JP2017128039A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct printing with high quality appropriately by suppressing bleeding of ink appropriately.SOLUTION: There is provided a printer 10 for conducting printing by an inkjet method to a medium 50, having an inkjet head 102 discharging ink drops by an inkjet method and an infrared light source 104 applying an infrared light, where the inkjet head 102 adheres an ink onto the medium 50 by discharging ink drops of an ink containing an infrared absorber which absorbs the infrared light and a solvent which dissolves or disperses the infrared absorber and the infrared light source 104 vaporization removes at least a part of the solvent contained in he ink by irradiating the infrared light to the ink adhered onto the medium 50.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing apparatus and a printing method.

  Conventionally, ink jet printers that perform printing by an ink jet method have been widely used (see, for example, Non-Patent Document 1). Further, as inks used in ink jet printers, water-based inks (water-based inks) such as water-based pigment inks, latex inks, and pigment-encapsulated resin-dispersed inks, solvent inks (solvent inks) that use organic solvents as solvents, and the like Evaporative drying inks are widely used. In this case, the evaporation-drying type ink is an ink that fixes the ink to a medium (media) by evaporating the solvent in the ink.

  In addition, in an ink jet printer using an evaporation drying type ink such as a water-based ink, the ink is dried by heating with a heater, thereby preventing ink bleeding and drying and fixing. As a more specific method in this case, the medium is heated with a heater (print heater) to stop bleeding, and then the ink is further dried and fixed with heating means (after-heating means) such as various heaters and infrared lamps. Etc. are also known. As a method for stopping ink bleeding, a method of forming an ink image-receiving layer on a medium to be printed (printed medium) has been conventionally known.

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  However, when a method for forming an image receiving layer on a medium is used, printing can be performed only on a specific medium on which the image receiving layer is formed in advance. In this case, the ink solvent remains in the image receiving layer, which may cause a problem. For example, in the case of a configuration in which the medium is wound after printing, there is a problem that show-through tends to occur during winding. In addition, when paper or the like is used as the base layer, which is a layer below the image receiving layer, for example, when printing with a large amount of ink such as printing of a color image (color printing) is performed, bleeding or curling of the medium occurs. There is also a risk of becoming easier.

  For example, when a fabric medium is used, it is necessary to prepare a fabric coated with a pretreatment agent (glue or the like) having a function of preventing bleeding or assisting color development as an image receiving layer. Therefore, in this case, it is necessary to request a specialist for preprocessing, which causes problems of time loss and cost increase.

  Further, when bleeding is stopped by heating the medium with a print heater, for example, in order to increase the printing speed, it is necessary to increase the heating temperature at the position of the platen facing the inkjet head. However, in this case, when the heating temperature is increased, the nozzle surface of the ink jet head is also heated, resulting in a problem that nozzle clogging is likely to occur.

  In this case, for example, it is also conceivable to suppress the occurrence of bleeding by using a solvent having a low boiling point as the solvent of the ink and facilitating evaporation of the ink. However, in this case, the ink is quickly evaporated at the nozzles, and nozzle clogging may occur frequently. Therefore, conventionally, when evaporating and drying ink is used, it may be difficult to prevent ink bleeding.

  In addition, as an ink used in an ink jet printer, conventionally, an ultraviolet curable ink (UV ink) that is cured by irradiation of ultraviolet rays is widely used in addition to an evaporation drying type ink. When ultraviolet curable ink is used, for example, by irradiating ultraviolet rays immediately after the ink droplets land on the medium, it is possible to instantaneously stop ink bleeding on the medium. Further, in this case, since there is no need to heat the medium, the problem of nozzle clogging or the like hardly occurs. However, in this case, since the ink is cured before the ink dots are sufficiently flattened, the ink surface is easily matted. In some cases, the ink is too thick. Therefore, depending on the printing application, the desired print quality may not be obtained. As a result, depending on the printing application, it is necessary to use evaporative drying ink instead of ultraviolet curable ink.

  Therefore, conventionally, there has been a demand for a method that can more appropriately suppress ink bleeding when using an evaporation-drying type ink. Accordingly, an object of the present invention is to provide a printing apparatus and a printing method that can solve the above-described problems.

  The inventor of the present application has conducted intensive research on a method that can suppress ink bleeding more appropriately in the case of using an evaporative drying type ink. In this case, the heating immediately after landing is not a method of simply heating with a heater, but an infrared absorber is included in the ink and heating is performed by irradiating infrared rays. If constituted in this way, for example, ink can be heated efficiently and the solvent in ink can be evaporated more appropriately. Further, it is possible to more appropriately suppress the occurrence of bleeding while preventing nozzle clogging and the like from occurring due to heating.

  That is, in order to solve the above problems, the present invention is a printing apparatus that performs printing on a medium by an inkjet method, an inkjet head that ejects ink droplets by an inkjet method, an infrared light source that irradiates infrared rays, The ink-jet head causes the ink to adhere onto the medium by ejecting ink droplets of an ink containing an infrared absorber that absorbs infrared rays and a solvent that dissolves or disperses the infrared absorber; The infrared light source volatilizes and removes at least a part of the solvent contained in the ink by irradiating the ink attached on the medium with infrared rays.

  When comprised in this way, an ink can be efficiently heated by infrared irradiation by including an infrared absorber in ink. Accordingly, for example, immediately after the ink droplets have landed, the ink can be efficiently heated and the solvent in the ink can be appropriately volatilized and removed while suppressing the influence on the nozzle surface of the inkjet head.

  Here, in this configuration, infrared is a general term for light in the range of near infrared to far infrared. Infrared rays are not limited to a specific wavelength, and infrared rays having all wavelengths in the range where the absorption wavelength of the infrared absorbent and the emission wavelength of the infrared light source overlap in the near infrared to far infrared range are preferably used. be able to. Further, the infrared light source, for example, volatilizes and removes at least a part of the solvent, thereby increasing the viscosity of the ink on the medium to at least a viscosity at which no bleeding occurs on the medium. In this case, the fact that bleeding does not occur may mean that bleeding does not substantially occur within an allowable range corresponding to the required printing accuracy.

  Further, the infrared light source volatilizes and removes the solvent in the ink, for example, appropriately fixing the ink to the medium while preventing the ink from bleeding. With this configuration, for example, the evaporation-drying type ink can be appropriately fixed on the medium. Further, the fixing of the ink to the medium may be completed by further heating the medium with another heater or the like after the infrared irradiation.

  In this configuration, the infrared absorbent is a substance that generates heat by absorbing infrared rays, for example. As the infrared absorber, it is preferable to use a substance having a peak wavelength of absorption in the infrared region. In addition, as the infrared absorber, it is preferable to use a colorless or light-colored substance that has little influence on the color of the ink. In this case, it is preferable to use an infrared absorbent having a light absorptance at a peak wavelength that is twice or more the maximum value of the absorptance in the visible light region. Moreover, the light absorptance at the peak wavelength is preferably 5 times or more, more preferably 10 times or more, and still more preferably 20 times the maximum value of the absorptance in the visible light region.

  In this configuration, the solvent contained in the ink is, for example, an organic solvent. The solvent contained in the ink may be an aqueous solvent such as water. In this configuration, as the infrared light source, for example, a semiconductor light source such as an infrared LED or an infrared LD (laser diode) can be suitably used. The infrared light source preferably irradiates infrared rays so that the continuous irradiation time is shorter than the thermal time constant of heat dissipation of the medium, for example, and heats the ink at once in a short time. In addition, it is preferable that the infrared irradiation is performed on the ink outside the region facing the inkjet head in the medium. Further, the heating for suppressing bleeding may be performed using a heater in combination instead of using only the infrared light source.

  In this configuration, the printing apparatus may perform printing by a multi-pass method, for example. In this case, the number of printing passes may be 8 passes or less. Further, the number of passes may be less than 8 passes (for example, 4 passes or less). According to this configuration, for example, when printing is performed using the multi-pass method, it is possible to appropriately reduce the number of passes and perform high-speed printing more appropriately. Also, in this case, even if the amount of ink that lands in a unit time per unit area is increased by reducing the number of passes by removing the solvent in the ink by volatilization and removal by infrared irradiation, the bleeding occurs. Can be suppressed appropriately.

  In addition, as a configuration of the present invention, it is conceivable to use a printing method having the same characteristics as described above. In this case, for example, the same effect as described above can be obtained.

  According to the present invention, it is possible to more appropriately suppress ink bleeding. Thereby, for example, high quality printing can be performed more appropriately.

1 is a diagram illustrating an example of a configuration of a printing apparatus 10 according to an embodiment of the present invention. FIGS. 1A and 1B are a top view and a cross-sectional view illustrating an example of a configuration of a main part of the printing apparatus 10. It is a figure which simplifies and shows an example of the printing operation in the conventional printing apparatus. FIG. 2A shows an example of an operation for ejecting ink droplets onto the medium 50. FIG. 2B shows an example of the medium 50 after completion of the printing operation. It is a figure which simplifies and shows an example of the printing operation by the printing apparatus 10 of this example. FIG. 3A shows an example of an operation for ejecting ink droplets onto the medium 50. FIG. 3B shows an example of the medium 50 after completion of the printing operation. FIG. 3C shows an example of the medium 50 after the completion of the printing operation when the non-permeable medium is used.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a printing apparatus 10 according to an embodiment of the present invention. FIGS. 1A and 1B are a top view and a cross-sectional view illustrating an example of a configuration of a main part of the printing apparatus 10. In this example, the printing apparatus 10 is an inkjet printer that performs printing on a medium (medium) 50 to be printed by an inkjet method, and includes a head unit 12, a guide rail 14, a scanning drive unit 16, a platen 18, a preheater 20, A print heater 22, an after heater 24, and a control unit 26 are provided.

  Except as described below, the printing apparatus 10 may have the same or similar features as a known inkjet printer. For example, in addition to the configuration described below, the printing apparatus 10 may further include a known configuration necessary for a printing operation or the like.

  The head unit 12 is a portion (IJ head unit) that ejects ink droplets onto the medium 50, and includes a carriage 100, a plurality of inkjet heads 102, and a plurality of infrared light sources 104. The carriage 100 is a holding member that holds other components of the head unit 12.

  The plurality of inkjet heads 102 are ejection heads that eject ink droplets by an inkjet method. Each of the plurality of inkjet heads 102, for example, ejects ink droplets of different colors and deposits the ink of each color on the medium 50. In addition, each inkjet head 102 ejects ink droplets of ink including at least an infrared absorbent and a solvent. In this case, the infrared absorber is a substance that absorbs infrared rays, and generates heat by absorbing infrared rays, for example. The solvent is a liquid that dissolves or disperses the infrared absorber. Further, this ink may further contain the same or similar components as known inks. For example, in this example, each color ink used in each inkjet head 102 further includes a color material (pigment or dye) of each color.

  Each of the plurality of inkjet heads 102 ejects ink droplets of different colors, for example. More specifically, each of the plurality of inkjet heads 102 ejects ink droplets of each color of process colors for color printing. The process colors are, for example, yellow (Y), magenta (M), cyan (C), and black (K).

  The plurality of inkjet heads 102 are arranged in a predetermined main scanning direction (Y direction in the figure), and perform a main scanning operation of ejecting ink droplets while moving in the main scanning direction, thereby Ink is attached to 50. In this example, the plurality of inkjet heads 102 perform bidirectional (both directions) main scanning operations in one direction and the other direction in the main scanning direction.

  Here, the ink used in this example is, for example, an evaporation-drying type ink that is fixed to the medium 50 by volatilizing and removing the solvent. For example, an ink using an organic solvent as a solvent may be used as the evaporation drying type ink. In this case, the organic solvent may be, for example, a hydrophobic organic solvent. The hydrophobic organic solvent is, for example, an organic solvent that is incompatible with water. In this case, the solvent dissolves, for example, an infrared absorbent in the ink. The organic solvent may be a volatile organic solvent. Moreover, it is preferable that the boiling point of the organic solvent used as a solvent is 200 degrees C or less, for example. In this case, for example, it is conceivable to use an organic solvent having a boiling point lower than that of water. The boiling point of the organic solvent may be 80 ° C. or less, for example. More specifically, as such an ink, for example, an ink obtained by adding an infrared absorber to a solvent ink can be suitably used. In this case, the solvent ink is, for example, an ink using a hydrophobic organic solvent as a solvent.

  Further, as the ink, for example, an ink containing an aqueous solvent may be used. More specifically, as such an ink, for example, an ink obtained by adding an infrared absorber to various water-based inks can be suitably used. In this case, as the water-based ink, for example, water-based pigment ink, water-based dye ink, and the like can be suitably used. Further, for example, water-based inks having a structure in which resin particles are dispersed, such as latex ink and pigment-encapsulated resin-dispersed ink, can be suitably used. Moreover, as an infrared absorber, it is also conceivable to use a substance that is difficult to dissolve in an aqueous solvent, for example. In this case, the solvent may disperse the infrared absorbent in a solid state, for example, in the ink. Thereby, the ink becomes, for example, an emulsion type (dispersion type) ink in which at least a part of the components is dispersed in the solvent.

  In addition, as the infrared absorber, it is preferable to use a substance having a peak wavelength of absorption in the infrared region. In addition, as the infrared absorber, it is preferable to use a colorless or light-colored substance that has little influence on the color of the ink. In this case, it is preferable to use an infrared absorbent having a light absorptance at a peak wavelength that is twice or more the maximum value of the absorptance in the visible light region. Moreover, the light absorptance at the peak wavelength is preferably 5 times or more, more preferably 10 times or more, and still more preferably 20 times the maximum value of the absorptance in the visible light region.

  Moreover, in this example, it is preferable that an ink contains the infrared absorber of the quantity used as 0.1-10 weight% (wt%) with respect to the total weight. The content of the infrared absorber is more preferably 1.0 to 3.0% by weight with respect to the total weight of the ink. Moreover, when using multiple colors of ink as in this example, the preferred content of the infrared absorber may differ from color to color. Therefore, the content of the infrared absorber may be different for each color. In this case, it is preferable to adjust the content of the infrared absorbent in the ink of each color so that the difference in sensitivity of the ink of each color with respect to the infrared is within about ± 50%. The sensitivity of the ink with respect to infrared rays may be, for example, the sensitivity corresponding to the drying rate or temperature increase rate of the ink caused by irradiating infrared rays.

  As described above, in this example, the solvent in the ink dissolves or disperses the infrared absorber. In this case, it is also conceivable to dissolve or disperse the infrared absorber in other components in the ink, such as a binder resin, instead of directly dissolving or dispersing the infrared absorber in the solvent. Also in this case, for example, the infrared absorbent can be dissolved or dispersed in the solvent by dissolving or dispersing the binder resin or the like in the solvent. The ink used in this example will be described in more detail later.

  The plurality of infrared light sources 104 are light sources that irradiate infrared rays, and heat the ink by irradiating the ink adhered on the medium 50 with infrared rays. Accordingly, the infrared light source 104 volatilizes and removes at least a part of the solvent contained in the ink.

  Moreover, in this example, the infrared light source 104 volatilizes and removes the solvent in the ink by heating the ink together with the heater such as the print heater 22. Each of the plurality of infrared light sources 104 is arranged on one side and the other side in the main scanning direction with respect to the plurality of ink jet heads 102 and moves together with the ink jet heads 102 during the main scanning operation. Therefore, during the main scanning operation, one of the plurality of infrared light sources 104 is located on the rear side in the movement direction with respect to the inkjet head 102 and the other is located on the front side in the movement direction. In the bidirectional main scanning operation, the infrared light source 104 located behind the inkjet head 102 irradiates the ink on the medium 50 with infrared rays according to the direction of movement of the inkjet head 102. Thereby, the infrared light source 104 irradiates the ink on the medium 50 with infrared rays immediately after landing on the medium 50, for example. Then, the ink viscosity is increased before bleeding occurs on the medium 50, and the occurrence of bleeding is suppressed.

  As the infrared light source 104, it is preferable to use a light source that can be turned on / off and can emit infrared light (infrared light, near infrared light, middle infrared light, or far infrared light). Moreover, as such a light source, for example, a light source (semiconductor light source) using a semiconductor that generates infrared rays, such as an infrared LED (infrared LED irradiator) or an infrared LD (laser diode, laser infrared irradiator), is preferably used. be able to. If comprised in this way, infrared rays can be irradiated with high precision at a desired timing, for example. More specifically, in this example, the infrared light source 104 is a light source using an infrared LED. In this case, it is more preferable to use a condensing infrared LED irradiator having a condensing function as the infrared light source 104.

  Further, in this example, the infrared light source 104 is disposed so as to be shifted in position from the plurality of inkjet heads 102, thereby irradiating the ink outside the region facing the inkjet heads 102 in the medium 50 with infrared rays. More specifically, in the illustrated configuration, the infrared light source 104 is disposed by shifting the position in the main scanning direction from the inkjet head 102, thereby irradiating the ink outside the region facing the inkjet head 102 with infrared rays. To do. In this case, for example, by changing the distance between the inkjet head 102 and the infrared light source 104, the time until the infrared ray is irradiated after landing on the medium 50 can be appropriately adjusted. Further, by adjusting the width of the infrared light source 104 in the main scanning direction, it is possible to appropriately adjust the time for which the infrared light source 104 irradiates infrared rays (continuous irradiation time).

  In addition, the width of the infrared light source 104 in the sub-scanning direction (X direction in the drawing) orthogonal to the main scanning direction is preferably the same as or larger than the print width of the inkjet head 102. In this case, the print width by the inkjet head 102 is, for example, the width in the sub-scanning direction of a region where the inkjet head 102 ejects ink droplets in one main scanning operation. In this example, the sub-scanning direction is a direction parallel to the conveyance direction (paper feeding direction) in which the medium 50 is conveyed.

  In this example, as shown in FIG. 1A, the infrared light source 104 has a width in the sub-scanning direction that is larger than the print width, and the portion deviated from the inkjet head 102 in the sub-scanning direction. Even irradiate with infrared rays. Accordingly, the infrared light source 104 irradiates infrared light not only on the portion overlapping the inkjet head 102 but also on the downstream side of the inkjet head 102 in the conveyance direction of the medium 50. If comprised in this way, the timing (complete evaporation drying time after a heating) which complete | finishes the heating by the infrared light source 104 can be adjusted appropriately, for example. In this case, for example, the complete evaporation drying time after heating may be shortened by making the width of the infrared light source 104 in the sub-scanning direction shorter than the configuration shown in the drawing.

  Further, in this example, the infrared light source 104 evaporates and removes at least a part of the solvent, for example, to increase the viscosity of the ink on the medium 50 to at least a viscosity at which no bleeding occurs on the medium 50. In this case, the bleeding is, for example, an intercolor bleeding that occurs when inks of different colors are mixed. The viscosity at which no bleeding occurs is, for example, a viscosity at which no bleeding occurs until the ink is completely dried and fixed on the medium 50. Further, the phrase “no blurring” may mean, for example, that blurring does not substantially occur within an allowable range corresponding to the required printing accuracy. More specifically, the infrared light source 104 raises the viscosity of the ink on the medium 50 to, for example, 50 mPa · s or more, preferably 100 mPa · s or more, and more preferably 200 mPa · s or more by irradiation with infrared rays.

  In addition, the directivity of infrared rays emitted from the infrared light source 104 is preferably set so that infrared rays do not reach the nozzle surface of the inkjet head 102. With this configuration, it is possible to appropriately prevent the inkjet head 102 from being affected by the heating performed by the infrared light source 104. Further, the method of irradiating infrared rays by the infrared light source 104 will be described in more detail later.

  The guide rail 14 is a rail member that extends in the main scanning direction, and guides the movement of the carriage 100 during the main scanning operation. The scanning drive unit 16 is a drive unit that causes the inkjet head 102 to perform a main scanning operation and a sub-scanning operation.

  More specifically, in this example, the scanning drive unit 16 moves the carriage 100 along the guide rail 14 to move the inkjet head 102 and the like held by the carriage 100 in the main scanning direction. Then, the inkjet head 102 is caused to perform a main scanning operation by ejecting ink droplets to the moving inkjet head 102 based on print data indicating an image to be printed.

  Further, to cause the inkjet head 102 to perform the sub-scanning operation is, for example, to move the inkjet head 102 in the sub-scanning direction relative to the medium 50. More specifically, in this example, the scan driving unit 16 causes the inkjet head 102 to perform a sub-scanning operation by transporting the medium 50 in the transport direction parallel to the sub-scanning direction. Further, the scan driving unit 16 changes the area of the medium 50 that faces the inkjet head 102 in the next main scanning operation by conveying the medium 50 between the main scanning operations. Accordingly, the scan driving unit 16 causes the ink jet head 102 to eject ink droplets to each position of the medium 50. Further, in this example, the scanning drive unit 16 further moves the infrared light source 104 together with the inkjet head 102 during the main scanning operation, thereby irradiating the infrared light source 104 with infrared rays according to the ink droplet ejection position. Let

  The platen 18 is a trapezoidal member disposed at a position facing the head unit 12, and supports the medium 50 by facing the head unit 12 by placing the medium 50 on the upper surface. In this example, the platen 18 accommodates therein a pre-heater 20 that is a heater (heating heater) for heating the medium 50, a print heater 22, and an after-heater 24.

  The pre-heater 20, the print heater 22, and the after-heater 24 are heating means for heating the medium 50. By heating the ink on the medium 50 through the medium 50, the solvent in the ink is volatilized and removed. Dry. By using these heating means in addition to the infrared light source 104, the solvent in the ink can be volatilized and removed more appropriately, and the drying of the ink can be further promoted. This also makes it possible to more appropriately fix the ink on the medium 50.

  More specifically, the preheater 20 is a heater that preheats the medium 50, and is disposed upstream of the inkjet head 102 in the conveyance direction of the medium 50, whereby ink droplets land on the medium 50. Heat the previous area. The print heater 22 is a heater that heats the medium 50 at a position facing the inkjet head 102. In this case, the infrared light source 104 volatilizes and removes at least a part of the solvent contained in the ink together with the print heater 22 by irradiating the ink on the medium 50 heated by the print heater 22 with infrared rays. If comprised in this way, the solvent in ink can be volatilized and removed more appropriately from the ink immediately after landing on the medium 50, for example. In addition, this makes it possible to increase the viscosity of the ink more appropriately before bleeding occurs on the medium 50.

  The after heater 24 is a heater disposed on the downstream side of the inkjet head 102 in the transport direction, and further heats the medium 50 after passing through the positions of the print heater 22 and the infrared light source 104, whereby the infrared light source 104 and The solvent that could not be removed by the print heater 22 is removed. Thereby, the after-heater 24 dries the ink on the medium 50 more reliably and fixes it to the medium 50, for example.

  In FIG. 1, a heat transfer heater that heats the medium 50 by heat conduction from the inside of the platen 18 is illustrated as the after heater 24. However, when the medium 50 that is difficult to transmit heat is used, a heater other than the heat transfer type may be used as the after heater 24. In this case, as the after heater 24, for example, a dryer such as a warm air heater or an infrared heater may be used. In addition to the heat transfer type after-heater 24, these configurations may be further used.

  The control unit 26 is, for example, a CPU of the printing apparatus 10 and controls each unit of the printing apparatus 10. According to this example, for example, printing on the medium 50 can be performed appropriately.

  Further, in this example, by including an infrared absorbent in the ink, for example, immediately after the ink droplets have landed, the ink can be efficiently heated by infrared irradiation. Accordingly, even when the print heater 22 or the like that heats the medium 50 at a position facing the ink jet head 102 is used as in this example, the heating temperature by the print heater 22 or the like can be appropriately suppressed. Therefore, according to this example, it is possible to appropriately volatilize and remove the solvent in the ink while suppressing the influence on the nozzle surface of the inkjet head 102, for example. This also makes it possible to appropriately increase the viscosity of the ink before ink bleeding occurs, for example.

  In this case, the ink can be appropriately fixed on the medium 50 by drying the ink by infrared irradiation or the like. Furthermore, in this example, by heating the medium 50 with the preheater 20, the print heater 22, and the afterheater 24, the ink can be dried more appropriately than when the heating is performed only with the infrared light source 104, for example. it can. Thus, according to this example, for example, in the case of using evaporation-drying ink, it is possible to appropriately suppress ink bleeding. Thereby, for example, high quality printing can be appropriately performed.

  When only considering heating the ink with infrared rays, it seems that the ink can be heated to some extent without using an infrared absorber. However, in this case, a difference occurs in the heating method depending on the color of the ink. More specifically, for example, when a normal pigment ink is used, only the black (K) carbon black pigment absorbs infrared rays well. Therefore, if the intensity of infrared rays is set so that other color inks such as YMC can be appropriately dried, the black ink will be burnt. Conversely, when the intensity of infrared rays is set in accordance with the black ink, the level of drying varies depending on the color. Therefore, when ink that does not contain an infrared absorber is used, it is difficult to appropriately heat the ink as in this example.

  In addition, the configuration of the printing apparatus 10 in this example can be considered as a configuration in which a plurality of heating units are used as a unit (fixing unit) for drying the evaporation-drying ink, for example. In this case, more specifically, for example, the print heater 22 or the like is used as the first heating unit that heats the medium 50 from the back side at a position (printing position) at which the ink droplets are ejected by the inkjet head 102. In addition, it can be considered that the infrared light source 104 is used as the second heating means.

  Further, in the modified example of the configuration of the printing apparatus 10, it may be considered that the first heating unit is omitted from the first and second heating units. In this case, for example, the ink is heated only by the infrared light source 104 without using a heater such as the print heater 22. Further, in a further modification of the configuration of the printing apparatus 10, for example, another heating unit may be used in addition to the infrared light source 104 and the print heater 22. For example, as indicated by a broken line in the drawing, it may be possible to further use an infrared light source 32, a guide rail 34, and the like in the printing apparatus 10. The infrared light source 32 is a light source (post-heating infrared irradiator unit) that irradiates infrared rays toward the medium 50 at a position facing the after heater 24, and is disposed downstream of the inkjet head 102 in the transport direction. Thus, after the ink is fixed to the medium 50 together with the after heater 24, heating is performed. As the infrared light source 32, a light source using an infrared LED can be suitably used. If comprised in this way, the ink on the medium 50 can be dried more reliably and appropriately, for example. Further, when using a heating means such as the infrared light source 32, it may be omitted as the after heater 24.

  In the illustrated configuration, the infrared light source 32 is disposed so as to be movable independently of the carriage 100 that holds the inkjet head 102 and the like. The infrared light source 32 is configured to be movable in the main scanning direction along the guide rail 34, and irradiates each position on the medium 50 by irradiating infrared light while moving in the main scanning direction. The guide rail 34 is a rail member extending in the main scanning direction in parallel with the guide rail 14 and guides the movement of the infrared light source 32 in the main scanning direction. If comprised in this way, the solvent which remains in the ink on the medium 50 can be removed more reliably, for example.

  Next, the operation (printing operation) for printing on the medium 50 in this example will be described in more detail. First, for convenience of explanation, an example of a printing operation in a conventional printing apparatus will be described.

  FIG. 2 is a diagram showing an example of printing operation in a conventional printing apparatus in a simplified manner (modeling), where ink that does not include an infrared absorbent is used (case that ink that includes an infrared absorbent is not used). An example of a printing operation when ink is dried using only a heater (print heater 22 or the like) provided in the platen 18 will be described.

  In the printing operation shown in FIG. 2, for example, a printing device having the same or similar configuration as the configuration in which the infrared light source 104 is omitted from the printing device 10 shown in FIG. 1 is used. In this case, it is preferable to appropriately adjust the heating temperature and the like of the print heater 22 according to the difference from the configuration of FIG.

  FIG. 2A shows an example of an operation for ejecting ink droplets onto the medium 50. FIG. 2B is a cross-sectional view illustrating an example of the medium 50 after the printing operation is completed.

  Further, the ink used in the configuration shown in FIG. 2 may be the same or similar to the ink used in the printing apparatus 10 shown in FIG. 1 except that it does not contain an infrared absorber, for example. Further, this ink may be, for example, a known evaporative drying ink. More specifically, FIG. 2 shows a case where a known aqueous ink is used. Further, as the medium 50, a medium 50 (permeable medium) having a property of absorbing ink before the solvent is volatilized and removed is used. More specifically, the medium 50 is paper, cloth (cloth), or the like.

  When printing is performed with a conventional printing apparatus configured to use evaporative drying ink or the like, the entire medium 50 is heated with a heater such as the print heater 22. This also volatilizes and removes the solvent in the ink and suppresses ink bleeding on the medium 50. In this case, for example, as shown in FIG. 2A, ink droplets are ejected onto the medium 50 by the inkjet head 102 while being heated by the print heater 22.

  More specifically, in this case, the entire area where the ink droplets land on the medium 50 is reduced to, for example, 60 ° C. or less (for example, 60 ° C. or less) by the print heater 22 disposed in the platen 18 at a position facing the inkjet head 102. 50 to 60 ° C.). In addition, thereby, the ink layer formed on the surface of the medium 50 is heated to increase the viscosity of the ink, thereby suppressing the occurrence of ink bleeding.

  Here, when the medium 50 is heated by the print heater 22, the inkjet head 102 located at the position facing the print heater 22 with the medium 50 interposed therebetween is also affected by thermal radiation. Therefore, if the heating temperature by the print heater 22 is set to a higher temperature than the above temperature, the influence of thermal radiation on the ink jet head 102 is increased. As a result, for example, ink in the vicinity of the nozzles in the inkjet head 102 is dried, and nozzle clogging is likely to occur. Therefore, it is difficult to raise the heating temperature from the above range. Further, when the heating temperature is increased and the evaporation rate of the solvent is increased, for example, the evaporated solvent is agglomerated and adhered to the inkjet head 102 at a relatively low temperature, thereby preventing stable ink ejection. Therefore, also in this respect, it is difficult to increase the heating temperature by the print heater 22.

  On the other hand, if the heating temperature is lower than the above temperature, it takes a long time to dry the ink. As a result, for example, the problem of bleeding increases. In addition, there is a possibility that the amount of ink penetrating into the medium 50 before drying becomes too large. Therefore, it is difficult to make the heating temperature lower than the above range. Therefore, when the ink is dried by the print heater 22 or the like, the heating temperature of the medium 50 is preferably set to the above temperature (medium temperature). That is, by heating the medium 50 at such an intermediate temperature by the print heater 22, the solvent in the ink can be volatilized and removed while suppressing the influence of heat radiation.

  However, in this case as well, for example, if the printing speed is increased, the ink drying speed becomes lower than the printing speed, and problems such as bleeding occur. Further, when the printing speed is increased, for example, the number of printing passes is reduced. In this case, since the amount of ink that lands on a unit area per unit time increases, the drying speed may not be in time. In this case, for example, as shown by a shaded pattern in the medium 50 in the figure, the ink penetrates deep into the medium 50 with the passage of time after landing, and the amount of ink remaining on the surface of the medium 50 decreases. It will be. As a result, the printing density is lowered and the printed color becomes lighter. In addition, problems such as a blurred print result (printed matter) are likely to occur. That is, when printing is performed with a conventional printing apparatus, if the printing speed is increased, the color of the printing result becomes lighter and the problem of bleeding tends to occur.

  On the other hand, in order to suppress problems such as ink bleeding, it seems that the temperature of the print heater 22 may be increased. If comprised in this way, since the evaporation rate of a solvent becomes quick, problems, such as a bleed, can be improved. However, as described above, when the heating temperature by the print heater 22 is increased, the nozzle surface of the inkjet head 102 located at a position facing the print heater 22 is affected by radiant heat, and problems such as nozzle clogging are likely to occur. . For this reason, it can be said that the heating temperature by the print heater 22 has an upper limit temperature for maintaining stable ejection of ink droplets. As a result, if the printing speed is increased, the printing apparatus configured to increase the amount of ink landed per unit time with respect to the unit area has a limit on speeding up.

  For this reason, when printing is performed by a conventional printing apparatus, the heating temperature by the print heater 22 is usually selected in the range of 50 to 60 ° C. as described above. However, when heating is performed at such a temperature, if the printing speed is increased, problems such as ink bleeding and penetration of a large amount of ink into the medium 50 occur as described above. As a result, the surface of the medium 50 and the ink near the surface are reduced, the printing density is lowered, and the printing result (printed matter) may appear blurred. Such a problem becomes more prominent when the heating temperature of the print heater 22 is lowered (for example, about 40 ° C.).

  More specifically, in order to increase the printing speed, for example, when the number of printing passes is reduced to about 8 or less (1 to 8 passes), the amount of ink landed per unit time with respect to the unit area is reduced. In the temperature range that increases and can avoid ejection failure, it becomes more difficult to prevent bleeding using only the print heater 22. Therefore, when printing is performed with a conventional printing apparatus, it is difficult to perform printing at high speed while suppressing problems such as bleeding.

  In order to increase the ink evaporation rate, a method of selecting a low boiling point of the solvent in the ink is also conceivable. However, in this case, since the ink is easily evaporated in the inkjet head 102, nozzle clogging, ejection failure, and the like are likely to occur as in the case where the heating temperature of the print heater 22 is increased. Therefore, it is difficult to solve the above problem even with such a method.

  On the other hand, in the printing apparatus 10 of this example described with reference to FIG. 1, these problems are appropriately solved by using ink containing an infrared absorber. FIG. 3 is a diagram (simplified) showing an example of a printing operation by the printing apparatus 10 of the present example. FIG. 3A shows an example of an operation for ejecting ink droplets onto the medium 50.

  As described above, when printing is performed by the printing apparatus 10 of this example, the solvent in the ink is volatilized and removed using the infrared light source 104 and the print heater 22. This also dries the ink immediately after landing on the medium 50 and increases the viscosity of the ink to a viscosity at which no bleeding occurs. In this case, for example, the temperature of heating by the print heater 22 can be set lower than when the ink is dried only by the print heater 22. The heating temperature by the print heater 22 is, for example, the heating temperature of the print heater 22 with respect to a region facing the inkjet head 102.

  In this case, since the radiant heat generated by the heating of the print heater 22 is also reduced, ink drying on the nozzle surface of the inkjet head 102, nozzle clogging, and the like are less likely to occur. Further, as illustrated in FIG. 3A, in this example, the infrared light source 104 irradiates the ink outside the region facing the inkjet head 102 in the medium 50 with infrared rays. In this case, the ink solvent evaporates relatively slowly only by heating of the print heater 22 at a position facing the inkjet head 102 in the medium 50. Therefore, it is possible to appropriately prevent the problem that the evaporated solvent agglomerates and adheres to the inkjet head 102. In addition, this makes it possible to improve the ejection stability more appropriately.

  More specifically, in this case, the ink ejected by the inkjet head 102 and landed on the medium 50 is subjected to 60 by the print heater 22 in a region facing the inkjet head 102 before being irradiated with infrared rays by the infrared light source 104. Preheating is performed at a relatively low temperature of not higher than ° C (for example, not higher than about 20-50 ° C). The heating temperature by the print heater 22 is more preferably set to a temperature of about 20 to 45 ° C. The heating temperature by the print heater 22 may be, for example, about the heating temperature of the print heater in a known low-speed printer that does not perform high-speed printing.

  In this example, the infrared light source 104 irradiates the vicinity of the region facing the ink jet head 102 with the infrared light source 104 to directly heat the ink in the region to rapidly evaporate the ink solvent. Increase the viscosity of the ink. If comprised in this way, the viscosity of an ink can be raised before a blurring generate | occur | produces, for example, and the blurring of an ink can be prevented appropriately. In this case, for example, the viscosity of the ink can be increased before a large amount of ink is absorbed by the medium 50, so that the ink layer does not become thin on the surface of the medium 50. Further, in this case, by irradiating infrared rays while avoiding the region facing the inkjet head 102, it is possible to appropriately prevent the inkjet head 102 from being affected by radiant heat and solvent evaporation caused by irradiation of the infrared light source 104. . Therefore, according to this example, it is possible to increase the viscosity of the ink immediately after landing, for example, without disturbing the stable ejection of the ink.

  More specifically, in the configuration shown in FIGS. 1 and 3, the infrared light source 104 moves in the main scanning direction together with the inkjet head 102 during the main scanning operation. Infrared light is emitted toward the ink on the medium 50 by the infrared light source 104 located on the rear side in the moving direction of the inkjet head 102. With this configuration, for example, each position of the medium 50 can be irradiated with infrared rays by the infrared light source 104 immediately after passing through the inkjet head 102, and only the landed ink can selectively absorb infrared rays. This also allows selective rapid heating of only the ink layer on the medium 50. In addition, by removing the solvent in the ink by volatilization by this heating and increasing the viscosity of the ink, it is possible to appropriately prevent the ink from bleeding.

  Further, as described above, evaporative drying ink is used in this example. In this case, for example, the solvent in the ink is volatilized and removed by the print heater 22 and the infrared light source 104, so that the ink can be appropriately fixed to the medium 50. Further, in the configuration illustrated in FIGS. 1 and 3, the ink can be dried more reliably by heating with the after heater 24 on the downstream side of the infrared light source 104 in the conveyance direction of the medium 50. . Therefore, according to this example, for example, the ink can be more reliably fixed to the medium 50.

  FIG. 3B is a cross-sectional view illustrating an example of the medium 50 after the printing operation is completed. As described above, in this example, even when a permeable medium is used as the medium 50, the viscosity of the ink is increased before a large amount of ink is absorbed by the medium 50, and the ink is rapidly dried near the surface of the medium 50. can do. In this case, since a large amount of ink remains in the vicinity of the surface of the medium 50, the thickness of the ink on the surface can be sufficiently increased. In addition, this makes it possible to appropriately prevent a printed color from being thinned and perform clear printing. Therefore, according to this example, it is possible to appropriately perform printing on the medium 50 while suppressing the occurrence of bleeding and the like. Further, by using the infrared light source 104 or the like, it is possible to reduce the remaining rate and remaining time of the solvent remaining in the medium 50 which is, for example, a permeable medium. This also makes it possible to appropriately prevent the occurrence of cockling, curling, etc. that occur when a medium 50 such as paper is used.

  In this example, the solvent in the ink is volatilized and removed by infrared irradiation, so that the ink can be dried more reliably in a short time. More specifically, the inventors of the present application have confirmed through experiments and the like that about 80% of the solvent in the ink can be removed by irradiating infrared light from the infrared light source 104. For this reason, in the configuration of this example, it is also possible to remove most of the solvent in the ink and fix the ink to the medium 50 only by irradiating infrared rays, for example.

  In this example, the solvent in the ink is volatilized and removed by infrared irradiation, so that the ink can be dried more reliably in a short time. Therefore, for example, the medium 50 after printing can be quickly transferred to a subsequent process. Further, for example, when using the printing apparatus 10 configured to wind up the medium 50 after printing, a show-through problem or the like that occurs after winding can be appropriately prevented even with a high-speed machine that has increased printing speed.

  In the case where the permeable medium is used, even if the infrared light source 104 is used as in this example, the ink slightly penetrates into the medium 50 as shown in FIG. 3B, for example. However, even if the ink permeates slightly, for example, the amount of ink permeation can be greatly reduced as compared with the case where printing is performed with a conventional configuration that does not use the infrared light source 104.

  Further, the type of the medium 50 used in the printing apparatus 10 of this example is not particularly limited. For this reason, in the printing apparatus 10, it may be considered to use a medium 50 (non-permeable medium, non-absorbable medium) having a property that ink does not penetrate into the inside at all.

  FIG. 3C is a cross-sectional view illustrating an example of the medium 50 after completion of the printing operation in the case where the non-permeable medium is used. When a non-permeable medium is used, the medium 50 does not absorb ink before the viscosity of the ink is increased by heating with the print heater 22 or infrared irradiation. Therefore, in this case, the surface of the medium 50 remains thick in the state after printing. Also in this case, it is possible to appropriately prevent the occurrence of bleeding by increasing the viscosity of the ink by the infrared light source 104. This also makes it possible to appropriately perform printing on the medium 50 while suppressing the occurrence of bleeding and the like.

  In this case, since the ink does not penetrate into the medium 50, the amount of ink attached to the medium 50 can be reduced as compared with the case where the permeable medium 50 is used. With such a configuration, for example, it is possible to appropriately suppress ink bleeding or the like and appropriately perform dark color printing with a smaller amount of ink.

  Next, various features related to the configuration of this example will be described in more detail. First, the increase in printing speed that can be realized by the configuration of this example will be described.

  As described above, in this example, by irradiating infrared rays from the infrared light source 104, the viscosity of the ink can be appropriately increased after landing on the medium 50 and before bleeding occurs. In addition, this makes it possible to increase the printing speed by increasing the amount of ink landed per unit time per unit area, for example.

  More specifically, when printing is performed by an inkjet method as in the printing apparatus 10 of the present example, printing by a multipass method in which a plurality of main scanning operations are performed on each position of the medium 50 is widely performed. Yes. In this case, if printing is performed with a conventional configuration using evaporative drying ink or the like, for example, the amount of ink ejected in one main scanning operation (pass) is reduced in order to prevent bleeding. It will be necessary.

  For example, when printing is performed using four colors of YMCK ink, which is widely used as color printing ink, it is not a multi-pass method, and is performed once for each position of the medium 50. If printing is performed in one pass in which only the scanning operation is performed, the maximum amount of ink per color is 100%, so the total of four colors reaches 400%. However, when such a large amount of ink is ejected by one main scanning operation in the conventional configuration, blurring usually occurs and it is difficult to perform printing appropriately.

  For this reason, in a conventional printing apparatus, printing is usually performed by a multipass method of at least 8 passes. In this case, the ink discharge amount in one main scanning operation is 12.5% at maximum per color and 50% in total for four colors. Further, in order to perform printing with higher accuracy, it is necessary to use a larger number of passes (for example, 16 passes, 32 passes, etc.).

  As described above, in the conventional configuration, it is necessary to print with a certain number of passes in order to prevent bleeding. However, if the number of printing passes is increased, the printing speed is greatly reduced. Therefore, in the conventional configuration, it can be said that it is difficult to increase the printing speed due to the problem of bleeding that occurs in the process of drying the ink solvent.

  On the other hand, in this example, it is assumed that the amount of ink landed per unit time with respect to the unit area is increased by reducing the number of passes, for example, by volatilizing and removing the solvent in the ink by infrared irradiation. However, the occurrence of bleeding can be appropriately suppressed. Therefore, according to the present example, for example, when printing is performed by the multi-pass method, it is possible to appropriately reduce the number of passes and perform high-speed printing (high-speed printing) more appropriately. In addition, this makes it possible to print without causing bleeding even when the speed is increased beyond the limit of the conventional method.

  More specifically, in this example, for example, when the number of printing passes is about 8 or less (1 to 8 passes), the amount of ink ejected per unit time per unit area increases, and the print heater Even when only 22 or the like is in a condition where bleeding cannot be prevented, the infrared light source 104 can be used to appropriately prevent bleeding. Thereby, for example, high quality printing can be performed more appropriately than in the past. That is, according to this example, for example, a high-speed printing apparatus (high-speed printer) in which the number of printing passes is 8 or less can be appropriately realized.

  Also, the number of paths can be less than 8 paths (for example, 4 paths or less). In addition, the effect of preventing bleeding by using the infrared light source 104 is particularly remarkable when, for example, the number of printing passes is about 1 to 4 passes. Furthermore, according to this example, for example, it is possible to perform printing in one pass without performing printing in the multi-pass method. For example, when ink having a slow drying speed is used, a remarkable effect can be obtained even when the number of passes is four or more. In this example, for example, the viscosity of adjacent ink dots can be sufficiently increased before mixing. Therefore, for example, it is possible to prevent streaks and the like from being formed by connecting ink dots.

  Further, the effect of preventing bleeding by using the infrared light source 104 is a useful effect other than for a high-speed printer that performs high-speed printing, for example. For example, when the medium 50 that easily causes bleeding such as paper or cloth is used, it can be said that the effect of preventing bleeding is great even when printing is performed at high speed. Therefore, the printing apparatus 10 of this example can be suitably used for printing in various fields, not limited to a specific field (such as the SG field) for high-speed printing.

  Subsequently, the characteristics of the ink used in this example will be described in more detail. As described above, the ink used in this example includes an infrared absorber, a solvent, a coloring material, and the like. More specifically, in this configuration, it is preferable to use a substance having an absorption characteristic matched to the wavelength of infrared rays generated by the infrared light source 104 as the infrared absorber. In addition, for this relationship, for example, it can be said that it is preferable to select the infrared light source 104 that emits infrared light within the wavelength range absorbed by the infrared absorbent to be used. In this case, it can be said that it is preferable that the emission wavelength of the infrared light source 104 substantially matches the infrared absorption band of the infrared absorbent contained in the ink.

  In this case, for example, if the wavelength is too far from the far infrared side, it may be difficult to perform heating appropriately when an organic solvent or the like is used as the solvent. As the light source of the infrared light source 104, it is preferable to use a widely used infrared LED or the like. Therefore, as the infrared light source 104, for example, a near infrared LED having a light emission center wavelength in a range of 800 to 900 nm (for example, about 850 nm) can be suitably used.

  Moreover, as an infrared absorber, for example, it is preferable to use a substance that selectively absorbs the wavelength of such an infrared LED and does not have significant absorption characteristics in the visible light region. Moreover, as such a substance, a well-known functional organic color material etc. can be used, for example. By using such an infrared absorber, the ink on the medium 50 can be directly and selectively heated.

  Moreover, as the functional organic color material, for example, a functional organic color material that has greatly advanced in recent years and that has a strong absorption characteristic only in a predetermined wavelength range of infrared rays can be suitably used. Such a functional organic color material is, for example, a substance that absorbs infrared rays and is transparent to visible light. More specifically, the infrared absorber is selected from, for example, anthraquinone, phthalocyanine, diionium salt, anthraquinone, polymethane, octathiophenyl phthalocyanine derivatives, perimidine-based squarylium, naphthalocyanine-based, or squarylium-based materials. It is conceivable to use at least one of the above. With this configuration, for example, the visible light region does not have a large absorption characteristic, and selectively has a large absorption characteristic at an infrared wavelength corresponding to the emission wavelength of an infrared LED used as the infrared light source 104. An infrared absorber can be used appropriately.

  Moreover, it is preferable that the transmittance | permeability of the infrared absorber with respect to the light of visible region is 60% or more. If comprised in this way, the infrared absorber can be made substantially transparent with respect to visible light, and the change of the color of the ink by including an infrared absorber can be suppressed appropriately. The transmittance of the infrared absorber with respect to light in the visible light region is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. Further, depending on the color and application of the ink, for example, it may be possible to use, as the functional organic color material, a substance having a strong absorption characteristic in a predetermined wavelength region of infrared light or a part of visible light region.

  As described above, in the ink of this example, the infrared absorber is added so as to be dissolved or dispersed in a solvent, for example. In addition to the configuration in which the infrared absorber is directly dissolved or dispersed in the solvent, for example, it may be possible to dissolve or disperse the infrared absorber in other components in the ink. In this case, the other component in the ink is, for example, a component resin included in the ink. The component resin is a resin that the ink contains as a component. More specifically, the component resin may be, for example, a binder resin. Also in this case, the infrared absorbent can be dissolved or dispersed in the solvent by dissolving or dispersing the binder resin or the like in the solvent.

  In addition, many infrared absorbers (functional organic colorants and the like) preferable for use in this example are hardly soluble in water. Therefore, when the main component of the solvent of the ink is water, it is preferable to use an ink having a configuration in which an infrared absorber is dissolved or dispersed in a binder resin or the like, or a configuration in which an infrared absorber is dispersed in water.

  Moreover, in this example, the ink contains the color material of each color as described above. For this reason, the color of the ink is not particularly limited. For example, in this example, the ink having the above-described configuration is used for each color of YMCK. In the printing apparatus 10, when another color ink is further used, it is preferable to use the ink having the above-described configuration for the other color ink. As other color inks, for example, it is conceivable to use inks of colors such as white, clear, red (R), green (G), blue (B), and orange (Org).

  Further, depending on the color of the color material (background color) included in the ink, even if the infrared absorber has a certain color, it may not be noticeable. In this case, it is also conceivable to use an infrared absorbent that also absorbs light in the visible light region. More specifically, in the case of dark ink, it is conceivable to use an inorganic infrared absorbing colorant such as antimony-doped tin oxide that also absorbs light in the visible light region. In this case, an infrared-absorbing colorant that is different from other colors of ink in some colors may be used. More specifically, for example, an inorganic infrared absorbing colorant is used as an infrared absorber for some dark inks, and an infrared absorber for other color inks has low absorption in the visible light region. An organic color material or the like may be used.

  In the ink of this example, the solvent is the main component of the ink. In this case, a main component is a component contained most by weight ratio, for example. In the ink of this example, the solvent is preferably a component that occupies 50% by weight or more of the total weight of the ink, for example. If comprised in this way, the viscosity of the ink before discharge from the inkjet head 102 can be appropriately adjusted to the low viscosity suitable for discharge by an inkjet system, for example. As the solvent for the ink, for example, it is conceivable to use a solvent (organic solvent) having a boiling point of 200 ° C. or less as the main component, water, or the like.

  By using such ink, for example, after landing on the medium 50, it is possible to appropriately prevent the ink from bleeding by evaporating the solvent as the main component by infrared irradiation or the like. Further, by evaporating the solvent, the evaporation-drying type ink can be appropriately fixed (dry-fixed) to the medium 50.

  In this case, for example, since the ink can be dried in a short time by irradiating infrared rays, a combination of the ink and the medium 50, which is difficult to print properly with the conventional configuration, is realized. Etc. are also possible. More specifically, various evaporative drying inks can be used even when, for example, a paper on which an image receiving layer is not formed, a cloth that is not pretreated, or the like is used as the medium 50. Thereby, for example, the running cost of printing can be significantly reduced.

  In addition, when printing is performed with a conventional configuration using a conventional solvent ink such as a porous medium 50, non-permeable PET, PC (polycarbonate), etc., printing is appropriately performed due to a bleeding problem. Even when the medium 50 that is difficult to do is used, for example, by using an ink in which an infrared absorbent as described above is included in a solvent ink, and heating with infrared rays, printing can be performed more appropriately. . Similarly, when printing is performed with a conventional configuration using a conventional latex ink, for example, when the medium 50 is difficult to be printed appropriately due to a bleeding problem or the like, for example, the latex ink is configured as described above. It is possible to perform printing more appropriately by using ink containing a suitable infrared absorber and heating with infrared rays. As described above, according to this example, for example, inks having various characteristics can be used in combination with more various media 50.

  Next, the method of irradiating infrared rays by the infrared light source 104 will be described in more detail. In addition to semiconductor light sources such as infrared LEDs and infrared LDs, infrared lamps and the like are also known as light sources for irradiating infrared rays. For example, in the printing apparatus 10, a configuration in which an infrared lamp is used as a heating unit that additionally heats the medium 50 like the after heater 24 (see FIG. 1) is also known. When these configurations are referred to, in principle, an infrared lamp or the like may be used as the infrared light source 104 in this example instead of a semiconductor light source.

  However, unlike a semiconductor light source, an infrared lamp usually cannot be switched on and off at high speed. Moreover, an infrared lamp normally heats a wide range simultaneously compared with infrared LED etc. Therefore, when an infrared lamp is used as the infrared light source 104, the medium 50 having low heat resistance cannot be used, for example, under conditions of high temperature drying that can volatilize and remove the solvent in a short time. In this case, the medium 50 and the ink may be burned or discolored.

  Furthermore, the infrared lamp usually generates light containing a large amount of visible light or the like that has low conversion efficiency into infrared rays effective for heat sensitivity and low effectiveness for heating. In this case, it becomes difficult to selectively heat only the ink, and the medium 50 and surrounding members are also heated simultaneously with the ink. In addition, much of the energy input to the infrared lamp becomes heat and is dissipated through the medium 50, resulting in loss. In addition, as a result, there is a disadvantage that the energy utilization efficiency used for drying the ink is lowered.

  Therefore, it is preferable to use a semiconductor light source such as an infrared LED as the infrared light source 104 as described above. If comprised in this way, the infrared rays of a specific wavelength range can be irradiated efficiently. Further, by using an ink containing an infrared absorbent that matches the wavelength range of infrared rays to be used, the ink can be appropriately heated while suppressing the influence on the medium 50 and the like. Moreover, this can prevent the occurrence of bleeding appropriately.

  Also, when irradiating infrared light using a semiconductor light source, it is possible to switch on / off at high speed, etc., unlike using an infrared lamp. Therefore, if comprised in this way, on-off of the infrared light source 104 can also be switched appropriately as needed, for example.

  As for the method of heating the ink by the infrared light source 104, it is preferable to heat the ink on the medium 50 at once in a short time. In this case, it is preferable to irradiate infrared rays from the infrared light source 104 so that, for example, the continuous irradiation time of infrared rays to the same position on the medium 50 is shorter than the thermal time constant of heat dissipation of the medium 50. In this case, it is preferable that the temperature of the ink solvent is raised to a temperature equal to or higher than the boiling point at the position where the infrared ray is irradiated by the infrared ray irradiation for such a continuous irradiation time. The boiling point of the solvent of the ink is, for example, the boiling point of the solvent that is the main component of the ink.

  By raising the temperature of the solvent of the ink to a temperature equal to or higher than the boiling point, for example, the solvent component in the ink can be evaporated at once and bleeding can be appropriately prevented. In this case, for example, not only the bleeding in the surface direction parallel to the surface of the medium 50 but also the bleeding in the thickness direction of the medium 50 can be appropriately prevented. In this case, as described above, by increasing the viscosity of the ink before the large amount of ink is absorbed by the medium 50, a large amount of ink can be left on the surface of the medium 50. Therefore, for example, even when a permeable medium is used as the medium 50, a dark color image, a monochrome image, or the like can be printed more appropriately. Thereby, clear printing can be performed more appropriately.

  Here, when the ink is heated by infrared irradiation, it is necessary to consider the amount of heat radiated through the medium 50, the loss of heat energy, and the like. More specifically, for example, when the irradiation intensity of the infrared light source 104 is small, it is difficult to sufficiently raise the temperature by the heat escaping through the medium 50. As a result, it becomes difficult to appropriately prevent ink bleeding.

Further, in order to reduce the influence of the amount of heat radiated through the medium 50 (temperature decrease, etc.) and the influence of loss of thermal energy, for example, it is sufficiently strong as long as the medium 50 and the ink are not burned. It is preferable to irradiate infrared rays and to make the continuous irradiation time of infrared rays sufficiently shorter than the thermal time constant of heat radiation of the medium 50 as described above. With this configuration, for example, the temperature can be appropriately raised in a short time to a temperature close to the boiling point of the solvent of the ink. More specifically, as the infrared light source 104, it is preferable to use a light source (infrared LED irradiator or the like) having an intensity of at least 0.3 W / cm ² or more.

Note that the transfer rate of heat escaping through the medium 50 is determined by a thermal time constant τ expressed by the following equation.
τ (thermal time constant) = heat capacity x thermal resistance = heat capacity x thickness ÷ thermal conductivity

  And when intense infrared rays are irradiated in the time shorter than the thermal time constant of the medium 50, it becomes close to adiabatic heating conditions, and a heat dissipation loss can be reduced. Further, the thermal time constant of the medium 50 varies depending on the material and thickness of the medium 50 to be used. More specifically, for example, in a normal PVC film having a thickness of about 1 mm, the thermal time constant is about 10 seconds. Also, when other types of media (for example, various plastic media) are used as the media 50, in many cases, the thermal time constant is considered to be approximately the same.

  In such a case, it can be considered that the continuous irradiation time of infrared rays is, for example, 3 seconds or less, preferably 0.2 seconds or less. Further, the inventors of the present application have confirmed through experiments and the like that only the ink layer on the medium 50 can be efficiently heated to a high temperature when the infrared continuous irradiation time is set in this way. Furthermore, it was confirmed that the thermal efficiency of heating was further increased by setting the continuous irradiation time to 0.1 seconds or less.

  Further, when the configuration like the printing apparatus 10 of the present example is used, the infrared light source 104 is moved at the same moving speed as the inkjet head 102 during the main scanning operation. In this case, the heating time (continuous irradiation time) using infrared rays can be adjusted, for example, by adjusting the width of the infrared light source 104 in the main scanning direction. More specifically, the moving speed of the inkjet head 102 during the main scanning operation is usually about 500 to 1000 mm / s. In this case, if the width of the infrared light source 104 in the main scanning direction is about 50 mm, the continuous irradiation time to the same region on the medium 50 is about 50 / (500 to 1000) = 0.1 to 0.05 seconds. become. Therefore, if comprised in this way, a preferable continuous irradiation time can be implement | achieved appropriately, for example.

  In this case, the heating temperature of the ink can be adjusted by adjusting the irradiation intensity of the infrared light source 104. Further, this makes it possible to appropriately and sufficiently volatilize and remove the ink solvent within the set continuous irradiation time. Further, in this case, by heating while moving the infrared light source 104, the medium 50 and ink can be prevented from being burned by overheating, and heating of each position of the medium 50 for a short time with strong infrared light is realized. It can be said that.

  More specifically, for example, when it is considered to irradiate infrared rays with a longer continuous irradiation time with a configuration different from this example, problems such as burning of the medium 50 and the like occur when strong infrared rays are used. It will be. Therefore, in this case, it is necessary to use weak infrared rays that do not cause burning or the like even after continuous irradiation for a long time. However, in this case, most of the heat generated by the infrared irradiation escapes from the medium 50, and the ink temperature does not rise. Therefore, in this case, the solvent of the ink cannot be properly volatilized and removed by irradiation with infrared rays. As a result, it is not possible to appropriately prevent ink bleeding. On the other hand, in this example, the structure which can irradiate strong infrared rays in a short time is realized using the structure which performs the main scanning operation. In addition, this makes it possible to appropriately heat the ink while preventing the medium 50 from burning.

More specifically, the irradiation intensity (necessary energy of the infrared light source 104) necessary for heating the ink (steady heating of the ink layer), the amount of heat escaping from the medium, and the like can be calculated as follows. it can. For example, regarding the irradiation intensity (energy) necessary for heating the ink, the thickness of the ink on the medium 50 is D (cm), the infrared absorption rate is α, and the specific heat of the ink is 4.2 (Joule / gr). The irradiation energy Ei required to raise the ink layer having an area of 1 cm ² and a thickness D (cm) by 10 ° C. is:
Ei = (10 × D × 4.2) / α (Joule) Formula (1)
It is. And when D (= 20 μm) = 0.002 cm,
Ei≈0.083 / α (Joule / cm ² )
become.

In addition, when the irradiation time is 1 second, the required irradiation intensity from the infrared LED used in the infrared light source 104 is α = 1.
0.083 (W / cm ² ) Formula (2)
become.

In addition, the amount of heat escaping from the medium (heat dissipation loss energy amount) is approximately 1 cm, assuming that the thermal conductivity is 0.25 (W / mK), the temperature difference between the front and back of the medium 50 is 10 ° C., the thickness is 1 mm. ^The energy El escaping in one second through the medium 50 of area ² (per cm ² ) is
El = (0.25 × 10 × 0.0001 ÷ 0.001) = 0.25 (W) (Joule / sec) Equation (3)
become.

  This energy E1 can also be considered as a heat loss during steady heating in which the medium 50 is slowly heated. In this case, the energy of three times the energy for heating the ink layer is lost through the medium 50 when the heating is performed under the normal equilibrium condition where the heating is performed slowly from the comparison of the equations (2) and (3). I understand that

  Further, from these equations, in order to avoid such a problem, the infrared light source 104 irradiates a strong infrared ray in a continuous irradiation time shorter than the thermal time constant (= heat capacity × thermal resistance) of the medium 50 and rapidly heats. Can be seen to be effective. That is, efficient heating can be performed by supplying small energy close to Equation (1) under short-time heating conditions with little heat loss. Further, in this case, the ink evaporation rate can be accelerated at an instant by instantaneously raising the temperature of the solvent to a temperature equal to or higher than the boiling point of the solvent contained in the ink. However, in this case as well, there is an upper limit on the heating rate, and it is necessary to keep the temperature within a range in which the ink to be used and the medium 50 in contact with the ink do not burn.

In addition, the inventors of the present application used an ink containing, for example, a near-infrared absorbing material FDN-003 manufactured by Yamada Chemical Co., Ltd. having an absorption maximum wavelength of 853 nm as an infrared absorber in a specific experiment. As the infrared light source 104, a near-infrared LED having an emission center wavelength at 850 nm was used. Then, it was confirmed that the ink bleeding can be efficiently and appropriately suppressed by irradiating the infrared rays under the conditions that the infrared irradiation intensity is various and the continuous irradiation time is 2 to 0.3 seconds or less. In addition, it was confirmed that the conditions for avoiding scorching due to overheating of the medium 50 and ink can be appropriately realized. Further, it was confirmed that the infrared irradiation intensity is preferably 0.3 W / cm ² or more. The infrared irradiation intensity is more preferably 1 W / cm ² or more, and still more preferably 5 W / cm ² or more. Further, further experiments and examinations have confirmed that these points are not limited to the case of using a specific infrared absorber or infrared LED.

  Next, various modified examples and preferred application examples of the printing apparatus 10 of this example will be described. In the above description, the case where permeable media such as paper and cloth (cloth, T-shirt, etc.) are mainly used as the medium 50 used in the printing apparatus 10 has been described. According to this example, for example, when printing is performed at high speed on a permeable medium that is likely to cause bleeding, a remarkable effect of preventing bleeding can be obtained.

  Further, in the printing apparatus 10, not only the medium 50 described above but also various media 50 can be used. For example, not only when the permeable medium is used, but also when a non-permeable medium is used, the effect of preventing bleeding can be appropriately obtained by the configuration in which the ink is rapidly dried. More specifically, in the printing apparatus 10, for example, various porous media, non-permeable plastic films (PET), vinyl chloride sheets, polycarbonate, or other media 50 may be used. Further, in this case, for example, a high-definition color printing or the like can be appropriately performed by preventing bleeding by rapid drying even on a medium 50 that cannot easily be printed due to the tendency of the printing apparatus having a conventional configuration. Can be done.

  Further, in this example, since it is possible to appropriately prevent bleeding without performing special processing or the like on the medium 50, for example, paper that does not have an image receiving layer, cloth that has not been pretreated, T-shirts, etc. For fabric products (sewn products), it is possible to appropriately print dark colors with high image quality and high definition. Thereby, for example, the running cost of printing can be appropriately reduced. That is, in this example, as the medium 50, for example, permeable media (paper, cloth, etc.) that does not form an image receiving layer, non-permeable media (eg, non-coated media, etc.), and the like can be widely used. In addition, the medium 50 having an image receiving layer is not limited to this, and can be preferably used.

  Further, in FIG. 1 and the like, a configuration for performing bidirectional main scanning operation is illustrated as a configuration of the printing apparatus 10. However, in the modification of the printing apparatus 10, for example, only the main scanning operation in one direction (one-way printing) may be performed. In this case, the infrared light source 104 may be disposed only on one side of the inkjet head 102 that is behind the inkjet head 102 during the main scanning operation.

  In addition to the above, the specific configuration of the printing apparatus 10 can be variously changed. For example, the color of ink (color ink) used in the inkjet head 102 is not limited to a specific color. For this reason, in the inkjet head 102, not only YMC and the like, but also various colors of YMCRGB and special colors such as white, pearl, and metallic may be used. Also, the number of colors is not limited to a specific number of colors, and may be one or more colors.

  Further, as long as it is possible to irradiate the ink after landing on the medium 50 with infrared rays, the configuration of the printing apparatus 10 is not limited to the serial method in which the main scanning operation is performed, but may be modified to a configuration of a line printer method, for example. In this case, for example, an infrared light source 104 (infrared LED irradiator or the like) may be disposed on the downstream side of the inkjet head 102 in the conveyance direction of the medium 50. In the case of a line printer type configuration, it is conceivable to arrange the infrared light source 104 individually or collectively on the downstream side for each color of ink to be used.

  For example, even when a serial configuration is used, the position where the infrared light source 104 is disposed may be other than the position adjacent to the inkjet head 102 in the main scanning direction (such as both sides of the inkjet head 102). For example, the infrared light source 104 may be disposed at a position downstream of the inkjet head 102 in the conveyance direction of the medium 50. In this case, the infrared light source 104 may be disposed at both the position adjacent to the inkjet head 102 in the main scanning direction and the downstream side of the inkjet head 102 in the transport direction.

  In addition, as described above, the infrared energy (maximum supply energy of irradiation energy) irradiated by the infrared light source 104 is determined according to the irradiation intensity and irradiation time of the infrared light source 104. In addition, the maximum supply energy needs to be set within a range in which the medium 50 and the ink are not burned. In this case, in order to set the maximum supply energy of the irradiation energy within an appropriate range, at least one of the irradiation intensity of the infrared light source 104 and the irradiation time, the printing speed (printing speed), the number of printing passes, the medium 50 It is preferable that the density is automatically changed based on at least one of the density of dots (print dot density) of the ink formed on the top. Further, such a change may be performed manually by an operator, for example.

  Further, as described above, in this example, the infrared light source 104 irradiates the ink layer on the medium 50 with infrared rays while moving with the inkjet head 102 during the main scanning operation. In this case, it is preferable that the amount of infrared light irradiated from the infrared light source 104 to the ink layer be uniform within a range of the discharge width discharged at least at the same time. In this case, to make the infrared irradiation amount uniform within at least the range of the ejection width ejected at the same time, for example, the width (in which ink droplets are ejected by one inkjet head 102 in at least one main scanning operation) ( It is to make it uniform within the range of the discharge width in the same pass.

  Further, as described above, the infrared light source 104 is not limited to the infrared LED or the like, and a laser light source such as a semiconductor laser (infrared LD) may be used. And when using a laser light source as an infrared irradiation source, it is preferable to comprise so that a fixed area may be irradiated uniformly using a beam expander, a saddle type lens, etc., for example. More specifically, in this case, for example, the beam may be expanded in the nozzle row direction of the inkjet head 102, and the light may be condensed only in a certain region in one direction in the movement direction (main scanning direction) of the inkjet head 102. Conceivable.

  Further, the directivity of infrared irradiation by the infrared light source 104 is preferably set so as not to heat the nozzle surface of the inkjet head 102 or the ink in the nozzle. More specifically, for example, the directivity of infrared irradiation by the infrared light source 104 is preferably set so as not to emit infrared rays in the direction of the inkjet head 102. In addition, it is preferable to adjust the directivity so that infrared rays (reflection components) reflected from the medium 50 and reaching the inkjet head 102 can be appropriately reduced.

  In the main scanning operation, for example, the infrared light source 104 moves in the main scanning direction together with the inkjet head 102 while continuously irradiating infrared rays (continuous lighting). The method of lighting the infrared light source 104 is not limited to continuous lighting, and for example, pulse lighting may be performed.

  In the above, a plurality of inkjet heads 102 (for example, inkjet heads 102 for each color of YMCK) that eject ink droplets of different colors are aligned in the sub-scanning direction and aligned in the main scanning direction. The configuration arranged in the above was explained. However, the arrangement of the plurality of inkjet heads 102 is not limited to the above, and can be variously changed. For example, a part of the plurality of inkjet heads 102 may be disposed with a position in the sub-scanning direction shifted from that of the other inkjet heads 102. More specifically, for example, YMCK ink jet heads 102 for two colors or more are arranged on the same Y axis, and one or more color ink jet heads 102 are distributed in the X axis direction. May be. In this case, disposing the inkjet head 102 on the Y-axis means, for example, arranging them in the main scanning direction. Further, the dispersive arrangement in the X-axis direction means, for example, that the positions in the sub-scanning direction are shifted. If comprised in this way, the quantity of the ink discharged to the same area | region in each main scanning operation | movement can be reduced, for example. Thereby, for example, the occurrence of bleeding can be prevented more appropriately.

  In the above description, the case where ink droplets are directly ejected to the medium 50 to be printed has been described. In this case, the medium 50 to be printed is a medium 50 in which the state after printing becomes a printed product. Further, in a modified example of the printing apparatus 10, for example, a transfer medium may be used as the medium. In this case, the transfer medium is, for example, a medium on which a printed image is transferred to another medium.

  The present invention can be suitably used for a printing apparatus, for example.

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 12 ... Head part, 14 ... Guide rail, 16 ... Scanning drive part, 18 ... Platen, 20 ... Pre-heater, 22 ... Print heater, 24. ..After heater, 26 ... control unit, 32 ... infrared light source, 34 ... guide rail, 50 ... medium, 100 ... carriage, 102 ... inkjet head, 104 ... infrared ray light source

Claims (11)

A printing apparatus that performs printing on a medium by an inkjet method,
An inkjet head that ejects ink droplets by an inkjet method;
An infrared light source that emits infrared light,
The ink-jet head causes the ink to adhere onto the medium by ejecting ink droplets of an ink containing an infrared absorber that absorbs infrared rays and a solvent that dissolves or disperses the infrared absorber.
The printing apparatus according to claim 1, wherein the infrared light source volatilizes and removes at least a part of the solvent contained in the ink by irradiating the ink attached on the medium with infrared light.   The printing apparatus according to claim 1, wherein the infrared light source irradiates an ink outside a region facing the ink jet head in the medium.   The infrared light source irradiates the ink on the medium with infrared rays so that the continuous irradiation time of infrared rays to the same position on the medium is shorter than the thermal time constant of heat dissipation of the medium. The printing apparatus according to claim 1 or 2. A heater for heating the medium;
The said infrared light source volatilizes and removes at least a part of the solvent contained in the ink together with the heater by irradiating the ink on the medium heated by the heater with infrared rays. The printing apparatus according to any one of 1 to 3.   The printing apparatus according to claim 1, wherein a transmittance of the infrared absorbent with respect to light in a visible light region is 60% or more.   The infrared absorber is an anthraquinone-based, phthalocyanine-based, diionium salt-based, anthraquinone-based, polymethane-based, octathiophenyl phthalocyanine derivative, perimidine-based squarylium, naphthalocyanine-based, or squarylium-based material. The printing apparatus according to any one of 1 to 5.   The printing apparatus according to claim 1, wherein the infrared light source is a light source using a semiconductor that generates infrared light.   The printing apparatus according to claim 1, wherein the solvent included in the ink is an organic solvent.   The printing apparatus according to claim 1, wherein the solvent included in the ink is an aqueous solvent.   The printing apparatus according to claim 1, wherein the medium is a medium having a property of absorbing the ink before the solvent is volatilized and removed. A printing method for printing on a medium by an inkjet method,
An inkjet head that ejects ink droplets by an inkjet method;
An infrared light source that emits infrared light;
Use
By ejecting ink droplets of an ink containing an infrared absorbent that absorbs infrared rays and a solvent that dissolves or disperses the infrared absorbent by the inkjet head, the ink is attached onto the medium,
A printing method, wherein at least a part of the solvent contained in the ink is volatilized and removed by irradiating the ink attached on the medium with infrared light from the infrared light source.

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