JPH0899409A - Ink jet type printing head - Google Patents

Abstract

PURPOSE: To provide an ink jet type printing head, with which the enhancement of printing quality in a side-chute type head is contrived. CONSTITUTION: An ink jet type printing head 2 is equipped with board 6, on which heating resistors 4 are installed, flow passage wall 10, which serves as some part of ink flow passage 8, an orifice plate 14, which has ink discharge ports 12 connecting with the flow passage 8 and is laminated through the flow passage wall 10 onto the board 6, and ink solution chamber 16. Each heating resistor 4 is set at the position off the corresponding region of the ink discharge port 12 to the ink solution chamber 16 so as to satisfy the condition: XOH>(d01 + LH)/2, in which d01 is the diameter on the board side of the ink discharge port 12, LH is the length along the ink flow passage 8 of the heating resistor 4 and XOH is the distance between the centers of the ink discharge port 12 and of the heating resistor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head used in a non-impact printer, and more particularly to a so-called bubble jet type ink jet print head utilizing heat energy, particularly a side shoot type ink jet print head.

[0002]

2. Description of the Related Art Conventionally, as this type of ink jet type print head, there are an edge shoot type and a side shoot type. As shown in FIG. 6, the edge chute type has a configuration in which an orifice plate 36 having an ink ejection port 34 intersects with an ink flow path 32 equipped with a heating resistor 30 at a substantially right angle. Resistor 30
When the power is turned on, a bubble 38 is generated in the ink flow path 32 on the heat generating resistor 30, and pressure propagation due to the volume increase of the bubble 38 causes a first drop (main drop, hereinafter referred to as “1st drop”) from the ink ejection port 34. 40) is ejected.

However, in this method, a second drop (hereinafter referred to as "2nd drop") that causes so-called satellite dots is liable to occur due to the droplet generation mechanism, which causes deterioration of print quality. was there. That is, as shown in FIG. 7, 1st drop 4
After the ejection of 0, the ink moves in the direction of the arrow as the bubble 38 disappears, and thereafter, as shown in FIG.
Clash on. 2nd drop 4 due to the impact of this collision
2 is generated. Here, 2nd drop 42
The discharge course of is on the center line 44 of the ink flow path 32.

In order to prevent the occurrence of the second drop 42 and improve the printing quality, for example, Japanese Patent Laid-Open No. 3-1019.
In Japanese Patent Laid-Open No. 61, paying attention to the fact that the second drop occurs inside the orifice plate, a configuration is proposed in which the center line of the ink flow path and the center line of the ink ejection port intersect. This is as shown in FIG.
6 intersects the ink flow path 32 such that the center line 44 of the ink flow path 32 and the center line 46 of the ink ejection port 34 have an inclination angle θ.

According to this structure, the 2nd drop whose ejection course is on the center line 44 of the ink flow path 32 collides with the orifice plate 36 which stands up on the extension line thereof, so that the 2nd drop collides with the orifice plate 36 from the ink ejection port 34. No discharge,
As a result, in printing, only the 1st drop 40 is printed, and as a result, good printing quality can be obtained. Here, in the above-mentioned publication, the tilt angle θ is 0 ° to 20 ° (not 0 °). Further, in Japanese Patent Application Laid-Open No. 3-101962, the range of the tilt angle θ ₁ is 0 ° ≦ θ for ease of manufacturing.
It is disclosed that ≦ 90 ° is preferable, and 3 ° ≦ θ ≦ 45 ° is particularly preferable.

On the other hand, as shown in FIGS. 10 and 11, the side shoot type is an orifice plate having a substrate 48 having a heating resistor 30 on its surface and an ink ejection port 50 for ejecting ink in a predetermined direction. 52 and the substrate 4
8 and a flow path wall 56 that is provided to join the orifice plate 52 and defines and forms the ink flow path 54;
And an ink liquid chamber 58. In this side chute type, as is clear from the figure, the ink ejection port 50
The inclination angle θ between the center line 60 of the ink flow path and the center line 62 of the ink flow path 54 is originally 90 °, and the heating resistor 30 is arranged to face the ink ejection port 50.

[0007]

By the way, the problem of the 2nd drop in the edge shoot type is described in the above-mentioned Japanese Patent Laid-Open No.
It can be said that this can be solved by the measures disclosed in Japanese Patent Laid-Open No. 101961. However, in the case of the side chute type, as described above, the center line of the ink ejection port and the center line of the ink flow path are originally inclined. Due to the basic configuration having the corners, the above-mentioned improvement measure in the edge shoot type could not be applied to the problem of 2nd drop peculiar to this type.

That is, in the side shoot type, when the distance between the center of the ink discharge port 50 and the center of the heat generating resistor 30 is 0, the flow of ink from the direction of the ink discharge port and the direction of the ink liquid chamber after the disappearance of air bubbles. Since the collision occurs on the heat generating resistor 30 directly below the ink ejection port 50, the collision is generated as shown in FIGS.
As shown in 3, after the 1st drop 64 is discharged, 2
The nd drop 66 is discharged.

Also, in this side shoot type, 2nd
At the same time, it has another problem than the drop problem. That is, as shown in FIGS. 14 and 15, the heating resistor 30
With the disappearance of the upper bubble 68, the ink flowing into the space where the bubble 68 existed is repelled by the flow path wall 56 that is located near the heat generating resistor 30 and forms the ink flow path 54, and as a result, originally Ink droplets different from the 1st drop 60 which is the ink droplet, that is, a so-called splash 70 may be ejected.

When the splash 70 occurs, the ink droplets are ejected in a direction different from the ejection direction of the 1st drop 66, which is the original ink droplet, so that it becomes a satellite dot on the recording paper, resulting in a marked deterioration in printing quality. I am Furthermore, in addition to such a direct problem, when ink adheres to the surface of the orifice plate 52 near the ink ejection port 50, as shown in FIG. 16, the adhered ink serves as a core to surround the ink ejection port 50. There is an indirect problem that the ink overflow 72 is induced, and the ink overflow 72 causes an ejection directionality defect of the first drop 66, which is an original ink drop, resulting in deterioration of print quality.

The generation mechanism of the splash 70 is shown in FIG.
This will be described in more detail with reference to FIG. 4 and FIG. That is, the substrate 48 for ejecting ink
The bubbles 68 generated on the upper heating resistor 30 become smaller and disappear as the temperature of the heating resistor 30 lowers.
At that time, the ink 74 around the bubble 68 flows into the portion (space) where the bubble 68 was present. This inflow of ink is caused by the direction of the ink droplet 66 (not yet separated) in the ejection process and the ink liquid chamber 5 as shown by the arrow.
It originates from 8 directions.

The ink that flows in is the substrate 48 and the flow path wall 5.
It is repelled by 6, and the direction of the flow changes to the direction of the ink ejection port 50. Then, there is a disadvantage that the ink that has rebounded is not completely stored in the ink ejection port 50 and is ejected as a splash 70 from the ink ejection port 50.

[0013]

It is an object of the present invention to provide an ink jet print head capable of suppressing the discharge of the second drop after the first drop discharge and the discharge of the splash at the time of the first drop discharge, which can improve the print quality. The purpose is to do.

[0014]

The present invention focuses on the positional relationship between the ink discharge port and the heat generating resistor. In claim 1, the heat generating resistor is provided facing the ink flow path. A substrate, an orifice plate that has an ink ejection port connected to an ink flow path and is stacked on a substrate via a flow path wall that defines the ink flow path, and an ink liquid chamber that supplies ink to the ink flow path. In the inkjet print head provided, the heating resistor is arranged on the ink liquid chamber side, which is removed from the region corresponding to the ink ejection port.

According to a second aspect of the present invention, a substrate provided with a heating resistor facing the ink flow channel and a substrate laminated on the substrate via a flow channel wall that regulates the tip position of the ink flow channel are provided. An ink jet print head provided with an orifice plate that forms the ink flow path between the substrate and an ink discharge port that is connected to the ink flow path, and an ink liquid chamber that supplies ink to the ink flow path. , The diameter d _{01 of the} ink ejection port on the substrate side, the length L _H of the heating resistor along the ink flow path, and the distance X _OH between the ink ejection port and each center of the heating resistor. The relationship is set to "X _OH > (d ₀₁ + L _H ) / 2".

Further, in the third aspect, the ink ejection port has a structure in which the relationship between the diameter d ₀₁ on the substrate side and the diameter d ₀₂ on the ink ejection side is set to d ₀₁ ≧ d ₀₂ . . This aims to achieve the above-mentioned object.

[0017]

According to the present invention, when the heating resistor is energized,
Bubbles are generated at a position outside the area corresponding to the ink ejection port. Due to the pressure propagation due to the increase in the volume of the bubbles, the 1st drop is ejected from the ink ejection port. Even if a 2nd drop occurs due to the impact of collision due to the inflow of ink due to the disappearance of bubbles, it is blocked by the orifice plate due to the displacement of the ink ejection port, so that ejection is not performed.

Further, after the first drop is ejected, most of the ink is directed to the air bubbles distant from the ink ejection port, so that almost no ink is directed to the ink ejection port due to rebounding, and thus no splash is generated.

Further, according to the ink jet type print head of the third aspect, particularly when d ₀₁ > d ₀₂ , the diaphragm function due to the tapered nozzle shape is exhibited, whereby 1st
Stabilization of the drop ejection direction, adjustment of the ink amount of the first drop, and the like are performed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4, the ink jet print head 2 according to the present embodiment is provided with a substrate 6 as a so-called thermal head having a heating resistor 4 on the surface thereof and a part of a partition formation of an ink flow path 8. The flow channel wall 10 and the ink discharge port 12 connected to the ink flow channel 8
And an ink liquid chamber 16 for supplying ink to the ink flow path 8.

The ink flow path 8 is a space defined by the substrate 6, the flow path wall 10 and the orifice plate 14, the front end position of which is regulated by the flow path wall 10 and the rear end side of which is the ink liquid chamber 16 It is connected to. The flow path wall 10 is formed of, for example, a photosensitive resin.

The heat generating resistor 4 is installed near the ink liquid chamber 16 outside the corresponding area of the ink discharge port 12.
Strictly speaking, the diameter d ₀₁ of the ink discharge port 12 on the substrate 6 side,
In the relationship between the length L _{H of the} heating resistor 4 along the ink flow path 8 and the distance X _OH between the ink ejection port 12 and each center of the heating resistor 4, “X _OH > (d ₀₁ + L _H )” It is installed so as to satisfy the condition of "/ 2".

In addition, the ink ejection port 12 has a "d ₀₁ ≥
It is desirable to be formed so as to satisfy the condition of “d ₀₂ ”, and in this example, d ₀₁ > d ₀₂ and a shape having a curved tapered surface is formed. The ink jet print head 2 shown in this example is a multi-nozzle type, and a part of it is shown in the drawing.

Next, the ink jet type print head 2
The ink droplet ejection operation by will be described. As shown in FIG. 3, when the heating resistor 4 is energized, Joule heat is generated and bubbles 18 are generated on the heating resistor 4. When the bubble 18 is generated, the first drop (main drop) 20 is ejected from the ink ejection port 12 due to the pressure propagation due to the increase in volume of the bubble 18.

With the disappearance of the bubbles 18, the ink flows from the ink ejection port 12 side and the ink liquid chamber 16 side into the bubbles 18. Some of the ink flow from the ink ejection port 12 side is repelled by the substrate 6 and flows toward the ink ejection port 12, but most of it flows to the bubble 18. Therefore, the flow of ink that is repelled by the flow path wall 10 does not occur,
No splash occurs.

After that, the bubble 18 disappears, and the ink flow after the first drop 20 is ejected is as shown in FIG. Ink ejection port 1 after the 1st drop 20 is ejected
The flow of ink from the two directions and the flow of ink from the direction of the ink liquid chamber 16 collide in the vicinity of the heating resistor 4, but the flow of ink repelled by this collision flows parallel to the substrate 6, The ink in the path to the flow path wall 10 and the flow path wall 10 are relieved by colliding with the flow path wall 10. Therefore, the flow of ink toward the ink ejection port 12 is weakened, and the second drop is not ejected.

In addition, the ink ejection port 12 has a "d ₀₁ ≥
d ₀₂ ”, and in this example, d
Since it is formed in a tapered nozzle shape with ₀₁ > d ₀₂ , the diaphragm action stabilizes the ejection direction of the 1st drop 20, and the ejection amount can be adjusted. Further, as a result of the experiment, it was found that there is an effect of suppressing the splash and the 2nd drop based on this shape.

In the above example, the inner surface of the ink ejection port 12 is a tapered surface having a curved cross section, but it may be a tapered surface having a linear cross section as in the ink ejection port 15 shown in FIG.

[0029]

According to the present invention, it is possible to suppress the occurrence of splash at the time of first drop ejection and the ejection of the second drop after the first drop ejection by the configuration in which the corresponding positions of the ink ejection port and the heating resistor are displaced. The print quality can be improved in the chute type.

Further, according to the ink jet type print head of the third aspect, it is possible to stabilize the ejection direction of the first drop, especially by the squeezing action of the tapered nozzle shape.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of an ink jet print head according to the present invention.

FIG. 2 is a vertical sectional view taken along the line AA in FIG.

FIG. 3 is a schematic diagram illustrating the flow of ink during the bubble disappearance process in FIG.

FIG. 4 is a schematic diagram illustrating the flow of ink after the disappearance of bubbles in FIG.

FIG. 5 is a vertical sectional view corresponding to FIG. 2 showing another embodiment.

FIG. 6 is a schematic diagram showing a first drop ejection state in an edge shoot type of a conventional example.

FIG. 7 is a schematic diagram showing an ink flow when a bubble disappears in an edge shoot type of a conventional example.

FIG. 8 is a schematic diagram showing a state of occurrence of a second drop in the edge shoot type of the conventional example.

FIG. 9 is a schematic cross-sectional view of an essential part showing an improved conventional edge chute type.

FIG. 10 is a plan view of relevant parts showing a conventional side chute type.

11 is a vertical sectional view taken along the line BB in FIG.

FIG. 12 is a schematic diagram showing a first drop ejection state in a side shoot type of a conventional example.

FIG. 13 is a schematic diagram showing a state of occurrence of a second drop in a side shoot type of a conventional example.

FIG. 14 is a schematic diagram illustrating the flow of ink during a bubble disappearance process in a side shoot type of a conventional example.

FIG. 15 is a schematic diagram showing a state where a splash is generated in a side shoot type of a conventional example.

FIG. 16 is a schematic perspective view of essential parts showing ink overflow due to splash in a side shoot type of a conventional example.

[Explanation of symbols]

 4 Heat generating resistor 6 Substrate 8 Ink flow path 10 Flow path wall 12, 15 Ink ejection port 14 Orifice plate 16 Ink liquid chamber

Claims (3)

[Claims] 1. A substrate provided with a heating resistor facing an ink flow path, an ink discharge port connected to the ink flow path, and a flow path wall partitioning the ink flow path on the substrate. In an ink-jet printhead including an orifice plate stacked through the ink flow path and an ink liquid chamber that supplies ink to the ink flow path, the heating resistor is removed from a region corresponding to the ink ejection port, and the ink An ink jet type print head characterized by being arranged on the liquid chamber side. 2. A substrate provided with a heating resistor facing the ink flow channel, and a substrate laminated on the substrate via a flow channel wall that regulates the tip position of the ink flow channel. An ink jet type print head comprising: an orifice plate that forms the ink flow path and has an ink discharge port that is continuous with the ink flow path; and an ink liquid chamber that supplies ink to the ink flow path. The relationship between the diameter d ₀₁ of the outlet on the substrate side, the length L _H of the heat generating resistor along the ink flow path, and the distance X _OH between the ink discharge port and each center of the heat generating resistor, An inkjet print head characterized by being set to "X _OH > (d ₀₁ + L _H ) / 2". 3. The ink discharge port has a diameter d ₀₁ on the substrate side.
3. The ink jet print head according to claim 1, wherein the relationship between the ink discharge side diameter d ₀₂ is set to d ₀₁ ≧ d ₀₂ .