JP6702748B2 - Recording device and liquid ejection head - Google Patents

Description

The present invention relates to a recording device, a liquid ejection head, a recording method, and a program.

In an inkjet liquid ejection head, volatile components in the ink evaporate from the ejection port, causing color unevenness in the image due to a change in color material concentration near the ejection port, and a change in ejection speed that results in an increase in viscosity near the ejection port. There is a problem such as the deterioration of the impact accuracy. In particular, when the rest time is long, the viscosity increases remarkably, and the solid component of the ink adheres to the vicinity of the ejection port. Since the solid component remarkably increases the fluid resistance of the ink, defective ejection of the ink occurs.

As one of the measures against such an ink thickening phenomenon near the ejection port, a method of circulating the ink to be supplied to the liquid ejection head through a circulation path is known. Patent Document 1 discloses an inkjet liquid ejection in which a head substrate having a plurality of ejection energy generating elements and an ejection port member having a plurality of ink ejection ports are arranged with a predetermined gap, and ink is circulated in the gap. The head is listed.

JP 2002-254643 A

However, when the conventional inkjet liquid ejection head is used, the evaporation rate of the volatile components in the ink from the ejection port greatly changes due to changes in the temperature, environmental temperature, and humidity of the liquid ejection head itself, and There was a problem that the state would change. The reason why such a phenomenon occurs can be explained by the flow due to evaporation from the discharge port, the flow forcedly flowing into the discharge port, and the diffusion degree of the coloring material in the solvent due to these flows.

FIG. 14A shows the supply flow path 16 and the ejection port portion 13 when the ink flow is in a steady state when the temperature of the liquid ejection head and the environmental temperature are 25° C. and the humidity is 50%, respectively. It is the figure which represented the flow in the area|region containing (it is also called a discharge part) by the vector diagram. FIG. 14B is a vector diagram showing the flow of the discharge unit when the ink flow is in a steady state when the temperature of the liquid discharge head and the ambient temperature are 50° C. and the humidity is 10%. It is a figure. In these figures, the length of each vector does not represent the magnitude of the velocity of the ink flow, but is constant for all velocity values. As shown in FIG. 14A, when the temperature of the liquid ejection head and the ambient temperature are 25° C. and the humidity is 50% (when the evaporation rate is relatively slow), the ink of the ejection port 13 and the supply are supplied. A flow that replaces the ink flowing from the flow path 16 is generated. On the other hand, as shown in FIG. 14B, when the temperature of the liquid ejection head and the environmental temperature are respectively 50° C. and the humidity is 10% (when the evaporation rate is relatively high), The flow for replacing the ink flowing in from the supply channel 16 is weaker than that in the case of FIG. As a result, compared with the case of FIG. 14A, the concentration of the non-volatile component increases near the ejection port 11, and the ink viscosity is likely to locally increase.

FIG. 15A shows how ink droplets land when ink is ejected from the liquid ejection head 43 in the state shown in FIG. 14A, and FIG. 15B shows in FIG. A state in which ink droplets land when ink is ejected from the liquid ejection head 43 in the state shown is shown. In the case of FIG. 15B, as compared with the case of FIG. 15A, the work amount of the bubbles to the droplets is lost due to the increase in the ink viscosity, the ejection speed becomes slower, and as a result, the droplets are made to come to a predetermined size. You will not be able to land at the position. In the worst case, the viscosity of the ink may be too high to eject the ink from the ejection port. In addition, if the density of the coloring material in the flying ink is high due to the change of the flow field, the dot density after landing on the recording medium may become high. When the flow rate at the discharge port changes due to the change in the evaporation rate depending on the environment in this way, deterioration of image quality is induced.

The present invention has been made under such a technical background. An object of the present invention is to cause unevenness in image quality and landing accuracy caused by evaporation of volatile components contained in a liquid such as ink from ejection ports even when the environment changes during printing or non-printing. It is to suppress the occurrence of discharge deterioration and discharge failure.

The present invention relates to a discharge port for discharging a liquid, an element for generating energy used for discharging the liquid, a pressure chamber having the element therein, a pressure chamber communicating with the pressure chamber, and a liquid for the pressure chamber. A liquid discharge head including a first flow path to be supplied and a second flow path that is in communication with the pressure chamber and recovers liquid from the pressure chamber; the first flow path, the pressure chamber, and the second flow path. Generating means for generating a flow of the liquid flowing in the order of, an acquisition means for acquiring information on the evaporation of the liquid from the discharge port, based on the acquired information, a control means for controlling the flow rate of the flow, have a, as the acquisition unit, and the head temperature detecting means for detecting the temperature of the liquid ejection head, and the ambient temperature detecting means for detecting the temperature of the environment in which it is installed, humidity detecting means for detecting the humidity of the environment And at least one of the temperature of the liquid ejection head, the temperature of the environment, and the humidity is associated with the flow rate corresponding to the amount of evaporation from the ejection port. The recording apparatus further comprises a table .

According to the present invention, it is possible to suppress color unevenness of an image, deterioration of landing accuracy, and ejection failure due to a change in environment, and to suppress deterioration of image quality.

Schematic diagram of an ejection unit in the liquid ejection head according to the first embodiment. Schematic diagram showing the flow field of the ink flow in the ejection unit according to the first embodiment. The figure showing the time change of the evaporation rate from the discharge port which concerns on 1st Embodiment. The figure showing the time change of the non-volatile solvent concentration in the ejection opening part concerning a 1st embodiment. The figure showing the time change of the evaporation rate from the discharge port which concerns on 1st Embodiment. Schematic diagram showing the flow field of the ink flow in the ejection port portion according to the first embodiment. The figure showing the concentration distribution of the non-volatile solvent in the discharge port part which concerns on 1st Embodiment. The figure showing the time change of the non-volatile solvent concentration in the ejection opening part concerning a 1st embodiment. The schematic diagram showing the flow field of the ink flow in the ejection port when the amount of ink supplied per unit time according to the first embodiment is increased. FIG. 3 is a diagram showing a temporal change in the concentration of the non-volatile solvent in the ejection port portion when the amount of ink supplied per unit time according to the first embodiment is increased. The figure showing the concentration distribution of the non-volatile solvent in the ejection port when the amount of ink supplied per unit time according to the first embodiment is increased. Schematic diagram showing the flow field of the ink flow in the ejection port portion according to the second embodiment. The figure showing the time change of the non-volatile solvent concentration in an ejection opening part when the amount of ink supplied per unit time according to the second embodiment is increased. Schematic diagram showing the flow field of the ink flow in the ejection unit Schematic diagram showing landing of ink droplets when ink is ejected from a liquid ejection head 1 is an external perspective view of a recording apparatus according to the present invention. Block diagram of an ink supply system included in the recording apparatus according to the present invention Block diagram of a recording apparatus according to the present invention

Hereinafter, a recording apparatus and a recording method according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, the inkjet recording device and the inkjet liquid ejection head will be described using specific configurations, but the present invention is not limited to these. INDUSTRIAL APPLICABILITY The recording apparatus and recording method of the present invention can be applied to an apparatus such as a printer, a copying machine, a facsimile having a communication system, a word processor having a printer unit, and an industrial recording apparatus combined with various processing apparatuses. For example, it can be used for applications such as biochip production, electronic circuit printing, and semiconductor substrate production. In addition, the embodiments described below are appropriate specific examples of the present invention, and thus various technically preferable limitations are attached. However, the embodiments are not limited to the contents described in the present specification and other specific methods as long as they are in accordance with the idea of the present invention.

16 to 18 are diagrams for explaining an example of the configuration of an inkjet recording apparatus (liquid ejection apparatus) in which the liquid ejection head of the present invention can be mounted prior to the description of the embodiments of the present invention. 16 is an external perspective view showing a mechanical configuration example of an inkjet recording apparatus in which the liquid ejection head of the present invention can be mounted, and FIG. 17 is an example of a liquid (ink) supply system included in the inkjet recording apparatus. It is a block diagram showing.

As shown in FIG. 16, the inkjet recording apparatus includes a chassis 40, a medium feeding unit 41, a medium transporting unit 42, and a liquid ejection head 43. The chassis 40 is composed of a plurality of plate-shaped metal members having a predetermined rigidity, and forms the skeleton of this inkjet recording device. A medium feeding unit 41, a medium transporting unit 42, and a liquid ejection head 43 are attached to the chassis 40. The medium feeding unit 41 automatically feeds a sheet-shaped recording medium (not shown) into the inkjet recording apparatus. The medium carrying section 42 guides the recording mediums fed one by one from the medium feeding section 41 to a predetermined recording position along the direction of arrow A in the figure. The liquid ejection head 43 performs a recording operation of ejecting ink on the recording medium conveyed to the recording position based on image data. The orifice plate (ejection port member) of the liquid ejection head 43 is arranged below the liquid ejection head 43, and a plurality of ejection ports for ejecting ink are formed on the orifice plate. The liquid ejection head 43 ejects a predetermined amount of ink from a predetermined ejection port based on image data during a recording operation.

As shown in FIG. 17, the inkjet recording apparatus includes a liquid ejection head 43, a supply ink tank 44 for supplying ink to the liquid ejection head 43, and a recovery ink for recovering ink from the liquid ejection head 43. It has an ink supply system including a tank 45. The supply ink tank (supply liquid storage container) 44 stores a liquid such as ink to be supplied to the supply channel 16 described later. The recovery ink tank (recovery liquid storage container) 45 stores the ink recovered from the recovery channel 17 described later. As the ink to be flowed, a non-volatile solvent in the ink, a volatile solvent, and a coloring material whose concentrations are adjusted according to the use are used, and the viscosity is adjusted to 0.002 to 0.100 Pa·s. ing. A liquid supply system may be adopted which has a structure for returning the ink recovered in the recovery ink tank 45 to the supply ink tank and circulates the ink between the pressure chamber 15 and the outside of the liquid ejection head 43. .. In this case, the ink circulates in the order of the supply ink tank 44, the liquid ejection head 43, the recovery ink tank 45, the supply ink tank 44,....

FIG. 18 is a block diagram showing an example of the configuration of an inkjet recording apparatus according to the present invention, and is a diagram for explaining components related to control of the inkjet recording apparatus. The inkjet recording apparatus includes a control unit 47, a liquid ejection head control unit 46, a sensor control unit 48, a mechanical control unit 50, a liquid ejection head 43, a sensor unit 49, and a mechanical unit 51. The control unit 47 is composed of a CPU, a RAM, a ROM and the like, and controls the elements of the inkjet recording apparatus as a whole.

The liquid ejection head control unit 46 controls the liquid ejection head 43 so as to perform recording based on the image data according to a command from the control unit 47. Further, the liquid ejection head control unit 46 detects the temperature indicating the state of the liquid ejection head 43, and sends information on the detected temperature to the control unit 47. At this time, a diode sensor or the like provided in the liquid ejection head may be used as the head temperature detection means for detecting the temperature of the liquid ejection head. The temperature of the liquid ejection head is substantially the same as the temperature at the ejection port and the ejection port. The sensor unit 49 includes various sensors that detect the temperature and humidity in the environment where the inkjet recording apparatus is installed (hereinafter referred to as the installation environment), the carriage position, the flow rate of the ink flow, and the like. It functions as an information acquisition unit such as an ink supply amount detection unit. The sensor unit 49 sends the detected value to the sensor control unit 48. The sensor control unit 48 controls the sensor unit 49 according to a command from the control unit 47 and transfers the value sent from the sensor unit 49 to the control unit 47.

The mechanical unit 51 includes a pump for generating an ink flow, a negative pressure control unit for controlling the pressure (negative pressure) in the flow path, a valve for opening and closing the flow path, and the like. The mechanical control unit 50 controls driving of the mechanical unit 51 according to a command from the control unit 47.

In the inkjet recording apparatus, the evaporation rate (evaporation amount per unit time) varies greatly depending on the temperature and humidity in the installation environment. Therefore, in the present invention, the mechanical section 51 is adjusted on the assumption that the inkjet recording apparatus is installed in an environment where the evaporation rate from the ejection port is high (for example, a high temperature and low humidity environment).

For example, a table in which at least one of the temperature of the liquid ejection head, the temperature of the installation environment, and the humidity of the installation environment is associated with the necessary flow rate of the ink flow corresponding to the evaporation rate from the ejection port, based on a preliminary investigation or the like. You may ask for. An example of the table is given below.

Then, an embodiment is conceivable in which the adjusted setting value is stored in the ROM of the control unit 47 based on the obtained table (or, the table itself as described above is stored in the ROM of the control unit 47. It may be.). In such an embodiment, the CPU of the control unit 47 can set the flow rate of the ink flow by referring to the value stored in the ROM. Hereinafter, embodiments to which the present invention can be suitably applied will be described.

<First Embodiment> (Structure in which vortex flow is generated at the discharge port)
Hereinafter, an inkjet recording apparatus and an inkjet liquid ejection head according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 11. In the following description, it is assumed that the temperature of the liquid ejection head and the temperature of the installation environment are the same.

(About the basic structure of the discharge part)
FIG. 1A is a plan view of the ejection portion of the liquid ejection head according to this embodiment. FIG. 1B is a sectional view taken along the section line AA′ of FIG. FIG. 1C is a perspective view showing a section taken along a section line AA′ in FIG. As shown in FIG. 1B, an orifice plate 18 is arranged on the supporting substrate 12 on which a pressure generating element (hereinafter, heater) 14 is formed so as to form a gap of 5 to 20 μm. In the present embodiment, a heater that generates thermal energy will be described as a pressure generating element that generates energy used to eject liquid, but the present invention is not limited to this and various pressure generating elements such as piezoelectric elements can be used. Is. The heater 14 is an element that generates energy used for ejecting ink. As shown in FIGS. 1B and 1C, the orifice plate 18 is provided with a plurality of ejection openings 11 for ejecting ink, each of which faces the heater 14. The discharge port portion 13 is formed. The pressure chamber 15 is a region in the space between the orifice plate 18 and the support substrate 12 that communicates with the discharge port portion 13. In the ejection portion, a pressure chamber 15 having a heater 14 therein and a supply channel 16 that is a channel for allowing ink to flow into the pressure chamber 15 communicate with each other, and the pressure chamber 15 and the ink flow out from the pressure chamber 15. It has a configuration in which the recovery flow path 17, which is a flow path for the communication, communicates. By forcibly generating an ink flow in the ejection portion having such a configuration, the ink retained in the pressure chamber 15 and the ejection port portion 13 that communicates the ejection port 11 with the pressure chamber 15 is caused to flow. Is possible. The ink is filled so as to fill the space formed between the support substrate 12 and the orifice plate 18. In this embodiment, an ink having a non-volatile solvent concentration of 30% and a viscosity of 0.002 Pa·s was used.

(Regarding flow field of ink flow and solvent concentration in ejection part)
FIG. 2 shows the ink flow when the ink flow is in a steady state when the ink is forced to flow from the supply channel 16 under the conditions that the head temperature and the environmental temperature are 25° C. and the humidity is 50%. It is a schematic diagram showing the flow field of. For the sake of explanation, coordinate axes are set as shown in the figure. In addition, in this figure, the length of each vector does not represent the magnitude of the velocity of the ink flow, but is constant for all velocity values. In this embodiment, the thickness of the orifice plate 18 is 11 μm, and the thickness of the gap between the orifice plate 18 and the support substrate 12 is 14 μm. The amount of ink supplied from the supply channel 16 per unit time is 8.7×10̂−5 ml/min. At this time, when the length of the pressure chamber 15 in the x direction is 25 μm and the length in the z direction perpendicular thereto is 20 μm, the average flow velocity of the ink flow in the pressure chamber 15 is about 6.3 mm/s.

FIG. 3 is a graph showing the change over time in the evaporation rate from the discharge port 11 under the above conditions. The solid line in the figure shows the case where the ink flow is forcibly generated and the circulation flow is generated in the ejection port portion 13. On the other hand, the broken line shows the case where there is no compulsory ink flow and the circulation flow does not occur in the ejection port portion 13. Note that the ejection port 11 is covered with a cap member in a substantially sealed state, and the time when the ejection port 11 is opened to the atmosphere is t=0 by removing the cap member from the liquid ejection head. When there is no compulsory ink flow, the volatile components in the ink are evaporated from the ejection port 11 to accumulate the non-volatile components near the ejection port 11 and in the ejection port portion 13. Therefore, as indicated by the broken line in the figure, the evaporation rate decreases as the amount of the volatile solvent existing on the surface of the discharge port 11 decreases with the passage of time. On the other hand, when there is a forced ink flow (when an ink flow is generated in the pressure chamber 15), the volatile component in the ink is evaporated from the ejection port 11 but flows into the pressure chamber 15 from the supply flow path 16. A part of the incoming ink flow flows into the ejection port portion 13. As a result, a vortex flow is generated in the discharge port portion 13 (see FIG. 2). Due to this vortex flow, a phenomenon occurs in which the ink having a high concentration of non-volatile components due to evaporation from the ejection port 11 and the ink flowing in from the supply channel 16 are replaced. As a result, after a lapse of a certain time, the effect of evaporation of the volatile component and the effect of the ink inflow are balanced to reach an equilibrium state, and the ratio of exposure of the volatile component and the non-volatile component at the gas-liquid interface of the ejection port 11 is increased. It becomes almost constant. Therefore, as shown by the solid line in the figure, the evaporation rate is kept higher than in the case where there is no forced ink flow.

FIG. 4 shows a case in which the evaporation rate from the ejection port 11 is different depending on the presence or absence of the forced ink flow as described above with reference to FIG. 3 (when there is a forced ink flow and when there is no forced ink flow). 5 is a graph showing the change over time in the concentration of the non-volatile solvent in the ink at the ejection port portion 13). The solid line in the figure shows the case where the ink flow is forcibly generated and the circulation flow is generated at the ejection port portion 13. On the other hand, the broken line shows the case where there is no compulsory ink flow (only natural convection due to evaporation) and the circulation flow does not occur at the ejection port portion 13. Note that, similarly to the above, the time when the discharge port 11 is opened to the atmosphere is t=0. As indicated by the solid line in the figure, the non-volatile solvent concentration reaches an equilibrium state in about 0.4 seconds as in the case of the evaporation rate over time (see FIG. 3) by generating a forced ink flow. On the other hand, as indicated by the broken line in the figure, the non-volatile solvent concentration continues to increase when the forced ink flow is not generated.

(Regarding the flow field and solvent concentration at the discharge port, which varies depending on the installation environment)
As described above, it has been found that by generating the forced ink flow, the ink staying in the ejection port portion 13 and the ink flowing in from the supply flow path 16 are replaced. It was clarified by our experiment that the degree depends on the installation environment. FIG. 5 is a graph for explaining that the time change of the evaporation rate when the forced ink flow is generated differs depending on the installation environment. In the figure, the solid line indicates the evaporation rate (=evaporation amount/ejection area) from the ejection port 11 when the liquid ejection head temperature and the environmental temperature are 25° C. and the humidity is 50%. The broken line indicates the evaporation rate when the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%, and the alternate long and short dash line indicates the liquid discharge head temperature and the environmental temperature are 50° C., respectively. Shows the evaporation rate in the case of 10%. The instant when the discharge port 11 is open to the atmosphere is t=0. Here, looking at the evaporation rate at t=0 in each installation environment, it can be seen that when the temperature rises from 25° C. to 50° C. at a humidity of 50%, the evaporation rate becomes about four times. It can be seen that when the temperature is 50° C. and the humidity is reduced from 50% to 10%, the evaporation rate doubles. When the evaporation rate at t=0 is high (in this example, the temperature is 50° C. and the humidity is 10%), the concentration of the non-volatile components in the ink near the ejection port 11 increases, so that the time elapses with time in the initial stage. The evaporation rate continues to decrease. However, by forcibly generating the ink flow, fresh ink (ink stored in the supply ink tank 44 and having an initial ratio of volatile components and non-volatile components) flows into the ejection port portion 13. come. Therefore, as in the case where the evaporation rate at t=0 is slow, the evaporation rate reaches a substantially equilibrium state after a certain period of time.

FIG. 6 is a schematic diagram showing the flow field of the ink flow in the ejection port portion 13 having the shape according to the present embodiment when the forced ink flow is generated. 6 shows that when the ink amount supplied from the supply flow path 16 to the pressure chamber 15 per unit time is 8.7×10^−5 ml/min, the discharge port portion 13 is in a steady state. It represents the flow field of the ink flow. 6A shows the case where the liquid discharge head temperature and the environmental temperature are 25° C. and the humidity is 50%, and FIG. 6B shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%. 6C shows the case where the liquid ejection head temperature and the environmental temperature are 50° C. and the humidity is 10%. For the sake of explanation, coordinate axes are set as shown in the figure. Further, in these figures, the length of each vector does not represent the magnitude of the velocity of the ink flow, but is constant for all velocity values. FIG. 7 is a diagram showing the concentration distribution of the non-volatile solvent in the ink at the ejection opening portion 13 using the contour lines under the same conditions as in FIG. 7A shows the case where the liquid discharge head temperature and the environmental temperature are 25° C. and the humidity is 50%, and FIG. 7B shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%. FIG. 7C shows the case where the liquid ejection head temperature and the environmental temperature are 50° C. and the humidity is 10%.

6(a) and 6(b), when the humidity is 50% and the temperature is increased from 25° C. to 50° C. (in other words, when the evaporation rate is four times), the flow field Explain the changes. As shown in FIG. 6A, when the humidity is 50% and the temperature is 25° C., most of the ink flow in the vicinity of the ejection port 11 is in the direction opposite to the direction in which the ink flows in the flow path (−x direction). is occupying. On the other hand, as shown in FIG. 6B, when the humidity is 50% and the temperature is 50° C., the flow in which the components are combined in the direction of the ejection port 11 (+y direction) is increasing. Along with that, the center of the vortex flow generated in the ejection port portion 13 by the forced ink flow is shifted from the center of the ejection port portion 13 toward the supply flow path side (−x direction). This is because the amount of evaporation from the ejection port 11 is increased and the vortex generated by the forced ink flow is reduced. Therefore, the effect of circulating the ink accumulated in the ejection port portion 13 is reduced, and as a result, the concentration of the non-volatile solvent in the ink in the ejection port portion 13 is increased as shown in FIG. 7B. From this state, when the temperature is constant (50° C.) and the humidity is reduced from 50% to 10% (in other words, when the evaporation rate is further doubled), the change in the flow field is shown in FIG. This will be described with reference to (b) and FIG. 6(c). Referring to FIGS. 6B and 6C, since the evaporation rate is doubled, the ink flow in the vicinity of the ejection port 11 further has a component in the ejection port 11 direction (+y direction). , You can see that the vortex shrinks. As the vortex shrinks in this way, the effect of circulating the ink retained in the ejection port portion 13 becomes weaker, and as shown in FIG. 7C, the concentration of the non-volatile solvent in the ink at the ejection port portion 13 is reduced. It was deduced from our analysis results that the value of γ increased further.

FIG. 8 is a graph showing the time change of the concentration of the non-volatile solvent in the ejection port portion 13 when a forced ink flow is generated for each installation environment of the recording apparatus. In the figure, the solid line shows the case where the liquid discharge head temperature and the environmental temperature are 25° C. and the humidity is 50%, and the broken line shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%. , The liquid ejection head temperature and the environmental temperature are 50° C., and the humidity is 10%. The instant when the discharge port 11 is opened is t=0. As shown in FIG. 8, when the evaporation rate is high (in this example, the temperature is 50° C. and the humidity is 10%), the rising is steep, and the concentration value in a steady state after a certain period of time is also the evaporation rate. Is higher than slower. When the results shown in FIG. 8 are compared with the ink ejection speed when ink is actually ejected and the dot density after landing, a strong correlation is shown. However, it was supported by the theory that the change in evaporation rate is dominant.

(Regarding the effect on the flow field and solvent concentration at the ejection port that is caused by the increase in the amount of ink supplied per unit time)
In the present embodiment, the amount of ink to be supplied is increased in order to cope with the decrease in the effect of circulating in the ejection port due to the increase in evaporation rate due to the change in installation environment. This makes it possible to effectively circulate the ink that has accumulated in the ejection port portion 13. Hereinafter, the effect of increasing the amount of ink supplied per unit time will be described.

FIG. 9 is a diagram for explaining the effect of increasing the amount of ink supplied per unit time. Each of the diagrams in FIG. 9 shows the discharge port portion 13 in a steady state when the ink amount per unit time supplied from the supply passage 16 to the pressure chamber 15 is 1.3×10̂−3 ml/min. It represents the flow field of the ink flow. This flow rate of 1.3×10^-3 ml/min is about 15 times the flow rate of 8.7×10^-5 ml/min which is the flow rate described above with reference to FIG. 9A shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%, and FIG. 9B shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 10%. Represent For the sake of explanation, coordinate axes are set as shown in the figure. Further, in these figures, the length of each vector does not represent the magnitude of the velocity of the ink flow, but is constant for all velocity values.

Comparing FIG. 6C and FIG. 9B, the flow rate of the ink flow flowing into the ejection port portion 13 increases as the flow rate is increased, and the flow due to evaporation is relatively higher than the flow due to convection caused by the ink flow. As a result, the center of the vortex shifts to the vicinity of the center of the discharge port portion 13. Therefore, in the case shown in FIG. 9B (when the flow rate is high), the ink circulates in the ejection port portion 13 more efficiently than in the case shown in FIG. 6C (when the flow rate is low). FIG. 10 shows the time variation of the concentration of the non-volatile solvent in the discharge port portion 13 at this time, and FIG. 11 shows the solvent concentration distribution in the steady state. 8 and FIG. 10 or FIG. 8 shows that a strong swirl is generated in the ejection port 13 due to an increase in the amount of ink flowing into the ejection port 13 and thereby the replacement effect is increased. It can be understood both numerically and visually by comparing 7 and FIG. When the ink ejection speed from the ejection port 11 and the dot density after landing, which are directly related to the image quality, are measured, it can be seen that the replacement effect decreases due to the increase in the evaporation rate due to the change in the installation environment. It was suppressed. As described above, in order to increase the efficiency of the replacement effect, it is desirable to set the flow rate per unit time such that the center of the vortex generated by the forced ink flow is near the center of the ejection opening 13. In the case of the flow path dimensions in the present embodiment, in order for the center of the vortex to be near the center of the ejection port portion 13, it is necessary to supply ink from the supply flow path 16 at a flow rate of 600 times or more the evaporation amount. When the flow rate per unit time is further increased, the effect of suppressing the increase in the ink viscosity and the color material concentration increases, but the contribution rate of the increase in the flow rate gradually decreases. On the other hand, the pressure loss in the flow path increases as the flow rate increases, and it becomes difficult to control the pressure at the discharge port 11. Therefore, it is not preferable to increase the flow rate unnecessarily. Therefore, for example, it is desirable to set the required flow rate when the evaporation rate is the highest in the assumed installation environment. Further, it is also possible to preferably employ a configuration in which the supply flow rate is controlled by measuring the temperature and humidity according to each installation environment and referring to the evaporation rate at that time from a table that is provided in advance.

<Second Embodiment> (Structure in which no vortex is generated at the discharge port)
Hereinafter, an inkjet recording device and an inkjet liquid ejection head according to a second embodiment of the present invention will be described. In the following description, only the parts different from the first embodiment will be mainly described, and the description of the same parts as the first embodiment will be omitted.

(Regarding the flow field and solvent concentration at the discharge port, which varies depending on the installation environment)
FIG. 12 is a schematic diagram showing the flow field of the ink flow in the ejection port portion 13 having the shape according to the present embodiment when the ink flow is forcibly generated in the supply channel 16 and the pressure chamber 15. 12 shows that when the ink amount supplied per unit time from the supply channel 16 to the pressure chamber 15 is 8.7×10̂−5 ml/min, the discharge port portion 13 is in a steady state. It represents the flow field of the ink flow. 12A shows the case where the liquid discharge head temperature and the environmental temperature are 25° C. and the humidity is 50%, and FIG. 12B shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%. FIG. 12C shows a case where the liquid ejection head temperature and the environmental temperature are 50° C. and the humidity is 10%. For the sake of explanation, coordinate axes are set as shown in the figure. Further, in these figures, the length of each vector does not represent the magnitude of the velocity of the ink flow, but is constant for all velocity values.

As can be seen by comparing FIGS. 6 and 12, the present embodiment employs the ejection port portion (ejection portion) having a shape different from that of the first embodiment. In this embodiment, the thickness of the orifice plate 18 is 5 μm, and the gap between the orifice plate 18 and the support substrate 12 is 14 μm. The amount of ink supplied from the supply channel 16 per unit time is 8.7×10̂−5 ml/min. At this time, when the length of the pressure chamber 15 in the x direction is 25 μm and the length in the z direction perpendicular thereto is 20 μm, the average flow velocity of the ink flow in the pressure chamber 15 is about 6.3 mm/s.

One of the features of this embodiment is that the thickness of the orifice plate 18 is thinner than that of the first embodiment, so that the vortex flow in the ejection port portion due to the forced ink flow that occurs in the first embodiment is generated. It does not appear. That is, in the present embodiment, the vortex does not replace the ink that has accumulated in the ejection port portion 13 with the ink that has flowed in from the supply passage 16. In the present embodiment, as shown in FIG. 12A, the ink flow of the ink that has flowed into the pressure chamber 15 and the ejection port portion 13 from the supply flow path 16 is on the upstream side of the ejection port portion 13 in the ejection port 11 direction (y Direction), and flows into the vicinity of the discharge port 11. Then, a velocity component in the direction (−y direction, heater 14 direction) opposite to the discharge port 11 direction is obtained on the downstream side of the discharge port portion 13 and flows into the pressure chamber 15 and the recovery passageway 17. By generating such a flow field of the ink flow, at least a part of the ink in the ejection port portion 13 is replaced with the ink flowing in from the supply channel 16. Here, it has been confirmed that the replacement effect varies depending on the environment in which the recording apparatus is installed, as in the first embodiment in which the vortex is generated by the forced ink flow.

FIG. 13 shows a temporal change in the concentration of the non-volatile solvent in the ejection port portion 13 when the amount of ink supplied from the supply passage 16 to the pressure chamber 15 per unit time is increased. In the figure, the solid line shows the case where the liquid discharge head temperature and the environmental temperature are 25° C. and the humidity is 50%, and the broken line shows the case where the liquid discharge head temperature and the environmental temperature are 50° C. and the humidity is 50%. , The liquid ejection head temperature and the environmental temperature are 50° C., and the humidity is 10%. In the present embodiment as well, as in the first embodiment, the amount of ink supplied per unit time is increased in order to cope with the decrease in the replacement effect due to the increase in the evaporation rate due to the change in the installation environment. That is, when the amount of evaporation from the ejection port increases, the amount of ink supplied to the pressure chamber is increased. As a result, the flow in the direction of the heater 14 (−y direction) becomes stronger on the downstream side of the discharge port portion 13, and the replacement effect becomes greater.

The flow channel shape in the above-described embodiment is merely an example. For example, when the gap between the orifice plate 18 and the supporting substrate 12 is 14 μm and the opening diameter of the ejection port 11 in the x direction is 12 μm, the thickness of the orifice plate 18 is 6 μm or less, which is the same as in the present embodiment. It becomes a system in which no eddy current is generated at the discharge port portion 13.

In the above-mentioned embodiment, the supply flow path and the recovery flow path are explained on the premise that they are arranged on a straight line. However, the supply flow path and the recovery flow path are not arranged on a straight line, and the offset It may be the case. Further, the flow path height, the discharge port cross-sectional shape, the orifice plate thickness, and the like in the above-described embodiment are merely examples, and a discharge portion having a different shape may be adopted as long as it complies with the concept of the present invention. good.

INDUSTRIAL APPLICABILITY The present invention is configured by a combination of a plurality of liquid ejection heads, which is included in an inkjet recording apparatus including a full-line type liquid ejection head having a length corresponding to the maximum width of a recording medium, or integrally formed. It is applicable to any of the liquid ejection heads. Further, the present invention is applicable to various types such as a serial type, a type fixed to an apparatus, a chip type that enables electrical connection and ink supply when mounted, a type in which an ink tank is provided in the liquid ejection head itself. It is applicable to the liquid ejection head of

Incidentally, in each of the above-described embodiments, the data are shown for three main points of temperature and humidity (when the temperature is 25° C., 50° C., the humidity is 50% and 10%) as the environment in which the recording apparatus is installed. However, the present invention is not limited to this. Generally, the higher the temperature, the faster the evaporation rate, and the lower the humidity, the faster the evaporation rate. Further, as the evaporation rate increases, the concentration of the non-volatile solvent in the liquid at the ejection port 11 and the ejection port portion 13 tends to increase. The flow rate of the liquid flowing in the pressure chamber 15 may be determined based on this tendency.

<Other Examples>
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

11... Ejection port 13... Ejection port portion 15... Pressure chamber 16... Supply channel 17... Recovery channel 43... Liquid ejection head 47... Control unit 49... Sensor unit 50... Mechanical control unit 51... Mechanical unit

Claims (8)

A discharge port for discharging a liquid, an element for generating energy used for discharging the liquid, a pressure chamber having the element therein, and a pressure chamber communicating with the pressure chamber for supplying the liquid to the pressure chamber A liquid discharge head including a flow path and a second flow path communicating with the pressure chamber and collecting liquid from the pressure chamber;
Generating means for generating a flow of the liquid flowing in the order of the first flow path, the pressure chamber, and the second flow path;
An acquisition means for acquiring information on the evaporation of the liquid from the discharge port,
Control means for controlling the flow rate of the flow based on the acquired information;
Have a,
Of the head temperature detecting means for detecting the temperature of the liquid ejection head, the environmental temperature detecting means for detecting the temperature of the environment in which the liquid is ejected, and the humidity detecting means for detecting the humidity of the environment, as the acquisition means. Have at least one,
At least one of the temperature of the liquid ejection head, the temperature of the environment, and the humidity, and a table in which the flow rate corresponding to the evaporation amount from the ejection port is associated with each other. apparatus. The recording apparatus according to claim 1, wherein the control unit increases the flow rate when the evaporation amount from the ejection port increases. A discharge port for discharging a liquid, an element for generating energy used for discharging the liquid, a pressure chamber having the element therein, and a pressure chamber communicating with the pressure chamber for supplying the liquid to the pressure chamber A liquid discharge head including a flow path and a second flow path communicating with the pressure chamber and collecting liquid from the pressure chamber;
Generating means for generating a flow of the liquid flowing in the order of the first flow path, the pressure chamber, and the second flow path;
An acquisition means for acquiring information on the evaporation of the liquid from the discharge port,
Control means for controlling the flow rate of the flow based on the acquired information;
Have
The control means associates at least one of the temperature of the liquid ejection head, the temperature of the installed environment, and the humidity of the environment with the flow rate corresponding to the evaporation amount from the ejection port. by using the table, the temperature of the liquid ejection head, record device you and sets the flow rate based on at least one of said temperature of the environment, and the humidity. A discharge port for discharging a liquid, an element for generating energy used for discharging the liquid, a pressure chamber having the element therein, and a pressure chamber communicating with the pressure chamber for supplying the liquid to the pressure chamber A liquid discharge head including a flow path and a second flow path communicating with the pressure chamber and collecting liquid from the pressure chamber;
Generating means for generating a flow of the liquid flowing in the order of the first flow path, the pressure chamber, and the second flow path;
An acquisition means for acquiring information on the evaporation of the liquid from the discharge port,
Control means for controlling the flow rate of the flow based on the acquired information;
Have
The liquid discharge head further includes a discharge port portion that communicates the discharge port and the pressure chamber,
Said first passage, said pressure chamber, flows into a part the discharge port portion of said liquid flowing in the order of the second flow path, you characterized in that the vortex flow is generated inside the discharge port portion record apparatus. The recording apparatus according to claim 4, wherein the control unit sets the flow rate such that the center of the vortex becomes the center of the ejection port portion. The liquid discharge head further includes a discharge port portion that communicates the discharge port and the pressure chamber,
Part of the liquid flowing in the order of the first flow path, the pressure chamber, and the second flow path flows into the discharge port portion,
The liquid flow on the side of the first flow path inside the discharge port has a velocity component in the direction from the pressure chamber to the discharge port, and the liquid on the side of the second flow path inside the discharge port. The recording apparatus according to any one of claims 1 to 3, wherein the flow has a velocity component in a direction opposite to the direction. A discharge port for discharging a liquid, an element for generating energy used for discharging the liquid, a pressure chamber having the element therein, and a pressure chamber communicating with the pressure chamber for supplying the liquid to the pressure chamber A liquid discharge head including a flow path and a second flow path communicating with the pressure chamber and collecting liquid from the pressure chamber;
Generating means for generating a flow of the liquid flowing in the order of the first flow path, the pressure chamber, and the second flow path;
An acquisition means for acquiring information on the evaporation of the liquid from the discharge port,
Control means for controlling the flow rate of the flow based on the acquired information;
The has information about the evaporation of the liquid, record device you characterized by a vaporization amount per unit time of the liquid evaporates from the discharge port. A liquid ejection head mounted on the recording apparatus according to any one of claims 1 to 7 , wherein the liquid inside the pressure chamber is circulated between the liquid outside the pressure chamber and the outside. Liquid ejection head.

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