KR102335316B1 - Adhesive composition and protection film using the same - Google Patents

Abstract

The present invention relates to an acrylic copolymer formed by polymerizing a (meth)acrylate-based monomer containing a branched alkyl group, a macromonomer, and a monomer mixture containing a (meth)acrylic-based monomer containing a carboxyl group; And it relates to a protective film comprising a curing agent, and a pressure-sensitive adhesive composition having a gel fraction of 90% or more after curing, and a pressure-sensitive adhesive layer formed thereby.

Description

Adhesive composition and protective film using the same {ADHESIVE COMPOSITION AND PROTECTION FILM USING THE SAME}

The present invention relates to an adhesive composition and a protective film using the same, and more particularly, to an adhesive composition having excellent stability over time and less contamination after removal, and a protective film manufactured using the same.

The protective film is used to prevent damage to the surface of a product due to physical impact that may occur in the process of transport, storage, and/or assembly of the product, and is usually on one or both sides of a plastic base film such as polyethylene terephthalate. It has a structure in which an adhesive layer is formed.

Such a protective film is peeled off and removed from the surface of the product when transport, storage and/or assembly is completed. If the adhesive strength of the protective film is stronger than necessary, a problem of damaging or contaminating the surface of the product may occur during the removal process, in particular, There was a problem in that the workability was deteriorated because the peeling was not performed properly during the high-speed peeling.

In addition, when the cohesive force of the protective film is too low, adhesion to the base film is poor, and the adhesive is transferred to the surface of the product after peeling, thereby causing defects such as stains on the surface of the product. In addition, when the wettability of the pressure-sensitive adhesive is low, in addition to contamination by components transferred from the pressure-sensitive adhesive, moisture or the like penetrates between the protective film and the surface of the product to leave stains.

On the other hand, in the case of the conventionally used adhesives for protective films, there is also a problem in that the physical properties of the adhesive layer change over time, resulting in poor stability over time.

Therefore, there is a demand for the development of an adhesive for a protective film that has excellent stability over time and can minimize the occurrence of contamination on the surface of the product.

Korean Patent Publication No. 10-2013-0133721 (2013.12.09)

An object of the present invention is to solve the above problems, and to provide a pressure-sensitive adhesive composition having excellent stability over time and minimizing the occurrence of contamination on the product surface, and a protective film manufactured using the same.

In one aspect, the present invention provides an acrylic copolymer formed by polymerizing a (meth)acrylate-based monomer including a branched alkyl group, a macromonomer, and a monomer mixture including a (meth)acrylic monomer including a carboxyl group; and a curing agent, and provides a pressure-sensitive adhesive composition having a gel fraction of 90% or more after curing.

In another aspect, the present invention provides a protective film comprising a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition according to the present invention.

Since the pressure-sensitive adhesive composition according to the present invention has a high cohesive strength of the pressure-sensitive adhesive composition using a macro monomer, it is possible to minimize the transfer of the pressure-sensitive adhesive to the adherend during peeling.

In addition, the pressure-sensitive adhesive composition according to the present invention uses a (meth)acrylic monomer including a carboxyl group to have excellent wetting to the substrate, thereby effectively preventing the penetration of contaminants from the outside.

In addition, since the adhesive layer formed by the pressure-sensitive adhesive composition according to the present invention has a high gel fraction of 90% or more, an additional crosslinking reaction hardly occurs after forming the adhesive layer, and thus excellent stability over time can be realized.

In addition, the pressure-sensitive adhesive composition according to the present invention can implement a low viscosity by using a branched alkyl (meth) acrylate-based monomer, and thus has excellent coatability when forming an adhesive layer, and has a relatively high solid content in the coating solution. It can be maintained, so it is advantageous to control the thickness of the adhesive layer.

Hereinafter, the present invention will be described in detail.

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, cases including the plural are included unless otherwise explicitly stated.

In interpreting the components, it is construed as including an error range even if there is no separate explicit description.

In this specification, "(meth)acryl" is a generic term for acryl and methacryl. For example, (meth)acrylate includes methacrylate and acrylate, and (meth)acrylic acid includes acrylic acid and methacrylic acid.

In this specification, "X to Y" which shows a range means "X or more and Y or less".

In the present specification, the weight average molecular weight means a polystyrene conversion value measured by gel permeation chromatography (GPC).

adhesive composition

The pressure-sensitive adhesive composition according to the present invention includes (A) an acrylic copolymer and (B) a curing agent. Specifically, the pressure-sensitive adhesive composition according to the present invention includes a (meth)acrylate-based monomer (a1) containing a branched alkyl group, a macromonomer (a2), and a (meth)acrylic-based monomer (a3) containing a carboxyl group and an acrylic copolymer (A) and a curing agent (B) formed by polymerizing the monomer mixture.

Hereinafter, each component of the pressure-sensitive adhesive composition according to the present invention will be described in detail.

(A) acrylic copolymer

The acrylic copolymer of the present invention is obtained by polymerizing a monomer mixture comprising (a1) a (meth)acrylate-based monomer containing a branched alkyl group, (a2) a macromonomer, and (a3) a (meth)acrylic-based monomer containing a carboxyl group. is formed

The (a1) (meth) acrylate-based monomer containing a branched alkyl group is, for example, ethylhexyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, isoamyl ( It may be at least one selected from the group consisting of meth)acrylate, isodecyl (meth)acrylate, and isotetradecyl (meth)acrylate.

In the case of a pressure-sensitive adhesive composition comprising an acrylic copolymer prepared by using the branched alkyl (meth) acrylate-based monomer as described above, it has the same level of weight average molecular weight and uses a linear alkyl (meth) acrylate-based monomer. It has a low viscosity characteristic compared to the pressure-sensitive adhesive composition using the acrylic copolymer. When the viscosity of the pressure-sensitive adhesive composition is high, the coating property is not sufficient, and there is a difficulty in forming the pressure-sensitive adhesive layer. Therefore, conventionally, a method of lowering the viscosity of the pressure-sensitive adhesive composition by diluting the pressure-sensitive adhesive composition by adding a solvent during coating was used. However, when the solid content in the coating solution is low, there are problems in that productivity is lowered and it is difficult to precisely control the thickness of the adhesive layer.

In contrast, since the pressure-sensitive adhesive composition according to the present invention has a low viscosity characteristic, sufficient coating properties can be obtained even when it has a relatively high solid content compared to conventional pressure-sensitive adhesive compositions.

On the other hand, the (a1) (meth) acrylate-based monomer containing a branched alkyl group, based on 100 parts by weight of the monomer mixture, 70 to 98 parts by weight, preferably 75 to 98 parts by weight, more preferably 80 to It is included in 96 parts by weight. (a1) When the content of the monomer satisfies the above range, excellent adhesion properties and viscosity lowering effect can be obtained.

Next, the macromonomer (a2) is to improve the cohesiveness of the pressure-sensitive adhesive to prevent the pressure-sensitive adhesive from being transferred to the product surface after peeling.

The macromonomer (a2) is a high molecular weight monomer having a polymerizable functional group (polymerizable group), and includes a polymer chain portion and a polymerizable group portion.

The polymerizable group reacts with the (a1) monomer and/or the (a3) monomer to form the main chain structure of (A) the acrylic copolymer, and the polymer chain portion forms the side chain structure of the acrylic copolymer. The side chain forms a microdomain in the pressure-sensitive adhesive composition, thereby improving cohesiveness.

Meanwhile, the polymerizable group may be a group including an ethylenically unsaturated double bond, for example, a vinyl group, an allyl group, a (meth)acrylic group, a propenyl group, a vinylidene group. It may be a vinylene group or the like. Among these, a (meth)acryl group is especially preferable.

The polymer chain portion may have a polymer structure including a repeating unit derived from an alkyl (meth)acrylate having 1 to 10 carbon atoms, styrene, acrylonitrile, and the like. These polymer chain portions may be composed of a single repeating unit, or may be composed of a plurality of repeating units.

As the macromonomer (a2), a commercially available product may be used, for example, a macromonomer having a methacryloyl group at the terminal and methylmethacrylate as a segment (product name: AA-6S, Toagosei) product), macromonomer whose segment is styrene (product name: AS-6S, product of Toagosei Co., Ltd.), macromonomer whose segment is a copolymer of styrene/acrylonitrile (product name: AN-6S, product of Toagosei Co., Ltd.), whose segment is Butyl acrylate macromonomer (product name: AB-6, manufactured by Toagosei Co., Ltd.)) may be used, but is not limited thereto.

Meanwhile, the (a2) macromonomer may be included in an amount of 1 to 20 parts by weight, preferably 2 to 10 parts by weight, more preferably 3 to 5 parts by weight, based on 100 parts by weight of the monomer mixture. When the content of the macromonomer is less than 1 part by mass, sufficient cohesive force is not obtained, so it is difficult to see an improvement effect in terms of substrate contamination.

Next, the (a3) (meth)acrylic monomer including a carboxyl group is for increasing the wetting of the pressure-sensitive adhesive composition. When the (a2) macromonomer is used during polymerization of the acrylic copolymer, the cohesive force of the pressure-sensitive adhesive is improved and thus the pressure-sensitive adhesive transfer can be suppressed. Therefore, in the present invention (a3) by using the (meth)acrylic monomer including a carboxyl group, the wettability of the pressure-sensitive adhesive composition can be improved.

Examples of the (a3) carboxyl-containing (meth)acrylic monomer include (meth)acrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, and 4-(meth) Acryloyloxy butyric acid, an acrylic acid double, itaconic acid, maleic acid, maleic anhydride, etc. are mentioned.

The (a3) carboxyl-containing (meth)acrylic monomer may be included in an amount of 1 to 10 parts by weight, preferably 1 to 8 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the monomer mixture. When the acrylic acid content is less than 1 part by weight, it is difficult to ensure sufficient wettability, and when it exceeds 10 parts by weight, the adhesive strength increases too much, so that it is difficult to peel it off after being prepared as a protective film.

The acrylic copolymer according to the present invention may be prepared by mixing each of the above-described monomers to prepare a monomer mixture, and then polymerizing the same. In this case, the polymerization method is not particularly limited, and various polymerization methods known in the art may be used, for example, polymerization methods such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. In the present invention, in particular, the acrylic resin can be prepared using a solution polymerization method, and the solution polymerization is preferably performed at a polymerization temperature of 50° C. to 140° C. by adding an initiator in a state where each monomer is uniformly mixed. . Examples of the initiator that can be used in this process include azo initiators such as azobisisobutyronitrile or azobiscyclohexane carbonitrile; and/or a conventional initiator such as a peroxide such as benzoyl peroxide or acetyl peroxide, and one or a mixture of two or more of the above may be used, but the present invention is not limited thereto.

Meanwhile, the acrylic copolymer may have a weight average molecular weight of 700,000 or less, preferably 200,000 to 700,000, and more preferably 200,000 to 650,000. When the weight average molecular weight of the acrylic copolymer exceeds 700,000, it is difficult to realize low viscosity characteristics at a solid content concentration of 40% by weight or more.

(2) hardener

The curing agent is for improving the durability of the pressure-sensitive adhesive layer by forming a cross-linking structure, the type is not particularly limited, and various curing agents used in the art, for example, isocyanate compounds, epoxy compounds, aziridine compounds , and at least one selected from the group consisting of metal chelate-based compounds may be used.

As the isocyanate-based compound, a conventional compound known in the art may be used, for example, toluene diisocyanate, 2,4-trylene diisocyanate, 2,6-trylene diisocyanate, hydrogenated torylene diisocyanate, Isoform diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4-diisocyanate, 1,3-bisisocyanatomethyl cyclohexane, tetramethylxylene diisocyanate, 1 ,5-naphthalene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, trimethylolpropane modified toluene diisocyanate, trimethylolpropane modified tolylene diisocyanate, torylene diisocyanate adduct of trimethylolpropane, xylene diisocyanate adduct of trimethylolpropane, triphenylmethanetoisocyanate, methylenebistriisocyanate, polyols (trimethylolpropane) or mixtures thereof, etc. can be used

Examples of the epoxy compound include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N,N,N',N'-tetraglycidylethylenediamine, glycerin Diglycidyl ether or a mixture thereof may be used.

Examples of the aziridine-based compound include N,N'-toluene-2.4-bis(1-aziridinecarboxamide), N,N'-diphenylmethane-4,4'-bis(1-aziri). dincarboxamide), triethylene melamine, bisisoprotaloyl-1-(2-methylaziridine), tri-1-aziridinylphosphine oxide, or a mixture thereof, and the like can be used.

As the metal chelate-based compound, for example, a compound in which a polyvalent metal such as aluminum, iron, zinc, tin, titanium, antimony, magnesium and/or vanadium is coordinated with acetyl acetone or ethyl acetoacetate may be mentioned. , but is not limited thereto.

The curing agent is preferably included in an amount of 1 to 10 parts by weight, preferably 2 to 8 parts by weight, more preferably 3 to 7 parts by weight based on 100 parts by weight of the acrylic copolymer. When the content of the curing agent is less than 1 part by weight, it is difficult to secure sufficient durability and cohesion of the pressure-sensitive adhesive composition due to insufficient crosslinking degree, and when the content of the curing agent exceeds 10 parts by weight, the curing agent remaining without participating in the crosslinking may remain as a contamination source on the attachment surface later.

(3) solvent

The pressure-sensitive adhesive composition of the present invention may further include a solvent for viscosity control. In this case, as the solvent, for example, ethyl acetate, n-pentane, isopentane, neopentane, n-hexane, n-octane, n-heptane, methyl ethyl ketone, acetone, toluene, etc. may be used, but are limited thereto. it is not

The solvent may be included in an amount such that the solid content in the pressure-sensitive adhesive composition is 40% by weight or more, preferably 40 to 60% by weight.

(4) other ingredients

The pressure-sensitive adhesive composition of the present invention may further include other components such as a silane coupling agent, a tackifying resin, an additive, and the like, in addition to the above-described components for controlling physical properties.

The pressure-sensitive adhesive composition of the present invention may further include a silane coupling agent. The silane coupling agent improves the adhesion and adhesion stability between the pressure-sensitive adhesive and the glass substrate, improves heat resistance and moisture resistance, and also improves adhesion reliability when the pressure-sensitive adhesive is left for a long time under high temperature and/or high humidity conditions. . Examples of the coupling agent that can be used in the present invention include γ-glycidoxypropyl triethoxy silane, γ-glycidoxypropyl trimethoxy silane, γ-glycidoxypropyl methyldiethoxy silane, γ-glycidoxy propyl triethoxy silane, 3-mercaptopropyl trimethoxy silane, vinyltrimethoxysilane, vinyltriethoxy silane, γ-methacryloxypropyl trimethoxy silane, γ-methacryloxypropyl triethoxy silane, γ-aminopropyl trimethoxy silane, γ-aminopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, γ-acetoacetatepropyl trimethoxysilane, γ-acetoacetatepropyl triethoxy silane, and β-cyanoacetyl trimethoxy silane, β-cyanoacetyl triethoxy silane, and acetoxyaceto trimethoxy silane, and one or a mixture of two or more of the above may be used. In the present invention, it is preferable to use a silane-based coupling agent having an acetoacetate group or a β-cyanoacetyl group, but is not limited thereto. In the composition of the present invention, the silane-based coupling agent may be included in an amount of 0.01 parts by weight to 5 parts by weight, preferably 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of the acrylic copolymer. If the content of the coupling agent is less than 0.01 parts by weight, the effect of increasing the adhesive strength is insignificant, and when it exceeds 5 parts by weight, there is a risk of lowering durability.

The pressure-sensitive adhesive composition of the present invention may further include 1 part by weight to 100 parts by weight of a tackifying resin based on 100 parts by weight of the acrylic copolymer from the viewpoint of adjusting the adhesive performance. The kind of such tackifying resin is not particularly limited, and for example, (hydrogenated) hydrocarbon-based resin, (hydrogenated) rosin resin, (hydrogenated) rosin ester resin, (hydrogenated) terpene resin, (hydrogenated) terpene phenol resin, One kind or a mixture of two or more kinds of polymerized rosin resin or polymerized rosin ester resin may be used. When the content of the tackifying resin is less than 1 part by weight, there is a fear that the effect of addition is insignificant, and when it exceeds 100 parts by weight, there is a fear that compatibility and/or the effect of improving cohesion may be reduced.

The pressure-sensitive adhesive composition of the present invention also includes one or more additives selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, and a plasticizer to the extent that the effect of the invention is not affected. may further include.

On the other hand, the pressure-sensitive adhesive composition of the present invention comprising the above components has a high gel fraction after curing and low viscosity. Specifically, the pressure-sensitive adhesive composition according to the present invention has a high gel fraction of 90% or more after curing, and thus has excellent stability over time. In addition, the pressure-sensitive adhesive composition according to the present invention has a low viscosity at 23° C. of 500 to 4,000 cP, preferably 500 to 3000 cP when the solid content is 40% by weight or more, and has excellent coating properties.

protective film

Next, the protective film which concerns on this invention is demonstrated. The protective film of the present invention includes an adhesive layer formed by the pressure-sensitive adhesive composition according to the present invention. More specifically, the protective film according to the present invention may include a base film and an adhesive layer formed on one or both surfaces of the base film and formed by the pressure-sensitive adhesive composition according to the present invention.

As the base film, various films used as a base material for a protective film in the art, for example, polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, ethylene vinyl acetate aerial Synthetic resin films such as copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, and polyvinyl chloride may be used, and are not particularly limited.

The base film may be formed of a single-layer body or a multi-layer body, and may have a thickness of about 5 to 500 μm.

In addition, the surface of the base film may be subjected to surface treatment such as corona discharge treatment, plasma treatment, blast treatment, chemical etching treatment, primer treatment, etc. for improving the adhesion to the adhesive layer.

On the other hand, the pressure-sensitive adhesive layer may be formed by applying the pressure-sensitive adhesive composition according to the present invention on the base film, followed by drying. Application can be generally performed by a knife coater, a roll coater, a calender coater, a comma coater, or the like. In addition, it can also be carried out by a gravure coater, a rod coater, etc. depending on the coating thickness or the viscosity of a coating liquid.

Meanwhile, the drying may be performed, for example, at a temperature of 70°C to 120°C, preferably 90°C to 100°C, for 60 seconds to 300 seconds. The solvent in the pressure-sensitive adhesive composition is volatilized by the heat supplied in the drying process, and a curing reaction between the curing agent and the acrylic copolymer proceeds.

In addition, if necessary, after the drying process is completed, an aging process for completing the crosslinking reaction may be additionally performed. The aging process may be performed, for example, at a temperature range of 30° C. to 60° C. for 1 to 7 days.

The protective film of the present invention prepared as described above has an adhesive layer having a gel fraction of 90% or more, and has excellent stability over time. When the gel fraction of the adhesive layer is less than 90%, the physical properties of the adhesive layer may be changed by the unreacted curing agent. Therefore, in the present invention, the gel fraction was formed as high as 90% or more to improve stability over time.

Specifically, the protective film according to the present invention has a peel force change rate defined by the following formula (1) of 10% or less, and has excellent stability over time.

Equation (1): Peel force change rate (%) = (A ₁ -A ₀ /A ₀ ) ×100

In the above formula (1), A ₀ is the peel force required to attach the protective film on the glass substrate and then peel the protective film from the glass substrate, and A ₁ is the protection stored at 70° C. for 7 days. It is the peeling force required to peel the said protective film from a glass substrate after adhering a film on a glass substrate.

In addition, the protective film according to the present invention has less adhesion layer transfer after peeling, less contamination due to penetration of external substances, and has excellent stain resistance.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Example One

A monomer mixture containing 95 parts by weight of ethylhexyl acrylate (EHA), 3 parts by weight of macromonomer AA-6S, (Manufacturer: Toagosei Co., Ltd.) and 2 parts by weight of acrylic acid was added to the reactor, and 100 parts by weight of ethyl acetate was added as a solvent did Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 63°C. Then, with respect to 100 parts by weight of the monomer mixture, 0.08 parts by weight of a polymerization initiator (V-59, manufacturer: Wako Co., Ltd.) and 0.04 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator were added and reacted for 8 hours. A copolymer was prepared. At this time, the polymerization initiator was added in two divided doses while checking the degree of exotherm. After the polymerization reaction was completed, 60 parts by weight of ethyl acetate was added to the prepared copolymer to finally obtain a diluted acrylic copolymer.

A pressure-sensitive adhesive composition was prepared by mixing 4 parts by weight of a curing agent (T-706B (45 wt% in ethyl acetate), manufacturer: Soken) with 100 parts by weight of the acrylic copolymer.

After the pressure-sensitive adhesive composition was applied on a PET film, dried at 90° C. for 90 seconds, and aged at 50° C. for 2 days to prepare a protective film.

Example 2

An acrylic copolymer, a pressure-sensitive adhesive composition, and a protective film were prepared in the same manner as in Example 1, except that AB-6 (manufacturer: Toagosei Co., Ltd.) was used as a macro monomer instead of AA-6S.

Example 3

An acrylic copolymer, a pressure-sensitive adhesive composition, and a protective film were prepared in the same manner as in Example 1, except that isoamyl acrylate was used instead of ethylhexyl acrylate (EHA).

comparative example One

A monomer mixture containing 98 parts by weight of ethylhexyl acrylate (EHA) and 2 parts by weight of acrylic acid was added to the reactor, and 100 parts by weight of ethyl acetate was added as a solvent. Then, nitrogen gas was purged for 60 minutes to remove oxygen, and then the temperature was maintained at 63. Then, with respect to 100 parts by weight of the monomer mixture, 0.08 parts by weight of a polymerization initiator (V-59, manufacturer: Wako Co., Ltd.) and 0.04 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator were added and reacted for 8 hours. A copolymer was prepared. At this time, the polymerization initiator was added in two divided doses while checking the degree of exotherm. After the polymerization reaction was completed, 60 parts by weight of ethyl acetate was added to the prepared copolymer to finally obtain a diluted acrylic copolymer.

1.16 parts by weight of macromonomer AA-6S (manufacturer: Toagosei Co., Ltd.), 4 parts by weight of a curing agent (T-706B (45 wt% in ethyl acetate), manufacturer: Soken) to 100 parts by weight of the acrylic copolymer to prepare a pressure-sensitive adhesive composition prepared.

After the pressure-sensitive adhesive composition was applied on a PET film, dried at 90° C. for 90 seconds, and aged at 50° C. for 2 days to prepare a protective film.

comparative example 2

An acrylic copolymer was prepared in the same manner as in Comparative Example 1, and 4 parts by weight of a curing agent (T-706B (45 wt% in ethyl acetate), manufacturer: Soken) was mixed with 100 parts by weight of the acrylic copolymer to prepare an adhesive composition. .

After the pressure-sensitive adhesive composition was applied on a PET film, dried at 90° C. for 90 seconds, and aged at 50° C. for 2 days to prepare a protective film.

comparative example 3

Acrylic copolymer, pressure-sensitive adhesive composition and protection in the same manner as in Example 1, except that 0.8 parts by weight of a curing agent (T-706B (45wt% in ethyl acetate), manufacturer: Soken) was mixed with 100 parts by weight of the acrylic copolymer. A film was prepared.

comparative example 4

An acrylic copolymer, a pressure-sensitive adhesive composition, and a protective film were prepared in the same manner as in Example 1, except that butyl acrylate (BA) was used instead of ethylhexyl acrylate (EHA).

Experimental example 1 - gel fraction

Each of the pressure-sensitive adhesive compositions prepared in Examples 1 to 3 and Comparative 1 to 4 were applied on a release film, dried at 90° C. for 90 seconds, and aged at 50° C. for 2 days to form an adhesive layer.

Then, a sample was collected by separating the adhesive layer from the release film, and the weight W ₁ of the sample was measured. Then, 100 g of ethyl acetate was added to the adhesive layer, left for 48 hours, filtered through a 200-mesh wire mesh (weight: Ag), and the residue was dried at 150° C. for 0.5 hour. the W ₃ measurements, it was calculated by subtracting the weight of the wire mesh in the measured weight value W ₂ W ₃ calculates a (W ₃ -A), a gel fraction according to the following formula (2). The measurement results are shown in Table 1 below.

Equation (2): Gel fraction (%) = (W ₂ /W ₁ ) × 100

gel fraction Example 1 90% Example 2 94% Example 3 91% Comparative Example 1 90% Comparative Example 2 92% Comparative Example 3 75% Comparative Example 4 91%

As shown in Table 1, the adhesive layer formed by curing the pressure-sensitive adhesive composition of Examples 1 to 3 according to the present invention exhibited a gel fraction of 90% or more, and the pressure-sensitive adhesive composition of Comparative Examples 1, 2 and 4 was cured It was also found that the adhesive layer formed by this process had a gel fraction of 90% or more. However, the adhesive layer formed by curing the pressure-sensitive adhesive composition of Comparative Example 3 had a low gel fraction of 75%.

Experimental example 2: Evaluation of viscosity properties

The viscosity of the pressure-sensitive adhesive composition prepared in Example 1 and the pressure-sensitive adhesive composition prepared in Comparative Example 4 was measured according to the following method. At this time, the solid content of the pressure-sensitive adhesive composition was 40% by weight. The measurement results are shown in [Table 2] below.

Put about 220 mL of the pressure-sensitive adhesive composition in a 250 mL PE bottle, close the lid so that the solvent does not volatilize, seal it sufficiently with parafilm, etc., and then leave it sufficiently under constant temperature / constant humidity (23 ° C., 50% relative humidity) conditions to remove air bubbles. Then, after removing the seal and lid, a spindle was placed at an angle to prevent bubbles from forming in the pressure-sensitive adhesive composition, the spindle was connected to a viscometer, and the liquid level of the pressure-sensitive adhesive composition was adjusted to fit into the groove of the spindle. Then, the viscosity was measured under the rpm condition in which the torque was 20% (±1%).

Viscosity (cP) Example 1 2,500 Comparative Example 4 8,200

As shown in [Table 2], in the case of the pressure-sensitive adhesive composition of Example 1 using a (meth)acrylate-based monomer containing a branched alkyl group, the viscosity is low, whereas (meth)acrylate containing a linear alkyl group It can be seen that the pressure-sensitive adhesive composition of Comparative Example 4 using the system monomer has a high viscosity.

Experimental example 3: Pollution resistance evaluation

After laminating the protective films prepared in Examples 1 to 3 and Comparative Examples 1 to 4 on a glass substrate, and leaving them in an oven at a temperature of 60° C. and a humidity of 90% for 3 days, the protective film is removed, The contamination on the surface of the glass substrate was visually observed.

When the surface of the glass substrate was clean, it was evaluated as ○, when the adhesive remained, or when contamination was observed, it was evaluated as X. The evaluation results are shown in [Table 3] below.

Experimental example 4: Evaluation of changes over time

_{After laminating the protective films prepared by Examples 1 to 3 and Comparative Examples 1 to 4 on a glass substrate, peel force A 0} required to peel the protective film from the glass substrate at a peeling rate of 0.3 m/min and a peeling angle of 180 degrees was measured.

In addition, the protective films prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were left at 70° C. for 7 days, and then the film was laminated on a glass substrate, and then the peel force A _{1 under the same peeling conditions as above.} was measured.

Then, the peel force change rate was measured by the following formula (1), the case where the peel force change rate was 10% or less was evaluated as ○, the case where the peel force change rate was 10% or less was evaluated as △, and the case where it exceeded 20% was evaluated as X. The evaluation results are shown in [Table 3] below.

stain resistance change over time Example 1 ○ ○ Example 2 ○ ○ Example 3 ○ ○ Comparative Example 1 X ○ Comparative Example 2 X ○ Comparative Example 3 ○ X Comparative Example 4 poor coating poor coating

As can be seen from Table 3 above, in the case of Examples 1 to 3 using the copolymer in which the macromonomer is introduced into the copolymer and the pressure-sensitive adhesive composition having a gel fraction of 90% or more after curing, both stain resistance and aging characteristics are excellent. On the other hand, when the macro-monomer was simply mixed with the pressure-sensitive adhesive composition (Comparative Example 1) or when the macro-monomer was not used (Comparative Example 2), it can be seen that stain resistance was poor.

In addition, in the case of Comparative Example 3 using a copolymer in which a macromonomer was introduced into the resin, but using a pressure-sensitive adhesive composition having a gel fraction of 75%, the property of change with time was poor, and Comparative Example 4 using a linear alkyl (meth)acrylate In this case, evaluation was impossible because the viscosity of the pressure-sensitive adhesive composition was too high and it was difficult to coat the pressure-sensitive adhesive layer.

Claims (9)

an acrylic copolymer formed by polymerizing a (meth)acrylate-based monomer containing a branched alkyl group, a macromonomer, and a monomer mixture containing a (meth)acrylic monomer containing a carboxyl group;
hardener; and
contains a solvent;
The solid content is 40% by weight or more,
A pressure-sensitive adhesive composition having a gel fraction of 90% or more after curing.
According to claim 1,
The monomer mixture contains 70 to 98 parts by weight of a (meth)acrylate-based monomer including a branched alkyl group, 1 to 20 parts by weight of a macromonomer, and 1 to 10 parts by weight of a carboxyl group based on 100 parts by weight of the monomer mixture ( Meth) A pressure-sensitive adhesive composition comprising an acrylic monomer.
According to claim 1,
The (meth) acrylate-based monomer including the branched alkyl group is ethylhexyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, isoamyl (meth) acrylate, isodecyl ( At least one pressure-sensitive adhesive composition selected from the group consisting of meth) acrylate, and isotetradecyl (meth) acrylate.
According to claim 1,
The acrylic copolymer is a pressure-sensitive adhesive composition having a weight average molecular weight of 700,000 or less.
According to claim 1,
The curing agent is an adhesive composition that is included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer.
delete According to claim 1,
The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition having a viscosity of 500cp to 4000cp at 23 ℃.
A protective film comprising an adhesive layer formed by the pressure-sensitive adhesive composition of any one of claims 1 to 5 and 7.
9. The method of claim 8,
The protective film is a protective film having a peel force change rate of 10% or less, which is defined by the following formula (1).
Equation (1): Peel force change rate (%) = (A ₁ -A ₀ /A ₀ ) ×100
In the above formula (1), A ₀ is the peel force required to attach the protective film on the glass substrate and then peel the protective film from the glass substrate, and A ₁ is the protection stored at 70° C. for 7 days. The peel force required to peel the protective film from the glass substrate after attaching the film on the glass substrate.