JP2005290277A - Surface-protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a surface protection film that uses excellent adhesive power and cohesive power of an elastomer, excellently adjusts adhesive properties without depending only upon a tackifier, has excellent sticking properties to an article, is readily peeled and separated and has slight paste remaining on an article. <P>SOLUTION: The surface protection film is obtained by forming an adhesive layer 2 composed of an adhesive composition that comprises an acid-modified polystyrene-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer and a crosslinking agent on one side of a substrate 1 in a surface protection film F to be used for an optical sheet of an article such as a polarizing plate, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface protective film that is attached to a polarizing plate, a lens sheet or the like and used for storage, transportation or processing of the polarizing plate or the lens sheet.

Conventionally, rubber adhesives mainly composed of diene rubber occupy most of the adhesives for surface protective films, but this has the following problems.
That is, since the structure contains an unsaturated double bond, the weather resistance and heat resistance are poor. Moreover, the anchoring property (adhesiveness with a base film) with respect to a base film is weak, and there exist some which peel between a base material and an adhesive layer.

  Therefore, as a method for solving the above-described problems, a protective film coated with an acid-modified polystyrene elastomer, a tackifier, and an adhesive containing an epoxy resin has been proposed (see, for example, Patent Document 1).

JP-A-5-186747

This has the disadvantage that the pressure-sensitive adhesive is hardened and the familiarity or initial tackiness is lowered because the adhesive strength is adjusted by the amount of the tackifier. Also, there is a risk of contamination due to bleed out of the low molecular weight tackifier.
On the other hand, when the ratio of the tackifier is small, there is a problem that proper adhesive strength cannot be obtained.
Therefore, in the use of surface protection for articles such as building materials, there may be a case where the adjustment range of some adhesive force is wide, but surface protection used for optical sheets of articles such as polarizing plates. In the case of a film, it was extremely difficult to control the physical properties of the adhesive to the required peel strength.

  As described above, the polystyrene-based thermoplastic elastomer alone has poor adhesion to the base film, whereas the present invention can be improved by adding an acid-modified polystyrene-based thermoplastic elastomer and a crosslinking agent. It is the one that paid attention. Further, the present invention can also solve the problem that the adhesive strength cannot be controlled and adjusted only with the acid-modified polystyrene-based thermoplastic elastomer.

  The present invention has been made to solve the above-described problems. An acid-modified polystyrene-based thermoplastic elastomer and polystyrene are provided on one side of a substrate in a surface protective film used for an optical sheet of an article such as a polarizing plate. By providing a thermoplastic elastomer and a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition having a crosslinking agent, the adhesive strength and cohesive strength of the elastomer can be used, and without relying solely on the tackifier, It aims at providing the surface protection film which can adjust a physical property favorably.

The present invention for achieving the above-described object is as follows.
A pressure-sensitive adhesive comprising a pressure-sensitive adhesive composition having an acid-modified polystyrene-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, and a crosslinking agent on one side of a substrate in a surface protective film used for an optical sheet of an article such as a polarizing plate The surface protection film is provided with a layer.

Also,
On one side of a substrate in a surface protective film used for an optical sheet of an article such as a polarizing plate, 100 parts by weight of an acid-modified polystyrene-based thermoplastic elastomer, 20 parts by weight to 400 parts by weight of a polystyrene-based thermoplastic elastomer, and a crosslinking agent It exists in the structure of the surface protection film which provided the adhesive layer which consists of an adhesive composition which has 0.2 weight part-6 weight part.

  Adhesiveness is good on an article such as an optical sheet such as a polarizing plate or a resin plate, and after sticking, there is little adhesive residue on the article and it can be easily peeled and separated.

Next, an example of the implementation of the surface protective film according to the present invention will be described with reference to the drawings.
FIG. 1 is an example showing an enlarged cross section of a part of the surface protective film F of the embodiment of the present invention, and is basically composed of a base material 1 and an adhesive layer 2. In addition, as a structure, in order to improve peelability, a mold release process may be performed to the base material 1 timely, and the peeling film 3 can also be stuck.

  This surface protective film F is, for example, a surface to be attached to an article such as a polarizing plate by sticking the pressure-sensitive adhesive layer 2 side to the surface of the article such as a polarizing plate of a display screen of a personal computer, a television or the like. When the protective film F has finished its role of preventing scratches and dirt on the polarizing plate during the manufacturing process of the article such as the polarizing plate, and protecting the surface when the article is stored or transported At the time of completion, it is peeled off from the surface (peeling surface) of the article such as the polarizing plate.

For example, polyethylene, polypropylene, polyester, polyimide, and the like are used for the base material 1 described above, and the material of the base material 1 is not particularly limited, but a film made of a polyolefin resin or the like is preferable.
The base film may be a single layer film or a laminated film. As thickness of a base film, 20 micrometers-100 micrometers are preferable.

  The pressure-sensitive adhesive layer 2 provided on one side of the base material 1 comprises 100 parts by weight of an acid-modified polystyrene-based thermoplastic elastomer, 20 parts by weight to 400 parts by weight of a polystyrene-based thermoplastic elastomer, and 0.2 part by weight of a crosslinking agent. It consists of a pressure-sensitive adhesive composition having 6 parts by weight.

  Among these, acid-modified polystyrene-based thermoplastic elastomers include, for example, SEBS (styrene-ethylene-butylene-styrene), SBS (styrene-butylene-styrene), SIS (styrene-isoprene-styrene), and SBBS (styrene-butadiene-butylene-styrene). Examples of the acid for modifying the rubber block of styrene) with an acid include maleic anhydride, stearic acid, (meth) acrylic acid, and the like.

  The polystyrene-based thermoplastic elastomer is a block copolymer comprising at least two polymer blocks A mainly composed of vinyl aromatic compounds and at least one polymer block B mainly composed of conjugated diene compounds. That are obtained by hydrogenation, or a mixture thereof, for example, vinyl aromatic compounds having a structure such as ABA, BABA, ABAABA, etc. -Examples include conjugated diene compound block copolymers or hydrogenated products thereof.

  Moreover, the above-mentioned crosslinking agent is added for the purpose of performing intermolecular crosslinking. As the crosslinking agent, polyisocyanate is representative, and then epoxy resin, urea resin, melamine resin, polyvalent resin. Metal compounds are used.

And the compounding quantity of the adhesive layer which consists of these acid-modified polystyrene-type thermoplastic elastomers, a polystyrene-type thermoplastic elastomer, and the adhesive composition which has a crosslinking agent is 100 weight part of acid-modified polystyrene-type thermoplastic elastomers. The polystyrene-based thermoplastic elastomer is 20 to 400 parts by weight.
When the polystyrene-based thermoplastic elastomer is less than 20 parts by weight, it is difficult to control the adhesive force.
When the polystyrene-based thermoplastic elastomer exceeds 400 parts by weight, the adhesion with the base film is poor. A preferred blending amount is 30 to 130 parts by weight, particularly 60 to 100 parts by weight.

Moreover, a crosslinking agent is 0.2-6 weight part. When the crosslinking agent is less than 0.2 parts by weight, the adhesion to the substrate 1 is poor, and there is a possibility that adhesive residue on an adherend (article) such as a polarizing plate may be generated.
When the crosslinking agent exceeds 6 parts by weight, the pressure-sensitive adhesive layer 2 becomes hard and the initial adhesiveness is inferior. A preferable blending amount is 0.3 to 5.0 parts by weight, particularly 0.8 to 3.0 parts by weight.

In addition, a tackifier can also be added as needed, The compounding quantity is 5-150 with respect to a total of 100 weight part of an acid-modified polystyrene type thermoplastic elastomer and a polystyrene type thermoplastic elastomer. Parts by weight.
When the tackifier is less than 5 parts by weight, workability is poor because the initial adhesive force is low and the film is easily peeled off. Moreover, when a tackifier exceeds 150 weight part, adhesive force is too strong and it is hard to peel off from articles | goods after use. Preferably it is 10-100 weight part.
Examples of the tackifier include hydrogenated rosin ester, terpene resin, hydrogenated terpene resin, terpene phenol resin, aliphatic petroleum resin, hydrogenated aliphatic petroleum resin, and the like.

The method for preparing the pressure-sensitive adhesive composition of the acid-modified polystyrene-based thermoplastic elastomer, the polystyrene-based thermoplastic elastomer, and the crosslinking agent is not particularly limited, and each component is dissolved in a known aromatic organic solvent. They may be mixed or heated and mixed in a molten state.
The pressure-sensitive adhesive composition thus obtained is applied to at least one side surface (one side) of the base film to form the pressure-sensitive adhesive layer 2.
The thickness of the pressure-sensitive adhesive layer 2 is preferably 2 μm to 20 μm.

(Example 1)
A polypropylene / polyethylene blend film having a thickness of 40 μm was prepared as a base film.
With respect to 100 parts by weight of acid-modified SEBS (trade name: Clayton FG1901X manufactured by Shell Chemical Co., Ltd.), 100 parts by weight of SEBS (trade name: manufactured by Clayton G1657 Shell Chemical Co., Ltd.) and hydrogenated aliphatic petroleum resin as a tackifier ( Product name: Alcon P-100 Arakawa Chemical Co., Ltd.) 50 parts by weight, polyfunctional isocyanate cross-linking agent (trade name: Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) 2 parts by weight, toluene 1000 parts by weight as a solvent and completely dissolved. Thus, a pressure-sensitive adhesive composition was obtained.
This pressure-sensitive adhesive composition was applied onto a substrate film so as to have a thickness of 6 μm and dried to obtain a surface protective film.

(Example 2)
Surface in the same manner as in Example 1 except that the polystyrene-based thermoplastic elastomer SEBS in the pressure-sensitive adhesive composition was changed to 100 parts by weight of SBBS (trade name: Tuftec P1000 manufactured by Asahi Kasei Co., Ltd.) instead of Kraton G1657. A protective film was obtained.

(Example 3)
As a tackifier in the pressure-sensitive adhesive composition, instead of hydrogenated aliphatic petroleum resin (trade name: Alcon P100), 50 parts by weight of hydrogenated terpene resin (trade name: Clearon P125, manufactured by Yasuhara Chemical Co., Ltd.) is used. A surface protective film was obtained in the same manner as in Example 1 except that.

(Comparative Example 1)
As a base film, hydrogenated aliphatic petroleum resin (trade name: trade name: 100 parts by weight of acid-modified SEBS (trade name: Clayton FG1901X Shell Chemical Co., Ltd.) on a polypropylene / polyethylene blend film having a thickness of 40 μm. Alcon P-100 (Arakawa Chemical Co., Ltd.) 60 parts by weight, epoxy resin 0.3 parts by weight, toluene 640 parts by weight as a solvent, and completely dissolved, the pressure-sensitive adhesive composition is 6 μm thick. And dried to obtain a surface protective film.

(Comparative Example 2)
As a base film, a hydrogenated aliphatic petroleum resin (as a tackifier for 100 parts by weight of acid-modified SEBS (trade name: manufactured by Clayton G1657 Shell Chemical Co., Ltd.) on a polypropylene / polyethylene blend film having a thickness of 40 μm ( (Product name: Alcon P-100, manufactured by Arakawa Chemical Co., Ltd.) 25 parts by weight and 500 parts by weight of toluene as a solvent were added, and the adhesive composition obtained by complete dissolution was applied and dried to a thickness of 6 μm. A surface protective film was obtained.

Examples 1 to 3 all have good adhesion and substrate adhesion, while Comparative Example 1 has good substrate adhesion, but adheres to polarizing plates and the like. The adhesiveness to the body (article) was inferior, and floating from the adherend (article) was observed due to insufficient initial adhesiveness.
Moreover, although the adhesiveness was favorable, it was confirmed that the comparative example 2 is inferior to base-material adhesiveness, and is unsuitable (refer Table 1).

It is explanatory drawing which expands and shows a part of surface protection film regarding this invention.

Explanation of symbols

  F: Surface protective film. 1 ... Base material. 2 ... Adhesive layer.

Claims (2)

  A pressure-sensitive adhesive comprising a pressure-sensitive adhesive composition having an acid-modified polystyrene-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, and a crosslinking agent on one side of a substrate in a surface protective film used for an optical sheet of an article such as a polarizing plate A surface protective film provided with a layer.   On one side of a substrate in a surface protective film used for an optical sheet of an article such as a polarizing plate, 100 parts by weight of an acid-modified polystyrene-based thermoplastic elastomer, 20-400 parts by weight of a polystyrene-based thermoplastic elastomer, and a crosslinking agent A surface protective film comprising a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition having 0.2 to 6 parts by weight.

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