Pressure-sensitive adhesive for quick-tearing polaroid, preparation method of pressure-sensitive adhesive and protective film

Abstract

The invention discloses a pressure-sensitive adhesive for a quick-tearing polaroid, a preparation method of the pressure-sensitive adhesive and a protective film. The pressure-sensitive adhesive comprises the following raw materials in parts by weight: 100 parts of a polymer, 0.5-1 part of an antistatic agent, 1-3 parts of a cross-linking agent and 20-40 parts of a diluent, wherein the polymer is prepared from the following raw materials in parts by weight: 70 to 90 parts of 2-ethylhexyl acrylate, 5 to 10 parts of a functional monomer, 10 to 30 parts of methoxy polyethylene glycol methacrylate, 0.02 to 0.1 part of an initiator and 55 to 60 parts of a solvent. The stripping force of a conventional polaroid protective film in fast tearing is generally 50-100 gf / 25 mm, the long-chain ether bond monomer, namely methoxyl polyethylene glycol methacrylate, is added, so that the stripping force of fast tearing is effectively reduced to 50 gf / 25 mm or below, the efficiency of the application process is higher, meanwhile, a large number of ether bonds and hydroxyl groups form a hydrophilic structure, static electricity is more favorably released, and the service life of the polaroid protective film is prolonged. The resistance value of the rubber surface is reduced, so that the antistatic effect is better.

Description

Technical Field

[0001] This invention relates to the field of protective film materials, and in particular to a quick-tear pressure-sensitive adhesive for polarizing films, its preparation method, and a protective film thereof. Background Technology

[0002] Polarizing film is a functional thin film used to protect the optical layers (such as PVA, TAC, etc.) on the surface of polarizing film. It is mainly used to prevent the polarizing film from being scratched, contaminated or corroded by moisture during production, transportation, storage and processing, so as to ensure its optical performance and yield. The protective film is also known as the "physical protective shield for the optical surface of polarizing film".

[0003] Its main application scenario is that after the polarizer is produced, a protective film is immediately applied for winding or cutting; the protective film must remain intact until it is laminated to the LCD module, and is removed during final assembly. This not only requires the protective film to have a balance between high light transmittance and low haze, a balance between the adhesion and flexibility of the hardened coating, antistatic properties, high temperature resistance and structural stability, corrosion and moisture poisoning resistance, and non-polluting and low-emission properties; it also requires improved efficiency to enhance competitiveness; therefore, the rapid removal of the protective film has become the mainstream demand in the current market.

[0005] Traditional polarizer protective films have a rapid peel strength of 50~140gf / 25mm. The adhesive layer of the polarizer protective film in this application has low tack, requiring minimal force to remove, thus avoiding damage to the substrate by the adhesive layer (residual adhesive). It is suitable for polarizers with brittle PVA layers or coatings. CN25S7757A19931519A discloses an acrylate polymer for polarizer protective film. Polarizer protective film can be made using this polymer and has certain requirements for high-speed peel force, with a peel force of 50~100gf / 25min at a speed of 30000mm / min. However, existing applications require a peel force of <50gf / 25mm under rapid tearing conditions of 30000mm / min, and the current patented product is difficult to meet the requirements.

[0006] Therefore, it is now necessary to develop a polarizer protective film product that can be quickly peeled off, has low basis weight, leaves no residue, and has no afterimages under high temperature conditions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a pressure-sensitive adhesive for quick-tear polarizer, its preparation method and protective film, in order to address the shortcomings of the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In the first aspect of the present invention, a pressure-sensitive adhesive for quick-tear polarizing film is provided, comprising the following raw materials in parts by weight: 100 parts of polymer, 0.5-1 parts of antistatic agent, 1-3 parts of crosslinking agent, and 20-40 parts of diluent; The raw materials for preparing the polymer include, by weight, 70-90 parts of isooctyl acrylate, 5-10 parts of functional monomer, 10-30 parts of methoxy polyethylene glycol methacrylate, 0.02-0.1 parts of initiator, and 55-60 parts of solvent.

[0009] Preferably, the functional monomer is hydroxybutyl acrylate.

[0010] Preferably, the solvent is one or more of ethyl acetate (EAc), toluene (To), butanone (MEK), and butyl acetate (BuAC).

[0011] Preferably, the initiator is one or more of azobisisobutyronitrile (AIBN) and benzoyl (BPO).

[0012] Preferably, the polymer is prepared by the following steps: S1. Add 70-90 parts of isooctyl acrylate, 5-10 parts of functional monomer, methoxy polyethylene glycol methacrylate and solvent into the reactor, heat and purge the air from the reactor with nitrogen. S2. After heating to about 65℃, add the first part of the initiator, react for 2.5 hours, and then heat to 75±1℃. S3. Add the second part of the initiator and maintain the temperature inside the reactor at 75±1℃ for 3 hours to continue the reaction. S4. Add the remaining third initiator, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer.

[0013] Preferably, the antistatic agent is at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0014] Preferably, the crosslinking agent is one or a mixture of two of 1,4-tetramethylxylenyl diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; Preferably, the diluent is at least one of ethyl acetate (EAc), toluene (To), butanone (MEK), and butyl acetate (BuAC).

[0015] In a second aspect, the present invention provides a method for preparing the quick-tear pressure-sensitive adhesive for polarizing film as described above, comprising the following steps: mixing a polymer, an antistatic agent, a crosslinking agent, and a diluent, stirring evenly to obtain the quick-tear pressure-sensitive adhesive for polarizing film.

[0016] In a third aspect, the present invention provides a protective film for quick-tear polarizers, which is prepared by the following method: uniformly coating a quick-tear polarizer pressure-sensitive adhesive as described above onto a substrate, drying and curing, and aging to obtain the protective film for quick-tear polarizers.

[0017] The beneficial effects of this invention are: This invention provides a quick-tear pressure-sensitive adhesive for polarizing films, its preparation method, and a protective film. Conventional polarizing film protective films typically have a peel force of 50-100 gf / 25 mm during quick tearing. This invention, by adding a long-chain ether monomer, methoxy polyethylene glycol methacrylate, not only effectively reduces the peel force to below 50 gf / 25 mm, making the application process more efficient, but also the large number of ether bonds and hydroxyl groups form a hydrophilic structure, which is more conducive to releasing static electricity, reducing the adhesive surface resistance value, and making the antistatic effect better. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0019] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0021] This invention provides a pressure-sensitive adhesive for quick-tear polarizing film, comprising the following raw materials in parts by weight: 100 parts polymer, 0.5-1 parts antistatic agent, 1-2 parts crosslinking agent, and 20-40 parts diluent; The raw materials for polymer preparation include, by weight: 70-90 parts isooctyl acrylate, 5-10 parts functional monomer, 10-30 parts methoxy polyethylene glycol methacrylate, 0.02-0.1 parts initiator, and 55-60 parts solvent.

[0022] In a preferred embodiment, the functional monomer is hydroxybutyl acrylate.

[0023] In the formulation of this invention, isooctyl acrylate and methoxy polyethylene glycol methacrylate are used as main monomers, and hydroxybutyl acrylate is used as a functional monomer, thereby achieving a softer adhesive with low peel strength under rapid tearing conditions. The addition of methoxy polyethylene glycol methacrylate effectively reduces the peel weight under rapid peeling; this material is a long-chain acrylate monomer with ether bonds, and it also effectively improves antistatic properties.

[0024] In a preferred embodiment, the solvent is one or more of ethyl acetate (EAc), toluene (To), butanone (MEK), and butyl acetate (BuAC).

[0025] In a preferred embodiment, the initiator is one or more of azobisisobutyronitrile (AIBN) and benzoyl (BPO).

[0026] In a preferred embodiment, the polymer is prepared by the following steps: S1. Add 70-90 parts of isooctyl acrylate, 5-10 parts of functional monomer, methoxy polyethylene glycol methacrylate and solvent into the reactor, heat and purge the air from the reactor with nitrogen. S2. After heating to about 65℃, add the first part of the initiator, react for 2.5 hours, and then heat to 75±1℃. S3. Add the second part of the initiator and maintain the temperature inside the reactor at 75±1℃ for 3 hours to continue the reaction. S4. Add the remaining third part of the initiator, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer.

[0027] In a preferred embodiment, the antistatic agent is at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0028] In a preferred embodiment, the crosslinking agent is one or a mixture of two of 1,4-tetramethylxylenyl diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. In a preferred embodiment, the diluent is at least one of ethyl acetate (EAc), toluene (To), butanone (MEK), and butyl acetate (BuAC).

[0029] A second aspect of the present invention provides a method for preparing a quick-tear pressure-sensitive adhesive for polarizing films, comprising the following steps: mixing a polymer, an antistatic agent, a crosslinking agent, and a diluent, and stirring until homogeneous to obtain a quick-tear pressure-sensitive adhesive for polarizing films.

[0030] In a third aspect, the present invention provides a protective film for quick-tear polarizers, which is prepared by the following method: the quick-tear polarizer is uniformly coated on a substrate with pressure-sensitive adhesive, dried and cured, and aged to obtain a protective film for quick-tear polarizers.

[0031] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0032] Example 1 A quick-tear pressure-sensitive adhesive for polarizing film comprises the following raw materials in parts by weight: 100 parts polymer, 0.7 parts antistatic agent, 2 parts crosslinking agent, and 30 parts diluent; The antistatic agent is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the crosslinking agent is 1,4-tetramethylxylene diisocyanate, and the diluent is ethyl acetate.

[0033] The polymer comprises the following raw materials in parts by weight: The optimal composition is 73 parts of isooctyl acrylate (2-EHA), 7 parts of hydroxybutyl acrylate (4-HBA), 20 parts of methoxy polyethylene glycol methacrylate (MPEG-MA), 0.07 parts of initiator (specifically AIBN), and solvents: 55 parts of ethyl acetate (EAc) and 5 parts of methyl ethyl ketone (MEK).

[0034] The preparation method of pressure-sensitive adhesive includes the following steps: S1. Add isooctyl acrylate, hydroxybutyl acrylate, methoxy polyethylene glycol methacrylate and solvent into the reaction vessel, heat and purge the air from the vessel with nitrogen; S2. After the temperature stabilizes at around 65℃, add 0.01 parts of AIBN. The temperature will rise naturally by 0.3~0.5℃ to mark the start of the reaction. After 2.5 hours of reaction, slowly raise the temperature to around 75℃. S3. Add 0.02 parts of AIBN again, and continue the reaction by dropping the solution at 75±1℃ for 3 hours. S4. Add 0.04 parts of AIBN again, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer; S5. Mix the polymer, antistatic agent, crosslinking agent and diluent, and stir for 10 minutes to obtain pressure-sensitive adhesive for quick-tear polarizing film.

[0035] A quick-tear protective film for polarizers is prepared by the following method: The quick-tear polarizing film is coated with pressure-sensitive adhesive onto a polyethylene terephthalate (PET) film and cured at around 120°C for 2 minutes to form a 20μm dry adhesive layer. After attaching a release film to the adhesive surface, it is cured at 55°C for two days to obtain the quick-tear polarizing film protective film.

[0036] Example 2 A quick-tear pressure-sensitive adhesive for polarizing film comprises the following raw materials in parts by weight: 100 parts polymer, 0.7 parts antistatic agent, 2 parts crosslinking agent, and 30 parts diluent; The antistatic agent is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the crosslinking agent is 1,4-tetramethylxylene diisocyanate, and the diluent is ethyl acetate.

[0037] The polymer comprises the following raw materials in parts by weight: 78 parts of isooctyl acrylate (2-EHA), 7 parts of hydroxybutyl acrylate (4-HBA), 15 parts of methoxy polyethylene glycol methacrylate (MPEG-MA), 0.07 parts of (specifically AIBN), solvents: 55 parts of ethyl acetate (EAc) and 5 parts of methyl ethyl ketone (MEK).

[0038] The preparation method of pressure-sensitive adhesive includes the following steps: S1. Add isooctyl acrylate, hydroxybutyl acrylate, methoxy polyethylene glycol methacrylate and solvent into the reaction vessel, heat and purge the air from the vessel with nitrogen; S2. After the temperature stabilizes at around 65℃, add 0.01 parts of AIBN. The temperature will rise naturally by 0.3~0.5℃ to mark the start of the reaction. After 2.5 hours of reaction, slowly raise the temperature to around 75℃. S3. Add 0.02 parts of AIBN again, and continue the reaction by dropping the solution at 75±1℃ for 3 hours. S4. Add 0.04 parts of AIBN again, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer; S5. Mix the polymer, antistatic agent, crosslinking agent and diluent, and stir for 10 minutes to obtain pressure-sensitive adhesive for quick-tear polarizing film.

[0039] A quick-tear protective film for polarizers is prepared by the following method: The quick-tear polarizing film is coated with pressure-sensitive adhesive onto a polyethylene terephthalate (PET) film and cured at around 120°C for 2 minutes to form a 20μm dry adhesive layer. After attaching a release film to the adhesive surface, it is cured at 55°C for two days to obtain the quick-tear polarizing film protective film.

[0040] Compare with Example 1 A quick-tear pressure-sensitive adhesive for polarizing film comprises the following raw materials in parts by weight: 100 parts polymer, 0.7 parts antistatic agent, 2 parts crosslinking agent, and 30 parts diluent; The antistatic agent is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the crosslinking agent is 1,4-tetramethylxylene diisocyanate, and the diluent is ethyl acetate.

[0041] The polymer comprises the following raw materials in parts by weight: 90 parts of isooctyl acrylate (2-EHA), 10 parts of hydroxybutyl acrylate (4-HBA), 0.07 parts of initiator (specifically AIBN), and solvents: 55 parts of ethyl acetate (EAc) and 5 parts of butanone (MEK).

[0042] The preparation method of pressure-sensitive adhesive includes the following steps: S1. Add isooctyl acrylate, hydroxybutyl acrylate and solvent into the reaction vessel, heat and purge the air from the vessel with nitrogen gas. S2. After the temperature stabilizes at around 65℃, add 0.01 parts of AIBN. The temperature will rise naturally by 0.3~0.5℃ to mark the start of the reaction. After 2.5 hours of reaction, slowly raise the temperature to around 75℃. S3. Add 0.02 parts of AIBN again, and continue the reaction by dropping the solution at 75±1℃ for 3 hours. S4. Add 0.04 parts of AIBN again, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer; S5. Mix the polymer, antistatic agent, crosslinking agent and diluent, and stir for 10 minutes to obtain pressure-sensitive adhesive for quick-tear polarizing film.

[0043] A quick-tear protective film for polarizers is prepared by the following method: The quick-tear polarizing film is coated with pressure-sensitive adhesive onto a polyethylene terephthalate (PET) film and cured at around 120°C for 2 minutes to form a 20μm dry adhesive layer. After attaching a release film to the adhesive surface, it is cured at 55°C for two days to obtain the quick-tear polarizing film protective film.

[0044] Compare with Example 2 A quick-tear pressure-sensitive adhesive for polarizing film comprises the following raw materials in parts by weight: 100 parts polymer, 0.7 parts antistatic agent, 2 parts crosslinking agent, and 30 parts diluent; The antistatic agent is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, the crosslinking agent is 1,4-tetramethylxylene diisocyanate, and the diluent is ethyl acetate.

[0045] The polymer comprises the following raw materials in parts by weight: 73 parts of isooctyl acrylate (2-EHA), 7 parts of hydroxybutyl acrylate (4-HBA), 20 parts of ethoxyethoxyethyl acrylate (EOEOEA), 0.07 parts of initiator (specifically AIBN), and solvents: 55 parts of ethyl acetate (EAc) and 5 parts of butanone (MEK).

[0046] The preparation method of pressure-sensitive adhesive includes the following steps: S1. Add isooctyl acrylate, hydroxybutyl acrylate, methoxy polyethylene glycol methacrylate and solvent into the reaction vessel, heat and purge the air from the vessel with nitrogen; S2. After the temperature stabilizes at around 65℃, add 0.01 parts of AIBN. The temperature will rise naturally by 0.3~0.5℃ to mark the start of the reaction. After 2.5 hours of reaction, slowly raise the temperature to around 75℃. S3. Add 0.02 parts of AIBN again, and continue the reaction by dropping the solution at 75±1℃ for 3 hours. S4. Add 0.04 parts of AIBN again, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer; S5. Mix the polymer, antistatic agent, crosslinking agent and diluent, and stir for 10 minutes to obtain pressure-sensitive adhesive for quick-tear polarizing film.

[0047] A quick-tear protective film for polarizers is prepared by the following method: The quick-tear polarizing film is coated with pressure-sensitive adhesive onto a polyethylene terephthalate (PET) film and cured at around 120°C for 2 minutes to form a 20μm dry adhesive layer. After attaching a release film to the adhesive surface, it is cured at 55°C for two days to obtain the quick-tear polarizing film protective film.

[0048] The samples prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to performance tests according to their respective test standards: Peel strength, the test standard is: ASTM D3330 The surface resistivity of the adhesive, the test method or standard is: ASTM S257 The high-temperature image retention test for polarizers is conducted as follows: The polarizer with a protective film is placed in an environment at 40℃ or 70℃ for 72 hours. After removal, the protective film is peeled off, and the surface is observed for any residual shadows. Aging test, the test method or standard is: 65℃ / 95% simulated extreme environment performance test. The test results are shown in Table 1.

[0049] Table 1. Performance test results of the adhesives in the examples and comparative examples. Note: "√" indicates no abnormality in the test; "×" indicates an abnormality in the test.

[0050] As shown in Table 1, the addition of methoxy polyethylene glycol methacrylate in Examples 1 and 2 significantly reduced the quick-peel force of the protective film; it also showed excellent performance in high-temperature image retention testing; and the abundant ether bonds and hydroxyl groups made it more hydrophilic, which facilitated the release of static electricity and reduced the surface resistance of the adhesive.

[0051] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A pressure-sensitive adhesive for quick-tear polarizing films, characterized in that, The raw materials include the following parts by weight: 100 parts polymer, 0.5-1 part antistatic agent, 1-3 parts crosslinking agent, and 20-40 parts diluent; The raw materials for preparing the polymer include, by weight, 70-90 parts of isooctyl acrylate, 5-10 parts of functional monomer, 10-30 parts of methoxy polyethylene glycol methacrylate, 0.02-0.1 parts of initiator, and 55-60 parts of solvent.

2. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 1, characterized in that, The functional monomer is hydroxybutyl acrylate.

3. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 2, characterized in that, The solvent is one or more of ethyl acetate, toluene, butanone, and butyl acetate.

4. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 3, characterized in that, The initiator is one or more of azobisisobutyronitrile and benzoyl peroxide.

5. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 4, characterized in that, The polymer is prepared by the following steps: S1. Add isooctyl acrylate, functional monomer, methoxy polyethylene glycol methacrylate and solvent into the reactor, heat and purge the air from the reactor with nitrogen gas. S2. After heating to about 65℃, add the first part of the initiator, react for 2.5 hours, and then heat to 75±1℃. S3. Add the second part of the initiator and maintain the temperature inside the reactor at 75±1℃ for 3 hours to continue the reaction. S4. Add the remaining third initiator, control the temperature at 77~80℃, react for 2.5h, cool down, and obtain the polymer.

6. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 1, characterized in that, The antistatic agent is at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

7. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 1, characterized in that, The crosslinking agent is one or a mixture of two of 1,4-tetramethylxylenyl diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

8. The pressure-sensitive adhesive for quick-tear polarizing film according to claim 1, characterized in that, The diluent is at least one of ethyl acetate, toluene, butanone, and butyl acetate.

9. A method for preparing a pressure-sensitive adhesive for quick-tear polarizing film as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing the polymer, antistatic agent, crosslinking agent, and diluent, stirring until homogeneous, to obtain the pressure-sensitive adhesive for quick-tear polarizing film.

10. A protective film for quick-tear polarizing films, characterized in that, It is prepared by the following method: the quick-tear polarizer pressure-sensitive adhesive as described in any one of claims 1-8 is uniformly coated on the substrate, dried and cured, and aged to obtain the quick-tear polarizer protective film.

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