JP2011062996A - Liquid ejecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce heat generation since the heat generation due to the irradiation of normal curing light is large. <P>SOLUTION: The liquid ejecting apparatus includes: a head configured to eject liquid which is cured with light irradiation; a first carriage configured to move the head in a moving direction perpendicular to a medium conveying direction; a temporary curing light source for irradiating dots, which have been formed by the liquid ejected from the moving head and landed on the medium, with temporary curing light; a second carriage disposed on the downstream side of the first carriage in the conveying direction, and configured to move in a moving direction independently from the first carriage; and a normal curing light source disposed on the second carriage, and configured to irradiate the dots, which have been irradiated with the light emitted from the temporary curing light source, with the normal curing light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus.

  There is known a liquid ejecting apparatus that performs printing using a liquid (for example, UV ink) that is cured by irradiation with light (a kind of electromagnetic wave, for example, ultraviolet (UV)). In such a liquid ejecting apparatus, a liquid is ejected from a nozzle of a head onto a medium, and then light is irradiated to dots formed on the medium. By doing so, the dots are cured and fixed to the medium, so that it is possible to perform good printing even on a medium that hardly absorbs liquid (for example, see Patent Document 1).

JP 2000-158793 A

In addition, as a liquid ejecting apparatus as described above, an apparatus that performs two-stage curing has been proposed. For example, by irradiating light with weak irradiation energy immediately after dot formation, bleeding between inks and spread of dots are suppressed (temporary curing). After that, the pre-cured dots are irradiated with light of strong energy. As a result, the dots are completely cured (main curing). In this case, the light source for irradiating the main curing light (main curing light source) has a length in the moving direction at the most downstream side of the medium to be printed on the downstream side of the head in the transport direction (for example, the position immediately before the paper discharge). It was set so as to be longer than a great deal.
However, such a liquid ejecting apparatus has a problem that heat generation due to irradiation of light for main curing is large.
Therefore, an object of the present invention is to reduce heat generation.

The main invention for achieving the above object is:
(A) a head that discharges a liquid that is cured by light irradiation;
(B) a first carriage that moves the head in a movement direction that intersects the medium conveyance direction;
(C) a temporary curing light source that is provided on the first carriage and that irradiates the dots formed by the liquid ejected from the moving head landing on the medium with light for preliminary curing;
(D) a second carriage that is provided downstream of the first carriage in the transport direction and moves in the movement direction independently of the first carriage;
(E) a main curing light source that is provided on the second carriage and that irradiates light for main curing to dots irradiated with light from the temporary curing light source;
It is a liquid discharge apparatus characterized by having.

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

FIG. 2 is a block diagram illustrating a configuration of a printer. FIG. 2 is a schematic view around a printer head. 3A and 3B are cross-sectional views of the printer. It is explanatory drawing of a structure of a head. 5A to 5C are explanatory diagrams of the relationship between the shape of the UV ink (dots) landed on the medium and the UV irradiation energy for temporary curing. 6A to 6E are explanatory views of the state of image formation according to the first embodiment. It is a figure which shows the evaluation result of the irradiation conditions of this hardening. It is a figure which shows the evaluation result of the irradiation conditions of temporary hardening. It is the schematic of the head periphery of a comparative example. FIG. 10A to FIG. 10E are explanatory views of the state of image formation according to the second embodiment.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(A) a head that discharges liquid that is cured by light irradiation; (B) a first carriage that moves the head in a movement direction that intersects the medium conveyance direction; and (C) the first carriage. A temporary curing light source that irradiates dots formed by the liquid ejected from the moving head landing on the medium; and (D) a downstream of the first carriage in the transport direction. A second carriage that moves in the moving direction independently of the first carriage; and (E) a dot that is provided on the second carriage and irradiated with light from the temporary curing light source. A liquid ejecting apparatus including the main curing light source that emits the curing light is clarified.
According to such a liquid ejecting apparatus, the main curing light source can be made small, so that heat generation can be reduced.

In this liquid ejection apparatus, it is preferable that the main curing light source is an LED.
Such a liquid ejecting apparatus is suitable for mounting on the second carriage because the heat generation is small.

In this liquid ejection apparatus, it is preferable that the main curing light source has a wider wavelength band than the temporary curing light source.
According to such a liquid discharge apparatus, the main curing can be surely performed.

In this liquid ejection apparatus, it is preferable that the moving speed of the second carriage in the moving direction is faster than the moving speed of the first carriage in the moving direction.
According to such a liquid ejecting apparatus, light for main curing can be uniformly irradiated.

In this liquid ejection apparatus, a dot forming operation for ejecting liquid from the head while reciprocating the first carriage in the movement direction and a conveyance operation for conveying the medium in the conveyance direction are alternately performed. The main curing light source may move in the moving direction together with the second carriage during the transport operation, and irradiate the medium with the main curing light.
According to such a liquid ejecting apparatus, it is possible to lengthen the time for irradiating the light for main curing, and it is possible to reliably perform the main curing on the image after the temporary curing.

In this liquid discharge apparatus, it is preferable that the irradiation energy of the light for main curing by the light source for main curing is 200 to 500 mJ / cm ² .
According to such a liquid ejecting apparatus, quality can be improved.

In this liquid discharge apparatus, it is preferable that the irradiation energy of the temporary curing light from the temporary curing light source is 3 to 30 mJ / cm ² .
According to such a liquid ejecting apparatus, it is possible to improve the image quality.

In such a liquid ejecting apparatus, it is desirable that the degree of curing of the dots irradiated with the temporary curing light is 20 to 35%.
According to such a liquid ejecting apparatus, it is possible to improve the image quality.

  In the following embodiments, an ink jet printer (hereinafter also referred to as a printer 1) will be described as an example of the liquid ejection device.

=== First Embodiment ===
<About printer configuration>
Hereinafter, the printer 1 of the present embodiment will be described with reference to FIGS. 1, 2, 3 </ b> A, and 3 </ b> B. FIG. 1 is a block diagram illustrating a configuration of the printer 1. FIG. 2 is a schematic view around the head of the printer 1. 3A and 3B are cross-sectional views of the printer 1. 3A corresponds to the AA cross section of FIG. 2, and FIG. 3B corresponds to the BB cross section of FIG.

  The printer 1 of the present embodiment ejects ultraviolet curable ink (hereinafter referred to as UV ink) that is cured by irradiation with ultraviolet light (hereinafter referred to as UV) as an example of a liquid toward a medium such as paper, cloth, or film sheet. Thus, the apparatus prints an image on a medium. When UV ink is irradiated with UV, it is cured by a photopolymerization reaction. Note that the printer 1 of this embodiment prints an image using four colors of CMYK UV ink.

  The printer 1 includes a transport unit 10, a carriage unit 20, a head unit 30, an irradiation unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 that is an external device controls each unit (the transport unit 10, the carriage unit 20, the head unit 30, and the irradiation unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on a medium. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 10 is for transporting a medium (for example, paper) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 10 includes a paper feed roller 11, a transport motor (not shown), a transport roller 13, a platen 14, and a paper discharge roller 15. The paper feed roller 11 is a roller for feeding the medium inserted into the paper insertion slot into the printer. The transport roller 13 is a roller that transports the medium fed by the paper feed roller 11 to a printable area, and is driven by a transport motor. The platen 14 supports the medium being printed. The paper discharge roller 15 is a roller for discharging the medium to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

  The carriage unit 20 is for moving (also referred to as “scanning”) the head in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 20 includes a carriage 21 (corresponding to a first carriage) and a carriage 22 (corresponding to a second carriage), and a carriage motor (not shown) that drives each carriage. The carriage 22 is provided downstream of the carriage 21 in the transport direction. The carriage 21 detachably holds an ink cartridge that stores UV ink. The carriage 21 is reciprocated along the guide shaft 24 by a carriage motor while being supported by a guide shaft 24 that intersects a conveyance direction described later. The carriage 22 is reciprocated along the guide shaft 25 by the carriage motor while being supported by the guide shaft 25 intersecting the transport direction.

The head unit 30 is for ejecting liquid (UV ink in this embodiment) onto a medium. The head unit 30 includes a head 31 having a plurality of nozzles. Since the head 31 is provided on the carriage 21, when the carriage 21 moves in the movement direction, the head 31 also moves in the movement direction. Then, when the head 31 is intermittently ejected while moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the medium. In the following description, a path moving from one end side to the other end side in FIG. 2 is referred to as a forward path, and a path moving from the other end side to one end side is referred to as a return path. In the present embodiment, UV ink is ejected during both the forward and return periods. That is, the printer 1 of the present embodiment performs bidirectional printing.
The configuration of the head 31 will be described later.

  The irradiation unit 40 irradiates UV toward the UV ink (dots) landed on the medium. The dots formed on the medium are cured by receiving UV irradiation from the irradiation unit 40. Note that the irradiation unit 40 of this embodiment includes provisional curing irradiation units 42 a and 42 b and a main curing irradiation unit 43.

  The provisional curing irradiation portions 42a and 42b are provided on one end side and the other end side in the moving direction of the carriage 21 so as to sandwich the head 31, respectively. That is, the pre-curing irradiation units 42a and 42b are provided at positions aligned with the head 31 in the moving direction. Further, the length in the transport direction of the pre-curing irradiation units 42 a and 42 b is substantially the same as the length of the nozzle row of the head 31. Then, the pre-curing irradiation units 42a and 42b move together with the carriage 21 (head 31) to irradiate the dots formed on the medium with UV. As the light source for temporary curing, a light source having a peak at 365 to 420 nm is desirable, and the light irradiation diodes 42a and 42b for temporary curing according to the present embodiment have a single wavelength light emitting diode having a peak at about 395 nm as a light source for UV irradiation. (LED: Light Emitting Diode). In addition, LED can change irradiation energy easily by controlling the magnitude | size of input current.

  The main curing irradiation unit 43 is provided on the carriage 22. In other words, the main curing irradiation unit 43 is provided at a position downstream in the transport direction from the printing region where ink is landed on the medium and dots are formed.

The length in the transport direction of the main curing irradiation unit 43 is substantially the same as the length of the nozzle row of the head 31. Then, the main curing irradiation unit 43 moves together with the carriage 22 and irradiates the dots formed on the medium with main curing UV. In addition, the main curing irradiation unit 43 of the present embodiment includes a plurality of units (for example, several tens) including a plurality of LEDs having different wavelengths as light sources for UV irradiation. Accordingly, the main curing irradiation unit 43 has a wider wavelength band than the provisional curing amount irradiation units 42a and 42b. The LED is suitable for being mounted on the carriage 22 because it generates less heat than other light sources such as a lamp (for example, a metal halide lamp, a mercury lamp) and has directivity.
The details of temporary curing and main curing will be described later.

  The detector group 50 includes a linear encoder (not shown), a rotary encoder (not shown), a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder detects the position of the carriage 21 in the moving direction. The rotary encoder detects the rotation amount of the transport roller 13. The paper detection sensor 53 detects the position of the leading edge of the paper being fed. The optical sensor 54 detects the presence or absence of paper by a light emitting unit and a light receiving unit attached to the carriage 21. The optical sensor 54 can detect the position of the edge of the paper while being moved by the carriage 31, and can detect the width of the paper. The optical sensor 54 also detects the leading end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can.

  The controller 60 is a control unit (control unit) for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  When printing, the controller 60 alternately repeats a dot forming operation for ejecting UV ink from the head 31 moving in the forward direction and the backward direction and a transport operation for transporting paper in the transport direction, as will be described later. An image composed of a plurality of dots is printed on paper. Hereinafter, the dot forming operation is referred to as “pass”. The n-th pass is called a pass n.

<Printing procedure>
The controller 60 causes each unit of the printer 1 to perform the following processing when printing the print data received from the computer 110.

  First, the controller 60 rotates the paper feed roller 11 to send a medium to be printed (here, paper S) to the transport roller 13. Next, the controller 60 rotates the transport roller 13 by driving a transport motor (not shown). When the transport roller 13 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount.

  When the paper S is transported to the lower part of the head 31, the controller 60 rotates a carriage motor (not shown). In accordance with the rotation of the carriage motor, the carriage 21 and the carriage 22 move independently in the movement direction. Further, as the carriage 21 moves, the head 31 and the pre-curing irradiation units 42a and 42b provided on the carriage 21 simultaneously move in the movement direction. The main curing irradiation unit 43 provided on the carriage 22 also moves in the movement direction together with the carriage 22. Then, the controller 60 intermittently ejects ink droplets from the head 31 while the head 31 is moving in the movement direction. When the ink droplets land on the paper S, a dot row in which a plurality of dots are arranged in the moving direction is formed. Further, the controller 60 causes the provisional curing irradiation units 42 a and 42 b and the main curing irradiation unit 43 to appropriately perform UV irradiation while the head 31 is moving in the moving direction. Details of the UV irradiation will be described later.

  Further, the controller 60 drives the transport motor between the time when the head 31 reciprocates. The transport motor generates a driving force in the rotation direction according to the commanded driving amount from the controller 60. And a conveyance motor rotates the conveyance roller 13 using this drive force. When the transport roller 13 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount. That is, the transport amount of the paper S is determined according to the rotation amount of the transport roller 13. In this way, the reciprocating movement of the head 31 and the conveyance of the paper S are alternately repeated to form dots on each pixel of the paper S.

  The printed paper S is discharged by a paper discharge roller 15 that rotates in synchronization with the transport roller 13. Thus, an image is printed on the paper S.

<About the configuration of the head 31>
FIG. 4 is an explanatory diagram of an example of the configuration of the head 31. As shown in FIG. 4, a black ink nozzle group K, a cyan ink nozzle row C, a magenta ink nozzle row M, and a yellow ink nozzle row Y are formed on the lower surface of the head 31. Each nozzle row includes a plurality of nozzles (180 in the present embodiment) that are ejection openings for ejecting each color of UV ink.

  The plurality of nozzles in each nozzle row are aligned at a constant interval (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the medium). K is an integer of 1 or more. For example, when the nozzle pitch is 180 dpi (1/180 inch) and the dot pitch in the transport direction is 720 dpi (1/720 inch), k = 4.

  The nozzles in each nozzle row are assigned a lower number toward the downstream side in the transport direction. Each nozzle is provided with a piezo element (not shown) as a drive element for discharging UV ink from each nozzle. By driving this piezo element with a drive signal, droplet-like UV ink is ejected from each nozzle. The discharged UV ink lands on the medium and forms dots.

<About temporary curing and main curing>
In the present embodiment, the dots are cured by irradiating UV to the UV ink that has landed on the medium. In the printer 1 of the present embodiment, the irradiation unit 40 includes provisional curing irradiation units 42a and 42b that perform UV irradiation for temporary curing of UV ink, and a main curing irradiation unit 43 that performs UV irradiation for main curing. Two-stage curing is performed. The temporary curing is for suppressing bleeding between UV inks that have landed on the medium and the spread of dots, and the main curing is for completely curing the UV ink. For this reason, the UV irradiation energy of the main curing is larger than the UV irradiation energy of the temporary curing.

  In the present embodiment, the provisional curing irradiation units 42 a and 42 b are provided on the carriage 21. Accordingly, as the carriage 21 moves, the head 31 and the pre-curing irradiation units 42a and 42b also move in the movement direction integrally. That is, when the nozzle rows of each color of the head 31 reciprocate in the movement direction, the provisional curing irradiation units 42a and 42b and the main curing irradiation unit 43 reciprocate while maintaining the relative positions with respect to the nozzle rows of each color.

  The provisional curing irradiation unit 42a is provided at a position aligned with the head 31 on one end side in the movement direction of the carriage 21, and the provisional curing irradiation unit 42b is disposed on the other end side in the movement direction of the carriage 21 with the head 31. It is provided at a position lined up in the moving direction. When the carriage 21 moves in the moving direction, UV is irradiated toward the medium from the pre-curing irradiation units 42a and 42b. The head 31 is irradiated with UV from a pre-curing irradiation unit located downstream in the moving direction. Specifically, UV is irradiated from the pre-curing irradiation unit 42a during the forward path, and UV is irradiated from the temporary curing irradiation unit 42b during the return path. As described above, the temporary curing is performed during the period in which the head 31 moves in the movement direction, and is performed in the same pass as the formation of dots.

  The main curing irradiation unit 43 is provided on the carriage 22 downstream of the carriage 21 in the transport direction. Accordingly, as the carriage 22 moves in the moving direction, the main curing irradiation unit 43 also moves in the moving direction. In the present embodiment, the distance in the transport direction between the head 31 of the carriage 22 and the main curing irradiation unit 43 of the carriage 21 is substantially the same as the nozzle row length of the head 31. The carriage 22 (in other words, the main curing irradiation unit 43) can move in the movement direction independently of the carriage 21. In the present embodiment, the moving speed of the carriage 22 in the moving direction is faster than the moving speed of the carriage 21 in the moving direction. The main curing irradiation unit 43 irradiates the medium with UV for main curing when reciprocating in the moving direction.

  As described above, in the printer 1 of the present embodiment, printing is performed by curing the UV ink by two-stage curing, that is, temporary curing and main curing. By the way, the temporary curing is to control the spread between the UV inks that have landed on the medium and the spread of the dots, and the shape of the dots is almost determined by the temporary curing.

5A to 5C are explanatory diagrams of the relationship between the shape of the UV ink (dots) landed on the medium and the UV irradiation energy for temporary curing. Note that the UV irradiation energy decreases in the order of FIGS. 5A, 5B, and 5C. The UV irradiation energy (mJ / cm ² ) refers to UV irradiation intensity (mW / cm ² ) × time (sec).
When the UV irradiation energy for temporary curing is large, for example, as shown in FIG. 5A. In this case, it is possible to suppress bleeding between inks and spread of dots, but the gloss becomes worse because the unevenness of the medium surface constituted by the dots becomes large.
On the other hand, when the UV irradiation energy for temporary curing is small, for example, as shown in FIG. 5C. In this case, the gloss is good. However, bleeding easily occurs between other inks, and the spread of dots increases.

<About printing operation>
Next, the printing operation of the first embodiment will be described.

  6A to 6E are explanatory views of the state of image formation according to the first embodiment. For convenience of explanation, the description will start from the state during printing. Further, in each figure, portions to be used (perform UV irradiation) among the pre-curing irradiation units 42a and 42b and the main curing irradiation unit 43 are indicated by hatching.

  FIG. 6A shows a state after the second pass (pass 2). Note that the lower side (image A) of the printed image in the figure is an image printed in the pass (pass 1) before the pass 2, and the UV of the temporary curing UV from the temporary curing irradiation unit 42a. Temporarily cured by irradiation. The image A is located between the head 31 and the main curing irradiation unit 43 in the transport direction. Further, the upper side (image B) of the print image of the medium in the drawing is an image printed in pass 2, and is temporarily cured by irradiation of temporary curing UV from the temporary curing irradiation unit 42b. .

  After pass 2, the controller 60 conveys the medium by a predetermined amount (conveying operation). By this transport operation, as shown in FIG. 6B, the print image of FIG. 6A is transported downstream in the transport direction. By this transport operation, the position of the image B in the transport direction is between the head 31 and the main curing irradiation unit 43. Further, the position of the image A in the transport direction is the same as that of the main curing irradiation unit 43.

  In the next pass (pass 3), as shown in FIG. 6B, the controller 60 discharges UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (forward direction). Further, the controller 60 discharges ink from the head 31, and then outputs UV from the temporary curing irradiation unit (in this case, the preliminary curing irradiation unit 42 a that is hatched) on the upstream side in the moving direction of the head 31. Irradiate. As a result, the dots formed on the medium are temporarily cured. In the present embodiment, the pre-curing irradiation units 42a and 42b are provided at positions aligned with the head 31 of the carriage 21 in the moving direction, so that UV irradiation for pre-curing can be performed immediately after dot formation. Thus, by performing temporary curing immediately after dot formation, bleeding between dots can be prevented, and the spread of dots can be suppressed.

  Further, the controller 60 reciprocates the carriage 22 (in other words, the main curing irradiation unit 43) in the moving direction faster than the carriage 21 during this pass. In this way, the carriage 22 is reciprocated in the movement direction (for example, one reciprocation) per pass. Then, during the movement, the main curing UV is irradiated from the main curing irradiation unit 43 of the carriage 22. As a result, the image A is completely cured by receiving the UV for main curing from the irradiation unit 43 for main curing.

  By this pass 3, as shown in FIG. 6C, the image C is printed on the upper side of the image B (upstream side in the transport direction). At this time, image A is in a state after main curing, and image B and image C are in a state after temporary curing.

  After pass 3, the controller 60 conveys the medium by a predetermined amount (conveying operation). By this transport operation, the print image of FIG. 6C is transported downstream in the transport direction. Thereby, the position of the image C in the conveyance direction is between the head 31 and the main curing irradiation unit 43. Further, the position of the image B in the transport direction is the same as that of the main curing irradiation unit 43. Further, in the image A, the position in the transport direction is on the downstream side of the main curing irradiation unit 43.

  After the carrying operation, the controller 60 causes the next pass (pass 4) to be performed. As shown in FIG. 6D, the controller 60 discharges UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (return path direction). In addition, after the ink is ejected from the head 31, the controller 60 temporarily cures from the pre-curing irradiation unit (in this case, the pre-curing irradiation unit 42b that is hatched) on the upstream side in the moving direction of the head 31. UV is irradiated for pre-curing. In FIG. 6D, since the moving direction is reverse to that in FIG. 6B, the temporary effect irradiation section used for temporary curing is reverse to that in FIG. 6B.

  Further, the controller 60 reciprocates the carriage 22 (in other words, the main curing irradiation unit 43) in the moving direction faster than the carriage 21 during this pass. Then, during the reciprocation, the main curing UV is irradiated from the main curing irradiation unit 43 of the carriage 22. As a result, the image B is completely cured by receiving UV for main curing from the main curing irradiation unit 43.

  With this pass 4, as shown in FIG. 6E, the image D is printed on the upper side (the upstream side in the transport direction) of the image C of the medium. At this time, the image A and the image B are in a state after the main curing, and the image C and the image D are in a state after the temporary curing.

  Thereafter, similarly, the controller 60 repeatedly performs the pass and the transport operation alternately. Further, the controller 60 irradiates the main curing UV from the main curing irradiation unit 43 while reciprocating the carriage 22 in the moving direction during the pass.

  In the present embodiment, the moving speed of the carriage 22 in the moving direction is faster than the moving speed of the carriage 21. Thereby, UV for main curing can be uniformly irradiated to the image (dot) on a medium.

<About irradiation conditions>
As described above, the dot shape differs depending on the UV irradiation condition, resulting in a difference in image quality. Therefore, the optimum conditions were evaluated for each of the two stages of UV irradiation.
The UV ink is prepared by adding auxiliary agents such as a polymerization inhibitor and a surfactant to a mixture of oligomers and monomers having photopolymerization curability, a photopolymerization initiator, and a pigment. When the ink containing these photopolymerization initiators is irradiated with light, the photopolymerization initiator contained in the ink absorbs light of a specific wavelength and generates radicals. Then, the radical attacks the monomer, and the polymerization reaction proceeds (curing progresses).
Since the irradiation energy for main curing is very large (for example, 100 times or more) with respect to the irradiation energy for temporary curing, first, the irradiation conditions for main curing were evaluated.

FIG. 7 is a diagram showing the evaluation results of the irradiation conditions for the main curing. In the present embodiment, the irradiation energy of the main curing is in the range of 150 (mJ / cm ² ) to 550 (mJ / cm ² ), as shown in the figure, adhesion, abrasion resistance, color stability (yellowing, etc.) Was evaluated. The adhesion was evaluated by a tape peeling test, and the abrasion resistance was evaluated by a Gakushin type abrasion tester. The color stability was evaluated visually.

From the figure, it can be seen that when the UV irradiation energy of the main curing is 180 mJ / cm ² or less, the adhesion and the abrasion resistance are deteriorated. The UV irradiation energy of the main curing is 200 J / cm ² or more, and the adhesion and scuff resistance are good.
On the other hand, when the UV irradiation energy of the main curing is 520 mJ / cm ² or more, the color stability is deteriorated (yellowing occurs). The UV irradiation energy is 500 mJ / cm ² or less, and the color stability is good. Yellowing is a phenomenon in which the color of ink changes to yellow, and it is more likely to occur as the UV irradiation energy increases.
Therefore, 200 to 500 (mJ / cm ² ) is suitable as the irradiation energy for the main curing.

Subsequently, the irradiation conditions of the pre-curing UV were evaluated. In this embodiment, the test pattern was printed while changing the irradiation energy of the pre-curing UV within the range of the main curing conditions (200 to 500 mJ / cm ² ), and the image quality was evaluated.

FIG. 8 is a diagram showing the evaluation results of the pre-curing irradiation conditions. As shown in the figure, in the range of the irradiation energy of the main curing of 1 to 33 (mJ / cm ² ), as shown in the figure, evaluations about bleed, unevenness, filling, and gloss were performed, respectively. In addition, evaluation shown to a figure was determined visually.

Bleed is bleeding that occurs at the boundary between different ink colors. As described above, bleeding tends to occur when the UV irradiation energy for temporary curing is small. The bleed was good when the irradiation energy for temporary curing was 3 mJ / cm ² or more.

Unevenness is also likely to occur when the UV irradiation energy for pre-curing is small, as with bleed. As shown in the figure, the unevenness was good when the pre-curing irradiation energy was 3 mJ / cm ² or more.

Filling is an evaluation of whether or not streaks occur in the scanning direction (moving direction in the present embodiment) when printing a high gradation image such as a so-called solid image. Contrary to the case of bleeding or unevenness, the filling becomes better when the UV irradiation energy for temporary curing is small. This is because if the UV irradiation energy for pre-curing is small, the dots are likely to spread (see FIG. 5C). As shown in the drawing, the filling was good when the UV irradiation energy for pre-curing was 30 mJ / cm ² or less.

Gloss is an evaluation of the surface condition of a printed image. If the surface is smooth, the gloss is improved, and if the surface is uneven, the gloss is deteriorated. Therefore, the gloss is also good when the UV irradiation energy for pre-curing is small as in the case of filling. As shown in the figure, the gloss was good when the UV energy of pre-curing was 30 mJ / cm ² or less. In particular, the pre-curing UV irradiation energy was better at 15 mJ / cm ² or less.

Thus, 3-30 (mJ / cm < ² >) is suitable as UV irradiation energy of temporary hardening. Furthermore, when the irradiation energy for temporary curing is 3 to 15 (mJ / cm ² ), the image quality can be further improved. Incidentally, the irradiation energy (also referred to as polymerization rate) 3~15 (mJ / cm ²⁾ cure rate after temporary curing in was 20 to 35%. The curing rate is the ratio of the double bond that has disappeared when the double bond of the monomer in the ink has completely disappeared and 100%. For example, when the curing rate is 20%, the double bond disappeared in the ink is 20%, and the double bond not disappeared is 80%. From the above, it is possible to improve the image quality by setting the curing rate after temporary curing to 20 to 35% and completely curing with UV irradiation of main curing.

<Comparative example>
FIG. 9 is a schematic view around the head of the comparative example.
In this comparative example, the main curing irradiation unit 43 ′ has a length in the moving direction longer than the maximum width of the medium to be printed on the downstream side of the carriage 21 in the transport direction (for example, the position immediately before the paper discharge). It is provided to become.
In this comparative example, the main curing irradiation unit 43 ′ performs UV irradiation for main curing toward the medium being conveyed immediately before the medium after printing is discharged without moving in the moving direction. In this way, the dots on the medium (dots after temporary curing) are fully cured.
However, in the case of this comparative example, since UV irradiation for main curing is performed in the region of the maximum width of the medium to be printed, there is a problem that heat generation is large. In the comparative example, it is difficult to reduce the size of the apparatus. Furthermore, in the comparative example, UV irradiation corresponding to the size of the medium cannot be performed.

  In contrast, in the present embodiment, the main curing irradiation unit 43 is provided on the carriage 22 that moves in the movement direction. Then, as the carriage 22 moves in the moving direction, the main curing irradiation unit 43 also moves in the moving direction, so that the dots (temporarily cured dots) formed by the pass are irradiated with the main curing UV. ing. Thereby, in this embodiment, the irradiation part 43 for main curing can be comprised smaller than a comparative example, and heat_generation | fever can be reduced. In addition, the size of the apparatus can be reduced.

Further, in the present embodiment, the range of UV irradiation for main curing can be changed corresponding to the size of the medium to be printed, and main curing can be performed efficiently.
In the present embodiment, an LED is used as the light source of the main curing irradiation unit 43. Since the LED generates less heat than the lamp and has directivity, the LED is suitable for mounting on the carriage 22.
In the present embodiment, the light source of the main curing irradiation unit 43 is configured by collecting a plurality of units including a plurality of LEDs having different wavelengths, and has a wavelength that is greater than that of the light sources of the provisional curing irradiation units 42a and 42b. The bandwidth is widened. Thereby, regardless of the composition of the ink, it is possible to surely cure the dots.

=== Second Embodiment ===
The second embodiment is different from the first embodiment in that the carriage 22 always reciprocates in the moving direction regardless of the path and the transport operation. Note that the configuration of the printer is the same as in the first embodiment, and a description thereof will be omitted.

  FIG. 10A to FIG. 10E are explanatory views of the state of image formation according to the second embodiment. Note that, similarly to the first embodiment, a description will be given from a state during printing. Further, in each figure, portions to be used (perform UV irradiation) among the pre-curing irradiation units 42a and 42b and the main curing irradiation unit 43 are indicated by hatching.

  FIG. 10A shows a state after the second pass (pass 2). Note that the lower side (image A) of the printed image in the figure is an image printed in the pass (pass 1) before the pass 2, and the UV for temporary curing from the temporary curing irradiation unit 42a. Temporarily cured by irradiation. Further, the image A is located between the head 31 and the main curing irradiation unit 43 in the transport direction. Further, the upper side (image B) of the print image of the medium in the drawing is an image printed in pass 2, and is temporarily cured by irradiation of the UV for temporary curing from the irradiation unit 42b for temporary curing. . In the second embodiment, the controller 60 always reciprocates the carriage 22 (in other words, the main curing irradiation unit 43) in the moving direction. Further, the moving speed of the carriage 22 in the moving direction is faster than the moving speed of the carriage 21.

  After pass 2, the controller 60 conveys the medium by a predetermined amount (conveying operation). By this transport operation, as shown in FIG. 10B, the print image of FIG. 10A is transported downstream in the transport direction. As a result, the position of the image B in the transport direction is between the head 31 and the main curing irradiation unit 43. Further, the position of the image A in the transport direction is the same as that of the main curing irradiation unit 43. Since the controller 60 always reciprocates the carriage 22 in the moving direction, the main curing irradiation unit 43 passes over the image A during the transport operation. The controller 60 then irradiates the image on the medium with UV for main curing from the main curing irradiation unit 43 during the transport operation.

  In the next pass (pass 3), as shown in FIG. 10B, the controller 60 discharges UV ink from the nozzles of the head 31 while moving the carriage 21 in the moving direction (forward direction). Further, the controller 60 discharges ink from the head 31, and then outputs UV from the temporary curing irradiation unit (in this case, the preliminary curing irradiation unit 42 a that is hatched) on the upstream side in the moving direction of the head 31. Irradiate. As a result, the dots formed on the medium are temporarily cured. In the present embodiment, the pre-curing irradiation units 42a and 42b are provided at positions aligned with the head 31 of the carriage 21 in the moving direction, so that UV irradiation for pre-curing can be performed immediately after dot formation. Thus, by performing temporary curing immediately after dot formation, bleeding between dots can be prevented, and the spread of dots can be suppressed.

  Also during this pass, the controller 60 reciprocates the carriage 22 in the movement direction, and the image A is irradiated with UV for main curing from the main curing irradiation unit 43.

  With this pass 3, as shown in FIG. 10C, the image C is printed on the upper side of the image B (upstream side in the transport direction). At this time, image A is in a state after main curing, and image B and image C are in a state after temporary curing.

  After pass 3, the controller 60 conveys the medium by a predetermined amount (conveying operation). By this transport operation, the print image in FIG. 10C is transported downstream in the transport direction. Thereby, the position of the image C in the conveyance direction is between the head 31 and the main curing irradiation unit 43. Further, the position of the image B in the transport direction is the same as that of the main curing irradiation unit 43. Further, in the image A, the position in the transport direction is on the downstream side of the main curing irradiation unit 43. Since the controller 60 always moves the carriage 22 back and forth in the moving direction, the main curing irradiation unit 43 passes over the image B during this transport operation. The controller 60 then irradiates the image on the medium with UV for main curing from the main curing irradiation unit 43 during the transport operation.

  After the carrying operation, the controller 60 causes the next pass (pass 4) to be performed. As shown in FIG. 10E, the controller 60 ejects UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (return path direction). In addition, after the ink is ejected from the head 31, the controller 60 temporarily cures from the pre-curing irradiation unit (in this case, the pre-curing irradiation unit 42b that is hatched) on the upstream side in the moving direction of the head 31. UV is irradiated for pre-curing. In FIG. 10D, since the moving direction is reverse to that in FIG. 10B, the temporary effect irradiation unit used for temporary curing is reverse to that in FIG. 10B.

  Also during this pass, the controller 60 reciprocates the carriage 22 in the movement direction, and the image B is irradiated with UV for main curing from the main curing irradiation unit 43.

  With this pass 4, as shown in FIG. 10E, the image D is printed on the upper side (upstream side in the transport direction) of the image C of the medium. At this time, the image A and the image B are in a state after the main curing, and the image C and the image D are in a state after the temporary curing.

  Thereafter, similarly, the controller 60 repeatedly performs the pass and the transport operation alternately. Further, the controller 60 irradiates the main curing UV from the main curing irradiation unit 43 while reciprocating the carriage 22 in the moving direction regardless of the path and the transport operation.

  In the second embodiment, even during the conveyance of the medium, the carriage 22 is reciprocated in the moving direction to irradiate the UV for main curing from the main curing irradiation unit 43. As a result, the time for irradiating the image with UV for main curing can be lengthened, and the image after temporary curing can be surely main cured.

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the printer has been described as an example of the liquid ejection apparatus, but the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various devices to which inkjet technology is applied, such as a device and a DNA chip manufacturing device.

<About nozzle>
In the above-described embodiment, ink is ejected using a piezoelectric element (piezo element). However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About ink>
In the above-described embodiment, ink (UV ink) that is cured by being irradiated with ultraviolet rays (UV) is ejected from the nozzles. However, the liquid ejected from the nozzle is not limited to such ink, and a liquid that is cured by irradiation with light other than UV (for example, visible light) may be ejected from the nozzle. In this case, light (such as visible light) for curing the liquid may be irradiated from the pre-curing irradiation units 42 a and 42 b and the main curing irradiation unit 43.
In this embodiment, the CMYK four-color UV ink is used, but other colors of UV ink may be used. For example, white ink for background or clear and colorless clear ink may be used.

<About dot formation>
In the above-described embodiment, bidirectional printing is performed, but the present invention is not limited to this. That is, unidirectional printing may be used. In this case, at least one provisional curing irradiation unit may be provided on the downstream side in the moving direction of the head 31 when forming dots.
Further, in the present embodiment, the case where the raster lines corresponding to the nozzle row length are formed by one pass (band printing) has been described, but the raster lines corresponding to the nozzle row length may be formed by a plurality of passes. Good. For example, interlace printing may be used. In this case, the UV irradiation energy to each dot may be the same as that in the above-described embodiment.

1 printer, 10 transport unit, 11 paper feed roller,
13 transport roller, 14 platen, 15 paper discharge roller,
20 Carriage unit, 21, 22 Carriage, 24, 25 Guide shaft,
30 head units, 31 heads,
40 irradiation unit, 42a, 42b irradiation part for temporary curing, 43 irradiation part for main curing,
50 detector group, 53 paper detection sensor, 54 optical sensor 60 controller, 61 interface unit, 62 CPU,
63 memory, 64 unit control circuit,
110 computer

Claims (8)

(A) a head that discharges a liquid that is cured by light irradiation;
(B) a first carriage that moves the head in a movement direction that intersects the medium conveyance direction;
(C) a temporary curing light source that is provided on the first carriage and that irradiates the dots formed by the liquid ejected from the moving head landing on the medium with light for preliminary curing;
(D) a second carriage that is provided downstream of the first carriage in the transport direction and moves in the movement direction independently of the first carriage;
(E) a main curing light source that is provided on the second carriage and that irradiates light for main curing to dots irradiated with light from the temporary curing light source;
A liquid ejecting apparatus comprising: The liquid ejection device according to claim 1,
The liquid discharge apparatus, wherein the main curing light source is an LED. The liquid ejection device according to claim 1 or 2,
The liquid discharge apparatus, wherein the main curing light source has a wider wavelength band than the temporary curing light source. The liquid ejection device according to any one of claims 1 to 3,
The liquid ejecting apparatus according to claim 1, wherein a moving speed of the second carriage in the moving direction is faster than a moving speed of the first carriage in the moving direction. A liquid ejection apparatus according to any one of claims 1 to 4,
A dot forming operation for ejecting liquid from the head while reciprocating the first carriage in the moving direction and a transport operation for transporting the medium in the transport direction are alternately performed.
The main curing light source moves in the moving direction together with the second carriage during the transport operation, and irradiates the medium with the main curing light. A liquid ejection apparatus according to any one of claims 1 to 5,
The liquid ejection apparatus according to claim 1, wherein irradiation energy of the light for main curing by the light source for main curing is 200 to 500 mJ / cm ² . The liquid ejection device according to any one of claims 1 to 6,
The liquid ejection apparatus according to claim 1, wherein irradiation energy of the temporary curing light from the temporary curing light source is 3 to 30 mJ / cm ² . A liquid ejection apparatus according to any one of claims 1 to 7,
The liquid ejection apparatus according to claim 1, wherein the degree of curing of the dots irradiated with the temporary curing light is 20 to 35%.

Images