JP5663997B2 - Ink set - Google Patents

Description

  The present invention relates to an ink set that can be used in a droplet discharge device that includes switching means for discharging a plurality of inks from the same nozzle.

  In a droplet discharge apparatus such as an ink jet recording apparatus, the ink cartridge can be replaced according to the purpose of recording. If you want to record with an ink different from the currently installed ink cartridge, you can remove the currently installed ink cartridge and replace it with an ink cartridge filled with the desired ink. .

  However, the replacement of the ink cartridge is a cumbersome operation for the user of the droplet discharge device, which imposes an excessive burden on the user.

  Therefore, Patent Document 1 proposes a droplet discharge device including a switching unit that can replace ink discharged from the same nozzle as needed without replacing the ink cartridge. According to this, for example, one of photo black and mat black can be selectively ejected from the same nozzle.

  On the other hand, in such a droplet discharge device, if the nozzle is filled with ink for a long time, the nozzle may be clogged due to ink sticking or the like, and the ink droplet may not be discharged normally. . In such a case, since accurate dots cannot be formed on the recording medium, it becomes impossible to perform clean recording. From such a viewpoint, there has been proposed a droplet discharge device including a switching unit between ink and a cleaning liquid for cleaning the nozzle (see, for example, Patent Documents 1 to 3).

JP 2007-230006 A JP 2006-240010 A JP 2009-269291 A

  However, when switching is performed in the droplet discharge device provided with the switching means between the ink and the cleaning liquid discharged from the same nozzle as described above, the two are mixed with each other at the time of switching, and the amount of liquid required for switching is very large. There was a problem that it took a lot of time.

  One of the objects according to some aspects of the present invention is an ink set provided in a droplet discharge device having a switching unit that switches and discharges a plurality of types of ink from the same nozzle. An object of the present invention is to provide an ink set capable of reducing the amount.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the ink set according to the present invention is:
An ink set that includes a first ink and a second ink that are used in a droplet discharge device that includes a switching unit that switches a plurality of types of ink and discharges each type of ink from the same nozzle.
The first ink contains a colorant;
The viscosity of the first ink is higher than the viscosity of the second ink.

  According to the ink set of Application Example 1, it is possible to reduce the amount of the first ink used in the ink switching.

[Application Example 2]
In application example 1,
The difference in viscosity between the first ink and the second ink may be 0.04 mPa · s or more.

  According to the ink set of Application Example 2, it is possible to further reduce the amount of the first ink used in the ink switching.

[Application Example 3]
In application example 1 or application example 2,
A third ink that is switched by the switching means;
The viscosity of the first ink, the viscosity of the second ink, and the viscosity of the third ink are:
(Viscosity of the second ink) <(Viscosity of the first ink) <(Viscosity of the third ink)
Can be in a relationship.

  According to the ink set of Application Example 3, it is possible to reduce the amount of the first ink used in the ink switching, and it is possible to shorten the time required for the ink switching.

[Application Example 4]
In application example 3,
The difference in viscosity between the first ink and the third ink may be 0.04 mPa · s or more.

  According to the ink set of Application Example 4, it is possible to reduce the usage amount of the third ink in the ink switching.

[Application Example 5]
In any one of Application Examples 1 to 4,
The color material of the first ink may be at least one selected from pigments, dyes, metal oxides, and particles having a hollow structure.

[Application Example 6]
In any one of Application Examples 3 to 5,
The second ink and the third ink may be a cleaning liquid.

  According to the ink set of Application Example 6, ink can be switched efficiently and nozzle clogging can be reduced.

FIG. 3 is a schematic perspective view illustrating a main configuration part of a printer including a switching unit. FIG. 2 is a block diagram illustrating an electrical configuration of the printer illustrated in FIG. 1. 6 is a flowchart for explaining a flow of switching processing performed when the printer is powered on. 6 is a flowchart for explaining a flow of switching processing performed before the printer is turned off.

  Hereinafter, preferred embodiments of the present invention will be described. Embodiment described below demonstrates an example of this invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described in the following embodiments are indispensable constituent requirements of the present invention.

  The ink set according to the following embodiment is used in a droplet discharge device including a switching unit for discharging a plurality of types of ink from the same nozzle.

  Since the ink set according to the present embodiment is used for a droplet discharge device provided with a switching unit for discharging a plurality of types of ink from the same nozzle, first, an outline of the droplet discharge device is first described. A specific example of the ink set will be described in detail.

1. Hereinafter, a preferred embodiment of a liquid discharge apparatus will be described in detail with reference to the drawings. An ink jet printer (hereinafter referred to as “printer”) will be described as an example of the droplet discharge device. FIG. 1 is a schematic perspective view showing the main components of a printer provided with switching means, and FIG. 2 is a block diagram showing the electrical configuration of the printer shown in FIG.

  In the present embodiment, the printer 20 having the switching unit 56 that can switch between two types of ink is described as a switching unit using FIGS. 1 and 2. However, the switching unit included in the printer according to the present invention includes: Three or more types of ink may be switched. In the following description, it is assumed that the first ink has a property of a dispersion in which a pigment is dispersed, and the pigment component may precipitate due to settling for a long period of time. The second ink is assumed to be a solution that is unlikely to cause precipitation, such as a cleaning liquid. In the case where the third ink is provided, the third ink is a solution having a property that hardly causes precipitation, such as a cleaning liquid.

  The printer 20 shown in FIG. 1 includes a paper stacker 22, a paper feed roller 24 driven by a step motor (not shown), a platen 26, a carriage 28, a carriage motor 30, and a traction belt driven by the carriage motor 30. 32 and a guide rail 34 for guiding the scanning of the carriage 28. A recording head 36 having a large number of nozzles is mounted on the carriage 28.

  The recording head 36 is connected to the cartridges 11 a, 11 b, 12, 13, 14, and 15 via liquid supply paths 41, 42, 43, 44, and 45. The cartridge 12 contains black ink (K), the cartridge 13 contains cyan ink (C), the cartridge 14 contains magenta ink (M), and the cartridge 15 contains yellow ink (Y). Further, the cartridge 11a contains a first ink, and the cartridge 11b contains a second ink. The second ink is filled in the nozzles from which the first ink is ejected among the nozzles provided in the recording head 36. That is, the nozzle from which the first ink is ejected is selectively filled with the first ink and the second ink via the switching means 56. In addition, a cartridge (not shown) is further provided, and the third ink is accommodated in the cartridge, and the first ink, the second ink, and the second ink are supplied to the nozzle from which the third ink is ejected via the switching unit 56. You may comprise so that 3 inks may be filled selectively. In this case, the switching unit 56 is appropriately configured so that the three types of ink can be switched.

  Each cartridge includes an ink pack containing each ink (image forming liquid), and an air chamber is formed around the ink pack. Ink in each ink pack is supplied to the recording head 36 via the liquid supply paths 41, 42, 43, 44, 45 by pressurizing the air chamber by a pressurizing unit (not shown). Thus, in this embodiment, the printer 20 is different from a so-called on-carriage type printer in which an ink cartridge is mounted on the carriage 28, and is an off-carriage type that is fixedly mounted at a predetermined position of the main body of the printer 20. An inkjet printer is exemplified. In addition, here, a mode in which replacement is performed by ejecting (pushing out) ink from the nozzle by the pressurizing unit is illustrated, but a mode in which replacement is performed by ejecting (extracting) ink from the nozzle side using the suction unit. There may be.

  The recording paper P (recording medium) is taken up by the paper feed roller 24 from the paper stacker 22 and fed on the surface of the platen 26 in the sub-scanning direction orthogonal to the main scanning direction of the recording head 36. The carriage 28 is pulled by a pulling belt 32 driven by a carriage motor 30 and moves in the main scanning direction along the guide rail 34.

  As shown in FIG. 2, the printer 20 includes a reception buffer memory 50 that receives a signal supplied from the host computer 90, an image buffer 54 that stores image data, and a system controller 51 that controls the operation of the entire printer 20 ( Control means), a main memory 52, and an EEPROM 53. Various operations of the printer 20 are realized by reading the firmware stored in the EEPROM 53 into the main memory 52 and executing it.

  The system controller 51 is connected to a main scanning drive circuit 61 that drives the carriage motor 30, a sub-scanning drive circuit 62 that drives the paper feed motor 31, and a head drive circuit 63 that drives the recording head 36. ing. The sub-scanning drive circuit 62, the paper feed motor 31 and the paper feed roller 24 constitute a paper feed mechanism.

  The system controller 51 controls the main scanning drive circuit 61 and the sub-scanning drive circuit 62 according to various commands included in the recording data received by the reception buffer memory 50 and setting conditions written in the EEPROM 53 in advance.

  For example, when it is set to record a high-quality image, a so-called interlace method in which an image is recorded while a raster is intermittently formed in the sub-scanning direction by the main scanning driving circuit 61 and the sub-scanning driving circuit 62. Record. It is also possible to perform so-called overlap type recording in which nozzles forming one raster are driven at intermittent timing.

  Further, the system controller 51 is connected with display means 55, switching means 56, time measuring means 57, and nozzle discharge inspection means 58. The display means 55 displays the display content on the liquid crystal display screen of the printer 20. Alternatively, the display content is transmitted to the printer driver 91 of the host computer 90 and displayed on the driver display screen 91. The switching unit 56 is like a switching valve, and automatically switches the liquid supplied to the liquid supply path 41 to either the first ink or the second ink in response to an instruction from the system controller 51. Although not shown, the switching unit 56 may be configured to switch between three or more types of ink. The time measuring means 57 measures the time during which the specific nozzle of the recording head 36 is filled with the first ink and there is no ejection operation (first filling state), that is, the standing time.

  The nozzle ejection inspecting means 58 is disposed in a non-recording area that is out of the area that can be recorded by the recording head 36 on the carriage 28. The carriage 28 moves from the recording area to the non-recording area along the main scanning direction, so that the ejection state is inspected. The nozzle discharge inspection means 58 is disposed below the recording head 36 so as to face each nozzle of the recording head 36 that has moved to the non-recording area. The nozzle ejection inspecting means 58 detects the induced current generated in the conductive ink absorber due to the proximity of the charged ink droplet and the conductive ink absorber for receiving the ink droplet ejected from each nozzle of the recording head 36. A detecting unit that performs charging, a voltage applying unit that applies a voltage to the conductive ink absorber so as to charge the ink droplet when the ink droplet is ejected from each nozzle, and a bottomed container for housing the conductive ink absorber And.

  When the charged ink droplet is ejected from each nozzle toward the conductive ink absorber, an induced current is generated in the conductive ink absorber based on an electrostatic induction phenomenon or the like as the ink droplet approaches. That is, as the ink droplet approaches, an induced current flows through the conductive ink absorber so that a charge having a polarity opposite to that of the ink droplet is induced. The nozzle clogging is inspected based on whether or not the induced current is detected.

  A method of switching between the first ink and the second ink in the printer 20 having the above configuration will be described. From the first filling state in which the first ink is filled in the specific nozzle in which the first ink and the second ink are selectively filled, the system controller 51 is filled with the second ink in the same nozzle. Control is performed to switch to the second filling state according to a predetermined condition. Hereinafter, a switching process performed when the printer 20 is turned on and a switching process performed before the printer 20 is turned off will be described.

  FIG. 3 is a flowchart for explaining the flow of switching processing performed when the printer is powered on. When the power supply of the printer 20 is ON, the system controller 51 continues the state in which the specific ink from the nozzles of the recording head 36 to which the first ink is ejected is filled with the first ink. An instruction is given to measure the time, that is, the time for which the printer 20 is left. If there is an ejection operation from the nozzles of the recording head 36 within a preset time, the timing means 57 is reset and the timing is restarted.

  The preset time can be set to one month, for example. The time of one month is a value empirically obtained as the maximum period during which the nozzle does not clog when the first ink is filled in the nozzle and left to stand. This value is different for each ink, and here, as an example, it is 1 month. Therefore, the value varies depending on the installation environment of the printer 20, the ink composition, and the like, and is a value that can be appropriately changed by a command or the like. Here, the description will be made on the assumption that the pigment-based first ink is employed. Note that if the period is set too short in order to reliably prevent clogging, the second ink is frequently filled, so that the consumption of the second ink is large and the cost performance may be deteriorated.

  The system controller 51 confirms the leaving time counted by the time measuring means 57 (step S11). It is determined whether or not the leaving time is one month or longer, and if it is determined that the leaving time is one month or longer (step S12: Yes), the system controller 51 switches the valve on the first ink side to the switching means 56. Close and instruct to open the valve on the second ink side. Next, a pressure unit (not shown) of the cartridge 11 b is driven to supply the second ink to the recording head 36 via the liquid supply path 41. The second ink supplied to the recording head 36 is filled in the nozzle filled with the first ink. That is, the first ink that has been filled is pushed out from the nozzle by the second ink and switched to the second ink (step S13).

  On the other hand, if it is determined in step S12 that the standing time is shorter than one month (step S12: No), the system controller 51 instructs the nozzle discharge inspection means 58 to execute the nozzle discharge inspection. The nozzle discharge inspection means 58 performs a nozzle discharge inspection (step S14), and determines whether or not there is a missing nozzle in the nozzle filled with the first ink based on the inspection result. When a missing nozzle is found in the nozzle filled with the first ink (step S15: Yes), the first ink is switched to the second ink (step S13). On the other hand, if no missing nozzle is found in the nozzle filled with the first ink (step S15: No), the process returns to step S11, resets the time measuring means 57, and restarts the measurement of the standing time.

  As described above, the first ink and the second ink are selectively filled into specific nozzles according to predetermined conditions. Therefore, when the ink ejection operation is not performed for a long period of time, if the specific nozzle is switched to be filled with the second ink, the specific nozzle will not be clogged. Accordingly, it is possible to prevent a specific nozzle from being left for a long period of time while being filled with the first ink having a particle size larger than that of the multicolor ink and easily causing clogging.

  Further, as a time when clogging occurs in a specific nozzle, an empirically obtained value is set in advance, and if the set one month is compared with the actual leaving time, the second ink is supplied. Switching can be minimized to the extent that clogging can be prevented. Thereby, it is possible to prevent the second ink from being wasted.

  Even when the leaving time is less than the preset one month, when the missing nozzle is detected, it is possible to switch to the second ink. Therefore, the second ink is filled even when the missing nozzle is detected without depending on the empirically obtained value of 1 month as the time for occurrence of clogging in a specific nozzle, so that clogging is further performed. Can be prevented from deteriorating.

  Next, switching processing performed before the printer 20 is turned off will be described. FIG. 4 is a flowchart for explaining the flow of switching processing performed before the printer is turned off. When there is an instruction to turn off the power of the printer 20 from the outside (step S21: Yes), the system controller 51 instructs the printer driver 91 of the host computer 90 to display a message that prompts the user to input the scheduled power off duration time. (Step S22). When the user who has read the displayed message inputs the scheduled power-off duration, the input value is transmitted to the printer 20.

  When the system controller 51 detects an input (step S23: Yes), the system controller 51 determines whether or not the scheduled power-off continuation time transmitted from the printer driver 91 is longer than a preset month (step S24). If it is determined that the scheduled power off duration is one month or more (step S24: Yes), the system controller 51 closes the first ink side valve and opens the second ink side valve with respect to the switching means 56. Instruct. Next, a pressure unit (not shown) of the cartridge 11 b is driven to supply the second ink to the recording head 36 via the liquid supply path 41. Then, the second ink supplied to the recording head 36 is filled in the nozzle filled with the first ink. That is, the first ink that has been filled up to that point is pushed out of the nozzle by the second ink, and after switching to the second ink, the power-off process is executed (steps S25 and S26).

  On the other hand, if it is determined in step S24 that the scheduled power OFF duration is shorter than one month (step S24: No), the power OFF process is executed as it is without switching the first ink to the second ink (step S26). ).

  As described above, even when there is an instruction to turn off the power, it is possible to switch from the state filled with the first ink to the state filled with the second ink before executing the power-off process. That is, the second ink can be filled in the nozzles of the first ink while the power is off. Thereby, it is possible to prevent the nozzle from being left for a long time while being filled with the first ink. On the other hand, when the scheduled power-off duration is shorter than one month, which is empirically obtained as the time at which the nozzle of the first ink is clogged, the power is turned off without being filled with the second ink. That is, since the power is turned on before the clogging occurs and the ejection operation is scheduled to be performed, the possibility of clogging is low, and the power is turned off without filling the second ink. Thereby, it is possible to prevent the second ink from being wasted.

  As described above, the printer 20 includes the switching unit 56 that automatically switches from the first filling state to the second filling state in accordance with an instruction from the system controller 51 under a predetermined condition. Since the switching means 56 automatically switches from the first filling state to the second filling state, there is no need for the user to switch manually. For this reason, even if the user is not near the printer 20, the nozzles of the first ink are automatically filled with the second ink.

  Contrary to the above, the switching means 56 of the printer 20 can automatically switch from the second filling state to the first filling state in accordance with an instruction from the system controller 51 under a predetermined condition. . Even when the switching means 56 automatically switches from the second filling state to the first filling state, it is not necessary for the user to switch manually. Such a switching operation can be performed using the above-described apparatus configuration. The timing for switching from the second filling state to the first filling state is not particularly limited. For example, when the printer 20 receives a command (recording command) for discharging the first ink from the nozzles, the power source of the printer 20 is switched on. It can be set as appropriate when the state changes from the OFF state to the ON state (recording standby state). Then, the second ink filled in the nozzle can be replaced with the first ink, and the first ink can be ejected from the nozzle.

  Furthermore, when the switching unit 56 is configured to switch between three or more types of ink and switches between the first ink, the second ink, and the third ink, the switching unit 56 receives an instruction from the system controller 51. Accordingly, the first filling state, the second filling state, and the third filling state in which a specific nozzle is filled with the third ink can be switched at any timing. In this way, it is possible to fill each nozzle with a desired type of ink in an arbitrary period.

  Although the above embodiment has been described on the assumption of a so-called off-carriage type ink jet printer, a so-called on-carriage type ink jet printer can also be applied in the present invention. In this case, in step S13 of FIG. 3 and step 25 of FIG. 4, the user may be notified to replace the cartridge containing the first ink with the cartridge containing the second ink. That is, the system controller 51 may display a message for prompting replacement of the cartridge on the display means 55 (notification means).

2. Ink Set Hereinafter, the ink set according to the present embodiment will be described. First, the first ink, the second ink, and the third ink will be described, and then, the first mode including the first ink and the second ink. The ink set and the ink set of the second mode including the third ink will be sequentially described.

2.1. Each component of the first ink, the second ink, and the third ink is not particularly limited. For example, water, an organic solvent, a coloring material, a surfactant, and At least one of the other components can be appropriately blended. The properties of the first ink, the second ink, and the third ink are all liquids or dispersions.

  Hereinafter, the components that can be blended in each of the first ink, the second ink, and the third ink will be described, but the first ink, the second ink, and the third ink may contain different components. The same component may be contained and the content of each component may be different. Therefore, in the following description in “2.1. First ink, second ink, and third ink” in this section, any one of the first ink, the second ink, and the third ink is simply referred to as “ink”. It explains as a name.

(1) Water The ink of the present embodiment can contain water. Examples of water that can be used for the ink include pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, or ultrapure water. Ions or the like may be present in the water as long as the above-described particle dispersion is not hindered. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is more preferable because it can suppress the generation of mold and bacteria for a long period of time and can keep the ink stable for a long period of time.

  The water content when water is contained in the ink of the present embodiment is not limited, but is preferably 50% by mass or more and 95% by mass or less with respect to the total amount of the ink. When the content of water in the ink is within this range, for example, the dispersibility of the pigment when the pigment is blended with the ink can be enhanced, and the storage stability of the ink can be enhanced.

  In addition, that content of water is 50 mass% or more and 95 mass% or less has shown that content of components other than water is 5 mass% or more and 50 mass% or less. In the present specification, components other than water may be referred to as solid content, and the content of water is 50% by mass or more and 95% by mass or less means that the concentration of solid content in the ink is 5% by mass or more. It means that it is 50 mass% or less.

(2) Penetration aid or humectant The ink of the present embodiment may contain at least one of a penetration aid and a humectant, if necessary. One of the functions of the penetration aid is to increase the wettability of the recording surface such as a recording medium to increase the ink permeability. One of the functions of the humectant is to suppress drying of the ink.

  Typical examples of penetration aids and humectants include polyhydric alcohols, amino acid derivatives, pyrrolidone derivatives, and sugars. Among these, polyhydric alcohols may be able to perform both functions of a penetration aid and a humectant even if they are a single compound.

  Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol and other alkanediols having 4 to 8 carbon atoms, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylol Examples include propane and glycol ethers.

  As glycol ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol Mention may be made of lower alkyl ethers of polyhydric alcohols such as monomethyl ether, triethylene glycol monobutyl ether and tripropylene glycol monomethyl ether. Among these, when triethylene glycol monobutyl ether is blended in the ink, better recording quality can be obtained.

  These polyhydric alcohols have the effect of preventing ink from drying, preventing clogging in the ink jet recording head portion, and improving the permeability of the ink into the recording medium when the ink is applied to the ink jet recording apparatus. It can have at least one.

  Of the alkanediols described above, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, from the viewpoint of excellent effect of improving the permeability of the ink into the recording medium, A 1,2-alkanediol having 4 to 8 carbon atoms such as 1,2-heptanediol and 1,2-octanediol is preferable. Further, among these, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol having 6 to 8 carbon atoms are particularly preferable because they have a particularly good effect of increasing permeability. .

  Examples of the amino acid derivatives include glycine betaine, atrinin, carnitine, γ-butyrobetaine, trigonelline, β-alanine betaine, homarine, homoserine betaine, ampleurine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, taurobetaine, stachydrin. And betaines which are N-trialkyl-substituted products of amino acids such as betaine glutamate and phenylalanine betaine.

  Examples of pyrrolidone derivatives include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone, N-butyl-2-pyrrolidone, 5-methyl-2-pyrrolidone, polyvinyl Examples include pyrrolidone and the like.

  Examples of the saccharide include monosaccharides, oligosaccharides, and polysaccharides, such as glucose, mannose, galactose, fucose, ribose, fructose, xylose, arabinose, maltose, cellobiose, lactose, sucrose, trehalose, raffinose, panose, ilmaltose. , Stachyose, gentiobis, gentianose and the like.

  Amino acid derivatives, pyrrolidone derivatives, and saccharides prevent ink from drying and prevent clogging in the ink jet recording head when ink is applied to an ink jet recording apparatus, and increase the permeability of the ink to the recording medium. At least one of the following.

  In the case where the ink of this embodiment is applied to an ink jet recording apparatus and the ink contains a penetration aid and a humectant, the content thereof is preferably 0. 0 relative to the total mass of the ink. It is 1 mass% or more and 20 mass% or less, More preferably, it is 1 mass% or more and 15 mass% or less.

(3) Viscosity modifier The ink of this embodiment can contain a viscosity modifier. The viscosity modifier has a function of adjusting the viscosity of the ink. Use of a viscosity modifier is preferable from the viewpoint of easy adjustment of the viscosity of the ink. The viscosity adjustment of the ink does not have to be performed by the viscosity adjusting agent, and can be performed by adjusting the content of the component contained in the ink.

  Examples of the viscosity modifier include alginic acids, cellulose derivatives, and the above-described humectants. Among these, the moisturizing agent described above can be preferably used from the viewpoint that clogging in the ink jet recording head portion can be prevented simultaneously with the adjustment of the viscosity of the ink.

  Examples of alginic acids include alginates such as sodium alginate, potassium alginate and ammonium alginate, and alginic acid derivatives such as alginates.

  Examples of the cellulose derivative include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose and the like.

  When a viscosity modifier is used in the ink of this embodiment, the addition amount may be adjusted so as to obtain a desired viscosity, and the addition amount is not particularly limited.

(4) Surfactant The ink of the present embodiment can contain a surfactant. Examples of the surfactant suitable for the ink of the present embodiment include at least one of an acetylene glycol surfactant and a polysiloxane surfactant. When these surfactants are blended in the ink, the wettability of the recording medium to the recording surface is increased, and the permeability of the ink into the recording medium can be further improved.

  Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, Examples include 5-dimethyl-1-hexyn-3-ol, 2,4-dimethyl-5-hexyn-3-ol, and the like. Moreover, a commercial item can also be utilized for acetylene glycol type-surfactant, for example, Orphine E1010, STG, Y (above, Nissin Chemical Co., Ltd. product), Surfinol 104, 82, 465, 485, TG (above , Air Products and Chemicals Inc.). Commercially available products can be used as the polysiloxane surfactant, and examples thereof include BYK-347, BYK-348, BYK-UV3500 (manufactured by Big Chemie Japan Co., Ltd.) and the like. Furthermore, other surfactants such as an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant may be added to the ink composition of the present embodiment.

  When a surfactant is contained in the ink of the present embodiment, the content of the surfactant is preferably 0.01% by mass or more and 5% by mass or less, more preferably based on the total mass of the ink. It is 0.1 mass% or more and 0.5 mass% or less.

(5) pH adjuster The ink of the present embodiment may contain a pH adjuster. The pH adjuster suitable for the ink of the present embodiment is not particularly limited, and examples thereof include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, and triethanol. Examples thereof include at least one of amine, triisopropanolamine, potassium carbonate, sodium carbonate, and sodium hydrogen carbonate. Of these, when a tertiary amine such as triethanolamine or triisopropanolamine is selected as a pH adjuster, it becomes easier to adjust the pH of the ink. When the ink contains a pH adjuster, the content thereof is preferably 0.01% by mass or more and 10% by mass, more preferably 0.1% by mass or more and 2% by mass with respect to the total mass of the ink. % Or less.

(6) Coloring material The ink of the present embodiment may contain at least one selected from pigments, dyes, metal oxides, and particles having a hollow structure as a coloring material. The content of the coloring material in the ink of the present embodiment is preferably 1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less with respect to the total mass of the ink.

(6-1) Pigment The pigment that can be used in the present embodiment is not particularly limited, and examples thereof include inorganic pigments and organic pigments.

  As the inorganic pigment, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone. Polycyclic pigments such as pigments, dye chelates (for example, basic dye type chelates, acidic dye type chelates), dyeing lakes (basic dye type lakes, acid dye type lakes), nitro pigments, nitroso pigments, aniline black, A daylight fluorescent pigment is mentioned. The said pigment may be used individually by 1 type, and may use 2 or more types together.

  More specifically, examples of the inorganic pigment used for black include the following carbon blacks, for example, No. manufactured by Mitsubishi Chemical. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, or No2200B, etc .; Columbia Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc .; Cabot Regal 400R, Regal 330R, Regal 660L, Monal 660R 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc .; or Color Black FW1, Color Black FW2, Clk Black FW2C, Decksa's Color Black FW2 FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, and Special Black 5S.

  Examples of yellow organic pigments include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 167, 172, 180 and the like.

  Examples of magenta organic pigments include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or C.I. I. Pigment violet 19, 23, 32, 33, 36, 38, 43, 50 and the like.

  Examples of cyan organic pigments include C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 15:34, 16, 18, 22, 25, 60, 65, 66, C.I. I. Bat Blue 4, 60 and the like.

  Examples of organic pigments other than magenta, cyan and yellow include C.I. I. Pigment green 7, 10, C.I. I. Pigment brown 3, 5, 25, 26, C.I. I. Pigment orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63, and the like.

(6-2) Dyes As dyes, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, and the like are used for normal inkjet recording. Various dyes can be used.

  Examples of yellow dyes include C.I. I. Acid Yellow 1, 3, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 59, 61, 70, 72, 75, 76, 78, 79, 98, 99, 110, 111, 127, 131, 135, 142, 162, 164, 165, C.I. I. Direct Yellow 1, 8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 110, 132, 142, 144, C.I. I. Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42, C.I. I. Food Yellow 3, 4, C.I. I. Solvent yellow 15, 19, 21, 30, 109 etc. are mentioned.

  Examples of magenta dyes include C.I. I. Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211, 215, 219, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, C.I. I. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, C.I. I. Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, C.I. I. Sorbize red 1, C.I. I. Food red 7, 9, 14 etc. are mentioned.

  Examples of cyan dyes include C.I. I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 199, 203, 204, 205, 229, 234, 236, 249, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249, C.I. I. Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33 , 34, 37, 38, 39, 40, 41, 43, 44, 46, C.I. I. Solvize Bat Blue 1, 5, 41, C.I. I. Bat Blue 4, 29, 60, C.I. I. Food Blue 1, 2, C.I. I. Basic blue 9, 25, 28, 29, 44 etc. are mentioned.

  Examples of dyes other than magenta, cyan and yellow include C.I. I. Acid Green 7, 12, 25, 27, 35, 36, 40, 43, 44, 65, 79, C.I. I. Direct Green 1, 6, 8, 26, 28, 30, 31, 37, 59, 63, 64, C.I. I. Reactive Green 6, 7, C.I. I. Acid Violet 15, 43, 66, 78, 106, C.I. I. Direct violet 2, 48, 63, 90, C.I. I. Reactive violet 1, 5, 9, 10, C.I. I. Direct black 154 etc. are mentioned.

(6-3) Metal oxide particles Examples of the metal oxide particles include particles of titanium dioxide, zinc oxide, alumina, magnesium oxide and the like.

The average particle diameter (d ₅₀ ) of the metal oxide particles is preferably 30 nm or more and 600 nm or less, and more preferably 200 nm or more and 400 nm or less. When the average particle diameter exceeds the above range, the dispersion stability may be impaired due to precipitation of particles in the ink composition, and the reliability such as clogging of the head may be impaired. On the other hand, if the average particle size is less than the above range, a desired color may not be obtained.

The average particle size d ₅₀ in the present specification can be measured using a particle size accumulation curve. The particle size accumulation curve is obtained by statistically processing the results of measurements that can determine the diameter of particles and the number of particles present in particles dispersed in a dispersion medium such as water. A kind of curve. The particle size accumulation curve in this specification takes the diameter of the particle on the horizontal axis, and the mass of the particle (the product of the volume, the density of the particle, and the number when the particle is regarded as a sphere) is larger than the particle having a smaller diameter. The value (integrated value) integrated toward the particle is plotted on the vertical axis. The particle size d ₅₀ is a value obtained by standardizing the vertical axis in the particle size accumulation curve (the total mass of the measured particles is 1) and the vertical axis value is 50% (0.50). The value on the horizontal axis, that is, the particle diameter.

  The particle size accumulation curve can be obtained, for example, by using a particle size distribution measuring apparatus based on the dynamic light scattering method. In the dynamic light scattering method, dispersed organic particles are irradiated with laser light, and the scattered light is observed with a photon detector. In general, dispersed particles usually have a Brownian motion. The speed of particle movement is larger for particles with a larger particle diameter and smaller for particles with a smaller particle diameter. When laser light is irradiated onto particles that are in Brownian motion, fluctuations corresponding to the Brownian motion of each particle are observed in the scattered light. This fluctuation is measured, an autocorrelation function is obtained by a photon correlation method or the like, and the particle diameter and the frequency (number) of particles corresponding to the diameter can be obtained by using a cumulant method or a histogram method analysis. The dynamic light scattering method is suitable for a sample including submicron-sized particles such as the metal oxide particles used in this embodiment, and the particle size can be relatively easily increased by the dynamic light scattering method. A product curve can be obtained. Examples of the particle size distribution measuring apparatus based on the dynamic light scattering method include Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), ELSZ-2, DLS-8000 (above, manufactured by Otsuka Electronics Co., Ltd.), LB-550 (stock) (Manufactured by Horiba, Ltd.).

(6-4) Particles having a hollow structure The particles having a hollow structure are not particularly limited, and known ones such as those formed from organic compounds such as styrene-acrylic resins and those formed from inorganic compounds. Can be used.

  As the particles having a hollow structure and made of an organic compound, for example, particles described in specifications such as US Pat. No. 4,880,465 and Japanese Patent No. 3,562,754 can be preferably used. The method for preparing particles having a hollow structure and made of an organic compound is not particularly limited, and for example, the following known methods can be applied. Examples of a method for preparing particles made of an organic compound having a hollow structure include, for example, particles having a hollow structure by stirring a vinyl monomer, a surfactant, a polymerization initiator, and an aqueous dispersion medium while heating in a nitrogen atmosphere. A so-called emulsion polymerization method for forming an emulsion or a production method described in JP 2000-500113 A, JP 2009-234854 A, or the like can be used. Commercially available particles can be used as the particles having a hollow structure and made of an organic compound.

  Commercially available particles may be used as the particles having a hollow structure and made of an inorganic compound. When producing particles made of an inorganic compound having a hollow structure, the production method is not particularly limited, and for example, a method of producing using heat-induced foaming, producing using an emulsion in a liquid phase Examples thereof include a method and a method of forming a cavity by forming a shell of a desired inorganic compound around a core (template) having properties that can be removed later, and then removing the core by oxidation, dissolution, or the like.

The average particle diameter (d ₅₀ : outer diameter of the shell described above) of the particles having a hollow structure is preferably 200 nm or more and 1000 nm or less, more preferably 400 nm or more and 800 nm or less. If the outer diameter of the particles having a hollow structure is in such a range, the dispersion in the ink composition can be kept good, and a desired color can be exhibited when attached to the recording medium. . On the other hand, if the outer diameter exceeds 1,000 nm, the particles may settle and the dispersion stability may be impaired, and the reliability such as clogging of the recording head may be impaired. On the other hand, if the outer diameter is less than 200 nm, a desired color may not be obtained. The inner diameter of the particles having a hollow structure (that is, the outer diameter of the core described above) is suitably about 100 nm to 800 nm. The average particle size d ₅₀ of the particles having a hollow structure can be measured by the same method as the average particle size d ₅₀ of the metal oxide particles.

(7) Other components When the ink of the present embodiment contains a pigment, a pigment dispersant for dispersing the pigment may be added. As a preferable dispersant, a dispersant conventionally used for preparing a pigment dispersion, for example, a polymer dispersant can be used. As such a dispersant, any dispersant used in normal ink can be used. The content when the pigment dispersant is contained in the ink is 5 to 200% by mass, preferably 30 to 120% by mass with respect to the content of the pigment in the ink, and is appropriately selected depending on the pigment to be dispersed. Good.

  The ink of the present embodiment may contain a resin for the purpose of fixing an image to a recording medium, for example. Examples of such resins include acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinyl pyrrolidone, vinyl pyridine. , Vinyl carbazole, vinyl imidazole, vinylidene chloride homopolymer or copolymer, or modified products thereof, polyurethane, fluororesin, natural resin, and the like. The copolymer may be in any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer. When polyurethane is used as the resin, polycarbonate-based or polyether-based polyurethane is preferable in terms of good dispersibility in the ink and good adhesion to the recording medium when attached to the recording medium. Furthermore, when using polyurethane, a known method can be applied to the synthesis of the polyurethane. For example, a compound having two or more isocyanate groups is reacted with a compound having two or more hydroxyl groups. The method can be used. One of the functions of the resin is to fix the pigment on the recording medium.

  The ink of this embodiment may contain a polymerization initiator as necessary. For example, the ink may contain a compound having a polymerizable functional group. In that case, the ink can be polymerized by applying heat or irradiating with radiation. When it is necessary to increase the temperature, a thermal polymerization initiator or a radiation polymerization initiator can be added.

  When the ink is water-based, the polymerization initiator is not necessarily water-soluble, may be oil-soluble, or may be poorly soluble. This is because, for example, when the polymerization initiator is oil-soluble, the polymerization initiator is present in the oil phase in the water-based ink, and when it is poorly soluble, the polymerization initiator is, for example, After the image forming step, when water is removed to some extent on the recording medium, it comes into contact with the polymerizable functional group and can exhibit a desired action. Furthermore, the polymerization initiator may have a property of moving between phases, and can be appropriately selected according to the formulation of the ink and as necessary.

  Further, an organic solvent may be added to the ink of this embodiment. Such an organic solvent is not particularly limited, but a polar organic solvent, for example, alcohols (for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, fluorinated alcohol, etc.), ketones (for example, Acetone, methyl ethyl ketone, cyclohexanone, etc.), carboxylic acid esters (eg, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.), or ethers (eg, diethyl ether, dipropyl ether, Tetrahydrofuran, dioxane, etc.), 2-pyrrolidone, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane, etc. can be used. .

  Further, the ink of the present embodiment includes a fixing agent such as a water-soluble rosin, an antifungal / preservative such as sodium benzoate, an antioxidant such as allophanates, a wetting agent, an ultraviolet absorber, a chelating agent, and an oxygen absorber. Additives such as preservatives and fungicides may be included. These additives can be used singly or in combination of two or more.

  The ink of this embodiment can be prepared in the same manner as the conventional ink using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, or the like. In the preparation, it is preferable to remove coarse particles using a membrane filter or a mesh filter.

2.2. Relationship between Viscosities of First Ink, Second Ink, and Third Ink The ink set of the present embodiment includes a first ink and a second ink. The viscosity of the second ink is lower than that of the first ink. When the viscosity of the second ink is lower than the viscosity of the first ink, the second ink can be easily pushed out by the first ink when the filling of the first ink into the nozzle filled with the second ink is started. . Thereby, compared with the case where the relationship of a viscosity is reverse, the consumption amount of a 1st ink is small, and the inside of a nozzle can be replaced with a 1st ink from a 2nd ink in a short time. Therefore, as will be described later, when the first ink is an ink containing a color material and the second ink is used as a cleaning liquid, the consumption amount of the ink (first ink) can be reduced, or the droplet discharge device Can be shortened (time required for switching from the second ink to the first ink).

  The difference in viscosity between the first ink and the second ink is preferably 0.04 mPa · s or more, more preferably 0.79 mPa · s or more, and 2.61 mPa · s or more and 10 mPa · s or less. Is more preferable. When the difference in viscosity between the first ink and the second ink is 0.04 mPa · s or more, the replacement from the second ink to the first ink can be performed in a shorter time, and the consumption of the first ink is reduced. can do. On the other hand, if the difference in viscosity between the first ink and the second ink is less than 0.04 mPa · s, the replacement speed from the second ink to the first ink decreases, or the consumption of the first ink increases. There is a case. Further, when the difference in viscosity between the first ink and the second ink exceeds 10 mPa · s, the ejection stability of the ink from the nozzle may be lowered, or it may be difficult to discharge the ink from the nozzle.

  The ink set according to the present embodiment may include a third ink in addition to the first ink and the second ink. When the ink set includes the third ink, the viscosity of each ink is preferably in the relationship of (second ink viscosity) <(first ink viscosity) <(third ink viscosity). When the viscosity of each ink is in the above relationship, it becomes easy to fill the first ink into the nozzle filled with the second ink as described above. For the same reason, when the filling of the third ink into the nozzle filled with the first ink is started, the first ink is easily pushed out by the third ink. In this way, when low-viscosity ink is extruded with high-viscosity ink, the amount of ink consumed on the extruding side (high-viscosity ink) is less than that when the viscosity relationship is reversed, and in a short time. The ink in the nozzle can be replaced. Therefore, as will be described later, when the first ink is an ink containing a coloring material and the second ink and the third ink are used as cleaning liquids, the consumption of ink (first ink) can be reduced, Operation time when the droplet discharge device is stopped (time required for switching from the first ink to the third ink), activation time of the droplet discharge device (time required for switching from the second ink to the first ink), etc. Can be shortened.

  Further, the viscosity difference between the first ink and the third ink is preferably 0.04 mPa · s or more, more preferably 0.79 mPa · s or more, and 2.61 mPa · s or more and 10 mPa · s or less. Is more preferable. When the difference in viscosity between the first ink and the second ink is 0.04 mPa · s or more, the replacement from the second ink to the first ink can be performed in a shorter time, and the consumption of the first ink is reduced. can do. On the other hand, when the difference in viscosity between the first ink and the second ink is less than 0.04 mPa · s, the replacement speed from the third ink to the first ink decreases, or the consumption of the first ink increases. There is a case. Further, when the difference in viscosity between the first ink and the third ink exceeds 10 mPa · s, the ejection stability of the ink from the nozzle may be lowered, or it may be difficult to discharge the ink from the nozzle.

  The viscosity of each ink of the present embodiment is preferably 2 mPa · s or more and 12 mPa · s or less, and more preferably 3 mPa · s or more and 6 mPa · s or less. When the viscosity of each ink is within the above range, it becomes easy to improve the ejection stability of the ink from the nozzle or to discharge the ink from the nozzle.

  In addition, the viscosity of each ink of this embodiment can be measured by maintaining the temperature of the ink at 20 ° C. using, for example, a vibration viscometer VM-100AL (manufactured by Yamaichi Electronics Co., Ltd.).

  Further, the viscosity of each ink can be adjusted by changing the above-described blending and blending amount. In particular, it is preferable to use a viscosity modifier because the viscosity can be easily adjusted. For example, the following adjustment is possible when adjusting the viscosity of the ink with the viscosity adjusting agent. Specifically, among the exemplified compounds, glycerin has a viscosity of 1500 mPa · s (at 20 ° C.). Therefore, when it is desired to increase the viscosity of ink containing glycerin, the viscosity of the ink can be increased by increasing the blending amount of glycerin. In this way, an ink having a desired viscosity can be easily obtained by changing the type and blending amount of the viscosity modifier.

3. Ink switching In the ink set according to the present embodiment, the ink set including the first ink and the second ink is the first aspect, and the ink set including the first ink, the second ink, and the third ink is the second aspect. In the following, ink switching in each aspect will be described in detail.

3.1. First Aspect The ink set according to the first aspect comprises the first ink and the second ink described above. In the ink set of this aspect, the selection of the type of the first ink and the second ink is arbitrary. For example, both of them may be inks that are used to form an image by adhering to the recording medium. Ink (cleaning liquid or the like) used for maintenance of the nozzle may be used. Alternatively, one may be ink used to form an image by adhering to a recording medium, and the other may be a cleaning liquid or the like used to perform nozzle maintenance.

  In the ink set of this aspect, the first ink is an ink containing a color material, that is, an ink used for forming an image by adhering to a recording medium in a droplet discharge device, and the second ink is in a nozzle The following effects can be obtained when the cleaning liquid is used for cleaning.

  For example, the droplet discharge device is set to the first filling state in which the nozzle is filled with the first ink, the image is recorded on the recording medium, and then the nozzle is replaced with the second ink to be in the second filling state. Then, as described in the section “1. Liquid droplet ejection device”, the next recording is performed by returning the nozzle to the first filling state. In such a case, the time required to shift from the second filling state to the first filling state and the amount of the first ink used during the transition can be reduced.

  On the other hand, in such a case, since the second ink introduced into the nozzle when shifting from the first filling state to the second filling state is a cleaning liquid, there is no need to suppress the amount used compared to the first ink. Low. In such a case, for example, since the transition is to prepare for leaving for a long period of time, the time required to transition from the first filling state to the second filling state is shifted from the second filling state to the first filling state. There is no need to reduce it as much as it takes. Therefore, although the efficiency of the transition from the first filling state to the second filling state is slightly reduced, the efficiency of the transition from the second filling state to the first filling state is improved, and waste of the first ink can be eliminated. At the same time, it is possible to quickly return to the first filling state, that is, the recording preparation state.

  As described above, in the ink set of this aspect, when the viscosity of the second ink is adjusted to be lower than the viscosity of the first ink, the first ink from the second ink is compared with the case where the viscosity relationship is reversed. The time for replacement with ink can be shortened, and the consumption of the first ink can be reduced. When the first ink is an ink containing a color material and the second ink is a cleaning liquid while satisfying the above-described viscosity relationship between the inks, the first ink is provided in the above-described droplet discharge device. It is possible to reduce the amount of ink used and improve the return speed after the droplet discharge device is left. When the first ink includes a color material that easily precipitates, the nozzle is replaced with the second ink and stored when the droplet discharge device is left (for example, for one month). Clogging can be reduced. Even in such a case, if the ink set of this aspect is used, the amount of the first ink used can be reduced, and the return speed of the droplet discharge device after being left can be improved.

3.2. Second Aspect The ink set in the second aspect comprises the first ink, the second ink, and the third ink described above. Also in the ink set of this aspect, the selection of the types of the first ink, the second ink, and the third ink is arbitrary. For example, all of them are inks that are used to form an image by being attached to a recording medium. It may be ink that is used for maintenance of the nozzles. Further, at least one of them may be ink used for forming an image by adhering to a recording medium, and the remaining ink may be used for maintenance of nozzles.

  In the ink set of this aspect, the first ink is an ink containing a color material, that is, an ink used to form an image by being attached to a recording medium in a droplet discharge device, and the second ink and the third ink. When the cleaning liquid for cleaning the inside of the nozzle is used, the following effects can be obtained.

  For example, after the droplet discharge device is in a state where the nozzle is filled with the first ink (first filling state) and an image is recorded on the recording medium, the inside of the nozzle is replaced with the third ink, To do. At this time, since the viscosity of the third ink is higher than the viscosity of the first ink, the time required for shifting from the second filling state to the third filling state and the amount of the third ink used at the time of shifting are reduced. can do. Thereby, for example, the operation when the droplet discharge device is stopped can be shortened.

  Next, the third ink in the nozzle is replaced with the second ink to shift from the third filling state to the second filling state. This transition operation may be performed at any time after the droplet discharge device is stopped and brought to the third filling state until the next time the droplet discharge device is operated. Further, the transition may be performed when the droplet discharge device is operated (power is turned on) or may be shifted in conjunction with other operations. Then, when the next recording is performed, the recording is performed from the second filling state to the state in which the nozzles are filled with the first ink (first filling state).

  In such a case, as in the case of the ink set of the first aspect described above, the time required to shift from the second filling state to the first filling state and the amount of the first ink used during the transition are reduced. be able to. Furthermore, the time required for shifting from the first filling state to the third filling state can be shortened, and the time required for shifting from the second filling state to the first filling state can also be shortened. Therefore, it is possible to speed up the operation when stopping and starting the droplet discharge device.

  As described above, in the ink set of this aspect, the viscosity of each of the first ink, the second ink, and the third ink is expressed as follows: (viscosity of the second ink) <(viscosity of the first ink) <(viscosity of the third ink) Viscosity), the replacement time from the second ink to the first ink and the replacement time from the first ink to the third ink can be shortened, and the consumption amount of the first ink and the third ink Consumption can be reduced. In the case where the first ink is an ink containing a color material and the second ink and the third ink are cleaning liquids and the liquid droplet ejection apparatus is provided with the first ink while satisfying the viscosity relationship between the inks. Can reduce the amount of the first ink used when switching the ink, and can improve the operation speed when the droplet discharge device is stopped and when it is returned after being left standing. When the first ink contains a color material that easily precipitates, when the droplet discharge device is left (for example, one month), it is replaced with the second ink or the third ink and stored. , Nozzle clogging can be reduced. Even in such a case, if the ink set of this aspect is used, the amount of the first ink used can be reduced, and the return speed of the droplet discharge device after being left can be improved.

4). Examples, Comparative Examples and Examples Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

4.1. Preparation of ink In the blending amounts shown in Table 1, color materials, organic solvents (penetration aids, humectants), tertiary amines, surfactants and ion-exchanged water are mixed and stirred, and filtered through a metal filter with a pore size of 5 μm. Then, deaeration treatment was performed using a vacuum pump. In this way, inks containing coloring materials were prepared. In addition, the unit of the density | concentration described in Table 1 is the mass%, and is the solid content conversion density | concentration about the column of particle | grains.

  In addition, with the blending amounts shown in Table 2, the viscosity modifier, organic solvent (penetration aid, moisturizer), tertiary amine, surfactant and ion-exchanged water are mixed and stirred, and filtered through a metal filter with a pore size of 5 μm. Then, deaeration treatment was performed using a vacuum pump. In this way, inks containing no color material were prepared. These inks that do not contain a color material correspond to the cleaning liquid described above. In addition, the unit of the density | concentration described in Table 2 is the mass%.

Each component shown in Table 1 and Table 2 is as follows.
・ Cyan pigment (CI Pigment Blue 15: 6)
-Magenta pigment (CI Pigment Violet 19)
・ Yellow pigment (CI Pigment Yellow 74)
・ Black pigment (carbon black)
-Organic particles having a hollow structure (manufactured by JSR Corporation, trade name “SX8782 (D)”, water-dispersed type of styrene-acrylic resin particles having a hollow structure, outer diameter 1,000 nm, inner diameter 800 nm, solid content concentration 28% )
・ Titanium dioxide particles (trade name “NanoTek (R) Slurry”, manufactured by CI Kasei Co., Ltd., solid content concentration 15%, average particle diameter 300 nm)
・ Glycerin (manufactured by Kanto Chemical Co., Ltd.)
・ 1,2-Hexanediol (Mitsubishi Gas Chemical Co., Ltd.)
・ Triethanolamine (manufactured by Nacalai Tesque)
-BYK-348 (trade name, manufactured by Big Chemie Japan, polysiloxane surfactant)
・ Trimethylolpropane (manufactured by Kanto Chemical Co., Inc.)
・ Metroze (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., methylcellulose)
・ Sodium alginate (Matsuo Pharmaceutical Co., Ltd.)
Amino coat (trade name, manufactured by Asahi Kasei Chemicals Corporation, glycine betaine)
・ Rubicol K30 (trade name, manufactured by BASF Japan Ltd., polyvinylpyrrolidone)

4.2. Ink set As shown in Table 3, ink sets of Examples and Comparative Examples were prepared. Each ink set is a combination of an ink (A) containing a color material and an ink (B) not containing a color material. Table 3 shows the relationship between the viscosity of each ink in each ink set. In Comparative Example 5, white ink (ICWW57, manufactured by Seiko Epson Corporation) was used as ink (A), and cleaning liquid (ICWCLL, manufactured by Seiko Epson Corporation) was used as ink (B).

4.3. Ink Replacement Test An ink jet printer provided with switching means 56 as shown in FIG. 1 was prepared and filled with each ink set. The cartridge 11a was filled with ink (A) containing a color material, and the cartridge 11b was filled with ink (B) not containing a color material.

4.3.1. Replacement from (B) to (A) For each ink set, the switching means 56 allows the ink (B) not containing a colorant to be supplied to the recording head 36, and the recording head 36, the supply path 41, and the switching. Means 56 was filled with ink (B) containing no colorant. Next, an operation of allowing the switching means 56 to supply the ink (A) containing the color material to the recording head 36 and replacing the ink (B) not containing the color material with the ink (A) containing the color material. went. When the total content of the recording head 36, the supply path 41, and the switching means 56 is 100, the amount of ink (A) containing the color material necessary for replacement was measured.

  Specifically, it is a liquid discharged from the recording head 36 when the supply amount of the ink (A) containing the color material is 150, 180, 210, 240, 300, and a PET film (trade name “Lumirror”, Toray Industries, Inc.). The sample for evaluation was produced by recording on the product. The recording was performed at a resolution of 1440 × 720 dpi, and the recording pattern was a 100% duty solid pattern. “Duty” is a value calculated by the following equation (1).

duty (%) = number of actual recording dots / (vertical resolution × horizontal resolution) × 100 (1)
(In the formula, “number of actual recording dots” is the number of actual recording dots per unit area, and “vertical resolution” and “horizontal resolution” are resolutions per unit area, respectively.)

  Separately, for each ink set, recording is performed on a PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) in a state where the recording head 36 is completely filled with the ink (A) containing the coloring material. As a result, a recorded material (reference) was obtained. The recording was performed at a resolution of 1440 × 720 dpi, and the recording pattern was a 100% duty solid pattern.

About each of the obtained sample for evaluation and reference, L ^* a ^* b ^* value was measured using Gretag Macbeth Sptroscan and Spectrolino (made by X-Rite). When the difference ΔE (color difference) between the L ^* a ^* b ^* value of the sample for evaluation and the L ^* a ^* b ^* value of the reference was 3 or less, it was considered that the ink replacement was completed. The evaluation criteria indicating the ease of ink replacement are as follows, and the evaluation results are also shown in Table 3.

The amount of ink when the total content of the recording head 36, the supply path 41, and the switching means 56 is 100,
A: Necessary ink amount is less than 150 B: Necessary ink amount is 150 or more and less than 180 C: Necessary ink amount is 180 or more and less than 210 D: Necessary ink amount is 210 or more and less than 240 E: Necessary ink The amount is 240 or more and less than 300 F: The required ink amount is 300 or more

4.3.2.3 Replacement of Three Kinds of Inks Experiments shown in Table 4 were performed on an ink set composed of three kinds of ink and an ink set composed of two kinds of ink.

  An ink jet printer provided with a switching unit 56 capable of switching three types of inks was prepared. Each of the three cartridges was filled with an ink (A) containing a coloring material, an ink (B) containing no coloring material, and an ink (C) containing no coloring material. In this experiment, the relationship between the viscosity of the ink (A) containing the color material, the ink (B) not containing the color material, and the ink (C) containing no color material is as shown in Table 4.

  In Examples 1 and 2, first, the switching unit 56 allows the ink (A) containing the color material to be supplied to the recording head 36, and the recording head 36, the supply path 41, and the switching unit 56 contain the color material. Filled with ink (A). Next, an operation of allowing the switching means 56 to supply the ink (B) containing no color material to the recording head 36 and replacing the ink (A) containing the color material with the ink (B) containing no color material. went.

  Next, an operation of allowing the switching means 56 to supply the ink (C) containing no color material to the recording head 36 and replacing the ink (B) containing no color material with the ink (C) containing no color material. went. The amount of the ink (C) that does not contain the color material used at this time was set to 300 when the total content of the recording head 36, the supply path 41, and the switching means 56 is 100.

  Next, an operation of allowing the switching means 56 to supply the ink (A) containing the color material to the recording head 36 and replacing the ink (C) not containing the color material with the ink (A) containing the color material. went. Then, evaluation samples and references were prepared and evaluated in the same manner as described in “4.3.1. Replacement from (B) to (A)”. The results are shown in Table 4.

  On the other hand, in Example 3, first, the switching unit 56 enables the ink (A) containing the color material to be supplied to the recording head 36, and the recording head 36, the supply path 41, and the switching unit 56 are set to the ink containing the color material. Filled with (A). Next, an operation of allowing the switching means 56 to supply the ink (B) containing no color material to the recording head 36 and replacing the ink (A) containing the color material with the ink (B) containing no color material. went.

  Next, the ink (A) containing the color material can be supplied to the recording head 36 by the switching means 56 without replacing the ink (B) containing no color material with the ink (C) containing no color material. Then, the operation of replacing the ink (B) containing no color material with the ink (A) containing the color material was performed. Then, evaluation samples and references were prepared and evaluated in the same manner as described in “4.3.1. Replacement from (B) to (A)”. The results are shown in Table 4.

4.4. Evaluation Results In each of the ink sets of Examples 1 to 15 shown in Table 3, the ink (B) having a relatively low viscosity is replaced with the ink (A) having a relatively high viscosity ((B) → ( In the case of replacement with A), it has been found that the amount of ink (A) required for replacement is small.

  In contrast, in the ink sets of Comparative Examples 1 to 5, the ink (B) having a relatively high viscosity is replaced with the ink (A) having a relatively low viscosity (from (B) to (A). In the case of (replacement), it has been found that the amount of ink (A) required for the replacement increases.

  From the above, it has been found that when the ink having a relatively low viscosity is replaced with an ink having a relatively high viscosity, the amount of the latter ink can be reduced. As in each of the examples, if the viscosity of the ink (A) (recording ink) containing the color material is higher than the viscosity of the ink (B) (cleaning liquid) containing no color material, It has been found that consumption can be kept small. In particular, as shown in Example 7, Example 8, and Example 15, the viscosity of the ink (A) (recording ink) containing the color material and the viscosity of the ink (B) (cleaning liquid) not containing the color material. It has been found that the consumption of the recording ink can be further suppressed when the difference is 2.61 mPa · s or more.

  On the other hand, in the experiments of Examples 1 to 3 shown in Table 4, the ink (A) containing the color material is replaced by the ink (B) not containing the color material (replacement from (A) to (B). ) In Examples 1 to 3, the efficiency was high. However, in Example 1 and Example 2 in which the operation of replacing the ink (B) containing the color material with the ink (C) containing no color material (replacement from (B) to (C)) is performed, this is performed. Compared with Example 3 that does not, the ink containing no color material is replaced by the subsequent ink containing the color material (A) (substitution from (B) → (A) and (C) → (A) There was a significant difference in the operation.

  That is, in Example 3, the efficiency in replacing the recording ink with the cleaning liquid is high, but the efficiency in replacing the cleaning liquid with the recording ink is poor. On the other hand, in Examples 1 and 2, it was found that both the efficiency when replacing the recording ink with the cleaning liquid and the efficiency when replacing the cleaning liquid with the recording ink are good. That is, in the ink sets of Example 1 and Example 2, the efficiency for replacing the cleaning liquid with the recording ink again is obtained by replacing the recording ink with a high-viscosity cleaning liquid and replacing the high-viscosity cleaning liquid with a low-viscosity cleaning liquid. Can be increased.

  Thus, according to the ink sets of Example 1 and Example 2, although the low-viscosity cleaning liquid is consumed, the amount of the recording ink used can be reduced in the replacement from the cleaning liquid to the recording ink. I understood. Furthermore, according to the ink sets of Examples 1 and 2, although the speed when replacing the high viscosity cleaning liquid with the low viscosity cleaning liquid becomes slow, the replacement of the cleaning liquid with the recording ink and the cleaning liquid with the recording ink It was found that the replacement can be accelerated in both cases.

  The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

11a, 11b, 12, 13, 14, 15 ... cartridge, 20 ... printer, 22 ... paper stacker, 24 ... paper feed roller, 26 ... platen, 28 ... carriage, 30 ... carriage motor, 31 ... paper feed motor, 32 ... Towing belt, 34 ... guide rail, 36 ... recording head, 41, 42, 43, 44, 45 ... liquid supply path, 50 ... receiving buffer memory, 51 ... system controller, 52 ... main memory, 53 ... EEPROM, 54 ... image Buffer 55: Display means 56 ... Switching means 57 ... Timekeeping means 58 ... Nozzle inspection means 61 ... Main scan drive circuit 62 ... Sub scan drive circuit 63 ... Head drive circuit 90 ... Host computer 91 ... Printer driver, P ... recording medium

Claims (5)

An ink set that includes a first ink and a second ink that are used in a droplet discharge device that includes a switching unit that switches a plurality of types of ink and discharges each type of ink from the same nozzle.
The first ink contains a colorant;
A third ink that is switched by the switching means;
The viscosity of the first ink, the viscosity of the second ink, and the viscosity of the third ink are:
An ink set having a relationship of (viscosity of second ink) <(viscosity of first ink) <(viscosity of third ink) . In claim 1,
The ink set, wherein a difference in viscosity between the first ink and the second ink is 0.04 mPa · s or more. In claim 1 or 2 ,
The ink set, wherein a viscosity difference between the first ink and the third ink is 0.04 mPa · s or more. In any one of Claims 1 thru | or 3 ,
The color set of the first ink is an ink set that is at least one selected from pigments, dyes, metal oxides, and particles having a hollow structure. In any one of Claims 1 thru | or 4 ,
The ink set, wherein the second ink and the third ink are cleaning liquids.

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