Antistatic surface protection film and optical film

Abstract

To provide an antistatic surface protective film with reduced contamination to an adherend, featuring excellent peeling antistatic performance without time degradation, and an optical film.SOLUTION: An adhesive layer 2 is formed on one side of a base film 1, the adhesive layer 2 composed of an adhesive composition that contains an acrylic polymer of a copolymer resulting from the copolymerzation of (A) a (meth)acrylic acid ester monomer with a C4 to C18 alkyl group and (B) a copolymerizable monomer containing a hydroxyl group, excluding copolymerizable monomers containing carboxyl groups, as a copolymerizable monomer group, (C) a di- or higher functional isocyanate compound, (D) a crosslinking accelerator, (E) a ketoenol tautomer compound, and (G) a polyether-modified siloxane compound with an HLB value of 7 to 15. A release film 7 is applied to the surface of the adhesive layer 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a surface protective film. More specifically, the present invention relates to an antistatic surface protective film having antistatic properties. More specifically, the present invention provides a method for producing an antistatic surface protective film that has low staining to an adherend, does not deteriorate over time, and has excellent antistatic properties upon peeling, and an antistatic surface protective film. [Background technology]

[0002] When optical films such as polarizing plates, retardation plates, lens films for displays, antireflection films, hard coat films, and transparent conductive films for touch panels, and optical products such as displays using the same, are manufactured and transported by laminating a surface protective film to the surface of the optical film to prevent the surface from being soiled or scratched in later processes. In order to improve work efficiency by eliminating the need to peel off and re-laminate the surface protective film, visual inspection of the optical film product is sometimes performed with the surface protective film still attached to the optical film. Conventionally, surface protection films having a pressure-sensitive adhesive layer provided on one side of a substrate film have been commonly used to prevent scratches and dirt from adhering during the manufacturing process of optical products. The surface protection film is attached to the optical film via a pressure-sensitive adhesive layer with weak adhesive strength. The pressure-sensitive adhesive layer has weak adhesive strength so that it can be easily peeled off when a used surface protection film is peeled off from the surface of the optical film, and so that the pressure-sensitive adhesive does not adhere to and remain on the optical film of the adherend (preventing the occurrence of so-called adhesive residue).

[0003] In recent years, during the production process of liquid crystal display panels, there have been a few cases where the peeling charge voltage generated when peeling off and removing the surface protection film attached to the optical film has destroyed circuit components such as driver ICs that control the display screen of the liquid crystal display panel, or damaged the alignment of liquid crystal molecules. Furthermore, in order to reduce the power consumption of LCD panels, the driving voltage of liquid crystal materials has been lowered, and as a result, the breakdown voltage of driver ICs has also been lowered.Recently, there has been a demand for the peeling electrification voltage to be within the range of +0.7kV to -0.7kV. For this reason, in order to prevent problems caused by high peeling electrification voltage when peeling the surface protection film from the adherend, an adhesive layer containing an antistatic agent for keeping the peeling electrification voltage low has been proposed.

[0004] For example, Patent Document 1 discloses a surface protection film that uses a pressure-sensitive adhesive made of an alkyltrimethylammonium salt, a hydroxyl group-containing acrylic polymer, and a polyisocyanate. Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive composition comprising an ionic liquid and an acrylic polymer having an acid value of 1.0 or less, and pressure-sensitive adhesive sheets using the same. Furthermore, Patent Document 3 discloses an adhesive composition comprising an acrylic polymer, a polyether polyol compound, and an alkali metal salt treated with an anion-adsorbing compound, and a surface protection film using the same. Furthermore, Patent Document 4 discloses a pressure-sensitive adhesive composition comprising an ionic liquid, an alkali metal salt, and a polymer having a glass transition temperature of 0° C. or lower, and a surface protection film using the same. Furthermore, Patent Documents 5 and 6 disclose mixing polyether-modified silicone into the pressure-sensitive adhesive layer of a surface protection film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-131957 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-330464 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-314476 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-152235 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-275128 [Patent Document 6] Patent No. 4537450 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above Patent Documents 1 to 4, an antistatic agent is added to the inside of the pressure-sensitive adhesive layer, but as the thickness of the pressure-sensitive adhesive layer increases and as time passes, the amount of antistatic agent that migrates from the pressure-sensitive adhesive layer to the adherend to which the surface protective film is attached increases. Furthermore, in optical films such as LR (low reflective) polarizing plates and AG (antiglare)-LR polarizing plates, the surface of the optical film is treated with an anti-fouling agent such as a silicone compound or a fluorine compound, and therefore the peeling electrification voltage increases when the surface protective film used for such optical films is peeled from the optical film as the adherend.

[0007] Furthermore, when polyether-modified silicone is mixed into the pressure-sensitive adhesive layer as described in Patent Documents 5 and 6, it is difficult to fine-tune the adhesive strength of the surface protection film. Furthermore, because polyether-modified silicone is mixed into the pressure-sensitive adhesive layer, changes in the conditions for applying and drying the pressure-sensitive adhesive composition onto a substrate film can subtly change the surface characteristics of the pressure-sensitive adhesive layer on which the surface protection film is formed. Furthermore, from the perspective of protecting the surface of the optical film, the thickness of the pressure-sensitive adhesive layer cannot be made extremely thin. Therefore, the amount of polyether-modified silicone mixed into the pressure-sensitive adhesive layer must be increased depending on the thickness of the pressure-sensitive adhesive layer. As a result, the surface of the adherend becomes more susceptible to contamination, and the adhesive strength and the tendency to contaminate the adherend change over time.

[0008] In recent years, with the spread of 3D displays (stereoscopic displays), there are products in which an FPR (Film Patterned Retarder) film is laminated to the surface of an optical film such as a polarizing plate. The FPR film is laminated after peeling off the surface protection film that was previously laminated to the surface of the optical film such as a polarizing plate. However, if the surface of the optical film such as a polarizing plate is contaminated by the adhesive or antistatic agent used in the surface protection film, there is a problem in that the FPR film is difficult to adhere to. For this reason, surface protection films used in such applications are required to be ones that cause minimal contamination to the adherend.

[0009] On the other hand, some LCD panel manufacturers have adopted a method for evaluating the fouling properties of surface protection films on substrates, in which the surface protection film attached to an optical film such as a polarizing plate is first peeled off, reattached in a state where air bubbles are mixed in, and then heat-treated under specified conditions. The surface protection film is then peeled off and the surface of the substrate is observed. With this evaluation method, even if the surface contamination of the substrate is minimal, if there is a difference in the surface contamination between the area where the air bubbles are mixed in and the area where the adhesive of the surface protection film was in contact, air bubble marks (sometimes called "bubble stains") will remain. Therefore, this is a very strict evaluation method for the fouling properties of the substrate surface. In recent years, there has been a demand for surface protection films that do not cause problems with fouling properties on the substrate surface, even when evaluated using such a strict evaluation method. However, previously proposed surface protection films using an adhesive layer containing an antistatic agent have had difficulty resolving this issue.

[0010] Therefore, there is a need for a surface protection film for use with an optical film that causes very little contamination to an adherend and that does not change with time in terms of contamination properties to the adherend.Furthermore, there is a need for a surface protection film that exhibits a low peel electrification voltage when peeled from an adherend.

[0011] The present inventors have conducted extensive research to solve this problem. In order to minimize contamination of adherends and to minimize changes in antistatic performance over time, it is necessary to reduce the amount of antistatic agent added, which is presumed to be the cause of contamination of adherends. However, reducing the amount of antistatic agent added increases the peeling electrification voltage when the surface protection film is peeled from the adherend. The present inventors investigated a method for reducing the peeling electrification voltage when the surface protection film is peeled from the adherend without increasing the absolute amount of antistatic agent added. As a result, they discovered that, rather than adding and mixing an antistatic agent into a pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer, the peeling electrification voltage when the surface protection film is peeled from the optical film (adherend) can be reduced by applying an appropriate amount of antistatic agent component to the surface of the pressure-sensitive adhesive layer after coating and drying the pressure-sensitive adhesive composition, thereby completing the present invention.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an antistatic surface protective film that causes little contamination of an adherend, does not deteriorate over time, and has excellent peel-off antistatic performance. [Means for solving the problem]

[0013] In order to solve the above problems, the technical concept of the antistatic surface protection film of the present invention is to apply an appropriate amount of antistatic agent to the surface of the adhesive layer after coating and drying an adhesive composition to laminate the adhesive layer, thereby minimizing contamination of the adherend and minimizing peel electrification voltage when peeled off from the adherend, i.e., the optical film.

[0014] In order to solve the above-mentioned problems, the present invention provides an antistatic surface protection film, characterized in that: a substrate film made of a transparent resin; (A) an acrylic polymer of a copolymer obtained by copolymerizing at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C4 to C18 with, as a copolymerizable monomer group, (B) at least one copolymerizable monomer containing a hydroxyl group, but not including a copolymerizable monomer containing a carboxyl group; and a pressure-sensitive adhesive layer formed on one side of the substrate film; the pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing (C) a difunctional or higher isocyanate compound, (D) a crosslinking accelerator, and (E) a keto-enol tautomer compound; and a release film comprising a resin film and a release agent layer containing an antistatic agent laminated on one side thereof, the release agent layer being bonded to the surface of the pressure-sensitive adhesive layer via the release agent layer; the release agent layer being formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane and an antistatic agent, and the antistatic agent in the release agent layer being transferred to the surface of the pressure-sensitive adhesive layer.

[0015] The copolymerizable monomer group preferably further includes (F) a polyalkylene glycol mono(meth)acrylate monomer.

[0016] Furthermore, it is preferred that the (D) crosslinking accelerator is at least one selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds, and that the crosslinking accelerator is contained in an amount of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the acrylic polymer of the copolymer, and that the (E) keto-enol tautomer compound is contained in an amount of 0.1 to 300 parts by weight, with the weight ratio of (E) / (D) being 70 to 1000.

[0017] Furthermore, it is preferable that the (B) hydroxyl group-containing copolymerizable monomer is at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide, and that the amount of the monomer is 0.1 to 10 parts by weight per 100 parts by weight of the acrylic polymer in the copolymer.

[0018] Furthermore, the copolymerizable monomer group may or may not further include (F) a polyalkylene glycol mono(meth)acrylic acid ester monomer, and the (F) polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate, and the amount of the (F) polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably 0 to 50 parts by weight per 100 parts by weight of the acrylic polymer of the copolymer.

[0019] Furthermore, as the (C) difunctional or higher isocyanate compound, the difunctional isocyanate compound is an acyclic aliphatic isocyanate compound, which is a compound produced by reacting a diisocyanate compound with a diol compound, and the diisocyanate compound is an aliphatic diisocyanate selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, and the diol compound is 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, polypropylene The trifunctional isocyanate compound is one selected from the group consisting of pyrene glycol, and is preferably an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a biuret of a hexamethylene diisocyanate compound, a biuret of an isophorone diisocyanate compound, an isocyanurate of a tolylene diisocyanate compound, an isocyanurate of a xylylene diisocyanate compound, an isocyanurate of a hydrogenated xylylene diisocyanate compound, an adduct of a tolylene diisocyanate compound, an adduct of a xylylene diisocyanate compound, or an adduct of a hydrogenated xylylene diisocyanate compound, and is preferably 0.1 to 10 parts by weight per 100 parts by weight of the acrylic polymer of the copolymer.

[0020] The pressure-sensitive adhesive composition preferably contains (G) a polyether-modified siloxane compound having an HLB value of 7 to 15 in an amount of 1.0 part by weight or less (excluding the case of 0 part by weight) per 100 parts by weight of the acrylic polymer of the copolymer.

[0021] The antistatic agent in the release agent layer is preferably an alkali metal salt.

[0022] The antistatic agent in the release agent layer is preferably a Li salt, and is at least one selected from the group consisting of Li(CF3SO2)2N, Li(FSO2)2N, and LiCF3SO3.

[0023] Furthermore, in order to solve the above-mentioned problems, the present invention provides an antistatic surface protection film comprising: a substrate film made of a transparent resin; an acrylic polymer of a copolymer comprising (A) at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C4 to C18 and, as a copolymerizable monomer group, not including a copolymerizable monomer containing a carboxyl group but including (B) at least one copolymerizable monomer containing a hydroxyl group; and a pressure-sensitive adhesive layer formed on one side of the substrate film; the pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing (C) a difunctional or higher isocyanate compound, (D) a crosslinking accelerator, and (E) a keto-enol tautomer compound; and a release film comprising a resin film and a release agent layer containing an antistatic agent laminated on one side thereof, bonded to the surface of the pressure-sensitive adhesive layer via the release agent layer; the release agent layer being formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane and an antistatic agent.

[0024] The copolymerizable monomer group preferably further includes (F) a polyalkylene glycol mono(meth)acrylate monomer.

[0025] The pressure-sensitive adhesive composition preferably contains (G) a polyether-modified siloxane compound having an HLB value of 7 to 15 in an amount of 1.0 part by weight or less (excluding the case of 0 part by weight) per 100 parts by weight of the acrylic polymer of the copolymer.

[0026] The antistatic agent in the release agent layer is preferably an alkali metal salt.

[0027] The antistatic agent in the release agent layer is preferably a Li salt, and is at least one selected from the group consisting of Li(CF3SO2)2N, Li(FSO2)2N, and LiCF3SO3.

[0028] The present invention also provides an optical film having the above antistatic surface protection film laminated thereto.

[0029] The present invention also provides an optical component to which the above-mentioned antistatic surface protection film is attached. [Effects of the Invention]

[0030] The antistatic surface protective film of the present invention causes little contamination to an adherend, and its low contamination property to an adherend does not change over time. Furthermore, according to the present invention, even if the adherend is an optical film such as an LR polarizing plate or an AG-LR polarizing plate, the peeling electrification voltage generated when the antistatic surface protective film is peeled off from the adherend can be kept low, and an antistatic surface protective film having excellent peel-off antistatic performance without deterioration over time can be provided. The antistatic surface protective film of the present invention can reliably protect the surface of an optical film, thereby improving productivity and yield. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a cross-sectional view illustrating the concept of an antistatic surface protective film of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a state in which the release film has been peeled off from the antistatic surface protective film of the present invention. [Figure 3] FIG. 1 is a cross-sectional view showing one embodiment of an optical component of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be described in detail below based on embodiments. 1 is a cross-sectional view showing the concept of the antistatic surface protective film of the present invention. This antistatic surface protective film 10 has a pressure-sensitive adhesive layer 2 formed on one surface of a transparent substrate film 1. A release film 5, which has a release agent layer 4 formed on the surface of a resin film 3, is attached to the surface of this pressure-sensitive adhesive layer 2.

[0033] The substrate film 1 used in the antistatic surface protection film 10 of the present invention is made of a transparent and flexible resin. This allows for visual inspection of the optical component, which is the adherend, with the antistatic surface protection film attached to the optical component. The transparent resin film used as the substrate film 1 is preferably a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate. In addition to polyester films, films made of other resins can also be used as long as they have the required strength and optical suitability. The substrate film 1 may be a non-stretched film or a uniaxially or biaxially stretched film. The stretch ratio of the stretched film and the axial orientation angle formed by crystallization of the stretched film may be controlled to specific values. The thickness of the substrate film 1 used in the antistatic surface protection film 10 according to the present invention is not particularly limited, but is preferably about 12 to 100 μm, and more preferably about 20 to 50 μm for ease of handling. If necessary, an antifouling layer for preventing surface contamination, an antistatic layer, a hard coat layer for preventing scratches, etc. may be provided on the surface of the base film 1 opposite to the surface on which the pressure-sensitive adhesive layer 2 is formed. The surface of the base film 1 may also be subjected to an adhesion-enhancing treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0034] Furthermore, the adhesive layer 2 used in the antistatic surface protection film 10 of the present invention is not particularly limited as long as it adheres to the surface of the adherend, can be easily peeled off after use, and is unlikely to contaminate the adherend. However, taking into consideration durability after application to an optical film, it is common to use an acrylic adhesive obtained by crosslinking a (meth)acrylate copolymer.

[0035] In particular, a pressure-sensitive adhesive layer is preferred in which the main component of the acrylic pressure-sensitive adhesive is made of an acrylic polymer copolymer containing (A) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18, and (B) at least one copolymerizable monomer containing a hydroxyl group, but not including a copolymerizable monomer containing a carboxyl group. The copolymerizable monomer group may further include (F) a polyalkylene glycol mono(meth)acrylate monomer. Furthermore, a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing, in addition to the acrylic polymer, (C) a difunctional or higher isocyanate compound, (D) a crosslinking accelerator, and (E) a keto-enol tautomer compound is preferred.

[0036] (A) Examples of (meth)acrylic acid ester monomers having an alkyl group with a carbon number of 4 to 18 include butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and undecyl (meth)acrylate. (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, myristyl (meth)acrylate, isomyristyl (meth)acrylate, cetyl (meth)acrylate, isocetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and the like. When the total amount of the acrylic polymers in the copolymer is taken as 100 parts by weight, it is preferable that the copolymer contains 50 to 95 parts by weight of (A) (meth)acrylic acid ester monomers having an alkyl group with carbon atoms of C4 to C18.

[0037] (B) Examples of copolymerizable monomers containing a hydroxyl group include hydroxyalkyl (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate, and hydroxyl group-containing (meth)acrylamides such as N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide. It is preferable that the compound is at least one selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide. When the total amount of the acrylic polymers in the copolymer is taken as 100 parts by weight, the copolymer preferably contains 0.1 to 10 parts by weight of the (B) copolymerizable monomer containing a hydroxyl group.

[0038] The (C) bifunctional or higher isocyanate compound may be at least one or more selected from polyisocyanate compounds having at least two isocyanate (NCO) groups per molecule. Polyisocyanate compounds are classified into aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, alicyclic isocyanates, etc., and any of these may be used. Specific examples of polyisocyanate compounds include aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI), and aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylene diisocyanate (TODI), and tolylene diisocyanate (TDI). Examples of tri- or higher functional isocyanate compounds include biuret-modified and isocyanurate-modified difunctional isocyanate compounds (compounds having two NCO groups in one molecule), and adducts (polyol-modified compounds) with tri- or higher polyols (compounds having at least three OH groups in one molecule) such as trimethylolpropane (TMP) and glycerin. As the difunctional or higher functional isocyanate compound (C), it is possible to use only the trifunctional isocyanate compound (C-1) or only the difunctional isocyanate compound (C-2).It is also possible to use a combination of the trifunctional isocyanate compound (C-1) and the difunctional isocyanate compound (C-2).

[0039] Furthermore, the (C-1) trifunctional isocyanate compound used in the present invention is selected from the (C-1-1) first aliphatic isocyanate compound group consisting of an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a biuret of a hexamethylene diisocyanate compound, and a biuret of an isophorone diisocyanate compound. In addition, it is preferable to include at least one or more selected from (C-1-2) a second group of aromatic isocyanate compounds consisting of an isocyanurate of a tolylene diisocyanate compound, an isocyanurate of a xylylene diisocyanate compound, an isocyanurate of a hydrogenated xylylene diisocyanate compound, an adduct of a tolylene diisocyanate compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound. It is preferable to use the (C-1-1) first group of aliphatic isocyanate compounds and the (C-1-2) second group of aromatic isocyanate compounds in combination. In the present invention, the balance of adhesive strength between the slow peeling speed region and the fast peeling speed region can be further improved by using, as the (C-1) trifunctional isocyanate compound, at least one selected from the (C-1-1) first group of aliphatic isocyanate compounds and at least one selected from the (C-1-2) second group of aromatic isocyanate compounds in combination.

[0040] The trifunctional isocyanate compound (C-1) preferably contains at least one selected from the first group of aliphatic isocyanate compounds (C-1-1) and at least one selected from the second group of aromatic isocyanate compounds (C-1-2), with a total content of 0.5 to 5.0 parts by weight per 100 parts by weight of the acrylic polymer of the copolymer. The mixing ratio of the at least one selected from the first group of aliphatic isocyanate compounds (C-1-1) and the at least one selected from the second group of aromatic isocyanate compounds (C-1-2) is preferably within the range of 10%:90% to 90%:10% by weight.

[0041] Furthermore, the (C-2) bifunctional isocyanate compound used in the present invention is preferably an acyclic aliphatic isocyanate compound, which is a compound produced by reacting a diisocyanate compound with a diol compound. For example, when a diisocyanate compound is represented by the general formula "O=C=NXN=C=O" (where X is a divalent group) and a diol compound is represented by the general formula "HO-Y-OH" (where Y is a divalent group), examples of compounds produced by reacting a diisocyanate compound with a diol compound include compounds represented by the following general formula Z.

[0042] [General formula Z] O=C=NX-(NH-CO-OYO-CO-NH-X) n -N=C=O

[0043] Here, n is an integer of 0 or more. When n is 0, the general formula Z represents "O=C=NXN=C=O". The bifunctional acyclic aliphatic isocyanate compound may contain a compound in which n is 0 in the general formula Z (a diisocyanate compound that has not reacted with the diol compound), but it is preferable to contain a compound in which n is an integer of 1 or more as an essential component. The bifunctional acyclic aliphatic isocyanate compound may be a mixture of multiple compounds in which n in the general formula Z is different.

[0044] The diisocyanate compound represented by the general formula "O=C=NXN=C=O" is an aliphatic diisocyanate. X is preferably an acyclic aliphatic divalent group. The aliphatic diisocyanate is preferably one or more compounds selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0045] The diol compound represented by the general formula "HO-Y-OH" is an aliphatic diol. Y is preferably an acyclic aliphatic divalent group. The diol compound is preferably one or more selected from the group consisting of 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol.

[0046] The weight ratio (C-1 / C-2) of the (C-1) trifunctional isocyanate compound to the (C-2) difunctional isocyanate compound is preferably 1 to 90. The (C) di- or higher functional isocyanate compound is preferably 0.1 to 10 parts by weight per 100 parts by weight of the acrylic polymer of the copolymer.

[0047] The (D) crosslinking accelerator may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent when a polyisocyanate compound is used as the crosslinking agent, and examples thereof include amine compounds such as tertiary amines, metal chelate compounds, organotin compounds, organolead compounds, organozinc compounds, and other organometallic compounds. In the present invention, metal chelate compounds and organotin compounds are preferred as the crosslinking accelerator.

[0048] A metal chelate compound is a compound in which one or more polydentate ligands L are bonded to a central metal atom M. The metal chelate compound may or may not have one or more monodentate ligands X bonded to the metal atom M. For example, the general formula of a metal chelate compound having one metal atom M is M(L) m (X) n When m is 2 or more, m L's may be the same or different ligands. When n is 2 or more, n X's may be the same or different ligands.

[0049] Examples of the metal atom M include Fe, Ni, Mn, Cr, V, Ti, Ru, Zn, Al, Zr, and Sn. Examples of the polydentate ligand L include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone (also known as 2,4-pentanedione), 2,4-hexanedione, and benzoylacetone. These are keto-enol tautomer compounds, and in the polydentate ligand L, the enol may be deprotonated to form an enolate (e.g., acetylacetonate). Examples of the monodentate ligand X include halogen atoms such as chlorine and bromine atoms, acyloxy groups such as pentanoyl, hexanoyl, 2-ethylhexanoyl, octanoyl, nonanoyl, decanoyl, dodecanoyl, and octadecanoyl groups, and alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, and butoxy groups.

[0050] Specific examples of metal chelate compounds include iron tris(2,4-pentanedionato)(III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum trisacetylacetonate, zirconium tetrakisacetylacetonate, iron tris(2,4-hexanedionato)(III), zinc bis(2,4-hexanedionato), titanium tris(2,4-hexanedionato), aluminum tris(2,4-hexanedionato), and zirconium tetrakis(2,4-hexanedionato).

[0051] Examples of organotin compounds include dialkyltin oxides, fatty acid salts of dialkyltins, and fatty acid salts of stannous tin. Traditionally, dibutyltin compounds have been widely used, but in recent years, the toxicity of organotin compounds has been highlighted, and tributyltin (TBT), contained in dibutyltin compounds, in particular, is of concern as an endocrine disruptor. From a safety perspective, long-chain alkyltin compounds such as dioctyltin compounds are preferred. Specific examples of organotin compounds include dioctyltin oxide and dioctyltin dilaurate. While Sn compounds can be used provisionally, in light of the trend toward the use of safer substances, it is preferable to use metal chelate compounds of Al, Ti, Fe, etc., which are safer than Sn. The crosslinking accelerator (D) in the pressure-sensitive adhesive composition according to the present invention is preferably at least one selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds. The crosslinking accelerator (D) is preferably contained in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the acrylic polymer in the copolymer.

[0052] Examples of the (E) keto-enol tautomer compound include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. In a pressure-sensitive adhesive composition using a polyisocyanate compound as a crosslinking agent, these compounds block the isocyanate groups of the crosslinking agent, thereby suppressing excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after blending the crosslinking agent and extending the pot life of the pressure-sensitive adhesive composition. The (E) keto-enol tautomer compound is preferably contained in an amount of 0.1 to 300 parts by weight per 100 parts by weight of the acrylic polymer in the copolymer.

[0053] Since the (E) keto-enol tautomer compound has the effect of inhibiting crosslinking, in contrast to the (D) crosslinking accelerator, it is preferable to appropriately set the ratio of the (E) keto-enol tautomer compound to the (D) crosslinking accelerator. In order to extend the pot life and improve the storage stability of the pressure-sensitive adhesive composition, the weight ratio of (E) / (D) is preferably 70 to 1,000.

[0054] The acrylic polymer may optionally further contain (F) a polyalkylene glycol mono(meth)acrylate monomer as one of the copolymerizable monomers. The (F) polyalkylene glycol mono(meth)acrylate monomer may be a compound in which one of the hydroxyl groups of a polyalkylene glycol is esterified as a (meth)acrylate. The (meth)acrylate group serves as a polymerizable group, allowing it to be copolymerized with the base polymer. The other hydroxyl groups may remain as OH or may be converted into alkyl ethers such as methyl ether or ethyl ether, saturated carboxylic acid esters such as acetate ester, or the like. Examples of alkylene groups in polyalkylene glycol include, but are not limited to, ethylene, propylene, and butylene groups. The polyalkylene glycol may be a copolymer of two or more polyalkylene glycols, such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of polyalkylene glycol copolymers include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol, and the copolymers may be block copolymers or random copolymers. It is preferable that the (F) polyalkylene glycol mono(meth)acrylate monomer has an average repeat number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The "average repeat number of alkylene oxides" refers to the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion contained in the molecular structure of the (F) polyalkylene glycol mono(meth)acrylate monomer.

[0055] The (F) polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate. More specifically, polyethylene glycol-mono(meth)acrylate, polypropylene glycol-mono(meth)acrylate, polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-mono(meth)acrylate, polyethylene glycol-polybutylene glycol-mono(meth)acrylate, polypropylene glycol-polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-polybutylene glycol-mono(meth)acrylate; methoxypolyethylene glycol-(meth)acrylate, methoxypolypropylene glycol-(meth)acrylate, methoxypolybutylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, methoxy-polyethylene glycol ethoxypolyethylene glycol-(meth)acrylate, ethoxypolypropylene glycol-(meth)acrylate, ethoxypolybutylene glycol-(meth)acrylate, ethoxypolyethylene glycol-polypropylene glycol-(meth)acrylate, ethoxypolybutylene glycol-(meth)acrylate, ethoxypolyethylene glycol-polypropylene glycol-(meth)acrylate, ethoxypolyethylene glycol-polybutylene glycol-(meth)acrylate, ethoxypolyethylene glycol-polybutylene glycol-(meth)acrylate, ethoxypolypropylene glycol-polybutylene glycol-(meth)acrylate, ethoxypolyethylene glycol-polypropylene glycol-polybutylene glycol-(meth)acrylate, and the like. When the total amount of the acrylic polymers in the copolymer is taken as 100 parts by weight, the (F) polyalkylene glycol mono(meth)acrylate monomer is preferably contained in an amount of 0 to 50 parts by weight. In the pressure-sensitive adhesive layer according to the present invention, the pressure-sensitive adhesive composition does not necessarily contain the (F) polyalkylene glycol mono(meth)acrylate monomer.

[0056] The pressure-sensitive adhesive composition may optionally contain a polyether-modified siloxane compound having a (G) HLB value of 7 to 15. The polyether-modified siloxane compound is a siloxane compound having a polyether group, and has a general siloxane unit [—SiR 1 2-O-)], as well as siloxane units with polyether groups [—SiR 1 (R 2 O(R 3 O) n R 4 )-O-], where R 1 is one or more alkyl or aryl groups, R 2 and R 3 is one or more alkylene groups, R 4 indicates one or more alkyl groups, acyl groups, etc. (terminal groups). The polyether group is a polyoxyethylene group [(C2H4O) n ] and polyoxypropylene group [(C3H6O) n and the like.

[0057] The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having a (G)HLB value of 7 to 15. The content of the polyether-modified siloxane compound having a (G)HLB value of 7 to 15 is preferably 0.01 to 1.0 part by weight, more preferably 0.1 to 0.5 part by weight, per 100 parts by weight of the acrylic polymer of the copolymer. HLB is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) defined in, for example, JIS K3211 (surfactant terminology).

[0058] Polyether-modified siloxane compounds can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group onto a polyorganosiloxane main chain having silicon hydride groups via a hydrosilylation reaction. Specific examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymers, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymers, and dimethylsiloxane-methyl(polyoxypropylene)siloxane polymers. The HLB value of polyether-modified siloxane compounds can be adjusted by selecting the ratio of polyether groups to siloxane groups. (G) The adhesive strength and reworkability of the adhesive can be improved by blending the adhesive composition with a polyether-modified siloxane compound having an HLB value of 7 to 15. If the adhesive composition does not contain a polyether-modified siloxane compound, the cost will be lower.

[0059] Furthermore, other components that can be appropriately blended include known additives such as copolymerizable alkylene oxide-containing (meth)acrylic monomers, (meth)acrylamide monomers, dialkyl-substituted acrylamide monomers, surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, antioxidants, and antioxidants. These may be used alone or in combination of two or more.

[0060] The copolymer used as the base component in the pressure-sensitive adhesive composition of the present invention can be synthesized by copolymerizing (A) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of 4 to 18 and (B) at least one copolymerizable monomer containing a hydroxyl group, but not including a copolymerizable monomer containing a carboxyl group. The copolymerizable monomers may further include (F) a polyalkylene glycol mono(meth)acrylic acid ester monomer. The polymerization method for the copolymer is not particularly limited, and any suitable polymerization method such as solution polymerization or emulsion polymerization can be used. The pressure-sensitive adhesive composition of the present invention can be prepared by blending the above-mentioned copolymer with (C) a difunctional or higher isocyanate compound, (D) a crosslinking accelerator, (E) a keto-enol tautomer compound, and further any additives as appropriate.

[0061] The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of an acrylic monomer such as a (meth)acrylic acid ester monomer, (meth)acrylic acid, or a (meth)acrylamide. The acrylic polymer does not contain a copolymerizable monomer containing a carboxyl group as a copolymerizable monomer group, which is effective in improving the crosslinking rate and stabilizing adhesive strength. It is preferable to use a copolymerizable monomer containing a hydroxyl group (B) as a monomer that reacts with a difunctional or higher isocyanate compound (C) used as a crosslinking agent. Preferred monomer compositions for the copolymer include one or more types each of (A) and (B), and one or more types each of (A), (B), and (F).

[0062] The adhesive layer obtained by crosslinking the adhesive composition preferably has an adhesive strength of 0.05 to 0.1 N / 25 mm at a low peel speed of 0.3 m / min and an adhesive strength of 1.0 N / 25 mm or less at a high peel speed of 30 m / min. This allows for little change in adhesive strength despite the peel speed, enabling rapid peeling even at high peel speeds. Furthermore, even when the surface protection film is peeled off for re-adhesion, excessive force is not required, and it can be easily peeled off from the adherend.

[0063] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 5.0 × 10 +12Preferably, the surface resistivity is Ω / □ or less, and the peeling electrification voltage is "±0.6 kV or less." In the present invention, "±0.6 kV or less" means 0 to -0.6 kV and 0 to +0.6 kV, i.e., -0.6 to +0.6 kV. If the surface resistivity is high, the performance of dissipating static electricity generated by charging during peeling is poor. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage generated by static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend is reduced, and it is possible to suppress the peeling electrification voltage from affecting the electrical control circuits, etc. of the adherend.

[0064] The pressure-sensitive adhesive layer (pressure-sensitive adhesive after crosslinking) obtained by crosslinking the pressure-sensitive adhesive composition of the present invention preferably has a gel fraction of 95 to 100%. Such a high gel fraction prevents excessive adhesive strength at low peel speeds, reduces elution of unpolymerized monomers or oligomers from the copolymer, improves reworkability and durability at high temperatures and high humidity, and suppresses contamination of the adherend.

[0065] The pressure-sensitive adhesive film of the present invention comprises a pressure-sensitive adhesive layer formed on one or both sides of a resin film by crosslinking the pressure-sensitive adhesive composition of the present invention. The surface protection film of the present invention comprises a pressure-sensitive adhesive layer formed on one side of a resin film by crosslinking the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive composition of the present invention contains the above-mentioned components (A) to (E) in a well-balanced blend, and therefore has excellent antistatic properties, a well-balanced adhesive strength at both low and high peel speeds, and excellent durability and reworkability (no transfer of contamination to the adherend after tracing the surface protection film with a ballpoint pen through the pressure-sensitive adhesive layer). Therefore, the pressure-sensitive adhesive composition of the present invention can be suitably used as a surface protection film for polarizing plates.

[0066] The thickness of the pressure-sensitive adhesive layer 2 used in the antistatic surface protection film 10 according to the present invention is not particularly limited, but is preferably about 5 to 40 μm, and more preferably about 10 to 30 μm. It is preferable that the pressure-sensitive adhesive layer 2 have a weak adhesive strength, i.e., a peel strength (adhesion) of the antistatic surface protection film to the surface of the adherend of about 0.03 to 0.3 N / 25 mm, because this provides excellent operability when peeling the antistatic surface protection film from the adherend. Furthermore, it is preferable that the peel strength of the release film 5 from the pressure-sensitive adhesive layer 2 be 0.2 N / 50 mm or less, because this provides excellent operability when peeling the release film 5 from the antistatic surface protection film 10.

[0067] Furthermore, the release film 5 used in the antistatic surface protective film 10 according to the present invention has a release agent layer 4 formed on one side of the resin film 3, the release agent being mainly composed of dimethylpolysiloxane, and a resin composition containing an antistatic agent.

[0068] Examples of the resin film 3 include polyester film, polyamide film, polyethylene film, polypropylene film, and polyimide film, but polyester film is particularly preferred due to its excellent transparency and relatively low price. The resin film may be unstretched or uniaxially or biaxially stretched. The stretching ratio of the stretched film and the orientation angle in the axial direction formed by crystallization of the stretched film may be controlled to a specific value. The thickness of the resin film 3 is not particularly limited, but is preferably about 12 to 100 μm, and more preferably about 20 to 50 μm, as this is easy to handle. If necessary, the surface of the resin film 3 may be subjected to an easy-adhesion treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0069] The release agent containing dimethylpolysiloxane as a main component that constitutes the release agent layer 4 includes known silicone-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. Examples of commercially available products as addition reaction type silicone-based release agents include KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, and LTC-310 (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available products as condensation reaction type release agents include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available cationic polymerization products include TPR-6501, TPR-6500, UV9300, VU9315, and UV9430 (manufactured by Momentive Performance Materials), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available radical polymerization products include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0070] The antistatic agent constituting the release agent layer 4 preferably has good dispersibility in the release agent solution containing dimethylpolysiloxane as the main component and does not inhibit the hardening of the release agent containing dimethylpolysiloxane as the main component. Alkali metal salts are suitable as such antistatic agents.

[0071] Examples of alkali metal salts include metal salts of lithium, sodium, and potassium. + , Na + , K. + and a cation consisting of Cl - , Br - , I - , BF4 - , PF6 - , SCN - , ClO4 - , CF3SO3 - , (FSO2)2N - , (CF3SO2)2N -, (C2F5SO2)2N - , (CF3SO2)3C - Metal salts composed of anions such as the following are preferably used. Among these, lithium salts (Li salts) such as LiBr, LiI, LiBF, LiPF, LiSCN, LiClO, LiCFSO, Li(FSO)N, Li(CFSO)N, Li(C2F5SO)N, and Li(CFSO)C are particularly preferred, including Li(CFSO)N (abbreviated as LiTFSI), Li(FSO)N (abbreviated as LiFSI), and LiCFSO (abbreviated as LiTF or LiTf). These alkali metal salts may be used alone or in combination. To stabilize the ionic substance, a compound containing a polyoxyalkylene structure may be added. The amount of antistatic agent added to a release agent containing dimethylpolysiloxane as a main component varies depending on the type of antistatic agent and the degree of affinity with the release agent, but can be set taking into consideration the desired peel electrification voltage, staining properties on the adherend, adhesive properties, etc. when the antistatic surface protection film is peeled from the adherend.

[0072] There are no particular limitations on the method for mixing the dimethylpolysiloxane-based release agent with the antistatic agent. Any of the following methods may be used: adding the antistatic agent to the dimethylpolysiloxane-based release agent, mixing, and then adding and mixing a catalyst for curing the release agent; diluting the dimethylpolysiloxane-based release agent with an organic solvent, then adding and mixing the antistatic agent and catalyst for curing the release agent; or diluting the siloxane-based release agent with an organic solvent, adding and mixing the catalyst, and then adding and mixing the antistatic agent. Furthermore, if necessary, a material that enhances the antistatic effect, such as a silane coupling agent or a compound containing a polyoxyalkylene group, may be added.

[0073] The mixing ratio of the dimethylpolysiloxane-based release agent and the antistatic agent is not particularly limited, but a ratio of about 5 to 100 parts by solids of the antistatic agent per 100 parts by solids of the dimethylpolysiloxane-based release agent is preferred. If the amount of antistatic agent added, calculated as solids, is less than 5 parts by solids per 100 parts by solids of the dimethylpolysiloxane-based release agent, the amount of antistatic agent transferred to the surface of the adhesive layer will be reduced, making it difficult for the adhesive to exhibit its antistatic function. Furthermore, if the amount of antistatic agent added, calculated as solids, is more than 100 parts by solids per 100 parts by solids of the dimethylpolysiloxane-based release agent, both the antistatic agent and the dimethylpolysiloxane-based release agent will be transferred to the surface of the adhesive layer, potentially reducing the adhesive properties of the adhesive.

[0074] The method for forming the pressure-sensitive adhesive layer 2 on the base film 1 of the antistatic surface protection film 10 according to the present invention and the method for laminating the release film 5 thereto may be any known method, and are not particularly limited. Specific examples include (1) a method in which a resin composition for forming the pressure-sensitive adhesive layer 2 is applied to one side of the base film 1, dried to form a pressure-sensitive adhesive layer, and then laminating the release film 5, and (2) a method in which a resin composition for forming the pressure-sensitive adhesive layer 2 is applied to the surface of the release film 5, dried to form a pressure-sensitive adhesive layer, and then laminating the base film 1, and either method may be used.

[0075] The pressure-sensitive adhesive layer 2 may be formed on the surface of the base film 1 by a known method. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating can be used.

[0076] Similarly, the release agent layer 4 may be formed on the resin film 3 by a known method. Specifically, known coating methods such as gravure coating, Mayer bar coating, and air knife coating can be used.

[0077] FIG. 2 is a cross-sectional view showing the state in which the release film has been peeled off from the antistatic surface protection film of the present invention. When the release film 5 is peeled off from the antistatic surface protection film 10 shown in Fig. 1, a portion of the antistatic agent (reference numeral 7) contained in the release agent layer 4 of the release film 5 is transferred (adhered) to the surface of the pressure-sensitive adhesive layer 2 of the antistatic surface protection film 10. Therefore, in Fig. 2, the antistatic agent transferred to the surface of the pressure-sensitive adhesive layer 2 of the antistatic surface protection film is schematically shown by spots reference numeral 7. In the antistatic surface protective film according to the present invention, when the antistatic surface protective film 11 shown in Fig. 2 with the release film peeled off is attached to an adherend, the antistatic agent transferred to the surface of the pressure-sensitive adhesive layer 2 comes into contact with the surface of the adherend, thereby making it possible to keep the peeling electrification voltage low when the antistatic surface protective film is peeled off again from the adherend.

[0078] FIG. 3 is a cross-sectional view showing an embodiment of an optical component according to the present invention. The release film 5 is peeled off from the antistatic surface protection film 10 of the present invention, and in a state where the pressure-sensitive adhesive layer 2 is exposed, the film is stuck to an optical component 8 as an adherend via the pressure-sensitive adhesive layer 2 . FIG. 3 shows an optical component 20 to which an antistatic surface protective film 10 of the present invention is attached. Examples of optical components include optical films such as polarizing plates, retardation plates, lens films, polarizing plates that also function as retardation plates, and polarizing plates that also function as lens films. These optical components are used as components of liquid crystal display devices such as liquid crystal display panels, optical systems for various instruments, and the like. Other examples of optical components include optical films such as antireflection films, hard coat films, and transparent conductive films for touch panels. In particular, the antistatic surface protective film can be suitably used as an antifouling surface protective film to be attached to the antifouling surface of optical films such as low-reflection polarizing plates (LR polarizing plates) and anti-glare low-reflection polarizing plates (AG-LR polarizing plates), whose surfaces have been treated with a silicone compound, a fluorine compound, or the like to be antifouling-treated. According to the optical component of the present invention, when the antistatic surface protective film 10 is peeled off from the adherend, that is, the optical component (optical film), the peeling electrification voltage can be kept sufficiently low, so there is no risk of damaging circuit components such as driver ICs, TFT elements, and gate line driving circuits, and production efficiency in the process of manufacturing liquid crystal display panels, etc. can be improved and the reliability of the production process can be maintained. [Example]

[0079] The present invention will now be further illustrated by examples.

[0080] <Production of Pressure-Sensitive Adhesive Composition> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air inside the reactor was replaced with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 4.5 parts by weight of 8-hydroxyoctyl acrylate, 10 parts by weight of polypropylene glycol monoacrylate (n=12), and 60 parts by weight of solvent (ethyl acetate) were added to the reactor. 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was then added dropwise over 2 hours, and the mixture was allowed to react at 65°C for 6 hours to obtain an acrylic copolymer solution of Example 1 with a weight-average molecular weight of 500,000. 8.5 parts by weight of acetylacetone was added to the acrylic copolymer solution and stirred. Then, 2.5 parts by weight of Coronate HX (an isocyanurate derivative of a hexamethylene diisocyanate compound) and 0.1 parts by weight of titanium trisacetylacetonate were added and mixed with stirring to obtain the pressure-sensitive adhesive composition of Example 1.

[0081] [Examples 2 to 6 and Comparative Examples 1 to 3] The pressure-sensitive adhesive compositions of Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the formulations of the pressure-sensitive adhesive composition of Example 1 were changed as shown in Tables 1 and 2. In Tables 1 and 2, the monomers contained (copolymerized) in the acrylic copolymer are (A), (B), (F), and a "carboxyl group-containing monomer."

[0082] [Table 1]

[0083] [Table 2]

[0084] Tables 1 and 2 are two separate tables showing the compounding ratios of each component, and in both cases, the numerical values ​​in parts by weight, calculated with the total for group (A) being 100 parts by weight, are enclosed in parentheses. The compound names of the abbreviations for each component used in Tables 1 and 2 are shown in Tables 3 and 4. Coronate (registered trademark) HX, HL, and L are product names of Nippon Polyurethane Industry Co., Ltd., and Takenate (registered trademark) D-140N, D-127N, and D-110N are product names of Mitsui Chemicals, Inc. In the "Antistatic Agent" section of Table 2 and in Table 7 described below, LiTFSI represents Li(CF3SO2)2N, LiFSI represents Li(FSO2)2N, LiTF represents LiCF3SO3, and SH8400 represents polyether-modified silicone (manufactured by Dow Corning Toray Co., Ltd., product name: SH8400, main component: dimethyl, methyl (polyethylene oxide acetate) siloxane).

[0085] [Table 3]

[0086] [Table 4]

[0087] <Synthesis of bifunctional isocyanate compounds> The bifunctional isocyanate compounds of Synthesis Examples 1 and 2 were synthesized by the following method: As shown in Tables 5 and 6, a diisocyanate and a diol compound were mixed in a molar ratio of NCO / OH=16 and reacted at 120°C for 3 hours, and then the unreacted diisocyanate was removed under reduced pressure using a thin-film evaporator to obtain the desired bifunctional isocyanate compounds.

[0088] [Table 5]

[0089] [Table 6]

[0090] <Preparation of antistatic surface protection film> [Example 1] 5 parts by weight of addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 0.5 parts by weight of Li(CF3SO2)2N, 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 Catalyst) were combined, stirred, and mixed to prepare a coating material for forming the release agent layer of Example 1. The coating material for forming the release agent layer of Example 1 was applied to the surface of a 38 μm thick polyethylene terephthalate film using a Mayer bar to a dry thickness of 0.2 μm, and the mixture was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Example 1. The pressure-sensitive adhesive composition of Example 1 was applied to the surface of a 38 μm-thick polyethylene terephthalate film so that the dried thickness would be 20 μm, and then dried for 2 minutes in a hot air circulating oven at 100°C to form a pressure-sensitive adhesive layer. The release agent layer (silicone-treated surface) of the release film of Example 1 prepared above was then attached to the surface of this pressure-sensitive adhesive layer. The resulting pressure-sensitive adhesive film was kept warm in an environment of 40°C for 5 days to cure the pressure-sensitive adhesive, thereby obtaining the antistatic surface protection film of Example 1.

[0091] [Example 2] The antistatic surface protection film of Example 2 was obtained in the same manner as Example 1, except that the adhesive composition of Example 1 was replaced with the adhesive composition of Example 2 and the antistatic agent used in the release agent layer was changed to LiCF3SO3.

[0092] [Examples 3 to 6] The antistatic surface protection films of Examples 3 to 6 were obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition of Example 1 was replaced with the pressure-sensitive adhesive compositions of Examples 3 to 6, and the antistatic agent used in the release agent layer was changed to Li(FSO2)2N.

[0093] [Comparative Example 1] 5 parts by weight of addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 Catalyst) were combined, stirred, and mixed to prepare a coating material for forming the release agent layer of Comparative Example 1. The coating material for forming the release agent layer of Comparative Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm using a Mayer bar so that the thickness after drying would be 0.2 μm, and the coating was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Comparative Example 1. The adhesive composition of Comparative Example 1 was applied to the surface of a 38 μm-thick polyethylene terephthalate film so that the dried thickness would be 20 μm, and then dried for 2 minutes in a hot air circulating oven at 100°C to form an adhesive layer. The release agent layer (silicone-treated surface) of the release film of Comparative Example 1 prepared above was then attached to the surface of this adhesive layer. The resulting adhesive film was kept warm in an environment of 40°C for 5 days to cure the adhesive, thereby obtaining an antistatic surface protection film of Comparative Example 1.

[0094] Comparative Example 2 An antistatic surface protection film of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the adhesive composition of Comparative Example 1 was replaced with the adhesive composition of Comparative Example 2.

[0095] Comparative Example 3 An antistatic surface protection film of Comparative Example 3 was obtained in the same manner as in Example 1, except that the adhesive composition of Example 1 was replaced with the adhesive composition of Comparative Example 3 and the antistatic agent used in the release agent layer was changed to Li(FSO2)2N.

[0096] Table 7 shows the compositions of the release agent layers in the antistatic surface protection films of Examples 1 to 6 and Comparative Examples 1 to 3.

[0097] [Table 7]

[0098] <Test method and evaluation> The surface protection films of Examples 1 to 6 and Comparative Examples 1 to 3 were aged for 7 days in an atmosphere of 23°C and 50% RH, and then the release film (a silicone resin-coated PET film) was peeled off to expose the adhesive layer, which was used as a sample for measuring surface resistivity. Furthermore, this surface protection film with the adhesive layer exposed was attached to the surface of a polarizing plate attached to a liquid crystal cell via the adhesive layer, and after leaving it for one day, it was autoclaved at 50°C and 5 atmospheres for 20 minutes, and then left at room temperature for a further 12 hours to be used as a sample for measuring adhesive strength, peeling electrification voltage, and reworkability.

[0099] <Adhesive strength> The measurement sample obtained above (a 25 mm wide surface protection film attached to the surface of a polarizing plate) was peeled in a 180° direction using a tensile tester at a low peeling speed (0.3 m / min) and a high peeling speed (30 m / min), and the measured peel strength was taken as the adhesive strength.

[0100] <Surface resistivity> After aging and before bonding to the polarizing plate, the release film (a silicone resin-coated PET film) was peeled off to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter, Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech).

[0101] <Peeling electrification voltage> The measurement sample obtained above was peeled off at an angle of 180° at a tensile speed of 30 m / min, and the voltage (charged voltage) generated when the polarizing plate was charged was measured using high-precision electrostatic sensors SK-035 and SK-200 (manufactured by Keyence Corporation). The maximum measured value was taken as the peeling charged voltage.

[0102] <Reworkability> The surface protection film of the measurement sample obtained above was traced with a ballpoint pen (500 g load, 3 strokes back and forth), and then the surface protection film was peeled off from the polarizing plate and the surface of the polarizing plate was observed to confirm that no contamination had been transferred to the polarizing plate. The evaluation criteria were as follows: "○" if there was no contamination transfer to the polarizing plate, "△" if contamination transfer was confirmed in at least a portion along the ballpoint pen trace, and "×" if contamination transfer was confirmed along the ballpoint pen trace and adhesive detachment was confirmed from the adhesive surface.

[0103] The evaluation results are shown in Table 8. The surface resistivity is expressed as "m×10 +n " is expressed as "mE+n" (where m is any real number and n is a positive integer).

[0104] [Table 8]

[0105] The measurement results shown in Table 8 reveal the following: The antistatic surface protection films of Examples 1 to 6 according to the present invention have suitable adhesive strength, do not contaminate the surface of the adherend, and exhibit low peel electrification voltage when peeled from the adherend. On the other hand, the antistatic surface protective film of Comparative Example 1, in which a silicone compound and an antistatic agent were added to the adhesive layer, had a low and favorable surface resistivity of the adhesive layer, but due to its high adhesive strength, the peeling electrification voltage was high and the reworkability was poor. Furthermore, in Comparative Example 2, the adhesive gelled and became uncoatable, possibly due to the large amount of crosslinking accelerator added. Furthermore, in Comparative Example 3, due to the inclusion of a monomer containing a carboxyl group, the adhesive strength was high and the reworkability was somewhat poor. That is, in Comparative Examples 1 and 2, in which a silicone compound and an antistatic agent were mixed into the pressure-sensitive adhesive, it was difficult to achieve both a reduction in peeling electrification voltage and resistance to staining of the adherend. On the other hand, in Examples 1 to 6, in which an antistatic agent was added to the release agent layer and then transferred to the surface of the pressure-sensitive adhesive layer, a small amount of the antistatic agent was effective in reducing peeling electrification voltage, and no staining of the adherend occurred, resulting in a good antistatic surface protection film. [Industrial Applicability]

[0106] The antistatic surface protective film of the present invention can be used to protect the surfaces of optical films such as polarizing plates, retardation plates, and lens films for displays, as well as various other optical components, in the production processes of these optical components, etc. In particular, when used as an antistatic surface protective film for optical films such as LR polarizing plates and AG-LR polarizing plates, the surface of which has been treated with a silicone compound, a fluorine compound, or the like to prevent contamination, the amount of static electricity generated when peeled from the adherend can be reduced. The antistatic surface protective film of the present invention causes little contamination to the adherend, and furthermore, has excellent antistatic properties against peeling without deterioration over time, and therefore can improve the yield of the production process, and is of great industrial value. [Explanation of symbols]

[0107] 1...base film, 2...adhesive layer, 3...resin film, 4...release agent layer, 5...release film, 7...antistatic agent, 8...adherend (optical component), 10...antistatic surface protective film, 11...antistatic surface protective film with release film removed, 20...optical component with antistatic surface protective film attached.

Claims

1. a pressure-sensitive adhesive layer formed on one side of a substrate film made of a transparent resin, the pressure-sensitive adhesive layer being made of an acrylic polymer of a copolymer obtained by copolymerizing (A) at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of 4 to 18 with (B) at least one copolymerizable monomer containing a hydroxyl group, but not including a copolymerizable monomer containing a carboxyl group, and the copolymerizable monomer group being further made of a pressure-sensitive adhesive composition containing (C) a difunctional or higher isocyanate compound, (D) a crosslinking accelerator, (E) a keto-enol tautomer compound, and (G) a polyether-modified siloxane compound having an HLB value of 7 to 15; a release film, which has a release agent layer containing an antistatic agent laminated on one surface of a resin film, is bonded to the surface of the pressure-sensitive adhesive layer via the release agent layer; the release agent layer is formed from a resin composition containing a release agent containing dimethylpolysiloxane as a main component and an antistatic agent, An antistatic surface protection film, characterized in that the antistatic agent is applied to the surface of the pressure-sensitive adhesive layer.

2. An optical film having the antistatic surface protective film according to claim 1 laminated thereto.

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