Printing apparatus

Abstract

This invention relates to a printing apparatus, characterized in that it comprises: an optical unit above a substrate for magnifying and displaying ink landing points; and a nozzle unit for spraying ink, the nozzle unit comprising: a nozzle body disposed obliquely relative to the substrate; and a nozzle coupled to the nozzle body, the nozzle forming a flow path for spraying ink and having an end portion bent toward the substrate.

Description

Technical Field

[0001] This invention relates to a printing apparatus, and more specifically to a printing apparatus capable of printing while observing the ink landing point, thereby improving the landing accuracy. Background Technology

[0002] In general, inkjet devices that eject fluid in the form of droplets were mainly used in inkjet printers in the past, but recently they have been widely used in cutting-edge industries such as display manufacturing, printed circuit board manufacturing and DNA chip manufacturing.

[0003] Inkjet printers are devices used to eject droplets of ink in a fluid state. They are divided into two main types according to the way the droplets are ejected: thermal type and piezoelectric type. Recently, electrostatic inkjet printers that utilize electrodynamics have been widely used for ultra-fine printing.

[0004] Electrostatic inkjet printers utilize the electrostatic force generated by the potential difference created by applying a voltage between the nozzle and the substrate to eject charged ink. As is well known, electrostatic inkjet printers use the force of electrostatic pull on the liquid surface to eject droplets or continuous jets, thus differing from other types of inkjet printers and possessing various advantages, such as the ability to achieve nanoscale patterning, the ability to eject high-viscosity inks, and the generation of uniform droplets.

[0005] In addition, in order to perform precise printing, a printing device was attempted that tilts the nozzle unit relative to the substrate, which serves as the landing point, and sprays ink. The position of the nozzle is adjusted while the landing point of the ink is observed above the substrate using an optical unit such as a camera.

[0006] At this point, the droplet is ejected along the tilt direction of the nozzle unit and lands on the substrate. In the absence of an electric field, the droplet may land on the substrate due to gravity and inertial forces. When an electric field of electrohydrodynamic nature is applied, the droplet's trajectory varies depending on the droplet's charge density and the strength of the electric field, and the droplet will land on the substrate according to the distribution of the electric field.

[0007] When printing is performed while simultaneously ejecting droplets along an inclined direction using an inclined nozzle unit as described above, the nozzle unit may be moved along the Z-axis (perpendicular to the substrate) during printing, depending on the situation. In this case, even a slight movement of the nozzle unit along the Z-axis can cause a significant change in the droplet landing position due to the nozzle's tilt angle. That is, as the nozzle unit is tilted, the increased movement distance of the nozzle unit along the Z-axis leads to a significant decrease in ink landing accuracy.

[0008] Therefore, the present invention proposes a printing apparatus that can improve ink landing accuracy while maintaining an inclined nozzle unit, spraying ink in an inclined direction, and observing the ink landing point above the substrate to perform the basic structure of printing.

[0009] Patent document: Korean Patent Publication No. 10-2017-0072748 Summary of the Invention

[0010] The present invention is proposed to solve the problems mentioned above, and its object is to provide a printing apparatus in which the nozzle tip of a nozzle unit arranged at an angle relative to a substrate is bent toward the substrate, so that high landing accuracy can be maintained even when printing is performed while the nozzle unit is moved in the Z-axis direction.

[0011] The technical problem to be solved by this invention is not limited to the problems mentioned above. For other problems not mentioned, those skilled in the art should be able to understand them clearly from the following description.

[0012] The above objective can be achieved by the printing apparatus of the present invention, which includes: an optical unit for magnifying and displaying the ink landing point above a substrate; and a nozzle unit for spraying ink, the nozzle unit including: a nozzle body disposed at an angle relative to the substrate; and a nozzle coupled to the nozzle body, the nozzle forming a flow path for spraying ink and having an end portion bent toward the substrate.

[0013] Here, the optical unit can magnify and display the ink landing point vertically above the substrate.

[0014] Here, the nozzle unit may further include an electrode to which a high voltage is applied, the nozzle unit being used to eject ink using an electrostatic force generated by the potential difference between the electrode and the substrate.

[0015] Here, the electrode may be inserted inside the nozzle unit or formed on the inner surface of the nozzle unit.

[0016] Here, the electrode can be separated by an insulator so that it does not come into contact with the ink inside the nozzle unit.

[0017] Here, the nozzle unit may further include an air-purging section for applying air pressure to the interior of the nozzle body, thereby ejecting ink present in the nozzle before printing.

[0018] This may further include: a nozzle alignment portion for aligning the rotatable position of the bent end portion of the nozzle with the axial direction of the nozzle body as the center.

[0019] Here, the nozzle alignment part may include a rotary drive part for axially rotating the nozzle body.

[0020] Here, the optical unit can obtain an image of the nozzle head vertically above the substrate, and the nozzle alignment part is used to align the rotational position of the nozzle based on the information of the obtained image.

[0021] Here, the nozzle can be interchangeably mounted on the nozzle body.

[0022] Here, the end of the nozzle is bent such that the angle between the normal of the substrate and the end of the nozzle is within 45 degrees.

[0023] The diameter of the nozzle can be less than tens of μm.

[0024] The diameter of the nozzle can be less than 1 μm.

[0025] According to the printing apparatus of the present invention as described above, printing is performed by spraying ink in an inclined direction through a nozzle unit that is inclined relative to the substrate while observing the landing point of the ink using an optical unit located above the substrate. Therefore, it has the advantage of high printing accuracy.

[0026] Furthermore, since the nozzle tip of the inclined nozzle unit is bent toward the substrate, it also has the advantage of maintaining high printing accuracy even when printing is performed while the nozzle unit is moved along the Z-axis. Attached Figure Description

[0027] Figure 1 This is a perspective view of a printing apparatus according to an embodiment of the present invention.

[0028] Figure 2 express Figure 1 The main view.

[0029] Figure 3 Magnification Figure 1 The nozzle unit in the middle.

[0030] Figure 4 These are photographs of nozzles in various forms produced according to the present invention.

[0031] Figure 5 The results of spraying experiments using conventional straight nozzles and the bent nozzle of the present invention are presented. Detailed Implementation

[0032] The specific details of the embodiments are included in the detailed implementation methods and accompanying drawings.

[0033] The advantages and features of the invention, as well as the methods for achieving these advantages and features, will become clearer when referred to the accompanying drawings and the embodiments detailed below. However, the invention is not limited to the embodiments disclosed below, but can be implemented in many different forms. These embodiments are provided merely to fully disclose the invention and to fully inform those skilled in the art of its scope, which is defined only by the scope of the claims. Throughout this specification, the same reference numerals denote the same structural elements.

[0034] The present invention will now be described through embodiments thereof, with reference to the accompanying drawings illustrating the printing apparatus.

[0035] Figure 1 This is a perspective view showing a printing apparatus according to an embodiment of the present invention. Figure 2 express Figure 1 The main view, Figure 3 Magnification Figure 1 The nozzle unit in the middle, Figure 4 These are photographs of nozzles in various forms produced according to the present invention. Figure 5 The results of spraying experiments using conventional straight nozzles and the bent nozzle of the present invention are presented.

[0036] A printing apparatus according to an embodiment of the present invention may be configured to include an optical unit 110 and a nozzle unit 120. Furthermore, it may further include a ranging unit 130 or a moving unit 150.

[0037] The optical unit 110 is a camera located above the substrate 10, which displays a magnified image of the ink landing point via an additional display device (not shown).

[0038] Preferably, the optical unit 110 photographs the landing point of the ink from a vertical position above the substrate 10 where the ink is applied, facing downwards. This is because image distortion may occur when photographing the landing point in an oblique direction, while photographing the landing point from a vertical position above the substrate 10 allows for the capture of an image of the landing point without distortion. However, an additional optical unit 150 may also be included to photograph the landing point from the side.

[0039] The nozzle unit 120 sprays ink toward the substrate 10. In this embodiment, the nozzle unit 120 uses electrohydrodynamics to spray charged ink in droplet form by electrostatic force generated by the electric field between the substrate 10 and the nozzle unit 120. However, it is not limited to this and ink can also be sprayed by heating, pressurizing, or a combination of the above methods.

[0040] In one embodiment of the present invention, the nozzle unit 120 may be configured to include a nozzle body 122 and a nozzle 125. Furthermore, it may also include an air-purging section or a nozzle alignment section.

[0041] The nozzle body 122 is the main body forming the nozzle unit 120, and may have a closed chamber for storing ink inside. An ink injection port communicating with the outside is additionally formed in the chamber, so that depleted ink can be filled from an injection pump (not shown) or the like.

[0042] In this invention, the nozzle body 122 is disposed at an angle relative to the substrate 10. With the nozzle body 122 disposed at an angle, ink is ejected along the angled direction. Therefore, an image of the ink landing point can be captured undisturbed by the optical unit 110 disposed above the landing point. Thus, printing can be performed while moving the nozzle unit 120 based on the image information obtained from capturing the ink landing point, thereby further improving the accuracy of ink droplet landing.

[0043] The nozzle 125 is combined with the nozzle body 122, and a flow path is formed inside the nozzle 125 to eject the ink stored in the nozzle body 122 to the outside. In this invention, the nozzle 125 is formed with its end portion bent downward toward the substrate 10. Therefore, the flow path inside the nozzle 125 can also be formed in a bent form.

[0044] In this invention, the nozzle unit 120 can perform printing while moving along the Z-axis (perpendicular to the substrate 10) during the printing process. However, due to the inclined arrangement of the nozzle 125, including the inclined arrangement of the nozzle unit 120, a significant change in the landing point occurs when the nozzle unit 120 moves along the Z-axis. However, since the end portion of the nozzle 125 is formed in a bent manner towards the substrate 10 in this invention, the angle of ink ejection can be minimized based on the normal direction perpendicular to the substrate 10. Therefore, even when the nozzle unit 120 moves along the Z-axis while performing printing, high landing accuracy can be maintained. Furthermore, an image of the ink droplet landing point, including an image of the end portion of the nozzle 125, can be captured undisturbed by an optical unit 110 located vertically above the substrate 10.

[0045] Droplets ejected via electrohydrodynamic inkjet printing become charged, and electrostatic forces continuously act on them through an electric field distributed in space. The trajectory of the droplet toward the substrate is determined by the electrostatic force, gravity, and inertial forces acting on it. The electric field is represented by Maxwell's equations.

[0046]

[0047]

[0048] Here, E is the external electric field (V / m), φ is the electric potential (V), ε is the permittivity (Coulomb / Vm), and ρ is the charge density (Coulomb / m). 3 )).

[0049] The velocity and trajectory of the droplet can be obtained from the following equation based on Newton's second law.

[0050]

[0051] Here, v is the velocity of the droplet (m / s), t is the time (seconds), g is the acceleration due to gravity, and q is the velocity of the droplet. drop Let be the charge of the droplet (coulomb), and m be the mass of the droplet (kg).

[0052] Therefore, by bending the nozzle, the droplet spray direction can be made closer to perpendicular to the substrate, thereby improving the accuracy and precision of landing. The distribution of the electric field can vary depending on the position and shape of the nozzle applying the voltage, the size of the substrate, the material of the substrate, the printing environment, the viscosity of the ink, the density of the ink, the conductivity of the ink, and the dielectric constant of the ink.

[0053] The bent nozzle can create a streamlined electric field in the vertical direction between the nozzle and the substrate, which helps to improve the accuracy of charged droplets landing on the substrate.

[0054] Figure 4 The nozzle 125 can be manufactured in various forms, but it can be manufactured and replaced on the nozzle body 122 by changing various aspects such as the diameter of the flow path inside the nozzle 125, the bend angle of the nozzle 125 end, and the length of the bent nozzle 125 end. In this case, the diameter of the nozzle can be set to various values ​​in the range of a few μm to tens of μm. Alternatively, the diameter of the nozzle can also be less than 1 μm.

[0055] Assuming the nozzle body 122 is arranged at approximately 45 degrees relative to the substrate 10, it is preferable that the bend angle of the nozzle 125 tip is within 45 degrees. Therefore, the tip of the nozzle 125 can be bent such that the angle between the normal to the substrate 10 and the tip of the nozzle 125 is within 45 degrees. The angle of the tip of the nozzle 125 can be varied depending on the angle of the inclined arrangement of the nozzle body 122, but the arrangement angle of the nozzle body 122 and the bend angle of the nozzle 125 tip are preferably set to an angle at which the tip of the nozzle 125 and the ink ejected through the tip of the nozzle 125 can be captured by the optical unit 110 above the substrate 10.

[0056] In this invention, the nozzle unit 120 ejects ink via electrohydrodynamics, and thus electrodes (not shown) to which a high voltage is applied can be formed inside or outside the nozzle unit 120.

[0057] The electrode can be inserted inside the nozzle 125 or formed on the inner surface of the chamber or nozzle 125, thereby being configured to directly contact the ink. Alternatively, the electrode can be separated by an insulator, thereby being disposed inside or outside the nozzle 125 in a manner that does not directly contact the ink inside the nozzle 125. For example, the electrode can be formed by coating an insulator and inserting it inside the nozzle 125. As another method, the nozzle 125 can also be formed using an insulator, and the electrode can be disposed on the outer wall of the nozzle 125 or at a location spaced apart from the nozzle 125. As yet another method, the nozzle 125 itself can be formed of a conductive material and used as an electrode, and the nozzle 125 can be coated with an insulator. In this way, even if the electrode to which a high voltage is applied does not directly contact the ink inside the nozzle 125, the ink separated by the insulator can be charged by using an induced electromotive force, the electrode can form an electric field toward the substrate, and the charged ink can be ejected by electrostatic force.

[0058] In addition, the nozzle unit 120 may further include an air purging section for applying air pressure to the interior of the nozzle body 122.

[0059] As previously described, the nozzle 125 of the present invention is formed by bending at the end. During the process of filling the nozzle 125 with ink before printing, air may be trapped, and the ink may not be ejected normally in the initial stage. Therefore, in the present invention, air pressure can be applied to the inside of the nozzle body 122 by an air purging unit before printing, thereby ejecting the ink filled in the nozzle 125 and then performing printing.

[0060] like Figure 3 As shown, an air injection port 126 communicating with an internal chamber is formed on the outside of the nozzle body 122. High-pressure air can be supplied to the inside of the nozzle unit 120 through the air injection port 126, thereby spraying out the ink filled inside the nozzle 125 before printing.

[0061] Therefore, the air purging unit may be configured to include: an air pump 128 connected to an air injection port 126 for supplying high-pressure air; and a control unit (not shown) for controlling the nozzle unit 120 to move to a predetermined position before printing and operating the air pump 128 to eject ink from the nozzle 125.

[0062] Furthermore, the nozzle unit 120 may further include a nozzle alignment portion. As previously described, the end portion of the nozzle 125 of the present invention is bent, therefore, aligning the position of the bent end portion is important. More specifically, it is important to align the nozzle 125, including the bent end portion, on an imaginary surface formed by the normal to the substrate 10 from which the droplet is ejected and the axis of the nozzle body 122.

[0063] Therefore, the nozzle alignment section is aligned with the rotational position of the bent end of the nozzle 125, centered on the axial direction of the nozzle body 122. As an example, the nozzle alignment section can be constructed using a rotation drive unit 129, which is used to rotate the nozzle body 122 axially. As shown, the rear end of the nozzle body 122 is connected to the rotation drive unit 129, thereby receiving power from the rotation drive unit 129 and rotating the nozzle body 122 axially. With the axial rotation of the nozzle body 122, the nozzle 125, which is coupled to the nozzle body 122, also rotates axially. Therefore, while the optical unit 110 captures an image of the bent end (nozzle head) of the nozzle 125, the position of the nozzle 125's end can be aligned by rotating the nozzle body 122 via the rotation drive unit 129 based on the information from the captured image.

[0064] The printing apparatus according to an embodiment of the present invention may further include a ranging unit 130 and a moving unit 150.

[0065] The distance between the substrate 10 and the end of the nozzle 125 is kept constant by operating the ranging unit 130 and the moving unit 150.

[0066] The ranging unit 130 is used to measure the distance between itself and the substrate 10, and can be formed, for example, by a laser distance sensor that uses laser to measure distance. As shown, the ranging unit 130 can be formed on one side of the optical unit 110 to irradiate the main body of the optical unit 110 with laser. A reflector (not shown) for changing the laser path is formed at a predetermined position on the main body of the optical unit 110, so that the laser irradiated from the ranging unit 130 can be irradiated towards the substrate 10, and the laser reflected from the substrate 10 can be received again. The distance between itself and the substrate 10 can be measured using the laser speed and the time difference between transmission and reception.

[0067] If the distance obtained by the ranging unit 130 and the position of the nozzle unit 120 are known, the distance between the substrate 10 and the end of the nozzle 125 can be determined. The distance between the end of the nozzle 125 of the nozzle unit 120 and the substrate 10 can be kept constant by operating the moving unit 150 for moving the nozzle unit 120 in the X, Y and Z axes.

[0068] The moving unit 150 is a unit that uses a motor to move the nozzle unit 120 in three axes. Its structure is the same as that of the conventional technology, so a detailed description of the moving unit is omitted.

[0069] Figure 5 This is the result of changing the z-axis distance from the nozzle tip to the substrate and performing a spray evaluation. When a straight nozzle (Normal Nozzle) is configured at an angle, not only are there problems with landing accuracy, but also, because the nozzle is angled relative to the substrate, the concentration of the electric field at the nozzle head is dispersed, resulting in uneven droplet spraying and a tendency for the droplets to splash onto the substrate. Conversely, when a bent nozzle (Bended Nozzle) is configured at an angle as in this invention, since the nozzle tip can be configured almost perpendicular to the substrate, the electric field distribution formed in a vertical direction toward the substrate can be confirmed, and the electric field at the nozzle head is concentrated on the droplets, resulting in uniform droplet spraying and thus improving landing accuracy.

[0070] The scope of this invention is not limited to the embodiments described above, and can be implemented by various embodiments within the scope of the appended claims. Various modifications that can be made by those skilled in the art without departing from the spirit of the invention as claimed also fall within the scope of the claims.

[0071] Explanation of reference numerals in the attached figures

[0072] 10: Substrate

[0073] 110: Optical Unit

[0074] 120: Nozzle unit

[0075] 122: Nozzle body

[0076] 125: Nozzle

[0077] 126: Air Inlet

[0078] 128: Air pump

[0079] 129: Rotary drive unit

[0080] 130: Distance measuring unit

[0081] 140: Moving Unit

Claims

1. A printing apparatus, comprising: An optical unit, located above the substrate, is used to magnify and display the ink droplet point; and Nozzle unit, used for spraying ink. The nozzle unit includes: The nozzle body is disposed at an angle relative to the substrate; and The nozzle, which is combined with the nozzle body and is configured at an angle together with the nozzle body, forms a flow path for spraying ink and its end is bent toward the normal direction perpendicular to the substrate.

2. The printing apparatus according to claim 1, wherein, The optical unit magnifies and displays the ink landing point vertically above the substrate.

3. The printing apparatus according to claim 1, wherein, The nozzle unit further includes electrodes to which a high voltage is applied. The nozzle unit is used to eject ink using electrostatic force generated by the potential difference between the electrode and the substrate.

4. The printing apparatus according to claim 3, wherein, The electrode is inserted inside the nozzle unit or formed on the inner side of the nozzle unit.

5. The printing apparatus according to claim 3, wherein, The electrode is separated by an insulator so that it does not come into contact with the ink inside the nozzle unit.

6. The printing apparatus according to claim 1, wherein, The nozzle unit further includes an air purging section for applying air pressure to the interior of the nozzle body, thereby ejecting ink present in the nozzle before printing.

7. The printing apparatus according to claim 1, further comprising: The nozzle alignment section is used to align the rotatable position of the bent end portion of the nozzle with the axial direction of the nozzle body as the center.

8. The printing apparatus according to claim 7, wherein, The nozzle alignment part includes a rotary drive part for axially rotating the nozzle body.

9. The printing apparatus according to claim 7, wherein, The optical unit obtains an image of the nozzle head vertically above the substrate. The nozzle alignment section is used to align the rotational position of the nozzle based on information from the acquired image.

10. The printing apparatus according to claim 1, wherein, The nozzle can be interchangeably mounted on the nozzle body.

11. The printing apparatus according to claim 1, wherein, The end of the nozzle is bent such that the angle between the normal of the substrate and the end of the nozzle is within 45 degrees.

12. The printing apparatus according to claim 1, wherein, The diameter of the nozzle is less than 1 μm.

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