TWI828799B - Surface-protective film and optical component attached with the same - Google Patents

Abstract

A surface-protective film and an optiacla compoenet attached with the same are provided by the present invention. The surface-protective film has a good effect of inhibiting the curl of the optical film, improves handling ability of optical film attached with the surface-protective film, is easily to be peeled off after used, and the does not required reattached and wipped out dirt when shipment. The surface-protective film (P) has a first transparent film (1), a first adhesive layer (2), a second transparent film (3), and a second adhesive layer (4) laminated in this order. The storage modulus of the first adhesive layer (2) at 23℃ is equal to or more than 1.0×10⁴ Pa and is less than 8.0×10⁴ Pa, and the adhesive force of the first adhesive layer (2) to glass is equal to or less than 5N/25mm.

Description

Surface protective film and optical components with the surface protective film attached

The present invention relates to a surface protective film and an optical component attached with the surface protective film.

Optical films such as polarizing plates, retardation plates, display lens films, anti-reflection films, hard coat films, and transparent conductive films for touch panels are used in optical products such as displays. When manufacturing and transporting optical films or optical components, a surface protective film is attached to the surface of the optical film to prevent surface dirt, scratches, etc. in subsequent steps. In some cases, the appearance of the optical film is inspected directly with the surface protective film attached.

Surface protection films based on the prior art typically have a structure in which a slightly adhesive adhesive layer is provided on one side of the base film. The adhesive layer is a layer for attaching the surface protective film to the optical film. The reason why the adhesive layer is slightly adhesive is that when the surface protective film is peeled off from the surface of the optical film after use, it can be peeled off smoothly without leaving any adhesive residue.

In recent years, displays have become thinner and more refined, and optical films have also become thinner. In addition, in order to reduce the thickness of the optical film, not only the thickness of each structural member is thinned, but also the structure is changed such as removing unnecessary components or integrating the functions of multiple components into one component to reduce the number of components. For example, an increasing number of polarizing plates have a structure in which a polarizing protective layer is laminated on only one side of a polarizer instead of both sides. In the case of a polarizing plate with only one polarizing protective layer provided for the polarizer, the structure holding the polarizer is asymmetrical between the inside and outside, and therefore has the property of being easily bent (easy to warp) on one side. Therefore, methods for suppressing warpage of optical films have been proposed.

For example, Patent Document 1 proposes a method of suppressing warpage of a polarizing plate by bonding a protective film (surface protective film) with a Gurley method stiffness of 1.0×10 ² mgf or more and 1.0×10 ⁵ mgf or less. How to make the song. Specific examples include protective films in which the thickness of the base film made of biaxially stretched polyester resin is in the range of 25 μm or more and 120 μm or less.

Patent Document 2 proposes a polarizing plate in which the rigidity of a laminate composed of a polarizing plate body and a protective film (surface protective film) is specified. A specific example includes a polarizing plate using a protective film having a base film made of a biaxially stretched polyester resin and having a thickness of 50 μm.

Patent Document 3 proposes a protective film that can effectively suppress crook (warp) of a polarizing plate. Specifically, a protective film having a first resin layer, an adhesive layer, a second resin layer and an adhesive layer in this order is proposed. The ratio of the thickness of the adhesive layer to the sum of the thickness of the first resin layer and the thickness of the second resin layer is 0.40 or less. The storage modulus of the adhesive layer at 23°C is from 8.0×10 ⁴ Pa to less than 1.0×10 ⁷ Pa. The protective film is attached to the surface of the polarizer as a whole and peeled off as a whole.

The surface protective films shown in Patent Documents 1 to 3 increase the thickness of the base film or use a laminated film in which a resin layer/adhesive layer/resin layer is laminated as the base film. Therefore, although the elasticity of the film becomes stronger, , the warpage suppressing effect of the optical film can be obtained, but on the other hand, there is a problem that the peeling force becomes stronger when the surface protective film is peeled off after use. When peeling off the surface protective film, peel off the surface protective film at a peeling angle close to 180° with respect to the optical film. The peeling force of the surface protective film at this time is the total force of the force required for the adhesive of the surface protective film to adhere to the optical film as the adherend and the force required to bend the surface protective film itself by 180°. If the elasticity of the surface protective film becomes stronger, the force required to bend the surface protective film itself by 180° will also increase, thus causing the peeling force of the surface protective film to become stronger. In recent years, in televisions and digital signage applications, displays have become larger in size as displays become thinner and more precise. It is difficult to use the optical film used in such a large display because the surface protective film has a strong peeling force when peeled off.

In the past, in the manufacturing of displays, components such as liquid crystal panels, backlight modules, and surface filters were purchased by panel manufacturers in the form of complete sets. Call it mod sourcing. However, in recent years, a procurement method called "open cell procurement" has become mainstream especially for television applications. In open cell procurement, components such as LCD panels, backlight modules, and surface filters are purchased separately and assembled at TV manufacturers, OEM destinations, etc. Therefore, the number of liquid crystal panels being distributed in a semi-finished state is increasing.

During module procurement, the surface protective film attached to the polarizer is peeled off after panelization. However, with the adoption of open cell procurement, in order to prevent the adhesion of dust and foreign matter when transporting liquid crystal panels, there are more and more cases where the surface protective film is not peeled off after panelization and before assembly (set). When shipping and transporting LCD panels, there are increasing cases in which the surface protective film that was contaminated during panelization is re-attached or the stains on the surface protective film are wiped off to keep the surface protective film in a clean state. For the surface protective films shown in Patent Documents 1 to 3, it is necessary to re-attach the surface protective film or wipe off the stains on the surface protective film before shipment of the liquid crystal panel, and it is impossible to reduce the number of steps or improve the operability. existing technical documents patent documents

Patent Document 1: Japanese Patent Application Publication No. 2012-053078 Patent Document 2: Japanese Republication List No. WO2016/039296 Patent Document 3: Japanese Patent No. 5461640

Technical problems to be solved by the present invention

One embodiment of the present invention was completed in view of the above-mentioned actual situation, and its technical problem is to provide a surface protective film that has a high effect of inhibiting warpage of optical films and an optical component using the surface protective film. , and the processing performance of the optical film laminated with the surface protective film is improved, and it is easy to peel and remove after use. There is no need to re-attach the surface protective film, wipe off stains, etc. during shipment. Technical means to solve technical problems

One embodiment of the present invention provides a surface protection film, which is sequentially laminated with a first transparent film, a first adhesive layer, a second transparent film and a second adhesive layer, and the first adhesive layer is The storage modulus is 1.0×10 ⁴ Pa or more and less than 8.0×10 ⁴ Pa, and the adhesion force of the first adhesive layer to glass is 5N/25mm or less.

The second adhesive layer can use a (meth)acrylic polymer as a base polymer.

Preferably: the adhesion force of the second adhesive layer to glass is less than 0.5N/25mm, and the adhesion force of the first adhesive layer to glass is higher than the adhesion force of the second adhesive layer to glass.

Preferably, the surface resistivity of the second adhesive layer is less than 1×10 ¹³ [Ω/□].

Another embodiment of the present invention provides an optical component to which the surface protective film is attached. Invention effect

According to one embodiment of the present invention, it is possible to provide a surface protective film that has a high inhibitory effect on warpage of optical films and an optical component to which the surface protective film is bonded, and an optical component using the surface protective film. The processing performance of the film is improved, and it is easy to peel off and remove after use. There is no need to re-attach the surface protective film or wipe off stains when shipping the LCD panel.

means of carrying out the invention

Hereinafter, the present invention will be described in detail based on implementation modes. FIG. 1 is a schematic structural diagram of the surface protection film P according to the embodiment. As shown in FIG. 1 , the surface protection film P is provided with a first adhesive layer 2 on one side of the first transparent film 1 . A second transparent film 3 is provided on the side of the first adhesive layer 2 opposite to the first transparent film 1 . A second adhesive layer 4 is provided on the opposite side of the second transparent film 3 to the first adhesive layer 2 . The release film 5 for protecting the adhesive surface is overlapped on the surface of the second adhesive layer 4 . That is, the surface protection film P is configured by laminating the first transparent film 1, the first adhesive layer 2, the second transparent film 3, the second adhesive layer 4, and the release film 5 in this order. In addition, the surface protection film P shown in FIG. 1 may include the release film 5 removed, that is, the first transparent film 1, the first adhesive layer 2, the second transparent film 3 and the second transparent film 3 may be laminated in this order. The film of adhesive layer 4 is called surface protection film P.

As the first transparent film 1 (base film), a transparent plastic film is used. By providing transparency to the first transparent film 1 and the second transparent film 3, the appearance inspection of the optical component can be performed with the surface protective film P attached. As the plastic film for the first transparent film 1, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate are suitably used. Ester film. In addition to polyester films, other plastic films may be used as long as they have the required strength and optical suitability. The first transparent film 1 may be a non-stretched film, or may be uniaxially or biaxially stretched. The first transparent film 1 may be a plastic film in which the stretching ratio, the angle in the axial direction due to crystallization due to stretching, and the like are controlled.

The thickness of the first transparent film 1 is not particularly limited, but is, for example, about 12 to 100 μm, and particularly about 20 to 50 μm. As needed, an antifouling layer, an antistatic layer, or an antifouling layer for the purpose of preventing surface dirt can be provided on the first transparent film 1 on the opposite side to the first adhesive layer 2 (the upper surface in Figure 1). Hard coating to prevent scratches, or easy adhesion treatment such as corona discharge treatment and anchor coat treatment.

When the surface protection film P is bonded to the optical film, the first adhesive layer 2 is used for the purpose of absorbing and relaxing stress associated with warping of the optical film. The material of the first adhesive layer 2 is not particularly limited as long as it satisfies characteristics such as no adverse effects on the adhesion to the transparent film, adhesion properties, stability, etc., and known materials can be used.

Examples of the material of the first adhesive layer 2 include rubber-based, acrylic-based, urethane-based adhesives, and the like. The rubber adhesive may be an adhesive in which an elastomer such as natural rubber or synthetic rubber is mixed with a tackifier, a softener, an anti-aging agent, a filler, etc., and a cross-linking agent may be added as needed. The acrylic adhesive is, for example, an adhesive obtained by adding a curing agent, a tackifier, etc. to a (meth)acrylic polymer as necessary. (Meth)acrylic polymers are usually composed of main monomers such as butyl acrylate (such as n-butyl acrylate), 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, etc.; acrylonitrile, acetic acid Comonomers of vinyl ester, methyl acrylate, methyl methacrylate, ethyl acrylate, etc.; and acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, dimethacrylate A polymer formed by the copolymerization of functional monomers such as amide, N-hydroxymethylmethacrylamide, hydroxyl-containing acrylic monomer, carboxyl-containing acrylate, and polyoxyalkylene-containing acrylic monomer. The (meth)acrylic polymer may have an appropriate composition selected based on required characteristics. (Meth)acrylic polymers can be used as base polymers.

Examples of the curing agent include isocyanate compounds, epoxy compounds, melamine compounds, metal chelate compounds, and the like. Examples of thickeners include rosins, coumarone-indenes, terpenes, petroleums, phenols, and the like. Additives such as a curing catalyst, a pot life extender, an antistatic agent, an ultraviolet absorber, and an antioxidant may also be added to the first adhesive layer 2 as needed. As the material of the first adhesive layer 2 , it is also possible to add a photoinitiator and a photocurable monomer or oligomer to the above-mentioned adhesive, and polymerize the monomer or oligomer after light irradiation to generate adhesive force. Changing adhesives.

Examples of the urethane adhesive include those in which the types and composition ratios of hard segments and soft segments are adjusted. As a material for the first adhesive layer 2 , an acrylic adhesive is particularly preferred from the viewpoint of heat resistance, durability, adhesion to the second transparent film 3 , and the like.

In the first adhesive layer 2, an adhesive whose adhesive force is reduced by irradiating ultraviolet rays may be used. The adhesive contains an ultraviolet initiator and an ultraviolet curable monomer or oligomer. By using this adhesive, when shipping and transporting the liquid crystal panel, the first transparent film and the first adhesive layer can be easily peeled off and removed from the second transparent film. The first adhesive layer 2 may also use an adhesive in which a thermal foaming agent is added to reduce the adhesive force by heating within a range that does not weaken the transparency.

The first adhesive layer 2 is an adhesive layer whose adhesive force to glass is 5N/25mm or less. It is preferable that the adhesive force of the first adhesive layer 2 when peeled off from glass at 180° and at a peeling speed of 300 mm/minute is 5 N/25 mm or less. If the adhesion force of the first adhesive layer 2 to the glass is greater than 5N/25mm, the peeling force when peeling off the surface protective film P becomes larger, which may reduce the operability. In addition, if the adhesion force of the first adhesive layer 2 to glass is greater than 5N/25mm, it may be difficult to seal the first transparent film 1 and the first adhesive layer 2 when necessary (when shipping the liquid crystal panel, etc.) The adhesive film is peeled off from the second transparent film 3 .

The adhesive force of the first adhesive layer 2 to glass can be set to 1 N/25 mm or more, for example. If the adhesive force of the first adhesive layer 2 to glass is 1 N/25 mm or more, the adhesive film composed of the first transparent film 1 and the first adhesive layer 2 is unlikely to be accidentally peeled off.

Considering the operability when peeling and removing the surface protective film P, it is preferable that the adhesive force of the first adhesive layer 2 is higher than the adhesive force of the second adhesive layer 4 . This makes it easy to peel the adhesive film composed of the first transparent film 1 and the first adhesive layer 2 from the second transparent film 3 when the liquid crystal panel is shipped.

The storage modulus of the first adhesive layer 2 at 23°C is 1.0×10 ⁴ Pa or more and less than 8.0×10 ⁴ Pa. If the storage modulus of the first adhesive layer 2 is less than 1.0×10 ⁴ Pa, when the surface protective film P is rolled into a roll for storage, the adhesive may be extruded from the edges and foreign matter may easily adhere to the edges. Wait for bad situations. In addition, the warpage-inhibiting effect of the optical film may be reduced. If the storage modulus of the first adhesive layer 2 is 8.0×10 ⁴ Pa or more, the peeling force when peeling and removing the surface protective film P becomes large, and the operability may be reduced.

The thickness of the first adhesive layer 2 is not particularly limited, but is usually about 3 to 30 μm. By setting the thickness of the first adhesive layer 2 to 3 μm or more, a predetermined adhesive force can be obtained. By setting the thickness of the first adhesive layer 2 to 30 μm or less, costs can be suppressed.

As a method of forming the first adhesive layer 2 on the first transparent film 1, a known method may be used. For example, a method of applying an adhesive on the first transparent film 1 and drying and curing it, or a method of applying an adhesive on the second transparent film and drying and curing it and then laminating the first transparent film, etc. . 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.

As the second transparent film 3, a transparent plastic film can be used. By providing transparency to the first transparent film 1 and the second transparent film 3, the appearance inspection of the optical component can be performed in a state where the surface protective film is bonded. As the plastic film used for the second transparent film 3, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate are suitably used. Ester film. In addition to polyester films, other plastic films can be used as long as they have the required strength and optical suitability. The second transparent film 3 may be a non-stretched film, or may be uniaxially or biaxially stretched. The second transparent film 3 may also be a plastic film in which the stretching ratio, the angle in the axial direction due to crystallization due to stretching, and the like are controlled.

The thickness of the second transparent film 3 is not particularly limited, but is, for example, about 12 to 100 μm, and particularly about 19 to 50 μm. The side of the second transparent film 3 that is in contact with the first adhesive layer 2 may also be subjected to an easy-adhesion treatment or an antistatic treatment such as corona discharge treatment and primer treatment as needed. In addition, an easy-adhesion treatment such as antistatic treatment, corona discharge treatment, and primer treatment may be performed on the side opposite to the first adhesive layer 2 (lower surface in FIG. 1 ) of the second transparent film 3 .

The second adhesive layer 4 is provided in order to bond the surface protection film P to the optical film as an adherend. The second adhesive layer 4 is a layer composed of a slightly adhesive adhesive. The reason for using an adhesive with slight adhesion is to prevent the surface protective film P from peeling off during the manufacturing process of the optical film, and to ensure that the surface protective film P can be peeled off and removed smoothly from the surface of the optical film after use. It peels off smoothly without leaving any adhesive residue.

The material of the second adhesive layer 4 is not particularly limited, and known materials such as rubber, acrylic, and urethane adhesives can be used. Among them, acrylic adhesives are suitable. An acrylic adhesive is, for example, an adhesive obtained by adding a curing agent, a tackifier, etc. to a (meth)acrylic polymer as necessary. (Meth)acrylic polymers are usually composed of main monomers such as butyl acrylate (such as n-butyl acrylate), 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, etc.; acrylonitrile, acetic acid Comonomers of vinyl ester, methyl acrylate, methyl methacrylate, ethyl acrylate, etc.; and acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, dimethacrylate A polymer formed by the copolymerization of functional monomers such as amide, N-hydroxymethylmethacrylamide, hydroxyl-containing acrylic monomer, carboxyl-containing acrylate, and polyoxyalkylene-containing acrylic monomer. The (meth)acrylic polymer may have an appropriate composition selected based on required characteristics. (Meth)acrylic polymers can be used as base polymers.

Examples of the curing agent include isocyanate compounds, epoxy compounds, melamine compounds, metal chelate compounds, and the like. Examples of thickeners include rosins, coumarone-indenes, terpenes, petroleums, phenols, and the like. Additives such as curing catalysts, pot life extenders, antistatic agents, ultraviolet absorbers, and antioxidants can also be added to the acrylic adhesive as needed.

The antistatic agent may be one that has good dispersion or compatibility with (meth)acrylic polymers, and examples thereof include surfactants, ionic liquids, ionic solids, alkali metal salts, Metal oxides, metal particles, conductive polymers, carbon, carbon nanotubes, etc. As the antistatic agent, surfactants, ionic liquids, ionic solids, alkali metal salts, etc. are preferred from the viewpoint of transparency, affinity for (meth)acrylic polymers, and the like.

Examples of surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Ethylene fatty acid esters, glycerin fatty acid esters, propylene glycol fatty acid esters, polyoxyalkylene modified silicones, etc. Examples of cationic surfactants include alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and the like. Examples of anionic surfactants include monoalkyl sulfates, alkyl polyoxyethylene sulfates, alkyl benzene sulfonates, monoalkyl phosphates, and the like. Examples of amphoteric surfactants include alkyldimethylamine oxide, alkylcarboxybetaine, and the like.

Ionic liquids refer to non-polymer substances that contain anions and cations and are liquid at room temperature. Examples of the cation moiety include cyclic amidine ions such as imidazolium ions, pyridinium ions, ammonium ions, sulfonium ions, and phosphonium ions. Examples of the anion part include C _n H _2n+1 COO ^- , C _n F _2n+1 COO ^- , NO ₃ ^- , C _n F _2n+1 SO ₃ ^- , (C _n F _2n+1 SO ₂ ) ₂ N ^- , (C _n F _2n+1 SO ₂ ) ₃ C ^- , PO ₄ ^2- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , ClO ₄ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^-wait .

Ionic solids refer to non-polymer substances that contain anions and cations and are solid at room temperature. Examples of the cation moiety include nitrogen-containing onium ions (onium ions) such as pyridinium ions, imidazolium ions, pyrimidinium ions, pyrazolium ions, pyrrolidinium ions, and ammonium ions, or phosphonium ions and sulfonium ions. Examples of the anion part include hexafluorophosphate (PF ₆ ^- ), thiocyanate (SCN ^- ), alkylbenzene sulfonate (RC ₆ H ₄ SO ₃ ^- ), and perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ^- ) and other compounds as inorganic or organic anions. By selecting the chain length of the alkyl group, the position and number of the substituents, etc., an ionic solid that is solid at room temperature can be obtained.

Examples of alkali metal salts include metal salts containing alkali metals such as lithium, sodium, and potassium. Examples of the alkali metal salt include lithium trifluoromethanesulfonate (CF ₃ LiO ₃ S). In order to stabilize ionic substances, a compound containing a polyoxyalkylene structure may be added to the antistatic agent.

The amount of an antistatic agent component added to a base polymer such as a (meth)acrylic polymer varies depending on the type of antistatic component or the degree of compatibility with the base polymer. Just set it according to the material contamination property, adhesion characteristics, etc. Additives such as curing catalysts, pot life extenders, UV absorbers, and antioxidants can be added to acrylic adhesives as needed.

When the surface protective film P is used in a situation where peeling static voltage may be generated during peeling and removal, it is suitable to add an antistatic component (antistatic agent) to the second adhesive layer 4 . At this time, it is preferable that the surface resistivity of the second adhesive layer 4 is less than 1×10 ¹³ [Ω/□]. If the surface resistivity of the second adhesive layer 4 is less than 1×10 ¹³ [Ω/□], the peeling static voltage when removing the surface protective film can be reduced. Therefore, the antistatic performance can be improved.

The thickness of the second adhesive layer 4 is not particularly limited, but is, for example, about 3 to 50 μm, and in particular is usually about 5 to 30 μm.

The adhesion force of the second adhesive layer 4 to glass depends on the type of surface treatment of the optical film to which the surface protective film P is attached, but is suitably 0.5N/25mm or less. It is preferable that the adhesive force of the second adhesive layer 4 at 180° peeling from glass at a peeling speed of 300 mm/min is 0.5 N/25 mm or less. If the adhesive force of the second adhesive layer 4 is 0.5 N/25 mm or less, the peeling force when peeling and removing the surface protective film P becomes low, so the workability can be improved.

It is preferable that the second adhesive layer 4 is a micro-adhesive layer having slight adhesiveness with a peel strength of about 0.03 to 0.3 N/25 mm to the surface of the adherend (optical film). If the adhesive force of the second adhesive layer 4 is 0.03N/25mm or more, the surface protection film P can be suppressed from being lifted (ie, partially peeled off) during the optical film manufacturing process, transportation process, and the like. In addition, the surface protective film P is less likely to be erroneously peeled off. When the adhesive force of the second adhesive layer 4 is 0.3N/25mm or less, operability can be improved.

The second adhesive layer 4 may be laminated on the second transparent film 3 using a known method, and is not particularly limited. Specifically, (1) the adhesive forming the second adhesive layer 4 is applied to the second transparent film 3 and dried to form the second adhesive layer 4, and then the release film 5 is bonded to the second transparent film 3. Method for forming the surface of the adhesive layer 4; (2) Coating the adhesive forming the second adhesive layer 4 on the release film 5, drying it to form the second adhesive layer 4, and then laminating the second transparent film 3 wait.

The second adhesive layer 4 can be formed on the second transparent film 3 using a known method. Specifically, the adhesive may be applied by coating means such as reverse coating, comma coating, gravure coating, sandwich extrusion coating, Meyer rod coating, and air knife coating.

The surface protection film P usually uses a release film 5 to protect the surface of the adhesive layer 4 of an adhesive sheet in which the first adhesive layer 2, the second transparent film 3, and the second adhesive layer 4 are formed on the first transparent film 1. composition. If necessary, the surface protection film P may be a product in which the first transparent film 1/first adhesive layer 2/second transparent film 3/second adhesive layer 4 are rolled into a tape shape without using the release film 5. form.

The release film 5 is not particularly limited. Examples thereof include a release film in which the surface of a film such as a polyester film is subjected to a release treatment using a release agent such as a silicone release agent.

FIG. 2 is an example of an optical component using the surface protective film P according to the embodiment, and is a schematic structural diagram of the optical component D. As shown in FIG. 2 , the optical component D is obtained by bonding the surface protection film P shown in FIG. 1 to the surface of the optical film C using the adhesive layer 4 . Examples of the optical film C include a polarizing plate, a retardation plate, a lens film, a polarizing plate that doubles as a retardation plate, a polarizing plate that doubles as a lens film, and the like. This optical component D can be used in the manufacture of liquid crystal display devices such as liquid crystal display panels, optical system devices such as various measuring instruments, and the like.

Since the surface protection film P of the embodiment has a multilayer structure including two transparent films and two adhesive layers, it is highly effective in suppressing warpage of the optical film C. The above-mentioned structure of the surface protective film P prevents bends, unevenness, etc. from easily occurring on the optical film C. Therefore, the handling performance of the optical film C can be improved. Generally, when a thicker surface protective film is formed, warpage suppression and handling properties become higher, but the peelability of the surface protective film decreases. In contrast, since the surface protective film P of the embodiment uses the first adhesive layer 2 having the above characteristics, it has the advantage of being easily peeled off and removed after use.

Since the surface protection film P uses the first adhesive layer 2 having the above characteristics, the adhesive film composed of the first transparent film 1 and the first adhesive layer 2 can be peeled and removed from other parts. For example, FIG. 3 is a schematic structural diagram showing a structure for peeling and removing the adhesive film composed of the first transparent film 1 and the first adhesive layer 2 from the optical component D. As shown in Figure 3. By peeling and removing the adhesive film, the clean surface of the surface protective film can be exposed. Therefore, there is no need to reapply the surface protective film or wipe off stains when shipping the LCD panel. Therefore, the number of steps can be reduced, and improvements in yield, productivity, and operability can be achieved. Especially for optical films that have been thinned, the surface protective film P has a high inhibitory effect on the warpage of the optical film, and the optical film laminated with the surface protective film has improved handling properties and is easy to peel off after use. Remove. Therefore, it is possible to achieve improvements in the yield, productivity, and workability of the manufacturing step of thinning the optical film. Example

Next, the present invention will be further described with reference to examples. Hereinafter, "parts by mass" may be simply referred to as "parts". (Preparation of surface protective film of Example 1) To 100 parts of a base polymer composed of butyl acrylate, methyl acrylate, dimethacrylamide, and hydroxyl-containing acrylic monomer, 0.3 parts of an isocyanate curing agent is blended as a curing agent to obtain adhesive A. The adhesive layer formed by coating Adhesive A on a biaxially stretched polyester film with a thickness of 38 μm (coating thickness after drying is 10 μm) has an adhesion force to glass of 3.8N/25mm.

To 100 parts of a base polymer composed of 2-ethylhexyl acrylate and a hydroxyl-containing acrylic monomer, 3 parts of an isocyanate curing agent was blended as a curing agent to obtain adhesive B. The adhesive layer formed by coating Adhesive B on a biaxially stretched polyester film with a thickness of 38 μm (coating thickness after drying is 20 μm) has an adhesion to glass of 0.2N/25mm.

After applying adhesive A to a colorless and transparent biaxially stretched polyester film (first transparent film) with a thickness of 25 μm so that the coating thickness after drying becomes 10 μm, dry it using a hot air circulation oven at 120°C 2 minute. Next, a colorless and transparent biaxially stretched polyester film (second transparent film) with a thickness of 38 μm was bonded to the surface of the adhesive A (the adhesive A-coated surface). After applying Adhesive B on the opposite side of the laminated biaxially stretched polyester film to Adhesive A so that the dried coating thickness becomes 20 μm, dry it using a 120°C hot air circulation oven 2 minute.

A release film (release film) coated with a silicone release agent on a biaxially stretched polyester film with a thickness of 25 μm, so that the surface of the adhesive B is in contact with the release agent-treated surface (the silicone release agent is coated) surface) in contact with each other and adhere to the surface of Adhesive B (the surface coated with Adhesive B). The obtained sample was aged for 3 days in a hot air circulation oven at 40°C to obtain the surface protective film of Example 1. The adhesive layer formed with adhesive A is the first adhesive layer. The adhesive layer formed with adhesive B is the second adhesive layer.

(Preparation of surface protective film of Example 2) For 100 parts of the base polymer composed of butyl acrylate, methyl acrylate, dimethylacrylamide, hydroxyl-containing acrylic monomer, and carboxyl-containing acrylate, 0.5 part of isocyanate curing agent is blended as the curing agent , get adhesive C. The adhesive force formed by applying adhesive C to a biaxially stretched polyester film with a thickness of 38 μm (coating thickness after drying is 10 μm) has an adhesion to glass of 4.8N/25mm. The surface protection film of Example 2 was obtained in the same manner as Example 1 except that adhesive C was used instead of adhesive A.

(Preparation of surface protective film of Example 3) To 100 parts of a base polymer composed of butyl acrylate, methyl acrylate, dimethacrylamide, and hydroxyl-containing acrylic monomer, 1.5 parts of an isocyanate curing agent is blended as a curing agent to obtain adhesive D. The adhesive layer formed by coating adhesive D on a biaxially stretched polyester film with a thickness of 38 μm (coating thickness after drying is 10 μm) has an adhesion force to glass of 1.6N/25mm. The surface protection film of Example 3 was obtained in the same manner as Example 1 except that adhesive D was used instead of adhesive A.

(Preparation of surface protective film of Example 4) The surface of Example 4 was obtained in the same manner as in Example 1, except that a colorless and transparent biaxially stretched polyester film with a thickness of 25 μm was used instead of the biaxially stretched polyester film with a thickness of 38 μm (second transparent film). Protective film.

(Preparation of surface protective film in Example 5) To 100 parts of a base polymer composed of 2-ethylhexyl acrylate, a polyoxyalkylene group-containing acrylic monomer, and a hydroxyl-containing acrylic monomer, 0.1 was blended lithium trifluoromethanesulfonate as an antistatic agent, and 3.0 parts of an isocyanate curing agent as a curing agent to obtain adhesive E. The adhesive force of the adhesive layer formed by coating adhesive E on a biaxially stretched polyester film with a thickness of 38 μm (the coating thickness after drying is 20 μm) is 0.15N/25mm. The surface resistance value of the adhesive surface is 0.15N/25mm. is 6.0×10 ¹¹ Ω/□. Except using adhesive E instead of adhesive B, the surface protection film of Example 5 was obtained in the same manner as Example 1.

(Preparation of surface protective film of Comparative Example 1) Adhesive B was applied to a colorless and transparent biaxially stretched polyester film with a thickness of 38 μm so that the coating thickness after drying would be 20 μm, and then dried using a hot air circulation oven at 120° C. for 2 minutes. A release film (release film) coated with a silicone release agent on a biaxially stretched polyester film with a thickness of 25 μm, so that the surface of the adhesive B is in contact with the release agent-treated surface (the silicone release agent is coated) surface) in contact with each other and adhere to the surface of Adhesive B (the surface coated with Adhesive B). The obtained sample was aged in a hot air circulation oven at 40° C. for 3 days to obtain the surface protective film of Comparative Example 1. The adhesive B becomes the adhesive layer.

(Preparation of surface protective film of Comparative Example 2) The surface protection film of Comparative Example 2 was obtained in the same manner as Comparative Example 1 except that a colorless and transparent biaxially stretched polyester film with a thickness of 75 μm was used instead of the biaxially stretched polyester film with a thickness of 38 μm.

(Preparation of surface protective film of Comparative Example 3) The surface protection film of Comparative Example 3 was obtained in the same manner as Comparative Example 1 except that a colorless and transparent biaxially stretched polyester film with a thickness of 100 μm was used instead of the biaxially stretched polyester film with a thickness of 38 μm.

(Preparation of surface protective film of Comparative Example 4) For 100 parts of the base polymer composed of butyl acrylate, methyl acrylate, dimethylacrylamide, hydroxyl-containing acrylic monomer, and carboxyl-containing acrylate, 0.2 parts of isocyanate curing agent is mixed as the curing agent , get adhesive F. The adhesive force formed by applying adhesive F to a biaxially stretched polyester film with a thickness of 38 μm (the coating thickness after drying is 10 μm) has an adhesion to glass of 6.5N/25mm. A surface protective film of Comparative Example 4 was obtained in the same manner as Example 1 except that adhesive F was used instead of adhesive A.

(Preparation of surface protective film of Comparative Example 5) To 100 parts of a base polymer composed of butyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, and hydroxyl-containing acrylic monomer, 0.3 parts of an isocyanate curing agent is mixed as a curing agent to obtain adhesive G. . The adhesive layer formed by coating adhesive G on a biaxially stretched polyester film with a thickness of 38 μm (coating thickness after drying is 10 μm) has an adhesion force to glass of 3.2N/25mm. The surface protective film of Comparative Example 5 was obtained in the same manner as in Example 1 except that adhesive G was used instead of adhesive A.

(Preparation of surface protective film of Comparative Example 6) To 100 parts of a base polymer composed of 2-ethylhexyl acrylate, a hydroxyl-containing acrylic monomer, and a carboxyl-containing acrylic monomer, 2.0 parts of an isocyanate curing agent was blended as a curing agent to obtain adhesive H. The adhesive force formed by applying adhesive H to a biaxially stretched polyester film with a thickness of 38 μm (the coating thickness after drying is 20 μm) has an adhesion to glass of 0.6N/25mm. A surface protective film of Comparative Example 6 was obtained in the same manner as Example 1 except that adhesive H was used instead of adhesive B.

The evaluation test method is shown below. (Measurement of the adhesive force of the adhesive layer) After the adhesive is applied to a biaxially stretched polyester film with a thickness of 38 μm, it is dried in a hot air circulation oven at 120°C for 2 minutes. A release film made of a biaxially stretched polyester film with a thickness of 25 μm and coated with a silicone release agent was bonded to the adhesive surface (adhesive coated surface). The obtained sample was aged for 3 days in a hot air circulation oven at 40°C. Cut the sample to 25mm wide and 150mm long. After peeling off the release film from the sample, the sample (surface protective film) was bonded to the glass plate. The sample was pressed against the glass plate by rolling a 2kg rubber roller back and forth over the sample once. Then, the sample and the glass plate were left for 1 hour at a temperature of 23°C and a relative humidity of 50%, and then a tensile testing machine was used to measure the strength of the surface protective film when peeled off at a peeling angle of 180° and a peeling speed of 300mm/minute.

(Measurement of storage modulus) After the adhesive is applied to a biaxially stretched polyester film with a thickness of 38 μm, it is dried in a hot air circulation oven at 120°C for 2 minutes. A release film made of a biaxially stretched polyester film with a thickness of 25 μm and coated with a silicone release agent was bonded to the adhesive surface (adhesive coated surface). The obtained sample was aged for 3 days in a hot air circulation oven at 40°C. The adhesive becomes the adhesive layer. After peeling off the release film from the sample, use a viscoelasticity measuring device (dynamic viscoelasticity testing device Rheogel-E4000 manufactured by UBM Company) to measure the storage modulus of the adhesive layer at 23°C.

(Evaluation of processing performance) A polarizing plate sample (total thickness: 48 μm) in which a triacetylcellulose (acetylcellulose) film was bonded to one side of a polarizing lens made of iodine and polyvinyl alcohol was cut into A4 size (210 mm × 297 mm). Use a desktop laminator to laminate the surface protective film to the polarizer. Pinch one of the four corners of the polarizing plate laminated with a surface protective film, wave it back and forth 30 times, and visually inspect the polarizing plate for any appearance defects such as bends or unevenness. The case without defects was rated as ○, and the case with defects was rated as ×.

(Evaluation of warpage inhibitory properties) A polarizing plate sample (total thickness: 48 μm) in which a triacetyl cellulose film was bonded to one side of a polarizing lens made of iodine and polyvinyl alcohol was cut into A4 size (210 mm × 297 mm). Use a desktop laminator to laminate the surface protective film to the polarizer. Place it on the experimental bench with the warped convex surface facing downwards. Measure the floating distance of the four corners from the surface of the test bench, and set the largest value as the amount of warpage. The case where the amount of warpage is less than 10 mm is evaluated as ○, the case where the amount of warpage is 10 mm or more and less than 20 mm is evaluated as Δ, and the case where the amount of warpage is 20 mm or more is evaluated as ×.

(Evaluation of protective film peelability) A polarizing plate (total thickness: 48 μm) with a triacetylcellulose film laminated on one side of the polarizer was prepared. Cut the sample of the surface protective film (protective film) into a width of 25 mm and a length of 150 mm. After peeling off the release film from the sample, the sample was attached to the triacetylcellulose film surface of the polarizing plate. By rolling a 2kg rubber roller back and forth over the sample once, press it toward the polarizing plate. Then, the sample and the polarizing plate were left for 24 hours at a temperature of 23°C and a relative humidity of 50%. Then, a high-speed peeling tester was used to measure the strength of the surface protective film when peeled off at a peeling angle of 180° and a peeling speed of 30m/min. Rating is ○ for less than 1.8N/25mm, △ for 1.8N/25mm or more and less than 2.5N/25mm, and × for 2.5N/25mm or more.

(Releasability of the first adhesive layer) Prepare a polarizing plate in which a cellulose triacetate film is laminated on one side of a polarizer, and an adhesive layer and a release film attached to the surface of the adhesive layer are provided on the side of the polarizer opposite to the cellulose triacetate film. Total thickness is 48μm). Cut the surface protective film sample to a width of 25mm and a length of 150mm. After peeling off the release film from the sample, the sample was bonded to the cellulose triacetate film surface of the polarizing plate to obtain a polarizing plate with a surface protective film. Press the sample toward the polarizing plate by rolling a 2kg rubber roller back and forth on the sample once. Then, the release film attached to the polarizing plate was peeled off, and the polarizing plate with the surface protective film was attached to the glass plate using a desktop laminator. Then, after placing the polarizer and glass plate with the surface protective film at a temperature of 23°C and a relative humidity of 50% for 24 hours, press the second transparent film part with your hand while connecting the first transparent film and the first transparent film. When the adhesive film composed of the adhesive layer is peeled off from the second transparent film, the case where the adhesive film is peeled off without peeling off the second adhesive layer is rated as good (○), and the case where peeling occurs on the second adhesive layer or If it floats, it is rated as bad (×).

Table 1 shows the measurement results of each sample. In addition, as a reference value, the measurement results of the electrostatic voltage when peeling off the surface protective film of Examples 1 and 5 are shown in Table 2.

[Table 1]

[Table 2] Project unit Example 1 Example 5 Surface resistance value of the second adhesive layer Ω/□ 5.80E+13 6.00E+11 Stripping static voltage kV 1.2 0.1

From Table 1 and Table 2, the following contents can be seen. The surface protective films of Examples 1 to 5 have a high inhibitory effect on the warpage of optical films, and the optical films to which the surface protective films are bonded have good handling properties. From the peeling force results, it can be seen that the surface protective films of Examples 1 to 5 are surface protective films that can be easily peeled off and removed after use. According to the peelability results of the first adhesive layer, the surface protective films of Examples 1 to 5 can peel and remove the adhesive film composed of the first transparent film and the first adhesive layer. Example 5 in which an antistatic agent was added to the second adhesive layer provided a surface protective film with a low peeling static voltage when the surface protective film was removed.

In contrast, the surface protective films of Comparative Examples 1 to 3 in which only the second adhesive layer was provided on the polyester film had good handling performance and warpage suppression properties by increasing the thickness of the film. Reduced peelability. That is, the surface protective films of Comparative Examples 1 to 3 were unable to improve all of warpage suppression properties, handling performance, and peelability. The surface protective film of Comparative Example 4, which has a high adhesive force of the first adhesive layer, has good handling properties and warpage inhibition properties, but the peeling force and the peelability of the first adhesive layer cannot be said to be good. The surface protective film of Comparative Example 5 in which the storage modulus of the first adhesive layer was low was poor in warpage suppression properties. Perhaps due to warping, the peelability has deteriorated. The surface protective film of Comparative Example 6, which has a high adhesive force in the second adhesive layer, has good handling properties and warpage-inhibiting properties, but the peelability cannot be said to be good. Industrial applicability

The present invention can be used, for example, in the production process of optical films such as polarizing plates, phase plates, and lens films, and optical components, etc., to be bonded to the surfaces of the optical components and the like to protect the surfaces. In particular, optical films that have been thinned have a high inhibitory effect on warpage of the optical film, and the optical film to which the surface protective film is bonded has improved handling properties and can be easily peeled off and removed after use. Therefore, it is possible to improve the productivity of the manufacturing step of thinning the optical film and improve the productivity. In addition, since there is no need to reattach the surface protective film or wipe off stains during shipment, etc., it is possible to improve operability and improve productivity.

1: First transparent film 2: First adhesive layer 3: Second transparent film 4: Second adhesive layer 5: Peel off film C: Optical film D: Optical components P:Surface protective film

FIG. 1 is a schematic structural diagram of the surface protective film according to the embodiment. FIG. 2 is a schematic structural diagram of an example of an optical component using the surface protective film according to the embodiment. FIG. 3 is a schematic structural diagram showing the structure after peeling off the adhesive film composed of the first transparent film and the first adhesive layer from the optical component shown in FIG. 2 .

1: First transparent film

2: First adhesive layer

3: Second transparent film

4: Second adhesive layer

5: Peel off film

P:Surface protective film

Claims (4)

A surface protection film, which is sequentially laminated with a first transparent film, a first adhesive layer, a second transparent film and a second adhesive layer. The storage modulus of the first adhesive layer at 23°C is 1.0× 10 ⁴ Pa or more and less than 8.0 × 10 ⁴ Pa, and the adhesion force of the first adhesive layer to glass is more than 1N/25mm and less than 5N/25mm, and the adhesion force of the second adhesive layer to glass is 0.15 N/25mm or more, 0.5N/25mm or less. The surface protection film according to claim 1, wherein the second adhesive layer uses a (meth)acrylic polymer as a base polymer. The surface protection film according to claim 1 or 2, wherein the surface resistivity of the second adhesive layer is less than 1×10 ¹³ [Ω/□]. An optical component attached with the surface protective film described in any one of claims 1 to 3.

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