JP2010155976A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film in which migration of a peeling agent to a self-adhesive layer is suppressed and a certain degree of peeling resistance is imparted between the self-adhesive layer and a peeling layer, and which enables stable peeling when the peeling layer is peeled from a base material layer/self-adhesive layer. <P>SOLUTION: In the surface protective film, a base material layer, a self-adhesive layer and a peeling layer are laminated in this order. The peeling layer is formed of a polypropylene film, and the surface protective film satisfies following requirements (1) to (3): (1) surface roughness (Ra) of the surface of the peeling layer in contact with the self-adhesive layer is 0.10-0.30 μm, (2) flexural stiffness of the peeling layer, measured with a loop stiffness tester, is 0.2×10<SP>-3</SP>to 10.0×10<SP>-3</SP>N/20 mm, and (3) peeling resistance between the self-adhesive layer and the peeling layer is 0.16 to 0.30 N/25 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a surface protective film provided with a release layer that has excellent peelability and does not affect the tackiness of a pressure-sensitive adhesive.

Surface protective films are widely used in various places to protect members during processing from scratches and foreign substances, and adherends are widely used from inorganic materials such as metal and glass to organic materials such as plastic films. The surface protective film is basically composed of a base material layer and an adhesive layer, but a release layer is generally provided so that foreign matter does not adhere to the surface of the adhesive layer (the surface in contact with the adherend). It is.
In the release layer, it is described in Patent Document 1 that a release agent such as a silicone compound is used between the adhesive layer and the release layer, and is generally used because it can be easily peeled off. However, in recent years, in surface protective films used for optical members such as polarizing plates and retardation plates, the release agent may move to the adhesive layer for some reason, thereby causing poor adhesion to the object to be protected and the appearance. It is causing a defect. Therefore, a release layer that does not transfer the release agent to the adhesive layer is required, and Patent Documents 2 and 3 describe that the release layer can be eliminated by using a polyolefin-based resin. However, in Patent Documents 2 and 3, since the peeling force between the adhesive layer and the peeling layer is too small, wrinkles and meandering may occur in the film during peeling.

JP 2007-224203 A JP 2002-363510 A JP 2008-231352 A

The present invention eliminates the transfer of the release agent to the adhesive layer, which has been a problem until now, and provides the release layer with a certain degree of release resistance between the adhesive layer and the release layer, thereby making the release layer a base layer / adhesive layer. An object of the present invention is to provide a surface protective film that can be stably peeled off when peeled off.

As a result of intensive studies in view of such circumstances, the present inventors have found that the present invention solves the above problems.
That is, the present invention is a surface protective film in which a base material layer, an adhesive layer, and a release layer are laminated in this order, wherein the release layer is a polypropylene film and satisfies the following requirements (1) to (3) It relates to a protective film.
(1) The surface roughness (Ra) of the surface in contact with the adhesive layer of the release layer is 0.10 to 0.30 μm.
(2) The flexural rigidity of the release layer measured by the loop stiffness tester is 0.2 × 10 ^{−3 to} 10.0 × 10 ⁻³ N / 20 mm.
(3) The peel resistance between the adhesive layer and the release layer is 0.16 to 0.30 N / 25 mm.
Moreover, this invention relates to the said surface protection film whose maximum surface roughness (Rz) of the surface which contacts the adhesion layer of a peeling layer is 0.1-10.0 micrometers. Moreover, it is related with the said surface protection film which is a surface protection film for optical members. Furthermore, this invention relates to the manufacturing method of the surface protection film which laminates this adhesion layer and a peeling layer, after coating an adhesive to a base material layer and forming an adhesion layer.

The present invention provides a surface protective film having a pressure-sensitive adhesive layer without transfer of a release agent, and enables stable peeling by giving a certain degree of resistance when peeling the release layer from the base material layer / pressure-sensitive adhesive layer. Become.

The resin used for the base material layer of the present invention is not particularly limited as long as it is a thermoplastic resin. For example, an olefin resin such as polyethylene or polypropylene, a saturated ester resin such as polyethylene terephthalate or polybutylene terephthalate, a polystyrene resin or an acrylic resin. Examples of such resins include polycarbonate resins, polycarbonates, and triacetyl cellulose, and saturated ester resins are preferred from the viewpoint of productivity and quality.

The thickness of the base material layer of the present invention is preferably 3 to 500 μm, more preferably 5 to 200 μm, from the viewpoint of ease of handling as a film and post-processing properties such as coating.

For the base material layer of the present invention, for example, plasma treatment, corona treatment, anchor coat treatment, primer treatment, acid treatment, alkali treatment, etc. are performed on the surface in contact with the adhesion layer in order to increase the adhesion with the adhesion layer. However, the functional coating such as antistatic treatment, ultraviolet treatment, and antifouling treatment can also be carried out on the surface of the base material layer opposite to the surface in contact with the adhesive layer.

Examples of the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer of the present invention include acrylic pressure-sensitive adhesives, styrene-butylene-styrene copolymers (SBS), synthetic rubber pressure-sensitive adhesives such as polyisobutylene and butyl rubber, natural rubber pressure-sensitive adhesives, Olefin-based pressure-sensitive adhesives such as ethylene-vinyl acetate copolymer (EVA) -based pressure-sensitive adhesives and amorphous or low-crystalline olefin-based polymers can be used. These pressure-sensitive adhesives may be used alone or in combination of two or more, and a cross-linked acrylic pressure-sensitive adhesive is preferable from the viewpoint of the peelability of the pressure-sensitive adhesive.

The thickness of the pressure-sensitive adhesive layer in the present invention can be appropriately selected within a range that does not impair the pressure-sensitive adhesive performance, follows the unevenness of the surface of the object to be protected, reduces waste due to excessive application of the pressure-sensitive adhesive, insufficient drying, From the viewpoint of reducing the occurrence of defects such as unevenness in work, the thickness is preferably 1 to 100 μm, more preferably 2 to 30 μm.

The polypropylene film forming the release layer of the present invention includes a biaxially stretched film, a uniaxially stretched film, and an unstretched film, and any of them can be used, but a biaxially stretched film is particularly versatile and can be preferably used. Examples of the polypropylene resin used as a raw material include propylene homopolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-1 -Heptene copolymer, propylene-1-nonene copolymer, propylene-1-decene copolymer, propylene-1-undecene copolymer, propylene-1-dodecene copolymer, propylene-1-tridecene copolymer , Propylene-1-tetradecene copolymer, propylene-1-pentadecene copolymer, propylene-1-hexadecene copolymer, propylene-1-heptadecene copolymer, propylene-1-octadecene copolymer, propylene-1- Nanodecene copolymer, propylene-1-eicocene copolymer, ethylene A propylene-1-octene copolymer, an ethylene-1-butene-1-hexene copolymer, and the like can be mentioned, and a propylene homopolymer, a propylene-ethylene copolymer, a propylene-1-butene copolymer, It is an ethylene-propylene-1-butene copolymer. These polypropylene resins may be used alone or in combination of two or more.

The thickness of the release layer of the present invention can be appropriately selected within a range that does not impair the releasability, and is preferably 3 to 500 μm, more preferably 12 to 200 μm, from the viewpoints of flexibility, suitability for bonding with an adhesive layer, and peelability. More preferably, it is 20-60 micrometers.

The surface roughness (Ra) of the surface in contact with the adhesive layer of the release layer of the present invention is 0.10 to 0.30 μm, preferably 0.13 to 0.25 μm. When the surface roughness Ra exceeds 0.30 μm, the contact area with the pressure-sensitive adhesive increases, and the peeling resistance increases. Therefore, when the peeling layer is peeled off from the base material layer / the pressure-sensitive adhesive layer, it cannot be peeled stably. Conversely, when the surface roughness Ra is less than 0.10 μm, the contact area with the adhesive is reduced and the peeling resistance is lowered, so that the peeling layer becomes unstable when the peeling layer is peeled off from the base layer / adhesive layer. . Here, the surface roughness Ra is an arithmetic average roughness defined in JIS B0601.
Moreover, it is preferable that the maximum surface roughness (Rz) of the surface which contacts the adhesion layer of the peeling layer in this invention is 0.1-10.0 micrometers, More preferably, it is 0.2-9.0 micrometers. . If the maximum surface roughness (Rz) is less than 0.1 μm, the film may not slip when wound up as a film, which may cause bone and ear height defects. Conversely, if the maximum surface roughness exceeds 10.0 μm The unevenness on the surface of the release layer is transferred to the pressure-sensitive adhesive layer, and bubbles may be generated when the pressure-sensitive adhesive layer is bonded to an object, resulting in poor appearance. Here, the maximum surface roughness Rz is the maximum height defined by JISB0601.

The flexural rigidity measured with the loop stiffness tester of the release layer of the present invention is 0.2 × 10 ^{−3 to} 10.0 × 10 ⁻³ N / 20 mm, more preferably 0.5 × 10 ⁻³ to 5.0 × 10 ⁻³ N / 20 mm. If the flexural rigidity is less than 0.2 × 10 ⁻³ N / 20 mm, defects such as wrinkles are likely to occur when bonding with the adhesive layer, and the peeling resistance at the time of peeling may be too high, resulting in lack of peeling stability. is there. When the bending rigidity exceeds 10.0 × 10 ⁻³ N / 20 mm, it is difficult to bend the adhesive layer when peeling the release layer from the base material layer / adhesive layer, and thus stable peeling cannot be obtained. If the flexural rigidity is 0.2 × 10 ^{−3 to} 10.0 × 10 ⁻³ N / 20 mm, the film has an appropriate waist, so that it can be easily held and bent when tension is applied, and is excellent in handling. The bending stiffness is a bending stiffness measured with a D-type or DA-type loop stiffness tester manufactured by Toyo Seiki Seisakusho Co., Ltd.

The peeling resistance between the adhesive layer and the peeling layer in the present invention is 0.16 to 0.30 N / 25 mm, more preferably 0.18 to 0.25 N / 25 mm. If the peel resistance is less than 0.16 N / 25 mm, the peelability may be too good and defects such as wrinkles, talmi, and meandering may occur on the peelable layer during peeling, which may cause the adhesive layer to become unstable. There is. When the peeling resistance exceeds 0.30 N / 25 mm, when the peeling layer is peeled from the base material layer / adhesive layer, a lot of tension is required to be applied to the peeling layer, so that the tension control is difficult and peeling becomes unstable. When the peel resistance is 0.16N to 0.30N / 25mm, it is easy to control the tension at the time of peeling, and it is possible to peel the film without causing wrinkles or tarmi by applying a certain tension to the peeling layer. is there. The peeling resistance here is a value measured at room temperature with a peeling speed of 300 mm / min in a state where the peeling layer is bent 180 degrees.

Although it does not specifically limit as a manufacturing method of the surface protection film of this invention, The method of coating an adhesive to a base material layer is preferable. As a method of coating the adhesive on the base material layer, any method can be used as long as it is a method of applying a liquid such as direct gravure coating, reverse gravure coating, cast coating, comma coating, and micro gravure coating. The coated adhesive is held in a drying oven for the purpose of removing the solvent, preferably at a temperature of 50 to 200 ° C. for 0.1 to 60 seconds. After drying, the substrate is quickly laminated with the release layer and laminated on the base material layer / adhesive layer / release layer. In order to cure the adhesive, it is preferably 20 to 90 ° C., more preferably 30 to 60 ° C. At a temperature of preferably 1 to 14 days, more preferably 2 to 7 days. After storage, the surface protective film of the present invention is obtained.

As a method of using the surface protective film of the present invention, for example, it is used for the purpose of protecting the surface by peeling the release layer immediately before use and bringing it into intimate contact with the object for protecting the adhesive layer surface of the base layer / adhesive layer. The method to be mentioned is mentioned. The peeling direction of the peeling layer at the time of peeling may be any angle between 1 and 180 degrees, preferably 90 to 180 degrees, more preferably 120 to 180, when the base layer / adhesive layer is 0 degrees. When peeling at an angle of degrees, the peeling position is easy to stabilize, and the conditions can be set easily.

Examples of the use of the surface protective film of the present invention include metal plates such as stainless steel plates, aluminum plates and steel plates for building materials, plastic plates such as resin plates, acrylic plates and polycarbonate plates, decorative plywood, glass plates, and home appliances. Although it can be used as a surface protective film for products, precision machines, automobile bodies, etc., it is particularly suitably used as a surface protective film for polarizing plates, retardation plates, diffuser plates, light guide plates and the like that are optical members.

Hereinafter, although an Example demonstrates concretely, this invention is not limited to this.

Example 1
100% by weight of a propylene resin (“Nobrene FLX80E4” manufactured by Sumitomo Chemical Co., Ltd .; propylene homopolymer) is supplied to a single-screw extruder having a cylinder diameter of 50 mm, the resin temperature is 250 ° C., and the take-up speed is 10.7 m / min. Then, extrusion molding was performed using an air chamber at a cooling roll of 70 ° C. to obtain a release layer having an average thickness of 60 μm. Surface roughness Ra of the surface which contacts the adhesion layer of the obtained peeling layer was 0.14 micrometer, Rz was 3.3 micrometer, and bending rigidity was 3.23 * 10 < ^-3 > N / 20mm.
[Creation of surface protective film]
As the base material layer, a biaxially stretched polyester film (“Embret S” manufactured by Unitika Ltd .; single-sided corona treatment, thickness 12 μm) was used. A mixture of 1 part by weight of an isocyanate curing agent (“D90” manufactured by Soken Chemical Co., Ltd.) with respect to 1000 parts by weight of an acrylic adhesive main agent (“MM149” manufactured by Soken Chemical Co., Ltd.) It was applied to the corona-treated surface of the material layer at a thickness of 70 to 75 μm, then held in a drying oven (set temperature 90 ° C.) for 2 minutes to sufficiently evaporate the solvent, and after drying, an adhesive layer having a thickness of 20 μm was formed. . Immediately after forming the adhesive layer, the adhesive layer and the release layer are pressure-bonded with a rubber roll and bonded together, and then aged in an oven (40 ° C.) for 4 days to form a surface protective film comprising a base material layer / adhesive layer / release layer. Got. The evaluation results of the obtained surface protective film are shown in Table 1. When the release stability of the film was evaluated, it was easy to control the tension when the release layer was peeled off from the base layer / adhesive layer, and a certain tension was applied to the release layer. It was easy to peel off and was excellent in peeling stability.

Example 2
(Manufacture of release layer)
100% by weight of a propylene resin (“Nobrene FLX80E4” manufactured by Sumitomo Chemical Co., Ltd .; propylene homopolymer) is supplied to a single-screw extruder having a cylinder diameter of 50 mm, the resin temperature is 250 ° C., and the take-up speed is 15.5 m / min. Then, extrusion molding was performed using an air chamber at a cooling roll of 10 ° C. to obtain a release layer having an average thickness of 40 μm. Surface roughness Ra of the surface which contacts the adhesion layer of the obtained peeling layer was 0.13 micrometer, Rz was 2.1 micrometer, and bending rigidity was 0.75 * 10 < ^-3 > N / 20mm.
[Creation of surface protective film]
Bonding was performed in the same manner as in Example 1 to obtain a surface protective film. The evaluation results of the obtained surface protective film are shown in Table 1. When the release stability of the film was evaluated, it was easy to control the tension when the release layer was peeled off from the base layer / adhesive layer, and a certain tension was applied to the release layer. It was easy to peel off and was excellent in peeling stability.

Comparative Example 1
(Manufacture of release layer)
100% by weight of a propylene resin (“Nobrene FLX80E4” manufactured by Sumitomo Chemical Co., Ltd .; propylene homopolymer) is supplied to a single screw extruder having a cylinder diameter of 50 mm, the resin temperature is 250 ° C., and the take-up speed is 32.2 m / min. Then, extrusion molding was performed using an air chamber at a cooling roll of 70 ° C. to obtain a release layer having an average thickness of 20 μm. The obtained release layer had a surface roughness Ra of 0.11 μm, Rz of 15.1 μm, and a flexural rigidity of 0.12 × 10 ⁻³ N / 20 mm on the surface in contact with the adhesive layer.
[Creation of surface protective film]
Bonding was performed in the same manner as in Example 1 to obtain a surface protective film. The evaluation results of the obtained surface protective film are shown in Table 1. The film had a high peel resistance, and when the release layer was peeled from the base material layer / adhesive layer, it was difficult to control the tension of the release layer, and defects were likely to occur.

Comparative Example 2
(Manufacture of release layer)
As the release layer, a polyester film coated with a silicone release agent (thickness 38 μm) was used. The surface roughness Ra of the surface in contact with the adhesive layer of this film was 0.12 μm, Rz was 9.5 μm, and the bending rigidity was 2.68 × 10 ⁻³ N / 20 mm.
[Creation of surface protective film]
Bonding was performed in the same manner as in Example 1 to obtain a surface protective film. The evaluation results of the obtained surface protective film are shown in Table 1. Since this film had too good peelability, when the release layer was peeled from the base material layer / adhesive layer, defects such as wrinkles, talmi, and meandering occurred on the release layer side, and the adhesive layer side became unstable.

About the film of the said Example and comparative example, it measured by the following method.
(1) The surface of the surface roughness release layer that is in contact with the adhesive layer is measured with a laser surface roughness meter (VK-8500 manufactured by Keyence Corporation), and the arithmetic average roughness is calculated as the surface roughness Ra of the release layer, the maximum The surface roughness was Rz. The range of the measurement surface at this time is 298 × 224 μm.
(2) Create a strip of 150 mm length and 20 mm width with the MD direction at the time of film formation as the longitudinal direction using the film of the bending rigidity release layer, and make it a loop stiffness tester (D type) manufactured by Toyo Seiki Seisakusho Co., Ltd. The bending stiffness was measured. Bending rigidity is a measurement of the load required to deform a circle by 10 mm at a displacement speed of 3.5 mm / sec.
(3) Using a surface protection film composed of a base material layer / adhesive layer / peeling layer prepared as a peeling resistance, a strip having a length of 150 mm and a width of 25 mm is created with the MD direction at the time of film formation as the longitudinal direction, and the peeling layer is 180 The peel resistance was measured when the substrate layer was bent and pulled in the direction completely opposite to the base material layer / adhesive layer. At this time, the base layer / adhesive layer side was fixed to a metal plate with a double-sided tape so that the peeling angle was constant. For measurement, a Tensilon tester (Orientec Co., Ltd., RTA-1T) was used and peeled at a peeling speed of 300 mm / min.
(4) A surface protective film consisting of a base material layer / adhesive layer / release layer having a peel stability film width of 1480 mm is attached to a feeding portion of a generally used film feeding / winding device, and from the feeding portion to the winding portion. The release layer was peeled from the base material layer / adhesive layer in the meantime, and the work of winding the release layer at another winding part was performed.
When the above operation was carried out, the peeling layer was peeled from the base material layer / adhesive layer, and the state of the peeled peeling layer film (wrinkles, presence or absence of tarmi, etc.) was visually confirmed to evaluate the peeling stability.
(5) Appearance at the time of peeling use After removing the peeling layer of the surface protective film consisting of the base material layer / adhesive layer / peeling layer, place it so that the adhesive layer surface is in contact with a smooth metal plate and press with a hand roll Then, the base material layer / adhesive layer was bonded to the metal plate, and it was visually confirmed whether air bubbles were mixed between the adhesive layer and the metal plate. Appearance testability is inferior when air bubbles enter, and x when no air bubbles are present.

Claims (4)

The surface protective film in which the base material layer, the adhesive layer, and the release layer are laminated in this order, wherein the release layer is a polypropylene film and satisfies the following requirements (1) to (3).
(1) The surface roughness (Ra) of the surface in contact with the adhesive layer of the release layer is 0.10 to 0.30 μm.
(2) The flexural rigidity of the release layer measured by the loop stiffness tester is 0.2 × 10 ^{−3 to} 10.0 × 10 ⁻³ N / 20 mm.
(3) The peel resistance between the adhesive layer and the release layer is 0.16 to 0.30 N / 25 mm. The surface protective film according to claim 1, wherein the maximum surface roughness (Rz) of the surface of the release layer that contacts the adhesive layer is 0.1 to 10.0 μm. The surface protective film according to claim 1, which is a surface protective film for an optical member. A method for producing the surface protective film according to any one of claims 1 to 3, wherein the adhesive layer is coated on the base material layer to form an adhesive layer, and then the adhesive layer and the release layer are laminated. A method for producing a protective film.