JP2725612B2 - 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 a print head for an ink jet printer which performs printing by discharging ink.

[0002]

2. Description of the Related Art As this type of ink jet type print head, a side chute type print head as shown in FIGS. 7 and 8 (a sectional view taken along line BB in FIG. 7) is known. This is a so-called multi-nozzle type, a part of which is shown in the drawings.

[0003] To explain the structure, as shown in the figure, a substrate 36 having a through hole 30 (generally called a slot) for supplying ink and having a heating resistor 34 facing the ink flow path 32 is provided. , A nozzle plate 40 having a discharge section 38 connected to the ink flow path 32, and a single film-shaped flow path forming member 42 provided between the nozzle plate 40 and the substrate 36.

The height T ₃ of the ink flow path 32 is formed by the thickness of the flow path forming member 42. The flow path forming member 42 has a tapered guide that tapers on a horizontal plane toward the ejection section 38. A portion 44 and a small chamber portion 46 that partitions the periphery of the heating resistor 34 are formed. In FIG. 7, the nozzle plate 40 is omitted. In the same figure, reference numeral 48 denotes a common electrode, and 49 denotes an individual electrode. Although not shown, the through-hole 30 has a role of connecting the ink tank and the ink flow path 32.

When the heating resistor 34 is energized, bubbles are generated in the ink flow path 32 on the heating resistor 34, and the ink droplets are ejected from the ejection unit 38 by pressure propagation due to the increase in the volume of the bubbles. Presents a jet mechanism.

[0006]

By the way, the role of the ink flow path in this type of multi-nozzle type is to guide the ink supplied from the through-hole to the discharge section, and also to perform the ink flow until the next discharge. (Hereinafter, referred to as refilling behavior) is made equal for all the discharge portions to make the discharge performance uniform.

The refilling behavior of the ink is mainly governed by the inertia force at the time of refill flow, the resistance of the flow path, and the meniscus force generated at the ejection portion. Is a very large factor.

Accordingly, in order to make the ink refill behavior equal for all the ejection parts and to make the ejection performance uniform, the shape of the flow path from the ink supply source through hole to the ejection part is uniform for all the ejection parts. Then, the conclusion is made.

However, in the above-mentioned conventional side-chute type ink jet print head, since several discharge ports simultaneously perform discharge sequentially while performing a spacing operation, the absolute position of each discharge portion in the spacing direction is absolute. The positions are different. For this reason, the distance from the through hole on the substrate to the discharge unit (hereinafter, referred to as a flow path length) has a different value in each discharge unit. The variation in the flow path length results in a difference in the ink refill behavior, resulting in a variation in the ejection performance.

That is, for example, in a discharge section having a substantially average flow path length in the whole, when the next discharge is performed at the timing when the ink has just refilled to the surface of the discharge section, the flow path length becomes the largest. In a long discharge portion, the resistance to the flow is large, so that refilling cannot be performed in time, and as a result, the droplet amount of the discharged ink is reduced. In addition, in the discharge section having the shortest flow path length, since the resistance to the flow is small, the next discharge is performed in a state where the refilled ink projects to the discharge section surface due to the inertial force of the ink. , Overflow on the surface of the ejection portion, poor directivity of flying ink droplets due to the influence of the overflowed ink, and the like.

[0011] The cause of the variation of the flow path length is as follows.
In addition to the variation at the time of design, there is also a processing accuracy of the through hole. Means for drilling through holes in the substrate to supply ink from the storage unit to the ejection unit include methods such as YAG laser, excimer laser, sandblast, and anisotropic etching. Is small, about ± 30 μm, and large, ± 100 μm, which is also a major factor in the variation of the flow path length.

In view of such a situation, for example, Japanese Patent Publication No. Sho 62
As described in JP-A-32111, various approaches for improvement have been made such as controlling a valve arranged in an ink flow path to change a flow path cross-sectional area and making a flow path resistance uniform. However, there have been problems in that the configuration is complicated, or that the analysis data is difficult to produce in realizing the analysis data.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet print head which can solve the disadvantages of the prior art and can achieve uniform ink refill behavior with a simple structure which is easy to approach.

[0014]

According to the present invention, an ink flow path is formed between a substrate having a heat generating resistor and a nozzle plate having a discharge section via a flow path forming member, and the heat generating resistor is provided. In an ink jet print head, in which a small chamber surrounding a body is formed and ink droplets are ejected from the ejection unit by pressure of bubbles generated by heat generation of the heating resistor, the ink flow path has a high flow path height. And a portion having a low flow path height on the discharge section side.

Further, according to the present invention, it is possible to adopt a configuration in which the high and low portions of the flow path are formed by a laminated structure of flow path forming members.

[0016]

In the refilling behavior of the ink after the ink droplet is ejected, the variation in the resistance and the inertia caused by the variation in the flow path length is absorbed by the high flow path portion, that is, the large volume portion. These variations are so small that they do not affect the ejection performance. The ink flow whose variation is absorbed in the high channel height portion is given a desired refill behavior speed in the low channel height portion.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. It should be noted that a part of the multi-nozzle type is shown similarly to the above-mentioned conventional technology. FIG. 1 is a perspective view showing a state where a nozzle plate is removed, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

The ink jet print head 2 includes a substrate 8 having a heating resistor 4 and formed with a through hole 6 communicating with an ink tank (not shown), a nozzle plate 12 formed with a discharge section 10, and a substrate 8. A first flow path forming member 14 and a second flow path forming member 16 are provided in a stacked state between the nozzle plate 12 and the nozzle plate 12, and a through hole is provided between the substrate 8 and the nozzle plate 12. An ink flow path 18 communicating with the ejection section 6 and the ejection section 10 is formed.

The heating resistor 4 is provided at a position opposed to the ejection section 10. The periphery of the heating resistor 4 is used to ensure the generation of bubbles due to heat generation and the ejection of droplets from the ejection section 10. It is partitioned as a small chamber portion 20 communicating with the ink flow path 18. Reference numeral 21 denotes a common electrode, 2
Reference numeral 3 denotes an individual electrode.

The ink flow path 18 is formed by the first flow path forming member 1.
Due to the laminated structure of the fourth and second flow path forming members 16, the flow path has a high part and a low part, and is formed in a shape in which the flow path height changes on the way. That is, the through hole 6 side is formed as an error absorbing portion 22 as a portion with a high flow path height (height T ₁ ), and the discharge portion 10 side is a portion with a low flow path height (height T ₂ ). The resistance adjusting section 24 is formed. The horizontal plane shape of the resistance adjusting unit 24 is formed in a tapered shape that tapers toward the ejection unit 10 side, and communicates with the small chamber unit 20.

As a method of changing the flow path height, different patterning is performed on two or more film-shaped flow path forming members. More specifically, first, the first flow path forming member 14 is attached on the surface of the substrate 8 shown in FIG. 3, and thereafter, as shown in FIG. 4, patterning for forming the small chamber portion 20 is performed. . Next, the first
The second flow path forming member 16 is pasted on the flow path forming member 14 and patterning is performed so that the resistance adjusting section 24 and the small chamber section 20 are connected as shown in FIG. By repeating this operation several times, the flow path height can be adjusted in multiple stages.
The alignment between the first flow path forming member 14 and the second flow path forming member 16 can be performed with high precision because the patterning is performed after the film is attached.

Next, the roles of the resistance adjusting section 24 and the error absorbing section 22 will be described. First, the resistance adjusting unit 24 controls the refill behavior of the ink, and the following are mainly used as control guidelines. Refill should be as fast as possible or comparable to drive frequency. After the refilling, the ink protrudes from the ejection unit 10 to form a convex meniscus, and then attenuates while repeating vibration. The amount of protrusion at this time must be sufficiently small. Meniscus vibration must be sufficiently attenuated at the drive frequency timing. The channel shape is optimized by means of computer simulation or the like so as to achieve any one or some of these.

The error absorbing section 22 has a function of absorbing variations in resistance and inertia caused by variations in flow path length due to various causes. In particular,
By setting the flow path height T ₁ sufficiently high, both the resistance and the inertia are set to very small values as compared with the resistance adjustment unit 24. Thereby, the resistance force due to the variation in the flow path length and the variation width of the inertial force are also reduced by the resistance adjusting unit 2.
4, these values are much smaller than those values, and the influence of the variation on the ejection performance is very small.

The relationship between the channel height T ₁ of the error absorption section 22, a channel height T ₂ of the resistance adjusting unit _{24, 2 × T 2 ≦ T 1} ≦
About 5 × T ₂ is desirable.

As described above, when the height of the ink flow path 18 is changed, the error absorption portion 22 having a high flow path height causes a variation in resistance and the like due to the flow path length difference in the ink refilling behavior. Is corrected, and the ink flow refill is returned to an optimal state by the resistance adjustment unit 24 having a low flow path height, so that the ejection performance of each ejection unit 10 in the multi-nozzle can be made uniform.

[0026]

As described above, according to the present invention, the discharge performance of each discharge portion in the multi-nozzle type can be made uniform by a simple ink passage height configuration that can be easily optimized by computer simulation or the like. Therefore, improvement of image quality can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a main part of a state in which a nozzle plate according to an embodiment of the present invention is removed.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a schematic perspective view of a main part of a substrate before a first flow path forming member is attached.

FIG. 4 is a schematic perspective view of a main part showing a state where a first flow path forming member is attached.

FIG. 5 is a schematic perspective view of a main part showing a state where a second flow path forming member is adhered on the first flow path forming member.

FIG. 6 is a schematic perspective view of a main part showing a state where a nozzle plate is attached from the state of FIG. 5;

FIG. 7 is a schematic perspective view of a main part showing a conventional example.

FIG. 8 is a sectional view taken along line BB in FIG. 7;

[Explanation of symbols]

Reference Signs List 4 heating resistor 8 substrate 10 discharge unit 12 nozzle plate 14 first flow path forming member (flow path forming member) 16 second flow path forming member (flow path forming member) 18 ink flow path 20 small chamber 22 error absorption Part (high flow path height) 24 Resistance adjusting part (low flow path height) T ₁ Height of high flow path height T ₂ Height of low flow path height part

Claims (4)

(57) [Claims] An ink flow path is formed between a substrate having a heating resistor and a nozzle plate having a discharge portion via a flow path forming member, and a small chamber surrounding the heating resistor is formed. In an ink jet print head that ejects ink droplets from the ejection unit with the pressure of bubbles generated by the heat generated by the heating resistor, the ink flow path is:
An ink jet print head having a portion with a high flow channel height and a portion with a low flow channel height on the ejection section side. 2. The ink jet print head according to claim 1, wherein the high and low portions of the flow path are formed by a laminated structure of the flow path forming members. 3. The ink jet print head according to claim 2, wherein the flow path forming members are individually and individually patterned in a flow path shape from a lower layer. 4. A height T ₁ of the high portion of the flow path,
The relationship with the height T _{2 of the} portion where the flow path height is low is expressed as “2 × T ₂
4. The ink jet print head according to claim _{1, wherein} ≦ T ₁ ≦ 5 × T ₂ ”.