JPS6058701B2 - Inkjet recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording head used in an inkjet recording apparatus.

Conventionally, in this type of inkjet recording head, when the operation is stopped, ink tends to accumulate on the outside of the nozzle, which disturbs the ink flow or the trajectory of the ink particles when ejecting the head again.

In addition, ink tends to evaporate to dryness, causing nozzle clogging. For this reason, various measures have been considered to prevent ink from forming on the outside of the nozzle, but none have been found to be sufficiently effective. Among these, those with a structure shown in FIGS. 1 and 2 have a considerable effect during a relatively short suspension period. First, the cylindrical nozzle holding member 1
A liquid chamber 3 for the ink 2 is formed inside the liquid chamber 3, and a nozzle plate 6 having a small-diameter nozzle 5 in the center is fixed to a step 4 formed at the end of the liquid chamber 3. . A space 8 is formed on the outside of the nozzle plate 6 by a flange 7 that is integrated with the nozzle holding member 1.
Capillary grooves 9 with equal spacing and having a predetermined depth are formed in the end face of the flange 7 to communicate between the space 8 and the outer peripheral surface. In the conventional device having such a structure, an ink pool 10 as shown in FIG. It is removed from the space 8 by suction.

Therefore, when re-jetting is started, there is no ink pool 10 outside the nozzle 5, which eliminates the phenomenon of misalignment of the jetting direction. However, since the nozzle holding member 1 is usually made of metal, it has physical properties that make it easily wetted by the ink 2. During long-term use, the ink that has evaporated to dryness will stick to the inner wall of the capillary groove 9, causing the capillary to become wet. This will cause the groove 9 to become clogged. If the capillary grooves 9 become clogged in this manner, there is a drawback that the ability to remove the ink pool 10 is significantly reduced. Therefore, although there is no problem when used for a short period of time, the intended purpose cannot be achieved when used for a long period of time. SUMMARY OF THE INVENTION The present invention has been devised in view of these points, and an object of the present invention is to provide an inkjet recording head that can remove ink pools and operate normally even during long-term use.

In the present invention, the shape of the capillary grooves on the outside of the nozzle is such that the groove interval decreases as the distance from the nozzle increases,
By changing the properties of the inner wall so that the ink contact angle is 90 degrees or less, it is possible to sufficiently achieve the function of suctioning ink puddles in the space and to effectively remove them from the inside of the capillary grooves. The structure is such that the ability to remove ink puddles does not deteriorate even when used for a period of time.

A first embodiment of the present invention will be described based on FIGS. 3 to 5.

Components that are the same as those described in FIGS. 1 and 2 are designated by the same reference numerals, and explanations thereof will be omitted. The capillary grooves 11 in this embodiment are shaped so that the groove interval decreases as the distance from the nozzle 5 increases, and the reduction angle α is preferably 15 degrees or more on one side. The inner wall 12 of the capillary groove 11 is made hydrophilic. Specifically, the material of the nozzle holding member 1 is a metal such as nickel, chromium, or stainless steel. Also,. By providing the surface with fine irregularities, the wettability of the inner wall 12 with the ink 2 is increased, and a favorable result for the sew layer can be obtained. Further, the outer surface of the nozzle plate 6 is not easily wetted by the ink 2 or has water repellency. It is desirable to do so.

In order to provide such properties, a base may be made of stainless steel, nickel, etc., and its surface may be coated with a water repellent such as a fluorine compound or a silicon compound. In such a configuration, immediately after the ejection of the ink 2 is stopped, an ink pool 10 occurs in the space 8 outside the nozzle 5 as shown in FIG. As time passes, the ink pool 10 is sucked into the capillary groove 11 and becomes an ink meniscus 13 as shown in FIG.

Since this capillary groove 11 is decreasing downward, the contact angle θ
1 and the contact angle θ2 have a relationship of θ1>θ2, and since this ink meniscus 13 has the property of moving toward the larger contact angle 0, it rapidly moves downward and eventually becomes an ink droplet (not shown). Fall. Therefore, the ink pool 10 is rapidly removed from the vicinity of the nozzle 5, and the ink pool 10 is not left behind. Also, the ink 2 does not evaporate and harden in the capillary groove 11, and the ink remains normal for a long period of time. condition is maintained. Next, a second embodiment of the present invention will be described based on FIG. 6.

This embodiment relates to a multi-nozzle head, in which a plurality of nozzles 5 are formed on a nozzle plate 6, and flanges 7 of a nozzle holding member 1 are vertically opposed to form a space 8. The space portion 8 is provided in the lower flange 7.
A capillary groove 11 is formed for each nozzle 5, in which the groove interval decreases as the distance from the nozzle 5 increases, and the contact angle of the inner wall 12 with the ink 2 is set to 90 degrees or less. . The operation of removing the ink pool 10 in such a structure is also performed in exactly the same manner as in the previous embodiment. As described above, the present invention has the shape of the capillary groove communicating with the space outside the nozzle so that the groove interval decreases as the distance from the nozzle increases, and the inner wall has a contact angle with the ink. Since the angle is set to be less than 90 degrees, the ink pools on the outside of the nozzle can be reliably sucked into the capillary grooves, and the ink can be rapidly discharged within the capillary grooves. It is possible to eliminate the negative effects of re-ejection, and there is no ink evaporation to dryness in the capillary grooves, eliminating clogging, and the vicinity of the nozzle can always be maintained normally, resulting in stable ink ejection. can be carried out over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of a conventional example immediately after stopping ink jetting, FIG. 2 is a front view thereof, and FIG. 3 is a longitudinal sectional side view of a first embodiment of the present invention immediately after stopping ink jetting. FIG. 4 is a front view thereof, FIG. 5 is an enlarged front view of the capillary groove, and FIG. 6 is a partially cutaway perspective view showing a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Nozzle holding member, 2... Ink, 5... Nozzle, 8... Space part, 11...
...capillary groove, 12...inner wall.

Claims (1)

[Scope of Claims] 1. A nozzle plate having nozzles for ejecting ink is held by a cylindrical nozzle holding member, and a space is formed in the front surface of the nozzle plate by the nozzle holding member,
A capillary groove is formed in the lower front surface of the nozzle plate, and the groove interval decreases as the distance downward from the nozzle increases, and the inner wall of the capillary groove is formed so that the contact angle with the ink is 90 degrees or less. An inkjet recording head characterized in that it is set to prevent ink from accumulating. 2. The inkjet recording head according to claim 1, wherein the outer surface of the nozzle plate is made water repellent. 3. The inkjet recording head according to claim 1, wherein the inner wall of the capillary groove is made hydrophilic.