Liquid ejection head, liquid ejection head production method and liquid ejection head production system

The liquid ejection head has a structure in which three or more head modules including a plurality of ejection elements are arranged along a single direction, and the liquid ejection head includes a first head module, a second head module and a third head module which are arranged in ascending order of slope of ejection volume distribution in the single direction or are arranged in descending order of the slope of the ejection volume distribution in the single direction, the slope of the ejection volume distribution in the single direction being evaluated by subtracting an ejection volume at one end part in the single direction from an ejection volume at the other end part in the single direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-152106, filed on Jul. 31, 2015. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a liquid ejection head, a liquid ejection head production method and a liquid ejection head production system, and particularly, relates to a structure of a liquid ejection head having a structure in which a plurality of head modules are arrayed in a single direction.

Description of the Related Art

There is known an ink-jet printing apparatus including a line-type ink-jet head having a structure in which a plurality of nozzles are provided over a length corresponding to the total width of a medium. As the line-type ink-jet head, a structure of arraying, in the width direction of the medium, a plurality of head modules in each of which a plurality of nozzle parts are arranged in a matrix can be employed.

Japanese Patent Application Laid-Open No. 2015-047833 describes a liquid ejection head configured to joint, in a single direction, a plurality of head modules in each of which a plurality of nozzle parts to eject liquid are arrayed. The liquid ejection head described in Japanese Patent Application Laid-Open No. 2015-047833 is configured to alternately joint a first head module in which the ejection volume of the liquid at one end part of the head module with respect to the array direction of the head module is greater than the ejection volume of the liquid at the other end part and a second head module in which the ejection volume of the liquid at the other end part is greater than the ejection volume of the liquid at one end part, and thereby, the density unevenness at joint parts of the head modules is suppressed.

Here, the terms “droplet”, “ejection amount” and “recording head” described in Japanese Patent Application Laid-Open No. 2015-047833 correspond to the terms “liquid”, “ejection volume” and “liquid ejection head” in the specification, respectively.

Japanese Patent Application Laid-Open No. 2007-022092 describes an ink-jet recording apparatus that generates image data such that a line graph showing density change characteristic depicts a line having a grade when the density change characteristic of an image to be drawn by the liquid ejection head is shown as the line graph, and that performs the drawing based on the generated image data.

The ink-jet printing apparatus described in Japanese Patent Application Laid-Open No. 2007-022092 performs such a control that the density changes continuously and gradually, allowing for the inconspicuousness of the image degradation due to the density unevenness by the liquid ejection head.

Here, the terms “printing head” and “ink-jet printer” described in Japanese Patent Application Laid-Open No. 2007-022092 correspond to the terms “liquid ejection head” and “ink-jet recording apparatus” in the specification, respectively.

Japanese Patent Application Laid-Open No. 2007-160834 describes a liquid ejection head in which a plurality of head modules are arranged along the array direction of nozzles. By arranging the head modules in order of the magnitude of average ejection volume or by equalizing the first head module and the N-th head module in average ejection volume, the liquid ejection head described in Japanese Patent Application Laid-Open No. 2007-160834 reduces the density unevenness caused by the difference in ejection volume among the head modules, and achieves the improvement in image quality.

SUMMARY OF THE INVENTION

However, in the liquid ejection head described in Japanese Patent Application Laid-Open No. 2015-047833, in the case where the relative difference in ejection volume between the first head module and the second head module is large, it is difficult to suppress the appearance of the density unevenness at the joint part between the first head module and the second head module.

The ink-jet printing apparatus described in Japanese Patent Application Laid-Open No. 2007-022092, in the case where the difference in ejection volume between adjacently arranged head modules is large, fails to correct the image data, and it is difficult to suppress the appearance of the density unevenness.

In the liquid ejection head described in Japanese Patent Application Laid-Open No. 2007-160834, the variation in ejection volume within individual head modules is not considered, although the variation in average ejection volume between adjacently arranged head modules is considered. Hence, the difference in ejection volume between the mutually adjacent end parts of adjacently arranged head modules is sometimes large, and it is not possible to suppress the level difference in density at the joint part between the adjacently arranged head modules, resulting in a fear of the appearance of the density unevenness.

The present invention has been made in view of such a circumstance, and has an object to provide a liquid ejection head, a liquid ejection head production method and a liquid ejection head production system that make it possible to suppress the deterioration in image quality at the joint part between head modules of the liquid ejection head having a structure in which a plurality of head modules are jointed in a single direction.

For achieving the above object, the following invention aspects are provided.

A liquid ejection head according to a first aspect is a liquid ejection head having a structure in which three or more head modules are arranged along a single direction, each of the three or more head modules including a plurality of ejection elements, the liquid ejection head including: a first head module; a second head module that has a joint part with the first head module on one end side in the single direction, the second head module being arranged at an arrangement position that is adjacent to the other end side of the first head module in the single direction; and a third head module that has a joint part with the second head module on one end side in the single direction, the third head module being arranged at an arrangement position that is adjacent to the other end side of the second head module in the single direction, the first head module, the second head module and the third head module being arranged in ascending order of slope of ejection volume distribution in the single direction or being arranged in descending order of the slope of the ejection volume distribution in the single direction, the slope of the ejection volume distribution in the single direction being evaluated by subtracting an ejection volume at one end part in the single direction from an ejection volume at the other end part in the single direction.

According to the first aspect, the first head module, the second head module and the third head module are arranged in order of the slope of the ejection volume distribution in the single direction. Therefore, in the first head module, the second head module and the third head module, the ejection volume at the joint part between two head modules that are arranged at adjacent positions is close to the average ejection volume in the whole of the liquid ejection head, and the deterioration in ejection characteristic at the joint part is suppressed.

The ejection volume is the volume of a unit liquid that is ejected from the ejection element. The unit liquid is a liquid that forms one dot. As the mode in which the unit liquid is ejected, there is a mode in which all of the liquid that forms one dot is ejected by one ejection operation, or a mode in which all of the liquid that forms one dot is ejected by multiple ejection operations.

In the first aspect, the first head module, the second head module and the third head module can be configured to include head modules that are different in the positive and negative of the slope of the ejection volume distribution in the single direction.

According to such a mode, even when the positive and negative of the slope of the ejection volume distribution cannot be matched for all head modules, it is possible to suppress the deterioration in ejection characteristic at the joint part, as the whole of the liquid ejection head.

A second aspect, in the liquid ejection head of the first aspect, can adopt a configuration in which all head modules including the first head module, the second head module and the third head module are arranged in the ascending order of the slope of the ejection volume distribution in the single direction or are arranged in the descending order of the slope of the ejection volume distribution in the single direction.

According to the second aspect, since all head modules are arranged in the ascending order or descending order of the slope of the ejection volume distribution in the single direction, it is possible to suppress the deterioration in ejection characteristic at the joint part, as the whole of the liquid ejection head.

A third aspect, in the liquid ejection head of the first aspect or the second aspect, can adopt a configuration in which, in the first head module, the second head module and the third head module, the slopes of the ejection volume distributions in the single direction are all positive or all negative.

According to the third aspect, it is possible to restrain the ejection volume from being excessive at the joint part, and it is possible to obtain a preferable graininess.

A fourth aspect, in the liquid ejection head of the first aspect or the second aspect, can adopt a configuration in which, in all head modules including the first head module, the second head module and the third head module, the slopes of the ejection volume distributions in the single direction are all positive or all negative.

According to the fourth aspect, the ejection volume is restrained from being excessive at the joint part, as the whole of the liquid ejection head, and it is possible to obtain a preferable graininess.

A fifth aspect, in the liquid ejection head of any one aspect of the first aspect to the fourth aspect, can adopt a configuration in which, in head modules that are of the first head module, the second head module and the third head module and that are arranged at adjacent arrangement positions, an ejection volume of an ejection element provided in a head module in which an ejected liquid impacts earlier exceeds an ejection volume of an ejection element provided in a head module in which an ejected liquid impacts later.

According to the fifth aspect, the deviation of impact position due to impact interference is suppressed.

As a sixth aspect, in the liquid ejection head of any one aspect of the first aspect to the fifth aspect, each of the first head module, the second head module and the third head module includes an ejection volume distribution slope storage unit in which the slope of the ejection volume distribution in the single direction is stored.

According to the sixth aspect, when the slope of the ejection volume distribution of each head module is acquired, it is possible to use the slope of the ejection volume distribution that is stored in the ejection volume distribution slope storage unit provided in each head module. A seventh aspect, in the liquid ejection head of any one aspect of the first aspect to the sixth aspect, can adopt a configuration in which, for the first head module, the second head module and the third head module, the slope of the ejection volume distribution in the single direction is derived using a measurement value, the measurement value being obtained by measuring a liquid that is ejected by applying an ejection duty, the ejection duty being 80 percent or more of the maximum value of the ejection volume of a droplet that is used in liquid ejection.

According to the seventh aspect, the liquid ejection is performed by applying a high liquid ejection duty, and thereby, it is possible to use the slope of the ejection volume distribution that reflects the ejection characteristic of the real head module.

An eighth aspect is a liquid ejection head production method for producing a liquid ejection head having a structure in which three or more head modules are arranged along a single direction, each of the three or more head modules including a plurality of ejection elements, the liquid ejection head production method including: a selection step of collectively selecting three or more head modules or sequentially selecting three or more head modules; an ejection volume distribution slope acquisition step of acquiring slope of ejection volume distribution in the single direction, for each of the three or more head modules selected in the selection step, the slope of the ejection volume distribution in the single direction being derived from an ejection volume at one end part in the single direction and an ejection volume at the other end part in the single direction; a setting step of setting an arrangement in ascending order or descending order of the slope of the ejection volume distribution in the single direction for the three or more head modules acquired in the ejection volume distribution slope acquisition step; and an assembly step of arranging a first head module, a second head module and a third head module along the single direction, based on the arrangement order set in the setting step.

According to the eighth aspect, the first head module, the second head module and the third head module are arranged in order of the slope of the ejection volume distribution in the single direction. Therefore, it is possible to produce a liquid ejection head in which the ejection volume at the joint part between two head modules that are arranged at adjacent positions is close to the average ejection volume in the whole of the liquid ejection head and the deterioration in ejection characteristic at the joint part is suppressed.

In the eighth aspect, the slope of the ejection volume distribution in the single direction may be evaluated by subtracting the ejection volume at the one end part in the single direction from the ejection volume at the other end part in the single direction, or may be evaluated by dividing the ejection volume at the other end part in the single direction by the ejection volume at the one end part in the single direction.

In the eighth aspect, it is preferable that the setting step be a mode of setting the arrangement in the ascending order or descending order of the slope of the ejection volume distribution in the single direction for all head modules including the first head module, the second head module and the third head module.

According to such a mode, since all head modules are arranged in the ascending order or descending order of the slope of the ejection volume distribution in the single direction, it is possible to suppress the deterioration in ejection characteristic at the joint part, as the whole of the liquid ejection head.

In the eighth aspect, it is preferable that the setting step be a mode of setting the arrangement such that in the first head module, the second head module and the third head module, the slopes of the ejection volume distributions in the single direction are all positive or all negative.

According to such a mode, it is possible to restrain the ejection volume from being excessive at the joint part, and it is possible to obtain a preferable graininess.

In the eighth aspect, the arrangement, in the setting step, can be set such that in all head modules including the first head module, the second head module and the third head module, the slopes of the ejection volume distributions in the single direction are all positive or all negative.

According to such a mode, the ejection volume is restrained from being excessive at the joint part, as the whole of the liquid ejection head, and it is possible to obtain a preferable graininess.

In the eighth aspect, the setting step can be a configuration in which the first head module, the second head module and the third head module include head modules that are different in the positive and negative of the slope of the ejection volume distribution in the single direction.

According to such a mode, even when the positive and negative of the slope of the ejection volume distribution cannot be matched for all head modules, it is possible to suppress the deterioration in ejection characteristic at the joint part, as the whole of the liquid ejection head.

In the eighth aspect, the setting step can be a configuration in which, in head modules that are of the first head module, the second head module and the third head module and that are arranged at adjacent arrangement positions, an ejection volume of an ejection element provided in a head module in which an ejected liquid impacts earlier exceeds an ejection volume of an ejection element provided in a head module in which an ejected liquid impacts later.

According to such a mode, the deviation of impact position due to impact interference is suppressed.

In the eighth aspect, the first head module, the second head module and the third head module can be configured such that the slope of the ejection volume distribution in the single direction is stored.

According to such a mode, when the slope of the ejection volume distribution of each head module is acquired, it is possible to use the slope of the ejection volume distribution that is stored in an ejection volume distribution slope storage unit provided in each head module.

The eighth aspect can adopt a configuration in which, for the first head module, the second head module and the third head module, the slope of the ejection volume distribution in the single direction is derived using a measurement value, the measurement value being obtained by measuring a liquid that is ejected by applying an ejection duty, the ejection duty being 80 percent or more of the maximum value of the ejection volume of a droplet that is used in liquid ejection.

According to such a mode, the liquid ejection is performed by applying a high liquid ejection duty, and thereby, it is possible to use the slope of the ejection volume distribution that reflects the ejection characteristic of the real head module.

A ninth aspect, in the liquid ejection head production method of the eighth aspect, can adopt a configuration in which a first candidate head module that is a candidate for the first head module is selected in the selection step, the slope of the ejection volume distribution of the first candidate head module is acquired in the ejection volume distribution slope acquisition step, and the first candidate head module is set in the setting step as a head module that is arranged at an arrangement position of the first head module.

According to the ninth aspect, the first head module is set.

A tenth aspect, in the liquid ejection head production method of the eighth aspect or the ninth aspect, can adopt a configuration in which a second candidate head module that is a candidate for the second head module is selected in the selection step, the slope of the ejection volume distribution of the first head module and the slope of the ejection volume distribution of the second candidate head module are acquired in the ejection volume distribution slope acquisition step, and the second candidate head module is set in the setting step as a head module that is arranged at an arrangement position of the second head module, in a case where the slope of the ejection volume distribution of the first head module and the slope of the ejection volume distribution of the second candidate head module satisfy a relation of the ascending order or the descending order for the first head module and the second head module.

According to the tenth aspect, in the mode of sequentially selecting three or more head modules, it is possible to set the second head module that satisfies the condition of the slope of the ejection volume with respect to the first head module.

An eleventh aspect, in the liquid ejection head production method of any one aspect of the eighth aspect to the tenth aspect, can adopt a configuration in which a third candidate head module that is a candidate for the third head module is selected in the selection step, the slope of the ejection volume distribution of the second head module and the slope of the ejection volume distribution of the third candidate head module are acquired in the ejection volume distribution slope acquisition step, and the third candidate head module is set in the setting step as a head module that is arranged at an arrangement position of the third head module, in a case where the slope of the ejection volume distribution of the second head module and the slope of the ejection volume distribution of the third candidate head module satisfy a relation of the ascending order or the descending order for the second head module and the third head module.

According to the eleventh aspect, in the mode of sequentially selecting three or more head modules, it is possible to set the third head module that satisfies the condition of the slope of the ejection volume with respect to the second head module.

A twelfth aspect is a liquid ejection head production system for producing a liquid ejection head having a structure in which three or more head modules are arranged along a single direction, each of the three or more head modules including a plurality of ejection elements, the liquid ejection head production system including: a selection unit that selects three or more head modules; an election volume distribution slope acquisition unit that acquires slope of ejection volume distribution in the single direction, for each of the three or more head modules selected by the selection unit, the slope of the ejection volume distribution in the single direction being derived from an ejection volume at one end part in the single direction and an ejection volume at the other end part in the single direction; a head module setting unit that sets an arrangement in ascending order or descending order of the slope of the ejection volume distribution in the single direction for the three or more head modules acquired by the ejection volume distribution slope acquisition unit; and an assembly unit that arranges a first head module, a second head module and a third head module along the single direction, based on the arrangement order set by the head module setting unit.

According to the twelfth aspect, the first head module, the second head module and the third head module are arranged in order of the slope of the ejection volume distribution in the single direction. Therefore, it is possible to produce a liquid ejection head in which the ejection volume at the joint part between two head modules that are arranged at adjacent positions is close to the average ejection volume in the whole of the liquid ejection head and the deterioration in ejection characteristic at the joint part is suppressed.

According to the present invention, the first head module, the second head module and the third head module are arranged in order of the slope of the ejection volume distribution in the single direction. Therefore, in the first head module, the second head module and the third head module, the ejection volume at the joint part between two head modules that are arranged at adjacent positions is close to the average ejection volume in the whole of the liquid ejection head, and the deterioration in ejection characteristic at the joint part is suppressed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferable embodiments of the present invention are described in detail with reference to the accompanying drawings.

FIG. 1is a perspective plan view showing a structure example of an ink-jet head. An ink-jet head21shown inFIG. 1has a structure in which a plurality of head modules200are jointed in the width direction of a medium100that is the direction orthogonal to the feed direction of the medium100. The ink-jet head in the specification is a mode of the liquid ejection head.

The structure in which the plurality of head modules200are jointed in the width direction of the medium100in the embodiment is a mode of the structure in which a plurality of head modules are arranged along a single direction.

The term “orthogonal” in the specification includes the case of being substantially orthogonal that is of the case of a cross at an angle exceeding 90 degrees or the case of a cross at an angle less than 90 degrees and that exhibits a function effect identical to the case of a cross at an angle of 90 degrees.

Further, the term “parallel” in the specification includes the case of being substantially parallel that exhibits a function effect identical to the case of being parallel, although two directions cross. Furthermore, the term “identical” in the specification includes the case of being substantially identical that makes it possible to obtain a similar function effect to the case of being identical, although there a difference in the configuration of the object.

In the specification, the width direction of the medium100is sometime described as the X-direction. Further, the feed direction of the medium100is sometimes described as the Y-direction or the medium feed direction. These terms can be replaced with each other when appropriate.

The ink-jet head21shown inFIG. 1is a line-type ink-jet head in which a plurality of nozzle parts are arranged over a length equal to or greater than the total length Lmaxof the medium100in the width direction of the medium100. The nozzle part, which is not illustrated inFIG. 1, is illustrated inFIG. 4while reference numeral281is assigned.

An identical structure can be applied to the plurality of head modules200constituting the ink-jet head21. Further, the head module200can function alone, as the ink-jet head.

<Structure of Head Module>

FIG. 2is a perspective view of a head module, and is a diagram including a partial cross-section view. Hereinafter, identical reference numerals are assigned to constituents identical to constituents that are previously described, and the descriptions are omitted when appropriate.

Ink in the specification is a mode of the liquid, and the term “ink” and the term “liquid” can be replaced when appropriate. Further, in the specification, the term “discharge” and the term “ejection” can be treated as synonymous terms, and the term “discharge” and the term “ejection” can be replaced when appropriate.

The head module200has an ink supply unit including an ink supply chamber232, an ink circulation chamber236and the like, on the upper side inFIG. 2, which is the opposite side to a liquid ejection surface277of a nozzle plate275.

The ink supply chamber232is connected with an ink tank not illustrated, through a supply-side individual passage252, and the ink circulation chamber236is connected with a collection tank not illustrated, through a collection-side individual passage256.

FIG. 3is a perspective plan view of the liquid ejection surface of the head module. InFIG. 3, nozzle openings280to be arranged on the liquid ejection surface277are illustrated so as to be reduced in number, but on the liquid ejection surface277of one head module200, a plurality of nozzle openings280are arranged by a two-dimensional arrangement.

The head module200has a planar shape of a parallelogram that includes a long-side edge surface along a V-direction having a slope of an angle β with respect to the direction orthogonal to the medium feed direction and a short-side edge surface along a W-direction having a slope of an angle a with respect to the medium feed direction, and the plurality of nozzle openings280are arranged in a matrix, in a row direction along the V-direction and in a column direction along the W-direction.

The arrangement of the nozzle openings280is not limited to the mode illustrated inFIG. 3, and the plurality of nozzle openings280may be arranged in a row direction along the direction orthogonal to the medium feed direction and in a column direction crossing obliquely with respect to the direction orthogonal to the medium feed direction.

The matrix arrangement of the nozzle openings280is an arrangement of the nozzle openings280in which the arrangement intervals of the nozzle openings280are uniform on a projected nozzle array in the direction orthogonal to the medium feed direction, which is an array resulting from projecting the plurality of nozzle openings280in the direction orthogonal to the medium feed direction and arranging the plurality of nozzle openings280along the direction orthogonal to the medium feed direction.

FIG. 4is a cross-section view showing an internal structure of the ink-jet head. Reference numeral214designates an ink supply path, reference numeral218designates a pressure chamber, reference numeral216designates an individual supply path that connects each pressure chamber218and the ink supply path214, reference numeral220designates a nozzle communication path that is connected from the pressure chamber218to the nozzle opening280, and reference numeral226designates a circulation individual passage that connects the nozzle communication path220and a circulation common passage228. The pressure chamber218is sometimes referred to as a liquid chamber.

A vibration plate266is provided on a passage structure body210that configures the ink supply path214, the individual supply path216, the pressure chamber218, the nozzle communication path220, the circulation individual passage226and the circulation common passage228. A piezoelectric element230having a laminate structure of a lower electrode265, a piezoelectric substance layer231and an upper electrode264is provided on the vibration plate266, through an adhesion layer267. The lower electrode265is sometimes referred to as a common electrode, and the upper electrode264is sometimes referred to as an individual electrode.

The upper electrode264is an individual electrode that is patterned so as to correspond to the shape of each pressure chamber218, and the piezoelectric element230is provided for each pressure chamber218.

The ink supply path214is connected with the ink supply chamber232shown inFIG. 2, and the link is supplied from the ink supply path214through the individual supply path216to the pressure chamber218. Depending on input image data, a drive voltage is applied to the upper electrode264of the piezoelectric element230provided on the corresponding pressure chamber218. Thereby, the piezoelectric element230and the vibration plate266are transformed, and the volume of the pressure chamber218is changed. By a pressure change associated with this, the ink is discharged from the nozzle opening280through the nozzle communication path220.

It is possible to discharge the ink from the nozzle opening280, by controlling the drive of the piezoelectric element230corresponding to each nozzle opening280, depending on dot arrangement data that is generated from the input image data.

While the medium100is fed at a constant speed in the medium feed direction, the timing of the ink discharge from each nozzle opening280is controlled in concert with the feed speed, and thereby, it is possible to record a desired image on the medium100.

In the pressure chamber218provided so as to correspond to each nozzle opening280, the planar shape is a roughly square shape. At one of both corner parts on a diagonal line, an outlet to the nozzle opening280is provided, and at the other, the individual supply path216, which is an inlet of the supply ink, is provided. The illustration of the planar shape of the pressure chamber218is omitted.

Here, the planar shape of the pressure chamber is not limited to a square shape. As the planar shape of the pressure chamber, various shapes, as exemplified by a polygon such as a tetragon including a rhombus and a rectangle, a pentagon and a hexagon, a circle and an ellipse, are possible.

In the nozzle part281including the nozzle opening280and the nozzle communication path220, a circulation outlet is formed, and the nozzle part281is communicated with the circulation individual passage226through the circulation outlet. The ink that is of the ink in the nozzle communication path220and the nozzle opening280and that is not used for discharge is collected to the circulation common passage228through the circulation individual passage226.

The circulation common passage228is connected with the ink circulation chamber236shown inFIG. 2, and at all times, the ink is collected to the circulation common passage228through the circulation individual passage226, resulting in the prevention of the thickening of the ink near the nozzle opening280when the discharge is not performed.

As a mode of the ejection element included in the head module, there is a mode of including one nozzle part281, a passage such as the pressure chamber218communicated with the one nozzle part281, and the piezoelectric element230corresponding to the nozzle part281.

Hereinafter, the term “nozzle opening” and the term “nozzle part” in the specification can be replaced with “ejection element”, when appropriate. Further, the term “nozzle opening” can be replaced with the term “nozzle part”, when appropriate.

Examples of the piezoelectric element230include a piezoelectric element230having a structure of being individually separated so as to correspond to the nozzle opening280shown inFIG. 3. Needless to say, it is allowable to apply a structure in which the piezoelectric substance layer231is integrally formed for the plurality of nozzle parts281, the individual electrode is formed so as to correspond to each nozzle part281and an active region is formed for each nozzle part281.

It is allowable to apply a thermal system in which a heater is included within the pressure chamber218as a pressure generation element instead of the piezoelectric element, a drive voltage is supplied to the heater for heat generation and the ink in the pressure chamber218is discharged from the nozzle opening280by utilizing the film boiling phenomenon.

<Support Structure for Head Module>

FIG. 5is a perspective view showing a support structure for the head module.FIG. 5is a partial enlarged view of the ink-jet head21, and is a diagram when the head module200is viewed from the side of the liquid ejection surface277.

InFIG. 5, the direction shown while reference character X is assigned is the longitudinal direction of the ink-jet head21. The longitudinal direction of the ink-jet head21is the width direction of the medium in a state in which the ink-jet head21is used while the ink-jet head21shown inFIG. 1is mounted on the ink-jet recording apparatus.

Further, inFIG. 5, the direction shown while reference character Y is assigned is the short direction of the ink-jet head21. The short direction of the ink-jet head21is the feed direction of the medium in a state in which the ink-jet head21is used while the ink-jet head21shown inFIG. 1is mounted on the ink-jet recording apparatus.

In the specification, the “longitudinal direction of the ink-jet head21” and the “width direction of the medium” can be replaced with each other. Similarly, the “short direction of the ink-jet head21” and the “feed direction of the medium” can be replaced with each other.

Hereinafter, the longitudinal direction of the ink-jet head21is sometimes described as the X-direction. The short direction of the ink-jet head is sometimes described as the Y-direction.

FIG. 5illustrates a state in which one of the plurality of head modules200attached to base frames312has been detached from the base frames312. The arrow to which reference character200A is assigned inFIG. 5shows the attaching direction of the head module200to the base frames312.

As shown inFIG. 5, the head module200is attached to a bracket316. The bracket316includes a head module support part324that supports the head module200, and a base frame support part326that is joined to one edge of the head module support part324. The head module support part324is attached to the base frame support part326, using two screws345.

On the bracket316, an X-direction adjustment part and a Y-direction adjustment part, which are not illustrated, are provided. The X-direction adjustment part has a structure for adjusting the relative position in the X-direction between an arbitrary head module200and a different head module200arranged at a position adjacent to the arbitrary head module200.

The Y-direction adjustment part has a structure for adjusting the relative position in the Y-direction between an arbitrary head module200and a different head module200arranged at a position adjacent to the arbitrary head module200.

As shown inFIG. 5, the head modules200attached to the base frames312include head modules200in each of which the base frame support part326is attached to one side of the head module200in the Y-direction and head modules200in each of which the base frame support part326is attached to the other side of the head module200in the Y-direction.

The ink-jet head21has a structure of alternately arranging the head modules200in each of which the base frame support part326is attached to one side of the head module200in the Y-direction and the head modules200in each of which the base frame support part326is attached to the other side of the head module200in the Y-direction.

A guide post376functions as a device that fixes the head module200attached to the bracket316, on the base frames312, and functions as a device that urges the head module200attached to the bracket316, in the Y-direction.

A flexible substrate321to be connected with an electric wire of the head module200passes through the interval between the two facing base frames312, and is connected with a drive circuit substrate on the opposite side to the liquid ejection surface277of the head module200. The illustration of the drive circuit substrate is omitted.

The support structure for the head module200in the ink-jet head21shown inFIG. 5is an example, and another support structure may be applied.

<Description of Joint Part>

FIG. 6is a conceptual diagram of a joint part.FIG. 7is a partial enlarged view ofFIG. 6.FIG. 6andFIG. 7are perspective plan views of the liquid ejection surface277, similarly toFIG. 3.FIG. 6does not illustrate the nozzle parts281shown inFIG. 4individually, and schematically illustrates, by dotted lines, nozzle arrays281A each of which is constituted by a plurality of nozzle parts along the column direction shown inFIG. 3while reference character W is assigned.

FIG. 6andFIG. 7show only two head modules of the plurality of head modules200shown inFIG. 1. In the two head modules shown inFIG. 6andFIG. 7, the head module on the left side inFIG. 6is referred to as a first head module200B, and the head module on the right side inFIG. 6is referred to as a second head module200C.

InFIG. 7, reference character281B designates a nozzle part belonging to the first head module200B. Reference character281C designates a nozzle part belonging to the second head module200C.

The first head module200B and second head module200C shown inFIG. 6can be configured as follows.

The number of the nozzle parts that constitute a single nozzle array along the W-direction is 32, the number of the nozzle arrays along the V-direction is 64, and the print resolution in the X-direction is 1200 dots per inch. The numerical value showing the print resolution shows the number of nozzle parts per 1 inch.

Here, 1 inch is 25.4 millimeters. The print resolution shown as the number of dots per 1 inch can be converted into the number of dots per 1 millimeter, by being divided by 25.4.

The inverse number of the number of dots per 1 millimeter is the inter-dot pitch. That is, when a print resolution of 1200 dots per inch is converted into inter-dot pitch, the value rounded to the first decimal place is 21.2 micrometers.

As a configuration example of a joint part350shown inFIG. 6andFIG. 7, there is a mode in which 128 nozzle parts are included and the length in the X-direction is 2.5 millimeters.

InFIG. 6andFIG. 7, the region surrounded by a dashed line is the joint part350. The joint part350is a part that contains a position of the mechanical connection between the first head module200B and the second head module200C and that has a previously decided X-directional length.

InFIG. 6, the illustration of the position of the mechanical connection between the first head module200B and the second head module200C is omitted. The position of the mechanical connection between the first head module200B and the second head module200C is illustrated by a dashed line inFIG. 7, while reference numeral351is assigned.

At the joint part350shown inFIG. 7, there is a nozzle combining region352. The nozzle combining region352is a region where the print resolution of the ink-jet head21is actualized while nozzle parts281B belonging to the first head module200B and nozzle parts281C belonging to the second head module200C are combined.

Here, in the case where the nozzle parts are arranged in a matrix, the shape of the joint part350shown inFIG. 6andFIG. 7is complex, and therefore, the joint part350shown inFIG. 6andFIG. 7is simplified to the extent that the concept of the joint part350can be understood. Similarly, the nozzle combining region352shown inFIG. 7is also simplified to the extent that the concept of the nozzle combining region352can be understood.

FIG. 8is an explanatory diagram schematically showing an arrangement of nozzle parts at the nozzle combining region. A projected nozzle array281D shown on the lower row inFIG. 8includes nozzle parts281B belonging to the first head module200B shown inFIG. 6andFIG. 7, and has an arrangement of the nozzle parts281B that results from projecting the nozzle parts281B arranged at the nozzle combining region352in the X-direction and arranging them along the X-direction.

Further, a projected nozzle array281E shown on the upper row inFIG. 8includes nozzle parts281C belonging to the second head module200C shown inFIG. 6andFIG. 7, and has an arrangement of the nozzle parts281C that results from projecting the nozzle parts281C arranged at the nozzle combining region352in the X-direction and arranging them along the X-direction.

In the case where there is no error in the relative position between the first head module200B and second head module200C shown inFIG. 6andFIG. 7and where the first head module200B and the second head module200C are arranged at the theoretical positions, the X-directional positions of the nozzle parts281B belonging to the projected nozzle array281D, as shown inFIG. 8, coincide with the X-directional position of the nozzle parts281C belonging to the projected nozzle array281E, at the nozzle combining region352shown inFIG. 7.

Nozzle parts281F illustrated inFIG. 8by using the dotted lines are the nozzle parts belonging to the projected nozzle array281D in the case where there is no error in the relative position between the first head module200B and the second head module200C and where the first head module200B and the second head module200C are arranged.

Meanwhile, there is an error in position between the first head module200B and the second head module200C, and therefore, there is a deviation between the X-directional positions of the nozzle parts281B belonging to the projected nozzle array281D and the X-directional positions of the nozzle parts281C belonging to the projected nozzle array281E.

FIG. 8illustrates the nozzle parts281C belonging to the projected nozzle array281E in the case where the error in the relative position between the first head module200B and second head module200C shown inFIG. 6andFIG. 7is maximized.

Therefore, by performing the printing while appropriately selecting the nozzle parts281B belonging to the first head module200B and the nozzle parts281C belonging to the second head module200C at the joint part350, the resolution of the ink-jet head21is actualized at the joint part350also.

FIG. 9is a perspective plan view of a liquid ejection surface showing an alternative example of the joint part.FIG. 10is a perspective plan view of a liquid ejection surface showing a further alternative example of the joint part.

In an ink-jet head21A shown inFIG. 9, the planar shape of a surface containing a liquid ejection surface277A of a head module200H and the planar shape of the liquid ejection surface277A are rectangles. The ink-jet head21A shown inFIG. 9is arranged such that the positions of the head modules200H in the Y-direction are deviated alternately.

When the leftmost head module200H of the three head modules200H shown inFIG. 9is the first head module200B shown inFIG. 6andFIG. 7, the central head module200H inFIG. 9is the second head module200C shown inFIG. 6andFIG. 7.

At joint parts350A of the ink-jet head21A shown inFIG. 9, there are nozzle combining regions.

In an ink-jet head21B shown inFIG. 10, the planar shape of a surface containing a liquid ejection surface277B of a head module2001and the planar shape of the liquid ejection surface277B are trapezoids. The ink-jet head21B shown inFIG. 10is arranged such that the short sides and long sides of the surfaces containing the liquid ejection surfaces277B of the head modules200H are transposed alternately.

The correspondence relation between the three head modules2001shown inFIG. 10and the first head module200B and second head module200C shown inFIG. 6andFIG. 7is identical to the correspondence relation between the three head modules200H shown inFIG. 9and the first head module200B and second head module200C shown inFIG. 6andFIG. 7, and the description is omitted here.

Further, at joint parts350B of the ink-jet head21B shown inFIG. 10, there are nozzle combining regions.

FIG. 11is a perspective plan view of a liquid ejection surface showing a further alternative example of the joint part. An ink-jet head21C shown inFIG. 11includes joint parts350C at each of which there is no nozzle combining region352shown inFIG. 7.

In the ink-jet head21C shown inFIG. 11, head modules200J are arranged along the X-direction. In the ink-jet head21C, the planar shape of a surface containing a liquid ejection surface277C of the head module200J and the planar shape of the liquid ejection surface277C are parallelograms.

A joint part350C shown inFIG. 11, in the X-direction, has a previously decided length from a connection position351between one of adjacently arranged head modules200J and the other of the head modules200J.

The X-directional length of the joint part350C at which there is no nozzle combining region is decided in consideration of the X-directional length of the joint part in the case where there is the nozzle combining region, and the print resolution.

As an example of the X-directional length of the joint part350C at which there is no nozzle combining region, there is a mode in which the lengths from the connection position of the two adjacently arranged head modules to both sides in the X-direction are 1 millimeter in the case where the print resolution of each head module is 1200 dots per inch.

The correspondence between the head modules200J of the ink-jet head21C shown inFIG. 11and the first head module200B and second head module200C shown inFIG. 6andFIG. 7is the same as the ink-jet head21A shown inFIG. 9and the ink-jet head21B shown inFIG. 10, and the description is omitted here.

FIG. 12is an explanatory diagram schematically showing an arrangement of nozzle parts at the joint part shown inFIG. 11. Since there is no nozzle combining region at the joint part350C shown inFIG. 11, the switching between the projected nozzle array281D and the projected nozzle array281E is performed at the connection position351between the first head module200B and the second head module200C, as shown inFIG. 12.

The joint parts350shown inFIG. 9andFIG. 10and the joint part350C shown inFIG. 11are examples. Although the arrangement of the nozzle parts at the joint part varies depending on the arrangement of the nozzle parts in head modules to be used, an ink-jet head production method according to the embodiment can be applied to any arrangement of the nozzle parts.

[Image Quality at Joint Part]

In an ink-jet head having a structure in which a plurality of head modules are arrayed, the deterioration in image quality is likely to appear, at the joint part between adjacently arranged head modules. As a cause for the deterioration in image quality at the joint part, there is a mechanical positional deviation when the head modules are attached. Further, as another cause, there is a lag in ejection timing between the head modules. Furthermore, there is a complex cause of them.

The study by the inventor of the present invention has revealed that the deterioration in image quality at the joint part appears in the case where the ejection volume of the nozzle part arranged at the joint part is less than a standard ejection volume of the head module.

Here, the ejection volume is the volume of unit liquid that is ejected from the nozzle part. The unit liquid is a liquid that forms one dot. As the mode in which the unit liquid is ejected, there is a mode in which all of the liquid that forms one dot is ejected by one ejection operation, or a mode in which all of the liquid that forms one dot is ejected by multiple ejection operations.

The above study for the ejection volume was performed for a droplet type that is highest in use frequency in the case of a high-definition printing. Examples of the high-definition printing include a printing in which the print resolution is 1200 dots per inch. Examples of the droplet type that is highest in use frequency in the case of the high-definition printing include a droplet type having the smallest volume that is used in printing. By the droplet having the smallest volume, a dot having the smallest size that is used in printing is formed.

[Description of Adjustment of Ejection Volume]

For the ink-jet head, there is decided an average ejection volume target value, which is a target value of an average ejection volume that is decided from a specification of the ink-jet recording apparatus. The average ejection volume is an average value of the ejection volumes of all nozzle parts.

In the ink-jet head having a structure in which the plurality of head modules are arrayed, the adjustment of the ejection volume for matching the actual average ejection volume for each head module with the ejection volume target value of the ink-jet head is performed for each head module.

FIG. 13is an explanatory diagram of the amplification factor adjustment of the drive voltage. The horizontal series inFIG. 13indicates time, and the unit is microsecond. The “micro” is an auxiliary unit showing 10−6-fold. The vertical series inFIG. 13indicates voltage, and the unit is volt.

A drive voltage360shown inFIG. 13is a waveform of the drive voltage that is supplied to the piezoelectric element230when the ink is ejected from the nozzle part281shown inFIG. 4. The drive voltage360shown inFIG. 13is a voltage for ejecting the ink in the droplet state from the nozzle opening280shown inFIG. 4, by transforming the piezoelectric element230shown inFIG. 4to contract the pressure chamber218, expanding the contracted pressure chamber218to push put the ink in the pressure chamber218from the nozzle opening280, and restoring the expanded pressure chamber218to the former state to divide the ink pushed from the nozzle opening280.

That is, the drive voltage360shown inFIG. 13is a so-called pull-push waveform. A voltage E1of the drive voltage360is a voltage that is supplied to the piezoelectric element230when the piezoelectric element230shown inFIG. 4is put into a static state.

A voltage E2of the drive voltage360shown inFIG. 13is a voltage that is supplied to the piezoelectric element230when the pressure chamber218is put into the contracted state by transforming the piezoelectric element230shown inFIG. 4.

A voltage E3of the drive voltage360shown inFIG. 13is a voltage that is supplied to the piezoelectric element230when the pressure chamber218is put into the expanded state by transforming the piezoelectric element230shown inFIG. 4.

By changing the waveform of the drive voltage360shown inFIG. 13, it is possible to adjust the ejection voltage of the ink that is ejected from the nozzle part.

There is an individual difference in the ejection performance of the head module, and even when an identical drive voltage is supplied, there is a possibility that in some head modules, the actual ejection volumes are less than the target value of the ejection volume, and in some head modules, the actual ejection volumes are greater than the target value of the ejection voltage.

Hence, the drive voltage is adjusted for each head module, and the actual ejection volumes of all head modules are adjusted to the target value of the ejection volume of the ink-jet head.

A drive voltage362shown inFIG. 13is a drive voltage that is applied to a head module in which the average ejection volume is less than the average ejection volume target value, and has a waveform resulting from multiplying the waveform of the drive voltage360by an amplification factor exceeding 1.

A drive voltage364shown inFIG. 13is a drive voltage that is applied to a head module in which the average ejection volume exceeds the average ejection volume target value, and has a waveform resulting from multiplying the waveform of the drive voltage360by an amplification factor exceeding0and being less than 1.

FIG. 14is an explanatory diagram of the amplification factor of the drive voltage. The horizontal series inFIG. 14indicates the amplification factor of the drive voltage. The vertical series inFIG. 14indicates the average ejection volume for each head module, and the unit is picoliter. The average ejection volume of the head module is an average value of the ejection volumes of all nozzle parts that are included in the head module, and is calculated by dividing the total sum of the ejection volumes of the nozzle parts by the total number of the nozzle parts. Reference character G shown inFIG. 14designates the target value of the ejection volume that is applied to the ink-jet head.

To a head module having an ejection characteristic to which reference numeral370is assigned inFIG. 14, A1is applied as the amplification factor of the drive voltage. To a head module having an ejection characteristic to which reference numeral372is assigned, A2is applied as the amplification factor of the drive voltage. To a head module having an ejection characteristic to which reference numeral374is assigned, A3is applied as the amplification factor of the drive voltage.

In this way, the amplification factor of the drive voltage is decided for each head module, and the drive voltage is adjusted for each head module. Thereby, the average ejection volumes of all head modules constituting the ink-jet head are adjusted to the average ejection volume target value that is applied to the ink-jet head.

[Description of Ejection Volume Distribution]

Generally, the head module has a distribution of the ejection volume, in the longitudinal direction of the ink-jet head.FIG. 15toFIG. 22are explanatory diagrams of the ejection volume distribution of the head module.

The horizontal series inFIG. 15toFIG. 22indicates nozzle numbers. The nozzle numbers are consecutive numbers that are assigned in order from a number-1 nozzle part to a number-M nozzle part, where the number-1 nozzle part is the nozzle part at one end or the other end of a projected nozzle array that is an array resulting from projecting the plurality of nozzle parts provided in the head module in the longitudinal direction of the ink-jet head and arranging them along the longitudinal direction of the ink-jet head, and the number-M nozzle part is the nozzle part at the opposite end to the number-1 nozzle part.

In the embodiment, the number-1 nozzle is arranged at the end on the left side inFIG. 1andFIG. 3, and the number-M nozzle is arranged at the end on the right side. Then, the end where the number-1 nozzle is arranged is the end on the negative side in the longitudinal direction of the ink-jet head, and the end where the number-M nozzle is arranged is the end on the positive side in the longitudinal direction of the ink-jet head.

The end on the negative side of the head module in the embodiment corresponds to one end of the head module, and the end on the positive side of the head module in the embodiment corresponds to the other end of the head module.

The vertical series inFIG. 15toFIG. 22indicates the ejection volume for each nozzle part. The unit of the vertical series is picoliter. The prefix “pico” is an auxiliary unit showing 10−12-fold. The ejection volume of the nozzle part whose nozzle number is 1 is V1, and the ejection volume of the nozzle part whose nozzle number is M is VM.

The ejection volume distributions of the head module shown inFIG. 15toFIG. 17are ejection volume distributions when the slope is positive. The slope of the ejection volume distribution of the head module is expressed as (VM−V1) /(M−1), by using the ejection volume V1of the nozzle part whose nozzle number is 1, the ejection volume VMof the nozzle part whose nozzle number is M, and the total number M of the nozzle parts.

The slope of the ejection volume distribution of the head module is defined as being positive in the case of VM−V1>0, that is, M>V1.

The ejection volume distributions of the head module shown inFIG. 18toFIG. 20are ejection volume distributions when the slope is negative. The slope of the ejection volume distribution of the head module is defined as being negative in the case of VM−V1<0, that is, VM<V1.

The ejection volume distributions of the head module shown inFIG. 21andFIG. 22are ejection volume distributions when the slope is zero. The slope of the ejection volume distribution of the head module is defined as zero in the case of VM−V1=0, that is, VM=V1.

In the embodiment, the slope of the ejection volume distribution is defined using the ejection volume of the nozzle part that is the nozzle part at one end of the head module and whose nozzle number is 1 and the ejection volume of the nozzle part that is the nozzle part at the other end of the head module and whose nozzle number is M. However, the slope of the ejection volume distribution may be defined, for example, using the ejection volume of ten nozzle parts ranging from the nozzle part whose nozzle number is 1 to the nozzle part whose nozzle number is 10 as the ejection volume of the nozzle part at one end part of the head module, and using the ejection volume of ten nozzle parts ranging from the nozzle part whose nozzle number is M-9 to the nozzle part whose nozzle number is M as the ejection volume of the nozzle part at the other end part of the head module.

In other words, the slope of the ejection volume distribution of the head module can be defined using the ejection volume of a single or a plurality of nozzle parts arranged at one end part of the head module and the ejection volume of a single or a plurality of nozzle parts arranged at the other end part of the head module on the projected nozzle array shown inFIG. 3.

Examples of the one end part of the head module and the other end part of the head module include regions where a plurality of nozzles parts to be arranged at both ends of the head module or at the joint parts are arranged.

In the case where the slope of the ejection volume distribution of each head module is defined using the ejection volume of a plurality of nozzles, a representative value such as average value, maximum value or minimum value can be used as the ejection volume of the plurality of nozzles. In the embodiment, the average value is used as the ejection volume of the plurality of nozzles.

In the embodiment, a mode in which the slope of the ejection volume distribution of each head module is derived as the difference in the ejection volume is exemplified, but the slope of the ejection volume distribution of each head module can be derived also as the ratio of the ejection volume. The slope of the ejection volume distribution of each head module may be derived by dividing the ejection volume of the nozzle part at the other end part of the head module by the ejection volume of the nozzle part at the one end part of the head module.

In the case where the slope of the ejection volume distribution of each head module is derived by dividing the ejection volume of the nozzle part at the other end part of the head module by the ejection volume of the nozzle part at the one end part of the head module, a slope of 0 or greater and less than 1 corresponds to a negative slope in the case where the slope of the ejection volume distribution of each head module is derived as the difference in the ejection volume, and a slope of 1 or greater can be treated as a positive slope in the case where the slope of the ejection volume distribution of each head module is derived as the difference in the ejection volume.

As shown inFIG. 15toFIG. 22, the head module has a distribution of the ejection volume in the longitudinal direction of the ink-jet head, and therefore, at the joint part350shown inFIG. 6andFIG. 7, there can be a difference between the ejection volume of the nozzle parts belonging to the first head module200B and the ejection volume of the nozzle parts belonging to the second head module200C, even when the average ejection volume of the each head module is adjusted to the average ejection volume target value of the ink-jet head.

Hence, as shown below, the arrangement of the head modules is set in consideration of the ejection volumes of the nozzle parts arranged at the joint parts among three head modules that are arranged at adjacent positions, and thereby, the deterioration in image quality at the joint parts is suppressed.

[Detailed Description of Structure of Ink-Jet Head]

FIG. 23is an explanatory diagram schematically showing a structure example of the ink-jet head.FIG. 23illustrates the relation of the ejection volume distributions of the first head module200B, the second head module200C and the third head module200D, in the form of a graph.

The horizontal series inFIG. 23indicates the position in the longitudinal direction of the ink-jet head. The vertical series inFIG. 23indicates the ejection volume of the head module. InFIG. 23, similarly toFIG. 15toFIG. 22, the nozzle number increases from left to right, and the head module number increases from left to right.

The first head module200B, second head module200C and third head module200D shown inFIG. 23are three head modules arranged at arrangement positions that are adjacent in the longitudinal direction of the ink-jet head. At each end of the first head module200B, the second head module200C and the third head module200D, the joint part350is provided.

The longitudinal direction of the ink-jet head is a mode of the single direction. The single direction can be not only the direction from left to right inFIG. 23but also the direction from right to left. In the following description, the direction from left to right inFIG. 23, that is, the direction of the increase in the head module number corresponds to the single direction.

The first head module200B, second head module200C and third head module200D shown inFIG. 23are arranged in order from the head module that is smallest in the slope of the ejection volume distribution. That is, the first head module200B, the second head module200C and the third head module200D have such an arrangement that the slopes of the ejection volume distributions are in ascending order.

The slope Gr1of the ejection volume distribution of the first head module200B, the slope Gr2of the ejection volume distribution of the second head module200C and the slope Gr3of the ejection volume distribution of the third head module200D have a relation of Gr1≦Gr2≦Gr3. Further, in each of the first head module200B, the second head module200C and the third head module200D, the slope of the ejection volume distribution is positive. Although the illustration is omitted, the slope Gr1of the ejection volume distribution of the first head module200B, the slope Gr2of the ejection volume distribution of the second head module200C and the slope Gr3of the ejection volume distribution of the third head module200D may have a relation of Gr1≧Gr2≧Gr3. That is, the first head module200B, the second head module200C and the third head module200D may have a descending-order arrangement so as to be arrayed in order from the head module that is largest in the slope of the ejection volume distribution.

Further, in the first head module200B, the second head module200C and the third head module200D, the slopes of the ejection volume distributions may be all negative.

FIG. 24is an explanatory diagram schematically showing an alternative structure example of the ink-jet head. In the alternative structure example of the ink-jet head shown inFIG. 24, head modules in which the slopes of the ejection volume distributions are positive and head modules in which the slopes of the ejection volume distributions are negative are mixed.

In the first head module200B and second head module200C shown inFIG. 24, the slopes of the ejection volume distributions are positive. In the third head module200D, the slope of the ejection volume distribution is negative.

The first head module200B, second head module200C and third head module200D shown inFIG. 24have such an arrangement that the slopes of the ejection volume distributions are in descending order. Further, in the alternative structure example of the ink-jet head shown inFIG. 24, the positive/negative sign of the slope of the ejection volume distribution switches at one position between the second head module200C and the third head module200D.

Although the illustration is omitted, also in the case where the first head module200B, the second head module200C and the third head module200D have such an arrangement that the slopes of the ejection volume distributions are in ascending order, the positive/negative sign of the slope of the ejection volume distribution switches at one position, when head modules in which the slopes of the ejection volume distributions are positive and head modules in which the slopes of the ejection volume distributions are negative are mixed.

FIG. 25is an explanatory diagram schematically showing a structure example of an ink-jet head according to a comparative example. When the slopes of the ejection volume distributions of a first head module200K, second head module200L and third head module200M shown inFIG. 25are Gr11, Gr12and Gr13respectively, Gr11≧Gr12and Gr12≦Gr13hold, and the first head module200K, the second head module200L and the third head module200M have neither such an arrangement that the slopes of the ejection volume distributions are in ascending order nor such an arrangement that the slopes of the ejection volume distributions are in descending order.

Further, in the first head module200K and the third head module200M, the slopes of the ejection volume distributions are positive. In the second head module200L, the slope of the ejection volume distribution is negative.

Furthermore, the positive/negative sign of the slope of the ejection volume distribution switches between the first head module200K and the second head module200L, and the positive/negative sign of the slope of the ejection volume distribution switches between the second head module200L and the third head module200M. That is, the first head module200K, the second head module200L and the third head module200M have such an arrangement that the positive/negative sign of the slope of the ejection volume distribution switches at two positions.

In the ink-jet head according to the comparative example shown inFIG. 25, in some cases, the ejection volume at the joint part between the head modules becomes too small, or the ejection volume at the joint part between the head modules becomes too large, and there is a possibility of the occurrence of the deterioration in image quality at the joint part between the head modules.

On the other hand, when the three head modules arranged at the arrangement positions that are adjacent in the longitudinal direction of the ink-jet head have such an arrangement that the slopes of the ejection volume distributions are in ascending order or such an arrangement that the slopes of the ejection volume distributions are in descending order as shown inFIG. 23andFIG. 24, it is possible to make the ejection volume at the joint part between the head modules close to the average of the ejection volume in the whole of the head module, and it is possible to suppress the decrease in the ejection volume at the joint part.

Further, when the slopes of the ejection volume distributions are all positive or all negative in the three head modules arranged at the arrangement positions that are adjacent in the longitudinal direction of the ink-jet head, it is possible to suppress the increase in the ejection volume, and it is possible to prevent the degradation in the graininess of printed images when the ink-jet head is used in the printing of images, which appears in the case where the ejection volume is too large.

In the embodiment, the ink-jet head including three head modules has been described, but the above head module arrangement can be applied to an ink-jet head having a structure in which three or more head modules are arranged along a single direction. When N is an integer of 3 or more, a mode in which the slopes of the ejection volume distributions of all N head modules are positive or negative, or a mode in which the slopes of the ejection volume distributions are in ascending order or in descending order is possible.

The arrangement of three or more head modules can be actualized by acquiring the slope of the ejection volume distribution for all head modules, executing a permutation process whose variable is the slope of the ejection volume distribution for the head modules, and deciding the arrangement of the head modules.

When each head module includes an ejection volume distribution slope storage unit in which the slope of the ejection volume distribution is stored, it is possible to acquire the slope of the ejection volume of each head module exactly and surely.

<Application Example When Positive and Negative of Slope of Ejection Volume Distribution Are Mixed>

In the case where head modules in which the slopes of the ejection volume distributions are positive and head modules in which the slopes of the ejection volume distributions are negative are mixed, it is preferable to be a mode of arranging a head module in which the slope of the ejection volume distribution is 10 percent or less of the maximum value of the slope of the ejection volume distribution, at an arrangement position where the positive/negative sign of the slope of the ejection volume distribution switches.

In the case where head modules in which the slopes of the ejection volume distributions are positive and head modules in which the slopes of the ejection volume distributions are negative are mixed, it is more preferable to be a mode of arranging a head module in which the slope of the ejection volume distribution is zero or a head module in which the absolute value of the slope of the ejection volume distribution is the minimum, at an arrangement position where the positive/negative sign of the slope of the ejection volume distribution switches.

<Arrangement of Head Modules When Considering Impact Interference>

It can be said that the speed of a droplet is relatively high when the volume of the droplet is relatively large. It can be said that the impact position deviation is relatively small when the speed of the droplet is relatively high. As for two droplets that can contact on the medium, in consideration of the impact interference of the droplets that impact on the medium, it is desirable that the droplet having a larger volume impact earlier than the droplet having a smaller volume.

For example, focusing on the joint part350between the first head module200B and the second head module200C shown inFIG. 6, in the case where one droplet of two droplets that can contact on the medium is ejected from the nozzle part of the first head module200B and the other droplet is ejected from the nozzle part of the second head module200C, the one droplet ejected from the nozzle part of the first head module200B impacts on the medium earlier than the other droplet ejected from the nozzle part of the second head module200C.

Therefore, as for the first head module200B and the second head module200C, it is desirable that the head modules be arranged at the respective arrangement positions such that the ejection volume of the nozzle part arranged at the joint part350of the first head module200B exceeds the ejection volume of the nozzle part arranged at the joint part350of the second head module200C.

Further, it is desirable that the head modules be arranged at the respective arrangement positions such that the slope of the ejection volume distribution of the first head module200B and the slope of the ejection volume distribution of the second head module200C are both positive.

<Treatment When Slope of Ejection Volume Distribution is Zero>

In the case where the slope of the ejection volume distribution is zero, the slope of the ejection volume distribution is treated as being positive or negative. In the embodiment, for convenience, in the case where the slope of the ejection volume distribution is zero, the slope of the ejection volume distribution is treated as being positive.

Next, an ink-jet head production method according to the embodiment is described in detail. The ink-jet head production method in the embodiment corresponds to the liquid ejection head production method.

The ink-jet head production method according to the embodiment includes a production method for the reproduction of the ink-jet head when a single or a plurality of head modules of the plurality of head modules constituting the ink-jet head is replaced.

In the ink-jet head production method according to the embodiment, when N is an integer of 3 or more, N head modules constituting the ink-jet head are collectively selected or are sequentially selected, and the N selected head modules are arranged in the order of the slope of the ejection volume distribution. For the ink-jet head, a target value of the average value of the ejection volume in the whole of the ink-jet head has been set in advance. Further, the head module to be used has been adjusted to an arbitrary target value of the ejection volume. It is preferable that the adjustment of the target value of the ejection volume of the head module be the adjustment to the target value of the average value of the ejection volume in the whole of the ink-jet head.

The order of the slope of the ejection volume distribution may be the ascending order, or may be the descending order. The ascending order of the slope of the ejection volume distribution in the embodiment means the case where the slope of the ejection volume distribution monotonically increases from the head module at one end of the ink-jet head21shown inFIG. 1toward the head module at the other end.

Further, the descending order of the slope of the ejection volume distribution in the embodiment means the case where the slope of the ejection volume distribution monotonically decreases from the head module at one end in the longitudinal direction of the ink-jet head21shown inFIG. 1toward the head module at the other end.

In the embodiment, for convenience, the one end in the longitudinal direction of the ink-jet head21shown inFIG. 1is the end on the left side inFIG. 1.

FIG. 26is a flowchart showing a flow of the procedure of an ink-jet head production method. InFIG. 26, although the illustration is omitted, the target value of the ejection volume in the whole of the ink-jet head has been set in advance. Further, each head module has been adjusted to an arbitrary target value of the ejection volume.

In a head module selection step S10shown inFIG. 26, N head modules are selected. After the N head modules are selected, the flow proceeds to step S12.

In an ejection volume distribution slope acquisition step shown in step S12, the slope of the ejection volume distribution of each of the N head modules is acquired.

After the slope of the ejection volume distribution of each of the N head modules is acquired, the flow proceeds to step S14. In an ejection volume distribution slope storage step shown in step S14, the slope of the ejection volume distribution of each of the N head modules acquired in the ejection volume distribution slope acquisition step S12is stored in a previously decided memory.

After the slope of the ejection volume distribution of each of the N head modules is stored in the ejection volume distribution slope storage step S14, the flow proceeds to step S16. In the sort condition setting step shown in step S16, a sort condition for a sort process is set. The sort condition includes the information of whether to execute an ascending-order sort or a descending-order sort. The sort condition may be automatically set depending on the specification of the ink-jet head, or may be manually set by an operator. The sort process herein is synonymous with the permutation process.

After the sort condition is set in the sort condition setting step S16, the flow proceeds to step S18. In a sort step shown in step S18, the sort is executed while the slope of the ejection volume distribution of each of the N head modules stored in the ejection volume distribution slope storage step S14is adopted as the variable.

In the sort step S18, the ascending-order sort or the descending-order sort is executed based on the sort condition set in the sort condition setting step S16.

In the sort step S18, when the sort is executed while the slope of the ejection volume distribution of each of the N head modules is adopted as the variable, head module numbers of 1 to n are assigned to the N head modules respectively, based on the sort result.

After the head module numbers of 1 to n are assigned to the N head modules respectively in the sort step S18, the flow proceeds to step S20. In a head module number storage step S20shown in step S20, the head module number n for each head module, which is the sort result in the sort step S18and indicates the arrangement of the N head modules, is stored.

After the arrangement of the N head modules is stored in the head module number storage step S20, the flow proceeds to step S22. In an assembly step S22shown in step S22, the N head modules are arranged based on the head module numbers assigned to the N head modules, and the assembly of the ink-jet head is executed.

In the assembly step S22, the head module numbers assigned to the N head modules may be displayed. After the assembly step S22, an inspection step of inspecting whether the N head modules are arranged in the order of the head module numbers that are decided in the order of the slope of the ejection volume distribution may be included.

The steps shown inFIG. 26can be merged or divided when appropriate. For example, the sort condition setting step S16and the sort step S18may be merged, or the ejection volume distribution slope acquisition step S12and the ejection volume distribution slope storage step S14may be merged.

FIG. 26exemplifies a mode of collectively selecting the N head module and collectively executing the sort process for the N head modules. However, a mode of selecting the N head modules one by one as a candidate head module, determining whether the candidate head module satisfies a magnitude relation of the slope of the ejection volume distribution with a head module for which the arrangement is previously decided, and sequentially repeating the process for the N head modules is possible.

FIG. 27is a flowchart showing a flow of the procedure of an ink-jet head production method, and shows a flow of the procedure in the mode of performing the sequential process. In the ink-jet head production method described below, the head module to be arranged at the arrangement position of each head module number n is set in the order of the head module number n, from a head module whose head module number n is 1.

First, a head module whose head module number n is 1, which is a head module to be arranged at one end in the longitudinal direction of the ink-jet head, is decided. Next, a head module whose head module number n is 2 is decided.

In this way, in the order of the head module number n, head modules are decided for the arrangement positions of the head module numbers n of 1 to N.

In an initialization step shown in step S100ofFIG. 27, the head module number n is initialized. That is, zero is substituted for the head module number n.

The head module numbers n are numbers that are assigned in order from a number-1 head module, where the number-1 head module is the head module at one end in the longitudinal direction of the ink-jet head. The head module number n is an integer of 1 or more, and an integer equal to or less than the total number N of the head modules provided in the ink-jet head is used. In the embodiment, for convenience, the one end in the longitudinal direction of the ink-jet head21shown inFIG. 1is the end on the left side inFIG. 1.

In a head module number advancement step shown in step S102, a process of incrementing the head module number n by one is executed. That is, after a head module to be set as the number-n head module is decided, the flow proceeds to a process of setting the number-n+1 head module.

In an all-module setting determination step shown in step S104, whether the head module number n updated in the head module number advancement step S102has been set for all head modules that are arranged at the arrangement positions of 1 to N is determined. In the case of a NO determination in which all head modules have been decided in step S104, that is, in the case of n>N, the ink-jet head production method is ended. In the case of a YES determination in which there is an undecided head module in the all-module setting determination step S104, that is, in the case of 1≦n≦N, the flow proceeds to step S106.

In a candidate head module selection step shown in step S106, a candidate head module that is the object of the process is selected. After the candidate head module is selected in the candidate head module selection step S106, the flow proceeds to step S108. The candidate head module selection step is a mode of the head module selection step, and corresponds to the selection step of sequentially selecting three or more head modules.

In the case where the head module number n is 1, the candidate head module selection step S106corresponds to the first candidate head module selection step of selecting the first candidate head module. In the case where the head module number n is 2 or more, the candidate head module selection step S106corresponds to the second candidate head module selection step of selecting the second candidate head module, or the third candidate head module selection step of selecting the third candidate head module.

In an ejection volume distribution slope acquisition step shown in step S108, the slope of the ejection volume distribution of the candidate head module is acquired, and in an ejection volume distribution slope storage step shown in step S110, the acquired slope of the ejection volume distribution of the candidate head module is stored in a previously decided memory.

As the ejection volume distribution slope acquisition step S108, a mode of acquiring the slope of the ejection volume distribution of the first candidate head module, a mode of acquiring the slope of the ejection volume distribution of the second candidate head module, or a mode of acquiring the slope of the ejection volume distribution of the third candidate head module is possible. Further, a mode of acquiring the slope of the ejection volume distribution of the second candidate head module and the slope of the ejection volume distribution of the first candidate head module, or a mode of acquiring the slope of the ejection volume distribution of the third candidate head module and the slope of the ejection volume distribution of the first head module is possible.

As the ejection volume distribution slope storage step, a mode of storing the slope of the ejection volume distribution of the first candidate head module, a mode of storing the slope of the ejection volume distribution of the second candidate head module, or a mode of storing the slope of the ejection volume distribution of the third candidate head module is possible.

A mode of acquiring the slope of the ejection volume distribution of the first candidate head module as the slope of the ejection volume distribution of the first head module in the ejection volume distribution slope acquisition step S108is possible. A mode of acquiring the slope of the ejection volume distribution of the second candidate head module as the slope of the ejection volume distribution of the second head module in the ejection volume distribution slope acquisition step S108is possible. A mode of acquiring the slope of the ejection volume distribution of the third candidate head module as the slope of the ejection volume distribution of the third head module in the ejection volume distribution slope acquisition step S108is possible.

After the slope of the ejection volume distribution of the candidate head module is acquired in the ejection volume distribution slope acquisition step S108and the slope of the ejection volume distribution of the candidate head module is stored in the ejection volume distribution slope storage step5110, the flow proceeds to step S112.

In a determination step shown in step S112, whether the slope of the ejection volume distribution of the candidate head module acquired in the ejection volume distribution slope acquisition step S108satisfies the condition of the ascending order or descending order with the slope of the ejection volume distribution of the head module previously arranged at the position adjacent to the candidate head module is determined.

That is, in the determination step S112, whether the slope of the ejection volume distribution of the candidate head module and the slope of the ejection volume distribution of the head module previously arranged at the position adjacent to the candidate head module satisfy the relation of the ascending order or descending order for the two adjacent head modules is determined.

In the case where the head module number n is2or more, in the determination step S112, the slope of the ejection volume distribution of the head module that is arranged at the arrangement position adjacent to the candidate head module and that is compared with the candidate head module in the slope of the ejection volume distribution is read.

In the case where the slope of the ejection volume distribution of the candidate head module satisfies the condition of the ascending order or descending order with the slope of the ejection volume distribution of the head module previously arranged at the position adjacent to the candidate head module, which the case of the YES determination in the determination step S112, the flow proceeds to step S114. In a setting step shown in step S114, the candidate head module is set as the number-n head module. In the case where the head module number n is 1 or in the case where the head module number n is 2, the determination step S112is skipped, and the flow proceeds to the setting step S114.

On the other hand, in the case where the slope of the ejection volume distribution of the candidate head module does not satisfies the condition of the ascending order or descending order with the slope of the ejection volume distribution of the head module previously arranged at the position adjacent to the candidate head module, which is the case of the NO determination in the determination step S112, the flow proceeds to the candidate head module selection step S106, and another head module is selected as the candidate head module. Thereafter, the steps of step S106to step S112are repeatedly executed until the head module to be set is found.

After the head module whose head module number is n is set in the setting step S114, the steps of step S102to step S114are repeatedly executed until the N head modules are set.

Thus, the ink-jet head in which three or more head modules arranged at positions that are adjacent in the longitudinal direction of the ink-jet head have an arrangement of the ascending order or descending order of the slope of the ejection volume distribution is produced.

FIG. 27exemplifies the mode of setting the head modules in the order of the head module number from the head module whose head module number is 1 while the head module at one end of the ink-jet head is adopted as the head module whose head module number is 1. However, the head modules may be set in the order from a head module other than both ends of the ink-jet head, for example, from the head module at the center, to both sides.

In the case where the head modules are set in the order from a head module other than both ends of the ink-jet head toward both sides, by setting head modules to one end side in the descending order of the slope of the ejection volume distribution and setting head modules to the other end side in the ascending order of the slope of the ejection volume distribution, the arrangement of the head modules in which the slopes of the ejection volume distributions are in ascending order as the whole of the ink-jet head is actualized.

By setting the head modules to the one end side in the ascending order of the slope of the ejection volume distribution and setting the head modules to the other end side in the descending order of the slope of the ejection volume distribution, the arrangement of the head modules in which the slopes of the ejection volume distributions are in descending order as the whole of the ink-jet head is actualized.

In the case where the head modules are set in the order from a head module other than both ends of the ink-jet head toward both sides and where head modules in which the slopes of the ejection volume distributions are positive and head modules in which the slopes of the ejection volume distributions are negative are mixed, it is possible to perform in parallel a process for the head modules in which the slopes of the ejection volume distributions are positive and a process for the head modules in which the slopes of the ejection volume distributions are negative, by adopting, as the reference position, a position where the positive and negative of the slope of the ejection volume distribution switches.

In the embodiment, the mode in which all head modules constituting the ink-jet head are arranged in the ascending order or descending order of the slope of the ejection volume distribution had been exemplified. However, in an ink-jet head constituted by three or more head modules, it is only necessary that at least three head modules that are adjacent in the longitudinal direction of the ink-jet head are arranged in the ascending order or descending order of the slope of the ejection volume distribution.

For example, in an ink-jet head constituted by five head modules, when the three head modules except the two head modules arranged at both ends in the longitudinal direction of the ink-jet head are arranged in the ascending order or descending order of the slope of the ejection volume distribution, it is possible to secure a certain level of ejection performance, in a region where the ejection frequency is high.

<Care for Replacement of Head Module>

FIG. 28is a flowchart showing a flow of the procedure of an ink-jet head production method, and shows a flow of the procedure in the case where an arbitrary one of the head modules constituting the ink-jet head is replaced.

The replacement procedure for the head module described below is a procedure in the case of replacing the second head module200C of the first head module200B, second head module200C and third head module200D shown inFIG. 23andFIG. 24.

In a candidate head module selection step shown in step S200ofFIG. 28, a candidate head module to be arranged at the arrangement position of a replacement-object head module is selected. After the candidate head module is selected in the candidate head module selection step S200, the flow proceeds to step S202.

In a candidate-head-module ejection volume distribution slope acquisition step shown in step S202, the slope of the ejection volume distribution of the candidate head module is acquired. After the slope of the ejection volume distribution of the candidate head module is acquired in the candidate-head-module ejection volume distribution slope acquisition step S202, the flow proceeds to step S204.

In an adjacent-head-module ejection volume distribution slope acquisition step shown in step S204, the slopes of the ejection volume distributions of the head modules arranged at the positions adjacent to the replacement-object head module are acquired.

In the case where the replacement-object head module is other than the head modules at both ends in the longitudinal direction of the ink-jet head, the slopes of the ejection volume distributions of the head modules arranged at the adjacent positions on both sides of the replacement-object head module are acquired.

In the case where the replacement-object head module is of the head modules at both ends in the longitudinal direction of the ink-jet head, a single head module is arranged at the position adjacent to the replacement-object head module, and a single slope is acquired as the slope of the ejection volume distribution of the head module arranged at the position adjacent to the replacement-object head module.

After the slope of the ejection volume distribution of the head module arranged at the position adjacent to the replacement-object head module is acquired in the adjacent-head-module ejection volume distribution slope acquisition step S204, the flow proceeds to step S206.

In a determination step shown in step S206, whether the slope of the ejection volume distribution of the candidate head module acquired in the candidate-head-module ejection volume distribution slope acquisition step S202and the slope of the ejection volume distribution of the head module arranged at the position adjacent to the candidate head module acquired in the adjacent-head-module ejection volume distribution slope acquisition step S204satisfy the condition of the ascending order or descending order is determined.

In the case where the slope of the ejection volume distribution of the candidate head module and the slope of the ejection volume distribution of the head module arranged at the position adjacent to the candidate head module satisfy the condition of the ascending order or descending order, which is the case of the YES determination in the determination step S206, the flow proceeds to step S208. In a setting step shown in step S208, the candidate head module is set as the replacement-object head module.

On the other hand, in the case where the slope of the ejection volume distribution of the candidate head module and the slope of the ejection volume distribution of the head module arranged at the position adjacent to the candidate head module do not satisfy the condition of the ascending order or descending order, which is the case of the NO determination in the determination step S206, the flow proceeds to the candidate-head-module selection step S200, and another head module is selected as the candidate head module. Thereafter, the steps of step S200to step S206are repeatedly executed until the head module to be set is found.

After the candidate head module is set as the replacement-object head module in the setting step S208, the ink-jet head production method is ended.

Thus, when an arbitrary head module is replaced, a head module allowing the slope of the ejection volume distribution to be in ascending order or descending order is arranged at the arrangement position of the replacement-object head module, in consideration of the slopes of the ejection volume distributions of the head modules arranged at the adjacent positions, and thereby, the ejection performance of the ink-jet head is maintained even when an arbitrary head module is replaced.

[Description of Derivation of Slope of Ejection Volume Distribution]

It is preferable to acquire the slope of the ejection volume distribution for each head module at the time of the shipment inspection of the head module.

The slope of the ejection volume distribution of the head module may be evaluated from the ejection volume of all nozzle parts provided in the head module, or may be evaluated using the ejection volume of the nozzle parts arranged at the joint parts that are present on both sides of the head module in the longitudinal direction of the ink-jet head. The ejection volume of the nozzle parts may be the total sum, or may be the average value.

For example, the slope of the ejection volume distribution of the head module can be obtained by subtracting the average value of the ejection volumes of the nozzle parts arranged at the joint part on one end of the head module in the longitudinal direction of the ink-jet head from the average value of the ejection volumes of the nozzle parts arranged at the joint part on the other end of the head module in the longitudinal direction of the ink-jet head.

In the case where the average value of the ejection volumes of the nozzle parts arranged at the joint part on the one end of the head module in the longitudinal direction of the ink-jet head is 1.9 picoliter and the average value of the ejection volumes of the nozzle parts arranged at the joint part on the other end of the head module in the longitudinal direction of the ink-jet head is 2.1 picoliter, the slope of the ejection volume distribution of the head module is plus 0.2.

In the case where the average value of the ejection volumes of the nozzle parts arranged at the joint part on the one end of the head module in the longitudinal direction of the ink-jet head is 2.1 picoliter and the average value of the ejection volumes of the nozzle parts arranged at the joint part on the other end of the head module in the longitudinal direction of the ink-jet head is 1.9 picoliter, the slope of the ejection volume distribution of the head module is minus 0.2.

In the following, methods for deriving the ejection volume of each nozzle part are described. Suppose that the average of the ejection volume in the whole of each head module has been adjusted to the average ejection volume target value of the ink-jet head in advance, at the time of the execution of the methods for deriving the ejection volume of each nozzle part described below.

In other words, suppose that the amplification factor of the drive voltage of each head module has been evaluated in advance, at the time of the execution of the methods for deriving the ejection volume of each nozzle part.

In the case where redundant nozzles are included in the joint part, the ejection volumes of the redundant nozzles may be included in the ejection volume of the whole of each head module.

A dot diameter evaluation chart is formed, using an object head module. Examples of the dot diameter evaluation chart include a chart in which the dots formed by the nozzle parts are arranged in an isolated state.

FIG. 29is an explanatory diagram schematically showing an example of the dot diameter evaluation chart, and schematically illustrates a dot diameter evaluation chart380that is formed on the medium100using the head module200.FIG. 30is a partial enlarged view ofFIG. 29, and is an enlarged view of the region shown by a circle that is shown inFIG. 29while reference numeral382is assigned.

The dot diameter evaluation chart380shown inFIG. 29andFIG. 30is read using a scanner, a microscope or the like, and the diameter Ddof a dot384formed by each nozzle part is measured.

The diameter Ddof the dot formed by each nozzle part can be converted into the ejection volume Vdof each nozzle part, using an expansion ratio Gaddecided from the kind of the medium100on which the dot diameter evaluation chart380is formed and the surface treatment condition of the medium100on which the dot diameter evaluation chart380is formed. The relation of the ejection volume Vdof each nozzle part, the diameter Ddof the dot384formed by each nozzle part and the expansion ratio Gadis expressed as Vd=Dd/Gad.

Here, as the way to decide the expansion ratio Gad, the expansion ratio can be decided in advance, by printing the dot while feeding the medium in a state of ensuring that a liquid having a known volume is ejected from an arbitrary nozzle part, and using the known ejection volume and the diameter of the printed dot.

A line width evaluation chart is formed, using an object head module. Examples of the line width evaluation chart include a chart in which lines formed by the nozzle parts and having a certain length are arranged in an isolated state.

FIG. 31is an explanatory diagram schematically showing an example of the line width evaluation chart, and schematically illustrates a line width evaluation chart380A that is formed on the medium100using the head module200.FIG. 32is a partial enlarged view ofFIG. 31, and is an enlarged view of the region shown by a circle that is shown inFIG. 31while reference character382A is assigned.

The line width evaluation chart380A shown inFIG. 31andFIG. 32is read using a scanner, a microscope or the like, and the width DLof a line384A formed by each nozzle part is measured. The relation of the width DLof the line and the ejection volume VLis decided from the kind of the medium100on which the line width evaluation chart380A is formed and the surface treatment condition of the medium100on which the line width evaluation chart380A is formed, and therefore, by previously acquiring the information about the kind of the medium100on which the line width evaluation chart380A is formed and the information about the surface treatment condition of the medium100on which the line width evaluation chart380A is formed, it is possible to convert the measurement result of the width DLof the line384A formed by each nozzle part into the ejection volume VLof each nozzle part.

The relation of the ejection volume VLof each nozzle part, the width DLof the line384A formed by each nozzle part and a coefficient GaLto be decided from the kind or surface treatment condition of the medium100can be expressed as VL=DL/GaL.

The mass of the liquid ejected from each nozzle part of an object head module is measured, and the mass of the liquid ejected from each nozzle part is converted into the volume. For example, the ejection is performed from each nozzle part of the object head module a previously decided number of times, and the mass difference of the medium between before and after the ejection is measured. It is possible to keep the measurement accuracy constant, by increasing the number of times of the ejection. It is preferable that the number of times of the ejection be approximately ten thousands to one million.

The mass difference of the medium between before and after the ejection is the mass of the liquid that is ejected a previously decided number of times of the ejection. The mass of the liquid can be converted into the volume, using the specific gravity of the liquid.

The relation of the ejection volume Vwof each nozzle part, the mass W of the liquid ejected from each nozzle part, the specific gravity dwof the liquid and the number Twof times of the ejection of each nozzle part can be expressed as Vw=W/Tw/dw.

For maintaining a certain level of measurement accuracy and shortening the measurement period, the ejections from a plurality of nozzle parts may be simultaneously performed a previously decided number of times, and the mass difference of the medium between before and after the ejection may be measured. When the nozzle parts arranged at the joint part are applied as the plurality of nozzle parts, the mass of the liquid that is ejected from the nozzle parts arranged at the joint part is measured, and the ejection volume of the nozzle parts arranged at the joint part is evaluated.

FIG. 33is an explanatory diagram of an example in which the nozzle parts arranged at the joint part are applied as the plurality of nozzle parts. As shown inFIG. 33, the ejection volume of the nozzle parts arranged at a joint part350D on one end side in the longitudinal direction of the ink-jet head and the ejection volume of the nozzle parts arranged at a joint part350E on the other end side in the longitudinal direction of the ink-jet head are measured.

The ejection volume of each nozzle part in the case of using a plurality of nozzle parts is the value resulting from dividing the ejection volume VWof the nozzle parts in the above formula by the number of the nozzle parts that are measurement objects, and is evaluated as the average value of the ejection volume in the ejection when the plurality of nozzle parts are used.

<Modification of Method 3>

When the ejection volume is collectively measured for a plurality of nozzle parts in Method 3, all nozzle parts belonging to the nozzle array along the W-direction shown inFIG. 3can be applied as the plurality of nozzle parts. Further, the nozzle array may be a single array, or may be a plurality of arrays.

The ejection volume of the liquid can be measured using a micro-syringe, instead of the mass measurement of the liquid in Method 3.

FIG. 34is an explanatory diagram schematically showing the measurement of the ejection volume of the liquid with use of the micro-syringe. As shown inFIG. 34, a micro-syringe390is attached to a liquid supply part201of the head module200, and the movement amount on a scale of the micro-syringe390is measured.

The relation of the ejection volume Vsof each nozzle part, the movement amount S on the scale of the micro-syringe, the number Tsof times of the ejection of each nozzle part and the density Dsof the liquid can be expressed as Vs=S/Ts/Ds.

<Modification of Method 4>

When the ejection volume is collectively measured for a plurality of nozzle parts in Method 4, all nozzle parts belonging to the nozzle array along the W-direction shown inFIG. 3can be applied as the plurality of nozzle parts. Further, the nozzle array may be a single array, or may be a plurality of arrays. Furthermore, in the case where the nozzle parts to be arranged at the joint part are decided, the nozzle parts to be arranged at the joint part may be applied as the plurality of nozzle parts.

In the case where the ejection volume distribution of the head module can be approximated by a straight line, the slope of the ejection volume distribution of the head module can be measured by measuring the ejection volume of the whole of the head module and using the measurement result of the ejection volume of the whole of the head module. Method 5 is a measurement method by which the measurement error is small and the measurement accuracy is high.

FIG. 35is a conceptual diagram of the measurement of the slope of the ejection volume distribution according to Method 5.FIG. 36is an explanatory diagram of the slope of the ejection volume distribution of the head module that is derived by Method 5.

First, a head module filled with the liquid is prepared. As shown inFIG. 35, the whole of the head module200is divided into eight regions D1to D8. The division number of the head module200only needs to be three or more. By increasing the division number of the head module200, it is possible to improve the measurement accuracy. By decreasing the division number of the head module200, it is possible to shorten the measurement period and the computation period for the measurement result.

The ejection volume is measured for each of the eight regions D1to D8. As the measurement of the ejection volume, Method 3 can be applied. For example, the number of the nozzle parts of each of the regions D1to D8is set to 256, the ejection is performed from each nozzle part to the medium hundred thousand times, the mass of the liquid is measured, and the average value of the ejection volume is derived for each region.

The relation of the ejection volume VD, the mass WDof the liquid, the number TDof times of the ejection and the density DeDof the liquid is expressed as the ejection volume VD=WD/TD/DeD. Here, the number of the nozzle parts can be arbitrarily set.

As shown inFIG. 36, an approximation straight line396of the ejection volume distribution of the head module200shown inFIG. 35is derived based on the respective ejection volumes VD1to VD8for the regions D1to D8derived by the above formula. VDis the collective expression of VD1to VD8.

Then, the value of the ejection volume for the region D1on the approximation straight line396shown inFIG. 36is subtracted from the value of the ejection volume for the region D8on the approximation straight line396, and thereby, the slope of the ejection volume distribution of the head module200shown inFIG. 35is derived.

FIG. 37is an explanatory diagram schematically showing a measurement method for the ejection volume at the joint part with use of a density evaluation pattern. In Method 6, using the nozzle parts arranged at the joint part350of the head module200, a density evaluation pattern380B is formed on the medium100, the density of the density evaluation pattern380B is measured, and the measured density value of the density evaluation pattern380B is converted into the ejection volume of the nozzle parts arranged at the joint part350of the head module200.

First, the head module200filled with the liquid, and the medium100on which the density evaluation pattern380B is formed are prepared. The density evaluation pattern380B is formed on the medium100, by ejecting the liquid from the nozzle parts arranged at the joint part350of the head module200while feeding the medium100.

The feed direction of the medium100is the medium feed direction shown inFIG. 1while reference character Y is assigned. The length of the density evaluation pattern380B in the medium feed direction is decided from the standpoint of the accuracy of the density measurement of the density evaluation pattern380B. For the density measurement of the density evaluation pattern380B, an optical densitometer can be used. The optical densitometer may be a reflection type, or may be a transmission type.

The relation of the average value VDENof the ejection volumes of the nozzle parts arranged at the joint part350of the head module200and the density measurement value MVis expressed as VDEN=MV/KDEN. Here, KDENis a constant.

The constant KDENis a constant that is decided based on the kind of the medium100and the kind of the liquid. For example, in a state of ensuring that a liquid having a known volume is ejected from an arbitrary nozzle part, a pattern for density measurement that is the same as the density evaluation pattern380B shown inFIG. 37is formed, and the density of the pattern for density measurement is measured. Thereby, the constant KDENcan be derived from the measurement value of the pattern for density measurement and the known ejection volume. It is preferable that the constant KDENbe derived for each density setting value.

The constant KDENderived in this way is associated with the kind of the medium and the kind of the liquid, and is stored.

The ejection volume of the nozzle parts arranged at the joint part350of the head module200is evaluated from the density measurement value of the density evaluation pattern380B shown inFIG. 37, and then, the slope of the ejection volume distribution is evaluated from the ejection volume of the nozzle parts arranged at the joint part350of the head module200.

<Condition of Ejection Volume Measurement>

In the measurement of the ejection voltage of each nozzle part, it is preferable to perform the ejection while applying the highest printing duty that can be used in the actual printing. The printing duty corresponds to the liquid ejection duty.

Generally, in the ink-jet head, in the case where the ejection volume to be ejected in a unit of time within the same head module is relatively large, a cross talk occurs, and the ejection volume distribution within the head module changes. In addition, in the image quality for the case where the printing duty is high, the unevenness is visually recognized more easily than in the image quality for the case where the printing duty is low.

Therefore, it is preferable to evaluate the ejection volume for each nozzle part, using the measurement value of the ink ejected by applying the highest printing duty, which is an ejection condition in which a cross talk occurs easily and the unevenness is visually recognized easily.

Here, the high duty, as a guide, may be 80 percent or more of the maximum value of the volume of the ink droplet that can be used in the actual printing. In the case where multiple kinds of ink droplets different in volume are used in the actual printing, the maximum value of the volume of the ink droplet can be evaluated by multiplying the volumes of the respective kinds of ink droplets by the use ratios and adding the resulting values with respect to all kinds of ink droplets that are used.

For example, in the case where two droplet types of 2.0 picoliter and 6.0 picoliter are used at a use ratio of 50 percent, the maximum value of the volume of the ink droplet is calculated to 4.0 picoliter, and therefore, a printing duty by which the volume of the ink droplet is 3.2 picoliter or more and 4.0 picoliter or less may be applied.

Examples of the dot diameter evaluation chart to be formed in the above Method 1 include a configuration in which a high density pattern is formed by applying the highest printing duty, ink droplets having the smallest volume that is used in printing are ejected from the nozzle parts after the formation of the high density pattern and the ink droplets ejected from the nozzle parts are discretely arranged.

[Application Example of System Invention]

It is possible to configure an ink-jet head production system that includes an apparatus corresponding to the steps shown inFIG. 26toFIG. 28.

FIG. 38is a block diagram showing a schematic configuration of the ink-jet head production system. The ink-jet head production system in the embodiment is a mode of the liquid ejection head production system.

In an ink-jet head production system400shown inFIG. 38, a system control unit402integrally controls the units of the system.

The ink-jet head production system400includes a head module selection unit404that selects head modules that are candidates to be arranged at the arrangement positions of the head module numbers of 1 to n, an ejection volume distribution slope acquisition unit406that acquires the slopes of the ejection volume distributions of the head modules selected by the head module selection unit404, a sort condition setting unit408that sets a sort condition for sorting the head modules selected by the head module selection unit404while adopting the slope of the ejection volume distribution as the variable, and a sort unit410that executes the sort based on the sort condition set by the sort condition setting unit408.

The ink-jet head production system400includes a storage unit412in which the head module numbers respectively decided for the head modules based on the sort result of the sort unit410are stored.

Further, the ink-jet head production system400can include devices that actualize the functions and processes of the steps in the ink-jet head production method described previously. The ink-jet head production system400includes a determination unit414that determines whether the slopes of the ejection volume distributions of three or more adjacent head modules are in the ascending order or descending order, a head module setting unit416that sets, as the three or more adjacent head modules, head modules for which the determination unit414determines that the slopes of the ejection volume distributions are in the ascending order or descending order, an assembly unit417that executes the arrangement based on the arrangement order set by the head module setting unit416, and an average ejection volume target value setting unit418that sets the target value of the ejection volume in the whole of the ink-jet head.

Furthermore, the ink-jet head production system400includes a display unit420that functions as a device that displays a variety of information, an operation unit422such as a keyboard and a mouse, an input unit424that functions as an input device for the information acquired from the exterior, and a storage unit426in which at least one piece of information of a variety of input information and the information to be used for computation and determination is stored.

Each constituent of the ink-jet head production system400shown inFIG. 38can be modified, deleted or added, when appropriate.

Furthermore, the above ink-jet head production system can function as a production support system that supports the optimization of the arrangement of the head modules.

[Configuration Example of Apparatus to Which Liquid Ejection Head is Applied]

Next, a configuration example of an apparatus to which an ink-jet head according to the embodiment is applied is described. In a liquid ejection apparatus including multiple ink-jet heads, which is an apparatus including an ink-jet head for each of multiple kinds of liquid, it is preferable to be a mode of having an identical configuration for all ink-jet heads.

In an ink-jet recording apparatus that forms a color image using multiple colors, for example, in the case where all head modules are arranged in the ascending order of the slope of the ejection volume distribution in an ink-jet head corresponding to an arbitrary one color, all head modules are arranged in the ascending order of the slope of the ejection volume distribution, also in ink-jet heads corresponding to the other colors.

In the ink-jet recording apparatus that forms a color image using multiple colors, when the slopes of the ejection volume distributions are in the ascending order or descending order for all ink-jet heads in this way, the appearance of the color deviation at the central part in the longitudinal direction of the ink-jet head is suppressed.

In the embodiments in the present invention described above, the constituent elements can be modified, added or deleted, when appropriate, in a range without departing from the spirit of the present invention. The present invention is not limited to the embodiments described above, and many modifications can be made by a person having common knowledge in the art, within the technical idea of the present invention.