JP2023000794A - Liquid discharge unit and liquid discharge device - Google Patents

Abstract

To provide a liquid discharge unit which can inhibit reduction of a concentration of a liquid, and to provide a device which discharges the liquid.SOLUTION: A liquid discharge unit includes: a circulation path 220 in which a liquid circulates; and a liquid discharge head 100 provided at the circulation path 220. The circulation path 200 includes a supply path 221 and a recovery path 222. The supply path 221 has: a first path 205 which allows the liquid to flow through a filter 208; a second path 222 which allows the liquid to flow without passing through the filter 208; and a switch valve 204 which switches between the first path 221 and the second path 222.SELECTED DRAWING: Figure 3

Description

The present invention relates to a liquid ejection unit and an apparatus for ejecting liquid.

2. Description of the Related Art As an apparatus using a liquid ejection head for ejecting liquid (hereinafter also simply referred to as "head"), there is a device that uses a flow-through type head to circulate liquid.

Conventionally, a head is provided with a supply path that supplies liquid through a filter that removes foreign matter, and a filter bypass path that bypasses the filter of the supply path and supplies liquid, so that air bubbles remaining in the filter can be discharged. The thing which did it is known (patent document 1).

JP-A-09-141890

By the way, in a device that circulates and discharges a liquid, if the liquid containing white pigments, metal particles, etc. is constantly circulated, there is a problem that the particles contained in the liquid are captured by the filter, resulting in a decrease in concentration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to suppress a decrease in liquid concentration.

In order to solve the above problems, the liquid ejection unit according to the present invention includes:
a circulation path through which the liquid circulates;
a liquid ejection head provided in the circulation path;
The circulation route is
a first path through the liquid through a filter;
a second path through the liquid without passing through the filter;
and a switching valve for switching between the first path and the second path.

ADVANTAGE OF THE INVENTION According to this invention, the density|concentration fall of a liquid can be suppressed.

1 is a schematic illustration of an example of a device for ejecting liquid according to the present invention; FIG. It is a plane explanatory view of an example of the head unit of the apparatus. FIG. 4 is a schematic explanatory diagram of a portion related to liquid circulation in the liquid ejection unit according to the first embodiment of the present invention; FIG. 9 is a schematic explanatory diagram of a portion related to liquid circulation in a liquid ejection unit according to a second embodiment of the present invention; FIG. 11 is a flow diagram of a sequence in which a printing apparatus transitions from a non-printing state to a printing state for explaining a third embodiment of the present invention; FIG. 11 is a schematic explanatory diagram of a liquid ejection unit according to a fourth embodiment of the present invention; FIG. 11 is an explanatory diagram showing an example of measurement results of the number of coarse particles with respect to the particle diameter in liquid, for explaining the fifth embodiment of the present invention; It is similarly an explanatory view of an example of experimental results of the relationship between the presence or absence of a filter, the number of coarse particles, and the decrease in concentration. FIG. 11 is a schematic explanatory diagram of a liquid ejection unit according to a sixth embodiment of the present invention; FIG. 11 is a schematic explanatory diagram of a liquid ejection unit according to a seventh embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, an example of a printing apparatus as an apparatus for ejecting liquid according to the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic explanatory view of one example of the same printing apparatus, and FIG. 2 is a plan view of the portion of the printing means of the same apparatus.

The printing apparatus 1 is an apparatus for ejecting liquid, and includes a carrying-in means 10, a guiding/conveying means 30, a printing means 50, a drying means 70, a carrying-out means 90, and the like.

The carrying-in unit 10 carries in a sheet material P such as continuous paper. The guide conveying means 30 guides and conveys the sheet material P carried in from the carry-in means 10 to the printing means 50 . The printing unit 50 ejects liquid onto the sheet material P to form an image or the like. The drying means 70 dries the sheet material P to which the liquid is applied by heating. The carrying-out means 90 carries out the sheet material P. As shown in FIG.

The sheet material P is sent out from the main winding roller 11 of the carry-in means 10 , guided and carried by rollers of the carry-in means 10 , the guide/conveyance means 30 , the drying means 70 , and the carry-out means 90 . is taken up by

The sheet material P is conveyed facing the liquid ejection unit 51 in the printing means 50 , and an image is formed by the liquid ejected from the liquid ejection unit 51 .

In the liquid ejection unit 51, for example, full-line head arrays 501 (501A to 501F) for six colors are arranged from the upstream side in the transport direction. The head array 501 is liquid ejection means. The head array 501A ejects black K, the head array 501B ejects cyan C, the head array 501C ejects magenta M, and the head array 501D ejects yellow Y onto the conveyed sheet material P. The head array 501E ejects white W liquid. The head array 501F ejects gold or silver liquid. Note that the types and number of colors are not limited to this.

A head array 501 has a plurality of heads 100 arranged in a staggered manner on a base member 502 . A head 100 has a nozzle surface 101 on which a plurality of nozzles 102 for ejecting liquid are arranged.

Next, a liquid ejection unit according to the first embodiment of the invention will be described with reference to FIG. FIG. 3 is a schematic explanatory diagram of a portion related to liquid circulation in the same liquid ejection unit.

A liquid ejection unit 200 including a liquid circulation device includes a circulation path 220 through which liquid circulates, and a liquid ejection head 100 provided in the circulation path 220 .

The circulation path 220 includes a supply path 221 that supplies the liquid (ink) ejected from the head 100 from the sub-tank 201 that temporarily stores the liquid to the head 100, and a recovery path 222 that recovers the liquid from the head 100 to the sub-tank 201. have. Liquid is supplied to the sub-tank 201 from a main tank, which is a liquid storage means.

The supply path 221 includes a first path 205 that conducts liquid through filter 208 and a second path 206 that conducts liquid bypassing filter 208 . Filter 208 is, for example, a porous membrane.

A switching valve 204 is arranged to selectively switch between the first path 205 and the second path 206 . The switching valve 204 is, for example, a three-way valve.

The supply path 221 includes, from the sub-tank 201 side, a liquid feed pump 217, a degassing device 202, a heater 203, a switching valve 204, a first path 205 including a filter 208, a second path 206 bypassing the filter 208, a pressure manifold 210 are arranged in the order of A pressurized manifold 210 distributes liquid to multiple heads 100 .

Accordingly, the first path 205 including the filter 208 and the second path 206 bypassing the filter 208 are arranged on the upstream side of the liquid ejection head 100 , that is, on the side that supplies the liquid to the head 100 .

A decompression manifold 211 and a recovery pump 218 communicating with a plurality of heads 100 are arranged in the recovery path 222 .

An air pump 209A is connected to the pressure manifold 210 and an air pump 209B is connected to the pressure reduction manifold 211 . By driving the air pumps 209 (209A, 209B), the pressure in the pressure manifold 210 and the pressure reduction manifold 211 can be adjusted.

A pump control device 816 adjusts the pressure of the pressure manifold 210 and the pressure reduction manifold 211 using the air pump 209 . The pump controller 816 drives and controls the air pump 209 to increase the pressure when the pressure of the pressurization manifold 210 and decompression manifold 211 changes from a predetermined pressure by a threshold value or more. For this reason, the pressurization manifold 210 and the decompression manifold 211 are also equipped with an air release valve and a pressure sensor.

In the liquid discharge unit 200 configured as described above, the liquid transfer pump 217 and the recovery pump 218 are driven to transfer the liquid in the sub-tank 201 to the pressure manifold 210 through the supply path 221 and to the plurality of heads 100. Distribute and supply. Then, the liquid is recovered from the plurality of heads 100 to the decompression manifold 211 and returned to the sub-tank 201 through the recovery path 222 .

During printing, the liquid circulates in the circulation path 220 at a flow rate greater than the amount of liquid ejected from the head 100, and when the amount of liquid in the sub-tank 201 decreases, the sub-tank 201 is replenished with liquid from the main tank. supplied.

Next, the switching operation between the first route and the second route in this embodiment will be described.

In the present embodiment, the state of the printing apparatus 1 is defined as a "non-printing state" (also referred to as "not printing"), a "printing standby state" (also referred to as "printing preparation"), a "printing state" (" (also referred to as "printing" or "printing").

A "non-printing state" is a state in which there is no print instruction for a certain period of time, or a state in which there is no power supply to devices other than the liquid path. The "printing standby state" is defined as a state within a certain period of time immediately after power supply to the device including the liquid path is started. The "printing state" is a state in which there is a print instruction or a state in which printing is being continued. This printing state is a state in which an instruction to eject liquid from the head 100 is issued or the ejection operation is continuously performed.

First, in the print standby state and the print state, the switching valve 204 is switched to the first path 205 side. As a result, the liquid in the sub-tank 201 is supplied to the head 100 via the degassing device 202 , the heater 203 , the filter 208 and the pressure manifold 210 through the supply path 221 . The liquid recovered from the head 100 is returned to the sub-tank 201 from the decompression manifold 211 through the recovery path 222 .

As a result, foreign substances are removed by the filter 208 while the liquid is circulated through the circulation path 220 , thereby preventing foreign substances from entering the head 100 .

On the other hand, in the non-printing state, the switching valve 204 is switched to the second path 206 side. As a result, the liquid in the sub-tank 201 is supplied to the head 100 via the degassing device 202 , the heater 203 and the pressure manifold 210 through the supply path 221 . The liquid recovered from the head 100 is returned to the sub-tank 201 from the decompression manifold 211 through the recovery path 222 .

As a result, in the non-printing state, the liquid circulates without passing through the filter 208, thereby preventing the pigment contained in the liquid from adhering to the filter 208 and reducing the density.

In addition, even when the liquid supply is started, it is expected that the amount of foreign matter mixed in will increase, so the liquid is passed through the first path 205 for about one hour after the start of circulation. This can prevent foreign matter in the liquid from entering the head.

Next, a liquid ejection unit according to a second embodiment of the invention will be described with reference to FIG. FIG. 4 is a schematic explanatory diagram of a portion related to liquid circulation in the same liquid ejection unit.

In this embodiment, supply path 221 includes first path 205 through filter 208A, third path 207 through filter 208B, and liquid through filter 208A and filter 208B. and a second path 206 .

Here, the filter 208B of the third path 207 has a larger opening diameter than the filter 208A of the first path 205 is used. For example, the representative aperture diameter of the filter 208A of the first path 205 is 5 μm, and the representative aperture diameter of the filter 208B of the third path 207 is 10 μm.

A switching valve 204 for selectively switching among the first path 205, the second path 206 and the third path 207 is arranged. The switching valve 204 is, for example, a four-way valve in this embodiment.

Next, the switching operation of the first route, the second route and the third route in this embodiment will be described.

In the non-printing state, the switching valve 204 is switched to the second path 206 side to circulate the liquid bypassing the filters 208 (208A, 208B), as in the first embodiment. This suppresses a decrease in the concentration of the pigment component in the liquid.

In the printing state, the switching valve 204 is switched to the first path 205 side to circulate the liquid through the filter 208A, as in the first embodiment. This removes foreign matter in the liquid.

In the print preparation state or during cleaning, the switching valve 204 is switched to the third path 207 side to circulate the liquid through the filter 208B. Accordingly, since the filter 208B has a coarser mesh than the filter 208A used in the printing state, it is possible to prevent foreign substances from entering the head 100 and reduce the density of the liquid.

As for the flow rate, the pressures of the pressure manifold 210 and the decompression manifold 211 are set so that the flow rate is small in the non-printing state. In the printing state, the pressures of the pressure manifold 210 and the pressure reduction manifold 211 are set to increase the flow rate. In the print standby state or during cleaning, the pressures of the pressure manifold 210 and the decompression manifold 211 are set to medium flow rates (higher than the flow rate in the non-printing state and lower than the flow rate in the printing state).

These flow rate switching (changes) are performed before switching among the first path 205 , the second path 206 and the third path 207 .

For example, when switching from the printing state to the non-printing state, the first path 205 is switched to the second path 206 . At this time, the liquid passing through the filter 208A does not pass through the filter 208A, so that the liquid flows easily. Therefore, if the flow rate is changed to the second path 206 while the flow rate is large in the printing state, the liquid may leak from the head 100 . Therefore, when switching from the first path 205 to the second path 206 , the flow rate is changed (reduced) to prevent the liquid from leaking out of the head 100 .

On the other hand, when shifting from the non-printing state to the printing state, the second route 206 is switched to the first route 205 . At this time, the liquid that has not passed through the filter 208A passes through the filter 208A, and the fluid resistance increases, making it difficult to flow. Therefore, if the flow rate is changed to the first path 205 while maintaining the low flow rate in the non-printing state, there is a risk that the liquid supply to the head 100 will be insufficient. Therefore, when switching from the second path 206 to the first path 205 , the flow rate is greatly changed (increased) to prevent insufficient liquid supply to the head 100 .

In this way, by changing the flow rate before switching among the first path 205, the second path 206, and the third path 207, the liquid leaks from the head 100 or is supplied to the head 100 during printing. Shortages can be prevented.

Next, a third embodiment of the invention will be described with reference to FIG. FIG. 5 is a flow diagram of a sequence in which the printing apparatus transitions from a non-printing state to a printing state, for explaining the embodiment.

The printing apparatus 1 is initially in a non-printing state (during non-printing), and shifts from the ON/OFF state of the monitor power source and the ON/OFF state of the main body power source to the print preparation mode. If a print image is selected in the print preparation mode, the mode shifts to the print mode, and when the job is completed, the mode returns to the standby mode.

By adopting such a sequence, it is possible to switch between the first route and the second route of the supply route at each switching timing, and it is possible to suppress the loss of the liquid due to the decrease in the concentration of the liquid.

Referring to FIG. 5, in the non-printing state, the monitor power source is turned off, and only the liquid circulation device (supply device) of the liquid ejection unit 200 is operated to circulate the liquid (step S1, hereinafter simply referred to as "S1"). be written as such.)

After that, it is determined whether or not the monitor power supply has been turned on (S2). At this time, if the supply of power to the monitor power supply has not started, the process returns to step S1.

Then, when the monitor power source starts to be energized, the elapsed time from the energization is measured, and it is determined whether or not the elapsed time is within one hour (S3). At this time, if the elapsed time from the start of energization is one hour or more, the non-printing mode is set and the process returns to step S1.

Here, if the elapsed time from the start of energization is within one hour, the print preparation mode is entered (S4).

Then, in the print preparation mode, it is determined whether the print image is selected or the cleaning operation is selected (S5).

Here, when the cleaning operation is selected, the print preparation mode is continued, and the process returns to step S4.

When the print image is selected, the print mode is entered (S6).

After that, when the job is completed, the printer waits in the print preparation mode, shifts to the non-printing mode after waiting, and returns to step S1.

In each of these non-printing mode, print preparation mode, and print mode, the switching operation of the switching valve as described in the first embodiment or the second embodiment is performed to Route switching is performed between the route 206 and the third route 207 (only in the case of the second embodiment).

As a result, it is possible to prevent foreign matter from entering the head and suppress a decrease in liquid concentration.

Next, a liquid ejection unit according to a fourth embodiment of the invention will be described with reference to FIG. FIG. 6 is a schematic explanatory diagram of the same liquid ejection unit.

In this embodiment, a signal generator 813, a control device 814, and a control PC 815 as an information processing device are connected to the liquid ejection unit 200 according to the first embodiment.

Thereby, the switching operation of the switching valve 204 can be operated by a user or an external input signal from the control PC 815 .

Patterns for such applications include, in particular, printing operations and liquid replenishing operations. For example, the printing operation is controlled by the control PC 815 according to the sequence described in the third embodiment. At this time, a command is transmitted from the control device 814 to the signal generator 813 in accordance with the user's operation, and the signal generator 813 gives a switching instruction to the switching valve 204 . As a result, switching to the first route 205 or the second route 206 is made.

By switching the switching valve 204 in response to other operations without a direct instruction from the user in this way, it is possible to reduce the time required for the user's operation and suppress the decrease in the concentration of the pigment in the liquid. .

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG. FIG. 7 is an explanatory diagram showing an example of measurement results of the number of coarse particles with respect to the particle diameter in the liquid, and FIG. 8 is an explanatory diagram of an example of experimental results of the relationship between the presence or absence of a filter, the number of coarse particles, and the decrease in concentration.

As a surrogate characteristic of the concentration in the liquid (ink), the number of coarse particles with respect to the particle size in the ink was measured. The number of coarse particles was measured using, for example, a particle counter for liquids. The horizontal axis of FIG. 7 is the particle size, and the vertical axis is the number of coarse particles.

From this measurement result, it can be seen that the particles in the ink are occupied by particles of 1 μm or less.

It has been found that even with ink having such a particle size distribution, the density decreases when thousands of liters of ink are circulated through the filter 208 (208A) with a representative opening diameter of 5 μm.

Here, as shown in FIG. 8, three ink samples with 125 billion, 50 billion, and 25 billion coarse particles per 0.1 ul of ink were circulated through a filter. The presence or absence (degree) of reduction in concentration when circulating without mediation was measured.

As an indicator of the decrease in density, the coating was applied solidly on the OPP film, the hiding rate was measured with a density measuring instrument, and the results were divided into classes of .circleincircle., .DELTA., and x. "⊚" indicates less than 2% decrease in concealment rate, "Δ" indicates 2 to 10% decrease in concealment rate, and "×" indicates more than 10% decrease in concealment rate.

According to the results of FIG. 8, when circulation is performed through a filter, the concentration decrease is "x" when the number of coarse particles is 125 billion / 0.1 ul, and the number of coarse particles is 50 billion / 0.1 ul. "Δ" when the number of coarse particles was 25 billion/0.1 ul (Experiment Nos. 1 to 3).

On the other hand, when circulation was performed without passing through a filter, the decrease in concentration was "A" regardless of the number of coarse particles (Experiment Nos. 4 to 6).

Therefore, for the head 100 that uses a liquid containing 50 billion or more particles with an average particle size of 0.5 μm or more in 0.1 μl, the second path 206 that bypasses the filter 208 in the non-printing state A decrease in concentration can be suppressed by circulating the liquid through.

On the other hand, the second path 206 and the switching valve 204 are provided for the circulation path 220 of the head 100 that uses a liquid that does not contain 50 billion or more particles with an average particle size of 0.5 μm or more per 0.1 μl. Instead, it circulates through the filter 208 even in the non-printing state. Even in this case, the density does not decrease, so the configuration is simplified.

Also, regarding the circulation path 220 of the head 100 using white, gold, and silver liquids in which the number of particles having an average particle diameter of 0.5 μm or more is relatively larger than that of liquids of other colors, for example, can also provide a second path 206 and a switching valve 204 . In this case, the second path 206 and the switching valve 204 are not provided in the circulation path 220 of the head 100 that uses YMCK liquid. This makes it possible to simplify the configuration while suppressing the decrease in density.

Next, a liquid ejection unit according to a sixth embodiment of the invention will be described with reference to FIG. FIG. 9 is a schematic explanatory diagram of the same liquid ejection unit.

In this embodiment, the signal generator 813 outputs a pressure control signal to the pump control device 816 when switching the switching valve 204 in the fourth embodiment.

When switching the switching valve 204 to the second path 206 side from the state in which the switching valve 204 is set to the first path 205 side to circulate, the signal generator 813 causes the pump control device 816 to: Outputs a pressure control signal that decreases the pressure and reduces the flow rate.

Further, when switching the switching valve 204 to the first path 205 side from a state in which the switching valve 204 is on the second path 206 side for circulation, the signal generator 813 causes the pump control device 816 to to output a pressure control signal that increases the pressure and increases the flow rate.

That is, pressure loss occurs due to the filter 208 when circulating via the first path 205, but pressure loss due to the filter 208 does not occur when circulating via the second path 206. FIG.

Therefore, the pressure of the air pump 209 is adjusted by the pressure fluctuation caused by removing the pressure loss due to the filter 208 or the pressure fluctuation caused by increasing the pressure loss due to the filter 208, and the pressure manifold 210 and the pressure reduction manifold 211 The pressure of is adjusted by an atmospheric release valve and a pressure sensor.

As a result, when the path is switched between the first path 205 and the second path 206, it is possible to prevent a phenomenon in which liquid leaks from the head 100 or air is drawn into the head 100. FIG.

As a specific switching procedure, during printing, when shifting to the printing standby state, the output of the air pump 209 is changed by the pump control device 816 to set the flow rate to the printing pressure (high flow rate). is switched from the second path 206 side to the first path 205 side.

When shifting to the non-printing state, the output of the air pump 209 is changed by the pump control device 816 to set the flow rate to the non-printing pressure (low flow rate), and then the switching valve 204 is moved from the first path 205 side to the first 2 route 206 side.

Next, a liquid ejection unit according to a seventh embodiment of the invention will be described with reference to FIG. FIG. 10 is a schematic explanatory diagram of the same liquid ejection unit.

This embodiment combines the sixth embodiment with the second embodiment.

In this embodiment, the liquid is circulated through the second path 206 in the non-printing state, through the third path 207 in the printing standby state, and through the first path 205 in the printing state.

At this time, by transmitting the operation of the air pump 209 from the signal generator 813 to the pump control device 816 according to the pressure loss in each flow path, the optimal negative pressure state can be maintained in the head 100 . This can prevent liquid from leaking from the head 100 and air from being drawn into the head 100 .

As a specific switching procedure, when shifting to printing, the output of the air pump 209 is changed by the pump control device 816 to set the flow rate to the printing pressure (high flow rate), and then the switching valve 204 is switched to the first path 205. switch to the side.

When shifting to the print standby state, the pump control device 816 changes the output of the air pump 209 to set the flow rate to the print standby pressure (medium flow rate), and then switches the switching valve 204 to the third path 207 side. .

Further, when shifting to the non-printing state, the pump control device 816 changes the output of the air pump 209 to set the flow rate to the non-printing pressure (low flow rate), and then switches the switching valve 204 to the second path 206 side. .

In the present application, the “liquid” to be ejected is not particularly limited as long as it has a viscosity and surface tension that can be ejected from the head. It is preferable that More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, functional-imparting materials such as polymerizable compounds, resins, and surfactants, biocompatible materials such as DNA, amino acids, proteins, and calcium. , edible materials such as natural pigments, solutions, suspensions, emulsions, etc. These are, for example, inkjet inks, surface treatment liquids, components of electronic elements and light emitting elements, and formation of electronic circuit resist patterns It can be used for applications such as liquids for liquids and material liquids for three-dimensional modeling.

The "liquid ejection head" includes a piezoelectric actuator (laminated piezoelectric element and thin film piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, a vibration plate, and a counter electrode as energy sources for ejecting liquid. It includes those using an electrostatic actuator made of.

The "apparatus for ejecting liquid" includes an apparatus for ejecting liquid by driving a liquid ejection head. Devices that eject liquid include not only devices that can eject liquid onto an object to which liquid can adhere, but also devices that eject liquid into air or liquid.

The "liquid ejecting device" can include means for feeding, transporting, and ejecting an object to which liquid can adhere, as well as a pre-processing device, a post-processing device, and the like.

For example, as a "device that ejects liquid", an image forming device that ejects ink to form an image on paper, and powder is formed in layers to form a three-dimensional object (three-dimensional object). There is a three-dimensional modeling apparatus (three-dimensional modeling apparatus) that ejects a modeling liquid onto a formed powder layer.

Further, the "apparatus for ejecting liquid" is not limited to one that visualizes significant images such as characters and figures with the ejected liquid. For example, it includes those that form patterns that have no meaning per se, and those that form three-dimensional images.

The above-mentioned "substance to which a liquid can adhere" means a substance to which a liquid can adhere at least temporarily, such as a substance to which a liquid adheres and adheres, a substance which adheres and permeates, and the like. Specific examples include media such as recording media such as paper, recording paper, recording paper, film, and cloth, electronic components such as electronic substrates and piezoelectric elements, powder layers (powder layers), organ models, and test cells. Yes, and unless otherwise specified, includes anything that has liquid on it.

The material of the above-mentioned "thing to which a liquid can adhere" may be paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc., as long as the liquid can adhere even temporarily.

Further, the ``device for ejecting liquid'' includes a device in which a liquid ejection head and an object to which liquid can be adhered move relatively, but is not limited to this. Specific examples include a serial type apparatus in which the liquid ejection head is moved and a line type apparatus in which the liquid ejection head is not moved.

In addition, the "apparatus for ejecting liquid" also includes a treatment liquid coating device that ejects a treatment liquid onto the paper for the purpose of modifying the surface of the paper. There is an injection granulator that granulates fine particles of the raw material by injecting a composition liquid in which raw materials are dispersed in a solution through a nozzle.

The terms used in the present application, such as image formation, recording, printing, copying, printing, and molding, are synonymous.

1 Printing device (a device that ejects liquid)
50 printing means 100 liquid ejection head (head)
200 liquid discharge unit 201 subtank 202 degassing device 204 switching valve 205 first path 206 second path 207 third path 208 filter 210 pressure manifold 211 decompression manifold 220 circulation path 221 supply path 222 recovery path 813 signal generator 814 control device 816 pump controller

Claims (7)

a circulation path through which the liquid circulates;
a liquid ejection head provided in the circulation path;
The circulation route is
a first path through the liquid through a filter;
a second path through the liquid without passing through the filter;
and a switching valve for switching between the first path and the second path. 2. The liquid ejection unit according to claim 1, wherein the first path and the second path are arranged upstream of the liquid ejection head. 3. The liquid ejection unit according to claim 1, wherein the liquid ejection head switches to the second path when the liquid ejection head does not continuously eject the liquid. 4. The liquid ejection unit according to claim 1, wherein the flow rate is changed before switching between the first path and the second path. 5. The liquid ejection unit according to claim 1, wherein 0.1 .mu.l of said liquid contains 50 billion or more particles having an average particle diameter of 0.5 .mu.m or more. 6. The liquid ejection unit according to claim 1, wherein the liquid is at least one of white, gold, and silver. A device for ejecting liquid, comprising the liquid ejection unit according to any one of claims 1 to 6.

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