JP4115775B2 - Surface protection sheet - Google Patents

Description

表１から、実施例の表面保護シートは、良好な巻戻し性を有し、汚染も発生せず、かつ罫書き性にも優れていることがわかる。
【図面の簡単な説明】
【図１】本発明の表面保護シートの一例の断面図である。
【図２】本発明の表面保護シートの一例の断面図である。
【符号の説明】
１ ：基材層
１ａ：背面層となる基材層
２ ：粘着層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface protective sheet. The surface protective sheet of the present invention includes, for example, a metal plate, a paint plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminated steel plate, a glass plate, an optical member such as a polarizing film, a liquid crystal panel, an electronic member, etc. When transporting, processing or curing, it is used for purposes such as sticking to and protecting the surface of these members.
[0002]
[Prior art]
The surface protective sheet is usually provided with an adhesive layer on one side of the base sheet, and a release layer is usually provided on the other side to ensure releasability when the sheet is rewound from the roll body. ing. Such a surface protective sheet is required to have protective performance, and as necessary functions, importance is placed on the peelability after storage over time, the stainability after peeling, and the like. In particular, the contamination property is important when the adherend is an optical member, an electronic member, a painted plate, a specular metal plate, or the like. Conventionally, the pressure-sensitive adhesive layer and the release layer of the surface protective sheet for such applications have been formed by applying and drying a back surface treatment agent or a pressure-sensitive adhesive solution dissolved in an organic solvent on a base sheet. That is, a solvent-type surface protective sheet is common. However, in recent years, there has been an increasing demand for a surface protection sheet that does not use an organic solvent, from the viewpoint of environmental conservation and from the viewpoint of reducing failure of electronic components due to outgas (organic solvent gas) from the adhesive layer or release layer.
[0003]
As one of the methods not using an organic solvent, there has been proposed a surface protection sheet formed by co-extrusion of a base material layer made of a polyolefin resin and an adhesive layer made of a thermoplastic adhesive resin (Japanese Patent Laid-Open No. 61-103975). Issue gazette). However, since the surface protective sheet is composed only of the base material layer and the adhesive layer, when it is made into a roll body, the rewinding property is poor and it may be impossible to rewind.
[0004]
Therefore, various mold release treatment methods have been proposed for the surface protective sheet obtained by the coextrusion method. For example, Japanese Patent Application Laid-Open No. 57-139163 proposes a mold release treatment method in which a fatty acid amide is added to a base material layer or an adhesive layer. However, the mold release treatment method has a problem that the fatty acid amide causes transfer to the surface of the adhesive layer, which further transfers to the adherend, causing contamination and lowering the adhesive strength. Japanese Patent Application Laid-Open No. 2-252777 proposes a method of rubbing the back surface of the base material layer with a roll, cloth or the like. However, the mold release treatment method has a problem that a uniform friction treatment is difficult, so that a good mold release property cannot be obtained, and the unwinding force cannot be reduced sufficiently. Depending on the composition of the base material layer, the release effect may vary. Furthermore, it is impossible to completely remove the resin powder generated during friction, which causes contamination and the like.
[0005]
Moreover, the surface protection sheet affixed to adherends, such as a metal plate and an optical member, may be printed on the back side with ink etc. for the purpose of identification. It is desired that the print does not disappear even when the adherends protected by the surface protection sheet are stacked and transported (this characteristic is called ruledness). However, the surface protective sheet formed by the coextrusion method sometimes disappears on the back side due to friction or the like during transportation, and the printing may not be identified. In addition, the rubbing treatment, which is performed on the back surface of the base material layer and imparts releasability, is effective only for the polyethylene resin. .
[0006]
JP-A-8-12948 proposes an adhesive sheet having a release layer formed of a polyvinyl alcohol solution. The pressure-sensitive adhesive sheet has no problem in ruledness. However, the release layer formed of polyvinyl alcohol alone has poor moisture resistance, and if it is stored under humidification or left outdoors, it dissolves and the print disappears, and the back layer is contaminated. There is. On the other hand, moisture resistance is improved to some extent by crosslinking polyvinyl alcohol. In this case, after preparing a solution in which polyvinyl alcohol and a crosslinking agent are dissolved in an organic solvent or water, a step of applying and releasing a release layer There is a problem that the production process becomes complicated and outgas such as an organic solvent is generated.
[0007]
Moreover, in the surface protection sheet obtained by the co-extrusion method, as a release treatment method by an addition system, JP-A No. 11-43655 proposes that a long-chain alkyl-based back treatment agent is added to the release layer. Has been. However, if the number of additions of the back surface treatment agent is increased so that a good unwinding force can be obtained, contamination tends to occur. Furthermore, it is necessary to add a large amount in order to improve the ruled lineability, but this also easily causes contamination.
[0008]
[Problems to be solved by the invention]
The present invention is a surface protection sheet in which a base material layer and an adhesive layer are formed by coextrusion, and has good rewinding properties from a wound body and the like, and there is no transfer of a release component to the adhesive layer An object of the present invention is to provide a surface protective sheet that is free from contamination problems and has excellent scoring properties.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found the following surface protective sheet and have completed the present invention.
[0010]
That is, the present invention is a surface protection sheet in which a base material layer containing at least one thermoplastic resin and an adhesive layer containing a thermoplastic adhesive resin are formed by coextrusion,
The surface protection sheet | seat characterized by the base material layer used as a back layer with respect to an adhesion layer containing an ethylene-vinyl alcohol copolymer.
[0011]
When the surface protective sheet has at least two base material layers, the base material layer serving as the back layer with respect to the adhesive layer contains an ethylene / vinyl alcohol copolymer.
[0012]
In the surface protective sheet, the base material layer serving as the back layer preferably contains 20% by weight or more of an ethylene / vinyl alcohol copolymer as a thermoplastic resin. In the surface protective sheet, the base material layer serving as the back layer preferably contains only an ethylene / vinyl alcohol copolymer as a thermoplastic resin.
[0013]
Moreover, it is preferable that the said surface protection sheet is 2 [N / 20mm] or less in the low speed unwinding force in JISZ0237.
[0014]
In the surface protection sheet of the present invention, the base material layer and the adhesive layer are formed by coextrusion, and the back layer for the adhesive layer contains an ethylene / vinyl alcohol copolymer in the base material layer. And has good unwinding properties. Therefore, the surface protection sheet of the present invention can realize a low-speed rewinding force of 2 [N / 20 mm] or less in JIS Z 0237 (2000). The low-speed unwinding force is preferably as small as possible, and is preferably 0.1 to 1.8 [N / 20 mm] or less.
[0015]
Since the back layer does not contain a fatty acid amide or a long-chain alkyl back treatment agent, no contamination occurs. Therefore, the release component is not transferred to the adhesive layer, and the stability of the adhesive layer is good. In addition, the ethylene / vinyl alcohol copolymer does not dissolve in water and has good affinity with ink, and therefore has good ruledness. Furthermore, since ethylene-vinyl alcohol copolymer is a thermoplastic resin, it can be easily extruded by the T-die method or inflation method, and can be formed by co-extrusion as a base material layer. Can be
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views of a surface protective sheet, in which a base material layer 1 and an adhesive layer 2 are formed by a coextrusion method. The base material layer 1 has at least one layer. In FIG. 1, the base material layer 1 is a single layer. In this case, the base material layer 1 itself is a back layer for the adhesive layer 2. In FIG. 2, the base material layer 1 has two layers of a base material layer 1 a and a base material layer 1 b. In FIG. 2, the base material layer 1a is the back layer.
[0017]
The base material layer (the base material layer 1 in FIG. 1 and the base material layer 1a in FIG. 2) serving as the back layer contains an ethylene / vinyl alcohol copolymer. The ethylene / vinyl alcohol copolymer can be obtained by saponifying a copolymer of ethylene and vinyl carboxylate such as vinyl acetate, vinyl formate, vinyl propionate or vinyl butyrate. The degree of saponification is 50% or more, preferably 70% or more, more preferably 90% or more, and particularly preferably 95% to 100%. If the degree of saponification is less than 50%, good releasability (rewinding property) cannot be obtained.
[0018]
In order to obtain good releasability, the ethylene content of the ethylene / vinyl alcohol copolymer is preferably 20 to 90 mol%, more preferably 25 to 80 mol%, and particularly preferably 30 to 50 mol%. When the ethylene content exceeds 90 mol%, good releasability may not be obtained. When the ethylene content is less than 20 mol%, the back layer tends to expand and contract due to the influence of moisture, which may cause the surface protection sheet to float. .
[0019]
Specific examples of the ethylene-vinyl alcohol copolymer include, for example, “Soarnol” (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), “Eval” (manufactured by Kuraray Co., Ltd.), “Mersen H” (Tosoh Corporation) ), "Technolink" (Taoka Chemical Industry Co., Ltd.), etc. are available. These ethylene / vinyl alcohol copolymers can be used singly or in combination of two or more.
[0020]
The ethylene-vinyl alcohol copolymer preferably has a back layer formed in a state where the hydroxyl group contained in the molecule remains without reacting with other components from the viewpoint of rewinding and scoring. . In particular, from the viewpoint of reducing contamination, the thermoplastic resin forming the back layer is preferably made of only an ethylene / vinyl alcohol copolymer. Note that the thermoplastic resin of the back layer is “consisting only of an ethylene / vinyl alcohol copolymer” means that an ethylene / vinyl alcohol copolymer is used alone as the thermoplastic resin for forming the back layer. The alcohol copolymer is limited to a completely saponified product, and does not mean to exclude a partially saponified product. In addition, the addition of components other than the thermoplastic resin to the back layer is not excluded.
[0021]
The base material layer serving as the back layer may contain other thermoplastic resin in addition to the ethylene / vinyl alcohol copolymer. As other thermoplastic resins, those not showing reactivity with the hydroxyl group contained in the molecule of the ethylene / vinyl alcohol copolymer are preferable.
[0022]
Thermoplastic resins that do not react with hydroxyl groups contained in the ethylene / vinyl alcohol copolymer molecules include polyolefin resins, polyester resins, polyamide resins, and polycarbonate resins. Known thermoplastic resins such as polystyrene resins can be used. These thermoplastic resins can be used individually by 1 type or in mixture of 2 or more types.
[0023]
Among the thermoplastic resins, polyolefin resins are preferable from the viewpoint of incineration and recyclability. Specifically, polypropylene or a block or random propylene polymer comprising a propylene component and an ethylene component; an ethylene polymer such as a low density, high density, linear low density polyethylene; an ethylene-α olefin copolymer Examples thereof include olefin polymers such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and other olefin polymers such as ethylene monomers and other monomers. These polyolefin resins can be used alone or in combination of two or more.
[0024]
When adding the said thermoplastic resin to a back layer, it mix | blends to such an extent that the releasability of a back layer is not impaired. The content of the ethylene / vinyl alcohol copolymer in the back layer is desirably 20% by weight or more. When the blending amount of the ethylene / vinyl alcohol copolymer is less than 20% by weight, the releasability may decrease, and when mixed with an olefin resin, the scribing property may decrease. The content of the ethylene / vinyl alcohol copolymer in the back layer is 30% by weight or more, and further 50% by weight or more.
[0025]
Further, the back layer can be subjected to heat treatment or the like, with daily improvement in moisture resistance. Further, for the purpose of preventing deterioration, the back layer is provided with, for example, an antioxidant, an ultraviolet absorber, a light stabilizer such as a hindered amine light stabilizer, an antistatic agent, and the like, for example, calcium oxide, magnesium oxide, silica, zinc oxide. In addition, suitable additives such as fillers such as titanium oxide, pigments, anti-fogging agents, lubricants and anti-blocking agents can be blended.
[0026]
When the base material layer 1 consists of at least two layers, the base material layer other than the back surface layer (the base material layer 1b in FIG. 2) is coextruded together with the back surface layer (the base material layer 1a in FIG. 2). The base material layer other than the back layer can be a single layer or a multilayer structure of two or more layers. Examples of the thermoplastic resin that can be used for the base layer other than the back layer include polyolefin resins, polyester resins, polyamide resins, and polycarbonate resins. Known thermoplastic resins such as polystyrene resins can be used. These thermoplastic resins can be used individually by 1 type or in mixture of 2 or more types.
[0027]
Among the thermoplastic resins, polyolefin resins are preferable from the viewpoint of incineration and recyclability. Specifically, polypropylene or a block or random propylene polymer comprising a propylene component and an ethylene component; an ethylene polymer such as a low density, high density, linear low density polyethylene; an ethylene-α olefin copolymer Examples thereof include olefin polymers such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and other olefin polymers such as ethylene monomers and other monomers. Furthermore, the above-mentioned ethylene / vinyl alcohol copolymer can be exemplified. These polyolefin resins can be used alone or in combination of two or more. In addition, the same various additive as what was applied to the back layer can be mix | blended with a base material layer. Although the thickness of the base material layer 1 is not particularly limited, it is generally about 20 to 300 μm, preferably 30 to 250 μm, more preferably 40 to 200 μm. When the base material layer 1 consists of at least two layers as shown in FIG. 2, the back layer (base material layer 1a in FIG. 2) is about 0.5 to 40 μm, preferably 1 to 20 μm, more preferably 5 10 μm.
[0028]
For the adhesive layer 2, a known thermoplastic adhesive resin such as a styrene adhesive resin, a urethane adhesive resin, an ester adhesive resin, or an olefin adhesive resin can be used. Preferred are block polymers and random polymers of styrene and a diene component, and styrene-based adhesive resins such as hydrogenated products thereof, olefin-based adhesive resins, and the like. Specifically, AB type diblock polymers such as styrene / butadiene (SB), styrene / isoprene (SI), styrene / ethylene-butylene copolymer (SEB), and styrene / ethylene / propylene copolymer (SEP). A- such as styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-butylene copolymer / styrene (SEBS), styrene / ethylene-propylene copolymer / styrene (SEPS) Multi-block polymer of B-A type triblock or A-B-A-B type tetrablock or more, styrene random copolymer such as styrene / butadiene rubber (SBR), styrene / ethylene-butylene copolymer / olefin crystal ABC type styrene o such as (SEBC) Styrenic adhesive resin such as fin crystal block polymer, olefin crystal block copolymer such as olefin crystal / ethylene-butylene copolymer / olefin crystal (CEBC), ethylene-α olefin, ethylene-propylene Examples of the base polymer include olefin-based adhesive resins such as -α-olefin, propylene-α-olefin, ethylene / vinyl acetate copolymer, and hydrogenated products thereof. These can be used individually by 1 type or in mixture of 2 or more types.
[0029]
When forming the adhesive layer 2, for the purpose of controlling adhesive properties, etc., for example, softeners, olefin resins such as those used for the base material layer, silicone polymers, liquid acrylic copolymers, phosphorus Acid ester compounds, tackifiers, anti-aging agents, hindered amine light stabilizers, UV absorbers, and other fillers and pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide Additives can be appropriately blended.
[0030]
Among the additives, the addition of a tackifier is effective for improving the adhesive strength of the pressure-sensitive adhesive layer 2. 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 any particular restrictions. These tackifiers can be used alone or in combination of two or more. Hydrogenated tackifiers are preferred from the standpoint of peelability and weather resistance. In addition, what is marketed as a blend with an olefin resin can also be used for a tackifier.
[0031]
When using a tackifier, the blending amount is not particularly limited, but from the viewpoint of improving the adhesive force and avoiding the occurrence of adhesive residue problems due to a decrease in cohesive force, for 100 parts by weight of the thermoplastic adhesive resin, It is preferably 80 parts by weight or less, more preferably 60 parts by weight or less, and particularly preferably 50 parts by weight or less. When the blending amount exceeds 100 parts by weight, the adhesive residue at the time of high temperature or outdoor exposure becomes remarkable.
[0032]
Further, when a softening agent is blended as the additive, it is usually effective for improving the adhesive force. Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, ethylene propylene rubber, and derivatives thereof. Examples of the derivative include those having an OH group or a COOH group at one end or both ends. Specifically, hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, hydrogenated polyisoprene. Monool and so on. In particular, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable for the purpose of suppressing improvement in adhesion to adherends. Specifically, “Kuraprene LIR-200” manufactured by Kuraray Co., Ltd. is available. These softeners can be used alone or in combination of two or more.
[0033]
The molecular weight of the softening agent is not particularly limited and can be set appropriately. However, if the molecular weight is small, there is a risk of causing material transfer from the adhesive layer 2 to the adherend or heavy peeling, while the molecular weight is low. Since the effect of improving the adhesive strength tends to be poor when the value of the softening agent increases, the number average molecular weight of the softening agent is preferably about 5000 to 100,000, and more preferably 10,000 to 50,000.
[0034]
When using a softener, the blending amount is not particularly limited, but as the blending amount increases, the adhesive residue tends to increase at high temperatures and when exposed to the outdoors. The amount is preferably 60 parts by weight or less, more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight or less with respect to 100 parts by weight of the agent composition.
[0035]
The thickness of the pressure-sensitive adhesive layer 2 is not particularly limited and may be appropriately determined according to the required adhesive force and the like, but is usually about 1 to 50 μm, preferably 2 to 40 μm, more preferably 5 to 5 μm. 20 μm.
[0036]
In addition, the surface of the adhesive layer 2 needs surface treatment for the purpose of adhesiveness control, pasting workability, etc., such as corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment and sputter etching treatment, for example. It can also be applied accordingly. Furthermore, a separator or the like can be temporarily attached to the pressure-sensitive adhesive layer 2 as needed until it is put to practical use.
[0037]
The production of the surface protection sheet is carried out in accordance with a forming method such as a method in which at least one base material layer 1 and an adhesive layer 2 are co-extruded by a T-die method or an inflation method in two or multiple layers. Can do. The method for forming the surface protective sheet by the coextrusion method is preferable from the viewpoint of productivity and cost. Moreover, you may give an embossing, an uneven | corrugated process, etc. to the back surface layer side of a surface protection sheet for hand cutting property or slip resistance provision.
[0038]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0039]
Example 1
A back layer (base material layer) forming material composed of an ethylene / vinyl alcohol copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Soarnol AT4403) having an ethylene content of 44 mol%, and linear low density polyethylene (Mitsui Chemicals) Co., Ltd., Evolue SP2020) 100 parts by weight of white pigment (Daiichi Seika Kogyo Co., Ltd., HCM2035W) 4 parts by weight of a base material layer forming material, styrene / ethylene butylene / styrene polymer (Asahi Kasei) A pressure-sensitive adhesive layer forming material made by Toughtech H1221) is co-extruded at a die temperature of 240 ° C. by an inflation method to form a film, and a surface protective sheet having a back layer of 10 μm / base material layer of 100 μm / adhesive layer of 10 μm is obtained. It was.
[0040]
Example 2
Low-density polyethylene (Nippon Polychem Co., Ltd., Novatec LDLF580) 30 weights with respect to 100 parts by weight of ethylene / vinyl alcohol copolymer (Nippon Synthetic Chemical Co., Ltd., Soarnol DT2903) having an ethylene content of 29 mol% 100 parts by weight of polypropylene (Idemitsu Petrochemical Co., Ltd., IDEMITSU PP F-7 44) to 100 parts by weight of polypropylene (Idemitsu Petrochemical Co., Ltd., IDEMITSU PPF-704) Part and linear low density polyethylene (Mitsui Chemicals Co., Ltd., Evolue SP2040) base material layer forming material, and a propylene content of 80% by weight ethylene propylene butene-1 The layer forming material was coextruded at a die temperature of 260 ° C. by the T-die method to form a film, To obtain a surface protection sheet of the surface layer 5 [mu] m / substrate layer 40 [mu] m / adhesive layer 10 [mu] m.
[0041]
Example 3
From a back layer forming material comprising an ethylene / vinyl alcohol copolymer (Nippon Synthetic Chemical Industry Co., Ltd., Soarnol AT4403) having an ethylene content of 44 mol%, and low density polyethylene (Tosoh Corp., Petrocene 173) A base material layer forming material and a density of 0.903 g / cm ^Three An adhesive layer forming material comprising an ethylene-α olefin copolymer (manufactured by Nippon Polychem Co., Ltd., Kernel KF260) is coextruded at a die temperature of 220 ° C. by an inflation method, and a back layer of 5 μm / A surface protective sheet having a base material layer of 45 μm and an adhesive layer of 10 μm was obtained.
[0042]
Comparative Example 1
In Example 1, a surface protective sheet was produced according to Example 1 except that low-density polyethylene (Tosoh Corp., Betrocene 173) was used as the back layer forming material.
[0043]
Comparative Example 2
The surface of the back surface layer of the surface protective sheet prepared in Comparative Example 1 was subjected to a friction treatment with a polyester nonwoven fabric (manufactured by Asahi Kasei Co., Ltd., Eltas) to prepare a surface protective sheet.
[0044]
Comparative Example 3
A base layer forming material obtained by adding 4 parts by weight of a white pigment (Daiichi Seika Kogyo Co., Ltd., HCM2035W) to 100 parts by weight of linear low density polyethylene (Mitsui Chemicals, Evolue SP2020); An adhesive layer forming material made of styrene / ethylene butylene / styrene polymer (Taftec H1221 manufactured by Asahi Kasei Co., Ltd.) is coextruded at a die temperature of 240 ° C. by an inflation method to form a surface of a substrate layer of 100 μm / adhesive layer of 10 μm. A protective sheet was obtained. The surface protective sheet was subjected to corona treatment on the substrate layer side. Next, an aqueous polyvinyl alcohol solution (manufactured by Kuraray Co., Ltd., Poval PVA120) was applied, and a surface protective sheet was formed on which a back layer having a thickness of 1 μm was formed after drying.
[0045]
Comparative Example 4
In Example 2, as a back layer forming material, a long-chain alkyl back treatment agent (on the other hand, Oil & Fats Co., Ltd., Pyroyl 1200) is used with respect to 100 parts by weight of a linear low density polyethylene (Mitsui Chemicals, Evolution SP2040). ) A surface protective sheet was produced according to Example 2 except that the back layer forming material added with 2 parts by weight was used.
[0046]
Comparative Example 5
In Example 2, as a back layer forming material, 0.3 parts by weight of ethylene bisstearylamide (Nippon Kasei Co., Ltd.) is added to 100 parts by weight of linear low density polyethylene (Mitsui Chemicals, Evolue SP2040). A surface protective sheet was produced according to Example 3 except that the added back layer forming material was used.
[0047]
The following evaluation was performed about the surface protection sheet obtained by the Example and the comparative example. The results are shown in Table 1.
[0048]
(Rewind force)
After the roll product of the surface protection sheet was stored at 50 ° C. for 1 week, it was measured with an Instron type tensile tester (manufactured by Shimadzu Corporation, Autograph) based on JIS Z 0237 (2000) at a tensile speed of 300 mm / In min, the sheet was rewound so that the angle between the sheet to be rewound and the roll surface was vertical, and the low-speed unwinding force (N / 20 mm) was measured.
[0049]
(Contamination)
The roll product of the surface protection sheet is stored for 1 week in an environment of 50 ° C./95% RH, and then applied to a stainless steel mirror plate (SUS304) and a black polyester melamine coating plate, and further at 50 ° C./95% RH. It was stored for 1 week in the environment and peeled off at room temperature (23 ° C.). At that time, the presence or absence of contamination of the adherend surface was confirmed.
[0050]
(Rule writing)
The back layer of the surface protective sheet was written with a commercially available oil-based ink. Thereafter, the surface was subjected to 10 reciprocating friction treatments with a polyester non-woven fabric (manufactured by Asahi Kasei Co., Ltd., Eltas), and the disappearance of the pen characters was confirmed. At that time, the case where there was no disappearance of the pen character was indicated as “◯”, and the case where it was present was indicated as “X”.
[0051]
[Table 1]

From Table 1, it can be seen that the surface protective sheets of the examples have good unwinding properties, do not cause contamination, and are excellent in scribing properties.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a surface protective sheet of the present invention.
FIG. 2 is a cross-sectional view of an example of the surface protective sheet of the present invention.
[Explanation of symbols]
1: Base material layer
1a: Base material layer to be a back layer
2: Adhesive layer

Claims (7)

A surface protection sheet in which a base material layer containing at least two thermoplastic resins and an adhesive layer containing a thermoplastic adhesive resin are formed by coextrusion,
The base material layer serving as the back layer with respect to the adhesive layer contains an ethylene / vinyl alcohol copolymer, and the adhesive layer containing the thermoplastic adhesive resin is a polymer of styrene and a diene component, ethylene-α olefin A surface protective sheet selected from the group consisting of a copolymer and ethylene / propylene / butene-1 . The surface protective sheet according to claim 1, wherein the polymer of styrene and a diene component is a styrene / ethylene butylene / styrene polymer.   The surface protective sheet according to claim 1 or 2, wherein the base material layer serving as the back layer contains 20% by weight or more of an ethylene / vinyl alcohol copolymer as a thermoplastic resin.   The surface protective sheet according to any one of claims 1 to 3, wherein the base material layer serving as the back layer contains only an ethylene / vinyl alcohol copolymer as a thermoplastic resin. The surface protection sheet according to any one of claims 1 to 4, wherein the ethylene content of the ethylene-vinyl alcohol copolymer is 30 to 50 mol%. The surface protection sheet according to any one of claims 1 to 5, wherein the thickness of the base material layer serving as the back layer is in the range of 0.5 µm to 10 µm. The surface protection sheet according to any one of claims 1 to 6 , wherein a low-speed rewinding force in JIS Z 0237 is 2 [N / 20 mm] or less.

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