Liquid discharge apparatus, liquid discharge method, and non-transitory recording medium

A liquid discharge apparatus includes a discharge device configured to discharge a liquid curable by active-energy rays onto a discharge target to form a liquid discharge surface, an irradiator configured to irradiate the liquid discharge surface with the active-energy rays, a carriage mounting the discharge device and the irradiator, the carriage configure to move in a main-scanning direction, and circuitry configured to relatively move the carriage and the discharge target in the main-scanning direction, relatively move the carriage and the discharge target in a sub-scanning direction perpendicular to the main-scanning direction, and control illuminance of the active-energy rays emitted from the irradiator to the liquid discharge surface on the discharge target according to a length of a discharge range of the liquid discharge surface on the discharge target in the main-scanning direction.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-139220, filed on Jul. 29, 2019, in the Japan Patent Office, the entire disclosures of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relate to a liquid discharge apparatus, a liquid discharge method, and a non-transitory recording medium.

Related Art

A liquid discharge apparatus irradiates an active-energy ray curable ink discharged from the liquid discharge apparatus with an active energy rays such as ultraviolet (UV) light to cure the active-energy ray curable ink.

In such a technique, curing wrinkles may occur due to curing shrinkage at a boundary between a cured region cured by irradiation with active-energy rays and an unirradiated uncured region in an ink region of the discharged ink. In attempting to reduce curing wrinkles, a height that is a distance between an irradiator and a liquid discharge surface is adjusted according to a width of the liquid discharge surface in a sub-scanning direction. The irradiator emits the active energy rays.

SUMMARY

In an aspect of this disclosure, a liquid discharge apparatus includes a discharge device configured to discharge a liquid curable by active-energy rays onto a discharge target to form a liquid discharge surface, an irradiator configured to irradiate the liquid discharge surface with the active-energy rays, a carriage mounting the discharge device and the irradiator, the carriage configure to move in a main-scanning direction, and circuitry configured to relatively move the carriage and the discharge target in the main-scanning direction, relatively move the carriage and the discharge target in a sub-scanning direction perpendicular to the main-scanning direction, and control illuminance of the active-energy rays emitted from the irradiator to the liquid discharge surface on the discharge target according to a length of a discharge range of the liquid discharge surface on the discharge target in the main-scanning direction.

In another aspect of this disclosure, a liquid discharge method for discharging a liquid onto a discharge target includes: discharging a liquid curable by active-energy rays onto the discharge target to form a liquid discharge surface, irradiating the liquid discharge surface with the active-energy rays, moving a discharge position of the liquid onto the discharge target in a main-scanning direction, moving the discharge position in a sub-scanning direction perpendicular to the main-scanning direction, and controlling illuminance of the active-energy rays emitted to the liquid discharge surface on the discharge target according to a length of a discharge range of the liquid discharge surface on the discharge target in the main-scanning direction.

DETAILED DESCRIPTION

Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of a liquid discharge apparatus, a liquid discharge method, and a recording medium is described in detail below with reference to the accompanying drawings. An example of application of the liquid discharge apparatus to an image forming apparatus according to the present embodiment is described below. The liquid discharge apparatus includes a liquid discharge head that discharges an ink as a liquid onto a substrate as a discharge target to form an image on the substrate. However, a target for the application of the liquid discharge apparatus is not limited to the image forming apparatus. For example, the liquid discharge apparatus may be applied to a three-dimensional fabrication apparatus that discharges the liquid from the liquid discharge head to fabricate a three-dimensional object.

FIG. 1is a block diagram illustrating a functional configuration of liquid discharge apparatus1according to the present embodiment.FIG. 2is a schematic front view of the liquid discharge apparatus1.FIG. 3is a schematic plan view of the liquid discharge apparatus1.

As illustrated inFIG. 1, the liquid discharge apparatus1according to the present embodiment includes a controller3, a sensor group4, a conveyor100, a carriage200, a head device300, an irradiator400, and a maintenance device500.

The controller3has a computer configuration, and includes a unit control circuit31, a memory32that stores various data, a Central Processing Unit (CPU)33as a main control, and an interface (I/F)34.

The unit control circuit31controls an operation of each unit such as the conveyor100, the carriage200, the head device300, the irradiator400, the maintenance device500of the liquid discharge apparatus1according to an instruction from the CPU33.

The I/F34is an interface to connect the liquid discharge apparatus1to an external personal computer (PC)2. The liquid discharge apparatus1and the PC2may be connected in any form. For example, the liquid discharge apparatus1and the PC2may be connected via a network or directly connected by a communication cable.

The sensor group4is, for example, various sensors in the liquid discharge apparatus1such as a height sensor41illustrated inFIGS. 2 and 3.

The memory32stores various programs and data executable by the CPU33. As the memory32, for example, an optical, magnetic, or electrical recording medium such as a hard disk, a compact disc read-only memory (CD-ROM), a digital versatile disk (DVD) can be used. Various programs are stored in the memory32in a data format readable by the CPU33.

Various programs executed by the liquid discharge apparatus1according to the present embodiment is recorded and provided in a computer-readable recording medium, such as the CD-ROM, a flexible disk (FD), a compact disc-recordable (CD-R), or the DVD, in a file in installable or executable format.

Various programs executed by the liquid discharge apparatus1according to the present embodiment may be stored in a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, various programs executed by the liquid discharge apparatus1according to the present embodiment may be provided or distributed via a network such as the Internet.

The CPU33of the controller3uses the memory32as a work area to control the operation of each unit of the liquid discharge apparatus1such as the conveyor100, the carriage200, the head device300, the irradiator400, and the maintenance device500via the unit control circuit31. Specifically, the CPU33control operations of each unit such as the conveyor100, the carriage200, the head device300, the irradiator400, and the maintenance device500based on the recording data received from the PC2and the data detected by the sensor group4. The CPU33thus can form an image as the liquid discharge surface102on the substrate101as the discharge target as illustrated inFIG. 2.

The substrate101is an example of a discharge target. The substrate101is, for example, a medium such as a recording sheet of paper, but is not limited to the recording sheet of paper.

A printer driver is installed in the PC2, and the printer driver generates recording data to be transmitted to the liquid discharge apparatus1from print data. The recording data includes command data to operate the conveyor100of the liquid discharge apparatus1and the like, and print data related to an image (liquid discharge surface102). The print data is composed of, for example, 2-bit data for each pixel, and is represented by 4 gradations.

As illustrated inFIG. 2, the conveyor100includes a stage130and a suction mechanism120. The suction mechanism120includes fans110and a plurality of suction holes100aprovided in the stage130. The suction mechanism120drives the fans110to suck the substrate101through the suction holes100ato temporarily fix the substrate101to the conveyor100. The suction mechanism120may attract the substrate101using electrostatic attraction.

The conveyor100moves in a Y-axis direction (sub-scanning direction Y) under the control of the drive signal from the CPU33via the unit control circuit31.

As illustrated inFIG. 3, the conveyor100includes a conveyance controller210, a roller105, and a motor104. The conveyance controller210drives the motor104to rotate the roller105to move the substrate101in the Y-axis direction (sub-scanning direction Y).

The conveyor100may move the carriage200instead of the substrate101in the Y-axis direction (sub-scanning direction Y). That is, the conveyor100relatively moves at least one of the substrate101and the carriage200in the Y-axis direction (sub-scanning direction Y).

As illustrated on the right side ofFIG. 3, the conveyor100includes a side plate407bthat supports two guides201to guide the carriage200in the X-axis direction (main-scanning direction X), a base406that supports the side plate407b, a belt404fixed to the base406, a drive pulley403and a driven pulley402around which the belt404is wound, and a motor405that rotationally drives the drive pulley403.

As illustrated on the left side ofFIG. 3, the conveyor100includes a side plate407athat supports the two guides201that guide the carriage200in the X-axis direction (main-scanning direction X), a base408that slidably supports the side plate407a, and a groove409formed in the base408and guides the side plate407ain the sub-scanning direction Y.

The conveyor100controls the conveyance controller210to drive the motor405to rotate the drive pulley403and move the belt404in the Y-axis direction (sub-scanning direction Y). The base406that supports the carriage200moves in the Y-axis direction (sub-scanning direction Y) together with the movement of the belt404. Thus, the carriage200is movable in the Y-axis direction (sub-scanning direction Y). The side plate407amoves in the Y-axis direction (sub-scanning direction Y) along the groove409in the table408as the base406moves in the Y-axis direction (sub-scanning direction Y).

The carriage200is controlled to move in the Z-axis direction (height direction Z) and the X-axis direction (main-scanning direction X) based on a drive signal from the CPU33(unit control circuit31) that functions as a movement controller.

The carriage200scans and moves along the guide201in the main-scanning direction X (X-axis direction). A scanner206includes a drive pulley203, a driven pulley204, a drive belt202, and a motor205. The carriage200is fixed to the drive belt202wound around the drive pulley203and the driven pulley204. The motor205drives to rotate the drive pulley203to move the drive belt202and the carriage200so that the carriage200moves and scans right and left in the main-scanning direction X. The guide201is supported by side plates211A and211B of an apparatus body of the liquid discharge apparatus1.

A height adjuster207includes a motor209and a slider208. The height adjuster207drives the motor209to move the slider208up and down to move the guide201up and down. As the guide201moves up and down, the carriage200moves up and down. Thus, the height adjuster207can adjust a height of the carriage200with respect to the substrate101. Thus, the height adjuster207adjusts an irradiation distance (irradiation height) of the irradiator400on the head device300with respect to the substrate101as the discharge target.

The head device300is an example of a discharge part. The head device300discharges a liquid of an active-energy ray curable type. Following describes an example of the head device300according to the present embodiment that discharges an ink as the liquid.

Irradiation of the active energy rays cures the ink (liquid) discharged from the head device300. Examples of such ink include UV curable ink, electron beam curable ink, and the like. The UV curable ink is, for example, an ink containing a methacrylate monomer. Methacrylate monomer has an advantage of relatively weak skin sensitization, which is a phenomenon that causes skin irritation due to excessive immune reactions caused by chemical substances. However, methacrylate monomer has a characteristic that a degree of curing shrinkage is larger than a degree of curing shrinkage of general ink.

The active energy rays are, for example, ultraviolet rays (UV rays), ultraviolet light (UV light) rays, electron rays, or the like.

The ink in the present embodiment is an ultraviolet (UV) curable ink that is cured by irradiation with UV light. The following example uses the UV light as the active energy rays.

The carriage200mounts the head device300on a lower surface of the carriage200. The head device300includes heads300K,300C,300M,300Y, and300CL that respectively discharge inks of, for example, black K, cyan C, magenta M, yellow Y, and transparent clear CL containing no colorant. Hereinafter, the “liquid discharge head” is simply referred to as the “head.”

In the present embodiment, the clear CL is a UV curable ink (active-energy ray curable ink) among the black K, cyan C, magenta M, yellow Y, and clear CL inks. Further, the inks of black K, cyan C, magenta M, and yellow Y are UV uncurable inks (active-energy ray uncurable ink) that are not cured even when the inks are irradiated with the active-energy rays, as an example. At least one of the black K, cyan C, magenta M, yellow Y, and clear CL inks may be UV curable ink (active-energy ray curable ink). Thus, the present embodiment is not limited to the above-described example in which only the clear CL ink is the UV curable ink. For example, the ink other than the clear CL ink, such as black K may be the UV curable ink.

Each head of the head device300includes a piezo element (piezoelectric element). When a drive signal is applied to the head device300by the CPU33(unit control circuit31), the piezo element (piezoelectric element) in the head device300contracts and causes pressure change in the head device300due to contraction of the piezo element to discharge the ink onto the substrate101. Thus, the liquid discharge surface102made of the ink is formed on the substrate101.

FIG. 4is a schematic plan view of an example of a configurations of the head device300and the irradiator400viewed from bottom side of the head device300.

The head device300includes a plurality of heads (for example, six heads) arranged at mutually different positions in a staggered arrangement in the main-scanning direction X and the sub-scanning direction Y, for example. As illustrated inFIG. 4, the heads (300CL1and300CL2) that discharge clear CL inks are arranged on an upstream side (arrow Y2side that directs downward inFIG. 4) of the heads (300CM2,300CM1,300YK1, and300YK2) that discharge inks of other inks (cyan C, magenta M, black K) in the sub-scanning direction Y.

InFIG. 4in the present embodiment, the upstream side in the sub-scanning direction Y is an arrow Y1side directed upward inFIG. 4that is a moving direction of the head device300and the substrate101relatively moved in the sub-scanning direction Y. An upstream direction (arrow Y1direction) is opposite to a downstream direction (arrow Y2direction) in the sub-scanning direction Y. Further, the downstream side in the sub-scanning direction Y is an arrow Y2side directed downward inFIG. 4that is another moving direction of the head device300and the substrate101relatively moved opposite to the arrow Y1direction in the sub-scanning direction Y.

Specifically, inFIG. 4in the present embodiment, the head (head300CL2) arranged at the downstream end (end in the arrow Y2direction) in the sub-scanning direction Y is the head of the clear CL ink.

Further, the heads300CM2and300CM1are arranged in an order from the head300CL2that is arranged on the downstream end (end in the arrow Y2direction) toward the upstream side (arrow Y1direction) in the sub-scanning direction Y inFIG. 4. Further, the heads300CM2and300CM1are arranged in a right side of the head300CL2in the main-scanning direction X (seeFIG. 4). The heads300CM1and300CM2respectively include heads (300C1and300C2) that discharge the cyan C ink and heads (300M1and300M2) that discharge the magenta M ink.

Further, the heads300YK2and300YK1are arranged in an order from the head300CL1that is arranged on the downstream end (end in the arrow Y2direction) toward the upstream side (arrow Y1direction) in the sub-scanning direction Y inFIG. 4. Further, the heads300YK2and300YK1are arranged in the right side of the head300CL1in the main-scanning direction X (seeFIG. 4). The heads300YK1and300YK2respectively include heads (300Y1and300Y2) that discharge the yellow Y ink and heads (300M1and300M2) that discharge the black K ink.

Thus, the carriage200and the substrate101relatively move in the arrow Y1direction in the sub-scanning direction Y. The heads300CM1,300CM2,300YK1, and300YK2arranged downstream side (arrow Y1side) in the sub-scanning direction Y discharge any one of color inks (cyan C, magenta M, and black K) onto the substrate101. Specifically, inFIG. 4in the present embodiment, the heads (300CL1and300CL2) arranged at the downstream end (end in the arrow Y2direction) in the sub-scanning direction Y discharge the clear CL ink that is UV curable ink.

The “upstream side” in the sub-scanning direction Y is also referred to as “one side” in the sub-scanning direction Y. The “downstream side” in the sub-scanning direction Y is also referred to as “another side” in the sub-scanning direction Y.

The carriage200mounts the irradiator400on each side surface (both end surfaces in the main-scanning direction X) of the carriage200. The irradiator400irradiates UV light, which is an example of active-energy rays, based on a drive signal from the CPU33(unit control circuit31).

As illustrated inFIG. 4, the irradiator400includes a plurality of irradiation devices401arranged along the sub-scanning direction Y. The irradiation devices401include irradiation devices401L1to401L10and irradiation devices401R1to401R10.

Thus, the irradiator400includes a plurality of irradiation devices401arrayed in the sub-scanning direction Y.

The liquid discharge apparatus1thus configured moves the carriage200that mounts the head devices300and the irradiators400in the sub-scanning direction Y based on the drive signal from the CPU33(unit control circuit31) to an initial position to form an image (liquid discharge surface102) on the substrate101.

Then, the height adjuster207moves the head device300to a height suitable for ink discharge based on a drive signal from the CPU33(unit control circuit31). The height sensor41detects a height of the head device300so that the CPU33controls the height of the head device300.

The carriage200reciprocally moves in the main-scanning direction X based on the drive signal from the CPU33(unit control circuit31). During the reciprocal movement of the carriage200, the head device300discharges ink based on the drive signal from the CPU33(unit control circuit31). Thus, an image (liquid discharge surface102) for one scan in the main-scanning direction X is formed on the substrate101. When the image (liquid discharge surface102) for one scan in the main-scanning direction X is formed on the substrate101, the conveyor100moves the carriage200or the substrate101in the sub-scanning direction Y based on the drive signal from the CPU33(unit control circuit31). Repetition of the scanning movement of the carriage200in the main-scanning direction X and scanning movement of the carriage200or the substrate101in the sub-scanning direction Y forms the image (liquid discharge surface102) of ink on the substrate101.

As described above, the carriage200mounts the irradiator400on both end surfaces of the carriage200in the main-scanning direction X. The irradiator400irradiates the substrate101with UV light while the head device300moves in the main-scanning direction X under the control of the CPU33(unit control circuit31). Therefore, the irradiator400irradiates the ink discharged on the substrate101with the UV light to cure the ink (liquid discharge surface102) on the substrate101.

As described above, the liquid discharge apparatus1controls the head device300to discharge the ink on the substrate101and controls the irradiator400to irradiate the UV light on the ink (liquid discharge surface102) on the substrate101while moving the carriage200in the main-scanning direction X. Thus, the liquid discharge apparatus1irradiates the ink (liquid discharge surface102) on the substrate101with the UV light emitted from the irradiator400while discharging the ink from the head device300.

The higher a resolution of the image to be formed on the substrate101, the larger a number of scans of the carriage200in the main-scanning direction X. Therefore, the irradiator400frequently irradiates the UV light on the substrate101, and the ink discharged onto the substrate101may be cured before the ink is leveled (flattened). The ink is irradiated with the UV light to be cured after a predetermined time has been elapsed after the ink is discharged onto the substrate101so that the ink is leveled (flattened). Therefore, the controller3preferably turns off a part of the plurality of irradiation devices401in the irradiator400and irradiates the substrate101with the UV light from only another part of the irradiation devices401during scanning of the head device300in the main-scanning direction X.

Specifically, the present embodiment describes an example in which the clear CL ink is the UV curable ink (active-energy ray curable ink) as described above.

If the clear CL ink is the UV curable ink, the controller3turns off the irradiation devices401including the irradiation device401L6to401L8and401R6to401R8arranged at positions overlapping with a position of the head300CL2in the sub-scanning direction Y among the plurality of irradiation devices401in the irradiator400arranged at both ends of the head device300in the main-scanning direction X.

The head300CL2discharges the clear CL ink. Then, the irradiation devices401other than the above-described irradiation devices401are turned on such as the irradiation devices401L1to401L5, the irradiation devices401L9to401L10, the irradiation devices401R1to401R5, and the irradiation devices401R9to401R10.

As a result, the clear CL ink discharged from the head300CL2onto the substrate101is leveled (flattened) on the substrate101, and the irradiation device401including the irradiation devices401L9,401L10,401R9, and401R10then irradiates the clear CL ink with the UV light. Thus, the clear CL ink can effectively produce image gross because the clear CL ink is cured by irradiation of the UV light after the clear CL ink is discharged onto the substrate101and leveled.

The active-energy ray curable ink such as the UV curable ink is discharged onto the substrate101, leveled (flattened) on the substrate101, and then irradiated with UV light (active-energy rays) so that an irradiation region of the UV light in the ink (liquid discharge surface102) is cured and shrunk. Thus, wrinkles due to curing occur between an irradiated region in which the ink is cured and shrunk and an unirradiated region in which the ink is not irradiated with UV light. Hereinafter, the wrinkles due to curing is referred to as “curing wrinkles.”

The curing wrinkles occur more significantly with increase of a time from an irradiation of the UV light during scanning of the carriage200in the main-scanning direction X to an irradiation of the UV light during subsequent scanning of the carriage200in the main-scanning direction X because of progress of curing. Thus, the curing wrinkles occur significantly with increase of a length of a discharge range of the ink on the substrate101as the discharge target in the main-scanning direction X.

FIG. 5is a schematic plan view of the liquid discharge apparatus1illustrating an example in which a length of a print range “E” as a discharge range in the main-scanning direction X is short.

The print range E is a discharge range in the substrate101as the discharge target. The active-energy ray curable ink such as the UV-curable ink is discharged onto the print range E in the substrate101. That is, the print range E is a region in the substrate101onto which the active-energy ray curable ink such as the UV-curable ink is discharged. CPU33generates recording data based on print data related to an image (liquid discharge surface102) and controls the head device300to discharge the ink according to a drive signal corresponding to the print data. Thus, an image is formed on the print range E in the substrate101. Thus, the print range E is the range of the image (liquid discharge surface102) formed on the substrate101based on the print data.

InFIG. 5, the print range “E1” is illustrated as an example of the print range E having a short length in the main-scanning direction X. A length of the print range E1is indicated by arrow “L1” inFIG. 5. When the length of the print range E1in the main-scanning direction X (see L1inFIG. 5) is short, the carriage200mounting the head device300and the irradiator400scans in the main-scanning direction X so that the head device300discharges the ink onto the substrate101and the irradiator400irradiates the discharged ink after leveled (flattened) with the UV light.

After the carriage200and the substrate101relatively move in the sub-scanning direction Y, the carriage200scans again in the main-scanning direction X so that the head device300discharges the ink onto the substrate101and the irradiator400irradiates the discharged ink after leveled (flattened) with the UV light immediately after the previous irradiation of the UV light. Thus, if the length L of the print range E1in the main-scanning direction X is short (L=L1), it is short a time difference between an irradiation timing to irradiate an irradiated region in the print range E1in the substrate101with the UV light and an irradiation timing to irradiate an unirradiated region adjacent to the irradiated region in the sub-scanning direction Y. Thus, the curing wrinkles are difficult to occur.

Therefore, if the length L of the print range E1in the main-scanning direction X is short (L=L1), even the illumination is increased to promote polymerizing reaction of the UV curable ink, a next print range of the UV curable ink is immediately irradiated with the UV light. Thus, the CPU33can prevent an occurrence of the curing wrinkles.

FIG. 6is a schematic plan view of the liquid discharge apparatus1illustrating an example in which a length of a print range “E” as a discharge range in the main-scanning direction X is long.

InFIG. 6, the print range “E2” is illustrated as an example of the print range E having a long length in the main-scanning direction X. A length of the print range E2is indicated by arrow “L2” inFIG. 6. When the length of the print range E2in the main-scanning direction X (see L2inFIG. 6) is long, the carriage200mounting the head device300and the irradiator400scans in the main-scanning direction X so that the head device300discharges the ink onto the substrate101and the irradiator400irradiates the discharged ink after leveled (flattened) with the UV light.

After the carriage200and the substrate101relatively move in the sub-scanning direction Y, the carriage200scans again in the main-scanning direction X so that the head device300discharges the ink onto the substrate101and the irradiator400irradiates the discharged ink after leveled (flattened) with the UV light after a certain time has passed since the previous irradiation of the UV light.

Thus, if the length L of the print range E2in the main-scanning direction X is long (L=L2), it is long a time difference between an irradiation timing to irradiate an irradiated region in the print range E2in the substrate101with the UV light and an irradiation timing to irradiate an unirradiated region adjacent to the irradiated region in the sub-scanning direction Y. Thus, the curing wrinkles are likely to occur.

Therefore, the CPU33(unit control circuit31) in the liquid discharge apparatus1according to the present embodiment controls illuminance of UV light according to a length of the printing range E (discharge range) in the main-scanning direction X by the ink discharged onto the substrate101as the discharge target.

Following describes details of an illumination control of the irradiator400according to a first embodiment of the present disclosure.FIG. 7is a schematic block diagram of an example of a functional configuration of the controller3.

The controller3includes a movement controller36and an irradiation controller38. The CPU33of the controller3executes a program stored in the memory32so that the controller3achieves functions of the movement controller36and the irradiation controller38. Some or all of the functions achieved by the controller3of the liquid discharge apparatus1may be configured using a dedicated processing circuit such as an integrated circuit (IC).

The movement controller36controls the scanner206to move the carriage200(head device300and irradiator400) in the main-scanning direction X, controls the height adjuster207to control a height of the carriage with respect to the substrate101, and controls the conveyance controller210to relatively move the substrate101on the conveyor100and the carriage200in the sub-scanning direction Y.

The irradiation controller38controls the irradiator400to irradiate the liquid discharge surface102with UV light and cures the liquid discharge surface102while the irradiator400(carriage200) moves in the main-scanning direction X.

The irradiation controller38in the first embodiment controls an illuminance of the UV light with which the liquid discharge surface102on the substrate101is irradiated from the irradiator400according to the length L of the print range E printed by the ink discharged onto the substrate101as the discharge target in the main-scanning direction X.

More specifically, the irradiation controller38controls the illuminance of the UV light with which the liquid discharge surface102on the substrate101is irradiated from the irradiator400so that an illuminance per unit area of the UV light, with which the substrate101as the discharge target is irradiated, decreases with an increase in the length L of the printing range E in the main-scanning direction X.

Thus, the irradiation controller38controls the illuminance of the UV light with which the liquid discharge surface102on the substrate101is irradiated from the irradiator400so that the illuminance per unit area of the UV light, with which the substrate101is irradiated, increases with a decrease in the length L of the printing range E in the main-scanning direction X.

The illuminance per unit area is controlled by adjusting at least one of an irradiation intensity of the irradiator400and an irradiation distance that is a distance between the irradiator400and the substrate101.

The irradiation controller38controls the irradiation intensity of the irradiator400so that the irradiation intensity of the UV light irradiated from the irradiator400decreases with an increase in the length L of the print range E in the main-scanning direction X. In other words, the irradiation controller38controls the irradiation intensity of the irradiator400so that the irradiation intensity of the UV light irradiated from the irradiator400increases with a decrease in the length L of the print range E in the main-scanning direction X.

Specifically, the irradiation controller38previously stores a first relation information50indicating a relation between an irradiation intensity of the UV light and a length of the print data, which is original data used to discharge the ink on the print range E, in the main-scanning direction X. The length of the print data in the main-scanning direction X corresponds to the length L of the print range E in the main-scanning direction X. The liquid discharge surface102in the print range E in the substrate101is formed by the ink discharged onto the substrate101based on the print data.

FIG. 8is a graph illustrating an example of a first relation information50. InFIG. 8, the first relation information50is illustrated by a line indicating relation between the length L of the print data in the main-scanning direction X (X-axis) and the irradiation intensity (Y-axis). As illustrated inFIG. 8, the irradiation intensity decreases with an increase in the length of the print data (printing range E) in the main-scanning direction X in the first relation information50.

Specifically, the CPU33(unit control circuit31) in the controller3of the liquid discharge apparatus1may previously calculate the first relation information50and previously store the calculated first relation information50in the memory32. The first relation information50indicates a relation between the length of the print data in the main-scanning direction X and the irradiation intensity that effectively reduces the curing wrinkles.

As illustrated inFIG. 8, the irradiation intensity decreases with an increase in the length of the print data (printing range E) in the main-scanning direction X in the first relation information50to reduce the curing wrinkles.

Then, the irradiation controller38may read, from the first relation information50, the irradiation intensity (for example, the irradiation intensity A inFIG. 8) corresponding to the length L of the print range E that is derived from the print data in the main scanning direction X to determine the irradiation intensity. The irradiation intensity of the first relation information50may be represented by a voltage value of an applied voltage applied to each of the plurality of irradiation devices401in the irradiator400.

The irradiation controller38may set the determined irradiation intensity as the irradiation intensity of the irradiation device401in the irradiator400and output a drive signal for irradiation of the UV light having set irradiation intensity to the irradiation devices401.

Thus, the ink (UV curable ink) discharged onto the substrate101is irradiated with UV light having the set irradiation intensity from the irradiation devices401by the above-described processes.

Further, the irradiation controller38may adjust the irradiation distance as described above.

Thus, the irradiation controller38controls the height adjuster207so that the irradiation distance (height) that is a distance between the irradiator400(irradiation devices401) and the substrate101increases with an increase in the length of the printing range E (discharge range) in the main-scanning direction X. In other words, the irradiation controller38controls the height adjuster207so that the irradiation distance (height) that is the distance between the irradiator400(irradiation devices401) and the substrate101decreases with a decrease in the length L of the print range E in the main-scanning direction X.

Since the irradiator400includes a plurality of the irradiation devices401, the irradiation controller38controls the height adjuster207so that the irradiation distances (heights) between the irradiation devices401and the substrate101increase with an increase in the length of the printing range E (discharge range) in the main-scanning direction X

Specifically, the irradiation controller38previously stores a second relation information52in the memory32. The second relation information52indicates a relation between the irradiation distance (height) and the length of the print data, which is original data used to discharge the ink on the print range E, in the main-scanning direction X.FIG. 9is a graph illustrating an example of a second relation information52.

InFIG. 9, the second relation information52is illustrated by a line of a relation between the length L of the print data in the main-scanning direction X in X-axis and a height (irradiation height) in Y-axis. The height corresponds to the irradiation distance, as described above. As illustrated inFIG. 9, the longer the length of the print data (printing range E) in the main-scanning direction X, the larger the irradiation distance (height) in the second relation information52.

Specifically, the CPU33(unit control circuit31) in the controller3of the liquid discharge apparatus1may previously calculate the second relation information52and previously store the calculated second relation information52in the memory32. The second relation information52indicates a relation between the length of the print data in the main-scanning direction X and the irradiation distance (height) that effectively reduces the curing wrinkles. As illustrated inFIG. 9, the irradiation distance increases with an increase in the length of the print data (printing range E) in the main-scanning direction X in the second relation information52to reduce the curing wrinkles.

Then, the irradiation controller38may read the height (for example, the height B) corresponding to the length of the print range E derived from the print data in the main-scanning direction X from the second relation information52to set the irradiation distance (height).

The irradiation controller38controls the height adjuster207to vertically move the carriage200so that the irradiation distance (height) becomes the set irradiation distance. Thus, the irradiation controller38controls the distance between the substrate101and the irradiation devices401(irradiator400) to be the set irradiation distance.

Further, the irradiation controller38may adjust at least one of the irradiation intensity of the irradiator400and the irradiation distance that is the distance between the irradiator400and the substrate101to control the illuminance per unit area of the UV light emitted from the irradiator400to the substrate101. Following describes an example in which the irradiation controller38controls the irradiation intensity of the irradiator400to control the illuminance per unit area of the UV light with which the substrate101is irradiated from the irradiator400.

When the UV light having the irradiation intensity set as described above is applied, an integrated light amount per unit area of the UV light, with which the liquid discharge surface102of ink (UV curable ink) discharged on the substrate101is irradiated, becomes less than an integrated amount of UV light necessary for curing the ink. The “integrated amount of UV light necessary for curing the ink” is also referred to as the “integrated amount of UV light to cure the ink.”

Therefore, the irradiation controller38preferably determines whether the integrated light amount per unit area of the UV light with which the liquid discharge surface102on the substrate101is irradiated is equal to or larger than an integrated light amount of the UV light necessary for curing the ink. The “integrated light amount per unit area of the UV light with which the liquid discharge surface102on the substrate101is irradiated” is determined based on an integrated light amount of the UV light when the substrate101is irradiated with the UV light having the irradiation intensity set according to the length of the printing range E in the main-scanning direction X.

When the irradiation controller38determines that the integrated light amount per unit area of the UV light is equal to or larger than the integrated light amount necessary for curing the ink, the irradiation controller38sets the irradiation intensity of each of one or more of the irradiation devices401to the irradiation intensity set according to the length of the printing range E in the main-scanning direction X. The one or more of the irradiation devices401irradiates, a region of the liquid discharge surface102on the substrate101onto which the UV curable ink is discharged, with the UV light.

FIG. 4is used to illustrate below the above-described illumination control. For example, the clear CL ink is assumed to be a UV curable ink. If the clear CL ink is the UV curable ink, the irradiation devices401that irradiate the clear CL ink discharged on the substrate101with the UV light by the scanning movement of the carriage200mounting the irradiator400and the head device300in the main-scanning direction X are the irradiation devices401L9,401L10,401R9, and401R10.

When the irradiation controller38determines that the integrated light amount per unit area of the UV light is equal to or larger than the integrated light amount of UV light necessary for curing the ink, the irradiation controller38sets the irradiation intensity of each of the irradiation devices401L9,401L10,401R9, and401R10to the irradiation intensity set according to the length of the print range E in the main-scanning direction X.

Following describes a case in which the irradiation controller38determines that the integrated light amount per unit area of the UV light is less than the integrated light amount of UV light necessary for curing the ink. Then, the irradiation controller38sets the irradiation intensity of a part of the irradiation devices401(irradiation devices401L9and401R9) to the set irradiation intensity set according to the length of the print range E in the main-scanning direction X. The part of the irradiation devices401L9and401R9are arranged in a downstream side (arrow Y2direction) in the sub-scanning direction Y among the plurality of irradiation devices401to cure the clear CL ink arranged in the sub-scanning direction Y.

Then, the irradiation controller38sets the irradiation intensity of the irradiation devices401(irradiation devices401L10and401R10) other than the irradiation devices401L9and401R9among the plurality of irradiation devices401for curing the clear CL ink to the illuminance higher than the set irradiation intensity so that the irradiation intensity of the irradiation devices401L10and401R10to be equal to or higher than the integrated light amount of UV light necessary for curing the ink.

Specifically, the irradiation controller38sets the irradiation intensity of the irradiation devices401L9and401R9to the irradiation intensity set according to the length of the print range E in the main-scanning direction X in the above-described case, for example. Further, the irradiation controller38sets the irradiation intensity of the irradiation devices401L10and401R10to be higher than the set irradiation intensity set according to the length of the print range E in the main-scanning direction X so that the irradiation intensity of the irradiation devices401L10and401R10becomes equal to larger than the integrated light amount of UV light necessary for curing the ink.

Next, an example of a flow of a method to set an illuminance executed by the liquid discharge apparatus1according to the present embodiment is described below.

FIG. 10is a flowchart illustrating an example of the flow to set the illuminance executed by the liquid discharge apparatus1(controller3). The liquid discharge apparatus1may execute a process illustrated inFIG. 10before discharging the ink (before an image formation) according to the print data.

The irradiation controller38determines the irradiation intensity from the length of the print range E (discharge range) of the ink discharged on the substrate101as the discharge target in the main-scanning direction X (step S400). In step S400, the irradiation controller38determines the irradiation intensity by reading the irradiation intensity corresponding to the length of the print range E in the main-scanning direction X from the first relation information50. Hereinafter, the irradiation intensity determined in step S400is referred to as an “irradiation intensity P.”

Next, the irradiation controller38determines whether the integrated light amount based on the irradiation intensity P is equal to or larger than the integrated light amount U of UV light necessary for curing the UV curable ink discharged onto the substrate101(step S402). The “integrated light amount based on the irradiation intensity P” is an integrated light amount calculated in an assumption in which the irradiation devices401irradiate the substrate101with the UV light having the irradiation intensity P determined in step S400. The integrated light amount U of the UV light necessary for curing the UV curable ink may be previously stored in the memory32.

If the irradiation controller38determines in step S402that the integrated light amount is equal to or larger than the integrated light amount U (step S402: Yes), the process proceeds to step S404. In step S404, the irradiation controller38sets the irradiation intensity of each of the plurality of irradiation devices401(the irradiation devices401L9,401L10,401R9, and401R10, for example) to the irradiation intensity determined in step S404(step S404).

The plurality of irradiation devices401L9,401L10,401R9, and401R10irradiates the liquid discharge surface102onto which the UV curable ink is discharged with the UV light Then, the present routine that sets the illuminance ends.

Conversely, if the irradiation controller38determines in step S402that the integrated light amount is less than the integrated light amount U (step S402: No), the process proceeds to step S406.

In step S404, the irradiation controller38sets, to the irradiation intensity P determined in step S400(step S406), the irradiation intensity of part of the irradiation devices401(the irradiation devices401L9and401R9) arranged in the upstream part (arrow Y1direction) in the sub-scanning direction Y among the plurality of irradiation devices401(irradiation devices401L9,401L10,401R9, and401R10, for example) to irradiate the liquid discharge surface102onto which the UV curable ink is discharged with the UV light.

In step S406, the irradiation controller38sets, to an irradiation intensity larger than the irradiation intensity P determined in step S400and equal to or larger than the integrated light amount U (step S406), the irradiation intensity of part of the irradiation devices401(the irradiation devices401L10and401R10) arranged in the downstream part (arrow Y2direction) in the sub-scanning direction Y. The irradiation devices401L10and401R10are part of the plurality of irradiation devices401(irradiation devices401L9,401L10,401R9, and401R10, for example) to irradiate the liquid discharge surface102onto which the UV curable ink is discharged with the UV light other than the irradiation devices401to which the irradiation intensity determined in step S400is set. Then, the present routine that sets the illuminance ends.

Then, the irradiation controller38controls the irradiation devices401(irradiator400) so that the irradiation devices401irradiate the liquid discharge surface102with the UV light having the irradiation intensity set in step S404or step S404when the head device300discharges the ink according to the print data.

As described above, the CPU33(unit control circuit31) in the controller3of the liquid discharge apparatus1according to the present embodiment controls at least one of the irradiation devices401and the height adjuster207to adjust the illuminance of the UV light with which the liquid discharge surface102on the substrate101is irradiated from the irradiation devices401so that the longer the length of the printing range E in the main-scanning direction X, the lower the illuminance of the UV light emitted from the irradiation devices401(irradiator400) onto the liquid discharge surface102on the substrate101.

Therefore, if the length L of the print range E1in the main-scanning direction X is long (L=L2), the illumination is decreased to slow (delay) polymerizing reaction of the UV curable ink that slows (delays) progress of curing shrinkage. Thus, the CPU33can prevent an occurrence of the curing wrinkles.

Therefore, the liquid discharge apparatus1according to the present embodiment irradiates the active-energy ray curable ink such as the UV curable ink discharged onto the substrate101with the UV light (active-energy rays) so that the liquid discharge apparatus1can reduce an occurrence of the curing wrinkles between the irradiated region in which the ink is cured and shrunk and the unirradiated region in which the UV light is not irradiated.

As described above, the liquid discharge apparatus1according to the present embodiment includes the head device300(discharge device), the irradiator400(irradiator), the movement controller36, and the irradiation controller38. The head device300(discharge unit) moves in the main-scanning direction X with the movement of the carriage200and discharges the UV curable ink (active-energy ray curable ink) while moving in the main-scanning direction X. The UV curable ink is an example of a liquid. The irradiation devices401(irradiator400) moves in the main-scanning direction X and irradiates the ink (liquid) discharged from the head device300with the UV light (active-energy rays) from the irradiation devices401(irradiator400) while moving in the main-scanning direction X.

The movement controller36relatively moves at least one of the carriage200and the substrate101(discharge target) in the main-scanning direction X and then relatively moves at least one of the carriage200and the substrate101(discharge target) in the sub-scanning direction Y perpendicular to the main-scanning direction X. The carriage200mounts the head device300and the irradiator400.

The irradiation controller38controls the illuminance of the UV light (active-energy rays) emitted from the irradiator400to the liquid discharge surface102on the substrate101according to the length L of the printing range E of the ink (liquid) on the substrate101(discharge target) in the main-scanning direction X.

Therefore, the liquid discharge apparatus1according to the present embodiment can reduce the curing wrinkles.

FIG. 11is a schematic side view of the carriage200mounting the head device300and the irradiator400illustrating an example of an arrangement of the irradiator400according to a variation 1.

The irradiator400in the variation 1 has a configuration including a plurality of irradiation devices401arranged in the sub-scanning direction Y as in the above-described embodiments (seeFIG. 4). Further, as described with reference toFIG. 4in the above-described embodiments, the head device300includes a plurality of heads (for example, six heads) arranged at different positions in a staggered manner in the main-scanning direction X and the sub-scanning direction Y.

Further, as described with reference toFIG. 4in the above-described embodiments, the heads (300CL1and300CL2) to discharge the clear CL ink are disposed at downstream side (arrow Y2direction) in the sub-scanning direction Y of the other heads (300CM2,300CM1,300YK1,300YK2) that discharge the other inks (cyan C, magenta M, and black K). The clear CL ink is the UV curable ink. The other inks (cyan C, magenta M, and black K) are the UV-uncurable inks.

The heads300CL1and300CL2are first heads (first discharge devices), and the heads300CM1,300CM2,300YK1, and300YK2are second heads (second discharge devices).

In the above-described case, the plurality of irradiation devices401is preferably arranged such that the irradiation distance of the irradiator400with respect to the substrate101(discharge target) decreases toward the downstream side (arrow Y2direction) in the sub-scanning direction Y as illustrated inFIG. 11.

That is, the irradiation distance between the irradiation devices401arranged on the downstream side (arrow Y2direction) in the sub-scanning direction Y and the substrate101is smaller than the irradiation distance between the irradiation devices401arranged on the upstream side (arrow Y1direction) in the sub-scanning direction Y and the substrate101. The irradiation devices401arranged on the downstream side (arrow Y2direction) in the sub-scanning direction Y irradiates the clear CL ink discharged from the head300CL (head300CL2) that discharges the clear CL ink as the UV curable ink with the UV light.

Such a configuration of the irradiator400can increase the illuminance of the UV light with which the substrate101is irradiated regardless of the irradiation intensity of the UV light irradiated from the irradiation devices401. Therefore, the irradiation controller38can easily increase the integrated light amount of the UV light with emitted to the substrate101.

The irradiation controller38may adjust an inclination of the irradiator400according to the integrated light amount based on the irradiation intensity P determined in step S400inFIG. 10in the above-described embodiments. The integrated light amount based on the irradiation intensity P is determined in step S400in an assumption that the irradiator400irradiates the liquid discharge surface102on the substrate101with the UV light having the irradiation intensity determined in step S400.

To adjust the inclination of the irradiator400, the irradiator400may include a driver to adjust the inclination of the irradiator400with respect to the surface of the substrate101(liquid discharge surface102). The driver may have a mechanism that rotatably drives the irradiator400in a circumferential direction around the main-scanning direction X as a rotation axis. Then, the irradiation controller38may adjust the inclination of the irradiator400so that the irradiation distance between the irradiation devices401L10and401R10and the substrate101decreases with a decrease in the integrated light amount based on the irradiation intensity P determined in step S400inFIG. 10in the above-described embodiments.

The integrated light amount based on the irradiation intensity P is determined in step S400in an assumption that the irradiator400irradiates the liquid discharge surface102on the substrate101with the UV light having the irradiation intensity determined in step S400.

The irradiation controller38described in the above embodiments may control the illuminance of the UV light (active-energy rays) emitted to the substrate101according to the length of the printing range E (discharge range) in the main-scanning direction X and a type of the substrate101as the discharge target.

To control the illuminance of the UV light, the irradiation controller38may previously store the first relation information50and the second relation information52in the memory32for each type of the substrate101(discharge target). Then, the irradiation controller38reads the first relation information50and the second relation information52corresponding to the type of the substrate101(discharge target) from the memory32to control the illuminance of the UV light (active-energy rays) as in the above-described embodiments.

Further, the irradiation controller38may control the illuminance of the UV light (active-energy rays) emitted to the substrate101according to the length of the print range E (discharge range) in the main-scanning direction X and at least one of the type of the substrate101(discharge target) and the type of UV curable ink to be discharged.

To control the illuminance of the UV light, the irradiation controller38may previously store the first relation information50and the second relation information52in the memory32for combinations of a type of the substrate101(discharge target) and a type of the UV curable ink discharged onto the substrate101. Then, the irradiation controller38reads the first relation information50and the second relation information52corresponding to the combination of the type of the substrate101(discharge target) and the type of the UV curable ink (discharge liquid) from the memory32to control the illuminance of the UV light (active-energy rays) as in the above-described embodiments.

In the above-described embodiments and modified examples, the “liquid discharge apparatus” is a device that includes a liquid discharge head or a liquid discharge device and drives the liquid discharge head to discharge the liquid. The term “liquid discharge apparatus” used here includes, in addition to apparatuses to discharge liquid to materials on which the liquid can adhere, apparatuses to discharge the liquid into gas (air) or liquid.

The “liquid discharge apparatus” may include devices to feed, convey, and eject the material on which liquid can adhere. The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged.

The “liquid discharge apparatus” may be, for example, an image forming apparatus to form an image on a sheet by discharging ink, or a three-dimensional fabrication apparatus to discharge a fabrication liquid to a powder layer in which powder material is formed in layers to form a three-dimensional fabrication object.

The term “liquid discharge apparatus” is not limited to an apparatus to discharge liquid to visualize meaningful images, such as letters or figures. For example, the liquid discharge apparatus may be an apparatus to form arbitrary images, such as arbitrary patterns, or fabricate three-dimensional images.

The above-described term “material onto which liquid can adhere” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate. Examples of the “material onto which liquid can adhere” include recording media, such as paper sheet, recording paper, recording sheet of paper, film, and cloth, electronic component, such as electronic substrate and piezoelectric element, and media, such as powder layer, organ model, and testing cell. The “material onto which liquid can adhere” includes any material on which liquid is adhered, unless particularly limited.

Examples of the “material onto which liquid can adhere” include any materials on which liquid can adhere even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic.

Further, the term “liquid” includes any liquid having a viscosity or a surface tension that can be discharged from the head. However, preferably, the viscosity of the liquid is not greater than 30 mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. Examples of the liquid include a solution, a suspension, or an emulsion that contains, for example, a solvent, such as water or an organic solvent, a colorant, such as dye or pigment, a functional material, such as a polymerizable compound, a resin, or a surfactant, a biocompatible material, such as DNA, amino acid, protein, or calcium, or an edible material, such as a natural colorant. Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication.

The “liquid discharge apparatus” may be an apparatus to relatively move the head and a material onto which liquid can adhere. However, the liquid discharge apparatus is not limited to such an apparatus. For example, the liquid discharge apparatus may be a serial head apparatus that moves the head or a line head apparatus that does not move the head.

Examples of the “liquid discharge apparatus” further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat, with the treatment liquid, a sheet surface to reform the sheet surface and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is discharged through nozzles to granulate fine particles of the raw materials.

Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above. The methods described above can be provided as program codes stored in a recording medium, to cause a processor to execute the method when executed by at least one processor.

A non-transitory recording medium such as read-only memory (ROM) stores instructions which, when executed by one or more processors such as the CPU33, cause the processors to perform the method as described in the present disclosure.