JP2021055093A - Aqueous inkjet ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based inkjet ink set for obtaining a high-quality printed matter. SOLUTION: The dark ink contains a pretreatment agent and a dark ink and a light ink having the same hue as each other, and the pretreatment agent contains a surfactant having an HLB value of 10.0 or more and water. Is a surfactant having an HLB value of less than 10.0 and a difference from the HLB value of the surfactant contained in the pretreatment agent of 2.0 or more, and has an SP value of 15.5 (cal / cm3). The light ink contains a solvent and water of 1/2 or less, and the light ink contains a solvent and water having an SP value of 15.5 (cal / cm3) 1/2 or less, and the light ink contains 15 SP values. The concentration (% by mass) of the solvent of .5 (cal / cm3) 1/2 or less is the concentration (% by mass) of the solvent having an SP value of 15.5 (cal / cm3) 1/2 or less contained in the dark ink. Aqueous inkjet ink set, which is 1.1 times or more the viscosity of the light ink (mPa · s) at 23 ° C. and 1.05 times or more the viscosity (mPa · s) of the dark ink. Is. [Selection diagram] None

Description

The present invention relates to a water-based inkjet ink set.

The inkjet recording system is a printing system in which highly fluid liquid ink is ejected from a fine nozzle and adhered to a base material for printing. This system is a relatively inexpensive device, and has the feature of being able to print high-resolution, high-definition images at high speed and with low noise, and has been rapidly becoming widespread recently.
As inks, water-based inks are widely used because high-quality printed matter can be obtained at low cost. The water-based ink is an ink whose drying property is improved by containing water, and also has an advantage of being excellent in environmental friendliness.

In an inkjet recording system, ink is applied in dots on a substrate to form an image. The shape, size, spacing, etc. of the dots affect the image quality of the printed image. For example, if the dot diameter is small and the distance between the dots is long, graininess may be observed in the printed image.
For example, there is a technique of using dark ink and light ink to obtain one hue and adjusting the gradation from the intermediate density portion to the high density portion to reduce the graininess of the printed image and make it smooth.

In Patent Document 1, a dark color ink and a light color ink are used to specify an organic solvent to be blended in the dark color ink and the light color ink, and further, a viscosity difference between the dark color ink and the light color ink is specified. , An ink set for a water-based ink jet that improves printability on a printing medium having low absorbency such as coated paper has been proposed.
According to Patent Document 1, if the viscosities of the inks are significantly different, the amount of droplets ejected will be different, and the difference in the amount of droplets will cause non-uniform dot diameters and cause problems such as graininess. It is disclosed that

Japanese Unexamined Patent Publication No. 2016-17103

When a penetrating component such as a surfactant is mixed with the water-based ink, there is a problem that the water-based ink wets and spreads on various base materials, causing blurring of a printed image. Further, in multicolor printing, if it takes time to dry the water-based ink on the base material, there is a problem that the colors are easily mixed with each other.
Further, in a low-permeability base material such as a resin sheet, when water-based ink is used, there is a problem that the ink is repelled from the base material before the ink dries on the base material, and it is difficult to fix the printed image. Further, since the water-based ink has a low affinity for a resin sheet or the like, the fixability to the base material may decrease.

Therefore, there is a technique of pretreating the base material before applying the ink in order to further fix the water-based ink on the base material and prevent bleeding of the printed image. By applying the pretreatment agent to the base material, the fixability of the ink on the base material can be improved and the ink bleeding can be prevented. On the other hand, the action of the pretreatment agent makes it difficult for the dot diameter of the ink to spread, which may cause a problem of graininess.
Patent Document 1 targets a print medium having low absorbency such as coated paper, but it has not been studied to use a pretreatment agent before applying ink in order to prevent blurring of a printed image.

One object of the present invention is to provide a water-based inkjet ink set for obtaining a high-quality printed matter.

One aspect of the present invention comprises a pretreatment agent, a dark ink and a light ink having the same hue as each other, and the pretreatment agent contains a surfactant having an HLB value of 10.0 or more, and water. The dark ink has an HLB value of less than 10.0, a surfactant having a difference of 2.0 or more from the HLB value of the surfactant contained in the pretreatment agent, and an SP value of 15.5 (cal). / Cm ³ ) ^1/2 or less solvent and water are contained, and the light ink contains a solvent and water having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less and is contained in the light ink. the SP value 15.5 (cal / cm ^{3) 1/2} or less of the concentration of the solvent (mass%), the SP value contained in dark ink is 15.5 (cal / cm ^{3) 1/2} or less of It is 1.1 times or more with respect to the concentration (mass%) of the solvent, and the viscosity (mPa · s) of the light ink is 1.05 times or more with respect to the viscosity (mPa · s) of the dark ink at 23 ° C. It is a water-based inkjet ink set.

According to one embodiment of the present invention, it is possible to provide a water-based inkjet ink set that obtains a high-quality printed matter.

Hereinafter, the present invention will be described using one embodiment. The illustrations in the following embodiments do not limit the invention.

The water-based inkjet ink set according to one embodiment includes a pretreatment agent, dark ink and light ink having the same hue as each other, and the pretreatment agent includes a surfactant having an HLB value of 10.0 or more, and water. The dark ink contains, and the HLB value is less than 10.0, and the difference from the HLB value of the surfactant contained in the pretreatment agent is 2.0 or more. The surfactant has an SP value of 15.5 (15.5). cal / cm ^{3) 1/2} or less of the solvent, and comprises water, light ink comprises SP value 15.5 (cal / cm ^{3) 1/2} or less of the solvent, and water, contained in the light ink SP value 15.5 (cal / cm ^{3) 1/2} or less of the concentration of the solvent (% by mass), SP value included in the dark ink is 15.5 (cal / cm ^{3) 1/2} of the following solvents It is 1.1 times or more with respect to the density (mass%), and the viscosity (mPa · s) of the light ink is 1.05 times or more with respect to the viscosity (mPa · s) of the dark ink at 23 ° C. It is characterized by.
According to this, a high-quality printed matter can be obtained. In particular, the graininess of the printed image is reduced, and the image quality can be further improved.

Hereinafter, the solvent having an HLB value of 10.0 or more blended in the pretreatment agent is also referred to as a surfactant (a), and the HLB value blended in the dark ink is less than 10.0 and the pretreatment agent. A surfactant having a difference of 2.0 or more from the HLB value of the surfactant contained in is also referred to as a surfactant (b), and the SP value blended in the dark ink is 15.5 (cal / cm ³ ). ^1/2 the following solvents also marked solvent (c1), SP value to be incorporated in the light ink is also referred to as 15.5 (cal / cm ^{3) 1/2} or less of the solvent the solvent (c2).

In the water-based inkjet ink set according to one embodiment, the base material is treated with a pretreatment agent, one of the dark ink and the light ink is ejected to the base material, and then the other of the dark ink and the light ink is used as the base material. A printed matter can be obtained by discharging the ink into the ink jet. In a preferred embodiment, it is preferable to discharge the ink after applying the pretreatment agent to the base material. As one method of image formation, by ejecting the ink afterwards so as to be adjacent to the dots of the ink ejected earlier on the base material, the colorant density differs between the adjacent dots, so that the hue of the hue The tone can be adjusted.
The water-based inkjet ink set according to the embodiment can appropriately widen the dot diameter of the dark ink on the pretreated base material by having the above characteristics. Thereby, in the obtained printed matter, the graininess of the printed image can be reduced and the image quality can be improved.

This mechanism will be described below, but the detailed mechanism is unknown and is not binding on the present invention.
On the base material, the dots of the light ink are dense because the concentration of the solvent (c2) having a low SP value capable of dissolving the surfactant (b) having an HLB value of 10.0 or less blended in the dark ink is high. It functions to take in the surfactant (b) in the dots of the ink. Further, if the dots of the light ink spread too much on the base material, this action is reduced, so that the viscosity of the light ink is increased to prevent the dots of the light ink from spreading on the base material.
Further, when the HLB value of the surfactant (a) of the pretreatment agent is larger than the HLB value of the surfactant (b) in the dark ink and the difference is 2.0 or more, on the substrate, The effect of widening the dot diameter of dark ink is exhibited. It is considered that the reason is that the dots of the dark ink act to take in the surfactant (a) in the pretreatment agent on the base material to which the pretreatment agent is applied.
That is, on the base material, the dots of the dark ink try to spit out the surfactant (b) having an HLB value of less than 10.0 in the dark ink, and the light ink rich in the solvent (c2) having a low SP value. On the substrate, the dark ink dots approach the dots of the above, and the dark ink dots try to take in the surfactant (a) having an HLB value of 10.0 or more of the pretreatment agent applied in advance. It is thought that the diameter will be wider.
By further expanding the dot diameter of the dark ink on the base material, it is possible to reduce the graininess of the printed image and obtain a high-quality printed matter.

In one embodiment, the HLB value of the surfactant (a) blended in the pretreatment agent is 10.0 or more, and the HLB value of the surfactant (b) blended in the dark ink is less than 10.0. It is preferable that the difference between the HLB value of the surfactant (a) and the HLB value of the surfactant (b) is 2.0 or more. This difference in HLB value is also referred to as a difference in HLB value (ab).

The HLB value of the surfactant (a) blended in the pretreatment agent is preferably 10.0 or more, more preferably 11.0 or more, still more preferably 12.0 or more. As a result, the graininess of the printed image can be further reduced, and a printed matter having higher image quality can be obtained.
The HLB value of the surfactant (a) blended in the pretreatment agent is not particularly limited and may be 20 or less, preferably 18.0 or less, more preferably 16.0 or less, and 15.0 or less. Is even more preferable. As a result, the surfactant shows a sufficient balance between hydrophilicity and lipophilicity, the affinity with the base material to which the pretreatment agent is applied is enhanced, and the pretreatment agent can be more uniformly applied to the base material. Become. In addition, the fixability of the ink on the base material to which the pretreatment agent is applied can be further improved.
For example, the HLB value of the surfactant (a) is preferably 10.0 to 18.0, more preferably 11.0 to 16.0, and even more preferably 12.0 to 15.0.

The HLB value of the surfactant (b) blended in the dark ink is preferably less than 10.0, more preferably 9.5 or less, and even more preferably 9.0 or less. As a result, the graininess of the printed image can be further reduced, and a printed matter having higher image quality can be obtained.
The HLB value of the surfactant (b) blended in the dark ink is not particularly limited, and may be 1.0 or more, preferably 2.0 or more, and more preferably 3.0 or more. As a result, the surfactant exhibits a sufficient balance between hydrophilicity and lipophilicity in the water-based dark ink, and it is possible to prevent a decrease in the storage stability of the ink. When the HLB value of the surfactant (b) becomes low, the solubility in water decreases, and there may be restrictions such as having to increase the amount of the solvent in the dark ink.
For example, the HLB value of the surfactant (b) is preferably 1.0 to 10.0, more preferably 2.0 to 9.5, and even more preferably 3.0 to 9.0.
Further, by including a surfactant having an HLB value in the above range in the dark ink, the affinity between the dark ink and the base material can be enhanced, and the fixability of the dark ink to the base material can be further improved. it can.

The difference (ab) between the HLB value of the surfactant (a) blended in the pretreatment agent and the HLB value of the surfactant (b) blended in the dark ink is preferably 2.0 or more. 3.0 or more is more preferable, and 4.0 or more is further preferable. As a result, the graininess of the printed image can be further reduced, and a printed matter having higher image quality can be obtained.
The difference (ab) in HLB value is preferably 15.0 or less, more preferably 10.0 or less, and even more preferably 6.0 or less. As a result, the solubility of each surfactant in the pretreatment agent or the dark ink becomes high, and the function as the surfactant can be more exhibited.
For example, the difference (ab) in HLB value is preferably 2.0 to 15.0, more preferably 3.0 to 10.0, and even more preferably 4.0 to 6.0.

Here, the HLB value is one of the scales showing the properties of the surfactant, and is a numerical value of the balance between the hydrophilic group and the lipophilic group in the molecule. The HLB value has been proposed by several calculation methods, but in the present specification, it is a value calculated by the Griffin method, and is calculated by the following formula (1).
HLB value = 20 x (formula weight of hydrophilic part) / (molecular weight of surfactant) ... formula (1)

Here, the "hydrophilic portion" indicates a hydrophilic portion contained in the molecular structure of the surfactant, preferably a polyoxyalkylene group, an alcohol group having 3 or less carbon atoms in the main chain with respect to the hydroxyl group, and the like. Or a combination of these. When the surfactant contains a plurality of hydrophilic portions, the formula amount of the hydrophilic portion in the above formula (1) is the total amount of these.
Examples of the polyoxyalkylene group include a polyoxyethylene group (polyethylene oxide; EO:-(CH ₂ CH ₂ O) _n- ) and a polyoxypropylene group (polypropylene oxide; PO:-(CH ₂ CH ₂ CH ₂ O) _n-). -) Etc. can be mentioned.
As the alcohol group, a group derived from methanol, ethanol, propanol, isopropanol, glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, sucrose (sucrose), mannitol, glycols and the like (for example, ethanol). If so, −CH ₂ CH ₂ OH) can be mentioned.

The "hydrophobic portion" indicates a hydrophobic portion contained in the molecular structure of the surfactant, and is preferably derived from an aliphatic alcohol, an alkylphenol, a fatty acid or the like having 4 or more carbon atoms in the main chain with respect to the hydroxyl group. Aliphatic hydrocarbon groups, aromatic hydrocarbon groups, organic siloxanes, alkyl halides, etc., or combinations thereof.

Further, in one embodiment, the dark ink contains ^{a solvent (c1) having an SP value of 15.5 (cal / cm 3} ) ^1/2 or less, and the light ink has an SP value of 15.5 (cal / cm ³ ). ^{A solvent (c2) of 1/2} or less is contained, and the SP value contained in the light ink is 15.5 (cal / cm ^{3 ). The concentration of the solvent (c2) of 1/2} or less is the SP value contained in the dark ink. Is preferably 1.1 times or more with respect to the concentration of the solvent (c1) of 15.5 (cal / cm ³ ) ^{1/2 or less.} This concentration ratio is also referred to as a concentration ratio (c2 / c1). The unit of the concentration of the solvent (c1) and the solvent (c2) is mass%, respectively.

The concentration of SP value 15.5 contained in dark ink (cal / cm ^{3) 1/2} or less of the solvent (c1), based on the total weight of the dark ink, the SP value is 15.5 (cal / cm ³ ) It can be expressed as a ratio (mass%) of the mass of the solvent (c1) of ^{1/2 or less.} When the dark ink contains two or more types of solvent (c1) with an SP value of 15.5 (cal / cm ³ ) ^1/2 or less, the SP value of two or more types is 15 with respect to the total mass of the dark ink. The concentration of the solvent (c1) is the ratio (mass%) of the total mass of the solvent (c1) of .5 (cal / cm ³ ) ^{1/2 or less.
Similarly, the concentration of the solvent (c2) having an SP value of 15.5 (cal / cm 3} ) ^1/2 or less contained in the light ink has an SP value of 15.5 (cal) with respect to the total mass of the light ink. / Cm ³ ) It can be expressed by the mass ratio (mass%) of the solvent (c2) of ^{1/2 or less.} When the light ink contains two or more types of solvent (c2) having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less, the SP value of two or more types is 15 with respect to the total mass of the light ink. The concentration of the solvent (c2) is the ratio (mass%) of the total mass of the solvent (c2) of .5 (cal / cm ³ ) ^{1/2 or less.}

The concentration ratio (c2 / c1) is preferably 1.1 times or more, more preferably 1.12 times or more, still more preferably 1.15 times or more. As a result, the graininess of the printed image can be further reduced, and a printed matter having higher image quality can be obtained.
The concentration ratio (c2 / c1) is not particularly limited, and is preferably 10 times or less, more preferably 5 times or less, and even more preferably 2 times or less. This prevents the dark ink surfactant from moving excessively from the dark ink dots to the light ink dots between the adjacent dark ink dots and the hue density. The overall gradient can be maintained to form a smooth image.
For example, the concentration ratio (c2 / c1) is preferably 1.1 to 10 times, more preferably 1.12 to 5 times, and even more preferably 1.15 to 2 times.

The dark ink and the light ink each independently ^{preferably contain a solvent having an SP value of 15.5 (cal / cm 3 ) 1/2} or less, and more preferably an SP value of 15.3 (cal / cm 3). ³ ) ^{A solvent of 1/2} or less, more preferably a solvent having an SP value of 15.0 (cal / cm ³ ) ^1/2 or less. As a result, the solubility of the surfactant (b) having an HLB value of less than 10.0 in dark ink can be further enhanced, and the affinity between the ink and the base material, the ejection performance of the ink, and the like can be further improved. .. This also applies when the light ink contains a surfactant. Further, on the substrate, the dark ink surfactant (b) can be moved from the dark ink dots to the light ink dots to further widen the dot diameter of the dark ink and reduce the graininess.
In the dark ink and the light ink, the solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably an SP value of 5 (cal / cm ³ ) ^1/2 or more, respectively. (cal / cm3) ^1/2 or more ^{preferably, 12 (cal / cm 3)} 1/2 or more is more preferable. Thereby, in each of the dark ink and the light ink, the aqueous solvent forms a single phase, and the storage stability of the ink can be further improved.
For example, dark ink and light ink are, each independently, SP value 5~15.5 (cal / cm ^{3) 1/2} is ^{preferable, 10~15.3 (cal / cm 3)} 1/2 Gayori Preferably, 15.0 to 12 (cal / cm ³ ) ^1/2 is even more preferred.

Here, the SP value is a solubility parameter and is defined by the square root of the aggregation energy density of the molecule. There are various calculation methods, but here, the value calculated by the estimation method (Formula 1) proposed by Fedor is used.
[Formula 1]
δ (SP value) = [ΣE _coh / ΣV] ^1/2 ... (1)
Here, E _coh indicates a constant peculiar to each functional group, and V represents a molar molecule (“SP value basics / applications and calculation methods”, pp. 66-67, Information Organization Co., Ltd., March 31, 2005. See issue).

As the solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less, it is preferable to use a water-soluble organic solvent. The water-soluble organic solvent preferably exhibits compatibility with water. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and can be dissolved or miscible in water can be used, and a water-soluble organic solvent that uniformly mixes with the same volume of water at 20 ° C. at 1 atm is used. Is preferable.

Specific examples of a solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less include diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monohexyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoisopropyl. Ether, dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol propyl ether, diethylene glycol monomethyl ether, ethylene glycol allyl ether, diethylene glycol benzyl ether, diethylene glycol phenyl ether, 1,2-hexanediol, N-methyl-2-pyrrolidone ( NMP), 1,2-butanediol, 1,2-propanediol, 1,6-hexanediol, dipropylene glycol, 1,3-propanediol, 2-pyrrolidone, ethylene glycol, diethylene glycol, 1,4-butanediol And so on.
These are preferably used within the range of forming a single phase with water, and may be used alone or in combination of two or more.

In the dark ink, the solvent (c1) having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably 5% by mass or more, more preferably 10% by mass or more, and 20% by mass, based on the total amount of the dark ink. % Or more is more preferable.
In the dark ink, the solvent (c1) having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably 50% by mass or less, more preferably 40% by mass or less, and 25% by mass, based on the total amount of the dark ink. % Or less is more preferable.
When the content of the solvent (c1) in the dark ink is in the above range, the density ratio (c2 / c1) can be appropriately adjusted, and the graininess of the printed image can be further reduced.

In the light ink, the solvent (c2) having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably 10% by mass or more, more preferably 20% by mass or more, and 30% by mass, based on the total amount of the light ink. % Or more is more preferable.
In the light ink, the solvent (c2) having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably 50% by mass or less, more preferably 40% by mass or less, and 30% by mass, based on the total amount of the light ink. % Or less is more preferable.
When the content of the solvent (c1) in the light ink is in the above range, the density ratio (c2 / c1) can be appropriately adjusted, and the graininess of the printed image can be further reduced.
In the dark ink and the light ink, ^{when two or more kinds of solvents having an SP value of 15.5 (cal / cm 3 ) 1/2} or less are contained, the SP value of two or more kinds is 15.5 (cal / cm 3). ³ ) It is preferable that the total mass of the solvent of ^{1/2 or less satisfies the above range.}

Further, in one embodiment, it is preferable that the viscosity of the light ink is 1.05 times or more the viscosity of the dark ink at 23 ° C. Hereinafter, the viscosity of the dark ink is also referred to as v1, the viscosity of the light ink is also referred to as v2, and this viscosity ratio is also referred to as the viscosity ratio (v2 / v1). The units of the viscosity (v1) of the dark ink and the viscosity (v2) of the light ink are mPa · s, respectively.
This viscosity ratio (v2 / v1) is preferably 1.05 times or more, more preferably 1.10 times or more, still more preferably 1.15 times or more. As a result, the graininess of the printed image can be further reduced, and a printed matter having higher image quality can be obtained. Specifically, on the substrate, the dot diameter of the light ink having a higher viscosity is prevented from widening, and the surfactant (b) of the dark ink is changed from the dots of the dark ink having a lower viscosity to the dots of the light ink. By moving the ink, it is possible to prevent the dot diameter of the dark ink from spreading and reduce the graininess while maintaining the density gradient to some extent.
The viscosity ratio (v2 / v1) is not particularly limited, and is preferably 2 times or less, more preferably 1.5 times or less, and further preferably 1.3 times or less. As a result, it is possible to prevent the difference in viscosity between the two inks from becoming large, and to more easily print the dark ink and the light ink using the same inkjet printing apparatus. For example, the ejection performance from the inkjet nozzle can be improved for both dark ink and light ink.
For example, this viscosity ratio (v2 / v1) is preferably 1.05 to 2 times, more preferably 1.10 to 1.5 times, and even more preferably 1.15 to 1.3 times.

The viscosity of the dark ink is preferably 2 mPa · s or more, more preferably 5 mPa · s or more, further preferably 8 mPa · s or more, and may be 9 mPa · s or more.
The viscosity of the dark ink is preferably 30 mPa · s or less, more preferably 15 mPa · s or less, and even more preferably 13 mPa · s or less.
When the viscosity (v1) of the dark ink is in the above range, the viscosity ratio (v2 / v1) can be appropriately adjusted, and the graininess of the printed image can be further reduced.

The viscosity of the light ink is preferably 2 mPa · s or more, more preferably 5 mPa · s or more, further preferably 7 mPa · s or more, and may be 10 mPa · s or more.
The viscosity of the light ink is preferably 30 mPa · s or less, more preferably 15 mPa · s or less, and even more preferably 15 mPa · s or less.
When the viscosity (v2) of the light ink is in the above range, the viscosity ratio (v2 / v1) can be appropriately adjusted, and the graininess of the printed image can be further reduced.

Here, the viscosity of the ink represents a value at 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C.
The viscosity ratio of the ink can be determined from the viscosity (v1) of the dark ink and the viscosity (v2) of the light ink measured according to the above procedure and the ratio (v2 / v1).

The water-based inkjet ink set according to the embodiment can provide a printed matter having higher image quality by reducing the graininess of the printed image by providing the pretreatment agent, the dark ink, and the light ink with the above-mentioned physical characteristics. ..

"Pretreatment agent"
Hereinafter, the pretreatment agent will be described.
The pretreatment agent according to one embodiment includes a surfactant having an HLB value of 10.0 or more, and water.
Relationship between the HLB value of the surfactant (a) contained in the pretreatment agent, the HLB value of the surfactant (a) contained in the pretreatment agent, and the HLB value of the surfactant (b) contained in the dark ink. Is as described above.

By including the surfactant in the pretreatment agent, the affinity of the pretreatment agent for the base material can be improved and the pretreatment agent can be more uniformly applied onto the base material.
For example, most of the low-permeability base materials have a hydrophobic base material surface in the untreated state. Therefore, the printing dots on the base material may become non-uniform and the image quality may deteriorate. On the other hand, by using a base material treated with a pretreatment agent containing a surfactant, the wettability between the base material and the water-based ink can be further improved.

The surfactant (a) is a surfactant having an HLB value of 10.0 or more. As the surfactant (a), a nonionic surfactant can be preferably used. Further, either a low molecular weight surfactant or a high molecular weight surfactant may be used.

Examples of the nonionic surfactant include ester-type surfactants such as glycerin fatty acid ester and fatty acid sorbitan ester; ether-type surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether and polyoxypropylene alkyl ether. Agents; ether ester-type surfactants such as polyoxyethylene sorbitan fatty acid ester; acetylene-based surfactants; silicone-based surfactants; fluorine-based surfactants and the like. Among them, acetylene-based surfactants and silicone-based surfactants can be preferably used. The surfactant may be used alone or in combination of two or more.

Examples of the acetylene-based surfactant include an acetylene glycol-based surfactant, an acetylene alcohol-based surfactant, and a surfactant having an acetylene group.
The acetylene glycol-based surfactant is a glycol having an acetylene group, preferably a glycol having a symmetrical structure in which the acetylene group is located in the center, and has a structure in which ethylene oxide is added to acetylene glycol. May be good.

When acetylene glycol to which ethylene oxide is added is used as the acetylene glycol-based surfactant, the number of moles of ethylene oxide added is preferably 6 or more, more preferably 8 or more, still more preferably 10 or more.

Examples of commercially available acetylene-based surfactants having an HLB value of 10.0 or more include "Orfin E1010, E1006, E1020" and "Surfinol 465, 485" (all manufactured by Nissin Chemical Industry Co., Ltd.). Can be (both are product names).

Examples of the silicone-based surfactant include a polyether-modified silicone-based surfactant, an alkyl-aralkyl co-modified silicone-based surfactant, and an acrylic silicone-based surfactant.

As the silicone-based surfactant, for example, a compound having a polyalkylene glycol chain in the polysiloxane skeleton can be used. Specifically, a compound in which at least one polyalkylene glycol chain is bonded to at least one Si element selected from the 1-, 3-, and 6-position Si elements of trisiloxane can be used. In this compound, the polyalkylene glycol chain may be a polyethylene glycol chain, a polypropylene glycol chain, a polytrimethylene glycol chain, or the like, but a polyethylene glycol chain is preferable.

Among them, it is preferable to use heptamethyltrisiloxane having a polyethylene glycol chain having 7 or more moles of ethylene oxide added as the silicone-based surfactant. In this surfactant, the number of moles of ethylene oxide added is more preferably 7 to 40, still more preferably 9 to 35, and even more preferably 8 to 30. Further, in this surfactant, the methyl group bonded to the siloxane skeleton may be replaced with another hydrophobic group such as an alkyl group having 2 or more carbon atoms.
Further, as the silicone-based surfactant, it is preferable to use nonamethyltetrasiloxane having a polyethylene glycol chain having 9 or more moles of ethylene oxide added. In this surfactant, the number of moles of ethylene oxide added is more preferably 11 to 40, still more preferably 13 to 35. Further, in this surfactant, the methyl group bonded to the siloxane skeleton may be replaced with another hydrophobic group such as an alkyl group having 2 or more carbon atoms.

Further, as the surfactant (a), a polyoxyethylene alkyl ether represented by _{the general formula "Cm} H _2m + 1-O- (CH ₂ CH ₂ O) _{n-H" can be used.} In this general formula, it is preferable that n = 1 and m = 1, n = 2 and m = 1-5, n = 3 and m = 1-8, n = 4 and m = 1-11.

The amount of the active ingredient of the surfactant (a) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, based on the total amount of the pretreatment agent. As a result, the graininess of the printed image can be further reduced and the image quality can be further improved. Specifically, on the substrate, the amount of the surfactant (a) of the pretreatment agent moving from the base pretreatment agent to the dots of the dark ink becomes larger, and the dot diameter of the dark ink becomes wider. The graininess can be further reduced. In addition, the affinity between the pretreatment agent and the base material can be further improved.
The amount of the active ingredient of the surfactant (a) is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on the total amount of the pretreatment agent. This makes it possible to prevent a decrease in storage stability of the pretreatment agent.
For example, the amount of the active ingredient of the surfactant (a) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and 0.7 to 1% by mass with respect to the total amount of the pretreatment agent. Is even more preferable.

The pretreatment agent can further include a flocculant. When the water-based ink is applied to the base material treated by the pretreatment agent because the pretreatment agent contains a coagulant, the color material of the water-based ink is coagulated on the base material by the coagulant in the pretreatment agent. However, blurring of the image can be suppressed and the image quality can be further improved.
As the flocculant, a cationic resin, a polyvalent metal salt, an organic acid, an inorganic acid, a salt of an inorganic acid, or a combination thereof can be used.

The cationic resin may be either a cationic water-soluble resin or a cationic water-dispersible resin, and these may be used in combination.

Examples of the cationic water-soluble resin include polyethyleneimine (PEI), polyvinylamine, polyallylamine and salts thereof, polyvinylpyridine, and a copolymer of cationic acrylamide. More specifically, polydiallyl dimethylammonium chloride or the like can be used.

Commercially available products of cationic water-soluble resin include, for example, Charol series "DC-303P, DC-902P" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Unisense series "FCA1000L, FPA100L" manufactured by Senka Co., Ltd., etc., Osaka Organic Co., Ltd. HC polymer series "1S, 1N, 1NS, 2, 2L" manufactured by Kagaku Kogyo Co., Ltd., Himax series "Himax SC-103, SC-506, SC-700L" manufactured by Hymo Co., Ltd., etc. can be mentioned. Product name).

Examples of commercially available polyethyleneimine products include Epomin series "SP-006, SP-012, SP-018, SP-200" manufactured by Nippon Shokubai Co., Ltd .; "Lupasol FG, Lupasol G20" manufactured by BASF Japan Ltd. "Waterfree, Lupasol PR 8515" and the like (both are trade names).
Examples of commercially available products of polyallylamine include "allylamine polymers PAA-01, PAA-03, PAA-05, and allylamine hydrochloride polymers PAA-HCL-01, PAA-" manufactured by Nitto Spinning Co., Ltd. HCL-03, PAA-HCL-05, PAA-SA, which is an allylamine amide hydrochloride polymer, and the like (all are trade names).

Examples of the cationic water-dispersible resin include urethane resin, (meth) acrylic resin, styrene / (meth) acrylic resin, polyester resin, olefin resin, vinyl chloride resin, vinyl acetate resin, melamine resin, amide resin, and ethylene-. In vinyl chloride copolymer resin, styrene-maleic anhydride copolymer resin, vinyl acetate- (meth) acrylic copolymer resin, vinyl acetate-ethylene copolymer resin, and composite resins thereof, cations are added to these resins. A positive functional group may be introduced, or a surface treated with a cationic dispersant or the like to give a positive surface charge can be used. The cationic functional group is typically a primary, secondary or tertiary amino group, a pyridine group, an imidazole group, a benzimidazole group, a triazole group, a benzotriazole group, a pyrazole group, a benzopyrazole group and the like. Can be mentioned. Examples of the cationic dispersant include primary, secondary, tertiary or quaternary amino group-containing acrylic polymers, polyethyleneimine, cationic polyvinyl alcohol resins, and cationic water-soluble polybranched polyesteramide resins. Here, "(meth) acrylic resin" refers to an acrylic resin, a methacrylic resin, or a copolymer thereof.

Commercially available products of the cationic water-dispersible resin include, for example, "PINTRITE DP375" manufactured by Lubrizol, "PP-17" manufactured by Meisei Chemical Works, Ltd., and "Polysol AP-1350" manufactured by Showa Dic Corporation. AP-1370, AE-803, AM-3400, etc., DIC Corporation's "Boncoat SFC-55", etc., Japan Coating Resin Co., Ltd.'s "Aquatex AC-3100", DIC Corporation's "Hydran CP7610," Examples thereof include "CP7050", "Superflex 620, 650" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and "Mobile 7820" manufactured by Nippon Synthetic Chemical Industries, Ltd. (all are trade names).
These may be used alone or in combination of two or more.
When a cationic resin is used, the cationic resin (active ingredient) is preferably 1 to 50% by mass, more preferably 3 to 20% by mass, based on the total amount of the pretreatment agent.

Examples of the polyvalent metal salt include halides of divalent or higher valent metals such as Mg, Ca, Al, Zn and Ba, nitrates, sulfates, acetates, fatty acid salts and lactates. Specific examples thereof include calcium nitrate, magnesium nitrate, copper nitrate, calcium acetate, magnesium acetate, calcium chloride, barium sulfate, aluminum sulfate and the like. These may be used alone or in combination of two or more.
When a polyvalent metal salt is used, the polyvalent metal salt is preferably 0.1 to 10% by mass based on the total amount of the pretreatment agent.

Examples of the organic acid include formic acid, acetic acid, oxalic acid, polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, ascorbic acid, succinic acid, glutaric acid, and the like. Fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, pyrrolidonecarboxylic acid, pyroncarboxylic acid, pyrrolcarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumarin acid, thiophenecarboxylic acid, nicotinic acid, etc. Be done. These may be used alone or in combination of two or more.
When an organic acid is used, the organic acid is preferably 1 to 30% by mass based on the total amount of the pretreatment agent.

As the inorganic acid, for example, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid and the like, or salts thereof can be used. These may be used alone or in combination of two or more.
When an inorganic acid is used, the amount of the inorganic acid is preferably 1 to 30% by mass with respect to the total amount of the pretreatment agent.

The total amount of the flocculant containing the cationic resin, the polyvalent metal salt, the organic acid, and the inorganic acid is preferably 1 to 50% by mass, more preferably 3 to 20% by mass, based on the total amount of the pretreatment agent.

The pretreatment agent can further include a binder resin.
The binder resin may be any of a cationic resin, an anionic resin, an amphoteric resin, and a nonionic resin, but a cationic resin, an amphoteric resin, and a nonionic resin can be preferably used. By using the above-mentioned cationic resin as the flocculant, it is possible to obtain the action of the binder resin.
Examples of the amphoteric resin and nonionic resin include "Boncoat 40-418EF (amphoteric)" manufactured by DIC Corporation, "Superflex 500M (nonionic)" and E-2000 (nonionic) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (Both are product names). Since these can be used in combination with the above-mentioned cationic resin as a flocculant, they can be preferably used.
The binder resin (active ingredient) is preferably 0.5 to 20.0% by mass with respect to the total amount of the pretreatment agent.

The pretreatment agent preferably contains water as an aqueous solvent, and the main solvent may be water.
The water is not particularly limited, but water containing as little ionic component as possible is preferable.
In particular, from the viewpoint of ink storage stability, it is preferable that the content of multivalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, or the like may be used.
The water may be the balance of each component, but for example, it is preferably contained in an amount of 20% by mass to 90% by mass, more preferably 50% by mass to 80% by mass, based on the total amount of the pretreatment agent. ..

The pretreatment agent can contain a water-soluble organic solvent from the viewpoint of viscosity adjustment and moisturizing effect. The pretreatment agent may contain a solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less as a water-soluble organic solvent. The details of the solvent having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less are as described above.} The solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is preferably 1 to 50% by mass, and may be 10 to 30% by mass, based on the total amount of the pretreatment agent.
The pretreatment agent can include other water-soluble organic solvents such as glycerin. From the viewpoint of viscosity adjustment and moisturizing effect, other water-soluble organic solvents can be contained in an amount of 1% by mass to 30% by mass, more preferably 10% by mass to 20% by mass, based on the total amount of the pretreatment agent. ..

Further, in addition to the above-mentioned components, the pretreatment agent may optionally include a wetting agent (moisturizer), a surface tension adjusting agent (penetrating agent), a defoaming agent, a fixing agent, an antioxidant, a preservative, a pH adjusting agent, etc. Can be appropriately contained.
The method for producing the pretreatment agent is not particularly limited, and each component can be mixed and produced. For example, it can be obtained by adding and mixing all the components of the pretreatment agent all at once or in divided portions.

"Dark ink and light ink"
Hereinafter, dark ink and light ink will be described.
The water-based inkjet ink set according to one embodiment can include dark ink and light ink having the same hue as each other.
The dark ink and the light ink can be provided as inks having the same hue and different densities by containing color materials having the same hue at different densities. The dark ink and the light ink preferably contain color materials having the same components as each other, but may contain color materials having different components as long as they have the same hue. Specifically, it is preferable that the dark ink and the light ink contain colorants having the same hue and the same component at different concentrations.
For example, the light ink preferably contains a color material having a color similar to that of the dark ink in the KCMY color system and having a mass of the color material of 1/3 or less with respect to the mass of the color material of the dark ink.

Further, the dark ink and the light ink can be used by continuously printing an image on a base material using the same printing apparatus. In contrast to dark ink, light ink may be referred to as gray ink, light cyan, light magenta, light cyan, light magenta, or the like.

The dark ink has a surfactant (b) having an HLB value of less than 10.0 and a difference from the HLB value of the surfactant contained in the pretreatment agent of 2.0 or more, and an SP value of 15.5 (cal). / Cm ³ ) ^1/2 or less solvent (c1) and water can be contained.
What is the relationship between the HLB value of the surfactant (b) contained in the dark ink, the HLB value of the surfactant (a) contained in the pretreatment agent, and the HLB value of the surfactant (b) contained in the dark ink? , As mentioned above.

The surfactant (b) is a surfactant having an HLB value of less than 10.0. As the surfactant (b), a nonionic surfactant can be preferably used. Further, either a low molecular weight surfactant or a high molecular weight surfactant may be used.

Examples of the nonionic surfactant include ester-type surfactants such as glycerin fatty acid ester and fatty acid sorbitan ester; ether-type surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether and polyoxypropylene alkyl ether. Agents; ether ester-type surfactants such as polyoxyethylene sorbitan fatty acid ester; acetylene-based surfactants; silicone-based surfactants; fluorine-based surfactants and the like. Among them, acetylene-based surfactants and silicone-based surfactants can be preferably used. It is preferable to use one type of surfactant alone, but two or more types may be used in combination.

Examples of the acetylene-based surfactant include an acetylene glycol-based surfactant, an acetylene alcohol-based surfactant, and a surfactant having an acetylene group.
The acetylene glycol-based surfactant is a glycol having an acetylene group, preferably a glycol having a symmetrical structure in which the acetylene group is located in the center, and has a structure in which ethylene oxide is added to acetylene glycol. May be good.

When acetylene glycol to which ethylene oxide is added is used as the acetylene glycol-based surfactant, the number of moles of ethylene oxide added is preferably 5 or less, more preferably 4 or less, still more preferably 3 or less.
Examples of commercially available acetylene-based surfactants having an HLB value of less than 10.0 include "Orfin E1004" and "Surfinol 420, 440, 104" (all manufactured by Nissin Chemical Industry Co., Ltd.). Yes (both are product names).

Examples of the silicone-based surfactant include a polyether-modified silicone-based surfactant, an alkyl-aralkyl co-modified silicone-based surfactant, and an acrylic silicone-based surfactant.

As the silicone-based surfactant, for example, a compound having a polyalkylene glycol chain in the polysiloxane skeleton can be used. Specifically, a compound in which at least one polyalkylene glycol chain is bonded to at least one Si element selected from the 1-, 3-, and 6-position Si elements of trisiloxane can be used. In this compound, the polyalkylene glycol chain may be a polyethylene glycol chain, a polypropylene glycol chain, a polytrimethylene glycol chain, or the like, but a polyethylene glycol chain is preferable.

Among them, as the silicone-based surfactant, it is preferable to use heptamethyltrisiloxane having a polyethylene glycol chain having an addition molar number of ethylene oxide of 0 to 6, more preferably 1 to 4. In this surfactant, the methyl group bonded to the siloxane skeleton may be replaced with another hydrophobic group such as an alkyl group having 2 or more carbon atoms.
Further, as the silicone-based surfactant, it is preferable to use nonamethyltetrasiloxane having a polyethylene glycol chain having an addition molar number of ethylene oxide of 0 to 8, more preferably 1 to 6. In this surfactant, the methyl group bonded to the siloxane skeleton may be replaced with another hydrophobic group such as an alkyl group having 2 or more carbon atoms.

Further, as the surfactant (b), a polyoxyethylene alkyl ether represented by _{the general formula "Cm} H _{2m + 1-} O- (CH ₂ CH ₂ O) _{n-H" can be used.} In this general formula, it is preferable that n = 1 and m = 2 or more, n = 2 and m = 6 or more, n = 3 and m = 9 or more, n = 4 and m = 12 or more.

The amount of the active ingredient of the surfactant (b) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, based on the total amount of the dark ink. As a result, the graininess of the printed image can be further reduced and the image quality can be further improved. Specifically, the amount of the dark ink surfactant (b) that moves from the dark ink dots to the light ink dots on the base material increases, widens the dot diameter of the dark ink, and gives a grainy feeling. It can be further reduced. Moreover, the affinity with the base material can be further improved.
The amount of the active ingredient of the surfactant (b) is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on the total amount of the dark ink. This makes it possible to prevent a decrease in storage stability in dark ink.
For example, the amount of the active ingredient of the surfactant (b) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and 0.7 to 1% by mass with respect to the total amount of the dark ink. More preferred.

The dark ink preferably contains water as an aqueous solvent, and the main solvent may be water. When water is contained as a solvent in the pigment dispersion described later, the water in the pigment dispersion is converted into a part of the water in the ink to prepare the ink.
The water is not particularly limited, but water containing as little ionic component as possible is preferable.
In particular, from the viewpoint of ink storage stability, it is preferable that the content of multivalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, or the like may be used.
From the viewpoint of adjusting the ink viscosity, water is preferably contained in an amount of 20% by mass to 90% by mass, more preferably 30% by mass to 80% by mass, based on the total amount of the dark ink.

The dark ink can contain a solvent (c1) having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less.} The solvent (c1) preferably exhibits compatibility with water.
The relationship between the SP value of the solvent (c1) contained in the dark ink and the solvent (c1) contained in the dark ink and the solvent (c2) contained in the light ink is as described above. Further, the solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is as described above.

The dark ink can contain other water-soluble organic solvents in addition to the solvent (c1) having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less.} Examples of other water-soluble organic solvents include glycerin and the like.
The other water-soluble organic solvent can be contained in an amount of 1% by mass to 30% by mass, more preferably 10% by mass to 20% by mass, based on the total amount of the dark ink, from the viewpoint of viscosity adjustment and moisturizing effect.

The dark ink can contain a pigment, a dye, or a combination thereof as a coloring material.
From the viewpoint of weather resistance and color development of the image, a pigment can be preferably used as the coloring material.

The pigment can be preferably blended into the ink as a pigment dispersion.
The pigment dispersion may be one in which the pigment can be dispersed in a solvent and the pigment is in a dispersed state in the ink. For example, a pigment dispersed in water with a pigment dispersant, a self-dispersing pigment dispersed in water, a microencapsulated pigment in which the pigment is coated with a resin, and the like dispersed in water can be used. ..

As the pigment, for example, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments and dyed lake pigments; and inorganic pigments such as carbon black and metal oxides can be used. Examples of the azo pigment include soluble azo lake pigments, insoluble azo pigments and condensed azo pigments.
Examples of the phthalocyanine pigment include metal phthalocyanine pigments such as copper phthalocyanine pigments and metal-free phthalocyanine pigments. Polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindolin pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthracinone pigments, quinophthalone pigments, and metal complex pigments. , And diketopyrrolopyrrole (DPP) and the like. Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of the metal oxide include titanium oxide and zinc oxide.
The average particle size of these pigments is preferably 50 to 500 nm, more preferably 50 to 200 nm. The average particle size of these pigments is preferably 50 nm or more from the viewpoint of color development, and preferably 500 nm or less from the viewpoint of discharge stability.

In order to stably disperse the pigment in the ink, a pigment dispersant typified by a polymer dispersant or a surfactant can be preferably used.
Commercially available polymer dispersants include, for example, the TEGO Disperse series "TEGO Disperse 740W, 750W, 755W, 757W, 760W" manufactured by EVONIK, and the Solsperse series "Solsperse 20000, 27000" manufactured by Japan Lubrizol Co., Ltd. 41000, 41090, 43000, 44000, 46000 ", Johnson Polymer's John Krill series" John Krill 57, 60, 62, 63, 71, 501 ", BYK's" DISPERBYK-102, 185, 190, 193, 199 ". , Polyvinylpyrrolidone "K-30, K-90" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (both are trade names).

As the surfactant-type dispersant, a nonionic surfactant can be preferably used in consideration of the dispersion stability of the pigment in the ink and the influence of ionicity from the pretreatment agent.
Nonionic surfactants such as the Emulgen series "Emulgen A-60, A-90, A-500, B-40, L-40, 420" manufactured by Kao Corporation as commercially available surfactant-type dispersants. Examples include agents (both are trade names).

These pigment dispersants can be used alone or in combination of two or more.
When a pigment dispersant is used, the amount of the pigment dispersant added varies depending on the type and is not particularly limited. For example, the pigment dispersant can be added in the range of 0.005 to 0.5 with respect to the pigment 1 in terms of the mass ratio of the active ingredient.

A self-dispersing pigment may be blended as a coloring material. A self-dispersing pigment is a pigment in which a hydrophilic functional group is introduced into the surface of the pigment by a chemical treatment or a physical treatment. The hydrophilic functional group to be introduced into the self-dispersible pigment is preferably an ionic one, and by charging the pigment surface anionicly or cationically, the pigment particles are stably dispersed in water by electrostatic repulsive force. be able to. As the anionic functional group, a sulfonic acid group, a carboxy group, a carbonyl group, a hydroxy group, a phosphonic acid group and the like are preferable. As the cationic functional group, a quaternary ammonium group, a quaternary phosphonium group and the like are preferable.

These hydrophilic functional groups may be bonded directly to the pigment surface or may be bonded via other atomic groups. Examples of other atomic groups include, but are not limited to, an alkylene group, a phenylene group, a naphthylene group and the like. Examples of the pigment surface treatment method include diazotization treatment, sulfonation treatment, hypochlorous acid treatment, humic acid treatment, vacuum plasma treatment and the like.

Examples of the self-dispersing pigment include CAB-O-JET series "CAB-O-JET200, 300, 250C, 260M, 270" manufactured by Cabot Corporation, and "BONJET BLACK CW-1, CW-2" manufactured by Orient Chemical Industries Co., Ltd. , CW-4 "and the like can be preferably used (all are trade names).

A pigment dispersion in which pigments are pre-dispersed with a pigment dispersant may be used. Examples of commercially available products of pigment dispersions dispersed with pigment dispersants include HOSTAJET series manufactured by Clariant AG and FUJI SP series manufactured by Fuji Dye Co., Ltd. (both are trade names). A pigment dispersion dispersed with the above-mentioned pigment dispersant may be used. Further, a microencapsulated pigment in which the pigment is coated with a resin may be used.

A dye may be blended as a coloring material. As the dye, a dye generally used in the technical field of printing can be used, and the dye is not particularly limited. Specific examples thereof include basic dyes, acidic dyes, direct dyes, soluble bat dyes, acidic mordant dyes, mordant dyes, reactive dyes, bat dyes, sulfide dyes and the like. Of these, those that are water-soluble and those that become water-soluble by reduction or the like can be preferably used. More specifically, azo dyes, rhodamine dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, triphenylmethane dyes, diphenylmethane dyes, methylene blue and the like can be mentioned.

The above-mentioned coloring materials can be used alone or in combination of two or more.
The amount of the active ingredient of the coloring material is preferably 0.1% by mass to 25% by mass, more preferably 1% by mass to 20% by mass, still more preferably 3% by mass to 15% by mass, based on the total amount of the ink.

The dark ink may further contain a water-soluble resin, a water-dispersible resin, or a combination thereof. Thereby, the fixability of the coloring material to the base material can be further improved.
The water-soluble resin and the water-dispersible resin may be any of a cationic resin, an anionic resin, an amphoteric resin, and a nonionic resin, respectively. Many of the coloring materials suitable for water-based inks show anionicity in the surface charge of the coloring material to be dispersed in water. Therefore, in consideration of the stability of the coloring material in water, anionic resin, amphoteric resin, and nonionic property are taken into consideration. A resin can be preferably used, more preferably an anionic resin.
In a configuration in which the color material of the water-based ink is stabilized by an anionic resin, when the water-based ink is applied to the base material treated by the pretreatment agent by containing a cationic flocculant in the pretreatment agent, Due to the cationic flocculant in the pretreatment agent, the coloring material of the water-based ink is aggregated on the substrate, blurring of the image can be suppressed, and the image quality can be further improved.
The water-soluble resin and the water-dispersible resin are preferably resins that form a transparent coating film on the base material, respectively. Thereby, the influence of the water-based ink on the color development can be reduced.

Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, neutralized polyacrylic acid, acrylic acid / maleic acid copolymer, acrylic acid / sulfonic acid copolymer, styrene / maleic acid copolymer and the like. Be done. Further, an anionic water-soluble resin in which an anionic functional group is introduced into these resins can be used. These can be used alone or in combination of two or more.

Examples of the water-dispersible resin include ethylene-vinyl chloride copolymer resin, (meth) acrylic resin, styrene-maleic anhydride copolymer resin, urethane resin, vinyl acetate- (meth) acrylic copolymer resin, and vinyl acetate. -Examples include ethylene copolymer resin. These can be used alone or in combination of two or more.
The water-dispersible resin can be added to the ink as an oil-in-water (O / W) type resin emulsion.

As the water-dispersible resin, it is preferable to use anionic resin particles having a negatively charged resin particle surface and a negative charge. This is capable of forming an oil-in-water (O / W) type resin emulsion by dispersing in particles without being dissolved in water. An anionic functional group of the resin may be present on the surface of the resin particles, such as a self-emulsifying resin, or a surface treatment such as attaching an anionic dispersant to the surface of the resin particles may be performed. .. The anionic functional group is typically a carboxy group, a sulfo group or the like, and the anionic dispersant is an anionic surfactant or the like. The resin serving as the skeleton is as described above.

The water-dispersible resin includes a urethane resin emulsion, a (meth) acrylic resin emulsion, a resin emulsion of a (meth) acrylic resin copolymer, or a resin emulsion thereof from the viewpoint of adhesion to a base material, stability in ink, and the like. It is preferable to use a combination.
Examples of commercially available urethane resin emulsion products include "Superflex 460, 420, 470, 460S", "Superflex 740, 860", and "Superflex 870" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .; Examples thereof include "NeoRez R-9660, R-2170", "NeoRez R-986, R-9603";"TakelacWS-5100" manufactured by Mitsui Chemicals, Inc. (all are trade names).

Commercially available products of the (meth) acrylic resin emulsion and the resin emulsion of the (meth) acrylic resin copolymer include, for example, "Mobile 966A, 6963, 6960, 6696D" manufactured by Nippon Synthetic Chemical Industry Co., Ltd .; "BASF" manufactured by BASF. John Krill 7100, PDX-7370, PDX-7341 ";" Boncote EC-905EF, 5400EF, CG-8400 "manufactured by DIC Corporation;" NeoCryl A-1125 "manufactured by DSM (all trade names). ..

The total amount (active ingredient) of the water-soluble resin and the water-dispersible resin is preferably 0.5 to 10 and more preferably 1 to 5 with respect to the coloring material 1 in terms of mass ratio.
The total amount (active ingredient) of the water-soluble resin and the water-dispersible resin is preferably 1 to 20% by mass, more preferably 3 to 10% by mass, based on the total amount of the dark ink.

The dark ink can further contain a binder resin.
The binder resin can be blended in order to fix the solid content such as a coloring material more strongly on the base material and increase the strength of the coating film. The binder resin may be any of a cationic resin, an anionic resin, an amphoteric resin, and a nonionic resin. Many of the coloring materials suitable for water-based inks show anionic charge on the surface charge of the coloring material to be dispersed in water. Therefore, in consideration of the stability of the coloring material in water, the binder resin is an anionic resin. A nonionic resin can be preferably used. By using the water-soluble resin and the water-dispersible resin as the resin components described above, it is possible to obtain the action of the binder resin.
The binder resin (active ingredient) is preferably 1 to 20% by mass with respect to the total amount of the dark ink.

In addition to the above components, the dark ink may optionally include a wetting agent (moisturizer), surface tension adjusting agent (penetrating agent), defoaming agent, fixing agent, pH adjusting agent, antioxidant, preservative, etc. Can be appropriately contained.
The method for producing dark ink is not particularly limited, but a desired ink can be obtained by appropriately mixing each component. For example, when a pigment dispersion is used as a coloring material, it can be obtained by mixing the pigment dispersion with a solution in which a water-soluble organic solvent or an additive is appropriately added to water. Moreover, you may filter the obtained composition with a filter or the like.

The light ink can contain a solvent (c2) having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less, and water.}

The light ink preferably contains water as an aqueous solvent, and the main solvent may be water. When water is contained as a solvent in the pigment dispersion described later, the water in the pigment dispersion is converted into a part of the water in the ink to prepare the ink.
The water is not particularly limited, but water containing as little ionic component as possible is preferable.
In particular, from the viewpoint of ink storage stability, it is preferable that the content of multivalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, or the like may be used.
From the viewpoint of adjusting the ink viscosity, water is preferably contained in an amount of 20% by mass to 90% by mass, more preferably 30% by mass to 80% by mass, based on the total amount of the light ink.

The light ink can contain a solvent (c2) having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less.} The solvent (c2) preferably exhibits compatibility with water.
The relationship between the SP value of the solvent (c2) contained in the light ink, the solvent (c1) contained in the dark ink, and the solvent (c2) contained in the light ink is as described above. Further, the solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is as described above.

The light ink can contain other water-soluble organic solvents in addition to the solvent (c1) having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less.} Examples of other water-soluble organic solvents include glycerin and the like.
The other water-soluble organic solvent can be contained in an amount of 1% by mass to 30% by mass, more preferably 10% by mass to 20% by mass, based on the total amount of the light ink, from the viewpoint of viscosity adjustment and moisturizing effect.

The light ink may further contain a surfactant.
The surfactant blended in the dark ink and the surfactant blended in the light ink may be the same as each other, or may be partially or completely different from each other. When printing dark ink and light ink using the same inkjet printing device, it is preferable that the ink properties of both are similar. Therefore, the surfactant blended in the dark ink and the surfactant blended in the light ink Is preferably a surfactant that is the same as each other, partially the same, or has similar HLB values to each other.
The surfactant that can be blended in the light ink preferably has an HLB value of 1.0 to 20, preferably 2.0 to 15, and more preferably 3.0 or more and less than 10.0.

As the surfactant that can be blended in the light ink, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant may be used. Of these, a nonionic surfactant is preferable from the viewpoint of preventing foaming of the pretreatment agent. Further, either a low molecular weight surfactant or a high molecular weight surfactant may be used.

Examples of the nonionic surfactant include ester-type surfactants such as glycerin fatty acid ester and fatty acid sorbitan ester; ether-type surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxypropylene alkyl ether. Agents; ether ester-type surfactants such as polyoxyethylene sorbitan fatty acid ester; acetylene-based surfactants; silicone-based surfactants; fluorine-based surfactants and the like. Among them, acetylene-based surfactants and silicone-based surfactants can be preferably used. It is preferable to use one type of surfactant alone, but two or more types may be used in combination.

Examples of the acetylene-based surfactant include an acetylene glycol-based surfactant, an acetylene alcohol-based surfactant, and a surfactant having an acetylene group.
Examples of the silicone-based surfactant include a polyether-modified silicone-based surfactant, an alkyl-aralkyl co-modified silicone-based surfactant, and an acrylic silicone-based surfactant.

Specifically, it is appropriately selected from the above-mentioned surfactant (a) that can be blended with the pretreatment agent and the surfactant (b) that can be blended with the dark ink, and used as the surfactant for the light ink. Is possible. It is also possible to use an ionic surfactant that can be blended with ordinary ink as a surfactant for light ink.

When a surfactant is blended in the light ink, the amount of the active ingredient of the surfactant in the light ink is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the light ink. 0.7% by mass or more is more preferable.
The amount of the active ingredient of the light ink surfactant is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on the total amount of the light ink.
For example, the amount of the active ingredient of the light ink surfactant is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and 0.7 to 1% by mass with respect to the total amount of the light ink. More preferred.
By using a surfactant in the above range, it is possible to prevent a decrease in storage stability while further improving the affinity with the base material in the light ink.

The light ink may contain a pigment, a dye, or a combination thereof as a coloring material. From the viewpoint of image weather resistance and print density, pigments can be preferably used as the coloring material. The pigment is preferably blended with the ink as a pigment dispersion. The color material of the light ink is preferably a color material having the same hue as the dark ink. The color material of the light ink may have the same component as the dark ink or may have a different component, but it is preferable that the color material has the same component. As the color material of the light ink, the one described in the above-mentioned dark ink can be used.

The mass ratio of the mass ratio of the coloring material to the total amount of light ink (coloring material density 2) to the mass ratio of the coloring material to the total amount of dark ink (coloring material density 1) (coloring material concentration 2 / coloring material density 1) is 1. It is preferably less than or less than 1, more preferably 0.5 or less, further preferably 0.35 or less, and may be 0.3 or less.
The mass ratio (color material concentration 2 / color material concentration 1) is preferably 0.05 or more, more preferably 0.1 or more.
In the light ink, the amount of the active ingredient of the coloring material is preferably 0.1% by mass to 10% by mass, more preferably 0.3% by mass to 5% by mass, and 0.5% by mass to the total amount of the light ink. 3% by mass is more preferable.

The light ink may further contain a water-soluble resin, a water-dispersible resin, or a combination thereof. Thereby, the fixability of the coloring material to the base material can be further improved.
In the light ink, the water-soluble resin, the water-dispersible resin, or a combination thereof can be the one described in the above-mentioned dark ink. These components may be the same component between the dark ink and the light ink, or may be partially or wholly different components, but are preferably the same component. By using the same resin component between the dark ink and the light ink, the resin film can be formed more uniformly on the base material, and the fixability of the coloring material can be further improved.

The total amount (active ingredient) of the water-soluble resin and the water-dispersible resin is preferably 0.5 to 15 and more preferably 1 to 10 with respect to 1 of the coloring material in terms of mass ratio.
The total amount (active ingredient) of the water-soluble resin and the water-dispersible resin is preferably 1 to 20% by mass, more preferably 3 to 10% by mass, based on the total amount of the light ink.

The light ink can further contain a binder resin. As the binder resin for the light ink, the one described in the above-mentioned dark ink can be used.

In addition to the above components, light ink includes optionally a wetting agent (moisturizer), surface tension adjusting agent (penetrating agent), defoaming agent, fixing agent, pH adjusting agent, antioxidant, preservative, etc. Can be appropriately contained.
The method for producing the light ink is not particularly limited, and the light ink can be produced by the same method as the above-mentioned dark ink.

"Manufacturing method of printed matter"
Hereinafter, an example of a method for manufacturing a printed matter will be described.
A method for producing a printed matter can include, for example, printing on a substrate using an aqueous inkjet ink set. As the water-based inkjet ink set, the above-mentioned water-based inkjet ink set can be used.
For example, a method for producing a printed matter can include treating a substrate with a pretreatment agent and forming an image on the substrate with dark and light inks.

As a method of treating the base material using the pretreatment agent, for example, the pretreatment agent may be uniformly applied to the surface of the base material using a brush, a roller, a bar coater, an air knife coater, a spray, or the like. Alternatively, the pretreatment agent may be printed on the image area by a printing method such as inkjet printing, gravure printing, or flexographic printing. The coating area may be the entire surface of the base material, or may be selectively applied only to the image area. Alternatively, the pretreatment agent can be applied only to a portion to which a certain amount or more of ink is applied per unit area, such as a solid image portion.
When the pretreatment agent is uniformly applied to a large area of the base material, it is preferably applied by spraying.
Further, when the pretreatment agent is applied according to the image area to be printed on the base material, printing by inkjet printing is preferable.

The pretreatment agent does not need to be particularly provided with a drying step, and a printing step can be subsequently carried out. If necessary, it may be heated and dried at a temperature of 25 ° C. to 120 ° C. before the printing step. The heating time is preferably 1 minute to 120 minutes, more preferably 10 minutes to 60 minutes, depending on the type and amount of the volatile matter in the pretreatment agent. When the pretreatment agent contains a resin component, the resin is melted or softened on the base material by heat treatment after the pretreatment agent is applied, so that the pretreatment agent layer is more strongly fixed to the base material. be able to.

The amount of the pretreatment agent applied to the substrate is the amount of the active ingredient, preferably 0.5 to 200 g / m ^{2 and} more preferably ^{1 to 50 g / m 2 per unit area of the coated area.}

As a method of forming an image on a base material using dark ink and light ink, one of dark ink and light ink is applied to the base material, and then the other of dark ink and light ink is applied to the base material. Can be done with.
In the water-based inkjet ink set according to the embodiment, the pretreatment agent, the dark ink, and the light ink have the above-mentioned physical characteristics, so that the dots of the dark ink can be appropriately spread regardless of the order in which the dark ink and the light ink are applied. It can be adjusted to, and the image quality of printed matter can be further improved.
In a preferred form, the pretreatment agent, the light ink, and the dark ink can be applied to the substrate in this order.

The method of printing the dark ink and the light ink on the substrate can be performed by using an inkjet printing method. The inkjet printing method can form an image easily and freely on demand without contacting the base material.
The inkjet printing apparatus may be of any method such as a piezo method, an electrostatic method, or a thermal method. Ink is ejected from the inkjet head based on a digital signal, and the ejected ink droplets are used as a base material. Make it adhere.

For example, dark ink and light ink can be printed using a line head type inkjet printing apparatus. Using an inkjet printing device in which a plurality of line-shaped inkjet heads intersecting in the transport direction of the base material are arranged in the transport direction of the base material, light ink is applied to the line head on the upstream side in the transport direction of the base material. Loading, loading dark ink into the downstream line head, ejecting light ink from the upstream line head and then ejecting dark ink from the downstream line head in one transfer of the base material. Can form an image. The order of dark ink and light ink may be reversed.

In addition, dark ink and light ink can be printed using a serial head type inkjet printing apparatus. Using a printing device equipped with an inkjet head that is movable in a direction intersecting the transport direction of the base material and in which a plurality of nozzle rows are arranged along the movement direction, light ink is applied to one of the plurality of nozzle rows. An image can be formed by loading, loading the other with dark ink, and ejecting light ink while reciprocating the inkjet head while transporting the base material, and then ejecting dark ink. .. The order of dark ink and light ink may be reversed.
In both the line head type and the serial head type, the colorant density differs between the adjacent dots by ejecting the subsequent ink so as to be adjacent to the dots of the ink ejected earlier on the base material. , The hue tone can be adjusted. At this time, by using the dark ink and the light ink according to one embodiment, the graininess of the printed image can be reduced and a high-quality image can be obtained.

The obtained printed matter is preferably heat-treated to remove volatile matter. The heat treatment temperature is preferably 25 ° C. to 150 ° C., more preferably 50 ° C. to 120 ° C. The heat treatment time is preferably 1 minute to 24 hours, more preferably 10 minutes to 200 minutes, depending on the type and amount of the volatile matter of the ink, the coating thickness, and the like.
When the ink contains a resin component, the obtained decorative article is heat-treated to melt or soften the resin component in the ink to form a uniform resin film, thereby increasing the strength of the ink image layer. Can be enhanced.

The water-based inkjet ink set according to one embodiment can be applied to both a permeable base material and a low permeable base material. In particular, when printing with a water-based ink on a low-permeability substrate treated with a pretreatment agent, it is possible to more effectively prevent the graininess of the printed image.

The low-permeability base material is a base material in which the liquid does not permeate into the base material, and specifically, a base material in which most of the liquid in the ink stays on the surface of the base material.
Examples of the low-permeability base material include metal base materials such as metal plates such as aluminum, iron, copper, titanium, tin, chromium, cadmium, and alloys (for example, stainless steel, steel, etc.); borosilicate glass, quartz glass, soda. Glass base material such as flat glass such as lime glass; resin sheet such as PET film, OHT sheet, polyester sheet, polypropylene sheet, resin base material such as acrylic plate; molded body such as alumina, zirconia, steatite, silicon nitride, etc. Ceramic base material and the like.
These base materials may have a plating layer, a metal oxide layer, a resin layer, or the like formed on them, or may be surface-treated using a surfactant, a corona treatment, or the like. The water-based inkjet ink set according to the embodiment can exert its effect even when it is treated on an untreated substrate.

Examples of the permeable base material include printing paper such as plain paper, coated paper, and special paper; cloth; porous building materials for humidity control, sound absorption, heat insulation, etc .; wood, concrete, and the like. Among the permeable base materials, one embodiment is used for a base material such as cloth, a porous building material, wood, etc., in which ink is excessively penetrated into the base material and strike-through or image bleeding is likely to occur. By using the water-based inkjet ink set according to the above, it is possible to suppress the spread of dots and improve the image quality more effectively.

Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited to the following examples.
In the following description, "%" indicates "mass%" unless otherwise specified.
Tables 1 to 4 show the preparations of the pretreatment agents, the cyan-based dark ink, and the cyan-based light ink of Examples and Comparative Examples, and the evaluation results of the printed matter. In each table, when the solvent or the like is contained in each component, the blending ratio of the amount of the active ingredient is shown, and the solvent or the like is treated as being contained in the residual water. In each table, the unit of the amount of active ingredient represented by parentheses is mass%, and the unit of SP value is (cal / cm ³ ) ^1/2 .

<Preparation of pretreatment agent>
Each component was mixed in each ratio according to the formulation of the pretreatment agent shown in each table to obtain a pretreatment liquid. The water content was adjusted so that the total amount of the pretreatment agent was 100% by mass.

<Making dark ink and light ink>
Each component was mixed according to the formulation of the pretreatment agent shown in each table, and then filtered through a membrane filter having a pore size of 3 μm to obtain a cyan-based dark ink and a cyan-based light ink. The dark ink and the light ink were adjusted so that the image densities were different, mainly by making the densities of the cyanide self-dispersing pigments different. The water content was adjusted so that the total amount of ink was 100% by mass.

The components used are as follows.
(Activator)
Acetylene-based surfactant (1); HLB 8.8: "Orphine E1004" manufactured by Nisshin Kagaku Kogyo Co., Ltd., 100% by mass of active ingredient.
Acetylene-based surfactant (2); HLB 13.2: "Orphine E1010" manufactured by Nisshin Kagaku Kogyo Co., Ltd., 100% by mass of active ingredient.
Acetylene-based surfactant (3); HLB 4.0: "Surfinol 420" manufactured by Nissin Chemical Industry Co., Ltd., 100% by mass of active ingredient.
Acetylene-based surfactant (4); HLB 10.8: "Orphine E1006" manufactured by Nissin Chemical Industry Co., Ltd., 100% by mass of active ingredient.
Silicone-based surfactant (1); HLB12.2: Synthesized by the following procedure. 100% by mass of active ingredient.
Silicone-based surfactant (2); HLB 2.7: Synthesized by the following procedure. 100% by mass of active ingredient.
Silicone-based surfactant (3); HLB 7.7: Synthesized by the following procedure. 100% by mass of active ingredient.

(Pretreatment agent component)
Coagulant; Water-soluble cationic resin: Himax SC-700L, active ingredient amount 30%.
Coagulant; Multivalent metal salt: Calcium chloride anhydride, purity 95%, manufactured by Yoneyama Yakuhin Kogyo Co., Ltd.
Binder; Cationic resin emulsion: Ester urethane, "Superflex 620" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient amount 30%, particle size 0.02 μm.
Binder; Cationic resin emulsion: Acrylic acid ester / methacrylate ester copolymer emulsion, "Mobile 7820" manufactured by Japan Coating Resin Co., Ltd., active ingredient amount 45%, particle size 0.4 μm.
Diethylene glycol: water-soluble organic solvent, SP value 15.0 (cal / cm ³ ) ^1/2 .

(Ink component)
Glycerin: Water-soluble organic solvent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., SP value 16.4 (cal / cm ³ ) ^1/2 .
Diethylene glycol: water-soluble organic solvent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., SP value 15.0 (cal / cm ³ ) ^1/2 .
1,3-Propanediol: Water-soluble organic solvent, manufactured by Tokyo Chemical Industry Co., Ltd., SP value 13.7 (cal / cm ³ ) ^1/2 .
1,2-Hexanediol: water-soluble organic solvent, manufactured by Tokyo Chemical Industry Co., Ltd., SP value 11.8 (cal / cm ³ ) ^1/2 .
Urethane resin emulsion: Aromatic isocyanate-based, ether-based urethane, anionic resin emulsion, "Superflex 870" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., particle size 30 nm, active ingredient amount 30%.
Acrylic resin emulsion: DSM Coating Resins, LLC. Manufactured by "NeoCryl A-1125", anionic resin emulsion, active ingredient amount 19.5%.
Cyanide pigment dispersion: "CAB-0-JET-250C" manufactured by Cabot Corporation, self-dispersing pigment, amount of active ingredient 10% by mass.

The HLB value of the surfactant is a numerical value obtained from the molecular structure of the surfactant by the following formula (1) according to the Griffin method.
HLB value = 20 x (formula weight of hydrophilic part) / (molecular weight of surfactant) ... formula (1)
The SP value of the solvent is a numerical value based on the estimation method proposed by Fedor.
The ink viscosity was measured at 23 ° C. using a "rheometer MCR302" manufactured by AntonioPaar. Specifically, the viscosity value at 10 Pa when the shear stress was increased from 0 Pa at a rate of 0.1 Pa / s was obtained.

<Preparation of Silicone Surfactant (1)>
In order to obtain the compound represented by the following chemical formula (1), the following components were placed in a flask together with an ARP platinum catalyst, heated and stirred at 70 ° C. for 5 hours under a nitrogen atmosphere, and reacted. The product was filtered and toluene was removed under reduced pressure. The obtained compound was used as a silicone-based surfactant (1).
Hydroxypolyethoxy (10) allyl ether (98%) 20.7% by mass;
Methylbis (trimethylsilyloxy) silane 9.3% by mass;
Toluene: 70.0% by mass.

<Preparation of Silicone Surfactant (2)>
In order to obtain the compound represented by the following chemical formula (2), the following components were placed in a flask together with an ARP platinum catalyst, heated and stirred at 70 ° C. for 5 hours under a nitrogen atmosphere, and reacted. The product was filtered and toluene was removed under reduced pressure. The obtained compound was used as a silicone-based surfactant (2).
Ethylene glycol monoallyl ether 9.4% by mass;
Methylbis (trimethylsilyloxy) silane 20.6% by mass;
Toluene 70.0% by mass.

<Preparation of Silicone Surfactant (3)>
In order to obtain the compound represented by the following chemical formula (3), the following components were placed in a flask together with an ARP platinum catalyst, heated and stirred at 70 ° C. for 5 hours under a nitrogen atmosphere, and reacted. The product was filtered and toluene was removed under reduced pressure. The obtained compound was used as a silicone-based surfactant (3).
2- [2- [2- [2- (2-rop-2-enoxyethoxy) ethanoly] ethanoly] ethanol 15.4% by mass;
Methylbis (trimethylsilyloxy) silane 14.6% by mass;
Toluene 70.0% by mass.

The components used are as follows.
Hydroxypolyethoxy (10) allyl ether (98%): manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.
Methylbis (trimethylsilyloxy) silane: Made by Tokyo Chemical Industry Co., Ltd.
Ethylene glycol monoallyl ether: Made by Tokyo Chemical Industry Co., Ltd.
2- [2- [2- (2-rop-2-enoxyethoxy) ethanoly] ethanoly] ethanol Aurora Fine Chemicals.
ARP Platinum: Made by Fujifilm Wako Pure Chemical Industries, Ltd.
Toluene: Made by Fujifilm Wako Pure Chemical Industries, Ltd.

<Evaluation method>
A PET film was used as the base material.
The pretreatment agent was sprayed onto the PET film. The amount of the active ingredient was 20 g / m ² . After applying the pretreatment agent, the PET film was heat-treated at 90 ° C. for 20 minutes.
A 600 × 600 dpi grayscale (dark cyan to light cyan) image was formed on the pretreated PET film using “mPower mP5i / SOLD” manufactured by ANAJET to obtain a printed matter. For printing, light ink and dark ink are loaded into adjacent nozzle rows of a serial head type inkjet head, and the light ink and dark ink are applied to the base material while the inkjet head is reciprocated in a direction orthogonal to the transport direction of the base material. The ink was ejected in this order. On the base material, the dots of the light ink and the dark ink were adjacent to each other, and the light ink and the dark ink were printed so as to be 600 × 600 dpi to form a solid image.
The obtained printed matter was heat-treated at 100 ° C. for 120 minutes.

The printed matter of each Example and Comparative Example was visually observed with a magnifying glass on the printed surface and evaluated according to the following criteria.
A: I don't care about the graininess.
B: There is a little graininess.
C: I'm worried about the graininess.

As shown in each table, in the printed matter of each example, the graininess was reduced and good image quality was obtained.
Examples 1 to 7 are examples in which the composition of the surfactant is changed between the dark ink and the light ink.
From Examples 1 to 7, when the difference between the HLB value of the surfactant (a) of the pretreatment agent and the HLB value of the surfactant (b) of the dark ink is equal to or more than a predetermined value, the graininess of the printed matter is deteriorated. It can be seen that it is reduced.
From Examples 1 to 4, it can be seen that when the content of the surfactant (b) in the dark ink is 0.7% by mass or more, the graininess of the printed matter is further reduced.
Examples 5 and 7 are examples in which the surfactant of the light ink was changed, but the graininess of the printed matter could be reduced.
Example 6 is an example in which the HLB value of the surfactant (b) of the dark ink is smaller, but the graininess of the printed matter could be reduced.

Examples 8 to 11 are examples in which the composition of the solvent is changed between the dark ink and the light ink.
From Examples 8 and 9, it can be seen that when the viscosity ratio (v2 / v1) of the dark ink and the light ink is at least a predetermined value, the graininess of the printed matter is reduced.
From Example 10, it can be seen that the graininess of the printed matter is reduced when the concentration ratio (c2 / c1) of the solvent having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less is equal to or more than a predetermined value.} ..
From Example 11, it can be seen that the graininess of the printed matter is reduced regardless of the type of solvent having an SP value of 15.5 (cal / cm ³ ) ^{1/2 or less.}

Examples 12 to 14 are examples in which the composition of the pretreatment agent is changed.
Example 12 is an example in which a silicone-based surfactant was used as the surfactant (a) of the pretreatment agent, but the graininess of the printed matter could be reduced.
From Examples 13 and 14, it can be seen that the graininess of the printed matter is reduced regardless of the type of the coagulant and the binder of the pretreatment agent.

Examples 15 to 19 are examples in which the composition of the surfactant is changed between the dark ink and the light ink.
In Examples 15 and 16, although the amount of the surfactant (b) in the dark ink was small, the graininess of the printed matter could be reduced.
Examples 17 to 19 are examples in which a silicone-based surfactant was used as the surfactant (b) of the dark ink, but the graininess of the printed matter could be reduced.

Comparative Example 1 is an example in which the viscosity ratio (v2 / v1) of the dark ink and the light ink is small, and a grainy feeling was observed in the printed matter.
Comparative Example 2 is an example in which the concentration ratio (c2 / c1) of the solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less is small, and a grainy feeling was observed in the printed matter.
Comparative Example 3 is an example in which the HLB value of the surfactant of the dark ink is large, and a grainy feeling was observed in the printed matter.
Comparative Examples 4 and 5 are examples in which the HLB value of the surfactant of the pretreatment agent is small and the difference between the surfactant of the pretreatment agent and the surfactant (b) of the dark ink is small, and the printed matter has a grainy appearance. Was observed.
Comparative Example 6 is an example in which the pretreatment agent was not applied to the base material, and the dark ink and the light ink did not fix on the base material, and the image was not formed well.

Claims (6)

A pretreatment agent and dark ink and light ink having the same hue as each other are provided.
The pretreatment agent contains a surfactant having an HLB value of 10.0 or more, and water.
The dark ink has an HLB value of less than 10.0, a surfactant having a difference of 2.0 or more from the HLB value of the surfactant contained in the pretreatment agent, and an SP value of 15.5 (cal). / Cm ³ ) ^Contains less than 1/2 solvent and water,
The light ink contains a solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less, and water.
The SP value contained in the light ink is 15.5 (cal / cm ^{3) 1/2} or less of the concentration of the solvent (mass%), the SP value contained in dark ink is 15.5 (cal / cm ³⁾ It is 1.1 times or more with respect to the concentration (mass%) of the solvent of ^{1/2 or less.}
A water-based inkjet ink set in which the viscosity (mPa · s) of the light ink is 1.05 times or more the viscosity (mPa · s) of the dark ink at 23 ° C. The HLB value contained in the dark ink is less than 10.0, and the difference from the HLB value of the surfactant contained in the pretreatment agent is 2.0 or more, which is 0 with respect to the total amount of the dark ink. The water-based inkjet ink set according to claim 1, which is 7.7% by mass or more. The aqueous inkjet ink according to claim 1 or 2, wherein the surfactant contained in the pretreatment agent having an HLB value of 10.0 or more contains at least one of an acetylene-based surfactant and a silicone-based surfactant. set. The surfactants in which the HLB value contained in the dark ink is less than 10.0 and the difference from the HLB value of the surfactant contained in the pretreatment agent is 2.0 or more are acetylene-based surfactants and The water-based inkjet ink set according to any one of claims 1 to 3, which contains at least one of a silicone-based surfactant. The water-based inkjet ink set according to any one of claims 1 to 4, wherein the light ink further contains a surfactant. The solvent having an SP value of 15.5 (cal / cm ³ ) ^1/2 or less contains at least one selected from the group consisting of diethylene glycol, 1,3-propanediol, and 1,2-hexanediol. The water-based inkjet ink set according to any one of claims 1 to 5.