JP2785712B2 - Ink jet print head - Google Patents

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 thermal energy, and more particularly to a side chute type ink jet print head.

[0002]

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

However, in this method, a second drop (hereinafter, referred to as "2nd drop") which causes a so-called satellite dot is liable to occur due to the droplet generation mechanism, resulting in a decrease in print quality. was there. That is, as shown in FIG.
After the ejection of 0, the ink moves in the direction of the arrow as the bubbles 38 disappear, and thereafter, as shown in FIG.
Clash on. 2nd drop 4 due to the impact of this collision
2 occurs. Here, 2nd drop 42
Is on the center line 44 of the ink flow path 32.

In order to prevent the occurrence of the second drop 42 and to improve the print quality, for example, Japanese Patent Laid-Open No.
No. 61, noting that a second drop occurs inside the orifice plate, proposes a configuration in which the center line of the ink flow path and the center line of the ink discharge port intersect. As shown in FIG.
6 intersects the ink flow path 32 so that the center line 44 of the ink flow path 32 and the center line 46 of the ink discharge port 34 have an inclination angle θ.

According to this configuration, the 2nd drop whose ejection course is on the center line 44 of the ink flow path 32 collides with the orifice plate 36 standing on the extension of the drop, and collides with the orifice plate 36. Without discharging
As a result, in printing, only the first drop 40 becomes print dots, and as a result, good print quality is obtained. Here, in the above publication, the inclination angle θ is set to 0 ° to 20 ° (not 0 °). In Japanese Patent Application Laid-Open No. Hei 3-101962, the range of the inclination angle θ ₁ is set to 0 ° ≦ θ from the viewpoint of ease of manufacturing.
It is disclosed that the angle is preferably ≦ 90 °, and particularly preferably 3 ° ≦ θ ≦ 45 °.

On the other hand, as shown in FIGS. 10 and 11, the side chute type has a substrate 48 having a heating resistor 30 on its surface and an orifice plate 50 having an ink discharge port 50 for discharging ink in a predetermined direction. 52 and the substrate 4
A flow path wall 56 that is provided to join the orifice plate 52 with the flow path 8 and that defines the ink flow path 54;
And an ink liquid chamber 58. In this side chute type, as is apparent from the figure, the ink ejection port 50
The inclination angle θ between the center line 60 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]

The problem of the 2nd drop in the edge shoot type is described in Japanese Patent Application Laid-Open No.
It can be said that this can be solved by a measure as disclosed in Japanese Patent Application Laid-Open No. 10-1961. 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. Because of the basic configuration having corners, the above-described remedy in the edge shoot type could not be applied to the problem of the 2nd drop peculiar to this type.

That is, in the side chute type, when the distance between the ink discharge port 50 and the center of the heating resistor 30 is 0, the flow of ink from the ink discharge port direction and the ink liquid chamber direction after the bubble disappears. Since the collision occurs on the heating resistor 30 directly below the ink discharge port 50, FIG.
As shown in FIG. 3, after the first drop 64 is ejected,
The second drop 66 is ejected.

In this side shoot type, 2nd
I have another problem at the same time as the drop problem. That is, as shown in FIG. 14 and FIG.
With the disappearance of the upper air bubble 68, the ink flowing into the space where the air bubble 68 exists is located near the heating resistor 30 and rebounds by the flow path wall 56 forming the ink flow path 54. In some cases, a so-called splash 70, which is different from the first drop 60, is ejected.

When the splash 70 occurs, the ink droplets are ejected in a direction different from the ejection direction of the first ink droplets 66, which are the original ink droplets, so that the ink droplets become satellite dots on the recording paper, resulting in a significant reduction in print quality. Have been. Further, in addition to such a direct problem, when ink adheres to the surface of the orifice plate 52 in the vicinity of the ink discharge port 50, as shown in FIG. This causes an indirect problem that the ink overflow 72 is induced, and the ink overflow 72 causes a defect in the ejection direction of the first drop 66, which is the original ink droplet, resulting in a decrease in print quality.

FIG. 1 shows the mechanism of generation of the splash 70.
4 and FIG. 15 will be described in more detail. That is, in order to eject ink,
The bubbles 68 generated on the upper heating resistor 30 become smaller and disappear as the temperature of the heating resistor 30 decreases.
At that time, the ink 74 around the bubble 68 flows into the portion (space) where the bubble 68 was present. As shown by the arrow, the flow of the ink depends on the direction of the ink droplet 66 (not yet separated) in the discharging process and the ink liquid chamber 5.
It occurs from eight directions.

The ink flowing into the substrate 48 and the flow path wall 5
6, the direction of the flow is changed to the direction of the ink ejection port 50. Then, the rebounded ink cannot be completely settled in the ink discharge port 50, and has a disadvantage that the ink is discharged from the ink discharge port 50 as a splash 70.

[0013]

An object of the present invention is to provide an ink jet print head which can suppress the ejection of a second drop after the first drop ejection and the ejection of a splash at the time of the first drop ejection, particularly in a side chute type, thereby improving the printing quality. To do that.

[0014] Delete

[0015]

According to the first aspect of the present invention, there is provided a substrate provided with a heating resistor facing an ink flow path, and a flow restricting the front end position of the ink flow path on the substrate. An orifice plate having an ink discharge port connected to the ink flow path while forming the ink flow path between the substrate and the substrate stacked via a road wall; and an ink liquid chamber for supplying ink to the ink flow path. the ink jet print head provided with the diameter d ₀₁ of the substrate side of the ink discharge port, wherein a length L _H along the ink flow path of the heating resistor, the ink discharge port and the heat generating resistor The relation with the distance X _OH between the respective centers is expressed as “X _OH > (d ₀₁ + L _H )
/ 2 ".

[0016] Still further, in the second aspect, the ink discharge ports described above, the diameter d ₀₁ of the substrate side and the ink discharge side of the diameter d ₀₂
Is set as d ₀₁ ≧ d ₀₂ . This aims to achieve the above-mentioned object.

[0017]

According to the first aspect of the present invention, when the heating resistor is energized, bubbles are generated at positions outside the area corresponding to the ink discharge ports. Due to the pressure propagation due to the increase in the volume of the bubble, a first 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, the ink is not ejected because it is blocked by the orifice plate due to the displacement of the ink ejection port.

Further, after the first drop is ejected, most of the ink goes to the bubbles separated from the ink ejection port, so that almost no ink goes to the ink ejection port due to the rebound, so that no splash occurs.

Further, according to the ink jet print head of the second aspect , especially when d ₀₁ > d ₀₂ , a narrowing function due to the tapered nozzle shape is realized, and as a result, the first stop is achieved.
Stabilization of the drop ejection direction, adjustment of the first drop ink amount, and the like are performed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In FIGS. 1 to 4, the ink jet print head 2 according to the present embodiment includes a substrate 6 as a so-called thermal head provided with a heating resistor 4 on the surface, and a part of the partitioning of the ink flow path 8. A flow path wall 10 for carrying the ink and an ink discharge port 12 connected to the ink flow path 8
And an orifice plate 14 laminated on the substrate 6 via the flow path wall 10 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 is regulated by the flow path wall 10, and the rear end side is the ink liquid chamber 16. It is connected to. The channel wall 10 is formed of, for example, a photosensitive resin or the like.

The heating resistor 4 is disposed near the ink liquid chamber 16 outside the area corresponding to the ink ejection port 12.
Strictly speaking, the diameter d ₀₁ of the ink ejection 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 discharge port 12 and each center of the heating resistor 4, “X _OH > (d ₀₁ + L _H )”. / 2 ".

In addition, the ink discharge port 12 is provided with "d ₀₁ ≧
d ₀₂ ”is preferably satisfied, and in this example, it is formed in a shape of d ₀₁ > d ₀₂ and having a curved tapered surface. The ink jet print head 2 shown in this example is of a multi-nozzle type, and a part thereof is shown in the drawing.

Next, the ink jet print head 2
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, a first drop (main drop) 20 is ejected from the ink ejection port 12 by pressure propagation due to the increase in the volume of the bubble 18.

As the bubbles 18 disappear, the ink flows from the ink discharge ports 12 and the ink liquid chamber 16 to the bubbles 18. Some of the ink flow from the ink ejection port 12 is rebounded by the substrate 6 and flows toward the ink ejection port 12, but most of the ink flows into the bubble 18. Therefore, the ink does not flow back to the flow path wall 10,
No splash occurs.

Thereafter, the flow of ink after the bubbles 18 have disappeared and the first drop 20 has been ejected is as shown in FIG. Ink ejection port 1 after ejection of first drop 20
The flow of ink from the two directions and the flow of ink from the direction of the ink liquid chamber 16 collide near the heating resistor 4. The flow of ink rebounded by the collision flows parallel to the substrate 6. It is alleviated by colliding with the ink on the path to the flow path wall 10 and the flow path wall 10. Therefore, the flow of ink toward the ink ejection port 12 is weakened, and the 2nd drop is not ejected.

In addition, the ink discharge port 12 is set to “d ₀₁ ≧
d ₀₂ ”, and particularly in this example, d _02
01> because it is formed in a convergent nozzle shaped d _02, along with the stabilization of discharge direction of 1st drop 20 is obtained by the squeezing action, it is possible to adjust the discharge amount. Further, as a result of an experiment, it was found that there was an effect of suppressing splash and 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. However, as in the ink ejection port 15 shown in FIG.

[0029]

According to the first aspect of the present invention, the occurrence of the splash at the time of the first drop ejection and the ejection of the second drop after the first drop ejection are achieved by the configuration in which the corresponding positions of the ink ejection port and the heating resistor are shifted. Since it can be suppressed, the printing quality can be improved in the side chute type.

Furthermore, according to the ink jet print head according to claim 2, the throttling effect of the convergent nozzle shape in particular, it is possible to stabilize the ejection direction of first drop or the like.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic diagram illustrating a flow of ink during a bubble disappearing process in FIG. 2;

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

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

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

FIG. 7 is a schematic diagram showing the flow of ink when bubbles are eliminated in a conventional edge chute type.

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

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

FIG. 10 is a plan view of a main part showing a conventional side chute type.

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

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

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

FIG. 14 is a schematic diagram illustrating the flow of ink during a bubble disappearing process in a conventional side chute type.

FIG. 15 is a schematic view showing a state of occurrence of splash in a conventional side chute type.

FIG. 16 is a schematic perspective view of a main part showing ink overflow due to splash in a conventional side chute type.

[Explanation of symbols]

 Reference Signs List 4 heating resistor 6 substrate 8 ink flow path 10 flow path wall 12, 15 ink discharge port 14 orifice plate 16 ink liquid chamber

Claims (2)

(57) [Claims] 1. A substrate provided with a heating resistor facing an ink flow path, and a substrate laminated on the substrate via a flow path wall for regulating a tip position of the ink flow path. An ink jet print head comprising: an orifice plate having an ink discharge port formed with the ink flow path and connected to the ink flow path; and an ink liquid chamber for supplying 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 heating resistor along the ink flow path, and the distance X _OH between the ink ejection port and each center of the heating resistor, An ink jet print head, wherein "X _OH > (d ₀₁ + L _H ) / 2" is set. 2. The ink ejection port has a diameter d ₀₁ on the substrate side.
And the relationship between the diameter d ₀₂ of the ink discharge side, the ink jet print head according to claim 1 Symbol placement was characterized by that it is set to d ₀₁ ≧ d _02.