JP7468029B2 - LIQUID EJECTION APPARATUS AND IMAGE RECORDING APPARATUS EQUIPPED WITH THE SAME - Google Patents

Description

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

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 ultraviolet-curable ink in this way, it is possible to print on materials other than paper, such as resin and metal, and to obtain substrates with a glossy finish.

In the liquid ejection device of the above document, a plurality of light-emitting diode chips are provided on an array. The light-emitting diode chips are arranged in a matrix along the short side direction (main scanning direction) and the 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, since the desired illuminance distribution cannot be obtained by simply arranging the plurality of light-emitting diode chips in such a regular manner, the above liquid ejection device drives the plurality of light-emitting diode chips so that the illuminance of the 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. With this configuration, it is said that ultraviolet light can be uniformly irradiated in the sub-scanning direction, and unevenness in the amount of irradiation light is suppressed.

JP 2019-209494 A

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

The present invention aims to provide a liquid ejection device that can suppress oxygen inhibition at the ends of the nozzle row, and an image recording device equipped with the same.

The liquid ejection device of the present invention is a liquid ejection device that cures ultraviolet-curable ink ejected onto a substrate by ultraviolet light, and includes at least one nozzle row including a plurality of nozzles arranged in a sub-scanning direction in a main scanning direction, which is a direction perpendicular to the sub-scanning direction, and an ejection head that moves in the main scanning direction, and an ultraviolet irradiation device that has at least one chip row including a plurality of light-emitting diode chips arranged in a sub-scanning direction in the main scanning direction and moves in the main scanning direction, and in at least one of the chip rows, the chip density, which is the number of light-emitting diode chips per unit length in the sub-scanning direction at an end in the sub-scanning direction, is higher than the chip density in the center in the sub-scanning direction, the illuminance at the end is higher than the illuminance at the center, and at least one of the light-emitting diode chips is located outside the sub-scanning direction from the nozzle located at the nozzle end, which is the end of the nozzle row.

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 disposed outside in the sub-scanning direction the nozzles located at the nozzle ends, so that 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 to a greater extent than in the past.

The present invention provides a liquid ejection device that can suppress oxygen inhibition at the ends of the nozzle row, and an image recording device equipped with the same.

1 is a perspective view showing an image recording apparatus according to a first embodiment of the present invention; 2 is a plan view showing an example of the arrangement of a discharge head and an ultraviolet ray irradiation device mounted on the carriage in FIG. 1 . FIG. 2 is a block diagram showing a configuration of the image recording apparatus shown in FIG. 1 . 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. FIG. 2 is a diagram illustrating an internal configuration of an ultraviolet irradiation device. FIG. 1 shows a high gap and a low gap. FIG. 1A is a diagram for explaining an example of an end arrangement pitch and an adjacent arrangement pitch, and FIG. 1B is a diagram for explaining another example of the end arrangement pitch and the adjacent arrangement pitch. 1A and 1B are diagrams 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. 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 in FIG. 8 . 13 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. 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. 10 .

A liquid ejection device and an image recording device including the same according to an embodiment of the present invention will be described below with reference to the drawings. The liquid ejection device and image recording device 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 are possible without departing from the spirit of the present invention.

Figure 1 is a perspective view showing an image recording device 1 according to one embodiment of the present invention. In Figure 1, directions that are perpendicular to each other 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 device 1 not only prints on a substrate W such as printing paper, but also performs goods printing, printing on a substrate W (Figure 6) such as resin for printing on various goods, for example.

As shown in FIG. 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. 3.

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

The carriage 3 is configured to be capable of reciprocating along the main scanning direction Ds. As shown in FIG. 2, the carriage 3 is equipped with a liquid ejection device 50. The liquid ejection device 50 includes two ejection heads 10 (10A, 10B) and two ultraviolet irradiation devices 40 (40A, 40B). The ejection head 10 may be, for example, an inkjet head that ejects 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 ultraviolet light to cure the ink ejected by the ejection head 10. The ejection head 10A and the ejection head 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 along the main scanning direction Ds. The ultraviolet irradiation device 40B is disposed to the right of the ejection head 10B.

In FIG. 2, the carriage 3 moves to the left in the main scanning direction Ds during one pass of the printing process. As a result, the ejection head 10 and the ultraviolet ray 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 to the left in the main scanning direction Ds, and the ultraviolet ray irradiation device 40 irradiates ultraviolet rays onto the ink that has landed on the printing substrate W while moving to the left in the main scanning direction Ds. As a result, the ultraviolet ray 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.

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. This causes the ejection head 10 and the ultraviolet ray irradiation device 40 to 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 ray 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.

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 ink. The ejection head 10A has nozzle rows NL that eject each of these inks extending along the sub-scanning direction Df. Each nozzle row NL is arranged at regular intervals along the main scanning direction Ds. The arrangement order of each nozzle row 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 the left as shown in FIG. 2, and can be set appropriately.

On the other hand, the ejection head 10B ejects white (W) ink and clear (Cr) ink. The ejection head 10B has nozzle rows NL that eject these inks extending along the sub-scanning direction Df. Each nozzle row NL is arranged at a constant interval along the main scanning direction Ds. The interval between each nozzle row NL in the ejection head 10B in the main scanning direction Ds may be different from the interval between each nozzle row NL in the ejection head 10A in the main scanning direction Ds (example of FIG. 2), or may be the same. The arrangement order of each nozzle row 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 side as shown in FIG. 2, and may be arranged in reverse. A color image is printed on the printing substrate W by ejecting the above six colors of ink onto the printing substrate W. Specifically, when printing a color image on a fabric as the print substrate W, white ink is ejected first as a base ink to reduce the effect on the color and material of the fabric, and color inks are ejected on top of the white ink. Clear ink is ejected to impart gloss or to protect the printed area.

The platen 6 is configured so that the printing material W can be placed on it. The platen 6 has a predetermined thickness and is configured, for example, of a rectangular plate material with the sub-scanning direction Df as the 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 material W and a detachment position where the printing material 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 material W can be placed on the platen 6. During printing, the platen 6 moves in the sub-scanning direction Df, so the printing material W placed on the platen 6 is transported in the sub-scanning direction Df.

When the front part of the upper cover 7 is lifted, it rotates upward around the rotatable base end, which serves as a fulcrum. This exposes the inside of the housing 2.

Next, the functions of each component of the image recording device 1 of this embodiment will be described with reference to the 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, 31, head driver ICs 32, 36, a transport motor 33, a carriage motor 34, irradiation device driver ICs 37, 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.

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

The CPU 20 executes various functions by executing a specific program 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.

The ROM 21 stores a print control program for the CPU 20 to execute the print process. The RAM 22 stores the results of calculations by 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 that the image recording device 1 receives from the outside and includes a user ID that identifies the sender, user usage history information that includes a user ID in the job data, secure job data that includes a password and data related to a secure job, print history, and cloud setting data. The information about the user includes, for example, telephone directory information, email address information, administrator (security administrator) information for 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.

The ASIC 25 is connected to the motor driver ICs 30 and 31, the head driver ICs 32 and 36, and the 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 the print control program. The ASIC 25 drives each of the driver ICs 30 to 32, 36 to 38 based on the print command. The CPU 20 drives the conveying motor 33 by the motor driver IC 30 to move the platen 6 in the sub-scanning direction Df, and the printing substrate W is conveyed. The CPU 20 also drives the carriage motor 34 by 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 moved by the head driver ICs 32 and 36, and prints image data on the printing substrate W being conveyed. Furthermore, the CPU 20 causes the irradiation device driver ICs 37 and 38 to irradiate ultraviolet light for curing the ink from the ultraviolet irradiation devices 40A and 40B. The printing process is carried out in this manner.

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.

Next, the arrangement of the multiple 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 ejection head 10A will be described below as representatives, the ultraviolet irradiation device 40B and the ejection head 10B can also be configured in the same way as the ultraviolet irradiation device 40A and the ejection head 10A.

As shown in FIG. 4, the ultraviolet irradiation device 40A includes a support substrate 41 that is formed, for example, in a rectangular shape in a plan view. The support substrate 41 is, for example, an aluminum substrate. Note that 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.

Each light-emitting diode chip DT is arranged in a matrix. Each light-emitting diode chip DT is arranged, for example, based on the center of a rectangular unit lattice having sides along the longitudinal and lateral directions of the support substrate 41. As a result, each light-emitting diode chip DT is arranged at regular intervals along the main scanning direction Ds and at regular intervals along the sub-scanning direction Df. Therefore, each light-emitting diode chip DT is 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 arranged in the left-right direction and 5 columns of light-emitting diode chips DT arranged in the front-rear direction. A group of a plurality of light-emitting diode chips DT arranged at regular intervals along the sub-scanning direction Df is called a chip row DL. Therefore, FIG. 4 shows an example in which five chip rows DL are arranged. The number of light-emitting diode chips DT placed on the support substrate 41 is not limited to the above, but is determined based on the integrated light amount and power consumption during one pass, etc.

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 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 of the sub-scanning direction Df is defined as the nozzle length Lh. Note that FIG. 4 only shows the nozzle row NL that ejects black (K) ink, and the other three nozzle rows are omitted.

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 the sub-scanning direction Df, is taken 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.

The light-emitting diode chips DT are arranged 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.

Next, the heat dissipation structure of the ultraviolet irradiation device 40 will be described. FIG. 5 is a diagram showing an internal configuration of the ultraviolet irradiation device 40. As shown in FIG. 5, the ultraviolet irradiation device 40 includes the above-mentioned support substrate 41 that 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 to 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 arranged 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 a plurality of electrodes 45 are provided on these electronic components corresponding to the light-emitting diode chips DT. Each electrode 45 is electrically connected to each light-emitting diode chip DT. The lower surface of the support substrate 41 is covered with an insulating film 44 with a portion of each electrode 45 exposed. In this configuration, heat generated by each light-emitting diode chip DT is dissipated upward through the heat sink 42.

The image recording device 1 of this embodiment can print on the substrate at a low gap and a high gap. As shown in FIG. 6, the substrate W includes, for example, a low part T1 whose distance from the ultraviolet irradiated surface TS of the light emitting diode chip DT is a high gap GH, and a high part T2 whose distance from the ultraviolet irradiated surface TS is a low gap GL that 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.

Next, the arrangement pitch of each light-emitting diode chip DT in the sub-scanning direction Df will be explained with reference to the drawings.

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 of the sub-scanning direction Df is higher than the chip density in the center of the sub-scanning direction Df. The end of the sub-scanning direction Df is an area 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 of 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, each include 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. This will be described in detail below.

In FIG. 7A, the light-emitting diode chip DT closest to the nozzle end in the sub-scanning direction Df is the end light-emitting diode chip DTt. In the example of FIG. 7A, the position of the end 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 of the light-emitting diode chip DT adjacent to such an end light-emitting diode chip DTt on at least one side (both sides in the example of FIG. 7A) of the outside and inside of the sub-scanning direction Df is the end arrangement pitch Pt. Also, the arrangement pitch of the light-emitting diode chip DT located inside the end light-emitting diode chip DTt and the light-emitting diode chip DT located further inside the light-emitting diode chip DT is the adjacent arrangement pitch Pr. At this time, the end arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr. In this way, at least one chip row DL in which the end 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 of the sub-scanning direction Df is higher than the chip density at the center. Also, as shown in the figure, at least one chip row DL includes at least one light-emitting diode chip DT located outside in the sub-scanning direction Df from the nozzle Nz located at the nozzle end, which is the end of the nozzle row NL. In the example of FIG. 7(a), there is one light-emitting diode chip DT located on the 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 at the center.

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

Based on the configurations of Figures 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.

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

Comparative example 1 is an embodiment in which there are no light-emitting diode chips DT located outside the nozzle end 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.

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. In other words, 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 4.5 mm.

In addition, in Examples 3 to 5, 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 end arrangement pitch Pt, the front end arrangement pitch Pt, and the adjacent arrangement pitch Pr are 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 end arrangement pitch Pt and the adjacent arrangement pitch Pr are 4.5 mm, and the rear 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 4 mm.

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, which corresponds 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 obviously lower than the illuminance at the center. In contrast, in Examples 1 to 5, the illuminance at the nozzle end was equal to or higher than the illuminance at the center. In particular, in Example 5, the illuminance at the nozzle end was significantly higher than the illuminance at the center. And, in Example 5, the maximum illuminance (peak illuminance) appeared in the 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 center is, for example, 0.1 W/cm ² or more.

Next, we will explain other specific examples of the arrangement of the light-emitting diode chips DT in this embodiment.

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

Comparative example 2 is an embodiment in which there are no light-emitting diode chips DT located outside the nozzle end 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.

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 pitch between adjacent light-emitting diode chips DT is all 6.0 mm. In other words, the end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same.

In addition, in Examples 7 to 10, 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 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 on the rear side of the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto is 4 mm, and the remaining arrangement pitch is all 6.0 mm. That is, the rear end arrangement pitch Pt, the front end arrangement pitch Pt, 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 on the rear side of the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto, and the rear end arrangement pitch Pt are 4 mm, and the remaining arrangement pitch is all 6.0 mm. That is, the front end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. Furthermore, in Example 10, except for the rear end arrangement pitch Pt and the front end arrangement pitch Pt being 4.0 mm, the remaining arrangement pitches, including the adjacent arrangement pitch Pr, are all 6.0 mm.

Furthermore, in Example 11, 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 the remaining arrangement pitches are 6.0 mm. In other words, the front end arrangement pitch Pt and the adjacent arrangement pitch Pr are the same. In Example 12, 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 on the rear side of the end light-emitting diode chip DTt and the light-emitting diode chip DT adjacent thereto, the rear end arrangement pitch Pt, and the front end arrangement pitch Pt are 4.0 mm, and all the remaining arrangement pitches including the adjacent arrangement pitch Pr are 6.0 mm.

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 in FIG. 10. As shown in FIG. 11, in Comparative Example 2, the illuminance at the nozzle end was clearly lower than the illuminance at the center. In contrast, in Examples 6 to 12, the illuminance at the nozzle end was equal to or higher than the illuminance at the center. In particular, in Examples 9 to 12, the illuminance at the nozzle end was significantly higher than the illuminance at the center. And in Examples 7, 8, 9, and 11, the highest illuminance appeared in the area outside the nozzle end in the sub-scanning direction Df (to the left of the nozzle end in FIG. 11).

As described above, according to the liquid ejection device 50 of this embodiment, the chip density at the end in the sub-scanning direction Df is higher than the chip density at the center, and the illuminance at the end in the sub-scanning direction Df is higher than the illuminance at the center, thereby suppressing oxygen inhibition at the end of the nozzle row. In particular, since at least one light-emitting diode chip DT is arranged outside in the sub-scanning direction Df the nozzle Nz located at the nozzle end, it is possible to reliably make the illuminance at the end in the sub-scanning direction Df higher than the illuminance at the center. This makes it possible to suppress oxygen inhibition at the end of the nozzle row to a greater extent than before.

In addition, in this embodiment, the end arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr, so that 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. This makes it possible to make the illuminance at the end in the sub-scanning direction Df higher than the illuminance in the center.

In addition, in this embodiment, two light-emitting diode chips DT can be arranged outside the sub-scanning direction Df with the end light-emitting diode chip DTt as a reference, and the arrangement pitch between one of the two light-emitting diode chips DT and the other light-emitting diode chip DT can be made the same as the end arrangement pitch Pt. This makes it possible to make the illuminance at the end in the sub-scanning direction Df higher than the illuminance at the center.

In addition, 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, making it less likely that oxygen inhibition will occur at the nozzle end and ensuring sufficient ink curing properties.

Furthermore, in this embodiment, the difference in illuminance between 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/ ^cm2 or more, making it less likely for oxygen inhibition to occur in the region outside the nozzle end in the sub-scanning direction Df, thereby ensuring sufficient ink curing properties.

In addition, in this embodiment, the highest illuminance can be achieved in the area outside the nozzle end in the sub-scanning direction Df. This makes it even less likely that oxygen inhibition will occur in the area outside the nozzle end in the sub-scanning direction Df, making it possible to reliably ensure sufficient ink curing.

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

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

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, 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.

In addition, 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.

In addition, in the above embodiment, all chip rows DL are configured so that there is at least one light-emitting diode chip DT located outside in the sub-scanning direction Df more than 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.

In addition, in the above embodiment, the end arrangement pitch Pt is smaller than the adjacent arrangement pitch Pr, but this is not limited to this. With the end arrangement pitch Pt set to the same value as the adjacent arrangement pitch Pr, 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.

In addition, 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 the above 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.

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 thereto, and it may be equipped with only the ejection head 10A and the ultraviolet irradiation device 40A.

1 Image recording device 3 Carriage 10, 10A, 10B Discharge head 40, 40A, 40B Ultraviolet ray irradiation device 50 Liquid discharge device Df Sub-scanning direction DL Chip row Ds Main scanning direction Ds1 Forward path Ds2 Return path DT Light-emitting diode chip DTt End light-emitting diode chip NL Nozzle row Nz Nozzle Pr Adjacent arrangement pitch Pt End arrangement pitch W Printing substrate

Claims (6)

A liquid ejection device that ejects ultraviolet-curable ink onto a substrate and cures the ink by ultraviolet light,
an ejection head that has at least one nozzle row in a main scanning direction, the main scanning direction being a direction perpendicular to the sub-scanning direction, the nozzle row including a plurality of nozzles arranged in parallel in the sub-scanning direction, and that moves in the main scanning direction;
an ultraviolet ray 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 in parallel in the sub-scanning direction, and moves in the main scanning direction;
In at least one of the chip rows ,
The illuminance at the end portion is higher than the illuminance at the center portion, and
at least one of the light-emitting diode chips is located on the outer side in the sub-scanning direction of the nozzles located at a nozzle end that is an end of the nozzle row ,
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, is smaller than an adjacent arrangement pitch, which is an arrangement pitch between the light-emitting diode chip located on the inner side of the end light-emitting diode chip and the light-emitting diode chip located further on the inner side of the end light-emitting diode chip;
a liquid ejection device in which two light-emitting diode chips are arranged on the outside of the sub-scanning direction based on the end light-emitting diode chip, and an arrangement pitch between one of the two light-emitting diode chips and the other light-emitting diode chip is the same as the end arrangement pitch . The liquid ejection device according to claim 1 , wherein the chip row includes the light-emitting diode chips arranged at the same position as the nozzle end in the sub-scanning direction. A liquid ejection device that ejects ultraviolet-curable ink onto a substrate and cures the ink by ultraviolet light,
an ejection head that has at least one nozzle row in a main scanning direction, the main scanning direction being a direction perpendicular to the sub-scanning direction, the nozzle row including a plurality of nozzles arranged in parallel in the sub-scanning direction, and that moves in the main scanning direction;
an ultraviolet ray 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 in parallel in the sub-scanning direction, and moves in the main scanning direction;
In at least one of the chip rows,
The illuminance at the end portion is higher than the illuminance at the center portion, and
at least one of the light-emitting diode chips is located on the outer side in the sub-scanning direction of the nozzles located at a nozzle end that is an end of the nozzle row,
A liquid ejection device, wherein a difference in illuminance between an end portion in the sub-scanning direction and a central portion in the sub-scanning direction is 0.1 W/cm ² or more. The liquid ejection device according to claim 1 , wherein the illuminance at the end portion in the sub-scanning direction includes a maximum illuminance. The liquid ejection device according to claim 4 , wherein the end in the sub-scanning direction is an area on the outer side of the nozzle end in the sub-scanning direction. An image recording apparatus comprising: the liquid ejection device according to claim 1 ; and a carriage on which the liquid ejection device is provided.

Images