JP7230998B2 - Aqueous inkjet ink and method for producing inkjet printed matter - Google Patents

Description

The present invention uses C.I. I. The present invention relates to an aqueous inkjet ink containing Pigment Orange 64 and a method for producing inkjet prints using the aqueous inkjet ink.

The digital printing method is spreading rapidly as printing lots become smaller and needs diversify. Since the digital printing method does not require a printing plate, it is possible to realize small-lot production, cost reduction, and downsizing of the printing apparatus.

The inkjet printing method, which is a type of digital printing method, is a method in which fine droplets of ink are ejected and landed on a recording medium from an inkjet head, and images and characters (hereinafter collectively referred to as "printed matter") are printed on the recording medium. It is a method of forming a Compared to other digital printing methods, it is superior in terms of the size and cost of printing equipment, the running cost during printing, and the ease of full-color printing.In recent years, it has been used for industrial printing.

There are many types of inks used in inkjet printing, including oil-based, solvent-based, active energy ray-curable, and water-based inks. So far, solvent-based and active energy ray-curable inks have been used for industrial printing applications. However, in recent years, the demand for water-based inks has been increasing from the viewpoint of consideration and countermeasures against harmfulness to the environment and people.

Moreover, in recent years, amid the demand for expanded applications of the inkjet printing method, in addition to industrial printing applications, there is a demand for expansion to packaging applications such as paper containers, labels, and packaging films. In that case, color reproducibility and image quality are high for low-permeability substrates such as coated paper and art paper, and non-permeable substrates such as polypropylene film and polyethylene terephthalate (PET) film. Therefore, it is required to form a printed matter having properties that can withstand actual use.

Particularly in packaging applications, red color reproducibility is often required as a design for sales promotion, a corporate color of a company, a national color of an emerging country, and the like. In general, red color is formed by superimposing yellow color and magenta color, but in order to further improve color reproducibility in the red region, attempts have been made to set orange and red special color inks ( See Patent Documents 1 to 3).

Generally, an orange colorant is used to obtain an orange spot color ink. Dyes and pigments are known as colorants, but pigments are preferably selected because they are excellent in light fastness and moisture fastness of printed materials in consideration of properties required for packaging applications. There are also various types of orange pigments, one of which is the benzimidazolone pigment. Benzimidazolone pigments are known as pigments with an excellent balance of color developability, light resistance, chemical resistance, and the like. I. Pigment Orange 64 is often studied for solvent-based and active energy ray-curable inkjet inks (see Patent Documents 4 and 5).

On the other hand, C.I. I. Water-based inkjet inks containing Pigment Orange 64 have hardly been studied. As one of the few examined examples, Patent Document 6 discloses C.I. I. A water-based inkjet ink containing Pigment Orange 64 is disclosed. However, in Patent Document 6, C.I. I. There is no mention of materials suitable for combination with Pigment Orange 64. In addition, since the orange ink composition described in the examples does not contain a binder resin and contains 15% by mass of glycerin, When printed on a permeable base material, it is easily expected that the printed material will be inferior in drying property, image quality and scratch resistance.

JP 2004-276397 A JP 2015-199849 A WO2017/61507 JP 2016-172822 A JP 2017-132907 A JP 2009-173853 A

The present invention has been made to solve the above problems, and the purpose thereof is to provide excellent drying properties, image quality of printed matter, and resistance (scratch resistance) of printed matter, as well as dispersion stability and ejection stability. Also excellent in C.I. I. An object of the present invention is to provide a water-based inkjet ink containing Pigment Orange 64. A further object of the present invention is to obtain a printed matter excellent in adhesion and color reproducibility in addition to the above properties even on non-permeable substrates such as plastic substrates. I. An object of the present invention is to provide a water-based inkjet ink containing Pigment Orange 64.

The inventors of the present invention conducted intensive studies to solve the above problems, and found that a binder resin having a specific acid value, a surfactant, a water-soluble organic solvent, C.I. I. Pigment Orange 64 is used in combination, and the content of the compound having 3 or more hydroxyl groups is limited.

That is, the present invention provides a water-based inkjet ink containing a colorant, a pigment dispersion resin, a binder resin (A), a surfactant, and a water-soluble organic solvent,
The colorant is C.I. I. including Pigment Orange 64,
The above C.I. I. Pigment Orange 64, the amount of impurities present in the C.I. I. Pigment Orange 64 is 8% by mass or less with respect to the total amount,
The binder resin (A) contains a binder resin (a-1) having an acid value of 1 to 60 mgKOH/g,
The content of the water-soluble organic solvent having a boiling point of 240° C. or higher under 1 atm is 5% by mass or less with respect to the total amount of the inkjet ink,
The content of the compound having 3 or more hydroxyl groups is 2.5 % by mass or less with respect to the total amount of the inkjet ink ,
It relates to a water-based inkjet ink, wherein the water-soluble organic solvent contains an alkanediol having 3 carbon atoms .

Further, in the present invention, the binder resin (a-1) is at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, and olefin resins. It relates to inkjet ink.

The present invention also relates to the water-based inkjet ink described above, wherein the surfactant contains a surfactant having an HLB value of 0 to 8.

The present invention also relates to a method for producing an inkjet printed matter, wherein the water-based inkjet ink is ejected from an inkjet head and applied to an impermeable substrate.
The present invention also relates to an ink-pretreatment liquid set containing the water-based inkjet ink and a pretreatment liquid containing a flocculant.
The present invention also relates to the above ink-pretreatment liquid set, wherein the flocculant contains a polyvalent metal ion salt selected from the group consisting of Ca ²⁺ , Mg ²⁺ , Zn ²⁺ and Al ³⁺ .

According to the present invention, C.I. I. It is now possible to provide water-based inkjet inks containing Pigment Orange 64. In addition to the above properties, C.I. I. It is now possible to provide water-based inkjet inks containing Pigment Orange 64.

The water-based inkjet ink of the present invention (hereinafter also simply referred to as "water-based ink" or "ink") will be described below with reference to preferred embodiments. As used herein, the term "aqueous medium" means a liquid medium containing at least water.

The C.I. contained in the water-based ink of the present invention. I. Pigment Orange 64 has the following structure and is known as a pigment with excellent color development and light resistance.

According to the above structure, C.I. I. Pigment Orange 64 contains many nitrogen atoms and oxygen atoms in its molecular structure and also has an aromatic ring structure, so it is considered that intermolecular interactions such as hydrogen bonding and π interaction are strong.

In water-based inks, pigments are generally present in the aqueous medium in a dispersed state. However, C.I. I. Pigments with strong intermolecular interactions, such as Pigment Orange 64, are likely to lose their dispersed state due to subtle changes in balance in the water-based ink. Especially in the case of inkjet ink, it is necessary to control physical properties such as viscosity, surface tension, and pH in order to stably eject from the inkjet head, and the materials that can be used are limited. becomes difficult. That is, C.I. I. In a water-based inkjet ink containing Pigment Orange 64, it can be said that it is a big problem for those skilled in the art to achieve both maintenance of a suitable dispersed state and properties as an inkjet ink.

For example, water-based inkjet inks often use low-volatility, high-boiling-point solvents in order to ensure wetting and spreading on a recording medium and to obtain prints with excellent image quality. However, when printing on a non-permeable substrate or the like, which will be described later, water-based ink droplets tend to remain on the recording medium for a long time, and coalescence of the ink droplets occurs, resulting in bleeding and uneven density. may occur. Moreover, the high boiling point solvent remaining in the printed matter may deteriorate the abrasion resistance of the printed matter.

In order to solve the above problem, for example, measures such as using a highly volatile solvent together or reducing the amount of a low volatile high boiling point solvent are conceivable. However, highly volatile solvents generally tend to destroy the dispersed state of pigments, so C.I. I. It is difficult to use together with a pigment having a strong intermolecular interaction such as Pigment Orange 64. In addition, the ink dries before it is sufficiently wetted and spreads on the recording medium, causing white spots, and it dries and solidifies on the nozzle surface of the inkjet head, which may cause problems such as crooked ejection or non-ejection. .

Further, a binder resin is sometimes added to water-based inkjet ink for the purpose of improving the scratch resistance of printed matter. However, there is a possibility that the acid group or the like present in the binder resin interacts with the polar group in the pigment or the material that contributes to the dispersion of the pigment, destroying the dispersed state. In particular, as noted above, C.I. I. Since Pigment Orange 64 contains many nitrogen atoms and oxygen atoms in its molecular structure, there is a high possibility that the dispersion stability will be deteriorated. Ink containing a binder resin tends to dry and solidify on the nozzle surface, and the ejection stability tends to decrease.

Therefore, as a result of intensive studies by the present inventors, a binder resin having a specific acid value, a surfactant, and a water-soluble organic solvent are used in combination, and the content of a compound having 3 or more hydroxyl groups is limited. As a result, the inventors have found that a water-based inkjet ink that satisfies all of dispersion stability, ejection stability, drying property, image quality of printed matter, and abrasion resistance of printed matter. Although the reason is not clear, the following may be considered.

First, the water-based ink of the present invention contains a binder resin (a-1) having a low acid value and a low affinity for water, which is the main component of the ink. Therefore, it is thought that the binder resin (a-1) moves quickly to the air-liquid interface during the drying process after the water-based ink droplets land on the recording medium. Further, when the proportion of the water-soluble organic solvent increases as the ink droplets dry on the recording medium, the binder resin (a-1) dissolves in the water-soluble organic solvent and locally forms at the air-liquid interface. thickening or film formation. As a result, bleeding between ink droplets and uneven density are suppressed, and image quality is improved.

Further, by specifying the amount of acid value present in the binder resin (a-1) and limiting the amount of acid groups in the binder resin (a-1), C.I. I. The pigment orange 64 is maintained in a dispersed state.

On the other hand, the binder resin (a-1) having a small acid value does not easily return to its original state even in the presence of an aqueous medium once a film is formed. This is preferable from the viewpoint of improving the scratch resistance of printed matter. Since it is difficult to return to the state of , there is a risk of causing deterioration in ejection stability. Therefore, in the present invention, this problem is solved by using a surfactant in combination. Surfactants generally have a hydrophobic group and a hydrophilic group in the molecule. In the ink of the present invention, it is considered that the binder resin (a-1) and the hydrophobic group in the surfactant molecule have an affinity, and water and the hydrophilic group in the surfactant molecule have an affinity, respectively. It is thought that the binder resin (a-1) is protected by the surfactant in the ink in the ink jet head, and the film formation of the binder resin (a-1) is suppressed. On the other hand, in the ink droplets that have landed on the recording medium, the surfactant moves to the solid-liquid interface formed between the recording medium and the ink due to the change in the abundance ratio of the constituent materials in the ink due to drying. Conceivable. As a result, the ink droplets spread quickly on the recording medium, and together with the effect of thickening or film formation by the binder resin (a-1), it is considered that the ink is excellent in image quality and drying property of the printed matter. .

In addition, the water-based inkjet ink of the present invention may contain a compound having 3 or more hydroxyl groups. A compound having 3 or more hydroxyl groups is C.I. I. It is thought to form a hydrogen bond with Pigment Orange 64. As a result, there is concern that the dispersed state of the pigment will be destroyed, and that these compounds will remain in the printed matter, resulting in deterioration of drying properties. In addition, since the compatibility with the binder resin (a-1) having a small acid value is considered to be poor, the distribution of the binder resin (a-1) in the printed matter is uneven, and the abrasion resistance and image quality of the printed matter may lead to deterioration of As described above, in the present invention, by limiting the amount of the compound having 3 or more hydroxyl groups in the water-based inkjet ink, it is possible to improve the dispersion stability, the drying property, and the scratch resistance of the printed matter.

As described above, C.I. I. In order to obtain a water-based inkjet ink that contains Pigment Orange 64 and is compatible with all of dispersion stability, ejection stability, drying property, image quality of printed matter, and abrasion resistance of printed matter, the configuration of the present invention is considered essential.

Next, each component constituting the water-based inkjet ink of the present invention will be described below.

<C. I. Pigment Orange 64>
The water-based inkjet ink of the present invention contains C.I. I. Contains Pigment Orange 64. As mentioned above, C.I. I. Pigment Orange 64 is excellent in color developability and lightfastness, and when used in combination with a yellow ink and a magenta ink, printed matter with excellent color reproducibility can be obtained.

From the viewpoint of obtaining printed matter with excellent color reproducibility, the C.I. I. The content of Pigment Orange 64 is preferably 0.5 to 10% by mass, more preferably 1 to 9% by mass, and particularly preferably 2 to 8% by mass, relative to the total amount of the water-based ink. .

On the other hand, C.I. I. When using Pigment Orange 64, it is preferable to pay attention to its impurity levels. Existence of a large amount of impurities causes foaming and inhibition of adsorption between the pigment and the pigment dispersion resin (described later) in the pigment dispersion process during ink production, resulting in poor color reproducibility, dispersion stability, and ejection stability of the printed matter. is likely to deteriorate. C. I. The amount of impurities present in Pigment Orange 64 is determined by the C.I. I. Pigment Orange 64 is preferably 8% by mass or less, more preferably 6% by mass or less, and particularly preferably 4% by mass or less, relative to the total amount of Pigment Orange 64.

C. I. As a method for reducing the impurities present in Pigment Orange 64, the C.I. I. There is a method of washing Pigment Orange 64 with water or an organic solvent. In particular, it is preferable to perform the washing step using water and the washing step using an organic solvent once or more. Further, it is preferable to use pure water or ion-exchanged water as the water.

In addition, C.I. I. The amount of impurities in Pigment Orange 64 can be measured by the method described below. 95 g of ion-exchanged water was placed in a 250-ml polypropylene wide-mouthed bottle (I-Boy [registered trademark] manufactured by AS ONE), and the target C.I. I. Add 5 g of Pigment Orange 64 and seal. After shaking and stirring with a shaker for 1 hour, the sample is placed in an oven at 70° C. for 7 days. After allowing to stand and allowing to cool to room temperature, the residue is removed by decantation, and the remaining supernatant is centrifuged at 30,000 rpm for 6 hours using a centrifuge. Then, the content of impurities in the pigment is calculated by measuring the solid content of the supernatant after the sediment is removed.

In the present invention, C.I. I. A pigment other than Pigment Orange 64 may be used in combination.

The above C.I. I. As pigments other than Pigment Orange 64, yellow pigments, orange pigments, magenta pigments, violet pigments, and the like can be suitably used, and from the viewpoint of obtaining printed matter with excellent color reproducibility in the red region, magenta pigments and/or violet pigments are preferably used. It is particularly preferred to include In addition, the above C. I. When a magenta pigment and/or a violet pigment is used as a pigment other than Pigment Orange 64, the blending amount thereof is C.I. I. It is preferably 10 to 100% by mass, particularly preferably 20 to 70% by mass, based on the amount of Pigment Orange 64 blended.

C. I. Examples of yellow pigments that can be used with Pigment Orange 64 are C.I. I. Pigment Yellow 10, 11, 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like. Among them, C.I. I. Pigment Orange 64 is less likely to be destroyed, and the C.I. I. Pigment Orange 64, C.I. I. Pigment Yellow 12, 14, 74, 120, 139, 154, 180 and 185 are preferably used.

Also, C.I. I. Examples of orange pigments that can be used with Pigment Orange 64 are C.I. I. Pigment Orange 13, 16, 17, 22, 24, 34, 36, 38, 40, 43, 51, 60, 62, 71, 72, 73 and the like. Among them, C.I. I. Pigment Orange 64 is less likely to be destroyed, and the C.I. I. Pigment Orange 64, C.I. I. One or more selected from the group consisting of Pigment Orange 36, 38, 43, 60, 62 and 72 can be preferably used.

Also, C.I. I. Examples of magenta organic pigments that can be used with Pigment Orange 64 are C.I. I. Pigment Red 5, 7, 12, 22, 23, 31, 48(Ca), 48(Mn), 49, 52, 53, 57(Ca), 57:1, 112, 122, 146, 147, 150, 185 , 202, 207, 209, 238, 242, 254, 255, 266, 269, 282 and the like. Among them, C.I. I. Pigment Orange 64 is less likely to be destroyed, and the C.I. I. Pigment Orange 64, C.I. I. One or more selected from the group consisting of Pigment Red 122, 150, 185, 202, 209 and 282 can be preferably used.

Also, C.I. I. Examples of violet pigments that can be used with Pigment Orange 64 are C.I. I. pigment violet 19, 23, 29, 30, 37, 40, 42, 43, 50; Among them, C.I. I. Pigment Orange 64 is less likely to be destroyed, and the C.I. I. Pigment Orange 64, C.I. I. One or more selected from the group consisting of Pigment Violet 19, 23, 32 and 42 can be preferably used.

Among the pigments exemplified and selected above, benzimidazolone pigments and/or quinacridone pigments are particularly preferably selected. Both pigments are C.I. I. Pigment Orange 64 and similar partial structures, C.I. I. This is because it is difficult to destroy the dispersed state of Pigment Orange 64, and a water-based ink having excellent dispersion stability can be obtained.

The pigments exemplified and selected above may be used alone, or two or more pigments may be used in combination. The two or more types of pigments may form a solid solution, in which case it is preferable to use a solid solution containing a quinacridone pigment from the viewpoint of dispersion stability and improved color reproducibility of printed matter. Specific examples of solid solutions that can be preferably used in the present invention include C.I. I. Pigment Red 122 and C.I. I. Pigment Violet 19, C.I. I. Pigment Red 202 and C.I. I. Pigment Violet 19, C.I. I. Pigment Red 209 and C.I. I. Pigment Violet 19, C.I. I. Pigment Red 282 and C.I. I. Pigment Violet 19, C.I. I. Pigment Red 122 and C.I. I. Pigment Red 146, C.I. I. Pigment Red 122 and C.I. I. Pigment Red 150, C.I. I. Pigment Red 122 and C.I. I. Pigment Red 254, C.I. I. Pigment Red 122 and C.I. I. Pigment Red 269 and the like.

<Pigment dispersion resin>
C. I. As a method for stably dispersing and holding a pigment containing Pigment Orange 64 in an aqueous inkjet ink, (1) a method of coating at least a portion of the pigment surface with a pigment dispersing resin, (2) water-soluble and/or water-dispersible (3) A method of chemically and physically introducing a hydrophilic functional group onto the surface of the pigment and dispersing it in the ink without a dispersing resin or surfactant (self-dispersing pigment ) and the like.

For the water-based inkjet ink of the present invention, the method (1) above, that is, the method using a pigment dispersion resin is preferably selected. This is because by selecting and examining the composition and molecular weight of the polymerizable monomers constituting the resin, it is possible to easily adjust the ability of the pigment dispersing resin to cover the pigment and the charge of the pigment dispersing resin. This is because it is possible to impart dispersion stability even with the addition of a soluble solvent, and furthermore, a printed matter having excellent ejection stability, color development, and color reproducibility can be obtained.

The type of the pigment dispersion resin is not particularly limited. (Polycondensates of) and the like can be used, but are not limited to these. Among them, it is preferable to use one or more selected from the group consisting of acrylic resins, styrene-acrylic resins, urethane resins, and ester resins in terms of material selectivity and ease of synthesis. From the viewpoint of improving the dispersion stability and ejection stability of the water-based ink, it is preferable to use the same type of resin as the binder resin (A) described later.

The above pigment dispersion resin can be synthesized by a known method, or a commercially available product can be used. The structure is also not particularly limited, and for example, resins having a random structure, block structure, comb structure, star structure, or the like can be used. Furthermore, a water-soluble resin or a water-insoluble resin may be selected as the pigment dispersion resin. The term "water-insoluble resin" refers to a pigment-dispersing resin that is not transparent when viewed with the naked eye when mixed with water at 25°C and 1% by mass.

In the present invention, when a water-soluble resin is used as the pigment dispersion resin, its acid value is preferably 50 to 450 mgKOH/g, more preferably 100 to 400 mgKOH/g. Especially preferred is 150 to 350 mgKOH/g. By setting the acid value within the above range, it is possible to maintain the dispersion stability of the pigment and to stably eject the pigment from the inkjet head. In addition, it becomes possible to maintain ejection stability on the inkjet head. Furthermore, the solubility of the pigment dispersion resin in water can be ensured, and the interaction between the pigment dispersion resins becomes suitable, which is preferable in that the viscosity of the pigment dispersion can be suppressed.

On the other hand, when a water-insoluble resin is used as the pigment dispersion resin, its acid value is preferably 0 to 100 mgKOH/g, more preferably 5 to 90 mgKOH/g, and further preferably 10 to 80 mgKOH/g. preferable. If the acid value is within the above range, a printed matter having excellent drying properties and scratch resistance can be obtained.

The acid value of the resin in this specification can be measured by potentiometric titration using a known device such as AT-610 manufactured by Kyoto Electronics Industry Co., Ltd.

In the water-based inkjet ink of the present invention, it is preferable to introduce an aromatic group into the pigment dispersing resin from the viewpoint of improving the adsorption ability to the pigment and ensuring the dispersion stability. Especially in the case of the present invention, C.I. I. Pigment Orange 64 interacts with the aromatic ring structure contained in the pigment dispersing resin, whereby the C.I. I. The ability of the pigment dispersing resin to adsorb Pigment Orange 64 is remarkably improved. As a result, even if the pigment is finely dispersed, it is possible to ensure the dispersion stability of the water-based ink, the ejection stability, and the color reproducibility of the printed matter over a long period of time. The aromatic group includes, but is not limited to, phenyl group, naphthyl group, anthryl group, tolyl group, xylyl group, mesityl group, and anisyl group. Among them, a phenyl group and a tolyl group are preferable from the viewpoint of sufficiently ensuring dispersion stability.

C. I. From the viewpoint of compatibility between dispersion stability, print quality, and drying property of ink containing Pigment Orange 64, the content of the monomer containing the aromatic ring is 5 to 75% by mass based on the total amount of the pigment dispersion resin. Preferably, it is 5 to 65% by mass, and even more preferably 10 to 50% by mass.

In addition to the aromatic group, it is particularly preferable to introduce an alkyl group having 8 to 36 carbon atoms into the pigment dispersing resin. C.I. I. This is because the dispersion stability of the ink containing Pigment Orange 64 can be improved and the ejection stability can be realized. The number of carbon atoms in the alkyl group is preferably 10 to 30 carbon atoms, more preferably 12 to 24 carbon atoms. As long as the alkyl group has 8 to 36 carbon atoms, either a straight-chain or branched-chain alkyl group can be used, but the straight-chain one is preferred. Linear alkyl groups include ethylhexyl group (C8), lauryl group (C12), myristyl group (C14), cetyl group (C16), stearyl group (C18), aralkyl group (C20), behenyl group (C22), Lignoceryl group (C24), cerotoyl group (C26), montanyl group (C28), melisyl group (C30), dotriacontanyl group (C32), tetratriacontanyl group (C34), hexatriacontanyl group (C36) etc.

The content of the monomer containing an alkyl chain having 8 to 36 carbon atoms is 5 to 60% by mass based on the total amount of the pigment dispersion resin, from the viewpoint of achieving both low viscosity of the pigment dispersion and scratch resistance of the printed matter. is preferred, 10 to 55 mass % is more preferred, and 15 to 50 mass % is particularly preferred.

When a water-soluble resin is used as the pigment dispersion resin, it is preferable that the acid groups in the resin are neutralized with a base in order to increase the solubility in water-based ink. Whether or not the amount of the base added is excessive can be confirmed, for example, by preparing a 10% by mass aqueous solution of the pigment dispersion resin and measuring the pH of the aqueous solution. C. I. From the viewpoint of improving the dispersion stability of the ink containing Pigment Orange 64, the pH of the aqueous solution is preferably 7 to 11, more preferably 7.5 to 10.5.

Examples of bases for neutralizing the pigment dispersion resin include organic amine solvents such as triethylamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol and aminomethylpropanol, aqueous ammonia, and water. Alkali metal hydroxides such as lithium oxide, sodium hydroxide, and potassium hydroxide, and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate, but are not limited thereto. .

When a water-soluble resin is used as the pigment dispersion resin, its weight average molecular weight is preferably in the range of 1,000 to 50,000, more preferably in the range of 5,000 to 40,000. 000 to 35,000, and particularly preferably 15,000 to 30,000. When the weight average molecular weight is within the above range, C.I. I. Pigment Orange 64 is stably dispersed in water, and it is easy to adjust viscosity when applied to water-based ink. When the weight-average molecular weight is 1,000 or more, the pigment dispersion resin becomes difficult to dissolve in the water-soluble organic solvent added to the water-based ink. I. The adsorption of the pigment dispersion resin to Pigment Orange 64 is strengthened, and the dispersion stability is improved. When the weight-average molecular weight is 50,000 or less, the viscosity at the time of dispersion can be kept low, and the dispersion stability of the ink and the ejection stability from the inkjet head are improved, and stable printing over a long period of time becomes possible.

The blending amount of the pigment dispersing resin is preferably 1 to 100% by mass with respect to the blending amount of the pigment. By setting the ratio of the pigment dispersion resin within the above range, the viscosity of the pigment dispersion is suppressed, and the dispersion stability and ejection stability of the water-based inkjet ink are improved. The ratio of pigment to pigment dispersing resin is more preferably 2 to 50% by mass, and particularly preferably 4 to 45% by mass.

<Binder resin (A)>
In the water-based inkjet ink of the present invention, a binder resin (A) is used to improve the scratch resistance of printed matter. Two or more resins may be used in combination as the binder resin (A), in which case at least one of the two or more resins is the binder resin (a-1) described later.

The "binder resin" as used herein is a resin used for binding a layer (print layer, ink layer) of a printed matter to a recording medium. As will be described later, the ink of the present invention may contain a pigment dispersing resin, and the pigment dispersing resin and the binder resin are distinguished by their adsorption rate to the pigment. That is, a resin having a pigment adsorption rate of 50% by mass or more based on the total amount of the mixture is determined as a pigment dispersing resin, and a resin having less than 50% by mass is determined as a binder resin.

As a method for confirming whether or not the resin present in the water-based ink is the binder resin in the present specification, there is a method of measuring the adsorption rate with respect to the pigment. For example, the water-based ink diluted with water as necessary is centrifuged (for example, at 30,000 rpm for 4 hours) to separate the pigment from the supernatant. Then, when the solid content contained in the supernatant liquid is measured, if the solid content is larger than 50% by mass with respect to the total amount of resin contained in the water-based ink, the resin is judged to be the binder resin.

Water-soluble resins and fine resin particles are generally known as forms of binder resins for water-based inks, and either one of them may be selected and used in the present invention, or both may be used in combination. For example, resin fine particles have a higher molecular weight than water-soluble resins, so that they can improve the scratch resistance of printed matter, and the image quality of printed matter is also excellent. Moreover, water-based inkjet inks using a water-soluble resin as a binder resin are excellent in ejection stability. As used herein, the term "water-soluble resin" refers to a resin that is not the water-insoluble resin described above, that is, a mixture of the target resin at 25°C and 1% by mass in water that is transparent to the naked eye. .

As described above, the inkjet ink of the present invention contains a binder resin (a-1) having an acid value of 1 to 80 mgKOH/g as the binder resin (A). Also, C.I. I. From the viewpoint of ensuring the dispersion stability of Pigment Orange 64 and further moving quickly to the gas-liquid interface to obtain a printed matter with excellent image quality, it is preferably 3 to 60 mgKOH / g, particularly preferably 5 to 40 mg KOH/g. The acid value of the binder resin (a-1) can be measured in the same manner as the acid value of the pigment dispersion resin.

Examples of the binder resin (A) used in the present invention include acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, styrene-butadiene resins, vinyl chloride resins, styrene-maleic acid resins, ester resins, and olefin resins. be done. Among them, the binder resin (a-1) is selected from acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, and olefin resins, from the viewpoint of obtaining ink excellent in dispersion stability and ejection stability. It preferably contains one or more resins selected from the group consisting of:

The glass transition temperature of the binder resin (A) can be selected, for example, as follows, depending on the properties required. Specifically, it improves the ejection stability and scratch resistance of printed matter, and is also excellent in drying properties and blocking resistance (a phenomenon in which the printed layer sticks to another recording medium when printing media are stacked). The glass transition temperature is preferably 60 to 140.degree. C., more preferably 70 to 135.degree. C., and particularly preferably 80 to 130.degree.

On the other hand, when the ink of the present invention is used on non-permeable substrates such as plastic substrates, urethane resins, urethane-acrylic composite resins, and olefin resins are used from the viewpoint of image quality and adhesion. and/or a glass transition temperature of -120 to 45°C (preferably -80 to 25°C, more preferably -60 to 15°C). It is preferable to use one or more resins selected from the group consisting of acrylic resins and styrene-acrylic resins.

The glass transition temperature is a value measured using a DSC (differential scanning calorimeter), and can be measured, for example, as follows. About 2 mg of a sample obtained by drying the resin is weighed on an aluminum pan, and the aluminum pan is set as a test container in a holder in a DSC measuring device (for example, DSC-60 Plus manufactured by Shimadzu Corporation). Then, the measurement is performed under the temperature rising condition of 5° C./min, and the temperature of the baseline shift read from the obtained DSC chart is defined as the glass transition temperature in the present specification.

Furthermore, from the viewpoint of adhesion to plastic substrates, scratch resistance of printed matter, and blocking resistance, olefin resins, acrylic resins, styrene-acrylic resins, urethane resins, and urethane resins can be used as the binder resin (a-1). - It is preferable to include one or more resins selected from acrylic composite resins.

Binder resin (A) can be synthesized by a known method, or a commercially available product can be used. The structure is also not particularly limited, and for example, resins having a random structure, block structure, comb structure, star structure, or the like can be used.

When a water-soluble resin is used as the binder resin (a-1) in the present invention, its weight-average molecular weight ensures ejection stability from the inkjet nozzle, and provides excellent adhesion and resistance to various substrates. From the viewpoint of obtaining a print having abrasion resistance, it is preferably from 5,000 to 50,000, more preferably from 8,000 to 45,000, and preferably from 10,000 to 40,000. More preferred.

The weight average molecular weight of the binder resin (a-1) in the invention can be measured by a conventional method. For example, a TSKgel column manufactured by Tosoh Corporation and a GPC measurement device (HLC-8120GPC manufactured by Tosoh Corporation) equipped with an RI detector were measured using THF as a developing solvent. molecular weight.

The content of the binder resin (A) with respect to the total amount of the ink is preferably 1 to 15% by mass, more preferably 2 to 12% by mass, more preferably 4 to 10% by mass in terms of solid content. preferable. By setting the amount of the binder resin (A) within the above range, it is possible to obtain an ink excellent in scratch resistance, drying property, and image quality of printed matter without lowering dispersion stability and ejection stability. can.

In addition, from the viewpoint of obtaining an ink that is excellent in dispersion stability and ejection stability, and also excellent in adhesion to plastic substrates and image quality, the content of the binder resin (a-1) is ) is preferably 20 to 100% by mass, more preferably 35 to 100% by mass, and particularly preferably 50 to 100% by mass, based on the total amount.

<Surfactant>
In the present invention, the surfactant is used in combination with the binder resin (a-1) from the viewpoint of obtaining a water-based inkjet ink excellent in ejection stability, image quality of printed matter, and drying property. Includes more than one species. Generally, various surfactants such as acetylene diol-based, acetylene alcohol-based, siloxane-based, acrylic, fluorine-based, and polyoxyalkylene-based surfactants are known according to the application. , preferably contains an acetylenediol-based surfactant. Acetylene diol-based surfactants have a very fast orientation speed to the interface in water-based ink droplets after landing on the recording medium, and improve the wettability of water-based inks even on impermeable substrates. It is possible to quickly smooth the ink droplets. As a result, it is possible to obtain a printed material excellent in image quality with less bleeding between droplets and less unevenness in light and shade, in addition to improved drying properties.

In the present invention, it is particularly preferable to use a siloxane-based surfactant and/or a polyoxyalkylene-based surfactant in addition to the acetylenediol-based surfactant. Although the detailed cause is unknown, siloxane-based surfactants can stabilize the wetting and spreading of ink droplets after they land, and are effective in improving drying properties and image quality. In addition to improving image quality, polyoxyalkylene-based surfactants are thought to contribute to improving dispersion stability.

Acetylene diol-based surfactants used in the present invention include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,5,8,11-tetramethyl-6-dodecyne. -5,8-diol, hexadec-8-yn-7,10-diol, 6,9-dimethyl-tetradeca-7-yn-6,9-diol, 7,10-dimethylhexadec-8-yn-7 , 10-diols, and ethylene oxide and/or propylene oxide adducts thereof.

As a siloxane-based surfactant that can be suitably used in the present invention, for example, one or more ethylene oxide groups and/or one or more propylene oxide groups are present on the side chains and/or both ends of the polydimethylsiloxane chain. Examples include siloxane-based surfactants. Specifically, 8032ADDITIVE manufactured by Dow Corning Toray Co., Ltd., FZ-2104, FZ-2120, FZ-2122, FZ-2162, FZ-2164, FZ-2166, FZ-2404, FZ-7001, FZ-7002, FZ-7006, L-7001, L-7002, SF8427, SF8428, SH3748, SH3749, SH3771M, SH3772M, SH3773M, SH3775M, SH8400, BYK-331, BYK-333, BYK-345, BYK-346 manufactured by BYK-Chemie ＢＹＫ－３４７、ＢＹＫ－３４８、ＢＹＫ－３４９、ＢＹＫ－ＵＶ３５００、ＢＹＫ－ＵＶ３５１０、ＢＹＫ－ＵＶ３５３０、ＢＹＫ－ＵＶ３５７０、エボニック社製のＴＥＧＯＷｅｔ２５０、ＴＥＧＯＷｅｔ２６０、ＴＥＧＯＷｅｔ２７０、ＴＥＧＯＷｅｔ２８０、ＴＥＧＯＧｌｉｄｅ４１０、ＴＥＧＯＧｌｉｄｅ４３２、ＴＥＧＯＧｌｉｄｅ４３５、ＴＥＧＯＧｌｉｄｅ４４０、ＴＥＧＯＧｌｉｄｅ４５０、 Shin-Etsu Chemical Co., Ltd. KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, Examples include KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22-4515, Silface SAG series manufactured by Nissin Chemical Industry Co., Ltd., and the like.

Examples of polyoxyalkylene surfactants suitable for use in the present invention include compounds represented by the following general formula (1).

General formula (1):

RO-(EO)m-(PO)n-H

In the above general formula (1), R is an alkyl group having 8 to 22 carbon atoms, an alkenyl group having 8 to 22 carbon atoms, an alkylcarbonyl group having 8 to 22 carbon atoms, or a group having 8 to 22 carbon atoms. represents an alkenylcarbonyl group. In addition, said R may be a branched structure. EO represents an ethylene oxide group, and PO represents a propylene oxide group. m represents the average added mole number of EO and is a number from 2 to 50, and n represents the average added mole number of PO and is a number from 0 to 50. When n is not 0, the addition order of (EO)m and (PO)n does not matter, and the addition may be block or random.

The surfactant used in the present invention preferably has a hydrophobic group and a hydrophilic group in the molecule. Therefore, among the surfactants exemplified above, those having a hydrophilic ethylene oxide group are particularly preferably selected.

In addition, from the viewpoint of obtaining ink with excellent dispersion stability by increasing affinity with the binder resin (a-1) and obtaining printed matter with excellent image quality without bleeding or unevenness of light and shade, the HLB value is It is preferred to use surfactants from 0 to 8. Further, from the viewpoint of obtaining an ink having excellent ejection stability, it is particularly preferable to include a surfactant having an HLB value of 0 to 4.

In particular, in addition to dispersion stability and ejection stability, on non-permeable substrates such as plastic substrates, from the viewpoint of obtaining printed matter having excellent image quality with little bleeding between ink droplets and less unevenness in density, It is preferable to use a surfactant with an HLB value of 0 to 4 and a surfactant with an HLB value of 4 to 18 in combination.

The HLB (Hydrophile-Lipophile Balance) value is one of the parameters representing the hydrophilicity/hydrophobicity of a material. Various methods for calculating the HLB value from the chemical structure are known, and various methods for actual measurement are also known. When the structure of the compound is clearly known, the HLB value is calculated using the Griffin method. The Griffin method is a method of calculating the HLB value using the following formula (2) using the molecular structure and molecular weight of the target material.

Formula (2):

HLB value = 20 x (total molecular weight of hydrophilic portion) ÷ (molecular weight of material)

On the other hand, when a compound with an unknown structure is included, such as a siloxane-based surfactant, for example, "Surfactant Handbook" (edited by Nishiichiro et al., Sangyo Tosho Co., Ltd., 1960), p. 324, the HLB value of surfactants can be experimentally determined by the following method. Specifically, after dissolving 0.5 g of a surfactant in 5 mL of ethanol, the solution is titrated with a 2% by mass phenol aqueous solution while stirring at 25° C. The end point is when the solution becomes turbid. . The HLB value can be calculated by the following formula (3), where A (mL) is the amount of the aqueous phenol solution required to reach the end point.

Formula (3):

HLB value = 0.89 x A + 1.11

The content of the surfactant (B) in the inkjet ink of the present invention is preferably 0.2 to 4% by mass relative to the total amount of the ink. More preferably, it is 0.5 to 2% by mass.

<Compound having 3 or more hydroxyl groups>
As described above, in the present invention, the amount of the compound having 3 or more hydroxyl groups is 8% by mass or less with respect to the total amount of the ink, from the viewpoint of preventing deterioration of dispersion stability, drying property, and scratch resistance of the printed matter. (It may be 0% by mass). Since it is considered that the more the amount of the compound having 3 or more hydroxyl groups in the water-based inkjet ink, the worse the above properties occur, the smaller the amount, the better. Specifically, the amount of the compound having 3 or more hydroxyl groups is more preferably 5% by mass or less (may be 0% by mass) relative to the total amount of the water-based ink, and is 2.5% by mass or less. It is more preferable to have (may be 0% by mass), and it is particularly preferable to be substantially free. In this specification, "substantially free" means that the compound is not intentionally added, and does not deny the existence of small amounts of by-products and impurities contained in other materials. In the present specification, it means that the content of the compound is 1% by mass or less (may be 0% by mass). In addition, "0% by mass" in the present specification means that a compound having 3 or more hydroxyl groups is not included.

The compound having 3 or more hydroxyl groups may be liquid or solid at room temperature (25° C.). Specific compounds include glycerin, trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, diglycerin, erythritol, threitol, ribitol, xylitol, sorbitol, mannitol, and galactitol. , and alkylene oxide adducts of the above compounds, polyol compounds having a cyclic structure such as glucose, sucrose, maltose, lactose, cellobiose, trehalose, fructose, isomalt, lactitol, maltitol, pinpolytol, bornesitol, ononitol, pinitol, inositol, quinic acid, shikimic acid, and other cyclitol compounds. When using the said compound, you may use individually by 1 type, and may use 2 or more types together.

<Water-soluble organic solvent>
The water-based inkjet ink of the present invention contains a water-soluble organic solvent. In the present invention, alcohol-based solvents, glycol ether-based solvents, polyalkylene glycol-based solvents, etc. can be suitably used as water-soluble organic solvents. The term "water-soluble organic solvent" as used herein refers to a solvent that has a solubility in water of 5 g/100 g H ₂ O or more at 25° C. and 1 atm and is liquid. Among compounds having 3 or more hydroxyl groups, such as glycerin, compounds satisfying the above conditions are also included in water-soluble organic solvents.

In the aqueous inkjet ink of the present invention, the content of the water-soluble organic solvent having a boiling point of 240° C. or higher under 1 atmosphere is 8% by mass or less (may be 0% by mass) relative to the total amount of the aqueous inkjet ink. is preferred. In particular, from the viewpoint of obtaining prints having excellent drying properties, image quality, and scratch resistance on impermeable substrates such as plastic substrates, a water-soluble organic solvent having a boiling point of 240°C or higher at 1 atm. The solvent content is more preferably 5% by mass or less (may be 0% by mass), more preferably 2% by mass or less (may be 0% by mass), and 1% by mass. (It may be 0% by mass) is particularly preferable.

The boiling point under 1 atm can be measured using a thermal analysis device such as DSC (differential scanning calorimetry).

Examples of water-soluble organic solvents having a boiling point of 240° C. or higher under 1 atmosphere include glycerin, 3-methyl-1,5-pentanediol, 1,6-hexanediol, triethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, Diethylene glycol, triethylene glycol, tripropylene glycol, 2-pyrrolidone, ε-caprolactone, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 and the like.

The water-soluble organic solvent used in the present invention preferably has a weighted average boiling point of 100 to 235°C at 1 atm, more preferably 120 to 210°C, more preferably 120 to 195°C. Especially preferred. In addition, considering the image quality for impermeable substrates such as plastic substrates, a temperature of 120 to 180° C. is particularly suitable. When the weighted average boiling point of the water-soluble organic solvent under 1 atm is 100° C. or higher, the ejection stability from the inkjet head is improved. Further, when the weighted average value is 235° C. or less, there is no drying failure on the recording medium, and residual water-soluble organic solvent does not cause bleeding between water-based ink droplets, resulting in improved image quality. In addition, the adhesion to non-permeable substrates such as plastic substrates and the abrasion resistance of printed matter are improved. In addition, the calculation of the weighted average value of the boiling points includes water-soluble organic solvents having a boiling point of 240° C. or higher under 1 atmosphere. In addition, the weighted average value of the boiling point under 1 atmosphere is obtained by adding the product of the boiling point under 1 atmosphere calculated for each water-soluble organic solvent and the mass ratio with respect to the total amount of the water-soluble organic solvent. is the value obtained.

In addition, from the viewpoint of keeping the weighted average value of the boiling points of the water-soluble organic solvent within the above range, the amount of the water-soluble organic solvent having a boiling point of 100 to 220°C under 1 atm should be equal to the total amount of the water-soluble organic solvent in the ink. It is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 85% by mass or more.

Examples of water-soluble organic solvents suitable for use in the present invention include:
Alcohol solvents include ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 3-butanol, isobutanol, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, ethylene glycol. , 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2 -pentanediol, 1,3-pentanediol, 1,2-hexanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3- Butanediol etc.
Glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monoisopropyl ether, Diethylene glycol monoisobutyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol Methyl butyl ether, triethylene glycol methyl butyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol butyl methyl ether, propylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, propylene glycol dimethyl ether, tripropylene glycol dimethyl ether, etc.
As a polyalkylene glycol-based solvent, dipropylene glycol, etc.
Other water-soluble organic solvents include N-methylpyrrolidone, N-ethylpyrrolidone, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N,N-dimethyl-β-methoxypropionamide, N,N- dimethyl-β-ethoxypropionamide, N,N-dimethyl-β-butoxypropionamide, N,N-dimethyl-β-pentoxypropionamide, N,N-dimethyl-β-hexoxypropionamide, N,N- dimethyl-β-heptoxypropionamide, N,N-dimethyl-β-2-ethylhexoxypropionamide, N,N-dimethyl-β-octoxypropionamide, N,N-diethyl-β-butoxypropionamide, N,N-diethyl-β-pentoxypropionamide, N,N-diethyl-β-hexoxypropionamide, N,N-diethyl-β-heptoxypropionamide, N,N-diethyl-β-octoxypropionamide Each includes, but is not limited to, amides and the like.

The water-soluble organic solvent used in the present invention provides printed matter with excellent ejection stability, image quality, and drying properties, and is also excellent in compatibility with the binder resin (A) and surfactant, and the effects of the present invention are suitable. From the viewpoint that a water-based ink having a high molecular weight can be obtained, it is preferable to contain at least one type of alkanediol having 2 to 5 carbon atoms. Alkanediols having 3 to 4 carbon atoms are more preferred, and alkanediols having 3 carbon atoms are particularly preferred.

The content of the water-soluble organic solvent used in the present invention is preferably 1 to 30% by mass based on the total amount of the inkjet ink. In addition, from the viewpoint of ensuring ejection stability on the inkjet head and obtaining printed matter having excellent adhesion, drying property, and image quality even with non-permeable substrates, the content is preferably 3 to 27% by mass or less. More preferably, it is particularly preferably 5 to 25% by mass or less.

<Water>
The water contained in the water-based inkjet ink of the present invention is preferably ion-exchanged water (deionized water) rather than general water containing various ions. Moreover, the content thereof is preferably in the range of 20 to 90% by mass based on the total mass of the ink.

<Other ingredients>
In addition to the components described above, the water-based inkjet ink of the present invention may optionally contain a pH adjuster to provide the ink with desired physical properties. For basification, organic amine solvents such as triethylamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, aminomethylpropanol, ammonia water, lithium hydroxide, sodium hydroxide, hydroxide Alkali metal hydroxides such as potassium, alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and the like can be used, but are not limited thereto. For acidification, hydrochloric acid, sulfuric acid, acetic acid, citric acid, maleic acid, maleic anhydride, succinic acid, tartaric acid, malic acid, phosphoric acid, boric acid, fumaric acid, malonic acid, ascorbic acid, glutamic acid, etc. are used. can be, but are not limited to. The above pH adjusters may be used alone, or two or more of them may be used in combination.

The blending amount of the pH adjuster is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, more preferably 0.2 to 1.5% by mass, based on the total amount of the water-based inkjet ink. is most preferred.

In addition to the above components, the water-based inkjet ink of the present invention may optionally contain additives such as antifoaming agents, antiseptics, infrared absorbers, and ultraviolet absorbers in order to obtain inks with desired physical properties. can be added as appropriate. The amount of these additives to be added is preferably 0.01 to 10% by weight with respect to the total weight of the ink.

The water-based inkjet ink of the invention preferably does not substantially contain a polymerizable monomer.

<Method for producing water-based inkjet ink>
The water-based inkjet ink of the present invention comprising the components as described above can be produced by known methods. In particular, C.I. I. A manufacturing method is preferably selected in which a pigment dispersion containing Pigment Orange 64 is prepared in advance, and then the pigment dispersion, binder resin (a-1), surfactant and the like are mixed. Examples of the method for producing the water-based inkjet ink of the present invention are described below, but as described above, the production method is not limited to the following.

(1) Production of pigment dispersion (1-1) Dispersion treatment method using a water-soluble pigment dispersion resin When a water-soluble resin is used as the pigment dispersion resin, Aqueous organic solvent is mixed and stirred to prepare an aqueous pigment-dispersing resin solution. C.I. I. Pigment Orange 64 is added, mixed and stirred (premixed), and then dispersed using a disperser. Thereafter, centrifugation, filtration, and solid content adjustment are performed as necessary to obtain a pigment dispersion.

(1-2) Dispersion treatment method using a water-insoluble pigment dispersion resin Further, C.I. I. When producing a dispersion of Pigment Orange 64, a pigment dispersion resin is dissolved in an organic solvent such as methyl ethyl ketone in advance, and if necessary, the pigment dispersion resin is neutralized to prepare a pigment dispersion resin solution. C.I. is added to the pigment dispersion resin solution. I. Pigment Orange 64 and water are added, mixed and stirred (premixed), and then dispersed using a disperser. Thereafter, the organic solvent is removed by distillation under reduced pressure, and if necessary, centrifugation, filtration, and solid content are adjusted to obtain a pigment dispersion.

In the above methods (1-1) and (1-2), C.I. I. The dispersing machine used for dispersing Pigment Orange 64 may be any commonly used dispersing machine, and examples thereof include ball mills, roll mills, sand mills, bead mills and nanomizers. Among the above, a bead mill is preferably used, and specifically, it is commercially available under trade names such as Super Mill, Sand Grinder, Agitator Mill, Glen Mill, Dyno Mill, Pearl Mill and Kovol Mill.

In the above methods (1-1) and (1-2), the method for controlling the particle size distribution of the pigment dispersion is to adjust the size of the grinding media of the disperser listed above, or to change the material of the grinding media. increasing the filling rate of the grinding media, changing the shape of the stirring member (agitator), lengthening the dispersion treatment time, classifying with a filter or centrifugal separator after dispersion treatment, and these methods A combination of In order to keep the pigment within a suitable particle size range, it is preferable to set the diameter of the grinding media of the disperser to 0.1 to 3 mm. Glass, zircon, zirconia, and titania are preferably used as the material of the grinding media.

(1-3) Method of Grinding and Kneading Treatment Using Pigment Dispersing Resin Furthermore, in the present invention, the following method of grinding and kneading treatment can also be preferably used. C. I. Pigment Orange 64, a pigment dispersing resin, a water-soluble organic solvent, and an inorganic salt are kneaded with a kneader, water is added to the resulting mixture, and the mixture is mixed and stirred. Then, the inorganic salt and, if necessary, the water-soluble organic solvent are removed by centrifugation, filtration and washing, and the solid content is adjusted to obtain a pigment dispersion.

The kneading machine used in the method (1-3) may be any dispersing machine that is commonly used. A kneader or trimix is preferably used from the viewpoint of obtaining prints having excellent quality and color reproducibility. The particle size distribution of the resulting pigment dispersion can be controlled by adjusting the temperature during kneading.

As the inorganic salt, sodium chloride, barium chloride, potassium chloride, sodium sulfate, potassium sulfate and the like can be preferably used.

(2) Preparation of water-based inkjet ink To the pigment dispersion obtained above, a binder resin (a-1), a surfactant, a water-soluble organic solvent, water, and, if necessary, the above-mentioned pH adjuster or Add other additives and stir and mix. If necessary, the mixture may be stirred and mixed while being heated in the range of 40 to 100°C.

(3) Removal of Coarse Particles Coarse particles contained in the above mixture are removed by a technique such as filtration or centrifugation to obtain an aqueous inkjet ink. As a method for filtration and separation, known methods can be used as appropriate. When a filter is used, the pore size is preferably 0.3 to 5 μm, more preferably 0.5 to 3 μm. When performing filtration, a single kind of filter may be used, or multiple kinds of filters may be used in combination.

<Characteristics of water-based inkjet ink>
The viscosity of the water-based inkjet ink of the present invention is preferably adjusted to 3 to 20 mPa·s at 25°C. Within this viscosity range, stable ejection characteristics are exhibited in a head having a normal frequency of 4 to 10 kHz and a head having a high frequency of 10 to 70 kHz. In particular, by setting the viscosity at 25° C. to 4 to 10 mPa·s, stable ejection can be achieved even when used for an inkjet head having a design resolution of 600 dpi or more. In addition, the said viscosity can be measured by a conventional method. Specifically, it can be measured using an E-type viscometer (TVE25L type viscometer manufactured by Toki Sangyo Co., Ltd.) using 1 mL of ink.

In addition, the aqueous inkjet ink of the present invention should have a static surface tension of 18 to 35 mN/m at 25° C. in order to obtain a printed matter with excellent image quality while making the aqueous inkjet ink capable of being stably ejected. is preferred, and 20 to 32 mN/m is particularly preferred. The static surface tension refers to surface tension measured by the Wilhelmy method in an environment of 25° C., and can be measured using, for example, CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. using a platinum plate.

Furthermore, after landing on the recording medium, the surfactant of the present invention is quickly oriented and suitable wettability on the recording medium is obtained, thereby obtaining excellent image quality. is preferably 26-36 mN/m, more preferably 28-36 mN/m, particularly preferably 30-36 mN/m. The dynamic surface tension in the present invention can be measured at 25° C. using, for example, a bubble pressure dynamic surface tension meter BP100 manufactured by Kruss.

In the water-based inkjet ink of the present invention, the average secondary particle diameter (D50) of the pigment is preferably 40 to 500 nm, more preferably 50 to 400 nm, in order to obtain a printed matter having excellent color development. It is preferably 60 to 300 nm. In order to keep the average secondary particle size within the preferred range, the pigment dispersion treatment step may be controlled as described above. The average secondary particle diameter (D50) of the pigment represents the median diameter measured by the dynamic light scattering method using a particle size distribution analyzer (eg, Microtrac UPAEX-150 manufactured by Microtrac Bell).

<Setting water-based inkjet ink>
The water-based inkjet ink of the present invention may be used in a single color, but it can also be used as a set of water-based inkjet inks in which a plurality of colors are combined according to the application. Among others, when used in combination with a yellow ink and/or a magenta ink, it is possible to obtain a printed matter with particularly excellent color reproducibility in the red region. In addition, by adding black ink, the feeling of blackness can be improved, and the visibility of characters and the like can be improved. Furthermore, when printing on a recording medium other than white, a clear image can be obtained by using white ink together.

<Ink - pretreatment liquid set>
The water-based inkjet ink of the present invention can also be used in the form of an ink-pretreatment liquid set in combination with a pretreatment liquid containing a flocculant. By applying a pretreatment liquid containing a flocculating agent onto a recording medium, it is possible to form a layer (ink flocculation layer) in which the solid components contained in the water-based inkjet ink are intentionally flocculated. By allowing the water-based inkjet ink to land on the ink coagulation layer, it is possible to prevent bleeding between ink droplets and color unevenness, thereby significantly improving the image quality of printed matter. Furthermore, depending on the material used for the pretreatment liquid, the adhesion, scratch resistance, and blocking resistance of printed matter can also be improved.

The term "flocculant" as used herein refers to an agent that destroys the dispersed state of pigments and fine resin particles contained in the water-based inkjet ink to cause them to aggregate, and/or makes the water-soluble resin insoluble and increases the viscosity of the water-based inkjet ink. means a component that can The flocculant used in the pretreatment liquid to be combined with the water-based inkjet ink of the present invention preferably contains one or more selected from metal salts and cationic polymer compounds from the viewpoint of significantly improving image quality. Among them, from the viewpoint of obtaining excellent image quality, ^it is preferable ^{to use} a metal salt as ^the aggregating agent. It is particularly preferred to include ionic salts. When a metal salt is used as a flocculating agent, its content is preferably 2 to 30% by mass, particularly preferably 3 to 25% by mass, relative to the total amount of the pretreatment liquid.

In addition, an organic solvent, a surfactant, a pH adjuster, an antifoaming agent, an antiseptic, and the like can be appropriately added to the pretreatment liquid. Materials that can be specifically used for each are the same as in the case of the water-based inkjet ink.

The static surface tension of the pretreatment liquid is preferably 20 to 45 mN/m from the viewpoint of obtaining printed matter with excellent image quality when used in combination with the water-based inkjet ink of the present invention. More preferably, it is 23 to 40 mN/m. Particularly preferably, it is 25 to 37 mN/m. The static surface tension of the pretreatment liquid can be measured in the same manner as the static surface tension of water-based inkjet ink.

<Inkjet recording method>
The water-based inkjet ink of the present invention is used in a recording method in which the ink is ejected from an inkjet head and applied onto a recording medium.

As a pass system in the inkjet recording method, there is a single-pass system in which inkjet ink is ejected onto a recording medium only once for recording, and a short shuttle head is reciprocally scanned in a direction perpendicular to the conveying direction of the recording medium. Either a serial method in which ejection and printing are performed while the ink is being discharged may be adopted. However, in the case of the serial method, it is necessary to adjust the ejection timing in consideration of the movement of the ink jet head, and deviation of the landing position is likely to occur. Therefore, when printing the water-based inkjet ink of the present invention, a single-pass method, particularly a pass method in which a recording medium is passed under a fixed inkjet head, is preferably used.

There are no particular restrictions on the method of ejecting ink, and known methods include, for example, a drop-on-demand method (pressure pulse method) that utilizes the oscillating pressure of a piezo element, a method in which ink is heated to form bubbles, and pressure generated is A thermal ink jet (bubble jet (registered trademark)) method or the like can be used.

In addition, the amount of ink droplets ejected from the inkjet head is preferably 0.2 to 30 picoliters from the viewpoint of greatly reducing the drying load and improving color reproducibility and other image quality. Preferably, it is 1 to 20 picoliters.

After applying the water-based inkjet ink of the present invention onto a recording medium by an inkjet printing method, it is preferable to provide a mechanism for drying the ink on the recording medium. Drying methods used in the drying mechanism include heat drying, hot air drying, infrared (for example, infrared with a wavelength of 700 to 2500 nm) drying, microwave drying, and drum drying.

In the present invention, from the viewpoint of preventing bumping of the liquid component in the ink and obtaining a printed matter excellent in color reproducibility and image quality, it is preferable to set the drying temperature to 35 to 100° C. when the heat drying method is employed. When the hot air drying method is employed, the hot air temperature is preferably 50 to 250°C. From the same point of view, when the infrared drying method is employed, 50% or more of the integrated value of the total output of infrared rays used for infrared irradiation preferably exists in the wavelength region of 700 to 1500 nm.

The above drying methods may be used alone, may be used in succession, or may be used in combination at the same time. For example, by using the heat drying method and the hot air drying method together, the ink can be dried more quickly than when each method is used alone.

<Recording medium>
The recording medium on which the ink of the present invention is printed is not particularly limited, and any known medium can be used. Among them, non-permeable substrates or low-permeability substrates are preferable, and can be used particularly preferably for non-permeable substrates. In this specification, the permeability of a recording medium is determined by the amount of water absorption measured by a dynamic scanning absorptiometer. Specifically, a recording medium having a pure water absorption of less than 1 g/m ² at a contact time of 100 msec, measured by the following method, is defined as a “non-permeable substrate” and is 1 to 10 g/m ² . Let the recording medium be a "hardly permeable base material".

The water absorption amount of the recording medium can be measured, for example, under the following conditions. Using KM500win manufactured by Kumagai Riki Kogyo Co., Ltd. as a dynamic scanning absorptiometer, under the conditions of 23 ° C. and 50% RH, using a recording medium of about 15 to 20 cm square, pure water under the conditions shown below. Measure the amount of transition.
・Measurement method: Spiral Scanning (Spiral Method)
・Measurement start radius: 20mm
・Measurement end radius: 60mm
・Contact time: 10 to 1,000msec
・ Number of sampling points: 19 (measured at approximately equal intervals with respect to the square root of the contact time)
・Scan interval: 7mm
・Rotary table speed switching angle: 86.3 degrees ・Headbox conditions: width 5 mm, slit width 1 mm

Examples of non-permeable or impermeable substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, polyvinyl alcohol, coated paper, art paper, and cast paper. , metal substrates such as aluminum, iron, stainless steel and titanium, and glass substrates. The above base material may have a smooth surface, may have uneven surfaces, and may be transparent, translucent, or opaque. Also, two or more of these recording media may be pasted together. Further, a release adhesive layer or the like may be provided on the opposite side of the printed surface, or an adhesive layer or the like may be provided on the printed surface after printing. Further, the shape of the recording medium used in the ink jet recording method of the present invention may be roll-like or sheet-like.

In addition, since the wettability of the water-based inkjet ink of the present invention is improved, the image quality and drying property are improved, and the surface of the printed matter is made uniform, the abrasion resistance and adhesion can also be improved. It is also preferable to apply a surface modification method such as corona treatment or plasma treatment to the permeable or impermeable substrate.

<Coating treatment>
The printed matter produced using the ink set of the present invention may be coated on the printed surface, if necessary. Specific examples of the coating treatment include coating and printing of a coating composition, lamination processing by a dry lamination method, a solventless lamination method, an extrusion lamination method, and the like. Both may be combined.

In the case of applying a coating treatment to a printed matter by coating and printing a coating composition, the coating and printing method may be a method of printing in a non-contact manner with respect to a recording medium such as inkjet printing, or a method of printing on a recording medium Either of the methods in which the coating composition is brought into contact with the surface to be printed may be adopted. Further, when a method of printing the coating composition on the recording medium in a non-contact manner is selected, the coating composition substantially contains a colorant component excluding the pigment from the water-based inkjet ink of the present invention. It is preferable to use ink (clear ink) that does not

EXAMPLES The present invention will now be described more specifically with reference to examples and comparative examples. In the following description, "parts" and "%" represent "parts by mass" and "% by mass", respectively, unless otherwise specified.

<Production Example of Pigment Dispersion Resin 1>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser and a stirrer was charged with 93.4 parts of butanol and purged with nitrogen gas. The inside of the reaction vessel is heated to 110 ° C., and a mixture of 30 parts of acrylic acid, 35 parts of styrene, 35 parts of lauryl methacrylate as polymerizable monomers, and 6 parts of V-601 (manufactured by Wako Pure Chemical Industries) as a polymerization initiator is added. It was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was reacted at 110°C for 3 hours, then 0.6 part of V-601 was added, and the reaction was further continued at 110°C for 1 hour. Thereafter, after cooling the reaction system to room temperature, 39 parts of dimethylaminoethanol was added for neutralization, and then 100 parts of water was added. After that, the mixed solution is heated to 100° C. or higher to distill off butanol, and then adjusted with water so that the solid content becomes 30%, thereby obtaining an aqueous solution of pigment dispersion resin 1 (solid content: 30%). Obtained. The weight-average molecular weight and acid value of Pigment Dispersion Resin 1 were 16,000 and 230, respectively, measured by the methods described above.

<Production Example of Pigment Dispersion Resin 2>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser and a stirrer was charged with 95 parts of methyl ethyl ketone and purged with nitrogen gas. The inside of the reaction vessel is heated to 80 ° C., 70 parts of styrene as polymerizable monomers, 5 parts of acrylic acid, 10 parts of methyl methacrylate, 15 parts of polypropylene glycol methacrylate (Blenmer PP-500 manufactured by NOF Corporation), and polymerization initiation A mixture of 3.5 parts of V-65 (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 3 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was reacted at 80°C for 1 hour, then 0.7 part of V-65 was added, and the reaction was further continued at 80°C for 4 hours. After that, 25 parts of methyl ethyl ketone is added, the reaction system is cooled to room temperature, and then methyl ethyl ketone is used to adjust the solid content to 30%, thereby obtaining a methyl ethyl ketone solution of pigment dispersion resin 2 (solid content: 30%). rice field. The pigment dispersion resin 2 had a weight average molecular weight of 26,000 and an acid value of 30, which were measured by the methods described above.

<Production Example of Orange Pigment Dispersion Liquid 1>
In a mixing container equipped with a stirrer, 20 parts of TCO06401 (C.I. Pigment Orange 64) manufactured by Trustchem Co., 20 parts of an aqueous solution of pigment dispersion resin 1 (solid content: 30%), 60 parts of water, After sequentially charging, premixing was performed. After that, main dispersion was carried out using a Dyno mill with a volume of 0.6 L filled with 1800 g of zirconia beads with a diameter of 0.5 mm to obtain an orange pigment dispersion 1 (pigment concentration: 20%).

<Production Example of Orange Pigment Dispersion Liquid 2>
In a mixing container equipped with a stirrer, 20 parts of a methyl ethyl ketone solution (solid content: 30%) of the pigment dispersion resin 2 and 8 parts of methyl ethyl ketone are added, and then 50 parts of water and 0.3 of dimethylaminoethanol are added while stirring. , were added and stirred for 30 minutes. Then, 20 parts of TCO06401 (C.I. Pigment Orange 64) manufactured by Trustchem was added and premixed. After that, main dispersion was carried out using a Dyno mill with a volume of 0.6 L filled with 1800 g of zirconia beads with a diameter of 0.5 mm. Next, the obtained dispersion was taken out, 15 parts of water was added, and methyl ethyl ketone was distilled off under reduced pressure using an evaporator. Then, by adjusting the solid content concentration to 26%, an orange pigment dispersion liquid 2 (pigment concentration: 20%) was obtained.

<Production Example of Orange Pigment Dispersion 3>
25 parts of TCO06401 (C.I. Pigment Orange 64) manufactured by Trustchem Co., Ltd., 125 parts of sodium chloride, 8.8 parts of Ceramer 1608 (olefin maleic acid resin) manufactured by Toyo Adol Co., Ltd., and 15.2 parts of diethylene glycol were mixed with stainless steel. After being put into a manufacturing kneader, kneading treatment was performed at 80° C. for 3 hours. This mixture was added to a mixing vessel equipped with a stirrer, to which 726 parts of water had been added in advance, and then stirred for 1 hour while being heated to about 40°C to obtain a slurry mixture. After that, by repeating filtration and washing with water, sodium chloride and diethylene glycol are removed, and part of the water is distilled off under reduced pressure, and water is added as necessary until the solid content concentration reaches 27.04%. An orange pigment dispersion liquid 3 (pigment concentration: 20%) was obtained by adjusting as follows.

<Manufacturing Examples of Magenta Pigment Dispersions 1 and 2 and Violet Pigment Dispersion 1>
Magenta Pigment Dispersions 1 and 2 and Violet Pigment Dispersion 1 (each with a pigment concentration of 20%) were obtained in the same manner as Orange Pigment Dispersion 1 except that the following pigments were used.
・Magenta pigment dispersion liquid 1: Ink Jet Magenta ES
(Clariant C.I. Pigment Red 122)
・Magenta pigment dispersion liquid 2: NOVOPERM CARMINE HF4C
(Clariant C.I. Pigment Red 185)
- Violet pigment dispersion 1: Ink Jet Magenta E5B02
(Clariant CI Pigment Violet 19)

<Production examples of binder resins 1 to 8 (water-soluble acrylic resin, water-soluble styrene acrylic resin)>
Composition of mixture dropped into butanol (type and amount of polymerizable monomer, and amount of V-601), amount of V-601 added after reacting at 110 ° C. for 3 hours, and used for neutralization Binder Resins 1 to 8, which are water-soluble acrylic resins or water-soluble styrene-acrylic resins, were prepared in the same manner as in Pigment Dispersion Resin 1, except that the amount of dimethylaminoethanol added was changed as shown in Table 1. to obtain an aqueous solution (solid content: 30%).

Table 1 also shows the acid value, glass transition temperature and weight average molecular weight of the binder resins 1 to 8. Abbreviations of the polymerizable monomers listed in Table 1 are as follows.
・St: styrene ・MAA: methacrylic acid ・MMA: methyl methacrylate ・BA: butyl acrylate ・STMA: stearyl methacrylate

<Production example of binder resins 9 to 11 (styrene acrylic resin fine particles)>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 40 parts of water and 0.2 parts of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, and an aqueous solution of the surfactant was added. Created. In another mixing vessel, 50 parts of methyl methacrylate as polymerizable monomers, 29 parts of butyl acrylate, 20 parts of styrene, 1 part of methacrylic acid, 1.8 parts of Aqualon KH-10 as a surfactant, and 51 parts of water .2 parts were added and mixed well to prepare an emulsion precursor.

1.5 parts of the prepared emulsion precursor was added to the reaction vessel containing the aqueous surfactant solution and mixed well. Next, the inside of the reaction vessel was heated to 60° C. and purged with nitrogen gas, and then 1 part of a 5% potassium persulfate aqueous solution and 0.2 parts of an anhydrous 1% sodium bisulfite aqueous solution were added. was maintained at 60° C., the polymerization reaction was started. After reacting at 60° C. for 5 minutes, the remainder of the emulsion precursor (151.5 parts), 9 parts of 5% aqueous potassium persulfate solution, and 1.8 parts of 1% anhydrous sodium bisulfite aqueous solution were added to 1. It was added dropwise over 5 hours, and then the reaction was continued for another 2 hours. Then, after cooling the reaction system to 30° C., diethylaminoethanol is added to adjust the pH of the mixed solution to 8.5, and water is used to adjust the solid content to 30%, thereby producing a styrene methacrylic resin. An aqueous dispersion (solid content: 30%) of binder resin 9, which is fine particles, was obtained.

Further, an aqueous dispersion of binder resins 10 to 11 (solid content: 30%), which is styrene-acrylic resin fine particles, was prepared in the same manner as binder resin 9 except that the polymerizable monomer was changed as shown in Table 2. ).

Table 2 also shows the acid values and glass transition temperatures of the binder resins 9 to 11. In addition, among the abbreviations of the polymerizable monomers listed in Table 2, the abbreviations of the materials not listed in Table 1 are as follows.
・ PME-400: Methoxy polyethylene glycol methacrylate (Blenmer PME-400 manufactured by NOF Corporation)

<Production example of binder resin 12 (styrene acrylic resin fine particles) to 13 (acrylic resin fine particles)>
20 parts of toluene, 7.5 parts of methacrylic acid and 7.5 parts of methyl methacrylate as polymerizable monomers, and 2,2'- 0.9 parts of azobisisobutyronitrile and 3.6 parts of 2-(dodecylthiocarbonothioylthio)-isobutyric acid were charged and purged with nitrogen gas. A copolymer (A block) composed of methacrylic acid and methyl methacrylate was obtained by heating the inside of the reaction vessel to 75° C. and conducting a polymerization reaction for 3 hours.

After the completion of the polymerization reaction, the reaction system was cooled to room temperature, and then 60 parts of toluene and polymerizable monomers such as 15 parts of methyl methacrylate, 10 parts of styrene, 45 parts of butyl acrylate and 15 parts of lauryl methacrylate were added to the reaction vessel. was put in and replaced with nitrogen gas. Then, by heating the inside of the reaction vessel to 75° C. and performing a polymerization reaction for 3 hours, A-, in which a copolymer (B block) composed of methyl methacrylate, styrene, butyl acrylate, and lauryl methacrylate is added to the A block. A B block polymer (binder resin 12) was obtained.
Then, after cooling the reaction system to room temperature, 9.3 parts of dimethylaminoethanol was added to the reactor for neutralization, and then 200 parts of water was added. Next, after the mixed solution is heated to distill off the toluene, water is used to adjust the solid content to 30%, thereby obtaining an aqueous dispersion of the binder resin 12, which is styrene (meth)acrylic resin fine particles. (solid content 30%) was obtained.

Further, an aqueous dispersion of binder resin 13 (30% solid content), which is acrylic resin fine particles, was obtained by the same operation as binder resin 12 except that the polymerizable monomer was changed as shown in Table 3. rice field.

Table 3 also shows the acid value, glass transition temperature, and weight average molecular weight of binder resins 12 and 13. Among the abbreviations of polymerizable monomers listed in Table 3, abbreviations of materials not listed in Tables 1 and 2 are as follows.
・LMA: Lauryl methacrylate

<Production example of binder resins 14 to 16 (water-soluble urethane resin)>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser and a stirrer was charged with 43.5 parts of polypropylene glycol (molecular weight: 1,000) as polymerizable monomers, 44.5 parts of isophorone diisocyanate, and 0.5 parts of dibutyltin dilaurate. 007 parts of the reactor was charged, and after purging with nitrogen gas, the inside of the reaction vessel was heated to 100° C., and the polymerization reaction was carried out for 5 hours. After cooling the reaction system to about 60° C., 150 parts of methyl ethyl ketone, 9.0 parts of dimethylolpropionic acid, and 3 parts of neopentyl glycol are added, the inside of the reaction vessel is heated to 80° C., and the polymerization reaction is performed. rice field. Then, after cooling the reaction system to room temperature, 20 parts of methanol was added to terminate the reaction. Water was then added, and an aqueous potassium hydroxide solution was added with stirring to neutralize. Then, the mixed solution is heated under reduced pressure to distill off the methyl ethyl ketone and unreacted methanol, and then adjusted with water so that the solid content is 10%. An aqueous solution of 14 (10% solids) was obtained.
Further, an aqueous dispersion of binder resins 15 to 16 (solid content: 10%), which is a urethane water-soluble resin, was prepared in the same manner as for binder resin 14 except that the polymerizable monomer was changed as shown in Table 4. ).

Table 4 also shows the acid values and weight average molecular weights of the binder resins 14 to 16. Abbreviations of the polymerizable monomers listed in Table 4 are as follows.
・PPG1000: polypropylene glycol (molecular weight 1,000)
・PTMG2000: polytetramethylene ether glycol (molecular weight 2,000)
・IPDI: isophorone diisocyanate ・DMPA: dimethylolpropionic acid ・NPG: neopentyl glycol

<Production example of binder resins 17 to 18 (urethane resin fine particles)>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser and a stirrer was charged with 150 parts of methyl ethyl ketone, 34.3 parts of polypropylene glycol (molecular weight 2,000) as polymerizable monomers, 22.7 parts of isophorone diisocyanate, hexa After charging 17.2 parts of methylene diisocyanate and 23.9 parts of dimethylolpropionic acid and purging with nitrogen gas, the inside of the reaction vessel was heated to 80° C. and polymerization reaction was carried out for 6 hours. Then, 1.9 parts of trimethylolpropane was added and the reaction was continued at 80°C. Thereafter, the reaction system was cooled to room temperature, water was added, and an aqueous potassium hydroxide solution was further added with stirring to neutralize the reaction system. Then, after the mixed solution is heated under reduced pressure to distill off the methyl ethyl ketone, water is used to adjust the solid content to 20%, thereby obtaining an aqueous dispersion of the binder resin 17, which is urethane resin fine particles ( 20% solids) was obtained.
Further, an aqueous dispersion of binder resin 18 (10% solid content), which is urethane resin fine particles, was obtained by the same operation as binder resin 17 except that the polymerizable monomer was changed as shown in Table 5. rice field.

Table 5 also shows the acid values of binder resins 17 and 18. In addition, among the abbreviations of the polymerizable monomers listed in Table 5, the abbreviations of the materials not listed in Table 4 are as follows.
・PPG2000: polypropylene glycol (molecular weight 2,000)
・PC (HD) 2000: Polycarbonate diol with 1,6-hexanediol as the main skeleton (molecular weight 2,000)
・HDI: Hexamethylene diisocyanate ・TMP: Trimethylolpropane

<Binder resin 19 (urethane/acrylic composite resin fine particles), 20 to 21 (olefin resin fine particles)>
In the ink production examples described below, in addition to the binder resins 1 to 18, commercially available urethane-acrylic composite resin particles and olefin resin particles were used as the binder resins 19 to 21.
・ Binder resin 19: Uriano W600 (Urethane-acrylic composite resin fine particles manufactured by Arakawa Chemical Industries, solid content 35% (containing 5% isopropyl alcohol), acid value 20 mgKOH / g, glass transition temperature -55 ° C.)
・ Binder resin 20: Aurorene AE-301 (manufactured by Nippon Paper Industries Co., Ltd., solid content 30%, acid value 25 mgKOH / g, melting point 70 ° C.)
- Binder resin 21: ZE-1224 (manufactured by Seiko PMC Co., Ltd., solid content 30%, acid value 50 mgKOH/g, melting point 70 ° C.)

<Production examples of water-based inkjet inks 1 to 77>
The materials described below were sequentially charged into a mixing vessel while stirring with a disper, and stirred until they were sufficiently uniform. After that, filtration was performed with a membrane filter having a pore size of 1 μm to obtain water-based inkjet ink 1 .
・Orange pigment dispersion liquid 1 (pigment concentration: 20%) 10 parts ・Aqueous solution of binder resin 1 (solid content: 30%) 16.7 parts ・1,2-Propanediol 15 parts ・Surfinol 420 1 part ・Proxel GXL 0.5 parts 05 parts ion-exchanged water 57.25 parts

Water-based inkjet inks 2 to 77 were obtained in the same manner as for water-based inkjet ink 1, except that the materials listed in Table 6 below were used.

The materials listed in Table 6 are as follows (water-soluble organic solvent)
・IPA: isopropyl alcohol (boiling point: 83°C)
・MFG: propylene glycol monomethyl ether (boiling point: 120°C)
・ 1,2-PD: 1,2-propanediol (boiling point: 188 ° C.)
・1,2-BD: 1,2-butanediol (boiling point: 192°C)
・1,2-HD: 1,2-hexanediol (boiling point: 223°C)
- iPDG: diethylene glycol monoisopropyl ether (boiling point: 207°C)
・DMTG: triethylene glycol dimethyl ether (boiling point: 216°C)
・BDG: diethylene glycol monobutyl ether (boiling point: 231°C)
· DEG: diethylene glycol (boiling point: 244°C)
・GY: glycerin (boiling point: 290°C)
(Surfactant)
・S. 104: Surfynol 104 (Acetylene diol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 3.0)
・S. 420: Surfynol 420 (Acetylene diol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 4.0)
・S. 465: Surfynol 465 (Acetylene diol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 13.2)
・ TW280: TEGO Wet 280 (siloxane-based surfactant manufactured by Evonik, HLB value: 3.5)
・ TG432: TEGO Glide 432 (siloxane-based surfactant manufactured by Evonik, HLB value: 7.5)
· BYK347: BYK-347 (siloxane-based surfactant manufactured by BYK-Chemie, HLB value: 8.6)
· TG440: TEGO Glide 440 (siloxane-based surfactant manufactured by Evonik, HLB value: 13.5)
· S-202: Nonionic S-202 (NOF Corporation polyoxyalkylene surfactant, compound in which R is a cetyl group, m is 10, and n is 0 in the above general formula (1), HLB value: 4 .9)
· P-210: Nonionic P-210 (NOF Corporation polyoxyalkylene surfactant, compound in which R is a stearyl group, m is 2, and n is 0 in the above general formula (1), HLB value: 12 .9)
E750: Emarex 750 (a polyoxyalkylene surfactant manufactured by Nippon Emulsion Co., Ltd., a compound in which R is a lauryl group, m is 50 and n is 0 in the general formula (1) above, HLB value: 15.6)
(others)
・Proxel GXL: Arch Chemicals 1,2-benzisothiazol-3-one solution (preservative)

[Examples 1 to 71 (inkjet inks 1 to 71), Comparative Examples 1 to 6 (inkjet inks 72 to 77)]
Evaluations 1 to 5 shown below were performed on the water-based inkjet inks 1 to 77 produced above. The evaluation results were as shown in Table 7.

<Evaluation 1: Evaluation of dispersion stability>
The average secondary particle size (D50) of the aqueous inkjet inks 1 to 77 produced above was measured at 25° C. using Microtrac UPAEX-150 manufactured by Microtrac Bell. This ink was stored in a constant temperature machine at 70° C., accelerated for a predetermined period of time, and then D50 was measured again at 25° C. to confirm the change before and after aging to evaluate the dispersion stability. The evaluation criteria were as follows, and the evaluation criteria value of 2 to 3 was defined as a practical range.
3: The viscosity change rate after storage for 2 weeks was less than ±5% 2: The viscosity change rate after storage for 1 week was less than ±5%, but the viscosity change rate after storage for 2 weeks was ±5% 1: Viscosity change rate after storage for 1 week was ±5% or more

<Evaluation 2: Evaluation of ejection stability (standby ejection property)>
An inkjet head KJ4B-QA (manufactured by Kyocera Corporation, design resolution 600 dpi) was installed above a conveyor capable of transporting a recording medium, and each of the water-based inkjet inks 1 to 77 produced above was filled. A nozzle check pattern was printed, and after confirming that there was no missing nozzle, the substrate was allowed to stand by for a predetermined time under an environment of 25°C. Thereafter, a nozzle check pattern was printed again and the number of missing nozzles was counted to evaluate the ejection stability (standby ejection property). Evaluation criteria were as follows, and evaluation criteria values of 2 to 4 were defined as a practically feasible range.
4: No nozzle missing even after waiting for 3 hours 3: No nozzle missing even after waiting for 2 hours, but 1 nozzle missing after waiting for 3 hours 2: There were no missing nozzles even after waiting for 1 hour, but one or more missing nozzles occurred after waiting for 2 hours. 1: Waited for 1 hour. Later, one or more missing nozzles occurred.

<Evaluation 3: Evaluation of dryness>
After filling the inkjet printing device used in Evaluation 2 with each of the water-based inkjet inks 1 to 77 produced above, with a drop volume of 12 pL, OPU-1 manufactured by Mitsui Chemicals Tohcello (biaxially oriented polypropylene film, thickness 20 μm). A solid image (printing rate 100%) was printed thereon, and the printed matter was put into a 50° C. air oven within 10 seconds. Then, the printed material was taken out at predetermined time intervals, and the surface was rubbed with a finger to visually observe whether or not the ink could be removed, thereby evaluating the dryness. The evaluation criteria are as follows, and evaluation criteria values of 2 to 4 are defined as a practical range.
4: Even if the printed matter was rubbed with a finger after 30 seconds of drying time, the ink on the printed surface could not be removed. 2: After 45 seconds of drying time, the ink on the printed surface could be removed by rubbing the printed material with a finger, but the ink on the printed surface could not be removed even after 1 minute of drying time. 1: Drying time: 1 It did not dry even after a minute, and the ink on the printed surface was removed by rubbing the printed material with a finger.

<Evaluation 4: Evaluation of abrasion resistance>
After each of the water-based inkjet inks 1 to 77 produced above was filled in the inkjet printing apparatus used in Evaluation 2, the drop volume was 12 pL, and the OK top coat manufactured by Oji Paper Co., Ltd. + (coated paper, basis weight 104.7 g / m ² ) A solid image (100% print rate) was printed thereon, and the printed matter was placed in an air oven at 70°C within 10 seconds. After drying for 1 minute, the printed matter was taken out of the oven and rubbed with a white cotton cloth for testing (Kanakin No. 3) a predetermined number of times while applying a weight of 200 g. . The evaluation criteria were as follows, and the evaluation criteria value of 2 to 3 was defined as a practical range.
3: Even after rubbing 20 times, no scratches on the printed surface or peeling of ink were observed. 2: Even after rubbing 10 times, no scratches on the printed surface or peeling of ink were observed. Scratches on the surface and peeling of ink were observed Scratches on the printed surface and peeling of ink were observed after rubbing 1:10 times

<Evaluation 5: Evaluation of image quality (coated paper)>
After each of the water-based inkjet inks 1 to 77 produced above was filled in the inkjet printing apparatus used in Evaluation 2, the drop volume was 12 pL, and the OK top coat manufactured by Oji Paper Co., Ltd. + (coated paper, basis weight 104.7 g / m ² ) On top, a gradation patch image was printed with a printing rate varying by 10% between 10% and 80%, and the printed matter was placed in an air oven at 70°C within 10 seconds. After drying for 1 minute, the printed matter was taken out from the oven, and the presence or absence of uneven density was visually observed to evaluate the image quality of the coated paper. The evaluation criteria are as follows, and evaluation criteria values of 2 to 4 are defined as a practical range.
4: No shading unevenness was observed at any printing rate 3: No shading unevenness was observed at a printing rate of 70% or less 2: No shading unevenness was observed at a printing rate of 60% or less 1: Printing rate 60 % clearly showed uneven density

As a result of evaluation, the content of a compound containing a binder resin (a-1) having an acid value of 1 to 80 mgKOH/g, a surfactant, and a water-soluble organic solvent, and having 3 or more hydroxyl groups was 8. It was confirmed that the water-based inkjet inks 1 to 71, which are mass % or less, have practical quality in all of dispersion stability, ejection stability, drying property, scratch resistance of printed matter, and image quality. was done.

In contrast to the above, the water-based inkjet ink 73 (Comparative Example 2) using a binder resin having an acid value of 0 mgKOH/g was found to be inferior in ejection stability, and the binder resin having an acid value greater than 80 mgKOH/g It was confirmed that water-based inkjet inks 72 and 74 (Comparative Examples 1 and 3) using If the acid value of the binder resin is too small, clogging of the nozzle surface of the inkjet head cannot be prevented even if a surfactant is used in combination. but C.I. I. It is believed that it interacts with Pigment Orange 64 and the pigment dispersing resin, destroying the dispersed state.

On the other hand, when the binder resin was not used as in Water-Based Inkjet Ink 75 (Comparative Example 4), the dispersion stability and ejection stability were improved, but the printed material was significantly inferior in abrasion resistance and image quality. turn into. Further, when no surfactant was used as in Water-Based Inkjet Ink 76 (Comparative Example 5), film formation of the binder resin (a-1) in the ink could not be suppressed, resulting in poor ejection stability. It is thought that it will become ink. Further, deterioration in dispersion stability and drying property was confirmed in water-based inkjet ink 77 (Comparative Example 6) in which the content of glycerin, which is a compound having 3 or more hydroxyl groups, was 10% by mass. C.I. I. It is believed that the dispersed state of Pigment Orange 64 was destroyed and the glycerin remaining in the printed matter worsened the drying property.

[Examples 72 to 138, Comparative Examples 7 to 9]
As described above, when used for non-permeable substrates such as plastic substrates, the binder resin (a-1) is an acrylic resin having a glass transition temperature of 45 ° C. or less, and styrene acrylic. It is preferable to include one or more resins selected from the group consisting of resins and/or one or more resins selected from the group consisting of urethane resins, urethane-acrylic composite resins, and olefin resins. Therefore, among water-based inks containing a binder resin satisfying the above conditions (75 is a comparative example and does not contain a binder resin), water-based inkjet inks 1 to 8, 13 to 71, and 75 to 77 are described below. Evaluations 6 to 7 shown were also performed to evaluate image quality and adhesion to impermeable substrates. The results were as shown in Table 8.

<Evaluation 6: Evaluation of image quality (film)>
The image quality of the film was evaluated by the same method and evaluation criteria as in Evaluation 5 above, except that Mitsui Chemicals Tohcello OPU-1 (biaxially stretched polypropylene film, thickness 20 μm) was used as the recording medium. .

<Evaluation 7: Evaluation of adhesion>
After filling the inkjet printing apparatus used in Evaluation 2 with the water-based inkjet inks 1 to 8, 13 to 71, and 75 to 77 produced above, respectively, with a drop volume of 12 pL, Mitsui Chemicals Tohcello OPU-1 (biaxial A solid image (100% print rate) was printed on an oriented polypropylene film (thickness: 20 μm), and the printed matter was placed in an air oven at 70° C. within 10 seconds. After drying for 1 minute, the printed material was taken out from the oven, and cellophane tape (18 mm width) manufactured by Nichiban Co., Ltd. was firmly attached to the surface of the printed material with the pad of a finger. Then, the adhesiveness was evaluated by visually observing the surface of the printed matter after holding the tip of the cellophane tape and instantaneously pulling it off while maintaining an angle of 45 degrees. Evaluation criteria were as follows, and evaluation criteria values of 2 to 4 were defined as a practically feasible range.
4: The ratio of the peeled area to the area to which the cellophane tape was pasted was less than 10%. 3: The ratio of the peeled area to the area to which the cellophane tape was pasted was 10% or more and less than 20%. 2: The ratio of the peeled area to the area to which the cellophane tape was attached was 20% or more and less than 30%. 1: The peeled area of the cellophane tape with respect to the adhesion surface was 30% or more.

As a result of the evaluation, it was confirmed that all of the water-based inkjet inks 1 to 8 and 13 to 71 (Examples 72 to 138) were excellent in image quality and adhesion to polypropylene films. Among water-based inkjet inks 2, 13 to 25, which were evaluated by changing the type of binder resin (A), water-based inkjet inks 19 to 19 using urethane resin, urethane-acrylic composite resin, or olefin resin. 25 has an image quality evaluation reference value of 3 and an adhesion evaluation reference value of 3 to 4 for the film, and it was confirmed that inks using other resins have particularly excellent quality.

On the other hand, water-based inkjet inks 75 to 77 (Comparative Examples 7 to 9) had an image quality evaluation standard value of 1 for the film, which was confirmed to be at a practically problematic level. The above results show that the water-based inkjet ink having the structure of the present invention, particularly the water-based inkjet ink containing the binder resin selected from the above, is excellent in image quality and adhesion to impermeable substrates such as polypropylene films. is shown.

[Example 139]
The amount of impurities in TCO06401 (C.I. Pigment Orange 64) manufactured by TRUSTCHEM Co., Ltd. used for the production of Orange Pigment Dispersions 1 to 3 was measured according to the method described above, and was 6.7 mass with respect to the total amount of pigment. %Met. Therefore, washing with ethanol and water was performed, and the amount of impurities was measured again. After this washing, TCO06401 was used, and in the same manner as the orange pigment dispersion 1 except for this, an orange pigment dispersion 4 was produced. A water-based inkjet ink 78 was manufactured in the same manner as the water-based inkjet ink 21, except that the orange pigment dispersion 4 was used as the pigment dispersion.

As a result of carrying out the above evaluations 1 and 2 for this water-based inkjet ink 78, the evaluation reference value was 3 in both cases, and it was confirmed that the water-based inkjet ink 78 was better than the water-based inkjet ink 21. By reducing the amount of impurities contained in TCO06401, it is believed that foaming during pigment dispersion and inhibition of adsorption of the pigment dispersion resin could be suppressed.

Claims (6)

A water-based inkjet ink containing a colorant, a pigment dispersion resin, a binder resin (A), a surfactant, and a water-soluble organic solvent,
The colorant is C.I. I. including Pigment Orange 64,
The above C.I. I. Pigment Orange 64, the amount of impurities present in the C.I. I. Pigment Orange 64 is 8% by mass or less with respect to the total amount,
The binder resin (A) contains a binder resin (a-1) having an acid value of 1 to 60 mgKOH/g,
The content of the water-soluble organic solvent having a boiling point of 240° C. or higher under 1 atm is 5% by mass or less with respect to the total amount of the inkjet ink,
The content of the compound having 3 or more hydroxyl groups is 2.5 % by mass or less with respect to the total amount of the inkjet ink ,
A water-based inkjet ink , wherein the water-soluble organic solvent contains an alkanediol having 3 carbon atoms . The aqueous solution according to claim 1, wherein the binder resin (a-1) is at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, and olefin resins. inkjet ink. The water-based inkjet ink according to claim 1 or 2 , wherein the surfactant contains a surfactant having an HLB value of 0-8. A method for producing an inkjet printed matter, wherein the water-based inkjet ink according to any one of claims 1 to 3 is ejected from an inkjet head and applied to a non-permeable substrate. An ink-pretreatment liquid set comprising the water-based inkjet ink according to any one of claims 1 to 3 and a pretreatment liquid containing a flocculant. The flocculant contains Ca ²⁺ , Mg ²⁺ , Zn ²⁺ , Al ³⁺ 6. The ink-pretreatment liquid set according to claim 5, comprising a salt of a polyvalent metal ion selected from the group consisting of: