JPWO2011096350A1 - Surface protection film - Google Patents

Abstract

This invention makes it a subject to provide the surface protection film which has high adhesive force and the outstanding rewinding property. The present invention is a surface protective film comprising at least two layers of a surface layer (A) and an adhesive layer (X), the surface layer (A) is composed of a propylene polymer, and the surface roughness (Ra ) Is a surface protective film in the range of 0.2 to 2.0 μm. The surface protection film according to the above surface protection film, wherein the surface protection film has an adhesive strength to acrylic of 1 N / 50 mm, and the adhesive layer (X) is formed of an olefin elastomer and / or a styrene elastomer. It is a film.

Description

  The present invention relates to a surface protective film used for optical products, building materials, automobile parts and the like. Specifically, it has excellent adhesive properties, transparency, and heat resistance, has little contamination to the adherend, etc., and is easy to unwind when the film is unwound from a roll (hereinafter referred to as “unwinding property”). It is related with the surface protection film excellent in.

  The surface protective film is used by sticking to adherends such as resin products, metal products, glass products, etc. mainly for building materials and optical applications, and prevents them from being scratched or contaminated during transport, storage or processing. Plays. These surface protective films generally comprise a non-adhesive surface layer and an adhesive layer for adhering to the adherend. The surface layer is usually formed from a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate, or a vinyl polymer such as polyvinyl chloride.

  In recent years, development of members used for liquid crystal screens, plasma displays (PDP), rear projection screens, and so on, so-called optical products, has been progressing. For surface protection films for protecting these optical products, there are demands for characteristics such as transparency so that product inspection can be performed in a state where the surface protection film is applied, as well as scratches and foreign matter contamination.

  In addition, when a surface protection film is used for building materials or automotive parts, it may be thermoformed with the surface protection film attached, and high heat resistance that can be used as a surface protection film is required even at high temperatures. Has been.

  In addition, since the surface protective film having a relatively high adhesive strength does not have a sufficient payout property, it is in a roll state in which a release film is bonded to the adhesive layer and wound up, and is applied to an adherend. The release film is peeled off and used. When such a means is employed, a large amount of release film is generated as waste, so that a surface protective film having sufficient payout property without a release film is required.

  Patent Document 1 discloses a surface protective film mainly composed of a polyethylene component. However, the protective film of the same publication can be applied to some application members, but has low adhesive strength and insufficient transparency, and the application of the adherend is limited.

  Patent Document 2 discloses a protective film composed of a back layer and an adhesive layer obtained using a specific resin composition. However, the protective film of the same publication does not sufficiently prevent the generation of fish eyes, and particularly when used as a protective film for an optical member or the like, there is a risk of adversely affecting the adherend, and there is a need for improvement.

JP 2006-116769 A JP 2009-28938 A

  The object of the present invention is to provide properties required as a surface protective film for protecting optical products, building material products and automobile parts during storage, transportation, processing and inspection, in particular, adhesive properties, transparency and heat resistance. Another object of the present invention is to provide a surface protective film excellent in feeding performance.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by a surface protective film having a surface layer made of a specific resin composition, and have completed the present invention.

  That is, the present invention is a surface protective film comprising at least two layers of a surface layer (A) and an adhesive layer (X), the surface layer (A) is composed of a propylene-based polymer, and the surface layer has a surface roughness. It relates to a surface protective film having (Ra) in the range of 0.2 to 2.0 μm.

  Furthermore, the suitable aspect of this invention is the said surface protective film whose adhesive force with respect to an acryl is 1 N / 50mm or more, Furthermore, adhesive layer (X) is formed from an olefin-type elastomer and / or a styrene-type elastomer. It is the said surface protection film characterized by the above-mentioned.

  The surface protective film of the present invention is excellent in adhesive properties, transparency, roll-out property from a rolled-up state, and heat resistance, and is suitable as a surface protective film for optical use, building material use, and automotive part use.

  Next, the present invention will be described in detail.

  The surface protective film of the present invention comprises at least two layers of a surface layer (A) and an adhesive layer (X).

  The surface layer (A) is made of a propylene polymer.

  Examples of the propylene polymer include a propylene homopolymer, and a random or block copolymer of ethylene and / or an α-olefin having 4 to 20 carbon atoms together with propylene.

  Examples of the α-olefin having 4 to 20 carbon atoms used in the random or block copolymer include 1-butene, 4-methylpentene-1, 1-hexene, and 1-octene. Examples of such copolymer include propylene / ethylene copolymer, propylene / 1-butene copolymer, and propylene / ethylene / 1-butene copolymer.

  The propylene polymer preferably has a melting point of 50 to 170 ° C., more preferably 70 to 170 ° C., still more preferably 100 to 165 ° C., and most preferably 130 to 165 ° C. from the viewpoint of improving heat resistance. Here, the melting point is a value measured by a differential scanning calorimeter (DSC) at a temperature rising / falling rate of 10 ° C./min.

  The propylene polymer preferably has a melt flow rate (hereinafter abbreviated as MFR) measured at 230 ° C., preferably 0.01 to 500 g / 10 minutes, more preferably 0.1 to 100 g / 10 minutes, and still more preferably. It exists in the range of 0.3-50 g / 10min.

  The propylene polymer is not only a solid titanium catalyst mainly composed of a solid titanium compound and an alkylaluminum compound, but also a homopolymerization of propylene in the presence of a metallocene compound, a metallocene catalyst, a geometrically constrained catalyst, etc. Alternatively, it is obtained by copolymerizing ethylene and / or an α-olefin having 4 to 20 carbon atoms with propylene.

In the surface protective film of the present invention, the surface roughness (Ra) of the surface layer (A) made of the propylene polymer is in the range of 0.2 to 2.0 μm from the viewpoint of transparency and feedability. Among them, the surface roughness (Ra) is preferably 0.3 μm or more, and more preferably 0.4 μm or more. The surface roughness (Ra) is preferably 1.5 μm or less, and more preferably 1.2 μm or less. When the surface roughness is less than 0.2 μm, it is difficult for the surface layer to peel from the adhesive layer, and the feeding property is lowered. On the other hand, when the surface roughness exceeds 2.0 μm, sufficient transparency cannot be obtained due to irregular reflection of light rays on the surface.

Although there is no restriction | limiting in particular as a method of forming the surface roughness of the said surface layer, By transferring the embossing roll to a surface layer and forming surface roughness, or changing the molecular weight and composition of the said propylene polymer. A method for controlling the surface roughness is used. From the viewpoint of productivity, a method of controlling the molecular weight and composition of the propylene polymer is preferably employed. In order to achieve a suitable surface roughness, an example of the propylene polymer includes a method using a block copolymer of propylene and ethylene (hereinafter referred to as “propylene / ethylene block copolymer”). The MFR (230 ° C.) of the propylene / ethylene block copolymer is preferably in the range of 3 to 20 g / 10 minutes, more preferably 4 to 15 g / 10 minutes. The intrinsic viscosity ([η]) of the rubber component in the propylene / ethylene copolymer is preferably 2.0 dl / g or more.

  In the propylene polymer used as the surface layer (A), for the purpose of imparting antistatic properties and weather resistance to the surface protective film of the present invention, improving transparency and improving the appearance, an antistatic agent, a release agent, an oxidation agent It is also possible to add various additives such as inhibitors, weathering agents, crystal nucleating agents, and other resin modifiers such as other crystalline polyolefins such as polyethylene and polybutene, polyesters, polyamides, and elastomers.

  When an additive or a modifier is added to the propylene-based polymer as necessary, for example, after the addition of the additive, etc., the film is kneaded with a single-screw or twin-screw extruder, a feeder ruder, etc. Although it may be processed into a shape, it can be directly put into a T-die molding machine having an extruder and used as the surface layer (A) of the surface protective film of the present invention.

  As the pressure-sensitive adhesive layer (X) of the surface protective film of the present invention, any known pressure-sensitive adhesive used as the pressure-sensitive adhesive layer of the surface protective film can be used. From the viewpoint of damage of the adhesive and the transfer of the adhesive to the adherend, that is, the adhesive residue, an olefin elastomer and / or a styrene elastomer is preferable. More preferably, it is an olefin elastomer or a composition comprising an olefin elastomer and a styrene elastomer.

  As an olefin elastomer, a non-crystalline elastomer whose melting point by DSC measurement (measured at a temperature rising / falling rate of 10 ° C./min) is not observed in the range of 0 to 200 ° C. or observed in the range of 0 to 200 ° C. A microcrystalline elastomer in which a peak having a melting heat quantity of a melting point peak of 10 J / g or less is suitable, and more preferably, the amorphous elastomer or a microcrystalline elastomer having a melting heat quantity of a melting point peak of 7 J / g or less. It is.

  Examples of the olefin elastomer include an α-olefin polymer or copolymer having 2 to 20 carbon atoms, or a copolymer of ethylene and an unsaturated carboxylic acid or an unsaturated carboxylic acid ester. Specifically, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-methylpentene-1 copolymer, ethylene / 1-octene copolymer , Propylene homopolymer, propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, 1-butene homopolymer, 1-butene / ethylene copolymer, 1-butene / propylene copolymer, 4 -Methylpentene-1 homopolymer, 4-methylpentene-1 / propylene copolymer, 4-methylpentene-1 / 1-butene copolymer, 4-methylpentene-1 / propylene / 1-butene copolymer , Propylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / methacrylic acid copolymer, ethylene / methyl methacrylate copolymer, etc. It can be mentioned. From the viewpoint of stability of adhesive strength with time, a propylene homopolymer, a propylene / ethylene copolymer, a propylene / 1-butene copolymer, and a propylene / ethylene / 1-butene copolymer are preferable.

  As the styrene elastomer, a known styrene elastomer having a polystyrene phase as a hard segment can be used. Specifically, styrene / butadiene copolymer (SBR), styrene / isoprene / styrene copolymer (SIS), styrene / butadiene / styrene copolymer (SBS), and hydrides thereof (SEBS, SEPS, etc.) And styrene / isobutylene / styrene triblock copolymer (SIBS) and styrene / isobutylene diblock copolymer (SIB). From the viewpoint of adhesiveness to the adherend and feeding property, styrene / isobutylene / styrene triblock copolymer (SIBS) and styrene / isobutylene diblock copolymer (SIB) are preferable.

  The adhesive layer (X) in the surface protective film of the present invention can be formed by using the olefin-based elastomer and / or the styrene-based elastomer alone or by blending components having different compositions. Further, in the present invention, for the purpose of controlling the adhesive force, and within a range not impairing the effects of the present invention, polyolefins such as polyethylene and polypropylene, resin modifiers such as acid-modified polyolefin, polyester and polyamide, Various additives such as an inhibitor, a crystal nucleating agent and an antioxidant may be contained.

  When the olefin-based elastomer and / or the styrene-based elastomer is used for forming the adhesive layer (X) of the surface protective film of the present invention, the olefin-based elastomer comprises 0 to 80% by weight and the styrene-based elastomer 20 to 100% by weight. More preferably, it consists of 0 to 75% by weight of olefin elastomer and 25 to 100% by weight of styrene elastomer, more preferably 5 to 75% by weight of olefin elastomer and 25 to 95% by weight of styrene elastomer. (The adhesive layer may contain other components as necessary, but in order to explain the ratio between the olefin-based elastomer and the styrene-based elastomer, the total of only these is displayed as 100% by weight. ing).

  The adhesive layer (X) in the surface protective film of the present invention can be formed by using the olefin-based elastomer and / or the styrene-based elastomer alone or by blending components having different compositions. In the adhesive layer (X), for the purpose of controlling the adhesive force, a polyolefin modifier such as polyethylene and polypropylene, an acid-modified polyolefin, a polyester, a polyamide, and other resin modifiers, as long as the effects of the present invention are not impaired. Various additives such as an antistatic agent, a crystal nucleating agent and an antioxidant may be contained.

  The adhesive layer (X) composed of the olefin elastomer and / or styrene elastomer and, if necessary, a resin modifier or an additive is laminated with the surface layer (A), whereby the surface protective film of the present invention. It can be.

  The adhesive strength of the surface protective film of the present invention to the acrylic plate is an index of the feeding property and the adhesive strength to the adherend, and is preferably 1 N / 50 mm or more, more preferably in the range of 3 to 40 N / 50 mm. Preferably it exists in the range of 5-30 N / 50mm. By setting it as the adhesive force of such a range, favorable feeding property can be maintained and adhesiveness to various to-be-adhered bodies can be expressed. When the adhesive strength is less than 1 N / 50 mm, the adherence to the adherend may not be sufficient, and when it exceeds 40 N / 50 mm, the rewinding property may deteriorate, which is not preferable.

  The unwinding force of the surface protective film of the present invention refers to a peeling force when a roll-shaped film is unrolled, and serves as an index of unwinding property. In order to provide unwinding property, the unwinding force is 2.5 N / 50 mm or less is preferable, More preferably, it exists in the range of 0.01-2.0 N / 50mm.

  The method for laminating the surface layer (A) and the pressure-sensitive adhesive layer (X) is not particularly limited. However, known methods such as extrusion lamination and extrusion coating on a surface layer film obtained in advance by T-die molding or inflation molding. The method of laminating the adhesive layer by the laminating method of the above, the method of laminating each film by dry lamination after forming the surface layer and the film forming the adhesive layer independently as a film, etc. From the viewpoint of efficiency, a method in which each component of the surface layer and the pressure-sensitive adhesive layer is subjected to coextrusion molding using a multilayer extruder is preferable.

  In the present invention, at least one intermediate layer is also provided between the surface layer (A) and the adhesive layer (X). Although there is no restriction | limiting in particular as an intermediate | middle layer, Generally, crystalline polyolefins, such as a polypropylene and polyethylene with melting | fusing point of 100 or more, polyester, polyamide, polyolefin-type elastomer, etc. can be used. When the intermediate layer is used as an adhesive layer, modified polyolefin, polyolefin elastomer, styrene elastomer, polyester elastomer, or the like is used. Among these, from the viewpoint of productivity and transparency, it is preferable to use polypropylene or polyolefin elastomer as the intermediate layer.

  When the adhesive force between the surface layer (A) and the pressure-sensitive adhesive layer (X) is insufficient, the intermediate layer is an adhesive or a film for bonding the surface layer (A) and the pressure-sensitive adhesive layer (X). The material may be configured as an adhesive layer.

  The thickness of the surface layer (A) in the surface protective film of the present invention is usually 0.05 to 200 μm, preferably 0.5 to 100 μm, more preferably 1 to 30 μm, and still more preferably 1 to 15 μm. The thickness of the pressure-sensitive adhesive layer (X) is usually 0.05 to 50 μm, preferably 0.3 to 40 μm, more preferably 0.5 to 30 μm.

  Therefore, the thickness of the surface protective film of the present invention is usually 0.1 to 500 μm, preferably 0.5 to 400 μm, more preferably 3 to 300 μm, including an intermediate layer which may be provided as necessary.

  As transparency of the surface protection film of this invention, the haze measured at 50 micrometers according to JISK7105 has the preferable range of 20 to 90%, Most preferably, it exists in the range of 30 to 85%. Further, the number of fish eyes (FE number) of the surface protective film of the present invention is preferably 20 or less, more preferably 10 or less, 5 or less, and even more preferably 3 or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

[Evaluation method]
Surface roughness (Ra): The surface protective film of the present invention (in this example, adjusted to a total thickness of 50 microns (μm)) under the conditions of air temperature 23 ° C. ± 2 ° C. and humidity 50% ± 10%, 24 The film was cured for a period of time, cut into a 50 mm square, and used as a film sample. The film sample was measured using a non-contact surface roughness meter (model number: NT-2000 SYSTEM-Veeco).

  Adhesive strength: Acrylic plate is cut into a width of 50 mm and a length of 125 mm under conditions of an air temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 10%, a film sample is placed on the surface of the acrylic plate, and a 2 kg rubber roller Is attached to the acrylic plate by pressing the entire sample film with its own weight. Next, the peel force when peeled at a speed of 300 mm / min (180 degree peel) is measured, and the peel force per 50 mm width is defined as the adhesive strength (N / 50 mm).

  Unwinding force: Using a roll-shaped sample, the peeling force (N / 50 mm) when peeling from the roll at a speed of 300 mm / min is measured and used as the unwinding force.

Fish eye (FE): Using an off-line foreign matter inspection apparatus manufactured by Ayaha Engineering, FE having a size of 0.1 mm or more was counted to obtain the number of FEs per unit area (pieces / m ² ).

Haze: Measured with the surface protective film of the present invention (total thickness of 50 μm in this example) in accordance with JIS K7105.
[Example 1]
The raw material was supplied to a three-type three-layer T-die molding machine having a die width of 500 mm, which was combined with a single screw extruder of 30 mmφ for the surface layer and the adhesive layer and a 40 mmφ single screw extruder for the intermediate layer, and the thickness of the surface layer was 10 μm. A surface protective film of the present invention having a total thickness of 50 μm comprising an adhesive layer thickness of 10 μm and an intermediate layer thickness of 30 μm was obtained. Table 1 shows the evaluation results of the obtained surface protective film. In addition, the raw material which comprises the surface layer of an Example and a comparative example, an intermediate | middle layer, and an adhesion layer, and compounding quantity are shown in Table 1 with an evaluation result.
[Examples 2 to 4, Comparative Examples 1 to 3]
A surface protective film was obtained in the same manner as in Example 1 except that the resin compositions of the various layers were changed to the resin compositions shown in Table 1. The evaluation results of the obtained film are shown in Table 1.

h-PP;
Homopolypropylene (melting point = 160 ° C., MFR = 7 g / 10 min, manufactured by Prime Polymer)
b-PP-1;
Propylene / ethylene block copolymer (brand name: PC684A, melting point = 160 ° C., MFR = 6 g / 10 min, manufactured by Sun Allomer)

b-PP-2;
Propylene / ethylene block copolymer (brand name: BC3HF, melting point = 160 ° C., MFR = 8.5 g / 10 min, manufactured by Nippon Polypro Co., Ltd.)

b-PP-3;
Propylene / ethylene block copolymer (melting point = 160 ° C., MFR = 3 g / 10 min)

LDPE;
Low density polyethylene (high pressure method low density polyethylene, density = 0.917 g / cm ³ , MFR = 3 g / 10 min)

PEBR;
Propylene / ethylene / 1-butene copolymer (A melting point peak of 4J / g of heat of fusion is observed at 0 to 200 ° C., MFR = 7 g / 10 min)

SIBS;
Styrene / isobutylene copolymer (styrene / isobutylene / styrene triblock copolymer, Mw = 65,000, JIS-A hardness = 33), brand name: Shibster 072T (manufactured by Kaneka Corporation)

In Examples 1 to 4, the adhesive strength is 7 to 18 N / 50 mm, and sufficient adhesiveness is ensured. Moreover, it is understood that the unwinding force is 0.1 to 1.6 N / 50 mm, and that it has an excellent feeding property. This is because the surface roughness (Ra) is an appropriate roughness of 0.47 to 0.81 μm while having sufficient adhesive strength.

  Furthermore, in Examples 1 to 4, the haze is 60 to 70%, and the haze has excellent transparency as a surface protective film when it is required to have transparency of 80% or less. I understand.

  On the other hand, in Comparative Examples 1 and 2, the adhesive strength is 7 to 18 N / 50 mm, and sufficient adhesiveness is ensured. However, in Comparative Examples 1 and 2, the unwinding force is such that peeling does not occur, and the feeding property is extremely high. It turns out that it is inferior. This is because in Comparative Examples 1 and 2, the surface roughness (Ra) was as extremely small as 0.25 μm and 0.05 μm, respectively, which made peeling difficult.

  In Comparative Example 3, the surface roughness (Ra) is 0.28 μm, the adhesive strength is sufficient, and the unwinding force is also 0.5 N / 50 mm, that is, the feeding property is good. However, when the surface layer is composed of a composition of h-PP and LDPE (Comparative Example 3), the fish eye number (FE number) is large and is not suitable as a surface protective film.

Thus, from Examples 1 to 4 and Comparative Example 3, the surface layer needs to be composed of a propylene-based polymer.

  The surface protective film of the present invention is excellent in adhesive properties, transparency, unwinding properties and heat resistance, and has a very high industrial utility value as a protective film for optical applications, building materials applications and automotive parts applications.

Claims (3)

  It is a surface protective film comprising at least two layers of a surface layer (A) and an adhesive layer (X), the surface layer (A) is composed of a propylene-based polymer, and the surface layer has a surface roughness (Ra) of 0. A surface protective film in the range of 2 to 2.0 μm.   The surface protective film according to claim 1, wherein the adhesive strength to the acrylic plate is 1 N / 50 mm or more.   The surface protective film according to claim 1, wherein the adhesive layer (X) is formed of an olefin elastomer and / or a styrene elastomer.