JP6690122B2 - Inkjet ink composition - Google Patents

Description

  The present invention relates to inkjet ink compositions.

  2. Description of the Related Art Conventionally, there is known an inkjet recording method in which an image or a character is recorded on a water-absorbent recording medium such as paper with minute ink droplets ejected from a nozzle of an inkjet recording head. As an ink used in such an inkjet recording method, a water-based ink composition containing water as a main solvent is widely used.

  On the other hand, the inkjet recording method has come to be used for recording on various recording media in various fields. For example, a solvent-based ink composition has been proposed which can be recorded on a low-absorptive recording medium such as a printing actual paper, a synthetic paper and a film by an inkjet recording method.

  For example, Patent Document 1 discloses a solvent-based ink composition containing a hydrocarbon solvent, a solvent having an ester group and an ether group, and a solvent soluble in both of them. Patent Document 2 discloses a solvent-based ink composition containing an amide-based solvent. Further, Patent Document 3 discloses a solvent-based ink composition containing three kinds of alcohols having high, medium, and low boiling points. Each of these solvent-based ink compositions has a function and effect that the drying property after printing can be improved by defining the solvent composition.

JP2012-12432A JP 2012-46671 A JP, 2010-18730, A

  However, although the solvent-based ink composition disclosed in Patent Document 1 can improve the drying property by a hydrocarbon solvent, a solvent having an ester group and an ether group, the meniscus portion of the head nozzle has a drying property. Since it is easily affected, there was a concern that the printing stability would deteriorate.

  Further, it has been clarified that the amide-based solvent contained in the solvent-based ink composition disclosed in Patent Document 2 has high hygroscopicity, so that the drying property after printing is rather deteriorated. This is presumed to have an ether bond in the chemical structure of the amide solvent, and the ether bond enhances hygroscopicity.

  Further, the solvent-based ink composition disclosed in Patent Document 3 can improve the drying property by combining three kinds of alcohols having different boiling points, but the meniscus portion of the head nozzle is affected by the drying property. Since it is easy, there was a concern that the printing stability would deteriorate.

  As described above, it has been difficult for the conventional solvent-based ink composition to satisfy both the printing stability from the head nozzle and the drying property of the printed matter. Furthermore, it is important not only to achieve both of these, but also to improve the print image quality, that is, prevent unevenness in the printed matter, ensure glossiness, and ensure safety for the human body.

  Therefore, some aspects of the present invention, by solving at least a part of the above problems, both printing stability and dryness of the printed matter are good, and glossiness is prevented while preventing unevenness of the printed matter. An inkjet ink composition that can be secured is provided. In addition to these characteristics, some aspects of the present invention further provide an inkjet ink composition having excellent human safety by further reducing the odor of the ink.

  The present invention has been made to solve at least a part of the problems described above, and can be realized as the following aspects or application examples.

[Application example 1]
One aspect of the inkjet ink composition according to the present invention is
Contains a coloring material and a solvent,
As the solvent, the ink contains one or more compounds represented by the following general formula (1) in a total content of 60% by mass or more,
Among the compounds represented by the following general formula (1), the total content of the low water-soluble solvent having a solubility in water of 40% by mass or less is 5% by mass or more and 50% by mass or less in the ink. To do.
R ¹ O- (R ² O) _m -R ³ (1)
(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² is an alkylene group having 2 or 3 carbon atoms, and R ³ is a hydrogen atom, an acetyl group, or 1 to 4 carbon atoms. (However, R ¹ and R ³ are not both hydrogen atoms, and m is an integer of 1 to 4.)

  Conventionally, the drying property was improved by adding a large amount of a low boiling point solvent to the solvent-based ink composition, but when a large amount of a low boiling point solvent is added, the drying of the nozzle meniscus is likely to proceed and it is easy to induce clogging. There was a problem of becoming. According to the inkjet ink composition of Application Example 1, while using the compound represented by the general formula (1) as a main solvent, a predetermined amount of the low water-soluble solvent represented by the general formula (1) is blended. As a result, the water solubility (water absorption) of the entire ink can be reduced. As a result, not only the drying property of the printed matter is improved, but also the glossiness can be secured while preventing the unevenness of the printed matter. Further, since it is not necessary to add a large amount of a low boiling point solvent, reliability such as clogging of meniscus (that is, printing stability) is improved.

[Application example 2]
In the inkjet ink composition of Application Example 1,
Among the compounds represented by the general formula (1), the low water-soluble solvent may contain one or more compounds in which R ³ is not an acetyl group.

[Application example 3]
In the inkjet ink composition of Application Example 2,
The total content of the low water-soluble solvent in which R ³ is not an acetyl group may be 10% by mass or more and 50% by mass or less in the ink.

[Application example 4]
In the inkjet ink composition according to any one of Application Example 1 to Application Example 3,
The low water-soluble solvent may include a compound having a standard boiling point of 175 ° C. or lower.

[Application example 5]
In the inkjet ink composition according to any one of Application Example 1 to Application Example 4,
As the solvent other than the low water-soluble solvent among the compounds represented by the general formula (1), one or more compounds in which R ³ is not an acetyl group can be contained.

[Application example 6]
In the inkjet ink composition according to any one of Application Example 1 to Application Example 5,
A pigment may be contained as the coloring material.

[Application example 7]
In the inkjet ink composition according to any one of Application Example 1 to Application Example 6,
Furthermore, a cyclic lactone can be contained as a solvent.

[Application example 8]
In the inkjet ink composition of Application Example 7,
The cyclic lactone can be contained in the ink in an amount of 1% by mass or more and less than 40% by mass.

[Application example 9]
In the inkjet ink composition according to any one of Application Example 1 to Application Example 8,
Furthermore, a vinyl chloride resin can be contained.

  A preferred embodiment of the present invention will be described below. The embodiment described below describes an example of the present invention. Further, the present invention is not limited to the following embodiments, and includes various modified examples implemented within the scope of the present invention.

1. Inkjet Ink Composition The inkjet ink composition according to this embodiment (hereinafter, also simply referred to as “ink composition”) contains a coloring material and a solvent. Hereinafter, each component contained in the ink composition according to this embodiment will be described in detail.

  The ink composition according to this embodiment is preferably a “solvent-based ink composition”. The “solvent-based ink composition” in the present invention is an ink composition containing an organic solvent as a main solvent and not water as a main solvent. Preferably, the content of water in the composition is 3% by mass or less, more preferably 1% by mass or less, still more preferably less than 0.05% by mass, still more preferably less than 0.01% by mass, Still more preferably, it is less than 0.005% by mass, and most preferably less than 0.001% by mass. Alternatively, the ink composition may contain substantially no water. “Substantially free of” means not intentionally included.

1.1. Color Material The ink composition according to this embodiment contains a color material. Although a dye or a pigment can be used as the color material, a pigment is preferable from the viewpoint of having water resistance, gas resistance, light resistance and the like.

As such a pigment, any of conventionally known inorganic pigments and organic pigments can be used, but it is preferable to include one selected from the group consisting of organic pigments, metal oxide pigments and carbon black. Examples of organic pigments include azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments; phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthaloni pigments. And the like; dye lakes such as basic dye type lakes and acid dye type lakes; nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments and the like. Examples of the inorganic pigments include carbon black; metal oxide pigments such as titanium dioxide, zinc oxide, and chromium oxide.

  Examples of magenta or red pigments include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 254 and the like.

  Examples of pigments for orange or yellow include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Orange 64, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 150, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 180 and the like.

  Examples of pigments for green or cyan include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7, C.I. I. Pigment Green 36 and the like.

  Examples of black pigments include carbon black. Examples of white pigments include C.I. I. Pigment White 6, C.I. I. Pigment White 18, C.I. I. Pigment White 21 and the like.

  These pigments may be used alone or in combination of two or more. The average particle size of the pigment particles is not particularly limited, but is preferably 50 nm or more and 500 nm or less.

  The content of the coloring material can be appropriately selected depending on the use and the printing characteristics, but is preferably 0.5% by mass or more and 20% by mass or less when the total mass of the ink composition is 100% by mass. More preferably, it is 1% by mass or more and 10% by mass or less.

From the viewpoint of uniformly and stably dispersing the coloring material in the ink composition, it is also preferable to disperse the coloring material using a dispersant. Specifically, after thoroughly mixing and stirring a part of the dispersant and the solvent, the coloring material is added thereto, and the resulting dispersion obtained by further mixing and stirring is mixed with the remaining solvent and additional components. An ink composition can be prepared by Specific examples of such a dispersant include polyester polymers such as Hinoact KF1-M, T-6000, T-7000, T-8000, T-8350P, T-8000E (all manufactured by Takefu Fine Chemical Co., Ltd.). Compounds, Solsperse 20000, 24000, 32000, 32500, 33500, 34000, 35200, 37500 (all manufactured by LUBRIZOL), Disperbyk-161, 162, 163, 164, 166, 180, 190, 191, 192 (all are Big Chemie Japan. Company), Floren DOPA-17, 22, 33, G-700 (all manufactured by Kyoeisha Chemical Co., Ltd.), Azisper PB821, PB711 (all manufactured by Ajinomoto Co.), LP4010, LP4050, LP4055, P. LYMER400,401,402,403,450,451,453 (both EFKA Chemicals Co., Ltd.), and the like.

  The content ratio of the dispersant can be appropriately selected depending on the color material type, but is preferably 5 parts by mass or more and 200 parts by mass or less, and more preferably 100 parts by mass of the content of the coloring material in the ink composition. It is from 30 parts by mass to 120 parts by mass.

1.2. Solvent The ink composition according to this embodiment contains a solvent, and as the solvent, the ink contains one or more compounds represented by the following general formula (1) in a total content of 60% by mass or more.
R ¹ O- (R ² O) _m -R ³ (1)
(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² is an alkylene group having 2 or 3 carbon atoms, and R ³ is a hydrogen atom, an acetyl group, or 1 to 4 carbon atoms. (However, R ¹ and R ³ are not both hydrogen atoms, and m is an integer of 1 to 4.)

  The compound represented by the general formula (1) does not have so high solubility in a low-absorbent recording medium. Therefore, by containing one or more compounds represented by the general formula (1) in the ink in a total content of 60% by mass or more, the glossiness and line width of the printed matter can be secured, and the quality of the printed matter is improved. Can be improved. From such a viewpoint, the compound represented by the general formula (1) is preferably contained in the ink in an amount of 70% by mass or more and 95% by mass or less, and is contained in the ink in an amount of 75% by mass or more and 90% by mass or less. More preferable.

In the above general formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms may be a linear or branched alkyl group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, Examples thereof include sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, n-hexyl group and isohexyl group. However, when R ¹ is a hydrogen atom, R ³ is not a hydrogen atom.

In the general formula (1), R ² represents an alkylene group having 2 or 3 carbon atoms. Specifically, R ² represents an ethylene group or a propylene group.

In the above general formula (1), R ³ represents a hydrogen atom, an acetyl group, or an alkyl group having 1 to 4 carbon atoms. The alkyl group having 1 to 4 carbon atoms may be a linear or branched alkyl group, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, Examples thereof include sec-butyl group and tert-butyl group. However, when R ³ is a hydrogen atom, R ¹ is not a hydrogen atom.

  M in the general formula (1) represents the number of moles of the oxyalkylene group added. M is preferably an integer of 1 to 3, more preferably an integer of 1 to 2 from the viewpoint of balancing the dryness of the printed matter and the behavior of the wetting and spreading of the ink on the medium.

Specific examples of the compound represented by the general formula (1) include methyl glycol, methyl diglycol, methyl triglycol, isopropyl glycol, isopropyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, isobutyl glycol, isobutyl diglycol. Glycol, hexyl glycol, hexyl diglycol, methyl propylene glycol, methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, butyl propylene triglycol, methyl propylene glycol acetate Glycol monoethers such as; dimethyl glycol, dimethyl diglycol, dimethyl Glycol, methyl ethyl diglycol, diethyl diglycol, dibutyl diglycol, glycol ethers such as dimethyl propylene diene glycol. Among these, from the viewpoint of reducing the odor of the ink, it is preferable that R ³ in the general formula (1) is a compound that is not an acetyl group.

  The ink composition according to this embodiment is a low water-soluble solvent having a solubility in water of 40% by mass or less (hereinafter, also referred to as “specific low water-soluble solvent”) among the compounds represented by the general formula (1). .) Is 5 mass% or more and 50 mass% or less in the ink. The water solubility (water absorption) in the entire ink can be reduced by incorporating a specific amount of the specific low water-soluble solvent into the ink while using the compound represented by the general formula (1). As a result, not only the drying property of the printed matter is improved, but also the glossiness can be secured while preventing the unevenness of the printed matter. Further, since it is not necessary to add a large amount of a low boiling point solvent, reliability such as clogging of meniscus (that is, printing stability) is improved.

  Further, by reducing the water solubility (water absorption) in the entire ink, it is possible to suppress precipitation of electrolytic impurities existing in the ink and formation of foreign matter.

  The term "water-soluble" in the present invention means that pure water and a target solvent do not exist in two layers separated from each other after being added to pure water and gently stirred to stop the flow, and a mixed solution. It means that the state (uniformity) in which the color is not polarized can be visually confirmed, and this state is maintained for several hours or more. In addition, what reacts with water is not included in the concept of "water-soluble".

“Solubility in water” in the present invention means a value obtained by the following method. First, 100 g of pure water was put in a container, and various amounts of solvents were added thereto at 20 ° C. to confirm the above water solubility, and in the following formula (2), under 40% by mass or less A solvent which may be dissolved in water but which is not dissolved in water under the condition of more than 40% by mass (for example, 41% by mass) is referred to as a “low water-soluble solvent”. On the other hand, a solvent that is dissolved in water under the condition of exceeding 40% by mass (for example, 41% by mass) is referred to as “water-soluble solvent”. It is also said that a solvent having a maximum solubility in water of more than 40% by mass is referred to as a "water-soluble solvent" and a solvent having a maximum solubility in water of 40% by mass or less is referred to as a "low-water-soluble solvent". it can.
Solubility in water (% by mass)
= (Mass of solvent (g) / mass of water (g)) x 100 (2)

  Among the specific low water-soluble solvents, when a solvent having a lower water solubility (specifically, a specific low water-soluble solvent having a water solubility of 20% by mass or less) is added to the ink, a small amount of the ink is used. It is more preferable because the effect of reducing the water solubility (water absorption) in the whole can be obtained.

As the specific low water-soluble solvent, propylene glycol (mono or di) ether in which R ² in the general formula (1) has 3 carbon atoms from the viewpoint of effectively reducing the water solubility (water absorption) in the entire ink. Is preferred.

  Further, as the specific low water-soluble solvent, the standard boiling point is preferably 175 ° C. or lower, more preferably 170 ° C. or lower, and 160 ° C. or lower from the viewpoint of further improving the drying property of the printed matter. A compound having a temperature of 150 ° C. or lower is particularly preferable. By blending the specific low-water-soluble solvent having a standard boiling point in the above range, not only the drying property of the printed matter is further improved, but also the glossiness can be secured while preventing unevenness of the printed matter.

Among the specific low water-soluble solvents, from the viewpoint of reducing the odor of the ink, it is preferable to add a compound in which R ³ in the general formula (1) above is not an acetyl group, and the total content of the compound is in the ink. More preferably, it is 10% by mass or more and 50% by mass or less.

  The total content of the specific low water-soluble solvent in the ink composition according to the present embodiment is 5% by mass or more and 50% by mass or less when the total mass of the ink composition is 100% by mass, but 8% by mass % Or more and 45% by mass or less is preferable, and 10% by mass or more and 43% by mass or less is more preferable. When the total content of the specific low water-soluble solvent is within the above range, the water solubility (water absorption) in the entire ink can be sufficiently reduced, so that not only the dryness of the printed matter is further improved, but also the printed matter. It is possible to secure the glossiness while preventing the unevenness.

  The ink composition according to this embodiment also preferably contains a cyclic lactone. By containing the cyclic lactone, a part of the low-absorbent recording medium (for example, vinyl chloride resin) can be dissolved to allow the ink composition to penetrate into the recording medium. By thus penetrating the ink composition inside the recording medium, the abrasion resistance of the image recorded on the recording medium can be improved.

  In the present invention, “lactone” is a general term for cyclic compounds having an ester group (—CO—O—) in the ring. The lactone is not particularly limited as long as it is included in the above definition, but a lactone having 2 to 9 carbon atoms is preferable. Specific examples of such lactones include α-ethyl lactone, α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, ζ-enantiolactone, η-caprylolactone, Examples include γ-valerolactone, γ-heptalactone, γ-nonalactone, β-methyl-δ-valerolactone, 2-butyl-2-ethylpropiolactone, α, α-diethylpropiolactone, and the like. Of these, γ-butyrolactone is particularly preferable. The lactones exemplified above may be used alone or in combination of two or more.

  The content of the cyclic lactone is preferably 1% by mass or more and less than 40% by mass, more preferably 5% by mass or more and 30% by mass or less, and particularly preferably 100% by mass or less, when the total mass of the ink composition is 100% by mass. It is preferably 10% by mass or more and 20% by mass or less. When the content of the lactone is within the above range, it is easy to achieve both improvement in abrasion resistance and retention of glossiness of the recorded image.

  The ink composition according to this embodiment may contain a solvent other than the compound represented by the general formula (1) and the cyclic lactone. In addition, the ink composition according to the present embodiment may contain a solvent such as esters, ketones, alcohols, amides, alkanediols, and pyrrolidones other than the above-exemplified compounds.

1.3. Other Components Components other than the above components may be added to the ink composition according to the present embodiment. Examples of such components include surfactants, resins, chelating agents, preservatives, viscosity modifiers, solubilizing agents, antioxidants, antifungal agents and the like.

1.3.1. Surfactant In the ink composition according to the present embodiment, from the viewpoint of lowering the surface tension and improving the wettability with the recording medium, a silicon-based surfactant, a fluorine-based surfactant, or a nonionic surfactant is used. You may add the polyoxyethylene derivative which is an agent.

  As the silicon-based surfactant, it is preferable to use polyester-modified silicon or polyether-modified silicon. Specific examples include BYK-315, 315N, 347, 348, BYK-UV3500, 3510, 3530, and 3570 (all manufactured by Big Chemie Japan).

  As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and specific examples thereof include BYK-340 (manufactured by BYK Japan KK).

  As the polyoxyethylene derivative, it is preferable to use an acetylene glycol-based surfactant. Specific examples include Surfynol 82, 104, 465, 485, TG (all manufactured by Air Products Japan Co., Ltd.), Olfin STG, E1010 (all manufactured by Nisshin Chemical Co., Ltd.), Nissan Nonion A-10R, A-13R. (All manufactured by NOF CORPORATION), Floren TG-740W, D-90 (manufactured by Kyoeisha Chemical Co., Ltd.), Neugen CX-100 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and the like.

  The content of the surfactant in the ink composition according to this embodiment is preferably 0.05% by mass or more and 3% by mass or less, more preferably 0.5% by mass or more and 2% by mass or less.

1.3.2. Resin The ink composition according to the present embodiment may contain a resin (hereinafter, also referred to as “fixing resin”) for fixing the above-mentioned coloring material on the recording medium.

  As the fixing resin, acrylic resin, styrene acrylic resin, rosin-modified resin, phenol resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl acetate resin, vinyl chloride resin, fiber resin such as cellulose acetate butyrate, Examples thereof include vinyltoluene-α-methylstyrene copolymer resin. Among these, at least one resin selected from the group consisting of acrylic resins and vinyl chloride resins is preferable, and vinyl chloride resin is more preferable. By containing these fixing resins, the fixing property to the recording medium can be improved and the abrasion resistance is also improved.

  The solid content of the fixing resin in the ink composition according to the present embodiment is preferably 0.05% by mass or more and 15% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less. When the content of the fixing resin is within the above range, excellent fixability can be obtained for the low absorptive recording medium.

<Acrylic resin>
As the acrylic resin, a conventionally known copolymer composed of a polymerizable monomer can be used. Examples of the polymerizable monomer include acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, Methacrylic acid esters such as n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate; acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, monomaleic acid In addition to carboxyl group-containing monomers such as n-butyl, mono-n-butyl fumarate, and mono-n-butyl itaconic acid, hydroxyl group-containing (meth) acrylic acid esters, amide group-containing monomers, glycidyl group-containing monomers, cyano group-containing monomers Hydroxyl-containing allyl compounds may be used tertiary amino group-containing monomer, an alkoxysilyl group-containing monomers alone or in combination with.

As the acrylic resin, commercially available products may be used, for example, ACRYPET MF (trade name, Mitsubishi Rayon Co., acrylic resin), Sumipex LG (trade name, Sumitomo Chemical Co., acrylic resin), Paraloid B series. (Trade name, manufactured by Rohm and Haas, acrylic resin), Parapet G-1000P (trade name, manufactured by Kuraray, acrylic resin) and the like. In addition, in this invention, (meth) acrylic acid shall mean both acrylic acid and methacrylic acid, and (meth) acrylate shall mean both acrylate and methacrylate.

<Vinyl chloride resin>
Examples of the vinyl chloride resin include vinyl chloride and copolymers of vinyl acetate, vinylidene chloride, acrylic acid, maleic acid, and other monomers such as vinyl alcohol. Among these, vinyl chloride and vinyl acetate are included. A copolymer containing a constitutional unit derived from the copolymer (hereinafter, also referred to as “vinyl chloride / acetate copolymer”) is preferable, and a vinyl chloride / vinyl acetate copolymer having a glass transition temperature of 60 to 80 ° C. is more preferable.

  The vinyl chloride / vinyl acetate copolymer can be obtained by a conventional method, for example, suspension polymerization. Specifically, water, a dispersant, and a polymerization initiator are charged into the polymerization vessel, and after degassing, vinyl chloride and vinyl acetate are press-fitted to carry out suspension polymerization, or a part of vinyl chloride and vinyl acetate are press-fitted. Then, the reaction can be started, and suspension polymerization can be carried out while pressurizing the remaining vinyl chloride into the reaction.

  The vinyl chloride / vinyl chloride copolymer preferably contains 70 to 90% by mass of a vinyl chloride unit as its constitution. When the amount is within the above range, the compound is stably dissolved in the ink composition, and thus has excellent long-term storage stability. Furthermore, the ejection stability is excellent, and the excellent fixing property to the recording medium can be obtained.

  Further, the vinyl chloride / acetic acid copolymer may optionally include other constitutional units in addition to the vinyl chloride unit and the vinyl acetate unit, and examples thereof include a carboxylic acid unit, a vinyl alcohol unit, and a hydroxyalkyl acrylate unit. Of these, vinyl alcohol units are particularly preferable. It can be obtained by using a monomer corresponding to each unit described above. Specific examples of the monomer providing the carboxylic acid unit include maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, acrylic acid, and methacrylic acid. Specific examples of the monomer that gives the hydroxyalkyl acrylate unit include hydroxyethyl (meth) acrylate and hydroxyethyl vinyl ether. The content of these monomers is not limited as long as the effects of the present invention are not impaired, but for example, they can be copolymerized in the range of 15% by mass or less of the total amount of the monomers.

  The vinyl chloride-vinyl chloride copolymer may be a commercially available product, for example, solvine CN, solvine CNL, solvine C5R, solvine TA5R, solvine CL, solvine CLL (above, manufactured by Nisshin Chemical Industry Co., Ltd.). And so on.

  The average degree of polymerization of these resins is not particularly limited, but is preferably 150 to 1100, more preferably 200 to 750. When the average degree of polymerization of these resins is within the above range, the resins are stably dissolved in the ink composition according to the present embodiment, and thus the long-term storage stability is excellent. Furthermore, the ejection stability is excellent, and the excellent fixing property to the recording medium can be obtained. The average degree of polymerization of these resins is calculated from the measured specific viscosity, and can be determined according to the average degree of polymerization calculation method described in "JIS K6720-2".

  The number average molecular weight of these resins is not particularly limited, but is preferably 10,000 to 50,000, and more preferably 12,000 to 42,000. The number average molecular weight can be measured by GPC and can be obtained as a relative value in terms of polystyrene.

1.3.3. Others In addition to the above components, the ink composition according to the present embodiment has a chelating agent such as ethylenediaminetetraacetic acid salt (EDTA), a preservative, a viscosity modifier, a dissolution aid, an antioxidant, and an antifungal agent. A substance such as an agent for imparting predetermined performance can be contained.

1.4. Physical Properties Since the ink composition according to the present embodiment is used as an inkjet ink, the viscosity (viscosity at 25 ° C.) is preferably 2 mPa · s or more and 20 mPa · s or less, more preferably, by adjusting the composition or composition, for example. Is 3 mPa · s or more and 15 mPa · s or less. As a result, the ejection stability of the inkjet ink (stability of ejection amount, flight characteristics of droplets, etc.), ejection response (response speed, high frequency compatibility (frequency characteristics), etc.) can be improved. it can. The viscosity of the inkjet ink can be determined by measurement according to JIS Z8809 using a vibrating viscometer.

  The ink composition according to this embodiment preferably has a surface tension at 20 ° C. of 20 mN / m or more and 50 mN / m or more, and 25 mN / m or more, from the viewpoint of a balance between recording quality and reliability as an inkjet ink. It is more preferably 40 mN / m or less. The surface tension is measured by using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) and confirming the surface tension when the platinum plate is wetted with the ink in an environment of 20 ° C. be able to.

1.5. Uses The ink composition according to the present embodiment is excellent in image quality when recorded on a low-absorptive recording medium, and thus is suitable for sign applications to be exhibited outdoors.

The "low-absorbency recording medium" in the present specification refers to a recording medium having a water absorption amount of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method, at least the recording surface. Should have this property. According to this definition, the "low absorbent recording medium" in the present invention also includes a non-absorbent recording medium that does not absorb water at all. The Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Pulp and Paper Technology Association (JAPAN TAPPI). For details of the test method, refer to the standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000 Edition”. 51, "Paper and Paperboard-Liquid Absorption Test Method-Bristow Method".

  Specific examples of the low absorptive recording medium include a sheet, a film and a textile product containing a low absorptive material. The low-absorbent recording medium is a layer containing a low-absorbent material on the surface of a substrate (for example, paper, fiber, leather, plastic, glass, ceramics, metal, etc.) (hereinafter referred to as “low-absorbent layer”). (Also referred to as)). The low absorbent material is not particularly limited, and examples thereof include an olefin resin, an ester resin, a urethane resin, an acrylic resin, and a vinyl chloride resin.

  Among these, as the low absorptive recording medium, one having a recording surface containing a vinyl chloride resin can be preferably used. Specific examples of the vinyl chloride resin include polyvinyl chloride, vinyl chloride-ethylene copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl ether copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride. Examples include maleic acid ester copolymers, vinyl chloride- (meth) acrylic acid copolymers, vinyl chloride- (meth) acrylic acid ester copolymers, vinyl chloride-urethane copolymers. It should be noted that various characteristics such as thickness, shape, color, softening temperature, and hardness of the low absorptive recording medium are not particularly limited.

The ink composition according to the present embodiment enables the recording of an image on the untreated surface of a vinyl chloride resin substrate, and uses an expensive recording medium like a recording medium having a conventional receiving layer. Needless to say, although it has an excellent effect of eliminating the requirement, it can be applied even to a substrate surface-treated with an ink receiving layer.

2. Examples Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In addition, "part" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

2.1. Preparation of Ink Composition Various amounts of various solvents corresponding to the concentrations shown in Table 1 were charged into each container, and mixed and stirred for 30 minutes using a magnetic stirrer to obtain a mixed solvent.

  A part of the obtained mixed solvent is set aside, and Solsperse 37500 (trade name, dispersion resin manufactured by LUBRIZOL) is mixed therein, and then C.I. I. Pigment Blue 15: 3 (Copper phthalocyanine pigment manufactured by Client Co.) is added and pre-dispersed using a homogenizer, and then dispersed by a bead mill filled with zirconia beads having a diameter of 0.3 mm to obtain an average particle diameter. A 130 nm dispersion was obtained.

  Separately, a part of the mixed solvent was set aside, and Solvain CLL (manufactured by Nissin Chemical Industry Co., Ltd., chlorovinyl acetate resin) was added thereto, and the mixture was stirred and completely dissolved to obtain a resin solution.

  To the obtained dispersion, the balance of the mixed solvent, BYK-340 (manufactured by BYK Japan KK, fluorine-based surfactant) and the above resin solution were added, and the mixture was further stirred for 1 hour, and then the pore size was 5 μm. The cyan ink composition shown in Table 1 was obtained by filtering using a PTFE membrane filter. In addition, the numerical value in a table represents mass%.

2.2. Evaluation test 2.2.1. Evaluation of printing unevenness Using an inkjet printer (manufactured by Seiko Epson Corp., model “SC-S30650”), each ink was solid printed at 100% density on a PVC banner sheet (manufactured by 3M, “IJ51”), and 60 Allow to dry for minutes. Then, the printed surface was observed visually and using an optical microscope, and the one with less printing unevenness was defined as 6 points, and 1 point was evaluated in 6 levels. The evaluation criteria are as follows.
・ 6 to 5 points: Good because there is little printing unevenness on the printing surface.
4 to 1 point: defective because the printing unevenness on the printing surface is noticeable.

2.2.2. Gloss Evaluation Using an inkjet printer (manufactured by Seiko Epson Corp., model “SC-S30650”), each ink was placed on a glossy vinyl chloride sheet (Roland DG, “SV-G-1270G”) at 100% concentration. Solid printing was performed and dried at room temperature for 1 day to obtain a printed sample. Then, the 20 ° gloss of the solid printed portion was measured by MULTI GLOSS 268 (manufactured by Konica Minolta). The evaluation criteria are as follows, and if 6 to 4 points, it can be judged that the gloss is good, and if 3 to 1 points, it can be judged that the gloss is poor.
・ 6 points: 20 ° gloss is 34 or more.
・ 5 points: 20 ° gloss is 32 or more and less than 34.
・ 4 points: 20 ° gloss is 30 or more and less than 32.
・ 3 points: 20 ° gloss is 28 or more and less than 30.
・ 2 points: 20 ° gloss is 26 or more and less than 28.
・ 1 point: 20 ° gloss is less than 26.

2.2.3. Dot Size Judgment Test Using an inkjet printer (manufactured by Seiko Epson Corp., model “SC-S30650”), each ink was placed on a vinyl chloride banner sheet (manufactured by 3M, “IJ51”) at a concentration of 30% to measure 3 cm on a side. The squares were printed and then dried for 60 minutes. Then, the dot size was observed using an optical microscope, and the diameter was divided every 10 μm. If the bleeding is large, the dot shape will not be circular and cannot be measured. On the other hand, when the blur is small, the dot shape is close to a perfect circle, but the dot size is small. The evaluation criteria are as follows. A score of 6 to 4 can be judged to be good, and a score of 3 to 1 can be judged to be bad.
・ 6 points: The dot size exceeds 60 μm.
・ 5 points: Dot size is more than 50 μm and 60 μm or less.
・ 4 points: Dot size is more than 40 μm and 50 μm or less.
・ 3 points: Dot size is more than 30 μm and 40 μm or less.
・ 2 points: The dot size is more than 20 μm and 30 μm or less.
・ 1 point: Dot size is 20 μm or less.

2.2.4. Rubbing fastness test Using an inkjet printer (manufactured by Seiko Epson Corp., model "SC-S30650"), each ink was printed on a glossy polyvinyl chloride sheet (Roland DG, "SV-G-1270G") at 100%. Solid printing was performed at a density and dried at room temperature for 1 day to obtain a printed sample. Then, based on JIS L 0849, a dry test was conducted with an I type tester. Then, the OD value of the test cotton cloth was measured by Spectrolino (manufactured by Gretag Macbeth). The evaluation criteria are as follows, and when 6 to 4 points, it can be determined that the friction fastness is good, and when 3 to 1 points, the friction fastness can be determined to be poor.
・ 6 points: OD value is less than 0.20.
・ 5 points: OD value is 0.20 or more and less than 0.25.
・ 4 points: OD value is 0.25 or more and less than 0.30.
・ 3 points: OD value is 0.30 or more and less than 0.35.
・ 2 points: OD value is 0.35 or more and less than 0.40.
・ 1 point: OD value is 0.40 or more.

2.2.5. Surface Dryness Test Using an inkjet printer (manufactured by Seiko Epson Corp., model “SC-S30650”), each ink was placed on a glossy polyvinyl chloride sheet (Roland DG, “SV-G-1270G”) at 100%. Solid printing was performed with the density and dried for 3 minutes. Then, a scratch mark on the printed surface after winding was observed using a winding device. The observation method was to measure the surface roughness with a laser microscope ("VK-8700 Generation 2" manufactured by Keyence Corporation) to calculate the ratio of the area with the scratch mark. The evaluation criteria are as follows, and if 6 to 4 points, it can be judged that the surface dryness is good, and if 3 to 1 points, the surface dryness can be judged to be poor.
・ 6 points: No scratch mark area.
・ 5 points: Scratch area is more than 0% and 10% or less.
・ 4 points: Scratch area is more than 10% and 20% or less.
・ 3 points: Scratch area is more than 20% and 30% or less.
・ 2 points: Scratch area is more than 30% and 40% or less.
・ 1 point: Scratch mark area is over 40%.

2.2.6. Odor Using an inkjet printer (manufactured by Seiko Epson Corp., model “SC-S30650”), each ink was printed on a PVC banner sheet (manufactured by 3M, “IJ51”) at 100% concentration for 30 minutes for solid printing. went. During printing, odor was determined at a distance of 1 m in front of the inkjet printer. The evaluation criteria are as follows.
-A: No odor of solvent.
B: The solvent has an odor.

2.3. Evaluation Results Table 1 below shows the composition and evaluation results of the ink compositions of Examples and Comparative Examples. In addition, the solubility (mass%) in water and the standard boiling point (° C) of the solvent species used in each example and comparative example are summarized in Table 2 below. The solubility (mass%) of each solvent species in water was measured by the method described in the above definition of "solubility in water".

  As is clear from the results in Table 1, according to the ink compositions of Examples 1 to 5 in which the specific low water-soluble solvent was blended in a predetermined amount, the water solubility (water absorption) in the entire ink can be reduced, As a result, it was found that not only the dryness of the printed matter is good, but also the glossiness can be secured while preventing unevenness of the printed matter. It was also found that the dryness of the printed matter can be improved without adding a low boiling point solvent, and that the reliability such as clogging of a meniscus (that is, printing stability) is improved by not adding a low boiling point solvent. From the results of Examples 3 and 5, it was found that when methyl propylene glycol acetate was blended, a solvent odor from the ink was observed, and therefore there was a problem in terms of safety to the human body.

On the other hand, according to Comparative Examples 1 to 5 in which the specific low water-soluble solvent was not blended in a predetermined amount, any of the evaluation items became defective, and the ink composition was not excellent in balance.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations having the same function, method, and result, or configurations having the same object and effect). Further, the invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. In addition, the invention includes a configuration having the same effects as the configurations described in the embodiments or a configuration capable of achieving the same object. Further, the invention includes configurations in which known techniques are added to the configurations described in the embodiments.

Claims (6)

Contains a coloring material and a solvent,
As the solvent, the ink contains one or more compounds represented by the following general formula (1) in a total content of 60% by mass or more,
Among the compounds represented by the following general formula (1), as a low water-soluble solvent having a solubility in water of 40% by mass or less, R ² in the following general formula (1) has 3 carbon atoms and R ¹ is 8% by mass or more and 45% by mass or less of a compound in which R ³ is an alkyl group having 1 to 6 carbon atoms and R ³ is an alkyl group having 1 to 4 carbon atoms,
The inkjet ink composition further contains, as a solvent, 1% by mass or more and 10% by mass or less of cyclic lactone in the ink.
R ¹ O- (R ² O) m-R ³ (1)
(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² is an alkylene group having 2 or 3 carbon atoms, and R ³ is a hydrogen atom, an acetyl group, or 1 to 4 carbon atoms. (However, R ¹ and R ³ are not both hydrogen atoms, and m is an integer of 1 to 4.) The inkjet ink composition according to claim 1, comprising a compound having a normal boiling point of 175 ° C or lower as the low water-soluble solvent. The ink-jet ink composition according to claim 1 or 2, which contains one or more compounds in which R ³ is not an acetyl group, as a solvent other than the low water-soluble solvent among the compounds represented by the general formula (1). object. The inkjet ink composition according to any one of claims 1 to 3 , which contains a pigment as the coloring material. Further contains a vinyl chloride resin, an inkjet ink composition according to any one of claims 1 to 4. Among the compounds represented by the general formula (1), the low water-soluble solvent having a solubility in water of 40% by mass or less is one or more selected from butyl propylene glycol, dimethyl propylene diglycol and methyl propylene glycol acetate. The inkjet ink composition according to any one of claims 1 to 5 .