JP-7856697-B2 - Surface protective film for polarizing plates with AG treatment

Inventors

• 長倉 毅
• 長谷川 良
• 吉田 弘幸
• 菱沼 昌世
• 鈴木 史恵
• 大津賀 健太郎

Assignees

• ＺＡＣＲＯＳ株式会社

Dates

Publication Date

20260511

Application Date

20240620

Claims (2)

1. A surface protective film for polarizing plates that has undergone AG treatment, An adhesive layer is formed on one side of a resin film by crosslinking an adhesive composition containing an acrylic polymer, a crosslinking agent, and an antistatic agent which is an ionic compound that is solid at 25°C and has a melting point of 25 to 50°C. The aforementioned acrylic polymer (A) 100 parts by mass of at least one (meth)acrylic acid ester monomer having C4 to C18 in the alkyl group, (B) A total of 2 to 10 parts by mass of at least one copolymerizable monomer containing a hydroxyl group, (C) A total of 0.05 to 0.3 parts by mass of at least one copolymerizable monomer containing a carboxyl group, (D) A total of 3 to 40 parts by mass of at least one polyalkylene glycol mono(meth)acrylic acid ester monomer, (E) A total of 0.1 to 20 parts by mass of at least one alkyl (meth)acrylate monomer containing an alkoxy group, It consists of a copolymer obtained by copolymerizing the following: The adhesive composition is characterized in that it contains (A) 0.1 to 6 parts by mass of a trifunctional isocyanate compound as a crosslinking agent with respect to 100 parts by mass of at least one (meth)acrylic acid ester monomer having C4 to C18 in the alkyl group, and further contains (F) 0.001 to 0.5 parts by mass of at least one polyether-modified siloxane compound having an HLB value of 7 to 12.
2. The AG-treated surface protective film for polarizing plates according to claim 1, wherein one side of the resin film, opposite to the side on which the adhesive layer is formed, is treated with an antistatic and antifouling treatment.

Description

This invention relates to a surface protective film for polarizing plates. More specifically, it relates to a surface protective film for polarizing plates that exhibits an excellent balance of adhesive strength at both low and high peeling speeds, excellent adhesion to polarizing plates despite low adhesive strength, and also possesses excellent durability, reworkability, and antistatic properties. Conventionally, in the manufacturing process of optical components such as polarizers and phase difference plates, which are components of liquid crystal displays, a surface protection film is applied to temporarily protect the surface of the optical components. Such surface protection films are used only in the manufacturing process of the optical components and are peeled off and removed when the optical components are assembled into the liquid crystal display. Because such surface protection films are used only in the manufacturing process, they are sometimes commonly referred to as process films. In the process of manufacturing optical components, the surface protection film used is a polyethylene terephthalate (PET) resin film that is optically transparent, with an adhesive layer formed on one side. However, a release film, which has been treated to protect the adhesive layer, is laminated on top of the adhesive layer until it is bonded to the optical component. Furthermore, optical components such as polarizing plates and phase difference plates undergo product inspections that include optical evaluations of the liquid crystal display's display capability, hue, contrast, and foreign matter contamination while the surface protective film is attached. Therefore, the required performance of the surface protective film is that the adhesive layer is free of air bubbles and foreign matter. Furthermore, in recent years, there have been concerns that the static electricity generated when peeling the adhesive layer off optical components such as polarizing plates and phase difference plates may affect the electrical control circuits of liquid crystal displays, leading to a demand for adhesive layers with superior antistatic properties. Furthermore, when bonding a surface protective film to optical components such as polarizers and phase difference plates, it is sometimes necessary to peel off the surface protective film and reapply it for various reasons. In such cases, ease of removal from the optical component (reworkability) is required. Furthermore, when the surface protective film is finally peeled off from optical components such as polarizers and phase difference plates, it is required that it can be peeled off quickly. In other words, even with high-speed peeling, it is required that the adhesive strength does not change much with the peeling speed so that it can be peeled off quickly. Thus, in recent years, the required performance characteristics for the adhesive layer constituting surface protective films include (i) balancing adhesive strength at both low and high peeling speeds, (ii) excellent antistatic performance, and (iii) reworkability, all of which are desirable from the perspective of ease of use when using surface protective films. For example, (i) regarding balancing adhesive strength at low and high peeling speeds, the following proposals are known. Acrylic adhesive layers, primarily composed of a copolymer of an alkyl (meth)acrylate having an alkyl group with 7 or fewer carbon atoms and a copolymerizable compound containing a carboxyl group, and crosslinked with a crosslinking agent, have problems such as the adhesive transferring to the adherend during long-term adhesion and a significant increase in adhesive strength over time. To avoid this, an adhesive layer is known in which a copolymer of an alkyl (meth)acrylate having an alkyl group with 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group is used, and this copolymer is crosslinked with a crosslinking agent (Patent Document 1). Furthermore, it has been proposed that a small amount of copolymer of (meth)acrylate alkyl ester and carboxyl group-containing copolymerizable compound is added to the copolymer described above, and that this copolymer is crosslinked with a crosslinking agent to form an adhesive layer. However, when these are used for surface protection of plastic sheets with low surface tension and smooth surfaces, problems such as peeling due to heating during processing or storage, and poor re-peelability when peeled off at high speeds, which is the domain of manual work, have been reported. To solve these problems, an adhesive composition has been proposed in which a) 100 parts by weight of an alkyl (meth)acrylate mainly composed of an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms is added to a copolymer of monomer mixtures obtained by adding 1 to 15 parts by weight of a copolymer of a carboxyl group-containing copolymerizable compound and c) 3 to 100 parts by weigh