JP5597323B2 - Inkjet printer and printing method thereof - Google Patents

Description

  The present invention relates to an inkjet printer that performs printing by ejecting ink onto a printing medium and a printing method thereof.

  2. Description of the Related Art Conventionally, there is known an ink jet printer that prints on a print medium by ejecting ink while a print head disposed opposite to the platen is moved back and forth with respect to the print medium placed on the platen. ing. Among such ink jet printers, there is an ink jet printer that prints on a print medium by discharging an ultraviolet curable ink (hereinafter referred to as UV ink) having a property of being cured by being irradiated with ultraviolet rays from a print head. . Since this UV ink is excellent in weather resistance and water resistance, it becomes possible to use a printed matter on which printing has been applied, for example, for outdoor advertising flyers, etc., and the use of the printed matter as compared with the case where water-soluble ink is used. There is an advantage that the use is greatly expanded.

  By the way, an ink jet printer that performs printing by discharging UV ink is provided with an ultraviolet irradiation device for curing the UV ink attached to the printing medium. As an ultraviolet light source for emitting ultraviolet rays in this ultraviolet irradiation device, a configuration is known in which, for example, a mercury lamp, a metal halide lamp, and the like are detachably attached to the ultraviolet irradiation device. In recent years, an ultraviolet light emitting diode (hereinafter referred to as UVLED) is used as an ultraviolet light source. Here, the UVLED is an abbreviation for Ultra Bior Light Emitting Diode.

  In general, the ultraviolet light source exemplified above gradually decreases the intensity of ultraviolet light output according to the operating time. For this reason, when UV ink is cured using an ultraviolet light source that has been operating for a long time and has reached the end of its life, there may be a problem in that the UV ink is not sufficiently cured due to insufficient ultraviolet light quantity irradiated to the printing medium. . As a technique for avoiding the occurrence of such a problem, for example, in Patent Document 1, an operation time for reaching the lifetime of the ultraviolet light source is set in advance, and the operation time of the ultraviolet light source reaches the preset operation time. A method is disclosed that prompts the operator to replace the ultraviolet light source when it is determined whether or not the lifetime has been reached.

JP 2005-138476 A

  By the way, when the lifetime of the ultraviolet light source is determined as in the above-mentioned Patent Document 1, the intensity of the ultraviolet light just before the lifetime is determined decreases to near the lower limit output intensity capable of curing the UV ink attached to the print medium. There are many. For this reason, there is a possibility that the UV ink is hardened when the ultraviolet ray irradiation is started and just before the end of its life, resulting in variations in the cured state of the UV ink, which may deteriorate the print quality.

  In view of the above problems, an object of the present invention is to provide an ink jet printer that improves the print quality by correcting the intensity of the ultraviolet light output from the ultraviolet light source to be constant, and a printing method therefor.

  In order to solve the above problems, an ink jet printer according to the present invention provides a print head with respect to the print medium in a state where the print head is opposed to the print medium supported by the medium support means (for example, the vacuum table 12a in the embodiment). In an inkjet printer that performs desired printing on the surface of the print medium by ejecting ink from the print head while relatively moving, an ultraviolet light source that irradiates the print medium with ultraviolet light and cures the ink attached to the print medium ( For example, the ultraviolet irradiation means (for example, the right UVLED unit 70R and the left UVLED unit 70L in the embodiment) provided with the UVLED 72 in the embodiment, and the output control means (for example, the embodiment) for controlling the output ultraviolet light intensity from the ultraviolet light source. And a controller 23) It is. The output control means includes reference output characteristic data (for example, output characteristic data 79 in the embodiment) indicating the relationship between the output ultraviolet intensity of the ultraviolet light source and the operation time, and refers to the reference output characteristic data. Intensity correction is performed to increase the intensity of the output ultraviolet light from the ultraviolet light source.

  In the above-described inkjet printer according to the present invention, the ultraviolet light source has an output characteristic that outputs ultraviolet light having a substantially constant intensity from the start of ultraviolet light output until the initial operation time elapses, and the output control The means is preferably configured to perform the intensity correction after the initial operation time has elapsed.

  The output control means determines whether or not the output ultraviolet light intensity from the ultraviolet light source has decreased to a lower limit output intensity capable of curing the ink attached to the print medium, based on the reference output characteristic data. A configuration further comprising a lower limit determination unit (for example, a lower limit determination unit 78 in the embodiment) is preferable, and when the lower limit determination unit determines that the output ultraviolet intensity from the ultraviolet light source has decreased to the lower limit output intensity, The output control means preferably performs the intensity correction.

  The ink jet printer includes an intensity measuring unit (for example, an intensity measuring unit 80 in the embodiment) that measures the intensity of the output ultraviolet light from the ultraviolet light source, and the output control unit is provided on the print medium in the intensity measuring unit. A configuration may be used in which intensity correction is performed to increase the output ultraviolet intensity from the ultraviolet light source when the lower limit output intensity capable of curing the attached ink is detected.

  Further, in the ink jet printer configured as described above, the ultraviolet light source preferably uses a light emitting diode capable of outputting ultraviolet light.

  In order to solve the above problems, a printing method according to the present invention is a printing method performed using the ink jet printer configured as described above, wherein the print head and the ultraviolet irradiation means are supported by the medium support means. The ink was ejected from the print head and adhered to the print medium while being moved relative to the print medium, and the print medium was irradiated with the ultraviolet light output from the ultraviolet light source of the ultraviolet irradiation means. Curing the ink. When irradiating the printing medium with ultraviolet rays, the output control means performs control to correct the output ultraviolet ray intensity from the ultraviolet light source with reference to the reference output characteristic data.

  In the ink jet printer according to the present invention, the output control means includes reference output characteristic data indicating the relationship between the output ultraviolet intensity of the ultraviolet light source and the operation time, and the reference output characteristic data is referred to from the ultraviolet light source. Intensity correction is performed to increase the output ultraviolet intensity. By configuring in this way, the output control means, for example, measures the operating time of the ultraviolet light source and refers to the output characteristic data for reference to maintain the target output ultraviolet intensity at which timing (operation Time), how much intensity correction should be performed to increase the output ultraviolet intensity is required. Therefore, by correcting the intensity at the required timing, it is possible to output an ultraviolet light having a substantially constant intensity from the ultraviolet light source, thereby improving the printing quality.

  In the above-described ink jet printer according to the present invention, it is preferable that the output control unit performs the intensity correction after the initial operation time when the output of the ultraviolet light source starts to decrease. In such a configuration, the intensity correction is not performed until the initial operation time in which the output ultraviolet intensity is sufficiently secured has elapsed, so that the control burden on the output control means can be reduced. In addition, since the initial operation time can be grasped by referring to the reference output characteristic data, the control configuration of the output control means can be configured simply without complicating.

  In the above-described ink jet printer according to the present invention, the output control means determines whether or not the ink attached to the print medium has been reduced to the lower limit output intensity that can be cured based on the reference output characteristic data. A configuration including a determination unit is preferable. When configured in this way, the output control means can detect the output intensity of the ultraviolet light source during the measured operating time, for example, by referring to the reference output characteristic data while measuring the operating time of the ultraviolet light source, and has a lower limit. It can be determined whether or not the output intensity has decreased. Therefore, it is possible to grasp the timing of intensity correction and the correction amount at that time while making the output control means simple.

  It is preferable that the output control means corrects the intensity when the lower limit output intensity is detected by the intensity measuring means for measuring the output ultraviolet intensity from the ultraviolet light source. In such a configuration, there may be a slight error in the relationship between the operating time and the irradiation intensity due to, for example, manufacturing errors of the ultraviolet light source. Therefore, it is possible to perform intensity correction at an appropriate timing before falling below the lower limit output intensity.

  In the above-described ink jet printer according to the present invention, the ultraviolet light source preferably uses a light emitting diode capable of outputting ultraviolet light. When the light emitting diode is used as described above, for example, the supply current value for the light emitting diode is changed, and at the same time, the output ultraviolet ray intensity is changed. Therefore, it is possible to output ultraviolet rays having a desired output ultraviolet intensity and irradiate the print medium with almost no time lag with respect to the control of the output ultraviolet intensity, and to cure the UV ink attached to the print medium evenly. It becomes possible.

  In the printing method according to the present invention, the output control means performs control to correct the output ultraviolet intensity from the ultraviolet light source with reference to the reference output characteristic data indicating the relationship between the output ultraviolet intensity of the ultraviolet light source and the operation time. It is configured to do. From this configuration, by referring to the reference output characteristic data, the timing for performing intensity correction and the intensity correction amount are obtained in order to maintain the target output ultraviolet intensity according to the operation time of the ultraviolet light source. Therefore, by performing control to correct the intensity at the obtained timing, it is possible to output ultraviolet light having a substantially constant intensity from the ultraviolet light source.

1 is a perspective view showing an ink jet printer to which the present invention is applied. FIG. 3 is a perspective view illustrating the inside (partially omitted) of the printing unit according to the first embodiment. It is sectional drawing which showed the III-III part in FIG. 3 is a graph showing the relationship between the relative output of ultraviolet rays from the UVLED according to Example 1 and the operation time. FIG. 3 is a diagram illustrating a control system of the ink jet printer according to the first embodiment. 3 is a graph showing output characteristics of a UVLED according to Example 1. FIG. FIG. 10 is a perspective view illustrating the vicinity of a printing unit according to a second embodiment. FIG. 5 is a diagram illustrating a control system of an ink jet printer according to a second embodiment. 6 is a graph showing output characteristics of a UVLED according to Example 2. 6 is a graph showing the relationship between the relative output of ultraviolet rays from the UVLED according to Example 2 and the operation time.

  Examples 1 and 2 as preferred embodiments of the present invention will be described below with reference to the drawings. For convenience of explanation, the directions of arrows shown in the drawings will be referred to as front and rear, left and right, and top and bottom, respectively.

  First, Example 1 is demonstrated with reference to FIGS. In FIG. 1, as an example of an ink jet printer to which the present invention is applied, a printing unit is moved in two orthogonal axes (X-axis-Y-axis) directions in a horizontal plane with respect to a printing medium fixedly held on a table. The perspective view which looked at the inkjet printer 1 which performs desired printing with respect to a printing medium from diagonally forward is shown.

  The ink jet printer 1 includes a support portion 10 that forms a base portion in a lower portion, and a printing portion 50 that is disposed above the support portion 10 so as to be movable. The support unit 10 is mainly composed of a main body frame 11, a support table 12, a vacuum blower 13, and a control unit 20. The main body frame 11 horizontally supports a support table 12 mounted and fixed thereon, and serves as a mounting base for each mechanism. Guide grooves 12b, 12b extending in the front-rear direction are formed on the left and right end surfaces of the support table 12, and are fitted with front-rear guides 51a, 51a formed on the left and right of the printing unit 50 described later.

  A vacuum table 12 a is formed at the center of the support table 12 to place and fix the flat print medium 2 thereon. The surface of the vacuum table 12a is formed with a number of fine air holes penetrating vertically, and these air holes communicate with a decompression chamber (not shown) provided on the lower surface side of the vacuum table 12a. . The vacuum blower 13 communicates with the decompression chamber and exhausts the air in the decompression chamber to set a negative pressure, or feeds air into the decompression chamber and discharges it from the air hole. The print medium 2 is placed at the origin position on the vacuum table 12a, the vacuum chamber 13 is set to a negative pressure by the vacuum blower 13, and the print medium 2 is vacuum-adsorbed on the surface of the vacuum table 12a and fixedly held.

  The control unit 20 is installed at a front end portion of the support table 12 and mainly includes an operation panel 21, a stop button 22, and a controller 23. The operation panel 21 is provided with operation buttons (not shown) for operating the ink jet printer 1 and a display panel (not shown) for displaying the operation status. The stop button 22 is a button for stopping the operation of the inkjet printer 1. The controller 23 can output an operation signal to each component described later so that the inkjet printer 1 is in a desired operation state, and details thereof will be described later.

  The printing unit 50 is mainly composed of a base 51, a guide rail 52, and a printing unit 60. The base 51 is a substantially rectangular parallelepiped extending left and right, and front and rear guides 51a and 51a formed in the vicinity of the left and right ends are fitted with the guide grooves 12b and 12b, and slide back and forth across the upper side of the support table 12. It is supported movably. The guide rail 52 is formed on the front surface of the base 51 so as to extend left and right. Further, left and right guides 65 formed on the rear surface of a carriage 63, which will be described later, are fitted to the guide rails 52, and the printing unit 60 is supported so as to be slidable in the left and right directions. Various well-known techniques can be used for the front / rear drive mechanism 59 that slides the base 51 back and forth, and the left / right drive mechanism 69 that slides the print unit 60 left and right. Is omitted.

  As shown in FIGS. 1 and 2, the printing unit 60 is mainly composed of a print head 62, a carriage 63, a right UVLED unit 70 </ b> R, and a left UVLED unit 70 </ b> L, and an outer peripheral portion is covered with a cover 61. The carriage 63 is a mounting base for the print head 62, the right UVLED unit 70R, and the left UVLED unit 70L. A print head 62 is mounted and fixed near the front end of the carriage 63, and a right UVLED unit 70 </ b> R is disposed on the right side of the print head 62, and a left UVLED unit 70 </ b> L is disposed on the left side of the print head 62. The printing unit 60 configured as described above is reciprocated left and right above the print medium 2 by the left and right driving mechanism 69 and is slid back and forth by the front and rear driving mechanism 59.

  The print head 62 includes, for example, print heads 62M, 62Y, 62C for each color corresponding to UV inks of magenta (M), yellow (Y), cyan (C), black (K), and transparent clear (T). 62K, 62T. A plurality of nozzles (not shown) capable of ejecting UV ink of each color downward are formed on a plane extending in the front-rear and left-right directions on the lower surface of the color-specific print heads 62M, 62Y, 62C, 62K, 62T. It is arranged.

  A storage tank 53 that stores UV ink of each color is disposed on the upper surface of the left end of the base 51. The storage tank 53 is, for example, a color-specific storage tank 53M, 53Y, 53C, 53K, 53T corresponding to each color of magenta (M), yellow (Y), cyan (C), black (K), and clear (T). It is composed of A storage tank and a print head communicate with each color via a pipe line (not shown), and UV ink is appropriately sent from the storage tank to the color-specific print head. It is possible to perform glossy printing by attaching transparent clear (T) UV ink ejected from the color-specific print head 62T to the surface of the print medium 2.

  The right UVLED unit 70R and the left UVLED unit 70L have the same configuration, and the right UVLED unit 70R will be described below as an example. Here, it demonstrates, referring FIG. 2 and FIG. 3 which showed sectional drawing of the right UVLED unit 70R. The right UVLED unit 70R is mainly composed of a cover 71, a UVLED 72, and a mounting member 73. The front and rear side surfaces, the left and right side surfaces, and the upper surface are covered with a flat cover 71 and open downward. An attachment member 73 is fixed inside the cover 71, and a plurality (six) of UVLEDs 72 are attached to the attachment member 73. The UVLED 72 can be attached to and detached from the attachment member 73.

  The UVLED 72 is mainly composed of a main body 72 a and a condenser lens 72 b, and the main body 72 a is attached to the attachment member 73. Further, the UVLED 72 collects ultraviolet rays emitted from an LED chip (not shown) incorporated in the main body 72a by a condenser lens 72b and irradiates downward at a certain irradiation angle. The LED chip can output ultraviolet light having an intensity corresponding to the current value, for example, by controlling the current value of the supplied current by the controller 23. In Example 1, as will be described later, a case where UVLED 72 having a characteristic of outputting ultraviolet light of a certain intensity for a while from the start of operation and then gradually decreasing the output intensity is illustrated. Yes.

  The controller 23 is configured inside the control unit 20, and as shown in FIG. 5, the front-rear drive mechanism 59, the left-right drive mechanism 69, the right UVLED unit 70R (UVLED 72), the left UVLED unit 70L (UVLED 72), and the different colors The print heads 62M, 62Y, 62C, 62K, 62T and the like are connected to be able to output operation signals. In an internal memory (not shown) of the controller 23, output characteristic data 79 indicating the relationship between the (cumulative) operating time when the UVLED 72 outputs ultraviolet rays and operates, and the output intensity of ultraviolet rays at each operating time, Stored as a database. In addition, a lower limit determination unit 78 is configured inside the controller 23. As will be described later, the controller 23 controls the supply current value to the UVLED 72 based on the determination result of the lower limit determination unit 78, so The output intensity is controlled.

  The lower limit determination unit 78 can measure the (cumulative) operating time in which the current is supplied to the UVLED 72 (LED chip) and the UVLED 72 emits ultraviolet rays. Further, the lower limit determination unit 78 reads the output intensity of the ultraviolet rays from the UVLED 72 during the measured operation time by referring to the output characteristic data 79, and the read output intensity is the UV attached to the print medium 2. It is possible to determine whether or not the ink has lowered to a lower limit output intensity that can cure the ink (for example, an intensity of 70% relative output described later). Further, by referring to the output characteristic data 79, it is possible to grasp how much the UVLED 72 is operated, and how the relative output starts to decrease as will be described later. For this reason, the lower limit determination unit 78 continuously measures the operating time from the output initial state, while the determination as to whether or not the lower limit output intensity has been reduced starts after the relative output starts to decrease. ing. With this configuration, the control burden on the lower limit determination unit 78 is reduced. Further, the determination as to whether or not the lower limit output intensity has been reduced is performed at regular time intervals or continuously. The output characteristic data 79 is created based on the relationship between the relative output of ultraviolet rays obtained by actual measurement and the operation time, as shown in FIG. 6 described later, for example. Here, the average life 6a, Of the maximum life 6b and the minimum life 6c, the average life 6a is preferably used.

  Up to this point, each component of the inkjet printer 1 has been described. A printing method for printing on the print medium 2 using the inkjet printer 1 will be described below.

  First, the print medium 2 is placed and fixedly held on the vacuum table 12a, and the print unit 60 is moved to the rear end (or front end) of the print medium 2. While the print unit 60 is reciprocated left and right by the left and right drive mechanism 69, UV ink is ejected from the print head 62 toward the print medium 2 and adhered in a desired pattern. When the printing unit 60 is moving to the right, for example, the left UVLED unit 70L is operated to irradiate ultraviolet rays, and the UV ink attached to the printing medium 2 is cured. On the other hand, when the printing unit 60 is moving to the left, for example, the right UVLED unit 70R is operated to irradiate ultraviolet rays, and the UV ink attached to the printing medium 2 is cured. As described above, the printing unit 60 ejects UV ink and irradiates ultraviolet rays while reciprocating left and right, and is moved back and forth by the front and rear drive mechanism 59, whereby desired printing is performed on the print medium 2.

  Up to this point, the printing method by the ink jet printer 1 has been described. Hereinafter, the intensity characteristics of ultraviolet rays output from the UVLED 72 will be described with reference to FIG.

  In the case where a UVLED having the same characteristics as the UVLED 72 according to Example 1 is used in FIG. 6, in the initial output state in which the ultraviolet light is output, the ultraviolet light having the maximum intensity (relative output 100%) that the UVLED can output. For example, the relationship between the relative output of ultraviolet rays and the operation time when the supply current value is set so as to be output is shown. FIG. 6 is created by measuring the relative output of each UVLED for each operating time for a plurality of UVLEDs having the same specifications. There is some variation in the relative output for each UVLED, and the maximum life 6b is created by connecting the maximum values of the variations, while the minimum output is connected by connecting the minimum values of the variations. Is the minimum life 6c. The average life 6a is created by connecting the average values of the variations.

  As can be seen from, for example, the average life 6a shown in FIG. 6, the UVLED outputs ultraviolet light having a relative output of 100% for a while from the start of operation, but thereafter the relative output gradually decreases with the operation time. I will do it. Similarly, since the relative output of the UVLED 72 gradually decreases with the operation time, the amount of ultraviolet light applied to the print medium 2 at a certain point of time may be insufficient, and the UV ink may not be sufficiently cured, resulting in poor curing. In order to avoid the occurrence of such a curing failure, the intensity of the ultraviolet light output from the UVLED 72 is controlled as follows. In the following description, it is assumed that 70% intensity (relative output 70%) with respect to the maximum intensity that the UVLED 72 can output is the lower limit output intensity that can cure the UV ink. Therefore, when UV light having an intensity higher than 70% relative output is output, the UV ink attached to the print medium 2 is cured, whereas UV light having an intensity less than 70% relative output is output. Will be described assuming that curing failure may occur.

  The intensity characteristics of the ultraviolet rays output from the UVLED 72 have been described above. The intensity control of the ultraviolet rays output from the right UVLED unit 70R (UVLED72) and the left UVLED unit 70L (UVLED72) by the controller 23 will be described below with reference to FIG. This will be described with reference to the graphs 4b, 4c, 4d and FIG. Note that a graph 4a indicated by a two-dot chain line in FIG. 4 corresponds to the average life 6a in FIG. 6 and is described for reference although it is not directly related to the control in this embodiment. As can be seen from the graph 4a, if the controller 23 sets the supply current value to the UVLED 72 to be, for example, a1 so that the relative output is 100% in the output initial state in which the UVLED 72 outputs ultraviolet rays, the operating time t1 has elapsed. The relative output drops to 70%.

  In the control in this embodiment, the UVLED 72 having the intensity characteristic as shown in the graph 4a is used, and the supply current value to the UVLED 72 is first controlled to a2 so that the relative output becomes 80% in the initial output state, and then a2 The case of raising from a3 to a3 and further from a3 to a1 is illustrated. In the above control, it is preferable to perform control so that the supply current value to the UVLED 72 is finally increased to a1 which is the maximum settable supply current value. When control is performed in this manner, it is possible to output ultraviolet rays having a desired intensity over a longer period by fully utilizing the output performance of the UV LEDs 72. In this embodiment, the control in the case where the supply current value to the UVLED 72 is increased twice (from a2 to a3 and from a3 to a1) will be described. However, the control may be performed so as to increase once or three times or more.

  In the present embodiment, for example, when the supply current value to the UVLED 72 is controlled to a2 in the output initial state, it is assumed that the relative output decreases to 70% when the operation time t2 has elapsed. Here, the relationship between the operation time and the relative output is stored in the memory in the controller 23 as output characteristic data 79. Therefore, the lower limit determination unit 78 can detect that the relative output has decreased to 70% at the operation time t2 by measuring the operation time t2 and referring to the output characteristic data 79. Further, for example, when control is performed to increase the supply current value to the UVLED 72 from a2 to a3, the relative output decreases to 70% when the operation time t3 has elapsed. Further, for example, when control is performed to increase the supply current value to the UVLED 72 from a3 to a1, for example, the fact that the relative output decreases to 70% when the operation time t4 has elapsed is also stored as output characteristic data 79. In addition, the magnitude relationship of the supply current value to UVLED72 shall be a2 <a3 <a1.

  In the control in the present embodiment, first, in the output initial state, as shown in the graph 4b of FIG. 4, for example, the supply current value is set to a2 so that the relative output becomes 80%. By setting in this way, the UV LED 72 outputs an ultraviolet ray having an intensity of 80% relative output with almost no decrease in relative output until the operation time t0 has elapsed since the start of operation. At this time, the lower limit determination unit 78 continuously measures the operation time from the start of operation until the operation time t0 elapses. However, the lower limit determination unit 78 does not determine whether or not the lower limit output intensity has been reduced. Instead, it starts after the operating time t0 has elapsed. Here, compared with the case of the graph 4a, the supply current value to the UVLED 72 is lower, and the electrical load on the UVLED 72 (LED chip) is reduced, so the relative output is more than 70% when the operation time t1 has elapsed. High UV output is possible.

  For example, when the operation time t2 (> operation time t1) has elapsed, the relative output decreases to 70%. The lower limit determination unit 78 refers to the output characteristic data 79 and reads the output intensity of the ultraviolet rays from the UVLED 72 at the measured operation time t2, and detects that the read output intensity is 70% relative output. Thus, it is determined that the lower limit output intensity has been reduced. When the lower limit determination unit 78 determines that the relative output has decreased to 70%, the controller 23 performs control to increase the supply current value from a2 to a3 so that the relative output becomes 80% again, for example. In this way, by performing the control to increase the supply current value to a3, the UVLED 72 can again output ultraviolet light having a relative output of 80% as shown in the graph 4c.

  After the control to increase the supply current value to a3, the relative output of the ultraviolet light output from the UVLED 72 decreases with the operation time, and for example, when the operation time t3 has elapsed, the relative output decreases again to 70%. The lower limit determining unit 78 refers to the output characteristic data 79 and reads the output intensity of ultraviolet rays from the UVLED 72 at the measured operation time t3, and determines that the output has decreased to the lower limit output intensity. At this time, the controller 23 performs control to increase the supply current value from a3 to a1 so that the relative output becomes 80% again, for example. In this way, by performing the control to increase the supply current value to a1, the UVLED 72 can again output ultraviolet light with a relative output of 80% as shown in the graph 4d.

  After the above control, the relative output of the ultraviolet light output from the UVLED 72 decreases with the operating time, and for example, when the operating time t4 has elapsed, the relative output decreases again to 70%. The lower limit determination unit 78 refers to the output characteristic data 79 and reads the output intensity of the ultraviolet rays from the UVLED 72 at the measured operation time t4, thereby determining that the output has decreased to the lower limit output intensity. Here, if the UVLED 72 is continuously used beyond the operation time t4 without performing control to increase the relative output, curing failure may occur due to the output of ultraviolet rays having a relative output less than 70%. By the way, the supply current value a1 is the maximum supply current value that can be set for the UVLED 72, and it is not possible to increase the relative output by performing control to increase the supply current value any more. Therefore, when the operation time t4 has elapsed, the UVLED 72 is determined to have reached the end of its life and replaced.

  Here, the main effects of the ink jet printer 1 according to the first embodiment are summarized as follows. First, the controller 23 is configured to control the intensity so that the intensity of the ultraviolet light output from the UVLED 72 falls within a range of, for example, a relative output of 70% to a relative output of 80%. This intensity control ensures that at least the lower limit output intensity required to cure the UV ink, and does not output UV light having an excessively high relative output from the UVLED 72 to cure the UV ink. It has become. By controlling the intensity in this way, the UV ink is irradiated with ultraviolet rays having a substantially constant relative output, so that it is cured without unevenness, and the print quality can be improved.

  Secondly, when the relative output decreases with the operating time, for example, when the output decreases to the lower limit output intensity, control for increasing the supply current value to the UVLED 72 is performed, and intensity control for increasing the relative output is possible. By being able to perform such intensity control, the UVLED 72 whose UV intensity has once decreased to the lower limit output intensity can be output again, and the UVLED 72 can be continuously used. . Therefore, the operation time from the start of the operation of the UVLED 72 until it is determined to be a lifetime can be extended. Specifically, referring to FIG. 4, the conventional UVLED 72 is determined to have reached the end of life when the operating time t <b> 1 has elapsed, but according to the configuration of the first embodiment, the replacement time is extended to the operating time t <b> 4. Is possible.

  Thirdly, when the lower limit output intensity is converted to a relative output, for example, 70%, the supply current value to the UVLED 72 is controlled so that the relative output 80% is less than the upper limit output intensity in the initial output state. . For this reason, compared with the conventional case where the ultraviolet light having the relative output 1 is output in the initial output state, the supply current value to the UVLED 72 becomes lower, so that the electrical load on the UVLED 72 is reduced. Therefore, it is possible to extend the operation time until the relative output is reduced to the lower limit output intensity, and the replacement timing of the UVLED 72 can be delayed.

  Hereinafter, Example 2 will be described with reference to FIGS. 7 is a perspective view of the vicinity of the printing unit 60, FIG. 8 is a control system, FIG. 9 is an output characteristic of the UVLED 72 according to the second embodiment, and FIG. 10 is a relative output and operation of the ultraviolet light from the UVLED 72 according to the second embodiment. Each shows the relationship with time. The ink jet printer 1 'according to the second embodiment is mostly the same as the ink jet printer 1 described in the first embodiment, and the same parts are denoted by the same reference numerals and the description thereof is omitted. The description will focus on the configuration different from the inkjet printer 1.

  As shown in FIG. 7, a right control board 75R and a left control board 75L for controlling a supply current value to the UVLED 72 are mounted on the right UVLED unit 77R and the left UVLED unit 77L, respectively. An operation signal is output from the controller 23 to the right control board 75R and the left control board 75L, and the relative output of the UVLED 72 in each of the UVLED units 77R and 77L can be controlled via these control boards 75R and 75L (FIG. 8). reference). In the second embodiment, the case where the UVLED 72 having the characteristic that the relative output gradually decreases as the operation time elapses is illustrated (see FIG. 9).

  In FIG. 7, an intensity measuring unit 80 is mounted inside the left end of the base 51. The intensity measuring unit 80 is configured to be able to measure the intensity of ultraviolet rays irradiated downward from the UVLED 72 in each of the UVLED units 77R and 77L, and the measured intensity is output to the controller 23. Note that the mounting position of the strength measuring unit 80 is not limited to the inside of the left end of the base 51, and may be configured to be mounted on the carriage 63, for example.

  As shown in FIG. 8, the controller 23 includes output characteristic data 79 ′ of the UVLED 72 therein. FIG. 9 shows an example of the output characteristic data 79 ′. The UVLED 72 in Example 2 has a characteristic in which the reduction rate of the light amount varies depending on the magnitude of the supply current value, and the graph 9a has a large current value. The graph 9c shows a small case, and the graph 9b shows a case where these intermediate values are set. As can be seen from the graphs 9a to 9c, for example, when the operation time until the relative output K1 is decreased is compared, the graph 9a having a large current value has an operation time D1 and the graph 9c having a small current value has an operation time D3 ( > D1), the graph 9b shows the operating time D2 (D1 <D2 <D3).

  More specifically, the operation time until the output is reduced to a certain relative output has a characteristic that it is shortened in inverse proportion to the square of the magnitude of the supply current value. More specifically, when considering a case where a certain supply current value B1 is set and a case where the supply current value B2 is set to twice that supply current value B1, the supply current value B2 is set. In this case, the operating time is ¼ that of the supply current value B1. As can be seen from this, if an excessive supply current value is set, the output will suddenly drop within a short period of time, and the required relative output will not be obtained (the life will be reached). In order to extend the life of the UVLED 72, it is important to set the supply current value as small as possible while securing the relative output.

  Although the configuration of the inkjet printer 1 ′ has been described above, the intensity control of ultraviolet rays output from the UVLED 72 by the controller 23 will be described below with reference to FIG. In the following description, the supply current value at the initial stage of operation is set to 70% with respect to the maximum settable current value, and from 70% to 10% (from 70% to 77%, from 77% to 85%, from 85%) A description will be given by taking as an example the control for increasing (in order to 93%). The supply current value and the number of times of increase are not limited to the above case, and can be variously set according to the type of UV ink and the like. In the following, specific numerical values relating to the operation time are shown, but are examples for explaining the characteristics of the ink jet printer 1 ′ in an easy-to-understand manner, and are not construed as being limited to these numerical values.

  A graph 10a indicated by a one-dot chain line in FIG. 10 is described for comparison although it is not related to the present invention, and shows a case where the maximum supply current value is set to operate. In this case, the relative output greatly exceeds 70% in the initial stage of operation, and then gradually decreases. For example, when the ink is operated for about 2050 hours, the intensity required for curing the ink is 70%, for example. To drop. As described above, in the configuration in which the conventional intensity correction is not performed, the operation is performed at the maximum supply current value or a relatively high supply current value slightly lower than the maximum supply current value. Was replaced to ensure a relative output of 70% and prevent the occurrence of curing failure.

  In contrast to the above-described conventional configuration, in the inkjet printer 1 ′ according to the second embodiment, the controller 23 refers to the output characteristic data 79 ′ so that the output slightly exceeds the relative output 70% (for example, the relative output 80%). ) To be started (for example, 70% of the maximum supply current value), and operation is started (see graph 10b). At this time, the intensity measurement unit 80 continuously measures the intensity of the ultraviolet rays from the UVLED 72 and outputs the measurement result to the controller 23. For example, when about 1600 hours have elapsed from the start of operation, the relative output decreases to 70%, and this output is measured by the intensity measuring unit 80. The controller 23 can output UV light slightly higher than the relative output of 70% again from the UVLED 72 by controlling the supply current value to the UVLED 72 from 70% to 77% through the control boards 75R and 75L. (See graph 10c). Thus, since the intensity of the ultraviolet light output from the UVLED 72 is actually measured by the intensity measuring unit 80, the relative output is 70 even when the UVLED 72 is different from the average intensity decrease rate due to manufacturing errors, for example. % Can be accurately detected.

  As described above, after the supply current value is increased to 77%, the relative output decreases to 70% again when the operation is performed for about 1000 hours, and this output is measured by the intensity measuring unit 80. Also at this time, as described above, the controller 23 can output ultraviolet rays slightly exceeding the relative output 70% by performing control to increase the supply current value to the UVLED 72 from 77% to 85% (graph 10d). reference). After this control, when about 800 hours have passed, the relative output again decreases to 70%. At this time, the control further increases the supply current value from 85% to 93% (see graph 10e). By doing so, it is possible to output ultraviolet light slightly exceeding 70% relative output, and after setting this supply current value to 93%, the relative output drops to 70% after about 650 hours, and at this point The UVLED 72 is replaced when it is determined that the lifetime has expired. In addition, by further increasing the supply current value by 7% and setting it to the maximum value, it is possible to output ultraviolet light slightly exceeding the relative output of 70% again, thereby further extending the operation time (life). .

  In the conventional configuration in which the intensity control is not performed as described above, the life is determined to be replaced when it has been operated for about 2050 hours. On the other hand, in the inkjet printer 1 ′ according to the second embodiment, every time when the intensity measurement unit 80 detects that the relative output is 70%, the control is performed to increase the supply current value to the UVLED 72, so that the total amount is about It becomes possible to operate for 4050 hours, and the operation time can be extended about twice as compared with the conventional configuration.

  In the first embodiment described above, the lower limit determination unit 78 is configured to start determining whether or not the relative output has decreased to the lower limit output intensity after the operating time t0 has elapsed. The measurement of the operation time of the UVLED 72 in the unit 78 can also be performed as follows, for example. First, the lower limit determination unit 78 sets the operation time of the UVLED 72 from when the power supply of the ink jet printer 1 is turned on to the operation time of the current time, when the power supply of the ink jet printer 1 is turned off. In addition, the obtained operation time is stored. Then, when the power of the inkjet printer 1 is turned on next time, the lower limit determination unit 78 compares the stored operation time up to the previous time with the output characteristic data 79, and the operation time up to the previous time is the operation time. It can be determined whether or not t0 has been reached.

  In the first embodiment, the operation time of the UVLED 72 by the lower limit determination unit 78 can be obtained as shown in any one of the following first to fourth based on the number of printed sheets of the print medium 2. It is. First, the lower limit determination unit 78 can obtain the operating time of the UVLED 72 for each printed print medium 2. Second, the lower limit determination unit 78 stores a database showing the correspondence between the number of printed sheets and the operating time in advance, and compares the number of printed sheets of the printing medium 2 with the database each time to determine the operating time. It is possible to ask. Third, an approximate expression for calculating the operation time corresponding to the number of prints is stored in advance in the lower limit determination unit 78, and the operation time is obtained by applying the number of prints of the print medium 2 to the above approximate expression each time. Is possible. Fourth, the lower limit determination unit 78 does not calculate the operation time from the number of printed sheets, but stores a reference print number corresponding to the operation time in advance. Then, the lower limit determination unit 78 can obtain the operation time by comparing and referring to the number of printed sheets and the reference number of printed sheets. In this case, the lower limit determination unit 78 can determine the operation time even though it is configured to handle only the number of printed sheets of the print medium 2.

  Furthermore, in the above-described first embodiment, the method of obtaining the operation time of the UVLED 72 by the lower limit determination unit 78 may be obtained, for example, by associating the number of replacements of the storage tank 53 with the operation time. When comprised in this way, it is preferable to make the reference | standard the frequency | count of replacement | exchange of the storage tank classified by color of the color used most frequently.

  Further, in Example 1 described above, when the intensity of the ultraviolet ray is reduced to the relative output 70% which is the lower limit output intensity, the intensity of the ultraviolet ray is controlled so that the relative output is 80% which is a control target. However, the relative output 70% and the relative output 80% here are examples, and are not limited to this control method. For example, it is preferable to set an optimum lower limit output intensity and a relative output as a control target according to each printing condition such as the type of the printing medium 2, the type of UV ink, and the reciprocating speed of the printing unit 60.

Furthermore, in the above-described first embodiment, the database stored in the lower limit determination unit 78 is
It may be created based on the minimum life 6c shown in FIG. When the database is created in this way, even when the relative output decreases for each UVLED 72, the lower limit determination unit 78 makes a relative comparison before the ultraviolet intensity falls below the relative output 70%, which is the lower limit output intensity. It can be determined that the output has decreased to 70%. Therefore, it is possible to reliably prevent the occurrence of curing failure due to the output of ultraviolet light having an intensity lower than the lower limit output intensity.

  In the first and second embodiments described above, the intensity of the ultraviolet rays that are output by controlling the supply current value is controlled. However, the present invention is not limited to such an intensity control method. For example, a method of controlling the intensity of ultraviolet rays by controlling the voltage value applied to the UVLED 72 may be used.

  In the first and second embodiments described above, the printing medium 2 is fixedly held on the vacuum table 12a (so-called flat bed). However, the present invention is not limited to this configuration. For example, by additionally providing a feeding mechanism and a winding mechanism, the present invention can be applied to an inkjet printer that performs printing while conveying a sheet-like print medium.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Print medium 12a Vacuum table (medium support means)
23 Controller (output control means)
62 Print head 70R Right UVLED unit (ultraviolet irradiation means)
70L Left UVLED unit (ultraviolet irradiation means)
72 UVLED (ultraviolet light source)
78 Lower limit judgment part (lower limit judgment means)
79 Output characteristic data (reference output characteristic data)
80 Strength measuring unit (strength measuring means)

Claims (5)

Inkjet for performing desired printing on the surface of the printing medium by ejecting ink from the printing head while moving the printing head relative to the printing medium in a state of being opposed to the printing medium supported by the medium supporting means. In the printer
An ultraviolet irradiation means comprising an ultraviolet light source for irradiating the printing medium with ultraviolet rays to cure the ink adhering to the printing medium;
Output control means for controlling the intensity of the output ultraviolet light from the ultraviolet light source,
The output control means includes reference output characteristic data indicating a relationship between an output ultraviolet intensity of the ultraviolet light source and an operation time, and increases a supply current value to the ultraviolet light source with reference to the reference output characteristic data. It performs intensity correction to increase the output intensity of ultraviolet light from the ultraviolet light source by,
The output control means, wherein the reduced determines whether the output intensity of ultraviolet light from the ultraviolet light source to the ink curable a lower output intensity that has adhered to the print medium, the output characteristic data for the reference, the operating time further comprising a lower limit determining means for performing, based on the bets,
The output control means may output the intensity of ultraviolet light from the ultraviolet light source is repeatedly performed line intends operated before Symbol intensity correction when it is determined that the decreased to the lower limit output intensity at the lower limit determination means performs the operation In the case, the operation is performed such that the supply current value in the operation performed later is larger than the supply current value in the operation performed earlier ,
The output control means controls the output ultraviolet light intensity from the ultraviolet light source in the initial output state so that the ultraviolet light source does not output an ultraviolet light having an excessively high relative output with respect to curing the ink attached to the printing medium. An ink jet printer that is controlled to be less than an upper limit output intensity. The ultraviolet light source has an output characteristic that outputs ultraviolet light having a substantially constant intensity from the start of ultraviolet light output until the initial operation time has elapsed.
The inkjet printer according to claim 1, wherein the output control unit performs the intensity correction after the initial operation time has elapsed. The inkjet printer includes intensity measuring means for measuring the output ultraviolet intensity from the ultraviolet light source,
The output control means performs intensity correction to increase the output ultraviolet intensity from the ultraviolet light source when the intensity measuring means detects a lower limit output intensity capable of curing the ink attached to the print medium. The inkjet printer according to claim 1.   The inkjet printer according to any one of claims 1 to 3, wherein the ultraviolet light source is configured by using a light emitting diode capable of outputting ultraviolet light. A printing method using the inkjet printer according to any one of claims 1 to 4,
While moving the print head and the ultraviolet irradiation means relative to the print medium supported by the medium support means, ink is ejected from the print head to adhere to the print medium and the ultraviolet irradiation means Irradiating the printing medium with ultraviolet light output from an ultraviolet light source to cure the adhered ink;
The printing method, wherein when the printing medium is irradiated with ultraviolet rays, the output control means performs control to correct the output ultraviolet ray intensity from the ultraviolet light source with reference to the reference output characteristic data.

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