JP2002254644A - Liquid ejection method, liquid ejection head, and liquid ejection recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection method, a liquid ejection head and a liquid ejection recorder capable of uniforming the volume of liquid to be ejected as liquid drop regardless of a temperature rising, for example, stably recording a high quality image when recording an image using the liquid drop. SOLUTION: In the lowest temperature of an operation environment to eject ink 3 in a flow channel 10 from an ejection orifice 5, that is, in the lowest temperature wherein the liquid ejection head executes a normal liquid ejection operation, a bubble 6 is deformed so as to make a part of the bubble 6 come in contact with the orifice end 5a at the flow channel 10 side of the ejection orifice 5, then the bubble 6 is made to be communicated with the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid discharge method for discharging a liquid by using thermal energy, a liquid discharge head, and a liquid discharge recording apparatus.

[0002]

2. Description of the Related Art A liquid discharge recording method for recording an image by discharging a liquid from a discharge port by thermal energy and attaching the discharged liquid to a recording medium is described below.
It is capable of high resolution and high speed recording, and has high recording quality and low noise. In addition, it can be easily developed as a recording method of a multi-color image and can be recorded on plain paper. Various contrivances have been made on such a liquid discharge recording method from the past to the present.

For example, Japanese Patent Application Laid-Open No. 4-10941 describes a method for stabilizing the volume of ink droplets when the ink droplets are ejected from ejection openings by utilizing the foaming energy of bubbles. Have been. That is, under the condition where the first derivative of the moving speed of the tip of the bubble in the ejection direction is negative, the bubble is communicated with the atmosphere, thereby ejecting ink droplets and recording an image. According to this method, a heating resistor (hereinafter, also referred to as a “heater”) that generates bubbles in ink by generated thermal energy and an ejection port are opposed to each other, and the distance between them is shortened. Therefore, the ratio of the work amount of the bubble to the electric energy applied to the heater is better than that of the liquid ejection method in the previous recording method. Further, since almost all of the ink between the heater and the discharge port is discharged, the volume of the discharged ink is said to be stabilized.

[0004]

In the above-mentioned proposed method, the bubble is communicated to the atmosphere under the condition that the first derivative of the moving speed of the tip of the bubble in the discharge direction is negative,
An image is recorded by discharging ink. In a case where the ink discharge amount is stabilized by such a method so as to discharge almost all of the ink between the heater and the discharge port, it is not always possible to secure a stable ink discharge amount with respect to a temperature change. I understand that.

That is, as the temperature of an ink jet recording head (liquid ejection head) rises, the ink physical properties such as the density, viscosity and surface tension of the ink generally decrease, so that the ink tends to flow. At the same time, the foam in the foamed ink also easily expands, and the ink ejection amount increases. In order to print a high-quality image, it is essential to stably eject a small amount of ink droplets in a uniform amount, and the phenomenon that the ink ejection amount increases as the temperature rises becomes a serious problem.

According to the study of the present inventor, the main factor of the increase in the ink ejection amount due to the rise in the temperature of the ink jet recording head (increase in the temperature of the ink) is the easiness of the growth of bubbles, especially the ejection of the ink. It has been found that there is an increase in the displacement of the bubble surface in the ink ejection direction at the outlet portion.

[0007] Generally, fluctuations in the amount of ejected ink that fluctuate due to temperature changes are evaluated using an index called a "temperature coefficient". That is, the ink ejection amount V at the temperature T1 (° C.)
Assuming that the ink ejection amount Vd2 (picoliter) at d1 (picoliter) and temperature T2 (>T1; ° C.), a numerical value TC (unit:%) defined by the following equations (1) and (2)
/ ° C) is the temperature coefficient.

TC = ΔVd / Vd1 / (T2−T1) × 100 (1) ΔVd = Vd2−Vd1 (2)

The temperature T1 is the lowest temperature of the operating environment in which the ink is ejected from the ejection port, that is, the lowest temperature at which the liquid ejection head performs a normal ejection operation. The temperature T2 is a temperature within a temperature range of an operating environment in which the ink is ejected from the ejection port. In the case of a recording head that ejects small droplets of 10 picoliters or less, it is convenient for high-quality recording that the temperature coefficient TC is 0.75 or less, preferably 0.65 or less. Further, in order to print a higher definition image, the ink ejection amount is set to 8
It is preferred to be picoliter or less.

The present invention has been made in view of such a problem, and an object thereof is to make the volume of a liquid to be discharged as droplets uniform regardless of a rise in temperature. It is an object of the present invention to provide a liquid discharge method, a liquid discharge head, and a liquid discharge recording apparatus capable of stably recording a high-quality image when recording an image using droplets.

[0011]

According to the liquid discharge method of the present invention, a liquid in which a liquid in the flow path is discharged from a discharge port by forming bubbles in the liquid in the flow path by thermal energy of a heating element. In the discharge method, at the lowest temperature of the operating environment in which the liquid in the flow path is discharged from the discharge port, the bubble is formed so that a part of the bubble contacts the opening edge of the discharge port on the flow path side. The method includes a step of deforming, and a step of communicating the air bubbles with the atmosphere after the step.

In the liquid discharge head of the present invention, the liquid in the flow path is formed by forming bubbles in the liquid in the flow path communicating with the discharge port by the heat energy of the heating element provided on the substrate. In the liquid discharge head that discharges from the discharge port, a part of the bubble is brought into contact with the opening edge of the discharge port on the flow path side at the lowest temperature of the operating environment in which the liquid in the flow path is discharged from the discharge port. After the bubble is deformed, the bubble and the atmosphere communicate with each other.

[0013] A liquid discharge recording apparatus of the present invention comprises a moving means capable of relatively moving the liquid discharge head and a recording medium on which an image can be recorded by liquid discharged from the liquid discharge head; And a drive circuit for providing a drive signal to the heating element of the liquid ejection head.

According to the present invention, at the lowest temperature of the operating environment in which the liquid in the flow path is discharged from the discharge port, that is, at the lowest temperature at which the liquid discharge head performs a normal liquid discharge operation, the flow path side opening edge of the discharge port. The air bubbles are deformed so that some of the air bubbles come into contact with the air, and then the air bubbles are communicated with the outside air. As a result, even if the temperature of the liquid discharge head rises (the temperature of the ink also rises) and the bubbles easily expand, some of the bubbles come into contact with the opening edge of the discharge port on the flow path side. Suppress the expansion of bubbles. As a result,
The displacement of the bubble surface in the ejection port in the ejection direction of the liquid is suppressed, and the increase in the ejection amount of the liquid due to the temperature change is suppressed.

When recording an image on a recording medium by discharging small droplets of 10 picoliter or less, the temperature coefficient T
It is convenient for high-quality recording that C is 0.75 or less, preferably 0.65 or less. Further, in order to record a higher definition image, it is preferable that the ejection amount of the liquid is 8 picoliter or less. Further, it is preferable that the time from the formation of the bubble to the contact of a part of the bubble with the opening edge of the discharge port on the flow path side is within 3 μsec. More preferably, the time from when the heating element generates heat to when some of the bubbles come into contact with the opening edge of the discharge port on the flow path side is 2 hours.
Set within μsec.

[0016]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. First, the principle of liquid ejection in the present invention will be described.

(Principle of discharging liquid) FIGS. 1 (a) to 1 (f)
FIG. 1 is a schematic cross-sectional view of a liquid discharge head for describing a liquid discharge principle in the present invention.

In these figures, 1 is a substrate, 2 is an electrothermal converter (hereinafter also referred to as a “heater”) as a heating element,
Reference numeral 3 denotes ink as a liquid to be discharged, 4 denotes an orifice plate, 5 denotes a discharge port, 6 denotes a bubble, 7 denotes an ink droplet as a discharged liquid droplet, and 8 denotes an ink liquid column. An ink flow path 10 as a flow path is formed between the substrate 1 and the orifice plate 4, and a partition (not shown) is provided between the plurality of flow paths 10. The heater 2 is provided on the substrate 1 so as to face the discharge port 5, and a protective film or the like is formed on the surface of the heater 2. The ink 3 is supplied into each flow channel 10 from above in FIG. In the upper part of FIG.
A common liquid chamber communicating with each channel 10 may be provided, and ink may be supplied to each channel 10 from the common liquid chamber.

FIG. 1A shows an initial state in which the inside of the liquid flow path 10 is filled with the ink 3. When an electric signal corresponding to a recorded image is applied to the heater 2, the heater 2 generates heat.
As shown in (b), bubbles 6 are generated in the ink 3 near the heater 2. Then, due to the volume change (expansion) of the bubble 6, the ink liquid column 8 protrudes from the ejection port 5. Thereafter, the bubble 6 expands and grows until a part of the bubble 6 comes into contact with the opening edge 5 a of the discharge port 5 provided in the orifice plate 4 on the side of the flow path 10. Part of the bubble 6 is the discharge port 5
After contacting the opening edge 5a on the side of the flow path 10, the tip of the bubble 6 may grow further outward through the opening of the discharge port 5, as shown in FIG.

Thereafter, due to the balance between the volume (mass) of the portion of the ink liquid column 8 protruding outward from the discharge port 5 and the internal pressure of the bubble 6, the bubble 6 turns over and starts to collapse (FIG. 1 (d)). ). Eventually, the ink liquid column 8 flies as several ink droplets 7 and lands on a recording medium to form ink dots, as shown in FIG. An image is recorded by the ink dots. Thereafter, the ink 3 is replenished into the flow channel 10 (FIG. 1F), and the flow returns to the initial state.

By communicating the bubble 6 with the outside air in this way, it is possible to suppress rapid pressure fluctuation due to the defoaming of the bubble 6,
It is also possible to prevent an adverse effect due to the cavitation phenomenon accompanying the pressure fluctuation, that is, the occurrence of damage in the flow path 10. Further, before the bubbles 6 are communicated with the outside air in this manner, as shown in FIG.
Is extremely effective in making the volume of the ink droplet 7 uniform and stably recording a high-quality image, as described later.

The bubble 6 forms the opening edge 5 of the discharge port 5 on the side of the flow path 10.
The following method can be employed for detecting whether or not the contact has been made with the “a” and measuring the time when the contact has been made. Basically, pulse light such as a strobe, an LED, or a laser is applied to the bubble 6 from the outside or the side of the orifice plate 4 of the liquid discharge head, and observation is performed with a microscope or the like. In order to evaluate whether or not the bubble 6 has contacted the opening edge 5a of the discharge port 5 and to evaluate the time of contact, the microscope is focused on the opening edge 5a of the discharge port 5 in advance, and the orifice plate 4 Can be observed from the upper surface of the discharge port 5, and the bubble 6
When the surface starts to contact (approach), the surface of the bubble 6 can be clearly observed. The contact time between the bubble 6 and the opening edge 5a can be evaluated by the time when the surface of the bubble 6 looks clear.

(First Embodiment) FIGS. 2 to 5 are diagrams for explaining an example of the configuration of an ink jet recording apparatus (liquid ejection recording apparatus) capable of ejecting ink using the above-described liquid ejection principle. It is.

FIG. 4 is a perspective view for explaining a schematic configuration of the recording apparatus of this embodiment. The printing apparatus of this example is a printing apparatus of a serial scan system. Reference numeral 100 denotes a carriage for detachably mounting a recording head 110 (see FIG. 5) as a liquid ejection head. The recording heads 110 of this example are mounted in four types according to the type of the color of the ink as a liquid. Each head 110 has a yellow ink tank 101Y, a magenta ink tank 101M, a cyan ink tank 101C, and a black ink tank 101C. It is mounted on the carriage 100 together with the tank 101B.

The carriage 100 includes a guide shaft 10
2 and is reciprocally movable in the direction of arrow A on the guide shaft 102 by an endless belt 104 driven in a forward or reverse direction by a motor 103. Endless belt 104 is wound between pulleys 105 and 106.

A recording sheet P as a recording medium is intermittently conveyed in a direction indicated by an arrow B perpendicular to the direction indicated by an arrow A. Recording paper P
Is a pair of roller units 107 and 108 on the upstream side,
The recording head 11 is nipped by a pair of downstream roller units 109A and 109B and is applied with a constant tension.
It is conveyed while ensuring flatness with respect to zero. The application of the driving force to each roller unit is performed by the driving unit 111, but the driving unit may be used to drive the roller unit.

The carriage 100 stops at the home position as needed at the start of printing or during printing. At this position, a cap member 112 for capping the ejection port surface of each recording head 110 is provided. The cap member 112 is forcibly sucked into the ejection port on the ejection port surface and clogged in the ejection port. Is connected to suction recovery means (not shown) for preventing the above.

FIG. 5 is a schematic block diagram of a control system of such a recording apparatus. The recording device receives the record information from the host computer 300 as a control signal. The recording information is stored in an input / output interface 301 inside the recording apparatus.
At the same time, the data is converted into data that can be processed in the printing apparatus, and is input to the CPU 302 which also serves as a print head drive signal supply unit. The CPU 302 is a ROM
303 based on the control program stored in the
Data (image data) to process and record the data input to U302 using a peripheral unit such as RAM 304
Convert to

Further, the CPU 302 generates drive data of a drive motor 306 for moving the recording paper P and the recording head 110 in synchronization with the image data so as to record the image data at an appropriate position on the recording paper P. . The image data and the motor drive data are respectively stored in the head driver 307
And the recording head 11 via the motor driver 305.
0 and the drive motor 306, whereby an image is formed at a controlled timing. FIG. 2 is a plan view of a main part of the recording head 110 in this example, and FIG. 3 is a cross-sectional view taken along the line III-III of FIG. In FIGS. 2 and 3, FIGS. 1A to 1F described above are used.
The same reference numerals are given to the same parts in the recording head, and the description is omitted.

In the recording head 110 of this embodiment, the ink supply port 11 is formed on the silicon substrate 1 by anisotropic etching.
Was formed. The ink passes through the ink flow path 10 from the ink supply port 11 and is ejected from the ejection port 5 as ink droplets. The ejection ports 5 are arranged in a staggered manner, forming two rows of ink ejection ports. The heater 2 is arranged almost directly below each of the discharge ports 5. The flow path constituting members such as the partition walls 9 are formed by a known manufacturing method such as an exposure technique or etching. The discharge port 5 is a cylindrical hole having a diameter of 15 μm, and the size of the heater 2 is 24 μm × 24 μm. The height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is 10 μm, and the thickness W of the orifice plate 4 is 13.5 μm. The distance L between the substrate 1 and the outer surface of the orifice plate 4 is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 4.31 picoliter. The temperature T1 is the lowest temperature of the operating environment in which the ink is ejected from the ejection port, that is, the lowest temperature at which the liquid ejection head performs a normal ejection operation, and is usually 20 to 25 ° C. As a result of the above-described microscopic observation, the bubble 6 came into contact with the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. Bubble 6
Communicated with the outside air after coming into contact with the opening edge 5a of the discharge port 5.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 4.75 picoliter. The temperature T2 is a temperature within a temperature range of an operating environment in which the ink is ejected from the ejection port. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μm after the drive signal of the heater 2 was turned on.
s. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

Assuming that the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the following equations (1 ') and (2')
C (unit:% / ° C.) was “0.51”.

TC = ΔVd / Vd1 / (T2−T1) × 100 (1 ′) ΔVd = Vd2−Vd1 (2 ′)

The dot size of ink formed by ink droplets that land on the surface of the recording paper P is determined by the recording head 11
There was no difference when the temperature of 0 was 25 ° C. and 45 ° C., and an image of very good image quality was recorded. The reason is 2
In the recording head 110 at 5 ° C., a part of the bubble 6 is formed on the flow path side 10 of the ejection port 5 provided in the orifice plate 4.
It is considered that since the bubble 6 grows in the recording head 110 at 45 ° C. even when the bubble 6 easily expands, the bubble 6 is suppressed by the contact with the opening edge 5a. . That is, the bubble 6 and the opening edge 5
a, the displacement of the surface of the bubble 6 in the ink ejection direction in the ejection port 5 in the ejection port 5 is suppressed. Therefore, an increase in the amount of ink pushed out from the ejection port 5 to the outside is suppressed, and the ink amount is reduced. It is considered that the uniformity was achieved.

(Second Embodiment) Next, a recording head 110 according to a second embodiment of the present invention will be described.

In the recording head 110 of this embodiment, the height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is 11 μm, and the thickness W of the orifice plate 4 is 12.5 μm.
m, and other dimensions and the like are set to be the same as those in the first embodiment. Distance L between substrate 1 and outer surface of orifice plate 4
Is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 4.34 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Contacted the opening edge 5 a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 4.88 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.62”.

The dot size of ink formed by ink droplets that land on the surface of the recording paper P is determined by the size of the recording head 11.
There was no difference when the temperature of 0 was 25 ° C. and 45 ° C., and an image of very good image quality was recorded. The reason is 2
In the recording head 110 at 5 ° C., a part of the bubble 6 is formed on the flow path side 10 of the ejection port 5 provided in the orifice plate 4.
It is considered that since the bubble 6 grows in the recording head 110 at 45 ° C. even when the bubble 6 easily expands, the bubble 6 is suppressed by the contact with the opening edge 5a. . That is, the bubble 6 and the opening edge 5
a, the displacement of the surface of the bubble 6 in the ink ejection direction in the ejection port 5 in the ejection port 5 is suppressed. Therefore, an increase in the amount of ink pushed out from the ejection port 5 to the outside is suppressed, and the amount of ink is reduced. It is considered that the uniformity was achieved.

(Third Embodiment) Next, a recording head 110 according to a third embodiment of the present invention will be described.

In the recording head 110 of this embodiment, the height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is 12 μm, and the thickness W of the orifice plate 4 is 11.5 μm.
m, and other dimensions and the like are set to be the same as those in the first embodiment. Distance L between substrate 1 and outer surface of orifice plate 4
Is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 4.33 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Contacted the opening edge 5 a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 4.98 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.75”.

The dot size of ink formed by ink droplets that land on the recording paper P is determined by the size of the recording head 11.
There was no difference when the temperature of 0 was 25 ° C. and 45 ° C., and an image of very good image quality was recorded. The reason is 2
In the recording head 110 at 5 ° C., a part of the bubbles 6
It is considered that since the bubble 6 grows in the recording head 110 at 45 ° C. even when the bubble 6 easily expands, the bubble 6 is suppressed by the contact with the opening edge 5a. . That is, the bubble 6 and the opening edge 5
a, the displacement of the surface of the bubble 6 in the ink ejection direction in the ejection port 5 in the ejection port 5 is suppressed. Therefore, an increase in the amount of ink pushed out from the ejection port 5 to the outside is suppressed, and the ink amount is reduced. It is considered that the uniformity was achieved.

(First Comparative Example) Next, a first comparative example of the liquid discharge head will be described below.

Recording head 110 as a first comparative example
The height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is set to 13 μm, the thickness W of the orifice plate 4 is set to 10.5 μm, and other dimensions are set to be the same as those of the first embodiment. did. Substrate 1 and orifice plate 4
Is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 4.28 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Did not contact the opening edge 5a of the discharge port 5. Thereafter, the bubbles 6 communicated with the outside air.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 4.97 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink discharge amount Vd1 at the temperature T1 and the ink discharge amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.81”.

The dot size of the ink formed by the ink droplets that land on the surface of the recording paper P is determined by the recording head 11.
A difference was observed when the temperature of 0 was 25 ° C. and 45 ° C. The reason is that the recording head 110 at 25 ° C.
Since some of the bubbles 6 did not come into contact with the opening edge 5a of the discharge port 5 on the flow path side 10, the temperature of the recording head 110 was 25 ° C. and the temperature of the recording head 110 was 45 ° C., and the bubbles 6 were easily expanded. It is considered that the expansion of the bubble 6 was not similarly suppressed in both cases. That is, due to the contact between the bubble 6 and the opening edge 5a, the displacement of the surface of the bubble 6 in the ink discharge direction in the discharge port 5 is not effectively suppressed, and the amount of ink pushed out from the discharge port 5 to the outside is increased. This is probably because the dot size of the ink was not made uniform with respect to the temperature change without being suppressed.

(Second Comparative Example) Next, a second comparative example of the liquid discharge head will be described below.

Recording head 110 as a second comparative example
Sets the height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 to 14.5 μm,
Was set to 9 μm, and other dimensions and the like were set to be the same as those of the first embodiment. The distance L between the substrate 1 and the outer surface of the orifice plate 4 is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the discharge volume Vd1 of the ink 3 was about 4.17 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Did not contact the opening edge 5a of the discharge port 5. Thereafter, the bubbles 6 communicated with the outside air.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 4.83 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.79”.

The dot size of the ink formed by ink droplets that land on the surface of the recording paper P is determined by the recording head 11.
A difference was observed when the temperature of 0 was 25 ° C. and 45 ° C. The reason is that the recording head 110 at 25 ° C.
Since some of the bubbles 6 did not come into contact with the opening edge 5a on the flow path side 10 of the discharge port 5, the temperature of the recording head 110 was 25 ° C., and the temperature of the recording head 110 was 45 ° C., and the bubbles 6 were easily expanded. It is considered that the expansion of the bubble 6 was not similarly suppressed in both cases. That is, due to the contact between the bubble 6 and the opening edge 5a, the displacement of the surface of the bubble 6 in the ink discharge direction in the discharge port 5 is not effectively suppressed, and the amount of ink pushed out from the discharge port 5 to the outside is increased. It is considered that the dot size of the ink was not made uniform with respect to the temperature change without being suppressed.

In the first, second and third embodiments, and the first and second comparative examples, the distance L between the substrate 1 and the outer surface of the orifice plate 4 is set to a constant 23.5 μm.
I set it to consider. Further, since the thickness W of the orifice plate 4 cannot be made thinner than 9 μm in terms of strength, the height H of the flow path 10 which is a gap between the substrate 1 and the orifice plate 4 is made larger than 14.5 μm. Things could not be considered.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention.
FIG. 3 is an explanatory diagram of a recording head 110 according to the embodiment.

In the recording head 110 of this embodiment, the height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is 10 μm, and the thickness W of the orifice plate 4 is 13.5 μm.
m, and the discharge port 5 was formed into a tapered hole shape. The inner surface of the discharge port 5 is a tapered surface having a gradually decreasing diameter in the ink discharge direction.
Degrees. The diameter D of the opening of the discharge port 5 on the side of the flow path 10 was 15 μm, which is the same as in the above-described embodiment. Other dimensions and the like are set the same as in the first embodiment. The distance L between the substrate 1 and the outer surface of the orifice plate 4 is 23.5
μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the discharge volume Vd1 of the ink 3 was about 3.34 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Contacted the opening edge 5 a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 3.83 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.74”.

The dot size of the ink formed by ink droplets that land on the surface of the recording paper P is determined by the recording head 11.
There was no difference when the temperature of 0 was 25 ° C. and 45 ° C., and an image of very good image quality was recorded. The reason is 2
In the recording head 110 at 5 ° C., a part of the bubbles 6
It is considered that since the bubble 6 grows in the recording head 110 at 45 ° C. even when the bubble 6 easily expands, the bubble 6 is suppressed by the contact with the opening edge 5a. . That is, the bubble 6 and the opening edge 5
a, the displacement of the surface of the bubble 6 in the ink ejection direction in the ejection port 5 in the ejection port 5 is suppressed. Therefore, an increase in the amount of ink pushed out from the ejection port 5 to the outside is suppressed, and the amount of ink is reduced. It is considered that the uniformity was achieved.

(Third Comparative Example) Next, a third comparative example of the liquid discharge head will be described below.

Recording head 110 as a second comparative example
The height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is set to 11 μm, the thickness W of the orifice plate 4 is set to 12.5 μm, and other dimensions are set to be the same as those of the fourth embodiment. did. Substrate 1 and orifice plate 4
Is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 3.26 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Did not contact the opening edge 5a of the discharge port 5. Thereafter, the bubbles 6 communicated with the outside air.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 3.78 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.80”.

The dot size of the ink formed by ink droplets that land on the surface of the recording paper P is determined by the recording head 11
A difference was observed when the temperature of 0 was 25 ° C. and 45 ° C. The reason is that the recording head 110 at 25 ° C.
Since some of the bubbles 6 did not come into contact with the opening edge 5a on the flow path side 10 of the discharge port 5, the temperature of the recording head 110 was 25 ° C., and the temperature of the recording head 110 was 45 ° C., and the bubbles 6 were easily expanded. It is considered that the expansion of the bubble 6 was not similarly suppressed in both cases. That is, due to the contact between the bubble 6 and the opening edge 5a, the displacement of the surface of the bubble 6 in the ink discharge direction in the discharge port 5 is not effectively suppressed, and the amount of ink pushed out from the discharge port 5 to the outside is increased. It is considered that the dot size of the ink was not made uniform with respect to the temperature change without being suppressed.

(Fourth Comparative Example) Next, a fourth comparative example of the liquid discharge head will be described below.

Recording head 110 as a second comparative example
The height H of the flow path 10 formed between the substrate 1 and the orifice plate 4 is set to 12 μm, the thickness W of the orifice plate 4 is set to 11.5 μm, and other dimensions are set to be the same as those of the fourth embodiment. did. Substrate 1 and orifice plate 4
Is 23.5 μm.

When the recording head 110 was driven while the temperature of the recording head 110 was T1 = 25 ° C., the ejection volume Vd1 of the ink 3 was about 3.17 picoliter. As a result of the microscopic observation as described above, the bubbles 6
Did not contact the opening edge 5a of the discharge port 5. Thereafter, the bubbles 6 communicated with the outside air.

Next, when the temperature of the recording head 110 is T2 = 4
When the recording head 110 was driven at 5 ° C., the ejection volume Vd2 of the ink 3 was about 3.70 picoliter. As a result of microscopic observation, the bubbles 6 contacted the opening edge 5a of the discharge port 5, and the contact time was 2 μs after the drive signal of the heater 2 was turned on. The bubbles 6 communicated with the outside air after coming into contact with the opening edge 5 a of the discharge port 5.

When the ink ejection amount Vd1 at the temperature T1 and the ink ejection amount Vd2 at the temperature T2 (> T1),
Temperature coefficient T defined by the above equations (1 ') and (2')
C (unit:% / ° C.) was “0.83”.

The dot size of the ink formed by ink droplets that land on the surface of the recording paper P is determined by the recording head 11
A difference was observed when the temperature of 0 was 25 ° C. and 45 ° C. The reason is that the recording head 110 at 25 ° C.
Since some of the bubbles 6 did not come into contact with the opening edge 5a on the flow path side 10 of the discharge port 5, the temperature of the recording head 110 was 25 ° C., and the temperature of the recording head 110 was 45 ° C., and the bubbles 6 were easily expanded. It is considered that the expansion of the bubble 6 was not similarly suppressed in both cases. That is, due to the contact between the bubble 6 and the opening edge 5a, the displacement of the surface of the bubble 6 in the ink discharge direction in the discharge port 5 is not effectively suppressed, and the amount of ink pushed out from the discharge port 5 to the outside is increased. It is considered that the dot size of the ink was not made uniform with respect to the temperature change without being suppressed.

(Others) The present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As this pulse-shaped drive signal, those described in U.S. Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of a discharge port, a liquid path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, the recording head fixed to the apparatus main body or the electric connection with the apparatus main body and the ink from the apparatus main body are mounted on the apparatus main body by being attached to the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add ejection recovery means for the recording head, preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type and number of recording heads to be mounted are not limited to those provided only for one color ink, for example, and for a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start to solidify when reaching the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

Further, the form of the ink jet recording apparatus of the present invention is not limited to the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may take a form.

[0088]

As described above, according to the present invention,
At the lowest temperature of the operating environment where the liquid in the flow path is discharged from the discharge port, that is, at the lowest temperature at which the liquid discharge head performs a normal liquid discharge operation, a part of the bubble is brought into contact with the flow path side opening edge of the discharge port. After the bubbles are deformed, the temperature of the liquid ejection head rises (the temperature of the ink also rises) by communicating the bubbles with the atmosphere, and even if the bubbles easily expand, some of the bubbles Is brought into contact with the opening edge of the discharge port on the flow path side, so that the expansion of the bubble can be suppressed. Therefore, the displacement of the surface of the bubble in the liquid discharge direction can be suppressed, and the increase in the liquid discharge amount due to the temperature change can be suppressed.

As a result, for example, when an image is recorded on a recording medium with the liquid discharged from the liquid discharge head, the size of the liquid dots formed on the recording medium is made uniform, and high quality Images can be recorded.

[Brief description of the drawings]

FIG. 1 shows (a), (b), (c), (d), (e),
(F) is a schematic sectional view for explaining the time history of the liquid ejection state in the present invention.

FIG. 2 is a plan view of a main part for describing one embodiment of a liquid discharge head of the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a perspective view of a main part for describing one embodiment of a liquid discharge recording apparatus of the present invention.

FIG. 5 is a block diagram of a control system of the liquid ejection recording apparatus of FIG. 4;

FIG. 6 is a sectional view of a main part for explaining another embodiment of the liquid discharge head of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Heater 3 Ink 4 Orifice plate 5 Discharge port 5a Opening edge 6 Bubbles 7 Ink droplet 8 Ink column 9 Partition wall 10 Channel 110 Recording head (liquid ejection head)

Claims (21)

[Claims] 1. A liquid discharging method for discharging a liquid in a flow channel from a discharge port by forming bubbles in the liquid in the flow channel by thermal energy of a heating element, wherein the liquid in the flow channel is provided. Deforming the bubble so that a part of the bubble is brought into contact with the opening edge of the discharge port on the side of the flow path at the lowest temperature of the operating environment in which the bubble is discharged from the discharge port; And a step of communicating the air with the atmosphere. 2. The liquid discharging method according to claim 1, wherein the flow path communicates between a liquid chamber containing a liquid and the discharge port. 3. The liquid discharging method according to claim 1, wherein the heating element and the discharge port face each other with the flow path interposed therebetween. 4. The liquid discharging method according to claim 1, wherein the heating element is an electrothermal conversion element. 5. The liquid discharging method according to claim 1, wherein a discharge amount of the liquid is 8 picoliter or less. 6. The method according to claim 1, wherein an elapsed time from when the bubble is formed to when a part of the bubble comes into contact with an opening edge of the discharge port on the flow path side is within 3 μsec. 6. The liquid discharging method according to any one of 5. 7. A temperature T1 and a temperature T2 (> T1) within a temperature range of an operating environment for discharging the liquid from the discharge port, wherein the discharge amount of the liquid is 10 picoliters or less.
The discharge amount Vd1 (picoliter) of the liquid at 1 (° C.), and the discharge amount Vd2 of the liquid at a temperature T2 (° C.)
5. The liquid ejection device according to claim 1, wherein a temperature coefficient TC (% / ° C.) determined by the following equations (1) and (2) is 0.75 or less. 6. Method. TC = (ΔVd / Vd1) / (T2−T1) × 100 (1) ΔVd = Vd2−Vd1 (2) 8. The elapsed time from when the heating element generates heat to when a part of the bubble contacts the opening edge of the discharge port on the side of the flow path is within 2 μsec. 3. The liquid discharging method according to item 1. 9. The method according to claim 7, wherein the temperature T1 is 25 ° C., and the temperature T2 is 45 ° C.
3. The liquid discharging method according to item 1. 10. The liquid discharge method according to claim 1, wherein the discharge port has a shape that gradually becomes smaller in a direction in which the liquid is discharged. 11. A liquid for discharging the liquid in the flow path from the discharge port by forming bubbles in the liquid in the flow path communicating with the discharge port by thermal energy of a heating element provided on the substrate. In the discharge head, at the lowest temperature of the operating environment in which the liquid in the flow path is discharged from the discharge port, the bubble is deformed so that a part of the bubble contacts the opening edge of the discharge port on the flow path side. A liquid discharge head, wherein the air bubbles communicate with the atmosphere later. 12. The apparatus according to claim 11, wherein the flow path communicates between a liquid chamber containing a liquid and the discharge port.
3. The liquid ejection head according to item 1. 13. The heating element and the discharge port face each other with the flow path interposed therebetween.
3. The liquid discharge head according to 2. 14. The liquid discharge head according to claim 11, wherein the heating element is an electrothermal transducer. 15. The liquid discharge head according to claim 11, wherein the discharge amount of the liquid is 8 picoliters or less. 16. The method according to claim 11, wherein an elapsed time from when the bubble is formed to when a part of the bubble comes into contact with an opening edge of the discharge port on the flow path side is within 3 μsec. 16. The liquid ejection head according to any one of items 15. 17. A temperature T1 and a temperature T2 (> T1) within a temperature range of an operating environment for discharging the liquid from the discharge port, wherein the discharge amount of the liquid is 10 picoliters or less.
The discharge amount Vd1 (picoliter) of the liquid at 1 (° C.), and the discharge amount Vd2 of the liquid at a temperature T2 (° C.)
The liquid ejection according to any one of claims 11 to 14, wherein the temperature coefficient TC (% / ° C) obtained by the following equations (1) and (2) is 0.75 or less. head. TC = (ΔVd / Vd1) / (T2−T1) × 100 (1) ΔVd = Vd2−Vd1 (2) 18. An elapsed time from when the heating element generates heat to when a part of the bubble comes into contact with an opening edge of the discharge port on the flow path side is within 2 μsec. 3. The liquid ejection head according to item 1. 19. The liquid discharge head according to claim 17, wherein the temperature T1 is 25 ° C., and the temperature T2 is 45 ° C. 20. The liquid discharge head according to claim 11, wherein the discharge port has a shape whose diameter gradually decreases in a direction in which the liquid is discharged. 21. A moving means capable of relatively moving the liquid ejection head according to any one of claims 11 to 20 and a recording medium on which an image can be recorded by liquid ejected from the liquid ejection head. And a drive circuit for providing a drive signal to the heating element of the liquid discharge head.