JP5434039B2 - Gray ink composition - Google Patents

Description

  The present invention relates to a gray ink composition and an ink set including these gray ink compositions, and more particularly to an inkjet ink having no graininess and excellent black tone reproducibility.

  Conventionally, when an image is formed by an inkjet recording method or the like, an ink set containing a gray ink is sometimes used for the purpose of obtaining a high-quality image without graininess. For example, in addition to cyan ink, magenta ink, yellow ink, black ink, light cyan ink, and light magenta ink, gray ink may be added to obtain seven colors. The term “no graininess” as used herein means that dots are not seen when the printed matter is visually confirmed, and smooth printing is performed. The gray ink is a carbon black content lower than that of the black ink, and is used for the purpose of improving the color reproducibility with respect to a material feeling such as metal or smooth expression of human skin.

However, the conventional gray ink is not an achromatic color, it is a Hunter L, a, b color system, deviating from (a, b) = (0, 0), red when a value is +, a value is When it is-, it is greenish, when b is +, it is yellowish, and when b is-, it is bluish. The achromatic color here refers generally to white, black, and gray.
Methods for using gray ink compositions containing cyan organic pigments and magenta organic pigments to correct such shades of gray ink are known. However, unless the ratio of the cyan organic pigment and the magenta organic pigment is controlled well, the black tone reproducibility is poor, reddish, yellowish, bluish, greenish, etc., and not an achromatic image.
In addition to color problems, black and gray inks that use only carbon black have high dot visibility, so if only one type of gray ink is used, it will become grainy when printing gradation on black. A feeling is given and a problem remains as printed matter.
JP 2000-318293 A JP 2003-55592 A

  An object of the present invention is to use a gray ink composition, which is excellent in black tone reproducibility and capable of obtaining an image having no graininess, and an ink set including these plurality of gray inks, In particular, an inkjet ink composition is provided.

  The above object of the present invention is achieved by the following configurations.

That is, the present invention provides a gray ink composition containing carbon black, a cyan organic pigment, and a magenta organic pigment, wherein X is the total content of carbon black, cyan organic pigment, and magenta organic pigment contained in the gray ink. The present invention relates to a gray ink composition satisfying the following (formula 1), where C is the cyan organic pigment content in the gray ink composition and M is the magenta organic pigment content in the gray ink composition.
(Formula 1) 60 × X / 469 + 0.2 <M / C <60 × X / 469 + 4

Furthermore, when the total content of carbon black, cyan organic pigment and magenta organic pigment contained in the gray ink is 0.1 to 1.5%, and there are a plurality of gray inks, carbon black, cyan organic pigment and magenta organic pigment The total content of (X ₁ , X ₂ , X ₃ ... X _n , X _{n + 1} ...) Relates to a gray ink composition satisfying the following range. (However, the pigment content is X ₁ <X ₂ <X ₃ ... X _n <X _{n + 1} ..., N is an integer)
1.5 <X _{n + 1} / Xn <5

  Furthermore, the present invention relates to an ink set including cyan ink, magenta ink, yellow ink, and black ink in addition to a plurality of gray inks.

Furthermore, the present invention relates to an ink set containing light cyan ink and light magenta ink in the ink set described above.
Furthermore, it is related with said non-aqueous inkjet ink and printed matter printed using the same.

  According to the present invention, by combining carbon black, a magenta organic pigment, and a cyan organic pigment in gray ink and satisfying (Equation 1), an excellent black tone reproducibility can be realized and an image without graininess The present invention provides a gray ink composition that can be obtained, as well as an ink set comprising these gray inks, particularly an inkjet ink composition.

  The gray ink composition of the present invention uses carbon black, a magenta organic pigment, and a cyan organic pigment in combination.

  In the present invention, the magenta organic pigment and the cyan organic pigment are used in combination in order to cancel the slight coloring of the carbon black. When the total content of carbon black, cyan organic pigment, and magenta organic pigment contained in the gray ink is X, the cyan organic pigment content in the gray ink composition is C, and the magenta organic pigment content in the gray ink composition is C. When the content ratio is M, M / C is 60 × X / 469 + 0.2 <M / C <60 × X / 469 + 4, preferably 60 × A / 469 + 0.5 <M / C <60 × A / 469 + 2, more preferably 60 × X / 469 + 0.5 <M / C <60 × X / 469 + 1.5. For gray ink that satisfies this range, the a and b values of the Hunter L, a, and b color systems when applying to a white polyvinyl chloride resin sheet so that the ink film pressure is 12 μm is -3.5 <a <2.5 , -3.5 <b <2.5, and a gray ink with excellent black tone reproducibility. In order to achieve better black tone reproducibility, the a and b values are preferably -2.0 <a <1.0, -2.0 <b <1.0, more preferably -1.0 <a <0.0, -1.0 <b <0.0. It is good to be. When the a and b values are below -3.5, the ink becomes blue, green, or when it exceeds 2.5, the red ink and the yellow ink become conspicuous.

  Further, it has been found that by using a plurality of gray inks having different pigment concentrations, it is possible to form a printed image having no graininess that cannot be reproduced only by the black ink.

In the present invention, when the total content of carbon black, cyan organic pigment, and magenta organic pigment contained in the gray ink is 0.1 to 1.5%, and when a plurality of gray inks are present, carbon black and cyan organic pigment the total content of the magenta organic pigment _{(X 1, X 2, X} 3 ···· X n, X n + 1 ···) is _{1.5 <X n + 1 / Xn} <5, preferably 2 <X _{n + 1} / Xn <4, more preferably 2 <Xn _{+ 1} / Xn <3. If this range is not satisfied, the number of dots is reduced during black gradation printing, resulting in a noticeable grainy print, and smooth printing cannot be achieved.

  Pigment black 7, pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 60, and pigment used in gray ink, black ink, cyan ink, and magenta ink are indicated by color index. Red 9, 48, 49, 52, 53, 57, 97, 122, 149, 168, 177, 178, 179, 206, 207, 209, 242, 254, 255, pigment violet 19, and the like. As for carbon black, any carbon black such as neutral, acidic and basic can be used. The total content of carbon black, cyan organic pigment, and magenta organic pigment used in gray ink is preferably 0.1 to 1.5% in the ink. Pigment contained in black ink, cyan ink, and magenta ink It is desirable that the content of 0.1 to 10% is included. Among them, the pigment used for the gray ink is preferably neutral carbon black, pigment blue 15: 4, 15: 3, and pigment red 122 from the viewpoint of weather resistance, stability with time, and color developability. 15: 4 is more preferable.

  In the present invention, an ink set containing cyan ink, magenta ink, yellow ink, and black ink in addition to a plurality of gray inks can be used.

  The main solvent used in the present invention is most preferably a (poly) alkylene glycol derivative or a glycol acetate organic solvent as a main agent.

  These compounds include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether. , Diethylene glycol monobutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipro Glycols such as lenglycol monobutyl ether, propylene glycol n-propyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether And ethers.

  Further, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, ethylene glycol monomethyl ether propio , Ethylene glycol monoethyl ether propionate, ethylene glycol monobutyl ether propionate, diethylene glycol monomethyl ether propionate, diethylene glycol monoethyl ether propionate, diethylene glycol monobutyl ether propionate Propylene glycol monomethyl ether propionate, dipropylene glycol monomethyl ether propionate, ethylene glycol monomethyl ether butyrate, ethylene glycol monoethyl ether butyrate, ethylene glycol monobutyl ether butyrate, diethylene glycol monomethyl ether butyrate, diethylene glycol monoethyl Examples thereof include glycol monoacetates such as ether butyrate, diethylene glycol monobutyl ether butyrate, propylene glycol monomethyl ether butyrate and dipropylene glycol monomethyl ether butyrate.

  Ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, ethylene glycol propionate butyrate, ethylene glycol dipropionate, ethylene glycol dibuty Rate, diethylene glycol acetate propionate, diethylene glycol butyrate, diethylene glycol propionate butyrate, diethylene glycol dipropionate, diethylene glycol dibutyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, propylene glycol propionate butyrate, pro Glycols such as lenglycol dipropionate, propylene glycol dibutyrate, dipropylene glycol acetate propionate, dipropylene glycol acetate butyrate, dipropylene glycol propionate butyrate, dipropylene glycol dipropionate, dipropylene glycol dibutyrate Diacetates are mentioned.

  In addition to the above, the organic solvent that can be used as the mixed solvent is not particularly limited except for a solvent that corrodes the printer head or dissolves the pigment. Examples of the organic solvents that the inventors have examined use include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl Isopropyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, methyl isoamyl ketone, diethyl ketone, ethyl-n-propyl ketone, ethyl isopropyl ketone, ethyl-n-butyl ketone, ethyl isobutyl ketone, di-n -Ketones such as propyl ketone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, isophorone, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, vinegar Esters such as hexyl, octyl acetate, methyl lactate, propyl lactate, butyl lactate, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, n-hexane, isohexane, n-nonane, isononane, Saturated hydrocarbons such as dodecane and isododecane, unsaturated hydrocarbons such as 1-hexene, 1-heptene and 1-octene, cyclic saturated hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, cyclodecane and decalin, cyclohexene, Examples thereof include cyclic unsaturated hydrocarbons such as cycloheptene, cyclooctene, 1,1,3,5,7-cyclooctatetraene and cyclododecene, and aromatic hydrocarbons such as benzene, toluene and xylene.

  These solvents may be used alone or in combination of two types. Of these, (poly) ethylene glycol diether solvents and (poly) ethylene glycol monoether monoester solvents are preferred from the viewpoints of resin solubility and drying properties on the nozzle. Specific examples include ethylene glycol monobutyl ether acetate and diethylene glycol diethyl ether. Diethylene glycol diethyl ether is particularly preferred from the viewpoint of low odor.

  Furthermore, when a nitrogen-containing or lactone-based solvent is added in addition to the main solvent, the surface of the printing medium can be dissolved, so that fixing properties, weather resistance, and the like can be improved. Examples include 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, ε-caprolactone, and the like. The addition amount is preferably 1 to 20%, preferably 1 to 10%, more preferably 3 to 9%.

  As the pigment used in the ink set of the present invention, various pigments used for printing inks, paints, and the like can be used for yellow ink in addition to the above-mentioned pigment black, pigment blue, pigment red, and pigment violet. When such a pigment is indicated by a color index, Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137 , 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213, and the like. The pigment is desirably contained in the ink in an amount of 0.1 to 10% by weight.

  In the present invention, a resin is added in order to impart fixability to the substrate. Usable resins include acrylic resin, styrene-acrylic resin, styrene-maleic resin, rosin resin, rosin ester resin, ethylene-vinyl acetate resin, petroleum resin, coumarone indene resin, terpene phenol Resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, vinyl acetate resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric acid Examples thereof include resins.

    The ink composition of the present invention can use various additives such as a plasticizer, a surface conditioner, an ultraviolet light inhibitor, a light stabilizer, an antioxidant, and a hydrolysis inhibitor.

    Examples of the printing medium of the present invention include a polyvinyl chloride resin sheet, a polyolefin-based sheet, glass, metal and the like, and a polyvinyl chloride resin sheet is particularly preferable.

    Examples of the printing method of the ink composition of the present invention include gravure printing, flexographic printing, silk screen printing, ink jet printing, and the like, and the ink jet printing method is particularly preferable.

    The ink composition of the present invention is prepared by first dispersing a pigment in a single or mixed solvent with a resin or a dispersant using a paint shaker, sand mill, roll mill, medialess disperser, etc. It is manufactured by diluting with the solvent of the invention.

[Example]
EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples, “part” represents “part by weight”.

  First, pigment dispersions A to C were prepared by blending as shown in Table 1 below. This dispersion was prepared by adding a pigment and a dispersant into an organic solvent, stirring until uniform with a high speed mixer or the like, and then dispersing the obtained mill base with a horizontal sand mill for about 1 hour.

A black ink was prepared using the dispersion obtained as described above in the following composition.
-Dispersion C 14.29 parts-VYHD (Dow Chemical's vinyl acetate resin) 4.9 parts-Gamma-butyrolactone 10 parts-Diethylene glycol diethyl ether 70.81 parts In addition, Examples 1 to 13 and Comparative Examples 1 to 6 with the formulations shown in Table 2 The gray ink was made. The “M / C range” in the table indicates the range in which each gray ink should satisfy the formula (1).

Abbreviations in Table 2 DEDG: Diethylene glycol diethyl ether BGAc: Ethylene glycol monobutyl ether acetate GBL: Gamma butyrolactone
Measuring method of a, b value and OD value
Using X-Rite 528 made by X-Rite, apply it to Metamark MD5GL (IP-880) so that the ink film pressure is WET 12μm, and after drying, view angle 2 °, light source C, to calculation method hunter Measure the lab at any 5 locations on the color sample and calculate the average value.
The OD value is obtained by measuring the OD values at any five locations on the same color sample with the response G, and obtaining the average value.

As is clear from Table 2,
(Formula 1) 60 × X / 469 + 0.2 <M / C <60 × X / 469 + 4
In Examples 1 to 6, 8 to 11 using cyan organic pigments and magenta organic pigments within the range, both a and b values satisfy -3.5 <a <2.5 and -3.5 <b <2.5. . On the other hand, Example 7, the pigment content exceeds 1.5%, Comparative Example 7 exceeding the upper limit of (Formula 1), Comparative Example 8 below the lower limit of (Formula 1), Is outside the scope of the present invention. For Examples 12 to 14 using dispersions D and E having different cyan organic pigments and magenta organic pigments, both a and b values satisfy -3.5 <a <2.5 and -3.5 <b <2.5. It deviates from the most preferable -1 <a <0 and -1 <b <0. In addition, the a and b values were out of the scope of the present invention for Comparative Examples 1 to 6 in which only carbon black, only carbon black and cyan organic pigment, and only carbon black and magenta organic pigment were combined.

  The ink obtained as described above was used as an ink set in the combination of Table 3 below, and from white to black on a white polyvinyl chloride resin sheet with a solvent ink inkjet printer Color Painter 64S Plus manufactured by Seiko I Infotech Co., Ltd. Gradation printing was performed, and the presence or absence of graininess and the color were confirmed. As an evaluation standard for the graininess, have 50 people visually evaluate the dot visibility and describe the number of people who feel that there is a graininess. Also, as a color standard, have 50 people evaluate visually and describe the number of people who feel that they have a color other than black. That is, it can be said that an ink set having a smaller number of both graininess and color is an excellent ink set.

As is clear from Table 3, the black ink single color or the two-color ink set 1, 2, and 3 of black ink and one gray ink has a graininess, and more than three colors including black ink. A set is required. In addition, ink set 5 that does not fall within the range of 1.5 <X _{n + 1} / Xn <5 also has a grainy feel, and ink sets 4, 6 to 4 that fall within the range of 1.5 <X _{n + 1} / Xn <5 8, 10, and 11 have no graininess and can be printed smoothly. However, among ink sets without graininess, ink sets 10 and 11 that use gray inks with a and b values other than -3.5 <a and b <2.5 have color and black tone reproducibility. bad. Ink sets 7 and 8 using black ink with a and b values in the range of -2 <a and b <1 are more achromatic, and a and b values are -1 <a and b <0. Ink sets 4, 5 and 6 using a range of black inks were more achromatic.

Claims (5)

In a gray ink composition containing carbon black, pigment blue 15: 4 as a cyan organic pigment, and a magenta organic pigment, X is the total content of carbon black, cyan organic pigment, and magenta organic pigment contained in the gray ink. When the content of the cyan organic pigment in the gray ink composition is C and the content of the magenta organic pigment in the gray ink composition is M, the following formula 1 is satisfied and the white polyvinyl chloride resin sheet The characteristics of Hunter L, a, b color system a, b values satisfy -1.0 <a <0.0, -1.0 <b <0.0 when applied so that the ink film pressure is 12μm Water-based gray ink composition.
(Formula 1) 60 * X / 469 + 0.2 <M / C <60 * X / 469 + 4 When the total content of carbon black, cyan organic pigment, and magenta organic pigment contained in the gray ink is 0.1 to 1.5% and a plurality of gray inks are present, carbon black and cyan organic pigment The non-aqueous gray ink composition according to claim 1, wherein the total content of the magenta organic pigment (X1, X2, X3 ... Xn. Xn + 1, ...) satisfies the following range. (However, the pigment content is X1 <X2 <X3 ... Xn <Xn + 1 ..., where n is an integer)
1.5 <Xn + 1 / Xn <5 An ink set containing a cyan ink, a magenta ink, a yellow ink, and a black ink in addition to a plurality of gray inks containing the non-aqueous gray ink composition according to claim 1. 4. An ink set comprising light cyan ink and light magenta ink in the ink set of claim 3. A printed matter obtained by printing using the ink set according to claim 3 .