JP6268552B2 - Flexo print - Google Patents

Description

  The present invention relates to a flexographic print excellent in color reproducibility with high saturation in surface printing and back printing flexographic printing composed of yellow, red and indigo process colors in aqueous flexographic printing.

In the field of package printing, various printing methods such as gravure printing, flexographic printing, offset printing, ink jet printing, and silk screen printing have been used as techniques. Among them, gravure printing and flexographic printing have been conventionally used in various package printing such as paper, cardboard, non-woven fabric, cardboard, metal foil, and plastic film.
In recent years, various environmentally conscious printing inks such as offset inks using vegetable oil and non-toluene gravure inks have been developed from the viewpoint of environmental consideration. Therefore, flexographic printing methods with low solvent emissions are attracting attention in the field of packaging printing. Among them, water-based flexographic printing using water as the main solvent is one of the printing methods with the lowest solvent emissions. is there.
Process printing on various substrates in water-based flexographic printing includes surface printing and back printing. Surface printing with the ink layer as the top layer as viewed from the observer of the printed material is used for printing on paper, cardboard, non-woven fabric, cardboard and other plastic films, while back printing is viewed from the observer of the printed material. A water-based flexographic printing system is widely developed in the food packaging field and sanitary field.
Currently, the main ink printing order of process color printing of yellow, red, indigo and black, which are widely used, is the printing order of yellow, red and indigo ink in the four process colors represented by CMYK if it is surface printing. It is common to print in the order of yellow, red, and indigo, and in reverse printing, it is usually printed in the order of indigo, red, and yellow.
Both the front printing and the back printing use the printing order in which the yellow ink in the ink layer is the lowest layer as viewed from the observer of the printed matter.
This is because flexo yellow ink for process colors, which is currently used for general purposes, is generally opaque. For surface printing, yellow is printed first among process colors, and process color is used for back printing. This is because the most vivid hue can be obtained by the method of printing yellow last, but for example, in surface printing, yellow ink having higher saturation than red and indigo is viewed from the observer. Therefore, the color rendering properties of the yellow and red overlapped portion and the yellow and indigo overlapped portion may be inferior to those of the offset type printed matter having a highly transparent yellow ink as the uppermost layer.
In back printing, a transparent yellow pigment may be used in oil-based flexographic inks, and a printing method with yellow ink as the top layer may be selected from the viewpoint of an observer. The yellow pigment cannot be stably dispersed in an aqueous solvent and has not been adopted.
Opaque yellow ink has been widely used for yellow inks of water-based flexographic inks due to problems with the stability and dispersibility of water-based inks over time. The clear hue is lost due to the yellow ink hue and transparency problems in the overlapping part of yellow and the overlapping part of yellow and indigo.

  As means for improving the color rendering properties in flexographic printing, 6-color printing (Patent Document 1) in which Pantone Hexachrome (registered trademark) is added as a standard process color in packaging printing, commercial printing, etc. is used. A method of expanding the color gamut of the four-color process in flexographic printing (Patent Document 2) has been proposed, but in both cases, the secondary color gamut expansion by the yellow ink particle size and transparency and the surface printing in flexographic printing, It is not mentioned in the order of printing in the reverse printing process.

US Pat. No. 5,734,800 Special table 2015-530938 gazette

  The present invention has been made to solve such problems in the prior art, and the object of the present invention is to use a transparent yellow ink in surface printing and back printing flexo printing in aqueous flexo process color printing. To provide a high color rendering flexo print and a flexo process printing method that improve the yellow single color density and the secondary color sharpness by placing the top of the ink layer in the print laminate from the viewpoint of the print observer. It is.

  The present invention uses a high-concentration, high-concentration aqueous flexo yellow ink to improve the clarity of the secondary color part containing yellow when the yellow ink is at the top when viewed from the observer of the printed matter in flexographic printing. It is to obtain an improved water-based flexographic surface print and back print.

That is, the present invention is a flexographic print using yellow, red and indigo flexographic inks on a substrate, and the top layer of the ink layer portion is a yellow ink as viewed from the observer of the print. Ri, yellow flexographic ink is a yellow pigment, a surfactant, and comprises a resin, 50% cumulative average diameter of the yellow pigment, surface printing, characterized in der Rukoto below 400nm or reverse printing, It relates to flexographic prints.

  The present invention also relates to the above-mentioned flexographic printed matter in which the flexographic ink is all water-based.

  Moreover, this invention relates to the said flexo printed matter whose yellow pigment in the ink for yellow flexographic printing is 10 to 30 weight% of the whole ink for yellow flexographic printing.

  By using the water-based yellow flexographic printing ink provided by the present invention, it is possible to obtain a flexographic print having high vividness in a yellow single-color hue and a secondary color portion in conventional front-printed flexographic prints and back-printed flexographic prints.

  Various yellow inorganic and organic pigments conventionally used in flexographic printing can be used as the yellow pigment of the yellow flexographic printing ink used in the present invention. For example, Pigment Yellow 1, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 63, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 106, Pigment Yellow 114, Pigment Yellow 121, Pigment Yellow 126, Pigment Yellow 127, Pigment Yellow 136, Pigment Yellow 174, Pigment Yellow 176, Pigment Yellow 180, Pigment Yellow 188, and the like are preferable. Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 4, Pigment Yellow 83, Pigment Yellow 174, it is preferable to use 10-30% by weight of Pigment Yellow 176 in yellow ink.

  In the yellow flexographic printing ink used in the present invention, various extender pigments can be used in combination as a filler for the purpose of improving blocking resistance, drying property, laminate strength and the like in addition to the yellow pigment. Examples of extender pigments include those used in ordinary printing inks, such as carbonates such as calcium carbonate and magnesium carbonate, sulfates such as precipitated barium sulfate, silicates such as kaolin clay, silica, talc and mica. These may be used alone or in combination of two or more.

  In the present invention, various surfactants can be used for improving the dispersibility of the yellow pigment in an aqueous solvent and obtaining a highly transparent yellow flexographic printing ink. Specific examples of the surfactant include acetylenediol derivatives represented by 2,4,7,9-tetramethyl-5-decyne-4,7-diol, ethylene oxide adducts of the acetylenic diol derivatives, polyoxy Nonionic surfactants obtained by adding ethylene oxide to polypropylene glycol typified by ethylene polyoxypropylene block polymer are listed.

As the resin contained in the aqueous flexographic ink used in the present invention, various water-soluble solution resins or water-soluble emulsion resins can be used. As the water-soluble solution resin, a water-soluble solution resin obtained by neutralizing a styrene-acrylic copolymer with an alkali, an acrylic copolymer emulsion, an aqueous polyurethane resin, an aqueous urethane-acrylic urethane resin, an aqueous polyester resin, or the like can be used. .
These water-soluble solution resin or water-soluble emulsion resin may be used alone with a water solvent in order to disperse the yellow pigment, or may be used in combination as the surfactant.
The viscosity of the liquid resin for aqueous flexographic inks is preferably 50 mPa · s-20000 mPa · s, more preferably the range of 100 mPa · s-10000 mPa · s is the viscosity of the pigment dispersion base in the ink production and the final adjusted viscosity. This is preferable.

  In the case of using a water-soluble liquid resin, a water-miscible solvent can be added and mixed in addition to water. Examples of the water-miscible solvent include lower alcohols, polyhydric alcohols and alkyl ethers or alkyl esters thereof. Specifically, lower alcohols such as methanol, ethanol, normal propanol, isopropanol, ethylene glycol, Polyhydric alcohols such as propylene glycol, diethylene glycol, dipropylene glycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, preprene glycol acetate, diethylene glycol monomethyl ether, di Propylene glycol or the like can be used.

  The present invention includes paraffin-based, polyethylene-based or Teflon (registered trademark) waxes dispersed in an aqueous solvent for imparting friction resistance and slipperiness, silicon-based, non-foaming for suppressing foaming during printing. Silicon-based antifoaming agents and curing agents that accelerate ink film curing can be used as appropriate.

  The yellow flexographic printing ink used in the present invention is prepared by dispersing pigment particles using a ball mill, an attritor, a sand mill or the like in a pigment, an additive, a binder resin, water, or a solvent. The average particle diameter of the pigment is measured using a particle size distribution measuring instrument or the like, and the particle size distribution of the secondary color containing yellow ink is preferably when the 50% cumulative average diameter is 400 nm or less, more preferably 300 nm or less. Improve hue clarity. When the 50% cumulative average diameter is larger than 400 nm, the transparency of the yellow ink is remarkably lowered, and the sharpness of the secondary color hue containing the yellow ink is lowered. The 50% cumulative average diameter is defined as the particle diameter at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume of the powder group as 100%. The volume distribution of the powder population is determined by a dynamic light scattering method.

  A well-known ink can be used for the ink for red flexo printing and the ink for indigo color flexo printing used in the present invention. When the yellow flexographic ink is water-based, it is preferable that the red ink and the blue ink are also water-based.

  As the base material used in the present invention, coated paper, fine paper, coated cardboard, liner paper, paper base represented by cardboard, non-woven fabric formed from plastic fibers such as polyester fiber, polyolefin fiber, rayon fiber, polyester Examples thereof include plastic films such as films, stretched polypropylene films, unstretched polypropylene films, polystyrene films, stretched nylon films, polyethylene films, polyvinyl chloride films, and milk white polyethylene films. When there is a difficulty in the adhesion between the ink and the base material or the image formation in the plastic film, corona treatment can be appropriately applied.

  The color reproduction area reproduction method includes XYZ colorimeter (CIE1931 color system), X10Y10Z10 color system (CIE1964 color system), L * a * b color system (CIE1976), Hunter Lab color system, Munsell Color system, L * u * v color system (CIE1976), and the like.

  In the L * a * b color system, “lightness” is expressed as L * as a 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. a * and b * indicate the color direction, + a * indicates red, -a * indicates green, + b * indicates yellow, and -b * indicates blue. In each direction, the larger the absolute value, the brighter the color, and the closer to 0, the darker the color. “Saturation (C)” is defined as a method for quantifying the degree of sharpness, and can be obtained by the following equations.

Ｃに関しては絶対値が大きくなるほど鮮明さが向上され、値が小さくなるに従って鮮明さが失われたくすんだ色となる。

As for C, the larger the absolute value, the better the sharpness, and the smaller the value, the dull color is lost.

Flexographic printing machines include CI type multi-color flexographic printing machines, unit type multi-color flexographic printing machines, etc. The ink supply system can be a chamber system or a 2-roll system, and an appropriate printing machine can be used. it can.
As the flexographic plate, a suitable flexographic plate can be used, such as a photopolymer base material that cures a resin in UV light, or a rubber plate on which an image is engraved.
As the anilox roll, a chrome-plated anilox roll, a ceramic anilox roll or the like is used for general purposes, but is not limited to this as long as it can be used in a flexographic printing machine.

  In the process color printing of the present invention, black ink and special color ink can be added in any order as required, and white ink can be used as necessary. In the case of back printing, white ink can be applied after applying color ink to a transparent plastic film, and in surface printing, white ink can be applied as a base before applying color ink. it can.

The printing order of the process colors of the flexographic printed matter of the present invention is, for example, yellow, red, and indigo, as viewed from the observer for a printed matter that is a transparent yellow ink having a 50% cumulative average diameter of aqueous flexo yellow ink of 400 nm or less. Select the order.
Specifically, in front printing, for example, indigo, red, and yellow are printed in this order, so that yellow is the uppermost layer in the ink layer as viewed from the observer of the printed matter. The indigo and yellow overlapped portions of indigo and yellow and the underlying indigo and red hues are observed through highly transparent yellow. Since the ink is not concealed, the C value is increased as a result, and since the a value of the red ink is not concealed by the yellow ink in the overlapping portion of red and yellow, the C value is increased as a result. A high C value indicates high sharpness, that is, the printed material has high color rendering. The same applies to reverse printing that is printed on the back side of the substrate, and yellow is the uppermost layer of the ink layer as seen from the observer of the printed matter, and the indigo and yellow overlapping portions of the flexographic printed matter containing transparent yellow As in the case of surface printing, the C value of the overlapping portion of red and yellow is increased, and a high color rendering product can be obtained.

  The present invention will be described in detail by the following specific examples, but the present invention is not limited to these examples. Moreover, the part of the following description shows a weight part and% shows weight%.

Resin production example 1 (water-soluble solution resin A)
A reaction vessel equipped with a stirrer, a thermometer, two dropping funnels and a reflux condenser was charged with 94.0 parts of methyl isobutyl ketone, and the temperature was raised to 100 ° C. under nitrogen reflux while stirring. Subsequently, 50 parts of styrene, 5 parts of α-methylstyrene, and 30 parts of methacrylic acid and 15 parts of lauryl methacrylate were dropped in two dropping funnels over 3 hours. From the other side, 5 parts of dimethyl 2,2′-azobisisobutyrate was dissolved in 10 parts of methyl isobutyl ketone and added dropwise over 4 hours. After completion of the dropwise addition, the reaction was completed by further reacting for 10 hours. After cooling, the resulting pigment-dispersed resin solution was further neutralized by adding 19.5 parts of 25% aqueous ammonia. Further, ion-exchanged water was added, solvent substitution was performed while heating, and finally ion-exchanged water was further added to obtain a water-soluble liquid resin A having a weight average molecular weight of 10500, a solid content of 30%, and a viscosity of 6000 mPa · s. .

Resin production example 2 (water-soluble emulsion resin B)
A reaction vessel equipped with a stirrer, a thermometer, two dropping funnels and a reflux condenser was charged with 92 parts of ion-exchanged water and 114 parts of the water-soluble resin A prepared in Production Example 1, and the temperature was 80 under nitrogen reflux while stirring. The temperature was raised to 0 ° C. Subsequently, in two dropping funnels, 25 parts of styrene and 75 parts of n-butyl acrylate were dropped from one side over 2 hours. From the other side, 5 parts of a 20% aqueous solution of ammonium persulfate was added dropwise over 2 hours. After completion of the dropwise addition, the reaction was further continued for 4 hours. Further, ion-exchanged water was added to obtain a water-soluble emulsion resin B which is a core-shell emulsion resin having a solid content of 45%, a weight average molecular weight of 420,000, and a viscosity of 1000 mPa · s.

Yellow Ink Example and Comparative Example Pigment Yellow 13 (LIONOL YELLOW FG1314C manufactured by Toyocolor Co., Ltd.) or Pigment Yellow 14 (manufactured by Permanent Yellow GSO Clariant Pigment Yellow TT1407G manufactured by Toyocolor Co., Ltd.)
To 10-30 parts, water-soluble solution resin A, water-soluble emulsion resin B, water, polyethylene wax [Chemical Pearl W500, manufactured by Mitsui Chemicals] were added and dispersed with a sand mill to obtain yellow ink.
The dispersion time in the sand mill is 60 minutes in the yellow ink example 1-4, whereas it is 20 minutes in the comparative example 1.

Example of red and indigo inks Water-soluble resin A and nonionic resin with respect to 20 parts of Pigment Red 146 (LIONOL RED FG5620 manufactured by Toyocolor Co., Ltd.) or Pigment Blue 15 (manufactured by LIONOL BLUE FG7330 Toyocolor Co., Ltd.) according to the formulation shown in Table 1. Surfactant [Surfinol 420 manufactured by Nissin Chemical Industry], water, and polyethylene wax [Chemical Pearl W500 manufactured by Mitsui Chemicals] were added and dispersed in a sand mill for 60 minutes to obtain red ink and indigo ink.

Table 2 shows the measurement results of the 50% cumulative average diameter of the yellow ink.
The 50% cumulative average diameter of yellow ink Examples 1-4 and Comparative Example 1 was measured using a particle size distribution measuring apparatus (UPA-EX150, manufactured by Nikkiso Co., Ltd.) based on the dynamic light scattering method. The 50% cumulative average diameter is defined as the particle diameter at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume of the powder group as 100%.
The yellow ink of Example 1-3 had a 50% cumulative average diameter of 300 nm or less, the yellow ink of Example 4 was 340 nm, and the yellow ink of Comparative Example 1 was 495 nm.

The transparency of the yellow ink is shown in Table 3. Tables 4 and 5 show the evaluation results of the secondary ink including yellow ink density, hue, and yellow ink.
About the ink composition adjusted above, it applied to the process OPP base material (biaxially-stretched polypropylene film FOR film made by Futamura Chemical 20 micrometers in thickness) using the flexiproof 100 (anilox roll 400 lpi 6cc / cm < ² >).

The transparency of the yellow ink is determined by measuring the spectrophotometer (X-) from the ink coated surface using a black backing method in which a stack of five black papers is laid down on the yellow ink printed on the film under the above coating conditions. Rite eXact (manufactured by X-Rite Co., Ltd.) was used as a reference for determining the transparency of yellow ink by measuring the L value representing saturation.

Transparency standard for yellow ink 5: High transparency L value: less than 40
4: Slightly high transparency L value: 40 or more and less than 50
3: Medium transparency L value: 50 or more and less than 60
2: Slightly low transparency L value: 60 or more and less than 70
1: Low transparency L value: 70 or more

For the surface printing hue, the hue and density were measured with a spectrocolorimeter (X-rite eXact manufactured by X-Rite) from the ink coated side, that is, the ink coated surface, and the ink for the back printing hue was coated. Hue and density were measured with a spectrocolorimeter from the back side, that is, the film side. In Table 4, the base material (film) / red / yellow has yellow as the uppermost layer when viewed from the observer when printed on the surface, and red ink is the uppermost layer when viewed from the observer when printed on the back. Indicates.
Concentrations of yellow, red and indigo monochromatic solids, hues of monochromatic solids, hues of secondary colors containing yellow, ie yellow and red overprint composition, and yellow and indigo overprint composition (L * a * b * C value).

  Regarding the secondary color including the yellow example, the case where the yellow ink is the uppermost layer as viewed from the observer in the ink layer. In the printed surface print, the printed matter including the yellow ink example 1-4 is red and yellow. Compared with the printed material including the yellow ink comparative example 1, the printed material having a high C value, that is, sharpness, was obtained for both the overlapping portion and the indigo and yellow overlapping portions. As for the back-printed printed matter, the printed matter including yellow ink Example 1 has a higher C value for the indigo and yellow overlapping portions than the printed matter including yellow ink comparative example 1, and yellow ink example 2-4 is a yellow ink comparative example. As a printed matter containing 1, a red and yellow overlapping portion and an indigo and yellow overlapping portion have a high C value and a high sharpness.

Claims (3)

On the substrate, a yellow, a flexographic printed matter using red, and a flexographic printing ink of cyan, viewed from the printed matter of the observer, the uppermost portion of the ink layer is Ri Oh yellow ink, yellow flexographic printing ink, a yellow pigment, a surfactant, and comprises a resin, 50% cumulative average diameter of the yellow pigment, surface printing or reverse printing flexo printed matter, characterized der Rukoto below 400 nm. 2. The flexographic printed matter according to claim 1, wherein the flexographic ink is all water-based. The flexographic print according to claim 1 or 2 , wherein the yellow pigment in the yellow flexographic ink is 10 to 30% by weight of the entire yellow flexographic ink.