JPH08300659A - Recording head of bubble jet recording apparatus and ink emitting method - Google Patents

Abstract

PURPOSE: To apply flying ink to a recording medium as one spherical ink droplet without dividing the same. CONSTITUTION: When voltage is applied to a first heater 203, a plurality of air bubbles are generated in ink (b) and the ink 212 expands to the outside from the ink emitting surface of a nozzle tip (c). The voltage of the heater is released and air bubbles are gradually contracted but, since voltage is applied to a second heater 202 before the air bubbles are contracted, a plurality of air bubbles are generated in the ink (d). Therefore, the pressure in a nozzle 206 does not become negative and the air bubbles generated by the second heater 202 are gradually increased in vol. (e). As a result in 213 which has swelled on the ink-ejection surface to be a spherical form is cut off from the ink 212 in the nozzle (f), and flies out in the air (g) to hit the recording medium to stick on there.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of a bubble jet recording apparatus and an ink ejection method.

[0002]

2. Description of the Related Art In a recording head of a bubble jet recording apparatus of this type which has been conventionally used, heating and foaming of ink are performed by a single electric / heat converter (heater). Figure 5
Is a conceptual diagram showing a cross section of an ink jet nozzle of a conventional recording head and a state of generation and flight of ink droplets,
(A) to (g) show changes over time in the state of ink droplets.

In the figure, 503 is a heater, 506 is a nozzle, 5
Reference numeral 06a denotes an ink ejection surface of the nozzle, 512 denotes ink inside the nozzle, 513 denotes flying ink, and 514 denotes bubbles.

When a voltage is applied to the heater 503 for ejecting ink, a plurality of bubbles 514 are generated in the ink 512 contacting the heater 503 (b). With the passage of time, the bubbles 514 expand and coalesce into one bubble,
The ink 512 is pushed by 14 and swells to the outside from the ink ejection surface 506a at the tip of the nozzle (c). The bubble 514 further expands, and the ink 512 further swells to the outside to be spherical due to the surface tension (d). At this point, the voltage of the heater 503 is released and heat is no longer generated, so that the bubble 514 gradually shrinks, and the inside of the nozzle becomes a negative pressure, so that the ink 512 on the ink ejection surface 506a retreats inward and advances by inertia. The connection part becomes thin (e) away from the converted ink 513. When the bubbles shrink further, the connection is broken (f)
The divided ink 513 flies in the space (g) and lands on the recording medium.

FIG. 6 shows the applied voltage, nozzle internal pressure, and
It is a graph which shows the change of bubble volume, (a) of the horizontal axis-
(G) corresponds to each code of the process of FIG.
601 is a heater applied voltage, 603 is a nozzle pressure, 604
Indicates the bubble volume. The nozzle pressure is a negative pressure in the stages (e) to (f).

[0006]

In the prior art, since the bubbles for causing the ink to fly are generated by one heater, the following things may occur.
That is, before the spherical ink droplets are completely separated from the ink ejection surface, the air bubbles contract, a negative pressure is generated in the ink ejection nozzles, and a tailing phenomenon is caused in the ink that has started to fly, and the flying ink Will split. 5 (f) and 5 (g) show that state.

As described above, since the divided inks land on the recording medium in a scattered manner, there is a risk that the print quality may deteriorate.

An object of the present invention is to provide a recording head and a method for ejecting ink of a bubble jet recording apparatus in which the flying ink lands on a recording medium as one spherical ink droplet without being divided. .

[0009]

A recording head of a bubble jet recording apparatus according to the present invention causes thermal energy to be generated in an electric / heat converter inside a nozzle of the recording head, and causes bubbles due to film boiling in ink on a heat acting surface. In a recording head of a bubble jet recording apparatus for forming a recording medium by ejecting ink onto a recording medium, a plurality of independently operable electrothermal converters are arranged in the ink flow direction for each nozzle. Has been done.

In addition, an electrically / mechanical converter that can be operated independently may be arranged for each nozzle in the vicinity of the nozzle / ejector side of the electric / heat converter.

The ink jetting method in the print head of the bubble jet printing apparatus of the present invention is the ink jetting method in the print head of the above-mentioned bubble jet printing apparatus, wherein heat is applied to the electric / heat converter on the upstream side of the ink flow. After generating energy to generate bubbles in the ink, before the shrinking of the bubbles, thermal energy is generated in the downstream electric / thermal converter to continuously generate new bubbles, and the ink is ejected from the nozzles. Discharge.

In addition, after heat energy is generated in the electricity / heat converter on the upstream side of the ink flow to generate bubbles in the ink, the electricity / electricity arranged on the downstream side before the bubbles are reduced.
A voltage may be applied to the mechanical converter to mechanically apply pressure to the ink in the nozzle to eject the ink from the nozzle.

[0013]

In the recording head of the bubble jet recording apparatus having a plurality of electric / heat conversion elements in the nozzle, when a voltage is applied to the first electric / heat conversion element for ejecting ink, the electric / heat conversion is performed. Multiple bubbles are generated in the ink that contacts the body. Bubbles expand and coalesce with time
The bubbles form individual bubbles that are pushed by the bubbles to cause ink to bulge outside from the ink ejection surface at the tip of the nozzle. The bubbles expand further,
The ink further swells to the outside and becomes spherical due to the surface tension.

At this stage, since the voltage of the electric / heat converter is released, the bubbles generated by the first electric / heat converter gradually shrink, but before that, the voltage is applied to the second electric / heat converter. Since it is applied, a plurality of bubbles are generated in the ink that is in contact with the electric / heat converter. Both bubbles do not coexist in the nozzle and the inside of the nozzle does not become a negative pressure, and the volume of the bubbles generated in the second electric-heat converter close to the ink ejection surface gradually increases.

As a result, the spheroidized ink that swells from the ink ejection surface advances in a form of being pushed out and the connection with the ink in the nozzle is broken, and the spheroidized ink flies in the space and lands on the recording medium.

In a recording head of a bubble jet recording apparatus having an electric / mechanical converter which can be operated independently in the vicinity of the nozzle discharge port side of the electric / heat converter, in order to eject ink, the electric / heat converter is used. When a voltage is applied to the ink, a plurality of bubbles are generated in the ink that is in contact with the electrothermal converter. With the passage of time, the bubbles expand and coalesce into one bubble,
The ink is pushed by the bubbles and swells to the outside from the ink ejection surface at the tip of the nozzle. The bubbles further expand, and the ink further expands to the outside to be spherical due to the surface tension.

At this stage, the voltage of the electric-heat converter is released, so that the bubbles generated by the electric-heat converter gradually shrink, but before that, the voltage is applied to the electric-mechanical converter, so that the mechanical change occurs. Pressure is applied to the ink in the nozzle,
There is no negative pressure inside the nozzle, which causes the ink that swells and spheroidizes from the ink ejection surface to move forward in a form that pushes out, disconnects from the ink in the nozzle, and the spheroidized ink flies in space. And land on the recording medium.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an ink jet nozzle according to a first embodiment of the present invention. In the figure, 101 is a base plate, 102 is a second heater (electrical / thermal converter), 10
3 is a first heater, 104 is a first protective film, 105 is an electrode, 106 is a nozzle, 106a is an ink ejection surface of the nozzle, 107 is a glass top plate, 108 is a second protective film, 10
Reference numeral 9 is an ink supply port, 110 is a substrate, and 111 is a filter attached to the ink supply port.

FIG. 2 is a conceptual diagram showing the state of generation and flight of ink droplets in the ink jet nozzle of the recording head of the first embodiment. In the figure, 202 is a second heater, 203.
Is a first heater, 206 is a nozzle, 206a is an ink ejection surface of the nozzle, 212 is ink in the nozzle, 213 is ink in flight, 214 is bubbles, and (a) to (h) are ink droplets. The change over time is shown.

For discharging ink, the first heater 203
When a voltage is applied to the ink, a plurality of bubbles 214 are generated in the ink 212 that is in contact with the first heater 203 (b). With the lapse of time, the bubble 214 expands and coalesces into one bubble, and the ink 212 is pushed by the bubble 214 and bulges outside from the ink ejection surface 206a at the tip of the nozzle (c). The bubble 214 further expands, and the ink 212 further expands to the outside to be spherical due to the surface tension.

At this stage, since the voltage of the heater 203 is released and heat generation is stopped, the bubble 214 generated by the first heater 203 gradually shrinks, but before that, the voltage is applied to the second heater 202, so that the second heater 202 is applied. Heater 202
A plurality of bubbles 214 are generated in the ink 212 contacting with (d). Bubbles generated by the first heater 203 and the second heater 203 are mixed in the nozzle 206, and the inside of the nozzle does not become a negative pressure, and the second heater 202 gradually approaches the ink ejection surface 206a. The volume of bubbles generated increases (e).

As a result, the sphere-shaped ink 213 that bulges from the ink ejection surface 206a moves forward in a pushed-out manner, disconnects from the ink 212 in the nozzle, and (f) the sphered ink 213 flies in the space. (G) land on the recording medium. The ink ejection surface 206a that has once contracted after the spherical ink 213 has separated and started to fly returns to the initial state (h).

FIG. 3 is a graph showing changes in the applied voltage, the nozzle internal pressure, and the bubble volume in the embodiment of the present invention. The horizontal axes (a) to (h) correspond to the reference numerals of the respective processes in FIG. . Reference numeral 301 represents the first heater applied voltage, 302 the second heater applied voltage, 303 the nozzle pressure, and 304 the bubble volume. In this case, the nozzle pressure is spherical ink 21.
The pressure becomes negative at the stage (g) after 3 starts to separate and starts flying.

A second embodiment of the present invention is shown in FIG. In the figure, 401 is a heater, 402 is a piezoelectric element (electrical / mechanical converter), and 403 is a nozzle. In the first embodiment, the second heater is arranged on the ink ejection surface side of the nozzle of the first heater, and the nozzles are provided before the spherical ink is separated from the ink ejection surface by applying a voltage with a time difference. Although the inside is prevented from becoming a negative pressure and the ink is prevented from being divided during flight, in the present embodiment, instead of the second heater, the piezoelectric element 402 is arranged on the ink ejection surface side of the nozzle of the heater 401, By applying a voltage with a time difference, it was possible to prevent negative pressure in the nozzle before the spherical ink was separated from the ink ejection surface.

[0026]

The second heater is arranged on the nozzle ink ejection surface side of the first heater, and the voltage is applied with a time difference to generate the bubbles in two stages. Before the ink is separated from the ejection surface, it is possible to prevent negative pressure in the nozzle from causing a tailing phenomenon, and to prevent the ink from being divided during flight, so that the ink becomes one spherical droplet and becomes a recording medium. Land.

As a result, it is possible to prevent the defect that the divided inks are scattered on the recording medium due to the tailing phenomenon and cause the deterioration of the print quality, and to obtain the good print quality.

By arranging a piezoelectric element instead of the second heater on the nozzle ink ejection surface side of the heater and applying a voltage with a time difference, the nozzles can be separated before the spherical ink is separated from the ink ejection surface. The same effect can be obtained because it is possible to prevent a negative pressure inside.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inkjet nozzle according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing the generation and flight states of ink droplets in the inkjet nozzles of the recording head of the first embodiment.

FIG. 3 is a graph showing changes in applied voltage, nozzle internal pressure, and bubble volume in an example of the present invention.

FIG. 4 is a sectional view of an inkjet nozzle according to a second embodiment of the present invention.

FIG. 5 is a conceptual diagram showing a cross section of an inkjet nozzle of a conventional recording head and a state of ink droplet generation and flight.

FIG. 6 is a graph showing changes in applied voltage, nozzle internal pressure, and bubble volume in a conventional example.

[Explanation of symbols]

 101 Base Plate 102 Second Heater 103 First Heater 104 First Protective Film 105 Electrode 106 Nozzle 106a Nozzle Ink Ejection Surface 107 Glass Top Plate 108 Second Protective Film 109 Ink Supply Port 110 Substrate 111 Attached to Ink Supply Port Filter 202 Second heater 203 First heater 206, 506 Nozzle 206a, 506a Nozzle ink ejection surface 212, 512 Ink in nozzle 213, 513 Flying ink 214, 514 Bubble 301 First heater applied voltage 302 Second heater applied voltage 303, 603 Nozzle pressure 304, 604 Bubble volume 401 Heater 402 Piezoelectric element 403 Nozzle 503 Heater 601 Heater applied voltage

Claims (4)

[Claims] 1. Recording is performed by ejecting ink onto a recording medium by causing thermal energy to be generated in an electric / heat converting body in a nozzle of a recording head and forming bubbles in the ink on a heat acting surface by film boiling. In a recording head of a bubble jet recording apparatus, a plurality of independently operable electric / heat conversion elements are arranged in the ink flow direction for each nozzle, and the recording head of the bubble jet recording apparatus is characterized. . 2. The recording is performed by ejecting ink onto a recording medium by generating heat energy in an electric / heat converting body in a nozzle of a recording head and forming bubbles in the ink on a heat acting surface by film boiling. In a recording head of a bubble jet recording apparatus for performing, an electrically / mechanical converter that can operate independently is arranged for each nozzle in the vicinity of the nozzle discharge port side of the electric / heat converter. A recording head for a bubble jet recording device. 3. A method for ejecting ink in a recording head of a bubble jet recording apparatus according to claim 1, wherein thermal energy is generated in the electric / heat converter on the upstream side of the ink flow to cause bubbles in the ink. After the generation of the ink, before the reduction of the bubble, thermal energy is generated in the electric / heat converter on the downstream side to continuously generate a new bubble, and the ink is ejected from the nozzle. Discharge method. 4. A method of ejecting ink in a recording head of a bubble jet recording apparatus according to claim 2, wherein heat energy is generated in the electric / heat converter on the upstream side of the ink flow to generate bubbles in the ink. After the generation of the ink, a voltage is applied to the electro-mechanical converter disposed on the downstream side before the bubbles are reduced, and the ink in the nozzle is mechanically pressured to eject the ink from the nozzle. Characteristic ink ejection method.