Electrohydrodynamic inkjet printing method and device therefor

Abstract

The application provides an electrohydrodynamic inkjet printing method and an electrohydrodynamic inkjet printing device. The electrohydrodynamic inkjet printing method includes starting the gas pressure applying device and the electric field applying device in an acceleration movement section at the beginning of the movement of the nozzle or the receiving substrate in the horizontal direction, so that the nozzle starts to eject ink in the acceleration movement section. The electrohydrodynamic inkjet printing device provided by the application includes a base plate and a nozzle. The base plate is used to mount the receiving substrate to be printed. The nozzle and the receiving substrate are configured to be relatively movable in the horizontal direction. The electrohydrodynamic inkjet printing device provided by the application uses the aforementioned printing method.

Description

Technical Field

[0001] The present application relates to the field of printing technology, and in particular to an electrohydrodynamic inkjet printing method and device thereof. Background Art

[0002] Electro-hydrodynamic (EHD) inkjet printing devices use an externally applied electric field to pull out liquid ink, which helps to improve the resolution of the printed pattern.

[0003] However, the current electrohydrodynamic printing device has unstable morphology at the beginning of the printed line on the substrate. Figure 9A and Figure 9B For example, the printing starting position is prone to uneven line width "big head" and "small head" phenomena, and the printing quality has room for improvement.

[0004] Also, see Figure 7B The nozzle opening of the nozzle generally has ink accumulation phenomenon, which will affect the printing quality at the beginning position of the next print and increase the probability of the "big head" phenomenon. Summary of the Invention

[0005] In order to solve or improve at least one problem raised in the background technology, the present application provides an electrohydrodynamic inkjet printing method and an apparatus thereof.

[0006] The electrohydrodynamic inkjet printing method provided in the embodiment of the present application is applied to an electrohydrodynamic inkjet printing device, and the electrohydrodynamic inkjet printing device includes:

[0007] a bottom plate for mounting the receiving substrate to be printed;

[0008] a nozzle, wherein the nozzle and the receiving substrate are configured to be relatively movable in a horizontal direction, and the nozzle is configured to eject ink toward the receiving substrate in a vertical direction;

[0009] an air pressure applying device for applying air pressure to the ink to be ejected from the nozzle;

[0010] an electric field applying device for applying an electric field to cause the ink to be ejected toward the receiving substrate,

[0011] The electrohydrodynamic inkjet printing method includes: the horizontal movement process of the nozzle or the receiving substrate includes an accelerated movement section at the beginning of the movement, and the air pressure applying device and the electric field applying device are respectively turned on in the accelerated movement section, so that the nozzle starts to spray the ink in the accelerated movement section.

[0012] In at least one embodiment, when the viscosity of the ink is less than 5000 cps and the printed shapes are connected end to end, in the accelerated movement section, the electric field applying device is first turned on, and then the air pressure applying device is turned on and applied with positive pressure.

[0013] In at least one embodiment, when the viscosity of the ink is less than 5000 cps and the printed shape is not connected end to end, in the accelerated movement section, the air pressure applying device is first turned on and applied with positive pressure, and then the electric field applying device is turned on.

[0014] In at least one embodiment, when the viscosity of the ink is not less than 5000 cps, in the accelerated movement section, the air pressure applying device is first turned on to apply positive pressure, and then the electric field applying device is turned on.

[0015] In at least one embodiment, when the viscosity of the ink is not less than 5000 cps, in the accelerated movement section, the electric field applying device and the air pressure applying device are simultaneously turned on, and the air pressure applying device applies positive pressure.

[0016] In at least one embodiment, the horizontal movement process of the nozzle or the receiving substrate also includes a deceleration movement section when the movement ends, and the air pressure applying device and the electric field applying device are respectively closed in the deceleration movement section, so that the nozzle stops spraying the ink in the deceleration movement section.

[0017] In at least one embodiment, when the viscosity of the ink is less than 5000 cps, in the deceleration movement section, the air pressure applying device is first controlled to apply negative pressure, and then the electric field applying device is turned off, and then the air pressure applying device is controlled to switch to neutral or turn off.

[0018] The electrohydrodynamic inkjet printing device provided in the embodiment of the present application uses the electrohydrodynamic inkjet printing method described above.

[0019] In at least one embodiment, the movement process of the nozzle or the receiving substrate in the horizontal direction includes an acceleration movement section at the beginning of the movement and a deceleration movement section at the end of the movement, and the air pressure applying device and the electric field applying device are configured to be in a controlled switching state in the acceleration movement section and the deceleration movement section.

[0020] In at least one embodiment, the air pressure applying device may be configured to apply positive pressure, negative pressure, and switch to a neutral position.

[0021] The electrohydrodynamic inkjet printing method provided in the present application enables the air pressure applying device and the electric field applying device to be respectively turned on in the acceleration moving section of the horizontal moving device (nozzle or base plate), so that the nozzle discharge flow rate and the unstable state of the speed of the horizontal moving device coincide with each other, and the ratio of the nozzle discharge flow rate to the moving speed of the horizontal moving device can be kept unchanged to the greatest extent, thereby improving the uniformity of the line width, avoiding the big head and small head problems, and increasing the printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram showing the change in the spraying state of the liquid at the nozzle is shown.

[0023] Figure 2 A force analysis diagram showing the conical structure of the liquid at the nozzle.

[0024] Figure 3A The figure shows the printing effect of the ring in Example 1 of the present application.

[0025] Figure 3B The figure shows the printing effect at the beginning of the line segment in Example 1 of the present application.

[0026] Figure 4A The printing effect diagram of the ring in comparative example 1 of the present application is shown.

[0027] Figure 4B The printing effect diagram at the beginning of the line segment in Comparative Example 1 of the present application is shown.

[0028] Figure 5A The printing effect diagram of the ring in comparative example 2 of the present application is shown.

[0029] Figure 5B The printing effect diagram at the beginning of the line segment in Comparative Example 2 of the present application is shown.

[0030] Figure 6 The figure shows the printing effect at the end of the line segment in Example 2 of the present application.

[0031] Figure 7A The figure shows the printing effect at the end of the line segment in Comparative Example 3 of the present application.

[0032] Figure 7B A schematic diagram showing ink accumulation at the nozzle opening.

[0033] Figure 8A The figure shows the printing effect at the end of the line segment in Comparative Example 4 of the present application.

[0034] Figure 8B Another printing effect diagram at the end of the line segment in Comparative Example 4 of the present application is shown.

[0035] Figure 9AA schematic diagram showing a printed line presented as a large head known to the inventor is shown.

[0036] Figure 9B A schematic diagram showing a printed line presented as a small head known to the inventor is shown.

[0037] Description of Reference Numerals

[0038] 100 nozzles; 110 nozzle openings; 200 inks DETAILED DESCRIPTION

[0039] The following describes exemplary embodiments of the present application with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, and are not intended to exhaust all possible embodiments of the present application, nor to limit the scope of the present application.

[0040] The present application provides an electrohydrodynamic inkjet printing method and apparatus thereof, wherein the "ink" can be various materials such as resin, metal slurry, and adhesive.

[0041] The electrohydrodynamic inkjet printing method provided herein includes controlling an air pressure applying device and an electric field applying device (described later) in the electrohydrodynamic inkjet printing. For example, the electrohydrodynamic inkjet printing device may include a base plate, a nozzle 100, an air pressure applying device, and an electric field applying device.

[0042] The base plate is used to mount the receiving substrate to be printed. The nozzle 100 and the receiving substrate are configured to be movable horizontally relative to each other. For example, the base plate can be movable horizontally, thereby driving the receiving substrate mounted on the base plate to move horizontally, while the nozzle 100 remains stationary in the horizontal direction. Alternatively, the nozzle 100 can be movable horizontally, while the base plate and the receiving substrate remain stationary in the horizontal direction.

[0043] The nozzle 100 is also configured to eject ink vertically toward the receiving substrate. The air pressure applying device is used to apply air pressure to the ink to be ejected from the nozzle 100, and the electric field applying device is used to apply an electric field to eject the ink toward the receiving substrate.

[0044] The horizontal movement of the nozzle 100 or the receiving substrate includes an acceleration movement section at the beginning of the movement. The electrohydrodynamic inkjet printing method provided in this application includes: activating the air pressure applying device and the electric field applying device respectively during the acceleration movement section, so that the nozzle 100 begins to eject ink during the acceleration movement section.

[0045] The inventors found that, as shown in the following formula 1, when the distribution amount of ink per unit length is consistent, that is, when the ratio of the ejection flow rate of the nozzle 100 to the moving speed of the horizontal moving device (nozzle 100 or base plate) is constant, the line width of the printed line can be kept consistent and the printing quality is high.

[0046]

[0047] Wherein, Constant is a constant, ν is the ink volume, s is the ink length, Q is the ejection flow rate, V is the moving speed of the horizontal moving device, and Δt is the unit time.

[0048] like Figure 1 、 Figure 2 As shown in the following formula 2 and formula 3, after the air pressure applying device and the electric field applying device are turned on, the state of the ejection flow rate of the nozzle 100 generally includes a surge, a decrease, an increase, and a stabilization.

[0049]

[0050] Wherein, P is the pressure of the ink at a certain position in the nozzle 100, ρ is the ink density, v is the flow velocity of the ink at that point, g is the acceleration due to gravity, h is the height of the position, and C is a constant.

[0051]

[0052] Among them, P1 is the liquid pressure, F es is the electrostatic stress, P2 is the gas phase pressure of the external air, P st is the surface tension stress of the ink, σ is the surface tension of the ink, r is the inner radius of the nozzle opening 110, and θ is the angle between the cone surface and the top surface of the cone formed by the ink, also known as the angle of the Taylor cone.

[0053] For example Figure 1 In ① and ②, the flow velocity v of the ink in the nozzle 100 will surge when it starts to be ejected.

[0054] For example Figure 1 ③, the ink flow velocity v will become slightly smaller after the surge state relative to the surge state, the liquid phase pressure P1 will increase accordingly, and the angle θ of the Taylor cone will decrease.

[0055] For example Figure 1 In ④, further, the gas phase pressure P2 of the outside air tends to be stable, and the ink flow velocity v and flow rate Q also tend to be stable. Overall, the flow rate of the nozzle 100 can be considered to be first increasing as a whole and then tending to be stable.

[0056] The horizontal movement of the horizontal motion device (nozzle 100 or base plate) also generally consists of an acceleration phase upon activation and a steady-state phase. The nozzle 100's discharge flow rate and the horizontal motion device (nozzle 100 or base plate) are both unstable in the initial stages, potentially causing a "big head" or "small head" phenomenon.

[0057] The printing method provided in the application enables the air pressure applying device and the electric field applying device to be turned on respectively in the acceleration moving section, so that the unstable state of the ejection flow of the nozzle 100 and the speed of the horizontal moving device coincide, the ratio of the ejection flow of the nozzle 100 to the moving speed of the horizontal moving device (the nozzle 100 or the bottom plate) can be fixed to the maximum extent, and thus the uniformity of the line width can be improved, and the printing quality can be increased.

[0058] In one embodiment of the application, when the viscosity of the ink is less than 5000 cps, and the printed shape is connected at the beginning and the end, in the acceleration moving section, the electric field applying device is turned on first, and then the air pressure applying device is turned on and positive pressure is applied.

[0059] In one embodiment of the application, when the viscosity of the ink is less than 5000 cps, and the printed shape is not connected at the beginning and the end, in the acceleration moving section, the air pressure applying device is turned on first and positive pressure is applied, and then the electric field applying device is turned on.

[0060] In one embodiment of the application, when the viscosity of the ink is not less than 5000 cps, in the acceleration moving section, the electric field applying device is turned on first, and then the air pressure applying device is turned on and positive pressure is applied.

[0061] In one embodiment of the application, when the viscosity of the ink is not less than 5000 cps, in the acceleration moving section, the electric field applying device and the air pressure applying device are turned on at the same time, and the air pressure applying device applies positive pressure.

[0062] In one embodiment of the application, the movement of the nozzle 100 or the bottom plate in the horizontal direction further includes a deceleration moving section at the end of the movement, and the air pressure applying device and the electric field applying device are turned off respectively in the deceleration moving section, so that the nozzle 100 stops ejecting ink in the deceleration moving section.

[0063] It can be understood that, if the air pressure applying device and the electric field applying device are suddenly stopped to end the ink ejection in the state that the flow of the nozzle 100 and the horizontal moving speed are stable, the ratio of the horizontal moving speed to the ejection flow is unstable, and the phenomenon of small tail and inconsistent end position is caused. If the air pressure applying device and the electric field applying device are stopped to end the ink ejection in the state that the flow of the nozzle 100 is stable and the movement just stops, the ratio of the horizontal moving speed to the ejection flow is unstable, and the phenomenon of large tail is caused. Therefore, the nozzle 100 can stop ejecting ink in the deceleration moving section, the flow of the nozzle 100 and the horizontal moving speed are both reduced, and the uniformity of the line width is more optimal.

[0064] In one embodiment of the present application, when the viscosity of the ink is less than 5000 cps, during the deceleration phase, the air pressure applying device is first controlled to apply negative pressure, the electric field applying device is then turned off, and the air pressure applying device is then controlled to switch to a neutral position or be turned off. It will be understood that after switching to a neutral position or being turned off, the air pressure in the liquid reservoir (the mechanism that stores ink) is equal to or close to the external atmospheric pressure, and the liquid reservoir does not supply liquid to the nozzle 100 or absorb residual liquid from the nozzle 100.

[0065] Below, this application also provides some embodiments and comparative examples.

[0066] For the initial stage, see Example 1.1, Example 1.2, Comparative Example 1, and Comparative Example 2 below.

[0067] Example 1.1

[0068] The printed shape is connected end to end (for example, a circle, the same below), the viscosity of the ink is less than 5000cps, and in the accelerated movement section, the electric field applying device is turned on first, and then the air pressure applying device is turned on and applies positive pressure.

[0069] The results are as follows Figure 3A As shown, the width of the rings is consistent and the position where the ends meet is not obvious.

[0070] Example 1.2

[0071] Printing is performed simultaneously using two nozzles that are controlled identically, and the printed shapes are not connected end to end (e.g., line segments, the same applies below). The viscosity of the ink is less than 5000 cps. During the acceleration phase, the air pressure application device is first turned on to apply positive pressure, and then the electric field application device is turned on.

[0072] The results are as follows Figure 3B As shown, the starting points of the line segments are the same, and there is no uneven line width such as large ends or small ends.

[0073] Comparative Example 1

[0074] The viscosity of the ink is less than 5000 cps. At the moment when the nozzle or the receiving substrate starts to move horizontally, the electric field applying device and the air pressure applying device are turned on at the same time and the air pressure applying device applies positive pressure.

[0075] When printing a ring, the result is as follows Figure 4A As shown, the width uniformity of the ring is relatively poor, and the connection position between the beginning and the end of the ring is obvious.

[0076] When printing line segments, the result is as follows Figure 4B As shown, the big head phenomenon will appear.

[0077] Comparative Example 2

[0078] The viscosity of the ink is less than 5000cps. After the nozzle or the receiving substrate moves horizontally for a period of time (when in the acceleration section or the uniform speed section, the comparative example is taken when in the uniform speed section), the electric field applying device and the air pressure applying device are simultaneously turned on and the air pressure applying device applies positive pressure.

[0079] When printing a donut shape, the results in individual batches are as follows: Figure 5A As shown, the connection between the head and tail will be slightly wider.

[0080] When printing line segments simultaneously through two nozzles that control the same Figure 5B As shown in the figure, the small head phenomenon is easy to occur, and the beginnings of the two line segments are not on the same straight line. The faster the horizontal movement speed, the more serious the above situation will be.

[0081] After analysis, it was found that in Comparative Example 1, when the nozzle ejected ink, the horizontal speed did not keep up (the nozzle did not move horizontally fast enough at the beginning), so the big head phenomenon was likely to occur.

[0082] In Comparative Example 2, when both the electric field and air pressure devices are activated simultaneously, the electric field takes effect first, pulling the ink out of the nozzle. The slow response of the air pressure device prevents ink from being replenished in time, leading to a small-head phenomenon. This, coupled with the randomness of the liquid storage at the nozzle, results in the two line segments starting at different positions (not on the same starting line).

[0083] Example 1.1 of the present application utilizes the fact that small heads are easily generated when the electric field applying device is turned on first and then the air pressure applying device is turned on. This makes the junction of the head and tail pass through the small head, and the width of the junction is consistent and higher than the width of other parts, ensuring the overall line width consistency. Example 1.2 of the present application first turns on the air pressure applying device to ensure that there is sufficient ink at the nozzle, and then turns on the electric field applying device to spray the ink, ensuring a continuous supply of ink and avoiding the occurrence of large and small heads. There is sufficient ink at the nozzle, so that the starting positions of multiple line segments are consistent.

[0084] Furthermore, when the ink viscosity is not less than 5000 cps, the ink viscosity is relatively high, and the phenomenon of uneven line width caused by the electric field force pulling out the ink first is relatively less obvious. In this case, the air pressure applying device can be turned on first and applied positive pressure, and then the electric field applying device can be turned on. Alternatively, the electric field applying device and the air pressure applying device can be turned on simultaneously, and the air pressure applying device can be turned on to apply positive pressure.

[0085] For the final stage, see Example 2, Comparative Example 3, and Comparative Example 4 below.

[0086] Example 2

[0087] When the viscosity of the ink is less than 5000 cps, in the deceleration movement section, the air pressure applying device is first controlled to apply negative pressure, then the electric field applying device is turned off, and then the air pressure applying device is controlled to switch to neutral or turn off.

[0088] When printing line segments simultaneously through two nozzles with the same control, the printing results are as follows: Figure 6 As shown in the figure, the end points are neat, with no obvious large or small tails. In addition, there is no ink hanging on the nozzle wall.

[0089] Comparative Example 3

[0090] When the viscosity of the ink is less than 5000cps, the electric field applying device is turned off and the air pressure applying device is switched to neutral at the same time when the nozzle or the receiving substrate stops moving horizontally, or the electric field applying device is turned off and the air pressure applying device is switched to neutral after applying negative pressure.

[0091] Print results such as Figure 7A As shown, ink accumulates at the end point, forming a large tail phenomenon. In addition, the nozzle opening 110 is as shown in FIG. Figure 7B As shown, the ink 200 has a wall-hanging phenomenon and easily absorbs bubbles.

[0092] Comparative Example 4

[0093] When the viscosity of the ink is less than 5000cps and the nozzle or the receiving substrate is still in relative motion (constant speed section or deceleration section), the electric field applying device is turned off and the air pressure applying device is switched to neutral at the same time, or the electric field applying device is turned off and the air pressure applying device is switched to neutral after applying negative pressure at the same time.

[0094] If the nozzle or receiving substrate moves horizontally slowly, Figure 8A As shown in the figure, the end points are relatively neat, and the big tail or small tail phenomenon is not obvious. The printing effect is good. However, if the horizontal movement speed is fast, the printing result will be as follows: Figure 8B As shown, a small tail (arrow-shaped tail) is likely to appear. In addition, the ink tends to cling to the wall at the nozzle opening and is prone to absorbing bubbles.

[0095] Analysis shows that in Comparative Examples 3 and 4, if the electric field application device is turned off and the air pressure application device is directly controlled to switch to neutral, residual glue (residual ink) at the nozzle will be adsorbed and accumulated on the nozzle opening due to capillary action, forming a wall phenomenon and increasing the outer diameter of the nozzle opening. If it is not erased, it will affect the line width at the beginning of the next print and increase the possibility of satellite droplets when the electric field force is too strong.

[0096] If the electric field applicator is turned off first, the air pressure applicator is controlled to apply negative pressure, and then the ink is switched to neutral, the ink may not adhere to the wall. However, the need to use a large negative pressure or maintain the negative pressure for a long time may easily cause bubbles to be adsorbed in the ink. During the precision inkjet printing process, bubbles will increase the instability of ink discharge.

[0097] In Example 2 of the present application, the air pressure applying device is first controlled to apply negative pressure. At this time, the electric field force can pull the residual ink that has not been recovered in time onto the receiving substrate, and then the electric field applying device is turned off, and the air pressure applying device is switched to neutral, so that there will be no wall hanging phenomenon at the nozzle mouth, reducing the number of times the nozzle is wiped, triggering from the perspective of industrial production, and improving production efficiency. In addition, the negative pressure of the air pressure applying device can be smaller, and the duration of the negative pressure is shorter, so that there are fewer bubbles and the stability of the ink output is increased. In addition, the flow rate of the ink output is reduced at this time, so the above operation can be performed in the deceleration moving section, so that the line width is more consistent and there is no big tail or small tail phenomenon.

[0098] The present application also provides an electrohydrodynamic inkjet printing device, which can use the aforementioned electrohydrodynamic inkjet printing method.

[0099] The horizontal movement of the nozzle or receiving substrate includes an acceleration phase at the beginning of the movement and a deceleration phase at the end of the movement. The air pressure applying device and the electric field applying device are configured to switch between the acceleration phase and the deceleration phase in a controlled manner. The air pressure applying device can be configured to apply positive pressure, negative pressure, and switch to a neutral position.

[0100] The above is a preferred embodiment of the present application. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as within the scope of protection of the present application.

Claims

1. An electrohydrodynamic inkjet printing method, characterized in that: The electrohydrodynamic inkjet printing method is applied to an electrohydrodynamic inkjet printing device, and the electrohydrodynamic inkjet printing device comprises: a bottom plate for mounting the receiving substrate to be printed; a nozzle (100), the nozzle (100) and the receiving substrate being configured to be relatively movable in a horizontal direction, and the nozzle (100) being configured to eject ink toward the receiving substrate in a vertical direction; an air pressure applying device, the air pressure applying device being used to apply air pressure to the ink to be ejected from the nozzle (100); an electric field applying device for applying an electric field to cause the ink to be ejected toward the receiving substrate, The electrohydrodynamic inkjet printing method comprises: a horizontal movement process of the nozzle (100) or the receiving substrate includes an accelerated movement section at the beginning of the movement, the air pressure applying device and the electric field applying device are respectively turned on in the accelerated movement section, so that the nozzle (100) starts to eject the ink in the accelerated movement section, The movement process of the nozzle (100) or the receiving substrate in the horizontal direction also includes a deceleration movement section when the movement ends, and the air pressure applying device and the electric field applying device are respectively closed in the deceleration movement section, so that the nozzle (100) stops spraying the ink in the deceleration movement section.

2. The electrohydrodynamic inkjet printing method according to claim 1, wherein: When the viscosity of the ink is less than 5000 cps and the printed shapes are connected end to end, in the accelerated movement section, the electric field applying device is first turned on, and then the air pressure applying device is turned on to apply positive pressure.

3. The electrohydrodynamic inkjet printing method according to claim 2, wherein: When the viscosity of the ink is less than 5000 cps and the printed shape is not connected from beginning to end, in the accelerated movement section, the air pressure applying device is first turned on to apply positive pressure, and then the electric field applying device is turned on.

4. The electrohydrodynamic inkjet printing method according to claim 1, wherein: When the viscosity of the ink is not less than 5000 cps, in the acceleration movement section, the air pressure applying device is first turned on to apply positive pressure, and then the electric field applying device is turned on.

5. The electrohydrodynamic inkjet printing method according to claim 1, wherein: When the viscosity of the ink is not less than 5000 cps, in the accelerated movement section, the electric field applying device and the air pressure applying device are simultaneously turned on, and the air pressure applying device applies positive pressure.

6. The electrohydrodynamic inkjet printing method according to claim 1, wherein: When the viscosity of the ink is less than 5000 cps, in the deceleration movement section, the air pressure applying device is first controlled to apply negative pressure, and then the electric field applying device is turned off, and then the air pressure applying device is controlled to switch to neutral or turn off.

7. An electrohydrodynamic inkjet printing device, characterized in that: The electrohydrodynamic inkjet printing method according to any one of claims 1 to 6 is used.

8. The electrohydrodynamic inkjet printing device according to claim 7, characterized in that: The movement process of the nozzle (100) or the receiving substrate in the horizontal direction includes an acceleration movement section at the beginning of the movement and a deceleration movement section at the end of the movement, and the air pressure applying device and the electric field applying device are configured to be in a controlled switching state in the acceleration movement section and the deceleration movement section.

9. The electrohydrodynamic inkjet printing device according to claim 8, characterized in that: The air pressure applying device may be configured to be capable of applying positive pressure, negative pressure, and switching to a neutral position.

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