Polymerization inhibitor for printing ink, printing ink and application of polymerization inhibitor

Abstract

The invention discloses a polymerization inhibitor for printing ink, the printing ink and application of the printing ink. Relates to the field of ink polymerization inhibitors. The component of the polymerization inhibitor for the printing ink comprises p-hydroxyanisole, and the printing ink is selected from azo dye type printing ink or mixed printing ink of anthraquinone dye and azo dye. According to the polymerization inhibitor disclosed by the invention, p-hydroxyanisole is added into azo dye type ink or anthraquinone-azo mixed type ink as an active component, so that the reflux performance of an electrowetting display device after light aging can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of ink polymerization inhibitors, and in particular to a polymerization inhibitor for inks, inks, and their applications. Background Technology

[0002] Electrowetting electronic paper, a novel display technology based on the dielectric wetting effect, operates on the principle of switching the optical state of pixel units by controlling the contact angle of two immiscible fluids (typically a conductive liquid and an insulating ink) on the dielectric layer surface using voltage. Specifically, when a voltage is applied to the device, charge accumulation at the interface between the conductive liquid and the dielectric layer alters the interfacial tension, causing the conductive liquid to spread and compress the insulating ink, causing the ink to shrink to the pixel edge. At this point, the pixel is in an "on" state, increasing light transmittance. When the voltage is removed, the interfacial tension returns to its initial equilibrium, the ink flows back to the pixel center, and the pixel returns to a "off" state, decreasing light transmittance. This fluid dynamic equilibrium-based display mechanism endows electrowetting electronic paper with significant advantages such as low power consumption, high contrast, wide viewing angle, and sunlight visibility, making it a promising candidate for applications in e-book readers, smart wearable devices, and outdoor billboards. However, in practical applications, the display stability of electrowetting electronic paper still faces two major challenges: first, ink backflow, where after a period of continuous voltage application, the insulating ink, due to an imbalance between its internal cohesion and interfacial tension, cannot maintain its shrinkage state, leading to a decrease in pixel aperture ratio, contrast, and grayscale levels; second, insufficient ink light-induced stability, where the chemical structure of the insulating ink is prone to decomposition or polymerization reactions under long-term exposure to ultraviolet light or sunlight, causing molecular chain breakage, changes in cross-linking density, or component migration, further exacerbating ink backflow and severely restricting the long-term display reliability of the device. Especially in outdoor applications, the deterioration of ink performance is more significant under the combined effects of strong light and continuous voltage driving, becoming a core bottleneck restricting the development of electrowetting electronic paper towards high performance and long lifespan.

[0003] To address these issues, the industry has conducted extensive research on ink performance optimization, device structure improvement, and drive mode control, forming a multi-dimensional technological exploration system. Regarding ink formulation optimization, existing technologies primarily aim to improve the interfacial behavior and chemical stability of inks by adjusting the ratio of resin matrix, solvent system, and functional additives. For example, some studies introduce fluorocarbon resins or silicone resins as the main ink material, utilizing their low surface energy characteristics to reduce the adhesion between the ink and the dielectric layer, thus reducing the tendency for backflow. Simultaneously, the viscosity of the ink is adjusted by adding polar solvents such as esters and ketones, optimizing its flow response speed under voltage drive. In terms of functional additives, traditional solutions often use surfactants (such as perfluorooctyl sulfonate) to improve the interfacial compatibility between conductive liquids and inks, or add nanoparticles (such as silica and zinc oxide) to enhance the mechanical strength of the ink and inhibit molecular chain migration. At the device structure improvement level, researchers are attempting to improve stability by optimizing the dielectric layer material and thickness, designing microstructured pixel walls, and introducing protective layers.

[0004] While the aforementioned existing technologies alleviate the display stability issues of electrowetting electronic paper to some extent, they still have significant limitations in practical applications and cannot meet the long-term usage requirements of high-performance devices. Firstly, regarding ink formulation optimization, traditional resin materials (such as acrylates and polyurethanes), although possessing good film-forming properties and dielectric properties, are prone to oxidative degradation of unsaturated double bonds or ester groups in their molecular chains under light exposure, leading to increased ink viscosity and decreased flowability, which in turn exacerbates reflow. Meanwhile, specialty materials such as fluorocarbon resins are expensive and have poor compatibility with common solvents, easily resulting in phase separation and affecting display uniformity. Although the addition of surfactants can improve interfacial tension in the short term, they are prone to precipitating from the ink and adsorbing onto the dielectric layer surface during long-term use, causing interfacial contamination and reducing voltage-driven efficiency. The introduction of nanoparticles may cause localized stress concentration due to uneven dispersion, leading to ink layer cracking and further compromising display stability. Secondly, there is a contradiction between the complexity of the process and the balance between performance in the improved device structure: the preparation of the high dielectric constant dielectric layer requires precision processes such as atomic layer deposition (ALD), which significantly increases production costs; although the introduction of the protective layer can block some ultraviolet light, it will reduce the device transmittance and sacrifice display brightness, and if the adhesion between the protective layer and the ink is insufficient, peeling may occur, leading to new failure modes. Furthermore, the control of the driving method is essentially a passive mitigation of ink reflow, which cannot fundamentally solve the problem of insufficient chemical stability of the ink itself, and the introduction of pulse voltage may increase device power consumption, which contradicts the low power consumption advantage of electrowetting electronic paper.

[0005] In the research on functional additives for the chemical stability of inks, the limitations of existing anti-aging additives (such as antioxidants and UV absorbers) are particularly prominent. Traditional antioxidants (such as hindered phenols and phosphites) can inhibit free radical chain reactions, but their mechanism of action depends on their own oxidation and consumption. They gradually become ineffective under long-term light exposure or high temperature conditions, and have poor compatibility with ink resins, easily leading to "blooming". UV absorbers (such as benzophenones and benzotriazoles) absorb ultraviolet light and convert it into heat energy, but their absorption wavelength range is limited (mostly concentrated in 290-340nm), which cannot cover the full range of ultraviolet radiation in sunlight (200-400nm). Moreover, some UV absorbers undergo photoisomerization after absorbing energy, generating reactive intermediates, which actually accelerate ink decomposition. More critically, existing technologies lack specific solutions for regulating ink polymerization and degradation. Under the combined effects of light and voltage, inks not only undergo oxidative degradation of polymer chains but may also experience secondary polymerization due to residual unsaturated monomers. This leads to increased crosslinking density and elastic modulus, making it difficult for the ink to reflow smoothly after the voltage is removed or to maintain its shrinkage state under continuous voltage. Currently, there are no highly efficient polymerization inhibitors specifically designed for electrowetting inks. Existing polymerization inhibitors (such as hydroquinone and methylhydroquinone) are mostly used to terminate reactions during polymer synthesis. Their polymerization inhibition mechanism is singular (mainly through free radical capture) and cannot simultaneously inhibit degradation and polymerization reactions. Furthermore, these inhibitors have small molecular weights and high volatility, making them prone to loss during ink preparation and use, resulting in poor long-term polymerization inhibition effects. They may also undergo ion exchange reactions with conductive liquids, affecting the dielectric properties of devices. In addition, the preparation processes of existing polymerization inhibitors often rely on complex organic synthesis routes, such as multi-step substitution reactions or noble metal catalytic coupling, leading to high production costs that are difficult to meet the needs of large-scale industrialization of electrowetting electronic paper.

[0006] In summary, the root cause of the display stability problem in electrowetting electronic paper lies in the disruption of the mechanical balance of the ink under continuous voltage and the light-induced degradation of its chemical structure. Existing technologies suffer from insurmountable shortcomings in ink formulation optimization, device structure improvement, and the application of functional additives. In particular, there is a lack of a polymerization inhibitor that can efficiently inhibit ink polymerization and degradation while maintaining high compatibility with the electrowetting display system. Therefore, developing a novel polymerization inhibitor with high inhibition efficiency, excellent weather resistance, good compatibility, and a simple preparation process is crucial for solving the ink reflow problem and improving the outdoor applicability and long-term reliability of electrowetting electronic paper, representing a key technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0007] The purpose of this invention is to develop a novel polymerization inhibitor with high polymerization inhibition efficiency, excellent weather resistance, good compatibility and simple preparation process.

[0008] The first aspect of the present invention is: A polymerization inhibitor is provided.

[0009] The second aspect of the present invention is: An ink is provided.

[0010] The third aspect of the present invention is: The application of the ink.

[0011] Specifically, the technical solution adopted according to the first aspect of the present invention is as follows: A polymerization inhibitor for use in ink, wherein the inhibitor is composed of p-hydroxyanisole, and the ink is selected from azo dye type ink or a mixture of anthraquinone dye and azo dye ink.

[0012] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: The polymerization inhibitor of the present invention, by adding p-hydroxyanisole as an active ingredient to azo dye-type inks or anthraquinone-azo mixed inks, can significantly improve the reflow performance of electrowetting display devices after photoaging.

[0013] Its mechanism of action lies in the fact that the phenolic hydroxyl group (-OH) in the p-hydroxyanisole molecule can provide an active hydrogen atom, which reacts with the free radicals generated by photoaging (such as alkyl or aryl free radicals generated by homolytic cleavage of the "-N=N-" bond in azo dye molecules under ultraviolet light irradiation, and active free radicals generated by the reaction of the excited triplet state of anthraquinone dyes with surrounding substances), generating stable phenoxy free radicals. These phenoxy free radicals achieve electron delocalization through the conjugation effect of the benzene ring and the methoxy group (-OCH3), and are chemically stable, unable to initiate new polymerization reactions, thus interrupting the free radical chain reaction, reducing ink molecule decomposition, maintaining the contact angle stability of the ink on the dielectric layer surface, and reducing the reflow effect after photoaging. For azo dye-type inks, the photolysis of their azo groups is the main source of free radicals, and p-hydroxyanisole can directly target and scavenge these free radicals; for anthraquinone-azo mixed inks, the free radicals generated by the excited state of their anthraquinone dyes can also be efficiently scavenged. Therefore, this polymerization inhibitor has a universal inhibitory effect on both types of inks.

[0014] According to one embodiment of the present invention, the mass percentage of p-hydroxyanisole in the ink is 0.025wt%-0.25wt%. By limiting the effective concentration range, the free radical scavenging effect is ensured while avoiding negative impacts on ink performance. Preferably, the mass percentage of p-hydroxyanisole in the ink is 0.05wt%. The addition amount of 0.05wt% can significantly reduce the intensity of free radical signals after photoaging, while avoiding the side effects that may be caused by high concentrations. At this concentration, p-hydroxyanisole can efficiently scavenge free radicals generated by photoaging (such as alkyl / aryl free radicals from the photolysis of "-N=N-" bonds in azo dyes and active free radicals generated in the excited state of anthraquinone dyes) without affecting the initial properties of the ink, achieving the best balance between inhibiting free radical chain reactions and maintaining ink stability.

[0015] According to one embodiment of the present invention, the azo dye ink is a magenta ink.

[0016] According to one embodiment of the present invention, the mixed ink of anthraquinone dye and azo dye is a green ink.

[0017] Specifically, the technical solution adopted according to the second aspect of the present invention is as follows: An ink comprising the aforementioned polymerization inhibitor.

[0018] A method for preparing an ink includes the following steps: adding p-hydroxyanisole to the ink and subjecting it to ultrasonic treatment.

[0019] According to one embodiment of the present invention, the frequency of the ultrasonic treatment is 40KHz-60KHz.

[0020] According to one embodiment of the present invention, the ultrasonic treatment time is 5-6 minutes.

[0021] In another aspect, the present invention provides an electrowetting display device, comprising a lower substrate, an upper substrate, and the ink and electrolyte solution filled between the lower substrate and the upper substrate. The polymerization inhibitor maintains a stable contact angle of the ink on the dielectric layer by inhibiting ink decomposition, thereby reducing reflow.

[0022] According to one embodiment of the present invention, the lower substrate is based on ITO conductive glass, on which a dielectric layer with a thickness of 400-420 nm, a hydrophobic layer with a thickness of 400-420 nm, and a pixel wall with a height of 3.5-4.0 μm are sequentially arranged.

[0023] According to one embodiment of the present invention, the upper substrate is ITO conductive glass.

[0024] According to one embodiment of the present invention, the electrolyte solution is water or a water-ethylene glycol mixture.

[0025] According to one embodiment of the present invention, a pressure-sensitive adhesive is adhered to the surface of the upper substrate, and the upper substrate and the lower substrate are bonded together by the pressure-sensitive adhesive and their edges are sealed with UV adhesive. The presence of the pressure-sensitive adhesive enables the bonding of the upper substrate and the lower substrate.

[0026] According to one embodiment of the present invention, the components of the hydrophobic layer are selected from Hyflon AD 60, Cytop, or Teflon. Hyflon AD 60 is an amorphous perfluoropolymer; Cytop is a perfluoropolyether polymer; and Teflon is Teflon.

[0027] According to one embodiment of the present invention, the dielectric layer comprises photoresist. The photoresist provides uniform dielectric properties, ensuring a stable electric field for driving the ink.

[0028] According to one embodiment of the present invention, the pixel wall is composed of HN-008 photoresist.

[0029] According to one embodiment of the present invention, the method for preparing the electrowetting display device includes the following steps: preparing a lower substrate, wherein the lower substrate is based on ITO conductive glass, and a dielectric layer, a hydrophobic layer and a pixel wall are formed sequentially; using a self-assembly filling method, an electrolyte solution is injected into a filling tank and ink is added to form an oil-water interface, and the lower substrate is tilted and immersed into the oil-water interface to fill the pixel grid with ink; an upper substrate with pressure-sensitive adhesive is aligned and bonded to the filled lower substrate, and the pressure-sensitive adhesive is pressed and cured and then the edges are sealed with UV adhesive.

[0030] According to one embodiment of the present invention, the lower substrate is immersed at an angle of 10°-30° with the liquid surface, and the immersion speed is 2-3 mm / min.

[0031] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The images show electron paramagnetic resonance (EPR) images of the inks in Example 1 and Comparative Example 1.

[0033] Figure 2 The images show electron paramagnetic resonance (EPR) images of the inks in Example 2 and Comparative Example 2.

[0034] Figure 3 The graphs show the reflow performance test results of the inks in Example 3 and Comparative Example 1.

[0035] Figure 4The graphs show the reflux performance test results of the inks in Examples 1 and 4.

[0036] Figure 5 The graphs show the reflow performance test results of the inks in Example 5 and Comparative Example 2.

[0037] Figure 6 The graphs show the reflux performance test results of the inks in Examples 2 and 6.

[0038] Figure 7 The chart shows the aperture ratio test results for the inks in Examples 2, 5, 6, and Comparative Example 2.

[0039] Figure 8 The chart shows the opening rate test results of the inks from Examples 2, 5, 6, and Comparative Example 2 after aging.

[0040] Figure 9 The absorption spectra of the inks in Examples 1-2 and Comparative Examples 1-2 are shown.

[0041] Figure 10 This is a schematic diagram of an electrowetting display device. Detailed Implementation

[0042] The terms "preferred," "more preferred," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0043] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of the present invention.

[0045] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0046] In the examples and comparative examples, the azo dye ink is named magenta ink because its color is magenta.

[0047] In the examples and comparative examples, the anthraquinone dye and azo dye mixed ink is named green ink because its color is green.

[0048] In the embodiments, such as Figure 10 As shown, ink is filled between the upper and lower substrates of the electrowetting display device. When the ink is an azo dye ink, the encapsulation liquid is pure water; when the ink is a mixed ink of anthraquinone dye and azo dye, the encapsulation liquid is a mixed solution of water and ethylene glycol in a volume ratio of 3.7:7.2.

[0049] Example 1 An ink is a mixture of azo dyes and anthraquinone dyes, and contains 0.05 wt% of the polymerization inhibitor p-hydroxyanisole.

[0050] The preparation method of the above ink is as follows: Weigh 3 bottles of 10g mixed ink containing anthraquinone dye and azo dye separately using an electronic balance for later use; The p-hydroxyanisole powder was weighed using an electronic balance and added to the above-mentioned anthraquinone dye and azo dye mixed ink, so that the concentration of p-hydroxyanisole was 0.05wt%. Then, it was placed in an ultrasonic instrument and ultrasonicated at 60W power and 40KHz frequency for 5 minutes to obtain the above-mentioned ink.

[0051] An electrowetting display device, the electrowetting display device comprising a lower substrate and the ink, the lower substrate comprising a dielectric layer and a hydrophobic layer.

[0052] The fabrication method of the above-mentioned electrowetting display device is as follows: First, a 1.3-inch electrowetting device substrate is prepared and filled. The substrate structure is as follows: the base is made of ITO conductive glass, topped with a 400nm thick HN-018 photoresist dielectric layer, a 400nm thick Hyflon AD 60 hydrophobic layer, and the pixel walls are made of HN-008 photoresist with a height of 3.5μm. During the filling stage, a self-assembly filling method is used. An electrolyte solution is first poured into the filling tank, followed by ink to form a stable oil-water interface. The substrate is fixed on a tiltable stage at an angle of 10°-30° to the liquid surface, with the stage at approximately 10° to the direction of movement to reduce air bubbles. It is then immersed at a speed of 2 mm / min along the guide rail, allowing the pixel cells to sequentially contact the oil phase and be drawn in by capillary force. During this process, the hydrophobic properties of the hydrophobic insulating layer within the pixel cells and the blocking effect of the hydrophilic pixel walls on the ink are utilized. As the liquid level rises, the ink is actively adsorbed into the pixel cells and spread on the hydrophobic surface, thus forming a self-assembly filling effect. After filling, pressure-sensitive adhesive is first applied to the ITO glass surface of the upper substrate. Then, the upper and lower substrates are precisely aligned and bonded together. Subsequently, pressure is applied under a heavy object for 10 minutes. Finally, UV adhesive is used to seal the edges of the device, resulting in an electrowetting display device. A schematic diagram of the device structure is shown below. Figure 10 As shown.

[0053] Example 2 The difference between Example 2 and Example 1 is that the ink in Example 2 is an azo dye ink.

[0054] Example 3 The difference between Example 3 and Example 1 is that the concentration of p-hydroxyanisole in Example 3 is 0.025 wt%.

[0055] Example 4 The difference between Example 4 and Example 1 is that the concentration of p-hydroxyanisole in Example 4 is 0.15 wt%.

[0056] Example 5 The difference between Example 5 and Example 2 is that the concentration of p-hydroxyanisole in Example 5 is 0.025 wt%.

[0057] Example 6 The difference between Example 6 and Example 2 is that the concentration of p-hydroxyanisole in Example 6 is 0.25 wt%.

[0058] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the ink of Comparative Example 1 does not contain the polymerization inhibitor p-hydroxyanisole.

[0059] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the ink of Comparative Example 2 does not contain the polymerization inhibitor p-hydroxyanisole.

[0060] Performance testing: The inks from Example 1 and Comparative Example 1 were subjected to electron paramagnetic resonance (EPR) analysis to detect free radicals in the inks. Here, intensity represents the free radical intensity, and field represents the magnetic field strength. Figure 1 Figure 'a' represents the EPR detection graph with a magnetic field strength of 3350-3950. Figure 1 b is an EPR detection plot with a magnetic field strength of 3590-3640. From Figure 1 It is known that for the ink of Comparative Example 1 (green ink), before aging, the peak intensity of its free radicals was 0.02398. After aging in a xenon lamp weathering chamber for 25 hours, the peak intensity increased to 0.02820, meaning that after photoaging, the peak intensity of the free radicals increased by 0.00422. For the ink of Example 1, due to the addition of the polymerization inhibitor p-hydroxyanisole, after the same 25-hour aging, the peak intensity of the free radicals was 0.02678. Compared to the ink of Comparative Example 1 without p-hydroxyanisole, the increase in free radicals after photoaging of the ink of Example 1 was smaller, only 66% of that of the ink without p-hydroxyanisole.

[0061] The inks from Example 2 and Comparative Example 2 were subjected to electron paramagnetic resonance (EPR) analysis to detect free radicals in the inks. Here, intensity represents the free radical intensity, and field represents the magnetic field strength. Figure 2 Figure 'a' represents the EPR detection graph with a magnetic field strength of 3350-3950. Figure 2 b is an EPR detection plot with a magnetic field strength of 3590-3640. From Figure 2 It is known that for the ink of Comparative Example 2 (magenta ink), before aging, the peak intensity of its free radicals was 0.02551. After 10 hours of aging, the peak intensity increased to 0.03009. After photoaging, the peak intensity of free radicals increased by 0.00458. For the ink of Example 2, due to the addition of the polymerization inhibitor p-hydroxyanisole, after the same 10 hours of aging, the peak intensity of free radicals was 0.02815. Compared with the ink without the addition of the polymerization inhibitor p-hydroxyanisole, the increase in free radicals in the ink after photoaging was smaller.

[0062] from Figure 1-2 It is known that inks are prone to decomposition under light or ultraviolet light, generating free radicals, which leads to side reactions between ink molecules and the formation of unstable structures. The polymerization inhibitor p-hydroxyanisole, by scavenging and inhibiting the generation of free radicals, maintains the stability of the ink's interfacial properties. This stability directly reduces the reflow effect during the electrowetting process.

[0063] The devices from Example 3 and Comparative Example 1 were aged in a xenon lamp weathering chamber for 100 hours. The reflow performance of the devices was then measured using the following method: The electrowetting display device was placed in a spectrometer (model XDS-1B) so that it was in contact with light. A constant current voltage was applied using a DC regulated power supply, adjusted to 15V and 0.04A. The positive terminal of the instrument was connected to the upper substrate of the electrowetting display device sample, and the negative terminal was connected to the lower substrate. The instrument was started, and the detection time was 3 minutes. Spectral data for different samples were collected. The reflow performance of the samples was then analyzed to obtain a graph. The test results are shown below. Figure 3 As shown. Figure 3 In this context, Time represents time, and Transmissivity represents the transmittance. Figure 3 Figure 'a' shows the reflow performance of the device in Comparative Example 1. Figure 3 Figure b shows the reflow performance of the device in Comparative Example 1 after 100 hours of aging. Figure 3 c represents the reflow performance diagram of the device in Example 3. Figure 3 d represents the reflow performance of the device in Example 3 after 100 hours of aging. From... Figure 3 As can be seen, the device in Comparative Example 1 without p-hydroxyanisole and the device in Example 3 with 0.025 wt% p-hydroxyanisole both experienced almost complete reflux. The device in Comparative Example 1 had a ΔTransmissivity of 3.261%, while the device in Example 3 had a ΔTransmissivity of 6.066%.

[0064] That is, p-hydroxyanisole needs to meet a minimum effective concentration to fully scavenge free radicals and block the chain reaction. Comparative Example 1 was completely refluxed because "no p-hydroxyanisole was found", and Example 3 was unable to overcome the large number of free radicals generated by the ink after exposure to light because "the concentration of p-hydroxyanisole (0.025wt%) was lower than the effective threshold". Ultimately, both examples showed "almost complete reflux" due to the uncontrolled free radicals causing the ink structure to be destroyed.

[0065] The devices from Examples 1 and 4 were aged in a xenon lamp weathering chamber for 100 hours, and their reflow performance was measured. The test results are as follows: Figure 4 As shown. Figure 4 Figure 'a' represents the reflow performance of the device in Example 1. Figure 4 Figure b shows the reflow performance of the device in Example 1 after 100 hours of aging. Figure 4 c represents the reflow performance diagram of the device in Example 4. Figure 4 d represents the reflow performance of the device in Example 4 after 100 hours of aging. From... Figure 4 As can be seen, devices with the addition of 0.05wt% and 0.15wt% p-hydroxyanisole can still maintain incomplete ink reflow.

[0066] The devices from Example 5 and Comparative Example 2 were aged in a xenon lamp weathering chamber for 100 hours, and their reflow performance was measured. The test results are as follows: Figure 5 As shown. Figure 5 Figure 'a' shows the reflow performance of the device in Comparative Example 2. Figure 5 Figure b shows the reflow performance of the device in Comparative Example 2 after 100 hours of aging. Figure 5 c represents the reflow performance diagram of the device in Example 5. Figure 5 d represents the reflow performance of the device from Example 5 after 100 hours of aging. From Figure 5 As can be seen, after 10 hours of photoaging, both the devices in Example 5 and Comparative Example 2 exhibited significant reflow phenomena. The device in Comparative Example 2 experienced almost complete reflow within the test period, with a ΔTransmissivity of 28.308%, while the ΔTransmissivity of Example 5 was 21.375%.

[0067] The reason is that Comparative Example 2 does not contain p-hydroxyanisole, and the free radicals generated by light accumulate in large quantities and trigger a chain reaction, which continuously damages the ink structure and device stability, resulting in severe reflow.

[0068] In Example 5, p-hydroxyanisole significantly reduced the free radical concentration in the ink by scavenging active free radicals and generating stable products, thus inhibiting the occurrence of chain reactions and maintaining the stability of the ink structure and devices, resulting in a low degree of reflux.

[0069] The devices from Examples 2 and 6 were aged in a xenon lamp weathering chamber for 10 hours, and their reflow performance was measured. The test results are as follows: Figure 6 As shown. Figure 6 Figure 'a' shows the reflow performance of the device in Example 2. Figure 6 Figure b shows the reflow performance of the device in Example 2 after 10 hours of aging. Figure 6 c represents the reflow performance diagram of the device in Example 6. Figure 6 d represents the reflow performance of the device from Example 6 after 10 hours of aging. From... Figure 6 As can be seen, the devices with 0.05 wt% p-hydroxyanisole and 0.25 wt% p-hydroxyanisole added can maintain incomplete reflux. Among them, the device in Example 2 has a ΔTransmissivity of 19.925%, and the device in Example 6 has a ΔTransmissivity of 24.715%.

[0070] Devices from Examples 2, 5, 6, and Comparative Example 2 were used. The aperture ratio of the devices was tested without aging. The test method was as follows: A DC voltage of 15V was applied using a DC regulated power supply. The positive terminal of the instrument was connected to the upper substrate of the sample, and the negative terminal to the lower substrate. The sample was placed under a microscope. The instrument was started, and a linearly increasing voltage of 15V was applied to the sample first, followed by three pulses of 15V. The aperture size was observed under the microscope. The test results are as follows. Figure 7 As shown. Figure 7 In this context, "Time" represents time and "Opening ratio" represents the opening ratio. Figure 7 In the diagram, 'a' represents the test image of Comparative Example 2. Figure 7 In the diagram, b represents the test image of Example 5. Figure 7 In the diagram, 'c' represents the test image from Example 2. Figure 7 d is the test diagram of Example 6. From Figure 7 It can be seen that, without aging treatment, the devices of Example 2, Example 5, Example 6 and Comparative Example 2 can all open up their patterns when a linear voltage is applied.

[0071] The devices from Examples 2, 5, 6, and Comparative Example 2 were subjected to 10 hours of aging before the aperture ratio of the devices was tested. The test results are as follows: Figure 8 As shown. Figure 8 The "opening" in this context refers to the ability of the ink-formed pattern to maintain a preset structural or functional state under specific conditions, specifically in the ability to achieve the expected response during subsequent operations (such as applying voltage). Figure 8 In this context, "Time" represents time and "Opening ratio" represents the opening ratio. Figure 8 In the diagram, 'a' represents the test image of Comparative Example 2. Figure 8 In the diagram, b represents the test image of Example 5. Figure 8 In the diagram, 'c' represents the test image from Example 2. Figure 8 d represents the test diagram from Example 6. (From...) Figure 8 The test results show that, under the condition of applying a linear voltage, only the device with 0.05 wt% p-hydroxyanisole (Example 2) can still maintain the open state of the pattern (e.g., ...). Figure 7 (Same as above), while the device patterns of Comparative Example 2, Example 5 and Example 6 could not be opened, indicating that the ink with 0.05wt% p-hydroxyanisole added improved the reflow performance of the electrowetting device after photoaging.

[0072] The inks from Examples 1-2 and Comparative Examples 1-2 were used for ink absorption spectroscopy testing. The absorption spectroscopy testing steps are as follows: Turn on the instrument power and confirm that the light source (deuterium lamp / UV, tungsten lamp / visible), monochromator, and detector are normal; set parameters such as wavelength (accuracy ±0.1nm), slit (0.1-5nm, matching absorption intensity), and scanning mode; Preheat for 15-30 minutes until baseline drift is ≤ ±0.001 AU / 10 min; Select a cuvette that matches the wavelength range and check that the light-transmitting surface is free of scratches, cracks, or stains. Rinse the cuvette three times with distilled water and rinse the test solution two to three times (to avoid residual diluted sample). Prepare the test solution to ensure that the absorbance is in the range of 0.2-0.8 AU (if it exceeds this range, it needs to be diluted, in accordance with Lambert-Beer's Law). Add reference solution to two cuvettes (liquid level 3 / 4 of volume, no air bubbles), and wipe the light-transmitting side with lens paper in one direction only; Place the reference liquid in the reference position and the sample position respectively, and close the lid; start baseline correction (scan 300-800nm ​​or the target range) until the baseline is flat (A≈0). Keep the reference position unchanged, but replace the sample position with the same reference liquid dish; zero the container to A=0.0000 and T=100%. Sample measurement: Single point mode: Replace the sample with the test liquid vessel (to prevent spillage), let it stand for 1-2 seconds and then record the A / T value; Scan mode: Set the scan range to 300-800nm, start the scan and save the curve (including λmax and peak intensity data).

[0073] The results of ink absorption spectroscopy test are as follows Figure 9 , Figure 9 In this context, Wavelength represents wavelength, and Abs represents absorbance. Figure 9 In the diagram, 'a' represents the test graphs for Example 1 and Comparative Example 1. Figure 9 Figure b shows the test results for Example 2 and Comparative Example 2. During the tests, the absorbance of the ink, the absorbance of the ink after 10 or 25 hours of light aging treatment, and the absorbance of the ink without added p-hydroxyanisole (Comparative Example 1 or Comparative Example 2) after 10 or 25 hours of light aging treatment were recorded. Figure 9 As can be seen from the above, for Example 1 and Comparative Example 1 (both green inks), the ink of Example 1 with added p-hydroxyanisole polymerization inhibitor showed a decrease in absorption spectrum after photoaging. For Example 2 and Comparative Example 2 (both magenta inks), the ink of Example 2 with added p-hydroxyanisole polymerization inhibitor showed an increase in absorption spectrum after photoaging.

[0074] That is, for Example 1 and Comparative Example 1, the p-hydroxyanisole polymerization inhibitor provides hydrogen atoms through the phenolic hydroxyl group, effectively scavenging free radicals generated by the photoaging of anthraquinone dyes and blocking the chain reaction of polymerization / aggregation. At this time, the dye molecules remain in a dispersed state, the chromophore structure is not destroyed by polymerization / aggregation, and the absorption spectrum intensity recovers to a level closer to the normal level before photoaging (Example 1, compared to the abnormally high absorption state after photoaging in Comparative Example 1, shows a "reduced absorption spectrum"). For Example 2 and Comparative Example 2, the p-hydroxyanisole polymerization inhibitor provides hydrogen atoms through its phenolic hydroxyl groups, preferentially combining with the free radicals generated by the photolysis of the azo dye to generate stable phenoxy free radicals, thus blocking the chain reaction of dye decomposition. At this point, the "-N=N-" chromophore structure of the azo dye is preserved, and the absorption spectral intensity recovers to a level closer to the normal level before photoaging (Example 2, compared to the abnormally low absorption state after photoaging in Comparative Example 2, exhibits an "increased absorption spectrum"). Both demonstrate the protective effect of p-hydroxyanisole polymerization inhibitor on the photostability of dyes, but the absorption spectrum changes in opposite directions due to the different initial reaction directions of dye photoaging.

[0075] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A polymerization inhibitor for inks, characterized in that: The polymerization inhibitor is composed of p-hydroxyanisole, and the ink is selected from azo dye ink or a mixture of anthraquinone dye and azo dye ink.

2. The polymerization inhibitor for inks according to claim 1, characterized in that: The mass percentage of p-hydroxyanisole in the ink is 0.025wt%-0.25wt%.

3. An ink, characterized in that: Including the polymerization inhibitor as described in claim 1 or 2.

4. A method for preparing the ink according to claim 3, characterized in that: Includes the following steps: p-hydroxyanisole was added to the ink and then subjected to ultrasonic treatment.

5. The method according to claim 4, characterized in that: The frequency of the ultrasonic treatment is 40KHz-60KHz.

6. The method according to claim 4, characterized in that: The ultrasonic treatment time is 5-6 minutes.

7. An electrowetting display device, characterized in that: It includes a lower substrate, an upper substrate, and the ink and electrolyte solution as described in claim 3, which are filled between the lower substrate and the upper substrate.

8. The electrowetting display device according to claim 7, characterized in that: The lower substrate is based on ITO conductive glass, on which a dielectric layer with a thickness of 400-420nm, a hydrophobic layer with a thickness of 400-420nm, and a pixel wall with a height of 3.5-4.0μm are sequentially arranged.

9. The electrowetting display device according to claim 7, characterized in that: The electrolyte solution is water or a water-ethylene glycol mixture.

10. The electrowetting display device according to claim 7, characterized in that: The hydrophobic layer is composed of Hyflon AD 60, Cytop, or Teflon.

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