KR102635289B1 - Cleaning apparatus and cleaning method of ink-jet head and printing apparatus - Google Patents

Abstract

(Problem) To provide a cleaning device, cleaning method, and printing device for an inkjet head that reliably removes ink from the nozzle plate surface and ejects ink stably.
(Solution means) In order to solve the above problem, there is provided a suction portion having a suction port for sucking ink, and a support portion in contact with the nozzle plate of the inkjet head, and a contact angle α of the nozzle plate with respect to the ink and with respect to the ink. A cleaning device for an inkjet head is used where the relationship between the contact angle β of the support portion and the contact angle γ of the suction portion with respect to the ink is contact angle α>contact angle β>contact angle γ.

Description

Inkjet head cleaning device, cleaning method, and printing device {CLEANING APPARATUS AND CLEANING METHOD OF INK-JET HEAD AND PRINTING APPARATUS}

The present invention relates to an inkjet head cleaning device, a cleaning method, and a printing device using an inkjet head.

The nozzle plate of the inkjet head has nozzle holes through which ink is ejected. In such an inkjet head, the surface of the nozzle plate often maintains ink repellency so that no excess ink remains around the nozzle hole when ink is ejected from the nozzle hole. Figures 1(a) and 1(b) show the structure of the inkjet head.

The inkjet head includes a plurality of nozzles 100 that discharge liquid droplets, a pressure chamber 110 communicating with the nozzles, a partition wall 111 dividing the pressure chambers corresponding to different nozzles, and a diaphragm 112 forming a part of the pressure chamber. , it has a piezoelectric element 130 that vibrates the diaphragm, a piezoelectric member 140 that supports the partition, and a common electrode (not shown) that applies a voltage to the piezoelectric element 130. In addition, it has an inlet for liquid not shown.

Additionally, in the type of inkjet head that circulates liquid, it has a liquid inlet and an outlet, not shown, and discharges ink while flowing ink. The piezoelectric element 130 and the piezoelectric member 140 supporting the partition are separated from one piezoelectric member by dicing. The nozzles 100 of the inkjet head have a diameter of 20 μm to 50 μm and are lined up with 100 to 300 holes at intervals of 100 μm to 500 μm.

The inkjet head configured in this way operates as follows. When a voltage is applied between the common electrode (not shown) on the back side of the piezoelectric element 130 and the piezoelectric element 130, the piezoelectric element 130 changes from the state of FIG. 1(a) to that of FIG. 1(b). transformed into a state. When the piezoelectric element 130 is deformed (the lower part of the piezoelectric element 130 is deformed), the volume of the pressure chamber 110 decreases, allowing pressure to be applied to the liquid. The liquid droplet 150 is discharged by that pressure.

The structure of the inkjet head may be a structure using a thin film piezoelectric element. FIG. 2(a) and FIG. 2(b) are diagrams showing the structure of a thin film type inkjet head. In Figure 2(a), a nozzle 200 for discharging liquid, a pressure chamber 210 communicating with the nozzle, and a common pressure chamber 230 supplying liquid to the pressure chamber are connected. A thin film piezoelectric element 220 is formed on the top of the diaphragm 212, which forms part of the pressure chamber. The inkjet head configured in this way operates as follows. When voltage is applied to the thin film piezoelectric element 220, the thin film piezoelectric element 220 is transformed from the state of FIG. 2(a) to the state of FIG. 2(b). When the thin film piezoelectric element 220 is deformed, the volume of the pressure chamber 210 becomes smaller, allowing pressure to be transmitted to the liquid. The liquid droplet 150 is discharged by that pressure.

For such an inkjet head, there is a technology for cleaning ink, etc. adhering to the vicinity of the nozzle hole on the nozzle plate by suction using a suction nozzle.

For example, Figure 3 shows an ink suction nozzle in the prior art. It is shown that suction cleaning is performed by sliding the local suction means (4) connected to the negative pressure generating means (3) while contacting the head body (1) on which the nozzle (2) is disposed (Patent Document 1). The nozzle (2) is cleaned in the suction opening (5) of the local suction means (4). The local suction means (4) can be moved by the suction opening moving means (6). The local suction means 4 can control the suction force with the pressure change means 8.

Additionally, a method of performing suction cleaning by moving the local suction means 4 while maintaining a gap so as not to contact the nozzle 2 has been proposed (Patent Document 2).

Japanese Patent Publication No. 5-200128 Japanese Patent Publication No. 2009-137210

However, in the method shown in Patent Document 1, since the nozzle and the suction means come into contact, there is a high possibility that the nozzle will be damaged, and stable ejection cannot be achieved.

In the method shown in Patent Document 2, since there is no contact with the nozzle, it may be insufficient to remove ink from the plate surface. On the contrary, if the suction is too much, part of the ink inside the nozzle is sucked away. As a result, the ejection of ink becomes unstable.

Therefore, the object of the present application is to provide a cleaning device, a cleaning method, and a printing device for an inkjet head that reliably remove ink from the nozzle plate surface and eject ink stably.

In order to solve the above problem, it has a suction portion having a suction port for sucking ink, and a support portion in contact with a nozzle plate of an inkjet head, and a contact angle α of the nozzle plate with respect to the ink and a contact angle of the support portion with respect to the ink. A cleaning device for an inkjet head is used where the relationship between β and the contact angle γ of the suction portion with respect to the ink is contact angle α>contact angle β>contact angle γ.

Additionally, a cleaning device for the inkjet head and a printing device equipped with the inkjet device are used.

Additionally, an inkjet head cleaning method is used in which the inkjet head cleaning device is brought into contact with the nozzle plate of the inkjet head, and the cleaning device is moved relative to the nozzle plate to clean the nozzle plate.

According to the inkjet head cleaning device, the inkjet head cleaning method, and the printing device provided with the inkjet head cleaning device of the present invention, it is possible to suck ink without leaving ink on the nozzle plate, producing a print with excellent printing quality. It can be realized.

Figure 1 (a) shows the structure of a conventional bulk inkjet head, (b) shows the thin film type inkjet head of (a), and shows the state of the head when voltage is applied to the piezoelectric element.
Figure 2 (a) shows the structure of a conventional thin-film inkjet head, (b) shows the thin-film inkjet head of (a), and shows the state of the head when voltage is applied to the piezoelectric element.
Figure 3 is a diagram showing ink on a nozzle plate being sucked by a conventional method.
4(a) to 4(e) are diagrams showing the flow of ink suction in the embodiment.
5(a) to 5(f) are cross-sectional views of the inkjet head cleaning device in the embodiment showing differences in the suction state of ink droplets due to differences in wettability of constituent members.
6 (a) is a schematic diagram of the inkjet head cleaning device in the example, (b) is a schematic diagram of the inkjet head cleaning device in Comparative Examples 1 to 3, and (c) is a schematic diagram of the ink liquid in Comparative Examples 1 to 3. A schematic diagram showing the enemy overflowing out of the cleaning device.
7(a) to 7(b) are diagrams showing discharge characteristics by cleaning the inkjet head in the example.
8 (a) to (b) are perspective views showing the cleaning process in Embodiment 1, and (c) to (d) are cross-sectional views showing the cleaning process in Embodiment 1.
Fig. 9 is a diagram showing the final stage of the cleaning process in Embodiment 1;
Fig. 10 is a perspective view showing the cleaning device according to Embodiment 2.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention will be described with reference to the drawings.

(Embodiment 1)

An inkjet head cleaning device, an inkjet head cleaning method, and a printing device equipped with an inkjet head cleaning device according to an embodiment will be described. The structure of the inkjet head of the embodiment is the same as that of the bulk piezo head shown in FIG. 1.

<Ink droplet suction flow using a cleaning device>

4(a) to 4(e) are diagrams showing the flow of sucking the ink droplets 402 adhering to the nozzle plate 404 in Embodiment 1 using the cleaning device 403. The nozzle plate 404 is a part of the inkjet device where the nozzle emerges from the surface. When ink is ejected from the nozzle plate 404 for a long time, ink droplets 402 appear on the surface of the nozzle plate 404 (FIG. 4(b)).

At a certain timing, cleaning of the nozzle plate 404 starts. First, the inkjet head cleaning device 403 moves to just below the nozzle plate end A. Afterwards, the cleaning device 403 rises and the nozzle support portion (not shown) of the cleaning device 403 comes into contact with the nozzle plate and stops (FIG. 4(c)).

In this state, a vacuum pump (not shown) in communication with the cleaning device 403 operates to sweep the nozzle plate at a constant moving speed while sucking at a predetermined suction flow rate. At this time, the cleaning device 403 moves until it passes the end B of the nozzle plate opposite to the end A of the nozzle plate that starts the sweep (FIG. 4(d)). After passing the nozzle plate end B, the cleaning device 403 descends, and the suction operation of the ink droplet 402 is completed (FIG. 4(e)).

In this series of operations, the cleaning device 403 does not pass through the nozzle plate end B, but ends the sweep operation in the middle of the nozzle plate, and when the cleaning device 403 descends, the ink droplets 402 on the nozzle plate smiles but remains. Ink droplets smaller than the first suction port of the cleaning device 403 remain without being sucked.

Therefore, when sucking ink droplets, it may be desirable to move the cleaning device until it passes the end of the nozzle plate.

Additionally, the cleaning device 403 and the nozzle plate 404 can be moved relative to each other.

<Components of cleaning device>

5(a) to 5(f) are cross-sectional views when the nozzle plate 404 is cleaned using the cleaning device 403. The nozzle plate 404 is cleaned by the suction unit 503 located at the top of the cleaning device 403. Each figure shows differences in the suction state of the ink droplet 402.

Figures 5(a) to 5(c) are before cleaning, and Figures 5(d) to 5(f) are after cleaning.

The contact angles of the nozzle plate 404, the support portion 502, and the suction portion 503 with respect to the ink droplet 402 are set to contact angle α, contact angle β, and contact angle γ, respectively. The suction section 503 has a first suction port 601 for sucking the ink droplet 402.

Also, in this example, it is an aromatic polymer solution ink. The surface of the nozzle plate 404 is coated with a silicone-based water-repellent film, and this is the contact angle in the coating. Hereinafter, the first and second patterns are comparative examples, and the third pattern is an example.

The contact angle was measured using DSA100 manufactured by KRUSS.

In addition, since the support part 502 contacts and sweeps the nozzle plate 404, the hardness of the support part 502 is preferably softer than that of the nozzle plate 404. If the hardness is too hard, the surface of the nozzle plate 404 will be scratched.

<First pattern>

In Fig. 5(a), the contact angle α>>contact angle β=contact angle γ. Specifically, contact angle α = 66°, contact angle β = contact angle γ = 26°. The range of contact angle α is 60 to 70°. The range of contact angle β and contact angle γ is 15 to 30°, preferably 20 to 30°.

In this state, each member of the cleaning device 403 is heavily wetted with the ink droplet 402, and the ink droplet 402 attached to the nozzle plate 404 with low wettability moves to the suction unit 503. It is an easy state to do.

However, because it is very easy to get wet, a small amount of ink droplets 402 are likely to enter between the support portion 502 and the nozzle plate 404 due to capillary action, and are likely to remain on the nozzle plate 404 (Figure 5(d) )).

<Second pattern>

Figure 5(b) shows a state where contact angle α≥contact angle β=contact angle γ. Specifically, the contact angle α = 66°, the contact angle β = the contact angle γ = 42°. The range of contact angle α is 60 to 70°. The range of contact angle β and contact angle γ may be 35 to 55°, and preferably 40 to 50°. This state is a state in which each member of the cleaning device 403 is not very wet with the ink droplet 402, and the ink droplet 402 attached to the nozzle plate 404 is difficult to move to the suction part 503. It is a state.

As a result, ink droplets 402 often remain on the nozzle plate 404 (FIG. 5(e)).

<Third pattern>

Figure 5(c) shows a state where the contact angle α>contact angle β>contact angle γ. Specifically, the contact angle α = 66°, the contact angle β = 42°, and the contact angle γ = 26°. The contact angle α is 60 to 70°. The contact angle β is 35 to 55°, and is preferably 40 to 50°. The contact angle γ is 15 to 30°, and is preferably 20 to 30°. In this state, since the suction portion 503 has high ink wettability, the ink droplets 402 on the nozzle plate 404 with low wettability are likely to move to the suction portion 503. However, since the ink wettability of the support portion 502 is not very high, the ink droplets 402 have difficulty spreading to the support portion 502. Accordingly, the ink droplets 402 are efficiently sucked in, making it difficult for the ink droplets 402 to remain on the nozzle plate 404 (FIG. 5(f)).

<First suction port (601)>

Here, the first suction port 601 is arranged in a slit shape, and its width is about 0.5 mm. If the slit width is as large as about 1.0 mm, it cannot be completely suctioned, and ink droplets 402 remain on the nozzle plate 404. If the slit width is as small as about 0.2 mm, there are no remaining ink droplets 402, but the flow path resistance increases and it is necessary to increase the suction flow rate. As a result of the experiment, it was found that suction was possible without residual ink droplets when the slit width was between 0.25mm and 0.75mm.

<Result>

From the above, it can be seen that the wettability of the members constituting the cleaning device 403 is preferably that the wettability of the support portion 502 is high and that the wettability of the suction portion 503 is higher relative to the nozzle plate 404. In addition, this difference in wettability may be realized by changing the type of member, and even if it is the same member, it may be realized by surface treatment, etc.

(Example)

Figure 6(a) shows a cleaning device 403 in the embodiment.

The cleaning device 403 has a convex suction portion 503 at the top, and a support portion 502 at the top. There are two support portions 502 in a line shape. The support portion 502 is a portion that contacts the nozzle plate 404. To stabilize the contact, at least two support portions 502 are required. The suction portion 503 has a first suction port 601 for sucking ink. Between the plurality of support parts 502, there is a first suction port 601.

Below the suction part 503, there is a housing part 604. The housing portion 604 is located before and after the suction portion 503 and is a flat platform. The upper surface is preferably flat, but may be inclined, curved, or spherical.

In the housing portion 604, a guide portion 603 is disposed in succession with the support portion 502. Like the support portion 502, at least two guide portions 603 are required.

Additionally, the housing portion 604 is gently inclined from the outside toward the inside (toward the inside between the plurality of guide portions 603), and a second suction port 602 is disposed on the inside portion.

The material of the support portion 502 is polytetrafluoroethylene (PTFE). The material of the suction part 503 is polyetheretherketone (PEEK).

Additionally, the contact angle for ink is 42° for PTFE and 26° for PEEK. The nozzle plate 404 is coated with a silicone-based water-repellent film, and its contact angle is higher. The result corresponds to the third pattern. Regarding the comparative examples below, the materials and patterns are shown in Table 1.

The support portion 502 is taller than the suction portion 503, and the height difference is about 0.05 mm. The height difference between the housing portion 604 and the suction portion 503 is about 5 mm. This is because the diameter of the ink droplet oozing from the nozzle hole is generally 2 to 3 mm, so it is set to about 5 mm to absorb this size. Since the diameter of the ink droplet oozing from the nozzle is 2 to 3 mm, the difference in height between the housing portion 604 and the suction portion 503 does not have to be 5 mm, but can be 3 mm or more.

The material of the guide portion 603 is PTFE. The guide portion 603 is disposed to guide the ink that has fallen onto the housing portion 604 from the suction portion 503 to prevent it from overflowing out of the cleaning device 403 .

Due to this structure, ink on the nozzle plate that cannot be all suctioned through the first suction port 601 and spills onto the housing portion 604 is also efficiently suctioned through the second suction port 602.

<Test>

Using the cleaning devices of the examples and comparative examples, a suction test of ink droplets on the nozzle plate 404, a durability test by contact with the nozzle plate, and a test of ink droplets outside the cleaning device when a large amount of ink droplets were sucked in. A spillover test of ink droplets was performed.

The suction test was conducted at a suction flow rate of approximately 5 L/min and a sweep speed of 10 mm/sec. The amount of ink droplets oozing out from the nozzle hole was determined by allowing ink droplets with a diameter of about 1 mm to ooze out from a nozzle with 600 holes.

In the durability test by contact with the nozzle plate 404, the surface of the nozzle plate was visually observed after being swept 40,000 times.

In the ink droplet overflow test, the amount of ink droplet oozing out of the nozzle hole was set to a diameter of about 3 to 4 mm, and the ink droplet was sucked by sweeping with a cleaning device.

<Evaluation results>

In the examples, the aspiration test of the ink droplets did not reveal any remaining ink droplets. This is because it is the third pattern of contact angle.

Additionally, in the durability test upon contact with the nozzle plate 404, no physical damage such as scratches could be confirmed on the surface of the nozzle plate 404. This is because it is the material of the support portion 502. Additionally, in order to confirm damage, the contact angle was also measured. The result was that there was no difference in measured values between the contact portion and the non-contact portion of the nozzle plate 404 of the cleaning device, and there was no damage.

In the ink droplet overflow test, no ink droplet overflow was confirmed. This is because the height difference between the suction part 503 and the housing part 604 is large.

Hereinafter, the cleaning devices in Comparative Examples 1 to 3 are different from the examples in materials, dimensions, and structures. Table 1 shows the materials, dimensions, and test results. Figure 6(b) shows the cleaning devices in Comparative Examples 1 to 3. Compared to the cleaning device of the embodiment, the height difference between the housing portion 604 and the suction portion 503 is small, and the second suction port 602 is not disposed. There is also no guide unit 603.

(Comparative Example 1)

Aspiration test of ink droplets confirmed that residual ink droplets were on the nozzle plate. This is because PTFE has a low wettability of ink droplets, so all of the ink droplets on the nozzle plate could not be sucked up. The contact angle is not good due to the second pattern.

In the durability test in contact with the nozzle plate 404, no physical damage such as scratches could be confirmed on the surface of the nozzle plate 404. As a result of measuring the contact angle of the surface, there was no difference in the measured values between the nozzle plate contact part and the non-contact part of the cleaning device, and there was no damage. Additionally, PTFE's Rockwell hardness is 20 on the R scale, resulting in flexibility for the nozzle plate.

In the ink droplet overflow test, the results are shown in Fig. 6(c). It was seen that the ink 410 that had not been completely absorbed from the suction port was flowing out of the cleaning device. This is presumed to be because the height difference between the suction section and the ink housing section is small. Hereinafter, the same applies to Comparative Examples 2 and 3.

(Comparative Example 2)

Aspiration test of ink droplets confirmed that residual ink droplets were on the nozzle plate. However, it was difficult for residual liquid droplets to form compared to Comparative Example 1. However, due to lack of stability, residual droplets are likely to occur.

Durability testing at the nozzle plate contact revealed flaws on the nozzle plate surface. The Rockwell hardness of PEEK was 120 on the R scale, and it was found to be hard against the nozzle plate surface.

In the ink droplet overflow test, it was found that the ink droplets that were not completely sucked in from the first suction port were flowing out of the cleaning device. This is presumed to be because the height difference between the suction section and the ink housing section is small.

(Comparative Example 3)

A suction test of ink droplets revealed no remaining ink droplets.

In the durability test at the nozzle plate contact, no physical damage such as scratches could be confirmed on the nozzle plate surface. The contact angle measurement result also showed that there was no difference in measured values between the nozzle plate contact part and the non-contact part of the cleaning device, and there was no damage.

In the ink droplet overflow test, it was found that the ink droplets that were not completely sucked in from the first suction port were flowing out of the cleaning device.

(result)

From the above results, a relationship between the contact angles of the third pattern is required. In addition, it can be seen that the material of the support part 502 is preferably PTFE, the material of the suction part 503 is preferably PEEK, and the height difference between the suction part 503 and the housing part 604 is preferably about 5 mm.

In addition, regarding the durability test, it was confirmed that even if the contact portion with the nozzle plate was made of polyethylene terephthalate (PET), no scratches appeared on the nozzle plate surface. Additionally, PET's Rockwell hardness (R scale) is 56.

(Confirmation of cleaning performance of the inkjet head in the cleaning device in the example)

The following tests were conducted with Head 1 and Head 2 of the same specifications.

FIG. 7(a) shows the change in the effective number of discharge nozzles when a cleaning operation of the inkjet head is performed using the cleaning device structured in the embodiment. It can be seen that the effective number of nozzles increases after the cleaning operation compared to the effective number of nozzles before the cleaning operation. It is believed that by performing the cleaning operation, the ink in the nozzle hole is refreshed, ejection defects such as nozzle clogging are eliminated, and the effective number of nozzles is increased. Additionally, an effective nozzle is a normal nozzle without nozzle blockage or emergency bending.

Figure 7(b) shows the change in unevenness of the landing position of the liquid droplet ejected from the nozzle of the inkjet head on the substrate after the cleaning operation. If the cleaning operation causes poor suction of the ink droplets and the ink droplets remain on the nozzle plate, there is a risk that the impact position may become uneven. However, it can be seen that no change in the impact position unevenness is observed due to the cleaning operation. there is.

(Embodiment 2)

In the initial stage of ink filling, air bubbles in the head body 1 do not fall out, or adhesion to the surface of the nozzle plate 9 occurs while repeating printing on the object.

Additionally, when printing is not performed for a long period of time, nozzles that do not eject or nozzles that have a bent ejection direction that causes misalignment of the printing position may occur. Cleaning is performed to restore discharge from these problematic nozzles.

The cleaning process will be described in detail below using the drawings. To repair a problem nozzle, first remove air bubbles, dried ink, ink deposits, etc. accumulated on the nozzle surface or inside the nozzle to improve ink passage.

<Purge>

First, as shown in FIG. 8(a), purge is performed to discharge ink from within the nozzle 19. Fig. 8(a) shows only the surface of the nozzle 19 with respect to the inkjet head 11. The same applies to Figure 8(b).

One of the purge methods is a pressure purge in which ink is discharged from the nozzle 19 by setting the internal pressure of the inkjet head 11 to positive pressure.

Even if the internal pressure of the inkjet head 11 fluctuates by ±several kPa, liquid spillage or bubbles do not occur from the nozzle due to the surface tension of the ink, so a pressurized purge method was performed by maintaining the pressure +10 kPa for 5 seconds.

As a result, ink was discharged from the hole of the nozzle 19 of the inkjet head 11, and ink droplets 80 with a diameter of about 2 to 3 mm were generated on the hole surface of each nozzle 19.

In addition, another purge method is a suction method in which ink is discharged from the nozzle 19 by pressing a rubber cap against the surface of the nozzle 19 and vacuuming the sealed space between the surface of the nozzle 19 and the cap. There is a fudge.

When the sealed space within the cap was suctioned for 1 second with a vacuum pump at a suction speed of 10 L/min, droplets with a diameter of 2 to 3 mm could be discharged onto the surface of the nozzle 19.

<Cleaning>

Next, the process of cleaning the surface of the nozzle 19 to remove the ink droplet 80 discharged from the nozzle 19 will be described. 8(a) to 8(d) show the cleaning device 61 traveling along the nozzle surface from the left end to the right end of the inkjet head 11 to clean the nozzle surface.

In Fig. 8(a), the cleaning device 61 faces the nozzle surface of the inkjet head 11, and rises toward the nozzle surface from a slightly distant position. The upper surface of the support portion 73 of the cleaning device 61 contacts the nozzle surface of the inkjet head 11. At this time, a gap of 15 μm is ensured between the flat portion 71 having the slit-shaped suction port 72 and the nozzle surface due to the height of the support portion 73.

The cleaning device 61 advances from FIG. 8(a) to FIG. 8(b), and when the cleaning device 61 comes into contact with the ink droplet 80 attached to the surface of the nozzle 19, the ink droplet 80 Silver spreads into the gap between the surface of the nozzle 19 and the flat portion 71 of the cleaning device 61 by capillary action.

Figures 8(c) and 8(d) are side views showing the ink droplet 80 attached to the inkjet head 11 in contact with the cleaning device 61. When the ink droplet 80 first contacts the inclined surface of the cleaning device 61, it soon enters between the inkjet head 11 and the cleaning device 61 by capillary action (FIG. 8(c)). Since a gap is formed at a certain interval between the inkjet head 11 and the flat portion 71 of the cleaning device 61, the ink droplet 80 fills the gap, as shown in FIG. 8(d). It spreads.

FIG. 9 is a diagram showing the state as time progresses further from FIG. 8(d). Since the gap of 15 μm is very small compared to the droplet size of 2 to 3 mm, the ink quickly fills the gap and is sucked in from the suction port 72.

At this time, since a material with lower liquid repellency compared to the surface of the nozzle 19 is used for the flat portion 71 of the cleaning device 61, the ink moves toward the cleaning device 61 and enters the suction port. It is sucked in and discharged along (72).

The ink droplet 80 is attached to the nozzle surface by surface tension, and it is difficult to remove the ink droplet 80 only by suction force, and the ink droplet 80 is sucked in a broken state. Therefore, even if the ink droplet 80 is sucked, residual droplets with a diameter of 100 μm or less may be generated in the suction trace. In this embodiment, the ink droplets 80 adhering to the surface of the nozzle 19 are drawn to the suction port 72 by the surface tension of the ink, thereby suppressing the generation of remaining ink droplets 80.

The cleaning device 61 removes the ink droplet 80 on the surface of the nozzle 19, moves to the end of the nozzle surface shown in FIG. 9, and cleans one inkjet head 11 when it passes through the nozzle surface. Quit. The cleaning device 61 performed cleaning at a scanning speed of 10 to 100 mm/s, and no ink residue was generated in any case. Through the above cleaning process, the ink droplets 80 adhering to the nozzle surface of the inkjet head 11 can be removed without remaining droplets.

(Embodiment 3)

Fig. 10 is a perspective view showing a cleaning device according to Embodiment 3 of the present invention. Matters not described are the same as in Embodiments 1 and 2. Unlike Embodiments 1 and 2, a plurality of air supply holes 75 are formed on the upper surface of the support portion 73 of the cleaning device 61. The air supply hole 75 is effective for introducing pressure air, but may be a through hole.

When the nozzle surface of the inkjet head 11 and the cleaning device 61 are brought close to each other and suction is taken from the suction port 72, air flows upward from below the air supply hole 75. Due to this air flow (static pressure), a gap is generated between the surface of the nozzle 19 and the upper surface of the support portion 73. The cleaning device 61 travels along the nozzle surface of the inkjet head 11 while maintaining this gap to perform cleaning.

Here, the width of the support portion 73 is 1 mm, the height of the support portion 73 is 15 μm, and as the air supply hole 75, two through holes with a diameter of 0.3 mm are arranged at a 4 mm pitch for each support portion 73. Since an air layer is formed in a range of about 2 mm in diameter from the center of the air supply hole 75, the shortest distance between the air supply hole 75 and the suction port 72 can be 2 mm or more.

According to this, it was confirmed that an air layer (static pressure) was formed between the upper surface of the support portion 73 and the nozzle surface, and that there was no direct contact. When cleaning was performed, cleaning was possible without ink residue when the scanning speed of the cleaning device 61 was between 10 and 100 mm/s. As described above, according to Embodiment 2 of the present invention, the cleaning device 61 does not come into contact with the nozzle surface, and therefore can remove ink droplets adhering to the nozzle surface without damaging the nozzle surface.

(overall)

Embodiments 1 to 3 can be combined. The cleaning device of Embodiment 1 may be used in Embodiments 2 and 3.

The inkjet head cleaning device, the inkjet head cleaning method, and the printing device provided with the inkjet head cleaning device of the present invention can efficiently suck ink droplets on a nozzle plate with low wettability, thereby improving ink ejection performance. Thus, it can be applied to the discharge of ink of the light emitting layer of OLED, the discharge of decorative ink using UV curable ink, etc.

1:Head body
2:Nozzle
3: Negative pressure generating means
4: Local suction means
5: Suction opening
6: Suction opening moving means
8:Pressure fluctuation means
9:Nozzle plate
11:Inkjet head
19:Nozzle
20: diameter
61: Cleaning device
71: Flat part
72:Suction port
73: Support part
75: Air supply hole
80: Ink droplet
100:nozzle
110: Pressure room
111: Bulkhead
112:Diaphragm
130: Piezoelectric element
140: Piezoelectric member
150: droplet
200: nozzle
210: Pressure room
212:Diaphragm
220: Thin film piezoelectric element
402: Ink droplet
403: Cleaning device
404: Nozzle plate
410:ink
502: Support part
503: Suction part
601: First suction port
602: Second suction port
603: Guide section
604: Housing part

Claims (14)

a suction unit having a first suction port for sucking ink;
a support part disposed on the upper part of the suction part other than the upper part of the first suction port and in contact with the nozzle plate of the inkjet head;
It has a housing portion located below the suction portion,
The relationship between the contact angle α of the nozzle plate with respect to the ink, the contact angle β of the support portion with respect to the ink, and the contact angle γ of the suction portion with respect to the ink is equation 1 below,
A cleaning device for an inkjet head, wherein the housing portion has a plurality of guide portions that prevent leakage of the ink.
(Equation 1) Contact angle α > contact angle β > contact angle γ In claim 1,
A cleaning device for an inkjet head, wherein the support parts are plural, and the suction part is disposed between the plurality of support parts. In claim 1,
A cleaning device for an inkjet head, wherein the support portion has an air supply hole. delete In claim 1,
The cleaning device for an inkjet head, wherein the housing portion is inclined toward the inside of the plurality of guide portions. In claim 1,
A cleaning device for an inkjet head, wherein the housing portion has a second suction port for sucking the ink. In claim 1,
The contact angle β is 35° to 55°, and the contact angle γ is 15° to 30°. In claim 1,
A cleaning device for an inkjet head, wherein the first suction port has a slit shape. A printing device comprising the inkjet head cleaning device according to claim 1 and an inkjet device. A process of bringing the nozzle surface on which the plurality of nozzles of the application head are arranged and the flat part of the cleaning device into proximity;
The nozzle surface and the flat part are relatively moved in a parallel state in the arrangement direction of the plurality of nozzles, and ink is drawn into the gap between the nozzle surface and the flat part by capillary action, and a suction part disposed on the flat part is provided. It includes a suction process of sucking the ink,
The cleaning device,
a suction unit having a first suction port for sucking ink;
a support part disposed on the upper part of the suction part other than the upper part of the first suction port and in contact with the nozzle plate of the inkjet head;
It has a housing portion located below the suction portion,
The relationship between the contact angle α of the nozzle plate with respect to the ink, the contact angle β of the support portion with respect to the ink, and the contact angle γ of the suction portion with respect to the ink is the following equation 1,
A cleaning device for an inkjet head, wherein the housing has a plurality of guide parts to prevent leakage of the ink,
How to clean the applicator head.
(Equation 1) Contact angle α > contact angle β > contact angle γ In claim 10,
A cleaning method for an application head, wherein the flat portion includes a set of supports, and the ink is drawn into the support portion, the nozzle surface, and the flat portion by capillary action. In claim 11,
A cleaning method for an application head, wherein the distance between the nozzle surface and the flat portion is made constant by contacting the one set of support portions with the nozzle surface. In claim 11,
A cleaning method for an application head in which an air supply hole is formed in the set of supports, and a gap between the nozzle surface and the flat part is secured non-contactly by applying positive pressure between the support part and the nozzle surface. In claim 10,
A cleaning method of an application head further comprising a purge process of expelling the ink from the application head and forming droplets on the nozzle surface.

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