Method for Preparing Large-area Structural Chromogenic Pattern by Ink-jet Printing and Anti-counterfeiting Method Based on Structural Color Change

Abstract

A method for preparing a large-area structural chromogenic pattern by ink-jet printing, a structural chromogenic pattern obtained by the method, and an anti-counterfeiting method based on a structural color change. A dispersion liquid containing mono-disperse colloidal microspheres with high index of refraction is is printed onto a piece of paper by using an ink-jet printer, and nano-microspheres are arranged and assembled on the paper to obtain a micro-structure having the features of being ordered from a short distance and disordered from a long distance. A pretty structural color can be observed by means of the interaction of the structure with light, thus displaying a pattern, changing the angle of observation, changing the brightness of the structural color, and hiding and displaying the pattern. The method is simple and convenient, is widely applicable, and can achieve the preparation and anti-counterfeiting of a large-area structural color without external stimulation.

Claims

1. A method for preparing a large-area structural chromogenic pattern by ink-jet printing, comprising the following processing steps of: (1) preparing mono-disperse colloidal microspheres: mixing the mono-disperse colloidal microspheres with high refractive index, additive with high boiling point, ethanol, glycerol, surfactant, defoaming agent, adhesive, pH regulator and deionized water, and performing ultrasonic dispersion on the mixture to obtain a stable mixed solution as ink and feeding the ink into an ink box of an ink-jet printer; (2) designing a pattern through computer software; (3) using the ink prepared in step (1) to print the pattern designed in step (2) on paper through ink-jet printing technology to obtain a large-area structural color pattern; wherein, the mono-disperse nano-microspheres with high refractive index is mono-disperse colloidal microspheres with a refractive index greater than 2; and the additive with a high boiling point is organic solvent with boiling point greater than 180 C.

2. The method according to claim 1, wherein the mono-disperse colloidal microspheres with high refractive index are one of cadmium sulfide, cuprous oxide, titanium dioxide, zinc sulfide and zinc oxide, and the mono-disperse colloidal microspheres have a particle diameter of 90 nm to 400 nm.

3. The method according to claim 1, wherein in the stable mixed solution obtained in step (1), a content of the mono-disperse colloidal microspheres is 5 wt % to 20 wt %, a content of the additive with high boiling point is 5 wt % to 15 wt %, a content of the ethanol is 8 wt % to 20 wt %, a content of the glycerol is 1 wt % to 5 wt %, a content of the surfactant is 2 wt % to 5 wt %, a content of the defoaming agent is 0.1 wt % to 0.2 wt %, a content of the adhesive is 1 wt % to 4 wt %, a content of the pH regulator is 2 wt % to 4 wt %, and the balance is the deionized water.

4. The method according to claim 1, wherein the additive with high boiling point is ethylene glycol, diethylene glycol or formamide.

5. The method according to claim 1, wherein the surfactant is OP-10 or polyvinylpyrrolidone.

6. The method according to claim 1, wherein the defoaming agent is tributyl phosphate.

7. The method according to claim 1, wherein the adhesive is one of polyvinyl alcohol, polyurethane resin and acrylic resin.

8. The method according to claim 1, wherein the pH regulator is triethanolamine, diethanolamine or ethanolamine.

9. The method according to claim 1, wherein the paper is one of coated paper, resin coated photo paper and high gloss photographic paper.

10. A large-area structural chromogenic pattern obtained on paper by the method according to claim 1 through an ink-jet printing technology.

11. A method for using the large-area structural chromogenic pattern obtained by the method according to claim 1 for anti-counterfeiting, wherein preparing dispersion solution of the colloidal microspheres of different types and/or different particle diameters as inks of different colors, and different color parts of the pattern are printed with different inks.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIGS. 1a, 1b and 1c illustrate respectively a digital photo, a scanning electron microscope image and a reflection spectrum image of a large-area red structural color pattern printed by ink-jet printing in example 1;

[0028] FIGS. 2a, 2b and 2c illustrate respectively a digital photo, a scanning electron microscope image and a reflection spectrum image of a large-area green structural color pattern printed by ink-jet printing in example 2;

[0029] FIG. 3a illustrates a hidden digital photo of a pattern in example 3, and the whole pattern is all yellow;

[0030] FIG. 3b illustrates a displayed digital photo of the pattern in example 3, the butterfly in the upper left corner is red, the butterfly in the lower right corner is green, and the rest is yellow;

[0031] FIG. 4 panel a and panel b illustrate digital photos of a quick-response matrix code when being hidden in example 4, the whole pattern is all yellow; and

[0032] FIG. 4 panel c and panel d illustrate digital photos of the quick-response matrix code when being displayed in example 4, a red QR code can be observed in FIG. 4 panel c, the rest is yellow; and a green QR code is observed in FIG. 4 panel d, and the rest is yellow.

DETAILED DESCRIPTION OF THE INVENTION

[0033] The examples in the invention are described with reference to the drawings, so that the invention can be better understood by those skilled in the art, and the protection scope of the invention can be defined.

Example 1

[0034] A large-area red structural color pattern is obtained by ink-jet printing of CdS ink.

[0035] Firstly, mono-disperse CdS colloidal microspheres were prepared, and the detailed preparation method was as follows:

[0036] 5 g of polyvinylpyrrolidone (PVP) powder was added into 150 mL of diethylene glycol, then cadmium nitrate and thiourea powder with equal amount of substance were added, wherein the amount of substance of the cadmium nitrate and the thiourea was 20 mmol, and then the mixture was stirred until all the powder was completely dissolved. The above solution was heated to 160 C. and thermal reaction for 5 h, then naturally cooled to a room temperature, and a product was centrifuged and then dried after washing with ethanol and water for 3 times. Mono-disperse CdS nano-particles with an average particle diameter of 335 nm were obtained.

[0037] A certain amount of the mono-disperse CdS microsphere powder obtained above was fully grinded, wherein a content of the mono-disperse CdS microspheres added was 12 wt %, a content of ethylene glycol was 5 wt %, a content of ethanol was 10 wt %, a content of glycerol was 5 wt %, a content of PVP was 2.7 wt %, a content of tributyl phosphate was 0.1 wt %, a content of polyvinyl alcohol was 1 wt %, a content of triethanolamine was 3 wt %, and the balance was deionized water. Ultrasonic processing was performed for 30 min to prepare uniformly dispersed ink.

[0038] The prepared ink is fed into an ink box, and the designed pattern is printed by an ink-jet printer, so that CdS nano-particles in the ink are uniformly deposited on high-gloss photo paper to obtain a micro-structure ordered in short range and disordered in long range, as shown in FIG. 1a, a large-area red structural color pattern is obtained.

Example 2

[0039] A large-area green structural color pattern is obtained by ink-jet printing of CdS ink.

[0040] Firstly, mono-disperse CdS colloidal microspheres were prepared, and the detailed preparation method was as follows:

[0041] 5 g of polyvinylpyrrolidone (PVP) powder was added into 150 mL of diethylene glycol, then cadmium nitrate and thiourea powder with equal amount of substance were added, wherein the amount of substance of the cadmium nitrate and the thiourea was 15 mmol, and then the mixture was stirred until all the powder was completely dissolved. The above solution was heated to 162 C. and thermal reaction for 6 h, then naturally cooled to a room temperature, and a product was centrifuged and then dried after washing with ethanol and water for 3 times. Mono-disperse CdS nano-particles with an average particle diameter of 270 nm were obtained.

[0042] A certain amount of the mono-disperse CdS microsphere powder obtained above was fully grinded, wherein a content of the mono-disperse CdS colloidal microspheres added was 15 wt %, a content of ethylene glycol was 5 wt %, a content of ethanol was 10 wt %, a content of glycerol was 5 wt %, a content of PVP was 3 wt %, a content of tributyl phosphate was 0.1 wt %, a content of polyvinyl alcohol was 1.5 wt %, a content of triethanolamine was 3 wt %, and the balance was deionized water. Ultrasonic processing was performed for 30 min to prepare uniformly dispersed ink.

[0043] The prepared ink is fed into an ink box, and the designed pattern is printed by an ink-jet printer, so that CdS nano-particles in the ink are uniformly deposited on high-gloss photo paper, as shown in FIGS. 2a-2c, a large-area green structural color pattern is obtained.

Example 3

[0044] Preparation of a large-area structural color pattern, and its hide or display based on a structural color brightness change.

[0045] Firstly, mono-disperse CdS colloidal microspheres with different particle diameters were prepared, and the detailed preparation method was as follows:

[0046] 5 g of polyvinylpyrrolidone (PVP) powder was added into 150 mL of diethylene glycol solution, then cadmium nitrate and thiourea powder with a molar ratio of 1 were added, and stirring was performed until all the powder was completely dissolved. The above solution was heated to 150-160 C. and thermal reaction for 5 h, then naturally cooled to a room temperature, and a product was centrifuged and washed with ethanol and water for 3 times, then was dried and grinded to obtain CdS powder with particle diameter of 270 nm.

[0047] 4.5 g of polyvinylpyrrolidone (PVP) powder was added into 150 mL of diethylene glycol solution, then cadmium nitrate and thiourea powder with a molar ratio of 1 were added, and stirring was performed until all the powder was completely dissolved. The above solution was heated to 150-160 C. and thermal reaction for 5 h, then naturally cooled to a room temperature, and a product was centrifuged and washed with ethanol and water for 3 times then was dried and grinded to obtain CdS powder with particle diameter of 290 nm.

[0048] 5 g of polyvinylpyrrolidone (PVP) powder was added into 150 mL of diethylene glycol solution, then cadmium nitrate and thiourea powder with a molar ratio of 1 were added, and stirring was performed until all the powder was completely dissolved. The above solution was heated to 150-160 C. and thermal reaction for 5 h, then naturally cooled to a room temperature, and a product was centrifuged and washed with ethanol and water for 3 times, then was dried and grinded to obtain CdS powder with particle diameter of 335 nm.

[0049] A certain amount of mono-disperse CdS microsphere powder with the three particle diameters above was fully grinded respectively for preparing inks respectively to print different parts of the pattern. For the preparation of the ink, a content of mono-disperse colloidal microspheres added was 15 wt %, a content of ethylene glycol was 5 wt %, a content of ethanol was 10 wt %, a content of glycerol was 5 wt %, a content of PVP was 3 wt %, a content of tributyl phosphate was 0.1 wt %, a content of polyvinyl alcohol was 1.5 wt %, a content of triethanolamine was 3 wt %, and the balance was deionized water. Ultrasonic processing was performed for 30 min to prepare uniformly dispersed ink. Three inks were fed into three ink boxes respectively. A pattern with two butterflies was designed through computer software, and a computer was connected with a printer.

[0050] The ink is printed on high-gloss photographic paper by using an ink-jet printer, an experimental condition is a room temperature, and a large-area structural color pattern with different colors is finally obtained. As shown in FIGS. 3a and 3b, (wherein a background color is printed with ink prepared by CdS nano-particles with a particle diameter of 290 nm, and an orange-yellow structural color can be obtained), when an angle of observation is closer to vertical incidence, a contrast ratio of structural colors of two butterflies to a structural color of a background is more obvious, and a pattern with three pretty structural colors can be observed; and when the angle of observation deviates from a vertical incident angle (>30), the structural colors of the butterflies and the background are covered by the body colors, while the body colors of the butterflies and the background are similar and are all yellow. At the moment, the contrast ratio of colors of the butterflies to the background is low, and the butterflies are hidden in a background pattern.

Example 4

[0051] Anti-counterfeiting application of a quick-response matrix code based on a structural color brightness change is provided.

[0052] The ink in the third example is used, a quick-response matrix code with a background is generated through computer software design, and the ink is printed on high-gloss photographic paper by using an ink-jet printer to obtain a large-area pattern with two structural colors. As shown in FIG. 4, when an angle of observation is closer to vertical incidence, a contrast of colors of a matrix code to a background is more obvious, two pretty structural colors can be observed, while the matrix code can be scanned and a link is obtained. A quick-response matrix code which can be hidden or displayed is obtained, and when the pretty structural color can be observed, the matrix code can be scanned and the link is obtained; and when the angle of observation deviates from the vertical incident angle (>30), the structural colors of the matrix code and the background are covered by the body colors of the matrix code and the background, while the body colors of the matrix code and the background are both yellow. At the moment, the matrix code is hidden in the background pattern and cannot be observed, and the matrix code cannot be scanned due to the low contrast of the matrix code and the background.

Example 5

[0053] A large-area red structural color pattern is obtained by ink-jet printing of ZnS ink.

[0054] Firstly, mono-disperse ZnS colloidal microspheres were prepared, and the specific preparation method was as follows:

[0055] A certain amount of polyvinylpyrrolidone was placed in a 250 mL three-necked flask, 75 mL of deionized water was added, and slow stirring and heating were performed. When a temperature reached 80 C., 0.01 mol of thioacetamide was added into a system, and stirred for 10 min for even mixing, 100 L of concentrated nitric acid was added, then 0.02 mol of Zn(NO.sub.3).6H.sub.2O was prepared into 5 mL of water solution after the reaction for 10 min, and added into a three-necked flask, a rotation speed was immediately increased to mix the mixture evenly, the rotation speed was reduced to 500 rpm after a few minutes, and a reflux reaction was performed for 3 h at 75 C. A product obtained was washed with deionized water for 3 times to 4 times to obtain mono-disperse ZnS nano-particles with an average particle diameter of 230 nm. Centrifugation and vacuum drying were performed for later use.

[0056] A certain amount of the mono-disperse ZnS microsphere powder was fully grinded, wherein a content of mono-disperse colloidal microspheres added was 10 wt %, a content of formamide was 10 wt %, a content of ethanol was 10 wt %, a content of glycerol was 2 wt %, a content of PVP was 2 wt %, a content of tributyl phosphate was 0.1 wt %, a content of polyvinyl alcohol was 1 wt %, a content of triethanolamine was 2 wt %, and the balance was deionized water. Ultrasonic processing was performed for 30 min to prepare evenly dispersed ink.

[0057] The prepared ink is fed into an ink box, and the designed pattern is printed by using an ink-jet printer, so that ZnS nano-particles in the ink are evenly deposited on RC photographic paper, and a large-area red structural color pattern is finally obtained.