Printing apparatus

Abstract

To provide a printing apparatus which can secure sufficient curability of ink, furthermore can prevent the non-ejection of ink without increasing the dimension of a carriage.SOLUTION: A printing apparatus comprises: an ejection head which ejects ultraviolet curable ink to a printing object medium; a relative movement unit which relatively moves in the prescribed direction the printing object medium and the ejection head when ejecting the ink to the printing object medium from the ejection head; and a light source unit which has a plurality of light sources for curing the ink. The light source unit has: a first light source region in which the plurality of light sources are arranged; and a second light source region in which the plurality of light sources are arranged, the number of light sources per a unit area is smaller than that of the first light source region and a linear distance in parallel to the prescribed direction from the ejection head is shorter than that of the first light source region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a printing device that includes an ejection head that ejects ultraviolet-curable ink onto a print medium and a light source unit that has a light source that cures the ink. [Background technology]

[0002] Conventionally, a light source unit equipped with multiple light sources (LED elements) that irradiate ultraviolet rays onto ultraviolet-curable ink ejected onto a print medium by an ejection head is known (see Patent Document 1). Such an ejection head and light source unit are arranged side by side in the main scanning direction. The light source unit irradiates ultraviolet rays onto ink droplets that have landed on the print medium, thereby curing the ink and fixing it to the print medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-193089 Summary of the Invention [Problem to be solved by the invention]

[0004] However, ultraviolet light emitted from the light source unit can reflect off the surface of the platen or the surface of the print medium, and the reflected light can be directed onto the nozzle face of the ejection head. As a result, the ink in the nozzles can be cured by the reflected light, resulting in ink failure. One way to prevent this is to reduce the illuminance of the light source unit, but reducing the illuminance can lead to the ink not being sufficiently cured. Another possible solution is to increase the distance between the ejection head and the light source unit to prevent the reflected light from being directed onto the nozzle face, but this would increase the dimensions of the carriage.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a printing device that can prevent ink non-ejection while ensuring sufficient ink curing properties without increasing the dimensions of the carriage. [Means for solving the problem]

[0006] The printing device of the present invention comprises an ejection head that ejects ultraviolet-curable ink onto a print medium, a relative movement section that moves the print medium and the ejection head relatively in a predetermined direction when ejecting ink from the ejection head onto the print medium, and a light source unit that has a plurality of light sources that cure the ink, wherein the light source unit has a first light source region in which the plurality of light sources are arranged, and a second light source region in which the plurality of light sources are arranged, has a smaller number of light sources per unit area than the first light source region, and is shorter in linear distance from the ejection head parallel to the predetermined direction than the first light source region.

[0007] According to the present invention, a second light source region, which has fewer light sources per unit area than the first light source region, is positioned near the ejection head in a predetermined direction. This allows for the formation of sparse and dense regions of illuminance in the predetermined direction, rather than a uniform illuminance distribution. In this case, the ejection head side can be made a sparse region of illuminance in the predetermined direction, and the opposite side of the ejection head can be made a dense region of illuminance. This configuration allows the maximum value of the illuminance distribution (peak illuminance) to be positioned farther from the ejection head than the center of the light source unit in the predetermined direction. This reduces the reflected light irradiating the nozzle surface of the ejection head. This suppresses or prevents the ink in the nozzle holes from being cured by the reflected light, thereby preventing ink non-ejection. Meanwhile, by forming a dense region of illuminance as described above, the illuminance required to cure the ink ejected by the ejection head can be ensured. As described above, according to the present invention, it is possible to prevent ink non-ejection while ensuring sufficient ink curability without increasing the dimensions of the carriage. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a printing device that can prevent ink non-ejection while ensuring sufficient ink curing properties, without increasing the dimensions of the carriage. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a printing apparatus according to an embodiment of the present invention; [Figure 2] 2 is a diagram showing an example of the configuration of a discharge head and a light source unit mounted on the carriage of FIG. 1. FIG. [Figure 3] FIG. 2 is a block diagram showing the configuration of the printing device of FIG. [Figure 4] 10 is a graph showing an example of illuminance in the main scanning direction with the center of the light source unit as a reference. [Figure 5] FIG. 10 is a diagram illustrating an example of the positional relationship between a proximate nozzle row of an ejection head and light-emitting diode chips. [Figure 6] FIG. 10 is a diagram illustrating an example of the positional relationship between a proximate nozzle row of an ejection head and light-emitting diode chips. [Figure 7] FIG. 2 is a diagram illustrating an example of the configuration of a discharge head and a light source unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] A printing device according to an embodiment of the present invention will be described below with reference to the drawings. The printing device described below is 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.

[0011] (First embodiment) FIG. 1 is a perspective view showing a printing device 1 according to one embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of an ejection head 10 and a light source unit 40 mounted on the carriage 3 of FIG. 1. In FIG. 1, mutually orthogonal directions are defined as the up-down direction, the left-right direction, and the front-rear direction. The left-right direction corresponds to a predetermined direction, specifically the main scanning direction Ds described below, and the front-rear direction corresponds to the sub-scanning direction Df described below. This printing device 1 can not only print on a print medium W such as printing paper, but can also print goods on a print medium W such as goods made of resin.

[0012] As shown in Fig. 1, the printing 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 printing device 1 also includes a control unit 19 (Fig. 3). The control unit 19 will be described in detail later.

[0013] 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 from the user. The display unit 5 is configured, for example, as 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 and controls the display of the display unit 5 based on input from the operation keys 4 or external input via a communication interface (not shown).

[0014] The carriage 3 corresponds to a relative movement unit, and moves the print medium W and the ejection head 10 relative to each other in the main scanning direction Ds when ink is ejected from the ejection head 10 (described below) onto the print medium W. Specifically, the carriage 3 is configured to be able to move back and forth along the main scanning direction Ds, and moves the ejection head 10 in the main scanning direction Ds relative to the print medium W when ink is ejected from the ejection head 10 onto the print medium W.

[0015] As shown in FIG. 1, the carriage 3 is equipped with two ejection heads 10 (10A, 10B) and two light source units 40 (40A, 40B). The ejection head 10 may be, for example, an inkjet head that ejects ultraviolet-curable ink. The light source unit 40 has a plurality of light-emitting diode chips DT (FIG. 2) that irradiate ultraviolet light. The light-emitting diode chips DT correspond to the light source. The ink ejected onto the print medium W is cured by the ultraviolet light irradiated from each light-emitting diode chip DT of the light source unit 40. The light source units 40A and 40B may have the same configuration.

[0016] In this embodiment, the ejection head 10A and the ejection head 10B are arranged side by side in the sub-scanning direction Df. The ejection head B is arranged in front of the ejection head A. The light source unit 40A and the light source unit 40B are also arranged side by side in the sub-scanning direction Df. The light source unit 40B is arranged in front of the light source unit 40A. The ejection head 10A and the light source unit 40A are also arranged side by side in the main scanning direction Ds. The light source unit 40A is arranged to the right of the ejection head 10A. The ejection head 10B and the light source unit 40B are also arranged side by side in the main scanning direction Ds. The light source unit 40B is arranged to the right of the ejection head 10B. Note that the above-described arrangement is an example and is not limited to this.

[0017] Each light-emitting diode chip DT of the light source unit 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, thereby enabling ultraviolet light to be effectively irradiated onto ink droplets ejected from nozzles located at one end (i.e., the front end) and the other end (i.e., the rear end) of the nozzle row NL in the sub-scanning direction Df.

[0018] 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 light source unit 40 move to the left during the printing process. In this case, the ejection head 10 ejects ink onto the print medium W while moving left in the main scanning direction Ds, and the light source unit 40 irradiates ultraviolet light onto the ink that has landed on the print medium W while moving left in the main scanning direction Ds. In this way, the light source unit 40 is positioned behind the ejection head 10 in the movement direction of the carriage 3 during the printing process, so ultraviolet light can be irradiated onto the ink immediately after it has landed on the print medium W.

[0019] 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 light source unit 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 light source unit 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.

[0020] 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. FIG. 2 shows an ejection head 10A for ejecting color inks as an example of the ejection head 10. The ejection head 10A is provided with nozzle rows NL that eject each of the above inks, each extending in the sub-scanning direction Df. Each nozzle row NL is provided at regular intervals in the main scanning direction Ds. The nozzle rows NL may be arranged in the main scanning direction Ds in the order of, from left to right, the nozzle row NL that ejects yellow ink, the nozzle row NL that ejects magenta ink, the nozzle row NL that ejects cyan ink, and the nozzle row NL that ejects black ink.

[0021] 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 intervals 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 intervals between the nozzle rows NL in the ejection head 10A in the main scanning direction Ds. The arrangement order of the nozzle rows NL in the main scanning direction Ds may be, from the left, the nozzle row NL that ejects white ink, followed by the nozzle row NL that ejects clear ink.

[0022] The six colors of ink are ejected onto the print medium W, thereby printing a color image on the print medium W. Specifically, when printing a color image on a fabric or other material as the print medium W, white ink is ejected first as a base ink, and then the 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 also ejected to impart gloss or to protect the printed area.

[0023] The platen 6 is configured so that the print medium 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 print medium W and a detachment position where the print medium 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 print medium W can be placed on the platen 6. During printing, the platen 6 moves in the sub-scanning direction Df, so that the print medium W placed on the platen 6 is transported in the sub-scanning direction Df.

[0024] 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 during maintenance, etc.

[0025] 2, the light source unit 40A has a first light source region RK1 and a second light source region RK2. The first light source region RK1 and the second light source region RK2 are arranged side by side in the main scanning direction Ds. The following will representatively describe the light source unit 40A and the ejection head 10A adjacent to the light source unit 40A in the main scanning direction Ds, but the same applies to the light source unit 40B and the ejection head 10B adjacent to the light source unit 40B in the main scanning direction Ds.

[0026] The second light source region RK2 is positioned to the left of the first light source region RK1. More specifically, the second light source region RK2 is disposed such that a linear distance LT2 from the ejection head 10A parallel to the main scanning direction Ds is shorter than the linear distance LT1 from the first light source region RK1.

[0027] Here, in this embodiment, the linear distance LT2 is the distance from the proximate nozzle row KNL of the discharge head 10A to the left end of the light-emitting diode chip DT that is closest to the discharge head 10A in the main scanning direction Ds in the second light source region RK2. In this embodiment, the linear distance LT2 is the shortest distance from the proximate nozzle row KNL to the left end of the light-emitting diode chip DT (the distance related to the interval SP2 between the proximate nozzle row KNL and the left end of the light-emitting diode chip DT). This proximate nozzle row KNL is the nozzle row NL that is closest to the light source unit 40A, and in this embodiment, it is the rightmost nozzle row NL of the discharge head 10A. Note that the distance from the right end of the discharge head 10A to the proximate nozzle row KNL is, for example, 50 to 200 mm. Furthermore, like the linear distance LT2, the linear distance LT1 is the distance from the proximate nozzle row KNL of the discharge head 10A to the left end of the light-emitting diode chip DT that is closest to the discharge head 10A in the first light source region RK1 in the main scanning direction Ds. In this embodiment, the linear distance LT1 is the shortest distance from the proximate nozzle row KNL to the left end of the light-emitting diode chip DT (the distance related to the interval SP1 between the proximate nozzle row KNL and the left end of the light-emitting diode chip DT).

[0028] A plurality of light-emitting diode chips DT are arranged in each of the first light source region RK1 and the second light source region RK2 of the light source unit 40A. The light-emitting diode chips DT in the first light source region RK1 and the light-emitting diode chips DT in the second light source region RK2 are arranged in a matrix. In this case, the light-emitting diode chips DT are arranged in a row direction parallel to the main scanning direction Ds and in a column direction parallel to the sub-scanning direction Df. In FIG. 2, a group of a plurality of light-emitting diode chips DT arranged at predetermined intervals along the sub-scanning direction Df is shown as a chip row DL. Note that, to suppress heat generation, as shown in FIG. 2, the light-emitting diode chips DT may not be arranged in the center of the first light source region RK1.

[0029] The number of light-emitting diode chips DT per unit area in the second light source region RK2 is smaller than the number of light-emitting diode chips DT per unit area in the first light source region RK1. That is, in this embodiment, the number of light-emitting diode chips DT in the second light source region RK2 is sparser than in the first light source region RK1, and conversely, the number of light-emitting diode chips DT in the first light source region RK1 is denser than in the second light source region RK2.

[0030] The intervals between the light-emitting diode chips DT in the first light source region RK1 and the second light source region RK2 can be set as follows: That is, the intervals between the light-emitting diode chips DT in at least one of the main scanning direction Ds and the sub-scanning direction Df in the second light source region RK2 are wider than the intervals in the first light source region RK1.

[0031] The above intervals will be specifically described. In the first light source region RK1, the interval between adjacent light emitting diode chips DT in the main scanning direction Ds is defined as k1, and the interval between adjacent light emitting diode chips DT in the sub-scanning direction Df is defined as k2. In the second light source region RK2, the interval between adjacent light emitting diode chips DT in the main scanning direction Ds is defined as k3, and the interval between adjacent light emitting diode chips DT in the sub-scanning direction Df is defined as k4. In this case, the interval k3 is wider than the interval k1, and the interval k4 is wider than the interval k2. Note that the intervals k1 to k4 can be the distances between the centers of one adjacent light emitting diode chip DT and the other adjacent light emitting diode chip DT.

[0032] Next, as shown in FIG. 3, the printing device 1 includes, in addition to the above-mentioned components, motor driver ICs 30 and 31, head driver ICs 32 and 36, a conveying motor 33, a carriage motor 34, light source driver ICs 37 and 38, an internal power supply 15, and a power receiving unit 16.

[0033] 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 printing device 1, and is connected to the storage unit and controls the driver ICs 30-32, 36-38 and the display unit 5.

[0034] 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.

[0035] The ROM 21 stores a print control program that causes the CPU 20 to execute the print process. The RAM 22 stores the results of calculations performed by the CPU 20. The EEPROM 23 stores various initial setting information entered 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 printing 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 printing device 1, and network setting information. When the printing 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.

[0036] The ASIC 25 is connected to motor driver ICs 30 and 31, head driver ICs 32 and 36, and light source driver ICs 37 and 38. When the CPU 20 accepts 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 using the motor driver IC 30, causing the platen 6 to move in the sub-scanning direction Df, thereby conveying the print medium W in the sub-scanning direction Df. The CPU 20 also drives the carriage motor 34 using the motor driver IC 31 to move the carriage 3 in the main scanning direction Ds. The CPU 20 also controls the head driver ICs 32 and 36 to eject ink from the ejection heads 10 mounted on the carriage 3, which is moved, to print image data on the conveyed print medium W. Furthermore, the CPU 20 controls the light source driver ICs 37 and 38 to irradiate ultraviolet light from the light source units 40A and 40B to cure the ink.

[0037] 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 power supply of the printing 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 power supply is in the ON state, external power is supplied to each part of the printing device 1 via the power receiving unit 16. Regardless of the state of the main 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.

[0038] FIG. 4 is a graph showing an example of illuminance in the main scanning direction Ds relative to the center of the light source unit. As described above, in this embodiment, the light source unit 40A is provided with a first light source region RK1 and a second light source region RK2 having a sparser number of light-emitting diode chips DT than the first light source region RK1. With this configuration, as shown in FIG. 4, the peak value of illuminance can be positioned to the right of the center of the light source unit 40A in the main scanning direction Ds. This reduces the reflected light irradiated onto the nozzle surface of the ejection head 10A compared to when the peak value of illuminance is positioned at the same position as the center of the light source unit 40A in the main scanning direction Ds.

[0039] Next, the positional relationship between the discharge head 10A and the light-emitting diode chips DT in the light source unit 40A will be explained with reference to the drawings. Fig. 5 is a diagram for explaining the positional relationship between the proximate nozzle row KNL of the discharge head 10A and the light-emitting diode chips DT. Note that the symbol NLR in Fig. 5 indicates the entire area in which the four nozzle rows NL are provided.

[0040] In FIG. 5, L1 is the distance between the proximate nozzle row KNL of the ejection head 10A and the center of the light-emitting diode chip DT located on the left side in the main scanning direction Ds. H is the distance from the light-emitting diode chip DT to the platen 6, and H is the distance from the nozzle surface NS of the ejection head 10A to the platen 6. That is, in the example of FIG. 5, the nozzle surface NS of the ejection head 10A and the light-emitting diode chip DT are flush with each other. Furthermore, L2 is the horizontal component (main scanning direction component) of the vector related to the incident light IL emitted from the light-emitting diode chip DT, and L3 is the horizontal component (main scanning direction component) of the vector related to the reflected light RL from the platen 6. Furthermore, α1 is the angle of incidence of the incident light IL (the acute angle formed between the incident light IL and the platen 6), and α2 is the angle of reflection of the reflected light RL (the acute angle formed between the reflected light RL and the platen 6). Note that the reflection angle α2 is basically the same as the incident angle α1.

[0041] Based on the above assumptions, reflected light RL will be irradiated onto the proximate nozzle row KNL when L2 + L3 ≥ L1, or in other words, (H / tan α1) + (H / tan α2) ≥ L1, is satisfied. For the incident angle α1, α1 = atan(H / L2) holds. Similarly, for the reflection angle α2, α2 = atan(H / L3) holds.

[0042] One possible solution is to increase the distance between the ejection head 10A and the light-emitting diode chip DT as much as possible to prevent the reflected light RL from irradiating the proximate nozzle row KNL. However, this would make it difficult to make the carriage 3 compact. Generally, when the reflection angle α2 is less than 20°, the illuminance is reduced by approximately 60 to 70%. Taking this into account, one criterion is to provide the second light source region RK2 in the light source unit 40A when there is a positional relationship in which the reflected light RL, where the reflection angle α2 is 20° or more, is irradiated onto the proximate nozzle row KNL (in other words, when (H / tan 20°) + (H / tan 20°) ≥ L1 is satisfied). This can reduce the reflected light RL irradiated onto the proximate nozzle row KNL.

[0043] Next, we will explain the positional relationship between the light-emitting diode chip DT and the proximate nozzle row KNL of the ejection head 10A when the light-emitting diode chip DT is positioned above the nozzle surface NS of the ejection head 10A. Note that explanations of parameters that are the same as those in Fig. 5 will be omitted in Fig. 6.

[0044] When the light-emitting diode chip DT is positioned above the nozzle surface NS of the ejection head 10A, the situation is basically the same as in the case shown in Figure 5 above. Reflected light RL is irradiated onto the proximate nozzle row KNL when L2 + L3 ≥ L1, or in other words, when (H' / tan α1) + (H / tan α2) ≥ L1, is satisfied. For the angle of incidence α1, α1 = atan(H' / L2) holds, and similarly for the angle of reflection α2, α2 = atan(H / L3) holds.

[0045] In the embodiment of Fig. 6, just as in the embodiment of Fig. 5, given that illuminance decreases by approximately 70% when the reflection angle α2 is less than 20°, one criterion is to provide the light source unit 40A with a second light source region RK2 when the positional relationship is such that the proximate nozzle row KNL is irradiated with reflected light RL with a reflection angle α2 of 20° or more. This makes it possible to reduce the reflected light RL irradiated onto the proximate nozzle row KNL.

[0046] As described above, according to the printing device 1 of this embodiment, the second light source region RK2, which has a smaller number of light-emitting diode chips DT per unit area than the first light source region RK1, is disposed near the ejection head 10A in the main scanning direction Ds. This allows for the formation of sparse and dense regions of illuminance, rather than a uniform illuminance distribution in the main scanning direction Ds. In this case, the ejection head 10A side in the main scanning direction Ds can be made into a sparse region of illuminance, and the opposite side of the ejection head 10A can be made into a dense region of illuminance. This configuration allows the maximum value of the illuminance distribution (peak illuminance) to be positioned farther from the ejection head 10A than the center of the light source unit 40A in the main scanning direction Ds. This reduces the amount of reflected light RL irradiated onto the nozzle surface NS of the ejection head 10A. This suppresses or prevents the ink in the nozzle holes from being cured by the reflected light RL, thereby preventing ink ejection failures. Furthermore, by forming sparse illuminance regions, the illuminance distribution changes more gradually in the feed direction (sub-scanning direction Df) of the print medium W, making it less likely that streaks will occur when printing gloss ink (clear ink that forms the overcoat layer). On the other hand, by forming dense illuminance regions as described above, it is possible to ensure the illuminance necessary to cure the ink ejected by the ejection head 10A. As a result, it is possible to prevent ink non-ejection while ensuring sufficient ink curing without increasing the dimensions of the carriage 3.

[0047] Furthermore, in this embodiment, the linear distance LT1 is the shortest distance from the proximate nozzle row KNL to the first light source region RK1, and the linear distance LT2 is the shortest distance from the proximate nozzle row KNL to the second light source region RK2. This makes it possible to define the positional relationship between the first light source region RK1 and the second light source region RK2 using the proximate nozzle row KNL, which is most irradiated with reflected light RL, as a reference.

[0048] Furthermore, in this embodiment, by using the existing carriage 3 that moves in the main scanning direction Ds as the relative moving unit, the ejection head 10A can be moved relative to the print medium W with the same control as in the past.

[0049] Furthermore, in this embodiment, the interval k3 between the light-emitting diode chips DT in the main scanning direction Ds in the second light source region RK2 is wider than the interval k1 in the first light source region RK1, and the interval k4 between the light-emitting diode chips DT in the sub-scanning direction Df in the second light source region RK2 is wider than the interval k2 in the first light source region RK1. This makes it possible to easily form a sparse region of the light-emitting diode chips DT in the second light source region RK2, and to easily form a dense region of the light-emitting diode chips DT in the first light source region RK1.

[0050] (Second embodiment) Next, a second embodiment will be described. The second embodiment differs from the first embodiment in the following respects. That is, in the second embodiment, in addition to the first light source region RK1a and the second light source region RK2a, a third light source region RKt is provided in the light source unit 40A. This will be described in detail below. Figure 7 is a diagram showing an example of the configuration of the ejection head 10A and the light source unit 40A in the second embodiment.

[0051] As shown in FIG. 7, the light source unit 40A is provided with a third light source region RKt in which multiple light-emitting diode chips DT are arranged in a matrix, similar to the first light source region RK1a and the second light source region RK2a, and whose linear distance LTt from the discharge head 10A is longer than the linear distance LT1 of the first light source region RK1a. In other words, the third light source region RKt is positioned to the right of the first light source region RK1a. The linear distance LTt is the distance from the proximate nozzle row KNL to the left end of the light-emitting diode chip DT in the third light source region RKt that is closest to the discharge head 10A in the main scanning direction Ds. In this embodiment, the linear distance LTt is the shortest distance from the proximate nozzle row KNL to the left end of the light-emitting diode chip DT (the distance related to the interval SPt between the proximate nozzle row KNL and the left end of the light-emitting diode chip DT). Note that, to reduce heat generation, it is also possible not to provide a light-emitting diode chip DT in the center of the third light source region RKt, as shown in FIG. 7.

[0052] In this embodiment, the third light source region RKt has a larger number of light emitting diode chips DT per unit area than the first light source region RK1a and the second light source region RK2a. That is, the third light source region RKt has a higher density of light emitting diode chips DT than the second light source region RK2a and the first light source region RK1a, and conversely, the second light source region RK2a and the first light source region RK1a have a lower density of light emitting diode chips DT than the third light source region RKt.

[0053] The intervals between the light-emitting diode chips DT in the first light source region RK1a, the second light source region RK2a, and the third light source region RKt can be set as follows: That is, the intervals between the light-emitting diode chips DT in at least one of the main scanning direction Ds and the sub-scanning direction Df in the third light source region RKt are narrower than the intervals in the first light source region RK1a.

[0054] The above intervals will be specifically described. In the first light source region RK1a, the interval between adjacent light emitting diode chips DT in the main scanning direction Ds is defined as k1a, and the interval between adjacent light emitting diode chips DT in the sub-scanning direction Df is defined as k2a. In the second light source region RK2a, the interval between adjacent light emitting diode chips DT in the main scanning direction Ds is defined as k3a, and the interval between adjacent light emitting diode chips DT in the sub-scanning direction Df is defined as k4a. In the third light source region RKt, the interval between adjacent light emitting diode chips DT in the main scanning direction Ds is defined as kt1, and the interval between adjacent light emitting diode chips DT in the sub-scanning direction Df is defined as kt2. In this case, the interval k1a is narrower than the interval k3a, and the interval k2a is narrower than the interval k4a. In addition, the interval kt1 is narrower than the interval k1a, and the interval kt2 is narrower than the interval k2a.

[0055] As described above, this embodiment also achieves the same effects as the first embodiment. Specifically, it is possible to reduce the amount of reflected light irradiating the nozzle surface NS of the ejection head 10A. This suppresses or prevents the ink in the nozzle holes from curing due to the reflected light, thereby preventing ink non-ejection. Furthermore, by forming a sparse illuminance region, the illuminance distribution changes gradually in the feed direction of the print medium W (the sub-scanning direction when the predetermined direction is the main scanning direction), making it less likely for streaks to occur when printing gloss ink. On the other hand, by forming a dense illuminance region, it is possible to ensure the illuminance required to cure the ink ejected by the ejection head 10A. As a result, it is possible to prevent ink non-ejection while ensuring sufficient ink curability without increasing the dimensions of the carriage 3.

[0056] (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.

[0057] In the above embodiment, we have described an aspect in which the light source unit 40A is provided with two light source regions (first light source region RK1 and second light source region RK2) and an aspect in which it is provided with three light source regions (first light source region RK1a, second light source region RK2a, and third light source region RKt). However, this is not limitative, and the light source unit 40A may be provided with four or more light source regions. In this case, the number of light-emitting diode chips DT increases as the linear distance from the proximate nozzle row KNL in the ejection head 10A increases.

[0058] In the above embodiment, the interval k3 between the light-emitting diode chips DT in the main scanning direction Ds in the second light source region RK2 is wider than the interval k1 in the first light source region RK1, and the interval k4 between the light-emitting diode chips DT in the sub-scanning direction Df in the second light source region RK2 is wider than the interval k2 in the first light source region RK1. However, this is not limited thereto, and it is sufficient that the interval between the light-emitting diode chips DT in at least one of the main scanning direction Ds and the sub-scanning direction Df in the second light source region RK2 is wider than the corresponding interval in the first light source region RK1.

[0059] In the above embodiment, in order to form sparse regions and dense regions of the light-emitting diode chips DT in the light source unit 40A, the light-emitting diode chips DT are arranged at regular intervals in the main scanning direction Ds and the sub-scanning direction Df. However, this is not limited to this. In order to form sparse regions and dense regions of the light-emitting diode chips DT in the light source unit 40A, it is not essential to keep the intervals between the light-emitting diode chips DT constant, and the intervals do not necessarily have to be constant.

[0060] Furthermore, in the above embodiment, the carriage 3 is equipped with two ejection heads 10 (10A, 10B) and two light source units 40 (40A, 40B), but this is not limiting. The carriage 3 may be equipped with only the ejection head 10A and the light source unit 40A. [Explanation of symbols]

[0061] 1 Printing device 3 carriages 10, 10A, 10B Discharge head 40, 40A, 40B Light Source Unit Df Sub-scanning direction Ds Main scanning direction DT Light Emitting Diode Chip KNL Proximal Nozzle Row kt1,kt2,k1,k2,k3,k4,k1a,k2a,k3a,k4a Interval LT1,LT2,LTt Straight line distance NL nozzle row RK1,RK1a 1st light source area RK2,RK2a 2nd light source area RKt 3rd light source area W Printing medium

Claims

1. an ejection head that ejects ultraviolet curable ink onto a print medium; a relative movement unit that moves the print medium and the ejection head relatively in a predetermined direction when ejecting ink from the ejection head onto the print medium; a light source unit having a plurality of light sources that cure the ink, the light source unit includes a first light source region in which a plurality of the light sources are arranged, and a second light source region in which a plurality of the light sources are arranged, the second light source region having a smaller number of the light sources per unit area than the first light source region and a shorter linear distance from the ejection head in parallel to the predetermined direction than the first light source region; In the first light source region and the second light source region, the light sources are arranged in a matrix, A printing device, wherein an interval between the light sources in the second light source area in an intersecting direction intersecting the predetermined direction is wider than the interval between the light sources in the first light source area.

2. The printing device according to claim 1 , wherein the first light source area and the second light source area are arranged side by side in the predetermined direction.

3. the ejection head has a plurality of nozzle rows, each including a plurality of nozzles aligned in an intersecting direction that intersects the predetermined direction, and the plurality of nozzle rows includes a proximate nozzle row that is closest to the light source unit, The printing device according to claim 1 or 2, wherein the linear distance is the shortest distance from the proximate nozzle row to the first light source region or the second light source region.

4. 4. The printing apparatus according to claim 1, wherein the relative moving unit is a carriage that carries the ejection head and moves in the predetermined direction.

5. the light source unit further includes a third light source area in which a plurality of the light sources are arranged, and the linear distance from the ejection head is longer than that of the first light source area; The printing device according to claim 1 , wherein the third light source region has a larger number of light sources per unit area than the first light source region and the second light source region.

6. An ejection head that ejects ultraviolet-curable ink onto a print medium; a relative movement unit that moves the print medium and the ejection head relatively in a predetermined direction when ejecting ink from the ejection head onto the print medium; a light source unit having a plurality of light sources that cure the ink, the light source unit includes a first light source region in which a plurality of the light sources are arranged, and a second light source region in which a plurality of the light sources are arranged, the second light source region having a smaller number of the light sources per unit area than the first light source region and a shorter linear distance from the ejection head in parallel to the predetermined direction than the first light source region; the ejection head has a plurality of nozzle rows, each including a plurality of nozzles aligned in an intersecting direction that intersects the predetermined direction, and the plurality of nozzle rows includes a proximate nozzle row that is closest to the light source unit, the straight-line distance is the shortest distance from the proximate nozzle row to the first light source region or the second light source region, a platen on which the print medium is placed, Let us assume that the acute angle formed between the platen and the reflected light produced when ultraviolet light emitted from the light source is reflected off the platen is the reflection angle, the distance from the light source to the platen is H, and the distance between the proximate nozzle row and the center of the light source located closest to the proximate nozzle row in the predetermined direction is L1. a printing device in which the second light source area is provided in the light source unit when the positional relationship in which the reflected light with a reflection angle of 20° or greater is irradiated onto the proximate nozzle row satisfies (H / tan 20°) + (H / tan 20°) ≧ L1.

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