JP2008254182A - Active energy ray curable ink composition excellent in reproducibility of violet hue - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active energy ray curable ink printing method, which enables a color reproducing region of RGB, used to be represented through five-seven color printing by adding a special color such as violet or the like in addition to conventional four process colors such as yellow, red, indigo blue and black, especially the color reproducing region of B (blue-violet) is made reproducible through double printing of indigo blue and red. <P>SOLUTION: This active energy ray curable ink printing method so excellent in highly saturated color reproduction is characterized in that double printing is executed in the two color inks, the chromaticities of which on L*a*b* colorimetric system (according to JIS Z 8729) in the density ranges of red at 1.52-1.56 and of indigo blue at 1.63-1.67 lies within specified ranges in the active energy ray curable ink printing method, and in that the chromaticities of the double printed part fall within specified ranges such as L* in 17-23, a* in 51-46 and b* in -71 to -76. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is an active energy ray-curable ink printing method comprising four process colors of yellow, red, indigo and black, and is particularly excellent in color reproducibility of purple (blue violet) hue by red and indigo overprinting. The present invention relates to a printing method using an ink system.

  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 we 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 the lithographic offset printing consisting of the four main colors (CMYK) of yellow, red, indigo, and black, which are currently mainstream, because the hue is due to subtractive color mixing, the data submitted as “RGB” is narrower Color separation into CMYK in the color reproduction area, as well as turbidity in the hue each time colors are superimposed, inevitably the color reproduction area becomes narrower than that of RGB, and color reproducibility between digital data and printed matter The difference became a problem. In particular, the purple (blue violet, equivalent to RGB “B”) hue expressed in two colors, red and indigo, is inferior in both saturation and lightness to the color reproduction region expressed by a single purple pigment. It was difficult to reproduce the “B” area of the “RGB” submission data with four colors (YMCK).

As a means for solving these problems, in general lithographic offset printing, in Patent Document 1, a printing method using an ink set of 5 to 7 colors is established as a high-saturation printing system, and printing using an ink set having each specified hue As methods, six colors (hexachrome printing) in which orange and green are added to four process colors, seven colors (high fidelity printing) in which orange, green, and purple are added to four process colors are established. In addition, as represented by hexachrome ink, methods such as adding fluorescent pigments to some colors as a means of suppressing secondary and tertiary turbidity and expanding the color reproduction range are also available. There are also disadvantages such as deterioration of the image quality (transfer defect, gloss reduction, etc.) and 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. In addition, similar attempts have recently been investigated for ultraviolet curable inks.
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. In particular, it is to provide an active energy ray-curable printing ink that can express the B (blue violet) region as much as possible.

  In general, in order to widen 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), and the reflection spectrum of each ink is 100% for yellow ink in the wavelength range of 500 nm to 700 nm. The reflectance in the wavelength region of 400 nm to 500 nm is 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 the reflectance in the wavelength region of 500 nm to 600 nm. It is 0%, and indigo ink is said to be 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% (ideal The spectral reflectance curve is shown in FIG.

  However, the reflection spectrum of yellow, red, indigo, and black ink compositions composed of four process colors currently used 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 relates to the chromaticity according to the L * a * b * color system (JIS Z 8729) when printing is performed within the density range of 1.52 to 1.56 for red and 1.63 to 1.67 for indigo. )But,
Red ink, L *: 48-55, a *: 77-85, b *: -14 to -20
Indigo ink, L *: 52-58, a *: -38 to -43, b *: -46 to -54
The active energy ray-curable ink printing method is characterized in that the two colors of ink within the range are overprinted, wherein the chromaticity of the overprinted portion is L *: 17 to 23, a *: 51 to 51 46, b *: -71 to -76
The present invention relates to an active energy ray-curable ink printing method excellent in color reproduction with high saturation, which is characterized by being within the above range.

  In addition, the present invention provides L * a * b * in four process colors of yellow, red, indigo and black by combining the active energy ray curable ink described above with the active energy ray curable yellow and black ink. The present invention relates to an active energy ray-curable ink printing method excellent in high chroma color reproducibility capable of expanding a color reproduction region of a color system.

  Further, the present invention relates to the above-described printing method using an ink in which the reflection spectrum of the spectral reflection curve of the 100% solid color printing portion of each of (a) red and (b) indigo satisfies the following range conditions.

  (A) When the total reflection is 100% in the wavelength region of 400 nm to 700 nm, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 35% to 100%, and in the wavelength region of 500 nm to 560 nm. A red ink having a reflectance spectrum of 0 to 10%, a reflectance of 630 to 700 nm and a reflectance spectrum of 70 to 100%. (B) When indigo has a total reflection of 100% in the wavelength region of 400 nm to 700 nm, the maximum reflectance in the wavelength region of 400 nm to 530 nm is 50% to 100%, and the reflectance of 600 nm to 700 nm is 0 to 10%. An indigo ink having a reflection spectrum of%.

  By using the active energy ray curable ink printing method provided by the present invention, RGB, which has been represented by 5-7 color printing by adding special colors such as purple, in addition to the four colors of yellow, red, indigo, and black ink in the past. In particular, the color reproduction region of B (blue violet) can be reproduced with red and indigo overprinting. 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 is a pigment dispersant such as an aluminum chelate, if necessary, containing a pigment, a synthetic resin, a photopolymerization initiator, a monomer having an ethylenically unsaturated double bond, and an oligomer having an ethylenically unsaturated double bond. Using an active energy ray curable ink consisting of four colors of yellow, red, indigo and black, obtained by adding and mixing auxiliary agents such as anti-friction agents, ISO standard Japan color standard paper such as Mitsubishi Paper Industries Co., Ltd. ) “Tokuhishi Art Double Sided Plates / 110 kg” manufactured and manufactured by Gretag Macbeth D196 densitometer, the concentration values are 1.52-1.56 for red and 1.63-1. In the range of 67, 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 red ink, red ink, L *: 48 to 55, Preferably 49-54, a *: 77-85, preferably 78 83, b *: −14 to −20, preferably −16 to −20, C: 80 to 86, indigo ink, L *: 52 to 58, preferably 52 to 57, a *: −38 to −43, Preferably, it is within the range of -39 to -42, b *: -46 to -54, preferably -47 to -52, C: 61 to 66, and further, indigo ink x red ink It is characterized by being in the range of L *: 17 to 23, a *: 51 to 46, b *: −71 to −76, C: 85 to 91 by printing.

As a method for expressing the color reproduction area, an XYZ color system (CIE1931 color system), an X10Y10Z10 color system (CIE1964 color system), an L * a * b * color system (CIE1976), a 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 the L * a * b * color system, the color reproduction area of RGB “B (blue violet)” is L * of 50 or less, preferably 10 to 40, and a * of 20 to 80, preferably 30 to 70. , More preferably 30 to 60, b * is in the region represented by −20 to −80, preferably −30 to −70, and the point where both values of a * and b * of the corresponding color intersect is a circle. The closer to the outside, the higher the hue.

  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). 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.
Regarding the yellow and black inks used in the present invention, all conventionally known active energy ray-curable printing inks can be used.

  Examples of the active energy ray used in the present invention include ultraviolet rays and electron beams. However, it need not be limited to this.

  Examples of red pigments are rhodamine dyes such as molybdenum and tungsten metal lake compounds such as CI Pigment Red 81, Basic Red 12, CI Pigment Violet 1, etc., and 15 to 30%, preferably 18 to 29%, more preferably It is desirable to contain 20 to 28%. Furthermore, it is also possible to use C.I. Pigment Red 48: 1 as a complementary color by adding 0.01 to 0.10%, preferably 0.01 to 0.05% of the above red pigment.

  Examples of indigo pigments include copper phthalocyanine compounds such as CI Pigment Blue 15: 3, CI Pigment Blue 15: 4 and the like, and 10 to 28%, preferably 12 to 25%, more preferably 14 to 23 in the ink. % Content is desirable. Furthermore, it is also possible to use C.I. Pigment Green 7 as a complementary color by adding 5 to 15%, preferably 8 to 11% of the above indigo pigment.

  Examples of the synthetic resin used in the present invention include polyvinyl chloride, poly (meth) acrylic acid ester, epoxy resin, polyester resin, polyurethane resin, cellulose derivatives (for example, ethyl cellulose, cellulose acetate, nitrocellulose), vinyl chloride-acetic acid. Examples include vinyl copolymers, polyamide resins, polyvinyl acetal resins, diallyl phthalate resins, alkyd resins, rosin-modified alkyd resins, petroleum resins, urea resins, and synthetic rubbers such as butadiene-acrylonitrile copolymers. These resins can be used alone or in combination of two or more thereof. In either case, a resin that is soluble in a monomer having an ethylenically unsaturated double bond is used.

In the present invention, the monomer refers to monofunctional or polyfunctional (meth) acrylates, and the viscosity of the ink composition can be adjusted by appropriately using these monomers. The oligomer used in the present invention is an alkyd acrylate. Epoxy acrylate, urethane-modified acrylate, etc. are used. One or more photopolymerization initiators can be appropriately added to the active energy ray-curable ink as a component that accelerates the curing action.

  As photopolymerization initiators, benzophenone, 4-methylbenzophenone, 4,4-diethylaminobenzophenone, diethylthioxanthone, 2-methyl-1- (4-methylthio) phenyl-2-morpholinopropan-1-one, 4-benzoyl -4′-methyldiphenyl sulfide, 1-chloro-4-propoxythioxanthone, isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxy-cyclohexyl-phenyl ketone, bis-2, 6-dimethoxybenzoyl-2,4,4-trimethylpentylphosphine oxide, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2, 2-dimethyl-2-hydroxyacetate Enone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- (morpholinophenyl) -butan-1-one, etc. Is mentioned. A photo accelerator such as p-dimethylaminobenzoic acid ethyl ester or pentyl 4-dimethylaminobenzoate may be used in combination with the photopolymerization initiator.

  As auxiliary agents, for example, anti-friction agents, anti-blocking agents, slipping agents, anti-scratch agents, carnauba wax, wax, lanolin, montan wax, paraffin wax, microcrystalline wax and other natural waxes, Fischer-Trops wax Synthetic waxes such as polyethylene wax, polypropylene wax, polytetrafluoroethylene wax and polyamide wax, silicone additives, leveling agents, constitutions and the like can be used as appropriate.

The ink composition in the present invention includes an oligomer having an ethylenically unsaturated double bond or a monomer having an ethylenically unsaturated double bond: 5 to 60% by weight, a synthetic resin: 1 to 30% by weight, and a pigment: 1 to 30 This is an active energy ray-curable ink containing 0% by weight, 0-20% by weight of a photopolymerization initiator, and 0-15% by weight of other auxiliary agents.
The active energy ray-curable ink in the present invention can be printed by a known printing method such as offset printing, letterpress printing, screen printing, and flexographic printing in the same manner as ordinary printing ink.

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 varnish production)
30 parts of Dap Tote DT170 (manufactured by Tohto Kasei Co., Ltd.) is added to 70 parts of DPHA (manufactured by Nippon Kayaku Co., Ltd.) heated to 90 ° C. to 100 ° C., and heated and dissolved at 90 ° C. to 100 ° C. for 1 hour. Obtained.
(Ink Example) (Red ink)
As a pigment, C.I. I. Pigment red 81 / C.I. I. Pigment White 21 (Farnal Rose Toner 170 manufactured by Arimoto Chemical Co., Ltd.), C.I. I. Pigment red 81 / C.I. I. Basic Red 12 (Pink MP-617, manufactured by Arimoto Chemical Co., Ltd.), C.I. I. Pigment Red 48: 1 (LIONOL RED 2BFG3300 manufactured by Toyo Ink Manufacturing Co., Ltd.) was used, and three rolls were used until the blending ratio shown in Table 1 was 7.5 microns or less with a dispersed particle system measuring machine (grind meter). Kneaded to obtain red ink 1.
(Example of ink) (Indigo ink)
As a pigment, C.I. I. Using Pigment Blue 15: 3 (LIONOL BLUE FG7351 manufactured by Toyo Ink Manufacturing Co., Ltd.), using three rolls until the blending ratio shown in Table 1 is 7.5 microns or less with a dispersion particle system measuring machine (grindometer) The indigo ink 1 was obtained by kneading.
(Ink comparison example) (purple ink)
As a pigment, C.I. I. Using Pigment Violet 23 (LIONOGEN VIOLET R6200 manufactured by Toyo Ink Co., Ltd.), the mixture ratio shown in Table 1 is used to grind with three rolls until the dispersion particle system measuring machine (grind meter) is 7.5 microns or less. A purple ink was obtained.
(Ink comparison example) (Process 4 colors)
Here, FD Carton ACE colors, which are the most common UV curable inks, were used as comparative inks.

(Print evaluation test)
About the ink of the said Example and a comparative example, each solid density value of red and indigo is printed in the range of red: 1.52-1.56 and indigo: 1.63-1.67 under the following printing conditions. The printed matter was evaluated. In addition, yellow and black ink used the general active energy ray hardening-type printing ink, and it printed it in the density | concentration range of yellow: 1.40-1.44 and black: 1.85-1.90. For purple ink, since the density control is generally impossible, printing was performed with the ink transfer amount varied within an arbitrary hue range.

    Example: Printing with a combination of red and indigo inks and known yellow and black inks.

    Comparative Example 1: Printing with a combination of known yellow, red, indigo and black ink.

    Comparative Example 2: Purple ink was added under the same conditions as in Comparative Example 1, purple ink was used for the red and indigo solid part overprinted (blue violet hue), and only the purple ink was transferred in three stages. (Comparative Examples 2 to 4) were printed.

Printing conditions Printing machine: Heidelberg Speedmaster Kikuzen 5-color machine (Heidelberg Japan Ltd.)
Paper: Tokishi Art Double Sided 110Kg (Mitsubishi Paper Co., Ltd.)
Dampening solution: Astro Mark 3 (Niken Chemical Research Co., Ltd.) 2.0% tap water solution Printing speed: 10,000 sheets / hour Printed matter measurement conditions Concentration: Measure the density value of the solid solid part of the printed matter with Gretag Macbeth D196 Colorimetry: L *, a * of the single color solid portion (yellow, red, indigo, purple) and single color solid printed portion (yellow x red, red x indigo, indigo x yellow) of X-Rite 938 Measure b * value.

  The C value was obtained from L *, a *, b * by the following formula.

  The results are shown in FIG. Further, Table 2 shows L * a * b * C measurement values of the single-color solid portion and the overprint portion.

It can be seen that the C value of red x indigo of the example is larger than that of the comparative example, that is, the chroma of the printed matter is high, and is close to the case where purple ink is used. Furthermore, 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, the color reproduction region of the example with respect to the blue violet hue is You can see that it is wide.

  The obtained spectral reflectance curve is shown in FIG. 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. For this reason, the turbidity component of the ink is reduced, which contributes to the improvement of the C value representing the color saturation (Table 2).

“It is the figure which showed the printed matter evaluation result.” “It is a diagram showing the ideal spectral reflection curve (yellow, red, indigo).” “A diagram showing spectral reflection curves (yellow, red, indigo) obtained in Examples and Comparative Examples.”

Claims (3)

Chromaticity according to the L * a * b * color system when printing in the density range of 1.52 to 1.56 for red and 1.63 to 1.67 for indigo when printing active energy ray curable ink (JIS Z 8729)
Red ink, L *: 48-55, a *: 77-85, b *: -14 to -20
Indigo ink, L *: 52-58, a *: -38 to -43, b *: -46 to -54
The ink printing method is characterized in that the above two colors of ink within the range are overprinted, and the chromaticity of the overprinted portion is L *: 17 to 23, a *: 51 to 46, b *: -71 to -76
An ink printing method excellent in color reproduction with high saturation, characterized by being within the range of.   By combining the active energy ray curable ink according to claim 1 with the active energy ray curable yellow and black ink, an L * a * b * color system of four colors of yellow, red, indigo and black is used. An ink printing method with excellent color reproducibility with high saturation that can expand the color reproduction range. (A) In the reflection spectrum of the spectral reflection curve of the red and (b) indigo, each of which is a single color 100% solid print portion,
(A) When the total reflection is 100% in the wavelength region of 400 nm to 700 nm, the maximum reflectance in the wavelength region of 400 nm to 500 nm is 35% to 100%, and in the wavelength region of 500 nm to 560 nm. A red ink having a reflectance spectrum of 0 to 10%, a reflectance spectrum of 630 to 700 nm and a reflectance spectrum of 70 to 100%. (B) When indigo has a total reflection of 100% in the wavelength region of 400 nm to 700 nm, the maximum reflectance in the wavelength region of 400 nm to 530 nm is 50% to 100%, and the reflectance of 600 nm to 700 nm is 0 to 10%. The printing method according to claim 1, wherein each ink having a% reflection spectrum is used.