JP2008308559A - Surface-protecting film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-protecting film capable of rewinding a wound body reasonably even on making a wide width wound body, and also inhibiting the transfer of a releasing layer silicone into an adhesive layer as much as possible during the preservation of the wound body. <P>SOLUTION: This surface-protecting film obtained by co-extrusion is constituted by laminating a substrate material layer consisting mainly of a homopolypropylene and containing 0.5 to 5 wt.% ultrahigh molecular weight polysiloxane, an intermediate layer consisting of a polyolefin and the adhesive layer in this order. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface protective film used for preventing dust from adhering to an adherend surface and damage to the adherend surface.

  Conventionally, for example, when various articles and members such as optical devices, metal plates, painted steel plates, resin plates, glass plates, etc. are transported, processed, or cured, dirt adheres to these surfaces or the surface is damaged. A surface protective film is used to prevent this.

This type of surface protective film is formed by laminating an adhesive layer on a base material. The surface protective film is manufactured, for example, by applying a pressure-sensitive adhesive solution containing an elastomer or the like to a base material made of a synthetic resin or the like, or coextruding the base material and the pressure-sensitive adhesive layer.
In recent years, surface protective films have been used for optical members for liquid crystal displays. Some optical members have an uneven surface such as a prism sheet or a diffusion film. When pasted on these surfaces, it is necessary to form a pressure-sensitive adhesive layer having a strong adhesive force because the contact area cannot be obtained. .
Generally, the surface protective film is industrially manufactured as a wound body obtained by winding a long film in a roll shape, for example. In the surface protective film as such a wound body, when the wound body is unfolded, the outer surface protective film can be easily peeled off from the inner surface protective film, that is, the wound body is unwound. There is a strong demand for being easy. Therefore, the pressure-sensitive adhesive layer having a strong adhesive force needs to be subjected to a release treatment that exhibits higher releasability than usual so that the pressure-sensitive adhesive layer does not strongly adhere to the back surface of the inner surface protective film.

  As the surface protection film subjected to the mold release treatment, the base material made of polyolefin resin and the pressure-sensitive adhesive layer are laminated, and the back surface of the base material (opposite side to the pressure-sensitive adhesive layer lamination side of the base material, hereinafter the same) is solid. A surface protective film subjected to friction treatment is disclosed (for example, Patent Document 1).

  Further, as a method for forming a release layer of a surface protective film, a surface protective film in which a base material made of polyethylene having a polyorganosiloxane as a graft chain and an adhesive layer are laminated is disclosed (for example, Patent Document 2). Patent Document 2 also shows a configuration in which an intermediate layer made of a polyolefin-based resin is provided between a base material and an adhesive layer. It is said that the wound body can be well rewound after a lapse of time by forming the base material using polyethylene having a polyorganosiloxane as a graft chain.

On the other hand, in Patent Document 3 below, a surface layer containing a polyolefin-based resin and a pressure-sensitive adhesive layer containing a thermoplastic elastomer are laminated by a co-extrusion method, and then the surface pressure-sensitive adhesive layer is laminated. A surface protection sheet is disclosed in which a release layer made of a release agent is formed on the back surface opposite to the side on which it is formed by a coating method.
Patent Document 4 discloses a method for producing a laminate in which corona discharge treatment is performed on a polyolefin resin composition layer containing polysiloxane as a means for preventing silicone migration to an adhesive layer.
JP-A-2-252777 Japanese Patent Laid-Open No. 2-252782 JP 2003-41216 A JP-A-5-131598

  Although the friction process by the solid with respect to the back surface of a base material like patent document 1 can be performed comparatively simply in-line, it has not led to fully improving the rewinding property of a winding body only by performing a friction process. is the current situation. Moreover, the improvement effect of the rewinding property by friction treatment varies depending on the selection of the polyolefin resin constituting the substrate.

  In general, since the polyorganosiloxane described in Patent Document 2 has a high releasability, a relatively good releasability can be obtained, but the rewinding property of the wound body should also be sufficiently improved. I can't. Furthermore, since free polyorganosiloxane is present in the resin, these migrate to the pressure-sensitive adhesive layer, reduce the adhesive strength, and cause peeling.

  Furthermore, as described in Patent Document 3, when a release agent is applied to form a release layer, the thickness of the release layer is reduced to 1 to 1000 nm to reduce contamination on the adherend. It is said that the effect is great. However, the transfer of the release agent to the adhesive surface cannot be sufficiently suppressed, and the adhesive force is reduced.

  Moreover, although the transfer of silicone to the pressure-sensitive adhesive layer can be suppressed by corona discharge treatment as in Patent Document 4, polar groups such as a carbonyl group and a carboxyl group are generated by the surface treatment, and eventually the mold release property is lowered. Will be allowed to.

  The object of the present invention is to allow the winding body to be rewound without difficulty even in the case of a wide winding body in view of the current state of the prior art described above, and to release the release layer silicone during storage of the winding body. The object is to provide a surface protective film that minimizes the transition to the pressure-sensitive adhesive layer.

  As a result of intensive studies on the above problems and existing surface protection sheets, the present inventors have provided a layer obtained by adding ultrahigh molecular weight polydimethylsiloxane to homopolypropylene (PP), thereby imparting good unwinding properties. And found that the migration of the polyorganosiloxane to the pressure-sensitive adhesive layer during storage in a wound body can be minimized, and the present invention has been completed.

The surface protective film of the present invention is a surface protective film obtained by coextrusion, comprising a base layer comprising homopolypropylene as a main component and containing 0.5 to 5% by weight of ultrahigh molecular weight polysiloxane, An intermediate layer made of polyolefin and an adhesive layer are laminated in this order.
In such a surface protective film, the pressure-sensitive adhesive layer is preferably a layer mainly composed of a styrene-based thermoplastic elastomer.

According to the surface protective film of the present invention, high release properties can be imparted to the pressure-sensitive adhesive layer. As a result, even when the surface protective film of the present invention is a wound body, in particular, a wide wound body, the wound body can be rewound without difficulty.
In addition, the migration of the polyorganosiloxane to the pressure-sensitive adhesive layer during storage of the wound body can be suppressed as much as possible, the pressure-sensitive adhesive layer has a reduced adhesive strength, and contamination due to the residue of the pressure-sensitive adhesive layer on the adherend is prevented. A surface protective film that can be prevented is obtained.

  The surface protective film of the present invention is constituted by laminating a base material layer, an intermediate layer, and an adhesive layer in this order. That is, the intermediate layer is laminated on one surface of the base material layer, and the adhesive material layer is laminated on the side opposite to the side of the intermediate layer on which the base material layer is laminated.

The base material layer is formed from a composition containing homopolypropylene as a main component and containing ultrahigh molecular weight polydimethylsiloxane.
The base material layer contains homopolypropylene as a main component. Here, the main component refers to the component having the largest weight among the components constituting the base material layer. The amount is usually 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more with respect to the total weight of the base material layer. Homopolypropylene generally has higher stereoregularity than block polypropylene copolymers and random polypropylene copolymers. A material with high stereoregularity has high crystallinity and affinity between the same molecules, and low affinity with other molecules, so that it is difficult to adhere to the adhesive layer. Therefore, by using homopolypropylene with high stereoregularity, the peelability of the surface protective film adhered to the back surface of the base material layer can be further enhanced, and the wound body can be more easily deployed. .

  In addition to homopolypropylene, the resin component constituting the base material layer may contain other polyolefins as long as the object of the present invention is not impaired. The polyolefin is not particularly limited. For example, a propylene polymer such as a block system or a random system composed of a propylene component and an ethylene component; an ethylene polymer such as a low density, high density, linear low density polyethylene; and an ethylene-α-olefin copolymer. Examples thereof include olefin polymers such as polymers, olefin polymers of ethylene components such as ethylene-vinyl acetate copolymers and ethylene-methyl methacrylate copolymers and other monomers. In addition, the range which does not inhibit achievement of the subject of this invention is about 50 weight% or less with respect to the total weight of a base material layer, for example, Furthermore, about 40 weight% or less is mentioned.

Ultra high molecular weight polydimethylsiloxane is a polydimethylsiloxane having a molecular weight of about 1,000,000 or more, and is a gum-like solid at room temperature. Specifically, the kinematic viscosity is 10 ⁶ mm ² / s or more, preferably 5 × 10 ⁶ mm ² / s or more, and more preferably 10 ⁷ mm ² / s or more.

  The addition amount of the ultrahigh molecular weight polydimethylsiloxane is suitably about 0.5 to 5% by weight. If the addition amount is too small, the releasability cannot be obtained, and if it is too large, the transfer to the pressure-sensitive adhesive layer increases, and problems such as a decrease in adhesive strength may occur.

  An additive may be used for the base material layer as necessary. Examples of such additives include known light stabilizers such as ultraviolet absorbers, antioxidants, hindered amine light stabilizers, and antistatic agents. Furthermore, for example, known materials such as fillers such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide, pigments, plasticizers, and antiblocking agents can be appropriately blended as additives.

  The film thickness of the base material layer is not particularly limited, but is preferably about 0.1 to 50 μm in consideration of cost and moldability, about 0.5 to 30 μm or about 0.5 to 10 μm, and further 2 to 20 μm. More preferred.

The intermediate layer in the surface protective film of the present invention is provided between the base material layer and the pressure-sensitive adhesive layer. The intermediate layer preferably has good adhesion to both the base material layer and the pressure-sensitive adhesive layer.
The type of polyolefin in the intermediate layer is not particularly limited. For example, polypropylene or a propylene-based polymer such as a block or random system composed of a propylene component and an ethylene component; low density, high density, linear low density polyethylene, etc. Ethylene polymers: Olefin polymers such as ethylene-α-olefin copolymers, olefin polymers of ethylene components and other monomers such as ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, etc. . These polyolefins may be used alone or in combination of two or more.
The polyolefin of the intermediate layer is preferably the same type as the polyolefin used for the base material layer, that is, homopolypropylene, in terms of moldability and adhesion.
The film thickness of the intermediate layer is not particularly limited, but is preferably about 1 to 50 μm and more preferably about 2 to 20 μm in consideration of cost and moldability.

Although it does not specifically limit as a material which comprises an adhesive layer, The adhesive composition which has a rubber-type resin component as a main component is used preferably.
The rubber-based resin component is not particularly limited, and those used as a base polymer for pressure-sensitive adhesives such as styrene-based elastomers, urethane-based elastomers, ester-based elastomers, and olefin-based elastomers can be used. Among these, when a styrene-based elastomer is used, a surface protective film can be easily formed by coextrusion, and a surface protective film having good temporary adhesion to an adherend can be provided.

  Specific examples of styrene elastomers include styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene / butylene copolymer-styrene (SEBS), and styrene-ethylene / propylene copolymer. -ABA type block polymer such as styrene (SEPS); styrene-butadiene (SB), styrene-isoprene (SI), styrene-ethylene-butylene copolymer (SEB), styrene-ethylene / propylene copolymer AB block polymer such as (SEP); Styrene random copolymer such as styrene-butadiene rubber (SBR); ABC type such as styrene-ethylene-butylene copolymer-olefin crystal (SEBC) Styrene-olefin crystal block polymer C-B-C type olefin crystal block polymer such as crystal-ethylene / butylene copolymer-olefin crystal (CEBC); ethylene-α-olefin, ethylene-propylene-α-olefin, propylene-α-olefin, etc. Examples thereof include olefin-based elastomers and hydrogenated products thereof. These rubber-based resin components may be used alone or in combination of two or more.

In particular, when the rubber-based resin component has an unsaturated double bond derived from an olefin, the unsaturated double bond is preferably less from the viewpoint of improving heat resistance and weather resistance, and hydrogenated as necessary. It is preferable that
In a styrene-based elastomer, a double conjugated diene moiety in a conjugated diene polymer block that is an olefin polymer block (B) or a random copolymer block (B ′) of styrene and a conjugated diene that is an olefin. It is preferred that at least 80% of the bonds are saturated by hydrogenation. A more preferable ratio of hydrogenation is 90% or more, and further preferably 95 to 100%. This is to ensure heat resistance and weather resistance.

  The weight average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography) of the styrene elastomer is preferably in the range of 30,000 to 400,000, more preferably in the range of 50,000 to 200,000. This is because the cohesive force of the pressure-sensitive adhesive layer is ensured and adhesive residue on the adherend when the surface protective film is peeled off is prevented. Moreover, it is for ensuring a suitable adhesive force and preventing the increase in a solution viscosity and a melt viscosity at the time of preparation of an adhesive composition or manufacture of a surface protection film.

  By using a tackifier as a material constituting the pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer can be effectively increased. In this case, it is preferable to use the surface protective film in an amount that can prevent adhesive residue when the surface protective film is peeled off from the adherend. For example, the blending ratio of the tackifier is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less with respect to 100 parts by weight of the rubber-based resin component.

Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, and coumarone-indene resins. , Terpene resin, terpene phenol resin, rosin resin such as polymerized rosin, (alkyl) phenol resin, xylene resin or hydrogenated products thereof are generally used for adhesives Things can be used without particular limitation. These tackifiers may be used alone or in combination of two or more.
In order to improve the peelability and weather resistance, it is more preferable to use a hydrogenated tackifier. Moreover, you may use the tackifier marketed as a blend with an olefin resin.

When a softener is further used as the material constituting the pressure-sensitive adhesive layer, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer can be effectively increased.
Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of these derivatives include those having an OH group or a COOH group at one or both ends. Specific examples include hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool.
Of these, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, and olefinic softeners are preferred. This is because the adhesive strength of the pressure-sensitive adhesive layer can be appropriately increased. As such a softening agent, for example, “Kuraprene LIR-200” manufactured by Kuraray Co., Ltd. is used. These softeners may be used alone or in combination of two or more.

  The number average molecular weight of the softening agent is not particularly limited, but is preferably in the range of 5000 to 100,000, and more preferably in the range of 10,000 to 50,000. This is because the material transfer from the pressure-sensitive adhesive layer to the adherend can be suppressed to prevent heavy peeling and the like, and the improvement of the adhesive strength can be ensured.

  When the pressure-sensitive adhesive composition is composed of a rubber-based resin component and a softening agent, the amount of the softening agent is not particularly limited, but the total amount of the rubber-based resin component and the softening agent is 100 parts by weight. On the other hand, the blending ratio of the softener is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less. It is because the adhesive residue at the time of peeling from an adherend after high temperature or outdoor exposure can be reduced.

In addition, as a material which comprises an adhesive layer, you may use another additive as needed in the range which does not inhibit achievement of the subject of this invention. Examples of such additives include known ones such as ultraviolet absorbers, antioxidants, and adhesion progress inhibitors.
Examples of the ultraviolet absorber and the antioxidant are the same as described above.
Examples of the adhesion progress preventing agent include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 251”), tall oil-modified alkyd resins (for example, Arakawa). Chemical name, “Arachid 6300”, etc.).

Although the thickness in particular of an adhesive layer is not restrict | limited, It is about 0.5-50 micrometers, Preferably it is 1-30 micrometers, More preferably, it is 2-30 micrometers.
Accordingly, the total thickness of the surface protective film is suitably about 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

The substrate of the surface protective film of the present invention can be produced by lamination and integration by co-extrusion by a known method such as an inflation method or a T-die method.
Moreover, the surface protection film of this invention is manufactured industrially as a wound body which wound the elongate film in roll shape, for example. When the surface protective film is a wound body, the pressure-sensitive adhesive layer in another part is in close contact with the side of the base material layer opposite to the side where the pressure-sensitive adhesive layer is formed. In the present invention, even in such a case, and when the surface protective film is, for example, a relatively wide wound body, the pressure-sensitive adhesive layer can be easily peeled from the base material layer. . That is, the wound body can be easily rewound.

  Hereinafter, examples of the surface protective film of the present invention will be described in detail. However, the present invention is not limited to the following examples.

Example 1
As a material constituting the base material layer, a melting point of 165 ° C., a density of 0.91 g / cm ³ , MFR of 12 g / 10 min. 0.5 parts by weight was supplied by dry blending.
As a material constituting the intermediate layer, 100 parts by weight of the same homo PP as that used for the base material layer was prepared.
As a material constituting the pressure-sensitive adhesive layer, 100 parts by weight of a styrene elastomer (SEBS, manufactured by Kraton Polymer Co., Ltd., product number: Kraton G1657) and 5 parts by weight of Alcon P-125 (manufactured by Arakawa Chemical Industries) as a tackifier The blended pressure-sensitive adhesive composition was kneaded with a twin-screw extruder and pelletized.

  Each of the above materials is coextruded by a T-die method, and a surface protective film (width 1300 mm) having a three-layer structure of a base material layer (thickness 6 μm) / intermediate layer (thickness 28 μm) / adhesive layer (thickness 6 μm) is formed. Winded up.

(Example 2)
A film was formed and wound in the same manner as in Example 1 except that 5 parts by weight of the ultrahigh molecular weight polydimethylsiloxane (trade name: GENIOPLAST, manufactured by Wacker Chemie) of the base material layer was changed to 5 parts by weight.

(Comparative Example 1)
A film was formed and wound up in the same manner as in Example 1 except that the base layer and the intermediate layer were made of block PP copolymer (manufactured by Prime Polymer Co., Ltd., J715M).

(Comparative Example 2)
A film was formed and wound up in the same manner as in Example 2 except that low molecular weight polydimethylsiloxane (manufactured by Dow Corning Toray, SH200, kinematic viscosity 100000 mm ² / s) was used for the base material layer.

(Comparative Example 3)
A film was formed and wound up in the same manner as in Example 1 except that 7 parts by weight of ultrahigh molecular weight polydimethylsiloxane was used.

(Evaluation)
(1) Rewindability of wide wound body The film end of each 1300 mm wide wound body was held and pulled by hand, and the wound body was rewound by about 1 m. When rewinding, it was visually observed whether or not the surface protective film had partial elongation or deformation. The case where there was no partial expansion or deformation was judged as “◯”, and the case where there was partial expansion or deformation was judged as “x”.

(2) Transferability Ratio of the adhesive strength B of the surface protective film sampled after winding as a wound body with respect to the adhesive strength A of the surface protective film sampled before winding as a wound body (B / A) Evaluated.
Each surface protective film was attached to a flat acrylic plate at a speed of 2 m / min from the pressure-sensitive adhesive layer side using a 2 kg rubber roller. This was left in a room at 23 ° C. ± 2 ° C. for 30 minutes. Thereafter, in accordance with JIS Z 0237, the surface protective film was peeled off from the acrylic plate, and the 180 degree peel strength at 25 mm width was measured at a tensile speed of 30 m / min. The ratio (B / A) of adhesive strength is expressed as a percentage, where “◯” indicates a case of 85% or more, “Δ” indicates a case of 65% or more and less than 85%, and “x” indicates a case of less than 65%. It was judged.
The results are shown in Table 1. In the table, PDMS represents polydimethylsiloxane.

Claims (2)

A surface protective film obtained by coextrusion,
A base layer composed mainly of homopolypropylene and containing 0.5 to 5% by weight of ultrahigh molecular weight polydimethylsiloxane, an intermediate layer made of polyolefin, and an adhesive layer are laminated in this order. A surface protective film characterized by that.   The surface protective film according to claim 1, wherein the pressure-sensitive adhesive layer is a layer mainly composed of a styrene-based thermoplastic elastomer.