JP2014094549A - Printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain printed matters without bleeding.SOLUTION: An inkjet printer is used which includes: a print heater 70 that heats media 30 from the back side of an inked surface of the media; and preliminary heating means that heats the media from the back side of the inked surface before the media are disposed at the position opposite the ink-discharge face of a printhead. The print heating means and the preliminary heating means heat the media to be printed to make a surface temperature of the inked surface of the media 40°C or more and 60°C or less. An ink is used which is discharged from the printhead and which contains a binder resin having a surface minimum filming temperature of 0°C or less.

Description

  The present invention relates to a printing method for printing a recording medium using an inkjet printer.

  In an inkjet printer, as an inkjet printer provided with a pre-heater for pre-heating a recording medium before printing and an after-heater for heating the recording medium immediately after printing in order to prevent bleeding of a printed image, Inkjet printers described in Patent Document 1 and Patent Document 2 are known. An ink jet printer described in Patent Document 3 is known as an ink jet printer including a preheater, a print heater, and an after heater.

JP 62-144955 A (published June 29, 1987) German patent DE10056703C2 (published on November 21, 2002) JP 2010-30313 A (released on February 12, 2010)

  Here, with reference to FIG. 4, the structure of a conventional inkjet printer as described in Patent Documents 1 and 2 will be described. FIG. 4 is a side sectional view showing a schematic structure of a conventional ink jet printer. As shown in FIG. 4, the ink jet printer 3 ejects ink droplets from the nozzles 12 arranged on the bottom surface of the print head 14, and causes the ink droplets to land on the surface of the medium 30 arranged on the platen 20 in a dot shape. Then, the inkjet printer 3 prints a picture or a character composed of a plurality of ink dot arrays on the surface of the medium 30. As described above, when ink droplets are landed on the surface of the medium 30 in the form of dots, the ink droplets permeate widely around the landing location. Therefore, there is a problem that a picture or character composed of a plurality of ink dot arrays printed on the surface of the medium 30 is blurred or blurred.

  In order to solve such a problem, the ink jet printer 3 includes a preheater 40 and an afterheater 50. In the ink jet printer 3, as shown in FIG. 4, the pre-printing medium 30 conveyed on the platen front part 26 is preheated by a preheater 40. Then, the media 30 immediately after printing is heated by the after heater 50.

  In this way, by preheating and warming the pre-printing medium 30 by the pre-heater 40, the ink droplets that land on the surface of the medium 30 are dried quickly, and the ink droplets are placed around the landed portion. Prevents widespread penetration. In addition, the after-heater 50 dries partially undried ink droplets remaining on the surface of the medium 30 at an early stage to prevent the ink droplets from penetrating widely around the landing spot. As a result, if the surface of the medium 30 is made of a plurality of ink dots that do not bleed, pictures and characters can be printed clearly and clearly.

  Here, conventionally, general-purpose water-soluble inks and lactic acid inks (lactate inks) have been exclusively used in inkjet printers. However, such water-soluble ink and lactic acid ink have insufficient environmental characteristics and media characteristics. Therefore, a printer using such water-soluble ink or lactic acid ink is not suitable for printing a picture or a character on a medium for outdoor display advertisement or the like.

  On the other hand, latex ink, which is an ink in which a binder resin is dispersed or emulsified in water or a water-soluble solvent, has sufficient environmental characteristics and media characteristics, and is suitable for printing pictures and characters on media for outdoor display advertisements and the like. It is. However, latex ink has extremely high diffusibility (wet spread) with respect to media. Therefore, when the ink droplet is landed on the surface of the medium, the ink quickly spreads widely around the landed portion. For this reason, when latex ink is used, the ink dots cannot be clearly fixed at the ink landing positions on the media surface, and a non-bleeding picture or character consisting of a plurality of ink dot arrays cannot be printed clearly.

  In the ink jet printer 3 described in Patent Documents 1 and 2, ink droplets that have landed on the medium 30 are placed below the scanning movement range of the print head 14, that is, at a position facing the ink ejection surface of the print head 14. There is no print heater for heating on the spot. Therefore, when the latex ink as described above is used, in the inkjet printer 3, even if the pre-heater 40 and the after-heater 50 warm the media 30 before and after the ink landing, the surface of the medium 30 at the time of ink landing The temperature is not sufficient, and it is difficult to suppress the diffusion of latex ink.

  Here, since the print heater can heat the ink droplets that have landed on the medium 30 on the spot, the ink that has landed on the medium 30 can be quickly dried to suppress diffusion. Since it is provided at a position facing the ink ejection surface, there is a problem that the medium 30 is heated and at the same time, the heat solidifies in the small diameter nozzles 12 of the print head 14 and clogging occurs.

  In addition, for media used in inkjet printers, by applying various coating agents to the surface of the media, ink droplets that have landed on the surface do not permeate around the landed location, and ink is applied to the landed location with small-diameter dots. Media that can be fixed in a shape has been developed. However, media coated with such a coating agent are expensive and not universal.

  Furthermore, especially for media for outdoor display advertising, media that softens easily even when heated at low temperatures, such as vinyl chloride-based films, and media that do not soften easily when heated at high temperatures, such as polyester films. Various types of media are used.

  In the inkjet printer 3 as described in Patent Document 1 and Patent Document 2, the temperature at which the medium 30 is heated by the preheater 40 and the afterheater 50 shown in FIG. 4 is set to a certain relatively high temperature, Adjustment is impossible. Therefore, if the medium 30 is a vinyl chloride film or the like, it is heated to a high temperature by the pre-heater 40 and the after-heater 50 and is softened, so that it can not be smoothly conveyed on the platen 20. There is a problem that you can not.

  In order to solve these problems, the ink jet printer described in Patent Document 3 includes a preheater, a print heater, and an after heater, and controls the driving of each heater separately. However, the ink jet printer described in Patent Document 3 is limited to the case where solvent ink is used, and does not target various other inks.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a printing method for clearly printing without bleeding with a latex ink using an ink jet printer.

  In order to solve the above problems, a printing method according to the present invention includes a print head, a driving unit that relatively moves the positions of the recording medium and the print head, and a position that faces the ink ejection surface of the print head. Heating means for heating the recording medium disposed at the position by the driving means from the side facing away from the ink landing surface of the recording medium, and the recording medium comprising the print head Using an inkjet printer provided with preheating means for heating the recording medium from a surface facing away from the ink landing surface at a position before being disposed at a position facing the ink ejection surface, A printing method for printing a recording medium, wherein the heating means and the preliminary heating means are set so that the surface temperature of the ink landing surface of the recording medium is 40 ° C. or more and 60 ° C. or less. Further, the recording medium is heated and the ink ejected from the print head includes an ink containing a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent. The ink is characterized in that an ink having a minimum surface forming temperature of 0 ° C. or lower is used.

  According to said structure, a recording medium is printed using an inkjet printer. In an inkjet printer, printing is performed at a desired position on a recording medium by relatively moving the print head and the recording medium by a driving unit. At the time of printing, first, the recording medium is heated by the preheating means from the side facing away from the ink landing surface at a position before the position facing the ink ejection surface of the print head. Next, the recording medium heated by the preliminary heating unit is conveyed to a position facing the ink ejection surface of the print head by the driving unit. The conveyed recording medium is heated from the surface side facing away from the ink landing surface by a heating means provided at a position facing the ink ejection surface of the print head. The recording medium is heated by the heating unit and the preheating unit so that the surface temperature of the ink landing surface of the recording medium is 40 ° C. or more and 60 ° C. or less.

  The ink ejected from the print head is an ink containing a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent (hereinafter referred to as latex ink). An ink having a minimum surface forming temperature of 0 ° C. or lower is used. Such ink is particularly excellent in environmental characteristics and media characteristics.

  Thus, the latex ink ink ejected from the nozzles of the print head onto the surface of the recording medium heated to a surface temperature of 40 ° C. or more and 60 ° C. or less by the preheating means and the heating means. Drops can be landed. Therefore, the ink droplets can be quickly dried and fixed in a short time without being diffused on the recording medium around the landing spot, while being fixed in a dot shape at the landing spot. Then, it is possible to print a clear picture or character having no blur and comprising a plurality of latex ink dot arrays on the surface of the recording medium.

  Here, by heating the surface temperature of the recording medium to 40 ° C. or higher, the heating temperature that the latex ink droplets landed on the surface of the recording medium receive from the recording medium can be made sufficient. In addition, by heating the surface temperature of the recording medium to 60 ° C. or less, even when a film such as vinyl chloride having low heat resistance is used as the recording medium, the recording medium is not damaged by heat. The driving means can smoothly convey the platen. Therefore, according to the present invention, almost all recording media from a recording medium with low heat resistance to a recording medium with high heat resistance can be applied. As described above, the reason for heating the recording medium so that the surface temperature is 40 ° C. or more and 60 ° C. or less is that the surface of various recording media using the latex ink by the ink jet printer according to the present invention. Based on the results of experiments in which pictures and characters were actually printed, the present inventors diligently studied and derived.

  Further, the binder resin contained in the latex ink used in the present invention has a core / shell structure including a core portion located inside and a shell portion located on the surface. Since the minimum film forming temperature (MFT) on the surface of the binder resin is 0 ° C. or lower, the latex ink is dried on the recording medium heated so that the surface temperature is 40 ° C. or higher and 60 ° C. or lower. And fusion can be started quickly.

  Further, the surface temperature of the recording medium at the time of ink landing is set to 40 ° C. or more and 60 ° C. or less suitable for drying and fusing of the latex ink by heating in two stages by the preheating means and the heating means. To do. Therefore, even if the recording medium cannot be sufficiently heated to an appropriate temperature by only the heating means due to the thickness of the recording medium, the ambient temperature where the ink jet printer is placed, etc., the temperature of the recording medium is reduced to a certain level. When the ink is landed, the surface of the recording medium can be heated to a desired temperature.

  Further, since the heating means is disposed at a position facing the ink ejection surface of the print head, when the surface of the recording medium is heated to 40 ° C. or more and 60 ° C. or less with only the heating means, the heating means Due to this heat generation, there is a problem that the ink is solidified and clogged in the small nozzle of the print head. According to the present invention, the surface temperature of the recording medium at the time of ink landing is set to 40 ° C. or more and 60 ° C. or less by heating in two stages by the preheating means and the heating means. The surface of the recording medium can be heated to a desired temperature without heating the heating means at a high temperature by heating in advance to a certain temperature by the means. Therefore, it is possible to prevent the ink from solidifying in the nozzles of the print head due to heat generated from the heating means and causing clogging.

  According to the present invention, even for recording media used for outdoor display advertisements and industrial applications that require high environmental characteristics and media characteristics, high image quality and fixing stability of printed pictures and characters can be achieved. Can be realized.

  In the printing method according to the present invention, it is preferable that the binder resin has a minimum film forming temperature different between the surface and the inside.

  According to the above configuration, by varying the minimum film forming temperature between the surface and the inside of the core / shell structure of the binder resin, the timing of drying and fusing between the surface and the inside of the binder resin is shifted, Separation effect can be obtained. For example, after the surface of the binder resin is dried and fused on the recording medium appropriately heated by the preheating means and the heating means, the inside of the binder resin is dried, for example, after the ink has landed. You may comprise so that it may dry and fuse | melt by the drying means to make.

  The temperature when drying ink in a conventional ink jet printer is usually set to about 80 ° C., but the drying temperature of latex ink is actually assumed to be about 50 to 60 ° C. As described above, by separately drying and fusing the surface and the inside of the binder resin, the heating temperature by the heating means at the position facing the ink ejection surface of the print head is set to a temperature at which ink clogging can be avoided. In addition, the latex ink can be reliably dried and fixed by a preheating means, for example, an after heater or the like.

  In the printing method according to the present invention, the binder resin preferably has a minimum surface film forming temperature lower than an internal minimum film forming temperature.

  According to the above configuration, since the minimum film forming temperature inside the binder resin in the latex ink is higher than the minimum film forming temperature on the surface, the storage stability of the latex ink at a high temperature is improved. Then, the surface of the binder resin having the lowest minimum film forming temperature starts to be quickly dried and fused on the recording medium heated by the preheating means and the heating means. As a result, the surface of the binder resin having a low minimum film-forming temperature in latex ink, which has extremely high diffusibility (wetting and spreading) with respect to the recording medium, and ink droplets tend to diffuse widely around the landed area at an early stage. Can be clearly fixed on the landing spot without blurring of dots. Thereafter, for example, the latex ink that has landed on the recording medium is sufficiently dried and fused inside the binder resin having a high minimum film-forming temperature by an after heater or a drying means according to the recording medium conveyance direction. Sequential drying, fusing, and fixing can be performed.

  In the printing method according to the present invention, the solvent is at least one of water and a hydrophilic solvent, and the latex ink preferably contains 50% by weight or more of the solvent with respect to the total weight of the latex ink.

  According to the above configuration, the environmental load of the ink can be reduced due to the high content of at least one of water and the hydrophilic solvent in the latex ink.

  In the printing method according to the present invention, it is preferable that the heating temperature of the recording medium by the heating unit and the heating temperature of the recording medium by the preliminary heating unit are controlled to different temperatures.

  According to the above configuration, the temperature of the recording medium being conveyed can be separately controlled at each of a position facing the ink ejection surface of the print head and a position before the position. Therefore, the recording medium at each position can be accurately adjusted according to the type and thickness thereof, the temperature around the printer, and the like. Therefore, the temperature at the surface portion of the recording medium when the ink droplets ejected from the ink ejection surface of the print head land can be accurately adjusted to 40 ° C. or more and 60 ° C. or less.

  In the printing method according to the present invention, the preheating means heats the surface temperature of the ink landing surface of the recording medium to 30 ° C. or more and 50 ° C. or less, and the heating means sets the ink landing surface of the recording medium. It is preferable to heat the surface temperature to 40 ° C. or higher and 60 ° C. or lower.

  According to the above configuration, the surface temperature of the ink landing surface is preheated to 30 ° C. or more and 50 ° C. or less by the preheating unit before the recording medium is conveyed to the position facing the ink ejection surface of the print head. To do. Subsequently, the surface temperature of the ink landing surface is heated to 40 ° C. or more and 60 ° C. or less by the heating means for the recording medium conveyed to the position facing the ink ejection surface of the print head after preheating. As a result, when ink droplets ejected from the nozzles of the print head land on the recording medium, the surface temperature can be surely and reliably heated so that the surface temperature becomes 40 ° C. or more and 60 ° C. or less.

  In the printing method according to the present invention, it is preferable that the heating temperature of the recording medium by the heating unit and the heating temperature of the recording medium by the preliminary heating unit are controlled to the same temperature.

  According to the above configuration, the temperature control of the preheating means and the temperature control of the heating means can be controlled in the same manner, so that the temperature control can be simplified.

  In the printing method according to the present invention, as the recording medium, a vinyl chloride sheet, a PET sheet, a tarpaulin sheet, a coated paper not coated with a coating agent, and an uncoated polypropylene resin, glass, metal, and A recording medium selected from the group consisting of these molded products can be used.

  According to the above configuration, even a general-purpose recording medium to which a coating agent or the like is not applied can print high-quality pictorial figures and characters without bleeding with fixing stability. Moreover, according to said structure, it is possible to always convey smoothly smoothly various types of recording media including the recording medium softened at low temperature. That is, various recording media from a recording medium with low heat resistance to a recording medium with high heat resistance are transported without hindrance, and a high-quality picture image without blurring on such various recording media. And characters can be printed with fixing stability.

  In the printing method according to the present invention, the ink jet printer performs preheating means for heating the recording medium and temperature control of the heating means by an operation panel attached to the printer or a host computer for printer control to which the printer is connected. It is preferable that the configuration can be changed and adjusted.

  According to the above configuration, the operation panel attached to the printer or the printer control host is set in accordance with the preheating means and the heating temperature by the heating means in accordance with the type and thickness of the recording medium, the ambient temperature where the printer is placed, etc. Can be changed and adjusted by computer. In addition, various recording media that are softened at a low temperature and the like can always be smoothly transported, and high-quality pictorial figures and characters that do not bleed on such various recording media have fixing stability. Can be printed.

  In the method according to the present invention, the ink jet printer moves the print head to a maintenance station, performs a trial discharge (flushing) of ink droplets from the nozzle of the print head, and the latex ink is solidified in the nozzle of the print head. It is preferable to provide refresh mode means for preventing clogging.

  According to the above configuration, while printing a picture or character using latex ink, the print head is moved to the maintenance station using the refresh mode means, and ink droplets are ejected from the nozzle of the print head by trial ejection. Can do. Thereby, it is possible to prevent clogging caused by solidification of the latex ink in the nozzle of the print head or the like. As a result, dots are missing from a part of a picture or character printed on the surface of the recording medium using the clogged print head (the ink dot does not exist in a place where the ink dot should exist). Can be prevented.

  In the method according to the present invention, an ink jet printer provided with a refresh mode means moves the print head to a maintenance station at regular intervals, and ejects ink droplets from the nozzles of the print head. It is preferable to make it.

  According to the above configuration, the print head is moved to the maintenance station using the refresh mode means at regular intervals during the printing of pictures and characters using latex ink, and ink droplets are ejected from the nozzles of the print head. Test ejection can be forced. And while printing pictures and characters using latex ink, the print head is moved to the maintenance station using the refresh mode means, so by neglecting to eject ink droplets from the nozzles of the print head It is possible to reliably prevent the latex ink from solidifying in the nozzles of the print head and causing the nozzles to be clogged.

  In the method according to the present invention, the ink jet printer is a drying unit that dries the ink droplets attached to the surface of the recording medium by drying the recording medium after the ink droplets ejected from the print head have landed. It is preferable to provide.

  According to the above configuration, the ink droplets that are partly undried attached to the surface of the recording medium can be completely dried by the drying means. Then, after the recording, for example, when the recording medium is wound up by a winding means, partially undried ink droplets adhering to the landing spot on the surface of the recording medium wound up in a roll shape or the like, It can be prevented that the recording medium adheres to other portions of the recording medium and is stained.

  The printing method according to the present invention is a printing method for printing a recording medium using an inkjet printer, and heating is performed so that the surface temperature of the ink landing surface of the recording medium is 40 ° C. or more and 60 ° C. or less. The recording medium is heated by the means and the preheating means, and the ink discharged from the print head includes a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent. Since ink having a minimum film forming temperature of 0 ° C. or less on the surface of the binder resin is used, it is possible to print clear pictures and characters without bleeding.

It is side surface sectional drawing which shows schematic structure of the inkjet printer which concerns on this invention. 1 is a front view showing a schematic structure of an ink jet printer according to the present invention. It is side surface sectional drawing which shows schematic structure of the other inkjet printer which concerns on this invention. It is side surface sectional drawing which shows schematic structure of the conventional inkjet printer.

  A printing method according to an embodiment of the present invention is provided at a position facing the ink ejection surface of the print head, a driving unit that relatively moves the positions of the print head, the recording medium, and the print head, Heating means for heating the recording medium disposed at the position by the driving means from the side facing away from the ink landing surface of the recording medium, and the recording medium facing the ink ejection surface of the print head The recording medium is printed using an ink jet printer provided with a preheating unit that heats the recording medium from a side facing away from the ink landing surface at a position before the position where the recording medium is disposed. A method of printing, wherein the recording medium is recorded by the heating unit and the preheating unit so that the surface temperature of the ink landing surface of the recording medium is 40 ° C. or more and 60 ° C. or less. The ink that heats the body and is ejected from the print head includes a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent. An ink having a film temperature of 0 ° C. or lower is used.

<Inkjet printer 1>
First, an example of an inkjet printer used in a printing method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side sectional view showing a schematic structure of an ink jet printer according to the present invention, and FIG. 2 is a front view showing a schematic structure of the ink jet printer according to the present invention.

  As shown in FIGS. 1 and 2, the inkjet printer 1 includes a print head 14, a printing unit 10, a conveying unit 60, a print heater (heating unit) 70, and a preheater (preheating unit) 40. The printing unit 10 that scans the print head 14 and the conveyance unit 60 that conveys the medium 30 function as a driving unit (driving unit) that relatively moves the positions of the medium 30 and the print head 14.

[Print head 14]
The print head 14 has a structure in which ink droplets of latex ink, which will be described later, are ejected from the nozzles 12 arranged on the lower surface by a piezo method or the like. The print head 14 is supported by the head drive belt 16 constituting the printing means 10 shown in FIG.

[Printing means 10]
The printing unit 10 relatively moves the positions of the print head 14 and the medium 30 by causing the print head 14 to scan above the platen 20 in a direction intersecting the conveyance direction of the medium 30.

[Conveying means 60]
The conveying means 60 includes a feed roller 62 and a presser roller 64 that are provided to face each other with the platen 20 interposed therebetween. Then, the medium 30 is sandwiched between the feed roller 62 and the presser roller 64 and the feed roller 62 is rotated forward (in the direction of the arrow in FIG. 1), so that the media 30 is directed forward on the platen 20. It has a structure to convey.

[Print heater 70]
The print heater 70 is provided at a position facing the ink ejection surface of the print head 14, and heats the medium 30 disposed at the position by the transport unit 60 from the side facing away from the ink landing surface of the medium 30. . The print heater 70 is provided at a position facing the platen central portion 22 with the medium 30 interposed therebetween. The print heater 70 heats the medium 30 conveyed on the platen central portion 22 from the back surface of the ink droplet landing surface.

  The print heater 70 only needs to have a structure for heating the media 30 by transferring heat to the media 30 conveyed on the platen central portion 22 via the platen 20. As such a print heater 70, an electric heater using a ceramic or nichrome wire can be used.

[Preheater 40]
The pre-heater 40 heats the medium 30 from the side facing away from the ink landing surface at a position before the position facing the ink ejection surface of the print head 14. The pre-heater 40 is provided at a position facing the platen rear portion 24 with the medium 30 interposed therebetween. The preheater 40 preheats the medium 30 by heating the medium 30 conveyed on the platen rear part 24 from the back of the ink droplet landing surface.

  The pre-heater 40 may have a structure for preliminarily heating the medium 30 by transferring heat to the medium 30 conveyed on the platen rear portion 24 via the platen 20. As such a preheater 40, an electric heater using a ceramic or nichrome wire can be used.

[Temperature control means 80]
The ink jet printer 1 may further include a temperature control unit 80. The temperature controller 80 controls the preheater 40 and the print heater 70 so that the surface temperature of the ink landing surface of the medium 30 is 40 to 60 ° C. when the ink ejected from the print head 14 lands on the medium 30. Control the heating temperature. The temperature control means 80 can be composed of a combination of a sensor that detects the heat generation temperature of the preheater 40 and the print heater 70, an electronic circuit that controls the heat generation temperature, and the like.

  The temperature control means 80 may be configured such that the heating temperatures of the pre-heater 40 and the print heater 70 can be controlled independently. That is, the temperature control means 80 may control the heating temperatures of the preheater 40 and the print heater 70 to different temperatures. Thereby, the temperature control means 80 adjusts each heating temperature of the pre-heater 40 and the print heater 70 separately according to the type and thickness of the medium 30, the temperature around the ink jet printer, and the like. Can do. As a result, the surface temperature of the ink landing surface of the medium 30 can always be accurately heated so that the desired temperature is 40 ° C. or higher and 60 ° C. or lower.

  The temperature control means 80 may control the heating temperature of the preheater 40 and the print heater 70 to the same temperature. Thereby, the temperature control of the pre-heater 40 and the print heater 70 can be controlled in the same manner, so that the temperature control can be simplified.

  The temperature control means 80 controls the preheater 40 to heat the surface temperature of the ink landing surface of the medium 30 to 30 ° C. or more and 50 ° C. or less, and the print heater 70 controls the surface temperature of the ink landing surface of the medium 30. It is preferable to control so that it heats to 40 degreeC or more and 60 degrees C or less. As a result, when ink droplets land on the medium 30, the surface temperature can be always reliably heated so as to be 40 ° C. or more and 60 ° C. or less.

[Media 30]
In the inkjet printer 1, from the group consisting of a vinyl chloride sheet, a PET sheet, a tarpaulin sheet, a coated paper to which a coating agent is not applied, and a polypropylene resin, glass, metal, and a molded product that are not coated. The selected media can be used as the media 30.

  In the inkjet printer 1, even a general-purpose medium to which a coating agent or the like is not applied can print high-quality pictorial figures and characters without bleeding with fixing stability. In addition, in the inkjet printer 1, various types of media, including media that soften at low temperatures, can be appropriately heated and always conveyed smoothly. In other words, the inkjet printer 1 transports various media from media having low heat resistance to media having high heat resistance without any trouble, and high-quality pictures and characters that do not bleed on such various media. Can be printed with fixing stability.

[Host computer 120]
The inkjet printer 1 may further include a host computer 120. The host computer 120 controls heating by the preheater 40 and the print heater 70 and temperature control by the temperature control means 80. Further, the host computer 120 controls printing operations such as ejection of ink from the print head 14 and conveyance of the medium 30 by the conveyance unit 60. The host computer 120 may be an operation panel attached to the inkjet printer 1.

[Rewinding means 90 and winding means 100]
The inkjet printer 1 may further include rewinding means 90 and winding means 100. The rewinding means 90 is provided behind the platen 20 (in the direction opposite to the arrow direction in FIG. 1), rewinds the media 30 wound in a roll shape, and sends the media 30 toward the platen central portion 22.

  The winding means 100 is provided in front of the platen 20 (in the direction of the arrow in FIG. 1), and winds the printed medium 30 fed forward from the platen front portion 26 in a roll shape.

[Refresh mode means 140]
The inkjet printer 1 may include a refresh mode unit 140 as shown in FIG. The refresh mode unit 140 moves the print head 14 to the maintenance station 130 and causes ink droplets to be ejected from the nozzles 12 of the print head 14 into the tray 110 provided in the maintenance station 130 (flushing). Thereby, it is possible to prevent the latex ink from solidifying in the nozzle 12 and causing clogging. As a result, by using the clogged print head 14, it is possible to prevent missing dots in a part of a picture or character printed on the surface of the medium 30.

  In addition, the refresh mode unit 140 may cause the print head 14 to move to the maintenance station 130 and perform test ejection while printing a picture or character on the surface of the medium 30 using latex ink. Further, the refresh mode means 140 can also make a trial discharge by moving the print head 14 to the maintenance station 130 at regular intervals during the printing of pictures and characters on the surface of the medium 30 using latex ink. As a result, since it was neglected to eject ink droplets from the nozzle 12 of the print head 14 during printing, the latex ink is solidified in the nozzle 12 of the print head and the nozzle 12 is clogged. Can be surely prevented. The refresh mode means 140 may be constituted by an electronic circuit of the host computer 120 for printer control.

<Inkjet printer 2>
The ink jet printer 1 may further include a drying unit 150 and may be configured like the ink jet printer 2 shown in FIG. FIG. 3 is a side sectional view showing a schematic structure of another ink jet printer according to the present invention.

[Drying means 150]
As shown in FIG. 3, the inkjet printer 2 includes a drying unit 150 that dries ink droplets adhering to the surface of the medium 30 conveyed on the platen front portion 26. The drying unit 150 can dry ink that is partially undried out of the ink that has landed on the surface of the medium 30 ejected from the print head 14. As a result, the partially dried ink droplets attached to the surface of the medium 30 that is wound in a roll shape from the platen front portion 26 to the winding means 100 in front of the platen 26 are wound in the roll shape. It is possible to prevent the medium 30 from adhering to other portions and being stained with ink.

  As shown in FIG. 3, the drying unit 150 may dry the ink droplets from the ink landing surface side of the medium 30, or dry the ink droplets from the surface side facing away from the ink landing surface of the medium 30. It may be allowed. As such a drying means 150, a warm air dryer, an infrared dryer, a heater dryer using a ceramic, a nichrome wire, or the like can be used alone or in combination.

<Printing method>
A printing method according to the present invention using the ink jet printer 1 as described above will be described. First, the media 30 wound in a roll shape is rewound from the rewinding means 90 toward the platen rear part 24, and is conveyed onto the platen rear part 24 by the conveying means 60. Then, the media 30 conveyed onto the platen rear portion 24 is preheated by the preheater 40 from the surface side facing away from the ink landing surface.

  Next, the preheated medium 30 is transported onto the platen central portion 22 by the transport means 60. Here, the printing unit 10 scans the print head 14 to discharge latex ink from the ink discharge surface of the print head 14 at a desired position. At this time, the medium 30 is heated by the print heater 70 from the surface facing the ink landing surface.

  The temperature control means 80 controls the heating by the preheater 40 and the print heater 70 so that the surface temperature of the ink landing surface of the medium 30 when the ink ejected from the print head 14 lands on the medium 30 is 40 ° C. or higher. Set to 60 ° C or lower.

  Therefore, the ink droplets that have landed on the medium 30 can be quickly dried and fixed in a state where the ink droplets are fixed in the form of dots at the landing locations without spreading widely around the landing locations. Then, it is possible to print a clear picture or character having no blur and comprising a plurality of latex ink dot arrays on the surface of the medium 30.

  Here, by heating the surface temperature of the medium 30 to 40 ° C. or higher, the heating temperature that the latex ink droplets landed on the surface of the medium 30 receives from the medium 30 can be made sufficient. In addition, by heating the surface temperature of the medium 30 to 60 ° C. or less, even when a film such as vinyl chloride having low heat resistance is used as a recording medium, the recording medium is not damaged by heat, The top of the platen 20 can be smoothly transported by the transport means 60. Therefore, the printing method according to the present embodiment can apply almost all the media 30 from the media 30 with low heat resistance to the media 30 with high heat resistance. As described above, the reason why the medium 30 is heated so that the surface temperature is 40 ° C. or more and 60 ° C. or less is that the ink jet printer according to the present invention uses the latex ink to display the drawings on the surfaces of various media 30. Based on the experimental results of actually printing characters and characters, the present inventors have intensively studied and derived.

  Further, the binder resin contained in the latex ink has a core / shell structure including a core portion located inside and a shell portion located on the surface. Since the minimum film forming temperature (MFT) on the surface of the binder resin is 0 ° C. or less, the latex ink is dried and dried on the medium 30 heated so that the surface temperature is 40 ° C. or more and 60 ° C. or less. Fusion can be started quickly. Details of the latex ink will be described later.

  Further, the preheater 40 and the print heater 70 are used to heat in two stages, and finally the surface temperature of the medium 30 when ink is landed is set to 40 ° C. or more and 60 ° C. or less suitable for drying and fusing of the latex ink. . Therefore, due to the influence of the thickness of the medium 30 and the ambient temperature where the ink jet printer 1 is placed, the print medium 70 alone cannot sufficiently heat the medium 30 conveyed on the platen central portion 22 to an appropriate temperature. However, by preheating to a certain temperature with the preheater 40, the surface of the medium 30 can be heated to a desired temperature at the time of ink landing.

  Since the print heater 70 is disposed at a position facing the ink ejection surface of the print head 14, if the surface of the medium 30 is heated to 40 ° C. or more and 60 ° C. or less with only the print heater 70, the print heater 70 There is a problem that ink is solidified and clogged in the small nozzles of the print head 14 due to heat generated from the heater 70. In the printing method according to the present embodiment, the preheater 40 and the print heater 70 heat the ink in two stages so that the surface temperature of the medium 30 at the time of ink landing is 40 ° C. or higher and 60 ° C. or lower. By preheating to a certain temperature with the preheater 40, the surface of the media 30 can be heated to a desired temperature without causing the print heater 70 to generate heat at a high temperature. Therefore, it is possible to prevent the ink from solidifying in the nozzles of the print head 14 due to heat generated from the print heater 70 and causing clogging.

  In this way, the medium 30 on which the drawings and characters composed of a plurality of latex ink dot arrays are printed on the surface thereof is conveyed by the conveying means 60 from the platen central portion 22 to the platen front portion 26. . Then, the medium 30 is wound up in a roll shape by the winding means 100 in front of the platen 20, and the printing is finished.

<Latex ink>
The ink used in the printing method according to the present embodiment includes a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent, and the minimum film formation on the surface of the binder resin. The ink has a temperature of 0 ° C. or lower. An ink containing a solvent, a colorant, and a binder resin, in which the binder resin is dispersed or emulsified in the solvent, is referred to as a latex ink. The latex ink is an emulsion containing a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent.

〔solvent〕
The solvent contained in the latex ink is preferably at least one of water and a water-soluble organic solvent.

  Specific examples of the water-soluble organic solvent include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, and 1,3-butanediol. 3-methyl-1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol, 1,2,6-hexanetriol Polyhydric alcohols such as 1,2,4-butanetriol, 1,2,3-butanetriol, 2-methyl-2,4-pentanediol, petriol, 3-methoxy-3-methyl-1-butanediol Class: Ethylene glycol monoe Polyhydric alcohol alkyl ethers such as ether ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monophenyl ether, ethylene glycol monobenzyl Polyhydric alcohol aryl ethers such as ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, diethylene glycol isobutyl ether, triethylene glycol isobutyl ether, diethylene glycol isopropyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N- Nitrogen-containing heterocyclic compounds such as droxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; mono Amines such as ethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane, thiodiethanol, thiodiglycol; propylene carbonate, ethylene carbonate, trimethylolpropane, tetramethyl Examples include urea and urea.

  Among these water-soluble organic solvents, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butane Diol, 1,5-pentanediol, tetraethylene glycol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexane Triol, thiodiglycol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are more preferred. These water-soluble organic solvents are excellent in solubility and excellent in preventing poor jetting characteristics due to water evaporation.

  The latex ink may contain a water-soluble organic solvent as described above alone or in combination of two or more.

  The content of the solvent in the latex ink may be appropriately set according to the purpose of printing and the like. For example, it is preferably 50% by weight or more, and preferably 60% by weight or more with respect to the total amount of the latex ink. More preferably, it is most preferably 70% by weight or more. Latex inks preferably have a higher solvent content than ordinary aqueous inkjet inks. This is because latex ink is recognized as an eco ink that reduces the environmental burden.

[Colorant]
The colorant contained in the latex ink can be appropriately selected according to the purpose of printing. Examples of the colorant include water-soluble dyes, oil-soluble dyes, disperse dyes, and the like, and pigments. As the colorant, an oil-soluble dye and a disperse dye are preferable from the viewpoint of good adsorption and encapsulation, but a pigment is preferably used from the viewpoint of light resistance of the obtained image.

  The colorant is preferably a material that can be easily dissolved in a water-soluble organic solvent in order to be efficiently dissolved in the latex ink. For example, it is preferable that the colorant is 2 g / L or more in a ketone solvent. It is more preferable to dissolve ~ 600 g / L.

  The content of the colorant in the latex ink is preferably 10 to 200 parts by weight and more preferably 25 to 150 parts by weight with respect to 100 parts by weight of the latex ink.

  The colorant contained in the latex ink is more preferably polymer grafted. Examples of the polymer-grafted colorant include Synthesis Example 1 (carbon black), Synthesis Example 2 (yellow pigment), Synthesis Example 3 (magenta pigment), and Synthesis Example 4 (cyan pigment) in the following examples. And the polymer graft colorants shown.

  Moreover, it is more preferable that the colorant contained in the latex ink contains a polymer. Examples of the colorant containing the polymer include, in the following examples, Synthesis Example 5 (resin synthesis), Synthesis Example 6 (phthalocyanine), Synthesis Example 7 (quinacridone), Synthesis Example 8 (monoazo yellow pigment), and The polymer inclusion colorant shown to the synthesis example 9 (carbon black) is mentioned.

  Furthermore, a resin-coated colorant can also be suitably used as the colorant contained in the latex ink. The resin-coated colorant comprises a polymer emulsion in which polymer fine particles contain a water-insoluble or poorly water-soluble colorant. In the present specification, “containing a colorant” means either or both of a state in which a colorant is encapsulated in polymer fine particles and a state in which a colorant is adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all the colorant blended in the latex ink to be encapsulated or adsorbed in the polymer fine particles, even if the colorant is dispersed in the emulsion as long as the effect of the present invention is not impaired. Good. The colorant is not particularly limited as long as it is water-insoluble or poorly water-soluble and can be adsorbed by a polymer.

  In the present specification, when 10 parts by weight or more of the colorant is not dissolved in 100 parts by weight of water at 20 ° C., the colorant is assumed to be water-insoluble or poorly water-soluble. Under the same conditions, when no separation or sedimentation of the colorant is observed on the surface layer or lower layer of the aqueous solution, the colorant is water-soluble.

  As the polymer that forms the polymer emulsion, for example, vinyl polymers, polyester polymers, polyurethane polymers, and the like can be used. Polymers particularly preferably used are vinyl polymers and polyester polymers, and specifically disclosed in JP-A-2000-53897 (Reference 1) and JP-A-2001-139849 (Reference 2). Suitable polymers are mentioned.

  The colorant used in the present invention is more preferably a pigment. However, a dye can be used for the resin-coated colorant, and an example of this water-soluble dye is shown below. Those having excellent water resistance and light resistance are preferably used.

(Pigment)
Examples of the pigment used as the colorant include carbon black as a black pigment. Examples of the color pigment include anthraquinone, phthalocyanine blue, phthalocyanine green, diazo, monoazo, pyranthrone, perylene, heterocyclic yellow, quinacridone, and (thio) indigoid. Representative examples of phthalocyanine blue include copper phthalocyanine blue and its derivatives (Pigment Blue 15). Representative examples of quinacridone include Pigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Violet 19, and Pigment Violet 42. including. Representative examples of anthraquinone include Pigment Red 43, Pigment Red 194 (Perinone Red), Pigment Red 216 (brominated pyrantron red), and Pigment Red 226 (Pyrantron Red). Representative examples of pyrelin include Pigment Red 123 (Bell Million), Pigment Red 149 (Scarlet), Pigment Red 179 (Maroon), Pigment Red 190 (Red), Pigment Violet, Pigment Red 189 (Yellow Shade Red), And Pigment Red 224. Representative examples of thioindigoid include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181, Pigment Red 198, Pigment Violet 36, and Pigment Violet 38. Representative examples of heterocyclic yellow include pigment yellow 117 and pigment yellow 138.

  Examples of other suitable pigments include those described in The Color Index 3rd edition (The Society of Dyers and Colorists, 1982).

  As the pigment contained in the latex ink, a pigment having at least one hydrophilic group bonded to the pigment surface directly or through another atomic group and capable of being stably dispersed without using a dispersant is used. be able to. As the pigment having a hydrophilic group introduced on the surface, an ionic one is preferable, and an anionic charged one or a cationic one is preferable.

Examples of the anionic hydrophilic group, for _{example, -COOM, -SO 3 M, -PO} 3 HM, -PO 3 M 2, -SO 2 NH 2, -SO 2 NHCOR ( where, M in the formula is a hydrogen atom, Represents an alkali metal, ammonium or organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. It is done. Among these, it is particularly preferable to use those in which —COOM or —SO ₃ M is bonded to the pigment surface. Examples of a method for obtaining an anionically charged pigment include, but are not limited to, a method of oxidizing a pigment with sodium hypochlorite, a method of sulfonation, and a method of reacting a diazonium salt.

  The hydrophilic group bonded to the cation-charged color pigment surface can be, for example, a quaternary ammonium group. More preferably, a pigment in which at least one of the quaternary ammonium groups listed below is bonded to the pigment surface is used.

(Dispersant)
When the colorant contained in the latex ink is a pigment, a pigment dispersion in which the pigment is dispersed in a solvent by a dispersant may be used.

  As a preferable dispersant, a known dispersant used for preparing a pigment dispersion can be used. For example, polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer. Polymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, stin-methacrylic acid-acrylic acid Alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid copolymer-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, vinylnaphthalene -Maleic acid copolymer, vinyl acetate-ethylene copolymer, vinegar Examples thereof include polymer type dispersants such as vinyl acid-fatty acid vinylethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer.

  The nonionic or anionic dispersant used to disperse the pigment can be appropriately selected according to the pigment type or the ink formulation. Examples of the nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene Polyoxyethylene alkyl ethers such as oxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene α Naphthyl ether, polyoxyethylene beta naphthyl ether, polyoxyethylene monostyryl phenyl ether, polyoxyethylene distyryl phenyl ether, Examples thereof include polyoxyethylene alkyl naphthyl ether, polyoxyethylene monostyryl naphthyl ether, polyoxyethylene distyryl naphthyl ether, polyoxyethylene polyoxypropylene block copolymer, and the like.

  In addition, a dispersant obtained by replacing a part of polyoxyethylene in the above-described dispersant with polyoxypropylene, or a dispersant obtained by condensing a compound having an aromatic ring such as polyoxyethylene alkylphenyl ether with formalin or the like can also be used.

  The HLB of the nonionic dispersant is preferably from 12 to 19.5, more preferably from 13 to 19. By using a nonionic dispersant having an HLB of 12 or more, the familiarity of the dispersant with the dispersion medium is improved, and the dispersion stability is improved. Further, by using a nonionic dispersant having an HLB of 19.5 or less, the dispersant is easily adsorbed to the pigment, and the dispersion stability is improved. When a plurality of nonionic dispersants are mixed and used, the HLB after mixing may be adjusted to 12 or more and 19.5 or less.

  Anionic dispersants include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate, polyoxyethylene alkyl ether phosphate Salt, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl phenyl ether carboxyl Acid salt, polyoxyethylene monostyryl phenyl ether carboxylate, polyoxyethylene distyryl phenyl ether carboxylate, naphthalene sulfone Acid salt formalin condensate, melanin sulphonate formalin condensate, dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin sulphonate, alkylbenzene sulphonic acid Salts, alkyl naphthalene sulfonates, alkyl sulfonates, N-acyl amino acid salts, acylated peptides, soaps, etc., among these, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene Distyryl phenyl ether sulfate or phosphate is particularly preferred.

  The added amount of the dispersant is preferably 10% by weight or more and 50% by weight or less based on the total weight of the pigment. By making the addition amount of the dispersant 10% by weight or more with respect to the total weight of the pigment, the storage stability of the pigment dispersion and the ink can be maintained, and the time for dispersion can be shortened. By making the addition amount of the dispersant 50% by weight or less with respect to the total weight of the pigment, the viscosity of the ink can be lowered and the ejection stability can be improved.

  The polymer type dispersant, the nonionic dispersant, and the anionic dispersant described above may be used alone or in combination of two or more according to the purpose.

(dye)
Specific examples of dyes as colorants contained in latex inks include acid dyes and food dyes such as C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142; C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 289; I. Acid Blue 9, 29, 45, 92, 249; I. Acid Black 1, 2, 7, 24, 26, 94; I. Food Yellow 3, 4; I. Food red 7, 9, 14; I. Food black 1, 2 etc. are mentioned.

  Examples of direct dyes include C.I. I. Direct yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144; I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227; I. Direct orange 26, 29, 62, 102; I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202; I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 etc. are mentioned.

Examples of basic dyes include C.I. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91; I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112; I. Basic blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93, 105, 117, 120, 122, 1
24, 129, 137, 141, 147, 155; I. Basic black 2, 8 etc. are mentioned.

  Examples of reactive dyes include C.I. I. Reactive black 3, 4, 7, 11, 12, 17; I. Reactive Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67; I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97; I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95 etc. are mentioned.

  As the colorant contained in the latex ink, the above-mentioned pigments and dyes can be appropriately selected according to the purpose of printing, and the above-mentioned pigments and dyes are used alone or in combination of two or more. May be.

[Binder resin]
The binder resin contained in the latex ink has a core / shell structure composed of a core part (inside) and a shell part (surface) covering the core part, and the minimum film forming temperature (MFT) of the shell part. Is 0 ° C. or lower. Thereby, the drying and fusing of the latex ink can be quickly started on the medium 30 heated so that the surface temperature is 40 ° C. or more and 60 ° C. or less.

  In the binder resin, the minimum film forming temperature of the shell part and the minimum film forming temperature of the core part may be different.

  Thereby, the timing of the drying and fusion | bonding with the shell part and core part of binder resin can be shifted, and the function separation effect can be acquired. For example, after the binder resin shell portion is dried and fused on the medium 30 appropriately heated by the preheater 40 and the print heater 70, the binder resin core portion is, for example, a recording medium after ink landing. You may comprise so that it may dry and fuse | melt by the drying means 150 to dry.

  The temperature when drying ink in a conventional ink jet printer is usually set to about 80 ° C., but the drying temperature of latex ink is actually assumed to be about 50 to 60 ° C. Even if the heating temperature by the print heater 70 at a position facing the ink discharge surface of the print head is set to a temperature at which ink clogging can be avoided by separately drying and fusing the shell portion and the core portion of the binder resin, The latex ink can be reliably dried and fixed by the pre-heater 40 or, for example, a drying means.

  Another reason why the binder resin makes the minimum film forming temperature of the shell portion different from the minimum film forming temperature of the core portion is that the storage stability of the binder resin is more stable. Specifically, by utilizing the characteristics of both phases having different minimum film-forming temperatures (MFT) (hereinafter simply referred to as “MFT”), high MFT phase and low MFT phase, In particular, both the fixability and the storage stability can be enhanced while maintaining the balance. In addition, the latex ink according to the present invention including the binder resin having such a configuration has good reliability, printing quality such as bleeding, abrasion resistance, and ejection stability.

  Further, since the MFT of the shell portion is low, the film is formed immediately after being ejected and landed, so that it is possible to cope with high-speed printing.

  Although MFT of a shell part should just be lower than MFT of a core part, it is more preferable that it is 0 degrees C or less. A shell portion having an MFT of 0 ° C. or lower (hereinafter, also referred to as “low MFT phase”) can be formed into a film at room temperature, whereby the fixability upon ink landing can be improved. The MFT of the low MFT phase may be 0 ° C. or lower, but in order to further enhance the effect, it is preferably −20 ° C. or higher and 0 ° C. or lower.

  Moreover, although MFT of a core part should just be higher than MFT of a shell part, it is more preferable that it is 10 degreeC or more. In the core portion having an MFT of 10 ° C. or higher (hereinafter also referred to as “high MFT phase”), the binder resin particles are likely to spread on the medium 30 and the pigment as the colorant is easily fixed on the recording medium. Further, it is also preferable because the binding of paper fibers automatically proceeds without particularly performing treatment such as heating or drying on the image-formed image support. The MFT of the high MFT phase is preferably 10 ° C. or higher as described above, but more preferably 20 ° C. or higher in order to further enhance the effect.

  Here, “minimum film-forming temperature (MFT)” means that when an aqueous emulsion obtained by dispersing a binder resin in water is thinly cast on a metal plate such as aluminum and the temperature is raised. Defined as the lowest temperature at which a transparent continuous film is formed.

  Specifically, MFT is a value measured by an MFT measuring apparatus such as “film-forming temperature test apparatus” (manufactured by Imoto Seisakusho Co., Ltd.), “TP-801 MFT tester” (manufactured by Tester Sangyo Co., Ltd.), and the like. Moreover, it can also measure by the measuring method shown by JIS K6828-1996. The MFT controls, for example, the Tg (glass transition point) of the binder resin particles. In particular, when the binder resin particles are a copolymer, the proportion of the monomer that forms the copolymer (addition) The ratio can be adjusted by changing the ratio. Furthermore, in order to prepare particles of a binder resin having a low MFT, a film-forming aid can be added to the particles of a binder resin having a high MFT. This is because the film-forming temperature of the binder resin particles, that is, the MFT can be lowered by the addition of the film-forming aid.

  Examples of the binder resin include, for example, “polymer emulsion” particles. “Polymer emulsion” refers to an emulsion in which a polymer is dispersed or emulsified as an independent phase in a solvent containing a continuous phase in an aqueous system in the presence of a surfactant. The polymer emulsion is an emulsion of a polymer obtained by emulsion polymerization of an ethylenically unsaturated monomer. From the viewpoint of dispersion stability, the polymer emulsion is preferably a vinyl polymer emulsion. The polymers in these polymer emulsions can be used alone or in combination of two or more.

  The polymer of the polymer emulsion is more preferably one having a structural unit represented by the following formula (1) from the viewpoint of improving quick drying when printed on a medium.

—CH ₂ —C (R ¹ ) (COO—R ² —) — (1)
In the formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² may have a substituent, which has 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably an arylalkyl group having 7 to 12 carbon atoms, or 6 to 22 carbon atoms, preferably Represents an aryl group having 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms. The substituent may contain a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom.

Specific examples of R ² include a benzyl group, a phenethyl group (phenylethyl group), a phenoxyethyl group, a diphenylmethyl group, and a trityl group.

  Specific examples of the substituent include preferably an alkyl group, an alkoxy group or an acyloxy group, a hydroxyl group, an ether group, an ester group or a nitro group having 1 to 9 carbon atoms.

  As the structural unit represented by the formula (1), a structural unit derived from benzyl (meth) acrylate is particularly preferable from the viewpoint of developing high gloss.

  The structural unit represented by the formula (1) is preferably obtained by polymerizing a monomer represented by the following formula (1-1).

CH ₂ = CR ¹ COOR ² .. (1-1)
(In Formula (1-1), R ¹ and R ² are the same as those in Formula (1).)
Specifically, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthalyl acrylate, 2-naphthalyl (meth) acrylate, phthalimidomethyl ( Polymerizing (meth) acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acryloyloxyethylphthalic acid, etc. Thus, a polymer having the structural unit represented by the formula (1) can be synthesized. Among these, benzyl (meth) acrylate is particularly preferable. These structural units derived from (meth) acrylates can be used alone or in combination of two or more.

  As used herein, “(meth) acryl” means “acryl”, “methacryl”, or a mixture thereof.

  A preferable monomer structure of the binder resin contained in the latex ink will be described in detail.

  The binder resin includes (b) a structural unit derived from a macromonomer, (c) a structural unit derived from a hydrophobic monomer, (d) a structural unit derived from a hydroxyl group-containing monomer, and (e) a structural unit derived from an oxyalkylene group-containing monomer. It is particularly preferred.

  (A) a structural unit derived from a salt-forming group-containing monomer, (b) a structural unit derived from a macromonomer, (c) a structural unit derived from a hydrophobic monomer, (d) a structural unit derived from a hydroxyl group-containing monomer, (e) oxyalkylene The structural unit derived from the group-containing monomer may be contained alone, but among (a) to (e), it is preferable to include a plurality of types, and more preferably to include all types.

  The binder resin more preferably includes (a) a structural unit derived from a salt-forming group-containing monomer. Thereby, the dispersibility of a polymer can be improved. (A) Although the structural unit derived from the salt-forming group-containing monomer can be obtained by polymerizing the salt-forming group-containing monomer, the salt-forming group (anionic group or cationic group) is added to the polymer chain after the polymerization of the polymer. ) May be introduced. Examples of the salt-forming group include an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as an amino group and an ammonium group.

  (A) As a salt formation group containing monomer, (a-1) anionic monomer and (a-2) cationic monomer are more preferable.

  (A-1) As an anionic monomer, an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, an unsaturated phosphoric acid monomer, etc. are mentioned.

  Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.

  Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned.

  Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl A phosphate etc. are mentioned.

  (A-1) Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of ink viscosity and dischargeability.

  (A-2) Examples of the cationic monomer include unsaturated tertiary amine-containing vinyl monomers and unsaturated ammonium salt-containing vinyl monomers.

  Examples of the unsaturated tertiary amine-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N. -Dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine and the like.

  Examples of the unsaturated ammonium salt-containing monomer include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, N, N-dimethylaminopropyl (meth) Examples include acrylate quaternized products.

  (A-2) Among the cationic monomers, N, N-dimethylaminoethyl (meth) acrylate, NN-dimethylaminopropyl (meth) acrylamide and vinylpyrrolidone are more preferable.

  The (a) salt-forming group-containing monomer can be used alone or in combination of two or more.

  More preferably, the binder resin includes a structural unit derived from (b) a macromonomer. (B) The structural unit derived from a macromonomer is used from the viewpoint of improving storage stability and scratch resistance, and can be obtained by polymerizing a macromonomer having a polymerizable functional group at one end.

  Among (b) macromonomers, (b-1) a styrene macromonomer having a polymerizable functional group at one end, (b-2) an alkyl (meth) acrylate macromonomer having a polymerizable functional group at one end, (B-3) A silicone macromonomer having a polymerizable functional group at one end is more preferred. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and a polymer having a structural unit derived from a macromonomer can be obtained by copolymerizing these.

  (B-1) A styrene macromonomer having a polymerizable functional group at one end is a styrene homopolymer having a polymerizable functional group at one end, and styrene and other monomers having a polymerizable functional group at one end And a copolymer. Examples of the other monomer include (i) acrylonitrile, (ii) (meth) acryl having 1 to 22 carbon atoms, preferably 1 to 18 carbon atoms, and optionally having a hydroxy group and having an alkyl group. Acid esters, (iii) aromatic ring-containing monomers other than styrene, and the like.

  (Ii) (Meth) acrylic acid esters include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso or tertiary) ) Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) stearyl (meth) acrylate, and the like.

  In the present specification, “(iso or tertiary)” and “(iso)” are the case where the branched structure represented by “iso” or “tertiary” is present or not present (normal). Both are shown.

  (Iii) As aromatic ring-containing monomers other than styrene, for example, α-methylstyrene, vinyl toluene, vinyl naphthalene, ethyl vinyl benzene, 4-vinyl biphenyl, 1,1-diphenyl ethylene, benzyl (meth) acrylate, Examples thereof include vinyl monomers having an aromatic ring having 6 to 22 carbon atoms such as phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate.

  (B-1) The content of the structural unit derived from styrene in the styrenic macromonomer is preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more from the viewpoint of storage stability. It is. Examples of commercially available (b-1) styrenic macromonomers include product names of Toa Gosei Co., Ltd., AS-6, AS-6S, AN-6, AN-6S, HS-6, HS- 6S etc. are mentioned.

  (B-2) An alkyl (meth) acrylate macromonomer having a polymerizable functional group at one end is an alkyl (meth) acrylate homopolymer having a polymerizable functional group at one end, and a polymerizable functional group at one end And a copolymer of an alkyl (meth) acrylate and another monomer. Preferably it is a C1-C8 alkyl (meth) acrylate macromonomer, for example, a methyl methacrylate macromonomer, a butyl acrylate macromonomer, an isobutyl methacrylate macromonomer, etc. are mentioned.

  (B-3) The silicone-based macromonomer having a polymerizable functional group at one end is preferably a macromonomer represented by the following formula (2).

_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si _{(CH 3) 2} O] _{t-Si (CH 3) 3} ··· (2)
(In Formula (2), t shows the number of 8-40).

  (B) The number average molecular weight of the macromonomer is preferably 1,000 to 10,000, and preferably 2,000 to 8,000, from the viewpoint of keeping the viscosity low while increasing the copolymerization ratio in order to increase the dispersion stability. Is more preferable.

  The number average molecular weight of the macromonomer is a value measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.

  Said (b) macromonomer can be used individually or in combination of 2 or more types.

  The binder resin more preferably includes (c) a structural unit derived from a hydrophobic monomer.

  (C) The structural unit derived from the hydrophobic monomer is used, for example, from the viewpoint of storage stability and scratch resistance, and can be obtained by polymerizing the hydrophobic monomer. Hydrophobic monomers may be introduced.

  (C) As the hydrophobic monomer, (c-1) (meth) acrylate having an alkyl group having 1 to 22 carbon atoms or (c-2) an aromatic group-containing monomer represented by the following formula (3) is preferable. .

_{^{CH 2 = C (R 3)}} -R 4 ··· (3)
(In the formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ represents an aromatic group-containing hydrocarbon group having 6 to 22 carbon atoms.)
(C-1) As a (meth) acrylate having an alkyl group having 1 to 22 carbon atoms, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, Examples include heenyl (meth) acrylate.

  (C-2) As the aromatic group-containing monomer represented by the above formula (4), from the viewpoint of abrasion resistance, styrene, vinyl naphthalene, α-methylstyrene, vinyl toluene, ethyl vinyl benzene, 4-vinyl biphenyl. One or more selected from 1,1-diphenylethylene are preferred. Among these, styrene, α-methylstyrene, and vinyltoluene are more preferable from the viewpoint of scratch resistance and storage stability.

  Said (c) hydrophobic monomer can be used individually or in combination of 2 or more types.

  The binder resin preferably includes (d) a structural unit derived from a hydroxyl group-containing monomer.

  (D) By including a structural unit derived from a hydroxyl group-containing monomer, the dispersion stability of the binder resin can be improved, and the marker resistance can be improved in a short time when printing is performed. (D) The structural unit derived from a hydroxyl group-containing monomer can be obtained by polymerizing the hydroxyl group-containing monomer. For example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of moles added of the oxyalkylene group; the same applies hereinafter) (meth) acrylate Polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, polyethylene glycol methacrylate 2-ethylhexyl ether, etc. Is mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, polyethylene glycol methacrylate 2-ethylhexyl ether, and polypropylene glycol methacrylate are more preferable.

  The (d) hydroxyl group-containing monomer can be used alone or in combination of two or more.

  The binder resin preferably includes a structural unit derived from (e) an oxyalkylene group-containing monomer.

  (E) As an oxyalkylene group containing monomer, the monomer represented by following formula (4) is mentioned, for example.

CH ₂ = C (R ⁵ ) COO (R ⁶ O) pR ⁷ (4)
(In the formula (4), ^{R 5} is a divalent hydrocarbon group having an alkyl group, ^{R 6} is 1 to 30 carbon atoms which may contain a hetero atom having from 1 to 5 hydrogen atoms or carbon atoms, ^{R 7} is (The monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, p represents the average number of added moles, and is 1 to 60, preferably 1 to 30.)
When the binder resin contains a structural unit derived from (e) an oxyalkylene group-containing monomer, the ejection stability of the water-based ink can be improved. (E) The structural unit derived from an oxyalkylene group-containing monomer can be obtained by polymerizing the monomer represented by the above formula (4).

In the formula (4), examples of the hetero atom that R ⁶ or R ⁷ may have include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.

Representative examples of the group represented by R ⁶ or R ⁷ include aromatic groups having 6 to 30 carbon atoms, heterocyclic groups having 3 to 30 carbon atoms, alkylene groups having 1 to 30 carbon atoms, and the like. It may have a substituent. These groups may be a combination of two or more. Examples of the substituent include an aromatic group, a heterocyclic group, an alkyl group, a halogen atom, and an amino group.

R ⁶ includes a phenylene group optionally having a substituent having 1 to 24 carbon atoms, an aliphatic alkylene group having 1 to 30 carbon atoms, preferably an aliphatic alkylene group having 1 to 20 carbon atoms, and 7 to 7 carbon atoms having an aromatic ring. Preferable examples include 30 alkylene groups and C 4-30 alkylene groups having a heterocycle. Particularly preferable specific examples of the R ⁶ O group include an oxyethylene group, an oxy (iso) propylene group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, or a carbon number of 2 or more of these oxyalkylenes. ˜7 oxyalkylene groups and oxyphenylene groups.

R ⁷ includes a phenyl group, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably an aliphatic alkyl group having 1 to 20 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, or an alkyl group having 4 to 30 carbon atoms having a heterocycle. An alkyl group is preferred. More preferred examples of R ⁷ include methyl group, ethyl group, (iso) propyl group, (iso) butyl group, (iso) pentyl group, (iso) hexyl group, (iso) octyl group, (iso) decyl group. C1-C12 alkyl groups, such as (iso) dodecyl group, a phenyl group, etc. are mentioned.

  (E) As specific examples of the oxyalkylene group-containing monomer, p in methoxypolyethylene glycol formula (4) is 1 to 30) (meth) acrylate, methoxypolytetramethylene glycol (p = 1 to 30) (meth) acrylate, Ethoxypolyethylene glycol (p = 1-30) (meth) acrylate, (iso) propoxypolyethylene glycol (p = 1-30) (meth) acrylate, butoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxy Polyethylene glycol (p = 1-30) (meth) acrylate, phenoxypolyethylene glycol (p = 1-30) (meth) acrylate, methoxypolypropylene glycol (p = 1-30) (meth) acrylate, methoxy (ethylene glycol propylene (Pyrene glycol copolymer) (p = 1-30, in which ethylene glycol moiety is 1-29) (meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, in which Examples of the ethylene glycol moiety include 1-29) (meth) acrylate. Among these, methoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (p = 1-30) (meth) acrylate, phenoxypolyethylene glycol (p = 1-30) (meth) acrylate , Phenoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, ethylene glycol moiety therein is 1-29) (meth) acrylate is more preferable.

The (d) oxyalkylene group-containing monomer can be used alone or in combination of two or more types. The binder resin contained in the latex ink contains the monomer represented by the formula (1-1), Preferably, it further contains a salt-forming group-containing monomer (a). The binder resin more preferably further contains a macromonomer (b). Furthermore, most preferably it further comprises a hydrophobic monomer (c). The binder resin is a copolymer of a monomer mixture (hereinafter referred to as “monomer mixture”) containing one or more monomers selected from the group consisting of a hydroxyl group-containing monomer (d) and an oxyalkylene group-containing monomer (e). Is preferably obtained.

  The monomer content represented by the formula (1-1) in the monomer mixture or the content of the structural unit represented by the formula (1) in the polymer improves the scratch resistance and glossiness of the ink, and From the viewpoint of dispersion stability, it is preferably 10 to 80% by weight, more preferably 25 to 80% by weight, and particularly preferably 25 to 75% by weight.

  (A) content of the salt-forming group-containing monomer in the monomer mixture (content as an unneutralized amount; hereinafter, calculated as an unneutralized amount for the salt-forming group-containing monomer), or (a) salt in the polymer The content of the structural unit derived from the product group-containing monomer is preferably 3 to 30% by weight, and more preferably 5 to 25% by weight from the viewpoints of ink printing density, improvement in glossiness, and good dispersion stability. %, Particularly preferably 5 to 20% by weight.

  The weight ratio of [the structural unit represented by the formula (1) / (a) the structural unit derived from the salt-forming group-containing monomer] is preferably 10/1 to 1 from the viewpoint of improving the dispersibility and gloss of the polymer. / 1, more preferably 5/1 to 1/1.

  A binder resin containing a silicone-based or styrene-based macromonomer is generally excellent in dispersion stability. This is because of the molecular structure that side chains are likely to be oriented in the same form in the case of macromonomers, compared to the possibility that side chains are randomly oriented when polymerizing a single monomer. It is thought to be due to.

  The content of the (b) macromonomer in the monomer mixture or the content of the structural unit derived from the (b) macromonomer in the polymer is preferably 0 to 50 weight from the viewpoint of storage stability and scratch resistance of the ink. %, More preferably 5 to 35% by weight, particularly preferably 5 to 30% by weight. When the (b) macromonomer is a silicone-based macromonomer or a styrene-based macromonomer, the content of the (b) macromonomer may be 30% by weight or less with respect to the total amount of the monomer mixture constituting the binder resin. More preferred. The reason why the content of the macromonomer is preferably 30% by weight or less is that, in addition to the dispersion stability, the binder resin has a film forming property, adhesion property, abrasion resistance, glossiness, reactivity, and storage stability. This is because various functions such as sex are required, and each function depends on a monomer to be blended. Considering the realization of functions in other monomers, the content of the macromonomer is preferably 30% by weight or less.

  The weight ratio of [the structural unit represented by the formula (1) / (b) the structural unit derived from the macromonomer] is preferably 10/1 from the viewpoint of improving the storage stability, scratch resistance and gloss of the polymer. ~ 1/1, more preferably 5/1 to 1/1.

  The content of the (c) hydrophobic monomer in the monomer mixture or the content of the structural unit derived from the (c) hydrophobic monomer in the polymer is preferably 0 to 0 from the viewpoint of storage stability and scratch resistance of the ink. 40% by weight, more preferably 0 to 20% by weight.

  The content of the (d) hydroxyl group-containing monomer in the monomer mixture or the content of the structural unit derived from the (d) hydroxyl group-containing monomer in the polymer is preferably 0 to 40% by weight from the viewpoint of dispersion stability with respect to the ink. More preferably, it is 0 to 20% by weight.

  The content of the (e) oxyalkylene group-containing monomer in the monomer mixture or the content of the structural unit derived from the (e) oxyalkylene group-containing monomer in the polymer is preferably 0 to 0 from the viewpoint of ink ejection stability. 50% by weight, more preferably 10 to 40% by weight.

  When the binder resin has a salt-forming group, the salt-forming group derived from the salt-forming group-containing monomer is used after being neutralized with a neutralizing agent described later. The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.

  The degree of neutralization can be determined by the following formula when the salt-forming group is an anionic group.

{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
When the salt-forming group is a cationic group, the degree of neutralization can be determined by the following formula.

{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100
The acid value and amine value can be calculated from the structural unit of the water-insoluble vinyl polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in a suitable solvent (for example, methyl ethyl ketone) and titrated.

  The weight average molecular weight of the binder resin is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, particularly preferably from 10,000 to 300,000, from the viewpoint of ink gloss.

  The weight average molecular weight of the binder resin is measured using polystyrene as a standard substance by gel chromatography using dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent.

  The average particle diameter of the binder resin particles is preferably 0.16 μm or less in the latex ink.

  The content of the binder resin in the latex ink is preferably 8 to 20% by weight, more preferably 8 to 12% by weight in terms of solid content in the total amount of latex ink.

  More preferably, the binder resin contains at least one water-dispersible resin selected from the group consisting of an aqueous polyester resin, an aqueous polyurethane resin, an aqueous acrylic resin, and an aqueous vinyl chloride resin. Thereby, the dispersibility of binder resin with respect to water and a water-soluble organic solvent improves.

  Examples of commercially available binder resin products include Superflex 470 (NV 38%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) for urethane dispersion, and Superflex 126 (solid content 30%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) for polyurethane dispersion. ), Polyester emulsion, Elitel KA-5071S (solid content 30%, manufactured by Unitika), aqueous acrylic resin Jonkrill 63 (solid content 30%, manufactured by BASF), styrene acrylic emulsion (solid content 46%, BASF) Manufactured). In addition, sorbine CL (manufactured by Nissin Chemical Co., Ltd.) has been put to practical use as a vinyl chloride-vinyl acetate copolymer.

  The binder resin may be an emulsion polymerization polymer. The emulsion polymerization polymer contains a monomer represented by the formula (1-1) in the presence of a surfactant and / or a reactive surfactant, and (a) a salt-forming group-containing monomer, if necessary. It is a polymer obtained by emulsion polymerization of a monomer mixture containing b) a macromonomer, (c) a hydrophobic monomer, (d) a hydroxyl group-containing monomer, and / or (e) an oxyalkylene group-containing monomer by a conventional method.

  Reactive surfactants have one or more unsaturated double bonds capable of radical polymerization in the molecule, and have excellent monomer emulsifying properties, making them useful for the production of water dispersions with excellent stability. It is.

  As the reactive surfactant, at least one of hydrophobic groups such as a linear or branched alkyl group or alkenyl group having 8 to 30, preferably 12 to 22 carbon atoms, an ionic group, An anionic or nonionic group having at least one of hydrophilic groups such as an oxyalkylene group is preferred.

  Specific examples of the reactive surfactant include Latemul S-120P, S-180A (manufactured by Kao Corporation), and Eleminol JS-2 (manufactured by Sanyo Kasei Co., Ltd.) in the sulfosuccinate ester system. Examples of alkylphenol ethers include Aqualon HS-10 and RN-20 (Daiichi Kogyo Seiyaku Co., Ltd.).

  The D50 (the cumulative 50% value calculated from the small particle side in the scattering intensity frequency distribution) of the emulsion polymer (core part) thus obtained is the storage stability, glossiness, and scratch resistance of the aqueous dispersion. From the viewpoint of safety, 500 nm or less is preferable, 300 nm or less is more preferable, and 100 nm or less is particularly preferable. Moreover, from the ease of manufacture, the lower limit is preferably 10 nm or more, and more preferably 20 nm or more. That is, from these viewpoints, 10 to 500 nm is preferable, 50 to 300 nm is more preferable, and 60 to 250 nm is particularly preferable. Among these, it is preferable that a core part is 50-200 nm. This is because, since the film forming property is required as well as the reactivity, it is preferable that the shell portion is thinner than the core portion.

  In addition, D90 of emulsion polymerization polymer (cumulative 90% value calculated from the small particle side in the frequency distribution of scattering intensity) is preferably 2000 nm or less from the viewpoint of increasing the storage stability of the dispersion by reducing coarse particles. The following is more preferable, and 500 nm or less is particularly preferable. Moreover, from the ease of manufacture, the lower limit is preferably 20 nm or more, and more preferably 50 nm or more.

  D50 and D90 can be measured using a laser particle analysis system ELS-8000 (manufactured by Otsuka Electronics Co., Ltd.).

  The latex ink may further contain a penetrant. Examples of penetrants include polyols, more preferably polyols having 7 to 11 carbon atoms, and 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol are preferred. Further preferred.

  The content of the penetrant contained in the latex ink is preferably 0.1 wt% to 20 wt%, more preferably 0.1 wt% to 10 wt%, still more preferably 0.1 wt% to 7 wt%, particularly Preferably it is the range of 0.5 weight%-10 weight%. If the content of the penetrant is 0.1% by weight or more, the permeability to the medium 30 is increased, the roller is rubbed with a roller during transport, and stains are generated. This prevents ink from adhering to the ink and makes it possible to handle higher-speed printing. Further, if the content of penetrant is 20% by weight or less, the print dot diameter can be reduced, the line width of the character is reduced, and the image definition is improved.

  Moreover, in the latex ink, the weight blending ratio of 2-ethyl-1,3-hexanediol or 2,2,4-trimethyl-1,3-pentanediol and the binder resin is 1: 1 to 1: 5. It is more preferable. 2-ethyl-1,3-hexanediol or 2,2,4-trimethyl-1,3-pentanediol is an oily substance having a solubility in water of 8% by weight or less. Therefore, there is a limit to the blending ratio with the binder resin. A preferable blending ratio is 1: 1 to 1: 5, and is preferably equal to or higher than the ratio of the binder resin.

  The penetrant acts as a thickener. Since the penetrant has a low solubility in water, when it is added in a content up to the solubility limit, it rapidly precipitates as an oil component along with water evaporation. With the precipitation of the oil component, the precipitation of components other than the colorant such as the binder resin in the latex ink is promoted, and the ink gels rapidly.

  Latex ink further contains components such as antifungal agents, rust inhibitors, pH adjusters, wetting agents, surfactants, water-soluble ultraviolet absorbers, water-soluble infrared absorbers and the like as additives other than the components described so far. May be.

  Examples of the antifungal agent include 1,2-benzisothiazolin-3-one. When the latex ink contains an antifungal agent, it is possible to provide an ink having an excellent antifungal effect while ensuring reliability such as storage stability and ejection stability. In particular, in the combination with the above-described wetting agent, even if the content is conventionally considered difficult to suppress the generation of bacteria and wrinkles, the effect can be sufficiently exerted.

  Furthermore, by suppressing the content of 1,2-benzisothiazolin-3-one, phenomena such as particle aggregation and ink thickening can be prevented. Therefore, the ink performance can be exhibited over a long period of time. When the latex ink contains 1,2-benzisothiazolin-3-one as an antifungal agent, the content is preferably 0.01 to 0.04 parts by weight of the total amount of ink as an active ingredient amount. If the content is 0.01 parts by weight or more, a sufficient antifungal effect can be obtained. If the content is less than 0.04 parts by weight, particle aggregation can be suppressed when the ink is stored for a long period of time (for example, 2 years at room temperature, 1 to 3 months at 50-60 ° C.). Further, the problem that the ink viscosity is increased by 50% to 100% from the initial viscosity is solved, and the long-term storage stability is improved. Therefore, the initial printing performance can be maintained for a longer period.

  As the pH adjuster, any substance can be used as long as the pH can be adjusted to 7 or more without adversely affecting the ink to be prepared.

Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Other examples include aminopropanediol derivatives such as hydroxides, alkali metal carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate. Aminopropanediol derivatives are water-soluble organic basic compounds such as 1-amino-2,3-propanediol, 1-methylamino-2,3-propanediol, 2-amino-2-methyl-1, Examples thereof include 3-propanediol and 2-amino-2-ethyl-1,3-propanediol, and particularly preferred examples include 2-amino-2-ethyl-1,3-propanediol.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Examples of the surfactant include a polyalkylene glycol surfactant. The polyalkylene glycol surfactant is an ethylene oxide adduct, and it is also effective to substitute a part of ethylene oxide with an alkylene oxide such as propylene oxide or butylene oxide as long as water solubility can be maintained. The substitution rate is preferably 50% or less. Further, the HLB (hydrophilic / lipophilic ratio) of the polyalkylene glycol surfactant is more preferably 13-19. Dispersibility is further improved by adjusting the HLB within the range.

  The latex ink can be obtained by selecting the above-described materials as a solvent, a colorant, and a binder resin and mixing them. The order of mixing the materials is not particularly limited. It is preferable that the temperature of the liquid mixture when mixing each material is 5-50 degreeC.

  The latex ink can further contain additives such as a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, and a chelating agent, if necessary. There is no restriction | limiting in particular in the mixing method of each of these components.

  In the latex ink, the weight ratio of the binder resin to the colorant [binder resin / colorant] is preferably 1/10 to 10/1 from the viewpoints of high printing density, scratch resistance, gloss, and the like of the ink. / 5 to 5/1 is more preferable, 1/3 to 3/1 is particularly preferable, and 1/2 to 2/1 is most preferable.

  The preferable surface tension (20 ° C.) of the latex ink is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m as an aqueous dispersion (dispersion of colorant), and the ink is preferably It is 25-50 mN / m, More preferably, it is 27-45 mN / m.

  The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s in order to obtain a favorable viscosity when used as an ink. The viscosity (20 ° C.) of the latex ink is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s in order to maintain good ejection properties. The pH of the latex ink is preferably 4-10.

<Additional notes>
In order to solve the above-described problems, the printing method according to the present invention is directed to the print head 14, drive means for relatively moving the positions of the medium 30 and the print head 14, and the ink ejection surface of the print head 14. The print heater 70 that heats the medium 30 that is provided at the position that is disposed at the position by the driving means from the side facing away from the ink landing surface of the medium 30, and the medium 30 includes the print head 14. The ink jet printer 1 is provided with preheating means for heating the medium 30 from the side facing away from the ink landing surface at a position before being disposed at a position opposed to the ink ejection surface. A printing method for printing the medium 30, wherein the surface temperature of the ink landing surface of the medium 30 is 40 ° C. or higher and 60 ° C. or lower. As described above, the medium 30 is heated by the print heater 70 and the preheater 40, and the ink discharged from the print head 14 includes a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent. Ink having a minimum film forming temperature on the surface of the binder resin of 0 ° C. or lower is used.

  According to the above configuration, the medium 30 is printed using the inkjet printer 1. In the inkjet printer 1, printing is performed at a desired position on the medium 30 by relatively moving the print head 14 and the medium 30 by the driving unit. At the time of printing, first, the medium 30 is heated by the preheater 40 from the side facing away from the ink landing surface at a position before the position facing the ink ejection surface of the print head 14. Next, the medium 30 heated by the preheater 40 is transported to a position facing the ink ejection surface of the print head 14 by a driving unit. The conveyed medium 30 is heated from the side facing away from the ink landing surface by a print heater 70 provided at a position facing the ink ejection surface of the print head 14. The medium 30 is heated by the print heater 70 and the preheater 40 so that the surface temperature of the ink landing surface of the medium 30 is 40 ° C. or higher and 60 ° C. or lower.

  The ink ejected from the print head 14 is an ink containing a solvent, a colorant, and a binder resin, and the binder resin is dispersed or emulsified in the solvent (hereinafter referred to as latex ink), and the binder resin An ink having a minimum film forming temperature of 0 ° C. or lower is used. Such ink is particularly excellent in environmental characteristics and media characteristics.

  As described above, the latex ink ink ejected from the nozzles of the print head 14 onto the surface of the medium 30 heated so that the surface temperature thereof is 40 ° C. or more and 60 ° C. or less by the pre-heater 40 and the print heater 70. Drops can be landed. Therefore, the ink droplets can be quickly dried and fixed in a short time without being diffused on the medium 30 around the landing location, while being fixed in a dot shape at the landing location. Then, it is possible to print a clear picture or character having no blur and comprising a plurality of latex ink dot arrays on the surface of the medium 30.

  Here, by heating the surface temperature of the medium 30 to 40 ° C. or higher, the heating temperature that the latex ink droplets landed on the surface of the medium 30 receives from the medium 30 can be made sufficient. In addition, by heating the surface temperature of the medium 30 to 60 ° C. or less, even when a vinyl chloride film or the like having low heat resistance is used as the medium 30, the medium 30 is not damaged by heat, and the driving means Can be smoothly conveyed on the platen. Therefore, according to the present invention, almost all media 30 from the media 30 with low heat resistance to the media 30 with high heat resistance can be applied. As described above, the reason for heating the medium 30 so that the surface temperature is 40 ° C. or more and 60 ° C. or less is that the ink jet printer 1 according to the present invention is used to apply the latex 30 to the surface of various media 30. Based on the experimental results of actual printing of pictures and characters, the present inventors have intensively studied and derived.

  Further, the binder resin contained in the latex ink used in the present invention has a core / shell structure including a core portion located inside and a shell portion located on the surface. Since the minimum film forming temperature (MFT) on the surface of the binder resin is 0 ° C. or less, the latex ink is dried and dried on the medium 30 heated so that the surface temperature is 40 ° C. or more and 60 ° C. or less. Fusion can be started quickly.

  Further, the preheater 40 and the print heater 70 are used to heat in two stages, and finally the surface temperature of the medium 30 when ink is landed is set to 40 ° C. or more and 60 ° C. or less suitable for drying and fusing of the latex ink. . Therefore, even if the print heater 70 alone cannot sufficiently heat the medium 30 to an appropriate temperature due to the thickness of the medium 30 or the ambient temperature where the ink jet printer 1 is placed, the preheater 40 increases the temperature to a certain level. By heating in advance, the surface of the medium 30 can be heated to a desired temperature when the ink lands.

  Since the print heater 70 is disposed at a position facing the ink ejection surface of the print head 14, if the surface of the medium 30 is heated to 40 ° C. or more and 60 ° C. or less with only the print heater 70, the print heater 70 There is a problem that ink is solidified and clogged in the small nozzles of the print head 14 due to heat generated from the heater 70. According to the present invention, the preheater 40 and the print heater 70 are heated in two stages so that the surface temperature of the medium 30 at the time of ink landing is 40 ° C. or more and 60 ° C. or less. By heating in advance to a certain temperature, the surface of the media 30 can be heated to a desired temperature without causing the print heater 70 to generate heat at a high temperature. Therefore, it is possible to prevent the ink from solidifying in the nozzles of the print head 14 due to heat generated from the print heater 70 and causing clogging.

  According to the present invention, it is possible to achieve high image quality and fixing stability of pictures and characters to be printed even for media 30 used for outdoor display advertisements and industrial applications that require high environmental characteristics and media characteristics. Can be realized.

  In the printing method according to the present invention, the binder resin has a minimum film forming temperature different between the surface and the inside.

  According to the above configuration, by varying the minimum film forming temperature between the surface and the inside of the core / shell structure of the binder resin, the timing of drying and fusing between the surface and the inside of the binder resin is shifted, Separation effect can be obtained. For example, after the surface of the binder resin is dried and fused on the medium 30 appropriately heated by the preheater 40 and the print heater 70, the inside of the binder resin is dried to dry the medium 30 after ink landing, for example. You may comprise so that it may dry and fuse | melt by a means.

  The temperature at which the ink is dried in the conventional inkjet printer 1 is normally set to about 80 ° C., but the drying temperature of the latex ink is actually assumed to be about 50 to 60 ° C. As described above, by separately drying and fusing the surface and the inside of the binder resin, the heating temperature by the print heater 70 at a position facing the ink ejection surface of the print head 14 is set to a temperature at which ink clogging can be avoided. Even so, the latex ink can be reliably dried and fixed by the pre-heater 40 or, for example, the after-heater.

  In the printing method according to the present invention, the binder resin makes the minimum film-forming temperature on the surface lower than the internal minimum film-forming temperature.

  According to the above configuration, since the minimum film forming temperature inside the binder resin in the latex ink is higher than the minimum film forming temperature on the surface, the storage stability of the latex ink at a high temperature is improved. Then, the surface of the binder resin having the lowest minimum film forming temperature starts to be quickly dried and fused on the medium 30 heated by the preheater 40 and the print heater 70. As a result, the surface of the binder resin having a low minimum film-forming temperature can be obtained in latex ink that has extremely high diffusibility (wetting and spreading) with respect to the medium 30 and ink droplets tend to diffuse widely around the landing site. , It can be fixed clearly on the landing spot without blurring of dots. Thereafter, for example, the latex ink landed on the medium 30 is sequentially dried in accordance with the transport direction of the medium 30 by sufficiently drying and fusing the inside of the binder resin having a high minimum film-forming temperature by an after heater or a drying means. Can be fused and fixed.

  In the printing method according to the present invention, the solvent is at least one of water and a hydrophilic solvent, and the latex ink contains 50% by weight or more of the solvent with respect to the total weight of the latex ink.

  According to the above configuration, the environmental load of the ink can be reduced due to the high content of at least one of water and the hydrophilic solvent in the latex ink.

  In the printing method according to the present invention, the heating temperature of the medium 30 by the print heater 70 and the heating temperature of the medium 30 by the preheater 40 are controlled to different temperatures.

  According to the above configuration, the temperature of the medium 30 being conveyed can be separately controlled at each of a position facing the ink ejection surface of the print head 14 and a position before the position. Therefore, the media 30 at each position can be accurately adjusted according to the type and thickness thereof, the temperature around the printer, and the like. Therefore, the temperature at the surface portion of the medium 30 when the ink droplets ejected from the ink ejection surface of the print head 14 land can be accurately adjusted to 40 ° C. or more and 60 ° C. or less.

  In the printing method according to the present invention, the preheater 40 heats the surface temperature of the ink landing surface of the medium 30 to 30 ° C. or more and 50 ° C. or less, and the surface temperature of the ink landing surface of the medium 30 is increased by the print heater 70. Is heated to 40 ° C. or higher and 60 ° C. or lower.

  According to the above configuration, the surface temperature of the ink landing surface is preheated to 30 ° C. or more and 50 ° C. or less by the preheater 40 before the medium 30 is conveyed to a position facing the ink ejection surface of the print head 14. . Subsequently, the medium 30 transported to a position facing the ink ejection surface of the print head 14 after preheating is heated by the print heater 70 to a surface temperature of the ink landing surface of 40 ° C. or more and 60 ° C. or less. As a result, when ink droplets ejected from the nozzles of the print head 14 land on the medium 30, the surface temperature can always be reliably and reliably increased so as to be 40 ° C. or higher and 60 ° C. or lower.

  In the printing method according to the present invention, the heating temperature of the medium 30 by the print heater 70 and the heating temperature of the medium 30 by the preheater 40 are controlled to the same temperature.

  According to the above configuration, the temperature control of the preheater 40 and the temperature control of the print heater 70 can be controlled in the same manner, so that the temperature control can be simplified.

  In the printing method according to the present invention, as the medium 30, the vinyl chloride sheet, PET sheet, tarpaulin sheet, coated paper not coated with a coating agent, uncoated polypropylene resin, glass, metal, and the like are used as the medium 30. A medium 30 selected from the group consisting of the following moldings is used.

  According to the above configuration, even with a general-purpose medium 30 to which a coating agent or the like is not applied, it is possible to print high-quality pictorial figures and characters without bleeding with fixing stability. Moreover, according to said structure, it is possible to always convey smoothly smoothly various types of media 30 including the medium 30 softened at low temperature. That is, various media 30 from a low heat resistance medium 30 to a high heat resistance medium 30 can be transported without any trouble, and high-quality pictures and characters without bleeding can be transferred to such various media 30. Printing can be performed with fixing stability.

  In the printing method according to the present invention, the inkjet printer 1 controls the temperature of the preheater 40 and the print heater 70 for heating the medium 30 by an operation panel attached to the printer or a printer control host computer connected to the printer. Configure for change adjustment.

  According to the above configuration, the operation temperature attached to the printer or the host computer for printer control is adjusted according to the heating temperature of the preheater 40 and the print heater 70 according to the type and thickness of the medium 30 and the ambient temperature where the printer is placed. Can be changed and adjusted. Various media 30 that are softened at a low temperature and the like can always be smoothly transported. To such various media 30, high-quality pictures and characters that do not bleed are provided with fixing stability. Can be printed.

  In the method according to the present invention, the ink jet printer 1 moves the print head 14 to a maintenance station, causes ink droplets to be ejected from the nozzles of the print head 14 (flushing), and latex in the nozzles of the print head 14. A refresh mode means is provided for preventing ink from solidifying and causing clogging.

  According to the above-described configuration, the print head 14 is moved to the maintenance station by using the refresh mode means in the middle of printing the picture or character using the latex ink, and the ink droplet is trial ejected from the nozzle of the print head 14. Can be made. As a result, it is possible to prevent the latex ink from solidifying inside the nozzles of the print head 14 and causing clogging. As a result, a dot omission occurs in a part of a picture or character printed on the surface of the medium 30 by using the clogged print head 14 (a state in which no ink dot exists in a place where the ink dot should exist). Can be prevented.

  In the method according to the present invention, the ink jet printer 1 provided with the refresh mode means moves the print head 14 to the maintenance station at regular intervals, and the ink droplets from the nozzles of the print head 14 are transferred. Let the test discharge.

  According to the above configuration, the print head 14 is moved to the maintenance station by using the refresh mode means at regular intervals during the printing of pictures and characters using latex ink, and the ink from the nozzles of the print head 14 is transferred. Drops can be forcibly ejected by trial. In the middle of printing a picture or character using latex ink, the print head 14 is moved to the maintenance station using the refresh mode means, so it is neglected to eject ink droplets from the nozzles of the print head 14. As a result, it is possible to reliably prevent the latex ink from solidifying in the nozzles of the print head 14 and causing the nozzles to become clogged.

  In the method according to the present invention, the inkjet printer 1 is a drying unit that dries the ink droplets attached to the surface of the medium 30 by drying the medium 30 after the ink droplets ejected from the print head 14 have landed. Is provided.

  According to the above configuration, the ink droplets that are partly undried attached to the surface of the medium 30 can be completely dried by the drying means. Then, after the conveyance, for example, when the medium 30 is taken up by the take-up means, the ink droplets in a partially undried state adhering to the landing positions on the surface of the medium 30 taken up in a roll shape or the like are It is possible to prevent the media 30 from being attached to other portions and soiling.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in the embodiments are also included. It is included in the technical scope of the present invention.

  Hereinafter, although the Example and comparative example of this invention are shown, this invention is not limited to these. In addition, the amount of each component described in the examples is based on weight.

<Preparation of resin dispersion colorant>
[Production Example 1 (phthalocyanine pigment dispersion)]
C. I. 150 g of CI Pigment Cyan 15: 3, 3.0% SOLPERSE 43000 (polymer type dispersant, manufactured by Lubrizol), 3.0% SOLPERSE 44000 (polymer type dispersant, manufactured by Lubrizol), and 738 g of distilled water were mixed. After pre-dispersing the mixture, the mixture was circulated and dispersed for 20 hours in a disk type bead mill (Shinmaru Enterprises KDL type, media: 0.3 mmφ zirconia ball used) to obtain a phthalocyanine pigment dispersion (C-1).

[Production Example 2 (Dimethylquinacridone pigment dispersion)]
C. I. Pigment Cyan 15: 3 is changed to C.I. A dimethylquinacridone pigment dispersion (M-1) was obtained in the same manner as in Preparation Example 1, except that the pigment was changed to I Pigment Red 122 and changed to SOLSPERSE 43000, 3.38%, SOLSPERSE 44000, 3.38%.

[Production Example 3 (Monoazo Yellow Pigment Dispersion)]
C. I. Pigment Cyan 15: 3 is changed to C.I. A monoazo yellow pigment dispersion (Y-1) was obtained by performing the same procedure as in Preparation Example 1 except that the pigment was changed to I Pigment Yellow 74 and changed to SOLPERSE 43000, 1.3%, SOLPERSE 44000, 1.3%.

[Production Example 4 (carbon black pigment dispersion)]
C. I. Pigment Cyan 15: 3 is changed to C.I. A carbon black pigment dispersion (B-1) was obtained in the same manner as in Preparation Example 1 except that the carbon black was changed to SOLPERSE 43000, 2.3%, and SOLPERSE 44000, 2.3%.

<Preparation of polymer graft colorant>
[Synthesis Example 1 (Cyan Pigment Dispersion)]
C. I. Instead of CI Pigment Yellow 128, C.I. I. A surface-modified cyan pigment was prepared by the same procedure as in Synthesis Example 2 except that CI Pigment Cyan 15: 3 was used. As in Synthesis Example 2, the obtained surface-modified colored pigment is easily dispersed in an aqueous medium upon stirring, desalted and concentrated with an ultrafiltration membrane, and a cyan pigment dispersion (C -2).

[Synthesis Example 2 (magenta pigment dispersion)]
C. I. A surface-modified magenta pigment was prepared by the same procedure as in Synthesis Example 1 except that Pigment Red 122 was used instead of Pigment Yellow 128. As in Synthesis Example 2, the obtained surface-modified colored pigment is easily dispersed in an aqueous medium upon stirring, desalted and concentrated with an ultrafiltration membrane, and a magenta pigment dispersion (M -2).

[Synthesis Example 3 (yellow pigment dispersion)]
As a yellow pigment, C.I. I. Pigment Yellow 128 was subjected to low-temperature plasma treatment to prepare a pigment into which a carboxylic acid group was introduced. A dispersion of this in ion-exchanged water was desalted and concentrated with an ultrafiltration membrane to obtain a yellow pigment dispersion (Y-2) having a pigment concentration of 15%.

[Synthesis Example 4 (carbon black pigment dispersion)]
90 g of carbon black with a CTAB specific surface area of 150 m ² / g and DBP oil absorption of 100 ml / 100 g is added to 3000 ml of 2.5 N normal sodium sulfate solution, stirred at a temperature of 60 ° C. and a rotation speed of 300 rpm, and reacted for 10 hours for oxidation. Processing was performed. The reaction solution was filtered, and the carbon black separated by filtration was neutralized with a sodium hydroxide solution and subjected to ultrafiltration. The obtained carbon black (B-2) was washed with water, dried, and dispersed in pure water to 20% by weight.

<Synthesis Example of Polymer Encapsulating Colorant>
[Synthesis Example 5 (Preparation of polymer dispersion)]
After sufficiently replacing the inside of the 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas introduction tube, reflux tube and dropping funnel with nitrogen gas, 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer (product name AS-6, manufactured by Toa Gosei Co., Ltd.) and 0.4 g of mercaptoethanol were charged, and the temperature was raised to 65 ° C.

  Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxyethyl methacrylate, styrene macromer (product name AS-6, manufactured by Toagosei Co., Ltd.) A mixed solution of 0 g, mercaptoethanol 3.6 g, azobisdimethylvaleronitrile 2.4 g, and methyl ethyl ketone 18 g was dropped into the flask under stirring conditions over 2.5 hours.

  After completion of the dropwise addition, a mixed solution of 0.8 g of azobisdimethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask under stirring conditions over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobisdimethylvaleronitrile was added, and further aging was performed for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a solid content concentration of 50%.

[Synthesis Example 6 (phthalocyanine pigment-encapsulated polymer fine particle dispersion)]
After 28 g of the polymer solution prepared in Synthesis Example 5, 26 g of phthalocyanine pigment, 13.6 g of 1 mol / L potassium hydroxide solution, 20 g of methyl ethyl ketone, and 30 g of ion-exchanged water were sufficiently stirred, they were kneaded using a three-roll mill. The obtained paste was put into 200 g of ion-exchanged water and stirred sufficiently, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a cyan polymer fine particle dispersion (C-3).

[Synthesis Example 7 (Dimethylquinacridone pigment-encapsulated polymer fine particle dispersion)]
A magenta polymer fine particle dispersion (M-3) was obtained by performing the same procedure as in Synthesis Example 5 and Synthesis Example 6 except that the phthalocyanine pigment was changed to Pigment Red 122.

[Synthesis Example 8 (monoazo yellow pigment-encapsulated polymer fine particle dispersion)]
A yellow polymer fine particle dispersion (Y-3) was obtained by performing the same procedure as in Synthesis Example 5 and Synthesis Example 6 except that the phthalocyanine pigment was changed to Pigment Yellow 74.

[Synthesis Example 9 (carbon black pigment-encapsulated polymer fine particle dispersion)]
A black polymer fine particle dispersion (B-3) was obtained by performing the same procedure as in Synthesis Example 5 and Synthesis Example 6 except that the phthalocyanine pigment was changed to carbon black.

<Synthesis of binder resin core>
Next, a synthesis example of a core portion of a binder resin having a core / shell structure included in the latex ink according to the present invention will be described.

[Synthesis Example 10]
After sufficiently replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, Aqualon RN-20 (alkylphenol ether reactive surfactant, Daiichi Kogyo Seiyaku) 10 g, 1 g of potassium persulfate and 286 g of pure water were added, and the temperature was raised to 65 ° C.

  Next, 150 g of methyl methacrylate, 100 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 20 g of vinyltriethoxysilane, 10 g of Aqualon RN-20, 10 g of Aqualon RN-20, 4 g of potassium persulfate and 398.3 g of pure water Was added dropwise to the flask under stirring conditions over 2.5 hours. The mixture was further heated and aged at 80 ° C. for 3 hours and then cooled, and the pH was adjusted to 7 to 8 with potassium hydroxide. The average particle size of the resin measured using Microtrac UPA was 130 nm. The minimum film forming temperature (MFT) was 10 ° C.

[Synthesis Example 11]
After sufficiently replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, Aqualon RN-20 (alkylphenol ether reactive surfactant, Daiichi Kogyo Seiyaku) 10 g, 1 g of potassium persulfate and 286 g of pure water were added, and the temperature was raised to 65 ° C. Next, 150 g of methyl methacrylate, 100 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 40 g of hexyltrimethoxysilane, 10 g of Aqualon RN-20, 4 g of potassium persulfate and 398.3 g of pure water were taken over 3 hours. Then, it was dropped into the flask under stirring conditions. The mixture was further heated and aged at 80 ° C. for 3 hours and then cooled, and the pH was adjusted to 7 to 8 with potassium hydroxide. The average particle size of the resin measured using Microtrac UPA was 148 nm. The minimum film forming temperature (MFT) was 10 ° C.

[Synthesis Example 12]
After fully replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, 100 g of pure water, 3 g of sodium dodecylbenzenesulfonate and 1 g of polyethylene glycol nonylphenyl ether Were added, 1 g of ammonium persulfate and 0.2 g of sodium hydrogen sulfite were added, and the temperature was raised to 60 ° C.

  Next, 30 g of butyl acrylate, 40 g of methyl methacrylate, 19 g of butyl methacrylate, 10 g of vinylsilanetriol potassium salt and 1 g of 3-methacryloxypropylmethyldimethoxysilane were dropped into the flask under stirring conditions over 3 hours. At this time, the polymerization reaction solution was adjusted to pH 7 with an aqueous ammonia solution to carry out polymerization. The average particle size of the resin measured using Microtrac UPA was 160 nm. The minimum film forming temperature (MFT) was 15 ° C.

<Synthesis of binder resin shell>
Next, a synthesis example of a shell portion of a binder resin having a core / shell structure included in the latex ink according to the present invention will be described.

[Synthesis Example 13 (for Examples)]
A glass reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introducing tube, 100 g of ion-exchanged water, an ether sulfate type reactive surfactant (product name: Latemul PD-104, (Effective portion 20%, manufactured by Kao Corporation) 8 g and potassium persulfate 0.24 g were charged, and after nitrogen substitution, the temperature was raised to 70 ° C. in a hot water bath.

  To this, 100 g (solid content 45%) of the emulsion (P-10) synthesized in Synthesis Example 10 was added and stirred. Further, 30 g of a monomer mixture of (c) styrene / (a) acrylic acid / (c) 2-ethylhexyl acrylate / (c) butyl acrylate = 32/2/24/42 was added dropwise over 2 hours, and then 80 The mixture was aged at 2 ° C. for 2 hours to obtain an aqueous dispersion containing an emulsion (P-13). The average particle diameter of the obtained emulsion was 200 nm, and the solid content (effective content) of the emulsion solution having a core / shell structure was adjusted to 45% by adding an appropriate amount of ion-exchanged water. The minimum film forming temperature (MFT) of the shell part was 0 ° C.

[Synthesis Example 14 (for Examples)]
As the monomer mixture, (c) styrene / (a) acrylic acid / (c) 2-ethylhexyl acrylate = 49/2/49 was used, and the emulsion dispersion (P-11) synthesized in Synthesis Example 11 was used. Except for adding 100 g (solid content: 45%), the same procedure as in Synthesis Example 13 was performed to obtain an aqueous dispersion containing an emulsion (P-14). The average particle size of the obtained water-insoluble emulsion was 200 nm, and the solid content (effective content) of the water-insoluble emulsion solution was 45%. The minimum film forming temperature (MFT) of the shell part was −10 ° C.

[Synthesis Example 15 (for Examples)]
As a monomer mixture, (c) benzyl methacrylate / (a) methacrylic acid / (b) styrene macromer (product name AS-6, manufactured by Toa Gosei Co., Ltd.) / (E) polyethylene glycol methacrylate 2-ethylhexyl ether (product name NK ester) EH-4G (manufactured by Shin-Nakamura Chemical Co., Ltd.) = 44/16/15/25 (effective weight ratio) of the monomer mixture total 200 g was used, and the emulsion dispersion (P-12) synthesized in Synthesis Example 12 was used for this. Except for adding 100 g (solid content: 45%), the same procedure as in Synthesis Example 12 was performed to obtain an aqueous dispersion containing an emulsion (P-15). The average particle diameter of the obtained emulsion (P-15) was 200 nm, and the solid content (effective content) of the water-insoluble emulsion solution was 45%. The minimum film forming temperature (MFT) of the shell part was 0 ° C.

[Synthesis Example 16 (for Examples)]
The same as Synthesis Example 13 except that the monomer composition was changed to (c) styrene / (a) N, N-dimethylaminoethyl (meth) acrylate / (c) 2-ethylhexyl acrylate = 74/2/24 The procedure was performed to obtain an aqueous dispersion containing the emulsion (P-24). The average particle diameter of the obtained emulsion (P-16) was 200 nm, and the solid content (effective content) of the emulsion solution (P-16) was 45%. The minimum film forming temperature (MFT) of the shell part was -13 ° C.

[Synthesis Example 17 (for Examples)]
The same as Synthesis Example 14 except that (c) styrene / (a) NN-dimethylaminopropyl (meth) acrylamide / (c) 2-ethylhexyl acrylate = 32/2/66 was used as the monomer mixture. The procedure was performed to obtain an aqueous dispersion containing the emulsion (P-17). The average particle size of the obtained emulsion (P-17) was 200 nm, and the solid content (effective content) of the emulsion solution (P-17) was 45%. The minimum film forming temperature (MFT) of the shell part was 0 ° C.

[Synthesis Example 18 (for Examples)]
The monomer composition is (c) benzyl methacrylate / (a) vinyl pyrrolidone / (b) styrene macromer (product name AS-6, manufactured by Toa Gosei Co., Ltd.) / (E) polyethylene glycol methacrylate 2-ethylhexyl ether (product name NK ester) Except having changed to EH-4G (made by Shin-Nakamura Chemical Co., Ltd.), the same procedure as the synthesis example 15 was performed, and the water dispersion containing an emulsion (P-18) was obtained. The average particle size of the obtained emulsion (P-18) was 200 nm, and the solid content (effective content) of the emulsion solution (P-18) was 45%. The minimum film forming temperature (MFT) of the shell part was 0 ° C.

[Synthesis Example 19 (for Comparative Example)]
As the monomer mixture, (c) styrene / (a) acrylic acid / (c) 2-ethylhexyl acrylate / (c) butyl acrylate = 49/2/24/25 was used, and as the non-reactive surfactant, Water containing emulsion (P-19) was prepared by the same procedure as in Synthesis Example 15 except that 62 g of sodium oxyethylene alkyl ether sulfate (product name: Latemul E-118B, effective content: 26%, manufactured by Kao Corporation) was used. A dispersion was obtained. The average particle size of the obtained emulsion (P-19) was 215 nm, and the solid content (effective content) of the emulsion (P-19) solution was 45%. The minimum film forming temperature (MFT) of the shell part was 30 ° C.

[Synthesis Example 20 (for Comparative Example)]
The emulsion mixture (P-20) was prepared in the same manner as in Synthesis Example 13, except that (c) styrene / (a) acrylic acid / (c) 2-ethylhexyl acrylate = 19/2/79 was used as the monomer mixture. ) Was obtained. The average particle size of the obtained emulsion (P-20) was 230 nm, and the solid content (effective content) of the emulsion (P-20) solution was 45%. The minimum film forming temperature (MFT) of the shell part was 25 ° C.

[Synthesis Example 21 (for Comparative Example)]
The same as Synthesis Example 14 except that (c) styrene / (a) N, N-dimethylaminoethyl (meth) acrylate / (c) 2-ethylhexyl acrylate = 89/2/9 was used as the monomer mixture. The procedure was performed to obtain an aqueous dispersion containing the emulsion (P-21). The average particle size of the obtained emulsion (P-21) was 95 nm, and the solid content (effective content) of the emulsion (P-21) solution was 45%. The minimum film forming temperature (MFT) of the shell part was 30 ° C.

(Particle size measurement)
Using a laser particle analysis system ELS-8000 (cumulant analysis, manufactured by Otsuka Electronics Co., Ltd.), the temperature is 25 ° C., the angle between the incident light and the detector is 90 °, the number of integration is 100 times, and the refractive index of the dispersion solvent is 1.333. The particle size was measured by setting the conditions.

<Example of making latex ink>
A latex ink was prepared by blending water, a water-soluble organic solvent, a colorant, a binder resin, a wetting agent, a surfactant, and the like.

[Ink production example (1-1)]
Cyan pigment dispersion (C-1) of Preparation Example 1 6 wt% (solid content)
Binder resin (P-13) (solid content 45%) 10wt%
3-methyl-1,3-butanediol 15 wt%
Glycerin 15wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
2-ethyl-1,3-hexanediol 2wt%
Ion exchange water was added to make 100%.

[Ink production example (1-2)]
Magenta pigment dispersion (M-1) of Preparation Example 2 6 wt% (solid content)
Binder resin (P-14) (solid content 45%) 10wt%
Triethylene glycol isobutyl ether 2wt%
Glycerin 20wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
2-ethyl-1,3-hexanediol 2wt%
Ion exchange water was added to make 100%.

[Ink production example (1-3)]
Yellow pigment dispersion (Y-1) of Preparation Example 3 6 wt% (solid content)
Binder resin (P-15) (solid content 45%) 10wt%
1,3-butanediol 20wt%
Glycerin 20wt%
2-pyrrolidone 1wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
2,2,4-Trimethyl-1,3-pentanediol 2wt%
Ion exchange water was added to make 100%.

[Ink production example (1-4)]
Carbon black pigment dispersion liquid of Production Example 4 (B-1) 9 wt% (solid content)
Binder resin (P-16) (solid content 45%) 10wt%
3-methyl-1,3-butanediol 20wt%
Glycerin 15wt%
2-pyrrolidone 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
2-ethyl-1,3-hexanediol 2wt%
Ion exchange water was added to make 100%.

[Other ink production examples]
Ink production example (2-1):
Latex inks were prepared with the same formulation except that the cyan pigment dispersion (C-1) was changed to (C-2) and the binder resin (P-13) was changed to (P-17).

Ink production example (2-2):
A latex ink was prepared in the same manner except that the magenta pigment dispersion (M-1) was changed to (M-2) and the binder resins (P-14) and (P-18).

Ink production example (2-3):
A latex ink was prepared in the same manner except that the yellow pigment dispersion (Y-1) was changed to (Y-2) and the binder resin (P-15) was changed to (P-13).

Ink production example (2-4):
Latex inks were prepared with the same formulation except that the carbon black pigment dispersion (B-1) was changed to (B-2) and the binder resin P-16 was changed to (P-14).

Ink production example (3-1):
Latex inks were prepared in the same manner except that the cyan pigment dispersion (C-1) was changed to (C-3) and the binder resin (P-13) was changed to (P-15).

Ink production example (3-2):
A latex ink was prepared in the same manner except that the magenta pigment dispersion (M-1) was changed to (M-3) and the binder resin (P-14) was changed to (P-16).

Ink production example (3-3):
A latex ink was prepared in the same manner except that the yellow pigment dispersion (Y-1) was changed to (Y-3) and the binder resin (P-15) was changed to (P-17).

Ink production example (3-4):
A latex ink was prepared with the same composition except that the carbon black pigment dispersion (B-1) was changed to (B-3) and the binder resin (P-16) was changed to (P-18).

Ink production example (4-1):
A latex ink was prepared with the same composition except that the cyan pigment dispersion (C-1) was used and the binder resin (P-19) was used.

Ink production example (4-2):
A latex ink was prepared with the same formulation except that the magenta pigment dispersion (M-1) was used and the binder resin (P-20) was used.

Ink production example (4-3):
A latex ink was prepared in the same composition except that the yellow pigment dispersion (Y-1) was used and the binder resin (P-21) was used.

Ink production example (4-4):
Latex inks were prepared with the same formulation except that the carbon black pigment dispersion (B-1) was used and the binder resin (P-21) was used.

  Table 1 shows combinations of ink color materials and binder resins for each production example. Table 2 shows the physical properties of each ink.

[Inks used in Examples and Comparative Examples]
In Examples and Comparative Examples, combinations of inks shown in Table 3 were used.

<Evaluation of print quality>
Using an ink jet printer (product name JV33, manufactured by Mimaki Engineering Co., Ltd.), GEN5 (manufactured by Ricoh Co., Ltd.) is attached to the head, and each of the inks of Production Examples 1-1 to 4-4 is used on various media. The printed matter was wound around a media paper tube while printing under the following conditions. And the printed surface after winding up was confirmed visually, and the presence or absence of the occurrence of bleeding was examined. Table 4 shows the printing speed at this time. The print density was set based on the amount of ink applied per unit area.

[Printing conditions]
Printing speed:
(1) Draft: 540 × 1080 dpi / high speed mode (2) Fine: 720 × 1080 dpi / high speed mode Heater temperature:
(I) Preheater: OFF to 45 ° C
(Ii) Print heater: OFF to 45 ° C
(Iii) After heater: OFF to 50 ° C
[Evaluation method for print quality]
The image characteristics of the printed image were evaluated in the five items of feathering, color bleeding, beading, image density, and glossiness. Further, scratch resistance was evaluated as the reliability of the image. These results are shown in Table 5.

(Evaluation of image characteristics)
(Evaluation of feathering and color bleeding)
The presence and absence of feathering and color bleeding in the examples and comparative examples were visually observed and evaluated according to the following criteria.

(Evaluation criteria)
(Double-circle): It is clear printing without generation | occurrence | production of the whole paper.
○: Whisker-like bleeding occurs on some paper (recycled paper).
Δ: Whisker-like bleeding occurs on all papers.
X: The blur has occurred so that the outline of the character is not clear.

(Evaluation of beading)
The degree of beading of the green solid image portions of the examples and comparative examples was visually observed and evaluated according to the following criteria.

(Evaluation criteria)
5: Uniform printing without occurrence of beading.
4: The occurrence of beading is slightly observed, but it is at a level that does not matter at all.
3: The occurrence of beading is recognized, but the image quality is not impaired.
2: The occurrence of beading is clearly observed.
1: Significant beading is observed.

(Evaluation of image density)
The optical density of the magenta image portion of the example and the comparative example was measured with X-Rite 932 and evaluated according to the following criteria.

(Evaluation criteria)
◎: Magenta image density 1.6 or more ○: Magenta image density 1.3 or more Δ: Magenta image density 1.0 or more ×: Magenta image density less than 1.0 (Glossiness evaluation)
The degree of glossiness of the image portions of Examples and Comparative Examples was visually observed and evaluated according to the following criteria.

(Evaluation criteria)
: High gloss.
○: Glossy.
X: A glossiness is not recognized.

[Evaluation of image reliability]
(Evaluation of scratch resistance)
As an evaluation image, a black, cyan, magenta, yellow, red, green, blue square (3 cm × 3 cm) was used. 24 hours after printing, use a clock meter (CM-1 type), and white cotton cloth (JISL 0803 cotton 3) as a friction piece with double-sided adhesive foam tape (# 4016, t = 1.6, manufactured by 3M) Affixing and reciprocating friction were performed, and the density of the color material adhered to the cotton cloth was measured using a spectrocolorimetric densitometer (product name Model-938, manufactured by X-Rite).

(Evaluation criteria)
A: Color material concentration adhered to cotton cloth is less than 0.05 ○: Color material concentration adhered to cotton cloth is 0.05 or more and less than 0.1 ×: Color material concentration adhered to cotton cloth is 0.1 or more. Table 5 shows the results of image reliability evaluation.

[Evaluation of latex ink storage stability]
100 ml of each latex ink was placed in a glass container, sealed and stored under the following conditions, and changes in surface tension and viscosity were evaluated. The results are shown in Table 7.

(Storage conditions)
(I) Normal temperature (25 ° C) storage-28 days (ii) High temperature (50 ° C) storage-14 days (iii) Low temperature (0 ° C) storage-28 days (iv) Cycle test (0-50 ° C)-24 hours Table 7 shows the changes in surface tension and viscosity for 14 days at different temperatures. There was almost no change in physical properties of each ink.

[Evaluation of printing method]
Based on the above test results, an example in which pictures and characters are printed on various media surfaces by the ink jet printer 1 using the inks of Examples 1 to 3 and Comparative Example 1 will be described. In each example, the ink jet printer was carried out in a room temperature room at a room temperature of about 15 to 20 ° C. In the following tables, the media heating temperature of the preheater indicates the heating temperature by the preheater on the surface of the media conveyed on the back of the platen, and the media heating temperature of the print heater is carried on the center of the platen, The heating temperature by the print heater on the surface of the medium on which the ink droplet ejected from the print head is landed is shown. The image quality in each of the following tables is a comprehensive evaluation of the evaluation of the image characteristics (feathering, color bleeding, beading, image density, glossiness). The highest score is 10 points. “OFF” in each table below represents a state in which heating of the media by the preheater or the print heater is stopped without energizing the preheater or the print heater.

[Ink of Example 1]
MacMedia: 9829-00 (product name) was used as the media.

[Ink of Example 2]
As the media, Transparent PVC Film P-245RC: LINTEC (product name) was used.

[Ink of Example 3]
As the media, PVC Viewcal 880C: LINTEC (product name) was used.

[Ink of Comparative Example 1]
MacMedia: 9829-00 (product name) was used as the media.

  Based on these results when using the inks of Examples 1 to 3 and Comparative Example 1, the latex resin having a minimum film forming temperature of 0 ° C. or less on the surface of the binder resin was used to draw a picture by a preheater. The image quality of the pictures and characters printed on the media surface is preliminarily heated by using a printing method that preheats the media on which the characters are printed and heats the media that causes the ink droplets ejected from the print head to land on the print heater. Has been confirmed to improve.

  As described above, the printing method according to the present invention is suitable for printing high quality images with fixing stability on the surface of media such as outdoor display advertisements that require environmental characteristics and media characteristics. Is preferred. It is also suitable for printing pictures and characters on the surface of various industrial media that require scratch resistance.

DESCRIPTION OF SYMBOLS 1, 2 Inkjet printer 10 Printing means 12 Nozzle 14 Print head 16 Drive belt 20 Platen 22 Platen center part 24 Platen rear part 26 Platen front part 30 Media 40 Preheater 60 Conveying means 62 Feed roller 64 Pressing roller 70 Print heater 80 Temperature control means 100 Winding means 110 Trays 120 Host computer 130 Maintenance station 140 Refresh mode means 150 Drying means

Claims (8)

Driving means for relatively moving the positions of the print head, the recording medium, and the print head;
Heating means provided at a position facing the ink ejection surface of the print head and heating the recording medium disposed at the position by the driving means from the side facing away from the ink landing surface of the recording medium; ,
Preheating means for heating the recording medium from the side facing away from the ink landing surface at a position before the recording medium is disposed at a position facing the ink ejection surface of the print head. A printing method for printing a recording medium using an inkjet printer comprising:
Heating the recording medium by the heating means and the preliminary heating means so that the surface temperature of the ink landing surface of the recording medium is 40 ° C. or more and 60 ° C. or less;
The ink ejected from the print head is an ink containing a solvent, a colorant, and a binder resin, and the binder resin is dispersed or suspended in the solvent, and the minimum film forming temperature on the surface of the binder resin is 0 ° C. A printing method using the following ink.   The printing method according to claim 1, wherein the binder resin has a minimum film forming temperature different between the surface and the inside.   The printing method according to claim 2, wherein the binder resin has a minimum film forming temperature on the surface lower than an internal minimum film forming temperature. The solvent is at least one of water and a hydrophilic solvent,
The printing method according to claim 1, wherein the latex ink contains 50% by weight or more of the solvent with respect to the total weight of the latex ink.   5. The heating temperature of the recording medium by the heating unit and the heating temperature of the recording medium by the preliminary heating unit are controlled to different temperatures. 6. Printing method. The surface temperature of the ink landing surface of the recording medium is heated to 30 ° C. or more and 50 ° C. or less by the preheating means,
The printing method according to claim 5, wherein the surface temperature of the ink landing surface of the recording medium is heated to 40 ° C. or more and 60 ° C. or less by the heating unit.   5. The heating temperature of the recording medium by the heating unit and the heating temperature of the recording medium by the preliminary heating unit are controlled to be the same temperature. 6. Printing method.   As the recording medium, from the group consisting of a vinyl chloride sheet, PET sheet, tarpaulin sheet, coated paper, and uncoated polypropylene resin, glass, metal, and a molded product thereof. The printing method according to claim 1, wherein a recording medium to be selected is used.

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