Liquid ejection head and liquid ejection apparatus

Abstract

The liquid ejection head includes a flow path member and an actuator. The flow path member has a separate flow path that accommodates a liquid. The individual flow path has a pressurizing chamber, a partial flow path extending from the pressurizing chamber, and a nozzle that opens to the outside at the end of the partial flow path on the opposite side from the pressurizing chamber. The actuator applies pressure to the pressurizing chamber. The attenuation rate of the natural vibration (main vibration) of the liquid in the individual flow path is [gamma] 1 (rad / s). The angular frequency of the main vibration is set as [omega] 1 (rad / s). The angular frequency of the high-frequency vibration is set as [omega] 2 (rad / s). N is a positive integer. At this time, the following formula is satisfied. 0.95 * 2n (1 + 0.32 * gamma 1 / omega 1) < = omega 2 / omega 1 < = 1.05 * 2n (1 + 0.32 * gamma 1 / omega 1).

Description

Technical Field

[0001] The present invention discloses a liquid ejection head such as an inkjet head and a liquid ejection device having the liquid ejection head. Background Art

[0002] It is known to eject liquid droplets (e.g., ink droplets) onto a recording medium (e.g., paper) with a liquid ejection head (e.g., inkjet head) (e.g., Patent Document 1 below). Such a liquid ejection head includes, for example, a flow path member having a flow path 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 path of the flow path member includes, for example, a common flow path (sometimes also called a manifold); and a plurality of individual flow paths that supply liquid (e.g., ink) from the common flow path. The individual flow paths include, for example, a pressurized chamber (sometimes also called a pressure chamber) to which pressure is applied by the actuator; and a nozzle that passes through the pressurized chamber and opens to the outside.

[0003] In Patent Document 1, droplets are ejected from a nozzle by a so-called suction-emission driving method. In the suction-emission method, after the volume of the pressurized chamber is expanded and liquid is introduced into the pressurized chamber. The volume of the pressurized chamber is reduced to push out the liquid, thereby ejecting droplets from the nozzle. In order to realize the suction-emission method, the drive signal input to the actuator has a pulse waveform. The pulse waveform has: a falling edge of the signal intensity corresponding to the expansion of the volume of the pressurized chamber; and a rising edge of the signal intensity corresponding to the reduction of the volume of the pressurized chamber. In Patent Document 1, the time length from the falling edge to the rising edge is set to the length AL (μs) that is most resonant to the resonant frequency of the liquid in a single flow path. By setting the width (time length) of the pulse waveform in this way, for example, the volume of the pressurized chamber can be reduced to push out the liquid in accordance with the timing of the liquid introduced into the pressurized chamber turning over to the nozzle through the inherent vibration. As a result, the ejection speed of the liquid can be increased.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-37692 Summary of the invention

[0007] A liquid ejection head according to one embodiment of the present disclosure includes a flow path component and an actuator. The flow path component includes a separate flow path for containing liquid. The separate flow path includes a pressurized chamber, a partial flow path extending from the pressurized chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurized chamber. The actuator applies pressure to the pressurized chamber. The attenuation rate of the natural vibration of the liquid in the separate flow path is set to γ1 (rad / s). The angular frequency of the natural vibration of the liquid in the separate flow path is set to ω1 (rad / s). The angular frequency of the natural vibration of the liquid in the partial flow path is set to ω2 (rad / s). n is set to a positive integer. At this time, the following equation holds.

[0008] 0.95×2n(1+0.32×γ1 / ω1)≤ω2 / ω1≤1.05×2n(1+0.32×γ1 / ω1)

[0009] A liquid ejection head according to one embodiment of the present disclosure includes a flow path component and an actuator. The flow path component includes a separate flow path for containing liquid. The separate flow path includes a pressurized chamber, a partial flow path extending from the pressurized chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurized chamber. The actuator applies pressure to the pressurized chamber. The angular frequency of the natural vibration of the liquid in the separate flow path is set to ω1 (rad / s). The angular frequency of the natural vibration of the liquid in the partial flow path is set to ω2 (rad / s). At this time, the following equation holds.

[0010] 1.97≤ω2 / ω1≤2.39 or

[0011] 3.95≤ω2 / ω1≤4.88

[0012] A liquid ejection device according to one aspect of the present disclosure includes: the liquid ejection head described above; and a moving unit that moves the liquid ejection head and a recording medium relative to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A It is a side view schematically showing the recording device involved in the embodiment.

[0014] Figure 1B It is a plan view schematically showing a recording device according to the embodiment.

[0015] Figure 2A It is a perspective view of a liquid ejection head according to the embodiment.

[0016] Figure 2B is with Figure 2A A perspective view of the opposite side.

[0017] Figure 2C yes Figure 2A Cross-sectional view at line IIc-IIc.

[0018] Figure 3 yes Figure 2B Cross-sectional view at line III-III.

[0019] Figure 4 This is a conceptual diagram for explaining the ejection operation.

[0020] Figure 5A This is a conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid.

[0021] Figure 5B This is another conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid.

[0022] Figure 6 This is another conceptual diagram for explaining the principle of reducing the variation in the velocity of the liquid.

[0023] Fig. 7A This is a diagram showing an example of calculation results of an index related to the characteristics near the maximum value of the velocity of the liquid.

[0024] Figure 7B This is another diagram showing an example of calculation results of an index related to the characteristics near the maximum value of the velocity of the liquid.

[0025] Figure 8 It is still another figure which shows the example of the calculation result of the index concerning the characteristic in the vicinity of the maximum value of the velocity of the liquid.

[0026] Fig. 9A is from Figure 8 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.00).

[0027] Fig. 9B is from Figure 8 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.23).

[0028] Fig. 9C is from Figure 8 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.46).

[0029] Fig. 10A is from Figure 8 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.69).

[0030] Fig. 10B is from Figure 8 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.92).

[0031] Fig. 10Cis from Figure 8 The figure is represented by filling in part (the case of γ2 / ω1=1.15).

[0032] Fig.11 It is still another figure which shows the example of the calculation result of the index concerning the characteristic in the vicinity of the maximum value of the velocity of the liquid.

[0033] Fig. 12A is from Fig.11 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.00).

[0034] Fig. 12B is from Fig.11 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.23).

[0035] Fig. 12C is from Fig.11 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.46).

[0036] Fig.13A is from Fig.11 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.69).

[0037] Fig. 13B is from Fig.11 This graph shows a portion of the extracted data (the case where γ2 / ω1=0.92).

[0038] Fig. 13C is from Fig.11 This figure shows a part of the extracted data (the case where γ2 / ω1=1.15).

[0039] Fig.14 is a diagram showing an example of an amplitude spectrum. DETAILED DESCRIPTION

[0040] Hereinafter, the embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, the figures used in the following description are schematic. Therefore, for example, the dimensional ratios on the drawings are not necessarily consistent with the reality. In addition, the dimensional ratios are sometimes inconsistent with each other in the drawings. Sometimes specific shapes and / or dimensions are exaggerated, or details are omitted. However, the above does not deny that the actual shape and / or dimensions are as shown in the drawings, or that the characteristics of the shape and / or dimensions can be extracted from the drawings.

[0041] (Overview of Implementation Methods)

[0042] Figure 3 The liquid ejection head 2 (symbol Figure 1A . A cross-sectional view of a portion of the head 2) (sometimes simply referred to as the "head 2" below).

[0043] The head 2 has a discharge element 15 that discharges liquid droplets (eg, ink droplets) from a nozzle 5 toward the lower side (-D3 side) in the figure. Figure 3 , one ejection element 15 (one nozzle 5) is shown, but the head 2 has a plurality of ejection elements 15 (a plurality of nozzles 5) along a plane orthogonal to the D3 direction. The ejected droplets, for example, hit a recording medium (e.g., paper, not shown here) located on the -D3 side. Thus, for example, dots constituting an image are formed.

[0044] The head 2 has a flow path member 19, wherein the flow path member 19 has a flow path filled with liquid (e.g., ink). The ejection element 15 has a separate flow path 25 formed in the flow path member 19. The separate flow path 25 has, for example, a pressurized chamber 43; a partial flow path 45 (sometimes referred to as a descender) extending from the pressurized chamber 43 to the -D3 side; and the nozzle 5 described above, which opens to the outside at the end of the partial flow path 45 on the -D3 side (the side opposite to the pressurized chamber 43).

[0045] The actuator 17 (actuator substrate 21) is overlapped on the +D3 side (upper side in the figure) of the pressurizing chamber 43. The actuator 17 can bend and deform toward the pressurizing chamber 43 side and / or the side opposite to the pressurizing chamber 43. The bending and deformation apply pressure to the liquid in the pressurizing chamber 43. Then, liquid droplets are ejected from the nozzle 5.

[0046] Here, the attenuation rate of the natural vibration (hereinafter sometimes referred to as "main vibration") of the liquid in the separate flow path 25 (its entirety) is set to γ1 (rad / s). The angular frequency of the main vibration is set to 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 set to ω2 (rad / s). n is set to a positive integer. At this time, in the separate flow path 25, the following formula (1) holds.

[0047] 0.95×2n(1+0.32×γ1 / ω1)≤ω2 / ω1≤1.05×2n(1+0.32×γ1 / ω1) (1)

[0048] In addition, from another viewpoint, the following formula (2) or (3) is established instead of or in addition to formula (1).

[0049] 1.97≤ω2 / ω1≤2.39 (2)

[0050] 3.95≤ω2 / ω1≤4.88 (3)

[0051] The angular frequencies ω1 and ω2 and the attenuation rate γ1 can be defined as parameters when the speed v1 (t) of the main vibration and the speed v2 (t) of the high-frequency vibration are expressed as follows, for example.

[0052] v1(t)=-A1×e -γ1×t cos(ω1×t) (4)

[0053] v2(t)=-A2×e -γ2×t cos(ω2×t) (5)

[0054] In the above, A1 and A2 are the maximum amplitudes (m / s). t is time (s). γ2 is the attenuation rate of high-frequency vibration (rad / s). In addition, in theory, except for the difference in the value of the maximum amplitude and the value of the unit and initial phase, the displacement of the main vibration and the high-frequency vibration can be expressed by the same formula as above. That is, the attenuation rate and angular frequency are common to displacement and velocity. Therefore, in the following, when referring to the attenuation rate and angular frequency, sometimes no distinction is made between displacement and velocity.

[0055] In the formulas (1) to (3), γ1 / ω1 and ω2 / ω1 are dimensionless quantities. In addition, in the embodiment, the dimensionless quantity of γ2 / ω1 is used. Based on this, in the following description, the units of γ1, γ2, ω1, and ω2 are sometimes omitted for convenience.

[0056] When at least one of the equations (1) to (3) is satisfied, for example, the variation in the ejection speed of the droplets between the plurality of ejection elements 15 can be reduced. As a result, for example, the image quality can be improved. The specific principle will be described later.

[0057] The above is an overview of the head 2 according to the embodiment. Hereinafter, the head 2 and the printer 1 (an example of a liquid ejecting device) including the head 2 will be roughly described in the following order.

[0058] 1. Overall structure of the printer 1 ( Figure 1A as well as Figure 1B )

[0059] 2. The overall structure of head 2 ( Figure 2A to Figure 2C )

[0060] 3. Structure of the ejection element 15 ( Figure 3 )

[0061] 3.1. Overview of the Ejection Element 15

[0062] 3.2.Flow path component 19

[0063] 3.3. Actuator 17

[0064] 4. The action of the ejection element 15 ( Figure 4 )

[0065] 5. Principle of reducing the deviation of ejection speed ( Figure 5A to Figure 6 )

[0066] 5.1. Factors of deviation

[0067] 5.2. Overview of bias reduction methods

[0068] 5.3. Consideration of the influence of decay rate

[0069] 6. Derivation of equations (1) to (3) Figures 7A to 13C )

[0070] 6.1. Export Method

[0071] 6.2. Calculation results

[0072] 6.3. Amplitude

[0073] 7. Parameter adjustment method

[0074] 8. Method for determining parameters

[0075] 9. Summary of implementation methods

[0076] (1. Overall structure of the printer)

[0077] Figure 1A It is a schematic side view of the printer 1 according to the embodiment. Figure 1B It is a schematic top view of the printer 1 .

[0078] The printer 1 is configured as a color inkjet printer. The printer 1 moves the printing paper P (an example of a recording medium) relative to the head 2 by conveying the printing paper P from the paper feed roller 80A to the recovery roller 80B. In addition, the paper feed roller 80A and the recovery roller 80B and various rollers described later constitute a moving unit 85 that moves the printing paper P and the head 2 relative to each other. The control device 88 controls the head 2 based on data such as images and characters, that is, print data, etc., so that the head 2 ejects liquid onto the printing paper P, and the liquid droplets hit the printing paper P, so that printing and other recording are performed on the printing paper P.

[0079] 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. As another embodiment of the recording device, a so-called serial printer can be cited. In a serial printer, for example, the head 2 is reciprocated in a direction intersecting with the conveying direction of the printing paper P, for example, in a direction substantially orthogonal to the conveying direction of the printing paper P. During the reciprocating, the action of ejecting droplets and conveying the printing paper P are alternately performed.

[0080] Four flat head mounting frames 70 (hereinafter sometimes simply referred to as frames) are fixed to the printer 1 so as to be substantially parallel to the printing paper P. Five holes (not shown) are provided in each frame 70, and five heads 2 are mounted in the portions of the respective holes. The five heads 2 mounted on one frame 70 constitute one head group 72. The printer 1 has four head groups 72, and a total of 20 heads 2 are mounted.

[0081] The head 2 mounted on the frame 70 is arranged so that the portion where the liquid is ejected faces the printing paper P. The distance between the head 2 and the printing paper P is set to about 0.5 to 20 mm, for example.

[0082] 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 print data. For example, the control device 88 sends the print data to one distribution unit, and the one distribution unit can distribute the print data to the 20 heads 2. In addition, for example, the control device 88 distributes the print data to four distribution units corresponding to four head groups 72, and each distribution unit can distribute the print data to five heads 2 in the corresponding head group 72.

[0083] Head 2 has Figure 1A Go inwards from the front, Figure 1B The head 2 is in the shape of a long strip that is long and thin in the vertical direction. In one head group 72, three heads 2 are arranged side by side in a direction that intersects with the conveying direction of the printing paper P, for example, in a substantially orthogonal direction, and the other two heads 2 are arranged side by side one each between the three heads 2 at positions that deviate along the conveying direction. If another expression is set, the heads 2 are arranged in a staggered manner in one head group 72. The heads 2 are arranged so that the range that can be printed by each head 2 is connected in the width direction of the printing paper P, that is, in the direction that intersects with the conveying direction of the printing paper P, or the ends are overlapped, so that printing without gaps in the width direction of the printing paper P can be performed.

[0084] The four head groups 72 are arranged along the conveying direction of the printing paper P. Liquid, such as ink, is supplied to each head 2 from a liquid supply tank (not shown). The same color of ink is supplied to the heads 2 belonging to one head group 72, and four colors of ink can be printed using the four head groups 72. The colors of the ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). If such ink is printed under control of the control device 88, a color image can be printed.

[0085] Regarding the number of heads 2 mounted on the printer 1, if the printing is in a single color and within the range that can be printed by one head 2, then the number can be one. The number of heads 2 contained in the head group 72 and / or the number of head groups 72 can be appropriately changed according to the object to be printed and / or the printing conditions. For example, the number of head groups 72 can also be increased in order to further perform multi-color printing. In addition, if a plurality of head groups 72 for printing in the same color are configured and printing is performed alternately in the conveying direction, the conveying speed can be increased even if heads 2 with the same performance are used. Thus, the printing area per unit time can be increased. In addition, a plurality of head groups 72 for printing in the same color can also be prepared and configured to deviate in a direction intersecting the conveying direction to improve the resolution in the width direction of the printing paper P.

[0086] Furthermore, in addition to printing colored ink, in order to perform surface treatment of the printing paper P, the head 2 may be used to print a liquid such as a coating agent uniformly or in a pattern. For example, when a recording medium that is difficult to immerse in a liquid is used as the recording medium, a coating agent that forms a liquid-accommodating layer can be used as the coating agent to facilitate the fixing of the liquid. In addition, when a recording medium that is easy to immerse in a liquid is used as the recording medium, a coating agent that forms a liquid penetration inhibition layer can be used as the coating agent to prevent the penetration of the liquid from becoming too large and from being too mixed with other liquids nearby. In addition to printing by the head 2, the coating agent may also be uniformly applied by a coater 76 controlled by the control device 88.

[0087] The printer 1 prints on the printing paper P as a recording medium. The printing paper P is wound around the paper feed roller 80A, and the printing paper P fed from the paper feed roller 80A passes under the head 2 mounted on the frame 70, then passes between two conveying rollers 82C, and is finally collected by the collection roller 80B. When printing, the conveying roller 82C is rotated to convey the printing paper P at a certain speed, and printing is performed by the head 2.

[0088] Next, the printer 1 will be described in detail in the order of conveying the printing paper P. The printing paper P fed from the paper feed roller 80A passes between two guide rollers 82A and then passes under the coater 76. The coater 76 coats the printing paper P with the coating agent described above.

[0089] The printing paper P then enters the head chamber 74 of the frame 70 that houses the mounting head 2. The head chamber 74 is connected to the outside in a portion such as the portion where the printing paper P enters and exits, but is generally a space isolated from the outside. The head chamber 74 controls control factors such as temperature, humidity, and air pressure by a control device 88 as needed. In the head chamber 74, since the influence of external disturbances can be reduced compared to the outside where the printer 1 is installed, the range of variation of the above-mentioned control factors can be narrower than that of the outside.

[0090] Five guide rollers 82B are arranged in the head chamber 74, and the printing paper P is transported on the guide rollers 82B. When viewed from the side, the five guide rollers 82B are arranged so that the center becomes convex toward the arrangement frame 70. As a result, the printing paper P transported on the five guide rollers 82B becomes an arc shape when viewed from the side, and the printing paper P between the guide rollers 82B is stretched into a flat shape by applying tension to the printing paper P. One frame 70 is arranged between two guide rollers 82B. Each frame 70 changes the setting angle little by little so as to be parallel to the printing paper P transported thereunder.

[0091] The printing paper P coming out of the head chamber 74 passes between two conveying rollers 82C, passes through the dryer 78, passes between two guide rollers 82D, and is recovered by the recovery roller 80B. The conveying speed of the printing paper P is set to 100 m / min, for example. Each roller can be controlled by the control device 88 or manually operated by a person.

[0092] By drying in the dryer 78, it is difficult to cause the overlapping and wound printing papers P to stick to each other or the undried liquid to scratch the recovery roller 80B. In order to print at high speed, drying also needs to be performed quickly. In order to make the drying quick, in the dryer 78, drying can be performed in sequence by multiple drying methods, or multiple drying methods can be used in combination. As the drying method used at this time, there are, for example, hot air blowing, infrared irradiation, contact with a heated roller, etc. In the case of irradiating infrared rays, in order to reduce damage to the printing paper P and make the drying quick, infrared rays in a specific frequency range can be irradiated. In the case of making the printing paper P contact the heated roller, the heat transfer time can be extended by transporting the printing paper P along the cylindrical surface of the roller. The range of transportation along the cylindrical surface of the roller can be set to more than 1 / 4 of the cylindrical surface of the roller, and it is better to set it to more than 1 / 2 of the cylindrical surface of the roller. In the case of printing UV curing ink, etc., the dryer 78 can be replaced, or a UV irradiation light source can be additionally configured on the basis of the dryer 78. The UV irradiation light source may be disposed between the frames 70 .

[0093] The printer 1 may include a cleaning unit for cleaning the head 2. The cleaning unit performs, for example, wiping and / or cleaning of the cap. Wiping is performed, for example, by wiping the surface of the portion where the liquid is ejected, such as the ejection surface 3a (described later) with a soft wiper to remove the liquid attached to the surface. Cleaning of the cap is performed, for example, as follows. First, the portion where the liquid is ejected is covered, for example, by covering the ejection surface 3a (referred to as the cap), so that the ejection surface 3a and the cap are roughly sealed to create a space. In this state, the ejection of the liquid is repeated to remove the liquid that is more viscous than the standard state, and / or foreign matter, etc. that is blocked in the nozzle 5. By performing the capping, the liquid being cleaned is less likely to fly to the printer 1, and the liquid is less likely to adhere to the printing paper P, rollers, and other conveying mechanisms. The ejection surface 3a that has been cleaned may also be further wiped. Wiping and / or cleaning of the cap may be performed manually by a person operating a wiper and / or capping member installed in the printer 1 , or may be performed automatically by the control device 88 .

[0094] The recording medium may be a roll of cloth or the like in addition to the printing paper P. In addition, the printer 1 may also transport the conveyor belt instead of directly transporting the printing paper P, and place the recording medium on the conveyor belt for transportation. In this way, a single sheet of paper, cut cloth, wood, or tile, etc. can be used as a recording medium. Furthermore, a liquid containing conductive particles may be ejected from the head 2 to print wiring patterns of electronic devices, etc. Furthermore, a given amount of liquid chemical or liquid containing chemical may be ejected from the head 2 to a reaction container, etc., and reacted, etc., to produce chemicals.

[0095] Furthermore, position sensors, speed sensors, temperature sensors, etc. are installed in the printer 1, and the control device 88 can control each part of the printer 1 according to the status of each part of the printer 1 obtained from the information from each sensor. For example, in the case where 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 of the liquid in the liquid supply tank applied to the head 2 have an impact on the ejection characteristics of the ejected liquid, that is, the ejection amount and / or the ejection speed, etc., the drive signal for ejecting the liquid can be changed according to this information.

[0096] For the sake of convenience, the following description is basically based on one head 2. Therefore, for example, in the following, when all nozzles 5 are referred to, unless there are special circumstances, all nozzles 5 in one head 2 are referred to. When all nozzles 5 are referred to, unless there are special circumstances, the specific nozzles may be set to be nozzles different from the nozzles 5 specified by the term all nozzles 5. For example, in order to make the ejection characteristics of the nozzle 5 located at the end of the head 2 close to the ejection characteristics of the nozzle 5 located in the center of the head 2, sometimes a dummy nozzle that does not eject droplets is set further outside the above-mentioned nozzle 5 located at the end. Such a dummy nozzle may not be included in the nozzles in the case of all nozzles 5. The same applies to components other than the nozzle 5 (such as the separate flow path 25 and the actuator 17).

[0097] (2. The overall structure of the head)

[0098] Figure 2A This is a perspective view of the head main body 3 included in the head 2 as viewed from the side opposite to the recording medium (printing paper P). Figure 2B This is a perspective view of the head main body 3 as viewed from the recording medium side. Figure 2C yes Figure 2A Cross-sectional view at line IIc-IIc.

[0099] In these figures, an orthogonal coordinate system consisting of a D1 axis, a D2 axis, and a D3 axis is added for convenience. The D1 axis is defined as the direction of relative movement between the head body 3 and the recording medium ( Figure 1AThe relationship between the positive and negative of the D1 axis and the traveling direction of the recording medium relative to the head body 3 is not particularly investigated in the description of this embodiment. The D2 axis is defined as being parallel to the recording medium and orthogonal to the D1 axis. The positive and negative of the D2 axis is also not particularly investigated. The D3 axis is defined as being orthogonal to the recording medium. The -D3 side is defined as the direction from the head body 3 to the recording medium. The head body 3 can use any direction as the top or bottom. For convenience, the +D3 side is defined as the top and terms such as the lower surface are used.

[0100] A head 2 has a head body 3. The head body 3 is a part that directly bears the ejection of liquid, and has an ejection surface 3a opposite to 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 also has, for example, a circuit substrate connected to the head body 3 and / or a housing covering the upper part of the head body 3. In addition, regardless of whether the head 2 has components other than the head body 3, the head body 3 can be regarded as an example of the liquid ejection head disclosed in the present invention.

[0101] The plurality of nozzles 5 are arranged so that the positions in the D2 direction are different from each other. Therefore, while the head 2 and the recording medium are relatively moved in the D1 direction by the moving unit 85, ink drops are ejected from the plurality of nozzles 5, thereby forming an arbitrary two-dimensional image. The plurality of nozzles 5 may be arranged two-dimensionally as in the example shown in the figure, or may be arranged one-dimensionally unlike the example shown in the figure.

[0102] The specific size, number, pitch, arrangement pattern, etc. of the plurality of nozzles 5 can be appropriately set. Figure 2B Since this is a schematic diagram, the nozzle 5 is shown larger than the size of the head body 3, and the number of nozzles 5 in one head body 3 is shown smaller. Generally, the nozzle 5 is smaller and the number of nozzles 5 is greater than that in the illustrated example. For example, the number of nozzles 5 in one head body 3 may be more than 100 and less than 10,000. In addition, for example, one head body 3 may have a plurality of nozzles 5 at a pitch and in a configuration pattern such that the density of dots in the D2 direction is 800 dpi or more and 1,600 dpi or less.

[0103] The head body 3 includes, for example, the following components: a counter substrate 7 having a discharge surface 3a; a back member 9 fixed to the top of the counter substrate 7; one or more (two in the example shown in the figure) flexible substrates 11 electrically connected to the counter substrate 7; and one or more (two in the example shown in the figure) drivers 13 mounted on each of the flexible substrates 11.

[0104] The opposing substrate 7 directly contributes to the ejection of the droplets. The opposing substrate 7 has the flow path member 19 and the actuator 17 ( Figure 3). The shape and size of the opposing substrate 7 can be appropriately set. In the example shown in the figure, the opposing substrate 7 is roughly a rectangular flat plate. Its thickness (D3 direction) is, for example, not less than 0.5 mm and not more than 2 mm. In addition, the opposing substrate 7 can be regarded as an example of the liquid ejection head disclosed in the present invention.

[0105] The back member 9 contributes to, for example, the mediation between the opposing substrate 7 and other components. For example, the back member 9 contributes to the positioning of the opposing substrate 7 relative to the above-mentioned frame 70. Specifically, for example, the back member 9 has its lower surface bonded to a portion on the outer edge of the upper surface of the opposing substrate 7, and while the lower portion is inserted into the hole of the frame 70, the upper flange-shaped portion is supported by the frame 70. In addition, for example, the back member 9 mediates the unillustrated ink tank and the opposing substrate 7 with respect to the flow of ink. Specifically, the back member 9 has: an opening 9a opened on the upper surface; and an unillustrated opening opened on the surface of the lower surface bonded to the opposing substrate 7. The opening on the upper surface and the opening on the lower surface are connected by an unillustrated flow path in the back member 9. The opening 9a is connected to the ink tank via a tube, etc., which is not shown.

[0106] 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 the slit 9b that penetrates the back member 9 vertically. The portion of the flexible substrate 11 extending downward from the slit 9b is arranged opposite to the upper surface of the counter substrate 7, and is bonded to the upper surface of the counter substrate 7 via a conductive bump (for example, solder) not shown. The portion of the flexible substrate 11 extending upward from the slit 9b is connected to a cable (not shown) extending from the control device 88 via a connector mounted on the portion or a connector mounted on a rigid substrate connected to the flexible substrate 11.

[0107] The driver 13 contributes to the driving and control of the actuator 17 of the counter substrate 7, for example. Specifically, for example, the driver 13 receives a control signal from the control device 88 via the flexible substrate 11, generates driving power (driving signal from another point of view) based on the input control signal, and inputs the generated driving power to the actuator 17 via the flexible substrate 11. The sharing of functions between the driver 13 and the control device 88 can be appropriately set. For example, information that specifies the shape of the pulse Ps described later (pulse width PW from another point of view) can be possessed by the control device 88 or by the driver 13. The driver 13 is composed of, for example, an IC (Integrated Circuit). Its shape, size, number, position, etc. can be appropriately set.

[0108] (3. Structure of the ejection element)

[0109] (3.1. Overview of the ejection element)

[0110] Figure 3 yes Figure 2B That is, Figure 3 It is a schematic cross-sectional view showing a part of the counter substrate 7 in an enlarged manner.

[0111] The opposing 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 in the same manner as the plurality of nozzles 5. As already described, each ejection element 15 has a separate flow path 25 and an actuator 17. From another point of view, the opposing substrate 7 has: a roughly 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 separate flow paths 25. The actuator substrate 21 has a plurality of actuators 17. That is, the plurality of ejection elements 15 are composed of the flow path member 19 and the actuator substrate 21.

[0112] The structures of the plurality of ejection elements 15 can be set to be identical to each other, for example. Therefore, the description of one ejection element 15 in the embodiment can also be applied to any of the plurality of ejection elements 15 (excluding the specific ejection elements as already described) possessed by the head 2, unless there are special circumstances and unless there is any contradiction. In addition, the identical structures mentioned in this paragraph exclude the position and orientation of the ejection element 15 (or its constituent elements) in the head 2 when viewed from above (viewed in the D3 direction). In addition, in the head 2, the structure of a part and more than two ejection elements 15 and the structure of another part and more than two ejection elements 15 may also differ in details (for example, the specific shape and size of a part of the flow path 45).

[0113] (3.2. Flow path components)

[0114] The flow path member 19 is formed, for example, by stacking a plurality of plates 27A to 27J (hereinafter sometimes A to J are omitted). A plurality of holes (mainly through holes, which may also be recessed portions) constituting the flow path are formed in the plate 27. The thickness of the plurality of plates 27 and the number of stacking layers may be appropriately set in accordance with the shape of the flow path, etc. The plurality of plates 27 may be formed by an appropriate material. For example, the plurality of plates 27 may contain metal or resin. The thickness of the plate 27 may be, for example, greater than 10 μm and less than 300 μm. The plates 27 may be fixed to each other, for example, by an adhesive not shown interposed between the plates 27.

[0115] The flow path member 19 includes, for example, a common flow path 23 and a plurality of individual flow paths 25 ( Figure 3Ink supplied from the back member 9 to the flow path member 19 is supplied from the common flow path 23 to a plurality of individual flow paths 25. Each individual flow path 25 has, for example, a connection portion 37, a throttle 39, a supply path 41, a pressurizing chamber 43, a partial flow path 45, and a nozzle 5 in this order from the common flow path 23 side.

[0116] The specific shape and size of each flow path in the flow path member 19 can be set appropriately. In the example shown in the figure, it is as follows.

[0117] The common flow path 23 may extend in any direction along the ejection surface 3a. Only one common flow path 23 may be provided, or, for example, a plurality of common flow paths 23 may be provided in parallel with each other. The cross-sectional shape of the common flow path 23 is set to be rectangular.

[0118] The plurality of individual flow paths 25 (discharging elements 15 from another perspective) are arranged in the longitudinal direction of each common flow path 23. The plurality of nozzles 5 may be arranged in one row on one side of the common flow path 23 connected thereto, or in two or four rows on both sides.

[0119] The pressurized chamber 43 opens, for example, on the upper surface of the flow path member 19 (the surface on the side opposite to the ejection surface 3a) and is blocked by the actuator 17. Alternatively, the pressurized chamber 43 may be blocked by the plate 27. This may be considered as a question of whether the plate 27 blocking the pressurized chamber 43 is considered as a part of the flow path member 19 or as a part of the actuator 17. In either case, the pressurized chamber 43 is located at the upper portion of the flow path member 19.

[0120] The shapes of the plurality of pressurized chambers 43 are, for example, the same as each other. The shape of each pressurized chamber 43 can be appropriately set. For example, the pressurized chamber 43 is formed into a thin shape extending along the upper surface of the flow path member 19 with a certain thickness. The pressurized chamber 43 may also have portions with different thicknesses. The thin shape is, for example, a shape having a smaller thickness than any diameter when viewed from above.

[0121] In addition, for example, the planar shape of the pressurized chamber 43 may be a shape having a long side direction and a short side direction that are orthogonal to each other (e.g., a rhombus or an ellipse), or a shape that cannot be conceptualized as such a direction (e.g., a circle). In addition, the relationship between the long side direction and the short side direction and the arrangement of the plurality of pressurized chambers 43 is also arbitrary.

[0122] The partial flow path 45 extends from the lower surface of the pressurized chamber 43 to the ejection surface 3a. The shape of the partial flow path 45 is roughly cylindrical. The partial flow path 45 may extend obliquely in the up-down direction from the pressurized chamber 43 to the ejection surface 3a (the illustrated example), or may extend without being inclined, may extend in a straight line, or may be partially or entirely curved. The area of ​​the cross section of the partial flow path 45 may be constant in the longitudinal direction of the partial flow path 45, or may vary depending on the position in the longitudinal direction. When viewed from above (viewed in the D3 direction), the partial flow path 45 is connected to, for example, the end of the pressurized chamber 43 in a given direction (for example, the long side direction of the pressurized chamber 43 when viewed from above).

[0123] The nozzle 5 opens at a part of the bottom surface of the partial flow path 45 (the surface on the side opposite to the pressurized chamber 43). The nozzle 5 is, for example, located approximately at the center of the bottom surface of the partial flow path 45. The nozzle 5 may also be eccentrically arranged relative to the center of the bottom surface of the partial flow path 45. The shape of the longitudinal section of the nozzle 5 is set to be a cone shape with a smaller diameter as it approaches the ejection surface 3a side. The nozzle 5 may also be partially or entirely in an inverted cone shape.

[0124] The connection portion 37 extends upward from, for example, the upper surface of the common flow path 23. The throttle 39 extends from this portion in a direction along the plate 27. The supply path 41 extends upward from the throttle 39 and is connected to the lower surface of the pressurized chamber 43. When viewed from above (viewed in the D3 direction), the connection position of the supply path 41 to the pressurized chamber 43 is set to, for example, an end portion of the lower surface of the pressurized chamber 43 on the side opposite to the center of the lower surface and the partial flow path 45.

[0125] The cross section (cross section intersecting the flow direction) of the throttle 39 is smaller in area than the connection portion 37 and the supply path 41. In addition, for example, the cross section area is smallest in the separate flow path 25 except for the nozzle 5. With regard to the main vibration (natural vibration of the liquid in the separate flow path 25) already described, the pressure wave of the liquid is easily reflected by the throttle 39. Therefore, unlike the description of the embodiment, the flow path closer to the nozzle 5 side than the connection portion 37 or the flow path closer to the nozzle 5 side than the throttle 39 may be regarded as a separate flow path.

[0126] As described above, the structure of a part of two or more ejection elements 15 and the structure of another part of two or more ejection elements 15 may be different in detail. As such an example, the following method can be cited: in the single-side pressurized chambers 43 of the common flow path 23, two rows are arranged side by side, and because the distance between the common flow path 23 and the pressurized chamber 43 is different from row to row, the length of the restrictor 39 and / or the direction of the restrictor 39 relative to other flow paths (the flow path in the individual flow path 25 and / or the common flow path 23) are different from row to row (the same in each row). In addition, for example, the following method can be cited: in order to make the positions of the plurality of nozzles 5 connected to the plurality of pressurized chambers 43 arranged in one row parallel to the D1 direction (paper feeding direction) deviate from each other in the D2 direction, the shapes and sizes of the partial flow paths 45 are different from each other in the row (the structures of the rows are the same).

[0127] (3.3. Actuator)

[0128] The actuator substrate 21 is a roughly plate-shaped device having a size that covers a plurality of pressurized chambers 43. The actuator 17 is, for example, a piezoelectric actuator that applies pressure to ink by mechanical deformation of a piezoelectric body. A piezoelectric actuator is, for example, a so-called uni-piezoelectric actuator. In addition, the actuator 17 may also be composed of a piezoelectric actuator of another type, such as a bi-piezoelectric actuator. The uni-piezoelectric actuator 17 (actuator substrate 21) has, for example, a vibration plate 29, a common electrode 31, a piezoelectric layer 33, and a separate electrode 35 in order from the flow path member 19 side.

[0129] The vibration plate 29, the common electrode 31, and the piezoelectric layer 33 extend over the plurality of pressurized chambers 43, for example, in a plan view. That is, these are commonly provided in the plurality of pressurized chambers 43. The individual electrode 35 is provided for each pressurized chamber 43. The individual electrode 35 includes: a main body 35a overlapping the pressurized chamber 43; and an extraction electrode 35b extending from the main body 35a. The main body 35a has, for example, a shape and size roughly equivalent to the shape and size of the pressurized chamber 43.

[0130] The specific material and thickness of each layer can be set appropriately. For example, the material of the piezoelectric layer 33 can be set to ceramics such as PZT (lead zirconate titanate). The material of the vibration plate 29 can be set to ceramics with or without piezoelectricity. The common electrode 31 and the individual electrode 35 can be set to metals such as Ag or Au. The thickness of the vibration plate 29 and the piezoelectric layer 33 can be set to 10 μm or more and 40 μm or less, respectively. The thickness of the common electrode 31 can be set to 1 μm or more and 3 μm or less. The thickness of the individual electrode 35 can be set to 0.5 μm or more and 2 μm or less.

[0131] At least the portion of the piezoelectric layer 33 sandwiched by the main body 35a of the individual electrode 35 and the common electrode 31 is polarized in the thickness direction. Therefore, for example, if an electric field (voltage) is applied in the polarization direction of the piezoelectric layer 33 through the main body 35a and the common electrode 31, the piezoelectric layer 33 shrinks in the direction along the layer. This shrinkage is constrained by the vibration plate 29. As a result, the actuator 17 is flexed and deformed so as to protrude toward the side of the pressurization chamber 43. If an electric field (voltage) is applied in the opposite direction to the above through the main body 35a and the common electrode 31, the actuator 17 is flexed and deformed to the side opposite to the pressurization chamber 43. By utilizing such flexural deformation, as described above, the volume of the pressurization chamber 43 can be changed, and pressure can be applied to the ink in the pressurization chamber 43, so that the ink is ejected from the nozzle 5.

[0132] The common electrode 31 is given a constant potential with respect to the passage of time, for example, during printing. The constant potential is, for example, a reference potential. On the other hand, the individual electrodes 35 are input with a signal whose potential changes with respect to the passage of time, for example. As a result, the intensity of the electric field applied to the piezoelectric layer 33 changes. As a result, for example, as described above, the actuator 17 can be deformed. In addition, by inputting multiple signals to multiple individual electrodes 35 individually, the deformation of multiple actuators 17 can be controlled individually. Furthermore, the amount of droplets ejected from the multiple nozzles 5 can be controlled individually according to the content of the image to be printed.

[0133] The actuator 17 can be connected to an external control unit (e.g., the driver 13) as appropriate. For example, the flexible substrate 11 is disposed opposite to the upper surface of the actuator substrate 21. Furthermore, the unillustrated pad of the flexible substrate 11 and the end of the lead-out electrode 35b are bonded via a conductive bump pad. Thus, the individual electrode 35 and the driver 13 are connected via an unillustrated signal line of the flexible substrate 11. Furthermore, a signal can be input from the driver 13 to the individual electrode 35.

[0134] In addition, although not particularly shown, the actuator substrate 21 has a via conductor at an appropriate position in a plan view, which penetrates the piezoelectric layer 33, is connected to the common electrode 31, and is exposed on the upper surface of the piezoelectric layer 33. In addition, the pad (not shown) of the flexible substrate 11 and the via conductor are bonded via a conductive bump pad. Thus, for example, the common electrode 31 is connected to the reference potential wiring (not shown) of the flexible substrate 11. Furthermore, a reference potential can be given to the common electrode 31.

[0135] (4. Action of the ejection element)

[0136] As described above, the ejection element 15 ejects ink droplets by applying pressure to the pressurizing chamber 43 through the actuator 17. The driving method thereof may be, for example, a suction emission method. The ejection operation of ink droplets by the suction emission method is as follows.

[0137] Figure 4 It is a schematic diagram for explaining the discharge operation of the discharge element 15 .

[0138] In this figure, the horizontal axis represents the normalized time t / AL which is normalized by dividing the 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 curved liquid surface (the liquid surface of the ink in the nozzle 5). On the right vertical axis, the + side (the upper side of the figure) represents the displacement x and velocity v to the outside side (-D3 side) of the nozzle 5. Lines Lx and Lv respectively represent the temporal changes of the displacement x and velocity v.

[0139] 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, and the actuator 17 is bent toward the pressurized chamber 43. However, the potentials of the individual electrodes 35 and the common electrode 31 when the actuator 17 is bent toward the pressurized chamber 43 may be opposite to the description here.

[0140] Before a discharge request is made, the drive signal Sg1 (from another point of view, the individual electrode 35) is set to a potential higher than that of the common electrode 31 (hereinafter referred to as “high potential V H Then, whenever there is a request for ejection, the potential of the individual electrode 35 is set to be lower than the high potential V H The potential (hereinafter referred to as "low potential V L ”), and then set to high potential V again at a given timing H . Low potential V L The potential can be appropriately set, for example, to be the same potential as that of the common electrode 31. From another viewpoint, a pulse Ps having a pulse width PW is input to the individual electrode 35 every time there is a request for ejection.

[0141] Before the ejection request, the drive signal Sg1 is set to a high potential V H The actuator 17 becomes a shape bent toward the pressurizing chamber 43. The displacement x of the meniscus at this time is set to zero. In addition, the speed v of the meniscus at this time is substantially or ideally zero.

[0142] Next, the driving signal Sg1 becomes a low potential V L(t / AL=0), the actuator 17 returns to the shape before deformation (flat shape) (initial), and the volume of the pressurized chamber 43 increases. Furthermore, negative pressure is applied to the liquid in the pressurized chamber 43. As a result, the curved liquid surface is displaced toward the inner side of the nozzle 5, and the absolute value of the speed involved in the displacement increases. In addition, from another point of view, the liquid in the separate flow path 25 starts to vibrate with a natural vibration period.

[0143] After that, the absolute value of the speed of the meniscus reaches the top (t / AL = approximately 0.5) and starts to decrease. Furthermore, when t / AL becomes approximately 1, the volume of the pressurized chamber 43 becomes maximum and the pressure becomes approximately zero. At this time, the displacement x of the meniscus is located at the innermost side of the nozzle 5, and the speed v becomes approximately zero. Next, the volume of the pressurized chamber 43 starts to decrease, and the pressure continues to increase.

[0144] The driving signal Sg1 is set to a low potential V L Then it becomes high potential V H The actuator 17 begins to bend again toward the pressurized chamber 43. The vibration initially applied by the falling edge of the pulse Ps and the vibration subsequently applied by the rising edge of the pulse Ps overlap, applying a greater pressure to the liquid. This pressure propagates in the partial flow path 45, causing the liquid to be ejected from the nozzle 5.

[0145] That is, by setting the high potential V H As a reference, it becomes a low potential V for a certain period of time L The pulse Ps is supplied to the separate electrode 35, and droplets can be ejected. 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 separate flow path 25, in principle, the maximum value of the velocity v (referred to as the maximum velocity v max ) becomes maximum. Furthermore, the ejection speed and ejection amount of the liquid become maximum.

[0146] As mentioned in the above paragraph, as a concept, AL is half of the natural vibration period of the liquid in the separate flow path 25. However, it is not easy to obtain the natural vibration period theoretically. Therefore, although it is theoretical, for example, when the ejection operation is performed with various pulse widths PW, the maximum velocity v can be defined. max The length of the pulse width PW that becomes the maximum (or the ejection speed or the ejection amount) is AL, and it can be defined that twice is the natural vibration period of the liquid in the separate flow path 25. From another point of view, in determining the angular frequency ω1 of the separate flow path 25, the range of the separate flow path 25 (for example, whether it includes the throttle 39) may not be clearly defined. The same can be said about the angular frequency ω2 of the partial flow path 45.

[0147] Since there are other factors to consider, such as aggregating the ejected droplets into one, the pulse width PW can actually be set to a value of about 0.5AL to 1.5AL. In addition, the pulse width PW can reduce the ejection amount by setting it to a value deviating from AL, so it can also be set to a value deviating from AL to reduce the ejection amount.

[0148] The falling edge and / or rising edge of the pulse Ps may be inclined relative to the longitudinal axis or may change in a step-like manner. The drive signal Sg1 may include waveforms other than the pulse Ps. For example, it may also include a waveform that reduces the residual variation of the meniscus. Such other waveforms may be connected to the pulse Ps or may be separated.

[0149] The intended shade of the image (including characters) formed on the recording medium can be achieved by an appropriate method. For example, it can be achieved by the size of the dot diameter on the recording medium, or by the change in the number of dots per a certain area (density), or by a combination of these. The size of the dot diameter can be adjusted by the size of one droplet, or by the number of droplets hitting one point, or by a combination of these.

[0150] In addition, from another point of view, the intended shading can be achieved by using the high potential V of the drive signal Sg1. H With low potential V L It can be achieved by adjusting the size of the droplets ejected from the nozzle 5 by adjusting the potential difference, etc., or by increasing or decreasing the number of droplets by adjusting the number of pulses Ps contained in the drive signal Sg1 corresponding to the ejection request for one amount, or by increasing or decreasing the number of each fixed area of ​​the ejection element 15 performing the ejection action, or by a combination of these.

[0151] (5. Principle of reducing the deviation of ejection speed)

[0152] First, an example of a factor causing a variation in discharge speed will be described, and then an outline of a method for reducing the variation in discharge speed caused by the example of the factor will be described.

[0153] (5.1. Factors of deviation)

[0154] As reference Figure 4 As explained, in the attraction emission method, if the pulse width PW is AL, the maximum speed v max In other words, the maximum speed v corresponding to the pulse width PW max changes, the more the pulse width PW deviates from AL, the greater the maximum speed v max Getting smaller.

[0155] Figure 5A2 is a conceptual diagram showing the above phenomenon. In this figure, the horizontal axis represents the pulse width PW and the vertical axis represents the maximum velocity v of the meniscus. max The lines Ln1, Ln2, and Ln3 in the figure represent the pulse width PW and the maximum velocity v in different ejection elements 15. max relationship.

[0156] As shown by lines Ln1 to Ln3, the maximum speed v increases with increasing pulse width PW. max Furthermore, if the pulse width PW is increased continuously, the maximum speed v max It reaches the top and then keeps decreasing. It can be said that the pulse width PW when it reaches the top is AL.

[0157] As shown in the figure, AL may be different from one another in a plurality of ejection elements 15. That is, there is a deviation in AL. In the example shown in the figure, AL becomes longer in the order of line Ln1, line Ln2, and line Ln3. On the other hand, the shape of the pulse Ps for ejecting droplets at the same ejection amount (pulse width PW from another point of view) is common to a plurality of ejection elements 15, for example.

[0158] Therefore, if the AL of the ejection element 15 of line Ln1 (marked line La1) is used as the pulse width PW, the ejection elements 15 of lines Ln2 and Ln3 are input with a pulse width PW of a time length deviated from their own AL. As a result, in the ejection elements 15 of lines Ln2 and Ln3, the maximum speed v max The maximum velocity v of the ejection element 15 is not the maximum velocity for itself, and is likely to become smaller than the maximum velocity v of the ejection element 15 on the line Ln1. max .exist Figure 5A In the example, when the AL of the ejection element 15 of the line Ln1 is used, the maximum speed v of the ejection element 15 of the lines Ln1 to Ln3 is max (Intersection points of lines Ln1 to Ln3 and line La1) are different from each other and are indicated by three dotted lines parallel to the horizontal axis.

[0159] Due to the above reasons, the maximum velocity v between the plurality of ejection elements 15 is max Deviation. Maximum speed v max Since the ejection speed and the ejection amount of the droplets are strongly correlated, the ejection speed and the ejection amount vary among the plurality of ejection elements 15. As a result, for example, image quality is degraded.

[0160] As the factors for the variation of AL, various factors can be cited, for example, factors in design and factors in manufacturing. From another point of view, differences in intended shapes and sizes and differences in unintended shapes and sizes can be cited.

[0161] As design factors, for example, the differences in length and / or orientation of the plurality of throttles 39 caused by the differences in the positions of the plurality of pressurized chambers 43 described above, and the differences in the shapes of the plurality of partial flow paths 45 for mutually deviating the positions of the plurality of nozzles 5 in the D2 direction can be cited. In addition, the differences in the rigidity of the wall surfaces constituting the individual flow paths 25 caused by the differences in the positions of the plurality of 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 member 9 can be cited.

[0162] As a manufacturing factor, for example, the deviation of the size of the multiple individual flow paths 25 generated when the plate 27 is etched to form the holes constituting the flow path can be cited. In more detail, for example, the relative relationship between a given position of the individual flow path 25 and other flow paths (the flow path and / or the common flow path 23 in the individual flow path 25) is different in the multiple individual flow paths 25, and further, the density of the pattern is different in the multiple individual flow paths 25. As a result, the size deviation occurs due to the microscopic load effect. In addition, for example, as a manufacturing factor, the deviation generated when the multiple plates 27 are heated and pressurized for bonding can be cited. Specifically, for example, the temperature and / or pressure of the adhesive applied between the plates 27 are different depending on the position in the plate 27, and further, the size and / or rigidity deviation occurs in the multiple individual flow paths 25.

[0163] The description here assumes that the waveform of the pulse Ps corresponding to the same discharge amount is common to a plurality of discharge elements 15. The plurality of discharge elements 15 having the same waveform may be all the discharge elements 15 of the head 2 (except for the special ones as described above) or a part of the discharge elements 15. As the latter, for example, as described above, when the shapes of the individual flow paths 25 of the columns of the pressurized chamber 43 are different, the waveform of the pulse Ps may be different between the columns and the waveform may be the same within the column.

[0164] (5.2. Overview of methods for reducing bias)

[0165] Figure 6 This is a conceptual diagram for explaining a method for reducing the deviation of the ejection speed caused by the deviation of AL as described above. In this figure, the horizontal axis represents time t (μs). The vertical axis represents the speed v (m / s) of the meniscus. The 0, + side and - side of the vertical axis are Figure 4 The 0, +, and - sides of the vertical axis on the right side are the same.

[0166] This figure shows the Figure 4 The following describes the change with time of the velocity v when the droplets are ejected by the suction emission method. Figure 6 t=0 (μs) and Figure 4The line corresponding to "v1" in the explanatory note represents the time-dependent change of the velocity v of the main vibration (the natural vibration of the liquid in the separate flow path 25). As can be understood from the description so far, the velocity v1 of the main vibration vibrates with a period of 2AL (about 12μs in the example shown in the figure). The first peak of the main vibration (around 6μs) is equivalent to Figure 4 The peak of the rising edge of the pulse Ps is overlapped (including the maximum speed v max peak).

[0167] The liquid not only generates natural vibrations (main vibrations) that depend on the overall shape and size of the individual flow path 25, but also generates natural vibrations (high-frequency vibrations) that depend on the shape and size of the partial flow path 45. The line corresponding to "v2" in the explanation represents the temporal change of the speed v of the high-frequency vibration. The speed v2 of the high-frequency vibration vibrates at the natural vibration period of the liquid in the partial flow path 45 (about 6 μs in the example shown in the figure). The period of the high-frequency vibration is shorter than the period of the main vibration. In addition, the amplitude of the high-frequency vibration is smaller than the amplitude of the main vibration.

[0168] The line corresponding to "v3" in the legend shows the temporal change of the velocity v of the vibration synthesized by the main vibration and the high-frequency vibration (hereinafter sometimes referred to as "synthesized vibration"). If the first peak (around 6μs) of the main vibration for ejection overlaps with the valley of the high-frequency vibration, a peak with a flat top appears in the synthesized vibration. That is, the maximum velocity v max The change of the velocity v becomes gentle in the vicinity.

[0169] Figure 5B is the pulse width PW and the maximum speed v of the meniscus when the main vibration and the high-frequency vibration are combined as described above. max The relationship diagram is Figure 5A Same picture. Figure 5B Line Ln1~Ln3 and Figure 5A Similarly, the lines Ln1 to Ln3 represent the maximum speed v of the nozzles 5 which are different from each other. max Line La1 and Figure 5A Similarly, the line La1 shows the pulse width PW of AL of the ejection element 15 corresponding to the line Ln1.

[0170] As from Figure 5A and Figure 5B As can be understood from the comparison, by making the top of the first peak in the composite vibration flat, the tops of the lines Ln1 to Ln3 also become flat. That is, in the range of pulse width PW being AL or close to AL (horizontal axis), even if the pulse width PW is changed, the maximum speed v maxIt will not change greatly (it is roughly constant). From another point of view, the flat tops of lines Ln1 to Ln3 tend to overlap. In the range of the top overlap, in which of the lines Ln1 to Ln3 is the maximum speed v max are all close to the maximum value.

[0171] Therefore, for example, when the pulse width PW corresponding to the length of AL of the line Ln1 is commonly used in the ejection elements 15 of the lines Ln1 to Ln3, the maximum velocity v max The maximum velocity v is the maximum velocity of the ejection element 15 on lines Ln2 and Ln3. max As a result, as shown by a dotted line parallel to the horizontal axis, the maximum velocity v between the ejection elements 15 of the lines Ln1 to Ln3 is max Easy to approach. In turn, the maximum speed v max The correlation is strong with the deviation of the ejection speed and / or the ejection amount.

[0172] (5.3. Consideration of the influence of decay rate)

[0173] like Figure 6 As shown in , the speed v1 of the main vibration reaches a minimum value before the first peak (t = 0). Figure 4 As can be understood, the time point t=0 is roughly the time point when 0.5AL has passed from the falling edge of the pulse Ps. In addition, at this time point, the speed v2 of the high-frequency vibration also takes a minimum value. That is, at the minimum value before the first peak of the main vibration, the main vibration and the high-frequency vibration are in phase. Therefore, in a simple consideration, when the angular frequency of the main vibration is set to ω1 and the angular frequency of the high-frequency vibration is set to ω2, by setting ω2 / ω1 to a multiple of 2 ( Figure 6 In the case of a multiple of 2 (2), the high-frequency vibration valley can be overlapped with the first peak of the main vibration.

[0174] But the actual main vibration is Figure 6 In this case, if ω2 / ω1 is slightly larger than a multiple of 2, it is easy to make the top of the peak of the composite vibration velocity v3 flat. Figure 6 In the figure, the waveform of the high-frequency vibration is slightly shifted to the left side (the side with shorter elapsed time t) of the figure. As a result, the speed v1 on the side with elapsed time t shorter than the peak of the main vibration (before relatively attenuation) is relatively greatly reduced by the speed v2 of the valley of the high-frequency vibration. On the other hand, the speed v1 on the side with elapsed time t longer than the peak of the main vibration (after relatively attenuation) is reduced relatively less by the speed v2 of the valley of the high-frequency vibration. As a result, the time t at which the top of the peak of the speed v3 of the composite vibration becomes flat becomes longer.

[0175] Accordingly, in the above-described formula (1), the range of ω2 / ω1 is defined corresponding to the attenuation rate γ1. In formulas (2) and (3), the range of ω2 / ω1 is defined not by a range centered on 2 or 4 but by a range centered on a larger range than 2 or 4.

[0176] (6. Export of formula)

[0177] (6.1. Export method)

[0178] The method of deriving equations (1) to (3) is as follows.

[0179] Substitute specific values ​​for A1, A2, γ1, γ2, ω1, and ω2 in equations (4) and (5) to calculate the speed v1(t) of the main vibration and the speed v2(t) of the high-frequency vibration. Then, calculate the speed v3(t) of the composite vibration by v1(t)+v2(t). Of the calculated speed v3(t), find the maximum value (local maximum) in the first peak. Next, find the time length within the range of -5% of the maximum value based on the maximum value. Substitute the time length into Figure 6 The symbol in the middle is called FT (Flat Time).

[0180] If the accuracy 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 equivalent to Figure 4 The maximum speed v when vibration is generated only by the falling edge of pulse Ps (assuming that there is no rising edge of pulse Ps) max According to the applicant’s experience, if the deviation of the maximum value of the first peak of velocity v3(t) is within 5%, the maximum velocity v obtained by superposition of the natural vibration based on the falling edge of pulse Ps and the vibration based on the rising edge of pulse Ps is max There is a high probability that the deviation is within the allowable range.

[0181] Furthermore, according to the above, for example, if the difference between the pulse width PW and AL is less than FT, the difference gives the maximum speed v in the case of the rising edge of the pulse Ps. max From other perspectives, the maximum speed v max The probability that the deviation is within the allowable range is high. Figure 6 As shown in , FT is the time length of the flat portion of the peak of the synthetic natural vibration, but is different from Figure 5B The maximum speed v shown max This is an indicator that is strongly correlated with the length of time that the top of the peak becomes flat (the fluctuation range of the pulse width PW when the top becomes flat).

[0182] Moreover, the longer the FT is, the Figure 5B Thus, between the plurality of ejection elements 15, the maximum velocity v max That is, when a common pulse width PW is used in a plurality of ejection elements 15 with different AL, the longer FT is, the greater the maximum velocity v is between the ejection elements 15. max In addition, from another point of view, since the maximum speed v max From the same point of view, the permissible deviation of AL becomes larger.

[0183] The above-mentioned steps of obtaining FT are performed for various values ​​of ω2 / ω1. Thus, the relationship between ω2 / ω1 and FT is determined. Thus, for example, the ω2 / ω1 at which FT becomes the maximum value can be determined, or the range in which FT becomes greater than a given value can be determined. Formulas (1) to (3) are centered around the value of ω2 / ω1 at which FT becomes the maximum value, and define a range of ±5% of the center value.

[0184] In addition, as already described, FT is the length of time that v3(t) is within the range of -5% from its maximum value. The length of time that v3(t) is within the range of -10% from its maximum value is FT'. The inventors of the present application confirmed through calculation that there is no significant difference between the range of ±5% of the value centered on the value of ω2 / ω1 where FT' becomes a maximum value and the range of ±5% of the value centered on the value of ω2 / ω1 where FT becomes a maximum value. This shows the appropriateness of the definition of FT (-5% numerical value) and the range of ±5% centered on the maximum value of FT.

[0185] The step of obtaining FT is performed not only for various values ​​of ω2 / ω1, but also for various values ​​of γ1 / ω1 and γ2 / ω1. Thus, a favorable range of ω2 / ω1 corresponding to the values ​​of attenuation rates γ1 and γ2 is determined. In addition, γ1 / ω1 is the attenuation ratio of the main vibration.

[0186] Various values ​​used in the calculation are as follows.

[0187] A1: 10 (m / s)

[0188] A2: 1.5 (m / s)

[0189] ω2 / ω1: makes the difference between 0 and 9 be 0.01

[0190] γ1 / ω1: 0, 0.12, 0.23 or 0.46

[0191] γ2 / ω1: 0, 0.23, 0.46, 0.69, 0.92 or 1.15

[0192] The above values ​​are set based on the structure of the ejection element 15 specifically designed for the intended implementation. Among them, the above various values ​​also include virtual values ​​(unrealistic values). For example, γ1 / ω1=0 is a virtual value because it is a value when the main vibration is not attenuated. In addition, in the above, the value of the decimal part of the value used in the calculation is actually rounded off to an appropriate place (the same applies below).

[0193] (6.2. Calculation results)

[0194] Fig. 7A as well as Figure 7B These are graphs showing examples of calculation results of FT. In these graphs, the horizontal axis represents ω2 / ω1. The vertical axis represents FT (0.1 μs). The multiple lines in the graphs, which are different for various cases with respect to γ2 / ω1, represent the relationship between ω2 / ω1 and FT. Fig. 7A The results for the case where γ1 / ω1=0 are shown. Figure 7B The results for the case where γ1 / ω1=0.23 are shown.

[0195] like Fig. 7A As shown in , when the main vibration is not attenuated, FT reaches a maximum value when ω2 / ω1 is a multiple of 2. On the other hand, Figure 7B As shown, when the main vibration is attenuated, FT reaches a local maximum when ω2 / ω1 is slightly larger than a multiple of 2. The difference between ω2 / ω1 at which FT reaches a local maximum and a multiple of 2 is, for example, less than 0.5. Even if the value of γ2 / ω1 is different, the above tendency is the same.

[0196] Figure 8 is another example of the calculation result of FT. Fig. 7A as well as Figure 7B Same picture. Figure 8 and Figure 7B The results for the case of γ1 / ω1=0.23 are shown in the same way. Figure 7B There are some differences. In addition, regarding ω2 / ω1, in the ratio Figure 7B A wider range of calculations.

[0197] Figures 9A to 9C as well as Figures 10A to 10C They are respectively Figure 8 The graphs show the lines when γ2 / ω1 is a specific value. Specifically, as described in the respective graphs, these graphs show the FT when γ2 / ω1 is 0, 0.23, 0.46, 0.69, 0.92, or 1.15.

[0198] As can be understood from the comparison of these figures, the value of the multiple of 2 of ω2 / ω1 close to the maximum FT changes according to the value of γ2 / ω1. For example, when γ2 / ω1 is 0 or 0.23, FT is maximum when ω2 / ω1 is a value slightly deviated from 2. When γ2 / ω1 is 0.46 or 0.69, FT is maximum when ω2 / ω1 is a value slightly deviated from 4. When γ2 / ω1 is 0.92 or 1.15, FT when ω2 / ω1 is a value slightly deviated from 4 and FT when ω2 / ω1 is a value slightly deviated from 6 are approximately the same and maximum. In this way, the larger γ2 / ω1 is, the larger the value of the multiple of 2 of ω2 / ω1 close to the maximum FT becomes.

[0199] In addition to the above-mentioned tendency, it is also known that the larger γ2 / ω1 is, the smaller the maximum value of FT is, and the slope of the peak including the maximum value of FT becomes gentler. Therefore, for example, by setting γ2 / ω1 to be small (for example, setting it to 0.46 or less or 0.23 or less), the maximum value of FT can be increased. In addition, for example, by setting γ2 / ω1 to be relatively large (for example, setting it to 0.46 or more or 0.69 or more), the fluctuation of FT when ω2 / ω1 deviates from the design value can be reduced.

[0200] Fig.11 , Figures 12A to 12C as well as Figures 13A to 13C is the same as above Figure 8 , Figures 9A to 9C as well as Figures 10A to 10C The same figure. Among them, Fig.11 As described above, the results for the case where γ1 / ω1=0.46 are shown.

[0201] As shown in these figures, in the case of γ1 / ω1=0.46, a tendency substantially similar to that in the case of γ1 / ω1=0.23 can be confirmed. For example, it can be confirmed that the larger γ2 / ω1 is, the larger the value of ω2 / ω1, which is close to the value of 2 when FT becomes maximum, becomes.

[0202] As from Figure 8 and Fig.11 As can be understood from the comparison, the larger γ1 / ω1 is, the more ω2 / ω1, where FT reaches a maximum value, deviates from a multiple of 2. This tendency can be explained by Figure 6 Specifically, as γ1 increases, the right side of the graph (the side with longer elapsed time t) of the first peak of the main vibration (v1) becomes smaller relative to the left side of the graph. Therefore, if the shift of the high-frequency vibration (v2) to the left side of the graph is increased, FT can be extended.

[0203] like Figure 8 as well as Fig.11As shown, FT reaches a local maximum at positions slightly deviated from multiples of 2 (2, 4, 6, and 8). Furthermore, the larger the multiple of 2, the larger the deviation of ω2 / ω1 from the multiple of 2 at which FT reaches a local maximum.

[0204] According to the above, ω2 / ω1, where FT reaches a maximum value, is related to γ1 / ω1 and multiples of 2. In addition, the value of γ2 / ω1 has little effect on ω2 / ω1, where FT reaches a maximum value. Therefore, when n is set to a positive integer, a multivariate regression analysis with γ1 / ω1 and n (which is a multiple of 2, i.e., 2n, from another point of view) as independent variables and ω2 / ω1, where FT reaches a maximum value, as a dependent variable is used to derive a formula for finding ω2 / ω1, where FT reaches a maximum value, from γ1 / ω1 and 2n.

[0205] The combinations of n, γ1 / ω1, and ω2 / ω1 at which FT reaches a maximum value used in deriving the formula are as follows.

[0206] ･When γ1 / ω1=0, (n=1, ω2 / ω1=2), (n=2, ω2 / ω1=4), (n=3, ω2 / ω1=6)

[0207] ･When γ1 / ω1=0.115473, (n=1, ω2 / ω1=2.07), (n=2, ω2 / ω1=4.16), (n=3, ω2 / ω1=6.29)

[0208] ･When γ1 / ω1=0.230947, (n=1, ω2 / ω1=2.14), (n=2, ω2 / ω1=4.34), (n=3, ω2 / ω1=6.49)

[0209] ･When γ1 / ω1=0.461894, (n=1, ω2 / ω1=2.28), (n=2, ω2 / ω1=4.65), (n=3, ω2 / ω1=6.95)

[0210] Furthermore, as a formula for finding ω2 / ω1 where FT becomes a local maximum value based on γ1 / ω1 and n, the following formula can be obtained.

[0211] ω2 / ω1=2n (1+0.32×γ1 / ω1) (6)

[0212] The range of ±5% on the right side of the above-mentioned equation (6) is defined by equation (1).

[0213] In addition, the values ​​of ω2 / ω1 used in deriving the above-mentioned formula (6) are directly used to define the range of ±5% thereof in formula (2) and formula (3). Specifically, it is as follows.

[0214] Formula (2) is obtained as follows.

[0215] 2.07×0.95<ω2 / ω1<2.28×1.05

[0216] 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 is the value when γ1 / ω1=0.12, and the latter is the value when γ1 / ω1=0.46.

[0217] Formula (3) is obtained as follows.

[0218] 4.16×0.95<ω2 / ω1<4.65×1.05

[0219] 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 is the value when γ1 / ω1=0.12, and the latter is the value when γ1 / ω1=0.46.

[0220] (6.3. Amplitude)

[0221] Formulas (1) to (3) are calculation results based on assuming specific values ​​for A1 and A2. However, even if A1 and A2 are other values, by setting ω2 / ω1 to a value in a range centered around a value slightly larger than 2n, the maximum speed v of the meniscus that is likely to reduce the deviation caused by AL can be obtained. max In other words, even if A1 and A2 are other values, although the best effect cannot be obtained, a better effect can be obtained. Therefore, it is not necessary for A1 and A2 to be the values ​​used in the calculation. Among them, regarding A1 and A2, if their ratio A1 / A2 is the same, the above calculation results represent the same value. Therefore, A1 / A2 can be set to a value within the range of ±20%, ±10% or ±5% of its value.

[0222] Alternatively or on the basis of A1 / A2, the ratio (B2 / B1) of the peak intensity B2 of the amplitude spectrum of the high-frequency vibration at speed v2 to the peak intensity B1 of the amplitude spectrum of the main vibration at speed v1 may be within a given range. Specifically, as follows.

[0223] Fig.14 : is a diagram showing an example of an amplitude spectrum of velocity in the vibration of the meniscus. In this diagram, the horizontal axis represents the frequency f (kHz), and the vertical axis represents the intensity I of the spectrum, more specifically, the amplitude A (m / s) of the velocity.

[0224] As shown in the figure, the actual vibration of the meniscus is not formed by synthesizing only the main vibration and the high-frequency vibration, but by synthesizing the vibrations of various frequencies (it can be considered as such). In addition, the intensity becomes high at the frequencies corresponding to the main vibration and the high-frequency vibration and in the vicinity thereof (refer to the frequencies involved in B1 and B2).

[0225] The maximum value of the portion where the intensity becomes higher as described above is called the peak intensity. The peak intensity involved in the main vibration is set to B1, and the peak intensity involved in the high-frequency vibration is set to B2. In this case, B2 / B1 can be set to, for example, not less than 0.19 and not more than 0.25. This range is derived based on multiple experiments and multiple simulations conducted by the applicant under various conditions with different conditions.

[0226] (7. Parameter adjustment method)

[0227] The value of any parameter of ω1, ω2, and γ1 may be adjusted to satisfy equations (1) to (3). The value of the parameter depends on various factors. As various factors, for example, the shape, size, and rigidity of the inner wall (including the actuator 17) of each part of the separate flow path 25, and the density, elastic modulus, and viscosity of the liquid in the separate flow path 25 may be cited. When adjusting the value of the parameter, any of these factors may be adjusted.

[0228] For example, ω1 and γ1 (which is the schematic structure of the independent flow path 25 from another perspective) which are affected by the entirety of the independent flow path 25 can be set basically in accordance with the same design concept as in the past. In addition, the value of ω2 can be adjusted by adjusting the shape and size of the partial flow path 45, thereby satisfying equations (1) to (3).

[0229] In more detail, 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 a cylindrical shape with one end (the end on the nozzle 5 side) closed and the other end (the end on the pressurized chamber 43 side) open. The natural vibration in the closed tube generates standing waves with the closed end as a node and the open end as an antinode. That is, the wavelength of the natural vibration is approximately 4 times the length of the closed tube. On the other hand, there is a well-known relationship between the wavelength λ, the speed of sound c, and the angular frequency ω: λ=c×2π / ω. Therefore, ω2 can be adjusted by the length of the partial flow path 45. In addition, in actual design, the well-known open end correction can be considered.

[0230] When n is 1 or 2, ω2 / ω1 can be relatively small. In this case, the partial flow path 45 can be relatively long. For example, the length of the partial flow path 45 can be greater than the sum of the length of the flow direction of the pressurized chamber 43 (the maximum length in the plane direction) and the length of the flow direction of the throttle 39 (the maximum length in the plane direction). In addition, the thickness (height) of the common flow path 23 can be increased, thereby increasing the length of the partial flow path 45 as a result. In addition, the length of the above-mentioned partial flow path 45 can be the length of the center line of the flow path (the line passing through the center of the cross section). In addition, the length of the separate flow path 25 can be set, for example, to the length of the portion closer to the nozzle 5 side than the throttle 39, the length of the portion closer to the nozzle 5 side than the connecting portion 37, or the length on the nozzle 5 side from the connection position with the common flow path 23.

[0231] The length of the partial flow path 45 can 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.

[0232] 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, the wavelength of the high-frequency vibration can be changed by changing the diameter of the partial flow path 45, thereby adjusting ω2. In addition, for example, γ1 / ω1 can be adjusted by changing the physical properties of the liquid (changing the type of liquid to be used).

[0233] In the above, the adjustment of γ1, ω1 and ω2 contained in equations (1) to (3) is described. When adjusting γ2, A2 / A1 and / or B2 / B1, any of the various factors affecting them can also be adjusted. As factors affecting γ2, for example, the shape and size of the partial flow path 45 and the physical properties of the liquid can be cited. As factors affecting A2 / A1 and / or B2 / B1, factors cited as factors affecting ω1, ω2 and γ1 (already described) can be cited.

[0234] (8. Method for determining parameters)

[0235] Whether or not the equations (1) to (3) are satisfied can be determined by various methods. In other words, the values ​​of the various parameters of the equations (1) to (3) can be determined by various methods. An example thereof will be described below.

[0236] In the head 2 set as the measurement object, an experiment was conducted in which a driving signal Sg1 having a falling edge (without a rising edge) of a pulse Ps was input to the actuator 17. At this time, the speed of the meniscus was measured by a laser Doppler vibrometer. During the measurement, a laser was irradiated to the meniscus from the outside through the nozzle 5. And the frequency of the reflected laser was detected. Thus, it was possible to obtain Figure 6 The temporal change of the speed of such a meniscus (from another point of view, the waveform of vibration) is illustrated.

[0237] The obtained waveform includes waveforms of various frequencies, such as waveforms based on the main vibration and waveforms based on the high-frequency vibration. The waveform is decomposed into waveforms of each frequency by Fourier transform (for example, FFT: fast Fourier transform). In this way, the waveforms of the main vibration and the high-frequency vibration can be obtained. In addition, in order to apply the functions of equations (4) and (5) to each waveform, the amplitude (A1 or A2), attenuation rate (γ1 or γ2) and angular frequency (ω1 or ω2) are obtained. For example, since the spectrum of the attenuated vibration is Fourier transformed and squared, it becomes a distribution that follows the Lorentz function near the peak, this can be used to obtain it. Specifically, the intensity X (f) near the frequency f of the peak of the main vibration of equation (1) is expressed by the following equation, so it can be fitted to obtain the amplitude A1, attenuation rate γ1 and angular frequency ω1. For high-frequency vibration, parameters can also be obtained in the same way.

[0238] |X(f)| 2 =A1 2 / (4×(f-ω1 / 2π) 2 +(γ1 / π) 2 )

[0239] In addition, the amplitude, attenuation rate, and angular frequency can be obtained as follows. For example, the first valley ( Figure 6 When the values ​​of two adjacent maxima (or two adjacent minima) are set to y1 and y2, and the time points at which y1 and y2 are obtained are set to t1 and t2, the attenuation rate can be calculated by the following formula.

[0240] γ = ln (y1 / y2) / (t2-t1)

[0241] The angular frequency can be calculated by the following formula using the above-mentioned t1 and t2.

[0242] ω=2π(t2-t1)

[0243] B2 / B1 can be determined, for example, as follows. If Fourier transform is performed as described above, we can obtain Fig.14 Such a spectrum is exemplified. The highest value among the maximum values ​​of intensity is set as peak intensity B1. On the higher frequency side than peak intensity B1, the maximum value of intensity second only to peak intensity B1 is set as peak intensity B2. Of course, peak intensities B1 and B2 can be determined based on the maximum values ​​suitable for excluding noise.

[0244] In addition, the frequency of the peak intensity B1 is approximately ω1 / 2π, but it is not limited to these coincidences. Similarly, the frequency of the peak intensity B2 is approximately ω2 / 2π, but it is not limited to these coincidences. In addition, B2 / B1 becomes a value close to A2 / A1, but it is not limited to these coincidences.

[0245] (9. Summary of implementation methods)

[0246] As described above, the liquid ejection head 2 involved in the embodiment has a flow path member 19 and an actuator 17. The flow path member 19 has a separate flow path 25 for containing liquid. The separate flow path 25 has: a pressurized chamber 43; a partial flow path 45 extending from the pressurized chamber 43; and a nozzle 5 that opens to the outside at the end of the partial flow path 45 on the side opposite to the pressurized chamber 43. The actuator 17 applies pressure to the pressurized chamber 43. The attenuation rate of the natural vibration (main vibration) of the liquid in the separate flow path 25 is set to γ1 (rad / s). The angular frequency of the main vibration is set to ω1 (rad / s). The angular frequency of the natural vibration (high-frequency vibration) of the liquid in the partial flow path 45 is set to ω2 (rad / s). n is set to a positive integer. At this time, at least one of the above-described equations (1) to (3) is established.

[0247] From another viewpoint, the liquid ejecting device (printer 1 ) according to the embodiment includes: the head 2 as described above; and a moving unit 85 that moves the head 2 and a recording medium relative to each other.

[0248] Therefore, for example, as described so far, the top of the peak of the natural vibration of the speed of the meniscus can be made flat (refer to Figure 6 ), which in turn can reduce the variation of the pulse width PW (from other perspectives, the deviation of AL from PW) to the maximum velocity v of the meniscus max The impact ( Figure 5A as well as Figure 5B As a result, the maximum velocity v of the meniscus caused by the deviation of AL of the plurality of ejection elements 15 can be reduced. max Furthermore, for example, the deviation from the maximum speed v max The deviation of the relevant ejection speed and / or ejection amount can be improved.

[0249] Regarding ω2 and ω1, if we compare the principle of reducing deviation, the ratio ω2 / ω1 has an effect, but the absolute value (rad / s) has no effect. Therefore, ω2 and ω1 when applying equations (1) to (3) are arbitrary in principle.

[0250] In reality, γ1 / ω1 is greater than 0. In addition, when γ1 / ω1 is greater than 1, the speed of the meniscus becomes non-vibrating, and the principle of the attraction-emission formula does not hold. Based on this, the range of γ1 / ω1 values ​​used in the calculation overlaps a lot with the range of γ1 / ω1 values ​​in reality. In other words, when using equations (1) to (3), the value of γ1 / ω1 is not limited to the value used in the calculation. Among them, the value of γ1 / ω1 can be limited to less than 0.46, or less than 0.5 (including less than 0.54) rounded off.

[0251] The influence of γ2 / ω1 on the validity of equations (1) to (3) is small. Figures 9A to 9C That is, when equations (1) to (3) are used, the absolute values ​​(rad / s) of γ2 / ω1 and γ2 are arbitrary.

[0252] The physical properties of the liquid (or the type of liquid from another point of view) affect whether or not equations (1) to (3) hold true. Among them, the head 2 that has equations (1) to (3) as its requirements may not have liquid as a constituent element. In other words, it is possible to determine whether the technology disclosed in the present invention is applied to a head 2 that is not filled with liquid and circulates. Generally, the head 2 is configured to exert the intended performance, the performance required in the specification, or the optimal performance when using so-called genuine ink. Therefore, the physical properties of the liquid intended to be used in the head 2 can be determined based on the structure of the head 2 through analysis or experiments. That is, whether or not equations (1) to (3) hold true can be determined regardless of the presence or absence of liquid. Among them, the physical properties of the liquid can also be determined based on the specification or instruction manual. In addition, it is also possible to determine whether or not equations (1) to (3) hold true for a head 2 that is filled with liquid, which is different from the above.

[0253] Formulas (1) to (3) may be established for any number of the plurality of ejection elements 15 included in the head 2. For example, they may be established for all ejection elements 15 included in the head 2, or for two or more and a portion of the ejection elements 15. The portion may be, for example, less than 50%, 50% or more, or 80% or more.

[0254] In the above, the effect is explained from the viewpoint of the deviation between the plurality of ejection elements 15. When focusing on one ejection element 15, the effect of reducing the intended maximum velocity v caused by the deviation between the pulse width PW and AL can be achieved. max The actual maximum speed v max From this point of view, the number of ejection elements 15 included in the head 2 may be one.

[0255] N can be set to 1 or 2.

[0256] In this case, for example, Figure 8 to Figure 13C As shown, although it depends on the value of γ2 / ω1, the local maximum value of FT tends to become large. As a result, the effect of reducing the above-mentioned deviation is improved.

[0257] γ1 / ω1 can be set to 0.46 or less.

[0258] In this case, for example, if the comparison Figure 8 and Fig.11 As described above, since the smaller γ1 / ω1 is, the easier it is to increase FT, the more likely it is to obtain the effect of increasing FT. In addition, since the value of γ1 / ω1 used when calculating equations (1) to (3) is used, it is highly likely that the effect of increasing FT can be obtained.

[0259] When the attenuation rate of the natural vibration of the liquid in the partial flow path 45 is γ2 (rad / s), γ2 / ω1 can be set to 1.15 or less, preferably 0.92 or less, and more preferably 0.46 or less.

[0260] In this case, for example, as referenced Figures 9A to 10C As described above, since the smaller γ2 / ω1 is, the easier it is to increase FT, the more likely it is to obtain the effect of increasing FT. In addition, since the value of γ2 / ω1 used when calculating equations (1) to (3) is used, it is highly likely that the effect of increasing FT can be obtained.

[0261] The peak intensity B2 of the amplitude spectrum of the velocity of the natural vibration (main vibration) of the liquid in the separate flow path 25, i.e., B2 / B1, can be set to be greater than 0.19 and less than 0.25.

[0262] In this case, for example, by combining the high-frequency vibration of the above-mentioned intensity with the main vibration, the variation of the ejection speed of the droplets between the plurality of ejection elements 15 can be further reduced. When B2 / B1 is 0.19 or more, the high-frequency vibration has a suitable influence on the ejection. When B2 / B1 is 0.25 or less, the influence of the high-frequency vibration only on the ejection becomes large.

[0263] The head 2 may further have a driver 13 that drives the actuator 17 by attraction emission.

[0264] In this case, for example, the added value of the head 2 is improved. In addition, the above-mentioned effects can be obtained by the attraction-emission type driving.

[0265] In the above embodiment, the printer 1 is an example of a liquid ejecting device. The printing paper P is an example of a recording medium.

[0266] The technology involved in the present disclosure is not limited to the above-mentioned embodiments, and can be implemented in various forms.

[0267] The actuator is driven by generating the natural vibration of the main vibration and applying liquid pressure synchronously with the natural vibration. Therefore, it is typically a suction emission type, but a driving method that is improved from the suction emission type or a driving method that is difficult to be regarded as the suction emission type can also be adopted.

[0268] The liquid ejection head may also have a recovery flow path for recovering liquid from the partial flow path. The recovery flow path, for example, contributes to reducing the possibility of liquid being retained in the partial flow path. Thus, for example, the possibility of the viscosity of the liquid in the nozzle and the partial flow path becoming higher due to reduced evaporation of the solvent of the liquid near the nozzle.

[0269] The actuator is not limited to the unipolar type or the bipolar type. For example, the actuator may be a vertical piezoelectric element that is configured by stacking electrodes and piezoelectric layers and directly transmits contraction and expansion to a vibration plate.

[0270] The liquid ejection device can move the recording medium and the head relatively by moving the head with a robot or the like. In addition, the liquid ejection device can be moved by holding the entire device by the user's hand, thereby moving relative to the recording medium. The liquid ejection device is not limited to a device that attaches ink to paper or cloth, etc., and may also be a device that attaches paint to a vehicle body. In other words, the recording medium can be interpreted broadly.

[0271] Explanation of symbols

[0272] 1 ... liquid ejection head, 5 ... nozzle, 17 ... actuator, 19 ... flow path member, 25 ... separate flow path, 43 ... pressurizing chamber, 45 ... partial flow path.

Claims

1. A liquid ejection head, comprising: a flow path member having a separate flow path for containing a liquid, the separate flow path having a pressurized chamber, a partial flow path extending from the pressurized chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurized chamber; and an actuator which imparts pressure to the pressurized chamber, When the attenuation rate of the natural vibration of the liquid in the separate flow path is set to γ1, the angular frequency of the natural vibration of the liquid in the separate flow path is set to ω1, the angular frequency of the natural vibration of the liquid in the partial flow path is set to ω2, and n is set to a positive integer, where the unit of γ1 is rad / s, the unit of ω1 is rad / s, and the unit of ω2 is rad / s, the following equation holds, 0.95×2n (1+0.32×γ1 / ω1) ≤ ω2 / ω1 ≤ 1.05×2n (1+0.32×γ1 / ω1).

2. A liquid ejection head, comprising: a flow path member having a separate flow path for containing a liquid, the separate flow path having a pressurized chamber, a partial flow path extending from the pressurized chamber, and a nozzle opening to the outside at an end of the partial flow path on a side opposite to the pressurized chamber; and an actuator which imparts pressure to the pressurized chamber, When the angular frequency of the natural vibration of the liquid in the single flow path is set to ω1, and the angular frequency of the natural vibration of the liquid in the partial flow path is set to ω2, where the unit of ω1 is rad / s and the unit of ω2 is rad / s, the following equation holds: 1.97≤ω2 / ω1≤2.39 or 3.95≤ω2 / ω1≤4.

88.

3. The liquid ejection head according to claim 1, wherein: N is 1 or 2.

4. The liquid ejection head according to any one of claims 1 to 3, wherein: When the attenuation rate of the natural vibration of the liquid in the separate flow channel is γ1, where the unit of γ1 is rad / s, γ1 / ω1 is equal to or less than 0.

46.

5. The liquid ejection head according to any one of claims 1 to 4, wherein When the attenuation rate of the natural vibration of the liquid in the partial flow path is γ2, where the unit of γ2 is rad / s, γ2 / ω1 is 1.15 or less.

6. The liquid ejection head according to any one of claims 1 to 5, wherein: The peak intensity of the amplitude spectrum of the velocity of the natural vibration of the liquid in the partial flow channel is 0.19 or more and 0.25 or less relative to the peak intensity of the amplitude spectrum of the velocity of the natural vibration of the liquid in the single flow channel.

7. The liquid ejection head according to any one of claims 1 to 6, wherein: The liquid ejection head further includes a driver that drives the actuator by suction emission.

8. A liquid ejection device, comprising: The liquid ejection head according to any one of claims 1 to 7; and A moving unit moves the liquid ejection head and the recording medium relative to each other.

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