JP2008080662A - Offset ink printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing method which enables a color region being wider than an RGB color reproducing region having been expressed by a conventional yellow, red, indigo blue and a Japanese ink processing four-color printing. <P>SOLUTION: In an offset printing using either two or three from among a yellow ink, a red ink and an indigo blue ink, and the Japanese ink, each ink is printed independently or while being stacked within ranges for each concentration value for the yellow, the red and the indigo blue having been printed on a sheet of paper for the newspaper Japan color standard of the ISO specification such as 0.85 to 0.95 for the yellow, 0.88 to 1.00 for the red, and 0.84 to 1.00 for the indigo blue. In this case, the chromaticity by the L*a*b* color coordinate system stays in a specified range, and the chromaticity for an overlapped printing by two colors of the inks stays in a specified range by this offset ink printing method which is excellent in the color reproduction of a high chromaticity degree. In addition, (a) the yellow, (b) the red and (c) the indigo blue have specified reflection factors for the offset printing method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an offset 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 high color reproducibility.

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, 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.
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.

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 process colors of yellow, red, indigo and black, and an offset 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 4).

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.
Therefore, the present invention is an offset ink printing method using an ink selected from yellow, red, indigo and black ink, and is obtained by printing L * a when yellow, red and indigo inks are individually solid-printed at a reference density value. * b * values, and L * a * b * values for each color when two types selected from yellow, red and indigo inks are solid-printed at the standard density value are within the following ranges. The present invention relates to an offset ink printing method using ink.
Here, the standard density values printed on ISO standard newspaper Japan color standard paper are yellow 0.85 to 0.95, red 0.88 to 1.00, indigo 0.84 to 1.00,
Chromaticity according to L * a * b * color system (JIS Z 8729) is
Yellow ink, L *: 75 to 85, a *: 0 to -10, b *: 60 to 70
Red ink, L *: 52-62, a *: 46-56, b *: -5 to -15
Indigo ink, L *: 52-62, a *: -20 to -30, b *: -24 to -34
Red ink x yellow ink, L *: 50-60, a *: 37-50, b *: 27-37
Overprint of indigo ink x yellow ink, L *: 50 to 60, a *: −35 to −45, b *: 16 to 26
Overprint of indigo ink x red ink, L *: 35 to 45, a *: 10 to 20, b *: -30 to -40, and ink containing CI pigment red 169 is used as red ink It is characterized by.
Further, an offset ink printing method using an ink selected from yellow, red, indigo and black ink, the following yellow, red and indigo ink is used, and an ink containing CI pigment red 169 is used as the red ink The present invention relates to an offset ink printing method.

  When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the reflectance in 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%. Is yellow ink.

When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 50% to 100%, and the reflectance in the wavelength region of 500 nm to 560 nm is 1 to 20. A red ink having a reflectance of 90% to 100% in a wavelength region of 630 nm to 700 nm.
When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the reflectance in the wavelength region of 400 nm to 530 nm is 50 to 100%, and the reflectance in the wavelength region of 600 nm to 700 nm is 1 to 30%. An indigo ink.

  By using the offset ink printing method provided by the present invention, it is possible to reproduce a wider color area than the RGB color reproduction area expressed by the conventional four-color printing of yellow, red, indigo and black ink processes. Become. 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 0.95 for yellow, 0.88 to 1.00 for red, and 0.84 to 1.00 for indigo, monochromatic and each monochromatic The chromaticity (JIS Z 8729) according to the L * a * b * color system of the overprinting is yellow ink, L *: 75 to 85, preferably Is 78 to 83, a *: 0 to -10, preferably -2 to -8, b *: 60 to 70, preferably 62 to 68, red ink, L *: 52 to 62, preferably 55 to 58 A *: 46 to 56, preferably 47 to 50, b *: -5 to -15, preferably -7 to -10, indigo ink, L *: 52 to 62, preferably 56 to 60, a * : -20 to -30, preferably -24 to -27, b *: -24 to -34, preferably -27 to -30, and further, red ink x yellow ink, L *: 50 to 60, a *: 37 to 50, b *: 27 to 37, indigo ink x yellow ink, L *: 50 to 60, a *: −35 to −45, b *: 16 to 26, indigo It is characterized by being in the range of L *: 35 to 45, a *: 10 to 20, and b *: −30 to −40 when the ink × red ink is overprinted.

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.
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 a * and b * values, a * indicates a red (+) to green (−) direction, and b * indicates a 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.

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 as follows: a * is the horizontal axis, b * vertical axis 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.

     In the present invention, the color space (color space) in the L * a * b * color system is represented by the horizontal axis a * as a color rendering region considering not only the two dimensions of a * and b * but also the lightness “L *”. Is expressed in 10 step increments in the range of -80 to +80, vertical axis b * in the range of -80 to +80, and height L * is represented by slicing in increments of 10 steps from 0 to 100. The color reproduction area indicating the number is schematically expressed, and the larger the number of reproduced colors, the wider the color rendering area that can be reproduced by ink.

  Japan Color is a standard color for printing established by the ISO / TC130 National Committee. In Japan Color for Newspapers (hereinafter referred to as JCN), ISO 12642 SCID chart (928 colors), a pattern according to ISO 12647 ( 80 color) and color measurement values (L * a * b * values) using “JCN2002 chart” designed to examine the reproduction of important print colors (skin color, gray, vivid color) in newspaper printing Is shown. The printing conditions are based on the standard conditions of international standards ISO 2864-2 and ISO 12647-3 concerning newspaper printing. News inks and printing papers commonly used in Japan (the color characteristics of standard papers are determined in JCN) ) Is used. The L * a * b * values of yellow, red, indigo and single-color solid parts when printing JCN standard ink on JCN standard paper, and the C value calculated from them are yellow ink, L * : 77, a *: -4, b *: 58, C: 58, red ink, L *: 53, a *: 44, b *: 0, C: 44, indigo ink, L *: 58, It is said that a *: −23, b *: −26, and C: 35. The solid density at this time is 0.86 for yellow ink, 0.89 for red ink, and 0.85 for indigo ink.

  The yellow pigment used in the present invention is a disazo yellow compound such as CI Pigment Yellow 12, CI Pigment Yellow 13, etc., and has a black ink density value when printed on ISO standard newspaper Japan color standard paper. If the L * value has a transparency that does not exceed 31 when the density of the yellow ink is overprinted in the range of 0.85 to 0.95 over the range of 1.10 to 1.20, A good color reproduction region can be obtained with little influence on the underprinting ink when the secondary and tertiary colors are overprinted. Furthermore, it is also possible to use C.I. Pigment Yellow 83 as a complementary color by adding 0.5 to 10%, preferably 2 to 5% of the above yellow pigment.

   Examples of red pigments used in the present invention include rhodamine-based dyes such as rhodamine B, rhodamine 3G, rhodamine 6G, molybdenum, tungsten metal lake compounds, or ferrocyanide cylinder lake compounds. CI pigment red 169 is The content is necessarily 10 to 30%, more preferably 10 to 20%, based on the total ink.

 As the red pigment used in the present invention, the CI pigment red 169 may be used alone, or two or more types of CI pigment red 81 or CI pigment bio red 1 may be used in combination. .

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

  Furthermore, the offset ink composition of the present invention includes a gelling agent, a pigment dispersant, a metal dryer, a drying inhibitor, an antioxidant, an antifriction agent, an anti-set-off agent, and a nonionic surface active 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 (LIO manufactured by Toyo Ink Manufacturing Co., Ltd.)
NOL YELLOW 1245-P) was subjected to primary dehydration by gradually adding and kneading gel varnish A in a kneader at a temperature of 75 ° C. Next, the kneader temperature is 100 ° C to 120 ° C,
A vacuum was applied for 1 hour under the condition 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,
Soybean oil was 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 varnish A, soybean oil, compound,
AF solvent No. 5 was added 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 169 (FanalPink D4810 manufactured by BASF). Subsequently, the gel ink varnish A, soybean oil, the compound, and AF solvent No. 5 were added to the base ink 2 according to 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 (LIONOL BLUE FG 7330 manufactured by Toyo Ink Mfg Co., Ltd.) and varnish were mixed with a dispersed particle system measuring machine (grind meter) until 7.5 microns or less, and then 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 the yellow ink was evaluated by the following test method.
On the black ink printed within the density value range of 1.10 to 1.20, the yellow ink density was printed in the range of 0.80 to 1.10, and the L * value was measured. The results are shown in Table 5.
The yellow ink of the example does not exceed L * even when the density value is increased to 1.10, and does not affect the black ink of the underprint, and can be said to have excellent transparency (L * has a value) The smaller the color, the more black it is, and the larger the color, the whiter it is). On the other hand, L * is high in the comparative example, and it can be seen that the black ink of the underprinted ink is hindered because the yellow ink of the overprinted is opaque.
Printing Evaluation Test For the inks of the above examples and comparative examples, the solid density values of yellow, red, and indigo are yellow: 0.85-0.95, red: 0.88-1.00 under the following printing conditions. , Indigo: Printing was performed within the range of 0.84 to 1.00, 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.

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 solution: NEWSKING ALKY (Toyo Ink Manufacturing 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 *.

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７）。

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. 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 7).

Claims (2)

An offset ink printing method using an ink selected from yellow, red, indigo and black inks, wherein L * a * b * values when yellow, red and indigo inks are individually solid-printed with reference density values, and , Use yellow, red and indigo inks that have L * a * b * values in the following ranges when solid printing is performed with standard density values for two types selected from yellow, red and indigo inks A characteristic offset ink printing method.
Here, the standard density values printed on ISO standard newspaper Japan color standard paper are yellow 0.85 to 0.95, red 0.88 to 1.00, indigo 0.84 to 1.00,
Chromaticity according to L * a * b * color system (JIS Z 8729) is
Yellow ink, L *: 75 to 85, a *: 0 to -10, b *: 60 to 70
Red ink, L *: 52-62, a *: 46-56, b *: -5 to -15
Indigo ink, L *: 52-62, a *: -20 to -30, b *: -24 to -34
Red ink x yellow ink, L *: 50-60, a *: 37-50, b *: 27-37
Overprint of indigo ink x yellow ink, L *: 50 to 60, a *: −35 to −45, b *: 16 to 26
Overprint of indigo ink x red ink, L *: 35 to 45, a *: 10 to 20, b *: -30 to -40, and ink containing CI pigment red 169 is used as red ink It is characterized by.
An offset ink printing method using an ink selected from yellow, red, indigo and black ink, using the following yellow, red and indigo ink, and using an ink containing CI Pigment Red 169 as the red ink The offset ink printing method according to claim 1.
When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the reflectance in 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%. Is yellow ink.
When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 50% to 100%, and the reflectance in the wavelength region of 500 nm to 560 nm is 1 to 20. A red ink having a reflectance of 90% to 100% in a wavelength region of 630 nm to 700 nm.
When the maximum reflectance in the wavelength region of 400 nm to 700 nm is 100%, the reflectance in the wavelength region of 400 nm to 530 nm is 50 to 100%, and the reflectance in the wavelength region of 600 nm to 700 nm is 1 to 30%. An indigo ink.