JPH10202998A - Method for printing on curved face - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily print a body to be printed which has a curved face difficult to print conventionally, by transferring an ink increased in viscosity by a crosslinking process to a soft pad of an approximately similar shape to the body to be printed and carrying out transfer printing to the body. SOLUTION: At a first process, a flat original plate is directly printed by an ink-jet method. An ink on the flat original plate is increased in viscosity by a crosslinking process at a second process. At a third process, the ink is transferred from the flat original plate to a soft pad having a curved face of a similar shape to a curved face of a body to be printed. At a fourth step, the soft pad is brought in touch with a print surface of the body to be printed and the ink is transferred and fixed, thereby printing the curved face. Since the ink used in the direct printing by the ink-jet method includes a crosslinking agent and a surfactant of an amount not smaller than a limited micell value, the viscosity of ink is preferably 0.5-1P at the first process and 100-200P at the second process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method for printing on a printed body having a curved surface.

[0002]

2. Description of the Related Art It has been extremely difficult to perform accurate color printing on a printed material having a curved surface, particularly a relatively complicated curved surface. Of course, there is no means for color printing on a relatively simple curved surface. For example, there is a method in which a material printed in advance on a transfer paper is brought into contact with a printed material and transferred. However, the conventional method has various defects. In addition, there is an ink jet printing method as a printing method conforming to the computer age. In recent years, a clear printing of 720 dpi has been made possible by development. However, in this printing method, the printing material is mainly limited to paper or fiber products, and there is no example of printing this on a printing material of plastic or metal, or a printing material having a curved surface.

[0003] Among these ink jet systems, the on-demand system which ejects ink only when necessary, prints by controlling the ejection conditions based on instantaneous screen information.
The information of the print image itself and the change information of the shape of the printing medium to be printed can be simultaneously controlled, which is very desirable as a method of printing on a curved surface. However, at present, the target of the ink jet method is paper and textile products, and in recent years, the maximum resolution has been increased in order to improve the image quality, and it is required that the jetting particles to respond to this are extremely small. . For this reason, as the ink used in the ink jet method, a water-soluble ink having extremely low viscosity (about 0.1 to 1 Poise) and high permeability is used.

[0004] On the other hand, when the printing medium is made of a plastic or metal other than paper or textiles at least on the surface to be printed, unlike paper and textiles, it does not have permeability and ink fixing properties. Current inks for inkjet systems are not at all suitable for this printing.

[0005]

In order to apply conventional ink jet printing to a printing medium other than paper or textiles such as plastic and metal, the specifications of the ink used must be basically changed. That is, in order to eject ink at a high speed from a small-diameter nozzle or an orifice having a diameter of about 50 to 100 μm, it is necessary to reduce the flow resistance 、 as much as possible. No. In addition, it is necessary to print on a printing material such as plastic or metal having a curved surface with the ink viscosity for normal offset printing, and some intermediate means is required in conjunction with the method of printing on a curved surface. .

However, when printing on a printing material such as plastic or metal having a curved surface, basically printing is performed directly on a flat original plate which is easy to print with a low-viscosity ink by an ink jet method, and then the printing is performed. Means for transferring to a soft pad having almost the same curved surface as the body, and further transferring from the soft pad to the printing medium is required.
a) the ink is sufficiently applied on the surface of the flat original plate; b) the ink is sufficiently transferred to the soft pad; c) the ink is smoothly transferred and fixed from the soft pad to the printing medium;
d) It is required that evaporation and solidification of the ink be suppressed for a considerable time during this step, and e) it is required that the ink has a low viscosity for utilizing the ink jet system. There is a problem in that the conditions d) and e) are contradictory. These conditions cannot be satisfied with the ink used in the current ink jet system. The present invention proposes a printing method for printing on a curved surface with these defects eliminated.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for printing on a substrate having a curved surface by offset printing.
In the first step, direct printing is performed on the flat original by an ink jet method. In the second step, the ink on the flat original is thickened by a crosslinking treatment. Transferring to a soft pad having a curved surface, and in a fourth step, transferring and fixing the soft pad by contacting the soft pad with a printing surface of a printing medium; The ink used for direct printing contains a cross-linking agent and a surfactant in an amount equal to or greater than the limit micelle value,
In addition, the viscosity of the ink is 0.5 to 1 Pois in the first step.
e. In the second step, the problem is to be solved by being 100 to 200 Poise.

[0008]

DETAILED DESCRIPTION OF THE INVENTION It goes without saying that the basic composition of a printing ink consists of a colorant, a vehicle and auxiliaries. Therefore, considering these components as a total, the above a) to d)
Condition must be satisfied. B) and c)
For the conditions, a colorant selected from disperse dyes is used, and if at least the surface of the printing medium is plastic, heat dyeing is performed under appropriate heating conditions to remove the dye from the plastic surface. We can expect sufficient diffusion inside. In order to expect good diffusion efficiency, it is desirable to use a disperse dye composed of an anthraquinone-based, azo-based, nitro-based, quinoline-based or the like.

The conditions for the printing ink used in the present application are as follows: (1) The ink can be used in an ink jet system (low viscosity
(1) 0.5-1P) (2) Sufficient ink on the flat master (surface wettability) (3) Accurate and sufficient transfer to soft pad (appropriate viscosity 100-200P, adhesion) (4) Coating It is necessary that the transfer and fixation to the printed material be smooth (relative adhesiveness to the pad / substrate to be printed, heat fixability). Polymer emulsion type ink (A) + α, where α is a surfactant and a thickener having an effect. For condition (2), improvement in wettability with the surface of the flat original plate (solvent, surfactant It is necessary to take measures by selecting the effect up), the material of the flat original plate, and the surface condition. Further, for the condition (3), A + α +
Cross-linking treatment (thickening, evaporating delay), where α is a cross-linking agent,
The cross-linking treatment is performed by heat, ultraviolet rays, bridging gas or the like corresponding to the cross-linking agent. For condition (4), it is necessary to select an ink having a large difference in adhesiveness between the surface of the printing medium and the surface of the pad, and to select a relative material of the printing medium and the pad.

The contradictory conditions of b) and e) are that, as a result of the experiment, the initial required viscosity of the ink is 0.5 to 1 poise, and it is necessary to jet the ink at a high speed from the nozzle diameter of the ink jet of about 50 to 100 μm. In addition, it is important for the ink properties to be sufficiently loaded as molecular particles on the flat original plate, and there should be no bleeding or spots. That is, the condition is that there be sufficient relative wettability and adhesiveness.

Further, in order to transfer this printing ink from a flat original plate to a soft pad, the viscosity must be 100 to 200 Poi.
About se is required. Therefore, the initial viscosity of 0.5 to 1
It must be changed from P to 100 to 200P in a short time. The present invention is characterized in that a cross-linking agent inserted in advance is rapidly cross-linked on a flat original plate to obtain the cross-linking agent. Naturally, the cross-linking agent must not disturb the initial conditions as an ink for ink jet.

In the case of cross-linking by a cross-linking treatment, the larger the amount of the cross-linking agent, the better it is, and there is naturally a limit. That is, it is necessary that the viscosity of the ink after cross-linking is 100 to 500 Poise suitable for subsequent printing, and an amount of about 0.2 part is appropriate. However, the amount of the crosslinking agent does not satisfy the viscosity required for the ink jet method. In the present invention, this is intended to be solved by greatly increasing the amount of the surfactant whose input amount is usually not more than the limit micelle value.

That is, a polymer 10 in which the amount of a surfactant is greatly increased with respect to the critical micelle value with respect to 0.2 parts of a crosslinking agent.
The problem is to be solved by adding 10 to 50 parts per 0 parts. As is clear from the embodiment, by adding a suitable surfactant, both the ink-jet printing and the printing on the printing substrate can be carried out with a crosslinking agent having a suitable viscosity through a crosslinking treatment with a crosslinking agent. Can be obtained.

On the other hand, in Embodiment 4, the amount of the surfactant added is too large, and the amount of the surfactant is 62 parts per 100 parts of the polymer. However, the initial ink viscosity is extremely reduced, and the thickening due to the cross-linking treatment is not sufficient. In this case, there is much interference due to bleeding between particles during direct printing, and the thickening due to the cross-linking treatment is not sufficient. Since the transfer was not sufficient, the transfer accuracy to the soft pad and the transfer to the acrylic resin plate were poor in printing accuracy. This is presumably because the amount of the surfactant was too large and crosslinking was difficult.

Embodiment 5 is a case where the amount of the surfactant added is too small (6 parts per 100 parts of polymer), and the initial ink viscosity is as large as 1.8 Poise due to the effect of the crosslinking agent. Therefore, printing by the ink jet itself becomes unstable, and the printing accuracy is about 3 line segment errors.
%, The error between frames was not appreciable about 5%, and many spots were observed on the printed surface. This is considered to indicate the lower limit of the surfactant when the crosslinking agent is added. That is, the gist of the present invention can be sufficiently achieved by a combination of a crosslinking treatment with a surfactant and a crosslinking agent. However, as a limiting condition, the addition amount of the surfactant is 10% per 100 parts of the polymer. ~ 50 parts was confirmed to be appropriate.

The effects of the printing method of the present invention were confirmed by the following embodiments. Embodiment 1 A water-soluble printing ink was prepared according to the following formulation. 1) Anthraquinone-based disperse dye (Disperse Blue Extra, molecular weight 148) 3 parts 2) Acetone 8 parts 3) Nonionic surfactant (EMULGEN909 Kao Corporation) 1 part 4) Water 50 parts 5) 2-ethylhexyl acrylate-methacryl Acid-based nonionic aqueous polymer emulsion (solid content 8%) 125 parts 6) Castor oil (castor oil / acetone 1: 1) (evaporation retarder) 5 parts 7) Rosin acid (thickener) 5 parts 8) Diethylene glycol 10 Part 9) Al-acetylacetonato nitrate complex (crosslinking agent) 0.2 part First, 1) and 2) are mixed and dissolved, and 3) and 4) are further added and mixed, and 5), 6), 7) and 8) was added gradually, and 2 parts of 9) were added per 100 parts of the polymer to a well-mixed mixture and mixed well for about 3 hours. The viscosity at this time is 0.8
Poise. Using this printing ink, an aluminum flat plate was directly printed by an inkjet method (100 μm in diameter). This was subjected to a cross-linking treatment with hot air of 100 ° C. for 5 minutes. The viscosity rose to 150 Poise equivalent (viscosity comparison). This was transferred to a soft NBR pad, and further transferred and printed on an acrylic resin plate.
Heat fixing was performed in. Both direct printing and transfer conditions were good, and good transfer results were obtained in print accuracy, color tone, and diffusion condition.

Embodiment 2 A water-soluble printing ink was prepared according to the following formulation. 1) Diazo compound-based disperse dye (Disperse Red® molecular weight 238) 4 parts 2) acetone 15 parts 3) nonionic surfactant (Kao Corporation EMULGEN909) 1 part 4) water 50 parts 5) castor oil / acetone ( 1: 1) 5 parts 6) Rosin acid 5 parts 7) Solvent ethylene glycol monobutyl ether 10 parts 8) Water-dispersible polymer emulsion (2-ethylhexyl acrylate / non-ionic aqueous polymer emulsion of methacrylic acid polymer, solid content 8%) 125 parts 9) Crosslinking agent 0.2 parts of Al-acetylacetonate nitrate complex 1) to 4) are mixed in advance, 5) to 8) are added thereto, and the mixture is gradually mixed and dispersed. Then, the crosslinking agent of 9) is added thereto. Mix well for 3 hours. The viscosity in this state was 1.0 Poise. Using this printing ink, an aluminum plate was directly printed by an inkjet method (diameter: 100 μm) and subjected to a crosslinking treatment by heating with hot air at 120 ° C. for 5 minutes. This increased the viscosity to 190 Poise (viscosity comparison). This was transferred to a soft NBR pad, further transferred to an acrylic resin plate, and fixed by heating at 150 ° C. for 5 minutes. The results of direct printing and transfer were good, and the printing accuracy, color tone, and diffusion state were also good.

Embodiment 3 A water-soluble printing ink was prepared according to the following formulation. 1) Water-dispersible diazo dye (Disperse Fast Yellow 3 Molecular weight 192) 3 parts 2) Ethanol 8 parts 3) Water 50 parts 4) Anionic surfactant (dispersant demol LP (Kao Corporation) 1 part) 5) Castor Oil / ethanol (1: 1) 5 parts 6) rosin acid 5 parts 7) dodecyl alcohol 10 parts 8) water-dispersible polymer emulsion (2-ethylhexyl acrylate / methacrylic acid polymer anionic emulsion, solid content 8%, 125 parts) 9 ) Crosslinking agent Al-acetylacetonate nitrate complex 0.2 part First, 1) to 4) were dissolved and dispersed, and 5) to 8) were gradually added thereto and mixed well. Mix well for hours. The viscosity at this time was 1.2 Poise. This printing ink is used to print directly on an aluminum flat plate by an ink jet method (100 μm diameter).
Hot air heating was performed at 20 ° C. for 5 minutes. The viscosity is 210 Poi
It was equivalent to se (viscosity comparison). This was transferred to a soft NBR pad, further transferred to an acrylic resin plate, and heated and fixed at 120 ° C. for 5 minutes. Although there are some spots in direct printing, the transfer result is good, printing accuracy, color tone,
The diffusion state was generally good.

Embodiment 4 A water-soluble printing ink was prepared according to the following formulation. 1) diazo compound-based disperse dye (Disperse Red® molecular weight 238) 4 parts 2) acetone 15 parts 3) nonionic surfactant (Kao Corporation EMULGEN909) 2 parts 4) water 50 parts 5) castor oil / acetone ( 1: 1) 5 parts 6) Rosin acid 5 parts 7) Solvent ethylene glycol monobutyl ether 10 parts 8) Water-dispersible polymer emulsion (2-ethylhexyl acrylate / non-ionic aqueous polymer emulsion of methacrylic acid polymer, solid content 8%) 125 parts 9) Crosslinking agent 0.2 parts of Al-acetylacetonate nitrate complex 1) to 4) are mixed in advance, 5) to 8) are added thereto, and the mixture is gradually mixed and dispersed. Then, the crosslinking agent of 9) is added thereto. Mix well for 3 hours. The viscosity in this state was 0.2 Poise. Using this printing ink, an aluminum plate was directly printed by an inkjet method (diameter: 100 μm) and subjected to a crosslinking treatment by heating with hot air at 120 ° C. for 5 minutes. Thereby, the viscosity was equivalent to 60 Poise (viscosity comparison). This was transferred to a soft NBR pad, further transferred to an acrylic resin plate, and fixed by heating at 150 ° C. for 5 minutes. In this case, there was much interference due to bleeding between particles during direct printing, and the thickening due to the crosslinking treatment was not sufficient, and the printing accuracy was poor for both transfer to the soft pad and transfer to the acrylic resin plate. This is presumably because the amount of the surfactant was too large and crosslinking was difficult.

Embodiment 5 A water-soluble printing ink was prepared according to the following formulation. 1) Diazo compound-based disperse dye (Disperse Red® molecular weight 238) 4 parts 2) Acetone 15 parts 3) Nonionic surfactant (Kao Corporation EMULGEN 909) 0.2 parts 4) Water 50 parts 5) Castor oil / Acetone (1: 1) 5 parts 6) Rosin acid 5 parts 7) Solvent ethylene glycol monobutyl ether 10 parts 8) Water-dispersible polymer emulsion (non-ionic aqueous polymer emulsion of 2-ethylhexyl acrylate / methacrylic acid polymer, solid content 8%) 125 parts 9) Cross-linking agent Al-acetylacetonato nitrate complex 0.2 parts 1) to 4) are mixed in advance, and 5) to 8) are added thereto and mixed and dispersed gradually, and then the cross-linking agent of 9) is further added. Was added and mixed well for 3 hours. The viscosity in this state is 1.8 Poise
Met. Using this printing ink, an aluminum plate was directly printed by an inkjet method (diameter: 100 μm) and subjected to a crosslinking treatment by heating with hot air at 120 ° C. for 5 minutes. This resulted in a viscosity equivalent to 250 Poise (viscosity comparison). This was transferred to a soft NBR pad, further transferred to an acrylic resin plate, and fixed by heating at 150 ° C. for 5 minutes. In this case, the direct printing by the ink jet itself was unstable, many spots were observed on the printing surface, and the transfer accuracy to the soft pad and the transfer to the acrylic resin plate were poor. It is considered to indicate the lower limit of surfactant with the addition of a crosslinking agent.

In each of the embodiments, printing was performed in a grid pattern having a line width of 0.5 mm and a pitch of 5 mm, and printing defects such as errors in line width and grid spacing, spots, cuts, and unevenness were measured.
As for the quality of the diffusion state, the average depth of diffusion was measured based on the printed cross section, and 0.3 mm or more was determined to be good. The viscosity after the cross-linking treatment was estimated from a comparison between the viscosity measured in advance and the viscous state of the finger.

For a colorant having a relatively large effect on viscosity, it is necessary to use a dye or pigment having a small molecular weight. As a result of the experiment, it was found that a low molecular weight disperse dye having a molecular weight of 200 to 550 is preferable. The content is preferably a substituted anthraquinone or monoazo type. Further, the upper limit molecular weight was set to 550 from the limit of the molecular weight of the monoazo dye. The lower limit of the molecular weight is set by the limit of the molecular weight of the anthraquinone dye.

The flat original plate as the intermediate medium is of course capable of sufficiently withstanding the heating caused by the cross-linking treatment, but has a sufficient wettability for the printing ink to be applied during ink jet printing. It is necessary to use a metal plate such as an aluminum alloy or a rubber or rubber-like material such as nitrile rubber, styrene-butadiene rubber, or chloroprene rubber. The printing surface is desirably a surface having an appropriate roughness.

The soft pad to be transferred from the flat original plate must have an elongation rate and followability sufficient to cover a printing curved surface from a flat surface, and rubber or a rubber-like material is preferable. . The soft pad is basically of a solid type, but may be of a type (rubber pad) in which an elastic thin film is held by an air cushion.

When the printing medium is a metal, it is desirable that at least the printing surface is made of plastic and that the printing paint is diffused into the interior by heat fixing after printing to extend the life of the printing surface. In order to sufficiently transfer the ink on the soft pad in combination with the adhesiveness to the metal, it is necessary for the plastic to have a large surface energy of the ink / substrate relative to the ink / soft pad. Acrylic resin, polyester resin, nylon and the like are preferred.

In this case, the heating condition of the heat penetration fixing after the transfer to the printing medium is 50 to 160 ° C., which is lower than the pressure and heating condition in the normal transfer printing, and the heating time is 5 to 300 min. You need a degree. These conditions differ depending on the type of the disperse dye and the type of the plastic material provided on at least the surface of the printing medium. For example, if the plastic is nylon 6, 250 at 50-60 ° C.
~ 300 min. Condition.

It is not preferable that the ink jet system used in the present invention presupposes heating as in the bubble system. An electromechanical conversion type injection method using a piezoelectric element or a diaphragm is suitable. In this case, since the flow resistance ψ of the nozzle or orifice diameter is inversely proportional to the square of the diameter, the square root value of the viscosity increase factor, that is, about 2 to 4 times the normal diameter may be used.

According to the printing method of the present invention, transfer printing is premised. The diameter of the ink particles on the surface of the printing medium is enlarged by pressurization, and the gap between the ink particles is small even if the resolution dpi is small. At first glance, there is an effect that a sense of continuity is provided as if the dpi were increased. In particular, the effect is great in monocolor printing.

[0029]

As described above, the present invention relates to a method for printing on a printing substrate having a curved surface, wherein printing is performed directly on a flat original plate by an ink jet method using an appropriate ink, and the viscosity is increased by a crosslinking treatment. Is transferred to a soft pad that has a shape similar to that of the substrate, and then transferred to the substrate for printing. It is now possible to print.

Claims (4)

[Claims] 1. A method for printing on a printing substrate having a curved surface by an offset printing method, wherein a direct printing is performed on a flat original by an ink jet method as a first step, and an ink on the flat original is increased as a second step. Viscosity treatment, as a third step, transferred from the flat original plate to a soft pad having a curved surface substantially similar to the printing surface of the printing medium, and in the fourth step, transferring the soft pad to contact the printing surface of the printing object, A method for printing on a curved surface, comprising a fixing step. 2. An ink used for direct printing by the ink jet method, comprising a disperse dye, a cross-linking agent and a surfactant in an amount equal to or greater than a limit micelle value, wherein the thickening treatment is a cross-linking treatment. The method for printing on a curved surface according to claim 1. 3. The ink used for direct printing by the ink jet method has a crosslinking agent content of 0.1 to the total amount.
The method for printing on a curved surface according to claim 1 or 2, wherein the surfactant content is 10 to 50 parts per 100 parts of the polymer. 4. The ink used for direct printing by the ink jet method has a viscosity of 0.5 to 1 in the first step.
The method for printing on a curved surface according to any one of claims 1 to 3, wherein the second step is a Poise, and the second step is 100 to 200 Poise by a crosslinking treatment.