shows a time change as shown in Figure 21, and the second derivative d2V/dt'' of the volume until the bubble communicates approximately 2.1 μsec after the start of foaming is positive, and the internal pressure of the bubble is equal to the external pressure. It was confirmed that the pressure was higher than the atmospheric pressure.

[Comparative Example 2] Using the recording head (FIG. 5) and ink used in Example 1, 6. When ejecting was attempted by applying a pulse of 500 μsec and driving at 20 Hz, continuous ejection of droplets was observed.

However, when the image on the recording paper was observed, it was found that the image had a lot of background stains. We analyzed this phenomenon in more detail.

As in Example 1, when the process from bubbles being formed by the heating of the heater 2 to droplets being ejected from the ejection port 5 was observed using a strobe microscope, it was found that a large number of bubbles were generated within the liquid path 12. Furthermore, it was observed that micro droplets were ejected in the form of a mist along with the ejection of the main droplets.

Furthermore, when the driving frequency was increased to 1 kHz, the discharge stopped immediately.

<Effects of the Invention> As explained above, according to the liquid ejection method of the present invention, the generated bubbles are communicated with the outside air and the droplets are ejected, so the volume of the droplets is always stabilized and high-quality images can be produced. Obtainable.

In addition, since the pressure inside the bubble is lower than the outside pressure when communicating with the outside air, the gas inside the bubble is prevented from blowing out, resulting in dirt on the recording paper due to mist and splash, and the inside of the device. can prevent stains.

Furthermore, since the kinetic energy of the bubbles can be sufficiently transmitted to the ink, ejection efficiency is increased and clogging can be eliminated. Furthermore, since the droplet ejection speed is improved, the droplet ejection direction is stabilized, and the distance between the recording head and the recording paper can be increased, which facilitates device design.

Furthermore, since there is no defoaming process for generated bubbles, the phenomenon of heater destruction due to defoaming is eliminated, and the life of the recording head is improved.

Note that the liquid ejection method of the present invention is applicable to both the so-called on-demand type and continuous type, but in particular, in the case of the on-demand type, it is possible to Thermal energy is applied to the electrothermal transducer by applying at least one drive signal corresponding to recorded information to the electrothermal transducer disposed corresponding to the path and providing a rapid temperature rise exceeding nucleate boiling. This is effective because it generates film boiling on the heat-active surface of the recording head, resulting in the formation of bubbles in the liquid (ink) in one-to-one correspondence with this drive signal.

The recording head using the liquid ejection method of the present invention is not limited to those described in the above embodiments,
Many forms and modifications are conceivable, such as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus. Further, as a full-line type recording head, it may be configured to satisfy the length by combining multiple recording heads, or it may be configured as a single recording head formed integrally. The invention can more effectively exhibit the effects described above.

In addition, a replaceable chip-type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a chip-type recording head that is installed integrally with the recording head itself. The present invention is also effective when a cartridge type recording head is used.

Further, in addition to the recovery means for the recording head as described above, which is provided as a component of the recording apparatus of the present invention, it is preferable to add a preliminary auxiliary means etc., since this further stabilizes the effects of the present invention. It is something. These include, for example, cleaning means, preheating means for the recording head by means of an electrothermal transducer or a separate heating element, or a combination thereof. Furthermore, it is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the recording mode of the recording device is not limited to a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; Full color (
The present invention is also extremely effective for devices equipped with both.

[Brief explanation of drawings]

Figures 1(a) and 1(b) are schematic cross-sectional views for explaining the discharge state of the present invention, and Figures 2(a) to 2(e) are diagrams showing the internal pressure and volume of the bubble. A diagram explaining changes over time,
FIG. 3 is a schematic diagram for explaining the method of measuring droplet volume;
4(a) and 4(b) are schematic explanatory views of the ejected liquid seen from above and from the side, respectively, and FIG. 5 is an illustration of the recording head used in one embodiment of the present invention. FIG. 6 is a diagram illustrating a recording head used in another embodiment of the present invention.
Figure 7 is a diagram for explaining the change in bubble volume over time.
8(a) and 17(a) are schematic perspective views for explaining the recording head of the embodiment of the present invention, FIG. 8(b) to FIG. 16, and FIG. 17(b) to FIG. FIG. 19 is a schematic diagram for explaining the recording head of the embodiment of the present invention, and FIG. 20 (
a) and FIG. 20(b) are schematic cross-sectional views for explaining the comparative example, and FIG. 21 is a diagram for explaining the change in bubble volume over time in the comparative example. 11... Ink supply port. 12...Liquid path 1...Substrate, 2...Heater 3...Ink, 4...Top plate 5...Kiyaguchi,
7...Droplet゛8...Whole, 10.
...liquid chamber IO+ 6 flashes (α) (b) O! (b) Section a Section B Section Z Section a Section a Section S section 4.2 Day 13 O Section A Section ? A-section B-section procedural amendment (method) August 80, 1990 2゜3゜1990 Patent Application No. 112832 Name of the invention Liquid injection method and a case involving a person who corrects a recording device using the method Related Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100
) Canon Co., Ltd. Representative: Keizo Yamaji 44, Agent address: Canon Co., Ltd., 3-30-2 Shimomaruko, Ota-ku, Tokyo 146 (telephone: 758-2111) July 31, 1990 6, Subject of amendment: Specification 7, Contents of amendment (1) [Figure 1 (a) and Figure 1 (b)] on page 37, line 18 of the specification [Figure 1 (a) to Figure 1 (e)] ” he corrected. (2) “Figure 4 (
a) and Fig. 4(b)” to “Fig. 4(a) to Fig. 4(
C)”. (that's all)

Claims (2)

[Claims] (1) In a liquid ejecting method in which air bubbles are generated by heating ink and recording is performed by ejecting at least a portion of the ink using the air bubbles, the air bubbles are removed from the outside air under conditions where the internal pressure of the air bubbles is lower than the outside pressure. A liquid injection method characterized by communicating with. (2) A recording head having an ejection port for heating ink using an ejection energy generating means to generate bubbles and ejecting at least a part of the ink using the bubbles, and a recording head having an ejection port for ejecting at least a part of the ink by ejecting the air bubbles; A recording device comprising: a drive circuit for driving the ejection energy generating means to communicate the bubbles with outside air; and a platen provided at a position where the ejection port and the recording medium face each other. .