Ink circulation supply system and method for inkjet head

The present invention relates to an ink circulation supply system for an inkjet head. The system is configured to supply ink to the inkjet head having a plurality of nozzles for ejecting the ink, and includes: a meniscus reservoir; a circulation reservoir; and an ante reservoir, the reservoirs where a first pressure connection pipe with a first pressure valve, a second pressure connection pipe with a second pressure valve, a first ink connection pipe, and a second ink connection pipe with an ink valve are provided, wherein when the internal pressure of the circulation reservoir is controlled to be lower than that of the meniscus reservoir, the ink stored in the meniscus reservoir is moved to the circulation reservoir without requiring use of a separate pump.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2020-0031085, filed Mar. 13, 2020, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to an ink circulation supply system for circulating ink in a head of an inkjet printer. More particularly, the present invention relates to an ink circulation supply system capable of circulating ink without requiring use of a separate pump in an inkjet printer used in an industrial field.

Description of the Related Art

In general, inkjet printing in which liquid ink is jetted onto a surface of a medium in a droplet form according to a shape signal is used not only as a printing method for creating a document or a flyer, but also used in a solution process in the semiconductor and display fields.

Inkjet printing, which can form patterns of complex shapes on a substrate or eject ink accurately only at specific positions, has become increasingly used for a variety of applications. While small-sized inkjet printers for document creation have a structure in which ink is stored in an inkjet head that ejects ink droplets, large-sized document printers or industrial inkjet printers consume large amounts of ink and thus has a structure in which a reservoir for storing ink and an inkjet head are separated.

FIG. 13is a schematic view illustrating the structure of a typical industrial inkjet printer.

The typical industrial inkjet printer includes an inkjet head10, a head supply reservoir20, a pressure controller30, a buffer reservoir40, and an ink reservoir tank50.

The inkjet head10includes nozzles that eject ink and is configured to selectively eject ink at a required position to perform printing. The head supply reservoir20is a space for storing ink to be supplied to the inkjet head10and is configured to be continuously supplied with ink through a supply passage11connected to the head supply reservoir20. The ink may be supplied only in one direction toward the inkjet head10from the head supply reservoir20. However, it is common for the industrial inkjet printer to have a recovery passage12for returning ink remaining in the inkjet head10back to the head supply reservoir20in order to accurately control an ejection amount. The pressure controller30is configured to control the pressures of the inkjet head10and the head supply reservoir20for accurate ejection of ink, and a pressure control pipe31is connected to the head supply reservoir20. Due to the fact that the industrial inkjet printer consumes a large amount of ink, ink has to be continuously supplied to the head supply reservoir20. However, it is common that ink stored in the ink reservoir tank50located externally of the printer is additionally supplied to the head supply reservoir20via the buffer reservoir40rather than supplying ink directly to the head supply reservoir20. In this case, ink to be additionally supplied is moved in one direction from the ink reservoir tank50toward the buffer reservoir40.

In order to eject a correct amount of ink in an inkjet printing process, it is necessary for ink, which is ready to be ejected from the inkjet head, to maintain a meniscus state in which the surface of ink is curved inward with respect to a nozzle inlet by capillary action. To this end, it is common that the position of the head supply reservoir is higher than that of the inkjet head, and the inside of the head supply reservoir is maintained in a vacuum to generate a negative pressure in the head supply reservoir, thereby maintaining the meniscus state by preventing ink from flowing out of the inkjet head. However, if the head supply reservoir is maintained in a vacuum, evaporation of a solvent constituting ink is accelerated to change properties of ink, and the most problematic aspect is that viscosity of ink increases over time. The increased viscosity of ink may result in difficulty in effective jetting of ink from the inkjet head.

Further, in recent years, as application fields of inkjet printers have become wider, attempts to use ink in which particles are dispersed have increased, such as employing ink in which metal particles are dispersed for an electrode pattern, and there has been also attempts to employ ink in which a flat panel display material or organic light-emitting diode (OLED) material is dispersed. However, inkjet printing has not been employed in the aforementioned cases due to a problem in which dispersibility of ink is lowered, such as when the metal particles, the flat panel display material, or the OLED material sinks, due to their own weight in a state in which ink is stored in the head supply reservoir.

In an effort to solve this, a technology to circulate ink inside an inkjet printer using a piezoelectric pump so as to maintain a meniscus state has been developed (Korean Patent No. 10-1989375).

In this case, however, in the process in which ink including metal particles, a flat panel display material, or an OLED material passes the pump, a problem such as malfunction in the pump or shortening of life span of the pump may occur.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an objective of the present invention is to provide an ink circulation supply system that does not require use of a pump in the process of circulating ink between an inkjet head and a head supply reservoir, in order to maintain viscosity of ink or to maintain dispersibility and homogeneity of particles dispersed in ink.

In order to achieve the above objective, according to one aspect of the present invention, there is provided an ink circulation supply system for an inkjet head, the system being configured to supply ink to the inkjet head having a plurality of nozzles for ejecting the ink, the system including: a meniscus reservoir connected to the inkjet head through a supply passage, and configured to transfer the ink to the inkjet head; a circulation reservoir connected to the inkjet head through a recovery passage, and configured such that the ink recovered from the inkjet head is returned thereto; an ante reservoir connected to the circulation reservoir through a first pressure connection pipe connected to an upper portion of the ante reservoir, connected to the meniscus reservoir through a second pressure connection pipe connected to the upper portion of the ante reservoir, connected to the circulation reservoir through a first ink connection pipe connected to a lower portion of the ante reservoir, and connected to the meniscus reservoir through a second ink connection pipe connected to the lower portion of the ante reservoir; a first pressure controller connected to the meniscus reservoir through a first pressure control pipe, and configured to control internal pressure; and a second pressure controller connected to the circulation reservoir through a second pressure control pipe, and configured to control internal pressure, wherein a first pressure valve may be provided in the first pressure connection pipe, a second pressure valve may be provided in the second pressure connection pipe, and an ink valve may be provided in the second ink connection pipe.

Due to the fact that an industrial inkjet printer continuously performs a printing process, the printer is provided with a head supply reservoir for supplying ink to the inkjet head and an ink reservoir tank provided externally for supplying ink to the head supply reservoir. Here, supply of ink from the head supply reservoir to the inkjet head is expressed as internal supply or local ink supply, and supply of ink to the head supply reservoir directly from the ink reservoir tank or via a buffer reservoir is expressed as external supply or bulk ink supply. The present invention is a technique for circulating ink in an internal supply process in which ink is supplied to the inkjet head from the head supply reservoir.

In the present invention, apart from supplying ink to eject ink from the inkjet head, ink is circulated between the inkjet head and an ink reservoir, whereby ink is moved without stagnation, thereby maintaining dispersibility and homogeneity of ink. In this case, due to the fact that the present invention does not require use a pump to circulate ink between the inkjet head and the ink reservoir, a meniscus state of the ink reservoir and/or inkjet head is maintained by pulsation of the pump, and further, the problem of malfunction of the pump due to metal particles, a flat panel display material, or an OLED material does not occur.

In detail, the present invention is characterized in that spaces in which the ink is stored are separated, and ink is circulated due to a pressure difference between a portion where ink is supplied toward the inkjet head and a portion where ink recovered via the inkjet head, without requiring use of the pump. In this case, the portion where ink is supplied toward the inkjet head has to maintain a constant negative pressure to maintain the meniscus state, and thus the meniscus state of the inkjet head is maintained by positioning the ante reservoir between the meniscus reservoir and the circulation reservoir.

A flow sensor for measuring a flow rate of the ink may be provided in at least one of the supply passage and the recovery passage.

The system may further include an ink reservoir tank provided externally and configured to store the ink, wherein the ink may be additionally injected into one of the meniscus reservoir, the circulation reservoir, and the ante reservoir through a first injection pipe connected to the ink reservoir tank.

The system may further include: an ink reservoir tank provided externally and configured to store the ink; and a buffer reservoir configured to temporarily store the ink, wherein the ink may be additionally injected into one of the meniscus reservoir, the circulation reservoir, and the ante reservoir through a second injection pipe connected to the buffer reservoir, and the ink may be circulated between the buffer reservoir and the ink reservoir tank through two transport pipes connected to the buffer reservoir and the ink reservoir tank at positions therebetween.

According to another aspect of the present invention, there is provided an ink circulation supply method for an inkjet head, the method being circulating ink in the inkjet head without requiring use of a pump in the system having the above-described structure, wherein an internal pressure of the circulation reservoir may be controlled to be lower than an internal pressure of the meniscus reservoir, whereby the ink stored in the meniscus reservoir may be moved to the circulation reservoir via the inkjet head.

In detail, the internal pressure of the circulation reservoir may be controlled to be lower than the internal pressure of the meniscus reservoir, and the first pressure valve, the second pressure valve, and the ink valve may all remain closed, whereby the ink stored in the meniscus reservoir may be moved to the circulation reservoir via the inkjet head.

In this case, the internal pressure of the circulation reservoir may be controlled to change a difference between the internal pressure of the meniscus reservoir and the internal pressure of the circulation reservoir, whereby a flow rate at which the ink stored in the meniscus reservoir may be moved to the circulation reservoir via the inkjet head may be controlled. The internal pressure of the circulation reservoir may be controlled on the basis of the flow rate measured by the flow sensor provided in the supply passage or the recovery passage.

When a predetermined amount of the ink stored in the meniscus reservoir is moved to the circulation reservoir via the inkjet head, the first pressure valve may be opened, causing an internal pressure of the ante reservoir to match with the internal pressure of the circulation reservoir, and causing the ink stored in the circulation reservoir to be moved to the ante reservoir due to a difference in head pressure between the ink stored in the ante reservoir and the ink stored in the circulation reservoir.

When a predetermined amount of the ink stored in the circulation reservoir is moved to the ante reservoir, the first pressure valve may be closed and the second pressure valve may be opened, causing the internal pressure of the ante reservoir to match with the internal pressure of the circulation reservoir; and the ink valve may be opened, causing the ink stored in the ante reservoir to be moved to the meniscus reservoir due to a difference in head pressure between the ink stored in the ante reservoir and the ink stored in the meniscus reservoir

The present invention as described above enables circulation of ink between the inkjet head and the ink reservoir without requiring use of a pump, and thus there is an effect of maintaining fluidity, dispersibility, and homogeneity of ink, while not causing the problem due to malfunction of the pump.

Further, the present invention provides increased fluidity, dispersibility, and homogeneity of ink, and thus there is an excellent effect that the inkjet head can be supplied with ink having fluidity, dispersibility, and homogeneity maintained.

Furthermore, the inkjet printing process using ink in which metal particles, a flat panel display material, or an OLED material is dispersed can be employed in a product manufacturing process, and thus there is an effect in that the manufacturing process of the product can be accurate and easy.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

The description of the disclosed technology is only an example for structural and functional illustration, and thus the scope of the disclosure should not be construed as being limited by the embodiments described herein. That is, it should be understood that the embodiments of the present disclosure can be variously modified in many different forms, and thus the scope of the disclosure includes equivalents by which the technical spirit of the disclosure can be accomplished.

The terms used herein should be understood as follows.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, the scope of the disclosure should not be limited by these terms. These terms are only used to distinguish one element, from another element. For example, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Similarly, the second element could also be termed the first element.

FIG. 1is a view illustrating a structure of an ink circulation supply system for an inkjet head according to an embodiment of the present invention.

As illustrated, the ink circulation supply system of the present embodiment includes an inkjet head100and three reservoirs210,220, and230, and two pressure controllers310and320.

The inkjet head100is a part having a plurality of nozzles for ejecting ink, and an inkjet printer including the ink circulation supply system of the present embodiment is configured for industrial use and has a structure in which the inkjet head100and a head supply reservoir for storing ink to be supplied to the inkjet head100are separated. The technical configuration of an inkjet head, which has been used in the related art, can be employed within a range that does not impair the features of the present invention, and can also be employed in various modifications.

The head supply reservoir is a part for storing ink inside the inkjet printer to provide ink to the inkjet head100. In the related art, a head supply reservoir is generally composed of a single space, but in the present invention, the head supply reservoir is divided into the three reservoirs210,220, and230, each of which is provided with a separate space. Hereinafter, when describing a unique configuration and function of each of the reservoirs, description will be given using the name of each of the reservoirs, but when the three reservoirs collectively perform the same function as the head supply reservoir according to the related art, the reservoirs will be referred to as the head supply reservoir.

A first reservoir is a meniscus reservoir210.

The meniscus reservoir210is connected to a supply passage110for supplying ink to the inkjet head100, and is connected to a first pressure controller310located upstream of the meniscus reservoir210, through a first pressure control pipe312. Because the meniscus reservoir210is connected to the inkjet head100through the supply passage110, the control of the internal pressure of the meniscus reservoir210is necessary so that the inkjet head100maintains a meniscus state.

A second reservoir is a circulation reservoir220.

The circulation reservoir220is connected to a recovery passage120for returning ink remaining in the inkjet head100to the head supply reservoir, and is connected to a second pressure controller320located upstream of the circulation reservoir220, through a second pressure control pipe322. The circulation reservoir220is not related to maintaining the meniscus state, but is configured to form a pressure difference between the circulation reservoir220and the meniscus reservoir210, thereby causing ink of the meniscus reservoir210to be moved for circulation to the circulation reservoir220via the inkjet head100.

A third reservoir is an ante reservoir230.

The ante reservoir230is provided to move ink of the circulation reservoir220back to the meniscus reservoir210, the ink resulting from ink of the meniscus reservoir210being moved to the circulation reservoir220via the inkjet head100and collected in the circulation reservoir220due to the pressure difference between the meniscus reservoir210and the circulation reservoir220.

The ante reservoir230is connected to the circulation reservoir220through a first pressure connection pipe330provided at an upper portion of the ante reservoir230and connected to the meniscus reservoir210through a second pressure connection pipe340provided at the upper portion of the ante reservoir230. Further, the ante reservoir230is connected to the circulation reservoir220through a first ink connection pipe240provided at a lower portion of the ante reservoir230and connected to the meniscus reservoir210through a second ink connection pipe252provided at the lower portion of the ante reservoir230.

A first pressure valve332is provided in the first pressure connection pipe330, a second pressure valve342is provided in the second pressure connection pipe340, and an ink valve250is provided in the second ink connection pipe252.

The first pressure valve332, the second pressure valve342, and the ink valve250are configured to be properly opened and closed to control movement of ink so that ink of the meniscus reservoir210is moved to the circulation reservoir220via the inkjet head100or ink of the circulation reservoir220is moved to the meniscus reservoir210via the ante reservoir230. A detailed operation will be described later.

As described above, due to the fact that the present invention is a configuration in which ink exiting from the meniscus reservoir210is recovered to the circulation reservoir220via the inkjet head100, the three reservoirs are combined and function as an existing head supply reservoir, and each of the three reservoirs210,220, and230is a different component from an existing buffer reservoir or an existing ink reservoir tank provided externally.

InFIG. 1, a configuration in which ink is injected from an ink reservoir tank400to the circulation reservoir220through a first injection pipe410is illustrated. However, the circulation reservoir220as described above is a component different from the buffer reservoir provided in the middle of the path for injecting ink into the head supply reservoir in that ink remaining in the inkjet head100is recovered through the recovery passage120. Further, the first injection pipe410connected to the ink reservoir tank400may be connected to the meniscus reservoir210or the ante reservoir230as necessary.

An existing pressure controller is configured to control ink inside the inkjet head100to maintain the meniscus state by controlling the pressure of the head supply reservoir, and a single pressure controller is generally provided. Due to the fact that the ink circulation supply system according to the present invention is configured to circulate ink by means of a pressure difference between division reservoirs, in addition to pressure control for maintaining the meniscus state, the two pressure controllers310and320are provided.

The first pressure controller310is connected to the meniscus reservoir210through the first pressure control pipe312, and is configured to control the pressure of the meniscus reservoir210in the same manner as the existing pressure controller to enable the inkjet head100to maintain the meniscus state. Due to the fact that first pressure controller310employs a general structure separately connected to the meniscus reservoir210which is one constituting the head supply reservoir, pressure control devices, which have been conventionally used to maintain the meniscus state in inkjet printers, may be employed without modification.

The second pressure controller320is connected to the circulation reservoir220through the second pressure control pipe322, and is configured to perform a function of forming the pressure difference between the circulation reservoir220and the meniscus reservoir210.

In order for ink exiting from the meniscus reservoir210to be moved to the circulation reservoir220via the inkjet head100, the internal pressure of the circulation reservoir220has to be lower than that of the meniscus reservoir210. Controlling the internal pressure of the reservoir is the same as in the related art, except that the internal pressure of the circulation reservoir220is controlled to be lower than that of the meniscus reservoir210, and thus pressure control devices conventionally used in inkjet printers may be employed.

On the other hand, as will be described later in detail, in order to maintain the meniscus state of the meniscus reservoir210, the first pressure controller310is operated to maintain a constant internal pressure of the meniscus reservoir210. On the other hand, in order to control the flow rate of ink, it is necessary to control the internal pressure of the circulation reservoir220. Thus, the second pressure controller320is preferably configured to actively control the internal pressure of the circulation reservoir220.

In the present embodiment, a flow sensor130is provided in the recovery passage120and is configured to measure the flow rate of ink exiting from the meniscus reservoir210to the circulation reservoir220via the inkjet head100. The second pressure controller320controls the internal pressure of the circulation reservoir220so that a target flow rate is reached on the basis of the measured flow rate of ink. In detail, when the flow rate of ink exiting from the meniscus reservoir210and moved to the circulation reservoir220via the inkjet head100is less than the target flow rate, the pressure difference between the meniscus reservoir210and the circulation reservoir220is controlled to increase by further decreasing the internal pressure of the circulation reservoir220. On the other hand, when the flow rate of ink exiting from the meniscus reservoir210and moved to the circulation reservoir220via the inkjet head100is greater than the target flow rate, the pressure difference between the meniscus reservoir210and the circulation reservoir220is controlled to decrease by increasing the internal pressure of the circulation reservoir220.

Hereinafter, a specific operation of the ink circulation supply system for the inkjet head according to the embodiment illustrated inFIG. 1will be described.

FIGS. 2 to 4are views illustrating an operation of the ink circulation supply system for the inkjet head according to the embodiment of the present invention.

FIG. 2illustrates a state in which ink exiting from the meniscus reservoir210starts to be moved to the circulation reservoir220via the inkjet head100.

First,FIG. 2illustrates a state in which ink starts to circulate, and description will be given on the basis of a state in which the first pressure valve332, the second pressure valve342, and the ink valve250are all closed.

The meniscus reservoir210maintains a negative pressure condition for the inkjet head100to maintain the meniscus state, and the negative pressure of the meniscus reservoir210is maintained at a nearly constant pressure by the first pressure controller310. Further, the internal pressure of the circulation reservoir220is controlled to a lower pressure than the meniscus reservoir210by the second pressure controller320.

In this case, due to the fact that the first pressure valve332and the second pressure valve342are both closed, the pressure difference between the meniscus reservoir210and the circulation reservoir220is maintained. Even when the levels of ink filled in the circulation reservoir210and the circulation reservoir220are the same, ink of the meniscus reservoir210is moved to the circulation reservoir220due to the pressure difference between the meniscus reservoir210and the circulation reservoir220.

Further, due to the fact that the ink valve250is closed, ink of the meniscus reservoir210flows through the supply passage110and is moved, via the inkjet head100, to the circulation reservoir220through the recovery passage120.

Due to the fact that the negative pressure of the meniscus reservoir210is maintained at the nearly constant pressure, the pressure difference between the meniscus reservoir210and the circulation reservoir220may be controlled by controlling the internal pressure of the circulation reservoir220. Further, controlling the pressure difference between the meniscus reservoir210and the circulation reservoir220may enable control of the flow rate of ink moving through the supply passage110and the recovery passage120. The flow rate of ink increases with the increase in the pressure difference between the meniscus reservoir210and the circulation reservoir220, and the flow rate of ink decreases with the decrease in the pressure difference between the meniscus reservoir210and the circulation reservoir220.

This control of the flow rate of ink may be performed by a method of reaching the target flow rate on the basis of the flow rate measured by the flow sensor130provided in the path of movement of the ink. In the present embodiment, the flow sensor130is provided in the recovery passage120to measure the flow rate of ink. When the flow rate of ink flowing through the recovery passage120is less than the target flow rate, the pressure difference between the meniscus reservoir210and the circulation reservoir220is controlled to increase by controlling the second pressure controller320to further decrease the internal pressure of the circulation reservoir220. On the other hand, when the flow rate of ink flowing through the recovery passage120is greater than the target flow rate, the pressure difference between the meniscus reservoir210and the circulation reservoir220is controlled to decrease by controlling the second pressure controller320to increase the internal pressure of the circulation reservoir220.

When the state ofFIG. 2is maintained, ink of the meniscus reservoir210flows through the supply passage110and is moved, via the inkjet head100, to the circulation reservoir220through the recovery passage120. Thus, the level of ink of the meniscus reservoir210gradually decreases, the level of ink of the circulation reservoir220gradually increases, and the level of ink of the ante reservoir230remains the same, whereby a state as illustrated inFIG. 3is reached.

When the state as illustrated inFIG. 3is reached, the first pressure valve332is gradually opened, while the second pressure valve342and the ink valve250remain closed.

As the first pressure valve332is gradually opened, the internal pressure of the circulation reservoir220and the internal pressure of the ante reservoir230gradually become the same, and a difference in head pressure due to a difference in level of ink occurs. The head pressure of each reservoir is a value that is obtained by adding internal pressure, and pressure due to the level of ink therein. InFIG. 2, the first pressure valve332is closed, and there is a difference in internal pressure between the ante reservoir230and the circulation reservoir220, and thus ink of the circulation reservoir220is not moved to the ante reservoir230even though the ante reservoir230and the circulation reservoir220are connected to the first ink connection pipe240at which no separate valve is provided. On the other hand, when the first pressure valve332is gradually opened in the state ofFIG. 3and thus the internal pressure of the circulation reservoir220and the internal pressure of the ante reservoir230become the same, the difference in head pressure due to the difference in level of ink between the circulation reservoir220and the ante reservoir230occurs due to the same internal pressure, thereby causing ink of the circulation reservoir220to be moved to the ante reservoir230through the first ink connection pipe240.

In this case, due to the fact that the second pressure valve342remains closed, the internal pressure of the circulation reservoir220and the internal pressure of the ante reservoir230do not affect the internal pressure of the meniscus reservoir210. Additionally, due to the fact that the ink valve250remains closed, even when the level of ink of the ante reservoir230increases, ink of the ante reservoir230is not allowed to be moved to the meniscus reservoir210.

As such, movement of ink from the circulation reservoir220to the ante reservoir230through the first ink connection pipe240occurs due to the difference in head pressure due to the difference in level of ink. Thus, as illustrated inFIG. 4, the movement of ink continues until the levels of ink of the circulation reservoir220and the ante reservoir230become the same.

When a state ofFIG. 4is reached, the first pressure valve332is first closed, and the second pressure valve342and the ink valve250are then opened.

As the second pressure valve342is gradually opened, the internal pressure of the meniscus reservoir210and the internal pressure of the ante reservoir230gradually become the same, and a difference in head pressure due to a difference in level of ink occurs.

The meniscus reservoir210is in a constant negative pressure state by operating the first pressure controller310in order to maintain the meniscus state of the inkjet head100, and thus the internal pressure of the ante reservoir230is gradually adjusted to the internal pressure of the meniscus reservoir210. In this case, due to the fact that the first pressure valve332remains closed, the internal pressure of the circulation reservoir220does not affect the internal pressures of the ante reservoir230and the meniscus reservoir210.

As the internal pressure of the meniscus reservoir210and the internal pressure of the ante reservoir230gradually become the same, a difference in head pressure occurs due to a difference in level of ink between the meniscus reservoir210and the ante reservoir230, and when the ink valve250is opened, ink of the ante reservoir230is moved to the meniscus reservoir210through the second ink connection pipe252. In this case, when ink of the ante reservoir230is moved to the meniscus reservoir210too quickly, pulsation may occur due to a sudden change in level of ink and the meniscus state may not be maintained. Thus, the opening ratio of the ink valve250has to be appropriately controlled.

As described above, in the present embodiment, the ante reservoir230is located between the circulation reservoir220and the meniscus reservoir210, and the first pressure valve332and the second pressure valve342are provided in the first pressure connection pipe330and the second pressure connection pipe340connecting the respective reservoirs at upper portions thereof. Further, the first pressure valve332and the second pressure valve342are configured not to be simultaneously opened but all closed or only one thereof is opened so that the internal pressures of the meniscus reservoir210and the circulation reservoir220do not affect each other, thereby enabling the meniscus reservoir210to maintain a constant negative pressure state to maintain the meniscus state. Consequently, it is possible to configure the ink circulation supply system for the inkjet head, the system being capable of: circulating ink by means of a difference in internal pressure between the meniscus reservoir210and the circulation reservoir220, while maintaining the negative pressure state of the meniscus reservoir210constant; and circulating ink between the inkjet head the head supply reservoir, without requiring use of a pump.

In a state ofFIG. 4, due to the difference in level of ink stored in the meniscus reservoir210and the ante reservoir230, ink of the ante reservoir230is moved to the meniscus reservoir210, and finally the height of ink becomes the height as illustrated inFIG. 2. As illustrated inFIG. 2, when the levels of ink stored in the meniscus reservoir210and the ante reservoir230become the same, the second pressure valve342is closed and then the first pressure valve332is gradually opened. Although in describing the opening/closing process of the first pressure valve332and the second pressure valve342as set forth above, steps thereof have been described separately, the respective steps are performed continuously. In particular, in order to continuously circulate ink, the difference in head pressure between the meniscus reservoir210and the circulation reservoir220have to be maintained continuously. Thus, it is preferable to maintain the first pressure valve332always open, except when the second pressure valve342is opened.

Further, as illustrated, when the bottom height of the circulation reservoir220is higher than those of the meniscus reservoir210and the ante reservoir230, the effect of head pressure due to the difference in level of ink occurring between the reservoirs is improved. Thus, as illustrated inFIG. 5, it is possible that the meniscus reservoir210, the circulation reservoir220, and the ante reservoir230are configured to have the same bottom height. However, in order to improve circulation efficiency, it is preferable that the bottom height of the circulation reservoir220is relatively higher.

When the ink circulation supply system for the inkjet head according to the present invention is employed, it is possible to increase fluidity, dispersibility, and homogeneity of ink, thereby supplying ink having fluidity, dispersibility, and homogeneity maintained to the inkjet head. Additionally, due to the fact that use of a pump is not necessary, there is an excellent effect that a problem such as malfunction of the pump does not occur.

FIG. 6is a view illustrating an embodiment in which a buffer reservoir and an external circulation supply structure are added to the ink circulation supply system for the inkjet head ofFIG. 1.

While a structure in which ink is injected from the ink reservoir tank400provided externally to the circulation reservoir220through the first injection pipe410is illustrated inFIG. 1, the embodiment ofFIG. 6provides a structure in which a buffer reservoir500is additionally provided between the ink reservoir tank400and the circulation reservoir220, and ink of the buffer reservoir500is injected into the circulation reservoir220through a second injection pipe510. Further, two transport pipes420and430are connected to the buffer reservoir500and the ink reservoir tank400at positions therebetween and are configured to circulate ink in the process of externally supplying ink through the pipes. In this case, the second injection pipe510may be connected to the meniscus reservoir210or the ante reservoir230.

The buffer reservoir500is a component that temporarily stores ink before supplying ink to the circulation reservoir220constituting the head supply reservoir, and is configured to transfer ink between the ink reservoir tank400storing a large amount of ink and the head supply reservoir. The buffer reservoir500is generally provided inside the inkjet printer, but the present invention is not limited thereto. For example, the buffer reservoir500may be provided outside the inkjet printer depending on the structure of printers.

Conventionally, the buffer reservoir500is also used for the purpose of maintaining the meniscus state of the inkjet head100. In the present embodiment, the buffer reservoir500may be used to perform a function for maintaining the internal pressure of the circulation reservoir220controlled by the second pressure controller320. Further, the buffer reservoir500may simultaneously perform a function for maintaining the internal pressure of the circulation reservoir220and a function for maintaining fluidity, dispersibility, and homogeneity of ink.

The buffer reservoir500and the circulation reservoir220are connected to the second injection pipe510through which ink is moved, and ink of the buffer reservoir500is selectively supplied to the circulation reservoir220by a method such as providing a valve at the second injection pipe510.

The ink reservoir tank400is a configuration for storing a relatively large amount of ink and supplying ink to the buffer reservoir500. In general, an industrial inkjet printer consumes a large amount of ink, and thus is configured not only that the inkjet head100and the head supply reservoir are separated, but also that the ink reservoir tank400is separately provided externally of the inkjet printer to continuously supply ink to the head supply reservoir.

In the present embodiment, the structure in which ink is supplied from the ink reservoir tank400provided externally to the head supply reservoir via the buffer reservoir500is provided. Additionally, it is characterized in that the buffer reservoir500and the ink reservoir tank400are connected to each other by the two transport pipes420and430through which ink is moved, and thus unlike related art techniques using a single transport pipe to allow only one-directional movement of ink, ink may be continuously circulated between the buffer reservoir500and the ink reservoir tank400.

In detail, the first transport pipe420transports ink from the ink reservoir tank400to the buffer reservoir500, and the second transport pipe430transports ink from the buffer reservoir500to the ink reservoir tank400.

In order for the inkjet head100to operate in the inkjet printer according to the present embodiment, ink has to be continuously supplied. However, the process in which ink is supplied to the head supply reservoir in order to maintain the meniscus state and maintain the internal pressure of the circulation reservoir220is performed intermittently or at a slow speed. Due thereto, the buffer reservoir500and the ink reservoir tank400are in a state such that ink is stagnant for a long time. In this case, when using the kind of ink in which contents thereof tend to be easily separated from each other or ink in which metal particles, a flat panel display material, or an OLED material is dispersed, separation may occur in stagnant ink, thereby deteriorating homogeneity of ink, and there arises a problem that printing may not be performed smoothly due to supply of separated ink to the inkjet head100.

In the present embodiment, ink is not only supplied in one direction from the ink reservoir tank400toward the buffer reservoir500, but also transported from the buffer reservoir500toward the ink reservoir tank400through the second transport pipe430so that ink is circulated for continuous movement. Thus, this makes it possible to maintain dispersibility and homogeneity of ink. In detail, even when ink is not additionally supplied to the buffer reservoir500, ink may be circulated in a manner that ink is transported to the buffer reservoir500through the first transport pipe420while ink is returned to the ink reservoir tank400through the second transport pipe430. When ink needs to be additionally supplied to the buffer reservoir500, ink may be additionally supplied to the buffer reservoir500, while maintaining circulation thereof in such a manner of stopping transportation of ink through the second transport pipe430, or controlling the amount of ink so that the amount of ink moved through the first transport pipe420is greater than that moved through the second transport pipe430.

As a method of supplying ink from the ink reservoir tank400provided externally to the buffer reservoir500, both a method of pressurizing the ink reservoir tank400and a method of using a pump are possible, and it is preferable that a valve is provided in each of the first transport pipe420and the second transport pipe520in order to control whether ink is circulated and a circulation amount of ink.

In this case, an agitator for agitating stored ink may be provided inside the buffer reservoir500. As the agitator, a typical rotary agitator may be employed. In particular, a magnetic agitator that rotates by magnetic force may be employed. In general, it is difficult to maintain dispersibility and homogeneity of ink only by use of the agitator. However, in the present embodiment, due to the fact that ink is continuously circulated externally between the buffer reservoir500and the ink reservoir tank400, dispersibility and homogeneity of ink may be further increased by use of the agitator.

In order to maintain the internal pressure of the ink reservoir tank400in the process of additionally supplying ink from the ink reservoir tank400to the buffer reservoir500, a gas supplier for supplying clean dry air (CDA) or N2may be connected to the ink reservoir tank400, and a vent for maintaining the internal pressure of the buffer reservoir500may be connected to the buffer reservoir500. For the gas supplier and the vent, any known techniques may be employed without limitation, and thus a detailed description thereof will be omitted.

In the inkjet printer described above, ink is circulated internally between the inkjet head100and the head supply reservoir, and simultaneously ink is circulated externally between the ink reservoir tank400and the buffer reservoir500, and thus ink may be stored in the ink reservoir tank400and the buffer reservoir500while maintaining dispersibility and homogeneity thereof, and ink having dispersibility and homogeneity maintained may be supplied to the head supply reservoir. Thus, consequently, ink having dispersibility and homogeneity maintained may be supplied to the inkjet head100.

When the ink circulation supply system of the inkjet printer according to the present invention is employed, a product may be manufactured through an inkjet printing process using ink, which have recently been of interest, in which metal particles, a flat panel display material, or an OLED material is dispersed. Consequently, due to the characteristics of the inkjet printing process that can perform a precise process quickly, there is an excellent effect that efficiency of a process for manufacturing an electrode, a flat panel display, or an OLED is greatly improved.

FIG. 7is a view illustrating a structure of an ink circulation supply system for an inkjet head according to another embodiment of the present invention.

The ink circulation supply system for the inkjet head according to the present invention is characterized in that three reservoirs210,220, and230that function as the existing head supply reservoir are separated from each other.

In this case, the external structures of a meniscus reservoir210, a circulation reservoir220, and an ante reservoir230are not particularly limited, as long as the internal spaces of the respective reservoirs are separated from each other so that the internal pressures thereof are controlled independently.

InFIG. 1, a configuration in which the meniscus reservoir210and the ante reservoir230are located in separate spaces in the same casing, and the circulation reservoir220is located in a separate casing.

The embodiment illustrated inFIG. 7is a case in which the meniscus reservoir210, the circulation reservoir220, and the ante reservoir230are arranged independently in separate spaces in the same casing. In this case, a first pressure connection pipe330connects the circulation reservoir220and the ante reservoir230to each other at upper portions thereof, a second pressure connection pipe340connects the ante reservoir230and the meniscus reservoir210to each other at upper portions thereof, and a first pressure valve332and a second pressure valve342are provided in the first pressure connection pipe330and the second pressure connection pipe340, respectively. This structure is the same as that of the embodiment ofFIG. 1. Further, a first ink connection pipe240connects the circulation reservoir220and the ante reservoir230to each other at lower portions thereof, a second ink connection pipe252connects the ante reservoir230and the meniscus reservoir210to each other at lower portions thereof, and an ink valve250is provided only at the second ink connection pipe252. This structure is the same as that of the embodiment ofFIG. 1.

In this case, when the meniscus reservoir210, the circulation reservoir220, and the ante reservoir230are arranged independently in separate spaces in the same casing as illustrated inFIG. 7, the first pressure connection pipe330, the second pressure connection pipe340, the first ink connection pipe240, and the second ink connection pipe252may be configured as separate pipes as illustrated, but the present invention is not limited thereto. For example, these pipes may be configured as passages formed inside the casing.

In consideration of the fact that when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same and when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same, a difference in head pressure due to the level of ink stored therein occurs, the meniscus reservoir210and the ante reservoir230are designed to have the same bottom height while the circulation reservoir220is designed to have a relatively higher bottom height. This structure is also the same as that of the embodiment ofFIG. 1.

Other configurations and a method of circulating ink by means of a difference in internal pressure occurring between three reservoirs are the same as those of the embodiment ofFIG. 1described above, and thus a further description thereof will be omitted.

When the ink circulation supply system for the inkjet head as above is employed, it is possible to increase fluidity, dispersibility, and homogeneity of ink, thereby supplying ink having fluidity, dispersibility, and homogeneity maintained to the inkjet head. Additionally, due to the fact that use of a pump is not necessary, there is an excellent effect that a problem such as malfunction of the pump does not occur.

FIG. 8is a view illustrating an embodiment in which a buffer reservoir and an external circulation supply structure are added to the ink circulation supply system for the inkjet head ofFIG. 7.

While a structure in which ink is injected from an ink reservoir tank400provided externally to a circulation reservoir220through a first injection pipe410is illustrated inFIG. 7, the embodiment ofFIG. 8provides a structure in which a buffer reservoir500is additionally provided between an ink reservoir tank400provided externally and a circulation reservoir220, and ink of the buffer reservoir500is injected into the circulation reservoir220through a second injection pipe510. Further, two transport pipes420and430are connected to the buffer reservoir500and the ink reservoir tank400at positions therebetween and are configured to circulate ink in the process of externally supplying ink through the pipes.

Other configurations and a configuration in which ink is circulated externally between the buffer reservoir and the ink reservoir tank are the same as those of the embodiment ofFIG. 6described above, and thus a further description thereof will be omitted.

When the ink circulation supply system of the inkjet printer according to the present invention is employed, a product may be manufactured through an inkjet printing process using ink, which has recently been of interest, in which metal particles, a flat panel display material, or an OLED material is dispersed. Consequently, due to the characteristics of the inkjet printing process that can perform a precise process quickly, there is an excellent effect that efficiency of a process for manufacturing an electrode, a flat panel display, or an OLED is greatly improved.

FIG. 9is a view illustrating a structure of an ink circulation supply system for an inkjet head according to another embodiment of the present invention.

The ink circulation supply system for the inkjet head according to the present invention is characterized in that three reservoirs210,220, and230that function as the existing head supply reservoir are separated from each other.

In this case, the external structures of a meniscus reservoir210, a circulation reservoir220, and an ante reservoir230are not particularly limited, as long as the internal spaces of the respective reservoirs are separated from each other so that the internal pressures thereof are controlled independently.

InFIG. 1, a configuration in which the meniscus reservoir210and the ante reservoir230are located in separate spaces in the same casing, and the circulation reservoir220is located in a separate casing.

The embodiment illustrated inFIG. 9is a case in which the meniscus reservoir210, the circulation reservoir220, and the ante reservoir230are arranged independently in different casings. In this case, a first pressure connection pipe330connects the circulation reservoir220and the ante reservoir230to each other at upper portions thereof, a second pressure connection pipe340connects the ante reservoir230and the meniscus reservoir210to each other at upper portions thereof, and a first pressure valve332and a second pressure valve342are provided in the first pressure connection pipe330and the second pressure connection pipe340, respectively. This structure is the same as that of the embodiment ofFIG. 1. Further, a first ink connection pipe240connects the circulation reservoir220and the ante reservoir230to each other at lower portions thereof, a second ink connection pipe252connects the ante reservoir230and the meniscus reservoir210to each other at lower portions thereof, and an ink valve250is provided only at the second ink connection pipe252. This structure is the same as that of the embodiment ofFIG. 1.

In this case, in consideration of the fact that when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same and when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same, a difference in head pressure due to the level of ink stored therein occurs, the meniscus reservoir210and the ante reservoir230are designed to have the same bottom height while the circulation reservoir220is designed to have a relatively higher bottom height. This structure is also the same as that of the embodiment ofFIG. 1.

Other configurations and a method of circulating ink by means of a difference in internal pressure occurring between three reservoirs are the same as those of the embodiment ofFIG. 1described above, and thus a further description thereof will be omitted.

When the ink circulation supply system for the inkjet head as above is employed, it is possible to increase fluidity, dispersibility, and homogeneity of ink, thereby supplying ink having fluidity, dispersibility, and homogeneity maintained to the inkjet head. Additionally, due to the fact that use of a pump is not necessary, there is an excellent effect that a problem such as malfunction of the pump does not occur.

FIG. 10is a view illustrating an embodiment in which a buffer reservoir and an external circulation supply structure are added to the ink circulation supply system for the inkjet head ofFIG. 9.

While a structure in which ink is injected from an ink reservoir tank400provided externally to a circulation reservoir220through a first injection pipe410is illustrated inFIG. 9, the embodiment of FIG.10provides a structure in which a buffer reservoir500is additionally provided between an ink reservoir tank400provided externally and a circulation reservoir220, and ink of the buffer reservoir500is injected into the circulation reservoir220through a second injection pipe510. Further, two transport pipes420and430are connected to the buffer reservoir500and the ink reservoir tank400at positions therebetween and are configured to circulate ink in the process of externally supplying ink through the pipes.

Other configurations and a configuration in which ink is circulated externally between the buffer reservoir and the ink reservoir tank are the same as those of the embodiment ofFIG. 6described above, and thus a further description thereof will be omitted.

When the ink circulation supply system of the inkjet printer according to the present invention is employed, a product may be manufactured through an inkjet printing process using ink, which have recently been of interest, in which metal particles, a flat panel display material, or an OLED material is dispersed. Consequently, due to the characteristics of the inkjet printing process that can perform a precise process quickly, there is an excellent effect that efficiency of a process for manufacturing an electrode, a flat panel display, or an OLED is greatly improved.

FIG. 11is a view illustrating a structure of an ink circulation supply system for an inkjet head according to another embodiment of the present invention.

The ink circulation supply system for the inkjet head according to the present invention is characterized in that three reservoirs210,220, and230that function as the existing head supply reservoir are separated from each other.

In this case, the external structures of a meniscus reservoir210, a circulation reservoir220, and an ante reservoir230are not particularly limited, as long as the internal spaces of the respective reservoirs are separated from each other so that the internal pressures thereof are controlled independently.

InFIG. 1, a configuration in which the meniscus reservoir210and the ante reservoir230are located in separate spaces in the same casing, and the circulation reservoir220is located in a separate casing.

In the embodiment illustrated inFIG. 11, the meniscus reservoir210is located in a separate casing, and the ante reservoir230and the circulation reservoir220are located independently in separate spaces in the same casing. In this case, a first pressure connection pipe330connects the circulation reservoir220and the ante reservoir230to each other at upper portions thereof, a second pressure connection pipe340connects the ante reservoir230and the meniscus reservoir210to each other at upper portions thereof, and a first pressure valve332and a second pressure valve342are provided in the first pressure connection pipe330and the second pressure connection pipe340, respectively. This structure is the same as that of the embodiment ofFIG. 1. Further, a first ink connection pipe240connects the circulation reservoir220and the ante reservoir230to each other at lower portions thereof, a second ink connection pipe252connects the ante reservoir230and the meniscus reservoir210to each other at lower portions thereof, and an ink valve250is provided only at the second ink connection pipe252. This structure is the same as that of the embodiment ofFIG. 1.

In this case, when the circulation reservoir220and the ante reservoir230are arranged independently in separate spaces in the same casing as illustrated inFIG. 11, the first pressure connection pipe330and the first ink connection pipe240may be configured as separate pipes as illustrated, but the present invention is not limited thereto. For example, these pipes may be configured as passages formed inside the casing.

In consideration of the fact that when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same and when the internal pressures of the meniscus reservoir210and the ante reservoir230become the same, a difference in head pressure due to the level of ink stored therein occurs, the meniscus reservoir210and the ante reservoir230are designed to have the same bottom height while the circulation reservoir220is designed to have a relatively higher bottom height. This structure is also the same as that of the embodiment ofFIG. 1.

Other configurations and a method of circulating ink by means of a difference in internal pressure occurring between three reservoirs are the same as those of the embodiment ofFIG. 1described above, and thus a further description thereof will be omitted.

When the ink circulation supply system for the inkjet head as above is employed, it is possible to increase fluidity, dispersibility, and homogeneity of ink, thereby supplying ink having fluidity, dispersibility, and homogeneity maintained to the inkjet head. Additionally, due to the fact that use of a pump is not necessary, there is an excellent effect that a problem such as malfunction of the pump does not occur.

FIG. 12is a view illustrating an embodiment in which a buffer reservoir and an external circulation supply structure are added to the ink circulation supply system for the inkjet head ofFIG. 11.

While a structure in which ink is injected from an ink reservoir tank400provided externally to a circulation reservoir220through a first injection pipe410is illustrated inFIG. 11, the embodiment ofFIG. 12provides a structure in which a buffer reservoir500is additionally provided between an ink reservoir tank400provided externally and a circulation reservoir220, and ink of the buffer reservoir500is injected into the circulation reservoir220through a second injection pipe510. Further, two transport pipes420and430are connected to the buffer reservoir500and the ink reservoir tank400at positions therebetween and are configured to circulate ink in the process of externally supplying ink through the pipes.

Other configurations and a configuration in which ink is circulated externally between the buffer reservoir and the ink reservoir tank are the same as those of the embodiment ofFIG. 6described above, and thus a further description thereof will be omitted.

When the ink circulation supply system of the inkjet printer according to the present invention is employed, a product may be manufactured through an inkjet printing process using ink, which have recently been of interest, in which metal particles, a flat panel display material, or an OLED material is dispersed. Consequently, due to the characteristics of the inkjet printing process that can perform a precise process quickly, there is an excellent effect that efficiency of a process for manufacturing an electrode, a flat panel display, or an OLED is greatly improved.

While the exemplary embodiments of the present disclosure have been described above, the embodiments are only examples of the disclosure, and it will be understood by those skilled in the art that the disclosure can be modified in various forms without departing from the technical spirit of the disclosure. Thus, the scope of the disclosure should be determined on the basis of the descriptions in the appended claims, not any specific embodiment, and all equivalents thereof should belong to the scope of the disclosure.