Reversible color-changing anti-counterfeiting ink based on photoisomeric molecules as well as preparation method and application thereof

Abstract

The invention discloses reversible color-changing anti-counterfeiting ink based on photoisomeric molecules as well as a preparation method and application of the reversible color-changing anti-counterfeiting ink, and belongs to the technical field of functional materials and anti-counterfeiting. The ink is composed of 0.1%-5% of photoisomeric molecules, 15%-30% of a resin base material, 60%-80% of a solvent and 1%-5% of an auxiliary agent, the photoisomeric molecules are formed by mixing diarylethene and azobenzene derivatives, and through molecular structure optimization and polarity regulation and control of the resin base material, rapid reversible color change (response time lt, 5 seconds, delta lambda gt and 100 nm) under ultraviolet or visible light excitation is achieved. The innovation points comprise: 1) molecule-base material collaborative design, which inhibits free rotation of molecules to improve isomerization efficiency; 2) an ultraviolet absorbent and an antioxidant are added, so that environmental interference is shielded, and the stability (gt) of the ink is prolonged; 2 years); and 3) multi-mode anti-counterfeiting such as single-layer hidden pattern, multi-layer dynamic superposition, short-term verification failure and time-dependent verification is supported. The preparation method comprises ultrasonic dispersion, high-speed stirring and filtering processes, and is suitable for scenes such as silk-screen printing and ink-jet printing. The ink shows a high-contrast pattern after specific illumination, and the reversible cycle index is gt; the method can be widely applied to currency, certificates, medicine packaging and luxury anti-counterfeit labels, and the anti-counterfeit level and the user interaction experience are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-counterfeiting materials, and specifically relates to a light-responsive color-changing ink based on photoisomerizable molecules. The ink is suitable for anti-counterfeiting labels, security printing, smart packaging and other fields. It can achieve rapid and reversible color development / discoloration or color switching through light of a specific wavelength, and has high concealment, easy detectability and anti-counterfeiting properties. Background Art

[0002] Anti-counterfeiting technology has become a core means of ensuring product safety and brand reputation. Traditional anti-counterfeiting technologies (such as temperature-sensitive inks, fluorescent materials, and holographic patterns) are susceptible to imitation, rely on complex detection equipment, or suffer from irreversible color change. Photochromic materials are gaining attention due to their dynamic response properties, but the application of photochromic inks in existing technologies still suffers from the following drawbacks: 1. Slow light response: The color change process requires long periods of light exposure, making it difficult to meet rapid verification requirements; 2. Low contrast: The color changes are not obvious and difficult to distinguish with the naked eye; 3. Poor environmental stability: The ink is prone to spontaneous discoloration under natural light, resulting in information failure; 4. Irreversibility or poor recyclability: Most materials only support one-way color change or a limited number of cycles.

[0003] The present invention achieves high contrast, rapid reversible color change, and significantly improves environmental stability by optimizing the photoisomerization molecular structure and ink formula. Summary of the Invention

[0004] 1. Technical solution: The color-changing ink of the present invention is composed of the following components by mass percentage: Photoisomerizable molecules (0.1%-5%): A mixture of two molecules (diarylethenes and azobenzene derivatives) with reversible photoisomerization capabilities is selected. The isomerization wavelengths are in the ultraviolet (380 nm) and visible light (405 nm, 532 nm) ranges, and the two isomers have significant color differences (Δλ>100 nm). Resin base (15%-30%): acrylic resin or polyurethane resin, which provides ink film-forming properties and provides coating protection for photoisomerization molecules; Solvent (60%-80%): Environmentally friendly low-boiling point solvent (such as ethanol, ethyl acetate) to ensure the printability of ink; Additives (1%-5%): including dispersants, leveling agents, UV absorbers (used to suppress interference from non-excitation wavelengths) and antioxidants.

[0005] 2. Key innovations: Molecular-base collaborative design: By regulating the polarity of the resin base, the free rotation of photoisomerized molecules is restricted, thereby improving isomerization efficiency and color contrast; Dual protection mechanism: UV absorbers (such as benzotriazoles) are added to selectively shield ambient UV light, while antioxidants (such as vitamin E) delay molecular photofatigue, allowing the ink to be stored stably under natural light for more than 2 years; Multi-mode anti-counterfeiting: Supports rapid switching (5-10 seconds) between "display-hidden" and "color A-color B" to achieve multiple detections within a short period of time. It also supports slow switching (5-10 seconds for display and 1-2 hours for hiding) between "display-hidden" and "color A-color C" to prevent detection failure within a short period of time. Multi-layer printing can also be combined to achieve pattern overlay or information encryption.

[0006] 3. Preparation method: 1. Mix the photoisomerizable molecules with some solvent and disperse them by ultrasonication until they are completely dissolved; 2. Add the resin base and additives and stir at high speed to form a homogeneous system; 3. Filter to remove impurities, fill and store in a dark place. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to make the purpose and technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings: Figure 1 Schematic diagram of the two molecular structures involved in the patent.

[0008] Figure 2 The ink colors corresponding to the two isomers of diarylethenes.

[0009] Figure 3 These are the ink colors corresponding to the two isomers of azobenzene derivatives.

[0010] Figure 4 The ink color of a mixed solution of diarylethenes and azobenzene derivatives under different light conditions.

[0011] Figure 5 The ink color under different light conditions is obtained by spraying a mixed solution of diarylethenes and azobenzene derivatives on paper through a light-blocking plate with a specific pattern.

[0012] Figure 6 The color of the ink made from a mixed solution of diarylethenes and azobenzene derivatives appears when written on paper and exposed to different light. DETAILED DESCRIPTION

[0013] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0014] Components: Diarylethene ( Figure 2), azobenzene derivatives ( Figure 3 ) (4%), acrylic resin (20%), ethanol (75%), dispersant BYK-163 (1%), UV absorber Tinuvin 326 (2%).

[0015] Preparation: Dissolve diarylethenes and azobenzene derivatives in ethanol, add acrylic resin and additives, stir at 1000 rpm for 2 hours, and filter through a 0.2 μm filter membrane.

[0016] Features: Figure 4 As shown, the 405nm and 532nm light sources can achieve rapid "yellow-orange" switching (5-10s), enabling multiple detections in a short period of time. The 532nm and 380nm light sources can achieve slow "yellow / orange-purple" switching (development 5-10s, concealment 1-2h), rendering the detection ineffective in a short period of time, with a cycle number >1000 times.

[0017] 1. Single-layer label: such as Figure 5 、 Figure 6 As shown, printing hidden text or patterns requires a light source of a specific wavelength to activate; 2. Multi-layer label: The bottom layer is a permanent printed pattern, and the top layer is the ink of the present invention. After exposure to light, the two are superimposed to generate a dynamic anti-counterfeiting code; 3. Time-dependent anti-counterfeiting: Utilize the difference in ink fading speed to design "timeliness verification" (for example, after being irradiated with 380nm ultraviolet light, it cannot be verified again within a short period of time).

Claims

1. A photoisomerization color-changing ink, characterized in that It includes photoisomerizable molecules, resin base materials, solvents and additives, among which the photoisomerizable molecules account for 0.1%-5%, and the isomerization wavelength and color contrast meet Δλ>100 nm.

2. The ink according to claim 1, characterized in that The diarylethene molecules and the azobenzene derivative molecules synthesized by themselves. 3.An anti-counterfeiting mark, characterized in that Printing is performed using the ink described in claim 1, and reversible color change verification is achieved by irradiation with light of a specific wavelength.

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