JP6799517B2 - Adhesive composition and surface protective film - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition containing an antistatic agent and a surface protective film. More specifically, it has excellent adhesive performance for a surface protective film used for protecting the surface of a polarizing plate by being attached to a polarizing plate constituting a liquid crystal display, and excellent without deterioration over time. The present invention relates to a pressure-sensitive adhesive composition having antistatic performance and a surface protective film using the same.

Conventionally, in the manufacturing process of an optical member such as a polarizing plate, which is a member constituting a liquid crystal display, a surface protective film for temporarily protecting the surface of the optical member is attached. Such a surface protective film is used only in the process of manufacturing the optical member, and is peeled off from the optical member and removed when the optical member is incorporated into the liquid crystal display. Since such a surface protective film for protecting the surface of the optical member is used only in the manufacturing process, it is also generally called a process film.

In the surface protective film used in the process of manufacturing the optical member as described above, an adhesive layer is formed on one side of an optically transparent polyethylene terephthalate (PET) resin film. A release-treated release film for protecting the pressure-sensitive adhesive layer is bonded onto the pressure-sensitive adhesive layer until it is bonded to the optical member.
In addition, optical members such as polarizing plates undergo product inspections with optical evaluations such as display capability, hue, contrast, and foreign matter contamination of the liquid crystal display board with the surface protective film attached.
Therefore, as the required performance of the surface protective film, it is required that bubbles, foreign substances, and low molecular weight components of the pressure-sensitive adhesive composition do not adhere to the pressure-sensitive adhesive layer, that is, it has stain resistance.
Further, when the surface protective film is peeled off from an optical member such as a polarizing plate, the peeling charge generated by the static electricity generated when the adhesive layer is peeled off from the adherend affects the failure of the electric control circuit of the liquid crystal display. There is concern about doing so. Therefore, the pressure-sensitive adhesive layer is required to have excellent antistatic performance.
Furthermore, in recent years, as a protective layer (sometimes called a protective film) for the polarizing element of the polarizing plate, in addition to the conventional triacetyl cellulose (TAC), an acrylic resin such as polymethyl methacrylate (PMMA) and polyethylene terephthalate The use of materials such as polyester resins such as (PET), cyclic olefin polymers, and polycarbonates that easily cause peeling charge when the surface protective film of the polarizing plate is peeled off is increasing. Therefore, it is required that the antistatic performance required for the pressure-sensitive adhesive layer for the surface protective film of the polarizing plate is superior to that of the conventional one.
Further, when the surface protective film is finally peeled off from an optical member such as a polarizing plate, it is required to be able to peel off quickly. It is required that the adhesive strength does not change much depending on the peeling speed so that the peeling can be performed quickly even by so-called high-speed peeling.

As described above, in recent years, as the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (1) balancing the adhesive strength at a low peeling speed and a high peeling speed, and (2) stain resistance. It is required to have properties, (3) excellent antistatic performance, etc. from the viewpoint of ease of use when using a surface protective film.
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 pressure-sensitive adhesive layer for the surface protective film is required. It has been a difficult task to satisfy all the required performances (1) to (3) at the same time. Further, other than TAC, which is a conventionally used base material, the surface of a base material such as an acrylic resin such as polymethylmethacrylate (PMMA), a polyester resin such as polyethylene terephthalate (PET), a cyclic olefin polymer, and polycarbonate. It is also a very difficult task to form a pressure-sensitive adhesive layer of a surface protective film that can be used with respect to the above (1) to (3) from the same pressure-sensitive adhesive composition.

In order to solve such problems, for example, (1) balancing the adhesive force at a low peeling speed and a high peeling speed, (2) having stain resistance, and (3) The following proposals are known for excellent antistatic performance.

(1) Regarding balancing the adhesive strength at a low peeling speed and a high peeling speed, a (meth) acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymer compound. In the acrylic pressure-sensitive adhesive layer, which contains a copolymer of the above as a main component and is crosslinked with a cross-linking agent, the pressure-sensitive adhesive is transferred to the adherend side when adhered for a long period of time, and also to the adherend. There was a problem that the adhesive strength increased with time. In order to avoid this, a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymer compound having an alcoholic hydroxyl group was used, and this was crosslinked with a crosslinking agent. Those provided with an adhesive layer are known (Patent Document 1).
Further, a copolymer obtained by blending a small amount of a copolymer of a (meth) acrylic acid alkyl ester and a carboxyl group-containing copolymer in a copolymer similar to the above and cross-linking the copolymer with a cross-linking agent is provided. Etc. have been proposed. However, when these are used to protect the surface of plastic plates with low surface tension and a smooth surface, there is a problem that peeling phenomena such as floating occur due to heating during processing and storage, and at high speeds, which is a manual work area. There is also a problem that the re-peelability at the time of peeling is inferior.

In order to solve these problems, a) 100 parts by weight of the (meth) acrylic acid alkyl ester containing a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms as a main component b) contains a carboxyl group. The above b is added to a copolymer of a monomer mixture obtained by adding 1 to 15 parts by weight of a copolymerizable compound and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms. A pressure-sensitive adhesive composition in which an equivalent amount or more of a cross-linking agent is added to the carboxyl group of the component) has been proposed (Patent Document 2).
The pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as floating during processing or storage, and moreover, it has a small adhesive strength with time and is excellent in re-peeling property. It is said that it can be re-peeled with a small force even after long-term storage, especially in a high-temperature atmosphere, without leaving adhesive residue on the adherend, and it can be re-peeled with a small force even when high-speed peeling is performed.

Regarding (2) having stain resistance, a carboxyl group-containing monomer of 0 parts by mass or more and less than 0.5 parts by mass, a hydroxy group-containing (meth) acrylic monomer of 0.6 to 9 parts by mass, and 99. 100 parts by mass of (meth) acrylic copolymer consisting of 4 to 90.5 parts by mass of (meth) acrylic acid ester monomer and having a weight average molecular weight of 100,000 or more and less than 1 million; and carbodiimide-based cross-linking agent 0.1 A pressure-sensitive adhesive composition containing up to 5 parts by mass is disclosed (Patent Document 3).
The pressure-sensitive adhesive composition described in Patent Document 3 is characterized in that a carbodiimide-based cross-linking agent is used as a cross-linking agent for a (meth) acrylic copolymer having a specific composition. Thereby, the pressure-sensitive adhesive layer can be provided with a crosslinked structure capable of following the shrinkage due to pressure and temperature during the autoclave treatment. Therefore, 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 (during autoclave treatment), has excellent adherend contamination resistance, and is also excellent. , It is said that it is also excellent in transparency.

Further, regarding (3) excellent antistatic performance, a method of kneading an antistatic agent into the base film is shown as a method for imparting antistatic properties to the surface protective film.
Examples of the antistatic agent include (a) various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a primary to tertiary amino group, and (b) a sulfonic acid base and a sulfuric acid. Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases, and phosphonic acid bases, (c) amphoteric antistatic agents such as amino acid-based and aminosulfate-based, (d) aminoalcohol-based, and glycerin-based. , Nonionic antistatic agents such as polyethylene glycol type, (e) high molecular weight antistatic agents obtained by increasing the molecular weight of the above antistatic agents, and the like are disclosed (Patent Document 4).
Further, in recent years, it has been proposed that such an antistatic agent is contained in the base film, or is directly contained in the pressure-sensitive adhesive layer instead of being applied to the surface of the base film.

Further, the antistatic pressure-sensitive adhesive composition in which a salt having an anion having a fluoro group and a sulfonyl group is dispersed, and the salt having an anion having a fluoro group and a sulfonyl group is a polyether group. (Patent Document 5) discloses an antistatic pressure-sensitive adhesive composition characterized in that it is dispersed in a state of being dissolved in a polyether ester-based plasticizer containing the above (Patent Document 5).
In the pressure-sensitive adhesive composition described in Patent Document 5, 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 are used. It is disclosed to use an ester formed from or a plasticizer composed of an ester in which the unsaturated group in the unsaturated acyclic 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 for the pressure-sensitive adhesive layer. As a result, the compatibility with the antistatic pressure-sensitive adhesive composition is improved, and the plasticizer is suitably retained in the acrylic antistatic pressure-sensitive adhesive composition, so that bleed-out is suppressed.

JP-A-63-225677 Japanese Unexamined Patent Publication No. 11-256111 Japanese Unexamined Patent Publication No. 2011-12254 Japanese Unexamined Patent Publication No. 11-070629 Japanese Unexamined Patent Publication No. 2014-118469

As described above, in the prior art, the required performance for the adhesive layer constituting the surface protective film is to balance the adhesive force at a low peeling speed and a high peeling speed, and to have stain resistance. Although excellent antistatic performance has been required, it has not been possible to satisfy all the required performances required for the adhesive layer of the surface protective film at the same time, although each of them can satisfy the required performances.
Further, in the prior art, a pressure-sensitive adhesive layer that can be used for all surface substrates composed of TAC, PMMA, and PET and that simultaneously satisfies all the required performances required for the pressure-sensitive adhesive layer of the surface protective film. Could not be manufactured.

The present invention has been made in view of the above circumstances, and has an excellent balance of adhesive strength at a low peeling speed and a high peeling speed, and further has stain resistance and excellent adhesive performance. Further, a pressure-sensitive adhesive composition that can be used for a surface substrate composed of TAC, PMMA, and PET, and can form a pressure-sensitive adhesive layer having excellent antistatic performance without deterioration over time from the same pressure-sensitive adhesive composition and An object of the present invention is to provide a surface protective film.

In the pressure-sensitive adhesive composition having antistatic performance and the surface protective film using the same, the relationship between the antistatic performance and the stain resistance to the adherend is a trade-off relationship, and the antistatic performance is maintained. However, it was extremely difficult to improve the stain resistance.
Therefore, the inventors of the present invention have obtained a copolymerization of a copolymerizable monomer containing a carboxyl group without containing a polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer in the pressure-sensitive adhesive composition. 1 Acrylic polymer, a second acrylic polymer containing a polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer, preferably a polyether-containing silicone compound, and an anion having F7 or more fluorine atoms (for example). , Nonafluorobutane sulfonate anion), and a pressure-sensitive adhesive composition containing an ionic compound having a melting point of 25 ° C. or higher, is a technical idea of the present invention to solve this problem. We were able to.

In order to solve the above problems, the present invention is a pressure-sensitive adhesive composition containing an acrylic polymer, an antioxidant, and a cross-linking agent, wherein the acrylic polymer is the next first acrylic polymer. , A second acrylic polymer,
The first acrylic polymer is
(A) With respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group.
(B) The total of at least one or more copolymerizable monomers containing a hydroxyl group is 1.0 to 6.0 parts by weight.
(C) The total of at least one or more copolymerizable monomers containing a carboxyl group is 0.01 to 0.6 parts by weight.
, A copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and 1.2 million or less, which is copolymerized without containing a polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer. It is the first acrylic polymer of
The first acrylic polymer contains 70 parts by weight of 2-ethylhexyl acrylate out of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group. It is contained in the above ratio
The second acrylic polymer is
(A) At least one or more (meth) acrylic acid ester monomers having an alkyl group having C1 to C18 carbon atoms.
(B) At least one type of copolymerizable monomer containing a hydroxyl group and
(C) At least one or more of polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers and
Is a second acrylic polymer having a weight average molecular weight of more than 300,000 and 800,000 or less of the copolymer obtained by copolymerizing the above.
The (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer has an average number of repetitions of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14.
The diester content in the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is 0.2% or less.
The glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0 ° C. or lower.
The cross-linking agent is (D) a trifunctional or higher functional isocyanate compound.
The antistatic agent is an ionic compound having a (G) fluorine atom having an anion of F7 or more and having a melting point of 25 to 50 ° C. consisting of a cation and an anion.
Provided is a pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition further contains (E) a cross-linking retarder and (F) a cross-linking catalyst other than a tin compound as a cross-linking catalyst.

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

The anions of the ionic compounds are 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 selected from the above 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. It is preferable to do so.

The cation of the ionic compound is one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium and morpholinium. It is preferable that the ionic compound is contained in a ratio of 0.01 to 15 parts by weight with respect to 100 parts by weight of 1 acrylic polymer.

A composition for forming a low refractive index layer in which the surface resistance of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 1.0 × 10 ^{+ 12} Ω / □ or less and the adherend surface contains a fluorine compound. The peeling band voltage of the pressure-sensitive adhesive layer with respect to the low refractive index layer formed in use is in the range of −0.3 to +0.3 kV, and the polarization of the pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition. The adhesive strength to the plate at a low speed peeling speed of 0.3 m / min is 0.04 to 0.2 N / 25 mm, and the adhesive strength at a high speed peeling speed of 30 m / min is 2.0 N / 25 mm or less. Is preferable.

The copolymerizable monomer containing the (B) hydroxyl group of the first acrylic polymer and the copolymerizable monomer containing the (b) hydroxyl group of the second acrylic polymer are 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-hydroxy At least one selected from the compound group consisting of ethyl (meth) acrylamide, and the copolymerizable monomer containing the (C) carboxyl group is (meth) acrylic acid or carboxyethyl (meth) acrylate. , Carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- From a group of compounds consisting of (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid. It is preferably at least one selected.

The (E) cross-linking retarder is a compound of a ketoenol tether, and the ratio of the (E) cross-linking retarder is 0.1 to 300 parts by weight with respect to 100 parts by weight of the first acrylic polymer. The cross-linking catalyst (F) 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 is the first acrylic-based compound. The cross-linking catalyst (F) is contained in a ratio of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the polymer, and the ratio of parts (E) to parts (F) by weight is 80 to. It is preferably 1000.

The pressure-sensitive adhesive composition comprises 0.01 to 0.5 of a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight average molecular weight of 10,000 or less with respect to 100 parts by weight of the first acrylic polymer. It is preferably contained in a proportion of parts by weight.

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 the second acrylic polymer is contained. As a polymer, (a) at least one copolymerizable monomer containing a hydroxyl group with respect to at least one kind of (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in total of 100 parts by weight. A total of one or more types is 2.0 to 12.0 parts by weight, and a total of at least one type of (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is 1 to 30 parts by weight. It is preferable to use a polymerized copolymer. The weight average molecular weight of the copolymer is preferably more than 300,000 and less than 1 million, and particularly preferably more than 300,000 and less than 800,000.
Further, the (A) alkyl group of the first acrylic polymer can be copolymerized with the (B) hydroxyl group with respect to at least one or more 100 parts by weight of at least one of the (meth) acrylic acid ester monomers having C1 to C18 carbon atoms. Β1 = 100 × (B) / (A) in total by weight of at least one of the above-mentioned monomers, and (meth) acrylic acid having (a) alkyl groups having C1 to C18 carbon atoms in the second acrylic polymer. (B) Ratio K of at least one or more copolymerizable monomers containing a hydroxyl group to a total of 100 parts by weight β2 = 100 × (b) / (a) of at least one type of ester monomer. = Β2 / β1 is preferably in the range of 1.0 to 2.0.

The second acrylic polymer is a copolymer having a weight average molecular weight of more than 300,000 and 800,000 or less, and the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer constitutes an alkylene oxide forming a polyalkylene glycol chain. The average number of repetitions of the above is 3 to 14, the diester content in the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is 0.2% or less, and the polyalkylene glycol chain-containing mono (meth) acrylic acid. As the ester monomer, at least one selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate is selected from the second acrylic type. It is preferably contained in a proportion of 1 to 50 parts by weight based on 100 parts by weight of the polymer, more preferably 1 to 40 parts by weight, and particularly preferably 1 to 30 parts by weight.

The present invention also provides an adhesive film characterized in that an adhesive layer obtained by cross-linking the above-mentioned adhesive composition is laminated on one side of the resin film.

The present invention also provides a surface protective film in which the above-mentioned adhesive film is used.

The present invention also provides a surface protective film for a polarizing plate using the above-mentioned adhesive film.

The present invention also provides an optical film with a pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer obtained by cross-linking the above-mentioned pressure-sensitive adhesive composition is laminated on at least one surface of the optical film.

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

According to the present invention, a surface made of TAC, PMMA, and PET has an excellent balance of adhesive strength, stain resistance, and excellent adhesive performance at a low peeling speed and a high peeling speed. It is possible to provide an adhesive composition and a surface protective film that can be used for a base material and can form an adhesive layer having excellent antistatic performance without deterioration over time from the same adhesive composition.

Hereinafter, the present invention will be described based on a preferred embodiment.
The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition containing an acrylic polymer, an antioxidant, and a cross-linking agent, and the acrylic polymer is the following first acrylic polymer and the first 2 Acrylic polymer,
The first acrylic polymer is
(A) With respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group.
(B) The total of at least one or more copolymerizable monomers containing a hydroxyl group is 1.0 to 6.0 parts by weight.
(C) The total of at least one or more copolymerizable monomers containing a carboxyl group is 0.01 to 0.6 parts by weight.
, A copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and 1.2 million or less, which is copolymerized without containing a polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer. It is the first acrylic polymer of
The first acrylic polymer contains 70 parts by weight of 2-ethylhexyl acrylate out of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group. It is contained in the above ratio
The second acrylic polymer is
(A) At least one or more (meth) acrylic acid ester monomers having an alkyl group having C1 to C18 carbon atoms.
(B) At least one type of copolymerizable monomer containing a hydroxyl group and
(C) At least one or more of polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers and
It is a second acrylic polymer of the copolymer obtained by copolymerizing the above.
The glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0 ° C. or lower.
The cross-linking agent is (D) a trifunctional or higher functional isocyanate compound.
The antistatic agent is an ionic compound having a (G) fluorine atom having an anion of F7 or more and having a melting point of 25 to 50 ° C. consisting of a cation and an anion.
The pressure-sensitive adhesive composition is further characterized by containing (E) a cross-linking retarder and (F) a cross-linking catalyst other than a tin compound as a cross-linking catalyst.

The pressure-sensitive adhesive composition according to the present embodiment has excellent pressure-sensitive adhesive performance and excellent peeling antistatic performance without deterioration over time as compared with the conventional pressure-sensitive adhesive composition for surface protective films.
In particular, the surface protective film according to the present embodiment has an antifouling layer containing a fluorine compound or a low amount containing a fluorine compound on the surface of the optical film or the like on which an adherend such as an optical film is an adherend surface. In the case of laminating low refractive index layers formed by using the composition for forming a refractive index layer, it is superior in adhesive performance and without deterioration over time as compared with the surface protective film according to the prior art. It has peeling antistatic performance, and has a remarkable effect on both antistatic performance and stain resistance.
That is, the pressure-sensitive adhesive composition according to the present embodiment and the surface protective film using the pressure-sensitive adhesive composition have excellent adhesive performance and excellent peeling antistatic performance without deterioration over time, and thus have an industrial utility value. Is extremely large.

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

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment includes a first acrylic polymer containing no polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer and a polyalkylene glycol chain-containing mono (meth) acrylic acid. It is a second acrylic polymer containing an ester monomer.

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

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) having the (a) alkyl group carbon number of C1 to C18 in the second acrylic polymer. Acrylate ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and heptyl. (Meta) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (Meta) 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 can be mentioned. 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 is out of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C1 to C18 carbon atoms. , 2-Ethylhexyl acrylate is preferably contained in an amount of 70 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) hydroxyl-containing copolymerizable monomer of the first acrylic polymer and the (b) hydroxyl-containing copolymerizable monomer 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-hydroxyethyl (meth) ) It is preferable that at least one selected from the group of compounds consisting of acrylamide and the like.

The first acrylic polymer is a copolymer containing (B) a hydroxyl group with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C1 to C18 carbon atoms. 2. The total of at least one of the possible monomers is preferably contained in a proportion of 1.0 to 6.0 parts by weight, more preferably 1.6 to 5.8 parts by weight. It is particularly preferable to contain it in a proportion of 1 to 5.8 parts by weight.

The second acrylic polymer is a copolymer containing (b) a hydroxyl group with respect to (a) at least one kind of (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in total of 100 parts by weight. 4. The total of at least one of the possible monomers is preferably contained in a proportion of 2.0 to 12.0 parts by weight, more preferably 3.0 to 11.0 parts by weight. It is particularly preferable to contain it in a proportion of 0 to 10.0 parts by weight.

In the first acrylic polymer, (B) a (meth) acrylic acid having an alkyl group having C1 to C18 has a total weight portion β1 of at least one or more copolymerizable monomers containing a hydroxyl group. It is represented by β1 = 100 × (B) / (A) with respect to a total of 100 parts by weight of at least one type of ester monomer. Similarly, in the second acrylic polymer, (b) the total weight portion β2 of at least one or more copolymerizable monomers containing a hydroxyl group is (a) (meth) having an alkyl group having C1 to C18 carbon atoms. ) Β2 = 100 × (b) / (a) with respect to a total of 100 parts by weight of at least one of the acrylic acid ester monomers. The weight portion β2 of (b) in the second acrylic polymer is preferably equal to or more than the weight portion β1 of (B) in the first acrylic polymer, and the ratio K = β2 / β1 is 1.0 to 2.0. It is preferably within the range of.

The first acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (C) a copolymerizable monomer containing a carboxyl group. Examples of the copolymerizable monomer containing the (C) carboxyl group include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, and the like. 2- (Meta) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, It is preferably at least one selected from the group of compounds consisting of carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl tetrahydrophthalic acid and the like.

The first acrylic polymer contains (C) a carboxyl group based on a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C1 to C18 carbon atoms. The total of at least one or more polymerizable monomers is preferably contained in a proportion of 0.01 to 0.6 parts by weight, more preferably 0.01 to 0.5 parts by weight. , 0.01 to 0.4 parts by weight is particularly preferable.

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. Therefore, in the pressure-sensitive adhesive composition of the present embodiment, the second acrylic polymer containing the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer functions as an antistatic auxiliary agent. it is conceivable that. The second acrylic polymer is preferably contained in a proportion of 0.1 to 5.0 parts by weight, preferably 0.1 to 3.5 parts by weight, based on 100 parts by weight of the first acrylic polymer. It is more preferable that it is contained in 0.1 to 2.5 parts by weight, and it is particularly preferable that it is contained in a proportion of 0.1 to 2.5 parts by weight.
When the content of the second acrylic polymer is less than the above range, the surface resistivity and the peeling band voltage become high, and the antistatic performance deteriorates. In addition, the stain resistance to the polarizing plate deteriorates.

(C) The polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer may be a compound in which one hydroxyl group of the 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. It may be a polyalkylene glycol mono (meth) acrylate in which the other hydroxyl group remains OH, or an alkoxypolyalkylene glycol mono (meth) acrylate in which the other hydroxyl group is converted into an alkyl ether. Since the polyalkylene glycol mono (meth) acrylate corresponds to (c), it is not classified as (B) or (b) even if it contains a hydroxyl group.

The polyalkylene glycol constituting the polyalkylene glycol chain may be a glycol compound having one or more alkylene groups, for example, polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene glycol, polyethylene. Examples thereof include glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol and the like.

(C) The polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer preferably has an average number of repetitions of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The "average number of repetitions of alkylene oxide" is the average number of repetitions of the alkylene oxide unit in the portion of (c) the "polyalkylene glycol chain" contained in the molecular structure of the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer. It is a number.

Further, the diester content in the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is preferably 0.2% or less. The "diester content in the monomer" is (c) the content (% by weight) of the polyalkylene glycol di (meth) acrylic acid ester contained in the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer.

(C) The polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is included in the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. It is preferable that there is at least one selected from the above. 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, preferably 2 to 50 parts by weight, out of 100 parts by weight of the second acrylic polymer. The proportion of 35 parts by weight is more preferable, and the proportion of 2 to 25 parts by weight is particularly preferable.

Further, (c) as the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer, a group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. At least one selected from the above is preferably contained in a proportion of 1 to 50 parts by weight, more preferably 1 to 40 parts by weight, out of 100 parts by weight of the second acrylic polymer. 30 parts by weight is particularly preferable.
Further, (a) a polyalkylene glycol chain-containing mono (meth) acrylic acid with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C1 to C18 carbon atoms. The total of at least one of the ester monomers is preferably in the proportion of 1 to 30 parts by weight.

Examples of the monomer other than the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer copolymerized with the second acrylic polymer include the above-mentioned (a) alkyl group having C1 to C18 carbon atoms (meth). ) Acrylic acid ester monomer and (b) at least one or more copolymerizable monomer containing a hydroxyl group can be mentioned. 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 have to be copolymerized with a copolymerizable monomer containing a carboxyl group.

The method for producing the acrylic polymer contained in the pressure-sensitive adhesive composition according to the present embodiment is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. 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 is, for example, 300,000 or more and 1 million or less, preferably 300,000 or more and 800,000 or less, and preferably 400,000 or more and 800,000 or less.
If the weight average molecular weight of the copolymer of the second acrylic polymer is 300,000 or less, the stain resistance to the polarizing plate deteriorates, which is not preferable.

The acid value of the first acrylic polymer is preferably 0.1 to 1.0. Thereby, the stain resistance can be improved. Here, the "acid value" is one of the indexes showing the content of the acid, and is represented by the number of mg of potassium hydroxide required to neutralize 1 g of the 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 the copolymerizable monomer containing a carboxyl group is not copolymerized with the second acrylic polymer.

The pressure-sensitive adhesive composition according to this embodiment contains (G) an antistatic agent. The (G) antistatic agent of the present embodiment is an ionic compound composed of a cation and an anion 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 a solid at room temperature (for example, 25 ° C.). The ionic compound is preferably contained in a proportion of 0.01 to 15 parts by weight, more preferably 0.01 to 10 parts by weight, and 0.01 to 100 parts by weight of the first acrylic polymer. ~ 8 parts by weight is particularly preferable.

Examples of the anion of the ionic compound include 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 ⁻ , and 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 selected from the group consisting of. Here, n is an integer of 1 or more.
Examples of the cation of the ionic compound include at least one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium and morpholinium. Be done.

Specific examples of the (G) antistatic agent include, for example, methyltrioctylammonium tris (pentafluorobenzenesulfonyl) methyldo salt, 3-methyl-1-octylpyridinium nonaflatebutanesulfonate salt, 1-ethyl-3-methyl. Examples thereof include imidazolium tetrakispentafluorophenylborate salt, 1-butyl-1-methylpiperidinium bis (pentafluorobenzenesulfonyl) imide salt and the like.

The pressure-sensitive adhesive composition according to the present embodiment further contains (D) a trifunctional or higher functional isocyanate compound as a cross-linking agent. Examples of the trifunctional or higher functional isocyanate compound include bullet-modified products of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, isocyanurate-modified products, trimethylolpropane, and the like. Examples thereof include an adduct with a trivalent or higher valent polyol such as glycerin. (D) Examples of the ratio of the trifunctional or higher functional isocyanate compound include 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 this embodiment may contain (E) a cross-linking retarder. (E) Examples of the cross-linking retarder include β-ketoesters such as methyl acetoacetic acid, ethyl acetoacetate, octyl acetoacetic acid, oleyl acetoacetic acid, lauryl acetoacetic acid and stearyl acetoacetic acid, acetylacetone, 2,4-hexanedione and benzoylacetone. Etc., β-diketone and the like. These are compounds of the ketoenol tether, and in a pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, by blocking the isocyanate group contained in the cross-linking agent, the pressure-sensitive adhesive composition is excessive after the addition of the cross-linking agent. It is possible to suppress an increase in viscosity and gelation, and extend the pot life of the pressure-sensitive adhesive composition. The (E) cross-linking retarder is preferably a compound of a keto-enol tautomer, and is particularly preferably at least one selected from the compound group consisting of acetylacetone and ethyl acetoacetate. It is preferable that the (E) cross-linking retarder is contained in a ratio of 0.1 to 300 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 a cross-linking catalyst other than the tin compound as the (F) cross-linking catalyst. The (F) cross-linking catalyst may be a substance that functions as a catalyst for the reaction (cross-linking reaction) between the copolymer and the cross-linking agent when the polyisocyanate compound is used as the cross-linking agent. Examples of the cross-linking catalyst other than the tin compound include amine compounds such as tertiary amines, metal chelate compounds, organolead compounds, and organometallic compounds such as organozinc compounds.

(F) The metal chelate compound of the cross-linking catalyst is a compound in which one or more polydentate ligands L are bonded to the central metal atom M. The metal chelate compound may or may not have one or more bidentate ligands X that bind to the metal atom M. Specific examples of the metal chelate compound include tris (2,4-pentanedionato) iron (III), iron trisacetylacetonate, titaniumtrisacetylacetonate, rutheniumtrisacetylacetonate, zinc bisacetylacetonate, and aluminum tris. Acetylacetonate, zirconite tetrakis acetylacetonate, tris (2,4-hexanedionat) iron (III), bis (2,4-hexanedionat) zinc, tris (2,4-hexanedionat) titanium, tris Examples thereof include (2,4-hexane dionate) aluminum and tetrakis (2,4-hexane dionate) zirconium.

The (F) cross-linking 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 that the (F) cross-linking catalyst is contained in a ratio of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

Since the (E) cross-linking retarder has an effect of suppressing cross-linking as opposed to the (F) cross-linking catalyst, the ratio of the (E) cross-linking delaying agent to the (F) cross-linking catalyst can be appropriately set. preferable. In order to prolong the pot life of the pressure-sensitive adhesive composition and improve the storage stability, the weight ratio of (E) / (F) is preferably 80 to 1000. Here, the weight part ratio of (E) / (F) is a quotient value 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. The (H) polyether-modified siloxane compound is a siloxane compound having a polyether group, and is a siloxane unit having a polyether group [-SiR ¹ (R)] in addition to the usual siloxane unit [-SiR ¹ _2- O-]. ^{It has 2} O (R ³ O) _n R ⁴ ) -O-]. Here, R ¹ is one or more alkyl groups or aryl groups, R ² and R ³ are one or more alkylene groups, and R ⁴ is one or more alkyl groups or acyl groups. Etc. (terminal groups). Examples of the polyether group include a polyoxyalkylene group such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a polyoxypropylene group [(C ₃ H ₆ O) _n ]. In siloxane units having polyether groups, the ends of the polyether group may be an OH group (R ^{4 =} H in the general formula).

The (H) 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 with respect to 100 parts by weight of the first acrylic polymer, and 0.02 to 0.35 parts by weight. The proportion of parts is more preferable, and the proportion of 0.02 to 0.25 parts by weight is particularly preferable. The HLB value is, for example, a hydrophilic lipophilic balance (hydrophilic lipophilic ratio) defined in JIS K3211 (surfactant term) and the like.

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

By blending the (H) 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. The weight average molecular weight of the (H) polyether-modified siloxane compound is preferably 10,000 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, but the polyether-modified siloxane compound having a low molecular weight has a relatively high HLB value. , Excellent antistatic property can be obtained even if the compatibility with the polymer is slightly low.

The pressure-sensitive adhesive composition of the present embodiment is not limited to the above-mentioned additives, and is known to include surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, antioxidants, antioxidants and the like. Additives may be appropriately blended. These can be used alone or in combination of two or more.

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

Further, the surface treatment applied to the surface of the protective layer of the polarizing element of the polarizing plate was selected from the group consisting of untreated, AG treated, LR treated, AR treated, AG-LR treated, and AG-AR treated. It may be at least one kind. Here, AG is anti-glare, LR is low reflection, and AR is anti-reflection. In the pressure-sensitive adhesive composition of the present embodiment, the substrate on the surface of the polarizing plate is PMMA or PET, and at least one of the adherends subjected to AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. Contamination resistance can be improved for species and above.

In the pressure-sensitive adhesive layer obtained by cross-linking 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, and 5.0 × 10 ^{+ 11} Ω / □. It is more preferably 1.0 × 10 ^{+ 11} Ω / □ or less, and particularly preferably 1.0 × 10 ^{+ 11} Ω / □ or less. If the surface resistivity is large, the performance of releasing static electricity generated when the adhesive layer is peeled from the adherend is inferior. Therefore, by sufficiently reducing the surface resistivity, the peeling band voltage generated by the static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend is reduced, and the influence on the adherend is suppressed. Can be done.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive layer with respect to 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. The peeling band voltage is preferably in the range of −0.3 to +0.3 kV. Examples of the fluorine compound used in the composition for forming a low refractive index layer include fluorine-containing copolymers which are one or more polymers such as fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth) acrylates. Examples thereof include a polymer and a condensate such as a fluorinated alkyl group-containing silane compound. In the fluorine-containing copolymer, in addition to the fluorinated monomer, a non-fluorinated monomer such as olefins, vinyl ethers, and (meth) acrylate 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 obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment with respect to the polarizing plate at a low peeling speed of 0.3 m / min is 0.04 to 0.2 N / 25 mm, and is high-speed. The adhesive strength at a peeling speed of 30 m / min is preferably 2.0 N / 25 mm or less, and the adhesive strength at a high speed peeling speed of 30 m / min is more preferably 0.2 to 1.6 N / 25 mm. As a result, it is possible to obtain a performance in which the adhesive strength does not change much depending on the peeling speed, and it is possible to quickly peel even by high-speed peeling. Further, since it is reattached, even when the surface protective film is once peeled off, it does not require an excessive force and can be easily peeled off from the adherend.

The gel fraction of the pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present embodiment is preferably 95 to 100%, more preferably 97 to 100%. Due to such a high gel fraction, the adhesive force does not become excessive at a low peeling speed, the elution of unpolymerized monomers or oligomers from the copolymer is reduced, and the reworkability and high temperature / high humidity are satisfied. Durability is improved and contamination of the adherend can be suppressed.

The pressure-sensitive adhesive film of the present embodiment is formed by forming a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment on one side or both sides of the resin film. Further, the surface protective film of the present embodiment is a surface protective film formed by forming a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment on one side of a resin film. The pressure-sensitive adhesive composition of the present embodiment has excellent antistatic performance, has an excellent balance of adhesive strength at a low peeling speed and a high peeling speed, and has stain resistance. Therefore, it can be suitably used as a surface protective film for a polarizing plate.

As the base film of the pressure-sensitive adhesive layer and the release film (separator) that protects the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
Antistatic treatment and antifouling treatment may be applied to 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 and kneading of an antistatic agent. Examples of the antifouling treatment include treatment with a silicone-based or fluorine-based mold release agent, a coating agent, silica fine particles, and the like. The release film may be subjected to a release treatment with a silicone-based, fluorine-based, long-chain alkyl-based release agent or the like on the surface of the pressure-sensitive adhesive layer that is combined with the adhesive surface.

Further, an optical film with an adhesive layer can be obtained by laminating an adhesive layer obtained by cross-linking the adhesive composition of the present embodiment on at least one surface of the optical film. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness improving film. Examples of devices to which the optical member is applied include liquid crystal panels, organic EL panels, touch panels, and the like.
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.

Hereinafter, the present invention will be specifically described with reference to Examples.

<Manufacturing of first acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction pipe, and the air in the reactor 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. Then, 0.1 part 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]
Comparison with Examples 2 to 6 in the same manner as in the first acrylic polymer solution used in Example 1 above, except that the composition of the monomers was as described in Tables 1 (A) to (C). The first acrylic polymer solution used in Examples 1 to 3 was obtained.

<Manufacturing of adhesive composition and surface protective film>
[Example 1]
2.0 parts by weight of the cross-linking agent (Coronate HX), 9 parts by weight of the cross-linking retarder (acetylacetone), and a cross-linking catalyst (titanium trisacetylacetonate) with respect to the first acrylic polymer solution of Example 1 produced as described above. 0.1 part by weight, antistatic agent (methyltrioctylammonium tris (pentafluorobenzenesulfonyl) methide salt) 0.9 part by weight, polyether-modified siloxane compound (HLB = 7) 0.05 part by weight, copolymer B -1 (molecular weight 600,000) 0.2 parts by weight was added and mixed by stirring to obtain the pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was applied onto a release film (a PET film coated with a silicone resin) and then dried at 90 ° C. to remove the solvent to obtain a pressure-sensitive adhesive layer having a thickness of 20 μm. Then, the pressure-sensitive adhesive layer with a release film was transferred to the surface of the base film (a PET film whose one surface was antistatic and antifouling treated) opposite to the antistatic and antifouling surface. A surface protective film of Example 1 having a laminated structure of "base film / adhesive layer / release film" was obtained.
[Examples 2 to 6 and Comparative Examples 1 to 3]
Examples 2 to 6 are the same as the surface protective film of Example 1 above, except that the compositions of the additives are as described in Tables 1 (D) to (H) and copolymer B, respectively. And the surface protective films of Comparative Examples 1 to 3 were obtained.

In Table 1, the weight of each component was determined by taking the total of (meth) acrylic acid ester monomers having (A) alkyl groups having C1 to C18 as 100 parts by weight. Although "I-2" of Comparative Example 2 is described in the column of (A) for convenience, (A) the (meth) acrylic acid ester monomer having an alkyl group having C1 to C18 has a carbon number of C1 to C18. Not applicable.
In Table 1, in each column of (D), (E), (F), (G), (H), and (copolymer B), each component is based on 100 parts by weight of the first acrylic polymer. The content ratio (parts by weight) of is indicated by the numerical value in parentheses ().

The compound names of the abbreviations of each component used in Table 1 are shown in Tables 2 and 3. The second acrylic polymer in the above-described embodiment is "copolymer B", and the abbreviations of the component monomers (a), (b), and (c) have the meanings of (A), (B), and (B), respectively. It is described in (I). Coronate (registered trademark) HX, HL and L are trade names of Tosoh Corporation, and Takenate (registered trademark) D-140N is a trade name of Mitsui Chemicals, Inc.

(G) Among the antistatic agents, G-1 to G-4 are all solid ionic compounds having an anion having a fluorine atom number of F7 or more and a melting point of 25 ° C. or more. G-5 is a solid ionic compound having an anion having an F5 number of fluorine atoms and a melting point of 25 ° C. or higher.
Among the (H) polyether-modified siloxane compounds, all of H-1 to H-6 have a weight average molecular weight of 10,000 or less.
(I) Among the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers, I-1 to I-3 have a diester content of 0.2% or less in the monomer, and I-4 has a diester content in the monomer. The diester content is 0.8%. Further, n in the column of group (I) in Table 3 is a numerical value indicating the average number of repetitions of the alkylene oxide.

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

<Adhesive strength test method>
The release film was peeled off, and the surface protective film with the adhesive layer exposed was attached to the surface of the polarizing plate via the adhesive layer, left for 1 day, and then autoclaved at 50 ° C., 5 atm, and 20 minutes. The sample which was treated and left at room temperature for another 12 hours was used as a sample for measuring the adhesive strength. The peeling strength measured by peeling the obtained measurement sample in the 180 ° direction using a tensile tester at a low speed (0.3 m / min) or a high speed (30 m / min) was defined as the adhesive strength.
Here, the protective layer of the polarizer 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 protective layer of the polarizer of the polarizing plate is subjected to a low reflection surface treatment with a composition containing a fluorine compound.

<Test method of surface resistivity>
After aging the surface protective film and before attaching it to the polarizing plate, the release film is peeled off to expose the adhesive layer, and the resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech) is used to expose the adhesive layer. The surface resistivity of the film was measured.

<Test method for peeling band voltage>
The surface protective film from which the release film is peeled off to expose the pressure-sensitive adhesive layer has a low refractive index layer formed by using a composition for forming a low refractive index layer containing a fluorine compound on the adherend surface. It was affixed to a polarizing plate. High-precision electrostatic sensors SK-035 and SK-200 (manufactured by KEYENCE CORPORATION) measure the voltage (band voltage) generated by charging the adherend when the surface protective film is peeled off by 180 ° at a tensile speed of 30 m / min. ) Was used, and the maximum value of the measured value was taken as the peeling band voltage.

<Stain resistance test method>
Each polarizing plate selected from the five types shown in Table 4 was bonded onto one side of the glass plate via an adhesive layer (double-sided adhesive tape) using a bonding machine. Then, a surface protective film was bonded to the surface of each polarizing plate using a bonding machine. After storage in an environment of 23 ° C. and 50% RH for a period of 3 days and 30 days, the surface protective film was peeled off and the state of contamination on the surface of the polarizing plate was visually observed. The criteria for determining stain resistance were evaluated as "○" when there was no contamination on the surface of each polarizing plate, "Δ" when there was slight contamination, and "×" when there was contamination.

Table 4 shows the evaluation results of the surface protective film in Examples 1 to 6 and Comparative Examples 1 to 3. The "surface resistivity" is expressed by a method in which "m × 10 ^{+ n} " is set to "mE + n" (where m is an arbitrary real value and n is a positive integer). The column of "Stain resistance (surface base material / surface treatment)" shows the evaluation results for each material and surface treatment of the surface base material (protective layer of the polarizer) of the five types of polarizing plates. Plane of "surface treatment" means untreated.

The surface protective films of Examples 1 to 6 have an adhesive force of 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min with respect to the polarizing plate as an adherend, and have a high peeling speed. The adhesive strength at 30 m / min was 2.0 N / 25 mm or less, and the adhesive performance was excellent.
Further, the surface protective films of Examples 1 to 6 have a surface resistivity of the pressure-sensitive adhesive layer of 1.0 × 10 ⁺¹² Ω / □ or less, and are used for forming a low refractive index layer containing a fluorine compound on the adherend surface. The peeling band voltage of the pressure-sensitive adhesive layer with respect to the low refractive index layer formed by using the composition was in the range of −0.3 to +0.3 kV, and the antistatic performance was excellent.
Further, the surface protective films of Examples 1 to 6 were not contaminated with the polarizing plate as an adherend even after being stored for a period of 3 days and 30 days, and were excellent in stain resistance.
That is, the evaluation results shown in Table 4 for the surface protective films of Examples 1 to 6 demonstrate that the problem of the present invention could 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. Further, I-4 contained in the copolymer B-5 has a large diester content of 0.8% and a large average number of repetitions n = 23. Further, the component (b) contained in the copolymer B-5 of the second acrylic polymer is 3 parts by weight, which is more than 5.5 parts by weight of the component (B) contained in the first acrylic polymer. Few. The surface protective film of Comparative Example 1 using such an adhesive composition is excellent in stain resistance to the conventionally used polarizing plate based on TAC, but is based on PMMA or PET. The stain resistance was slightly poor for the two types of polarizing plates.

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

Further, in the pressure-sensitive adhesive composition of Comparative Example 3, the proportion of the copolymerizable monomer (C) containing a carboxyl group is as high as 1.5 parts by weight, and the antistatic agent is F5 having less than F7 fluorine atoms. It contains an anion that is. The surface protective film of Comparative Example 3 using such an adhesive composition has a high peeling band voltage of 0.6 kV, inferior antistatic performance, and poor stain resistance of the three types of polarizing plates. The stain resistance of one type of polarizing plate was slightly poor.

As described above, the surface protective films of Comparative Examples 1 to 3 could not solve the problem of the present invention.
In the case of the surface protective film prepared in the same manner as in Example 1 except that it does not contain the copolymer B, the surface resistivity is high, the peeling band voltage is high, and the antistatic performance is inferior. In addition, the stain resistance of the polarizing plate was also inferior.

Claims (8)

A pressure-sensitive adhesive composition containing an acrylic polymer, an antioxidant, and a cross-linking agent, wherein the acrylic polymer is the next first acrylic polymer and a second acrylic polymer.
The first acrylic polymer is
(A) With respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group.
(B) The total of at least one or more copolymerizable monomers containing a hydroxyl group is 1.0 to 6.0 parts by weight.
(C) The total of at least one or more copolymerizable monomers containing a carboxyl group is 0.01 to 0.6 parts by weight.
, A copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and 1.2 million or less, which is copolymerized without containing a polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer. It is the first acrylic polymer of
The first acrylic polymer contains 70 parts by weight of 2-ethylhexyl acrylate out of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group. It is contained in the above ratio
The second acrylic polymer is
(A) At least one or more (meth) acrylic acid ester monomers having an alkyl group having C1 to C18 carbon atoms.
(B) At least one type of copolymerizable monomer containing a hydroxyl group and
(C) At least one or more of polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers and
It is a second acrylic polymer having a weight average molecular weight of more than 300,000 and 800,000 or less of the copolymer obtained by copolymerizing the above.
The (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer has an average number of repetitions of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14.
The diester content in the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is 0.2% or less.
The glass transition temperature of the first acrylic polymer and the second acrylic polymer is 0 ° C. or lower.
The cross-linking agent is (D) a trifunctional or higher functional isocyanate compound.
The antistatic agent is an ionic compound having a (G) fluorine atom having an anion having an number of F7 or more and having a melting point of 25 to 50 ° C. consisting of a cation and an anion.
A pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition further contains (E) a cross-linking retarder and (F) a cross-linking catalyst other than a tin compound as a cross-linking catalyst. An pressure-sensitive adhesive composition for a surface protective film to be bonded to a protective layer of a polarizing element of a polarizing plate, wherein the protective layer of the polarizing element of the polarizing plate is composed of a TAC-based film, a PMMA-based film, and a PET-based film. The surface treatment that is one selected from the group and is applied to the surface of the protective layer of the polarizer of the polarizing plate is untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, AG. The pressure-sensitive adhesive composition according to claim 1, which is one selected from the group consisting of -AR treatment. The anions of the ionic compound are 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 selected from the group (where n is an integer of 1 or more) is contained as an anion.
The pressure-sensitive adhesive composition according to claim 1 or 2, wherein 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 one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium and morpholinium.
The adhesive according to any one of claims 1 to 3, wherein 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. Agent composition. The pressure-sensitive adhesive composition contains the second acrylic polymer in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the first acrylic polymer.
The second acrylic polymer is
(A) With respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group.
(B) The total of at least one or more copolymerizable monomers containing a hydroxyl group is 2.0 to 12.0 parts by weight.
(C) A copolymer in which a total of at least one or more polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers is copolymerized with 1 to 30 parts by weight and the weight average molecular weight is more than 300,000 and 1 million or less. And
The (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is included in the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. At least one selected from
A copolymerizable monomer containing a (B) hydroxyl group with respect to at least one or more 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 first acrylic polymer. Β1 = 100 × (B) / (A) in total of at least one of the above, and (meth) acrylic acid ester monomer having the number of carbon atoms of the (a) alkyl group of the second acrylic polymer of C1 to C18. (B) Ratio of at least one or more copolymerizable monomers containing a hydroxyl group to a total of 100 parts by weight β2 = 100 × (b) / (a) of at least one of the above K = β2 The pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein / β1 is in the range of 1.0 to 2.0. A pressure-sensitive adhesive film, wherein a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition according to any one of claims 1 to 5 is laminated on one side of the resin film. A surface protective film for a polarizing plate using the adhesive film according to claim 6 . An optical film with an adhesive layer in which an adhesive layer obtained by cross-linking the adhesive composition according to any one of claims 1 to 5 is laminated on at least one surface of the optical film.