Digital printing varnish and its preparation method

Abstract

This invention discloses a digital printing varnish and its preparation method. Based on the mass of the digital printing varnish (100%), the varnish comprises the following components in the following mass percentages: epoxy resin: 15%–30%, oxetane monomers: 25%–40%, acrylate monomers: 25%–40%, cationic photoinitiator: 7%–10%, free radical photoinitiator: 5%–10%, leveling agent: 0.1%–1%, and polymerization inhibitor: 0.1%–1%. The digital printing varnish of this invention exhibits good adhesion and flexibility to the substrate surface, excellent water resistance, wear and scratch resistance, and good hot stamping effect.

Description

Technical Field

[0001] This invention relates to the field of digital printing technology, specifically to digital printing varnishes and their preparation methods. Background Technology

[0002] Digital printing ultraviolet (UV) varnishes are widely used in the food, cosmetics, pharmaceutical, and luxury goods industries. Digital printing varnishes are mainly divided into enhancement varnishes and hot stamping varnishes based on their application. Enhancement varnishes require excellent scratch resistance and transparency after curing, while hot stamping varnishes require good adhesion after curing to adhere the electroplated aluminum layer on the hot stamping film, creating a beautiful hot stamping effect.

[0003] In related technologies, the curing of varnishes in the flexible packaging industry adopts a single free radical curing system. Enhanced varnishes contain a large number of cross-linking multifunctional monomers or resins. Although the resulting varnishes can improve gloss and increase wear and scratch resistance, they have extremely high cross-linking density. Excessive cross-linking density will result in insufficient viscosity after curing, making it unsuitable for hot stamping applications. At the same time, excessively high cross-linking density will lead to poor flexibility and insufficient adhesion after curing, resulting in a hard and brittle ink layer. Free radical polymerization reaction results in large volume shrinkage and high internal stress in the film layer, making it prone to cracking. In order to improve the adhesion of the varnish, a large amount of pure acrylic solid resin is often added to the formula, which will increase the risk of the varnish clogging the printhead during the printing process. Hydrophilic components are added to hot stamping varnishes to improve surface adhesion and enhance the hot stamping effect. However, the addition of hydrophilic components leads to poor water resistance in the varnish system, causing it to fog and whiten easily upon contact with water. In complex hot stamping processes, the hot stamping film severely obstructs and reflects UV light, reducing the curing efficiency and resulting in incomplete curing. This further accelerates the problem of poor adhesion of the cured film layer to the substrate during hot stamping. Therefore, under traditional free radical systems, it is difficult for varnishes to simultaneously achieve both hot stamping and performance enhancement applications. Summary of the Invention

[0004] In view of this, the present invention proposes a digital printing varnish and its preparation method, aiming to achieve a digital printing varnish that cures relatively completely, has the required adhesion to the substrate after curing, has suitable flexibility after film formation, good water resistance, good wear and scratch resistance, and can achieve a good hot stamping effect.

[0005] In a first aspect, the present invention provides a digital printing varnish, wherein, based on the mass of the digital printing varnish as 100%, the digital printing varnish has the following composition in mass percentage: epoxy resin: 15%~30%, oxetane monomer: 25%~40%, acrylate monomer: 25%~40%, cationic photoinitiator: 7%~10%, free radical photoinitiator: 5%~10%, leveling agent: 0.1%~1%, and polymerization inhibitor: 0.1%~1%.

[0006] As can be seen from the above technical solution, the digital printing varnish proposed in this invention, under external induced conditions, allows the acrylate monomers to rapidly undergo free radical polymerization under the action of a free radical photoinitiator, providing initial curing, drying, hardness, and adhesion for the initial stage of digital printing varnish curing. The cationic photoinitiator initiates the cationic polymerization reaction of the epoxy resin. The low shrinkage characteristics of the epoxy resin in the cationic polymerization reaction can reduce the internal stress of the ink layer caused by the polymerization of acrylate monomers during the free radical polymerization process. After the cationic photoinitiator is activated, it can continuously initiate the polymerization of the epoxy resin for a period of time, enabling curing even under complex hot stamping processes such as light-shielding conditions. This makes the cationic curing reaction more thorough, achieving a more complete curing process. The film layer exhibits the required adhesion to the substrate surface and good flexibility, maintaining stable performance even under complex hot stamping processes. After curing, the film layer demonstrates excellent water resistance. Oxycyclic butane monomers, activated by cationic photoinitiators, participate in cationic ring-opening polymerization, resulting in lower shrinkage and higher wetting ability, which enhances the adhesion and bending performance of the coating film. Through the synergistic effect of free radical polymerization and cationic polymerization, the varnish layer exhibits high surface hardness, scratch and abrasion resistance, forming a more stable film layer. The printing varnish raw material components do not require the addition of hydrophilic amine additives or hydrophilic monomers. Utilizing its own oxygen-free polymerization inhibition properties, it can solve the problem of poor water resistance caused by hydrophilic components in digital printing varnishes, thereby improving the hot stamping effect of digital printing varnishes.

[0007] Secondly, the present invention provides a method for preparing digital printing varnish, comprising the following steps: Under a safe light, epoxy resin, oxetane monomers, acrylate monomers, leveling agents, and polymerization inhibitors are added to a container according to a specified ratio and mixed to obtain a premix. Under light-protected conditions, a cationic photoinitiator and a free radical photoinitiator are added to the premix and mixed again, then filtered to obtain a digital printing varnish. The safe light is selected from either a yellow light or a red light. A disperser is used to stir and disperse the components added to the container. The speed of the disperser is 1500 r / min to 2000 r / min, and the stirring and dispersion time is 25 min to 45 min. The mixing time of the premix with the cationic photoinitiator and the free radical photoinitiator is 40 min to 60 min. A filter membrane with a thickness of 0.4 μm to 0.6 μm is used for filtration.

[0008] As can be seen from the above technical solution, its beneficial effects are as follows: Under safe lighting, mixing components such as epoxy resin, oxetane monomers, acrylate monomers, leveling agents, and polymerization inhibitors without reacting with each component helps to achieve uniform dispersion of each component; the digital printing varnish obtained by adding cationic photoinitiators and free radical photoinitiators to the premixed liquid can combine the advantages of the polymerization reaction process of cationic and free radical polymer components, achieving better flexibility and adhesion to the substrate surface after curing, and the film layer has good wear and scratch resistance and good hot stamping effect; the light-proof conditions allow the cationic photoinitiator and the free radical photoinitiator to fuse more stably; using a filter membrane can obtain digital printing varnish with higher purity, thereby enhancing storage stability.

[0009] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the embodiments of the present invention. Detailed Implementation

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] The technical solution of the present invention will be described in detail below: Digital printing varnishes can be divided into enhancement varnishes and hot stamping varnishes according to their applications, and currently, free radical curing systems are commonly used. Although enhancement varnishes have advantages such as high gloss, wear resistance, and scratch resistance after curing, their surface is relatively rigid; while hot stamping varnishes have good adhesion after curing, which can stably adhere the electroplated aluminum layer on the hot stamping film and achieve a good hot stamping effect.

[0012] To achieve the high gloss and scratch resistance required for varnishing, the flexible packaging industry typically uses high cross-linking density formulations. However, this results in a hard, brittle cured film with insufficient adhesion. Adding hydrophilic additives to overcome surface oxygen inhibition can cause the ink layer to fog up and turn white when exposed to water. Simultaneously, the free radical polymerization components undergo significant volume shrinkage during the reaction, further exacerbating insufficient adhesion. During the curing stage, the hot stamping film blocks and reflects UV light, leading to incomplete curing of the varnish, poor adhesion, and reduced water resistance. Furthermore, while high cross-linking density helps improve the gloss and scratch resistance of the varnished surface in the hot stamping process, it weakens the surface tack of the cured film, making it difficult to meet the adhesion requirements of the hot stamping process.

[0013] In view of this, this application proposes a digital printing varnish aimed at solving at least one of the aforementioned technical problems. This invention overcomes the oxygen inhibition problem by constructing a cationic-free radical dual curing system, utilizing the "toughness" and "strong adhesion" of cationic polymerization to balance the "brittleness" of free radical polymerization, and eliminating hydrophilic amine additives and hydrophilic monomers. This fundamentally solves the problem of poor water resistance in digital printing varnishes caused by the addition of hydrophilic components, thereby improving the hot stamping effect of digital printing varnishes.

[0014] The digital printing varnish according to this application is composed of the following components by mass percentage: Based on the mass of the digital printing varnish as 100%, the digital printing varnish has the following component composition by mass percentage: epoxy resin: 15%~30%, oxetane monomer: 25%~40%, acrylate monomer: 25%~40%, cationic photoinitiator: 7%~10%, free radical photoinitiator: 5%~10%, leveling agent: 0.1%~1%, polymerization inhibitor: 0.1%~1%.

[0015] It should be noted that the composition of the digital printing varnish by mass percentage in this application can be converted to weight percentage, and the weight percentage of each component in the digital printing varnish remains unchanged after conversion. It should also be noted that in this application, the mass percentage of each component in the digital printing varnish and the mass percentage of each component in the digital printing varnish have the same meaning and can be used interchangeably.

[0016] In this application, the cationic polymerization component includes epoxy resin, oxetane monomers, and a cationic photoinitiator, while the free radical polymerization component includes acrylate monomers and a free radical photoinitiator. The epoxy resin possesses strong adhesion and good color retention, providing flexibility and adhesion to the varnish, and maintaining the high gloss required for varnishing. The structure of the oxetane monomers gives them extremely low shrinkage and high wetting ability; their structure contains four-membered ring ethers, which, after ring-opening polymerization, can form a more flexible chain segment structure, thereby improving the adhesion and bending performance of the cured film on flexible substrates. The acrylate monomers enable rapid curing of the ink layer, increasing the curing speed. The cationic photoinitiator can initiate the polymerization of the epoxy resin and the oxetane monomers. The monomers undergo cationic polymerization to ensure deep curing during the hot stamping process, guaranteeing the performance of the ink layer. Free radical photoinitiators can rapidly initiate the polymerization of acrylate monomers, providing rapid surface curing and high hardness for the varnish, and providing a reaction basis. Leveling agents can improve the fluidity of the varnish system and reduce the surface tension of the varnish, making the cured ink layer smoother and flatter. The selection of polymerization inhibitors can improve the storage stability of the varnish, thereby inhibiting premature polymerization reactions of monomers under heat or low light conditions during the production and transportation of the varnish, allowing digital printing varnishes to be stored stably before use.

[0017] In the above embodiments, the epoxy resin accounts for 15% to 30% of the mass of the digital printing varnish. For example, the percentage includes values ​​such as 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 25%, 27%, 29%, and 30%, as well as a range of values ​​formed by any two of the above specific values ​​as endpoints. When the epoxy resin accounts for less than 15% of the mass percentage of digital printing varnish, it cannot sufficiently reduce the internal stress of the ink layer generated by the polymerization reaction of free radical polymers, resulting in poor flexibility and insufficient adhesion to the substrate after curing. Conversely, when the epoxy resin accounts for more than 30% of the mass percentage of digital printing varnish, the curing time may be longer. In this embodiment, the epoxy resin accounts for 15% to 30% of the mass percentage of digital printing varnish, which not only achieves a suitable curing rate and sufficient curing under complex hot stamping processes, but also fully utilizes the low shrinkage characteristics of epoxy resin in cationic polymerization to reduce the internal stress of the ink layer generated by the polymerization of acrylate monomers during free radical polymerization. This enhances the adhesion of the cured film to the substrate surface, which is beneficial for the application of digital printing varnish on flexible film materials such as polyethylene terephthalate (PET) and polypropylene (PP) used in the flexible packaging industry, and achieves better hot stamping effects.

[0018] In the above embodiments, the oxetane monomers account for 25% to 40% of the mass percentage of the digital printing varnish. For example, the percentages include 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%, as well as a range of values ​​including any two of the above specific values ​​as endpoints. When the oxetane monomers account for less than the lower limit of 25% of the mass percentage of the digital printing varnish, the proportion of cationic polymerizable components is insufficient, and the advantages of low shrinkage and high flexibility of oxetane cannot be fully utilized. The overall performance of the system tends to be more like that of a pure free radical system, and the bending flexibility and adhesion may decrease. When the oxetane monomers account for more than 40% of the mass percentage of the digital printing varnish, the proportion of free radical polymerizable components in the system may be relatively insufficient, affecting the initial curing speed and surface hardness. In this application, the oxetane monomer is controlled at 25%~40%. On the one hand, the oxetane monomer can synergistically form sufficient cationic polymerization components with epoxy resin, significantly reducing internal stress during the ink layer curing process and improving the adhesion and bending flexibility of the ink layer on flexible substrates. On the other hand, the oxetane monomer has extremely low viscosity and good wetting ability, which can effectively adjust the application viscosity of the varnish system, improve the spreadability and penetration of the varnish on the substrate surface, and thus further improve adhesion. At the same time, the cationic polymerization of oxetane is not affected by oxygen inhibition, and can achieve full curing under complex hot stamping process conditions.

[0019] In the above embodiments, the acrylate monomer accounts for 25% to 40% of the mass percentage of the digital printing varnish. For example, the percentage includes values ​​such as 25%, 26%, 27%, 28%, 29%, 30%, 32%, 34%, 36%, 38%, and 40%, as well as a range of values ​​formed by any two of the above specific values ​​as endpoints. When the acrylate monomer accounts for less than 25% of the mass percentage of the digital printing varnish, the proportion of free radical polymerization active reactive components is insufficient, which may lead to a decrease in curing speed and a low crosslinking density, thereby affecting the hardness, abrasion resistance, and scratch resistance of the ink layer, making it difficult to meet the surface strength requirements of high-speed printing and subsequent hot stamping processes. When the acrylate monomer accounts for more than 40% of the mass percentage of the digital printing varnish, it may lead to excessively low system viscosity, easily causing uneven ink layer distribution during printing. At the same time, a higher polymerization shrinkage rate will increase the internal stress of the ink layer, causing a decrease in the adhesion of the film layer on the flexible substrate, and even problems such as brittleness and wrinkling. In this embodiment, the acrylate monomer accounts for 25% to 40% of the mass of the digital printing varnish, forming a reasonable ternary main resin ratio with oxobutane monomers (25% to 40%) and epoxy resin (15% to 30%). This not only maintains an appropriate curing rate but also balances the hardness and flexibility of the film by controlling the crosslinking density and network structure of free radical polymerization and cationic polymerization. This avoids problems such as hot stamping layer peeling and pattern blurring caused by film performance defects in the hot stamping process, thus ensuring the appearance and performance of flexible packaging products.

[0020] In the above embodiments, the cationic photoinitiator accounts for 7% to 10% of the mass percentage of the digital printing varnish, such as 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%, as well as a range including any two of the above specific values ​​as endpoints. When the cationic photoinitiator accounts for less than the lower limit of 7% of the mass percentage of the digital printing varnish, the concentration of cationic activity generated by photolysis is insufficient, which cannot effectively trigger the cationic polymerization reaction of epoxy resin and oxetane monomers, resulting in incomplete curing of the system and residual unreacted oligomers in the film layer, leading to insufficient hardness and poor chemical resistance. When the cationic photoinitiator accounts for more than the upper limit of 10% of the mass percentage of the digital printing varnish, the photoinitiator may agglomerate in the system, reducing the uniformity of light absorption and causing local over-curing. In the embodiments of this application, the cationic photoinitiator accounts for 7% to 10% of the mass percentage of the digital printing varnish, which can achieve synergistic effect with the free radical photoinitiator, ensuring that the cationic polymerization reaction and the free radical polymerization reaction proceed simultaneously, ensuring that the varnish cures in a short time.

[0021] In the above embodiments, the free radical photoinitiator accounts for 5% to 10% of the mass percentage of the digital printing varnish, for example, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%, as well as a range of values ​​including any two of the above specific values ​​as endpoints. When the free radical photoinitiator accounts for less than the lower limit of 5% of the mass percentage of the digital printing varnish, the concentration of free radicals generated by light excitation is insufficient, which cannot fully initiate the free radical polymerization reaction of the acrylate monomers, resulting in a slow curing rate of the system. When the free radical photoinitiator accounts for more than the upper limit of 10% of the mass percentage of the digital printing varnish, the solubility of the photoinitiator in the varnish system may decrease, resulting in precipitation, uneven photocuring reaction, and local over-curing and yellowing of the lead film layer. At the same time, an excessively fast polymerization rate leads to increased local stress, affecting the adhesion and flexibility of the ink layer on the flexible substrate. In this embodiment, the mass percentage of the free radical photoinitiator is controlled at 5% to 10%, which can achieve a synergistic effect with the cationic photoinitiator, ensuring that the free radical polymerization and cationic polymerization proceed simultaneously and efficiently, and ensuring that the varnish is cured in a short time.

[0022] The leveling agent constitutes 0.1% to 1% of the digital printing varnish by mass, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%, as well as a range of values ​​including any two of the above specific values. Similarly, the polymerization inhibitor in the above embodiments constitutes 0.1% to 1% of the digital printing varnish by mass, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%, as well as a range of values ​​including any two of the above specific values.

[0023] As can be seen from the above, the digital printing varnish proposed in this invention uses oxocyclobutane monomers and epoxy resins to form a cationic polymer component. The "toughness" and "strong adhesion" of the cationic polymer component are used to balance the "brittleness" of free radical polymerization. This achieves more complete curing, higher adhesion to the substrate after curing, good water resistance and high hardness, wear resistance and scratch resistance after film formation, and also improves the hot stamping effect of the digital printing varnish.

[0024] In the preparation of the varnish, epoxy resin, oxetane monomers, acrylate monomers, leveling agents, and polymerization inhibitors are physically mixed under a safe light to obtain a premix. Under light-protected conditions, a cationic photoinitiator and a free radical photoinitiator are added to the premix and mixed. The free radical photoinitiator decomposes to release active free radicals, initiating the polymerization of carbon-carbon double bonds in the acrylate monomers. Simultaneously, the cationic photoinitiator decomposes to release cationic active species, initiating the ring-opening polymerization of the epoxy groups in the epoxy resin and the four-membered ring ethers in the oxetane monomers. After cationic polymerization, the shrinkage rate decreases, and the internal stress also decreases accordingly. The interpenetrating network structure formed by oxetane and epoxy resin provides the ink layer with high adhesion, good water resistance, and high hardness, wear resistance, and scratch resistance. It should be noted that the cationic polymerization system used in this embodiment does not rely on hydrophilic amine additives to overcome oxygen inhibition; complete curing can still be achieved through continuous reaction without the addition of hydrophilic amine additives.

[0025] Therefore, the digital printing varnish of this application can achieve high adhesion, good water resistance and high hardness and scratch resistance, and can also improve the hot stamping effect of digital printing varnish.

[0026] In some embodiments of this application, the epoxy resin is one or more of TTA-21 and TTA-16; wherein, when the epoxy resin includes both TTA-21 and TTA-16, the mass percentage of TTA-21 and TTA-16 is 7%~14.5%:8%~15.5%.

[0027] It should be noted that the mass percentages of TTA-21 and TTA-16 in this application are 7%-14.5% and 8%-15.5%, respectively. For example, the mass percentages include values ​​such as 7%:15.5%, 9%:13.5%, 10%:12%, 12%:10%, and 14.5%:8%, as well as any range defined by any two of these specific ratios. As long as the values ​​are within the above range, they conform to the TTA-21 and TTA-16 formulation of this application. By adding epoxy resins such as TTA-21 and TTA-16, the adhesion and bonding properties of the varnish can be improved, maintaining the high gloss required for varnishing, and further enhancing the abrasion resistance and adhesion of the ink layer. Specifically, TTA-21 provides good abrasion resistance to the varnish and also enhances its gloss, while TTA-16 provides flexibility and adhesion, effectively improving the varnish's adhesion.

[0028] In some embodiments, the mass ratio of epoxy resin to acrylate monomer is 0.4 to 1.2:1. Examples include values ​​such as 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, and 1.2:1, as well as values ​​within the range defined by any two of the aforementioned ratios. By controlling the ratio of epoxy resin to acrylate monomer, it is possible to ensure that the varnish system has a crosslinking density, forming a cured ink layer with adhesion and chemical resistance, while also adjusting the viscosity and reactivity of the epoxy resin to balance the hardness and toughness of the ink layer, resulting in good adhesion and flexibility of the cured ink layer on the substrate surface.

[0029] In some embodiments of this application, the oxetane monomer is one or more of TR-TCM101 and TR-TCM104. In embodiments that simultaneously include TR-TCM101 and TR-TCM104, the mass percentages of TR-TCM101 and TR-TCM104 are 11.5%~18.5% and 13.5%~21.5%, for example, the mass percentages include 11.5%:13.5%, 11.5%:21.5%, 12%:14%, 13.5%:19.5%, 14%:18%, 15%:16%, 15.5%:17.5%, 16%:15%, 17%:15.5%, 17%:18%, 18.5%:13.5%, 18.5%:21.5%, etc., as well as the range defined by any two of these specific ratios as endpoints. As long as the values ​​are within the above-mentioned range, they all conform to the ratio of TR-TCM101 and TR-TCM104 of this application. By selecting different combinations of oxetane monomers, the viscosity, curing speed, and overall performance of the cured film can be further optimized. When the oxetane monomers are only TR-TCM101 or TR-TCM104, the mass percentage of the oxetane monomers in the digital printing varnish is 25%~40%, for example, mass percentages of 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%, and the range of mass percentages including any two of the above specific values ​​as endpoints. TR-TCM101 and TR-TCM104 are available from Changzhou Qiangli Electronic New Materials Co., Ltd. TR-TCM101 is officially named 3-hydroxymethyl-3-ethyloxetane, and TR-TCM104 is officially named 3-benzyloxymethyl-3-ethyloxetane.

[0030] In some embodiments, the mass ratio of oxetane monomers to acrylate monomers is 0.65 to 1.6:1. Examples include values ​​such as 0.65:1, 0.8:1, 1:1, 1.2:1, 1.4:1, and 1.6:1, as well as values ​​within the range defined by any two of the aforementioned ratios. By controlling the ratio of oxetane monomers to acrylate monomers, a reasonable proportion can be achieved between the cationic polymerization component and the free radical polymerization component, allowing the advantages of both polymerization mechanisms to be fully utilized. This ensures a relatively fast initial curing speed while leveraging the low shrinkage and sustained curing characteristics of oxetane to achieve deep and thorough curing, further balancing the hardness and flexibility of the film layer.

[0031] In some embodiments, the cationic photoinitiator is one or more of PI-6976 and UVI-6976, and / or the cationic photoinitiator accounts for 0.7 to 2:1 of the mass percentage of the digital printing varnish, for example, the mass percentage includes values ​​such as 0.7:1, 0.9:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, and 2:1, as well as values ​​within the range defined by any two of the aforementioned ratios. By changing the mass percentage of PI-6976 and UVI-6976, not only can the cationic polymerization of epoxy resin and oxetane monomers be initiated simultaneously, ensuring that the hot stamping process can still achieve deep curing even under insufficient light, but it can also impart good flexibility and abrasion resistance to the varnish, while improving the gloss of the varnish. In addition, the synergistic effect of the cationic photoinitiator and the free radical polymerization component can balance the hardness and toughness of the ink layer, giving the varnish high hardness and scratch resistance, and overcoming the oxygen inhibition problem without the need to add hydrophilic additives, thus ensuring water resistance.

[0032] In some embodiments, the acrylate monomer is at least one of HDDA, CTFA, and THFA, wherein when the acrylate monomer simultaneously includes HDDA, CTFA, and THFA, the mass percentages of HDDA, CTFA, and THFA are 22%~26%:10%~13%:3%~11.4%. For example, values ​​include 22%:10%:11.4%, 23%:11%:9.4%, 24%:12%:7.4%, 25%:13%:5.4%, and 26%:10%:3%, as well as ranges defined by any two of the aforementioned ratios as endpoints. By controlling the ratio of HDDA, CTFA, and THFA, the compatibility of HDDA, CTFA, and THFA can be enhanced. The acrylate monomers work synergistically to promote the rapid curing of the varnish layer and improve curing efficiency. They can also work with components such as epoxy resin, oxetane monomers, and cationic photoinitiators to balance the "brittleness" of free radical polymerization, enhance the scratch resistance of the ink layer, and provide support for the hot stamping effect, adhesion, and scratch resistance of the varnish.

[0033] In some embodiments, the free radical photoinitiator is an acylphosphine oxide photoinitiator; and / or the free radical photoinitiator accounts for 5% to 8% of the mass percentage of the digital printing varnish. For example, the mass percentage of the acylphosphine oxide photoinitiator is equivalent to 5%, 6%, 7%, and 8%. The synergistic effect of the acylphosphine oxide photoinitiator and the cationic photoinitiator ensures a high crosslinking density in the varnish layer without excessively reducing the tack of the cured film.

[0034] In some further embodiments, the acylphosphine oxide photoinitiator of this application is selected from one or more of TPO, BAPO, or TPO-L. When the acylphosphine oxide photoinitiator includes TPO, BAPO, and TPO-L, the mass percentage of TPO is 5%, 4%, and 2% (equivalent), the corresponding mass percentage of BAPO is 1% and 2% (equivalent), and the mass percentage of TPO-L is 1%, 2%, and 3% (equivalent), and the total mass percentage of the three accounts for 5% to 8% of the mass percentage of the digital printing varnish. The acylphosphine oxide photoinitiator plays a key role in the varnish system. TPO can rapidly decompose to release free radicals, increasing the curing speed and forming a protective film; BAPO can penetrate deep into the ink layer to initiate a polymerization reaction, ensuring more thorough curing of the ink layer and avoiding uncured areas within the ink layer; TPO-L combines the advantages of both TPO and BAPO, enabling simultaneous curing of the surface and interior of the ink layer.

[0035] In some embodiments, the leveling agent is one or more of BYK-333 or TEGO Glide 410; and / or, the leveling agent accounts for 0.5% to 0.8% of the digital printing varnish by mass. For example, the leveling agent's mass percentage of the digital printing varnish includes values ​​such as 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, and 0.8%, as well as a range including any two of the aforementioned specific values. When the leveling agent includes both BYK-333 and TEGO Glide 410, the mass percentage of BYK-333 is equivalent to 0.25%, 0.3%, 0.35%, and 0.4%, and correspondingly, the mass percentage of TEGO Glide 410 is equivalent to 0.25%, 0.3%, 0.35%, and 0.4%, and the total mass percentage of both accounts for 0.5% to 0.8% of the digital printing varnish by mass. Among them, BYK-333 can effectively reduce the surface tension of the varnish, while TEGO Glide 410 has both excellent leveling properties and anti-cratering ability.

[0036] In some embodiments, the polymerization inhibitor is one or more of GENORAD16 or Lowilite 77; and / or, the polymerization inhibitor accounts for 0.1% to 0.3% of the digital printing varnish by mass. For example, the polymerization inhibitor as a percentage of the digital printing varnish by mass includes values ​​such as 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%, as well as ranges including any two of the aforementioned specific values. When the polymerization inhibitor includes both GENORAD16 and Lowilite 77, the GENORAD16 mass percentage is equivalent to 0.1%, 0.15%, 0.2%, and 0.25%, and the corresponding Lowilite 77 mass percentage is equivalent to 0.2%, 0.15%, 0.1%, and 0.05%, and the total mass percentage of both accounts for 0.1% to 0.3% of the digital printing varnish by mass. Among them, GENORAD16 can effectively inhibit the spontaneous polymerization reaction of varnish during storage and transportation, while Lowilite 77 can inhibit polymerization at room temperature, avoiding the phenomenon of internal stress and cracking of ink layer caused by excessively fast polymerization reaction.

[0037] The following describes, by way of example, a method for preparing digital printing varnish according to an embodiment of this application.

[0038] A method for preparing a digital printing varnish includes the following steps: under a safe light, epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container in a certain proportion and mixed to obtain a premix; under light-protected conditions, a cationic photoinitiator and a free radical photoinitiator are added to the premix and mixed, and then filtered to obtain the digital printing varnish.

[0039] As can be seen from the above, the digital printing varnish preparation method proposed in this application combines epoxy resin, oxetane monomers, acrylate monomers, leveling agents, and polymerization inhibitors, which can combine the advantages of high adhesion of cationic polymerization components and free radical polymerization components. This solves the problem of insufficient flexibility and adhesion, and hard and brittle ink layer after hot stamping varnish is cured. The light-proof conditions allow the cationic photoinitiator and the free radical photoinitiator to fuse more stably. The use of filter membrane filtration can obtain digital printing varnish with higher purity, thereby enhancing storage stability.

[0040] In some embodiments, epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container in proportion under a safe light and mixed to obtain a premix; under light-protected conditions, a cationic photoinitiator and a free radical photoinitiator are added to the premix and mixed, and then filtered to obtain a digital printing varnish.

[0041] In some embodiments, the safety lamp is selected from either a yellow light or a red light. The wavelength of the yellow light or the red light can avoid the absorption peak of the photoinitiator in the varnish system, which can effectively prevent the varnish from pre-curing during preparation, thereby ensuring the stability of the varnish in the hot stamping process.

[0042] In some embodiments, a disperser is used to stir and disperse the components added to the container; the speed of the disperser is 1500 r / min to 2000 r / min, for example, including values ​​such as 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min and 2000 r / min, as well as a range of values ​​including any two of the above specific values ​​as endpoints, so as to achieve uniform mixing and dispersion of the mixture.

[0043] In some embodiments, the stirring time is 25 min to 45 min, including values ​​such as 25 min, 30 min, 35 min, 40 min and 45 min, as well as a range of values ​​consisting of any two of the aforementioned specific values ​​as endpoints, thereby achieving uniform dispersion of the mixture.

[0044] In some embodiments, the mixing time of the premixed solution with the cationic photoinitiator and the free radical photoinitiator is 40 min to 60 min, for example, including values ​​of 40 min, 45 min, 50 min, 55 min and 60 min, as well as a range of values ​​including any two of the above specific values ​​as endpoints, so as to achieve further uniform mixing of the solution.

[0045] In some embodiments, in order to improve the purity and stability of the varnish system, the mixture after dispersion, stirring and mixing is usually filtered using a filter membrane. The pore size of the filter membrane is 0.4μm to 0.6μm, for example, the pore size values ​​include 0.4μm, 0.45μm, 0.5μm, 0.55μm and 0.6μm, as well as the range of values ​​including any two of the above specific values ​​as endpoints, thereby filtering out impurities and flocculants.

[0046] The following describes the digital printing varnish and its preparation method in conjunction with specific embodiments.

[0047] Example 1 The raw material composition of the digital printing varnish and its preparation method in this embodiment is shown in Table 1 below: Table 1

[0048] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0049] Example 2 Table 2

[0050] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0051] Example 3 Table 3

[0052] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1600 r / min for 35 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.45 μm filter membrane to obtain the varnish.

[0053] Example 4 Table 4

[0054] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1700 r / min for 40 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 50 min in the dark. Finally, the mixture is filtered through a 0.4 μm filter membrane to obtain the varnish.

[0055] Example 5 Table 5

[0056] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1800 r / min for 45 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 55 min in the dark. Finally, the mixture is filtered through a 0.55 μm filter membrane to obtain the varnish.

[0057] Example 6 Table 6

[0058] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1600 r / min for 35 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.45 μm filter membrane to obtain the varnish.

[0059] Example 7 Table 7

[0060] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 2000 r / min for 25 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 50 min in the dark. Finally, the mixture is filtered through a 0.6 μm filter membrane to obtain the varnish.

[0061] Example 8 Table 8

[0062] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 2000 r / min for 25 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 50 min in the dark. Finally, the mixture is filtered through a 0.6 μm filter membrane to obtain the varnish.

[0063] Example 9 Table 9

[0064] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 2000 r / min for 25 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 50 min in the dark. Finally, the mixture is filtered through a 0.6 μm filter membrane to obtain the varnish.

[0065] Example 10 Table 10

[0066] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0067] Comparative Example 1 Comparative Example 1 is a free radical curing system varnish, which is roughly the same as the raw material composition and preparation method of Example 1. The difference is that Comparative Example 1 does not contain epoxy resin, oxetane monomers, cationic photoinitiators, and adds hydrophilic amine additive B-27 by a mass percentage of 6% compared to Example 1. In addition, THFA is not added to the acrylate monomers, but ACMO and TMPTA are added, increasing the overall mass percentage of acrylate monomers to 81.4%.

[0068]

[0069] Table 11 Acrylate monomers, amine co-initiators, leveling agents, and polymerization inhibitors are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Free radical photoinitiators are added and stirring is continued for 45 min in the dark. The varnish is then obtained by filtering through a 0.5 μm filter membrane.

[0070] Comparative Example 2 Comparative Example 2 has roughly the same raw material composition and preparation method as Example 1. The difference is that Comparative Example 2 did not add epoxy resin, oxetane monomer, cationic photoinitiator, and added hydrophilic amine auxiliary agent B-27 by a mass percentage of 6% compared to Example 1. In addition, ACMO was added to the acrylate monomer, increasing the overall mass percentage of acrylate monomer to 81.4%.

[0071] Table 12

[0072] Acrylate monomers, amine co-initiators, leveling agents, and polymerization inhibitors are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Free radical photoinitiators are added and stirring is continued for 45 min in the dark. The varnish is then obtained by filtering through a 0.5 μm filter membrane.

[0073] Comparative Example 3 Comparative Example 3 uses roughly the same raw material composition and preparation method as Example 1, except that oxetane monomers are not added, and the original mass percentage of oxetane is adjusted to be incorporated into the epoxy resin and acrylate monomers. After adjustment, the total mass percentage of the epoxy resin is 32.4%, the total mass percentage of the acrylate monomers is 51%, and the contents of the remaining components are the same as in Example 1.

[0074] Epoxy resin, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0075] Comparative Example 4 Comparative Example 4 uses roughly the same raw material composition and preparation method as Example 1, except that the total mass percentage of oxetane monomers is 20%, lower than the 25% lower limit specified in this invention, with TR-TCM101 at 9% and TR-TCM104 at 11%. The reduced oxetane content is proportionally allocated to the epoxy resin and acrylate monomers. After adjustment, the total mass percentage of epoxy resin is 26%, the total mass percentage of acrylate monomers is 42%, and the content of the remaining components is consistent with that of Example 1.

[0076] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0077] Comparative Example 5 Comparative Example 5 uses roughly the same raw material composition and preparation method as Example 1, except that the total mass percentage of oxetane monomers is 45%, which is higher than the 40% upper limit specified in this invention, with TR-TCM101 at 20% and TR-TCM104 at 25%. The increased oxetane content is proportionally deducted from the epoxy resin and acrylate monomers. After adjustment, the total mass percentage of epoxy resin is 10%, the total mass percentage of acrylate monomers is 22%, and the content of the remaining components is the same as in Example 1.

[0078] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0079] Comparative Example 6 The raw material composition and preparation method of Comparative Example 6 are roughly the same as those of Example 1. The difference is that the mass percentage of the cationic photoinitiator is 11%, which is higher than the upper limit of 10% set by this invention. Correspondingly, the proportion of THFA in the acrylate monomer is reduced, and the total mass percentage of the acrylate monomer is 31.9%. The contents of the remaining components such as oxetane monomers and epoxy resin are the same as those in Example 1.

[0080] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0081] Comparative Example 7 The raw material composition and preparation method of Comparative Example 7 are roughly the same as those of Example 1. The difference is that the mass percentage of the cationic photoinitiator is 6%, which is lower than the 7% lower limit specified in this invention. Correspondingly, the proportion of HDDA in the acrylate monomer is increased, and the total mass percentage of the acrylate monomer is 34.9%. The contents of the remaining components such as oxetane monomers and epoxy resin are the same as those in Example 1.

[0082] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0083] Comparative Example 8 The raw material composition and preparation method of Comparative Example 8 are roughly the same as those of Example 1. The difference is that the total mass percentage of epoxy resin is 60.47%, which is much higher than the upper limit of 30% specified in this invention. Among them, TTA-21 is 25% and TTA-16 is 35.47%. The acrylate monomer is replaced with TMPTA and the mass percentage is reduced to 22.93%. No oxetane monomers are added. The content of the remaining components is the same as that of Example 1.

[0084] Epoxy resin, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0085] Comparative Example 9 Comparative Example 9 and Example 1 have roughly the same raw material composition and preparation method, except that the free radical photoinitiator is replaced by 1173 with a mass percentage of 3.67%; the proportion of HDDA in the acrylate monomer is increased accordingly, and the total mass percentage of acrylate monomer is 37.73%. The contents of other components such as oxetane monomers and epoxy resin are the same as in Example 1.

[0086] Epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and stirred and dispersed evenly in a high-speed disperser at a speed of 1500 r / min for 30 min. Then, cationic photoinitiator and free radical photoinitiator are added and stirred for another 45 min in the dark. Finally, the mixture is filtered through a 0.5 μm filter membrane to obtain the varnish.

[0087] Test case The digital printing varnish hot stamping effect, hardness, bending, adhesion and water resistance of the above embodiments and comparative examples were tested.

[0088] 1. Hot stamping effect Test method: The digital enhancement printer was used to print enhancement varnish and hot stamping samples. The printhead was Ricoh MH5420 fifth generation industrial printhead. The substrate was PET film. The ink layer thickness for the varnish effect was 50μm, and the ink layer thickness for the hot stamping effect was 15μm.

[0089] Evaluation criteria: Compare and observe the appearance of the hot stamping samples to see if there are any omissions in the hot stamping of the pattern.

[0090] 2. Hardness The test methods and evaluation criteria refer to the national standard GB / T 6739-2022 Pencil method for determining the hardness of paint film.

[0091] 3. Bending Test method: Fold the printed varnished samples of the example and comparison examples 180° in half.

[0092] Evaluation criteria: Observe the cracking state of the surface ink layer.

[0093] 4. Adhesion The test methods and evaluation criteria refer to GB / T 9286-1988 Cross-cut test for paint and varnish film.

[0094] 5. Water resistance Test method: Soak the printed hot foil stamping and varnishing samples in tap water for 24 hours.

[0095] Evaluation criteria: Observe whether there is any peeling or bubbling of the ink layer.

[0096] The test results of the examples and comparative examples obtained based on the above test methods and judgment criteria are shown in Table 13 below.

[0097] Table 13

[0098] As can be seen from the above test results, the digital printing varnish prepared in the embodiments of this application exhibits good comprehensive performance, specifically: good adhesion to the substrate surface, high ink layer hardness, wear and scratch resistance, good flexibility, and good water resistance.

[0099] This invention utilizes the synergistic effect of free radical polymerization and cationic polymerization, with the core being the complementary advantages of the two polymerization mechanisms. It leverages the characteristics of cationic polymerization to overcome the performance bottlenecks of traditional free radical systems. As shown in Examples 1-10, while maintaining the high hardness of 2H, it can achieve 180° bending without cracking, thus demonstrating the unique advantages of the free radical polymerization and cationic polymerization system in balancing hardness and flexibility. Similarly, regarding water resistance, whether for varnishing or hot stamping applications, there is no peeling or bubbling after immersion, confirming the effectiveness of eliminating hydrophilic components. Furthermore, the hot stamping adhesion reaches the highest level of 0, and the hot stamping effect is free of peeling and bubbling, demonstrating the synergistic effect of the components. The resulting digital printing ink has strong adaptability to hot stamping processes and produces excellent hot stamping results.

[0100] A comparison of the test results of Example 1 and Comparative Examples 1-2 shows that the addition of an amine co-initiator in the systems of Comparative Examples 1-2 leads to poor water resistance. Similarly, although Comparative Example 1 exhibits high hardness and water resistance, it suffers from poor hot stamping effect and flexibility, while Comparative Example 2 demonstrates good hot stamping effect and flexibility, but poor water resistance. The digital printing varnish of this application embodiment achieves enhanced varnishing and hot stamping sample surface adhesion without the need for an amine co-initiator, reducing the problem of poor water resistance caused by hydrophilic components.

[0101] By comparing the test results of Example 1 and Comparative Example 3, it can be seen that when the oxobutane monomers are completely removed from the cationic system and only the epoxy resin is retained, the internal stress of the ink layer cannot be effectively relieved, cracks appear after bending, the adhesion of hot stamping decreases, and the curing sufficiency of the hot stamping process decreases under the light-shielding conditions, resulting in slight missed hot stamping.

[0102] By comparing the test results of Example 1 with those of Comparative Examples 4 and 5, it can be seen that the content of oxetane monomers has a significant impact on the overall performance of the system: when the proportion of oxetane is too low, the shrinkage and toughening effects are insufficient, and the bending performance and hot stamping adhesion are slightly inferior to the optimal level; when the proportion of oxetane is too high, the free radical polymerizable components in the system are relatively insufficient, the initial curing speed decreases, and the ink layer hardness decreases, which cannot meet the requirements for wear resistance and scratch resistance.

[0103] By comparing the test results of Example 1 and Comparative Examples 6-7, it can be seen that both excessively high and excessively low proportions of cationic photoinitiator will lead to insufficient cationic activity concentration generated by photolysis, resulting in insufficient crosslinking density and poor performance in various aspects.

[0104] A comparison of the test results of Example 1 and Comparative Example 8 shows that when the ratio of epoxy resin to acrylate monomer is severely unbalanced and no oxetane is added, the curing rate and cross-linking network structure of the system are abnormal, resulting in obvious heat transfer defects, bending cracks, and a significant decrease in adhesion.

[0105] By comparing the test results of Example 1 and Comparative Example 9, it can be seen that after replacing the free radical photoinitiator TPO with 1173, the curing speed and hardness will eventually decrease because the initiation speed of 1173 is lower than that of TPO.

[0106] In summary, the digital printing varnish prepared in the embodiments of this application exhibits excellent comprehensive performance. The prepared digital printing varnish has good adhesion and flexibility on the substrate surface, good water resistance, wear and scratch resistance, and good hot stamping effect, thus meeting the practical application requirements of digital printing varnish and taking into account both hot stamping and varnishing enhancement applications.

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A digital printing varnish, characterized in that, Based on the mass of the digital printing varnish as 100%, the digital printing varnish has the following components in the following mass percentages: epoxy resin: 15%~30%, oxetane monomer: 25%~40%, acrylate monomer: 25%~40%, cationic photoinitiator: 7%~10%, free radical photoinitiator: 5%~10%, leveling agent: 0.1%~1%, polymerization inhibitor: 0.1%~1%.

2. The digital printing varnish as described in claim 1, characterized in that, The epoxy resin is one or more of TTA-21 and TTA-16.

3. The digital printing varnish as described in claim 2, characterized in that, The mass ratio of the epoxy resin to the acrylate monomer is 0.4~1.2:

1.

4. The digital printing varnish as described in claim 1, characterized in that, The oxobutane monomer is one or more of TR-TCM101 and TR-TCM104.

5. The digital printing varnish as described in claim 4, characterized in that, The mass ratio of the oxobutane monomer to the acrylate monomer is 0.65~1.6:

1.

6. The digital printing varnish as described in claim 1, characterized in that, The cationic photoinitiator is one or more of PI-6976 and UVI-6976.

7. The digital printing varnish as described in claim 6, characterized in that, The mass ratio of the cationic photoinitiator to the free radical photoinitiator is 0.7~2:

1.

8. The digital printing varnish as described in claim 1, characterized in that, The acrylate monomer is at least one of HDDA, CTFA, and THFA. When the acrylate monomer includes HDDA, CTFA, and THFA, the mass percentage of HDDA, CTFA, and THFA is 22%~26%: 10%~13%: 3%~11.4%.

9. The digital printing varnish as described in claim 1, characterized in that, The free radical photoinitiator is an acylphosphine oxide photoinitiator; and / or, the acylphosphine oxide photoinitiator is selected from one or more of TPO, BAPO, or TPO-L.

10. The digital printing varnish as described in claim 1, characterized in that, The leveling agent is one or more of BYK-333 or TEGOGlide 410; and / or, the leveling agent accounts for 0.5% to 0.8% of the mass of the digital printing varnish.

11. The digital printing varnish as described in claim 1, characterized in that, The polymerization inhibitor is one or more of GENORAD16 or Lowilite 77; and / or, the polymerization inhibitor accounts for 0.1% to 0.3% of the mass of the digital printing varnish.

12. A method for preparing a digital printing varnish according to any one of claims 1 to 11, characterized in that, Includes the following steps: Under a safe light, epoxy resin, oxetane monomer, acrylate monomer, leveling agent, and polymerization inhibitor are added to a container according to the specified ratio and mixed to obtain a premixed solution. Under light-protected conditions, a cationic photoinitiator and a free radical photoinitiator are added to the premixed liquid, and the mixture is then filtered to obtain a digital printing varnish.

13. The method for preparing digital printing varnish according to claim 12, characterized in that, The safety light is selected from either a yellow light or a red light; The components are stirred and dispersed in the container using a disperser; the speed of the disperser is 1500 r / min to 2000 r / min, and the stirring and dispersion time is 25 min to 45 min. The mixing time between the premixed solution and the cationic photoinitiator and the free radical photoinitiator is 40 min to 60 min. A filter membrane with a diameter of 0.4μm to 0.6μm is used for filtration.

Images