JP2007231222A - Offset ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permeation drying type printing ink reproducing a wider color reproduction region than color reproduction region of RGB expressed by conventional four process colors of yellow, red, indigo, black. <P>SOLUTION: The invention relates to the offset printing ink comprising following pigment combinations. A yellow ink comprising 5-15% of C.I. pigment yellow 12 or C.I pigment yellow 13 as disazo yellow compound, and having opacity exceeding 31 of L* value in overprinting with a density of 0.85-0.91 on a black ink with a density of 1.10-1.20. A red ink comprising 15-20% of C.I. pigment red 81 or C.I pigment violet 1 as a metal chelate compound of a rhodamine based dye. An indigo ink comprising 10-25% of C.I.pigment blue 15:3 or C.I.pigment blue 15:4 and/or 0.5-2.0% of C.I. pigment green 7 as a phthalocyanine based compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an offset ink composition comprising four process colors of yellow, red, indigo and black, and having excellent color reproducibility with four colors and high saturation.

The IT revolution that began in the 1990s has led the environment surrounding the printing site to the direction of digitalization. By this digitization, workflow of conventional printing methods (photographing, positive, scanning, data, design, EPS)・ Imposition, film, printing plate, printing) was a multi-stage process, but it has succeeded in dramatically shortening the process with digital camera shooting, DTP, CTP, and printing. As a result, “RGB” conversion of the submitted data is being standardized, and the current situation is that the data to be handled is shifting to a wider color reproduction region. However, lithographic offset printing consisting of four process colors (CMYK) of yellow, red, indigo, and black, which is currently the mainstream, has a hue due to subtractive color mixing. In addition, the color reproduction area becomes narrower than that of RGB, and the difference in color reproducibility between digital data and printed matter has become a problem. In particular, in paper printing (especially newspaper printing) using penetrating dry ink, there is a problem of whiteness and smoothness of paper, and the color reproduction area becomes narrower than that for coated paper. The difference in color reproducibility with the sample printed matter becomes a serious problem.
In addition, when printing on a renewal paper such as newsprint paper with inferior whiteness, it is desirable that the ink is not affected by the lower paper, has the original coloring property of yellow ink, and is opaque to obtain a wide color reproduction region.

As means for solving this, in Patent Document 1, a printing method using an ink set of 5 to 7 colors is established as a high-saturation printing system. As a printing method using an ink set having each specified hue, process 4 colors are used. 6 colors (hexachrome printing) with orange and green added to 7 colors and 7 colors (high fidelity printing) with orange, green and purple added to 4 process colors have been established. In addition, as represented by hexachrome ink, as a means of expanding the color reproduction area, a technique such as adding a fluorescent pigment to a part of the color is used. However, deterioration of printability (transfer defect, gloss reduction, etc.) There are also disadvantages such as fading of printed matter due to insufficient light resistance. Furthermore, the number of ink colors used is 6 or 7, and an expensive multicolor printing machine with 6 or more printing cylinders is required. It is an indispensable condition, and it is limited to using this system due to huge capital investment and complicated color management to start a new one.
JP 2001-260516 A

  The present invention has been made in order to solve such problems in the prior art, and the problem is that an RGB color reproduction region using a four-color printing machine that has been widely used in the past. Is to provide an offset ink consisting of four colors of yellow, red, indigo and black.

That is, in the present invention, any two or three of yellow ink, red ink, and indigo ink, and offset printing using black ink, yellow, red, and indigo are composed of combinations of the following pigment components: The present invention relates to offset printing ink.
As a disazo yellow compound, CI Pigment Yellow 12 or CI Pigment Yellow 13 is contained in an amount of 5 to 15% and printed over black ink having a density value of 1.10 to 1.20 in a density range of 0.85 to 0.91. Yellow ink having an opacity of L * value of 31 or more.
Red ink containing 15 to 20% of CI Pigment Red 81 or CI Pigment Violet 1 as a metal lake compound of a rhodamine dye.
An indigo ink containing 10 to 25% of CI pigment blue 15: 3 or CI pigment blue 15: 4 and 0.5 to 2.0% of CI pigment green 7 as a phthalocyanine compound.
Furthermore, the present invention relates to indigo ink having a specific surface area of 74 m ² / g or more of the above-described CI pigment blue 15: 3 or CI pigment blue 15: 4.
The present invention also relates to the above printing ink in which the offset printing ink is a osmotic drying type printing ink, and a printed matter obtained by printing the ink.

 By using the lithographic ink composition provided by the present invention, RGB which has conventionally been expressed by 6-color and 7-color printing including orange, green, purple, etc. in addition to 4 colors of yellow, red, indigo and black ink process Can be reproduced with four colors of yellow, red, indigo and black. Further, in the present invention, since a fluorescent pigment is not used as a means for improving the color reproduction region of the printed material, a highly saturated printed material can be obtained without deteriorating printability, fading with time of the printed material, and the like.

Next, the present invention will be described more specifically with reference to preferred embodiments.
The present invention comprises a pigment, a vehicle component obtained by heating and dissolving a synthetic resin, a vegetable oil, and a petroleum solvent together with a gelling agent such as aluminum stearate or aluminum chelate as necessary, and an auxiliary agent such as a friction-resistant agent. It is an offset ink consisting of four colors of yellow, red, indigo and black, and is an ISO standard newspaper color paper for newspapers such as Nippon Paper Industries' newspaper paper (based on JCN paper, weighing 43 g / m ² , L * : 82, a *: -0.4, b *: 4.6), yellow, red, and indigo colors Gretag Macbeth Spectro Eye (45/0, D50, 2 degree field of view: Status T) densitometer When the density values measured in the above are in the range of 0.85 to 0.91 for yellow, 0.88 to 0.94 for red, and 0.84 to 0.90 for indigo, and each single color Chromaticity (JIS Z 8729) according to the L * a * b * color system of the overprinting of L *: 77 to 85, preferably yellow ink 78-83, a *: -1 to -9, preferably -2 to -8, b *: 60 to 70, preferably 62 to 68, red ink, L *: 54 to 60, preferably 55 to 58, a *: 46-52, preferably 47-50, b *: -5 to -11, preferably -7 to -10, indigo ink, L *: 55 to 61, preferably 56 to 60, a *: −23 to −28, preferably −24 to −27, b *: −26 to −32, preferably −27 to −30, and further, red ink × yellow ink, L *: 52 -60, a *: 37-43, b *: 27-34, indigo ink x yellow ink, L *: 52-57, a *: -36 to -42, b *: 20-26, It is characterized in that it is in the range of L *: 38 to 45, a *: 11 to 18, b *: −30 to −36 by printing with indigo ink × red ink.

As a method for expressing the color reproduction area, an XYZ color system (CIE 1931 color system), an X ₁₀ Y ₁₀ Z ₁₀ color system (CIE 1964 color system), an L * a * b * color system (CIE 1976), Hunter Lab color system, Munsell color system, L * u * v * color system (CIE1976), and the like.

Ｃに関しても同様に、絶対値が大きくなるに従って色鮮やかになり、値が小さくなるにつれてくすんだ色になることを示している。 In the L * a * b * color system, “brightness” is expressed by L * as the degree of brightness that can be compared regardless of hue, and indicates that the color becomes brighter as L * increases and becomes darker as it decreases. . In addition, “hue” which differs depending on each color is indicated by a * and b * values, a * indicates red (+) to green (−) direction, and b * indicates yellow (+) to blue (−) direction, In each direction, the color becomes brighter as the absolute value increases, and the color becomes dull as it approaches 0. This makes it possible to digitize one color using L *, a *, and b *. In addition to “lightness” and “hue”, there is “saturation (C)” as a method for digitizing the degree of vividness, which can be obtained by the following calculation formula.

Similarly, C shows that the color becomes brighter as the absolute value increases, and the color becomes dull as the value decreases.

  All color reproduction areas that can be represented by a single printed matter (including color spaces other than printed matter) are called color rendering regions (gamut). In the two-dimensional space, the solid color part (yellow, red, indigo) and the solid color overprinting part (yellow x red, red x indigo, indigo x yellow) total of 6 colors a * vs b *, It can be expressed by the plotted hexagonal area. The larger the gamut area, the wider the color reproduction area.

The yellow pigment used in the present invention is a disazo yellow compound such as CI Pigment Yellow 12, CI Pigment Yellow 13, and the like on a black ink printed within a density value range of 1.10 to 1.20. Furthermore, if the density of the yellow ink is overprinted in the range of 0.85 to 0.91, if the L * value has an opacity of 31 or more, the smoothness used in newspaper printing is inferior and white. In the case of inferior paper, the original color developability of the yellow ink is obtained by concealing the lower paper, so that a wide color reproduction region can be obtained. If the L * value is less than 31, the original color developability of yellow ink cannot be obtained due to the influence of the lower paper. It is preferable to contain 5 to 15% of CI Pigment Yellow 12 or CI Pigment Yellow 13.
Further, CI pigment yellow 83 can be used as a complementary color by adding 0.5 to 10%, preferably 2 to 5% of the above yellow pigment.

  Examples of the red pigment used in the present invention include, but are not limited to, rhodamine-based dyes such as rhodamine B, rhodamine 3G, rhodamine 6G, molybdenum, and tungsten metal lake compounds. It is preferable to contain 15 to 20% of C.I. Pigment Red 81 or C.I. Pigment Violet 1.

The copper phthalocyanine compound, which is a cyan pigment used in the present invention, is a substance exhibiting a crystal polymorphism (homogeneous heterocrystal), and α, β, γ, ε, π, τ, ρ, χ depending on the crystal structure. However, it is preferable to use a β-type having excellent crystal stability and dispersibility, and further a fine β-type copper phthalocyanine having a specific surface area of 74 m ² / g or more. preferable. In the present invention, a copper halide phthalocyanine compound in which a hydrogen atom on a benzene ring of a phthalocyanine molecule is substituted with a halogen compound is added to the copper phthalocyanine compound in an amount of 5 to 15%, more preferably 8 to 11%. It is possible to expand the color reproduction region of green and purple when overprinting with yellow and red ink without impairing the color reproduction region of indigo ink single color. It is preferable to contain 10 to 25% of CI pigment blue 15: 3 or CI pigment blue 15: 4 and 0.5 to 2.0% of CI pigment green 7.

Examples of black pigments include carbon black, such as CI pigment black 7.
As the synthetic resin used in the present invention, rosin-modified phenol resin, petroleum resin, alkyd resin, rosin-modified alkyd resin, petroleum resin-modified alkyd resin, rosin ester and the like can be considered. Preferably, a rosin modified phenolic resin is used. The rosin-modified phenol resin is not particularly limited, but it is preferable to use a resin having a weight average molecular weight of 10,000 to 300,000. When the molecular weight is 10,000 or less, the viscoelasticity of the ink is lowered, and when it is 400,000 or more, the fluidity as the ink becomes insufficient.

  Examples of vegetable oils include those derived from vegetable oils such as palm kernel oil, palm oil, cottonseed oil, peanut oil, palm oil, corn oil, olive oil, linseed oil, corn oil, soybean oil, safflower oil, and tung oil, Those thermal polymerized oils and oxygen-blown polymerized oils can also be used. Moreover, in this invention, these vegetable oils may be used independently and can also be used in combination of 2 or more type.

  The petroleum solvent used in the ink has an aromatic hydrocarbon content of 1% or less, an aniline point of 75 to 95 ° C, preferably 80 to 95 ° C, and a boiling point of 260 to 350 ° C, preferably 280 to 350. It is a petroleum solvent in the range of ° C. If the aniline point is less than 75%, the ability to dissolve the resin is too high, which is not preferable because the ink setting property is slow, and if it exceeds 95 ° C., the resin solubility is poor, so Meat etc. are bad and not preferable. When the boiling point is less than 260 ° C., the evaporation of the ink solvent on the printing press increases, and the transferability of the ink to a roller, a blanket, a plate, or the like deteriorates due to the deterioration of the fluidity of the ink. Moreover, when it exceeds 350 degreeC, since drying of a heat-set type ink is inferior, it is unpreferable.

  Further, the lithographic ink composition of the present invention includes a gelling agent, a pigment dispersant, a metal dryer, a drying inhibitor, an antioxidant, an anti-friction agent, an anti-set-off agent, and a nonionic surfactant as required. Additives such as agents and polyhydric alcohols can be used as appropriate.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, the scope of the present invention is not limited to these description Example. In addition, the part of the following description represents a weight part and% represents weight%.

(Production of rosin-modified phenolic resin gel varnish A for offset)
38.5 parts of rosin modified phenolic resin (Arakawa Chemical Industries, Ltd .: weight average molecular weight 150,000, acid value 20, softening point 160 ° C.) in a four-necked flask equipped with a condenser, thermometer and stirrer, soybean oil 30 parts, 30 parts of AF Solvent No. 5 (manufactured by Nippon Oil Co., Ltd.) were charged, heated to 180 ° C., stirred at the same temperature for 30 minutes, allowed to cool, and ethyl acetoacetate aluminum as a gelling agent 1.0 part of diisopropoxide (ALCH manufactured by Kawaken Fine Chemical Co., Ltd.) was added and stirred at 180 ° C. for 30 minutes to obtain a rosin-modified phenol resin gel varnish A for offset (hereinafter referred to as gel varnish A).

Ink example (yellow ink)
In the formulation shown in Table 1, C.I. I. Pigment Yellow 12 (LIONOL YELLOW 1243-P manufactured by Toyo Ink Manufacturing Co., Ltd.) was subjected to primary dehydration by gradually adding and kneading gel varnish A in a kneader at a temperature of 75 ° C. Next, vacuum dehydration was performed for 1 hour under conditions of a kneader temperature of 100 ° C. to 120 ° C. and a degree of vacuum of 76 mmHg, and secondary dehydration was performed so that the water content in the base ink was 0.5% or less. After dehydration, the remaining gel varnish A, AF solvent No. 5 and soybean oil were added, kneaded and diluted, and the undispersed base ink was taken out from the kneader. The extracted base ink was kneaded using a three roll with a roll temperature of 60 ° C. with a dispersed particle measuring machine (grind meter) to 7.5 μm or less to obtain yellow base ink 1. Next, gel ink varnish A, soybean oil, compound and AF solvent No. 5 were added to the base ink 1 according to the formulation shown in Table 2 to obtain yellow ink 1.

Ink Example (Red ink)
As with the yellow ink, C.I. I. A red base ink 2 was obtained using Pigment Red 81 (Funal Rose RNN-P manufactured by Fuji Kasei Co., Ltd.). Subsequently, to the base ink 2, gel varnish A, soybean oil, compound and AF solvent No. 5 were added according to the formulation shown in Table 2 to obtain red ink 2.

Ink Example (Indigo Ink)
In the formulation of Table 2, C.I. I. Pigment Blue 15: 3 (LIONOL BLUE FG 7330 manufactured by Toyo Ink Mfg. Co., Ltd.) was mixed with varnish, and after milling with a dispersed particle measuring machine (grind meter) to 7.5 microns or less, soybean oil, Compound and AF solvent No. 5 were added to obtain indigo ink 3.
A comparative newspaper ink was used as a comparative ink.

The transparency of yellow ink was evaluated by the following test method.
Yellow ink was overprinted in the density range of 0.80 to 1.10 on the black ink printed in the density range of 1.10 to 1.20, and L * was measured. The results are shown in FIG.
In the yellow ink of the example, L * is always 31 or more in the measured density range, and the underlying black ink is concealed, and the original color developability of the yellow ink comes out and the color rendering is widened (L * is smaller as the value is smaller). Black indicates that the larger it is, the whiter it becomes)
On the other hand, the comparative ink has a low L * and is affected by the black ink of the base, resulting in a narrow color rendering.

Printing Evaluation Test With respect to the inks of the above Examples and Comparative Examples, yellow, red, and indigo solid density values under the following printing conditions are yellow: 0.85 to 0.91, and red: 0.88 to 0.94. , Indigo: Printing was performed within the range of 0.84 to 0.90, and the printed matter was evaluated. The ink used was a general offset newspaper printing ink, and was printed within a density range of 1.12 to 1.20.

結果を表３に示す。比較例と比べて実施例のＣ値が大きく、印刷物の彩度が高い。また、ａ*を横軸、ｂ*縦軸とした2次元空間に、各ａ*、ｂ*値をプロットし、２次元のガモットで比較した結果、実施例の色再現領域が広いことがわかる（図２）。
Printing conditions Printing machine: LITHOPIA BT2-800 NEO (Mitsubishi Heavy Industries, Ltd.)
: Printing order: Ink->Indigo->Red-> Yellow Paper: Newspaper for newspaper: Ultralight paper (weighing 43 g / m ² ) (Nippon Paper Industries Co., Ltd.)
(Colorimetric value: L *: 82, a *: -0.4, b *: 4.6)
Dampening water: NEWSKING ALKY (Toyo Ink Mfg. Co., Ltd.) 0.5% tap water printing speed: 100,000 parts / hour

Measurement conditions for printed matter Concentration: Measure the density value of the solid (yellow, red, indigo, black) solid portion of the printed matter with Gretag Macbeth Spectro Eye (45/0, D50, 2 degree field of view: Status T).
Colorimetry: Gretag Macbeth Spectro Eye (45/0, D50, 2-degree field of view: Status T), single-color solid part (yellow, red, indigo) of printed matter and single-color solid overprinted part (yellow x red, red x L *, a *, b * values of indigo, indigo × yellow) are measured.
The C value was determined from the following formula using a * and b *.

The results are shown in Table 3. Compared to the comparative example, the C value of the example is large, and the chroma of the printed matter is high. In addition, as a result of plotting each a * and b * value in a two-dimensional space with a * as the horizontal axis and b * vertical axis and comparing them with a two-dimensional gamut, it can be seen that the color reproduction region of the embodiment is wide. (FIG. 2).

(Figure 1)

(Figure 2)

By using the ink obtained in the present invention, RGB color reproduction regions can be expressed infinitely using a four-color printing machine that has been widely used in the past.

Claims (3)

In offset printing using any two or three of yellow ink, red ink, and indigo ink, and black ink, offset printing ink in which three colors of yellow, red, and indigo are a combination of the following pigment components.
As a disazo yellow compound, CI Pigment Yellow 12 or CI Pigment Yellow 13 is contained in an amount of 5 to 15% and printed over black ink having a density value of 1.10 to 1.20 in a density range of 0.85 to 0.91. Yellow ink having an opacity of L * value of 31 or more.
Red ink containing 15 to 20% of CI Pigment Red 81 or CI Pigment Violet 1 as a metal lake compound of a rhodamine dye.
An indigo ink containing 10 to 25% of CI pigment blue 15: 3 or CI pigment blue 15: 4 and 0.5 to 2.0% of CI pigment green 7 as a phthalocyanine compound.   The printing ink according to claim 1, wherein the offset printing ink is a permeation drying type printing ink. A printed matter obtained by printing the printing ink according to claim 1.