JP2008248223A - Pressure-sensitive adhesive composition for use in surface protecting sheet, and surface protecting sheet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive composition for use in surface protecting sheets which has a high adhesive strength at the time of low-speed peeling, a low peeling strength at the time of high-speed peeling, and no zipping, a good wettability, is little in the increase of the adhesive strength due to the rise in the peeling speed, is not contaminated under a hot condition, and form a transparent coating film, and to provide a surface protecting sheet using the composition. <P>SOLUTION: The pressure-sensitive adhesive composition for use in surface protecting sheets, contains component (A): a copolymer, which is formed by copolymerizing a (meth)acrylic acid alkyl ester and a functional group-containing monomer as the essential components and has a glass transition temperature of -50°C or lower, and component (B): a copolymer, which is formed by copolymerizing vinyl acetate and a functional group-containing monomer as the essential components and has a glass transition temperature of from -40°C to 15°C, with a ratio of 10-40 parts by mass of component (B) relative to 100 parts by mass of component (A); and the surface protecting sheet uses the same. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive composition for a surface protective sheet and a surface protective sheet using the same.

  An optical member such as a liquid crystal display is usually protected by attaching a surface protection sheet so that the surface thereof is not damaged or contaminated. Such a surface protective sheet is peeled and removed after each step when the surface protection is no longer necessary. However, the force required for peeling the surface protective sheet (hereinafter referred to as “peeling force”) with the recent increase in the size of liquid crystal displays. "Is abbreviated as"), the work efficiency is poor, and there is a problem that the optical member is damaged during the peeling work. In addition, there was a case where a large peeling sound called zipping occurred. Thus, development of a surface protective sheet that has a low peeling force during high-speed peeling (hereinafter abbreviated as “high-speed peeling force”) and does not cause zipping has been performed.

  However, if the peeling force at the time of low-speed peeling (hereinafter abbreviated as “low-speed peeling force”) is also lowered in order to reduce the high-speed peeling force, problems such as floating and peeling may occur during each process. Therefore, there is a demand for a surface protective sheet having a low speed peeling force that is not less than a certain level and a low high speed peeling force. Moreover, in the inspection process of a liquid crystal display, since a surface protection sheet may be once peeled off and attached again by manual work, good wettability is also required. Furthermore, there may be a problem that static electricity is generated when the surface protection sheet is peeled off and surrounding dust is involved, and that the liquid crystal and the electronic circuit are destroyed due to the generated static electricity.

  So far, a method for forming an easily peelable surface protective sheet with an adhesive layer containing a surfactant has been proposed for a pressure sensitive adhesive for a surface protective sheet involving a peeling step (see Patent Document 1). . However, the surface protective sheet containing the surfactant has a problem that the adherend is contaminated at a high temperature.

In addition, as a technique for reducing the high-speed peel force, a pressure-sensitive adhesive for a surface protective sheet, which is used in combination with (meth) acrylic polymers having different glass transition points and has a cross-linking reaction so that the gel fraction is a certain value or more. Is known (see Patent Document 2). However, when sufficient high-speed peelability is imparted, there are problems such as poor wettability with respect to the polarizing plate (antiglare surface), and depending on the combination, the adhesive strength increases with time, and the processed film becomes cloudy.
JP 2001-066430 A JP 2005-146151 A

The present invention has high adhesive strength at low speed peeling, low peeling strength at high speed peeling, no zipping, good wettability, little increase in adhesive strength due to an increase in peeling speed, and contamination under heating conditions. An object of the present invention is to provide a pressure-sensitive adhesive composition for a surface protective sheet which does not occur and has a transparent processed film. Furthermore, it aims at providing the adhesive composition for surface protection sheets with little generation | occurrence | production of the static electricity at the time of peeling in addition to said characteristic.
Moreover, an object of this invention is to provide the surface protection sheet formed by coating said adhesive composition for surface protection sheets on a support body.

  As a result of intensive studies, the present inventors have used a copolymer having a high glass transition point in combination with a copolymer having a low glass transition point obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer. The present inventors have found that a pressure-sensitive adhesive composition based on a pressure-sensitive adhesive composition and the cross-linked pressure-sensitive adhesive composition solves the above-mentioned problems, and have reached the present invention.

That is, the present invention is as follows.
(1) The following components (A) and (B) are contained at a ratio of 10 to 40 parts by mass (in terms of solid content) of component (B) with respect to 100 parts by mass (in terms of solid content) of component (A). A pressure-sensitive adhesive composition for a surface protective sheet.
(A) a copolymer having a glass transition temperature of −50 ° C. or less obtained by copolymerization of at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer; and (B) at least vinyl acetate and a functional group-containing monomer are copolymerized. Copolymer polymer having a glass transition temperature of −40 ° C. to 15 ° C. (2) The following components (A) and (B) contain a crosslinking agent as component (C), and 100 parts by mass of component (A) A pressure-sensitive adhesive composition for a surface protective sheet, wherein 10 to 40 parts by mass (in terms of solid content) of the component (B) is mixed and crosslinked with respect to (in terms of solid content).
(A) Copolymer having a glass transition temperature of −50 ° C. or less obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer. (B) At least vinyl acetate and a functional group-containing monomer are copolymerized. (1) The functional group-containing monomer is copolymerized in an amount of 0.1 to 10% by mass in the copolymer of the copolymer (3) component (A) having a glass transition temperature of −40 ° C. to 15 ° C. Or the adhesive composition for surface protection sheets as described in (2).
(4) The pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (3), wherein the functional group-containing monomer is copolymerized in an amount of 1 to 20% by mass in the copolymer of component (B). .
(5) The surface protective sheet according to any one of (1) to (4), wherein 3 to 25% by mass of an alkoxypolyalkylene glycol (meth) acrylate is further copolymerized in the copolymer (A). Pressure-sensitive adhesive composition.
(6) The pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (5), wherein 30% by mass or more of vinyl acetate is copolymerized in the copolymer of component (B).
(7) The pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (6), wherein the copolymer (B) has a weight average molecular weight of 100,000 or more.
(8) The component (C) is a compound having an isocyanate group, and the component (C) is blended in an amount of 0.1 to 5.0 parts by mass with respect to a total of 100 parts by mass of the component (A) and the component (B) ( The adhesive composition for surface protection sheets in any one of 1)-(7).
(9) The pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (8), further containing an ionic compound.
(10) The pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (9), wherein the ionic compound contains a lithium salt having a fluorine atom in the compound.
(11) A surface protective sheet obtained by coating the pressure-sensitive adhesive composition for a surface protective sheet according to any one of (1) to (10) on a support.

  The pressure-sensitive adhesive composition for a surface protective sheet of the present invention is characterized by containing two kinds of copolymer polymers having different glass transition points in a limited blending ratio. In addition, since the degree of cross-linking is adjusted with a cross-linking agent, when this is used as a pressure-sensitive adhesive for a surface protective sheet, it can be re-peeled with a low force at high-speed peeling, does not cause zipping, and has good wettability. is there. Even under heating conditions, the adherend is not contaminated after peeling, and the increase in adhesion due to an increase in peeling speed is small, so that a transparent surface protective sheet can be provided. Furthermore, by adding an ionic compound, static electricity is not generated when the surface protective sheet is peeled off, so that there is no possibility of surrounding dust getting involved or destroying the liquid crystal or the electronic circuit at the time of peeling.

The pressure-sensitive adhesive composition for a surface protective sheet of the present invention comprises the following components (A) and (B), and 10 components (B) with respect to 100 parts by mass (in terms of solid content) of the component (A). It is characterized by containing -40 mass parts (solid content conversion). Furthermore, in addition to the components (A) and (B), the following component (C) is mixed and crosslinked.
(A) a copolymer having a glass transition temperature of −50 ° C. or less obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer; and (B) at least vinyl acetate and a functional group-containing monomer being copolymerized. Copolymer (C) crosslinking agent having a glass transition temperature of −40 ° C. to 15 ° C.

  As the (meth) acrylic acid alkyl ester used in the copolymer of component (A), a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms can be used. Examples include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. it can. These are used alone or in combination of two or more. Among these (meth) acrylic acid alkyl esters, it is preferable to carry out copolymerization using (meth) acrylic acid alkyl esters having an alkyl group having 2 to 12 carbon atoms in terms of tackiness. Particularly preferred is n-butyl acrylate or 2-ethylhexyl acrylate having an n-butyl group or 2-ethylhexyl group. The (meth) acrylic acid alkyl ester is preferably 65 to 96.9% by mass with respect to all monomers used for copolymerization of the copolymer.

  The copolymer of component (B) contains vinyl acetate and a functional group-containing monomer as essential components. This is because the inclusion of vinyl acetate makes it easy to adjust the glass transition point, has excellent film properties, and makes it easy to obtain the desired adhesive force and peeling force. The vinyl acetate is preferably contained in an amount of 30% by mass or more, more preferably 30 to 90% by mass, and still more preferably 40 to 70% by mass with respect to the total monomers to be provided to the copolymer (B). %. If the vinyl acetate is less than 30% by mass, the high-speed peeling force increases. On the other hand, if it exceeds 90% by mass, the compatibility with the component (A) is deteriorated.

  The copolymer (B) is preferably used in combination with a (meth) acrylic acid alkyl ester in addition to the vinyl acetate and the functional group-containing monomer. This is because not only the glass transition point can be adjusted more easily, but also the film properties can be adjusted, and the desired performance can be obtained more easily. Examples of the (meth) acrylic acid alkyl ester that can be used include the same as those described in the component (A). The (meth) acrylic acid alkyl ester is preferably 9 to 69% by mass with respect to the total monomers used for copolymerization of the copolymer.

  Examples of the functional group-containing monomer used in the copolymer of component (A) and component (B) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 4- Examples include hydroxyl-containing monomers such as hydroxybutyl and monoglyceryl (meth) acrylate; and carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, and itaconic acid. These are used alone or in combination of two or more. Among these functional group-containing monomers, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable in terms of reactivity.

  In the (meth) acrylic polymer of the present invention, by co-polymerizing a functional group-containing monomer, the cross-linking agent of component (C) reacts with these functional groups to form a cross-linked structure. A pressure-sensitive adhesive having a good balance of properties can be obtained.

  In the case of the copolymer (A), the functional group-containing monomer is preferably 0.1 to 10% by mass, more preferably 0.5 to 6% by mass, based on the total monomers to be subjected to copolymerization. It is. If the functional group-containing monomer is less than 0.1% by mass, the degree of crosslinking and cohesion as an adhesive is insufficient, while if it exceeds 10% by mass, the degree of crosslinking becomes too high, resulting in zipping during high-speed peeling and wettability. Therefore, it becomes impossible to re-apply the surface protection sheet, and the production efficiency also deteriorates.

  In the case of the copolymer of the component (B), the functional group-containing monomer is preferably 1 to 20% by mass, more preferably 2 to 16% by mass, based on the total monomers used for copolymerization. When the functional group-containing monomer is less than 1% by mass, the degree of crosslinking and cohesion as an adhesive are insufficient. On the other hand, when it exceeds 20% by mass, the degree of crosslinking increases too much and wettability decreases.

  It is preferable to further copolymerize an alkoxypolyalkylene glycol (meth) acrylate with the copolymer (A). By copolymerizing such a monomer, flexibility can be imparted to the copolymer of component (A), and even when mixed with the copolymer of component (B), a decrease in wettability of the adhesive can be suppressed. .

  Examples of the alkoxypolyalkylene glycol (meth) acrylate monomer include alkoxy polyethylene glycol (n = 1-30) (meth) acrylate, alkoxypolypropylene glycol (n = 1-30) (meth) acrylate, and the like. Of these, methoxypolyethylene glycol (meth) acrylate is preferable from the viewpoint of flexibility, and n = 5-20 is particularly preferable. In addition, n shows the average added mole number of ethylene oxide.

  The alkoxy polyalkylene glycol (meth) acrylate monomer is preferably 3 to 25% by mass, more preferably 5 to 20% by mass, based on the total monomers used for copolymerization of the copolymer (A). is there. When the amount of the alkoxy polyalkylene glycol (meth) acrylate monomer is less than 3% by mass, the flexibility of the pressure-sensitive adhesive is lowered. On the other hand, when it exceeds 25% by mass, the high-speed peeling force is increased.

  In the present invention, the copolymer polymer of component (A) needs to have a glass transition temperature of −50 ° C. or less, and the copolymer polymer of component (B) needs to have a glass transition temperature of −40 ° C. to 15 ° C. When the glass transition point of the component (A) polymer is higher than −50 ° C., the wettability cannot be maintained, and the glass transition point of the component (B) is lower or higher than the above range. The balance between peeling force and high-speed peeling force cannot be maintained.

  The copolymer (A) component may have a weight average molecular weight in the range of 100,000 to 1,000,000. The copolymer (B) component preferably has a weight average molecular weight of 100,000 or more, and if it is less than 100,000, the high-speed peeling force increases.

  In the pressure-sensitive adhesive composition for a surface protective sheet of the present invention, as the crosslinking agent of component (C), a compound having an isocyanate group such as a known trifunctional isocyanate or diisocyanate compound, or a bifunctional or trifunctional or higher glycidyl group is used. A compound having an epoxy (epoxy compound) or a metal chelate compound can be preferably used. These compounds may be used alone or in combination of two or more.

  Specific examples of the compound having an isocyanate group include, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4 -Aromatic isocyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; adducts of tolylene diisocyanate (3 mol) and trimethylolpropane (1 mol), hexamethylene diisocyanate (3 mol) Trimethylolpropane (1 mol) adduct, isophorone diisocyanate (3 mol) and trimethylolpropane (1 mol) adduct, xylene diisocyanate (3 moles) with an isocyanate adduct of adduct of trimethylol propane (1 mole); and the like.

  Examples of the compound having a difunctional or trifunctional or higher glycidyl group include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6 -Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylamine, diamine glycidylamine, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N' -A compound having two or more epoxy groups in a molecule such as diamineglycidylaminomethyl) cyclohexane.

  Examples of the metal chelate compound include polyvalent metal chelate compounds such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

  When preparing the pressure-sensitive adhesive composition for a surface protective sheet of the present invention, the copolymer (A), the copolymer (B) and the crosslinking agent (C) are mixed to obtain an appropriate solid content. A pressure-sensitive adhesive composition in which the degree of crosslinking is adjusted by concentration is prepared. The copolymer (B) component is mixed in an amount of 10 to 40 parts by mass in terms of solid content with respect to 100 parts by mass (in terms of solid content) of the copolymer polymer (A). More preferably, it is 15-30 mass parts. When the mixing ratio of the component (B) is less than 10 parts by mass, the high-speed peeling force increases, and when it exceeds 40 parts by mass, the wettability is deteriorated. Further, the addition amount of the crosslinking agent is preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 2.5 parts by mass with respect to 100 parts by mass (in terms of solid content) of the copolymer. is there.

The pressure-sensitive adhesive composition for a surface protective sheet of the present invention may further contain an ionic compound. Such ionic _{compounds, NaCl, KCl, LiCl, LiBr} , LiI, LiBF 4, LiPF 6, LiSCN, LiClO 4, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, Li (CF 3 SO 2) 3 C, onium salts are mentioned. These ionic compounds may be used alone or in combination of two or more. In terms of antistatic properties, a lithium salt is preferable, and in order to reduce the adhesive strength at the time of high-speed peeling while lowering the adhesive strength at a low speed, lithium salt having a fluorine atom in the compound, LiCF ₃ SO ₃ , Li ( CF ₃ SO ₂ ) ₂ N and Li (CF ₃ SO ₂ ) ₃ C are more preferable. The ionic compound can be contained in the copolymer of component (A) or can be contained in the copolymer of component (B). Or you may make it contain in both components (A) and (B). Moreover, it can also add at the time of mixing of a component (A), a component (B), and a component (C). As for content of an ionic compound, 0.1-5 mass parts is preferable with respect to a total of 100 mass parts (solid content conversion) of a copolymer polymer, More preferably, it is 0.3-3 mass parts. When the content is less than 0.3 part by mass, the antistatic property is deteriorated.

  In the pressure-sensitive adhesive composition for a surface protective sheet of the present invention, for example, other acrylic pressure-sensitive adhesives can be used in combination as long as the object of the present invention is not impaired. Moreover, you may mix | blend additives, such as a tackifier, antioxidant, a ultraviolet absorber, an antifungal agent, an antifoamer, a pigment, and a vehicle, as needed.

  The surface protection sheet in which the adhesive layer was formed is obtained by applying the adhesive composition for surface protection sheets of this invention to the surface of a support body, and drying. Examples of the support include various plastic films such as a polyvinyl chloride film, a polyethylene film, a polypropylene film, a polyethylene terephthalate film, a polyurethane film, and a polyamide film, or a uniaxial or biaxially stretched film of these films.

  The surface protective sheet of the present invention can be suitably used as a surface protective sheet for optical members such as liquid crystal displays and plasma displays.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Production Example 1]
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, cooler, and dropping funnel, 88 parts by mass of 2-ethylhexyl acrylate (2EHA), M-90G (methoxypolyoxyethylene glycol methacrylate (Shin Nakamura) Chemical Industry Co., Ltd., EO 9 mol adduct) 8 parts by mass, 2-hydroxyethyl methacrylate (2HEMA) 2 parts by mass, 4-hydroxybutyl acrylate (4HBA) 2 parts by mass and ethyl acetate 44 parts by mass were prepared. 0.04 parts by mass of isobutyronitrile (AIBN) was added, and polymerization was performed in a nitrogen gas stream at 80 ° C. for 8 hours, and after completion of the reaction, diluted with toluene to adjust to a solid content of 30%, a weight average A copolymer having a molecular weight of 300,000 was obtained.

[Production Examples 2 to 8]
A copolymer having a solid content of 30% with a copolymerization ratio shown in Table 1 was obtained in the same manner as in Production Example 1 except that the type of monomer, the addition amount, and the addition amount of AIBN were changed as shown in Table 1.

  Table 1 shows the glass transition point (Tg) and the weight average molecular weight of the copolymer obtained in the above production example. The weight average molecular weight was measured by gel permeation chromatography (GPC) under the following conditions.

(GPC measurement conditions)
Column: TSKgel GMHXL (7.8 mm ID × 30 cm) × 2 + G2000HXL (7.8 mm ID × 30 cm (manufactured by Tosoh Corporation))
Moving bed and flow rate: THF (1.0 ml / min)
Oven temperature: 40 ° C
Detector: RI-101 (Showa Denko KK)
A calibration curve was prepared using TSK standard polystyrene (manufactured by Tosoh Corporation) as a standard substance, and the molecular weight of the sample was determined from the calibration curve.

Moreover, the glass transition point of the copolymer obtained in the above production example was determined from the following FOX equation as the glass transition temperature (Tgn, ° C) of the homopolymer by each monomer.
1 / (Tg + 273) = Σ [Wn / (Tgn + 273)]
Tg is the glass transition temperature (° C) of the copolymer, Wn is the mass fraction of each monomer, Tgn is the glass transition temperature (° C) of the homopolymer of each monomer, and n is the type of each monomer.

In addition, the glass transition temperature Tgn of each homopolymer is as follows.
2EHA: -70 ° C, 2HEMA: 55 ° C, 4HBA: -32 ° C, VAc: 32 ° C, BA: -55 ° C, MMA: 105 ° C, M-90G: -69 ° C

Example 1
100 parts by mass of the polymer obtained in Production Example 1 as the component (A), 10 parts by mass of the polymer obtained in Production Example 3 as the component (B), and Coronate HX (Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent for the component (C) A crosslinkable composition solution was obtained using 0.5 part by mass of an isocyanate-based crosslinking agent). The obtained solution was applied onto a polyethylene terephthalate (hereinafter abbreviated as “PET”) film having a thickness of 38 μm so that the thickness after drying was 25 μm, and the solvent was removed at 80 ° C. Next, a 38 μm-thick silicone-coated cover PET film was bonded to the dried surface and aged for 7 days in an atmosphere of 23 ° C. and 65% humidity to obtain a surface protective sheet.

(Examples 2-6 and Comparative Examples 1-6)
Example 1 except that the components (A) and (B) shown in Table 1 and the crosslinking agent (C) shown in Table 2 were used in the amounts shown in Table 2, respectively. Thus, a surface protective sheet was obtained.

  Table 2 shows the compositions of the crosslinkable composition solutions of Examples and Comparative Examples.

  Test Example: The following methods were used to test the surface protective sheets of the above Examples and Comparative Examples for low speed peel strength, high speed peel strength, wettability, film appearance, and antistatic performance. Tables 3 and 4 show the test results.

(Low speed peeling force)
Each of the above surface protective sheets was cut into 25 mm × 50 mm, the cover PET film was peeled off, and then attached to a polarizing plate (antiglare surface), and left for 1 hour in an atmosphere of 23 ° C. and humidity 65%. Thereafter, the pulling speed was 300 mm / min, the pulling was performed in the 180 ° direction (reverse direction), and the force for starting peeling was defined as the low-speed peeling force.

(High speed peeling force)
Each of the above surface protective sheets was cut into 25 mm × 50 mm, the cover PET film was peeled off, and then attached to a polarizing plate (antiglare surface), and left for 1 hour in an atmosphere of 23 ° C. and humidity 65%. Thereafter, the pulling speed was 40,000 mm / min, the pulling was performed in the 180 ° direction (reverse direction), and the force for starting the peeling was defined as the high-speed peeling force.

(Wettability)
Each said surface protection sheet was cut | judged to 25 mm x 50 mm, the PET film for covers was peeled off, and then the wetting speed when affixed to the polarizing plate (anti-glare surface) was visually observed. Evaluation was made according to the following criteria.
○: The polarizing plate was instantly wet Δ: The polarizing plate was slowly wet ×: The polarizing plate was hardly wet

(Film appearance)
Each surface protection sheet was visually observed to observe the transparency of the film.
○: The film is transparent ×: The film is cloudy

(Measurement of peeling voltage)
Cut the pressure-sensitive adhesive sheet into a size of 40 mm wide and 100 mm long, peel off the separator, and then put a rubber roller on the surface of the polarizing plate bonded to an acrylic plate with a thickness of 1 mm, width 50 mm, and length 150 mm that has been neutralized beforehand. Used for crimping. After being left for 2 hours in an atmosphere of 20 ° C. and humidity of 40%, the potential of the polarizing plate surface when peeled in the direction of 150 ° at a peeling speed of 10 mm / min was measured using a potential measuring device (KSD- 0103).

(Example 7)
To 100 parts by mass of the crosslinkable composition solution described in Example 1, 2.0 parts by mass of lithium perchlorate as an ionic compound was added and dissolved by stirring to obtain an antistatic crosslinkable composition solution. A surface protective sheet was obtained from the obtained solution in the same manner as in Example 1. Table 4 shows the antistatic performance of the obtained surface protective sheet.

(Example 8)
To 100 parts by mass of the crosslinkable composition solution described in Example 1, 1.0 part by mass of lithium perchlorate and 1.0 part by mass of lithium trifluoromethanesulfonate were added as an ionic compound, and dissolved by stirring. Sex composition was obtained. A surface protective sheet was obtained from the obtained solution in the same manner as in Example 1. Table 4 shows the antistatic performance of the obtained surface protective sheet.

Example 9
To 100 parts by mass of the crosslinkable composition solution described in Example 1, 2.0 parts by mass of lithium trifluoromethanesulfonate as an ionic compound was added and dissolved by stirring to obtain an antistatic crosslinkable composition. A surface protective sheet was obtained from the obtained solution in the same manner as in Example 1. Table 4 shows the antistatic performance of the obtained surface protective sheet.

  As shown in Table 3, the surface protective sheet using the adhesive for protective sheets of Examples has a low speed peel force of 0.06 N / 25 mm or more, a high speed peel force of 1.2 N / 25 mm or less, and a low speed peel force. Was high and the high-speed peeling force was low. Furthermore, no zipping occurred during high-speed peeling, and the wettability with respect to the polarizing plate was excellent. In addition, a processed product film having a transparent appearance was obtained. Furthermore, as shown in Table 4, by adding an ionic compound, good antistatic properties were obtained without deterioration in high-speed peelability and wettability.

  By using the protective sheet pressure-sensitive adhesive of the present invention, the high-speed peeling force is low, zipping does not occur, the wettability is good, and the change in the peeling force due to the change in the peeling speed is small (the low-speed peeling force is high, A surface protective sheet having a low high-speed peeling force can be provided. Furthermore, by containing an ionic compound, it can be set as the adhesive composition for surface protection sheets excellent in antistatic property, and can generate static electricity at the time of peeling. Therefore, the surface protective sheet using the pressure-sensitive adhesive for protective sheet of the present invention is not easily peeled off after sticking, but it is easy to peel off at high speed, and it is easy to stick even when sticking again, and an optical film used in the display field. And various plastic plates, metal plates such as stainless steel, glass plates and the like can be used advantageously.

Claims (11)

The following components (A) and (B) are contained at a ratio of 10 to 40 parts by mass (solid content conversion) with respect to 100 parts by mass (solid content conversion) of component (A). A pressure-sensitive adhesive composition for a surface protective sheet.
(A) a copolymer having a glass transition temperature of −50 ° C. or less obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer; and (B) at least vinyl acetate and a functional group-containing monomer being copolymerized. Copolymer having a glass transition temperature of −40 ° C. to 15 ° C. The following components (A) and (B) contain a crosslinking agent as the component (C), and 10 to 40 parts by mass of the component (B) with respect to 100 parts by mass (in terms of solid content) of the component (A). A pressure-sensitive adhesive composition for a surface protective sheet, which is mixed and cross-linked (in terms of solid content).
(A) a copolymer having a glass transition temperature of −50 ° C. or less obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer; and (B) at least vinyl acetate and a functional group-containing monomer being copolymerized. Copolymer having a glass transition temperature of −40 ° C. to 15 ° C.   The pressure-sensitive adhesive composition for a surface protective sheet according to claim 1 or 2, wherein 0.1 to 10% by mass of a functional group-containing monomer is copolymerized in the copolymer (A).   The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 3, wherein 1 to 20% by mass of a functional group-containing monomer is copolymerized in the copolymer (B).   The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 4, wherein 3 to 25% by mass of an alkoxypolyalkylene glycol (meth) acrylate is further copolymerized in the copolymer (A).   The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 5, wherein 30% by mass or more of vinyl acetate is copolymerized in the copolymer (B).   The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 6, wherein the copolymer (B) has a weight average molecular weight of 100,000 or more.   The component (C) is a compound having an isocyanate group, and 0.1 to 5.0 parts by mass of the component (C) is blended with respect to a total of 100 parts by mass of the component (A) and the component (B). The adhesive composition for surface protection sheets in any one.   Furthermore, the adhesive composition for surface protection sheets in any one of Claims 1-8 containing an ionic compound.   The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 9, wherein the ionic compound contains a lithium salt having a fluorine atom in the compound.   The surface protection sheet formed by coating the adhesive composition for surface protection sheets in any one of Claims 1-10 on a support body.