Surface protective films and optical components

Abstract

To provide a surface protection film and optical component that are less prone to an increase in surface resistivity and that are easy to inspect visually. [Solution] The surface protection film 10 comprises a base film 1 made of a transparent resin, an antistatic 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 to the antistatic layer 2. The antistatic layer 2 contains nanocarbon. The thickness of the antistatic layer 2 is 0.05 μm or more and 1.50 μm or less. The haze value of the surface protection film 10 is 4.0% or less. The total light transmittance of the surface protection film 10 is 80.0% or more.

Description

Technical Field

[0001] The present invention relates to a surface protection film and an optical component.

Background Art

[0002] Optical films such as polarizing plates, retardation plates, lens films for displays, antireflection films, hard coat films, transparent conductive films for touch panels, and optical products such as displays using these are used. When manufacturing and transporting optical products, a surface protection film can be laminated on the surface of the optical film to prevent surface contamination and damage in subsequent processes.

[0003] The appearance inspection of an optical product can be performed with the surface protection film laminated on the optical film. When performing the appearance inspection with the surface protection film laminated, the labor of peeling off the surface protection film and laminating it again can be saved, so the work efficiency can be improved.

[0004] The surface protection film is formed with, for example, an antistatic layer on the surface. By providing the antistatic layer, static electricity can be suppressed during the transportation and handling of the optical product laminated with the surface protection film in the manufacturing process of the optical product. Thereby, adsorption of dust and dirt in the environment can be suppressed.

[0005] Patent Document 1 discloses a surface protection film provided with an antistatic layer on one side of a polyester film and a stain prevention layer on that layer. The antistatic layer contains a conductive polymer obtained by polymerizing thiophene and / or a thiophene derivative. In this surface protection film, the surface resistivity may increase with the passage of time due to oxidative degradation and photo degradation.

[0006] The surface protection film disclosed in Patent Document 2 has an antistatic layer containing polyaniline sulfonic acid and polythiophenes. Patent Document 2 states that the use of polyaniline sulfonic acid in the antistatic layer can suppress the increase (degradation) of surface resistivity. However, the transparency of this surface protection film may be affected by the influence of polyaniline sulfonic acid. Therefore, there was room for improvement in terms of the ease of visual inspection.

[0007] The surface protective film disclosed in Patent Document 3 has an antistatic layer containing a resin having active hydrogen groups, a polyurethane resin, a polyisocyanate, and carbon nanotubes. This protective film may have a higher haze value and lower transparency, which could affect the ease of visual inspection. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-026817 [Patent Document 2] Republished Gazette No. WO2018 / 012545 [Patent Document 3] Japanese Patent Publication No. 2007-105928 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] One aspect of the present invention has been made in view of the above circumstances, and aims to provide a surface protective film and optical component that are less prone to an increase in surface resistivity and that are easy to inspect visually. [Means for solving the problem]

[0010] One aspect of the present invention provides a surface protection film comprising a base film made of a transparent resin, an antistatic layer formed on one side of the base film, and an adhesive layer formed on the side of the base film opposite to the antistatic layer, wherein the antistatic layer contains nanocarbon, the thickness of the antistatic layer is 0.05 μm or more and 1.50 μm or less, the haze value is 4.0% or less, and the total light transmittance is 80.0% or more.

[0011] Regarding the thickness of the antistatic layer, a thinner layer tends to result in a higher haze value, while a thicker layer tends to reduce the total light transmittance due to the color of the antistatic agent itself. Therefore, when transparency is a priority, the thickness of the antistatic layer is preferably around 0.10 μm to 0.5 μm, and most preferably around 0.15 μm to 0.25 μm.

[0012] The surface protective film may have a release film laminated to the side of the adhesive layer opposite to the base film.

[0013] The adhesive layer is preferably made of an acrylic adhesive.

[0014] Another aspect of the present invention provides an optical component in which the surface protective film is bonded to a substrate. [Effects of the Invention]

[0015] One aspect of the present invention provides a surface protective film and optical component that are less prone to an increase in surface resistivity and are easy to inspect visually. [Brief explanation of the drawing]

[0016] [Figure 1] This is a cross-sectional view showing the surface protective film of the embodiment. [Figure 2] This is a cross-sectional view showing a surface protective film with a release film attached to a surface protective film of the embodiment. [Figure 3] This is a cross-sectional view showing an example of an optical component.

Embodiments for Carrying out the Invention

[0017] Hereinafter, based on embodiments, the present invention will be described in detail. FIG. 1 is a cross-sectional view showing the surface protection film of the embodiment. As shown in FIG. 1, the surface protection film 10 according to the embodiment includes a base film 1, an antistatic layer 2, and an adhesive layer 3. The antistatic layer 2 is formed on one surface (the upper surface in FIG. 1) of the base film 1. The adhesive layer 3 is formed on the surface of the base film 1 opposite to the antistatic layer 2 (the lower surface in FIG. 1).

[0018] [Base Film] As the base film 1, a base film made of a resin having transparency and flexibility is used. Thereby, the appearance inspection of the optical product can be performed in a state where the surface protection film 10 is bonded to the optical product as the adherend. As the base film 1, preferably, a film (polyester film) formed of a polyester such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate is used. In addition to the polyester film, a film made of other resins can also be used as long as it has the required strength and optical suitability. The base film 1 may be an unstretched film or a uniaxially or biaxially stretched film. The stretching ratio of the stretched film and the orientation angle of the axis method formed with the crystallization of the stretched film may be controlled to specific values.

[0019] The haze value of the base film 1 is preferably 6.0% or less. By setting the haze value of the base film 1 to 6.0% or less, the haze value of the surface protection film 10 can be made 4.0% or less. The haze value of the surface protection film 10 tends to be lower than the haze value of the base film 1 alone. It is presumed that the reason for the lower haze value of the surface protection film 10 is as follows. Since the surface of the base film 1 is covered by the antistatic layer 2 and the adhesive layer 3, the fine irregularities on the surface of the base film 1 are less likely to appear on the surface of the surface protection film 10. Therefore, the scattered light caused by the surface irregularities is reduced. As a result, the haze value of the surface protection film 10 becomes lower. The "haze value" is also referred to as haze, haze, or Haze. The haze value can be measured, for example, in accordance with JIS K7136 "Plastics - Method for Determining Haze of Transparent Materials".

[0020] "Transparent" means, for example, that the visible light transmittance calculated as the average value of the transmittance in the thickness direction over the entire wavelength range when measured within the range of measurement wavelengths of 380 nm to 780 nm is 50% or more (preferably 70% or more, more preferably 80% or more). The light transmittance can be measured in accordance with "Plastics - Method for Determining Total Light Transmittance and Total Light Reflectance" specified in JIS K 7375:2008.

[0021] The thickness of the base film 1 is not particularly limited, but can be, for example, 12 μm to 100 μm. A thickness of the base film 1 of 20 μm to 50 μm is more preferable because it makes the base film 1 easier to handle. If necessary, the surface of the base film 1 may be subjected to an easy adhesion treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0022] [Antistatic layer] The antistatic layer 2 contains nanocarbon. Examples of nanocarbon used in the antistatic layer 2 include carbon nanotubes (CNTs), graphene, and fullerenes. Carbon nanotubes include single-walled (WW) CNTs and multi-walled (WML) CNTs. Single-walled CNTs, WML CNTs, graphene, and fullerenes all have excellent antistatic properties. Of these, WML CNTs, graphene, and fullerenes are expensive, so WML CNTs are easier to use. Nanocarbon may be made from a single material or from a combination of multiple materials.

[0023] The surface protective film 10 uses nanocarbon in the antistatic layer 2, thereby suppressing the increase (degradation) in surface resistivity due to oxidative degradation and photodegradation of the antistatic layer 2.

[0024] The amount of nanocarbon added to the antistatic layer 2 may be, for example, 0.1% by mass or more and 10% by mass or less. If the amount of nanocarbon added is above the lower limit of the above range, the effect of suppressing the increase (degradation) in surface resistivity due to oxidative degradation and photodegradation of the antistatic layer 2 can be enhanced. If the amount of nanocarbon added is below the upper limit of the above range, discoloration due to nanocarbon can be suppressed and the total light transmittance of the surface protective film 10 can be increased.

[0025] The antistatic layer 2 can be formed by applying an antistatic agent containing nanocarbon to the base film 1. Since nanocarbon alone has low film strength, it is preferable to add a binder resin, dispersant, etc., to the antistatic agent. Examples of binder resins include acrylic resin, epoxy resin, urethane resin, phenolic resin, and polyester resin. If necessary, a crosslinking agent may be added to the antistatic agent to crosslink (also called harden) the binder resin. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelate compounds.

[0026] To improve the coating properties of the antistatic agent, the adhesion between the antistatic layer 2 and the base film 1, the film strength of the antistatic layer 2, and the durability of the antistatic layer 2 (such as abrasion resistance and solvent resistance), ultraviolet absorbers, antioxidants, leveling agents (wettability improvers), adhesion improvers, etc., may be added to the antistatic agent.

[0027] As an antistatic agent, commercially available antistatic paints may be used. Examples of commercially available products include Denatron C-300, Denatron CD-001 (both manufactured by Nagase Chemtec), Corcoat CS-3002, and Corcoat CS-3202 (both manufactured by Corcoat Co., Ltd.).

[0028] The method for forming the antistatic layer 2 may be a known method. For example, the following method can be used to form the antistatic layer 2: A coating containing nanocarbon (for example, an antistatic agent containing nanocarbon and a binder resin) is applied to the surface of the base film 1 using a known coating method. Coating methods include reverse coating, comma coating, gravure coating, slot die coating, Meyer bar coating, and air knife coating. The formed coating is solidified by heating, ultraviolet irradiation, etc. This forms the antistatic layer 2.

[0029] The thickness of the antistatic layer 2 is between 0.05 μm and 1.50 μm. Since the thickness of the antistatic layer 2 is 0.05 μm or more, the effect of suppressing the influence of the fine irregularities on the surface of the base film 1 and lowering the haze value can be enhanced. Since the thickness of the antistatic layer 2 is 1.50 μm or less, discoloration by nanocarbon can be suppressed and the total light transmittance of the surface protective film 10 can be increased. Therefore, visual inspection of optical products becomes easier. The thickness of the antistatic layer 2 is the thickness after the paint (antistatic agent) has hardened.

[0030] If the thickness of the antistatic layer 2 is less than 0.05 μm, the effect of suppressing the influence of fine irregularities on the surface of the base film 1 and lowering the haze value is reduced. If the thickness of the antistatic layer 2 exceeds 1.50 μm, the total light transmittance of the surface protective film 10 decreases due to coloring by nanocarbon, which affects the ease of visual inspection of optical components.

[0031] Regarding the thickness of the antistatic layer 2, a thinner layer tends to result in a higher haze value, while a thicker layer tends to reduce the total light transmittance due to the color of the antistatic agent itself. Therefore, if transparency is a priority, a thickness of approximately 0.10 μm to 0.5 μm for the antistatic layer 2 is preferable. A thickness of approximately 0.15 μm to 0.25 μm is most preferable.

[0032] The thickness of the antistatic layer 2 is such that the surface resistivity of the antistatic layer 2 is 10 to the power of 7 (10 7 )~10 to the power of 9 (10 9 It is best to adjust it to approximately ). To adjust the surface resistivity, one method may be used by adjusting the thickness of the antistatic agent coating, or by adjusting the ratio of nanocarbon to binder resin, etc., in the antistatic agent. The surface resistivity can be measured using a high resistivity meter (HIRESTA®-UP, manufactured by Mitsubishi Chemical Analytec Co., Ltd.).

[0033] [Adhesive layer] The adhesive layer 3 preferably adheres to the surface of the adherend, can be easily peeled off after use, and does not easily contaminate the adherend. Examples of adhesives used in the adhesive layer 3 include acrylic adhesives, urethane adhesives, and rubber adhesives. Adhesive resins such as polyethylene vinyl acetate resin can also be used as adhesives. Among these, acrylic adhesives and urethane adhesives are particularly preferred.

[0034] As an acrylic adhesive, an adhesive obtained by adding a crosslinking agent to a (meth)acrylic polymer (acrylic resin composition) is preferred. The (meth)acrylic polymer is preferably a polymer copolymerized from a main monomer such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, or isononyl acrylate, a comonomer such as acrylonitrile, vinyl acetate, methyl methacrylate, or ethyl acrylate, and a functional monomer such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, or N-methylol methacrylamide. The monomer composition constituting the (meth)acrylic polymer is preferably 50% or more of (meth)acrylic monomers, and may also be 100% of (meth)acrylic monomers.

[0035] The crosslinking agent crosslinks the (meth)acrylic polymer. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, melamine compounds, and metal chelate compounds. The amount of crosslinking agent added should be determined considering the type of (meth)acrylic polymer, degree of polymerization, and amount of functional groups. The amount of crosslinking agent added is not particularly limited, but it is preferable to use about 0.5 to 1.0 parts by mass of the crosslinking agent per 100 parts by mass of the (meth)acrylic polymer.

[0036] As a urethane-based adhesive, a polyurethane resin containing a polyol component and a polyisocyanate component is preferred. The polyurethane resin should be selected considering factors such as tackiness, wettability, and adhesion to the substrate. The polyol component and polyisocyanate component are not particularly limited. The polyurethane resin may be used alone or in combination of two or more types.

[0037] Examples of polyol components include polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, and castor oil-based polyols. These polyol components may be used individually or in combination of two or more.

[0038] Polyisocyanate components that can be used include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and diisocyanate polymers. These polyisocyanate components may be used individually or in combination of two or more types.

[0039] Commercially available polyurethane adhesives include Cyabein® SH-101, SH-101M, SP-205, SP-220 (manufactured by Toyo Chem Co., Ltd.), Aracoat® FT100, FT200 (manufactured by Arakawa Chemical Industries, Ltd.), UN1175, UN1176 (manufactured by Daido Chemical Industries, Ltd.), and others. The adhesive layer may be formed by crosslinking or curing the polyurethane adhesive.

[0040] The adhesive layer 3 may optionally contain a crosslinking catalyst as an additive to promote the crosslinking reaction. The adhesive layer 3 may optionally contain an adhesion enhancer, such as a silane coupling agent, as an additive to improve the adhesion between the substrate film 1 and the adhesive. The adhesive layer 3 may optionally contain additives such as an antistatic agent, an antioxidant, or an ultraviolet absorber.

[0041] The thickness of the adhesive layer 3 is not particularly limited, but is preferably 5 μm to 40 μm, and more preferably 10 μm to 30 μm. The adhesive strength (low-speed adhesive strength) of the surface protective film 10 to the surface of the adherend at a peeling speed of 0.3 m / min is preferably 0.3 N / 25 mm or less, and more preferably 0.2 N / 25 mm or less.

[0042] The adhesive strength of the surface protective film 10 to the surface of the adherend at a peeling speed of 30 m / min (high-speed adhesive strength) is preferably 0.8 N / 25 mm or less. If the high-speed adhesive strength exceeds 0.8 N / 25 mm, there is a risk that the workability when peeling off the surface protective film 10 after use will be poor. Known methods can be used to adjust the adhesive strength, such as changing the adhesive composition, adjusting the amount of curing agent added, or adjusting the amount of tackifier or adhesive strength modifier added.

[0043] A known method can be used to form the adhesive layer 3 on the surface of the base film 1. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Meyer bar coating, and air knife coating can be used.

[0044] Known methods can be used for forming the adhesive layer 3 and for laminating the release film 4 to the adhesive layer 3. Specifically, examples include (1) applying a resin composition for forming the adhesive layer 3 to one side of the base film 1, drying it to form the adhesive layer 3, and then laminating the release film 4 to the adhesive layer 3, and (2) applying a resin composition for forming the adhesive layer 3 to the surface of the release film 4, drying it to form the adhesive layer 3, and then laminating the base film 1 to the adhesive layer 3. Any of these methods may be used.

[0045] The haze value of the surface protective film 10 is preferably 4.0% or less. A haze value of 4.0% or less provides good visibility, making it easy to perform visual inspection of the optical product to which the surface protective film 10 is attached.

[0046] The total light transmittance of the surface protective film 10 is preferably 80.0% or higher. When the total light transmittance is 80.0% or higher, visibility is good, and the appearance of the optical product to which the surface protective film 10 is attached can be easily inspected.

[0047] The surface resistivity of the surface protection film 10 is required to not increase significantly even when the surface protection film 10 is exposed to air. The surface resistivity is preferably between 1.0 × 10⁸ and 9.9 × 10⁹. For example, if the surface resistivity of the surface protection film 10 is 1.0 × 10⁸ before air exposure, it is preferable that it remains at 9.9 × 10⁹ or less (an increase of 9800% or less) even after 30 days of air exposure, and more preferably at 5.0 × 10⁹ or less (an increase of 4900% or less).

[0048] The durability of the surface protection film 10 when exposed to air is called "air exposure resistance." Air exposure resistance can be evaluated by the surface resistivity of the surface protection film 10 when exposed to air. For example, the following method can be used to evaluate the air exposure resistance characteristics: The surface protection film 10 is exposed to air under conditions of a temperature of 23°C and a relative humidity of 50%, and left for a predetermined period (for example, 30 days). The surface resistivity (Ω / □) of the surface protection film 10 is measured using a high-performance high-resistivity meter (High Resista®-UP manufactured by Nitto Seiko Analytech Co., Ltd.) under conditions of an applied voltage of 100V and a measurement time of 30 seconds.

[0049] Figure 2 is a cross-sectional view showing a surface protective film 11 with a release film 4 laminated to a surface protective film 10. As shown in Figure 2, any known release film can be used as the release film 4. The release film 4 may be a polyethylene film, a polyolefin film such as a polypropylene film, or a fluorofilm, and may be used as a standalone film. The release film 4 may also be a resin film 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, long-chain alkyl group-containing resins, and fluororesins. Among these, a release film 4 made by treating a PET film with a silicone-based release agent is preferred. The thickness of the release film 4 is not particularly limited, but 12 μm to 38 μm is preferred from the standpoint of workability and cost.

[0050] Figure 3 is a cross-sectional view showing an example of an optical component, an optical component 20. As shown in Figure 3, the optical component 20 has a surface protection film 10 laminated to the surface of an optical product 5. The optical component 20 is manufactured as follows: The release film 4 of the surface protection film 11 with a release film (see Figure 2) is peeled off to expose the adhesive layer 3, and then this surface protection film 10 is laminated to the optical product 5, which is the object to be adhered, by the adhesive layer 3.

[0051] Examples of optical products 5 include optical films such as polarizers, phase difference plates, lens films, polarizers that also function as phase difference plates, and polarizers that also function as lens films. Such optical products 5 are used as components of liquid crystal display devices such as liquid crystal display panels and various instruments. Optical products 5 also include optical films such as anti-reflective films, hard-coat films, and transparent conductive films for touch panels.

[0052] In the optical component 20, an antistatic layer 2 is present on the surface of the surface protective film 10. Therefore, static electricity can be kept low during the transport and handling of the optical component 20. Thus, the adhesion of foreign matter such as dust and dirt during the process is suppressed. In the optical component 20, when the surface protective film 10 is peeled off from the optical product 5, the peeling voltage can be kept low. Therefore, there is less risk of damaging circuit components such as driver ICs, TFT elements, and gate line drive circuits of the optical product 5. Thus, for example, production efficiency can be increased in the process of manufacturing liquid crystal display panels, and the reliability of the production process can be maintained. The surface protection film 10 can suppress the increase in surface resistivity when exposed to air. Because it can suppress the increase in surface resistivity over a long period, it has great industrial value. [Examples]

[0053] Next, the present invention will be further explained with reference to examples. (Example 1) Antistatic agent A was prepared containing a carbon nanotube dispersion (Denatron® CD-100, manufactured by Nagase ChemteX Corporation), an acrylic resin (Pesresin® SWX-079R, manufactured by Takamatsu Oil & Fat Co., Ltd.), and a methylated melamine crosslinking agent (Nikarac® MW-30HM, manufactured by Nippon Carbide Industries Co., Ltd.) in a solid content mass ratio of 10 / 100 / 10. Antistatic agent A is an antistatic agent composition containing nanocarbons.

[0054] An adhesive was prepared consisting of a copolymer of 80 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of butyl acrylate, 7 parts by mass of methoxypolyethylene glycol (400) methacrylate, and 3 parts by mass of 2-hydroxyethyl acrylate. This adhesive is an acrylic adhesive. To 100 parts by mass of a 40% ethyl acetate solution of this adhesive, 0.3 parts by mass of lithium bis(trifluoromethanesulfonyl)imide as an antistatic agent and 2 parts by mass of an isocyanate-based curing agent (Coronate® HX, manufactured by Tosoh Corporation) were added and mixed to obtain adhesive composition D.

[0055] Antistatic agent A was diluted 10 times with water / ethanol (water / ethanol mass ratio 50 / 50) to obtain antistatic coating B. Antistatic coating B was applied to the surface of a 38 μm thick polyethylene terephthalate film (PET film, base film) (haze value 4.6%) so that the thickness after drying was 0.05 μm, and the coating film was dried in a hot air circulating oven at 120°C for 1 minute. This formed an antistatic layer on the PET film.

[0056] Adhesive composition D was applied to the side of a PET film that did not have an antistatic layer laminated to it using an applicator, so that the thickness after drying was 20 μm. The coating was then dried in a hot air circulating oven at 120°C for 3 minutes. This formed an adhesive layer.

[0057] A release film (25 μm thick) treated with a silicone-based release agent (Mitsubishi Chemical Corporation's Diafoil® MRF-25) was laminated to the surface of the adhesive layer to obtain a surface protection film with a release film. The obtained surface protection film with a release film was aged at 40°C for 3 days to obtain the surface protection film of Example 1.

[0058] (Example 2) The surface protective film for Example 2 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 0.10 μm.

[0059] (Example 3) The surface protective film for Example 3 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 0.15 μm.

[0060] (Example 4) The surface protective film for Example 4 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 0.25 μm.

[0061] (Example 5) The surface protective film for Example 5 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 0.50 μm.

[0062] (Example 6) The surface protective film for Example 6 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 1.00 μm.

[0063] (Example 7) The surface protective film for Example 7 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic paint B were adjusted so that the thickness of the antistatic layer after drying was 1.50 μm.

[0064] (Example 8) The surface protective film for Example 8 was prepared in the same manner as in Example 4, except that a polyester resin (Vylonal® MD-1480 manufactured by Toyobo) was used instead of the acrylic resin (Pesresin® SWX-079R manufactured by Takamatsu Oil & Fat Co., Ltd.) used in Example 4.

[0065] (Example 9) Instead of the acrylic adhesive used in Example 4, a urethane adhesive (Aracoat® FT200, manufactured by Arakawa Chemical Industries, Ltd.) was used. Instead of 2 parts by mass of the isocyanate curing agent (Coronate HX) used in Example 4, 5.7 parts by mass of Aracoat® CL2503 (containing 40% by mass of non-volatile curing agent), manufactured by Arakawa Chemical Industries, Ltd., was used. The surface protective film of Example 9 was prepared in the same manner as in Example 4, except for these differences.

[0066] (Example 10) The surface protective film for Example 10 was prepared in the same manner as in Example 4, except that a PET film with a haze value of 5.6% was used instead of a PET film (base film) with a haze value of 4.6%.

[0067] (Comparative Example 1) A surface protective film for Comparative Example 1 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic coating B were adjusted so that the thickness of the antistatic layer after drying was 0.04 μm.

[0068] (Comparative Example 2) A surface protective film for Comparative Example 2 was prepared in the same manner as in Example 1, except that the dilution ratio and application amount of antistatic coating B were adjusted so that the thickness of the antistatic layer after drying was 2.00 μm.

[0069] (Comparative Example 3) A surface protection film for Comparative Example 3 was prepared in the same manner as in Example 4, except that a PET film with a haze value of 6.3% was used instead of a PET film (base film) with a haze value of 4.6%.

[0070] (Comparative Example 4) Antistatic agent C was prepared, containing a polythiophene-based antistatic agent (BAYTRON® PAG, manufactured by Stark GmbH), an acrylic resin (PESRESIN® SWX-079R, manufactured by Takamatsu Oil & Fat Co., Ltd.), and a methylated melamine crosslinking agent (Nikarac® MW-30HM, manufactured by Nippon Carbide Industries Co., Ltd.) in a solid content mass ratio of 30 / 100 / 10. Antistatic agent C is an antistatic agent composition containing a polythiophene-based antistatic agent. A surface protective film for Comparative Example 4 was prepared in the same manner as in Example 2, except that antistatic agent C was used instead of antistatic agent A.

[0071] The evaluation test methods and results are described below. (Method for measuring total light transmittance) The total light transmittance was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K7105.

[0072] (Method for measuring haze value) The haze value was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Co., Ltd.).

[0073] (Method for measuring the surface resistivity of a protective film) The surface resistivity (Ω / □) of the surface protective film was measured using a high-performance high-resistivity meter (HighResta®-UP, manufactured by Nitto Seiko Analytech Co., Ltd.) under the conditions of an applied voltage of 100V and a measurement time of 30 seconds.

[0074] (Method for measuring the thickness of the antistatic layer) The thickness of the antistatic layer of the surface protective film was determined using a JASCO V-770 ultraviolet-visible-near-infrared spectrophotometer, measuring the spectral reflectance in the measurement wavelength range of 300 to 900 nm at an incident angle of 5 degrees, and measured using the interference interval method.

[0075] (Method for evaluating resistance to air exposure) The surface protective film was left exposed to air at a temperature of 23°C and a relative humidity of 50% for a predetermined period (1 day or 30 days). The surface resistivity (Ω / □) of the surface protective film was measured using a high-performance high-resistivity meter (HighResta®-UP, manufactured by Nitto Seiko Analytech Co., Ltd.) under the conditions of an applied voltage of 100V and a measurement time of 30 seconds.

[0076] (Method for measuring the low-speed adhesive strength of surface protective film) A polarizing plate using TAC film as a polarizer protective film was laminated to the surface of a glass plate using a laminating machine. A surface protective film cut to a width of 25 mm was laminated to the surface of the polarizing plate. The polarizing plate with the surface protective film laminated was stored for one day in a test environment of 23°C × 50% RH. The strength was measured when the surface protective film was peeled off in a 180° direction at a peeling speed of 0.3 m / min using a tensile testing machine, and this was defined as the low-speed adhesive strength (N / 25 mm).

[0077] (Method for measuring the high-speed adhesive strength of surface protective films) A polarizing plate using TAC film as a polarizer protective film was laminated to the surface of a glass plate using a laminating machine. A surface protective film cut to a width of 25 mm was laminated to the surface of the polarizing plate. The polarizing plate with the surface protective film laminated was stored for one day in a test environment of 23°C × 50% RH. The strength when the surface protective film was peeled off at a peeling speed of 30 m / min using a high-speed peel tester (manufactured by Tester Industries) was measured and defined as the high-speed adhesive strength (N / 25 mm).

[0078] (Method for measuring the peel voltage of surface protective film) A polarizing plate using TAC film as a polarizer protective film was laminated to the surface of a glass plate using a laminating machine. A surface protective film cut to a width of 25 mm was laminated to the surface of the polarizing plate. The polarizing plate with the surface protective film laminated was stored for one day in a test environment of 23°C × 50% RH. While peeling off the surface protective film at a peeling speed of 30 m / min using a high-speed peel tester (manufactured by Tester Industries), the surface potential of the polarizing plate surface was measured every 10 ms using a surface potential meter (manufactured by Keyence Corporation), and the maximum absolute value of the surface potential was defined as the peel band voltage (kV).

[0079] (Method for checking the surface contamination properties of surface protective films) A polarizing plate using TAC film as a polarizer protective film was laminated to the surface of a glass plate using a laminating machine. A surface protective film cut to a width of 25 mm was laminated to the surface of the polarizing plate. The polarizing plate with the surface protective film laminated was stored for 3 days in a test environment of 23°C × 50% RH. The surface protective film was peeled off and the surface contamination of the polarizing plate was observed visually. As a criterion for judging surface contamination, "○" (Good) was used if there was no contamination transfer to the polarizing plate, and "×" (No Good) was used if contamination transfer to the polarizing plate was confirmed.

[0080] The measurement results for the surface protective films of Examples 1-10 and Comparative Examples 1-4 are shown in Tables 1-3. In Tables 1-3, "○" in "Antistatic Layer CNT" indicates that an antistatic agent containing carbon nanotubes is used. "○" in "Antistatic Layer PEDOT" indicates that an antistatic agent containing poly-3,4-ethylenedioxythiophene is used. "Antistatic Layer Lamination Thickness (μm)" indicates the thickness of the antistatic layer.

[0081] In the case of "acrylic resin," the circle "○" indicates that the binder resin of the antistatic layer is acrylic resin. In the case of "polyester resin," the circle "○" indicates that the binder resin of the antistatic layer is polyester resin.

[0082] "Base film Hz(%)" indicates the haze value of the PET used as the base material. "Protective film Hz(%)" indicates the haze value of the protective film, which has an antistatic layer and an adhesive layer applied to the PET.

[0083] In the section "Acrylic adhesive," the circle "○" indicates that an acrylic-based adhesive was used. In the section "Urethane adhesive," the circle "○" indicates that a urethane-based adhesive was used.

[0084] The surface resistivity of 1.0E+09 represents 1.0 × 10⁹.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] The following can be seen from the measurement results shown in Tables 1 to 3. In Examples 1-10, the surface resistivity of the antistatic layer of the surface protective film did not increase (deteriorate) even under air exposure. Furthermore, the haze value of the protective film was 4.0% or less, and the total light transmittance was 80.0% or more. On the other hand, in Comparative Example 1, where the antistatic layer was thin, the haze value of the protective film exceeded 4.0%. This is thought to be due to scattering caused by fine irregularities on the surface of the PET film. In Comparative Example 2, where the antistatic layer was thicker, the total light transmittance was 80.0% or less due to coloring with CNTs. In Comparative Example 3, where the base film had a high haze value, scattering due to fine irregularities on the surface of the PET film was suppressed, but because the haze value of the PET film itself was high, the haze value of the protective film was 4.0% or higher. In Comparative Example 4, where polythiophene was used as the antistatic agent, the surface resistivity of the surface protective film increased after 30 days of exposure to air, suggesting that static electricity is easily generated during the process. [Industrial applicability]

[0089] The surface protection film of the embodiment can be used to protect the surface of optical films such as polarizers, phase difference plates, and lens films, as well as various other optical components, by laminating them during the production process of such optical components. The surface protection film of the embodiment is less prone to an increase (deterioration) in the surface resistivity of the antistatic layer on its surface even when exposed to air. The surface protection film of the embodiment can suppress static electricity generated during the transport and handling of optical products to which the surface protection film has been laminated during the manufacturing process of optical products, thereby preventing the adhesion of dust and dirt from the environment. The surface protection film of the embodiment has a low haze value and high total light transmittance, making it easy to inspect the appearance of the surface with the surface protection film attached. When the surface protection film of the embodiment is peeled off from polarizers and phase difference plates incorporated into liquid crystal display panels after use, it suppresses significant peeling charge, preventing damage to circuits such as driver ICs. Therefore, it can improve the yield of the production process and has great industrial value. [Explanation of Symbols]

[0090] 1...Base film, 2...Antistatic layer, 3...Adhesive layer, 4...Release film, 5...Substrate (optical product), 10...Surface protection film, 20...Optical component.

Claims

1. The invention comprises a base film made of a transparent resin, an antistatic layer formed on one side of the base film, and an adhesive layer formed on the side of the base film opposite to the antistatic layer. The antistatic layer contains nanocarbon, The thickness of the antistatic layer is 0.05 μm or more and 1.50 μm or less. The haze value is 4.0% or less. A surface protection film with a total light transmittance of 80.0% or higher.

2. The surface protective film according to claim 1, wherein a release film is laminated to the side of the adhesive layer opposite to the base film.

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

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

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