JP6982680B2 - Inkjet recording ink composition, ink set and image recording method - Google Patents

Description

The present disclosure relates to an ink composition for inkjet recording, an ink set, and an image recording method.

Conventionally, recording of images on various materials has been expected, and an inkjet method has been proposed as one of the recording methods for that purpose. The inkjet method has come to be used in various fields because it is possible to attach droplets to a recording medium and record them using a simple device.

Generally, white paper or the like is used as the recording medium on which an image is recorded, but in recent years, the recording medium differs depending on the usage mode, and the image is recorded on a material that is not necessarily a white background. It is desired. When an image is recorded on a material other than a white background, the background may be colored or the back side of the material may be seen through, which may impair the visibility and sharpness of the recorded image.
Further, in order to improve the color quality of the entire image, it is indispensable to make the white part in the image good white.

In order to improve the above situation, the use of white ink has been conventionally proposed. By intentionally using non-chromatic white ink in combination with chromatic colored ink, the purpose of expressing white color and the purpose of improving visibility and image sharpness have been achieved.
Inorganic pigments are widely known as white materials used for white inks from the viewpoint of concealment, and titanium dioxide, for example, has come to be widely used.
On the other hand, since inorganic pigments such as titanium dioxide generally have a high specific gravity, a technique for suppressing the phenomenon that the inorganic pigments aggregate or settle in the white ink and are unevenly distributed in the ink by using a dispersant has been studied.

As a technique related to the above, water, a water-based inkjet ink containing water, titanium oxide having an average particle size of 250 nm or more and 300 nm or less, a pigment dispersant having an acid value of 5 mgKOH / g or more, and an organic solvent is disclosed (for example,). Japanese Patent Application Laid-Open No. 2015-124348).
Further, it has a structural unit derived from titanium oxide, an anionic group-containing monomer and a specific polyalkylene glycol (meth) acrylate, and contains a pigment dispersant having an acid value of 100 mgKOH / g or more, and is further organic. A water-based ink for inkjet recording using glycerin having a boiling point of 290 ° C. as a solvent is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2017-39922).

Further, a black ink in which an aqueous black pigment dispersion K-1 using carbon black and a polymer dispersant and an organic solvent such as glycerin is mixed is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2016-69487). Further, there is a disclosure regarding an inkjet pigment ink containing an organic pigment such as yellow and a pigment dispersion resin (see, for example, Japanese Patent Application Laid-Open No. 2012-188582).

As described above, various techniques for producing ink by mixing a pigment and a dispersant for dispersing the pigment have been studied.
A white-based inorganic pigment such as titanium dioxide tends to obtain a good white color, but has a property that the particle size is relatively large and the specific gravity is also large. Therefore, unlike other pigments such as organic pigments, inorganic pigments such as titanium dioxide tend to settle or aggregate in the prepared ink. Therefore, in order to eject ink containing titanium dioxide or the like by an inkjet method. , It is indispensable to improve the dispersibility of titanium dioxide and the like.
Further, as another method for improving the ejection property of the ink by the inkjet method, it is conceivable to stabilize the ink composition and suppress the thickening by using an organic solvent having a high boiling point. On the other hand, in the composition containing an organic solvent having a high boiling point, the organic solvent may remain in the image and the image may be easily sticky. The stickiness of the image not only contributes to the deterioration of the quality of the recorded image, but also makes it easy for the recorded materials to stick to each other through the image when the recorded materials on which the images are recorded are accumulated or stored. It may be damaged.

Among the above-mentioned prior arts, in the composition containing titanium dioxide disclosed in JP-A-2015-124348 and JP-A-2017-39922, the ejection property and the stickiness of the recorded image when ejected by the inkjet method are used. It is presumed that it is inferior in terms of.
Further, the pigments used in the inks disclosed in JP-A-2016-69487 and JP-A-2012-188582 are organic pigments such as carbon black or yellow pigments, while exhibiting good whiteness. It is not a technique planned to simultaneously realize the effect that a pigment having a large particle size and a large specific gravity is satisfactorily dispersed and contained, and an image with less stickiness can be obtained after recording.

The present disclosure is in light of the above.
The problem to be solved by one embodiment of the present invention is to improve the whiteness of the white part in the image by using a white inorganic pigment having a relatively large particle size, and to improve the ink ejection property and the stickiness of the recorded image. It is an object of the present invention to provide an improved ink composition for inkjet recording.
The problem to be solved by another embodiment of the present invention is to improve the whiteness of the white part in the image by using a white inorganic pigment having a relatively large particle size, and to improve the whiteness of the white part in the image, and to make the ink ejection property and the stickiness of the recorded image sticky. Is to provide an improved ink set and image recording method.

Specific means for solving the problem include the following aspects.
<1> Contains an organic solvent containing water, a white inorganic pigment having an average primary particle size of 150 nm to 400 nm, and a dispersion resin having a structural unit represented by the following formula 1 and having a boiling point of 270 ° C. or higher. The ink composition for inkjet recording has an amount of 5.5% by mass or less based on the total mass of the ink.

In formula 1, R ¹ represents a hydrogen atom or a methyl group, L ² represents −C (= O) O−, −OC (= O) −, or −C (= O) NR ²⁻ . R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 6 or more carbon atoms.

<2> Further, at least one low boiling point organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C. The ink composition for inkjet recording according to <1>, which contains 4% by mass or more and 35% by mass or less of the content of the low boiling point organic solvent with respect to the total mass of the ink.
<3> The dispersed resin is the ink composition for inkjet recording according to <1> or <2>, which is an acrylic resin.
<4> The ink composition for inkjet recording according to any one of <1> to <3> ^{, wherein R 3 is an alkyl group having 8 to 22 carbon atoms in the formula 1.}
<5> The ink composition for inkjet recording according to <4>, wherein ^{R 3 is an alkyl group having 15 to 22 carbon atoms.}
<6> The dispersion resin is the ink composition for inkjet recording according to any one of <1> to <5>, which further contains a structural unit derived from a (meth) acrylate having an aromatic ring.
<7> The dispersion resin is the ink composition for inkjet recording according to any one of <1> to <6>, which further contains a structural unit derived from a (meth) acrylate having a hydroxyl group.

<8> An ink set comprising the ink jet recording ink composition according to any one of <1> to <7> and a colored ink containing a colorant, which is different from the inkjet recording ink composition. ..
<9> The ink set according to <8>, wherein the content of the organic solvent having a boiling point of 270 ° C. or higher in the colored ink is 5.5% by mass or less with respect to the total mass of the colored ink.
<10> The colored ink is a low boiling point organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C. The ink set according to <8> or <9>, wherein the content of the low boiling point organic solvent is 4% by mass to 35% by mass with respect to the total mass of the colored ink.
<11> A non-absorbent medium using the inkjet recording ink composition according to any one of <1> to <7> or the ink set according to any one of <8> to <10>. This is an image recording method for recording an image.
<12> The image recording method according to <11>, wherein an image is recorded by ejecting an ink composition for inkjet recording by an inkjet method.

According to one embodiment of the present invention, an inkjet in which a white inorganic pigment having a relatively large particle size is used to improve the whiteness of a white portion in an image, and to improve the ink ejection property and the stickiness of a recorded image. A recording ink composition is provided.
According to another embodiment of the present invention, the whiteness of the white part in the image is improved by using the white inorganic pigment having a relatively large particle size, and the ink ejection property and the stickiness of the recorded image are improved. An ink set and an image recording method are provided.

Hereinafter, the ink jet recording ink composition of the present disclosure, and the ink set and the image recording method of the present disclosure will be described in detail. Although the description described below may be based on the representative embodiments of the present disclosure, the present disclosure is not limited to such embodiments.

In this disclosure, "~" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. .. Further, in the numerical range described in this disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
Further, in the notation of a group (atomic group) in the present disclosure, the notation that does not describe substitution or non-substituent includes those having no substituent as well as those having a substituent. For example, the "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In addition, the term "process" in the present disclosure is included in this term as long as the intended purpose of the process is achieved, not only in an independent process but also in the case where it cannot be clearly distinguished from other processes. Is done.
Further, in the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.
Further, in the present disclosure, the amount of each component in the composition is the total amount of the plurality of applicable substances present in the composition when a plurality of the substances corresponding to each component are present in the composition, unless otherwise specified. Means.
Further, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

<Ink composition for inkjet recording>
The ink composition for inkjet recording of the present disclosure (hereinafter, also simply referred to as “ink composition”) is represented by water, a white inorganic pigment having an average primary particle size of 150 nm to 400 nm, and the following formula 1. The content of the organic solvent containing the dispersed resin having the structural unit and having a boiling point of 270 ° C. or higher is in the range of 5.5% by mass or less with respect to the total mass of the ink. Further, the ink jet recording ink composition of the present disclosure preferably contains an organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C., and if necessary, even if it has a composition containing other components. good.

Inorganic pigments such as titanium dioxide exhibit white color and have been conventionally used as white pigments. Among the white pigments, those having a large particle size are advantageous for enhancing the whiteness. However, when trying to secure good whiteness by using an inorganic pigment having a large particle size, the inorganic pigment such as titanium dioxide has a higher specific gravity than the organic pigment and the like, so that the inorganic pigment precipitates or aggregates in the ink. It is easy and disadvantageous for ejection by the inkjet method.
In order to eject an ink containing an inorganic pigment such as titanium dioxide by an inkjet method, it is considered indispensable to enhance the dispersibility of the inorganic pigment having a relatively large specific gravity.
On the other hand, as another method for improving the ejection property of ink by the inkjet method, there is a technique of using an organic solvent having a high boiling point. Since an organic solvent having a high boiling point does not easily volatilize, it has the effect of stabilizing the ink composition and suppressing thickening. However, in the case of a composition containing an organic solvent having a high boiling point, the organic solvent having a high boiling point tends to remain in the image, and as a result, stickiness may occur in the image. The stickiness of the image not only contributes to the deterioration of the quality of the recorded image, but also makes it easy for the recorded materials to stick to each other through the image when the recorded materials on which the images are recorded are accumulated or stored. It may be significantly impaired.

The composition containing titanium dioxide disclosed in JP-A-2015-124348 and JP-A-2017-39922 described above is inferior in ejection property when ejected by the inkjet method, and also in terms of stickiness of the recorded image. It is presumed to be inferior.
Further, since the pigments used in the inks disclosed in JP-A-2016-69487 and JP-A-2012-188582 are organic pigments such as carbon black or yellow pigments, pigments having a large specific gravity are used. It does not take into consideration the ejection property when it is present. Therefore, while exhibiting good whiteness by using an inorganic pigment having a relatively large particle size, the ejection property of the ink containing the pigment having a large specific gravity is improved according to the particle size, and the stickiness of the image after recording is improved. It is considered difficult to establish the effect of improvement.

In view of the above, the present disclosure realizes a good white concentration by using a relatively large-sized white inorganic pigment (preferably titanium dioxide) having an average primary particle size of 150 nm or more, while the content of an organic solvent having a high boiling point is high. When the amount of the ink is small or not, the dryness of the ink dropped on the non-absorbent medium is enhanced, and the stickiness of the image recorded on the non-absorbent medium is improved. The use of a white inorganic pigment having a large particle size is disadvantageous because the specific gravity is large, and the content of the organic solvent having a high boiling point is reduced, which is disadvantageous because the composition fluctuates and the viscosity is increased. In order to improve the problem of ejection property, a dispersed resin having a specific structure is selectively contained.
That is, in the present disclosure, it is a problem peculiar to the case where the composition uses a volatile organic solvent containing a white inorganic pigment having a large particle size and a heavy specific gravity and having little or no high boiling point organic solvent. The purpose is to improve the ejection property and to make the ink ejection property, the whiteness, and the stickiness of the image parallel.
In the present disclosure, while ensuring a good white density and improving the whiteness of the white part, the inkjet suitability as an ink composition for inkjet recording is also maintained well, and the ejection property at the time of inkjet recording is excellent, and the ink jet recording property is not good. The stickiness of the image when an absorbent base material is used is improved.

Subsequently, each component contained in the inkjet recording ink composition of the present disclosure will be described in detail.

-White inorganic pigment-
The ink jet recording ink composition of the present disclosure contains at least one of white inorganic pigments having an average primary particle size of 150 nm to 400 nm. Since it contains a white inorganic pigment having an average primary particle diameter of 150 nm or more, it has a high concealing property for the material to be recorded and can form a good white background.

Examples of the white inorganic pigment include titanium dioxide (TiO ₂ ), barium sulfate, calcium carbonate, silica, zinc oxide, zinc sulfide, mica, talc, pearl and the like. Among the white inorganic pigments, titanium dioxide, barium sulfate, calcium carbonate, or zinc oxide is preferable, and titanium dioxide is more preferable.

The average primary particle size of the white inorganic pigment is 150 nm to 400 nm.
When the average primary particle diameter is 150 nm or more, the concealing property to the recorded material is high, and a good white background can be formed. Further, when the average primary particle diameter is 400 nm or less, the ejection property is excellent when ejected by the inkjet method.
The average primary particle diameter is preferably in the range of 250 nm to 350 nm, more preferably in the range of 250 nm to 300 nm, for the same reason as described above.

The average primary particle size of the white inorganic pigment is a value measured using a transmission electron microscope (TEM). A transmission electron microscope 1200EX manufactured by JEOL Ltd. can be used for the measurement.
Specifically, from an image magnified 100,000 times by TEM after dropping an ink composition diluted 1,000 times on a Cu200 mesh (manufactured by JEOL Ltd.) to which a carbon film is attached and drying it. , The equivalent circle diameter of 300 independent particles that do not overlap is measured, and the measured values are averaged to obtain the average particle size.

The content of the white inorganic pigment in the ink composition is preferably 1 part by mass to 20 parts by mass, more preferably 3 parts by mass to 17 parts by mass, and 5 parts by mass to 15 parts by mass with respect to the total mass of the ink composition. The mass part is more preferable.
When the content of the white inorganic pigment is 1 part by mass or more, a good white density can be obtained and the concealing property is excellent. Further, when the content of the white inorganic pigment is 20 parts by mass or less, the mechanical strength, stability over time, durability, adhesion to the recording medium and the like are further improved.

-Dispersed resin-
The ink composition for inkjet recording of the present disclosure contains at least one kind of dispersed resin having a structural unit represented by the following formula 1 (hereinafter, also referred to as “specific resin”). By using a dispersed resin (specific resin) having a specific structural unit, a peculiar composition that occurs when a white inorganic pigment having a large particle size and a heavy specific gravity is included and the composition contains little or no high boiling organic solvent. Dischargeability, which is an issue, is effectively improved.

The specific resin has at least a structural unit represented by the formula 1 (hereinafter, also referred to as “constituent unit a-1”), and may further have another structural unit.

In formula 1, R ¹ represents a hydrogen atom or a methyl group, L ² represents −C (= O) O−, −OC (= O) −, or −C (= O) NR ²⁻ . R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 6 or more carbon atoms.

[Constructive unit a-1]
The structural unit a-1 is a structural unit represented by the above equation 1.
In formula 1, R ¹ is preferably a methyl group.
In Equation 1, L ² represents −C (= O) O−, −OC (= O) −, or −C (= O) NR ²⁻ , and is −C (= O) O− or. −C (= O) NR ² − is preferable, and −C (= O) O− is more preferable.
Further, R ² is preferably a hydrogen atom.
The description of -C (= O) O- indicates that the carbon atom in -C (= O) O- and the carbon atom to which R ¹ in the above formula 1 is bonded are directly bonded. The description of −OC (= O) − indicates that the carbon atom in −OC (= O) − and the carbon atom to which R ¹ is bonded in the above formula 1 are directly bonded.
^{Further, -C (= O) NR 2} - and description ^{of, -C (= O) NR 2} - and carbon atoms, indicated that the carbon atom ^{to which R 1} is bonded in the formula 1 is bonded directly ing.

In Formula 1, R ³ is preferably an alkyl group having 6 to 30 carbon atoms, more preferably an alkyl group having 8 to 22 carbon atoms, and more preferably an alkyl group having 8 to 22 carbon atoms, from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size. Alkyl groups having 12 to 22 carbon atoms are more preferable, alkyl groups having 15 to 22 carbon atoms are further preferable, and alkyl groups having 15 to 18 carbon atoms are particularly preferable. The alkyl group may be linear, branched or chain-like, or may have a ring structure.

Among the above, it is preferable that the structural unit a-1 is a structural unit derived from an alkyl (meth) acrylate compound or an alkyl (meth) acrylamide compound.

The specific resin is preferably an acrylic resin, and the constituent unit a-1 is more preferably an acrylic resin which is a constituent unit derived from an alkyl (meth) acrylate compound or an alkyl (meth) acrylamide compound.
Specifically, the specific resin is ^{preferably an acrylic resin in which L 2} in the formula 1 is −C (= O) O—, and further, when L ² is −C (= O) O−. It is preferable that the acrylic resin has a content ratio of the structural unit represented by the formula 1 of 5% by mass or more with respect to all the structural units.

The content of the structural unit a-1 may be 10% by mass to 40% by mass with respect to the total mass of the specific resin from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size of the white inorganic pigment. It is preferably 10% by mass to 30% by mass, more preferably 20% by mass to 30% by mass, and particularly preferably 20% by mass to 30% by mass.
The specific resin used in the present disclosure may contain only one type of the constituent unit a-1, or may contain two or more types. When the specific resin used in the present disclosure contains two or more kinds of constituent units a-1, the above-mentioned content means the total content of two or more kinds of constituent units a-1.

[Constructive unit a-2]
From the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size, the specific resin is also referred to as a structural unit having an aromatic ring (hereinafter, "constituent unit a-2") in addition to the above-mentioned structural unit a-1. It is preferable to have a structural unit derived from (meth) acrylate having an aromatic ring, and it is further preferable to have a structural unit represented by the following formula 2.
As the aromatic ring, an aromatic hydrocarbon ring is preferable, and a benzene ring is more preferable.

In formula 2, R ⁴ represents a hydrogen atom or a methyl group, and L ⁵ is a single bond or an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, −C (= O) −, −. O -, - S-, and, -NR ⁷ - represents a divalent linking group formed by combining two or more groups selected from the group consisting of, ^{R 6} is an alkyl group having 1 to 6 carbon atoms, carbon atoms Represents an alkoxy group of 1 to 15, an amino group, a halogen atom, an aryloxy group having 6 to 20 carbon atoms, or a silyl group, R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and m is 0. Represents an integer of ~ 5.

In the formula 2, ^{R 4} is preferably a methyl group.
In Formula 2, L ⁵ represents a single bond, or is preferably a group represented by the following formula 2-1 or formula 2-2, a single bond, or, a group represented by the following formula 2-1 It is more preferable to have.
The alkylene group for L ^5, preferably an alkylene group having 2 to 10 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms. The alkylene group may be linear or branched.
As the alkenylene group in L ^5, preferably an alkenylene group having 2 to 10 carbon atoms, more preferably an alkenylene group having 2 to 6 carbon atoms, more preferably an alkenylene group having 2 to 4 carbon atoms. The alkenylene group may be linear or branched.
^{R 7} represents a hydrogen atom.
In Formula 2, it is preferable that R ⁶ independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a halogen atom, or an aryloxy group having 6 to 20 carbon atoms. It is more preferable to represent an alkyl group having 1 to 6 carbon atoms, a halogen atom, or an aryloxy group having 6 to 20 carbon atoms.
Alkyl groups represented by R ^6, and the alkyl group contained in the alkoxy group may be linear or may be branched.
Aryloxy group represented by R ⁶ is preferably a naphthyloxy group or a phenyl group, more preferably a phenyl group.
In Equation 2, m is preferably 0 or 1, more preferably 0.

In formulas 2-1 and 2-2, L ¹¹ is represented by an alkylene group having 1 to 12 carbon atoms, an alkaneylene group having 2 to 12 carbon atoms, -O-, -S-, or a combination thereof. A group representing a group, preferably an alkylene group having 1 to 12 carbon atoms, -O-, or a group represented by a combination thereof is preferable, and an alkylene group having 1 to 8 carbon atoms, -O-, or a combination thereof is represented. The group to be used is more preferable, and an alkylene group having 1 to 4 carbon atoms, —O—, or a group represented by a combination thereof is further preferable.
Preferred embodiments of L ¹¹ include divalent linking groups represented by the following formulas 2-3, 2-4 or 2-5.
In formula 2-2, R ⁷ has the same ^{meaning as R 7 in} formula 2, and the preferred embodiment is also the same.
In Formula 2-1 and Formula 2-2, * represents a binding site to the carbon atom to which R ⁴ is bonded in the formula 2, the wavy line section represents the binding site to the benzene ring in formula 2.

In formulas 2-3 to 2-5, a represents a binding site with O in formula 2-1 or N in formula 2-2, and b is a wavy line portion in formulas 2-1 and 2-2. Similarly, in formula 2, the binding site with the benzene ring is represented, n3 represents an integer of 1 to 10, n4 represents an integer of 1 to 5, and n5 represents an integer of 1 to 5.
In Equation 2-3, n3 is preferably an integer of 1-5.
In Equation 2-4, n4 is preferably an integer of 1 to 3, and more preferably 2.
In Formula 2-5, n5 is preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 1.

The structural unit a-2 is a structural unit derived from styrene, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, or phenoxydiethylene glycol (meth) acrylate. It is more preferable, it is more preferably derived from benzyl (meth) acrylate or phenoxyethyl (meth) acrylate, and further preferably it is a structural unit derived from benzyl (meth) acrylate.

Among the above, from the viewpoint that the effects of the present disclosure are more effectively exerted, the specific resin in the present disclosure has at least a constituent unit a-1 and a constituent unit a-2, and in the constituent unit a-2, It is preferable that L ⁵ is a group represented by the formula 2-1 and ^{at least one of R 6} represents an aryloxy group having 6 to 20 carbon atoms, and R ⁴ represents a hydrogen atom or a methyl group.

The content of the structural unit a-2 is more preferably 10% by mass to 70% by mass, more preferably 20% by mass, from the viewpoint of reducing sedimentation inhibitory property, aggregation inhibitory property and average particle size with respect to the total mass of the specific resin. It is more preferably from mass% to 60% by mass, further preferably from 25% by mass to 50% by mass, and particularly preferably from 30% by mass to 45% by mass.
The specific resin may contain only one type of the structural unit a-2, or may contain two or more types. When the specific resin used in the present disclosure contains two or more kinds of constituent units a-2, the above-mentioned content means the total content of two or more kinds of constituent units a-2.

[Constructive unit a-3]
From the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size, the specific resin has a structural unit having an acidic group in addition to the structural unit represented by the above formula 1 (hereinafter, "constituent unit a-". It is also preferable to have 3 ”).
The acidic group in the present disclosure is a substituent having a dissociative proton, and means, for example, an acidic group such as a carboxy group, a phosphonyl group, a phosphoryl group, a sulfo group, and a borate group. Among them, the acidic group is preferably a carboxy group, a sulfo group or a phosphonyl group, and more preferably a carboxy group.
The acidic group may be in the form of a dissociated form by releasing a proton, or may form a salt.
Further, in the ink composition, the structural unit a-3 may form a salt with the amine compound.

The structural unit a-3 is a structural unit derived from (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, bis (methacrylicoxyethyl) phosphate or 2-acrylamide-2-methylpropanesulfonic acid. It is preferable, and it is more preferable that it is a structural unit derived from methacrylic acid or acrylic acid.

The content of the structural unit a-3 is preferably 3% by mass to 40% by mass, and 5% by mass, based on the total mass of the specific resin, from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size. More preferably, it is% to 30% by mass.
Further, the content of the structural unit a-3 is such that the acid value of the specific resin described later is 0.5 mmol / g to 3.5 mmol / g (preferably 1.0 mmol / g to 3.0 mmol / g, more preferably 1.0 mmol / g to 3.0 mmol / g). The amount is preferably 1.0 mmol / g to 2.5 mmol / g).
The specific resin may contain only one type of the structural unit a-3, or may contain two or more types. When the specific resin contains two or more kinds of constituent units a-3, the above-mentioned content means the total content of two or more kinds of constituent units a-3.

[Constructive unit a-4]
In addition to the above-mentioned structural unit a-1, the specific resin preferably has a structural unit other than the structural unit a-2 and the structural unit a-3 (hereinafter, “constituent unit a-4”). ..
As the structural unit a-4, a structural unit derived from a monofunctional (meth) acrylate compound or a structural unit derived from a monofunctional (meth) acrylamide compound is preferable, and a structural unit derived from the monofunctional (meth) acrylate compound is preferable. Is more preferable.
Further, the structural unit a-4 has at least one structure selected from the group consisting of a hydroxy group, an amino group and a polyalkyleneoxy structure from the viewpoint of suppressing sedimentation, suppressing aggregation and reducing the average particle size. A structural unit derived from a compound is more preferable, a structural unit derived from a compound having a hydroxyl group (hydroxy group) is more preferable, and a structural unit derived from a (meth) acrylate having a hydroxyl group is further preferable.

Examples of the monofunctional (meth) acrylate compound include 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, and n-propyl (meth) acrylate. , N-butyl (meth) acrylate and other alkyl (meth) acrylates; 2-methoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, 2- (2-methoxyethoxy) ethyl methacrylate, ethoxytriethylene glycol methacrylate, Examples thereof include methoxypolyethylene glycol (molecular weight 200 to 1,000) monomethacrylate, polyethylene glycol (molecular weight 200 to 1,000) monomethacrylate and the like.
Examples of monofunctional (meth) acrylamide compounds include dimethylacrylamide, hydroxyethyl (meth) acrylamide, hydroxypropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, isopropyl (meth) acrylamide, and die. Examples thereof include acetone and acrylamide.
Among them, hydroxyethyl (meth) acrylate, 2-methoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, methoxypolyethylene glycol (molecular weight 200 to 1,000) monomethacrylate, polyethylene glycol (molecular weight 200 to 1,000). Monomethacrylate or methyl (meth) acrylate is preferable, and methyl (meth) acrylate is more preferable.

The content of the structural unit a-4 is preferably 3% by mass to 40% by mass, and 5% by mass, based on the total mass of the specific resin, from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size. More preferably, it is% to 30% by mass.
The specific resin used in the present disclosure may contain only one type of structural unit a-4, or may contain two or more types. When the specific resin contains two or more kinds of constituent units a-4, the above-mentioned content means the total content of two or more kinds of constituent units a-4.

Further, the specific resin is preferably a resin having a structural unit represented by the formula 1 and a structural unit having an aromatic ring, from the viewpoint of suppressing sedimentation, suppressing aggregation and reducing the average particle size. A resin having a structural unit represented by 1, a structural unit having an aromatic ring, and a structural unit having an acidic group is more preferable, and a structural unit represented by the formula 1, a structural unit having an aromatic ring, and acidic. A resin having a structural unit having a group and a structural unit having at least one structure selected from the group consisting of a hydroxy group, an amino group and a polyalkyleneoxy structure is more preferable, and is represented by the formula 1. A resin having a structural unit, a structural unit having an aromatic ring, a structural unit having an acidic group, and a structural unit having a hydroxy group is particularly preferable.
Further, the specific resin is preferably an addition polymerization type resin, and more preferably an acrylic resin, from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size.
The acrylic resin in the present disclosure is a resin having 50% by mass or more of a structural unit derived from at least one compound selected from the group consisting of a (meth) acrylic compound and a (meth) acrylamide compound in an amount of 50% by mass or more. It is preferably 60% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.
Further, the specific resin may be a homopolymer or a copolymer, but it is preferably a copolymer.

The content of the specific resin is 3% by mass to 50% by mass with respect to the total mass of the pigment composition (pigment dispersion) used for preparing the ink composition from the viewpoint of suppressing sedimentation, suppressing aggregation and reducing the average particle size. It is preferably by mass, more preferably 5% by mass to 40% by mass, and even more preferably 10% by mass to 30% by mass.

-Acid value-
The acid value of the specific resin is preferably 0.5 mmol / g to 3.5 mmol / g, preferably 1.0 mmol / g to 3.0 mmol, from the viewpoint of suppressing sedimentation, suppressing aggregation, and reducing the average particle size. It is more preferably / g, and even more preferably 1.5 mmol / g to 2.5 mmol / g.
The acid value of the specific resin is measured according to JIS K0070 (1992) and calculated by converting it as 1 mmol / g = 56.1 mgKOH / g.

-Weight average molecular weight-
The weight average molecular weight of the specific resin is preferably 5,000 to 50,000, more preferably 8,000 to 40,000 from the viewpoint of sedimentation inhibitory property, aggregation inhibitory property and reducing the average particle size. It is preferable, and more preferably 10,000 to 30,000.
As used herein, the weight average molecular weight of the resin is measured by gel permeation chromatography (GPC). As GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and three columns, TSKgeL Super HZM-H, TSKgeL Super HZ4000, and TSKgeL Super HZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID x 15 cm) are connected in series. Use NMP (N-methylpyrrolidone) as the eluent. The conditions are as follows: sample concentration is 0.35% by mass, flow velocity is 0.35 ml / min, sample injection amount is 10 μl, measurement temperature is 40 ° C, and RI (Refractive Index) detector (differential refractive index detector). It is done using. The calibration curve is "Standard sample TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", It is prepared from 8 samples of "A-2500", "A-1000" and "n-propylbenzene".

-I / O value-
The I / O value (inorganic / organic value) of the specific resin is preferably 0.50 to 0.80, preferably 0.50 to 0.75, from the viewpoint of sedimentation inhibitory property and aggregation inhibitory property. Is more preferable.
The I / O value is a value that deals with the polarities of various organic compounds, which are also called inorganic / organic values, in an organic concept, and is one of the functional group contribution methods for setting parameters for each functional group. be.

The I / O value is explained in detail in the organic conceptual diagram (Yoshio Koda, Sankyo Publishing (1984)). The concept of I / O values divides the properties of compounds into organic groups that represent covalent bonds and inorganic groups that represent ionic bonds, and all organic compounds are named as organic axes and inorganic axes. It is shown by positioning it at each of the above points.

The inorganic value is a numerical value of the magnitude of the influence of various substituents and bonds on the boiling point of an organic compound on the basis of a hydroxyl group. Specifically, if the distance between the boiling point curve of linear alcohol and the boiling point curve of linear paraffin is taken near 5 carbon atoms, it will be about 100 ° C. Therefore, the influence of one hydroxyl group is set to 100 numerically. A value obtained by quantifying the influence of various substituents or various bonds on the boiling point based on this numerical value is the inorganic value of the substituent possessed by the organic compound. For example, the inorganic value of the carboxy group (−COOH group) is 150, and the inorganic value of the double bond is 2. Therefore, the inorganic value of a certain organic compound means the sum of the inorganic values of various substituents and bonds possessed by the compound.
The organic value is determined based on the influence of a carbon atom representing the methylene group on the boiling point, with the methylene group in the molecule as a unit. That is, since the average value of the increase in boiling point due to the addition of one carbon in the vicinity of 5 to 10 carbon atoms of the linear saturated hydrocarbon compound is 20 ° C., the organic value of one carbon atom is set to 20 based on this. The organic value is a value obtained by determining and quantifying the influence of various substituents and bonds on the boiling point based on this. For example, the organic value of the nitro group (−NO _{2) is 70.}
The closer the I / O value is to 0, the more polar (hydrophobic and organic) the organic compound is, and the larger the value is, the more polar (hydrophilic and inorganic) the organic compound is. Is shown.

In the present disclosure, the I / O value of the specific resin means that obtained by the following method. Based on the organic (O value) and inorganic (I value) described in Yoshio Koda, Organic Conceptual Diagram-Basics and Applications- (1984), page 13, I / of each monomer constituting the specific resin Calculate the O value (= I value / O value). For each monomer constituting the polymer, calculate the product of its (I / O value) and (mol% in the polymer), add them up, and round off to the third decimal place to obtain the I of the specific resin. The / O value.
However, as a method for calculating the inorganic value of each monomer, a double bond is generally added as an inorganic value 2, but since the double bond disappears when polymerized, the double bond is used as the inorganic value of the monomer in the present disclosure. The I / O value of the specific resin is calculated using the value not added to the bound amount.

In the present disclosure, the I / O value of the specific resin can be adjusted by adjusting the structure and content of the monomers constituting the specific resin.

Specific examples of the specific resin used in the present disclosure are shown below, but the present disclosure is not limited thereto.
In the following specific examples, the description in the columns of the structural units a-1 to the structural unit a-4 represents the structure of each structural unit. The description of "% by mass" means the content of each structural unit, the numerical value in the column of "Mw" indicates the weight average molecular weight, and the description of "-" indicates that the corresponding structural unit is not contained. ..

The details of the structure described by the abbreviations in Table 1 above are as follows. In the following structure, n represents the number of repetitions.

-Water-
The ink composition for inkjet recording of the present disclosure contains water and is prepared as a water-based ink.
The water content is preferably 30% by mass or more, more preferably 40% by mass or more, based on the total mass of the ink composition. The upper limit of the water content is not particularly limited, and is preferably 80% by mass or less with respect to the total mass of the ink composition.

-Organic solvent with a boiling point of 270 ° C or higher-
The content of the organic solvent having a boiling point of 270 ° C. or higher in the ink jet recording ink composition of the present disclosure is 5.5% by mass or less with respect to the total mass of the ink.
That is, the inkjet recording ink composition of the present disclosure does not contain an organic solvent having a boiling point of 270 ° C. or higher (that is, 0% by mass), or the content of the inkjet recording ink composition with respect to the total mass is 0% by mass. It is in the range of more than% and 5.5% by mass or less.
When the content of the organic solvent having a boiling point of 270 ° C. or higher is within the above range, good dispersibility is maintained in combination with the above-mentioned specific resin, and after the application of the ink composition is completed (for example,). It is possible to suppress the stickiness of the image within 30 seconds from the time when the ink application is completed).

The content of the organic solvent having a boiling point of 270 ° C. or higher is preferably 5% by mass or less, more preferably 2% by mass or less, based on the total mass of the ink composition. Further, the content of the organic solvent having a boiling point of 270 ° C. or higher may be 0% by mass with respect to the total mass of the ink (that is, an embodiment containing no organic solvent having a boiling point of 270 ° C. or higher).

The boiling point means the boiling point under 1 atm (101325 Pa).
The boiling point is a value measured by a boiling point meter, and can be measured using, for example, DosaTherm300 manufactured by Titan Technologies Co., Ltd.

Examples of the organic solvent having a boiling point of 270 ° C. or higher include glycerin (boiling point: 290 ° C.), tripropylene glycol (boiling point: 273 ° C.), triethylene glycol monobutyl ether (boiling point: 276 ° C.), and sulfolane (boiling point: 285 ° C.). ), Thiodiglycol (boiling point: 282 ° C.) and the like.

-Organic solvent with a boiling point of 120 ° C or higher and lower than 270 ° C-
The ink composition for inkjet recording of the present disclosure can contain at least one low boiling point organic solvent selected from organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C. By containing a low boiling point organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C., the dispersibility of the white inorganic pigment is well maintained in combination with the above-mentioned specific resin, and after the application of the ink composition is completed ( For example, it is possible to suppress the stickiness of the image within 30 seconds from the time when the ink application is completed).
The boiling point means a boiling point under 1 atm (101325 Pa), and the measuring method is the same as for an organic solvent having a boiling point of 270 ° C. or higher.

Examples of the organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amide compounds, amine compounds, sulfur-containing compounds and the like.

Examples of the polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. include propylene glycol (boiling point: 188 ° C.), 1,3-propanediol (boiling point: 210 ° C.), and 1,3-butanediol (boiling point: 203 ° C.). , 1,4-Butanediol (boiling point: 230 ° C), 1,5-pentanediol (boiling point: 242 ° C), ethylene glycol (boiling point: 197 ° C), diethylene glycol (boiling point: 244 ° C), dipropylene glycol (boiling point:) 232 ° C), 1,3-propanediol (boiling point: 210 ° C), 1,3-butanediol (boiling point: 203 ° C), 2-methyl-2,4-pentanediol (boiling point: 196 ° C), 1,2 -Hexylene diol (boiling point: 223 ° C), 1,6-hexanediol (boiling point: 250 ° C), 1,2,6-hexanetriol (boiling point: 178 ° C), 1,2,4-butanetriol (boiling point: 190 ° C) ° C.), 1,2,3-butanediol (boiling point: 175 ° C.), petriol (boiling point: 216 ° C.) and the like.

Examples of the polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C. include ethylene glycol monoethyl ether (boiling point: 135 ° C.), ethylene glycol monobutyl ether (boiling point: 171 ° C.), and diethylene glycol monomethyl ether (boiling point: 194 ° C.). , Diethylene glycol monoethyl ether (boiling point: 202 ° C.), Diethylene glycol monobutyl ether (also known as butyl carbitol) (boiling point: 230 ° C.), Dipropylene glycol monobutyl ether (boiling point: 227 ° C.), triethylene glycol monomethyl ether (boiling point: 122 ° C.) ℃), Triethylene glycol monoisobutyl ether (boiling point: 160 ℃), tripropylene glycol monomethyl ether (boiling point 243 ℃), tetraethylene glycol monomethyl ether (boiling point: 158 ℃), propylene glycol monoethyl ether (boiling point: 133 ℃) And so on.

Examples of the amide compound having a boiling point of 120 ° C. or higher and lower than 270 ° C. include formamide (boiling point: 210 ° C.), N-methylformamide (boiling point: 199 ° C.), N, N-dimethylformamide (boiling point: 153 ° C.) and the like. ..

Examples of the amine compound having a boiling point of 120 ° C. or higher and lower than 270 ° C. include monoethanolamine (boiling point: 170 ° C.), diethanolamine (boiling point: 217 ° C.), triethanolamine (boiling point: 208 ° C.) and the like.

Examples of the nitrogen-containing heterocyclic compound having a boiling point of 120 ° C. or higher and lower than 270 ° C. include N-methyl-2-pyrrolidone (boiling point: 202 ° C.), 2-pyrrolidone (boiling point: 245 ° C.), and 1,3-dimethyl-2-. Examples thereof include imidazolidinone (boiling point: 220 ° C.) and ε-caprolactum (boiling point: 136 ° C.).

Examples of the sulfur-containing compound having a boiling point of 120 ° C. or higher and lower than 270 ° C. include dimethyl sulfoxide (boiling point: 189 ° C.).

Low boiling point organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C. include polyhydric alcohols having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a boiling point of 120 ° C. or higher and 270 ° C. in terms of the drying property of the image portion after recording. It preferably contains a low boiling organic solvent selected from the group consisting of polyhydric alcohol alkyl ethers below ° C.

The content of the low boiling point organic solvent is preferably in the range of 4% by mass or more and 35% by mass or less, and preferably in the range of 10% by mass or more and 35% by mass or less with respect to the total mass of the ink composition. It is more preferably in the range of 15% by mass or more and 30% by mass or less.
When the content of the low boiling point organic solvent is 4% by mass or more, the dispersibility of the white inorganic pigment can be well maintained. Further, when the content of the low boiling point organic solvent is 35% by mass or less, the drying property after recording becomes better.

-Other ingredients-
In addition to the above components, the ink composition for inkjet recording of the present disclosure includes colorants (pigments, dyes, etc.) other than white inorganic pigments, organic solvents having a boiling point of 270 ° C. or higher, and organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C. Other organic solvents, surfactants, additives and the like can be contained.

(Colorant)
Colorants other than white inorganic pigments include pigments, dyes and the like, and among them, organic pigments or inorganic pigments are preferable.
Examples of the inorganic pigment include a valve handle, aluminum, carbon black and the like.
Examples of the organic pigment include phthalocyanine pigment, insoluble azo pigment, condensed azo pigment, dioxazine pigment, anthraquinone pigment, quinacridone pigment, perylene pigment, perinone pigment, thioindigo pigment and the like.
In addition to the above, examples of other pigments include various fluorescent pigments, metal powder pigments, extender pigments and the like.

(Other organic solvents)
Examples of other organic solvents include ethanol, propanol, butanol, dimethyl ether, ethyl methyl ether, triethylamine, ethyl methyl ketone, 1,4-dioxane, hexane and the like.

(Surfactant)
The ink composition may contain at least one of the surfactants.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants and the like. From the viewpoint of aggregation rate, an anionic surfactant or a nonionic surfactant is preferable.

The surfactant preferably contains an amount capable of adjusting the surface tension of the ink composition to 25 mN / m or more and 40 mN / m or less from the viewpoint of satisfactorily dropping droplets by the inkjet method. Above all, the content of the surfactant is preferably an amount capable of adjusting the surface tension to 27 mN / m to 37 mN / m.

The surfactant can also be used as an antifoaming agent.
As the surfactant, a fluorine-based compound, a silicone-based compound, a chelating agent typified by ethylenediaminetetraacetic acid (EDTA), and the like can also be used.

(Other ingredients)
The ink composition may further contain other additives in addition to the above components.
Other additives include, for example, anti-fading agents, emulsion stabilizers, penetration promoters, ultraviolet absorbers, preservatives, fungicides, pH regulators (neutralizing agents for organic bases, inorganic alkalis, etc.), defoaming agents. Known additives such as agents, viscosity regulators, dispersion stabilizers, rust preventives, chelating agents and the like can be mentioned. These various additives may be added directly after the ink composition is prepared, or may be added at the time of preparing the ink composition.

~ Physical characteristics of ink composition for inkjet recording ~
〔viscosity〕
The viscosity of the ink composition for inkjet recording of the present disclosure depends on the pigment concentration, but is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, and preferably 2 mPa · s or more and less than 13 mPa · s. More preferably, it is 2.5 mPa · s or more and less than 10 mPa · s.
The viscosity is a value measured at 25 ° C. using a VISCOMETER TV-22 type viscometer (manufactured by Toki Sangyo Co., Ltd.).

The surface tension of the ink composition for inkjet recording of the present disclosure is preferably 25 mN / m or more and 40 mN / m or less, and more preferably 27 mN / m or more and 37 mN / m or less.
The surface tension is a value measured at a temperature of 25 ° C. using Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Surface Science Co., Ltd.).

[PH]
The pH of the ink jet recording ink composition of the present disclosure at 25 ° C. is preferably pH 6 to 11, more preferably pH 7 to 10, and even more preferably pH 7 to 9 from the viewpoint of dispersion stability.
The pH is measured at 25 ° C. using a commercially available pH meter.

<Ink set>
The ink set of the present disclosure includes the above-mentioned ink jet recording ink composition of the present disclosure and a colored ink containing a colorant, which is different from the inkjet recording ink composition of the present disclosure.
As described above, the ink composition for inkjet recording of the present disclosure has good whiteness (white hue and density) in the white part of the recorded image, and is therefore used as an ink set in combination with, for example, a chromatic colored ink. If so, the image will be clearer.
Further, while the whiteness is improved, the inkjet suitability as an ink composition for inkjet recording is well maintained, and the ejection property when recording by the inkjet method is excellent. Further, although the composition has a small amount or no high boiling point organic solvent, the ink drying property on the substrate is improved, so that the stickiness of the image is improved even when a non-absorbable medium is used.

-Ink composition for inkjet recording-
Since the details of the ink composition for inkjet recording of the present disclosure are as described above, detailed description thereof will be omitted here.

-Colored ink-
The colored ink in the present disclosure contains at least a colorant, preferably an organic solvent, and may further contain other components such as additives, if necessary.

(Colorant)
Colored inks contain at least one of the colorants.
The colorant includes pigments, dyes and the like, and among them, organic pigments or inorganic pigments are preferable.

Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelate, nitro pigments, nitroso pigments, aniline black, and the like. Of these, azo pigments, polycyclic pigments and the like are more preferable.
Examples of the inorganic pigment include titanium dioxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, carbon black, and the like. Of these, carbon black is particularly preferred.
As the colorant, the colorant described in paragraphs 0996 to 0100 of JP-A-2009-241586 is preferably mentioned.

The content of the colorant is preferably 1% by mass to 25% by mass, more preferably 2% by mass to 20% by mass, still more preferably 2% by mass to 15% by mass, based on the total amount of the coloring ink.

(Dispersant)
The coloring ink may contain at least one of the dispersants for dispersing the colorant.
The dispersant may be either a polymer dispersant or a low-molecular-weight surfactant-type dispersant. Further, the polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.
As the dispersant, for example, the dispersant described in paragraphs 0080 to 0906 of JP-A-2016-145312 is preferably mentioned.

The mixed mass ratio (p: s) of the colorant (p) and the dispersant (s) is preferably in the range of 1: 0.06 to 1: 3, and preferably in the range of 1: 0.125 to 1: 2. It is more preferably 1: 0.125 to 1: 1.5.

For colorants and dispersants, paragraphs 0114 to 0136 of WO 2017/163738 may be referred to.

(Organic solvent)
The colored ink can be arbitrarily selected and contained at least one kind of organic solvent.
When the organic solvent has a boiling point of 270 ° C. or higher, the content of the organic solvent having a boiling point of 270 ° C. or higher in the colored ink is the same as that of the ink composition of the present disclosure described above. It is preferably 5.5% by mass or less with respect to the total mass of the coloring ink.
That is, the colored ink does not contain an organic solvent having a boiling point of 270 ° C. or higher, or the content of the organic solvent having a boiling point of 270 ° C. or higher is more than 0% by mass and 5.5 with respect to the total mass of the colored ink. It is preferably in the range of mass% or less.
When the content of the organic solvent having a boiling point of 270 ° C. or higher is within the above range, the stickiness of the image after the completion of the application of the ink composition (for example, within 30 seconds from the completion of the application of the ink) is further suppressed. Can be done.
Since the details of the organic solvent having a boiling point of 270 ° C. or higher are as described above, detailed description thereof will be omitted.

The colored ink can preferably contain a low boiling point organic solvent selected from organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C., similarly to the above-mentioned inkjet recording ink composition of the present disclosure. By containing a low boiling point organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C., the dispersibility is improved while suppressing the stickiness of the image after the application of the colored ink is completed (for example, within 30 seconds from the completion of the application of the ink). Can be held well.

Examples of the low boiling point organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amide compounds, amine compounds, sulfur-containing compounds and the like.
The organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. is selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C. A low boiling point organic solvent is preferred.
Since the details of the low boiling point organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. are as described above, detailed description thereof will be omitted.

The content of the low boiling point organic solvent in the colored ink is preferably in the range of 4% by mass to 35% by mass with respect to the total mass of the colored ink.
When the content of the low boiling point organic solvent is 4% by mass or more, the pigment dispersibility can be well maintained. Further, when the content of the low boiling point organic solvent is 35% by mass or less, the drying property after recording becomes better.

(Resin particles)
The colored ink may contain at least one of the resin particles.
The resin particles are resin particles that exist separately from the pigment, unlike the polymer dispersant for dispersing the colorant.

As the resin particles, water-insoluble or sparingly water-soluble resin particles are preferable.
"Water-insoluble or sparingly water-soluble" means that the amount of the resin particles dissolved is 15 g or less when the resin particles are dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. Say.
From the viewpoint of improving the ejection property of the colored ink, the dissolved amount of the resin particles is preferably 10 g or less, more preferably 5 g or less, still more preferably 1 g or less. The amount of dissolution is the amount of dissolution when 100% neutralized with sodium hydroxide or acetic acid, depending on the type of salt-forming group of the water-insoluble or sparingly water-soluble resin particles.

For the resin particles, the description in paragraphs 0137 to 0171 of International Publication No. 2017/163738 and paragraphs 0036 to 0081 of JP2010-07721A can be appropriately referred to.

(wax)
The colored ink may contain at least one of waxes.
By containing the wax, the scratch resistance after drying the image (rubbing resistance after drying) is further improved. Examples of the wax include natural wax and synthetic wax.

(Surfactant)
The colored ink may contain at least one of the surfactants.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants and the like. From the viewpoint of aggregation rate, an anionic surfactant or a nonionic surfactant is preferable.

The surfactant preferably contains an amount capable of adjusting the surface tension of the second ink to 25 mN / m or more and 40 mN / m or less from the viewpoint of satisfactorily dropping droplets by the inkjet method. Above all, the content of the surfactant is preferably an amount capable of adjusting the surface tension to 27 mN / m to 37 mN / m.

The surfactant can also be used as an antifoaming agent.
As the surfactant, a fluorine-based compound, a silicone-based compound, a chelating agent typified by ethylenediaminetetraacetic acid (EDTA), and the like can also be used.

(Other ingredients)
The colored ink may further contain other additives in addition to the above components.
Examples of other additives include organic solvents having a boiling point of 270 ° C. or higher and organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C. Known additives such as preservatives, fungicides, pH adjusters (neutralizing agents such as organic bases and inorganic alkalis), defoamers, viscosity regulators, dispersion stabilizers, rust preventives, chelating agents, etc. can be mentioned. .. These various additives may be added directly after the colored ink is prepared, or may be added at the time of preparing the colored ink.

Examples of other organic solvents include ethanol, propanol, butanol, dimethyl ether, ethyl methyl ether, triethylamine, ethyl methyl ketone, 1,4-dioxane, hexane and the like.

The pH of the colored ink is preferably 6 to 10, more preferably 7 to 10.
The viscosity of the colored ink is preferably in the range of 1 mPa · s to 30 mPa · s, more preferably in the range of 1 mPa · s to 20 mPa · s, and 2 mPa · s to 15 mPa from the viewpoint of ejection property when ejected by the inkjet method. The range of s is more preferable, and the range of 2 mPa · s to 10 mPa · s is particularly preferable.
Viscosity means a value measured under the condition of 25 ° C. The viscosity can be measured using, for example, VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

<Image recording method>
The image recording method of the present disclosure records an image on a non-absorbent medium using the above-mentioned ink composition for inkjet recording of the present disclosure or the above-mentioned ink set of the present disclosure.

It is preferable that the image is recorded by ejecting the ink composition for inkjet recording by the inkjet method.
The ejection method of the ink composition in the inkjet method is not particularly limited, and is a known method, for example, a charge control method for ejecting the ink composition using electrostatic attraction, and a drop-on using the vibration pressure of the piezo element. Demand method (pressure pulse method), acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink to eject the ink composition using radiation pressure, and the pressure generated by heating the ink to form bubbles. It may be any of the thermal inkjet (bubble jet (registered trademark)) method utilizing the above.
As the inkjet method, in particular, the method described in JP-A-54-59936 causes a rapid volume change in the ink composition subjected to the action of thermal energy, and the action force due to this state change causes the ink composition. Can be effectively used by the inkjet method of ejecting the ink from the nozzle.
As the inkjet method, the method described in paragraphs 093 to 0105 of JP-A-2003-306623 can also be applied.

The inkjet head method includes a shuttle method in which a short serial head is scanned in the width direction of the recording medium for recording, and a line in which recording elements are arranged in the entire area of one side of the recording medium. There is a line method using a head.
In the line method, the image can be recorded on the entire surface of the recorded medium by scanning the recorded medium in a direction intersecting the arrangement direction of the recording elements. The line system eliminates the need for a carriage system such as a carriage that scans a short head in the shuttle system. Further, in the line method, as compared with the shuttle method, the movement of the carriage and the complicated scanning control with the recorded medium become unnecessary, and only the recorded medium moves. Therefore, according to the line method, the speed of image recording is realized as compared with the shuttle method.

The ink composition is preferably applied using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi, still more preferably 800 dpi). Here, dpi is an abbreviation for dot per inch, and 1 inch (1 inch) is 2.54 cm.

The amount of droplets of the ink composition ejected from the nozzle of the inkjet head is preferably 1 pL (picolitre) to 10 pL, more preferably 1.5 pL to 6 pL, from the viewpoint of obtaining a high-definition image.
Further, from the viewpoint of improving the unevenness of the image and the connection of continuous gradation, it is also effective to discharge a combination of different liquid appropriate amounts.

After applying the ink composition, the applied ink composition may be heated and dried.
Examples of the means for performing heat drying include known heating means such as a heater, known blowing means such as a dryer, and means combining these.
As a method for heat-drying, for example, a method of applying heat with a heater or the like from the side opposite to the surface to which the ink composition of the non-absorbable medium is applied, and an ink composition of the non-absorbent medium are applied. A method of applying warm air or hot air to a surface, a method of applying heat with an infrared heater from the side opposite to the surface to which the ink composition of a non-absorbable medium is applied or the surface to which the ink composition is applied, and a plurality of these. A method in which the above are combined, and the like can be mentioned.

The heating temperature during heat drying is preferably 55 ° C. or higher, more preferably 60 ° C. or higher, and particularly preferably 65 ° C. or higher. The upper limit of the heating temperature is not particularly limited, but examples of the upper limit include 100 ° C., preferably 90 ° C.
The time for heating and drying the ink composition is not particularly limited, but is preferably 3 seconds to 60 seconds, more preferably 5 seconds to 60 seconds, and particularly preferably 10 seconds to 45 seconds.

Further, the non-absorbent medium may be heated in advance before applying the ink composition.
The heating temperature may be appropriately set, but the temperature of the non-absorbent medium is preferably 20 ° C to 50 ° C, more preferably 25 ° C to 40 ° C.

-Non-absorbent medium-
In the image recording method of the present disclosure, an image is recorded on a non-absorbent medium.
Non-absorbent refers to the property that the water absorption rate (mass%, 24 hr.) Is less than 0.2 in ASTM D570 of the ASTM test method.
The non-absorbent medium is not particularly limited, but a resin base material is preferable.
The resin base material is not particularly limited, and examples thereof include a thermoplastic resin base material. Examples of the resin base material include a base material obtained by molding a thermoplastic resin into a sheet or a film. The resin base material is preferably a base material containing polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

The resin base material may be a transparent resin base material, a colored resin base material, or at least a part thereof may be subjected to metal vapor deposition treatment or the like.
Here, "transparency" means that the transmittance of visible light having a wavelength of 400 nm to 700 nm is 80% or more (preferably 90% or more).

The shape of the resin base material is not particularly limited, but it is preferably a sheet-shaped resin base material, and from the viewpoint of productivity of the recording medium, it is a sheet-shaped resin base material capable of forming a roll by winding. Is more preferable.
The thickness of the resin base material is preferably 10 μm to 200 μm, more preferably 10 μm to 100 μm.

The resin base material may be surface-treated from the viewpoint of improving the surface energy.
Examples of the surface treatment include, but are not limited to, corona treatment, plasma treatment, frame treatment, heat treatment, wear treatment, light irradiation treatment (UV treatment), and flame treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. Unless otherwise specified, "part" is based on mass.

In the examples, HLC-8220GPC (manufactured by Tosoh Corporation) was used as the GPC, and TSKgeL Super HZM-H, TSKgeL Super HZ4000, and TSKgeL Super HZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) were used as columns. Three of them were connected in series, and NMP (N-methylpyrrolidone) was used as an eluent. The conditions are as follows: sample concentration is 0.35% by mass, flow velocity is 0.35 ml / min, sample injection amount is 10 μl, measurement temperature is 40 ° C, and RI (Refractive Index) detector (differential refractive index detector). Was performed using. The calibration curve is "Standard sample TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A". It was prepared from 8 samples of "-2500", "A-1000" and "n-propylbenzene".

-Synthesis of dispersed resin-
<Synthesis Example 1: Synthesis of Dispersed Resin P-1>
Dipropylene glycol was added to a three-necked flask equipped with a stirrer and a cooling tube in the same mass as the total amount of the monomers described below, and heated to 85 ° C. under a nitrogen atmosphere.
Solution I mixed 9.1 molar equivalents of stearyl methacrylate, 34.0 molar equivalents of benzyl methacrylate, 31.9 molar equivalents of hydroxyethyl methacrylate, 25.0 molar equivalents of methacrylic acid, and 0.8 molar equivalents of 2-mercaptopropionic acid. 1% by mass of t-butylperoxy-2-ethylhexanoate (Perbutyl O manufactured by Nichiyu Co., Ltd.) is dissolved in 20% by mass of dipropylene glycol based on the total mass of the monomer. The resulting solution II and the solution II were prepared respectively. Solution I was added dropwise to the three-necked flask over 5 hours, and solution II was added dropwise over 5 hours.
After completion of the dropping, the reaction was further carried out for 2 hours, the temperature was raised to 95 ° C., and the mixture was heated and stirred for 3 hours to react all the unreacted monomers. The disappearance of the monomer ^{was confirmed by the nuclear magnetic resonance (1} H-NMR) method.
The obtained reaction solution was heated to 70 ° C., 20.0 molar equivalents of dimethylaminoethanol (dimethylethanolamine) was added as an amine compound, propylene glycol was added and the mixture was stirred, and 30% by mass of the dispersed resin P-1 was added. A solution was obtained.
The constituents of the obtained polymer were ^{confirmed by 1} H-NMR. The weight average molecular weight (Mw) determined by GPC was 22,000.
The mass ratio of each structural unit in the dispersion resin P-1 is the structural unit derived from stearyl methacrylate (the structural unit represented by the formula 1) / the structural unit derived from benzyl methacrylate / the structural unit derived from hydroxyethyl methacrylate / methacrylic acid. The constituent unit of origin was 20/39/27/14. However, the above mass ratio is a value that does not include dimethylaminoethanol.
The numerical value at the lower right of the parentheses of each of the following structural units is the molar ratio.

<Synthesis Example 2: Synthesis of Dispersed Resin P-2>
Dispersion was carried out in the same manner as the synthesis of the dispersion resin P-1 except that the amount of each monomer used was changed so that the mass ratio of the structural unit derived from stearyl methacrylate to the structural unit derived from benzyl methacrylate was 15/44. Resin P-2 was synthesized. The weight average molecular weight (Mw) determined by GPC was 22,000.

<Synthesis Example 3: Synthesis of Dispersed Resin P-3>
Dispersion was carried out in the same manner as the synthesis of the dispersion resin P-1 except that the amount of each monomer used was changed so that the mass ratio of the structural unit derived from stearyl methacrylate to the structural unit derived from benzyl methacrylate was 45/14. Resin P-3 was synthesized. The weight average molecular weight (Mw) determined by GPC was 22,000.

<Synthesis Examples 4 to 6: Synthesis of Dispersed Resins P-4 to P-6>
Cyclohexyl methacrylate (CyHMA (constituent unit represented by the formula 1); dispersion resin P-4), n-octyl methacrylate (OctMA (constituent unit represented by the formula 1); dispersion resin P-5) instead of stearyl methacrylate. , Or 2-Ethylhexyl methacrylate (2-EHMA (constituent unit represented by the formula 1); dispersion resin P-6) was used in the same manner as in the synthesis of the dispersion resin P-1, except that equimolars of each were used. P-4 to P-6 were synthesized respectively. The structural units derived from each monomer are as follows. The weight average molecular weight (Mw) determined by GPC was 22,000.

<Synthesis Examples 7-9: Synthesis of Dispersed Resins P-7 to P-9>
Equal moles of phenoxyethyl methacrylate (PEA; dispersion resin P-7), 2-phenoxybenzyl acrylate (POB-A; dispersion resin P-8), or styrene (St; dispersion resin P-9) are used in place of benzyl methacrylate. Except for the use, the same procedure as for the synthesis of the dispersed resin P-1 was carried out, and the dispersed resins P-7 to P-9 were synthesized respectively. The structural units derived from each monomer are as follows. The weight average molecular weight (Mw) determined by GPC was 22,000.

<Synthesis Examples 10-12: Synthesis of Dispersed Resins P-10 to P-12>
N, N-dimethylacrylamide (DMAAm; dispersion resin P-10), methoxypolyethyleneethylene glycol methacrylate (PME; dispersion resin P-11), or diacetone acrylamide (DAAAm; dispersion resin P-12) instead of hydroxyethyl methacrylate. Was used in the same manner as in the synthesis of the dispersed resin P-1, except that the mass ratio of the corresponding constituent units was the same as that of the dispersed resin P-1, and the dispersed resins P-10 to P-12 were used, respectively. Synthesized. The structural units derived from each monomer are as follows. The weight average molecular weight (Mw) determined by GPC was 22,000.

-Preparation of resin particles A-
293 g of methyl ethyl ketone was placed in a 2-liter three-necked flask (hereinafter, also referred to as “reaction vessel”) equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, and the temperature was raised to 80 ° C. Next, while maintaining the temperature inside the reaction vessel at 80 ° C., here, 165.7 g of methyl methacrylate (manufactured by Mitsubishi Gas Chemical Industries, Ltd.), 63.7 g of isobornyl methacrylate (manufactured by Kyoeisha Chemical Industries, Ltd.), and methacrylic acid (Mitsubishi). A mixed solution consisting of 25.5 g (manufactured by Gas Chemical Co., Ltd.), 48 g of methyl ethyl ketone, and 1.25 g of "V-601" (manufactured by Wako Pure Chemical Industries, Ltd., polymerization initiator) is rapidly added dropwise in 2 hours. Dropped in. After the dropping was completed, a solution prepared by mixing 0.60 g of (1) "V-601" and 5.0 g of methyl ethyl ketone was added, and the mixture was further stirred for 2 hours. Then, the step (1) was repeated 4 times, a solution containing 0.60 g of "V-601" and 5.0 g of methyl ethyl ketone was added, and the mixture was stirred for 3 hours.
From the above, a polymer solution which is a solution of a methyl methacrylate / isobornyl methacrylate / methacrylic acid (= 65/25/10 [mass ratio]) copolymer was obtained.
The weight average molecular weight (Mw) of the copolymer in the polymer solution was 72,000, and the acid value was 62.9 mgKOH / g.
The acid value was measured according to the method described in Japanese Industrial Standards (JIS K0070: 1992). The weight average molecular weight was measured by GPC by the method described above.

Next, 588.2 g of the polymer solution was weighed in the reaction vessel, 165 g of isopropanol and 120.8 ml of a 1 mol / L sodium hydroxide (NaOH) aqueous solution were added, and the temperature inside the reaction vessel was raised to 80 ° C. Next, 718.0 g of distilled water was added dropwise to the reaction vessel at a rate of 20 ml / min to disperse the water. Then, the temperature inside the reaction vessel was kept at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the pressure inside the reaction vessel was reduced to add isopropanol, methyl ethyl ketone, and distilled water. The amount was 913.7 g, which was distilled off. In this way, an aqueous dispersion (emulsion) of the resin particles A having a solid content concentration of 23.2% by mass was obtained.
The resin constituting the resin particles A is a neutralized product of a copolymer having the following structure (that is, a copolymer of methyl methacrylate / isobornyl methacrylate / methacrylic acid (= 65/25/10 [mass ratio])). ..
The number at the bottom right of each structural unit in the structure below represents the mass ratio.

(Example 101)
-Preparation of TiO _{2 dispersion-}
Using a ready-mill model LSG-4U-08 (manufactured by IMEX), a TiO ₂ dispersion was prepared as follows. That is,
In a container made of zirconia, _{45 parts by mass of titanium dioxide (TiO 2} ; average primary particle diameter: 210 nm, trade name: PF-690, manufactured by Ishihara Sangyo Co., Ltd .; white inorganic pigment), the dispersion resin P- obtained in Synthesis Example 1 15 parts by mass of a 30% by mass solution of 1 and 40 parts by mass of ultrapure water were added. Further, 40 parts by mass of 0.5 mmφ zirconia beads (manufactured by TORAY, Trecerum beads) were added, and the mixture was lightly mixed with a spatula. The mixture was placed in a zirconia container in a ball mill and dispersed at a rotation speed of 1000 rpm (revolutions per minute) for 5 hours. After completion of the dispersion, the beads were removed by filtration through a filter cloth to prepare _{a TiO 2} dispersion, which is an aqueous pigment dispersion having _{a TiO 2 concentration of 45% by mass.}

-Preparation of water-based ink-
Each component shown in Table 2 was mixed to prepare an aqueous ink (ink composition for inkjet recording).

The average primary particle size of titanium dioxide in the water-based ink was measured using a transmission electron microscope 1200EX (TEM; manufactured by JEOL Ltd.).
Specifically, from an image magnified 100,000 times by TEM after dropping 1,000-fold diluted water-based ink onto a Cu200 mesh (manufactured by JEOL Ltd.) to which a carbon film is attached and drying it. The equivalent circle diameters of 300 independent particles that did not overlap were measured, and the measured values were averaged to obtain the average particle size.

The details of the components shown in Table 2 above are as follows.
PVP K15: Polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.)
Orfin E1010: Acetylene glycol-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd.)
Orfin E1020: Acetylene glycol-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd.)
Snowtex XS: Colloidal silica (manufactured by Nissan Chemical Industries, Ltd.); Solid content concentration 20.0% by mass)
BYK-024: Silicone defoamer (manufactured by Big Chemie Japan, solid content concentration 15.0% by mass)
Capstone FS-63: Fluorosurfactant (manufactured by DuPont, solid content concentration 35.0% by mass)

-Image recording-
Using the water-based ink obtained above, a biaxially stretched polypropylene (OPP) film (thickness 40 μm, surface treatment: corona discharge treatment, manufactured by Futamura Chemical Co., Ltd., abbreviation: OPP), which is a non-absorbent medium, is used. The image was recorded as follows.
(1) Recording method Using an inkjet recording device equipped with a transport system for transporting the substrate and an inkjet head, the above-mentioned water-based ink is ejected onto the corona discharge-treated surface of the OPP film under the following conditions by a single-pass method. A white solid image was recorded.
(2) Recording conditions Inkjet head: 1200 dpi / 20 inch width Piezo full line head Ink ejection amount: 4.0 pL
Drive frequency: 30 kHz (base material transfer speed: 635 mm / sec)

-Evaluation-
The following evaluations were made when recording images using the above water-based ink. The evaluation results are shown in Table 3.

(1) Dischargeability After recording a white solid image (image size: 50 mm × 50 mm) with a recording duty of 100% under the above-mentioned recording method and recording conditions, 30 under environmental conditions of a temperature of 25 ° C. and a relative humidity of 50%. The inkjet recording device was stopped for a minute, and the recording head was left exposed to the atmosphere. After 30 minutes had passed since the stop, the inkjet recording device was started and the nozzle check pattern was output. The output nozzle check pattern was visually observed, and the ejection performance was evaluated according to the following evaluation criteria. If the number of ejection failure nozzles is 6 or less, it is within the practically acceptable range.
The recording duty of 100% is recorded under the condition that one drop of water-based ink is applied to a unit area (1 pixel) of 1/1200 inch × 1/1200 inch with a resolution of 1200 dpi × 1200 dpi with a dropping amount of about 4.8 pL. Defined as an image.
<Evaluation criteria>
A: The number of ejection failure nozzles is 2 or less.
B: There are 3 to 4 ejection failure nozzles.
C: There are 5 to 6 ejection failure nozzles.
D: The number of ejection failure nozzles is 7 to 8 or more.
E: The number of ejection failure nozzles is 9 or more.

(2) Whiteness of white part Thickness: A 12 μm polyethylene terephthalate (PET) substrate (FE2001, manufactured by Futamura Chemical Co., Ltd.) is coated with the above-mentioned water-based ink at different film thicknesses, dried and solidified. Images were recorded and used as evaluation materials. The evaluation material was held over a fluorescent lamp (30 W), and the film thickness at which the fluorescent lamp became invisible was determined through the evaluation material, which was used as an index for evaluating the whiteness of the water-based ink.
The evaluation was performed with the distance between the evaluator and the evaluation image being 20 cm and the distance between the evaluation image and the fluorescent lamp tube being 2 m.
<Evaluation criteria>
A: When the thickness of the solid image is 1 μm, the fluorescent lamp tube cannot be visually recognized.
B: When the thickness of the solid image is 2 μm, the fluorescent lamp tube cannot be visually recognized.
C: When the thickness of the solid image is 3 μm, the fluorescent lamp tube cannot be visually recognized.
D: The fluorescent lamp tube cannot be visually recognized when the thickness of the solid image is 4 μm.
E: The fluorescent lamp tube can be visually recognized even if the thickness of the solid image exceeds 4 μm.

(3) Image stickiness A white solid image (image size: 50 mm × 50 mm) with a recording duty of 100% was recorded under the above-mentioned recording method and recording conditions.
After a certain period of time (10 seconds, 20 seconds, 30 seconds, or 40 seconds) has elapsed from the completion of applying the water-based ink, the recorded solid image is subjected to the conditions of a temperature of 25 ° C. and a relative humidity of 50%. It was touched by hand and evaluated according to the evaluation criteria shown below.
<Evaluation criteria>
A: The recording surface does not peel off even if the solid image is touched 10 seconds after the application of the water-based ink is completed.
B: When the solid image is touched 10 seconds after the application of the water-based ink is completed, the recording surface is peeled off, but when the solid image is touched 20 seconds after the application of the water-based ink is completed, the recording surface is peeled off. No.
C: When the solid image is touched 20 seconds after the application of the water-based ink is completed, the recording surface is peeled off, but when the solid image is touched 30 seconds after the application of the water-based ink is completed, the recording surface is peeled off. No.
D: When the solid image is touched 30 seconds after the application of the water-based ink is completed, the recording surface is peeled off, but when the solid image is touched 40 seconds after the application of the water-based ink is completed, the recording surface is peeled off. No.
E: Even if the solid image is touched 40 seconds after the application of the water-based ink is completed, the recording surface is peeled off.

(Examples 102 to 105)
In Example 101, a water-based ink was prepared and evaluated in the same manner as in Example 101 except that the average primary particle size of titanium dioxide was changed. The evaluation results are shown in Table 3.
The titanium dioxide used here is as follows.
Titanium dioxide with an average primary particle diameter of 250 nm: R-930, manufactured by Ishihara Sangyo Co., Ltd. Titanium dioxide with an average primary particle diameter of 300 nm: JR-301, manufactured by TAYCA Corporation Titanium dioxide with an average primary particle diameter of 350 nm: TY-150, Ishihara Sangyo Titanium dioxide with an average primary particle diameter of 400 nm: TY-50, manufactured by Ishihara Sangyo Co., Ltd.

(Examples 106 and 110 to 115)
In Example 102, a water-based ink was prepared and evaluated in the same manner as in Example 102, except that the type of the organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. was changed. The evaluation results are shown in Table 3.

(Examples 107 to 109)
In Example 102, a water-based ink was prepared and evaluated in the same manner as in Example 102, except that an organic solvent having a boiling point of 270 ° C. or higher was used as shown in Table 3. The evaluation results are shown in Table 3.

(Examples 116 to 126)
In Example 102, a water-based ink was prepared and evaluated in the same manner as in Example 102, except that the dispersion resin P1 was replaced with the dispersion resin shown in Table 3. The evaluation results are shown in Table 3.

(Example 127)
In Example 102, a water-based ink was prepared and evaluated in the same manner as in Example 102 except that propylene glycol was replaced with diethylene glycol monomethyl ether (boiling point: 105 ° C.). The evaluation results are shown in Table 3.

(Comparative Examples 101-102)
In Example 101, a water-based ink was prepared and evaluated in the same manner as in Example 101 except that the average primary particle size of titanium dioxide was changed. The evaluation results are shown in Table 3.
The titanium dioxide used here is as follows.
Titanium dioxide with an average primary particle diameter of 100 nm: MPT-141, manufactured by Ishihara Sangyo Co., Ltd. Titanium dioxide with an average primary particle diameter of 450 nm: TY-300, manufactured by Ishihara Sangyo Co., Ltd.

(Comparative Example 103)
In Example 102, a water-based ink was prepared and evaluated in the same manner as in Example 102 except that 10 parts by mass of glycerin (organic solvent having a boiling point of 270 ° C. or higher) was used. The evaluation results are shown in Table 3.

(Comparative Example 104)
In Example 102, a water-based ink was prepared in the same manner as in Example 102, except that the dispersion resin P1 was replaced with the following dispersion resin P20 (weight average molecular weight (Mw) = 22,000 determined by GPC). Evaluation was performed. The evaluation results are shown in Table 3.

As shown in Table 3, in the water-based inks of each example, the white color density in the white part in the image was secured, and the whiteness was excellent. In addition, the suitability for inkjet is well maintained, the ejection property is excellent when recorded by the inkjet method, and the composition is such that the content of the organic solvent having a high boiling point is low or not contained, but the ink drying property is improved. Even when a non-absorbent medium was used, the stickiness of the image was improved.

As is clear from the results of Examples 102 to 103, when the particle size of titanium dioxide is in the range of 250 nm to 300 nm, the ejection property and the whiteness and stickiness in the image can be effectively improved in a well-balanced manner.
In Examples 107 to 109, a high boiling point organic solvent having a boiling point of 270 ° C. or higher is further used, but if the content is in the range of 5.5% by mass or less, the ejection property and the whiteness and stickiness in the image are used. Was not significantly impaired.

Further, as shown in Example 118-120, the dispersion resin, the number of carbon atoms in the alkyl group R ³ in the structural unit represented by Formula 1 is greater (preferably at 10 or more carbon atoms), titanium dioxide Although the volume average particle size of the particle size did not change, the ejection property was further improved.
As can be seen from the result of Example 123 in which the (meth) acrylate having an aromatic ring used in Example 1 was replaced with styrene, when the dispersed resin has a structural unit derived from the (meth) acrylate having an aromatic ring, it is discharged. The sex can be further improved. Further, as can be seen from the results of Examples 124 to 126 in which the (meth) acrylate (hydroxyethyl methacrylate) having a hydroxyl group used in Example 101 was replaced with another monomer having no hydroxyl group, the dispersed resin has a hydroxyl group ( Having a structural unit derived from a meta) acrylate can further improve the ejection property.

On the other hand, in Comparative Example 101 using titanium dioxide having an average primary particle diameter of less than 150 nm, the white color density in the white portion in the image was insufficient, and the whiteness was inferior. On the contrary, in Comparative Example 102 using titanium dioxide having an average primary particle diameter of more than 400 nm, the particle size was too large to maintain good ejection properties.
Further, in Comparative Example 103 having a high content ratio of the high boiling point organic solvent having a boiling point of 270 ° C. or higher, the drying property was inferior and the image became sticky.
Further, as shown in Comparative Example 104, the dispersed resin having no structural unit represented by the formula 1 has good ejection performance when ejecting ink using titanium dioxide having a relatively large particle size by the inkjet method. It was difficult to hold in.

(Example 201)
In Example 101, titanium dioxide is replaced with Pigment Yellow 74 (yellow pigment), Pigment Red 122 (magenta pigment), or Pigment Blue 15: 3 (cyan pigment), respectively, with a yellow water-based ink Y and a magenta water-based ink. Three color inks, M and cyan water-based ink C, were prepared.
Then, the prepared three-color ink and the white water-based ink produced in Example 101 (hereinafter referred to as water-based ink W) were used to form an ink set 201.

Subsequently, the water-based ink C, the water-based ink M, the water-based ink Y, and the water-based ink were used under the same recording method and recording conditions as in the 101st embodiment except that the inkjet recording apparatus was loaded with the three color inks and the water-based ink W. A white solid image on a biaxially stretched polypropylene (OPP) film by ejecting ink W, a primary color solid image in which a yellow color, a magenta color, or a cyan color is added on a white solid image, and a white solid image. A pattern image including a secondary color solid image in which two colors selected from yellow, magenta, and cyan were superimposed on the image was recorded.
Then, the ejection property at the time of recording, the whiteness of the white portion of the recorded image, and the stickiness of the image were evaluated.

As a result of the evaluation, as in Example 101, the color density of white in the white part in the image was secured, and the whiteness was excellent. Therefore, the white part in the image is represented by a good white color, and the coloring of the colored part by the color ink becomes vivid by that amount, and a clear image is obtained. In addition, the suitability for inkjet is well maintained, the ejection property is excellent when recorded by the inkjet method, and a non-absorbable medium is used although the composition has a low or no content of an organic solvent having a high boiling point. Even if it was, the stickiness of the image was improved.

The ink jet recording ink composition and ink set and the image recording method of the present disclosure can be widely applied in applications for recording an image on an ink non-absorbent medium (for example, a glass substrate or a plastic substrate). .. Specific examples of applications include packaging, food storage, agriculture, civil engineering, fishing, automobile interior / exterior, ships, daily necessities, building material interior / exterior, housing equipment, medical / medical equipment, pharmaceuticals, etc. It can be used for image recording in various applications such as home appliances, furniture, stationery / office supplies, sales promotion, commercial use, electrical and electronic industry use, clothing use, and decorative use.

For packaging, it can be applied to image recording on packaging bags. The form of the packaging bag is two-way seal, three-way seal, four-way seal, pillow seal, standing pouch, envelope sticker, gusset, fusing seal, tube, caramel packaging, overhold, fin seal, manju packaging, twist, rocket, etc. The form is mentioned.
In addition to the wrapping bag, it can also be applied to a wrapping body (for example, a burger wrap for food), a wrapping paper, a wrapping sheet, a wrapping film, a decorative paper for building materials, and the like that wrap the contents.
It can also be applied to image recording on a packaging container. Examples of the packaging container include a container for food packaging, a tray for food packaging, a cup, a plate, a bottle, a tetra pack, a gable top, a brick, a carton can, and a cake box.
Further, it can be applied to the manufacture of a label on which an image is recorded. Labels include labels for glass bottles, labels for metal cans, labels for plastic bottles, and labels for other containers. Examples of the form of the label include a sticking label, a body-wrapping label, and the like.
In addition to the above, it is also suitable for manufacturing a lid material on which an image is recorded. Examples of the lid material include a lid material capable of forming a closed container by being in close contact with a bottomed tubular container (for example, a plastic container for food or daily necessities, a glass container, a metal can, a paper can, etc.). ..

The disclosure of Japanese patent application 2018-067100, filed March 30, 2018, is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated by reference herein.

Claims (13)

water and,
White inorganic pigments with an average primary particle size of 150 nm to 400 nm,
A dispersion resin containing a structural unit represented by the following formula 1 and a structural unit derived from (meth) acrylate having an aromatic ring.
An ink composition for inkjet recording, wherein the content of the organic solvent having a boiling point of 270 ° C. or higher is 5.5% by mass or less with respect to the total mass of the ink.

In Equation 1, R ¹ represents a hydrogen atom or a methyl group, L ² represents −C (= O) O−, −OC (= O) −, or −C (= O) NR ²⁻ . R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 6 or more carbon atoms. Further, it contains at least one low boiling point organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C.
The ink composition for inkjet recording according to claim 1, wherein the content of the low boiling point organic solvent is 4% by mass or more and 35% by mass or less with respect to the total mass of the ink. The ink composition for inkjet recording according to claim 1 or 2, wherein the dispersed resin is an acrylic resin. The ink jet recording ink composition according to any one of claims 1 to ³ , wherein R 3 is an alkyl group having 8 to 22 carbon atoms in the formula 1. The ink composition for inkjet recording according to claim 4, wherein R ³ is an alkyl group having 15 to 22 carbon atoms. The ink composition for inkjet recording according to any one of claims 1 to 5 , wherein the dispersed resin further contains a structural unit derived from a (meth) acrylate having a hydroxyl group. The dispersion resin further contains a structural unit derived from a compound having at least one structure selected from the group consisting of a hydroxyl group, an amino group and a polyalkylene oxy structure, and
In the formula 1, the R ³ The ink composition for inkjet recording according to any one of claims 1 to 5, wherein the ink composition is an alkyl group having 15 to 22 carbon atoms. The dispersed resin further contains a structural unit derived from a (meth) acrylate having a hydroxyl group, and
In the formula 1, the R ³ The ink composition for inkjet recording according to any one of claims 1 to 5, wherein the ink composition is an alkyl group having 15 to 22 carbon atoms. The ink composition for inkjet recording according to any one of claims 1 to 8.
A colored ink containing a colorant, which is different from the ink composition for inkjet recording,
Ink set with. The ink set according to claim 9 , wherein the content of the organic solvent having a boiling point of 270 ° C. or higher in the colored ink is 5.5% by mass or less with respect to the total mass of the colored ink. The colored ink further contains a low boiling organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or higher and lower than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or higher and lower than 270 ° C. ,
The ink set according to claim 9 or 10 , wherein the content of the low boiling point organic solvent is 4% by mass to 35% by mass with respect to the total mass of the colored ink. An image is printed on a non-absorbent medium using the ink jet recording ink composition according to any one of claims 1 to 8 or the ink set according to any one of claims 9 to 11. Image recording method to record. The image recording method according to claim 12 , wherein the image is recorded by ejecting an ink composition for inkjet recording by an inkjet method.