Surface protective film and optical member

Abstract

Provided are a surface protective film and an optical member. A surface protective film (10) includes: a base film (1) composed of a resin having transparency; an antistatic agent layer (2) formed on one side of the base film (1); and an adhesive layer (3) formed on the side of the base film (1) opposite the antistatic agent layer (2). The antistatic agent layer (2) includes: a first layer (2a) containing a conductive polymer; and a second layer (2b) disposed on the side opposite the base film (1) relative to the first layer (2a) and containing nanocarbon.

Description

Technical Field

[0001] This invention relates to a surface protective film and an optical component. Background Technology

[0002] When manufacturing and handling optical films such as polarizing plates, retardation plates, lens films for displays, anti-reflective films, hard coatings, and transparent conductive films for touch panels, as well as optical products such as displays using these films, a surface protective film is applied to the surface of the optical film to prevent surface stains or scratches in subsequent processes. To eliminate the hassle of peeling off and reapplying the surface protective film and improve work efficiency, visual inspection of the product (i.e., the optical film) can be performed while the surface protective film is applied to the optical film.

[0003] Traditionally, in the manufacturing process of optical products, a surface protective film with an adhesive layer on one side of the substrate film is used to prevent scratches or stains from adhering to the surface of the optical product. The surface protective film is bonded to the optical film by the adhesive layer with micro-adhesion. The reason for the adhesive layer having micro-adhesion is that it can be easily peeled off from the surface of the optical film after use, and it prevents the adhesive from adhering to the substrate, i.e., the optical film of the product, and leaving residue (preventing the formation of so-called adhesive residue).

[0004] As a surface protective film, an antistatic layer is often used on the side of the substrate film opposite to the adhesive layer. By providing an antistatic layer on the surface of the surface protective film, static electricity generated during the handling or processing of optical products with the surface protective film applied during the manufacturing process of optical products is suppressed. This prevents the adsorption of dust or particles from the environment and facilitates visual inspection when the surface protective film is applied to the optical film. In addition, when the used surface protective film is peeled off from the polarizing plate or retardation plate assembled to the liquid crystal display panel, significant peeling static electricity is suppressed, thereby preventing damage to circuits such as driver ICs.

[0005] As an antistatic layer on the surface of a protective film, proposed antistatic layers include layers composed of various surfactants (nonionic, cationic, anionic, amphoteric surfactants) or polymers containing ionic groups, layers of vapor-deposited metals or metal oxides, and layers composed of particles of metals or metal oxides.

[0006] Antistatic layers containing surfactants or polymers with ionic groups are susceptible to the effects of ambient humidity. They exhibit high antistatic performance in high-humidity environments, but their performance deteriorates significantly in low-humidity environments. On the other hand, antistatic layers containing metal or metal oxide particles are less affected by ambient humidity; however, they lack transparency and cannot be used for inspecting optical products, especially when inspecting them with a protective film attached. Examples of transparent antistatic layers that are less affected by ambient humidity include those deposited with indium tin oxide (ITO) or antimony tin oxide (ATO), but the cost of vapor deposition is very high.

[0007] Patent Document 1 discloses a surface protective film having an antistatic layer on one side of a polyester film, an antifouling layer on that layer, and a micro-adhesive layer on the opposite side. The antistatic layer comprises a conductive polymer obtained by polymerizing thiophene and / or thiophene derivatives. However, a problem exists where, when the conductive polymer is used to form the antistatic layer, over time, problems such as increased surface resistivity (deterioration) accompanied by oxidative or photodeterioration occur.

[0008] To address this issue of surface resistivity increasing (deterioration) over time, Patent Document 2 proposes a surface protective film containing an antistatic layer of polyaniline sulfonic acid, a polythiophene doped with a polyanion, and a binder. This surface protective film suppresses surface resistivity increase (deterioration) over time by using an antistatic layer and polyaniline sulfonic acid; however, it is susceptible to discoloration from yellow to green by the polyaniline, making it unsuitable for use in optical components.

[0009] Patent document 3 proposes an antistatic film that is transparent (total light transmittance) and has good adhesion to the substrate as an antistatic layer. It also has a conductive layer comprising nano-carbon and a polymer, and the surface resistivity of the antistatic film is 1×10⁻⁶. 11 An antistatic film with a resistance of Ω / □ or less. However, the problem is that, since this antistatic film uses nano-carbon such as carbon nanotubes as an antistatic agent, although the surface resistance increases little over time, it increases (deteriorates) when exposed to humid and hot environments (such as 60°C and 90% relative humidity).

[0010] Patent document 4 discloses a thermosetting antistatic coating containing polythiophene and a conductive filler. This thermosetting antistatic coating exhibits minimal change in surface resistivity even over time. However, a problem arises when the thermosetting antistatic coating is subjected to high-temperature, humid conditions (e.g., 60°C, 90% relative humidity), resulting in an increase (deterioration) in surface resistivity.

[0011] Patent Document 1: Japanese Patent Application Publication No. 2000-026817

[0012] Patent Document 2: Japanese Re-appearance No. 2018-012545

[0013] Patent Document 3: Japanese Patent Application Publication No. 2012-166452

[0014] Patent Document 4: Japanese Patent Application Publication No. 2016-216714 Summary of the Invention

[0015] One embodiment of the present invention was made in view of the above circumstances, and its object is to provide a surface protective film and an optical component that do not easily cause an increase in surface resistivity.

[0016] One embodiment of the present invention provides a surface protective film comprising: a substrate film made of a transparent resin; an antistatic agent layer formed on one side of the substrate film; and an adhesive layer formed on the side of the substrate film opposite to the antistatic agent layer. The antistatic agent layer comprises: a first layer comprising a conductive polymer; and a second layer disposed opposite to the first layer on the side opposite to the substrate film and comprising nano-carbon.

[0017] Alternatively, the surface protective film may have a release film attached to the adhesive layer on the opposite side to the substrate film.

[0018] Preferably, the adhesive layer is made of an acrylic adhesive.

[0019] Another embodiment of the present invention provides an optical component to which the surface protective film is attached.

[0020] One embodiment of the present invention can provide a surface protective film and an optical component that do not easily cause an increase in surface resistivity. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view showing the surface protective film of an embodiment.

[0022] Figure 2 This is a cross-sectional view showing a surface protective film with a release film attached to the surface protective film in an embodiment.

[0023] Figure 3 This is a cross-sectional view illustrating one embodiment of the optical component of the present invention.

[0024] (Explanation of reference numerals in the attached diagram)

[0025] 1: Substrate film, 2: Antistatic agent layer, 2a: First layer, 2b: Second layer, 3: Adhesive layer, 4: Release film, 5: Adhesive (optical component), 10: Surface protective film, 11: Surface protective film with release film, 20: Optical component. Detailed Implementation

[0026] The present invention will now be described in detail based on its embodiments.

[0027] Figure 1 This is a cross-sectional view illustrating the surface protective film of an embodiment. (e.g.) Figure 1 As shown, the surface protective film 10 involved in the embodiment is on one surface of the substrate film 1 ( Figure 1 An antistatic agent layer 2 is formed on the surface of the substrate film 1 opposite to the antistatic agent layer 2. Figure 1 An adhesive layer 3 is formed on the lower part of the middle section.

[0028] [Substrate Film]

[0029] As the substrate film 1, a substrate film made of a transparent and flexible resin is used. Therefore, with the surface protective film 10 bonded to the substrate, i.e., the optical component, visual inspection of the optical component can be performed. For the substrate film 1 used as the substrate film 1, a film (polyester film) formed of polyesters such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate is preferable. Besides polyester films, films made of other resins can also be used, provided they possess the required strength and optical adaptability. The substrate film 1 can be a non-stretched film, or a uniaxially or biaxially stretched film. Furthermore, the stretch ratio of the stretched film and the orientation angle of the axial method accompanying the crystallization of the stretched film can be controlled to specific values.

[0030] "Transparent" means, for example, when the measurement is performed in the wavelength range of 380 nm to 780 nm, that the visible light transmittance, calculated as the average transmittance in the thickness direction across the entire wavelength region, is 50% or more (preferably 70% or more, more preferably 80% or more). The light transmittance can be measured according to the method for "Determination of Total Light Transmittance and Total Light Reflectance of Plastics" specified in JIS K 7375:2008.

[0031] The thickness of the substrate film 1 is not particularly limited. For example, a thickness of about 12 μm to 100 μm is preferred. A thickness of about 20 μm to 50 μm is easier to process and is more preferred.

[0032] In addition, as needed, the surface of the substrate film 1 can be subjected to surface modification based on corona discharge, coating with a primer, and other easy-to-adhere treatments.

[0033] [Antistatic agent layer]

[0034] The antistatic agent layer 2 is formed by sequentially stacking a first layer 2a containing a conductive polymer and a second layer 2b containing nano-carbon from the substrate film 1 side. The second layer 2b is disposed on the opposite side of the substrate film 1 relative to the first layer 2a. Figure 1 (Upper middle side).

[0035] Over time, the surface resistivity of a layer containing conductive polymer may increase due to oxidation or photodegradation. However, in the surface protective film 10, by providing a second layer 2b containing nano-carbon on the surface of the first layer 2a (the side opposite to the substrate film 1), the technical problem of oxidation or photodegradation of the first layer 2a containing conductive polymer is overcome.

[0036] When the layer containing nano-carbon is in a humid and hot environment (e.g., 60°C, 90% relative humidity, etc.), the surface resistance value may increase (deteriorate). However, in the surface protective film 10, the technical problem of the second layer 2b deteriorating in a humid and hot environment is also overcome by the antistatic effect of the first layer 2a existing between the second layer 2b and the substrate film 1.

[0037] Examples of conductive polymers used for the first layer 2a include polyaniline, polythiophene, polypyrrole, and their derivatives.

[0038] As polyaniline and its derivatives, the following can be obtained: polyaniline (manufactured by ALDRICH Corporation), polyaniline (emeraldine) (manufactured by ALDRICH Corporation), OMEGACON (registered trademark) D1033W, OMEGACON (registered trademark) NW-D102MT, OMEGACON (registered trademark) NW-F102ET, OMEGACON (registered trademark) NW-F101MEK (all of the above are manufactured by Nissan Chemical Industries, Ltd.), AQUAPASS (registered trademark) 01X (manufactured by Mitsubishi Chemical Corporation), and polyaniline toluene solution PANT (manufactured by Kaken Sangyo Co., Ltd.), etc.

[0039] Commercially available products of polythiophene and its derivatives include: 3,4-ethylenedioxythiophene (BAYTRON MV2), 3,4-polyethylenedioxythiophene / polystyrene sulfonate (BAYTRON P, BAYTRON C), BAYTRON FE, BAYTRON MV2, BAYTRON P, BAYTRON PAG, and BAYTRON PHC. V4, BAYTRON (registered trademark) PHS, BAYTRON (registered trademark) PH, BAYTRON (registered trademark) PH500, BAYTRON (registered trademark) PH510 (and above, manufactured by STARK Corporation), SEPLEGYDA (registered trademark) AS-Q, SEPLEGYDA (registered trademark) AS-D, SEPLEGYDA (registered trademark) AS-H (and above, manufactured by Shin-Etsu Polymer Corporation), conductive coating S-983, conductive coating S-495, conductive coating S-948 (and above, manufactured by Chukyo Oils & Fats Corporation), Denatron P-502RG, Denatron P-560ST, Denatron P-500NT, Denatron P-200HC, Denatron P-800SL (and above, manufactured by NAGASE CHEM TEX Corporation), PED500 (manufactured by Kaken Sangyo Corporation), etc.

[0040] As polypyrrole and its derivatives, polypyrrole (manufactured by ALDRICH) and SSPY (manufactured by Kaken Sangyo Co., Ltd.) can be obtained.

[0041] As a conductive polymer, polythiophene is preferred in terms of antistatic properties and colorability (color sensitivity). Polyethylene oxythiophene is preferred, and polyethylene dioxythiophene (PEDOT) is particularly preferred. Polyethylene dioxythiophene is preferably doped with polystyrene sulfonic acid (PSS) as a dopant. PSS-doped polyethylene dioxythiophene is readily soluble in water and exhibits excellent heat resistance, moisture resistance, and UV stability.

[0042] Conductive polymers can be used alone or in combination. Furthermore, to improve the coating properties of the antistatic agent on the substrate film 1, the adhesion of the antistatic agent layer to the substrate film, the film strength of the antistatic agent layer, and the durability of the film (abrasion resistance or solvent resistance, etc.), binder resins, crosslinking agents, ultraviolet absorbers, antioxidants, leveling agents (wetting improvers), and adhesion enhancers can be added to the conductive polymer.

[0043] To form the first layer 2a, it is preferable to coat the conductive polymer with an added binder resin rather than coating the conductive polymer alone. Examples of binder resins include acrylic resins, epoxy resins, urethane resins, phenolic resins, and polyester resins. To crosslink (also known as curing) these resins, a crosslinking agent may be added to the binder resin as needed. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelating compounds.

[0044] The method for forming the first layer 2a on the substrate film 1 can be a known method. For example, a coating containing an antistatic agent (a coating containing an antistatic agent and a binder resin) can be applied to the substrate film 1 using a known coating method. The first layer 2a can then be formed by curing the coating film by heating or ultraviolet irradiation. Coating methods include reverse coating, comma blade coating, gravure coating, slot coating, Mehler rod coating, air knife coating, etc.

[0045] Examples of carbon nanotubes (CNTs), graphene, and fullerenes used for the second layer 2b include carbon nanotubes (CNTs). Carbon nanotubes include monolayer and multilayer CNTs. Monolayer CNTs, multilayer CNTs, graphene, and fullerenes all exhibit excellent antistatic properties; however, monolayer CNTs, graphene, and fullerenes are expensive, making multilayer CNTs easier to use. To prevent the first layer 2a from being exposed to air, the second layer 2b is formed on the surface of the first layer 2a. Therefore, the first layer 2a is not directly exposed to air, and thus is less prone to oxidation and degradation.

[0046] Since nano-carbon alone cannot exhibit film strength, it is preferable to use it as a coating by adding binder resins or dispersants. Furthermore, to improve the coatability of the antistatic agent, the adhesion of the antistatic agent layer (relative to the adhesion of the first layer 2a), the film strength of the antistatic agent layer, and the durability of the film (abrasion resistance or solvent resistance, etc.), crosslinking agents, ultraviolet absorbers, antioxidants, leveling agents (wetting improvers), and adhesion enhancers can be added to the nano-carbon.

[0047] Nanocarbon can be used in one or more forms. Examples of binder resins include acrylic resins, epoxy resins, urethane resins, phenolic resins, and polyester resins. To crosslink these resins (also known as curing), crosslinking agents can be added to the binder resin as needed. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelating compounds.

[0048] To form the second layer 2b, commercially available coatings can be used as antistatic agents. Examples of commercially available products include: Denatron C-300, Denatron CD-001 (and above, manufactured by NAGASE CHEMTEX), COLCOAT CS-3002, and COLCOAT CS-3202 (and above, manufactured by COLCOAT).

[0049] The method for forming the second layer 2b on the surface of the first layer 2a can be a known method. For example, a coating containing nano-carbon (a coating containing nano-carbon and a binder resin) can be applied to the surface of the first layer 2a using a known coating method. The second layer 2b can then be formed by curing the resulting coating film through heating or ultraviolet irradiation. Coating methods include reverse coating, comma blade coating, gravure coating, slotted beam coating, Mehler rod coating, and air knife coating.

[0050] The thicknesses of the first layer 2a and the second layer 2b are not particularly limited. The thickness of the first layer 2a is determined by the amount of conductive polymer and binder resin. The thickness of the second layer 2b is determined by the amount of nano-carbon and binder resin. The thicknesses of the first layer 2a and the second layer 2b can be adjusted such that the surface resistivity is 10^7 (10^7) while the first layer 2a and the second layer 2b are stacked. 7 ) ~ 10 to the power of 9 (10 9 )about.

[0051] [Adhesive layer]

[0052] The adhesive layer 3 preferably has the characteristics of adhering to the surface of the adherend, being easy to peel off after use, and not easily contaminating the adherend. Examples of adhesives used for the adhesive layer 3 include acrylic adhesives, urethane adhesives, rubber adhesives, etc. Adhesive resins such as polyethylene vinyl acetate resin can also be used as adhesives. Among these, acrylic adhesives and urethane adhesives are particularly preferred.

[0053] As an acrylic adhesive, an adhesive in which a crosslinking agent is added to a (meth)acrylic polymer (acrylic resin composition) is preferred. The (meth)acrylic polymer is preferably a polymer copolymerized from main monomers such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate; comonomers such as acrylonitrile, vinyl acetate, methyl methacrylate, and ethyl acrylate; and functional monomers such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, and N-hydroxymethylmethacrylamide. The monomer composition constituting the (meth)acrylic polymer is preferably 50% or more of (meth)acrylic monomers, and may also be 100% (meth)acrylic monomers.

[0054] Crosslinking agents crosslink (meth)acrylic polymers. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, melamine compounds, and metal chelating compounds. The amount of crosslinking agent added can be determined by considering the type, degree of polymerization, and amount of functional groups of the (meth)acrylic polymer. The amount of crosslinking agent added is not particularly limited, but preferably, it is about 0.5 to 1.0 parts by weight of crosslinking agent relative to 100 parts by weight of the (meth)acrylic polymer.

[0055] As a urethane adhesive, a urethane resin containing both polyol and polyisocyanate components is preferred. The urethane resin can be selected considering factors such as adhesion, wettability, and staining properties on the adhered object. There are no particular limitations on the polyol and polyisocyanate components. The urethane resin can be used alone or in combination with two or more components.

[0056] Examples of polyol components include, for example, polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, and castor oil polyols. These polyol components can be used alone or in combination of two or more.

[0057] As polyisocyanate components, polymers of aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and diisocyanates are used. These polyisocyanate components can be used alone or in combination of two or more.

[0058] Commercially available polyurethane adhesives include: Cyabine (registered trademark) SH-101, SH-101M, SP-205, SP-220 (manufactured by TOYOCHEM Co., Ltd.), ARACOAT (registered trademark) FT100, FT200 (manufactured by Arakawa Chemical Industry Co., Ltd.), UN1175, UN1176 (manufactured by Daido Kasei Corporation), etc. The adhesive layer is formed by cross-linking or curing polyurethane adhesives.

[0059] To promote the crosslinking reaction, a crosslinking catalyst may be added to the adhesive layer 3 as an additive, if needed. To improve the adhesion between the substrate film 1 and the adhesive, an adhesion enhancer such as a silane coupling agent may be added to the adhesive layer 3 as an additive, if needed. Antistatic agents, antioxidants, UV absorbers, and other additives may be added to the adhesive layer 3 as needed.

[0060] The thickness of the adhesive layer 3 is not particularly limited, but is preferably about 5 μm to 40 μm, and more preferably about 10 μm to 30 μm. Furthermore, the adhesive force (low-speed adhesive force) at a peel speed of 0.3 m / min relative to the surface of the substrate to which the protective film is adhered is preferably 0.3 N / 25 mm or less, and more preferably 0.2 N / 25 mm or less. Additionally, the adhesive force at a peel speed of 30 m / min (high-speed adhesive force) is preferably 0.8 N / 25 mm or less. If the high-speed adhesive force is greater than 0.8 N / 25 mm, the workability when peeling off the protective film after use may deteriorate. The adhesive force can be adjusted using known methods such as changing the adhesive composition, adjusting the amount of curing agent added, or adjusting the amount of tackifier or adhesive strength modifier added. These methods allow the adhesive force of the adhesive layer 3 to match a predetermined adhesive force.

[0061] As a method for forming the adhesive layer 3 on the surface of the substrate film 1, known methods can be used. Specifically, known coating methods such as reverse coating, comma blade coating, gravure coating, slot coating, Meller rod coating, and air knife coating can be used.

[0062] Figure 2 This is a cross-sectional view showing a surface protective film 11 with a release film 4 attached to a surface protective film 10. (See diagram below.) Figure 2As shown, known release films can be used as release film 4. Polyolefin films such as polyethylene film and polypropylene film, or fluoropolymer films, can be used as the film monomers for release film 4. Release film 4 can be a release film for which a resin film has been treated with a release agent (also called a release agent). Examples of resin films include polyester films such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), and polyamide films. Examples of release agents include silicone resins, resins containing long-chain alkyl groups, and fluoropolymers. Preferably, a release film for which a silicone-based release agent has been used to treat the PET film is used.

[0063] The thickness of the release film is not particularly limited, but considering workability and cost, release films with a thickness of 12μm to 38μm are commonly used.

[0064] The method of forming the adhesive layer 3 on the substrate film 1 and the method of bonding the release film 4 to the adhesive layer 3 can be carried out by known methods and are not particularly limited. Specifically, examples include: (1) coating one side of the substrate film 1 with a resin composition for forming the adhesive layer 3 and drying it to form the adhesive layer 3, and then bonding the release film 4 to the adhesive layer 3; (2) coating the surface of the release film 4 with a resin composition for forming the adhesive layer 3 and drying it to form the adhesive layer 3, and then bonding the substrate film 1 to the adhesive layer 3, etc., but any method can be used.

[0065] Figure 3 This is a cross-sectional view illustrating an embodiment of the optical component of the present invention. Figure 3 An optical component 20 with a surface protective film 10 attached is shown. For example... Figure 3 As shown, the surface protective film 11 with the peel-off film (refer to) Figure 2 The surface protective film (see reference) is in a state where the release film 4 is peeled off, exposing the adhesive layer 3. Figure 1 It is bonded to the substrate, namely the optical component 5, through the adhesive layer 3.

[0066] Examples of optical components include: 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 constituent parts of liquid crystal display devices such as liquid crystal display panels, and various optical devices such as measuring instruments. Other examples of optical components include: anti-reflective films, hard coatings, and transparent conductive films for touch panels.

[0067] According to the embodiment of the optical component, an antistatic agent layer is present on the surface of the surface protective film when the surface protective film is adhered to the substrate, i.e., the optical component (optical film). This reduces static electricity generated during handling or processing of the optical component. Consequently, the adsorption of substances that cause foreign matter such as dust or grime during the process can be suppressed, resulting in an optical component with fewer defects. Furthermore, when the surface protective film is peeled off from the optical component, the peeling static voltage is kept low, thus minimizing the possibility of damage to circuit components such as driver ICs, TFT elements, and gate line drive circuits. Therefore, for example, production efficiency in processes such as manufacturing liquid crystal display panels can be improved, and the reliability of the production process can be maintained.

[0068] Even when exposed to external gases or humid and hot environments, the surface protective film of the embodiment can suppress the increase (deterioration) of the surface resistivity of the antistatic agent layer on the surface. Therefore, the above-mentioned effect is not easily changed over time, thus having great industrial application value.

[0069] [Example]

[0070] Next, the invention will be further illustrated through examples.

[0071] (Example 1)

[0072] As an antistatic agent composition containing a conductive polymer, an antistatic agent A was formulated containing a polythiophene antistatic agent (BAYTRON PAG manufactured by STARK Corporation), an acrylic resin (PESRESIN SWX-079R manufactured by Takamatsu Oils & Fats Co., Ltd.), and a methylated melamine crosslinking agent (NICARAK MW-30HM manufactured by CARBIDE Industries, Ltd., Japan) in a solid component mass ratio of 30 / 100 / 10.

[0073] As an antistatic agent composition containing nano-carbon, an antistatic agent B was formulated containing a carbon nanotube dispersion (DENATRON CD-100 manufactured by NAGASE CHEMTEX), an acrylic resin (PESRESIN SWX-079R manufactured by Takamatsu Oils & Fats Co., Ltd.), and a methylated melamine crosslinking agent (NICARAK MW-30HM manufactured by CARBIDE Industries, Ltd., Japan) in a solid component mass ratio of 10 / 100 / 10.

[0074] An adhesive was formulated consisting of a copolymer of 80 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of butyl acrylate, 7 parts by weight of methoxy polyethylene glycol (400) methacrylate, and 3 parts by weight of 2-hydroxyethyl acrylate. This adhesive is an acrylic adhesive. To obtain adhesive composition 1, 0.3 parts by weight of lithium bis(trifluoromethanesulfonyl)imide as an antistatic agent and 2 parts by weight of "CORONATE HX (manufactured by TOSOH Corporation)" as an isocyanate curing agent were added to 100 parts by weight of a 40% ethyl acetate solution of this adhesive, and the mixture was stirred and mixed.

[0075] Antistatic agent A was diluted 10 times with water / ethanol (water / ethanol mass ratio 50 / 50) to obtain a first coating. The first coating was applied to the surface of a 38 μm thick polyethylene terephthalate film (PET film, substrate film) to achieve a thickness of 0.15 μm after drying, and then dried in a 120°C hot air circulating oven for 1 minute. This formed the first layer.

[0076] Antistatic agent B was diluted 10 times with water / ethanol (water / ethanol mass ratio 50 / 50) to obtain a second coating. The second coating was applied to the surface of the first layer to achieve a thickness of 0.05 μm after drying, and then dried in a hot air circulating oven at 120°C for 1 minute. This formed the second layer.

[0077] Through the above processes, an antistatic film is obtained by stacking the substrate film (PET film), the first layer (antistatic agent A), and the second layer (antistatic agent B) in this order.

[0078] On the side of the PET film without the antistatic agent layer, adhesive composition 1 is applied using a spreader to achieve a thickness of 20 μm after drying, and then dried in a hot air circulating oven at 120°C for 3 minutes. This forms the adhesive layer.

[0079] A release film (25 μm thick) treated with a silicone release agent (DIAFOIL MRF-25 manufactured by Mitsubishi Chemical Corporation) was laminated onto the surface of the adhesive layer to obtain a surface protective film with the release film. The obtained surface protective film with the release film was cured at 40°C for 3 days to obtain the surface protective film of Example 1.

[0080] (Example 2)

[0081] Except that the thickness of both the first and second layers is set to 0.1 μm, the surface protective film of Example 2 is made in the same manner as in Example 1.

[0082] (Example 3)

[0083] Except that the thickness of the first layer is set to 0.05 μm and the thickness of the second layer is set to 0.15 μm, the surface protective film of Example 3 is made in the same manner as in Example 1.

[0084] (Example 4)

[0085] Except for the adhesive and curing agent, the surface protective film of Example 4 was made in the same manner as in Example 2.

[0086] As an adhesive, urethane adhesive (ARACOAT FT200 manufactured by Arakawa Chemical Industry Co., Ltd.) is used instead of acrylic adhesive. As a curing agent, 5.7 parts by weight of "ARACOAT CL2503 manufactured by Arakawa Chemical Industry Co., Ltd. (containing 40% by weight of non-volatile components)" is used instead of 2 parts by weight of "CORONATE HX manufactured by TOSOH Co., Ltd."

[0087] (Example 5)

[0088] Except that polyester resin (VYLONAL MD-1480 manufactured by Toyobo) was used instead of acrylic resin (PESRESIN SWX-079R manufactured by Takamatsu Oil Co., Ltd.), the surface protective film of Example 5 was made in the same manner as in Example 2.

[0089] (Comparative Example 1)

[0090] Except that the thickness of the first layer was set to 0.2 μm and there was no second layer, the surface protective film of Comparative Example 1 was obtained in the same manner as in Example 1.

[0091] (Comparative Example 2)

[0092] Except for the absence of a first layer and the setting of the thickness of the second layer to 0.2 μm, the surface protective film of Comparative Example 2 was obtained in the same manner as in Example 1.

[0093] (Comparative Example 3)

[0094] Except that a single-layer antistatic agent layer was used instead of a two-layer antistatic agent layer, the surface protective film of Comparative Example 3 was made in the same manner as in Example 2.

[0095] The single-layer antistatic agent layer is formed by coating an antistatic agent to achieve a thickness of 0.2 μm after drying. The antistatic agent is a mixture of antistatic agent A and antistatic agent B in a solid component mass ratio of 50 / 50.

[0096] (Comparative Example 4)

[0097] Except for reversing the positions of the first and second layers, the surface protective film of Comparative Example 4 was obtained in the same manner as in Example 2.

[0098] (Comparative Example 5)

[0099] Except for the absence of the first and second layers, the surface protective film of Comparative Example 5 was made in the same manner as in Example 1.

[0100] The following describes the methods and results of the evaluation experiment.

[0101] (Method for determining the inherent surface resistivity of a protective film)

[0102] The surface intrinsic resistance (Ω / □) of the surface protective film was measured using a high-performance high resistivity meter (HIRESTA-UP manufactured by Mitsubishi Chemical Analysis Technology Co., Ltd., under the conditions of applying a voltage of 100V and measuring for 30 seconds.

[0103] (Evaluation method for resistance to damp heat)

[0104] After the surface protective film was placed at 60°C and 90% relative humidity for a predetermined period (1 day or 30 days), it was placed at 23°C and 50% relative humidity for 1 hour. The intrinsic surface resistivity (Ω / □) of the surface protective film was measured using a high-performance high resistivity meter (HIRESTA-UP, manufactured by Mitsubishi Chemical Analytical Technology Co., Ltd., with an applied voltage of 100V and a measurement time of 30 seconds.

[0105] (Evaluation methods for exposure resistance)

[0106] The surface protective film was placed in an air-exposed state at a temperature of 23°C and a relative humidity of 50% for a predetermined period (1 day or 30 days). The intrinsic surface resistivity (Ω / □) of the surface protective film was measured using a high-performance high resistivity meter (HIRESTA-UP, manufactured by Mitsubishi Chemical Analytical Technology Co., Ltd., with an applied voltage of 100V and a measurement time of 30 seconds).

[0107] <Method for determining the low-speed adhesion of surface protective films>

[0108] The TAC film used as a protective film for polarizers was laminated onto the surface of a glass plate using a laminating machine. Then, a protective film cut to a width of 25 mm was laminated onto the surface of the polarizer and stored for one day at 23°C and 50% RH. Afterward, the strength of the protective film when peeled at a peel speed of 0.3 m / min in a 180° direction was measured using a tensile testing machine and taken as the low-speed adhesive force (N / 25 mm).

[0109] <Method for determining the high-speed adhesion of surface protective films>

[0110] The TAC film used as a protective film for polarizers was laminated onto the surface of a glass plate using a laminating machine. Then, a protective film cut to a width of 25 mm was laminated onto the surface of the polarizer and stored for one day at 23°C and 50% RH. Afterward, the strength of the protective film when peeled at a peeling speed of 30 m / min was measured using a high-speed peel tester (TESTER Industrial Manufacturing), and this was taken as the high-speed adhesive force (N / 25 mm).

[0111] <Method for determining the peel electrostatic voltage of the surface protective film>

[0112] The TAC film used as a protective film for polarizers was laminated onto the surface of a glass plate using a laminating machine. Then, a surface protective film cut to a width of 25 mm was laminated onto the surface of the polarizer and stored for one day at 23°C and 50% RH. Afterwards, the surface protective film was peeled off using a high-speed peel tester (TESTER Industrial Co., Ltd.) at a peeling speed of 30 m / min, while simultaneously measuring the surface potential of the polarizer surface every 10 ms using a surface potentiometer (KEYENCE Co., Ltd.). The maximum absolute value of this surface potential was taken as the peel electrostatic voltage (kV).

[0113] <Methods for confirming the surface contamination of surface protective films>

[0114] The TAC film used as a protective film for polarizers was laminated onto the surface of a glass plate using a laminating machine. Then, a surface protective film cut to a width of 25 mm was laminated onto the surface of the polarizer and stored for 3 days at 23°C and 50% RH. Afterward, the surface protective film was peeled off, and the surface contamination of the polarizer was visually observed. As a criterion for judging surface contamination, a condition with no contamination transfer was marked as "○" (good), and a condition with confirmed contamination transfer was marked as "×" (bad).

[0115] Regarding the surface protective films of Examples 1-5 and Comparative Examples 1-5, the measurement results are shown in Tables 1-3. In Tables 1-3, "CNT" represents the ratio of the thickness of the second layer to the total thickness of the first and second layers. "PEDOT" represents the ratio of the thickness of the first layer to the total thickness of the first and second layers. "CNT / PEDOT(Mix)" represents the mixing ratio of antistatic agent B and antistatic agent A in the antistatic agent (mixture) when a single-layer structure antistatic agent layer is used. "100 (50 / 50)" means that the mass ratio of the solid components of antistatic agent A and antistatic agent B is 50%.

[0116] "Antistatic agent layer stacking order" indicates the stacking sequence of the first and second layers. "○" indicates that the stacking sequence of the substrate film, the first layer, and the second layer is "substrate film / second layer / first layer".

[0117] The "○" in "acrylic resin" indicates that the adhesive resin for the first and second layers is acrylic resin. The "○" in "polyester resin" indicates that the adhesive resin for the first and second layers is polyester resin.

[0118] The "○" in "Acrylic adhesive" indicates that an acrylic adhesive is used as the binder. The "○" in "Ethyl urethane adhesive" indicates that an urethane adhesive is used as the binder. The intrinsic surface resistivity of 1.0E+09 represents 1.0 × 10⁹. 1.0E+13< indicates that the measurement exceeds the measurement limit (1.0 × 10¹³) of the measuring device (high-performance high resistivity meter), thus exceeding the range.

[0119] Table 1

[0120] Example 1 Example 2 Example 3 Example 4 CNT (%) 25 50 75 50 PEDOT (%) 75 50 25 50 CNT / PEDOT(Mix) Antistatic agent layered forward and reverse acrylic resin ○ ○ ○ ○ Polyester resin acrylic adhesives ○ ○ ○ urethane adhesive ○ Inherent surface resistivity (Ω / □) 1.0E+09 9.4E+08 8.2E+08 9.2E+08 Moist heat resistance for 1 day 8.7E+08 9.1E+08 8.8E+08 9.2E+08 30 days 9.8E+08 9.6E+08 1.0E+09 9.7E+08 Exposure resistance for 1 day 1.1E+09 9.5E+08 8.3E+08 9.3E+08 30 days 1.3E+09 9.3E+08 8.6E+08 9.3E+08 Low-speed adhesion (N / 25mm) 0.04 0.04 0.04 0.02 High-speed adhesion (N / 25m) 0.62 0.60 0.62 0.43 Stripping static voltage (kV) 0.3 0.3 0.2 0.3 Surface contamination for 3 days ○ ○ ○ ○

[0121] Table 2

[0122] Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 CNT (%) 50 100 PEDOT (%) 50 100 CNT / PEDOT(Mix) 100(50 / 50) Antistatic agent layered forward and reverse acrylic resin ○ ○ ○ Polyester resin ○ acrylic adhesives ○ ○ ○ ○ urethane adhesive Inherent surface resistivity (Ω / □) 8.4E+08 9.0E+08 7.5E+08 8.3E+08 Moist heat resistance for 1 day 8.3E+08 5.3E+08 8.9E+08 8.8E+08 30 days 9.1E+08 5.1E+10 6.8E+10 4.2E+09 Exposure resistance for 1 day 8.4E+08 1.1E+09 7.7E+09 8.6E+08 30 days 9.5E+08 7.7E+11 8.9E+11 3.7E+10 Low-speed adhesion (N / 25mm) 0.04 0.04 0.03 0.04 High-speed adhesion (N / 25mm) 0.61 0.64 0.60 0.61 Stripping static voltage (kV) 0.3 0.3 0.3 0.3 Surface contamination for 3 days ○ ○ ○ ○

[0123] Table 3

[0124] Comparative Example 4 Comparative Example 5 CNT (%) 50 PEDOT (%) 50 CNT / PEDOT(Mix) Antistatic agent layered forward and reverse ○ acrylic resin ○ ○ Polyester resin acrylic adhesives ○ ○ urethane adhesive Inherent surface resistivity (Ω / □) 9.1E+08 1.0E+13< Moist heat resistance for 1 day 8.7E+08 1.0E+13< 30 days 9.8E+09 1.0E+13< Exposure resistance for 1 day 1.03E+09 1.0E+13< 30 days 4.4E+10 1.0E+13< Low-speed adhesion (N / 25mm) 0.04 0.04 High-speed adhesion (N / 25mm) 0.61 0.68 Stripping static voltage (kV) 0.3 0.9 Surface contamination for 3 days ○ ○

[0125] The following information can be obtained from the measurement results shown in Tables 1 to 3.

[0126] Even when exposed to external gases and humid and hot environments, the surface resistivity of the antistatic agent layer in Examples 1-5 did not increase (deteriorate).

[0127] On the other hand, in Comparative Example 1, where the antistatic agent layer was formed only by the first layer (containing a conductive polymer), it was observed that the surface resistance of the antistatic agent layer increased (deteriorated) when exposed to external gases.

[0128] In Comparative Example 2, where the antistatic agent layer was formed only by the second layer (containing nano-carbon), it was observed that the surface resistance of the antistatic agent layer on the surface increased (deteriorated) under humid and hot conditions.

[0129] In Comparative Example 3, where the antistatic agent layer is a single-layer structure composed of a mixture of antistatic agents A and B instead of a two-layer structure, the surface resistivity of the antistatic agent layer slightly increases (deterioration) under humid and hot conditions. Under conditions exposed to external gases, the surface resistivity of the antistatic agent layer on the surface increases significantly (deterioration).

[0130] In Comparative Example 4, where the order of the antistatic agent layers was reversed compared to Examples 1-5, it was observed that the surface resistance of the antistatic agent layer increased (deteriorated) in environments exposed to external gases and in humid and hot environments.

[0131] In Comparative Example 5, where no antistatic agent layer was provided, it was assumed that static electricity would be easily generated during the process due to the high surface resistance of the surface protective film.

[0132] The surface protective film of this embodiment can be bonded to optical components such as polarizers, retardation plates, lens films, and other various optical components during manufacturing processes to protect their surfaces. Even when exposed to external gases or humid environments, the surface protective film of this embodiment can suppress the increase (deterioration) of the surface resistivity of the antistatic agent layer. The surface protective film of this embodiment can suppress static electricity generated during the handling or processing of optical products with the surface protective film bonded to them during the manufacturing process, thereby reducing the adsorption of dust or particulate matter from the environment. When peeling off the used surface protective film from the polarizer or retardation plate assembled into the liquid crystal display panel, the surface protective film of this embodiment can suppress significant peeling static electricity, thus minimizing the possibility of damage to circuits such as driver ICs. Therefore, it can improve the yield rate of the manufacturing process and has significant industrial application value.

Claims

1. A surface protective film, wherein, have: The substrate film is made of a transparent resin; An antistatic agent layer is formed on one side of the substrate film; and An adhesive layer is formed on the side of the substrate film opposite to the antistatic agent layer. The antistatic agent layer comprises: The first layer comprises a conductive polymer; and The second layer is disposed on the opposite side of the substrate film relative to the first layer and contains nano-carbon.

2. The surface protective film according to claim 1, wherein, A release film is attached to the adhesive layer on the opposite side to the substrate film.

3. The surface protective film according to claim 1 or 2, wherein, The adhesive layer is composed of an acrylic adhesive.

4. An optical component having a surface protective film adhered to it according to any one of claims 1 to 3.

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