JP2017210599A - White ink, ink set, ink storage container, inkjet recording method, inkjet recording device and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white ink that is resistant to color blurring and has excellent dryability and fixability.SOLUTION: A white ink contains an organic solvent, the organic solvent contains an amide compound, for example, 3-methoxy-N, N-dimethylpropionamide, and a content of the amide compound is 40 mass% or more relative to the whole organic solvent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a white ink, an ink set, an ink container, an ink jet recording method, an ink jet recording apparatus, and a printing method.

  In order to improve durability such as light resistance, water resistance, and abrasion resistance in industrial applications such as advertising and billboards, for example, non-permeable recording media such as plastic films are used. Various inks used in the field have been developed.

As such an ink, for example, a solvent-based ink using an organic solvent as a solvent, an ultraviolet curable ink mainly containing a polymerizable monomer, and the like are widely used. However, there is a concern that the solvent-based ink may affect the environment due to evaporation of the organic solvent. The UV curable ink may have a limited choice of polymerizable monomers used from the viewpoint of safety.
Therefore, an ink set including an aqueous ink that has a low environmental load and can be directly recorded on a non-permeable recording medium has been proposed (see, for example, Patent Documents 1 to 3).

Among non-permeable recording media, there is a demand for forming a white image as a background when an image is formed on a transparent film by an ink jet recording method. As an ink jet recording method, after a first recording step of forming a white image with a white ink on a recording medium, after a drying step, a non-white image is formed with an ink containing a non-white color material superimposed on the white image. After the first printing method in which two recording steps are performed and the first recording step in which a non-white image is formed with ink containing a non-white color material on the recording medium, a white step is performed by superimposing the non-white image on the non-white image. There is a second printing method in which a second recording process for forming a white image with ink is performed.
In general, in the first printing method, the surface on the side on which an image is formed with respect to the recording medium becomes a table as a recorded material, and in the second recording method, the side on which no image is formed on the recording medium becomes a table.

  In any of the ink jet recording methods, it is a problem to prevent a non-white image from causing color bleeding with respect to a white image as a background. In each of the first printing method and the second printing method, the ink was overlapped in the second recording step as the drying rate of the ink in which the image was previously formed in the first recording step in the drying step was increased. At this time, it becomes difficult for the color to blur. However, even if it is intended to obtain a high ink drying rate at a high temperature, the drying temperature is limited by the heat resistance of the recording medium. In general, an inexpensive and transparent film-like recording medium such as a PET film or a PP film preferably has a drying temperature of about 60 ° C. or less in order not to cause distortion due to heat. For this reason, it has been necessary to provide a long drying time between the first recording process and the second recording process.

  In order to avoid the above-mentioned problem of color bleeding, the prior art includes an example of using an ink set made of a solvent ink made of a solvent-based ink having a high drying speed, or a UV ink containing a resin that is polymerized by light such as UV. An example using an ink set is well known. However, these inks are inferior in safety, and there is a need for water-based inks with a lower proportion of safer organic solvents.

  As a water-based ink, for example, Patent Document 4 discloses a first recording step of recording a white image on a recording medium using a white ink that substantially does not contain an alkyl polyol having a boiling point corresponding to 1 atm of 280 ° C. or higher, A drying step of drying the white image to a drying rate of 40% to 80%; an alkyl having a surface tension of 30 mN / m or less, a colorant, and a boiling point of 280 ° C. or higher corresponding to 1 atm. An ink jet recording method comprising: a second recording step of recording a colored image on the white image having a drying rate of 40% to 80% by an ink jet method using a color ink substantially containing no polyol; Has proposed. In this technique, by using an ink set that does not contain an alkyl polyol having a boiling point of 280 ° C. or higher, drying of both the white ink and the color ink is accelerated. Nevertheless, it is necessary to provide a long drying time in order to obtain a drying rate of 40% to 80%.

  Patent Document 5 contains at least an organic solvent, a surfactant, and water. As the organic solvent, at least (A) a water-soluble organic solvent having a boiling point of 100 ° C. or higher and 180 ° C. or lower and (B) a boiling point of 200 ° C. or higher. And an organic solvent having a surface tension of 20 mN / m or more and 30 mN / m or less, wherein the surfactant is a polysiloxane surfactant. . As an effect of the invention of Patent Document 5, the ejection stability is increased, and by increasing the proportion of the solvent having a low boiling point, the drying property of the ink is accelerated, the bleeding of the printing is eliminated, and the printing can be performed at a high speed. It is described.

  As described above, it is known that the drying speed is increased by limiting the organic solvent contained in the ink to a solvent having a relatively low boiling point. However, the drying time is not short enough. Therefore, in order to realize a recording method capable of forming a good image at high speed, a white ink that suppresses color bleeding and has excellent drying and fixing properties is desired.

  An object of the present invention is to provide a white ink in which color bleeding is suppressed and the drying property and fixing property are excellent.

The above problem is solved by the configuration 1) below.
1) An organic solvent is contained, the organic solvent contains an amide compound represented by the following formula (1), and the ratio of the amide compound to the whole organic solvent is 40% by mass or more ink.

(Wherein R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, R ₂ and R ₃ represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, R ₂ and R ₃ may be the same or different.)

  According to the present invention, it is possible to provide a white ink that suppresses color bleeding and is excellent in drying and fixing properties.

It is a perspective view for demonstrating an example of the inkjet recording device of this invention. It is a perspective view for demonstrating an example of the ink storage container of this invention. It is the schematic which shows an example of a heating means.

(White ink, ink set)
The white ink of the present invention contains an organic solvent, the organic solvent contains an amide compound represented by the following formula (1), and the ratio of the amide compound to the whole organic solvent is 40% by mass or more. It is characterized by. In addition, the white ink contains, for example, water, a surfactant, and resin particles.

In the formula, R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, R ₂ and R ₃ represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and R ₂ And R ₃ may be the same or different. The carbon number of R ₁ is preferably 1 to _2, and the carbon number of R ₂ and R ₃ is preferably 0 to 2. As the amide compound represented by the formula (1), a commercially available one can be used, and when it is synthesized, it can be synthesized according to known means.

  In addition, the ink set of the present invention includes the white ink of the present invention and at least two colors of ink composed of a non-white ink having a different color from the white ink. The non-white ink contains an organic solvent, the organic solvent contains an amide compound represented by the formula (1), and a ratio of the amide compound to the whole organic solvent is 40% by mass or more. preferable. In addition, the non-white ink contains, for example, water, a surfactant, and resin particles.

The present inventors have found the following.
As described above, in the case of forming an image on a transparent material to be printed, as an ink jet recording method, after the first recording step of forming a white image with white ink on the material to be printed, the white image is overlaid with a non-white ink. After the first printing method for performing the second recording process for forming the non-white image and the first recording process for forming the non-white image with the non-white ink on the substrate, the white ink is superimposed on the non-white image with the white ink. There is a second printing method in which a second recording process for forming an image is performed.
In the recording method having a step of superposing a white image and a non-white image as in the first printing method or the second printing method, the amide compound represented by the formula (1) with respect to the entire organic solvent in the ink It has been found that the ink drying property is remarkably improved by occupying 40% by mass or more. Although the reason for this is not clear, it is presumed that the film forming property is improved by using the amide compound and the resin particles in combination.
Furthermore, by improving the drying property of the ink to the non-permeable recording medium, even during high-speed recording, adjacent ink droplets coalesce and contract after landing (beading) and color bleeding on the background is suppressed. It has also been found that high-quality images can be obtained.

  Regarding the color blur, the white ink of the present invention is particularly excellent in the effect of suppressing color blur in the first printing method. In addition, the ink set of the present invention is preferable because the first printing method and the second printing method are excellent in suppressing color bleeding.

  The content of the amide compound with respect to the whole organic solvent is preferably 40% by mass or more, more preferably 40% by mass or more and 80% by mass or less in order to obtain good ejection stability, and excellent drying and fixing properties are obtained. Therefore, 60 mass% or more and 80 mass% or less are more preferable.

<Water>
There is no restriction | limiting in particular as said water, According to the objective, it can select suitably, For example, pure water, such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, ultrapure water, etc. are mentioned. . These may be used individually by 1 type and may use 2 or more types together.

  The content of the water is preferably 15% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 40% by mass or less with respect to the total amount of the ink. When the content is 15% by mass or more, high viscosity can be prevented and ejection stability can be improved. When the content is 60% by mass or less, wettability to a non-permeable recording medium is preferable. Image quality can be improved.

  The ink of the present invention contains an amide compound represented by the formula (1) in an organic solvent, but other organic solvents can also be used. Other organic solvents will be described.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines and sulfur-containing compounds.
Specific examples of the water-soluble organic solvent include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, Glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-he Polyhydric alcohols such as sundiol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, petriol, ethylene glycol mono Polyhydric alcohol alkyl ethers such as ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol mono Polyhydric alcohol aryl ethers such as benzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl- -N-containing heterocyclic compounds such as pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, Amides such as N-dimethylpropionamide and 3-butoxy-N, N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate, Examples thereof include ethylene carbonate.
In addition to functioning as a wetting agent, it is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because good drying properties can be obtained.

  The content of the organic solvent is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 60% by mass or less, with respect to the total amount of ink, from the viewpoints of ink drying properties and ejection reliability. .

<Surfactant>
As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants and anionic surfactants can be used.
There is no restriction | limiting in particular in silicone type surfactant, According to the objective, it can select suitably. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, both terminal modified polydimethylsiloxane, one terminal modified polydimethylsiloxane, and side chain both terminal modified polydimethylsiloxane. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as an aqueous surfactant. In addition, as the silicone surfactant, a polyether-modified silicone surfactant can be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.
Examples of the fluorosurfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. Polyoxyalkylene ether polymer compounds are particularly preferred because of their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, and the like. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylate. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain and a perfluoroalkyl ether group in the side chain. Examples thereof include salts of polyoxyalkylene ether polymers. As counter ions of salts in these fluorosurfactants, Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH) ₃ etc. are mentioned.
Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.
These may be used alone or in combination of two or more.
From the viewpoint of obtaining good ejection stability, it is preferable to select a polysiloxane surfactant as the surfactant.

<Polysiloxane surfactant>
Examples of the polysiloxane surfactant include a compound having a hydrophilic group or a hydrophilic polymer chain in the side chain of a compound having a polysiloxane structure (silicone compound) such as polydimethylsiloxane, as described above, and polydimethylsiloxane. Examples thereof include a compound having a hydrophilic group or a hydrophilic polymer chain at the terminal of a compound having a polysiloxane structure (silicone compound) such as siloxane. The polysiloxane surfactant only needs to have a polysiloxane structure in its structure.

Examples of the hydrophilic group and the hydrophilic polymer chain include a polyether group (polyethylene oxide, polypropylene oxide, copolymers thereof, and the like), polyglycerin (C _{3 ６ 6} O (CH ₂ CH (OH)). CH ₂ O) _n —H), pyrrolidone, betaine (C ₃ Ｃ ₆ N ⁺ (C ₂ H ₄ ) ₂ —CH ₂ COO ⁻ etc.), sulfate (C ₃ H ₆ O (C ₂ H ₄ O), etc.) _n -SO ₃ Na, etc.), phosphate _{(C 3 Η 6 O (C} 2 H 4 O) n -P (= O) OHONa etc.), quaternary salt ^{_{(C 3 H 6 n + (}} C 2 H 4 ) ₃ Cl ^-, etc.) and the like. However, in said chemical formula, n represents an integer greater than or equal to 1. Among these, it is preferable to have a polyether group.
Also, polydimethylsiloxane having a polymerizable vinyl group at the terminal and other monomers copolymerizable (hydrophilic monomers such as (meth) acrylic acid or salts thereof may be used for at least a part of the monomers. Preferable examples include vinyl copolymers having a silicone compound chain such as polydimethylsiloxane in the side chain obtained by copolymerization.
Among these, a compound having a polysiloxane structure and a compound having a hydrophilic polymer chain is preferable, and it is more preferable that the hydrophilic polymer chain contains a polyether group, and the polysiloxane surfactant is a hydrophobic group. A nonionic surfactant having a methylpolysiloxane as a hydrophilic group and a polyoxyethylene structure as a hydrophilic group is particularly preferable.

  Commercially available products can be used as the polysiloxane-based surfactant. Examples of the commercially available products include Silface SAG005 (HLB value: 7.0), Silface SAG008 (HLB value: 7.0), (Nippon Chemical Industry Co., Ltd.), FZ2110 (HLB: 1.0), FZ2166 (HLB value: 5.8), SH-3772M (HLB value: 6.0), L7001 (HLB value: 7. 4), SH-3773M (HLB value: 8.0), (manufactured by Toray Dow Co., Ltd.), KF-945 (HLB value: 4.0), KF-6017 (HLB value: 4.5), (Shin-Etsu Chemical Co., Ltd.), FormBan MS-575 (Ultra Additives Inc., HLB value: 5.0), and the like.

  The content of the surfactant is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less, based on the total amount of the ink, from the viewpoint of the drying property of the ink. .

<Resin particles>
The type of resin particles contained in the ink is not particularly limited and can be appropriately selected according to the purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene And resin particles made of a resin, a styrene-butadiene resin, a vinyl chloride resin, an acrylic styrene resin, an acrylic silicone resin, and the like. An ink can be obtained by mixing resin particles with a material such as a colorant or an organic solvent in a resin emulsion state in which water is dispersed as a dispersion medium. As said resin particle, what was synthesize | combined suitably may be used and a commercial item may be used. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types of resin particles.
It is preferable to select polyurethane resin particles as the resin particles because good drying properties of the good ink, high image glossiness, and scratch resistance can be obtained.

<< Polyurethane resin particles >>
By using the amide compound and polyurethane resin particles in combination, the solvent resistance can be greatly improved in addition to the good drying property of the ink, high image glossiness, and scratch resistance.
The glass transition temperature (Tg) of the polyurethane resin particles is preferably 0 ° C. or lower. When the glass transition temperature is 0 ° C. or lower, it is possible to form an ink film at the liquid-air interface from a low evaporation rate. Moreover, high image glossiness can be obtained.
In addition, fixing to a printing medium such as a recording medium becomes stronger, and adhesion and fixing properties are improved. Furthermore, nozzle clogging when ink is ejected from the head can be suppressed, and the occurrence rate of ejection defects can be reduced.

  Examples of the polyurethane resin particles include polyether-based polyurethane resin particles, polycarbonate-based polyurethane resin particles, and polyester-based polyurethane resin particles.

  There is no restriction | limiting in particular as said polyurethane resin particle, According to the objective, it can select suitably, For example, the polyurethane resin particle etc. which are obtained by making a polyol and polyisocyanate react are mentioned.

-Polyol-
Examples of the polyol include polyether polyol, polycarbonate polyol, and polyester polyol. These may be used individually by 1 type and may use 2 or more types together.

--Polyether polyol--
Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxide using at least one compound having two or more active hydrogen atoms as a starting material.

  Examples of the compound having two or more active hydrogen atoms include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, and 1,6-hexane. Diol, glycerin, trimethylolethane, trimethylolpropane and the like can be mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran. These may be used individually by 1 type and may use 2 or more types together.

  The polyether polyol is not particularly limited and may be appropriately selected depending on the intended purpose. From the viewpoint of obtaining a binder for ink that can impart very excellent scratch resistance, polyoxytetramethylene glycol, polyoxy Propylene glycol is preferred. These may be used individually by 1 type and may use 2 or more types together.

--Polycarbonate polyol--
Examples of the polycarbonate polyol that can be used for the production of the polyurethane resin particles include those obtained by reacting a carbonate with a polyol, and those obtained by reacting phosgene with bisphenol A and the like. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the carbonate ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, and diphenyl carbonate. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the polyol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1, 2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8 -Octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcinol , Bisphenol-A, bisphe Relatively low molecular weight dihydroxy compounds such as polyol-F, 4,4′-biphenol; polyether polyols such as polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol; polyhexamethylene adipate, polyhexamethylene succinate, poly Examples thereof include polyester polyols such as caprolactone. These may be used individually by 1 type and may use 2 or more types together.

--Polyester polyol--
Examples of the polyester polyol include those obtained by esterifying low molecular weight polyols and polycarboxylic acids, polyesters obtained by ring-opening polymerization reaction of cyclic ester compounds such as ε-caprolactone, and copolymers thereof. Examples include polyester. These may be used individually by 1 type and may use 2 or more types together.

Examples of the low molecular weight polyol include ethylene glycol and propylene glycol. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polycarboxylic acid include succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, anhydrides or ester-forming derivatives thereof. These may be used individually by 1 type and may use 2 or more types together.

-Polyisocyanate-
Examples of the polyisocyanate include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate and naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene Examples thereof include aliphatic or alicyclic diisocyanates such as diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate. These may be used individually by 1 type and may use 2 or more types together. Among these, since the ink of the present invention is also used for outdoor applications such as posters and signboards, it requires a coating film with very high long-term weather resistance. From the viewpoint of long-term weather resistance, alicyclic Formula diisocyanates are preferred.

Furthermore, the use of at least one alicyclic diisocyanate makes it easy to obtain the desired coating strength and scratch resistance.
Examples of the alicyclic diisocyanate include isophorone diisocyanate and dicyclohexylmethane diisocyanate.
As content of the said alicyclic diisocyanate, 60 mass% or more is preferable with respect to the isocyanate compound whole quantity.

[Production method of polyurethane resin particles]
The polyurethane resin particles can be obtained by a conventionally used production method, and examples thereof include the following methods.
First, in the absence of a solvent or in the presence of an organic solvent, the polyol and the polyisocyanate are reacted at an equivalent ratio in which an isocyanate group becomes excessive to produce an isocyanate-terminated urethane prepolymer.
Next, the anionic group in the isocyanate-terminated urethane prepolymer is neutralized with a neutralizing agent as necessary, and then reacted with a chain extender, and finally the organic solvent in the system is removed as necessary. Can be obtained.

Examples of the organic solvent that can be used in the production of the polyurethane resin particles include ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; acetates such as ethyl acetate and butyl acetate; nitriles such as acetonitrile; Examples include amides such as formamide, N-methylpyrrolidone, and N-ethylpyrrolidone. These may be used individually by 1 type and may use 2 or more types together.
Examples of the chain extender include polyamines and other active hydrogen group-containing compounds.

  Examples of the polyamine include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4′-dicyclohexylmethanediamine, and 1,4-cyclohexane. Diamines such as diamines; Polyamines such as diethylenetriamine, dipropylenetriamine and triethylenetetramine; Hydrazines such as hydrazine, N, N′-dimethylhydrazine and 1,6-hexamethylenebishydrazine; Succinic dihydrazide, Adipic dihydrazide And dihydrazides such as glutaric acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the other active hydrogen group-containing compounds include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, Glycols such as saccharose, methylene glycol, glycerin, sorbitol; phenols such as bisphenol A, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, hydroquinone Kind; water etc. are mentioned. These may be used alone or in combination of two or more.

  The polyurethane resin particles are preferably polycarbonate polyurethane resin particles from the viewpoint of water resistance, heat resistance, abrasion resistance, weather resistance, and image scratch resistance due to the high cohesive strength of carbonate groups. When the polycarbonate-based polyurethane resin particles are used, an ink suitable for a printed material used in a harsh environment such as an outdoor application can be obtained.

  As the polyurethane resin particles, commercially available products may be used. For example, WBR-600U (manufactured by Taisei Fine Chemical Co., Ltd., glass transition point = −30 ° C.), Jonkrill 585 (manufactured by BASF, glass transition point = −). 20 ° C.), Superflex 300 (Daiichi Kogyo Seiyaku Co., Ltd., glass transition point = −42 ° C.), Superflex 470 (Daiichi Kogyo Seiyaku Co., Ltd., glass transition point = −31 ° C.), and the like. These may be used individually by 1 type and may use 2 or more types together.

  The content of the resin particles is preferably 1% by mass or more and 15% by mass or less, and more preferably 2% by mass or more and 10% by mass or less based on the total amount of the ink from the viewpoint of the drying property of the ink.

<Other ingredients>
Examples of the other components include coloring materials, antiseptic / antifungal agents, rust preventives, pH adjusters, rubbers such as hindered phenols and hindered phenol amines, and colorless anti-aging agents for plastics.

<Color material>
The standard of whiteness of white ink is ISO-2469 (JIS-8148). Generally, when the value is 70 or more, it is used as a white color material.
Examples of the metal oxide used for the white ink include titanium oxide, iron oxide, tin oxide, zirconium oxide, and iron titanate (complex oxide of iron and titanium).

Examples of the non-white ink having a color different from that of the white ink include color ink, black ink, gray ink, clear ink, and metallic ink. The clear ink means an ink that does not contain a colorant and mainly comprises resin particles, an organic solvent, and water.
Examples of the color ink include cyan ink, magenta ink, yellow ink, light cyan ink, light magenta ink, red ink, green ink, blue ink, orange ink, and violet ink.

The color material used for the non-white ink is not particularly limited as long as it exhibits a non-white color, and can be appropriately selected according to the purpose, and examples thereof include dyes and pigments. These may be used alone or in combination of two or more. Among these, a pigment is preferable.
Examples of the pigment include inorganic pigments and organic pigments.

  As the inorganic pigment, for example, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, it is manufactured by a known method such as a contact method, a furnace method, or a thermal method. And carbon black. These may be used individually by 1 type and may use 2 or more types together.

Examples of the organic pigment include azo pigments (for example, azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments). , Quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (eg basic dye chelates, acidic dye chelates), nitro pigments, nitroso pigments, aniline black, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.
In addition, use of hollow resin particles and inorganic hollow particles is also possible.
Of these pigments, those having good affinity with the solvent are preferably used.

  In the pigment, for black, for example, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, copper, iron (CI pigment black 11), And organic pigments such as aniline black (CI Pigment Black 1). These may be used individually by 1 type and may use 2 or more types together.

  For color, for example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155; I. Pigment orange 5, 13, 16, 17, 36, 43, 51; C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 ( Cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219; I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142; I. Acid Red 52, 80, 82, 249, 254, 289; I. Acid Blue 9, 45, 249; C.I. I. Acid Black 1, 2, 24, 94; C.I. I. Food black 1, 2; I. Direct yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173; I. Direct Red 1, 4, 9, 80, 81, 225, 227; I. Direct blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202; I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195; I. Reactive red 14, 32, 55, 79, 249; I. Reactive black 3, 4, 35 etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.

  The color material used for the metallic ink is, for example, a fine powder obtained by finely pulverizing a metal simple substance, an alloy, or a metal compound, and more specifically, aluminum, silver, gold, nickel, chromium, tin, zinc, It may be any one or more of a group of simple metals consisting of indium, titanium, silicon, copper, or platinum, or may be an alloy obtained by combining these groups of metals, or these It can be obtained by finely pulverizing any one or a plurality of oxides, nitrides, sulfides or carbides of a group of simple metals or alloys.

In order to disperse the pigment in the ink, a method of introducing a hydrophilic functional group into the pigment to form a self-dispersing pigment, a method of dispersing the pigment surface by coating with a resin, a method of dispersing using a dispersant, Etc.
Examples of a method for introducing a hydrophilic functional group into a pigment to form a self-dispersing pigment include a self-dispersing pigment that can be dispersed in water by adding a functional group such as a sulfone group or a carboxyl group to the pigment (for example, carbon). Can be used.
As a method for coating the surface of the pigment with a resin and dispersing it, a method in which the pigment is included in microcapsules and can be dispersed in water can be used. This can be paraphrased as a resin-coated pigment. In this case, it is not necessary that all pigments blended in the ink are coated with a resin, and within a range where the effects of the present invention are not impaired, uncoated pigments and partially coated pigments are dispersed in the ink. It may be.
Examples of the method of dispersing using a dispersant include a method of dispersing using a known low-molecular type dispersant or high-molecular type dispersant represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and naphthalenesulfonic acid Na formalin condensate can also be suitably used as a dispersant.
A dispersing agent may be used individually by 1 type, or may use 2 or more types together.

<Pigment dispersion>
An ink can be obtained by mixing a material such as water or an organic solvent with a color material. Further, it is also possible to produce an ink by mixing a pigment, other water, a dispersant, and the like into a pigment dispersion and mixing a material such as water or an organic solvent.
The pigment dispersion is obtained by dispersing water, a pigment, a pigment dispersant, and other components as required, and adjusting the particle size. For dispersion, a disperser is preferably used.
The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency is 20 nm or more in terms of maximum number because the pigment dispersion stability is good and the image quality such as ejection stability and image density is also high. 500 nm or less is preferable and 20 nm or more and 150 nm or less are more preferable. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good ejection stability and increasing the image density, 0.1% by mass. % To 50% by mass is preferable, and 0.1% to 30% by mass is more preferable.
The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.

The number average particle diameter of the pigment is not particularly limited and may be appropriately selected depending on the intended purpose, but the maximum frequency is preferably 20 nm or more and 150 nm or less in terms of the maximum number. When the number average particle size is 20 nm or more, dispersion operation and classification operation are facilitated, and when it is 150 nm or less, not only pigment dispersion stability as ink is improved, but also ejection stability is excellent. Image quality such as image density is also high, which is preferable.
The number average particle diameter can be measured using, for example, a particle size analyzer (Microtrac Model UPA9340, manufactured by Nikkiso Co., Ltd.).

  The content of the color material is preferably 0.1% by mass or more and 15% by mass or less, and preferably 1% by mass or more and 10% by mass or less based on the total amount of ink from the viewpoint of image density, fixability, and ejection stability. Is more preferable. When the content is from 0.1% by mass to 15% by mass, the ejection reliability is high and an image with high saturation can be obtained.

[Ink production method]
The ink can be produced, for example, by stirring and mixing the water, the organic solvent, the surfactant, the resin particles, and, if necessary, the other components. As the stirring and mixing, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a stirrer using a normal stirrer blade, a magnetic stirrer, a high-speed disperser, or the like can be used.

There is no restriction | limiting in particular as a physical property of an ink, According to the objective, it can select suitably, For example, it is preferable that a viscosity, surface tension, pH, etc. are the following ranges.
The viscosity at 25 ° C. of the ink is preferably 5 mPa · s or more and 30 mPa · s or less, preferably 5 mPa · s or more and 25 mPa · s or less from the viewpoint of improving the printing density and character quality and obtaining good discharge properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. Measurement conditions are 25 ° C., standard cone rotor (1 ° 34 ′ × R24), sample liquid amount 1.2 mL, rotation speed 50 rpm, and measurement is possible for 3 minutes.
The surface tension of the ink is preferably 30 mN / m or less, more preferably 27 mN / m or less at 25 ° C. from the viewpoint that the ink is suitably leveled on the recording medium and the drying time of the ink is shortened. However, when the surface tension is 18 mN / m or less, it is difficult to ensure the defoaming property of the ink, and thus the ejection stability is deteriorated.
The pH of the ink is preferably 7 to 12 and more preferably 8 to 11 from the viewpoint of preventing corrosion of the metal member in contact with the liquid.

<Substrate>
The material to be printed is not particularly limited and is not limited to those used as a general recording medium, and building materials such as wallpaper and flooring, cloth for clothing, textiles, leather, and the like can be appropriately used. Moreover, ceramics, glass, and metal can also be used by adjusting the structure of the path | route which conveys to-be-printed material. Next, the recording medium will be described, but the printed material is not limited to this.

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, and the like can be used, but good image formation is possible even with a non-permeable recording medium.
The non-permeable recording medium is a substrate having a surface with low water permeability and absorbency, and includes a material that does not open to the outside even if there are many cavities inside, more quantitatively. In the Bristow method, the recording medium has a water absorption amount of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 .
As the non-permeable recording medium, for example, a plastic film such as a vinyl chloride resin film, a polyethylene terephthalate (PET) film, polypropylene, polyethylene, or a polycarbonate film can be suitably used.

<Ink container>
The ink container of the present invention contains each ink in the ink set of the present invention in an ink container, and further includes other members appropriately selected as necessary.

  There is no restriction | limiting in particular as said ink accommodating part, Various containers are mentioned, The shape, a structure, a magnitude | size, a material, etc. can be suitably selected according to the objective, For example, an aluminum laminate film, a resin film, etc. And those having at least an ink bag or the like formed in (1).

<Inkjet recording method and recording apparatus>
The inkjet recording method and recording apparatus of the present invention will be described. In addition, although the case where a recording medium is used as a printing material will be described, the present invention is not limited to this.

The ink jet recording method of the present invention includes an ink discharging step in which ink contained in an ink set is discharged and applied to a substrate to be printed. The ink jet recording apparatus of the present invention is an apparatus that has at least the ink container and an ink discharge unit that discharges the ink, and records an image on a printing material using the ink. Examples of the ink jet recording apparatus include a printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, and a three-dimensional modeling apparatus.
Ink jet recording method and recording apparatus, in addition to ink ejection process and ink ejection means, processes and means for feeding, transporting, and discharging a recording medium, and other processes and means for pre-processing and / or post-processing Can be included.
The ink jet recording method and the recording apparatus may have a heating step and a heating unit, a drying step and a drying unit. These steps and means include, for example, steps and means for heating and drying the printing surface and back surface of the recording medium. Specifically, a warm air heater, an infrared heater, or the like can be used. Heating and drying can be performed before printing, during printing, after printing, and the like.
Further, the image formed by the ink jet recording method and the recording apparatus of the present invention is not limited to a significant image such as characters and figures by ink. For example, what forms patterns, such as a geometric pattern, etc. includes what forms a three-dimensional image.
The ink discharge means in the ink jet recording apparatus of the present invention is not particularly limited, and may be a known discharge head, and includes both a serial type apparatus that moves the discharge head and a line type apparatus that does not move the discharge head.
Furthermore, in the ink jet recording apparatus of the present invention, not only the desktop type but also a wide recording apparatus that can print on an A0 size recording medium, or continuous paper wound up in a roll shape, for example, is used as the recording medium. A continuous book printer that can do this is also included.

FIG. 1 is a perspective view for explaining an example of the ink jet recording apparatus of the present invention, and FIG. 2 is a perspective view for explaining an example of the ink container of the present invention. An image forming apparatus 400 as an example of a recording apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided in the exterior 401 of the image forming apparatus 400. Each ink storage portion 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), yellow (Y) is packaged, for example, an aluminum laminate film It is formed by a member. The ink storage unit 411 is stored in, for example, a plastic container 414. As a result, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 (ink container) is provided on the back side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. Thus, the ink discharge ports 413 of the main tank 410 and the discharge heads 434 for the respective colors communicate with each other via the supply tubes 436 for the respective colors, and ink can be discharged from the discharge heads 434 to the recording medium.

<< Heating step and heating means >>
The heating step and heating means are preferably a step and means for heating a recording medium on which an image is recorded.
The image formed by the ink jet recording method and the recording apparatus of the present invention can provide a high quality image even if the recording medium is an impermeable recording medium, but it has a higher image quality and scratch resistance. It is preferable to heat the image after recording in order to be able to cope with formation of an image with high adhesion and high-speed recording conditions. By heating the image, film formation of the resin particles contained in the ink is promoted, so that the image hardness of the printed matter can be improved.

FIG. 3 is a schematic view showing an example of the heating means. As shown in FIG. 3, by driving the recording head in accordance with the image signal while moving the carriage 133, ink droplets are ejected onto the stopped recording medium 142 to form an image. The guide member 153 supports the recording medium 142. The recording medium 142 is transported in the transport direction on a transport belt 151 that is stretched between a transport roller 157 and a tension roller 158. Hot air 202 is blown by the heating fan 201 as a hot air generating unit on the image formed on the recording medium 142. As a result, the image is heated.
A heater group 203 is provided on the opposite side of the conveying belt 151 (the side on which the recording medium 142 is not placed), and the recording medium 142 on which an image is formed can be heated.

<Printing method>
The printing method of the present invention includes a first recording step of forming a non-white image on a substrate using the non-white ink in the ink set of the present invention, and a non-white image on the non-white image using the white ink of the present invention. And a second recording step for forming a white image. Since the white ink and ink set of the present invention have good drying properties, according to the printing method, color bleeding of the non-white image with respect to the background white image can be remarkably suppressed, and non-penetration can be achieved. High gloss, good scratch resistance and the like can be obtained even on a recording medium. Note that the order of the first recording step and the second recording step may be reversed.
At this time, the white ink can be applied to the entire surface of the printing material, or may be applied to a part of the printing material. In the case of applying to a part of the substrate, for example, it may be applied to the same part as the part where the non-white image is formed, or may be applied to a part which is partially common with the part where the non-white image is formed Good.

The printing method of the present invention is not limited to the ink jet recording method and can be widely used. In addition to inkjet recording methods, for example, blade coating method, gravure coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method , Smoothing coating method, micro gravure coating method, reverse roll coating method, 4 to 5 roll coating method, dip coating method, curtain coating method, slide coating method, die coating method, spray coating method and the like.
As an example of the embodiment, when the white ink is applied to the entire surface of the printing material, a method other than the ink jet printing recording method is performed, and when the non-white ink is applied to the printing material, the ink jet recording method is used. Can do.

(Printed matter)
The printed matter of the present invention has a printed layer formed using the ink set of the present invention on, for example, a recording medium that is a substrate to be printed.
For example, it can be recorded by an inkjet recording method and a recording apparatus to obtain a printed matter.

  Note that the terms “image formation”, “recording”, “printing”, “printing”, etc. in the terms of the present invention are all synonymous.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not restrict | limited to these examples. The term “part” refers to part by mass unless otherwise specified.

(Preparation Example 1 of Pigment Dispersion)
<Preparation of black pigment dispersion>
After premixing the following prescription mixture, it was circulated and dispersed for 7 hours in a disk-type bead mill (Shinmaru Enterprises Co., Ltd., KDL type, media: 0.3 mm diameter zirconia ball used) to obtain a black pigment dispersion (pigment solid (Min. Concentration: 15% by mass).
Carbon black pigment (trade name: Monarch 800, manufactured by Cabot Corporation) 15 parts by mass Anionic surfactant (trade name: Pionein A-51-B, manufactured by Takemoto Yushi Co., Ltd.) 2 parts by mass Ion exchange water ... 83 parts by mass

(Preparation Example 2 of Pigment Dispersion)
<Preparation of cyan pigment dispersion>
In Preparation Example 1 of Pigment Dispersion, the same procedure as in Preparation Example 1 of Pigment Dispersion was performed except that the carbon black pigment was changed to Pigment Blue 15: 3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.). Thus, a cyan pigment dispersion (pigment solid content concentration: 15% by mass) was obtained.

(Preparation Example 3 of Pigment Dispersion)
<Preparation of magenta pigment dispersion>
Magenta was prepared in the same manner as in Preparation 1 of pigment dispersion, except that the carbon black pigment was changed to Pigment Red 122 (trade name: Toner Magenta EO02, manufactured by Clariant Japan Co., Ltd.). A pigment dispersion (pigment solid content concentration: 15% by mass) was obtained.

(Preparation Example 4 of Pigment Dispersion)
<Preparation of Yellow Pigment Dispersion 1>
In the same manner as in Preparation Example 1 of the pigment dispersion, except that the carbon black pigment was changed to Pigment Yellow 155 (trade name: TONER YELLOW 3GP, manufactured by Clariant Japan) in Preparation Example 1 of the pigment dispersion. Dispersion 1 (pigment solid content concentration: 15% by mass) was obtained.

(Preparation Example 5 of Pigment Dispersion)
<Preparation of white pigment dispersion 1>
Titanium oxide (trade name: STR-100W, manufactured by Sakai Chemical Industry Co., Ltd.) 25 parts, pigment dispersant (trade name: TEGO Dispers 651, manufactured by Evonik Co., Ltd.) 5 parts, and water 70 parts are mixed, and a bead mill (trade name: Research). (Lab, manufactured by Shinmaru Enterprises Co., Ltd.) 0.3 mmφ zirconia beads were dispersed for 5 minutes at a filling rate of 60% and 8 m / s to obtain a white pigment dispersion.

<Preparation of polyurethane resin emulsion 1>
In a 2 L reactor equipped with a stirrer, thermometer, nitrogen seal tube and condenser, 100 parts by mass of methyl ethyl ketone, polyester polyol (1) (iPA / AA = 6/4 (molar ratio) and EG / NPG = 1) Polyester polyol obtained from A / 9 (molar ratio), number average molecular weight = 2,000, average number of functional groups = 2, iPA: isophthalic acid, AA: adipic acid, EG: ethylene glycol, NPG: neopentyl glycol 345 parts by mass) and 9.92 parts by mass of 2,2-dimethylolpropionic acid DMPA were mixed and uniformly mixed at 60 ° C.
Thereafter, 45.1 parts by mass of triethylene glycol diisocyanate TEGDI and 0.08 parts by mass of dioctyltin dilaurate DOTDL were charged and reacted at 72 ° C. for 3 hours to obtain a polyurethane solution.
The polyurethane solution was charged with 80 parts by mass of isopropyl alcohol IPA, 220 parts by mass of methyl ethyl ketone MEK, 3.74 parts by mass of triethylamine TEA, and 596 parts by mass of water. After phase inversion, MEK, IPA and The TEA was removed to obtain a polyurethane resin emulsion 1.
The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 30% by mass and pH 8.
Using this emulsion 1, the glass transition point (= Tg) measured by “Thermo plus EVO2” (manufactured by Rigaku) was 0 ° C.

<Preparation of polyurethane resin emulsion 2>
Polycarbonate diol (reaction product of 3-methyl-1,5-pentanediol and diphenyl carbonate) (number average molecular weight Mn = 1200) 1500 g, 2,2-into a reaction vessel into which a stirrer, a reflux condenser and a thermometer were inserted. Dimethylolpropionic acid (DMPA) (220 g) and N-methylpyrrolidone (NMP) (1347 g) were charged in a nitrogen stream and heated to 60 ° C. to dissolve DMPA. Subsequently, 1445 g of 4,4′-dicyclohexylmethane diisocyanate and 2.6 g of dibutyltin dilaurate (catalyst) were added and heated to 90 ° C. to carry out a urethanization reaction for 5 hours to obtain an isocyanate-terminated urethane prepolymer. The reaction mixture was cooled to 80 ° C., 4340 g was extracted from the mixture in which 149 g of triethylamine was added and mixed, and added to a mixed solution of 5400 g of water and 15 g of triethylamine with vigorous stirring. Next, 1500 g of ice was added, 626 g of 35% 1,6-hexamethylenediamine aqueous solution was added to carry out chain extension reaction, the solvent was distilled off so that the solid content concentration was 30%, and polyurethane resin emulsion 2 was obtained. Obtained.
Using this emulsion 2, the glass transition point (= Tg) measured with “Thermo plus EVO2” (manufactured by Rigaku) was 10 ° C.

Example 1
As color ink (non-white ink), pigment dispersion 20% by mass, resin emulsion 1 15% by mass, surfactant (BYK-348, manufactured by BYK Chemie) 1.0% by mass, 1,2-propanediol 14% by mass 1,5-butanediol 5% by mass, 1,2-hexanediol 5% by mass, 3-methoxy-N, N-dimethylpropionamide (Ecamide M100, manufactured by Idemitsu Kosan Co., Ltd.) 12% by mass, diethylene glycol monobutyl ether 4 Polypropylene filter having a mean pore size of 0.2 μm (product: Proxel LV (manufactured by Avicia) 0.1 mass%) and high-pure water were added so as to be the remaining amount, and mixed and stirred. Name: Betafine polypropylene pleated filter PPG series, manufactured by 3M). The click was prepared.
As white ink, pigment dispersion 20% by mass, resin emulsion 1 15% by mass, surfactant (BYK-348, manufactured by BYK Chemie) 1.0% by mass, 1,2-propanediol 10% by mass, 1,3- Butanediol 5% by mass, 1,2-hexanediol 5% by mass, 3-methoxy-N, N-dimethylpropionamide (Ecamide M100, manufactured by Idemitsu Kosan Co., Ltd.) 16% by mass, diethylene glycol monobutyl ether 4% by mass, preservative As a trade name: Proxel LV (manufactured by Avicia) 0.1 mass% and high-purity water are added so as to be the remaining amount, mixed and stirred, and a polypropylene filter having an average pore size of 0.2 μm (trade name: Betafine polypropylene pleats) White ink was prepared by filtering with a filter PPG series (manufactured by 3M).
An ink set containing the above non-white ink and white ink was prepared.

(Example 2)
1. Pigment dispersion 20% by mass, resin emulsion (trade name: Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content concentration: 30% by mass), 15% by mass, surfactant (BYK-348, manufactured by BYK Chemie) 0% by mass, 1,2-propanediol 10% by mass, 1,2-hexanediol 3% by mass, 3-methoxy-N, N-dimethylpropionamide (Ecamide M100, manufactured by Idemitsu Kosan Co., Ltd.) 24% by mass, diethylene glycol Polybutyl ether having an average pore size of 0.2 μm, 3% by mass of monobutyl ether, 0.1% by mass of Proxel LV (manufactured by Avicia) as a preservative, and high-purity water were added so as to be the remaining amount, mixed and stirred. By filtering with a filter (trade name: Betafine polypropylene pleated filter PPG series, 3M) To prepare an ink set including the respective color inks.

(Examples 3-8 and Comparative Examples 1-2)
In Example 2, the inks of Examples 3 to 8 and Comparative Examples 1 and 2 were used in the same manner as Example 2 except that the composition and content described in Tables 1 to 4 below were changed. An ink set containing the same was prepared.

In Tables 1 to 4, the names of the components and the names of the manufacturing companies are as follows.
-Urethane resin emulsion 3: Trade name: Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content concentration: 30% by mass, Tg: -42 ° C
Acrylic-silicone resin emulsion: Trade name: AE980, manufactured by Etec Co., Ltd., solid content concentration: 50% by mass, Tg: -14 ° C
-Surfactant: BYK-348, manufactured by BYK Chemie, polyether polysiloxane surfactant-Surfactant: FS300, manufactured by Dupont, fluorinated surfactant-Amide compound: Ecamide M100, manufactured by Idemitsu Kosan Co., Ltd., 3- Methoxy-N, N-dimethylpropionamide, additive: Proxel LV, manufactured by Avicia

[Formation of solid image with white ink advance]
An ink cartridge filled with each of the inks of the examples and comparative examples was loaded into an inkjet printer (RICOH Pro L4160, manufactured by Ricoh Co., Ltd.), and a non-porous transparent PET sheet LLPET 1223 (manufactured by Sakurai Co., Ltd.) After the first recording step of discharging the white ink shown in Table 4 to form a solid image, heating and drying, and then forming a solid image by discharging color ink (non-white ink) over the white ink. Two recording steps were performed, and a color evaluation chart composed of cyan, magenta, yellow, and black was printed. Further, the evaluation chart was dried for 1 hour on a hot plate (NINOS ND-1, manufactured by AS ONE Corporation) set to 60 ° C. immediately after output.

(Formation of solid image with color advance)
An ink cartridge filled with each of the inks of the examples and comparative examples was loaded into an inkjet printer (RICOH Pro L4160, manufactured by Ricoh Co., Ltd.), and a non-porous transparent PET sheet LLPET 1223 (manufactured by Sakurai Co., Ltd.) After the first recording step of forming a solid image by discharging the color ink shown in Table 4, the second recording step of forming a solid image by heating and drying and discharging the white ink on the color ink is performed. The evaluation chart was printed. As the evaluation chart, the same color evaluation chart as that described above was used. Further, the evaluation chart was dried for 1 hour on a hot plate (NINOS ND-1, manufactured by AS ONE Corporation) set to 60 ° C. immediately after output.

  Next, “image blur”, “drying”, “fixing property (beading)”, “ejection stability”, “image gloss”, and “scratch resistance” were evaluated as follows. The results are shown in Table 5.

  Considering the use for outdoor use, the evaluation of “fixability (beading)” was adopted, which is considerably stricter than the case of recording on general paper.

<Evaluation of bleeding on white ink pre-launched image>
With respect to the solid image of the white ink pre-applied, the test pattern printed on the evaluation chart was visually observed to evaluate the degree of occurrence of image abnormality such as bleeding and beading. Evaluation was performed from the ink printing surface side using a solid image of white ink advance.
The evaluation was performed by a five-step evaluation. Among these, evaluation B or higher was set as an evaluation value having no practical problem.
[Bleeding evaluation]
A: No occurrence of bleeding A: Very slight bleeding is confirmed in some places B: Slight bleeding is confirmed in the entire boundary portion C: Bleeding is confirmed in the entire boundary portion D: Bleeding is confirmed throughout the belt pattern

<Evaluation of bleeding in color ink pre-launched image>
With respect to the solid image with color advance, the test pattern printed on the evaluation chart was visually observed to evaluate the degree of occurrence of image abnormality such as bleeding and beading. Evaluation was performed from the recording medium side through the transparent PET sheet by using a solid image with color advance.
The evaluation was performed by a five-step evaluation. Among these, evaluation B or higher was set as an evaluation value having no practical problem.
[Bleeding evaluation]
A: No occurrence of bleeding A: Very slight bleeding is confirmed in some places B: Slight bleeding is confirmed in the entire boundary portion C: Bleeding is confirmed in the entire boundary portion D: Bleeding is confirmed throughout the belt pattern

<Drying>
An ink cartridge filled with each of the inks of the examples and comparative examples was loaded into an inkjet printer (RICOH Pro L4160 manufactured by Ricoh Co., Ltd.), and the ink was applied to a transparent PET sheet LLPET1223 (manufactured by Sakurai Co., Ltd.), which is a non-porous substrate. A solid image was produced with an adhesion amount of 0.6 g / cm ² . The solid image was dried on a hot plate (NINOS ND-1, manufactured by AS ONE Corporation) set to 50 ° C. The filter paper was pressed against the solid portion of the solid image after drying, and the transfer of the ink onto the filter paper was visually observed, and “dryability” was evaluated based on the following evaluation criteria.
In the evaluation, all colors were evaluated individually. In the evaluation results, there was no difference by color.
[Evaluation criteria]
AA: No transfer to filter paper under drying conditions at 50 ° C. for 3 minutes or less A: No transfer to filter paper under drying conditions at 50 ° C. for more than 3 minutes for 5 minutes or less B: Drying conditions for 5 minutes at 50 ° C. for more than 8 minutes C: No transfer to filter paper C: No transfer to filter paper under drying conditions of 50 ° C. for more than 8 minutes and 10 minutes or less D: No transfer to filter paper even under drying conditions of 50 ° C. for more than 10 minutes

<Fixability (Beading)>
The recording unevenness of the solid image produced by the above <Dryability> evaluation was visually observed, and "Fixability (beading)" was evaluated based on the following evaluation criteria. It is desirable in practical use that the evaluation is B or more.
[Evaluation criteria]
A: Very good (no beading)
B: Good (slight beading was observed)
C: Normal (there was beading)
D: Defect (there was significant beading)

Example 1 is an example in the ink set of the present invention, and it can be seen that there is little bleeding in the white ink pre-cooked image, and it has high drying and fixing properties.
Examples 2 and 3 are preferable examples in the ink set of the present invention, and it can be seen that an image having low drying and fixing properties can be obtained with little image blurring during two-layer printing.
Example 4 is an example in which the content of the amide compound is slightly high, and the image blur was slightly inferior to Examples 2 and 3.
Example 5 is an example in which the content of the amide compound is slightly less, and the drying property and the fixing property are inferior to those of Examples 2 and 3.
Example 6 was an example in which a fluorosurfactant was used as the surfactant, and the fixing property was inferior to those of Examples 2 and 3.
Example 7 was an example in which an acrylic-silicone resin was used as the resin particles, and the image bleeding was inferior to Examples 2 and 3.
Example 8 is an example in which the glass transition point of the polyurethane resin is 0 ° C. or higher, and the drying property is inferior to Examples 2 and 3.

  On the other hand, Comparative Example 1 is an example in which the content of the amide compound is small. Compared with Example 2, the image bleeding, drying property, and fixing property were particularly inferior. Comparative Example 2 is an example that does not contain an amide compound. Compared with Comparative Example 1, the image was further blurred and had poor drying and fixing properties.

133 Carriage 142 Recording medium 151 Conveying belt 153 Guide member 157 Conveying roller 158 Tension roller 201 Heating fan 202 Hot air 203 Heater group 400 Image forming apparatus 401 Exterior 401c Cover 404 Cartridge holder (ink container)
410 Main tank 411 Ink storage portion 413 Ink discharge port 414 Container 420 Mechanism portion 434 Discharge head 436 Supply tube

JP 2011-252169 A Japanese Patent No. 5770209 JP 2014-205767 A JP 2013-95078 A JP 2014-205768 A

Claims (12)

A white ink comprising an organic solvent, wherein the organic solvent contains an amide compound represented by the following formula (1), and a ratio of the amide compound to the whole organic solvent is 40% by mass or more.

(Wherein R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, R ₂ and R ₃ represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, R ₂ and R ₃ may be the same or different.)   An ink set comprising: the white ink according to claim 1; and at least two colors of non-white ink different in color from the white ink.   The non-white ink contains an organic solvent, the organic solvent contains the amide compound represented by the formula (1), and the ratio of the amide compound to the whole organic solvent is 40% by mass or more. The ink set according to claim 2, wherein the ink set is an ink set.   4. The ink set according to claim 2, wherein the amide compound is contained in an amount of 60% by mass or more and 80% by mass or less based on the entire organic solvent. At least one of the white ink and the non-white ink contains a surfactant,
The ink set according to claim 2, wherein the surfactant is a polysiloxane surfactant. At least one of the white ink and the non-white ink contains resin particles,
The ink set according to claim 2, wherein the resin particles are polyurethane resin particles.   The ink set according to claim 6, wherein the polyurethane resin particles have a glass transition point of 0 ° C. or lower.   An ink storage container comprising an ink storage section for storing each ink in the ink set, wherein the ink set is the ink set according to any one of claims 2 to 7.   An ink jet recording method comprising: an ink ejecting step of ejecting the ink contained in the ink set according to any one of claims 2 to 7 and applying and ejecting the ink to a printing material.   The inkjet recording method according to claim 9, further comprising a step of heating the substrate.   An ink jet recording apparatus that has at least an ink storage container including an ink storage unit that stores each ink in an ink set, and an ink discharge unit that discharges the ink, and records an image on a printing material using the ink, An ink jet recording apparatus, wherein the ink container is the ink container according to claim 8. A printing method for printing on a substrate using the ink set according to claim 2,
A first recording step of forming a non-white image on the substrate using the non-white ink; and a second recording step of forming a white image on the non-white image using the white ink. A printing method characterized by the above.

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