JP5085277B2 - Gravure printing ink for solid surface printing - Google Patents

Description

The present invention relates to a gravure printing ink for solid surface printing used for process printing by a gravure printing method .

  Gravure printing has traditionally been widely used as a printing method that can print high-quality images on various substrates such as plastic film and paper with smooth reproducibility. In the case where a precise image including a gradation portion such as a photograph is printed on a base material printed with a solid, there are various problems in terms of the finished print quality. That is, when surface printing is performed on a solid substrate by gravure printing, for example, yellow, red, indigo or black color inks are overprinted in this order, so that the state of the solid surface is the transfer of each color ink. Fixability will be greatly affected. In general, the solid printing surface repels the ink to be printed later, so that it is difficult to ensure sufficient transfer fixing property, and the solid printing surface is smooth when printing highlight portions. Although it is preferable, on the other hand, in a solid portion or a halftone dot portion with a halftone dot area ratio of about 90 to 80%, the halftone dots are too close to each other or too far apart, and the printing surface becomes non-uniform. The grade may be significantly impaired. On the contrary, if the solid printing surface is rough, the ink transfer property in the shadow portion is improved, but there is a possibility that the ink cannot be sufficiently transferred and fixed in the highlight portion, particularly in the dot portion where the dot area ratio is 20% or less. Ink sometimes cannot be transferred at all, or can only be transferred to spots, and it may be difficult to reproduce a photograph clearly.

On the other hand, as a general method for improving the transfer and fixability of ink during surface printing by gravure printing, in addition to the method of improving the ink composition of binder resin, solvent, etc., the ink viscosity is adjusted, and the impression cylinder is changed. Although it has been proposed to increase the printing pressure, devise how to apply the doctor, or adjust the printing speed (see Non-Patent Document 1, for example), it is not always sufficient. Moreover, although it is said that the electrostatic printing system is also effective for the same purpose (for example, refer nonpatent literature 2), in this system, a special apparatus is required or an adaptive base material is restricted. In addition, when printing on a plastic film having a smooth surface, there is a drawback that the transfer and fixing properties of the ink in the highlight portion are not always satisfactory.
Edited by Processing Technology Study Group “Gravure Printing Handbook” (issued July 25, 1981) p. 121-122 “Convertec 1991.1” p. 12-16

The present invention has been found as a result of intensive studies to solve the above-mentioned problems in the background art, and the problem is that when the surface ink is printed by gravure printing on a solid base ink, Regardless of the halftone dot area ratio, stable transfer / fixability of gravure ink of each color can be ensured in all areas from the area to the highlight area, and it is clear even on substrates with high surface smoothness, such as plastic film An object of the present invention is to provide a gravure printing ink for solid surface printing that can be printed.

The present invention
A gravure printing ink for solid surface printing, comprising an inert fine particle filler having an average particle size of 0.5 to 2.5 μm, a pigment, a binder resin and a solvent;
Consists of.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a gravure printing ink for solid surface printing of the present invention and a method for using the same will be described in detail including embodiments and examples of the present invention.
<Inert particulate filler>
The inert fine particle filler in the present invention is not affected by other components constituting the gravure printing ink for solid surface printing, and the components of the gravure printing ink used for printing on the solid printing layer, particularly by the solvent. In addition, as long as it is sufficiently stable under the usage environment of the printed matter after drying, it is not particularly limited. Examples thereof include olefin resins such as polyethylene and polypropylene; polystyrene, styrene-acrylonitrile copolymer, and the like. Styrene resin; acrylic resin such as polymethyl methacrylate and styrene-methyl methacrylate copolymer; vinyl chloride resin such as polyvinyl chloride and ethylene-vinyl chloride copolymer; polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer Polymer, tetrafluoroethylene-hexafluoropropylene Fluorine resins such as polyethylene copolymers; Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polycarbonate; Polyimide resins; Resin materials such as polysiloxane resins; and inorganic materials such as silica and alumina. .

  Of these inert fine particle fillers, styrene resins and acrylic resins are preferred. Examples of commercially available products (trade names) of these preferable inert fine particle fillers include MX series, MP series (manufactured by Soken Chemical Co., Ltd.) and the like.

The average particle diameter of the inert fine particle filler is 0.5 to 2.5 μm, particularly preferably 1.0 to 2.0 μm. In the gravure printing ink for solid surface printing according to the present invention, it is considered that the desired effect is realized by the fact that the inert fine particle filler protrudes from the surface of the solid printing layer after drying and the surface is uneven. Therefore, the average particle diameter of the inert fine particle filler used and the thickness of the solid printing layer after drying need to be adjusted appropriately in relation to each other, but the thickness of the solid printing layer after drying is about 1 μm. In this case, a particularly preferable range of the average particle diameter of the inert fine particle filler is about (1.5 ± 0.4) to (2.0 ± 0.4) μm. In this case, if the average particle size of the inert fine particle filler is too small or too large, the effect of improving the ink transfer fixing property of the formed solid printing layer becomes insufficient, which is not preferable.

  Further, it is desirable that the inert fine particle filler has as sharp a particle size distribution as possible. Here, with respect to the cumulative distribution in which the horizontal axis represents the particle size and the vertical axis represents the weight percentage of particles smaller than each particle size, an example of a desirable particle size distribution of the inert fine particle filler is 10 particles smaller than the particle size. The particle size which is% by weight is d (0.1), the particle size which is smaller than 50% by weight is d (0.5), and the particle size which is smaller than 90% by weight. Is d (0.9), d (0.1) = 1.10 to 1.50 μm (typically 1.30 to 1.40 μm), d (0.5) = 1.60 2.00 μm (typically 1.80 to 1.90 μm) and d (0.9) = 2.30 to 2.80 μm (typically 2.40 to 2.75 μm).

The shape of the inert fine particle filler is not particularly limited, but a spherical shape or a shape close thereto is preferable.
Fine particle fillers of various materials and grades are sold by multiple manufacturers. When using commercially available fine particle fillers, in addition to the material and average particle size, the particle size distribution and shape are also appropriate. It is desirable to select.
In the present invention, the inert fine particle filler can be used alone or in admixture of two or more.

  The amount of the inert fine particle filler used in the present invention is preferably 0.5 to 5.0% by weight, particularly preferably 0.8 to 2.0% by weight, based on the entire ink. In this case, if the amount of the inert fine particle filler used is too small, the effect of improving the ink transfer fixing property of the formed solid printing layer becomes insufficient, while if too large, the original characteristics of the solid printing layer, for example, to the substrate. Adhesion, durability, color tone and the like may be impaired, which is not preferable.

<Pigment>
The pigment in the present invention is not particularly limited, and an appropriate pigment conventionally used for gravure printing can be used, and either an inorganic pigment or an organic pigment may be used.
Examples of the inorganic pigment include white pigments such as titanium oxide, zinc white, antimony oxide, and lithopone; black pigments such as carbon black and metal oxide black; reds such as molybdenum red, cadmium red, petal, and cerium sulfide. Pigments; Yellow pigments such as chrome yellow, cadmium yellow, and bismuth yellow; Green pigments such as chromium oxide green and metal oxide green; Blue pigments such as bitumen, ultramarine, and metal oxide blue; and metal oxide-coated mica In addition to these pearlescent pigments, for example, extender pigments such as calcium carbonate, barium sulfate, talc, clay, silica, and white carbon can be used.

  Examples of the organic pigment include monoazo, diazo, azo chelate, diazo condensation, benzimidazolone, β-naphthol, naphthol AS, isoindoline, isoindolinone, metal complex, Examples include phthalocyanine, quinacridone, dioxazine, diketopyrrolopyrrole, quinophthalone, berylene, perinone, thioindigo, and anthraquinone.

The color tone of the solid printing layer in the case of performing solid printing using the gravure printing ink for solid surface printing of the present invention is not particularly limited, and may be white or colored (for example, yellow), but is generally white. Or a color close to that is used. Therefore, as a solid printing pigment, a white pigment is preferable, and titanium oxide is particularly preferable. In addition, when making a solid printing layer into color, it cannot be overemphasized that the appropriate colored pigment conventionally used for gravure printing ink can be used.

The average particle size of the pigment used is desirably sufficiently smaller than the average particle size of the inert fine particle filler, preferably less than 0.5 μm, and particularly preferably 0.2 μm or less. The lower limit of the average particle diameter of the pigment is not particularly limited, but can be appropriately selected in consideration of ease of acquisition or manufacture, handleability, storability, price, and the like.
In the present invention, the pigments can be used alone or in admixture of two or more. In some cases, one or more dyes or natural pigments can be used in combination with the pigment.

<Binder resin>
As the binder resin in the present invention, various binder resins conventionally used in gravure printing inks can be used, and are not particularly limited. Examples thereof include rosin or a salt thereof, a polyvalent resin. Rosin such as alcohol-modified rosin or its salt; phenol resin such as phenol resin, rosin-modified phenol resin or its salt; petroleum resin, petroleum resin of rosin-modified petroleum resin or its salt; alkyd resin, rosin-modified alkyd resin or Alkyd resins such as salts thereof; Amino resins such as urea resins and melamine resins; Cellulosic resins such as nitrified cotton, cellulose acetate and nitrocellulose; Polyamide resins such as polyε-caprolactam and polyhexamethylene didipate; Polyurethane Resin; polymethyl acrylate, polyacrylic Acrylic resins such as ethyl, polymethyl methacrylate, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer; cyclized rubbers, and the like. These binder resins are used in the form of varnish. can do. In addition, in this invention, what has reactivity, such as thermosetting and photocurability, can also be used as binder resin if desired.

Of these binder resins, nitrified cotton, polyamide resins, polyurethane resins and the like are particularly preferable. Examples of commercially available products (trade names) of these preferable binder resins include nitrone (manufactured by Taisei Technochemical Co., Ltd.), newmide (manufactured by Harima Kasei Co., Ltd.), and the like.
In this invention, binder resin can be used individually or in mixture of 2 or more types.

  The amount of the binder resin used is preferably 10 to 25% by weight, particularly preferably 15 to 20% by weight, based on the entire ink.

<solvent>
As the solvent in the present invention, various solvents conventionally used in gravure printing inks can be used, and are not particularly limited. Examples thereof include ethanol, n-propanol, and i-propanol. Alcohols such as n-butanol, i-butanol and t-butanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-i-propyl ether, diethylene glycol monomethyl ether, (Poly) alkylene glycol monoalkyl ethers such as diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-i-propyl ether; ethylene (Poly) alkylene glycol monoalkyl ether acetates such as recall monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate and diethylene glycol monoethyl ether acetate; other ethers such as diethylene glycol dimethyl ether and diethylene glycol diethyl ether; methyl ethyl ketone, Ketones such as cyclohexanone, 2-heptanone, 3-heptanone; esters such as ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate; 3-methoxybutyl acetate, 3-methyl Esters such as -3-methoxybutyl acetate; aromatic hydrocarbons such as toluene and xylene; N-methylpyrrolide , N, N- dimethylformamide, N, amides such as N- dimethylacetamide; can be mentioned aroma-free petroleum solvent or the like.

Among these solvents, those containing a solvent having a boiling point of preferably 60 to 120 ° C., particularly preferably 80 to 100 ° C., such as alcohols and esters, are desirable.
In this invention, a solvent can be used individually or in mixture of 2 or more types.

  The amount of the solvent used is such that the solid content in the ink is preferably 10 to 50% by weight, particularly preferably 20 to 40% by weight.

<Additive>
The solid surface printing gravure printing ink of the present invention may contain various additives in addition to the above-described components.
Examples of the additive include a dispersant, an antifoaming agent, a lubricant, an antistatic agent, a wettability improving agent, a fluidity adjusting agent, a viscosity adjusting agent, an abrasion resistance improving agent, a flexibility imparting agent, and a drying property adjusting. Agents, anti-set-off agents, curing agents and the like.

<General characteristics of gravure printing ink for solid surface printing>
The total solid concentration of the gravure printing ink for solid surface printing of the present invention is preferably 10 to 50% by weight, particularly preferably 20 to 40% by weight.
Further, the viscosity of the gravure printing ink for solid surface printing of the present invention is preferably 10 to 40 seconds, particularly preferably 15 to 30 seconds, when measured with Zahn Cup # 3.

<Preparation method of gravure printing ink for solid surface printing>
The method for preparing the gravure printing ink for solid surface printing of the present invention is not particularly limited as long as the inert fine particle filler can be uniformly dispersed in the ink base containing a binder resin, a pigment, a solvent, etc. More specifically,
(A) A method in which inert fine particle filler is gradually added and mixed with a kneading machine while stirring the pigment, binder resin, solvent, etc. at a high speed, and then the inert fine particle filler is uniformly dispersed at the same time; Examples thereof include a method in which an inert fine particle filler is added to and mixed with an ink base kneaded with a binder resin, a solvent, etc., and then stirred at a high speed to uniformly disperse the inert fine particle filler.
In this case, for example, an impeller stirrer or a bead mill can be used as a disperser used for dispersing the inert fine particle filler. Additives other than the pigment can be added at an appropriate stage in the methods (a) and (b), and a solvent can be further added to adjust the concentration and viscosity of the ink as appropriate. .

<Gravure printing method>
In the gravure printing method using the gravure printing ink for solid surface printing of the present invention, a predetermined image is obtained by forming a solid printing layer in a single layer or multiple layers on the surface of a desired substrate and then performing gravure printing by a conventional method. The process of printing is included. In the case of forming a multilayer solid printing layer, it is necessary to use the gravure printing ink for solid surface printing of the present invention at least in the outermost solid printing layer. Examples of the multilayer solid printing layer include one in which two or more white solid printing layers are formed, and one in which a yellow solid printing layer is formed on the white solid printing layer.

As the base material, an appropriate base material to which gravure printing is conventionally applied can be used, and is not particularly limited. For example, plastic (film or sheet), paper (thick paper, thin paper) Recycled paper (thick paper, thin paper), aluminum (foil or sheet), copper (foil or sheet), stainless steel (foil or sheet), laminate material or sand material containing two or more of these materials, etc. Can do.
In order to improve the adhesion of the solid printing layer, these substrates can be subjected to appropriate pretreatments such as discharge treatment, coating / coating, chemical treatment, and sandblast treatment.

When the gravure printing ink for solid surface printing of the present invention is used, controlled uniform and fine irregularities are formed on the surface of the solid printing layer on the substrate, and as a result, when printing is performed by gravure printing, Regardless of the dot area ratio, the entire area up to the light area can ensure stable transfer and fixability of gravure inks of each color, and prints clearly even on substrates with high surface smoothness, such as plastic films. It is also possible to adjust the surface appearance of the solid printing layer from high gloss to matte tone by adjusting the average particle size and amount of inert fine particle filler, and the range of expression of the printed material is expanded. Various printing effects can be obtained.

Example 1
After adding 1 part by weight of the following inert fine particle filler to an ink base having a composition described below (total 100 parts by weight), a white gravure printing ink for solid surface printing was prepared by stirring at high speed.
-Ink base-
White pigment (total 25 parts by weight):
Titanium oxide (average particle size 0.1 μm) 25 parts by weight Binder resin (total 20 parts by weight):
Nitrified cotton 5 parts by weight Polyamide resin (Brand name Newmide 838, manufactured by Harima Kasei Co., Ltd.)
15 parts by weight Solvent (total 50 parts by weight):
Ethyl acetate 15 parts by weight i-propanol 30 parts by weight Ethylene glycol mono-i-propyl ether
5 parts by weight additive (total 5 parts by weight):
2 parts by weight of wax Defoamer 1 part by weight Titanium chelate (curing agent) 2 parts by weight

-Inert particulate filler-
Ingredients: Acrylic resin (trade name MX-180 TA, manufactured by Soken Chemical Co., Ltd.)
Volume-based average particle diameter by laser diffraction / scattering method: 1.91 μm
Particle size distribution: d (0.1) 1.32 μm
d (0.5) 1.85 μm
d (0.9) 2.59 μm

Thereafter, the obtained gravure printing ink for solid surface printing was solid-printed on the surface of a polypropylene film (OPP) to form a solid printing layer having a thickness of 1 μm after drying. Next, using a test intaglio (laser plate making, 175 lines, plate depth of 30 μ) having different areas of 10% from 3%, 5%, 8%, and further from 10% to 100%, Gravure printing inks prepared in yellow, red, indigo and black colors (ink viscosity: Zaan Cup # 3 14 seconds, trade name PIXESS, manufactured by T & K Tohka Co., Ltd.) for each color test Evaluation was performed by changing the intaglio and performing gravure printing (printing speed: 120 m / min) on the surface of the solid printing layer. As a result, even in a gradation region where the dot area ratio is 100% (solid portion) to 80%, a gradual decrease in density is confirmed. No leakage was observed.

Comparative Example 1
In Example 1, except that the inert fine particle filler was not added, the same ink base as in Example 1 was used, except that the surface of the polypropylene film (OPP) was solidly printed, as in Example 1, Gravure printing was performed for evaluation.
As a result, in the gradation region where the halftone dot area ratio is 100% (solid portion) to 80%, the density drop is excessively large, and in the region where the halftone dot area ratio is 20% or less, speckles are generated. Admitted.

By using the gravure printing ink for solid surface printing according to the present invention, highlighting from the shadow portion when surface printing by gravure printing is performed on a substrate (for example, plastic, paper, metal, etc.) having a solid printing layer on the surface. Regardless of the dot area ratio, it is possible to ensure stable transfer and fixability of gravure inks of each color, and to print clearly on substrates with high surface smoothness such as plastic films, etc. It is also possible to adjust the surface appearance of the solid printing layer from high gloss to matte, and it is possible to print fine images on a wide range of substrates with good reproducibility. Greatly contributes to expansion and improved print quality.

Claims (3)

A gravure printing ink for solid surface printing, comprising an inert fine particle filler having an average particle size of 0.5 to 2.5 μm, a pigment, a binder resin, and a solvent. 2. The gravure printing ink for solid surface printing according to claim 1, wherein the amount of the inert fine particle filler used is 0.5 to 5.0% by weight of the whole ink. The solid surface printing gravure printing ink according to claim 1, wherein the pigment contains a white pigment.