JP7590263B2 - Surface protection films and optical components - Google Patents

Description

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

When manufacturing and transporting optical films such as polarizing plates, retardation plates, lens films for displays, anti-reflection films, hard coat films, transparent conductive films for touch panels, and other optical products such as displays using the same, a surface protective film is applied to the surface of the optical film to prevent the surface from becoming dirty or scratched in later processes. Visual inspection of the optical film product is sometimes performed with the surface protective film still applied to the optical film, in order to increase work efficiency by eliminating the need to peel off and reapply the surface protective film.

Conventionally, surface protection films having an adhesive layer on one side of a base film have been commonly used in the manufacturing process of optical products to prevent scratches and dirt from adhering to the surface of optical products. The surface protection film is attached to the optical film via an adhesive layer with weak adhesion. The adhesive layer has weak adhesion so that it can be easily peeled off when used surface protection film is peeled off from the surface of the optical film, and so that the adhesive does not adhere to and remain on the optical film of the product that is the adherend (preventing the occurrence of so-called glue residue).

Surface protection films that are often used have an antistatic layer on the side of the base film opposite the adhesive layer. By providing an antistatic layer on the surface of the surface protection film, static electricity that occurs during transportation and handling of the optical product to which the surface protection film is attached during the manufacturing process of the optical product is suppressed. This prevents the adhesion of dust and dirt in the environment, and makes it easier to perform visual inspections of the surface protection film while it is attached to the optical film. In addition, when the surface protection film is peeled off and removed from the polarizing plate or retardation plate built into the liquid crystal display panel after use, significant peeling static electricity is suppressed, which prevents damage to circuits such as the driver IC.

For the antistatic layer on the surface of the surface protection film, there have been proposals for layers containing various surfactants (nonionic, cationic, anionic, amphoteric surfactants) or ionic group-containing polymers, vapor deposition of metal or metal oxide, or layers containing metal or metal oxide particles.
Antistatic layers containing surfactants or ionic group-containing polymers are susceptible to the humidity of the environment, and have a high antistatic effect in a high humidity environment, but have a problem that their antistatic performance is significantly deteriorated in a low humidity environment. On the other hand, antistatic layers containing metal or metal oxide particles are not susceptible to the humidity of the environment, but are difficult to achieve transparency, and cannot be used for optical products, particularly for inspections with a surface protection film attached. Examples of antistatic layers that are not susceptible to the humidity of the environment and have transparency include antistatic layers formed by vapor deposition of metal oxides such as indium tin oxide (ITO) and antimony tin oxide (ATO), but have a problem that the cost of vapor deposition is very high.

Patent Document 1 discloses a surface protection film in which an antistatic layer is provided on one side of a polyester film, an antifouling layer is provided on the antistatic layer, and a weak adhesive layer is provided on the opposite side. The antistatic layer contains a conductive polymer obtained by polymerizing thiophene and/or a thiophene derivative. However, when the antistatic layer is formed using the conductive polymer, there is a problem that problems such as an increase (deterioration) in surface resistivity due to oxidation degradation and photodegradation occur over time.

In order to solve this problem of surface resistivity increasing (deteriorating) over time, Patent Document 2 proposes a surface protection film in which the antistatic layer contains polyaniline sulfonic acid, polythiophenes doped with polyanions, and a binder. This surface protection film is said to be able to suppress the increase (deterioration) in surface resistivity over time by using polyaniline sulfonic acid in the antistatic layer, but there is a risk of the polyaniline causing coloring from yellow to green, making it difficult to use for optical components.

Patent Document 3 proposes an antistatic film having good transparency (total light transmittance) and good adhesion of the antistatic layer to the substrate, further comprising a conductive layer containing nanocarbon and a polymer, and having a surface resistivity of 1× ¹⁰ Ω/□ or less. However, since this antistatic film uses nanocarbon such as carbon nanotubes as an antistatic agent, there is a problem that the surface resistance increases (deteriorates) when the film is placed in a humid and hot environment (e.g., conditions of 60° C. and relative humidity of 90%), although the increase in the surface resistance is small over time.

Patent Document 4 proposes a thermosetting antistatic coating agent that contains polythiophene and a conductive filler. This thermosetting antistatic coating agent has little change in surface resistivity over time. However, this thermosetting antistatic coating agent has the problem that the surface resistance value increases (deteriorates) when placed in a high-temperature, humid and hot condition (such as a temperature of 60°C and a relative humidity of 90%).

JP 2000-026817 A Re-table No. 2018-012545 JP 2012-166452 A JP 2016-216714 A

One aspect of the present invention has been made in consideration of the above circumstances, and aims to provide a surface protection film and optical components that are less likely to cause an increase in surface resistance.

One aspect of the present invention provides a surface protection 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 the antistatic agent layer, the antistatic agent layer comprising a first layer containing a conductive polymer, and a second layer containing nanocarbon and provided on the opposite side of the substrate film relative to the first layer.

The surface protection film may have a release film attached to the side of the pressure-sensitive adhesive layer opposite the base film.

The adhesive layer is preferably made of an acrylic adhesive.

Another aspect of the present invention provides an optical component to which the surface protection film is attached.

One aspect of the present invention is to provide a surface protection film and optical components that are less susceptible to an increase in surface resistance.

FIG. 2 is a cross-sectional view showing a surface protection film according to an embodiment. 1 is a cross-sectional view showing a surface protective film with a release film in which a release film is bonded to a surface protective film of an embodiment. FIG. 1 is a cross-sectional view showing one embodiment of an optical component according to the present invention.

Hereinafter, the present invention will be described in detail based on the embodiments.
Fig. 1 is a cross-sectional view showing a surface protection film of an embodiment. As shown in Fig. 1, a surface protection film 10 according to the embodiment has an antistatic agent layer 2 formed on one surface (upper surface in Fig. 1) of a base film 1. A pressure-sensitive adhesive layer 3 is formed on the surface of the base film 1 opposite to the antistatic agent layer 2 (lower surface in Fig. 1).

[Base film]
As the base film 1, a base film made of a resin having transparency and flexibility is used. This allows the appearance inspection of the optical component to be performed in a state in which the surface protection film 10 is attached to the optical component as the adherend. The base film 1 used as the base film 1 is preferably a film (polyester film) formed of polyester such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, etc. In addition to polyester films, films made of other resins can also be used as long as they have the necessary strength and optical suitability. The base film 1 may be a non-stretched film, or a uniaxially or biaxially stretched film. In addition, the stretching ratio of the stretched film and the orientation angle in the axial direction formed with the crystallization of the stretched film may be controlled to a specific value.

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

The thickness of the base film 1 is not particularly limited, but is preferably about 12 to 100 μm, and more preferably about 20 to 50 μm for ease of handling.
If necessary, the surface of the base film 1 may be subjected to a treatment for improving adhesion, such as surface modification by corona discharge or application of an anchor coating agent.

[Antistatic agent layer]
The antistatic agent layer 2 is formed by laminating a first layer 2a containing a conductive polymer and a second layer 2b containing nanocarbon in this order from the side of the base film 1. The second layer 2b is provided on the opposite side of the first layer 2a to the base film 1 (the upper side in FIG. 1 ).

Over time, a layer containing a conductive polymer may experience an increase in surface resistivity (deterioration) due to oxidation or photodegradation. However, the surface protection film 10 overcomes the problem of oxidation or photodegradation of the first layer 2a containing a conductive polymer by providing a second layer 2b containing nanocarbon on the surface of the first layer 2a (the surface opposite to the substrate film 1).

The layer containing nanocarbon may experience an increase in surface resistance (deterioration) when placed in a humid and hot environment (e.g., conditions of 60°C and relative humidity of 90%), but the surface protective film 10 overcomes the problem of deterioration of the second layer 2b in a humid and hot environment due to the antistatic effect of the first layer 2a between the second layer 2b and the base film 1.

Examples of the conductive polymer used in the first layer 2a include polyaniline, polythiophene, polypyrrole, and derivatives thereof.
Available examples of polyaniline and its derivatives include polyaniline (manufactured by Aldrich Chemical Industry), polyaniline (eleraldine salt) (manufactured by Aldrich Chemical Industry), OMEGACON (registered trademark) D1033W, OMEGACON (registered trademark) NW-D102MT, OMEGACON (registered trademark) NW-F102ET, OMEGACON (registered trademark) NW-F101MEK (all 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.).

Commercially available polythiophenes and their derivatives include 3,4-ethylenedioxythiophene (BAYTRON® MV2), 3,4-polyethylenedioxythiophene/polystyrenesulfonate (BAYTRON® P, BAYTRON® C), BAYTRON® FE, BAYTRON® MV2, BAYTRON® P, BAYTRON® PAG, BAYTRON® PHC V4, BAYTRON® PHS, BAYTRON® PH, and BAYTRON® PH500. , BAYTRON (registered trademark) PH510 (all manufactured by Starck), SEPLEGYDA (registered trademark) AS-Q, SEPLEGYDA (registered trademark) AS-D, SEPLEGYDA (registered trademark) AS-H (all manufactured by Shin-Etsu Polymer Co., Ltd.), Conductive Coat S-983, Conductive Coat S-495, Conductive Coat S-948 (all manufactured by Chukyo Yushi Co., Ltd.), Denatron P-502RG, Denatron P-560ST, Denatron P-500NT, Denatron P-200HC, Denatron P-800SL (all manufactured by Nagase Chemtec Corporation), PED500 (manufactured by Kaken Sangyo Co., Ltd.), etc. are available.

Polypyrrole and its derivatives are available as polypyrrole (manufactured by Aldrich) and SSPY (manufactured by Kaken Sangyo Co., Ltd.).

As a conductive polymer, polythiophene is preferred in terms of antistatic properties and coloring properties (color). As a polythiophene, polyethyleneoxythiophene is preferred, and polyethylenedioxythiophene (PEDOT) is particularly good. Polyethylenedioxythiophene is preferably doped with polystyrene sulfonic acid (PSS) as a dopant. Polyethylenedioxythiophene doped with PSS has the advantages of being highly soluble in water and having excellent heat resistance, moisture resistance, and UV stability.

The conductive polymer may be used alone or in combination with several other types. In addition, binder resins, crosslinking agents, UV absorbers, antioxidants, leveling agents (wettability improvers), adhesion improvers, etc. may be added to the conductive polymer for the purpose of improving the coatability of the antistatic agent on the base film 1, the adhesion of the antistatic agent layer to the base film, the film strength of the antistatic agent layer, and the durability of the film (such as abrasion resistance and solvent resistance).

To form the first layer 2a, it is preferable to form a film of a conductive polymer to which a binder resin has been added, rather than forming a film of a conductive polymer alone. Examples of binder resins include acrylic resins, epoxy resins, urethane resins, phenolic resins, and polyester resins. If necessary, a crosslinking agent may be added to the binder resin in order to crosslink (also called harden) these resins. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelate compounds.

The method for forming the first layer 2a on the base film 1 may be a known method. For example, a paint containing an antistatic agent (a paint containing an antistatic agent and a binder resin) is applied to the base film 1 by a known coating method. The first layer 2a can be formed by solidifying the formed coating film by heating or irradiating it with ultraviolet light. Coating methods include reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating.

Examples of nanocarbons used in the second layer 2b include carbon nanotubes (CNT), graphene, and fullerene. Carbon nanotubes include single-walled CNT and multi-walled CNT. Single-walled CNT, multi-walled CNT, graphene, and fullerene all have excellent antistatic properties, but since single-walled CNT, graphene, and fullerene are expensive, multi-walled CNT is easier to use. The second layer 2b is formed on the surface of the first layer 2a to prevent the first layer 2a from being exposed to air. As a result, the first layer 2a is not directly exposed to air, making the first layer 2a less susceptible to oxidation deterioration.

Nanocarbon alone does not provide sufficient film strength, so it is preferable to add a binder resin, a dispersant, etc. to make a paint and use it. In addition, crosslinking agents, UV absorbers, antioxidants, leveling agents (wettability improvers), adhesion improvers, etc. may be added to nanocarbon for the purpose of improving the coatability of the antistatic agent, the adhesion of the antistatic agent layer (adhesion to the first layer 2a), the film strength of the antistatic agent layer, and the durability of the film (abrasion resistance, solvent resistance, etc.).

One type of nanocarbon may be used, or multiple types may be used in combination. Examples of binder resins include acrylic resins, epoxy resins, urethane resins, phenolic resins, and polyester resins. If necessary, a crosslinking agent may be added to the binder resin in order to crosslink (also called harden) these resins. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy compounds, and metal chelate compounds.

To form the second layer 2b, a commercially available antistatic paint may be used. Commercially available products include Denatron C-300, Denatron CD-001 (both manufactured by Nagase Chemtec Corporation), Colcoat CS-3002, and Colcoat CS-3202 (both manufactured by Colcoat Co., Ltd.).

The method for forming the second layer 2b on the surface of the first layer 2a may be a known method. For example, a paint containing nanocarbon (a paint containing nanocarbon and a binder resin) is applied to the surface of the first layer 2a using a known coating method. The second layer 2b can be formed by solidifying the formed coating film by heating or irradiating it with ultraviolet light. Coating methods include reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating.

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 nanocarbon and binder resin. The thicknesses of the first layer 2a and the second layer 2b may be adjusted so that the surface resistivity is about 10 to the power of 7 (10 ⁷ ) to 10 to the power of 9 (10 ⁹ ) when the first layer 2a and the second layer 2b are laminated.

[Adhesive layer]
The adhesive layer 3 preferably has the properties of adhering to the surface of the adherend, being easily peelable after use, and not easily contaminating 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 the adhesive. Among these, acrylic adhesives and urethane adhesives are particularly preferred.

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

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 can be determined taking into consideration the type of (meth)acrylic polymer, the degree of polymerization, and the amount of functional groups. The amount of crosslinking agent added is not particularly limited, but it is preferable to add about 0.5 to 1.0 parts by mass of crosslinking agent per 100 parts by mass of (meth)acrylic polymer.

As the urethane-based adhesive, a polyurethane-based resin containing a polyol component and a polyisocyanate component is preferable. The polyurethane-based resin may be selected taking into consideration the adhesiveness, wettability, and adherend contamination. There are no particular limitations on the polyol component and the polyisocyanate component. The polyurethane-based resin may be used alone or in a mixture of two or more types.

Examples of polyol components include polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, castor oil polyols, etc. These polyol components may be used alone or in combination of two or more.

As the polyisocyanate component, an aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic polyisocyanate, a diisocyanate polymer, etc. are used. These polyisocyanate components may be used alone or in combination of two or more kinds.

Commercially available polyurethane adhesives include Cyabain (registered trademark) SH-101, SH-101M, SP-205, and SP-220 (manufactured by Toyochem Co., Ltd.), Aracoat (registered trademark) FT100 and FT200 (manufactured by Arakawa Chemical Industries Co., Ltd.), and UN1175 and UN1176 (manufactured by Daido Chemical Industry Co., Ltd.). The adhesive layer may be formed by crosslinking or curing a polyurethane adhesive.

If necessary, a crosslinking catalyst may be added as an additive to the adhesive layer 3 to promote the crosslinking reaction. If necessary, an adhesion improver such as a silane coupling agent may be added as an additive to the adhesive layer 3 to improve the adhesion between the base film 1 and the adhesive. If necessary, additives such as an antistatic agent, an antioxidant, and an ultraviolet absorber may be added to the adhesive layer 3.

The thickness of the adhesive layer 3 is not particularly limited, but is preferably about 5 to 40 μm, and more preferably about 10 to 30 μm. The adhesive strength of the surface protective film to the surface of the adherend at a peeling speed of 0.3 m/min (low-speed adhesive strength) is preferably 0.3 N/25 mm or less, and more preferably 0.2 N/25 mm or less. The adhesive strength 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, the workability when peeling off the protective film after use may be deteriorated. To adjust the adhesive strength, known methods such as changing the adhesive composition, adjusting the amount of curing agent added, and adjusting the amount of tackifier and adhesive strength adjuster added can be used. By these methods, the adhesive strength of the adhesive layer 3 can be adjusted to a predetermined adhesive strength.

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, Mayer bar coating, and air knife coating can be used.

FIG. 2 is a cross-sectional view showing a surface protection film 11 with a release film 4 laminated to a surface protection film 10. As shown in FIG. 2, a known release film may be used as the release film 4. As the release film 4, a polyolefin film such as a polyethylene film or a polypropylene film, or a fluorine film may be used alone. The release film 4 may be a release film obtained by treating a resin film with a release agent (also called a release agent). Examples of the resin film include polyester films such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), and polyamide films. Examples of the release agent include silicone resins, long-chain alkyl group-containing resins, and fluorine resins. Among them, a release film obtained by treating a PET film with a silicone-based release agent is preferable.
The thickness of the release film is not particularly limited, but from the standpoint of workability and cost, a release film having a thickness of 12 to 38 μm is often used.

The method of forming the adhesive layer 3 on the base film 1 and the method of laminating the release film 4 to the adhesive layer 3 may be performed by a known method, and are not particularly limited. Specifically, there are (1) a method of applying a resin composition for forming the adhesive layer 3 to one side of the base film 1, drying the resin composition to form the adhesive layer 3, and then laminating the release film 4 to the adhesive layer 3, and (2) a method of applying a resin composition for forming the adhesive layer 3 to the surface of the release film 4, drying the resin composition to form the adhesive layer 3, and then laminating the base film 1 to the adhesive layer 3, and any of these methods may be used.

Figure 3 is a cross-sectional view showing an embodiment of an optical component of the present invention. Figure 3 shows an optical component 20 to which a surface protection film 10 is attached. As shown in Figure 3, the release film-attached surface protection film 11 (see Figure 2) is in a state in which the release film 4 has been peeled off and the adhesive layer 3 is exposed. This surface protection film (see Figure 1) is attached to the optical component 5, which is the adherend, by the adhesive layer 3.

Optical components include optical films such as polarizing plates, retardation plates, lens films, polarizing plates that also serve as retardation plates, and polarizing plates that also serve as lens films. Such optical components are used as components of liquid crystal display devices such as liquid crystal display panels, optical devices for various instruments, etc. Other examples of optical components include optical films such as anti-reflection films, hard coat films, and transparent conductive films for touch panels.

According to the optical component of the embodiment, when the surface protection film is attached to the optical component (optical film) as the adherend, the surface of the surface protection film has an antistatic agent layer. Therefore, it is possible to suppress static electricity generated during transportation and handling of the optical component. Therefore, it is possible to suppress the adsorption of substances that cause foreign matter such as dust and dirt during the process, and to obtain optical components with fewer defects. In addition, when the surface protection film is peeled off and removed from the optical component, the peeling electrification voltage can be suppressed to a low level, so there is little risk of damaging circuit components such as driver ICs, TFT elements, and gate line driving circuits. Therefore, for example, it is possible to increase the production efficiency in the process of manufacturing liquid crystal display panels and the like, and maintain the reliability of the production process.
The surface protection film of the embodiment can suppress an increase (deterioration) in the surface resistance value of the antistatic agent layer on the surface even when exposed to outdoor air or in a humid and hot environment, and the above-mentioned effects are unlikely to change over time, so that the surface protection film has great industrial utility.

The present invention will now be further described with reference to examples.
Example 1
As an antistatic agent composition containing a conductive polymer, an antistatic agent A was prepared which contained a polythiophene-based antistatic agent (BAYTRON (registered trademark) PAG manufactured by Starck), an acrylic resin (PESRESIN (registered trademark) SWX-079R manufactured by Takamatsu Oil Co., Ltd.), and a methylated melamine crosslinking agent (NIKALAC (registered trademark) MW-30HM manufactured by Nippon Carbide Industries Co., Ltd.) in a solid content mass ratio of 30/100/10.

Antistatic agent B was prepared as an antistatic agent composition containing nanocarbon, containing a carbon nanotube dispersion (Denatron (registered trademark) CD-100 manufactured by Nagase ChemteX Corporation), an acrylic resin (PES Resin (registered trademark) SWX-079R manufactured by Takamatsu Oil Co., Ltd.), and a methylated melamine crosslinking agent (Nicalac (registered trademark) MW-30HM manufactured by Nippon Carbide Industries Co., Ltd.) in a solids mass ratio of 10/100/10.

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 "Coronate (registered trademark) HX manufactured by Tosoh Corporation" as an isocyanate curing agent were added, and the mixture was stirred and mixed to obtain adhesive composition 1.

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

The antistatic agent B was diluted 10 times with water/ethanol (mass ratio of water/ethanol: 50/50) to obtain a second coating material. The second coating material was applied to the surface of the first layer so that the thickness after drying was 0.05 μm, and dried for 1 minute in a hot air circulating oven at 120° C. Thus, a second layer was formed.
Through the above steps, an antistatic film was obtained in which the base film (PET film)/first layer (antistatic agent A)/second layer (antistatic agent B) were laminated in this order.

Adhesive composition 1 was applied to the surface of the PET film that did not have an antistatic layer using an applicator so that the thickness after drying would be 20 μm, and then dried for 3 minutes in a hot air circulating oven at 120°C. This formed an adhesive layer.

A release film (25 μm thick) treated with a silicone-based release agent (Diafoil (registered trademark) MRF-25, manufactured by Mitsubishi Chemical Corporation) was attached to the surface of the adhesive layer to obtain a surface protection film with a release film. The obtained surface protection film with the release film was aged at 40°C for 3 days to obtain the surface protection film of Example 1.

Example 2
A surface protective film of Example 2 was produced in the same manner as in Example 1, except that the thicknesses of the first layer and the second layer were both 0.1 μm.

Example 3
A surface protective film of Example 3 was produced in the same manner as in Example 1, except that the thickness of the first layer was 0.05 μm and the thickness of the second layer was 0.15 μm.

Example 4
A surface protective film of Example 4 was produced in the same manner as in Example 2 except for the adhesive and curing agent.
As the adhesive, a urethane adhesive (Arakawa Chemical Industries, Ltd., Alacoat (registered trademark) FT200) was used instead of an acrylic adhesive. As the hardener, 5.7 parts by mass of "Arakawa Chemical Industries, Ltd., Alacoat (registered trademark) CL2503 (hardener non-volatile content is 40% by mass)" was used instead of 2 parts by mass of "Tosoh Corporation, Coronate (registered trademark) HX."

Example 5
The surface protection film of Example 5 was prepared in the same manner as in Example 2, except that a polyester resin (Vylonal (registered trademark) MD-1480 manufactured by Toyobo) was used instead of the acrylic resin (Pesresin (registered trademark) SWX-079R manufactured by Takamatsu Oil Co., Ltd.).

(Comparative Example 1)
A surface protection film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the thickness of the first layer was 0.2 μm and that the second layer was not provided.

(Comparative Example 2)
A surface protection film of Comparative Example 2 was obtained in the same manner as in Example 1, except that the first layer was not present and the thickness of the second layer was set to 0.2 μm.

(Comparative Example 3)
A surface protection film of Comparative Example 3 was prepared in the same manner as in Example 2, except that an antistatic agent layer of a single layer structure was used instead of the antistatic agent layer of a two-layer structure.
The single-layer antistatic agent layer was formed by coating an antistatic agent prepared by mixing antistatic agent A and antistatic agent B in a solid content mass ratio of 50/50, so as to have a thickness of 0.2 μm after drying.

(Comparative Example 4)
A surface protection film of Comparative Example 4 was obtained in the same manner as in Example 2, except that the positions of the first layer and the second layer were reversed.

(Comparative Example 5)
A surface protection film of Comparative Example 5 was produced in the same manner as in Example 1, except that the first layer and the second layer were not included.

The evaluation test methods and results are shown below.
(Method for measuring surface resistivity of surface protective film)
The surface resistivity (Ω/□) of the surface protective film was measured using a high performance resistivity meter (Hiresta (registered trademark)-UP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) under conditions of an applied voltage of 100 V and a measurement time of 30 seconds.

(Method of evaluating moist heat resistance)
The surface protection film was left for a predetermined period (1 day or 30 days) under conditions of a temperature of 60° C. and a relative humidity of 90%, and then left for 1 hour under conditions of a temperature of 23° C. and a relative humidity of 50%. The surface resistivity value (Ω/□) of the surface protection film was measured using a high-performance high resistivity meter (Hiresta (registered trademark)-UP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) under conditions of an applied voltage of 100 V and a measurement time of 30 seconds.

(Exposure resistance evaluation method)
The surface protection film was left exposed to air at a temperature of 23° C. and a relative humidity of 50% for a predetermined period of time (1 day or 30 days). The surface resistivity (Ω/□) of the surface protection film was measured using a high-performance high resistivity meter (Hiresta (registered trademark)-UP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) at an applied voltage of 100 V and a measurement time of 30 seconds.

<Method for measuring low speed adhesive strength of surface protection film>
A polarizing plate using a TAC film as a polarizer protective film was laminated on the surface of a glass plate using a laminating machine. After that, a surface protective film cut to a width of 25 mm was laminated on the surface of the polarizing plate, and the plate was stored for one day under a test environment of 23°C x 50% RH. Then, the strength was measured when the surface protective film was peeled off in the direction of 180° at a peeling speed of 0.3 m/min using a tensile tester, and this was taken as the low-speed adhesive strength (N/25 mm).

<Method for measuring high-speed adhesive strength of surface protection film>
A polarizing plate using a TAC film as a polarizer protective film was laminated on the surface of a glass plate using a laminating machine. After that, a surface protective film cut to a width of 25 mm was laminated on the surface of the polarizing plate, and the plate was stored for one day under a test environment of 23°C x 50% RH. Then, the strength was measured when the surface protective film was peeled off at a peeling speed of 30 m per minute using a high-speed peeling tester (manufactured by Tester Sangyo Co., Ltd.), and this was taken as the high-speed adhesive strength (N/25 mm).

<Method for measuring the peeling electrification voltage of surface protection film>
A polarizing plate using a TAC film as a polarizer protective film was laminated on the surface of a glass plate using a laminating machine. After that, a surface protective film cut to a width of 25 mm was laminated on the surface of the polarizing plate, and then the polarizing plate was stored for one day under a test environment of 23°C x 50% RH. Then, the surface protective film was peeled off at a peeling speed of 30 m per minute using a high-speed peeling tester (manufactured by Tester Sangyo Co., Ltd.), and 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 taken as the peeling electrification voltage (kV).

<Method for checking surface contamination of surface protection film>
A polarizing plate using a TAC film as a polarizer protective film was laminated on the surface of a glass plate using a laminating machine. Then, a surface protective film cut to a width of 25 mm was laminated on the surface of the polarizing plate, and the plate was stored for 3 days under a test environment of 23°C x 50% RH. Then, the surface protective film was peeled off, and the surface contamination of the polarizing plate was visually observed. As the criterion for the surface contamination, the case where there was no contamination transfer to the polarizing plate was rated as "○" (Good), and the case where contamination transfer was confirmed to the polarizing plate was rated as "×" (No Good).

The measurement results for the surface protection films of Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Tables 1 to 3. In Tables 1 to 3, "CNT" indicates the ratio of the thickness of the second layer to the total thickness of the first layer and the second layer. "PEDOT" indicates the ratio of the thickness of the first layer to the total thickness of the first layer and the second layer. "CNT/PEDOT (Mix)" indicates 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 solid mass ratio of antistatic agent A and antistatic agent B is both 50%.

"Antistatic agent layer stacking order reversed" indicates the stacking order of the first layer and the second layer. "◯" indicates that the stacking order of the base film, the first layer, and the second layer is "base film/second layer/first layer".
The "◯" in "acrylic resin" indicates that the binder resin in the first layer and the second layer is an acrylic resin. The "◯" in "polyester resin" indicates that the binder resin in the first layer and the second layer is a polyester resin.
The "◯" in "acrylic adhesive" indicates that an acrylic adhesive was used as the adhesive. The "◯" in "urethane adhesive" indicates that a urethane adhesive was used as the adhesive. The surface resistivity value of 1.0E+09 represents 1.0×10 to the power of 9. 1.0E+13< represents that the value exceeds the measurement limit (1.0×10 to the power of 13) of the measuring device (high performance high resistivity meter) and is over the range.

The measurement results shown in Tables 1 to 3 reveal the following.
In the surface protection films of Examples 1 to 5, the surface resistance value of the antistatic agent layer did not increase (deteriorate) even when exposed to the outside air and in a moist and hot environment.
On the other hand, in Comparative Example 1 in which the antistatic agent layer was formed only with the first layer (containing a conductive polymer), an increase (deterioration) in the surface resistance value of the antistatic agent layer was observed when exposed to the outside air.
In Comparative Example 2 in which the antistatic agent layer was formed only with the second layer (containing nanocarbon), an increase (deterioration) in the surface resistance value of the antistatic agent layer on the surface was observed in a humid and hot environment.
In Comparative Example 3, in which the antistatic agent layer had a single-layer structure made of a mixture of antistatic agents A and B instead of a two-layer structure, the surface resistance value of the antistatic agent layer increased (deteriorated) slightly in a humid and hot environment, whereas the surface resistance value of the antistatic agent layer on the surface increased (deteriorated) significantly in an outdoor air exposure environment.
In Comparative Example 4, in which the order of laminating the antistatic agent layers was reversed from that in Examples 1 to 5, an increase (deterioration) in the surface resistance value of the antistatic agent layer on the surface was observed in an outdoor air exposure environment and a moist heat environment.
In Comparative Example 5 in which no antistatic agent layer was provided, it is presumed that static electricity is easily generated during the process because the surface resistivity of the surface protection film is high.

The surface protection film of the embodiment can be used to protect the surface of optical components, for example, in the production process of optical films such as polarizing plates, retardation plates, lens films, and various other optical components. The surface protection film of the embodiment can suppress the increase (deterioration) in the surface resistance value of the antistatic agent layer on the surface even when exposed to the outside air or in a humid and hot environment. The surface protection film of the embodiment can suppress static electricity generated during transportation or handling of an optical product to which the surface protection film is attached in the manufacturing process of an optical product, thereby reducing the adsorption of dust and dirt in the environment. The surface protection film of the embodiment can suppress significant peeling charge when peeling and removing the surface protection film after use from a polarizing plate or retardation plate incorporated in a liquid crystal display panel, so there is little risk of damaging circuits such as driver ICs. Therefore, the yield of the production process can be improved, and the industrial utility value is great.

1...base film, 2...antistatic agent layer, 2a...first layer, 2b...second layer, 3...adhesive layer, 4...release film, 5...adherend (optical component), 10...surface protection film, 11...surface protection film with release film, 20...optical component.

Claims (4)

A substrate film made of a transparent resin;
an antistatic agent layer formed on one surface of the base film;
a pressure-sensitive adhesive layer formed on a surface of the base film opposite to the antistatic agent layer;
Equipped with
The antistatic agent layer is
a first layer comprising a conductive polymer;
a second layer including nanocarbon and disposed on the opposite side of the first layer from the base film;
A surface protection film comprising: The surface protection film according to claim 1, in which a release film is attached to the side of the adhesive layer opposite the base film. The surface protection film according to claim 1 or 2, wherein the adhesive layer is made of an acrylic adhesive. An optical component to which the surface protection film according to any one of claims 1 to 3 has been attached.

Images