Liquid ejection head, method for operating liquid ejection head, and liquid ejection device

Abstract

The present invention relates to a liquid ejection head, an operating method of the liquid ejection head and a liquid ejection device. The liquid ejection head includes a plurality of flow paths. The plurality of flow paths include a first flow path through which a first liquid flows and a second flow path arranged adjacent to the first flow path. A second liquid having a higher average spectral reflectance at a wavelength in a visible light region than the first liquid flows through the second flow path. When pressure is applied to the first liquid, the pressure of the first liquid applied to the first flow path is lower than the pressure of the second liquid applied to the second flow path.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head that ejects a plurality of types of liquids having different colors, an operating method of the liquid ejection head, and a liquid ejection apparatus including the liquid ejection head. Background Art

[0002] Some liquid ejection heads that eject liquid from an ejection port to record on a recording medium include a liquid ejection head having a plurality of ejection ports to eject different types of liquids (e.g., inks of different colors) from the plurality of ejection ports. In such a liquid ejection head, when liquids of different colors are mixed, the image quality perceived and recognized in the image recorded on the recording medium may be reduced. In the following description, the reduction in image quality refers to the degradation of the perceived recognition of the image recorded by ejection. In order to suppress the reduction in image quality, Japanese Patent Laid-Open No. 2014-12353 discloses controlling the order of wiping the ejection ports in a wiping operation of wiping liquid attached to the periphery of the ejection port. In the control described in Japanese Patent Laid-Open No. 2014-12353, when a small amount of light liquid is mixed with a dark liquid, the perceptible color change is smaller than when a small amount of dark liquid is mixed with a light liquid, so the ejection port corresponding to the light liquid is wiped first.

[0003] The method described in Japanese Patent Laid-Open No. 2014-12353 can suppress image quality degradation caused by mixing of liquids attached to the periphery of the ejection orifice, but cannot suppress image quality degradation when liquids mix inside the ejection orifice or in a flow path communicating with the ejection orifice. Summary of the invention

[0004] According to one aspect of the present invention, a liquid ejection head includes: a plurality of flow paths, wherein the plurality of flow paths include a first flow path and a second flow path, a first liquid will flow through the first flow path, the second flow path is arranged adjacent to the first flow path, and a second liquid having a higher average spectral reflectance at a wavelength in a visible light region than the first liquid will flow through the second flow path, and wherein, when pressure is applied to the first liquid, the pressure applied to the first liquid in the first flow path is lower than the pressure applied to the second liquid in the second flow path.

[0005] According to another aspect of the present invention, a method for operating a liquid ejection head, the liquid ejection head comprising a plurality of flow paths and a liquid chamber, wherein the liquid chamber is configured to be connected to a ejection port and hold liquid for each of the plurality of flow paths, the operating method comprising: causing a first liquid to flow in one of two adjacent flow paths; causing a second liquid having a higher average spectral wavelength at a wavelength in a visible light region than that of the first liquid to flow in the other of the two adjacent flow paths; and setting a pressure applied to the second liquid held in a liquid chamber of the flow path through which the second liquid flows, so that when the first liquid and the second liquid are caused to flow, the pressure applied to the second liquid is higher than the pressure applied to the first liquid held in the liquid chamber of the flow path through which the first liquid flows.

[0006] According to another aspect of the present invention, a liquid ejection device includes: the above-mentioned liquid ejection head; a pressure generator, which is connected to the multiple flow paths and can generate different pressures for each of the multiple flow paths; and a control unit, which is configured to control the pressure generator.

[0007] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic cross-sectional view showing a liquid ejection head according to a first embodiment.

[0009] Figure 2A and Figure 2B It is shown Figure 1 A schematic diagram of the flow of liquid in the liquid ejection head is shown.

[0010] Figure 3A , Figure 3B and Figure 3C is a graph showing the spectral reflectance of the liquid to be ejected.

[0011] Figure 4 is a schematic end view showing another example of the liquid ejection head.

[0012] Figure 5 is a schematic cross-sectional view showing another example of the liquid ejection head.

[0013] Figure 6 is a schematic cross-sectional view showing another example of the liquid ejection head.

[0014] Fig. 7A and Figure 7B is a diagram showing a liquid ejection head according to a second embodiment.

[0015] Figure 8It is a diagram for explaining a liquid ejecting device.

[0016] Fig. 9 is a schematic cross-sectional view showing liquid to be ejected.

[0017] Fig.10 It is a schematic cross-sectional view for explaining the liquid to be ejected. DETAILED DESCRIPTION

[0018] The present invention discloses a liquid ejection head, an operation method of the liquid ejection head, and a liquid ejection device, which can suppress the degradation of image quality even when liquids of different colors are mixed in a flow path extending to a jet outlet. In an example, in a liquid ejection head, when a first liquid and a second liquid having a higher average spectral reflectance at a wavelength in a visible light region than the first liquid are caused to flow through a first flow path and a second flow path adjacent to the first flow path, a pressure applied to the second liquid in the second flow path is higher than a pressure applied to the first liquid in the first flow path.

[0019] Next, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are only used to illustrate the present invention, and do not limit the present invention. Common reference numerals are given to common elements in multiple drawings.

[0020] (First embodiment)

[0021] Figure 1 A liquid ejection head 10 according to a first embodiment of the present invention is schematically shown. The liquid ejection head 10 is formed by laminating and joining a plurality of plate-like members. In the illustrated example, a jet forming member 11 and a liquid chamber forming member 12, both of which are plate-like members, are laminated and joined to each other. In the jet forming member 11, a plurality of jets 13a to 13e are formed as through holes. The liquid chamber forming member 12 is provided with liquid chambers 14a to 14e, which are respectively connected to the jets 13a to 13e and hold the liquid to be ejected from the jets 13a to 13e (i.e., the liquid to be ejected). In the liquid chamber forming member 12, supply paths 15a to 15e for supplying liquid to the liquid chambers 14a to 14e are further formed so as to extend to the opposite side of the jets 13a to 13e. The liquid chambers 14a to 14e and the supply paths 15a to 15e constitute flow paths 16a to 16e. The ejection ports 13a to 13e have the same shape and size, and the flow paths 16a to 16e have the same shape and size. The flow paths 16a to 16e are in contact with the joint interface between the ejection port forming member 11 and the liquid chamber forming member 12.

[0022] The liquid ejection head 10 according to the present embodiment ejects a plurality of liquids of different colors (e.g., ink) onto a recording medium such as paper to record using a color image. In the case of recording using a color image, a black (B) liquid and three color liquids of yellow (Y), cyan (C), and magenta (M) are generally used as recording liquids. These four colors, i.e., four types of liquids, are also used in the liquid ejection head 10 according to the present embodiment. Cyan liquid is supplied to flow path 16a, black liquid is supplied to flow paths 16b and 16d, magenta liquid is supplied to flow path 16c, and yellow liquid is supplied to flow path 16e.

[0023] Figure 2A and Figure 2B 1 is a diagram showing the flow of liquid with a focus on the relationship between two adjacent flow paths in the liquid ejection head 10. Figure 2A and Figure 2B , the flow path 16a of the cyan liquid and the flow path 16b of the black liquid are shown as two adjacent flow paths, and the white arrow indicates the flow of the cyan liquid and the black arrow indicates the flow of the black liquid. In the liquid chamber forming member 12, the portion arranged between the adjacent flow paths 16a and 16b is a partition wall 20 that partitions the flow paths 16a and 16b. Although the ejection port forming member 11 and the liquid chamber forming member 12 are joined, as shown in FIG. Figure 2A As shown, a tiny defect 18 through which the flow paths 16a and 16b communicate with each other may be formed at the joint interface. When the defect 18 exists, there is a possibility that the liquids in the flow paths 16a and 16b may flow toward the defect 18 and mix with each other through the defect 18. That is, the cyan liquid in the flow path 16a and the black liquid in the flow path 16b may mix via the defect 18. Although the defect 18 is formed at the joint interface between the ejection port forming member 11 and the liquid chamber forming member 12 in this example, since the partition wall 20 separating the adjacent flow paths 16a and 16b deteriorates, a defect through which the liquid can pass may occur in the partition wall 20 itself.

[0024] In the case where defect 18 occurs and a small amount of black liquid flows into the cyan liquid, the perceptible change when the user observes the image formed by ejecting the cyan liquid is large. On the other hand, even in the case where a small amount of cyan liquid flows into the black liquid, there is almost no perceptible change when the user observes the image formed by ejecting the black liquid. Therefore, in the present embodiment, in the case where there is a possibility that liquids of different colors may be mixed, the flow direction of the liquid at the defect 18 is controlled so that the perceptible change in the recorded image when color mixing occurs is smaller. Specifically, as Figure 2BAs shown, in the defect 18, the cyan liquid permeates and flows from the flow path 16a toward the flow path 16b, and the black liquid does not flow in the opposite direction. As a method of enabling the liquid to flow in only one direction as described above, for example, the pressure applied to the cyan liquid in the flow path 16a may be set higher than the pressure applied to the black liquid in the flow path 16b. In the example shown here, the pressure applied to the liquid in the flow paths 16a and 16b is the pressure applied to the liquid in the liquid chambers 14a and 14b provided at the positions where the flow paths 16a and 16b are connected to the ejection ports 13a and 13b, respectively.

[0025] exist Figure 3A , Figure 3B and Figure 3C , with the horizontal axis representing wavelength and the vertical axis representing reflectivity, the spectral reflectivity in the visible light region (in this example, the wavelength region equal to or greater than 400 nm and equal to or less than 700 nm) of the liquid of each color ejected from the liquid ejection head 10 as the liquid to be ejected is shown. Figure 3A shows the spectral reflectance of the cyan liquid, Figure 3B shows the spectral reflectance of the magenta liquid, and Figure 3C The spectral reflectance of the yellow liquid is shown. Although not shown here, the reflectance of the black liquid is close to 0 at any wavelength in the visible light region, and is lower than the reflectance of any liquid in the cyan, magenta and yellow liquids at any wavelength in the visible light region. In the liquid ejection head 10 according to the present invention, when liquids of different colors flow in adjacent flow paths, the flow path to which a higher pressure is applied to the liquid is determined based on the average value of the spectral reflectance of each liquid at the wavelength in the visible light region. The average value of the spectral reflectance can be calculated, for example, by obtaining the spectral reflectance at a predetermined wavelength interval (e.g., 10nm or less) and averaging the spectral reflectance. The pressure of the liquid to be applied to the flow path of the liquid with a higher average spectral reflectance is set to be higher than the pressure applied to the liquid with a lower average spectral reflectance. For example, it is considered that the first flow path and the second flow path are adjacent to each other in the liquid ejection head 10, and the first liquid with a relatively low average spectral reflectance at the wavelength in the visible light region flows through the first flow path, and the second liquid with a relatively high average spectral reflectance at the wavelength in the visible light region flows through the second flow path. In this case, with the pressure of the second liquid applied to the second flow path being set higher than the pressure of the first liquid applied to the first flow path, the second liquid flows unidirectionally from the second flow path toward the first flow path. As a result, the second liquid having a high average spectral reflectance (e.g., a liquid having a higher brightness) is mixed with the first liquid having a low average spectral reflectance (e.g., a liquid having a lower brightness). Even in the case where a small amount of liquid having a relatively high average spectral reflectance is mixed with a liquid having a relatively low average spectral reflectance, the perceptible change in the recorded image is small, and degradation in image quality can be suppressed. Figure 2A and Figure 2B In the example shown, the black liquid corresponds to the first liquid, the cyan liquid corresponds to the second liquid, the flow path 16b corresponds to the first flow path, and the flow path 16a corresponds to the second flow path. As a method of operating the liquid ejection head 10, the pressure of the second liquid applied to the liquid chamber of the flow path through which the second liquid flows may be set higher than the pressure of the first liquid applied to the liquid chamber of the flow path through which the first liquid flows, wherein the average value of the spectral reflectance of the second liquid at a wavelength in the visible light region is higher than the average value of the spectral reflectance of the first liquid at a wavelength in the visible light region.

[0026] There are several methods for setting the pressure of the second liquid applied to the second flow path higher than the pressure of the first liquid applied to the first flow path. As will be described later, a pressure generator may be provided in a liquid ejection device including a liquid ejection head 10, and the pressure generator may be connected to each flow path 16a to 16e of the liquid ejection head 10, and the liquid to be ejected whose pressure is adjusted by the pressure generator may be supplied to the liquid ejection head 10. Alternatively, a first buffer tank connected to the first flow path and storing the first liquid and a second buffer tank connected to the second flow path and storing the second liquid may be provided, and the water level difference of the second buffer tank may be higher than the water level difference of the first buffer tank.

[0027] The flow paths 16a to 16e are of the same size and shape, and when liquid is supplied to the flow paths 16a to 16e at the same supply pressure, the difference between the pressures of the liquids applied to the liquid chambers 14a to 14e can be set by changing the viscosity of the liquids. Figure 2A and Figure 2B In the case shown, it is assumed that the black liquid is supplied to the flow path 16b as the first flow path, and the cyan liquid is supplied to the flow path 16a as the second flow path. As the viscosity increases, the pressure drop caused by the flow increases. Therefore, in the case where the viscosity of the black liquid is higher than the viscosity of the cyan liquid and the pressure in the liquid chamber 14a is compared with the pressure in the liquid chamber 14b, the pressure applied to the black liquid in the liquid chamber 14b is lower than the pressure applied to the cyan liquid in the liquid chamber 14a. As a result, the cyan liquid flows from the liquid chamber 14a through the defect 18 toward the liquid chamber 14b in one direction. In the case of setting the viscosity difference between the liquids flowing through the flow paths 16a and 16b, the viscosity of each liquid is adjusted so that the pressure difference between the adjacent liquid chambers 14a and 14b is about 100Pa. In the case of changing the viscosity for each liquid, in addition to the method of using liquid materials with different viscosities, there is a method of changing the viscosity of each liquid by controlling the heat to be applied to the liquid in the flow paths 16a to 16e or its upstream. In addition, the viscosity difference between the liquids can be generated by another mechanism or structure.

[0028] When liquid is supplied to the flow paths 16a to 16e at the same supply pressure, the difference between the pressures of the liquids applied to the liquid chambers 14a to 14e can be set by changing the flow velocity in the flow paths 16a to 16e. As a method of changing the flow velocity in the flow paths 16a to 16e, there is a method of changing the cross-sectional area of ​​the flow paths 16a to 16e, especially the cross-sectional area at the position where the flow paths 16a to 16e are connected to the ejection ports 13a to 13e, respectively. The cross-sectional area of ​​each flow path refers to the cross-sectional area cut along a plane perpendicular to the flow direction of the liquid in the flow path. Figure 4 Show Figure 1 The liquid ejection head 10 shown in the figure has a difference in cross-sectional area between the flow paths 16a to 16e. By providing a difference in cross-sectional area, a difference also occurs in the volume of the liquid chambers 14a to 14e. More specifically, Figure 4 In the example shown, Figure 1 Compared with the example shown in FIG. 1 , in the flow paths 16b and 16d of the black liquid, the widths of the liquid chambers 14b and 14d provided in the portions communicating with the ejection ports 13b and 13d are increased to increase the cross-sectional area as the flow paths. When the cross-sectional area of ​​the flow paths in the liquid chambers 14b and 14d is made about 45% wider than the cross-sectional area of ​​the flow paths in the liquid chambers 14a, 14c, and 14e, the flow velocity is reduced by about half, thereby producing an effect of reducing the pressure by about 100Pa.

[0029] Furthermore, by changing the flow resistance in the flow paths 16a to 16e, the difference between the pressures applied to the liquid in the flow paths 16a to 16e (particularly the liquid chambers 14a to 14e) can be set. As a method of changing the flow resistance, there are a method of changing the length of the liquid chambers 14a to 14e in the flow direction of the liquid in the liquid chambers 14a to 14e, a method of forming concavities and convexities on the inner wall surfaces of the flow paths 16a to 16e, and the like. Any method of changing the flow resistance of each flow path is included in the scope of the present invention.

[0030] exist Figure 1In the liquid ejection head 10 shown, the ejection port forming member 11 and the liquid chamber forming member 12 may be integrally formed in a single member, or may be formed by joining different members or the same member. The liquid chamber forming member 12 itself may be formed by joining a plurality of members. In the case where the ejection port forming member 11 and the liquid chamber forming member 12 are to be joined, an adhesive or the like may be applied to the interface between the ejection port forming member 11 and the liquid chamber forming member 12 to join the ejection port forming member 11 and the liquid chamber forming member 12 to each other to form an integral joined product, or the ejection port forming member 11 and the liquid chamber forming member 12 may be joined to each other by direct joining so that chemical bonding is generated at the interface. In addition, in the liquid ejection head 10 according to the present invention, in addition to the joining interface between the ejection port forming member 11 and the liquid chamber forming member 12, there may be a joining interface between the plate-like members. By applying the present invention, it is also possible to suppress the degradation of image quality caused by the mixing of liquids in adjacent flow paths via defects existing at the joining interface other than the joining interface between the ejection port forming member 11 and the liquid chamber forming member 12. Furthermore, by applying the present invention, it is also possible to suppress degradation of image quality due to liquid mixing via defects formed in a partition wall between adjacent flow paths at a position other than the bonding interface.

[0031] Figure 5 The liquid ejection head 10 shown is formed by Figure 1 The liquid ejection head 10 shown is obtained by joining a cover plate 21 as a plate-like member to the surface of the liquid chamber forming member 12 on the opposite side of the joining interface with the ejection outlet forming member 11. In the cover plate 21, openings 22a to 22e connected to the supply paths 15a to 15e are formed as through holes so that liquid can be supplied to the liquid chambers 14a to 14e. The openings 22a to 22e respectively constitute a part of the flow paths 16a to 16e. The cover plate 21 can be formed by a member different from or the same as the liquid chamber forming member 12. In the case where the flow rate in the flow paths 16a to 16e is changed to change the pressure of the liquid applied to the liquid chambers 14a to 14e, the flow rate in the flow paths 16a to 16e can be changed by making the cross-sectional areas of the openings 22a to 22e different while keeping the size of the liquid chambers 14a to 14e the same.

[0032] In reference Figures 1 to 5 In the liquid ejection head 10 described above, five flow paths 16a to 16e are used, and the black liquid flows through two flow paths 16b and 16d among the flow paths 16a to 16e. However, the configuration of the flow paths in the liquid ejection head 10 is not limited thereto. Figure 6In the liquid ejection head 10 shown, four flow paths 16a to 16d are provided. With respect to the four flow paths 16a to 16d, yellow liquid is supplied to flow path 16a, cyan liquid is supplied to flow path 16b, magenta liquid is supplied to flow path 16c, and black liquid is supplied to flow path 16d. Furthermore, in the liquid ejection head 10, the pressure of the liquid to be applied to each of the flow paths 16a to 16d is set based on the fact that a small amount of one of two liquids of different colors flowing in adjacent flow paths has a small effect when mixed with the other liquid. The liquid that has the least effect on image quality degradation as the liquid to be mixed with the other liquid is the yellow liquid, the liquid that has the second smallest effect is the cyan liquid, the liquid that has the third smallest effect is the magenta liquid, and the liquid that has the largest effect is the black liquid. Therefore, the pressures of the liquids applied to the liquid chambers 14a to 14d are P, respectively. a , P b , P c and P d In the case of satisfying P a >P b >P c >P d Since the pressure is set in this way, even in the case where there is a defect that causes the flow paths to communicate with each other, control can be performed so that the liquid flows only from the liquid chamber 14a to the liquid chamber 14b, from the liquid chamber 14b to the liquid chamber 14c, and from the liquid chamber 14c to the liquid chamber 14d. With this structure, it is possible to minimize the degradation of image quality caused by mixing of liquid of different colors with another of these liquids.

[0033] Figure 6 The example shown represents a case where four liquids of different colors are supplied to four flow paths 16a to 16d, respectively. However, even in a case where the number of flow paths increases according to an increase in the type of liquid, the degradation of image quality can be minimized by setting the pressure in a similar manner. The method of setting the pressure when there are three or more flow paths will be roughly described as follows. Consider the following case: a first flow path through which a first liquid flows and a second flow path through which a second liquid flows are adjacent to each other, a third flow path is arranged adjacent to the second flow path on the opposite side of the first flow path in a state where the second flow path is inserted between the first flow path and the third flow path, and a third liquid flows through the third flow path. Assume that the average spectral reflectance of the second liquid at a wavelength in the visible light region is higher than the average spectral reflectance of the first liquid at a wavelength in the visible light region, and the average spectral reflectance of the third liquid at a wavelength in the visible light region is higher than the average spectral reflectance of the second liquid at a wavelength in the visible light region. In this case, the pressure of the first liquid applied to the first flow path is set lower than the pressure of the second liquid applied to the second flow path, and the pressure of the second liquid applied to the second flow path is set lower than the pressure of the third liquid applied to the third flow path. In Figure 6 In the example shown, when focusing on the flow paths 16a to 16c, the flow path 16a through which the yellow liquid flows corresponds to the third flow path, the flow path 16b through which the cyan liquid flows corresponds to the second flow path, and the flow path 16c through which the magenta liquid flows corresponds to the first flow path.

[0034] As a method of setting such a pressure difference between the first flow path to the third flow path, for example, there is a method of setting the first buffer tank to the third buffer tank respectively connected to the first flow path to the third flow path to set the difference between the water level differences of the buffer tanks. In this case, the water level difference of the second buffer tank is set to be higher than the water level difference of the first buffer tank, and the water level difference of the third buffer tank is set to be higher than the water level difference of the second buffer tank. Optionally, the cross-sectional area of ​​the first flow path may be set to be larger than the cross-sectional area of ​​the second flow path, and the cross-sectional area of ​​the second flow path may be set to be larger than the cross-sectional area of ​​the third flow path to form a pressure difference between the flow paths. In addition, the viscosity of the first liquid may be made higher than the viscosity of the second liquid, and the viscosity of the second liquid may be made higher than the viscosity of the third liquid to form a pressure difference between the flow paths.

[0035] (Second embodiment)

[0036] Fig. 7A and Figure 7B A liquid ejection head 30 according to a second embodiment of the present invention is shown. The liquid ejection head 30 is formed by laminating and joining an ejection port forming member 31 and a liquid chamber forming member 32 (both of which are plate-like members), and is a type in which liquid to be ejected circulates. In the figure, an area in which two ejection ports 33a and 33b of liquids of different colors are provided is shown. Fig. 7A is a plan view showing the liquid ejection head 30 according to the present embodiment, and Figure 7B It is along Fig. 7A A cross-sectional view taken along line AA. Fig. 7A In order to facilitate understanding of the structure of the liquid ejection head 30 , the ejection port forming member 31 is indicated by a dotted line, and the liquid chamber forming member 32 is indicated by a solid line in the absence of the ejection port forming member 31 . Fig. 7A The shaded portion in FIG. 1 represents the region where the ejection port forming member 31 and the liquid chamber forming member 32 are joined. A plurality of ejection ports 33a of a liquid of one color are arranged along Fig. 7A The horizontal direction of the plurality of ejection ports 33a is arranged and configured in a row to form an ejection port array. Similarly, the plurality of ejection ports 33b of the liquid of another color is also arranged and configured in a row to form an ejection port array.

[0037] When focusing on each ejection port 33a, at a position where the ejection port 33a is provided, in the surface of the ejection port forming member 31 facing the liquid chamber forming member 32, an elongated recess communicating with the ejection port 33a is formed for each ejection port 33a. The recess constitutes a pressure chamber 34a through which the liquid to be ejected can pass when the ejection port forming member 31 and the liquid chamber forming member 32 are engaged. On the surface of the liquid chamber forming member 32 at a position facing the ejection port 33a communicating with the pressure chamber 34a, an energy generating element 35 such as an electrothermal converter or the like that generates energy for ejecting the liquid from the ejection port 33a is provided. Supply ports 38a and 39a are provided in the liquid chamber forming member 32 to correspond to both ends of the pressure chamber 34a in the long side direction of the pressure chamber 34a. The supply ports 38a and 39a are communicated with the individual liquid chambers 36a and 37a formed in the liquid chamber forming member 32. When liquid is not ejected from the ejection port 33a, liquid flows from the individual liquid chamber 36a to the individual liquid chamber 37a via the supply port 38a, the pressure chamber 34a and the supply port 39a. Then, the liquid flowing into the individual liquid chamber 37a is recovered via a tube arranged outside the liquid ejection head 30, and is supplied to the individual liquid chamber 36a again via a tank, etc. In the entire liquid ejection device including the liquid ejection head 30, the liquid to be ejected circulates. When the energy generating element 35 is driven, a part of the liquid in the pressure chamber 34a is ejected from the ejection port 33a, and the liquid flows from the individual liquid chambers 36a and 37a to the pressure chamber 34a via the supply ports 38a and 39a to replenish the ejected liquid. The pressure in the individual liquid chambers 36a and 37a is kept constant. The individual liquid chamber 36a and the supply port 38a constitute a flow path 4 connected to the ejection port 33a, and the individual liquid chamber 37a and the supply port 39a also constitute a flow path connected to the same ejection port 33a. Similarly, the pressure chamber 34b, the energy generating element 35, the individual liquid chambers 36b and 37b, and the supply ports 38b and 39b are provided corresponding to each ejection port 33b.

[0038] Assuming that the flow resistance of the pressure chamber 34a and the supply ports 38a and 39a is low and the liquid is supplied to the individual liquid chamber 36a from a buffer tank (not shown), it can be considered that the pressure applied to the liquid in the individual liquid chambers 36a and 37a corresponding to the ejection port 33a is the same. Similarly, it can be considered that the pressure applied to the liquid in the two individual liquid chambers 36b and 37b corresponding to the ejection port 33b is the same. Here, the case where cyan liquid is ejected from the ejection port 33a and black liquid is ejected from the ejection port 33b will be considered. The flow path including the individual liquid chamber 37a and the supply port 39a and the flow path including the individual liquid chamber 36b and the supply port 38b are adjacent in the liquid chamber forming member 32 and are the flow paths through which liquids of different colors flow. In this embodiment, as in the case of the first embodiment, the pressure applied to the liquid in the flow path through which the cyan liquid flows is set to be higher than the pressure applied to the liquid in the flow path through which the black liquid flows. As a result, even if there is a defect that allows the two flow paths to communicate with each other, a small amount of cyan liquid flows from the individual liquid chamber 37a that applies higher pressure to the cyan liquid to the individual liquid chamber 36b that applies lower pressure to the black liquid, causing a small amount of cyan liquid to mix into the black liquid.

[0039] Assume that there is a defect with a width of 1 μm and a height of 0.5 μm, through which the flow path including the individual liquid chamber 37a and the supply port 39a is connected to the flow path including the individual liquid chamber 36b and the supply port 38b, specifically, the individual liquid chamber 37a is connected to the individual liquid chamber 36b through the defect. When the pressure applied to the liquid in the individual liquid chamber 37a is set to be 10Pa higher than the pressure applied to the liquid in the individual liquid chamber 36b, the cyan liquid in the individual liquid chamber 37a flows into the black liquid in the individual liquid chamber 36b at a rate of about 130 pL per 24 hours. The black liquid does not flow in the opposite direction. The amount of about 130 pL of liquid that flows for 24 hours is, for example, about 0.005% of the volume of the individual liquid chamber 36b, and even if the black liquid that flows into the cyan liquid is ejected from the ejection port 33b for recording, the quality of the recorded image is not affected. By further reducing the pressure difference between the individual liquid chambers 37a and 36b to a level below 10Pa, the amount of cyan liquid mixed into the black liquid can be reduced. If the set pressure difference is too small, there is a possibility that the liquid may flow in the opposite direction from the individual liquid chamber 37a to the individual liquid chamber 36b due to pressure fluctuations that may occur in the individual liquid chambers 37a and 36b. In the case of a liquid ejection head of a type of liquid circulation, it is necessary to set the pressure difference between adjacent flow paths of liquids of different colors to about 3000Pa or less so as not to interfere with refilling the pressure chamber with liquid after the liquid is ejected.

[0040] Although the above description includes a liquid ejection head 30 including an ejection port array including the ejection port 33a and an ejection port array including the ejection port 33b and ejecting two liquids of different colors, the liquid ejection head according to the second embodiment may be configured to eject liquids of three or more colors. For example, the liquid ejection head according to the second embodiment may be configured to eject liquids of three or more colors by Figure 1 , Figure 3A , Figure 3B , Figure 3C , Figure 4 and Figure 5 The pressure chamber connected to the ejection port is provided in the liquid ejection head shown so that the liquid circulates in the pressure chamber. In the second embodiment, as in the case of the first embodiment, examples of methods of setting the pressure difference between the flow paths include a method using a pressure generator, a method using the difference between the water level differences in the buffer tank, a method using the viscosity difference between the liquids, and a method using the difference between the cross-sectional areas of the flow paths or the difference between the flow resistances of the flow paths.

[0041] (Liquid spraying equipment)

[0042] Figure 8 is a diagram for explaining a liquid ejection device including a liquid ejection head according to the present invention. The liquid ejection device includes a liquid ejection head 30 according to the second embodiment, and includes a controller 51 as a control unit and a pressure generator 52 controlled by the controller 51. The pressure generator 52 is connected to each flow path of the liquid ejection head 30 to supply the liquid to be ejected to each flow path, and can simultaneously generate pressures different for each flow path. Liquids of each color are supplied to the liquid ejection head 30 from the pressure generator 52, and liquid not ejected by the liquid ejection head 30 returns to the pressure generator 52, whereby the liquid circulates between the pressure generator 52 and the liquid ejection head 30. The controller 51 controls the pressure generator 52 to change the pressure to be applied to the liquid to be supplied to the liquid ejection head 30, thereby generating a pressure difference between adjacent flow paths in the liquid ejection head 30 as described above. The pressure generator 52 may include a buffer tank group (not shown) connected to the flow paths of the liquids of each color, and generates a difference between the supply pressures to be applied to the liquid due to the difference between the water level differences in the buffer tanks. Similarly, in a liquid ejection device using the liquid ejection head 10 according to the first embodiment, a pressure generator 52 is provided in which the supply pressure to be applied to the liquid is controlled by a controller 51, and liquids of each color can be supplied from the pressure generator 52 to each flow path of the liquid ejection head 10.

[0043] The liquid ejection heads 10 and 30 according to the various embodiments are used to suppress the degradation of image quality by setting a pressure difference between the flow paths when there is a defect connected to the flow path between adjacent flow paths through which liquids of different colors flow. In this case, the defect can be blocked using the liquid to be ejected (i.e., the liquid to be ejected). Hereinafter, the blocking of the defect using the liquid to be ejected will be described.

[0044] Fig. 9 An example of a method of plugging a defect using a liquid to be ejected is shown. Figure 3A , Figure 3B and Figure 3C As in the case shown in FIG. 1 , it is assumed that the flow paths 16a and 16b are adjacent to each other with the partition wall 20 interposed therebetween, and a defect 18 in which the flow paths 16a and 16b communicate with each other is formed at the joint interface between the ejection port forming member 11 and the liquid chamber forming member 12. The liquid flowing through the flow path 16a is a yellow liquid, the liquid flowing through the flow path 16b is a black liquid, and the pressure applied to the liquid in the flow path 16a is higher than the pressure applied to the liquid in the flow path 16b. The liquid supplied to the flow path 16a to which a higher pressure is applied contains filler particles 53, wherein the size of the filler particles 53 is smaller than the diameter of the ejection port 13a in a state where the filler particles 53 are dispersed in the liquid. The filler particles 53 are made of, for example, a transparent polymer, and their diameter is, for example, greater than or equal to 1 nm and less than or equal to 5 μm, and are used by mixing filler particles 53 of various sizes. Since the pressure applied to the liquid in the flow path 16a is higher than the pressure applied to the liquid in the flow path 16b, the liquid containing the filler particles 53 tends to flow from the flow path 16a through the defect 18 toward the flow path 16b. In this case, the filler particles 53 dispersed in the liquid are captured and deposited on the side wall of the defect 18. As a result, the defect 18 is blocked, and the liquid in the flow path 16a is prevented from continuing to mix with the liquid in the flow path 16b. Since filler particles 53 of various sizes are contained in the liquid, the liquid can be prevented from flowing through the gaps between the deposited filler particles 53, and defects 18 of various sizes and shapes can be blocked. The filler particles 53 that are not related to the blocking of the defect 18 are ejected from the ejection port 13a.

[0045] Fig.10 Another example of a method of plugging a defect using a liquid to be ejected is shown. Fig.10 The example shown represents the following situation: Fig. 9In the example shown, instead of the filler particles 53, a curable material is contained in the liquid flowing through the flow path 16a on the high-pressure side, and a curing initiator is contained in the liquid flowing through the flow path 16b on the low-pressure side. The curing initiator contained in the liquid flowing through the flow path 16b is a chemical reagent that starts the curing of the curing initiator contained in the liquid flowing through the flow path 16a. As an example, the curable material is a polymer having polymerizability, and the curing initiator is a polymerization initiator corresponding to the polymer. When the liquid containing the curable material flows from the flow path 16a into the flow path 16b via the defect 18, the curable material begins to cure by the action of the curing initiator contained in the liquid in the flow path 16b when flowing into the flow path 16b. As a result, a solidified material 54 is formed near the outlet of the defect 18 on the flow path 16b side, and the outlet of the defect 18 is blocked, whereby the defect 18 is blocked. The curable material that does not contribute to the formation of the cured product 54 is ejected from the ejection port 13 a , and the curing initiator that does not contribute to the formation of the cured product 54 is ejected from the ejection port 13 b .

[0046] Here, reference has been made Fig. 9 and Fig.10 The case of plugging the defect 18 formed between two adjacent flow paths 16a and 16b is described. The method of plugging a defect using a liquid to be ejected as described herein can be performed on the liquid ejection head described above in each embodiment including more flow paths.

[0047] Other embodiments

[0048] The embodiments of the present invention may also be implemented by providing software (program) for performing the functions of the above-described embodiments to a system or device via a network or various storage media, and a computer or a central processing unit (CPU) or a microprocessing unit (MPU) of the system or device reads and executes the program.

[0049] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications, equivalent structures and functions.

Claims

1. A liquid ejection head, comprising: Multiple flow paths, The plurality of flow paths include a first flow path through which a first liquid will flow, and a second flow path through which a second liquid having a higher average spectral reflectance at a wavelength in the visible light region than the first liquid will flow, wherein, in the case where pressure is applied to the first liquid, the pressure of the first liquid applied to the first flow path is lower than the pressure of the second liquid applied to the second flow path, wherein the cross-sectional area of ​​the first flow path is greater than the cross-sectional area of ​​the second flow path, and Wherein, the viscosity of the first liquid is higher than the viscosity of the second liquid.

2. The liquid ejection head according to claim 1, wherein: The second liquid contains filler particles configured to fill a defect formed between the first flow path and the second flow path.

3. The liquid ejection head according to claim 1, wherein: The second liquid comprises a curable material, and the first liquid comprises a cure initiator configured to initiate cure of the curable material.

4. The liquid ejection head according to claim 1, further comprising: a first buffer tank configured to communicate with the first flow path; as well as A second buffer tank is configured to have a water head difference higher than that of the first buffer tank and is in communication with the second flow path.

5. The liquid ejection head according to claim 1, in, The plurality of flow paths further include a third flow path which is arranged on the opposite side of the first flow path and adjacent to the second flow path in a state where the second flow path is inserted between the first flow path and the third flow path, and through which a third liquid having a higher average spectral reflectance at a wavelength in the visible light region than the second liquid flows, and The pressure of the second liquid applied to the second flow path is lower than the pressure of the third liquid applied to the third flow path.

6. The liquid ejection head according to claim 5, further comprising: a first buffer tank configured to communicate with the first flow path; a second buffer tank configured to have a water head difference higher than that of the first buffer tank and communicated with the second flow path; as well as A third buffer tank is configured to have a higher water head difference than that of the second buffer tank and is in communication with the third flow path.

7. The liquid ejection head according to claim 5, wherein: A cross-sectional area of ​​the first flow path is larger than a cross-sectional area of ​​the second flow path, and a cross-sectional area of ​​the second flow path is larger than a cross-sectional area of ​​the third flow path.

8. The liquid ejection head according to claim 5, wherein: The viscosity of the first liquid is higher than the viscosity of the second liquid, and the viscosity of the second liquid is higher than the viscosity of the third liquid.

9. The liquid ejection head according to claim 1, wherein: A plurality of plate-like members are laminated and bonded, and the plurality of flow paths are in contact with bonding interfaces between the plurality of plate-like members.

10. A liquid ejection head, comprising: Multiple flow paths, The plurality of flow paths include a first flow path through which a first liquid will flow, and a second flow path through which a second liquid having a higher average spectral reflectance at a wavelength in the visible light region than the first liquid will flow, wherein, in the case where pressure is applied to the first liquid, the pressure of the first liquid applied to the first flow path is lower than the pressure of the second liquid applied to the second flow path, and The second liquid includes filler particles configured to fill defects formed between the first flow path and the second flow path.

11. The liquid ejection head according to claim 10, wherein: The viscosity of the first liquid is higher than the viscosity of the second liquid.

12. The liquid ejection head according to claim 10, wherein: The second liquid comprises a curable material, and the first liquid comprises a cure initiator configured to initiate cure of the curable material.

13. The liquid ejection head according to claim 10, further comprising: a first buffer tank configured to communicate with the first flow path; as well as A second buffer tank is configured to have a water head difference higher than that of the first buffer tank and is in communication with the second flow path.

14. The liquid ejection head according to claim 10, in, The plurality of flow paths further include a third flow path which is arranged on the opposite side of the first flow path and adjacent to the second flow path in a state where the second flow path is inserted between the first flow path and the third flow path, and through which a third liquid having a higher average spectral reflectance at a wavelength in the visible light region than the second liquid flows, and The pressure of the second liquid applied to the second flow path is lower than the pressure of the third liquid applied to the third flow path.

15. The liquid ejection head according to claim 14, further comprising: a first buffer tank configured to communicate with the first flow path; a second buffer tank configured to have a water head difference higher than that of the first buffer tank and communicated with the second flow path; as well as A third buffer tank is configured to have a higher water head difference than that of the second buffer tank and is in communication with the third flow path.

16. The liquid ejection head according to claim 14, wherein: A cross-sectional area of ​​the first flow path is larger than a cross-sectional area of ​​the second flow path, and a cross-sectional area of ​​the second flow path is larger than a cross-sectional area of ​​the third flow path.

17. The liquid ejection head according to claim 14, wherein: The viscosity of the first liquid is higher than the viscosity of the second liquid, and the viscosity of the second liquid is higher than the viscosity of the third liquid.

18. The liquid ejection head according to claim 10, wherein A plurality of plate-like members are laminated and bonded, and the plurality of flow paths are in contact with bonding interfaces between the plurality of plate-like members.

19. A liquid ejection head, comprising: Multiple flow paths, The plurality of flow paths include a first flow path through which a first liquid will flow, and a second flow path through which a second liquid having a higher average spectral reflectance at a wavelength in the visible light region than the first liquid will flow, wherein, in the case where pressure is applied to the first liquid, the pressure of the first liquid applied to the first flow path is lower than the pressure of the second liquid applied to the second flow path, and Wherein the second liquid comprises a curable material and the first liquid comprises a curing initiator configured to initiate curing of the curable material.

20. The liquid ejection head according to claim 19, wherein The viscosity of the first liquid is higher than the viscosity of the second liquid.

21. The liquid ejection head according to claim 19, further comprising: a first buffer tank configured to communicate with the first flow path; as well as A second buffer tank is configured to have a water head difference higher than that of the first buffer tank and is in communication with the second flow path.

22. The liquid ejection head according to claim 19, in, The plurality of flow paths further include a third flow path which is arranged on the opposite side of the first flow path and adjacent to the second flow path in a state where the second flow path is inserted between the first flow path and the third flow path, and through which a third liquid having a higher average spectral reflectance at a wavelength in the visible light region than the second liquid flows, and The pressure of the second liquid applied to the second flow path is lower than the pressure of the third liquid applied to the third flow path.

23. The liquid ejection head according to claim 22, further comprising: a first buffer tank configured to communicate with the first flow path; a second buffer tank configured to have a water head difference higher than that of the first buffer tank and communicated with the second flow path; as well as A third buffer tank is configured to have a higher water head difference than that of the second buffer tank and is in communication with the third flow path.

24. The liquid ejection head according to claim 22, wherein: A cross-sectional area of ​​the first flow path is larger than a cross-sectional area of ​​the second flow path, and a cross-sectional area of ​​the second flow path is larger than a cross-sectional area of ​​the third flow path.

25. The liquid ejection head according to claim 22, wherein: The viscosity of the first liquid is higher than the viscosity of the second liquid, and the viscosity of the second liquid is higher than the viscosity of the third liquid.

26. The liquid ejection head according to claim 19, wherein A plurality of plate-like members are laminated and bonded, and the plurality of flow paths are in contact with bonding interfaces between the plurality of plate-like members.

27. A method for operating a liquid ejection head, the liquid ejection head comprising a plurality of flow paths and a liquid chamber, wherein the liquid chamber is configured to communicate with an ejection port for each of the plurality of flow paths and to hold liquid, the method comprising: causing a first liquid to flow in one of two adjacent flow paths; causing a second liquid having a higher average spectral reflectance at wavelengths in the visible light region than the first liquid to flow in the other of the two adjacent flow paths; setting a pressure applied to the second liquid held in a liquid chamber of a flow path through which the second liquid flows so that, in a case where the first liquid and the second liquid are caused to flow, the pressure applied to the second liquid is higher than the pressure applied to the first liquid held in the liquid chamber of the flow path through which the first liquid flows; as well as A defect formed between the two adjacent flow paths is filled with filler particles contained in the second liquid.

28. The operating method according to claim 27, wherein: The viscosity of the first liquid is higher than the viscosity of the second liquid.

29. The operating method according to claim 27, further comprising: The curing of the curable material contained in the second liquid is initiated using the curing initiator contained in the first liquid.

30. A liquid ejection device, comprising: A liquid ejection head according to any one of claims 1 to 26; a pressure generator connected to the plurality of flow paths and capable of generating a pressure different for each of the plurality of flow paths; as well as A control unit is configured to control the pressure generator.

31. The liquid ejection device according to claim 30, wherein: The pressure generator includes a plurality of buffer tanks.

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