WO2014112474A1

WO2014112474A1 - Inkjet printer and printing method

Info

Publication number: WO2014112474A1
Application number: PCT/JP2014/050455
Authority: WO
Inventors: 亮文関; 大西　勝; 博徳橋詰
Original assignee: 株式会社ミマキエンジニアリング
Priority date: 2013-01-21
Filing date: 2014-01-14
Publication date: 2014-07-24
Also published as: CN104936785B; JP2014138989A; JP6166048B2; CN104936785A

Abstract

This invention addresses the problem of appropriately forming a plurality of ink layers on a non-absorbent medium. The solution means is an inkjet printer (10) for performing printing by the inkjet method on a non-absorbent medium (50) which does not absorb ink, the inkjet printer (10) being provided with: inkjet heads (12y-12k) for discharging ink droplets of a first ink; a sub-scan driving unit (20), which is a facing-position changing unit for causing the positions of the medium (50) along a preset direction of movement to sequentially face the inkjet heads (12y-12k); an inkjet head (14) for discharging ink droplets of a second ink, which is different from the first ink, the inkjet head (14) being disposed further downstream of the inkjet heads (12y-12k) with respect to the direction of movement of the medium (50); and a print heater (24). The first ink is a colloidal solution.

Description

Inkjet printer and printing method

The present invention relates to an inkjet printer and a printing method.

In recent years, inkjet printers have been used for various purposes (see, for example, Non-Patent Document 1). For example, in recent years, inkjet printers are used for printing advertisements and the like installed outdoors. And in such a use, in order to improve the weather resistance of printed matter, non-absorbing media (media), such as vinyl chloride and PET, are widely used. Also, UV ink (ultraviolet curable ink) is widely used as an ink suitable for printing on such a medium. Furthermore, it is widely practiced to form an overcoat layer with clear ink on the surface of a printed material printed with UV ink for the purpose of further improving the weather resistance of the printed material or increasing the gloss of the printed material. It has been broken.

Clear ink is usually colorless and transparent ink. For this reason, when an overcoat layer (hereinafter referred to as a clear layer) of clear ink is formed, if ink of other colors is mixed with the clear ink, ink bleeding is conspicuous and the quality of the printed matter is greatly reduced. Therefore, when forming a clear layer on a layer (colored layer) that has been printed with color ink or the like, a condition in which the ink of the colored layer that has been printed previously and the clear ink that is ejected onto the layer is not mixed It is necessary to print with.

On the other hand, UV ink hardens quickly by ultraviolet irradiation and is fixed on the medium. Therefore, when the clear layer is formed on the UV ink layer, if the UV ink is irradiated with ultraviolet rays before the clear ink is overlaid, the UV ink and the clear ink can be appropriately prevented from being mixed. And since there exists such an advantage, conventionally the clear layer is normally used with UV ink. In addition, it is not common to form a clear layer on an ink layer formed of ink other than UV ink.

However, it may be difficult for the UV ink to sufficiently improve the flatness (smoothness) of the ink dots in a state where the UV ink is cured by irradiation with ultraviolet rays. Therefore, even if the clear layer is formed thereon, sufficient glossiness may not be obtained. In addition, since the printing surface on which the UV ink dots are arranged has large irregularities, air may enter between the clear layer and the like formed thereon. As a result, the quality of the printed material may deteriorate.

Therefore, in order to obtain a high-quality printed material that can obtain sufficient weather resistance and glossiness, for example, it is desired to perform printing by a new method different from the conventional one. Moreover, as the method, for example, a method of more appropriately forming a plurality of ink layers on a non-absorbing medium is desired. Accordingly, an object of the present invention is to provide an ink jet printer and a printing method that can solve the above-described problems.

In order to solve the above-mentioned problems, the inventors of the present application first considered using an ink other than UV ink in combination with a clear ink. And first, examination and various experiments etc. were performed about the case where a colored layer is formed using water-based ink, solvent ink, etc., and a clear layer is formed on it. In the case of these inks, if the colored layer is not sufficiently dried, the ink of the colored layer is mixed with the clear ink, and an extra color is formed on the originally clear layer. Therefore, it is necessary to sufficiently dry the colored layer before forming the clear layer. Then, the following method was examined as a method of fully drying a colored layer before forming a clear layer.

First, it was studied to reduce the thickness of the colored layer to improve the drying property. However, in this case, the weather resistance is lowered, and the required weather resistance may not be obtained in applications such as outdoor advertising. In addition, color development may be insufficient. Therefore, it is difficult to perform printing appropriately by this method.

Therefore, next, the temperature of the printer heater for drying the ink was raised, and it was examined to dry the ink in a shorter time. However, in this case, if the heating temperature is too high, problems such as cockling of the medium occur. Further, when the temperature of the print heater becomes high, problems such as drying of the nozzles of the ink jet head tend to occur. Therefore, it is difficult to greatly increase the heating temperature. As a result, it is also difficult to perform printing appropriately by this method.

Also, in order to sufficiently dry the colored layer before forming the clear layer, for example, the colored layer is first printed on the entire surface of the medium, and then the clear layer is formed after sufficiently drying. Is also possible. However, with this method, the time required for printing increases and the workability is greatly reduced. For this reason, it is difficult to perform printing appropriately by this method.

Therefore, the inventors of the present application next focused on the difference in drying method (characteristic) depending on the type of ink. For various inks, the relationship between the volatilization ratio of the solvent and the ink viscosity was confirmed by experiments.

Then, through this experiment, first, it was found that the viscosity of the latex ink was increased in a state where the evaporation amount (evaporation ratio) of the solvent was smaller than that of the solvent ink or the like. That is, it has been found that by using latex ink, it is possible to realize a state in which the dry amount of the ink is less than that of the other ink and it is difficult to mix with the clear ink. In addition, subsequent earnest studies have found that this characteristic of latex ink is due to the fact that it is a colloidal solution ink.

Furthermore, by arranging the inkjet head for forming the colored layer and the inkjet head for the clear ink in accordance with the characteristics of the latex ink, even if the temperature of the print heater is kept low, It has been found that the mixing of the ink and the clear ink can be prevented appropriately. Further, since the following earnest research, the same effect can be obtained not only in the case where the colored layer and the clear layer are overlapped but also in the case where a plurality of ink layers are formed in an overlapping manner. I found out. The present invention which the inventor of the present application has arrived based on the above knowledge has the following configuration.

(Configuration 1) An inkjet printer that performs printing by an inkjet method on a non-absorbing medium that does not absorb ink, and a first inkjet head that ejects ink droplets of the first ink toward the medium; An opposing position changing unit that sequentially feeds each position of the medium in the movement direction to the first inkjet head by sending the medium relative to the first inkjet head in the set movement direction; A second ink is disposed downstream of the first inkjet head in the medium moving direction relative to the head and ejects ink droplets of a second ink different from the first ink toward the medium. An inkjet head, and a heater disposed at a position facing at least the first inkjet head across the medium, 1 ink is an ink of the colloidal solution.

In this configuration, the first inkjet head and the second inkjet head are arranged with their positions shifted in the relative movement direction of the medium. Therefore, when configured in this way, for example, until the second ink-jet head ejects a second ink droplet onto the first ink dot formed by the first ink-jet head. In the meantime, heating can be performed by a heater disposed in a printing region immediately below the first inkjet head. In addition, by using the first ink that is the ink of the colloidal solution, it is possible to realize a state in which it is difficult to mix with the second ink while the amount of ink dried is relatively small.

Therefore, with this configuration, for example, at least the first ink and the second ink are not mixed before the second ink overlaps the dot of the ink formed with the first ink. The first ink can be dried appropriately and sufficiently. In addition, as a result, the ink layer formed by the first ink and the ink layer formed by the second ink can be appropriately stacked.

In addition, about the 1st inkjet head and the 2nd inkjet head, shifting the position in the relative moving direction of the medium means that these heads are positioned substantially shifted. That may be. For example, the nozzles that are set so as to eject ink droplets in each head are shifted in the moving direction of the medium. is there. The nozzles set to eject ink droplets in each head are, for example, nozzles other than dummy nozzles set so as not to eject ink droplets in a part of the nozzle row.

Further, when configured in this way, printing can be appropriately performed on a non-absorbing medium by using a colloidal solution ink. Therefore, if constituted in this way, a plurality of ink layers can be appropriately formed on a non-absorbent medium, for example.

Here, the non-absorbing medium is, for example, a medium formed of a material that does not absorb the ink solvent. As the non-absorbing medium, for example, a medium such as vinyl chloride or PET can be suitably used. If comprised in this way, the weather resistance of printed matter can be improved appropriately, for example. As the non-absorbing medium, for example, a metal or the like can be used.

In this configuration, the first ink is, for example, a color ink for forming a colored layer. For example, the first ink may be any color ink of YMCK ink. Regarding the configuration of the first ink, the colloidal solution ink may be, for example, a suspension (dispersion) type ink or an emulsion (emulsification) type ink. More specifically, for example, latex ink can be suitably used as the first ink. If comprised in this way, a colored layer can be appropriately formed with respect to media, such as vinyl chloride and PET, for example.

The second ink layer is, for example, an overcoat layer that covers the colored layer. In this case, the second ink layer is formed by solid printing (solid printing) in which a certain area on the medium is painted with a certain density. The second ink is, for example, clear ink. In this case, for example, by forming a clear layer on the colored layer, the weather resistance of the printed matter can be improved more appropriately. The second ink may be an ink other than the clear ink. For example, the second ink may be an achromatic ink other than clear. More specifically, the second ink may be a special color ink such as white, metallic, or pearl.

When the ink as described above is used as the second ink, it is considered that bleeding is particularly noticeable when the ink of the colored layer and the second ink are mixed. Therefore, when these inks are used as the second ink, the quality of the printed matter is particularly deteriorated when the first ink and the second ink are mixed. On the other hand, if comprised as mentioned above, it can prevent appropriately mixing a 1st ink and a 2nd ink, for example. This also makes it possible to perform high-quality printing more appropriately.

(Configuration 2) The first ink is latex ink. If comprised in this way, it can print appropriately with respect to non-absorbing media, such as a vinyl chloride, PET, or a metal, for example.

Further, when latex ink is used as the first ink, it is possible to more appropriately realize a state in which the drying amount of the ink is relatively small and it is difficult to mix with the second ink. Therefore, if constituted in this way, a plurality of ink layers can be more appropriately formed on a non-absorbent medium, for example.

(Structure 3) The heater heats the medium at a position facing the first ink jet head, so that the ink droplet of the second ink is ejected on the first ink to each position of the medium. In addition, the colloid contained in the first ink is aggregated. According to this configuration, for example, it is possible to more appropriately realize a state in which the first ink and the second ink are less likely to be mixed with a relatively small amount of ink dried. Thereby, for example, a plurality of ink layers can be more appropriately formed on a non-absorbent medium.

(Configuration 4) The first ink is an ink for forming a colored layer that is a layer of colored ink, and the first ink jet head ejects ink droplets of the first ink onto the medium, so that at least The first ink layer, which is a colored layer containing the first ink, is formed, and the second ink jet head ejects ink droplets of the second ink onto the first ink layer, thereby A second ink layer is formed to cover the first ink layer.

The second ink layer is, for example, an overcoat layer that covers the first ink layer. If comprised in this way, the 2nd ink layer which covers a colored layer can be formed more appropriately, for example. Thereby, it is possible to more appropriately print a printed matter in which a plurality of ink layers are laminated.

(Configuration 5) The second ink is a clear ink, and the second ink jet head performs a solid print that fills a predetermined area on the medium with a constant density, thereby forming the second ink layer with the clear ink. Form. If comprised in this way, a clear layer can be appropriately formed on a colored layer, for example. Thereby, for example, the weather resistance and gloss of the printed material can be further improved.

(Configuration 6) The second ink is an ink that does not dissolve the first ink after being fixed on the medium. If comprised in this way, it can prevent more appropriately that a 1st ink and a 2nd ink are mixed, for example.

Here, for example, depending on the composition contained in each of the first ink and the second ink, when the second ink is superimposed on the first ink, the first ink is used as the solvent of the second ink. There is a possibility that the ink is dissolved again and the ink is mixed. For example, when a colored layer is formed with a solvent ink (solvent ink) containing an organic solvent as a solvent and a clear ink containing an organic solvent is layered thereon, even if the solvent ink is once dried, the organic in the clear ink The solvent ink in the colored layer may be redissolved by the solvent. On the other hand, if comprised like the structure 6, remelting of the 1st ink can be prevented appropriately, for example.

More specifically, for example, when an aqueous latex ink is used as the first ink, an ink using an organic solvent as a solvent can be suitably used as the second ink. More specifically, when an aqueous latex ink is used as the first ink, the second ink such as a clear ink is preferably an ink using, for example, an organic solvent that does not dissolve the latex ink after fixing. Can be used. Such an organic solvent is, for example, a hydrophobic (nonpolar) organic solvent.

(Configuration 7) The heater heats the medium so that the temperature of the medium is in the range of 35 to 80 ° C. at a position facing the first inkjet head. The upper limit of the heating temperature is set according to the heat resistant temperature of the medium, for example. If comprised in this way, a medium can be heated appropriately, for example, without raising the temperature of a medium too much. In addition, this makes it possible to appropriately prevent cockling of the medium, drying of the nozzles of the inkjet head, and the like.

Furthermore, by heating the medium to 35 ° C. or higher, the first ink can be dried appropriately and sufficiently so that at least the first ink and the second ink are not mixed. In addition, this can appropriately prevent the first ink and the second ink from being mixed and causing bleeding.

(Configuration 8) The first inkjet head and the second inkjet head perform printing on a medium by performing a main scanning operation of ejecting ink droplets while moving in a preset main scanning direction, and the movement direction Is a direction parallel to the sub-scanning direction orthogonal to the main scanning direction. If comprised in this way, it can print appropriately with respect to each part of a medium with a 1st inkjet head and a 2nd inkjet head, for example. Thereby, for example, a plurality of ink layers can be more appropriately formed on the medium.

(Configuration 9) The second inkjet head is disposed so that the position in the movement direction can be changed, and the position in the movement direction of the second inkjet head is an ink layer formed by the first inkjet head. It is set according to at least one of the thickness of a certain first ink layer, the temperature of the heater, or the time for drying the first ink layer.

When configured in this manner, by changing the position of the second inkjet head, for example, for the operation after the first ink dot is formed, the timing of overlaying the second ink on the operation is appropriately adjusted. it can. This also makes it possible to appropriately adjust the drying amount of the first ink at the timing when the second ink overlaps. Therefore, if constituted in this way, a plurality of ink layers can be more appropriately formed on a medium, for example. Note that the position of the second inkjet head may be changed manually, for example, or automatically by driving a motor or the like.

(Configuration 10) An inkjet printer that performs printing on a medium by an inkjet method, and a first inkjet head that ejects ink droplets of a first ink toward the medium, and a first moving direction set in advance. An opposing position changing unit for sequentially opposing each position of the medium in the moving direction to the first inkjet head by feeding the medium relative to the inkjet head, and a medium relative to the first inkjet head A second inkjet head disposed on the downstream side of the first inkjet head in the moving direction and ejecting ink droplets of a second ink different from the first ink toward the medium, and at least the first A second ink jet head comprising an ink jet head and a heater disposed at a position facing each other across the medium The position of the second ink jet head in the moving direction can be changed. The position of the second ink jet head in the moving direction is the thickness of the first ink layer that is the ink layer formed by the first ink jet head, the heater It is set according to at least one of temperature and time for drying the first ink layer.

When configured in this way, for example, after the first ink dot is formed on the medium, the area where the first ink is formed on the medium before the second ink is overlaid on the medium. Can be heated properly. In addition, by changing the position of the second ink jet head, for example, the operation after forming the first ink dots can appropriately adjust the timing of overlaying the second ink thereon.

Therefore, with this configuration, for example, it is possible to appropriately adjust the amount of drying of the first ink at the timing when the second ink overlaps. In addition, by this adjustment, for example, the first ink can be appropriately dried to the extent that the first ink and the second ink are not mixed at least until the timing at which the second ink overlaps. In addition, for example, a plurality of ink layers can be appropriately formed on the medium.

(Structure 11) A printing method for performing printing by an inkjet method on a non-absorbing medium that does not absorb ink, the first inkjet head ejecting ink droplets of the first ink toward the medium; An opposing position changing unit that sequentially feeds each position of the medium in the movement direction to the first inkjet head by sending the medium relative to the first inkjet head in the set movement direction; A second ink is disposed downstream of the first inkjet head in the medium moving direction relative to the head and ejects ink droplets of a second ink different from the first ink toward the medium. First ink using an inkjet head and a heater disposed at a position facing at least the first inkjet head and a medium , It is the ink of the colloidal solution. If comprised in this way, the effect similar to the structure 1 can be acquired, for example.

(Configuration 12) A printing method for performing printing on a medium by an ink jet method, the first ink jet head ejecting ink droplets of the first ink toward the medium, and a first moving direction set in advance. An opposing position changing unit for sequentially opposing each position of the medium in the moving direction to the first inkjet head by feeding the medium relative to the inkjet head, and a medium relative to the first inkjet head A second inkjet head disposed on the downstream side of the first inkjet head in the moving direction and ejecting ink droplets of a second ink different from the first ink toward the medium, and at least the first The second inkjet head is moved in the moving direction by using an inkjet head and a heater disposed at a position facing the medium. The position in the moving direction of the second inkjet head is the position of the first ink layer that is the ink layer formed by the first inkjet head, the temperature of the heater, or The first ink layer is set according to at least one of the drying times. If comprised in this way, the effect similar to the structure 10 can be acquired, for example.

According to the present invention, for example, a plurality of ink layers can be appropriately formed on a non-absorbent medium.

1A to 1C are diagrams illustrating an example of an inkjet printer 10 according to an embodiment of the present invention. FIG. 1A is a side view illustrating an example of the configuration of the inkjet printer 10. FIG. 1B is a top view illustrating an example of a configuration of a main part of the inkjet printer 10. FIG. 1C shows an example of the state of the medium 50 after printing by the inkjet printer 10. It is a table | surface which shows the measured value of the viscosity of the ink in each drying time. It is a graph showing the result shown in FIG. It is a table | surface which shows the measured value of the viscosity and weight reduction rate of an ink. It is a graph showing the result shown in FIG. FIG. 6A to FIG. 6C show experimental results relating to the time lag after the colored layer is formed until the ink droplet of the clear ink is landed thereon. FIG. 6A shows the experimental conditions. FIG. 6B shows the results of blur determination for various time lags and print heater temperatures. FIG. 6C shows a trial calculation result of the color-clear distance L.

Embodiments according to the present invention will be described below with reference to the drawings. 1A to 1C are diagrams illustrating an example of an inkjet printer 10 according to an embodiment of the present invention. FIG. 1A is a side view illustrating an example of the configuration of the inkjet printer 10. FIG. 1B is a top view illustrating an example of a configuration of a main part of the inkjet printer 10. FIG. 1C shows an example of the state of the medium 50 after printing by the inkjet printer 10.

In this example, the inkjet printer 10 is a printing apparatus that performs printing by an inkjet method on a non-absorbing medium (medium) 50 that does not absorb ink. The non-absorbable medium 50 is a film medium such as vinyl chloride or PET. The medium 50 may be a roll-shaped medium, for example. As the non-absorbing medium 50, for example, a metal or the like can be used. The medium 50 may be a medium formed of various other materials that do not absorb the ink solvent.

In this example, the inkjet printer 10 includes a control unit 28, a plurality of

inkjet heads

12y, 12m, 12c, 12k, 14, a platen 16, a main scanning drive unit 18, a sub-scanning drive unit 20, a preheater 22, a print heater 24, and An after heater 26 is provided.

Further, in the inkjet printer 10, a main scanning direction indicated as a Y direction in the drawing and a sub-scanning direction indicated as an X direction in the drawing are set in advance. This main scanning direction is a direction parallel to the moving direction of each inkjet head in the main scanning operation. The main scanning operation is a printing operation (scanning operation) in which each inkjet head moves while ejecting ink droplets. The sub-scanning direction is a direction parallel to the moving direction (conveying direction) of the medium 50 in the sub-scanning operation for feeding the medium 50 relative to each inkjet head.

The control unit 28 is, for example, a CPU of the ink jet printer 10 and controls the operation of each unit of the ink jet printer 10. Further, the control unit 28 controls each unit of the inkjet printer 10 in accordance with an instruction received from, for example, a host computer of the inkjet printer 10.

Of the plurality of

inkjet heads

12y, 12m, 12c, 12k, and 14, each of the plurality of

inkjet heads

12y, 12m, 12c, and 12k (hereinafter referred to as inkjet heads 12y to 12k) is a colloidal solution ink. This is an example of a first inkjet head that ejects ink droplets of one ink, and ejects ink droplets of latex ink (Latex ink) that is an example of the first ink toward the medium 50. In this example, the first ink is also a color ink for forming a colored layer. Each of the inkjet heads 12y to 12k discharges ink droplets of latex inks of yellow (Y), magenta (M), cyan (C), and black (K), respectively, so that FIG. As shown in FIG. 3, the colored layer 102 is formed on the medium 50. The colored layer 102 is an example of a first ink layer containing at least a first ink.

The latex ink is ink that fixes a polymer material to a medium by drying, for example. This polymer material is, for example, an aqueous polymer material. The polymer material is, for example, a rubbery polymer material. The latex ink contains, as its components, for example, a latex resin that is a polymer material, water, a solvent, an additive, a smoothing agent, a viscosity modifier, an ultraviolet absorber, a colorant, and the like. Among these, the ultraviolet absorber is a component for preventing color ink from fading and protecting the medium. The colorant is a component that colors the ink thinly. According to this example, it is possible to appropriately print on various non-absorbent media 50.

It is also conceivable to use a colloidal solution ink other than the latex ink as the first ink. The ink of the colloidal solution is, for example, a suspension (dispersion) type or an emulsion (emulsification) type ink. The characteristics of the latex ink, which is an example of the first ink, will be described in more detail later.

The inkjet head 14 is an example of a second inkjet head that ejects ink droplets of a second ink different from the first ink. In this example, the second ink is a clear ink. The ink jet head 14 performs solid printing in which a predetermined area on the medium 50 is filled with a constant density by ejecting clear ink droplets toward the medium 50.

Further, the inkjet head 14 is disposed downstream of the inkjet heads 12y to 12k in the conveyance direction of the medium 50, so that the position in the sub-scanning direction is shifted from the inkjet heads 12y to 12k. In this example, the ink jet head 14 is disposed away from the ink jet heads 12y to 12k in the sub-scanning direction. The ink jet head 14 may be arranged with the position in the sub-scanning direction shifted from the ink jet heads 12y to 12k, for example, by staggered arrangement.

With this arrangement, the inkjet head 14 ejects clear ink droplets after printing is performed by the inkjet heads 12 y to 12 k on each position of the medium 50. Accordingly, as shown in FIG. 1C, the inkjet head 14 forms the clear layer 104 covering the colored layer 102 with the clear ink on the colored layer 102 formed by the inkjet heads 12y to 12k. The clear layer 104 is an example of a second ink layer that is a second ink layer.

According to this example, the clear layer 104 can be appropriately formed on the colored layer 102. Thereby, for example, the weather resistance and gloss of the printed material can be further improved.

In this example, the clear ink contains a UV absorber. In this case, for example, the weather resistance of the colored layer 102 under the clear layer 104 varies depending on the application amount of the clear ink. Therefore, the inkjet head 14 may have a configuration that can change the discharge amount of the clear ink according to the required weather resistance, for example. For example, the inkjet head 14 fills the print area with a density of 50% in addition to the clear layer 104 with a predetermined thickness by solid printing that fills the print area with a density of 100%. It may be possible to form a clear layer 104 of half the thickness. Further, it may be possible to form the clear layer 104 having a thickness twice as large as that of the above-mentioned one layer by painting the printing region with a density of 200%.

It is also conceivable to use an ink other than the clear ink as the second ink. For example, the second ink may be an achromatic ink other than clear. More specifically, the second ink may be a special color ink such as white, metallic, or pearl. Also when these inks are used, the inkjet head 14 forms, for example, an overcoat layer covering the colored layer 102 as the second ink layer, for example.

The platen 16 is a table that holds the medium 50 so as to face the plurality of inkjet heads 12y to 12k. The main scanning drive unit 18 is configured to cause the plurality of inkjet heads 12y to 12k, 14 to perform a main scanning operation, and includes, for example, a carriage and a guide rail. In this case, the carriage holds the plurality of inkjet heads 12 y to 12 k, 14 facing the medium 50. The guide rail guides the movement of the carriage in the main scanning direction. As a result, the plurality of inkjet heads 12y to 12k, 14 perform a main scanning operation of ejecting ink droplets toward the medium 50 while moving in the main scanning direction. In the main scanning operation, the plurality of inkjet heads 12y to 12k, 14 eject ink droplets in both forward and backward directions that move in the main scanning direction and cross the medium 50, for example.

The sub-scanning drive unit 20 is configured to transport the medium 50 in the sub-scanning direction. The sub-scanning drive unit 20 may be a drive unit that drives a roller that conveys the medium 50, for example. Further, this roller may be, for example, a roller that winds up the medium 50 after printing by the ink jet heads 12y to 12k.

Further, the sub-scanning drive unit 20 performs a sub-scanning operation for transporting the medium 50 in the sub-scanning direction between main scanning operations by the plurality of inkjet heads 12y to 12k. As a result, the sub-scanning drive unit 20 sequentially makes each position of the medium 50 in the sub-scanning direction face each of the plurality of ink jet heads 12y to 12k.

In this example, the sub-scanning drive unit 20 is an example of a facing position changing unit. The sub-scanning drive unit 20 conveys the medium 50 to send the medium 50 in the sub-scanning direction relative to the plurality of inkjet heads 12y to 12k, and each position of the medium 50 in the sub-scanning direction is The respective inkjet heads 12y to 12 and 14 are sequentially opposed to each other. Further, in the modified example of the configuration of the inkjet printer 10, a configuration in which the medium 50 is transported by a method different from this example may be used as the facing position changing unit. Further, the facing position changing unit may move the ink jet heads 12y to 12k, 14 side with respect to the medium 50 whose position is fixed.

The preheater 22, the print heater 24, and the after heater 26 are heaters that heat the medium 50. Among these, the pre-heater 22 is a heater disposed at a position upstream of any of the plurality of ink jet heads 12 y to 12 k in the conveyance direction of the medium 50. The medium 50 is heated at a position before the droplet is ejected.

The print heater 24 is an example of a heater disposed at a position facing the inkjet heads 12y to 12k, which are first inkjet heads. In this example, the print heater 24 is disposed at a position facing the plurality of ink jet heads 12 y to 12 k with the medium 50 interposed therebetween, so that ink droplets are generated on the medium 50 by the ink jet heads 12 y to 12 k. The discharged part is heated.

Further, in this example, the print heater 24 heats the medium 50 at a position facing the ink jet heads 12y to 12k, so that the latex ink layer formed by the ink jet heads 12y to 12k on each position of the medium 50. Before the ink droplets of clear ink are ejected onto the substrate, the latex ink is dried to sufficiently increase the viscosity of the latex ink.

Here, the drying of the latex ink by the print heater 24 is not necessarily limited to the case of drying completely, and may be, for example, sufficiently drying to prevent mixing with the clear ink. Further, the phenomenon that the viscosity of the latex ink is increased by heating will be described in more detail later.

In addition, the print heater 24 heats the medium 50 so that the temperature of the medium 50 is in a range of 35 to 80 ° C., for example, at a position facing the ink jet heads 12y to 12k. If comprised in this way, the medium 50 can be heated appropriately, for example, without raising the temperature of the medium 50 too much. Further, it is possible to appropriately prevent cockling of the medium 50 and drying of nozzles such as the ink jet heads 12y to 12k.

The upper limit of the heating temperature is set according to the heat resistant temperature of the medium 50, for example. For example, when a PET medium is used as the medium 50, the medium 50 can be heated to about 80 ° C. However, for example, when a vinyl chloride medium is used as the medium 50, it is preferable to lower the upper limit of the heating temperature of the medium 50. When the vinyl chloride medium 50 is used, the heating temperature of the medium 50 by the print heater 24 is, for example, 35 to 70 ° C., more preferably 35 to 60 ° C.

In addition, when heating in the above temperature range, by further heating at 35 ° C. or higher, the latex ink is at least not mixed with the latex ink, which is the color layer forming ink, and the clear ink. Can be dried appropriately and sufficiently. In addition, this can appropriately prevent the color layer forming ink and the clear ink from being mixed and causing bleeding.

The after heater 26 is a heater that heats the medium 50 downstream of the print heater 24 in the conveyance direction of the medium 50, and heats the medium 50 after printing by the plurality of inkjet heads 12y to 12k. According to this example, for example, the medium 50 can be heated over time as necessary. Thereby, for example, the heating temperature by the print heater 24 can be suppressed. Further, for example, the clear layer 104 formed by solid printing can be sufficiently dried.

When configured as described above, for example, the colored layer 102 can be appropriately formed on the non-absorbent medium 50 by using latex ink as the colored layer forming ink. In addition, the main scanning operation and the sub scanning operation performed by the main scanning driving unit 18 and the sub scanning driving unit 20 appropriately perform printing on each part of the medium 50 using the plurality of inkjet heads 12y to 12k. Can do. Further, the clear layer 104 can be appropriately formed on the colored layer 102 by disposing the ink jet heads 12y to 12k on the upstream side and the ink jet head 14 on the downstream side in the conveyance direction of the medium 50. . Therefore, according to this example, the colored layer 102 and the clear layer 104 that are a plurality of ink layers can be appropriately formed on the non-absorbent medium 50. Thereby, for example, the weather resistance and gloss of the printed matter can be appropriately increased.

Further, in this example, as described above, the inkjet heads 12y to 12k and the inkjet head 14 are arranged with their positions in the sub-scanning direction shifted. For example, as shown in FIG. 1B, the inkjet heads 12y to 12k and the inkjet head 14 are spaced apart from each other by a predetermined distance L. As a result, the timing at which printing is performed by the inkjet heads 12y to 12k and the timing at which printing by the inkjet head 14 is performed at the same position on the medium 50 is at least a time interval during which the medium 50 is transported a distance therebetween. become.

Therefore, according to this example, for example, after the ink dots for forming the colored layer are formed by the ink jet heads 12y to 12k, the time until the ink droplets of the clear ink are ejected by the ink jet head 14 thereon is set. It can be evacuated appropriately. In addition, by this, the medium 50 on which the dots of the ink for forming the colored layer are formed can be heated by the print heater 24 in the meantime.

Further, as will be described in more detail later, in this example, by using a latex ink, which is a colloidal solution ink, as a colored layer forming ink, a clear ink can be obtained with a relatively small amount of ink dried. It is possible to achieve a state that is difficult to mix. Therefore, according to this example, for example, before the clear ink overlaps the dots of the color layer forming ink, at least the color layer forming ink and the clear ink are not mixed with each other. The ink can be sufficiently dried. Thereby, the colored layer 102 and the clear layer 104 can be appropriately overlapped and formed.

Here, the distance L between the inkjet heads 12y to 12k and the inkjet head 14 may be the distance between the nozzle rows in each of the inkjet heads 12y to 12k and the nozzle rows in the inkjet head 14. Further, it is preferable that the distance L between the inkjet heads 12y to 12k and the inkjet head 14 can be changed. For example, the inkjet head 14 is preferably arranged so that the position in the sub-scanning direction can be changed. In this case, the position of the inkjet head 14 may be changed manually, for example, or automatically by driving a motor or the like. The position of the inkjet head 14 in the sub-scanning direction is, for example, at least one of the thickness of the colored layer 102 formed by the inkjet heads 12y to 12k, the temperature of the print heater 24, and the time for drying the colored layer 102. It is preferable to set accordingly.

In such a configuration, by changing the position of the inkjet head 14, for example, with respect to the operation after forming the ink dots for the colored layer, it is possible to appropriately adjust the timing of overlaying the clear ink thereon. This also makes it possible to appropriately adjust the drying amount of the colored layer ink at the timing when the clear ink overlaps. Therefore, with this configuration, for example, a plurality of ink layers can be more appropriately formed on the medium 50.

Subsequently, characteristics of latex ink, which is an example of colloidal solution ink, will be described in more detail. 2 to 5 are diagrams showing experimental results regarding the viscosity of the latex ink. 2 and 3 show experimental results regarding the relationship between the drying time and the viscosity of the ink. FIG. 2 is a table showing measured values of ink viscosity at each drying time. FIG. 3 is a graph showing the results shown in FIG. 4 and 5 show experimental results on the relationship between the viscosity of the ink and the weight reduction rate. FIG. 4 is a table showing measured values of ink viscosity and weight loss rate. FIG. 5 is a graph showing the results shown in FIG.

When printing with an inkjet printer, the ink that has landed on the medium increases in viscosity due to, for example, heating or the like, and eventually becomes solid, thereby fixing to the medium. Therefore, when the ink is fixed to the medium by drying, the state where the ink is not sufficiently dried can be said to be a state where the viscosity of the ink is not sufficiently increased. Accordingly, the inventors of the present application paid attention to the change in the viscosity of the ink due to heating, and conducted an experiment to measure the relationship between the drying time and the viscosity of the ink and the relationship between the viscosity of the ink and the weight reduction rate.

In this experiment, two types of latex ink and one type of solvent ink were used as inks to be measured. As the two types of latex inks, a known latex ink (hereinafter referred to as latex ink 1) manufactured by Mimaki Engineering Co., Ltd. and a known latex ink (hereinafter referred to as latex ink 2) manufactured by another company were used.

Here, these latex inks are latex inks having a general composition. For example, the latex ink 1 contains 10-30% of a glycol ether solvent, 20-40% of an alcohol solvent, 1-5% of an organic pigment (yellow), and 5-10% of other organic components. The remaining part is water. The latex ink 2 also has a similar composition.

Also, as one type of solvent ink, a known solvent ink (hereinafter referred to as solvent ink 1) manufactured by Mimaki Engineering Co., Ltd. was used. This solvent ink 1 is a solvent ink (solvent ink) having a general composition, 70 to 80% of a glycol ether solvent, 10 to 20% of a lactone solvent, 5% of a nickel compound, and a vinyl resin. Contains 1-5%. In this experiment, yellow ink was used as each of the inks for convenience of the experiment. However, it is considered that similar results can be obtained even when inks of other colors are used.

In the experiment, the viscosity was measured while measuring the weight reduction rate (wt%) for the above three types of ink (latex ink 1, latex ink 2, and solvent ink 1). Specifically, each of the above three types of ink is placed in a thermostatic bath at a temperature of 60 ° C., and each time the drying time elapses, the viscosity is measured with a viscometer and the weight reduction rate of the ink is measured. went. Note that the amount of each ink sample in the thermostat is 10 g. Moreover, the temperature of the thermostat in a viscometer was 25 degreeC.

As can be seen from the graph shown in FIG. 3 and the like, the viscosity of each of the above three types of ink increases as the drying time elapses. However, the way of increasing the viscosity is greatly different between the latex ink 1 and the latex ink 2 and the solvent ink 1.

For example, in the latex ink 1 and the latex ink 2, the viscosity rapidly rises when the drying time is relatively short. On the other hand, in the solvent ink 1, the viscosity only rises gently until a certain drying time elapses. For this reason, it is considered that the viscosity of the latex ink 1 and the latex ink 2 is increased by a principle different from that of the solvent ink 1.

As can be seen from the graph shown in FIG. 5 and the like, the viscosity of all three types of ink increases as the weight reduction rate of the ink increases. This is considered to indicate that the viscosity of the ink increases as the solvent in the ink evaporates. However, in this case as well, the way of increasing the viscosity is greatly different between the latex ink 1 and the latex ink 2 and the solvent ink 1.

For example, in the latex ink 1 and the latex ink 2, the viscosity rapidly increases when the ink weight reduction rate reaches a certain rate. More specifically, for example, as can be seen from the results shown in the table of FIG. 4, the viscosity of the latex ink 1 is 25 at the timing when the weight reduction rate of the ink changes from 44.0% to 44.2%. It has risen more than twice. Further, the viscosity of the latex ink 2 greatly increases over 30 times at the timing when the weight reduction rate of the ink changes from 50.5% to 53.9%. On the other hand, in the solvent ink 1, such a rapid increase in viscosity does not occur, and the viscosity gradually increases gradually as compared with the latex ink 1 and the latex ink 2. Therefore, also from this result, it is considered that the viscosity of the latex ink 1 and the latex ink 2 is increased on the principle different from that of the solvent ink 1.

Here, when considering based on the results shown in FIG. 3 and FIG. 5 and the composition of the ink, the solvent ink (solvent ink 1) has a solvent content in the ink as the solvent in the ink evaporates. It is thought that the ratio decreased, and as a result, the viscosity gradually increased. On the other hand, in the case of latex ink, it is considered not only that the solvent evaporates but also that some phase change occurs in the ink as the solvent decreases, and the viscosity rapidly increases.

Therefore, the inventor of the present application has further studied the reason why the viscosity of the latex ink rapidly increases, and that the size of particles contained in the ink is larger than that of the solvent ink or the like, or that the ink is a colloidal solution. Focused on. That is, since latex ink is an ink containing a polymer material, it can be said that it contains particles having a size larger than that of solvent ink or the like. In a state where the amount of the solvent is sufficiently large, the polymer material is considered to be uniformly dispersed in the ink.

However, when large size particles are included, the frictional force generated between the particles in the ink increases. In addition, when the ratio of the solvent in the ink is decreased, the distance between the particles is shortened, and the influence of the frictional force is considered to increase rapidly. Therefore, in the case of latex ink, it is considered that the influence of friction between particles cannot be ignored if the ratio of the solvent decreases to a certain level due to evaporation of the solvent. As a result, the viscosity of the ink is considered to rise rapidly due to a phenomenon such as thixotropy (thixotropy).

On the other hand, in the solvent ink, since the size of the particles contained in the ink is smaller than that of the latex ink, it is considered that most of the solvent evaporates before such a phenomenon occurs. As a result, it is considered that the solvent ink does not cause a sharp increase in viscosity unlike the latex ink.

Also, for particles dispersed in a solution, generally, the larger the particle size, the greater the attractive force between the particles. Furthermore, when the particles are colloidal particles, it is considered that the attractive force between the molecules becomes particularly large due to the influence of charging or the like. For this reason, in the latex ink, when the ratio of the solvent is reduced to a certain level or less, the attractive force between the particles becomes larger than the force for dispersing the particles in the solvent, and the particles are considered to gather. As a result, it is considered that the viscosity rapidly increases. In addition, it is considered that the colloid contained in the latex ink aggregates due to heating by the print heater 24 and increases the viscosity of the ink. In this case, the colloid is considered to be solidified by heating, for example.

And when these points are considered, in the inkjet printer 10 of this example, the viscosity is sufficiently increased in a shorter drying time by using the latex ink that is the ink of the colloidal solution as the colored layer forming ink. It can be said that it is difficult to mix with other inks. Further, by shifting the positions of the inkjet heads 12y to 12k and the inkjet head 14 in the sub-scanning direction and disposing the print heater 24 at a position facing the inkjet heads 12y to 12k, a practical printing speed can be achieved. It can be said that the ink for the colored layer can be sufficiently dried until the ink droplet of the clear ink is ejected onto the colored layer within the range to be realized. Therefore, according to this example, it is possible to appropriately prevent the colored layer ink and the clear ink from being mixed, for example. Thereby, a clear layer can be appropriately formed on the colored layer.

In addition, in the above, the experimental result was demonstrated only about the latex ink 1, the latex ink 2, and the solvent ink 1 from a viewpoint which demonstrates a required matter in relation to this invention. However, the inventors of the present application conducted similar experiments and studies on various inks (for example, water-based inks) other than the above inks. From these results, it can be said that the phenomenon in which the viscosity rapidly rises as described above is a phenomenon peculiar to colloidal solutions such as latex ink, and a phenomenon that does not occur in ordinary solvent ink or water-based ink. In the case of water-based ink, it is not suitable for printing on a non-absorbent medium. For this reason, when forming a plurality of ink layers on a non-absorbing medium, it is not usually used as an ink for a colored layer.

Also, as described above, in order to appropriately prevent the colored layer ink and the clear ink from being mixed, it is effective to dry the colored layer ink in a short time. Therefore, it seems that a solvent ink containing a volatile solvent having a low boiling point may be used as the ink for the colored layer in terms of simply drying the ink quickly.

However, the solvent ink containing such a volatile organic solvent has a large environmental load and may need to be avoided. In addition, when the colored layer is formed of the solvent ink, there is a possibility that when the clear ink is overlaid on the colored layer, there is a problem of redissolving that the colored layer ink is dissolved again by the solvent contained in the clear ink. As a result, bleeding may occur in the clear layer.

On the other hand, when the ink for the colored layer is used as the ink of the colloidal solution such as latex ink, the burden on the environment can be suppressed as compared with the case where the solvent ink containing the volatile solvent is used. Therefore, it is possible to perform printing more appropriately in various environments.

Also, as in this example, using a colloidal solution ink such as latex ink is also effective in preventing re-dissolution of the ink. That is, it is considered that the particles in the latex ink are aggregated in a state of sticking to each other when the viscosity is increased by heating. In this state, since the distance between the particles is small, it is considered that the attractive force acting between the particles is extremely large as compared with the state where the particles are dispersed in the solvent. Therefore, it is considered that re-dissolution of the ink hardly occurs even when another ink is superimposed on the latex ink layer in a state where the viscosity is increased. That is, when the clear layer is formed on the colored layer of the latex ink, it can be said that the clear ink is an ink that does not dissolve the latex ink after fixing on the medium 50 with respect to the relationship between the latex ink and the clear ink. Therefore, according to this example, it is possible to more appropriately prevent the color layer ink and the clear ink from being mixed.

More specifically, for example, when an aqueous latex ink is used as the colored layer ink, it is conceivable to use a clear ink using an organic solvent as a solvent. Further, as a solvent for the clear ink, for example, it is conceivable to use an ink using a hydrophobic (nonpolar) organic solvent or the like as a solvent. If comprised in this way, remelting can be prevented more appropriately, for example.

In this example, the latex ink is used as the color layer ink, thereby realizing a configuration in which the viscosity of the ink is increased with a smaller amount of drying. Therefore, for example, it can be said that the heating temperature by the print heater 24 can be lowered. Moreover, this can prevent appropriately that the heating temperature of the medium 50 increases excessively. Furthermore, in this example, it can be said that by using the preheater 22 and the afterheater 26 in addition to the print heater 24, it is possible to more appropriately prevent the temperature of the medium 50 from being excessively increased.

For example, as described above, in this example, the latex ink, which is an ink for the colored layer, increases the viscosity of the ink with a small amount of drying. Therefore, the temperature of the print heater 24 disposed at the position facing the ink jet heads 12y to 12k can be set to a low temperature that can prevent cockling and the like. However, when the temperature of the print heater 24 is low, the rate of temperature increase of the medium 50 becomes slow, and it may be difficult to perform appropriate heating within a required time. On the other hand, in this example, the medium 50 is preheated by the preheater 22 upstream of the print heater 24 in the transport direction. Therefore, according to this example, even when the print heater 24 having a low temperature is used, the medium 50 can be heated more appropriately.

In this example, an after heater 26 is further arranged on the downstream side of the print heater 24 in the transport direction. Therefore, at the position of the print heater 24, it is sufficient that the ink can be sufficiently dried within a range in which the viscosity is increased so as not to be mixed with the clear ink. For example, it is necessary when considering the winding operation after printing and the influence during storage. It is not always necessary to dry to a certain level. Further, it is not necessary to completely dry the clear layer formed by the inkjet head 14.

Also in this case, it is possible to sufficiently dry the medium 50 at the position of the after-heater 26 as compared with the case where the medium 50 is heated only by the preheater 22 and the print heater 24, for example. Thereby, a colored layer and a clear layer can be dried appropriately and sufficiently. Therefore, according to this example, the heating temperature by the print heater 24 etc. can be suppressed more appropriately. Further, this can prevent problems caused by heating the medium 50 more appropriately.

In addition, the inventor of the present application has confirmed through experiments and the like that, in earnest research related to the present invention, the configuration of the inkjet printer 10 of the present example enables appropriate printing under practically reasonable printing conditions. Did. Therefore, this point will also be described below.

The inventor of the present application conducted various experiments regarding the time lag (time difference) from the formation of the colored layer to the landing of the ink drop of clear ink on the colored layer. The ink jet printer used in this experiment is an ink jet printer in which necessary changes and adjustments are made as necessary with respect to the configuration of the ink jet head, the printing speed, and the like based on the ink jet printer JV400-130LX manufactured by Mimaki Engineering.

FIG. 6A to FIG. 6C show the experimental results regarding the time lag from the formation of the colored layer until the ink droplet of the clear ink is landed thereon. FIG. 6A shows the experimental conditions. FIG. 6B shows the results of blur determination for various time lags and print heater temperatures. In the following description, the average moving speed of the head is the average moving speed of the inkjet head in the main scanning operation. The average media feed speed is the average transport speed of the medium in the sub-scanning operation. In an inkjet printer, the printing speed is determined according to these speeds. The distance in the sub-scanning direction between the colored layer forming inkjet head and the clear layer forming inkjet head is defined as a color-clear distance L. The color-clear distance L is a distance corresponding to the distance L shown in FIG. 1B.

When the experiment was performed under the printing conditions shown in FIG. 6A, as shown in FIG. 6B, when the temperature of the print heater is 70 ° C., the clear layer does not bleed even if the time lag is 0.5 to 0.6 seconds. Was confirmed. This time lag corresponds to the case where the color-clear distance L is 0.169 mm. Thereby, for example, when the temperature of the print heater is set to about 70 ° C., it has been confirmed that the bleeding of the clear layer is appropriately suppressed by the configuration of the realistic ink jet printer.

In addition, when the temperature of the print heater was 60 ° C. or higher, it was confirmed that bleeding did not occur in the clear layer due to the configuration with a time lag of 97.7 seconds. This time lag corresponds to the case where the color-clear distance L is 18.457 mm. Thereby, for example, even when the temperature of the print heater was about 60 ° C., it was confirmed that the bleeding of the clear layer was appropriately suppressed by the realistic configuration of the ink jet printer. In addition, for example, it was confirmed that the temperature of the print heater can be suppressed to about 60 ° C. by setting the time lag to about 100 seconds or more.

In addition, when the temperature of the print heater was 50 ° C. or higher, it was confirmed that bleeding did not occur in the clear layer due to the configuration with a time lag of 178.5 seconds. This time lag corresponds to the case where the color-clear distance L is 27.263 mm. Thereby, for example, even when the temperature of the print heater was about 50 ° C., it was confirmed that the bleeding of the clear layer was appropriately suppressed by the configuration of the realistic ink jet printer. Further, for example, it was confirmed that the temperature of the print heater can be suppressed to about 50 ° C. by setting the time lag to about 180 seconds or more.

Also, based on these results, a trial calculation was performed for the color-clear distance L determined according to the printing speed (average moving speed of the head, average feeding speed of the medium) and the print heater temperature. FIG. 6C shows a trial calculation result of the color-clear distance L. From this trial calculation result, it can be seen that the configuration of the ink jet printer 10 of the present example enables appropriate printing under practically appropriate printing conditions.

In addition, although detailed description was abbreviate | omitted, the inventor of this application performed various experiments also about the case where the temperature of a print heater was set to less than 50 degreeC. Even if the temperature of the print heater is less than 50 ° C., for example, if the heating is performed so that the temperature of the medium becomes about 35 ° C. or more, the bleeding of the clear layer is appropriately suppressed by a realistic ink jet printer configuration. That was confirmed. Therefore, in this case as well, it can be said that the configuration of the ink jet printer 10 of this example enables appropriate printing under practically appropriate printing conditions.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

The present invention can be suitably used for, for example, an ink jet printer.

DESCRIPTION OF SYMBOLS 10 ... Inkjet printer, 12y-k ... Inkjet head (first inkjet head), 14 ... Inkjet head (second inkjet head), 16 ... Platen, 18 ... Main scanning drive 20, sub-scanning drive unit (opposite position changing unit), 22, preheater, 24, print heater, 26, after heater, 28, control unit, 50, medium, 102 ... colored layer, 104 ... clear layer

Claims

An inkjet printer that performs printing by an inkjet method on a non-absorbing medium that does not absorb ink,
A first inkjet head that ejects ink droplets of a first ink toward the medium;
An opposing position changing unit that sequentially causes each position of the medium in the movement direction to face the first inkjet head by sending the medium relative to the first inkjet head in a preset movement direction. When,
The second ink is disposed on the downstream side of the first ink jet head in the moving direction of the medium relative to the first ink jet head, and is different from the first ink toward the medium. A second inkjet head that ejects ink droplets of ink;
A heater disposed at a position facing at least the first inkjet head and the medium,
The ink-jet printer, wherein the first ink is a colloidal solution ink.
2. The ink jet printer according to claim 1, wherein the first ink is a latex ink.
The heater heats the medium at a position facing the first inkjet head, thereby ejecting ink droplets of the second ink onto the first ink to each position of the medium. 2. The ink jet printer according to claim 1, wherein the colloid contained in the first ink is aggregated before the ink is discharged.
The first ink is a colored layer forming ink that is a layer of colored ink,
The first inkjet head forms a first ink layer, which is a colored layer containing at least the first ink, by ejecting ink droplets of the first ink onto the medium;
The second ink jet head forms a second ink layer that covers the first ink layer with the second ink by ejecting ink droplets of the second ink onto the first ink layer. The inkjet printer according to claim 1.
The second ink is a clear ink;
The said 2nd inkjet head forms the said 2nd ink layer by the said clear ink by performing the solid printing which fills the predetermined area | region on the said medium with a fixed density | concentration, The said 2nd ink layer is formed. The inkjet printer as described.
2. The ink jet printer according to claim 1, wherein the second ink is an ink that does not dissolve the first ink after being fixed to the medium.
2. The ink jet printer according to claim 1, wherein the heater heats the medium so that the temperature of the medium is in a range of 35 to 80 ° C. at a position facing the first ink jet head.
The first inkjet head and the second inkjet head perform printing on the medium by performing a main scanning operation of ejecting ink droplets while moving in a preset main scanning direction,
The inkjet printer according to claim 1, wherein the moving direction is a direction parallel to a sub-scanning direction orthogonal to the main scanning direction.
The second inkjet head is disposed so that the position in the moving direction can be changed,
The position of the second inkjet head in the moving direction is the thickness of the first ink layer, the temperature of the heater, or the first ink layer that is an ink layer formed by the first inkjet head. The ink jet printer according to claim 1, wherein the ink jet printer is set according to at least one of the time periods.
An inkjet printer that performs printing on a medium by an inkjet method,
A first inkjet head that ejects ink droplets of a first ink toward the medium;
An opposing position changing unit that sequentially causes each position of the medium in the movement direction to face the first inkjet head by sending the medium relative to the first inkjet head in a preset movement direction. When,
The second ink is disposed on the downstream side of the first ink jet head in the moving direction of the medium relative to the first ink jet head, and is different from the first ink toward the medium. A second inkjet head that ejects ink droplets of ink;
A heater disposed at a position facing at least the first inkjet head and the medium,
The second inkjet head is disposed so that the position in the moving direction can be changed,
The position of the second inkjet head in the moving direction is the thickness of the first ink layer, the temperature of the heater, or the first ink layer that is an ink layer formed by the first inkjet head. An ink jet printer, which is set according to at least one of the time to be performed.
A printing method for printing on a non-absorbent medium that does not absorb ink by an inkjet method,
A first inkjet head that ejects ink droplets of a first ink toward the medium;
An opposing position changing unit that sequentially causes each position of the medium in the movement direction to face the first inkjet head by sending the medium relative to the first inkjet head in a preset movement direction. When,
The second ink is disposed on the downstream side of the first ink jet head in the moving direction of the medium relative to the first ink jet head, and is different from the first ink toward the medium. A second inkjet head that ejects ink droplets of ink;
Using a heater disposed at a position facing at least the first inkjet head and the medium,
The printing method, wherein the first ink is a colloidal solution ink.
A printing method for printing on a medium by an inkjet method,
A first inkjet head that ejects ink droplets of a first ink toward the medium;
An opposing position changing unit that sequentially causes each position of the medium in the movement direction to face the first inkjet head by sending the medium relative to the first inkjet head in a preset movement direction. When,
The second ink is disposed on the downstream side of the first ink jet head in the moving direction of the medium relative to the first ink jet head, and is different from the first ink toward the medium. A second inkjet head that ejects ink droplets of ink;
Using a heater disposed at a position facing at least the first inkjet head and the medium,
The second inkjet head is disposed so that the position in the moving direction can be changed,
The position of the second ink jet head in the moving direction is determined based on the thickness of the first ink layer, the temperature of the heater, or the first ink layer, which is an ink layer formed by the first ink jet head. The printing method is characterized in that the printing method is set according to at least one of the time periods.