JP2012144698A - Method for printing on nonpermeable printing medium, and ink set - Google Patents

Abstract

An ink fixing property that is sufficiently strong that an image does not peel off even when rubbed with a finger or nail when printed on a non-permeable printing medium such as a PET sheet using an aqueous ink containing an encapsulated pigment as a pigment. Provide a printing method to achieve the above.
An epoxy resin-containing resin is encapsulated on a treated surface of a non-permeable printing medium surface-treated with an amine-based silane coupling agent, a vinyl-based silane coupling agent or a pretreatment agent containing polyethyleneimine. A method for printing on a non-permeable printing medium, characterized in that an image is formed with a water-based ink comprising the prepared pigment as a color material.
[Selection figure] None

Description

  The present invention relates to a method for printing on a non-permeable printing medium using water-based ink and an ink set used in the method.

  Inkjet printers can easily perform full-color printing, and can also print on non-permeable printing media other than paper. Examples of printed matter using such a non-permeable printing medium include seals, labels, posters, bulletin boards, outdoor sign displays, bath wrapping, etc. In such printed matter, in addition to weather resistance, water resistance, strong ink fixing Sex is required. At present, in order to satisfy weather resistance, water resistance and ink fixing property, a transparent sheet is laminated on the surface of a printed material, but there is a problem in that it leads to cost increase.

  As a non-permeable printing medium conventionally used in these applications, a soft vinyl chloride sheet is generally used. However, in order to satisfy further weather resistance, heat resistance, environmental suitability, etc., a polyethylene terephthalate (PET) sheet is used. In many cases, use is required. However, even though the PET sheet has better heat resistance and environmental suitability than the vinyl chloride sheet, it has poor ink fixability.

  Examples of inks conventionally used for printing on such non-permeable printing media include oil-based inks such as UV ink (Patent Document 1) and low-boiling-point solvent ink (Patent Document 2) containing a pigment as a colorant. However, these require additional equipment such as a UV irradiation device and an exhaust equipment, and also have environmental suitability problems such as safety and odor of solvents and monomers.

  On the other hand, the water-based ink is advantageous in that it has few environmental suitability problems and does not require additional equipment as described above. Water-based inks containing pigments as coloring materials include pigments dispersed with a dispersant, those using self-dispersing pigments with hydrophilic groups added to the pigments themselves, and water-insoluble polymer fine particles containing pigments. Some use encapsulated pigments dispersed in water. A pigment dispersed with a dispersant has a drawback of being inferior in long-term dispersion stability. Self-dispersing pigments have no problem in dispersion stability, but have a drawback of poor water resistance. In contrast, encapsulated pigments are advantageous in that they are excellent in storage stability and water resistance.

  Further, as a method for improving the pigment fixing property of water-based inks, it has been conventionally proposed to add a water-soluble resin or a water-insoluble resin aqueous emulsion to the ink (Patent Documents 3 and 4). However, the water-soluble resin is inferior in water resistance, and in the case of an inkjet ink, there is a risk of impairing ejection stability. In addition, aqueous emulsions of water-insoluble resins have water resistance but are poor in storage stability, and in the case of inkjet inks, there is a risk of clogging of nozzles when left in the head, recovery of ejection properties, etc. There is a problem. In contrast, the encapsulated pigment can impart fixing performance to the capsule resin, and it is not necessary to include an additional resin component in the ink. In the case of an inkjet ink, it has excellent storage stability and good ejection properties. This is advantageous.

  However, even when printing on a PET sheet with water-based ink with improved pigment fixability by the above method, the ink fixability required for seal and label applications, that is, enough that the image does not peel off even when rubbed with a nail It was difficult to ensure strong fixability.

JP 2002-241654 A JP 2005-330460 A Japanese Patent Laid-Open No. 10-245513 JP-A-4-18462

  An object of the present invention is to fix an ink sufficiently strong that an image is not peeled even when rubbed with a nail when printed on a non-permeable printing medium such as a PET sheet using an aqueous ink containing an encapsulated pigment as a pigment. To achieve sex.

  As a result of intensive studies under the above-mentioned objectives, the present inventors have surfaced a non-permeable printing medium such as a PET sheet with an amine-based silane coupling agent, a vinyl-based silane coupling agent, or a pretreatment agent containing polyethyleneimine. After the treatment, it was found that the above object can be achieved by printing on the treated surface with an aqueous ink provided with a pigment encapsulated with a resin containing an epoxy group as a coloring material, and the present invention has been completed. .

  That is, according to one aspect of the present invention, an epoxy group is formed on the treated surface of a non-permeable printing medium surface-treated with a pretreatment agent containing an amine-based silane coupling agent, a vinyl-based silane coupling agent, or polyethyleneimine. There is provided a method for printing on a non-permeable printing medium, characterized in that an image is formed with a water-based ink provided with a pigment encapsulated with a resin containing a coloring material. In order to improve the fixability of the ink, the image may be further heated after the image is formed on the treated surface with the water-based ink.

  According to another aspect of the present invention, an ink set for printing on a non-permeable printing medium, an amine-based silane coupling agent, a vinyl-based silane coupling agent, or a pretreatment agent containing polyethyleneimine, An ink set comprising at least a water-based ink provided with a pigment encapsulated with a resin containing an epoxy group as a coloring material is provided.

According to a preferred embodiment of the present invention, the surface of the non-permeable printing medium is subjected to surface treatment with the pretreatment agent, particularly with the pretreatment agent containing an amine-based silane coupling agent or a vinyl-based silane coupling agent. Corona treatment or excimer UV treatment.
According to another preferred embodiment of the present invention, the pretreatment agent comprises a mixture of polyethyleneimine and a cationic or nonionic aqueous resin emulsion.

  According to the present invention, an impermeable printing medium is surface-treated with an amine-based silane coupling agent, a vinyl-based silane coupling agent or a pretreatment agent containing polyethyleneimine, and then encapsulated with a resin containing an epoxy group. Printing on the treated surface with a water-based ink comprising a pigment as a coloring material, the pretreatment agent on the surface of the print medium reacts with the epoxy group of the encapsulating resin and binds firmly, and ink fixability Is remarkably improved, and a printed matter excellent in water resistance, weather resistance and scratch resistance is obtained.

  Hereinafter, the present invention will be described in more detail. In the present specification, “(meth) acryl” and “(meth) acrylate” mean “acryl and / or methacryl” and “acrylate and / or methacrylate”, respectively.

(1) Water-based ink The water-based ink used in the present invention includes a pigment encapsulated with a resin containing an epoxy group as a color material.

  The pigment encapsulated with a resin containing an epoxy group is not particularly limited as long as the resin coating the pigment contains an epoxy group. Such encapsulated pigments can be produced by an acid precipitation re-dissolution method, a phase inversion method, a miniemulsion polymerization method, or the like. Among these, the miniemulsion polymerization method is preferable from the viewpoint of easy introduction of epoxy groups.

  In the acid precipitation re-dissolution method, a pigment is dispersed in an aqueous medium neutralized with an anionic group-containing resin, and the resin and the pigment are precipitated by making the pH of the aqueous medium acidic, and the resin is fixed to the pigment. Thereafter, an anionic group is neutralized using a basic compound, and the encapsulated pigment is re-dissolved in an aqueous medium. For example, it is described in JP-A-9-151342.

  In the phase inversion method, a pigment is dispersed in an organic solvent solution of an anionic group-containing resin, a basic compound is added, water is added while irradiating ultrasonic waves, phase inversion emulsification is performed, and then the solvent is distilled off. For example, it is described in JP-A-9-151342.

  In the mini-emulsion polymerization method, a pigment dispersion is prepared by adding a pigment in an oil-soluble radical polymerizable monomer and a hydrophobe having a solubility in water lower than that of the monomer, and then emulsifying the pigment dispersion in water and leaving the radical as it is. This is a method for producing an encapsulated pigment in which a pigment is coated with a resin by polymerization, and is described in, for example, JP-A Nos. 2001-131213 and 2008-163059. In this method, the encapsulated pigment used in the present invention can be obtained by including a vinyl monomer containing an epoxy group in the oil-soluble radical polymerizable monomer.

  Examples of the vinyl monomer containing an epoxy group used in the miniemulsion polymerization method include glycidyl methacrylate, 3,4 epoxy cyclohexyl methyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, acrylic glycidyl ether, and vinyl glycidyl ether. Radical polymerizable monomers other than vinyl monomers containing epoxy groups include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic. Acid (n-, i-, t-) butyl, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, (meth ) Alkyl ester or cycloalkyl ester of (meth) acrylic acid such as lauryl acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate; methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, ( An alkoxyalkyl ester of (meth) acrylic acid such as ethoxybutyl acrylate; , N- dimethylaminoethyl (meth) acrylate, N, N- diethylaminoethyl (meth) nitrogen-containing alkyl acrylates such as (meth) acrylate; vinyl acetate, styrene, alpha-chlorostyrene, and acrylonitrile. Further, the radical polymerizable monomer may contain a radical polymerizable oligomer having two or more acryloyl groups or methacryloyl groups in one molecule. Examples of the radical polymerizable oligomer include at least one selected from the group consisting of urethane acrylate, epoxy acrylate, and polyester acrylate. In order to facilitate emulsification of the pigment dispersion, a known emulsifier may be further added.

  The oil-soluble radically polymerizable monomer may further contain an organic solvent having no radical polymerizability in order to adjust the viscosity of the pigment dispersion. Such an organic solvent is not particularly limited as long as it is insoluble in water and miscible with the monomer and oligomer, but may be a low-boiling water-insoluble organic solvent in order to facilitate removal after polymerization. preferable. As the low-boiling water-insoluble organic solvent, those having a boiling point of 100 ° C. or less are preferable. Specific examples include ketone solvents and ester solvents (for example, ethyl acetate). Such an organic solvent need not be added if the pigment dispersion composed of the oligomer, monomer and pigment has a low viscosity. However, the lower the viscosity of the solution, the better the dispersibility of the pigment and the smaller the particle size of the oil phase particles of the O / W emulsion, so the addition of such an organic solvent is useful. The blending amount of the organic solvent is preferably 0 to 80% by mass based on 100% by mass of the entire pigment dispersion.

  In the present invention, as the pigment, any of inorganic pigments and organic pigments can be used. Specifically, carbon black, cadmium red, chrome yellow, cadmium yellow, chromium oxide, viridian, titanium cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindo Rinone pigments, dioxazine pigments, selenium pigments, perylene pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments and the like can be suitably used. These pigments may be used alone or in appropriate combination.

  The encapsulated pigment aqueous dispersion obtained as described above can be used as it is as an aqueous ink, but when used as an inkjet ink, it is produced during the coarse particles contained in the aqueous dispersion or during polymerization. It is necessary to remove the aggregate of the emulsion particles. Therefore, an inkjet ink can be prepared by applying the aqueous dispersion of the encapsulated pigment obtained as described above to a centrifuge or a filter.

  In order to adjust the surface tension of the inkjet ink to 40 mN / m or less suitable for ink ejection, a surfactant or an additional solvent is added to the aqueous dispersion of the encapsulated pigment obtained as described above. You can also In addition, in order to improve the storage stability and on-machine stability of inkjet ink, or to adjust the ink viscosity, a high boiling water-soluble organic solvent (glycerin, glycol solvent, glycol ether solvent) may be added. Good.

(2) Pretreatment agent In the present invention, before printing with the aqueous ink, the surface of the non-permeable printing medium contains a pretreatment agent containing an amine-based silane coupling agent and a vinyl-based silane coupling agent in advance. It is necessary to perform surface treatment with a pretreatment agent or a pretreatment agent containing polyethyleneimine. For this surface treatment, an amine-based silane coupling agent, a vinyl-based silane coupling agent, or a pretreatment solution in which polyethyleneimine is dissolved in an appropriate solvent can be used. Examples of the solvent include water and an acetic acid aqueous solution. The concentration of the silane coupling agent or polyethyleneimine in the pretreatment liquid is preferably 1 to 30% by mass.

Examples of the amine-based silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane N-2- (aminoethyl) -3-aminopropyltrimethoxysilane N-2- (aminoethyl). ) -3-Aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine and its partial hydrolysis Products, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, and the like.
Examples of the vinyl silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, and vinylethoxysilane.
As the polyethyleneimine, polyethyleneimine having a molecular weight of 300 to 70000 is preferably used. In the case where the pretreatment agent contains polyethyleneimine, it is preferable to mix a cationic or nonionic aqueous resin emulsion with the pretreatment agent in order to enhance the fixability thereof. Examples of cationic aqueous resin emulsions include Hydran CP7050, Hydran CP7610 (manufactured by DIC), Superflex 620, Superflex 650 (Daiichi Kogyo Seiyaku), Arrow Base CB1200 (manufactured by Unitika), Vinibrand 2651 (manufactured by Nisshin Chemical) Etc. Examples of nonionic water-based resin emulsions include Superflex, Superflex 500M, Superflex E2000, Superflex E4000 (Daiichi Kogyo Seiyaku), Bondick 2210, Bondick 2220 (DIC), and Vinibrand 2685 (Nisshin Chemical). Manufactured) and the like.

(3) Printing method The printing method of the present invention is performed by surface-treating a non-permeable printing medium with the pretreatment agent and then forming an image on the treated surface using the aqueous ink by a method such as printing. can do. Then, by heating the formed image, the reaction between the treated surface and the ink can be promoted, and a strong ink fixing property can be achieved. As a heating method, an existing method such as leaving the print medium in a room maintained at a high temperature, applying hot air to the print medium, or transporting the print medium under a heated roll can be used.

  The surface treatment of the non-permeable printing medium using the pretreatment agent may be performed by uniformly coating the surface of the printing medium with a pretreatment liquid using a brush, a roller, a bar coater, or the like, or by inkjet The print medium surface may be treated in whole or in part by printing means such as printing and gravure printing. The surface of the pretreated non-permeable printing medium is preferably dried before printing. As a drying method, an existing method such as leaving the print medium in a room kept at a high temperature, applying hot air to the print medium, or transporting the print medium under a heated roll can be used.

  The image forming method using the water-based ink is not particularly limited, and various printing methods such as gravure printing, stencil printing, and ink jet printing can be used.

  The printing method of the present invention can also be carried out by printing a pretreatment liquid on a print medium by ink jet printing and then printing the aqueous ink on the pretreatment liquid on the print medium by ink jet printing. .

  It is advantageous to constitute and sell an ink set including at least the pretreatment liquid and the oil-based ink so that the printing method of the present invention, particularly the inkjet printing method, can be easily performed.

  In the present invention, the impermeable printing medium is not particularly limited, and a resin film made of plastic such as vinyl chloride, PET, and polycarbonate, an OHP sheet, a disk, and a metal plate can be used.

  In the present invention, the surface of the non-permeable printing medium is subjected to a corona discharge treatment or a surface treatment with a pretreatment agent, particularly a pretreatment agent containing an amine silane coupling agent or a vinyl silane coupling agent. Excimer UV irradiation treatment is preferable. By performing such a treatment, the adhesion between the pretreatment agent and the print medium can be strengthened, and the ink fixability can be further strengthened.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this Example.

Example 1
(1) Production of Encapsulated Pigment Dispersion The following components were mixed in the following amounts and dispersed with a bead mill to obtain a pigment dispersion.

Carbon black (MA11 (trade name) manufactured by Mitsubishi Chemical) 7g
Pigment dispersant (Solsperse 32000 (trade name) manufactured by Lubrizol) 2g
1,9-nonanediol diacrylate monomer (manufactured by Kyoeisha Chemical) 2g
4-hydroxybutyl acrylate glycidyl ether monomer (Nippon Kasei) 2g
Urethane oligomer UV3200 (trade name; manufactured by Nihon Gosei) 2g
30 g of ethyl acetate (manufactured by Wako Pure Chemical Industries)
Total 45g

(2) Preparation process of O / W type emulsion The following components were mixed with the following compounding quantity, and the water phase was obtained.

52g of water (distilled water)
Reactive emulsifier (AQUALON KH-10 (trade name), manufactured by Daiichi Kogyo Seiyaku) 1g
Polyethylene glycol monomethacrylate (PE200 (trade name) manufactured by NOF Corporation) 2g
Total 55g

  Into 45 g of the pigment dispersion obtained in (1) above, 0.1 g of an initiator (azobisisobutyronitrile) is added, and then added to the aqueous phase and emulsified with an ultrasonic disperser. An O / W type mini-emulsion was obtained.

(3) Polymerization step of O / W type emulsion The O / W type emulsion prepared in (2) above was heated to 70 ° C. under a nitrogen atmosphere and stirred for 4 hours to prepare an aqueous dispersion of encapsulated pigment fine particles. .

(4) Solvent Removal Step The aqueous dispersion of encapsulated pigment fine particles prepared in (3) above was heated under reduced pressure with an evaporator to remove ethyl acetate.

(5) Ink production process The aqueous dispersion of encapsulated pigment fine particles obtained in (4) above is centrifuged at 20000 G for 6 minutes to remove aggregates and coarse particles. Mix to create ink.

80 g of an aqueous dispersion of encapsulated pigment fine particles obtained above
Diethylene glycol 19g
Surfynol 465 (trade name; manufactured by Air Products) 1g
Total 100g

(6) Pretreatment of PET sheet 10% amine-based silane coupling agent N-2- (aminoethyl) -3-aminopropyltrimethoxysilane KBM603 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.) in 2% acetic acid aqueous solution % Diluted was prepared as a pretreatment agent.
After a 50 μm PET sheet was subjected to corona discharge treatment, the pretreatment agent was applied with a 4 mill bar coater and dried by heating at 120 ° C. for 10 minutes.

(7) Printing with water-based ink After printing with a commercially available ink jet printer (manufactured by Epson) using the water-based ink prepared in (5) above, the surface of the PET sheet pretreated in (6) above is 120 ° C. for 20 minutes. Heat-dried.

(8) Evaluation of Printed Image The ink fixability of the printed matter obtained in (7) above was evaluated by the following method. The results are shown in Table 1.
(8-1) Finger rubbing A tissue was applied to the fingertip and the image was rubbed strongly, and evaluation was performed according to the following criteria.
Evaluation criteria:
○: The tissue is not soiled.
X: The tissue is lightly colored.

(8-2) Wet friction A cotton cloth moistened with water was attached to the clock meter, and was reciprocated 10 times, and evaluated according to the following criteria.
Evaluation criteria:
○: Cotton cloth is not soiled.
Δ: The cotton cloth is lightly colored.
X: Cotton cloth is dirty with color.

(8-3) Nail rubbing A nail was rubbed strongly against an image and evaluated according to the following criteria.
Evaluation criteria:
○: No change in image.
Δ: The image is slightly peeled off.
X: The image is peeled off.

Example 2
The same procedure as in Example 1 was carried out except that a glycidyl methacrylate monomer was used in place of the 4-hydroxybutyl acrylate glycidyl ether monomer when the pigment dispersion of Example 1 (1) was prepared, and an encapsulated pigment dispersion was prepared. . The results are shown in Table 1.

Example 3
The same procedure as in Example 1 was performed except that the corona treatment performed in the pretreatment of the PET sheet of Example 1 (6) was omitted. The results are shown in Table 1.

Example 4
Instead of the amine silane coupling agent KBM603 in the pretreatment of the PET sheet of Example 1 (6), a vinyl silane coupling agent vinyltriethoxysilane KBM1003 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.) was used. Except for this, the same procedure as in Example 1 was performed. The results are shown in Table 1.

Example 5
The same procedure as in Example 1 was performed except that the excimer UV treatment was performed instead of the corona treatment performed in the pretreatment of the PET sheet of Example 1 (6). The results are shown in Table 1.

Comparative Example 1
An encapsulated pigment dispersion was prepared without using the 4-hydroxybutyl acrylate glycidyl ether monomer at the time of preparing the pigment dispersion of Example 1 (1), and the PET sheet was used as it was without any pretreatment. The same procedure as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 2
The same procedure as in Example 1 was conducted except that the encapsulated pigment dispersion was prepared without using the 4-hydroxybutyl acrylate glycidyl ether monomer at the time of preparing the pigment dispersion of Example 1 (1). The results are shown in Table 1.

Comparative Example 3
In the pretreatment of the PET sheet of Example 1 (6), only the corona treatment was performed, and the same treatment as in Example 1 was performed except that the pretreatment agent was not used. The results are shown in Table 1.

Comparative Example 4
In the pre-treatment of the PET sheet of Example 1 (6), instead of the amine silane coupling agent KBM603, the epoxy silane coupling agent 3-glycidoxypropyltriethoxysilane KBE403 (trade name; Shin-Etsu Chemical Co., Ltd.) This was performed in the same manner as in Example 1 except that the above product was used. The results are shown in Table 1.

Comparative Example 5
In the pretreatment of the PET sheet of Example 1 (6), instead of the amine silane coupling agent KBM603, methacryloxy silane coupling agent 3-methacryloxypropyltrimethoxysilane KBM503 (trade name; Shin-Etsu Chemical Co., Ltd.) The same procedure as in Example 1 was conducted except that the The results are shown in Table 1.

Comparative Example 6
In the pretreatment of the PET sheet of Example 1 (6), instead of the amine silane coupling agent KBM603, a mercapto silane coupling agent 3-mercaptopropyltrimethoxysilane KBM803 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.) ) Was carried out in the same manner as in Example 1. The results are shown in Table 1.

  From the results of Table 1, in Examples 1 to 5, the PET sheet was surface-treated with an amine-based silane coupling agent or a vinyl-based silane coupling agent, and encapsulated with a resin containing an epoxy group as a coloring material for aqueous ink. Since the pigment used was used, the ink fixing property, in particular, the resistance to scratching was excellent. On the other hand, in Comparative Examples 1 to 6, since at least one of the silane coupling agent and the pigment does not satisfy the requirements of the present invention, the ink fixing property, in particular, wet friction or nail scratch resistance was inferior.

Example 6
In the pretreatment of the PET sheet of Example 1 (6), instead of the amine-based silane coupling agent KBM603, 1 part of Epomin P1000 (manufactured by Nippon Shokubai Co., Ltd.) and a cationic aqueous resin emulsion (Superflex 620 (No. 1) A polyethyleneimine-based pretreatment agent mixed with 9 parts of Ichiko Pharmaceutical Co., Ltd.) was prepared, and the pretreatment agent was applied to a 50 μm PET sheet with an 8 mill bar coater and then dried. Except this, the same procedure as in Example 1 was performed. The results are shown in Table 2.

Example 7
When preparing the pigment dispersion of Example 1 (1), a glycidyl methacrylate monomer was used in place of the 4-hydroxybutyl acrylate glycidyl ether monomer, and the same procedure was performed as in Example 6 except that an encapsulated pigment dispersion was prepared. . The results are shown in Table 2.

Example 8
This was performed in the same manner as in Example 6 except that a nonionic aqueous resin emulsion (Bondic 2220 (manufactured by DIC Corporation)) was used instead of the cationic aqueous resin emulsion, and the results are shown in Table 2.

Comparative Example 7
Example 6 except that only 10 parts of cationic resin emulsion (Superflex 620 (Daiichi Kogyo Seiyaku Co., Ltd.)) was used without using Epomin P1000 (Nippon Shokubai Co., Ltd.) as a pretreatment agent. The same was done. The results are shown in Table 2.

Comparative Example 8
The same procedure as in Example 6 was performed except that the encapsulated pigment dispersion was prepared without using the 4-hydroxybutyl acrylate glycidyl ether monomer when the pigment dispersion of Example 1 (1) was prepared. The results are shown in Table 2.

  From the results of Table 2, in Examples 6 to 8, the PET sheet was surface-treated with a polyethyleneimine-based pretreatment agent, and a pigment encapsulated with a resin containing an epoxy group was used as a colorant for aqueous ink. Excellent ink fixability. On the other hand, in Comparative Examples 1 and 2, since at least one of the pretreatment agent and the pigment does not satisfy the requirements of the present invention, the ink fixing property, particularly wet friction resistance, was inferior.

  The present invention provides a printing method using a water-based ink excellent in ink fixability to a non-permeable printing medium such as a PET sheet, and can be used in the field of printing using a water-based ink, particularly in the field of inkjet printing.

Claims (9)

A pigment encapsulated with a resin containing an epoxy group on a treated surface of a non-permeable printing medium surface-treated with a pretreatment agent containing an amine-based silane coupling agent, a vinyl-based silane coupling agent or polyethyleneimine. An image is formed with a water-based ink provided as a color material. 2. The method for printing on a non-permeable printing medium according to claim 1, further comprising heating the image after forming the image on the treated surface with the water-based ink. The printing method according to claim 1, wherein the surface of the non-permeable printing medium is subjected to corona treatment or excimer UV treatment before the surface treatment with the pretreatment agent. The printing method according to claim 1 or 2, wherein the pretreatment agent comprises a mixture of polyethyleneimine and a cationic or nonionic aqueous resin emulsion. The printing method according to claim 1, wherein the encapsulated pigment is produced by a miniemulsion polymerization method. An ink set for printing on a non-permeable printing medium, encapsulated with an amine-based silane coupling agent, a vinyl-based silane coupling agent or a pretreatment agent containing polyethyleneimine, and an epoxy group-containing resin. An ink set comprising at least a water-based ink comprising a pigment as a coloring material. The ink set according to claim 6, wherein the ink set is used for printing on a surface of a non-permeable printing medium that has been subjected to corona treatment or excimer UV treatment. The ink set according to claim 6, wherein the pretreatment agent comprises a mixture of polyethyleneimine and a cationic or nonionic aqueous resin emulsion. The ink set according to any one of claims 6 to 8, wherein the encapsulated pigment is prepared by a miniemulsion polymerization method.