A release film base film for a flame-retardant OCA and a method for manufacturing the same

Abstract

The application belongs to the technical field of optical adhesive base film, and particularly relates to a release film base film for flame-retardant OCA and a preparation method thereof. The release film base film for flame-retardant OCA prepared by the application has excellent product performance and meets relevant product standards. In addition, the release film base film has excellent flame-retardant performance, achieves a UL-94 V-0 flame-retardant grade, and has a high LOI value of 39.8%, and has good industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of optical adhesive film technology, specifically relating to a release film base for flame-retardant OCA and its preparation method. Background Technology

[0002] Optically clear adhesives (OCA) are bonding materials made of polymers such as polyurethane, acrylic, and silicone. They possess high transparency, a low coefficient of thermal expansion, excellent interfacial bonding strength, strong flexibility, and weather resistance, making them widely used in optical displays, electronic packaging, and medical devices. Their superior performance is primarily reflected in two aspects: First, their optical properties are extremely excellent, with light transmittance generally exceeding 90%, haze controllable below 1%, and a refractive index matched to the glass substrate. These characteristics ensure high definition and color reproduction in display devices. Second, their excellent bonding performance enables a strong bond between the layers of the display panel while maintaining good stress distribution, effectively improving the reliability and lifespan of the equipment.

[0003] Release film is a material with low surface energy, made from polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), polyethylene (PE), carbonated polypropylene (PC), polystyrene (PS), or polypropylene (CPP) as the base material. It is a key component of OCA tape. Release film mainly consists of a base film, a release layer, and a functional coating. It allows for easy peeling or removal of the release material from the adjacent adhesive without damaging the adhesive properties. Release film is characterized by a smooth surface, high cleanliness, stable dimensions during subsequent processing, adjustable transparency and color, and a wide range of selectable film thickness and base material types.

[0004] Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic polyester. Due to its excellent mechanical strength, dimensional stability, chemical resistance, and optical properties, it has become one of the preferred materials for release film base films. However, PET's molecular structure contains flammable hydrocarbon segments. When heated, these chains easily break, producing flammable gases. These gases mix with oxygen in the air to form a flammable mixture, making it a highly flammable material. This poses a safety hazard in the trend of miniaturization and high integration in electronic products, especially when short circuits or overheating occur inside the equipment, as traditional PET release films may become a medium for fire spread. To improve the flame retardant properties of PET materials, the industry has explored various technical approaches, mainly including copolymer modification, the addition of flame retardants, and surface treatment. However, while these methods improve flame retardancy, they also reduce the optical and mechanical properties of the base film.

[0005] Therefore, it is of great significance to develop a release film base film for OCA that combines excellent optical properties, mechanical properties and flame retardant properties. Summary of the Invention

[0006] The main objective of this invention is to provide a flame-retardant release film base film for OCA and its preparation method, thereby solving the current problem of difficulty in simultaneously achieving optical, mechanical, and flame-retardant properties. This invention will be achieved through the following technical solutions:

[0007] A method for preparing a release film base film for flame-retardant OCA includes the following steps:

[0008] Step 1: Preparation of flame-retardant PET polyester masterbatch

[0009] Terephthalic acid, ethylene glycol, flame-retardant modified monomer X, and catalyst Sb2O3 were added to a reactor and stirred until homogeneous. The reaction solution underwent esterification, pre-condensation, and final condensation reactions to obtain polyester. Then, it was granulated by twin-screw extrusion and dried to obtain flame-retardant PET polyester masterbatch.

[0010] The structural formula of the flame-retardant modified monomer X is: ;

[0011] Step 2: Preparation of release film base film for flame-retardant OCA

[0012] By weight, 100 parts of PET polyester chips, 30-50 parts of flame-retardant PET polyester masterbatch, 1-3 parts of antioxidant, 1-5 parts of nano-inorganic filler, and 3-5 parts of silane coupling agent are mixed evenly, and then melt-extruded and cast into sheets to form a sheet. After biaxial stretching and traction winding, the flame-retardant OCA release film base film is obtained.

[0013] In some embodiments, the thickness of the release film base film for the flame-retardant OCA is 50~150μm.

[0014] In some embodiments, the molar ratio of phthalic acid to ethylene glycol is 1:(1~1.2); the molar ratio of phthalic acid to flame-retardant modified monomer X is 1:(0.1~0.5); and the molar ratio of phthalic acid to catalyst Sb2O3 is 1:(0.05~0.2).

[0015] In some implementations, in step 1, the esterification reaction conditions are: heating to 200-250°C at a rate of 5-10°C / min and reacting for 1-10 hours; the pre-condensation reaction conditions are: heating to 230-260°C after the esterification reaction, evacuating to 1-5 kPa, and reacting for 1-5 hours; the final condensation reaction conditions are: heating to 250-300°C after the pre-condensation reaction, evacuating to 0.1-0.5 kPa, and reacting for 1-5 hours.

[0016] In some implementations, in step 1, the twin-screw extruder rotates at 100-150 r / min, and the temperatures in zones one, two, three, four, and five are 250-270°C, 260-290°C, 280-300°C, and 280-300°C respectively.

[0017] In some embodiments, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0018] In some embodiments, the nano-inorganic filler is selected from one or more of nano-silica, nano-alumina, nano-titanium dioxide, and nano-calcium carbonate.

[0019] In some embodiments, the coupling agent is selected from one or more of KH-550, KH-560, KH-570, KH-792 and KH-791.

[0020] In some implementations, in step 2, the melt extrusion temperature is 260~300℃; the casting temperature is 20~40℃; the transverse stretching ratio is 3~5 and the longitudinal stretching ratio is 2~4 during biaxial stretching, the stretching temperature is 90~120℃, and the stretching rate is 100~150mm / s.

[0021] This invention also protects the flame-retardant OCA release film base film prepared by the above method.

[0022] The present invention has achieved the following beneficial effects:

[0023] 1) The flame-retardant OCA release film base film prepared by this invention has excellent product performance (high light transmittance, low shrinkage, low haze, low surface roughness, etc.) and meets relevant product standards;

[0024] 2) The flame-retardant OCA release film base film prepared by this invention exhibits excellent flame-retardant properties, achieving a UL-94V-0 flame-retardant rating with an LOI value as high as 39.8%, significantly superior to existing technologies. The main reason for this is that the flame-retardant modified monomer X prepared by this invention has a novel structure and simultaneously contains three flame-retardant elements: Si, N, and P, enabling synergistic and efficient flame retardancy. Detailed Implementation

[0025] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the invention, but rather as a more detailed description of certain aspects, features, and embodiments of the invention. Furthermore, the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Additionally, for numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included within the scope of this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. Furthermore, unless otherwise stated, all materials used in this invention are commercially available.

[0027]

[0028] Under nitrogen atmosphere, compound 1 (0.1 mol), compound 2 (0.25 mol), triethylamine (0.1 mol), and anhydrous THF (300 mL) were added to a reactor, and the mixture was heated to 65 °C and stirred for 10 h. After the reaction was complete, the mixture was filtered, and the filtrate was washed three times with water (100 mL x 3). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography to obtain intermediate compound 3 with a yield of 72.6% and an HPLC purity of 99.5%.

[0029] LC-MS(ESI):[M+H] + =666.2.

[0030] Under nitrogen atmosphere, intermediate compound 3 (0.1 mol), compound 4 (0.3 mol), and chloroform (300 mL) were added to a reactor, and the mixture was heated to 60 °C and stirred for 12 h. After the reaction was complete, the mixture was concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography to obtain flame-retardant modified monomer X with a yield of 85.1% and an HPLC purity of 99.3%.

[0031] LC-MS(ESI):[M+H] + =752.3.

[0032] 1H-NMR (500 MHz, CDCl3): δ(ppm): 8.95 (s,2H), 8.19-8.12(m,4H), 7.91-7.80(m,2H), 7.75-7.63(m,8H), 7.42-7.35(m,2H), 6.05-5.94 (m,4H), 4.72-4.62 (m,4H), 4.35 (s,2H), 0.31 (s,18H).

[0033] Example 1: A method for preparing a release film base film for flame-retardant OCA, comprising the following steps:

[0034] Terephthalic acid, ethylene glycol, flame-retardant modified monomer X, and catalyst Sb₂O₃ in a molar ratio of 1:1:0.2:0.05 were added to a reactor and stirred until homogeneous. The system was checked for air tightness, and nitrogen was introduced to purge the air from the reactor. The reaction solution underwent esterification, pre-condensation, and final condensation reactions to obtain polyester, which was then granulated by twin-screw extrusion and dried to obtain flame-retardant PET polyester masterbatch.

[0035] The reaction process includes: esterification reaction: heating to 230℃ at 5℃ / min for 3 hours; pre-condensation reaction: heating to 250℃ after esterification reaction, vacuuming to 2.0kPa, and reacting for 2 hours; final condensation reaction: heating to 280℃ after pre-condensation reaction, vacuuming to 0.1kPa, and reacting for 2 hours.

[0036] The twin-screw extruder has a rotation speed of 100 r / min and extruder zone temperatures of 260℃ in zone 1, 270℃ in zone 2, 280℃ in zone 3, 290℃ in zone 4, and 290℃ in zone 5.

[0037] By weight, 100 parts of PET polyester chips (brand name Wankai WK-821), 40 parts of flame-retardant PET polyester masterbatch, 2 parts of antioxidant 1010, 3 parts of nano silica, and 5 parts of coupling agent KH-550 are mixed evenly, and then melt-extruded and cast into sheets to form a sheet. After biaxial stretching and traction winding, the flame-retardant OCA release film base film with a thickness of 50μm is obtained.

[0038] The melt extrusion temperature is 280℃; the casting temperature is 30℃; the transverse stretching ratio is 4 and the longitudinal stretching ratio is 3 during biaxial stretching, the stretching temperature is 100℃, and the stretching rate is 120mm / s.

[0039] Example 2: A method for preparing a release film base film for flame-retardant OCA, comprising the following steps:

[0040] Terephthalic acid, ethylene glycol, flame-retardant modified monomer X, and catalyst Sb₂O₃ in a molar ratio of 1:1:0.15:0.1 were added to a reactor and stirred until homogeneous. The system was checked for air tightness, and nitrogen was introduced to purge the air from the reactor. The reaction solution underwent esterification, pre-condensation, and final condensation reactions to obtain polyester, which was then granulated by twin-screw extrusion and dried to obtain flame-retardant PET polyester masterbatch.

[0041] The reaction process includes: esterification reaction: heating to 230℃ at 5℃ / min for 3 hours; pre-condensation reaction: heating to 250℃ after esterification reaction, vacuuming to 2.0kPa, and reacting for 2 hours; final condensation reaction: heating to 280℃ after pre-condensation reaction, vacuuming to 0.1kPa, and reacting for 2 hours.

[0042] The twin-screw extruder has a rotation speed of 100 r / min and extruder zone temperatures of 260℃ in zone 1, 270℃ in zone 2, 280℃ in zone 3, 290℃ in zone 4, and 290℃ in zone 5.

[0043] By weight, 100 parts of PET polyester chips (brand name Wankai WK-821), 45 parts of flame-retardant PET polyester masterbatch, 1.5 parts of antioxidant 168, 5 parts of nano silica, and 4 parts of coupling agent KH-570 are mixed evenly, and then melt-extruded and cast into sheets to form a sheet. After biaxial stretching and traction winding, the flame-retardant OCA release film base film with a thickness of 50μm is obtained.

[0044] The melt extrusion temperature is 280℃; the casting temperature is 30℃; the transverse stretching ratio is 4 and the longitudinal stretching ratio is 3 during biaxial stretching, the stretching temperature is 100℃, and the stretching rate is 120mm / s.

[0045] Example 3: A method for preparing a release film base film for flame-retardant OCA, comprising the following steps:

[0046] Terephthalic acid, ethylene glycol, flame-retardant modified monomer X, and catalyst Sb₂O₃ in a molar ratio of 1:1:0.2:0.1 were added to a reactor and stirred until homogeneous. The system was checked for air tightness, and nitrogen was introduced to purge the air from the reactor. The reaction solution underwent esterification, pre-condensation, and final condensation reactions to obtain polyester, which was then granulated by twin-screw extrusion and dried to obtain flame-retardant PET polyester masterbatch.

[0047] The reaction process includes: esterification reaction: heating to 230℃ at 5℃ / min for 3 hours; pre-condensation reaction: heating to 250℃ after esterification reaction, vacuuming to 2.0kPa, and reacting for 2 hours; final condensation reaction: heating to 280℃ after pre-condensation reaction, vacuuming to 0.1kPa, and reacting for 2 hours.

[0048] The twin-screw extruder has a rotation speed of 100 r / min and extruder zone temperatures of 260℃ in zone 1, 270℃ in zone 2, 280℃ in zone 3, 290℃ in zone 4, and 290℃ in zone 5.

[0049] By weight, 100 parts of PET polyester chips (brand name Wankai WK-821), 35 parts of flame-retardant PET polyester masterbatch, 2 parts of antioxidant 1076, 3 parts of nano aluminum oxide, and 5 parts of coupling agent KH-550 are mixed evenly, and then melt-extruded and cast into sheets to form a sheet. After biaxial stretching and traction winding, the flame-retardant OCA release film base film with a thickness of 50μm is obtained.

[0050] The melt extrusion temperature is 280℃; the casting temperature is 30℃; the transverse stretching ratio is 4 and the longitudinal stretching ratio is 3 during biaxial stretching, the stretching temperature is 100℃, and the stretching rate is 120mm / s.

[0051] Based on Example 1, the flame-retardant modified monomer X was replaced with... Other operating steps and conditions are the same as in Example 1.

[0052] Based on Example 1, the flame-retardant modified monomer X was replaced with... Other operating steps and conditions are the same as in Example 1.

[0053] The product performance (light transmittance, haze, heat shrinkage rate, and Ra) and flame retardant properties of the OCA release film base films of Examples 1-3 and Comparative Examples 1-2 were measured according to the following standards:

[0054] 1) Light transmittance and haze: measured in accordance with GB / T2410-2008 standard;

[0055] 2) Longitudinal / transverse heat shrinkage rate: determined according to GB / T27584-2011 standard. Five sets of data were collected for each sample. The sample size was 300mm × 300mm. The samples were placed in an oven at 150℃ and cooled to room temperature for 2 hours before measuring the dimensional changes of MD (longitudinal) and TD (transverse).

[0056] 3) Surface roughness R a The determination was carried out in accordance with the GB / T1031-2009 standard; the surface roughness of the base film was tested using a VK-X160K, and 5 sets of data were taken for each sample, and the average value was taken.

[0057] 4) Limiting Oxygen Index (LOI) Test:

[0058] The LOI of the base film was tested using a JF-3 oxygen index tester, and the test standard was GB / T2406.2-2009.

[0059] 5) Vertical burning UL-94 test

[0060] The base film was tested using an SCZ-3 horizontal and vertical combustion tester, and the test standard was GB / T2408-2021.

[0061] The results are shown in Tables 1 and 2.

[0062] Table 1 Product Performance Test Results

[0063]

[0064] As shown in Table 1, the flame-retardant OCA release film base film prepared by the present invention has excellent product performance (high light transmittance, low shrinkage, low haze, low surface roughness, etc.) and meets the relevant product standards.

[0065] Table 2 Flame retardant performance test results

[0066]

[0067] As shown in Table 2, the flame-retardant OCA release film base film prepared by this invention exhibits excellent flame-retardant properties, achieving a UL-94V-0 flame-retardant rating with an LOI value as high as 39.8%, significantly superior to existing technologies. The main reason for this is that the flame-retardant modified monomer X prepared by this invention has a novel structure and simultaneously contains three flame-retardant elements: Si, N, and P, enabling synergistic and efficient flame retardancy.

[0068] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a flame-retardant OCA release film base film, comprising the following steps: Step 1: preparation of flame-retardant PET polyester masterbatch terephthalic acid, ethylene glycol, flame-retardant modifying monomer X and catalyst Sb2O3 are added into a reaction kettle and stirred uniformly, the reaction solution is subjected to esterification, pre-polycondensation and final polycondensation to obtain polyester, and then the polyester is subjected to double-screw extrusion granulation and drying to obtain the flame-retardant PET polyester masterbatch; The structural formula of the flame-retardant modifying monomer X is: ; Step 2: preparation of the flame-retardant OCA release film base film 100 parts of PET polyester chips, 30-50 parts of the flame-retardant PET polyester masterbatch, 1-3 parts of antioxidant, 1-5 parts of nano inorganic filler and 3-5 parts of silane coupling agent are mixed uniformly, and then subjected to melt extrusion, casting and sheet forming, and then bidirectional stretching and traction winding to obtain the flame-retardant OCA release film base film.

2. The production method according to claim 1, characterized by, The thickness of the flame-retardant OCA release film base film is 50-150 μm.

3. The preparation method according to claim 1, characterized in that, The molar ratio of terephthalic acid to ethylene glycol is 1: (1-1.2), the molar ratio of terephthalic acid to flame-retardant modifying monomer X is 1: (0.1-0.5), and the molar ratio of terephthalic acid to catalyst Sb2O3 is 1: (0.05-0.2).

4. The method of claim 1, wherein, In step 1, the reaction conditions for esterification are as follows: increasing the temperature to 200-250 ℃ at a rate of 5-10 ℃ / min and reacting for 1-10 h; the reaction conditions for pre-polycondensation are as follows: increasing the temperature to 230-260 ℃ after esterification, vacuumizing to 1-5 kPa and reacting for 1-5 h; and the reaction conditions for final polycondensation are as follows: increasing the temperature to 250-300 ℃ after pre-polycondensation, vacuumizing to 0.1-0.5 kPa and reacting for 1-5 h.

5. The preparation method according to claim 1, characterized in that, In step 1, the rotating speed of the double-screw extruder is 100-150 r / min, the temperature of the extruder zone 1 is 250-270 ℃, the temperature of the extruder zone 2 is 260-290 ℃, the temperature of the extruder zone 3 is 260-290 ℃, the temperature of the extruder zone 4 is 280-300 ℃, and the temperature of the extruder zone 5 is 280-300 ℃.

6. The method of claim 1, wherein, The antioxidant is selected from one or more of antioxidant 1010, antioxidant 168 and antioxidant 1076.

7. The preparation method according to claim 1, characterized in that, The nano inorganic filler is selected from one or more of nano silicon dioxide, nano aluminum trioxide, nano titanium dioxide and nano calcium carbonate.

8. The method of claim 1, wherein, The coupling agent is selected from one or more of KH-550, KH-560, KH-570, KH-792 and KH-791.

9. The method of claim 1, wherein, In step 2, the melt extrusion temperature is 260-300 ℃, the casting temperature is 20-40 ℃, the lateral stretching ratio is 3-5, the longitudinal stretching ratio is 2-4, the stretching temperature is 90-120 ℃, and the stretching speed is 100-150 mm / s. 10.A flame-retardant OCA release film base film prepared by the method according to any one of claims 1-9.

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