Liquid ejecting method, liquid ejecting head, and liquid ejecting apparatus

Provided is a liquid ejecting method, including: ejecting a liquid from a liquid ejecting head, wherein the viscosity of the liquid is in a range from 6 mPa·s to 20 mPa·s, wherein the liquid ejecting head includes: nozzles which eject the liquid; a pressure chamber which applies a pressure variation to the liquid in order to eject the liquid from the nozzles; and a supply unit which communicates with the pressure chamber and supplies the liquid to the pressure chamber, and wherein the opening area of the nozzles on the side in which the liquid is ejected is 1/10 or less of the opening area of the opening of the supply unit on the pressure chamber side.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejecting method, a liquid ejecting head, and a liquid ejecting apparatus.

2. Related Art

A liquid ejecting apparatus such as an ink jet printer includes a liquid ejecting head including nozzles for ejecting a liquid, a pressure chamber for providing a pressure variation to the liquid such that the liquid is ejected from the nozzles, and a supply unit for supplying the liquid stored in a reservoir to the pressure chamber. In this liquid ejecting head, the size of a liquid channel in the head is determined on the basis of a liquid having viscosity close to that of water (See JP-A-2005-34998).

Recently, a liquid having viscosity higher than that of a general ink attempts to be ejected using an ink jet technology. In addition, if the liquid having the high viscosity is ejected by a head having the existing shape, the ejection of the liquid becomes unstable. For example, flight deflection of the liquid occurs or shortage of the ejection amount of the liquid occurs.

SUMMARY

An advantage of some aspects of the invention is that the ejection of a liquid having viscosity higher than that of a general ink becomes stable.

According to an aspect of the invention, there is provided a liquid ejecting method, including ejecting a liquid from a liquid ejecting head, wherein the viscosity of the liquid is in a range from 6 mPa·s to 20 mPa·s, wherein the liquid ejecting head includes: nozzles which eject the liquid; a pressure chamber which applies a pressure variation to the liquid in order to eject the liquid from the nozzles; and a supply unit which communicates with the pressure chamber and supplies the liquid to the pressure chamber, and wherein the opening area of the nozzles on the side in which the liquid is ejected is 1/10 or less of the opening area of the opening of the supply unit on the pressure chamber side.

The other features of the invention will become apparent from the description of the present specification and the accompanying drawings.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least the following will become apparent from the specification and the accompanying drawings.

That is, it will become apparent that, as a liquid ejecting method, a liquid ejecting method, including ejecting a liquid from a liquid ejecting head, wherein the viscosity of the liquid is in a range from 6 mPa·s to 20 mPa·s, wherein the liquid ejecting head includes: nozzles which eject the liquid; a pressure chamber which applies a pressure variation to the liquid in order to eject the liquid from the nozzles; and a supply unit which communicates with the pressure chamber and supplies the liquid to the pressure chamber, and wherein the opening area of the nozzles on the side in which the liquid is ejected is 1/10 or less of the opening area of the opening of the supply unit on the pressure chamber side can be realized.

According to this liquid ejecting method, it is possible to optimize the amount of liquid ejected from the nozzles and the amount of liquid supplied to the pressure chamber. Accordingly, it is possible to improve the shortage of the supply of the liquid to the pressure chamber and to stabilize the ejection of the liquid.

In the liquid ejecting method, the opening area of the nozzles on the side in which the liquid is ejected may be 1/20 or more of the opening area of the opening of the supply unit.

According to this liquid ejecting method, it is possible to stabilize the ejection of the liquid.

In the liquid ejecting method, the length of the nozzles may be in a range from 40 μm to 100 μm.

According to this liquid ejecting method, it is possible to stabilize the ejection of the liquid.

In the liquid ejecting method, the opening of the supply unit may have a rectangular shape, the length of one side of the opening may be in a range from 30 μm to 500 μm, and the length of the other side of the opening may be in a range from 20 μm to 300 μm.

According to this liquid ejecting method, it is possible to supply the liquid having viscosity in a range from 6 mPa·s to 20 mPa·s to the pressure chamber with certainty.

In the liquid ejecting method, the outer edge of the opening of the supply unit may be smaller than that of the surface partitioning the pressure chamber and communicating with the supply unit.

According to this liquid ejecting method, it is possible to attenuate the pressure vibration applied to the liquid in the supply unit. Accordingly, it is possible to increase the ejection frequency of the liquid.

In the liquid ejecting method, the inertance of the nozzles may be smaller than that of the supply unit.

According to this liquid ejecting method, it is possible to efficiently eject the liquid by the pressure vibration applied to the liquid.

In the liquid ejecting method, the pressure chamber may have a partitioning portion which partitions a portion of the pressure chamber and applies the pressure variation to the liquid by deformation.

According to this liquid ejecting method, it is possible to efficiently apply the pressure variation to the liquid contained in the pressure chamber.

In the liquid ejecting method, the liquid ejecting head may include an element which deforms the partitioning portion by the degree according to a potential variation pattern of an applied ejection pulse.

According to this liquid ejecting method, it is possible to control the pressure of the liquid contained in the pressure chamber with high accuracy.

In addition, it will become apparent that the following liquid ejecting head can be realized.

That is, it will become apparent that a liquid ejecting head including: nozzles which eject the liquid; a pressure chamber which applies a pressure variation to the liquid in order to eject the liquid from the nozzles; and a supply unit which communicates with the pressure chamber and supplies the liquid to the pressure chamber, wherein the opening area of the nozzles on the side in which the liquid is ejected is 1/10 or less of the opening area of the opening of the supply unit on the pressure chamber side can be realized.

In addition, it will become apparent that the following liquid ejecting apparatus can be realized.

That is, it will become apparent that a liquid ejecting apparatus including: an ejection pulse generation unit which generates an ejection pulse; and a liquid ejection head which ejects a liquid from nozzles and includes: a pressure chamber which deforms a partitioning portion and applies a pressure variation to the liquid in order to eject the liquid from the nozzles; an element which deforms the partitioning portion by the degree according to a potential variation pattern of an applied ejection pulse; and a supply unit which communicates with the pressure chamber and supplies the liquid to the pressure chamber, wherein the opening area of the nozzles on the side in which the liquid is ejected is 1/10 or less of the opening area of the opening of the supply unit on the pressure chamber side can be realized.

First Embodiment

Printing System

The printing system shown inFIG. 1includes a printer1and a computer CP. The printer1corresponds to a liquid ejecting apparatus, which ejects an ink, which is a liquid, onto a medium such as paper, cloth, or a film. The medium is an object onto which the liquid is ejected. The computer CP is connected to and is communicated with the printer1. In order to print an image by the printer1, the computer CP transmits printing data according to the image to the printer1.

Outline of Printer1

The printer1includes a sheet transportation mechanism10, a carriage movement mechanism20, a driving signal generation circuit30, a head unit40, a detector group50and a printer controller60.

The sheet transportation mechanism10transports a sheet in a transportation direction. The carriage movement mechanism20moves a carriage, in which the head unit40is mounted, in a predetermined movement direction (for example, a paper width direction). The driving signal generation circuit30generates a driving signal COM. This driving signal COM is applied to a head HD (piezo-element433, seeFIG. 2A) at the time of printing of the sheet, and is a series of signals including ejection pulses PS like an example ofFIG. 4. The ejection pulses PS allow the piezo-element433to perform a predetermined operation in order to eject a droplet-shaped ink from the head HD. Since the driving signal COM includes the ejection pulses PS, the driving signal generation circuit30corresponds to an ejection pulse generation unit. In addition, the configuration of the driving signal generation circuit30or the ejection pulses PS will be described later. The head unit40includes the head HD and a head controller HC. The head HD is a liquid ejection head, which ejects an ink onto a sheet. The head controller HC controls the head HD on the basis of a head control signal from the printer controller60. In addition, the head HD will be described later. The detector group50includes a plurality of detectors for monitoring the status of the printer1. The detected result of the detectors is output to the printer controller60. The printer controller60performs the whole control of the printer1. This printer controller60will be described later.

Main Portions of Printer1

Head HD

As shown inFIG. 2A, the head HD includes a case41, a channel unit42, and a piezo-element unit43. The case41is a member in which a storage space411for storing and fixing the piezo-element unit43is provided. The case41is formed of, for example, resin. In addition, the channel unit42is adhered to a front end surface of the case41.

The channel unit42includes a channel forming substrate421, a nozzle plate422and a vibration plate423. In addition, the nozzle plate422is adhered to one surface of the channel forming substrate421and the vibration plate423is adhered to the other surface of the channel forming substrate. A groove which becomes a pressure chamber424, a groove which becomes an ink supply path425and an opening which becomes a common ink chamber426are formed in the channel forming substrate421. This channel forming substrate421is formed of, for example, a silicon substrate. The pressure chamber424is formed as a chamber which is elongated in a direction perpendicular to the arrangement direction of nozzles427. The ink supply path425allows the pressure chamber424to communicate with the common ink chamber426. This ink supply path425supplies an ink (a liquid) stored in the common ink chamber426to the pressure chamber424. Accordingly, the ink supply path425is a supply unit for supplying the liquid to the pressure chamber424. The common ink chamber426is a portion for temporarily storing the ink supplied from an ink cartridge (not shown) and corresponds to a common liquid storage chamber.

In the nozzle plate422, the plurality of nozzles427is provided at a predetermined interval in the predetermined arrangement direction. The ink is ejected from the head HD via the nozzles427. This nozzle plate422is formed of, for example, a stainless plate or a silicon substrate.

The vibration plate423has, for example, a double structure in which an elastic film429made of resin is laminated on a support plate428made of stainless. In the portion of the vibration plate423corresponding to the pressure chamber424, the support plate428is etched in an annular shape. An island portion428ais formed in the annular portion. The island portion428aand the elastic film429alocated around the island portion configure a diaphragm portion423a. This diaphragm portion423ais deformed by the piezo-element433of the piezo-element unit43and varies the volume of the pressure chamber424. That is, the diaphragm portion423apartitions a portion of the pressure chamber424and corresponds to a partitioning portion for applying a pressure variation to the ink (liquid) in the pressure chamber424by the deformation.

The piezo-element unit43includes a piezo-element group431and a fixed plate432. The piezo-element group431has a comb tooth-like shape. One comb tooth is the piezo-element433. The front end surface of the piezo-element433is adhered to the island portion428acorresponding thereto. The fixed plate432supports the piezo-element group431and becomes a mounting unit of the case41. This fixed plate432is formed of, for example, a stainless plate and is adhered to the inner wall of the storage space411.

The piezo-element433is an electromechanical conversion element and corresponds to an element which performs an operation (deformation operation) for applying a pressure variation to the liquid in the pressure chamber424. The piezo-element433shown inFIG. 2Aexpands and contracts in an element's longitudinal direction perpendicular to a lamination direction by applying a potential difference between neighboring electrodes. That is, the electrodes include a common electrode434having a predetermined potential and a driving electrode435having a potential according to the driving signal COM (ejection pulses PS). In addition, a piezoelectric body436sandwiched between the electrodes434and435is deformed by the degree according to the potential difference between the common electrode434and the driving electrode435. The piezo-element433expands and contracts in the element's longitudinal direction by the deformation of the piezoelectric body436. In the present embodiment, the common electrode434has a ground potential or a bias potential higher than the ground potential by a predetermined potential. The piezo-element433contracts as the potential of the driving electrode435becomes higher than that of the common electrode434. In contrast, the piezo-element expands as the potential of the driving electrode435becomes close to that of the common electrode434or becomes lower than that of the common electrode434.

As described above, the piezo-element unit43is mounted in the case41via the fixed plate432. If the piezo-element433contracts, the diaphragm portion423ais pulled to be separated from the pressure chamber424. Accordingly, the pressure chamber424expands. In contrast, if the piezo-element433expands, the diaphragm portion423ais pulled to the side of the pressure chamber424. Accordingly, the pressure chamber424contracts. The pressure variation occurs in the ink contained in the pressure chamber424due to the expansion or the contraction of the pressure chamber424. That is, the ink contained in the pressure chamber424is pressurized by the contraction of the pressure chamber424and the ink contained in the pressure chamber424is depressurized by the expansion of the pressure chamber424. Since the expansion and the contraction of the piezo-element433are determined by the potential of the driving electrode435, the volume of the pressure chamber424is also determined by the potential of the driving electrode435. Accordingly, the piezo-element433is an element for deforming the diaphragm portion423a(partitioning portion) by the degree according to the potential variation pattern of the applied ejection pulses PS. In addition, the pressurized degree or the depressurized degree of the ink contained in the pressure chamber424may be determined by a potential variation of the driving electrode435per unit time.

Ink Channel

In the head HD, a plurality of ink channels (corresponding to a liquid channel in which the liquid is filled) which extends from the common ink chamber426to the nozzles427is formed according to the number of nozzles427. In the ink channels, the thin nozzles427and the ink supply path425communicate with the thick pressure chamber424. Accordingly, if the characteristic of the ink, such as the flow of the ink, is analyzed, the viewpoint of a Helmholtz resonator is applied.FIG. 2Bis a schematic view explaining the structure of the head HD based on this viewpoint.

In the general head HD, the length L424of the pressure chamber424is determined in a range from 200 μm to 2000 μm. The width W424of the pressure chamber424is determined in a range from 20 μm to 300 μm, and the height H424of the pressure chamber424is determined in a range from 30 μm to 500 μm. In addition, the length L425of the ink supply path425is determined in a range from 50 μm to 2000 μm. The width W425of the ink supply path425is determined in a range from 20 μm to 300 μm, and the height H425of the ink supply path425is determined in a range from 30 μm to 500 μm. In addition, the diameter φ427of the nozzles427is determined in a range from 10 μm to 40 μm and the length L427of the nozzles427is determined in a range from 40 μm to 100 μm.

The width W425or the height H425of the ink supply path425is set to equal to or less than the width W424or the height H424of the pressure chamber424. If one of the width W425or the height H425of the ink supply path425is aligned with one of the width W424or the height H424of the pressure chamber424, the other of the width W425or the height H425of the ink supply path425is set to the other of the width W424or the height H424of the pressure chamber424.

FIG. 2Bis a schematic view explaining the ink channel. Accordingly, the ink channel has a shape different from an actual shape. However, the ink supply path425is actually configured as a rectangular parallelepiped space having a rectangular opening. Accordingly, the size of the opening of the ink supply path425is set to be smaller than that of the outer edge of the surface communicating with the ink supply path425as the surface partitioning the pressure chamber424.

In such an ink channel, by applying the pressure variation to the ink contained in the pressure chamber424, the ink is ejected from the nozzles427. At this time, the pressure chamber424, the ink supply path425and the nozzles427function as the Helmholtz resonator. Accordingly, if the pressure is applied to the ink contained in the pressure chamber424, the level of this pressure varies in an inherent period called a Helmholtz period. That is, a pressure vibration occurs in the ink.

The Helmholtz period (inherent vibration period of the ink) Tc may be expressed by following Equation (1).
Tc=1/f
f=½π√[(Mn+Ms)/(Mn×Ms×(Cc+ci))]  (1)

In Equation (1), Mn denotes the inertance of the nozzles427(the mass of the ink per unit cross-sectional area, which will be described later), Ms denotes the inertance of the ink supply path425, the Cc denotes the compliance (a volume variation per unit pressure and a degree of softness) of the pressure chamber424, and Ci denotes the compliance of the ink (Ci=volume V/[density ρ×sound velocity c2]).

The amplitude of the pressure vibration is gradually decreased as the ink flows in the ink channel. For example, the pressure vibration attenuates due to the loss of the nozzles427or the ink supply path425and the loss of the wall portion partitioning the pressure chamber424.

In the general head HD, the Helmholtz period of the pressure chamber424is determined in a range from 5 μs to 10 μs. For example, in the ink channel ofFIG. 2B, if the width W424of the pressure chamber424is 100 μm, the height H424thereof is 70 μm, and the length L424thereof is 1000 μm, the width W425of the ink supply path425is 50 μm, the height H425thereof is 70 μm, and the length L425thereof is 500 μm, and the diameter Φ427of the nozzles427is 30 μm and the length L427thereof is 100 μm, the Helmholtz period becomes about 8 μs. In addition, the Helmholtz period varies according to the thickness of the wall portion partitioning the neighboring pressure chambers424, the thickness or the compliance of the elastic film429, or the material of the channel forming substrate421or the nozzle plate422.

The printer controller60performs the whole control of the printer1. For example, the printer controller controls control objects on the basis of the detected result of the detectors or the printing data received from the computer CP and prints the image on the sheet. As shown inFIG. 1, the printer controller60includes an interface61, a CPU62and a memory63. The interface61transmits or receives data to or from the computer CP. The CPU62performs the whole control of the printer1. The memory63ensures an area for storing a computer program, a working area or the like. The CPU62controls the control objects according to the computer program stored in the memory63. For example, the CPU62controls the sheet transportation mechanism10or the carriage movement mechanism20. In addition, the CPU62transmits a head control signal for controlling the operation of the head HD to the head controller HC or transmits a control signal for generating the driving signal COM to the driving signal generation circuit30.

The control signal for generating the driving signal COM is also called DAC data and is, for example, plural-bit digital data. This DAC data decides the variation pattern of the potential of the generated driving signal COM. Accordingly, this DAC data is called data representing the potential of the ejection pulses PS or the driving signal COM. This DAC data is stored in a predetermined area of the memory63, is read at the time of the generation of the driving signal COM, and is output to the driving signal generation circuit30.

Driving Signal Generation Circuit30

The driving signal generation circuit30functions as an ejection pulse generation unit and generates the driving signal COM having the ejection pulses PS on the basis of the DAC data. As shown inFIG. 3, the driving signal generation circuit30includes a DAC circuit31, a voltage amplification circuit32, and a current amplification circuit33. The DAC circuit31converts digital DAC data into an analog signal. The voltage amplification circuit32amplifies the voltage of the analog signal converted by the DAC circuit31to a level for driving the piezo-element433. In this printer1, while the analog signal output from the DAC circuit31has 3.3 V at the maximum, the analog signal (for convenience, also called a waveform signal) after the amplification output from the voltage amplification circuit32is 42 V at the maximum. The current amplification circuit33amplifies the current with respect to the waveform signal from the voltage amplification circuit32and outputs the driving signal COM. This current amplification circuit33is, for example, composed of a pair of transistors push-pull connected to each other.

Head Controller HC

The head controller HC selects a necessary portion of the driving signal COM generated by the driving signal generation circuit30on the basis of the head control signal and applies the necessary portion to the piezo-element433. Accordingly, as shown inFIG. 3, the head controller HC includes a plurality of switches44respectively provided in the piezo-elements433midway the supply line of the driving signal COM. In addition, the head controller HC generates a switch control signal from the head control signal. By controlling the switches44by the switch control signal, the necessary portion (for example, the ejection pulses PS) of the driving signal COM is applied to the piezo-element433. At this time, the ejection of the ink from the nozzles427can be controlled by the selection method of the necessary portion.

Driving Signal COM

Next, the driving signal COM generated by the driving signal generation circuit30will be described. As shown inFIG. 4, the plurality of ejection pulses PS which is repeatedly generated is included in the driving signal COM. Such ejection pulses PS have the same waveform, that is, have the same potential variation pattern. As described above, this driving signal COM is applied to the driving electrode435of the piezo-element433. Accordingly, a potential difference according to the potential variation pattern occurs between the driving electrode and the common electrode434having a fixed potential. As a result, each of the piezo-element433expands and contracts according to the potential variation pattern and the volume of the pressure chamber424varies.

The potential of each ejection pulse PS shown rises from a medium potential VB as a reference potential to a highest potential VH and then falls to a lowest potential VL. Then, the potential of each ejection pulse rises to the intermediate potential VB. As described above, the piezo-element433contracts as the potential of the driving electrode435is higher than that of the common electrode434, and the volume of the pressure chamber424is increased.

Accordingly, if the ejection pulses PS are applied to the piezo-element433, the pressure chamber424expands from a reference volume corresponding to the intermediate potential VB to a maximum volume corresponding to a highest potential VH. Thereafter, the pressure chamber424contracts to a minimum volume corresponding to the lowest potential VL and expands to the reference volume. When the pressure chamber contracts from the maximum volume to the minimum volume, the ink contained in the pressure chamber424is pressurized and ink droplets are ejected from the nozzles427. Accordingly, the portion of each ejection pulse PS which varies from the highest potential VH to the lowest potential VL corresponds to the ejection portion for ejecting the ink.

The ejection frequency of the ink droplet is determined by the interval between the ejection portions which are generated in tandem. For example, in the example ofFIG. 4, the ink droplet is ejected in every period Ta in the driving signal COM denoted by a solid line and the ink droplet is ejected in every period Tb in the driving signal COM denoted by a dashed-dotted line. Accordingly, the ejection frequency according to the driving signal COM denoted by the solid line is higher than the ejection frequency according to the driving signal COM denoted by the dashed-dotted line.

Ejecting Operation

Outline

In this type of printer, there is a need for stabilizing the ejection of the ink. For example, when the ink droplet is ejected with a low frequency and when the ink droplet is ejected with a high frequency, there is a need for equalizing the amount of ink droplet, a flight direction or a flying speed. However, when an ink having viscosity which is sufficiently higher than the viscosity (about 1 mPa·s) of a general ink and, more particularly, an ink having viscosity of 6 to 20 mPa·s (for convenience, also called a high-viscosity ink) is ejected by the existing head, the ejection of the ink becomes unstable.FIG. 5Ais a view showing the case where an ink having high viscosity is ejected in a stable state.FIG. 5Bis a view showing the case where the ink having high viscosity is ejected in an unstable state. When these drawings are compared, an ink droplet having an insufficient flying speed or an ink droplet, in which ejection deflection occurs, exists in the unstable state.

Various factors for making the ejection of the ink unstable may be considered, but, among them, the shortage of the supply of the ink is considered as one factor. The high-viscosity ink is hard to pass through the ink supply path425compared with a general ink. Accordingly, when the supply of the ink to the pressure chamber424is insufficient and the operation for ejecting the ink is performed in a state in which the ink is insufficient, the ejection of the inks becomes unstable.

In the light of these circumstances, in the head HD of the present embodiment, the opening area of the nozzles427is set on the basis of the opening area of the ink supply path425. That is, as shown inFIG. 2B, the opening area Snzl of the nozzles427on the ejection side is 1/10 or less of the opening area Ssup of the ink supply path425on the side of the pressure chamber424. Accordingly, the supply amount of the ink to the pressure chamber424is ensured while the ejection amount of the ink droplets from the nozzles427is restricted. As a result, the shortage of the supply of the ink to the pressure chamber424can be solved and the ejection of the ink can be stabilized. Hereinafter, this will be described in detail.

Ejection Pulse PS

First, each of the ejection pulses PS used in evaluation will be described.FIG. 6is a view explaining an ejection pulse PS1. In addition, inFIG. 6, a vertical axis denotes the potential of the driving signal, and an intermediate potential VB as a reference potential is 0 V. In addition, a horizontal axis denotes a time.

The ejection pulse PS1shown inFIG. 6has a plurality of portions denoted by reference numerals P1to P5. That is, the ejection pulse PS1includes a first depressurization portion P1, a first potential holding portion P2, a pressurization portion P3, a second potential holding portion P4, and a second depressurization portion P5.

The first depressurization portion P1is a portion generated from a timing t0to a timing t1a. In this first depressurization portion P1, the potential of the timing t0(corresponds to a start potential) is the intermediate potential VB and the potential of the timing t1a(corresponding to an end potential) is the highest potential VH. Accordingly, if the first depressurization portion P1is applied to the piezo-element433, the pressure chamber424expands from the reference volume to the maximum volume in the generation period of the first depressurization portion P1.

The intermediate potential VB of the ejection pulse PS1is set to a potential higher than the lowest potential VL of the ejection pulse PS1by 30% of a difference (hereinafter, referred to as a driving voltage Vh) from the highest potential VH to the lowest potential VL. In addition, the driving voltage Vh of the ejection pulse PS1is 25 V. Accordingly, the intermediate potential VB is higher than the lowest potential VL by 7.5 V, and the highest potential VH is higher than the intermediate potential VB by 17.5. In addition, the generation period of the first depressurization portion P1is 3.5 μs.

The first potential holding portion P2is a portion generated from the timing t1ato a timing t2a. This first potential holding portion P2is held at the highest potential VH. Accordingly, if the first potential holding portion P2is applied to the piezo-element433, the pressure chamber424holds the maximum volume in the generation period of the first potential holding portion P2. In this ejection pulse PS1, the generation period of the first potential holding portion P2is 2 μs.

The pressurization portion P3is a portion generated from the timing t2ato a timing t3a. In this pressurization portion P3, a start potential is the highest potential VH and an end potential is the lowest potential VL. Accordingly, if the pressurization portion P3is applied to the piezo-element433, the pressure chamber424contracts from the maximum volume to the minimum volume in the generation period of the pressurization portion P3. Since the ink is ejected by the contraction of this pressure chamber424, the pressurization portion P3corresponds to the ejection portion for ejecting the ink droplet. In this ejection pulse PS1, the generation period of the pressurization portion P3is 3 μs.

The second potential holding portion P4is a portion generated from the timing t3ato a timing t4a. This second potential holding portion P4is held at the lowest potential VL. Accordingly, if the second potential holding portion P4is applied to the piezo-element433, the pressure chamber424holds the minimum volume in the generation period of the second potential holding portion P4. In this ejection pulse PS1, the generation period of the second potential holding portion P4is 5 μs.

The second depressurization portion P5is a portion generated from a timing t4ato a timing t5a. In this second depressurization portion P5, a start potential is the lowest potential VL and an end potential is the intermediate potential VB. Accordingly, if the second depressurization portion P5is applied to the piezo-element433, the pressure chamber424expands from the minimum volume to the reference volume in the generation period of the second depressurization portion P5. The second depressurization portion P5allows the piezo-element433to perform an operation for expanding the pressure chamber424in the contraction state to the reference volume after the ejection of the ink droplets. In this ejection pulse PS1, the generation period of the second depressurization portion P5is 3.5 μs.

Ink having Viscosity of 20 mPa·s

FIG. 7is a view explaining the ejection of ink droplets by a head HD in which the opening area Snzl of nozzles427is set to about 1/10 of the opening area Ssup of the ink supply path425. As shown inFIG. 2B, the opening area Snzl is the area of the opening located at the side, in which the ink droplets are ejected, of the nozzles427. The opening area Ssup is the area of the opening of the side, which communicates with the pressure chamber424, of two openings of the ink supply path425.

InFIG. 7, a vertical axis denotes the amount of ink in a meniscus (a free surface of the ink exposed by each of the nozzles427) state and a horizontal axis denotes a time. In the vertical axis, 0 ng denotes the position of the meniscus in a normal state. As a value is increased in a positive side, the meniscus is pushed out in an ejection direction and, as a value is increased in a negative side, the meniscus is drawn into the side of the pressure chamber424.FIG. 7is obtained by a simulation. The other drawings explaining the ejection of the ink droplets are obtained by simulations.

In this head HD, the width W424of the pressure chamber424is 100 μm, the height H424thereof is 70 μm, and the length L424is 1000 μm. The diameter φ427of the nozzles427is 25 μm and the length of the nozzles427is 100 μm. The width W425of the ink supply path425is 100 μm, the height H425thereof is 55 μm, and the length L425thereof is 500 μm. Accordingly, the opening area Snzl of the nozzles427becomes about 500 μm2(more accurately, 491 μm2), and the opening area Ssup of the ink supply path425becomes 5500 μm2. Accordingly, the opening area of the nozzles427is about 1/10 (more accurately 1/11) of the opening area of the ink supply path425.

In the head HD having such an ink channel, when the ejection pulse PS1ofFIG. 6is applied to the piezo-element433, the ink droplets are ejected from the nozzles427. At this time, the meniscus is moved as shown inFIG. 7. First, when the first depressurization portion P1is applied to the piezo-element433, the pressure chamber424expands from a reference volume to a maximum volume. By this expansion, the ink contained in the pressure chamber424is made a negative pressure and the ink is introduced into the side of the pressure chamber424via the ink supply path425. In addition, by making the ink the negative pressure, the meniscus is drawn into the side of the pressure chamber424in the nozzles427.

The movement of the meniscus to the pressure chamber424is continuously performed even after the applying of the first depressurization portion P1is finished. That is, by compliance or the like of the vibration plate423or the wall portion partitioning the pressure chamber424, the meniscus is moved to the side of the pressure chamber424even during the applying of the first potential holding portion P2. Thereafter, the movement direction of the meniscus is inverted in a direction which becomes distant from the pressure chamber424(a timing denoted by a reference numeral A1ofFIG. 7). At this time, since the contraction of the pressure chamber424is applied by the applying of the pressurization portion P3, the movement speed of the meniscus is rapid. The meniscus moved by the applying of the pressurization portion P3has a columnar shape. Until the applying of the second potential holding portion P4to the piezo-element433is finished, a portion of the front end side of the meniscus having the columnar shape is broken and the ink is ejected with a drop shape (a timing denoted by a reference numeral B1ofFIG. 7).

By reaction to the ejection, the meniscus is returned to the side of the pressure chamber424at a fast speed. At this time, the second depressurization portion P5is applied to the piezo-element433. By the applying of the second depressurization portion P5, the pressure chamber424expands. By this expansion, the ink contained in the pressure chamber424is made a negative pressure and the ink is introduced into the side of the pressure chamber424via the ink supply path425.

After the second depressurization portion P5is applied, the meniscus gradually becomes close to the position of the normal state (ink amount of 0 ng) while the movement direction thereof is switched to the ejection side and the side of the pressure chamber424(for example, timings denoted by reference numerals C1and D1ofFIG. 7). The reason why the meniscus becomes close to the position of the normal state is because the ink contained in the pressure chamber424is increased. Accordingly, while the meniscus becomes close to the position of the normal state, the ink is supplied from the ink supply path425to the pressure chamber424. The returning of the meniscus to the position of the normal state indicates that a sufficient amount of ink is supplied into the pressure chamber424. Accordingly, when the ejection pulse PS1is applied to the piezo-element433after this time point, it is possible to prevent an ink ejection failure due to the shortage of the supply of the ink. In the example ofFIG. 7, the meniscus is substantially returned to the position of the normal state at a time point when 100 μs is elapsed from the start of the applying of the first depressurization portion P1to the piezo-element433.

In the present embodiment, the returning of the meniscus to the position of the normal state at the time point when 100 μs is elapsed from the start of the applying of the first depressurization portion P1becomes a determination reference for performing the stable ejection even in a high frequency of 40 kHz or more. If only a time of 100 μs is considered, an ejection frequency becomes about 10 kHz as a maximum. However, if the ejection frequency is increased, since the ink droplets are sequentially ejected, the flow of the ink from the side of the common ink chamber426to the side of the nozzles427occurs in the ink channels (a series of channels from the common ink chamber426to the nozzles427). This flow of the ink is accelerated as the ejection frequency is increased. Since the ink is supplied to the pressure chamber424by this flow, the determination reference is set.

As one of reasons why the meniscus is rapidly returned to the position of the normal state, there is a ratio of the opening area Snzl of the nozzles427to the opening area Ssup of the ink supply path425. That is, in this head HD, the opening area Snzl of the nozzles427is set to about 1/10 of the opening area Ssup of the ink supply path425. Accordingly, when the pressure of the ink contained in the pressure chamber424is changed, the ease of the flowing of the ink in the nozzles427is made different from that in the ink supply path425. That is, the ink may more easily flow in the ink supply path425than in the nozzles427. In addition, since the opening area Snzl of the nozzles427is sufficiently smaller than the opening area Ssup of the ink supply path425, it is possible to suppress the ejection capability of the ink droplets.

Accordingly, when the ink contained in the pressure chamber424is depressurized, the ink is easily supplied from the ink supply path425to the pressure chamber424and the shortage of the supply of the ink is improved. This can be understood from that the meniscus is largely moved between the timing C1and the timing D1ofFIG. 7. That is, the ink flows from the ink supply path425into the side of the pressure chamber424by the reaction in which the ink is largely depressurized at the timing C1and the meniscus becomes close to the position of the normal state at the timing D1.

FIG. 8is a view explaining the ejection of the ink droplets by a head HD of a comparative example. The head HD of the comparative example is different from the head HD used inFIG. 7in that the opening area Snzl of the nozzles427is set to about 1/6.7 (ratio of 0.15) of the opening area Ssup of the ink supply path425. From the comparison ofFIGS. 8 and 7, it can be seen that the head HD of the comparative example ejects a larger amount of ink. That is, while the amount of ink at a timing B2is 12 ng, the amount of ink at a timing B1is 7 ng. It can be seen that the head HD of the comparative example is larger than the head HD used inFIG. 7in the drawing amount of meniscus. That is, while the amount of ink at a timing C2is −15 ng, the amount of ink at a timing C1is −10.5 ng. This is because the ink more easily flows in the nozzles427in the head HD of the comparative example, compared with the head HD used inFIG. 7. From the sufficiently large drawing amount of meniscus, it can be seen that, even in the head HD of the comparative example, the ink contained in the pressure chamber424is sufficiently depressurized by the applying of the second depressurization portion P5to the piezo-element433.

However, after this depressurization, in the head HD of the comparative example, the returning amount of meniscus is smaller than that of the head HD used inFIG. 7. In detail, while the amount of ink at a timing D2is −6 ng, the amount of ink at a timing D1is −2 ng. As described above, the returning amount of meniscus is associated with the supply amount of ink to the pressure chamber424. That is, as the ink is supplied to the pressure chamber424, the meniscus becomes close to the position of the normal state. Accordingly, in the head HD used inFIG. 7, after the ejection of the ink droplets, a sufficient amount of ink is rapidly supplied to the pressure chamber424via the ink supply path425. In contrast, in the head HD of the comparative example, after the ejection of the ink droplets, the amount of ink supplied to the pressure chamber424is smaller than that of the head HD used inFIG. 7. Accordingly, the time consumed for returning the meniscus to the position of the normal state is increased. This is because, in the head HD of the comparative example, the shortage of the supply of the ink easily occurs compared with the head HD used inFIG. 7.

Relationship with Area of Pressure Chamber424

Next, the relationship between the area Scav of the pressure chamber424and the opening area Ssup of the ink supply path425will be described. As shown inFIG. 2B, the area Scav of the pressure chamber424is the cross-sectional area of the surface crossing the ink flowing direction, that is, the thickness of the pressure chamber424. In the following description, if only the area Scav of the pressure chamber424is described, it indicates the cross-sectional area of the surface crossing the ink flowing direction.

FIG. 9is a view explaining the ejection of ink droplets by a head HD in which the opening area Ssup of the ink supply path425is 0.34 times of the area Scav of the pressure chamber424.FIG. 10is a view explaining the ejection of ink droplets by a head HD in which the opening area of the ink supply path425is 0.32 times of the area of the pressure chamber424. The head HD used inFIG. 9satisfies a condition of Scav<3×Ssup and is the head of the boundary of this condition. In contrast, the head HD used inFIG. 10does not satisfies of Scav<3×Ssup and is the head of the boundary of this condition. In these drawings, the viscosity of the ink to be ejected is 20 mPa·s.

WhenFIGS. 9 and 10are compared, the head HD used inFIG. 9and the head HD used inFIG. 10are hardly different from each other in the movement of the meniscus until the ink droplets are ejected and the ink contained in the pressure chamber424is depressurized. For example, while the amount of ink at a timing B3is 11 ng or less, the amount of ink at a timing B4is 11 ng or more. While the amount of ink at a timing C3is −15 ng or more, the amount of ink at a timing C4is −15 ng or less.

However, these heads HD are different from each other in the method of returning the meniscus after the depressurization of the ink. For example, while the amount of ink at a timing D3is −3 ng, the amount of ink at a timing D4is −4 ng. In addition, while the amount of ink at a timing E3is −1 ng, the amount of ink at a timing E4is −3 ng. In the head HD used inFIG. 9, the time consumed for causing the meniscus to become close to the position of the normal state is shorter than that of the head HD used inFIG. 10. From this characteristic, it can be understood that, in the head HD used inFIG. 9, the supply amount of ink after the ejection of the ink droplets is larger than that of the head HD used inFIG. 10.

Accordingly, by using the head HD satisfying the condition of Scav<3×Ssup, the shortage of the supply of the ink to the pressure chamber424is hard to occur and the ejection stability of the ink having high viscosity can be further improved.

Discussion

From the above-described result, by setting the opening area Snzl of the nozzles427(the opening area of the side in which the ink droplets are ejected) to 1/10 or less of the opening area Ssup of the ink supply path425(the opening area of the side of the pressure chamber424), it is possible to optimize the balance of the amount of ink supplied to the pressure chamber424and the amount of ink ejected from the nozzles427and to improve the shortage of the supply of the ink to the pressure chamber424. As a result, it is possible to suppress the shortage of the supply of the ink even when the ink having high viscosity is used and stabilize the ejection of the ink droplets.

However, as described above, the opening area Snzl or the length L427of the nozzles427and the opening area Ssup or the length L425of the ink supply path425may have various values. By changing these values, it is possible to change the balance of the ease of the flowing of the ink at the side of the nozzles427and the ease of the flowing of the ink at the side of the ink supply path425.

In consideration of the effect in which the shortage of the supply of the ink to the pressure chamber424is suppressed and the ejection is stabilized, if the shortage of the supply of the ink does not occur even although the ink is easiest to flow in the nozzles427and the ink is hardest to flow in the ink supply path425(worst state), the above-described effect can be obtained regardless of the other elements such as the length L427of the nozzles427or the length L425of the ink supply path425.

On the basis of this viewpoint, in the worst state, a simulation was performed using the head HD in which the opening area Snzl of the nozzles427is set to 1/10 of the opening area Ssup of the ink supply path425.FIG. 11is a view explaining the ejection of ink droplets by a head HD in this simulation result, in the worst state.

The head HD used inFIG. 11, the diameter φ427of the nozzles427is 50 μm (opening area Snzl: about 1963 μm2), the length L427of the nozzles427is 40 μm, the width W425of the ink supply path425is 200 μm, the height H425thereof is 100 μm (opening area Ssup: 20000 μm2), and the length L425of the ink supply path425is 2000 μm. In the pressure chamber424, the width W424is 300 μm, the height H424is 100 μm, and the length L424is 800 μm. That is, this head HD, the diameter φ427of the nozzles427is largest, the length L427of the nozzles427is shortest, the length L425of the ink supply path425is longest, and the opening area Snzl of the nozzles427is substantially set to 1/10 of the opening area Ssup of the ink supply path425. The viscosity of the ink to be ejected is 20 mPa·s.

In this head HD, the ejection amount of ink is larger than that of the above-described heads HD. That is, the amount of ink at a timing B5is 30 ng. This is because the diameter φ427of the nozzles427is set to a maximum value which may be used by the general head HD and the length L427of the nozzles427is set to a minimum value which may be used by the general head HD.

At a timing D5or a timing E5after the ejection of the ink droplets, the amount of ink is about −11 ng, but, thereafter, the meniscus becomes to the position of the normal state and substantially returns to the position of the normal state at a timing after 75 μs is elapsed from the start of the applying of the first depressurization portion P1. From this, it can be seen that, after the ejection of the ink droplets, the ink is rapidly supplied to the pressure chamber424. Accordingly, by setting the opening area Snzl of the nozzles427to 1/10 or less of the opening area Ssup of the ink supply path425, it is possible to suppress the shortage of the supply of the ink to the pressure chamber424even when the ink having high viscosity is ejected and to stabilize the ejection of the ink droplets.

Difference in Viscosity

The above-described embodiment is an experimental result (simulation result) of the ink having high viscosity of 20 mPa·s, but the viscosity of the ink having high viscosity has a width. Accordingly, the influence due to a difference in the viscosity of the ink will be described.FIG. 12is a view explaining the ejection of ink droplets when an ink having viscosity of 5 mPa·s is ejected.FIG. 13is a view explaining the ejection of ink droplets when an ink having viscosity of 6 mPa·s is ejected. The heads HD used in these drawings are equal to the head HD used inFIG. 7.

Referring toFIG. 12, the amount of ink in a period X1after the ejection of the ink droplets is convex at a positive side. This indicates that the supply of the ink to the pressure chamber424is excessive and thus the meniscus is located at the ejection side rather than the edge of the opening of each of the nozzles427. The movement of the meniscus to the convex side is a factor for making the ejection of the ink unstable and thus is not preferable. In contrast, referring toFIG. 13, the amount of ink in a period X2after the ejection of the ink droplets is located at a positive side, but is substantially close to the position of the normal state. This indicates that the meniscus slightly vibrates at a place close to the position of the normal state. That is, the meniscus is stabilized at the position of the normal state.

Accordingly, if the viscosity of the ink is in a range from 6 mPa·s to 20 mPa·s, it is possible to stabilize the ejection of the ink droplets by setting the opening area Snzl of the nozzles427to 1/10 or less of the opening area Ssup of the ink supply path425.

Opening Area Snzl of Nozzles427

As described above, in view of the stabilization of the ejection of the ink droplets, the opening area Snzl of the nozzles427is set to 1/10 or less of the opening area Ssup of the ink supply path425. As the opening area Snzl of the nozzles427is smaller than the opening surface Ssup of the ink supply path425, the ink is hard to flow in the nozzles427. Accordingly, the ink depressurized in the pressure chamber424largely flows to the ink supply path425. In addition, if the opening area Snzl of the nozzles427is excessively small, the ink droplets are not ejected from the nozzles427although the ink is pressurized in the pressure chamber424.

In order to prevent an ejection failure of the ink droplets, the opening area Snzl of the nozzles427is set to 1/20 or more of the opening area Ssup of the ink supply path425. Accordingly, it is possible to cause the flowing of the ink in the nozzles427when the ink is pressurized in the pressure chambers424and to eject the ink droplets with certainty.

In addition, even when the opening area Snzl of the nozzles427is 1/20 or more of the opening area Ssup of the ink supply path425, the diameter φ427of the nozzles427cannot be smaller than the minimum value. That is, the diameter φ427of the nozzles427cannot be smaller than 10 μm. This is because a necessary amount of ink cannot be structurally ejected.

Opening Area Ssup of Ink Supply Path425

From the above description, the opening area Ssup of the ink supply path425may be set in a range from 10 times to 20 times of the opening area Snzl of the nozzles427. In addition, in the relationship with the area Scav (thickness) of the pressure chamber424, the opening area Ssup of the ink supply path425is preferably set to be longer than ⅓ of the area Scav of the pressure chamber424(corresponding to the surface communicating with the ink supply path425as the area of the surface partitioning the pressure chamber424). The ink supply path425has a function for attenuating the pressure vibration of the ink after the ejection of the ink droplets in addition to the function for supplying the ink from the common ink chamber426to the pressure chamber424. If this function is focused on, the opening area Ssup of the ink supply path425needs to be smaller than the area Scav of the pressure chamber424. This is because the channel resistance is increased by reducing the opening area.

The channel resistance is internal loss of a medium, and, in the present embodiment, is force which is applied to the ink flowing in the ink channel and is force reverse to the direction in which the ink flows. The channel resistance may be expressed by Equations (2) and (3). That is, like the pressure chamber424or the ink supply path425, the channel resistance Rrectangularin the channel having a rectangular parallelepiped shape may be expressed by Equation (2). In addition, like the nozzles427, the channel resistance Rcircularof the channel having a circular cross section may be expressed by Equation (3).
Channel resistanceRrectangular=(12×viscosity μ×lengthL)/(widthW×heightH3)  (2)
Channel resistanceRcircular=(8×viscosity μ×lengthL)/(π×radiusr4)  (3)

In such Equations (2) and (3), the viscosity μ denotes the viscosity of the ink, L denotes the length of the channel, W denotes the width of the channel, H denotes the height of the channel, and r denote the radius of the channel having the circular cross section.

In addition, by making the channel resistance of the ink supply path425higher than the channel resistance of the pressure chamber424, it is possible to efficiently attenuate the pressure vibration of the ink in the pressure chamber424in the ink supply path425. As a result, it is possible to promptly stabilize the meniscus after the ejection of the ink droplets. That is, this is suitable for the ejection of the ink droplets at a high frequency.

The nozzles427and the ink supply path425may be considered as a pipe in which the ink (medium) flows. Accordingly, when the pressure is applied from the outside of the pipe, as the diameter of the pipe is increased, the ink is easy to be moved and, as the mass of the ink in the pipe is increased, the ink in the pipe is hard to be moved. From such a characteristic, the ease of the movement of the ink in the pipe is expressed by inertance of an acoustic circuit. When the density of the ink is ρ, the cross-sectional area of the surface perpendicular to the ink flowing direction of the channel is S, and the length of the channel is L, the inertance M may be approximately expressed by Equation (4). As shown inFIG. 2B, the length L or the cross-sectional area S of the channel is expressed by the length or the cross-sectional area of each portion of the modeled ink channel. The length L is the length of the ink flowing direction. The cross-sectional area S is the area of the surface substantially perpendicular to the ink flowing direction.
InertanceM=(density ρ×lengthL)/cross-sectional areaS(4)

From Equation (4), the inertance may be considered as the mass of the ink per unit cross-sectional area. In addition, it is difficult to move the ink according to the ink pressure of the pressure chamber424as the inertance is increased, and it is easy to move the ink according to the pressure of the pressure chamber424as the inertance is decreased.

When the ink having high viscosity is ejected, the inertance of the nozzles427is preferably smaller than the inertance of the ink supply path425. This is because the movement of the meniscus is efficiently performed on the basis of the pressure vibration applied to the ink contained in the pressure chamber424.

Other Embodiments

Although the printing system having the printer as the liquid ejecting apparatus is described in the above-described embodiments, the disclosure of the liquid ejecting method, the liquid ejecting system and the method of setting the ejection pulse are included. In addition, these embodiments are intended to facilitate the understanding of the invention and not to limit the invention. The invention may be modified or improved without departing the scope thereof and the invention includes the equivalent thereof. In particular, the following embodiments are included in the invention.

Other Heads HD′

In the heads HD of the above-described embodiments, an element which performs an operation for increasing the volume of the pressure chamber424as the potential applied by the ejection pulse PS1is increased was used as the piezo-element433. Other types of heads may be used. Another head HD′ shown inFIG. 14uses piezo-elements which perform the operation for decreasing the volume of a pressure chamber73as the potential applied by the ejection pulse PS2(seeFIG. 15) is increased, as piezo-elements75.

In brief, another head HD′ includes a common ink chamber71, ink supply openings72, pressure chambers73, and nozzles74. A plurality of ink channels from the common ink chamber71to the nozzles74via the pressure chambers73is included in correspondence with the nozzles74. Even in another head HD′, the volumes of the pressure chambers73vary by the operation of the piezo-elements75. That is, a portion of the pressure chambers73is partitioned by a vibration plate76, and the piezo-elements75are provided on the surface of the vibration plate76which becomes the opposite side of the pressure chambers73.

A plurality of piezo-elements75is provided in correspondence with the pressure chambers73. Each of the piezo-elements75is configured by sandwiching a piezoelectric body between an upper electrode and a lower electrode (all not shown) and is deformed by applying a potential difference to these electrodes. In this example, if the potential of the upper electrode is increased, the piezoelectric body is charged and thus each piezo-element75is bend to be convex to each pressure chamber73. Accordingly, each pressure chamber73contracts. In addition, in another head HD′, the portion of the vibration plate76which partitions each pressure chamber73corresponds to the partitioning portion.

The ejection pulse PS2for another head HD′ has, for example, the waveform shown inFIG. 15. In brief, this ejection pulse PS2has the waveform obtained by inverting the above-described ejection pulse PS2in a potential direction (pitch direction). Accordingly, this ejection pulse PS2includes a first depressurization portion P11, a first potential holding portion P12, a pressurization portion P13, a second potential holding portion P14and a second depressurization portion P15.

The first depressurization portion P11has a start potential which is set to an intermediate potential VB and an end potential which is set to a lowest potential VL and is generated from a timing t0to a timing t1b. The first potential holding portion P12is held in the lowest potential VL and is generated from the timing t1bto a timing t2b. The pressurization portion P13has a start potential which is set to the lowest potential VL and an end potential which is set to a highest potential VH and is generated from the timing t2bto a timing t3b. The second potential holding portion P14is held in the highest potential VH and is generated from the timing t3bto a timing t4b. The second depressurization portion P15has a start potential which is set to the highest potential VH and an end potential which is set to the intermediate potential VB and is generated from the timing t4bto a timing t5b.

The functions of the portions P11to P15of the ejection pulse PS2for another head HD′ are equal to the functions of the portions P1to P5of the above-described ejection pulse PS1. The intermediate potential VB is set to a potential lower than the highest potential VH of the ejection pulse PS2by 30% of the driving voltage Vh.

Even another head HD′ having such a configuration, if the viscosity of the ink is in a range from 6 mPa·s to 20 mPa·s, it is possible to stabilize the ejection of the ink droplets by setting the opening area of the nozzles74on the ejection side to 1/10 or less of the opening area of the ink supply openings72on the side of the pressure chamber73.

Ejection Pulse PS

The above-described ejection pulses PS1and PS2are only examples. The waveform (potential variation pattern) of the ejection pulse PS is properly set according to the ejection amount of ink or the viscosity of the ink.

Element for Performing Ejection Operation

In this printer1, as an element for performing an operation (ejection operation) for ejecting the ink, piezo-elements433and75are used. The element for performing the ejecting operation is not limited to the above-described piezo-elements433and75. For example, a heating element or a magnetostrictive element may be used. If the piezo-elements433and75are used as this element like the above-described embodiment, the volumes of the pressure chambers424and73can be controlled with accuracy on the basis of the potential of the ejection pulse PS.

Shape of Nozzle427, Ink Supply Path425or the Like

In the above-described embodiments, the nozzles427have a circular opening shape and are configured by holes penetrating through the nozzle plates422in the thickness direction. In other words, the nozzles are configured by through-holes partitioning a circular cylindrical space. In addition, the ink supply path425has a rectangular opening shape and is configured by a hole communicating the pressure chamber424with the common ink chamber426. In other words, the ink supply path is configured by a communicating hole partitioning a rectangular cylindrical space.

The nozzle427or the ink supply path425may have various shapes. For example, the nozzle427may be configured by substantially funnel-shaped through-holes as shown inFIG. 16A. The shown nozzle427has a tapered portion427aand a straight portion427b. The tapered portion427ais a portion partitioning a circular truncated cone-shaped space and the opening area thereof is decreased as separated from the pressure chamber424. That is, the tapered portion is provided in a tapered shape. The straight portion427bis provided in communication with a small-diameter end of the tapered portion427a. This straight portion427bis a portion partitioning a circular cylindrical space and a portion of which the cross-sectional area is substantially constant in the surface perpendicular to the nozzle direction.

This nozzle427may be, for example, as shown inFIG. 16B, analyzed by defining the tapered portion427aas a portion partitioning a plurality of disc-like spaces of which the diameters are stepwise decreased. As shown inFIG. 16A, the nozzle may be analyzed by defining the nozzle427of which the cross-sectional area of the surface perpendicular to the nozzle direction is constant, which is equivalent to the funnel-shaped nozzle427.

In addition, the ink supply path425may be, for example, as shown inFIG. 16C, configured by a channel having an opening having a vertically elongated ellipse-shape (having a shape obtained by connecting two semicircles having the same radius at a common circumscribed line). In this case, the cross-sectional area Ssup of the ink supply path425corresponds to the area of the ellipse-shaped portion denoted by oblique lines. The ink supply path425having the ellipse-shaped opening may be analyzed by defining a channel having a rectangular opening equivalent thereto. In this case, the height H425of the ink supply path425is slightly lower than a maximum height of the actual ink supply path425. In addition, the same is true although the opening of the ink supply path425has an ellipse shape.

In addition, the same is true in the pressure chamber424. As shown inFIG. 16C, if the surface perpendicular to the longitudinal direction of the pressure chamber424has a horizontal elongated hexagonal shape, the pressure chamber may be analyzed by defining a channel having a rectangular cross section equivalent thereto. That is, the pressure chamber may be analyzed by defining a channel having the rectangular cross-section of which the height is H424and the width W424is slightly smaller than a maximum width of the pressure chamber424.

Other Application Examples

Although the printer is described as the liquid ejecting apparatus in the above-described embodiments, the invention is not limited to this. For example, the same technique as the present embodiment is applicable to various types of liquid ejecting apparatus using an ink jet technique, such as a color filter manufacturing apparatus, a dyeing apparatus, a microfabricated apparatus, a semiconductor manufacturing apparatus, a surface treatment apparatus, a three-dimensional modeling apparatus, a fluid-vaporizing apparatus, an organic EL manufacturing apparatus (more particularly, a polymer EL manufacturing apparatus), a display manufacturing apparatus, a film forming apparatus, a DNA chip manufacturing apparatus, and so on. In addition, methods or manufacturing methods thereof are included in the application range.

The entire disclosure of Japanese Patent Application No: 2008-081746, filed Mar. 26, 2008 and No: 2008-305331, filed Nov. 28, 2008 are expressly incorporated by reference herein.