KR20200127142A - Adhesive composition and surface-protective film - Google Patents

Abstract

The present invention relates to an adhesive composition and a surface-protective film. The adhesive composition shows an excellent adhesion balance at a low peeling rate and a high peeling rate, has excellent anti-fouling and adhesive properties, can be used for surface substrates including TAC, PMMA and PET, and can form an adhesive layer causing no deterioration with time and having excellent anti-static properties. The adhesive composition includes a first acrylic polymer having an acid value of 0.1-1.0 and copolymerized in the absence of a polyalkylene glycol chain-containing mono(meth)acrylate monomer, a second acrylic polymer copolymerized from a polyalkylene glycol chain-containing mono(meth)acrylate monomer, (D) a tri-functional or higher functional isocyanate compound, (G) an ionic compound having an anion with a fluorine atom number of F7 or higher and a melting point of 25-50°C, (E) a crosslinking-delaying agent, and (F) a crosslinking catalyst other than a tin compound.

Description

Pressure-sensitive adhesive composition and surface protective film TECHNICAL FIELD [ADHESIVE COMPOSITION AND SURFACE-PROTECTIVE FILM}

The present invention relates to a pressure-sensitive adhesive composition and a surface protective film containing an antistatic agent. More specifically, it relates to a pressure-sensitive adhesive composition containing an antistatic agent, and a surface protective film using the same, forming a pressure-sensitive adhesive layer of a surface protective film used for the purpose of protecting the surface of the polarizing plate by attaching to a polarizing plate constituting a liquid crystal display. will be. The pressure-sensitive adhesive composition of the present invention has excellent adhesive performance and excellent antistatic performance without deteriorating with time.

Conventionally, in the process of manufacturing an optical member such as a polarizing plate, which is a member constituting a liquid crystal display, a surface protective film is adhered for temporary protection of the surface of the optical member. Such a surface protection film is used only in the process of manufacturing an optical member, and is removed by peeling from the optical member when the optical member is included in a liquid crystal display. Since the surface protective film for protecting the surface of such an optical member is used only in the manufacturing process, it is also generally referred to as a process film.

The surface protective film used in the process of manufacturing the optical member as described above has a configuration in which an adhesive layer is formed on one side of a polyethylene terephthalate (PET) resin film having optical transparency. On the pressure-sensitive adhesive layer of the surface protection film until bonding to the optical member, the mold-releasing film is adhered to the pressure-sensitive adhesive layer in order to protect the pressure-sensitive adhesive layer.

Further, an optical member such as a polarizing plate is subjected to a product inspection accompanying optical evaluation such as display capability, color, contrast, and foreign matter mixing of the liquid crystal display panel in a state in which the surface protection film is attached.

For this reason, as a required performance for the surface protective film, it is required that no air bubbles or foreign matters and the low molecular weight component of the pressure-sensitive adhesive composition adhere to the pressure-sensitive adhesive layer, that is, have stain resistance.

In addition, when peeling the surface protective film from an optical member such as a polarizing plate, there is a concern that the peeling charge caused by static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend affects the failure of the electric control circuit of the liquid crystal display. . For this reason, the pressure-sensitive adhesive layer constituting the surface protective film is required to have excellent antistatic performance.

In addition, in recent years, as a polarizer protective layer (also referred to as a protective film) of a polarizing plate, acrylic resin such as polymethyl methacrylate (PMMA) in addition to the conventional triacetyl cellulose (TAC), poly(polymethyl methacrylate) such as polyethylene terephthalate (PET) The adoption of materials such as ester resin, cyclic olefin polymer, and polycarbonate is expanding. When the protective layer made of these materials peels the surface protective film bonded to the polarizing plate, peeling charging is easily generated, and therefore, the pressure-sensitive adhesive layer for the surface protective film of the polarizing plate needs excellent antistatic performance compared to the conventional one.

In addition, when finally peeling the surface protective film from an optical member such as a polarizing plate, it is necessary to be able to peel quickly. In order to be able to be quickly peeled even by so-called high-speed peeling, it is required that there is little change in adhesive force depending on the peeling speed.

As described above, in recent years, in terms of ease of use in using the surface protective film, as a required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (1) having a balance of adhesive strength in a low-speed peeling speed and a high-speed peeling speed. Things, (2) having stain resistance, (3) excellent antistatic performance, and the like are required.

However, although each of these (1) to (3), which is the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, can be satisfied, the (1) to (3) required for the pressure-sensitive adhesive layer of the surface protective film It was a difficult task to simultaneously satisfy all of the required performance of ). In addition, materials such as acrylic resins such as polymethyl methacrylate (PMMA) other than TAC, which are conventional protective layer materials, polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonates, are used. It was also a very difficult subject to form the pressure-sensitive adhesive layer of the surface protective film that can be used for the surface of the protective layer employed and satisfies the required performance of these (1) to (3) with the same pressure-sensitive adhesive composition.

In order to solve these problems, for example, (1) having a balance of adhesive strength in a low-speed peeling rate and a high-speed peeling rate, (2) having stain resistance, and (3) imparting excellent antistatic performance. The following proposals are known.

(1) Regarding the balance of adhesive force in the low-speed peeling rate and the high-speed peeling rate, a copolymer of a (meth)acrylate alkyl ester having an alkyl group having 7 or less carbon atoms and a copolymerizable compound containing a carboxyl group is used as a main component, and a crosslinking agent In the acrylic pressure-sensitive adhesive layer obtained by cross-linking treatment, there is a problem that the pressure-sensitive adhesive adheres to the adherend side when adhered for a long period of time, and the increase in the adhesive force to the adherend with time is large. In order to avoid this, it is known that a copolymer of a (meth)acrylate alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group is used, and a pressure-sensitive adhesive layer is crosslinked with the crosslinking agent ( Patent Document 1).

Further, it is proposed that a small amount of a copolymer of an alkyl (meth)acrylate and a copolymerizable compound containing a carboxyl group is blended in the same copolymer as described above, and an adhesive layer obtained by crosslinking the copolymer with a crosslinking agent is formed. However, if they are used to protect the surface of a plastic plate with a smooth surface due to their low surface tension, peeling phenomena such as lifting may occur due to heating during processing or storage, or re-peel when peeling at high speed, which is a manual area. There was also a problem of poor sex.

In order to solve these problems, a) 100 parts by weight of an alkyl (meth)acrylate containing an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms as a main component, b) 1 to 15 parts by weight of a copolymerizable compound containing a carboxyl group A pressure-sensitive adhesive composition comprising a copolymer of a monomer mixture obtained by adding parts and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms, and a crosslinking agent equivalent to or more than the carboxyl group of the component b). It has been proposed (Patent Document 2).

In the pressure-sensitive adhesive composition described in Patent Document 2, peeling, such as lifting, does not occur during processing or storage, and the increase in adhesion with time is small, so that the re-peelability is excellent, and long-term storage, especially in high-temperature atmosphere, is small. It is said that it is possible to re-peel with force, and at that time, no adhesive residue is generated on the adherend, and even when high-speed peeling is performed, re-peelability is possible with a small force.

In addition, (2) for those having fouling resistance, 0 parts by mass or more and less than 0.5 parts by mass of a carboxyl group-containing monomer, 0.6 to 9 parts by mass of a hydroxy group-containing (meth)acrylic monomer, and 99.4 to 90.5 parts by mass of a (meth)acrylic acid ester monomer. A pressure-sensitive adhesive composition comprising 100 parts by mass of a (meth)acrylic copolymer having a weight average molecular weight of 100,000 or more and less than 1 million; and 0.1 to 5 parts by mass of a carbodiimide crosslinking agent is disclosed (Patent Document 3).

The pressure-sensitive adhesive composition described in Patent Document 3 is characterized by using a carbodiimide-based cross-linking agent as a cross-linking agent for a (meth)acrylic copolymer having a specific composition. Thereby, a crosslinked structure capable of following the shrinkage due to pressure and temperature during autoclave treatment can be formed in the pressure-sensitive adhesive layer. For this reason, it is said that the pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive composition can suppress and prevent foaming even under high temperature and high pressure conditions (at the time of autoclave treatment), has excellent adherend contamination resistance, and also has excellent transparency.

In addition, as for (3) excellent antistatic performance, as a method for imparting antistatic properties to a surface protective film, a method of including an antistatic agent in a base film is known.

Antistatic agents include, for example, (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups, (b) sulfonate groups, sulfate ester bases, and phosphoric acid esters. Anionic antistatic agents having anionic groups such as bases and phosphonic acid groups, (c) amphoteric antistatic agents such as amino acid and amino sulfuric acid esters, (d) nonionics such as amino alcohols, glycerin and polyethylene glycols Antistatic agents, (e) high molecular weight antistatic agents, such as a high molecular weight antistatic agent as described above, are disclosed (Patent Document 4).

Further, in recent years, it has been proposed to contain such an antistatic agent in the base film or to contain it in the pressure-sensitive adhesive layer without being applied to the surface of the base film.

In addition, as an antistatic pressure-sensitive adhesive composition obtained by dispersing a salt having an anion having a fluoro group and a sulfonyl group, the salt having an anion having a fluoro group and a sulfonyl group is a polyether ester containing a polyether group in the main chain. An antistatic pressure-sensitive adhesive composition characterized in that it is dispersed in a state dissolved in a plasticizer is disclosed (Patent Document 5).

In the pressure-sensitive adhesive composition described in Patent Document 5, an ester formed of an alcohol having a mono or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group as a plasticizer and an alcohol having an acyclic hydrocarbon group having 1 to 20 carbon atoms, or the above unsaturated acyclic hydrocarbon group It is disclosed to use a plasticizer comprising an ester in which the unsaturated group in the hydrocarbon group is epoxidized. The mono or dicarboxylic acid having such a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to that of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer, thereby improving compatibility with the antistatic pressure-sensitive adhesive composition, Since it is preferably held in the plasticizer acrylic antistatic pressure-sensitive adhesive composition, bleed-out is suppressed.

Japanese Laid-Open Patent Publication No. 63-225677 Japanese Laid-Open Patent Publication No. Hei 11-256111 Japanese Unexamined Patent Publication No. 2011-122054 Japanese Laid-Open Patent Publication No. Hei 11-070629 Japanese Unexamined Patent Publication No. 2014-118469

As described above, in the prior art, as required performance for the pressure-sensitive adhesive layer constituting the surface protective film, having a balance of adhesive force in a low-speed peeling speed and a high-speed peeling speed, having stain resistance, and having excellent antistatic performance Has been demanded. However, although each individual required performance could be satisfied, all of the required performance required for the pressure-sensitive adhesive layer of the surface protection film could not be simultaneously satisfied.

Further, in the prior art, a pressure-sensitive adhesive layer that can be used for all of the surface substrates made of TAC, PMMA, and PET and satisfies all the required performances required for the pressure-sensitive adhesive layer of the surface protective film at the same time could not be produced.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a pressure-sensitive adhesive composition and a surface protective film having excellent balance of adhesive force in low-speed peeling speed and high-speed peeling speed, and having stain resistance and excellent adhesive performance. . In addition, it is a task to provide a pressure-sensitive adhesive composition and a surface protective film capable of forming a pressure-sensitive adhesive layer with the same pressure-sensitive adhesive composition, which can be used for a surface substrate made of TAC, PMMA, and PET, and has excellent antistatic performance without deteriorating with time. do.

In the pressure-sensitive adhesive composition with antistatic performance and the surface protective film using the same, the relationship between antistatic performance and stain resistance to an adherend is a trade-off relationship, and improving stain resistance while maintaining antistatic performance It was very difficult.

Accordingly, the inventors of the present invention have prepared a first acrylic polymer copolymerized with a copolymerizable monomer containing a carboxyl group without containing a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer, and a polyalkylene glycol. A melting point 25 having a second acrylic polymer containing a chain-containing mono(meth)acrylic acid ester monomer, and preferably a polyether-containing silicone compound and an anion having a fluorine atom number of F7 or more (for example, a nonafluorobutanesulfonate anion). This problem could be solved by setting it as the technical idea of this invention what it is the pressure-sensitive adhesive composition containing an antistatic agent which consists of an ionic compound of degreeC or more.

In order to solve the above problems, the present invention is a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, wherein the acrylic polymer is the following first acrylic polymer and the second acrylic polymer,

The first acrylic polymer,

(A) with respect to 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group,

(B) 1.0 to 6.0 parts by weight in total of at least one or more copolymerizable monomers containing a hydroxyl group,

(C) 0.01 to 0.6 parts by weight in total of at least one copolymerizable monomer containing a carboxyl group

It is the first acrylic polymer of a copolymer copolymerized without containing a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer and having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1.2 million,

The first acrylic polymer contains 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more in a total of 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the (A) alkyl group. Done,

The second acrylic polymer,

(a) at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group, and

(b) at least one or more copolymerizable monomers containing a hydroxyl group, and

(c) at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers

It is the second acrylic polymer of the copolymerized copolymer,

A glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0°C or less,

The crosslinking agent (D) is a trifunctional or higher isocyanate compound,

The antistatic agent (G) is an ionic compound having a melting point of 25 to 50°C, comprising a cation and an anion having an anion having an anion having a number of fluorine atoms of F7 or more,

There is provided a pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition further contains (E) a crosslinking retarder and (F) a crosslinking catalyst other than a tin compound as a crosslinking catalyst.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition for a surface protective film bonded to a polarizer protective layer of a polarizing plate, wherein the polarizer protective layer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and It is preferable that the surface treatment applied to the surface of the polarizer protective layer of the polarizing plate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

Wherein the anions of ionic compounds _{C 6 F 5 (CF 2)} n COO -, C 6 F 5 (CF 2) n SO 3 -, C 6 F 5 (CF 2) n O -, C 6 F 5 O ( ^{_{CF 2) n SO 3 -,}} (C 6 F 5 CO) 2 n -, (C 6 F 5 CO) 3 C -, (C 6 F 5 SO 2) 2 n -, (C 6 F 5 SO 2) ^{_{3 C -, (C 6 F}} 5 OSO 2) 2 N -, (C 6 F 5 OSO 2) 3 C -, (C 6 F 5) 4 B -, CF 3 (CF 2) 3 SO 3 - consisting of It is preferred that at least one selected from the group is contained as an anion, and the ionic compound is contained in a ratio of 0.01 to 15 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

The cation of the ionic compound is pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, lithium, It is one type selected from the group consisting of morpholium, and it is preferable to contain the ionic compound in a ratio of 0.01 to 15 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

The surface resistivity of the pressure-sensitive adhesive layer crosslinked with the pressure-sensitive adhesive composition is 1.0×10 ⁺¹² Ω/□ or less, and peeling of the pressure-sensitive adhesive layer to the low-refractive-index layer formed using the composition for forming a low-refractive-index layer containing a fluorine compound on the adherend The high voltage is in the range of -0.3 to +0.3 kV, and the adhesive force of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition to the polarizing plate at a low speed of 0.3 m/min is 0.04 to 0.2 N/25 mm, and the high-speed peeling speed It is preferable that the adhesive force at 30 m/min is 2.0 N/25 mm or less.

The (B) copolymerizable monomer containing a hydroxyl group of the first acrylic polymer and the (b) copolymerizable monomer containing a hydroxyl group of the second acrylic polymer are 8-hydroxyoctyl (meth)acrylate, 6-hydroxy Roxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy (meth)acrylamide, N-hydroxymethyl (meth)acrylamide , At least one selected from the group of compounds consisting of N-hydroxyethyl (meth)acrylamide, and the (C) copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (Meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth) ) In the compound group consisting of acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylmaleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyltetrahydrophthalic acid It is preferable that it is at least one or more selected.

The (E) crosslinking retardant is a ketoenol tautomer compound, and the (E) crosslinking retardant is contained in an amount of 0.1 to 300 parts by weight based on 100 parts by weight of the first acrylic polymer, and the (F) The crosslinking catalyst is at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound, and 0.001 to 0.5 weight of the (F) crosslinking catalyst per 100 parts by weight of the first acrylic polymer It contains in a ratio of parts, and it is preferable that the weight part ratio of said (E)/ said (F) is 80-1000.

It is preferable that the pressure-sensitive adhesive composition contains a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight average molecular weight of 10000 or less in a ratio of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

The pressure-sensitive adhesive composition contains the second acrylic polymer in a ratio of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the first acrylic polymer, and as the second acrylic polymer, (a) the alkyl group has C1 to C18 carbon atoms. (B) 2.0 to 12.0 parts by weight of a total of at least one copolymerizable monomer containing a hydroxyl group and (c) a mono containing a polyalkylene glycol chain based on 100 parts by weight of the total of at least one type of (meth)acrylic acid ester monomer It is preferable to use a copolymer obtained by copolymerizing a total of 1 to 30 parts by weight of at least one or more (meth)acrylic acid ester monomers. And as the weight average molecular weight of the said copolymer, more than 300,000 and 1 million or less are preferable, and especially, more than 300,000 and 800,000 or less are preferable.

In addition, (B) at least one copolymerizable monomer containing a hydroxyl group based on 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1-C18 carbon atoms in the (A) alkyl group of the first acrylic polymer. 100 parts by weight of at least one (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the (a) alkyl group of the second acrylic polymer (β1 = 100×(B)/(A)) The ratio (K = β2/β1) of at least one or more total weight parts (β2 = 100 × (b) / (a)) of at least one copolymerizable monomer containing a hydroxyl group to the part (K = β2 / β1) is within the range of 1.0 to 2.0 It is desirable.

The second acrylic polymer is a copolymer having a weight average molecular weight of more than 300,000 and not more than 800,000, and the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer constitutes a polyalkylene glycol chain. 3 to 14, the diester content in the polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer is 0.2% or less, and as the polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer, polyalkylene glycol mono (meta ) At least one selected from the group consisting of acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate from 1 to 50 parts by weight of the second acrylic polymer It is preferably contained in a proportion of parts by weight, more preferably 1 to 40 parts by weight, and particularly preferably 1 to 30 parts by weight.

Further, the present invention provides a pressure-sensitive adhesive film, characterized in that the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is laminated on one side of a resin film.

In addition, the present invention provides a surface protective film in which the adhesive film is used.

In addition, the present invention provides a surface protective film for a polarizing plate in which the adhesive film is used.

In addition, the present invention provides an optical film in which a pressure-sensitive adhesive layer is formed in which a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is laminated on at least one side of an optical film.

In addition, the present invention provides a pressure-sensitive adhesive film having antistatic treatment and antifouling treatment on one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed.

Advantageous Effects of Invention According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and a surface protective film having excellent balance of adhesive force in low-speed peeling speed and high-speed peeling speed, and having stain resistance and excellent adhesive performance. In addition, it is possible to provide a pressure-sensitive adhesive composition and a surface protective film capable of forming a pressure-sensitive adhesive layer with the same pressure-sensitive adhesive composition, which can be used for a surface substrate made of TAC, PMMA, and PET, and has excellent antistatic performance without deteriorating over time.

Hereinafter, the present invention will be described based on preferred embodiments.

The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, wherein the acrylic polymer is the following first acrylic polymer and a second acrylic polymer,

The first acrylic polymer,

(A) with respect to 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group,

(B) 1.0 to 6.0 parts by weight in total of at least one or more copolymerizable monomers containing a hydroxyl group,

(C) 0.01 to 0.6 parts by weight in total of at least one copolymerizable monomer containing a carboxyl group

It is the first acrylic polymer of a copolymer copolymerized without containing a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer and having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1.2 million,

The first acrylic polymer contains 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more in a total of 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the (A) alkyl group. Done,

The second acrylic polymer,

(a) at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group, and

(b) at least one or more copolymerizable monomers containing a hydroxyl group, and

(c) at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers

It is the second acrylic polymer of the copolymerized copolymer,

The glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0°C or less,

The crosslinking agent (D) is a trifunctional or higher isocyanate compound,

The antistatic agent (G) is an ionic compound having a melting point of 25 to 50°C, comprising a cation and an anion having an anion having an anion having a number of fluorine atoms of F7 or more,

The pressure-sensitive adhesive composition is characterized in that it further contains (E) a crosslinking retardant and (F) a crosslinking catalyst other than a tin compound as a crosslinking catalyst.

The pressure-sensitive adhesive composition according to the present embodiment has excellent adhesive performance and excellent peeling antistatic performance without deteriorating with time, as compared with the conventional pressure-sensitive adhesive composition for a surface protective film.

In particular, the surface protection film according to the present embodiment uses a composition for forming an antifouling layer containing a fluorine compound or a low refractive index layer containing a fluorine compound on the surface of an optical film, etc., on which an adherend such as an optical film is an adherend. In the case of laminating a low refractive index layer formed as a result, it has excellent adhesion performance and excellent peeling antistatic performance without deteriorating over time compared to the conventional surface protection film, and is remarkable that both antistatic performance and stain resistance can be achieved. It shows the effect.

That is, the pressure-sensitive adhesive composition according to the present embodiment and the surface protective film using the same have excellent adhesive performance and excellent peeling antistatic performance without deteriorating over time, and thus have great industrial value.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment is a main polymer of the pressure-sensitive adhesive composition, and has a glass transition temperature of 0°C or less. Further, the acrylic polymer is preferably a copolymer containing (A) a (meth)acrylic acid ester monomer having an alkyl group having C1 to C18 as a main component.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains a first acrylic polymer that does not contain a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer, and a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer. It is a second acrylic polymer.

The first acrylic polymer comprises (A) a (meth)acrylic acid ester monomer having an alkyl group having C1 to C18 carbon atoms, (B) a copolymerizable monomer containing a hydroxyl group, and (C) a copolymerizable monomer containing a carboxyl group. It is a copolymer having a glass transition temperature of 0°C or lower, which is copolymerized without containing a ene glycol chain-containing mono(meth)acrylic acid ester monomer. In addition, the second acrylic polymer comprises (a) at least one or more (meth)acrylic acid ester monomers having C1-C18 alkyl groups, (b) at least one or more copolymerizable monomers containing a hydroxyl group, and (c ) A copolymer having a glass transition temperature of 0° C. or less obtained by copolymerizing at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers.

Examples of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group of the first acrylic polymer and the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the second acrylic polymer (a) the alkyl group include methyl ( Meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl ( Meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylic Rate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, Heptadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic.

The first acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (A) 2-ethylhexyl acrylate in a total of 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group. It is preferable to contain it in a proportion of parts by weight or more.

The first acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (B) a copolymerizable monomer containing a hydroxyl group. Further, the second acrylic polymer contains (b) a copolymerizable monomer containing a hydroxyl group. Examples of the (B) copolymerizable monomer containing a hydroxyl group of the first acrylic polymer and the copolymerizable monomer containing (b) a hydroxyl group of the second acrylic polymer include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (Meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N -It is preferably at least one or more selected from the group of compounds consisting of hydroxyethyl (meth)acrylamide and the like.

The first acrylic polymer is (A) a total of at least one copolymerizable monomer containing a hydroxyl group based on 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group. It is preferable to contain in a ratio of -6.0 parts by weight, more preferably in a ratio of 1.6 to 5.8 parts by weight, and particularly preferably in a ratio of 2.1 to 5.8 parts by weight.

The second acrylic polymer is (a) a total of at least one or more copolymerizable monomers containing a hydroxyl group based on 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group. It is preferable to contain in a ratio of -12.0 parts by weight, more preferably in a ratio of 3.0 to 11.0 parts by weight, and particularly preferably in a ratio of 4.0 to 10.0 parts by weight.

The total weight part β1 of at least one or more copolymerizable monomers containing (B) hydroxyl groups in the first acrylic polymer is (A) at least one or more (meth)acrylic acid ester monomers having C1 to C18 alkyl groups. With respect to 100 parts by weight in total, it is expressed as β1 = 100×(B)/(A). Similarly, the total weight part β2 of at least one or more copolymerizable monomers containing (b) hydroxyl groups in the second acrylic polymer is (a) at least 1 of the (meth)acrylic acid ester monomers having C1-C18 alkyl groups. For a total of 100 parts by weight or more, it is expressed by β2 = 100×(b)/(a). The weight part β2 of (b) in the second acrylic polymer is preferably not less than the weight part β1 of (B) in the first acrylic polymer, and the ratio (K = β2/β1) is in the range of 1.0 to 2.0. desirable.

The first acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (C) a copolymerizable monomer containing a carboxyl group. (C) As a copolymerizable monomer containing a carboxyl group, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-( Meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylmaleic acid, carboxypoly It is preferably at least one or more selected from the group of compounds consisting of caprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid.

The first acrylic polymer comprises (A) the sum of at least one or more copolymerizable monomers containing a carboxyl group based on 100 parts by weight of the total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group. It is preferably contained in a proportion of 0.01 to 0.6 parts by weight, more preferably contained in a proportion of 0.01 to 0.5 parts by weight, and particularly preferably contained in a proportion of 0.01 to 0.4 parts by weight.

The second acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. For this reason, in the adhesive composition of this embodiment, it is considered that the 2nd acrylic polymer containing this (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer functions as an antistatic auxiliary agent. The second acrylic polymer is preferably contained in a proportion of 0.1 to 5.0 parts by weight, more preferably 0.1 to 3.5 parts by weight, and contained in a proportion of 0.1 to 2.5 parts by weight based on 100 parts by weight of the first acrylic polymer. It is particularly preferred to be.

When the content of the second acrylic polymer is less than the above range, the surface resistivity and the peeling electrification voltage increase, and the antistatic performance decreases. In addition, the contamination resistance to the polarizing plate is poor.

(c) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer may be a compound in which one hydroxyl group among a plurality of hydroxyl groups of the polyalkylene glycol is esterified as a (meth)acrylic acid ester. Since the (meth)acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the second acrylic polymer. Polyalkylene glycol mono(meth)acrylate in which other hydroxyl groups are OH as it is may be sufficient, and alkoxypolyalkylene glycol mono(meth)acrylate in which other hydroxyl groups are converted to alkyl ether may be used. On the other hand, since polyalkylene glycol mono(meth)acrylate corresponds to (c), even if it contains a hydroxyl group, it is not classified as (B) or (b).

The polyalkylene glycol constituting the polyalkylene glycol chain may be a glycol compound having one or two or more alkylene groups. For example, polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene Glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol, and the like.

(c) It is preferable that the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repetition number of 3 to 14 of the alkylene oxide constituting the polyalkylene glycol chain. "Average number of repetitions of alkylene oxide" means (c) the average of repeating alkylene oxide units in the "polyalkylene glycol chain" part contained in the molecular structure of the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. Is the number of

Moreover, it is preferable that the diester content in (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 0.2% or less. "The diester content in a monomer" is the content rate (weight%) of the polyalkylene glycol di(meth)acrylic acid ester contained in (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

(c) Polyalkylene glycol chain-containing mono (meth) acrylate monomers include polyalkylene glycol mono (meth) acrylate, methoxy polyalkylene glycol (meth) acrylate, and ethoxy polyalkylene glycol (meth). It is preferred that it is at least one or more selected from the group consisting of acrylates. The ratio of the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer in the second acrylic polymer is preferably 1 to 50 parts by weight, and 2 to 35 parts by weight based on 100 parts by weight of the second acrylic polymer. The proportion is more preferable, and the proportion of 2 to 25 parts by weight is particularly preferable.

In addition, (c) polyalkylene glycol mono (meth) acrylate, methoxy polyalkylene glycol (meth) acrylate, ethoxy polyalkylene glycol (meth) as a polyalkylene glycol chain-containing mono (meth) acrylate monomer ) It is preferable to contain at least one or more selected from the group consisting of acrylates in a ratio of 1 to 50 parts by weight of 100 parts by weight of the second acrylic polymer, more preferably 1 to 40 parts by weight, and 1 to 30 parts by weight. It is particularly preferred.

In addition, (a) at least one of (c) polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomers based on 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group. It is preferable that the total of more than one species is 1 to 30 parts by weight.

As monomers other than the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer copolymerized with the second acrylic polymer, the above-described (a) a (meth)acrylic acid ester monomer having C1 to C18 in the alkyl group and ( b) at least one or more of a copolymerizable monomer containing a hydroxyl group. The monomers (a) and (b) copolymerized with the second acrylic polymer may be different from the monomers (A) and (B) copolymerized with the first acrylic polymer. The second acrylic polymer does not need to copolymerize a copolymerizable monomer containing a carboxyl group.

The method for producing the acrylic polymer to be contained in the pressure-sensitive adhesive composition according to the present embodiment is not particularly limited, and a known polymerization method such as a solution polymerization method or an emulsion polymerization method may be appropriately used. The weight average molecular weight of the copolymer of the first acrylic polymer is, for example, more than 300,000 and 1.2 million or less. The weight average molecular weight of the copolymer of the second acrylic polymer may be, for example, more than 300,000 and 1 million or less, preferably more than 300,000 and 800,000 or less, and more than 400,000 and 800,000 or less.

When the weight average molecular weight of the copolymer of the second acrylic polymer is 300,000 or less, stain resistance to the polarizing plate is poor, which is not preferable.

It is preferable that the acid value of the first acrylic polymer is 0.1 to 1.0. Accordingly, contamination resistance can be improved. Here, the "acid value" is one of the indexes indicating the content of the acid, and is expressed as the number of mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group. The acid value of the second acrylic polymer is preferably 1.0 or less, and may be 0.0 when a copolymerizable monomer containing a carboxyl group is not copolymerized with the second acrylic polymer.

The pressure-sensitive adhesive composition according to the present embodiment contains (G) an antistatic agent. The antistatic agent (G) of the present embodiment is an ionic compound composed of an anion and a cation having an anion having a fluorine atom number of F7 or more. This ionic compound has a melting point of 25 to 50°C and is preferably solid at room temperature (eg, 25°C). It is preferable to contain the ionic compound in a ratio of 0.01 to 15 parts by weight, more preferably 0.01 to 10 parts by weight, and particularly preferably 0.01 to 8 parts by weight, based on 100 parts by weight of the first acrylic polymer.

As the anion of the ionic _{compound, C 6 F 5 (CF 2} ) n COO -, C 6 F 5 (CF 2) n SO 3 -, C 6 F 5 (CF 2) n O -, C 6 F 5 _{O (CF 2) n SO 3} -, (C 6 F 5 CO) 2 N -, (C 6 F 5 CO) 3 C -, (C 6 F 5 SO 2) 2 N -, (C 6 F 5 SO ^{_{2) 3 C -, (C}} 6 F 5 OSO 2) 2 N -, (C 6 F 5 OSO 2) 3 C -, (C 6 F 5) 4 B -, CF 3 (CF 2) 3 SO 3 - At least one or more selected from the group consisting of may be mentioned. Here, n is an integer of 1 or more.

Examples of the cation of the ionic compound include pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, At least one or more selected from the group consisting of lithium and morpholium may be mentioned.

(G) Specific examples of the antistatic agent include, for example, methyltrioctylammonium tris(pentafluorobenzenesulfonyl)methide salt, 3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, 1- Ethyl-3-methylimidazolium tetrakispentafluorophenylborate salt, 1-butyl-1-methylpiperidinium bis(pentafluorobenzenesulfonyl)imide salt, etc. are mentioned.

The pressure-sensitive adhesive composition according to the present embodiment further contains (D) a trifunctional or higher isocyanate compound as a crosslinking agent. (D) Examples of trifunctional or higher isocyanate compounds include biuret modified products and isocyanates of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. And adducts with trivalent or higher polyols such as a rate-modified product, trimethylolpropane, and glycerin. (D) The ratio of the trifunctional or higher isocyanate compound is, for example, a ratio of 0.01 to 5 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

The pressure-sensitive adhesive composition according to the present embodiment may contain (E) a crosslinking retarder. (E) As a crosslinking retardant, β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone, 2,4-hexanedione And β-diketones such as benzoyl acetone. These are ketoenol tautomer compounds, and in a pressure-sensitive adhesive composition using a polyisocyanate compound as a crosslinking agent, by blocking an isocyanate group possessed by the crosslinking agent, excessive viscosity increase or gelation of the pressure-sensitive adhesive composition after blending of the crosslinking agent is suppressed, and the pot of the pressure-sensitive adhesive composition Life can be extended. (E) The crosslinking retarder is preferably a ketoenol tautomer compound, and particularly preferably at least one or more selected from the group consisting of acetylacetone and ethyl acetoacetate. It is preferable to contain (E) a crosslinking retardant in a ratio of 0.1 to 300 parts by weight per 100 parts by weight of the first acrylic polymer.

The pressure-sensitive adhesive composition according to the present embodiment may contain a crosslinking catalyst other than a tin compound as (F) a crosslinking catalyst. (F) The crosslinking catalyst may be a material that functions as a catalyst for the reaction (crosslinking reaction) of the copolymer and the crosslinking agent when the polyisocyanate compound is used as a crosslinking agent. Examples of the crosslinking catalyst other than the tin compound include amine compounds such as tertiary amines, metal chelate compounds, organic lead compounds, and organometallic compounds such as organic zinc compounds.

(F) As a metal chelate compound of a crosslinking catalyst, it is a compound in which one or more polydentate ligand L bonded to a central metal atom M. The metal chelate compound may or may not have at least one monodentate ligand X bonded to the metal atom M. Specific examples of the metal chelate compound include tris (2,4-pentanedionate) iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris Acetylacetonate, zirconium tetrakisacetylacetonate, tris (2,4-hexanedionate) iron (III), bis (2,4-hexanedionate) zinc, tris (2,4-hexanedionate) titanium, Tris (2,4-hexanedionate) aluminum, tetrakis (2,4-hexanedionate) zirconium, and the like.

(F) The crosslinking catalyst is preferably at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound. It is preferable to contain the (F) crosslinking catalyst in a proportion of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

Since the (E) crosslinking retardant has an effect of suppressing crosslinking as opposed to the (F) crosslinking catalyst, it is preferable to appropriately set the ratio of the (E) crosslinking retardant and (F) the crosslinking catalyst. In order to lengthen the pot life of the pressure-sensitive adhesive composition and improve storage stability, it is preferable that the ratio of (E)/(F) by weight is 80 to 1000. Here, the weight part ratio of (E)/(F) is a value of the quotient obtained by dividing the weight part of (E) by the weight part of (F).

The pressure-sensitive adhesive composition according to the present embodiment may contain (H) a polyether-modified siloxane compound as an optional component. (H) The polyether-modified siloxane compound is a siloxane compound having a polyether group, and in addition to the usual siloxane unit [-SiR ¹ ₂ -O-], a siloxane unit having a polyether group [-SiR ¹ (R ² O(R ³ O)) ) _n R ⁴ )-O-]. Here, R ¹ is one or two or more alkyl or aryl groups, R ² and R ³ are one or two or more alkylene groups, and R ⁴ is one or two or more alkyl or acyl groups (terminal groups). Show. Examples of the polyether group include polyoxyalkylene groups such as polyoxyethylene group [(C ₂ H ₄ O) _n ] and polyoxypropylene group [(C ₃ H ₆ O) _n ]. In the siloxane unit having a polyether group, the terminal of the polyether group may be an OH group (R ⁴ =H in the above general formula).

(H) The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 6 to 12. Further, it is preferable that the (H) polyether-modified siloxane compound is contained in a ratio of 0.01 to 0.5 parts by weight, more preferably 0.02 to 0.35 parts by weight, more preferably 0.02 to 0.25 parts by weight, based on 100 parts by weight of the first acrylic polymer. The ratio is particularly preferred. The HLB value is, for example, a hydrophilic lipophilic balance (hydrophilic lipophilicity ratio) specified in JIS K3211 (terminal surfactant).

The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group to a polyorganosiloxane main chain having a silicon hydride group by hydrosilylation reaction. Specifically, dimethylsiloxane/methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxyethylene) siloxane/methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxypropylene) siloxane polymer, etc. Can be mentioned.

(H) By blending the polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the adhesive strength and rework performance of the pressure-sensitive adhesive layer can be improved. (H) It is preferable that the weight average molecular weight of the polyether-modified siloxane compound is 10000 or less. From the viewpoint of compatibility with the first acrylic polymer, the lower the HLB value and the lower the molecular weight, the better the compatibility.However, if the polyether-modified siloxane compound has a low molecular weight, the HLB value is relatively high and the compatibility with the polymer is slightly lower, but excellent charging. Prevention is obtained.

The pressure-sensitive adhesive composition of the present embodiment is not limited to the above-described additives, and known additives such as surfactants, curing accelerators, plasticizers, fillers, curing retardants, processing aids, anti-aging agents, and antioxidants may be appropriately blended. These can be used alone or in combination of two or more.

The pressure-sensitive adhesive composition of this embodiment is preferable as the pressure-sensitive adhesive composition for surface protective films bonded to the polarizer protective layer of a polarizing plate. Here, the polarizer protective layer of the polarizing plate includes at least one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film. Here, TAC is an abbreviation of triacetyl cellulose, PMMA is polymethyl methacrylate, and PET is an abbreviation of polyethylene terephthalate. The pressure-sensitive adhesive composition of this embodiment may be made usable for three or more types of surface substrates made of TAC, PMMA, and PET by the same pressure-sensitive adhesive layer.

Further, the surface treatment applied to the surface of the polarizer protective layer of the polarizing plate may be at least one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. Here, AG refers to anti-glare, LR refers to low reflection, and AR refers to anti-reflection. In the pressure-sensitive adhesive composition of this embodiment, the substrate on the surface of the polarizing plate is PMMA or PET, and it is possible to improve stain resistance for at least one or more of the AG-treated, LR-treated, AR-treated, AG-LR-treated, and AG-AR-treated adherends. I can.

In the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment, the surface resistivity of the pressure-sensitive adhesive layer is preferably 1.0×10 ⁺¹² Ω/□ or less, more preferably 5.0×10 ⁺¹¹ Ω/□ or less, and 1.0×10 ⁺¹¹ Ω/□ It is particularly preferable that it is the following. If the surface resistivity is large, the performance of discharging static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend becomes poor. For this reason, by making the surface resistivity sufficiently small, it is possible to suppress an influence on the adherend by reducing the peeling electrification voltage caused by static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend.

The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment has a peeling electrification voltage of -0.3 to +0.3 kV for the low-refractive-index layer formed by using the composition for forming a low-refractive-index layer containing a fluorine compound on the adherend surface. It is desirable to be internal. As the fluorine compound used in the composition for forming a low refractive index layer, a fluorine-containing copolymer such as one or two or more polymers such as fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates, fluorinated alkyl group-containing silane compounds, etc. Condensation products of. In the fluorine-containing copolymer, in addition to the fluorinated monomer, a non-fluorinated monomer such as olefins, vinyl ethers, and (meth)acrylates may be copolymerized. The low refractive index layer may be combined with a high refractive index layer or the like to form an antireflection layer.

The adhesive force of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of the present embodiment with respect to the polarizing plate at a low-speed peeling rate of 0.3 m/min is 0.04 to 0.2 N/25 mm, and the adhesive force at a high-speed peeling rate of 30 m/min is 2.0 N/25. It is preferable that it is mm or less, and it is more preferable that the adhesive force at a high-speed peeling speed of 30 m/min is 0.2 to 1.6 N/25 mm. As a result, performance in which the adhesive force is less changed depending on the peeling speed is obtained, and rapid peeling is possible even by high-speed peeling. Further, even when once peeling the surface protection film for reattachment, it is easy to peel from the adherend without requiring excessive force.

The gel fraction of the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment is preferably 95 to 100%, more preferably 97 to 100%. By such a high gel fraction, the adhesive strength does not become excessive at a low-speed peeling rate, the elution of unpolymerized monomers or oligomers from the copolymer is reduced, and rework properties and durability at high temperatures and high humidity are improved, and adherends Pollution can be suppressed.

The pressure-sensitive adhesive film of this embodiment is formed by forming a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of this embodiment on one side or both sides of a resin film. In addition, the surface protection film of this embodiment is a surface protection film formed by forming the adhesive layer which crosslinked the adhesive composition of this embodiment on one surface of a resin film. The pressure-sensitive adhesive composition of the present embodiment has excellent antistatic performance, has excellent balance of adhesive strength in low-speed peeling speed and high-speed peeling speed, and has stain resistance. For this reason, it can be used suitably as the use of the surface protection film of a polarizing plate.

Resin films, such as a polyester film, can be used as a release film (separator) which protects the base film of an adhesive layer and an adhesive surface.

Antistatic treatment and antifouling treatment may be applied on one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed. Examples of the antistatic treatment include application or inclusion of an antistatic agent. The antifouling treatment includes treatment with a silicone-based or fluorine-based releasing agent, a coating agent, or silica fine particles. The release film may be subjected to a release treatment with a silicone-based, fluorine-based, or long-chain alkyl-based releasing agent or the like on the side of the pressure-sensitive adhesive layer on the side to be joined with the adhesive surface.

In addition, by laminating the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment on at least one surface of the optical film, an optical film in which the pressure-sensitive adhesive layer is formed can be obtained. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare (anti-glare) film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness improving film. Devices to which the optical member is applied include a liquid crystal panel, an organic EL panel, and a touch panel.

In the case of an optical surface protective film and an adhesive film such as a surface protective film for a polarizing plate, it is preferable that the base film and the adhesive layer have sufficient transparency.

Example

Hereinafter, the present invention will be described in detail with reference to examples.

<Production of the first acrylic polymer>

[Example 1]

Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen gas. Then, a solvent (ethyl acetate) was added to the reaction apparatus together with 90 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of methyl acrylate, 5.5 parts by weight of 8-hydroxyoctyl acrylate, and 0.2 parts by weight of acrylic acid. Thereafter, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65° C. for 6 hours to obtain a first acrylic polymer used in Example 1.

[Examples 2 to 6 and Comparative Examples 1 to 3]

Examples 2 to 6 and Comparative Examples 1 to 3 were carried out in the same manner as in the first acrylic polymer solution used in Example 1, except that the composition of the monomer was as described in Table 1 (A) to (C), respectively. The 1st acrylic polymer solution used for was obtained.

<Production of adhesive composition and surface protection film>

[Example 1]

With respect to the first acrylic polymer solution of Example 1 prepared as described above, 2.0 parts by weight of a crosslinking agent (coronate HX), 9 parts by weight of a crosslinking retardant (acetylacetone), 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), Antistatic agent (methyltrioctylammonium tris (pentafluorobenzenesulfonyl) methide salt) 0.9 parts by weight, polyether-modified siloxane compound (HLB = 7) 0.05 parts by weight, copolymer B-1 (molecular weight 600,000) 0.2 parts Part was added and mixed with stirring to obtain the pressure-sensitive adhesive composition of Example 1. After applying this pressure-sensitive adhesive composition on a release film (silicone resin coated PET film), the solvent was removed by drying at 90°C to obtain a pressure-sensitive adhesive layer having a thickness of 20 μm. After that, by transferring the pressure-sensitive adhesive layer on which the release film was formed on the side opposite to the anti-static and anti-soiling side of the base film (antistatic and antifouling treated PET film on one side), ``Base film/adhesive layer/release The surface protective film of Example 1 which has a lamination structure of "film" was obtained.

[Examples 2 to 6 and Comparative Examples 1 to 3]

Examples 2 to 6 and Comparative Examples 1 to 3 were carried out in the same manner as the surface protective film of Example 1, except that the composition of the additive was as described in Table 1 (D) to (H) and Copolymer B, respectively. The surface protection film of was obtained.

In Table 1, the weight part of each component was calculated|required as 100 weight part of the total of (A) C1-C18 (meth)acrylic acid ester monomers of the alkyl group. On the other hand, "I-2" of Comparative Example 2 is conveniently described in the column (A), but does not correspond to (A) a (meth)acrylic acid ester monomer having an alkyl group having C1 to C18 carbon atoms.

On the other hand, in Table 1, each column of (D), (E), (F), (G), (H), and (Copolymer B) contains 100 parts by weight of the first acrylic polymer, and the content ratio of each component ( Parts by weight) are represented by numerical values in parentheses ().

In addition, the compound names of the abbreviation symbols of each component used in Table 1 are shown in Tables 2-3. The second acrylic polymer in the above-described embodiment is ``copolymer B,'' and the meaning of the abbreviated symbols of the component monomers (a), (b), and (c) are (A), (B), (I), respectively. ). On the other hand, Coronate (registered trademark) HX, HL and L are brand names of Tosoh Corporation, and Takenate (registered trademark) D-140N is a brand name of Mitsui Chemicals Corporation.

(G) Among the antistatic agents, all of G-1 to G-4 are solid ionic compounds having an anion having a fluorine atom number of F7 or higher and a melting point of 25°C or higher. G-5 is a solid ionic compound having an anion having a fluorine atom number of F5 and a melting point of 25°C or higher.

(H) Among the polyether-modified siloxane compounds, all of H-1 to H-6 have a weight average molecular weight of 10000 or less.

(I) Polyalkylene glycol chain-containing mono(meth)acrylic acid ester In the monomers I-1 to I-3, the diester content in the monomer is 0.2% or less, and in I-4, the diester content in the monomer is 0.8%. In addition, n in the (I) group column of Table 3 is a numerical value showing the average repeat number of the alkylene oxide.

<Test method and evaluation>

The surface protective films in Examples 1 to 6 and Comparative Examples 1 to 3 were aged for 7 days in an atmosphere at 23°C and 50% RH, respectively, and then evaluated by the following test method.

<Test method of adhesive force>

After peeling the release film to expose the pressure-sensitive adhesive layer, the surface protective film was bonded to the surface of the polarizing plate through the pressure-sensitive adhesive layer, left to stand for 1 day, then autoclaved at 50°C, 5 atm, 20 minutes, and left at room temperature for an additional 12 hours What was done was used as the measurement sample of adhesive force. The obtained measurement sample was peeled at a low speed (0.3 m/min) or a high speed (30 m/min) using a tensile tester in the 180° direction, and the measured peel strength was taken as the adhesive force.

Here, the polarizer protective layer of the polarizing plate is one selected from the group consisting of triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET).

Further, in the LR polarizing plate and the AG-LR polarizing plate, the surface of the polarizer protective layer of the polarizing plate is a composition containing a fluorine compound and has been subjected to a low-reflection surface treatment.

<Test method of surface resistivity>

After aging the surface protection film, before bonding to the polarizing plate, the release film was peeled to expose the pressure-sensitive adhesive layer, and the surface resistivity of the pressure-sensitive adhesive layer was measured using a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech). .

<Test method of peeling large voltage>

The surface protective film from which the release film was peeled to expose the pressure-sensitive adhesive layer was bonded to a polarizing plate having a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound on the adherend. When the surface protection film is peeled 180° at a tensile speed of 30 m/min, the voltage (high voltage) generated by charging the adherend is measured using high-precision electrostatic sensors SK-035 and SK-200 (manufactured by Keyence Corporation). And the maximum value of the measured value was taken as the peeling voltage.

<Test method for stain resistance>

On one side of the glass plate, each polarizing plate selected from the five types shown in Table 4 was bonded through an adhesive layer (double-sided adhesive tape) using a bonding machine. Then, the surface protection film was attached to the surface of each polarizing plate using a bonding machine. After storage over a period of 3 days and 30 days in an environment of 23°C and 50% RH, the surface protection film was peeled off, and the contamination state of the surface of the polarizing plate was visually observed. The stain resistance judgment criterion evaluated each polarizing plate surface as "○" for no contamination, "△" for a slight contamination, and "x" for the presence of contamination.

Table 4 shows the evaluation results for the surface protective films in Examples 1 to 6 and Comparative Examples 1 to 3. "Surface resistivity" was expressed in accordance with the method in which "m×10 ⁺ⁿ " is "mE+n" (where m is an arbitrary real value and n is a positive integer). The column "staining resistance (surface substrate/surface treatment)" shows the evaluation results for each material and surface treatment of the five types of polarizing plate surface substrates (polarizer protective layer). Plain of "surface treatment" means untreated.

The surface protection films of Examples 1 to 6 had an adhesive strength of 0.04 to 0.2 N/25 mm to a polarizing plate as an adherend at a low-speed peeling rate of 0.3 m/min, and an adhesive strength of 2.0 N/25 mm at a high-speed peeling speed of 30 m/min. The adhesion performance was excellent below.

In addition, the surface protective films of Examples 1 to 6 have a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less of the pressure-sensitive adhesive layer, and a low refractive index layer formed using the composition for forming a low refractive index layer containing a fluorine compound on the adherend surface. The peeling voltage of the pressure-sensitive adhesive layer was within the range of -0.3 to +0.3 kV, and the antistatic performance was excellent.

In addition, even after storing the surface protective films of Examples 1 to 6 over a period of 3 days and 30 days, there was no contamination to the polarizing plate as an adherend, and the contamination resistance was also excellent.

That is, from the evaluation results shown in Table 4 for the surface protective films of Examples 1 to 6, it has been demonstrated that the subject of the present invention can be solved.

In the pressure-sensitive adhesive composition of Comparative Example 1, the weight average molecular weight of the copolymer B-5 is as small as 10,000. Moreover, the diester content of I-4 contained in the copolymer B-5 is as large as 0.8%, and the average repetition number n=23 is large. In addition, the component (b) contained in the copolymer B-5 of the second acrylic polymer is 3 parts by weight, which is less than 5.5 parts by weight of the component (B) contained in the first acrylic polymer. The surface protective film of Comparative Example 1 using this pressure-sensitive adhesive composition has excellent stain resistance for the conventionally used TAC-based polarizing plate, but the stain resistance is somewhat inferior to the two types of polarizing plates based on PMMA or PET. .

Further, in the pressure-sensitive adhesive composition of Comparative Example 2, a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is copolymerized with the first acrylic polymer, and the proportion of (B) a copolymerizable monomer containing a hydroxyl group is as large as 6.5 parts by weight. The surface protective film of Comparative Example 2 using such a pressure-sensitive adhesive composition has a low adhesive strength of 0.03 N/25 mm at a low-speed peeling rate of 0.3 m/min, poor adhesive performance, and poor stain resistance for two types of polarizing plates. , The stain resistance was somewhat poor for the other type of polarizing plate.

In addition, in the pressure-sensitive adhesive composition of Comparative Example 3, (C) the ratio of the copolymerizable monomer containing a carboxyl group is as large as 1.5 parts by weight, and the antistatic agent contains an anion of F5 having less than F7 of fluorine atoms. The surface protective film of Comparative Example 3 using such a pressure-sensitive adhesive composition has a high peeling electrification voltage of 0.6 kV and poor antistatic performance, and also has poor stain resistance for three types of polarizing plates, and has poor stain resistance for another type of polarizing plate. This was rather poor.

Thus, in the surface protective film of Comparative Examples 1 to 3, the subject of the present invention could not be solved.

On the other hand, in the case of the surface protective film prepared in the same manner as in Example 1 except that the copolymer B was not contained, the surface resistivity was increased, the peeling voltage was increased, the antistatic performance was poor, and the polarizing plate was Pollution resistance was also poor.

Claims (8)

A pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, wherein the acrylic polymer is the following first acrylic polymer and a second acrylic polymer,
The first acrylic polymer,
(A) 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group,
(B) 1.0 to 6.0 parts by weight in total of at least one or more copolymerizable monomers containing a hydroxyl group,
(C) 0.01 to 0.6 parts by weight in total of at least one copolymerizable monomer containing a carboxyl group
It is the first acrylic polymer of a copolymer copolymerized without containing a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer and having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1.2 million,
The first acrylic polymer contains 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more in a total of 100 parts by weight of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the (A) alkyl group Done,
The second acrylic polymer,
(a) at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group, and
(b) at least one or more copolymerizable monomers containing a hydroxyl group, and
(c) at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers
It is the second acrylic polymer of the copolymerized copolymer,
The diester content in the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 0.2% or less,
A glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0°C or less,
The crosslinking agent (D) is a trifunctional or higher isocyanate compound,
The antistatic agent (G) is an ionic compound having a melting point of 25 to 50°C consisting of a cation and an anion having an anion having a fluorine atom number of F7 or more,
The pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition further contains (E) a crosslinking retardant and (F) a crosslinking catalyst other than a tin compound as a crosslinking catalyst. The method of claim 1,
A pressure-sensitive adhesive composition for a surface protective film bonded to a polarizer protective layer of a polarizing plate, wherein the polarizer protective layer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and further protects the polarizer of the polarizing plate. A pressure-sensitive adhesive composition, wherein the surface treatment applied to the surface of the layer is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. The method according to claim 1 or 2,
Wherein the anions of ionic compounds _{C 6 F 5 (CF 2)} n COO -, C 6 F 5 (CF 2) n SO 3 -, C 6 F 5 (CF 2) n O -, C 6 F 5 O ( ^{_{CF 2) n SO 3 -,}} (C 6 F 5 CO) 2 N -, (C 6 F 5 CO) 3 C -, (C 6 F 5 SO 2) 2 N -, (C 6 F 5 SO 2) ^{_{3 C -, (C 6 F}} 5 OSO 2) 2 N -, (C 6 F 5 OSO 2) 3 C -, (C 6 F 5) 4 B -, CF 3 (CF 2) 3 SO 3 - consisting of Consisting of containing at least one or more selected from the group (where n is an integer of 1 or more) as an anion,
A pressure-sensitive adhesive composition comprising 0.01 to 15 parts by weight of the ionic compound with respect to 100 parts by weight of the first acrylic polymer. The method according to claim 1 or 2,
The cation of the ionic compound is pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, lithium, It is one kind selected from the group consisting of morpholium,
A pressure-sensitive adhesive composition comprising 0.01 to 15 parts by weight of the ionic compound with respect to 100 parts by weight of the first acrylic polymer. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition is made by containing the second acrylic polymer in a ratio of 0.1 to 5.0 parts by weight relative to 100 parts by weight of the first acrylic polymer,
The second acrylic polymer,
(a) 100 parts by weight in total of at least one or more (meth)acrylic acid ester monomers having C1-C18 carbon atoms in the alkyl group,
(b) 2.0 to 12.0 parts by weight of a total of at least one copolymerizable monomer containing a hydroxyl group,
(c) 1 to 30 parts by weight in total of at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers
It is a copolymerized copolymer,
(B) the total of at least one copolymerizable monomer containing a hydroxyl group to 100 parts by weight of the total of at least one or more (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the (A) alkyl group of the first acrylic polymer 100 parts by weight (β1 = 100×(B)/(A)) and at least one (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the (a) alkyl group of the second acrylic polymer in total The ratio (K = β2 / β1) of at least one or more total weight parts (β2 = 100 × (b) / (a)) of the copolymerizable monomer containing a hydroxyl group to (b) is within the range of 1.0 to 2.0. Pressure-sensitive adhesive composition. An adhesive film, wherein an adhesive layer obtained by crosslinking the adhesive composition of claim 1 or 2 is laminated on one side of a resin film. A surface protective film for a polarizing plate in which the adhesive film of claim 6 is used. An optical film in which a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of claim 1 or 2 is laminated on at least one side of the optical film.