Patent Grant
9340042
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2014-265489 filed on Dec. 26, 2014.
The present invention relates to a drying device, a printing apparatus, and a computer readable medium storing a program causing a computer to function as a control unit of the drying device.
According to an aspect of the invention, there is provided a drying device comprising: an irradiation unit that irradiates, with laser light, a printing medium onto which ink droplets have been ejected from a droplets ejecting unit; and a control unit that controls the irradiation unit so that the temperature of ink on the printing medium becomes an ink target temperature that is determined using a thermal deformation temperature of the printing medium as a reference if the thermal deformation temperature of the printing medium is lower than or equal to an ink drying temperature, and becomes an ink target temperature that is determined using the ink drying temperature as a reference if the thermal deformation temperature of the printing medium is higher than the ink drying temperature.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
Exemplary embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings.
First, a printing apparatus 10 according to a first exemplary embodiment will be described. As shown in
The control unit 20 controls the rotation of the conveying rollers 100 which are connected to a conveying motor by such a mechanism as gears by driving a roller drive unit 100a (see
The control unit 20 acquires image information of a print subject image for printing on the continuous sheet S and controls the head drive unit 40 on the basis of pixel-by-pixel color information included in the image information. Controlled by the control unit 20, the head drive unit 40 drives the recording heads 50 which are connected to the head drive unit 40 according to ink droplets ejecting timing that is determined on the basis of the print subject image and thereby causes the recording heads 50 to eject ink droplets (droplets) onto the continuous sheet S being conveyed. As a result, an image corresponding to the image information is printed on the continuous sheet S being conveyed. Printing processing is performed in this manner by the printing apparatus 10.
The image information representing the print subject image is stored in a nonvolatile memory 20d, for example. Color information of each pixel of the image information includes information indicating a color of the pixel uniquely. Although in the exemplary embodiment the color information of each pixel of image information is represented by densities of yellow (Y), magenta (M), cyan (C), and black (K), any of other representation methods capable of representing a color of each pixel uniquely may be used.
The recording heads 50 are four recording heads 50Y, 50M, 50C, and 50K which correspond to the four respective colors Y, M, C, and K, and each recording head 50 ejects ink droplets of a corresponding color from its ink ejecting outlet. There are no limitations on the drive method for causing each recording head 50 to eject ink droplets; any of known drive methods such as a thermal method and a piezoelectric method may be employed.
Whereas general printing apparatus employ water-based inks, solvent inks with low melting temperature solvents, ultraviolet-curing inks, etc., the exemplary embodiment is directed to a case of using water-based inks. In the following description, when the term “ink” or “ink droplets” is used alone, it means a water-based ink or water-based ink droplets. Each water-based ink contains a low boiling temperature solvent (mainly formed of water) at 90 wt %, a pigment at 5 wt %, and other additives (surfactant, glycerol, etc.) at 5 wt %, and dries through evaporation of the low boiling temperature solvent.
The inks of Y, M, C, and K used in the exemplary embodiment are added with an IR (infrared) absorbent and their degrees of laser light absorption are thereby adjusted. That is, whereas the inks other than the black ink are added with the IR absorbent because they are lower in IR absorption efficiency than the black ink, the black ink need not always be added with the IR absorbent. In the exemplary embodiment, the addition amounts of the IR absorbent in the inks of the respective colors are adjusted so that the inks have the same IR absorption absorbance.
The laser drive unit 60 is equipped with switching elements such as FETs (field-effect transistors) for on/off-controlling laser elements included in each of the laser drying devices 70A-70F (hereinafter referred to as a laser drying device 70). The laser drive unit 60 adjusts the irradiation intensity of laser light emitted from each laser element by controlling the pulse duty ratio by driving the corresponding switching element under the control of the control unit 20. More specifically, the irradiation intensity of laser light becomes higher as the pulse duty ratio increases.
As shown in
The above-described unit of driving of the laser drive unit 60 is just an example; for example, the laser drive unit 60 may drive the surface-emitting laser devices 72 in units of a laser block that includes surface-emitting laser devices 72 that are arranged in line in the conveying direction of a continuous sheet S.
As shown in
As described above, the plural vertical cavity laser elements 74 are arranged on the laser emission surface of each VCSEL 72 in lattice form in the conveying direction A and the width direction B. The laser elements 74 emit laser beams according to a drive control on each VCSEL 72. The number and the arrangement form, shown in
By controlling the laser drive unit 60, the control unit 20 causes the laser drying device 70 to emit laser light toward the printing surface of a continuous sheet S that has been subjected to printing processing for a predetermined irradiation time and thereby dry the inks of a printed image on the continuous sheet S. As a result, the printed image on the continuous sheet S is fixed. Drying processing is performed in this manner by the printing apparatus 10.
The continuous sheet S that has been subjected to the drying processing is conveyed to the take-up roll 90 as the conveying rollers 100 are rotated and is taken up by the take-up roll 90.
Disposed, for example, at such a position as to be opposed to the printing surface of a continuous sheet S, the conveyance speed detection sensor 110 detects a conveyance speed of a continuous sheet S in the conveying direction A. The control unit 20 calculates a time when an image forming region on a continuous sheet S will be conveyed to within a laser light irradiation range of the laser drying device 70 on the basis of a conveyance speed communicated from the conveyance speed detection sensor 110 and a distance from the recording heads 50 to the laser drying device 70. Then the control unit 20 controls the laser drive unit 60 so that the inks are irradiated with laser beams emitted from the laser drying device 70 with such timing that the image forming region on the continuous sheet S is located within the laser light irradiation range of the laser drying device 70.
There are no limitations on the method by which the conveyance speed detection sensor 110 detects a conveyance speed of a continuous sheet S; any of known methods may be employed. The conveyance speed detection sensor 110 is not indispensable in the printing apparatus 10 according to the exemplary embodiment. For example, the conveyance speed detection sensor 110 may be omitted in the case where a conveyance speed of a continuous sheet S is set in advance.
Next, an electrical configuration of the printing apparatus 10 according to the exemplary embodiment will be described. As shown in
A manipulation unit 24 to be manipulated by a user, a display unit 26 for displaying various kinds of information, and a communication unit 28 for communicating with an external device. The above-described roller drive unit 100a, head drive unit 40, laser drive unit 60, and conveyance speed detection sensor 110 are also connected to the I/O interface 22.
In general printing apparatus, to dry the inks efficiently after printing has been performed by ejecting ink droplets onto a printing medium, it is desirable to preferable to raise the temperature of the inks to an ink drying temperature. If the ink temperature becomes high, heat is transmitted from the inks to the printing medium, as a result of which its temperature is also increased. If the temperature of the printing medium exceeds its thermal deformation temperature, the printing medium may be deformed by heat.
The term “drying temperature” as used herein means a boiling temperature of a solvent that is used most abundantly among the ink solvents used. In the exemplary embodiment, the evaporation rate of inks is increased by raising the temperature of inks to the above their boiling temperatures.
For example, as shown in
In view of the above, in the printing apparatus 10 according to the invention, to suppress thermal deformation of a printing medium, in the case where the thermal deformation temperature of the printing medium is lower than or equal to the ink drying temperature, laser light irradiation is controlled so that the ink temperature is raised to a target temperature that is determined with the thermal deformation temperature of a printing medium as a reference. Furthermore, in the printing apparatus 10 according to the invention, in the case where the thermal deformation temperature of a printing medium is higher than the ink drying temperature, laser light irradiation is controlled so that the ink temperature is raised to a target temperature that is determined with the ink drying temperature as a reference.
The exemplary embodiment is directed to a case that a resin film that is prone to be deformed by heat is used as a printing medium. However, the exemplary embodiment is applicable to a case that a paper sheet is used as a printing medium because even a paper sheet coated with a resin may be rendered prone to be changed in color depending on the coating material.
It is preferable to use a printing medium that is white, of light yellow, or transparent. This is because where a printing medium that is darker than these colors is used, the printing medium itself may be heated and deformed when irradiated with laser beams emitted from the laser drying device 70.
In the exemplary embodiment, as shown in
Furthermore, the nonvolatile memory 20d is stored with laser light irradiation profiles that are set for respective ink target temperatures. For example, the irradiation profiles are generated in advance by experiments. The laser drive unit 60 controls the emission intensities of the respective VCSELs 72 according to an irradiation profile.
As shown in
On the other hand, where the ink target temperature is set at 70° C., first, laser beams having a third irradiation energy value corresponding to the target temperature 70° C. are applied until the ink temperature is raised to 70° C. Laser beams having a fourth irradiation energy value that is smaller than the third one are applied thereafter. In this manner, the laser drive unit 60 is controlled according to the irradiation profile for 70° C. so that the ink temperature is approximately kept at 70° C.
Where the ink target temperature is low, the ink drying efficiency is lower and the drying takes longer time than where the ink target temperature is high. In view of this, the irradiation profiles are formed so that the total irradiation energy is constant irrespective of the ink target temperature or increases as the ink target temperature lowers.
Example methods for adjusting the total irradiation energy are a method of adjusting the laser light irradiation time and a method of adjusting the irradiation energy within the confines that a printing medium is not deformed by heat. In the exemplary embodiment, the laser drive unit 60 is controlled according to such irradiation profiles that the irradiation time of laser beams having the second or fourth irradiation energy is made longer as the ink target temperature lowers. As shown in
Next, a procedure that the CPU 20a of the printing apparatus 10 according to this exemplary embodiment follows in executing a printing control process will be described with reference to a flowchart of
At step S101, the CPU 20a controls the display unit 26 so that it displays an input picture for input of an ink type and a printing medium type. Watching the input picture, a user inputs type information including information indicating an ink type and information indicating a printing medium type by manipulating the manipulation unit 24.
At the next step S103, the CPU 20a judges whether type information has been input or not. If it is judged that type information has been input (S103: Y), the process moves to step S105. If it is judged that no type information has been input yet (S103: N), step S103 is executed again.
At step S105, the CPU 20a judges whether or not the correspondence information 120A includes drying temperature information corresponding to the ink type indicated by the received type information. If the judgment result is affirmative (S105: Y), the process moves to step S111. If the judgment result is negative (S105: N), the process moves to step S107.
At step S107, the CPU 20a controls the display unit 26 so that it displays an input picture for input of an ink drying temperature. Watching the input picture, the user inputs drying temperature information indicating an ink drying temperature by manipulating the manipulation unit 24.
At step S109, the CPU 20a judges whether drying temperature information has been input or not. If it is judged that drying temperature information has been input (S109: Y), the process moves to step S111. If it is judged that no drying temperature information has been input yet (S109: N), step S109 is executed again.
At step S111, the CPU 20a acquires drying temperature information corresponding to the ink type indicated by the received type information from the correspondence information 120A or the drying temperature information indicating the ink drying temperature that was input at step S109.
At the next step S113, the CPU 20a judges whether or not the correspondence information 120B includes thermal deformation temperature information corresponding to the printing medium type indicated by the received type information. If the judgment result is affirmative (S113: Y), the process moves to step S119. If the judgment result is negative (S113: N), the process moves to step S115.
At step S115, the CPU 20a controls the display unit 26 so that it displays an input picture for input of a thermal deformation temperature of a printing medium. Watching the input picture, the user inputs thermal deformation temperature information indicating a thermal deformation temperature of a printing medium by manipulating the manipulation unit 24.
At step S117, the CPU 20a judges whether thermal deformation temperature information has been input or not. If it is judged that thermal deformation temperature information has been input (S117: Y), the process moves to step S119. If it is judged that no thermal deformation temperature information has been input yet (S117: N), the process moves to step S117 is executed again.
At step S119, the CPU 20a acquires thermal deformation temperature information corresponding to the printing medium type indicated by the received type information from the correspondence information 120B or the thermal deformation temperature information indicating the thermal deformation temperature that was input at step S117.
The method for acquiring ink drying temperature information and thermal deformation temperature information of a printing medium is not limited to the above-described method. For example, where an ink type and a printing medium type are specified in advance, drying temperature information indicating the specified ink type and thermal deformation temperature information indicating the specified printing medium type may be stored in the nonvolatile memory 20d in advance. In this case, the CPU 20a acquires the stored drying temperature information and thermal deformation temperature information.
At the next step S121, the CPU 20a judges whether or not the thermal deformation temperature of the printing medium is higher than the ink drying temperature. If it is judged that the thermal deformation temperature of the printing medium is higher than the ink drying temperature (S121: Y), the process moves to step S123. If it is judged that the thermal deformation temperature of the printing medium is lower than or equal to the ink drying temperature (S121: N), the process moves to step S125.
At step S123, the CPU 20a determines an ink target temperature using the ink drying temperature as a reference and acquires an irradiation profile corresponding to the determine ink target temperature. In the exemplary embodiment, considering the fact that the ink drying efficiency increases as the ink target temperature becomes higher, if the ink drying temperature is, for example, 100° C., the CPU 20a sets the ink target temperature at 100° C., that is, the ink drying temperature. The method for setting an ink target temperature is not limited to this method; the ink target temperature may be set a little lower than the ink drying temperature or at a temperature that is a little higher than the ink drying temperature and does not exceed the thermal deformation temperature of the printing medium.
On the other hand, at step S125, the CPU 20a determines an ink target temperature using the thermal deformation temperature of the printing medium as a reference and acquires an irradiation profile corresponding to the determined ink target temperature. In the exemplary embodiment, to suppress deformation of a printing medium more reliably, if the ink drying temperature is, for example, 80° C., the CPU 20a sets the ink target temperature at 70° C. with a margin of a predetermined temperature (e.g., 10° C.). The method for determining an ink target temperature is not limited to this method; for example, the ink target temperature may be set at a temperature that is equal to the thermal deformation temperature of the printing medium multiplied by a positive coefficient that is smaller than 1 (e.g., 0.9).
At step S127, the CPU 20a controls the roller drive unit 100a, the head drive unit 40, and the laser drive unit 60 so as to start printing processing (described above) and drying processing that uses the irradiation profile acquired at step S123 or S125.
At the next step S129, the CPU 20a judges whether the printing processing and the drying processing have completed or not. If judging that the printing processing and the drying processing have not completed yet (S129: N), the CPU 20a continues the printing processing and the drying processing. If judging that the printing processing and the drying processing have completed (S129: Y), the CPU 20a finishes running the program.
The physical configuration of a printing apparatus 10 according to a second exemplary embodiment is the same as the printing apparatus 10 according to the first exemplary embodiment, and hence descriptions therefor will be omitted.
In the first exemplary embodiment, an ink target temperature is set without taking the amount of ink used for printing into consideration. In contrast, the second exemplary embodiment is directed to a case that the ink target temperature is adjusted according to the amount of ink used for printing.
Next, a procedure that the CPU 20a of the printing apparatus 10 according to this exemplary embodiment follows in executing a printing control process will be described with reference to a flowchart of
Steps S201-S219 are the same as steps S101-S119 of the first embodiment, respectively. The process moves to step S221 after execution of step S219.
At step S221, information indicating an amount of ink used for printing is acquired. In the exemplary embodiment, an amount of ink used for printing of a printing subject image is calculated on the basis of image information representing the printing subject image. For example, an amount of ink is obtained by multiplying an ink amount per pixel by the number of pixels in an image forming area of the printing subject image. Where the printing subject image is a color image, an amount of ink is calculated as the total of ink amounts of the respective colors.
At the next step S223, the CPU 20a judges whether or not the thermal deformation temperature of the printing medium is higher than the ink drying temperature. If the thermal deformation temperature of the printing medium is higher than the ink drying temperature (S223: Y), the process moves to step S225. If the thermal deformation temperature of the printing medium is lower than or equal to the ink drying temperature (S223: N), the process moves to step S227.
At step S225, the CPU 20a determines an ink target temperature using the ink drying temperature as a reference as at step S123 shown in
On the other hand, at step S227, the CPU 20a determines an ink target temperature using the thermal deformation temperature of the printing medium as a reference as at step S125 shown in
At step S229, the CPU 20a controls the roller drive unit 100a, the head drive unit 40, and the laser drive unit 60 so as to start printing processing (described above) and drying processing that uses the irradiation profile acquired at step S225 or S227.
At the next step S231, the CPU 20a judges whether the printing processing and the drying processing have completed or not. If judging that the printing processing and the drying processing have not completed yet (S231: N), the CPU 20a continues the printing processing and the drying processing. If judging that the printing processing and the drying processing have completed (S129: Y), the CPU 20a finishes running the program.
Although in the second exemplary embodiment the ink target temperature is adjusted according to the amount of ink used in printing, the invention is not limited to such a case. The laser light irradiation time may be adjusted according to the ink amount. In this case, the laser light irradiation time is adjusted so as to be made longer as the ink amount increases.
Although in the second exemplary embodiment an amount of ink used for the entire printing subject image is calculated, the invention is not limited to such a case. An ink amount may be calculated for each partial region of an image forming area. In this case, an irradiation profile may be set according to an ink amount of each partial region that corresponds to a VCSEL 72, for example. As a further alternative, an irradiation profile may be set according to an ink amount of each partial region that correspond to a column of VCSELs 72.
The laser drive unit 60 may be controlled so that no laser light shines on a non-image-forming area on a printing medium (i.e., a non-ejecting area to which no ink droplets are ejected). Also in this case, for example, switching may be made between irradiation profiles that are set according to ink amounts of respective VCSELs 72 or respective columns of VCSELs 72.
The physical configuration of a printing apparatus 10 according to a third exemplary embodiment is the same as the printing apparatus 10 according to the first and second exemplary embodiment, and hence descriptions therefor will be omitted.
In the first and second exemplary embodiments, a printing medium is conveyed at a constant speed. In contrast, the third exemplary embodiment is directed to a case that the conveyance speed of a printing medium is varied according to the ink target temperature.
Next, a procedure that the CPU 20a of the printing apparatus 10 according to this exemplary embodiment follows in executing a printing control process will be described with reference to a flowchart of
The exemplary embodiment is directed to a case that a conveyance speed of a printing medium was input through the manipulation unit 24 in advance and is stored in the nonvolatile memory 20d and that when printing processing and drying processing are performed a printing medium is conveyed at the stored conveyance speed.
Steps S301-S325 are the same as steps S101-S125 of the first embodiment, respectively. The process moves to step S327 after execution of step S325.
At step S327, the CPU 20a judges whether or not the ink target temperature is lower than a predetermined reference temperature. In the exemplary embodiment, taking into consideration drying efficiency levels at respective ink temperatures, the reference temperature is set at 70° C., for example.
If it is judged that the ink target temperature is lower than the reference temperature (S327: Y), the process moves to step S329. If the ink target temperature is higher than or equal to the reference temperature (S327: N), the process moves to step S331.
At step S329, considering that the ink drying efficiency is low because of a low ink temperature, to dry the inks more, the CPU 20a controls the roller drive unit 100a so as to lower the conveying speed of the printing medium. In the exemplary embodiment, a new conveyance speed is calculated by subtracting a predetermined speed (e.g., 50 m/min) from a current conveyance speed of the printing medium (e.g., 150 m/min). However, the method for changing the conveyance speed is not limited to this method; for example, the conveyance speed may be reduced as the ink target temperature becomes lower.
At step S331, the CPU 20a controls the roller drive unit 100a, the head drive unit 40, and the laser drive unit 60 so as to start printing processing and drying processing.
At the next step S333, the CPU 20a judges whether the printing processing and the drying processing have completed or not. If judging that the printing processing and the drying processing have not completed yet (S333: N), the CPU 20a continues the printing processing and the drying processing. If judging that the printing processing and the drying processing have completed (S333: Y), the CPU 20a finishes running the program.
Although the first to third exemplary embodiments are directed to the case that irradiation profiles corresponding to respective ink target temperatures are stored in the nonvolatile memory 20d in advance, the invention is not limited to such a case. For example, it is possible to equip the printing apparatus 10 with a temperature sensor for measuring an ink temperature and generate irradiation profiles for respective ink target temperatures while a temperature measurement is performed.
Although the first to third exemplary embodiments an irradiation profile is determined according to an ink target temperature and laser beams are emitted according to the determined irradiation profile, the invention is not limited to such a case. For example, it is possible to equip the printing apparatus 10 with a temperature sensor for measuring an ink temperature and switch from one irradiation profile to another according to a measured ink temperature.
Although the first to third exemplary embodiments are directed to the case that correspondence information 120A, correspondence information 120B, and irradiation profiles are stored in the nonvolatile memory 20d in advance, the invention is not limited to such a case. For example, correspondence information 120A, correspondence information 120B, and irradiation profiles may be received and acquired from an external device via the communication unit 28.
The foregoing description of the embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-265489 | Dec 2014 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5784090 | Selensky | Jul 1998 | A |
| 7510277 | Konno | Mar 2009 | B2 |
| 20010052920 | Matsumoto | Dec 2001 | A1 |
| 20090244236 | Houjou | Oct 2009 | A1 |
| 20130195534 | Oohara et al. | Aug 2013 | A1 |
| 20130257964 | Itogawa | Oct 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| H10-171202 | Jun 1998 | JP |
| 2012-155126 | Aug 2012 | JP |
| 2014-083762 | May 2014 | JP |
| Entry |
|---|
| Abstract and machine translation of JP2014-083762. |
| Abstract and machine translation of JP2012-155126. |
| Abstract and machine translation of JP H10-171202. |
