Black ink for preventing oxidation discoloration during gold stamping and preparation method of black ink

Abstract

The invention discloses black ink capable of preventing oxidation discoloration during gold stamping, the black ink comprises a photocuring subsystem material and a latent thermocuring subsystem material, the photocuring subsystem material comprises hydrophobic low-functionality acrylic resin or isocyanate-based polyurethane acrylic resin, and the latent thermocuring subsystem material comprises hydrophobic low-functionality acrylic resin or isocyanate-based polyurethane acrylic resin. The latent thermal curing subsystem material comprises hydrophilic double-bond grafted water-based hydroxy acrylic resin and a latent thermal initiator of a PEG-PU-peroxide bond copolymer, and the black ink is characterized in that the photocuring subsystem material is quickly crosslinked and cured by utilizing low-energy UV light; the partial hydrophilic material can be rearranged and gathered on the surface during UV curing, and then the partial hydrophilic material and the thermosetting gilding adhesive layer are bonded through heating and pressurizing to complete gilding process preparation. A low-migration-rate ink layer is prepared through primary UV curing, a latent heat curing subsystem is caused to strengthen crosslinking through secondary heat curing, a compact diaphragm is prepared, and therefore carbon black migration is prevented in a multiple mode, and the gold stamping effect is prevented from being oxidized and discolored.

Description

Technical Field

[0001] The invention relates to the technical field of inks, and in particular to a black ink that prevents hot stamping, oxidation and discoloration, and a preparation method thereof. Background Art

[0002] In traditional hot stamping processes, black ink often uses carbon black as a pigment. However, carbon black contains acidic and alkaline impurities, and long-term contact with electroplated metal foil (especially aluminum) can easily cause oxidative corrosion, leading to shedding and discoloration of the hot stamping layer. To mitigate the effects of carbon black on electroplated aluminum foil, existing technologies have contributed the following solutions: (1) CN105462341A relates to a black ink for preventing oxidative discoloration of hot stamping and its preparation method and application method. The black ink for preventing oxidative discoloration of hot stamping is made by uniformly mixing yellow ink, red ink, blue ink and photoluminescent blue. When the black ink for preventing oxidative discoloration of hot stamping is used for printing, it is printed several times in an overlapping manner, so that the concentration requirements and blackness effect requirements can be met. The black ink for preventing oxidative discoloration of hot stamping of the present invention is a black ink prepared by mixing yellow ink, red ink, blue ink and photoluminescent blue, which meets the requirement of not containing carbon black, and solves the problem of oxidative discoloration caused by the contact of black ink with carbon black in the prior art with hot stamping materials to the greatest extent, and has the advantage of good hot stamping effect.

[0003] (2) CN115466539A discloses a hot stamping resistant black ink, comprising specific acidic carbon black, red pigment, blue pigment, varnish, oil, polytetrafluoroethylene wax and additives. The present invention uses carbon black with a pH value between 2.0 and 4.0, and the oxidation degree of the ink will be lower than that of conventional alkaline carbon black. In addition, on the basis of ensuring the black hue, the amount of blue pigment and red pigment used is increased to reduce the impact of black pigment on electroplated aluminum. In addition, during production, a wet production mode is used, first filling the capillaries of the pigment with water, and then replacing the water with a connecting material, which greatly reduces the adsorption of the capillaries. In addition, the present invention also adds a special micronized polytetrafluoroethylene wax to the ink composition. The characteristic of this wax is that it will float to the surface of the ink film after drying, which is equivalent to adding a protective layer between the carbon black and the electroplated aluminum, blocking the absorption of the pigment on the electroplated aluminum.

[0004] Other existing technologies to prevent oxidative discoloration of printed materials containing black pigments after hot stamping include: (1) adding an isolation layer between the ink and the aluminum foil, which increases printing cost and time; (2) adding antioxidants, which has limited effect and may affect the ink curing properties; (3) replacing neutral black inorganic pigments, which sacrifices blackness or is too costly. None of the existing technologies can effectively solve the oxidation effect of the carbon black in black ink on the anodized aluminum foil. Summary of the Invention

[0005] In response to the related problems, the present invention provides a black ink for preventing hot stamping from oxidative discoloration and a preparation method thereof.

[0006] The present invention addresses the challenges of the prior art by employing the following technical solution: a dual-curing black ink, both photo-curable and thermal-curable, is used in conjunction with an acrylic-based, heat-curable adhesive, an electrochemical metal foil. A first high-crosslink density cure is achieved through the photocuring subsystem, followed by a second heat cure of the patterned area using the heat and pressure conditions of the hot stamping process. This second heat cure utilizes the latent heat-curing components of the black ink to cross-link with the heat-curing adhesive, creating a dense barrier layer. This creates a multi-layer barrier effect against carbon black and provides the hot stamping layer with its antioxidant properties.

[0007] The specific content of the invention is as follows: A black ink for preventing hot stamping from oxidative discoloration, the black ink comprising a photocurable subsystem material and a latent thermal curing subsystem material, the latent thermal curing ink subsystem material comprising an ink having a double-bond grafted water-based hydroxyl acrylic resin as a thermal curing matrix and a PEG-PU-peroxide bond copolymer as a latent thermal initiator.

[0008] Preferably, the black ink composition ratio is: Photocuring subsystem materials: 40-60 parts of photocuring resin, 10-20 parts of photocuring crosslinking agent, 5-10 parts of active monomer, 3-5 parts of photoinitiator Latent thermal curing subsystem materials: 15-25 parts of thermal curing resin, 3-5 parts of thermal curing agent, 1-3 parts of latent thermal initiator, 3-5 parts of thermal accelerator Other components: 8-12 parts of carbon black and / or 2-5 parts of auxiliary filler, and / or 3-5 parts of dispersant, and / or 0.1-1 part of leveling agent, and / or 0.1-1 part of defoaming agent, and / or 0.5-3 parts of adhesion promoter, and / or 1-3 parts of silane coupling agent, and / or 0.02-0.05 part of polymerization inhibitor.

[0009] Preferably, the light-curable resin is one of low-functionality acrylic resin, epoxy acrylate and polyurethane acrylate.

[0010] More preferably, the light-curable resin is one of a bifunctional acrylic resin and an isocyanate-based polyurethane acrylic resin.

[0011] More preferably, the isocyanate-based polyurethane acrylate resin is one of an aliphatic polyurethane acrylate resin and an aromatic polyurethane acrylate resin.

[0012] Preferably, the photocurable crosslinking agent is one or more of trimethylolpropane ethoxy triacrylate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and p-phenylene diisocyanate.

[0013] Preferably, the reactive monomer is one or more of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, ethoxylated pentaerythritol tetraacrylate, ethoxyethoxyethyl acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate.

[0014] Preferably, the photoinitiator is one of TPO, 184, 1173, 369, 819, 2959, 907 and 754.

[0015] Preferably, the thermosetting resin is a double-bond grafted water-based hydroxy acrylic resin.

[0016] Preferably, the thermal curing agent is an isocyanate curing agent.

[0017] More preferably, the isocyanate curing agent is one of aliphatic polyisocyanate and blocked isocyanate with a neutral pH value.

[0018] Preferably, the thermal initiator is a PEG-PU-peroxide bond copolymer latent thermal initiator.

[0019] Preferably, the thermal accelerator is a tertiary amine thermal accelerator.

[0020] More preferably, the tertiary amine thermal accelerator is buffered with a weakly alkaline sodium salt and compounded to a neutral pH before use.

[0021] Preferably, the carbon black is surface-grafted via epoxy groups.

[0022] Preferably, the auxiliary filler is one or more of nano-silicon dioxide, nano-titanium dioxide, nano-zinc oxide, nano-organic pigments and nano-inorganic pigments.

[0023] Preferably, the dispersant is one or more of fatty acid, fatty acid ester, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, polyoxyethylene alkylamide, polysiloxane, polysorbate and sodium perfluorooctanoate.

[0024] Preferably, the leveling agent is one or more of BYK366, BYK333, BYK307 and BYK394.

[0025] Preferably, the defoaming agent is one of an organosilicon defoaming agent and a polyether grafted organosilicon defoaming agent.

[0026] More preferably, the defoaming agent is one or more of BYK055, BYK088 and BYK067A.

[0027] Preferably, the silane coupling agent is one or more of KH550, KH560 and KH570.

[0028] Preferably, the adhesion promoter is a phosphate ester.

[0029] More preferably, the phosphate ester is one of hydroxyethyl methacrylate phosphate and phosphorylated acrylate.

[0030] Preferably, the polymerization inhibitor is one of BHT, polymerization inhibitor 510 and polymerization inhibitor 702.

[0031] The base resin of the latent heat curing subsystem is a double-bond grafted water-based hydroxy acrylic resin, and the specific preparation method is as follows: S1: Premix the monomers, mixing 40-45 parts of acrylic soft monomer, 50-55 parts of acrylic hard monomer, 5-10 parts of acrylic functional monomer and 50 parts of ether solvent, and stirring evenly; S2: Matrix polymerization: 90% wt monomer premix prepared in S1 is deoxygenated by nitrogen gas, an azo thermal initiator is added, the temperature is raised to 75-80°C, the remaining monomer premix is ​​slowly added dropwise, the reaction is continued for 4-5 hours, the mixture is cooled to 50°C, 0.1% wt polyphenol polymerization inhibitor is added, and the mixture is stirred for 30 minutes; S3: Water-based modification: slowly add an amine neutralizer to the product of step S2, adjust the pH to 7.5-8.5, and neutralize the carboxylic acid groups; S4: Remove the solvent, evaporate it with stirring, add deionized water to dilute to a solid content of 40% wt, and disperse at 3000 r / min for 30 min; S5: filtering and drying, retaining reactants with a molecular weight greater than 5000, removing unreacted monomers, and freeze-drying to obtain a double-bond grafted water-based acrylic resin matrix.

[0032] More preferably, the acrylic soft monomer is one or more of hydroxyethyl acrylate, butyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl acrylate, and isooctyl acrylate.

[0033] More preferably, the acrylic hard monomer is one or more of methacrylic acid, methyl methacrylate, acrylamide, and glycidyl methacrylate.

[0034] More preferably, the functional acrylic monomer is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0035] More preferably, the ether solvent is one of ethylene glycol methyl ether, propylene glycol methyl ether, ethylene glycol dimethyl ether, and propylene glycol dimethyl ether.

[0036] More preferably, the azo thermal initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile or dimethyl azobisisobutyrate.

[0037] More preferably, the amine neutralizing agent is one of benzyldimethylamine, o-hydroxybenzyldimethylamine, triethylamine and triethanolamine.

[0038] More preferably, the polyphenol polymerization inhibitor is one of hydroquinone, p-tert-butylcatechol and 2,6-di-tert-butyl-p-methylphenol.

[0039] The specific method of grafting epoxy groups on the carbon black surface is as follows: S1: basic carbon black is mixed with concentrated H2SO4:HNO3=3:1 by weight, and ultrasonically oxidized for 1 hour to generate oxidized carbon black containing carboxylic acid groups; S2: Disperse oxidized carbon black in toluene at a ratio of 1:10, add 20 parts of hydroxyethyl acrylate and 0.2 parts of azobisisobutyronitrile, react at 80°C for 12 hours under nitrogen protection, and prepare epoxy grafted carbon black after washing and drying.

[0040] The preparation method of the latent thermal initiator PEG-PU-peroxide bond copolymer used in the latent thermal curing subsystem is as follows: S1: Prepare polyurethane prepolymer (PU), 8-10 parts of 2000-4000 molecular weight PEG, 4-5 parts of polyurethane segment donor, 0.05-0.1 parts of tin metal catalyst, react at 70-80°C under nitrogen protection for 2-3 hours to generate PEG-PU prepolymer; S2: Peroxide bond grafting: cool the PEG-PU prepolymer to 60°C, add 2-4 parts of peroxide bond donor and 0.02-0.05 parts of azo thermal initiator, slowly raise the temperature to 65-70°C under nitrogen protection, and react for 3-4 hours to generate PEG-PU-peroxide bond copolymer; S3: Hydrophilic modification: cool the product prepared in S2 to 60°C, add 1 part of hydroxy acrylic resin, stir and react for 2 hours, add a terminator to generate a hydroxyl-grafted PEG-PU-peroxide bond copolymer.

[0041] S4: Wash and dry, drop the product prepared in S3 into ice ether for precipitation, filter and wash with ethanol, and then vacuum dry to complete the preparation.

[0042] More preferably, the polyurethane segment donor is one of HDI and IPDI.

[0043] More preferably, the peroxide bond donor is one of peroxydicarbonate and peroxide bond-containing acrylate.

[0044] More preferably, the tin metal catalyst is one of dibutyltin dilaurate (DBTDL) and stannous octoate.

[0045] More preferably, the azo thermal initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile or dimethyl azobisisobutyrate.

[0046] More preferably, the amount of the peroxide bond donor added controls the decomposition temperature of the latent thermal initiator to be 100-150°C.

[0047] More preferably, the latent thermal initiator is partially hydrophilic, and the hydrophilicity is regulated by the addition amount of PEG and hydroxy acrylic resin.

[0048] A method for preparing black ink for preventing hot stamping from oxidative discoloration comprises the following steps: S1: Add light-curing subsystem materials and latent heat-curing subsystem materials into a magnetic stirring cup, heat in a water bath at 55-65°C, and magnetically stir at 200-400 rpm for 1-2 hours until the materials are completely dissolved; S2: Add silane coupling agent, continue stirring for 30 to 50 minutes, and cool to below 40°C; S3: Add dispersant, leveling agent, defoamer, adhesion adsorbent and polymerization inhibitor, stir at 1600r / min with a planetary mixer for 3 minutes, and cool to below 40°C; S4: Add carbon black and auxiliary nanofillers, stir at 1800 rpm for 3 min using a planetary vacuum mixer, and cool to below 40°C; S5: Grind with a three-roll mill to a fineness of less than 5 μm, and adjust the roller spacing from 100 μm to 15 μm.

[0049] A hot stamping adhesive layer component used in conjunction with the black ink includes: 45-55 parts of a thermosetting resin, 10-15 parts of a high cross-linking density monomer, 1-3 parts of a nano-SiO2 dispersion, 8-12 parts of a thermal cross-linking agent, 1-3 parts of a thermal initiator and / or 3-5 parts of a dispersant, and / or 0.1-1 part of a leveling agent, and / or 0.1-1 part of a defoaming agent, and / or 0.5-3 parts of an adhesion promoter, and / or 1-3 parts of a silane coupling agent.

[0050] Preferably, the thermosetting resin is one of epoxy acrylic resin and hydroxy acrylic resin.

[0051] Preferably, the high cross-linking density monomer is one of a multifunctional monomer and trimethylolpropane triacrylate.

[0052] Preferably, the particle size of the nano-SiO2 dispersion is 30 to 50 nm.

[0053] Preferably, the thermal crosslinking agent is HDI trimer to improve the final strength.

[0054] Preferably, the thermal initiator is di-tert-butyl peroxide.

[0055] Preferably, the dispersant is BYK163, the leveling agent is BYK366, and the defoaming agent is BYK055.

[0056] Preferably, the adhesion promoter is hydroxyethyl methacrylate phosphate.

[0057] Preferably, the silane coupling agent is KH550.

[0058] A method for preparing the hot stamping adhesive layer comprises the following steps: S1: Add thermal crosslinking agent, high crosslinking density monomer and thermosetting resin to a magnetic stirring cup, heat in a water bath at 55-65°C, and stir magnetically at 200-400 rpm for 1-2 hours until the materials are completely dissolved; S2: Add silane coupling agent, continue stirring for 30 to 50 minutes, and cool to below 40°C; S3: Add dispersant, leveling agent and defoamer, stir with planetary mixer at 1600r / min for 3min, and cool to below 40℃; S4: Add nano-SiO2 dispersion, stir with planetary vacuum mixer at 1800 rpm for 3 min, and cool to below 40°C; S5: Grind with a three-roll mill to a fineness of less than 5 μm, and adjust the roller spacing from 100 μm to 15 μm.

[0059] A method for applying black ink to prevent hot stamping from oxidative discoloration is as follows: S1: Print the black ink onto a substrate (such as paper or plastic), and perform photocuring using a UV light source (wavelength 360-400 nm, energy 1200-1600 mJ / cm²) to form a carbon black-containing bottom layer.

[0060] S2: coating the hot stamping adhesive layer on the surface of the aluminum foil of the hot stamping electroplated aluminum; S3: Bond the materials of S1 and S2 so that the black ink and the hot stamping adhesive layer are in contact. The secondary thermal curing is triggered by heating (110-150°C) and pressurizing (0.5-1.5MPa) to form a dense isolation layer (5-20μm thick) between the bottom ink and the electroplated aluminum. This layer does not contain carbon black and has a high cross-linking density, which blocks the migration of acidic and alkaline carbon black.

[0061] Compared with the prior art, the present invention has the following beneficial effects: 1. Physical barrier: Isolate carbon black and anodized aluminum layer to avoid direct contact.

[0062] 2. Chemical inertness: The cross-linked network of thermosetting resin is stable and has excellent acid and alkali resistance.

[0063] 3. Enhanced adhesion: The dual curing mechanism chemically bonds the base layer to the isolation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 It is the process route diagram of the present invention. DETAILED DESCRIPTION

[0066] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in this invention.

[0067] 1. Carbon black modification The purpose of preparing epoxy-grafted carbon black in this invention is to prepare concentrated acid carboxyl groups on basic carbon black prepared by a furnace process, followed by grafting of epoxy groups. This facilitates sufficient polar crosslinking with the photocurable resin matrix, thereby constraining the carbon black through a high-crosslink density, three-dimensional crosslinked network and reducing its mobility. The impact of varying the parameters of this preparation method on the black ink of this invention is relatively minor, so in the specific embodiment, only a typical preparation is presented. The specific preparation steps are as follows: S1: 5 parts of alkaline PRINTEX45 carbon black were mixed with 30 parts of acid solution with a weight ratio of concentrated H2SO4:HNO3=3:1, and oxidized for 1 hour under 20KHz ultrasonic and 300r / min magnetic stirring conditions to generate oxidized carbon black containing carboxylic acid groups, which was then filtered, washed and dried; S2: 5 parts of oxidized carbon black were dispersed in 40 parts of toluene, 20 parts of hydroxyethyl acrylate and 0.2 parts of azobisisobutyronitrile were added, and the mixture was reacted with magnetic stirring at 80°C under nitrogen protection for 12 hours. After cleaning and drying, epoxy grafted carbon black was prepared.

[0068] The carbon black is prepared to have a particle size of 30 to 40 nm and a specific surface area of ​​100 m2 / g, pH is 7-8, and epoxy group equivalent is 50-80.

[0069] 2. Preparation of double-bond grafted waterborne hydroxyl acrylic resin According to the invention, a method for preparing a double-bond grafted waterborne hydroxylated acrylic resin was used to prepare three resin matrices with different properties, named TSR1, TSR2, and TSR3. Specific material amounts and variable process parameters are shown in Table 1.

[0070] Table 1 The main material used in the preparation of TSR1-3 is: Hydroxyethyl Acrylate Carbowax ® 2-HEA, Joncryl butyl acrylate ® 1695、Acrypet ® VR L40, Glycidyl Methacrylate Visiomer ® GMA, hydroxypropyl acrylate Sigma-Aldrich 486278.

[0071] 3. Preparation of Latent Thermal Initiator PEG-PU-Peroxide Bond Copolymer According to the preparation method of the latent thermal initiator PEG-PU-peroxide bond copolymer described in the invention summary, three PEG-PU-peroxide bond copolymers were prepared and named PPG1, PPG2, and PPG3. The specific material variables and process variables are shown in Table 2: Table 2 The main material used to prepare PPG1-2 is manufactured by the brand: HD1-Desmodur ® N 3600, IPDI-Vestanat ® IPDI, Peroxydicarbonate-Perkadox ® 16. Peroxide-containing acrylate-CN975 ® , CARBOWAX™ PEG2000, CARBOWAX™ PEG 3000, CARBOWAX™ PEG4000.

[0072] 4. Preparation of Electrochemical Aluminum Foil According to the invention, the electrochemical aluminum foil for preparing the hot stamping adhesive layer has the following raw material composition ratio: 50 parts of HDI trimer, 12 parts of pentaerythritol triacrylate, 48 parts of epoxy acrylic resin, 2 parts of di-tert-butyl peroxide, 2 parts of nano-SiO2 dispersion, 4 parts of BYK163 dispersant, 0.5 parts of BYK366 leveling agent, 0.5 parts of BYK055 defoaming agent, 2 parts of KH550 silane coupling agent, and 1 part of hydroxyethyl methacrylate phosphate.

[0073] The preparation method of the adhesive layer is as follows: S1: Add HDI trimer, pentaerythritol triacrylate, di-tert-butyl peroxide, and epoxy acrylate resin in proportion to each other in a magnetic stirring cup. Set the water bath temperature to 60°C and the magnetic stirring speed to 300 r / min. Stir for 1.5 hours until all solid raw materials are completely dissolved to form a uniform premixed solution. S2: While stirring continuously, slowly add the silane coupling agent and continue stirring at 300 r / min for 40 minutes to ensure that the silane coupling agent is fully dispersed and reacted. Then, cool the mixture to below 35°C; S3: Add dispersant, leveling agent and defoamer in sequence, and stir at 1600 rpm using a planetary mixer for 3 minutes to fully disperse and evenly mix the additives in the system. Then, cool the mixture to below 35°C. S4: Add nano-SiO2 dispersion, set the stirring speed to 1800r / min in a planetary vacuum mixer, stir for 3 minutes, and then cool the mixture to below 35°C; S5: The mixed solution is transferred to a three-roll mill, with the initial roller spacing set to 100 μm and gradually adjusted to 15 μm until the fineness of the mixed solution reaches less than 5 μm; S6: A water-based release coating layer, a laser imaging coating layer, a peeling layer, and an aluminum-plated layer are prepared on the PET base film from the inside out, the mixed solution prepared in step S5 is coated on the aluminum-plated layer, and a hot stamping adhesive layer is formed after low-temperature drying at 80°C for 10 minutes, thereby completing the preparation of the electrochemical aluminum foil.

[0074] 5. Preparation and testing of black ink According to the above-prepared epoxy grafted carbon black, double bond grafted water-based hydroxy acrylic resin TSR1-3, and latent thermal initiator PEG-PU-peroxide bond copolymer PPG1-3, an embodiment of the present invention for preventing hot stamping oxidative discoloration is prepared as follows: Example 1, black ink component ratio and preparation method: (1) Black ink component ratio Light-curing subsystem materials: 50 parts of difunctional acrylic resin, 7 parts of 2-hydroxyethyl acrylate, 15 parts of trimethylolpropane ethoxy triacrylate, and 4 parts of TPO photoinitiator; Thermal curing subsystem materials: 20 parts of TSR1 double-bond grafted water-based hydroxyl acrylic resin, 4 parts of aliphatic polyisocyanate, 2 parts of PPG1 latent thermal initiator, 4 parts of tert-benzyldimethylamine, and 2 parts of sodium dihydrogen phosphate; 10 parts of epoxy group grafted carbon black, 3 parts of nano-silica, 4 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of BYK366 leveling agent, 0.5 parts of BYK055 defoamer, 1 part of phosphate ester hydroxyethyl methacrylate, 2 parts of KH550 silane coupling agent, and 0.03 parts of polymerization inhibitor BHT.

[0075] (2) Preparation method S1: Add the light-curing subsystem materials and the heat-curing subsystem materials into a magnetic stirring cup according to the formula ratio, heat to 60°C in a water bath, and stir magnetically at 300 rpm for 1.5 hours until the resin is completely dissolved; S2: Add silane coupling agent, continue stirring for 40 minutes, and cool to 35°C; S3: Add dispersant, leveling agent, and defoamer, stir at 1600 rpm for 3 minutes using a planetary mixer, and cool to 35°C. S4: Add epoxy grafted carbon black and nano-silica, stir at 1800 rpm for 3 minutes using a planetary vacuum mixer, and cool to 35°C; S5: Grind to a fineness of less than 5 μm using a three-roll mill, adjusting the roller spacing from 100 μm to 15 μm; S6: Print the prepared ink onto the substrate and perform a primary curing using UV light at 370 nm, 1400 mJ / cm², and 12 seconds. S7: The electrochemical aluminum foil is bonded to the cured ink layer through the hot stamping equipment, heated to 130℃, pressurized to 1MPa, and triggered to perform secondary heat curing for 20s to complete the hot stamping.

[0076] Test results: A dense isolation layer is formed between the ink layer and the anodized aluminum layer, the hot stamping effect is good, and there is no obvious oxidation discoloration after aging.

[0077] Based on the component ratio of Example 1, the types and quantities of the components were varied to prepare Examples 2-3 and Comparative Examples 1-4. The specific component ratios are shown in Table 3: The details of the changes in Table 3 are: (1) Changes in Example 2 relative to Example 1 The photoinitiator was changed from TPO to 184, and the dosage was increased from 4 parts to 5 parts; Thermosetting resin was changed from TSR1 to TSR2; The thermal curing agent was changed from aliphatic polyisocyanate to blocked isocyanate; The latent thermal initiator was changed from PPG1 to PPG2; The amount of epoxy grafted carbon black was adjusted from 10 parts to 8 parts; The auxiliary filler was changed from nano-silicon dioxide to nano-titanium dioxide, and the dosage was adjusted from 3 parts to 2 parts.

[0078] (2) Changes in Example 3 relative to Example 1 The light-curing resin was changed from bifunctional acrylic resin to aliphatic polyurethane acrylic resin, and the dosage was increased from 50 parts to 55 parts; The active monomer was changed from 2-hydroxyethyl acrylate to 2-hydroxyethyl methacrylate, and the dosage was adjusted from 7 parts to 8 parts; The photocuring crosslinker was changed from trimethylolpropane ethoxy triacrylate to dicyclohexylmethane diisocyanate, and the dosage was increased from 15 parts to 18 parts; Thermosetting resin was changed from TSR1 to TSR3; The thermal curing agent was changed from aliphatic polyisocyanate to blocked isocyanate; The latent thermal initiator was changed from PPG1 to PPG3, and the dosage was increased from 2 parts to 2.5 parts; The thermal accelerator was changed from tert-benzyl dimethylamine to DMP-30, and the dosage was increased from 2 parts to 3 parts; The amount of carbon black was adjusted from 10 parts to 11 parts; Removed nanosilica; The dispersant was changed from sodium dodecylbenzenesulfonate to polyoxyethylene alkylamide, and the dosage was reduced from 4 parts to 3 parts.

[0079] (3) Changes in Comparative Example 1 relative to Example 1 All heat-curing subsystem materials have been removed; only UV light is used for primary curing, without secondary heat curing.

[0080] (4) Changes in Comparative Example 2 relative to Example 1 The PPG1 latent thermal initiator was replaced by the conventional thermal initiator di-tert-butyl peroxide.

[0081] (5) Changes in Comparative Example 3 relative to Example 1 Latent thermal initiator in the thermal curing subsystem material: prepared using water-based hydroxy acrylic resin as the thermal curing matrix, and other formula ingredients remain unchanged.

[0082] (6) Changes in Comparative Example 4 relative to Example 1 Carbon black that was not grafted with epoxy groups was used, and the other formulation components remained unchanged.

[0083] Table 3 Composition distribution table of Examples 1-3 and Comparative Examples 1-4 Based on the changes in material types and quantities in Table 3, and taking the preparation method of Example 1 as a benchmark, a comparison of corresponding preparation methods is performed, as shown in Table 4.

[0084] Table 4 Preparation methods and product effects of Examples 1-3 and Comparative Examples 1-4 Table 4 shows the main process parameters of the preparation methods of Examples 1-3 and Comparative Examples 1-4. The main difference lies in different dissolution adjustments and different curing conditions according to different material formulations.

[0085] By using different material types, components and preparation methods in Examples 1-3 and Comparative Examples 1-4, the hot stamping products prepared were subjected to the following sample preparation and testing to compare the performance improvement capabilities of the present invention: 1. Sample preparation A black ink layer is printed on the substrate of PET plastic using UV printing equipment, and telephone aluminum foil is thermally transferred on the black ink layer. The hot stamping pattern is set to have multiple square pattern samples with an area of ​​100 mm×100 mm for each embodiment. 2. Adhesion test Use 3M600 tape to adhere the stamped square pattern. Quickly peel the tape at a 90° angle and measure the remaining area of ​​the pattern. Adhesion (%) = remaining area / total pattern area. The results are shown in Table 5.

[0086] 3. Hot stamping integrity Use a 3W strong flashlight to illuminate the back of the hot stamping material and observe the hot stamping pattern from the front. If there is no missing hot stamping, no broken line, and no blistering or sticking, it is considered qualified. The rest are unqualified. The results are shown in Table 5.

[0087] 4. High temperature and high humidity aging Aging was performed at 50°C and 85% RH for 48 hours, and the reflectance was measured using a visible light photometer. rate, test the degree of oxidation.

[0088] Table 5 Performance test results of Examples 1-3 and Comparative Examples 1-4 By comparing the performance of Table 2, Table 4, and Table 5, we can find that: (1) Example 1 forms a dense isolation layer through a dual photothermal curing mechanism, effectively preventing the migration of carbon black. The ink layer has strong adhesion to the anodized aluminum layer, and the hot stamping effect is good. After aging testing, there is no obvious oxidation discoloration. The ink layer also exhibits good chemical stability.

[0089] (2) Example 2 uses a double-bond grafted water-based hydroxyl acrylic resin prepared from acrylic hard body as the thermosetting resin matrix. Although the adhesion of the electroplated aluminum layer is slightly weakened, the curing speed is accelerated, thereby improving the manufacturing efficiency.

[0090] (3) Example 3 uses aliphatic polyurethane acrylic resin to replace difunctional acrylic resin, and the thermosetting resin is changed to TSR3. Although it is a balanced configuration, the final adhesion obtained is the best and the hot stamping effect of the material is the most stable.

[0091] (4) In Comparative Example 1, due to the lack of thermal curing subsystem materials, a dense isolation layer was not formed between the ink layer and the anodized aluminum layer. This resulted in the carbon black easily reacting with the anodized aluminum layer, causing oxidation and discoloration. In addition, the adhesion was significantly reduced, and the hot stamping pattern showed bubbling and peeling.

[0092] (5) Comparative Example 2 uses conventional thermal initiators instead of latent thermal initiators, which causes the ink layer to solidify prematurely and cannot form a relatively dense isolation layer. The UV curing and thermal curing adhesive layers are easily mismatched, resulting in line breakage during aging and causing migration and erosion of carbon black.

[0093] (6) Comparative Example 3 uses a water-based hydroxyl acrylic resin without double bonds as a thermosetting matrix, which forms a separation of hydrophobic and hydrophilic materials during UV curing, which easily causes material mismatch within the black ink layer, thereby directly affecting the stability of the substrate and accelerating the migration of carbon black.

[0094] (7) The pH of the unmodified carbon black in Comparative Example 4 caused unstable curing, increased mobility, and easy reaction with the anodized aluminum layer, causing oxidation discoloration. At the same time, the adhesion was significantly reduced, and the hot stamping pattern showed blistering and shedding.

[0095] Summarizing the effects of the embodiments of the present invention, it can be seen that the embodiments of the present invention have successfully solved the problem of easy oxidation and discoloration of traditional black ink in the hot stamping process through material combination and light and heat dual curing mechanism. The ink layer in the embodiment can not only form a dense isolation layer to effectively prevent the migration of carbon black, but also show good adhesion, wear resistance and chemical stability. The choice of material type has a significant impact on the technical effect of the ink layer. For example, the acrylic hard monomer in Example 2 improves the hardness, wear resistance and initiation efficiency of the ink layer; the use of aliphatic polyurethane acrylic resin in Example 3 significantly improves the hardness of the ink layer. In contrast, the comparative example has unstable hot stamping effect, easy oxidation and discoloration, and reduced adhesion due to the lack of effective isolation layer materials, slow curing speed, high carbon black migration rate or low decomposition temperature of conventional thermal initiators.

[0096] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A black ink for preventing hot stamping from oxidative discoloration, characterized in that: The black ink comprises a photocurable subsystem material and a latent thermal curing subsystem material. The latent thermal curing ink subsystem material comprises an ink with a double-bond grafted water-based hydroxyl acrylic resin as a thermal curing matrix and a PEG-PU-peroxide bond copolymer as a latent thermal initiator, and includes the following parts by weight: The photocuring subsystem materials include: 40-60 parts of photocuring resin, 5-10 parts of active monomer, 10-20 parts of photocuring crosslinking agent, and 3-5 parts of photoinitiator. The latent heat curing subsystem materials: 15-25 parts of heat curing resin, 3-5 parts of heat curing agent, 1-3 parts of latent heat initiator, and 3-5 parts of heat accelerator. 8-12 parts carbon black and / or 2 to 5 parts of auxiliary nanofillers and / or 3 to 5 parts of dispersant, 0.1 to 1 part of leveling agent, 0.1 to 1 part of defoaming agent, 0.5 to 3 parts of adhesion promoter, 1 to 3 parts of silane coupling agent, and 0.02 to 0.05 part of polymerization inhibitor.

2. The black ink according to claim 1, characterized in that The preparation method of the double-bond grafted water-based hydroxy acrylic resin is as follows: S1: Premix the monomers by mixing 40-45 parts of acrylic soft monomer, 50-55 parts of acrylic hard monomer, 5-10 parts of acrylic functional monomer and 50 parts of ether solvent, and stirring evenly; S2: Matrix polymerization: nitrogen is passed through 90% wt of the monomer premix, an azo thermal initiator is added, the temperature is raised to 75-80°C, the remaining monomer premix is ​​slowly added dropwise, the reaction is continued for 4-5 hours, and then the temperature is cooled to 50°C. 0.1% wt of a polyphenol inhibitor is added and the mixture is stirred for 30 minutes; S3: Aqueous grafting: slowly add an amine neutralizer to the product of step S2 to adjust the pH to 7.5-8.5 to neutralize the carboxylic acid groups; S4: Remove the solvent, evaporate it with stirring, add deionized water to dilute to a solid content of 40% wt, and disperse at 3000 r / min for 30 min; S5: filtering and drying, retaining reactants with a molecular weight greater than 5000, removing unreacted monomers, and freeze-drying to obtain a double-bond grafted water-based acrylic resin matrix.

3. The black ink according to claim 1, characterized in that The preparation method of the PEG-PU-peroxide bond copolymer as a latent thermal initiator is as follows: S1: Prepare polyurethane prepolymer (PU), 8-10 parts of 2000-4000 molecular weight PEG, 4-5 parts of polyurethane segment donor, 0.05-0.1 parts of tin metal catalyst, react at 70-80°C under nitrogen protection for 2-3 hours to generate PEG-PU prepolymer; S2: Peroxide bond grafting: cool the PEG-PU prepolymer to 60°C, add 2-4 parts of peroxide bond donor and 0.02-0.05 parts of azo thermal initiator, slowly raise the temperature to 65-70°C under nitrogen protection, and react for 3-4 hours to generate PEG-PU-peroxide bond copolymer; S3: Hydrophilic grafting: cool the product prepared in S2 to 60°C, add 1 part of hydroxy acrylic resin, stir and react for 2 hours, add a terminator to generate a hydroxy grafted PEG-PU-peroxide bond copolymer. S4: Wash and dry, drop the product prepared in S3 into ice ether for precipitation, filter and wash with ethanol, and then vacuum dry to complete the preparation.

4. The black ink according to claim 1, characterized in that The photocurable resin of the photocurable subsystem is one of a difunctional acrylic resin and an isocyanate-based polyurethane acrylic resin, the photocurable crosslinker is one or more of trimethylolpropane ethoxy triacrylate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and p-phenylene diisocyanate, the reactive monomer is one or more of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, ethoxylated pentaerythritol tetraacrylate, ethoxyethoxyethyl acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate, and the photoinitiator is one of TPO, 184, 1173, 369, 819, 2959, 907 and 754.

5. The black ink according to claim 1, characterized in that The thermal curing agent is one of aliphatic polyisocyanate or blocked isocyanate with neutral pH, and the thermal accelerator is a tertiary amine thermal accelerator, which is compounded to neutral pH by weak alkaline sodium salt buffering.

6. The black ink according to claim 1, characterized in that The carbon black is carbon black grafted with epoxy groups.

7. The black ink according to claim 1, characterized in that The auxiliary nano-filler is one or more of nano-silicon dioxide, nano-titanium dioxide, nano-zinc oxide, nano-organic pigments, and nano-inorganic pigments.

8. The black ink according to claim 1, characterized in that The dispersant is one or more selected from the group consisting of fatty acid, fatty acid ester, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, polyoxyethylene alkylamide, polysiloxane, polysorbate, and sodium perfluorooctanoate; the leveling agent is one or more selected from the group consisting of BYK366, BYK333, BYK307, and BYK394; the defoamer is one or more selected from the group consisting of silicone defoamers and polyether-grafted silicone defoamers; the silane coupling agent is one or more selected from the group consisting of KH550, KH560, and KH570; the adhesion promoter is one selected from the group consisting of phosphate ester hydroxyethyl methacrylate and phosphated acrylate; and the polymerization inhibitor is one selected from the group consisting of BHT, polymerization inhibitor 510, and polymerization inhibitor 702.

9. A method for preparing the black ink according to any one of claims 1, 4, 5, 6, 7, and 8, characterized in that: The following steps are involved: S1: Add the light-curing subsystem material and the latent heat-curing subsystem material to the magnetic stirring cup in sequence, heat in a water bath at 55-65°C, and stir magnetically at 200-400 rpm for 1-2 hours until the resin is completely dissolved; S2: Add silane coupling agent, continue stirring for 30 to 50 minutes, and cool to below 40°C; S3: Add dispersant, leveling agent and defoamer, stir with planetary mixer at 1600r / min for 3min, and cool to below 40℃; S4: Add carbon black and auxiliary fillers, stir at 1800 rpm for 3 min using a planetary vacuum mixer, and cool to below 40°C; S5: Grind with a three-roll mill to a fineness of less than 5 μm, and adjust the roller spacing from 100 μm to 15 μm.

10. The black ink according to any one of claims 1, 4, 5, 6, 7, and 8, characterized in that: The black ink is cured on the substrate using UV light of 360-400nm and 1200-1600mJ / cm² for one time, and is bonded to the thermosetting hot stamping adhesive layer by heating, and a dense diaphragm is prepared by secondary thermal curing.

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