JP2006342323A - Black ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a black ink composition affording records having effectively suppressed fine surface defects on the records. <P>SOLUTION: The black ink composition comprising water, carbon black and a water-soluble polyurethane resin is obtained. Furthermore, the solid content of the water-soluble polyurethane resin is ≥0.67 to ≤2.5 times of the content of the carbon black when the content of the carbon black is ≥0.4 to <1.5 wt.%. The solid content of the water-soluble polyurethane resin is ≥7.5 times of the content of the carbon black when the content of the carbon black is <0.4 wt.%. Thereby, formation of the surface defects on the records can be avoided or suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a black ink composition, and in particular, to a black ink composition, an ink set including the black ink composition, a recording method using the ink set, and a recorded matter using the ink set.

Ink jet recording methods or the like may use an ink set containing two or three or more types of black inks having different carbon black concentrations for the purpose of obtaining good monochrome images and gray scales. As this type of black ink, there is disclosed a black ink composition that defines a carbon black concentration and a solid content concentration of a predetermined amount of fine particle emulsion corresponding to the carbon black concentration (Patent Documents 1 and 2). According to these black ink compositions, a phenomenon in which reflected light generated when a fluorescent lamp or external light is reflected on an image recorded using the thin black ink composition generates a golden gloss (golden gloss) In the image recorded using the black ink composition for intermediate gradation, the phase shift (the observation angle of the observer is changed with respect to the recording image printed on the recording medium, or the irradiation angle of the light source is changed). Accordingly, it is possible to suppress a phenomenon in which the original gray brightness is observed to be shifted to the black side or the white side in a part of the recording area.
JP 2004-225036 A JP 2004-225037 A

  In the process from the formation of an image on a recording medium such as recording paper after the ink composition adheres to the ejection from the printer, the recorded material contact member such as a recording paper presser provided in the printer may touch the recorded image. is there. In many cases, the recording paper pressing member is a gear-like rotating body in which the image contact portion is formed into a fine protrusion in consideration of the influence on the image. When the present inventors investigated the recorded matter by the conventional black ink composition having the above-mentioned predetermined composition, extremely fine concave dots were sometimes formed in a line shape in the recorded matter after continuous printing. Such a finding on the recorded material was not recognized in other ink compositions, and when examined, it was found that the concave dot was a contact locus of a recorded material contact member such as a recording paper presser.

  Therefore, the present invention provides a black ink composition, an ink set, a recording method using the ink set, and a recorded material that can obtain a recorded material in which such fine surface defects on the recorded material are effectively suppressed. For the purpose. In addition, the present invention provides a black ink composition, an ink set, a recording method using the ink set, and a recording method using the ink set, in which surface defects can be effectively suppressed and a recorded matter having a good monochrome image or grayscale image can be obtained. Another purpose is to provide records.

  In order to solve the above-described problems, the present inventors have intensively studied, and by containing a predetermined amount of a water-soluble polyurethane resin in such a black ink composition, while preventing or preventing golden gloss and phase shift, recorded matter The inventors have found that the occurrence of surface defects can be avoided or suppressed, and the present invention has been completed. That is, according to the present invention, the following means are provided.

According to the present invention, a black ink composition containing water, carbon black, and a water-soluble polyurethane resin,
When the carbon black content is 0.4 wt% or more and less than 1.5 wt%, the solid content of the water-soluble polyurethane resin is 0.67 to 2.5 times the carbon black content. And
When the content of the carbon black is less than 0.4% by weight, a composition is provided in which the solid content of the water-soluble polyurethane resin is 7.5 times or more the content of the carbon black.

The water-soluble polyurethane resin has an acid value of 10 to 300, a weight average molecular weight of 100 to 200,000, a glass transition temperature of −50 ° C. to 200 ° C., and a maximum particle size of 0.3 μm. It can be as follows. In this composition, when the content of the carbon black is 0.4 wt% or more and less than 1.5 wt%, the water-soluble polyurethane resin has a solid content of 0.2 wt% or more and 4 wt% or less. In addition, when the content of the carbon black is less than 0.4% by weight, the solid content of the water-soluble polyurethane resin can be 1% by weight or more and 10% by weight or less.

  Moreover, the other preferable aspect of the composition of this invention can contain fine particle emulsion. Further, the fine particle emulsion may be selected from polyalkylene type emulsions. The total content of the solid content of the water-soluble polyurethane resin and the solid content of the fine particle emulsion may be 0.5 wt% or more and 20 wt% or less.

Further, according to the present invention, there is provided a black ink composition containing water and carbon black, in combination with another black ink composition having a carbon black concentration higher than the carbon black concentration of the black ink composition. A black ink composition for use comprising:
Contains water-soluble polyurethane resin,
A composition is provided in which the solid content of the water-soluble polyurethane resin is 0.2 wt% or more and 10 wt% or less.

  In a preferred embodiment of the present invention, the solid content of the water-soluble polyurethane resin is 0.5 wt% or more and 5 wt% or less, and another preferred embodiment is one containing a fine particle emulsion. When the fine particle emulsion is contained, the solid content of the water-soluble polyurethane resin is 40% by weight or more and 80% by weight or less of the total amount of the water-soluble polyurethane resin and the solid content of the fine particle emulsion. preferable. In another preferred embodiment, the other black ink composition contains 1.5% by weight or more of carbon black. The other black ink composition may contain 6% by weight or more of carbon black. This other black ink composition may contain self-dispersing carbon black.

  In another preferred embodiment, the carbon black content is 0.4 wt% or more and less than 1.5 wt%, and the water-soluble polyurethane resin has a solid content content of 0.2 wt% or more. 4% by weight or less, and the other is that the content of the carbon black is less than 0.4% by weight, and the solid content of the water-soluble polyurethane resin is 1% by weight or more and 10% by weight or less. It is a black ink composition.

  Furthermore, in another preferred embodiment, at least a part of the water-soluble polyurethane resin contains a water-soluble polyurethane resin, a water-soluble organic solvent, and water, and has no substantial viscosity change. A black ink composition added as

  In this embodiment, the water-soluble organic solvent is preferably one or more diols. The water-soluble organic solvent is also preferably contained in an amount of 10 wt% to 50 wt% with respect to the water-soluble polyurethane resin solid content. Furthermore, in the polyurethane resin composition, the water-soluble organic solvent preferably contains one or more diols and one or more triols, and the triols contain glycerin. preferable.

Furthermore, the polyurethane resin composition may contain the triol in an amount of 10 wt% to 100 wt% based on the water-soluble polyurethane resin solid content, and the diol contains 1,2-hexanediol, The triols may contain glycerin. Furthermore, the polyurethane resin composition may contain the water-soluble organic solvent in an amount of 0.5 wt% or more and 20 wt% or less, and may contain the water-soluble polyurethane resin in an amount of 5 wt% or more and 50 wt% or less. The polyurethane resin composition is preferably obtained by aging with heating. Furthermore, a predetermined amount of the polyurethane resin composition was sealed and allowed to stand at a constant temperature of 70 ° C. ± 3 ° C. for 24 hours, and the viscosity at the start and after the standing period was measured. The composition according to any one of claims 15 to 24, wherein a viscosity change rate (ΔV) obtained based on the formula (1) is 2.5% or less.
ΔV (%) = | V−V ₀ | / V ₀ × 100 (1)

  Moreover, the black ink composition of these various aspects can contain the coloring agent for complementary colors. Furthermore, it can be set as the ink composition for inkjet recording.

According to the present invention, one or more black ink compositions according to any one of the above aspects, and
Other black ink compositions having a carbon black concentration higher than the carbon black concentration of these black ink compositions;
An ink set is provided.

  According to a preferred embodiment of the present invention, the one or more black ink compositions of any of the above embodiments comprise a black ink composition having a carbon black content of less than 0.4% by weight and carbon black. The black ink composition has an amount of 0.4 wt% or more and less than 1.5 wt%, and the other black ink composition is a composition having a carbon black content of 1.5 wt% or more.

  The other black ink composition may contain 6% by weight or more of carbon black. This other black ink composition may contain self-dispersing carbon black.

  Another preferred embodiment is an ink set including a cyan ink composition, a magenta ink composition, and a yellow ink composition. Further, it preferably contains a light cyan ink composition and a light magenta ink composition.

  Further, the color ink composition other than the black ink composition can contain a water-soluble polyurethane resin, and at least a part of the water-soluble polyurethane resin in the color ink composition is composed of a water-soluble polyurethane resin and a water-soluble organic solvent. It is preferable that it is added as a polyurethane resin composition containing water and water and having no substantial viscosity change.

Furthermore, according to the present invention, there is provided a recording method for forming an image by discharging droplets of an ink composition and attaching the droplets to a recording medium.
A recording method using the ink set according to any one of the above aspects is provided.

A preferred embodiment of the present invention is a recorded matter having an image on a recording medium,
There is provided a recorded matter having an image composed of an adhering layer of the ink composition contained in the ink set of any one of the above aspects on the recording medium.

  Embodiments of the present invention include various aspects such as a black ink composition, an ink set, a recording method using the ink set, and a recorded matter. All of these various aspects of the invention relate to black ink compositions. According to the black ink composition of the present invention, by containing a predetermined amount of the water-soluble polyurethane resin, it is possible to provide a recorded matter in a good state in which surface defects and the like are avoided or suppressed. Further, the black ink composition of the present invention avoids or suppresses surface defects, and contains a predetermined amount of carbon black, thereby effectively preventing or suppressing golden gloss or phase shift and the like. A recorded matter having a scale image can be provided. According to the black ink composition of the present invention, by containing a predetermined amount of the water-soluble urethane resin, the adhesion of the resin component of the ink composition to the recorded material contact member or the like is lowered, thereby solidifying the deposit. Thus, problems such as enlarging the contact member are suppressed. For this reason, even if it repeats that a contact member contacts a recorded matter, a contact part will not become enormous and it will become difficult to leave the trace of contact. Further, since the black ink composition contains a predetermined amount of water-soluble urethane resin, it has a fluidity that does not leave a contact trace even when the contact member comes into contact with the black ink composition before solidification on the recorded matter ( (Viscosity) can be maintained for a certain period. Hereinafter, various aspects of the black ink composition, ink set, recording method, and recorded matter of the present invention will be described in detail.

(Black ink composition)
The black ink composition of the present invention is a black ink composition that may be used in combination with one or more other black ink compositions. By such a combination, “phase shift” and “golden gloss” can be avoided or suppressed.

As described above, “phase shift” means a black ink composition for intermediate gradations when the observation angle of an observer or the irradiation angle of a light source is changed with respect to a recorded image printed on a recording medium. This is a phenomenon in which the gray brightness is shifted in a part of the area recorded in the above and is observed shifted to the black side or the white side from the original gray. When the phase shift occurs, the area looks lighter gray than the original gray, looks dark gray, or becomes completely black, so that it is very difficult to discriminate even the contour of the image. Such a phenomenon is particularly likely to occur when recording on a glossy recording medium such as a glossy tone or a semi-glossy tone, and is relatively difficult to occur with a matte tone recording medium.

  A region where a phase shift occurs will be described with reference to FIG. As schematically shown in FIG. 1, by changing the usage ratios of the dark black ink composition K1, the intermediate gradation black ink composition K2, and the thin black ink composition K3, a gray color from black to white can be obtained. A scale can be created appropriately. As described above, when the three types of black ink compositions K1, K2, and K3 are used, the gray balance stability and metamerism can be drastically improved as described above. However, as shown in the “phase shift generation region” in FIG. 1, a phase shift occurs mainly in a region recorded with the black ink composition K2 for intermediate gradation.

  The “phase shift occurrence region” extends from about 30 to about 60 with a gray level of about 35 to about 55 as the center (here, gray level 0 is absolute black and gray level 255 is absolute white). And). Further, the brightness range of the “phase shift generation region” ranges from about 25 to about 30 as a central region and ranges from about 20 to about 35. When recording a black-and-white monochrome image using two or more kinds of black ink compositions, the black ink composition used for recording the phase shift occurrence region is usually carbon black as a whole of the black ink composition. A black ink composition for intermediate gradation having an amount of 0.4% by weight or more and 1.5% by weight or less based on the weight (hereinafter referred to as a black ink composition containing carbon black in the concentration range, particularly the first black Referred to as an ink composition).

On the other hand, “golden gloss” (hereinafter may be abbreviated as GG) is, as described above, changing the observation angle of the observer with respect to the recorded image printed on the recording medium, When the irradiation angle of the light source is changed, a part of the area recorded with the thin black ink composition shines in gold. According to the inventor's research, golden gloss occurs only in certain areas. When this golden gloss occurs, it becomes impossible to determine the color tone of the recorded matter not only in the generating area but also in the neighboring area, and it becomes very difficult to determine the contour of the recorded image.

  The area where the golden gloss is generated is an area recorded mainly by the thin black ink composition K3 as shown in “GG generation area” (that is, the golden gloss generation area) in FIG. The “GG generation region” extends from about 90 to about 160 with a gray level of about 100 to about 140 as the center (where gray level 0 is absolute black and gray level 255 is absolute white). To do). In addition, the brightness range of the “GG generation region” ranges from about 50 to about 60 as a central region and ranges from about 40 to about 70. When recording a black-and-white monochrome image using two or more kinds of black ink compositions, the black ink composition used for recording the GG generation region is usually carbon black and the total weight of the black ink composition. And a relatively thin black ink composition having a concentration of less than 0.4% by weight (particularly, an amount of 0.01% by weight or more and less than 0.4% by weight) (hereinafter referred to as carbon in the concentration range). A black ink composition containing black is particularly referred to as a second black ink composition).

(Water-soluble polyurethane resin)
The black ink composition contains a water-soluble polyurethane resin. The water-soluble polyurethane resin is not particularly limited, and a water-soluble polyurethane resin obtained by reacting a diisocyanate compound and a diol compound can be used. Examples of the diisocyanate compound include alicyclic diisocyanate compounds such as hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate. Examples include araliphatic diisocyanate compounds such as xylylene diisocyanate and tetramethylxylylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products of these diisocyanates (carbodiimide, uretdione, uretoimine-containing modified products, etc.) It is done.

  Examples of the diol compound include diol compounds obtained by (co) polymerizing alkylene oxides such as ethylene oxide and propylene oxide, and heterocyclic ethers such as tetrahydrofuran. Specific examples of such diol compounds include polyether diols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methyl. Examples thereof include polyester diols such as pentyl adipate, polyethylene / butylene adipate, polyneopentyl / hexyl adipate, polylactone diols such as polycaprolactone diol, and polycarbonate diol. Among these, one or more of polyether, polyester and polycarbonate are preferable.

  In addition to the above, a diol compound having an acidic group such as a carboxylic acid group or a sulfonic acid group can also be used. Specific examples thereof include dimethylolacetic acid, dimethylolpropionic acid, and dimethylolbutyric acid. Of these, dimethylolpropionic acid is preferred. Two or more of these diol compounds may be used in combination.

  In the synthesis of the water-soluble polyurethane resin, a low molecular weight polyhydroxy compound may be added. Examples of the low molecular weight polyhydroxy compound include a trihydric alcohol such as glycol, alkylene oxide low-mole adduct, glycerin, trimethylolethane, trimethylolpropane, and the like, which are used as a raw material for polyester diol, and its alkylene oxide low-mole adduct. Can be mentioned. Further, the urethane prepolymer thus obtained can be subjected to water extension or chain extension with di (tri) amine after neutralizing or neutralizing the acid group derived from dimethylolalkanoic acid. Examples of the polyamine used for chain extension include hexamethylene diamine, isophorone diamine, hydrazine, and piperazine, and these may be used in combination of two or more.

  Desirably, the water-soluble polyurethane resin includes a polyether polyurethane resin, a polyester polyurethane resin, and a polycarbonate polyurethane resin obtained by using a polyether-based, polyester-based, or polycarbonate-based diol as a diol compound. The form of the water-soluble polyurethane resin is not particularly limited. Typically, an emulsion type, for example, a self-emulsifying emulsion or a self-stabilizing type can be mentioned. In particular, among the above compounds, diols having acidic groups such as carboxylic acid groups and sulfonic acid groups are used, low molecular weight polyhydroxy compounds are added, urethane resins introduced with acidic groups, especially those having carboxyl groups Is desirable. Furthermore, it is desirable to crosslink these functional groups such as carboxyl groups by the cross-linking treatment described later from the viewpoints of improving gloss and improving abrasion resistance.

  As the water-soluble polyurethane resin, a neutralized one can be used. Examples of the base used for neutralization include alkylamines such as butylamine and triethylamine, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and inorganic bases such as morpholine, ammonia and sodium hydroxide.

The acid value of the polyurethane resin is preferably 10 to 300, more preferably 20 to 100, from the viewpoint of suppressing surface defects and golden gloss or phase shift on the recorded material. The acid value is the mg amount of KOH required to neutralize 1 g of resin. The weight average molecular weight (Mw) before crosslinking of the polyurethane resin is preferably from 100 to 200,000, more preferably from 1000 to 5 from the viewpoint of suppressing surface defects and golden gloss or phase shift on the recorded matter. It is ten thousand. Mw is, for example, GPC (gel permeation chromatography)
Measure with The glass transition temperature (Tg; measured according to JIS K6900) of the polyurethane resin is preferably −50 to 200 ° C., more preferably −50 from the viewpoint of suppressing surface defects and golden gloss or phase shift on the recorded material. ~ 100 ° C. Further, the polyurethane resin may be dispersed in the form of fine particles in the pigment dispersion of the present invention or adsorbed to the pigment, but suppresses surface defects and golden gloss or phase shift on the recorded matter. From the viewpoint, the maximum particle size of the polyurethane resin is preferably 0.3 μm or less, and the average particle size is more preferably 0.2 μm or less (more preferably 0.1 μm or less). The average particle diameter is an average value of molecular diameter (volume 50% diameter) as particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

  Preferred specific examples of the water-soluble polyurethane resin include NeoRez R-960 (manufactured by Zeneca), NeoRez R-989 (manufactured by Zeneca), NeoRez R-9320 (manufactured by Zeneca), NeoRad NR-440 (manufactured by Zeneca), Hydran AP- 30 (Dainippon Ink Industry Co., Ltd.), Hydran APX-601 (Dainippon Ink Industry Co., Ltd.), Hydran SP-510 (Dainippon Ink Industries Co., Ltd.), Hydran SP-97 (Dainippon Ink Co., Ltd.) Kogyo Co., Ltd.), Elastolon MF-60 (Daiichi Kogyo Seiyaku Co., Ltd.), Elastoron MF-9 (Daiichi Kogyo Seiyaku Co., Ltd.), M-1064 (Daiichi Kogyo Seiyaku Co., Ltd.) , Iserlux S-1020 (Hodogaya Chemical Co., Ltd.), Iserax S-1040 (Hodogaya Chemical Co., Ltd.), Iserax S-1085 C (manufactured by Hodogaya Chemical Co., Ltd.), Iserlux S-4040N (manufactured by Hodogaya Chemical Co., Ltd.), Neotan UE-5000 (manufactured by Toagosei Co., Ltd.), RU-40 series (manufactured by Stahl Japan), UCOAT UWS -145 (manufactured by Sanyo Chemical Co., Ltd.), Permarin UA-150 (manufactured by Sanyo Chemical Co., Ltd.), WF-41 series (manufactured by Stahl Japan), WPC-101 (manufactured by Nippon Urethane Industry Co., Ltd.). .

(Aged water-soluble polyurethane resin composition)
An aged water-soluble polyurethane resin composition can be used together with or as the water-soluble polyurethane resin. The aged polyurethane resin composition is a composition containing a water-soluble polyurethane resin, a water-soluble organic solvent and water and having no substantial change in viscosity, a method for producing the composition, and the composition. A method for producing a water-based ink composition and a water-based ink composition.

  By using the aged water-soluble polyurethane resin composition, a water-based ink composition in which a change in viscosity is avoided or suppressed can be obtained. The polyurethane resin composition of the present invention can be preferably obtained by carrying out an aging step for reducing the viscosity of the mixture, which comprises a water-soluble polyurethane resin, a water-soluble organic solvent, and water. The aqueous ink composition can be prepared using the polyurethane resin composition of the present invention, a pigment dispersion containing water and a pigment, and the remaining components. By mixing the polyurethane resin composition of the present invention in the pigment dispersion, it is possible to obtain an aqueous ink in which the viscosity change is easily avoided or suppressed. When the aqueous ink composition thus produced is used as an ink composition for an inkjet printer, it is possible to provide an ink in which ejection stability from a nozzle is ensured. In addition, according to such a water-based ink composition, it is not necessary to wait for the viscosity and the like to stabilize and supply it to the market, so that efficient production and supply are possible.

  In particular, the black ink composition of the present invention and the light color ink composition to be described later contain a relatively large amount of water-soluble polyurethane resin solids, so that the influence of the viscosity change of the ink composition over time is large. Although it is considered that the aged water-soluble polyurethane resin composition is at least a part of the water-soluble polyurethane resin, preferably by containing the water-soluble polyurethane resin as an aged water-soluble polyurethane resin composition, The viscosity of the ink composition can be stabilized without adding a treatment for suppressing a change in viscosity to the ink composition or adding an additive therefor to the ink composition. Moreover, even when an aged water-soluble polyurethane resin composition is used, viscosity stability can be secured without hindering the original purpose of the water-soluble polyurethane resin contained in the black ink composition of the present invention. It is.

  This composition contains a water-soluble polyurethane resin, a water-soluble organic solvent, and water. On the other hand, this composition does not contain a pigment. Here, water-soluble means that it is dispersible, preferably soluble, in water or an aqueous medium containing water.

(Water-soluble organic solvent)
The polyurethane resin composition can contain one or more water-soluble organic solvents. The water-soluble organic solvent can be used without particular limitation as long as it is an organic solvent miscible with water. However, the water-soluble organic solvent constitutes an aqueous medium of the aqueous ink composition, and when mixed with a polyurethane resin, It is preferable to use a water-soluble organic solvent whose viscosity increases or changes. Examples of such water-soluble organic solvents include lower alkyl ethers of polyhydric alcohols, pyrrolidones, and diols. Of these, diols are preferred. The diol is preferably a linear alkyl diol having 5 to 7 carbon atoms, and more preferably 1,2-hexanediol. This is because 1,2-hexanediol is a preferable water-soluble organic solvent in the water-based ink composition and its viscosity increases when mixed with a polyurethane resin. Therefore, an aging resin excellent in stability such as viscosity can be obtained by previously mixing the polyurethane resin and 1,2-hexanediol to stabilize the viscosity. The total amount of the water-soluble organic solvent used in the water-based ink composition need not be supplied from the polyurethane resin composition, and the polyurethane resin composition contains an effective amount of the water-soluble organic solvent for aging the polyurethane resin. It only has to be done.

  Triols are also preferred as the water-soluble organic solvent. Triols have good compatibility with water and diols, and triols can suppress freezing of the resin composition and increase in viscosity due to freezing when the polyurethane resin composition is stored at a low temperature. Because. Such triols are preferably linear alkyltriols having 3 to 5 carbon atoms, more preferably glycerin (1,2,3-propanetriol). Since glycerin is also a humectant component of the water-based ink composition, it can be used without greatly changing the composition and physical properties of the water-based ink composition using the polyurethane resin composition.

  Moreover, it is preferable that the density | concentration of the water-soluble organic solvent in this polyurethane resin composition is 0.5 wt% or more and 20 wt% or less. This is because if it is less than 0.5 wt%, it is difficult to obtain an aging effect, and if it exceeds 20 wt%, a stable composition cannot be prepared. More preferably, they are 1 wt% or more and 15 wt% or less.

  The weight ratio between the polyurethane resin and the water-soluble organic solvent in the polyurethane resin composition is not particularly limited. Although depending on the amount of resin in the water-based ink composition to be finally obtained, the water-soluble organic solvent in the mixture can be 10 wt% or more and 100 wt% or less with respect to the solid content of the polyurethane resin. This is because aging can be effectively performed within this range.

  The water-soluble organic solvent such as diol can be 50 wt% or more and 100 wt% or less with respect to the solid content of the polyurethane resin. Within this range, an effective viscosity stabilizing effect can be obtained in an aqueous ink composition having a pigment concentration such as carbon black of 1.5 wt% or more. More preferably, it is 80 wt% or less, More preferably, it is 73 wt% or less. The lower limit is more preferably 60 wt% or more.

  Moreover, it is preferable that water-soluble organic solvents, such as diol, are 10 wt% or more and less than 50 wt% with respect to solid content of a polyurethane resin. Within this range, an effective viscosity stabilizing effect can be obtained in an aqueous ink composition having a pigment content such as carbon black of less than 1.5 wt% (particularly less than 0.4 wt%). When such a water-based ink composition having a low pigment content contains a relatively large amount of a water-soluble polyurethane resin, the viscosity change caused by the water-soluble polyurethane resin can be effectively suppressed by containing a water-soluble organic solvent in the above ratio. . More preferably, it is 15 wt% or more, More preferably, it is 20 wt% or more. The upper limit is more preferably 40 wt% or less. The aqueous ink composition having a pigment concentration of less than 1.5 wt% will be described later.

  The water-soluble organic solvent such as triol is preferably 10 wt% or more and 100 wt% or less with respect to the solid content of the polyurethane resin. More preferably, it is 15 wt% or more. More preferably, it is 30 wt% or more, More preferably, it is 50% or more.

(Other ingredients)
The polyurethane resin composition contains at least a water-soluble polyurethane resin and a water-soluble organic solvent, and may be composed only of these. Since both of these can be dispersed or dissolved in water, the mixture is preferably water. Is included. For example, this composition can be comprised only from a polyurethane resin, a water-soluble organic solvent, and water. Water is a main medium component in water-based ink compositions and ink compositions, and can be effectively aged by aging in a state containing water. It is preferable to use water of grade higher than filtered ion exchange water. In addition, it is preferable that this composition does not contain a pigment.

  The polyurethane resin composition may contain a basic compound such as alkali or amines so that the polyurethane resin can be dispersed or dissolved in water. In addition, the composition may contain other components of the water-based ink composition other than the pigment as long as the aging process is not adversely affected. For example, in preparing the aqueous ink composition, it is possible to add components such as a surfactant and a pH adjuster to be used. The surfactant, pH adjuster and the like will be described later.

  The method for preparing the mixture is not particularly limited. After mixing a predetermined amount of the polyurethane resin and the water-soluble organic solvent, water can be added as needed, or the polyurethane resin, the water-soluble organic solvent and water can be mixed approximately at the same time. After preparing a mixed liquid of either a resin or a water-soluble organic solvent and water, the remainder may be added and mixed. From the viewpoint of ensuring the stability of the polyurethane resin, it is preferable to use an aqueous solution of the polyurethane resin in the mixture.

The water-soluble polyurethane resin composition used in the present invention does not have a substantial viscosity change. Here, having no substantial change in viscosity means that the viscosity does not change greatly with the passage of time and is substantially constant. Specifically, such a characteristic is obtained by enclosing a predetermined amount of the polyurethane resin composition in a sealable container (sealing container capable of eliminating the influence of evaporation and the like on the viscosity) and a predetermined temperature (for example, 70 The viscosity change rate (ΔV) obtained based on the following formula (1) from these viscosities by measuring the viscosity at the start and after the standing period. It can also be determined based on
ΔV (%) = | V−V ₀ | / V ₀ × 100 (1)
However, V0 is the viscosity at the start of the standing period, and V is the viscosity after the standing period. The viscosity measurement temperature is preferably 20 ° C.

For the polyurethane resin composition of the present invention, when the standing period is 1 day, the viscosity change rate is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2 0.0% or less. If it is 3.0% or less, the viscosity change of the water-based ink composition to be finally obtained can be avoided or suppressed.
The viscosity in the polyurethane resin composition is measured as kinematic viscosity (unit Pa · s), and the measurement is based on a measurement method using a backflow type viscosity tube or a measurement method that can obtain the same accuracy and accuracy. Is preferred. Specifically, it can be measured by the moving time of the liquid (ink) in the tube at 20 ° C. using a Cannon Fenceke-type reverse flow type viscosity tube (typically, VMC-252 type manufactured by Koiso Co., Ltd.). .

  Moreover, in the polyurethane resin composition containing triols such as glycerin, there is no substantial change in viscosity at low temperatures. In the present specification, low temperature means 5 ° C. or lower, preferably 0 ° C. or lower, more preferably −5 ° C. or lower, and still more preferably −10 ° C. or lower. Moreover, having substantially no viscosity change is synonymous with that already described. Specifically, the characteristics at such low temperatures are such that a predetermined amount of the polyurethane resin composition is sealed in a sealable container (sealing container capable of eliminating the influence of evaporation and the like on the viscosity) at a predetermined low temperature. (For example, −20 ° C. ± 3 ° C.) is allowed to stand for a predetermined period of time, the viscosity at the start and end of the standing period is measured, and the viscosity obtained from these viscosities based on the above formula (1) It can also be determined based on the rate of change (ΔV). The viscosity measurement temperature is preferably 20 ° C.

  For polyurethane resin compositions containing triols, the rate of change in viscosity is preferably less than 10.0%, more preferably, when the standing period at −20 ° C. ± 3 ° C. is 4 days. Less than 0%. If it is less than 10.0%, the viscosity change of the water-based ink composition to be finally obtained can be avoided or suppressed.

(Method for producing water-soluble polyurethane resin composition)
In order to impart such characteristics to the polyurethane resin composition of the present invention, a mixture of a water-soluble polyurethane and a water-soluble organic solvent (hereinafter, the polyurethane resin composition before reaching a state where there is no substantial change in viscosity is referred to as a mixture). The aging step of reducing the viscosity of In the present invention, aging refers to a phenomenon in which a substance undergoes a chemical change or other phenomenon over time, or an operation for causing such a phenomenon. Therefore, the aging step in the present invention requires time for the mixture to such an extent that the physical properties of the liquid such as the viscosity can be improved or stabilized at the time of preparing the aqueous ink composition and / or after the preparation, compared with the case where aging is not performed. It is sufficient if the process is allowed to pass, and it is not always necessary to artificially impart any action (temperature, etc.) from the outside. Therefore, the aging process may be a lapse of a fixed time in an atmosphere during standby or storage between processes, or may be accompanied by another process instead of an independent process.

  The aging process is performed, for example, until the viscosity of the mixture itself is stabilized, or stabilized so that the viscosity change in a certain period after the preparation of the ink composition to be finally obtained can be suppressed to a certain value or less. Can be done. The viscosity of the mixture may be a viscosity measurement method used in the field of ink, for example, and for example, a method using a Cannon-Fenske type reverse flow viscosity tube can be used.

  It is preferable that the temperature of an aging process is 40 degreeC or more. This is because if the temperature is 40 ° C. or higher, the aging process can be completed within an appropriate period. More preferably, it is 50 degreeC or more, More preferably, it is 60 degreeC or more. Moreover, it is preferable that the said temperature is 80 degrees C or less. This is because the physical properties and the like of the polyurethane resin composition for ink are maintained at 80 ° C. or lower. Therefore, in the aging process, it is preferably 40 ° C. or higher and 80 ° C. or lower, more preferably 60 ° C. or higher and 80 ° C. or lower. Most preferably, it is about 70 ° C. In order to secure such an aging temperature, it is preferable to carry out the aging process with heating.

  The time for the aging process is preferably 24 hours or more. This is because if it is 24 hours or longer, the effect of aging can be obtained. More preferably, it is 48 hours or more, More preferably, it is 72 hours or more. In some cases, it may be preferable to be 120 hours or longer. Moreover, an aging process can be made into 216 hours or less. This is because if it is within 216 hours, an effect corresponding to the time can be easily obtained. From the viewpoint of production efficiency, it is preferably 168 hours or less. More preferably, it is 144 hours or less. Accordingly, examples of a preferable range of time required for the aging process include 24 hours to 168 hours, 48 hours to 144 hours, 72 hours to 216 hours, 120 hours to 216 hours, and the like.

  The time required for the aging process may differ depending on the amount of the water-soluble organic solvent in the mixture. For example, as the amount of water-soluble organic solvent is larger than the amount of water-soluble polyurethane resin (solid content), the time required for aging tends to be relatively shorter, and as the amount of water-soluble organic solvent is smaller, the time required for aging is relatively longer. Tend to be longer. Therefore, in a mixture in which the water-soluble organic solvent is 10 wt% or more and less than 50 wt% with respect to the solid content of the water-soluble polyurethane resin, it is preferably 120 hours or more and 216 hours or less, and more preferably 168 hours or more and 216 hours. preferable. Moreover, it is preferable that it is 24 hours or more and 168 hours or less for the mixture whose water-soluble organic solvent is 50 wt% or more and 100 wt% or less, and it is more preferable that it is 72 hours or more and 120 hours or less.

  From the above, as a preferable aging process, it is possible to set at about 70 ° C. for 48 hours or longer and 144 hours or shorter. More preferably, it may be 72 hours or more and 120 hours or less at about 70 ° C. Further, other aging conditions may be used as long as the same effects as the aging effects that can be imparted to the mixture by these aging conditions may be used (hereinafter, such other aging conditions are equivalent to the aging conditions). Called). An aging condition equivalent to one aging condition can be obtained by evaluating an effect obtained by performing the aging process under a condition in which time and / or temperature is changed.

  Another preferred aging step is a period of about 120 hours to 216 hours at about 70 ° C. More preferably, it is 168 hours or more and 216 hours or less at about 70 degreeC. Further, aging conditions that can achieve an aging effect equivalent to these conditions can be mentioned.

  The polyurethane resin composition thus obtained through the aging process is stabilized by aging to reduce the change in viscosity and the like over time, and the physicochemical characteristics including physical properties such as the viscosity are different from those simply mixed. It has become a thing. Therefore, the polyurethane resin composition after the aging step is a polyurethane resin composition suitable for the preparation of the water-based ink composition.

  In addition, the polyurethane resin composition obtained by aging a mixture containing triols can be modified by freezing and freezing (for example, viscosity) even when stored at a low temperature. Physical properties suitable for the preparation of the water-based ink composition can be maintained.

  The black ink composition of the present invention preferably contains a water-soluble polyurethane resin in the range of 0.2 wt% to 10 wt% as the resin solid content. Within this range, the adhesion and viscosity of the black ink composition can be effectively reduced, and surface defects on the recorded matter can be avoided or suppressed. Further, phase shift and golden gloss can be avoided or suppressed more effectively at the same time. More preferably, it is 0.5% by weight or more and 5% by weight or less.

  In particular, in the first black ink composition, the solid content of the water-soluble polyurethane resin is preferably 0.2% by weight or more and 4% by weight or less. Within this range, surface defects can be effectively avoided or suppressed in the carbon black concentration range of the first black ink composition. Further, phase shift can be effectively avoided or suppressed. More preferably, it is 0.5% by weight or more and 2% by weight or less. When it is 0.5% by weight or more, a golden gloss can be avoided or suppressed by providing a resin layer having an appropriate thickness to the ink layer formed by the first black ink composition. This is because if it is 2% by weight or less, the viscosity of the first black ink composition can be easily maintained in an appropriate range, and the ejection stability can be secured. More preferably, it is 1.5 weight% or less.

  In the second black ink composition, the solid content of the water-soluble polyurethane resin is preferably 1% by weight or more and 10% by weight or less. Within this range, surface defects can be effectively avoided or suppressed in the carbon black concentration range of the second black ink composition. Also, the golden gloss can be effectively avoided or suppressed. More preferably, it is 2% by weight or more and 6% by weight or less. When it is 2% by weight or more, a resin layer having an appropriate film thickness can be imparted to the ink layer formed by the second black ink composition to avoid or suppress golden gloss more. When it is 6% by weight or less, This is because it is easy to maintain the viscosity of the black ink composition No. 2 in an appropriate range, and discharge stability can be secured. More preferably, it is 4% by weight or less.

  Further, for example, when used in combination with the first black ink composition, the second black ink composition, and another black ink composition having a higher carbon black concentration (for example, 1.5% by weight or more), In the relationship between the black ink composition and the second black ink composition, the solid content concentration of the water-soluble polyurethane resin in the second black ink composition is preferably higher than the first solid content concentration. This is because when the carbon black content is low and the absolute amount of the solid content of the water-soluble polyurethane resin is large, an ink layer including a resin film having a stable film thickness can be formed. The resin solid content concentration of the water-soluble polyurethane resin of the second black ink composition is preferably 2 times or more, more preferably 3 times or more the solid content concentration of the same resin of the first black ink composition. It is. Considering the carbon black concentration difference between the first black ink composition and the second black ink composition, if the concentration ratio is 2 times or more, the resin having a stable film thickness regardless of the carbon black concentration. A film can be formed, and surface defects, phase shifts, and golden gloss on the recorded material can be effectively avoided or suppressed in each composition.

In the first black ink composition, the solid content of the water-soluble polyurethane resin is preferably 0.67 to 2.5 times the carbon black content. When the concentration ratio is within this range, surface defects on the recorded material can be suppressed while avoiding or suppressing phase shift. More preferably, it is 1.0 times or more, and further preferably 1.2 times or more. Further, it is more preferably 2.0 times or less, and still more preferably 1.6 times or less.

  In the second black ink composition, the solid content of the water-soluble polyurethane resin is preferably 7.5 times or more the carbon black content. When it is 7.5 times or more, surface defects on the recorded material can be suppressed while avoiding or suppressing golden gloss. More preferably, it is 10 times or more, more preferably 12 times or more, and most preferably 13 times or more.

(Fine particle emulsion)
The black ink composition of the present invention may contain a fine particle emulsion. The fine particle emulsion that can be contained in the black ink composition of the present invention can take the form of an aqueous dispersion in which the dispersion medium is water and the dispersoid is polymer fine particles. The minimum film-forming temperature (MFT) of the polymer fine particles contained in the fine particle emulsion is not particularly limited, but is preferably 25 ° C. or less, more preferably 0 to 25 ° C., and further preferably 10 to 20 ° C. . MFT is measured according to JIS K 6800. By printing on a recording medium using the ink composition according to the present invention containing an emulsion having an MFT in the above range, a protective film covering the printing surface at room temperature is automatically formed.

  The glass transition temperature (Tg) of the polymer fine particles contained in the fine particle emulsion is preferably −15 to 10 ° C., and preferably −5 to 5 ° C. from the viewpoint of adjusting the MFT of the emulsion within the above range. More preferably. Tg is measured according to JIS K6900. As another method for adjusting the MFT of the emulsion within the above range, a method using a commercially available MFT depressant can be mentioned.

  The polymer fine particles preferably have an average particle diameter of 5 to 200 nm, and more preferably 5 to 100 nm, from the viewpoint of dispersion stability in the ink composition.

  The polymer fine particles preferably have a hydrophilic portion and a hydrophobic portion. The polymer fine particles may have a single-phase structure, a multiphase structure (core-shell structure), or the like. The core-shell structure may be a structure in which two or more different types of polymers are present in phase separation. For example, the shell part completely covers the core part, and the shell part covers a part of the core part. Structure in which a part of the shell polymer forms a domain or the like in the core polymer, one or more layers between the core and the shell, and three or more layers including layers having different compositions It may be a structure.

  When the polymer fine particle having the core-shell structure is used, it is preferable that the core part is made of a polymer having an epoxy group and the shell part is made of a polymer having a carboxyl group. By including such polymer fine particles in the ink composition, when the protective film is formed, the epoxy group of the core portion and the carboxyl group of the shell portion are combined to form a network structure. The strength of the film can be improved.

  The polymer fine particles preferably have a structure derived from an unsaturated vinyl monomer having a carboxyl group in an amount of 1% by weight to 10% by weight, and preferably have two or more polymerizable double bonds, more preferably three. What has 0.2 to 4 weight% of the structure bridge | crosslinked by the crosslinkable monomer which has the above (structure derived from a crosslinkable monomer) is preferable. By including such polymer fine particles in the ink composition, the surface of the nozzle plate is hardly wetted by the ink, so that the flight of the ink droplets can be prevented and the ejection stability can be further improved. Can do.

  Examples of the unsaturated vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid, and methacrylic acid is particularly preferable.

  Examples of the crosslinkable monomer include polyethylene glycol acrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanediol diacrylate, and neopentyl glycol diacrylate. Acrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2-bis (4-acryloxydiethoxyphenyl) propane, etc. Diacrylate compounds; triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate; ditrimethyloltetraacrylate Tetraacrylate compounds such as relate, tetramethylolmethane tetraacrylate, pentaerythritol tetraacrylate; hexaacrylate compounds such as dipentaerythritol hexaacrylate; ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1 , 3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, 2 , 2'-bis (4-methacryloxy And dimethacrylate compounds such as sidiethoxyphenyl) propane; trimethacrylate compounds such as trimethylolpropane methacrylate and trimethylolethane trimethacrylate; methylebisacrylamide and divinylbenzene.

  The polymer fine particles are contained in the ink composition according to the present invention as the emulsion, and the emulsion can be produced by a known emulsion polymerization. For example, the emulsion of the polymer fine particles is produced by emulsion polymerization of an unsaturated vinyl monomer in water in the presence of a surfactant (emulsifier), a polymerization catalyst, a polymerization initiator, a molecular weight modifier, a neutralizing agent, and the like. Is done.

  Examples of the unsaturated vinyl monomer (monomers constituting the polymer fine particles) include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl generally used in emulsion polymerization. Cyanide monomers, halogenated monomers, olefin monomers, diene monomers and the like can be mentioned. Specifically, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, octadecyl Acrylic esters such as acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexylme Methacrylates such as acrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate; vinyl esters such as vinyl acetate; vinyl cyanides such as acrylonitrile; vinylidene chloride Halogenated monomers such as vinyl chloride; aromatic vinyl monomers such as styrene, 2-methylstyrene vinyl toluene, tert-butyl styrene, chlorostyrene, vinyl anisole, vinyl naphthalene; ethylene, propylene, isopropylene, etc. Olefins; Dienes such as butadiene and chloroprene; Vinyl monomers such as vinyl ether, vinyl ketone and vinyl pyrrolidone It can be given over class.

  Examples of the surfactant include an anionic surfactant (sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, etc.) and a nonionic surfactant (polyoxyethylene alkyl ether, Polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc.), and one or more of these may be used. Can do. Alternatively, acetylene glycol [olefin Y and surfinol 82, 104, 440, 465, and 485 (both manufactured by Air Products and Chemicals Inc.)] can also be used.

  At the time of production of the emulsion (the polymer fine particles), from the viewpoint of improving printing stability, the emulsion polymerization is selected from the group consisting of acrylamides and hydroxyl group-containing monomers in addition to the unsaturated vinyl monomer. It is preferable to mix 1 type (s) or 2 or more types. Examples of the acrylamides include acrylamide and N, N′-dimethylacrylamide. In use, one or more of these can be used. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and the like, and one or more of these can be used.

  In addition, when the polymer fine particle having the core-shell structure is used, an emulsion containing the fine polymer particle is, for example, a method disclosed in JP-A-4-76004 (multistage emulsion polymerization of the unsaturated vinyl monomer). ) And the like. As described above, it is preferable that the core-shell polymer fine particles are made of a polymer having an epoxy group in the core part. However, as an introduction method of the epoxy group into the core part, for example, unsaturated having an epoxy group A method of copolymerizing vinyl monomers glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, etc. with other unsaturated vinyl monomers, or preparing one core portion (core particle) by polymerizing one or more unsaturated vinyl monomers And a method of simultaneously adding an epoxy compound and combining them. In particular, the former method is preferable in terms of ease of polymerization, polymerization stability, and the like.

  The solid content concentration of the fine particle emulsion in the black ink composition is preferably 0.5 wt% or more and 20 wt% or less. More preferably, it is 1% by weight or more. More preferably, the content is 0.5% by weight or more and 10% by weight or less. More preferably, it is 1% by weight or more. When the added amount is 0.5% by weight or more, it is easy to obtain the print quality by suppressing golden gloss and phase shift, and when it is 10% by weight or less, the ink storage stability and clogging recovery are ensured. can do.

  The solid content concentration of the fine particle emulsion in the first black ink composition is preferably 0.5 wt% or more and 5 wt% or less. More preferably, it is 3% by weight or less. The solid content concentration of the fine particle emulsion in the second black ink composition is preferably 1% by weight or more and 10% by weight or less. More preferably, it is 8% by weight or less. More preferably, it is 5 weight% or less.

  When the present black ink composition contains a fine particle emulsion, the total amount of the solid content of the water-soluble polyurethane resin and the solid content of the fine particle emulsion is preferably 0.5% by weight or more and 20% by weight or less. This is because the viscosity of the black ink composition can be easily maintained in an appropriate range within this range, and the ejection stability can be ensured. More preferably, it is 1 weight% or more, More preferably, it is 1.5 weight% or more. More preferably, it is 10 weight% or less, More preferably, it is 8 weight% or less.

  Further, when the first black ink composition contains a fine particle emulsion, the total amount of the solid content of the water-soluble polyurethane resin and the solid content of the fine particle emulsion may be 0.8 wt% or more and 10 wt% or less. preferable. This is because the viscosity of the black ink composition can be easily maintained in an appropriate range within this range, and the ejection stability can be ensured. More preferably, it is 1 weight% or more, More preferably, it is 1.5 weight% or more. Further, it is more preferably 8% by weight or less, and further preferably 5% by weight or less.

  When the second black ink composition contains a fine particle emulsion, the total amount of the solid content of the water-soluble polyurethane resin and the solid content of the fine particle emulsion is preferably 0.2% by weight or more and 20% by weight or less. This is because, within this range, good print quality and ejection stability can be secured, and ink reliability can be secured. More preferably, it is 0.5 weight% or more, More preferably, it is 1 weight% or more. Further, it is more preferably 15% by weight or less, and further preferably 8% by weight or less.

  In the first black ink composition of the present invention, the solid content of the fine particle emulsion is at least twice the content of the carbon black. The upper limit is not particularly limited, but if it is 10 times or more the content of the carbon black, ejection failure may occur. When the content of the fine particle emulsion is less than twice the content of the carbon black, the phase shift cannot be sufficiently suppressed.

  In the second black ink composition of the present invention, the solid content of the fine particle emulsion is 20 times or more the content of the carbon black. The upper limit is not particularly limited, but if it is 50 times or more the content of the carbon black, ejection failure may occur. When the content of the fine particle emulsion is less than 20 times the content of the carbon black, the golden gloss cannot be sufficiently suppressed.

  In addition, solid content of water-soluble polyurethane resin can be 40 to 80 weight% of the total amount with solid content of fine particle emulsion. If it is less than 40% by weight, it becomes difficult to suppress or avoid surface defects, golden gloss, and phase shift on the recorded material, and if it exceeds 80% by weight, it is difficult to maintain the viscosity of the black ink composition within an appropriate range. This is because it becomes difficult to ensure stability. In the first black ink composition, the solid content of the water-soluble polyurethane resin is preferably 40% by weight or more and 60% by weight or less of the total amount, and in the second black ink composition, it is 50% by weight. It is preferable that the weight is not less than 80% by weight. In the relationship between the first black ink composition and the second black ink composition, it is preferable that the ratio of the water-soluble polyurethane resin in the second black ink composition to the total amount of solids is high.

(Polyalkylene emulsion)
As the resin component constituting the polymer fine particles, in particular, a polyalkylene resin can be used. That is, the black ink composition can contain an emulsion of a polyalkylene resin (hereinafter referred to as a polyalkylene type emulsion). As the polyalkylene-based resin, a polymer mainly composed of an olefin-based skeleton can be used.

  In the present invention, preferred examples of the polyalkylene resin include high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene, polybutene, poly-4-methylpentene-1, a copolymer of ethylene and α-olefin, ethylene -Propylene rubber, ethylene-propylene-diene terpolymer (EPDM), ethylene-vinyl acetate copolymer, butyl rubber, butadiene rubber, low crystalline ethylene-propylene copolymer, propylene-butene copolymer, ethylene- A vinyl ester copolymer is mentioned. Two or more of these resins can be used. Examples of the polyalkylene resin include emulsions of polyolefin resins such as polyethylene and polypropylene. Among these, a polypropylene polymer is preferably used. The polyalkylene resin can be used in the form of an emulsion by a known method. The polyalkylene type emulsion is usually applied to the black ink composition as an aqueous emulsion.

  The polyalkylene resin may be modified with an unsaturated carboxylic acid or an anhydride thereof. Unsaturated carboxylic acid or its anhydride for modification includes acrylic acid, methacrylic acid, crotonic acid, maleic acid, cinnamic acid, itaconic acid, citraconic acid, fumaric acid, etc .; and maleic anhydride, itaconic anhydride, anhydrous And unsaturated carboxylic acid anhydrides such as citraconic acid.

  When the black ink composition of the present invention contains a polyalkylene type emulsion, the solid content of the polyalkylene type emulsion is preferably 0.5% by weight or more and 10% by weight or less. More preferably, it is 1% by weight or more. Further, it is more preferably 5% by weight or less, and further preferably 3% by weight or less. The solid content concentration of the polyalkylene emulsion in the first black ink composition is preferably 0.5 wt% or more and 5 wt% or less. More preferably, it is 3% by weight or less. The solid content concentration of the polyalkylene emulsion in the second black ink composition is preferably 1% by weight or more and 10% by weight or less. More preferably, it is 8% by weight or less. More preferably, it is 5 weight% or less.

  The total amount of the solid content of the water-soluble polyurethane resin and the solid content of the polyalkylene type emulsion is preferably 0.5% by weight or more and 20% by weight or less. This is because, within this range, the viscosity of the black ink composition can be easily maintained within an appropriate range, and discharge stability can be ensured. More preferably, it is 1 weight% or more, More preferably, it is 1.5 weight% or more. More preferably, it is 10 weight% or less, More preferably, it is 8 weight% or less.

  When the first black ink composition contains a polyalkylene type emulsion, the total amount of the solid content of the water-soluble polyurethane resin and the solid content of the polyalkylene type emulsion is 0.8 wt% or more and 10 wt% or less. It is preferable that This is because it is possible to ensure good print quality and ejection stability within this range. More preferably, it is 1 weight% or more, More preferably, it is 1.5 weight% or more. Further, it is more preferably 8% by weight or less, and further preferably 5% by weight or less.

  When the second black ink composition contains a polyalkylene type emulsion, the total amount of the solid content of the water-soluble polyurethane resin and the solid content of the polyalkylene type emulsion is 0.2% by weight or more and 20% by weight or less. It is preferable. This is because it is possible to ensure good print quality and ejection stability within this range. More preferably, it is 0.5 weight% or more, More preferably, it is 1 weight% or more. Further, it is more preferably 15% by weight or less, and further preferably 8% by weight or less.

(Other resin components)
Further, the black ink composition of the present invention may contain other resin components depending on circumstances. The other resin component means a resin component usually used in the production of a black ink composition. For example, a resin-based dispersant such as polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer. Polymers, acrylic resins such as potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid Styrene-acrylic such as copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer Resin, styrene-maleic acid copolymer, styrene-maleic anhydride Rain acid copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer Polymers, vinyl acetate copolymers such as vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer and their salts, and resin surfactants such as polyoxyethylene alkyl ether, polyoxy Examples thereof include ethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, polyoxyethylene alkyl amides, and the like.

(Carbon black)
As the carbon black used in the black ink composition of the present invention, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used in addition to titanium oxide and iron oxide.

In the present invention, self-dispersing carbon black can also be used in that it is particularly excellent in the color development of matte media and plain paper. Self-dispersing carbon black is carbon black that can be dispersed and / or dissolved in an aqueous medium without using a dispersant. Here, “dispersing and / or dissolving in an aqueous medium without a dispersing agent” refers to a state in which the dispersing agent is stably present in an aqueous medium without using a dispersing agent for dispersing carbon black. Such self-dispersing carbon black has a large number of hydrophilic functional groups and / or salts thereof (hereinafter referred to as dispersibility-imparting groups) directly or indirectly via alkyl groups, alkyl ether groups, aryl groups, etc. Examples of these are combined.

Examples of the hydrophilicity-imparting group include acidic groups such as —COOH, —CO, —OH, —SO ₃ H, and —PO ₃ H _2, quaternary ammonium, and salts thereof.

  The self-dispersing carbon black, for example, bonds the active species having the dispersibility-imparting group or the dispersibility-imparting group to the surface of the carbon black (graft) by performing physical treatment or chemical treatment on the surface of the carbon black. Manufactured by making. Examples of the physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water, and a method in which a carboxyl group is bonded via a phenyl group by bonding p-aminobenzoic acid to the pigment surface. It can be illustrated.

  In the present invention, a self-dispersing pigment that is surface-treated by oxidation treatment with hypohalous acid and / or hypohalite or oxidation treatment with ozone is preferable in terms of high color development. The self-dispersing carbon black in the present invention typically includes oxidized carbon black in which the acidic group or a salt thereof has been introduced by such oxidation treatment.

As described above, the carbon black used in the present invention is specifically No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 900, HCF88, No. 33, no. 20B, no. 40, no. 45, no. 52, MA7, MA8, MA100, No2200B, etc. are Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc. manufactured by Colombia, Regal400R, Regal330R, Regal660R, onchalM900 , Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 and the like are Color Black FW1, Color Black FW2, Color Black FW 2V, Color Black FW 18, Color Black FW 200, Color Black FW 200, Color Black FW 200 manufactured by Degussa. Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 6, Special Black 4A, Special Black, etc.

  The particle size of the carbon black is not particularly limited, but is preferably 10 μm or less, more preferably 0.1 μm or less. In the ink set according to the present invention, the carbon black contained in each black ink composition may be the same or different.

  In the first black ink composition of the present invention, the carbon black content is an amount that can be used for recording the phase shift occurrence region, and specifically, 0% with respect to the total weight of the black ink composition. 0.4 wt% or more and less than 1.5 wt%, more preferably 0.5 wt% or more and 1.2 wt% or less, particularly 0.6 wt% or more and 1.0 wt% or less. In addition, the carbon black content in the second black ink composition is an amount that can be used for recording the GG generation region, and specifically, 0.4 wt.% With respect to the total weight of the black ink composition. %, Particularly 0.01% or more and less than 0.4% by weight, preferably 0.05% or more and 0.3% or less, more preferably 0.1% or more and 0.25% by weight or less. It is as follows.

  In addition, the black ink composition of the present invention is intended to neutralize the chromaticity inherently possessed by carbon black (redness in dark portions, or particularly yellowness in light portions). It is also possible to contain a colorant for complementary colors. The complementary colorant means a colorant to be contained in the black ink composition in order to reduce or eliminate the band color generated in the recorded image by the black ink and obtain an achromatic image. Pigment Blue 60 (C.I.PB60), Color Index / Pigment Blue 15: 3, and Color Index / Pigment Blue 15: 4.

  The pigment blue 60 is preferably used in a black ink composition having a carbon black content of 0.01% by weight or more and 1% by weight or less, and the content thereof is not particularly limited. The amount is preferably 0.01 to 0.5% by weight based on the total weight of the composition. The pigment blue 15: 3 and the pigment blue 15: 4 are preferably used in a black ink composition having a carbon black content of 1 wt% to 10 wt%, and the content thereof is not particularly limited. For example, it is preferably 0.1 parts by weight or more and 5 parts by weight or less based on the total weight of the black ink composition.

(Composition and production method of black ink composition)
The black ink composition of the present invention can be prepared as a water-based ink containing the same components as those of conventionally known black ink compositions. Moreover, it can utilize as conventionally well-known various inks for recording methods, Preferably it can utilize as ink for inkjet recording.

  Hereinafter, the components other than those described above and the ink production method will be briefly described in the case where the black ink composition of the present invention is for inkjet recording, and in particular, is an aqueous ink composition.

  In the black ink composition of the present invention, carbon black is preferably added to the ink composition as a pigment dispersion liquid dispersed in an aqueous medium with a dispersant, for example. As the dispersant used for preparing the pigment dispersion, a dispersant generally used for preparing the pigment dispersion, for example, a polymer dispersant or a surfactant can be used.

  The amount of the dispersant contained in the black ink composition of the present invention is not particularly limited, but is preferably 0.01% by weight to 10% by weight, more preferably 0.1% by weight to 5% by weight. The range is as follows. When the content of the dispersant is less than 0.01% by weight, a sufficient surface-active effect cannot be obtained. When the content exceeds 10% by weight, ejection failure due to crystal precipitation, liquid crystal formation, or pigment stability decrease is caused. In some cases,

  As the dispersant, besides a conventional surfactant, a dispersant commonly used for preparing a pigment dispersion, for example, a polymer dispersant can be suitably used. It will be apparent to those skilled in the art that the dispersant contained in the pigment dispersion will also function as a dispersant and a surfactant for the black ink composition. As a more preferable dispersant, a polymer dispersant, particularly a resin dispersant can be used. Preferred examples of the polymer dispersant include natural polymers. Specific examples thereof include proteins such as glue, gelatin, gazein, or albumin, natural gums such as gum arabic or tragacanth, glucosides such as saponin, alginic acid, or propylene glycol alginate, triethanolamine alginate, or Examples thereof include alginic acid derivatives such as ammonium alginate, cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and ethylhydroxycellulose.

  A preferred example of the polymer dispersant is a synthetic polymer. Specific examples thereof include polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, or acrylic acid. -Acrylic resin such as acrylic ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic ester copolymer, styrene-α-methylstyrene-acrylic acid Copolymers or styrene-acrylic resins such as styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers, styrene-maleic acid copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic acid resins , Rosin-modified maleic resin, vinyl naphthalene -Acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, or vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-croton Mention may be made of acid copolymers or vinyl acetate copolymers such as vinyl acetate-acrylic acid copolymers and their salts. Among these, a styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, an acrylic acid-acrylic acid ester copolymer, and a styrene-maleic anhydride copolymer are preferable as the dispersant.

  Moreover, as a resin dispersing agent, a commercially available thing can be used, As the specific example, Johnson polymer company make, Jonkrill 68 (molecular weight 10000, acid value 195), Jonkrill 61J (molecular weight 10000, acid) 195), joncryl 680 (molecular weight 3900, acid value 215), joncryl 682 (molecular weight 1600, acid value 235), joncryl 550 (molecular weight 7500, acid value 200), joncryl 555 (molecular weight 5000, acid value 200) ), Joncryl 586 (molecular weight 3100, acid value 105), Joncryl 683 (molecular weight 7300, acid value 150), Joncryl B-36 (molecular weight 6800, acid value 250), and the like.

  The black ink composition of the present invention can contain a surfactant. Specific examples of the surfactant include an anionic surfactant (for example, sodium dodecylbenzenesulfonate, sodium laurate, or ammonium salt of polyoxyethylene alkyl ether sulfate), a nonionic surfactant (for example, polyoxyethylene). Ethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, or polyoxyethylene alkylamide), amphoteric surfactants (for example, N, N- Dimethyl-N-alkyl-N-carboxymethylammonium betaine, N, N-dialkylaminoalkylenecarboxylate, N, N, N-trialkyl-N-sulfoalkyleneammonium In, N, N-dialkyl-N, N-bispolyoxyethyleneammonium sulfate betaine, or 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine). Or two or more types can be used in combination.

By this addition, the penetrability of the black ink composition into the recording medium can be improved, and recording with less bleeding can be expected on various recording media. Preferable specific examples of the acetylene glycol surfactant used in the black ink composition used in the present invention include the general formula (1):
[Wherein, 0 ≦ m + n ≦ 50, and R ¹ , R ² , R ³ , and R ⁴ are each an independent alkyl group, preferably an alkyl group having 6 or less carbon atoms]. Can do.

  Among the compounds represented by the general formula (1), 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3 is particularly preferable. , 6-diol, 3,5-dimethyl-1-hexyne-3ol, and the like. Commercially available products can also be used as the acetylene glycol surfactant represented by the general formula (1), and specific examples thereof include Surfynol 104, 82, 465, 485, or TG (all are Air Products). and Olfin STG, Olfin E1010 (all are trade names manufactured by Nissin Chemical Co., Ltd.).

The black ink composition of the present invention has the general formula (2):
(Wherein R ^{11 to} R ¹⁷ independently represent a C 1-6 alkyl group, j and k independently represent an integer of 1 or more, EO represents an ethyleneoxy group, and PO represents propylene. Represents an oxy group, s and t represent an integer of 0 or more, provided that s + t represents an integer of 1 or more, and EO and PO are in the order in [] and are random even if they are blocks. It is preferable to include a silicone-based surfactant represented by This addition can improve the penetrability of the black ink composition into the recording medium.

A preferable compound in the silicone surfactant represented by the general formula (2) is that in the general formula (2), R ^{11 to} R ¹⁷ are independently a C 1-6 alkyl group, more preferably a methyl group. And j and k are each independently an integer of 1 or more, more preferably 1 to 2, and s and t represent an integer of 0 or more, provided that s + t is an integer of 1 or more, more preferably s + t Is a compound that is 2-4.

A particularly preferable compound in the silicone surfactant represented by the general formula (2) is a compound in which j and k are the same number in the formula (2), and 1 to 3, particularly 1 or 2. In the compound represented by the general formula (2), R ^{11 to} R ¹⁷ all represent a methyl group, j represents 1, k represents 1, u represents 1, and s represents It is a compound that represents an integer of 1 or more, particularly an integer of 1 to 5, and t represents 0.

  The amount of the silicone surfactant represented by the general formula (2) may be appropriately determined, but is preferably 0.03 to 3% by weight based on the total weight of the black ink composition used in the present invention. More preferably, it is about 0.1 to 2 weight%, More preferably, it is about 0.3 to 1 weight%.

  The silicone-based surfactant represented by the general formula (2) is commercially available and can be used. For example, a silicone surfactant BYK-347 or BYK-348 commercially available from Big Chemie Japan Co., Ltd. can be used.

When the surfactant content is less than 0.01% by weight, a sufficient surfactant effect cannot be obtained. When the surfactant content exceeds 10% by weight, ejection failure due to crystal precipitation, liquid crystal formation, or pigment stability decrease is caused. Cases that cause it are recognized.

The content of the water-soluble organic solvent added to each black ink composition is preferably about 0.5 wt% to 40 wt%, more preferably 2 wt%, based on the total weight of the black ink composition. % To 30% by weight. As the water-soluble organic solvent, a water-soluble organic solvent blended in an ordinary aqueous pigment ink composition can be used. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol Polyhydric alcohols such as polypropylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, or trimethylolpropane; ethylene glycol mono Ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl Alkyl ethers of polyhydric alcohols such as ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, or triethylene glycol monobutyl ether; or 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3- Mention may be made of dimethyl-2-imidazolidinone or triethanolamine.

  When using an aged polyurethane resin composition containing an organic solvent and a polyurethane resin as the water-soluble polyurethane resin, the ink composition may be prepared using the same water-soluble organic solvent as the organic solvent used. Alternatively, another water-soluble organic solvent other than the already used water-soluble organic solvent may be used, or these may be used in combination.

  The black ink composition of the present invention preferably further contains a preservative, a metal ion scavenger, and / or a rust inhibitor. Here, the preservative is preferably one or more compounds selected from the group consisting of alkylisothiazolones, chloroalkylisothiazolones, benzisothiazolones, bromonitroalcohols, oxazolidine compounds, and chlorxylenol, and the metal ion scavenger is ethylenediamine. Tetraacetate is preferable, and dicyclohexylammonium nitrate and / or benzotriazole is preferably used as the rust inhibitor.

In addition, the number of carbons such as ethanol, methanol, butanol, propanol, or isopropanol as a component that improves the solubility of the ink component, further improves the permeability to a recording medium such as paper, or prevents nozzle clogging. Examples thereof include 1 to 4 alkyl alcohols, formamide, acetamide, dimethyl sulfoxide, sorbite, sorbitan, acetin, diacetin, triacetin, sulfolane and the like, which can be appropriately selected and used.

  In addition, pH adjusters, amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, inorganic hydroxides such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, quaternary Examples thereof include ammonium salts (such as tetramethylammonium), carbonates such as potassium carbonate, sodium carbonate, and lithium carbonate, and phosphates. Other additives include ureas such as urea, thiourea and tetramethylurea, allophanates such as allophanate and methylallohanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, and L-ascorbic acid and its salts Commercially available antioxidants, ultraviolet absorbers and the like can also be used.

  Further, the black ink composition of the present invention preferably has a surface tension of 45 mN / m or less, more preferably in the range of 25 to 45 mN / m. When the surface tension exceeds 45 mN / m, the drying property of the printing is deteriorated, bleeding is likely to occur, and color bleeding is generated, so that it is difficult to obtain a good recorded image. Also, when the surface tension is less than 25 mN / m, the periphery of the nozzles of the printer head is likely to get wet, so that problems such as a flying curve of ink droplets are likely to occur. The surface tension can be measured by a commonly used surface tension meter. The surface tension of the ink can be set within the above range by adjusting the type and composition ratio of each component constituting the ink. The first black ink composition and the second black ink composition contained in the ink set for inkjet recording of the present invention can be prepared by a usual method.

  Furthermore, the black ink composition of the present invention preferably contains a tertiary amine as a pH adjuster. Examples of the tertiary amine that can be added to the black ink composition of the present invention include trimethylamine, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, triisopropenolamine, and butyldiethanolamine. These may be used alone or in combination. The amount of these tertiary amines added to the black ink composition of the present invention is from 0.1% by weight to 10% by weight, more preferably from 0.5% by weight to 5% by weight.

The black ink composition of the present invention can also contain a penetration enhancer, sugar, and / or alginic acid derivative. Examples of the penetration enhancer include alkyl ether derivatives of polyhydric alcohols having 3 or more carbon atoms, such as diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, or dipropylene glycol monobutyl ether. 1 type, or 2 or more types of these can be used. Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid. , Glucitol, (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. In addition, as derivatives of these saccharides,
Reducing sugars of the above-mentioned sugars (for example, sugar alcohol (general formula HOCH2 (CHOH) nCH2OH (where n represents an integer of 2 to 5)), oxidized sugar (for example, aldonic acid, uronic acid, etc. ), Amino acids, thio sugars, etc. Sugar alcohols are particularly preferable, and specific examples include maltitol, sorbit, etc. Moreover, HS-500 or HS-300 (Hayashibara Biochemistry) is a commercially available product. Research Institute) etc. The amount of these saccharides added is preferably about 0.1 to 40% by weight, more preferably about 1 to 30% by weight.

  Preferable examples of the alginic acid derivative include alginic acid alkali metal salts (for example, sodium salt and potassium salt), alginic acid organic salts (for example, triethanolamine salt), and alginic acid ammonium salt. The amount of the alginic acid derivative added to the black ink composition is preferably about 0.01 to 1% by weight, more preferably about 0.05 to 0.5% by weight. The reason why a good image can be obtained by the addition of the alginic acid derivative is not clear, but the polyvalent metal salt present in the reaction solution reacts with the alginic acid derivative in the black ink composition to change the dispersion state of the colorant, This is thought to be due to the accelerated fixing of the colorant to the recording medium. In addition to the black ink composition of the present invention, a preservative, a fungicide, and / or a phosphorus-based antioxidant may be added as necessary.

  The black ink composition of the present invention can be prepared by a conventional method. For example, the black ink composition can be produced by dispersing and mixing the above-described components by an appropriate method. Preferably, first, a pigment, a polymer dispersant, and ion exchange water are appropriately dispersed (for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, an ang mill). Etc.) to prepare a uniform pigment dispersion. Next, in addition to the water-soluble polyurethane resin and the aged water-soluble polyurethane resin composition, if necessary, the above fine particle emulsion (particularly pH adjusting resin emulsion, polyalkylene type emulsion), ion-exchanged water, water-soluble organic solvent The ink solvent is prepared by sufficiently stirring the antiseptic and / or antifungal agent at room temperature. The pigment dispersion is gradually added dropwise to a state where the ink solvent is stirred by a suitable dispersing machine, and the ink solvent is sufficiently stirred. After sufficiently stirring, the target black ink composition can be obtained by performing filtration in order to remove coarse particles and foreign matters that cause clogging. In addition, the said polyalkylene type emulsion can use a commercially available thing. For example, AQ593, AQ513, or PEM-17 commercially available from Big Chemie Japan Co., Ltd. can be used.

(Ink set)
The black ink composition of the various aspects described above can constitute an ink set including one or more black ink compositions having a carbon black concentration different from the carbon black concentration of the black ink composition. The first black ink composition and / or the second black ink composition can be combined with another black ink composition having a higher carbon black concentration. Examples of the other black ink composition include black ink compositions having a carbon black concentration of 1.5% by weight or more. More preferably, the black ink composition has a carbon black concentration of 2% by weight or more. The black ink composition preferably has a carbon black concentration of less than 6% by weight, and the carbon black is a carbon black that is not self-dispersing. The other black ink composition is a black ink composition having a carbon black concentration of 6% by weight or more, and preferably includes a black ink composition containing the self-dispersing carbon black described above. The other black ink composition includes both a black ink composition having a carbon black concentration of 1.5 wt% or more and less than 6 wt% and a black ink composition having a carbon black concentration of 6 wt% or more. Alternatively, either one of them may be included.

  In addition to the first black ink composition and the second black ink composition that are the black ink composition of the present invention, the ink set of the present invention preferably has a carbon black concentration of 1.5% by weight or more (preferably Is an ink set containing less than 6% by weight of a black ink composition containing carbon black that is not self-dispersing. According to this ink set, phase shift and GG are avoided or suppressed, and surface defects on the recorded material are also avoided or suppressed, so that a recorded material having a high-quality monochrome image or grayscale image can be obtained. . Moreover, according to such an aspect, the optical density and gray balance which were excellent with the above-mentioned effect especially in a glossy medium can be obtained.

In another preferred embodiment of the ink set of the present invention, in addition to the first black ink composition and the second black ink composition which are the black ink composition of the present invention, the carbon black concentration is 6% by weight or more (preferably Is a self-dispersing carbon black) black ink composition.
According to this ink set, it is possible to obtain a high-quality monochrome image or gray scale image, and an excellent optical density and gray balance, particularly in a non-glossy medium such as matte paper.

  Still another preferred embodiment of the ink set of the present invention is that, in addition to the first black ink composition and the second black ink composition, which are the black ink composition of the present invention, the carbon black concentration is 1.5% by weight. Black ink composition of the above (preferably less than 6% by weight and containing non-self-dispersible carbon black) and black ink having a carbon black concentration of 6% by weight or more (preferably self-dispersed carbon black) An ink set containing the composition. According to this ink set, the effects of both aspects described above can be obtained by switching and using other black ink compositions according to the type of the medium, which is good with the above effects regardless of the glossiness of the medium. A recorded image of optical density and gray balance can be obtained.

  The ink set of the present invention can be an ink set for monochrome recording or an ink set for color recording. In the case of monochrome recording, an ink set is composed of a plurality of types of black ink compositions. Each black ink composition can contain an appropriate complementary colorant, and a color ink composition capable of printing, for example, a complementary color on a monochrome recording ink set, for example, light magenta and light cyan. A color ink composition of a combination, a combination of light magenta, light cyan and yellow can also be included.

(Color recording ink set)
In the case of a color recording ink set, the ink set is composed of a chromatic color ink composition such as cyan, magenta and yellow in addition to the black ink composition. Exemplary ink sets according to the present invention include, for example, a yellow ink composition, a cyan ink composition, a magenta ink composition, a first black ink composition, and a black ink composition containing a higher concentration of carbon black. In addition, a five-color ink set; a seven-color ink set obtained by adding a light cyan ink composition and a light magenta ink composition to the five-color ink set; an eight-color ink set obtained by adding a dark yellow ink composition to the seven-color ink set An ink set; an eight-color ink set obtained by adding a red ink composition, a green ink composition, and a blue ink composition to the five-color ink set; an orange ink composition, a green ink composition, and the five-color ink set; An eight-color ink set to which a blue ink composition is added; and the five-color ink set And an ink set of 8 colors in which an orange ink composition, a green ink composition, and a violet ink composition are added; and an ink set in which a second black ink composition is added to each of the ink sets. it can.

  The “light magenta” and “light cyan” ink compositions are generally colorant concentrations of the magenta ink composition and the cyan ink composition, respectively, for the purpose of improving the image quality of the recorded image by density modulation. Is an ink composition having a reduced viscosity. The “dark yellow” ink composition is a yellow ink that uses a color material (pigment) having lightness and saturation lower than those of the yellow ink composition for the purpose of improving color reproducibility for dark colors such as shadow portions. It is a composition. In addition, each ink composition of “red”, “orange”, “green”, “blue”, and “violet” is used as an element constituting an intermediate color of yellow, magenta, and cyan in order to improve the color reproduction range. It is the ink composition used.

(Color ink composition)
In the various color ink compositions used in the ink set of the present invention and the color ink composition used independently of the ink set of the present invention, the above-described water-soluble polyurethane resin and aged water-soluble polyurethane resin composition may be used. it can. That is, for a color ink composition containing a chromatic pigment other than black, it is effective to use a water-soluble polyurethane resin and an aged water-soluble polyurethane resin composition. As in the case of the black ink composition of the present invention, magenta ink compositions (magenta, light magenta) having different concentrations and cyan ink compositions (cyan, light cyan) having different concentrations according to the pigment concentration contained in the composition. The concentration of the water-soluble polyurethane resin and the like can be set. The light magenta ink composition and the light cyan ink composition can be used in combination with a normal magenta ink composition and a cyan ink composition, respectively.

  For example, an aqueous ink composition having a chromatic color pigment concentration of 0.5 wt% or more and less than 1.5 wt% can be used as the light color ink composition. As a light color ink composition having a chromatic pigment content of 0.5 wt% or more and less than 1.5 wt%, for example, the solid content of the water-soluble polyurethane resin is 0.67 times the content of the chromatic pigment. More than 2.5 times can be set. In this light color ink composition, the solid content of the water-soluble polyurethane resin can be 0.3 wt% or more and 4 wt% or less. In such a light color ink composition, since a water-soluble polyurethane resin is a main resin, it is effective to use an aged water-soluble polyurethane resin.

  The color ink composition that may be used in combination with such a light color ink composition may have a chromatic pigment content of 1.5 wt% or more and less than 7 wt%. In such a color ink composition, for example, the solid content of the water-soluble polyurethane resin can be 0.04 to 0.35 times the content of the chromatic pigment. In the color ink composition, the solid content of the water-soluble polyurethane resin may be 0.05 wt% or more and 2.5 wt% or less. Even in such a color ink composition, since a water-soluble polyurethane resin is a main resin, it is effective to use an aged water-soluble polyurethane resin.

  By using a water-soluble polyurethane resin and / or an aged water-soluble polyurethane resin composition according to the pigment concentration, an ink composition whose surface glossiness is stable regardless of the printing duty, that is, gloss unevenness is avoided or suppressed. Ink composition can be obtained. When ink is recorded with large gloss unevenness, the gloss level is different between a region where the amount of shot is large and a region where the amount of ink is small on the recorded image, so that the image appears to sink or a sense of incongruity with the surroundings may occur. Therefore, by using the ink composition with improved gloss unevenness, a good image free from such problems can be obtained. In particular, gloss unevenness is likely to appear in a color ink composition having a low pigment concentration, and thus is effective in a color ink composition having a low pigment concentration.

  In addition to the water-soluble polyurethane resin and the aged water-soluble polyurethane resin composition, such a color ink composition can use the same ink components as the black ink composition of the present invention and can be produced in the same manner. it can.

  Examples of pigments used in the yellow ink composition include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, 185, etc., preferably C.I. I. 1 or a mixture of two or more selected from the group consisting of CI Pigment Yellow 74, 109, 110, 128 and 138.

Examples of the pigment used in the magenta ink composition and the light magenta ink composition include C.I. I. Pigment Red, 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 15: 1, 112, 122, 123, 168, 184, 202, 209 and C.I. I. Pigment violet 19 and the like, preferably C.I. I. Pigment red 122, 202, 209 and C.I. I. One or a mixture of two or more selected from the group consisting of pigment violet 19.

  Furthermore, examples of the pigment used in the cyan ink composition and the light cyan ink composition include C.I. I. Pigment blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60 and C.I. I. Bat blue 4, 60, and the like, preferably C.I. I. Pigment Blue 15: 3, 15: 4, and one or a mixture of two or more selected from the group consisting of 60.

(Water-based ink composition produced using an aged water-soluble polyurethane resin)
The water-based ink composition produced using the aged water-soluble polyurethane resin composition is stabilized in physical properties such as viscosity immediately after its preparation or after the preparation as compared with the case where the polyurethane resin composition is not used. . Therefore, for example, it has good ejection stability as a water-based ink composition for an inkjet printer. In particular, when the water-soluble polyurethane resin composition is used as at least a part or all of the water-soluble polyurethane resin used in all ink compositions constituting the ink set, the ejection of all ink compositions in the ink set is performed. Since the stability is stabilized, the entire ink set can be used stably.

Further, such a water-based ink composition is kept static for a period of time until a predetermined period of time has passed at a predetermined temperature (preferably target temperature ± 3 ° C.) after a predetermined amount of the composition is sealed in a sealable container. The viscosity change rate (ΔV) calculated from the following formula (1) from these viscosities is less than or less than a predetermined value. Is a preferred form.
ΔV (%) = | V−V ₀ | / V ₀ × 100 (1)
However, V ₀ is the viscosity at the start of the hold periods, V is the viscosity after the end of hold periods. The standing period can be started from the time when standing is started at a predetermined temperature. For example, it can be started from the production of the water-based ink composition. When the aqueous ink composition is manufactured, the time when the aqueous ink composition is prepared in the tank or the like (first time point), the time when the storage container is filled from the tank (second time point), or the water-based ink composition It can be the time (third time) when the composition is filled in a packaging container or the like.

  Moreover, as an evaluation standard of such a water-based ink composition, the target temperature can be set to one temperature in the range of 50 ° C to 70 ° C. Specifically, they are 50 degreeC, 60 degreeC, 70 degreeC, etc. Moreover, although it sets suitably as said stationary period, it can be made into 3 days or more. Further, the rate of change in viscosity varies depending on the properties required based on the use of the water-based ink composition and the nozzle structure. For example, when stored at 70 ° C. ± 3 ° C., it is less than 10% in 6 days. Preferably less than 7%, more preferably less than 4%.

  In addition, the viscosity in such an aqueous ink composition is measured as a kinematic viscosity (unit Pa · s), and the measurement is performed by a measurement method using a backflow type viscosity tube or a measurement method that can obtain the same accuracy and accuracy. It is preferable. Specifically, it can be measured by the moving time of the liquid (ink) in the tube at 20 ° C. using a Cannon Fenceke-type reverse flow type viscosity tube (typically, VMC-252 type manufactured by Koiso Co., Ltd.). .

  The ink set of the present invention can be used as various conventionally known inks for recording methods. A preferred ink set is water-based, and particularly an ink set for inkjet recording. The recording method of the present invention is a recording method for performing recording by discharging a droplet of an ink composition and attaching the droplet to a recording medium, and uses the ink set of the present invention. Here, in the recording method, an ink cartridge containing the ink set of the present invention (an ink cartridge containing each black ink composition individually) is mounted on a known ink jet recording apparatus and recorded on a recording medium. By doing so, it can be suitably performed. Here, as the ink jet recording apparatus, an electrostrictive element that can vibrate based on an electric signal is mounted, and the ink included in the ink set according to the present invention can be ejected by the vibration of the electrostrictive element. An ink jet recording apparatus constructed as described above is preferable. Further, as the ink cartridge (accommodating case) for accommodating the ink set, a known cartridge can be suitably used. Further, the recorded matter of the present invention has an image composed of the deposit layer of the ink set of the present invention of various aspects. In this image, occurrence of phase shift and GG are satisfactorily suppressed, and surface defects such as minute concave dots are avoided or suppressed.

  The black ink composition and ink set of the present invention can be used in any recording method, and can be suitably used, for example, as a water-based gravure ink, water-based flexographic ink, or water-based ink for ink jet recording. It can also be used as a water-based paint.

  The black ink composition of the present invention has, as a recording medium, a colorant (particularly a pigment), a water-soluble polyurethane resin, and a resin component of a fine particle emulsion (polyalkylene type emulsion) contained on the surface of the black ink composition. It is preferably used for a recording medium that substantially remains, but substantially absorbs the liquid component of the black ink composition. In such a recording medium, for example, the average pore diameter on the surface is smaller than the average particle diameter of the pigment. A preferable recording medium is a recording medium including an ink receiving layer having an average pore diameter smaller than the average particle diameter of the pigment.

  As a preferable recording medium for the black ink composition and the ink set of the present invention, a recording medium in which an ink receiving layer containing a porous pigment is provided on a substrate can be used. The ink receiving layer may be the uppermost layer of the recording medium, or may be an intermediate layer having, for example, a glossy layer thereon. As such a recording medium, a so-called absorption type (also referred to as a void type) recording medium containing a porous pigment and a binder resin in the ink receiving layer, and casein, modified polyvinyl alcohol (in the ink receiving layer) A so-called swelling type recording medium further containing a resin such as PVA), gelatin, or modified urethane is known, and the black ink composition of the present invention can be used for any recording medium. Examples of the porous pigment contained in the ink receiving layer of the absorption-type recording medium include silica-based such as precipitation method, gel type, or gas-phase method, alumina hydrate such as pseudoboehmite, and silica / alumina hybrid sol. , Smectite clay, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, kaolin, clay, talc, magnesium silicate, calcium silicate, and the like, and one or more of these can be used.

  Further, the binder resin contained in the ink receiving layer of the absorption type recording medium is not particularly limited as long as it is a compound that has a binding ability and can increase the strength of the ink receiving layer. For example, polyvinyl alcohol Silanol-modified polyvinyl alcohol, cellulose derivatives such as vinyl acetate, starch, carboxymethyl cellulose, casein, gelatin, conjugated diene copolymer latex such as styrene-butadiene copolymer, vinyl copolymer such as ethylene-vinyl acetate copolymer, etc. An acrylic copolymer latex such as a polymer latex and a polymer of acrylic acid and methacrylic acid can be used.

  The ink receiving layer may be a fixing agent, a fluorescent whitening agent, a water-proofing agent, a fungicide, if necessary, in the case of an ink receiving layer of an absorption type recording medium or an ink receiving layer of a swelling type recording medium. Various additives such as an agent, an antiseptic, a dispersant, a surfactant, a thickener, a pH adjuster, an antifoaming agent, and / or a water retention agent can also be contained. Examples of the substrate on which each of the ink receiving layers is provided include paper (including sized paper); resin-coated paper obtained by coating polyethylene, polypropylene, or polyester on paper; baryta paper; polyethylene terephthalate, polyethylene, or polypropylene. And a thermoplastic resin film such as synthetic paper; a sheet-like material formed of synthetic fibers.

The recording medium of a particularly preferred embodiment is a recording medium having the base material and the ink receiving layer as the uppermost layer provided thereon, and the base material and the ink receiving layer also have the following physical properties, for example. What has is preferable. As the base material, preferably paper (those containing wood pulp), but its basis weight is preferably from 100 g / ^{m 2} or more 350 g / ^{m 2} or less, still more preferably 180~260g / ^{m 2.} The thickness is preferably 100 μm or more and 400 μm or less, more preferably 180 μm or more and 260 μm or less. The ink receiving layer contains, based on the weight of the entire ink receiving layer, a wet method silica gel as the porous pigment in an amount of 50 wt% to 60 wt% in terms of solid content, and the binder resin is polyvinyl alcohol. Is preferably contained in an amount of 30% by weight to 40% by weight from the viewpoint of ink absorbability and printing fastness. The coating amount of the ink receiving layer is preferably 5 g / m ² or more and 50 g / m ² or less in terms of ink absorptivity in terms of solid content. The thickness of the ink receiving layer itself is preferably 10 μm or more and 40 μm or less, more preferably 20 μm or more and 30 μm or less. In the recording medium for recording the black ink composition of the present invention, the average pore diameter of the surface of the recording medium (particularly, the ink receiving layer) is preferably 50 nm or less, and more preferably 30 nm or less. When the average pore diameter exceeds 300 nm, the pigment may penetrate into the ink receiving layer and color developability may deteriorate.

  Hereinafter, the present invention will be described more specifically with reference to examples, but these do not limit the scope of the present invention. In the examples, “%” and “parts” are based on weight unless otherwise specified.

Example I
(1) Preparation of black ink composition For the nine black ink compositions shown in Table 1 below, a pigment dispersion was prepared as follows, and then a water-soluble polyurethane resin and the like were added and mixed. A black ink composition was obtained.

Specifically, the pigment (carbon black, pigment blue 15: 3) shown in Table 1 and a water-soluble resin (dispersant) are mixed to prepare a pigment dispersion, and further a water-soluble polyurethane resin (polyester polyurethane resin, Acid value 50, neutralized with triethylamine) and the like, and dispersed in a sand mill (manufactured by Yasukawa Seisakusho) with glass beads (diameter = 1.7 mm; 1.5 times the weight (weight) of the mixture) for 2 hours. An ink composition was obtained. That is, a high-density black ink composition K1 having a high density for one type of carbon black, K2, K4 (Examples) and K6, K8 (Comparative Examples) as medium-density black ink compositions for four types of halftones, and K3 and K5 (Examples) and K7 and K9 (Comparative Examples) were obtained as four types of low-concentration black ink compositions. As the water-soluble resin (dispersant) shown in Table 1, a styrene-acrylic acid copolymer (molecular weight = 15000; acid value = 100) was used. AQ593 is a polypropylene type emulsion (manufactured by Big Chemie Japan Co., Ltd.), and BYK348 is a silicone surfactant. In Table 1, the unit is weight% except for the 3rd row from the bottom column, and each ink contains pure water with 100% as a whole.

(2) Ink set Each black ink composition shown in Table 1, and a light cyan ink composition, a light magenta composition, and a yellow ink composition are combined as shown in Table 2, and compared with the ink sets of Examples 1 and 2. The ink sets of Examples 1 and 2 were constructed. The pigments of the light cyan ink composition (1%), the light magenta composition (1%), and the yellow ink composition (5.0%) are PB-15: 3, PV-19, and PY-74, respectively. Using.

(3) Evaluation method 1 (phase shift and golden gloss)
[1] Recording Method Each ink set of Examples 1 and 2 and Comparative Examples 1 and 2 is used in a black ink chamber (high concentration black ink composition K1) of a dedicated cartridge of an ink jet printer (PM-4000PX; manufactured by Seiko Epson Corporation). ), Gray ink chambers (K2, K4, K6, and K8 intermediate tone black ink compositions) and cyan ink chambers (K3, K5, K7, and K9 low-density black ink compositions), respectively. Similarly, a light cyan ink composition, a light magenta ink composition, and a yellow ink composition were also filled in the ink chambers shown in Table 3 below.

  For each ink set, output is performed on a dedicated inkjet recording paper (PM photo paper: manufactured by Seiko Epson Corporation) at a resolution of 1440 × 720 dpi, and a gray gradation pattern (gray scale) from white to black, respectively. Was performed steplessly without dividing the gradation. The output was performed by distributing the discharge amount of each ink.

[2] Confirmation and evaluation of phase shift The phase shift was evaluated by five observers. The recorded matter that was output was placed on a desk 1.5 m directly below the fluorescent lamp, which is room light, and an observer stood beside the desk. The observer observed the printed matter by moving the line of sight at various viewing angles from the right end to the left end of the printed matter so as not to interrupt the light from an upright state. The observation results are shown in Table 4 below. In a recorded matter in which a phase shift has occurred, when observed with a line of sight at a certain angle, the light from the fluorescent lamp is strongly reflected in white in the black output color in the gray level range of 40 to 60. , It looks like it was flipped. In Table 4, the denominator indicates the number of all observers (5 persons), and the numerator indicates the number of persons who have confirmed the phase shift.

[3] Confirmation evaluation of golden gloss Evaluation of golden gloss was performed by five observers. The recorded matter that was output was placed on a desk 1.5 m directly below the fluorescent lamp, which is room light, and an observer stood beside the desk. The observer observed the printed matter by moving his / her line of sight at various viewing angles from the right end to the left end of the printed matter so as not to block light from an upright state. The observation results are shown in Table 5 below. In the recorded matter in which the golden gloss is generated, when observed with a line of sight at a certain angle, in the black output color in the range around the gray level 140, the light of the fluorescent lamp is strongly reflected in the gold color. I can see it. In Table 5, the denominator indicates the number of all observers (5), and the numerator indicates the number of persons who have confirmed the golden gloss.

  As shown in Tables 4 and 5, it was found that both the phase shift and the golden gloss were avoided according to the ink set of the example. Therefore, according to the ink set of the example, it was found that a recorded matter in which phase shift and GG were effectively avoided or suppressed was obtained.

(4) Evaluation method 2 (surface defect)
[1] Recording Method Each ink set of Examples 1-2 and Comparative Examples 1-2 was used as a black ink chamber (high-concentration black ink composition K1) in a dedicated cartridge for an inkjet printer (PX-G900; manufactured by Seiko Epson Corporation). ), Matte black ink chambers (K2, K4, K6, and K8 intermediate tone black ink compositions) and yellow ink chambers (K3, K5, K7, and K9 low-density black ink compositions), respectively. Similarly, a light cyan ink composition, a light magenta ink composition, and a yellow ink composition were also filled in the ink chambers shown in Table 6 below.

  The output is divided gray solids with four resolutions of gray levels 140, 100, 50, and 20 shown in FIG. 2 with a resolution of 2880 × 1440 dpi for inkjet recording paper (PM photo paper: manufactured by Seiko Epson Corporation). The pattern was printed continuously for 100 pages.

[2] Confirmation and Evaluation of Surface Defects For the recorded matter after continuous printing, the surface defect consisting of the contact traces of the recording paper pressing member of the output matter was observed by five observers. This contact trace is a trace of a minute concave dot (roller trace) by the protrusion of a roller, which is a gear-shaped thin plate that serves as a recording paper presser, or when the resin component adheres to the image surface of the recorded matter. Formed by leaving. Table 7 shows the observation results. In Table 7, the denominator indicates the number of all observers (5), and the numerator indicates the number of persons who have confirmed surface defects.

  As shown in FIG. 2 and Table 7, according to the ink set of the example, it was found that surface defects such as roller marks were avoided over a wide gray level. Therefore, according to the ink set of the example, it was found that a phase difference and GG can be effectively avoided or suppressed, and a recorded matter having a high-quality surface without surface defects can be provided.

Example II
Next, K1 (photo black ink composition-carbon black which is not self-dispersing) and K10 (matte black ink composition-self-dispersing carbon black) are changed and combined with medium and low density black inks. An example of a recorded matter obtained by printing an image on a non-glossy medium (matte medium) will be described.

(1) Preparation of Black Ink Composition Regarding the black ink composition of K10 shown in Table 8 below, an aqueous medium or the like was added and mixed as follows to obtain a black ink composition.

  Specifically, a pigment (self-dispersing carbon black) is mixed with an aqueous medium based on Table 8, and glass beads [diameter = 1.7 mm; 1.5 times the amount of the mixture (by Yaskawa Seisakusho) ( Weight)] for 2 hours to obtain a black ink composition containing K10 self-dispersing carbon black.

(2) Ink set In addition to the K2 and K3 black ink compositions shown in Table 1 and the K10 black ink composition prepared by the above method, a cyan ink composition, a light cyan ink composition, a magenta composition, The light magenta ink composition and the yellow ink composition were combined as shown in Table 9 to form an ink set of Example 3. Further, as shown in Table 9, each ink composition of these ink sets was filled in each ink chamber of a dedicated cartridge of an inkjet printer A (PX-G900; manufactured by Seiko Epson Corporation). Hereinafter, this printer is referred to as printer A (Example 3).

Cyan ink composition (4.0%), light cyan ink composition (1%), magenta ink composition (5.5%), light magenta composition (1%), and yellow ink composition (
PB-15: 3, PV-19, and PY-74 were used as 5.0% pigments. As comparative examples, a commercially available PX-G900 ink cartridge (photo black ink composition (carbon black concentration 1.5%), mat black ink composition (carbon black concentration 6%), cyan ink composition, magenta ink) The ink set of the composition, the blue ink composition, the red ink composition, and the gloss optimizer ink composition was filled in each ink chamber) was mounted on an inkjet printer A (PX-G900; manufactured by Seiko Epson Corporation). Hereinafter, this printer is referred to as Printer B (Comparative Example 3).

(3) Evaluation method (evaluation of hue change due to occurrence of ink weight variation)
Using printers A and B, printing was performed at a resolution of 1440 × 720 on dedicated recording paper (Photomat paper, manufactured by Seiko Epson Corporation), and a gray scale having 18 gradation patches was output. Both used output data such that the output colors were almost the same. Furthermore, at that time, only the discharge ink weight of one ink composition included in each ink set is reduced by 10%, and the type of the ink composition that reduces the discharge ink weight by 10% in order is changed. The same data was output for combinations of ink weights. The driving voltage for obtaining the specified ink weight was determined by changing the voltage for driving the head to eject ink and actually measuring the ink weight.

The output data obtained with the normal ink weight and the output data obtained by reducing the ink weight are respectively measured using a Gretag Macbeth SPM50 manufactured by Gretag Co., and for each patch, an a * defined by CIE b * values were determined. The color measurement conditions were light source D50, no light source filter, white reference as absolute white, and viewing angle of 2 degrees. The degree of change Δa * b * between the output data obtained with the normal ink weight and the output data obtained by reducing the ink weight was calculated and evaluated according to the following criteria. The results are shown in Table 10.
A: Δa * b * is 2 or less in all patches B: Δa * b * exceeds 2 in 3 or less patches, but 2 or less in other patches C: Δa * b * is 6 or less in patches 2 but less than 2 for other patches D: Δa * b * exceeds 2 for 7 or more patches

As shown in Table 10, in the printer A, Δa * b * was 2 or less in all patches and the result was A, whereas when the printer B was used, the result was C. From the above, it has been found that the ink set used in the printer A can stably obtain a preferable gray scale in a non-glossy medium such as photomat paper. FIG. 3 and FIG. 4 illustrate the relationship between the ink usage amount of each ink composition and the gray level at the time of producing a good gray scale patch in the printers A and B.

In addition, for each of the black ink compositions K1, K2, K3, and K10, two types of printing duty within a range of 10 to 100% using an inkjet printer A (PX-G900; manufactured by Seiko Epson Corporation) are used. Printing paper (photo matte paper and PM photographic paper (glossy paper), both manufactured by Seiko Epson Corporation) at a resolution of 1440 × 720, and colorimetric using Gretag Macbeth SPM50 manufactured by Gretag The optical density was measured. The color measurement conditions were light source D50, no light source filter, white reference as absolute white, and viewing angle of 2 degrees. The results are shown in Table 11 and FIGS.

As shown in Table 11 and FIGS. 5 and 6, the black ink composition K1 exhibited an excellent optical density in PM photographic paper, and the black ink composition K10 exhibited an excellent optical density in photomat paper. . Therefore, by using the black ink composition K1 and the black ink composition K10 for the glossy medium and the non-glossy medium, respectively, a good gray scale recorded image can be obtained without surface defects regardless of the gloss of the medium. It was also found that a recorded image with a good optical density was obtained.

(Example III)
(1) Preparation of Aged Water-soluble Polyurethane Resin Solution A polyurethane resin composition (resin solution) having a resin solid content of 15% of a water-dispersible polyester-based polyurethane resin (acid value 50, triethylamine neutralized) and a composition shown in Table 12 It was prepared as follows. This resin solution was filled in an airtight container and allowed to stand under the conditions shown in Table 12, and an aging process was performed to obtain an aqueous polyurethane resin solution. In addition, this resin aqueous solution contained 33.3% of 1,2-hexanediol with respect to the water-soluble polyurethane resin solid content. Although the water-soluble polyurethane resin aqueous solution has a high viscosity before the start of the aging process, the viscosity is remarkably lowered after 5 days from the start of the aging, and then stabilized, and at the end of the aging process, the viscosity changes substantially. It was a liquid that did not have.

(2) Preparation of pH adjustment resin emulsion 60 parts ethyl methacrylate, 36 parts methyl methacrylate, 4 parts methacrylic acid, 3 parts octyl thioglycolate as molecular weight regulator, 1 part polyvinyl alcohol and 280 parts ion-exchanged water Thus, a dispersion of the monomer mixture was prepared. In a separate reactor equipped with a stirrer, 130 parts of ion exchange water and 2 parts of potassium persulfate were charged, the temperature was raised to 80 ° C., and the dispersion of the monomer mixture was continuously added over 4 hours for polymerization. . After completion of the continuous addition, a post-reaction was performed at 80 ° C. for 30 minutes. The polymerization conversion rate was 99% or more. Next, 10% aqueous sodium hydroxide solution in an amount corresponding to the charged methacrylic acid and an equimolar amount of sodium hydroxide was added to the reactor, followed by heat treatment at 80 ° C. for 1 hour, and then an appropriate amount of ion-exchanged water was added. In addition, a pH-adjusted resin emulsion A having a solid content concentration of 15% was obtained. The acid value of this pH-adjusted resin emulsion A was 30.

(3) Preparation of Black Ink Composition Next, four types of black ink compositions (K11 to K14) and two types of black ink compositions (K15 and K16) were prepared according to the compositions described in Table 13 below. . Specifically, the pigment (carbon black, pigment blue 15: 3) shown in Table 13 and a water-soluble resin (dispersant) are mixed to prepare a pigment dispersion, and the aqueous aging polyurethane resin solution prepared in (1) Alternatively, pH-adjusted resin emulsion A is added and dispersed in a sand mill (manufactured by Yasukawa Seisakusho) with glass beads [diameter = 1.7 mm; 1.5 times the weight (weight) of the mixture] for 2 hours to obtain six types of black ink compositions. Got. That is, K11, K13 (Examples) and K15 (Comparative Examples) as medium-density black ink compositions for three types of halftones, and K12, K14 (Examples) and three types of low-density black ink compositions. K16 (comparative example) was obtained. In addition, as a water-soluble resin (dispersing agent) described in Table 13, a styrene-acrylic acid copolymer (molecular weight = 15000; acid value = 100) was used. HS-500 is a solvent mainly composed of sugar.

(4) Composition of ink set Ink sets of Examples 4 to 7 and comparative examples in which the prepared black ink composition, light cyan ink composition, light magenta ink composition and yellow ink composition were combined as shown in Table 14 Four to six ink sets were constructed. The black ink compositions K1 to K9 were the same as those already prepared in Examples 1 and 2.

(5) Evaluation method 1 (phase shift and golden gloss)
[1] Recording method As shown in Table 15, the ink sets of Examples 4 to 7 and Comparative Examples 4 to 6 are assigned to various ink chambers of a dedicated cartridge of an inkjet printer (PM-4000PX; manufactured by Seiko Epson Corporation). Respectively. The output was performed in the same manner as in Examples 1 and 2 for each ink set.

[2] Confirmation Evaluation of Phase Shift and Golden Gloss The evaluation of phase shift and the evaluation of golden gloss were performed in the same manner as in Examples 1 and 2 by five observers. The results are shown in Table 16.

  As shown in Table 16, according to the ink set of the example, it was found that phase shift and golden gloss were all avoided. That is, it was found that even when a water-soluble polyurethane resin solution or an aged water-soluble polyurethane resin solution was used instead of the pH-adjusted resin emulsion A of Comparative Example 6, the phase shift and golden gloss were improved.

(6) Evaluation method 2 (surface defect)
[1] Recording Method Each ink set of Examples 4 to 7 and Comparative Examples 4 to 6 is assigned as shown in Table 17 to various ink chambers of a dedicated cartridge of an ink jet printer (PX-G900; manufactured by Seiko Epson Corporation). Respectively. The output was performed in the same manner as in Examples 1 and 2.

[2] Confirmation and Evaluation of Surface Defects For the recorded matter after continuous printing, the surface defect consisting of the contact traces of the recording paper pressing member of the output matter was observed by five observers. The results are shown in Table 18.

  As shown in Table 18, according to the ink set of the example, it was found that surface defects such as roller marks were avoided over a wide gray level. In other words, by using a water-soluble polyurethane resin solution or an aged water-soluble polyurethane resin solution in place of the pH-adjusted resin emulsion, the phase shift and golden gloss are improved, and the recording has a high-quality surface without surface defects. It turns out that things can be provided.

(7) Evaluation method 3 (ink storage stability)
Next, ink storage stability of various black ink compositions (K2 to K9, K11 to K16) used in the ink sets of Examples (Examples 4 to 7) and the ink sets of Comparative Examples (Comparative Examples 4 to 6) are shown. Sexuality was evaluated. In the evaluation method, 50 cc of the water-based ink composition was sealed in an ink pack immediately after preparation, and left in a 70 ° C. environment for 6 days (144 hours). The viscosity of the ink composition before and after being allowed to stand was measured using a viscoelasticity tester manufactured by Physica (measurement temperature: 20 ° C.), and the viscosity change rate (ΔV) was determined by the following formula. The rate of change in viscosity was evaluated according to the following criteria. The results are shown in Table 19.
ΔV (%) = | V−V ₀ | / V ₀ × 100
However, V ₀ is the viscosity at the time of leaving, V is the viscosity of the time over a period of 6 days.
Evaluation A: The viscosity change of the ink was less than 4%.
Evaluation B: The viscosity change of the ink was 4% or more and less than 7%.
Evaluation C: The change in the viscosity of the ink was 7% or more.

  As shown in Table 19, the black ink compositions (K11 to K14) using the aged water-soluble polyurethane resin showed good storage stability. On the other hand, none of the black ink compositions K2 to K5 using a water-soluble polyurethane resin that had not been aged had good storage stability. Thus, it was found that good storage stability can be obtained by using an aged water-soluble polyurethane resin aqueous solution. Note that black ink compositions not using a water-soluble polyurethane resin (K6 to K9, K15 and K16 (using pH-adjusted resin emulsion A)) also show good storage stability, and the use of a water-soluble polyurethane resin is an ink composition. It was clear that the storage stability of the was reduced.

Table 20 shows a summary of the results of the above evaluation methods 1 to 3 for the black ink set.

  As shown in Table 20, the ink sets of Examples 6 to 7 using the black ink composition using the aged water-soluble polyurethane resin have excellent characteristics (an improvement in phase shift and golden gloss as well as an improvement in phase shift and golden gloss). It was found that the storage instability caused by the water-soluble polyurethane resin was eliminated and the storage stability was good. That is, by using an aged water-soluble polyurethane resin, it was possible to improve storage stability while maintaining good surface characteristics obtained by the water-soluble polyurethane resin.

(Example IV)
In the following examples, various color ink compositions were prepared, and gloss unevenness and storage stability were evaluated.

(1) Preparation of Color Ink Composition According to the composition shown in Table 21, 10 types of color ink compositions of Examples and 5 types of color ink compositions of Comparative Examples were prepared. Specifically, various pigments shown in Table 21 and a water-soluble resin (dispersant) are mixed to prepare a pigment dispersion, and the aging polyurethane resin aqueous solution prepared in Example III or the polyurethane resin aqueous solution before aging is prepared. In addition, the mixture was dispersed in a sand mill (manufactured by Yasukawa Seisakusho) together with glass beads [diameter = 1.7 mm; 1.5 times the weight (weight) of the mixture] for 2 hours to obtain a total of 15 color ink compositions. In addition, as a water-soluble resin (dispersing agent) described in Table 21, a styrene-acrylic acid copolymer (molecular weight = 15000; acid value = 100) was used.

(2) Evaluation method 1 (gloss unevenness)
The prepared various color ink compositions (C1 to C15) and black ink compositions (K1 to K3, K6, K7, K11 and K12, see Examples I and III) were transferred to an inkjet printer (PM-G900; Seiko Epson Corporation). As shown in Table 22, the ink chambers were filled with various ink chambers.

The output was 10 patches of 10 to 100% duty for each ink with a single color at a resolution of 1440 × 720 dpi on inkjet recording paper (PM photo paper: manufactured by Seiko Epson Corporation). After the printed sample was dried for one day, a 45 degree glossiness measurement was performed using an automatic goniophotometer (GP-200 Murakami Color Research Laboratory Co., Ltd.). The results are shown in Table 23 and FIGS. The black ink composition was measured in the same manner. The results are shown in Table 24 and FIGS. Table 25 shows the evaluation results of gloss unevenness evaluated according to the following criteria.
A: The difference between the duty value of the 45-degree gloss of 10 patches up to 10 to 100% and the duty value of 0 to less than 30 B: The difference between the duty value of the 45-degree gloss of 10 patches up to 10 to 100% and the duty value 30 or more and less than 60 C: The difference between the Duty value and Duty value of 45 degree gloss of 10 patches from 10 to 100% Duty is 60 or more

  As shown in Table 23 and FIGS. 7 to 11, the color ink compositions of the examples (C1, C2, C4, C5, C7, C8, C10, C11, C13, C14) are the color ink compositions of the comparative examples, respectively. Compared to the products (C3, C6, C9, C12, C15), the glossiness was stable over a wide range of driving amounts. In particular, it was remarkable in a color ink composition having a low pigment concentration, but it was found that such a problem was avoided or suppressed by using a water-soluble polyurethane resin. Further, as shown in Table 24 and FIGS. 12 and 13, it was found that gloss unevenness can also be avoided or suppressed by using a water-soluble polyurethane resin in the black ink composition.

(3) Evaluation method 2 (ink storage stability)
Next, the ink storage stability of the color ink composition of the example and the color ink composition of the comparative example was evaluated. In the evaluation method, 50 cc of the water-based ink composition was sealed in an ink pack immediately after preparation, and left in a 70 ° C. environment for 6 days (144 hours). The viscosity of the ink composition before and after being allowed to stand was measured using a viscoelasticity tester manufactured by Physica (measurement temperature: 20 ° C.), and the viscosity change rate (ΔV) was determined by the following formula. The rate of change in viscosity was evaluated according to the following criteria. The results are shown in Table 25.
ΔV (%) = | V−V ₀ | / V ₀ × 100
However, V ₀ is the viscosity at the time of leaving, V is the viscosity of the time over a period of 6 days.
Evaluation A: The viscosity change of the ink was less than 4%.
Evaluation B: The viscosity change of the ink was 4% or more and less than 7%.
Evaluation C: The change in the viscosity of the ink was 7% or more.

  As shown in Table 25, the color ink compositions (C2, C5, C8, C11, C14) using the aged water-soluble polyurethane resin showed good storage stability. On the other hand, the storage stability of the color ink compositions (C1, C4, C7, C10, C13) using the water-soluble polyurethane resin that was not aged was not good. As a result, it was found that good storage stability can also be obtained in the color ink composition by using an aged water-soluble polyurethane resin aqueous solution. Color ink compositions (C3, C6, C9, C12, C15) that do not use a water-soluble polyurethane resin exhibit good storage stability, and the use of a water-soluble polyurethane resin reduces the storage stability of the ink composition. It was clear that

  From the above, as shown in Table 25, the color ink composition using the aged water-soluble polyurethane resin has excellent characteristics (avoidance or suppression of gloss unevenness) due to the use of the water-soluble polyurethane resin, and is water-soluble. It was found that the storage instability caused by the water-soluble polyurethane resin was eliminated and the storage stability was also good. That is, by using an aged water-soluble polyurethane resin, it was possible to improve storage stability while maintaining good surface characteristics obtained by the water-soluble polyurethane resin.

The graph which shows typically the area | region where a phase shift and golden gloss generate | occur | produce when printing a gray scale using 3 types of black ink compositions. The graph which shows the relationship between the gray level of the black ink composition whose gray levels are 140, 100, 50, and 20 and a printing duty. FIG. 4 is a diagram illustrating a relationship between an ink usage amount of each ink composition and a gray level when a favorable gray scale patch is manufactured in the printer A. FIG. 4 is a diagram illustrating a relationship between an ink usage amount of each ink composition and a gray level when a favorable gray scale patch is produced in the printer B. The figure which shows the relationship between the printing duty of various black ink compositions, and optical density. The figure which shows the relationship between the printing duty of various black ink compositions, and optical density. The figure which shows the relationship between the printing duty of a light magenta ink composition, and glossiness. The figure which shows the relationship between the printing duty of a light cyan ink composition, and glossiness. The figure which shows the relationship between the printing duty of a magenta ink composition, and glossiness. The figure which shows the relationship between the printing duty of a cyan ink composition, and glossiness. The figure which shows the relationship between the printing duty of a yellow ink composition, and glossiness. The figure which shows the relationship between the printing duty of a medium density | concentration black ink composition, and glossiness. The figure which shows the relationship between the printing duty of a low concentration black ink composition, and glossiness.

Claims (36)

A black ink composition containing water, carbon black, and a water-soluble polyurethane resin,
When the carbon black content is 0.4 wt% or more and less than 1.5 wt%, the solid content of the water-soluble polyurethane resin is 0.67 to 2.5 times the carbon black content. And
When the content of the carbon black is less than 0.4% by weight, the solid content of the water-soluble polyurethane resin is 7.5 times or more the content of the carbon black. When the content of the carbon black is 0.4 wt% or more and less than 1.5 wt%, the solid content of the water-soluble polyurethane resin is 0.2 wt% or more and 4 wt% or less,
2. The composition according to claim 1, wherein when the content of the carbon black is less than 0.4 wt%, the solid content of the water-soluble polyurethane resin is 1 wt% or more and 10 wt% or less.   The composition according to claim 1 or 2, comprising a fine particle emulsion.   4. A composition according to claim 3, wherein the particulate emulsion is selected from polyalkylene type emulsions.   The composition according to claim 3 or 4, wherein the total content of the solid content of the water-soluble polyurethane resin and the solid content of the fine particle emulsion is 0.5 wt% or more and 20 wt% or less. A black ink composition comprising water and carbon black, the black ink composition for use in combination with another black ink composition having a carbon black concentration higher than the carbon black concentration of the black ink composition Because
Contains water-soluble polyurethane resin,
The composition whose solid content of this water-soluble polyurethane resin is 0.2 weight% or more and 10 weight% or less.   The composition of Claim 6 whose solid content of the said water-soluble polyurethane resin is 0.5 weight% or more and 5 weight% or less.   The fine particle emulsion is contained, and the solid content of the water-soluble polyurethane resin is 40% by weight or more and 80% by weight or less of the total amount of the water-soluble polyurethane resin and the solid content of the fine particle emulsion. 8. The composition according to 7.   The composition according to any one of claims 6 to 8, wherein the other black ink composition contains 1.5% by weight or more of carbon black.   The said other black ink composition is a composition in any one of Claims 6-9 containing 6 weight% or more of carbon black.   The composition according to claim 10, wherein the other black ink composition contains self-dispersing carbon black.   The carbon black content is 0.4 wt% or more and less than 1.5 wt%, and the solid content of the water-soluble polyurethane resin is 0.2 wt% or more and 4 wt% or less. 12. The composition according to any one of 11 above.   The composition according to any one of claims 6 to 11, wherein the carbon black content is less than 0.4 wt%, and the solid content of the water-soluble polyurethane resin is 1 wt% or more and 10 wt% or less. object.   The composition in any one of Claims 1-13 containing the coloring agent for complementary colors.   At least one part of the said water-soluble polyurethane resin contains a water-soluble polyurethane resin, a water-soluble organic solvent, and water, and is added as a polyurethane resin composition which does not have a substantial viscosity change. The composition in any one of.   The composition according to claim 15, wherein the water-soluble solvent is one or more diols.   The composition of Claim 15 or 16 which contains the said water-soluble organic solvent 10 to 50 wt% with respect to the said water-soluble polyurethane resin solid content.   The composition according to any one of claims 15 to 17, wherein the water-soluble organic solvent contains one or more diols and one or more triols.   The composition of claim 18, wherein the triols comprise glycerin.   The composition according to claim 18 or 19, wherein the triol is contained in an amount of 10 wt% to 100 wt% with respect to the water-soluble polyurethane resin solid content.   The composition according to any one of claims 16 to 20, wherein the diol includes 1,2-hexanediol, and the triol includes glycerin.   The composition according to any one of claims 15 to 21, wherein the polyurethane resin composition contains the water-soluble organic solvent in an amount of 0.5 wt% to 20 wt%.   The said polyurethane resin composition is a composition in any one of Claims 15-22 containing the said water-soluble polyurethane resin 5 wt% or more and 50 wt% or less.   The said polyurethane resin composition is a composition in any one of Claims 15-23 obtained by giving aging with a heating. A predetermined amount of the polyurethane resin composition is sealed and allowed to stand at a constant temperature of 70 ° C. ± 3 ° C. for 24 hours, and the viscosity at the start and end of the standing period is measured. 25) The composition according to any one of claims 15 to 24, which has a viscosity change rate (ΔV) of 2.5% or less.
ΔV (%) = | V−V ₀ | / V ₀ × 100 (1)   The composition according to any one of claims 1 to 25, which is an ink composition for inkjet recording. One or more black ink compositions according to any one of claims 1 to 26;
Other black ink compositions having a carbon black concentration higher than the carbon black concentration of these black ink compositions;
Including ink set. 27. The one or more black ink compositions according to any one of claims 1 to 26 have a carbon black content and a carbon black content of less than 0.4% by weight of carbon black. 0.4% by weight or more and less than 1.5% by weight of a black ink composition,
28. The ink set according to claim 27, wherein the other black ink composition is a composition having a carbon black content of 1.5% by weight or more.   The ink set according to claim 27 or 28, wherein the other black ink composition is a composition containing 6% by weight or more of carbon black.   30. The ink set according to claim 29, wherein the other black ink composition is a composition containing self-dispersing carbon black.   The ink set according to any one of claims 27 to 30, comprising a cyan ink composition, a magenta ink composition, and a yellow ink composition.   32. The ink set according to claim 31, comprising a light cyan ink composition and a light magenta ink composition.   The ink set according to claim 31 or 32, wherein the color ink composition other than the black ink composition contains a water-soluble polyurethane resin.   At least a part of the water-soluble polyurethane resin in the color ink composition contains a water-soluble polyurethane resin, a water-soluble organic solvent, and water, and is added as a polyurethane resin composition having no substantial viscosity change. The ink set according to claim 33. A recording method for forming an image by ejecting droplets of an ink composition and attaching the droplets to a recording medium,
A recording method using the ink set according to any one of claims 27 to 34. A recorded matter having an image on a recording medium,
35. A recorded matter having an image composed of an adherent layer of an ink composition contained in the ink set according to any one of claims 27 to 34 on the recording medium.