High-temperature-resistant PU protective film for liquid crystal display panel and preparation method of high-temperature-resistant PU protective film

Abstract

The invention discloses a high-temperature-resistant PU protective film for a liquid crystal panel and a preparation method of the high-temperature-resistant PU protective film. The high-temperature-resistant PU protective film for the liquid crystal panel comprises a release layer, a PU glue coating, an antistatic coating and a base material layer from top to bottom in sequence, the PU glue coating is prepared by compounding polyurethane, a curing agent and a tackifier; the base material layer is prepared by compounding PET (Polyethylene Terephthalate) and a plasticizer; the antistatic coating is prepared by compounding a cationic quaternary ammonium salt type surfactant, a flatting agent, a conductive agent, acetic ether and acrylic resin; the cationic quaternary ammonium salt type surfactant has a structure as shown in a formula A in the specification. The antistatic coating is prepared by adding the cationic quaternary ammonium salt type surfactant, the flatting agent, the conductive agent, the acetic ether and the acrylic resin into the PU protective film in a compounding manner, so that the weather resistance and the high-temperature resistance of the protective film can be remarkably improved, and the prepared protective film has excellent surface cleanliness and exhaust property; the protective film can be widely applied to the field of protective films of liquid crystal panels.

Description

Technical Field

[0001] This invention relates to the field of protective film technology, specifically to a high-temperature resistant PU protective film for liquid crystal panels and its preparation method. Background Technology

[0002] With the rapid development and advancement of electronics and semiconductor technology, various types of mobile devices and wearable devices, such as laptops, tablets, tablet phones, smartphones, smartwatches, and smart bracelets, have already permeated modern life in large numbers.

[0003] Protective films are required to protect the surfaces of electronic product glass covers, precision plastic parts, and precision electronic components from contamination and damage during manufacturing or transportation. Therefore, the protective films must be easy to apply and remove, have an optical-grade appearance and cleanliness, and also have anti-static properties to prevent damage to components caused by electrostatic discharge during film removal. When used for screen protection, the protective films must also have excellent wetting properties and self-exhausting capabilities.

[0004] Currently, LCD screen protectors are typically produced by applying metal films or plating gold layers, making it difficult to obtain transparent protective films. Moreover, the functions of ordinary LCD screen protectors on the market are relatively limited, which can hardly meet the growing demand for various functions from consumers. Therefore, there is a need for an LCD screen protector that can solve the above problems and add new functions.

[0005] PU protective film is a functional protective film made of transparent PET film as the base material, coated with polyurethane adhesive on one side, and laminated with a release film on the back. It is currently mainly used for high-temperature control process protection of LCD panels and for shipping protection of ITO and glass panels. PU protective film has many excellent properties: smooth and flat surface, good air venting performance, and good adsorption performance; good chemical resistance of the adhesive layer, no silicone components, and no silicone transfer; good adhesion performance, no residue at high temperatures, and stable adhesion; good weather resistance to general high temperature and humidity; no residue or marks after application and peeling, and no white fogging; high transmittance material, ensuring high-definition image quality; produced in a cleanroom with dust-free coating, high cleanliness, and excellent appearance performance. Product features include high light transmittance, strong weather resistance, easy peeling, no residue, and high temperature resistance.

[0006] However, the surface cleanliness and air permeability of the PU protective film in the existing technology still need to be improved, which may affect the display effect of the display device. Furthermore, as the application range of display devices expands, the demand for the weather resistance and high temperature resistance of the protective film is also gradually increasing.

[0007] Therefore, there is an urgent need for a high-temperature resistant PU protective film for LCD panels that has excellent surface cleanliness, strong weather resistance, and high temperature resistance. Summary of the Invention

[0008] Purpose of the invention: In view of the deficiencies of the prior art, the purpose of this invention is to provide a high-temperature resistant PU protective film for liquid crystal panels with excellent surface cleanliness, strong weather resistance and high temperature resistance, and its preparation method.

[0009] Technical solution:

[0010] A high-temperature resistant PU protective film for LCD panels comprises, from top to bottom, a release layer, a PU adhesive coating, an antistatic coating, and a substrate layer;

[0011] The PU adhesive coating is prepared by combining polyurethane, curing agent and tackifier;

[0012] The substrate layer is made by laminating PET and a plasticizer;

[0013] The antistatic coating is prepared by compounding cationic quaternary ammonium salt surfactant, leveling agent, conductive agent, ethyl acetate and acrylic resin;

[0014] The cationic quaternary ammonium salt surfactant has the structure shown in Formula A:

[0015]

[0016] This invention, by adding cationic quaternary ammonium salt surfactants to the antistatic coating, can not only significantly improve the surface cleanliness and air permeability of the PU protective film, but also enhance its weather resistance and high-temperature resistance.

[0017] Further, the cationic quaternary ammonium salt surfactant is prepared by the following steps: In a reactor, N,N,N',N'-tetramethyl-1,6-hexanediamine and dimethyl sulfoxide are added, and the temperature is raised to 50-60°C under nitrogen protection. After stirring evenly, 5-benzyl-2-bromopyridine is added. After reacting at this temperature for 3-4 hours, the mixture is cooled, filtered, washed, and dried to obtain the cationic surfactant.

[0018] On the one hand, the quaternary ammonium structure, pyridine structure, and long-chain alkanes in cationic quaternary ammonium salt surfactants can endow them with excellent surface activity, thereby enabling the protective film to effectively remove impurities such as dust and air that affect the display effect, significantly improving the surface cleanliness and air venting of the protective film; on the other hand, the pyridine structure and benzene ring structure in cationic quaternary ammonium salt surfactants can endow them with excellent chemical stability, thereby effectively improving the weather resistance and high temperature resistance of the protective film.

[0019] Furthermore, the mass ratio of N,N,N',N'-tetramethyl-1,6-hexanediamine and 5-benzyl-2-bromopyridine is 1:2.5-3.

[0020] Furthermore, the leveling agent in the antistatic coating is selected from one of GLP588, GLP388, GLP599 or PV88; the conductive agent is selected from one of conductive carbon black, acetylene black or carbon nanotubes.

[0021] Furthermore, based on a total mass fraction of 100%, the mass percentage of each component in the antistatic coating is as follows:

[0022]

[0023] This invention, by adding an antistatic coating structure to the protective film, can prevent damage to the components of the liquid crystal panel caused by electrostatic breakdown, thus playing a role in electrostatic protection. Furthermore, the antistatic coating can improve the weather resistance and high temperature resistance of the protective film, which not only improves the protective ability and service life of the protective film, but also expands the application range of the liquid crystal panel in harsh environments and enhances its application value.

[0024] Furthermore, the curing agent in the PU adhesive coating is selected from one of methyl ethyl ketone peroxide, m-phenylenediamine, or diaminodiphenyl sulfone; the tackifier is selected from one of hydrogenated rosin resin, esterified rosin resin, or terpene resin.

[0025] Furthermore, the mass ratio of polyurethane, curing agent and tackifier in the PU adhesive coating is (15-20):(1-2):(2-3).

[0026] Based on the structure of its PU protective film, this invention has good mechanical and adsorption properties, which can effectively adhere to the surface of the liquid crystal panel to prevent pollution and damage. It also has good surface cleanliness, transparency and air permeability, and will not affect the display effect of the liquid crystal panel.

[0027] Furthermore, the plasticizer in the substrate layer is selected from dibutyl phthalate or diethyl phthalate; the mass ratio of PTE to plasticizer is 25-30:1.

[0028] Furthermore, the release layer has a thickness of 0.1-0.2 mm, the PU adhesive coating has a thickness of 0.08-0.1 mm, the antistatic coating has a thickness of 0.05-0.08 mm, and the substrate layer has a thickness of 0.1-0.15 mm.

[0029] The method for preparing the high-temperature resistant PU protective film for LCD panels described above includes the following steps:

[0030] (1) PET and plasticizer are added in proportion in an internal mixer, heated to 160-180℃, stirred and melted, and then extruded and blown to obtain the substrate layer;

[0031] (2) Add polyurethane, curing agent and tackifier to the reactor in proportion, heat to 40-50℃ and stir evenly to obtain PU adhesive coating material;

[0032] (3) Add cationic quaternary ammonium salt surfactant, leveling agent, conductive agent, ethyl acetate and acrylic resin in proportion to the reactor, heat to 35-40℃ and stir evenly to obtain antistatic coating material.

[0033] (4) The antistatic coating material, PU adhesive coating material and release layer are bonded sequentially on the substrate layer, and the high-temperature resistant PU protective film for LCD panels is obtained after extrusion molding and encapsulation.

[0034] Beneficial effects:

[0035] (1) The high-temperature resistant PU protective film for LCD panels provided by the present invention is composed of a release layer, a PU adhesive coating, an antistatic coating and a substrate layer. The antistatic coating, which is prepared by adding cationic quaternary ammonium salt surfactant, leveling agent, conductive agent, ethyl acetate and acrylic resin to the PU protective film, can significantly improve the weather resistance and high temperature resistance of the protective film. The resulting protective film has excellent surface cleanliness and air venting properties and can be widely used in the field of protective films for LCD panels.

[0036] (2) The high-temperature resistant PU protective film for liquid crystal panels provided by the present invention has good mechanical properties and adsorption properties based on the structure of its PU protective film. It can be effectively attached to the surface of the liquid crystal panel to play a protective role in preventing pollution and damage. It also has good surface cleanliness, transparency and air venting, and will not affect the display effect of the liquid crystal panel.

[0037] (3) The high-temperature resistant PU protective film for liquid crystal panels provided by the present invention can avoid damage to liquid crystal panel components caused by electrostatic breakdown by adding an antistatic coating structure to the protective film, thus playing a role in electrostatic protection. Furthermore, the antistatic coating can improve the weather resistance and high-temperature resistance of the protective film, which can not only improve the protective ability and service life of the protective film, but also expand the application range of liquid crystal panels in harsh environments and improve the application value.

[0038] (4) The high-temperature resistant PU protective film for liquid crystal panels provided by the present invention can significantly improve the surface cleanliness and air venting of the PU protective film by adding cationic quaternary ammonium salt surfactant to the antistatic coating, and can also improve its weather resistance and high temperature resistance.

[0039] (5) In the high-temperature resistant PU protective film for liquid crystal panels provided by the present invention, on the one hand, the quaternary ammonium structure, pyridine structure and long-chain alkanes in the cationic quaternary ammonium salt surfactant can endow it with excellent surface activity, thereby enabling the protective film to effectively remove impurities such as dust and air that affect the display effect, and significantly improve the surface cleanliness and air venting of the protective film; on the other hand, the pyridine structure and benzene ring structure in the cationic quaternary ammonium salt surfactant can endow it with excellent chemical stability, thereby effectively improving the weather resistance and high temperature resistance of the protective film. Attached Figure Description

[0040] Figure 1 This is a structural diagram of the high-temperature resistant PU protective film used in LCD panels according to this application. Detailed Implementation

[0041] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0042] The commercially available PU protective film was a TP touchscreen protective film purchased from Desco Electronics Technology (Kunshan) Co., Ltd.; the other reagents and equipment were standard reagents and equipment used in this technical field.

[0043] Preparation of cationic quaternary ammonium salt surfactants

[0044] Cationic quaternary ammonium salt surfactants are prepared by the following steps:

[0045] In a reactor, 0.5 g of N,N,N',N'-tetramethyl-1,6-hexanediamine and 50 mL of dimethyl sulfoxide were added. The mixture was heated to 60 °C under nitrogen protection and stirred until homogeneous. Then, 1.2 g of 5-benzyl-2-bromopyridine was added. After reacting at this temperature for 3 hours, the mixture was cooled, filtered, washed, and dried to obtain the cationic surfactant.

[0046] Mass spectrometry data of cationic quaternary ammonium salt surfactants: The products were analyzed by LC-MS, and the m / z of the products were 254.18 (100.0%), 254.68 (38.8%), and 255.18 (7.3%).

[0047] Example 1

[0048] The high-temperature resistant PU protective film for LCD panels is prepared by the following steps:

[0049] (1) PET and dibutyl phthalate were added in a mixer in proportion, heated to 180°C, stirred and melted, and then extruded and blown to obtain the substrate layer.

[0050] (2) Polyurethane, m-phenylenediamine and hydrogenated rosin resin are added to the reactor in proportion, heated to 50°C and stirred evenly to obtain PU adhesive coating material.

[0051] (3) Add cationic quaternary ammonium salt surfactant, GLP588, acetylene black, ethyl acetate and acrylic resin in proportion to the reactor, heat to 40°C and stir evenly to obtain antistatic coating material.

[0052] (4) The antistatic coating material, PU adhesive coating material and release layer are bonded sequentially on the substrate layer, and the high temperature resistant PU protective film for the LCD panel is obtained after extrusion molding and encapsulation.

[0053] The mass ratio of PET to dibutyl phthalate in the substrate layer is 25:1 by weight.

[0054] The mass ratio of polyurethane, m-phenylenediamine, and hydrogenated rosin resin in the PU adhesive coating is 20:1:2 by weight.

[0055] Based on a total mass fraction of 100%, the mass percentage of each component in the antistatic coating is as follows:

[0056]

[0057] The resulting PU protective film has a release layer thickness of 0.15 mm, a PU adhesive coating thickness of 0.1 mm, an antistatic coating thickness of 0.08 mm, and a substrate layer thickness of 0.1 mm.

[0058] Example 2

[0059] Basically the same as in Example 1, except that, by weight, the mass ratio of PET to dibutyl phthalate in the substrate layer is 30:1;

[0060] The mass ratio of polyurethane, m-phenylenediamine, and hydrogenated rosin resin in the PU adhesive coating is 15:2:3 by weight.

[0061] Based on a total mass fraction of 100%, the mass percentage of each component in the antistatic coating is as follows:

[0062]

[0063] Example 3

[0064] Basically the same as in Example 1, except that, by weight, the mass ratio of PET to dibutyl phthalate in the substrate layer is 30:1;

[0065] The mass ratio of polyurethane, m-phenylenediamine, and hydrogenated rosin resin in the PU adhesive coating is 18:1.5:2 by weight.

[0066] Based on a total mass fraction of 100%, the mass percentage of each component in the antistatic coating is as follows:

[0067]

[0068] Comparative Example 1

[0069] Commercially available PU protective film.

[0070] Comparative Example 2

[0071] The process is basically the same as in Example 1, except that the cationic quaternary ammonium salt surfactant is replaced with an equal amount of sodium dodecyl sulfate.

[0072] Comparative Example 3

[0073] The process is basically the same as in Example 1, except that the cationic quaternary ammonium salt surfactant is replaced with an equal amount of octadecyltrimethylammonium chloride.

[0074] Performance testing

[0075] Surface cleanliness test: The surface roughness Ra of the products of Examples 1-3 and Comparative Examples 1-3 were tested according to the JIS B 0601 surface roughness test standard.

[0076] Moisture and high temperature resistance test: The product strips of Examples 1-3 and Comparative Examples 1-3 were attached to the surface of the acrylic high-gloss board and tested for moisture and high temperature resistance under the conditions of 85°C, 85% humidity and 144h. The presence of residual adhesive was recorded.

[0077] The test results are shown in the table below:

[0078] Roughness Ra (μm) Is there any residual glue? Example 1 0.2 no Example 2 0.2 no Example 3 0.2 no Comparative Example 1 1.1 yes Comparative Example 2 0.9 yes Comparative Example 3 0.8 yes

[0079] According to the comparison of the test results of Examples 1-3 and Comparative Example 1, the high-temperature resistant PU protective film for LCD panels provided by the present invention has better surface cleanliness, weather resistance and high temperature resistance than the PU protective film in the prior art, and can be widely used in the field of protective film for page panels.

[0080] According to the comparison of the test results of Examples 1-3 and Comparative Examples 2-3, it can be seen that the high-temperature resistant PU protective film for liquid crystal panels provided by the present invention can further improve the surface cleanliness, weather resistance and high-temperature resistance of the PU protective film by adding cationic quaternary ammonium salt surfactants with quaternary ammonium, pyridine and benzene ring structures to the antistatic coating.

[0081] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high temperature resistant PU protective film for liquid crystal panel, characterized in that, From top to bottom, the layers are: release layer, PU adhesive coating, antistatic coating, and substrate layer. The PU adhesive coating is prepared by combining polyurethane, curing agent and tackifier; The substrate layer is made by laminating PET and a plasticizer; The antistatic coating is prepared by compounding cationic quaternary ammonium salt surfactant, leveling agent, conductive agent, ethyl acetate and acrylic resin; The cationic quaternary ammonium salt surfactant has the structure shown in Formula A: 2.The high-temperature-resistant PU protective film for a liquid crystal panel according to claim 1, characterized in that, The cationic quaternary ammonium salt surfactant is prepared by the following steps: In a reactor, N,N,N',N'-tetramethyl-1,6-hexanediamine and dimethyl sulfoxide are added, and the temperature is raised to 50-60°C under nitrogen protection. After stirring evenly, 5-benzyl-2-bromopyridine is added. After reacting at this temperature for 3-4 hours, the mixture is cooled, filtered, washed, and dried to obtain the cationic surfactant. 3.The high-temperature-resistant PU protective film for liquid crystal panels according to claim 2, characterized in that, The mass ratio of N,N,N',N'-tetramethyl-1,6-hexanediamine and 5-benzyl-2-bromopyridine is 1:2.5-3. 4.The high-temperature-resistant PU protective film for liquid crystal panels according to claim 1, characterized in that, The leveling agent in the antistatic coating is selected from one of GLP588, GLP388, GLP599 or PV88; the conductive agent is selected from one of conductive carbon black, acetylene black or carbon nanotubes. 5.The high-temperature-resistant PU protective film for liquid crystal panel according to claim 1, characterized in that, Based on a total mass fraction of 100%, the mass percentage of each component in the antistatic coating is as follows: 6.The high-temperature-resistant PU protective film for liquid crystal panel according to claim 1, characterized in that, The curing agent in the PU adhesive coating is selected from one of methyl ethyl ketone peroxide, m-phenylenediamine, or diaminodiphenyl sulfone; the tackifier is selected from one of hydrogenated rosin resin, esterified rosin resin, or terpene resin.

7. The high-temperature resistant PU protective film for liquid crystal panels according to claim 1, characterized in that, The mass ratio of polyurethane, curing agent and tackifier in the PU adhesive coating is (15-20):(1-2):(2-3).

8. The high-temperature resistant PU protective film for liquid crystal panels according to claim 1, characterized in that, The plasticizer in the substrate layer is selected from dibutyl phthalate or diethyl phthalate; the mass ratio of PTE to plasticizer is 25-30:

1.

9. The high-temperature resistant PU protective film for liquid crystal panels according to claim 1, characterized in that, The release layer has a thickness of 0.1-0.2 mm, the PU adhesive coating has a thickness of 0.08-0.1 mm, the antistatic coating has a thickness of 0.05-0.08 mm, and the substrate layer has a thickness of 0.1-0.15 mm.

10. The method for preparing the high-temperature resistant PU protective film for a liquid crystal panel according to any one of claims 1-9, characterized in that, Includes the following steps: (1) PET and plasticizer are added in proportion in an internal mixer, heated to 160-180℃, stirred and melted, and then extruded and blown to obtain the substrate layer; (2) Add polyurethane, curing agent and tackifier to the reactor in proportion, heat to 40-50℃ and stir evenly to obtain PU adhesive coating material; (3) Add cationic quaternary ammonium salt surfactant, leveling agent, conductive agent, ethyl acetate and acrylic resin in proportion to the reactor, heat to 35-40℃ and stir evenly to obtain antistatic coating material. (4) The antistatic coating material, PU adhesive coating material and release layer are bonded sequentially on the substrate layer, and the high-temperature resistant PU protective film for LCD panels is obtained after extrusion molding and encapsulation.

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