Liquid ejection device and image recording device including the same

Abstract

To provide a liquid discharge device suppressing oxygen inhibition on a nozzle array end part, and an image recorder comprising the same.SOLUTION: A liquid discharge device comprises: a discharge head comprising at least one row of a nozzle row including a plurality of nozzles which are arranged in a sub scanning direction, in a main scanning direction, and moving in the main scanning direction; and an ultraviolet lamp including at least one row of a chip row including a plurality of light emitting diode chips which is arranged in the sub scanning direction, in the main scanning direction, and moving in the main scanning direction. In at least one chip row, chip density which is the number of the light emitting diode chips for a unit length in the sub scanning direction on an end part of the sub scanning direction, is greater than chip density on a center in the sub scanning direction, illuminance on the end part is greater than illuminance on a center, and at least one light emitting diode chip is provided at outside of the sub scanning direction relative to the nozzle provided on a nozzle end being an end part of the nozzle row.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet irradiation device that irradiates ultraviolet rays to cure ultraviolet-curable ink, and to an image recording device such as an inkjet printer that is equipped with the same. [Background technology]

[0002] In recent years, as shown in Patent Document 1, for example, a device (referred to as a liquid ejection device in Patent Document 1) has become known that is used in image recording devices such as inkjet printers and that irradiates ultraviolet rays onto ultraviolet-curable ink that is cured by ultraviolet rays. The liquid ejection device disclosed in this document irradiates ultraviolet rays onto ink droplets that have landed on a substrate, thereby curing the ink and fixing it to the substrate. By using such ultraviolet-curable ink, it is possible to print on materials other than paper, such as resin and metal, and to obtain a glossy printed substrate.

[0003] In the liquid ejection device described in the above document, multiple light-emitting diode chips are arranged in an array. The light-emitting diode chips are arranged in a matrix along the short-side direction (main scanning direction) and long-side direction (sub-scanning direction) of the array. The light-emitting diode chips are arranged at a constant pitch in the main scanning direction and also at a constant pitch in the sub-scanning direction. However, simply arranging multiple light-emitting diode chips in this manner does not provide a desired illuminance distribution. Therefore, in the liquid ejection device described above, the multiple light-emitting diode chips are driven so that the illuminance of ultraviolet light at the ends in the sub-scanning direction is greater than the illuminance at the center. In this case, the illuminance of each light-emitting diode chip is controlled by adjusting the current supplied to each light-emitting diode chip. This configuration is said to enable uniform irradiation of ultraviolet light in the sub-scanning direction and reduce unevenness in the amount of irradiation light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-209494 Summary of the Invention [Problem to be solved by the invention]

[0005] However, at the ends of the nozzle row, oxygen inhibition occurs, a phenomenon in which the monomers in UV-curable ink are captured by oxygen, making it difficult for the ink to cure. In particular, when performing solid printing using clear ink or the like, the surface area of the liquid that lands on the substrate is larger at the ends of the nozzle row than at the center of the nozzle row, so the impact of oxygen inhibition at the ends of the nozzle row is greater than in other areas. However, in the above-mentioned conventional liquid ejection device, there is room for further suppression of oxygen inhibition at the ends of the nozzle row.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid ejection device that can suppress oxygen inhibition at the ends of the nozzle rows, and an image recording apparatus including the same. [Means for solving the problem]

[0007] The liquid ejection device of the present invention is a liquid ejection device that cures ultraviolet-curable ink ejected onto a substrate using ultraviolet rays, and is equipped with: an ejection head that has at least one nozzle row in a main scanning direction, which is a direction perpendicular to the sub-scanning direction, and that moves in the main scanning direction, and an ultraviolet irradiation device that has at least one chip row in the main scanning direction, which has a plurality of light-emitting diode chips that are arranged in the sub-scanning direction, and that moves in the main scanning direction, and in which at least one chip row has a chip density, which is the number of light-emitting diode chips per unit length in the sub-scanning direction, at an end of the sub-scanning direction, that is higher than the chip density at a central part of the sub-scanning direction, and the illuminance at the end is higher than the illuminance at the central part, and at least one light-emitting diode chip is included that is located outside the sub-scanning direction of a nozzle located at a nozzle end, which is the end of the nozzle row.

[0008] According to the present invention, the chip density at the ends in the sub-scanning direction is higher than the chip density in the center, and the illuminance at the ends in the sub-scanning direction is higher than the illuminance at the center, thereby suppressing oxygen inhibition at the ends of the nozzle row. In particular, in the present invention, at least one light-emitting diode chip is arranged further outward in the sub-scanning direction than the nozzles located at the nozzle ends, so the illuminance at the ends in the sub-scanning direction can be reliably made higher than the illuminance at the center. This makes it possible to suppress oxygen inhibition at the ends of the nozzle row more significantly than in the past. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a liquid ejection device that can suppress oxygen inhibition at the ends of the nozzle row, and an image recording apparatus including the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an image recording apparatus according to a first embodiment of the present invention. [Figure 2] 2 is a plan view showing an example of the arrangement of a discharge head and an ultraviolet irradiation device mounted on the carriage of FIG. 1. FIG. [Figure 3] FIG. 2 is a block diagram showing the configuration of the image recording device of FIG. 1. [Figure 4] 2 is a bottom view showing an example of the arrangement of nozzle rows in the ejection head of FIG. 1 and light-emitting diode chips in an ultraviolet irradiation device. FIG. [Figure 5] FIG. 2 is a diagram schematically illustrating the internal configuration of an ultraviolet irradiation device. [Figure 6] FIG. 1 shows a high gap and a low gap. [Figure 7] FIG. 10(a) is a diagram for explaining an example of an end arrangement pitch and an adjacent arrangement pitch, and FIG. 10(b) is a diagram for explaining another example of an end arrangement pitch and an adjacent arrangement pitch. [Figure 8]FIG. 1 is a diagram showing light-emitting diode chips arranged at an end arrangement pitch and an adjacent arrangement pitch in Comparative Example 1 and Examples 1 to 5. [Figure 9] 9 is a graph showing the relationship between the position in the sub-scanning direction in the nozzle row and the illuminance, obtained by simulation, corresponding to Comparative Example 1 and Examples 1 to 5 of FIG. [Figure 10] 10 is a diagram showing light-emitting diode chips arranged at an end arrangement pitch and an adjacent arrangement pitch in Comparative Example 2 and Examples 6 to 12. FIG. [Figure 11] 11 is a graph showing the relationship between the position in the sub-scanning direction in the nozzle row and the illuminance, obtained by simulation, corresponding to Comparative Example 2 and Examples 6 to 12 in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] A liquid ejection apparatus and an image recording apparatus including the same according to an embodiment of the present invention will be described below with reference to the drawings. The liquid ejection apparatus and image recording apparatus described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiment, and additions, deletions, and modifications can be made without departing from the spirit of the present invention.

[0012] FIG. 1 is a perspective view showing an image recording apparatus 1 according to one embodiment of the present invention. In FIG. 1, directions that are perpendicular to one another are the up-down direction, the left-right direction, and the front-rear direction. The left-right direction is the main scanning direction Ds, which will be described later, and the front-rear direction is the sub-scanning direction Df, which will be described later. This image recording apparatus 1 not only prints on a printing substrate W such as printing paper, but also performs merchandise printing, printing on a printing substrate W (FIG. 6) made of resin or the like, for example, for printing on various merchandise.

[0013] 1, the image recording device 1 of this embodiment includes a housing 2, a carriage 3, operation keys 4, a display unit 5, a platen 6, and an upper cover 7. The image recording device 1 also includes a control unit 19 shown in FIG.

[0014] The housing 2 is formed in a box shape. The housing 2 has an opening 2a on the front side and an opening (not shown) on the back side. Operation keys 4 are provided at a position on the front right side of the housing 2. A display unit 5 is provided behind the operation keys 4. The operation keys 4 accept operation inputs by the user. The display unit 5 is formed, for example, by a touch panel, and displays predetermined information. A part of the display unit 5 also functions as an operation key at a predetermined timing. The control unit 19 realizes the printing function based on input from the operation keys 4 or external input via a communication interface (not shown) and also controls the display of the display unit 5.

[0015] The carriage 3 is configured to be able to reciprocate along the main scanning direction Ds. As shown in FIG. 2, a liquid ejection device 50 is mounted on the carriage 3. This liquid ejection device 50 includes two ejection heads 10 (10A, 10B) and two ultraviolet irradiation devices 40 (40A, 40B). The ejection heads 10 may be, for example, inkjet heads that eject ultraviolet-curable ink. The ultraviolet irradiation device 40 has a plurality of light-emitting diode chips DT (FIG. 4) that emit ultraviolet light, and irradiates the ink ejected by the ejection head 10 with ultraviolet light to cure the ink. The ejection heads 10A and 10B are arranged side by side along the sub-scanning direction Df. The ejection head B is arranged in front of the ejection head A. The ultraviolet irradiation device 40A and the ultraviolet irradiation device 40B are arranged side by side along the sub-scanning direction Df. The ultraviolet irradiation device 40B is arranged in front of the ultraviolet irradiation device 40A. The ejection head 10A and the ultraviolet irradiation device 40A are arranged side by side along the main scanning direction Ds. The ultraviolet irradiation device 40A is disposed to the right of the ejection head 10A. The ejection head 10B and the ultraviolet irradiation device 40B are disposed side by side in the main scanning direction Ds. The ultraviolet irradiation device 40B is disposed to the right of the ejection head 10B.

[0016] 2, during one pass of the printing process, the carriage 3 moves to the left in the main scanning direction Ds. As a result, the ejection head 10 and the ultraviolet irradiation device 40 move to the left during the printing process. In this case, the ejection head 10 ejects ink onto the printing substrate W while moving left in the main scanning direction Ds, and the ultraviolet irradiation device 40 irradiates ultraviolet rays onto the ink that has landed on the printing substrate W while moving left in the main scanning direction Ds. As a result, the ultraviolet irradiation device 40 is positioned behind the ejection head 10 in the movement direction of the carriage 3 during the printing process, so that ultraviolet rays can be irradiated onto the ink immediately after it has landed on the printing substrate W.

[0017] Furthermore, when one pass of the printing process is completed, the carriage 3 moves to the right in the main scanning direction Ds and returns to a predetermined position in the main scanning direction Ds. As a result, the ejection head 10 and the ultraviolet irradiation device 40 move to the right in the main scanning direction Ds. In this case, the ejection head 10 moves to the right in the main scanning direction Ds without ejecting ink, and the ultraviolet irradiation device 40 irradiates ultraviolet rays onto the ink ejected during the printing process while moving to the right in the main scanning direction Ds. This allows the ink to be sufficiently irradiated with ultraviolet rays, improving the curing properties of the ink.

[0018] In this embodiment, the ejection head 10A ejects ink of each color: yellow (Y), magenta (M), cyan (C), and black (K), which are sometimes collectively referred to as color inks. The ejection head 10A is provided with nozzle rows NL that eject each of these inks, each extending along the sub-scanning direction Df. The nozzle rows NL are provided at regular intervals along the main scanning direction Ds. Note that the arrangement order of the nozzle rows NL in the main scanning direction Ds is not limited to the order of the nozzle row NL ejecting yellow (Y) ink, the nozzle row NL ejecting magenta (M) ink, the nozzle row NL ejecting cyan (C) ink, and the nozzle row NL ejecting black (K) ink from left to right as shown in FIG. 2, and can be set as appropriate.

[0019] On the other hand, the ejection head 10B ejects white (W) ink and clear (Cr) ink. The ejection head 10B is provided with nozzle rows NL that eject each of these inks, each extending along the sub-scanning direction Df. The nozzle rows NL are arranged at regular intervals along the main scanning direction Ds. The spacing between the nozzle rows NL in the ejection head 10B in the main scanning direction Ds may be different from or the same as the spacing between the nozzle rows NL in the ejection head 10A in the main scanning direction Ds (as shown in the example of FIG. 2). The arrangement order of the nozzle rows NL in the main scanning direction Ds is not limited to the order of the nozzle row NL ejecting white (W) ink and the nozzle row NL ejecting clear (K) ink from the left as shown in FIG. 2, and the nozzle rows NL may be arranged in the opposite order. A color image is printed on the printing substrate W by ejecting the six color inks described above onto the printing substrate W. Specifically, when printing a color image on fabric as the printing substrate W, white ink is ejected first as a base ink, and then color inks are ejected on top of the white ink to reduce the effect on the color and material of the fabric. Clear ink is ejected to impart gloss or to protect the printed area.

[0020] The platen 6 is configured so that a printing substrate W can be placed on it. The platen 6 has a predetermined thickness and is made of, for example, a rectangular plate material with the sub-scanning direction Df as its longitudinal direction. The platen 6 is removably supported by a platen support base (not shown). The platen support base is configured so that it can move between a printing position where printing is performed on the printing substrate W and a detachment position where the printing substrate W is detached from the platen 6. The printing position is a position where the platen 6 faces the ejection head 10, and the detachment position is a position where the platen support base is disposed outside the housing 2 and where the printing substrate W can be placed on the platen 6. During printing, the platen 6 moves in the sub-scanning direction Df, so that the printing substrate W placed on the platen 6 is transported in the sub-scanning direction Df.

[0021] When the front portion of the upper cover 7 is lifted, it rotates upward around a rotatable base end, which serves as a fulcrum, thereby exposing the inside of the housing 2.

[0022] Next, the functions of each component of the image recording device 1 of this embodiment will be described with reference to a block diagram. As shown in Fig. 3, in addition to the components described above, the image recording device 1 of this embodiment is equipped with motor driver ICs 30 and 31, head driver ICs 32 and 36, a transport motor 33, a carriage motor 34, irradiation device driver ICs 37 and 38, an internal power supply 15, and a power receiving unit 16. The image recording device 1 is equipped with an ink tank (not shown) that stores ink to be supplied to the ejection head 10.

[0023] The control unit 19 has a CPU 20, a storage unit (ROM 21, RAM 22, EEPROM 23, HDD 24), and an ASIC 25. The CPU 20 is a control unit of the image recording device 1, and is connected to the storage unit and controls the driver ICs 30 to 32, 36 to 38 and the display unit 5.

[0024] The CPU 20 performs various functions by executing predetermined programs stored in the ROM 21. The CPU 20 may be implemented as a single processor in the control unit 19, or may be implemented as multiple processors that cooperate with each other.

[0025] The ROM 21 stores a print control program that causes the CPU 20 to execute a print process. The RAM 22 stores calculation results of the CPU 20. The EEPROM 23 stores various initial setting information input by the user. The HDD 24 stores specific information and the like. This specific information is highly confidential information that should not be leaked to the outside, and includes, for example, information about the user, job data received by the image recording device 1 from outside and including a user ID that identifies the sender, user usage history information including the user ID in the job data, secure job data including a password and data related to the secure job, print history, and cloud setting data. The user information includes, for example, phone book information, email address information, information about the administrator (security administrator) of the image recording device 1, and network setting information. When the image recording device 1 receives job data, the CPU 20 stores the user usage history information including the user ID in the job data in the HDD 24.

[0026] The ASIC 25 is connected to motor driver ICs 30 and 31, head driver ICs 32 and 36, and irradiation device driver ICs 37 and 38. When the CPU 20 receives a print job from a user, it outputs a print command to the ASIC 25 based on a print control program. The ASIC 25 drives the driver ICs 30-32, 36-38 based on the print command. The CPU 20 drives the conveyance motor 33 via the motor driver IC 30, thereby moving the platen 6 in the sub-scanning direction Df and conveying the printing substrate W. The CPU 20 also drives the carriage motor 34 via the motor driver IC 31 to move the carriage 3. The CPU 20 also ejects ink from the ejection head 10 mounted on the carriage 3, which is moved by the head driver ICs 32 and 36, to print image data on the conveyed printing substrate W. The CPU 20 also controls the irradiation device driver ICs 37 and 38 to irradiate ultraviolet light from the ultraviolet irradiation devices 40A and 40B to cure the ink. The printing process is carried out in this manner.

[0027] The internal power supply 15 is provided at a predetermined position within the housing 2. The internal power supply 15 enables the control unit 19 to operate when the main body power supply of the image recording device 1 is in the OFF state. The internal power supply 15 is, for example, a secondary battery. The power receiving unit 16 is provided so as to be exposed to the outside from the housing 2, and receives power from an external power supply. When the main body power supply is in the ON state, external power is supplied to each part of the image recording device 1 via the power receiving unit 16. Regardless of the state of the main body power supply, external power is supplied to the internal power supply 15 via the power receiving unit 16, and the internal power supply 15 is charged by this power.

[0028] Next, the arrangement of the plurality of light-emitting diode chips DT in the ultraviolet irradiation device 40 of this embodiment will be described. In this embodiment, the light-emitting diode chips DT are semiconductor elements that generate ultraviolet rays. Note that, although the ultraviolet irradiation device 40A and the discharge head 10A will be described below as representatives, the ultraviolet irradiation device 40B and the discharge head 10B can also be configured in the same way as the ultraviolet irradiation device 40A and the discharge head 10A.

[0029] 4, the ultraviolet irradiation device 40A includes a support substrate 41 formed, for example, in a rectangular shape in a plan view. The support substrate 41 is, for example, an aluminum substrate. The support substrate 41 may also be formed of other metals such as copper. Each light-emitting diode chip DT is disposed on the support substrate 41.

[0030] When each light-emitting diode chip DT irradiates ink with ultraviolet light, a photopolymerization initiator contained in the ink reacts, polymerizing the monomer contained in the ink and fixing the ink to the printing substrate W. The light-emitting diode chips DT are arranged in a matrix. Each light-emitting diode chip DT is arranged, for example, based on the center of a rectangular unit cell having sides along the longitudinal and lateral directions of the support substrate 41. As a result, the light-emitting diode chips DT are arranged at regular intervals along the main scanning direction Ds and at regular intervals along the sub-scanning direction Df. Therefore, the light-emitting diode chips DT are arranged along a row direction parallel to the main scanning direction Ds and a column direction parallel to the sub-scanning direction Df. FIG. 4 shows an example in which there are 11 rows of light-emitting diode chips DT aligned in the left-right direction and 5 columns of light-emitting diode chips DT aligned in the front-rear direction. A group of multiple light-emitting diode chips DT aligned at regular intervals along the sub-scanning direction Df is referred to as a chip row DL. Therefore, FIG. 4 shows an example in which five chip rows DL are arranged. Note that the number of light-emitting diode chips DT arranged on the support substrate 41 is not limited to the above, and is determined based on the integrated light amount and power consumption during one pass, etc.

[0031] As described above, the ejection head 10A is provided with four nozzle rows NL. Each nozzle row NL includes a plurality of nozzles Nz arranged side by side at regular intervals along the sub-scanning direction Df. Ink is ejected from the nozzles Nz. The distance from the nozzle Nz located at the front end of each nozzle row NL in the sub-scanning direction Df to the nozzle Nz located at the rear end in the sub-scanning direction Df is defined as the nozzle length Lh. Note that Figure 4 only shows the nozzle row NL that ejects black (K) ink; the other three nozzle rows are omitted.

[0032] Each light-emitting diode chip DT of the ultraviolet irradiation device 40A is arranged so that the ultraviolet light emission area of the light-emitting diode chip DT is larger than the nozzle row NL in the sub-scanning direction Df. As a result, when the length of each chip row DL in the sub-scanning direction Df, that is, the distance from the light-emitting diode chip DT located at the front end of each chip row DL in the sub-scanning direction Df to the light-emitting diode chip DT located at the rear end of each chip row DL in the sub-scanning direction Df, is defined as the light-emitting length Ld, this light-emitting length Ld can be made larger than the nozzle length Lh. Therefore, ultraviolet light can be effectively irradiated onto ink droplets ejected from the nozzles Nz located at the front and rear ends of the nozzle row NL.

[0033] The light emitting diode chips DT are arranged side by side at a predetermined pitch in the main scanning direction Ds. The arrangement pitch of the light emitting diode chips DT in the sub scanning direction Df will be described later.

[0034] Next, the heat dissipation structure of the ultraviolet irradiation device 40 will be described. FIG. 5 is a diagram schematically illustrating the internal configuration of the ultraviolet irradiation device 40. As shown in FIG. 5, the ultraviolet irradiation device 40 includes the support substrate 41 described above, which supports a plurality of light-emitting diode chips DT, and a plate-shaped heat sink 42 provided on the surface (upper surface) of the support substrate 41 opposite the surface (lower surface) on which the plurality of light-emitting diode chips DT are provided. The heat sink 42 includes a base portion 42a disposed on the support substrate 41 and a plurality of heat sinks (fins) 42b extending upward on the base portion 42a. The heat sinks 42b are arranged at equal intervals. In addition, electronic components (not shown) are provided on the lower surface of the support substrate 41, and these electronic components are provided with a plurality of electrodes 45 corresponding to the light-emitting diode chips DT. Each light-emitting diode chip DT is electrically connected to each electrode 45. The lower surface of the support substrate 41 is covered with an insulating film 44, with portions of the electrodes 45 exposed. In this configuration, heat generated by each light-emitting diode chip DT is dissipated upward via the heat sink 42.

[0035] The image recording device 1 of this embodiment can print on a substrate at both a low gap and a high gap. As shown in FIG. 6, the substrate W includes, for example, a low portion T1, whose distance from the ultraviolet irradiated surface TS of the light-emitting diode chip DT is a high gap GH, and a high portion T2, whose distance from the ultraviolet irradiated surface TS is a low gap GL, which is smaller than the high gap GH. The high gap GH is, for example, 18 mm. The low gap GL is, for example, 2 mm.

[0036] Next, the arrangement pitch of the light-emitting diode chips DT in the sub-scanning direction Df will be described with reference to the drawings.

[0037] In this embodiment, in at least one chip row DL (e.g., all chip rows DL), the chip density, which is the number of light-emitting diode chips DT per unit length in the sub-scanning direction Df, at the end in the sub-scanning direction Df is higher than the chip density in the center in the sub-scanning direction Df. The end in the sub-scanning direction Df is a region outside the nozzle end in the sub-scanning direction Df. Also, in at least one chip row DL (e.g., all chip rows DL), the illuminance at the end in the sub-scanning direction Df is higher than the illuminance in the center. Furthermore, at least one chip row DL, for example, all chip rows DL, includes at least one light-emitting diode chip DT located outside in the sub-scanning direction Df a nozzle Nz located at the nozzle end, which is the end of the nozzle row NL. This will be explained in detail below.

[0038] In FIG. 7(a), the light-emitting diode chip DT closest to the nozzle end in the sub-scanning direction Df is referred to as the edge light-emitting diode chip DTt. In the example of FIG. 7(a), the position of the edge light-emitting diode chip DTt in the sub-scanning direction Df is the same as the position of the nozzle end in the sub-scanning direction Df. The arrangement pitch between the edge light-emitting diode chip DTt and the adjacent light-emitting diode chip DT on at least one side (both sides in the example of FIG. 7(a)) of the edge light-emitting diode chip DTt in the sub-scanning direction Df is referred to as the edge arrangement pitch Pt. Furthermore, the arrangement pitch between the light-emitting diode chip DT located inside the edge light-emitting diode chip DTt and the light-emitting diode chip DT located further inside the edge light-emitting diode chip DTt is referred to as the adjacent arrangement pitch Pr. In this case, the edge arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr. In this way, at least one chip row DL in which the edge arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr is provided. With this configuration, the chip density of the light-emitting diode chips DT at the end in the sub-scanning direction Df is higher than the chip density in the center. 7A, at least one chip row DL includes at least one light-emitting diode chip DT located outside in the sub-scanning direction Df the nozzle Nz located at the nozzle end, which is the end of the nozzle row NL. In the example of FIG. 7A, there is one light-emitting diode chip DT located outside. With the above configuration, in at least one chip row DL, the illuminance at the end in the sub-scanning direction Df is higher than the illuminance in the center.

[0039] 7(b), the light-emitting diode chip DT closest to the nozzle end may be used as the end light-emitting diode chip DTt even if it is not at the same position as the nozzle end in the sub-scanning direction Df. In the example of FIG. 7(b), there is also one light-emitting diode chip DT located on the outer side.

[0040] Based on the configurations of FIGS. 7(a) and 7(b) described above, a specific example of the arrangement of the light-emitting diode chips DT in this embodiment will be described.

[0041] Fig. 8 shows the arrangement of the light-emitting diode chips DT in Comparative Example 1 and five Examples (Examples 1 to 5). Note that Fig. 8 only shows the arrangement of the light-emitting diode chips DT in the region from one nozzle end to the center in the nozzle row NL (upper arrangement), and the arrangement of the light-emitting diode chips DT in the region from the other nozzle end to the center is the same as the upper arrangement described above, and is therefore omitted.

[0042] Comparative Example 1 is an embodiment in which there are no light-emitting diode chips DT located outside the nozzle ends in the sub-scanning direction Df. In Comparative Example 1, the arrangement pitch between adjacent light-emitting diode chips DT is all 4.5 mm.

[0043] In contrast, in Example 1 and Example 2, there is one light-emitting diode chip DT located outside the nozzle end in the sub-scanning direction Df. In Example 1, the arrangement pitch between adjacent light-emitting diode chips DT is all 4.5 mm. That is, the end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. On the other hand, in Example 2, only the end arrangement pitch Pt on the rear side is 4 mm, and the end arrangement pitch Pt and the adjacent arrangement pitch Pr on the front side are both 4.5 mm.

[0044] In addition, Examples 3 to 5 are embodiments in which there are two light-emitting diode chips DT located outside the nozzle end in the sub-scanning direction Df. In Example 3, the arrangement pitch between adjacent light-emitting diode chips DT is all 4.5 mm. That is, the end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. In Example 4, the rear-side end arrangement pitch Pt, the front-side end arrangement pitch Pt, and the adjacent arrangement pitch Pr are all 4.5 mm, and the arrangement pitch between the light-emitting diode chip DT located behind the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto is 4 mm. On the other hand, in Example 5, the front-side end arrangement pitch Pt and the adjacent arrangement pitch Pr are all 4.5 mm, and the rear-side end arrangement pitch Pt and the arrangement pitch between the light-emitting diode chip DT located behind the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto are all 4 mm.

[0045] Using each aspect of Comparative Example 1 and Examples 1 to 5, the relationship between the position in the sub-scanning direction Df in the nozzle row NL and the illuminance was obtained by simulation. FIG. 9 is a graph showing the relationship between the position in the sub-scanning direction Df in the nozzle row NL and the illuminance, corresponding to Comparative Example 1 and Examples 1 to 5 in FIG. 8. As shown in FIG. 9, in Comparative Example 1, the illuminance at the nozzle end was clearly lower than the illuminance in the central portion. In contrast, in Examples 1 to 5, the illuminance at the nozzle end was equal to or higher than the illuminance in the central portion. In particular, in Example 5, the illuminance at the nozzle end was significantly higher than the illuminance in the central portion. Furthermore, in Example 5, the highest illuminance (peak illuminance) appeared in an area outside the nozzle end in the sub-scanning direction Df (to the left of the nozzle end in FIG. 9). In this embodiment, the difference between the illuminance at the nozzle end and the illuminance at the central portion is, for example, 0.1 w / cm 2 That's all.

[0046] Next, another specific example of the arrangement of the light-emitting diode chips DT in this embodiment will be described.

[0047] Fig. 10 shows the arrangement of the light-emitting diode chips DT in Comparative Example 2 and seven Examples (Examples 6 to 12). Note that, similar to Fig. 8, Fig. 10 only shows the arrangement of the light-emitting diode chips DT in the region from one nozzle end to the center in the nozzle row NL (upper arrangement), and the arrangement of the light-emitting diode chips DT in the region from the other nozzle end to the center is the same as the upper arrangement described above, and is therefore omitted.

[0048] Comparative Example 2 is an embodiment in which there are no light-emitting diode chips DT located outside the nozzle ends in the sub-scanning direction Df. In Comparative Example 2, the arrangement pitch between adjacent light-emitting diode chips DT is all 6.0 mm.

[0049] In contrast, Example 6 is an embodiment in which there is one light-emitting diode chip DT located outside the nozzle end in the sub-scanning direction Df. In Example 6, the arrangement pitches between adjacent light-emitting diode chips DT are all 6.0 mm. In other words, the end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same.

[0050] In addition, Examples 7 to 10 are embodiments in which there are two light-emitting diode chips DT located outside the nozzle end in the sub-scanning direction Df. In Example 7, the arrangement pitch between adjacent light-emitting diode chips DT is all 6.0 mm. That is, the end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. On the other hand, in Example 8, the arrangement pitch between the light-emitting diode chip DT located behind the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto is 4 mm, and the remaining arrangement pitches are all 6.0 mm. That is, the end arrangement pitch Pt on the rear side, the end arrangement pitch Pt on the front side, and the adjacent arrangement pitch Pr are the same. In addition, in Example 9, the arrangement pitch between the light-emitting diode chip DT located behind the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto, and the end arrangement pitch Pt on the rear side are 4 mm, and the remaining arrangement pitches are all 6.0 mm. That is, the end arrangement pitch Pt on the front side and the adjacent arrangement pitch Pr are the same. Furthermore, in Example 10, the rear end arrangement pitch Pt and the front end arrangement pitch Pt are set to 4.0 mm, and the remaining arrangement pitches including the adjacent arrangement pitch Pr are all set to 6.0 mm.

[0051] Furthermore, Example 11 is an embodiment in which there is one light-emitting diode chip DT located outside the nozzle end in the sub-scanning direction Df. In Example 11, the rear end arrangement pitch Pt is 4.0 mm, and all remaining arrangement pitches are 6.0 mm. That is, the front end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. Furthermore, Example 12 is an embodiment in which there are two light-emitting diode chips DT located outside the nozzle end in the sub-scanning direction Df. In Example 12, the arrangement pitch between the light-emitting diode chip DT located behind the end light-emitting diode chip DTt and the adjacent light-emitting diode chip DT, the rear end arrangement pitch Pt, and the front end arrangement pitch Pt are all 4.0 mm, and all remaining arrangement pitches, including the adjacent arrangement pitch Pr, are 6.0 mm.

[0052] Using each of the aspects of Comparative Example 2 and Examples 6 to 12, the relationship between the position in the sub-scanning direction Df in the nozzle row NL and the illuminance was obtained by simulation. FIG. 11 is a graph showing the relationship between the position in the sub-scanning direction Df in the nozzle row NL and the illuminance, corresponding to Comparative Example 2 and Examples 6 to 12 of FIG. 10. As shown in FIG. 11, in Comparative Example 2, the illuminance at the nozzle ends was clearly lower than the illuminance in the central portion. In contrast, in Examples 6 to 12, the illuminance at the nozzle ends was equal to or higher than the illuminance in the central portion. In particular, in Examples 9 to 12, the illuminance at the nozzle ends was significantly higher than the illuminance in the central portion. Furthermore, in Examples 7, 8, 9, and 11, the highest illuminance appeared in an area outside the nozzle ends in the sub-scanning direction Df (to the left of the nozzle ends in FIG. 11).

[0053] As described above, according to the liquid ejection device 50 of this embodiment, the chip density at the ends in the sub-scanning direction Df is higher than the chip density in the center, and the illuminance at the ends in the sub-scanning direction Df is higher than the illuminance at the center, thereby suppressing oxygen inhibition at the ends of the nozzle row. In particular, since at least one light-emitting diode chip DT is disposed further outward in the sub-scanning direction Df than the nozzle Nz located at the nozzle end, it is possible to reliably make the illuminance at the ends in the sub-scanning direction Df higher than the illuminance at the center. This makes it possible to suppress oxygen inhibition at the ends of the nozzle row more significantly than in the past.

[0054] In this embodiment, since the end arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr, the chip density of the light-emitting diode chips DT at the end in the sub-scanning direction Df is higher than the chip density at the center, which makes it possible to make the illuminance at the end in the sub-scanning direction Df higher than the illuminance at the center.

[0055] In this embodiment, two light-emitting diode chips DT can be arranged outside the edge light-emitting diode chip DTt in the sub-scanning direction Df, and the arrangement pitch between one light-emitting diode chip DT and the other light-emitting diode chip DT of the two light-emitting diode chips DT can be made the same as the edge arrangement pitch Pt, thereby making the illuminance at the edge in the sub-scanning direction Df higher than the illuminance at the center.

[0056] Furthermore, in this embodiment, the chip row DL includes a light-emitting diode chip DT that is positioned at the same position as the nozzle end in the sub-scanning direction Df, which makes it less likely for oxygen inhibition to occur at the nozzle end, ensuring sufficient ink curing properties.

[0057] In this embodiment, the difference between the illuminance at the end portion in the sub-scanning direction Df (the region outside the nozzle end in the sub-scanning direction Df) and the illuminance at the center is 0.1 w / cm 2 As a result, oxygen inhibition is less likely to occur in the region outside the nozzle end in the sub-scanning direction Df, and sufficient ink curing properties can be ensured.

[0058] Furthermore, in this embodiment, the highest illuminance can be achieved in the area outside the nozzle end in the sub-scanning direction Df, which makes it even less likely that oxygen inhibition will occur in the area outside the nozzle end in the sub-scanning direction Df, ensuring sufficient ink curability.

[0059] Furthermore, by providing the above-described liquid ejection device 50 in the image recording apparatus 1, oxygen inhibition at the end of the nozzle row in the image recording apparatus 1 can be suppressed.

[0060] (Variation) The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible.

[0061] In the above embodiment, in all chip rows DL, the chip density of the light-emitting diode chips DT at the ends in the sub-scanning direction Df is higher than the chip density at the center thereof, but this is not limited to this, and the above configuration may be adopted for, for example, only one chip row DL or half of the chip rows DL.

[0062] Furthermore, in the above embodiment, the illuminance at the ends in the sub-scanning direction Df is higher than the illuminance at the center in all chip rows DL, but this is not limited to this, and the above configuration may be adopted for, for example, only one chip row DL or half of the chip rows DL.

[0063] Furthermore, in the above embodiment, all chip rows DL are configured so that there is at least one light-emitting diode chip DT located outside the sub-scanning direction Df of the nozzle Nz located at the nozzle end, which is the end of the nozzle row NL, but this is not limited to this, and the above configuration may be adopted for, for example, only one chip row DL or half of the chip rows DL.

[0064] Furthermore, in the above embodiment, the end arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr, but this is not limited to this, and the end arrangement pitch Pt may be set to the same value as the adjacent arrangement pitch Pr, and at least one light-emitting diode chip DT may be configured to be positioned outside the nozzle Nz located at the nozzle end in the sub-scanning direction Df.

[0065] In the above embodiment, the high gap GH is 15 mm and the low gap GL is 2 mm, but the high gap GH and the low gap GL are not limited to these values, and it is sufficient that the low gap GL is smaller than the high gap GH. For example, the high gap GH is 7 mm or more, and the difference between the high gap GH and the low gap GL is 5 mm or more.

[0066] Furthermore, in the above embodiment, the carriage 3 is equipped with two ejection heads 10 (10A, 10B) and two ultraviolet irradiation devices 40 (40A, 40B), but this is not limited to this, and it may be equipped with only the ejection head 10A and the ultraviolet irradiation device 40A. [Explanation of symbols]

[0067] 1 Image recording device 3 Carriage 10, 10A, 10B Discharge head 40,40A,40B UV irradiation equipment 50 Liquid dispensing device Df Sub-scanning direction DL chip row Ds Main scanning direction Ds1 outbound Ds2 Return DT Light Emitting Diode Chip DTt Edge Light Emitting Diode Chip NL nozzle row Nz nozzle Pr Adjacent placement pitch Pt end arrangement pitch W Printing material

Claims

[Claim 1] A liquid ejection device that ejects ultraviolet-curable ink onto a printing substrate and cures it with ultraviolet light, an ejection head that has at least one nozzle row in a main scanning direction, which is a direction perpendicular to the sub-scanning direction, the nozzle row including a plurality of nozzles arranged side by side in the sub-scanning direction, and that moves in the main scanning direction; an ultraviolet irradiation device that has at least one chip row in the main scanning direction, the chip row including a plurality of light-emitting diode chips arranged side by side in the sub-scanning direction, and that moves in the main scanning direction; In at least one of the chip rows, at least two of the light-emitting diode chips are located outside the nozzles located at nozzle ends that are ends of the nozzle row in the sub-scanning direction, an end arrangement pitch, which is an arrangement pitch between an end light-emitting diode chip that is the light-emitting diode chip closest to the nozzle end in the sub-scanning direction and the light-emitting diode chip adjacent to the end light-emitting diode chip on at least one of the outer side and the inner side in the sub-scanning direction, a liquid ejection device characterized in that the arrangement pitch of one of the two light-emitting diode chips located outside the end light-emitting diode chip in the sub-scanning direction is smaller than the arrangement pitch between the other light-emitting diode chip and one of the two light-emitting diode chips located outside the end light-emitting diode chip in the sub-scanning direction.

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