JP6569083B2 - INK JET HEAD CLEANING DEVICE, CLEANING METHOD, AND PRINTING DEVICE - Google Patents

Description

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

  The nozzle plate of the inkjet head has nozzle holes for ejecting ink. In such an inkjet head, the surface of the nozzle plate is often kept ink repellent so that when ink is ejected from the nozzle holes, no extra ink remains around the nozzle holes. FIG. 1A and FIG. 1B show the structure of the inkjet head.

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

  In addition, an ink jet head that circulates liquid has a liquid inlet and outlet (not shown), and ejects ink while flowing ink. The piezoelectric element 130 and the piezoelectric member 140 that supports the partition walls are separated from one piezoelectric member by dicing. The nozzle 100 included in the inkjet head has a diameter of 20 μm to 50 μm, and 100 holes to 300 holes are arranged at intervals of 100 μm to 500 μm.

  The ink jet head configured as described above 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 is deformed from the state of FIG. 1A to the state of FIG. When the piezoelectric element 130 is deformed (the lower part of the piezoelectric element 130 is deformed), the volume of the pressure chamber 110 is reduced, and pressure can be applied to the liquid. The droplet 150 is ejected at that pressure.

  The structure of the inkjet head may be a structure using a thin film piezoelectric element. FIG. 2A and FIG. 2B are diagrams showing the structure of a thin film ink jet head. 2A, a nozzle 200 for discharging liquid, a pressure chamber 210 communicating with the nozzle, and a common pressure chamber 230 for supplying liquid to the pressure chamber are connected. A thin film piezoelectric element 220 is formed on the upper part of the diaphragm 212 which forms a part of the pressure chamber. The ink jet head configured as described above operates as follows. When a voltage is applied to the thin film piezoelectric element 220, the thin film piezoelectric element 220 is deformed 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 is reduced and the pressure can be transmitted to the liquid. The droplet 150 is ejected at that pressure.

  For such an ink jet head, there is a technique in which cleaning of ink or the like adhering to the vicinity of a nozzle hole on a nozzle plate is performed by suction cleaning with a suction nozzle.

  For example, FIG. 3 shows a conventional ink suction nozzle. It is shown that the suction cleaning is performed by sliding the local suction means 4 communicated with the negative pressure generating means 3 while making contact with the head body 1 in which the nozzles 2 are arranged (Patent Document 1). The nozzle 2 is cleaned by the suction opening 5 of the local suction means 4. The local suction means 4 can be moved by a suction opening moving means 6. The local suction means 4 can control the suction force by the pressure fluctuation means 8.

  Further, a method has been proposed in which suction cleaning is performed by moving the local suction means 4 while keeping a gap so as not to contact the nozzle 2 (Patent Document 2).

JP-A-5-201028 JP 2009-137210 A

  However, in the method shown in Patent Document 1, since the nozzle and the suction unit are in contact with each other, there is a high possibility that the nozzle is damaged, and stable ejection cannot be performed.

  In the method shown in Patent Document 2, there is a case where it is insufficient to remove the ink on the plate surface because the nozzle is not in contact with the nozzle. On the other hand, if the ink is sucked too much, a part of the ink inside the nozzle is sucked. As a result, ink ejection becomes unstable.

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

In order to solve the above-mentioned problem, a suction part having a suction port for sucking ink and a support part that comes into contact with a nozzle plate of an inkjet head, a contact angle α of the nozzle plate with respect to the ink, and the ink An inkjet head cleaning device is used in which the relationship between 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 satisfies the following relationship: contact angle α> contact angle β> contact angle γ.
In addition, a printing apparatus including the inkjet head cleaning device and the inkjet device is used.

  Further, the inkjet head cleaning device is used in which the inkjet head cleaning device is brought into contact with the nozzle plate of the inkjet head, the cleaning device is moved relative to the nozzle plate, and the nozzle plate is cleaned.

  According to the inkjet head cleaning apparatus, inkjet head cleaning method, and inkjet head cleaning apparatus according to the present invention, it is possible to perform suction without leaving ink on the nozzle plate, thereby improving the print quality. Excellent printing can be realized.

(A) Structure of a conventional bulk type ink jet head, (b) In the thin film type ink jet head of (a), a diagram showing a state of the head when a voltage is applied to a piezoelectric element (A) Structure of a conventional thin film type ink jet head, (b) A diagram showing the state of the head when a voltage is applied to a piezoelectric element in the thin film type ink jet head of (a). The figure which shows a mode that the ink on a nozzle plate is attracted | sucked by the conventional method (A)-(e) The figure which shows the flow of the ink suction in embodiment (A)-(f) Sectional drawing of the inkjet head cleaning apparatus in embodiment which shows the difference in the suction state of an ink droplet by the difference in the wettability of a structural member (A) Schematic diagram of inkjet head cleaning device in example, (b) Schematic diagram of inkjet head cleaning device in comparative examples 1-3, (c) Ink droplet cleaning device in comparative examples 1-3 Schematic showing that it overflows outside (A)-(b) The figure which shows the characteristic of the discharge by the cleaning of the inkjet head in an Example

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment)
An inkjet head cleaning device, an inkjet head cleaning method, and a printing apparatus including an inkjet head cleaning device according to an embodiment will be described. The structure of the ink jet head of the embodiment is the same as the head structure of the bulk type piezo shown in FIG.

<Ink droplet suction flow using a cleaning device>
FIG. 4A to FIG. 4E are diagrams illustrating a flow of sucking the ink droplets 402 attached on the nozzle plate 404 according to the embodiment using the cleaning device 403. The nozzle plate 404 is a portion where the nozzle appears on the surface of the ink jet apparatus. 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. 4B).

  At a certain timing, cleaning of the nozzle plate 404 is started. First, the inkjet head cleaning device 403 moves to a position directly below the nozzle plate end A. Thereafter, the cleaning device 403 is raised and the nozzle support (not shown) of the cleaning device 403 comes into contact with the nozzle plate and stops (FIG. 4C).

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

  In this series of operations, when the cleaning device 403 does not pass through the nozzle plate end B and completes the sweeping operation in the middle of the nozzle plate, and the cleaning device 403 descends, the ink droplet 402 on the nozzle plate. Will remain a little. Ink droplets smaller in size than the first suction port of the cleaning device 403 remain without being sucked.

  Therefore, it can be said that when the ink droplet is sucked, it is desirable to move the cleaning device until it passes through the end of the nozzle plate.

  The cleaning device 403 and the nozzle plate 404 may be moved relatively.

<Components of the cleaning device>
FIG. 5A to FIG. 5F are cross-sectional views when the nozzle plate 404 is cleaned with the cleaning device 403. The nozzle plate 404 is cleaned by the suction unit 503 located at the upper part of the cleaning device 403. Each figure shows the difference in the suction state of the ink droplet 402.

  5A to 5C are before cleaning, and FIGS. 5D to 5F are after cleaning.

  The contact angles of the nozzle plate 404, the support unit 502, and the suction unit 503 with respect to the ink droplet 402 are defined as a contact angle α, a contact angle β, and a contact angle γ, respectively.

  In this example, it is an aromatic polymer solution ink. The nozzle plate 404 is coated with a silicon-based water repellent film on the surface, and has a 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.
Further, since the support portion 502 contacts and sweeps against the nozzle plate 404, it is desirable that the hardness of the support portion 502 is softer than that of the nozzle plate 404. If the hardness is too high, the surface of the nozzle plate 404 will be scratched.

<First pattern>
In FIG. 5A, the contact angle α >> contact angle β = contact angle γ. Specifically, contact angle α = 66 ° and contact angle β = contact angle γ = 26 °. The range of the contact angle α is 60 to 70 °. The range of the contact angle β and the contact angle γ is 15 to 30 °, preferably 20 to 30 °.

  In this state, each member of the cleaning device 403 is very wet with respect to the ink droplet 402, and the ink droplet 402 attached on the nozzle plate 404 having low wettability easily moves toward the suction unit 503. State.

  However, since it is very easy to wet, a small amount of ink droplet 402 is likely to enter between the support portion 502 and the nozzle plate 404 by capillary action, and easily remains on the nozzle plate 404 (FIG. 5D). .

<Second pattern>
FIG. 5B shows a state in which contact angle α ≧ contact angle β = contact angle γ. Specifically, contact angle α = 66 °, contact angle β = contact angle γ = 42 °. The range of the contact angle α is 60 to 70 °. The range of the contact angle β and the contact angle γ is 35 to 55 °, preferably 40 to 50 °. This state is a state in which each member of the cleaning device 403 is not so wet with the ink droplet 402, and the ink droplet 402 attached on the nozzle plate 404 is difficult to move toward the suction unit 503.

  As a result, the ink droplet 402 often remains on the nozzle plate 404 (FIG. 5E).

<Third pattern>
FIG. 5C shows a state in which 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 °, preferably 40 to 50 °. The contact angle γ is 15 to 30 °, preferably 20 to 30 °. In this state, since the suction unit 503 has high ink wettability, the ink droplet 402 on the nozzle plate 404 having low wettability easily moves to the suction unit 503. However, since the ink wettability of the support portion 502 is not so high, the ink droplet 402 is difficult to spread to the support portion 502. Accordingly, the ink droplets 402 are efficiently sucked, and the ink droplets 402 hardly remain on the nozzle plate 404 (FIG. 5F).

<First suction port 601>
Here, the 1st suction port 601 is arrange | positioned by slit shape, and the width | variety is about 0.5 mm. When the slit width is as large as about 1.0 mm, the ink droplet 402 remains on the nozzle plate 404 without being completely sucked. If the slit width is as small as about 0.2 mm, the ink droplet 402 does not remain, but the flow path resistance increases and the suction flow rate needs to be increased. As a result of the experiment, it has been found that when the slit width is between 0.25 mm and 0.75 mm, the ink droplets can be sucked without remaining.

<Result>
From the above, it can be seen that the wettability of the members constituting the cleaning device 403 is desirably higher for the support portion 502 and higher for the suction portion 503 with respect to the nozzle plate 404. This difference in wettability may be realized by changing the type of member, or even the same member may be realized by surface treatment or the like.

(Example)
FIG. 6A shows a cleaning device 403 in the embodiment.

  The cleaning device 403 has a convex suction part 503 at the top, and a support part 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. In order to stabilize the contact, at least two supports 502 are required. The suction unit 503 has a first suction port 601 for sucking ink. There is a first suction port 601 between the plurality of support portions 502.

A housing part 604 is provided below the suction part 503. The housing unit 604 is in front of and behind the suction unit 503 and is a flat table. The upper surface is preferably a flat surface, but may be inclined, curved, or spherical.
A guide portion 603 is disposed in the housing portion 604 continuously with the support portion 502. Similar to the support portion 502, at least two guide portions 603 are required.

  The casing 604 is gently inclined from the outside to the inside (to the inside between the plurality of guides 603), and the second suction port 602 is disposed on the inside.

  The support portion 502 is made of polytetrafluoroethylene (PTFE). Polyether ether ketone (PEEK) is used as the material of the suction part 503.

  The contact angle with respect to ink is 42 ° for PTFE and 26 ° for PEEK. The nozzle plate 404 is coated with a silicon-based water-repellent film and has a higher contact angle than those. As a result, it corresponds to the third pattern. Regarding the following comparative examples, the materials and the patterns are shown in Table 1.

  The support portion 502 is higher than the suction portion 503, and the height difference is about 0.05 mm. The difference in height between the housing portion 604 and the suction portion 503 is about 5 mm. Since the diameter of the ink droplet that oozes out from the nozzle hole is about 2 to 3 mm, it is set to about 5 mm so as to absorb this size. Since the diameter of the ink droplet that exudes from the nozzle is 2 to 3 mm, the difference in height between the housing portion 604 and the suction portion 503 is not limited to 5 mm but may be 3 mm or more.

  The material of the guide part 603 is PTFE. The guide unit 603 is arranged to guide the ink that has fallen from the suction unit 503 to the housing unit 604 so that the ink does not spill out of the cleaning device 403.

  With this structure, of the ink on the nozzle plate, the ink that has not been completely sucked by the first suction port 601 and has flowed down to the housing 604 is also efficiently sucked from the second suction port 602.

<Test>
Using the cleaning device of the example and the comparative example, the ink droplet suction test on the nozzle plate 404, the durability test by contact with the nozzle plate, and the ink droplets when a large amount of ink droplets are sucked An overflow test of ink droplets outside the cleaning device was performed.

  The suction test was performed at a suction flow rate of about 5 L / min and a sweep speed of 10 mm / sec. The amount of ink droplets that ooze out from the nozzle holes was determined by oozing out an appropriate amount of ink liquid having a diameter of about 1 mm from the nozzles of 600 holes.

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

  In the ink droplet overflow test, an appropriate amount of ink liquid to ooze out from the nozzle hole was set to about 3 to 4 mm in diameter, and ink droplet suction was performed by sweeping the cleaning device.

<Evaluation results>
In the examples, the ink droplet suction test did not confirm the remainder of the ink droplets. This is because of the third pattern of contact angles.

  Further, in the durability test in contact with the nozzle plate 404, physical damage such as scratches on the surface of the nozzle plate 404 could not be confirmed. This is because of the material of the support portion 502. Furthermore, in order to confirm the damage, the contact angle was also measured. 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 overflow test of the ink droplet, no overflow of the ink droplet was confirmed. This is because the difference in height between the suction portion 503 and the housing portion 604 is large.

  Hereinafter, the cleaning devices in Comparative Examples 1 to 3 are different in the material, dimensions, and structure from the examples. Table 1 shows the material, dimensions, and test results. FIG. 6B shows cleaning devices in Comparative Examples 1 to 3. Compared to the cleaning device of the embodiment, the difference in height 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 part 603.

(Comparative Example 1)
In the ink droplet suction test, the remaining ink droplets were confirmed on the nozzle plate. This is because PTFE has a low wettability with respect to ink droplets, so that the ink droplets on the nozzle plate cannot be completely sucked. The contact angle may not be the second pattern.

  In the durability test in contact with the nozzle plate 404, physical damage such as scratches on the surface of the nozzle plate 404 could not be confirmed. Even in the measurement result of the contact angle of the surface, there was no difference in the measured value between the nozzle plate contact portion and the non-contact portion of the cleaning device, and there was no damage. The Rockwell hardness of PTFE is 20 on the R scale, which is a result soft against the nozzle plate.

  In the ink droplet overflow test, the results are shown in FIG. It was found that the ink 410 that could not be sucked out from the suction port was flowing out of the cleaning device. This is presumably because the difference in height between the suction part and the ink casing part is small. The same applies to Comparative Examples 2 and 3 below.

(Comparative Example 2)
In the ink droplet suction test, the remaining ink droplets were confirmed on the nozzle plate. However, the droplets were less likely to remain than Comparative Example 1. However, it lacks stability and tends to cause residual liquid picking.

  In the durability test in contact with the nozzle plate, scratches were confirmed on the nozzle plate surface. PEEK had a Rockwell hardness of 120 on the R scale, indicating that it was hard against the nozzle plate surface.

  In the ink droplet overflow test, it was found that ink droplets that could not be sucked out from the first suction port flowed out of the cleaning device. This is presumably because the difference in height between the suction part and the ink casing part is small.

(Comparative Example 3)
In the ink droplet suction test, the remainder of the ink droplet was not confirmed.

  In the durability test in contact with the nozzle plate, physical damage such as scratches on the nozzle plate surface could not be confirmed. The measurement result of the contact angle was also the result that there was no damage between the nozzle plate contact portion and the non-contact portion of the cleaning device, and there was no damage.

  In the ink droplet overflow test, it was found that ink droplets that could not be sucked out from the first suction port flowed out of the cleaning device.

(result)
From the above result, the relationship of the contact angle of the third pattern is necessary. Further, it can be seen that the material of the support part 502 is PTFE, the material of the suction part 503 is good PEEK, and the difference in height between the suction part 503 and the housing part 604 is preferably about 5 mm.

  Further, regarding the durability test, it has been confirmed that the nozzle plate surface is not scratched even when the contact portion with the nozzle plate is polyethylene terephthalate (PET). Incidentally, the Rockwell hardness (R scale) of PET is 56.

(Confirmation of cleaning performance of inkjet head in cleaning device in embodiment)
FIG. 7A shows the transition of the number of effective nozzles of the discharge nozzle when the inkjet head cleaning operation is performed using the cleaning device having the structure in the embodiment. It can be seen that the number of effective nozzles increased after the cleaning operation compared to the number of effective nozzles before the cleaning operation. By performing the cleaning operation, it is considered that the ink in the nozzle holes is refreshed, ejection defects such as nozzle clogging are eliminated, and the number of effective nozzles is increased. The effective nozzle is a normal nozzle having no nozzle, that is, a flying curve.

  FIG. 7B shows the transition of the dispersion of the landing positions of the droplets ejected from the nozzles of the inkjet head on the substrate after the cleaning operation. If the ink droplet suction failure occurs due to the cleaning operation and ink droplets remain on the nozzle plate, the landing position may vary, but there may be no change in the landing position variation due to the cleaning operation. Recognize.

  The inkjet head cleaning apparatus, inkjet head cleaning method, and inkjet head cleaning apparatus according to the present invention can efficiently suck ink droplets on a nozzle plate with low wettability, and This can be applied to the discharge of ink from the light emitting layer of an OLED or the discharge of decorative ink using UV curable ink.

DESCRIPTION OF SYMBOLS 1 Head main body 2 Nozzle 3 Negative pressure production | generation means 4 Local suction means 5 Suction opening 6 Suction opening moving means 8 Pressure fluctuation means 100 Nozzle 110 Pressure chamber 111 Partition 112 Diaphragm 130 Piezoelectric element 140 Piezoelectric member 200 Nozzle 210 Pressure chamber 212 Diaphragm 220 Thin Film Piezoelectric Element 402 Ink Droplet 403 Cleaning Device 404 Nozzle Plate 410 Ink 502 Support Unit 503 Suction Unit 601 First Suction Port 602 Second Suction Port 603 Guide Unit 604 Housing Unit

Claims (11)

A suction part having a first suction port for sucking ink;
A support portion in contact with the nozzle plate of the inkjet head,
Relationship between the contact angle γ of said suction portion with respect to the ink contact angle β of the supporting portion with respect to the ink contact angle α of the nozzle plate relative to the ink, Ri following formula 1 der,
Furthermore, it has a housing part located under the suction part,
An inkjet head cleaning device, wherein the housing has a plurality of guides for preventing leakage of the ink .
(Formula 1) Contact angle α> Contact angle β> Contact angle γ The inkjet head cleaning device according to claim 1, wherein there are a plurality of the support portions, and the suction portion is disposed between the plurality of support portions. The inkjet head cleaning device according to claim 1, wherein the housing has a second suction port for sucking the ink. 4. The inkjet head cleaning device according to claim 1, wherein the housing portion is inclined inward of the plurality of guide portions. 5. The upper surface of the suction portion, said from housing portion, a cleaning apparatus of an ink jet head according to any one of 4 height from 3~5mm higher claims 1. The contact angle β is 35 ° to 55 °, the contact angle γ cleaning apparatus of an ink jet head according to any one of claims 1-5 which is 15 ° to 30 °. Wherein the first suction port is slit-shaped, the width in the transverse direction, the cleaning apparatus of an ink jet head according to any one of claims 1 to 6 is 0.25Mm～0.75Mm. The hardness of the support portion, a cleaning apparatus of an ink jet head according to any one of the nozzle plate 7 of a soft claims 1 than. The cleaning apparatus of an ink jet head according to any one of Rockwell hardness of the support portion of claims 1 is 20 to 50 (R scale) 8. And a cleaning apparatus of an ink jet head according to any one of claims 1 to 9, the printing apparatus having an inkjet device. The cleaning apparatus of an ink jet head according to any one of claims 1-9, is contacted with the nozzle plate of the ink jet head, the cleaning device, are moved relatively to the nozzle plate, cleaning the nozzle plate Ink jet head cleaning method.

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