JP2009191208A - Manufacturing method of surface-protecting film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a surface-protecting film that exhibits sufficient mold releasability by simple facilities and treatments without exerting bad influences on other adhesive properties. <P>SOLUTION: The manufacturing method of the surface-protecting film includes subjecting an adhesive layer surface of a surface-protecting film, which is composed of a substrate layer and an adhesive layer laminated thereon and includes not been subjected to a mold release treatment with a mold releasing agent, to a corona discharge treatment or a plasma discharge treatment and subsequently winding up the surface-protecting film so that the adhesive layer is brought into direct contact with the back surface of the substrate layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a surface protective film wound up in a roll shape, and more particularly to a method for producing a surface protective film produced mainly by coextrusion.

  Conventionally, when various articles and members such as optical devices, metal plates, coated steel plates, resin plates, glass plates, etc. are transported, processed, or cured, they are prevented from being contaminated or damaged. For this reason, a surface protective film is used.

This type of surface protective film is manufactured by, for example, applying a pressure-sensitive adhesive solution containing an elastomer or the like to a base material layer made of a synthetic resin or the like, or coextruding the base material layer and the pressure-sensitive adhesive layer. It has a laminated structure.
In particular, in recent years, surface protective films used for optical members for liquid crystal displays are not suitable for sticking to optical members with uneven surfaces such as prism sheets and diffusion films because the contact area cannot be increased. A strong adhesive layer is required.

  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. However, since the pressure-sensitive adhesive layer having strong adhesive force strongly adheres to the back surface of the base material layer of the surface protective film on the inner side (the opposite surface of the base material layer to the pressure-sensitive adhesive layer lamination side, the same applies hereinafter), On the back surface of the base material layer of such a surface protective film, a release treatment that exhibits higher release properties than usual is required.

On the other hand, a surface protection film in which a base material layer made of a polyolefin resin and an adhesive layer are laminated as a surface protection film subjected to a release treatment, and the back surface of the base material layer is friction-treated with a solid. A film has been proposed (for example, Patent Document 1).
Moreover, after the base material layer and the pressure-sensitive adhesive layer are coextruded, a surface protective film in which a long-chain alkyl release agent is applied to the back surface of the base material layer has been proposed (for example, Patent Document 2).
Furthermore, a releasable laminated film in which a thermoplastic resin layer in which a releasable material is added is formed on a substrate has been proposed (for example, Patent Document 3).
On the other hand, a method for improving the adhesive strength has been proposed in which the surface of the adhesive layer to be applied is subjected to corona discharge treatment or plasma treatment to improve the adhesive strength of the treated surface (for example, Patent Document 4). ).
JP-A-2-252777 JP 2003-41216 A Japanese Patent Publication No. 60-5628 JP-A-7-173441

  In Patent Document 1, the back surface of the base material layer is friction-treated with a solid, and this friction treatment can be performed inline relatively easily. However, the effect of the friction treatment may differ depending on the material constituting the base material layer, and it is difficult to rewind the surface protection film or surface protection film having a strong adhesive force only by the friction treatment. When rewinding, problems such as film deformation may occur.

  In addition, when the release agent of Patent Document 2 is used, a relatively high release property can be obtained, but the temperature must be applied to the film when drying the solvent, and deformation of the film becomes a problem. . Furthermore, there is a problem that the equipment area and equipment cost are increased, for example, a coating / drying device is installed behind the extruder.

In patent document 3, the mold release material is easy to bleed out, and the problem which transfers to the opposing adhesive surface and changes adhesive force is unavoidable.
Patent Document 4 proposes a method for improving the adhesive force by performing corona discharge treatment or plasma treatment on the adhesive surface. This is due to the transfer of the release agent applied to the surface of the base material layer to the adhesive layer. In order to compensate for the decrease in adhesive strength, or in the case of double-sided tape, it expresses different adhesive strength on both sides, and is also intended to compensate for the decrease in adhesive strength due to the release agent transfer from the separator, Actually, it is assumed that the pressure-sensitive adhesive tape has a release agent in contact with the surface of the pressure-sensitive adhesive layer.

  An object of the present invention is to provide a method for producing a surface protective film capable of obtaining sufficient releasability with simple equipment and processing without adversely affecting other adhesive physical properties in view of the above-described conventional state of the art. That is.

The method for producing a surface protective film of the present invention comprises the steps of corona discharge treatment or plasma treatment on the surface of the pressure-sensitive adhesive layer of the surface protective film in which the base material layer and the pressure-sensitive adhesive layer that have not been subjected to the mold release treatment are laminated. After the discharge treatment, the surface protective film is wound up so that the pressure-sensitive adhesive layer is in direct contact with the back surface of the base material layer.
In the method for producing the surface protective film, the base material layer and the pressure-sensitive adhesive layer are preferably coextruded and laminated.
Further, it is preferable that the base material layer is made of polyolefin, or the pressure sensitive adhesive is made of styrene elastomer.

  According to the method for producing a surface protective film of the present invention, it is not necessary to add or apply a release agent to the base material layer, and the surface can be easily rewound by a simpler treatment of the pressure-sensitive adhesive layer surface. A protective film can be produced.

The surface protective film in this invention consists of an at least 1 base material layer and an adhesive layer.
The material of the base material layer is not particularly limited. For example, a thermoplastic resin such as polyolefin, polycycloolefin, polyester, polyamide, polyvinyl alcohol, or ethylene-polyvinyl alcohol copolymer is used. However, polyolefin is preferably used from the viewpoint of cost and moldability.
Although it does not restrict | limit especially as polyolefin, For example, propylene-type polymers, such as a block system which consists of a homopolypropylene or a propylene component, and an ethylene component, a random type; Ethylene-type polymers, such as a low density, a high density, a linear low density polyethylene; Examples thereof include olefin polymers such as α-olefin copolymers, olefin polymers of ethylene components and other monomers such as ethylene-vinyl acetate copolymers and ethylene-methyl methacrylate copolymers. These polyolefins may be used alone or in combination of two or more.

The polypropylene polymer may be a homopolymer, a block copolymer, or a random copolymer, but the use of a homopolymer is preferable because the releasability is improved.
The base material layer may be either a single layer or a laminated structure of two or more layers. However, in the case of a laminated structure of two or more layers, the surface layer, that is, the surface (back surface) opposite to the surface on which the adhesive layer described later is laminated may contain polyolefin, particularly polypropylene. preferable. In addition, when the base material layer has a laminated structure, the layers other than the back surface may be formed of any material, but are made of polyolefin in consideration of adhesion to the base material layer located on the back surface. Is preferred. In particular, the same polyolefin as that used for the back layer is more preferred.
The content of polyolefin is usually 10% by weight or more, preferably 30% by weight or more based on the total weight of the base material layer (or its surface layer).

  In the present invention, the base material layer is not subjected to release treatment with a release agent. This is because the release agent that has been used conventionally is not blended in the material constituting the base material layer, or the release layer containing the release agent component is not formed on the base material surface. means.

  If necessary, other additives may be used in the above-described base material layer as long as the object of the present invention is not impaired. Examples of such additives include known light stabilizers such as ultraviolet absorbers, antioxidants, hindered amine light stabilizers, and antistatic agents. Furthermore, for example, known substances such as fillers such as calcium carbonate, magnesium carbonate, silica, zinc oxide, and titanium oxide, pigments, anti-tarnish agents, lubricants, and anti-blocking agents can be appropriately blended as additives. .

  The thickness of the substrate layer is not particularly limited, but is preferably about 5 to 180 μm, more preferably about 10 to 130 μm, and more preferably about 20 to 100 μm in consideration of handling properties, 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.
As a rubber-type resin component, what is used as a base polymer of adhesives, such as a styrene-type elastomer, a urethane-type elastomer, an ester-type elastomer, an olefin-type elastomer, can be especially used without a restriction | limiting. Especially, when a styrene-type elastomer is used, a surface protective film can be easily formed by coextrusion, and the surface protective film which has favorable temporary attachment with respect to a to-be-adhered body can be provided.

  Specific examples of the styrene elastomer include styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene-butylene-styrene (SEBS), and styrene-ethylene-propylene-styrene (SEPS). ABA type block polymers such as styrene-isobutylene-styrene (SIBS); styrene-butadiene (SB), styrene-isoprene (SI), styrene-ethylene-butylene (SEB), styrene-ethylene-propylene (SEP) ), A-B type block polymer such as styrene-isobutylene (SIB); Styrene random such as styrene-butadiene rubber (SBR); ABC type such as styrene-ethylene-butylene-olefin crystal (SEBC) Styrene-Olef Emissions crystalline block polymers, and the like. These rubber-based resin components may be used alone or in combination of two or more.

  When the rubber-based resin component has an unsaturated double bond derived from an olefin or a conjugated diene, the number of unsaturated double bonds is preferably smaller from the viewpoint of improving heat resistance and weather resistance. It is preferable that it is added. For example, in the styrene-based elastomer, the conjugated diene moiety in the conjugated diene polymer block that is the olefin polymer block (B) or in the random copolymer block (B ′) of styrene and the conjugated diene that is the olefin. At least 80% of the double bonds are preferably saturated by hydrogenation, preferably 90% or more, and more preferably 95-100%.

  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 or 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 does not cause adhesive residue when peeling off the adherend. For example, the blending ratio of the tackifier is preferably 40 parts by weight or less, more preferably 30 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, process oil, castor oil, tall oil, natural oil, liquid polyisobutylene resin, polybutene, rosin resin such as polymerized rosin, (alkyl) phenol resin, xylene resin Or what is generally used for adhesives, such as these hydrogenated substances, can be especially used without a restriction | limiting. 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.

For the purpose of controlling the adhesive strength, the pressure-sensitive adhesive layer can be appropriately mixed with known additives such as an ultraviolet absorber, an antioxidant, and an antiadhesive agent as necessary.
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.).

Other additives can be the same as those added to the base material layer described above.
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.
About 10-200 micrometers is suitable for the total film thickness of a surface protective film, 20-150 micrometers, Furthermore, 30-100 micrometers is more preferable.

In the surface protective film of the present invention, the adhesive layer may be laminated on the substrate layer by forming a substrate layer by extrusion or the like and then applying the solution using a solution in which the adhesive is dissolved. Usually, it is preferable that the base material layer and the pressure-sensitive adhesive layer are laminated and integrated by co-extrusion by a known method such as an inflation method or a T-die method.
In any of the production methods, the surface protective film of the present invention can be industrially produced, for example, as a wound body obtained by winding a long film into a roll shape. When the surface protective film is a wound body, the pressure-sensitive adhesive layer adheres to the side of the base material layer opposite to the side where the pressure-sensitive adhesive layer is formed. In the present invention, in such a case, the wound body can be easily rewound by performing the following operation on the surface of the pressure-sensitive adhesive layer.

In the present invention, the surface of the pressure-sensitive adhesive layer is subjected to corona discharge treatment or plasma discharge treatment.
Corona discharge treatment in the present invention are readily rewind can, from the viewpoint of preventing damage to the film itself, the energy density usually ^{0.01W · sec / cm 2 ~20W ·} sec / cm 2 or so, preferably ^{0.05W · sec / cm 2 ~15W ·} sec / cm 2 or so, particularly preferably he is appropriate to the ^{0.1W · sec / cm 2 ~10W ·} sec / cm 2 approximately.

The plasma discharge treatment can be performed by, for example, a method described in Japanese Patent Application Laid-Open No. 2007-155753 or a method based thereon.
Specifically, a method of treating at normal pressure, pressurization, or reduced pressure using plasma of oxygen, nitrogen, inert gas, or the like or a mixture thereof can be given.
For example, an inert gas having an oxygen concentration of 15% by volume or less is used, and a voltage is applied to the gas guided between the electrodes in the plasma processing apparatus to excite the gas to form a plasma gas. Process.
This plasma processing apparatus is made of, for example, a single metal such as copper or aluminum, an alloy such as stainless steel or brass, a metal compound, etc. as an electrode. An electrode structure such as a flat plate type or a coaxial cylindrical type can be used. Further, the voltage to be applied is preferably a pulse voltage, and may be an impulse type, a square wave type, a modulation type waveform, or a positive or negative polarity.

Examples of the pulse voltage include not less than the minimum voltage required for generating plasma and not more than 100 kV.
Although it does not specifically limit as a frequency of a pulse voltage, 0.5 kHz or more and 100 kHz or less are mentioned.
Examples of the pulse duration include 1000 μs or less and 1 μs or more.
Examples of the pressure of the normal pressure plasma treatment include 100 Torr (about 1.33 × 10 ⁴ Pa) or more and 800 Torr (about 10.6 × 10 ⁴ Pa) or less.

  In the present invention, in addition to performing corona discharge treatment or plasma discharge treatment on the surface of the pressure-sensitive adhesive layer, a friction treatment may be performed on the back surface of the substrate. By using these in combination, rewinding becomes easier.

  Hereinafter, the Example of the manufacturing method of the surface protection film of this invention is described in detail. However, the present invention is not limited to the following examples.

Example 1
In this example, a surface protective film (width 700 mm) composed of two layers of a base material layer (thickness 34 μm) / adhesive layer (thickness 6 μm) was produced by coextrusion by a T-die method.
100 parts by weight of block PP was used as a material for forming the base material layer in the surface protective film.
As a material constituting the pressure-sensitive adhesive layer, 100 parts by weight of a styrene-based elastomer (SEBS, manufactured by Kraton Polymer Co., Ltd., product number: G1657) made of a hydrogenated styrene-butadiene copolymer was added to Alcon P- as a tackifier. A pressure-sensitive adhesive composition containing 5 parts by weight of 125 (manufactured by Arakawa Chemical Industries) was kneaded with a twin screw extruder and pelletized.
After extruding and before winding on a paper core, the pressure-sensitive adhesive layer surface was subjected to corona discharge treatment under the condition of 0.5 W · sec / cm ² and wound at a speed of 10 m / min.

(Example 2)
The surface of the pressure-sensitive adhesive layer of the surface protective film after coextrusion was subjected to corona discharge treatment under the condition of 1.7 W · sec / cm ² , and wound up in the same manner as in Example 1.

(Example 3)
Instead of the pressure-sensitive adhesive composition used in Example 1, 20 parts by weight of PA95 (manufactured by Kobe Oil Chemical Co., Ltd.) as a tackifier was added to 100 parts by weight of a styrene elastomer (SIBS, manufactured by Kaneka Corporation, product number 102T). A surface protective film was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition was kneaded with a twin screw extruder and pelletized.

Example 4
It was wound up in the same manner as in Example 2 except that the back surface of the base material layer was subjected to friction treatment before in-line corona discharge treatment after extrusion. The friction treatment was performed by rotating a rotating roll attached with a polyester cloth at 400 rpm in the reverse direction with respect to the film conveyance direction.

(Comparative Example 1)
It manufactured similarly to Example 1 except not having performed a corona discharge process, and wound up.

(Comparative Example 2)
Production was carried out in the same manner as in Example 1 except that the corona discharge treatment was not performed, and the back surface of the base material layer was subjected to a friction treatment at 600 rpm using a reverse rotating roll wound with gauze.
(Comparative Example 3)
It manufactured similarly to Example 3 except not having performed corona discharge treatment, and wound up.

(Evaluation)
(1) Self-back surface peeling force Each surface protection film obtained by the said Example and the comparative example was affixed on the whole surface of the smooth acrylic board from the adhesive layer side. Moreover, each surface protection film cut out to the magnitude | size of width 25mm x length 150mm was prepared separately.
Each cut out surface protective film of the same type was attached to the back surface of each surface protective film attached to the acrylic plate from the pressure-sensitive adhesive layer side using a 2 kg rubber roller at a speed of 2 m / min. This was left in a room at 23 ± 2 ° C. for 30 minutes. Thereafter, in accordance with JIS Z 0237, peeling between the surface protective films was performed, and the 180 degree peel strength at a width of 25 mm was measured at a speed of 30 m / min.

(2) Deformation during rewinding The rolled surface protective film having a width of 700 mm was manually rewound, and deformation of the surface protective film during rewinding was observed. The results are shown in Tables 1 and 2 below.

  The method for producing the surface protective film of the present invention is not limited to various articles and members such as optical devices, metal plates, painted steel plates, resin plates, glass plates, etc., and prevents contamination and scratches during transportation, processing or curing. It can be used for the production of a surface protective film that can be used for all adherends that are required.

Claims (4)

  The pressure-sensitive adhesive layer is subjected to corona discharge treatment or plasma discharge treatment on the surface of the pressure-sensitive adhesive layer of the surface protective film in which the base material layer and the pressure-sensitive adhesive layer that have not been subjected to the mold release treatment are laminated. The surface protective film is wound up in a roll shape so as to be in direct contact with the back surface of the base material layer.   The method for producing a surface protective film according to claim 1, wherein the base material layer and the pressure-sensitive adhesive layer are coextruded and laminated.   The manufacturing method of the surface protection film of Claim 1 or 2 in which a base material layer consists of polyolefin.   The method for producing a surface protective film according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive comprises a styrene elastomer.