JP2007125879A - Lithographic ink printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic ink printing method which makes it possible to reproduce with four colors of yellow, red, indigo and black the color reproduction area of RGB that has so far been expressed by six-color or seven-color printing with orange, green, purple, etc. in addition to four process colors of yellow, red, indigo and black. <P>SOLUTION: In lithographic printing using any two or three inks of yellow, red and indigo and also a black ink and at the time when the individual color ink is printed solely or in superposition in the ranges wherein the respective density values of yellow, red and indigo are 1.40-1.44, 1.52-1.56 and 1.63-1.67, the chromaticity of superposed printing according to an L*a*b* color model is in the range of L*: 51-56, a*: 65-70 and b*: 56-61 in the superposed printing of the red ink×the yellow ink, in the range of L*: 47-53, a*: -77 to -83 and b*: 25-32 in the superposed printing of the indigo ink×the yellow ink and in the range of L*: 23-29, a*: 28-33 and b*: -63 to -68 in the superposed printing of the indigo ink×the red ink, in this lithographic printing method excellent in high-saturation color reproduction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a lithographic ink printing method comprising four colors of yellow, red, indigo and black, and relates to a printing method using an ink system having four colors and excellent color reproducibility.

The IT revolution that began in the 1990s has led the environment surrounding the printing site to the direction of digitalization, and with this digitalization, the workflow of conventional printing methods (shooting and shooting)
(Position, Scan, Data, Design, EPS, Imposition, Film, Plate, Printing) was a multi-step process, but it was dramatically shortened with digital camera shooting, DTP, CTP, and printing. Succeeded in doing. 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, in lithographic offset printing consisting of four process colors (CMYK) of yellow, red, indigo and black, which are currently mainstream, the color reproduction area is necessarily narrower than that of RGB because of the hue due to subtractive color mixing. The difference in color reproducibility between digital data and printed matter became a problem.

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 colors of the ink used is 6 colors,
In addition to requiring an expensive multi-color printing machine with 7 colors and a printing machine with 6 or more cylinders, the same number of multi-color separated versions is a prerequisite, and it is a huge facility to start a new The use of this system is limited due to investment and complicated color management.
JP 2001-260516 A

The present invention has been made to solve such problems in the prior art,
The problem is that a lithographic ink consisting of four process colors of yellow, red, indigo, and black, which can express the RGB color reproduction area as much as possible using a four-color printing machine that has been widely used in the past. And a planographic ink printing method using these.

In general, in order to expand the color reproduction region, it is necessary to approximate the ideal spectral reflectance curve of each color. That is, the wavelength range in which a person recognizes color is 400 nm to 700 nm light (this wavelength is referred to as visible light). In yellow ink, the reflectance in the wavelength range of 500 nm to 700 nm is 100%, and the wavelength range of 400 nm to 500 nm. The red ink has a reflectance of 0%, and the red ink has a reflectance of 100% in the wavelength region of 400 nm to 500 nm and 600 nm to 700 nm, and a reflectance of 0% in the wavelength region of 500 nm to 600 nm. Therefore, it is said that it is ideal that the reflectance in the wavelength region of 400 nm to 600 nm is 100% and the reflectance in the wavelength region of 600 nm to 700 nm is 0% (the spectral reflectance of the ideal process ink) Curves are shown in Table 5). However, the reflection spectrum of the ink composition for offset printing of yellow, red, indigo and black, which is currently used in four process colors, is far from the ideal reflection spectrum. Since there is unnecessary absorption in the part that must be completely reflected, a turbid component of the ink exists, and the color reproducibility is narrowed.

That is, the present invention is any two or three of yellow ink, red ink, and indigo ink,
In lithographic printing using black ink, each density value of yellow, red, and indigo is 1.40
-1.44, red is 1.52-1.56, and indigo is 1.63-1.67, when each color ink is printed individually or by overlay, it depends on the L * a * b * color system Chromaticity (JIS Z 8729)
Yellow ink, L *: 87 to 95, a *: -4 to -12, b *: 90 to 100
Red ink, L *: 50 to 55, a *: 75 to 83, b *: -14 to -20
Indigo ink, L *: 52 to 58, a *: −40 to −45, b *: −45 to −53
And the chromaticity of the two ink overprints of the above ink is
Red * yellow ink, L *: 51-56, a *: 65-70, b *: 56-61
L *: 47-53, a *: -77 to -83, b *: 25
32
L *: 23 to 29, a *: 28 to 33, b *: −63 to −
68
A lithographic printing method excellent in color reproduction with high saturation, characterized by being in the range of
The color space of the L * a * b * color system can be expanded by printing with a combination of colors, a combination of the above two colors and black ink, and a combination of the above three colors and black ink. The present invention relates to a possible lithographic ink printing method.

Furthermore, these (a) yellow, (b) red, and (c) indigo relate to the above printing method having the following reflectance.
(A) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the wavelength region of 400 nm to 480 nm is 1 to 20%, and the reflectance in the wavelength region of 530 nm to 700 nm is 90 to 100%. A yellow ink containing 5 to 15% by weight of a yellow phase compound having a reflection spectrum with respect to the total weight of the ink.

(B) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 50% to 100%, 500 nm.
The reflectance in the wavelength region of ˜560 nm is 1 to 20%, and the reflectance of 630 nm to 700 nm is 9
A red ink containing 15 to 30% by weight of a red hue compound having a reflection spectrum of 0% to 100% based on the total weight of the ink.
(C) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the reflectance in the wavelength region of 400 nm to 530 nm is 50 to 100%, 600 nm to 700 n.
An indigo ink comprising 10 to 25% by weight of an indigo hue compound having a reflectance spectrum of 1 to 30% of the reflectance of m based on the total weight of the ink.

By using the lithographic ink printing method provided by the present invention, the conventional RGB, which is expressed by printing in six colors and seven colors, including orange, green, purple, etc. in addition to the four colors of yellow, red, indigo, and black ink The color reproduction area 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 a lithographic ink consisting of four colors, yellow, red, indigo, and black, and is printed on ISO standard Japan color standard paper, for example, “Special Rhibo Art Double Sided Plate / 110 kg” manufactured by Mitsubishi Paper Industries, Inc. When the red and indigo colors were measured with a Gretag Macbeth D196 densitometer, the density values were 1.40 to 1.44 for yellow, 1.52 to 1.56 for red, and 1.63 to 1.67 for indigo. The chromaticity (JIS Z 8729) according to the L * a * b * color system of the single color and the overprint of each single color is yellow ink, L *: 87 to 95, preferably 88 to 93. A *: −4 to −12, preferably −5 to −10, b *: 90 to 100, Is Mashiku 92-98, in red ink, L *: 50~5
5, preferably 51 to 54, a *: 75 to 83, preferably 76 to 81, b *: −14 to −
20, preferably -15 to -18, indigo ink, L *: 52 to 58, preferably 52 to 57
A *: −40 to −45, preferably −41 to −44, b *: −45 to −53, preferably −46 to −51, and L * : 51-56, a *: 65
-70, b *: 56-61, indigo ink x yellow ink, L *: 47-53, a *:-
77--83, b *: 25-32, indigo ink x red ink, L *: 23-29, a
*: 28 to 33, b *: Within the range of −63 to −68.

As a method for expressing the color reproduction region, an XYZ color system (CIE 1931 color system), X ₁₀ Y ₁₀ Z _1
0 color system (CIE 1964 color system), L * a * b * color system (CIE 1976), Hunter La
b color system, Munsell color system, L * u * v * color system (CIE1976), and the like.
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” that differs depending on each color is indicated by the values of a * and b *, where a * is red (+) to green (−).
The direction and b * indicate the direction from yellow (+) to blue (-), and 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 *. Also "brightness"
Aside from “hue”, there is “saturation (C)” as a method for digitizing the degree of vividness, which can be obtained by the following calculation formula.

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。

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). The simplest way to represent gamut is a * on the horizontal axis and b *.
In the two-dimensional space with the vertical axis, solid monochrome parts (yellow, red, indigo) and monochromatic solid overprint parts (yellow x
(Red, red x indigo, indigo x yellow) It is possible to express the a * vs. b * values of a total of six colors as a 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 black ink printed within a density value range of 1.85 to 1.90. In addition, if the L * value has a transparency not exceeding 17 when the density of the yellow ink is overprinted in the range of 1.40 to 2.10, the secondary and tertiary colors are overprinted. It is possible to obtain a good color reproduction region with little influence on the underprint ink. Further, C.I. Pigment Yellow 83 may be used as a complementary color by adding 0.5 to 10% by weight, preferably 2 to 5% by weight, based on the total weight of the yellow pigment.

Examples of red pigments include, but are not limited to, rhodamine dyes such as rhodamine B, rhodamine 3G and rhodamine 6G, molybdenum, tungsten metal lake compounds such as CI Pigment Red 81 and CI Pigment Violet 1.

  Examples of indigo pigments include phthalocyanine compounds such as C.I. Pigment Blue 15: 3 and C.I. Pigment Blue 15: 4. Furthermore, C.I. Pigment Green 7 may be used as a complementary color by adding 5 to 15% by weight, preferably 8 to 11% by weight, based on the total weight of the indigo pigment.

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.

  Examples of the black pigment include carbon black such as C.I. 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%,
Since the ability to dissolve the resin is too high, the setting property of the ink becomes slow, which is not preferable.
When the temperature exceeds 5 ° C., the resin is poorly soluble, so that the gloss and the inking are deteriorated.
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 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.
[Example]
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%.

Example of production of rosin-modified phenolic resin To a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 1000 parts of P-octylphenol, 850 parts of 35% formalin, 60 parts of 93% sodium hydroxide, 1000 parts of toluene, The reaction was carried out at 90 ° C. for 6 hours. Then, 125 parts of 6N hydrochloric acid and 1000 parts of tap water were added, stirred and allowed to stand, and the upper layer part was taken out to obtain 2000 parts of a toluene solution of a resole type phenol resin having a nonvolatile content of 49%. It was.
Gum rosin 1000 is added to a four-necked flask equipped with a stirrer, a condenser with a water separator, and a thermometer.
The resol solution 1 prepared above was dissolved at 200 ° C. while blowing nitrogen gas.
After adding 800 parts and reacting at 230 ° C. for 4 hours while removing toluene, 110 parts of glycerin was added and reacted at 260 ° C. for 10 hours. The acid value was 20 or less, the weight average molecular weight was 50000, and Nippon Petrochemical A rosin-modified phenol resin having a cloudiness temperature of 90 ° C. obtained from AF Solvent No. 6 was obtained.

Example of varnish production 40 parts of rosin-modified phenolic resin, 15 parts of tung oil, 30 parts of soybean oil, AF solvent 7 (
14 parts of Nippon Petrochemical Co., Ltd. solvent and 1.0 part of ALCH (Kawaken Fine Chemical Co., Ltd. gelling agent) were heated and stirred at 190 ° C. for 1 hour to obtain a varnish.

Ink example (yellow ink)
In the formulation shown in Table 1, C.I. I. Pigment Yellow 12 (LI made by Toyo Ink Manufacturing Co., Ltd.)
ONOL YELLOW 1235-P) was subjected to primary dehydration by gradually adding varnish and kneading 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 varnish and petroleum solvent 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. Subsequently, varnish, soybean oil, a compound, a metal dryer, and a drying inhibitor were added to the base ink 1 according to the formulation shown in Table 2 to obtain a 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.). Next, soybean oil 2, a compound, a metal dryer, and a drying inhibitor were added to the base ink 2 in the formulation shown in Table 2 to obtain a red ink 2.

Ink Example (Indigo Ink)
In the formulation of Table 2, C.I. I. Pigment Blue 15: 3 (Toyo Ink Manufacturing Co., Ltd. LIO
NOL BLUE GLA-SD), C.I. I. Pigment Green 7 (Toyo Ink Manufacturing (
LIONOL GREEN YS-2A) manufactured by Co., Ltd.
After grinding the mixture to 7.5 microns or less with a grindometer, soybean oil, a compound, a metal dryer, and a drying inhibitor were added to obtain indigo ink 3.

A comparative oxidation polymerization type lithographic printing ink was used as a comparative ink.

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: 1.40 to 1.44, red: 1.52 to 1.56. , Indigo: Printing was performed within the range of 1.63 to 1.67, and the printed matter was evaluated. The black ink was printed using a general oxidation polymerization type lithographic printing ink within a density value range of 1.88 to 1.92.

Printing conditions Printing machine: Heidelberg Speedmaster Kikuzen 4-color machine (Heidelberg Japan Ltd.)
Paper: Tokishi Art Double Sided 110Kg (Mitsubishi Paper Co., Ltd.)
Dampening water: Astro Mark 3 (Niken Chemical Laboratory, Inc.) 2.0% tap water printing speed: 10,000 sheets / hour

Printed matter measurement conditions Density: Measure the density value of the solid (yellow, red, indigo, black) solid portion of the printed matter with Gretag Macbeth D196 Colorimetry: Monochromatic solid portion of the printed matter (yellow, red, indigo) with X-Rite 938 In addition, L *, a *, and b * values of the single-color solid-printed overlapping portion (yellow × red, red × indigo, indigo × yellow) were measured.

          The C value was obtained from the following formula using a * and b *.

光沢 ：村上色彩技術研究所製、デジタル光沢計にて６０°−６０°反射光沢を測定。

Gloss: Measured 60 ° -60 ° gloss with a digital gloss meter manufactured by Murakami Color Research Laboratory.

  The results are shown in Table 3. Compared with the comparative example, the C value of the example is large and the saturation 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 with two-dimensional gamut, it can be seen that the color reproduction range of the embodiment is wide. (Table 4).

また、得られた分光反射率曲線を表６に示す。比較例の従来インキに比べ、実施例のインキの方が理想の分光反射率曲線に近くなっており、完全反射しなければならない部分の不必要吸収が少なくなっている。そのため、インキの濁り成分が減少し、色再現領域が広がっている（表４）。

Further, Table 6 shows the obtained spectral reflectance curve. Compared to the conventional ink of the comparative example, the ink of the example is closer to the ideal spectral reflectance curve, and unnecessary absorption of the portion that must be completely reflected is reduced. Therefore, the turbidity component of the ink is reduced and the color reproduction area is widened (Table 4).

Claims (2)

In lithographic printing using any two or three of yellow ink, red ink and indigo ink, and black ink, each density value of yellow, red and indigo is set to 1.40 to 1.44 for yellow. Red is 1.
When each color ink is printed by single or superposition within the range of 52 to 1.56 and indigo in the range of 1.63 to 1.67, the chromaticity (JIS Z 8729) by the L * a * b * color system is
Yellow ink, L *: 87 to 95, a *: -4 to -12, b *: 90 to 100
Red ink, L *: 50 to 55, a *: 75 to 83, b *: -14 to -20
Indigo ink, L *: 52 to 58, a *: −40 to −45, b *: −45 to −53
And the chromaticity of the two ink overprints of the above ink is
Red * yellow ink, L *: 51-56, a *: 65-70, b *: 56-
61
L *: 47 to 53, a *: -77 to -83, b *: 2
5-32
L *: 23-29, a *: 28-33, b *: -63
~ -68
A lithographic printing method excellent in color reproduction with high saturation, characterized by being in the range of
The color space of the L * a * b * color system can be expanded by printing with a combination of colors, a combination of the above two colors and black ink, and a combination of the above three colors and black ink. Possible lithographic ink printing method. In lithographic printing using any two or three of yellow ink, red ink, and indigo ink, and black ink, the reflectance of (a) yellow, (b) red, (c) indigo is The lithographic ink printing method according to claim 1, wherein:
(A) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the wavelength region of 400 nm to 480 nm is 1 to 20%, and the reflectance in the wavelength region of 530 nm to 700 nm is 90 to 100%. A yellow ink containing 5 to 15% by weight of a yellow phase compound having a reflection spectrum with respect to the total weight of the ink.
(B) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 50% to 100%, 500 nm.
The reflectance in the wavelength region of ˜560 nm is 1 to 20%, and the reflectance of 630 nm to 700 nm is 9
A red ink containing 15 to 30% by weight of a red hue compound having a reflection spectrum of 0% to 100% based on the total weight of the ink.
(C) In the wavelength region of 400 nm to 700 nm, when the maximum reflectance is 100%, the reflectance in the wavelength region of 400 nm to 530 nm is 50 to 100%, 600 nm to 700 n.
An indigo ink comprising 10 to 25% by weight of an indigo hue compound having a reflectance spectrum of 1 to 30% of the reflectance of m based on the total weight of the ink.