JP5563788B2 - Surface protective adhesive sheet - Google Patents

Description

  The present invention relates to a surface protective adhesive sheet, and more particularly, to adhere a member such as an optical device to the surface of the member when transporting, processing or curing, and to prevent adhesion and scratches of dust. The present invention relates to a surface protective adhesive sheet to be used.

Conventionally, a surface in which an adhesive layer is laminated on one side of a sheet-like substrate to protect the surface of various members such as optical devices, metal plates, painted metal plates, resin plates, glass plates, etc. Protective adhesive sheets are widely used. In particular, in the optical field, an optical sheet having irregularities on its surface, such as a diffusion sheet or a prism sheet, is used as an optical device. In order not to damage such irregularities, the surface is used prior to use. (Especially the uneven outer surface) is protected by a surface protective adhesive sheet.
Generally, the surface protective adhesive sheet is industrially manufactured as a wound body obtained by winding a long sheet into a roll shape. It is known that the surface protective adhesive sheet having such a wound body tends to have a large increase in adhesive strength over time, but the force (deployment force) required to deploy the wound body during use is small. That is, it is strongly demanded that the wound body can be easily rewound.
Further, since the surface protective adhesive sheet is peeled and removed after use, it is required to have smooth peelability and no adherend contamination due to adhesive residue.

By the way, as a material such as a diffusion sheet, polar polymers such as acrylic resins and polycarbonate resins are frequently used. In addition, these optical sheets are shipped to an optical device manufacturer after the surface protective adhesive sheet is attached, but they may be exposed to high temperatures during transportation and storage.
For this reason, particularly for application to optical sheets, the pressure-sensitive adhesive layer constituting the surface protective adhesive sheet does not use an acrylic pressure-sensitive adhesive that has a particularly large increase in adhesive strength over time. System adhesives were mainly used. This avoids an increase in adhesive force over time, and is intended to smoothly peel the surface protective adhesive sheet from the surface of the optical sheet.

  However, since rubber-based adhesive is generally a solution-coated type, it has problems of environmental pollution and energy waste during solvent drying, and the back side of the commonly used olefin substrate layer (the side on which the adhesive layer is laminated) Also requires mold release treatment on the opposite surface. Moreover, if it is a hot-melt-type adhesive, the former problem can be eliminated or reduced, but the back surface release treatment cannot be avoided.

  On the other hand, a surface protective adhesive sheet formed by co-extrusion with an olefin substrate layer using an adhesive layer mainly composed of a styrene elastomer instead of natural rubber has been proposed (for example, Patent Document 1). ). Thus, it is described that a sufficient protection function and adhesion characteristics for the adherend can be satisfied at the same time.

  Also, a surface formed by laminating a surface layer containing a polyolefin-based resin and a pressure-sensitive adhesive layer containing a thermoplastic elastomer by a coextrusion method, and then forming a release layer on the back surface of the surface layer by a coating method A protective film has been proposed (for example, Patent Document 2). Here, it is described that when the thickness of the release layer is reduced to 1 to 1000 nm, the effect of reducing contamination on the adherend is great.

  Further, the surface protective adhesive sheet is required to have no or even very little float (for example, 5 area%, preferably 1 area%) from the adherend.

JP 2001-234149 A JP 2003-41216 A

However, even with the surface protective sheet of Patent Document 1, the developability of the surface protective sheet from the wound body has not necessarily reached a satisfactory level as compared with the case where the release layer is formed. In some cases, the unfolding force increases, making it difficult to unwind the wound body.
Further, in the surface protective film of Patent Document 2, a long-chain alkyl polymer type release agent or a UV curable silicone release agent is used in the examples, but a long-chain alkyl type polymer provides sufficient release properties. In addition, although a UV curable silicone release agent can provide release properties, the UV curing reaction time is required, so the line speed cannot be increased freely. Therefore, the present condition has not yet obtained what should satisfy both quality and productivity.

  The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and even when applied to an adherend having an uneven surface, there is no adhesive residue after peeling, excellent spreadability, and floating from the adherend. An object of the present invention is to provide a surface protective adhesive sheet having a very small amount.

  As a result of intensive research on the possibility of acrylic pressure-sensitive adhesives, the present inventors can dramatically suppress the progress of adhesion over time by a very simple method of adjusting the thickness of the acrylic pressure-sensitive adhesive, and The inventors found that a surface protective film that does not require the back treatment of the base material layer can be obtained, and as a result of further research, the present invention has been completed.

  According to the surface protective adhesive sheet of the present invention, the pressure-sensitive adhesive layer comprises a polyolefin base layer and a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer has a thickness of 0.1 μm or more and 2.0 μm or less by a pressure-sensitive adhesive made of (meth) acrylic resin. It is formed by.

The pressure-sensitive adhesive layer is
A block copolymer (I) represented by the general formula A-B-A or a block copolymer (I) represented by the general formula A-B-A and a block copolymer represented by the general formula A-B Combined (II)
(However, A is a methacrylic ester block, B is an acrylate block, and the glass transition temperature of the methacrylic ester polymer is 60 ° C. or more, and the glass transition temperature of the acrylate ester polymer is 10 ° C. Is the following)
Is formed by.

The pressure-sensitive adhesive layer contains the block copolymer (I), the block copolymer (II), and a tackifying resin.
The weight ratio of the block copolymer (I) and the block copolymer (II) is 95: 5 to 50:50.
Further, the content of the tackifying resin is 5 to 50 parts by weight with respect to 100 parts by weight of the total weight of the block copolymer (I) and the block copolymer (II) (that is, the weight of the adhesive). is there.

That is, the surface protective adhesive sheet of the present invention is
Having a polyolefin base layer and an adhesive layer,
The pressure-sensitive adhesive layer is
A block copolymer (I) represented by the general formula A-B-A and a block copolymer (II) represented by the general formula A-B (where A is a methacrylate block, B Is an acrylate block, and the glass transition temperature of the methacrylic ester polymer is 60 ° C. or higher, and the glass transition temperature of the acrylate polymer is 10 ° C. or lower)
And containing 100 parts by weight of a pressure-sensitive adhesive in which the weight ratio of the block copolymer (I) and the block copolymer (II) is 95: 5 to 50:50 and 5 to 50 parts by weight of a tackifier resin And
The weight average molecular weight of the block copolymer (I) and the block copolymer (II) is in the range of 50,000 to 300,000 in terms of polystyrene by GPC method (gel permeation chromatography),
And it has a thickness of 0.1 μm or more and 2.0 μm or less.

  The tackifier resin is preferably at least one selected from terpene phenol resins, hydrogenated terpene phenol resins, and rosin resins.

Preferably, the surface protective adhesive sheet further includes an anchor layer made of a styrene resin between the polyolefin base material layer and the pressure-sensitive adhesive layer.
The anchor layer is
A block copolymer represented by the general formula CDC or a block copolymer represented by the general formula CDC and a block copolymer represented by the general formula CD (where C Is a styrene polymer block, and D is a hydrocarbon polymer block)
It is preferable that it is formed by.

  The surface protective adhesive sheet is particularly advantageous when applied to an optical sheet having irregularities on the surface.

The surface protective adhesive sheet of the present invention easily peels off the surface protective adhesive sheet adhered from the back surface of the polyolefin base material layer even when the pressure sensitive adhesive layer is adhered to the back surface of the polyolefin base material layer to form a wound body. It is possible to rewind the wound body without difficulty.
The present inventors use a (meth) acrylic resin for the pressure-sensitive adhesive layer, thereby widening the polarity difference between the polyolefin base layer and the pressure-sensitive adhesive layer, and making the pressure-sensitive adhesive layer thin. However, the present invention is not limited to those having such a mechanism.
Moreover, even when the surface protective adhesive sheet of the present invention is applied to an adherend having an uneven surface, there is no adhesive residue on the adherend upon peeling from the adherend.
Moreover, even when the surface protective adhesive sheet of the present invention is applied to an adherend having an uneven surface, there is very little floating from the adherend.

The surface protective adhesive sheet of the present invention mainly comprises a polyolefin base layer and an adhesive layer.
The polyolefin base layer is composed of low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene. -It can form by the 1 type selected from a methyl acrylate copolymer, an ethylene- n-butyl acrylate copolymer, a polypropylene (a homopolymer, a random copolymer, a block copolymer), or a 2 or more types of mixture.
The polyolefin base layer usually contains 90% by weight or more of such a polymer.
The base material layer may have a multilayer structure composed of two or more layers having different compositions.
The thickness of the entire polyolefin base material layer can be appropriately adjusted depending on the use of the surface protective adhesive sheet, and is generally set to about 10 to 80 μm.

The pressure-sensitive adhesive layer is a layer formed by being directly or indirectly laminated on the polyolefin base material layer as described later, and is formed of a pressure-sensitive adhesive made of a (meth) acrylic resin.
The thickness of the pressure-sensitive adhesive layer is 0.1 μm or more and 2.0 μm or less.
When the thickness of the pressure-sensitive adhesive layer exceeds 2.0 μm, an adhesive residue is generated at the time of peeling from the adherend (particularly, the adherend having irregularities on the surface) due to an increase in adhesive strength with time. There is a fear. On the other hand, when the thickness of the pressure-sensitive adhesive is less than 0.1 μm, there is a possibility that sufficient adhesion to an adherend (particularly, an adherend having irregularities on the surface) cannot be ensured. Moreover, by setting it as the thickness of this range, it can be produced comparatively easily as a surface protection adhesive sheet.

  The pressure-sensitive adhesive is made of a (meth) acrylic resin. That is, the pressure-sensitive adhesive layer is formed from a (meth) acrylic resin. Thereby, the improvement of expandability is achieved. Here, “formation” means that “(meth) acrylic resin” constructs a three-dimensional shape of an “adhesive layer” and mainly has an adhesive function. The (meth) acrylic resin used in the present invention is a block copolymer containing a methacrylic ester block and an acrylate block.

The block copolymer in the present invention comprises a block copolymer (I) represented by the general formula A-B-A and a block copolymer (II) represented by the general formula A-B.
The weight ratio of the block copolymer (I) to the block copolymer (II) is 95: 5 to 50:50, preferably 80:20 to 55:45.
From the viewpoint of suppressing the occurrence of floating from the adherend with the passage of time, the ratio of the block copolymer (I) is preferably not too high. On the other hand, peeling due to an increase in adhesive force with the passage of time. From the viewpoint of suppressing the occurrence of adhesive residue on the adherend during the treatment, the ratio of the block copolymer (I) is preferably not too low.
In the above formula, A means a methacrylic acid ester block, and B means an acrylic acid ester block. Further, when a methacrylate polymer is obtained using the methacrylate monomer constituting the methacrylate block A, that is, when an independent methacrylate block is obtained, the glass transition temperature is 60 ° C. or higher. is there. Similarly, the glass transition temperature of an acrylate polymer, ie, an independent acrylate block, is 10 ° C. or less.
By setting the glass transition temperature of the methacrylic acid ester polymer to 60 ° C. or higher, the surface protective adhesive sheet is uneven when the surface protective adhesive sheet is peeled off while appropriately maintaining the adhesion to the sheet having unevenness on the surface of the adherend. The adhesive residue on the sheet can be minimized.
Moreover, the adhesiveness to an uneven | corrugated sheet can be ensured moderately by making the glass transition temperature of an acrylic ester polymer into 10 degrees C or less.

For this reason, as the methacrylic ester monomer that can constitute the methacrylic ester block A in the block copolymer, it is necessary to set the glass transition temperature of the polymer obtained thereby to 60 ° C. or higher. , Ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, 2-cyanoethyl methacrylate And one or more selected from phenyl methacrylate and the like.
In addition, the methacrylic acid ester block A has a small proportion (for example, the glass transition temperature of the polymer block is not lower than 60 ° C.) and methacrylic acid such as n-butyl methacrylate, glycidyl methacrylate, and allyl methacrylate. Ester; Olefin such as methyl acrylate: ethyl, propylene, etc .: Constituent components (constituent units) derived from monomers such as lactones such as ε-caprolactone and parerolactone may be contained.

As the acrylate monomer that can constitute the acrylate block B in the block copolymer, the glass transition temperature of the polymer obtained thereby needs to be 10 ° C. or lower. For example, methyl acrylate, ethyl acrylate, acrylic One selected from n-propyl acid, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, n-tetradecyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, and the like Or 2 or more types are mentioned.
In addition, the acrylic ester block B contains other constituents (structural units) as described above as long as the ratio is small (for example, the glass transition temperature of the polymer block does not exceed 10 ° C.). Also good.

  A block copolymer having a weight average molecular weight in the range of about 50,000 to 300,000 in terms of polystyrene by GPC (gel permeation chromatography) is suitable, and in the range of about 60,000 to 200,000. Are preferred. By setting the weight average molecular weight within this range, it is possible to prevent adhesive residue on an adherend such as a concavo-convex sheet during re-peeling without reducing the cohesive force of the pressure-sensitive adhesive. It is possible to obtain good fluidity while ensuring adequately.

  The ratio of the methacrylic ester block A and the acrylate block B constituting the block copolymer is suitably 5:95 to 80:20 by weight. By setting the ratio in this range, it is possible to prevent the adhesive residue on the adherend such as the uneven sheet and the like, and to reduce the adhesive force appropriately, without reducing the cohesive force of the pressure sensitive adhesive. It can be secured.

The pressure-sensitive adhesive layer formed of such a block copolymer preferably has a shear storage elastic modulus at a frequency of 10 Hz of 1.0 × 10 ^{5 to} 6.5 × 10 ⁶ Pa at 23 ° C. By having a shear storage elastic modulus in such a range, sufficient adhesive force can be secured while maintaining good workability in the peeling step. Therefore, it is possible to prevent the surface protective adhesive sheet from being peeled off from the adherend during transportation due to insufficient adhesive force.

In the surface protective adhesive sheet of the present invention, other additives known in the art can be appropriately added to the pressure-sensitive adhesive layer as necessary within a range not inhibiting the pressure-sensitive adhesive performance. Examples of such additives include ultraviolet absorbers, light stabilizers, antioxidants, tackifiers (tackifier resins), adhesion progress inhibitors, softeners, fillers, and the like.
The ultraviolet absorber is not particularly limited, and examples thereof include salicylic acid series, benzophenone series, benzotriazole series, and cyanoacrylate series.
Examples of the light stabilizer include hindered amine compounds.
The antioxidant is not particularly limited, and examples thereof include commonly used ones such as phenolic (monophenolic, bisphenolic, and polymeric phenolic), sulfur, and phosphorus.
The tackifying resin is not particularly limited, for example,
Rosin resin such as rosin ester resin, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin;
Terpene phenolic resins;
Hydrogenated terpene phenolic resin;
a terpene resin mainly composed of α-pinene, β-pinene, limonene or the like;
(Hydrogenated) petroleum resin;
Coumarone-indene resin;
Hydrogenated aromatic copolymers;
Styrenic resin;
Phenolic resins; and xylene resins.
These additives may be used alone or in combination of two or more.

  The content of the tackifier in the pressure-sensitive adhesive layer can appropriately increase the pressure-sensitive adhesive force while suppressing the occurrence of adhesive residue due to a decrease in cohesive force, so 50 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive It is as follows. On the other hand, the amount is 5 parts by weight in order to exhibit the function as a tackifier.

  In the surface protective adhesive sheet of the present invention, if necessary, the surface of the polyolefin substrate layer is subjected to corona discharge treatment or plasma discharge treatment in order to increase anchoring force (anchor force) between the polyolefin substrate layer and the pressure-sensitive adhesive layer. Or an anchor layer may be formed between the polyolefin substrate layer and the pressure-sensitive adhesive layer.

The anchor layer is suitably formed from, for example, a styrene resin, and is made of a block copolymer represented by the general formula C-D-C and / or a block copolymer represented by C-D. What is formed is exemplified. Among them, depending on either the block copolymer represented by the general formula C-D-C or the block copolymer represented by the general formula C-D-C and the block copolymer represented by CD What is formed is preferable. In the formula, C means a styrene polymer block, and D means a hydrocarbon polymer block. Among these, it is more preferable that the hydrocarbon polymer block is obtained by hydrogenating a butadiene polymer block and / or an isoprene polymer block.
Specifically, styrene-butadiene-styrene (SBS), styrene-butadiene, styrene-isoprene-styrene (SIS), styrene-isoprene, styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene ( SEPS) and the like are exemplified.

The polystyrene-converted weight average molecular weight measured by GPC of such a block copolymer is, for example, in the range of about 30,000 to 400,000.
The ratio of the C component and the D component in the block copolymer is suitably 5:95 to 50:50 by weight. By setting the ratio in this range, it is possible to maintain the cohesive force of the anchor agent in the anchor layer and prevent the anchor agent from functioning as an adhesive. By this, the adhesive residue of an anchor agent can be maintained by moderate intensity | strength, and the adhesive residue at the time of peeling can be prevented. Moreover, the excessive fall of the adhesive force as an anchor agent can be prevented, and the anchor force of a polyolefin base material layer and an adhesive layer can be ensured.
Although the thickness of an anchor layer is not specifically limited, About 0.1-3 micrometers is suitable.
By providing such an anchor layer, the anchoring force between the olefin substrate layer and the pressure-sensitive adhesive layer can be secured, and three layers can be co-extruded, resulting in high productivity and low manufacturing cost. Can be realized.

The manufacturing method of the surface protection adhesive sheet of this invention is not specifically limited, For example, the adhesive composition which comprises an adhesive layer, the composition which comprises a polyolefin-type base material layer, and an anchor agent are comprised arbitrarily. A method of laminating and integrating by co-extrusion of the composition, or laminating and integrating by arbitrarily laminating an anchoring agent composition and a pressure-sensitive adhesive composition on a polyolefin substrate layer that has been formed. And a method of laminating and integrating the pressure-sensitive adhesive composition on the anchor layer after coextruding the composition constituting the polyolefin-based substrate layer and the composition constituting the anchor agent, etc. It is done.
When the base material layer has a multilayer structure, the base material layer components may be co-extruded and laminated together with the anchor layer and the pressure-sensitive adhesive layer, or only the base material layer components may be co-extruded. After obtaining the base material layer having a multiphase structure, the anchor layer and the pressure-sensitive adhesive layer may optionally be laminated and integrated.

As a method of laminating and integrating the polyolefin-based substrate layer and the pressure-sensitive adhesive composition by coextrusion, known methods such as an inflation method and a T-die method can be used.
Examples of the method for laminating the pressure-sensitive adhesive composition on the polyolefin-based substrate layer include a solution coating method in which a pressure-sensitive adhesive solution or an anchor agent solution is applied, a dry lamination method, and an extrusion coating method using a T-die.
Especially, since a high quality laminated body can be obtained and it can manufacture economically, the co-extrusion method by a T die is preferable. In particular, when forming an anchor layer, a coextrusion method is preferable.

As described above, the surface protective adhesive sheet of the present invention can be applied to various devices such as an optical device, a metal plate, a painted metal plate, a resin plate, and a glass plate. Among these, it is particularly advantageous to use an optical sheet having irregularities on the surface as an adherend. Examples of the optical sheet having projections and depressions herein include what are generally called diffusion sheets and prism sheets.
For example, the prism sheet has a plurality of substantially triangular prisms on the surface, and the center distance (pitch) between adjacent prisms is about 10 to 1000 μm (preferably about 10 to 500 μm, usually 100 μm), It can be suitably used for a vertex angle of about 50 to 120 °. The height of the triangular prism is determined by the prism pitch and the apex angle. The thickness of a prism sheet is not specifically limited, About 25-1000 micrometers, Furthermore, about 50-200 micrometers is illustrated.
Examples of the diffusion sheet include a sheet in which uniform or non-uniform convex portions are distributed at a level equal to or less than the pitch, instead of the prism.

Hereinafter, the present invention will be described in detail using Examples and Comparative Examples of the surface protective adhesive sheet of the present invention. However, the present invention is not limited to the following examples.
(Materials used)
(Comparative Example 1)
Adhesive layer: A-B-A acrylic block copolymer (LA2140e manufactured by Kuraray Co., Ltd., MMA (methyl methacrylate, glass transition temperature: 100 ° C.)-BA (butyl acrylate, glass transition temperature: −50 ° C.)-MMA) , Toluene (Wako Pure Chemical Industries)
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
Polypropylene was coextruded by a T-die method to produce a polypropylene sheet having a thickness of 38 μm.
One surface of the obtained sheet is subjected to corona discharge treatment, and then the acrylic block copolymer solution (concentration: 20% by weight) dissolved in toluene is applied to the treated surface and dried at 100 ° C. for 5 minutes. Then, a 2 μm thick adhesive layer was laminated and integrated.
This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Comparative Example 2)
Adhesive layer: ABA acrylic block copolymer (LA2140e manufactured by Kuraray Co., Ltd.), toluene (manufactured by Wako Pure Chemical Industries, Ltd.)
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
Anchor layer: SEBS (Dynalon 8903P manufactured by JSR)
Polypropylene and SEBS were coextruded by a T-die method to produce a sheet in which a polypropylene substrate layer having a thickness of 37 μm and an anchor layer having a thickness of 2 μm were laminated and integrated.
An acrylic block copolymer solution (concentration: 20% by weight) dissolved in toluene is applied onto the obtained sheet, dried at 100 ° C. for 5 minutes, and an adhesive layer having a thickness of 0.8 μm is laminated and integrated. did.
This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Comparative Example 3)
A wound body of the surface protective adhesive sheet was obtained using the same material and the same method as in Comparative Example 2 except that the pressure-sensitive adhesive layer was 0.5 μm thick and the polyolefin base material layer was 39 μm thick.

(Comparative Example 4)
Adhesive layer: SEBS (DYNARON 8903P manufactured by JSR), Alcon P115 (manufactured by Arakawa Chemical Industries, hydrogenated petroleum resin)
Olefin base layer: Polypropylene (Prime Polymer J715)
A pressure-sensitive adhesive composition containing 100 parts by weight of SEBS as a styrenic elastomer, 20 parts by weight of Alcon P115 as a tackifier, and polyolefin are coextruded by a T-die method, a polypropylene substrate layer having a thickness of 34 μm, and 6 μm A sheet in which a thick adhesive layer was laminated and integrated was produced. This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Comparative Example 5)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Comparative Example 2 except that the thicknesses of the polyolefin base material layer and the pressure-sensitive adhesive layer were as shown in Table 1.

(Comparative Example 6)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Comparative Example 2 except that the thicknesses of the polyolefin base material layer and the pressure-sensitive adhesive layer were as shown in Table 1.

(Comparative Example 7)
According to Comparative Example 1, the pressure-sensitive adhesive layer having a thickness smaller than 0.1 μm was formed by changing the concentration of the acrylic block copolymer in the toluene solution. As a result, a pressure-sensitive adhesive layer as a uniform layer could not be obtained.

(Evaluation of surface protective adhesive sheets of Comparative Examples 1 to 6)
The following items were evaluated for each surface protective adhesive sheet obtained as described above. The results are shown in Table 2.
Although not shown in the table, the surface protective adhesive sheets of Comparative Examples 1 to 3 were observed to float from the adherend.
(1) Shear storage elastic modulus The shear storage elastic modulus of the pressure-sensitive adhesive layer was measured at a frequency of 10 Hz and a temperature increase rate of 6 ° C / min with a dynamic viscoelasticity spectrum measurement device (IT Measurement Control Co., Ltd., product number: DVA200). It measured in the range of -50 degreeC-+150 degreeC, and calculated | required the shear storage elastic modulus in 23 degreeC.

(2) Initial adhesive force Each surface protection adhesive sheet of an Example and a comparative example was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered. A prism sheet made of an acrylic resin having a thickness of 130 μm and having a prism center distance of 50 μm and a height of 30 μm was prepared. Affixing conditions are as follows: a room temperature of 23 ° C. and a relative humidity of 50%, each using a 2 kg pressure-bonded rubber roller, affixed at a speed of 300 mm / min, left in that state for 30 minutes, and in accordance with JIS Z0237. The 180 degree peel strength at 25 mm width was measured at a speed of 300 mm / min. The peel strength measured in this way was used as the initial adhesive strength.

(3) Adhesive strength with time 2 kg of each surface protective adhesive sheet of Examples and Comparative Examples was applied to the surface of the prism sheet used in the initial adhesive strength evaluation of (2) under the environment of room temperature 23 ° C. and relative humidity 50%. Using a pressure-bonded rubber roller, affixed at a speed of 300 mm / min. Thereafter, the prism sheet was sandwiched between polycarbonate plates (thickness: 2 mm), a pressure of 6.0 × 10 ⁻³ MPa was applied, and the mixture was allowed to stand for 48 hours in an environment of 60 ° C. and relative humidity of 90%. Subsequently, in accordance with JIS Z0237, a 180-degree peel strength at a width of 25 mm was measured at a speed of 300 mm / min. The peel strength measured in this way was defined as the adhesive strength with time.

(4) Adhesive residue evaluation After peeling measurement in (3), the lens surface of the prism sheet was visually observed with a digital microscope (VHX-200 manufactured by Keyence Corporation).
The case where no adhesive residue was observed on the lens surface of the prism sheet was evaluated as “Good”, and the case where adhesive residue was observed was evaluated as “Poor”.

(5) Unfolding force The force required when the 50 mm-wide wound body of each surface protective adhesive sheet of Examples and Comparative Examples was rewound at a speed of 20 m / min was measured to determine the unfolding force.

(6) Unfolding force with time After the 50 mm-wide wound bodies of the surface protective adhesive sheets of Examples and Comparative Examples were left in an environment of 60 ° C. and 50% relative humidity for 1 week, they were rewound at a speed of 20 m / min. The force required at the time of measurement was measured, and the deployment force over time was determined.
When both the initial and temporal development forces were 5.0 N / 50 mm or less, the evaluation was ○ (good), and when the initial or temporal development forces exceeded 5.0 N / 50 mm, the evaluation was x (defect).

Example 1
Adhesive layer: A-B-A acrylic triblock copolymer (LA2250, MMA (methyl methacrylate, glass transition temperature: 100 ° C.)-BA (butyl acrylate, glass transition temperature: −50 ° C.)-MMA, manufactured by Kuraray Co., Ltd. ), AB acrylic diblock copolymer (manufactured by Kuraray, LA410L, MMA (methyl acrylate) -BA (butyl acrylate)), tackifier resin (TH130, terpene phenol based by Yashara Chemical), toluene (Wako Pure) (Made by Yakusha)
Anchor layer: SEBS (JSR 8300P)
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
Polypropylene and SEBS were coextruded by a T-die method to produce a sheet in which a 36 μm thick polypropylene sheet and a 2 μm thick anchor layer were laminated and integrated.
On one surface of the obtained sheet, a solution (concentration: 20% by weight) containing 90 parts by weight of an acrylic triblock copolymer dissolved in toluene, 10 parts by weight of an acrylic diblock copolymer and 10 parts by weight of a tackifying resin. It was applied and dried at 100 ° C. for 5 minutes, and a 2 μm thick adhesive layer was laminated and integrated.
This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Example 2)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the base material layer and the composition of the pressure-sensitive adhesive layer were as shown in Table 3.

(Example 3)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the base material layer and the composition of the pressure-sensitive adhesive layer were as shown in Table 3.

(Comparative Example 8)
Adhesive layer: A-B-A acrylic block copolymer (LA2250, MMA (methyl methacrylate) -BA (butyl acrylate) -MMA) manufactured by Kuraray Co., Ltd.), tackifying resin (TH130, terpene phenol type manufactured by Yasuhara Chemical Co., Ltd.)
Anchor layer: SEBS (JSR 8300P)
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
Polypropylene and SEBS were coextruded by the T-die method to produce a sheet in which a 36 μm thick polypropylene sheet and a 2 μm thick anchor layer were laminated and integrated.
On one surface of the obtained sheet, a solution (concentration: 20% by weight) containing 100 parts by weight of an acrylic triblock copolymer dissolved in toluene and 20 parts by weight of a tackifier resin is applied and dried at 100 ° C. for 5 minutes. A 6 μm thick adhesive layer was laminated and integrated.

(Comparative Example 9)
Adhesive layer: A-A-A acrylic block copolymer (LA2250 manufactured by Kuraray Co., Ltd.), MMA (methyl methacrylate) -BA (butyl acrylate) -MMA, A-B acrylic block copolymer (LA410L MMA manufactured by Kuraray Co., Ltd.) Methyl methacrylate) -BA (butyl acrylate)), tackifying resin (Yasuhara Chemical TH130, terpene phenol),
Toluene (Wako Pure Chemical Industries)
Anchor layer: SEBS (JSR 8300P)
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
Polypropylene and SEBS were coextruded by a T-die method to produce a sheet in which a polypropylene sheet having a thickness of 32 μm and an anchor layer having a thickness of 2 μm were laminated and integrated.
One surface of the obtained sheet was subjected to a corona discharge treatment, and then, on the treated surface, 50 parts by weight of an acrylic triblock copolymer dissolved in toluene, 50 parts by weight of an acrylic diblock copolymer, and a tackifying resin 10 A solution containing parts by weight (concentration: 20% by weight) was applied, dried at 100 ° C. for 5 minutes, and an adhesive layer having a thickness of 6 μm was laminated and integrated.
This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Comparative Example 10)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Example 1 except that the composition and thickness of the pressure-sensitive adhesive layer were as shown in Table 3.

(Comparative Example 11)
A wound body of the surface protective adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the base material layer and the composition and thickness of the pressure-sensitive adhesive layer were as shown in Table 3.
(Comparative Example 12)
Adhesive layer: SEBS (manufactured by JSR 8300P), tackifying resin (Alcon P115, manufactured by Arakawa Chemical Industries, hydrogenated petroleum resin),
Polyolefin substrate layer: Polypropylene (Prime Polymer J715)
A pressure-sensitive adhesive composition containing 100 parts by weight of SEBS as a styrene elastomer, 20 parts by weight of Alcon P115, and polypropylene are coextruded by a T-die method, a polypropylene substrate layer having a thickness of 37 μm, and a pressure-sensitive adhesive having a thickness of 6 μm. A sheet in which the layers were laminated and integrated was produced. This was wound up on a paper core having an inner diameter of 3 inches to obtain a wound body of a surface protective adhesive sheet.

(Comparative Example 13)
According to Example 1, the pressure-sensitive adhesive layer having a thickness of less than 0.1 μm was formed by changing the concentration of the acrylic block copolymer toluene solution. As a result, a pressure-sensitive adhesive layer as a uniform layer could not be obtained.

(Evaluation of Examples 1 to 3 and Comparative Examples 8 to 12)
The following items were evaluated for each surface protective adhesive sheet obtained as described above. The results are shown in Table 4.
(1) Shear storage elastic modulus It evaluated by the method similar to the evaluation method of the surface protection adhesive sheet of Comparative Examples 1-6.

(2) Initial adhesive strength It evaluated by the method similar to the evaluation method of the surface protection adhesive sheet of Comparative Examples 1-6.
At this time, when the floating area is less than 1% with respect to 100% of the surface protective adhesive sheet and the prism sheet surface, ◎ (excellent), 1% to less than 5% ○ (good), 5% or more In the case of x, it was set as x (defect).

(3) Adhesive strength with time It evaluated by the method similar to the evaluation method of the surface protection adhesive sheet of Comparative Examples 1-6.
At this time, when the floating area is less than 1% with respect to 100% of the surface protective adhesive sheet and the prism sheet surface, ◎ (excellent), 1% to less than 5% ○ (good), 5% or more In the case of x, it was set as x (defect).

(4) Adhesive residue evaluation It evaluated by the method similar to the evaluation method of the surface protection adhesive sheet of Comparative Examples 1-6.

(5) Development force It evaluated by the method similar to the evaluation method of the surface protection adhesive sheet of Comparative Examples 1-6.

(6) Ability to develop over time It was evaluated by the same method as the method for evaluating the surface protective adhesive sheets of Comparative Examples 1 to 6. However, the evaluation criteria are ○ (good) when the initial and temporal deployment force is 5.0 N / 50 mm or less, and △ (good) when the temporal deployment force exceeds 5.0 N / 50 mm. And when the deployment force over time exceeded 5.0 N / 50 mm, it was set as x (defect).

Claims (5)

Having a polyolefin base layer and an adhesive layer,
The pressure-sensitive adhesive layer is
A block copolymer (I) represented by the general formula A-B-A and a block copolymer (II) represented by the general formula A-B (where A is a methacrylate block, B Is an acrylate block, and the glass transition temperature of the methacrylic ester polymer is 60 ° C. or higher, and the glass transition temperature of the acrylate polymer is 10 ° C. or lower)
And containing 100 parts by weight of a pressure-sensitive adhesive in which the weight ratio of the block copolymer (I) and the block copolymer (II) is 95: 5 to 50:50 and 5 to 50 parts by weight of a tackifier resin And
The weight average molecular weight of the block copolymer (I) and the block copolymer (II) is in the range of 50,000 to 300,000 in terms of polystyrene by GPC method (gel permeation chromatography),
And the surface protection adhesive sheet characterized by having thickness of 0.1 micrometer or more and 2.0 micrometers or less. The surface-protective adhesive sheet according to claim 1, wherein the tackifying resin is at least one selected from terpene phenol resins, hydrogenated terpene phenol resins, and rosin resins.   The surface protective adhesive sheet according to claim 1, further comprising an anchor layer formed of a styrene resin between the polyolefin base material layer and the pressure-sensitive adhesive layer. The anchor layer is
A block copolymer represented by the general formula CDC or a block copolymer represented by the general formula CDC and a block copolymer represented by the general formula CD (where C Is a styrene polymer block, and D is a hydrocarbon polymer block)
The surface protective adhesive sheet according to claim 3, which is formed by:   The surface protective adhesive sheet according to claim 1, which is applied to an optical sheet having irregularities on the surface.