Liquid discharge head and liquid discharge device

Abstract

A liquid discharge head according to the present invention comprises a flow path member and an actuator. The flow path member has an individual flow path for accommodating liquid. The individual flow path has a pressure chamber, a partial flow path that extends from the pressure chamber, and a nozzle that is open to the outside at an end portion of the partial flow path on the side opposite to the pressure chamber. The actuator applies pressure to the pressure chamber. A damping ratio of natural vibrations (main vibrations) of the liquid in the individual flow path is γ1 (rad / s). An angular frequency of the main vibrations is ω1 (rad / s). An angular frequency of high-frequency vibration is ω2 (rad / s). n is a positive integer. In this case, the formula below is satisfied.　0.95 × 2n (1 + 0.32 × γ1 / ω1) ≤ ω2 / ω1 ≤ 1.05 × 2n (1 + 0.32 × γ1 / / ω1)

Description

Liquid ejection head and liquid ejection device

[0001] The present disclosure relates to a liquid ejection head such as an inkjet head, and a liquid ejection apparatus having the liquid ejection head.

[0002] Liquid ejection heads (e.g., inkjet heads) that eject droplets (e.g., ink droplets) toward a recording medium (e.g., paper) are known (see, for example, Patent Document 1 listed below). Such liquid ejection heads include, for example, a flow path member having flow paths filled with ink, an actuator (e.g., a piezoelectric element) that applies pressure to the ink in the flow path member, and a driver that inputs a drive signal to the actuator. The flow paths of the flow path member include, for example, a common flow path (sometimes referred to as a manifold) and a plurality of individual flow paths to which liquid (e.g., ink) is supplied from the common flow path. The individual flow paths include, for example, a pressure chamber (sometimes referred to as a pressure chamber) to which pressure is applied by an actuator, and a nozzle that communicates with the pressure chamber and opens to the outside.

[0003] In Patent Document 1, droplets are ejected from a nozzle using a so-called pull-and-shoot drive system. In this system, the volume of a pressure chamber is expanded to draw liquid into the pressure chamber, and then the volume of the pressure chamber is reduced to expel the liquid, thereby ejecting droplets from the nozzle. To achieve this, the drive signal input to the actuator has a pulse waveform. The pulse waveform has a falling edge in signal strength corresponding to the expansion of the pressure chamber volume and a rising edge in signal strength corresponding to the reduction of the pressure chamber volume. In Patent Document 1, the time length from the falling edge to the rising edge is set to the length AL (μs) at which the signal most resonates with the resonant frequency of the liquid in the individual flow channel. By setting the width (duration) of the pulse waveform in this manner, for example, the volume of the pressure chamber can be reduced to coincide with the timing at which the liquid drawn into the pressure chamber reverses direction toward the nozzle due to its natural vibration, thereby expelling the liquid. As a result, the liquid ejection speed can be increased.

[0004] Japanese Patent Application Laid-Open No. 2021-37692

[0005] A liquid ejection head according to one aspect of the present disclosure includes a flow path member and an actuator. The flow path member has individual flow paths that accommodate liquid. The individual flow paths include a pressure chamber, a partial flow path extending from the pressure chamber, and a nozzle that opens to the outside at an end of the partial flow path opposite the pressure chamber. The actuator applies pressure to the pressure chamber. The damping rate of the natural vibration of the liquid in the individual flow path is defined as γ1 (rad / s). The angular frequency of the natural vibration of the liquid in the individual flow path is defined as ω1 (rad / s). The angular frequency of the natural vibration of the liquid in the partial flow path is defined as ω2 (rad / s). n is a positive integer. In this case, the following equation holds: 0.95×2n(1+0.32×γ1 / ω1)≦ω2 / ω1≦1.05×2n(1+0.32×γ1 / ω1)

[0006] A liquid ejection head according to one aspect of the present disclosure includes a flow path member and an actuator. The flow path member has individual flow paths that accommodate liquid. The individual flow paths have a pressure chamber, a partial flow path extending from the pressure chamber, and a nozzle that opens to the outside at an end of the partial flow path opposite the pressure chamber. The actuator applies pressure to the pressure chamber. The angular frequency of the natural vibration of the liquid in the individual flow path is ω1 (rad / s). The angular frequency of the natural vibration of the liquid in the partial flow path is ω2 (rad / s). In this case, the following formulas hold: 1.97≦ω2 / ω1≦2.39, or 3.95≦ω2 / ω1≦4.88

[0007] A liquid ejection device according to one aspect of the present disclosure includes the liquid ejection head and a moving unit that moves the liquid ejection head and a recording medium relative to each other.

[0008] 2B is a cross-sectional view taken along line IIc-IIc of FIG. 2A; and FIG. 2C is a cross-sectional view taken along line III-III of FIG. 2B. It is a conceptual diagram for explaining a discharge operation. It is a conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid. It is another conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid. It is another conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid. It is a diagram showing an example of the calculation results of an index relating to the characteristics near the maximum value of the velocity of the liquid. It is another diagram showing an example of the calculation results of an index relating to the characteristics near the maximum value of the velocity of the liquid. It is yet another diagram showing an example of the calculation results of an index relating to the characteristics near the maximum value of the velocity of the liquid. It is a diagram showing a part (case where γ2 / ω1=0.00) extracted from FIG. 8. It is a diagram showing a part (case where γ2 / ω1=0.23) extracted from FIG. 8. 11A and 11B are diagrams showing a portion extracted from FIG. 8 (when γ2 / ω1=0.46); a portion extracted from FIG. 8 (when γ2 / ω1=0.69); a portion extracted from FIG. 8 (when γ2 / ω1=0.92); a portion extracted from FIG. 8 (when γ2 / ω1=1.15); and still another diagram showing an example of calculation results of an index related to characteristics near the maximum value of the liquid velocity. a portion extracted from FIG. 11 (when γ2 / ω1=0.00); a portion extracted from FIG. 11 (when γ2 / ω1=0.23); a portion extracted from FIG. 11 (when γ2 / ω1=0.46); a portion extracted from FIG. 11 (when γ2 / ω1=0.69); and a portion extracted from FIG. 11 (when γ2 / ω1=0.92). 12 is a diagram showing a part (the case where γ2 / ω1=1.15) extracted from FIG. 11. FIG.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, the dimensional ratios in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional ratios may not match between drawings. Certain shapes and / or dimensions may be exaggerated, and details may be omitted. However, the above does not deny that the actual shapes and / or dimensions may be as shown in the drawings, or that features of shapes and / or dimensions may be extracted from the drawings.

[0010] (Outline of the embodiment) FIG. 3 is a cross-sectional view showing a part of a liquid ejection head 2 (reference numeral is shown in FIG. 1A; hereinafter, sometimes simply referred to as "head 2") according to the embodiment.

[0011] The head 2 has ejection elements 15 that eject droplets (e.g., ink droplets) from the nozzles 5 downward in the figure (toward the -D3 direction). While one ejection element 15 (one nozzle 5) is shown in FIG. 3, the head 2 has multiple ejection elements 15 (multiple nozzles 5) along a plane perpendicular to the D3 direction. The ejected droplets land on a recording medium (e.g., paper, not shown here) located on the -D3 side, for example. This forms, for example, dots that make up an image.

[0012] The head 2 has a flow path member 19 having a flow path filled with liquid (e.g., ink). The ejection element 15 has an individual flow path 25 formed in the flow path member 19. The individual flow path 25 has, for example, a pressure chamber 43, a partial flow path 45 (sometimes referred to as a descender) extending from the pressure chamber 43 toward the -D3 side, and the aforementioned nozzle 5 that opens to the outside at the end of the partial flow path 45 on the -D3 side (the side opposite the pressure chamber 43).

[0013] The actuator 17 (actuator substrate 21) overlaps the +D3 side (upper side in the figure) of the pressure chamber 43. The actuator 17 is capable of deflection deformation toward the pressure chamber 43 and / or the opposite side to the pressure chamber 43. This deflection deformation applies pressure to the liquid in the pressure chamber 43. Consequently, droplets are ejected from the nozzle 5.

[0014] Here, the damping rate of the natural vibration (hereinafter sometimes referred to as "main vibration") of the liquid in the individual flow path 25 (as a whole) is γ1 (rad / s). The angular frequency of the main vibration is ω1 (rad / s). The angular frequency of the natural vibration (hereinafter sometimes referred to as "high frequency vibration") of the liquid in the partial flow path 45 is ω2 (rad / s). n is a positive integer. In this case, the following equation (1) holds for the individual flow path 25: 0.95×2n(1+0.32×γ1 / ω1)≦ω2 / ω1≦1.05×2n(1+0.32×γ1 / ω1) (1)

[0015] From another perspective, the following formula (2) or (3) holds true instead of or in addition to formula (1): 1.97≦ω2 / ω1≦2.39 (2) 3.95≦ω2 / ω1≦4.88 (3)

[0016] The angular frequencies ω1 and ω2 and the damping rate γ1 may be defined as parameters when the velocity v1(t) of the main vibration and the velocity v2(t) of the high-frequency vibration are expressed as follows: v1(t)=−A1×e －γ１×ｔ cos(ω1×t) (4) v2(t)=-A2×e －γ２×ｔ cos(ω2×t) (5)

[0017] In the above, A1 and A2 are maximum amplitudes (m / s). t is time (s). γ2 is the damping rate (rad / s) of the high-frequency vibration. Theoretically, the displacements of the main vibration and the high-frequency vibration can also be expressed by the same formulas as above, except that the maximum amplitude value and unit and the initial phase value are different. In other words, the damping rate and angular frequency are common to both displacement and velocity. Therefore, hereinafter, when referring to damping rate and angular frequency, there may be no distinction between displacement and velocity.

[0018] In equations (1) to (3), γ1 / ω1 and ω2 / ω1 are both dimensionless quantities. In addition, in the embodiment, the dimensionless quantity γ2 / ω1 is used. For this reason, in the following description, for convenience, the units of γ1, γ2, ω1, and ω2 may be omitted.

[0019] When at least one of the formulas (1) to (3) is satisfied, for example, it is possible to reduce the variation in droplet ejection speed between the multiple ejection elements 15. As a result, for example, it is possible to improve image quality. The specific principle behind this will be described later.

[0020] The above is an overview of the head 2 according to the embodiment. Below, we will roughly explain the head 2 and the printer 1 (an example of a liquid ejection device) having the head 2, in the following order: 1. Overall configuration of the printer 1 (FIGS. 1A and 1B) 2. Overall configuration of the head 2 (FIGS. 2A to 2C) 3. Configuration of the ejection element 15 (FIG. 3) 3.1. Overview of the ejection element 15 3.2. Flow path member 19 3.3. Actuator 17 4. Operation of the ejection element 15 (FIG. 4) 5. Principle of reducing ejection speed variation (FIGS. 5A to 6) 5.1. Causes of variation 5.2. Overview of method for reducing variation 5.3. Consideration of the effect of attenuation rate 6. Derivation of equations (1) to (3)) (FIGS. 7A to 13C) 6.1. Derivation method 6.2. Calculation results 6.3. Amplitude 7. Parameter adjustment method 8. 9. Method for identifying parameters

[0021] (1. Overall Configuration of Printer) Fig. 1A is a schematic side view of a printer 1 according to an embodiment. Fig. 1B is a schematic plan view of the printer 1.

[0022] The printer 1 is configured as a color inkjet printer. The printer 1 moves print paper P (an example of a recording medium) relative to the head 2 by transporting the print paper P from a paper feed roller 80A to a collection roller 80B. The paper feed roller 80A, collection roller 80B, and various other rollers described below constitute a movement unit 85 that moves the print paper P and the head 2 relative to each other. A control device 88 controls the head 2 based on print data such as image and character data to eject liquid toward the print paper P, causing droplets to land on the print paper P and perform recording, such as printing, on the print paper P.

[0023] In this embodiment, the head 2 is fixed to the main body of the printer 1, and the printer 1 is a so-called line printer. Another embodiment of the recording device is a so-called serial printer. In a serial printer, for example, the head 2 is moved back and forth in a direction that intersects with the transport direction of the print paper P, for example, in a direction that is approximately perpendicular. During this reciprocation, the operation of ejecting droplets and the transport of the print paper P are performed alternately.

[0024] Four flat head mounting frames 70 (hereinafter sometimes simply referred to as frames) are fixed to the printer 1 so as to be approximately parallel to the printing paper P. Five holes (not shown) are formed in each frame 70, and five heads 2 are mounted in each hole. The five heads 2 mounted on one frame 70 make up one head group 72. The printer 1 has four head groups 72, and a total of 20 heads 2 are mounted thereon.

[0025] The head 2 mounted on the frame 70 is arranged so that the portion that ejects the liquid faces the printing paper P. The distance between the head 2 and the printing paper P is, for example, about 0.5 to 20 mm.

[0026] The 20 heads 2 may be directly connected to the control device 88, or may be connected to the control device 88 via a distribution unit that distributes the print data. For example, the control device 88 may send the print data to one distribution unit, and the one distribution unit may distribute the print data to the 20 heads 2. Alternatively, for example, the control device 88 may distribute the print data to four distribution units corresponding to the four head groups 72, and each distribution unit may distribute the print data to five heads 2 in the corresponding head group 72.

[0027] The heads 2 have an elongated shape extending from the front to the back in FIG. 1A , and vertically in FIG. 1B . In one head group 72, three heads 2 are lined up in a direction intersecting the transport direction of the print paper P, for example, in a direction approximately perpendicular to it, and the other two heads 2 are lined up one between each of the three heads 2 at offset positions along the transport direction. In other words, in one head group 72, the heads 2 are arranged in a staggered pattern. The heads 2 are arranged so that the printable area of ​​each head 2 is connected in the width direction of the print paper P, i.e., in the direction intersecting the transport direction of the print paper P, or so that the edges overlap, enabling printing without gaps in the width direction of the print paper P.

[0028] The four head groups 72 are arranged along the transport direction of the printing paper P. Each head 2 is supplied with liquid, for example, ink, from a liquid supply tank (not shown). The heads 2 belonging to one head group 72 are supplied with ink of the same color, and the four head groups 72 can print with ink of four colors. The colors of ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). Color images can be printed by controlling these inks with the control device 88.

[0029] The number of heads 2 mounted on the printer 1 may be one, as long as printing is performed in a single color within the printable range of one head 2. The number of heads 2 included in a head group 72 and / or the number of head groups 72 can be changed as appropriate depending on the object to be printed and / or the printing conditions. For example, the number of head groups 72 may be increased to print in more colors. Furthermore, by arranging multiple head groups 72 that print in the same color and printing alternately in the transport direction, the transport speed can be increased even when heads 2 with the same performance are used. This allows for a larger printing area per unit time. Furthermore, multiple head groups 72 that print in the same color may be prepared and arranged staggered in a direction intersecting the transport direction to increase the resolution in the width direction of the printing paper P.

[0030] Furthermore, in addition to printing colored inks, a liquid such as a coating agent may be printed uniformly or in a pattern using the head 2 to perform surface treatment on the printing paper P. For example, when a recording medium that is difficult for the liquid to penetrate is used, a coating agent that forms a liquid-receiving layer to facilitate the liquid's adhesion can be used. Alternatively, when a recording medium that is easy for the liquid to penetrate is used, a coating agent that forms a liquid-penetration suppressing layer to prevent excessive bleeding of the liquid or excessive mixing with other liquids that land adjacently can be used. In addition to printing the coating agent using the head 2, the coating agent may also be applied uniformly using the applicator 76 controlled by the control device 88.

[0031] The printer 1 prints on a recording medium, namely, printing paper P. The printing paper P is wound around a paper feed roller 80A, and the printing paper P sent out from the paper feed roller 80A passes below the head 2 mounted on the frame 70, then passes between two transport rollers 82C, and is finally collected by a collection roller 80B. When printing, the printing paper P is transported at a constant speed by rotating the transport roller 82C, and is printed on by the head 2.

[0032] Next, details of the printer 1 will be described in the order in which the printing paper P is transported. The printing paper P is fed from the paper feed roller 80A, passes between two guide rollers 82A, and then passes under the coater 76. The coater 76 applies the coating agent described above to the printing paper P.

[0033] The printing paper P then enters the head chamber 74, which houses the frame 70 on which the head 2 is mounted. The head chamber 74 is connected to the outside in some areas, such as the area where the printing paper P enters and exits, but is generally a space that is isolated from the outside. Control factors such as temperature, humidity, and air pressure in the head chamber 74 are controlled as needed by a control device 88 or the like. The head chamber 74 is less susceptible to external disturbances than the outside where the printer 1 is installed, so the range of variation of the above-mentioned control factors can be narrower than outside.

[0034] Five guide rollers 82B are arranged in the head chamber 74, and the printing paper P is transported over the guide rollers 82B. The five guide rollers 82B are arranged so that, when viewed from the side, their centers are convex, facing the direction in which the frame 70 is arranged. As a result, the printing paper P transported over the five guide rollers 82B has an arc shape when viewed from the side, and by applying tension to the printing paper P, the printing paper P is stretched so that it is flat between the guide rollers 82B. One frame 70 is arranged between two guide rollers 82B. The angle at which each frame 70 is installed is slightly changed so that it is parallel to the printing paper P transported underneath.

[0035] The printing paper P that leaves the head chamber 74 passes between two transport rollers 82C, through the dryer 78, between two guide rollers 82D, and is collected by the collection roller 80B. The transport speed of the printing paper P is set to, for example, 100 m / min. Each roller may be controlled by the control device 88, or may be operated manually by a person.

[0036] Drying in the dryer 78 prevents overlapping print paper P wound on the recovery roller 80B from adhering to each other and prevents undried liquid from rubbing against each other. High-speed printing requires fast drying. To speed up drying, the dryer 78 may use multiple drying methods sequentially or in combination. Examples of drying methods used in such cases include blowing hot air, irradiating with infrared rays, and contact with a heated roller. When irradiating with infrared rays, infrared rays within a specific frequency range may be used to speed up drying while minimizing damage to the print paper P. When contacting the print paper P with a heated roller, the print paper P may be transported along the cylindrical surface of the roller to extend the time for heat transfer. The range of transport along the cylindrical surface of the roller is preferably at least one-quarter of the circumference of the roller, and preferably at least one-half of the circumference of the roller. When printing with UV-curable ink, a UV irradiation light source may be installed instead of or in addition to the dryer 78. A UV irradiation source may be positioned between each frame 70 .

[0037] The printer 1 may be equipped with a cleaning unit that cleans the head 2. The cleaning unit performs cleaning by, for example, wiping and / or capping. Wiping involves, for example, using a flexible wiper to rub the surface from which the liquid is ejected, such as the ejection surface 3a (described below), to remove any liquid adhering to that surface. Cleaning by capping is performed, for example, as follows: First, a cap is placed over the area from which the liquid is ejected, such as the ejection surface 3a (this is called capping), creating a nearly sealed space between the ejection surface 3a and the cap. Repeated liquid ejection in this state removes any liquid clogged in the nozzles 5 that has become more viscous than normal and / or foreign matter. Capping prevents the liquid from splashing around the printer 1 during cleaning and from adhering to the print paper P, rollers, or other transport mechanisms. The ejection surface 3a may then be wiped after cleaning. Cleaning by wiping and / or capping may be performed manually by a person using a wiper and / or cap attached to the printer 1, or may be performed automatically by the control device 88.

[0038] The recording medium may be a roll of cloth in addition to printing paper P. Furthermore, instead of directly transporting printing paper P, the printer 1 may transport a conveyor belt and place the recording medium on the conveyor belt for transport. In this way, sheets of paper, cut pieces of cloth, wood, tiles, etc. can be used as recording media. Furthermore, a liquid containing conductive particles may be ejected from the head 2 to print wiring patterns for electronic devices. Furthermore, a chemical agent may be produced by ejecting a predetermined amount of liquid chemical agent or a liquid containing a chemical agent from the head 2 toward a reaction vessel or the like, causing a reaction.

[0039] Furthermore, position sensors, speed sensors, temperature sensors, etc. may be attached to the printer 1, and the control device 88 may control each part of the printer 1 according to the state of each part of the printer 1 determined from information from each sensor. For example, if the temperature of the head 2, the temperature of the liquid in the liquid supply tank that supplies the liquid to the head 2, and / or the pressure that the liquid in the liquid supply tank applies to the head 2 affect the ejection characteristics of the ejected liquid, i.e., the ejection amount and / or the ejection speed, etc., the drive signal for ejecting the liquid may be changed according to this information.

[0040] For convenience, the following description will basically focus on one head 2. Therefore, for example, hereinafter, when referring to all nozzles 5, unless otherwise specified, this refers to all nozzles 5 in one head 2. When referring to all nozzles 5, unless otherwise specified, a unique nozzle may be treated as a nozzle different from the nozzles 5 designated by the term "all nozzles 5." For example, in order to make the ejection characteristics of the nozzles 5 located at the ends of the head 2 closer to the ejection characteristics of the nozzles 5 located at the center of the head 2, dummy nozzles that do not eject droplets may be provided further outside the nozzles 5 located at the ends. Such dummy nozzles do not need to be included in the term "all nozzles 5." The same applies to components other than the nozzles 5 (e.g., individual flow paths 25 and actuators 17).

[0041] (2. Overall configuration of the head) Fig. 2A is a perspective view of the head main body 3 of the head 2, seen from the side opposite the recording medium (printing paper P). Fig. 2B is a perspective view of the head main body 3, seen from the recording medium side. Fig. 2C is a cross-sectional view taken along line IIc-IIc in Fig. 2A.

[0042] For convenience, these figures are provided with an orthogonal coordinate system consisting of the D1 axis, D2 axis, D3 axis, etc. The D1 axis is defined as being parallel to the direction of relative movement between the head main body 3 and the recording medium (the transport direction of the print paper P in FIG. 1A). The relationship between the positive and negative sides of the D1 axis and the direction of travel of the recording medium relative to the head main body 3 is not particularly important in the description of this embodiment. The D2 axis is defined as being parallel to the recording medium and perpendicular to the D1 axis. The positive and negative sides of the D2 axis are also not particularly important. The D3 axis is defined as being perpendicular to the recording medium. The -D3 side is considered to be the direction from the head main body 3 to the recording medium. Either direction of the head main body 3 may be used as the upper or lower side, but for convenience, the +D3 side may be considered to be the upper side, and terms such as the lower side may be used.

[0043] One head 2 has one head body 3. The head body 3 is the part directly responsible for ejecting liquid, and has an ejection surface 3a facing the recording medium. A plurality of nozzles 5 for ejecting liquid are opened on the ejection surface 3a. In addition to the head body 3, the head 2 may have, for example, a circuit board connected to the head body 3 and / or a housing covering the top of the head body 3. It should be noted that the head body 3 may be regarded as an example of a liquid ejection head of the present disclosure, regardless of whether the head 2 has components other than the head body 3.

[0044] The multiple nozzles 5 are arranged at different positions in the direction D2. Therefore, any two-dimensional image can be formed by ejecting ink droplets from the multiple nozzles 5 while moving the head 2 and the recording medium relatively in the direction D1 using the moving unit 85. The multiple nozzles 5 may be arranged two-dimensionally, as in the illustrated example, or may be arranged one-dimensionally, as in the illustrated example.

[0045] The specific size, number, pitch, arrangement pattern, etc. of the multiple nozzles 5 may be set as appropriate. Because FIG. 2B is a schematic diagram, the nozzles 5 are shown large relative to the size of the head body 3, and the number of nozzles 5 in one head body 3 is shown as being small. Generally, the nozzles 5 are smaller and the number of nozzles 5 is greater than in the illustrated example. For example, the number of nozzles 5 in one head body 3 may be 100 or more and 10,000 or less. Furthermore, for example, one head body 3 may have multiple nozzles 5 at a pitch and arrangement pattern such that the dot density in the D2 direction is 800 dpi or more and 1,600 dpi or less.

[0046] The head main body 3 includes, for example, the following components: An opposing substrate 7 having an ejection surface 3a; A back member 9 fixed above the opposing substrate 7; One or more (two in the illustrated example) flexible substrates 11 electrically connected to the opposing substrate 7; One or more (two in the illustrated example) drivers 13 mounted on each flexible substrate 11.

[0047] The opposing substrate 7 directly contributes to the ejection of droplets. The opposing substrate 7 has the flow path member 19 and the actuator 17 ( FIG. 3 ) described above. The shape, size, etc. of the opposing substrate 7 may be set as appropriate. In the illustrated example, the opposing substrate 7 is a generally rectangular flat plate. Its thickness (in the D3 direction) is, for example, 0.5 mm or more and 2 mm or less. The opposing substrate 7 may be regarded as an example of a liquid ejection head of the present disclosure.

[0048] The back member 9, for example, contributes to intermediary between the counter substrate 7 and other components. For example, the back member 9 contributes to positioning the counter substrate 7 with respect to the frame 70 described above. Specifically, for example, the lower surface of the back member 9 is adhered to the outer edge portion of the upper surface of the counter substrate 7, and the lower portion is inserted into a hole in the frame 70 while the upper flange-like portion is supported by the frame 70. Furthermore, for example, the back member 9 mediates between an ink tank (not shown) and the counter substrate 7 in terms of ink flow. Specifically, the back member 9 has an opening 9a opening on the upper surface and an opening (not shown) opening on the lower surface that is adhered to the counter substrate 7. The opening on the upper surface and the opening on the lower surface are connected by a flow path (not shown) in the back member 9. The opening 9a is connected to the ink tank via a tube (not shown) or the like (not shown).

[0049] The flexible substrate 11 contributes to the electrical connection between the counter substrate 7 and the control device 88. Specifically, for example, the flexible substrate 11 is inserted into a slit 9b that vertically penetrates the back member 9. The portion of the flexible substrate 11 that extends downward from the slit 9b is disposed opposite the upper surface of the counter substrate 7 and is joined to the upper surface of the counter substrate 7 by conductive bumps (e.g., solder) (not shown). The portion of the flexible substrate 11 that extends upward from the slit 9b is connected to a cable (not shown) extending from the control device 88 via a connector mounted on that portion or a connector mounted on a rigid substrate connected to the flexible substrate 11.

[0050] The driver 13 contributes to, for example, driving and controlling the actuators 17 on the opposing substrate 7. Specifically, for example, the driver 13 receives a control signal from the control device 88 via the flexible substrate 11, generates drive power (or, from another perspective, drive signal) based on the input control signal, and inputs the generated drive power to the actuators 17 via the flexible substrate 11. The division of roles between the driver 13 and the control device 88 may be set as appropriate. For example, information defining the shape of a pulse Ps (or, from another perspective, pulse width PW), which will be described later, may be held by the control device 88 or the driver 13. The driver 13 is configured, for example, by an IC (Integrated Circuit). The shape, size, number, position, etc., of the driver 13 may be set as appropriate.

[0051] (3. Configuration of Ejection Element) (3.1. Overview of Ejection Element) Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2B. That is, Fig. 3 is a schematic cross-sectional view showing an enlarged portion of the opposing substrate 7.

[0052] The counter substrate 7 has a plurality of ejection elements 15. The plurality of ejection elements 15 are arranged two-dimensionally (or one-dimensionally) along the ejection surface 3a, similar to the plurality of nozzles 5. As already described, each ejection element 15 has an individual flow path 25 and an actuator 17. From another perspective, the counter substrate 7 has a substantially plate-shaped flow path member 19 and an actuator substrate 21 overlapping the flow path member 19. The flow path member 19 has a plurality of individual flow paths 25. The actuator substrate 21 has a plurality of actuators 17. In other words, the plurality of ejection elements 15 are constituted by the flow path member 19 and the actuator substrate 21.

[0053] The configurations of the multiple ejection elements 15 may be identical to each other, for example. Therefore, unless otherwise specified and unless a contradiction arises, the description of one ejection element 15 in the embodiment may be applied to any of the multiple ejection elements 15 (excluding unique elements as described above) possessed by the head 2. Note that the "same configurations" referred to in this paragraph excludes the position and orientation of the ejection elements 15 (or their components) within the head 2 in a plan view (as viewed in the D3 direction). Furthermore, the configuration of some and two or more ejection elements 15 in the head 2 may differ in detail (for example, the specific shape and dimensions of the partial flow paths 45) from the configuration of other some and two or more ejection elements 15.

[0054] (3.2. Flow Channel Member) The flow channel member 19 is configured, for example, by stacking multiple plates 27A to 27J (hereinafter, A to J may be omitted). A plurality of holes (mainly through holes, but may also be recesses) that form the flow channel are formed in the plate 27. The thickness and number of stacked plates 27 may be set appropriately depending on the shape of the flow channel, etc. The multiple plates 27 may be formed from an appropriate material. For example, the multiple plates 27 are formed from metal or resin. The thickness of the plates 27 is, for example, 10 μm or more and 300 μm or less. The plates 27 are fixed to each other, for example, by an adhesive (not shown) interposed between the plates 27.

[0055] The flow path member 19 has, for example, a common flow path 23 and a plurality of individual flow paths 25 (only one is shown in FIG. 3 ) each connected to the common flow path 23. Ink supplied from the back surface member 9 to the flow path member 19 is supplied from the common flow path 23 to the plurality of individual flow paths 25. Each individual flow path 25 has, for example, a connection portion 37, a restrictor 39, a supply path 41, a pressure chamber 43, a partial flow path 45, and a nozzle 5 in this order from the common flow path 23 side.

[0056] The specific shape and dimensions of each flow path in the flow path member 19 may be set as appropriate. In the illustrated example, they are as follows.

[0057] The common flow path 23 may extend in any direction along the ejection surface 3 a. Although only one common flow path 23 may be provided, for example, a plurality of common flow paths 23 may be provided in parallel to each other. The cross section of the common flow path 23 is rectangular.

[0058] The plurality of individual flow paths 25 (or, from another perspective, the ejection elements 15) are arranged in the longitudinal direction of each common flow path 23. The plurality of nozzles 5 may be arranged, for example, in a single row on one side of the common flow path 23 to which they are connected, or in a total of two or four rows on both sides.

[0059] The pressurizing chamber 43 is open to, for example, the upper surface of the flow path member 19 (the surface opposite to the ejection surface 3a) and is blocked by the actuator 17. The pressurizing chamber 43 may be blocked by a plate 27. However, this can also be considered as a question of whether the plate 27 blocking the pressurizing chamber 43 should be regarded as part of the flow path member 19 or as part of the actuator 17. In either case, the pressurizing chamber 43 is located at the top of the flow path member 19.

[0060] The shapes of the multiple pressurizing chambers 43 are, for example, the same as each other. The shape of each pressurizing chamber 43 may be set as appropriate. For example, the pressurizing chamber 43 is formed in a thin shape that extends at a constant thickness along the upper surface of the flow path member 19. However, the pressurizing chamber 43 may have portions with different thicknesses. The thin shape is, for example, a shape whose thickness is smaller than any diameter in a plan view.

[0061] Furthermore, for example, the planar shape of the pressurizing chambers 43 may be a shape having longitudinal and lateral directions that are orthogonal to each other (e.g., a diamond or ellipse), or a shape that does not include such directions (e.g., a circle). Furthermore, the relationship between the longitudinal and lateral directions and the arrangement of the multiple pressurizing chambers 43 is also arbitrary.

[0062] The partial flow path 45 extends from the lower surface of the pressurizing chamber 43 toward the ejection surface 3a. The partial flow path 45 is generally cylindrical in shape. The partial flow path 45 may extend from the pressurizing chamber 43 toward the ejection surface 3a at an incline in the vertical direction (as in the illustrated example), or may extend without an incline, may extend linearly, or may be partially or entirely curved. The cross-sectional area of ​​the partial flow path 45 may be constant in the length direction of the partial flow path 45 or may vary depending on the position in the length direction. In a plan view (as viewed in the D3 direction), the partial flow path 45 is connected, for example, to an end of the pressurizing chamber 43 in a predetermined direction (for example, the longitudinal direction of the pressurizing chamber 43 in a plan view).

[0063] The nozzle 5 opens to a part of the bottom surface of the partial flow path 45 (the surface opposite to the pressurizing chamber 43). The nozzle 5 is located, for example, approximately in the center of the bottom surface of the partial flow path 45. However, the nozzle 5 may be provided eccentrically with respect to the center of the bottom surface of the partial flow path 45. The vertical cross section of the nozzle 5 is tapered so that the diameter becomes smaller toward the ejection surface 3a. However, the nozzle 5 may be partially or entirely reverse tapered.

[0064] The connection portion 37 extends upward from the upper surface of the common flow path 23, for example. The restrictor 39 extends from this portion in a direction along the plate 27. The supply path 41 extends upward from the restrictor 39 and is connected to the lower surface of the pressurizing chamber 43. In a plan view (viewed in the D3 direction), the connection position of the supply path 41 to the pressurizing chamber 43 is, for example, an end of the lower surface of the pressurizing chamber 43 on the opposite side to the partial flow path 45 with respect to the center of the lower surface.

[0065] The orifice 39 has a smaller cross-sectional area (cross-section intersecting the flow direction) than the connection part 37 and the supply path 41. Furthermore, for example, excluding the nozzle 5, the orifice 39 has the smallest cross-sectional area within the individual flow paths 25. With regard to the main vibration (natural vibration of the liquid in the individual flow paths 25) described above, pressure waves of the liquid are likely to be reflected by the orifice 39. Therefore, unlike the description of the embodiment, the flow path on the nozzle 5 side of the connection part 37 or the flow path on the nozzle 5 side of the orifice 39 may be considered as an individual flow path.

[0066] As described above, the configuration of some or two or more ejection elements 15 may differ in detail from the configuration of other some or two or more ejection elements 15. One such example is a configuration in which the pressure chambers 43 are lined up in two rows on one side of the common flow path 23, and the length of the throttle 39 and / or the orientation of the throttle 39 relative to the other flow paths (those in the individual flow paths 25 and / or the common flow path 23) differs between the rows (but is the same within each row) due to the difference in the distance between the common flow path 23 and the pressure chambers 43 between the rows. Another example is a configuration in which the shapes and dimensions of the partial flow paths 45 within a row differ from each other (but are the same within each row) in order to shift the positions of the plurality of nozzles 5 connected to the plurality of pressure chambers 43 lined up in a row parallel to the D1 direction (paper feed direction) from each other in the D2 direction.

[0067] (3.3. Actuator) The actuator substrate 21 is generally plate-shaped and has an area spanning the multiple pressure chambers 43. The actuator 17 is, for example, a piezoelectric type that applies pressure to ink by mechanical distortion of a piezoelectric body. The piezoelectric actuator is, for example, a so-called unimorph type. The actuator 17 may also be configured with other types of piezoelectric actuators, such as a bimorph type. The unimorph type actuator 17 (actuator substrate 21) has, for example, a vibration plate 29, a common electrode 31, a piezoelectric layer 33, and individual electrodes 35, in this order from the flow path member 19 side.

[0068] The vibration plate 29, common electrode 31, and piezoelectric layer 33 extend across the multiple pressure chambers 43 in a plan view, for example. That is, they are provided in common to the multiple pressure chambers 43. An individual electrode 35 is provided for each pressure chamber 43. The individual electrode 35 has a main body portion 35a that overlaps the pressure chamber 43 and an extraction electrode 35b that extends from the main body portion 35a. The main body portion 35a has, for example, roughly the same shape and size as the pressure chamber 43.

[0069] The specific material and thickness of each layer may be set as appropriate. For example, the material of the piezoelectric layer 33 may be a ceramic such as PZT (lead zirconate titanate). The material of the diaphragm 29 may be a ceramic with or without piezoelectricity. The common electrode 31 and the individual electrodes 35 may be a metal such as an Ag-based or Au-based metal. The thickness of the diaphragm 29 and the piezoelectric layer 33 may each be 10 μm or more and 40 μm or less. The thickness of the common electrode 31 may be 1 μm or more and 3 μm or less. The thickness of the individual electrodes 35 may be 0.5 μm or more and 2 μm or less.

[0070] At least the portion of the piezoelectric layer 33 sandwiched between the main body portion 35a of the individual electrode 35 and the common electrode 31 is polarized in the thickness direction. Therefore, for example, when an electric field (voltage) is applied in the polarization direction of the piezoelectric layer 33 by the main body portion 35a and the common electrode 31, the piezoelectric layer 33 contracts in a direction along the layer. This contraction is regulated by the vibration plate 29. As a result, the actuator 17 is flexed and deformed so as to be convex toward the pressure chamber 43. When an electric field (voltage) is applied in the opposite direction to the above by the main body portion 35a and the common electrode 31, the actuator 17 is flexed and deformed in a direction away from the pressure chamber 43. By utilizing this flexural deformation, the volume of the pressure chamber 43 can be changed, pressure can be applied to the ink in the pressure chamber 43, and ink can be ejected from the nozzle 5, as described above.

[0071] For example, during printing, the common electrode 31 is applied with a constant potential over time. This constant potential is, for example, a reference potential. On the other hand, for example, a signal whose potential changes over time is input to the individual electrodes 35. This changes the strength of the electric field applied to the piezoelectric layer 33. This, for example, can cause the actuators 17 to flex as described above. Furthermore, by individually inputting multiple signals to the multiple individual electrodes 35, the flexural deformation of the multiple actuators 17 can be individually controlled. Consequently, the amount of droplets ejected from the multiple nozzles 5 can be individually controlled depending on the content of the image intended to be printed.

[0072] The actuator 17 may be connected to an external control unit (e.g., driver 13) as appropriate. For example, the flexible substrate 11 is disposed opposite the upper surface of the actuator substrate 21. Pads (not shown) of the flexible substrate 11 are joined to ends of the extraction electrodes 35b via conductive bumps. This connects the individual electrodes 35 to the driver 13 via signal lines (not shown) that the flexible substrate 11 has. This in turn makes it possible to input signals from the driver 13 to the individual electrodes 35.

[0073] Furthermore, although not specifically shown, the actuator substrate 21 has via conductors at appropriate positions in a plan view that penetrate the piezoelectric layer 33, are connected to the common electrode 31, and are exposed on the upper surface of the piezoelectric layer 33. Pads (not shown) on the flexible substrate 11 are joined to the via conductors via conductive bumps. This allows, for example, the common electrode 31 to be connected to a reference potential wiring (not shown) on the flexible substrate 11. This makes it possible to apply a reference potential to the common electrode 31.

[0074] (4. Operation of Ejection Element) As described above, the ejection element 15 applies pressure to the pressure chamber 43 by the actuator 17 to eject ink droplets. The driving method may be, for example, a pull-and-shoot method. The ejection operation of ink droplets by the pull-and-shoot method is as follows.

[0075] FIG. 4 is a schematic diagram for explaining the ejection operation of the ejection element 15. As shown in FIG.

[0076] In this diagram, the horizontal axis represents normalized time t / AL, which is obtained by dividing time t by AL (Acoustic Length). AL will be described later. The vertical axis on the left represents the potential V of the drive signal Sg1 input by the driver 13 to the actuator 17 (more specifically, the individual electrode 35). The vertical axis on the right represents the displacement x and velocity v of the meniscus (the ink liquid surface inside the nozzle 5). The positive side (the upper side of the diagram) of the right vertical axis represents the displacement x and velocity v toward the outside of the nozzle 5 (the -D3 side). Lines Lx and Lv represent the changes over time in displacement x and velocity v, respectively.

[0077] In the description here, when the potential of the individual electrode 35 is higher than the potential of the common electrode 31, an electric field is applied to the piezoelectric layer 33 in the same direction as the polarization direction, causing the actuator 17 to bend toward the pressure chamber 43. However, the potential levels of the individual electrode 35 and the common electrode 31 when the actuator 17 is bent toward the pressure chamber 43 may be opposite to those described here.

[0078] Before an ejection request is made, the drive signal Sg1 (or the individual electrode 35 from another point of view) is at a potential higher than the common electrode 31 (hereinafter referred to as the "high potential V Ｈ Each time an ejection request is made, the potential of the individual electrode 35 is set to a high potential V Ｈ a potential lower than the Ｌ "), and then at a predetermined timing, the high potential V Ｈ Low potential V Ｌ may be set appropriately, for example, to the same potential as the common electrode 31. From another perspective, a pulse Ps with a pulse width PW is input to the individual electrode 35 every time an ejection request is made.

[0079] Before a discharge request, the drive signal Sg1 is at a high potential V Ｈ As a result, the actuator 17 is bent toward the pressure chamber 43. The displacement x of the meniscus at this time is set to zero. The velocity v of the meniscus at this time is basically or ideally zero.

[0080] Next, the drive signal Sg1 is set to the low potential V Ｌ When the displacement reaches t / AL=0, the actuator 17 begins to return to its pre-deformation shape (flat shape), and the volume of the pressurizing chamber 43 increases. Consequently, a negative pressure is applied to the liquid in the pressurizing chamber 43. This displaces the meniscus toward the inside of the nozzle 5, and the absolute value of the velocity associated with this displacement increases. From another perspective, the liquid in the individual flow paths 25 begins to vibrate at its natural vibration period.

[0081] Thereafter, the absolute value of the meniscus velocity plateaus (t / AL = approximately 0.5) and begins to decrease. Furthermore, when t / AL becomes approximately 1, the volume of the pressurizing chamber 43 becomes maximum and the pressure becomes approximately zero. At this time, the displacement x of the meniscus is located closest to the inside of the nozzle 5, and the velocity v becomes approximately zero. Next, the volume of the pressurizing chamber 43 begins to decrease and the pressure increases.

[0082] The drive signal Sg1 is at a low potential V Ｌ After that, a high potential V Ｈ As a result, the actuator 17 begins to bend again toward the pressure chamber 43. The vibration first applied by the falling edge of the pulse Ps and the vibration second applied by the rising edge of the pulse Ps overlap, and a larger pressure is applied to the liquid. This pressure propagates through the partial flow path 45, causing the liquid to be ejected from the nozzle 5.

[0083] That is, the high potential V Ｈ Based on this, a low potential V Ｌ When the pulse width PW of the pulse Ps is set to half the time (AL) of the natural vibration period of the liquid in the individual flow path 25, the maximum value of the velocity v (maximum velocity v ｍａｘ ) is maximized. As a result, the liquid ejection speed and ejection amount are maximized.

[0084] As mentioned in the above paragraph, AL is, in concept, half the natural vibration period of the liquid in the individual flow path 25. However, it is not easy to theoretically determine the natural vibration period. Therefore, paradoxically, when the ejection operation is performed with various pulse widths PW, for example, the maximum velocity v ｍａｘ The length of the pulse width PW at which the angular frequency ω1 (or the ejection speed or ejection amount) is maximized may be defined as AL, and twice that length may be defined as the natural vibration period of the liquid in the individual flow path 25. From another perspective, in specifying the angular frequency ω1 of the individual flow path 25, the range of the individual flow path 25 (for example, whether or not the throttle 39 is included) does not need to be clearly defined. The same can be said for the angular frequency ω2 of the partial flow path 45.

[0085] The pulse width PW may be set to a value of about 0.5AL to 1.5AL, since other factors must be taken into consideration, such as consolidating the ejected droplets into one. Furthermore, by setting the pulse width PW to a value outside the AL, the ejection amount can be reduced, so the pulse width PW may be set to a value outside the AL in order to reduce the ejection amount.

[0086] The falling and / or rising edges of the pulse Ps may be inclined with respect to the vertical axis or may change stepwise. The drive signal Sg1 may include a waveform other than the pulse Ps. For example, it may include a waveform that reduces residual fluctuations of the meniscus. Such other waveforms may be connected to or separated from the pulse Ps.

[0087] The intended shading in an image (including characters) formed on a recording medium may be achieved by any suitable method. For example, it may be achieved by varying the diameter of dots on the recording medium, by varying the number of dots per area (density), or by a combination of these. The dot diameter may be adjusted by the size of a single droplet, by adjusting the number of droplets landing at one location, or by a combination of these.

[0088] From another perspective, the intended shading is determined by the high potential V Ｈ and low potential V Ｌ This may be achieved by adjusting the size of the droplets ejected from the nozzle 5, which is adjusted by the potential difference between the nozzle 5 and the nozzle 5, or by increasing or decreasing the number of droplets, which is adjusted by the number of pulses Ps included in the drive signal Sg1 corresponding to one ejection request, or by increasing or decreasing the number of ejection elements 15 per certain area that perform the ejection operation, or by a combination of these.

[0089] (5. Principle of Reducing Variation in Discharge Speed) First, an example of a factor that causes variation in discharge speed will be described, and then an outline of a method for reducing variation in discharge speed caused by that example factor will be described.

[0090] (5.1. Causes of Variation) As explained with reference to FIG. 4, in the pull-and-shoot type, when the pulse width PW is AL, the maximum speed v ｍａｘ In other words, the maximum speed v ｍａｘ The more the pulse width PW deviates from AL, the greater the maximum speed v ｍａｘ becomes smaller.

[0091] 5A is a conceptual diagram illustrating the above phenomenon. In this diagram, the horizontal axis represents the pulse width PW, and the vertical axis represents the maximum meniscus velocity v ｍａｘ The lines Ln1, Ln2, and Ln3 in the figure represent the pulse width PW and maximum velocity v ｍａｘ This shows the relationship between

[0092] As shown by the lines Ln1 to Ln3, as the pulse width PW is increased, the maximum speed v ｍａｘ If the pulse width PW is further increased, the maximum speed v ｍａｘ The pulse width PW at this time can be said to be AL.

[0093] As shown in the figure, the AL may differ between multiple ejection elements 15. In other words, there is variation in AL. In the example shown, the AL is longest in the order of line Ln1, line Ln2, and line Ln3. On the other hand, the shape of the pulse Ps (or, from another perspective, the pulse width PW) for ejecting droplets at the same ejection volume is common to, for example, multiple ejection elements 15.

[0094] Therefore, if the AL (labeled with line La1) of the ejection element 15 of line Ln1 is used as the pulse width PW, the ejection elements 15 of lines Ln2 and Ln3 will receive a pulse width PW with a time length that is outside their own AL. As a result, the ejection elements 15 of lines Ln2 and Ln3 will be ejected at a maximum velocity v ｍａｘ does not become the maximum for itself, and the maximum velocity v of the ejection element 15 on the line Ln1 ｍａｘIn FIG. 5A, when the AL of the ejection elements 15 of the line Ln1 is used, the maximum velocity v ｍａｘ The fact that the intersections of the lines Ln1 to Ln3 with the line La1 are different from one another is indicated by three dotted lines parallel to the horizontal axis.

[0095] For the reasons described above, the maximum velocity v ｍａｘ The maximum speed v ｍａｘ Since the ejection speed and ejection amount of droplets are closely correlated with the ejection speed and ejection amount, the ejection speed and ejection amount vary among the plurality of ejection elements 15. As a result, for example, the image quality deteriorates.

[0096] There are various factors that cause variations in AL, such as design factors and manufacturing factors. From another perspective, these factors include differences in intended shape, size, etc. and differences in unintended shape, size, etc.

[0097] Design factors include, for example, the above-mentioned differences in length and / or orientation of the multiple throttles 39 resulting from differences in the positions of the multiple pressurizing chambers 43, and differences in shape of the multiple partial flow paths 45 for shifting the positions of the multiple nozzles 5 in the D2 direction from one another. Further examples include differences in rigidity of the wall surfaces constituting the individual flow paths 25 resulting from differences in the positions of the multiple individual flow paths 25 relative to the common flow path 23 or the flow path for connecting the common flow path 23 and the back surface member 9.

[0098] An example of a manufacturing factor is dimensional variations among the individual flow channels 25 that occur when holes constituting the flow channels are formed in the plate 27 by etching. More specifically, for example, the relative relationship between a predetermined portion of an individual flow channel 25 and other flow channels (those within the individual flow channels 25 and / or the common flow channel 23) differs among the individual flow channels 25, resulting in differences in the density of the patterns among the individual flow channels 25. As a result, dimensional variations occur due to the microloading effect. Another example of a manufacturing factor is dimensional variations that occur when the multiple plates 27 are bonded together by heating and pressurizing. Specifically, for example, the temperature and / or pressure applied to the adhesive between the plates 27 differs depending on the position within the plate 27, resulting in variations in the dimensions and / or rigidity among the multiple individual flow channels 25.

[0099] In the description here, it is assumed that the waveform of the pulse Ps corresponding to the same ejection amount is common to a plurality of ejection elements 15. The plurality of ejection elements 15 having a common waveform may be all of the ejection elements 15 of the head 2 (excluding unique ones as described above), or may be some of the ejection elements 15. An example of the latter is a case where, for example, as described above, when the shapes of the individual flow paths 25 differ between rows of pressure chambers 43, the waveform of the pulse Ps differs between rows and the waveform is the same within a row.

[0100] (5.2. Overview of Method for Reducing Variation) FIG. 6 is a conceptual diagram for explaining a method for reducing the variation in ejection speed caused by the variation in AL as described above. In this diagram, the horizontal axis represents time t (μs). The vertical axis represents the meniscus speed v (m / s). The 0, + side, and - side of the vertical axis are the same as the 0, + side, and - side of the vertical axis on the right side of FIG. 4.

[0101] This figure shows the change over time in the velocity v when droplets are ejected by the pull-and-shoot method described with reference to FIG. 4. t=0 (μs) in FIG. 6 roughly corresponds to t / AL=0.5 in FIG. 4. The line associated with "v1" in the legend shows the change over time in the velocity v of the main vibration (the natural vibration of the liquid in the individual flow path 25). As can be understood from the above explanation, the velocity v1 of the main vibration oscillates with a period of 2AL (approximately 12 μs in the illustrated example). The first peak of the main vibration (around 6 μs) is the peak where the rising edge of the pulse Ps is superimposed in FIG. 4 (maximum velocity v ｍａｘ It corresponds to the mountain including the

[0102] The liquid not only experiences natural vibrations (main vibrations) that depend on the overall shape and dimensions of the individual flow paths 25, but also natural vibrations (high-frequency vibrations) that depend on the shape and dimensions of the partial flow paths 45. The line associated with "v2" in the legend indicates the change over time in the velocity v of the high-frequency vibration. The velocity v2 of the high-frequency vibration oscillates at the natural vibration period of the liquid in the partial flow path 45 (approximately 6 μs in the illustrated example). The period of the high-frequency vibration is shorter than the period of the main vibration. Furthermore, the amplitude of the high-frequency vibration is smaller than the amplitude of the main vibration.

[0103] The line associated with "v3" in the legend indicates the change over time in the velocity v of the vibration (hereinafter sometimes referred to as "composite vibration") that is a combination of the main vibration and the high-frequency vibration. When the first peak (around 6 μs) of the main vibration that causes ejection overlaps with the valley of the high-frequency vibration, a peak with a flat top appears in the composite vibration. In other words, the maximum velocity v ｍａｘ The change in velocity v in the vicinity becomes slower.

[0104] FIG. 5B shows the relationship between the pulse width PW and the maximum meniscus velocity v when the main vibration and the high-frequency vibration are combined as described above. ｍａｘ 5B is a diagram similar to FIG. 5A. Lines Ln1 to Ln3 in FIG. 5B show the relationship between the maximum velocity v of the nozzles 5 different from each other, similar to lines Ln1 to Ln3 in FIG. 5A. ｍａｘ 5A, the line La1 indicates the pulse width PW corresponding to the AL of the ejection element 15 of the line Ln1.

[0105] 5A and 5B, the peak of the first peak in the resultant vibration is flattened, and the peaks of the lines Ln1 to Ln3 are also flattened. That is, in the range where the pulse width PW is at or close to AL (horizontal axis), even if the pulse width PW is changed, the maximum velocity v ｍａｘ does not change significantly (is roughly constant). From another perspective, the flat tops of the lines Ln1 to Ln3 tend to overlap. In the range where the tops overlap, the maximum velocity v ｍａｘ is close to the maximum value.

[0106] Therefore, for example, when a pulse width PW having a length corresponding to AL of the line Ln1 is commonly applied to the ejection elements 15 of the lines Ln1 to Ln3, the maximum velocity v ｍａｘ Not only does the ejection element 15 on the lines Ln2 and Ln3 have a maximum velocity v ｍａｘ As a result, as shown by a single dotted line parallel to the horizontal axis, the maximum velocity v ｍａｘ is easy to approach. ｍａｘ The variation in the ejection speed and / or ejection amount, which is highly correlated with the ejection speed, is reduced.

[0107] (5.3. Consideration of the Influence of Damping Rate) As shown in FIG. 6 , the velocity v1 of the main vibration reaches a minimum value just before the first peak (t = 0). As can be seen from FIG. 4 , the time point t = 0 is approximately the time point when 0.5 AL has elapsed since the falling edge of pulse Ps. At this time point, the velocity v2 of the high-frequency vibration also reaches a minimum value. In other words, at the minimum value just before the first peak of the main vibration, the main vibration and the high-frequency vibration are in phase. Therefore, in simple terms, when the angular frequency of the main vibration is ω1 and the angular frequency of the high-frequency vibration is ω2, the valley of the high-frequency vibration can be superimposed on the first peak of the main vibration by setting ω2 / ω1 to a multiple of 2 (2 in FIG. 6 ) or a value close to a multiple of 2.

[0108] However, the actual principal vibration decays as shown in FIG. 6 . In this case, setting ω2 / ω1 slightly larger than a multiple of 2 makes it easier to flatten the peak of the composite vibration velocity v3. That is, in FIG. 6 , the waveform of the high-frequency vibration is slightly shifted to the left side of the figure (the side with a shorter elapsed time t). As a result, the velocity v1 on the side with a shorter elapsed time t than the peak of the principal vibration (before relative damping has progressed) is reduced relatively more by the velocity v2 of the valley of the high-frequency vibration. On the other hand, the degree to which the velocity v1 on the side with a longer elapsed time t than the peak of the principal vibration (after relative damping has progressed) is reduced by the velocity v2 of the valley of the high-frequency vibration is reduced relatively less. As a result, the time t until the peak of the composite vibration velocity v3 is flattened is lengthened.

[0109] For this reason, in the above-mentioned formula (1), the range of ω2 / ω1 is defined according to the attenuation rate γ1. Furthermore, in formulas (2) and (3), the range of ω2 / ω1 is defined by a range whose center is greater than 2 or 4, rather than a range whose center is centered around 2 or 4.

[0110] (6. Derivation of Equations) (6.1. Derivation Method) The derivation method of equations (1) to (3) is as follows.

[0111] Specific values ​​are substituted into A1, A2, γ1, γ2, ω1, and ω2 in equations (4) and (5) to calculate the velocity v1(t) of the principal vibration and the velocity v2(t) of the high-frequency vibration. Furthermore, the velocity v3(t) of the composite vibration is calculated by v1(t) + v2(t). The maximum value (local maximum value) of the first peak of the calculated velocity v3(t) is found. Next, the length of time within a range of -5% of the maximum value is found. This length of time is referred to as FT (Flat Time), as indicated by the symbols in FIG. 6.

[0112] If strictness is ignored, the maximum value of the first peak of the velocity v3(t) calculated as above (the maximum value of the first peak of the natural vibration) is the maximum velocity v3(t) when vibration occurs only due to the falling edge of the pulse Ps in FIG. 4 (assuming that there is no rising edge of the pulse Ps). ｍａｘIn the applicant's experience, if the variation in the maximum value of the first peak of the velocity v3(t) is within 5%, the maximum velocity v obtained by superimposing the natural vibration due to the falling edge of the pulse Ps and the vibration due to the rising edge of the pulse Ps is equivalent to ｍａｘ The variability is likely to be within the acceptable range.

[0113] Furthermore, from the above, for example, if the difference between the pulse width PW and AL is equal to or less than FT, this difference is equal to the maximum speed v ｍａｘ From another perspective, the maximum speed v ｍａｘ Therefore, FT is directly the length of time during which the peak of the combined natural vibration is flat, as shown in FIG. 6, but it is also the maximum velocity v ｍａｘ This is an index that has a strong correlation with the time length of the portion where the peak of the peak becomes flat (the fluctuation range of the pulse width PW where the peak becomes flat).

[0114] As the FT becomes longer, the maximum velocity v ｍａｘ That is, when a common pulse width PW is applied to a plurality of ejection elements 15 having different ALs, the longer the FT, the more easily the ejection elements 15 can eject the ink at the maximum velocity v ｍａｘ From another perspective, the probability that the maximum velocity v ｍａｘ In order to make the AL uniform, the allowable variation in AL becomes larger.

[0115] The above procedure for determining FT is performed for various values ​​of ω2 / ω1. This identifies the relationship between ω2 / ω1 and FT. This makes it possible to identify, for example, the ω2 / ω1 at which FT is at its maximum value, or to identify a range in which FT is equal to or greater than a predetermined value. Equations (1) to (3) define a range of ±5% of the center value of ω2 / ω1 at which FT is at its maximum value.

[0116] As mentioned above, FT is the length of time during which v3(t) falls within a range of -5% from its maximum value. FT' is the length of time during which v3(t) falls within a range of -10% from its maximum value. The inventors of the present application have confirmed through calculations that the range of ±5% of the center value of ω2 / ω1 at which FT' reaches its maximum value is not significantly different from the range of ±5% of the center value of ω2 / ω1 at which FT reaches its maximum value. This demonstrates the validity of the definition of FT (a -5% value) and the range of ±5% centered on the maximum value of FT.

[0117] The procedure for determining FT is performed not only for various values ​​of ω2 / ω1, but also for various values ​​of γ1 / ω1 and γ2 / ω1, thereby identifying an advantageous range for ω2 / ω1 depending on the values ​​of the damping factors γ1 and γ2, where γ1 / ω1 is the damping ratio of the principal vibration.

[0118] The various values ​​used in the calculation are as follows: A1: 10 (m / s) A2: 1.5 (m / s) ω2 / ω1: varied in increments of 0.01 in the range of 0 to 9 γ1 / ω1: 0, 0.12, 0.23, or 0.46 γ2 / ω1: 0, 0.23, 0.46, 0.69, 0.92, or 1.15

[0119] The above values ​​are set based on the configuration of the ejection element 15 specifically designed for implementation. However, the various values ​​above also include hypothetical values ​​(unrealistic values). For example, γ1 / ω1 = 0 is a hypothetical value because it is used when the main vibration is undamped. Also, the above values ​​are values ​​obtained by rounding off the decimal part of the values ​​actually used in the calculation to an appropriate place (the same applies hereinafter).

[0120] (6.2. Calculation Results) Figures 7A and 7B are diagrams showing examples of calculation results for FT. In these figures, the horizontal axis represents ω2 / ω1. The vertical axis represents FT (0.1 μs). The multiple lines in the diagrams show the relationship between ω2 / ω1 and FT for multiple cases where γ2 / ω1 is different from one another. Figure 7A shows the results when γ1 / ω1=0. Figure 7B shows the results when γ1 / ω1=0.23.

[0121] As shown in Fig. 7A, when the primary vibration is not attenuated, FT reaches its maximum value when ω2 / ω1 is a multiple of 2. On the other hand, as shown in Fig. 7B, when the primary vibration is attenuated, FT reaches its maximum value when ω2 / ω1 is slightly larger than a multiple of 2. The difference between ω2 / ω1 at which FT reaches its maximum value and a multiple of 2 is, for example, less than 0.5. The above tendency remains the same even when the value of γ2 / ω1 is different.

[0122] Fig. 8 is a diagram similar to Figs. 7A and 7B, showing another example of the FT calculation results. Like Fig. 7B, Fig. 8 shows the results when γ1 / ω1 = 0.23. However, the condition for γ2 / ω1 is slightly different from that in Fig. 7B, and the calculation was performed over a wider range of ω2 / ω1 than in Fig. 7B.

[0123] 9A to 9C and 10A to 10C are diagrams each showing lines extracted from Fig. 8 when γ2 / ω1 is a specific value. Specifically, as indicated in each diagram, these diagrams show FT when γ2 / ω1 is 0, 0.23, 0.46, 0.69, 0.92, or 1.15.

[0124] As can be seen from comparing these figures, the value of the multiple of 2 close to ω2 / ω1 at which FT is maximized changes depending on the value of γ2 / ω1. For example, when γ2 / ω1 is 0 or 0.23, FT is maximized when ω2 / ω1 is a value slightly deviating from 2. When γ2 / ω1 is 0.46 or 0.69, FT is maximized when ω2 / ω1 is a value slightly deviating from 4. When γ2 / ω1 is 0.92 or 1.15, FT when ω2 / ω1 is a value slightly deviating from 4 and FT when ω2 / ω1 is a value slightly deviating from 6 are roughly equivalent and maximized. In this way, the larger γ2 / ω1 becomes, the larger the value of the multiple of 2 close to ω2 / ω1 at which FT is maximized becomes.

[0125] In addition to the above-mentioned trends, it can be seen that the larger γ2 / ω1, the smaller the maximum value of FT and the gentler the slope of the mountain containing the maximum value of FT. Therefore, for example, by setting γ2 / ω1 small (e.g., 0.46 or less or 0.23 or less), the maximum value of FT can be increased. Furthermore, for example, by setting γ2 / ω1 relatively large (e.g., 0.46 or more or 0.69 or more), the fluctuation of FT when ω2 / ω1 deviates from the design value can be reduced.

[0126] Figures 11, 12A to 12C, and 13A to 13C are similar to Figures 8, 9A to 9C, and 10A to 10C, except that, as noted in Figure 11, they show the results when γ1 / ω1=0.46.

[0127] As shown in these figures, even when γ1 / ω1 = 0.46, the same tendency as when γ1 / ω1 = 0.23 can be confirmed. For example, it can be confirmed that as γ2 / ω1 increases, the value of a multiple of 2 close to ω2 / ω1 at which FT is maximized tends to increase.

[0128] As can be seen from a comparison between Fig. 8 and Fig. 11, the larger γ1 / ω1 becomes, the more ω2 / ω1 at which FT reaches its maximum value deviates from a multiple of 2. This tendency can be explained from the waveform shown in Fig. 6. Specifically, the larger γ1 becomes, the smaller the first peak of the main vibration (v1) becomes on the right side of the diagram (the side where the elapsed time t is longer) compared to the left side of the diagram. Therefore, FT can be lengthened by increasing the amount of shift of the high-frequency vibration (v2) to the left of the diagram.

[0129] 8 and 11, FT reaches its maximum value at a position slightly shifted for each of the multiples of 2 (2, 4, 6, and 8). The larger the multiple of 2, the greater the shift between the multiple of 2 and ω2 / ω1 at which FT reaches its maximum value.

[0130] From the above, ω2 / ω1 at which FT has a maximum value is correlated with γ1 / ω1 and multiples of 2. Furthermore, the value of γ2 / ω1 does not fundamentally affect ω2 / ω1 at which FT has a maximum value. Therefore, when n is a positive integer, a formula for determining ω2 / ω1 at which FT has a maximum value from γ1 / ω1 and 2n was derived by multiple regression analysis with γ1 / ω1 and n (or, from another perspective, 2n, which is a multiple of 2) as independent variables and ω2 / ω1 at which FT has a maximum value as a dependent variable.

[0131] The combinations of n, γ1 / ω1, and ω2 / ω1 used to derive the formula, where FT has a maximum value, are as follows: When γ1 / ω1=0, (n=1, ω2 / ω1=2), (n=2, ω2 / ω1=4), (n=3, ω2 / ω1=6) When γ1 / ω1=0.115473, (n=1, ω2 / ω1=2.07), (n=2, ω2 / ω1=4.16), (n=3, ω2 / ω1=6.29) When γ1 / ω1=0.230947, (n=1, ω2 / ω1=2.14), (n=2, ω2 / ω1=4.34), (n=3, ω2 / ω1=6.49) When γ1 / ω1=0.461894, (n=1, ω2 / ω1=2.28), (n=2, ω2 / ω1=4.65), (n=3, ω2 / ω1=6.95)

[0132] Then, the following equation was obtained as an equation for finding ω2 / ω1 at which FT becomes a maximum value based on γ1 / ω1 and n: ω2 / ω1=2n(1+0.32×γ1 / ω1) (6) Equation (1) defines the ±5% range of the right-hand side of equation (6) above.

[0133] Furthermore, the value of ω2 / ω1 used in deriving the above formula (6) is directly used to define a range of ±5% of that value, which are given in formulas (2) and (3).

[0134] Equation (2) is found as follows: 2.07×0.95<ω2 / ω1<2.28×1.05 Here, 2.07 and 2.28 are the minimum and maximum values ​​of ω2 / ω1 when γ1 is not 0 and n is 1, the former being when γ1 / ω1=0.12 and the latter being when γ1 / ω1=0.46.

[0135] Equation (3) is found as follows: 4.16 × 0.95 < ω2 / ω1 < 4.65 × 1.05 Here, 4.16 and 4.65 are the minimum and maximum values ​​of ω2 / ω1 when γ1 is not 0 and n is 2, the former being when γ1 / ω1 = 0.12 and the latter being when γ1 / ω1 = 0.46.

[0136] (6.3. Amplitude) Equations (1) to (3) are based on calculation results assuming specific values ​​for A1 and A2. However, even if A1 and A2 are other values, by setting ω2 / ω1 to a value in the range centered on a value slightly larger than 2n, the maximum meniscus velocity v due to variations in AL can be reduced. ｍａｘ However, this does not change the fact that it is easier to reduce the variation in the ratio of A1 to A2. In other words, even if A1 and A2 are other values, the best effect may not necessarily be obtained, but a better effect may be obtained. Therefore, it is not essential that A1 and A2 are the values ​​used in the calculation. However, if the ratio A1 / A2 of A1 and A2 is the same, the above calculation results will show the same value. Therefore, A1 / A2 may be set to a value within a range of ±20%, ±10%, or ±5% of that value.

[0137] In addition to or instead of A1 / A2, the ratio (B2 / B1) of the peak intensity B2 of the amplitude spectrum of the high-frequency vibration velocity v2 to the peak intensity B1 of the amplitude spectrum of the principal vibration velocity v1 may be set to fall within a predetermined range.

[0138] 14 is a diagram showing an example of the amplitude spectrum of the velocity of meniscus vibration. In this diagram, the horizontal axis represents frequency f (kHz), and the vertical axis represents the intensity I of the spectrum, more specifically, the amplitude A (m / s) of the velocity.

[0139] As shown in this figure, the actual vibration of the meniscus is not made up of a combination of only the main vibration and the high-frequency vibration, but is made up of a combination of vibrations of various frequencies (or so it can be understood).The intensity increases at frequencies corresponding to the main vibration and the high-frequency vibration and in the vicinity thereof (see frequencies related to B1 and B2).

[0140] The maximum value of the portion where the intensity is high as described above is referred to as the peak intensity. The peak intensity related to the main vibration is designated as B1, and the peak intensity related to the high-frequency vibration is designated as B2. In this case, B2 / B1 may be set to, for example, 0.19 or more and 0.25 or less. This range was derived by the applicant based on multiple experiments and multiple simulations under various different conditions.

[0141] (7. Parameter Adjustment Method) The value of any of the parameters ω1, ω2, and γ1 may be adjusted to satisfy equations (1) to (3). The parameter values ​​depend on various factors. Examples of the various factors include the shape, dimensions, and rigidity of the inner walls (including the actuators 17) of each part of the individual flow path 25, as well as the density, elastic modulus, and viscosity of the liquid in the individual flow path 25. When adjusting the parameter values, any of these factors may be adjusted.

[0142] For example, ω1 and γ1, which are affected by the entire individual flow path 25 (or, from another perspective, the general configuration of the individual flow path 25), may be set basically according to the same design concept as in the past. Then, the value of ω2 may be adjusted by adjusting the shape and dimensions of the partial flow path 45, thereby satisfying the formulas (1) to (3).

[0143] More specifically, for example, the vibration of the liquid in the partial flow path 45 can be approximated or estimated by the vibration of the liquid in a well-known closed tube. The closed tube is cylindrical with one end (the end on the nozzle 5 side) closed and the other end (the end on the pressurizing chamber 43 side) open. The natural vibration in the closed tube generates a standing wave with the closed end as a node and the open end as an antinode. That is, the wavelength of the natural vibration is approximately four times the length of the closed tube. Meanwhile, there is a well-known relationship between the wavelength λ, the sound speed c, and the angular frequency ω: λ = c × 2π / ω. Therefore, ω2 can be adjusted by changing the length of the partial flow path 45. Note that well-known open-end correction may be taken into account in actual design.

[0144] When n is 1 or 2, it can be said that ω2 / ω1 is relatively small. In this case, the partial flow paths 45 may be relatively long. For example, the length of the partial flow paths 45 may be greater than the sum of the length of the pressure chamber 43 in the flow direction (maximum length in the planar direction) and the length of the orifice 39 in the flow direction (maximum length in the planar direction). Furthermore, the length of the partial flow paths 45 may be increased by increasing the thickness (height) of the common flow path 23. The length of the partial flow paths 45 may be the length of the center line of the flow path (a line passing through the center of the cross section). The length of the individual flow paths 25 may be, for example, the length of the portion of the individual flow paths 25 closer to the nozzle 5 than the orifice 39, the length of the portion of the individual flow paths 25 closer to the nozzle 5 than the connection portion 37, or the length from the connection position with the common flow path 23 closer to the nozzle 5.

[0145] The length of the partial flow path 45 may be adjusted by bending the partial flow path 45. In this case, the length of the partial flow path 45 can be adjusted without changing the thickness of the flow path member 19.

[0146] In addition to adjusting the length of the partial flow path 45, ω2 (or other parameters) can be adjusted by various methods. For example, as is understood from the well-known open-end correction, ω2 may be adjusted by changing the diameter of the partial flow path 45 to change the wavelength of the high-frequency vibration. Also, for example, γ1 / ω1 may be adjusted by changing the physical properties of the liquid (by changing the type of liquid expected to be used).

[0147] The above describes the adjustment of γ1, ω1, and ω2 included in formulas (1) to (3). When γ2, A2 / A1, and / or B2 / B1 are adjusted, any of the various factors that affect these may also be adjusted. Factors that affect γ2 include, for example, the shape and dimensions of the partial flow channel 45 and the physical properties of the liquid. Factors that affect A2 / A1 and / or B2 / B1 include the factors (already mentioned) that affect ω1, ω2, and γ1.

[0148] (8. Method of Specifying Parameters) Whether or not the formulas (1) to (3) are satisfied may be specified by various methods. In other words, the values ​​of the various parameters in the formulas (1) to (3) may be specified by various methods. An example of such a method will be described below.

[0149] In an experiment, a drive signal Sg1 having a falling edge (no rising edge) of the pulse Ps is input to the actuator 17 of the head 2 to be measured. At this time, the speed of the meniscus is measured using a laser Doppler vibrometer. In the measurement, a laser is irradiated onto the meniscus from the outside via the nozzle 5. The frequency of the reflected laser is then detected. This allows the change in the speed of the meniscus over time (or, from another perspective, the vibration waveform) to be obtained, as shown in FIG. 6.

[0150] The obtained waveform includes waveforms of various frequencies, such as waveforms due to the main vibration and waveforms due to high-frequency vibration. This waveform is decomposed into waveforms for each frequency using Fourier transform (e.g., FFT: fast Fourier transform). This results in the waveforms of the main vibration and high-frequency vibration. Then, the amplitude (A1 or A2), damping factor (γ1 or γ2), and angular frequency (ω1 or ω2) are calculated so that the functions of equations (4) and (5) apply to each waveform. For example, the spectrum obtained by Fourier transforming and squaring the damped vibration has a distribution according to a Lorentz function near the peak, and this can be used to calculate the parameters. Specifically, the intensity X(f) near the frequency f of the main vibration peak in equation (1) is expressed by the following equation, and by fitting this, the amplitude A1, damping factor γ1, and angular frequency ω1 can be calculated. Parameters for high-frequency vibration can also be calculated in a similar manner. |X(f)| ２ = A1 ２ / (4×(f-ω1 / 2π) ２ +(γ1 / π) ２ )

[0151] Furthermore, the amplitude, damping rate, and angular frequency may be calculated as follows. For example, the absolute value of the first valley (the minimum value at t=0 in FIG. 6) may be used as the amplitude. The damping rate may be calculated by the following formula, where y1 and y2 are the values ​​of two adjacent maximum values ​​(or two adjacent minimum values), and t1 and t2 are the times when y1 and y2 are obtained: γ=ln(y1 / y2) / (t2-t1) The angular frequency may be calculated by the following formula, using the above-mentioned t1 and t2: ω=2π(t2-t1)

[0152] B2 / B1 may be determined, for example, as follows: When the Fourier transform is performed as described above, a spectrum such as that shown in FIG. 14 can be obtained. The highest of the maximum intensity values ​​is set as peak intensity B1. The maximum intensity value next highest after peak intensity B1 on the higher frequency side than peak intensity B1 is set as peak intensity B2. Of course, peak intensities B1 and B2 may be determined after appropriately excluding maximum values ​​that are noisy.

[0153] The frequency of peak intensity B1 is approximately ω1 / 2π, but these do not necessarily coincide. Similarly, the frequency of peak intensity B2 is approximately ω2 / 2π, but these do not necessarily coincide. Furthermore, B2 / B1 is close to A2 / A1, but these do not necessarily coincide.

[0154] (9. Summary of the embodiment) As described above, the liquid ejection head 2 according to the embodiment includes a flow path member 19 and an actuator 17. The flow path member 19 includes individual flow paths 25 that accommodate liquid. The individual flow paths 25 include a pressure chamber 43, a partial flow path 45 extending from the pressure chamber 43, and a nozzle 5 that opens to the outside at the end of the partial flow path 45 opposite the pressure chamber 43. The actuator 17 applies pressure to the pressure chamber 43. The damping rate of the natural vibration (main vibration) of the liquid in the individual flow path 25 is defined as γ1 (rad / s). The angular frequency of the main vibration is defined as ω1 (rad / s). The angular frequency of the natural vibration (high-frequency vibration) of the liquid in the partial flow path 45 is defined as ω2 (rad / s). n is defined as a positive integer. In this case, at least one of the above-described formulas (1) to (3) holds.

[0155] From another perspective, the liquid ejection device (printer 1) according to the embodiment has the head 2 as described above, and a moving unit 85 that moves the head 2 and the recording medium relative to each other.

[0156] Therefore, for example, as described above, the peak of the natural oscillation of the meniscus velocity is flattened (see FIG. 6), and the change in the pulse width PW (or, from another point of view, the difference between AL and PW) can be used to change the maximum meniscus velocity v ｍａｘ As a result, the influence of the maximum meniscus velocity v due to the variation in AL of the ejection elements 15 can be reduced (FIGS. 5A and 5B). ｍａｘ This can reduce the variation in the maximum speed v ｍａｘ This reduces variations in the ejection speed and / or ejection amount, which are correlated with the ink ejection speed and / or the ejection amount, thereby improving image quality.

[0157] In light of the principle of reducing variation, the ratio ω2 / ω1 between the two has an effect, and the absolute value (rad / s) does not have an effect. Therefore, when formulas (1) to (3) are applied, ω2 and ω1 are, in principle, arbitrary.

[0158] In reality, γ1 / ω1 is greater than 0. Furthermore, when γ1 / ω1 is greater than 1, the meniscus velocity does not oscillate, and the principle of the pull-and-hit equation does not hold. For these reasons, there is a large overlap between the range of γ1 / ω1 values ​​used in the calculation and the realistic range of γ1 / ω1 values. In other words, when applying equations (1) to (3), the value of γ1 / ω1 is not limited to the value used in the calculation. However, the value of γ1 / ω1 may be limited to 0.46 or less, or 0.5 or less (including 0.54 or less) obtained by rounding this value up or down.

[0159] 9A to 9C, etc., the effect of γ2 / ω1 on the establishment of equations (1) to (3) is small. In other words, when applying equations (1) to (3), the absolute values ​​(rad / s) of γ2 / ω1 and γ2 are arbitrary.

[0160] Whether or not the formulas (1) to (3) hold is affected by the physical properties of the liquid (or, from another perspective, the type of liquid). However, a head 2 that satisfies the formulas (1) to (3) does not need to include a liquid as a constituent element. In other words, whether or not the technology disclosed herein is applied may be determined for a head 2 that is distributed without being filled with liquid. Generally, a head 2 is configured to exhibit intended performance, performance required by specifications, or optimal performance when so-called genuine ink is used. Therefore, the physical properties of the liquid intended to be used in the head 2 can be identified based on the configuration of the head 2 through analysis, experiment, or the like. In other words, whether or not the formulas (1) to (3) hold can be determined regardless of whether or not the liquid is present. However, the physical properties of the liquid may also be identified from specifications, instructions, or the like. Alternatively, whether or not the formulas (1) to (3) hold may be determined for a head 2 that is filled with liquid, unlike the above.

[0161] Equations (1) to (3) may hold for any number of the ejection elements 15 of the head 2. For example, they may hold for all of the ejection elements 15 of the head 2, or may hold for two or more but a portion of the ejection elements 15. The portion may be, for example, less than 50%, 50% or more, or 80% or more.

[0162] In the above, the effect has been explained from the viewpoint of the variation among the plurality of ejection elements 15. When focusing on one ejection element 15, the intended maximum velocity v ｍａｘ and the actual maximum speed v ｍａｘ From this perspective, the number of ejection elements 15 that the head 2 has may be one.

[0163] n may be 1 or 2.

[0164] 8 to 13C, for example, the maximum value of FT tends to become large, although this depends on the value of γ2 / ω1, and as a result, the effect of reducing the above-mentioned variations is improved.

[0165] γ1 / ω1 may be set to 0.46 or less.

[0166] In this case, as already described by comparing Fig. 8 with Fig. 11, for example, the smaller γ1 / ω1 is, the easier it is to increase FT, and therefore it becomes easier to obtain the effect of increasing FT. Furthermore, since the value of γ1 / ω1 used when formulas (1) to (3) are obtained is used, there is a high probability that the effect of increasing FT can be obtained.

[0167] When the damping rate of the natural vibration of the liquid in the partial flow path 45 is γ2 (rad / s), γ2 / ω1 may be set to 1.15 or less, preferably 0.92 or less, and more preferably 0.46 or less.

[0168] 9A to 10C, the smaller γ2 / ω1 is, the easier it is to increase FT, and therefore, it becomes easier to obtain the effect of increasing FT. Furthermore, since the value of γ2 / ω1 obtained when formulas (1) to (3) are used, it is highly likely that the effect of increasing FT can be obtained.

[0169] The ratio B2 / B1, which is the peak intensity B2 of the amplitude spectrum of the velocity of the natural vibration (main vibration) of the liquid in the individual flow path 25 relative to the peak intensity B1 of the amplitude spectrum of the velocity of the natural vibration (main vibration) of the liquid in the partial flow path 45, may be 0.19 or more and 0.25 or less.

[0170] In this case, for example, by combining the high-frequency vibration of the above-described intensity with the main vibration, it is possible to further reduce the variation in droplet ejection speed among the multiple ejection elements 15. By setting B2 / B1 to 0.19 or more, the high-frequency vibration appropriately affects the ejection. By setting B2 / B1 to 0.25 or less, the effect of the high-frequency vibration on the ejection is not too great.

[0171] The head 2 may further include a driver 13 that drives the actuator 17 by a pull-and-hit method.

[0172] In this case, for example, the added value of the head 2 is improved. Also, the above-mentioned effects can be obtained by the pull-and-hit drive.

[0173] In the above embodiment, the printer 1 is an example of a liquid ejection device, and the printing paper P is an example of a recording medium.

[0174] The technology according to the present disclosure is not limited to the above-described embodiments and may be implemented in various forms.

[0175] The actuator drive system may be any system that generates a natural frequency of the main vibration and applies pressure to the liquid in synchronization with the natural frequency. Therefore, a typical system is a pull-and-hit system, but an improved version of the pull-and-hit system or a system that is difficult to classify as a pull-and-hit system may also be used.

[0176] The liquid ejection head may have a recovery flow path that recovers liquid from the partial flow path. The recovery flow path contributes to, for example, reducing the likelihood of liquid stagnation in the partial flow path. This reduces the likelihood of the viscosity of the liquid in the nozzle and partial flow path increasing due to evaporation of the solvent in the liquid near the nozzle.

[0177] The actuator is not limited to a unimorph or bimorph type, and may be, for example, a vertical piezoelectric element configured by laminating an electrode layer and a piezoelectric layer, which directly transmits contraction and expansion to a diaphragm.

[0178] The liquid ejection device may be one in which the head is moved by a robot or the like, thereby moving the recording medium and the head relative to each other. The liquid ejection device may also be one in which the entire device is held and moved by a user's hand, moving relative to the recording medium. The liquid ejection device is not limited to one that applies ink to paper, cloth, etc., but may also be one that applies paint to a car body. In other words, the recording medium may be interpreted broadly.

[0179] 1... liquid ejection head, 5... nozzle, 17... actuator, 19... flow path member, 25... individual flow path, 43... pressure chamber, 45... partial flow path.

Claims

1. a flow path member having an individual flow path for accommodating a liquid, the individual flow path having a pressurizing chamber, a partial flow path extending from the pressurizing chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurizing chamber; an actuator that applies pressure to the pressure chamber; It has The damping rate of the natural vibration of the liquid in the individual flow path is γ1 (rad / s), the angular frequency of the natural vibration of the liquid in the individual flow path is ω1 (rad / s), the angular frequency of the natural vibration of the liquid in the partial flow path is ω2 (rad / s), and n is a positive integer, 0.95×2n(1+0.32×γ1 / ω1)≦ω2 / ω1≦1.05×2n(1+0.32×γ1 / ω1) holds true. Liquid ejection head.

2. a flow path member having an individual flow path for accommodating a liquid, the individual flow path having a pressurizing chamber, a partial flow path extending from the pressurizing chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurizing chamber; an actuator that applies pressure to the pressure chamber; It has When the angular frequency of the natural vibration of the liquid in the individual flow path is ω1 (rad / s) and the angular frequency of the natural vibration of the liquid in the partial flow path is ω2 (rad / s), the following formula is obtained: 1.97≦ω2 / ω1≦2.39, or 3.95≦ω2 / ω1≦4.88, holds true. Liquid ejection head.

3. n is 1 or 2 The liquid ejection head according to claim 1 .

4. When the damping rate of the natural vibration of the liquid in the individual flow path is γ1 (rad / s), γ1 / ω1 is 0.46 or less.

3. The liquid ejection head according to claim 1 or 2.

5. When the damping rate of the natural vibration of the liquid in the partial flow path is γ2 (rad / s), γ2 / ω1 is 1.15 or less.

3. The liquid ejection head according to claim 1 or 2.

6. a peak intensity of an amplitude spectrum of the velocity of the natural vibration of the liquid in the partial flow paths relative to a peak intensity of the amplitude spectrum of the velocity of the natural vibration of the liquid in the individual flow paths is 0.19 or more and 0.25 or less; 3. The liquid ejection head according to claim 1 or 2.

7. The actuator further includes a driver that drives the actuator by a pull-and-hit mechanism.

3. The liquid ejection head according to claim 1 or 2.

8. The liquid ejection head according to claim 1 or 2, a moving unit that moves the liquid ejection head and a recording medium relative to each other; A liquid ejection device comprising: