Black matte epoxy adhesive film for display module and preparation method thereof

Abstract

The application discloses a black matte epoxy adhesive film for a display module and a preparation method thereof. The adhesive film comprises, in sequence, a light release film layer, a transparent adhesive film layer, a black adhesive film layer and a heavy release film layer. The transparent adhesive film layer and the black adhesive film layer both contain raw materials such as epoxy resin, epoxy curing agent and modified UV resin in a specific ratio. The modified UV resin is prepared from polyol, isocyanate and hydroxy acrylate through a specific process. The black and transparent film layers are prepared by step-by-step preparation of glue, and the four-layer composite structure is formed through roll coating, compounding and weak light curing. The adhesive film has excellent matte effect and ink color consistency, low internal stress, firm adhesion, strong environmental stability, simple and efficient preparation process, small equipment investment, and is suitable for display module packaging requirements and mass production.

Description

Technical Field

[0001] This invention relates to the field of display module packaging materials technology, and in particular to a black matte epoxy film for display modules and its preparation method. Background Technology

[0002] In the chip packaging field of COB (Chip On Board) and MIP (Micro / MiniLED in Package) display panels, the performance of packaging materials and the efficiency of packaging processes directly affect the quality and production cost of display modules.

[0003] Common LED encapsulants are mainly epoxy and silicone. Silicone encapsulants have weak molecular polarity and small intermolecular forces, so they have poor barrier properties against water and oxygen in the air. The problem of moisture and oxygen permeability will cause a high defect rate of LED chips.

[0004] Epoxy adhesive film, with its excellent bonding strength, resistance to moisture and heat, and electrical insulation, has become one of the core materials for display panel encapsulation. However, existing epoxy adhesive films still face several key technical bottlenecks when adapting to the encapsulation requirements of high-end display panels: Firstly, epoxy resin has high hardness and rigidity, requiring high molding temperatures during compression molding. The epoxy adhesive cures rapidly, and the mismatch between the thermal expansion of the LED board during molding and the internal stress of the epoxy adhesive during curing can easily cause chip misalignment, leading to dead LEDs and significantly reducing product yield. Secondly, its mechanical stability is poor. During long-term service, it is susceptible to yellowing, cracking, and adhesive failure due to environmental factors such as temperature and humidity changes and light exposure, severely affecting the lifespan and display effect of the display panel. Furthermore, after the existing COB display panel encapsulation is completed, a layer of matte black semi-transparent OCA adhesive film is usually applied to the encapsulation surface to ensure consistent ink color. However, this OCA adhesive film is prone to edge lifting and peeling during actual use, seriously affecting the structural stability and lifespan of the display module. Summary of the Invention

[0005] The primary objective of this invention is to provide a matte black epoxy film for display modules. By designing a four-layer composite structure consisting of a light release film layer, a transparent film layer, a black film layer, and a heavy release film layer, and optimizing the raw material formulations for each adhesive layer, this invention addresses the shortcomings of existing COB display panel encapsulation molding adhesive equipment, such as high investment, low efficiency, high internal stress, severe warping, and difficult rework; easy edge peeling of OCA film; and poor ink color consistency, shadows, and uneven stress in existing black film layers. The invention achieves the goal of excellent matte finish, uniform ink color, strong adhesion, strong environmental stability, and low internal stress.

[0006] The second objective of this invention is to provide a method for preparing a black matte epoxy film for display modules.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] Firstly, this invention provides a black matte epoxy film for display modules, comprising, in sequence, a light release film layer, a transparent film layer, a black film layer, and a heavy release film layer; the transparent film layer, by weight, comprises the following raw materials: 30-45 parts of a first epoxy resin, 25-40 parts of a first epoxy curing agent, 0.01-2 parts of a first epoxy accelerator, 5-20 parts of a first modified UV resin, 0.5-2 parts of a first photoinitiator, 0-20 parts of a first light diffusing agent, 0.1-1 parts of a first antioxidant, 0.1-1 parts of a first coupling agent, 5-15 parts of a first toughening resin, and 0-10 parts of a first acrylate monomer; The black adhesive film layer comprises, by weight, the following raw materials: 30-45 parts of second epoxy resin, 25-40 parts of second epoxy curing agent, 0.01-2 parts of second epoxy accelerator, 5-15 parts of second modified UV resin, 0.5-2 parts of second photoinitiator, 3-20 parts of second light diffusing agent, 0.1-1 part of second antioxidant, 0-1 part of second coupling agent, 0.1-2 parts of black pigment, and 0-10 parts of second acrylate monomer. Furthermore, both the first epoxy resin and the second epoxy resin are selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, and alicyclic epoxy resin.

[0009] Furthermore, both the first epoxy curing agent and the second epoxy curing agent are selected from at least one of methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and tetrahydrophthalic anhydride; Both the first epoxy accelerator and the second epoxy accelerator are selected from at least one of tetramethylammonium bromide, tetrabutylammonium bromide, triphenylphosphine, benzyltriphenylphosphonium bromide, 2-ethyl-4-methylimidazolium, and 1,8-diazabicycloundec-7-ene.

[0010] Furthermore, both the first photoinitiator and the second photoinitiator are selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, methyl benzoylcarbamate, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphonate. Furthermore, both the first light diffusing agent and the second light diffusing agent are selected from at least one of polymethylsilsesquioxane and silicone resin microspheres; the particle size of the first light diffusing agent and the second light diffusing agent is ≤5μm, preferably ≤2μm.

[0011] Furthermore, both the first antioxidant and the second antioxidant are selected from at least one of 2,6-di-tert-butyl-4-methylphenol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, and 2,4-bis(n-octylthionyl)-6-methylphenol.

[0012] Furthermore, both the first coupling agent and the second coupling agent are selected from at least one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, and 3-acryloyloxypropyltriethoxysilane.

[0013] Furthermore, the black pigment is an azo metal complex or an anthraquinone fused ring structure pigment.

[0014] Furthermore, both the first acrylate monomer and the second acrylate monomer are selected from at least one of glycidyl methacrylate, glycidyl acrylate, 3,4-epoxycyclohexyl methacrylate, and 3,4-epoxycyclohexyl methacrylate.

[0015] Furthermore, the first toughening resin is selected from at least one of polyether polyol, polyester polyol, epoxidized polybutadiene, silicone-modified epoxy resin, polyurethane-modified epoxy resin, core-shell polymer, and hyperbranched polymer; preferably, the toughening resin is selected from polycaprolactone diol and adipic acid polyester diol, with an average molecular weight of 400-1500.

[0016] Furthermore, both the first modified UV resin and the second modified UV resin are prepared through the following steps: Prepare 60-85 parts of polyol, 5-20 parts of isocyanate and 5-15 parts of hydroxy acrylate by weight. The polyol was dehydrated at 100-130℃, ≤-94KPa, and 40-60rpm for 1.5-2.5h. Isocyanate was added to the dehydrated material under a nitrogen atmosphere, at 80-100℃ and with stirring at 40-60 rpm, and the reaction was carried out for 2-5 hours. Hydroxyacrylate was added to the system and reacted for 2-5 hours to obtain the modified UV resin.

[0017] Further, the polyol is a polyester diol polymerized from polyether polyol, polycaprolactone diol, or adipic acid or sebacic acid with neopentyl glycol, methyl propylene glycol, 3-methyl-1,5-pentanediol, and other diols containing side chains, and the average molecular weight of the polyol is 1000-4000, preferably 2000-3000. The isocyanate is at least one of IPDI, HDI, and HMDI; The hydroxy acrylate is at least one of HPA, HEA, HEMA, HBA, and caprolactone acrylate.

[0018] Furthermore, the thickness of the light release film layer is 25-75 μm, and the release force of the effective release surface of the light release film layer is ≤25g; The thickness of the heavy release film layer is 50-125μm, the base film of the heavy release film layer is a matte PET film, and the release force of the effective release surface of the heavy release film layer is ≤100g. The thickness of the heavy release film layer minus the thickness of the light release film layer is ≥25μm; The release force of the heavy release film layer is at least 3 times that of the light release film layer; The thickness of the transparent adhesive film layer is 50-150 μm; The thickness of the black adhesive film layer is 30-150 μm.

[0019] Furthermore, matte particles are added to the release layer of the heavy release film, and the matteness of the release surface of the heavy release film is 10-30 GU; The thickness of the black adhesive film layer accounts for 1 / 5 to 1 / 2 of the total thickness of the black matte epoxy adhesive film.

[0020] Secondly, this invention provides a method for preparing the above-mentioned black matte epoxy film for display modules, the specific steps of which are as follows: According to the formula of the black film layer, the second epoxy resin, the second light diffusing agent, the second antioxidant and the black pigment are put into the reaction vessel. Under the conditions of temperature 100-130℃ and vacuum degree ≤-94KPa, the mixture is dehydrated for 1.5-2.5h with stirring speed of 40-60rpm and dispersion speed of 500-2000rpm, and then cooled to room temperature. Nitrogen gas is introduced into the reactor, and then the second acrylate monomer, the second epoxy curing agent, the second epoxy accelerator, the second photoinitiator and the second coupling agent are added in sequence. The vacuum degree is maintained at ≤-94KPa, the stirring speed is 40-60rpm and the temperature is ≤35℃. The mixture is stirred for 0.5-1h, and then nitrogen gas is introduced to restore the atmospheric pressure to obtain a black film adhesive. According to the ratio of the transparent film layer, the first epoxy resin, the first light diffusing agent, the first antioxidant, and the first toughening resin are added into the reactor. Under the conditions of temperature 100-130℃ and vacuum degree ≤-94KPa, the mixture is dehydrated for 1.5-2.5h with stirring speed of 40-60rpm and dispersion speed of 500-2000rpm, and then cooled to room temperature. Nitrogen gas is introduced into the reactor, and then the first epoxy curing agent, the first epoxy accelerator, the first photoinitiator, the first acrylate monomer and the first coupling agent are added in sequence. The vacuum degree is maintained at ≤-94KPa, the stirring speed is 40-60rpm and the temperature is ≤35℃. The mixture is stirred for 0.5-1h, and then nitrogen gas is introduced to restore the atmospheric pressure to obtain a transparent film adhesive. The black film adhesive is applied using a roller coating process, with light and heavy release films as the coating substrates. The coating thickness is controlled at 30-150μm. The light release film, black film adhesive, and heavy release film are then laminated together and sent to a UV oven for low-light curing, with the light intensity controlled at ≤10mw / cm². 2 The adhesive surface temperature is ≤35℃, forming a composite structure of light release film - black adhesive film layer - heavy release film; The light release membrane in the light release membrane-black adhesive film layer-heavy release membrane composite structure is peeled off to form the black adhesive film layer-heavy release membrane composite structure; The transparent film adhesive is applied using a roller coating process. A black adhesive film-heavy release film composite structure and a light release film are used as the coating substrate, with the coating thickness controlled at 50-150 μm. The light release film, transparent film adhesive, and black adhesive film-heavy release film composite structure are then laminated. After lamination, the composite is placed in a UV oven for low-light curing, with the light intensity controlled to ≤10 mw / cm². 2 With a surface temperature ≤35℃, a black matte epoxy film with a four-layer composite structure consisting of a light release film, a transparent film layer, a black film layer, and a heavy release film is formed.

[0021] The black matte epoxy film of this invention adopts a four-layer composite structure. By optimizing the raw material formulation of the transparent film layer and the black film layer, the curing efficiency, light diffusion performance and mechanical stability of the film are improved. The matte effect is excellent and can effectively avoid reflection of the display panel and improve the display effect. In the entire preparation process, the adhesive has very short contact with air and hardly absorbs moisture. The UV film formation adopts low temperature and long time curing, which makes the UV crosslinking more complete, the molecular chains longer, and the film consistency and flexibility better. The adhesive film of the present invention exists in a film form, which is convenient for transportation and application. The construction process is simple, no large molding equipment is required, the equipment investment is small, and it can significantly improve production efficiency and reduce overall production costs. This invention, through the pre-fabrication of adhesive film, can precisely control the thickness of the adhesive film, improve the thickness uniformity of the finished product, and effectively reduce the internal stress of the adhesive film, thereby reducing the warping of the display module and improving product quality. The preparation method of the present invention is simple, highly controllable, and can ensure the performance stability of the adhesive film, making it suitable for large-scale mass production. The adhesive film of the present invention has good flexibility after curing, is easy to rework, can reduce product scrap rate, and further reduce production costs. Detailed Implementation

[0022] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0023] Unless otherwise specified, all reagents or instruments used in this invention are commercially available products.

[0024] Example 1 1. Preparation of modified UV resin Prepare 60 parts by weight of polyether polyol PPG (average molecular weight 3500), 25 parts of polycaprolactone diol (average molecular weight 2000), 12 parts of IPDI, and 5 parts of HPA; add PPG and polycaprolactone diol to a reaction vessel and dehydrate for 2.5 h at 100℃, -95 kPa, and 50 rpm. IPDI was added to the dehydrated material under a nitrogen atmosphere and at 80°C. After stirring at 50 rpm for 5 hours, HPA was added, and the stirring was continued for another 5 hours to obtain the modified UV resin.

[0025] 2. Preparation of black matte epoxy film (1) Preparation of transparent film adhesive: By mass percentage, the first epoxy resin (30 parts alicyclic epoxy resin), the first antioxidant (0.1 parts 2,6-di-tert-butyl-4-methylphenol), and the first toughening resin (5 parts polycaprolactone diol with an average molecular weight of 1200) were added to a reactor. The mixture was dehydrated for 2.5 hours at 100°C and -95 kPa with a stirring speed of 40 rpm and a dispersion speed of 500 rpm. The mixture was then cooled to room temperature. Nitrogen gas was introduced, and the first epoxy curing agent (25 parts methylhexahydrophthalic anhydride), the first epoxy accelerator (0.01 parts tetramethylammonium bromide), the first photoinitiator (0.5 parts 2-hydroxy-2-methyl-1-phenyl-1-propanone), and the first coupling agent (0.1 parts 3-glycidyl etheroxypropyltrimethoxysilane) were added sequentially. The mixture was kept under a vacuum of -95 kPa, a stirring speed of 40 rpm, and a temperature of 30°C for 1 hour. Nitrogen gas was then introduced to restore atmospheric pressure, yielding a transparent film adhesive.

[0026] (2) Preparation of black film adhesive: By mass percentage, the second epoxy resin (30 parts alicyclic epoxy resin), the second light diffusing agent (3 parts polymethylsilsesquioxane, particle size 2μm), the second antioxidant (0.1 parts 2,6-di-tert-butyl-4-methylphenol), and the black pigment (0.1 parts azo metal complex) were added to a reactor. The mixture was dehydrated for 2.5 hours at 100℃ and -95KPa with a stirring speed of 40 rpm and a dispersion speed of 500 rpm. The mixture was then cooled to room temperature. Nitrogen gas was introduced, and the second epoxy curing agent (25 parts methylhexahydrophthalic anhydride), the second epoxy accelerator (0.01 parts tetramethylammonium bromide), and the second photoinitiator (0.5 parts 2-hydroxy-2-methyl-1-phenyl-1-propanone) were added sequentially. The mixture was kept under a vacuum of -95KPa, a stirring speed of 40 rpm, and a temperature of 30℃ for 1 hour. Nitrogen gas was then introduced to restore atmospheric pressure, yielding a black film adhesive.

[0027] (3) Preparation of the black adhesive film composite structure: The black epoxy adhesive film was coated using a roller coating process. Light release film (single-sided silicone release film, release force 3g, thickness 25μm, base film is matte PET film, matte finish 10GU, silicone surface matte finish 10GU) and heavy release film (single-sided silicone release film, release force 20g, thickness 50μm, base film is matte PET film, matte finish 10GU, silicone surface matte finish 10GU) were used as coating substrates. The coating thickness of the black epoxy adhesive layer was controlled to be 30μm. After lamination, the film was placed in a UV oven for low-light curing at a light intensity of 5mw / cm². 2 The adhesive surface temperature is 30℃, forming a composite structure of light release film - black adhesive film layer - heavy release film.

[0028] (4) Preparation of four-layer composite film: The light release film in the above composite structure is peeled off to obtain a black adhesive film layer-heavy release film composite structure. The transparent film layer adhesive is applied using a roller coating process, with the above black adhesive film layer-heavy release film composite structure and the new light release film as the coating substrate. The coating thickness of the transparent film layer adhesive is controlled to be 50 μm. After lamination, the composite is placed in a UV oven for low-light curing at a light intensity of 5 mw / cm². 2 When the adhesive surface temperature is 30℃, a black matte epoxy film is obtained.

[0029] Example 2 1. Preparation of modified UV resin Prepare 50 parts by weight of polyether polyol PPG (average molecular weight 2000), 35 parts of polycaprolactone diol (average molecular weight 2500), 12 parts of HDI, and 8 parts of HEA; add PPG and polycaprolactone diol to a reaction vessel and dehydrate for 2 hours at 115℃, -96KPa, and 50rpm. Under a nitrogen atmosphere and at 90°C, HDI was added to the dehydrated material, and the mixture was stirred at 50 rpm for 3.5 h. HEA was then added, and the mixture was stirred for another 3.5 h to obtain the modified UV resin.

[0030] 2. Preparation of black matte epoxy film (1) Preparation of transparent film adhesive: By mass fraction, the first epoxy resin (40 parts alicyclic epoxy resin), the first light diffusing agent (silicone resin microspheres, particle size 2μm, 5 parts), the first antioxidant (0.6 parts β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester), and the first toughening resin (adipic acid polyester diol, average molecular weight 1500, 10 parts) were added to a reaction vessel and dehydrated for 2 hours at 115℃ and -96KPa with a stirring speed of 50rpm and a dispersion speed of 1200rpm, and then cooled to room temperature. Nitrogen gas was introduced, and the first epoxy curing agent (32 parts of methyltetrahydrophthalic anhydride), the first epoxy accelerator (1.1 parts of 2-ethyl-4-methylimidazolium), the first photoinitiator (1.3 parts of 1-hydroxycyclohexylphenyl ketone), the first coupling agent (0.6 parts of 3-acryloyloxypropyltrimethoxysilane), and the first acrylate monomer (5 parts of glycidyl acrylate) were added sequentially. The vacuum degree was maintained at -96 kPa, the stirring speed at 50 rpm, and the temperature at 32°C. The mixture was stirred for 0.8 h, and nitrogen gas was introduced to restore the atmospheric pressure, resulting in a transparent film adhesive.

[0031] (2) Preparation of black film adhesive: By weight, the following components were added to a reaction vessel: 38 parts of alicyclic epoxy resin and 2 parts of bisphenol F epoxy resin; 6 parts of a second light diffusing agent (silicone resin microspheres, 2 μm particle size); 0.6 parts of a second antioxidant (octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); and 1.2 parts of a black pigment (anthraquinone fused ring structure pigment). The mixture was dehydrated for 2 hours at 115℃ and -96 kPa with a stirring speed of 50 rpm and a dispersion speed of 1200 rpm. The mixture was then cooled to room temperature. Nitrogen was introduced into the reaction vessel. The following components were added sequentially: a second epoxy curing agent (32 parts methyltetrahydrophthalic anhydride), a second epoxy accelerator (1.1 parts 2-ethyl-4-methylimidazolium), a second photoinitiator (1.3 parts 1-hydroxycyclohexylphenyl ketone), a second coupling agent (0.5 parts 3-acryloyloxypropyltrimethoxysilane), and a second acrylate monomer (5 parts glycidyl methacrylate). The mixture was stirred at a vacuum of -96 kPa, a stirring speed of 50 rpm, and a temperature of 32 °C for 0.8 h. Nitrogen gas was then introduced to restore atmospheric pressure, resulting in a black film adhesive.

[0032] (3) Preparation of the black adhesive film composite structure: The black epoxy adhesive layer was coated using a roller coating process, with a light release film (single-sided silicone release film, release force 4g, thickness 50μm, base film is PET film) and a heavy release film (single-sided silicone release film, release force 30g, thickness 75μm, base film is matte PET film, matte finish 20GU, silicone surface matte finish 20GU) as coating substrates. The coating thickness of the black epoxy adhesive layer was controlled to be 90μm. After lamination, it was sent to a UV oven for low-light curing at a light intensity of 8mw / cm². 2 The adhesive surface temperature is 32℃, forming a composite structure of light release film - black adhesive film layer - heavy release film.

[0033] (4) Preparation of four-layer composite film: The light release film in the above composite structure is peeled off to obtain a black adhesive film layer-heavy release film composite structure. The transparent adhesive layer is coated using a roller coating process, with the above black adhesive film layer-heavy release film composite structure and the new light release film as the coating substrate. The coating thickness of the transparent adhesive layer is controlled to be 100 μm. After lamination, the composite is placed in a UV oven for low-light curing at a light intensity of 8 mw / cm². 2 With the adhesive surface temperature at 32℃, a black matte epoxy film is obtained.

[0034] Example 3 1. Preparation of modified UV resin Prepare 30 parts by weight of polyether polyol PPG (average molecular weight 1500), 15 parts by weight of polyester diol (average molecular weight 2000), 40 parts by weight of polycaprolactone diol (average molecular weight 3000), 20 parts by weight of HMDI, and 10 parts by weight of HEMA; add the polyether polyol, polyester diol, and polycaprolactone diol to a reaction vessel and dehydrate for 1.5 hours at 130℃, -94KPa, and 50rpm. Under a nitrogen atmosphere and at 90°C, HMDI was added to the dehydrated material, and the mixture was stirred at 50 rpm for 2 hours. Then HEMA was added, and the mixture was stirred for another 2 hours to obtain the modified UV resin.

[0035] 2. Preparation of black matte epoxy film (1) Preparation of transparent film adhesive: By weight, the following components were added to a reaction vessel: 5 parts of first epoxy resin (hydrogenated bisphenol A epoxy resin, 40 parts of alicyclic epoxy resin), 3 parts of first light diffusing agent (polymethylsilsesquioxane, particle size 1 μm), 1 part of first antioxidant (2,4-di(n-octylthionyl)-6-methylphenol), and 15 parts of first toughening resin (polycaprolactone diol, average molecular weight 1000). The mixture was dehydrated for 1.5 hours at 130℃ and -94 kPa with a stirring speed of 60 rpm and a dispersion speed of 2000 rpm. The mixture was then cooled to room temperature, and nitrogen gas was introduced. The first epoxy curing agent (40 parts hexahydrophthalic anhydride), the first epoxy accelerator (2 parts 1,8-diazabicycloundec-7-ene), the first photoinitiator (2 parts diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), the first coupling agent (1 part 3-glycidyl etheroxypropyltriethoxysilane), and the first acrylate monomer (10 parts 3,4-epoxycyclohexyl methacrylate) were added sequentially. The vacuum degree was maintained at -94 kPa, the stirring speed at 60 rpm, and the temperature at 35°C. The mixture was stirred for 0.5 h, and nitrogen gas was introduced to restore normal pressure to obtain a transparent film adhesive.

[0036] (2) Preparation of black film adhesive: By weight, the second epoxy resin (5 parts hydrogenated bisphenol A epoxy resin and 40 parts alicyclic epoxy resin), the second light diffusing agent (silicone resin microspheres, 1 μm particle size, 4 parts), the second antioxidant (1 part 2,4-di(n-octylthionyl)-6-methylphenol), and the black pigment (2 parts azo metal complex) were added to a reaction vessel and dehydrated for 1.5 h at 130℃ and -94 kPa with a stirring speed of 60 rpm and a dispersion speed of 2000 rpm. The mixture was then cooled to room temperature. Nitrogen gas was introduced, and the second epoxy resin was added sequentially. The following agents were used: 40 parts of hexahydrophthalic anhydride, 2 parts of a second epoxy accelerator (1,8-diazabicycloundec-7-ene), 2 parts of a second photoinitiator (2 parts of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), 1 part of a second coupling agent (3-glycidyl etheroxypropyltriethoxysilane), and 10 parts of a second acrylate monomer (3,4-epoxycyclohexyl methacrylate). The mixture was stirred for 0.5 h at a vacuum of -94 kPa, a stirring speed of 60 rpm, and a temperature of 35 °C. Nitrogen gas was then introduced to restore atmospheric pressure, resulting in a black film adhesive.

[0037] (3) Preparation of the black adhesive film composite structure: The black epoxy adhesive layer was coated using a roller coating process, with a light release film (single-sided silicone release film, release force 5g, thickness 75μm, base film is PET film) and a heavy release film (single-sided silicone release film, release force 40g, thickness 100μm, base film is matte PET film, matte finish 30GU, silicone surface matte finish 30GU) as coating substrates. The coating thickness of the black epoxy adhesive layer was controlled to be 150μm. After lamination, it was sent to a UV oven for low-light curing at a light intensity of 10mw / cm².2 The adhesive surface temperature is 35℃, forming a composite structure of light release film - black adhesive film layer - heavy release film.

[0038] (4) Preparation of four-layer composite film: The light release film in the above composite structure is peeled off to obtain a black film layer-heavy release film composite structure; the transparent film layer adhesive is coated using a roller coating process, with the above black film layer-heavy release film composite structure and the new light release film as the coating substrate, and the coating thickness of the transparent film layer adhesive is controlled to be 150μm. After lamination, it is sent to a UV oven for weak light curing with a light intensity of 10mw / cm. 2 A black matte epoxy film is obtained by setting the adhesive surface temperature to 35℃.

[0039] Example 4 1. Preparation of modified UV resin Prepare 55 parts by weight of polyether polyol PPG (average molecular weight 2000), 25 parts of polycaprolactone diol (average molecular weight 3000), 15 parts of IPDI, and 8 parts of caprolactone acrylate; add the polyether polyol and polycaprolactone diol to the reactor and dehydrate for 2 hours at 120℃, -95KPa, and 50rpm. IPDI was added to the dehydrated material under a nitrogen atmosphere and at 90°C. After stirring at 50 rpm for 3 hours, caprolactone acrylate was added, and the mixture was stirred for another 3 hours to obtain the modified UV resin.

[0040] 2. Preparation of black matte epoxy film (1) Preparation of transparent film adhesive: By mass percentage, the first epoxy resin (40 parts alicyclic epoxy resin), the first light diffusing agent (3 parts polymethylsilsesquioxane, particle size 1 μm), the first antioxidant (0.8 parts 2,6-di-tert-butyl-4-methylphenol), and the first toughening resin (12 parts adipate polyester diol, average molecular weight 1200) were added to a reaction vessel and dehydrated for 2 hours at 120℃ and -95KPa with a stirring speed of 55 rpm and a dispersion speed of 1500 rpm. The mixture was then cooled to room temperature. Nitrogen gas was introduced, and the first... An epoxy curing agent (tetrahydrophthalic anhydride 35 parts), a first epoxy accelerator (benzyltriphenylphosphonium bromide 1.5 parts), a first photoinitiator (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide 1.8 parts), a first coupling agent (3-acryloyloxypropyltriethoxysilane 0.8 parts), and a first acrylate monomer (3,4-epoxycyclohexyl methacrylate 8 parts) were mixed under a vacuum of -95 kPa, a stirring speed of 55 rpm, and a temperature of 33°C for 0.7 h. Nitrogen gas was then introduced to restore normal pressure to obtain a transparent film adhesive.

[0041] (2) Preparation of black film adhesive: By weight, the following components were added to a reaction vessel: 40 parts of second epoxy resin (alicyclic epoxy resin), 5 parts of second light diffusing agent (polymethylsilsesquioxane, 1 μm particle size), 0.8 parts of second antioxidant (2,6-di-tert-butyl-4-methylphenol), and 1.5 parts of black pigment (anthraquinone fused ring structure pigment). The mixture was dehydrated for 2 hours at 120℃ and -95 kPa with a stirring speed of 55 rpm and a dispersion speed of 1500 rpm. The mixture was then cooled to room temperature, and nitrogen gas was introduced. The second epoxy curing agent (35 parts tetrahydrophthalic anhydride), the second epoxy accelerator (1.5 parts benzyltriphenylphosphine bromide), the second photoinitiator (1.8 parts phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), and the second acrylate monomer (8 parts 3,4-epoxycyclohexyl methacrylate) were added sequentially. The vacuum degree was maintained at -95 kPa, the stirring speed at 55 rpm, and the temperature at 33 °C. The mixture was stirred for 0.7 h, and nitrogen gas was introduced to restore normal pressure, resulting in a black adhesive film.

[0042] (3) Preparation of the black adhesive film composite structure: The black adhesive film layer was coated using a roller coating process, with a light release film (single-sided silicone oil release film, release force 4.5g, thickness 50μm, base film is PET film) and a heavy release film (single-sided silicone oil release film, release force 35g, thickness 100μm, base film is matte PET film, matte finish 25GU, silicone oil surface matte finish 25GU) as coating substrates. The coating thickness of the black adhesive film layer was controlled to be 120μm. After lamination, it was sent to a UV oven for low-light curing at a light intensity of 9mw / cm². 2 The adhesive surface temperature is 34℃, forming a composite structure of light release film - black adhesive film layer - heavy release film.

[0043] (4) Preparation of four-layer composite film: The light release film in the above composite structure is peeled off to obtain a black adhesive film layer-heavy release film composite structure. The transparent film layer adhesive is applied using a roller coating process, with the above black adhesive film layer-heavy release film composite structure and the new light release film as the coating substrate. The coating thickness of the transparent film layer adhesive is controlled to be 120 μm. After lamination, the composite is placed in a UV oven for low-light curing at a light intensity of 9 mw / cm². 2 With the adhesive surface temperature at 34℃, a black matte epoxy film is obtained.

[0044] The application process of the black matte epoxy film prepared in Examples 1 to 4 is as follows: The light release film of the black matte epoxy film is removed, and it is roller-coated and attached to the COB display panel. It is then placed in a high-pressure degassing machine and degassed at 40°C and 0.5 MPa for 30 minutes. After curing at 120°C for 100 minutes, the heavy release film is removed, thus achieving the curing and encapsulation of the COB display panel. In this invention, the transparent film portion directly contacts the wafer, resulting in better toughness, lower internal stress, and better adhesion. The black film layer has higher density, providing better protection against water and scratches. The two film layers are largely consistent, and after coating, a transition layer is formed through a diffusion effect, avoiding stress concentration between the two layers and improving overall integrity.

[0045] The bill of materials for Examples 1 to 4 are shown in Table 1: Table 1

[0046] The performance tests of the epoxy films in each embodiment are shown in Table 2 below: Table 2

[0047] As can be seen from the test results in Table 1, 1. This invention uses silicon microspheres with a particle size ≤5μm as a light diffusing agent, which has good compatibility with epoxy resin and modified UV resin. It can form uniform light scattering centers inside the film. By adding soluble black color, the problem of black spots of varying sizes on the display surface caused by insoluble color powders such as carbon black is avoided. By using surface transfer printing, a stable matte effect is formed on the material surface, avoiding the problem of a significant decrease in light transmittance caused by the addition of light-blocking agents in traditional matte materials. This achieves both excellent matte effect and ensures light transmittance.

[0048] 2. The hardness of the cured adhesive film is 72-78D, which is within the reasonable hardness range required for display module packaging. This ensures both support and protection for the chip while avoiding the excessive internal stress caused by the high hardness (typically >80D) of existing molding adhesives after curing. This is thanks to the optimized preparation process of the modified UV resin. Through the stepwise reaction of polyols, isocyanates, and hydroxyacrylates, flexible segments are introduced into the resin molecular chain, reducing the brittleness caused by crosslinking density. At the same time, the addition of toughening resin further enhances the flexibility of the adhesive film. The test results of 0.25-0.38 N / 25mm for the initial tack strength indicate that the adhesive film has suitable initial bonding strength, enabling rapid positioning during construction and application, while preventing the introduction of too many air bubbles during bonding, which would affect the removal of air bubbles. The absence of peeling in the cross-cut adhesion test proves the strong adhesion between the adhesive film and the black ink substrate. This is closely related to the role of the coupling agent in the formulation—the coupling agent enhances the interfacial bonding force between the adhesive film and the substrate through chemical bonding, improving the stability of the packaging structure.

[0049] 3. In the 500-hour high temperature and high humidity test and the 200-cycle temperature shock test at -40℃ to 85℃, the film showed no abnormalities, and the water absorption rate was ≤0.6%, demonstrating excellent environmental stability. This is mainly due to two design aspects: First, the selected epoxy resin and other substrates themselves have good resistance to damp heat, and the cross-linked structure formed by the curing agent such as methyl hexahydrophthalic anhydride is dense, which can effectively block moisture penetration; second, the addition of antioxidants delays the oxidative aging process of the resin and improves the yellowing resistance of the film, so that the yellowing index after aging is ≤0.5, which meets the appearance stability requirements for long-term use of display modules.

[0050] 4. Comparing the test data of Example 1 and Example 3, it can be seen that as the amount of light diffusing agent increased from 3 parts to 20 parts, the haze of the film increased from 74 to 99; indicating that appropriately increasing the amount of light diffusing agent can further optimize the light diffusion performance. Meanwhile, Example 3 used a blend of hydrogenated bisphenol A epoxy resin and alicyclic epoxy resin, combined with polyurethane toughening resin, resulting in better tensile-related mechanical properties and more stable performance under warm shock, high temperature, and high humidity conditions, confirming the effectiveness of the resin blending and toughening system optimization in the formulation. Examples 2 and 4 further optimized the flexibility and curing crosslinking density of the film by adjusting the type and amount of acrylate monomers, demonstrating the precise control of performance through formulation fine-tuning.

[0051] The black matte epoxy films prepared in Examples 1-4 of this invention all meet the performance requirements specified in the appendix: they are all black semi-transparent solids, flexible and elastic before curing; after curing, their hardness is between 72-78D, meeting the hardness requirements for encapsulation; the initial tack is 0.25-0.38 N / 25mm, and the adhesion performance is stable; the amount of light diffusing powder added in Example 1 is small, resulting in low haze and a light transmittance ≥50%; they all comply with RoHS 2.0 and REACH environmental standards, meeting environmental protection requirements; they exhibit excellent yellowing resistance, with yellowing indices ≤0.5; they show no peeling, yellowing, or cracking in temperature shock and high temperature and humidity (500h tightening) tests, demonstrating strong environmental adaptability; in the adhesion test, there is no peeling in the cross-cut adhesion test, indicating strong adhesion; the surface gloss of the film is close to that of the release film, and the matte effect is stable and reliable, meeting the requirements. The above test results fully demonstrate that the black matte epoxy films prepared by this invention have excellent comprehensive performance and can meet the needs of display module encapsulation.

[0052] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A black matte epoxy film for display modules, characterized in that: The black matte epoxy film comprises, in sequence, a light release film layer, a transparent film layer, a black film layer, and a heavy release film layer; the transparent film layer comprises, by weight, the following raw materials: The composition comprises 30-45 parts of a first epoxy resin, 25-40 parts of a first epoxy curing agent, 0.01-2 parts of a first epoxy accelerator, 5-20 parts of a first modified UV resin, 0.5-2 parts of a first photoinitiator, 0-20 parts of a first light diffusing agent, 0.1-1 parts of a first antioxidant, 0.1-1 parts of a first coupling agent, 5-15 parts of a first toughening resin, and 0-10 parts of a first acrylate monomer. The black adhesive film layer comprises, by weight, the following raw materials: 30-45 parts of second epoxy resin, 25-40 parts of second epoxy curing agent, 0.01-2 parts of second epoxy accelerator, 5-15 parts of second modified UV resin, 0.5-2 parts of second photoinitiator, 3-20 parts of second light diffusing agent, 0.1-1 part of second antioxidant, 0-1 part of second coupling agent, 0.1-2 parts of black pigment, and 0-10 parts of second acrylate monomer.

2. The black matte epoxy film for display modules according to claim 1, characterized in that: The first epoxy resin and the second epoxy resin are both selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, and alicyclic epoxy resin.

3. The black matte epoxy film for display modules according to claim 1, characterized in that: Both the first epoxy curing agent and the second epoxy curing agent are selected from at least one of methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and tetrahydrophthalic anhydride; Both the first epoxy accelerator and the second epoxy accelerator are selected from at least one of tetramethylammonium bromide, tetrabutylammonium bromide, triphenylphosphine, benzyltriphenylphosphonium bromide, 2-ethyl-4-methylimidazolium, and 1,8-diazabicycloundec-7-ene.

4. The black matte epoxy film for display modules according to claim 1, characterized in that: Both the first photoinitiator and the second photoinitiator are selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, methyl benzoylcarbamate, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphonate. The first light diffusing agent and the second light diffusing agent are both selected from at least one of polymethylsilsesquioxane and silicone resin microspheres, and the particle size of the first light diffusing agent and the second light diffusing agent is ≤5μm. Both the first antioxidant and the second antioxidant are selected from at least one of 2,6-di-tert-butyl-4-methylphenol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, and 2,4-bis(n-octylthionyl)-6-methylphenol; Both the first coupling agent and the second coupling agent are selected from at least one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, and 3-acryloyloxypropyltriethoxysilane. The black pigment is an azo metal complex or an anthraquinone fused ring structure pigment.

5. The black matte epoxy film for display modules according to claim 1, characterized in that: Both the first acrylate monomer and the second acrylate monomer are selected from at least one of glycidyl methacrylate, glycidyl acrylate, 3,4-epoxycyclohexyl methacrylate, and 3,4-epoxycyclohexyl methacrylate. The first toughening resin is selected from at least one of polyether polyol, polyester polyol, epoxidized polybutadiene, silicone-modified epoxy resin, polyurethane-modified epoxy resin, core-shell polymer, and hyperbranched polymer.

6. The black matte epoxy film for display modules according to claim 1, characterized in that: Both the first modified UV resin and the second modified UV resin are prepared through the following steps: Prepare 60-85 parts of polyol, 5-20 parts of isocyanate and 5-15 parts of hydroxy acrylate by weight. The polyol was dehydrated at 100-130℃, ≤-94KPa, and 40-60rpm for 1.5-2.5h. Isocyanate was added to the dehydrated material under a nitrogen atmosphere and at 80-100℃. After stirring at 40-60 rpm for 2-5 hours, hydroxy acrylate was added to the system and the reaction was continued for another 2-5 hours to obtain the modified UV resin.

7. The black matte epoxy film for display modules according to claim 6, characterized in that: The polyol is a polyether polyol, a polycaprolactone diol, or a polyester diol, and the average molecular weight of the polyol is 1000-4000. The isocyanate is at least one of IPDI, HDI, and HMDI; The hydroxy acrylate is at least one of HPA, HEA, HEMA, HBA, and caprolactone acrylate.

8. The black matte epoxy film for display modules according to claim 1, characterized in that: The thickness of the light release film layer is 25-75μm, and the release force of the effective release surface of the light release film layer is ≤25g; The thickness of the heavy release film layer is 50-125μm, the base film of the heavy release film layer is a matte PET film, and the release force of the effective release surface of the heavy release film layer is ≤100g. The thickness of the heavy release film layer minus the thickness of the light release film layer is ≥25μm; The release force of the heavy release film layer is at least 3 times that of the light release film layer; The thickness of the transparent adhesive film layer is 50-150 μm; The thickness of the black adhesive film layer is 30-150 μm.

9. The black matte epoxy film for display modules according to claim 8, characterized in that: The re-release film layer has matte particles added to its release layer, and the matteness of the release surface of the re-release film layer is 10-30 GU; The thickness of the black adhesive film layer accounts for 1 / 5 to 1 / 2 of the total thickness of the black matte epoxy adhesive film.

10. A method for preparing a black matte epoxy film for a display module as described in any one of claims 1-9, characterized in that: The specific steps are as follows: According to the formula of the black film layer, the second epoxy resin, the second light diffusing agent, the second antioxidant and the black pigment are put into the reaction vessel. Under the conditions of temperature 100-130℃ and vacuum degree ≤-94KPa, the mixture is dehydrated for 1.5-2.5h with stirring speed of 40-60rpm and dispersion speed of 500-2000rpm, and then cooled to room temperature. Nitrogen gas is introduced into the reactor, and then the second acrylate monomer, the second epoxy curing agent, the second epoxy accelerator, the second photoinitiator and the second coupling agent are added in sequence. The vacuum degree is maintained at ≤-94KPa, the stirring speed is 40-60rpm and the temperature is ≤35℃. The mixture is stirred for 0.5-1h, and then nitrogen gas is introduced to restore the atmospheric pressure to obtain a black film adhesive. According to the ratio of the transparent film layer, the first epoxy resin, the first light diffusing agent, the first antioxidant, and the first toughening resin are added into the reactor. Under the conditions of temperature 100-130℃ and vacuum degree ≤-94KPa, the mixture is dehydrated for 1.5-2.5h with stirring speed of 40-60rpm and dispersion speed of 500-2000rpm, and then cooled to room temperature. Nitrogen gas is introduced into the reactor, and then the first epoxy curing agent, the first epoxy accelerator, the first photoinitiator, the first acrylate monomer and the first coupling agent are added in sequence. The vacuum degree is maintained at ≤-94KPa, the stirring speed is 40-60rpm and the temperature is ≤35℃. The mixture is stirred for 0.5-1h, and then nitrogen gas is introduced to restore the atmospheric pressure to obtain a transparent film adhesive. The black film adhesive is applied using a roller coating process, with light and heavy release films as the coating substrates. The coating thickness is controlled at 30-150μm. The light release film, black film adhesive, and heavy release film are then laminated together and sent to a UV oven for low-light curing, with the light intensity controlled at ≤10mw / cm². 2 The adhesive surface temperature is ≤35℃, forming a composite structure of light release film - black adhesive film layer - heavy release film; The light release membrane in the light release membrane-black adhesive film layer-heavy release membrane composite structure is peeled off to form the black adhesive film layer-heavy release membrane composite structure; The transparent film adhesive is applied using a roller coating process. A black adhesive film-heavy release film composite structure and a light release film are used as the coating substrate, with the coating thickness controlled at 50-150μm. The light release film, transparent film adhesive, and black adhesive film-heavy release film composite structure are then laminated. After lamination, the composite is placed in a UV oven for low-light curing, with the light intensity controlled to ≤10mw / cm². 2 With a surface temperature ≤35℃, a black matte epoxy film with a four-layer composite structure consisting of a light release film, a transparent film layer, a black film layer, and a heavy release film is formed.

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