TWI802530B - Surface-protective film and optical component attached with the same - Google Patents

Abstract

The present invention provides a surface protection film applicable for an optical film having an uneven surface, and an optical component using the same. The surface protection film has less contaminants to the adherend which does not change over time. Also, the surface protection film has excellent antistatic performance upon peeling which does not degrade over time. The surface protection film 10 is formed by attaching a release film 5 having a release agent layer 4 on an adhesive layer 2. The release film 5 is formed by laminating the release agent layer 4 on one side of a resin film, wherein the release agent layer 4 includes a release agent having dimethylpolysiloxane as the main component, an antistatic agent not reacting with the release agent, and an adjuvant of the antistatic agent. The component of the antistatic agent is an ionic compound having a melting point of less than 30℃. The component of the adjuvant of the antistatic agent is polyether-modified silicone. The antistatic agent and the adjuvant thereof are transferred to a surface of the adhesive layer 2 from the release agent layer 4 of the release film 5, thereby reducing the electrostatic voltage when the adhesive layer 2 is peeled off from the adherend.

Description

Surface protection film and optical element with the film attached

The present invention relates to a surface protection film bonded to the surface of an optical element (hereinafter, sometimes referred to as an optical film) such as a polarizing plate, a phase difference plate, and a lens film for a display. More specifically, to provide a surface protection film with less pollution to adherends, further, to provide a surface protection film with excellent anti-peeling static electricity without cracking over time, and an optical device using the above surface protection film. element.

Conventionally, optical films such as polarizing plates, retardation plates, lens films for displays, anti-reflective films, hard coat films, transparent conductive films for touch panels, and displays using these films have been used. When producing products, by attaching a surface protection film to the surface of the optical film, it is possible to prevent dirt, scratches, etc. on the surface in subsequent steps. In order to save the procedures of peeling off the surface protection film and re-bonding and improve work efficiency when inspecting the appearance of the optical film of optical products, it is sometimes carried out directly in the state where the surface protection film is bonded to the optical film.

In general, in the manufacturing process of optical products, in order to prevent adhesion of scratches, dirt, etc., the surface protection film which provided the adhesive agent layer on one side of a base film is used. The surface protection film is attached to the optical Use film on. The reason why the adhesive layer is set to be slightly viscous is that when the used surface protection film is peeled off from the surface of the optical film, it can be easily peeled off, and the adhesive does not remain attached (that is, to prevent the generation of adhesive residue) ) on the optical film of the product as the adherend.

In recent years, in the production steps of liquid crystal display panels, although the number of cases that have occurred is small, the peeling electrostatic voltage generated when the surface protective film bonded to the optical film is peeled off still occurs, making it difficult for control A phenomenon in which the circuit elements such as the driver IC of the display screen of the liquid crystal display panel are destroyed, and the alignment of the liquid crystal molecules is damaged.

In addition, in order to reduce the power consumption of the liquid crystal display panel, the driving voltage of the liquid crystal material is lowered, and the breakdown voltage of the driver IC is also lowered accordingly. Recently, the stripping electrostatic voltage is required to be in the range of +0.7kV~-0.7kV.

Moreover, with the spread of 3D displays (stereoscopic displays) in recent years, FPR (Film Patterned Retarder) films may be bonded to the surfaces of optical films such as polarizing plates. The FPR film is bonded after peeling off the surface protection film bonded on the surface of optical films, such as a polarizing plate. However, when the surface of an optical film such as a polarizing plate is contaminated with an adhesive or an antistatic agent used in a surface protection film, there is a problem that it is difficult to attach the FPR film. Therefore, the surface protective film used for the above-mentioned application is required to be less polluting to the adherend.

In addition, some manufacturers of liquid crystal panels adopt the method of temporarily peeling off the surface protection film attached to an optical film such as a polarizing plate as a method of evaluating the contamination of the adherend by the surface protection film, and then removing air bubbles in the Re-attach it under the condition, and heat it under the specified conditions, then peel off the surface protective film and observe the surface of the adherend. In the above evaluation method, even if the sticky The surface contamination of the object is slight, but if there is a difference in the surface contamination of the adhesive between the part where the air bubbles are mixed and the part that is in contact with the adhesive of the surface protection film, it will be traces of air bubbles (sometimes also known as bubble marks) form. Therefore, it is a very strict evaluation method as an evaluation method of contamination on the surface of the adherend. In recent years, there has been a demand for a surface protection film that does not pose a problem in terms of contamination of the surface of an adherend even as a result of evaluation based on such a strict evaluation method.

When the surface protective film is peeled from the optical film as the adherend, in order to prevent the occurrence of adverse conditions caused by high peeling electrostatic voltage, someone has proposed a method that can suppress the peeling electrostatic voltage. Antistatic agent for the surface protection film of the adhesive layer.

For example, Patent Document 1 discloses a surface protection film using an adhesive composed of an alkyltrimethylammonium salt, a hydroxyl-containing acrylic polymer, and polyisocyanate.

In addition, Patent Document 2 discloses an adhesive composition comprising an ionic liquid and an acrylic polymer having an acid value of 1.0 or less, and adhesive sheets using the adhesive composition.

In addition, Patent Document 3 discloses an adhesive composition comprising an acrylic polymer, a polyether alcohol compound, and an alkali metal salt treated with an anion-adsorbing compound, and a surface protection film using the adhesive composition.

In addition, Patent Document 4 discloses an adhesive composition composed of an ionic liquid, an alkali metal salt, and a polymer having a glass transition temperature of 0° C. or lower, and a surface protection film using the adhesive composition.

In addition, Patent Document 5 discloses a polymer containing liquid ionic salt An adhesive composition for a surface protection sheet of an optical element, and an adhesive sheet composed of materials.

[Prior Technical Literature] 〔Patent Document〕

Patent Document 1: Japanese Patent Laid-Open No. 2005-131957

Patent Document 2: Japanese Patent Laid-Open No. 2005-330464

Patent Document 3: Japanese Patent Laid-Open No. 2005-314476

Patent Document 4: Japanese Patent Laid-Open No. 2006-152235

Patent Document 5: Japanese Patent Laid-Open No. 2008-069261

In the aforementioned Patent Documents 1 to 5, an antistatic agent is added to the inside of the adhesive layer. However, the thicker the thickness of the adhesive layer, or the longer the time elapsed after being attached to the adherend, the antistatic agent is transferred from the adhesive layer to the adherend to which the surface protective film is attached. The amount of adherend increases. When the amount of the antistatic agent transferred to the adherend increases, the appearance quality of the optical film of the adherend decreases, and the adhesiveness of the FPR film may decrease when the FPR film is bonded.

If the thickness of the adhesive layer is reduced in order to reduce the time-dependent increase in transfer of the antistatic agent from the adhesive layer to the adherend, another problem arises. For example, when it is used for an optical film with irregularities on the surface, such as a polarizing plate treated for anti-glare, there are problems that air bubbles are mixed because the adhesive layer is difficult to follow the irregularities on the surface of the optical film, or the The adhesion area between the film and the adhesive layer is reduced, resulting in a decrease in adhesion, and the surface will be damaged during use. The protective film floats or peels off.

Therefore, for the surface protective film used for optical films, there is a need for an optical film that can be used even if the surface has unevenness, has very little pollution to the adherend, and is not polluted to the adherend even after a long time. A surface protection film that does not increase and, when the surface protection film is peeled from an adherend, can suppress the peeling electrostatic voltage to a low level.

The inventors of the present application conducted intensive studies to solve these problems.

In order to achieve less contamination of the adherend and reduce the increase in contamination over time, it is necessary to reduce the amount of the antistatic agent component in the adhesive layer that is presumed to be the cause of the contamination of the adherend. However, when reducing the antistatic agent component in an adhesive layer, the peeling electrostatic voltage at the time of peeling a surface protection film from an adherend increases. Therefore, the present inventors studied a method of suppressing the peeling electrostatic voltage when the surface protection film is peeled from the adherend to be low without increasing the absolute amount of the antistatic agent component in the adhesive layer.

As a result, it was found that instead of applying and drying an adhesive composition containing an antistatic agent on one surface of a base film to form an adhesive layer, it was found that an adhesive composition containing no antistatic agent was applied and dried. After drying and laminating into an adhesive layer, apply an appropriate amount of antistatic agent component only on the surface of the adhesive layer, which can suppress the peeling electrostatic voltage when the surface protection film is peeled from the optical film of the adherend. , thus completing the present invention.

The present invention is made in view of the above circumstances, and its object is to provide an optical film that has unevenness on the surface, which can be used, has little pollution to the adherend, and has low pollution to the adherend even after a long period of time. Surface Protection for Change film, and a surface protection film having excellent anti-stripping static performance that does not deteriorate over time, and an optical element using the above surface protection film.

In order to solve the above-mentioned problems, the technical idea of the present invention is that the surface protection film of the present invention is formed by coating and drying an adhesive composition not containing an antistatic agent on one surface of the base film to form an adhesive layer. After that, an appropriate amount of antistatic agent is given on the surface of the adhesive layer, thereby suppressing the contamination of the adherend to a low level, and at the same time suppressing the peeling static voltage when it is peeled off from the optical film of the adherend. lower.

In order to solve the above problems, the present invention provides a surface protection film comprising an adhesive layer formed on one surface of a base film formed of a transparent resin, and a film having a release agent layer bonded to the adhesive layer. It is characterized in that the above-mentioned release film is formed by laminating a release agent layer on one surface of the resin film, wherein the above-mentioned release agent layer contains a release agent mainly composed of dimethyl polysiloxane, not The antistatic agent and antistatic auxiliary agent that react with the above-mentioned release agent, the aforementioned antistatic agent component is an ionic compound with a melting point of less than 30°C, the aforementioned antistatic auxiliary agent is polyether modified polysiloxane, and the aforementioned antistatic agent component and the antistatic auxiliary agent are transferred from the release agent layer of the release film to the surface of the adhesive layer, so as to reduce the peeling static voltage when the adhesive layer is peeled from the adherend.

In addition, the aforementioned adhesive layer is preferably formed by cross-linking an adhesive composition containing a (meth)acrylate copolymer and a cross-linking agent.

Moreover, it is preferable that the peeling force at the time of peeling the said peeling film from the said adhesive layer is 0.2 N/50mm or less.

Moreover, this invention provides the optical element which bonded the said surface protection film.

The surface protection film of the present invention has little contamination to adherends, and the low contamination property to adherends does not change over time. Moreover, the surface protection film of this invention can also be used even if it is an optical film which has uneven|corrugated on the surface of an AG polarizing plate etc. as an adherend. In addition, according to the present invention, it is possible to provide a surface protection film that suppresses the peeling electrostatic voltage generated when peeling from an optical film as an adherend and has excellent peeling static resistance that does not deteriorate with time. , and an optical element using the above-mentioned surface protection film.

According to the surface protection film of this invention, since the surface of an optical film can be protected reliably, productivity improvement and yield improvement can be aimed at.

1‧‧‧Substrate film

2‧‧‧Adhesive layer

3‧‧‧Resin film

4‧‧‧Release agent layer

5‧‧‧Peeling film

7‧‧‧Antistatic agent and antistatic auxiliary agent

8‧‧‧Adheres (optical components)

10‧‧‧Surface protection film

11‧‧‧Peel off the surface protection film of the release film

20‧‧‧Optical components bonded with surface protection film

[Fig. 1] Fig. 1 is a sectional view showing the concept of the surface protective film of the present invention; [Fig. 2] Fig. 2 is a cross-sectional view showing a state in which the release film is peeled from the surface protection film of the present invention; [FIG. 3] FIG. 3 is a sectional view showing an embodiment of the optical element of the present invention.

Hereinafter, the present invention will be described in detail through embodiments.

Fig. 1 is a sectional view showing the concept of the surface protection film of the present invention. In the above-mentioned surface protection film 10 , an adhesive layer 2 is formed on one surface of a transparent base film 1 . On the surface of the adhesive layer 2, it is attached to the surface of the resin film 3 to form a The release film 5 of the release agent layer 4 .

As the base film 1 used for the surface protection film 10 of this invention, the base film which consists of resin which has transparency and flexibility is used. Thereby, the external appearance inspection of an optical element can be performed in the state which bonded the surface protection film to the optical element which is an adherend. As a film composed of a transparent resin used for the base film 1, it is preferable to use polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polyethylene Polyester films such as butylene terephthalate. In addition to the polyester film, a film composed of other resins may also be used as long as it has the required strength and is optically adaptable. The base film 1 may be an unstretched film, or a uniaxially or biaxially stretched film. In addition, the stretch ratio of the stretched film or the orientation angle in the axial direction accompanying the crystallization of the stretched film may be controlled to a specific value.

The thickness of the substrate film 1 used in the surface protection film 10 of the present invention is not particularly limited, for example, the thickness in the range of 12-100 μm is better, if the thickness in the range of 20-50 μm , is easier to manipulate and thus better.

In addition, an antifouling layer for preventing surface contamination, an antistatic layer, a hard coat layer for preventing scratches, etc. may be provided on the surface of the base film 1 opposite to the side where the adhesive layer 2 is formed, as required. In addition, surface modification by corona discharge, application of an anchor agent, and other adhesion-facilitating treatments may be performed on the surface of the base film 1 .

In addition, the adhesive layer 2 used in the surface protection film 10 of the present invention is not particularly important as long as it is attached to the surface of the adherend, can be easily peeled off after use, and is less likely to contaminate the adherend. As a limitation, if the durability after bonding to an optical film is considered, an acrylic adhesive obtained by crosslinking a (meth)acrylate copolymer is generally used.

Examples of (meth)acrylate copolymers include mixing main monomers such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate with acrylonitrile, vinyl acetate, methyl Co-monomers such as methyl acrylate and ethyl acrylate, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, N-methylolmethacrylamide and other functional Monomers, copolymers obtained by copolymerizing monomers containing polyoxyalkylene groups such as methoxypolyethylene glycol methacrylate. (Meth) acrylate copolymer, its main monomer and other monomers can be (meth) acrylate, as other monomers other than the main monomer, it can also contain one or more than two kinds of (meth) Monomers other than acrylates. Other monomers other than the main monomer may be selected from, but not particularly limited to, the aforementioned comonomers, functional monomers, polyoxyalkylene group-containing monomers, and the like.

Examples of the curing agent added to the adhesive layer 2 include isocyanate compounds, epoxy compounds, melamine compounds, metal chelate compounds, and the like for crosslinking the (meth)acrylate copolymer. In addition, examples of thickeners include rosin, lavone-indene, terpenes, petroleum, phenols, and the like.

The thickness of the adhesive layer 2 used in the surface protection film 10 of the present invention is not particularly limited, but it is preferably a thickness ranging from 5 to 40 μm , more preferably a thickness ranging from 10 to 30 μm thickness of. In addition, since the surface protection film has excellent operability when peeled from the adherend, the peel strength (adhesion force) of the surface protection film to the surface of the adherend is between 0.03 and 0.3N/25mm, and has a slight adhesion. Adhesive layer 2 is preferred. In addition, since the peeling force of the peeling film 5 from the surface protection film 10 is excellent, the peeling force when peeling the peeling film 5 from the adhesive layer 2 is preferably 0.2 N/50 mm or less, more preferably 0.14 N/50 mm or less. .

In addition, the release film 5 used in the surface protection film 10 of the present invention is formed by laminating the release agent layer 4 on one side of the resin film 3, and contains a release agent mainly composed of dimethylpolysiloxane, An antistatic agent that does not react with the aforementioned release agent, and an antistatic auxiliary agent. In the release film used in the surface protection film of the present invention, the aforementioned antistatic agent component is preferably an ionic compound having a melting point of less than 30°C. The aforementioned antistatic auxiliary agent is preferably polyether-modified polysiloxane.

As the resin film 3, a polyester film, a polyamide film, a polyethylene film, a polypropylene film, a polyimide film, etc. are mentioned, and since it has excellent transparency and a relatively low price, a polyester film is preferable. membrane. The resin film may be an unstretched 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 accompanying the crystallization of the stretched film can be controlled to specific values.

The thickness of the resin film 3 is not particularly limited, for example, a thickness in the range of 12-100 μm is preferable, and a thickness in the range of 16-50 μm is easy to handle, so it is more preferable.

In addition, surface modification by corona discharge, application of an anchoring agent, and other adhesion-facilitating treatments may be performed on the surface of the resin film 3 as needed.

The release agent comprising dimethylpolysiloxane as the main component of the release agent layer 4 includes known polysiloxane-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. agent. Addition-reaction type polysiloxane-based release agents on the market include, for example, KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (Shin-Etsu Chemical Co., Ltd. ( Stock) Manufacturing), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, LTC-310 (Dow Corning Toray Co., Ltd.), etc. Examples of commercially available condensation-reaction type silicone release agents include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray Co., Ltd.). Commercially available cationic polymerized silicone-based release agents include, for example, TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials Company), X62-7622 (manufactured by Shin-Etsu Chemical Industry ( stock) manufacturing), etc. Commercially available radical polymerizable silicone-based release agents include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

As the antistatic agent constituting the release agent layer 4, it is preferable that it has good dispersibility for the release agent solution mainly composed of dimethylpolysiloxane and does not hinder The main component of the release agent is cured antistatic agent. In addition, in order to transfer from the release agent layer 4 to the surface of the adhesive layer 2 and impart an antistatic effect to the adhesive layer 2, it is preferable to use an antistatic agent that does not react with a release agent mainly composed of dimethylpolysiloxane. agent. Ionic compounds with a melting point of less than 30° C. are very suitable as such antistatic agents.

The ionic compound having a melting point of less than 30° C. is an ionic compound having a cation and an anion, and examples of the cation include cyclic amidinium ions such as imidazolium ions, pyridinium cations, ammonium ions, percite ions, and phosphonium ions. In addition, examples of anions 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 ^3- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , ClO ₄ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- etc.

The amount of the antistatic agent added to the release agent mainly composed of dimethylpolysiloxane varies depending on the type of antistatic agent, the degree of affinity with the release agent, and the like. The amount of antistatic agent added, can consider the peeling of the surface protective film from the adherend Set the desired peeling electrostatic voltage, contamination of the adherend, and adhesive characteristics.

The purpose of the antistatic auxiliary agent constituting the release agent layer 4 is to improve the antistatic performance of the surface of the adhesive layer. As such an antistatic auxiliary agent, polyether-modified polysiloxane is preferable. The polyether chain in polyether-modified silicone is composed of ethylene oxide, propylene oxide, etc. For example, by selecting the molecular weight of polyethylene oxide used in the side chain, the phase with the silicone release agent can be adjusted. Physical properties such as capacitive and antistatic effects.

In addition, products marketed as polyether-modified silicones include, for example, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, and KF-642 (Shin-Etsu Chemical Co., Ltd. ), SH8400, SH8700, SF8410 (manufactured by Dow Corning Toray Co., Ltd.), TSF-4440, TSF-4441, TSF-4445, TSF-4446, TSF-4450 (manufactured by Momentive Performance Materials Co., Ltd. ), BYK-300, BYK-306, BYK-307, BYK-320, BYK-325, BYK-330 (manufactured by BYK).

The amount of polyether-modified silicone to be added to the release agent mainly composed of dimethylpolysiloxane varies depending on the type of polyether-modified silicone, the degree of compatibility with the release agent, etc. , can be set in consideration of the expected peeling electrostatic voltage when the surface protection film is peeled from the adherend, the contamination of the adherend, and the adhesion characteristics.

The method of mixing the release agent mainly composed of dimethylpolysiloxane, the antistatic agent and the antistatic auxiliary agent is not particularly limited. Any of the following methods can be used: add antistatic agent and antistatic auxiliary agent to the release agent with dimethyl polysiloxane as the main component, after mixing, add and mix the release agent to cure The method of using a catalyst; after diluting the release agent mainly composed of dimethyl polysiloxane with an organic solvent in advance, adding and mixing an antistatic agent, an antistatic auxiliary agent and a catalyst for curing the release agent; A release agent whose main component is methyl siloxane is diluted with an organic solvent in advance, a catalyst is added and mixed, and an antistatic agent and an antistatic auxiliary agent are added and mixed. In addition, if necessary, an adhesion improving agent such as a silane coupling agent, a polyoxyalkylene group-containing compound, and an auxiliary antistatic effect material may be added.

The mixing ratio of the release agent mainly composed of dimethylpolysiloxane to the antistatic agent and antistatic auxiliary agent is not particularly limited, but relative to the solid content of the release agent mainly composed of dimethylpolysiloxane When the composition is 100, the total solid content of the antistatic agent and antistatic auxiliary agent is preferably between 5 and 100. With respect to the solid content of the release agent mainly composed of dimethyl polysiloxane as 100, if the ratio of the added amount of the total solid content of the antistatic agent and antistatic auxiliary agent is less than 5, the antistatic agent and antistatic auxiliary agent The transfer amount of the antistatic auxiliary agent to the surface of the adhesive layer decreases, making it difficult to perform the function of imparting antistatic to the adhesive. In addition, if the solid content of the release agent mainly composed of dimethyl polysiloxane is 100, if the ratio of the added amount in terms of the total solid content of the antistatic agent and antistatic auxiliary agent exceeds 100, the ratio of two The release agent whose main component is methyl polysiloxane is also transferred onto the surface of the adhesive layer along with the antistatic agent and antistatic auxiliary agent, which may reduce the adhesive properties of the adhesive.

The method of forming the adhesive layer 2 on the base film 1 of the surface protection film 10 of this invention, and the method of bonding the peeling film 5 can be performed via a well-known method, and it does not specifically limit. Specifically, the following methods can be cited, and any method can be used: (1) coating on one side of the base film 1 After forming the resin composition of the adhesive layer 2, drying it to form the adhesive layer, the method of attaching the release film 5; (2) coating the resin for forming the adhesive layer 2 on the surface of the release film 5 The composition is dried and the adhesive layer is formed, followed by a method of laminating the base film 1 .

In addition, the method of forming the adhesive layer 2 on the surface of the base film 1 may be performed using a well-known method. Specifically, known coating methods such as reverse coating, knife coating, gravure coating, slot die coating, metered bar coating, and air knife coating can be used.

Moreover, what is necessary is just to form the release agent layer 4 on the resin film 3 similarly, and to use a well-known method. Specifically, known coating methods such as gravure coating, metered bar coating, and air knife coating can be used.

The surface protection film 10 of the present invention having the above structure preferably has a surface potential of +0.7kV to -0.7kV when the adhesive layer is peeled off from the optical film as an adherend. Furthermore, the surface potential is more preferably between +0.5kV~-0.5kV, and is particularly preferably between +0.1kV~-0.1kV. The above-mentioned surface potential can be adjusted by increasing or decreasing the type and amount of the antistatic agent and antistatic auxiliary agent contained in the release agent layer.

Fig. 2 is a cross-sectional view showing a state in which the release film is peeled off from the surface protection film of the present invention.

By peeling off the release film 5 from the surface protection film 10 shown in FIG. Adhesion) to the surface of the adhesive layer 2 of the surface protection film 10. Therefore, in FIG. 2 , the antistatic agent and antistatic auxiliary agent transferred on the surface of the adhesive layer 2 of the surface protection film 11 in the peeling film state are peeled off. It is represented by a dot with symbol 7. By transferring the component 7 of the antistatic agent and antistatic auxiliary agent from the release film 5 to the surface of the adhesive layer 2, the adhesive layer 2 is removed from the adherend compared with the adhesive layer 2 before transfer. The peeling electrostatic voltage at the time of peeling is lowered. In addition, the peeling electrostatic voltage when the adhesive layer is peeled from the adherend can be measured by a known method. For example, after attaching the surface protective film to an adherend such as a polarizing plate, use a high-speed peel tester (manufactured by TESTER SANGYO CO,.LTD.) to peel off the surface protective film at a peeling speed of 40m per minute, while using a surface potentiometer (manufactured by KEYENCE CORPORATION) The surface potential of the surface of the adherend was measured every 10 ms, and the maximum value of the absolute value of the surface potential at that time was defined as the peeling electrostatic voltage (kV).

As the surface protection film of the present invention, when the surface protection film 11 in the state of peeling off the release film as shown in FIG. Antistatic agents and antistatic auxiliary agents will be in contact with the surface of the adherend. Therefore, when the surface protection film is peeled off from the adherend again, the peeling electrostatic voltage can be kept low.

Fig. 3 is a cross-sectional view showing an example of the optical element of the present invention.

The release film 5 is peeled off from the surface protection film 10 of the present invention, and the surface of the adhesive layer 2 is exposed, and then bonded to the optical element 8 as an adherend via the adhesive layer 2 .

That is, FIG. 3 shows an optical element 20 bonded with the surface protection film 11 of the present invention. Examples of the optical element include optical films such as polarizing plates, retardation plates, lens films, polarizing plates serving both as retardation plates, and polarizing plates serving as lens films. The above-mentioned optical element can be used as a constituent element of liquid crystal display devices such as liquid crystal display panels, optical system devices of various measuring instruments, and the like. In addition, as an optical As an element, optical films, such as an antireflection film, a hard coat film, and a transparent conductive film used for a touch panel, are mentioned.

According to the optical element of the present invention, when the surface protection film 11 is peeled and removed from the optical element (optical film) as an adherend, the peeling electrostatic voltage can be sufficiently suppressed low. Therefore, there is no need to worry about damage to circuit components such as driver ICs, TFT elements, and gate line drive circuits, and the production efficiency in the manufacturing process of liquid crystal display panels and the like can be improved, and the reliability of the production process can be maintained.

[Example]

Next, the present invention will be further described according to the embodiments.

(Example 1)

(Preparation of surface protection film)

5 parts by weight of an addition-reactive polysiloxane (manufactured by Dow Corning Toray Co., Ltd., trade name: SRX-345), 7.5 parts by weight of tri-n-butylmethylammonium di-tri Fluoromethanesulfonyl imide (manufactured by 3M, FC-4400) 10% ethyl acetate solution, 0.3 parts by weight of polyether-modified silicone (manufactured by Dow Corning Toray Co., Ltd., trade name: SH8400), 95 Parts by weight of toluene and ethyl acetate as a mixed solvent of 1:1, 0.05 parts by weight of platinum catalyst (manufactured by Dow Corning Toray Co., Ltd., trade name: SRX-212) were mixed, stirred and mixed, and prepared for The paint for forming the release agent layer of Example 1. On the surface of a polyethylene terephthalate film with a thickness of 38 μm , the above-mentioned coating for forming the release agent layer of Example 1 was coated with a metering bar so that the thickness after drying was 0.2 μm , It dried for 1 minute using the hot-air circulation oven of 120 degreeC, and obtained the peeling film of Example 1. On the other hand, with respect to 100 parts by weight of an adhesive polymer solution (ethyl acetate solution with a solid content of 30%) obtained by dissolving 30 parts by weight of an acrylate copolymer in 70 parts by weight of ethyl acetate, add and Mix 1.2 parts by weight of HDI curing agent (manufactured by TOSOH CORPORATION, trade name: CORONATE (registered trademark) HX) to prepare the adhesive composition of Example 1, wherein the acrylate copolymer is made of 96:4 Weight ratio It is made by copolymerizing 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate, and its weight average molecular weight is 470,000. In addition, "HDI type" means "hexamethylene diisocyanate type."

After coating the adhesive composition of Example 1 on the surface of a polyethylene terephthalate film with a thickness of 38 μm so that the thickness after drying was 20 μm , a hot air circulation at 100° C. was used to Dry in an oven for 2 minutes to form an adhesive layer. Thereafter, the release agent layer (polysiloxane-treated surface) of the release film of Example 1 prepared above was bonded to the surface of the above-mentioned adhesive layer. The obtained adhesive film was kept at 40° C. for 5 days to cure the adhesive layer to obtain the surface protection film of Example 1.

(comparative example 1)

5 parts by weight of an addition reaction polysiloxane (manufactured by Dow Corning Toray Co., Ltd., trade name: SRX-345), 95 parts by weight of a mixed solvent of toluene and ethyl acetate at a ratio of 1:1, 0.05 Parts by weight of a platinum catalyst (manufactured by Dow Corning Toray Co., Ltd., trade name: SRX-212) were mixed, stirred and mixed to prepare a paint for forming the release agent layer of Comparative Example 1. On the surface of a polyethylene terephthalate film having a thickness of 38 μm , the above-mentioned coating for forming the release agent layer of Comparative Example 1 was coated using a metering bar so that the thickness after drying was 0.2 μm , It dried for 1 minute using the hot-air circulation oven of 120 degreeC, and obtained the peeling film of the comparative example 1. On the other hand, with respect to 100 parts by weight of the adhesive polymer solution of Example 1 (ethyl acetate solution with a solid content of 30%), 3 parts by weight of an ionic compound having a melting point of 27.5°C was added and mixed. 10% ethyl acetate solution of butylmethylammonium bistrifluoromethanesulfonimide (manufactured by 3M Company, FC-4400), 1.2 parts by weight of HDI-based curing agent (manufactured by TOSOH CORPORATION, trade name: CORONATE (registered trademark) HX) , The adhesive composition of Comparative Example 1 was prepared.

After coating the adhesive composition of Comparative Example 1 on the surface of a polyethylene terephthalate film with a thickness of 38 μm so that the thickness after drying was 20 μm, it was dried using a hot air circulation drying oven at 100°C After 2 minutes, an adhesive layer is formed. Thereafter, the release agent layer (polysiloxane-treated surface) of the release film of Comparative Example 1 prepared above was bonded to the surface of the adhesive layer. The obtained adhesive film was kept warm for 5 days in an environment of 40° C. to cure the adhesive layer, and the surface protection film of Comparative Example 1 was obtained.

(comparative example 2)

The surface protection film of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except that tri-n-butylmethylammonium bistrifluoromethanesulfonimide having a melting point of 27.5° C. was not contained in the adhesive layer.

(comparative example 3)

The surface protection film of the comparative example 3 was obtained similarly to Example 1 except not containing polyether denatured silicone in a release agent layer.

(Example 2)

In addition to modifying the adhesive composition of Example 1, an adhesive polymer solution (solid content of 30% ethyl acetate solution) 100 wt. 1.2 parts by weight of an HDI-based curing agent (manufactured by TOSOH CORPORATION, trade name: CORONATE (registered trademark) HX) was added and mixed. A surface protection film, wherein the above-mentioned acrylate copolymer is formed by copolymerizing 2-ethylhexyl acrylate, butyl acrylate and 2-hydroxyethyl acrylate in parts by weight of 60:36:4, and its weight average molecular weight is 48 Ten thousand.

(Example 3)

In addition to changing the adhesive composition of Example 1, an adhesive polymer solution (solid content 30% In addition to the adhesive composition formed by adding and mixing 1.2 parts by weight of HDI-based curing agent (manufactured by TOSOH CORPORATION, trade name: CORONATE (registered trademark) HX), and Example 1 Similarly, the surface protection film of Example 3 was obtained. Wherein, the (meth)acrylate copolymer is obtained by mixing 2-ethylhexyl acrylate, methoxypolyethylene glycol (400) methacrylate, and acrylic acid 2 in parts by weight of 86:10:4. -Hydroxyethyl ester copolymerization, its weight average molecular weight is 380,000.

The method and results of the evaluation test are shown below.

<Measuring method of peeling force of peeling film>

The sample of the surface protective film was cut out to a width of 50 mm and a length of 150 mm. Under the test environment of 23°C×50%RH, use a tensile testing machine to measure the strength when peeling off the peeling film at a peeling speed of 300mm/min along the direction of 180°, and use this as the peeling force of the peeling film (N/ 50mm).

<Measuring method of adhesion of surface protection film>

An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Then, after affixing a surface protective film cut to a width of 25 mm on the surface of the polarizing plate, it was stored in a test environment of 23° C.×50% RH for one day. Thereafter, the strength when peeling off the surface protection film was measured in a direction of 180° at a peeling speed of 300 mm/min using a tensile tester, and this was used as an adhesive force (N/25mm).

<Measurement method of peeling electrostatic voltage of surface protection film>

An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Thereafter, a surface protection film cut to a width of 25 mm was attached to the surface of the polarizing plate, and then stored in a test environment of 23° C.×50% RH for one day. Then use a high-speed peel tester (manufactured by TESTER SANGYO CO,. LTD.) to peel off the surface protective film at a peeling speed of 40 m per minute, while using a surface potentiometer (manufactured by KEYENCE CORPORATION) to measure the surface potential of the aforementioned polarizer surface every 10 ms, and The absolute maximum value of the surface potential at this time was defined as the peeling electrostatic voltage (kV).

<Confirmation method of surface contamination of surface protection film>

An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Then, a surface protection film cut to a width of 25 mm was attached to the surface of the polarizing plate, and then stored in a test environment of 23° C.×50% RH for 3 days and 30 days. After that, the surface protective film was peeled off, and the presence or absence of contamination on the surface of the polarizing plate was visually observed. As a criterion for judging surface contamination, the case where no contamination transfer on the polarizing plate was evaluated as (◯), and the case where contamination transfer was confirmed on the polarizing plate was evaluated as (×).

Tables 1-2 show the measurement results of the obtained surface protection films of Examples 1-3 and Comparative Examples 1-3. "2EHA" is 2-ethylhexyl acrylate, "HEA" is 2-hydroxyethyl acrylate, "BA" is butyl acrylate, "# 400G" is methoxypolyethylene glycol (400) methacrylate , "FC4400" is tri-n-butylmethylammonium bistrifluoromethanesulfonimide. In Tables 1 and 2, the composition of the adhesive layer is shown in parts by weight so that the total amount of the adhesive polymer (solid content) is approximately 100 parts by weight. Therefore, in the adhesive layer of Comparative Example 1, the weight ratio of the adhesive polymer (solid content) to FC4400 is 30 parts by weight: 0.3 parts by weight=100 parts by weight: 1.0 parts by weight.

〔Table 2〕

According to the measurement results shown in Table 1 and Table 2, the following conclusions can be drawn.

The surface protection films of Examples 1 to 3 of the present invention have moderate adhesive force, do not pollute the surface of the adherend, and have low peeling electrostatic voltage when the surface protection film is peeled from the adherend.

On the other hand, although the surface protection film of Comparative Example 1 containing an antistatic agent in the adhesive layer has a low and good peeling electrostatic voltage when the surface protection film is peeled from the adherend, it is not effective for the adherend after peeling. pollution increased.

In addition, in the surface protection film of Comparative Example 2 that does not contain an antistatic agent in both the adhesive layer of the surface protection film and the release agent layer of the release film, the contamination to the adherend is good, but the surface protection The peeling electrostatic voltage increases when the film is peeled from the adherend.

That is, a comparative example in which an antistatic agent is contained in the adhesive layer of the surface protection film In the surface protection film of 1 and the surface protection film of Comparative Example 2 that does not contain an antistatic agent in the adhesive layer of the surface protection film and the release agent layer of the release film, it is difficult to balance the reduction of the peeling electrostatic voltage and the effect on the adherend. pollution.

On the other hand, Example 1 where the antistatic agent and antistatic auxiliary agent of the release agent layer were transferred only on the surface of the adhesive layer after the release agent layer of the release film contained the antistatic agent and the antistatic auxiliary agent. In the surface protection film of ~3, by adding a small amount of antistatic auxiliary agent, it has a significant effect of reducing the peeling static voltage. Therefore, there is no pollution to the adherend, and the anti-static performance of peeling is also good.

In addition, in the surface protection film of Comparative Example 3, which contained only an antistatic agent in the release agent layer and did not contain an antistatic auxiliary agent, there was no contamination to the adherend, and the anti-static performance of peeling was also good. However, when compared with the surface protection films of Examples 1-3 which contained an antistatic agent and an antistatic auxiliary agent in a release agent layer, the peeling electrostatic voltage became high.

[Industrial Applicability]

The surface protection film of the present invention can be used for bonding to the above-mentioned optical elements to protect the surface during the production steps of optical films such as polarizing plates, retardation plates, and lens films, and other various optical elements. In addition, when the surface protection film of the present invention is peeled from the adherend, the amount of static electricity generated is low, and the anti-peeling static performance changes over time and the pollution to the adherend is small, which can improve the yield of the production step. The industrial utilization value is great.

1‧‧‧Substrate film

2‧‧‧Adhesive layer

3‧‧‧Resin film

4‧‧‧Release agent layer

5‧‧‧Peeling film

7‧‧‧Antistatic agent and antistatic auxiliary agent

10‧‧‧Surface protection film

Claims (3)

A surface protection film formed by forming an adhesive layer on one side of a base film made of a transparent resin, and attaching a release film with a release agent layer on the adhesive layer The surface protection film is characterized in that the adhesive layer is formed by crosslinking an adhesive composition containing a (meth)acrylate copolymer and a crosslinking agent, and the (meth)acrylate copolymer is only A copolymer of 2-ethylhexyl acrylate and hydroxyethyl acrylate, or a copolymer of only 2-ethylhexyl acrylate with butyl acrylate and hydroxyethyl acrylate, the release film is It is formed by laminating the release agent layer on one side of a resin film, wherein the release agent layer contains a release agent mainly composed of dimethyl polysiloxane, an antistatic agent that does not react with the release agent agent, and an antistatic auxiliary agent, the antistatic agent composition is tri-n-butylmethylammonium bistrifluoromethanesulfonimide, the antistatic auxiliary agent is polyether denatured polysiloxane, the antistatic agent composition and the antistatic The auxiliary agent is transferred from the release agent layer of the release film to the surface of the adhesive layer, reducing the peeling electrostatic voltage when the adhesive layer is peeled from an adherend, and peeling the adhesive layer from the optical film of the adherend. The surface potential of the adhesive layer is +0.1kV~-0.1kV, and the anti-glare and low-reflection treated polarizing plate is bonded to the surface of the glass plate with a double-sided adhesive tape using a laminating machine, and then pasted on the surface of the polarizing plate Cut into a surface protection film with a width of 25mm, under the test environment of 23℃×50%RH After 3 days and 30 days of storage, the surface protective film was peeled off, and when there was any contamination on the surface of the polarizing plate was visually observed, there was no transfer of pollution on the polarizing plate. The surface protection film as described in Claim 1, wherein the peeling force when the peeling film is peeled from the adhesive layer is 0.2N/50mm or less. An optical element formed by bonding the surface protection film described in item 1 or 2 of the scope of the patent application.

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