Inkjet recording apparatus and inkjet recording method

Abstract

The present disclosure relates to an inkjet recording apparatus including an inkjet recording head, the inkjet recording head including: an ejection port for ejecting the ink; a pressure chamber communicating with the ejection port and including therein a recording element substrate configured to generate energy for ejecting the ink; a supply passage communicating with the pressure chamber and configured to supply the ink to the pressure chamber; and a temperature adjusting unit configured to heat the ink. The ink contains titanium oxide and has a viscosity of 8 mPa.s or more at 25 DEG C. The present disclosure also relates to an inkjet recording method.

Description

Technical Field

[0001] The present disclosure relates to an inkjet recording apparatus and an inkjet recording method. Background Art

[0002] In recent years, inkjet recording apparatuses have been widely used to output advertisements and exhibits using recording media such as paper and resin films. For example, in order to form a clear color image even on a transparent recording medium, white ink is used in combination with black ink and inks of basic colors (hereinafter, these inks may be collectively referred to as color inks). Specifically, a recording method is used in which white ink is applied in advance to a portion of a transparent recording medium including an area in which an image is to be recorded for background color processing, and color inks are applied thereto, or inks are applied in reverse order (so-called reverse color printing).

[0003] Titanium oxide is widely used as a coloring material for white ink because it can be obtained at low cost and has good properties required for white ink (e.g., whiteness and hiding power). However, titanium oxide has the problem of easy sedimentation. So far, from the perspective of inhibiting the sedimentation of titanium oxide in white ink, methods for improving dispersion stability by surface treating titanium oxide have been studied. For example, PCT Japanese Translation Patent Publication No. 2017-521348 proposes a method for manufacturing a dried titanium dioxide product, which includes surface treating titanium dioxide with silicon dioxide, further surface treating titanium dioxide with a silane coupling agent, and drying so that part of the silane coupling agent is covalently bonded to the surface of the titanium dioxide particles.

[0004] International Publication No. 2018 / 190848 has proposed an ink containing titanium oxide surface-treated with aluminum oxide, a monovalent metal salt, and aluminum oxide particles. Summary of the invention

[0005] The present invention provides an inkjet recording device, which includes an inkjet recording head, and the inkjet recording head includes: an ejection port, the ejection port is used to eject the ink, a pressure chamber, the pressure chamber is connected to the ejection port and includes a recording element substrate configured to generate energy for ejecting the ink, a supply channel, the supply channel is connected to the pressure chamber and is configured to supply the ink to the pressure chamber, and a temperature adjustment unit, the temperature adjustment unit is configured to heat the ink, wherein the ink contains titanium oxide and has a viscosity of 8 mPa·s or more at 25°C.

[0006] 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

[0007] Figure 1A and Figure 1B are diagrams each illustrating a liquid ejection device according to one or more aspects of the present disclosure.

[0008] Figure 2 is an exploded perspective view of a liquid ejecting head.

[0009] Figure 3A and Figure 3B is a longitudinal cross-sectional view of a liquid ejection head and an enlarged cross-sectional view of an ejection module according to one or more aspects of the present disclosure.

[0010] Figure 4 is a schematic external view of a circulation unit according to one or more aspects of the present disclosure.

[0011] Figure 5 is a longitudinal cross-sectional view illustrating a circulation path according to one or more aspects of the present disclosure.

[0012] Figure 6 is a block diagram schematically illustrating a loop path according to one or more aspects of the present disclosure.

[0013] Fig. 7A , Figure 7B and Figure 7C are cross-sectional views each showing an example of a pressure regulating unit according to one or more aspects of the present disclosure.

[0014] Fig. 8A and Figure 8B is an external perspective view of a circulation pump according to one or more aspects of the present disclosure.

[0015] Fig. 9 According to one or more aspects of the present disclosure Fig. 8A A sectional view taken along line IX-IX in FIG. 1 and showing a circulation pump.

[0016] Fig. 10A , Fig. 10B , Fig. 10C , Fig. 10D and Fig. 10E are views each showing the flow of ink in a liquid ejection head according to one or more aspects of the present disclosure.

[0017] Fig.11A and Fig. 11B 2 are schematic diagrams each showing a circulation path in a spray unit according to one or more aspects of the present disclosure.

[0018] Fig.12 is a view showing an opening plate according to one or more aspects of the present disclosure.

[0019] Fig.13is a view showing an ejection element substrate according to one or more aspects of the present disclosure.

[0020] Fig.14A , Fig. 14B and Fig. 14C are cross-sectional views each illustrating a flow of ink in an ejection unit according to one or more aspects of the present disclosure.

[0021] Fig.15A and Fig. 15B are cross-sectional views each showing the vicinity of an injection port according to one or more aspects of the present disclosure.

[0022] Fig.16A and Fig. 16B are cross-sectional views each showing the vicinity of an injection port of a comparative example according to one or more aspects of the present disclosure.

[0023] Fig.17 are views each showing an ejection element substrate of a comparative example according to one or more aspects of the present disclosure.

[0024] Fig.18A and 18B are views each showing a channel configuration of a liquid ejection head according to one or more aspects of the present disclosure.

[0025] Fig.19 is a view showing a connection state of a main body and a liquid ejection head of a liquid ejection apparatus according to one or more aspects of the present disclosure. DETAILED DESCRIPTION

[0026] The inventors of the present disclosure have found that surface treatment of titanium oxide alone is not sufficient to suppress sedimentation. Therefore, the present disclosure provides an inkjet recording method that enables ejection of white ink containing titanium oxide while suppressing sedimentation.

[0027] First, the present inventors have studied the physical properties of white ink to further suppress and reduce the sedimentation of titanium oxide. As a result, it has been found that in order to effectively reduce the sedimentation of titanium oxide, the white ink needs to have a viscosity of 8 mPa·s or more at 25°C.

[0028] However, it has also been found that, although the viscosity of the white ink of 8 mPa·s or more enhances the effect of suppressing the sedimentation of titanium oxide, the ejection stability of the ink may be insufficient in some cases.

[0029] In view of the above, the present inventors have studied a method of solving the problem by the configuration of a liquid ejecting apparatus ejecting ink, and arrived at a method of providing a temperature adjustment unit configured to heat ink in an inkjet recording head ejecting ink.

[0030] Inkjet recording method

[0031] The inkjet recording method according to the present disclosure is a method for recording an image on a recording medium by ejecting ink described later from an inkjet type recording head.

[0032] There is no particular restriction on the recording medium, and a transparent or colored recording medium can be used. Alternatively, the recording medium can be a micro-absorbent medium (non-absorbent medium) with low absorption capacity for liquid media, such as a resin film. Multi-pass recording can be used, in which ink is applied to a unit area of ​​the recording medium in multiple relative scans of the recording head and the recording medium. In particular, the application of white ink and the application of colored ink to the unit area can be performed separately by different relative scans. This increases the time until the inks contact each other, and mixing may be suppressed. Such a unit area can be defined as any area (such as a single pixel or a single band).

[0033] (1) Liquid injection equipment

[0034] With regard to a liquid ejection device that can be used in an inkjet recording method according to the present disclosure, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the scope of the present disclosure. Not all combinations of the features described in the embodiments are necessary for implementing the present disclosure. The same components are represented by the same figure numerals. The present embodiment will be described using an example of a thermal method for ejecting liquid by generating bubbles using an electrothermal conversion element as an ejection element for ejecting liquid; however, the method is not limited to this. The present disclosure can be applied to a liquid ejection head that employs an ejection method or other ejection method that ejects liquid using a piezoelectric (piezo) element. In addition, the configurations of the pump, pressure regulating unit, etc. described below are also not limited to the configurations described in the embodiments and the accompanying drawings. In the following description, first, the basic configuration of the present disclosure will be described, and then, the features of the present disclosure will be described.

[0035] Liquid injection equipment

[0036] Figure 1A and Figure 1B 1 is a diagram for illustrating a liquid ejecting apparatus, and shows a liquid ejecting head of the liquid ejecting apparatus and its periphery in an enlarged view. Figure 1A and Figure 1B A schematic configuration of the liquid ejecting apparatus 50 of the present embodiment is described. Figure 1A 1 is a perspective view schematically showing a liquid ejecting apparatus including a liquid ejecting head 1. The liquid ejecting apparatus 50 of the present embodiment is a serial inkjet recording apparatus that ejects ink serving as liquid to perform recording on a recording medium P while causing the liquid ejecting head 1 to scan.

[0037] The liquid ejection head 1 is mounted on a carriage 60. The carriage 60 moves back and forth in the main scanning direction (X direction) along the guide shaft 51. The recording medium P is transported in a sub-scanning direction (Y direction) intersecting (orthogonal in this example) the main scanning direction by transport rollers 55, 56, 57 and 58. In the following drawings referenced below, the Z direction is a vertical direction and intersects (orthogonal in this example) an XY plane defined by the X direction and the Y direction. The liquid ejection head 1 is configured to be detachably attached to the carriage 60 by a user.

[0038] The liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 (see Figure 2 ). The specific configuration will be described below, and the ejection unit 3 includes a plurality of ejection ports and an energy generating element (hereinafter referred to as an ejection element) that generates ejection energy for ejecting liquid from each ejection port.

[0039] The liquid ejecting apparatus 50 includes an ink tank 2 as a supply source of ink and an external pump 21. The ink stored in the ink tank 2 is supplied to the circulation unit 54 through the ink supply tube 59 by the driving force of the external pump 21.

[0040] The liquid ejection device 50 forms a predetermined image on the recording medium P by repeating recording scanning (the liquid ejection head 1 mounted on the carriage 60 ejects ink while moving in the main scanning direction) and conveying the recording medium P in the sub-scanning direction. The liquid ejection head 1 of the present embodiment is capable of ejecting four types of ink, namely, black (K), cyan (C), magenta (M) and yellow (Y), and can record a full-color image using the ink. The ink that the liquid ejection head 1 can eject is not limited to the above four types of ink. The present disclosure can also be applied to liquid ejection heads for ejecting other types of ink. That is, the type and amount of ink ejected from the liquid ejection head are not limited.

[0041] The liquid ejection apparatus 50 includes a cap member (not shown) located at a position separated from the conveyance path of the recording medium P in the X direction, which can cover the ejection port surface in which the ejection ports of the liquid ejection head 1 are formed. The cap member covers the ejection port surface of the liquid ejection head 1 during non-recording operation, and is used to prevent the ejection ports from drying, protect the ejection ports, and perform ink suction operation from the ejection ports.

[0042] Figure 1AThe liquid ejection head 1 shown in FIG. 1 is an example of a liquid ejection head 1 including four circulation units 54 for four types of ink. Alternatively, the liquid ejection head 1 may include a circulation unit 54 according to the type of liquid ejected. A plurality of circulation units 54 may be provided for the same type of liquid. That is, the liquid ejection head 1 may include one or more circulation units. Not all four types of ink, but at least one type of ink may be circulated.

[0043] Figure 1B 1 is a block diagram showing a control system of the liquid ejection device 50. A central processing unit (CPU) 103 functions as a controller that controls the operations of components of the liquid ejection device 50 based on a program (e.g., a processing program) stored in a read-only memory (ROM) 101. A random access memory (RAM) 102 is used as, for example, a work area used when the CPU 103 performs processing. The CPU 103 receives image data from a host device 400 outside the liquid ejection device 50, and controls a head driver 1A to control the driving of an ejection element provided in the ejection unit 3. The CPU 103 also controls drivers of various actuators provided in the liquid ejection device 50. For example, the CPU 103 controls a motor driver 105A of a carriage motor 105 for moving the carriage 60 and a motor driver 104A of a conveying motor 104 for conveying a recording medium P. In addition, the CPU 103 controls, for example, a pump driver 500A for driving a circulation pump 500 described later and a pump driver 21A for an external pump 21. Figure 1B The configuration is shown for executing the process of receiving the image data from the host device 400. Alternatively, the process may be executed at the liquid ejection device 50 independently of the data from the host device 400.

[0044] Basic structure of liquid ejecting head

[0045] Figure 2 is an exploded perspective view of the liquid ejecting head 1 of this embodiment. Figure 3A It is along Figure 2 The liquid ejecting head 1 is shown in a cross-sectional view taken along line IIIA-IIIA in FIG. Figure 3A It is a longitudinal sectional view of the entire liquid jet head 1 . Figure 3B yes Figure 3A The following will mainly refer to Figure 2 as well as Figure 3A and Figure 3B and refer appropriately Figure 1A The basic configuration of the liquid ejecting head 1 of the present embodiment will be described.

[0046] like Figure 2As shown in FIG. 1 , the liquid ejecting head 1 includes a circulation unit 54 and an ejecting unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P. The liquid ejecting head 1 of this embodiment is fixed and supported by the carriage 60 using a positioning unit and an electrical contact (not shown) provided on the carriage 60 of the liquid ejecting apparatus 50. The liquid ejecting head 1 is moved along the carriage 60 together with the carriage 60. Figure 1A Ink is ejected while moving in the main scanning direction (X direction) shown to perform recording on the recording medium P.

[0047] The external pump 21 connected to the ink tank 2 serving as an ink supply source is provided with an ink supply tube 59 (see Figure 1A ). The ink supply tube 59 has a liquid connector (not shown) at its front end. When the liquid ejection head 1 is installed in the liquid ejection device 50, the liquid connector provided at the front end of the ink supply tube 59 is airtightly connected to the liquid connector insertion port 53a which serves as an inlet for the liquid and is provided in the head housing 53 of the liquid ejection head 1. Thus, an ink supply path is formed which extends from the ink tank 2 through the external pump 21 to the liquid ejection head 1. Since four types of ink are used in this embodiment, four sets of ink tanks 2, external pumps 21, ink supply tubes 59 and circulation units 54 are provided for each ink, and four ink supply paths for each ink are independently formed. Therefore, the liquid ejection device 50 of this embodiment includes an ink supply system for supplying ink from the ink tank 2 arranged outside the liquid ejection head 1. Note that the liquid ejection device 50 of this embodiment does not include an ink collection system for collecting ink in the liquid ejection head 1 into the ink tank 2. Therefore, the liquid ejection head 1 includes the liquid connector insertion port 53a for connecting the ink supply tube 59 of the ink tank 2, but does not include a connector insertion port for connecting a tube for collecting ink in the liquid ejection head 1 into the ink tank 2. The liquid connector insertion port 53a is provided for each ink.

[0048] exist Figure 3A In the embodiment, a black ink circulation unit 54B, a cyan ink circulation unit 54C, a magenta ink circulation unit 54M, and a yellow ink circulation unit 54Y are provided. The circulation units 54B, 54C, 54M, and 54Y have substantially the same configuration. When there is no particular distinction between the circulation units 54B, 54C, 54M, and 54Y, they are all referred to as "circulation units 54" in the present embodiment.

[0049] exist Figure 2 and Figure 3A In the embodiment, the spray unit 3 includes two spray modules 300, a first support member 4, a second support member 7, an electrical wiring member (electrical wiring tape) 5 and an electrical contact substrate 6. Figure 3BAs shown, each of the ejection modules 300 includes a silicon substrate 310 having a thickness of 0.5 to 1 mm, and a plurality of ejection elements 15 provided on one surface of the silicon substrate 310. The ejection element 15 in this embodiment is an electrothermal conversion element (heater) that generates heat energy as ejection energy for ejecting liquid. Electric power is supplied to each of the ejection elements 15 by electrical wiring formed on the silicon substrate 310 using a thin film deposition technique.

[0050] On the front side of the silicon substrate 310 ( Figure 3B A jet port forming member 320 is provided on the lower surface of the substrate 310. The jet port forming member 320 includes a plurality of pressure chambers 12 corresponding to the plurality of jet elements 15 and a plurality of jet ports 13, through which ink is ejected, and the pressure chambers 12 and the jet ports 13 are formed by photolithography. The silicon substrate 310 also includes a common supply channel 18 and a common collecting channel 19. The silicon substrate 310 also includes supply connecting channels 323 each of which connects the common supply channel 18 and the pressure chamber 12, and collecting connecting channels 324 each of which connects the common collecting channel 19 and the pressure chamber 12. In the present embodiment, one jet module 300 ejects two types of ink. That is, in Figure 3A In the two jet modules 300 shown in the figure, the jet module 300 located on the left side of the figure jets black ink and cyan ink, and the jet module 300 located on the right side of the figure jets magenta ink and yellow ink. This combination is only an example, and any other combination of inks can be used. One jet module can jet one type of ink, or three or more types of ink. The two jet modules 300 do not have to jet the same number of types of ink. One jet module 300 can be provided, or three or more jet modules 300 can be provided. Figure 3A and Figure 3B In the example shown, two ejection opening arrays extending in the Y direction are provided for one ink color. A pressure chamber 12, a common supply channel 18, and a common collection channel 19 are provided for each of the plurality of ejection openings 13 constituting each ejection opening array.

[0051] The silicon substrate 310 has a Figure 3B The ink supply port and the ink collection port (to be described later) are provided on the upper surface of the ink supply channel 48. The ink supply port is used to supply ink from the ink supply channel 48 to the plurality of common supply channels 18. The ink collection port is used to collect ink from the plurality of common collection channels 19 to the ink collection channel 49.

[0052] Here, the ink supply port and the ink collection port refer to openings for supplying and collecting ink during the circulation of the ink in the forward direction described later. Specifically, during the circulation of the ink in the forward direction, the ink is supplied from the ink supply port to the common supply channel 18, and is collected from the common collection channel 19 to the ink collection port. Ink circulation in which the ink flows in the reverse direction may also be performed. In this case, the ink is supplied from the above-mentioned ink collection port to the common collection channel 19, and is collected from the common supply channel 18 to the ink supply port.

[0053] like Figure 3A As shown, the back side of the injection module 300 ( Figure 3A The upper surface of the first support member 4 is bonded and fixed to one surface of the first support member 4 ( Figure 3A the lower surface in the middle).

[0054] The first support member 4 has an ink supply channel 48 and an ink collection channel 49 penetrating from one surface thereof to the other surface. One opening of the ink supply channel 48 is communicated with the above-mentioned ink supply port of the silicon substrate 310, and one opening of the ink collection channel 49 is communicated with the above-mentioned ink collection port of the silicon substrate 310. The ink supply channel 48 and the ink collection channel 49 are independently provided for each type of ink. In this case, the surface of the first support member 4 to which the jetting module 300 is fixed preferably has a flatness of 0.01 mm or less. In the present embodiment, in order to ensure the flatness, the first support member 4 is formed of a ceramic member.

[0055] With opening 7a (see Figure 2 The second support member 7 (through which the injection module 300 passes) is coupled and fixed to one surface of the first support member 4 ( Figure 3A the lower surface in the middle).

[0056] The second supporting member 7 holds the electric wiring member 5 electrically connected to each of the jetting modules 300. The electric wiring member 5 is a member for applying an electric signal for jetting ink to the jetting modules 300. The electrical connection portion between each of the jetting modules 300 and the electric wiring member 5 is sealed with a sealing material (not shown) to protect it from ink corrosion and external impact.

[0057] The electric contact substrate 6 is thermocompression-bonded to the end portion 5a of the electric wiring member 5 using an anisotropic conductive film (not shown). Figure 2 ), so that the electric wiring member 5 and the electric contact substrate 6 are electrically connected together. The electric contact substrate 6 has an external signal input terminal (not shown) for receiving an electric signal from the liquid ejection device 50.

[0058] In addition, the connecting member 8 (see Figure 3A) is arranged between the first support member 4 and the circulation unit 54. For each type of ink, the connecting member 8 has a supply port 88 and a collection port 89. The supply port 88 and the collection port 89 allow the ink supply channel 48 and the ink collection channel 49 of the first support member 4 to communicate with the channel formed in the circulation unit 54. Figure 3A In the embodiment, supply port 88B and collection port 89B are provided for black ink, and supply port 88C and collection port 89C are provided for cyan ink. Supply port 88M and collection port 89M are provided for magenta ink, and supply port 88Y and collection port 89Y are provided for yellow ink.

[0059] The opening at one end of each of the ink supply channel 48 and the ink collection channel 49 of the first support member 4 has a smaller opening area that matches the ink supply port and the ink collection port of the silicon substrate 310, respectively. In contrast, the opening at the other end of each of the ink supply channel 48 and the ink collection channel 49 of the first support member 4 has an expanded shape that is as large as the large opening area of ​​the connecting member 8 formed to match the channel in the circulation unit 54. This configuration can reduce the increase in the channel resistance of the ink collected through the collection channel. However, the shapes of the openings at one end and the other end of the ink supply channel 48 and the ink collection channel 49 are not limited to the above examples.

[0060] In the liquid ejection head 1 having the above-described configuration, the ink supplied to the circulation unit 54 passes through the supply port 88 of the connecting member 8 and the ink supply channel 48 of the first supporting member 4, and flows into the common supply channel 18 through the ink supply port of the ejection module 300. Subsequently, the ink flows from the common supply channel 18 into the pressure chamber 12 through the supply connection channel 323, and a portion of the ink flowing into the pressure chamber 12 is ejected from the ejection port 13 by the driving of the ejection element 15. The remaining ink that is not ejected passes through the pressure chamber 12, the collection connection channel 324, and the common collection channel 19, and flows into the ink collection channel 49 of the first supporting member 4 through the ink collection port. The ink that has flowed into the ink collection channel 49 flows into the circulation unit 54 through the collection port 89 of the connecting member 8, and is thus collected.

[0061] In this case, the end of the common collecting channel 19 preferably extends to the outside of the injection port present at the endmost part of the injection port array relative to the direction in which the injection ports are arranged, and the end of the collecting port 89 is preferably arranged outside the endmost part of the injection port array at a position where the common collecting channel 19 does not have a dead end. Similarly, the end of the common supply channel 18 may extend to the outside of the end of the injection port array, or there may be a supply port arranged outside the injection port array. That is, the end of at least one selected from the common supply channel and the common collecting channel preferably extends to the outside of the end of the injection port array. In addition, at least one or more of the supply port and the collecting port are preferably arranged outside the injection port array.

[0062] A common supply channel 18 and a common collection channel 19 are separately provided for each ink, and the number of common supply channels 18 arranged and the number of common collection channels 19 arranged are determined depending on the number of ejection port arrays for each color. In addition, the supply ports 88 and the collection ports 89 are arranged so that the number of each of the supply ports 88 and the collection ports 89 corresponds to the number of ejection ports of the ejection port array. The area farthest from the collection port and the area farthest from the supply port in the common channel are also located at the position where ink is supplied from two collection ports and two supply ports, and neither the common supply channel 18 nor the common collection channel 19 has a dead end. Therefore, the effect of preventing adhesion in the common channel (which may occur especially when using high-viscosity ink) can be expected.

[0063] Components of a circulation unit

[0064] Figure 4 1 is a schematic external view of a circulation unit 54 for one type of ink applied to the recording device of the present embodiment. In addition to the circulation pump 500, the circulation unit 54 may further include a filter 110, a first pressure regulating unit 120, and a second pressure regulating unit 150. Figure 5 and Figure 6 The respective channels shown connect these components to constitute a circulation path for supplying ink to and collecting ink from ejection modules 300 in liquid ejection head 1 .

[0065] Circulation path in liquid ejection head

[0066] Figure 5 1 is a longitudinal sectional view schematically showing a circulation path of one type of ink (one color of ink) formed in the liquid ejection head 1. In order to more clearly describe the circulation path, the Figure 5 The relative positions of the structures (the first pressure regulating unit 120, the second pressure regulating unit 150, the circulating pump 500, etc.) in the embodiment of the present invention are shown in FIG. Fig.19 The relative positions of the structures in are different. Figure 6 yes Figure 5 A schematic block diagram of the loop path is shown in FIG. Figure 5 and Figure 6 As shown, the first pressure regulating unit 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure regulating unit 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure regulating unit 120 is configured to have a control pressure higher than the control pressure of the second pressure regulating unit 150. In this embodiment, circulation within a certain pressure range in the circulation path is achieved by using two pressure regulating units 120 and 150.

[0067] The liquid ejection head 1 is configured so that ink flows through the pressure chamber 12 (ejection element 15) at a certain flow rate according to the pressure difference between the first pressure adjustment unit 120 and the second pressure adjustment unit 150. Figure 5 and Figure 6 Description is given of the circulation path in the liquid ejection head 1 and the flow of ink in the circulation path. Arrows in the figure indicate the direction in which the ink flows.

[0068] First, the connection state of the components in the liquid ejection head 1 will be described.

[0069] The ink tank 2 ( Figure 6 ) to the external pump 21 for pumping the ink in the liquid ejection head 1 is connected to the circulation unit 54, wherein the ink supply pipe 59 ( Figure 1A ) is located between the external pump and the circulation unit. The filter 110 is provided in the ink channel (inflow channel) located upstream of the circulation unit 54. The ink supply path (inflow channel) located downstream of the filter 110 is connected to the first valve chamber 121 of the first pressure regulating unit 120. The first valve chamber 121 is communicated with the first pressure control chamber 122 via the communication port 191A, and the communication port can be Figure 5 The valve 190A shown opens and closes. The inflow channel is a channel into the liquid ejection head 1 for supplying the liquid in the ink tank 2 arranged outside the liquid ejection head 1 to the pressure chamber 12.

[0070] The first pressure control chamber 122 is connected to the supply channel 130, the bypass channel 160, and the pump outlet channel 180 of the circulation pump 500. The supply channel 130 is connected to the common supply channel 18 via the above-mentioned ink supply port provided in the jetting module 300. The bypass channel 160 is connected to the second valve chamber 151 provided in the second pressure regulating unit 150. The second valve chamber 151 is communicated with the second pressure control chamber 152 via the communication port 191B, which is connected to the common supply channel 18 via the above-mentioned ink supply port provided in the jetting module 300. Figure 5 Valve 190B is shown open and closed. Figure 5 and Figure 6An example is shown in which one end of the bypass channel 160 is connected to the first pressure control chamber 122 of the first pressure regulating unit 120 and the other end of the bypass channel 160 is connected to the second valve chamber 151 of the second pressure regulating unit 150. Alternatively, one end of the bypass channel 160 may be connected to the supply channel 130 and the other end of the bypass channel may be connected to the second valve chamber 151.

[0071] The second pressure control chamber 152 is connected to the collection channel 140. The collection channel 140 is connected to the common collection channel 19 via the above-mentioned ink collection port provided in the jetting module 300. The second pressure control chamber 152 is connected to the circulation pump 500 via the pump inlet channel 170. Figure 5 , the pump inlet passage 170 has an inlet port 170a.

[0072] Next, the flow of ink in the liquid ejection head 1 having the above-described configuration will be described. Figure 6 As shown, the ink contained in the ink tank 2 is pressurized by the external pump 21 provided for the liquid ejecting apparatus 50 to form a positive-pressure ink flow, and is supplied to the circulation unit 54 of the liquid ejecting head 1 .

[0073] The ink supplied to the circulation unit 54 passes through the filter 110 so that impurities such as dust and bubbles are removed, and then flows into the first valve chamber 121 in the first pressure regulating unit 120. When the ink passes through the filter 110, the pressure of the ink decreases due to pressure loss; however, at this stage, the pressure of the ink is positive. When the valve 190A is opened, the ink flowing into the first valve chamber 121 then passes through the communication port 191A and flows into the first pressure control chamber 122. Due to the pressure loss when passing through the communication port 191A, the ink flowing into the first pressure control chamber 122 switches from positive pressure to negative pressure.

[0074] Next, the flow of ink in the circulation path will be described. The circulation pump 500 works to send the ink sucked from the upstream pump inlet channel 170 to the downstream pump outlet channel 180. The drive of the pump causes the ink supplied to the first pressure control chamber 122 to flow into the supply channel 130 and the bypass channel 160 together with the ink sent from the pump outlet channel 180. In the present embodiment, a piezoelectric diaphragm pump (which includes a piezoelectric element attached to a diaphragm as a driving source) is used as a circulation pump capable of conveying liquid, and the details will be described later. The piezoelectric diaphragm pump is a pump that changes the volume in the pump chamber by inputting a driving voltage to the piezoelectric element and pumps liquid by causing two check valves to move alternately due to pressure changes.

[0075] The ink flowing into the supply channel 130 flows into the pressure chamber 12 through the ink supply port of the ejection module 300 and the common supply channel 18, and part of the ink is ejected from the ejection port 13 by the driving (heating) of the ejection element 15. The remaining ink not used for ejection flows through the pressure chamber 12, passes through the common collection channel 19, and then flows into the collection channel 140 connected to the ejection module 300. The ink flowing into the collection channel 140 flows into the second pressure control chamber 152 of the second pressure regulating unit 150.

[0076] On the other hand, the ink flowing into the bypass channel 160 from the first pressure control chamber 122 flows into the second valve chamber 151, then passes through the communication port 191B, and flows into the second pressure control chamber 152. By the driving of the circulation pump 500, the ink flowing into the second pressure control chamber 152 through the bypass channel 160 and the ink collected from the collection channel 140 are sucked into the circulation pump 500 through the pump inlet channel 170. The ink sucked into the circulation pump 500 is sent to the pump outlet channel 180 and flows into the first pressure control chamber 122 again. Next, the ink flowing into the second pressure control chamber 152 from the first pressure control chamber 122 through the supply channel 130 and the jetting module 300 and the ink flowing into the second pressure control chamber 152 through the bypass channel 160 flow into the circulation pump 500. The ink is sent from the circulation pump 500 to the first pressure control chamber 122. Therefore, the ink circulates in the circulation path.

[0077] A temperature adjustment unit (hereinafter also referred to as "temperature adjustment mechanism") (not shown) is provided in the circulation path and driven to heat the ink flowing through the circulation path. This makes it possible to reduce the viscosity of the ink which is highly viscous at normal temperature and ensure ejection stability.

[0078] In this case, the temperature adjustment mechanism may be provided near the ejection port 13, and may be provided in the ejection module 300. The temperature adjustment mechanism may be provided on the recording element substrate. The temperature adjustment mechanism provided on the recording element substrate may be a sub-heater.

[0079] A temperature regulating mechanism may be provided in each of the supply channel and the collection channel. When a temperature regulating mechanism is provided in each of the supply channel and the collection channel, more temperature regulating mechanisms may be provided in the supply channel compared to the collection channel. Alternatively, when the total amount of energy applied to the temperature regulating mechanism provided in the collection channel and the temperature regulating mechanism provided in the supply channel is constant, the energy applied to the temperature regulating mechanism provided in the supply channel may be greater than the energy applied to the temperature regulating mechanism provided in the collection channel. The number of temperature regulating mechanisms provided in the supply channel may be greater than the number of temperature regulating mechanisms provided in the collection channel.

[0080] At least a portion of the liquid jet head 1 may be formed of a material having a thermal conductivity of 1.0 [W / m·K] or less. That is, a material having a thermal conductivity of 1.0 [W / m·K] or less may be contained. In particular, the material may be a resin material. In particular, a portion of the circulation path may be formed of such a material. This improves the heat insulation performance of the circulation path compared to a case where the circulation path is formed of a material having a high thermal conductivity (e.g., a metal); therefore, the circulation path may have improved thermal efficiency.

[0081] The circulation path in this embodiment is defined as a path extending from the first valve chamber 121 through the jet module 300, the second valve chamber 151 and the circulation pump 500 and returning to the first valve chamber 121. Since the liquid jet head 1 has the circulation pump 500 therein in this way, the circulation path can be completed within the liquid jet head 1. Compared with the configuration in which the liquid jet head has a circulation pump outside thereof and the circulation path is completed inside and outside the liquid jet head, this allows the total volume of the circulation path to be smaller. Therefore, the time required to stabilize the ink temperature of the entire system can be reduced to improve productivity.

[0082] Therefore, the total volume of the ink flowing through one circulation path is preferably 30 mL or less, more preferably 15 mL or less, preferably 5 mL or more, particularly 5 mL or more and 15 mL or less.

[0083] As described above, in the present embodiment, the circulation pump 500 enables the liquid to circulate along the circulation path formed in the liquid ejection head 1. This makes it possible to reduce the thickening of the ink and the deposition of the sedimentation components of the coloring material of the ink in the ejection module 300, and thus maintain the fluidity of the ink and the ejection characteristics at the ejection ports in the ejection module 300 in a good state.

[0084] Since the circulation path in this embodiment is completed in the liquid ejection head 1, the length of the circulation path can be significantly shortened compared to the case where ink circulates between the liquid ejection head 1 and the ink tank 2 arranged outside the liquid ejection head 1. Therefore, the circulation of ink can be performed using a compact circulation pump.

[0085] In addition, the channel connecting the liquid ejection head 1 and the ink tank 2 together is only a channel for supplying ink. That is, there is no need for a channel for collecting ink from the liquid ejection head 1 to the ink tank 2. Therefore, it is sufficient to only provide a tube for supplying ink to connect the ink tank 2 to the liquid ejection head 1, and there is no need to provide a tube for collecting ink. This makes the interior of the liquid ejection device 50 simple with a reduced number of tubes, thereby achieving a reduction in the size of the entire device. The reduction in the number of tubes makes it possible to reduce the pressure fluctuation of the ink caused by the oscillation of the tubes accompanying the main scanning of the liquid ejection head 1. The oscillation of the tubes during the main scanning of the liquid ejection head 1 acts as a driving load on the carriage motor that drives the carriage 60. The reduction in the number of tubes makes it possible to reduce the driving load on the carriage motor and simplify the main scanning mechanism including, for example, the carriage motor. In addition, it is not necessary to collect ink from the liquid ejection head to the ink tank, so the size of the external pump 21 can also be reduced. Therefore, according to this embodiment, the size and cost of the liquid ejection device 50 can be reduced.

[0086] Pressure regulating unit

[0087] FIG. 7A to FIG. 7C 2 is a diagram showing an example of a pressure regulating unit. FIG. 7A to FIG. 7C The configuration and operation of the pressure regulating units (the first pressure regulating unit 120 and the second pressure regulating unit 150) housed in the above-mentioned liquid ejection head 1 are described in more detail. The first pressure regulating unit 120 and the second pressure regulating unit 150 have substantially the same configuration. Therefore, the first pressure regulating unit 120 will be described as an example, and for the second pressure regulating unit 150, the reference numerals of the components corresponding to those of the first pressure regulating unit 120 will be written side by side. FIG. 7A to FIG. 7C In the case of the second pressure regulating unit 150 , the first valve chamber 121 described below is read as the second valve chamber 151 , and the first pressure control chamber 122 is read as the second pressure control chamber 152 .

[0088] The first pressure regulating unit 120 includes a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated from each other by a partition 123 provided in the cylindrical housing 125. However, the first valve chamber 121 is communicated with the first pressure control chamber 122 via a communication port 191 formed in the partition 123. The first valve chamber 121 is provided with a valve 190 that switches the communication and disconnection between the first valve chamber 121 and the first pressure control chamber 122 at the communication port 191. The valve 190 is held at a position facing the communication port 191 by a valve spring 200, and can be in close contact with the partition 123 by the urging force of the valve spring 200. When the valve 190 is in close contact with the partition 123, the flow of ink at the communication port 191 is blocked. In order to improve the tightness with the partition 123, the portion of the valve 190 to be in contact with the partition 123 may be formed by an elastic member. The valve shaft 190a is arranged at the center of the valve 190 to pass through the communication port 191. The valve shaft 190a is pressed against the urging force of the valve spring 200 so that the valve 190 is separated from the partition 123, thereby allowing ink to flow through the communication port 191. Hereinafter, the state in which the flow of ink is blocked by the valve 190 at the communication port 191 is referred to as a "closed state", and the state in which the ink can flow through the communication port 191 is referred to as an "open state".

[0089] The opening of the cylindrical housing 125 is closed by the flexible member 230 and the pressure plate 210. The flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition 123 form the first pressure control chamber 122. The pressure plate 210 can be displaced with the displacement of the flexible member 230. The pressure plate 210 and the flexible member 230 can be formed of any material. For example, the pressure plate 210 can be formed of a resin molded part, and the flexible member 230 can be formed of a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0090] The pressure regulating spring 220 (urging member) is arranged between the pressure plate 210 and the partition 123. The urging force of the pressure regulating spring 220 urges the pressure plate 210 and the flexible member 230 in the direction in which the internal volume of the first pressure control chamber 122 increases, such as Fig. 7A shown.

[0091] When the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 are displaced in the direction in which the internal volume of the first pressure control chamber 122 decreases against the pressure of the pressure adjustment spring 220. When the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 contacts the valve shaft 190a of the valve 190. Subsequently, when the internal volume of the first pressure control chamber 122 further decreases, the valve 190 moves together with the valve shaft 190a against the urging force of the valve spring 200 to separate from the partition 123. Therefore, the communication port 191 is in an open state ( Figure 7B status in ).

[0092] In the present embodiment, the connection in the circulation path is set so that the pressure in the first valve chamber 121 is higher than the pressure in the first pressure control chamber 122 when the communication port 191 is in the open state.

[0093] Therefore, when the communication port 191 is in an open state, ink flows from the first valve chamber 121 into the first pressure control chamber 122. The flow of ink causes the flexible member 230 and the pressure plate 210 to shift in a direction in which the internal volume of the first pressure control chamber 122 increases. Therefore, the pressure plate 210 is separated from the valve shaft 190a of the valve 190, and the valve 190 is in close contact with the partition 123 by the urging force of the valve spring 200, and therefore, the communication port 191 is in a closed state ( Figure 7C status in ).

[0094] Therefore, in the first pressure regulating unit 120 of the present embodiment, when the pressure in the first pressure control chamber 122 decreases below a certain pressure (for example, the negative pressure increases), the ink flows from the first valve chamber 121 into the first pressure control chamber 122 through the communication port 191. Therefore, the first pressure regulating unit 120 is configured so that the pressure in the first pressure control chamber 122 does not decrease further. Therefore, the pressure in the first pressure control chamber 122 is controlled within a certain range.

[0095] Next, the pressure in the first pressure control chamber 122 will be described in more detail.

[0096] Assume that as described above, the flexible member 230 and the pressure plate 210 are displaced according to the pressure in the first pressure control chamber 122 so that the pressure plate 210 contacts the valve shaft 190a, thereby allowing the communication port 191 to be in an open state ( Figure 7B At this time, the relationship between the forces acting on the pressure plate 210 is expressed by the following equation 1.

[0097] P2 × S2 + F2 + (P1 - P2) × S1 + F1 = 0 ··· Equation 1

[0098] When equation 1 is rearranged with respect to P2, P2 is expressed as follows.

[0099] P2=-(F1+F2+P1×S1) / (S2-S1) ···Equation 2

[0100] P1: Pressure in the first valve chamber 121 (gauge pressure)

[0101] P2: Pressure in the first pressure control chamber 122 (gauge pressure)

[0102] F1: Spring force of valve spring 200

[0103] F2: Spring force of pressure regulating spring 220

[0104] S1: Pressure area of ​​valve 190

[0105] S2: Pressure area of ​​pressure plate 210

[0106] Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure regulating spring 220 are in the direction of pressing the valve 190 and the pressure plate 210 (in FIG. 7A to FIG. 7C The pressure P1 of the first valve chamber 121 and the pressure P2 of the first pressure control chamber 122 are set so that P1 satisfies the relationship of P1 ≥ P2.

[0107] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is in the open state is determined by Equation 2. When the communication port 191 is in the open state, due to the relationship of P1 ≥ P2, ink flows from the first valve chamber 121 into the first pressure control chamber 122. Therefore, the pressure P2 in the first pressure control chamber 122 does not decrease further, and P2 is maintained at a pressure within a certain range.

[0108] On the other hand, when Figure 7C The relationship between the forces acting on the pressure plate 210 when the pressure plate 210 is shown to be out of contact with the valve shaft 190 a to allow the communication port 191 to be in a closed state is expressed by Equation 3.

[0109] P3 × S3 + F3 = 0 ··· Equation 3

[0110] When equation 3 is rearranged for P3, P3 is expressed as follows.

[0111] P3 = -F3 / S3 ··· Equation 4

[0112] F3: Spring force of the pressure regulating spring 220 when the pressure plate 210 and the valve shaft 190a are out of contact with each other

[0113] P3: Pressure (gauge pressure) of the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are out of contact with each other

[0114] S3: The pressure area of ​​the pressure plate 210 when the pressure plate 210 and the valve shaft 190a are out of contact with each other

[0115] Figure 7C The pressure plate 210 and the flexible member 230 are shown in the figure as being displaced to the left to the limit of displacement. Figure 7C In the state shown in FIG. 1 , the pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure regulating spring 220, and the pressure area S3 of the pressure plate 210 change according to the displacement amount. Specifically, when the pressure plate 210 and the flexible member 230 are in Figure 7B In Figure 7C As the pressure plate 210 moves further to the right, the pressure area S3 of the pressure plate 210 decreases, and the spring force F3 of the pressure regulating spring 220 increases. Therefore, due to the relationship of equation 4, the pressure P3 in the first pressure control chamber 122 decreases. Therefore, due to the relationship of equation 2 and equation 4, when Figure 7B Status to Figure 7C During the state of the first pressure control chamber 122, the pressure in the first pressure control chamber 122 gradually increases (i.e., the negative pressure decreases and approaches the positive pressure). That is, the pressure plate 210 and the flexible member 230 gradually shift to the left from the state in which the communication port 191 is in the open state, and the pressure in the first pressure control chamber 122 gradually increases until the internal volume of the first pressure control chamber 122 finally reaches the displaceable limit. That is, the negative pressure decreases.

[0116] Circulation pump

[0117] Next, we will refer to Fig. 8A and Figure 8B as well as Fig. 9 The configuration and operation of the circulation pump 500 accommodated in the above-described liquid ejection head 1 are described in detail.

[0118] Fig. 8A and Figure 8B is an external perspective view of the circulation pump 500 . Fig. 8A is an external perspective view showing the front side of the circulation pump 500, and Figure 8B 1 is an external perspective view showing the rear side of the circulation pump 500 .

[0119] The housing of the circulation pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing body 505a and a channel connecting member 505b fixed to the outer surface of the housing body 505a by bonding. The housing body 505a and the channel connecting member 505b have pairs of through holes that are connected to each other at two different positions. One pair of through holes in the pair of through holes set at one position forms a pump supply hole 501, and the other pair of through holes set at another position forms a pump discharge hole 502. The pump supply hole 501 is connected to the pump inlet channel 170 connected to the second pressure control chamber 152, and the pump discharge hole 502 is connected to the pump outlet channel 180 connected to the first pressure control chamber 122. The ink supplied from the pump supply hole 501 passes through the pump chamber 503 described later (see Fig. 9 ) and discharged from the pump discharge hole 502.

[0120] Fig. 9 is along Fig. 8A 500 is a cross-sectional view taken along line IX-IX in FIG. 505 , showing a circulation pump 500. A diaphragm 506 is bonded to the inner surface of a pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505. The pump chamber 503 is communicated with a pump supply hole 501 and a pump discharge hole 502 formed in the pump housing 505. A check valve 504a is provided in the middle portion of the pump supply hole 501, and a check valve 504b is provided in the middle portion of the pump discharge hole 502. Specifically, the check valve 504a is arranged so that a portion thereof can move to the left in the figure in a space 512a formed in the middle portion of the pump supply hole 501. The check valve 504b is arranged so that a portion thereof can move to the right in the figure in a space 512b formed in the middle portion of the pump discharge hole 502.

[0121] When the diaphragm 506 is displaced to increase the volume of the pump chamber 503 and the pump chamber 503 is thereby depressurized, the check valve 504a is separated from the opening of the pump supply hole 501 in the space 512a (i.e., moved to the left in the figure). The separation of the check valve 504a from the opening of the pump supply hole 501 in the space 512a leads to an open state in which ink is allowed to flow through the pump supply hole 501. When the diaphragm 506 is displaced to reduce the volume of the pump chamber 503 and the pump chamber 503 is thereby pressurized, the check valve 504a is in close contact with the peripheral wall of the opening of the pump supply hole 501. This leads to a closed state in which the flow of ink in the pump supply hole 501 is blocked.

[0122] In contrast, when the pump chamber 503 is depressurized, the check valve 504b is in close contact with the peripheral wall of the opening of the pump housing 505, resulting in a closed state in which the flow of ink in the pump discharge hole 502 is blocked. When the pump chamber 503 is pressurized, the check valve 504b is separated from the opening of the pump housing 505 to move toward the space 512b (i.e., rightward in the figure), thereby allowing ink to flow through the pump discharge hole 502.

[0123] The check valves 504a and 504b may be formed of any material that can be deformed in response to the pressure in the pump chamber 503, and may each be formed of, for example, an elastic member or elastomer made of ethylene propylene diene monomer (EPDM), or a film or sheet made of polypropylene, etc. However, the material of the check valves 504a and 504b is not limited thereto.

[0124] As described above, the pump chamber 503 is formed by combining the pump housing 505 and the diaphragm 506. Therefore, the pressure in the pump chamber 503 changes by the deformation of the diaphragm 506. For example, when the diaphragm 506 shifts toward the pump housing 505 (shifts to the right in the figure) to reduce the volume of the pump chamber 503, the pressure in the pump chamber 503 increases. This causes the check valve 504b arranged to face the pump discharge hole 502 to open, thereby discharging the ink in the pump chamber 503. At this time, the check valve 504a arranged to face the pump supply hole 501 is in close contact with the peripheral wall of the pump supply hole 501, thereby preventing the ink from flowing back from the pump chamber 503 to the pump supply hole 501.

[0125] In contrast, when the diaphragm 506 is displaced in the direction in which the pump chamber 503 expands, the pressure in the pump chamber 503 decreases. This causes the check valve 504a arranged to face the pump supply hole 501 to open, thereby supplying ink to the pump chamber 503. At this time, the check valve 504b arranged at the pump discharge hole 502 is in close contact with the peripheral wall of the opening formed in the pump housing 505 to close the opening. This prevents the ink from flowing back from the pump discharge hole 502 to the pump chamber 503.

[0126] Therefore, the circulation pump 500 sucks and discharges ink by changing the pressure in the pump chamber 503 by deforming the diaphragm 506. In this case, even if the diaphragm 506 is displaced, the bubbles entering the pump chamber 503 will reduce the pressure change in the pump chamber 503 due to the expansion and contraction of the bubbles, and the amount of liquid sent out is reduced. In view of this, the pump chamber 503 is arranged parallel to gravity so that the bubbles in the pump chamber 503 are gathered to the upper part of the pump chamber 503, and the pump discharge hole 502 is arranged above the center of the pump chamber 503. This makes it possible to improve the discharge performance of the bubbles in the pump and improve the stability of the flow rate.

[0127] Flow of ink in a liquid ejection head

[0128] FIG. 10A to FIG. 10Eis a diagram showing the flow of ink in a liquid ejection head. FIG. 10A to FIG. 10E The circulation of ink in the liquid ejection head 1 is described. In order to more clearly describe the ink circulation path, the FIG. 10A to FIG. 10E The relative positions of the structures (the first pressure regulating unit 120, the second pressure regulating unit 150, the circulating pump 500, etc.) in the embodiment of the present invention are shown in FIG. Fig.19 The relative positions of the structures are different. Fig. 10A The flow of ink in a recording operation for recording by ejecting ink from the ejection port 13 is schematically shown. The arrows in the figure indicate the flow of ink. In the present embodiment, in the recording operation, both the external pump 21 and the circulation pump 500 start driving. The external pump 21 and the circulation pump 500 may be driven regardless of the recording operation. The external pump 21 and the circulation pump 500 do not have to be driven together, but may be driven independently.

[0129] During the recording operation, the circulation pump 500 is in an ON state (driving state) in which the ink flowing out of the first pressure control chamber 122 flows into the supply channel 130 and the bypass channel 160. The ink flowing into the supply channel 130 passes through the ejection module 300, then flows into the collection channel 140, and is then supplied to the second pressure control chamber 152.

[0130] On the other hand, the ink flowing into the bypass channel 160 from the first pressure control chamber 122 passes through the second valve chamber 151 and flows into the second pressure control chamber 152. The ink flowing into the second pressure control chamber 152 passes through the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180, and then flows into the first pressure control chamber 122 again. At this time, based on the relationship of the above equation 2, the control pressure of the first valve chamber 121 is set to be higher than the control pressure of the first pressure control chamber 122. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again through the supply channel 130 without flowing into the first valve chamber 121. The ink flowing into the ejection module 300 passes through the collection channel 140, the second pressure control chamber 152, the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180, and flows into the first pressure control chamber 122 again. Therefore, the ink circulation completed in the liquid ejection head 1 is performed.

[0131] In the above-mentioned ink circulation, the amount (flow rate) of ink circulating in the jet module 300 is determined by the difference in control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. The pressure difference is set to provide a certain circulation amount so that the ink near the jet port in the jet module 300 can be prevented from thickening. Ink corresponding to the amount of ink consumed by recording is supplied from the ink tank 2 to the first pressure control chamber 122 through the filter 110 and the first valve chamber 121. The mechanism for supplying the consumed ink will be described in detail. Since the ink is reduced from the inside of the circulation path by the amount corresponding to the ink consumed by recording, the pressure in the first pressure control chamber 122 is reduced, and therefore, the ink in the first pressure control chamber 122 is also reduced. As the ink in the first pressure control chamber 122 is reduced, the internal volume of the first pressure control chamber 122 is reduced. The reduction in the internal volume of the first pressure control chamber 122 causes the communication port 191A to be in an open state, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. The supplied ink loses pressure when it flows from the first valve chamber 121 into the first pressure control chamber 122 through the communication port 191A. This causes the ink at positive pressure to switch to ink at negative pressure. The flow of ink from the first valve chamber 121 into the first pressure control chamber 122 increases the pressure in the first pressure control chamber 122, so that the internal volume of the first pressure control chamber 122 is increased, thereby causing the communication port 191A to be in a closed state. Therefore, the communication port 191A repeats the open state and the closed state according to the consumption of the ink. If the ink is not consumed, the communication port 191A remains in the closed state.

[0132] Fig. 10B The flow of ink immediately after the recording operation ends and the circulation pump 500 is in the OFF state (stop state) is schematically shown. When the recording operation ends and the circulation pump 500 is turned off, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both the controlled pressures during the recording operation. This causes the ink to flow according to the difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 as shown in FIG. Fig. 10B Specifically, the flow of ink supplied from the first pressure control chamber 122 to the jetting module 300 through the supply channel 130 and then reaching the second pressure control chamber 152 through the collecting channel 140 is continuously generated. The flow of ink reaching the second pressure control chamber 152 from the first pressure control chamber 122 through the bypass channel 160 and the second valve chamber 151 is also continuously generated.

[0133] The amount of ink corresponding to the amount of ink moved from the first pressure control chamber 122 to the second pressure control chamber 152 by the ink flow is supplied from the ink tank 2 to the first pressure control chamber 122 through the filter 110 and the first valve chamber 121. Therefore, the content inside the first pressure control chamber 122 is kept constant. When the content of the first pressure control chamber 122 is constant, the spring force F1 of the valve spring 200, the spring force F2 of the pressure adjustment spring 220, the pressure area S1 of the valve 190, and the pressure area S2 of the pressure plate 210 are kept constant according to the relationship of the above equation 2. Therefore, the pressure in the first pressure control chamber 122 is determined according to the change of the pressure (gauge pressure) P1 in the first valve chamber 121. Therefore, if the pressure P1 in the first valve chamber 121 does not change, the pressure P2 in the first pressure control chamber 122 is kept at the same pressure as the control pressure during the recording operation.

[0134] On the other hand, the pressure in the second pressure control chamber 152 changes with time according to the change in the content caused by the inflow of ink from the first pressure control chamber 122. Fig. 10B The state starts from the state in the middle until the communication port 191 is in the closed state so that the second valve chamber 151 and the second pressure control chamber 152 are in the disconnected state (such as Fig. 10C During this period of time (as shown in FIG. 2 ), the pressure in the second pressure control chamber 152 changes according to Equation 2. Subsequently, the pressure plate 210 and the valve shaft 190a are in a non-contact state to allow the communication port 191 to be in a closed state. Subsequently, ink flows from the collection channel 140 into the second pressure control chamber 152, as shown in FIG. Fig. 10D This inflow of ink displaces the pressure plate 210 and the flexible member 230, and the pressure in the second pressure control chamber 152 changes according to Equation 4, ie, increases, until the internal volume of the second pressure control chamber 152 becomes maximum.

[0135] exist Fig. 10C In the state, there is no ink flow from the first pressure control chamber 122 to the second pressure control chamber 152 through the bypass channel 160 and the second valve chamber 151. Therefore, only the ink in the first pressure control chamber 122 flows to the ejection module 300 through the supply channel 130 and then to the second pressure control chamber 152 through the collection channel 140.

[0136] As described above, according to the difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 , movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs.

[0137] Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of the ink stops.

[0138] When the pressure in the second pressure control chamber 152 is equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to Fig. 10D When the second pressure control chamber 152 is Fig. 10D When expanded as shown, a reservoir in which ink can be stored is formed in the second pressure control chamber 152. Fig. 10D The time of the state in depends on the shape and size of the channel and the properties of the ink, but is about 1 to 2 minutes. Fig. 10D When the circulation pump 500 is driven in the state where the ink is stored in the reservoir, the ink in the reservoir is supplied to the first pressure control chamber 122 through the circulation pump 500. Therefore, the amount of ink in the first pressure control chamber 122 increases, and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction, as shown in FIG. Fig. 10E When the circulation pump 500 continues to be driven, the state in the circulation path changes, as shown in FIG. Fig. 10A shown.

[0139] Although it has been described Fig. 10A As an example during recording operation, however, as described above, ink can be circulated without recording operation. FIG. 10A to FIG. 10E The flow of ink shown occurs in response to the driving and stopping of the circulation pump 500 .

[0140] In the present embodiment, as described above, when the circulation pump 500 is driven to circulate the ink, the communication port 191B of the second pressure regulating unit 150 is in an open state, and when the ink circulation stops, the communication port is in a closed state. However, the configuration is not limited to the above example. The control pressure may be set so that the communication port 191B of the second pressure regulating unit 150 is in a closed state even when the circulation pump 500 is driven to circulate the ink. This will be described in detail below together with the function of the bypass channel 160.

[0141] A bypass channel 160 is provided to connect the first pressure regulating unit 120 and the second pressure regulating unit 150 together, for example, to prevent the negative pressure generated in the circulation path from affecting the jetting module 300 when the negative pressure is higher than a predetermined value. The bypass channel 160 is also provided to supply ink to the pressure chamber 12 from both the supply channel 130 and the collection channel 140.

[0142] First, an example in which the bypass channel 160 is arranged to prevent a negative pressure higher than a predetermined value from affecting the jetting module 300 will be described. For example, the properties of the ink (e.g., viscosity) may change by a change in the ambient temperature. The change in the viscosity of the ink causes a change in the pressure loss in the circulation path. For example, a decrease in the viscosity of the ink reduces the pressure loss in the circulation path. Therefore, the flow rate of the circulation pump 500 driven at a constant driving amount increases, resulting in an increase in the flow rate of the jetting module 300. In contrast, the jetting module 300 is maintained at a constant temperature by a temperature adjustment mechanism (not shown), and therefore the viscosity of the ink in the jetting module 300 remains constant even if the ambient temperature changes. Since the viscosity of the ink in the jetting module 300 does not change, and the flow rate of the ink flowing in the jetting module 300 increases, the negative pressure in the jetting module 300 increases due to the flow resistance. When the negative pressure in the jetting module 300 is higher than a predetermined value, the meniscus at the jetting port 13 may be destroyed, and external air may be attracted into the circulation path, which may hinder normal jetting. Even if the meniscus is not broken, the negative pressure in the pressure chamber 12 is higher than the predetermined pressure, which may affect the ejection.

[0143] Therefore, a bypass channel 160 is formed in the circulation path. When the bypass channel 160 is provided and the negative pressure is higher than a predetermined value, the ink also flows through the bypass channel 160, and thus the pressure in the jetting module 300 can be kept constant. Therefore, for example, the control pressure of the second pressure regulating unit 150 can be set so that the communication port 191B is kept in a closed state even during the operation of the circulation pump 500. The control pressure of the second pressure regulating unit 150 can be set so that the communication port 191B of the second pressure regulating unit 150 is in an open state when the negative pressure is higher than a predetermined value. That is, as long as the meniscus is not destroyed or a predetermined negative pressure is maintained even if the flow rate of the pump changes due to a viscosity change caused by, for example, an environmental change, the communication port 191B can be in a closed state when the circulation pump 500 is driven.

[0144] Next, an example will be described in which the bypass channel 160 is provided to supply ink to the pressure chamber 12 from both the supply channel 130 and the collection channel 140. Pressure fluctuations in the circulation path may also be caused by an ejection operation using the ejection element 15. This is because the ejection operation causes a force that attracts ink to the pressure chamber 12.

[0145] The following will describe the case where ink is supplied from both the supply channel 130 and the collection channel 140 to the pressure chamber 12 when high-load recording is continuously performed. Although the definition of the load depends on various conditions, here, the load is set to 100% in a state where 4-pl ink droplets are recorded on a 1200 dpi grid at a time. High-load recording is recording at a load of, for example, 100%.

[0146] Continuous high-load recording reduces the amount of ink flowing from the pressure chamber 12 through the collecting channel 140 into the second pressure control chamber 152. At the same time, since the circulation pump 500 allows the ink to flow in a constant amount, the inflow and outflow in the second pressure control chamber 152 are unbalanced, the ink in the second pressure control chamber 152 is reduced, and the negative pressure in the second pressure control chamber 152 increases, thereby contracting the second pressure control chamber 152. The increase in the negative pressure in the second pressure control chamber 152 increases the amount of ink flowing into the second pressure control chamber 152 through the bypass channel 160, and the second pressure control chamber 152 is stabilized while the outflow and inflow are balanced. Therefore, the negative pressure in the second pressure control chamber 152 increases in response to the load. As described above, in the configuration in which the communication port 191B is in a closed state when the circulation pump 500 is driven, the communication port 191B becomes in an open state according to the load, so that the ink flows from the bypass channel 160 into the second pressure control chamber 152.

[0147] When high-load recording is further continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the collecting channel 140 decreases, while the amount of ink flowing into the second pressure control chamber 152 through the bypass channel 160 via the communication port 191B increases. When this state continues further, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the collecting channel 140 decreases to zero, and all the ink flowing to the circulation pump 500 comes from the communication port 191B. When this state continues still further, the ink flows back into the pressure chamber 12 from the second pressure control chamber 152 through the collecting channel 140. In this state, the ink flowing out of the second pressure control chamber 152 into the circulation pump 500 and the ink flowing into the pressure chamber 12 flow into the second pressure control chamber 152 through the bypass channel 160 via the communication port 191B. In this case, the pressure chamber 12 is filled with the ink from the supply channel 130 and the ink from the collecting channel 140, and then the ink is ejected.

[0148] The backflow of ink occurring at a high recording load is a phenomenon caused by the presence of the bypass channel 160. An example has been described above in which the communication port 191B in the second pressure regulating unit 150 becomes in an open state according to the backflow of ink. The backflow of ink may occur in a state in which the communication port 191B in the second pressure regulating unit 150 is in an open state. Even in a configuration without the second pressure regulating unit 150, the presence of the bypass channel 160 may cause the backflow of ink.

[0149] Structure of the injection unit

[0150] Fig.11A and Fig. 11B : is a schematic diagram of a circulation path of ink of one color in the ejection unit 3 of the present embodiment. Fig.11A1 is an exploded perspective view of the injection unit 3 as viewed from the first support member 4 . Fig. 11B is an exploded perspective view of the spray unit 3 viewed from the spray module 300 . Fig.11A and Fig. 11B The arrows indicated as "in" and "out" in the figure represent the flow of ink. Although the flow of ink is shown for only one color, this also applies to other colors. Fig.11A and Fig. 11B The second supporting member 7 and the wiring member 5 are omitted in FIG. 1 , and are also omitted in the following description of the configuration of the injection unit 3 . Fig.11A The first support member 4 is along Figure 3A The ejection module 300 includes an ejection element substrate 340 and an opening plate 330 . Fig.12 is a view showing the opening plate 330 . Fig.13 is a view showing the ejection element substrate 340 .

[0151] Ink is supplied from the circulation unit 54 to the ejection unit 3 via the coupling member 8 (see Figure 3A ). The ink path after the ink passes through the connecting member 8 until the ink returns to the connecting member 8 will be described. In the following drawings, the connecting member 8 is omitted.

[0152] The jetting module 300 includes a jetting element substrate 340 and an opening plate 330 constituting a silicon substrate 310, and also includes a jetting port forming member 320. The jetting element substrate 340, the opening plate 330, and the jetting port forming member 320 are stacked and combined together so that the passage of ink is communicated to form the jetting module 300, and the jetting module 300 is supported by the first supporting member 4. The jetting module 300 is supported by the first supporting member 4 to form the jetting unit 3. The jetting element substrate 340 includes the jetting port forming member 320, and the jetting port forming member 320 includes a plurality of jetting port arrays (a plurality of jetting ports 13 are arranged therein) and ejects a portion of the ink supplied through the ink passage in the jetting module 300 from the jetting ports 13. The un-ejected ink is collected through the ink passage in the jetting module 300.

[0153] like Fig.11A and Fig. 11B as well as Fig.12 As shown, the opening plate 330 includes a plurality of arranged ink supply ports 311 and a plurality of arranged ink collection ports 312. Fig.13 as well as FIG. 14A to FIG. 14CAs shown, the ejection element substrate 340 includes a plurality of arranged supply connection channels 323 and a plurality of arranged collection connection channels 324. The ejection element substrate 340 also includes a common supply channel 18 each communicating with the plurality of supply connection channels 323 and a common collection channel 19 each communicating with the plurality of collection connection channels 324. By making the ink supply channel 48 and the ink collection channel 49 (see the attached figure) provided in the first support member 4 Figure 3A ) communicates with a channel provided in the ejection module 300 to form an ink channel in the ejection unit 3. The support member supply port 211 is a cross-sectional opening forming the ink supply channel 48, and the support member collection port 212 is a cross-sectional opening forming the ink collection channel 49.

[0154] The ink to be supplied to the ejection unit 3 passes through the circulation unit 54 (see the attached drawing). Figure 3A ) is supplied to the ink supply channel 48 in the first support member 4 (see the attached Figure 3A The ink flowing through the support member supply port 211 in the ink supply channel 48 passes through the ink supply channel 48 (see Figure 3A ) and the ink supply port 311 of the opening plate 330 are supplied to the common supply channel 18 in the ejection element substrate 340, and enter the supply connection channel 323. This is the supply channel. Subsequently, the ink passes through the pressure chamber 12 of the ejection port forming member 320 (see the attached Figure 3B ) and flows into the collecting connection channel 324 of the collecting channel. The details of the flow of ink in the pressure chamber 12 will be described later.

[0155] In the collection channel, the ink that has entered the collection connection channel 324 flows into the common collection channel 19. Subsequently, the ink flows from the common collection channel 19 to the ink collection channel 49 in the first support member 4 through the ink collection port 312 of the opening plate 330, and is collected to the circulation unit 54 through the support member collection port 212.

[0156] The area of ​​the opening plate 330 having neither the ink supply port 311 nor the ink collection port 312 corresponds to the area for separating the support member supply port 211 and the support member collection port 212 in the first support member 4. The first support member 4 also has no openings in the said area. When the jetting module 300 and the first support member 4 are combined together, these areas are used as the combining area.

[0157] exist Fig.12 In the opening plate 330, multiple arrays of openings arranged in the X direction are arranged in the Y direction, and the supply (inlet) openings and the collection (outlet) openings are alternately arranged in the Y direction to deviate by half a pitch in the X direction. Fig.13, the ejection element substrate 340 includes a common supply channel 18 each connected to a plurality of supply connection channels 323 arranged in the Y direction and a common collection channel 19 each connected to a plurality of collection connection channels 324 arranged in the Y direction. The common supply channel 18 and the common collection channel 19 are arranged alternately in the X direction. For each type of ink, the common supply channel 18 and the common collection channel 19 are separated, and the number of arranged common supply channels 18 and the number of arranged common collection channels 19 are determined according to the number of ejection port arrays for each color. The supply connection channels 323 and the collection connection channels 324 are also arranged corresponding to the ejection ports 13 in terms of quantity. The supply connection channels 323 and the collection connection channels 324 do not necessarily have to correspond one to one with the ejection ports 13. One supply connection channel 323 and one collection connection channel 324 may be provided for a plurality of ejection ports 13.

[0158] The opening plate 330 and the ejection element substrate 340 are stacked and combined together so that the passage of ink communicates to form the ejection module 300, and are supported by the first support member 4. Thus, the ink passage including the above-mentioned supply passage and collection passage is formed.

[0159] FIG. 14A to FIG. 14C 3 is a cross-sectional view showing the ink flow in different parts of the ejection unit 3 . Fig.14A is along Fig.11A 1 is a sectional view taken along the line XIVA-XIVA of , and shows a cross section of a portion in which the ink supply channel 48 and the ink supply port 311 in the ejection unit 3 communicate with each other. Fig. 14B is along Fig.11A 1 is a sectional view taken along line XIVB-XIVB of FIG. 1 and shows a cross section of a portion in which the ink collection channel 49 and the ink collection port 312 in the ejection unit 3 communicate with each other. Fig. 14C is along Fig.11A 4 is a sectional view taken along line XIVC-XIVC of , and shows a cross section of a portion in which the ink supply port 311 and the ink collection port 312 are not communicated with the channel in the first supporting member 4 .

[0160] In the supply channel for supplying ink, ink is supplied from a portion where the ink supply channel 48 of the first supporting member 4 and the ink supply port 311 of the opening plate 330 overlap and communicate with each other, as shown in FIG. Fig.14A In the collection channel for collecting ink, ink is collected from the portion where the ink collection channel 49 of the first support member 4 overlaps and communicates with the ink collection port 312 of the opening plate 330, as shown in FIG. Fig. 14B The injection unit 3 also has an area where no opening is provided in the opening plate 330, as shown in FIG. Fig. 14CIn such an area, ink is neither supplied nor collected between the ejection element substrate 340 and the first support member 4. Fig.14A Ink is supplied in the area where the ink supply port 311 is provided as shown, and in Fig. 14B Ink is collected in the area where the ink collection port 312 is provided as shown. The present embodiment has been described using an example in which the opening plate 330 is employed. Alternatively, the opening plate 330 may be omitted. For example, channels corresponding to the ink supply channel 48 and the ink collection channel 49 may be formed in the first support member 4, and the ejection element substrate 340 may be coupled to the first support member 4.

[0161] Fig.15A and Fig. 15B 1 is a cross-sectional view showing the vicinity of the injection port 13 in the injection module 300 . Fig.16A and Fig. 16B is a cross-sectional view of an injection module of a comparative example, in which the common supply channel 18 and the common collection channel 19 are expanded in the X direction. Fig.15A and Fig. 15B as well as Fig.16A and Fig. 16B The thick arrows shown in the common supply channel 18 and the common collecting channel 19 in FIG. 3 represent the oscillation of the ink in the configuration using the serial liquid ejecting device 50. The ink supplied to the pressure chamber 12 through the common supply channel 18 and the supply connection channel 323 is ejected from the ejection port 13 by the driving of the ejection element 15. When the ejection element 15 is not driven, the ink is collected from the pressure chamber 12 to the common collecting channel 19 through the collecting connection channel 324 serving as a collecting channel.

[0162] When such a circulating ink ejection is performed in a configuration using the serial liquid ejection device 50, the ejection of the ink is not insignificantly affected by the oscillation of the ink in the ink channel due to the main scanning of the liquid ejection head 1. Specifically, the influence of the oscillation of the ink in the ink channel may cause a difference in the amount of the ejected ink or a deviation in the ejection direction. In the case where the common supply channel 18 and the common collection channel 19 have a wide cross-sectional shape in the X direction which is the main scanning direction, as shown in FIG. Fig.16A and Fig. 16B As shown, the ink in the common supply channel 18 and the common collecting channel 19 is easily affected by the inertial force in the main scanning direction, and a large oscillation occurs in the ink. Therefore, the oscillation of the ink may affect the ejection of the ink from the ejection port 13. In addition, the expansion of the common supply channel 18 and the common collecting channel 19 in the X direction may increase the distance between the colors, and the printing efficiency may be reduced.

[0163] In view of the above situation, the common supply channel 18 and the common collection channel 19 of this embodiment are Fig.15A and Fig. 15BIn the cross section shown, it extends along the Y direction, and also extends along the Z direction perpendicular to the X direction which is the main scanning direction. This construction makes it possible to reduce the width of the common supply channel 18 and the common collection channel 19 in the main scanning direction. The reduction in the width of the common supply channel 18 and the common collection channel 19 in the main scanning direction reduces the oscillation of the ink caused by the inertial force (thick arrow in the figure) acting on the ink in the common supply channel 18 and the common collection channel 19 in the direction opposite to the main scanning direction during the main scanning. This can reduce the influence of the oscillation of the ink on the ejection of the ink. The extension of the common supply channel 18 and the common collection channel 19 along the Z direction increases the cross-sectional area to reduce the channel pressure loss.

[0164] Although the oscillation of the ink in the common supply channel 18 and the common collecting channel 19 during the main scanning is reduced by reducing the width of the common supply channel 18 and the common collecting channel 19 in the main scanning direction as described above, the oscillation is not completely eliminated. In view of the above, in order to prevent the ejection difference between various types of inks (even the reduced oscillation may cause the ejection difference), the present embodiment is configured so that the common supply channel 18 and the common collecting channel 19 are arranged to overlap in the X direction.

[0165] As described above, in the present embodiment, the supply connection channel 323 and the collection connection channel 324 are arranged to correspond to the ejection port 13, and the supply connection channel 323 and the collection connection channel 324 are arranged side by side in the X direction, with the ejection port 13 located therebetween. Therefore, if there is a portion where the common supply channel 18 and the common collection channel 19 do not overlap in the X direction, and the corresponding relationship between the supply connection channel 323 and the collection connection channel 324 in the X direction is destroyed, the flow and ejection of the ink in the pressure chamber 12 in the X direction are affected. Together with the influence of the oscillation of the ink, therefore, the ejection of the ink from each ejection port may be affected.

[0166] Therefore, when the common supply channel 18 and the common collecting channel 19 are arranged to overlap in the X direction, the oscillation of the ink in the common supply channel 18 and the common collecting channel 19 during the main scanning becomes substantially equal at any position in the Y direction of the array ejection ports 13. Therefore, the pressure difference between the common supply channel 18 and the common collecting channel 19 in the pressure chamber 12 does not vary significantly, and stable ejection can be performed.

[0167] In some liquid ejection heads, a channel for supplying ink to the liquid ejection head and a channel for collecting ink are the same channel. In contrast, in the present embodiment, a common supply channel 18 and a common collecting channel 19 are different channels. The supply connection channel 323 and the pressure chamber 12 are communicated with each other, the pressure chamber 12 and the collecting connection channel 324 are communicated with each other, and ink is ejected from the ejection port 13 of the pressure chamber 12. That is, the pressure chamber 12 connecting the supply connection channel 323 and the collecting connection channel 324 includes the ejection port 13. Therefore, an ink flow from the supply connection channel 323 to the collecting connection channel 324 occurs in the pressure chamber 12, and the ink in the pressure chamber 12 circulates efficiently. The efficient circulation of ink in the pressure chamber 12 enables the ink in the pressure chamber 12, which is susceptible to the evaporation of ink from the ejection port 13, to remain fresh.

[0168] If it is necessary to eject at a high flow rate, the communication of the two channels (i.e., the common supply channel 18 and the common collection channel 19) with the pressure chamber 12 enables ink to be supplied through the two channels. That is, compared with a configuration in which only one channel is used for supply and collection of ink, the configuration of this embodiment has the advantage of being able to not only efficiently circulate but also eject at a high flow rate.

[0169] The common supply channel 18 and the common collection channel 19 may be arranged close to each other in the X direction to reduce the influence of oscillation of the ink. The interval between the common supply channel 18 and the common collection channel 19 is preferably 75 μm to 100 μm.

[0170] Fig.17 3 is a view showing an ejection element substrate 340 of a comparative example. Fig.17 , the supply connection channel 323 and the collection connection channel 324 are omitted. Since the ink flowing into the common collection channel 19 is subjected to the thermal energy of the ejection element 15 in the pressure chamber 12, the temperature of the ink is relatively higher than the temperature of the ink in the common supply channel 18. In the comparative example, the ejection element substrate 340 has a portion in the X direction where only the common collection channel 19 exists, such as Fig.17 In this case, the temperature locally rises in the portion, and temperature non-uniformity occurs in the injection module 300, which may affect the injection.

[0171] The temperature of the ink flowing in the common supply channel 18 is relatively lower than the temperature of the ink in the common collection channel 19. Therefore, when the common supply channel 18 and the common collection channel 19 are adjacent to each other, in the vicinity of the channel, the temperature can be partially offset by the common supply channel 18 and the common collection channel 19 to prevent the temperature from rising. Therefore, the common supply channel 18 and the common collection channel 19 may have substantially the same length, may exist at a position overlapping in the X direction, and may be adjacent to each other.

[0172] Fig.18A and Fig.18B 1 is a view showing a channel configuration of a liquid ejection head 1 for three colors of ink, namely, cyan (C), magenta (M), and yellow (Y). The liquid ejection head 1 includes circulation channels for the respective types of ink, such as Fig.18A The pressure chambers 12 are arranged along the X direction, which is the main scanning direction of the liquid ejecting head 1. Fig.18B As shown, the common supply channel 18 and the common collecting channel 19 are arranged along the ejection port array in which the ejection ports 13 are arranged, and the common supply channel 18 and the common collecting channel 19 extend along the Y direction, wherein the corresponding ejection port array is located therebetween.

[0173] Connection between the main body and the liquid ejection head

[0174] Fig.19 : is a schematic diagram showing in more detail the connection state of the ink tank 2 and the external pump 21 provided in the main body of the liquid ejection device 50 of the present embodiment with the liquid ejection head 1, and the arrangement of the circulation pump, etc. The liquid ejection device 50 of the present embodiment has a structure that only the liquid ejection head 1 can be easily replaced when a malfunction occurs in the liquid ejection head 1. Specifically, the liquid ejection device 50 includes a liquid connection unit 700, with which the connection and separation between the ink supply tube 59 connected to the external pump 21 and the liquid ejection head 1 can be easily performed. Therefore, only the liquid ejection head 1 can be easily attached to and detached from the liquid ejection device 50.

[0175] The liquid connection unit 700 includes a liquid connector insertion port 53a provided in a protruding manner on the head housing 53 of the liquid ejection head 1 and a cylindrical liquid connector 59a into which the liquid connector insertion port 53a can be inserted. Fig.19 The liquid connector insertion port 53a is connected to an ink supply channel (inflow channel) formed in the liquid ejection head 1 so as to provide a continuous liquid flow, and is connected to the first pressure regulating unit 120 through the above-mentioned filter 110. The liquid connector 59a is provided at the front end of the ink supply tube 59 connected to the external pump 21, which pressurizes the ink in the ink tank 2 and supplies it to the liquid ejection head 1.

[0176] As mentioned above, Fig.19The liquid ejection head 1 shown in the figure is configured so that the attachment / detachment and replacement of the liquid ejection head 1 can be easily performed using the liquid connection unit 700. However, if the sealing between the liquid connector insertion port 53a and the liquid connector 59a deteriorates, the ink pressurized and supplied by the external pump 21 may leak out from the liquid connection unit 700. If the leaked ink adheres to the circulation pump 500, etc., a malfunction may occur in the electrical system. In view of this, the circulation pump and other components in the present embodiment are arranged as described below.

[0177] Arrangement of circulation pumps, etc.

[0178] In this embodiment, in order to prevent the ink leaking from the liquid connection unit 700 from adhering to the circulation pump 500, the circulation pump 500 is arranged above the liquid connection unit 700 in the gravity direction. Fig.19 As shown. That is, the circulation pump 500 is arranged above the liquid connector insertion port 53a used as the liquid inlet of the liquid jet head 1 in the direction of gravity. In addition, the circulation pump 500 is arranged at a position where the circulation pump 500 does not contact the components constituting the liquid connection unit 700. With this configuration, even if ink leaks out from the liquid connection unit 700, the ink can flow in the horizontal direction (the direction in which the liquid connector 59a is opened) or in the vertical downward direction, thereby preventing the ink from reaching the circulation pump 500 arranged in the vertical upward direction. In addition, since the circulation pump 500 is arranged at a position away from the liquid connection unit 700, the possibility of ink traveling through these components to reach the circulation pump 500 is also reduced.

[0179] In addition, the electrical connection portion 515 is arranged above the liquid connection unit 700 in the gravity direction, and the electrical connection portion electrically connects the circulation pump 500 to the electrical contact substrate 6 through the flexible wiring member 514 located between the circulation pump and the electrical contact substrate. This makes it possible to reduce the possibility of electrical problems caused by ink from the liquid connection unit 700.

[0180] In the present embodiment, the wall portion 53 b of the head case 53 is provided. Therefore, even if ink is ejected from the opening 59 b of the liquid connection unit 700 , the ink can be blocked to reduce the possibility that the ink reaches the circulation pump 500 and the electrical connection portion 515 .

[0181] (2) Ink

[0182] Below, the ink that can be used in the inkjet recording method according to the present disclosure will be described in detail with reference to exemplary embodiments. In the present disclosure, when the compound is a salt, this salt is dissociated into ions in the ink; however, for convenience, the ink is described as "containing a salt". Titanium oxide and titanium oxide particles may be referred to as "pigment". Aqueous ink for inkjet may be referred to as "ink". Unless otherwise specified, physical property values ​​are values ​​at room temperature (25°C). In the case of recording an image with white ink, the white ink can be used for background color processing for color ink. In this case, the image can be recorded by applying color inks (e.g., black, cyan, magenta, and yellow inks) in a manner that overlaps at least a portion of an area to which white ink has been applied. Background color processing can also be applied to reverse color printing, in which white ink is applied in a manner that overlaps at least a portion of an area to which color ink has been applied.

[0183] Water-based ink and method for producing water-based ink

[0184] The ink according to the present disclosure is a white ink containing titanium oxide. The ink can be a white ink because titanium oxide is a white pigment. The ink according to the present disclosure does not have to be a so-called "curable ink". Therefore, the ink according to the present disclosure does not necessarily contain a compound such as a polymerizable monomer that can be polymerized by applying external energy such as heat or light. The components contained in the ink according to the present disclosure, the physical properties of the ink, the manufacturing method, etc. will be described in detail below.

[0185] Coloring Materials

[0186] The ink contains titanium oxide as a coloring material (pigment). Titanium oxide can be titanium oxide particles surface-treated with a specific inorganic oxide. That is, the ink can contain titanium oxide particles, which are titanium oxide particles whose surfaces are covered with a specific inorganic oxide. Based on the total mass of the ink, the titanium oxide particle content (mass %) in the ink is preferably greater than 0.10 mass % and less than 20.00 mass %. Based on the total mass of the ink, the titanium oxide particle content (mass %) in the ink is more preferably greater than 1.00 mass % and less than 20.00 mass %. Based on the total mass of the ink, the titanium oxide particle content (mass %) in the ink is particularly preferably greater than 1.00 mass % and less than 15.00 mass %.

[0187] Titanium oxide is a white pigment and has three crystal forms, namely, rutile, anatase and brookite. Among them, rutile titanium oxide can be used. Industrial methods for manufacturing titanium oxide include sulfuric acid method and chlorination method. Titanium oxide used in the present disclosure can be manufactured by any manufacturing method.

[0188] The 50% cumulative particle size based on volume of the titanium oxide particles (hereinafter also referred to as "average particle size") is preferably 200 nm or more and 500 nm or less. In particular, the 50% cumulative particle size based on volume of the titanium oxide particles is more preferably 200 nm or more and 400 nm or less.

[0189] The 50% cumulative particle size (D 50 ) is the diameter of the particles corresponding to 50% when the total volume of the measured particles is integrated from the small particle size side in the particle size accumulation curve. D of titanium oxide particles 50 The measurement can be performed under the following conditions: for example, SetZero: 30 seconds, number of measurements: three times, measurement time: 180 seconds, shape: non-spherical, refractive index: 2.60. The particle size distribution measurement device used can be a particle size analyzer using a dynamic light scattering method. Of course, the measurement conditions and the like are not limited to those described above.

[0190] The titanium oxide used can be surface-treated with aluminum oxide and silicon dioxide. This surface treatment is expected to suppress photocatalytic activity and improve dispersibility. In this specification, "alumina" is a general term for aluminum oxides (e.g., aluminum oxide). In this specification, "silica" is a general term for silicon dioxide and substances composed of silicon dioxide. Most of the aluminum oxide and silicon dioxide covering the titanium oxide exist in the form of aluminum oxide and silicon dioxide. In this specification, "alumina" is a general term for aluminum oxides (e.g., aluminum oxide). In this specification, "silicon dioxide" is a general term for silicon dioxide and substances composed of silicon dioxide. Most of the aluminum oxide and silicon dioxide covering the titanium oxide exist in the form of silicon dioxide and aluminum oxide.

[0191] Based on the total mass of the titanium oxide particles, the proportion (mass %) of titanium oxide in the titanium oxide particles is preferably 90.00 mass % or more. Based on the total mass of the titanium oxide particles, the proportion (mass %) of titanium oxide in the titanium oxide particles is preferably 98.50 mass % or less. In terms of mass ratio, the proportion (mass %) of aluminum oxide in the titanium oxide particles needs to be 0.50 times or more and 1.00 times or less than the proportion (mass %) of silicon dioxide. If the mass ratio is less than 0.50 times or exceeds 1.00 times, the jetting stability of the ink cannot be obtained. Based on the total mass of the titanium oxide particles, the proportion (mass %) of silicon dioxide in the titanium oxide particles is preferably 1.00 mass % or more and 4.00 mass % or less. If the proportion (mass %) of silicon dioxide is less than 1.00 mass %, the affinity for the compound represented by the following general formula (1) may be insufficient, and in some cases sufficient jetting stability of the ink cannot be obtained. If the proportion (mass %) of silicon dioxide exceeds 4.00 mass %, the amount of the compound represented by the general formula (1) and adsorbed on the titanium oxide particles may not decrease even if the surface treatment is performed with aluminum oxide, and sufficient ink ejection stability may not be obtained in some cases. The proportion (mass %) of aluminum oxide to the titanium oxide particles is preferably 0.50 mass % or more and 4.00 mass % or less based on the total mass of the titanium oxide particles.

[0192] The method for measuring the ratio of aluminum oxide and silicon dioxide to titanium oxide particles (i.e., the coverage of aluminum oxide and silicon dioxide) can be, for example, quantitative analysis of aluminum and silicon elements by inductively coupled plasma (ICP) optical emission spectroscopy. In this case, it is assumed that all atoms covering the surface are in the form of oxides, and the measured values ​​of aluminum and silicon are converted based on the oxides of aluminum and silicon (i.e., aluminum oxide and silicon dioxide) to determine the ratio. In terms of mass ratio, the ratio (mass %) of aluminum element to titanium oxide particles is 0.57 times or more and 1.13 times or less of the ratio (mass %) of silicon element, and the ratio is determined by inductively coupled plasma-optical emission spectroscopy. When these values ​​are converted based on their oxides (i.e., aluminum oxide and silicon dioxide), in terms of mass ratio, the ratio (mass %) of aluminum oxide to titanium oxide particles is 0.50 times or more and 1.00 times or less of the ratio of silicon dioxide.

[0193] The surface treatment method for titanium oxide can be, for example, a wet treatment or a dry treatment. For example, the surface treatment can be carried out by dispersing titanium oxide in a liquid medium and then reacting titanium oxide with a surface treatment agent (e.g., sodium aluminate and sodium silicate). The ratio of the surface treatment agent can be appropriately changed to adjust to the desired characteristics. For surface treatment, in addition to aluminum oxide and silicon dioxide, inorganic oxides such as zinc oxide and zirconium oxide and organic substances such as polyols can also be used, as long as the effect of the present disclosure is not impaired.

[0194] As long as the effect of the present disclosure is not impaired, the ink may contain other pigments besides titanium oxide. In this case, the ink may be a color ink besides white ink. Based on the total mass of the ink, the content (mass %) of other pigments in the ink is preferably 0.10 mass % or more and 5.00 mass % or less, more preferably 0.10 mass % or more and 1.00 mass % or less.

[0195] The compound represented by the general formula (1)

[0196] The ink may contain a compound represented by the following general formula (1) as a dispersant for dispersing titanium oxide particles. The content (mass %) of the compound represented by the general formula (1) in the ink is preferably 0.01 mass % or more and 1.00 mass % or less, and more preferably 0.02 mass % or more and 0.50 mass % or less, based on the total mass of the ink.

[0197]

[0198] In the general formula (1), R1, R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Each R4 is independently an alkylene group having 2 to 4 carbon atoms. X is a single bond or an alkylene group having 1 to 6 carbon atoms, and n is 6 to 24. a is 1 to 3, b is 0 to 2, and a+b=3.

[0199] In the general formula (1), R1, R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, isopropyl and n-butyl. Among them, from the perspective of easy hydrolysis, methyl is preferred. When R1, R2 and R3 are all alkyl groups having more than 4 carbon atoms, it is difficult to form a silanol group by hydrolysis, and affinity for titanium dioxide particles cannot be obtained. Therefore, titanium dioxide particles cannot be stably dispersed, and ink jetting stability cannot be obtained. In the general formula, a representing the number of R1O is 1 to 3, b representing the number of R2 is 0 to 2, and a+b=3. In particular, it is preferred that a is 3 and b is 0, specifically, the three substituents of the silicon atom are all R1O.

[0200] In the general formula (1), each R4 is independently an alkylene group having 2 to 4 carbon atoms. Examples of alkylene groups having 2 to 4 carbon atoms include vinyl, n-propenyl, isopropenyl and n-butenyl. Among them, vinyl is preferred. The number of OR4, i.e., n (average value) (which represents the number of oxyalkylene groups), is 6 to 24. When n is less than 6, the oxyalkylene chain is too short, so the repulsive force caused by steric hindrance cannot be fully obtained, and sufficient ink jetting stability cannot be obtained. When n is greater than 24, the oxyalkylene chain is too long, so that it has enhanced hydrophilicity, and may exist in an aqueous medium in a free form. Therefore, the affinity for the surface hydroxyl group of the titanium oxide particles cannot be fully obtained, and the aggregation of the titanium oxide particles cannot be suppressed. Therefore, the titanium oxide particles cannot be stably dispersed, and the ink jetting stability cannot be obtained.

[0201] In the general formula (1), X is a single bond or an alkylene group having 1 to 6 carbon atoms. When X is a single bond, it means that the silicon atom and OR4 are directly bonded to each other. Examples of alkylene groups having 1 to 6 carbon atoms include methylene, ethylene, n-propenyl, isopropenyl, n-butenyl, n-pentenyl and n-hexenyl. Among them, n-propenyl is preferred. When X is an alkylene group having more than 6 carbon atoms, the compound represented by the general formula (1) has too high hydrophobicity, so the titanium dioxide particles cannot be stably dispersed, and the jetting stability of the ink cannot be obtained.

[0202] The compound represented by the above general formula (1) and serving as a dispersant for titanium oxide particles may be a compound represented by the following general formula (2). The compound represented by the general formula (2) has three OR1s bonded to silicon atoms. Therefore, the compound can be partially hydrolyzed in an aqueous medium to form three hydroxyl groups bonded to silicon atoms, thereby increasing the moieties having affinity for titanium oxide particles. The compound represented by the following general formula (2) has a repeating structure of ethylene oxide groups. Therefore, the ethylene oxide chain is appropriately extended in an aqueous medium to provide a repulsive force due to steric hindrance.

[0203]

[0204] In the general formula (2), R1 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m is 8 to 24.

[0205] In terms of mass ratio, the content (mass %) of the compound represented by the general formula (1) in the ink is preferably 0.002 times or more and 0.10 times or less of the content (mass %) of the titanium oxide particles. If the mass ratio is less than 0.002 times, the effect of stably dispersing the titanium oxide particles is weak, and in some cases the jetting stability of the ink cannot be fully obtained. If the mass ratio exceeds 0.10 times, the proportion of the compound represented by the general formula (1) is too high, and intermolecular condensation (self-condensation) of the compound represented by the general formula (1) is likely to occur. Therefore, the compound represented by the general formula (1) is consumed without acting as a dispersant. Therefore, the effect of stably dispersing the titanium dioxide particles is weak, and in some cases the jetting stability of the ink cannot be fully obtained.

[0206] The compound represented by the general formula (1) forms a hydrogen bond with the surface hydroxyl group of the titanium oxide particles, and it is believed that a part of it forms a covalent bond due to a dehydration reaction. However, in the present disclosure, the compound represented by the general formula (1) can disperse the titanium oxide particles even if the compound does not form a covalent bond with the titanium oxide particles. That is, the amount of the compound represented by the general formula (1) and covalently bonded to the titanium oxide particles is very small and can be ignored. Therefore, the content of the titanium oxide particles is defined as excluding the amount of the compound represented by the general formula (1) and covalently bonded to the titanium oxide particles. As a result of research conducted by the inventor, it has been found that an excessive amount of the compound represented by the general formula (1) and covalently bonded to the titanium oxide particles can deteriorate the ejection stability of the ink. The reason is believed to be as follows: Generally, in a liquid medium with a high dielectric constant (e.g., water), electrostatic attraction is unlikely to work, and therefore the titanium oxide particles move freely without being significantly affected by the surrounding environment. However, when the compound represented by the general formula (1) is covalently bonded to the titanium oxide particles, the hydrophilic part (OR4 part) of the structure of the general formula (1) forms a hydrogen bond with the water molecule, which may affect the movement of the titanium oxide particles in some cases. Therefore, in the case where deformation caused by instantaneous pressure is applied to the liquid, such as in the case of inkjet injection, the above properties are manifested as differences in injection characteristics. Therefore, in terms of mass ratio, the amount (mass %) of the compound represented by the general formula (1) and covalently bonded to the titanium oxide particles is preferably less than 0.001 times the content (mass %) of the titanium oxide particles. When the mass ratio is greater than 0.001 times, in some cases the injection stability of the ink cannot be fully obtained. The mass ratio can be 0.000 times. The amount of the compound represented by the general formula (1) and covalently bonded to the titanium oxide particles can be calculated, for example, by thermogravimetric analysis.

[0207] Resin

[0208] The ink may contain a resin. Examples of the resin include acrylic resins, polyurethane resins, and urea-formaldehyde resins. Among them, acrylic resins are preferred. Based on the total mass of the ink, the resin content (mass %) in the ink is preferably 1.00 mass % or more and 25.00 mass % or less, more preferably 3.00 mass % or more and 15.00 mass % or less, and particularly preferably 5.00 mass % or more and 15.00 mass % or less.

[0209] For the purpose of improving various properties of the image to be recorded (e.g., scratch resistance and hiding power), a resin may be included in the ink. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin soluble in an aqueous medium, or may be resin particles dispersed in an aqueous medium. The resin particles may not necessarily contain a coloring material.

[0210] In this specification, the term "resin is water-soluble" means that when the resin is neutralized with an amount of alkali equal to the acid value, the resin exists in an aqueous medium without forming particles whose particle size can be measured by a dynamic light scattering method. Whether the resin is water-soluble can be determined according to the following method: First, a liquid (resin solid content: 10% by mass) containing a resin neutralized with an alkali corresponding to the acid value (e.g., sodium hydroxide or potassium hydroxide) is prepared. The prepared liquid is then diluted 10 times (based on volume) with pure water to prepare a sample solution.

[0211] Subsequently, when the particle size of the resin in the sample solution is measured by the dynamic light scattering method and no particles having the particle size are measured, it can be determined that the resin is water-soluble. The measurement conditions in this case can be set as follows: for example, SetZero: 30 seconds, number of measurements: three times, measurement time: 180 seconds. The particle size distribution measurement device used can be, for example, a particle size analyzer using a dynamic light scattering method (for example, trade name "UPA-EX150", manufactured by Nikkiso Co., Ltd.). Of course, the particle size distribution measurement device used, the measurement conditions, etc. are not limited to those described above.

[0212] The acid value of the water-soluble resin is preferably 80 mgKOH / g or more and 250 mgKOH / g or less, more preferably 100 mgKOH / g or more and 200 mgKOH / g or less. When resin particles are used, the acid value is preferably 0 mgKOH / g or more and 50 mgKOH / g or less. The weight average molecular weight of the resin is preferably 1,000 or more and 30,000 or less, more preferably 5,000 or more and 15,000 or less. The weight average molecular weight of the resin is a value converted to polystyrene by gel permeation chromatography (GPC).

[0213] Aqueous medium

[0214] The ink is an aqueous ink containing water as an aqueous medium. The ink may contain water or a mixed solvent of water and a water-soluble organic solvent as an aqueous medium. The water may be deionized water (ion exchange water). Based on the total mass of the ink, the water content (mass %) in the ink is preferably 50.00 mass % or more and 95.00 mass % or less.

[0215] There is no particular limitation on the water-soluble organic solvent as long as it is water-soluble (it can be an organic solvent that dissolves in water at any proportion at 25°C). Specific examples of water-soluble organic solvents that can be used include monohydric and polyhydric alcohols, alkylene glycols, glycol ethers, nitrogen-containing polar compounds, and sulfur-containing polar compounds. Based on the total mass of the ink, the content (mass %) of the water-soluble organic solvent in the ink is preferably 3.00 mass % or more and 50.00 mass % or less, more preferably 10.00 mass % or more and 40.00 mass % or less. If the content (mass %) of the water-soluble organic solvent is less than 3.00 mass %, the ink may adhere to the inkjet recording device, and the anti-adhesion property may be insufficient. If the content (mass %) of the water-soluble organic solvent exceeds 50.00 mass %, ink supply failure may occur.

[0216] Other additives

[0217] In addition to the above-mentioned additives, ink may include various additives, such as surfactants, pH regulators, corrosion inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation promoters and chelating agents, as required. In particular, ink may include surfactants. Based on the total mass of the ink, the content (mass %) of the surfactant in the ink is preferably 0.10 mass % or more and 5.00 mass % or less, more preferably 0.10 mass % or more and 2.00 mass % or less. The example of surfactant includes anionic surfactants, cationic surfactants and nonionic surfactants. Among them, nonionic surfactants having a low affinity for titanium oxide particles and providing an effect even in a small amount can be used, because surfactants are used to adjust the various physical properties of the ink.

[0218] Physical properties of ink

[0219] The ink is an ink applied to an inkjet system, and therefore its physical properties can be appropriately controlled. The surface tension of the ink at 25° C. is preferably 10 mN / m or more and 60 mN / m or less, and more preferably 20 mN / m or more and 40 mN / m or less. The surface tension of the ink can be adjusted by appropriately determining the type and amount of the surfactant in the ink. As described above, at 25° C., the viscosity of the white ink in the present disclosure needs to be 8 mPa·s or more, and preferably 9 mPa·s or more.

[0220] The viscosity is preferably 14 mPa·s or less, more preferably 12 mPa·s or less. The pH value of the ink at 25° C. is preferably 7.0 or more and 9.0 or less. When the pH value of the ink is within the above range, the formation of silanol groups due to the hydrolysis of the compound represented by the general formula (1) is performed, and thus the weak affinity between the titanium oxide particles and the compound represented by the general formula (1) is effectively exhibited. The pH value of the ink can be measured with a common pH meter including, for example, a glass electrode.

[0221] Method for making ink

[0222] The method for manufacturing ink according to the present disclosure includes the step of mixing a titanium oxide particle dispersion with other ink components. The titanium oxide particle dispersion used is a titanium oxide particle dispersion manufactured by a manufacturing method described later. Examples of other ink components include water, a water-soluble organic solvent, a resin, and the above-mentioned "other additives" to be further added. For example, the ink can be prepared by adding the titanium oxide particle dispersion and other ink components to a suitable container and stirring the mixture. Conditions such as stirring speed, temperature, time, etc. can be appropriately set according to the desired conditions. Other known manufacturing steps can be combined.

[0223] Method for producing a titanium oxide particle dispersion

[0224] The method for producing a titanium oxide particle dispersion according to the present disclosure is used to produce a water-based ink for inkjet. The method includes a step (first step) of reacting a predetermined treatment agent with the surface of titanium oxide to prepare titanium oxide particles (the titanium oxide particles are titanium oxide whose surfaces are covered with aluminum oxide and silicon dioxide). After the first step, the method also includes a dispersing step (second step) of dispersing the titanium oxide particles in a liquid medium using a compound represented by the general formula (1), the compound being used to disperse the titanium oxide particles.

[0225] Example

[0226] The present disclosure will be described in more detail below by way of examples. Without departing from the spirit and scope of the present disclosure, the present disclosure is not limited by the following examples. For the amount of each component, unless otherwise indicated, "parts" and "%" are based on mass. The titanium oxide particle dispersion is referred to as a "pigment dispersion".

[0227] Preparation of titanium oxide particles

[0228] Commercially available rutile titanium oxide particles that had been surface treated in advance were used. The volume-based 50% cumulative particle diameter (D 50). The properties of titanium oxide particles are shown in Table 1.

[0229] Table 1

[0230] Properties of titanium oxide particles

[0231]

[0232] Preparation of pigment dispersion

[0233] A styrene-methyl methacrylate-methacrylic acid copolymer (resin 1) having an acid value of 150 mgKOH / g and a weight average molecular weight of 10,000 was prepared. Subsequently, 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to its acid value, and an appropriate amount of pure water was added thereto to prepare an aqueous solution of resin 1 having a resin content (solid content) of 20.0%. Subsequently, 40.0 parts of titanium oxide particles 1, 40.0 parts of an aqueous solution of resin 1, and ion exchange water used in an amount such that the total amount of each component was 100.0 parts were mixed and a preliminary dispersion treatment was performed with a homogenizer. Then, a dispersion treatment (main dispersion treatment) was performed at 25°C for 12 hours using 0.5 mm zirconium oxide beads using a pigment mixer. The zirconium oxide beads were separated by filtration. An appropriate amount of ion exchange water was added as needed to prepare a pigment dispersion 1 having a titanium oxide particle content of 40.0% and a resin dispersant (resin 1) content of 8.0%.

[0234] Ink preparation

[0235] Ink 1

[0236] Next, 25.0 parts of the pigment dispersion liquid 1 and the following components were mixed and stirred. Subsequently, pressure filtration was performed with a membrane filter (manufactured by Sartorius) having a pore size of 5.0 μm to prepare Ink 1. The viscosity (Pa·s) of Ink 1 was 10 mPa·s.

[0237] The details of each mixing component are described below.

[0238] Acrylic resin particles (trade name "VINYBLAN 2685", manufactured by Nissin Chemical Industry Co., Ltd., resin particle content: 30%) 20.0 parts

[0239] Diethylene glycol: 20.0 parts

[0240] Diethylene glycol isobutyl ether: 20.0 parts

[0241] Fluorinated surfactant (trade name "Capstone FS-3100", manufactured by Chemours): 1.0 part

[0242] Ion exchange water: 34.0 parts

[0243] Ink 2

[0244] Ink 2 was prepared by the same procedure as that for preparing Ink 1, except that the amounts of diethylene glycol and diethylene glycol isobutyl ether used were changed to 10.0 parts and 10.0 parts, respectively. The viscosity (Pa·s) of Ink 2 was 8 mPa·s.

[0245] The ink described in the examples was used, and the ink was ejected using the above-described liquid ejection apparatus. As a result, it was confirmed that the effects of the present disclosure were sufficiently obtained.

[0246] The present disclosure can provide an inkjet recording method that enables ejection of white ink containing titanium oxide while achieving reduced sedimentation.

[0247] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure 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 modifications and equivalent structures and functions.

Claims

1. An inkjet recording device, comprising an inkjet recording head, wherein the inkjet recording head comprises: an ejection port for ejecting the ink, a pressure chamber communicating with the ejection port and including therein a recording element substrate configured to generate energy for ejecting the ink, a supply channel communicating with the pressure chamber and configured to supply the ink to the pressure chamber, and a temperature regulating unit configured to heat the ink, Here, the ink contains titanium oxide and has a viscosity of 8 mPa·s or more at 25°C.

2. The inkjet recording apparatus according to claim 1, wherein The temperature adjustment unit is disposed in the supply passage.

3. The inkjet recording apparatus according to claim 1, wherein The temperature adjustment unit is provided on the recording element substrate.

4. The inkjet recording apparatus according to claim 1, wherein The inkjet recording head further includes a collecting channel communicating with the pressure chamber and configured to collect the ink from the pressure chamber.

5. The inkjet recording apparatus according to claim 4, wherein The temperature adjustment unit is provided in each of the collecting channel and the supply channel, and The energy applied to the temperature regulating unit provided in the supply channel is greater than the energy applied to the temperature regulating unit provided in the collection channel.

6. The inkjet recording apparatus according to claim 4, wherein The inkjet recording head further includes a pump configured to cause the ink in the collection channel to flow into the supply channel.

7. The inkjet recording apparatus according to claim 6, wherein An ink circulation path has a volume of 30 mL or less, in which the ink circulates in the inkjet recording head, and includes the pump, the supply channel, the pressure chamber, and the collection channel.

8. The inkjet recording apparatus according to claim 6, wherein The inkjet recording head is configured to eject the ink while scanning in a scanning direction.

9. The inkjet recording apparatus according to claim 7, wherein The ink circulation path includes a material having a thermal conductivity of 1.0 W / m·K or less.

10. The inkjet recording apparatus according to claim 4, in, In the inkjet recording head, a plurality of the ejection ports are arranged in an array direction to form an ejection port array. The inkjet recording head includes a plurality of the pressure chambers, a plurality of the supply channels, and a plurality of the collecting channels so as to correspond to the plurality of ejection ports, a common supply channel configured to supply the ink to the plurality of supply channels, and a common collecting channel configured to collect the ink from the plurality of collecting channels extending in the array direction, and An end portion of at least one selected from the common supply channel and the common collection channel extends to the outside of an end portion of the injection port array.

11. The inkjet recording apparatus according to claim 10, in, The inkjet recording head includes a plurality of supply ports configured to supply the ink to the common supply channel and a plurality of collection ports configured to collect the ink from the common collection channel, and At least one or more of the supply port and the collection port are arranged outside the injection port array.

12. The inkjet recording apparatus according to claim 6, wherein The inkjet recording head further includes a first pressure adjusting unit configured to adjust the pressure of the ink in the supply channel.

13. The inkjet recording apparatus according to claim 12, wherein The first pressure regulating unit includes a first valve chamber, a first pressure control chamber, a first opening communicating the first valve chamber and the first pressure control chamber, and a first valve configured to open and close the first opening.

14. The inkjet recording apparatus according to claim 13, wherein A portion of the surface of the first pressure control chamber is composed of a first flexible member configured to be displaceable, and the first pressure control chamber includes a first pressure plate configured to be displaceable together with the first flexible member, and a first pushing member that pushes the first pressure plate in a direction to increase the volume of the first pressure control chamber, and the first pressure control chamber is configured so that the first valve can be opened and closed according to the displacement of the first pressure plate and the first flexible member.

15. The inkjet recording apparatus according to claim 12, wherein The inkjet recording head further includes a second pressure adjusting unit configured to adjust the pressure of the ink in the collecting channel.

16. An inkjet recording method, comprising ejecting ink from an inkjet recording head, in, The ink contains titanium oxide and has a viscosity of 8 mPa·s or more at 25° C., and The inkjet recording head comprises: Jet port, a pressure chamber communicating with the ejection port and including a recording element substrate therein, a supply passage communicating with the pressure chamber, and Temperature control unit, The method comprises: heating the ink using the temperature adjustment unit; supplying the ink to the pressure chamber; generating energy for ejecting the ink from the recording element substrate; and The ink is ejected from the ejection openings.

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