Liquid jet

Abstract

A liquid printhead is provided that can expand the grayscale range and ensure printout stability. The liquid printhead includes: a pressure chamber in communication with a nozzle that ejects liquid; an actuator that changes the volume of the pressure chamber in response to an electrical signal; and a drive circuit that generates an electrical signal to drive the actuator. The drive circuit outputs a drive waveform having an ejection waveform portion. When printing three or more grayscale levels by ejecting n (n = 3 or more) ink droplets, the period of a single inherent vibration in the state where the pressure chamber is filled with ink is set to λ, and n-1 ejection pulses are provided at intervals of 0.8 to 1.2λ. Each n-1 ejection pulse includes: a first ejection pulse having an expansion element that expands the pressure chamber and a contraction element that sets a voltage higher than the intermediate voltage after expansion; and a second ejection pulse having an expansion element that expands the pressure chamber and a contraction element that sets a voltage higher than the intermediate voltage after expansion.

Description

Technical Field

[0001] Embodiments of the present invention relate to liquid nozzles. Background Technology

[0002] In recent years, inkjet printheads and other liquid ejection devices have been required to deliver various printing performance characteristics, such as high image quality, high resolution, high productivity, and increased droplet volume.

[0003] For example, it is known that, in order to achieve high-speed or high-droplet ejection, a drive signal with multiple ejection pulses that eject ink droplets within a printing cycle is supplied based on an intermediate voltage. For example, to suppress residual vibrations caused by the ejection pulses, a drive waveform with an expansion element and a contraction element is used, wherein the expansion element expands the pressure chamber after the last ejection pulse, and the contraction element causes the pressure chamber, which has been expanded by the expansion element, to contract again and return to the intermediate voltage.

[0004] In this type of inkjet head, a wider and more stable grayscale range is required. Summary of the Invention

[0005] The problem the invention aims to solve

[0006] The problem to be solved by the present invention is to provide a liquid nozzle that can expand the grayscale range and ensure the stability of the spray.

[0007] Solution for solving the problem

[0008] The liquid nozzle according to the embodiment includes: a pressure chamber in communication with a nozzle that ejects liquid; an actuator that changes the volume of the pressure chamber in response to an electrical signal; and a drive circuit that generates an electrical signal to drive the actuator. The drive waveform output by the drive circuit includes an ejection waveform portion. When printing with three or more gray levels by ejecting n (an integer n = 3 or more) ink droplets, the period of a single natural vibration in the state where the pressure chamber is filled with ink is set to λ. The ejection waveform portion has n-1 ejection pulses at intervals of 0.8 to 1.2λ. The n-1 ejection pulses include: a first ejection pulse having an expansion element that expands the pressure chamber and a contraction element that sets an intermediate voltage after expansion; and a second ejection pulse having an expansion element that expands the pressure chamber and a contraction element that sets a voltage higher than the intermediate voltage after expansion. Attached Figure Description

[0009] Figure 1 This is a perspective view showing the configuration of the liquid nozzle according to the first embodiment.

[0010] Figure 2 This is a perspective view showing the structure of the head body of the liquid nozzle according to the first embodiment.

[0011] Figure 3 This is a bottom view showing a portion of the liquid nozzle configuration according to the first embodiment.

[0012] Figure 4 This is a cross-sectional view showing a portion of the head body structure as described in the first embodiment, with the latter omitted.

[0013] Figure 5 This is an explanatory diagram showing the configuration of the liquid ejection device according to the first embodiment.

[0014] Figure 6 This is an explanatory diagram showing the driving waveform involved in Embodiment 1.

[0015] Figure 7 This is a graph showing the simulation results of the flow rate in Example 1.

[0016] Figure 8 This is a graph showing the simulation results of the meniscus location in Example 1.

[0017] Figure 9 This is an explanatory diagram showing the driving waveform involved in Embodiment 2.

[0018] Figure 10 This is a graph showing the simulation results of the flow rate in Example 2.

[0019] Figure 11 This is a graph showing the simulation results of the meniscus location in Example 2.

[0020] Figure 12 This is an explanatory diagram showing the driving waveform involved in Embodiment 3.

[0021] Figure 13 This is a graph showing the simulation results of the flow rate in Example 3.

[0022] Figure 14 This is a graph showing the simulation results of the meniscus location in Example 3.

[0023] Figure 15 This is an explanatory diagram showing the driving waveform involved in Embodiment 4.

[0024] Figure 16 This is an explanatory diagram showing the driving waveform involved in Embodiment 5.

[0025] Figure 17 This is an explanatory diagram showing the driving waveform involved in Embodiment 6. Detailed Implementation

[0026] The following is for reference Figures 1 to 5The liquid nozzle 1 and the liquid ejection device 2 using the liquid nozzle 1 according to the first embodiment will be described. Figure 1 This is a perspective view showing the configuration of the liquid nozzle 1 according to the first embodiment. Figure 2 This is a perspective view showing the liquid nozzle 1 after a portion of the nozzle plate 114 has been removed from the head body 11 of the liquid nozzle 1. Figure 3 This is a bottom view showing the liquid nozzle 1 with the nozzle plate 114 omitted. Figure 4 This is a cross-sectional view showing the structure of the head body 11. Figure 5 This is an explanatory diagram showing the configuration of a liquid ejection device 2 using a liquid nozzle 1. It should be noted that the configuration has been appropriately enlarged, reduced, or omitted in the figures for illustrative purposes.

[0027] Liquid nozzle 1 is, for example, set in Figure 5 The inkjet recording device and other liquid ejection devices 2 shown share a wall-mounted inkjet head in a shared mode. The liquid printhead 1 is provided in the head unit 2130, which includes a supply tank 2132, which serves as a liquid receiving section, provided in the liquid ejection device 2.

[0028] The liquid printhead 1 supplies ink as a liquid stored in the supply tank 2132. It should be noted that the liquid printhead 1 can be a non-circulating printhead that does not circulate the ink, or it can be a circulating printhead that circulates the ink. In this embodiment, an example of a non-circulating printhead is used to illustrate the liquid printhead 1.

[0029] like Figures 1 to 4 As shown, the liquid nozzle 1 includes a head body 11, a manifold unit 12, a drive circuit 13, and a cover 14. For example, the liquid nozzle 1 is a side-firing type four-row integrated structure head with two sets of side-firing actuators 113 on the head body 11.

[0030] The head body 11 ejects liquid. The head body 11 includes a base plate 111, a frame 112, an actuator 113 having multiple pressure chambers 1131, and a nozzle plate 114.

[0031] The head body 11 has a common liquid chamber 116 communicating with the plurality of pressure chambers 1131 of the actuator 113. The primary side of the plurality of pressure chambers 1131 refers to the upstream side of the plurality of pressure chambers 1131 in the direction of liquid flow. The secondary side of the plurality of pressure chambers 1131 refers to the downstream side of the plurality of pressure chambers 1131 in the direction of liquid flow.

[0032] In addition, the head body 11 has multiple independent electrodes 118 (electrode portions) on the substrate 111 and the actuator 113 respectively driving multiple pressure chambers 1131 of the actuator 113.

[0033] In this embodiment, an example is used where the head body 11 has two actuators 113, and the common liquid chamber 116 has one first common liquid chamber 1161 and two second common liquid chambers 1162. The common liquid chamber 116, for example, has a first common liquid chamber 1161 that communicates with the openings (inlets of the pressure chambers 1131) on the primary side of the plurality of pressure chambers 1131 of the actuator 113, and a second common liquid chamber 1162 that communicates with the openings (outlets of the pressure chambers 1131) on the secondary side of the plurality of pressure chambers 1131 of the actuator 113.

[0034] The substrate 111 is formed into a rectangular plate shape, for example, from a ceramic material. The substrate 111 is formed into a rectangular shape that is elongated in one direction, for example.

[0035] Wiring 1181, which forms part of a plurality of independent electrodes 118, is formed on the wiring surface 115, which is one side of the substrate 111. The wiring on the substrate 111 is formed, for example, from a nickel thin film. The wiring 1181 has a prescribed pattern shape that is connected to the wiring formed on the actuator 113.

[0036] A pair of actuators 113 are arranged along the short side of the substrate 111. One side of the substrate 111 refers to one face of the substrate 111. The substrate 111 has a supply port 1111 and a plurality of discharge ports 1112. The supply port 1111 and the discharge ports 1112 are through holes that connect the two main faces of the substrate 111.

[0037] The supply port 1111 is the inlet for supplying ink to the first common liquid chamber 1161. The supply port 1111 is a through-hole formed at the center of the short side of the substrate 111. The supply port 1111 extends along the long side of the substrate 111. In other words, the supply port 1111 is, for example, an elongated hole extending in one direction along the long side of the actuator 113 and the long side of the first common liquid chamber 1161. The supply port 1111 is disposed between a pair of actuators 113 and opens at a position opposite to the first common liquid chamber 1161.

[0038] The discharge port 1112 is the outlet for discharging ink from the second common liquid chamber 1162. Multiple discharge ports 1112 are provided, for example, four. Each discharge port 1112 is located, for example, between the first common liquid chamber 1161 and each of the second common liquid chambers 1162, and is adjacent to both ends of the pair of actuators 113 in the long side direction. It should be noted that multiple discharge ports 1112 may also be provided within the second common liquid chamber 1162.

[0039] The frame 112 is fixed to a main surface of the substrate 111 by an adhesive or the like. The frame 112 surrounds the supply port 1111, multiple discharge ports 1112 and actuator 113 provided on the substrate 111.

[0040] For example, the frame 112 is formed as a rectangular frame, thereby forming an opening that extends in one direction along the long side of the frame 112. A pair of actuators 113, a supply port 1111, and four discharge ports 1112 are arranged in the opening of the frame 112.

[0041] A pair of actuators 113 are bonded to the mounting surface of the substrate 111. The pair of actuators 113 sandwich the supply port 1111 and are arranged in two rows on the substrate 111. The actuators 113 are formed as plates that are elongated in one direction. The actuators 113 are disposed in the opening of the frame 112 and are bonded to the main surface of the substrate 111.

[0042] like Figure 3 As shown, the actuator 113 has a plurality of pressure chambers 1131 arranged at equal intervals along its longitudinal direction on its central side. In other words, the actuator 113 has a plurality of pressure chambers 1131 arranged along its longitudinal direction.

[0043] The top surface of the actuator 113, which is the side opposite to the substrate 111, is bonded to the nozzle plate 114. The actuator 113 has a plurality of slots arranged at equal intervals along its long side and perpendicular to the long side direction. These slots form a plurality of pressure chambers 1131. In other words, the actuator 113 has a plurality of piezoelectric pillars 1133, which are driving elements arranged at equal intervals along its long side and form the walls between the slots. The plurality of piezoelectric pillars 1133 change the volume of the pressure chambers 1131 by forming a plurality of pressure chambers 1131 between adjacent piezoelectric pillars 1133 and by applying a driving voltage. That is, the actuator 113 changes the volume of the pressure chambers in response to an electrical signal.

[0044] The width of the actuator 113, for example, in the short side direction, gradually increases from the top side toward the substrate 111 side. The cross-sectional shape of the actuator 113 in the direction orthogonal to the long side direction (short side direction) is formed into a trapezoidal shape. That is, the actuator 113 has an inclined surface 1134 on the side portion in the short side direction. The side portion (inclined surface 1134) is arranged opposite to the first common liquid chamber 1161 and the second common liquid chamber 1162.

[0045] When printing or other actions are performed through the liquid nozzle 1, the pressure chamber 1131 deforms, causing ink to be ejected from the nozzle 1141. The inlet of the pressure chamber 1131 opens into the first common liquid chamber 1161, and the outlet opens into the second common liquid chamber 1162. In the pressure chamber 1131, ink flows in from the inlet and flows out from the outlet. It should be noted that the pressure chamber 1131 may also be configured such that ink flows in from the two openings described as the inlet and outlet.

[0046] The nozzle plate 114 is formed in a plate shape. The nozzle plate 114 is fixed to the main surface of the frame 112 opposite to the base plate 111 by an adhesive or the like. The nozzle plate 114 has a plurality of nozzles 1141 formed at positions opposite to the plurality of pressure chambers 1131. In this embodiment, the nozzle plate 114 has two rows of nozzles 1142, which are formed by arranging a plurality of nozzles 1141 in one direction.

[0047] A first common liquid chamber 1161 is formed between the central sides of a pair of actuators 113, excluding the two ends, forming a flow path for ink from the supply port 1111 toward the primary side of the plurality of pressure chambers 1131 of each actuator 113. The first common liquid chamber 1161 extends along the long side of the actuator 113.

[0048] Second common liquid chambers 1162 are formed between each actuator 113 and the frame 112. The second common liquid chamber 1162 forms a flow path for ink from the openings (outlets) on the secondary side of the plurality of pressure chambers 1131 toward the discharge port 1112. The second common liquid chamber 1162 extends along the long side of the actuator 113.

[0049] Multiple independent electrodes 118 are independent electrodes for independently applying driving voltages to multiple piezoelectric pillars 1133, which are piezoelectric elements. Multiple independent electrodes 118 cause each pressure chamber 1131 to deform independently. The independent electrodes 118 are composed of wiring formed on the actuator 113 and the substrate 111, respectively.

[0050] An independent electrode 118 extends from the inner surface of the pressure chamber 1131 to the inclined surface 1134 and the wiring surface 115 of the substrate 111, and extends towards the end of the substrate 111 in the short side direction, connecting to the drive circuit 13. The independent electrode 118 is formed, for example, of a nickel thin film. It should be noted that the independent electrode 118 is not limited to a nickel thin film; it can also be formed of a gold or copper thin film, for example. It should also be noted that a portion of the independent electrode 118 may be covered on the lower surface of the frame 112 by an adhesive that bonds the frame 112 to the substrate 111.

[0051] Individual electrodes 118 are connected to drive circuit 13, for example. Each individual electrode 118 is configured to be connected to control unit 2118, which is a drive unit, via wiring and a driver described later in the drive circuit 13, so that drive control can be performed by processor-based control.

[0052] like Figure 1 , Figure 3As shown, the manifold unit 12 includes a manifold 121, an ink supply pipe 123, an ink discharge pipe 124, and a temperature regulating water supply pipe 125 and a temperature regulating water discharge pipe as a pair of temperature regulating pipes. It should be noted that the number of ink supply pipe 123, ink discharge pipe 124, temperature regulating water supply pipe 125, and temperature regulating water discharge pipe can be appropriately set.

[0053] The manifold 121 is formed in the shape of a plate or a block. The manifold 121 includes: a supply flow path, which is continuous with the supply port 1111 of the substrate 111 to form a liquid supply flow path; a discharge flow path, which is continuous with the discharge port 1112 of the substrate 111 to form a liquid discharge flow path; and a temperature regulation flow path, which forms a flow path for temperature regulation fluid.

[0054] One main surface of the manifold 121 is fixed to the main surface of the substrate 111. In addition, for example, ink supply pipe 123, ink discharge pipe 124, temperature-regulating water supply pipe 125, and temperature-regulating water discharge pipe are fixed to the manifold 121.

[0055] The supply flow path is a flow path formed in the manifold 121 through holes or grooves. The supply flow path connects the ink supply pipe 123 to the supply port 1111 of the substrate 111 in a fluid manner.

[0056] The discharge path is a flow path formed in the manifold 121 through holes or grooves. The discharge path fluidly connects the ink discharge pipe 124 to the discharge port 1112 of the substrate 111.

[0057] The temperature regulating flow path is formed in the manifold 121 through holes or grooves. The temperature regulating flow path connects the temperature regulating water supply pipe 125 and the temperature regulating water discharge pipe in a fluid manner.

[0058] The two ends of the temperature regulating flow path are openings that connect to a temperature regulating water supply pipe 125 and a temperature regulating water discharge pipe provided on one main surface of the manifold 121. In addition, the temperature regulating flow path is configured to exchange heat with the substrate 111 fixed to the manifold 121.

[0059] Ink supply pipe 123 is connected to the supply flow path. Ink discharge pipe 124 is connected to the discharge flow path. Temperature regulating water supply pipe 125 and temperature regulating water discharge pipe are connected to the primary and secondary sides of the temperature regulating flow path, respectively.

[0060] like Figure 2 As shown, the driving circuit 13 includes: a wiring film 131, one end of which is connected to the substrate 111; a driver IC 132, which is mounted on the wiring film 131; and a printed wiring substrate 133, which is mounted on the other end of the wiring film 131.

[0061] The drive circuit 13 applies a drive voltage to the wiring pattern of the actuator 113 through the driver IC 132, thereby driving the actuator 113 to increase or decrease the volume of the pressure chamber 1131 and cause the droplets to be ejected from the nozzle 1141.

[0062] Wiring film 131 is connected to multiple independent electrodes 118. For example, wiring film 131 is fixed to the connection portion of substrate 111 by thermoforming or the like using an ACF (anisotropic conductive film). Multiple wiring films 131 are provided relative to a head body 11, for example. In this embodiment, two wiring films 131 are connected to one actuator 113. Wiring film 131 is, for example, a COF (Chip on Film) on which a driver IC 132 is mounted.

[0063] The driver IC 132 is connected to multiple independent electrodes 118 via a wiring film 131. It should be noted that the driver IC 132 may also be connected to multiple independent electrodes 118 via other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste) without using the wiring film 131.

[0064] The driver IC 132 generates control signals and drive signals for activating the piezoelectric columns 1133, which serve as driving elements. Based on the image signal input from the control unit 2118 of the liquid ejection device 2, the driver IC 132 generates control signals for timing the selection of ejected ink and controlling the piezoelectric columns 1133, etc., for ejecting ink. Additionally, the driver IC 132 generates a voltage, i.e., a drive signal (electrical signal), applied to the piezoelectric columns 1133 according to the control signals. When the driver IC 132 applies the drive signal to the piezoelectric columns 1133, the piezoelectric columns 1133 are driven, causing a change in the volume of the pressure chamber 1131. As a result, the ink filled in the pressure chamber 1131 is ejected from the nozzle 1141, which communicates with the pressure chamber 1131. It should be noted that the liquid printhead 1 can also achieve grayscale representation by changing the amount of ink droplets falling per pixel. Alternatively, the liquid printhead 1 can also change the amount of ink droplets falling per pixel by changing the number of ink ejections. Thus, the driver IC132 is an example of applying a drive signal to the application portion of the piezoelectric post 1133.

[0065] For example, the driver IC132 includes a data buffer, a decoder, and a driver. The data buffer stores the print data in a time sequence for each piezoelectric column 1133. The decoder controls the driver for each piezoelectric column 1133 based on the print data stored in the data buffer. The driver outputs a drive signal that actuates each piezoelectric column 1133 based on the decoder's control. The drive signal is the voltage applied to each piezoelectric column 1133.

[0066] The printed wiring board 133 is a PWA (Printed Wiring Assembly) that carries various electronic components or connectors.

[0067] The cover 14 includes, for example, an outer body 141 that covers the sides of the pair of head bodies 11, the manifold unit 12, and the drive circuit 13; and a cover plate that covers a portion of the nozzle plate 114 side of the pair of head bodies 11.

[0068] The outer body 141 exposes, for example, the ink supply pipe 123, ink discharge pipe 124, temperature-regulating water supply pipe 125 and temperature-regulating water discharge pipe in the manifold unit 12, as well as the end of the drive circuit 13, to the outside.

[0069] The cover plate covers the portion of the head body 11 except for the area around the multiple nozzles 1141 and the multiple nozzles 1141 of the nozzle plate 114.

[0070] The following is for reference Figure 5 The liquid ejection device 2, which includes a liquid nozzle 1, will be described. The liquid ejection device 2 includes a housing 2111, a media supply unit 2112, an image forming unit 2113, a media discharge unit 2114, a transport device 2115 serving as a support device, a maintenance device 2117, and a control unit 2118. Furthermore, the liquid ejection device 2 includes a temperature control device for adjusting the temperature of the ink supplied to the liquid nozzle 1.

[0071] The liquid ejection device 2 is an inkjet printer that ejects liquid such as ink along a predetermined transport path 2001 from the media supply unit 2112 through the image forming unit 2113 to the media discharge unit 2114, while transporting, for example, paper P as the ejection object, i.e., the recording medium, thereby performing image forming processing on the paper P.

[0072] The media supply unit 2112 includes multiple paper feed trays 21121. The image forming unit 2113 includes a support unit 2120 for supporting paper, and multiple head units 2130 disposed opposite each other above the support unit 2120. The media discharge unit 2114 includes a paper discharge tray 21141.

[0073] The support portion 2120 includes: a conveyor belt 21201 arranged in a ring in a predetermined area for image formation; a support plate 21202 supporting the conveyor belt 21201 from the back side; and a plurality of belt rollers 21203 disposed on the back side of the conveyor belt 21201.

[0074] The head unit 2130 includes: a liquid printhead 1, which is a plurality of inkjet heads; a plurality of supply tanks 2132, which are liquid tanks respectively mounted on each liquid printhead 1; a pump 2134 for supplying ink; and a connecting flow path 2135 for connecting the liquid printhead 1 to the supply tanks 2132.

[0075] In this embodiment, a four-color liquid nozzle 1 (cyan, magenta, yellow, and black) is provided as the liquid nozzle 1; and a four-color supply tank 2132 is provided to contain each of these colors of ink. The supply tank 2132 is connected to the liquid nozzle 1 via a connecting flow path 2135.

[0076] Pump 2134 is, for example, a liquid delivery pump composed of a piezoelectric pump. Pump 2134 is connected to control unit 2118 and is driven and controlled by control unit 2118.

[0077] The connecting flow path 2135 includes a supply flow path connected to the ink supply pipe 123 of the liquid printhead 1. Additionally, the connecting flow path 2135 includes a recovery flow path connected to the ink discharge pipe 124 of the liquid printhead 1. For example, in the case where the liquid printhead 1 is non-circulating, the recovery flow path is connected to the maintenance device 2117; in the case where the liquid printhead 1 is circulating, the recovery flow path is connected to the supply tank 2132.

[0078] The conveying device 2115 conveys paper P along a conveying path 2001 from the paper feed cassette 21121 of the media supply unit 2112 through the image forming unit 2113 to the paper discharge tray 21141 of the media discharge unit 2114. The conveying device 2115 includes multiple guide plates 21211-21218 arranged along the conveying path 2001, and multiple conveying rollers 21221-21228. The conveying device 2115 supports the paper P so that it can move relative to the liquid nozzle 1.

[0079] The maintenance device 2117, for example, draws in and recovers ink residue on the outer surface of the nozzle plate 114 during maintenance. Additionally, in the case where the liquid nozzle 1 is non-circulating, the maintenance device 2117 recovers ink from the head body 11 during maintenance. This maintenance device 2117 includes a tray or container for storing the recovered ink.

[0080] The control unit 2118 is, for example, a control board. The control unit 2118 is equipped with a processor, ROM (Read Only Memory), RAM (Random Access Memory), I / O ports as input / output ports, and image memory.

[0081] The processor is a processing circuit, including a CPU (Central Processing Unit), which acts as a controller. The processor controls the head unit 2130, drive motor, operating unit, and various sensors located in the liquid ejection device 2 via I / O ports. The processor sends the print data stored in the image memory to the drive circuit 13 in the order of drawing.

[0082] ROM stores various programs, etc. RAM temporarily stores various variable data or image data, etc. I / O ports are the interface for inputting and outputting data to external devices. Print data from externally connected devices is sent to the control unit through I / O ports and saved to the image memory.

[0083] Hereinafter, the characteristics of the liquid nozzle 1 used in the liquid ejection device 2 according to the embodiment and the drive waveform of the drive signal generated by the drive circuit 13 of the liquid nozzle 1 will be described. For example, the drive waveform of the liquid nozzle 1 is multi-drop drive and includes: an ejection waveform section having multiple ejection pulses; and a cancellation waveform section having a cancellation pulse following the ejection waveform section.

[0084] The ejection waveform section includes multiple ejection pulses Pa, Pb, and Pc. Each ejection pulse Pa, Pb, and Pc has an expansion element that lowers the voltage and a contraction element that raises the voltage after the expansion element. Furthermore, in the drive waveform of the liquid ejection device 2 according to this embodiment, the pressure voltage of the contraction elements of the multiple ejection pulses is set in two stages. That is, the drive waveform has at least two contraction elements that are pressurized with different voltages.

[0085] For example, when printing with three or more gray levels by ejecting ink droplets n times (n being an integer greater than or equal to 3), the ejection waveform, based on a first intermediate voltage Vb, includes the following from the 1st droplet to the (n-1)th droplet: (n-1) expansion elements, decreasing to voltage Va to expand the pressure chamber; contraction elements, causing the pressure chamber, expanded by each expansion element, to contract to the first intermediate voltage Vb to eject ink; and contraction elements, causing the pressure chamber, expanded by the expansion elements, to contract to a second intermediate voltage Vc, which is higher than the first intermediate voltage Vb, to eject ink. For example, voltage Va = 0V.

[0086] In this embodiment, the printing waveform of one printing cycle, including n ejection pulses and cancel pulses, falls within a time period shorter than (n+1.5)λ. Furthermore, in the driving waveform, the printing waveform of one printing cycle, including n ejection pulses and cancel pulses, falls within a time period shorter than (n+1)λ.

[0087] In this embodiment, the driving waveform has a period of λ for one natural vibration in the state where the pressure chamber 1131 is filled with ink. The centers (λ ± deviation) of each ejection pulse Pa, Pb, Pc and the cancellation pulse Pd are set with a period of 0.8 to 1.2λ. Furthermore, the overall configuration of the driving waveform, including the ejection waveform and the cancellation waveform, is shorter than (n+1)λ. By adopting this configuration, the range of ink droplet size that can be increased or decreased is expanded, and the ejection of ink droplets can be stabilized in grayscale printing.

[0088] [Example 1]

[0089] Figure 6 The driving waveform involved in Embodiment 1 is shown. This driving waveform is a three-drop waveform, with three ejection pulses, each expanding and contracting, arranged with a fixed period λ. The three ejection pulses Pa, Pb, and Pc each have an expansion element that expands the pressure chamber 1131 to introduce liquid into the pressure chamber 1131, and a contraction element that contracts the pressure chamber 1131 to eject the liquid. In this embodiment, the first ejection pulse Pa has an expansion element that lowers the voltage from a first intermediate voltage Vb to an expansion voltage Va, and a contraction element that raises the voltage to a second intermediate voltage Vc, which is higher than the first intermediate voltage Vb. For example, the second intermediate voltage Vc is greater than the first intermediate voltage Vb. That is, in this waveform, after the first ejection pulse Pa lowers the voltage from the first intermediate voltage Vb to the expansion voltage Va (=0V), it raises the voltage to a second intermediate voltage Vc, which is greater than the first intermediate voltage Vb. Then, in the second ejection pulse Pb, the voltage again lowers to the expansion voltage Va and then rises to the first intermediate voltage Vb. Furthermore, in the third ejection pulse Pc, after the voltage drops to the expansion voltage Va, it rises again to the first intermediate voltage Vb.

[0090] In Embodiment 1, the cancellation waveform section has a cancellation pulse Pd after the final ejection pulse Pc. The cancellation pulse Pd sequentially includes a contraction element that raises the voltage from a first intermediate voltage Vb to a larger second intermediate voltage Vc, and an expansion element that lowers the voltage back to the first intermediate voltage Vb. In this embodiment, multiple ejection pulses Pa, Pb, Pc and cancellation pulse Pd are arranged with a fixed period λ. In each ejection pulse Pa, Pb, Pc, the period from expansion to contraction and from contraction to expansion is λ / 2. Furthermore, in the cancellation pulse Pd, the period from the contraction of ejection pulse Pc to the contraction of cancellation pulse Pd, and the period from the contraction of cancellation pulse Pd to the expansion, are both λ / 2.

[0091] Figure 7 and Figure 8 The simulation results are shown when the meniscus is actuated with a voltage that does not spray out, as in Example 1. Figure 7The time-varying flow rates are shown when Vc / Vb = 1.4 and when Vc / Vb = 2.0. As a simulation condition, λ = 4 μs is used. Figure 8 The time-varying position of the meniscus is shown when Vc / Vb = 1.4 and when Vc / Vb = 2.0.

[0092] According to this embodiment, it is possible to simultaneously stabilize the ejection of ink droplets and expand the grayscale range. Furthermore, as... Figure 7 and Figure 8 As shown, residual vibration can be suppressed by adjusting the voltage ratio Vc / Vb.

[0093] [Example 2]

[0094] Figure 9 The driving waveform involved in Embodiment 2 is shown. This driving waveform is a three-drop waveform, with three ejection pulses, each expanding and contracting, arranged according to a fixed period λ. The three ejection pulses Pa, Pb, and Pc each have an expansion element that expands the pressure chamber 1131 to introduce liquid into the pressure chamber 1131, and a contraction element that contracts the pressure chamber 1131 to eject the liquid. In this embodiment, the first ejection pulse Pa has an expansion element that lowers the voltage from a first intermediate voltage Vb to an expansion voltage Va, and a contraction element that raises the voltage to a second intermediate voltage Vc, which is higher than the first intermediate voltage Vb. For example, the second intermediate voltage Vc is greater than the first intermediate voltage Vb. That is, in this waveform, after the first ejection pulse Pa lowers the voltage from the first intermediate voltage Vb to the expansion voltage Va (=0V), it raises the voltage to a second intermediate voltage Vc, which is greater than the first intermediate voltage Vb. Then, in the second ejection pulse Pb, the voltage again lowers to the expansion voltage Va and then rises to the first intermediate voltage Vb. Furthermore, in the third ejection pulse Pc, the voltage drops to the expansion voltage Va and then rises again to the second intermediate voltage Vc. In this embodiment, by rising to Vc, which is the maximum voltage, in the final ejection pulse and increasing the speed of the last droplet, the multiple ejected droplets can be combined into one.

[0095] In Embodiment 2, the cancellation waveform section has a cancellation pulse Pd in ​​the contraction element of the final ejection pulse Pc. The cancellation pulse Pd includes, in sequence: an expansion element, which causes the pressure chamber 1131, which has contracted by a second intermediate voltage Vc that is set to be higher than the first intermediate voltage Vb, to expand again and become an expansion voltage Va that is lower than the first intermediate voltage Vb; and a contraction element, which causes the pressure chamber 1131, which has expanded by the expansion element of the cancellation pulse section, to contract again and return to the first intermediate voltage Vb.

[0096] In this embodiment, multiple ejection pulses Pa, Pb, and Pc are arranged with a period of λ. In each ejection pulse Pa, Pb, and Pc, the period from expansion to contraction and from contraction to expansion is λ / 2. Furthermore, in the cancellation waveform section, the period from the contraction element of the ejection pulse Pc to the expansion element of the cancellation pulse Pd is λ, and the period from the expansion to contraction of the cancellation pulse Pd is 0.1λ to 0.4λ.

[0097] Figure 10 and Figure 11 The simulation results are shown in Example 2 when the meniscus is actuated with a voltage that does not spray. Figure 10 The time variation of the flow velocity is shown when Vc / Vb = 1.4 and when Vc / Vb = 2.0. As a simulation condition, λ = 4 μs is set. Figure 11 The time-varying position of the meniscus is shown when Vc / Vb = 1.4 and when Vc / Vb = 2.0.

[0098] According to this embodiment, it is possible to simultaneously stabilize the ejection of ink droplets and expand the grayscale range. Furthermore, as... Figure 10 , 11 As shown, residual vibration can be suppressed by adjusting the voltage ratio Vc / Vb.

[0099] [Example 3]

[0100] Figure 12 This is the driving waveform of Embodiment 3. The driving waveform of Embodiment 3 is a variation of the driving waveform of Embodiment 2, and has a step waveform. The step waveform adjusts the timing of a portion of the pulses in the start cancellation pulse section, and sets the expansion of the cancellation pulse Pd to two stages.

[0101] The cancellation waveform section of Embodiment 3 has a cancellation pulse Pd in ​​the contraction element of the final ejection pulse Pc. The cancellation pulse Pd sequentially includes: an expansion element, which includes a step waveform that causes the pressure chamber 1131, which has contracted by a second intermediate voltage Vc that is set to be higher than the first intermediate voltage Vb, to expand again and drop to the first intermediate voltage Vb, and then become an expansion voltage Va that is lower than the first intermediate voltage Vb; and a contraction element that causes the pressure chamber 1131, which has expanded by the expansion element of the cancellation pulse section, to contract again and return to the first intermediate voltage Vb.

[0102] In the cancellation waveform section, the period from the contraction element of the final ejection pulse Pc to the expansion element of the cancellation pulse Pd is λ, and the period from expansion to contraction of the cancellation pulse Pd is 0.1λ to 0.4λ. The other waveforms are the same as in Example 2.

[0103] In this embodiment, it is also possible to stabilize the ejection of ink droplets and expand the range of grayscale.

[0104] Figure 13 and Figure 14 The simulation results are shown in Example 3 when the meniscus is actuated with a voltage that does not spray. Figure 13 The time-varying flow rates are shown when Vc / Vb = 1.4 and when Vc / Vb = 2.0. As a simulation condition, λ = 4 μs is used. Figure 14 The diagram shows the time-varying position of the meniscus when Vc / Vb = 1.4 and when Vc / Vb = 2.0. Figure 13 , 14 As shown, residual vibration can be suppressed by adjusting the voltage ratio Vc / Vb.

[0105] [Example 4]

[0106] Figure 15 This is the driving waveform of Example 4. The driving waveform of Example 4 is a variation of the driving waveform of Example 2, and is an example after switching the voltage of the contraction elements of Pa and Pb.

[0107] The driving waveform in Example 4 is a three-droplet waveform, with three ejection pulses, each expanding and contracting, arranged with a fixed period λ. The three ejection pulses Pa, Pb, and Pc each have: an expansion element that expands the pressure chamber 1131 and introduces liquid into it; and a contraction element that contracts the pressure chamber 1131 and ejects the liquid. In this example, the first ejection pulse Pa has an expansion element that lowers the voltage from the first intermediate voltage Vb to the expansion voltage Va, and a contraction element that raises the voltage back to the first intermediate voltage Vb. The second ejection pulse Pb lowers the voltage back to the expansion voltage Va, then raises the voltage to a second intermediate voltage Vc, which is higher than the first intermediate voltage Vb. Then, in the third ejection pulse Pc, the voltage lowers to the expansion voltage Va and then rises again to the second intermediate voltage Vc. Other waveforms are the same as in Example 2. In this example, it is also possible to balance the stabilization of ink droplet ejection with an expanded grayscale range.

[0108] [Example 5]

[0109] Figure 16 This is the driving waveform of Embodiment 5. The driving waveform of Embodiment 5 is a variation of the driving waveform of Embodiment 2, and is an example in which Pa and Pb have a stepped waveform portion including an element that maintains the intermediate voltage for a fixed time, and the voltage is applied in stages. In this embodiment, the contraction element of the first ejection pulse Pa has a stepped waveform that stagesly increases the voltage, and the expansion element of the second ejection pulse Pb has a stepped waveform that stagesly decreases the voltage.

[0110] Example 5 shows a three-drop waveform, with three ejection pulses, each expanding and contracting, arranged with a fixed period λ. The three ejection pulses Pa, Pb, and Pc each have an expansion element that expands the pressure chamber 1131 to introduce liquid into it, and a contraction element that contracts the pressure chamber 1131 to eject the liquid. In this example, the first ejection pulse Pa has: an expansion element that causes the voltage to drop from a first intermediate voltage Vb to an expansion voltage Va; and a contraction element that causes the voltage to rise in stages to a second intermediate voltage Vc, which is greater than the first intermediate voltage Vb. For example, the second intermediate voltage Vc is greater than the first intermediate voltage Vb. The first ejection pulse Pa has a step waveform that causes the voltage to rise from the expansion voltage Va to the first intermediate voltage Vb, maintains the first intermediate voltage Vb for a fixed time, and then rises in stages to the second intermediate voltage Vc. In this waveform, the first ejected pulse Pa causes the voltage to drop from the first intermediate voltage Vb to the expansion voltage Va (=0V), then rises the voltage back to the first intermediate voltage Vb, and further rises the voltage to a second intermediate voltage Vc, which is greater than the first intermediate voltage Vb. The second ejected pulse Pb includes: an expansion element that causes the voltage to drop from the second intermediate voltage Vc to the first intermediate voltage Vb, maintains the first intermediate voltage Vb for a fixed time, and then causes the voltage to drop back to the expansion voltage Va; and a contraction element that causes the voltage to rise back to the first intermediate voltage Vb. Furthermore, the third ejected pulse Pc includes: an expansion element that causes the voltage to drop from the first intermediate voltage Vb to the expansion voltage Va; and a contraction element that causes the voltage to rise back to the first intermediate voltage Vb.

[0111] In addition, such as Figure 16 As shown, the cancellation waveform section of this embodiment has a stepped waveform that maintains the first intermediate voltage Vb for a fixed time. Specifically, the cancellation waveform section includes, in sequence, the contraction element of the final ejection pulse Pc: a contraction element, which, after rising to the first intermediate voltage Vb, maintains the first intermediate voltage Vb for a fixed time and then causes the voltage to rise to the second intermediate voltage Vc in stages; an expansion element, which causes the pressure chamber 1131, which has contracted due to the second intermediate voltage Vc, to expand again, and after maintaining the state of the first intermediate voltage Vb for a fixed time, it is set to change to the expanded voltage Va in stages; and a contraction element, which causes the expanded pressure chamber 1131 to contract again and return to the first intermediate voltage Vb.

[0112] The other waveforms are the same as in Example 2. In this example, it is also possible to balance the stabilization of ink droplet ejection with an expanded grayscale range.

[0113] [Example 6]

[0114] Figure 17This is the driving waveform of Embodiment 6. The driving waveform of Embodiment 6 is a variation of the driving waveform of Embodiment 2, and is an example in which an auxiliary waveform section is provided before the ejection waveform section. That is, in this embodiment, the auxiliary waveform section has an auxiliary pulse Pe before the expansion element of the first ejection pulse Pa, and the auxiliary pulse Pe has a contraction element that causes the voltage to rise from the first intermediate voltage Vb to the second intermediate voltage Vc. Regarding other waveforms, it is the same as in Embodiment 2. The first ink droplet can be accelerated by the auxiliary pulse.

[0115] In the liquid nozzle 1 and liquid ejection device configured in this way, grayscale can be achieved by increasing the intermediate voltage of the contraction element in the ejection pulse. That is, for example, if the voltage of the ejection pulse from the 1st droplet to the (n-1)th droplet is set to be the same, the size of the ejected ink droplets is limited. Therefore, for example, when printing multi-grayscale images by varying the size of the print dots, the range of increase or decrease in the size of the ink droplets is narrow, and the grayscale representation is limited. In contrast, according to this embodiment, by controlling the intermediate potential in two or more stages, the grayscale representation range can be expanded. In addition, according to this embodiment, by setting the period of one natural vibration in the state of ink filling the pressure chamber to λ and having n-1 ejection pulses at intervals of 0.8 to 1.2λ, ejection stability can be ensured. Therefore, both the expansion of the grayscale representation range and ejection stability can be achieved.

[0116] It should be noted that the embodiments of the present invention are not limited to the above-described configuration.

[0117] For example, although it is set to three drops, it is not limited to this and can also be four or more. Moreover, in this case, the voltage of the contraction element is not limited to two stages and can also be set to three stages or more.

[0118] For example, the configuration of liquid nozzle 1 is not limited to the examples described above, and can also be used for other types of nozzles.

[0119] According to at least one embodiment described above, it is possible to simultaneously stabilize the ejection of ink droplets and expand the range of grayscale.

[0120] While several embodiments of the invention have been described, these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and likewise within the scope of the invention as set forth in the claims and its equivalents.

[0121] Explanation of reference numerals in the attached figures

[0122] 1: Liquid printhead (inkjet head); 2: Liquid ejection device (inkjet recording device); 11: Head body; 12: Manifold unit; 13: Drive circuit; 14: Cover; 111: Substrate; 112: Frame; 113: Actuator; 114: Nozzle plate; 116: Common liquid chamber; 118: Independent electrode (electrode section); 121: Manifold; 123: Ink supply pipe; 124: Ink discharge pipe; 125: Temperature regulating water supply pipe; 131: Wiring film; 133: Printed wiring substrate; 141: Outer body; 1111: Supply port; 1112: Discharge port; 1131: Pressure chamber; 1133: Piezoelectric column (drive element); 1134: Inclined surface; 1141: Nozzle; 1142: Nozzle array; 161: First common liquid chamber; 1162: Second common liquid chamber; 2001: Conveying path; 2111: Housing; 2112: Media supply unit; 2113: Image forming unit; 2114: Media discharge unit; 2115: Conveying device; 2117: Maintenance device; 2118: Control unit; 2120: Support unit; 2130: Head unit; 2132: Supply tank; 2134: Pump; 2135: Connecting flow path; 21121: Paper feed box; 21141: Paper discharge tray; 21201: Conveyor belt; 21202: Support plate; 21203: Belt roller; 21211~21218: Guide plate pair; 21221~21228: Conveying roller; 132: Driver IC; P: Paper.

Claims

1. A liquid nozzle, comprising: The pressure chamber is connected to the nozzle from which the liquid is ejected; An actuator, in response to an electrical signal, causes a change in the volume of the pressure chamber; and The drive circuit generates an electrical signal to drive the actuator. The driving waveform output by the driving circuit has the following characteristics: In the case of printing with three or more gray levels by ejecting n ink droplets, the period of a single inherent vibration in the state where the pressure chamber is filled with ink is set to λ, and n ejection pulses are performed at intervals of 0.8 to 1.2λ; and The waveform section is removed and then continues after the ejected waveform section. The ejection waveform includes the following ejection pulses: An ejection pulse having an element that reduces the voltage to a first voltage and then increases it to a second voltage higher than the first voltage; and The ejection pulse has an element that reduces the voltage to the first voltage and then increases it to a third voltage higher than the second voltage. The cancellation waveform section includes a cancellation pulse, which has the following elements: raising the voltage to the third voltage and then lowering it to the second voltage. The final ejection pulse in the ejection waveform section is an ejection pulse that has the element of reducing the voltage to the first voltage and then rising to the third voltage, which is higher than the second voltage. The waveform of the cancellation pulse is as follows: starting from the state where the final ejection pulse changes to the third voltage, it drops to the first voltage, and then returns to the second voltage. in, n is an integer greater than or equal to 3.

2. The liquid nozzle according to claim 1, wherein, The ejected waveform section or the canceled waveform section has: a stepped waveform section that maintains the second voltage for a fixed time and causes the voltage to change in stages.

3. The liquid nozzle according to claim 1, wherein, Before the initial ejection pulse of the ejection waveform section, the driving waveform includes an auxiliary waveform section that raises the voltage to a voltage higher than the second voltage, and then returns to the second voltage.

4. The liquid nozzle according to claim 1, wherein, The actuator has an inclined surface on its side portion in the short side direction.

5. The liquid nozzle according to claim 1, wherein, The liquid nozzle comprises a head body, a manifold unit, a drive circuit, and a cap.

6. The liquid nozzle according to claim 5, wherein, The head body comprises: a substrate, which is formed into a rectangular plate shape from a ceramic material.

7. The liquid nozzle according to claim 5, wherein, The manifold unit includes a temperature-regulated water supply pipe and a temperature-regulated water discharge pipe.

8. The liquid nozzle according to claim 5, wherein, The cover has an outer profile and a cover plate.

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