WO2019187665A1 - Ink composition for inkjet recording, ink set, and image recording method - Google Patents

Abstract

An ink composition for inkjet recording is provided which contains water, a white inorganic pigment with an average primary particle diameter of 150-400 nm, and a dispersion resin having a constituent unit represented in formula 1, wherein the content of organic solvent with a boiling point of greater than or equal to 270°C is less than or equal to 5.5 mass% with respect to the total ink mass; an ink set and an image recording method are also provided. R1 represents a hydrogen atom or a methyl group, L2 represents -C(=O)O-, -OC(=O)- or -C(=O)NR2-, R2 represents a hydrogen atom or an alkyl group of 1 to 6 carbons, and R3 represents an alkyl group of 6 or more carbons.

Description

Ink composition for ink jet recording, ink set, and image recording method

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

Conventionally, recording of images on various materials is expected, and an inkjet method has been proposed as one of the recording methods therefor. The ink-jet method has been used in various fields because it can be recorded by attaching droplets to a recording medium using a simple apparatus.

In general, white paper or the like is often used as a recording medium on which an image is recorded, but in recent years, the recording medium differs depending on the use mode, and recording of an image on a material that is not necessarily a white background is possible. It is desired. When an image is recorded on a material that is not a white background, the visibility and clearness of the recorded image may be impaired due to coloring of the base or the back side of the material being seen through.
Further, in order to improve the color quality of the entire image, it is indispensable to make the white portion in the image good white.

In order to improve the above situation, the use of white ink has been proposed. The purpose of expressing white color and the purpose of improving the visibility and the sharpness of the image have been achieved by using a white ink that is not a chromatic color with a chromatic colored ink.
As the white material used for the white ink, inorganic pigments are widely known from the viewpoint of concealing properties. For example, titanium dioxide has been widely used.
On the other hand, since inorganic pigments such as titanium dioxide generally have a high specific gravity, a technique for suppressing the uneven distribution of the inorganic pigment in the ink due to aggregation or sedimentation of the inorganic pigment in the white ink by using a dispersant has been studied.

As technologies related to the above, water-based inkjet inks containing water, titanium oxide having an average particle diameter of 250 nm to 300 nm, a pigment dispersant having an acid value of 5 mgKOH / g or more, and an organic solvent are disclosed (for example, JP, 2015-124348, A).
In addition, titanium oxide, a structural unit derived from an anionic group-containing monomer and a structural unit derived from a specific polyalkylene glycol (meth) acrylate, a pigment dispersant having an acid value of 100 mgKOH / g or more, and further organic An aqueous ink for ink-jet recording using glycerin having a boiling point of 290 ° C. as a solvent has been disclosed (for example, see JP-A-2017-39922).

Further, a black ink is disclosed in which an aqueous black pigment dispersion K-1 using carbon black and a polymer dispersant is mixed with an organic solvent such as glycerin (see, for example, JP-A-2016-69487). In addition, there is a disclosure relating to an inkjet pigment ink containing an organic pigment such as yellow and a pigment dispersion resin (see, for example, JP-A-2012-188582).

As described above, various techniques for producing an ink by mixing a pigment and a dispersant for dispersing the pigment have been studied.
A white inorganic pigment such as titanium dioxide is likely to obtain a good white color, but has a property that the particle size is relatively large and the specific gravity is also large. For this reason, inorganic pigments such as titanium dioxide, unlike other pigments such as organic pigments, tend to settle or aggregate in the prepared ink, so that ink containing titanium dioxide or the like is ejected by the inkjet method. It is essential to increase the dispersibility of titanium dioxide and the like.
Further, as another method for improving the ink ejection property by the ink jet method, it is conceivable to use an organic solvent having a high boiling point to stabilize the ink composition and suppress the increase in viscosity. On the other hand, in a 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 when the recorded material on which the image is recorded is accumulated or stored in an overlapping manner, the recorded materials easily stick to each other via the image, and the handling property is improved. It may be damaged.

Among the above-described conventional techniques, the composition containing titanium dioxide disclosed in JP-A-2015-124348 and JP-A-2017-39922 discloses ejection properties when ejected by an inkjet method and stickiness of a recorded image. It is guessed that it is inferior.
In addition, 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 pigment, and exhibit good whiteness. However, this is not a technique planned to simultaneously achieve the effect that a pigment having a large particle size and specific gravity is well dispersed and an image with little stickiness can be obtained after recording.

The present disclosure has been made in view of the above.
A problem to be solved by an embodiment of the present invention is to improve whiteness of a white portion in an image by using a white inorganic pigment having a relatively large particle size, and to improve ink discharge properties and stickiness of a recorded image. An object of the present invention is to provide an improved ink composition for ink jet recording.
The problem to be solved by other embodiments of the present invention is to improve the whiteness of a white portion in an image by using a white inorganic pigment having a relatively large particle size, and to improve the ink discharge properties and the stickiness of a recorded image. Is to provide an improved ink set and image recording method.

Specific means for solving the problems include the following aspects.
<1> containing an organic solvent having a boiling point of 270 ° C. or higher, comprising water, a white inorganic pigment having an average primary particle diameter of 150 nm to 400 nm, and a dispersion resin having a structural unit represented by the following formula 1. It is an ink composition for inkjet recording whose quantity is 5.5 mass% or less with respect to 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 organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or more and less than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or more and less than 270 ° C. The ink composition for ink jet recording according to <1>, wherein the content of the low-boiling organic solvent is 4% by mass or more and 35% by mass or less with respect to the total mass of the ink.
<3> The dispersion resin is the ink composition for ink jet recording according to <1> or <2>, which is an acrylic resin.
<4> The ink composition for ink jet recording according to any one of <1> to <3>, wherein R ³ is an alkyl group having 8 to 22 carbon atoms in Formula 1.
<5> The ink composition for ink jet 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 ink jet recording according to any one of <1> to <5>, further including a structural unit derived from (meth) acrylate having an aromatic ring.
<7> The ink composition for ink jet recording according to any one of <1> to <6>, wherein the dispersion resin further includes a structural unit derived from a (meth) acrylate having a hydroxyl group.

<8> An ink set comprising the ink composition for ink jet recording according to any one of <1> to <7> and a color ink containing a colorant different from the ink composition for ink jet recording. .
<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 low-boiling point organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or more and less than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or more and less than 270 ° C. The ink set according to <8> or <9>, wherein the content of the low-boiling 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 ink composition for ink jet recording 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 the image is recorded by discharging an ink composition for ink jet recording by an ink jet method.

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

Hereinafter, the ink composition for inkjet recording of the present disclosure, the ink set of the present disclosure, and the image recording method will be described in detail. The following description may be made based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.

In the present disclosure, “˜” indicating a numerical range is used in a sense including numerical values described before and after the numerical value as a lower limit value and an upper limit value.
In the numerical ranges 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 another numerical description. . Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In addition, in the notation of groups (atomic groups) in the present disclosure, the notation that does not indicate substitution and non-substitution includes those not having a substituent and 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 not limited to an independent process, and even if it cannot be clearly distinguished from other processes, it is included in this term if the intended purpose of the process is achieved. It is.
In the present disclosure, “mass%” and “wt%” are synonymous, and “part by mass” and “part by weight” are synonymous.
Furthermore, in the present disclosure, the amount of each component in the composition is the total amount of the plurality of corresponding substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. Means.
Furthermore, 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 diameter of 150 nm to 400 nm, and Formula 1 shown below. And the content of the organic solvent having a boiling point of 270 ° C. or higher in a range of 5.5% by mass or less with respect to the total mass of the ink. In addition, the ink composition for inkjet recording of the present disclosure preferably includes an organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C., and may further include other components as necessary. Good.

Inorganic pigments such as titanium dioxide have been conventionally used as white pigments because they exhibit a white color. In order to enhance whiteness, white pigments having a large particle size are advantageous. However, when trying to secure good whiteness using an inorganic pigment having a large particle size, the inorganic pigment such as titanium dioxide has a larger specific gravity than the organic pigment, and thus the inorganic pigment precipitates or aggregates in the ink. It is easy and is disadvantageous when ejected by the ink jet method.
In order to eject an ink containing an inorganic pigment such as titanium dioxide by the ink jet method, it is considered indispensable to increase the dispersibility of the inorganic pigment having a relatively large specific gravity.
On the other hand, there is a technique using an organic solvent having a high boiling point as another method for improving the ink ejection property by the ink jet method. Since an organic solvent having a high boiling point is difficult to volatilize easily, the ink composition can be stabilized and the thickening can be suppressed. 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 when the recorded material on which the image is recorded is accumulated or stored in an overlapping manner, the recorded materials easily stick to each other via the image, and the handling property is improved. It may be seriously damaged.

The composition containing titanium dioxide disclosed in the above-mentioned JP-A-2015-124348 and JP-A-2017-39922 is inferior in ejection property when ejected by an ink jet method, and also in terms of stickiness of a recorded image. Inferred to be inferior.
In addition, 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 with a high specific gravity are used. The discharge performance is not considered. For this reason, while using an inorganic pigment having a relatively large particle size to achieve good whiteness, the ejection performance of ink containing a pigment having a large specific gravity in accordance with the particle size is improved, and the image stickiness after recording is increased. It is considered difficult to achieve the improvement effect.

In view of the above, the present disclosure realizes a good white density using a relatively large white inorganic pigment (preferably titanium dioxide) having an average primary particle size of 150 nm or more, while containing a high boiling point organic solvent. By reducing or not containing the ink, the drying property of the ink deposited on the non-absorbing medium is improved, and the stickiness of the image recorded on the non-absorbing medium is improved. And, it is disadvantageous to increase viscosity by changing composition by reducing the content of organic solvent with high boiling point, and dischargeability that is disadvantageous because the specific gravity increases by using white inorganic pigment with large particle size In order to improve the problem of ejection properties, a dispersion resin having a specific structure is selectively contained.
That is, in the present disclosure, there is a problem specific to a case where a white inorganic pigment having a large particle size and a high specific gravity is included, and a composition using a volatile organic solvent with little or no high boiling point organic solvent is used. It is intended to improve the ejection properties and to make the ink ejection properties, whiteness, and image stickiness parallel.
In the present disclosure, while ensuring a good white density and improving the whiteness of the white portion, the suitability of ink jet as an ink composition for ink jet recording is also maintained well, and the ejectability during ink jet recording is excellent. The stickiness of the image when using an absorbent substrate is improved.

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

-White inorganic pigment-
The ink composition for inkjet recording of the present disclosure contains at least one white inorganic pigment having an average primary particle diameter 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 concealability with respect to the recording material and can form a good white background.

Examples of white inorganic pigments 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 diameter of the white inorganic pigment is 150 nm to 400 nm.
When the average primary particle diameter is 150 nm or more, the concealability with respect to the recording material is high, and a good white background can be formed. In addition, when the average primary particle diameter is 400 nm or less, the ejectability when ejected by the ink jet method is excellent.
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 diameter of the white inorganic pigment is a value measured using a transmission electron microscope (TEM). For the measurement, a transmission electron microscope 1200EX manufactured by JEOL Ltd. can be used.
Specifically, the ink composition diluted 1,000 times was dropped on Cu200 mesh (manufactured by JEOL Ltd.) with a carbon film and dried, and then the image was magnified 100,000 times with TEM. 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 diameter.

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, with respect to the total mass of the ink composition. Part by mass 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 concealability is excellent. Further, when the content of the white inorganic pigment is 20 parts by mass or less, mechanical strength, stability over time, durability, adhesion to a recording medium, and the like are further improved.

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

The specific resin has at least a structural unit represented by Formula 1 (hereinafter, also referred to as “structural 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.

[Structural unit a-1]
The structural unit a-1 is a structural unit represented by the above formula 1.
In Formula 1, R ¹ is preferably a methyl group.
In Formula 1, L ² represents —C (═O) O—, —OC (═O) —, or —C (═O) NR ² —, and —C (═O) O—, or —C (═O) NR ² — is preferable, and —C (═O) O— is more preferable.
R ² is preferably a hydrogen atom.
The description of —C (═O) O— indicates that the carbon atom in —C (═O) O— is directly bonded to the carbon atom to which R ^{1 in} Formula ¹ is bonded. The description of —OC (═O) — indicates that the carbon atom in —OC (═O) — is directly bonded to the carbon atom to which R ^{1 in} Formula ¹ is 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, from the viewpoint of reducing sedimentation inhibition, aggregation inhibition performance, and average particle size. An alkyl group having 12 to 22 carbon atoms is more preferable, an alkyl group having 15 to 22 carbon atoms is more preferable, and an alkyl group having 15 to 18 carbon atoms is particularly preferable. The alkyl group may be linear or branched, and may have a ring structure.

Among the above, the structural unit a-1 is preferably 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 more preferably an acrylic resin in which the structural unit a-1 is a structural 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 Formula 1 is —C (═O) O—, and further, when L ² is —C (═O) O—. It is preferable that it is an acrylic resin whose content rate of the structural unit represented by Formula 1 is 5 mass% or more with respect to all the structural units.

The content of the structural unit a-1 is 10% by mass to 40% by mass with respect to the total mass of the specific resin from the viewpoint of reducing the sedimentation inhibiting property, aggregation inhibiting property, and 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.
The specific resin used in the present disclosure may contain only one type of structural unit a-1, or may contain two or more types. When the specific resin used in the present disclosure contains two or more types of structural unit a-1, the content refers to the total content of two or more types of structural unit a-1.

[Structural unit a-2]
In addition to the structural unit a-1 described above, the specific resin further includes a structural unit having an aromatic ring (hereinafter referred to as “structural unit a-2”) from the viewpoint of settling suppression, aggregation suppression, and average particle size. It is preferable to have a structural unit derived from (meth) acrylate having an aromatic ring, and it is more 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, L ⁵ represents a single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, —C (═O) —, — Represents a divalent linking group formed by combining two or more groups selected from the group consisting of O—, —S—, and —NR ⁷ —, wherein R ⁶ represents an alkyl group having 1 to 6 carbon atoms, R 1 represents an alkoxy group having 1 to 15 amino groups, 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 Formula 2, R ⁴ is preferably a methyl group.
In Formula 2, L ⁵ is preferably a single bond or a group represented by the following Formula 2-1 or the following Formula 2-2, and is a single bond or a group represented by the following Formula 2-1. More preferably.
As the alkylene group for L ^5, an alkylene group having 2 to 10 carbon atoms is preferable, an alkylene group having 1 to 5 carbon atoms is more preferable, and an alkylene group having 1 to 3 carbon atoms is more preferable. The alkylene group may be linear or branched.
The alkenylene group in L ⁵ is preferably an alkenylene group having 2 to 10 carbon atoms, more preferably an alkenylene group having 2 to 6 carbon atoms, and more preferably an alkenylene group having 2 to 4 carbon atoms. The alkenylene group may be linear or branched.
R ⁷ is preferably a hydrogen atom.
In Formula 2, each R ⁶ preferably 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, More preferably, it represents an alkyl group having 1 to 6 carbon atoms, a halogen atom, or an aryloxy group having 6 to 20 carbon atoms.
The alkyl group in R ^{6 and} the alkyl group contained in the alkoxy group may be linear or branched.
The aryloxy group in R ⁶ is preferably a naphthyloxy group or a phenyloxy group, and more preferably a phenyloxy group.
In Formula 2, m is preferably 0 or 1, and more preferably 0.

In Formula 2-1 and Formula 2-2, L ¹¹ is represented by an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, —O—, —S—, or a combination thereof. A group represented by an alkylene group having 1 to 12 carbon atoms, —O—, or a combination thereof, and a group represented by an alkylene group having 1 to 8 carbon atoms, —O—, or a combination thereof. And a group represented by an alkylene group having 1 to 4 carbon atoms, —O—, or a combination thereof is more preferable.
A preferred embodiment of L ¹¹ includes a divalent linking group represented by the following formula 2-3, formula 2-4 or formula 2-5.
In Formula 2-2, R ⁷ has the same meaning as R ^{7 in} Formula 2, and the preferred embodiments are also the same.
In Formula 2-1 and Formula 2-2, * represents a bonding site to the carbon atom to which R ^{4 in} Formula 2 is bonded, and a wavy line represents a bonding site to the benzene ring in Formula 2.

In Formula 2-3 to Formula 2-5, a represents a bonding site with O in Formula 2-1 or N in Formula 2-2, and b represents a wavy line in Formula 2-1 and Formula 2-2. Similarly, it represents a bonding site with the benzene ring in formula 2, 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 Formula 2-3, n3 is preferably an integer of 1 to 5.
In Formula 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 still 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 preferable that it is derived from benzyl (meth) acrylate or phenoxyethyl (meth) acrylate, and more preferably a structural unit derived from benzyl (meth) acrylate.

Among the above, from the viewpoint of more effectively exerting the effects of the present disclosure, the specific resin in the present disclosure has at least the structural unit a-1 and the structural unit a-2, and in the structural unit a-2, It is preferable that L ⁵ is a group represented by Formula 2-1, 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 with respect to the total mass of the specific resin, from the viewpoint of reducing sedimentation inhibition, aggregation inhibition, and average particle diameter, The mass is more preferably from 60% by 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 structural unit a-2, or may contain two or more types of structural unit a-2. When the specific resin used in the present disclosure contains two or more structural units a-2, the above content refers to the total content of two or more structural units a-2.

[Structural unit a-3]
In addition to the structural unit represented by Formula 1 above, the specific resin further includes a structural unit having an acidic group (hereinafter referred to as “structural unit a— 3 ”)).
The acidic group in the present disclosure is a substituent having a dissociative proton, and means an acidic group such as a carboxy group, a phosphonyl group, a phosphoryl group, a sulfo group, or a boric acid group. Among these, 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 a form dissociated by releasing a proton, or may form a salt.
In the ink composition, the structural unit a-3 may form a salt with an 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 (methacryloxyethyl) phosphate or 2-acrylamido-2-methylpropanesulfonic acid. It is preferably 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 with respect to the total mass of the specific resin, from the viewpoint of reducing the sedimentation inhibitory property, the aggregation inhibitory property, and the average particle diameter. % To 30% by mass is more preferable.
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 The amount is preferably 1.0 mmol / g to 2.5 mmol / g).
The specific resin may contain only one type of structural unit a-3, or may contain two or more types. When the specific resin contains two or more kinds of structural units a-3, the above content refers to the total content of two or more kinds of structural units a-3.

[Structural unit a-4]
In addition to the structural unit a-1, the specific resin preferably further includes a structural unit other than the structural unit a-2 and the structural unit a-3 (hereinafter “structural 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 a monofunctional (meth) acrylate compound Is more preferable.
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 viewpoints of settling suppression, aggregation suppression, 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 more preferable.

Monofunctional (meth) acrylate compounds include 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate Alkyl (meth) acrylates such as n-butyl (meth) acrylate; 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.
Monofunctional (meth) acrylamide compounds include dimethylacrylamide, hydroxyethyl (meth) acrylamide, hydroxypropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, isopropyl (meth) acrylamide, dye Acetone acrylamide etc. are mentioned.
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 with respect to the total mass of the specific resin, from the viewpoint of reducing sedimentation inhibition, aggregation inhibition, and average particle size. % To 30% by mass is more preferable.
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 types of structural unit a-4, the above content refers to the total content of two or more types of structural unit a-4.

In addition, the specific resin is preferably a resin having a structural unit represented by Formula 1 and a structural unit having an aromatic ring, from the viewpoint of reducing sedimentation inhibition, aggregation inhibition, and average particle size. More preferably, the resin is a resin having a structural unit represented by 1, a structural unit having an aromatic ring, and a structural unit having an acidic group. The structural unit represented by Formula 1, a structural unit having an aromatic ring, acidic More preferably, it is 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. 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.
In addition, the specific resin is preferably an addition polymerization resin, and more preferably an acrylic resin, from the viewpoint of settling suppression, aggregation suppression, and average particle size.
The acrylic resin in the present disclosure is a resin having 50% by mass or more of structural units derived from at least one compound selected from the group consisting of a (meth) acrylic compound and a (meth) acrylamide compound. Yes, preferably 60% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
The specific resin may be a homopolymer or a copolymer, but is preferably a copolymer.

The content of the specific resin is 3% by mass to 50% with respect to the total mass of the pigment composition (pigment dispersion) used for preparing the ink composition from the viewpoint of settling suppression, aggregation suppression, and reduction in average particle size. Preferably, the content is 5% by mass, more preferably 5% by mass to 40% by mass, and still 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 settling suppression, aggregation suppression, and reducing the average particle size. / G is more preferable, and 1.5 mmol / g to 2.5 mmol / g is still more preferable.
The acid value of the specific resin is calculated according to JIS K0070 (1992) and converted 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 settling inhibition, aggregation inhibition, and reduction in average particle size. Preferably, it is 10,000 to 30,000.
In the present specification, the weight average molecular weight of the resin is measured by gel permeation chromatography (GPC). GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and three columns of TSKgeL Super HZM-H, TSKgeL Super HZ4000, and TSKgeL Super HZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are connected in series. NMP (N-methylpyrrolidone) is used as the eluent. The conditions are as follows: sample concentration is 0.35% by mass, flow rate is 0.35 ml / min, sample injection volume is 10 μl, measurement temperature is 40 ° C., RI (Refractive Index) detector (differential refractive index detector) To do. 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 from 0.50 to 0.80, and preferably from 0.50 to 0.75, from the viewpoints of sedimentation inhibition and aggregation inhibition. It is more preferable.
The I / O value is a value that treats the polarity of various organic compounds, also called inorganic values / organic values, in terms of organic concepts, and is one of the functional group contribution methods for setting parameters for each functional group. is there.

The I / O value is described in detail in the organic conceptual diagram (by Yoshio Koda, Sankyo Publishing (1984)). The concept of the I / O value is that the properties of a compound are divided into an organic group that represents covalent bonding and an inorganic group that represents ionic bonding, and all organic compounds are orthogonal coordinates named organic axes and inorganic axes. Each of the above points is shown.

The inorganic value is obtained by quantifying the magnitude of the influence on the boiling point of various substituents and bonds of an organic compound, based on the hydroxyl group. Specifically, when the distance between the boiling point curve of a straight chain alcohol and the boiling point curve of a straight chain paraffin is about 100 ° C., the influence of one hydroxyl group is set to 100 as a numerical value. 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 that the organic compound has. For example, the inorganic value of a carboxy group (—COOH group) is 150, and the inorganic value of a double bond is 2. Therefore, the inorganic value of a certain kind of organic compound means the sum of inorganic values such as various substituents and bonds of the compound.
The organic value is determined based on the influence on the boiling point of the carbon atom representing the methylene group with the methylene group in the molecule as a unit. That is, since the average value of the boiling point increase 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 on the basis of this. A value obtained by quantifying the influence on the boiling point of various substituents and bonds based on this is the organic value. For example, the organic value of a nitro group (—NO ₂ ) is 70.
An I / O value closer to 0 indicates a non-polar (hydrophobic or organic) organic compound, and a larger value indicates a polar (hydrophilic or inorganic) organic compound. Indicates.

In the present disclosure, the I / O value of a specific resin means that obtained by the following method. Based on the organicity (O value) and inorganicity (I value) described in Yoshida Koda, Organic Conceptual Diagram-Basics and Applications (1984), p.13, etc. An O value (= I value / O value) is calculated. For each monomer constituting the polymer, the product of its (I / O value) and (mol% in the polymer) is calculated, and these products are summed and rounded off to the third decimal place. / O value.
However, as a method for calculating the inorganic value of each monomer, a double bond is generally added as an inorganic value of 2, but when polymerized, the double bond disappears. The I / O value of the specific resin is calculated using a numerical value that is not added to the bond.

In the present disclosure, the I / O value of the specific resin can be adjusted by adjusting the structure and content of the monomer 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 unit a-1 to the structural unit a-4 represents the structure of each structural unit. The description of “mass%” means the content of each structural unit, the numerical value in the “Mw” column indicates the weight average molecular weight, and the description of “−” indicates that the corresponding structural unit is not contained. .

 

 

In Table 1, the details of the structures described by abbreviations 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 and more preferably 40% by mass or more with respect to the total mass of the ink composition. There is no restriction | limiting in particular in the upper limit of water content, 80 mass% or less is preferable with respect to the total mass of an ink composition.

-Organic solvent with 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 composition for inkjet recording 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 include an organic solvent having a boiling point of 270 ° C. or higher (that is, 0% by mass), or the content with respect to the total mass of the inkjet recording ink composition is 0% by mass. It is set as the range of 5.5 mass% or less exceeding%.
When the content of the organic solvent having a boiling point of 270 ° C. or higher is in the above-described range, after completion of application of the ink composition while maintaining good dispersibility in combination with the specific resin described above (for example, It is possible to suppress image stickiness within 30 seconds from the completion of ink application.

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 not including an organic solvent having a boiling point of 270 ° C. or higher).

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

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.), sulfolane (boiling point: 285 ° C.). ), Thiodiglycol (boiling point: 282 ° C.), and the like.

-Organic solvent with 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 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 organic solvent having a boiling point of 120 ° C. or more and less than 270 ° C., the dispersion of the white inorganic pigment can be maintained well in combination with the specific resin described above (after completion of application of the ink composition) For example, it is possible to suppress image stickiness within 30 seconds from the completion of ink application.
The boiling point means a boiling point under 1 atm (101325 Pa), and the measuring method is the same as that of the 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, and sulfur-containing compounds.

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.), 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 -Hexanediol (boiling point: 223 ° C), 1,6-hexanediol (boiling point: 250 ° C), 1,2,6-hexanetriol (boiling point: 1 8 ° C.), 1,2,4-butanetriol (boiling point: 190 ℃), 1,2,3- butanetriol (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 more and less than 270 ° C. include ethylene glycol monoethyl ether (boiling point: 135 ° C.), ethylene glycol monobutyl ether (boiling point: 171 ° C.), 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 ° C), tripropylene glycol monomethyl ether (boiling point 243 ° C), tetraethylene glycol mono Chirueteru (boiling point: 158 ° C.), propylene glycol monoethyl ether (boiling point: 133 ° C.), and the like.

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.), 1,3-dimethyl-2- Examples include imidazolidinone (boiling point: 220 ° C.) and ε-caprolactam (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.).

Examples of the low boiling point organic solvent having a boiling point of 120 ° C. or more and less than 270 ° C. include polyhydric alcohols having a boiling point of 120 ° C. or more and less than 270 ° C., and a boiling point of 120 ° C. or more and 270 ° C. It is preferable to contain a low-boiling organic solvent selected from the group consisting of polyhydric alcohol alkyl ethers that are less than ° C.

The content of the low-boiling organic solvent is preferably in the range of 4% by mass to 35% by mass and preferably in the range of 10% by mass to 35% by mass with respect to the total mass of the ink composition. More preferably, 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 organic solvent is 4% by mass or more, the dispersibility of the white inorganic pigment can be satisfactorily 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 according to the present disclosure includes a colorant (a pigment and a dye) other than a white inorganic pigment, an organic solvent having a boiling point of 270 ° C. or higher, and an organic solvent 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.

(Coloring agent)
Colorants other than white inorganic pigments include pigments, dyes, etc. Among them, organic pigments or inorganic pigments are preferred.
Examples of inorganic pigments include petals, aluminum, and carbon black.
Examples of the organic pigment include a phthalocyanine pigment, an insoluble azo pigment, a condensed azo pigment, a dioxazine pigment, an anthraquinone pigment, a quinacridone pigment, a perylene pigment, a perinone pigment, and a thioindigo pigment.
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 surfactant.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants and the like. From the viewpoint of the 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 good droplet ejection by the inkjet method. Among them, 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, fluorine compounds, silicone compounds, chelating agents represented by ethylenediaminetetraacetic acid (EDTA), and the like can also be used.

(Other ingredients)
The ink composition can further contain other additives in addition to the above components.
Other additives include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters (neutralizing agents such as organic bases and inorganic alkalis), and antifoaming Known additives such as an agent, a viscosity modifier, a dispersion stabilizer, a rust inhibitor, and a chelating agent can be used. These various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared.

-Physical properties of ink composition for inkjet recording-
〔viscosity〕
The viscosity of the ink composition for inkjet recording of the present disclosure 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, depending on the pigment concentration. More preferably, it is preferably 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 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 an Automatic Surface Teniometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

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

<Ink set>
The ink set of the present disclosure has the ink composition for ink jet recording of the present disclosure described above and a color ink containing a colorant different from the ink composition for ink jet recording of the present disclosure.
As described above, the ink composition for inkjet recording according to the present disclosure has good whiteness (white hue and density) in a white portion of a recorded image, and is used as an ink set in combination with, for example, a chromatic color ink. In this case, the image becomes clearer.
Moreover, while improving whiteness, the inkjet suitability as an ink composition for inkjet recording is maintained favorable, and it is excellent in the discharge property at the time of recording by the inkjet method. In addition, although the composition has little or no high-boiling organic solvent, the ink drying property on the substrate is enhanced, so that the stickiness of the image is improved even when a non-absorbent medium is used.

-Ink composition for ink jet recording-
Details of the ink composition for inkjet recording of the present disclosure are as described above, and thus detailed description thereof is omitted here.

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

(Coloring agent)
The colored ink contains at least one colorant.
The colorant includes a pigment, a dye, and the like, and among them, an organic pigment or an inorganic pigment is preferable.

Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, aniline black, and the like. Of these, azo pigments and polycyclic pigments 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, and carbon black. Among these, carbon black is particularly preferable.
Preferable examples of the colorant include those described in JP-A-2009-241586, paragraphs 0096 to 0100.

The content of the colorant is preferably 1% by mass to 25% by mass, more preferably 2% by mass to 20% by mass, and still more preferably 2% by mass to 15% by mass with respect to the total amount of the color ink.

(Dispersant)
The colored ink may contain at least one dispersant for dispersing the colorant.
The dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.
As the dispersant, for example, the dispersants described in paragraphs 0080 to 0096 of JP-A No. 2016-1445312 are preferably exemplified.

The mixing mass ratio (p: s) between the colorant (p) and the dispersant (s) is preferably in the range of 1: 0.06 to 1: 3, and is preferably in the range of 1: 0.125 to 1: 2. More preferably, it is 1: 0.125 to 1: 1.5.

For the coloring agent and the dispersing agent, reference may be made to paragraphs 0114 to 0136 of International Publication No. 2017/163738.

(Organic solvent)
The colored ink can contain at least one organic solvent selected arbitrarily.
Among organic solvents, when an organic solvent having a boiling point of 270 ° C. or higher is contained, the content of the organic solvent having a boiling point of 270 ° C. or higher in the colored ink is similar to the ink composition of the present disclosure described above. It is preferably 5.5% by mass or less based on the total mass of the colored 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 exceeds 5.5% by mass with respect to the total mass of the colored ink. It is preferable that it is the range of the mass% or less.
When the content of the organic solvent having a boiling point of 270 ° C. or higher is in the above-described range, the stickiness of the image after completion of application of the ink composition (for example, within 30 seconds from the completion of application of the ink) is further suppressed. Can do.
The details of the organic solvent having a boiling point of 270 ° C. or higher are as described above, and thus detailed description thereof is omitted.

The colored ink can suitably contain a low-boiling organic solvent selected from organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C., as in the ink composition for inkjet recording of the present disclosure described above. By containing a low boiling point organic solvent having a boiling point of 120 ° C. or more and less than 270 ° C., dispersibility is suppressed while suppressing stickiness of the image after completion of application of the colored ink (for example, within 30 seconds from the completion of application of the ink). It 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, and sulfur-containing compounds.
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. Preferred are low boiling organic solvents.
Details of the low-boiling organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. are as described above, and thus detailed description thereof is 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 organic solvent is 4% by mass or more, the pigment dispersibility can be kept good. 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 resin particle.
Unlike the polymer dispersant for dispersing the colorant, the resin particles are resin particles that exist separately from the pigment.

The resin particles are preferably water-insoluble or poorly water-soluble resin particles.
“Non-water-soluble or sparingly water-soluble” means that when the resin particles are dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the dissolved amount is 15 g or less. Say.
From the viewpoint of improving the dischargeability of the colored ink, the resin particle dissolution amount is preferably 10 g or less, more preferably 5 g or less, and even more preferably 1 g or less. The dissolution amount is the dissolution amount when 100% neutralized with sodium hydroxide or acetic acid according to the type of salt-forming group of the water-insoluble or poorly water-soluble resin particles.

Regarding the resin particles, the description in paragraphs 0137 to 0171 of International Publication No. 2017/163738 and paragraphs 0036 to 0081 of JP 2010-077718 can be appropriately referred to.

(wax)
The colored ink may contain at least one wax.
By containing the wax, the rub 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 surfactant.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants and the like. From the viewpoint of the 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 good droplet ejection by the inkjet method. Among them, 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, fluorine compounds, silicone compounds, chelating agents represented by ethylenediaminetetraacetic acid (EDTA), and the like can also be used.

(Other ingredients)
The colored ink can further contain other additives in addition to the above components.
Other additives include, for example, organic solvents having a boiling point of 270 ° C. or higher and organic solvents other than organic solvents having a boiling point of 120 ° C. or higher and lower than 270 ° C., antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, Known additives such as antiseptics, antifungal agents, pH adjusters (neutralizing agents such as organic bases and inorganic alkalis), antifoaming agents, viscosity adjusting agents, dispersion stabilizers, rust preventives, chelating agents and the like can be mentioned. . These various additives may be added directly after the color ink is prepared, or may be added when the color ink is prepared.

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, and 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, from the viewpoint of dischargeability when discharged by the inkjet method, and 2 mPa · s to 15 mPa · s. The range of s is more preferable, and the range of 2 mPa · s to 10 mPa · s is particularly preferable.
The 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 ink composition for inkjet recording of the present disclosure described above or the ink set of the present disclosure described above.

An aspect in which image recording is performed by discharging an ink composition for ink jet recording by an ink jet method is preferable.
There is no particular limitation on the ink composition ejection method in the ink jet method, and a known method, for example, a charge control method in which the ink composition is ejected by using electrostatic attraction, or a drop-on method in which the vibration pressure of the piezoelectric element is utilized. Demand method (pressure pulse method), acoustic ink jet method that changes the electrical signal into an acoustic beam, irradiates the ink and ejects the ink composition using the radiation pressure, and the pressure generated by heating the ink to form bubbles Any of a thermal ink jet (bubble jet (registered trademark)) system using
As the ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. 54-59936 causes an abrupt volume change in the ink composition subjected to the action of thermal energy. An ink jet method in which the ink is discharged from the nozzle can be used effectively.
As the ink jet method, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can also be applied.

As an inkjet head system, a shuttle system that performs recording while a short serial head is scanned in the width direction of the recording medium, and a line in which recording elements are arranged corresponding to the entire area of one side of the recording medium. There is a line system using a head.
In the line system, image recording can be performed on the entire surface of the recording medium by scanning the recording medium in a direction crossing the arrangement direction of the recording elements. In the line system, a transport system such as a carriage for scanning a short head in the shuttle system is not required. Further, in the line method, compared with the shuttle method, complicated movement control of the carriage and the recording medium becomes unnecessary, and only the recording medium moves. For this reason, according to the line system, image recording speed can be increased compared to the shuttle system.

Application of the ink composition is preferably performed using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi, and 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 nozzles of the inkjet head is preferably 1 pL (picoliter) to 10 pL, more preferably 1.5 pL to 6 pL from the viewpoint of obtaining a high-definition image.
In addition, from the viewpoint of improving the unevenness of the image and the connection of the continuous gradation, it is also effective to discharge a combination of different liquid amounts.

After the application of the ink composition, the applied ink composition may be dried by heating.
Examples of means for performing heat drying include known heating means such as a heater, known blower means such as a dryer, and a combination of these.
As a method for performing 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-absorbent medium was applied, or the ink composition of the non-absorbent medium was applied. A method of applying warm air or hot air to the surface, a method of applying heat with an infrared heater from the surface to which the ink composition of the non-absorbent medium is applied, or the surface opposite to the surface to which the ink composition is applied, and a plurality of these And the like, and the like.

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. Although there is no restriction | limiting in particular in the upper limit of heating temperature, As an upper limit, 100 degreeC is mentioned, for example, 90 degreeC is preferable.
There is no particular limitation on the time for drying the ink composition, but it is preferably 3 to 60 seconds, more preferably 5 to 60 seconds, and particularly preferably 10 to 45 seconds.

Further, the non-absorbent medium may be heated in advance before application of the ink composition.
The heating temperature may be set as appropriate, 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-absorptive refers to a property having a water absorption (mass%, 24 hr.) Of less than 0.2 according to ASTM D570 of the ASTM test method.
Although there is no restriction | limiting in particular as a nonabsorbent medium, A resin base material is preferable.
There is no restriction | limiting in particular as a resin base material, For example, the base material of a thermoplastic resin is mentioned. As a resin base material, the base material which shape | molded the thermoplastic resin in the sheet form or the film form is mentioned, for example. The resin substrate is preferably a substrate containing polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

The resin base material may be a transparent resin base material or a colored resin base material, or may be subjected to metal vapor deposition or the like at least in part.
Here, transparent 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 substrate is not particularly limited, but is preferably a sheet-like resin substrate, and is a sheet-like resin substrate capable of forming a roll by winding from the viewpoint of productivity of the recording medium. It is more preferable.
The thickness of the resin substrate is preferably 10 μm to 200 μm, and more preferably 10 μm to 100 μm.

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

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Unless otherwise specified, “part” is based on mass.

In the examples, HLC-8220GPC (manufactured by Tosoh Corp.) was used as the GPC, and TSKgeL Super HZM-H, TSKgeL Super HZ4000, TSKgeL Super HZ2000 (Tosoh Corp., 4.6 mmID × 15 cm) were used as columns. Three were connected in series and NMP (N-methylpyrrolidone) was used as the eluent. The conditions are as follows: the sample concentration is 0.35 mass%, the flow rate is 0.35 ml / min, the sample injection volume is 10 μl, the measurement temperature is 40 ° C., and the RI (Refractive Index) detector (differential refractive index detector) It 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 -2500 "," A-1000 ", and" n-propylbenzene ".

-Synthesis of dispersed resin-
<Synthesis Example 1: Synthesis of Dispersing Resin P-1>
To a three-necked flask equipped with a stirrer and a condenser, dipropylene glycol was added in the same amount as the total amount of monomers described later, and heated to 85 ° C. in a nitrogen atmosphere.
Solution I in which 9.1 mole equivalent of stearyl methacrylate, 34.0 mole equivalent of benzyl methacrylate, 31.9 mole equivalent of hydroxyethyl methacrylate, 25.0 mole equivalent of methacrylic acid, and 0.8 mole equivalent of 2-mercaptopropionic acid were mixed 1% by mass of t-butylperoxy-2-ethylhexanoate (perbutyl O manufactured by NOF Corporation) with respect to the total mass of the monomer was dissolved in 20% by mass of dipropylene glycol with respect to the total mass of the monomer. And solution II obtained by the above were respectively prepared. Solution I was added dropwise to the three-necked flask over 4 hours and solution II over 5 hours.
After the completion of the dropwise addition, the reaction was further continued for 2 hours, and then the temperature was raised to 95 ° C. and heated and stirred for 3 hours to react all the unreacted monomers. The disappearance of the monomer was confirmed by a nuclear magnetic resonance ( ¹ H-NMR) method.
The obtained reaction solution was heated to 70 ° C., 20.0 molar equivalents of dimethylaminoethanol (dimethylethanolamine) as an amine compound was added, and then propylene glycol was added and stirred to obtain 30% by mass of the dispersion resin P-1. A solution was obtained.
The constituent components of the obtained polymer were confirmed by ¹ H-NMR. Moreover, the weight average molecular weight (Mw) calculated | required by GPC was 22,000.
The mass ratio of each structural unit in the dispersion resin P-1 is as follows: Stearyl methacrylate-derived structural unit (constituent unit represented by Formula 1) / benzyl methacrylate-derived structural unit / hydroxyethyl methacrylate-derived structural unit / methacrylic acid The derived structural unit was 20/39/27/14. However, the mass ratio is a value not including dimethylaminoethanol.
In addition, the numerical value of the lower right of the parenthesis of each structural unit below is a molar ratio.

<Synthesis Example 2: Synthesis of Dispersing Resin P-2>
The 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 Dispersing Resin P-3>
Dispersion was carried out in the same manner as the synthesis of 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 dispersion resins P-4 to P-6>
Instead of stearyl methacrylate, cyclohexyl methacrylate (CyHMA (constituent unit represented by formula 1); dispersion resin P-4), n-octyl methacrylate (OctMA (constituent unit represented by formula 1); dispersion resin P-5) Or 2-ethylhexyl methacrylate (2-EHMA (constituent unit represented by formula 1); dispersion resin P-6) was used in the same manner as the synthesis of dispersion resin P-1, except that each equimolar amount was used. P-4 to P-6 were respectively synthesized. The structural unit derived from each monomer is as follows. The weight average molecular weight (Mw) determined by GPC was 22,000.

<Synthesis Examples 7 to 9: Synthesis of dispersion resins P-7 to P-9>
Instead of benzyl methacrylate, equimolar amounts of phenoxyethyl methacrylate (PEA; dispersion resin P-7), 2-phenoxybenzyl acrylate (POB-A; dispersion resin P-8), or styrene (St; dispersion resin P-9), respectively The dispersion resins P-7 to P-9 were respectively synthesized in the same manner as the synthesis of the dispersion resin P-1, except that it was used. The structural unit derived from each monomer is as follows. The weight average molecular weight (Mw) determined by GPC was 22,000.

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

-Preparation of resin particles A-
Into 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, 293 g of methyl ethyl ketone was charged and heated to 80 ° C. Next, while maintaining the temperature in the reaction vessel at 80 ° C., 165.7 g of methyl methacrylate (Mitsubishi Gas Chemical Co., Ltd.), 63.7 g of isobornyl methacrylate (Kyoeisha Chemical Co., Ltd.), methacrylic acid (Mitsubishi) Gas Chemical Co., Ltd.) 25.5 g, methyl ethyl ketone 48 g, and “V-601” (Wako Pure Chemical Industries, Ltd., polymerization initiator) 1.25 g of mixed solution was mixed at a constant speed so that dripping was completed in 2 hours. It was dripped at. After completion of the addition, (1) a solution prepared by mixing 0.60 g of “V-601” and 5.0 g of methyl ethyl ketone was added, and the mixture was further stirred for 2 hours. Thereafter, the step (1) was repeated four times, and a solution obtained by mixing 0.60 g of “V-601” and 5.0 g of methyl ethyl ketone was added and stirred for 3 hours.
Thus, a polymer solution which was a solution of 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 Standard (JIS K0070: 1992). The weight average molecular weight was measured by GPC as 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 1 mol / L sodium hydroxide (NaOH) aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 718.0 g of distilled water was dropped into the reaction vessel at a rate of 20 ml / min to perform water dispersion. Thereafter, the temperature in the reaction vessel is maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours, and then the reaction vessel is depressurized to add isopropanol, methyl ethyl ketone, and distilled water. An amount of 913.7 g was distilled off. In this manner, an aqueous dispersion (emulsion) of resin particles A having a solid content concentration of 23.2% by mass was obtained.
The resin constituting the resin particle A is a neutralized product of a copolymer having the following structure (that is, a methyl methacrylate / isobornyl methacrylate / methacrylic acid (= 65/25/10 [mass ratio]) copolymer). .
The number on the lower right of each structural unit in the following structure represents a mass ratio.

(Example 101)
-Preparation of TiO ₂ dispersion-
Using a ready mill model LSG-4U-08 (manufactured by Imex Co., Ltd.), a TiO ₂ dispersion was prepared as follows. That is,
In a container made of zirconia, titanium dioxide (TiO ₂ ; average primary particle size: 210 nm, trade name: PF-690, manufactured by Ishihara Sangyo Co., Ltd .; white inorganic pigment), 45 parts by mass, dispersion resin P— obtained in Synthesis Example 1 15 parts by mass of 30% by mass of 1 and 40 parts by mass of ultrapure water were added. Furthermore, 40 parts by mass of 0.5 mmφ zirconia beads (manufactured by TORAY, Treceram beads) was added and lightly mixed with a spatula. A zirconia container was placed in a ball mill, and the mixture was dispersed for 5 hours at 1000 rpm (revolutions per minute). After the completion of dispersion, the beads were removed by filtration with 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 a water-based ink (ink-jet recording ink composition).

The average primary particle diameter 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 with TEM after dropping aqueous ink diluted 1,000 times on Cu200 mesh (manufactured by JEOL Ltd.) with a carbon film attached thereto and drying it. The equivalent circle diameter of 300 independent particles that did not overlap was measured, and the measured values were averaged to obtain an average particle diameter.

 

 

In addition, the detail of the component of the said Table 2 is as follows.
PVP K15: Polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.)
Olfine E1010: Acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd.)
Olfine E1020: Acetylene glycol 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-based antifoaming agent (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 below. The image was recorded as follows.
(1) Recording method Using the inkjet recording apparatus provided with the conveyance system for conveying the substrate and the inkjet head, the above water-based ink is ejected to the corona discharge treated surface of the OPP film by the single pass method under the following conditions. A white solid image was recorded.
(2) Recording conditions Inkjet head: 1200 dpi / 20 inch width piezo full line head Ink discharge amount: 4.0 pL
Drive frequency: 30 kHz (base material conveyance speed: 635 mm / second)

-Evaluation-
In recording an image using the above water-based ink, the following evaluation was performed. The evaluation results are shown in Table 3.

(1) Ejectability After recording a white solid image (image size: 50 mm × 50 mm) with a recording duty of 100% by the above-described recording method and recording conditions, the recording is performed under environmental conditions of a temperature of 25 ° C. and a relative humidity of 50%. The inkjet recording apparatus was stopped for a minute and the recording head was left exposed to the atmosphere. After 30 minutes from the stop, the ink jet recording apparatus was started and a nozzle check pattern was output. The output nozzle check pattern was visually observed, and the dischargeability was evaluated according to the following evaluation criteria. If the number of undischarge nozzles is 6 or less, it is practically acceptable.
The recording duty is 100% under the condition that a droplet is applied to a unit area (one pixel) of 1/1200 inch × 1/1200 inch with a resolution of 1200 dpi × 1200 dpi and one drop of water-based ink is applied. Defined image.
<Evaluation criteria>
A: The number of undischarge nozzles is 2 or less.
B: There are 3 to 4 discharge failure nozzles.
C: There are 5 to 6 undischarge nozzles.
D: There are 7 to 8 or more undischarge nozzles.
E: There are 9 or more undischarge nozzles.

(2) Whiteness of white part Thickness: A 12 μm polyethylene terephthalate (PET) base material (FE2001, manufactured by Phutamura Chemical Co., Ltd.) is coated with the above water-based ink while changing the film thickness, dried and solid. 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 could not be visually recognized was obtained through the evaluation material, which was used as an index for evaluating the whiteness of the aqueous 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: The fluorescent lamp tube cannot be visually recognized when the thickness of the solid image is 1 μm.
B: The fluorescent lamp tube cannot be visually recognized when the thickness of the solid image is 2 μm.
C: The fluorescent lamp tube cannot be visually recognized when the thickness of the solid image is 3 μm.
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 by the above recording method and recording conditions.
After a certain period of time (10 seconds, 20 seconds, 30 seconds, or 40 seconds) after the completion of application of the water-based ink, the recorded solid image is subjected to conditions of a temperature of 25 ° C. and a relative humidity of 50%. It touched with the hand and evaluated according to the evaluation criteria shown below.
<Evaluation criteria>
A: Even if the solid image is touched 10 seconds after the completion of the application of the water-based ink, the recording surface does not peel off.
B: When the solid image is touched 10 seconds after the completion of the application of the water-based ink, the recording surface peels off, but when the solid image is touched 20 seconds after the completion of the application of the water-based ink, the recording surface peels off. Absent.
C: When the solid image is touched 20 seconds after the completion of the application of the water-based ink, the recording surface peels off, but when the solid image is touched 30 seconds after the application of the water-based ink, the recording surface peels off. Absent.
D: When the solid image is touched 30 seconds after the completion of the application of the water-based ink, the recording surface is peeled off, but when the solid image is touched 40 seconds after the completion of the application of the water-based ink, the recording surface is peeled off. Absent.
E: Even when the solid image is touched 40 seconds after the completion of application of the water-based ink, the recording surface peels off.

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

(Example 106 and Examples 110 to 115)
A water-based ink was prepared and evaluated in the same manner as in Example 102 except that the kind of the organic solvent having a boiling point of 120 ° C. or higher and lower than 270 ° C. was changed in Example 102. 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)
A water-based ink was prepared and evaluated in the same manner as in Example 102 except that the dispersion resin P1 in Example 102 was replaced with the dispersion resin shown in Table 3. The evaluation results are shown in Table 3.

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

(Comparative Examples 101 to 102)
A water-based ink was prepared and evaluated in the same manner as in Example 101 except that the average primary particle diameter of titanium dioxide was changed in Example 101. The evaluation results are shown in Table 3.
The titanium dioxide used here is as follows.
Titanium dioxide with an average primary particle size of 100 nm: MPT-141, manufactured by Ishihara Sangyo Co., Ltd. Titanium dioxide with an average primary particle size 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 (an 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) determined by GPC = 22,000). Evaluation was performed. The evaluation results are shown in Table 3.

 

 

As shown in Table 3, in the water-based ink of each example, the white color density in the white portion in the image was secured, and the whiteness was excellent. Ink jet suitability is also maintained well, and the composition is excellent in dischargeability when recording by the ink jet method, and has a composition with little or no organic solvent having a high boiling point. 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 discharge performance, whiteness and stickiness in the image can be effectively improved in a balanced manner.
In Examples 107 to 109, a high-boiling organic solvent having a boiling point of 270 ° C. or higher is further used. However, if the content is in the range of 5.5% by mass or less, ejection properties, whiteness and stickiness in an image, and There was no significant damage.

Further, as shown in Examples 118 to 120, when the dispersion resin has a large number of carbon atoms in the alkyl group represented by R ^{3 in} the structural unit represented by Formula 1 (preferably having 10 or more carbon atoms), titanium dioxide Although the volume average particle diameter of the ink was not changed, the dischargeability was further improved.
As can be seen from the results of Example 123 in which the (meth) acrylate having an aromatic ring used in Example 1 is replaced with styrene, the dispersion resin has a structural unit derived from (meth) acrylate having an aromatic ring. Sex can be improved more. Further, as can be seen from the results of Examples 124 to 126 in which (meth) acrylate (hydroxyethyl methacrylate) having a hydroxyl group used in Example 101 is replaced with another monomer having no hydroxyl group, the dispersion resin has a hydroxyl group ( When having a structural unit derived from (meth) acrylate, the discharge property can be further improved.

On the other hand, in Comparative Example 101 using titanium dioxide having an average primary particle size 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 exceeding 400 nm, the particle size was too large to maintain the discharge property satisfactorily.
Further, in Comparative Example 103 in which the content of the high-boiling organic solvent having a boiling point of 270 ° C. or higher is high, the drying property is inferior and the image becomes sticky.
Furthermore, as shown in Comparative Example 104, the dispersion resin that does not have the structural unit represented by Formula 1 has good ejection properties when ink using titanium dioxide having a relatively large particle size is ejected by the inkjet method. It was difficult to hold on.

(Example 201)
In Example 101, yellow water-based ink Y and magenta water-based ink were used instead of Pigment Yellow 74 (yellow pigment), Pigment Red 122 (magenta pigment), or Pigment Blue 15: 3 (cyan pigment) in Example 101, respectively. Three color inks of M and cyan water-based ink C were prepared.
Then, an ink set 201 was prepared using the prepared three color inks and the white water-based ink (hereinafter, water-based ink W) prepared in Example 101.

Subsequently, water-based ink C, water-based ink M, water-based ink Y, and water-based ink were recorded under the same recording method and conditions as in Example 101 except that the ink-jet recording apparatus was loaded with three color inks and water-based ink W. Ink W is ejected on a biaxially oriented polypropylene (OPP) film, a white solid image, a primary color solid image in which a yellow, magenta or cyan color is imparted on a white solid image, and a white solid A pattern image including a secondary color solid image in which two colors selected from yellow, magenta and cyan are superimposed on the image was recorded.
Then, the ejection property during 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 white color density in the white portion in the image was secured, and the whiteness was excellent. Therefore, the white portion in the image is expressed as a good white color, and the coloring of the colored portion by the color ink becomes vivid, and a clear image is obtained. Also, the ink jet aptitude is maintained well, and the composition is excellent in dischargeability when recorded by the ink jet method and has a low or no high organic solvent content, but uses a non-absorbing medium. The stickiness of the image was improved even when

The ink composition for ink jet recording, the ink set, and the image recording method of the present disclosure can be widely applied in applications in which an image is recorded on a non-ink-absorbing medium (for example, a glass substrate or a plastic substrate). . Specific examples of uses include packaging, food storage, agriculture, civil engineering, fishery, automotive interior and exterior, marine, daily necessities, building materials interior and exterior, residential equipment, medical / medical equipment, pharmaceutical use, It can be used for image recording in various applications such as home appliances, furniture, stationery / office supplies, sales promotion, commercial, electrical and electronics industries, clothing, and decorations.

For packaging, it can be applied to image recording on packaging bags. Packing bag forms include two-side seals, three-side seals, four-side seals, pillow seals, standing pouches, envelope stickers, gussets, fusing seals, tubes, caramel packaging, overholds, fin seals, manju packaging, twists, rockets, etc. A form is mentioned.
In addition to packaging bags, the present invention can also be applied to packaging bodies that wrap contents (for example, burger wrap for foods), wrapping paper, packaging sheets, packaging films, decorative paper for building materials, and the like.
It can also be applied to image recording on a packaging container. Examples of the form of the packaging container include food packaging containers, food packaging trays, cups, dishes, bottles, tetra packs, gable tops, bricks, carton cans, cake boxes, and the like.
Furthermore, the present invention can be applied to manufacture of a label on which an image is recorded. Examples of labels include glass bottle labels, metal can labels, plastic bottle labels, and other container labels. Examples of the label form include a sticking label and a body-wound label.
In addition to the above, it is also suitable for manufacturing a lid member on which an image is recorded. Examples of the lid material include a lid material capable of forming a sealed container by being in close contact with a bottomed cylindrical container (for example, a plastic container for food or daily use, a glass container, a metal can, a paper can, etc.). .

The disclosure of Japanese Patent Application No. 2018-067100 filed on Mar. 30, 2018 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims (12)

water and,
A white inorganic pigment having an average primary particle size of 150 nm to 400 nm;
A dispersion resin having a structural unit represented by the following formula 1;
And an organic solvent having a boiling point of 270 ° C. or higher is 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. Furthermore, it includes at least one low-boiling organic solvent selected from the group consisting of a polyhydric alcohol having a boiling point of 120 ° C. or more and less than 270 ° C. and a polyhydric alcohol alkyl ether having a boiling point of 120 ° C. or more and less than 270 ° C.,
The ink composition for ink-jet recording according to claim 1, wherein the content of the low-boiling organic solvent is 4% by mass or more and 35% by mass or less based on the total mass of the ink. 3. The ink composition for ink jet recording according to claim 1, wherein the dispersion resin is an acrylic resin. The ink composition for ink jet recording according to any one of claims 1 to ³ , wherein in the formula 1, R ³ is an alkyl group having 8 to 22 carbon atoms. The ink composition for ink jet 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 dispersion resin further contains a structural unit derived from (meth) acrylate having an aromatic ring. The ink composition for ink jet recording according to any one of claims 1 to 6, wherein the dispersion resin further contains a structural unit derived from a (meth) acrylate having a hydroxyl group. An ink composition for ink jet recording according to any one of claims 1 to 7,
Different from the ink composition for inkjet recording, a colored ink containing a colorant,
An ink set. The ink set according to claim 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 based on the total mass of the colored ink. The colored ink further includes 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 8, 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 formed on a non-absorbent medium using the ink composition for ink jet recording according to any one of claims 1 to 7 or the ink set according to any one of claims 8 to 10. Image recording method for recording. The image recording method according to claim 11, wherein the image is recorded by discharging an ink composition for inkjet recording by an inkjet method.