UV (ultraviolet) tackifying film for flexible display process as well as preparation method and application of UV tackifying film

Abstract

The invention discloses a UV tackifying film for a flexible display process as well as a preparation method and application thereof, and relates to the technical field of functional polymer composite materials. The UV tackifying film comprises a first antistatic layer, a first transparent PET film layer, a second antistatic layer, a release agent layer, a UV tackifying adhesive layer, a third antistatic layer, a second transparent PET film layer and a fourth antistatic layer which are sequentially compounded, the UV tackifying adhesive comprises UV tackifying prepolymerized resin and the like, the UV tackifying prepolymerized resin is a mixture of modified acrylic resin and modified polyurethane resin, the modified acrylic resin comprises o-phenyl phenoxy ethyl acrylic resin and butyl acrylate, and the modified polyurethane resin comprises triethylene glycol di-2-ethylhexoate and acrylate modified polyurethane. The UV tackifying film can achieve function switching of low-viscosity protection before UV irradiation and high-viscosity supporting after UV irradiation, meets the requirements of the flexible display process, has excellent antistatic property and optical performance, is simple in preparation process and is convenient for industrial popularization.

Description

Technical Field

[0001] This invention relates to the field of functional polymer composite materials technology, and in particular to a UV adhesion-enhancing film for flexible display manufacturing processes, its preparation method, and its application. Background Technology

[0002] As consumer electronics products rapidly iterate towards thinner, lighter, and more deformable designs, touch display panel technology has gradually evolved from traditional rigid screens to flexible screens, with curved screens, foldable screens, and even rollable screens becoming the mainstream development direction in the market. These flexible display panels typically use CPI or hardened PET as the substrate layer. Although they possess excellent flexibility and light transmittance, their soft structure and lack of sufficient rigidity present numerous technical challenges during the manufacturing process: on the one hand, the panels are difficult for automated equipment to grip stably, resulting in low production efficiency; on the other hand, the panel surface is susceptible to external friction and dust contamination, affecting product yield.

[0003] To address the aforementioned issues, existing technologies typically employ a process mode that uses "protective film + support film" separately: during panel transportation and early stages of the manufacturing process, a protective film is applied to achieve surface protection; before entering the core manufacturing stage, the protective film must be peeled off and the support film reapplied to provide structural support.

[0004] The existing technology uses a process mode of using "protective film + support film" separately, which has certain drawbacks: On the one hand, the protective film must be applied first to protect the panel during transportation, and then the protective film must be peeled off and the support film reapplied before the manufacturing process. The multiple application and peeling operations not only increase the production steps and extend the process cycle, but also require precise control of each step. Otherwise, it is easy to cause panel positioning deviation, affecting the accuracy of subsequent processes, resulting in a cumbersome and inefficient process. On the other hand, high peeling voltage is easily generated when peeling off the protective film. Static electricity may damage the sensitive circuits inside the panel, and the peeling process may also cause scratches on the panel surface or leave adhesive residue, increasing the risk of panel damage and reducing product yield. At the same time, the two applications of the protective film and the support film may introduce air bubbles due to poor air venting, and the superimposed deviation in light transmittance may also impair the final optical effect of the display panel. In addition, the protective film and the support film need to be designed, produced and stored separately, increasing the cost of raw materials. Moreover, the peeled protective film cannot be reused, generating a large amount of industrial waste, which is not in line with the concept of green production. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a UV adhesion-enhancing film for flexible display manufacturing processes, its preparation method, and its application. This UV adhesion-enhancing film has low viscosity before UV irradiation and can be used as a protective film for panel transportation and early protection. After UV irradiation, its viscosity is significantly enhanced, and it can be used as a support film to provide process support without peeling or secondary lamination, thus optimizing the manufacturing process, reducing the risk of panel damage, and ensuring excellent optical and antistatic properties.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A UV tackifying film for flexible display manufacturing process includes a first antistatic layer, a first transparent PET film layer, a second antistatic layer, a release agent layer, a UV tackifying adhesive layer, a third antistatic layer, a second transparent PET film layer, and a fourth antistatic layer, which are sequentially laminated.

[0008] The UV-modified adhesive comprises the following components in parts by weight:

[0009] 100 parts of UV tackifying prepolymer resin with a solid content of 18-45%, 1-10 parts of thermosetting agent, 0.1-5 parts of photoinitiator, and 50-200 parts of diluent;

[0010] The UV-tackifying prepolymer resin comprises a mixture of modified acrylic resin and modified polyurethane resin;

[0011] The modified acrylic resin includes o-phenylphenoxyethyl acrylic resin and butyl acrylate;

[0012] The modified polyurethane resin includes triethylene glycol diisooctanoate and acrylate-modified polyurethane.

[0013] The solid content is the percentage of the mass of the remaining solids after the UV tackifying prepolymer resin has been dried to constant weight at 140–160°C, relative to the total mass of the UV tackifying prepolymer resin.

[0014] Preferably, the mass ratio of the modified acrylic resin to the modified polyurethane resin is 3:;

[0015] The mass ratio of the o-phenylphenoxyethyl acrylic resin to butyl acrylate is 1:;

[0016] The mass ratio of triethylene glycol diisooctanoate to acrylate-modified polyurethane is 10:1.

[0017] Preferably, the mass ratio of the modified acrylic resin to the modified polyurethane resin is 3:2;

[0018] The mass ratio of o-phenylphenoxyethyl acrylic resin to butyl acrylate is 1:1;

[0019] The mass ratio of triethylene glycol diisooctanoate to acrylate-modified polyurethane is 10:5.

[0020] Preferably, the thickness of the first transparent PET film layer and the first transparent PET film layer are both 50-150 μm;

[0021] The thicknesses of the first antistatic layer, the second antistatic layer, the release agent layer, the third antistatic layer, and the fourth antistatic layer are all 0.3–1 μm.

[0022] The thickness of the UV-adhesive layer is 5–40 μm.

[0023] Preferably, the thermosetting agent is an isocyanate compound selected from one or more of methyl diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), and hexamethylene diisocyanate (HDI).

[0024] Preferably, the photoinitiator is one or more of 1-hydroxy-cyclohexylbenzophenone (184 photoinitiator) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173 photoinitiator).

[0025] Preferably, the diluent is one or more of toluene, ethyl acetate, butanone, and cyclohexanone.

[0026] Furthermore, to achieve the above objectives, the present invention also provides a method for preparing a UV adhesion-enhancing film for flexible display manufacturing processes, wherein the entire preparation process is protected from UV light, and includes the following steps:

[0027] Step a: Add the UV tackifying prepolymer resin with solid content to the mixing tank, add the diluent at room temperature, stir evenly, then gradually add the thermosetting agent and photoinitiator, stir evenly, and obtain the UV tackifying adhesive.

[0028] Step b: On a coating machine, the UV tackifying adhesive obtained in step a is evenly coated onto the surface of the third antistatic layer of the double-sided antistatic polyester film B; then the coated double-sided antistatic polyester film B is dried to obtain a UV tackifying film semi-finished product.

[0029] Step c: Press the release agent layer of the double-sided antistatic release polyester film with the UV tackifying adhesive layer of the UV tackifying film semi-finished product; after pressing, roll up and cure to obtain the finished UV tackifying film for flexible display process.

[0030] Furthermore, the first antistatic layer, the first transparent PET film layer, and the second antistatic layer constitute a double-sided antistatic polyester film A; the third antistatic layer, the second transparent PET film layer, and the fourth antistatic layer constitute a double-sided antistatic polyester film B; and the release agent layer is attached to the surface of the second antistatic layer of the double-sided antistatic polyester film A to form a double-sided antistatic release polyester film.

[0031] Preferably, in step b, the specific drying steps are as follows: passing through a drying tunnel with a total length of 20-45m at a linear speed of 25-50m / min, with the following temperature gradients: Section I 50-65℃ → Section II 80-90℃ → Section III 90-100℃ → Section IV 100-110℃ → Section V 110-120℃ → Section VI 110-120℃ → Section VII 95-105℃ → Section VIII 55-65℃.

[0032] It is worth noting that the UV adhesion-enhancing film for flexible display manufacturing in this application, in addition to its application in conventional environments such as industrial cleanrooms with room temperature (20-25℃) and relative humidity of 40-60% (panel bonding, pre-transport protection), ambient temperature storage environments (pre-use storage of finished products), and indoor ambient temperature usage scenarios (such as flexible display assembly and debugging in offices), can also be used in harsh environments. Based on this, this application also provides the application of the UV adhesion-enhancing film for flexible display manufacturing in harsh environment-adaptive flexible display devices. These harsh environments include high-temperature environments with temperatures ≥60℃, high-humidity and heat environments with temperatures ≥60℃ and relative humidity ≥85%, and low-temperature environments with temperatures ≤-10℃. The flexible display devices include flexible foldable mobile phones, flexible rollable laptops, automotive flexible display terminals, and outdoor portable flexible display devices. When the UV adhesion-enhancing film is used in the panel manufacturing process of flexible display devices in the aforementioned harsh environments, it still maintains a state of no adhesive residue and no delamination.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. This invention integrates the functions of the protective film and the support film required in the flexible display manufacturing process into a single UV adhesion-enhancing film, by means of...

[0035] UV-enhanced adhesion enables functional switching: Before UV irradiation, it has low adhesion and can be used as a protective film for panel transportation and initial protection; after UV irradiation, the adhesion is significantly enhanced, and it directly transforms into a support film to provide stable support for the manufacturing process. Unlike existing technologies, there is no need to peel off the protective film and then apply the support film, which reduces the peeling and re-lamination processes in the manufacturing process, optimizes the traditional production process, improves production efficiency, avoids panel damage caused by multiple operations, and effectively improves product yield.

[0036] 2. A multi-layer antistatic layer is constructed using an antistatic coating method, resulting in a more stable and durable antistatic effect with minimal impact on the adhesion of the UV tackifying adhesive and no antistatic agent precipitation issues. The final UV tackifying film maintains a low peel voltage (peel voltage < 500V) and low surface resistance (surface resistance below 10) before and after UV irradiation. 5 -10 9Within the Ω range, it is far superior to the electrostatic level of protective films in existing technologies, which can effectively prevent electrostatic discharge from damaging sensitive circuits inside the panel, reduce process safety risks, and ensure panel performance.

[0037] 3. The UV-adhesive film prepared by this invention possesses excellent optical properties, with transmittance >93% and haze <2.5% before and after UV irradiation, meeting the optical clarity requirements of flexible displays. It also exhibits good air venting (air venting <10s), preventing the introduction of air bubbles during bonding and further ensuring the optical performance of the display panel. Regarding bonding performance, the adhesion strength (SUS, 180° peel) before UV irradiation is less than 10gf / 25mm, facilitating operation and preventing residual adhesive delamination. After UV irradiation, the adhesion strength (SUS, 180° peel) increases to over 1500gf / 25mm, with an adhesion strength exceeding 3500gf / 25mm for bonding to flexible display panels. This enables efficient and permanent bonding between two interfaces, providing strong support stability and excellent protection and support for the CPI or hardened PET layer at the bottom of the flexible display.

[0038] 4. Under harsh environmental conditions, such as high temperature environments with a temperature ≥60℃, high humidity and heat environments with a temperature ≥60℃ and relative humidity ≥85%, and low temperature environments with a temperature ≤-10℃, the UV tackifying film always maintains a stable state with no adhesive residue and no delamination. Its performance is not affected by the environment and can meet the usage requirements of different regions and different process environments, with a wide range of applications.

[0039] 5. The preparation process of this invention is simple, easy to operate, requires no special equipment, is highly practical, and is easy to promote industrially. Furthermore, because the UV adhesion-enhancing film integrates the functions of a protective film and a supporting film, it reduces the costs of designing, purchasing, producing, and storing the two films separately, thus lowering raw material costs. Moreover, the process does not require peeling off the protective film, generating no peeling waste, reducing resource waste, and conforming to the concept of green production. Attached Figure Description

[0040] Figure 1 : A cross-sectional structural schematic diagram of the UV adhesion-enhancing film used in the flexible display manufacturing process of the present invention;

[0041] Among them, 1-first antistatic layer, 2-first transparent PET film layer, 3-second antistatic layer, 4-release agent layer, 5-UV tackifying adhesive layer, 6-third antistatic layer, 7-second transparent PET film layer, and 8-fourth antistatic layer. Detailed Implementation

[0042] Example 1:

[0043] A UV adhesion-enhancing film for flexible display manufacturing processes, such as Figure 1As shown, it includes a first antistatic layer 1, a first transparent PET film layer 2, a second antistatic layer 3, a release agent layer 4, a UV tackifying adhesive layer 5, a third antistatic layer 6, a second transparent PET film layer 7, and a fourth antistatic layer 8, which are sequentially laminated.

[0044] The first antistatic layer 1, the first transparent PET film layer 2, and the second antistatic layer 3 constitute a double-sided antistatic polyester film A;

[0045] The third antistatic layer 6, the second transparent PET film layer 7, and the fourth antistatic layer 8 constitute the double-sided antistatic polyester film B;

[0046] Double-sided antistatic polyester film A and release agent layer 4 constitute a double-sided antistatic release polyester film.

[0047] The specific preparation method of the UV adhesion-enhancing film for flexible display manufacturing process is as follows:

[0048] S1. Prefabricated base film.

[0049] Preparation of double-sided antistatic polyester film A: On a coating machine, an antistatic agent (antistatic agent) is applied using a microgravure coating method.

[0050] TPL-25 is uniformly coated on both sides of the first transparent PET film layer 2 (thickness 80μm) with a coating thickness of 0.5μm. After coating, it passes through a drying tunnel with a total length of 42m at a linear speed of 30m / min. The temperature gradient of the drying tunnel is: Section I 75℃ → Section II 90℃ → Section III 100℃ → Section IV 110℃ → Section V 110℃ → Section VI 100℃. After drying, a double-sided antistatic polyester film A is obtained.

[0051] Preparation of double-sided antistatic polyester film B: Using the same preparation method as double-sided antistatic polyester film A, the antistatic agent is uniformly coated on both sides of the second transparent PET film layer 7 (thickness 80μm) with a coating thickness of 0.5μm. After drying with the same drying tunnel parameters, double-sided antistatic polyester film B is obtained.

[0052] Preparation of double-sided antistatic release polyester film: On a coating machine, a silicone-based release agent (release agent 7475) is coated on the surface of the second antistatic layer 3 of the double-sided antistatic polyester film A using a micro-gravure coating method, with a coating thickness of 0.5 μm; after coating, it passes through a drying tunnel with a total length of 42 m at a linear speed of 35 m / min, with the following temperature gradients: Section I 75℃ → Section II 90℃ → Section III 100℃ → Section IV 110℃ → Section V 110℃ → Section VI 100℃, and is then dried to obtain the final product.

[0053] S2. Preparation of UV thickening film.

[0054] Step a: Prepare the UV-modified adhesive (the entire process must be carried out under conditions that avoid UV light):

[0055] The raw materials were mixed at room temperature according to the following proportions: UV tackifying prepolymer resin (100 parts by weight, modified acrylic resin: modified polyurethane resin = 3:2; wherein the modified acrylic resin is o-phenylphenoxyethyl acrylic resin: butyl acrylate = 20:20, and the modified polyurethane resin is triethylene glycol diisooctanoate: acrylate modified polyurethane = 10:5), thermosetting agent hexamethylene diisocyanate (HDI, 1 part by weight), 184 photoinitiator (1 part by weight), and diluent toluene and ethyl acetate mixture (100 parts by weight, 1:1).

[0056] UV tackifying prepolymer resin was added to a mixing tank and stirred at 200 rpm. Diluent was added first at room temperature and stirred until homogeneous. Then, thermosetting agent and photoinitiator were gradually added and stirred for another 20 minutes to obtain UV tackifying adhesive.

[0057] Step b: Preparation of UV-adhesive film semi-finished product (the entire process must be carried out under UV-protected conditions):

[0058] On a coating machine, a comma-shaped doctor blade is used to uniformly coat the UV tackifying adhesive obtained in step a onto the surface of the third antistatic layer 6 of the double-sided antistatic polyester film B, with a coating thickness of 15 μm. The coated double-sided antistatic polyester film B is then run at a linear speed of 40 m / min through a drying tunnel with a total length of 32 m. The temperature gradient of the drying tunnel is as follows: Section I 60℃ → Section II 85℃ → Section III 95℃ → Section IV 105℃ → Section V 115℃ → Section VI 115℃ → Section VII 100℃ → Section VIII 60℃. After drying, the film is further polymerized and the solvent is removed to obtain a UV tackifying film semi-finished product.

[0059] Step c: Preparation of UV-adhesive film product N1 (the entire process must be carried out under UV-protected conditions):

[0060] The release agent layer 4 of the double-sided antistatic release polyester film is laminated with the UV tackifying adhesive layer 5 of the UV tackifying film semi-finished product under a pressure of 0.45 MPa and room temperature. After lamination, the film is wound up and placed in an environment of 40°C for 48 hours to obtain the UV tackifying film N1 for flexible display process.

[0061] Examples 2-5:

[0062] S1. Pre-fabricated base film: Same as in Example 1.

[0063] In S2, step a: the amount of thermosetting agent HDI was adjusted (Example 2: 1.5 parts by mass, Example 3: 2.5 parts by mass, Example 4: 5 parts by mass, Example 5: 10 parts by mass), and the remaining components and proportions were the same as in step a of Example 1, to obtain the UV tackifying adhesive.

[0064] Step b: Same as step b in Example 1, to obtain the UV adhesion-enhancing film semi-finished product.

[0065] Step c: Same as step c in Example 1, to obtain UV thickening films N2-N5.

[0066] Example 6:

[0067] S1. Pre-fabricated base film: Same as in Example 1.

[0068] S2. Preparation of UV thickening film.

[0069] Step a: Prepare the UV-modified adhesive (the entire process must be carried out under conditions that avoid UV light):

[0070] The components were mixed at room temperature according to the following ratios: UV tackifying prepolymer resin (100 parts by weight, modified acrylic resin: modified polyurethane resin = 3:2.5; wherein the modified acrylic resin is o-phenylphenoxyethyl acrylic resin: butyl acrylate = 1:1.2, and the modified polyurethane resin is triethylene glycol diisooctanoate: acrylate modified polyurethane = 10:6), thermosetting agent methyl diisocyanate (TDI, 1 part by weight), 184 photoinitiator (1 part by weight), and diluent toluene and ethyl acetate mixture (100 parts by weight, 1:1).

[0071] The preparation process is the same as step a in Example 1, and a UV tackifying adhesive is obtained.

[0072] Step b: Preparation of UV-adhesive film semi-finished product (the entire process must be carried out under UV-protected conditions):

[0073] On a coating machine, a comma-shaped doctor blade is used to uniformly coat the UV tackifying adhesive obtained in step a onto the surface of the third antistatic layer 6 of the double-sided antistatic polyester film B, with a coating thickness of 15 μm. The coated double-sided antistatic polyester film B is then run at a linear speed of 40 m / min through a drying tunnel with a total length of 32 m. The temperature gradient of the drying tunnel is adjusted as follows: Section I 55℃ → Section II 82℃ → Section III 92℃ → Section IV 102℃ → Section V 112℃ → Section VI 112℃ → Section VII 98℃ → Section VIII 58℃. After drying, the film is further polymerized and the solvent is removed to obtain a UV tackifying film semi-finished product.

[0074] Step c: Same as step c in Example 1, to obtain UV thickening film N6.

[0075] Examples 7-10:

[0076] S1. Pre-fabricated base film: Same as in Example 1.

[0077] In S2, step a: the amount of thermosetting agent TDI was adjusted (Example 7: 1.5 parts by mass, Example 8: 2.5 parts by mass, Example 9: 5 parts by mass, Example 10: 10 parts by mass), and the remaining components and proportions were the same as in step a of Example 6, to obtain the UV tackifying adhesive.

[0078] Step b: Same as step b in Example 6, to obtain the UV adhesion-enhancing film semi-finished product.

[0079] Step c: Same as step c in Example 6, to obtain UV thickening films N7-N10.

[0080] Example 11:

[0081] S1. Prefabricated base film.

[0082] Preparation of double-sided antistatic polyester film A: On a coating machine, an antistatic agent (same as in Example 1) is uniformly coated on both sides of the first transparent PET film layer 2 (thickness 100 μm) using a micro-gravure coating method, with a coating thickness of 0.6 μm; after coating, it passes through a drying tunnel with a total length of 42 m at a linear speed of 30 m / min, with the temperature gradient of the drying tunnel being the same as in Example 1, and after drying, double-sided antistatic polyester film A is obtained.

[0083] Preparation of double-sided antistatic polyester film B: Using the same preparation method as double-sided antistatic polyester film A, the antistatic agent is uniformly coated on both sides of the second transparent PET film layer 7 (thickness 100μm) with a coating thickness of 0.6μm. After drying with the same drying tunnel parameters, double-sided antistatic polyester film B is obtained.

[0084] Preparation of double-sided antistatic release polyester film: On a coating machine, a silicone-based release agent (same as in Example 1) is coated on the surface of the second antistatic layer 3 of the double-sided antistatic polyester film A using a micro-gravure coating method, with a coating thickness of 0.4 μm; after coating, it passes through a drying tunnel with a total length of 42 m at a linear speed of 35 m / min, with the same temperature gradient as in Example 1, and is then dried to obtain the final product.

[0085] In S2, step a: preparing the UV-adhesive adhesive (the entire process must be carried out under conditions that avoid UV light):

[0086] The components are mixed at room temperature according to the following ratio: 100 parts by weight of UV tackifying prepolymer resin with a solid content of 30%, 1.25 parts by weight of thermosetting agents HDI and TDI, 1.25 parts by weight of 184 photoinitiator, and 100 parts by weight of a mixture of toluene and ethyl acetate as diluent.

[0087] The preparation process is the same as step a in Example 1, and a UV tackifying adhesive is obtained.

[0088] Step b: Same as step b in Example 1, to obtain the UV adhesion-enhancing film semi-finished product.

[0089] Step c: Same as step c in Example 1, to obtain UV thickening film N11.

[0090] Examples 12-15:

[0091] S1. Pre-fabricated base film: Same as in Example 11.

[0092] In S2, step a: the ratio of thermosetting agent and the amount of photoinitiator were adjusted (Example 12: 2.5 parts by weight of HDI + 2.5 parts by weight of TDI, Example 13: 5 parts by weight of HDI + 5 parts by weight of TDI, Example 14: 2.5 parts by weight of HDI +

[0093] 3 parts by weight of 184 photoinitiator (Example 15: 2.5 parts by weight of TDI + 3 parts by weight of 184 photoinitiator), with the remaining components and proportions the same as in step a of Example 11, to prepare a UV tackifying adhesive.

[0094] Step b: Same as step b in Example 1, to obtain the UV adhesion-enhancing film semi-finished product.

[0095] Step c: Same as step c in Example 1, to obtain UV thickening films N12-N15.

[0096] Comparative Example 1

[0097] Compared to Example 1, only 100 parts by weight of the "modified acrylic resin + modified polyurethane resin mixture system" was replaced with 100 parts by weight of the "single modified acrylic resin".

[0098] The remaining components, parameters, and steps are the same as in Example 1, and a UV thickening film D1 is prepared.

[0099] Comparative Example 2

[0100] Compared to Example 1, the "mixture system of 100 parts by weight of modified acrylic resin and modified polyurethane resin" in Example 1 is replaced with "mixture system of 100 parts by weight of bisphenol A epoxy resin (E-51) and 5 parts by weight of epoxy curing agent methyl hexahydrophthalic anhydride".

[0101] The remaining components, parameters, and steps are the same as in Example 1, and a UV thickening film D2 is obtained.

[0102] Comparative Example 3

[0103] Compared to Example 1, the "1 part by weight of thermosetting agent HDI" was adjusted to "0.5 parts by weight of thermosetting agent HDI", and the remaining components, parameters and steps were the same as in Example 1, to obtain UV tackifying film D3.

[0104] Comparative Example 4

[0105] Compared to Example 1, the ratio of "o-phenylphenoxyethyl acrylic resin: butyl acrylate = 1:1" in the modified acrylic resin was adjusted to 1:2.

[0106] The remaining components, parameters, and steps are the same as in Example 1, and the UV thickening film D4 is obtained.

[0107] It is worth noting that all ratios in the above embodiments and comparative examples are mass ratios; technical contents not specifically described are the same as those in the prior art, and materials for which preparation methods are not specified are all commercially available products.

[0108] Experimental Example

[0109] The relevant properties of the UV thickening films prepared in Examples 1-15 and Comparative Examples 1-4 are compared, as shown in Tables 1 and 2.

[0110] Table 1. UV-prep properties of UV adhesion-enhancing films used in flexible display manufacturing processes:

[0111]

[0112]

[0113] Table 2. Post-UV performance of UV adhesion-enhancing films used in flexible display manufacturing processes:

[0114]

[0115] It is worth noting that the UV irradiation parameters during the above performance tests were: 160W / cm high-pressure mercury lamp with an irradiation energy of 1200mJ / cm2 for 10s.

[0116] The performance of 60℃ / 90% for 120hr, 85℃ / 85% for 120hr, and -40℃~80℃ (for 30min) 100 cycles (high temperature and high humidity, high and low temperature cycling test) is tested according to GB / T 2423 test standard. The test temperature is -40℃~80℃, with a minimum temperature of -40℃ and a maximum temperature of 80℃. The temperature change rate is 3℃ / min, and the temperature is maintained for 0.5h in the high and low temperature ranges. The number of cycles is 100. No residue and no delamination are indicated by ☆; residue and no delamination are indicated by △; no residue and delamination are indicated by ▲; and residue and delamination are indicated by ★.

[0117] As shown in Tables 1-2, Examples 1-15 use a mixture of modified acrylic acid and modified polyurethane resin as a system, with an 8-layer structure including four antistatic layers and two transparent PET films. Through UV-shielded adhesive preparation, segmented drying, and curing processes, the components, structure, and process are synergistic. The resulting UV-adhesive film is not only suitable for flexible display processes, possessing advantages such as functional integration, low static electricity, and high optical performance, but also remains stable under harsh environments such as high temperature and humidity, and high and low temperature cycling, without residual adhesive delamination issues, demonstrating significant environmental adaptability. Comparative Examples 1-4 deviate from the technical solution of this application and have defects in many aspects, failing to meet actual needs, as detailed below:

[0118] Comparative Example 1 uses a single modified acrylic resin to replace the mixed system. The lack of modified polyurethane resin makes it difficult to balance the adhesion before and after UV. The adhesion is high before UV, which easily damages the panel, and the support is poor after UV. In addition, the single resin has weak resistance to damp heat, and the molecular chain is prone to problems under high temperature and high humidity, resulting in residual adhesive.

[0119] Comparative Example 2 uses a bisphenol A epoxy resin system instead of the resin in this application. It is hard and brittle, making it difficult to adapt to the bending and folding of flexible panels. It is prone to cracking, and the poor optics affect the display effect. In harsh environments, it is also prone to interface peeling and residual glue delamination.

[0120] Comparative Example 3: The amount of thermosetting agent used was below the limit, resulting in insufficient curing, low cross-linking degree, poor adhesion stability, and easy abnormal increase during long-term storage. Under harsh conditions, the adhesive was prone to failure and delamination when bonded to the substrate.

[0121] Comparative Example 4 showed that the modified acrylic resin had an excessive monomer ratio, which damaged the molecular chain structure, reduced its antistatic and optical properties, weakened its resistance to high and low temperatures, and made it prone to interface separation and degumming under high and low temperature cycling, which also increased the risk of electrostatic breakdown of the panel.

Claims

1. A UV adhesion-enhancing film for flexible display manufacturing processes, characterized in that, The first antistatic layer (1), the first transparent PET film layer (2), the second antistatic layer (3), the release agent layer (4), the UV tackifying adhesive layer (5), the third antistatic layer (6), the second transparent PET film layer (7), and the fourth antistatic layer (8) are sequentially laminated. The UV-modified adhesive comprises the following components in parts by weight: 100 parts of UV tackifying prepolymer resin with a solid content of 18-45%, 1-10 parts of thermosetting agent, 0.1-5 parts of photoinitiator, and 50-200 parts of diluent; The UV-tackifying prepolymer resin comprises a mixture of modified acrylic resin and modified polyurethane resin; The modified acrylic resin includes o-phenylphenoxyethyl acrylic resin and butyl acrylate; The modified polyurethane resin includes triethylene glycol diisooctanoate and acrylate-modified polyurethane.

2. The UV adhesion-enhancing film for flexible display manufacturing according to claim 1, characterized in that, The mass ratio of the modified acrylic resin to the modified polyurethane resin is 3:(1.5-2.5); The mass ratio of o-phenylphenoxyethyl acrylic resin to butyl acrylate is 1:(1-1.5); The mass ratio of triethylene glycol diisooctanoate to acrylate-modified polyurethane is 10:(4-7).

3. The UV adhesion-enhancing film for flexible display manufacturing according to claim 1, characterized in that, The thickness of the first transparent PET film layer (2) and the first transparent PET film layer (7) is 50-150 μm; The thicknesses of the first antistatic layer (1), the second antistatic layer (3), the release agent layer (4), the third antistatic layer (6), and the fourth antistatic layer (8) are all 0.3 to 1 μm; The thickness of the UV-tackifying adhesive layer (5) is 5–40 μm.

4. The UV adhesion-enhancing film for flexible display manufacturing according to claim 1, characterized in that, The thermosetting agent is an isocyanate compound selected from one or more of methyl diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

5. The UV adhesion-enhancing film for flexible display manufacturing according to claim 1, characterized in that, The photoinitiator is one or more of 1-hydroxy-cyclohexylbenzophenone and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

6. The UV adhesion-enhancing film for flexible display manufacturing according to claim 1, characterized in that, The diluent is one or more of toluene, ethyl acetate, butanone, and cyclohexanone.

7. A method for preparing a UV adhesion-enhancing film for flexible display manufacturing as described in any one of claims 1-6, characterized in that, The entire preparation process is protected from UV light and includes the following steps: Step a: Add the UV tackifying prepolymer resin with solid content to the mixing tank, add the diluent at room temperature, stir evenly, then gradually add the thermosetting agent and photoinitiator, stir evenly, and obtain the UV tackifying adhesive. Step b: On a coating machine, the UV tackifying adhesive obtained in step a is evenly coated onto the surface of the third antistatic layer (6) of the double-sided antistatic polyester film B; then the coated double-sided antistatic polyester film B is dried to obtain the UV tackifying film semi-finished product. Step c: Press the release agent layer (4) of the double-sided antistatic release polyester film with the UV tackifying adhesive layer (5) of the UV tackifying film semi-finished product; after pressing, roll up and cure to obtain the finished UV tackifying film for flexible display process. The first antistatic layer (1), the first transparent PET film layer (2), and the second antistatic layer (3) constitute a double-sided antistatic polyester film A; the third antistatic layer (6), the second transparent PET film layer (7), and the fourth antistatic layer (8) constitute a double-sided antistatic polyester film B; the release agent layer (4) is attached to the surface of the second antistatic layer (3) of the double-sided antistatic polyester film A to form a double-sided antistatic release polyester film.

8. The method for preparing a UV adhesion-enhancing film for flexible display manufacturing according to claim 7, characterized in that, In step b, the specific drying steps are as follows: passing through a drying tunnel with a total length of 20-45m at a linear speed of 25-50m / min, with the following temperature gradients: Section I 50-65℃ → Section II 80-90℃ → Section III 90-100℃ → Section IV 100-110℃ → Section V 110-120℃ → Section VI 110-120℃ → Section VII 95-105℃ → Section VIII 55-65℃.

9. The application of a UV adhesion-enhancing film for flexible display manufacturing as described in any one of claims 1-6 in a flexible display device adapted to harsh environments, characterized in that, The harsh environments include high-temperature environments with temperatures ≥60℃, high-humidity and hot environments with temperatures ≥60℃ and relative humidity ≥85%, and low-temperature environments with temperatures ≤-10℃.

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