Surface protective film, optical component, and electronic device

Abstract

To provide a surface protective film, an optical component and an electronic device that include an antistatic layer having sufficient printability with alcohol-based ink.SOLUTION: The surface protective film comprises: a base film 1 made of a resin; an antistatic layer 2 formed on one surface of the base film 1; and an adhesive layer 3 formed on the surface of the base film 1 opposite to the antistatic layer 2. The thickness of the antistatic layer 2 is 0.05 μm or greater and 1.00 μm or less. The surface of the antistatic layer 2 opposite to the base film 1 is used as a measurement surface, a droplet of 3 μl of ethanol is formed at the tip of a 15 G needle, and then the needle tip is lowered perpendicularly toward the measurement surface at a speed of 0.06 m / min or less. Then, the ethanol smudge diameter measured 10 sec after the droplet adheres to the measurement surface is 15 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a surface protection film, an optical component, and an electronic device. [Background technology]

[0002] Optical films such as polarizing plates, retardation plates, lens films for displays, anti-reflection films, hard coat films, and transparent conductive films for touch panels, as well as optical products such as displays using the same, are used. When manufacturing and transporting optical products, a surface protective film can be attached to the surface of the optical film to prevent the surface from being soiled or scratched in later processes.

[0003] When the surface protective film is transparent, the appearance inspection of the optical product can be performed while the surface protective film is attached to the optical film. Performing the appearance inspection while the surface protective film is attached can eliminate the need to peel off the surface protective film and reattach it, thereby improving work efficiency.

[0004] The surface protection film has, for example, an antistatic layer formed on its surface. By providing an antistatic layer, static electricity can be suppressed during transportation and handling of the optical product to which the surface protection film is attached in the manufacturing process of the optical product. This makes it possible to suppress the adsorption of dust and dirt in the environment.

[0005] Meanwhile, there is a demand for the ability to mark and display identification numbers and defect markings for protected objects on surface protection films during the manufacturing process of optical products. Therefore, ink printability is required. For example, Patent Document 1 discloses that by having a top coat layer thickness of more than 10 nm and less than 50 nm, and the top coat layer surface satisfying the following properties: (A) a water contact angle of 75° or more, (B) a 180-degree peel strength of a standard acrylic adhesive tape of 1.0 N / 19 mm or more, and (C) a dynamic friction coefficient of 0.4 or less, it is possible to maintain a high level of appearance quality while improving water resistance after printing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-69541 Summary of the Invention [Problem to be solved by the invention]

[0007] Until now, solvent-based inks containing methyl ethyl ketone (MEK) and other solvents have been used. However, from an environmental perspective, there has been an increasing shift from solvent-based inks to alcohol-based inks such as ethanol. By switching from solvent-based to alcohol-based inks, problems have arisen where printing has been possible on surface protection films without any problems until now, such as bleeding after printing and making it difficult to check identification numbers and defect markings.

[0008] An object of the present invention is to provide a surface protection film, an optical component, and an electronic device that are provided with an antistatic layer that has sufficient printability with alcohol-based inks. [Means for solving the problem]

[0009] A first aspect of the surface protection film comprises a base film made of 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 the antistatic layer, wherein the thickness of the antistatic layer is 0.05 μm or more and 1.00 μm or less, and the antistatic layer has an ethanol bleeding diameter of 15 mm or less, measured 10 seconds after the droplet adheres to the measurement surface by creating a 3 μl droplet of ethanol on the tip of a 15G needle with the side opposite the base film as the measurement surface and then lowering the needle tip perpendicularly to the measurement surface at a speed of 0.06 m / min or less.

[0010] A second aspect of the surface protection film is the first aspect, wherein the antistatic layer contains a polyether-modified silicone-based additive having an HLB value of 11 or less. The surface protection film of the third aspect is the surface protection film of the first or second aspect, wherein the surface specific resistivity of the antistatic layer is 1.0×10 +10 It is Ω / □ or less. A fourth aspect of the surface protection film is the surface protection film of any one of the first to third aspects, wherein the antistatic layer contains a conductive polymer or nanocarbon. An optical component according to a fifth aspect has the surface protection film according to any one of the first to fourth aspects attached to an adherend. An electronic device according to a sixth aspect is equipped with the optical component according to the fifth aspect. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a surface protection film, an optical component, and an electronic device that are provided with an antistatic layer that has sufficient printability with alcohol-based inks. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating a surface protection film according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating an example of a surface protection film with a release film. [Figure 3] FIG. 1 is a cross-sectional view illustrating an optical component with a surface protection film. [Figure 4] FIG. 1 is an explanatory diagram illustrating a method for measuring an ethanol bleeding diameter. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on preferred embodiments.

[0014] 1 illustrates a surface protection film 10 according to an embodiment. The surface protection film 10 in the illustrated example includes a base film 1 made of resin, an antistatic layer 2 formed on one surface of the base film, and a pressure-sensitive adhesive layer 3 formed on the surface of the base film 1 opposite to the antistatic layer 2.

[0015] (antistatic layer) The antistatic layer 2 imparts antistatic properties to the surface protection film 10, making it less susceptible to foreign matter and dust. Furthermore, it preferably has solvent resistance so that surface changes such as film peeling are less likely to occur when the surface of the surface protection film 10 is washed with a solvent or water. It preferably has printability that allows stamps or ink printing for identification during processes in which the surface protection film 10 is used. It also preferably has scratch resistance so that it is less susceptible to scratches during processes.

[0016] In the surface protection film 10 of the embodiment, the thickness of the antistatic layer 2 is 0.05 μm or more and 1.00 μm or less. The antistatic layer 2 has a surface opposite to the base film 1 as a measurement surface. After creating a 3 μl droplet of ethanol on the tip of a 15G needle, the needle tip is lowered perpendicularly to the measurement surface at a speed of 0.06 m / min or less, and the diameter of the ethanol bleeding is measured 10 seconds after the droplet has adhered to the measurement surface. The diameter of the ethanol bleeding is 15 mm or less.

[0017] This makes it possible to provide a surface protection film 10 having an antistatic layer 2 that has sufficient printability for alcohol-based inks. The ethanol bleeding diameter is preferably 3 mm or more and 15 mm or less. As the ethanol, "Ethanol (99.5) Wako Grade 1," a product name manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., is used.

[0018] The antistatic layer 2 may be formed by applying an antistatic coating containing an antistatic agent and a binder resin to the substrate. Known antistatic agents include anionic, cationic, and amphoteric surfactants. Conductive polymers or nanocarbons can also be used as antistatic agents. The coating method for the antistatic coating is not particularly limited, but examples include reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating.

[0019] Examples of binder resins include acrylic resins, epoxy resins, urethane resins, phenolic resins, and polyester resins. A crosslinking agent may be added to crosslink or harden the binder resin. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelate compounds.

[0020] The antistatic layer 2 may contain an ultraviolet absorber, an antioxidant, a leveling agent (a wettability improver), an adhesion improver, and the like.

[0021] The antistatic layer 2 preferably contains a polyether-modified silicone additive having an HLB value of 11 or less. This makes it easier to obtain an antistatic layer 2 with reduced ethanol bleeding diameter. Preferred HLB values ​​include 1 to 11. More preferred HLB values ​​include 4 to 7.

[0022] HLB, also known as the hydrophilic-lipophilic balance, is an index divided into 20 equal parts, with HLB=0 for substances with only lipophilic groups and no hydrophilic groups, and HLB=20 for substances with only hydrophilic groups and no lipophilic groups. Emulsifiers that have both lipophilic and hydrophilic properties have values ​​between 0 and 20. The greater the hydrophilicity relative to the lipophilicity, the higher the HLB value, and the more easily the emulsifier dissolves in water. The greater the lipophilicity relative to the hydrophilicity, the smaller the HLB value, and the less easily the emulsifier dissolves in water.

[0023] The surface resistivity of the antistatic layer 2 is 1.0×10 +10 It is preferably Ω / □ or less, which makes it easier to obtain an antistatic layer 2 with sufficient antistatic properties.

[0024] The antistatic layer 2 preferably contains a conductive polymer or nanocarbon. The antistatic layer 2 may use only a conductive polymer or nanocarbon as an antistatic agent, or may use a conductive polymer or nanocarbon in combination with another antistatic agent.

[0025] Examples of conductive polymers include polythiophene, polyaniline, and polypyrrole. These conductive polymers may be derivatives having substituents on the thiophene, aniline, or pyrrole moieties. From the viewpoint of conductivity, inorganic semiconductors such as CuI, CuS, and FeO, and dopants such as polystyrene sulfonic acid (salt), p-toluenesulfonic acid (salt), camphorsulfonic acid (salt), and polystyrene-maleic acid (salt) copolymers may be included. One example is PEDOT / PSS (poly-3,4-ethylenedioxythiophene doped with polystyrene sulfonic acid). As the conductive polymer, one type of material may be used, or multiple types of materials may be used in combination.

[0026] Examples of nanocarbons include carbon nanotubes (CNTs), graphene, and fullerenes. Carbon nanotubes may be single-walled CNTs or multi-walled CNTs. As nanocarbons, one type of material may be used, or multiple types of materials may be used in combination.

[0027] (Base film) A substrate film made of resin is used as the substrate film 1. Using a transparent substrate film 1 is preferable because it allows visual inspection of the adherend with the surface protection film 10 attached to the adherend. The resin forming the substrate film 1 is not particularly limited, but examples include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate. The substrate film 1 may be an unstretched film or a uniaxially or biaxially stretched film.

[0028] The thickness of the base film 1 is not particularly limited, but may be, for example, 12 μm to 100 μm. If necessary, at least one surface of the base film 1 may be subjected to an adhesion-enhancing treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0029] (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 that can be used for 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 the adhesive. Of these, acrylic adhesives and urethane adhesives are particularly suitable. The use of a transparent adhesive layer 3 is preferred because it allows for visual inspection of the adherend with the surface protection film 10 attached to the adherend.

[0030] The acrylic adhesive is preferably an adhesive in which a crosslinking agent is added to a (meth)acrylic polymer. The (meth)acrylic polymer preferably contains a main monomer such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, or isononyl acrylate. Furthermore, 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-methylol methacrylamide may be copolymerized.

[0031] Examples of crosslinking agents for (meth)acrylic polymers include isocyanate compounds, epoxy compounds, melamine compounds, and metal chelate compounds. The amount of crosslinking agent added can be determined taking into consideration the type of (meth)acrylic polymer, the degree of polymerization, the amount of functional groups, etc. The amount of crosslinking agent added is not particularly limited, but is preferably about 0.5 to 1.0 parts by mass of crosslinking agent per 100 parts by mass of (meth)acrylic polymer.

[0032] The urethane-based adhesive is preferably a polyurethane-based resin obtained by using a polyol component and a polyisocyanate component. Examples of the polyol component include polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil polyol. Examples of the polyisocyanate component include aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, and diisocyanate polymers.

[0033] Known methods can be used to form the pressure-sensitive adhesive layer 3 on the surface of the base film 1. The pressure-sensitive adhesive coating method is not particularly limited, but examples include reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating. The thickness of the pressure-sensitive adhesive layer 3 is not particularly limited, but examples include 5 μm to 40 μm or 10 μm to 30 μm.

[0034] (Release film) Fig. 2 shows a surface protection film 11 with a release film 4 attached to a surface protection film 10. The release film 4 is used to protect the pressure-sensitive adhesive layer 3. When attaching the surface protection film 10 to an adherend, the release film 4 is peeled off and the pressure-sensitive adhesive layer 3 is pressed against the adherend.

[0035] The release film 4 may be a polyolefin film such as polyethylene or polypropylene, or a fluororesin film, which may be used alone. The release film 4 may also be a resin film with at least one surface treated with a release agent. Examples of resin films that serve as the base for the release agent include polyester films such as polyethylene terephthalate and polyethylene naphthalate, and polyamide films. Examples of release agents include silicone resins, resins containing long-chain alkyl groups, and fluororesins.

[0036] (Optical components) 3 shows an optical component 20 with a surface protective film in which a surface protective film 10 is attached to an optical component 5. Examples of the optical component 5 include optical films such as a polarizing plate, a retardation plate, a lens film, a polarizing plate that also serves as a retardation plate, and a polarizing plate that also serves as a lens film. Examples of the optical component 5 also include optical films such as an anti-reflection film, a hard coat film, and a transparent conductive film for touch panels.

[0037] These optical components 5 can be mounted in electronic devices. Examples of electronic devices include liquid crystal display devices such as liquid crystal display panels, organic EL display panels, touch panels, and various instruments. When mounting the optical component 5 in an electronic device, it is also possible to mount the optical component 5 in the electronic device after peeling the surface protective film 10 from the optical component 5. It is also possible to mount the optical component 20 with the surface protective film attached, in which the surface protective film 10 is attached to the optical component 5, in the electronic device. [Example]

[0038] The present invention will be specifically described below with reference to examples.

[0039] (Preparation of antistatic layer) The antistatic agent dispersion, binder resin component, methylated melamine crosslinker (Nikalac® MW-30HM, manufactured by Nippon Carbide Industries Co., Ltd.), and polyether-modified silicone additive were adjusted to a predetermined solids mass ratio and diluted 10 times with water / ethanol (water / ethanol mass ratio 50 / 50) to obtain an antistatic paint. The antistatic paint was applied to the surface of a 38 μm-thick polyethylene terephthalate film (PET film, base film), and the coating was dried for 1 minute in a hot air circulating oven at 120°C. This formed an antistatic layer on the PET film.

[0040] Tables 1 to 3 show the types of antistatic agents and resin components used in preparing the antistatic layer, the mass ratio of solid content in the antistatic coating material, and the thickness of the antistatic layer after drying. As the antistatic agent, a conductive polymer (manufactured by Agfa, Orgacon (registered trademark) ICP 1021) or nanocarbon (manufactured by Nagase ChemteX Corporation, Denatron (registered trademark) CD-100) was used. As the resin component, polyvinyl alcohol (PVA) resin (3-88, manufactured by Kuraray) or polyester resin (Pluscoat (registered trademark) RZ-570, manufactured by GOO Chemical Industry Co., Ltd.) was used.

[0041] (Preparation of surface protection film) An applicator was used to apply the adhesive composition to the surface of the PET film not having the antistatic layer, so that the thickness after drying would be 20 μm, and the coating was dried for 3 minutes in a hot air circulating oven at 120 ° C to form an adhesive layer. A release film (thickness 25 μm) treated with a silicone-based release agent (Diafoil (registered trademark) MRF-25, manufactured by Mitsubishi Chemical Corporation) 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.

[0042] The types of adhesives used in producing the surface protection films were acrylic adhesives or urethane adhesives, as shown in Tables 1 to 3. Specifically, the following urethane adhesive was used in Example 8, and the following acrylic adhesives were used in the other examples.

[0043] The acrylic adhesive was prepared from a copolymer of 80 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of butyl acrylate, 7 parts by weight of methoxypolyethylene glycol (400) methacrylate, and 3 parts by weight of 2-hydroxyethyl acrylate. 0.3 parts by weight of lithium bis(trifluoromethanesulfonyl)imide as an antistatic agent and 2 parts by weight of an isocyanate-based curing agent (Tosoh Corporation, Coronate® HX) were added to 100 parts by weight of a 40% ethyl acetate solution of this acrylic adhesive and mixed to obtain an adhesive composition.

[0044] The urethane adhesive used was ARACOAT (registered trademark) FT200 manufactured by Arakawa Chemical Industries, Ltd. To 100 parts by mass of a 40% ethyl acetate solution of this urethane adhesive, 0.3 parts by mass of lithium bis(trifluoromethanesulfonyl)imide as an antistatic agent and 5.7 parts by mass of ARACOAT (registered trademark) CL2503 (curing agent non-volatile content: 40% by mass) manufactured by Arakawa Chemical Industries, Ltd. were added and mixed to obtain an adhesive composition.

[0045] (Method for evaluating printability for ethanol solvent ink) The antistatic layer of the surface protection film was printed with a stamp using ink with an ethanol content of 70% or more, and then 30 seconds later, the presence or absence of bleeding was visually confirmed. If there was no bleeding, it was rated as pass (○), and if there was bleeding, it was rated as fail (×). The measurement environment was 23°C and 50% RH.

[0046] (Method for evaluating printability for MEK solvent ink) The antistatic layer of the surface protection film was printed with a stamp using ink with a methyl ethyl ketone (MEK) content of 75% or more, and then 30 seconds later, the presence or absence of bleeding was visually confirmed. If there was no bleeding, it was rated as pass (○), and if there was bleeding, it was rated as fail (×). The measurement environment was 23°C and 50% RH.

[0047] (Method for measuring ethanol bleeding diameter) The measurement device used was a contact angle meter (DropMaster Dmo-701, fully automatic contact angle meter, manufactured by Kyowa Interface Science Co., Ltd.). The ethanol used was "Ethanol (99.5) Wako Grade 1," manufactured by Fujifilm Wako Pure Chemical Corporation. Specifically, as shown in Figure 4(a), a 3 μl droplet 32 ​​was created on the tip of a 15G needle 31. The needle tip was then lowered perpendicular to the measurement surface at a speed of 0.06 m / min or less (1 mm / sec or less). The maximum diameter D of the wetting spread was measured 10 seconds after the droplet adhered to the measurement surface (the antistatic layer 2 of the surface protection film 10). As shown in Figure 4(b), graph paper 33 was placed under the surface protection film 10 and used to measure the diameter D. The measurement was performed in an environment of 23 °C and 50% RH, and the average value of N = 3 was used.

[0048] (Method for measuring water contact angle) A predetermined amount of water droplet was attached to the antistatic layer (measurement surface) of the surface protection film using a contact angle meter, and the contact angle (°) was measured.

[0049] (Method for measuring surface resistivity) The surface resistivity (Ω / □) of the antistatic layer of the surface protection film was measured using a high-performance resistivity meter (Hiresta (registered trademark)-UP, manufactured by Nitto Seiko Analytech Co., Ltd.) under conditions of an applied voltage of 100 V and a measurement time of 30 seconds. In the table, the surface resistivity is expressed in exponential notation. The exponential notation is m×10 where m is the number written before E and n is the number written after E. n Represents.

[0050] (Method for measuring low-speed adhesive strength) A polarizing plate using a triacetyl cellulose (TAC) film as a protective film for the polarizer 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 and 50% RH. Using a tensile tester, the surface protective film was peeled off in a 180° direction at a peeling speed of 0.3 m / min, and the strength was measured, which was taken as the low-speed adhesion strength (N / 25 mm).

[0051] (Method for measuring high-speed adhesive strength) A polarizing plate using a triacetyl cellulose (TAC) film as a protective film for the polarizer 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 and 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 Sangyo Co., Ltd.) was measured, and this was taken as the high-speed adhesive strength (N / 25 mm).

[0052] (Method for measuring electrostatic discharge (ESD) potential) A polarizing plate using a triacetyl cellulose (TAC) film as a protective film for the polarizer 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 laminated surface protective film was stored for one day in a test environment of 23°C x 50% RH. While peeling the surface protective film at a peeling speed of 30 m / min using a high-speed peel tester (manufactured by Tester Sangyo Co., Ltd.), the surface potential of the polarizing plate surface was measured every 10 ms using a surface potential meter (manufactured by Keyence Corporation). The maximum absolute value of the surface potential was recorded as the peel electrification voltage (kV).

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] As shown in Tables 1 to 3, antistatic layers with an ethanol bleeding diameter of 15 mm or less passed (○) in printability with MEK solvent ink and ethanol solvent ink, and were confirmed to have sufficient printability with no bleeding with alcohol-based ink. In contrast, antistatic layers with an ethanol bleeding diameter of more than 15 mm passed (○) in printability with MEK solvent ink but failed (×) in printability with ethanol solvent ink, showing bleeding with alcohol-based ink and demonstrating poor printability. [Explanation of symbols]

[0057] 1...base film, 2...antistatic layer, 3...adhesive layer, 4...release film, 5...optical component, 10...surface protection film, 11...surface protection film with release film, 20...optical component with surface protection film, 31...15G needle, 32...droplet, 33...graph paper.

Claims

1. The adhesive tape comprises a base film made of a resin, an antistatic layer formed on one surface of the base film, and a pressure-sensitive adhesive layer formed on the surface of the base film opposite to the antistatic layer, the thickness of the antistatic layer is 0.05 μm or more and 1.00 μm or less; The antistatic layer is a surface protection film in which the surface opposite to the base film is used as the measurement surface, a 3 μl droplet of ethanol is created on the tip of a 15G needle, the needle tip is then lowered perpendicularly to the measurement surface at a speed of 0.06 m / min or less, and the ethanol bleeding diameter is measured 10 seconds after the droplet has adhered to the measurement surface, and the diameter is 15 mm or less.

2. The surface protective film according to claim 1 , wherein the antistatic layer contains a polyether-modified silicone-based additive having an HLB value of 11 or less.

3. The surface resistivity of the antistatic layer is 1.0×10 ＋１０ The surface protection film according to claim 1 , having a resistance to moisture of Ω / □ or less.

4. The surface protective film according to claim 1 , wherein the antistatic layer comprises a conductive polymer or nanocarbon.

5. An optical component comprising the surface protective film according to any one of claims 1 to 4 attached to an adherend.

6. An electronic device equipped with the optical component according to claim 5.

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